US3653901A

US3653901A - Color kinescope production with a temporary mask

Info

Publication number: US3653901A
Application number: US872981A
Authority: US
Inventors: Robert William Etter
Original assignee: RCA Corp
Current assignee: RCA Licensing Corp
Priority date: 1969-10-31
Filing date: 1969-10-31
Publication date: 1972-04-04
Anticipated expiration: 1989-04-04
Also published as: CA936049A; DE2053413A1; DE2053413B2; JPS4835859B1; NL7015936A; FR2066583A5

Abstract

A method for producing a kinescope having an image screen and an apertured target mask, the apertures of the mask being temporarily reduced in size for use as a photographic master for producing the image screen. Such reduction in aperture size is achieved by providing the target mask with a coating of a filmforming material which exhibits shrinkage during drying thereof. The coating is comprised of a number of opaque film portions which individually close the mask apertures and preferably are disposed on the aperture walls. The coating is dried so as to remove the central regions of the film portions, thereby providing a temporary mask with light-transmitting corridors in the film portions, such corridors being smaller in cross-section than the mask apertures. The temporary mask is used in screen printing. The shrinkable material is eliminated from the mask, after which the screen and target mask are incorporated into a kinescope.

Description

United States Patent Etter 1 51 Apr. 4, 1972 [54] COLOR KINESCOPE PRODUCTION WITH A TEMPORARY MASK [72] Inventor: Robert William Etter, Lititz, Pa.

[73] Assignee: RCA Corporation [22] Filed: Oct. 31, 1969 211 App]. No.2 872,981

3 3,070,441 12/1962 Schwartz ..313/92 B X 3,231,380 1/1966 Law.... ..156/l8 X 3,406,068 10/1968 Law ..96/36 X II II II II I-/ II II II I I, l, I, I I

Primary Examiner-Harold Ansher Assistant Examiner-Joseph C. Gil Attorney-Glenn H. Bruestle ABSTRACT A method for producing a kinescope having an image screen and an apertured target mask, the apertures of the mask being temporarily reduced in size for use as a photographic master for producing the image screen. Such reduction in'aperture size is achieved by providing the target mask with a coating of a film-forming material which exhibits shrinkage during drying thereof. The coating is comprised of a number of opaque film portions which individually close the mask apertures and preferably are disposed on the aperture walls. The coating is dried so as toremove the central regions of the film portions,

thereby providing a temporary mask with light-transmitting corridors in the film portions, such corridors being smaller in cross-section than the mask apertures. The temporary mask is used in screen printing. The shrinkable material is eliminated from the mask, after which the screen and target mask are incorporated into a kinescope.

4 Claims, 7 Drawing Figures 1111111111! All It;

Patented April 4, 1972 3,653,901

2 Sheets-Sheet l Patented April 4, 1972 3,653,901

2 Sheets-Sheet 2 III IIIIIIIII '///////I II I l ornez/ BACKGROUND OF THE INVENTION The present invention relates to color kinescopes and particularly to a novel method for making a maskedtarget color kinescope wherein the image screen is produced with the use of the target mask having its apertures temporarily reduced in size. i

The prior art disclosed color kinescopes having both an image screen, or target, which includes a multiplicity of groups of closely spaced elemental phosphor deposits, the elemental deposits of each one of such groups emitting light of a different color when struck by an electron beam, and a colorselection, or target, mask disposed between the image screen and the electron source of the kinescope. Such target masks, including those of the non-focusing and focusing variety, and theirmode'of operation are well known. Such target masks may be of a planar or spherical or some other non-planar, contour, the contour of a particular target mask generally being similar to that of the image screen with which it is used. The apertures of the target masks can be of circular or some other cross-sectional configuration. Generally, commercial screen printing procedures involve using a target mask having apertures of a desired final size as a master for photographically printing the phosphor areas thereof. The target mask with the size of its apertures unchanged, is then used as such in a color kinescope for color selection. Those same-size apertures used for both the screen printing function and for the color selection function, are referred to herein as bifunctional apertureslHowever, the apertures of many target masks used in prior art color kinescopes are of such size and the electrode operating voltages of such target mask kinescopes are of such magnitudes that an electron beam usually impinges only a relatively small proportion of each one of its respective phosphor areas.

