CA1125347A - Deeply filtered television image display - Google Patents
Deeply filtered television image displayInfo
- Publication number
- CA1125347A CA1125347A CA338,741A CA338741A CA1125347A CA 1125347 A CA1125347 A CA 1125347A CA 338741 A CA338741 A CA 338741A CA 1125347 A CA1125347 A CA 1125347A
- Authority
- CA
- Canada
- Prior art keywords
- dispersion
- layer
- particles
- ambient light
- phosphor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
- H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
- H01J29/18—Luminescent screens
- H01J29/30—Luminescent screens with luminescent material discontinuously arranged, e.g. in dots, in lines
- H01J29/32—Luminescent screens with luminescent material discontinuously arranged, e.g. in dots, in lines with adjacent dots or lines of different luminescent material, e.g. for colour television
- H01J29/327—Black matrix materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
- H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
- H01J29/18—Luminescent screens
- H01J29/185—Luminescent screens measures against halo-phenomena
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
- H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
- H01J29/18—Luminescent screens
- H01J29/28—Luminescent screens with protective, conductive or reflective layers
Landscapes
- Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A low-cost, deeply filtered television image display is depicted. A viewing screen includes a patterned layer of phosphor particles disposed contiguous to the inner surface of the display. The layer when excited emits light of a predetermined color. The display includes means for exciting selected areas of the layer to produce a luminescent informational image. The image is subject to loss of contrast caused by reflection of ambient light from the layer. The improvement comprises a shallow, random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment having a body color corresponding generally to the predetermined color disposed directly on the viewing screen beneath the layer and not significantly admixed with the phosphor particles. The percentage of open area of the dispersion of pigment particles and the absorption characteristics thereof are such that the dispersion efficiently filters ambient light at its interface with the layer. This filtering is accomplished first by absorption of directly incident ambient light, and secondly by absorption of ambient light passing through the open dispersion and scattering back off the phosphor particles to the dispersion. The dispersion represents a tolerable impediment to image light emitted by the phosphor particles due to the shallowness and openness of the dispersion and its non-absorption of light of said predetermined color. The dispersion negligibly absorbs electron beam energy due to its location beneath the layer. As a result, deep filtration of ambient light and thus high picture contrast is made practicable without a disproportionately countervailing loss in picture brightness.
A low-cost, deeply filtered television image display is depicted. A viewing screen includes a patterned layer of phosphor particles disposed contiguous to the inner surface of the display. The layer when excited emits light of a predetermined color. The display includes means for exciting selected areas of the layer to produce a luminescent informational image. The image is subject to loss of contrast caused by reflection of ambient light from the layer. The improvement comprises a shallow, random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment having a body color corresponding generally to the predetermined color disposed directly on the viewing screen beneath the layer and not significantly admixed with the phosphor particles. The percentage of open area of the dispersion of pigment particles and the absorption characteristics thereof are such that the dispersion efficiently filters ambient light at its interface with the layer. This filtering is accomplished first by absorption of directly incident ambient light, and secondly by absorption of ambient light passing through the open dispersion and scattering back off the phosphor particles to the dispersion. The dispersion represents a tolerable impediment to image light emitted by the phosphor particles due to the shallowness and openness of the dispersion and its non-absorption of light of said predetermined color. The dispersion negligibly absorbs electron beam energy due to its location beneath the layer. As a result, deep filtration of ambient light and thus high picture contrast is made practicable without a disproportionately countervailing loss in picture brightness.
Description
~2~
~ SPECIFICATIQN
-Back~ o~ the Invention and Prior Art Statemet;t _ .~is invention rel~tes in general t~ Oe ~isplays including telev:islon cathocle r~y picture tu~es, and more ~articularly is concernecl wlth i~,provement in image display contrast by a reduction in the reflection of ambient light from the display ~aceplate~
It has long been a major goal in the image display art to provicle a display having a maximum image contrast together wi.th maximum brightness. Brightness has been e~lanced, for exalllple, by utilizing more ef-ficient phosphors and, in cathod.e ray icture tube displays, by impacting the phosphors with electron beams having increased energy.
Image contrast was enhanced in the earlier days o~ television by means of a neutral dc-nsity filter (t.ypically about 42% transmi.ssive!
positioned over or incorporated in the viewing :~aceplate. Ambient light striking ~he aceplate was subject to a first reduction i.n its passage ~hrough the ~ilter toward the phosphor screen, then to a.second reduction as it was reflected back to the viewer, again through the fil-ter. A
penalty was paid in the use of this system in ~hat light emi~ted by the p'nosphor was also attenuated in its single passage through ~le ~ilter.
A n~Ljor breakthrough in enhancing i~age contrast was achieved through the "black surround" system disclosed by Fiore et al in U.S.
Pate.nt No. 3,l46,368. A screen structure is disclosed wherein the phosphor deposits, instead of having tangential contact with one another, are reduced in size and separated o~7er the screen area. A light-~bsor~ing pigment is placc-d i.n the spaces ~et~reen thnse phosphor de.posit.s. The electron beam l&n~.ng area is larger at least- in the horizonta.1 directi.on then ~he p'nosp,lor d.eposits. l~ne ~lack s-urrn~rld strllcture so ~a-r~ediy i.ncreases contrast tha~ the facep~a~e g:lass cr.m be made clear and the brightne~s thereby doubled.
.. , . . ~
. .
Imaging screens having filter particle elements associated with a phosphor element are intended to provide foT
reduction in ambient li~lt reflection which more than o fsets the inevitable loss in brightness, Filters comprise materials that S are trallsmissive to light of certa~l wavelengtlls, but absorptive of light of other wavelengths. As indicated by figure LA, part of the beam 1 of white light falling on an optically continuous filter material 2 will be reflected, as indicated by beam 3, while part of the beam will be trar.smitted through the material as indicated by beam 4. If the filter material is blue, for example, light of all wavelengths other than blue will be absorbed, and only blue light will be able to pass through the filter material 2, as indicated by beam 4. Also, the reflected light indicated by beam 3 will appear to be blue. Examples of optically continuo-ls filter elements ~able lS in picture screens include the lusters n~nufactured by F~glehard Industries of Newar~, New Jersey. -Pigments can be considered as particulate filters with a high index of refraction. With reference to figure lB, a beam 5 of white light is shown as impinging upon a pigment particle 6.
The particle is highly absorptive of light of all wavelengths except those in a selected band9 or bands. Light of all other wavelengths is quickly absorbed as it enters the particle 6. Light within the selected band or bands is transmitted or reflected internally, exiting the particle 6 in all directions as shown by arrows 7, giving the pigment particle its characteristic color or hue. In effect, the pigment particle "scatters" light falling upon it. 1~ the particle of pi~nent comprises a blue pigment9 for example9 only ~lue light will bP
scattered, and light of all other wa~Jelengths will be absorbed. The amount of scattering depends, inter alia, upon the size of the particle, with maxinlum scattering occurring when t}le particle is of about the s~me size as the wavelength of the lig~ht impinging upon it. Fxamples of pi~nents include titL~nium dioxide, a white pig~mellt; cobalt, a bllle ..... ......... . .... . . .. .
.. , .. ~ . ... .. .. ..... . .. . .
.. . .
i . .
~ 5 ~
pigment; and ca~mium sulfoselenide, a red pigment.
Kaplan in U.S. Patent 2,959,483 discloses a color image repro~ucer and method of manufacture. One embodiment (see Figure 2 herein) comprises green, red and blue target elem~nts 10, 12 and 14 which are located between faceplate 16 and alumin-ml film 18. ~ach target element comprises two discrete layers: a phosphor layer 20 and a ilter layer 22. Layer 20 comprises a speciic color phosphor for each target element; for example green phosphor 24 in target element 10.
Filter layer 26 in tzrget element 10 comprises a continous green filter material whi*l selectively transmits light of the wavelength corresponding to the green primary color while sharply attenuating ~he red and blue primaries. The effect of color filter layer 26 upon three impinging rays of ambiellt light is illustrated by ~ines 28, 30 ~Id 32.
Line 32 represents ligllt of a wavelength corresponding to green in color, while lines 28 and 30 represent red and blue, respectively. Because of the selective light transmission characteristics of the color filter layer 26, the red and blue light represented by rays 2~ and 30 is sharply attenuated in passing through filter material 26 as light of ~uch colors is reflected rom the target element. In fact, filter 26 attenuates the impinging light tw~ce, once each timc it is required to trzverse the filter material. The same effect takes place with regard to the red target element 12 and the blue target elemen-t 14. The result is that much if not all of the ambient light impinging upon the target structure i5 absorbed by the respective filter layers to improve image contrast and color saturation under high-level ambient viewing conditions, a~d without substantially reducing image brightness.
rnis approach is feasible because an optically continuous ~ particulate) filtPr layer will transmit a major fraction of the ligll~ having waveleng~hs within it5 bandpass. Opt1cally continuou~s 3Q filt_r materials, as presently kno~ however, are impractical since their .... . . .. .... . .. . . .. .. ... .. . ......... . . .. . .. ... . . .. .
.. . . . ..... ... .. . . .. . . .. . .
.
~ 3~7 deposition methods are too costly for use in mass-production.
Because of the expense entailed in th~ir use, optically continuous filters, so ax as is known, have never been used commercially in the manufacture of color cathode ray tubes.
Another embodiment of Kapian '483 teaches the use of mixtures of luminescent materials and pigment-type color filter material having selective color-transmissive characteristics corresponding to the emission characteristics of the associated phosphor. A further embodiment of the '483 disclosure is similar to the discrete phosphor-filter layer system of figure 2~ except th2t the luminescent layer comprises a homogenous mixture which emits light in all three of the primary colors selected for image reproduction;
i~e. white light.
U.S. Patent No. 3,~86,394 to Lipp discloses an image display lS employing phosphor particles which are filter-coated. Figure 3 indicates3 according to Lipp, a light-emitting phosphor particle 33, the surface of which is coated with filter particles 33A comprisin~ a pigment which is said to absorb spectral components of light from ambient sources. It is alleged tha~ by only partially covering, ln the range of 20 to 80%, the phosphor particles with filter particles, the transmission, absorption and reflection of light may be "tailored"
to optimize the brightness and contrast of the display image where the ~bient light levei is relatively high. Two embodiments are disclosed:
one in which there is a single layer of phosphor particles coated as ~5 described, and the other consisting of two layers comprising the coated phosphor particles, and over this, a layer of phosphor particles whlch are uncoated.
Uehara et al, in an article entitled 'IHigh Contrast Color Picture Tube" (Hitachi l~eview, Vol. 27 (1978), No. 4, reviews variou filter phosphor screening techniques as follows ~quoting directly from .,, . , , ~, ~ 3~'7 the alticle):
"Phosphor screening processes with pigment are generally classified into the following three kinds depending upon how the pig~nt is involved in the screen:
~1) Filter preparation process ~2) Slurry nLiXtUre process (3) Pigmented phosphor process t'In the filter preparation process, the pigment layer is placed between a glass panel and the ordinary phosphor screen so that it works as a cut-o~f filter against any colors other than those emitted from the phosphor used. This conception has been known widely since before the black matrix screen was introduced. However the complexity of the process has prevented it from being applied to practical production.
