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Publication numberUS20020003090 A1
Publication typeApplication
Application numberUS 09/398,835
Publication dateJan 10, 2002
Filing dateSep 16, 1999
Priority dateJun 11, 1998
Also published asUS6319381, US6383696, US6406603, US6458260, US20010001193, US20010024683
Publication number09398835, 398835, US 2002/0003090 A1, US 2002/003090 A1, US 20020003090 A1, US 20020003090A1, US 2002003090 A1, US 2002003090A1, US-A1-20020003090, US-A1-2002003090, US2002/0003090A1, US2002/003090A1, US20020003090 A1, US20020003090A1, US2002003090 A1, US2002003090A1
InventorsJefferson O Nemelka
Original AssigneeJefferson O Nemelka
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Processing the photoresist using a heated aqueous developing solution including an acid such as lactic acid to dislodge and remove the first phosphor-comprising material from beneath developed photoresist
US 20020003090 A1
Abstract
Methods of forming face plate assemblies are described. In one implementation, a substrate is patterned with photoresist and a first phosphor-comprising material is formed over first surface areas of the substrate. The photoresist is stripped leaving some of the first phosphor-comprising material over substrate areas other than the first areas. Photoresist is again formed over the substrate and processed to expose second substrate areas which are different from the first substrate areas. In a preferred aspect, processing the photoresist comprises using a heated aqueous developing solution comprising an acid, e.g. lactic acid, effective to dislodge and remove first phosphor-comprising material from beneath the developed photoresist. A second phosphor-comprising material is formed over the substrate and the exposed second areas, with trace deposits being left over other substrate areas. The photoresist is subsequently stripped leaving some of the second phosphor-comprising material over substrate areas other than the first and second areas. Photoresist is again formed over the substrate and processed to expose third substrate areas which are different from the first and second areas. In a preferred aspect, processing the photoresist comprises using a heated aqueous developing solution comprising an acid, e.g. lactic acid, effective to dislodge and remove first and second phosphor-comprising material from beneath the removed photoresist. A third phosphor-comprising material is formed over the substrate and the exposed third areas.
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Claims(60)
1. A method of forming a face plate assembly of a color display comprising:
forming a phosphor-comprising material over a surface of the face plate;
forming photoresist over the phosphor comprising material; and
removing photoresist from over portions of the face plate surface with a heated aqueous developing solution effective to also remove phosphor-comprising material from the substrate beneath said removed photoresist during said removing.
2. The method of claim 1, wherein said developing solution comprises an inorganic acid.
3. The method of claim 2, wherein said inorganic acid comprises phosphoric acid.
4. The method of claim 2, wherein said inorganic acid comprises hydrochloric acid.
5. The method of claim 1, wherein said developing solution comprises an organic acid.
6. The method of claim 5, wherein said organic acid comprises lactic acid.
7. The method of claim 5, wherein said organic acid comprises acetic acid.
8. The method of claim 5, wherein said organic acid comprises glycolic acid.
9. The method of claim 5, wherein said developing solution has a concentration of said organic acid of less than about ten percent by volume.
10. The method of claim 9, wherein said developing solution is heated to a temperature from between about 25° C. to 50° C.
11. The method of claim 9, wherein said developing solution is heated to a temperature from between about 35° C. to 40° C.
12. The method of claim 5, wherein said developing solution has a concentration of said organic acid of less than about one percent by volume.
13. The method of claim 12, wherein said organic acid comprises lactic acid.
14. The method of claim 1 further comprising:
after said developing, forming a second phosphor-comprising material over said surface;
forming photoresist over said face plate surface;
second developing said photoresist from over different portions of the face plate surface with a developing solution effective to also remove first and second phosphor-comprising material from the substrate beneath said removed photoresist during said second developing; and
forming a third phosphor-comprising material over said different portions of the face plate surface.
15. The method of claim 14, wherein said developing and said second developing comprise using developing solutions comprising an organic acid.
16. A method of forming a face plate assembly of a color display comprising:
forming a phosphor-comprising material over a substrate comprising a portion of a face plate assembly of a color display, the material being formed over first substrate areas and second substrate areas; and
after said forming, exposing the substrate to an aqueous solution comprising phosphor-removing material effective to remove phosphor-comprising material from over said second areas and outwardly expose said second areas.
17. The method of claim 16 further comprising:
prior to said forming of said phosphor-comprising material, forming photoresist over the substrate, said photoresist defining areas within which said phosphor-comprising material is to be formed; and
prior to said exposing of the substrate to said aqueous solution, removing photoresist from over the substrate with a photoresist developing solution.
18. The method of claim 16, wherein said phosphor-removing material comprises an inorganic acid.
19. The method of claim 16, wherein said phosphor-removing material comprises an organic acid.
20. The method of claim 19, wherein said aqueous solution is heated to a temperature from between about 25° C. to 50° C.
21. The method of claim 19, wherein said aqueous solution comprises less than about ten percent of said organic acid by volume.
