US3884694A

US3884694A - Process for forming a color cathode ray tube screen structure having optical filter elements therein

Info

Publication number: US3884694A
Application number: US412142A
Authority: US
Inventors: Anthony V Gallaro; Robert A Hedler
Original assignee: GTE Sylvania Inc
Current assignee: GTE Sylvania Inc
Priority date: 1973-11-02
Filing date: 1973-11-02
Publication date: 1975-05-20
Anticipated expiration: 1992-05-20

Abstract

A process is provided for fabricating a multi-windowed screen structure for a color cathode ray tube effecting enhanced absorption of ambient light and providing contrast improvement of the image display. The process comprises the superposed deposition of primary, secondary, and tertiary layers of diversely-hued heat formable optical filter materials that are individually exposed in respective windows of the structure. The deposition of each filter layer involves the usage of a protective coating that prevents the intermixture of the overlaid heat formable filter materials and effects the photo-formation of the window areas. The coating comprises a negative photosensitive resist material admixed with an inert substance that is thermally and chemically inactive to the temperatures and materials encountered in the screening process. Since the discretely positioned windows in each filter layer are formed in accordance with the shaping of the apertures in a spatially related pattern mask, each of the windows exhibits a uniformly shaped periphery free of indentations, being so defined by a uniform opaque interstitial encompassment homogeneously made up of the three distinct layers of superposed filter materials. Disposed over the windows in the screen structure is a compatible pattern of cathodoluminescent phosphor elements, which produce color emissions that are colorimetrically related to the respective filter windows therebeneath.

Description

United States Patent Gallaro et al.

PROCESS FOR FORMING A COLOR Assignee:

Filed:

Inventors: Anthony V. Gallaro, Auburn;

Robert A. Hedler, Seneca Falls, both of NY.

GTE Sylvania Incorporated,

Stamford, Conn.

Nov. 2, 1973 Appl. No.: 412,142

US. Cl. 96/30; 96/1; 96/12; 96/36.1;96/36.2; 96/383; 96/35.1;

Int. Cl G03g 13/22 Field of Search lI7/33.5 CM, 33.5 C;

References Cited UNITED STATES PATENTS Hamilton 117/335 CM Lange 96/361 Kaplan 96/36.]

Lange 96/36.1

Robinder 96/36.1

Kachel 117/335 CM Kaplan 117/335 CM Kaplan 313/474 [451 May 20, 1975 5 7 ABSTRACT A process is provided for fabricating a multiwindowed screen structure for a color cathode ray tube effecting enhanced absorption of ambient light and providing contrast improvement of the image display. The process comprises the superposed deposition of primary, secondary, and tertiary layers of diversely-hued heat formable optical filter materials that are individually exposed in respective windows of the structure. The deposition of each filter layer involves the usage of a protective coating that prevents the intermixture of the overlaid heat formable filter materials and effects the photo-formation of the window areas. The coating comprises a negative photosensitive resist material admixed with an inert substance that is thermally and chemically inactive to the temperatures and materials encountered in the screening process. Since the discretely positioned windows in each filter layer are formed in accordance with the shaping of the apertures in a spatially related pattern mask, each of the windows exhibits a uniformly shaped periphery free of indentations, being so defined by a uniform opaque interstitial encompassment homogeneously made up of the three distinct layers of superposed filter materials. Disposed over the windows in the screen structure is a compatible pattern of cathodoluminescent phosphor elements, which produce color emissions that are colorimetrically related to the respective filter windows therebeneath.

8 Claims, 14 Drawing Figures PROCESS FOR FORMING A COLOR CATI-IODE RAY TUBE SCREEN STRUCTURE HAVING OPTICAL FILTER ELEMENTS THEREIN CROSS-REFERENCES TO RELATED APPLICATIONS This application contains matter disclosed but not claimed in three related US. Pat. applications filed concurrently herewith and assigned to the assignee of the present invention. These related applications are Ser. Nos. 412,143, 412,144 and 412.145.

BACKGROUND OF THE INVENTION This invention relates to color cathode ray tubes and more particularly to a process for fabricating a color cathode ray tube screen structure providing improved contrast of the color image display.

Cathode ray tubes, particularly those of the type employed in color television applications for presenting multi-colored display imagery, conventionally utilize patterned screens that are comprised of repetitive groups of related color-emitting phosphor materials. Such groupings are normally disposed relative to the interior surface of the viewing panel as bars. stripes, or dots depending upon the type of color tube structure under consideration. For example, in the well-known shadow mask tube construction, the screen pattern is conventionally composed of a great multitude of repetitive tri-color emissive areas formed of selected cathodoluminescent phosphors, which, upon predetermined electron beam excitation, produce additive primary hues to provide the desired color, imagery. Spatially related to the screen is a foraminous structure or patterned mask member having a vast number of discretely formed apertures therein. Each of these apertures in the patterned member is related to a specific tri-component grouping of related color-emitting phosphor areas of the screen pattern, in a spaced manner therefrom to enable the selected electron beams traversing the apertures to impinge the proper phosphor screen areas therebeneath.

With the advancement of the color television art, there has been a desire to improve the contrast ratio of the color screen display, whereof several approaches have been proposed. One such proposal to improve contrast by absorbing ambient light is the utilization of a neutral density filter member in the form of a tinted cover plate which is superposed over the viewing panel of the tube. Since neutral density filters are not appreciably selective in the visible band of the color spectrum, the intended absorptive efficiency cannot be fully realized in eliminating the reflective ambient light falling within the spectrum bandpass of the display emission. Another proposal for improving the contrast ratio of a color image display is the utilization of a tinted faceplate or viewing panel per se. Tinting or coloring of the faceplate attenuates the light transmission of that member, thereby reducing the evidenced brightness of the phosphor emissions emanating from the electron excited Screen. In addition, there are absorptive shortcomings similar to those of the aforementioned neutral density filter.

Another approach to improving the contrast of thecolor screen image, particularly in the dot-type pattcrned screen, has been the'development of a screen construction wherein the dot defining interstitial spacing between the respective color-emitting dots of the screen'pattern is formed of an opaque'light-absorbing material. In essence, each phosphor dot is enclosed or defined by a substantially dark encompassment which collectively comprise a foraminous pattern in the form of a windowed webbing having an array of substantially opaque connected interstices. While this black surround feature reduces the reflected ambient light in the non-fluorescing areas of the screen, it does not reduce the ambient light reflected from those panel areas associated with the phosphor dot, which areas evidence a high degree of reflectivity.