"qhe slurry mlxture process is far easier in the use of pigments, because they are simply mixed into the ordinary phosphor slurry whi.ch is very co~non for screening. In this case, however, it is ~ery difficult to completely avoid so-called pigment cross contamination which usually results in a brightness loss in the finished tuke.
'rAfter carefully studying these processes, we concluded that they could not be used for our purpose and a third process sholild be sought.
"Finally we developed the pigment phosphor process. Blue phosphor was coated with the blue pigment cobalt aluminate, red phosphor with the red pigment ferric oxide.'t In an article entitled"Black Stripe High Contrast Color Pieture Tube," by Ikegaki et al (Toshiba Review, August 1976~ a "graduated" pigment system is disclosed in which the blue phosphor particles have a pi.gment coating and in which the concentration of pigment varies through the blue phospllor field, with the heaviest ccncentration ,.. ~.... . . ..... .. .. . . . . . . . .. . . . .. ... . .. . ..
~3~ 3 4~
of pigment belng nearest the screen. A large increase in contrast over the standard Toshiba black-stripe tube is alleged.
The mixing of filter materials or pigment particles witl the phosphor can result in undesired side effects such as cross-contamination. In addition, such mixing can reduce the brightness o the images produced by the associated phosphor particles by shielding the phosphor particles from energizing electrons, and by absorption of the ligh-t enLit~ed by the phosphor particles near the point of origin. As will be explained in more detail hereinafter, a pigmented phosphor material can be used to produce a very slightly improved picture if the amount of pigmentation is very modest--e.g., that amount which reduces ambient light reflection, in comparison to one that is not pigmented, in the approximate range of 15% to 20%.
Attempts to make a "deep Eilter" tube or screen using the prior art pigmented phosp~or approach resulted in excessive brightness losses.
In the context of this application, a "deep filter" screen is considered to be so filtered that a reflectivity reduction of about 35% to 50% is provided with a corresponding higher picture contrast.
Hoyt in U.S. Patent No. 2,828,435 discloses means for making television screens in cathode ray tu~es by a decalcomania process.
In one of many illustrative decalcomania e~bodiments, a backing sheet is surmounted by pigment layer, a phosphor layer, and a protective clear surface layer. The backing sheet is removed, and the assembled layers are applied to the faceplate to form the screen with the pigment layer lylng 25 closest to the faceplate. The stated purpose is (quoting) 7'to slightly :- , .. ;
.
.1~L~ 4~7 shade or coior the image of cathode ray tubes."
In U.S. Patent No. 2~58,234, Ishler discloses a method ~or coating the insicle wall o:E a fluorescent lanlp envelope with a color-subtractive pigme.nt sai.d to have a l~iform thlchless and freedom froM
S streaking. I`he pigment, whl.ch operats~s by subtraction or absorption o undesired color to increase the proportion of the desired color in the spectral output is said to achieve a greater intensity or saturation of the desired color of the light emitted by fluorescent illuminating lamps.
Barnes--2,500,739 discloses the provision of a reflection-recluction coating between the material of the inner face of a cathode ray tube and the fluorescent screen. The coating is alleged to reduce halation by eliminating to a substantial degree the amount of light reflected from the surfaces of the tube face OlltO the fluorescent screen.
The preferred coating is said to be formed of "submicroscopic, micro-gran~a~' ~sic~ discrete approxinmately spherical particles less than 625 angstroms in diameter which are deposited on the glass surface so as to form minute projecting irregularities on the surface. Further, the concentration of the particles in the irregularities is said to decrease from the sur~acs~ of the tube face ou~ward., forming angularities whi.ch are alleged to increase the transmission of light rays from the s~r~ace with a consequent reduction in reflected light rays. ~:
In U.S. Patent No. 3,614,503 to Dietch, assigrled to the assignee of the present invention, a screen is discloss-~d for a color cathode ray tube comprised of interleaved deposits of phosphor material whis~ll en~it light of different colors; the deposits are surrounded by a light-absorbing material. A plurality of diffusely reflecting materia.ls -.s suuerposed over the phosphor deposits and the light-absorbing materïal.
T}le reflecting material ~ld the llght-absorbing material are spaced with r~spect to one another ts) simul.ate a multi.plicity of integrating spheres g ~f~34'~
.
surro~nding the phosphor deposits. It is said that multiple reflections from the surfaces per~it light developed by the phosphor dots and otherwise attenuated in the light-absorbin~ material to be added to the useful light output of the tube.
Dietch in U.S. Patent No. 3,952,225 ! assigned to the assignee of the present invention, cli:scloses a cathode ray tube image screen wherein a substantially n~n-reflective grille is provided on the faceplate. A reflective grille is provided in registration with the non-reflective grille, with a phosphor screen-over ~le reflective grille backed by an aluminum film. Light emitted in the open phosphor areas find its wa)~ out directly through the faceplate.
However, light emitted by the excited phosphor areas behind the black grille ~as seen from the viewing side), instead of being dissipated by the light absorption of the black grille, is subjected to multiple reflections between the reflective grille elem~nts and the aluminum backing layer. This l;ght is said to eventually reach the open phosphor areas whereupon it is also emitted by the faceplate. The invention is said to provide a new and greatly improved high-brightness, high-contrast cathode ray tube image screen for use in either monochromeor color picture tube environments.
Other prior art Patents:
426,789--Siemens (German)
~ SPECIFICATIQN
-Back~ o~ the Invention and Prior Art Statemet;t _ .~is invention rel~tes in general t~ Oe ~isplays including telev:islon cathocle r~y picture tu~es, and more ~articularly is concernecl wlth i~,provement in image display contrast by a reduction in the reflection of ambient light from the display ~aceplate~
It has long been a major goal in the image display art to provicle a display having a maximum image contrast together wi.th maximum brightness. Brightness has been e~lanced, for exalllple, by utilizing more ef-ficient phosphors and, in cathod.e ray icture tube displays, by impacting the phosphors with electron beams having increased energy.
Image contrast was enhanced in the earlier days o~ television by means of a neutral dc-nsity filter (t.ypically about 42% transmi.ssive!
positioned over or incorporated in the viewing :~aceplate. Ambient light striking ~he aceplate was subject to a first reduction i.n its passage ~hrough the ~ilter toward the phosphor screen, then to a.second reduction as it was reflected back to the viewer, again through the fil-ter. A
penalty was paid in the use of this system in ~hat light emi~ted by the p'nosphor was also attenuated in its single passage through ~le ~ilter.
A n~Ljor breakthrough in enhancing i~age contrast was achieved through the "black surround" system disclosed by Fiore et al in U.S.
Pate.nt No. 3,l46,368. A screen structure is disclosed wherein the phosphor deposits, instead of having tangential contact with one another, are reduced in size and separated o~7er the screen area. A light-~bsor~ing pigment is placc-d i.n the spaces ~et~reen thnse phosphor de.posit.s. The electron beam l&n~.ng area is larger at least- in the horizonta.1 directi.on then ~he p'nosp,lor d.eposits. l~ne ~lack s-urrn~rld strllcture so ~a-r~ediy i.ncreases contrast tha~ the facep~a~e g:lass cr.m be made clear and the brightne~s thereby doubled.
.. , . . ~
. .
Imaging screens having filter particle elements associated with a phosphor element are intended to provide foT
reduction in ambient li~lt reflection which more than o fsets the inevitable loss in brightness, Filters comprise materials that S are trallsmissive to light of certa~l wavelengtlls, but absorptive of light of other wavelengths. As indicated by figure LA, part of the beam 1 of white light falling on an optically continuous filter material 2 will be reflected, as indicated by beam 3, while part of the beam will be trar.smitted through the material as indicated by beam 4. If the filter material is blue, for example, light of all wavelengths other than blue will be absorbed, and only blue light will be able to pass through the filter material 2, as indicated by beam 4. Also, the reflected light indicated by beam 3 will appear to be blue. Examples of optically continuo-ls filter elements ~able lS in picture screens include the lusters n~nufactured by F~glehard Industries of Newar~, New Jersey. -Pigments can be considered as particulate filters with a high index of refraction. With reference to figure lB, a beam 5 of white light is shown as impinging upon a pigment particle 6.
The particle is highly absorptive of light of all wavelengths except those in a selected band9 or bands. Light of all other wavelengths is quickly absorbed as it enters the particle 6. Light within the selected band or bands is transmitted or reflected internally, exiting the particle 6 in all directions as shown by arrows 7, giving the pigment particle its characteristic color or hue. In effect, the pigment particle "scatters" light falling upon it. 1~ the particle of pi~nent comprises a blue pigment9 for example9 only ~lue light will bP
scattered, and light of all other wa~Jelengths will be absorbed. The amount of scattering depends, inter alia, upon the size of the particle, with maxinlum scattering occurring when t}le particle is of about the s~me size as the wavelength of the lig~ht impinging upon it. Fxamples of pi~nents include titL~nium dioxide, a white pig~mellt; cobalt, a bllle ..... ......... . .... . . .. .
.. , .. ~ . ... .. .. ..... . .. . .
.. . .
i . .
~ 5 ~
pigment; and ca~mium sulfoselenide, a red pigment.
Kaplan in U.S. Patent 2,959,483 discloses a color image repro~ucer and method of manufacture. One embodiment (see Figure 2 herein) comprises green, red and blue target elem~nts 10, 12 and 14 which are located between faceplate 16 and alumin-ml film 18. ~ach target element comprises two discrete layers: a phosphor layer 20 and a ilter layer 22. Layer 20 comprises a speciic color phosphor for each target element; for example green phosphor 24 in target element 10.
Filter layer 26 in tzrget element 10 comprises a continous green filter material whi*l selectively transmits light of the wavelength corresponding to the green primary color while sharply attenuating ~he red and blue primaries. The effect of color filter layer 26 upon three impinging rays of ambiellt light is illustrated by ~ines 28, 30 ~Id 32.
Line 32 represents ligllt of a wavelength corresponding to green in color, while lines 28 and 30 represent red and blue, respectively. Because of the selective light transmission characteristics of the color filter layer 26, the red and blue light represented by rays 2~ and 30 is sharply attenuated in passing through filter material 26 as light of ~uch colors is reflected rom the target element. In fact, filter 26 attenuates the impinging light tw~ce, once each timc it is required to trzverse the filter material. The same effect takes place with regard to the red target element 12 and the blue target elemen-t 14. The result is that much if not all of the ambient light impinging upon the target structure i5 absorbed by the respective filter layers to improve image contrast and color saturation under high-level ambient viewing conditions, a~d without substantially reducing image brightness.
rnis approach is feasible because an optically continuous ~ particulate) filtPr layer will transmit a major fraction of the ligll~ having waveleng~hs within it5 bandpass. Opt1cally continuou~s 3Q filt_r materials, as presently kno~ however, are impractical since their .... . . .. .... . .. . . .. .. ... .. . ......... . . .. . .. ... . . .. .
.. . . . ..... ... .. . . .. . . .. . .
.
~ 3~7 deposition methods are too costly for use in mass-production.
