CA1262651A - Photosensitive microcapsules useful in polychromatic imaging - Google Patents
Photosensitive microcapsules useful in polychromatic imagingInfo
- Publication number
- CA1262651A CA1262651A CA000477634A CA477634A CA1262651A CA 1262651 A CA1262651 A CA 1262651A CA 000477634 A CA000477634 A CA 000477634A CA 477634 A CA477634 A CA 477634A CA 1262651 A CA1262651 A CA 1262651A
- Authority
- CA
- Canada
- Prior art keywords
- microcapsules
- photosensitive
- absorber
- composition
- color former
- 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
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
- G03C1/00—Photosensitive materials
- G03C1/76—Photosensitive materials characterised by the base or auxiliary layers
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/002—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor using materials containing microcapsules; Preparing or processing such materials, e.g. by pressure; Devices or apparatus specially designed therefor
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
- Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
- Y10S430/1055—Radiation sensitive composition or product or process of making
- Y10S430/127—Spectral sensitizer containing
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
- Y10T428/2984—Microcapsule with fluid core [includes liposome]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
- Y10T428/2984—Microcapsule with fluid core [includes liposome]
- Y10T428/2985—Solid-walled microcapsule from synthetic polymer
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
- Y10T428/2989—Microcapsule with solid core [includes liposome]
Abstract
PHOTOSENSITIVE MICROCAPSULES USEFUL IN
POLYCHROMATIC IMAGING
Abstract Photosensitive microcapsules having radiation absorbers associated therewith such that the sensitivity of the microcapsules is reduced over a portion of their spectral sensitivity range; the spectral sensitivity of the microcapsules is thereby adjusted such that three sets of microcapsules having distinctly different spectral sensitivities and individually containing color formers for full color imaging can be provided on a single support surface and discriminately exposed in a manner which corresponds to the red, green and blue components of an original.
POLYCHROMATIC IMAGING
Abstract Photosensitive microcapsules having radiation absorbers associated therewith such that the sensitivity of the microcapsules is reduced over a portion of their spectral sensitivity range; the spectral sensitivity of the microcapsules is thereby adjusted such that three sets of microcapsules having distinctly different spectral sensitivities and individually containing color formers for full color imaging can be provided on a single support surface and discriminately exposed in a manner which corresponds to the red, green and blue components of an original.
Description
~ '3~
PHOTOSEN5ITIV~ MICROCAPSULES ~SEFUL IN
POLYCHROMATIC IMAGING
Back~round of the Invention The present invention relates to photosensitive microcapsules which are usef~l in forming polvchromatic or full color images using the imaging processes described in U.S. Patents 4,399,209 and 4,440,846 to The Mead Corporation. More particularly, the present invention relates to photosensitive microcapsules containing a Photosensitive composition in ~hich a radiation absorber is associated ~ith the microcapsules. The radiation absorber reduces the sensitivity of the microcapsules at certain wavelengths such that a set of microcapsules containing the color formers necessary for full color imaging can be designed in ~hich the microcapsules have sufficiently distinct spectral sensitivities that they can be discriminately hardened using exposures at distinctly different ~di~ion ~vele~gths.
Unit~d Kingdom Patent No. 2ll3860B; issued November 27, 19~5 to The Mead Corporation/ describes a photosensitive material useful in full color imaging comprising a support having on the surface thereof microcapsules ~hich individually contain cyan, magenta and yellow color formers and photosensitive compositions having distinctly different sensitivities. A uniform mixture of the microcapsules is distributed over the surface of the support. Images are formed by seParating the red, green and blue components of the image to be reProduced and translat7ng these components into different ~avelengths of actinic radiation to which the photosensitive compositions are distinctly sensitive. The A
.
i5~
photosensitive material is image-wise ex~osed to ~he translated radiation and thereafter i~ is subjected to a uniform rupturing force, such as pressure, which ca~ses the microcapsules in the underexposed and unexposed areas to ru~ture and release the color formers. The color formers then react with a developer material which is contained on the same or a different suPport and produce a full color image.
The spectral sensitivity of Photosensitive mic;ocapsules is ~rincipally a function of the photoinitiator used in the encapsulated photosensitive composition. In order to design photosensitive microcapsules useful in full color imaging having distinctly different spectral sensitivities, photoinitiators must be designed or selected which have mutua]ly exclusive sensitivities in at least three distinct wavelength regions. That is, the photoinitiator used in microcapsules containing a cyan color former must be substantially more sensitive in a ~avelength region in ~7hich the photoinitiators used in the microcapsu~es associated with the magenta and yello~7 color formers are substantially less sensitive or insensitive. Likewise, the photoinitiator used in the microcapsules containing the cyan color former must be substantially less sensitive and ideally insensitive in a wavelength region in which the photoinitiators used in the microcapsules containing the magenta and yellow color formers are preferentially sensitive. The same considerations govern the selection of the initiators associated with the microcapsules 3~ containing the yello~7 and magenta color formers.
~ MDX 017 P2 - 3 -The selection and/or design of microca~sules having mutually exclusive sensitivity characteristics as described above is simp]ified by associating a radiation absorber with the microcapsules in accordance ~7ith the ~resent invention.
, Summa7y of the Invention Tn accordance with the present invention, photosensitive microcapsules having sufficiently different spectral sensitivities to be useful in fu]l color imaging are obtained by associating a radiation absorber with the microcapsules such that the sensitivity of the microcapsules is reduced over a portion of their spectral sensitivity ranqe.
In accordance with the present invention, microcapsules useful in forming polychromatic images are obtained by coordinating the selection of the t photoinitiators used in the photosensitive compositions with the selection of the absorber such that the absorber "shields" the microcapsules from exposures intended for other microcapsules in the polychromatic system. For example, an absorber is selected for use with the cyan forming microcapsules which 7~revents those microcapsules from being e~7~osed by exposures within the sensitivity range of the magenta forming capsules. In this manner, the spectral sensitivity of the microcapsules can be more narrowly defined, there is greater exposure latitude and there is greater latitude in the selection of the other photoinitiators used in the system.
Accordingly, one embodiment of the present invention resides in a ~hotosensitive microcapsule ;tj~L
MDX 017 P2 - ~ -containin~ a photosensitive composition ~hich hardens upon exposure to actinic radiation, ~herein a radiation absorber is associated with the microcapsule such that the sensitivity of the microcapsule is reduced over a portion of its spectral sensitivity range. The absorber can be present in the Photosensitive composition itself, in the ~rall of a microcapsule having a discrete wall, in the binder forming the continuous phase of an open phase microcapsule, or in a binder in which microcapsules having discrete ~alls are dispersed. Preferab~y, the absorber is ~resent in the photosensitive composition or in the capsule wall.
Another embodiment of the present invention resides in a photosensitive material com~rising a suP~ort having a layer containing the aforementioned microcapsules on the surface thereof.
Another embodiment of the present invention resiæes in a photosensitive material useful in full co~or imaging which comprises a support having on the surface thereof microca~sules containing a cyan color former and a first photohardenable composition, microcapsules containing a magenta color former and a second photohardenable composition, and microcapsules containing a yel~ OW color former and a third photohardenable composition, at least one of the aforesaid microcapsules having associated therewith an absorber which reduces the sensitivity of the photohardenable composition encapsulated therein over a portion of its s~ectral sensitivity range such that the microcapsules have sufficient~y different sensitivity characteristics that the first photohardenable composition can be hardened upon s~
~1DX 0]7 P2 - 5 -exposure of the microcapsule to actinic radiation of a first wavelength without substantially hardening the encapsulated second and third photohardenable com~ositions, the second ~hotohardenable comPosition can be hardened upon exposure of the microcapsu]e to actinic radiation of a second wavelength without substantially hardening the encapsulated first and third photohardenable compositions, and the third photohardenab]e com~osition ~` can be hardened upon exposure of the microcapsule to actinic radiation of a third wavelength without substantially hardening the encapsulated first and second photohardenab]e compositions.
Definitions The term "microcapsule" as used herein includes ~; both microcapsules having a discrete capsule wall and so-cal]ed open phase microcaPsules formed by dispersing a solution of the photosensitive composition and the color former in an appropriate binder.
2Q The term "spectral sensitivity range" as used herein refers to the spectral regions in which a photosensitive composition or microcapsule responds to radiation.
The term "harden" as used herein means to increase the viscosity or hardness of the internal phase and is not limited strictly to solidification.
Brief Description of the Drawings The present invention will be explained in more detail by reference to the accom~anying drawings wherein:
5~
Fig. 1 i5 a gra~h of the sPectral sensitivity curves for a set of microcapsules useful in full color imaging.
Fig. 2 is a graph of the spectral sensitivity curves of the microca~sules described in Exam~le 4.
Fig. 3 is a graph of the spectral sensitivity of a microcapsule containing an absorber compound and the same microcapsule without the absorber (Example 2).
Fig. 4 is a graph similar to Fig. 3 for a microcapsule containing a different photoinitiator (Exam~le 3).
Fig. 5 is a graph of the spectral sensitivity curves of the microcapsules prepared in ~xample 5.
Detailed Description of the Invention Figure 1 contains the spectral sensitivity curves for a set of three microcapsules (A, B, and C) the spectral sensitivities of which are o~timally suited for use in full color imaging. Capsule A is sensitive in a first range, Ca~sule B is sensitive in a second range, and Capsule C is sensitive in a third range and none of Capsules A, B and C are substantial]y sensitive in the ranges in which the other capsules are sensitive. Because there is often significant overlap in the spectral sensitivities of ini~iators, it is difficult to achieve the relationship sho~n in Fig. 1.
Fig. 2 is a plot of the spectral sensitivity curves for the microcaPsules A', B', and C' of Example 4 below. As can be seen from Fig. 2, the spectral sensitivities of the microcapsules are not perfectly exclusive, but there are ~istinct ~avelen~th bands in ~hich each group of capsules can be exposed without substantially exposing the others. The .spectral sensitivity curve of Capsule B' overlaps with that of CaPsule A', ho~ever, by exDosing Capsule A' ~ith UV
radiation in the range of 340-360 nm and limiting the intensity, Capsule A' can be exposed ~ithout substantia]]y exposing Capsule B'. Similarly, although the spectral sensitivity of Capsule A' overlaps that of Capsule B', by exposing at 390-400 nm and limiting intensity, Capsule B' can be ex~osed ~ithout substantially exposing Capsule A' or C'. The exposure of Capsule C' can be carried out with much more latitude since at longer wavelengths its spectral sensitivity curve does not substantially overlap the others. Accordingly, microcapsules useful in forming full color images can be obtained by individually incorporating cyan, magenta and yel]ow color formers in the microcapsules of Fig. 2.
The present invention is useful in tailoring the sensitivities of microcapsules throughout the electromagnetic spectrum, but it is particularly useful in narrowing the sensitivity of microcapsu]es to ultraviolet radiation.
The function of the absorber in tailoring the sensitivity of microcapsules is illustrated in Fig. 3 wherein the spectral sensitivity curve (Curve B-l) corresponds to Curve B' in Fig. 2 and is shown in comparison to the spectral sensitivity curve for the same microcapsule without the ultraviolet absorber present (Curve B-2). The photosensitive composition encapsulated .,7 ~
in these microcapsules contains 2-isopropylthioxanthone and ethyl-4-dimethvlaminobenzoate as initiators. As can be seen from Curve B-2, this photoinitiator systern i5 quite sensitive at 350 nm as ~ell as at 390 nm. The present invention addresses the problem of decreasing the ; sensitivity of the system at 350 nm where photosensitivity is not desired.
It can be seen from a comparison of Curves s-l and s-2 that the UV absorber reduces the sensitivity of lQ the microcapsules in the range of 340-360 nm. In this manner, the absorber provides greater latitude in the exposure that may be used to expose Capsule A' in Fig. 2.
