US2606303A - Color television tube and process - Google Patents

Description

Aug. 5, 1952 J. BRAMLEY 2,605,303

COLOR TELEVISION TUBE-AN'D PRQCESS Filed Feb. 17, 1951 2 SHEETS-SHEET 1 CONDUCT/1V6 GRID A7 FIXED VOLTAGE C O/VDUC 7" //V6 LA YER VOLTAGE MODULA TED INVENTOR A g- J. BRAMLEY v COLOR TELEVISION TUBE AND PROCESS Filed Feb. 17, 1951 GRID ELEMENT 0F 55c0-0 557' A7 D/FFERENI' .975"

F/XED VOLTAGE GAP/0 ELEMENT AT F/XED VOLTAGE PHOSPA/Ol? sir/P VOLT/1 6E MODULATED Patented Aug. 5, 195? UNITED STATES PATENT OFFICE 20 Claims.

The present invention relates to television, and particularly to color television reception.

A purpose of the invention is to dispose semiconductor phosphor areas suitably of difierent colors in a particular geometric relationship in a color television tube adjoining the face plate, and to produce an image instantaneously having a particular color by deflecting an electron beam so that it will illuminate only areas of the desired color at the particular instant.

A further purpose is to obtain color television reception from a tube having the external appearance of a black-and-white television tube.

A further purpose is to enhance the brightness of the image on a color television tube.

A further purpose is to shift an electron beam repeatedly for a series of short time intervals into contact with a plurality of geometrically placed semiconductor phosphor areas, the electron beam impinging upon phosphor of a particular color at a particular instant, and impinging on phosphor of another color at the next instant.

A further purpose is to place a plurality of strips or other areas of semiconductor phosphor of a given color on a conducting layer adjoining the inside of the face plate.

A further purpose is to utilize semiconductor phosphor areas, each of which is a constituent of a multiplier element consisting of a conducting base, a thin layer of semiconductor phosphor dielectric and then a secondary-electron-emitting layer.

A further purpose is to pass the electron beam to the semiconductor phosphor through openings, which are suitably slits, in a grid located between the electron gun and the conducting layer adjoining the face plate, and to maintain a predetermined and selectively changing voltage relationship between the grid and the conducting layer, the conducting layer being preferably negative with respect to the grid and the grid being preferably at anode potential.

A further purpose is to shield the phosphor subjected to the electron beam passing through one grid opening or slit from the electron beam passing through another grid opening or slit by a baffie extending from the grid toward the conducting layer.

A further purpose is to provide a baflle of dielectric having a deposit of semiconductor on one or preferably both sides of the bafile.

A further purpose is to place the semiconductor phosphor of a particular color, preferably in the form of multiplier elements, on one side of each baflie.

A further purpose is to extend the phosphor areas as parallel strips running lengthwise of the slits in the battle, and to locate the strips of a particular color in the same geometrical relationship to each slit and in the path of the electron beam.

A further purpose is to project the electron beam diagonally with respect to the major plane of the grid.

A further purpose is to deflect the electron beam diagonally with respect to the major plane of the grid by electromagnetic or preferably by electrostatic means and to vary the extent of deflection instantaneously to show images of different colors.

A further purpose is to carry the semiconducting layer on the baflie into contact with the conducting layer on the face plate at, at least, some points.

A further purpose is to place the grid closer to the conducting layer on the face plate at the side of the face plate remote from that from which the diagonal electron beam comes than at the other side.

A further purpose is to place the grid closer to the conducting layer at the extremities than at the center.

A further purpose is to construct a color television cathode ray tube having an electron beam directed upon a, transparent plate adjacent to and across the face of the tube, to place a partially transparent conducting layer on the plate inside the tube, to mount a conducting grid extending across the tube between the electron gun and the plate adjacent the conducting layer and having openings, suitably slits, which pass the electron beam toward the plate, to provide semiconductor phosphor of a plurality of different colors arranged in different areas, suitably strips, in the path of the electron beam between the grid and the conducting layer beyond the respective openings, in electrical contact with the conducting layer, with the phosphor of a particular color in the path of the beam only at the same angular position beyond each opening, and to arrang means for maintaining the grid at a particular D. C. voltage and means for maintaining the conducting layer selectively at different D. C. voltages, at least all but one of which are difierent from the voltage of the grid.

A further purpose is to produce color images on the face plate of a color television cathode ray tube by introducing a transparent conducting layer across the tube inside of and adjacent the face plate, distributing semiconducting phosphor areas, preferably multiplier elements, over the tube adjacent and in electrical contact with the conducting layer in a geometrical pattern, suitably parallel strips, having a plurality of phosphor colors at each locality, projecting a scanning electron beam in the tube on phosphor of the same color in the different localities, and deflecting the scanning beam at frequent intervals to impinge it on phosphor of another color in the different localities.

A further purpose is to obtain electron multiplication in the electron multiplier phosphor elements much higher than that obtained in prior practice. This is accomplished in this invention by the proper construction of the composite surfaces which make up the multiplier elements. One method is to interpose a semiconductor phosphor dielectric between a layer with at least moderately high secondary electron emission properties and a. conducting base. The semiconductor phosphor layer plus the secondary-electron-emitting layer should have a thickness of between 2 and microns.