Because of the expense entailed in th~ir use, optically continuous filters, so ax as is known, have never been used commercially in the manufacture of color cathode ray tubes.
Another embodiment of Kapian '483 teaches the use of mixtures of luminescent materials and pigment-type color filter material having selective color-transmissive characteristics corresponding to the emission characteristics of the associated phosphor. A further embodiment of the '483 disclosure is similar to the discrete phosphor-filter layer system of figure 2~ except th2t the luminescent layer comprises a homogenous mixture which emits light in all three of the primary colors selected for image reproduction;
i~e. white light.
U.S. Patent No. 3,~86,394 to Lipp discloses an image display lS employing phosphor particles which are filter-coated. Figure 3 indicates3 according to Lipp, a light-emitting phosphor particle 33, the surface of which is coated with filter particles 33A comprisin~ a pigment which is said to absorb spectral components of light from ambient sources. It is alleged tha~ by only partially covering, ln the range of 20 to 80%, the phosphor particles with filter particles, the transmission, absorption and reflection of light may be "tailored"
to optimize the brightness and contrast of the display image where the ~bient light levei is relatively high. Two embodiments are disclosed:
one in which there is a single layer of phosphor particles coated as ~5 described, and the other consisting of two layers comprising the coated phosphor particles, and over this, a layer of phosphor particles whlch are uncoated.
Uehara et al, in an article entitled 'IHigh Contrast Color Picture Tube" (Hitachi l~eview, Vol. 27 (1978), No. 4, reviews variou filter phosphor screening techniques as follows ~quoting directly from .,, . , , ~, ~ 3~'7 the alticle):
"Phosphor screening processes with pigment are generally classified into the following three kinds depending upon how the pig~nt is involved in the screen:
~1) Filter preparation process ~2) Slurry nLiXtUre process (3) Pigmented phosphor process t'In the filter preparation process, the pigment layer is placed between a glass panel and the ordinary phosphor screen so that it works as a cut-o~f filter against any colors other than those emitted from the phosphor used. This conception has been known widely since before the black matrix screen was introduced. However the complexity of the process has prevented it from being applied to practical production.
"qhe slurry mlxture process is far easier in the use of pigments, because they are simply mixed into the ordinary phosphor slurry whi.ch is very co~non for screening. In this case, however, it is ~ery difficult to completely avoid so-called pigment cross contamination which usually results in a brightness loss in the finished tuke.
'rAfter carefully studying these processes, we concluded that they could not be used for our purpose and a third process sholild be sought.
"Finally we developed the pigment phosphor process. Blue phosphor was coated with the blue pigment cobalt aluminate, red phosphor with the red pigment ferric oxide.'t In an article entitled"Black Stripe High Contrast Color Pieture Tube," by Ikegaki et al (Toshiba Review, August 1976~ a "graduated" pigment system is disclosed in which the blue phosphor particles have a pi.gment coating and in which the concentration of pigment varies through the blue phospllor field, with the heaviest ccncentration ,.. ~.... . . ..... .. .. . . . . . . . .. . . . .. ... . .. . ..
~3~ 3 4~
of pigment belng nearest the screen. A large increase in contrast over the standard Toshiba black-stripe tube is alleged.
The mixing of filter materials or pigment particles witl the phosphor can result in undesired side effects such as cross-contamination. In addition, such mixing can reduce the brightness o the images produced by the associated phosphor particles by shielding the phosphor particles from energizing electrons, and by absorption of the ligh-t enLit~ed by the phosphor particles near the point of origin. As will be explained in more detail hereinafter, a pigmented phosphor material can be used to produce a very slightly improved picture if the amount of pigmentation is very modest--e.g., that amount which reduces ambient light reflection, in comparison to one that is not pigmented, in the approximate range of 15% to 20%.
Attempts to make a "deep Eilter" tube or screen using the prior art pigmented phosp~or approach resulted in excessive brightness losses.
In the context of this application, a "deep filter" screen is considered to be so filtered that a reflectivity reduction of about 35% to 50% is provided with a corresponding higher picture contrast.
Hoyt in U.S. Patent No. 2,828,435 discloses means for making television screens in cathode ray tu~es by a decalcomania process.
In one of many illustrative decalcomania e~bodiments, a backing sheet is surmounted by pigment layer, a phosphor layer, and a protective clear surface layer. The backing sheet is removed, and the assembled layers are applied to the faceplate to form the screen with the pigment layer lylng 25 closest to the faceplate. The stated purpose is (quoting) 7'to slightly :- , .. ;
.
.1~L~ 4~7 shade or coior the image of cathode ray tubes."
In U.S. Patent No. 2~58,234, Ishler discloses a method ~or coating the insicle wall o:E a fluorescent lanlp envelope with a color-subtractive pigme.nt sai.d to have a l~iform thlchless and freedom froM
S streaking. I`he pigment, whl.ch operats~s by subtraction or absorption o undesired color to increase the proportion of the desired color in the spectral output is said to achieve a greater intensity or saturation of the desired color of the light emitted by fluorescent illuminating lamps.
Barnes--2,500,739 discloses the provision of a reflection-recluction coating between the material of the inner face of a cathode ray tube and the fluorescent screen. The coating is alleged to reduce halation by eliminating to a substantial degree the amount of light reflected from the surfaces of the tube face OlltO the fluorescent screen.
The preferred coating is said to be formed of "submicroscopic, micro-gran~a~' ~sic~ discrete approxinmately spherical particles less than 625 angstroms in diameter which are deposited on the glass surface so as to form minute projecting irregularities on the surface. Further, the concentration of the particles in the irregularities is said to decrease from the sur~acs~ of the tube face ou~ward., forming angularities whi.ch are alleged to increase the transmission of light rays from the s~r~ace with a consequent reduction in reflected light rays. ~:
In U.S. Patent No. 3,614,503 to Dietch, assigrled to the assignee of the present invention, a screen is discloss-~d for a color cathode ray tube comprised of interleaved deposits of phosphor material whis~ll en~it light of different colors; the deposits are surrounded by a light-absorbing material. A plurality of diffusely reflecting materia.ls -.s suuerposed over the phosphor deposits and the light-absorbing materïal.
T}le reflecting material ~ld the llght-absorbing material are spaced with r~spect to one another ts) simul.ate a multi.plicity of integrating spheres g ~f~34'~
.
surro~nding the phosphor deposits. It is said that multiple reflections from the surfaces per~it light developed by the phosphor dots and otherwise attenuated in the light-absorbin~ material to be added to the useful light output of the tube.
Dietch in U.S. Patent No. 3,952,225 ! assigned to the assignee of the present invention, cli:scloses a cathode ray tube image screen wherein a substantially n~n-reflective grille is provided on the faceplate. A reflective grille is provided in registration with the non-reflective grille, with a phosphor screen-over ~le reflective grille backed by an aluminum film. Light emitted in the open phosphor areas find its wa)~ out directly through the faceplate.
However, light emitted by the excited phosphor areas behind the black grille ~as seen from the viewing side), instead of being dissipated by the light absorption of the black grille, is subjected to multiple reflections between the reflective grille elem~nts and the aluminum backing layer. This l;ght is said to eventually reach the open phosphor areas whereupon it is also emitted by the faceplate. The invention is said to provide a new and greatly improved high-brightness, high-contrast cathode ray tube image screen for use in either monochromeor color picture tube environments.
Other prior art Patents:
426,789--Siemens (German)
2,644,8S4--Sziklai 2,750,525--Palmer 2,~48,233--Yanagisawa et al 2,913,352--Windsor
3,C13,114--Bridges 3,454,715--Larach et al 3,812,394--Kaplan
4,087,280--Stookey et al --1 (,) -,, , 53~7 Objects _ f the Invention It is a general object of this invention to provide an improved television image d;splay having enhanced picture quality.
It is another general object to provide an image display having enhanced contrast.
It is a less general object to provide an image display which is not limited to shallow filter or medium filter applications wherein the maximum attainable improvement in brightness and contrast of a tube is modest, and of questionable effectiveness.
It is a specific object of the invention to provide an improved image display utili~ing a color-selective filter as part of the screen which yields an im~roved picture/brightness contrast factor, particularly in deep filter applications wherein the filter concentration is relatively high and the improvement dramatic.
It is another specific object to provide a filter-type image display capable of providing dramatically improved picture quality comparable to optically continuous filter approaches, but without the cost prohibition associated therewith.
Specifically, the invention is used in a low cost, deeply filtered image display having a faceplate with a viewing screen including a patterned layer of phosphor particles disposed contiguous to an inner surface thereof which, when excited emits light of a predetermined color, and having means for exciting selected areas of the layer to produce a luminescent informational image, the image being subject to loss of contrast caused by reflection of ambient light from the mb/~ - 11 -~L25~ct7 layer. The invention relates to the improvement comprising a shallow, random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment having a body color corresponding generally to the predetermined color locatecl directly on the face-plate beneath the layer and not signiEicantly admixed with the phosphor particles, the percentage of open area of the dispersion of pigment particles and the absorption characteristics thereof being such that the dispersion efficiently filters ambient light at its interface with the layer, first by absorption of directly incident ambient light, and second by absorption of ambient light passing through the open dispersion and scattering back off the phosphor particles to the dispersion, the dispersion representing a tolerable impediment to image light emitted by the phosphor particles due to the shallowness and openness of the dispersion and its non-absorption of light of the predetermined color, the dispersion negligibly absorbing electron beam energy due to its location beneath the layer, making practicable deep Eiltration of ambient light and thus high picture contrast without a dispro-portionately countervailing loss in pic-ture brightness.
Brief Descr ption of the Drawings The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify like elements and in which:
i": ~
mb/~D - lla -3~7 Figures lA and lB show schematically the effect of a beam of white light falling on an optically continuous filter material and a pigment particle, respectively.
Figure 2 is an elllarged cross-sectional view of a portion of the imaging screen of a prior art color television image display.
mb/J~ - llb -s~
Fi~ure 3 is an idealized sectional view of a pigment-coated phosphor particle emplo~ed in a prior art viewing screen.
Figure 4 is a schematic top view in longituclinal c.ross-section ofa prior art color televislon cathode ray ~ube image display S in which the inventioll may be advantageously employed; figure 4A is an cnlarged cletail vi.ew also .in section o:E a portion o:E the tube shown by figule 4.
Figure 5 is an enlarged schematic cross-sectional view of a fragment of a viewing screen comprising a preferred embodiment of the invention;
Figures 5A and 5B are copies of scanning electron microp~lotographs of 1700X and 3700X magnification respcciively, showing an open dispersion of pi~nent particles according to the invention; figure 5C is a low-contrast copy print of figure 5B in which deep fi'tering means according to the invention is illustrated diagrammatically;
Figures 6A and 6B are diagrams indicati.ng in greater detail the means for deep filtering according to the invention;
Figure 7 is an enlarged schematic cross-sec.tional view of a fragment of a faceplate showing another embodiment of the invention. ~ ;~
escription of the Preferred Embodiment This invention finds useful application in image displays wherein a phosphor is deposited contiguous to a transparent imaging screen. Deep filtration of ambient light; that is, filtrati.vn that provides a reduction in reflection of ambient light of 35% to 50%
ma~ing possible high picture contras~.