As Curve B-l demonstrates, without the UV absorber, Capsule B' would be much more sensitive in the range of 340-360 nm, making it more difficult to select an ex7~osure wavelength for Capsule A' and limit the intensity so as to ~; expose Capsule A' without exPosing Capsule B'.
The effect of the absorber is further illustrated in Fig. 4 for Ca~sule C' where Curve C-l is the spectral sensitivity Curve in Fig. 2 and Curve C-2 is the sensitivity curve for the same microcapsule without the UV
absorber. The initiator used in these microcapsules, 7-diethylamino-3-cinnamoylcoumarin (U.S. Patent 4,147,552) and ethyl-4-dimethylaminobenzoate, is highly sensitive at 470 nm and also imparts significant sensitivity at shorter wavelengths. By narrowing the sensitivity of Capsule C', Capsule B' can be exposed at higher wavelengths with less likelihood of exposing Capsule A'.
Hereinbelow, the considerations which govern the sele-tion of the absorber are summarized.
, , ', s~
An absorber should be selected which reduces the sensitivity of the microcapsule in those portions of its spectral sensitivi~y range which interfere with the exposure of microcapsules at other wavelengths (its inactive range) without overly reducing the sensitivity of the microcapsule in those portions of the spectral sensitivity range in which the microcapsule is intended to be exposed (its active range). In some cases it may be necessary to balance the absorption characteristics of the absorber in the active range and the inactive range to achieve optimum exposure charac~eristics. Generally absorbers having an extinction coefficient greater than about 100/M c~ in the inactive range and less than about 100,000/M cm in the active range of the microcapsule are preferred. ~hen the absorber is directly incorporated into the ~hotosensitive composition, ideally, it should not inhibit free radical polymerization, and it should not generate free radicals upon exposure.
The absorbers used in the present invention can be selected from among those absorbers which are known in the photographic art. Examples of such compounds include dyes conventionally used as silver halide sensitizing dyes in color photography (e.g., cyanine, merocyanine, hemicyanine and styryl dyes) and ultraviolet absorbers. A
number of colored dyes which absorb outside the desired sensitivity ranqe of the microcapsules and do not absorb heavily within the range could also be used as absorbers in the present invention. Among these, Sudan I, Sudan II, Sudan III, Sudan Orange G, Oil Red O, Oil Blue N, and Fast Garnet GBC are exam~les of potentially useful compounds.
t Ultraviolet absorbers ~hat are useful in the present invention are selected from hydroxybenzophenones, hydroxyDhenylbenzo-triazoles and formamidines. The absorbers may be used alone or in combination to achieve S the spectral sensitivity characteristics that a~e desired.
Representative examples of useful hydroxybenzophenones are 2-hydroxy-4-n-octoxybenzophenone (UV-CHEK AM-300 from Ferro Chemical Division, Mark 1413*
from Argus Chemical Division, Witco Chem. Corp., and 10 Cyasorb*UV-531 Light Absorber from American Cyanamid), 4-dodecyl-2-hydroxybenzophenone (Eastman Inhibitor D~BP
from Eastman Kodak), 2-hydroxy-4-methoxybenzophenone (Cyasorb UV-9 Liqht Absorber from American Cyanamid), and
PHOTOSEN5ITIV~ MICROCAPSULES ~SEFUL IN
POLYCHROMATIC IMAGING
Back~round of the Invention The present invention relates to photosensitive microcapsules which are usef~l in forming polvchromatic or full color images using the imaging processes described in U.S. Patents 4,399,209 and 4,440,846 to The Mead Corporation. More particularly, the present invention relates to photosensitive microcapsules containing a Photosensitive composition in ~hich a radiation absorber is associated ~ith the microcapsules. The radiation absorber reduces the sensitivity of the microcapsules at certain wavelengths such that a set of microcapsules containing the color formers necessary for full color imaging can be designed in ~hich the microcapsules have sufficiently distinct spectral sensitivities that they can be discriminately hardened using exposures at distinctly different ~di~ion ~vele~gths.
Unit~d Kingdom Patent No. 2ll3860B; issued November 27, 19~5 to The Mead Corporation/ describes a photosensitive material useful in full color imaging comprising a support having on the surface thereof microcapsules ~hich individually contain cyan, magenta and yellow color formers and photosensitive compositions having distinctly different sensitivities. A uniform mixture of the microcapsules is distributed over the surface of the support. Images are formed by seParating the red, green and blue components of the image to be reProduced and translat7ng these components into different ~avelengths of actinic radiation to which the photosensitive compositions are distinctly sensitive. The A
.
i5~
photosensitive material is image-wise ex~osed to ~he translated radiation and thereafter i~ is subjected to a uniform rupturing force, such as pressure, which ca~ses the microcapsules in the underexposed and unexposed areas to ru~ture and release the color formers. The color formers then react with a developer material which is contained on the same or a different suPport and produce a full color image.
The spectral sensitivity of Photosensitive mic;ocapsules is ~rincipally a function of the photoinitiator used in the encapsulated photosensitive composition. In order to design photosensitive microcapsules useful in full color imaging having distinctly different spectral sensitivities, photoinitiators must be designed or selected which have mutua]ly exclusive sensitivities in at least three distinct wavelength regions. That is, the photoinitiator used in microcapsules containing a cyan color former must be substantially more sensitive in a ~avelength region in ~7hich the photoinitiators used in the microcapsu~es associated with the magenta and yello~7 color formers are substantially less sensitive or insensitive. Likewise, the photoinitiator used in the microcapsules containing the cyan color former must be substantially less sensitive and ideally insensitive in a wavelength region in which the photoinitiators used in the microcapsules containing the magenta and yellow color formers are preferentially sensitive. The same considerations govern the selection of the initiators associated with the microcapsules 3~ containing the yello~7 and magenta color formers.
~ MDX 017 P2 - 3 -The selection and/or design of microca~sules having mutually exclusive sensitivity characteristics as described above is simp]ified by associating a radiation absorber with the microcapsules in accordance ~7ith the ~resent invention.
, Summa7y of the Invention Tn accordance with the present invention, photosensitive microcapsules having sufficiently different spectral sensitivities to be useful in fu]l color imaging are obtained by associating a radiation absorber with the microcapsules such that the sensitivity of the microcapsules is reduced over a portion of their spectral sensitivity ranqe.
In accordance with the present invention, microcapsules useful in forming polychromatic images are obtained by coordinating the selection of the t photoinitiators used in the photosensitive compositions with the selection of the absorber such that the absorber "shields" the microcapsules from exposures intended for other microcapsules in the polychromatic system. For example, an absorber is selected for use with the cyan forming microcapsules which 7~revents those microcapsules from being e~7~osed by exposures within the sensitivity range of the magenta forming capsules. In this manner, the spectral sensitivity of the microcapsules can be more narrowly defined, there is greater exposure latitude and there is greater latitude in the selection of the other photoinitiators used in the system.
Accordingly, one embodiment of the present invention resides in a ~hotosensitive microcapsule ;tj~L
MDX 017 P2 - ~ -containin~ a photosensitive composition ~hich hardens upon exposure to actinic radiation, ~herein a radiation absorber is associated with the microcapsule such that the sensitivity of the microcapsule is reduced over a portion of its spectral sensitivity range. The absorber can be present in the Photosensitive composition itself, in the ~rall of a microcapsule having a discrete wall, in the binder forming the continuous phase of an open phase microcapsule, or in a binder in which microcapsules having discrete ~alls are dispersed. Preferab~y, the absorber is ~resent in the photosensitive composition or in the capsule wall.
Another embodiment of the present invention resides in a photosensitive material com~rising a suP~ort having a layer containing the aforementioned microcapsules on the surface thereof.
Another embodiment of the present invention resiæes in a photosensitive material useful in full co~or imaging which comprises a support having on the surface thereof microca~sules containing a cyan color former and a first photohardenable composition, microcapsules containing a magenta color former and a second photohardenable composition, and microcapsules containing a yel~ OW color former and a third photohardenable composition, at least one of the aforesaid microcapsules having associated therewith an absorber which reduces the sensitivity of the photohardenable composition encapsulated therein over a portion of its s~ectral sensitivity range such that the microcapsules have sufficient~y different sensitivity characteristics that the first photohardenable composition can be hardened upon s~
~1DX 0]7 P2 - 5 -exposure of the microcapsule to actinic radiation of a first wavelength without substantially hardening the encapsulated second and third photohardenable com~ositions, the second ~hotohardenable comPosition can be hardened upon exposure of the microcapsu]e to actinic radiation of a second wavelength without substantially hardening the encapsulated first and third photohardenable compositions, and the third photohardenab]e com~osition ~` can be hardened upon exposure of the microcapsule to actinic radiation of a third wavelength without substantially hardening the encapsulated first and second photohardenab]e compositions.
Definitions The term "microcapsule" as used herein includes ~; both microcapsules having a discrete capsule wall and so-cal]ed open phase microcaPsules formed by dispersing a solution of the photosensitive composition and the color former in an appropriate binder.
2Q The term "spectral sensitivity range" as used herein refers to the spectral regions in which a photosensitive composition or microcapsule responds to radiation.
The term "harden" as used herein means to increase the viscosity or hardness of the internal phase and is not limited strictly to solidification.
Brief Description of the Drawings The present invention will be explained in more detail by reference to the accom~anying drawings wherein:
5~
Fig. 1 i5 a gra~h of the sPectral sensitivity curves for a set of microcapsules useful in full color imaging.
Fig. 2 is a graph of the spectral sensitivity curves of the microca~sules described in Exam~le 4.
Fig. 3 is a graph of the spectral sensitivity of a microcapsule containing an absorber compound and the same microcapsule without the absorber (Example 2).
Fig. 4 is a graph similar to Fig. 3 for a microcapsule containing a different photoinitiator (Exam~le 3).
Fig. 5 is a graph of the spectral sensitivity curves of the microcapsules prepared in ~xample 5.
Detailed Description of the Invention Figure 1 contains the spectral sensitivity curves for a set of three microcapsules (A, B, and C) the spectral sensitivities of which are o~timally suited for use in full color imaging. Capsule A is sensitive in a first range, Ca~sule B is sensitive in a second range, and Capsule C is sensitive in a third range and none of Capsules A, B and C are substantial]y sensitive in the ranges in which the other capsules are sensitive. Because there is often significant overlap in the spectral sensitivities of ini~iators, it is difficult to achieve the relationship sho~n in Fig. 1.
Fig. 2 is a plot of the spectral sensitivity curves for the microcaPsules A', B', and C' of Example 4 below. As can be seen from Fig. 2, the spectral sensitivities of the microcapsules are not perfectly exclusive, but there are ~istinct ~avelen~th bands in ~hich each group of capsules can be exposed without substantially exposing the others. The .spectral sensitivity curve of Capsule B' overlaps with that of CaPsule A', ho~ever, by exDosing Capsule A' ~ith UV
radiation in the range of 340-360 nm and limiting the intensity, Capsule A' can be exposed ~ithout substantia]]y exposing Capsule B'. Similarly, although the spectral sensitivity of Capsule A' overlaps that of Capsule B', by exposing at 390-400 nm and limiting intensity, Capsule B' can be ex~osed ~ithout substantially exposing Capsule A' or C'. The exposure of Capsule C' can be carried out with much more latitude since at longer wavelengths its spectral sensitivity curve does not substantially overlap the others. Accordingly, microcapsules useful in forming full color images can be obtained by individually incorporating cyan, magenta and yel]ow color formers in the microcapsules of Fig. 2.
The present invention is useful in tailoring the sensitivities of microcapsules throughout the electromagnetic spectrum, but it is particularly useful in narrowing the sensitivity of microcapsu]es to ultraviolet radiation.