22. The method of claim 16, wherein said phosphor-removing material comprises lactic acid.
23. The method of claim 22, wherein said aqueous solution comprises less than about ten percent of said lactic acid by volume.
24. The method of claim 16 further comprising:
after said exposing, forming a second phosphor-comprising material over said second areas;
exposing said substrate to an aqueous solution comprising a phosphor-removing material effective to remove first and second phosphor-comprising materials from over and outwardly expose third substrate areas which are different from said first and second substrate areas; and
forming a third phosphor-comprising material over the exposed third substrate areas.
25. A method of forming a face plate assembly of a color display comprising:
providing a substrate comprising a portion of a face plate assembly of a color display and having a patterned masking layer thereover defining a plurality of openings over first substrate areas;
forming a phosphor-comprising material over the first substrate areas; and
after forming the phosphor-comprising material, exposing the substrate to an aqueous solution comprising phosphor-removing material effective to remove phosphor-comprising material from over and outwardly expose second substrate areas which are different from the first substrate areas.
26. The method of claim 25, wherein said aqueous solution is heated to a temperature from between about 25° C. to 50° C.
27. The method of claim 25, wherein said aqueous solution comprises less than about ten percent of an organic acid by volume.
28. The method of claim 27, wherein said organic acid comprises lactic acid.
29. The method of claim 25 further comprising prior to exposing said substrate to said aqueous solution, forming a second masking layer over said substrate, wherein said aqueous solution is effective to remove portions of said second masking layer from over said second substrate areas.
30. The method of claim 29, wherein said second masking layer comprises negative photoresist and further comprising prior to said exposing, light processing photoresist other than those portions which are removed from over said second substrate areas.
31. The method of claim 29, wherein said aqueous solution comprises less than about ten percent of an organic acid by volume.
32. The method of claim 29 further comprising forming a second phosphor-comprising material over said second substrate areas and thereafter, exposing said substrate to an aqueous solution comprising phosphor-removing material effective to remove second phosphor-comprising material from over and outwardly expose third substrate areas which are different from the second substrate areas.
33. The method of claim 32 further comprising:
prior to exposing said third substrate areas, forming a third masking layer over said substrate;
wherein said aqueous solution which is effective to remove second phosphor-comprising material is also effective to remove portions of said third masking layer from over said third substrate areas; and
after said exposing of said third substrate areas, forming a third phosphor-comprising material over said third substrate areas.
34. A method of forming a face plate assembly of a color display comprising:
forming a matrix material over a surface of a face plate, said matrix material defining a plurality of areas over which phosphor-comprising material is to be formed;
forming a phosphor-comprising material over the face plate within one of said areas;
forming photoresist over the matrix material and the phosphor-comprising material;
exposing selected portions of the photoresist to radiant energy;
developing unexposed portions of the photoresist with a developing solution effective to remove said unexposed portions from over areas which are different from said one area;
after said developing, treating said different areas with a heated aqueous solution comprising a phosphor-removing material effective to remove trace deposits of said phosphor-comprising material within said different areas.
35. The method of claim 34, wherein said heated aqueous solution comprises an acid having a concentration less than about ten percent by volume.
36. The method of claim 35, wherein said acid comprises an organic acid.
37. The method of claim 35, wherein said acid comprises an inorganic acid.
38. A method of forming a face plate assembly of a color display comprising:
electrophoretically depositing a first phosphor-comprising material on first portions of a surface of a face plate, at least some of said first phosphor-comprising material forming on second portions of said surface;
forming photoresist over the first phosphor-comprising material received on the first and second portions of said surface;
light processing the photoresist on the first and second portions differently;
after said light processing, stripping photoresist from over the second portions of the face plate surface with a stripping solution effective to also remove first phosphor-comprising material from the substrate beneath said stripped photoresist during said stripping; and
after the stripping, electrophoretically depositing a second phosphor comprising material on the second portions of said surface.
39. The method of claim 38, wherein said stripping solution comprises an aqueous solution comprising an organic acid.
40. The method of claim 39, wherein said organic acid comprises lactic acid.
41. The method of claim 39, wherein said organic acid comprises acetic acid.
42. The method of claim 39, wherein said aqueous solution has a concentration of said organic acid of less than about ten percent by volume.
43. The method of claim 39, wherein said aqueous solution has a concentration of said organic acid of less than about one percent by volume.
44. The method of claim 39, further comprising:
after electrophoretically depositing said second phosphor-comprising material, forming photoresist at least over said first portion of said surface;
second light processing said photoresist on said first portion differently;