To increase the brightness of the image of a color kinescope, the prior art discloses target masks having apertures which are individually larger than the respective phosphor areas of the image screens associated therewith. Such larger (in comparison with the phosphor areas) apertures provide electron beam spots of greater size (as measured at the screen) than the respective individual phosphor areas, so that for non-focusing-type tubes and those focusing-type tubes where the focusing action is not sufficient to completely offset the increase in the size of the electron beam spots, a larger proportion of each phosphor area is impinged than in previous kinescopes. A mask-type color tube in which the electron beam spot is greater in size than its respective phosphor areas is referred to as a negative leaving tolerance tube. Such target masks with larger apertures are not satisfactory for screen printing because they generally lead (due to p'enumbra-umbra effect) to oversize (and, therefore, overlapping) phosphor areas and associated p roblems with color purity and white uniformity.

In a method disclosed by H.B. Law in an application Ser. No. 872,978 filed currently herewith on Oct. 3 l, 1969, and assigned to the present assignee, a coating of a film-forming material is provided on a completed target mask having finalsize apertures, the coating being comprised of opaque film portions which are disposed at and substantially close the various apertures of the target mask. After drying, the central regions of these film portions are then either reduced in thickness sufficiently to cause them to be pellucid or completely eliminated by, for example, exposing the coated mask to a controlled flash of radiant energy form, for example, a Xenonlamp, thereby "burning" or vaporizing the material at these central regions or by dissolution of these central regions with suitable solvents. The temporary mask so produced is thereafter used for screen printing, the printing light passing through and being defined by corridors (unobstructed openings or very thin areas which are pellucid) in the film portions, these corridors being smaller in size than the target mask apertures. Then the coating is completely eliminated to restore the completed target mask to its original condition, the target mask and screen thereafter being incorporated into a kinescope.

SUMMARY OF THE INVENTION The present invention relates to a novel method for producing a color kinescope of the type comprising an image screen, including a mosaic of phosphor areas and, optionally, a lightabsorbing matrix and a target mask having final-size apertures therein. The mask, with its apertures temporarily reduced in size, is used as a photographic master in screen printing. The mask aperture size is reduced by providing to the target mask a coating of a film-forming material which is characterized by its physical shrinkage during the drying thereof, such shrinkage being sufficient to provide light-transmitting corridors in the film portions. The coating is comprised of a number of opaque film portions which are individually disposed at and substantially close the various apertures, the film portions preferably being disposed on the walls of the apertures. Alternatively, the coating can be disposed at a major surface of the target mask with the film portions disposed above the apertures. The film portions preferably have relatively thin central regions and relatively thick peripheral regions adjacent to the aperture walls. The coating is dried so as to shrink the film portions and thereby remove the central regions of the film portions, thus producing opaque bands of the coating material at the aperture walls. Alternatively, the shrinkable film portions can be non-opaque, these non-opaque film portions or the bands produced therefrom thereafter being converted to an opaque condition, the central regions of such converted v film portions then being removed by drying, as above. The

opaque bands are comprised of at least parts of the peripheral regions of the film portions and define radiation-transmitting corridors of a desired size smaller than respective ones of the apertures. The temporary mask is then used to provide the image screen by steps including photographic exposure through the above corridors. These bands and any other remaining parts of the coating material are then eliminated from the target mask, preferably by air baking, evaporation, or chemical dissolution, the employed coating material preferably leaving substantially no residue. The target mask and the image screen produced therewith, are then incorporated into a kinescope.

The present invention produces the light-transmitting corridors of the temporary mask simultaneous with the drying of the coating thereof, thereby avoiding separate operations for the drying of the coating and subsequent provision of the corridors. The avoidance of the use of solvents for producing such light-transmitting corridors obviates the need for the equipment (e.g., separate tanks, pumps, etc.) usually associated with such solvent removal, thereby providing a capital savings. As a result, such color kinescopes can be produced with greater economy and facility.

BRIEF DESCRIPTION OF THE DRAWINGS thereof to a temporary mask according to one embodiment of the present invention.

