CA2255871C - Moisture insensitive electroluminescent phosphor - Google Patents
Moisture insensitive electroluminescent phosphor Download PDFInfo
- Publication number
- CA2255871C CA2255871C CA002255871A CA2255871A CA2255871C CA 2255871 C CA2255871 C CA 2255871C CA 002255871 A CA002255871 A CA 002255871A CA 2255871 A CA2255871 A CA 2255871A CA 2255871 C CA2255871 C CA 2255871C
- Authority
- CA
- Canada
- Prior art keywords
- reaction vessel
- phosphor
- coating
- particles
- nitride
- 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 - Fee Related
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/02—Use of particular materials as binders, particle coatings or suspension media therefor
- C09K11/025—Use of particular materials as binders, particle coatings or suspension media therefor non-luminescent particle coatings or suspension media
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/58—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing copper, silver or gold
- C09K11/582—Chalcogenides
- C09K11/584—Chalcogenides with zinc or cadmium
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B33/00—Electroluminescent light sources
- H05B33/12—Light sources with substantially two-dimensional radiating surfaces
- H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
-
- 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.]
- Y10T428/2991—Coated
-
- 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.]
- Y10T428/2991—Coated
- Y10T428/2993—Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]
Abstract
A phosphor particle having thereon a conformal coating of aluminum nitride. By conformal coating is meant a coating that follows the surface contours of the individual particles. The method of making such phosphors comprises the steps of introducing an inert gas into a reaction vessel; charging phosphor particles into the reaction vessel;
heating the reaction vessel to a reaction temperature; introducing a nitride coating precursor into the reaction vessel; introducing a coreactant into the reaction vessel; and maintaining the inert gas flow, coreactant flow and precursor supply for a time sufficient to coat the phosphor particles. The nitride coated phosphor particles produced by this method have excellent efficacy ratings and strong luminance values in lamps after 100 hours use in high humidity (i.e., >95%).
heating the reaction vessel to a reaction temperature; introducing a nitride coating precursor into the reaction vessel; introducing a coreactant into the reaction vessel; and maintaining the inert gas flow, coreactant flow and precursor supply for a time sufficient to coat the phosphor particles. The nitride coated phosphor particles produced by this method have excellent efficacy ratings and strong luminance values in lamps after 100 hours use in high humidity (i.e., >95%).
Description
MOISTURE INSENSITIVE ELECTROLUMINESCENT PHOSPHOR
TECHNICAL FIELD
This invention relates to coated particles and more particularly to particles having a conformal coating thereon. More particularly, this invention relates to phosphors and still more particularly to electroluminescent phosphors having thereon a coating that protects the phosphor from moisture absorption and greatly increases the life and efficacy.
BACKGROUND ART
Coated phosphors are known from U.S. Patent Nos. 4,585,673; 4,825,124;
5,080,928;
5,118,529; 5,156,885; 5,220,243; 5.244, 750; and 5,418,062. It is known from some of the just-mentioned patents that a coating precursor and oxygen can be used to apply a protective coating. See, for example, U.S. Patent Nos. 5,244,750 and 4,585,673. The coating processes in several of the others of these patents employ chemical vapor deposition to apply a protective coating by hydrolysis. It also has been reported that chemical vapor deposition, at atmospheric pressure, can be used to deposit thin films of aluminum nitride coatings from hexakis(dimethylamido)dialuminum and ammonia precursors upon silicon, vitreous carbon and glass substrates. S~e, for example, "Atmospheric pressure chemical vapor deposition of aluminum nitride films at °C", Cordon, et al., Journal Material Resources. Vol. 6, No. 1, Jan.
1991; and "Chemical vapor deposition of aluminum nitride thin films", Cordon, et al., Journal Material Resources, Vol. 7, No. 7, Jul. 1992. It would be an advance in the art if a coating process could be developed that operated in the absence of water or water vapor. It would be a further advance in the art to increase the efficacy and the life of such coated phosphors. It would be a still further advance in the art to provide a coating and process that did not rely upon oxygen. It would be a still further advance in the art to provide an electroluminescent phosphor with an alurninurrt nitride coating.
DISCLOSURE OF INVENTION
It is, therefore, an object of the invention to obviate the disadvantages of the prior art.
It is another object of the invention to enhance the operation of coated phosphors.
Yet another object of the invention is the provision of a phosphor coating method that does not employ water or water vapor, or oxygen.
These objects are accomplished, in one aspect of the invention, by the provision of a phosphor particle having thereon a conformal coating of aluminum nitride. By conformal coating is meant a coating that follows the surface contours of the individual particles.