The function of the absorber in tailoring the sensitivity of microcapsules is illustrated in Fig. 3 wherein the spectral sensitivity curve (Curve B-l) corresponds to Curve B' in Fig. 2 and is shown in comparison to the spectral sensitivity curve for the same microcapsule without the ultraviolet absorber present (Curve B-2). The photosensitive composition encapsulated .,7 ~
in these microcapsules contains 2-isopropylthioxanthone and ethyl-4-dimethvlaminobenzoate as initiators. As can be seen from Curve B-2, this photoinitiator systern i5 quite sensitive at 350 nm as ~ell as at 390 nm. The present invention addresses the problem of decreasing the ; sensitivity of the system at 350 nm where photosensitivity is not desired.
It can be seen from a comparison of Curves s-l and s-2 that the UV absorber reduces the sensitivity of lQ the microcapsules in the range of 340-360 nm. In this manner, the absorber provides greater latitude in the exposure that may be used to expose Capsule A' in Fig. 2.
As Curve B-l demonstrates, without the UV absorber, Capsule B' would be much more sensitive in the range of 340-360 nm, making it more difficult to select an ex7~osure wavelength for Capsule A' and limit the intensity so as to ~; expose Capsule A' without exPosing Capsule B'.
The effect of the absorber is further illustrated in Fig. 4 for Ca~sule C' where Curve C-l is the spectral sensitivity Curve in Fig. 2 and Curve C-2 is the sensitivity curve for the same microcapsule without the UV
absorber. The initiator used in these microcapsules, 7-diethylamino-3-cinnamoylcoumarin (U.S. Patent 4,147,552) and ethyl-4-dimethylaminobenzoate, is highly sensitive at 470 nm and also imparts significant sensitivity at shorter wavelengths. By narrowing the sensitivity of Capsule C', Capsule B' can be exposed at higher wavelengths with less likelihood of exposing Capsule A'.
Hereinbelow, the considerations which govern the sele-tion of the absorber are summarized.
, , ', s~
An absorber should be selected which reduces the sensitivity of the microcapsule in those portions of its spectral sensitivi~y range which interfere with the exposure of microcapsules at other wavelengths (its inactive range) without overly reducing the sensitivity of the microcapsule in those portions of the spectral sensitivity range in which the microcapsule is intended to be exposed (its active range). In some cases it may be necessary to balance the absorption characteristics of the absorber in the active range and the inactive range to achieve optimum exposure charac~eristics. Generally absorbers having an extinction coefficient greater than about 100/M c~ in the inactive range and less than about 100,000/M cm in the active range of the microcapsule are preferred. ~hen the absorber is directly incorporated into the ~hotosensitive composition, ideally, it should not inhibit free radical polymerization, and it should not generate free radicals upon exposure.
The absorbers used in the present invention can be selected from among those absorbers which are known in the photographic art. Examples of such compounds include dyes conventionally used as silver halide sensitizing dyes in color photography (e.g., cyanine, merocyanine, hemicyanine and styryl dyes) and ultraviolet absorbers. A
number of colored dyes which absorb outside the desired sensitivity ranqe of the microcapsules and do not absorb heavily within the range could also be used as absorbers in the present invention. Among these, Sudan I, Sudan II, Sudan III, Sudan Orange G, Oil Red O, Oil Blue N, and Fast Garnet GBC are exam~les of potentially useful compounds.
t Ultraviolet absorbers ~hat are useful in the present invention are selected from hydroxybenzophenones, hydroxyDhenylbenzo-triazoles and formamidines. The absorbers may be used alone or in combination to achieve S the spectral sensitivity characteristics that a~e desired.
Representative examples of useful hydroxybenzophenones are 2-hydroxy-4-n-octoxybenzophenone (UV-CHEK AM-300 from Ferro Chemical Division, Mark 1413*
from Argus Chemical Division, Witco Chem. Corp., and 10 Cyasorb*UV-531 Light Absorber from American Cyanamid), 4-dodecyl-2-hydroxybenzophenone (Eastman Inhibitor D~BP
from Eastman Kodak), 2-hydroxy-4-methoxybenzophenone (Cyasorb UV-9 Liqht Absorber from American Cyanamid), and
2~2l-dihydroxy-4-methoxybenzophenone (Cyasorb W-24 Light 15 Absorber from American Cyanamid). Representative examples of useful hydroxybenzophenyl benzotriazoles are 2-(2'-hvdroxy-5'-methylphenyl) benzotriazole (Tinuvin*P
from Ciba-Geigy Additives Dept.), 2-t3',5'-ditert-butyl-2' hydroxyphenyl)-5-chlorobenzotriazole (Tinuvin 327 from 2U Ciba-Geigy), and 2-(2-hydroxy-5-t-octylphenyl) benzotriazole (Cyasorb UV-5411 Light Absorber from American Cyanamid). Representative examples of useful formamidines are described in U.S. 4,021,471 and include N-(p-ethoxy-carbonylphenyl)-N'-ethyl-N'-phenylformamidine 25 (Givsorb*UV-2 from Givaudan Corp.). The optimum absorber and concentration of absorber for a particular application depends on both the absorption maximum and extinction coefficient of the absorber candidates and the spectral sensitivity characteristics of the associated 30 photoinitiators.
* trade marks ,4" ~
~'ith the exception of the incorPoration of an ultraviolet absorber, the microcapsules, photosensitive ~., compositions, image-forming agents, developers, and development techniques described in U.5. Patents 4,39g,209 and 4,440,846 can be used in the present invention.
The mechanism by which irnages are formed using encapsulated photosensitive compositions is described in U.S. Patents 4,399,209 and 4,4~0,846. Summari~ing, exposure Produces an increase in the viscosity of the internal phase in the microcapsules which controls the amount of color former which is released ~rom the ca~sules and is reacted ~ith the developer. This increase in viscosity prevents a fully exPosed capsule from rupturing and releasing the internal phase. The imaging mechanism is unclear in that the fully exposed capsule either does not rupture or it ruptures but does not release the internal phase. In the unexposed and underexposed areas, the capsules rupture and release the internal phase and the amount of the internal phase released is a function of the degree of exposure. Tonal characteristics can be achie~7ed when desired. Again, the imaging mechanism is not clear. All the capsules may rupture or because the size of the ca~sules varies the number of capsules which rupture may be a function of the degree o~ exposure.
; 25 In addition to pressure, the ca~sules can be ruptured by other means including by peeling development, thermal development, so~vent vapor, ultrasonic energy or ` the like. A gas generating agent can be incorporated in ; the capsules so that they can be ru~tured by heating.
Known photohardenable compositions can be used in the present invention. The compositions which are most , . , useful are those which are curab~e by free radical initiated, addition polymerization or crosslinking. The most common examples of such compositions are cornpositions ~hich contain an ethylenically unsaturated compound, e.g., a com~ound containing terminal or pendant vinyl or allvlic groups. Such compounds are well known in the art and include acrylic and methacrylic esters of po]yhydric alcohols such as trimethylolpropane, pentaerythritol, and the like. Representative examples include ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate (TMPTA), pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, hexanediol-1,6-dimethacrylate, and diethyleneglycol dimethacrylate.
Photoinitiators are selected based on their spectral sensitivities such that there is minimum overlap in their spectral sensitivities and the microcapsules have adequate sensitivity in their respective active ranges.
As a general rule, the photosensitive composition containing the photoinitiator should provide a microcapsule having a sensitivity (E) less than lO,000 ergs/cm in the desired exposure range. The term "sensitivity" corresponds to the amount of incident radiation required to produce a first loss in density of 0.10 density units. The photosensitive microcapsules of the present invention are by nature positive working.
Consequently, when unexposed the microcapsules rupture and activate the color former which reacts with the developer to produce a maximum image density. Thus, the term "sensitivity" represents the minimum exposure necessary to effect a substantive reduction (0.10 density units) in that maximum density.
~seful initiators include photoinitiators which generate free radicals upon photochemical cleavage (homolytic initiators) such as certain benzoin ethers and initiators which function via hydrogen abstraction.
Preferred initiators are soluble in the radiation sensitive composition. Xanthones, thioxanthones, polycyclic quinones, acetophenones, 3 substituted coumarins, diaryl ketones, diaryl diketones, and benzoin alkyl ethers are particularly useful. Specific examples of useful initiators are benzophenone, Michler's ketone, benzoin methyl ether, 2,2-dimethoxy-2-phenyl-acetophenone9 isopropylthioxanthone, ethyl para-dimethylaminobenzoate, 3-cinnamoyl-7-diethylamino coumarins, etc~
To provide a color system which is visible light-sensitivel a potentially useful red initiator is N,N,N',N'-tetra-n-butylthionine; a potentially useful green initiator is N,N,N',N'-tetramethyl-4'-dodecylsafranine, and a potential blue initiator is phenanthraquinone.
Another initiator system useful in a red or green light-sensitive microcapsule is described in U~S. Patent Nol 3,495,987.
The photoinitiator is present in the photosensitive composition in an amount sufficient to initiate polymerization or crosslinking within a suitable exposure time. For example, benzoin methyl ether is typically present in an amount up to about 10% by weight based on the weight of the photocrosslinkable or photopolymerizable species. The exact amount of photoinitiator used will vary with the nature of the photosensitive composition.
M~X 017 P2 In accordance with one embodiment of the present invention, the radiation sensitive composition may additionally include a polythiol to increase the film speed of the microcapsules.
Useful polythiols include ethylene glycol bis (thioglycolate), ethylene g1ycol bis (~-mercapto-propionate)~ trimethylolpropane tris (thioglycolate), pentaerythritol tetrakis (thioglycolate) and the most preferred pentaerythritol tetrakis (~-mercapto-propionate) and trimethylolpropane tris (~-mercapto-propionate), and mixtures thereof. These compounds are commercially available. Certain polymeric polythiols such as polypropylene ether glycol bis (~-mercaptopropionate~
which is prepared by esterification of polypropylene ether glycol may also be useful.
Various oligomers or polymers can also he used in the present invention to improve the film speed of the microcapsules. These materials increase the rate with which the viscosity of the internal Phase of the microcapsules builds to a level at which differential release of the internal phase is achieved. These materials must be soluble in the photosensitive composition and not interfere with the photopolymerization reaction. Reactive oligomers contain terminal or pendant ethylenic unsaturation and include urethane, ester and epoxy based reactive acrylate, methacrylate, vinyl and allyl prepolymers. Useful non-reactive oligomers or polymers are solid or viscous liquids at room temperature but solub e in the unreacted photosensitive composition.
Representative examples of some commercially available oligomers or polymers which are use~ul in the present invention include reactive materials such as diallyl o-phthalate prepolymer tPolysciences), U Vithane 893 ~Morton Thiokol, Inc.), ~bercryl* 270 (Virginia Chemicals) and non-reactive materils such as ethyl cellulose, or Lucite*
The color former may be associated with the microcapsules in various ~ays such that uPon rupturing the microcapsule and releasing of the internal phase, the color former is able to react and/or migra~e to ~he developer and produce an image. For example, the color former may be encapsulated hith the photosensitive composition or incorporated in the wall of a microcapsule having a discrete wall. In the latter case, the photosensitive composition released from the capsules dissolves the color former and transports it to the developer.
One example of a useful color former in the invention is a colorless electron donating compound.
Representative examples of such color formers include substantially colorless compounds having in their partial skeleton a lactone, a lactam, a sultone, a spiropyran, an ester or an amido structure such as triarylmethane compounds, bisphenylmethane compounds, xanthene compounds, fluorans, thiazine compounds, spiropyran compounds and the like.