after said second light processing, second stripping said photoresist from over and outwardly exposing some of said first portion of said surface with a stripping solution effective to also remove first and second phosphor-comprising material from the substrate beneath said stripped photoresist during said second stripping; and
after said second stripping, electrophoretically depositing a third phosphor-comprising material on said exposed first portion.
45. A method of forming a face plate assembly of a color display comprising:
forming a first phosphor-comprising material over a surface of the face plate;
forming negative photoresist over the first phosphor-comprising material;
masking first portions of the negative photoresist while leaving second portions exposed;
exposing the second portions to selected light;
after the exposing, removing the mask;
after removing the mask, exposing the negative photoresist to a solution comprising aqueous organic acid effective to strip the non-light-exposed photoresist and first phosphor-comprising material therebeneath from over the face plate surface; and
after stripping the non-light-exposed photoresist and first phosphor-comprising material therebeneath, forming second phosphor-comprising material at least over the surface of the face plate from which the non-light-exposed photoresist and first phosphor-comprising material was stripped.
46. The method of claim 45, wherein said organic acid comprises lactic acid.
47. The method of claim 45, wherein said organic acid comprises lactic acid having a concentration of less than about ten percent by volume.
48. A method of forming a face plate assembly of a color display comprising:
providing a substrate having a first patterned masking layer defining a first plurality of openings over first substrate areas, the substrate comprising a portion of a face plate assembly of a color display;
forming a first phosphor-comprising material over the first substrate areas;
removing the first patterned masking layer;
forming a second patterned masking layer over the substrate defining a second plurality of openings over second substrate areas which are different from the first substrate areas, said forming of the second patterned masking layer comprising exposing the substrate to a phosphor-removing solution which is effective to remove at least some of any remnant first phosphor-comprising material from within the second openings over said second substrate areas; and
forming a second phosphor-comprising material over the second substrate areas.
49. The method of claim 48, wherein said phosphor-removing solution comprises an aqueous organic acid solution.
50. The method of claim 49, wherein said solution comprises a concentration of less than about ten percent lactic acid by volume.
51. The method of claim 48 further comprising:
forming a third patterned masking layer over the substrate defining a third plurality of openings over third substrate areas which are different from said second substrate areas, said forming of said third patterned masking layer comprising exposing said substrate to a phosphor-removing solution which is effective to remove at least some of any remnant first and second phosphor-comprising materials from within the third openings over said third substrate areas; and
forming a third phosphor-comprising material over said third substrate areas.
52. The method of claim 51, wherein both of said phosphor-removing solutions comprise aqueous organic acid solutions having a concentration of less than about ten percent organic acid by volume.
53. The method of claim 52, wherein the organic acid in one of said solutions comprises lactic acid.
54. A method of forming a face plate assembly of a color display comprising:
providing a substrate having a first patterned masking layer defining a first plurality of openings over first substrate areas, the substrate comprising a portion of a face plate assembly of a color display and comprising second substrate areas;
forming a first phosphor-comprising material within the first openings over the first substrate areas and over the first patterned masking layer over the second substrate areas;
removing the first patterned masking layer and leaving some first phosphor-comprising material over the substrate in the second substrate areas;
forming a second patterned masking layer comprising photoresist over the substrate leaving a second plurality of openings over the second substrate areas, said forming of the second patterned masking layer comprising exposing the substrate to a photoresist-developing solution which is effective to substantially remove second masking layer material and the first phosphor-comprising material from over said second substrate areas; and
forming a second phosphor-comprising material over the second substrate areas.
55. The method of claim 54, wherein said photoresist-developing solution comprises an aqueous organic acid solution.
56. The method of claim 55, wherein said photoresist-developing solution comprises a concentration of less than about ten percent lactic acid by volume.
57. The method of claim 55, wherein said photoresist-developing solution comprises a concentration of less than about ten percent acetic acid by volume.
58. The method of claim 54 further comprising:
removing said second patterned masking layer and leaving some second phosphor-comprising material over the substrate in third substrate areas;
forming a third patterned masking layer comprising photoresist over said substrate leaving a third plurality of openings over said third substrate areas, said forming of said third patterned masking layer comprising exposing the substrate to a photoresist-developing solution which is effective to substantially remove third masking layer material and first and second phosphor-comprising material from over said third substrate areas; and
forming a third phosphor-comprising material within said third openings over said third substrate areas.
59. The method of claim 58, wherein both of said developing solutions comprise aqueous organic acid solutions.
60. The method of claim 59, wherein one of the solutions comprises a concentration of lactic acid of less than about ten percent by volume.
Description
PATENT RIGHTS STATEMENT