The objects are further accomplished in a process of applying a moisture resistant nitride coating to particles of electroluminescent phcasphor, the steps comprising:
introducing an inert gas into a reaction vessel that is charged with phosphor particles; heating said reaction vessel to a reaction temperature; introducing a nitride coating precursor into said reaction vessel;
introducing a coreactant into said reaction vessel; and maintaining said inert gas flow, coreactant flow and precursor supply for a time sufficient to coat said phosphor particles with said moisture resistant nitride.
The invention also provides a process of applying a moisture resistant nitride coating to particles of electroluminescent phosphor, the steps comprising fluidizing phosphor particles in a reaction vessel with an inert gas; heating said reaction vessel to a reaction temperature;
introducing a nitride coating precursor into said reaction vessel; introducing a c.oreactant into said reaction vessel; and maintaining said inert gas Claw, coreactant flow and precursor supply for a time sufficient to coat said phosphor particles with said moisture resistant nitride.
The nitride coated phosphor particles produced by this method had excellent efficacy ratings and strong luminance values in lamps after 100 hours use in high humidity (i.e., >95%).
In particular, the particles of phosphor preferably have a coating thickness >
2000A and the electroluminescent lamps containing the coated phosphor particles preferably have a luminance of greater than l7fL after 100 hours exposure in a relative humidity of > 95 % .
In another aspect, the electroluminescent lamp containing the phosphor having the nitride coating, after 100 hours of operation in an environment of > 95 % relative humidity, has a luminance greater than four times that of a similar lamp employing the same phosphor without the nitride coating.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a graph of the precursor transport rate vs. reciprocal temperature;
Fig. 2 is a graph of the same data expressed as a vapor pressure curve; and Fig. 3 is a graph of the precursor transport rate vs. the flow rate of the carrier gas.
4a BEST MODE FOR CARRYING OUT THE INVENTION
S For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above-described drawings.
In a preferred embodiment of the invention the coating reaction was carried out in a gas-fluidized bed reaction vessel that comprised a one inch O.D. (2.54 crn) glass tube with a coarse porosity, fitted glass disk as the gas distributor. The phosphor employed was a Type 723 electroluminescent phosphor (ZnS:C'uj available from Osram Sylvania Inc., Towanda PA and the phosphor was fluidized by the injection of an inert gas such as nitrogen.
The nitride coatings (which can contain amounts of hydrogen as well as the aluminum nitride) were formed via the reaction of ammonia with hexakis(dimethylamido)dialuminum(A12(N(CH3)z)~).
The aluminum nitride precursor was obtained from Strem Chemicals, Newburyport, MA, and contained within a stainless steel bubbler. The bubbler was maintained at 100°C and the precursor was transported to the reaction vessel by a carrier of purified nitrogen. The precursor-entrained nitrogen was flowed upwards through the fitted glass distributor through lines that were maintained 20 to 30°C above the temperature of the bubbler.
Preferably, the precursor is earned from the supply to the reaction vessel by purified utrogen gas through lines maintained at a temperature of from about 130 to about 140°C'. The anhydrous ammonia coreactant, which was obtained from Matheson Chemicals, Gloucester, MA, was passed through a Unit mass flow controller prior to entering the fluidized bed via a central glass tube having a fritted glass tip. The ammonia was diluted with purified nitrogen prior to entering the bed. Additionally, the nitrogen carrier was purified by passing through a Centorr purifier followed by a Matheson Nanochem gas purifier. The ammonia, also, was passed through a Nanochem purifier.
The gas handling system was constructed from stainless steel tubing and fittings. Glass-to-metal seals were employed between the glass reactor parts and the gas lines.
Four coating runs were made on a well-sealed system. The phosphor weight was grams and the bubbler temperature was 110°C in each run. The coating temperatures (i.e., the reaction vessel temperature), times and gas flows are shown in Table I.
Table I
N2 CarrierNH3 N2 Diluent Run No. Temp. (C) Time (hours)Flow (sccm)Flow (sccm)Flow (sccm) L250312 200 4.5 1000 200 300 L2503-13 150 5.0 500 100 150 L2503-14 150 20.0 250 200 100 L2503-16 225 12 500 ~ 100 ~ 150 Prior to the coating runs, the vapor pressure of the nitride precursor was determined at temperatures between 95 and 120°C via transport measurements using as a carrier gas highly purified nitrogen flowing at 1000 sccm. Then, with a 100°C
bubbler temperature, the transport rate was determined with Garner flows ranging between 10 and 1000 sccm. The results are shown in Fig. 1. Fig. 2 contains the same data expressed as a vapor pressure curve. The transport data obtained as a function of carrier flow with a 100°C bubbler temperature are shown in Fig. 3. The Figs.
illustrate that the vapor pressures are high enough to make the use of a bubbler a practical means of delivering the chemical to the fluidized bed reaction vessel. The linearity of the transport data versus the flow curve, over two orders of magnitude (between 10 and 1000 sccm N2), also indicates the suitability of this mode of precursor delivery.