A well-k~o~n ex~ls? of an image display co~prises a multi-color cathode ray picture ~be of the aperture mask t~pe, sho~n by f-igu.re 4, whe-rein the in~enti.on may be aslvantageously em~loye~. Primary . ,., : ,., .. ,. , , . . ........ . . .. . . ,... ,, .. ., . . ., .. . ~ . .
- ~ .
~L~ 3~7 components of the picture tube 34 comprise an evacuated envelo-~e including a neck 36, a f~mnel 38 and a faceplate 40 havi~g a viewing screen 41 on its inner surace. A pattern o~ triads of tar~et elements is deposited contiguous to the scrcen 41, typi~icd by elements 4~, 44 and 46. Each targc~ element oE each triad has assigned a layer of one of three types of phosphors emitting, when excited, either red, green or blue light. The display includes ancillary means such as circuits and components ~not shown) for selectively exciting on~s of said target elements to produce a luminous informatior,al image, as is well-kno~m in the art. I`he target elemtnts may comprise a dot pattern; alte m atively, the pattern may comprise triads of stripes, rectangles, or other shapes also as is well-known in the art. A foraminated electrode ~l8 termed an aperture mask is employed for color selection.
An electron gun 50 is disposed within neck 36 substantially as sh~n. Electron gun 50 is installed in axial alignment with a center line X-X of picture tube 34. Electron gun 50 is shown as being the type that emits three electron beams 5~, 54 and 56 which selectively excite the pattern of target elements typified by elements 42, 44 and 46. Electron gun 50 may be of the unitized in-line type, or a gun of delta corlfiguration.
Base 58 provides entrance means for a plurality of electrically conductive lead-in pins 60. Relatively low voltages in the range of 1-15 kilovolts provide for operation of the electron gun 50 of tube 34. The relatively high voltage; that is, a voltage typically in the range of twenty-four to thirty-two kilovolts provides for excitation of the scr&en and the fina7 anode of the main focusing lens of gun S0.
Lead 62 cond~lcts the high voltage to ~node button 64, which penetrates the ~unnel 3S to make contact with the inner conductive coating 66.
~e high voltage is conducted to the fi~al focus electrode of gun 50 by snubber springs 48. ~ ycke 7Q provi~es, in conjunction witn ~mcillarY
circuits ~not sho~l), de~lection of beams 52, 54 and 56 for scal~ling aceplate 40.
.
~ ~L.~S 3~'7 Figure 4A is a detai]ed view of the faceplate 40 of figure 4, showing additionally a film of aluminum 72 and black surround 74, components well-lcno~l in the picture tube art. Red-light-emitting target element 42, comprising a layer oE phosphor, is shown c~s emitting light 7G, indicated by the arrow, when excited by the "red" beam 52 emitted by electrGn gun 50.
Figure 5 is an enlarged cross-sectional, representational vicw of a fragment of a faceplate and viewing screen comprising a deeply-filtered image display representing a preferred embodimen~ of the invention. The screen shown may comprise a part of a three-beam color cathode ray tube of the aperture mask type. A faceplate 78 has a pattern of target elements deposited contiguous to its sur:face. The -fragment of the faceplate shown is an illustration of one triad comprising target elements 80, 82 and 84. Each target element is assigned a layer of one of three kinds of phosphors 86, 88 and 90 which emit, when excited, red, green and blue light, respectively. Means for selectively exciting the phosphors is provided by energy source 92, indicated schematically by the bracketed arrows, and shown as imp mging upon target element 80.
The excitation source may comprise an electron beam which is caused to scan the target elements. Light-absorbing areas 94 are shown as being interspersed between the phosphor layers; these areas constitute the blacl; surround well-known in the art. An elec~ron-permeable film 96 reflects light emitted by the phosphor toward the viewer; film 96 may co~prise a very thin layer of aluminum.
~5 The improvement according to the invention comprises a sna]low, random, clumped, discontinuoùs, open dispersion of contrast-enhancing particles of pigment 98, 100 and 102, which are shown as being associated with target elements 80, 82 and 84, recpectively. Particles of pi~r.ent 98, 100 and 10~ are. prefeI?.kly, two or more orders of magnitude ~0 smaller in vnll~me ~han the acsociated phosphor particles indicated by .. . . ... .. . .
3~7 86, 88 and 90. Th.e particles of pigment are disposed directly on faceplate 7$ beneath the associated layer of phosphor particles and are not significantly admixed with the phosphor particles. Particles of pigment 98, 100 cmd 102 have a bo(~ color correspollding generally to S the color of light emitted by the associat~d phosphor layer. ~br example, a dispersion of particles of plgment 98 have a body color corresponding to the color of the light emitted by the layer of phosphor 86 sh~n by graphic symbology as being red-:light-emitting.
The "body color" of the contrast-enhancing particles of pigment comprises the intrinsic hue of the pigment in reflected ambient light. In the context of this disclosure, bod)~ color is in contradistinction to the color of the light emitted by the associated phosphor when excited, termed "image light." Thus the discontinuouE
open dispersion o contrast-enhancing particles o pigment 98~ 100 and 102 have a body color corresponding generally to the color of the light emitted by the associated phosphor layers 86, 88 and 90, indicated by graphic symbology as red-, green-, and blue-light-emitting phosphors.
As a result Qf the means according to the invention, ref;ection OI ~n~ient light is lowered to a deep-filtration range of 35% to 50% relative to the body color of the associated phosphor taken as unity.
A realization of the invention is shown ~y figures 5A, 5B and SC, which compIise scanning electron microscope photographs of the arrangement and relationship of phosphor particles and particles of pigmellt according to the invention, as deposited on a glass slide su~strate in simulation of the glass of the cathode ray tube faceplate.
(The particles of pi~nent shown are those having a red body color.) F;gure SA is aJI o~ ue plan vie-~l of-` a substrate 103 ~ld a sha]low, random, cll~cd, disc~lltinuol~, open dispersion of contrast--- . . . . . . . ........... . ....... .
: ,~
enhancing particles of pigment 104 located directly on the substra~e 103 according to ~he invention. The p~rticles of pigment 10-~ are located on the faceplate beneath a layer of phosphor particles lG5;
in figure ~SA, most of the phosphor particles 105 have been removcd to clearly reveal the open dispersion of particles o~ pigment 104. It will be seen that the individual particles of pigment 104, shown as being clumped, are preferably two or more orders o:E magnltude smaller in volume than the phospho~ particle 105. It is observable also -from figure 5A (as it is in 5B and 5C) that the particles of pigment 104 are not significantly admixed wi~h phosphor particles 105.
Pigure 5B comprises scanning electroll microscope photographs of a section of a glass slide fractured to display in cross-section the arrangement and relationship of phosphor particles and particles of pigment according to the invention. A layer of phosphor partic]es 106 is shown as being disposed contiguous to a glass slide su~s^trate 107, representing the picture tube faceplate. The phosphor particles when excited emi-t light of a predetermined color. The random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment 108 according to the invention is indicated by the arrow;
the particles of pigmcnt 108 have a body color corresponding generally to the aforesaid predetermined color and are located directly on the faceplate beneath layer of phosphor particles 106 but not significcmtly admixed with layer 106.
Figure 5C comprises a low-contrast print copy of figure SB
which more clearly shows the benefits of the invention with regard to the ~ffect on ambient light and image light. The dash-line arrows rePreser.t light emitted by the particles of phosphor 108~ and the solid-line arrows represent c~ient light falling upon the glass substrate 107, representi;lg the faceplate.
Light of the predeter~,ined color emitted by the phosphor, or -l6-image lig~lt sho~ by arrclws 110, "sees" effective light reflectors and sca~terers and eventually finds its way out to the viewor through the openings 112 in the dispersion of pigmen~ parti.cles. l~ese light reflectors and scatterers comprise, in addition to the phosphor particles, the particles of pignlent themselves which are reflective of image light of the predetermined color of the associated phosphor.
Ambient "white" light (with the exception of the blue complemRnt), "sees" an open dispersion of particles of pigment which effectively c~bsorbs the ambient light rays upon contact and prevents the re-emergence from openings 112 of ambient light which may pass into the phosphor la~er th-rough the openlngs 112 in the disperslon. lhe direct absorption of red and green ambient light by particles of pigment is indicated by arrow 114. The c~bsorption of red and green rays of ambient light ~hat find thoir way through ones of openings 112 is indicated by arrows 116.
Figures 5A and 6B show diagrammatically the action of the mec-~s according to the invention for deep filtrati.on of ambient light without a disproportionately countervailing loss in picture brightness. In figure 6A, rays 118 indicated by the bracket, representing only the red a~ld green complements-of inciclent white light, are shown by arrows as falling upon the highly schematic representation of the random~ cl~ed, discontinuous, open dispersion of particles of pigment 120 according to the invention sho~n schematically by ~he dash line as a la~er; in this example, the body color of the particlès of pigment 120 should be considered as being blue. The front surface of a lc-iyer of phosphor particles emitting~ when excited, blue light, is indicated by irregular line 122 in figures 6A and 6B. Rays 124 of directly incidellt light having red and green complements are shown as being intercepted by the open dispersion 120 of particles of pigment ~nd being absorbed. Rays 126 of directly incident l.i.ght are shown as passing through the olpeTlings in the dispersion 120 c~ld being scattered back of-f the phosphor par~icl.es to the dispersion 120 of pigment particles ~ihere the rays are intercepted and a second absorption occurs, as indicated. ~ssume that the percentage o:~ open area of the dispersion causes ~1 area-associated tr~lsmission factor of ~; the total absorption factor, very roughly, is A2 e.g.~ if A is 0.3 (absorption is 70%) then ~2 is 0.09 (absorption is about 90%)O
Figure 6B indicates schematically the effect of the open dispersion 120 of pigment particles according to the invention on rays of blue light 128~ indicated by the bracket, emitted by phosphor layer 122. Rays l.~0 are shown as emerging directly through the openings in the dispersion 120 while other rays 132 are shown as rcflec-~ing between the particl.es of pigment and layer of phosphor particles ].22 beEore finding their way out through openings in the dispersion 120 of pi~nent particles. The result is to provide high picture contrast without a disproportionately countervaiiing loss in picture brigh-tness.
Prior art displays utilizing pigments for reduction of reflection Oc ambient light, such as those disclosed by Lipp and Ikegaki et al (op. cito) annong others, provide for variously ac~nixing particles of pigment with phosphor particles. T~e benefits of disposing a random, clwnped, discontinuous, open dispersion of contrast-enhancillg particles of pigment clirectly on the faceplate beneath the phosphor layer but not significantly admixed with the phosphor particles according to the inventi.on including the following:
1. ~nbient li.ght "sees" the pigment particles firs-t, and a substantial amount of the ambient light is absorbed before it reaches the associated phosphor particles. In contrast~ Ul the pri.or art systems described heretofore, a large proportion of the piglnent particles are inaccessible to .~.~bient ligllt ~Icl perf.o~n little or none of the desired reflectivi~y reducti.oll~
2 By d.isposing the co]ltras.-enhanci.ng particles of pi~ment .i.8-., .. . . ~
~lf~
directly on the faceplate oetween the phosphor layer but not significantly admixed with the layer according to the invention, it is possible to use a greater ratio of pigmellt particles to phosphor particles wlthout a disproportionately countervailing loss in picture ~)rightness. Ii~nen the pigment particles are admi~ed with -~he phosphor particles according to the cited prior art examples, if ~he ratio of pigment-to-phosphor is too great, the resulting briglltness loss severely limits the light-emitting capabilities of the phosphor.