A further proposal for enhancing contrast of the color screen display has been the use of optical filter elements disposed relative to the respective coloremitting phosphors comprising the screen pattern. One such optical filter proposal utilizes circular filter elements having large oversize diameters, dimensioned so that their outer peripheral portions overlap in a nonuniform manner to produce an irregularly shaped or indented filter area surrounded by a non-uniform interstitial webbing. These variations in the dot surround webbing effect a variable absorbency of the ambient light thereby detracting from the complete achievement of the intended contrast enhancement.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned disadvantages and to provide a process for fabricating an improved screen structure for a color cathode ray tube evidencing improved display contrast. It is another object to provide a process for fabricating an improved color cathode ray tube screen structure incorporating optical filter windows therein, each window in the screen structure having a uniform peripheral encompassment free of indentations. A further object is to provide a process for fabricating an improved color cathode ray tube screen structure comprising optical filter windows which are surrounded by a uniformopaque interstitial encompassment.

These and other objects and advantages are achieved in one aspect of the invention by a discretely patterned multi-window color screen structure disposed on the inner surface of a cathode ray tube viewing panel. The window areas define discrete optical filter elements, each being surrounded by a uniform opaque interstitial encompassment that exhibits a peripherally defined smoothness free of indentations, such window shapings being similar to the shape of the apertures in a spatially related pattern mask member. The initial step in the screen fabrication process of the invention comprises coating the interior of the panel with a uniform layer of a negative photosensitive resist material which is admixed with an inert protective substance. The coated panel is then exposed by directing actinic radiations, emanating from two spaced-apart positions, through the apertures in the pattern mask to light-polymerize those portions of the photo-sensitive coating mixture in the area'sof the screen subsequently occupied by the second and third filter pattern windows, After a development stepwhich removes the unexposed photosensitive coating mixture, the panel is overcoated with a uniform primary layer of a heat formable first optical filter material and heated to thermally degrade the polymerized window elements formed of the resist material,

. and to'adhere a substantially continuous and transparent primary layer of the first optical filter material to the surface of the panel. The panel is then treated to remove the loosely retained heat degraded materials therefrom, whereupon the primary layer of the first optical filter material evidences a plurality second and third pattern open filter windows therein. The panel is again coated with a uniform layer of the mixture of the photoresist material and the inert protective substance, and again light exposed to actinic radiations emanating from two spaced-apart positions to light-polymerize portions of the photosensitive coating mixture in those areas eventually occupied by the first and third filter pattern windows. Development removes the unexposed portions of the photosensitive mixture. The panel is next overcoated with a uniform secondary layer of a heat formable second optical filter material, and heated to thermally degrade the polymerized window elements formed of the resist mixture and to adhere a substantially continuous and transparent secondary layer of the second optical filter material to portions of the primary filter layer. Upon removal of the loosely retained degraded materials associated with the exposed areas of the secondary layer, the secondary filter layer has first and third pattern open filter windows therein. The panel is coated for the third time with a uniform layer of the mixture of photoresist and the inert protective material, then light-exposed from two positions to polymerize portions of the photosensitive coating mixture in those areas subsequently occupied by the first and second filter patterned windows, the unexposed portions of the coating mixture are removed by development. Upon uniform application of the tertiary layer of a heat formable third optical filter material, the panel is heated to thermally degrade the respective polymerized window elements formed therein and to provide adherence of a substantially continuous and transparent tertiary layer of a third optical filter material to portions of the secondary filter layer. The panel is then treated to remove the areas of degraded loosely retained materials therefrom, to provide a tertiary filter layer having first and second pattern open filter windows therein. The combination of the superimposed discretely patterened primary, secondary, and tertiary filter layers provides a substantially opaque uniformly structured interstitial webbing fully surounding each of the respective optical filter windows in the screen structure whereof the uniform peripheral encompassment of each filter window is free of indentations.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1a through 1c are cross-sectional views illustrating deposition of the primary layer of the first optical filter material;

FIGS. 1d through lfare cross-sectional views relating to the deposition of the secondary layer of a second optical filter material;

FIGS. lg through 1i are sectional views illustrating the deposition of tertiary layer of the third optical filter material;

FIG. lj is a sectional view showing the completed screen structure;

FIG. 2 is a plan view of a partially constructed screen structure taken along the line 2-2 of FIG. showing the primary layer of the first opticial filter material having open second and third pattern window areas formed therein;

FIG. 3 is a plan view of a partially constructed screen structure taken along the line 3-3 of FIG. 1f illustrating the superposed primary and secondary filter material layers and the window elements associated respectively therewith;

FIG. 4 is a plan view of the screen structure taken along the line 4-4 of FIG. 11' showing the relationship of the superposed primary, secondary and tertiary layers of the diverse optical filter materials and the respective filter windows formed therein; and

FIG. 5 is a plan view of the completed screen structure taken along the line 5-5 of FIG. lj.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawings.

The multi-windowed color cathode ray tube structure resulting from the process described herein, will be delineated as having substantially round filter window areas therein surrounded by a substantially uniform opaque interstitial encompassment; each of the window areas having a defined peripheral smoothness free of indentations. Other window configurations, such as elongated and ovate shapings, are intended to be in keeping with this disclosure. such configurations being similar to the shape of the apertures in a spacially related pattern mask member. The screen structure so described may be utilized in either post deflection or shadow mask types of color cathode ray tube constructions.