The aluminum content, expressed as a percentage of total sample weight (%Al), B.E.T.
surface area (S.A.(m2/gm)), percent coverage (% coverage) from Electron Spectroscopy for Chemical Analysis (ESCA) and approximate coating thickness, from Sputtered Neutral Mass Spectroscopy (SNMS) measurements vs. Si02 as a reference material, are shown in Table II.
Table II
Run No. % Al S.A. (m /g) % Coverage 'Thickness L2503-12 2.9 0.07 99 2700 L2503-13 1.5 0.05 98 800 L2503-14 2.5 0.06 99 2200 L2503-16 3.3 0.05 100 4300 Comparing the data in Tables 1 and 2 and Fig. 1, it will be seen that substantially all of the precursor reacts within the fluidized bed to form a coating which covers practically all of the phosphor particles. X-ray photoelectron spectroscopy (XPS) surface analysis shows a relatively high surface oxygen concentration, a result that is in agreement with the well known surface reactivity of CVD-deposited aluminum nitride. However, SNMS analyses of the coated phosphors has indicated no apparent correlation between the relatively low oxygen signal levels and those of Zn, S, Al, and N, suggesting a relatively constant oxygen background that is not specifically associated with the aluminum nitride coating. Further, as shown in Table III, EDS analyses indicated relative oxygen concentrations comparable to that found in a sample of pure A1N.
Table III
Atomic Composition From EDS
(%) _ ~
Run No. A1 N O Zn S
L2503-12 16 71 5.1 4.3 2.6 L2503-14 18 70 3.6 4.5 3.3 L2503-16 20 70 ~ 2.8 4.1 1.8 Pure A1N 28 67 ~ 4.8 -__- -___ Electroluminescent lamps were made containing uncoated phosphor as well as coated phosphors from each of the Kuns. The lamps were packaged in Mylar TM, a water permeable material, so that the moisture sensitivity of the various materials could be determined and compared. Identical lamps were operated at 100V and 400Hz in two environments; with less than 1 U % relative humidity and with more than 9S %
relative humidity. The efficacy (in lumens per watt) was also determined. These results are summarized in Table IV.
Table IV
Luminance Luminance (fL) (fL) with with Efficacy <10% >95%
R.H. R.H.
Run No. (Lumens/Vl~0 hr. 0 hr.
hr. hr.
100 100hr.
hr.
L2503-12 5.26 22.6 22.0 20.0 23.0 23.6 17.6 L2503-13 4.23 26.0 24.9 2 26.2 26.4 6.1 2.0 L2503-14 4.26 22.6 22.1 _ 22.4 21.9 17.5 19.4 L2503-16 5.90 22.8 21.7 19.5 22.9 23.5 21.9 Uncoated 1.75 29.9 31.6 24.9 30.5 10.0 3.7 The lamp performance data clearly show the advantages of the aluminum nitride coating when pxoperly applied. The comparison with the uncoated phosphor, whose performance falls off drastically in a humid environment after 100 hours, and that of the adequately coated materials, such as L2503-12, L2503-14 and L2503-16, is readily apparent. Even a coated material (L2503-1.3) without an adequate cover (note from Table II that this latter material has only 98°/. coverage and a thickness of 80D A) does not fare well in the harsh environment.
g Accordingly, there is here provided an electroluminescent phosphor that has good efficacy, long life and a suitability for use in a humid environment.
While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.
TECHNICAL FIELD
This invention relates to coated particles and more particularly to particles having a conformal coating thereon. More particularly, this invention relates to phosphors and still more particularly to electroluminescent phosphors having thereon a coating that protects the phosphor from moisture absorption and greatly increases the life and efficacy.
BACKGROUND ART
Coated phosphors are known from U.S. Patent Nos. 4,585,673; 4,825,124;
5,080,928;
5,118,529; 5,156,885; 5,220,243; 5.244, 750; and 5,418,062. It is known from some of the just-mentioned patents that a coating precursor and oxygen can be used to apply a protective coating. See, for example, U.S. Patent Nos. 5,244,750 and 4,585,673. The coating processes in several of the others of these patents employ chemical vapor deposition to apply a protective coating by hydrolysis. It also has been reported that chemical vapor deposition, at atmospheric pressure, can be used to deposit thin films of aluminum nitride coatings from hexakis(dimethylamido)dialuminum and ammonia precursors upon silicon, vitreous carbon and glass substrates. S~e, for example, "Atmospheric pressure chemical vapor deposition of aluminum nitride films at °C", Cordon, et al., Journal Material Resources. Vol. 6, No. 1, Jan.
1991; and "Chemical vapor deposition of aluminum nitride thin films", Cordon, et al., Journal Material Resources, Vol. 7, No. 7, Jul. 1992. It would be an advance in the art if a coating process could be developed that operated in the absence of water or water vapor. It would be a further advance in the art to increase the efficacy and the life of such coated phosphors. It would be a still further advance in the art to provide a coating and process that did not rely upon oxygen. It would be a still further advance in the art to provide an electroluminescent phosphor with an alurninurrt nitride coating.