Cyan, magenta and yellow color precursors useful in the Presen~ invention can be selected from commercially available materials. Reakt Yellow (186) (a product of BASF), Copikem XI and Copikem*XIV (products of Hilton-Davis Chemical Co.) are useEul yellow color formers; Cyan S-29663 (an experimental compound from * trade marks s~
Hilton Davis), Co~ikem X (a product of ~ilton-Davis) and color formers described in U.S. Patent No. 4,32Z,352 are useful cyan color formers and Copikem XX (a product of Hilton Davis) and Pergascript*Red (Ciba-Geigy) are useful as magenta color formers. Other examples of useful color formers are s own below:
..
* trade mark A
.
MDX 017 P2 - ] 7 -Ye l l o~
~OCH2CH3 ~?
H 3 CO ~ _OCH 3 Cyan color precursors:
(CH3)2N~5~N(CH3)2 ~0 '3 MDX 017 P2 - lfl -
from Ciba-Geigy Additives Dept.), 2-t3',5'-ditert-butyl-2' hydroxyphenyl)-5-chlorobenzotriazole (Tinuvin 327 from 2U Ciba-Geigy), and 2-(2-hydroxy-5-t-octylphenyl) benzotriazole (Cyasorb UV-5411 Light Absorber from American Cyanamid). Representative examples of useful formamidines are described in U.S. 4,021,471 and include N-(p-ethoxy-carbonylphenyl)-N'-ethyl-N'-phenylformamidine 25 (Givsorb*UV-2 from Givaudan Corp.). The optimum absorber and concentration of absorber for a particular application depends on both the absorption maximum and extinction coefficient of the absorber candidates and the spectral sensitivity characteristics of the associated 30 photoinitiators.
* trade marks ,4" ~
~'ith the exception of the incorPoration of an ultraviolet absorber, the microcapsules, photosensitive ~., compositions, image-forming agents, developers, and development techniques described in U.5. Patents 4,39g,209 and 4,440,846 can be used in the present invention.
The mechanism by which irnages are formed using encapsulated photosensitive compositions is described in U.S. Patents 4,399,209 and 4,4~0,846. Summari~ing, exposure Produces an increase in the viscosity of the internal phase in the microcapsules which controls the amount of color former which is released ~rom the ca~sules and is reacted ~ith the developer. This increase in viscosity prevents a fully exPosed capsule from rupturing and releasing the internal phase. The imaging mechanism is unclear in that the fully exposed capsule either does not rupture or it ruptures but does not release the internal phase. In the unexposed and underexposed areas, the capsules rupture and release the internal phase and the amount of the internal phase released is a function of the degree of exposure. Tonal characteristics can be achie~7ed when desired. Again, the imaging mechanism is not clear. All the capsules may rupture or because the size of the ca~sules varies the number of capsules which rupture may be a function of the degree o~ exposure.
; 25 In addition to pressure, the ca~sules can be ruptured by other means including by peeling development, thermal development, so~vent vapor, ultrasonic energy or ` the like. A gas generating agent can be incorporated in ; the capsules so that they can be ru~tured by heating.
Known photohardenable compositions can be used in the present invention. The compositions which are most , . , useful are those which are curab~e by free radical initiated, addition polymerization or crosslinking. The most common examples of such compositions are cornpositions ~hich contain an ethylenically unsaturated compound, e.g., a com~ound containing terminal or pendant vinyl or allvlic groups. Such compounds are well known in the art and include acrylic and methacrylic esters of po]yhydric alcohols such as trimethylolpropane, pentaerythritol, and the like. Representative examples include ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate (TMPTA), pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, hexanediol-1,6-dimethacrylate, and diethyleneglycol dimethacrylate.
Photoinitiators are selected based on their spectral sensitivities such that there is minimum overlap in their spectral sensitivities and the microcapsules have adequate sensitivity in their respective active ranges.
As a general rule, the photosensitive composition containing the photoinitiator should provide a microcapsule having a sensitivity (E) less than lO,000 ergs/cm in the desired exposure range. The term "sensitivity" corresponds to the amount of incident radiation required to produce a first loss in density of 0.10 density units. The photosensitive microcapsules of the present invention are by nature positive working.
Consequently, when unexposed the microcapsules rupture and activate the color former which reacts with the developer to produce a maximum image density. Thus, the term "sensitivity" represents the minimum exposure necessary to effect a substantive reduction (0.10 density units) in that maximum density.
~seful initiators include photoinitiators which generate free radicals upon photochemical cleavage (homolytic initiators) such as certain benzoin ethers and initiators which function via hydrogen abstraction.
Preferred initiators are soluble in the radiation sensitive composition. Xanthones, thioxanthones, polycyclic quinones, acetophenones, 3 substituted coumarins, diaryl ketones, diaryl diketones, and benzoin alkyl ethers are particularly useful. Specific examples of useful initiators are benzophenone, Michler's ketone, benzoin methyl ether, 2,2-dimethoxy-2-phenyl-acetophenone9 isopropylthioxanthone, ethyl para-dimethylaminobenzoate, 3-cinnamoyl-7-diethylamino coumarins, etc~
To provide a color system which is visible light-sensitivel a potentially useful red initiator is N,N,N',N'-tetra-n-butylthionine; a potentially useful green initiator is N,N,N',N'-tetramethyl-4'-dodecylsafranine, and a potential blue initiator is phenanthraquinone.
Another initiator system useful in a red or green light-sensitive microcapsule is described in U~S. Patent Nol 3,495,987.
The photoinitiator is present in the photosensitive composition in an amount sufficient to initiate polymerization or crosslinking within a suitable exposure time. For example, benzoin methyl ether is typically present in an amount up to about 10% by weight based on the weight of the photocrosslinkable or photopolymerizable species. The exact amount of photoinitiator used will vary with the nature of the photosensitive composition.
M~X 017 P2 In accordance with one embodiment of the present invention, the radiation sensitive composition may additionally include a polythiol to increase the film speed of the microcapsules.
Useful polythiols include ethylene glycol bis (thioglycolate), ethylene g1ycol bis (~-mercapto-propionate)~ trimethylolpropane tris (thioglycolate), pentaerythritol tetrakis (thioglycolate) and the most preferred pentaerythritol tetrakis (~-mercapto-propionate) and trimethylolpropane tris (~-mercapto-propionate), and mixtures thereof. These compounds are commercially available. Certain polymeric polythiols such as polypropylene ether glycol bis (~-mercaptopropionate~
which is prepared by esterification of polypropylene ether glycol may also be useful.
Various oligomers or polymers can also he used in the present invention to improve the film speed of the microcapsules. These materials increase the rate with which the viscosity of the internal Phase of the microcapsules builds to a level at which differential release of the internal phase is achieved. These materials must be soluble in the photosensitive composition and not interfere with the photopolymerization reaction. Reactive oligomers contain terminal or pendant ethylenic unsaturation and include urethane, ester and epoxy based reactive acrylate, methacrylate, vinyl and allyl prepolymers. Useful non-reactive oligomers or polymers are solid or viscous liquids at room temperature but solub e in the unreacted photosensitive composition.
Representative examples of some commercially available oligomers or polymers which are use~ul in the present invention include reactive materials such as diallyl o-phthalate prepolymer tPolysciences), U Vithane 893 ~Morton Thiokol, Inc.), ~bercryl* 270 (Virginia Chemicals) and non-reactive materils such as ethyl cellulose, or Lucite*
The color former may be associated with the microcapsules in various ~ays such that uPon rupturing the microcapsule and releasing of the internal phase, the color former is able to react and/or migra~e to ~he developer and produce an image. For example, the color former may be encapsulated hith the photosensitive composition or incorporated in the wall of a microcapsule having a discrete wall. In the latter case, the photosensitive composition released from the capsules dissolves the color former and transports it to the developer.
One example of a useful color former in the invention is a colorless electron donating compound.
Representative examples of such color formers include substantially colorless compounds having in their partial skeleton a lactone, a lactam, a sultone, a spiropyran, an ester or an amido structure such as triarylmethane compounds, bisphenylmethane compounds, xanthene compounds, fluorans, thiazine compounds, spiropyran compounds and the like.
Cyan, magenta and yellow color precursors useful in the Presen~ invention can be selected from commercially available materials. Reakt Yellow (186) (a product of BASF), Copikem XI and Copikem*XIV (products of Hilton-Davis Chemical Co.) are useEul yellow color formers; Cyan S-29663 (an experimental compound from * trade marks s~
Hilton Davis), Co~ikem X (a product of ~ilton-Davis) and color formers described in U.S. Patent No. 4,32Z,352 are useful cyan color formers and Copikem XX (a product of Hilton Davis) and Pergascript*Red (Ciba-Geigy) are useful as magenta color formers. Other examples of useful color formers are s own below:
..
* trade mark A
.
MDX 017 P2 - ] 7 -Ye l l o~
~OCH2CH3 ~?
H 3 CO ~ _OCH 3 Cyan color precursors:
(CH3)2N~5~N(CH3)2 ~0 '3 MDX 017 P2 - lfl -
3 2 2 ~ 0_~' (C~32C~33) 2 ~N~
C = O
(CH3cH2~ 2~CII~ (CH2CH3) 2 NH
~3 Cl (CH3CH2) 2N ~CN~ (CH2CH3) 2 C= O
Magenta color precurosors:
33CI 2)2 ~c32cH3~2 H 3 ~ CH 3 (C32C113~2 C~3 (C33C32~2N ~3 .
~ , .
The color former is incorPorated in the internal phase in an amount suEficient to produce a visible image of the desired density upon reaction with a developer or upon transfer. In general, the image former is present in an amount of approximately 0.5 to 20% by weight based on the weight of the internal phase. A preferred range is about 2 to 10% by weight. Transfer imaging materials usually contain about 6% by weight of the color former whereas self-contained materials contain about 1.5 to 3 by weight of the image-forming agent. ~he relative amounts of the cyan, magenta and yellow color formers in the microcapsules are adjusted to provide satisfactory color balance. In conjunction with this, the relative amounts o the microcapsules in the coating composition can be adjusted to improve color balance.
In addition to the photosensitive composition, the internal phase may additionally include a diluent oil. Inclusion of the oil often improves half tone gradation in visual images~ Preferred diluent oils are weakly polar solvents having boiling points above 170C
and preferably in the range of 180 to 300C. Examples of carrier oils are alkylated biphenyls (e.g., monoisopropylbiphenyl), polychlorinated biphenyls, castor oil, mineral oil, deodorized kerosene, naphthenic mineral oils, dibutyl phthalate, dibutyl fumerate, brominated paraffin and mixtures thereof. Alkylated biphenyls and kerosene are generally less toxic and preferred. The amount of diluent oil incorporated in the microcapsules will depend upon the photographic characteristics that are desired in the photosensitive materials. Typically, the diluen~ oil is used in an amount of approximately 10 to 20% by weight based on the weight of the internal phase.
The photosensitive microcapsules uf the present invention can be formed using kno~n encapsulation techniques. The p~lotosensitive composition and associated agents can be encapsulated in hydrophilic wall-forming materials such as gelatin-~ype materials (see U.S. Patent Nos. 2,730,456 and 2,800,457 to Green et al) including qum arabic, polyvinyl alcohol, carboxy-methyl-cellulose;
resorcinol-formaldehyde ~7all formers ~see U.S. Patent No.
3,755,190 to Hart et al); isocyanate wall-formers tsee U.S. Patent No. 3,914,511 to Vassiliades);
isocyanate-polyol wall-formers (see U.S. Patent No.
3,796,669 to Kirintani et al); urea formaldehyde wall-formers, particularly urea-resorcinol-formaldehyde in which oleophilicity is enhanced by the addition of resorcinol (see U.S. Patent Nos. 4,001,140;
C = O
(CH3cH2~ 2~CII~ (CH2CH3) 2 NH
~3 Cl (CH3CH2) 2N ~CN~ (CH2CH3) 2 C= O
Magenta color precurosors:
33CI 2)2 ~c32cH3~2 H 3 ~ CH 3 (C32C113~2 C~3 (C33C32~2N ~3 .