The multi-element filter window screen structure 11 resultant of the process of the invention, as illustrated in FIGS. lj and 5 is of the type, for example, as that used in a conventional shadow mask type of color cathode ray tube. As is well known, conventional tubes of this kind utilize several electron beams which are directed to converge at a multi-apertured shadow mask, not shown, and thence pass through the apertures therein to impinge selected areas of the composite screen structure spaced therebeneath. The multilayered screen structure 11, as shown in FIGS. lj and 5, is disposed on the inner surface of the cathode ray tube viewing panel 13. The visible light transmissivity of this glass panel is relatively high being preferably in the neighborhood of percent, the light attenuation of the glass per se being inherent to the elemental composition thereof. Adhered to the inner surface of this panel is a substantially continuous and substantially transparent primary layer 21 of a first heat formable optical filter material. This primary layer has substantially round second and third patterns of related open window areas, 25 and 27 respectively, formed therein, each being free of peripheral indentations. The hue of this primary layer'2l is a primary color as, for example, green g, and is of a first organo-metallic luster composition as will be more fully explained subsequently in this specification. Superposed on this primary filter layer 21 it is substantially continuous and substantially transparent secondary layer 31 of a second heat formable optical filter 'material differing in hue from that of the primary layer, as for example a blue b" coloration resultant of another or second organo-metallic luster composition. This secondary layer 31 overlays and fills in the second of the window pattern areas 25 formed in the primary layer 21 to provide an array of windowdefined second filter elements 26 in the screen structure 11. Additionally, the secondary layer 31 has first and third patterns of window areas, 33 and 37 respectively, formed therein whereof the first window pattern array 33 defines areal portions of the primary layer 21 to provide first filter elements 24 in the screen structure. The third window pattern 37 in the secondary layer 31 is superimposed over the third window pattern 27 in the primary layer 21. A substantially continuous and a substantially transparent tertiary layer 41 of a third heat formable optical filter material is superposed over the secondary layer 31 and fills in the third window pattern areas therein and the underlying window pattern areas 27 to provide the array of defined third filter elements 36 in the screen structure 11. This tertiary layer is of a hue differing from that of the primary and secondary layers, as for example red r", and is formed of a third. organt'i-metallic luster material. The pattern definition of the tertiary layer provides open first and second window patterns, 43 and 45 respectively, that are superposed on like

window areas

33 and 25 in the secondary and primary filter layers 31 and 21 respectively. The three

superimposed layers

21, 31, and 41 of diverse optical filter materials comprising the multi-window structure 11 are combined in a discrete manner to provide a substantially opaque uniform interstitial webbing 49 that fully surrounds each of the respective filter windows in the screen structure 11 by an opaque uniform peripheral encompassment that is free of indentations. Disposed over these respective filter window areas in the screen structure are patterned groupings 53 of compatible green G", blue B, and red R cathodoluminescent phosphor elements, which upon electron excitation produce color emissions that are color-metrically related to respective filter windows 24 g, 26 h, and 36 r therebeneath. The color emissions of the phosphor materials are selectively enhanced by transmission through the associated filtering components.

Portions of the process for fabricating the aforedescribed interstitially defined first 24, second 26 and third 36 filter window areas comprising the color cath- .ode ray tube screen structure 11, are delineated in FIGS. 1a through 11' of the drawings.

The process for fabricating the improved multiwindow screen structure is initiated by coating the clean interior surface of the viewing portion of the glass face panel 13 with a uniform layer ofa negative photosensitive resist materialadmixed with an inert protective substance. A negative photosensitiveresist composition is a light-activated material-that becomes polymeri zed when exposed to actinic radiation. An example of-a negative photosensitive resist composition commonly utilized in cathode ray tube screen fabrication, is a water-alcohol solution of polyvinyl alcohol sensitized with ammonium dich'romate. In the process of the invention. the aforementioned polyvinyl alcohol system known as Kaolin, zinc oxide, calcium carbonate, and materials related thereto. Preparation of this protective coating material 15, which is also referred to as a stopoff photoresist, is a two-step formulation procedure.

' An initial suspension is first prepared wherein, for example, 40 grams of aluminum silicate and 20 grams of polyvinyl alcohol solids are added to 400 cubic centimeters (00) of deionized water and ball-milled to provide a complete suspension, which is then filtered to remove any lumps and air bubbles therefrom. Equal volumes of this basic suspension and a monohydric alcohol, such as ethanol or methanol, areadmixed and the mixture then sensitized with 3 percent by volume of a l2,5 weight percent of ammonium dichromate solution. As previously mentioned, a uniform coating 15 of this protective material is applied to the face panel as by spraying, flowing, or spinning, whereupon the coated panel is dried.

The apertured pattern mask 16 is positioned in spaced relationship to the coated surface of the panel 13, as shown in FIG. 1a, whereupon the protective photosensitive coating 15 is discretely light exposed by directing actinic radiations Y" and 2 from two spaced apart positions 17 and 18 through the multiple apertures in the pattern mask one of which is shown. The respective light beams, originating from

sources

17 and 18 oriented to expose the second and the third window patterns, are sized by the mask aperture 19 whereupon the light impinged second and third window areas, 25 and 27 respectively, of the protective coating 15 are photo-polymerized by areas of light exposure that are usually slightly larger than the area of the formative aperture 19 in the maskfAfter exposure, the pattern mask 16 is removed from the proximity of the panel. The light exposed panel coating 15 is then developed, such as by water rinsing, which removes the unexposed photosensitive coating mixture from the panel surface to provide second and third polymerized filter pattern window elements 25' and 27' which are disposed on the bare glass of, the panel 13.

The patterned panelis then overcoated with a uniform primary layer of a heat formable first optical filter material 20, such being illustrated in FIG. 1b. An efficient and appropriate class of heat formable optical filter materials, is that represented by the organometallic luster compounds, which are commonly known as liquid luster preparations. Such compositions are base metal organic solutions of metals such as tin, iron, bismuth, titanium and the like, which may contain additions of metallo-organic compounds of precious metals dissolved in organic solvents. The initial color of such liquid luster preparation usually bears no semblance to the desired optical filter hue resultant from subsequent heat transformation. While luster preparations are available commercially, their formularly compositions are usually considered to be proprietary with the manufacturer of the product. A metallic luster material suitable for use as the first optical component of the primary filter layer 21 in this screen structure 11 may be, for example, a green-producing luster mateiral, such as A-l 128, which is commercially material, from Hanovia Liquid Gold Division, Englehard Industries, Inc., East Newark, NJ. Aproprietary luster thinning composition is added to the luster material to provide a coating thickness evidencing desired optical attenuation and to adjust the viscosity of the liquid luster material to expedite efficient application thereof over the patterned panel surface. It has been found that a coating viscosity in the order of 8 to ID centipoises is appropriate for spin application of the luster material. when rotating the panel in substantially the range of 90 to I50 rpm, whereupon a uniformly applied coating thickness in the order of 2.5 to 4.0 microns is achieved.

Upon drying, the overcoated panel is heated or fired in a controlled oxygen atmosphere at a temperature in the range of 450 to 500 Centigrade, for a time period such as from 2 to 3 hours. This environmentally controlled heating thermally degrades the polymerized sec ond 25' and third 27 patterned window elements formed of the protective resist mixture. In addition. the heating step transforms and oxidizes the first luster material changing the color thereof to a green-hued optical filter material; and further adherence of a substantially continuous and transparent glassy primary layer 21 of the transformed optical filter material wherein the defined second and third pattern window areas have residuals of the heat degraded protective resist 'mixture and the associated superposed filter material,

loosely retained therein.