DISCLOSURE OF INVENTION
It is, therefore, an object of the invention to obviate the disadvantages of the prior art.
It is another object of the invention to enhance the operation of coated phosphors.
Yet another object of the invention is the provision of a phosphor coating method that does not employ water or water vapor, or oxygen.
These objects are accomplished, in one aspect of the invention, by the provision of a phosphor particle having thereon a conformal coating of aluminum nitride. By conformal coating is meant a coating that follows the surface contours of the individual particles.
The objects are further accomplished in a process of applying a moisture resistant nitride coating to particles of electroluminescent phcasphor, the steps comprising:
introducing an inert gas into a reaction vessel that is charged with phosphor particles; heating said reaction vessel to a reaction temperature; introducing a nitride coating precursor into said reaction vessel;
introducing a coreactant into said reaction vessel; and maintaining said inert gas flow, coreactant flow and precursor supply for a time sufficient to coat said phosphor particles with said moisture resistant nitride.
The invention also provides a process of applying a moisture resistant nitride coating to particles of electroluminescent phosphor, the steps comprising fluidizing phosphor particles in a reaction vessel with an inert gas; heating said reaction vessel to a reaction temperature;
introducing a nitride coating precursor into said reaction vessel; introducing a c.oreactant into said reaction vessel; and maintaining said inert gas Claw, coreactant flow and precursor supply for a time sufficient to coat said phosphor particles with said moisture resistant nitride.
The nitride coated phosphor particles produced by this method had excellent efficacy ratings and strong luminance values in lamps after 100 hours use in high humidity (i.e., >95%).
In particular, the particles of phosphor preferably have a coating thickness >
2000A and the electroluminescent lamps containing the coated phosphor particles preferably have a luminance of greater than l7fL after 100 hours exposure in a relative humidity of > 95 % .
In another aspect, the electroluminescent lamp containing the phosphor having the nitride coating, after 100 hours of operation in an environment of > 95 % relative humidity, has a luminance greater than four times that of a similar lamp employing the same phosphor without the nitride coating.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a graph of the precursor transport rate vs. reciprocal temperature;
Fig. 2 is a graph of the same data expressed as a vapor pressure curve; and Fig. 3 is a graph of the precursor transport rate vs. the flow rate of the carrier gas.
4a BEST MODE FOR CARRYING OUT THE INVENTION
S For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above-described drawings.
In a preferred embodiment of the invention the coating reaction was carried out in a gas-fluidized bed reaction vessel that comprised a one inch O.D. (2.54 crn) glass tube with a coarse porosity, fitted glass disk as the gas distributor. The phosphor employed was a Type 723 electroluminescent phosphor (ZnS:C'uj available from Osram Sylvania Inc., Towanda PA and the phosphor was fluidized by the injection of an inert gas such as nitrogen.
The nitride coatings (which can contain amounts of hydrogen as well as the aluminum nitride) were formed via the reaction of ammonia with hexakis(dimethylamido)dialuminum(A12(N(CH3)z)~).
The aluminum nitride precursor was obtained from Strem Chemicals, Newburyport, MA, and contained within a stainless steel bubbler. The bubbler was maintained at 100°C and the precursor was transported to the reaction vessel by a carrier of purified nitrogen. The precursor-entrained nitrogen was flowed upwards through the fitted glass distributor through lines that were maintained 20 to 30°C above the temperature of the bubbler.
Preferably, the precursor is earned from the supply to the reaction vessel by purified utrogen gas through lines maintained at a temperature of from about 130 to about 140°C'. The anhydrous ammonia coreactant, which was obtained from Matheson Chemicals, Gloucester, MA, was passed through a Unit mass flow controller prior to entering the fluidized bed via a central glass tube having a fritted glass tip. The ammonia was diluted with purified nitrogen prior to entering the bed. Additionally, the nitrogen carrier was purified by passing through a Centorr purifier followed by a Matheson Nanochem gas purifier. The ammonia, also, was passed through a Nanochem purifier.
The gas handling system was constructed from stainless steel tubing and fittings. Glass-to-metal seals were employed between the glass reactor parts and the gas lines.
Four coating runs were made on a well-sealed system. The phosphor weight was grams and the bubbler temperature was 110°C in each run. The coating temperatures (i.e., the reaction vessel temperature), times and gas flows are shown in Table I.