[0001] This invention was made with Government support under Contract No. DABT63-97-C-0001 awarded by Advanced Research Projects Agency (ARPA). The Government has certain rights in this invention.

TECHNICAL FIELD

[0002] The present invention relates to methods of forming a face plate assembly of a color display.

BACKGROUND OF THE INVENTION

[0003] Field emission displays and cathode ray tubes are types of color displays which can function by having a layer of phosphor-comprising material applied on an internal surface of a face plate known as an anode, cathodeluminescent screen, display screen, or display electrode. Color displays typically include three different types of phosphor, namely red, green, and blue (RGB), which, when excited in various combinations, produce colors for presentation through the face plate of the display. The phosphor-comprising material is typically oriented or arranged in a series of pixels. Pixels are typically discrete areas of phosphor-comprising material formed on the internal surface of the face plate.

[0004] A technique by which such areas are provided on a face plate involves the use of photolithographic techniques to pattern the phosphor-comprising material. Typically, a faceplate will be coated with a thin layer of conductive material, generally Indium Tin Oxide (ITO). This conductive layer of material is coated with a layer of photoresist, which in turn, is used to pattern phosphor-comprising material into a color array of pixels. It may also serve for patterning black matrix material into a pixel pattern. Black matrix material is used in order to give greater contrast in color displays. Pixels, or holes, will be opened up in the photoresist using photolithographic techniques, thereby exposing distinct regions of the conductive material. The photolithographic techniques used to open the pixels or holes in the photoresist typically involve the use of developer solutions. For negative resists, developer solutions selectively dissolve and remove regions of the photoresist that have not been exposed to radiation actinic to the photoresist used. The black matrix and phosphor-comprising materials can then be electrophoretically deposited into the holes opened in the photoresist. The conductive layer is used as an electrode for depositing phosphors comprising materials through electrophoresis. Electrophoresis, or electrophoretic deposition, in simply the migration of charged particles through a solution under the influence of an applied electric field applied by immersing two electrodes in the solution. Exemplary methods of depositing black matrix material and phosphor-comprising material are described in U.S. Pat. No. 4,891,110, the disclosure of which is incorporated by reference. Exemplary color displays are described in U.S. Pat. Nos. 5,712,534, 5,705,079, 5,697,825 and 5,688,438, the disclosures of which are incorporated by reference.

[0005] Photolithographic color patterning of a display typically involves the use of incident radiation, photomasks, and wet-chemical developers to selectively expose various pixels for deposition of black matrix material and different colors of phosphor-comprising material therein. Despite the use of these developers, electrophoretic deposition of powdered materials such as manganese carbonate and phosphor-comprising material can result in trace deposits undesirably remaining over adjacent areas or pixels. Such trace deposits can result in black spots and color cross-contamination with undesired color phosphor remaining in adjacent pixels dedicated to other colors, thus leading to color bleed and a less desirable display.

[0006] This invention arose out of concerns associated with improving the methods by which phosphor-comprising material is formed over face plates of color displays. This invention also arose out of concerns associated with providing improved color displays.