The panel is next treated in a manner to remove the loosely retained inert protective and associated filter materials from the second and third pattern window areas. One removal procedure is in the form of lightly brushing the panel with a non-abrasive means, such as a soft-hair brush. This may be followed by the application of a sweeping of low pressure air, or a water rinse. Another successful removal means is in the form of immersing the screen area in an aqueous solution, such as water and a compatible wetting agent, and then submitting the screen environment to a controlled application of ultrasonic vibrations, after which the screen area is rinsed with water, to completely remove the residuals, and dried. This stage of the partially fabricatedscreen structure is clearly referenced in FIGS. 10 and 2 wherein the respective open second and

third window patterns

25 and 27 in the primary filter layer 21 are delineated. The inert component in the resist mixture prevents the first luster material from adhering to the glass surface of the open window pattern areas. The desired thickness of the transformed green-hued luster filter material is extremely thin being less than 0.5 microns. It has been found that the thickness of the respective optical filter materials comprising the layered screen structure should each exhibit a light transmission in the order of 60 percent to provide the desired opacity of the combined layers of filters comprising the interstitial webbing discretely defining the window areas.

The patterned panel, having the primary layer of first filter maerial adhered thereon, is next material with a uniform layer of the aforementioned protective coating which coating has been described as being formed of a negative photoresist material admixed with an inert substance such as previously disclosed. With reference to FIG. 1d, this coating is exposed by directing actinic radiations X and Z emanating from two spaced apart positions through the apertures of the repositioned pattern mask to light polymerize portions of the photosensitive coating mixture 15' in those

areas

33 and 37 subsequently to be occupied by the first and third filter pattern windows. The exposed panel is then developed, as before, by removing the unexposed protective photosensitive mixture therefrom to provide a plurality of first polymerized filter pattern elements 33' superimposed on the first optical filter material 21 in a manner to define the protective first filter pattern window areas 33, and a plurality of protective third polymerized filter pattern elements 37 disposed in the open third pattern window areas 27 of the primary filter layer 21.

In referring to FIG. Ie, the panel is then overcoated with a uniform secondary layer of a heat formable second optical filter material 30, as for example, a second color-producing liquid organo-metallic luster compound. The second luster filter material may be, for example, a blue-producing composition such as No. I30- F, which is also available from Englehard Industries.

The patterned panel 13 is again reheated in the priorly described controlled oxygen atmosphere whereby the polymerized protective resist mixture forming the second 33' and third 37 'patterned window elements, is thermally degraded, but loosely retained with the as sociated second filter material in the respective window areas. The inert protective material contained in the photosensitive resist mixture prevents the second luster material from contaminating the underlying first filter material. This second heating step, additionally transforms and oxidizes the second luster material changing the color thereof to a blue-hued optical filter-material, and further effects adherence of a substantially continuous and transparent glassy'seeondary layer 31 of the transformed optical filter material to portions .of the primary filter layer 21 including deposition in the second filter pattern window areas 25thereof. The panel is next treated, as before-described, to remove the loosely retained materials from the affected first and third window areas. Thus, the primary filter layer 21 is covered with the secondary filter layer 31 of the second optical filter material having first 33 and third 37 pat- .tern open filter windows therein, as shown in FIGS. If

At this stage, the panel is again .recoa ted with a uniform layer of the aforementioned protective coating 15" which is formed of the negative photoresist material admixed with an inert substance. Ensuing exposure of the coated panel is consummated by directing actinic radiations X and Y, emanating from twospac'edapart positions, to light polymerize portions of the photosensitive coating mixture 15" in those

areas

43 and 45 subsequently't'o be occupied by the-first and second filter pattern windows, such being illustrated in FIG. 1 g. Development of the exposed panel coating removes the unexposed photosensitive coating mixture and provides a plurality of first polymerized filter pattern elements 43' disposed in the open first pattern window areas 33 of the secondary filter layer 31, and a plurality of second polymerized filter pattern elements 45' dis posed over the second pattern filter areas 26 of the-secondary filter layer 31. A uniform tertiary coating 40 of a heat formable third optical filter material, such as another or third organometallic luster compound, is' applied as an overcoating to the patterned panel as shown in FIG. 1h. The luster preparation for this thirdfilter layer may, for example, be a red-producing luster,such as Red Rose No. 9736 or Ruby'Red v No. 9761, such compositions being commercially available from Englehard Industries.

The overcoated panel is subjected to a repeat or third heating in a controlled oxygen. atmosphere'wherein the polymerized first 43. and second 45' pattern window elements formed of the protective resist mixture are thermally degraded, and the third luster material is transformed, oxidized, and adhered as a substantially continuous and transparent tertiary layer 41 of the third red-hued optical filter material to portions of the secondary filter layer 31 including deposition in the third filter pattern windows 36 thereof. The tertiary layer evidences defined first 43 and, second 45 filter pattern window areas therein wherein the degraded protective mixture and associated third filter materials are loosely retained. Removal of these looselyretained materials, as by brushing and rinsing, or by ultrasonic means, produces first 43 and second 45 pattern open filter windows in the tertiary layer wherein the previously disposed first 24 and second 26 optical filter elements are evidenced, as delineated in FlGS. 1i and 4. The third 36 filter element window associated with the tertiary layer 41 is defined by the third pattern superimposed

open windows

27 and 37 previously formed in the primary and secondary filter layers. The superimposed primary 21, secondary 31, andtertiary 41 filter layers, namely green, blue and red filtering components, provide in combination a substantially opaque uniform interstitial webbing 49 fully surrounding each of the respective round windows in the multi-windowed screen structure 11. Each filter window is evenly defined by a uniform peripheral encompassment that is free of indentations.

With reference to FIG. lj and 5, upon completing fabrication of the interstitially defined multi-windowed optical filter screen structure ashereinbefore described, the respective green G, red R and blue B cathodoluminescent phosphor elements are suitably disposed as a patterned screen 53 over the appropriate g, r, and [7 filter windows. Deposition of the pattern of color emitting phosphor elements is accomplished in a conventional manner by one of the procedures well known in the art. Therefore, further details of the phosphor screening process will not be considered herein.