The means according to the invention permits larger amoun's of pigments to be used which contributes substantially to the achievement of deep filtration of ambient light.
3. The energy of the phosphor-exci~ing source; e.g., the electron beam in a cathode ray tube image dispiay, is relatively unaffected by the open dispersion of pigment particles according l:o the invention because the particles are located on the side of the phosphor particles opposite the beam, so absorption of beam energy is negligible. In the admixed pigment phosphor systems of the prior art, however, a substantial proportion of the pigment particles will be located between the phosphor particles and the electron beam to absorb an appreciable amount of the energy of the beam, resultlllg in reduced brigh~ness of the.image.
A practical way to determine the effectiveness of the means according to the invention in providmg deep filtration of ambient light is expediently accomplished by prepari~lg a two-inch by three-inch slide, with half of the slide coated with pigment particles in the open dispersion according to the invention~ The entire slide is then coated with phospllor particles of interest, after which the phosphor is coated with a thin ~ilm of aluminum by means weil-~lown in the art.
The llg}lt reflected by each of ~le two areas, as viewed through ~he glass of ~he slide, under a~lent ligh~ i.s co-mlpared using a standaJ~ reflec-to~ter.
-1~-.. .. .. . . . . .. . . . . . . . . . .. .. ..
.. -. :
The relative brightness can be deter~ined by the well-known m.eans wherein the aforesaid slide is installed in an ai-r-evacuated chamber and illununated from the aluninized side with an electron beam having an energy of known magnitude. The relative brightness of the pigmented and unpigmented areas is then determined by means of a precision light meter. Concurrently, the color coordinates are measured to determine the degree o color saturation.
Another embodiment of the invention is the application of the inventive concept to an image display having a viewing faceplate for exhibiting a diatonal achroma-tic image subject to loss of contrast by reflection of ambient light from the faceplate. A fragment of the faceplate of this type is shown in cross-section in figure 7. Faceplate 142 is shown as having disposed contiguous to its inner surface a pattern of pairs 144 of spaced target elements, indicated by the brackets.
I5 Each element of each pair 144 is assigned one of two types of phosphor emitting, when excited, blue or yellow light. For exarnple, the blue-light-enutting phosphor is indicated by reference number 146, and the yellow-light-emitting phosphor is indicated by reference number 148. The combined light emission of the pairs 144 when excited, produce the ~esired ~ atonal achromatic lmage. The eye of the viewer perceives this ~ -microstructure as an image exhibiting various gray tones.
An improv~mRnt according to the ~lvention comprises a random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment 150 and 152 preferabl~ two or ~ore orders of magnitude smaller in vol~ne than the associated phosphor particles. 17lc particles of pigment 150 and 152 are located directly on faceplate 142 beneath phosphor layers 146 and 14~, respectively, bu~ not si~lificantly admixed with the phosphor particles. ~le percentage of open area of the dispersion of pigment particles 100 and 152 ~nd the absolption characteristics thereof are such that the dispersiol~ efficlently filters ambient light at ~he interface ~Jith the la~ers of phosphor particles 146 ancl 14 ~ 5~3~'7 Thus,~efficient ~iltration is accomplished first by absorption of directly incident ambient light, and second, by absorption of ambient light passing through the open dispersion and scattering back of~ the phosphor particles to the dispersion. The dispersion re~resents a tolerable impediment to image light emitted by the phosphor particles due to the shallowness and openness of the dispersion and its non-absorption of light o the respective associated phosphor particles. The dispersion also negligibly absorbs electron beam energy due to its location beneath the layer. .~s a result, deep filtration of ambient ]ight is made practicable and thus high picture contrast is achieved without a disproportionately countervailing loss in picture brightness .
With regard to relative dimensions, the layers of phosphor may have a thickness of about 40 to 60 microns, for example. The particles of pigment may have a thickness of about 1 to 5 microns depending largely on the particle size of the particular pigment, whether red, green or blue. These dimensions and other measurements and values set forth herein are not intended to be limiting, but exemplary only.
Examples of pigments which may be used according to the invention comprise extremely fine inorganic particula*es which are commercially available. For example, a suitable red pi~nent may comprise cadmium sulfoselenide (Cd-S-Se) having a particle size of ~bout 0.5 micron. A suitable pigment of this composition is Cadmium Medi~ Light Red No. 2010 supplied by General Color Company, Newark, New Jersey. Another red pignent is iron oYide. A bluc pigment mav comprisc cobalt aluminate such as Harshaw No. 75~6 su~plied by Harshaw Chemical Co., Cle-~eland, Ohio. i~nothe-r suitable blue pigment supplied by Harshaw is designated MGteor Coba]t ~lue R~ ~o. 7536, and comprises cobalt silica zinc.
'7 :-. 1.
It should be noted that at present, only red and blue pigments are utilizable because an acceptahle green pigment is not available. As presently constituted, green pigments absorb too much of the light output of the associated phosphor. However~ if perchance the use of a green contrast-enhancing pigment ij desired in association with a green-light-emitting phosphor, a modified chromic oxide may bs used.
The random, clumped discontinuous open dispersion of contrast-; enhanc~ng particles of pigment located directly on the faceplate according to the invention may be applied by any of a number of well-Xno~n schemes such as slurrying, settling, or electrodeposition. The slurry process will be descrlbed as exemplary.
It is to be noted that the slurry process of application is so well-known in the art that it was deemed ~necessary to provide all the details of the process other than those directly relevant to pigment 15 - application.
A suitable formula for a slurry comprising particles of pigment having a body color of blue is as follows--Meteor Cobalt Blue Pigment, Harshaw No. 7536; 50 grams.
Polyvinyl alcohol, 10% concentration in water; 150 grams.
; 20 Deionized water: lO0 milliliters.
The components are mixed and ball-milled for at least one hou~ to obtain a dispersed suspension free of aggregates. To the ball-milled suspension is added 500 milliliters of delonized water and
It is another general object to provide an image display having enhanced contrast.
It is a less general object to provide an image display which is not limited to shallow filter or medium filter applications wherein the maximum attainable improvement in brightness and contrast of a tube is modest, and of questionable effectiveness.
It is a specific object of the invention to provide an improved image display utili~ing a color-selective filter as part of the screen which yields an im~roved picture/brightness contrast factor, particularly in deep filter applications wherein the filter concentration is relatively high and the improvement dramatic.
It is another specific object to provide a filter-type image display capable of providing dramatically improved picture quality comparable to optically continuous filter approaches, but without the cost prohibition associated therewith.
Specifically, the invention is used in a low cost, deeply filtered image display having a faceplate with a viewing screen including a patterned layer of phosphor particles disposed contiguous to an inner surface thereof which, when excited emits light of a predetermined color, and having means for exciting selected areas of the layer to produce a luminescent informational image, the image being subject to loss of contrast caused by reflection of ambient light from the mb/~ - 11 -~L25~ct7 layer. The invention relates to the improvement comprising a shallow, random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment having a body color corresponding generally to the predetermined color locatecl directly on the face-plate beneath the layer and not signiEicantly admixed with the phosphor particles, the percentage of open area of the dispersion of pigment particles and the absorption characteristics thereof being such that the dispersion efficiently filters ambient light at its interface with the layer, first by absorption of directly incident ambient light, and second by absorption of ambient light passing through the open dispersion and scattering back off the phosphor particles to the dispersion, the dispersion representing a tolerable impediment to image light emitted by the phosphor particles due to the shallowness and openness of the dispersion and its non-absorption of light of the predetermined color, the dispersion negligibly absorbing electron beam energy due to its location beneath the layer, making practicable deep Eiltration of ambient light and thus high picture contrast without a dispro-portionately countervailing loss in pic-ture brightness.
Brief Descr ption of the Drawings The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify like elements and in which:
i": ~
mb/~D - lla -3~7 Figures lA and lB show schematically the effect of a beam of white light falling on an optically continuous filter material and a pigment particle, respectively.
Figure 2 is an elllarged cross-sectional view of a portion of the imaging screen of a prior art color television image display.
mb/J~ - llb -s~
Fi~ure 3 is an idealized sectional view of a pigment-coated phosphor particle emplo~ed in a prior art viewing screen.
Figure 4 is a schematic top view in longituclinal c.ross-section ofa prior art color televislon cathode ray ~ube image display S in which the inventioll may be advantageously employed; figure 4A is an cnlarged cletail vi.ew also .in section o:E a portion o:E the tube shown by figule 4.
Figure 5 is an enlarged schematic cross-sectional view of a fragment of a viewing screen comprising a preferred embodiment of the invention;
Figures 5A and 5B are copies of scanning electron microp~lotographs of 1700X and 3700X magnification respcciively, showing an open dispersion of pi~nent particles according to the invention; figure 5C is a low-contrast copy print of figure 5B in which deep fi'tering means according to the invention is illustrated diagrammatically;
Figures 6A and 6B are diagrams indicati.ng in greater detail the means for deep filtering according to the invention;
Figure 7 is an enlarged schematic cross-sec.tional view of a fragment of a faceplate showing another embodiment of the invention. ~ ;~
escription of the Preferred Embodiment This invention finds useful application in image displays wherein a phosphor is deposited contiguous to a transparent imaging screen. Deep filtration of ambient light; that is, filtrati.vn that provides a reduction in reflection of ambient light of 35% to 50%
ma~ing possible high picture contras~.
A well-k~o~n ex~ls? of an image display co~prises a multi-color cathode ray picture ~be of the aperture mask t~pe, sho~n by f-igu.re 4, whe-rein the in~enti.on may be aslvantageously em~loye~. Primary . ,., : ,., .. ,. , , . . ........ . . .. . . ,... ,, .. ., . . ., .. . ~ . .
- ~ .
~L~ 3~7 components of the picture tube 34 comprise an evacuated envelo-~e including a neck 36, a f~mnel 38 and a faceplate 40 havi~g a viewing screen 41 on its inner surace. A pattern o~ triads of tar~et elements is deposited contiguous to the scrcen 41, typi~icd by elements 4~, 44 and 46. Each targc~ element oE each triad has assigned a layer of one of three types of phosphors emitting, when excited, either red, green or blue light. The display includes ancillary means such as circuits and components ~not shown) for selectively exciting on~s of said target elements to produce a luminous informatior,al image, as is well-kno~m in the art. I`he target elemtnts may comprise a dot pattern; alte m atively, the pattern may comprise triads of stripes, rectangles, or other shapes also as is well-known in the art. A foraminated electrode ~l8 termed an aperture mask is employed for color selection.
