U.S. patent application number 10/851298 was filed with the patent office on 2004-10-28 for electroluminescent phosphor with plural moisture resistant coatings thereon.
Invention is credited to Klinedinst, Keith A..
Application Number | 20040214501 10/851298 |
Document ID | / |
Family ID | 26813420 |
Filed Date | 2004-10-28 |
United States Patent
Application |
20040214501 |
Kind Code |
A1 |
Klinedinst, Keith A. |
October 28, 2004 |
Electroluminescent phosphor with plural moisture resistant coatings
thereon
Abstract
A moisture-resistant electroluminescent phosphor is provided
wherein the individual phosphor particles have a first coating of
an inorganic moisture-resistant coating and a second coating of an
organic moisture-resistant coating. The process for making the
moisture-resistant phosphor comprises applying a first layer of an
inorganic moisture-resistant coating to individual particles of an
electroluminescent phosphor to form a first-coated phosphor,
substantially isolating said first-coated phosphor from contact
with atmospheric oxygen and moisture, and applying a second layer
of an organic moisture-resistant coating to the first-coated
phosphor to form a second-coated phosphor.
Inventors: |
Klinedinst, Keith A.;
(Hudson, MA) |
Correspondence
Address: |
OSRAM SYLVANIA INC
100 ENDICOTT STREET
DANVERS
MA
01923
US
|
Family ID: |
26813420 |
Appl. No.: |
10/851298 |
Filed: |
May 21, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10851298 |
May 21, 2004 |
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10115645 |
Apr 3, 2002 |
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60282391 |
Apr 6, 2001 |
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Current U.S.
Class: |
445/24 ;
427/66 |
Current CPC
Class: |
Y10T 428/2998 20150115;
C09K 11/025 20130101; C09K 11/584 20130101; Y10T 428/2991
20150115 |
Class at
Publication: |
445/024 ;
427/066 |
International
Class: |
H01J 009/00; B05D
005/12 |
Claims
1. A process for providing a moisture-resistant electroluminescent
phosphor comprising the steps of: applying a first layer of an
inorganic moisture-resistant coating to individual particles of a
phosphor to form a first-coated phosphor, substantially isolating
said first-coated phosphor from contact with atmospheric oxygen and
moisture; and applying a second layer of an organic
moisture-resistant coating to form a second-coated phosphor.
2. The process of claim 1 wherein said first layer is an aluminum
nitride.
3. The process of claim 1 wherein said electroluminescent phosphor
comprises zinc sulfide activated with one or more activators.
4. The process of claim 1 wherein said organic coating is
substantially transmissive of visible light, electrically
insulating, and has low moisture permeability.
5. The process of claim 1 wherein the second layer is a parylene,
polyester, polyalkylacrylate, or vinyl-epoxy resin.
6. The process of claim 5 wherein the first layer is an aluminum
nitride.
7. The process of claim 2 wherein the second layer is a
parylene.
8. The process of claim 2 wherein the second layer is
poly(p-xylylene) or poly(p-.alpha.-xylylene) with .alpha.=H, Cl,
Br, F, alkyl or amino.
9-16. (canceled).
Description
[0001] This application claims priority from Provisional
Application No. 60/282,391, filed Apr. 6, 2001.
TECHNICAL FIELD
[0002] This invention relates to electroluminescent phosphors and
more particularly to electroluminescent phosphors that have been
treated to be moisture resistant. More particularly, this invention
relates to electroluminescent phosphors having greatly reduced
moisture absorption, greatly increased life and efficacy, and an
economical manufacturing cost.