Table I
N2 CarrierNH3 N2 Diluent Run No. Temp. (C) Time (hours)Flow (sccm)Flow (sccm)Flow (sccm) L250312 200 4.5 1000 200 300 L2503-13 150 5.0 500 100 150 L2503-14 150 20.0 250 200 100 L2503-16 225 12 500 ~ 100 ~ 150 Prior to the coating runs, the vapor pressure of the nitride precursor was determined at temperatures between 95 and 120°C via transport measurements using as a carrier gas highly purified nitrogen flowing at 1000 sccm. Then, with a 100°C
bubbler temperature, the transport rate was determined with Garner flows ranging between 10 and 1000 sccm. The results are shown in Fig. 1. Fig. 2 contains the same data expressed as a vapor pressure curve. The transport data obtained as a function of carrier flow with a 100°C bubbler temperature are shown in Fig. 3. The Figs.
illustrate that the vapor pressures are high enough to make the use of a bubbler a practical means of delivering the chemical to the fluidized bed reaction vessel. The linearity of the transport data versus the flow curve, over two orders of magnitude (between 10 and 1000 sccm N2), also indicates the suitability of this mode of precursor delivery.
The aluminum content, expressed as a percentage of total sample weight (%Al), B.E.T.
surface area (S.A.(m2/gm)), percent coverage (% coverage) from Electron Spectroscopy for Chemical Analysis (ESCA) and approximate coating thickness, from Sputtered Neutral Mass Spectroscopy (SNMS) measurements vs. Si02 as a reference material, are shown in Table II.
Table II
Run No. % Al S.A. (m /g) % Coverage 'Thickness L2503-12 2.9 0.07 99 2700 L2503-13 1.5 0.05 98 800 L2503-14 2.5 0.06 99 2200 L2503-16 3.3 0.05 100 4300 Comparing the data in Tables 1 and 2 and Fig. 1, it will be seen that substantially all of the precursor reacts within the fluidized bed to form a coating which covers practically all of the phosphor particles. X-ray photoelectron spectroscopy (XPS) surface analysis shows a relatively high surface oxygen concentration, a result that is in agreement with the well known surface reactivity of CVD-deposited aluminum nitride. However, SNMS analyses of the coated phosphors has indicated no apparent correlation between the relatively low oxygen signal levels and those of Zn, S, Al, and N, suggesting a relatively constant oxygen background that is not specifically associated with the aluminum nitride coating. Further, as shown in Table III, EDS analyses indicated relative oxygen concentrations comparable to that found in a sample of pure A1N.
Table III
Atomic Composition From EDS
(%) _ ~
Run No. A1 N O Zn S
L2503-12 16 71 5.1 4.3 2.6 L2503-14 18 70 3.6 4.5 3.3 L2503-16 20 70 ~ 2.8 4.1 1.8 Pure A1N 28 67 ~ 4.8 -__- -___ Electroluminescent lamps were made containing uncoated phosphor as well as coated phosphors from each of the Kuns. The lamps were packaged in Mylar TM, a water permeable material, so that the moisture sensitivity of the various materials could be determined and compared. Identical lamps were operated at 100V and 400Hz in two environments; with less than 1 U % relative humidity and with more than 9S %
relative humidity. The efficacy (in lumens per watt) was also determined. These results are summarized in Table IV.
Table IV
Luminance Luminance (fL) (fL) with with Efficacy <10% >95%
R.H. R.H.
Run No. (Lumens/Vl~0 hr. 0 hr.
hr. hr.
100 100hr.
hr.
L2503-12 5.26 22.6 22.0 20.0 23.0 23.6 17.6 L2503-13 4.23 26.0 24.9 2 26.2 26.4 6.1 2.0 L2503-14 4.26 22.6 22.1 _ 22.4 21.9 17.5 19.4 L2503-16 5.90 22.8 21.7 19.5 22.9 23.5 21.9 Uncoated 1.75 29.9 31.6 24.9 30.5 10.0 3.7 The lamp performance data clearly show the advantages of the aluminum nitride coating when pxoperly applied. The comparison with the uncoated phosphor, whose performance falls off drastically in a humid environment after 100 hours, and that of the adequately coated materials, such as L2503-12, L2503-14 and L2503-16, is readily apparent. Even a coated material (L2503-1.3) without an adequate cover (note from Table II that this latter material has only 98°/. coverage and a thickness of 80D A) does not fare well in the harsh environment.
g Accordingly, there is here provided an electroluminescent phosphor that has good efficacy, long life and a suitability for use in a humid environment.
While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.
Claims (13)
1. An electroluminescent phosphor comprised of particles, each of which has thereon a conformal coating of aluminum nitride.
2. An electroluminescent lamp containing a light source resistant to moisture, said light source comprising the electroluminescent phosphor of Claim 1.
3. The lamp of Claim 2 wherein said lamp has a luminance of greater than 17fL
after 100 hours exposure in a relative humidity of > 95%.
after 100 hours exposure in a relative humidity of > 95%.
