US2539442A

US2539442A - Process of preparing a double-sided mosaic electrode

Info

Publication number: US2539442A
Application number: US680798A
Authority: US
Inventors: Christian C Larson
Original assignee: Farnsworth Research Corp
Current assignee: Farnsworth Research Corp
Priority date: 1946-07-01
Filing date: 1946-07-01
Publication date: 1951-01-30
Anticipated expiration: 1968-01-30

Description

c. c. LARSON Jan. 30, 1951 PROCESS OF PREPARING A DOUBLE-SIDED MOSAIC ELECTRODE Filed July 1, 1946 FIG. 2

j W w ,7 l I FIG? FIGS

l34-IOII m w S M ML 0 N m T S R H C A T TO R N E Y i atented jan. 30,

PROCESS OF PREPARING A DOUBLE-SIDED MOSAIC ELECTRODE Christian C. Larson, Fort Wayne, Ind., assignor, by mesne assignments, to Farnsworth Research Corporation, a corporation of Indiana Application July 1, 1946, Serial No. 680,798

Claims. (01. 204-'-24 This invention relates to electrodes for television tubes and particularly to a novel process of preparing a double-sided mosaic electrode for use in certain types of picture analyzing devices.

A double-sided mosaic electrode may be arranged in a picture signal generating tube of the charge storage type in such a manner as to have an optical image of the object projected upon one of its surfaces, while its opposite surface is scanned by an electron beam for developing .picture signals. It is well known in the art that a double-sided mosaic electrode will appreciably improve the performance of picture signal generating tubes of the charge storage type. It is feasible, for example, to provide an accelerating electrode opposite the photosensitive surface of the mosaicfor collecting the photoelectrons which are liberated from the mosaic by the action of the light. This will increase the signal output of the tube by saturating the photoemission and improve the signal-to-noise ratio. Furthermore, the scanning beam which may be arranged to the rear of the mosaic electrode may have a common axis with the optical system provided for imaging the object on the mosaic electrode. Thus, the so-called keystone effect is eliminated which is caused ina conventional picture analyzing tube of the cathode ray type by the necessity to arrange the scanning beam at an acute angle with respect to the mosaic electrode. An appreciable improvement of the signal-to-noise ratio of the image orthicon may also be expected by utilizing a double-sided mosaic electrode therein.

Numerous attempts have been made to provide a double-sided mosaic electrode which essentially consists of an insulating sheet or foil having a multitude of metallic plugs extending .therethrough and insulated from each other. Thus, it has been suggested to provide a wire screenwith an insulating layer and to fill the interstices of the insulated screen with a paste of a metal oxide suspended in abinder which isthereafter heated to reduce the oxide and evaporate the binder of the paste. However, since the thickness of the wire screen is of the order of .001 inch, it is obviously extremely difficult to fill the very small interstices in the wire screen uniformly with a metallic paste. It has also been suggested to electroplate a metal onto a'continuous conductor provided on one of the surfaces of the insulated wire screen,

thereby to fill the interstices of thescreen with metallic plugs. However, the difficulties of removing this conductor again, such as by grinding, are appreciable. Furthermore, the thus applied metal will normally not adhere to the walls of the interstices of the insulated wire screen so that the metallicplugs are liable to fall out.

t is the principal object of the present invention, therefore, to provide a novel processof preparing a double-sided mosaic electrode suitable foruse in cathode ray television trans mitting tubes.

. A further object of the invention is to provide a simple and convenient method of preparing a double-sided mosaic electrodeadapted for use in a picture analyzing device for the transmission of television pictures of high definition.

In accordance with the present invention, the

process of preparing a double-sided mosaic electrode from a fine mesh metallic screen comprises the steps of coating the screen with an'i electrically insulating substance, and then coating one face of the screen and the inner walls of the interstices thereof with an electrically conducting material. The face of the screen coated with the conducting material is now covered with a removable insulating layer, and the interstices of the screen are filled with a metal by electroplating it onto the conductingmaterial,

that is, onto the conducting material on the in the appended claims.