BACKGROUND ART
[0003] Treated phosphors are known from U.S. Pat. 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. Pat. Nos. 5,244,750 and
4,585,673. The treatment 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 anhydrous ammonia precursors
upon silicon, vitreous carbon and glass substrates. See, for
example, "Atmospheric pressure chemical vapor deposition of
aluminum nitride films at 200-250.degree. C.", Gordon, et al.,
Journal Material Resources, Vol. 6, No. 1, January 1991; and
"Chemical vapor deposition of aluminum nitride thin films", Gordon,
et al., Journal Material Resources, Vol. 7, No. 7, July 1992. See,
also, U.S. Pat. Nos. 5,139,825 and 5,178,911, Gordon, which also
disclose transition metal nitrides and other metallic nitrides such
as gallium and tin, respectively. U.S. Pat. No. 5,856,009 discloses
a high temperature process (i.e., 300 to 700.degree. C.) for
applying a silicon nitride coating over a previously applied heat
resistant coating on phosphor particles. U.S. Pat. No. 6,064,150
(incorporated herein by reference) discloses an aluminum nitride
coating process using a highly reactive
hexakis(dimethylamido)dialuminum. The freshly applied nitride
coating is susceptible to absorbing, or reacting with, atmospheric
oxygen and moisture upon removal from the coating reactor.
SUMMARY OF THE INVENTION
[0004] It is, therefore, an object of the present invention to
obviate the disadvantages of the prior art.
[0005] It is another object of the invention to enhance
electroluminescent phosphors.
[0006] These objects are accomplished, in one aspect of the
invention, by a process for providing a moisture-resistant
electroluminescent phosphor that comprises the steps of providing
individual particles of the phosphor with a first layer of an
inorganic moisture-resistant coating to form a first-coated
phosphor, substantially isolating the first-coated phosphor from
contact with atmospheric oxygen and moisture, and providing the
first-coated phosphor with a second layer of an organic
moisture-resistant coating to form a second-coated phosphor. The
second layer inhibiting the first layer from absorbing, or reacting
with, atmospheric oxygen or moisture.
DETAILED DESCRIPTION OF THE INVENTION
[0007] 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.
[0008] Referring now to the invention with greater particularity, a
process for providing a moisture-resistant electroluminescent
phosphor comprises the steps of providing individual particles of
the phosphor with a first layer of an inorganic moisture-resistant
coating to form a first-coated phosphor. In a preferred embodiment
of the invention, the electroluminescent phosphor can be
copper-activated zinc sulfide (ZnS:Cu) and the first coating can be
an aluminum nitride such as that disclosed in the above-mentioned
U.S. Pat. No. 6,064,150. This material is an excellent moisture
inhibitor but is susceptible to absorbing, or reacting with,
atmospheric oxygen and water vapor following removal from the
coating processing chamber and exposure to ambient conditions.
Thus, additional handling procedures must be put into place to
protect the phosphor until its incorporation into a lamp.
[0009] This problem is solved by substantially isolating the
first-coated phosphor from contact with atmospheric oxygen and
moisture after its initial coating and providing the first-coated
phosphor with a second layer of an organic moisture-resistant
coating to form a second-coated phosphor. Ideally, the second
operation is performed in the same apparatus as the first, without
removing the first-coated phosphor. Suitable apparatus for coating
the phosphors is shown in the above-cited U.S. Pat. No.
6,064,150
[0010] The organic layer must be substantially transmissive of
visible light, a good electrical insulator (electroluminescent
lamps operate on a capacitive principle, emitting light when placed
in an alternating electric field) and must have low moisture
permeability. Such materials can be selected from polyesters,
polyalkylacrylates, or vinyl-epoxy resins. These materials have
been used in the past to reduce the moisture sensitivity of metal
halide radiographic phosphors.
[0011] Similarly, organic coatings have been suggested for use
singly to reduce the moisture sensitivity of electroluminescent
phosphors. In the latter case, parylenes, including
poly(p-xylylene), and poly(p-.alpha.-xylylene) with .alpha.=H, Cl,
Br, F, alkyl or amino, have been suggested.
[0012] The use of two layers of different moisture-resistant
coatings provides an electroluminescent phosphor with excellent
lamp properties and long life. Additionally, the coatings are
applied at low temperatures, that is, below 300.degree. C., thus
avoiding the potential elimination of sulfur that occurs if a high
temperature coating process is employed.
[0013] While there have been shown and described what are at
present considered to be the preferred embodiments of the
invention, it will be apparent to those skilled in the art that
various changes and modification can be made herein without
departing from the scope of the invention as defined by the
appended claims.
* * * * *