~ , .
The color former is incorPorated in the internal phase in an amount suEficient to produce a visible image of the desired density upon reaction with a developer or upon transfer. In general, the image former is present in an amount of approximately 0.5 to 20% by weight based on the weight of the internal phase. A preferred range is about 2 to 10% by weight. Transfer imaging materials usually contain about 6% by weight of the color former whereas self-contained materials contain about 1.5 to 3 by weight of the image-forming agent. ~he relative amounts of the cyan, magenta and yellow color formers in the microcapsules are adjusted to provide satisfactory color balance. In conjunction with this, the relative amounts o the microcapsules in the coating composition can be adjusted to improve color balance.
In addition to the photosensitive composition, the internal phase may additionally include a diluent oil. Inclusion of the oil often improves half tone gradation in visual images~ Preferred diluent oils are weakly polar solvents having boiling points above 170C
and preferably in the range of 180 to 300C. Examples of carrier oils are alkylated biphenyls (e.g., monoisopropylbiphenyl), polychlorinated biphenyls, castor oil, mineral oil, deodorized kerosene, naphthenic mineral oils, dibutyl phthalate, dibutyl fumerate, brominated paraffin and mixtures thereof. Alkylated biphenyls and kerosene are generally less toxic and preferred. The amount of diluent oil incorporated in the microcapsules will depend upon the photographic characteristics that are desired in the photosensitive materials. Typically, the diluen~ oil is used in an amount of approximately 10 to 20% by weight based on the weight of the internal phase.
The photosensitive microcapsules uf the present invention can be formed using kno~n encapsulation techniques. The p~lotosensitive composition and associated agents can be encapsulated in hydrophilic wall-forming materials such as gelatin-~ype materials (see U.S. Patent Nos. 2,730,456 and 2,800,457 to Green et al) including qum arabic, polyvinyl alcohol, carboxy-methyl-cellulose;
resorcinol-formaldehyde ~7all formers ~see U.S. Patent No.
3,755,190 to Hart et al); isocyanate wall-formers tsee U.S. Patent No. 3,914,511 to Vassiliades);
isocyanate-polyol wall-formers (see U.S. Patent No.
3,796,669 to Kirintani et al); urea formaldehyde wall-formers, particularly urea-resorcinol-formaldehyde in which oleophilicity is enhanced by the addition of resorcinol (see U.S. Patent Nos. 4,001,140;
4,087,376 and 4,089,802 to Foris et al); and melamine-formaldehyde resin and hydroxypropyl cellulose (see commonly assigned U.S. Patent No. 4,025,455 to Shackle).
` Urea-formaldehyde microcapsules are preferred for use in the present invention. Methods for producing urea formaldehyde capsules which are particularly useful are described in U.S. Patents 4,251,386 and 4,138,362.
The mean size of the microcapsules of the present invention generally ranges from ap~roximately 1 to 25 microns. As a general rule, image resolution improves as capsule size decreases except that if the capsule size is ~ too small, the capsules may disappear in the Pore or fiber ; structure of some substrates.
The microcapsules of the present invention can be used to form either transfer or self-contained imaging systems, i.e., systems in which the developer is on the .~
.
~: `
.~
', , .
same or a separate support from the microcapsules. A
detailed description of trans~er materials can be found in U.S. Patent No. 4,399,209. Self contained systems are the sub~ect of commonly assigned U.S. Patent 4,~40,846.
Illustrative examples of color developers useful with the electron donating type color precursors are clay minerals such as acid clay, active clay, attapulgite, etc.; organic acids such as tannic acid, gallic acid, propyl gallate, etc.; acid polymers such as phenol-formaldehyde resins, phenol acetylene condensation resins, condensates between an organic carboxylic acid having at least one hydroxy group and formaldehyde, etc.;
metal salts or aroma~ic carboxylic acids such as zinc salicylate, tin salicylate, zinc 2-hydroxy naphthoate, 5 zinc 3,5 di-tert~butyl salicylate, zinc 3-cyclohexyl-5--dimethylbenzyl) salicylate (see U.S. Patents 3,864,146 and 3,934,070), oil soluble metal salts or phenol-formaldehyde novolak resins (e.g~, see ~.S. Patent Nos. 3,672,935; 3,732,120 and 3,737,410) such as zinc modified oil soluble phenol-formaldehyde resin as disclosed in U.S. Patent No. 3,732,120, zinc carbonate etc~ and mixtures thereof.
The most common substrate for the photosensitive material of this invention is paper. The paper may be a commercial impact raw stock, or a special grade paper such as cast-coated paper or chrome-rolled paper. Transparent substrates such as polyethylene terephthalate and translucent substrates can also be used in this invention.
Photosensitive materials are typically prepared by forming a slurry of the photosensitive microcapsules and coating this slurry on the surface of the appropriate subs~rate using conventional coating techniques. The coating composltions rnay additionally contain additi~es to improve the handling characteristics of the material.
Ty~ical examples of such additives are a stilt material such as starch particles and silica particles which prevent specking when the photosensitive material is passed through the nip between two pressure rollers.
In coating the microcapsules on the support, it is generally desirable to pre-mi~ the cyanr magenta and yellow forming capsules rather than to use sequential coating techniques. If the capsules are sequentially coated, a coating sequence should be adopted that assures that the absorber in one capsule does not shield the photosensitive composition in another capsule. The reason ~or this is that absorbers are selected such that they are active (in terms of absorptivity) in the wavelength regions in which other microcapsules are designed to be sensitive. Hence/ unless this precaution is taken using sequential coating, one group of capsules could detrimentally shield another group of capsules from exposure.
Where the microcapsules are respectively sensitive to red, green and blue light, the exposure apparatus requires only a light source, means of focusing the light source from the original onto the imaging sheet, means to join the imaging sheet with the developer sheet tin the case of a transfer material), and means for rupturing the microcapsules. Simplified means such as this can be used with the invention because development is essentially a dry process with the internal phase and the developer in~eracting in only infinitesimal dro-olets.
When the microcapsules are not sensitive to visible light, it is necessary to include means for separating the red, green and blue components of the original and translating them into three distinct bands of actinic radiation. Any of the conventional means for electronically processing a visible image may be used for this purpose including a Dunn camera or a matrix camera.
Generally, conventional means for accomplishing image translation include color filters to resolve the original into its component images, photoreceptors for sensing the respective component images, means for scanning those photoreceptors and generating an electrical output, and imaging tubes for converting the output to an appropriate radiation wavelength. In accordance with one exposure device, red, green and blue signals are separated in a color terminal and sent to a Dunn camera. Black and white signals are then sequentially generated on the Dunn CRT
screen corresponding to the color signals. Three separate exposures are used through three filters each of which ~ 20 provides a distinct band of actinic radaion to which the `i cyan, magenta and yellow producing microcapsules are l respectively sensitive. Alternatively, an exposure device ~i could be constructed which includes three CRT tubes, each of which has a different output wavelength.
The present invention is illustrated in more detail by the following non-limiting Examples wherein the ` following procedures were used to prepare the microcapsules and the developer sheet.
i `j r-~
Capsule Preparation 1. Into a 1200 ml stainless steel beaker, 416 g ~ater and ~9. 2 g isob~tylene maleic anhydride copolymer (18%) are weighed.
2. The beaker is clamped in place on a hot plate under an overhead mixer. A six-bladed, 45 pitch, turbine impeller is used on the mixer.
3. After thoroughly mixing, 12.4 9 pectin (polygalacturonic acid methyl ester) is slowly sifted into the beaker. This mixture is stirred for 20 minutes.
4. The pH is adjusted to 4.0 using a 20%
solution of H2SO4, and 0.4 9 Quadrol (2-hydroxypropyl ethylenediamine with propylene oxide from BASF) is added.
` Urea-formaldehyde microcapsules are preferred for use in the present invention. Methods for producing urea formaldehyde capsules which are particularly useful are described in U.S. Patents 4,251,386 and 4,138,362.
The mean size of the microcapsules of the present invention generally ranges from ap~roximately 1 to 25 microns. As a general rule, image resolution improves as capsule size decreases except that if the capsule size is ~ too small, the capsules may disappear in the Pore or fiber ; structure of some substrates.
The microcapsules of the present invention can be used to form either transfer or self-contained imaging systems, i.e., systems in which the developer is on the .~
.
~: `
.~
', , .
same or a separate support from the microcapsules. A
detailed description of trans~er materials can be found in U.S. Patent No. 4,399,209. Self contained systems are the sub~ect of commonly assigned U.S. Patent 4,~40,846.
Illustrative examples of color developers useful with the electron donating type color precursors are clay minerals such as acid clay, active clay, attapulgite, etc.; organic acids such as tannic acid, gallic acid, propyl gallate, etc.; acid polymers such as phenol-formaldehyde resins, phenol acetylene condensation resins, condensates between an organic carboxylic acid having at least one hydroxy group and formaldehyde, etc.;
metal salts or aroma~ic carboxylic acids such as zinc salicylate, tin salicylate, zinc 2-hydroxy naphthoate, 5 zinc 3,5 di-tert~butyl salicylate, zinc 3-cyclohexyl-5--dimethylbenzyl) salicylate (see U.S. Patents 3,864,146 and 3,934,070), oil soluble metal salts or phenol-formaldehyde novolak resins (e.g~, see ~.S. Patent Nos. 3,672,935; 3,732,120 and 3,737,410) such as zinc modified oil soluble phenol-formaldehyde resin as disclosed in U.S. Patent No. 3,732,120, zinc carbonate etc~ and mixtures thereof.
The most common substrate for the photosensitive material of this invention is paper. The paper may be a commercial impact raw stock, or a special grade paper such as cast-coated paper or chrome-rolled paper. Transparent substrates such as polyethylene terephthalate and translucent substrates can also be used in this invention.
Photosensitive materials are typically prepared by forming a slurry of the photosensitive microcapsules and coating this slurry on the surface of the appropriate subs~rate using conventional coating techniques. The coating composltions rnay additionally contain additi~es to improve the handling characteristics of the material.
Ty~ical examples of such additives are a stilt material such as starch particles and silica particles which prevent specking when the photosensitive material is passed through the nip between two pressure rollers.
In coating the microcapsules on the support, it is generally desirable to pre-mi~ the cyanr magenta and yellow forming capsules rather than to use sequential coating techniques. If the capsules are sequentially coated, a coating sequence should be adopted that assures that the absorber in one capsule does not shield the photosensitive composition in another capsule. The reason ~or this is that absorbers are selected such that they are active (in terms of absorptivity) in the wavelength regions in which other microcapsules are designed to be sensitive. Hence/ unless this precaution is taken using sequential coating, one group of capsules could detrimentally shield another group of capsules from exposure.
Where the microcapsules are respectively sensitive to red, green and blue light, the exposure apparatus requires only a light source, means of focusing the light source from the original onto the imaging sheet, means to join the imaging sheet with the developer sheet tin the case of a transfer material), and means for rupturing the microcapsules. Simplified means such as this can be used with the invention because development is essentially a dry process with the internal phase and the developer in~eracting in only infinitesimal dro-olets.
When the microcapsules are not sensitive to visible light, it is necessary to include means for separating the red, green and blue components of the original and translating them into three distinct bands of actinic radiation. Any of the conventional means for electronically processing a visible image may be used for this purpose including a Dunn camera or a matrix camera.