An electron gun 50 is disposed within neck 36 substantially as sh~n. Electron gun 50 is installed in axial alignment with a center line X-X of picture tube 34. Electron gun 50 is shown as being the type that emits three electron beams 5~, 54 and 56 which selectively excite the pattern of target elements typified by elements 42, 44 and 46. Electron gun 50 may be of the unitized in-line type, or a gun of delta corlfiguration.
Base 58 provides entrance means for a plurality of electrically conductive lead-in pins 60. Relatively low voltages in the range of 1-15 kilovolts provide for operation of the electron gun 50 of tube 34. The relatively high voltage; that is, a voltage typically in the range of twenty-four to thirty-two kilovolts provides for excitation of the scr&en and the fina7 anode of the main focusing lens of gun S0.
Lead 62 cond~lcts the high voltage to ~node button 64, which penetrates the ~unnel 3S to make contact with the inner conductive coating 66.
~e high voltage is conducted to the fi~al focus electrode of gun 50 by snubber springs 48. ~ ycke 7Q provi~es, in conjunction witn ~mcillarY
circuits ~not sho~l), de~lection of beams 52, 54 and 56 for scal~ling aceplate 40.
.
~ ~L.~S 3~'7 Figure 4A is a detai]ed view of the faceplate 40 of figure 4, showing additionally a film of aluminum 72 and black surround 74, components well-lcno~l in the picture tube art. Red-light-emitting target element 42, comprising a layer oE phosphor, is shown c~s emitting light 7G, indicated by the arrow, when excited by the "red" beam 52 emitted by electrGn gun 50.
Figure 5 is an enlarged cross-sectional, representational vicw of a fragment of a faceplate and viewing screen comprising a deeply-filtered image display representing a preferred embodimen~ of the invention. The screen shown may comprise a part of a three-beam color cathode ray tube of the aperture mask type. A faceplate 78 has a pattern of target elements deposited contiguous to its sur:face. The -fragment of the faceplate shown is an illustration of one triad comprising target elements 80, 82 and 84. Each target element is assigned a layer of one of three kinds of phosphors 86, 88 and 90 which emit, when excited, red, green and blue light, respectively. Means for selectively exciting the phosphors is provided by energy source 92, indicated schematically by the bracketed arrows, and shown as imp mging upon target element 80.
The excitation source may comprise an electron beam which is caused to scan the target elements. Light-absorbing areas 94 are shown as being interspersed between the phosphor layers; these areas constitute the blacl; surround well-known in the art. An elec~ron-permeable film 96 reflects light emitted by the phosphor toward the viewer; film 96 may co~prise a very thin layer of aluminum.
~5 The improvement according to the invention comprises a sna]low, random, clumped, discontinuoùs, open dispersion of contrast-enhancing particles of pigment 98, 100 and 102, which are shown as being associated with target elements 80, 82 and 84, recpectively. Particles of pi~r.ent 98, 100 and 10~ are. prefeI?.kly, two or more orders of magnitude ~0 smaller in vnll~me ~han the acsociated phosphor particles indicated by .. . . ... .. . .
3~7 86, 88 and 90. Th.e particles of pigment are disposed directly on faceplate 7$ beneath the associated layer of phosphor particles and are not significantly admixed with the phosphor particles. Particles of pigment 98, 100 cmd 102 have a bo(~ color correspollding generally to S the color of light emitted by the associat~d phosphor layer. ~br example, a dispersion of particles of plgment 98 have a body color corresponding to the color of the light emitted by the layer of phosphor 86 sh~n by graphic symbology as being red-:light-emitting.
The "body color" of the contrast-enhancing particles of pigment comprises the intrinsic hue of the pigment in reflected ambient light. In the context of this disclosure, bod)~ color is in contradistinction to the color of the light emitted by the associated phosphor when excited, termed "image light." Thus the discontinuouE
open dispersion o contrast-enhancing particles o pigment 98~ 100 and 102 have a body color corresponding generally to the color of the light emitted by the associated phosphor layers 86, 88 and 90, indicated by graphic symbology as red-, green-, and blue-light-emitting phosphors.
As a result Qf the means according to the invention, ref;ection OI ~n~ient light is lowered to a deep-filtration range of 35% to 50% relative to the body color of the associated phosphor taken as unity.
A realization of the invention is shown ~y figures 5A, 5B and SC, which compIise scanning electron microscope photographs of the arrangement and relationship of phosphor particles and particles of pigmellt according to the invention, as deposited on a glass slide su~strate in simulation of the glass of the cathode ray tube faceplate.
(The particles of pi~nent shown are those having a red body color.) F;gure SA is aJI o~ ue plan vie-~l of-` a substrate 103 ~ld a sha]low, random, cll~cd, disc~lltinuol~, open dispersion of contrast--- . . . . . . . ........... . ....... .
: ,~
enhancing particles of pigment 104 located directly on the substra~e 103 according to ~he invention. The p~rticles of pigment 10-~ are located on the faceplate beneath a layer of phosphor particles lG5;
in figure ~SA, most of the phosphor particles 105 have been removcd to clearly reveal the open dispersion of particles o~ pigment 104. It will be seen that the individual particles of pigment 104, shown as being clumped, are preferably two or more orders o:E magnltude smaller in volume than the phospho~ particle 105. It is observable also -from figure 5A (as it is in 5B and 5C) that the particles of pigment 104 are not significantly admixed wi~h phosphor particles 105.
Pigure 5B comprises scanning electroll microscope photographs of a section of a glass slide fractured to display in cross-section the arrangement and relationship of phosphor particles and particles of pigment according to the invention. A layer of phosphor partic]es 106 is shown as being disposed contiguous to a glass slide su~s^trate 107, representing the picture tube faceplate. The phosphor particles when excited emi-t light of a predetermined color. The random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment 108 according to the invention is indicated by the arrow;
the particles of pigmcnt 108 have a body color corresponding generally to the aforesaid predetermined color and are located directly on the faceplate beneath layer of phosphor particles 106 but not significcmtly admixed with layer 106.
Figure 5C comprises a low-contrast print copy of figure SB
which more clearly shows the benefits of the invention with regard to the ~ffect on ambient light and image light. The dash-line arrows rePreser.t light emitted by the particles of phosphor 108~ and the solid-line arrows represent c~ient light falling upon the glass substrate 107, representi;lg the faceplate.
Light of the predeter~,ined color emitted by the phosphor, or -l6-image lig~lt sho~ by arrclws 110, "sees" effective light reflectors and sca~terers and eventually finds its way out to the viewor through the openings 112 in the dispersion of pigmen~ parti.cles. l~ese light reflectors and scatterers comprise, in addition to the phosphor particles, the particles of pignlent themselves which are reflective of image light of the predetermined color of the associated phosphor.
Ambient "white" light (with the exception of the blue complemRnt), "sees" an open dispersion of particles of pigment which effectively c~bsorbs the ambient light rays upon contact and prevents the re-emergence from openings 112 of ambient light which may pass into the phosphor la~er th-rough the openlngs 112 in the disperslon. lhe direct absorption of red and green ambient light by particles of pigment is indicated by arrow 114. The c~bsorption of red and green rays of ambient light ~hat find thoir way through ones of openings 112 is indicated by arrows 116.
Figures 5A and 6B show diagrammatically the action of the mec-~s according to the invention for deep filtrati.on of ambient light without a disproportionately countervailing loss in picture brightness. In figure 6A, rays 118 indicated by the bracket, representing only the red a~ld green complements-of inciclent white light, are shown by arrows as falling upon the highly schematic representation of the random~ cl~ed, discontinuous, open dispersion of particles of pigment 120 according to the invention sho~n schematically by ~he dash line as a la~er; in this example, the body color of the particlès of pigment 120 should be considered as being blue. The front surface of a lc-iyer of phosphor particles emitting~ when excited, blue light, is indicated by irregular line 122 in figures 6A and 6B. Rays 124 of directly incidellt light having red and green complements are shown as being intercepted by the open dispersion 120 of particles of pigment ~nd being absorbed. Rays 126 of directly incident l.i.ght are shown as passing through the olpeTlings in the dispersion 120 c~ld being scattered back of-f the phosphor par~icl.es to the dispersion 120 of pigment particles ~ihere the rays are intercepted and a second absorption occurs, as indicated. ~ssume that the percentage o:~ open area of the dispersion causes ~1 area-associated tr~lsmission factor of ~; the total absorption factor, very roughly, is A2 e.g.~ if A is 0.3 (absorption is 70%) then ~2 is 0.09 (absorption is about 90%)O
Figure 6B indicates schematically the effect of the open dispersion 120 of pigment particles according to the invention on rays of blue light 128~ indicated by the bracket, emitted by phosphor layer 122. Rays l.~0 are shown as emerging directly through the openings in the dispersion 120 while other rays 132 are shown as rcflec-~ing between the particl.es of pigment and layer of phosphor particles ].22 beEore finding their way out through openings in the dispersion 120 of pi~nent particles. The result is to provide high picture contrast without a disproportionately countervaiiing loss in picture brigh-tness.
Prior art displays utilizing pigments for reduction of reflection Oc ambient light, such as those disclosed by Lipp and Ikegaki et al (op. cito) annong others, provide for variously ac~nixing particles of pigment with phosphor particles. T~e benefits of disposing a random, clwnped, discontinuous, open dispersion of contrast-enhancillg particles of pigment clirectly on the faceplate beneath the phosphor layer but not significantly admixed with the phosphor particles according to the inventi.on including the following:
1. ~nbient li.ght "sees" the pigment particles firs-t, and a substantial amount of the ambient light is absorbed before it reaches the associated phosphor particles. In contrast~ Ul the pri.or art systems described heretofore, a large proportion of the piglnent particles are inaccessible to .~.~bient ligllt ~Icl perf.o~n little or none of the desired reflectivi~y reducti.oll~
2 By d.isposing the co]ltras.-enhanci.ng particles of pi~ment .i.8-., .. . . ~
~lf~
directly on the faceplate oetween the phosphor layer but not significantly admixed with the layer according to the invention, it is possible to use a greater ratio of pigmellt particles to phosphor particles wlthout a disproportionately countervailing loss in picture ~)rightness. Ii~nen the pigment particles are admi~ed with -~he phosphor particles according to the cited prior art examples, if ~he ratio of pigment-to-phosphor is too great, the resulting briglltness loss severely limits the light-emitting capabilities of the phosphor.
The means according to the invention permits larger amoun's of pigments to be used which contributes substantially to the achievement of deep filtration of ambient light.
3. The energy of the phosphor-exci~ing source; e.g., the electron beam in a cathode ray tube image dispiay, is relatively unaffected by the open dispersion of pigment particles according l:o the invention because the particles are located on the side of the phosphor particles opposite the beam, so absorption of beam energy is negligible. In the admixed pigment phosphor systems of the prior art, however, a substantial proportion of the pigment particles will be located between the phosphor particles and the electron beam to absorb an appreciable amount of the energy of the beam, resultlllg in reduced brigh~ness of the.image.
A practical way to determine the effectiveness of the means according to the invention in providmg deep filtration of ambient light is expediently accomplished by prepari~lg a two-inch by three-inch slide, with half of the slide coated with pigment particles in the open dispersion according to the invention~ The entire slide is then coated with phospllor particles of interest, after which the phosphor is coated with a thin ~ilm of aluminum by means weil-~lown in the art.