FIG. 5 is a fragmentary transverse sectional view of a temporary mask produced from the structure shown in FIG. 2 according to the embodiments of the present invention shown in FIGS. 3 and 4.

FIG. 6 is a fragmentary plan view of the temporary mask shown in FIG. 5.

FIG. 7 is a fragmentary transverse sectional view of a color selection mask during the processing for the conversion thereof to a temporary mask according to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a color kinescope 10 produced by the novel method disclosed herein, which kinescope 10 includes a glass envelope 12 comprising a funnel l4 and a cap 16, which cap 16 includes a transparent faceplate 18. A plurality of elemental phosphor areas 20, which collectively comprise two or more groups of different phosphors and which are individually capable of emitting luminescence of a particular color (e.g., red, blue, or green) on being struck by an electron beam 21, are deposited on the internal surface 22 of the transparent faceplate 18. The faceplate 18 with the phosphor areas 20, and, optionally, a light-absorbing matrix 23 (discussed below) disposed thereon are collectively referred to herein as an image screen 24. Generally, there is included on the image screen an electron-permeable, light-reflecting, conductive layer (not shown) of aluminum, for example, which covers the phosphor areas and serves as an electrode. The phosphor areas are, for illustration purposes, exaggerated in size and proportion (as are other parts of FIG. 1 and the other figures) and shown as having a dot configuration, which dots may be arranged in the well-known hexagonal dot pattern (not shown). Alternatively, each phosphor area may have a stripe configuration (not shown) which is known in the art, these stripesbeing arranged in an alternating array of different color phosphors to provide a line screen. The kinescope 10 further includes a number of electron guns and either electrostatic or magnetic deflection and convergence means, none of which are shown, for simplicity. In generally parallel, spaced relation with the screen 24 is a color selection mask 30 which can be, for example, of the focusing or non-focusing variety, both of which are known in the art. A suitable frame 32 or other means can be used to support the mask 30. Unless stated otherwise, for purposes of illustration, the mask 30 is understood to be of the non-focusing variety, which is operated at substantially the same potential as the screen 24 to form a field-free region therebetween. The mask 30 is made from a thin sheet or band of conducting material (e.g., cold-rolled steel) and has a plurality of apertures 34 of desired final size therein. While the apertures 34 are, for simplicity, shown in FIG. 1 to be substantially circular in shape, apertures having other shapes may be used. For example, the mask may be of the grill type (not shown), having slot-shaped apertures. The apertures 34 are related in size and position to respective phosphor areas 20 of the image screen 24, the size relationship being so that, where the mask 30 is of the non-focusing variety, each final-size aperture 34 is of such dimension as to be capable of passing an electron beam 21 whose dimensions, as measured at the screen 24 (i.e., the spot size of the beam), are atleast substantially equal to, or preferably, larger than, the dimensions of the individual phosphor areas 20 upon which the electron beam impinges. The electron beam spot size preferably is sufficiently greater than the size of the individual phosphor areas as to provide a negative leaving tolerance (i.e., the electron beam spot is larger than a corresponding phosphor area) but not so great that the electron beam impinges any ones other than the intended phosphor areas. In general, with a prior art mask having bifunctional apertures of a given size, the size of the light spots produced during screen printing substantially exceeds that of the elec tron beam spots produced in the operation of the kinescope. This is because of the more extensive penumbra-umbra effect that exists in screen printing, such size differences and the penumbra-umbra effect being known to the art. This greater size of the light spots (compared to the electron beam spots) results in the individual phosphor areas being significantly larger than their associated electron beam spot so that the beam impinges only a portion of each phosphor areas. In the present invention therefore, the final-size apertures 34 of the mask 30 (considered to be a non-focusing mask) should be of such size that the electron beam spot is at least equal in size to, and preferably larger than, the respective phosphor areas. Generally, it is preferred that the final size apertures 34 exceed in size their associated phosphor areas 20. Where a kinescope contains a focusing-type mask, the final-size apertures of such a mask are significantly greater in size than their respective individual phosphor areas whether the kinescope is of the positive leaving tolerance (i.e., the beam spot is smaller than a corresponding phosphor area) or the negative leaving tolerance variety. In most color kinescopes in the prior art, there is a single aperture in the color selection mask for each trio of phosphor dots (i.e., one dot each of red, green, and blue phosphors). However, for purposes of simplicity, each aperture 34 is shown in FIG. 1 to correspond in position with only one phosphor area 20.

In the operation of the kinescope 10, electrons are emitted by the electron guns (not shown) and thereafter directed, by means known in the art, as electron beams 21, through the apertures 34 to impinge upon the phosphor areas 20. Because a larger electron beam spot is produced and impinges upon an entire individual phosphor area, the kinescope 10 exhibits improved characteristics, such as increased image brightness and contrast, over prior art kinescopes.

According to the present invention, a color kinescope (e.g., 10 of FIG. 1) is manufactured by steps including the production of a temporary mask 50 (FIG. 5) used for screen printing, from a completed mask 52 (FIG. 2). The mask 52 (focusing or non-focusing type) is produced by methods known in the art and is usually curved and contains final-size apertures 58. The apertures preferably have a substantially double frusto-conical shape, both cones 55 and 57 (FIG. 2) having their narrowest dimension located between the

major surfaces

66 and 68 of the mask so as to form a knife-edge 59 therebetween. The first step (FIG. 3) in making the temporary mask 50 is the provision to the mask 52 of a coating 54 of a film-forming material which is characterized by its physical shrinkage during the drying thereof, to make a coated mask 56. Such physical shrinkage of the film-forming material should be such that light transmitting corridors can be produced in film portions of such material, as discussed below.

The coating 54 (FIG. 3) is comprised of opaque film portions 60 which are disposed at and substantially close the mask apertures 58. These film portions 60 are preferably disposed on the walls 62 of the apertures 58, in which case the coating 54 optionally can be further comprised of coating portions 64 which are disposed at the

major surfaces

66 and 68 of the mask 52 and are integral with the film portions 60. Alternatively, the coating 54' (FIG. 7) is comprised of opaque film portions 60' disposed at the apertures 58 and supported solely by a major surface 66 of the mask 52 with the film portions 60 overhanging the apertures 58 (as shown in FIG. 7) or extending into the apertures. Numerals in FIG. 7 identical with those of FIG. 3 indicate corresponding elements.

The coating 52 can be applied by, for example, immersing the mask 52 into a room temperature bath of a film-forming material which is shrinkable during drying thereof or by spraying such material onto the target mask 52. Coating 54 can be applied, for example, by controllably wetting one surface 66 of the mask in a bath of the shrinkable film-forming material. The material can be provided in the fluid state by dissolving it in a suitable evaporable solvent (e.g., water, tolune, or alcohol); by heating the material; or by selecting a material that naturally occurs in a fluid state. Such immersion of the mask 52 can be done with the use of simple tanks (not shown) containing the shrinkable film-forming material in a fiuid state, batch-type or continuous process being employable for coating the target mask 52.

The

film portions

60 and 60 preferably are of substantially concave-concave shape and therefore have relatively thin respective

central regions

70 and 70 and relatively thick respective

peripheral regions

72 and 72, both of which are preferred. Such a concavo-concave shape is attributable to surface tension forces acting on the fluid material during coating of the mask. For this reason, it is preferred that the fluid film-forming material be capable of wetting the mask which is going to be coated, those film-forming materials exhibiting relatively high surface tension properties being. more desirable.

A film-forming material is defined herein to be one which, when applied in a fluid condition to a mask, is capable of wetting the mask so as to provide film portions at respective ones of the apertures, each film portion in a wet condition substantially closing the aperture and preferably (but not necessarily) having a relatively thin central region and a relatively thick peripheral region. To carry out the present invention, the film-forming material should exhibit a physical shrinkage (or contraction) during drying thereof which shrinkage adjusting the specific composition and/or the concentration of the materialthat is used and can be carried out sufficiently to provide light-transmitting corridors in the film portions. The film portions are preferably of a concavo-concave or a plano-concave configuration, but they can be of some other (e.g., concavo-convex) configuration. The film portions should be substantially opaque, so that the film-forming materials should exhibit a substantial natural opacity or should be provided with opaquing materials known in the art. Alternatively, the filmforming materials can be such as provide non-opaque film portions, the central regions of which film portions are removed, as discussed below, and the other regions of those film portions are subsequently converted to an opaque condition (e.g., by coating these other regions with a pigment or an opaque material, such as carbon). As used herein with respect to the film portions and parts thereof, opaque is defined to include both those which are impervious to radiant energy and those which scatter or diffuse radiant energy so as to redirect theradiant energy from its original path, thereby substantially limitingin the screen printing operation, the radiant energy performing the screen printing to that passing through corridors in the film portions, as discussed below.

The shrinkable, film-forming material is eliminable from the mask by, preferably, air combustion and/or vaporization (either or both of these preferably being able to be done at or below processing temperatures generally employed in color kinescope manufacturing, for example, at or below 500 C.) and/or dissolution in agents (preferably, but not necessarily limited to, water) which are not detrimental to the mask, and preferably leaves substantially no residue. A suitable temperature for such combustion or evaporation is that (e.g., about 400 to 450 C.) at which resist deposits (not shown), which are located on the image screen 24 (FIG. 1) and employed in the manufacture thereof, are burned off in manufacturing processes known in the art.

Those compositions which are suitable film-forming materials exhibiting physical shrinkage during drying include acrylic emulsions (e.g., Rhoplex B74, produced by Rohm and Haas and containing about 38 weight percent solids) which are alkaline. Plasticizers (e.g., glycol ethers) preferably are added to the acrylic emulsions to minimize tearing of the film portions during the shrinkage thereof, as discussed below. A specific composition that can be used contains between 18 and 50 volume percent acrylic emulsion (where the emulsion contains'about 38 percent solids by weight); I to 5 volume percent ethylene glycol (which serves as a plasticizer); and the balance water. Alternatively, there can be used, for example, a composition containing from 14 to 42 volume percent acrylic emulsion; (where the solids content of the emulsion is about 38 percent by weight) to 15 volume percent dipropylene glycol methyl ether (which serves as a plasticizer) and the balance water. The pH of these compositions is adjusted (with sodium hydroxide, for example) to exceed 7.0, a pH value of between 9.0 and 10.0 generally being preferred for the compositions containing acrylic emulsions. Where the film-forming material provides non-opaque film portions, opaquing materials (e.g., pigments) may be added either to the filmforming material or on the film portions provided on the mask.

After the coated mask 56 (FIG. 3) is made, the central regions 70 of the shrinkable film portions 60 are removed by drying the coating 54. The drying can be done in still air or in a moderately warm air stream, for example, so long as substantially all of the surfaces of the coating are exposed to the drying medium to achieve substantially uniform drying. FIG. 4il- Iustrates the coated mask at one point during the drying process, the drying to that timehaving caused a general thinning of the central regions 70 and the peripheral regions 72a of the film portions 60a. It is believed that as the more volatile constituents of the film portions are removed by drying, the increasing solids content thereof causes an increase in the surface tension at these film portions. This increased surface tension is believed then to cause the shrinkage of the film portions, which shrinkage continues until the moisture content thereof is reduced to a point where the film portions exhibit a behavior resembling solid materials. This point where theshrinkage of the film portions or parts thereof substantially ceases varies according to the composition and the concentration of the shrinkable film-forming material that is used, those materials containing a higher proportion of volatile materials generally exhibiting more extensive shrinking. This point at which shrinkage substantially ceases preferably occurs at substantially the time that light-transmitting corridors of desired size are provided in the film portions. This preferred situation (and, therefore, adjustment of the corridor size) can be accomplished by adjusting the composition and/or concentration of the shrinkable, film-forming material that is used. It may be desirable to'print the screen with a temporary mask wherein the desired-size corridors have been provided before the shrinkable, film-forming material of the temporary mask has dried to the point where shrinkage thereof substantially ceases. In this case, however, there is the possibility that shrinkage will occur during the screen printing operation and cause the enlargement of the corridors, thereby providing phosphor dots which are larger than intended.

As used herein, the term remove with respect to the provision of the light-transmitting corridors includes both the total elimination of the central regions of the film to produce unobstructed openings, or holes, thereat and the reduction in thickness of such central regions to a dimension which renders these central regions substantially pellucid, as the case may be. The unobstructed openings as well as the thin, pellucid parts of the central regions are included. in the definition of corridors.

The removal of the thinner central regions 70 of the film portions 60 produces a temporary mask 50 (FIG. 5) having opaque bands 74 disposed at the walls 62 of the various apertures 58. These bands 74 are comprised of at least part of the peripheral regions 72 of the opaque film portions 60 (FIG. 3) and define the light-transmitting corridors 76 which are substantially smaller in size than the mask apertures 58. By controlling the composition and/or the concentration of the shrinkable, film-forming material, the size of the corridors 76 can be adjusted with a comparatively high degree of accuracy to provide, by screen printing, phosphor dots (e.g., 20 of FIG. 1) of the desired dimension. By way of example, with the firstmentioned composition above, a corridor of about 12 mils in diameter can be provided at a mask aperture of about 15.4 mils diameter (i.e., the aperture diameter is closed by about 3.4 mils) the aperture providing an electron beam spot of about 17.8 mils diameter and the corridor providing a phosphor dot of about I4 mils diameter. The thickness dis tribution of the various film portions 60 FIG. 3) are comparable so that their respective central regions 70 can be removed substantially uniformly, thereby providing corridors 76 (FIG. 5) of substantially uniform size and shape. The bands 74 are located on the walls 62 of the apertures 58, thereby being strengthened and having comparatively high resistance to breaking and other injury.

The temporary mask 50 is then (not shown) positioned in spaced relation with a suitable transparent substrate (e.g., a faceplate panel) and used as a photographic master to print the various elemental phosphor areas. The printing process is known in the art (see, for example, U.S. Pat. No. 3,406,068 to BB. Law). Briefly, one surface of a transparent substrate (not shown) is coated with a mixture comprising a first one of the desired phosphors and a suitable photosensitive material and the phosphor coating is then exposed to a suitable light which is passed through the corridors (e.g., 76 of FIG. of the temporary mask (e.g., 50). The opaque bands 74 of the temporary mask 50 define the printing light beams by substantially restricting the passage of the printing light to the corridors. Those portions of the phosphor coating struck by the light beams are hardened, the unhardened portions of the coating being removed, by washing, for example, to leave a pattern of phosphors of a first color mixed with the hardened resist material. This sequence of steps is repeated for the other phosphors. The hardened resist material is subsequently removed from the phosphor dots by baking or by chemical dissolution methods known in the art.

The screen printing operation may include providing, with the use of the temporary mask 50 (FIG. 5) disclosed herein, a light-absorbing matrix (e.g., 23 in FIG. 1) of an opaque, nonlight-reflective material to the image screen (e.g., 24 of FIG. 1). As previously mentioned, the term image screen is defined herein to include the phosphor deposits and, optionally, a light-absorbing matrix on a transparent substrate. The provision of such a matrix can be done, for example, by coating a surface (e.g., 22 of FIG. 1) of the bare transparent substrate with a relatively translucent mixture (not shown) comprised of a material which has a relatively low light absorption and is convertible to a condition which is more lightabsorbing (e.g., manganese oxalate or manganese carbonate, which can be converted from a comparatively translucent condition to an opaque, non-light-reflective condition by heating in a manner known in the art) and a positive-type" photosensitive resist (i.e., one which is soluble where it has been exposed to light) and then exposing the coating to suitable light passed through the corridors of the temporary mask. Then, the soluble portions of the coating are washed away and the relatively low light-absorbing material of the remaining portions of the coating is converted to its light-absorbing condition. The phosphor areas are then printed at openings in the matrix, as described above. The phosphor areas may, if desired, be somewhat larger than the openings of the matrix so that portions of the respective phosphor areas are disposed on the matrix itself. The effective size of such phosphor areas is, therefore, equal to the size of the respective matrix openings. As used with respect to the phosphor areas of a matrix-bearing image screen, the term size is defined to be the effective size thereof. Where it is desired, the phosphor areas may be printed before the conversion of the material to its light absorbing condition. Alternatively, the phosphor areas may be printed before the provision of the matrix, the preliminary mask being used for producing both. Where it is desired, a light-absorbing matrix can, with a temporary mask, be provided to a transparent substrate, with the subsequent phosphor printing being done by applying a phosphor-photoresist mixture to the substrate surface on which the matrix is located and, then, exposing the mixture to light from a source located on the side of the substrate opposite the surface thereof bearing the matrix. The light passes through and is defined by the matrix openings.

Upon completion of the printing of the image screen, the bands 74 of the temporary mask 50 are eliminated (by baking or chemical dissolution) to restore the mask 52 to its original condition (similar to 30 of FIG. 1). Such elimination of the techniques simultaneously to both. In this way, existin equi ment can be used for restoring the mask to its origma con ition with no increase in the number of processing steps being required to eliminate the bands. The mask 52 is then incorporated into a kinescope in the manner shown in FIG. 1.

In addition to those advantages recited in the abovementioned concurrently filed application of HE. Law, the present invention provides a simplified and relatively inexpensive method for temporarily reducing, for screen printing, the size of the apertures of a mask without the use of solvents or etchants to provide light-transmitting corridors. By producing a color kinescope according to the present invention, an additional benefit that is gained is that the light-transmitting corridors of the temporary mask can be produced simultaneously with the drying of the coating thereof, thereby avoiding separate operations for the drying of the coating and subsequent provision of the corridors. The avoidance of the use of solvents for producing such light-transmitting corridors obviates the need for the equipment (e.g., separate tanks, pumps, etc.) usually associated with such solvent removal, thereby providing a capital savings. As a result, such color kinescopes can be produced with greater economy and facility.

I claim:

1. A method for producing a color kinescope having an image screen and a multi-apertured mask wherein said image screen is produced with the use of said mask having the apertures temporarily reduced in size, said method comprising the steps of:

a. disposing a coating of an emulsion of an alkaline acrylic film-forming material and a plasticizing agent on said mask, said coating comprising a plurality of opaque film portions individually disposed at and substantially closing the apertures of said mask, said material and a plasticizing agent being characterized by physical shrinkage during the drying thereof;

b. drying said coating so as to shrink said film portions and thereby remove the central regions thereof, thus producing opaque bands of said material and a plasticizing agent at the periphery of said apertures, said bands being comprised of at least peripheral parts of said film portions and defining radiation-transmitting corridors of a desired size smaller in dimension than respective ones of said apertures;

c. providing said image screen by steps including photographic exposure through said corridors; eliminating said bands from said mask; and then e. incorporating said mask and said image screen into said kinescope.

2. The method as described in claim 1 wherein said plasticizing agent is selected from the group consisting essentially of a glycol ether and ethylene glycol.

3. The method as described in claim 1 wherein said material consists essentially of from about 18 to about 50 volume percent acrylic emulsion, said emulsion being comprised of about 38 weight percent solids, from about 1 to about 5 volume percent ethylene glycol, and the balance water, said material having a pH greater than 7.0.

4. The method as described in claim 1 wherein said material consists essentially of from about 14 to about 42 volume percent acrylic emulsion, said emulsion being comprised of about 38 weight percent solids, from about 10 to about 15 volume percent dipropylene glycol methyl ether, and the balance water, said material having a pH greater than 7.0.

nun-m

Claims

2. The method as described in claim 1 wherein said plasticizing agent is selected from the group consisting essentially of a glycol ether and ethylene glycol.
3. The method as described in claim 1 wherein said material consists essentially of from about 18 to about 50 volume percent acrylic emulsion, said emulsion being comprised of about 38 weight percent solids, from about 1 to about 5 volume percent ethylene glycol, and the balance water, said material having a pH greater than 7.0.
4. The method as described in claim 1 wherein said material consists essentially of from about 14 to about 42 volume percent acrylic emulsion, said emulsion being comprised of about 38 weight percent solids, from about 10 to about 15 volume percent dipropylene glycol methyl ether, and the balance water, said material having a pH greater than 7.0.