SUMMARY OF THE INVENTION

[0007] Methods of forming face plate assemblies are described. In one implementation, a substrate is patterned with photoresist and a first phosphor-comprising material is formed over first surface areas of the substrate. The photoresist is stripped leaving some of the first phosphor-comprising material over substrate areas other than the first areas. Photoresist is again formed over the substrate and processed to expose second substrate areas which are different from the first substrate areas. In a preferred aspect, processing the photoresist comprises using a heated aqueous developing solution comprising an acid, e.g. lactic acid, effective to dislodge and remove first phosphor-comprising material from beneath the developed photoresist. A second phosphor-comprising material is formed over the substrate and the exposed second areas, with trace deposits being left over other substrate areas. The photoresist is subsequently stripped leaving some of the second phosphor-comprising material over substrate areas other than the first and second areas. Photoresist is again formed over the substrate and processed to expose third substrate areas which are different from the first and second areas. In a preferred aspect, processing the photoresist comprises using a heated aqueous developing solution comprising an acid, e.g. lactic acid, effective to dislodge and remove first and second phosphor-comprising material from beneath the removed photoresist. A third phosphor-comprising material is formed over the substrate and the exposed third areas.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Preferred embodiments of the invention are described below with reference to the following accompanying drawings.

[0009]FIG. 1 is a diagrammatic sectional view of a substrate comprising a portion of a face plate assembly of a color display.

[0010]FIG. 2 is a view of the FIG. 1 substrate at a different processing step.

[0011]FIG. 3 is a view of the FIG. 2 substrate at a different processing step.

[0012]FIG. 4 is an enlarged view of the FIG. 3 substrate at a different processing step.

[0013]FIG. 5 is a view of the FIG. 4 substrate at a different processing step.

[0014]FIG. 6 is a view of the FIG. 5 substrate at a different processing step.

[0015]FIG. 7 is a view of the FIG. 6 substrate at a different processing step.

[0016]FIG. 8 is a view of the FIG. 7 substrate at a different processing step.

[0017]FIG. 9 is a view of the FIG. 8 substrate at a different processing step.

[0018]FIG. 10 is a view of the FIG. 9 substrate at a different processing step.

[0019]FIG. 11 is a view of the FIG. 10 substrate at a different processing step.

[0020]FIG. 12 is a view of the FIG. 11 substrate at a different processing step.

[0021]FIG. 13 is a view of the FIG. 12 substrate at a different processing step.

[0022]FIG. 14 is a view of the FIG. 13 substrate at a different processing step.

[0023]FIG. 15 is a view of the FIG. 14 substrate at a different processing step.

[0024]FIG. 16 is a view of the FIG. 15 substrate at a different processing step.

[0025]FIG. 17 is a view of the FIG. 16 substrate at a different processing step.

[0026]FIG. 18 is a view of the FIG. 17 substrate at a different processing step.

[0027]FIG. 19 is a view of the FIG. 18 substrate at a different processing step.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).

[0029] Referring to FIG. 1, a substrate is shown generally at 20 and comprises a portion of a face plate assembly of a color display. Substrate 20 includes an outer surface 22.

[0030] Referring to FIG. 2, a layer 24 is formed over surface 22 and comprises a conductive material such as indium tin oxide.

[0031] Referring to FIG. 3, a layer 25 is formed over substrate 20 and comprises a masking material such as photoresist.

[0032] Referring to FIG. 4, layer 25 is patterned to define a plurality of openings (not specifically designated) over the substrate.

[0033] Referring to FIG. 5, black matrix material 27 is formed over the substrate and within the openings in layer 25.

[0034] Referring to FIG. 6, layer 25 is removed and leaves the deposited black matrix material over the substrate. Such material defines substrate areas over which phosphor-comprising material is to be deposited.

[0035] Referring to FIG. 7, a layer 26 is formed over substrate 20 and comprises a masking material such as photoresist. While positive photoresists can be used, negative photoresists such as polyvinyl alcohol are preferred.

[0036] Referring to FIG. 8, layer 26 is patterned to define a first plurality of openings 28 over first substrate areas 30.