Generally, conventional means for accomplishing image translation include color filters to resolve the original into its component images, photoreceptors for sensing the respective component images, means for scanning those photoreceptors and generating an electrical output, and imaging tubes for converting the output to an appropriate radiation wavelength. In accordance with one exposure device, red, green and blue signals are separated in a color terminal and sent to a Dunn camera. Black and white signals are then sequentially generated on the Dunn CRT
screen corresponding to the color signals. Three separate exposures are used through three filters each of which ~ 20 provides a distinct band of actinic radaion to which the `i cyan, magenta and yellow producing microcapsules are l respectively sensitive. Alternatively, an exposure device ~i could be constructed which includes three CRT tubes, each of which has a different output wavelength.
The present invention is illustrated in more detail by the following non-limiting Examples wherein the ` following procedures were used to prepare the microcapsules and the developer sheet.
i `j r-~
Capsule Preparation 1. Into a 1200 ml stainless steel beaker, 416 g ~ater and ~9. 2 g isob~tylene maleic anhydride copolymer (18%) are weighed.
2. The beaker is clamped in place on a hot plate under an overhead mixer. A six-bladed, 45 pitch, turbine impeller is used on the mixer.
3. After thoroughly mixing, 12.4 9 pectin (polygalacturonic acid methyl ester) is slowly sifted into the beaker. This mixture is stirred for 20 minutes.
4. The pH is adjusted to 4.0 using a 20%
solution of H2SO4, and 0.4 9 Quadrol (2-hydroxypropyl ethylenediamine with propylene oxide from BASF) is added.
5. The mixer is turned up to 3000 rpm and the internal phase is added over a period of 10-15 seconds.
Emulsification is continued for 10 minutes.
Emulsification is continued for 10 minutes.
6. At the start of emulsification, the hot plate is turned up so heating continues during emulsification.
7. After I0 minutes, the mixing speed is reduced to 2000 rpm and 66.4 g urea solution (50% w/w), 3.2 g resorcinol in 20 g water, 85.6 g formaldehvde (37%), and 2.4 9 ammonium sulfate in 40 ml water are added at two-minute intervals.
8. The beaker is covered with foil and a heat gun is used to hel~ bring the temperature of the preparation to 65C. When 65C is reached, the hot plate is adjusted to maintain this temperature for a two to three hour cure time during which the capsule walls are formed.
9. After curing, the heat is turned of~ and the pH is adjusted to 9.0 using a 20% NaOH solution.
10. Dry sodium bisulfite (11.2 g) is added and the capsule preparation is cooled to room temperature.
Developer Sheet Preparation A mixture of 852 g water, 250 g 25% Tamol 731 (Rohm & Haas Chemical Co.3, 75 g HT clay, 1000 g KC-ll (a synthetic developer manufactured by Fuji Photo Film Company, Ltd~), 15 9 Calgon ~ (Calgon, Inc.) 30 9 Dequest 2006 (~onsanto Co.) was ground to a particle size less 1~ than 5 microns. To this mixture was added 25 parts ~T
clay and 10 parts DOw 501 latex per 65 parts of the mixture. The resultant material was coated with a #10 Meyer bar on 80 lb Black and White Enamel base stock at 30 to 35% solids.
Exam~e 1 An initiator useful in imparting blue-light sensitivity to capsules is 7-diethylamino-3-cinnamoylcoumarin ~U.S. 4,147,552, Specht and Farid).
Although highly sensitive at 470 nm, this compound also imparts a significant sensitivity to the capsules at shorter wavelengths. This shorter wavelength sensitivity ~` is a problem which can be dealt with by the inclusion of a ~ UV absorber.
; A series of capsule batches with different absorbers was produced (as described above) which ` contained the following internal phase:
TMPTA (trimethylol propane triacrylate) 200 g 7-diethylamino-3-cinnamoylcoumarin 0.4 g Quanticure*EPD (Ward-Blenkinsop, Ltd.) 8 g Reakt Yellow (BASF) 20 9 Absorber 4 g * trade marks i5.~
Each of the resultant capsule emulsions was diluted l:1 by weight ~ith water containing 0.5~ Triton X-100 surfactant (Rohm and Haas) and coated onto 80 lb.
Black and White glossy paper (Mead Corp~) with a No. 12 wire-~ound rod. After drying, capsule sheets were exposed with a Kratos lO00~ monochrometer system at 350, 390, and 470 nm (20 nm bandpass) through a ~ step wedge (V~R).
The geometry of the system and exposure times were such that the exposure was lO,000 ergs/cm2 at 350 nm, 13,000 ergs/cm2 at 390 nm, and 23,500 ergs/cm2 at 470 nm.
Every two steps down the step tablet resulted in a decrease in exposure by a factor of two. Thusl the larger the number in the below table, the less energy is required for a given response.
First Loss of Exposure to Density (Step #~ Dmin (Step #) 350 nm390 mn 470 nm None 2.5 6 6 Tinuvin 327 0 4 6 Tinuvin P 0 5 6 Tinuvin 328 0 5 - Givsorb UV-2 0 6 6 Tinuvin 326 0 1 5 Cyasorb*UV-24 l 5 6 As can be seen from the data, addition of the absorber decreases the photographic speed at 350 nm in each case and at 390 nm in most cases. Differences in speed among absorbers are due to differences in molecular weightj extinction coefficient, and the shape of the absorption curve.
* trade mark ., ~
Example 2 Capsules (B-l) were produced as outlined above which contained the following internal phase:
TMPTA 200 g Quanticure ITX (~ard-Blenkinsop, Ltd.) 2.0 9 S Quanticure EPD (Ward-Blenkinsop, Ltd.) 8.0 g Experimental Cyan Precursor (Hilton-Davis) 24 9 Givsorb UV-2 6 g A second capsule batch (B-2) was produced as above, but no Givsorb UV-2 was added. Both capsule batches were coated as in Example 1. With the exposure device described in Example 1, a series of stepwedge (64 secO~ exposures (20 nm bandpass) were made at 10 nm intervals to give the spectral s~nsitivity curves shown in Fig. 3. As can be seen by an examination of Fig~ 3, the spectral sensitivity curve for ITX is appreciably sharpened by addition of the UV absorber. This allows the use of an initiator which absorbs maximally at 350 nm in the three-color system. At 350 nm, the capsule batch containing the absorber requires about 2.83 (three steps) times more light than the capsule batch without absorber to effect the same photographic response.
Example 3 Capsules (C-l) were produced as outlined above which contained the following internal phase:
5~
TMPTA 2U0 g 7-diethylamino-3-cinnamoylcoumarin0.4 g Quanticure ÆPD 8 9 Reakt Yelloh 20 g Tinuvin 326 6 9 (2-(3'-tert-butyl-5'methyl-2'-hydroxyphenyl)-5-chlorobenzotriazole) A second capsule batch (C-2) was produced as above, but no Tinuvin 326 was added. Both capsules types were coated as in Example 1. A series of stepwedge exposures (20 nm bandwidth, 64 seconds) was rnade at 10 nm intervals to obtain the spectral sensitivity curves sho~n in Fig. 4.
As can be seen, addition of the absorber lowered the sensitivity of the system at shorter wavelengths, thus decreasing the spectral overlap in the three-color system shown in Fig. 2. At 390 nm, for example, the system is slowed by two stops (a factor of four) by addition of the UV absorber.
Example 4 A photopolymerizable, microencapsulated, ; full-color, imaging system involving three types of microcapsules each containing a different dye precursor and sensitive at one of three wavelengths was prepared.
Capsules A' are sensitive at 350 nm and contain a magenta precursor; Capsules B' are sensitive at 390 nm and contain a cyan precursor; and Capsules C' are sensitive at 470 nm and contain a yellow precursor.
Capsules A', B', and C' were Prepared using the above procedure and the following internal phases. The internal phases were prepared by adding the monomer, ~ ,~" ~j f,~ ~ rj ~
: photoinitiator, and color former to a 400 ml beaker, heating to 100C and stirring until all three had dissolved. Thereafter the isocyanate was added and emulsified.
Internal Phases i) Capsule A' 200 g - TMPTA (Trimethylolpropane Triacrylate from Sartomer) ?4 g - Quanticure BMS ~4-Benzoyl-4'-Methyldiphenyl Sulphide from Ward-Blenkinsop) 8 g - Quanticure EPD (Ethyl-4-Dimethylaminobenzoate from Ward-Blenkinsop) 48 g - Copikem XX (from Hilton-Davis - purified) by silica gel column chromotography to remove inhibiting impurties 6 g - SF-50*(Union Carbide Isocyanate) 12 g - N-lOO*(Polyisocyanate Resin from Desmodur) ii) Capsule B' 200 g - TMPTA
4 9 - Quanticure ITX (2-Isopropylthioxanthone from Ward-Blenkinsop) 8 g - Quanticure EPD
24 9 - Cyan S-29663 (from Hilton-Davis) 6 9 - Givsorb W -2 (N-(p-Ethoxycarbonylphenyl)-N'-phenylformamidine from Givaudan) 12 g - N-100 iii) Capsule C' 0.4 9 - 3-Cinnamoyl-7-Diethylamino coumarin (U.S. Patent No. 4,147,552) 8 9 - Quanticure EPD
20 g - Reakt Yellow 186 (BASF) 6 9 - Tinuvin 326 (2-(3'-tert-Butyl-5'-Methyl-2'-hydroxy-phenyl)-5-Chlorobenzotriazole feom Ciba-Geigy) 12 g - N-100 * trade marks ,f ~., Capsules A', B', and C' are mixed such that the combination of the three gives a neutral black when developed. The formulation used for coating is 113 y Capsule A', 150 g Capsule B' and 188 9 Capsule C', 225 g 1~ Triton X-100, 20 drops Triton X-100 and 120 g S% Klucel L. The capsules and the Triton X-100 with water are mixed together and put in an ultrasonic bath for approximately 10 minutes to facilitate good mixing and break up any agglomerates that may have formed. The mixture is then filtered throuyh 3-6 layers of cheesecloth. Finally, the Klucel L is stirred into the mixture and it is ready for coating.
The coating machine used is a Talboys ~odel #1217 coater. The above described formulation is coated on this machine using a #12 wire-wound Meyer bar on 8-1/2 inch wide 80~ Black and White Glossy basestock. This gives a capsule coatweight of 4-6 g/m2. ~ight sensitive, full color, imaging paper is thus produced.
Exposure and Development The paper produced as described above is exposed with a Kratos Monochromatic Illumination System, Model MIS
1000 having a 1000 watt Xenon arc light source fitted with a GM 252 hi~h intensity grating in which the converging lens has been removed. This modification gives an exposure field large enough to expose 8" x 10" sheets at a distance of about 58 inches from the monochrometer. Color separation masks (Accucolor* Dayton, Ohio) are used in which a picture is taken through red, green, and blue filters and each is printed on a transparent base film.
The green filter mask thus produced is placed over the * trade marks i ~ .
light sensitive paper with proper registration. The monochrometer is set at 350 nm with a 20 nm bandwidth.
The capsules are exposed through the mask for 15-30 seconds. The green filter mask is removed and the red filter mask is placed over the imaging sheet and registered. The monochrometer is set at 390 nm with a 20 nm bandwidth. The capsules are exposed for 20-30 seconds. This mask is then removed and replaced with the ; blue filter mask. Wavelength is set at 470 nm, again with a 20 nm bandwidth, and the capsules are exposed for 10-20 seconds. The exposed sheet is placed face down against a resin developer sheet prepared as set forth above. These two sheets are run together through a calender stack with nip pressure of about 500 pli which breaks the unexposed or underexposed capsules, transfers the oil to the developer sheet, develops the dye, and forms a full color image. The speed of ~evelopment can be enhanced by heating the sh~et for about 30 seconds at 90C.
Sensitivity The spectral sensitivities of the capsules are graphed in Fig. 2. These curves were generated by exposing paper coated with one of the three capsule types through a 21 step photographic step table at each 10 nm increment through the wavelength range 300-500 nm on the monochrometer described above with a 20 nm bandwidth. The densities of each stepwedge image produced was read on a Macbeth densitometer and H and D curves were plotted at each wavelength measured with the aid of a computer program which takes into account the spectral output of the light source and the exposure time so that the curves ~ 35 plotted are in ergs/cm2. The speeds at g0~ density and at 10% density are calculated where 100% density or Dmax is unexposed and 0% density or Dmin is fully exposed.
Fiq. 2 plots the speeds at 10~ density for capsules A', B', and C'. Capsule A' has a 350 nm sensitivity of 300 ergs/cm2 at 90% density and 800 ergs/cm2,at 10%
density. This capsule is exposed at 350 nm rather than 360 nm because capsule B' is more sensitive at 360 nm than at 350 nm. Capsule B' has a 390 nm sensitivity of 450 ergs/cm2 at 90~ density and 1100 ergs/cm2 at 20~
density. Capsule C' has a 470 nm sensitivity of 550 ergs/cm2 at 90% density and 2300 ergs/cm2 at 10%
density. The sensitivity of the photosensitive material is between about 800 and 2300 ergs/cm2.
Example 5 A microencapsulated full color imaging system was prepared and evaluated as in Example 4 except as noted below.
Capsules A", B" and C" were prepared by following the encapsulation procedure set forth above using the following internal phase compositions:
Capsule A"
180 g - Photomer 4149 (from Diamond Shamrock) 16 g - Propylene Carbonate 24 g - Quanticure BMS
8 9 - Quanticure EPD
6 g - PIP+pF~ (Diphenyliodonium Hexafluoro-phosphate prepared from Crivello, J.V.; Lam, J.H.W., ~. POlym. Sci. Polym. Chem., 17 (1979), 977) 48 g - Copikem XX (Hilton Davis) 6 g - SF-50 12 g - N-100 2~j5~
MDX 017 P2 - 3~ -Caps~le B"
180 9 - Photomer 4149 16 g - Propylene Carbonate 4 9 - Quanticure ITX
8 g - Quanticure EPD
6 9 - PIP+PF~
24 9 - Experimental Cyan S-29663 6 g - Givsorb Uv-2 12 9 - N-lO0 Capsule C"
Same as C' in Example 4.
The internal phase was prepared by dissolving the monomer, photoinitiator and color former as in Example 4;
cooling the solution to room temperature and adding the " propylene carbonate having the PIP+PF6 dissolved therein; adding the isocyanates, mixing thoroughly for two minutes, and emulsifying.
The capsules were mixed to give neutral black when developed and coated on a support as in Example 4.
The spectral sensitivities of the capsules are plotted in Fig. 5. Capsule A" has a 350 nm sensitivity of 200 ergs/cm2 at gO% density and 500 ergs/cm2 at lO~
density. Capsule B" has a 390 nm sensitivity of 180 ergs/cm2 at 90% density and 380 ergs/cm2 at 10%
density. Capsule C" has a 470 nm sensitivity of 550 ergs/cm2 at 90% density and 2300 ergs/cm2 at 10%
density. Capsule C" did not include the diphenyliodonium hexafluorophosphate, which would make the system faster.
Had the capsules included the PIP~PF6, the speed at 470 nm would have been increased, but the sPeeds at 390 nm and 350 nm would also have been increased making color separation difficult. The sensitivity of the system, then, is between 380 and 2300 ergs/cm2.
s~
Having described the invention in detail and by reference to specific embodiments thereo, it ~ill be apparent that numerous modifications and variations are possible without departing from the spirit and scope of the invention defined by the following claims.
l~hat is ~laimed is:
i:
~ .
. .
Developer Sheet Preparation A mixture of 852 g water, 250 g 25% Tamol 731 (Rohm & Haas Chemical Co.3, 75 g HT clay, 1000 g KC-ll (a synthetic developer manufactured by Fuji Photo Film Company, Ltd~), 15 9 Calgon ~ (Calgon, Inc.) 30 9 Dequest 2006 (~onsanto Co.) was ground to a particle size less 1~ than 5 microns. To this mixture was added 25 parts ~T
clay and 10 parts DOw 501 latex per 65 parts of the mixture. The resultant material was coated with a #10 Meyer bar on 80 lb Black and White Enamel base stock at 30 to 35% solids.
Exam~e 1 An initiator useful in imparting blue-light sensitivity to capsules is 7-diethylamino-3-cinnamoylcoumarin ~U.S. 4,147,552, Specht and Farid).
Although highly sensitive at 470 nm, this compound also imparts a significant sensitivity to the capsules at shorter wavelengths. This shorter wavelength sensitivity ~` is a problem which can be dealt with by the inclusion of a ~ UV absorber.
; A series of capsule batches with different absorbers was produced (as described above) which ` contained the following internal phase:
TMPTA (trimethylol propane triacrylate) 200 g 7-diethylamino-3-cinnamoylcoumarin 0.4 g Quanticure*EPD (Ward-Blenkinsop, Ltd.) 8 g Reakt Yellow (BASF) 20 9 Absorber 4 g * trade marks i5.~
Each of the resultant capsule emulsions was diluted l:1 by weight ~ith water containing 0.5~ Triton X-100 surfactant (Rohm and Haas) and coated onto 80 lb.
Black and White glossy paper (Mead Corp~) with a No. 12 wire-~ound rod. After drying, capsule sheets were exposed with a Kratos lO00~ monochrometer system at 350, 390, and 470 nm (20 nm bandpass) through a ~ step wedge (V~R).
The geometry of the system and exposure times were such that the exposure was lO,000 ergs/cm2 at 350 nm, 13,000 ergs/cm2 at 390 nm, and 23,500 ergs/cm2 at 470 nm.
Every two steps down the step tablet resulted in a decrease in exposure by a factor of two. Thusl the larger the number in the below table, the less energy is required for a given response.
First Loss of Exposure to Density (Step #~ Dmin (Step #) 350 nm390 mn 470 nm None 2.5 6 6 Tinuvin 327 0 4 6 Tinuvin P 0 5 6 Tinuvin 328 0 5 - Givsorb UV-2 0 6 6 Tinuvin 326 0 1 5 Cyasorb*UV-24 l 5 6 As can be seen from the data, addition of the absorber decreases the photographic speed at 350 nm in each case and at 390 nm in most cases. Differences in speed among absorbers are due to differences in molecular weightj extinction coefficient, and the shape of the absorption curve.
* trade mark ., ~
Example 2 Capsules (B-l) were produced as outlined above which contained the following internal phase:
TMPTA 200 g Quanticure ITX (~ard-Blenkinsop, Ltd.) 2.0 9 S Quanticure EPD (Ward-Blenkinsop, Ltd.) 8.0 g Experimental Cyan Precursor (Hilton-Davis) 24 9 Givsorb UV-2 6 g A second capsule batch (B-2) was produced as above, but no Givsorb UV-2 was added. Both capsule batches were coated as in Example 1. With the exposure device described in Example 1, a series of stepwedge (64 secO~ exposures (20 nm bandpass) were made at 10 nm intervals to give the spectral s~nsitivity curves shown in Fig. 3. As can be seen by an examination of Fig~ 3, the spectral sensitivity curve for ITX is appreciably sharpened by addition of the UV absorber. This allows the use of an initiator which absorbs maximally at 350 nm in the three-color system. At 350 nm, the capsule batch containing the absorber requires about 2.83 (three steps) times more light than the capsule batch without absorber to effect the same photographic response.
Example 3 Capsules (C-l) were produced as outlined above which contained the following internal phase:
5~
TMPTA 2U0 g 7-diethylamino-3-cinnamoylcoumarin0.4 g Quanticure ÆPD 8 9 Reakt Yelloh 20 g Tinuvin 326 6 9 (2-(3'-tert-butyl-5'methyl-2'-hydroxyphenyl)-5-chlorobenzotriazole) A second capsule batch (C-2) was produced as above, but no Tinuvin 326 was added. Both capsules types were coated as in Example 1. A series of stepwedge exposures (20 nm bandwidth, 64 seconds) was rnade at 10 nm intervals to obtain the spectral sensitivity curves sho~n in Fig. 4.
As can be seen, addition of the absorber lowered the sensitivity of the system at shorter wavelengths, thus decreasing the spectral overlap in the three-color system shown in Fig. 2. At 390 nm, for example, the system is slowed by two stops (a factor of four) by addition of the UV absorber.
Example 4 A photopolymerizable, microencapsulated, ; full-color, imaging system involving three types of microcapsules each containing a different dye precursor and sensitive at one of three wavelengths was prepared.
Capsules A' are sensitive at 350 nm and contain a magenta precursor; Capsules B' are sensitive at 390 nm and contain a cyan precursor; and Capsules C' are sensitive at 470 nm and contain a yellow precursor.
Capsules A', B', and C' were Prepared using the above procedure and the following internal phases. The internal phases were prepared by adding the monomer, ~ ,~" ~j f,~ ~ rj ~
: photoinitiator, and color former to a 400 ml beaker, heating to 100C and stirring until all three had dissolved. Thereafter the isocyanate was added and emulsified.
Internal Phases i) Capsule A' 200 g - TMPTA (Trimethylolpropane Triacrylate from Sartomer) ?4 g - Quanticure BMS ~4-Benzoyl-4'-Methyldiphenyl Sulphide from Ward-Blenkinsop) 8 g - Quanticure EPD (Ethyl-4-Dimethylaminobenzoate from Ward-Blenkinsop) 48 g - Copikem XX (from Hilton-Davis - purified) by silica gel column chromotography to remove inhibiting impurties 6 g - SF-50*(Union Carbide Isocyanate) 12 g - N-lOO*(Polyisocyanate Resin from Desmodur) ii) Capsule B' 200 g - TMPTA
4 9 - Quanticure ITX (2-Isopropylthioxanthone from Ward-Blenkinsop) 8 g - Quanticure EPD
24 9 - Cyan S-29663 (from Hilton-Davis) 6 9 - Givsorb W -2 (N-(p-Ethoxycarbonylphenyl)-N'-phenylformamidine from Givaudan) 12 g - N-100 iii) Capsule C' 0.4 9 - 3-Cinnamoyl-7-Diethylamino coumarin (U.S. Patent No. 4,147,552) 8 9 - Quanticure EPD
20 g - Reakt Yellow 186 (BASF) 6 9 - Tinuvin 326 (2-(3'-tert-Butyl-5'-Methyl-2'-hydroxy-phenyl)-5-Chlorobenzotriazole feom Ciba-Geigy) 12 g - N-100 * trade marks ,f ~., Capsules A', B', and C' are mixed such that the combination of the three gives a neutral black when developed. The formulation used for coating is 113 y Capsule A', 150 g Capsule B' and 188 9 Capsule C', 225 g 1~ Triton X-100, 20 drops Triton X-100 and 120 g S% Klucel L. The capsules and the Triton X-100 with water are mixed together and put in an ultrasonic bath for approximately 10 minutes to facilitate good mixing and break up any agglomerates that may have formed. The mixture is then filtered throuyh 3-6 layers of cheesecloth. Finally, the Klucel L is stirred into the mixture and it is ready for coating.
The coating machine used is a Talboys ~odel #1217 coater. The above described formulation is coated on this machine using a #12 wire-wound Meyer bar on 8-1/2 inch wide 80~ Black and White Glossy basestock. This gives a capsule coatweight of 4-6 g/m2. ~ight sensitive, full color, imaging paper is thus produced.
Exposure and Development The paper produced as described above is exposed with a Kratos Monochromatic Illumination System, Model MIS
1000 having a 1000 watt Xenon arc light source fitted with a GM 252 hi~h intensity grating in which the converging lens has been removed. This modification gives an exposure field large enough to expose 8" x 10" sheets at a distance of about 58 inches from the monochrometer. Color separation masks (Accucolor* Dayton, Ohio) are used in which a picture is taken through red, green, and blue filters and each is printed on a transparent base film.