4. The lamp of Claim 3 wherein the particles of said phosphor have a coating thickness of > 2000.ANG..
5. In a process of applying a moisture resistant nitride coating to particles of electroluminescent phosphor, the steps comprising: introducing an inert gas into a reaction vessel that is charged with phosphor particles; heating said reaction vessel to a reaction temperature; introducing a nitride coating precursor into said reaction vessel;
introducing a coreactant into said reaction vessel; and maintaining said inert gas flow, coreactant flow and precursor supply for a time sufficient to coat said phosphor particles with said moisture resistant nitride.
introducing a coreactant into said reaction vessel; and maintaining said inert gas flow, coreactant flow and precursor supply for a time sufficient to coat said phosphor particles with said moisture resistant nitride.
6. The process of Claim 5 wherein said nitride coating precursor is hexakis(dimethylamido)dialuminum and said coating is aluminum nitride.
7. The process of Claim 6 wherein said coreactant is anhydrous ammonia.
8. The process of Claim 7 wherein said precursor is carried from a supply thereof which is maintained at about 100°C.
9. The process of Claim 8 wherein said precursor is carried from said supply to said reaction vessel by purified nitrogen gas through lines maintained at a temperature of from about 130 to about 140°C.
10. The process of Claim 9 wherein said anhydrous ammonia is diluted with purified nitrogen prior to entering the reaction vessel.
11. In a process of applying a moisture resistant nitride coating to particles of electroluminescent phosphor, the steps comprising: fluidizing phosphor particles in a reaction vessel with an inert gas; heating said reaction vessel to a reaction temperature;
introduing a nitride coating precursor into said reaction vessel; introduing a coreactant into said reaction vessel; and maintaining said inert gas flow, coreactant flow and precursor supply for a time sufficient to coat said phosphor particles with said moisture resistant nitride.
introduing a nitride coating precursor into said reaction vessel; introduing a coreactant into said reaction vessel; and maintaining said inert gas flow, coreactant flow and precursor supply for a time sufficient to coat said phosphor particles with said moisture resistant nitride.
12. An electroluminescent lamp containing therein a coated electroluminescent phosphor having thereon a nitride coating, said lamp having a luminance, after 100 hours of operation in an environment of > 95% relative humidity, greater than 4 times that of a similar lamp employing the same phosphor without said nitride coating.
13. An electroluminscent phosphor comprised of particles each of which has thereon a coating produced by the method of Claim 7.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US7251098P | 1998-01-12 | 1998-01-12 | |
| US60/072,510 | 1998-01-12 | ||
| US09/175,787 | 1998-10-20 | ||
| US09/175,787 US6064150A (en) | 1998-01-12 | 1998-10-20 | Nitride coated particle and composition of matter comprised of such particles |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2255871A1 CA2255871A1 (en) | 1999-07-12 |
| CA2255871C true CA2255871C (en) | 2003-10-07 |
Family
ID=26753443
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002255871A Expired - Fee Related CA2255871C (en) | 1998-01-12 | 1998-12-07 | Moisture insensitive electroluminescent phosphor |
Country Status (7)
| Country | Link |
|---|---|
| US (3) | US6064150A (en) |
| EP (1) | EP0928826B1 (en) |
| JP (1) | JPH11260557A (en) |
| KR (1) | KR100306356B1 (en) |
| CN (1) | CN1121471C (en) |
| CA (1) | CA2255871C (en) |
| DE (1) | DE69904246T2 (en) |
Families Citing this family (34)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6064150A (en) * | 1998-01-12 | 2000-05-16 | Osram Sylvania Inc. | Nitride coated particle and composition of matter comprised of such particles |
| US6458512B1 (en) * | 1998-10-13 | 2002-10-01 | 3M Innovative Properties Company | Oxynitride encapsulated electroluminescent phosphor particles |
| US6171650B1 (en) * | 1999-09-28 | 2001-01-09 | Osram Sylvania Inc. | Moisture insensitive electroluminescent phosphor |
| WO2001086716A1 (en) * | 2000-05-12 | 2001-11-15 | Matsushita Electric Industrial Co., Ltd. | Semiconductor device mounting circuit board, method of producing the same, and method of producing mounting structure using the same |