A further purpose is to obtain high multiplication in a secondary-electron-emitter having a phosphor dielectric without the undesirable features of photo-electric effects due to the presence of photo-electric material, such as caesium, in the layer emitting secondary electrons.

A further purpose is to maintain close time coordination between the excitation of a phosphor and the primary current by providing for the-neutralization by electrons of the positive charge in the phosphor layer at a rate predetermined by the primary current. One method of accomplishing this is by depositing a secondaryelectron-emitting layer on an extremely thin layer of porous phosphor dielectric which itself rests on a conducting base, and intruding particles of the secondary electron-emitting-layer into the pores of the phosphor dielectric to assist in neutralizing the positive charge by electrons.

A further purpose is to increase the efficiency of cathode ray tubes by employingafine wire mesh with a surface having enhanced secondaryelectron-emitting properties in a cathode ray tube in which a screen, suitably double layer, is settled on a thin transparent conducting layer on the inside of the face plate. Aluminum constitutes a suitable choice for the conducting layer while the double layer may consist, for example, of ZnBeSiOi; Mn and ZnSzAg. The mesh may be at a negative potential with respect to the metal film on the face plate.

By proper choice of the emitting surface, the time lag between the primary current and the secondary emission from the wire mesh can be made comparable to the time between scanning frames. This is equivalent to a storage effect and will materially reduce the primary current needed to excite luminescence. Besides the screen materials mentioned above, the following may be used as components of the screen: Any organic crystalline or vitreous phosphor, or crystals of alkali halides impregnated with rare earth, such as sodium chloride with europium or alkaline earth halides with rare earth elements in the solution such as calcium fluoride with samarium.

The type of cathode ray tubes in which the screen comprises multiple layers of phosphors which emit radiation of suitably chosen wave length can be utilized to produce color images provided the variation in potential difference between the mesh and the conducting layer on the face is synchronized with the color frame frequency of the total picture frame transmitted. By proper choice of the potential, relative to the cathode, of the mesh and of the conducting layer on the face plate the picture rasters of each color can be adjusted for perfect superposition.

The color will, to some extent, depend on the time lag and the current density of the secondaries emitted by the mesh scanned by the primary beam. Since phosphors vary in emission time and saturation of emitted radiation under uniform electron bombardment, the instantaneous color of any point on the phosphor screen will be characterized by the time distribution of the secondary electrons.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the numerous embodiments in which my invention may appear, selecting the forms shown from the standpoints of convenience in illustration, satisfactory operation, and clear demonstration of the principles involved.

Figure 1 is a side elevation, partly in central longitudinal section, showing a skew-neck tube to which the principles of the invention have been applied.

Figure 2 is a faceplate elevation of the tube of Figure 1.

Figure 3 is a fragmentary enlargement of Figure 1 showing the transverse section through the grid, bafiles, conducting layer, and face plate, in the direction transverse to the length of the slits in the grid.

Figure 3 is a fragmentary enlarged plan view of the grid from the side opposite to the face plate looking toward the face plate.

Figure 3 is a fragmentary variation of Figure 3*.

Figure 4 is an enlargement of a portion of Figure 3 showing the manner of holding the baflies and showing the semi-conducting coating on the baffles.

Figure 5 is an enlarged fragmentary variation of Figure 3 showing phosphor multiplier elements applied to the baiiles and to the conducting layer.

Figure 6 is an enlarged variation similar to Figure 3 showing phosphor strips located entirely on the conducting layer.

Figure 7 is a fragmentary side elevation of a cathode ray television tube having electromagnetic modulation of the electron beam.

Figure 8 is a fragmentary diagrammatic side elevation, partly in central longitudinal section, showing a variant form of vacuum tube embodying the invention.

Figure 9 is a diagrammatic view similar to Figure 3 showing a different form of grid construction.

Figure 10 is a diagrammatic perspective view illustrating a synchronizing device.

In the drawings like numerals refer to like parts throughout.

The present invention is applicable particularly to color television of the character which depends upon persistence of vision of the .observer to visualize a color picture when he in fact may see a rapidly changing sequence of pictures, each at an individual different color. The individual pictures -will desirably be of three difi'erent primary colors, red, blue and green, shown to the observer in rapid succession. In the prior practice this result has been achieved by mechanically moving a filter, thus necessitating the employment of rather bulky mechanism adjoining the face plate. One of the important advantages of the present invention is that the color television image is produced by a cathode ray tube having an external appearance which is similar to that of an ordinary television tube. The cathode ray tube of the invention, however,

provides near the face plate a plurality of areas of phosphors each of a difi'erent color and arranged according to a geometrical pattern. The phosphors desirably will emit red, blue and green light respectively. By the invention it is possible to excite the phosphors of different colors one at a time and have each phosphor cease luminescence promptly. The shift from one phosphor color to another can be accomplished in a matter of microseconds. Since phosphors have normally been insulators, an important aspect of the invention is the employment of phosphors which are semiconductors, either due to the composition of the phosphor itself or due to the employment of multiplier elements which render the phosphors semiconductors. The shift of the excitation from one color phosphor to another is desirably accomplished by maintaining the phosphors at suitable potentials and changing these potentials at very short intervals.