The green filter mask thus produced is placed over the * trade marks i ~ .
light sensitive paper with proper registration. The monochrometer is set at 350 nm with a 20 nm bandwidth.
The capsules are exposed through the mask for 15-30 seconds. The green filter mask is removed and the red filter mask is placed over the imaging sheet and registered. The monochrometer is set at 390 nm with a 20 nm bandwidth. The capsules are exposed for 20-30 seconds. This mask is then removed and replaced with the ; blue filter mask. Wavelength is set at 470 nm, again with a 20 nm bandwidth, and the capsules are exposed for 10-20 seconds. The exposed sheet is placed face down against a resin developer sheet prepared as set forth above. These two sheets are run together through a calender stack with nip pressure of about 500 pli which breaks the unexposed or underexposed capsules, transfers the oil to the developer sheet, develops the dye, and forms a full color image. The speed of ~evelopment can be enhanced by heating the sh~et for about 30 seconds at 90C.
Sensitivity The spectral sensitivities of the capsules are graphed in Fig. 2. These curves were generated by exposing paper coated with one of the three capsule types through a 21 step photographic step table at each 10 nm increment through the wavelength range 300-500 nm on the monochrometer described above with a 20 nm bandwidth. The densities of each stepwedge image produced was read on a Macbeth densitometer and H and D curves were plotted at each wavelength measured with the aid of a computer program which takes into account the spectral output of the light source and the exposure time so that the curves ~ 35 plotted are in ergs/cm2. The speeds at g0~ density and at 10% density are calculated where 100% density or Dmax is unexposed and 0% density or Dmin is fully exposed.
Fiq. 2 plots the speeds at 10~ density for capsules A', B', and C'. Capsule A' has a 350 nm sensitivity of 300 ergs/cm2 at 90% density and 800 ergs/cm2,at 10%
density. This capsule is exposed at 350 nm rather than 360 nm because capsule B' is more sensitive at 360 nm than at 350 nm. Capsule B' has a 390 nm sensitivity of 450 ergs/cm2 at 90~ density and 1100 ergs/cm2 at 20~
density. Capsule C' has a 470 nm sensitivity of 550 ergs/cm2 at 90% density and 2300 ergs/cm2 at 10%
density. The sensitivity of the photosensitive material is between about 800 and 2300 ergs/cm2.
Example 5 A microencapsulated full color imaging system was prepared and evaluated as in Example 4 except as noted below.
Capsules A", B" and C" were prepared by following the encapsulation procedure set forth above using the following internal phase compositions:
Capsule A"
180 g - Photomer 4149 (from Diamond Shamrock) 16 g - Propylene Carbonate 24 g - Quanticure BMS
8 9 - Quanticure EPD
6 g - PIP+pF~ (Diphenyliodonium Hexafluoro-phosphate prepared from Crivello, J.V.; Lam, J.H.W., ~. POlym. Sci. Polym. Chem., 17 (1979), 977) 48 g - Copikem XX (Hilton Davis) 6 g - SF-50 12 g - N-100 2~j5~
MDX 017 P2 - 3~ -Caps~le B"
180 9 - Photomer 4149 16 g - Propylene Carbonate 4 9 - Quanticure ITX
8 g - Quanticure EPD
6 9 - PIP+PF~
24 9 - Experimental Cyan S-29663 6 g - Givsorb Uv-2 12 9 - N-lO0 Capsule C"
Same as C' in Example 4.
The internal phase was prepared by dissolving the monomer, photoinitiator and color former as in Example 4;
cooling the solution to room temperature and adding the " propylene carbonate having the PIP+PF6 dissolved therein; adding the isocyanates, mixing thoroughly for two minutes, and emulsifying.
The capsules were mixed to give neutral black when developed and coated on a support as in Example 4.
The spectral sensitivities of the capsules are plotted in Fig. 5. Capsule A" has a 350 nm sensitivity of 200 ergs/cm2 at gO% density and 500 ergs/cm2 at lO~
density. Capsule B" has a 390 nm sensitivity of 180 ergs/cm2 at 90% density and 380 ergs/cm2 at 10%
density. Capsule C" has a 470 nm sensitivity of 550 ergs/cm2 at 90% density and 2300 ergs/cm2 at 10%
density. Capsule C" did not include the diphenyliodonium hexafluorophosphate, which would make the system faster.
Had the capsules included the PIP~PF6, the speed at 470 nm would have been increased, but the sPeeds at 390 nm and 350 nm would also have been increased making color separation difficult. The sensitivity of the system, then, is between 380 and 2300 ergs/cm2.
s~
Having described the invention in detail and by reference to specific embodiments thereo, it ~ill be apparent that numerous modifications and variations are possible without departing from the spirit and scope of the invention defined by the following claims.
l~hat is ~laimed is:
i:
~ .
. .
Claims (23)
1. Photosensitive microcapsules useful in the formation of polychromatic images, said microcapsules including an internal phase containing a photosensitive composition having a spectral sensitivity range within which said composition hardens upon exposure to radiation, said microcapsules having associated therewith a color former and an absorber compound which reduces the sensitivity of said microcapsules to actinic radiation over a portion of said spectral sensitivity range.
2. The photosensitive microcapsules of claim 1 wherein said microcapsules include a discrete capsule wall.
3. The photosensitive microcapsules of claim 2 wherein said absorber compound is present in said internal phase with said photosensitive composition.
4. The photosensitive microcapsules of claim 3 wherein said photosensitive composition includes an ethylenically unsaturated compound and a photoinitiator.
5. The photosensitive microcapsules of claim 4 wherein said absorber compound is further characterized in that said compound does not substantially inhibit or Promote free radical initiated polymerization and said compound Possesses an extinction coefficient greater than 100/M cm.
6. The photosensitive microcapsules of claim 5 wherein said color former is present within said internal phase.
7. The photosensitive microcapsules of claim 6 wherein said color former is selected from the group consisting of a cyan, magenta and yellow color formers.
8. The photosensitive microcapsules of claim 7 wherein said photosensitive composition is sensitive to ultraviolet radiation.
9. The photosensitive microcapsules of claim 8 wherein said absorber absorbs ultraviolet radiation.
10. The photosensitive microcapsules of claim 9 wherein said absorber is selected from the group consisting of hydroxybenzophenones, hydroxyphenylbenzo-triazoles, and formamidines.
11. The photosensitive microcapsules of claim 7 wherein said photosensitive composition is sensitive to visible light.
12. A photosensitive material comprising a support having on the surface thereof a layer of photosensitive microcapsules, said photosensitive microcapsules including an internal phase containing a photosensitive composition having a spectral sensitivity range within which said composition hardens upon exposure to radiation, said microcapsules having associated therewith a color former and an absorber compound which reduces the sensitivity of said microcapsules to actinic radiation over a portion of said spectral sensitivity range.
13. The photosensitive material of claim 12 wherein said microcapsules include a discrete capsule wall.
14. The photosensitive material of claim 13 wherein said absorber compound is present in said internal phase with said photosensitive composition.
15. The photosensitive material of claim 14 wherein said photosensitive compositions include an ethylenically unsaturated compound and a photoinitiator.
16. The photosensitive material of claim 15 wherein said associated color former is present in said internal phases.
17. The photosensitive material of claim 16 wherein said absorber is further characterized in that said absorber does not substantially inhibit or promote free radical polymerization and said absorber possesses an extinction coefficient greater than 100/M cm.
18. The photosensitive material of claim 17 wherein said photosensitive microcapsules include a first set of microcapsules associated with a cyan color former and containing a first photohardenable composition, a second set of microcapsules associated with a magenta color former and containing a second photohardenable composition, and a third set of microcapsules associated with a yellow color former and containing a third photohardenable composition, at least one of said first, second and third sets of microcapsules having associated therewith an absorber which reduces the sensitivity of said microcapsules over a portion of the spectral sensitivity range of the encapsulated photohardenable composition such that said first, second and third sets of microcapsules have sufficiently different sensitivity characteristics that said first photohardenable composition can be hardened upon exposure of said first microcapsules to actinic radiation of a first wavelength without substantially hardening the encapsulated second and third photohardenable compositions, said second photohardenable composition can be hardened upon exposure of said second microcapsules to actinic radiation of a second wavelength without substantially hardening said encapsulated first and third photohardenable compositions, and said third photohardenable composition can be hardened upon exposure of said third microcapsules to actinic radiation of a third wavelength without substantially hardening said encapsulated first and second photohardenable compositions.
13. The photosensitive material of claim 18 wherein at least one of said first, second and third sets of microcapsules is sensitive to ultraviolet radiation.
20. The photosensitive material of claim 18 wherein at least one of said first, second and third photohardenable compositions is sensitive to blue light.
21. The photosensitive material of claim 20 wherein said absorber compound absorbs ultraviolet radiation.
22. The photosensitive material of claim 21 wherein said absorber compound is selected from the group consisting of hydroxybenzophenones, hydroxyphenylbenzo-triazoles, and formamidines.
23. A process for imaging which comprises image-wise exposing a photosensitive material comprising a support having on the surface thereof a layer of photosensitive microcapsules, said photosensitive microcapsules including an internal phase containing a photosensitive composition which hardens upon exposure to actinic radiation within its spectral sensitivity range, said microcapsules having associated therewith a color former and an absorber compound which reduces the sensitivity of said microcapsules to actinic radiation over a portion of said spectral sensitivity range;
subjecting said microcapsules to a force which causes said microcapsules to release said internal phase and thereby activate said color former; and contacting said released color former with a dry developer which reacts with said color former to form a color image.
subjecting said microcapsules to a force which causes said microcapsules to release said internal phase and thereby activate said color former; and contacting said released color former with a dry developer which reacts with said color former to form a color image.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/620,994 US4576891A (en) | 1984-06-15 | 1984-06-15 | Photosensitive microcapsules useful in polychromatic imaging having radiation absorber |
| US620,994 | 1984-06-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1262651A true CA1262651A (en) | 1989-11-07 |
Family
ID=24488287
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000477634A Expired CA1262651A (en) | 1984-06-15 | 1985-03-27 | Photosensitive microcapsules useful in polychromatic imaging |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4576891A (en) |
| EP (1) | EP0164931B1 (en) |
| JP (1) | JPS6124495A (en) |
| KR (1) | KR920005767B1 (en) |
| CA (1) | CA1262651A (en) |
| DE (1) | DE3579946D1 (en) |
| DK (1) | DK161269B (en) |
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-
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- 1985-03-27 CA CA000477634A patent/CA1262651A/en not_active Expired
- 1985-05-17 EP EP85303484A patent/EP0164931B1/en not_active Expired - Lifetime
- 1985-05-17 DE DE8585303484T patent/DE3579946D1/en not_active Expired - Lifetime
- 1985-06-13 DK DK268385A patent/DK161269B/en not_active Application Discontinuation
- 1985-06-14 KR KR1019850004194A patent/KR920005767B1/en active IP Right Grant
- 1985-06-15 JP JP13066585A patent/JPS6124495A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| KR860000581A (en) | 1986-01-29 |
| DK268385A (en) | 1985-12-16 |
| DE3579946D1 (en) | 1990-11-08 |
| EP0164931B1 (en) | 1990-10-03 |
| US4576891A (en) | 1986-03-18 |
| EP0164931A3 (en) | 1987-01-21 |
| DK161269B (en) | 1991-06-17 |
| KR920005767B1 (en) | 1992-07-18 |
| JPS6124495A (en) | 1986-02-03 |
| DK268385D0 (en) | 1985-06-13 |
| EP0164931A2 (en) | 1985-12-18 |
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Legal Events
| Date | Code | Title | Description |
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| MKLA | Lapsed |