It may be considered expedient from the standpoint of phosphor brightness and color emission, to form a multi-windowed screen structure wherein only two of the window areas have respective optical filter materials disposed therein. Whether or not a filter material is evidenced in a defined window area of the screen structure is determined by the selection of the light exposure positions during fabrication; for example, if it is found beneficial to have a window area open or free of discrete optical filtering material, that window area has a specific actinic radiation directed to it during each of the primary, secondary, and tertiary filter layer exposures.

lt may be desired to modify the sizes of the apertures in the patterned mask member either before or after forming of the screen structure; as for example, having filter window openings in the opaque interstitial webbing that are smaller than the associated apertures in the patterned mask member subsequently utilized in the operable tube. In one consideration, the maskjapertures initially utilized in forming the filter windows and the defining interstitial webbing, may be subjected to a subsequential chemical etching process to enlarge their sizes thereby effecting a desired dimensional differential between the final sized apertures used in tube operation and the initially sized apertures utilized in forming the windows in the interstitial webbing. Prior art is replete with. a variety of techniques for modifying the sizes of the pattern mask apertures utilized in the forming of or the operation of specific types of color screen structures. There are several disclosures wherein changing of the aperture sizes is executed by deposition within the aperture openings of peripheral fill-in substances applied, as for example, by painting, dipping, electrophoresis, electroplating and vaporization. Such modifications of the apertures of the mask member may be utilized as. desired'in conjunction with the screen structure of the invention.

Thus, there is provided a process for fabricating an improved color cathode ray tube screen structure that incorporates smoothly defined optical filter elements therein which are surrounded by an opaque interstitial webbing of uniform thickness. A screen structure having uniformity of the opaque interstitial encompassment, as provided by this process,'effects enhanced absorbency of the ambient light impinging the exterior surface of the viewing panel thereby producing improved contrast of the color display emanating from the screen of the tube, 7

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

I. In the viewing panel of a color cathode ray tube whereon a patterned screen structure formed of a plurality of pattern elements is disposed on the interior surface of said panel relative to a multiple apertured pattern mask member spatially positioned adjacent thereto, an improved process for forming a multiwindowed screen structure defined by a webbing of uniform opaque interstices disposed on an interior surface of said panel prior to the fabrication of the phosphor screen thereon, said windows defining areas of transparent optical filter materials and evidencing peripheral shapings free of indentations similar to those of the respective formative apertures in said pattern mask, said improved process comprising the steps of:

coating the interior of said panel with a uniform layer of a protective coating formed of a negative photosensitive resist material admixed with an inert substance; exposing said eoated panel by directing actinic radiations emanating from at least two spaced-apart positions through the apertures in said pattern mask to light-polymerize those portions of said photosensitive coating mixture in said exposed areas;

developing said light exposed areas of said panel coating to provide a plurality of polymerized filter pattern window elements on the bare glass of said panel;

overcoating said patterned panel with a uniform liquid primary layer of a heat formable first optical filter material;

heating said overcoated panel to thermally degrade said polymerized window elements formed of said resist mixture and to transform and adhere a substantially continuous and transparent primary layer of said optical filter material to the glass surface of said panel, said primary layer having a defined plurality of filter pattern window areas therein wherein the degraded materials resultant of said heat are loosely retained;

ter pattern window areas in said primary layer;

coating said panel with a uniform layer of said protective coating formed of said negative photoresist material admixed with said inert substance;

exposing said coated panel to actinic radiations emanating from at least two spaced apart positions to light-polymerize a plurality of discrete portions of said photosensitive coating mixture;

developing said light-exposed panel to provide a plurality of filter pattern elements definitively superimposed on the primary layer of said first optical filter material;

overcoating said patterned panel with a uniform liquid secondary layer of a heat formable second optical filter material;

heating said overcoated panel to thermally degrade said polymerized window elements formed of said resist mixture and to transform and adhere a substantially continuous and transparent secondary layer of said second optical filter material to selected portions of said primary filter layer, said secondary layer having a defined plurality of at least two filter pattern window elements therein wherein said degraded mixture and associated second filter materials are loosely retained;

removing said loosely retained materials from the plurality of at least two open filter window areas in said secondary filter layer;

exposing said coated panel by directing actinic radiations emanating from at least two spaced apart positions to light-polymerize discrete portions of said photosensitive coating mixture;

developing said light exposed panel coating to provide a plurality of at least two polymerized filter patterned elements disposed on selected portions of said secondary filter layer;

overcoating said patterned panel with a uniform liquid tertiary layer of a heat formable third optical filter material;

heating said overcoated panel to thermally degrade said polymerized window elements formed of said resist mixture and to transform and adhere a substantially continuous and transparent tertiary layer of said third optical filter material to selected portions of said secondary filter layer, said tertiary layer having a plurality of at least two defined filter pattern window areas therein wherein said degraded mixture and associated third filter material are loosely retained; and

removing said loosely retained materials from the plurality of filter patterned window areas in said tertiary layer to provide at least two open filter window areas therein, said superimposed patterned primary, secondary, and tertiary filter layers providing at least two window areas having specific filter materials disposed therein, and wherein said superposed filter layers provide in combination a substantially opaque and uniform interstitial webbing fully surrounding each of respective window areas in said screen structure whereof the uniform peripheral encompassment of each window area is free of indentations.

2. In the viewing panel of a color cathode ray tube whereon a patterned screen structure formed of first, second and third pattern elements in disposed on the interior surface of said panel relative to a multiple apertured pattern mask spatially positioned adjacent thereto. an improved process for forming an improved multi-windowed screen structure defined by a webbing of uniform opaque interstices disposed on the interior surface of said panel prior to the fabrication of the phosphor screen thereon, each of said windows defining an area of a selected substantially transparent optical filter material and evidencing a peripheral shaping free of indentations similar to that of the respective formative aperture in said pattern mask, said improved process comprising the steps of:

coating the interior of said panel with a uniform layer of a protective coating formed of a negative photosensitive resist material admixed with an inert substance; exposing said coated panel by directing actinic radiations emanating from two spaced apart positions through the apertures in said pattern mask to lightpolymerize those portions of said photosensitive coating mixture in the areas subsequently occupied by said second and third filter pattern windows; developing said light exposed panel coating by removing the unexposed photosensitive coating mixture therefrom to provide second and third polymerized filter pattern window elements on the bare glass of said panel; overcoating said patterned panel with a uniform liquid primary layer of a heat formable first optical filter material; heating said overcoated panel in a controlled oxygen atmosphere to thermally degrade said polymerized window elements formed of said resist mixture and oxidize said first optical material and adhere a sub stantially continuous and transparent primary layer of said first optical filter material to the glass surface of said panel, said primary layer having defined second and third filter pattern window areas therein wherein said degraded mixture and associated first filter materials are loosely retained; treating said panel to remove said loosely retained materials from said second and third filter pattern window areas to provide a primary layer of said first optical filter material having second and third pattern open filter windows therein; coating said panel with a uniform layer of said pro tective coating formed of said negative photoresist material admixed with said inert substance; exposing said coated panel by directing actinic radiations emanating from two spaced apart positions through the apertures of said pattern mask to lightpolymerize discrete portions of said photosensitive coating mixture in those areas subsequently occu pied by said first and third filter pattern windows; developing said light-exposed panel coating by removing the unexposed photosensitive mixture therefrom to provide a plurality of first polymerized filter pattern elements superimposed on said first optical filter material in a manner to define the first filter pattern window areas, and a plurality of third polymerized filter pattern elements disposed in the open third pattern window areas of said primary filter layer; overcoating said patterned panel with a uniform liquid secondary layer ofa heat formable second optical filter material;

heating said overcoated panel in a controlled oxygen atmosphere to thermally degrade said polymerized window elements formed of said resist mixture and oxidize and adhere a substantially continuous and transparent secondary layer of said second optical filter material to portions of said primary filter layer including deposition in the second filter pattern windows thereof. said secondary layer having defined first and third filter pattern window areas therein wherein said degraded mixture and associated second filter materials are loosely retained;

treating said panel to remove said loosely retained materials from said first and third filter window areas whereupon said primary filter layer is covered with said secondary layer of the second optical filter material having first and third pattern open filter windows therein.

exposing said coated panel by directing actinic radiations emanating from two spaced apart positions through the apertures in said pattern mask to light polymerize discrete portions of said photosensitive coating mixture in those areas subsequently occupied by said first and second filter pattern windows;

developing said light exposed panel coating by removing the unexposed photosensitive coating mixture therefrom to provide a plurality of first polymerized filter pattern elements deposed in said open first pattern window areas of said secondary filter layer, and a plurality of second polymerized filter pattern elements disposed in the open second pattern window areas of said secondary filter layer;

heating said overcoated panel in a controlled oxygen atmosphere to thermally degrade said polymerized window elements formed of said resist mixture and oxidize and adhere a substantially continuous and transparent tertiary layer of said third optical filter material to portions of said secondary filter layer including deposition in the third filter pattern windows thereof, said teritary layer having defined first and second filter .pattern window areas therein wherein said degraded mixture and associated third filter materials are loosely retained; and

treating said panel to remove said loosely retained materials from said first and second filter pattern window areas whereupon the secondary filter layer is recovered with said tertiary layer of a third optical filter material having first and second pattern open filter windows therein, the combination of said superimposed primary, secondary and tertiary filter layers provides a substantially opaque uniformly structured interstitial webbing fully surrounding each of the respective optical filter windows in said screen structure whereof the uniform peripheral encompassment of each filter window is free of indentations.

3. The process for forming the improved multiwindowed screen structure according to claim 2 wherein the negative photosensitive resist material is a water-alcohol solution of polyvinyl alcohol sensitized with ammonium dichromate, and wherein said inert protective substance is a material that is thermally and chemically inactive to the temperatures and materials encountered in said process, and one that does not substantially alter the pH of the polyvinyl alcohol system.

4. The process for forming the improved multiwindowed screen structure according to claim 3 wherein said inert protective substance associated with said negative photosensitive resist material is at least one selected from the group comprising aluminum silicate. zinc oxide, calcium carbonate, and materials related thereto.

5. A process for forming the improved multiwindowed screen structure according to claim 2 wherein the heat formable optical filter materials are organometallic luster compositions.

6. A process for forming the improved multiwindowed screen structure according to claim 2 wherein said heating of the overcoated panel is within the range of substantially 450 to 500 Centigrade.

7. A process for forming the improved multiwindowed screen structure according to claim 2 wherein the treating of said panel to remove the loosely retained materials resultant from heating is in the form oflightly brushing the panel with a non-abrasive means.

8. A process for forming the improved multiwindowed screen structure according to claim 2 wherein the treating of said panel to remove the loosely retained materials resultant from heating involves immersing the screen area in an aqueous solution and subjecting the environment to ultrasonic vibrations.

Claims

1. In the viewing panel of a color cathode ray tube whereon a patterned screen structure formed of a plurality of pattern elements is disposed on the interior surface of said panel relative to a multiple apertured pattern mask member spatially positioned adjacent thereto, an improved process for forming a multi-windowed screen structure defined by a webbing of uniform opaque interstices disposed on an interior surface of said panel prior to the fabrication of the phosphor Screen thereon, said windows defining areas of transparent optical filter materials and evidencing peripheral shapings free of indentations similar to those of the respective formative apertures in said pattern mask, said improved process comprising the steps of: coating the interior of said panel with a uniform layer of a protective coating formed of a negative photosensitive resist material admixed with an inert substance; exposing said coated panel by directing actinic radiations emanating from at least two spaced-apart positions through the apertures in said pattern mask to light-polymerize those portions of said photosensitive coating mixture in said exposed areas; developing said light exposed areas of said panel coating to provide a plurality of polymerized filter pattern window elements on the bare glass of said panel; overcoating said patterned panel with a uniform liquid primary layer of a heat formable first optical filter material; heating said overcoated panel to thermally degrade said polymerized window elements formed of said resist mixture and to transform and adhere a substantially continuous and transparent primary layer of said optical filter material to the glass surface of said panel, said primary layer having a defined plurality of filter pattern window areas therein wherein the degraded materials resultant of said heat are loosely retained; removing said loosely retained materials from the filter pattern window areas in said primary layer; coating said panel with a uniform layer of said protective coating formed of said negative photoresist material admixed with said inert substance; exposing said coated panel to actinic radiations emanating from at least two spaced apart positions to light-polymerize a plurality of discrete portions of said photosensitive coating mixture; developing said light-exposed panel to provide a plurality of filter pattern elements definitively superimposed on the primary layer of said first optical filter material; overcoating said patterned panel with a uniform liquid secondary layer of a heat formable second optical filter material; heating said overcoated panel to thermally degrade said polymerized window elements formed of said resist mixture and to transform and adhere a substantially continuous and transparent secondary layer of said second optical filter material to selected portions of said primary filter layer, said secondary layer having a defined plurality of at least two filter pattern window elements therein wherein said degraded mixture and associated second filter materials are loosely retained; removing said loosely retained materials from the plurality of at least two open filter window areas in said secondary filter layer; coating said panel with a uniform layer of said protective coating formed of said negative photoresist material admixed with said inert substance; exposing said coated panel by directing actinic radiations emanating from at least two spaced apart positions to light-polymerize discrete portions of said photosensitive coating mixture; developing said light exposed panel coating to provide a plurality of at least two polymerized filter patterned elements disposed on selected portions of said secondary filter layer; overcoating said patterned panel with a uniform liquid tertiary layer of a heat formable third optical filter material; heating said overcoated panel to thermally degrade said polymerized window elements formed of said resist mixture and to transform and adhere a substantially continuous and transparent tertiary layer of said third optical filter material to selected portions of said secondary filter layer, said tertiary layer having a plurality of at least two defined filter pattern window areas therein wherein said degraded mixture and associated third filter material are loosely retained; and removing said loosely retained materials from the plurality of filter patterned window areas in said tertiAry layer to provide at least two open filter window areas therein, said superimposed patterned primary, secondary, and tertiary filter layers providing at least two window areas having specific filter materials disposed therein, and wherein said superposed filter layers provide in combination a substantially opaque and uniform interstitial webbing fully surrounding each of respective window areas in said screen structure whereof the uniform peripheral encompassment of each window area is free of indentations.