The llg}lt reflected by each of ~le two areas, as viewed through ~he glass of ~he slide, under a~lent ligh~ i.s co-mlpared using a standaJ~ reflec-to~ter.
-1~-.. .. .. . . . . .. . . . . . . . . . .. .. ..
.. -. :
The relative brightness can be deter~ined by the well-known m.eans wherein the aforesaid slide is installed in an ai-r-evacuated chamber and illununated from the aluninized side with an electron beam having an energy of known magnitude. The relative brightness of the pigmented and unpigmented areas is then determined by means of a precision light meter. Concurrently, the color coordinates are measured to determine the degree o color saturation.
Another embodiment of the invention is the application of the inventive concept to an image display having a viewing faceplate for exhibiting a diatonal achroma-tic image subject to loss of contrast by reflection of ambient light from the faceplate. A fragment of the faceplate of this type is shown in cross-section in figure 7. Faceplate 142 is shown as having disposed contiguous to its inner surface a pattern of pairs 144 of spaced target elements, indicated by the brackets.
I5 Each element of each pair 144 is assigned one of two types of phosphor emitting, when excited, blue or yellow light. For exarnple, the blue-light-enutting phosphor is indicated by reference number 146, and the yellow-light-emitting phosphor is indicated by reference number 148. The combined light emission of the pairs 144 when excited, produce the ~esired ~ atonal achromatic lmage. The eye of the viewer perceives this ~ -microstructure as an image exhibiting various gray tones.
An improv~mRnt according to the ~lvention comprises a random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment 150 and 152 preferabl~ two or ~ore orders of magnitude smaller in vol~ne than the associated phosphor particles. 17lc particles of pigment 150 and 152 are located directly on faceplate 142 beneath phosphor layers 146 and 14~, respectively, bu~ not si~lificantly admixed with the phosphor particles. ~le percentage of open area of the dispersion of pigment particles 100 and 152 ~nd the absolption characteristics thereof are such that the dispersiol~ efficlently filters ambient light at ~he interface ~Jith the la~ers of phosphor particles 146 ancl 14 ~ 5~3~'7 Thus,~efficient ~iltration is accomplished first by absorption of directly incident ambient light, and second, by absorption of ambient light passing through the open dispersion and scattering back of~ the phosphor particles to the dispersion. The dispersion re~resents a tolerable impediment to image light emitted by the phosphor particles due to the shallowness and openness of the dispersion and its non-absorption of light o the respective associated phosphor particles. The dispersion also negligibly absorbs electron beam energy due to its location beneath the layer. .~s a result, deep filtration of ambient ]ight is made practicable and thus high picture contrast is achieved without a disproportionately countervailing loss in picture brightness .
With regard to relative dimensions, the layers of phosphor may have a thickness of about 40 to 60 microns, for example. The particles of pigment may have a thickness of about 1 to 5 microns depending largely on the particle size of the particular pigment, whether red, green or blue. These dimensions and other measurements and values set forth herein are not intended to be limiting, but exemplary only.
Examples of pigments which may be used according to the invention comprise extremely fine inorganic particula*es which are commercially available. For example, a suitable red pi~nent may comprise cadmium sulfoselenide (Cd-S-Se) having a particle size of ~bout 0.5 micron. A suitable pigment of this composition is Cadmium Medi~ Light Red No. 2010 supplied by General Color Company, Newark, New Jersey. Another red pignent is iron oYide. A bluc pigment mav comprisc cobalt aluminate such as Harshaw No. 75~6 su~plied by Harshaw Chemical Co., Cle-~eland, Ohio. i~nothe-r suitable blue pigment supplied by Harshaw is designated MGteor Coba]t ~lue R~ ~o. 7536, and comprises cobalt silica zinc.
'7 :-. 1.
It should be noted that at present, only red and blue pigments are utilizable because an acceptahle green pigment is not available. As presently constituted, green pigments absorb too much of the light output of the associated phosphor. However~ if perchance the use of a green contrast-enhancing pigment ij desired in association with a green-light-emitting phosphor, a modified chromic oxide may bs used.
The random, clumped discontinuous open dispersion of contrast-; enhanc~ng particles of pigment located directly on the faceplate according to the invention may be applied by any of a number of well-Xno~n schemes such as slurrying, settling, or electrodeposition. The slurry process will be descrlbed as exemplary.
It is to be noted that the slurry process of application is so well-known in the art that it was deemed ~necessary to provide all the details of the process other than those directly relevant to pigment 15 - application.
A suitable formula for a slurry comprising particles of pigment having a body color of blue is as follows--Meteor Cobalt Blue Pigment, Harshaw No. 7536; 50 grams.
Polyvinyl alcohol, 10% concentration in water; 150 grams.
; 20 Deionized water: lO0 milliliters.
The components are mixed and ball-milled for at least one hou~ to obtain a dispersed suspension free of aggregates. To the ball-milled suspension is added 500 milliliters of delonized water and
5 milliliters of ammonium dichromate, 10% solution. The slurry is poured ~5 , over a horizontally oriented faceplate which is, for example, of 13-inch diagonal measure. The faceplate is tilted to a vertical orientation and rotated at abou'~ 200 rpm until dry. ~le areas where the particles of pigment are to be permanently fixed are subject to ultraviolet light directcd to the scresn -through an assoc;ated aperture mask. I~e faceplate 3~ is then "developed" to remove the particles o pigment from all other elemental areas of the faceplate except ~hose which have been exposed.
, . . .
A similar slurry process is used for depositing the blue phosphor, which for example may be P22, directly on the elemental areas of the faceplate ha~.ri.ng a deposit of the blue pigment particles. The process is then repeated for pigments and associated phosphors of other colors as desired. ~he final process comprises alumillizing the faceplate by means well-hncwn in the àrt.
The reflectivity of a blue-light-emitting phosphor, for example, pigmented accordin~ to the invention, as compared to an unpigmented "blue" phosphor, is about 0.25 ~the unpigmented phosphor b~ing taken as 1.0).
l~e order of deposition is optional. It may be determined that it is preferable, for example, to deposit the red pigment and associated phosphor first; alternatively, both the red and blue pigments could as well be deposited initially, followed by the respective phosphors.
The formula for a slurry containing a pigment for deposit in association with and having a body color corresponding generally of a red-light-emitting phosphor, for example, is very similar to the formula described supra for the blue pigment slurry. Considerable latitude consists in pigment slurry formulations; quantities of pi~ents required are dependent upon the desired amount of filtration desired, and the exact formufations can be determined without undue experimentation by one having ordinary skill in the art. As noted, layers of particles of pigment are preferably applied in association with only the red- and blue-light-emitting phospllors, as an acceptable green colorant is considered as not being presently available.
The effectiveness of the me~ns according to the invention ir makîng practicable deep filtration of an~ient light and thus high picture contrast without a disproportionately countervailing loss in picture brightness lS shol~n by ~le results of laboratory tests described as follows. A control base-line was established by averaging the white ~3 .: . . .,,, . .... , , .... - - . , ield (7500K) brightness and reflectivity (absolute) characteristics of standard production-line 25-inch striped-screen black matrix picture tubes. The brightness and reflectivity characteristics of a test picture tu~e similar in respect to the control tubes, e~cept that the faceplate was red- and blue- pignlented by the me~s according to the invention, was measured, with the follol~ing results--Control Pigmented Tube Brightness, fL ~0 68 Reflecti~i.ty 0.50 0.261 Accordingly, the actual reduction in the reflection of ambient light of the pigmented tube is about 48%, with a brightness loss of 15%. If the pigme.nting according to the invention was such as to provide a reduction i-n reflection of 40%, for example (well within the range deined as "deep filter"), the resulting brightness loss would be about 9%. This loss could conceivably be urther reduced by~ :.for example, the use of more efficient combinations of pi.gments and phosphors.
While particular embodiments of the invention 'nave been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the învention in its broader aspects, and t'nerefore the aim in the appended d air~s is to co~rer all such Ghanges and modifications as fall within the true spirit and scope of the invention.
-~4-
, . . .
A similar slurry process is used for depositing the blue phosphor, which for example may be P22, directly on the elemental areas of the faceplate ha~.ri.ng a deposit of the blue pigment particles. The process is then repeated for pigments and associated phosphors of other colors as desired. ~he final process comprises alumillizing the faceplate by means well-hncwn in the àrt.
The reflectivity of a blue-light-emitting phosphor, for example, pigmented accordin~ to the invention, as compared to an unpigmented "blue" phosphor, is about 0.25 ~the unpigmented phosphor b~ing taken as 1.0).
l~e order of deposition is optional. It may be determined that it is preferable, for example, to deposit the red pigment and associated phosphor first; alternatively, both the red and blue pigments could as well be deposited initially, followed by the respective phosphors.
The formula for a slurry containing a pigment for deposit in association with and having a body color corresponding generally of a red-light-emitting phosphor, for example, is very similar to the formula described supra for the blue pigment slurry. Considerable latitude consists in pigment slurry formulations; quantities of pi~ents required are dependent upon the desired amount of filtration desired, and the exact formufations can be determined without undue experimentation by one having ordinary skill in the art. As noted, layers of particles of pigment are preferably applied in association with only the red- and blue-light-emitting phospllors, as an acceptable green colorant is considered as not being presently available.
The effectiveness of the me~ns according to the invention ir makîng practicable deep filtration of an~ient light and thus high picture contrast without a disproportionately countervailing loss in picture brightness lS shol~n by ~le results of laboratory tests described as follows. A control base-line was established by averaging the white ~3 .: . . .,,, . .... , , .... - - . , ield (7500K) brightness and reflectivity (absolute) characteristics of standard production-line 25-inch striped-screen black matrix picture tubes. The brightness and reflectivity characteristics of a test picture tu~e similar in respect to the control tubes, e~cept that the faceplate was red- and blue- pignlented by the me~s according to the invention, was measured, with the follol~ing results--Control Pigmented Tube Brightness, fL ~0 68 Reflecti~i.ty 0.50 0.261 Accordingly, the actual reduction in the reflection of ambient light of the pigmented tube is about 48%, with a brightness loss of 15%. If the pigme.nting according to the invention was such as to provide a reduction i-n reflection of 40%, for example (well within the range deined as "deep filter"), the resulting brightness loss would be about 9%. This loss could conceivably be urther reduced by~ :.for example, the use of more efficient combinations of pi.gments and phosphors.
While particular embodiments of the invention 'nave been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the învention in its broader aspects, and t'nerefore the aim in the appended d air~s is to co~rer all such Ghanges and modifications as fall within the true spirit and scope of the invention.
