US3003873A - Color kinescopes and methods of making the same - Google Patents

Description

Oct. 10, 1961 V. K- ZWORYKIN 3,003,873

COLOR KINESCOPES AND METHODS OF MAKING THE v'SAME Filed Deo. 25, 1953 2 Sheets-Sheet 1 .4 I' raaf/mf INI/EN TOR.

ZWDRYKIN d TTORNE Y VLHDIMIRK.

Oct. 10, 1961 v. K. zwoRYKlN 3,003,873

METHODS oF MAKING THE SAME COLOR KINESCOPES AND Filed Dec. 23, 1955 2 Sheets-Sheet 2 INI/ENTOR.

1l TTORNE Y Unired States Patent 3,003,873 COLOR KINESCGPES AND METHDS F MAKING THE SAN@ Vladimir K. Zworykin, Princeton, NJ., assigner to Radio Corporation of America, a corporation of Delaware Filed Dec. 23, 1953, Ser. No. 400,040 4 Claims. (Cl. 96-34) This invention relates to improvements in the art of manufacturing color-kinescopes and other cathode-ray (CR) tubes of the kind having a plane-of-detlection (or centerofscan) and containing a screen-'unit comprising (i) a mask containing a multiplicity of systematically arranged apertures through which Vbeam-electrons pass along different angularly related paths in their transit 'from said plane-ofdeection to (ii) selected ones of the metallized dot-like or line-like elemental areas on the target-surface of a nearby screen-plate.

rihe problem of making a satisfactory mosaic-screen for use in color-kinescopes and analogous (e.g., camera and stereoscopidj CR tubes has long been recognized and has engaged the attention of many scientists and experts in the television and photoengraving arts.

Thus, Dr. Zworykin, in his U.S. Patent 1,691,324 (filed July 13, 1925), proposed a three-color screen of the Paget type placed in front of a conventional (bla'ck andwhite) ylluorescent screen. (The idea of using an optical color lter in conjunction with a blacksand-white screen is a recurrent one, but one not likely to be adopted, commercially, because the thickness dimension of the tubes window introduces problems of parallax.) y

Dr. Goldsmith in his U.S. Patent 2,630,542 (which is based on an application tiled August 5, 1944), proposed (column ll) to use the mask of his screen-unit as a stencil through which the different color-phosphore are laid down in dilierent positions by shifting said stencil. Dr. VGoldsmith also proposed (column 'to form his screen by weaving extremely thin wires carrying fluorescent material as an adherent coating.

The above ,mentioned Zworykin and Goldsmith meth- -ods of making mosaic screens were followed (a) by the printing-plate method of Hansen, 2,568,448; (b) the silkscreen printing method of Law, 2,625,734, and (c) the direct photographic method of Law, described and claimed in'copencling application Serial No. `.l39,358,` filed July Y30, 1.951.

Y The Hansen method and the Law silk-screen method, like the method described yin column ll of the Goldsmith patent, have va disadvantage common to all three. That is to say, they each use a single printing plate (or stencil) for laying down two or more colors. Hence, the vprinting element must be shifted (with respect to the screen-plate) between the separate printingoperations; thus introducing problems of color-registration. An analogous problem is encountered inthe Law direct photographic method (Serial No. 239,358) wherein the screen-unit must be disassembled several times (for the purpose of sensitizing the separately photographed red, blue and green vphosphor patterns on the screen-plate) and subsequently reassembled prior to aligning said unit with the battery of electron-guns in the tube in which said screen-unit or target assembly is to be used.

Accordingly, the principal object of 'the present invention is to provide an improved 'CR tube of the maskedtarget variety and one characterized by its freedom from alignment and re-alignment problems encountered inthe manufacture of present-day tubes wherein the mask-toscreen spacing is ynot permanently established until after the entire mosaic pattern has been laid-down on the screen-plate.

Another and related object of the invention is to provide improvements inthe Law direct photographic method Patented Oct. 10, 1961 of plotting and laying down electron-'sensitive materials of dilierent color-response characteristics upon a curved (o1 flat) target-surface of a screen-plate, and which dispense with the auxiliary light-house, jigs, etc. required in the practice of earlier analogous methods.

Another object of the present invention is to provide a method of and means for applying an velectron-permeable metal coating of substantially uniform thickness to a permanently masked screen-plate.

tated generally, the foregoing and related 'objects are achieved in accordance with .the 'method of the present invention by (a) lirst permanently securing the mask and the curved, or ilat, foundation plate for the colorscreen in the required spacedeapart relationship and (b) thereafter recording the masks pattern of apertures on said screen-plate. When the direct photographic meth od of Law is employed the mask is of a special open-work construction which permits the photosensitive materials to be applied to the screen-,plate without clogging the electron-transparent openings in Ythe mask. The method is preferably carried out within the main chamber of a tube envelope of a novel indexed construction which ensures accurate locationnot only of the .photographic light-source, but of the electron-gun assembly as well.

When, as is usually the case, the electron-sensitive mosaic pattern on the screen-plate is to be provided with fan electron-transparent metal (e.g., aluminum) layer, the entire screen-unit is vimmersed in a vacuum and subjected to movement with respect to the source of metal, whereby particles of the metal are deposited substantially uniformly upon said mosaic surface irrespective of the presence of the mask in the path of the vaporized metal.

The invention is described in greater detail in connection with the accompanying two sheets of drawings wherein: y

FIG. l is a partly diagrammatic longitudinal sectional view of a 3-gun tri-color kinescope of the shadow-mask dot-screen variety, the bulb or envelope of the kinescope and the screen-unit or target-assembly therein being constructed in accordance with the principle of the inventon;

PEG. 2 is a fragmentary rear elevational view of the screen-unit of the color-kinescope of FIG. l, showing a conventional (hexagonal) pattern of mask-apertures and color-dots;

FIG. 3 is a diagram showing the relative location of the three beams, with respect to the tube axis, in the plane of dellection;

FIG. 4 is an elevational view of the mask of the screenunit; said mask being provided with openings adjacent to its periphery to permit access to the 'screen-plate which lis therebeneath;

FlG. 5 is partly diagrammatic sectional view of a tubeenvelope containing a screen-unit at a 'stage of its manufacture whereat it is subjected to centrifugal force in order to spread a photosensitive material evenly over the targetsuriace of its screen-pate;

FIG. 6 is a partly diagrammatic sectional view of a tube-envelope containing a source of light-rays for projectng the pattern of mask lapertures 'on the photo'sensitized screen-plate;

yFlG. 7 Yis an elevational view, partlyjin section, of a vacuum apparatus employed iin metalizing the mosaic target-surface of the screen-plate ofthe unit.

ln the drawings the invention is shown as applied yto the manufacture of a 3-gun tri-color vkinescope of the socalled masked-target dot-screenV variety (see Schroede 2,595,548) wherein -the red (R), blue (B) and green (G) phosphor dots (see FIG. 2) are arranged in a hexagonal mosaic-pattern on the vrear or target surface of a glass screen plate 1. The glassplate 1 may vbe Ioff any desired shape (eg. circular or rectangular) `rand Vnirvature (e.g. at or spherical). In the instant case it is in the form of a circular section of a spherical shell. Alternatively, as shown, for example, in the Schroeder patent, the color-screen may comprise a flat glass plate independently mounted behind the window. The mask 3 `for the screen-plate 1 may be made of perforated glass which has been metallized to render its surface conducting, or it may be formed of thin-metal or of any other conducting material which is immune to the materials employed in laying down the pattern of phosphor dots on the screen-plate 1.

When, as in the instant case, the mosaic screen pattern is to be laid down directly on the curved face plate 1 of the tube envelope 5, the mask 3 is appropriately curved so as to be approximately concentric with the curved inner or target-surface of said plate. In the finished tube of FIG. l, the reference character a designates the spacing between the mask 3 and screen 1. The spacing a between these elements 3 and 1 of the screen-unit is approximately uniform throughout the picture area of the unit. The apertures 3a in the picture area 3p (see FIG. 4) of the mask 3 are arranged in the same (hexagonal) pattern as the phosphor triads R, B and G which are to be laid down on lthe screen-plate 1. In the instant case the apertures 3a `which make up the picture area 3p of the mask 3 are of circular contour with a constant separation d between their centers. With such an hexagonal arrangement of apertures the red," blue and green scanning beams (see FIG. 1) pass through the tubes plane-of-deection P-P with the beamcenters equally 'spaced from each other and at a common distance s from the tube axis, as indicated in FIG. 3. The relation between the spacing a, the distance s, the aperture spacing d on the mask, and the separation L between the plane-of-deflection P--P and the mask 3 then becomes, for uniform coverage of the screen by phosphor dots,

a=Ld/(3s-d) (l) Thus, if L=14, d=0.023, s=0.225", a=0.495. A comparable relation may be derived if, for example, a line-screen pattern is desired and slits, stablized by thin cross-bars, are provided on the mask, as in Flechsigs French Patent 866,065.

While the invention is applicable to masked-target tubes of both the line-screen and dot-screen varieties the rest of this description will be limited, in the interest of brevity, to tubes of the latter variety. In such tubes the dot-like apertures 3a in the picture area 3p of the mask 3 can ordinarily be no larger than:

d 2 w/a in diameter although they may be made larger if a voltage is to be applied between the mask and the screen (post acceleration focusing). In that event the herein described light-ray method of plotting the location of the color-dots can be modiiied by the substitution of electronexposure (as taught by Law in copending application Serial No. 277,133, now U.S.P. 2,727,828), in place of light-exposure. In the rest of this description it will be `assumed that the mask 3 and screen 1 are to be operated at the same Voltage (as claimed by Law in U.S. Patent No. 2,663,821, issued December 22, 1953).

As previously mentioned, the present invention contemplates, and its practice provides, a screen-unit of the masked-target variety wherein the screen-plate 1 and its mask 3 are permanently joined, in the required spacedapart relationship, prior to laying down the electron-sensitive mosaic pattern on the target surface of the screen. When the screen plate 1 and mask 3 are permanently united they may be handled as a single unit throughout all of the chemical and mechanical operations incident to the manufacture of a nished tube. As a consequence, image-defects, heretofore occasioned by the necessity of sensitive materials used in the registering the mask apertures with the elemental or subelemental screen-areas, are obviated.

In practicing the invention it is preferable to weld, or otherwise aliix the screen-unit 1-3 to the large end of the shell or body-portion of the tube envelope 5 prior to laying down the dot-like pattern R, B, G on the target surface of the screen 1. One very real advantage of securing the screen-unit to the tube-shell prior to laying down the mosaic pattern on the screen-plate is that the heat employed in making the required hermetic seal cannot adversely affect the phosphors or other electron-sensitive or photosensitive materials of which said pattern is formed. Furthermore, the tube when thus assembled may be used as the light-house during the plotting operation (cf., Law 2,532,511).

Accordingly, in carrying the method of the invention into effect the rst step is to weld, or otherwise permanently secure, the marginal edge of the mask 3 to a metal sealing ring 7 or to mount it firmly in any other manner, at the desired distance from the target surface of the face-plate 1 or other foundation member upon which the mosaic screen-pattern is to be formed. Thereafter, the sealing ring 7 on the unfinished screen- unit 1, 3 is preferably sealed, as by a weld 9 about its periphery, to a complementary ring 11 on the large open end of the glass (or metal) shell 5 comprising the main chamber 13 of the kinescope.

The main body or shell of the envelope 5 includes the portion 1511 of the neck 15 upon which the beam-deflection yoke 17 (FIG. 1) of the kinescope is mounted. This portion 1Sn of the neck extends beyond the plane-ofdeection P-P of the tube and is provided adjacent to its end with an indexed seat, which here takes the form of a number (say, three) of inwardly extending glass or metal studs 19 spaced (say 120) apart for engagement with a similar number of complementary lands (or grooves) 21 in a flange 23 on the gun-assembly of the tube. Alternatively, the lands and grooves may be impressed on a pair of metal flanges similar to the ones (7 and 11) at the front end of the tube, in which case the horizontal and vertical deecting coils in the yoke 17 can be assembled in situ on the neck of the tube. After the color-areas R, B and G have been laid down on the screen, and the gun-assembly properly oriented on its indexed seat, the gun-supporting glass end-portion 2S of the neck is hermetically sealed to the adjacent free end 1511 of the neck as by means of a low-temperature glassfrit material, not shown. As will hereinafter more fully appear, prior to mounting the gun-assembly in the tube, the indexed seat 19, 21 also serves as support for certain auxiliary apparatus employed in laying down the mosaic pattern on the screen-unit.

The mosaic of red (R), blue (B) and green (G) phosphor dots may be laid down on the masked screen-plate 1 in any of various ways. For example, any of the four direct photographic methods described and claimed by Law (in application Serial No. 239,358) may be employed.

In order that the various photosensitive and electron- Law photographic methods may be deposited on the masked screen-plate Without clogging the apertures 3a in the mask 3 (see FIG. 3), the mask is provided with one or more openings Sn large enough to accommodate to spout, pipe, siphon or the like for said materials. As shown in FIG. 4 duplicate groups of openings 311 may be disposed on opposite sides of the apertured target area 3p of the mask.

In forming a tri-color mosaic in accordance with the Law photographic method the different color-phosphors are laid down one at a time on the screen-plate. Assuming that the red pattern is the iirst to be laid down, a red-phosphor powder in a liquid gelatine potassium bichromate emulsion is introduced through the large openings 3u in the mask. As indicated by the arrow adjacent to the pulley 31 in FIG. 5 the "tube envelope 5 is then spun about its vertical axis, to cause van even distribution `of the emulsion 33 over the curved face-plate 1, until the emulsion .has solidified. If R is the radius of curvature of the face-plate, the vappropriate rnumber of revolutions per second is:

Where g is the acceleration of gravity. Thus, .'for a radius of curvature of 24 inches, a speed of 38 revolutions per minute is appropriate.

Referring now to FIG. 6: As in the Law direct photographic methods, the photosensitive layer 33 is next exposed to a point-source of light 35 (such as a zirconium arc) positioned a point (r) corresponding to the point at the center-of-scan P-P which is allotted to the iirst color (in this case red) to be laid down on the screenplate. When, as in the instant cast, the neck-portion 15m of the tube is provided with an indexed seat 19 the lamp 35 is provided with an indexed baseplate 37 through which a pair of rod-like current leads 39 extend, oifcenter, the exact distance required to locate the point source of light in the plane of dellection. 'I'he base-plate 37, like the gun mounting-llange 23, is triply indexed, that is to say it is marked with three radial lands or grooves 37a, 37b, etc. permitting it to be shifted from a position corresponding to that of the red beam to that of the green and blue beams. As an alternative, a lamp with three point sources (not shown) which can be switched on in succession, mounted on a singly indexed base-plate may be employed as the removable insert.

When light-rays, from the point r, pass through the mask apertures 3a the photosensitive layer 33 on the screen-plate 1 is rendered insoluble at the positions of all of the red phosphor dots R in the mosaic.

The remaining soluble emulsion is then dissolved and drawn oif (see FIG. through a piece of tubing 41 presented to the screen-plate 1 through one of the large mask-openings 3u 4and which is connected to an aspirator 43 through a universal joint 45. When the soluble emulsion has been drawn off, and the screen-plate properly cleansed, a photosensive emulsion containing the blue phosphor is introduced, then dried and the exposure repeated With the light source 35 (FIG. 6) at the point at the center-of-scan P-P which is allotted to the blue electron-beam (FIG. l). Again the process is repeated, this time with a green-phosphor emulsion, leaving red, blue and green phosphor-dots in the proper position to be scanned by the red, blue and green electron-beams (FIG. l).

In order to provide the tri-color mosaic with an electron-pervious light-reflecting conductive coating, the screen-plate 1 is covered with water in an amount sufcient to produce a layer less than the mask-screen separation in thickness. The tube is then spun (as in FIG. 5), with the velocity mentioned above, to make the water layer of uniform thickness and a few drops of collodionsolution are introduced through the large mask-openings 371 and spread over the surface of the spinning layer of water forming a solid film. The Water is then siphoned off; the velocity of rotation being increased gradually to bring the water to the edge of the screen-plate. After drying, the unit is placed in an evacuable chamber or bell jar 47 (FIG. 7) and a piece of aluminum 49 is evapo rated by a means of a heating current supplied through rod-like leads 51 which extend through a llexible seal, such as a Sylphon bellows 53 at the top of the chamber. Some of the evaporated aluminum settles on the mask 3 and some of it passes through the dot-like mask apertures 3a and settles upon the collodion blanket 55 covering the screen plate. A rotating movement is applied to the rod-like leads 51 through the exible bellows 53 by a drive shaft 57, during evaporation of the metal. The

=ar'ea :scanned lby the lsource of aluminum V(49) in `.the plainefof-deflection should be, approximately, "a circle with a diameter 3s (FIG. 3) about the tube axis to ensure a complete and yeven -coating of aluminum on the target area oi" the mosaic screen; irrespective of the shadowing effect of the mask 3. After evaporating the collodion layer or blanket I55, the -base portion 25 of the neck `of the tube, with the three-electron-guns already mounted therein, is sealed to the small end 15a of the tube envelope 5 and the entire envelope subjected to evacuation in the 'usual way. Y

It should now be apparent that the present invention provides lan improved screen-unit ofthe masked-target" variety and one characterized by its freedom from alignment and re-alignment problems encountered in presentday screen-units wherein the mask-to-screen spacing is not permanently established until after the entire mosaic pattern has been laid down on the screen-plate.

What is claimed is:

' 1. Method of making a color-kinescope of the kind that includes a target-assembly comprising a mask containing a systematic pattern of apertures and a trans-y parent envelope portion having a color-phosphor mosaic on its inner surface yand a mask-supporting rim portion surrounding said mosaic, said method comprising: permanently securing said mask to said rim portion and thereafter coating said inner surface with a photosensitized organic gel containing phosphor particles of one color, exposing said coating to light rays through the apertures in said mask whereby photographically to record the pattern of said mask apertures on said surface, washing said surface to develop the photograph thereon, repeating said coating, exposing and developing steps for each of the other colors of said mosaic and then heating said surface to volatalize and remove said organic gel therefrom.

2. The invention as set forth in claim l and including the additional step of depositing metal in a inely divided state upon said color-phosphor mosaic through the apertures in said permanently secured mask.

3. The invention as set forth in claim 2 and wherein said permanently secured mask and envelope portion are rotated with respect to the source of said finely divided metal during the deposition of said metal, whereby said metal is deposited substantially uniformly upon said mosaic irrespective of the shadowing effect resulting from the presence of said mask in the path of said nely divided metal. f

4. Method of making a tri-colorrkinescope of the kind having a plane-of-detlection and containing a target assembly comprising (a) a mask having a multiplicity of systematically arranged apertures therein through which beam-electrons pass in their transit from said plane-ofdeilection to (b) selected ones of the elemental areas on the mosaic target surface of a nearby tri-color phosphor screen; said method comprising the following steps in the order indicated, (l) permanently securing said mask and the foundation plate of said screen in the required spacedrapart relationship, (2) coating said target surface with a film comprising phosphor of a iirst color contained in a photosensitive material, (3) directing light rays upon said permanently secured apertured mask from a rst point in a plane corresponding to said plane-of-deflection whereby to provide a phosphor-containing photograph upon said target surface of the mosaic pattern resulting from the passage of said light rays through the apertures in said mask, (4) developing said photograph, (5) coating said target surface and the photograph thereon with a film comprising phosphor particles of a second color contained in a photosensitive material, (6) directing light rays upon said permanently secured apertured mask from a second point offset from said first point in said plane whereby to provide a second phosphor-containing photograph upon said target surface, (7) developing said second photograph, (8) coating said target surface, and the `photographs thereon, with a lm comprising phosphor References Cited in the le of this patent UNITED STATES PATENTS 1,099,934 Rafn et a1. June 16, 1914 8 OBrien June 6, 1939 Kerridge Feb. 10, 1948 Filmer Aug. 10, 1948 Kaplan Feb. 16, 1954 Sanford June 29, 1954 Neugebauer Aug. 3l, 1954 Morrell July 17, 1956 Epstein Oct. 23, 1956 OTHER REFERENCES Electronics, pp. 86-88, May 1951.

UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No 3,003,873 Octobea7J lOq 1961 Vladimir` K Zworykin It is h'ereby certified that error appears in the Aabove number-ed pat ent requiring correction and 'that the said Letters Patent should read as corrected below.

Column 8, list of references cited underl UNITED STATES PATENTS, add the following:

Signed `and sealed this 150th day of April l92 (SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

Claims (1)

1. METHOD OF MAKING A COLOR-KINESCOPE OF THE KIND THAT INCLUDES A TARGET-ASSEMBLY COMPRISING A MASK CONTAINING A SYSTEMATIC PATTERN OF APERTURES AND A TRANSPARENT ENVELOPE PORTION HAVING A COLOR-PHOSPHOR MOSAIC ON ITS INNER SURFACE AND A MASK-SUPPORTING RIM PORTION SURROUNDING SAID MOISAC, SAID METHOD COMPISING: PERMANENTLY SECURING SAID MASK TO SAID RIM PORTION AND THEREAFTER COATING SAID INNER SURFACE WITH A PHOTOSENSITIZED ORGANIC GEL CONTAINING PHOSPHOR PARTICLES OF ONE COLOR, EXPOSING SAID COATING TO LIGHT RAYS THROUGH THE APERTURES IN SAID MASK WHEREBY PHOTOGRAPHICALLY TO RECORD THE PATTERN OF SAID MASK APERTURES ON SAID SURFACE, WASHING SAID SURFACE TO DEVELOP THE PHOTOGRAPH THEREON, REPEATING SAID COATING, EXPOSING AND DEVELOPING STEPS FOR EACH OF THE OTHER COLORS OF SAID MOISAIC AND THEN HEATING SAID SURFACE TO VOLATALIZE AND REMOVE SAID ORGANIC GEL THEREFROM.

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