| US6733826B2 (en) * | 2000-12-18 | 2004-05-11 | Osram Sylvania Inc. | Method and apparatus for coating electroluminescent phosphors |
| US6562260B2 (en) | 2000-12-18 | 2003-05-13 | Osram Sylvania Inc. | Recovery of electroluminescsent phosphor from encapsulated material |
| US6569357B2 (en) * | 2000-12-18 | 2003-05-27 | Osram Sylvania Inc. | Method of making electroluminescent phosphor |
| US7001665B2 (en) * | 2001-04-06 | 2006-02-21 | Osram Sylvania Inc. | Electroluminescent phosphor with plural moisture resistant coatings thereon |
| JP4114331B2 (en) * | 2001-06-15 | 2008-07-09 | 豊田合成株式会社 | Light emitting device |
| US6602547B2 (en) * | 2001-09-27 | 2003-08-05 | Osram Sylvania Inc. | Method of coating particles by vapor deposition |
| US6562460B1 (en) | 2001-11-20 | 2003-05-13 | Encap Technologies, Llc | Microencapsulated particles and process for manufacturing same |
| US6833191B2 (en) * | 2001-11-20 | 2004-12-21 | Encap Technologies, Llc | Microencapsulated particles and process for manufacturing same |
| KR100507463B1 (en) * | 2002-01-25 | 2005-08-10 | 한국전자통신연구원 | Flat panel display and method for forming a passivation layer in flat panel display |
| US6734466B2 (en) * | 2002-03-05 | 2004-05-11 | Agilent Technologies, Inc. | Coated phosphor filler and a method of forming the coated phosphor filler |
| US7358658B2 (en) * | 2002-03-08 | 2008-04-15 | Chien-Min Sung | Amorphous diamond materials and associated methods for the use and manufacture thereof |
| US20070126312A1 (en) * | 2002-03-08 | 2007-06-07 | Chien-Min Sung | DLC field emission with nano-diamond impregnated metals |
| US7235912B2 (en) * | 2002-03-08 | 2007-06-26 | Chien-Min Sung | Diamond-like carbon thermoelectric conversion devices and methods for the use and manufacture thereof |
| US6899958B2 (en) | 2002-06-21 | 2005-05-31 | Encap Technologies, Llc. | Moisture barrier resins |
| JP4529349B2 (en) * | 2002-11-08 | 2010-08-25 | 日亜化学工業株式会社 | Nitride-based phosphor and light emitting device |
| KR20050089971A (en) * | 2002-12-20 | 2005-09-09 | 이화이어 테크놀로지 코포레이션 | Aluminum nitride passivated phosphors for electroluminescent displays |
| DE10326645A1 (en) * | 2003-06-11 | 2005-01-13 | Bundesdruckerei Gmbh | Value document with a security element and method for producing the value document |
| US20050126446A1 (en) * | 2003-12-10 | 2005-06-16 | Nobles Joe A. | Table-mounted screen apparatus |
| US7157845B2 (en) * | 2004-09-29 | 2007-01-02 | Osram Sylvania Inc | Single-component yellow-emitting electroluminescent phosphor |
| US8278816B2 (en) * | 2004-09-30 | 2012-10-02 | Global Tungsten & Powders Corp. | High CRI electroluminescent lamp |
| US7452483B2 (en) * | 2004-09-30 | 2008-11-18 | Global Tungsten & Powders Corp. | Yellow-emitting phosphor blend for electroluminescent lamps |
| US7749405B2 (en) * | 2004-09-30 | 2010-07-06 | Global Tungsten & Powders Corp. | White-emitting phosphor blend and electroluminescent lamp containing same |
| US7989064B2 (en) * | 2005-01-24 | 2011-08-02 | Global Tungsten & Powders Corp. | Ceramic-coated tungsten powder |
| US7288216B2 (en) * | 2005-03-30 | 2007-10-30 | Osram Sylvania Inc. | Method of making electroluminescent phosphors with small particle sizes and powder with D50 value of no more than 10 micrometers |
| US7291291B2 (en) * | 2005-03-30 | 2007-11-06 | Osram Sylvania Inc. | Electroluminescent phosphor powder with D50 value of less than 12 μm and method of making |
| US20070096635A1 (en) * | 2005-11-03 | 2007-05-03 | Osram Sylvania Inc. | Long-Afterglow Electroluminescent Lamp |
| US7833437B2 (en) * | 2006-01-26 | 2010-11-16 | Global Tungsten & Powders Corp. | Moisture-resistant electroluminescent phosphor with high initial brightness and method of making |
| US8298666B2 (en) * | 2006-01-26 | 2012-10-30 | Global Tungsten & Powders Corp. | Moisture resistant electroluminescent phosphor with high initial brightness and method of making |
| DE102013114496A1 (en) | 2013-12-19 | 2015-06-25 | Bundesdruckerei Gmbh | Zinc sulfide phosphor with photo and electroluminescent behavior, process for its preparation and security document, security feature and method for its detection |
| US10174242B1 (en) * | 2018-05-17 | 2019-01-08 | Eie Materials, Inc. | Coated thioaluminate phosphor particles |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4585673A (en) * | 1984-05-07 | 1986-04-29 | Gte Laboratories Incorporated | Method for coating phosphor particles |