In the accompanying drawing: 7 Fig. 1 is a plan view on greatly enlarged scale of a fragmentary portion of a very fine mesh metallic screen utilized as a base of a double sided mosaic electrode in accordance with the invention;

Fig. 2 is a sectional view taken on line '2-2 of Fig. 1 of the fine mesh metallic screen;

Figs. 3 to 9 are sectional views similar to Fig.

2 illustrating consecutive steps in the process of preparing a double-sided mosaic electrode in accordance with the present invention; v

Fig. 3 illustrates the screen coated with a reinforcing metallic layer;

Fig. 4 illustrates the screen of Fig. 3 provided with an insulating substance;

Fig. 5 illustrates the screen of Fig. 4 covered on one of its faces and on the inner walls of its interstices with a conducting. material;

Fig. 6 illustrates the screen of Fig. 5 covered on its metal coated surface with an insulating layer applied thereto by a glass plate;

Fig. '7 illustrates the screen of Fig. 6 provided with metallic plugs in" the interstices of the screen;

Fig. 8 illustrates the screen of Fig. '7 with the insulating layer removed; and

Fig. 9 illustrates the screen of Fig. 8 with the conducting material removed from the face of the screen, the screen being now ready for use.

Referring to the drawing, there is shown in Figs. 1 and 2 a very fine mesh metallic screen I which may, for example, consist of copper. Metallic screen I is provided with a multiplicity of apertures or interstices 2 which preferably are of circular shape as illustrated in Fig. 1. Metallic screen I may be an 800 or 1,000 mesh screen, that is, there are 800 or 1,000 holes per linear inch, respectively, corresponding to 640,000 holes or. 1,000,000 holes persquare inch. Thus, the number of interstices 2 is so large that at.v least three and. preferably. four interstices or holes are covered. by any picture element. in a conventional. picture analyzingv tube of the cathode ray type. Screen I. may have a thickness of .0001 inch. Alternatively, screen I may consist of a very fine mesh Wire screen instead of a very fine mesh perforated metallic sheet or foil.

Metallic screen I may now be coveredas shown in Fig. 3 with a reinforcing metallic layer 3 which may be applied, for example, by evaporation. Metallic layer 3 covers both faces of, screen I as well'as the inner walls ofinterstices 2. Metallic layer. 3 may, for example, consist of gold for a purposeto be explained hereinafter. However, it is to be understood thatit is not necessary tocoat screen I with a metallic layer such as 3.

Metallic screen I Which may or may not be covered withmetallic layer 3 is now coated with an electrically insulating substance indicated at 4 in Fig. 4 which covers the entire surface of screen I including the inner-walls of interstices 2. Insulating substance 4 may, consist, for example, of calcium fluoride or silicium oxide. Thus, insulating substance 4 maybe applied, for example, by evaporating quartz onto metallic screen I in such a manner that; the entire surface thereof is covered with a quartz layer. Screen I is now electrically insulated,

The thus insulated metallic screen I is then coated with an electrically conducting material.

5, such as copper which may be dissolved with. an acid, or with aluminum which may be dissolved with an alkaline hydroxideincludingsodium hydroxide and potassium hydroxide. Conducting material 5 is applied, such as by evaporation, to face li Of screen I and to the inner walls ofinterstices 2 as shown in Fig.5. Accordingly, the opposite face of. metallic screen. Iis free from conducting material 5 so that insulating, sub.- stance 4 is uncovered.

Face '6 of metallic screen Iwhich has previously been coated with electrically conducting material 5 is now covered with a removable insulating layer indicated at I in Fig. 6. Removable insulating layer I may, for example, consist of a lacquer which may be pressed against face 6 of screen I by glass plate 8- Thus, conducting material 5 on face 6 of screen I is entirely covered by insulatinglayer 'I- while the conducting material 5 is still exposed .in the inner walls of interstices 2.

Conducting,,ma terial 5. on the inner walls of.

interstices 2 which may consist of copper or aluminum as pointed out hereinbefore, may be used in accordance with the present invention as an electrode for filling interstices 2 with a metal III which is electroplated onto conducting material 5. Conducting material 5 on face 6 of screen I is covered by insulating layer I so that metal I0 cannot be deposited thereon. As shown in Fig. '7, interstices 2 are filled by metallic plugs II] which may, for example, consist of gold or platinum, that is, of any metal which is resistant against acids or bases. Electrical contact may be made to conducting material 5 on the inner walls of interstices 2 from face 6 of screen I. Metallic plugs I0 will strongly adhere to conducting material 5 on the inner walls of interstices 2.

The exposed faces of metallic plugs I0 may be provided at this stage with caps I I by electroplating a metal, such as silver thereon, which may be made photosensitive in accordance with conventional practice. Electrical contact for the electrodeposition of caps II may be made again through metallic plugs IIlto conducting material 5 onface Gofscreen I.

Insulating layer I and glass plate 8. are. now removed by dissolving layer I, in a. suitable solvent, andthe resulting screen, is illustrated in Fig. 8. Accordingly, conducting material 5 on face 6 of screenI is exposed again.

The last step of the process of the invention consists in removing conducting material. 5 from face 6 of screen I. If conducting material 5 consists, forexample, of copper, it may be re-. moved by a suitable acid such as nitric acid, sulphuric acid or. hydrochloric acid, which will not dissolve metallic plugs I0 which may consist of gold or platinum. Caps II may consist of a.

silver layer of such a thickness that the silver will not be dissolved before copper layer 5 on face 6 of screen I has been entirely dissolved. Alternatively, conducting material 5 may consist of aluminum. In that case aluminum layer 5 exposed on face 6 of screen I, may be dissolved by sodium hydroxide or potassium hydroxide. Metallic plugs I0 should consistof a material such as gold or platinum which is resistant to the alka. line hydroxide used for dissolving aluminum layer 5.

It is to be, understood that caps II need not beprovided in casemetallic-plugs I0 consist of gold because gold may also be made photosensitive.

The-finished screen is-illustrated in Fig. 9 and consists of .a rnultiplicity of; metallic plugs It insulated from each other by insulating substance 4. One of the facesof metallic plugs I0 may be made photosensitive in order to develop an electricalcharge image when light image is projected thereon. The, reverse face of screen I, which may be face 6, maythen be scannedby an electron beam for developing picture signals.

Reinforcing metallic layer '3' which may consistof gold further serves the purpose of protecting screen l--wh-ich may consist of a base metal, such as copper, frornthe. action of the acid .or the alkaline hydroxide .utilized for removing the exposed portion of conductingmaterial 5. the-acid or base maydissolve, metallic screen I through pin. holesor cracks-in'insulating substance 4 which normally would protect metallic screen I from the action of the. acid or base. Sincethethiclmess ofmetallic screen I is of the order of .0001inch, abasemetal-such as copper willbe dissolvedlalmost instantly by anacid if it is not'pr'ote'cted over its entire surface-by insulat-.

ing substance 4..

Thus,

While there has been described what is at present considered the preferred embodiment of the invention, it will be obviousto those skilled in-the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

What is claimed is:

1. The process of preparing a double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with an elec- -trically insulating substance, coating one face of "said screen and the inner walls of the interstices thereof with an electrically conducting material, covering the face of said screen coated with said conducting material with a removable insulating layer, filling said interstices with a metal by electroplating it onto said conducting material, and removing said insulating layer and said conducting material from the face of said screen coated therewith.

2. The process of preparing a double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with an electrically insulating substance, coating one face of said screen and the inner walls of the interstices thereof withan electrically conducting material, covering the surface of said screen coated with said conducting material with a removable insulating layer, filling said interstices with a metal by electroplating it onto said conducting material, electroplating onto one of the exposed surfaces of said metal in said interstices a substance which may be photosensitized, and removing said insulating layer and said conducting material from the face of said screen coated therewith.

3. The method of preparing a double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with a metallic layer, coating said metallic layer with an electrically insulating substance, thereafter coating one face of said screen and the inner walls of the interstices thereof with an electrically conducting material, covering the face of said screen coated with said conducting material with a removable insulator, filling said interstices with a metal by electroplating it onto said conducting material on'said inner walls, and removing said insulator and said conducting material from the face of said screen coated therewith.

4. The method of preparing a double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with a metallic layer, coating said metallic layer with an electrically insulating substance, thereafter coating one face of said screen and the inner walls of the interstices thereof with an electrically conducting material, covering the face of said screen coated with said conducting material with a removable insulator, filling said interstices with a metal by electroplating it onto said conducting material on said inner walls, electroplating onto one of the exposed surfaces of said metal in said interstices a'substance which may be photosensitized, and removing said insulator and said conducting material from the face of-said screen coated therewith.

5. The method of preparing a double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with an electrically insulating substance, thereafter coating one face of said screen and the inner Walls of the interstices thereof with a first metal which may be dissolved by a predetermined sol-' vent, covering the face of said screen coated with said first metal with a removable insulating layer, filling said interstices with a second metal which is substantially not dissolved by said solvent by electroplating it onto said first metal on said inner walls, removing said insulating layer, and removin said first metal from the face of said screen coated therewith by dissolving it with said solvent.

6. The method of preparing a double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with a material which is resistant to a predetermined solvent, coating said material with an electrically insulating substance, thereafter coating one face of said screen and the inner walls of the interstices thereof with afirst metal which may be dissolved by said solvent, covering the face of said screen coatedwith said first metal with a removable insulating layer, filling said interstices with a second metal which is substantially not dissolved by said solvent by electroplating it onto said first metal on said inner walls, removing said insulating layer, and removing said first metal from the face of said screen coated therewith by dissolving it with said solvent.

7. The method of preparing a double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with a material which is resistant to a predetermined solvent, coating said material with an electrically insulating substance, thereafter coating one face of said screen and the inner walls of the interstices thereof with a first metal which may be dissolved by said solvent, covering the face of said screen coated with said first metal with a removable insulating layer, filling said interstices with a second metal which is substantially not dissolved by said solvent by electroplating it onto said first metal on said inner walls, electroplating onto one of the exposed surfaces of said second metal in said interstices a substance which may be photosensitized, removing said insulating layer, and removing said first metal from the face of said screen coated therewith by dissolving it with said solvent.

8. The process of preparing a double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with an electrically insulating substance, thereafter coating one face of said screen and the inner walls of the interstices thereof with a first metal which may be dissolved by a predetermined acid, covering the face of said screen coated with said metal with a removable insulating layer, filling said interstices with a second metal which is not dissolved by said acid by electroplating it onto said first metal on said inner walls, removing said insulating layer, and removing said first metal from the face of said screen coated therewith by dissolving it with said-acid.

9. The process of preparing a double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with a first metal resistant to a predetermined acid, coating said metal with an electrically insulating substance, thereafter coating one face of said screen and the inner walls of the interstices thereof with a second metal which may be dissolved by said acid, covering the face of said screen coated with said second metal with a removable insulating layer, filling said interstices With a metal which is not dissolved by said acid by electroplating it onto said second metal on said inner smears walls, i'emoving'said insulating l'ayer,rand:removing saidsecond metalifrom the face-of said screen coated -therewith -by dissolving it with said :acid. 10. "The 'process of preparing a idouble-sided mosaic electrodefrom a fine mesh metallic screen which comprises coating said screen with an electrically insulating substance, thereafter-coating one face-of said screen and the'inner walls: of theinterstices thereof with copp'er,-covering the face of said screen coatedwith said copper with a rem'ovable insulating'1ayer,'filling said interstices wvith gold by electroplating it onto said copper on said inner walls,- removing said insulating' -layer, and removing said copper 'from the :face of said screen coated therewith by-dissolving it' with an-acid.

11. The processof preparing a double-sided 1 mosaic electrodefrom a fine mesh metallic screen which comprises coating said screen with-gold, coatingsaid gold with an electrically insulating sub'stance, thereafter coating one face of said s'creen -and the inner walls of the interstices thereof With copper, coveringlthe face of said screen coated with said copper with a remova- "ble insulating layer,'filling said interstices with gold by electroplating it onto said copper on said inner walls, removing said insulatinglayer, and removing said copper from the face of said screen :co'ated-therewithby dissolving it with an acid. 12. The method of preparinga.double-sided mosaic electrode from a fine mesh metallic screen which comprises coating said screen with an electrically insulating substance, thereafter coat- "in'g ione face: of said screen and the inner walls er the interstices thereof with a base metal which -may" be "dissolved by a predetermined alkaline hydroxide, covering-the face of said screen coat 'ed'withsaid' base metal with a removable insulating layer, filling said interstices with a noble metal which is not dissolved by said alkaline hy- 1droxideby electroplating it onto said base metal .on' saidinner walls, removing said insulating layer, ancl removing said base metal from the :faceJof: said screen coated therewith by dissolv- -.ing itwith said alkaline hydroxide.

13. LThemethod of preparing a double-sided mosaic electrode from a fine mesh metallicscreen which comprises coating said screen with a metal- 110i layer resistant to a predetermined alkaline :hydroxide, coating said metallic. layer with an electrically insulating substance, thereafter coat- :ing one face of said screen and the innerwalls o1 the. interstices thereof with a base -metal which maybe 'dissolvedby said alkaline hydroxide, cov- -ering the face of said screen coated with said base metal rwith a removable insulating layer, r-filling' said interstices with a noble metal which 8 is :not dissolved bysaid valkaline :hydroxide by electroplating'it ontosaid-base metalon said-:in-

ner awalls, :removing said insulating layer, and -removing said'base metal from the face of said screen coated .therewith by dissolving .-it with said alkaline hydroxide.

:14. The .method .of preparing a doublesided mosaic electrode from a fine meshiinetallic screen which comprises coating said screen with an elec- 11 trically insulating substance thereafter coating one face of said-screen and the inner walls of {the interstices thereof with aluminum,.cover ing the face i of said gscreen coated with said alumihum with a removable insulating layer filling said 15 interstices with gold by electroplating it onto .-,said aluminum on Said inner walls, removing ;said insulating layer and removing said aluminumfrom the face of.-said j screen coated there- .-with byrdissolving it with an alkaline hydroxide, 15. The method of preparing a double-sided ,-mosaicelectrode from a fine mesh metallic screen vWhichcomprises. coating said screenwitha gold layer, coating said gold layer with an electrically insulatingsubstance; thereafter coating one face of said screen and the inner walls of'the interstices thereof .with aluminum, covering the face of said screen coated with saidaluminum .with a removable insulating layer, filling said interstices -.with gold byelectroplating it onto said aluminum qon said innerswalls, removing said insulating layer,. and removing saidaluminum from the face of said screen coated therewith by dissolving itwith :an alkaline hydroxide.

CHRISTIAN C. LARSON.

.REFEBENCES orrsn .'The following references are-of record in; the file of this patent:

UNITED STATES PATENTS :Number Name Date 577,070 ;Sandham Feb. 16, 1897 .-997-,6-10 -Feldkamp July 11, 1911 1,243,654 Clark Oct. 16, 1917 A 1,323,167 1Denny Nov. 25, 1919 ,1,7 92,197 Stresau, Feb. 10,1931 2,045,984 Flory June 30, 1936 2,047,369 Hickok July 14, 19.36 2,182,578 Blumlein et a1 Dec. 5, 1939 2,217,334 Diggory Oct.;8, 1940 2,226,384 Vorris Dec. 24, 19.40

.FOREIGN PATENTS Number Country Date 335,161 Great Britain Apr. 14, 1930 52 4,354 Great, Britain Aug. 5, 1940

Claims

1. THE PROCESS OF PREPARING A DOUBLE-SIDED MOSAIC ELECTRODE FROM A FINE MESH METALLIC SCREEN WHICH COMPRISES COATING SAID SCREEN WITH AN ELECTRICALLY INSULATING SUBSTANCE, COATING ONE FACE OF SAID SCREEN AND THE INNER WALLS OF THE INTERSTICES THEREOF WITH AN ELECTRICALLY CONDUCTING MATERIAL, COVERING THE FACE OF SAID SCREEN COATED WITH SAID CONDUCTING MATERIAL WITH A REMOVABLE INSULATING LAYER, FILLING SAID INTERSTICES WITH A METAL BY ELECTROPLATING IT ONTO SAID CONDUCTING MATERIAL, AND REMOVING SAID INSULATING LAYER AND SAID CONDUCTING MATERIAL FROM THE FACE OF SAID SCREEN COATED THEREWITH.