[0037] Referring to FIG. 9, a first phosphor-comprising material 32 is formed over the substrate and within first openings 28 over first substrate areas 30. Phosphor-comprising material 32 is also formed in trace amounts over patterned masking layer 26 and second and third substrate areas 34, 38. Phosphor-comprising material 32 is preferably electrophoretically deposited over first substrate areas 30. Generally, an electrophoretic solution is made up of a nonaqueous liquid, such as isopropyl alcohol, and an electrolyte, such as a salt of magnesium, zinc, aluminum, lanthanum, cerium, or yttrium. The phosphor-comprising material is typically an inorganic material with certain impurities or dopants. Examples of commonly used red, green, and blue phosphor-comprising materials are Y2O3:Eu, Zn2SiO4:Mn, and ZnS:Ag, respectively.

[0038] An exemplary solution used for electrophoretic deposition is as follows:

Component Weight Percent
Isopropyl Alcohol 99.5
Mg2(NO3)2 0.1
Y2O3:Eu 0.4

[0039] An electrode is ideally immersed in a room temperature solution along with the substrate to be coated. An electric field is applied between two electrodes such that the substrate is at a negative potential relative to the other electrode. Typically, a voltage differential of 200 Volts is applied to the two electrodes for about one minute, during which time the phosphor-comprising material is deposited on the substrate. An exemplary first phosphor-comprising material is Y2O3:Eu.

[0040] Referring to FIG. 10, first patterned masking layer 26 is removed or stripped from over substrate 20 as by plasma gas, wet chemical, or thermal methods which are known. For example, polyvinyl alcohol can be stripped using an aqueous, hydrogen peroxide solution or by baking in air at 400° C. The removal of the masking layer undesirably leaves trace amounts 36 of first phosphor-comprising material 32 over the substrate in areas other than first areas 30, e.g. over second areas 34 and third areas 38. For purposes of the continuing discussion, adjacent substrate areas 30, 38 comprise first portions of the surface of the face plate over which first phosphor-comprising material is deposited. Second substrate area 34 comprises a second portion of the surface over which trace amounts of the first phosphor-comprising material are deposited.

[0041] Referring to FIGS. 11 and 12, a second layer 40 of masking material is formed over substrate 20 and phosphor-comprising material 32, 36. In the illustrated example, second masking layer 40 comprises photoresist, with negative photoresist being preferred. Second portions of layer 40, i.e. those portions of the photoresist which are formed over the second surface portions defined by substrate areas 34, are masked while first portions of the photoresist, i.e. those portions over second areas 30, 38 are exposed to selected light or light processed as indicated by the grouped arrows. After light exposure, the mask is removed. The first and second photoresist portions are accordingly light processed differently.

[0042] Referring to FIG. 13, photoresist from over the second surface portions, e.g. second substrate areas 34, is removed with a developing solution which is effective in dislodging and removing remnant first phosphor-comprising material 36 (FIG. 12) from the substrate beneath the removed photoresist. In the illustrated and preferred embodiment, the removal of the photoresist and remnant first phosphor-comprising material takes place by exposing the substrate to a heated aqueous solution comprising a phosphor-removing material which is sufficient to outwardly expose second areas 34 through photodevelopment. Such aqueous developing solution preferably includes an acid having a concentration of less than about 10% by volume, at a temperature from between about 25° C. to 50° C. Even more preferably, the aqueous solution has a temperature from between about 35° C. to 40° C., and an acid concentration of less than about 1% by volume. A preferred acid is lactic acid, while other acids such as acetic, glycolic, phosphoric, or hydrochloric acids can be utilized. A suitable solution constituent is available from Shipley Company located at 455 Forest Street, Marlborough, Mass., and sold under the trade name “Eagle 2005 Developer” and bearing the product code 15020. The solution constituent includes the following component parts (with volume percentages being indicated parenthetically): water (24-25), lactic acid (22-23), and polyglycol (53-54). The preferred aqueous solution was formed by providing about four percent of the “Eagle 2005 Developer” by volume into about 96 percent water by volume.

[0043] In another embodiment, unexposed regions of photoresist can be treated with a suitable developing solution which is sufficient to remove the photoresist, but not trace material 36 (FIG. 12). Subsequently, to dislodge and remove the trace material over the substrate, the substrate can be further exposed to the heated aqueous solution mentioned above. The presence of an acid, preferably an organic acid, in the solution is believed to destroy the weak bonds that hold the phosphor-comprising material 36 to the substrate, thereby making it possible for the elevated temperature solution to draw the phosphor-comprising material into the bulk of the solution. The use of some inorganic acids, such as hydrochloric acid, can be equally as effective, though its use may be limited due to possible corrosive effects relative to conductive layer 22.