2. IN THE VIEWING PANEL OF A COLOR CATHODE RAY TUBE WHEREON A PATTERNED SCREEN STRUCTURE FORMED OF FIRST, SECOND AND THIRD PATTERN ELEMENTS IN DISPOSED ON THE INTERIOR SURFACE OF SAID PANEL RELATIVE TO A MULTIPLE APERTURED PATTERN MASK SPATIALLY POSITIONED ADJACENT THERETO, AN IMPROVED PROCESS FOR FORMING AN IMPROVED MULTI-WINDOWED SCREEN STRUCTURE DEFINED BY A WEBBING OF UNIFORM OPAQUE INTERSTICES DISPOSED ON THE INTERIOR SURFACE OF SAID PANEL PRIOR TO THE FABRICATION OF THE PHOSPHOR SCREEN THEREON, EACH OF SAID WINDOWS DEFINING AN AREA OF A SELECTED SUBSTANTIALLY TRANSPARENT OPTICAL FILTER MATERIAL AND EVIDENCING A PERIPHERAL SHAPING FREE OF INDENTATIONS SIMILAR TO THAT OF THE RESPECTIVE FORMATIVE APERTURE IN SAID PATTERN MASK, SAID IMPROVED PROCESS COMPRISING THE STEPS OF: COATING THE INTERIOR OF SID PANEL WITH A UNIFORM LAYER OF A PROTECTIVE COATING FORMED OF A NEGATIVE PHOTOSENSITIVE RESIST MATERIAL ADMIXED WITH AN INERT SUBSTANCE; EXPOSING SAID COATED PANEL BY DIRECTING ACTINIC RADIATIONS EMANATING FROM TWO SPACED APART POSITIONS THROUGH THE APERTURES IN SAID PATTERN MASK TO LIGHT-POLYMERIZE THOSE PORTIONS OF SAID PHOTOSENSITIVE COATING MIXTURE IN THE AREAS SUBSEQUENTLY OCCUPIED BY SAID SECOND AND THIRD FILTER PATTERN WINDOWS; DEVELOPING SAID LIGHT EXPOSED PANEL COATING BY REMOVING THE UNEXPOSED PHOTOSENSITIVE COATING MIXTURE THEREFROM TO PROVIDE SECOND AND THIRD POLYMERIZED FILTER PATTERN WINDOW ELEMENTS ON THE BARE GLASS OF SAID PANEL; OVERCOATING SAID PATTERNED PANEL WITH A UNIFORM LIQUID PRIMARY LAYER OF A HEAT FORMABLE FIRST OPTICAL FILTER MATERIAL; HEATING SAID OVERCOATED PANEL IN A CONTROLLED OXYGEN ATMOSPHERE TO THERMALLY DEGRADE SAID POLYMERIZED WINDOW ELEMENTS FORMED OF SAID RESIST MIXTURE AND OXIDIZE SAID FIRST OPTICAL MATERIAL AND ADHERE A SUBSTANTIALLY CONTINUOUS AND TRANSPARENT PRIMARY LAYER OF SAID FIRST OPTICAL FILTER MATERIAL TO THE GLASS SURFACE OF SAID PANEL, SAID PRIMARY LAYER HAVING DEFINED SECOND AND THIRD FILTER PATTERN WINDOW AREAS THEREIN WHEREIN SAID DEGRADED MIXTURE AND ASSOCIATED FIRST FILTER MATERIALS ARE LOOSELY RETAINED; TREATING SAID PANEL TO REMOVE SAID LOOSELY RETAINED MATERIALS FROM SAID SECOND AND THIRD FILTER PATTERN WINDOW AREAS TO PROVIDE A PRIMARY LAYER OF SAID FIRST OPTICAL FILTER MATERIAL HAVING A SECOND AND THIRD PATTERN OPEN FILTER WINDOWS THEREIN; COATING SAID PANEL WITH A UNIFORM LAYER OF SAID PROTECTIVE COATING FORMED OF SAID NEGATIVE PHOROTESIST MATERIAL ADMIXED WITH SAID INERT SUBSTANCE; EXPOSING SAID COATED PANEL BY DIRECTING ACTINIC RADIATIONS EMANATING FROM TWO SPACED APART POSITIONS THROUGH THE APERTURES OF SAID PATTERN MASK TO LIGHT-POLYMERIZE DISCRETE PORTIONS OF SAID PHOTOSENSITIVE COATING MIXTURE IN THOSE AREAS SUBSEQUENTLY OCCUPIED BY SAID FIRST AND THIRD FILTER PATTERN WINDOWS; DEVELOPING SAID LIGHT-EXPOSED PANEL COATING BY REMOVING THE UNEXPOSED PHOTOSENSITIVE MIXTURE THEREFROM TO PROVIDE A PLURALITY OF FIRST POLYMERIZED FILTER PATTERN ELEMENTS SUPERIMPOSED ON SAID FIRST OPTICAL FILTER MATERIAL IN A MANNER TO DEFINE THE FIRST FILTER PATTERN WINDOW AREAS, AND A PLURALITY OF THIRD POLYMERIZED FILTER PATTERN ELEMENTS DISPOSED IN THE OPEN THIRD PATTERN WINDOW AREAS OF SAID PRIMARY FILTER LAYER; OVERCOATING SAID PATTERNED PANEL WITH A UNIFORM LIQUID SECONDARY LAYER OF A HEAT FORMABLE SECOND OPTICAL FILTER MATERIAL; HEATING SAID OVERCOATED PANEL IN A CONTROLLED OXYGEN ATMOSPHERE TO THERMALLY DEGRADE SAID POLYMERIZED WINDOW ELEMENTS FORMED OF SAID RESIST MIXTURE AND OXIDIZE AND ADHERE A SUBSTANTIALLY CONTINOUS AND TRANSPARENT SECONDARY LAYER OF SAID SECOND OPTICAL FILTER MATERIAL TO PORTIONS OF SAID PRIMARY FILTER LAYER INCLUDING DEPOSITION IN THE SECOND FILTER PATTERN WINDOWS THEREOF, SAID SECONDARY LAYER HAVING DEFINED FIRST AND THIRD FILTER PATTERN WINDOW AREAS THEREIN WHEREIN SAID DEGRADED MIXTURE AND ASSOCIATED SECOND FILTER MATERIALS ARE LOOSELY RETAINED; TREATING SAID PANEL TO REMOVE SAID LOOSELY RETAINED MATERIALS FROM SAID FIRST AND THIRD FILTER WINDOW AREAS WHEREUPON SAID PRIMARY FILTER LAYER IS COVERED WITH SAID SECONDARY LAYER OF THE SECOND OPTICAL FILTER MATERIAL HAVING FIRST AND THIRD PATTERN OPEN FILTER WINDOWS THEREIN; COATING SAID PANEL WITH A UNIFORM LAYER OF SAID PROTECTIVE COATING FORMED OF SAID NEGATIVE PHOSORESIST MATERIAL ADMIXED WITH SAID INERT SUBSTANCE; EXPOSING SAID COATED PANEL BY DIRECTING ACTINIC RADIATIONS EMANATING FROM TWO SPACED APART POSITIONS THROUGH THE APERTURES IN SAID PATTERN MASK TO LIGHT POLYMERIZE DISCRETE PORTIONS OF SAID PHOTOSENSITIVE COATING MIXTURE IN THOSE AREAS SUBSEQUENTLY OCCUPIED BY SAID FIRST AND SECOND FILTER PATTERN WINDOWS; DEVELOPING SAID LIGHT EXPOSED PANEL COATING BY REMOVING THE UNEXPOSED PHOTOSENSITIVE COATING MIXTURE THEREFROM TO PROVIDE A PLURALITY OF FIRST POLYMERIZED FILTER PATTERN ELEMENTS DEPOSED IN SAID OPEN FIRST PATTERN WINDOW AREAS OF SAID SECONDARY FILTER LAYER, AND A PLURALITY OF SECOND POLYMERIZED FILTER PATTERN ELEMENTS DISPOSED IN THE OPEN SECOND PATTERN WINDOW AREAS OF SAID SECONDARY FILTER LAYER; OVERCOATING SAID PATTERNED PANEL WITH A UNIFORM LIQUID TERTIARY LAYER OF HEAT FORMABLE THIRD OPTICAL FILTER MATERIAL; HEATING SAID OVERCOATED PANEL IN A CONTROLLED OXYGEN ATMOSPHERE TO THERMALLY DEGRADE SAID POLYMERIZED WINDOW ELEMENTS FORMED OF SAID RESIST MIXTURE AND OXIDIZE AND ADHERE A SUBSTANTIALLY CONTINOUS AND TRANSPARENT TERTIARY LAYER OF SAID THIRD OPTICAL FILTER MATERIAL TO PORTIONS OF SAID SECONDARY FILTER LAYER INCLUDING DEPOSITION IN THE THIRD FILTER PATTERN WINDOWS THEREOF, SAID TERTIARY LAYER HAVING DEFINED FIRST AND SECOND FILTER PATTERN WINDOW AREAS THEREIN WHEREIN SAID DEGRADED MIXTURE AND ASSOCIATED THIRD FILTER MATERIALS ARE LOOSELY RETAINED; AND TREATING SAID PANEL TO REMOVE SAID LOOSELY RETAINED MATERIALS FROM SAID FIRST AND SECOND FILTER PATTERN WINDOW AREAS WHEREUPON THE SECONDARY FILTER LAYER IS RECOVERD WITH SAID TERTIARY LAYER OF A THIRD OPTICAL FILTER MATERIAL HAVING FIRST AND SECOND PATTERN OPEN FILTER WINDOWS THEREIN, THE COMBINATION OF SAID SUPERIMPOSED PRIMARY, SECONDARY AND TERTIARY FILTER LAYERS PROVIDES A SUBSTANTIALLY OPAQUE UNIFORMLY STRUCTURED INTERSTITIAL WEBBING FULLY SURROUNDING EACH OF THE RESPECTIVE OPTICAL FILTER WINDOWS IN SAID SCREEN STRUCTURE WHEREOF THE UNIFORM PERIPHERAL ENCOMPASSMENT OF EACH FILTER WINDOW IS FREE OF INDENTATIONS.