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Claims (8)
- I CLAIM:
l. In a low cost, deeply filtered image display having a faceplate with a viewing screen including a patterned layer of phosphor particles disposed contiguous to an inner surface thereof which, when excited emits light of a predetermined color, and having means for exciting selected areas of said layer to produce a luminescent informational image, said image being subject of less of contrast caused by reflection of ambient light from said layer, an improvement comprising a shallow, random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment having a body color corresponding generally to said predetermined color located directly on said faceplate beneath said layer and not significantly admixed with said phosphor particles, the percentage of open area of said dispersion of pigment particles and the absorption characteristics thereof being such that said dispersion efficiently filters ambient light at its interface with said layer, first by absorption of directly incident ambient light, and second by absorption of ambient light passing through said open dispersion and scattering back off said phosphor particles to said dispersion, said dispersion representing a tolerable impediment to image light emitted by said phosphor particles due to the shallowness and openness of said dispersion and its non-absorption of light of said prefetermined color, said dispersion negligibly absorbing electron beam energy due to its location beneath said layer, making practicable deep filtration of ambient light and thus high picture contrast without a disproportionately countervailing loss in picture brightness. - 2. The image display defined by claim 1 wherein said reflection of ambient light is lowered to a deep filtration range of 35% to 50%
relative to the body color of the phosphor taken as unity. - 3. The image display defined by claim 1 wherein said particles of pigment are selected from a group consisting of cadmium sulfeselenide, iron oxide, cobalt aluminate, cobalt silica zinc and chromic oxide.
- 4. A low-cost, deeply filtered television image display comprising a multi-color cathode ray picture tube of the aperture-mask type, said tube having a three-beam electron gun, a color selection aperture mask, and a faceplate with a viewing screen including a pattern of triads of target elements deposited contiguous thereto, each target element of each triad having assigned a layer of one of three kinds of phosphor particles emitting, when excited, red, green or blue light, and means for selectively exciting ones of said target elements to produce a luminous informational image, said image being subject to loss of contrast caused by reflection of ambient light from said layers, an improvement comprising a shallow, random, clumped discontinuous open dispersion of contrast-enhancing particles of pigment two or more orders of magnitude smaller in volume than said phosphor particles associated with each of at least two of said target elements constituting said triads and having a body color corresponding generally to the color of the light emitted by the associated phosphor layer located directly on said faceplate beneath said phosphor layer and not significantly claimed with said phosphor particles, the percentage of open area of said dispersion of pigment particles and the absorption characteristics thereof being such that said dispersion efficiently filters ambient light at its interface with said layer, first by absorption of directly incident ambient light, and second by absorption of ambient light passing through said open dispersion and scattering back off said phosphor particles to said dispersion, said dispersion representing a tolerable impediment to image light emitted by said phosphor particles due to the shallowness and openness of said dispersion and its non-absorption of light of the color emitted by the associated phosphor layer, said dispersion negligibly absorbing electron beam energy due to its location beneath said layer, making practicable deep filtration of ambient light and thus high picture contrast without a disproportionately countervailing loss in picture brightness.
- 5. A low-cost, deeply filtered television image display comprising a multi-color cathode ray picture tube of the aperture-mask type, said tube having a three-beam electron gun, a color selection aperture mask, and a faceplate with a viewing screen including a pattern of triads of target elements deposited contiguous to an inner surface thereof, each target element of each triad having assigned a layer of one of three kinds of phosphor particles emitting, when excited, red, green or blue light, and means for selectively exciting ones of said target elements to produce a luminous informational image, said image being subject to loss of contrast caused by reflection of ambient light from said layers, an improvement comprising a random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment two or more orders of magnitude smaller in volume than said phosphor particles associated with those target elements having phosphor layers emitting either red or blue light, said particles of pigment having a body color corresponding generally to the color of the light emitted by the associated phosphor layer located directly on said faceplate beneath said layer but not significantly admixed with said layer, the percentage of open area of said dispersion of pigment particles and the absorption characteristics thereof being such that said dispersion efficiently filters ambient light at its interface with said layer, first by absorption of directly incident ambient light, and second by absorption of ambient light passing through said open dispersion and scattering back off said phosphor particles to said dispersion, said dispersion representing a tolerable impediment to image light emitted by said phosphor particles due to the shallowness and openness of said dispersion and its non-absorption of light of the color emitted by the associated phosphor layer, said dispersion negligibly absorbing electron beam energy due to its location beneath said layer, making practicable deep filtration of ambient light and thus high picture contrast without a disproportionately countervailing loss in picture brightness.
- 6. In a low cost, deeply filtered television image display having a faceplate with a viewing screen including a patterned layer of phosphor particles disposed contiguous to an inner surface thereof which, when excited emits light of a predetermined color, and having means for exciting selected areas of said layer to produce a luminescent informational image, said image being subject to loss of contrast caused by reflection of ambient light from said layer, an improvement comprising a shallow, random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment two or more orders of magnitude smaller in volume than said phosphor particles, said particles of pigment having a body color corresponding generally to said predetermined color located directly on said faceplate beneath said layer and not significantly admixed with said phosphor particles, the percentage of open area of said dispersion of pigment particles and the absorption characteristics thereof being such that said dispersion efficiently filters ambient light at its interface with said layer, first by absorption of directly incident ambient light, and second by absorption of ambient light passing through said open dispersion and scattering back off said phosphor particles to said dispersion, said dispersion representing a tolerable impediment to image light emitted by said phosphor particles due to the shallowness and openness of said dispersion and its non-absorption of light of said predetermined color, said dispersion negligibly absorbing electron beam energy due to its location beneath said layer, making practicable deep filtration of ambient light and thus high picture contrast without a disproportionately countervailing loss in picture brightness, and wherein said reflection of ambient light is lowered to a deep-filtration range of 35% to 50% relative to the body color said phosphor taken as unity.
- 7. In a low cost, deeply filtered television image display having a faceplate with a viewing screen including a patterned layer of phosphor particles disposed contiguous to an inner surface thereof which, when excited emits light of a predetermined color, and having means for exciting selected areas of said layer to produce a luminescent informational image, said image being subject to loss of contrast caused by reflection of ambient light from said layer, an improvement comprising a shallow, random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment two or more orders of magnitude smaller in volume than said phosphor particles, said particles of pigment having a body color corresponding generally to said predetermined color located directly on said faceplate beneath said layer and not significantly admixed with said phosphor particles, the percentage of open area of said dispersion of pigment particles and the absortion characteristics thereof being such that said dispersion efficiently filters ambient light at its interface with said layer, first by absorption of directly incident ambient light, and second by absorption of ambient light passing through said open dispersion and scattering back off said phosphor particles to said dispersion, said dispersion representing a tolerable impediment to image light emitted by said phosphor particles due to the shallowness and openness of said dispersion and its non-absorption of light of said predetermined color, said dispersion negligibly absorbing electron beam energy due to its location beneath said layer, making practicable deep filtration of ambient light and thus high picture contrast without a disproportionately countervailing loss in picture brightness, and wherein said particles of pigment are selected from a group consisting of cadmium sulfoselenide, iron oxide, cobalt aluminate, cobalt silica zinc, and chromic oxide.
- 8. A low cost, deeply filtered image display for exhibiting a diatonal achromatic image, said display having a faceplate with a viewing screen including a layer of phosphor particles comprising pairs of spaced target elements disposed contiguous to the inner surface of said faceplate, each element of each pair being assigned one of two types of phosphors emitting, when excited, blue or yellow light, the combined emissions of said pairs producing said diatonal achromatic image, am improvement comprising a random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment two or more orders of magnitude smaller in volume than said phosphor particles, said particles of pigment having a body color corresponding generally to the light emitted by the associated phosphor, said particles of pigment being located directly on the faceplate beneath said layer of phosphor and not significantly admixed with said phosphor particles, the percentage of open area of said dispersion of pigment particles and the absorption characteristics thereof being such that said dispersion efficiently filters ambient light at its interface with said layers first by absorption of directly incident ambient light, and second by absorption of ambient light passing through said open dispersion and scattering back off said phosphor particles to said dispersion, said dispersion representing a tolerable impediment to image light emitted by said phosphor particles due to the shallowness and openness of said dispersion and its non-absorption of light of the respective associated phosphor particles, said dispersion negligibly absorbing electron beam energy due to its location beneath said layer, making practicable deep filtration of ambient light and thus high picture contrast without a disproportionately countervailing loss in picture brightness.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/011,961 US4392077A (en) | 1979-02-14 | 1979-02-14 | Deeply filtered television image display |
| US011,961 | 1979-02-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1125347A true CA1125347A (en) | 1982-06-08 |
Family
ID=21752711
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA338,741A Expired CA1125347A (en) | 1979-02-14 | 1979-10-30 | Deeply filtered television image display |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4392077A (en) |
| CA (1) | CA1125347A (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4954747A (en) * | 1988-11-17 | 1990-09-04 | Tuenge Richard T | Multi-colored thin-film electroluminescent display with filter |
| GB2240213A (en) * | 1990-01-23 | 1991-07-24 | British Broadcasting Corp | Colour display device |
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| JP3297929B2 (en) * | 1992-03-25 | 2002-07-02 | ソニー株式会社 | Method for forming fluorescent screen of cathode ray tube |
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| MY118433A (en) * | 1994-12-26 | 2004-11-30 | Toshiba Kk | Display screen, method of manufacturing the same, and cathode ray tube |
| DE69507874T2 (en) * | 1994-12-26 | 1999-07-29 | Toshiba Kawasaki Kk | Screen and method of making the same |
| JP3276105B2 (en) * | 1996-10-08 | 2002-04-22 | 松下電器産業株式会社 | Color picture tube |
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| US6025097A (en) * | 1997-02-28 | 2000-02-15 | Candescent Technologies Corporation | Method for creating a color filter layer on a field emission display screen structure |
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| US10365407B2 (en) * | 2014-09-25 | 2019-07-30 | Prysm, Inc. | Optically excited phosphor display screens having coloring filtering pigments embedded in phosphor mixtures |
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| GB426789A (en) | 1933-07-06 | 1935-04-05 | Siemens Reiniger Werke Ag | Improvements in and relating to fluorescent screens |
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| NL243662A (en) * | 1955-08-23 | |||
| US2959483A (en) * | 1955-09-06 | 1960-11-08 | Zenith Radio Corp | Color image reproducer and method of manufacture |
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| US3013114A (en) * | 1958-02-21 | 1961-12-12 | Warwick Mfg Corp | Display device with contrast improving optical filter |
| US3146368A (en) * | 1961-04-04 | 1964-08-25 | Rauland Corp | Cathode-ray tube with color dots spaced by light absorbing areas |
| US3454715A (en) * | 1964-01-16 | 1969-07-08 | Rca Corp | Luminescent image device and combinations thereof with optical filters |
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| US3812394A (en) * | 1971-10-06 | 1974-05-21 | Zenith Radio Corp | Image screen with single,optically continuous filter |
| US3886394A (en) * | 1973-09-04 | 1975-05-27 | Rca Corp | Image display employing filter coated phosphor particles |
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| US4132919A (en) * | 1977-12-12 | 1979-01-02 | Lockheed Missiles & Space Company, Inc. | Absorbing inhomogeneous film for high contrast display devices |
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-
1979
- 1979-02-14 US US06/011,961 patent/US4392077A/en not_active Expired - Lifetime
- 1979-10-30 CA CA338,741A patent/CA1125347A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4392077A (en) | 1983-07-05 |
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