[0044] Other types of photoresists can be used which employ organic-based developers which do not effectively dislodge and remove the trace deposits of the phosphor-comprising material. In these instances, the use of the preferred heated, aqueous solution can effectively dislodge and remove the phosphor-comprising material 36 from the exposed substrate areas.

[0045] Use of the preferred, heated, aqueous solution can effectively remove the phosphor-comprising material 36, thereby leaving behind a clean substrate area 34 for deposition of a second color phosphor-comprising material.

[0046] Developing the photoresist as just described forms a second patterned masking layer over substrate 20 which leaves or defines a second plurality of openings 42 over second substrate areas 34. Use of the preferred solution is effective to substantially, e.g. around 95%, if not completely, remove any remnant first phosphor-comprising material from over second substrate areas 34.

[0047] Referring to FIG. 14, a second phosphor-comprising material 44 is formed over substrate 20 within openings 42 and over second areas 34. Phosphor-comprising material 44 is preferably electrophoretically deposited over second substrate areas 34. Preferred processing conditions for electrophoretically depositing phosphor-comprising material 44 are the same as those used for the first phosphor-comprising material, with an exception being that the phosphor-comprising material is different, for example, ZnSiO4:Mn, green. Trace amounts 46 of phosphor-comprising material 44 can be deposited over masking layer 40.

[0048] Referring to FIG. 15, second masking layer 40 is developed or otherwise stripped from over substrate 20 as described above. Such can undesirably leave remnant second phosphor-comprising material 46 over the substrate including areas other than the second areas, particularly within third substrate areas 38 over remnant first phosphor-comprising material 36 and over areas 30. Trace deposits tend to accumulate over areas 38, where the lower topography creates regions that can trap the material.

[0049] Referring to FIG. 16, a third masking layer 48 is formed over substrate 20 and over third substrate areas 38. Third masking layer 48 preferably comprises photoresist, with negative photoresist being preferred. The photoresist is subsequently light processed (second light processed), which exposes it to radiation actinic to the particular photoresist being used. In the illustrated example, photoresist over the first portion of the substrate surface (e.g., over areas 30, 38) is light processed differently such that photoresist over areas 38 is not exposed.

[0050] Referring to FIG. 17, photoresist from over some of the first portion, e.g. area 38, is removed with a developing solution which is effective to also remove, preferably completely, remnant first and second phosphor-comprising material 36, 46 (FIG. 16) from the substrate beneath the stripped photoresist. Such is accomplished utilizing the preferred, heated aqueous solution described above comprising a phosphor-removing material which is effective to remove both first and second phosphor-comprising materials. Exemplary aqueous solutions can, and preferably do comprise those solutions described above. Removal of material of the third masking layer constitutes forming a third patterned masking layer which leaves or defines a third plurality of openings 50 over third substrate areas 38. It will be appreciated that different individual materials can have their own stripping solution.

[0051] Referring to FIG. 18, a third phosphor-comprising material 52 is formed over substrate 20 within openings 50 and over substrate areas 38. Such material can also be deposited in trace amounts over layer 48. Phosphor-comprising material 52 is preferably electrophoretically deposited over third substrate areas 38. Preferred processing conditions for electrophoretically depositing phosphor-comprising material 52 are the same as those used for the first and second phosphor-comprising materials, with an exception being that the third phosphor-comprising material comprises a different color, e.g. ZnS:Ag, blue.

[0052] Referring to FIG. 19, photoresist 48 is subsequently stripped as described above to provide the color display face plate assembly.

[0053] The above-described processing methodologies can significantly reduce the risk that trace amounts of phosphor-comprising material are deposited over areas other than those specific areas which are intended Accordingly, displays with better color purity and uniformity are provided.

[0054] In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.

Classifications
U.S. Classification204/485, 430/7
International ClassificationC08F2/58, C23C26/00, C23C28/00
Cooperative ClassificationC23C26/00
European ClassificationC23C26/00
Legal Events
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Jan 24, 2014REMIMaintenance fee reminder mailed
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May 6, 2003CCCertificate of correction