The present invention is a continuation-inpart of my copending application Serial No. 612,197, filed August 23, 1945 for Secondary-Electron-Emitting Surfaces, now Patent No. 2,548,514, and contains subject matter related to my U. S. Patent No. 2,527,981, issued October 31, 1950.

The employment of the phosphors emitting light of different colors as components of composite surfaces gives rise to enhanced secondary electron emission. The conductivity of the phosphors is suitably adjusted to keep the charges from accumulation at the surfaces and it is therefore possible to keep bombarded surfaces of the phosphors at the potential of the conducting base. It is desirable to correlate the thickness of the phosphor layer and the velocity of the bombarded electrons to obtain maximum light output of the desired color.

The color television tube of the invention may desirably have the external appearance of the present skew-neck black-and-white cathode ray tube except for an extra electrode which may be considered to be an extra anode (although it need not be at anode potential). The color of the picture presented on the face plate depends on the voltage applied to this extra electrode. For example, changing the color of the picture from red to blue requires only a voltage change on the extra electrode. The potential of the first or standard anode is unchanged. Thus there is no over-all change in the deflection or focusing of the electron beam.

One great advantage of the invention is that it increases the brightness of the image on the color television tube.

Referring to Figures 1 to 4 inclusive, in the preferred embodiment, the cathode ray color television tube has a face plate 2! provided with the usual television screen which is scanned at any suitable rate according to any scanning system involving for example 525 line elements, 405 line elements or any other suitable number of line element as desired. The electron gun assembly 22 of any standard character is assembled in a skew-neck which projects a diagonal electron beam on the inside of the face plate. A semitransparent conducting layer 23 (called transparent elsewhere in the specification) extends across the tube adjacent the inside of the.

face plate. No particular advantage exists in depositing this layer on a separate .plateand therefore in most cases it is deposited on the inside of the face plate itself as shown.

The layer 23 is designated herein as a con ducting layer although it will in most cases be a semiconductor, and may have the same composition as the semiconductor layer later referred to. The conducting layer 23 is connected by a separate insulated terminal 24 which is led out through the glass or other wall material of the envelope of the vacuum tube and is insulated from all other terminals.

The technique of providing transparent conducting layers on glass as normally used for the face plate is well known. This is described in Leverenz, Luminescence of Solids (1950) 471, which refers to Pittsburgh Plate Glass Company Technical Glass Bulletin No. 15 on Nesa Coated Glass, Corning Glass Works Bulletin on E. H. Coated Glass and J. W. Littleton U. S. Patent 2,118,795, granted May 24, 1938. Common techniques for depositing transparent conducting coatings on glass are the evaporation of aluminum in vacuum, and the deposition of tin by decomposing tin chloride. Any other well known method may be used as required.

Semiconductor phosphor of different colors is placed in different areas adjacent the conducting coating and in the preferred embodiment is directly placed on it as shown in Figure 3. In any case the phosphor should be in electrical connection with the conducting layer 23.

The semiconductor phosphor may be produced in one of two manners (1) It may be a single layer of phosphor containing impurity centers and processed to create a semiconductor as later explained; or (2) It may be a multiplier element as later explained. As best seen in Figure 3, semiconductor phosphor areas 25 and 26 are shown on the conducting layer 23, located successively in a sequence in which the areas bear the same geometrical relation to one another, all of the areas 25 having phosphor of one color and all of the areas 26 having phosphors which luminesce in another color. In the form shown the phosphor areas are parallel longitudinal strips, but it will be understood that they may take any suitable form in which the phosphor of one color can be selectively energized by the electron beam. The character of the phosphor itself will be discussed at a later stage in the application.

The individual colors assigned to the phosphor areas 25 and 26 will be a matter of choice; for example 25 may luminesce green and phosphor 26 may luminesce blue. Since in the preferred embodiment different voltages will be applied to energize difierent phosphors, the green luminescing phosphor will desirably have a thickness corresponding, for example, to a maximum light output at 5.4 kv. bombarding electron-voltage, while the blue luminescing phosphor will have a thickness corresponding to that which gives maximum light output at say 6.2 kv. bombarding electron voltage, the thickness relations being well known in the art.

Placed across the tube between the electron gun 22 and the conducting layer 23 is a grid 21 suitably of metallic wire or sheet. A satisfactory material for the grid is aluminum, nickel or stainless steel or any of the structural alloys. In the preferred embodiment as best seen in Figures 3 and 3, the grid 21 consists of a stamp.-

7, ing having-longitudinally extending metallic strips 28sspaced by longitudinally extending slits Inrthe preferred. embodiment the slits will extend-uninterruptedl'y from one side to the other of the-grid, having merely cross connection-at theends so asnot to create theshadow on: the-screen incident to cross connection at intermediatepoints'. 'Thegrid'is located close to the conductive layer, the distance between thegridL-andthe' conductive layer being desirably of the order of 2 There-should be one grid slit .for everyrline on the screen, and the lateral distance from the center of one slit to the center of the next slit may desirablybe of the order of 1 mm. Theslits'on the grid run perpendicular to the line in-thescanning of the screen. The structurewhich :is being shown for a few grid slits will be repeated for each one of the line elements of the grid system.

The grid has an external terminal 3| which is insulated from all other terminals and led out through the glass or other envelope of the tube.

Itwill: be obvious fromFigure 3 that each of thephosphor- strips 25 and 26 extends parallel tothegridslit, and is oflset-with respect to the grid slit away from the direction from which the electron beam: enters diagonally so that the phosphor :strips will be within or close to the pathof the electron beam depending on the voltages.

An anode-coating 32 is placed on the inside wall of the tube from -a point near the forward end of the. electron gun to a point rearward of the grid and this coating 32, suitably of graphite (Aquadag) is connected to terminal 33 which is insulated from all other terminals and extends through the envelope of the tube. Anode coatings of this character are well known.

In order to confinethe electron beam passing through each slit to the phosphor corresponding to that line element, and also in order to support'an additional set of phosphor strips in the preferred embodiment, baiiles 34 extend from the grid toward the conducting layer and at an angle suitably approximating the angle of the diagonal electron beam. Where the electron beam approaches the grid at 45 degrees, the angle between the bafiies and the major plane in the grid will desirably be made about 42 so as to allow adequate space for beam deflection to encounter the'proper phosphor.

The baille is suitably made of an insulator such as mica or glass, and in the preferred form where phosphor is placed on the baflle, the bafile is coated on oneor preferably both sides by a semiconductor layer 35 which extends suitably the full length of the baiiie. The semiconductor layer 35 may consist of a layer of aluminum or tin or any other suitable metal as explained in connection with the composition of conducting layer 23. In fact it may be the same as conducting layer 23 except that it must have a resistance of at least one megohm per baiile, while no such limit is necessary on the conducting layer. This limit is imposed on the semiconducting layer to avoid short circuiting the grid to the conducting layer.

The baflles desirably extend far enough so that at least in places the semiconducting layer 35 on the 'baiile touches the conducting layer 23 at the face plate at forward ends 36. This allows a progressive voltage drop to occur from the grid to the conducting layer.

The :manner of mounting the haflle on the grid is not critical in the present invention, the form shown involving thecreati'on of reverse bends-'31 running across the grid which are angular-1y dis posedin thedirection to be taken by the-baffle,

and which receive and grip the end ofthemaifle and electrically connect its semiconductinglayers- 35 to the grid.

At the side of the baflie remote from the side at which the diagonal electron beam enters,' and extending along the full length of the baflle which corresponds with the full length of the -grid-slits and the full length of the screen, I place semiconductor phosphor areas, suitably strips 38, which luminesce in a difierent color from' the phosphor on the conducting layer 23. As shown, the strips 38 extend along near the ends of the baiiles adjoining the conducting coating-.23. If the strips 25 luminesce green and thestrips 26 luminesce blue, the strips 38 will luminesce red to provide the other desired primary color. An important aspect is that the strips 25 andv 26'are spaced by a distance approximately equal to the width of the strips, and the phosphor strips 38- are placed immediately behind the spaces 40 between the phosphor strips 25 and 26 so that the luminescence of the phosphor strips 38'will be seen at the front of the face plate through the gaps All between the phosphor strips 25 and 26.

In a suitable embodiment, the apertures -'between the metallic grid strips may be of the order of 0.30 mm. while the widths 'of the strips- 25 and 26 of phosphor and the spaces between them may suitably be of the order of 0.25 mm- The width of the phosphor strips 38 may conveniently be the same or somewhat wider in view of' t'he angularity.

It will be evident that the separation between the grid and the conducting layer on the face plate should be suficient to maintain the necessary voltage between them without arcing, and of course the semi-conductor layers 35 should have a high enough resistance so as not to interfere with adequate insulation of the grid from the conducting coating at the face plate.

The red luminescing phosphor 38 is suitably of a thickness which will give a maximum light output at a bombarding electron voltage of approximately one-half the anode voltage.

The electron beam in the cathode ray television tube is deflected so as to encounter one color of phosphor at a time, and the picture in that color is broadcast at the same instant so that this particular color of phosphor is energized. In the form of Figures 1 to 4, the deflection of the electron beam is accomplished electrostatically. The grid '21 will desirably, although not necessarily, be at anode potential, and whatever its potential it will be maintained at a constant D. C. potential. The conducting layer 23 on the other hand will vary its potential depending upon the color of image which is being produced by the tube. The voltage of the conducting layer may be either negative or positive with respect to the grid, but it is decidedly preferable to make'it negative, as this gives a much more powerful beam deflection than would be the case if it were positive with respect to the grid. All the grid elements in this form are at the same potential. The normal procedure therefore would be to maintain the conductive layer 23 at a particular voltage negative to the grid (or possibly at the same voltage as the grid) to energize the phosphor 26, to make the conducting layer 28' to energize the phosphor 38. As you 'make'the conducting layer more negative with respect to the grid, you deflect the electron beam farther away from its original diagonal axis.

Thus to obtain a picture in the one color, say blue, the conducting layer might preferably be connected to a voltage slightly negative with respect to the grid and will energize the blue phosphor 26 at each line element; After the beam has scanned the face plate to'form a picture in blue, the potential of' the conducting layer is shifted to a value more negative with respect to the grid, shifting the electron beam'to impinge on the phosphor areas 25 and energizing'the green phosphor. When this shift in beam deflection occurs, the blue phosphor 26 immediately ceases to be luminescent, due to the elimination of time lag by the semiconductor action of the phosphor already described, while luminescence of the green phosphor begins immediately. The beam then scans the screen and creates a green picture. The conducting layer 23 is then made still more negative with respective to the grid and the electron beam past each slit shifts to encounter the red phospher 38. At the same time; due to the absence of time lag in the semiconductor phosphor, the green phosphor 25 immediately ceases to luminesce. The luminescence of the red phospher 38 shows through the gaps between the blue and the green phosphor.

Of course the color of the phosphor applied at the different places may be shifted around as desired, and the red, blue or green phosphors may be at any of the areas 25, 2B or 38 as preferred.

It is highly desirable to use a skew-neck tube which will give a normally diagonal relationship of the electron beam to the major plane of the grid. This makes the deflection much more sensitive to changes in potential of the conducting layer 23 relative to the potential of the grid.

It is preferred in the skew-neck tube to make the grid curve as shown in Figure l and to place the grid closer to the coating 23 at the side 4| opposite to that from which the diagonal beam is directed and farther away at the side 42 adjoining that from which the electron beam is directed. This corrects for the remoteness of the electron beam source at the side 41.

The curvature of the face plate 2| (it is normally a portion of the surface of a sphere) can if desired be predetermined in relation to the angle of skew of the electron gun so that the electron beam will pass through all slits in the grid 2'! at the same angle, in which case the grid 21 will have the same curvature as the face plate and will everywhere he at the same distance from the face plate. Where, however, it is not desired to employ this condition of uniform spacing of the grid with respect to the face plate, the tube designer may employ the option of spacing the grid farther from the face plate the steeper the angle of incidence of the electron beam on the grid. This in effect calls for a variation in steepness in the angle of the electron beam on the different slits of the grid so that the beam will encounter phosphor strips at the same geometrical position for the same potential difference be tween the grid and the conducting layer at all line elements across the grid. If the angle of incidence of the electron beam varies over the grid and it is not desired to fully correct for this by variation in the spacing of the grid from the conducting layer,-correction can be made by varying the spacing of the phosphor strip with re- I0 spect to the normal from the center of the grid slit within limits.

In the illustrations in the drawings the slits 30 of the grid have been shown to be horizontal. In this case the scanning will normally follow-a series of vertical lines. It .will be understood however that the slitsin the grid may if desired be 'vertical in whichcase the scanning should preferably be horizontal. While there are advantages in both vertical and horizontal scanning, I prefer to employ horizontal scanning (with vertical grid slits). The reason that this last embodiment is preferable arises from 'the fact that the electron beam as well known inthe art must change its focus as it travels from one end of the raster to the' other because the distance between the gun and the point of impingement of the electron beam on the phosphor varies from point to point on the face plate. as you move up vertically.

The exact voltages used in modulating the conducting coating for color will vary, but the following is a suitable example: The anode potential and the potential of the grid 21 is 10 kv. The conducting layer-23 is set'at 6 kv., for blue light (phosphor 26) 5.5 kv. for green light (phosphor 25) and 5 kv. for red light (phosphor 38). During each setting of the voltage of the conducting layer 23, the grid of the electron gun is modulated to scan the picture for that color image.

The radiation produced under any particular phosphor color doesnot of course need to be percent pure. Thus in green the light produced may be 8 percent blue, 8 percent red and 86 percent green, while in blue the color produced maybe 12 percent red, 6 percent green and 82 percent blue, but in either case this color purity is acceptable.

It will be seen that this type of three-color cathode ray tube is particularly well adapted to the C. B. S. or C. T. I. systems of color broadcasting. There are two special advantages over the mechanically operated color filter now recommended for C. B. S. reception:

1. The three-color cathode ray television tube can be made in the same sizes as the conventional cathode ray tubes, while tubes having a diameter over 12 inches are not practical in the mechanical system using rotating filters.

2. The brightness of the picture is greatly increased. The brightness of the picture obtained with the C. B. S. mechanical color filter is reduced to one-seventh that obtained from the standard black-and-white cathode ray tube, with the same power input to the scanning beam. On the other hand, the brightness of the picture obtained from the three-color cathode ray tube of the present invention is approximately one-third that obtained with the standard blackand-white cathode ray tube, using the same power input in the scanning beam. This means that a color picture can be readily obtained with a brightness to which the public is not accustomed in present day color television reception.

Figure 3b shows a grid 21 having a series of short slits 30' in line, which may less desirably be used instead of the long slits 30.

The form of Figures 1 to4 can be still further improved in the best embodiment by using multiplier elements at the phosphor areas. These multiplier elements will comprise a conducting base, which in this case is the conducting layer 23 or the semiconducting layer 35 as the case may be, covered by a thin layer of semiconductlng; phosphor dielectric 43.- described' below and superimposed by secondary electrons-emitting layer;

The; light :emitted'ishowsthrough .the' extremely thinlsecondary-electron -emitting layer: 44 in 1311850359 of the-phosphor strips amounted on thesemieconducting layers 35; It.-will be understood-without repeating-the illustrations that in each-:case in. which a phosphor layer isshown, there will preferably he a.- multiplier element consisting.ofconductingbase; then a semiconducting phosphor dielectric; layer and then a: secondary-electron-emitting-rlayer on the opposite side: of the dielectric layer. The -.multiplier ele:- ment--more-reliably neutralizes .thecharge on the phosphor and: assures.- absence of time lag;

In: somecases-i it isdesirabletoplace all: of theaphosphor strips on'ztheiconducting layer: 23 instead: of placing one:- .set: on the .bafiiesi In Figure 6 I show strips 38,: which: maysuitably beethesreiphosphor positioned beside the strips 25.;and: 26::withsuitable spacing-40 between to avoidiunintentional, energizing by overlapping; of the-areas energized by the beam. Thesesistrips 255.26zand ,38' will desirably eachtie-multiplier elements. The bafiiess-are optionallyi omittedrin Figure 6. They may: bezused 'if desired .to re-v duce scatteringror-serve aszsupports;

While in -n1ost cases .it ;is :preferable :to. use-.an electrostatic; :beam: deflection; system, the. beam can be deflected in addition electromagnetically ascshown' in Figure; '7. 'Ihisccreates an :acute angle between: the entered: beam and :thegrid 21:1 'I'he grid,.Figure Zymay. be of theziorm already describedcin-Figuresl'toad;. The usual COIIVBI'? gencezcoil 45 is provided. (if the focusing .is -.electromagnetic; and .otherwise the. focus will beaccomplishedzin the gun structure) :and; the usual anastigmatic deflection yoke; 46 is: employed; mcoilfl forlinear deflection surrounds the gun awayvfrom the faceplate withrespect to the -convergenceicoil 45.andthis deflects theelectron beamangularlyin much the same-way which the skew-tneckitube deflects zit angularly. Thedeflec tion coil 41 is energized froma suitable alternating current: source. In the electro-magnetic form of-ideflection, if the curvature of .the face plate and gridare not set to give the same angular relationshipzat:.all points on: thezgrid, then the grid is placeds-closer to the faceplate at 481near the extremities than at 49'near the center of the face plate-to correct -for the difierence in angle--of the electron beamat thestwo points. Bafilesif usedshould slope one way on one side .of the cen terrandithe otherv way-v on the other side. of the center.

Andmportant aspect of the invention relates .to the production of electron-tubesof highemission ofisecondary electronsas a consequence of strong electrostaticfields initiated by 'bombardmentwith primary-electrons of composite surfaces.- constructedlin-accordance with-the invention. There must-of;:course-sbe--a-; suitable, source of primary electrons and these electrons: should have .aspeed such, that "the-ratio of the :secondary electrons released from the secondary-electron-emitting elementto the primary-electrons of thebeam :impinging on the secondary electron emitting element; is greater than unity such velocity furthermore-beingsuchthatinacathode ray tube the time .lag-;between impact of the electrons -in-the scanning, .-beam .and the emission of secondary electronsless thanthe time of persistence of vision., There .must be a perforated surface between:;the;.-.primary source and thephosphor. di-.

12 electriczof thezseconda lemittingsurfacerrwhich perforatedsurfaceswill allow-the-beam notconly to go through: it; butinrits travel in-the scanning path-to find aeperforated .surfacefat allzpoints through which. it: can;pass.- Theinventionmay-be usefullyz-appliedtin image converterorcathoderayctubes-orlight-waives to.:intensiy the. images produced by-electromime pacton fiuorescentor-zlight valvascreensz- While the example-,igivenzbelow has fbeerrdirected par ticularlyz-toicathode ray; tubes, eit'WillzbE? evident to those skilled in;the art that it 'c'anzbeiapplied equallyzwellg-tozimage convertors andlig'ht valves:

Eon" cathode: ray; tubes; the; conducting layer on the inside of theziacelplatezshotrldrbemapabl of transmitting at-least %:ofltherlight impin ed upon ;it:- It-is desirable: tomave-iameanseofiade justing the: conductingjlayen to; az-zdeflniterpo tential. For-:example-ain Figure-8 lthez-film-l 50 on the-interior surface of the. face.:-plate.:ofid:he cathode;- ray: tube: is: connected; to terminal; 511 Layer-25 1s; a.:phosphor:-lay.er:orrlayers ofrzdifirent phosphorsssettlednore otherwise deposited onthe conducting layer "58 Therlayer :50 may: be ofthe same character. 25213116 conductingzlayeian already described. The; potential of? the grid is maintained. at the value of "the ianodetpotential by connecting the- :grid. .52;':to' the colloidal graphite coating 32 on cthez;inside of theetubev Thea-grid should bezcoated'andpreparedto :produceanuenhanced-rsecondary; electron emissionw Thef very high secondaryeelectronz emissiomleads towcori responding. increases the efiiciency light emission as measured in terms of lumense'per watt of electrical. energ-y inputrbyproperadjustment of the conductivity. of .the=.dielectric in-the compositev surface emittingasecondary, electrons. The bombardmentv of thescreenbycthesecondary e16Ct1OnS .C8-l1 be extended. ovenar-sizable fraction of the frame-period of-sthe ,scanningsbeanr. Thisisequiizalent toastorage efiect...

Figure 8 showsa cathode ray tube, .inL which, however, the conventionaLelectrongun and the electrode .system. for. accelerating, focusing and deflectingtheelectrons have been omitted from the drawing.

In the previous .description the. grid 21Ihasiin all cases been maintained at the same voltage throughout. The invention can also be appliedin a form using a grid having alternate elements of different potentials. Figure 9 illustrates. grid wires 53 at anode potential which extend in parallel relationship with. respectto grid.'wires 54 which are electrically negative with respect tolthe wires 53. The grid is positioned between the eleca tron gun and the conducting layer 23 'as.'in Figures l to 4 inclusive. Grid wires 53 andf54 are insulated from one another. The respective D. C. voltages of the grid wires 53 and 54 do not change during, the operation. The conducting coating 23 is maintained at diflerent voltages as'in the form of Figures 1 to 4 to deflect the electron beam. Bafiles 34 "suitably provided with asemiconduct ing layer 35 on one or preferably both sides are carried on one side of each wire 53,"attached'-in any suitable way as by adhesive. The'bafiles' are desirably :disposed 'at an angle-to the normaksufficientrto provide for the proper'angle ofxiflec= tion of :the electronbeam; suitably'15 degrees; In this 'case, simplyas-an illustration that any suitableselection of colors may be made, one'set of phosphor strips-25 is provided-onthe conductive layer '23, although a second set as-in 'Figure 3 may-be used if desired. Aset of phosphor strips 38 is provided on: the. semiconductinglayer 35 on 13 the side of the baffle which may be bombarded by electrons deflected by the positive and negative wires of the grid system which form part of the deflection system.

In this construction only alternate grid slits or apertures are useful. When the coating on the face plate becomes more negative with respect to the anode potential, the beam is shifted toward the bafiie on the positive grid element.

The manner of changing the voltage applied to the conducting layer to coordinate with the broadcasting will vary with the particular installation, the simplest procedure being to use the well known system by which a synchronous motor operates the C. B. S. rotating color disc in step with the broadcast to bring the proper color filter into proper position at the correct time. I illustrate this diagrammatically in Figure where a synchronous motor 55 turns a shaft 56 in synchronism with the broadcasting, turning a contact block 5'! having respective contacts 58, E8 and 6! at different positions, which receive voltages proper for the three voltage settings of conducting layer 23 through slip rings '62, 63 and 64 connected to the respective contacts 58, 60 and El and insulated from the other contacts. A brush 55 rides the contacts 58, E9 and GI and successively applies the difierent voltages to the connection 24 of the conducting layer 23. Thus the picture impulse and scanning operations are performed three times, once for each color, in synchronism with the sending station, for each picture.

Phosphor composition The phosphor forms what is termed by Leverenz, Introduction to Luminescence of Solids (1950) p. 452 and 453, a line structure screen. The phosphor need not in all cases be a multiplier element consisting of separate layers, but may in some cases be a single layer converted into a semiconductor by proper treatment as later explained. Any suitable phosphor may be used either for the single layer or multiplier element phosphor. examples being given by Leverenz at pages 452 and 453. Thus the blue phosphor may desirably be the blue emitting hexagonal ZnSzAg, while the green emitting phosphor may be green emitting rhombohedral ZnzSiOuMn and the red may be red emitting (ldzBz-oszMn (the element following the colon is the activator as in the usual nomenclature). The preparation of the zinc sulphide and cadmium sulphide for phosphors is described by Leverenz in Appendix I. Any one of the phosphors may be made from zinc sulphide and cadmium sulphide by varying the proportions to give the different colors as explained in Leverenz and shown by the curves on page 196.

Where a single layer is to be employed as the phosphor element without making a multiplier element, the phosphor may be converted into a semiconductor in one of several ways:

1. First have an excess of the metal above the stoichiometric proportions in a metallic compound. Zinc oxide prepared by burning zinc in insufficient oxygen to obtain complete oxidation is an example of such a semiconductor phosphor.

2. Another method is to replace one of the atoms in the phosphor crystal by another atom which is isomorphous, comes within the Hume Rothery Volume relation (about excess atomic size), and has a valence one higher than the atom which it replaces. This free electron then becomes a conducting electron in the crystal. An example of this type of semiconductor is zinc silicate, ZnzSiO4:Mn to which a small percentage of impurity is introduced during the heat treatment. The procedure is to heat zinc silicate with a small percentage of manganese activator at a temperature of 900 to 1000 C. in an atmosphere of methane for about 15 minutes. This intro duces impurities into the lattice. The same procedure can be used with other phosphors. Zinc sulphide with a small percentage of silver activator is heated in an atmosphere of methane at 700 to 856 C. for about '60 minutes. ductor is formed.