3. The process for forming the improved multi-windowed screen structure according to claim 2 wherein the negative photosensitive resist material is a water-alcohol solution of polyvinyl alcohol sensitized with ammonium dichromate, and wherein said inert protective substance is a material that is thermally and chemically inactive to the temperatures and materials encountered in said process, and one that does not substantially alter the pH of the polyvinyl alcohol system.

4. The process for forming the improved multi-windowed screen structure according to claim 3 wherein said inert protective substance associated with said negative photosensitive resist material is at least one selected from the group comprising aluminum silicate, zinc oxide, calcium carbonate, and materials related thereto.

5. A process for forming the improved multi-windowed screen structure according to claim 2 wherein the heat formable optical filter materials are organometallic luster compositions.

6. A process for forming the improved multi-windowed screen structure according to claim 2 wherein said heating of the overcoated panel is within the range of suBstantially 450* to 500* Centigrade.

7. A process for forming the improved multi-windowed screen structure according to claim 2 wherein the treating of said panel to remove the loosely retained materials resultant from heating is in the form of lightly brushing the panel with a non-abrasive means.

8. A process for forming the improved multi-windowed screen structure according to claim 2 wherein the treating of said panel to remove the loosely retained materials resultant from heating involves immersing the screen area in an aqueous solution and subjecting the environment to ultrasonic vibrations.