| US4825124A (en) * | 1984-05-07 | 1989-04-25 | Gte Laboratories Incorporated | Phosphor particle, fluorescent lamp, and manufacturing method |
| JPH02113085A (en) * | 1988-10-21 | 1990-04-25 | Nichia Chem Ind Ltd | Fluorescent substance for el panel |
| US5139825A (en) * | 1989-11-30 | 1992-08-18 | President And Fellows Of Harvard College | Process for chemical vapor deposition of transition metal nitrides |
| US5178911A (en) * | 1989-11-30 | 1993-01-12 | The President And Fellows Of Harvard College | Process for chemical vapor deposition of main group metal nitrides |
| US5156885A (en) * | 1990-04-25 | 1992-10-20 | Minnesota Mining And Manufacturing Company | Method for encapsulating electroluminescent phosphor particles |
| US5118529A (en) | 1990-06-18 | 1992-06-02 | Gte Laboratories Incorporated | Process for coating finely divided material with titania |
| US5220243A (en) * | 1990-10-05 | 1993-06-15 | Gte Products Corporation | Moisture insensitive zinc sulfide electroluminescent materials and an electroluminescent device made therefrom |
| US5080928A (en) * | 1990-10-05 | 1992-01-14 | Gte Laboratories Incorporated | Method for making moisture insensitive zinc sulfide based luminescent materials |
| US5126166A (en) * | 1990-12-21 | 1992-06-30 | Gte Products Corporation | Method of reducing the degradation of the red phosphor, Y203:EU, in water base lamp suspensions |
| JPH0559357A (en) * | 1991-09-03 | 1993-03-09 | Nichia Chem Ind Ltd | Fluorescent substance having surface treated with boron nitride |
| JPH09104863A (en) * | 1995-10-12 | 1997-04-22 | Nec Kansai Ltd | Covered fluorescent body, covering treatment of fluorescent body and electric field light emitting lamp using the same |
| JP2950240B2 (en) * | 1996-06-24 | 1999-09-20 | 関西日本電気株式会社 | Electroluminescent lamp |
| US6064150A (en) * | 1998-01-12 | 2000-05-16 | Osram Sylvania Inc. | Nitride coated particle and composition of matter comprised of such particles |
| US6171650B1 (en) * | 1999-09-28 | 2001-01-09 | Osram Sylvania Inc. | Moisture insensitive electroluminescent phosphor |
-
1998
- 1998-10-20 US US09/175,787 patent/US6064150A/en not_active Expired - Lifetime
- 1998-12-07 CA CA002255871A patent/CA2255871C/en not_active Expired - Fee Related
-
1999
- 1999-01-11 JP JP11003834A patent/JPH11260557A/en active Pending
- 1999-01-11 KR KR1019990000404A patent/KR100306356B1/en not_active IP Right Cessation
- 1999-01-12 CN CN99101071A patent/CN1121471C/en not_active Expired - Fee Related
- 1999-01-12 DE DE69904246T patent/DE69904246T2/en not_active Expired - Lifetime
- 1999-01-12 EP EP99100500A patent/EP0928826B1/en not_active Expired - Lifetime
- 1999-03-29 US US09/277,875 patent/US6456002B1/en not_active Expired - Lifetime
-
2001
- 2001-05-18 US US09/861,190 patent/US6509058B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0928826A1 (en) | 1999-07-14 |
| US6064150A (en) | 2000-05-16 |
| US20020011781A1 (en) | 2002-01-31 |
| US6509058B2 (en) | 2003-01-21 |
| KR100306356B1 (en) | 2001-09-24 |
| KR19990067828A (en) | 1999-08-25 |
| US6456002B1 (en) | 2002-09-24 |
| CA2255871A1 (en) | 1999-07-12 |
| EP0928826B1 (en) | 2002-12-04 |
| CN1121471C (en) | 2003-09-17 |
| DE69904246D1 (en) | 2003-01-16 |
| JPH11260557A (en) | 1999-09-24 |
| DE69904246T2 (en) | 2003-04-17 |
| CN1227862A (en) | 1999-09-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2255871C (en) | Moisture insensitive electroluminescent phosphor | |
| JP4795501B2 (en) | Electroluminescent phosphor particles encapsulated with a multi-oxide coating based on aluminum oxide | |
| CN101360803B (en) | Moisture-resistant electroluminescent phosphor with high initial brightness and method of making | |
| JP4515634B2 (en) | Oxynitride encapsulated electroluminescent phosphor particles, production method and use | |
| JP2002527569A5 (en) | ||
| US8298666B2 (en) | Moisture resistant electroluminescent phosphor with high initial brightness and method of making | |
| US7001665B2 (en) | Electroluminescent phosphor with plural moisture resistant coatings thereon | |
| US6171650B1 (en) | Moisture insensitive electroluminescent phosphor | |
| US6426115B1 (en) | Method for making high-efficacy and long life electroluminescent phosphor | |
| JPS6222394A (en) | Making of film of manganese-containing zinc sulfide | |
| CN1366016A (en) | Stabilization of colour in heated inorganic electroluminescence material |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |