US3631576A

US3631576A - Method of producing a color kinescope

Info

Publication number: US3631576A
Application number: US20209A
Authority: US
Inventors: Harold Bell Law; Ray Hui-Chung Lee
Original assignee: RCA Corp
Current assignee: RCA Licensing Corp
Priority date: 1970-03-17
Filing date: 1970-03-17
Publication date: 1972-01-04
Anticipated expiration: 1989-01-04
Also published as: GB1331716A; DE2111740A1; JPS517543B1; NL7103498A

Abstract

A method for producing a color kinescope having an image screen and a color-selection mask comprising final-size apertures. The method includes the steps of providing at least one perforated resist layer on a metal substrate and removing through the perforations of the resist layer both certain portions of the substrate so as to provide corridors of a given size through the substrate and other portions of the substrate adjacent to the corridors, so as to provide recesses extending only partially through the substrate thereby producing a preliminary mask. The image screen is produced with the preliminary mask, and, then, portions of the substrate located beneath the various recesses are removed so as to produce a color-selection mask comprising final-size apertures of larger size than the corridors. The color selection mask is then incorporated in a kinescope.

Description

tates atet [72] Inventors Harold Bell Law Princeton, NJ.;

Ray Hui-Chung Lee, Richardson, Tex. [21] Appl. No. 20,209 [22] Filed Mar. 17, 1970 [45] Patented Jan. 4, 1972 [73] Assignee RCA Corporation [54] METHOD OF PRODUCING A COLOR KINESCOPE 21 Claims, 18 Drawing Figs.

[52] US. Cl 29/25.13, 29/25. 1 8

[51] Int. Cl H01j 9/16, l-lOlj 9/44 [50] Field of Search 29/25. 1

Primary Examiner-John F. Campbell Assistant Examiner-Richard Bernard Lazarus AttorneyGlenn H. Bruestle ABSTRACT: A method for producing a color kinescope having an image screen and a color-selection mask comprising final-size apertures. The method includes the steps of providing at least one perforated resist layer on a metal substrate and removing through the perforations of the resist layer both certain portions of the substrate so as to provide corridors of a given size through the substrate and other portions of the substrate adjacent to the corridors, so as to provide recesses extending only partially through the substrate thereby producing a preliminary mask. The image screen is produced with the preliminary mask, and, then, portions of the substrate located beneath the various recesses are removed so as to produce a color-selection mask comprising final-size apertures of larger size than the corridors. The color selection mask is then incorporated in a kinescope.

PATENTEDJAN 41972 3,631,575

SHEET 1 BF 6 l N VEN'I'ORS BY 4 [ii PAIENTED JAN 41972 SHEET 2 BF 6 INVENTORS a d [4W 6 PATENTED JAN 4 m2 SHEET 8 0F 6 IN VENTORS 1947010 5. (AW By 161) hi [5! Able/way 1 METHOD OF PRODUCING A COLOR KINESCOPE BACKGROUND OF THE INVENTION The present invention relates to color kinescopes and particularly to a novel method for making a masked-target color kinescope wherein the image screen is produced with the use of a preliminary mask having temporary apertures of given size which preliminary mask is subsequently converted to a color-selection mask having larger apertures.

The prior art discloses color kinescopes having both an image screen, which includes a multiplicity of groups of closely spaced elemental phosphor deposits, the elemental deposits of each of such groups emitting light of a particular color when struck by an electron beam, and a color-selection mask disposed between the image screen and the electron source of the kinescope. Such masks (including focusing and nonfocusing masks) and their mode of operation are well known and may be of a planar, or spherical, or some other nonplanar contour, the contour of a particular mask generally being similar to that of the image screen with which it is used.

in the conventional nonfocusing shadow mask color kinescope, the mask apertures and also the beam spots on the screen are somewhat smaller than the phosphor areas. Generally, commercial screen-printing procedures involve using a color-selection mask having apertures of a desired final size as a master for photographically printing the phosphor areas thereof. The mask, with the size of its apertures unchanged, is then used in a color kinescope for color selection. Those same size apertures used for both the screenprinting function and for the color-selection function, are usually referred to as bifunctional apertures."

To increase the electron transmission of the color-selection mask and the proportion of each phosphor area impinged by an electron beam, so that the brightness of the image of a color kinescope can be increased, the prior art discloses masks having apertures which are individually larger than those in a conventional shadow mask kinescope, and may be larger than the respective phosphor areas of the image screens associated therewith. Such larger apertures provide electron beam spots of greater size (as measured at the screen and if no focusing action is involved), so that a larger proportion or all of each phosphor area is impinged than in conventional color kinescopes. In focusing-type color kinescopes, the beam spot size at the screen is reduced to approximately the phosphor area size by focusing the beamlets in the space between the mask and the screen.

Because of optical considerations (i.e., penumbra-umbra effect) known in the art, the increase in electron beam spot size with the use of masks with larger apertures is accompanied by an even larger increase in the size of the phosphor areas printed with such masks; that is, the spreading of the printinglight beams passing through the mask apertures is greater than the spreading of the electron beamlets passing through these apertures. Therefore, masks with such larger apertures are not satisfactory for direct screen printing because they generally lead to oversize (and, therefore, overlapping) phosphor areas and associated problems with color purity and white uniformity.

To obtain higher image brightness in focusing-type kinescopes, the focusing masks have final-size apertures which are considerably larger than the individual phosphor areas associated therewith, so that greater electron transmission by the mask can be obtained. However, focusing masks, as such, are not satisfactory for printing the phosphor areas of the image screen because the larger final-size apertures would provide corresponding larger (and overlapping) phosphor dots. In order to allow the use of a focusing mask, first, as a photographic master for screen printing and, then, as a focusing mask exhibiting increased electron transmissivity, the prior art has sought ways to provide, and use for screen printing, a preliminary mask" having temporary apertures of a first size and convert, thereafter, the preliminary mask to a focusing mask having the desired larger final-size apertures,

this with the substantial maintenance of the desired kinescope operating tolerances.

The use of a preliminary mask" having temporary apertures of suitable dimensions as a photographic master for printing" the phosphor areas of image screens and thereafter providing larger ultimate-size apertures therein to convert the preliminary mask to a color-selection mask for use as such in a color kinescope, is referred to herein as post-printing aperture enlargement." As used with respect to this invention, a color-selection mask," is not a preliminary mask since the apertures of the former are larger in size and the former is used only for the color-selection function (including focusing). not screen printing. Preliminary masks," which are used for screen printing, have temporary apertures, these temporary apertures being enlarged subsequently to provide a colorselection mask,

One method disclosed in the prior art for achieving this post-printing aperture enlargement" involves applying to each major surface of an unperforated sheet of conductive material, a coating of a photosensitive resist material, such as bichromated glue or shellac. Each photosensitive coating is then provided, by photographic methods known in the art, with a matching pattern of perforations of a predetermined size to leave the conductive sheet partially coated with resist. This partially coated sheet is then immersed in an etching solution to open, in uncoated portions thereof, apertures of a final size desired for the colorselection mask. These apertures of final size are greater than the individual perforations in the resist coating so that portions of the resist coating overhang the final-size apertures in the conductive sheet and form printing apertures of smaller size. Then the partially coated sheet is used as a master in the well-known image screen-printing operation, the light rays utilized for printing passing through and being defined by the small perforations in the resist coating. The resist coatings are subsequently removed so that the apertured conductive sheet can be used as a color-selection mask. However, for several reasons, this method is not completely satisfactory commercially. The resist pattern, which is provided initially to the unperforated conductive sheet and allowed to remain on the sheet throughout the entire mask-making operation, is not satisfactorily resistant to the annealing temperatures (e.g. 900 F.) employed in the continuous processes that are generally used in producing such color-selection masks, especially those masks that are nonplanar in contour. This is because the bichromated glue and shellac, as well as comparable materials, deteriorate upon exposure to the annealing temperatures generally employed in the art so that this method is generally not satisfactory in those color-selection mask-production operations involving annealing. Also, the overhanging portions of the resist coating are relatively fragile so that care must be exercised to avoid breaking them. Furthermore, many such photosensitive coating materials are not opaque so that steps must be taken to provide opaquing materials thereto.

In another method, a conductive sheet is provided with a perforated resist coating, as in the method discussed above and then immersed in an etching solution to open, in the uncoated portions thereof, apertures of an initial size which is substantially equal to the size of the resist perforations. The apertured, coated sheet is then utilized as a master in the printing of the phosphor areas of the image screen. Thereafter, the apertured, coated sheet is again immersed in the etching solution to remove additional material from beneath the resist coating, enlarging the apertures of initial size and thereby providing apertures of the desired larger final dimension. The resist coatings are then removed and the conductive sheet with apertures of final dimension is used as a color-selection mask. This method is not completely satisfactory because of the relatively poor resistance of the resist materials to the temperatures involved in the annealing steps. Furthermore, the later etching operation (after screen printing) generally results in nonuniformly shaped apertures and/or poor dimensional control of the apertures.

This invention relates to a novel method for producing a color kinescope of the type comprising an image screen including a mosaic of phosphor areas, alone or with a light-absorbing matrix, and a color-selection mask having final-size apertures therein. The color-selection mask is produced by steps comprising the provision in a substrate of a plurality of light-transmitting corridors at least one recess adjacent to each one of the corridors, thereby producing a preliminary mask. The corridors extend completely through the substrate but the recesses extend only partially through the substrate, there being portions of the substrate located beneath the recesses. The image screen is produced by steps that include photographic exposure through the corridors and portions of the substrate that are located beneath the recesses are removed to produce the color-selection mask that includes the final-size apertures. The color-selection mask is then incor porated into the kinescope.

In one embodiment, a perforated resist layer of special pattern is provided on a major surface of a metal substrate. A preliminary mask is then produced by removing, as by etching through the perforations of the resist layer, certain portions of the substrate so as to produce the light-printing corridors of given size, extending completely through the substrate, and also other portions of the substrate adjacent to the respective corridors and extending only partially through the substrate. These other portions are removed so as to produce recesses adjacent to the corridors, which recesses may be separated from the corridors by wall-like portions of the substrate or may be next to the corridors with no intervening substrate portions therebetween. The image screen is produced by the steps including photographic exposure through the corridors, and the portions of the preliminary mask located beneath the recesses are subsequently removed so as to provide final-size apertures of larger size than the corridors, thereby producing the color-selection mask. The perforated resist layer of special pattern preferably comprises a plurality offirst openings and a plurality of second openings adjacent to, but separated from, the first openings by striplike portions of the resist layer. The first openings preferably are broader than the second openings.

In another embodiment, a perforated resist layer is provided on each one of the oppositely disposed major surfaces of the substrate, a first one of the resist layers comprising first and second openings, as mentioned above. The second one of the resist layers also comprises openings, and the removal of portions of the substrate is done through these openings in both resist layers. The first openings and the openings ofthe second resist layer are circular and substantially in register, and the second openings are annular in shape and surround respective ones of the first openings. Alternatively, the first and second openings and the openings of the second resist layer are rectangular, the second openings being disposed lateral to the first openings.

In still another embodiment, a perforated resist layer of special pattern is provided on each one of two oppositely disposed major surfaces of the substrate, a first one of these resist layers comprising first and second openings and the second one of these resist layers comprising similar third and fourth openings. The first and third, as well as the second and fourth openings, are substantially in register. The first and third openings are circular in form whereas the second and fourth openings are annular, and respective ones ofthe second openings surround the first openings and respective ones of the fourth openings surround the third openings, Alternatively, all of the openings are rectangularly shaped, with the second openings and the fourth openings disposed lateral to the first and third openings, respectively.

In one embodiment, there is provided on one major surface of a substrate a perforated resist layer comprising first and second openings, there being provided on the opposite major surface a continuous resist layer that is optional. The first openings can he of circular shape while the second openings are annular and surround respective ones ofthe first openings Alternatively, the first and second openings can be rectangularly shaped with the second openings disposed lateral to the first openings. Removal of the substrate portions is done through the first and second openings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side view, partly in axial section, ofa mask-type color kinescope including an image screen prepared with the use of a preliminary mask made by the present invention, which preliminary mask is later converted to a color-selection mask ofthe kinescope.

FIG. 2 is a fragmentary plan view ofa resist coated substrate during the conversion thereof to a preliminary mask according to one embodiment ofthe present invention.

FIG. 3 is a fragmentary, transverse sectional view, along axis 3-3, of the structure shown in FIG. 2.

FIG. 4 is a fragmentary transverse sectional view of the structure shown in FIG. 3 at a subsequent processing step of the present invention to produce a preliminary mask.

FIG. 5 is a fragmentary transverse sectional view of a preliminary mask produced from the structure shown in FIG. 4, the mask including corridors and recesses that are separated by wall-like portions of the mask that extend to the upper major surface.

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

FIG. 7 is a fragmentary transverse sectional view of a preliminary mask produced according to another embodiment of the present invention the mask including corridors and recesses that are separated by wall-like portions that do not extend to the upper major surface.

FIG. 8 is a fragmentary perspective view of the preliminary mask shown in either of FIGS. 5 and 7 in position for use as a photographic master in preparing an image screen for a color kinescope.

FIG. 9 is a fragmentary transverse sectional view ofa colorselection mask made from the structure shown in FIGS. 5 and 6, the color-selection mask including final-size apertures.

FIG. 10 is a fragmentary transverse sectional view of a preliminary mask produced according to another embodiment, the mask including corridors and recesses that are not separated by wall-like portions of the mask.

FIG. 11 is a fragmentary transverse sectional view of the color-selection mask made from the preliminary mask produced from the substrate shown in FIG. 10, the colorselection mask including final-size aperture.

FIGS. I2 and 13 are respective fragmentary transverse sectional views of a resist-coated substrate during the conversion thereof to a preliminary mask according to respective further embodiments of the present invention.

FIG. 14 is a fragmentary transverse sectional view of a color-selection mask produced from the structure shown in FIG. 13.

FIG. 15 is a fragmentary transverse sectional view of a resist-coated substrate during conversion thereofto a preliminary mask according to another embodiment, the mask including rectangularly shaped recesses and corridors.

FIG. 16 is a fragmentary transverse sectional view of the color-selection mask produced from the preliminary mask shown in FIG. 15, the color-selection mask including rectangular apertures.

FIGS. 17 and 18 are respective fragmentary transverse sectional views of a resist-coated substrate during conversion thereof to a preliminary mask according to respective other embodiments of the present invention.

preliminary mask DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a mask-type color kinescope 10 produced by the novel method and temporary mask structure disclosed herein, which kinescope 10 includes a glass envelope I2 comprising a funnel portion 14 and a panel or 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 deposits of two or more different phosphors, the deposits of each group being individually capable of emitting luminescence ofa particular color (e.g., red, blue, or green) when struck by an electron beam 22, are deposited on the internal surface 24 of the transparent faceplate 18. The faceplate 18 (or other transparent substrate). the phosphor areas 20 and, optionally, a light-absorbing matrix 26 (discussed below), are collectively referred to herein as an image screen 28. Generally, there is included on the image screen a light-reflective conductive layer (not shown) of aluminum, for example, which covers the phosphor areas and also serves as an electrode. The phosphor areas 20, are, for illustration purposes, exaggerated in size and proportion (as are other parts of FIG. I and the other figures) and shown as having a dot configuration, which dots may be arranged in the well-known hexagonal dot pattern (FIG. 8). Alternatively, each phosphor area may have a well-known stripe configuration (not shown), these stripes being arranged in an alternating array of different color phosphors to provide a line color screen. The kinescope further includes a number of electron guns equal to the number of different colors in the screen and either electrostatic or magnetic deflection and convergence means, none of which are shown for simplicity. In generally parallel, spaced relation with the screen 28 is a color-selection mask (or mask electrode) 30 which may be, for example, of the focusing or nonfocusing 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 example, the color-selection mask 30 is understood to be of the nonfocusing mask variety, which is operated at substantially the same potential as the screen 28 to form a field-free region therebetween. The mask 30 is made from a sheet or band of electrically conducting material (e.g., cold-rolled steel) and has a plurality of apertures 34 ofdesired final size therein. While the apertures 34 are, for simplicity, shown in FIG. 1 to be substantially circular in shape, apertures having other shapes (e.g., slot shaped) may be used. For example, the mask may be of the grill" type (e.g., FIG. 16), having slot-shaped apertures and used with a line screen. The apertures 34 are related in size and position to respective phosphor areas of the image screen 28. In the present invention, the size relationship is such that, where the colorselection mask is of the nonfocusing variety, each final-size aperture 34 is of such dimension as to be capable of passing an electron beam 22 whose spot dimensions, as measured at the screen 28, (i.e., the spot size of the beam) are at least substantially equal to, or preferably larger than, the dimensions ofthe individual phosphor areas 20 upon which the electron beam impinges. The electron beam spot size is preferably sufficiently large to provide a negative leaving tolerance but not so great that the electron beam impinges any ones other than the intended phosphor areas. However, with prior art color-selection mask having bifunctional apertures of a given size, the size of the light spots produced during screen printing generally exceeds by a significant amount that of the electron beam spots produced in the operation of the kinescope. This results in the size of the individual phosphor areas being considerably greater than the spot size of their associated electron beam so that the beam impinges only a portion of each phosphor area. Such differences in size between the printing light spots and the electron beam dots are familiar to the art, the difference therebetween being to the more extensive penumbra-umbra effect taking place in the screen-printing process.

Generally, it is preferred that the finalsize apertures 34 ex ceed in size their associated phosphor areas 20. The final-size apertures of a focusing-type mask are much greater in size than their respective individual phosphor areas whether the color tube is of the positive leaving tolerance type (i.e., the beam spot is smaller than a corresponding phosphor area) or the negative leaving tolerance type. In most color kinescopes in the prior art, there is a single aperture in the color-selection barrier 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. I to correspond in position with only one phosphor area 20.

In the operation of the kinescope l0, electrons are emitted by the electron guns (not shown) and thereafter directed, by means known in the art, as electron beams 22, through the apertures 34 to impinge upon the phosphor areas 20. Because a larger electron beam spot is produced and impinges upon substantially an entire individual phosphor area, the kinescope I0 exhibits improved characteristics, such as increased image brightness and contrast, over positive tolerance kinescopes.

In one embodiment (FIGS. 2 through 6 and 9) of the present invention, a color kinescope (e.g., 10 of FIG. 1) is manufactured by steps including the production ofa temporary mask 50 (FIGS. 5 and 6) for screen printing. The first step in making the temporary mask 50 is the provision of a perforated layer 52 (FIG. 3) of a photosensitive resist material (e.g., bichromated fish glue) on a major surface 54 of a substrate 56 ofa suitable material (e.g., cold-rolled steel) and, optionally, a continuous layer 58 of a photosensitive resist material on the second major surface 60 of the substrate 56, the continuous layer 58 serving to avoid etching the second surface 60. The perforated layer 52 is produced by methods known in the art (e.g., light exposure through a suitable stencil and subsequent selective removal). The perforated layer 52 comprises a plurality of first openings 62 disposed at and substantially concentric with the sites where final-size apertures (78 in FIG. 9) are intended and a corresponding number of adjacent second openings 64 that individually surround respective ones of the first openings 62. Preferably, the second openings 64 are of a substantially annular configuration, are separated from the first openings 62 (which, preferably, are substantially circular) by annular striplike portions 66 of the resist layer 52, and are substantially concentric therewith. The breadth of the first openings 62 (i.e., the diameter in the case of circular first openings, as shown in FIGS. 2 and 3) is significantly greater than the breadth (indicated as in FIGS. 2 and 3) of the annular second openings 64, which breadth is the distance between the striplike portions 66 and adjacent other parts ofthe resist layer 52.

First openings 62 having a breadth (i.e., diameter) of about 12 mils and second openings 64 having a breadth of about 4 mils, where the width of the striplike portions (e.g., 66) of the resist layer is about 4 mils (i.e., the inside diameter of the annular second openings is about 20 mils), have been found to be satisfactory. While the width of the striplike portions 66 can be varied, it is preferred that the width be at least about twice the thickness of the substrate 56.

Those portions of the substrate 56 (FIG. 4) at the first openings 62 are completely removed, or perforated, as by etching, so as to provide corridors 70 thereat while those parts of the substrate 56 generally located beneath the second openings 64 are only partially removed to produce recesses, or

channels, 72 adjacent to respective ones of the corridors 70.'

The recesses 72, are annular and extend through only a part (i.e., a major part) of the substrate thickness from the upper major surface 54. Where the width of the striplike portions 66 are sufficiently large, the recesses 72 are separated from the corridors 70 by a wall-like portion 74 of the substrate 56, and preferably have their major axis substantially perpendicular to the upper major surface 54. It is not necessary that the walllike portion of a substrate extend to the upper major surface (e.g., 54) as shown in FIG. 4, but can, instead, terminate at a point somewhere between the two

major surfaces

54a and 60a of the substrate 56a as shown in FIG. 7 (i.e., the recesses extend from a certain point 75 below the major surface 54 a). where the recess, or channel, 72a, is separated from the corridor 70a by the wall-like portion 74a, which has a height indicated by b. Moreover, even the portion 74a may be removed, so that the recess 72a extends to the corridor 70a, as discussed below. It is preferred in all these embodiments that a substrate portion remaining beneath the second openings after etching is carried out e.g., the portion 76 in FIG. 4, between the recess 72 and the second major surface 60) generally have a thickness (e.g., 2 mils) that is substantially less than the difference in size between the corridor 70 and the final aperture subsequently produced at the corridor, This hastens the process of final-size aperture production. It is preferred that the second openings 64 be located such that the principal axes of the respective recesses (which principal axes are shown as AA in FIGS. 4 and and pass through substantially the deepest parts of the respective recesses) substantially define (e.g., smallest dimension of their subsequently provided, respective final-size apertures 78 (FlG. 9) as shown by the dashed, curved lines 77 in FIG. 4. The provision of the corridors and recesses includes adjusting the relative breadths of the first and second openings, respectively, of the resist layer such that the rate of removal, or etching, at the substrate portions at the first openings (e.g., 62 in FIG. 3) exceeds that at the substrate parts at the second openings (e.g., 64), this difference in the removal rate being attributable to the greater breadth ofthe first openings 62 in comparison with the second openings 64. Such greater breadth results in a greater ease with which the etchant (in the case of removal by etching) comes in contact with these substrate portions and in a more rapid refreshment of the etchant at these substrate portions, thereby resulting in a faster etch rate thereat.

The presence of the recesses (e.g., 72 in FIG. 6) in the temporary mask 50 allows the more rapid enlargement of the perforations in the substrate to produce the final-size apertures 78 (FIG. 9) and further allows an improved definition and dimensional control of these apertures, by virtue of the fact that there need be removed substantially only the substrate portion (e.g., 76 in FIG. 4) between the bottom of the recess e.g., 72) and the opposite major surface e.g., 60) of the substrate, and by virtue of the fact that the recess substantially defines the final-size apertures. It is preferred that the thickness ofthe substrate portion e.g., 76) beneath the respective recesses be less than the difference in size of the corridors and the final-size apertures. As used herein, the size" of the corridors and the final-size aperture generally refers to their respective minimum dimension.

After formation of the corridors 70 and recesses 72, the resist

layers

52 and 58 are removed (FIGS. 5 and 6) by methods known in the art (e.g., solvent removal) and the preliminary mask 50 (FIGS. 5 and 6) thus produced is then positioned (FIG. 8) in spaced relation with a suitable transparent substrate 80 (e.g., a faceplate) and used as a photographic master to print" the various

elemental phosphor areas

82, 84, and 86 of the respective phosphor groups (e.g., red, blue, and green) on the substrate 80. The printing process is known in the art (see, for example, U.S. Pat. No. 3,406,068 to H. B. Law). Where color-selection masks of nonplanar configuration are desired, the shaping of the temporary mask to this configuration is done after the temporary mask-making and before screen printing. it is possible to remove the resist layers 52 and 58 (FlG. 3) from the temporary mask by baking them off during the annealing steps that accompany the shaping process. Briefly, in the screen-printing process, one surface 88 of the transparent substrate 80 is coated with a mixture (not shown) comprising a first one of the desired phosphors and a suitable photosensitive material and then exposed to a suitable light which is passed through the corridors 70 of the temporary mask 50. Those portions of the phosphor coating (not shown) struck by the light rays are hardened, and then the unhardened portions ofthe coating are removed, by washing, for example, to leave a pattern (not shown) of phosphors ofa 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. In first-order color printing, a light source (not shown) intended for a particular phosphor group is located at a point (90, 92, or 94) so as to be in substantially the same spatial relation with the image screen (e.g., 28 of FIG, I) as the apparent source of the electron beam (not shown) used for exciting that particular phosphor group. The paths followed by the light rays during printing and by the electrons during operation of the kinescope are indicated, for purposes ofillustration, by the

lines

96, 98, and 100.

The screen-printing operation may include providing, with the use of the temporary mask 50 disclosed herein, a light-absorbing matrix (e.g., 26 of FIG. I) of an opaque, nonlightreflective material on the image screen (e.g., 28 of FIG. 1). For purposes of this invention, where such a matrix is provided on an image screen, it is considered to be included in the term image screen." This matrix production can be done, for example, by coating a surface of the bare transparent substrate (e.g., of FIG. 8) with a relatively translucent mixture (not shown) comprising a material which has a relatively low light absorption and is convertible to a condition which is more light absorbing (e.g., manganese oxalate or manganese carbonate, which can be converted from a comparatively translucent condition to an opaque, nonlight-reflective condition by heating in a manner known in the art) and a positivetype photosensitive resist (i.e., one which is soluble where exposed to light and remains insoluble elsewhere) and then exposing the coating to suitable light passed through the corridors 70 of the preliminary mask 50. Then, the unhardencd 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 (e.g., 82, 84, and 86 of FIG. 8) 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, however, equal to the size of their 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 of these. Where it is desired, a light-absorbing matrix can, with a temporary mask, be provided on 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 screen-printing operation, the preliminary mask 50 (FIGS. 5 and 6) is converted to a colorselection mask 79 (FIG. 9) that is similar to mask 30 in FIG. 1, by removing those regions 76 located between the bottom of the respective recesses 72 and the opposite major surface 60 of the substrate. Such removal is carried out, for example, by a second etching operation utilizing ferric chloride, such an etching process being familiar to the art. Such a second etching operation may result in a slight reduction in the thickness of the mask, but such a reduction can be compensated for by selecting a substrate of appropriate thickness (e.g., 7 mils). Since the regions 76 beneath the recesses 72 are relatively thin compared to other regions of the mask, the rate at which the final-size apertures 78 can be produced is significantly greater than those prior art techniques utilizing a second etching operation without the benefit of recesses or other removed parts of the substrate adjacent to the corridors. Furthermore, the fact that the recesses are, in the preferred situation, provided such that their respective principal axes substantially define the smallest dimension of their respective final-size apertures 78 serves to better define the boundaries of these apertures, thereby providing a color-selection mask and color kinescope ofimproved accuracy and quality In another embodiment, the recesses 72b (FIG. 10) in the substrate 56b comprising a temporary mask 50b are next to the circular corridors 70b thereof with no portion of the substrate intervening therebetween, the recesses 72b being of annular shape. Such recesses (i.e., 72b can be produced, for example, by adjusting the width of the striplike portion (similar to 66 in FIG. 2) of the resist layer (not shown) provided on the substrate 56b to a value smaller than twice the substrate thickness. After this temporary mask 50b is used in the screenprinting operation similar to that discussed above, the corridors 70b are enlarged, as by a further etching operation to produce a color-selection mask 7% (FIG. 11) that includes final-size apertures 78b. It is preferred that the thickness of the substrate portions 76b located beneath the reflective recesses 72b generally be less than the difference in size between the corridors 70b and the subsequently provided final-size apertures 78b, the latter being shown, for illustrative purposes, by the dashed lines 77b. The color-selection mask 79b is subsequently incorporated into a color kinescope in the manner shown in FIG. 1, for example.

In a further embodiment (FIG. 12), there is formed on a first major surface of an unperforated electrically conducting substrate (not shown) corresponding to substrate 56 in FIG. 3, a perforated layer 102 of a suitable photosensitive material. The layer 102 corresponds to that indicated as 52 in FIG. 3 and includes preferably circular first openings 104 and preferably annular second openings 106, these

openings

104 and 106 being separated by annular strip portions 108 of the resist layer 102. Also, a second perforated layer 114 of the photosensitive resist material is formed on a second major surface 128 of the substrate. FIG. 12 shows the resist-bearing preliminary mask 120 including corridors 122 and annular recesses 124, the surface 126 being the remaining part of the first major surface of the original substrate while the surface 128 is the remaining part of the second major surface of the original substrate. The-second layer 114 includes openings 130 that are preferably circular and are in substantial register with the first openings 104. The openings 130 of the second layer may be larger than (as shown in FIG. 12), equal to, or smaller than the first openings 104. The substrate is etched to produce the corridors 122 and the adjacent recesses 124, the etching being carried out from both sides of the substrate-resist assembly so that a double frustoconical corridor, including a knife edge 123, is produced. It is preferred that the thickness of the substrate portions 132 located beneath the recesses 124 generally be less than the difference in size of the corridors 122 and the final-size apertures (indicated by the dashed lines 134) produced thereat. The resist layers 102 and 114 are then removed, and the preliminary mask 120 is used for screen printing as described above. The color-selection mask produced from the preliminary mask 120 by a second etching step, is similar to that shown in FIG. 9, such a color-selection mask subsequently being incorporated into a color kinescope.

In still another embodiment (FIGS. 13 and 14) of the invention, each one of the opposing major surfaces (indicated by the parts thereof remaining after etching, as 140 and 142, are respectively) of a substrate (not shown, but similar to 56 in FIG. 3) is provided with a respective perforated layer 144 and 146 of a suitable photosensitive resist material (e.g., bichromated fish glue). Each one of the layers 144 and 146 includes a plurality of first openings 148 and 150, respectively, that preferably are circular in shape and a corresponding number of associated second openings 152 and 154, respectively, that preferably are annular and individually surround their respective first openings from which they are separated by striplike portions 156 and 158 of the resist layers. The first openings 148 and 150 of the respective layers 144 and 146 are substantially in register as are the second openings 152 and 154. The first openings (e.g., 150) of one layer may be larger than (as shown in FIG. 13), equal to, or smaller than those (e.g., 148) of the other layer, the same being true for the second openings of the respective layers. The resist-bearing substrate is etched (e.g., with ferric chloride) from both major surfaces so as to produce double frustoconical corridors 160 with adjacent first and second annular recesses 162 and 164, respectively, that are substantially in register. Each one of the first and second recesses 162 and 164, respectively, extends through only a part of the substrate thickness, the first and second recesses together e extending preferably through a major part of the substrate thickness. The portions 168 of the substrate located beneath the first recesses 162 (i.e., between the first and second recesses) have a minimum thickness that is less than the size difference between the corridors 160 and the finalsize apertures 174 (FIG. 14) produced therefrom. The resist layers 144 and 146 are then removed, and the preliminary mask 170 so produced is used as described above, the preliminary mask 170 subsequently being converted to a color-selection mask 172 (FIG. 14) including final-size apertures 174 having knife edges 175 of desired size, by the methods outlined above.

In still another embodiment (FIG. 15), a preliminary mask 200 comprising elongated corridors of substantially rectangular configuration is used to produce a line screen (not shown) and is subsequently converted to a color-selection mask including substantially parallel final-size apertures of substantially rectangular configuration, such color-selection masks commonly being referred to as grill masks." Line screens and grill masks are familiar to the art, the former generally comprising a plurality of alternating rectangular strips of different phosphor materials. The preliminary mask 200 is produced by providing on one major surface 202 of an imperforate substrate (the preliminary mask 200 being the remnant of the substrate after the processing thereof, the substrate corresponding to 56 in FIG. 3) a perforated layer 204 ofa resist material. The perforations of layer 204 comprise parallel, substantially rectangular first and

second openings

206 and 208, respectively, in the resist layer 204, the second openings 208 being adjacently (i.e., laterally) disposed to the first openings 206 and separated therefrom by striplike parts 210 of the resist layer 204. To avoid etching of the substrate from the other surface 212, this surface 212 is covered with an imperforate resist layer 214. The imperforate resist layer 214 can be disposed with, however, where etching of the other surface 212 is not objectionable or where other measures are taken to avoid such etching. The portions of the substrate located beneath the first and

second openings

206 and 208, respectively, are removed, as by etching, so as to produce linear corridors 215 at the first openings 206 with substantially parallel adjacent (i.e., lateral) linear recesses 216. While the recesses 216 are shown to be separated from the corridors 215 by walllike portions 218 of the substrate, the preliminary mask can be made so that the recesses are next to the corridors with no intervening substrate portions (i.e., as in the embodiment in FIG. 10).

The perforate resist layer 204 includes a strip portions 220 located at the respective ends of the first and

second openings

206 and 208, respectively, and extending in a direction substantially perpendicular to the first and second openings 207 and 208, respectively, such strip portions 220 preventing the removal of certain areas 222 of the substrate located at the ends of the various corridors 215 and recesses 216. These areas 222 subsequently serve as crossties to support the linear elements 230 (FIG. 16) of the color-selection mask 232. After the kinescope screen is produced with the preliminary mask 200, the color-selection masks 232 are produced by removing the substrate portions 226 (FIG. 15) that are located beneath the recesses 216 and that substantially define the final-size apertures 234. The final-size apertures 234 are linear and are for purposes of illustration, indicated by the dotted lines 224 in FIG. 15. The substrate areas serving as crossties may comprise a framelike structure at the ends of the linear elements 230 of the mask or may comprise several linear strips (e.g., such as those shown in FIG. 17) that extend across the colorselection mask and are perpendicular to the final-size apertures. Theses strips are located at respective points intermediate the ends of the final-size aperture of the mask. The

Ell

color-selection mask is subsequently incorporated in a color kinescope.

In another embodiment. a preliminary mask 240 (FIG. 17) is produced from a substrate (not shown, corresponding to 56 in FlG. 3) by providing on each one of the major surfaces thereof, 242 and 244, respectively, (242 and 244 indicate the remnant of these major surfaces after the substrate is converted to a preliminary mask) a perforated resist layer 246 and 248, respectively. One resist layer 246 includes a plurality of linear first and second openings 250 and 252 similar to FIG. 15, and the second resist layer 248 includes a plurality of linear individual openings 254 orthogonally disposed with respect to the first and second openings 250 and 252 (Le, at least part of the respective openings 254 are in register with portions of the first openings 250). By etching the substrate from both sides, there are produced corridors 256 and recesses 258 adjacent thereto. While the recesses 258 are shown to be separated from the corridors 256 by wall-like portions 260 of the preliminary mask, the preliminary mask can be made so that the recesses are next to the corridors with no intervening mask portions (e.g., as in the embodiment in FIG.

In still another embodiment (FIG. 18), a preliminary mask 270 is produced from a substrate (not shown and corresponding to 56 in H6. 3) by providing a perforated resist layer 272 and 274 on the

major surfaces

276 and 278, respectively, of the substrate. The remnants of these major surfaces after conversion of the substrate to the preliminary mask 270 are indicated by 276 and 278. Each of the first and second resist layers 272 and 274, respectively, includes rectangular first openings and adjacent rectangular second openings, the

numerals

280 and 282 indicating the first and second openings, respectively, of the

first layer

272, 284 and 286 indicating the first and second openings, respectively, of the second layer 274. The

second openings

282 and 286 are substantially narrower than their respective

first openings

280 and 284 and are laterally disposed thereto; the respective first openings having two associated second openings. The first and second opening of one resist layer (e.g., 272) are in substantial register with those of the other layer (274). By etching the substrate from both sides, the recesses 290 and 292 and the corridors 294 and 296 are produced in the substrate, the preliminary mask so produced being used as described above and subsequently converted to a color-selection mask with final-size elongated apertures (not shown), as above.

The present invention provides several benefits and advantages among which are the improved definition and dimensional control of the final-size apertures and the relative facility of provision of the final-size apertures. Also, once the preliminary mask is completely made, there is no need to retain any resist layer on the substrate so that any deterioration of the resist layer due to shaping and/or annealing of the preliminary mask is not objectionable and no special measures need be taken to protect this resist layer. Furthermore, there is no need to take measures to render the resist layer opaque for screen-printing purposes.

We claim:

1. A method of producing a color kinescope comprising a color-selection mask having final-size apertures of a first dimension and an image screen, said image screen being produced with a preliminary mask having corridors of a second dimension substantially smaller than said first dimension, said method comprising:

a. producing in a substrate a plurality of said corridors and at least one recess adjacent to each of said corridors thereby producing said preliminary mask, said corridors extending completely through said substrate and said recesses extending only partially through said substrate portions of said substrate being located beneath said recesses,

b. producing said image screen by steps including photographic exposure through said corridors,

c. removing said portions of said substrate located beneath said recesses to produce said color-selection mask comprising said final-size apertures; and

incorporating said color selection mask into said kinescope.

2. The method as defined in claim 1, wherein said corridors are substantially circular and said recesses are substantially annular, each one of said recesses being substantially concentric with and surrounding a respective one of said corridors, the subsequently produced apertures also being substantially circular.

3. The method as defined in claim 1, wherein said corridors and said recesses are substantially rectangular, said recesses being laterally disposed with respect to respective ones of said corridors, the subsequently produced apertures also being substantially rectangular.

4. The method as defined in claim I, wherein said recesses are separated from said corridors by wall-like portions of said substrate.

5. The method as defined in claim 1, wherein said recesses are next to said corridors with no portions of said substrate intervening therebetween.

6. The method as defined in claim 1, wherein said portions of said substrate located beneath said recesses after step (a) have a thickness less than the difference between said first and second dimensions.

7. A method of producing a color kinescope comprising a color-selection mask having final-size apertures of a first dimension and an image screen, said image screen being produced with a preliminary mask having corridors of a second dimension substantially smaller than said first dimension, said method comprising:

a. providing a resist layer on a major surface of a substrate, said resist layer containing a plurality of first openings and at least one second opening adjacent to each of said first openings and separated therefrom by a portion of said resist layer, said first and second openings extending through said resist layer;

b. removing portions of said substrate so as to form corridors through said substrate at those areas located beneath respective ones of said first openings and to form recesses in said substrate located beneath respective ones ofsaid second openings, said recesses extending only partially through said substrate, thereby producing said preliminary mask;

c. producing said image screen by steps including photographic exposure through said corridors;

d. removing the portions of said substrate remaining beneath said second openings to produce said color selec tion mask comprising said final-size apertures; and

e. incorporating said color-selection mask into said kinescope.

8. The method as defined in claim 7, wherein said recesses extend from said major surface and are separated from said corridors by parts of said substrate, said parts comprising the respective walls of said corridors and said recesses.

9. The method as defined in claim 8, wherein a major axis of said recesses is substantially perpendicular to said major surface.

10. The method as defined in claim 7, wherein said portions of resist layer separating said first and said second openings have a width equal to at least twice the thickness of said substrate.

11. The method as defined in claim 7, wherein said recesses extend from a certain point below said major surface and are separated from said corridors by parts of said substrate, said parts comprising the respective walls ofsaid corridors and said orifices.

12. The method as defined in claim 7, wherein said recesses extend through a major part ofthe thickness of said substrate.

13. The method as defined in claim 7, wherein the thinnest parts of said portions of said substrate remaining beneath said second openings have a maximum thickness of 2 mils.

14. The method as defined in claim 7, wherein said substrate comprises a metal.

15. The method as defined in claim 7, wherein said portions of said substrate are removed by etching.

16. The method as defined in claim 7, wherein said first openings are substantially circular in form and said second openings are substantially annular in form and are concentrically disposed with respect to and surround said first openings.

17. the method as defined in claim 7, wherein said first and second openings are substantially rectangular in form, said second openings being laterally disposed with respect to said first openings and substantially parallel thereto.

18. A method of producing a color kinescope comprising a color-selection mask having final-size apertures of a first dimension and an image screen, said image screen being produced with a preliminary mask having corridors of a second dimension, said second dimension being substantially smaller in size than said first dimension, said method comprising:

a. providing a first resist layer on a major surface of a substrate, said first resist layer containing a plurality of first openings and at least one second opening adjacent to each of said first openings, said first and second openings extending completely through said first resist layer;

b. providing a second resist layer on a second major surface of said substrate, said second resist layer containing a plurality of openings, at least portions of said openings of said second resist layer being substantially in register with portions of said first openings of said first resist layer;

c. removing certain portions of said substrate between said first openings of said first resist layer and said openings of said second resist layer to form corridors through said substrate, and removing other portions of said substrate located beneath said second openings to form recesses in said substrate adjacent to respective ones of said corridors, said recesses extending partially through said substrate;

d. producing said image screen by steps including photographic exposure through said corridors;

e. removing the portions of said preliminary mask located between said recesses and said second major surface to produce said color-selection mask comprising said finalsize apertures; and

incorporating said color-selection mask into said kinescope.

19. the method as defined in claim 18, wherein said first openings are substantially circular and said second openings are equal in number to said first openings and are substantially annular, said second openings being substantially concentric with and surrounding said first openings, and

said openings of said second resist layer are substantially circular.

20. The method as claimed in claim 18, wherein said first and second openings are substantially rectangular and substantially mutually parallel and said openings of said second resist layer are substantially rectangular.

21. A method of producing a color kinescope comprising a color-selection mask having final-size apertures of a first dimension and an image screen, said image screen being produced with a preliminary mask having corridors of a second dimension, said second dimension being substantially smaller in size than said first dimension, said method compris ing:

a. providing a first resist layer on a major surface of a substrate, said resist layer containing a plurality of first openings and at least one second opening adjacent to each of said first openings, said first and second openings extending completely through said resist layer;

b. providing a second resist layer on a second major surface of said substrate, said second resist layer containing a plurality of third openings substantially in register with respective ones of said first openings and a plurality of fourth openings adjacent to said third openings and sub stantially in register-with said second openin s; removing certain portions of sald substrate located between said first openings and said third openings to form corridors through said substrate, and removing other portions of said substrate located between said second openings and said fourth openings to form oppositely disposed recesses extending from said first and said second major surfaces, respectively, through only portions of the thickness of said substrate, portions of said substrate being located between oppositely disposed ones of said recesses, thereby producing said preliminary mask comprising said corridors and said recesses;

e. removing the respective remaining said portions of said substrate located between said recesses to produce said color-selection mask including said final-size apertures; and

f. incorporating said color-selection mask into said kinescope.

Claims

1. A method of producing a color kinescope comprising a colorselection mask having final-size apertures of a first dimension and an image screen, said image screen being produced with a preliminary mask having corridors of a second dimension substantially smaller than said first dimension, said method comprising: a. producing in a substrate a plurality of said corridors and at least one recess adjacent to each of said corridors thereby producing said preliminary mask, said corridors extending completely through said substrate and said recesses extending only partially through said substrate portions of said substrate being located beneath said recesses, b. producing said image screen by steps including photographic exposure through said corridors, c. removing said portions of said substrate located beneath said recesses to produce said color-selection mask comprising said final-size apertures; and d. incorporating said color-selection mask into said kinescope.

4. The method as defined in claim 1, wherein said recesses are separated from said corridors by wall-like portions of said substrate.

7. A method of producing a color kinescope comprising a color-selection mask having final-size apertures of a first dimension and an image screen, said image screen being produced with a preliminary mask having corridors of a second dimension substantially smaller than said first dimension, said method comprising: a. providing a resist layer on a major surface of a substrate, said resist layer containing a plurality of first openings and at least one second opening adjacent to each of said first openings and separated therefrom by a portion of said resist layer, said first and second openings extending through said resist layer; b. removing portions of said substrate so as to form corridors through said substrate at those areas located beneath respective ones of said first openings and to form recesses in said substrate located beneath respective ones of said second openings, said recesses extending only partially through said substrate, thereby producing said preliminary mask; c. producing said image screen by steps including photographic exposure through said corridors; d. removing the portions of said substrate remaining beneath said second openings to produce said color selection mask comprising said final-size apertures; and e. incorporating said color-selection mask into said kinescope.

11. The method as defined in claim 7, wherein said recesses extend from a certain point below said major surface and are separated from said corridors by parts of said substrate, said parts comprising the respective walls of said corridors and said orifices.

12. The method as defined in claim 7, wherein said recesses extend through a major part of the thickness of said substrate.

14. The method as defined in claim 7, wherein said substrate comprises a metal.

18. A method of producing a color kinescope comprising a color-selection mask having final-size apertures of a first dimension and an image screen, said image screen being produced with a preliminary mask having corridors of a second dimension, said second dimension being substantially smaller in size than said first dimension, said method comprising: a. providing a first resist layer on a major surface of a substrate, said first resist layer containing a plurality of first openings and at least one second opening adjacent to each of said first openings, said first and second openings extending completely through said first resist layer; b. providing a second resist layer on a second major surface of said substrate, said second resist layer containing a plurality of openings, at least portions of said openings of said second resist layer being substantially in register with portions of said first openings of said first resist layer; c. removing certain portions of said substrate between said first openings of said first resist layer and said openings of said second resist layer to form corridors through said substrate, and removing other portions of said substrate located beneath said second openings to form recesses in said substrate adjacent to respective ones of said corridors, said recesses extending partially through said substrate; d. producing said image screen by steps including photographic exposure through said corridors; e. removing the portions of said preliminary mask located between said recesses and said second major surface to produce said color-selection mask comprising said final-size apertures; and f. incorporating said color-selection mask into said kinescope.

19. the method as defined in claim 18, wherein said first openings are substantially circular and said second openings are equal in number to said first openings and are substantially annular, said second openings being substantially concentric with and surrounding said first openings, and said openings of said second resist layer are substantially circular.

20. The method as defined in claim 18, wherein said first and second openings are substantially rectangular and substantially mutually parallel and said openings of said second resist layer are substantially rectangular.

21. A method of producing a color kinescope comprising a color-selection mask having final-size apertures of a first dimension and an image screen, said image screen being produced with a preliminary mask having corridors of a second dimension, said second dimension being substantially smaller in size than said first dimension, said method comprising: a. pRoviding a first resist layer on a major surface of a substrate, said resist layer containing a plurality of first openings and at least one second opening adjacent to each of said first openings, said first and second openings extending completely through said resist layer; b. providing a second resist layer on a second major surface of said substrate, said second resist layer containing a plurality of third openings substantially in register with respective ones of said first openings and a plurality of fourth openings adjacent to said third openings and substantially in register with said second openings; c. removing certain portions of said substrate located between said first openings and said third openings to form corridors through said substrate, and removing other portions of said substrate located between said second openings and said fourth openings to form oppositely disposed recesses extending from said first and said second major surfaces, respectively, through only portions of the thickness of said substrate, portions of said substrate being located between oppositely disposed ones of said recesses, thereby producing said preliminary mask comprising said corridors and said recesses; d. producing said image screen by steps including photographic exposure through said corridors; e. removing the respective remaining said portions of said substrate located between said recesses to produce said color-selection mask including said final-size apertures; and f. incorporating said color-selection mask into said kinescope.