The various other phosphors may be converted into semiconductors by using any suitable method A semicon- 'as above described, and in such case the phosphors are suitable for use as semiconductor phosphor layers in the present invention without employing multiplier elements. In most cases, however, it is preferable to obtain the semiconducting properties by using the phosphor as the dielectric of a multiplier element.

The method of applying the phosphor layer may be as pointed out in Leverenz, pages 381 and 382. Wet spraying and settling are suitable methods. The techniques of applying phosphor discussed in C. H. Bachman, Techniques in Experimental Electronics (Wiley 1948) pp. 198 to 207 may be used. Phosphor may be applied by evaporization using the technique employed in evaporating metals from tantalum boats. The evaporation may be carried out according to the technique of Bachman, pages 120 to 125.

Multiplier elements Many phosphors are likely to load up with electrons and cease to emit light because no beam electrons can strike them, since they repel the beam electrons. It is very desirable, therefore, that the phosphor should be part of a multiplier element which will discharge electrons into the tube and permit beam electrons to collide with the phosphor and produce continued luminescence. Accordingly it is very desirable to employ multiplier elements as the phosphor strips or areas, rather than to rely on semiconductor phosphor as a single layer.

The multiplier element consists of a conducting base, a thin layer of phosphor dielectric and a secondary electron emitting layer. It is in effect a sandwich with the phosphor dielectric between the base and the secondary electron emitter.

Where, as in Figure 5, the phosphor strips are applied on the conducting layer 23, this layer functions as the conducting base of these multiplier elements. In the case of the phosphor strip applied to the bafile, the semiconducting layer 35 on the bafiie makes the conducting base for the multiplier element on the bailie.

The base of the multiplier element is covered by an extremely thin layer 43 of phosphor dielec trio. Any one of the phosphors referred to above may be used as the dielectric. In this case they will be treated to make them semiconductors as part of the treatment of the multiplier element, and they need not be separately treated.

On the dielectric is deposited a thin layer 44 of a substance which is a good emitter of secondary electrons such as beryllium; beryllium oxide, IBeO; alloys of beryllium, particularly alloys of beryllium and copper; magnesium oxide; oxidized magnesium alloys; aluminum; alloys predominantly consisting of aluminum such as duralumin of any of the recognized varieties, especially aluminum alloys 173 (Al Cu 4%,

Mgi.0.5%,;-Mn:0.5%) or aluminum alloy 245 ,(A1 93.8%,. Cu -.i: Mg 1.51%, Mn 0.5% orcthe aluminumI-magneSium (1,0%';or-30%) alloy, or. the .aluminum beryllium alloys, of which the one containing 30 beryllium :appears the most eflicient. Among :the above the aluminum alloys are unexpectedly efl'ective out-f allproportions-to any characteristics previously, suspected and greatly exceedmure aluminum in multiplication.

Thedayer '44 -is sufiiciently discontinuous to be partially transparent so that light from the phosphor can be emitted through it and electronsfrom the gun can pass through it to excite thephosphor. When this top ,secondary-electron-emittinglayer 44 is struck by;primary electrons under suitable. potential conditions it emits a large number-ofsecondary:electrons; and thus becomes positively charged-and creates a strong. electrostatic fieldcbetween the conducting base and the dielectriclayer-43. Thiselectrostatic field pulls out electrons from the conducting .base throughxthe dielectric, thus producing-high multiplication of electrons.

The combined thickness of the dielectric layer andy-of the layer emitting secondary electrons mustbe very small, the desired range being hetween-.2 and 20 microns. While :not in every .casemssentiaL-this range "of thickness should-be use'clziorbest results.

One of the problems in the-prior art has been to causerthe secondary-electronv emission to start and stop either in coincidence-with the primary current or after only a brief and controllable time interval. Malter (Marconi) British Patent 481,170, issued September 7, '1936, uses caesium andis' troubled'by time lag between-.the-starting of-the primarycurrentand the starting. of the highsecondary-electrcn emission, as "well as between stopping ofrthe primary current and the stopping of the secondary electron emission. '(Malter, Physical Review, vol. 49, page 478and page' 879 (1936).) Furthermore, caesium deteriorates by volatilization in vacuo and causes objectionable photoelectric effects which prohibit the use of the layer as an emitting surface in-a photomultiplier tube. In the present invention the electron emitting layer is non-photoelectric, and many advantages and avoidance of-much difficulty are thereby obtained.

In order to prevent excessive time lag, the positive charge in the secondary-electron-emit ting layer must be neutralized by electrons from the dielectric layer very quickly, but not quickly enough'to interfere with extraction-of secondary electrons by the electrostatic field; The extraction time hasbeen estimated as about '10-' seconds.

The phosphor dielectric layer may-be deposited by spraying, settling, evaporation or similar methods as already discussed in connection with the depositing of the phosphor layer when it is the'only layer on top of the conducting layer. The secondary-electron-emitting layer can be deposited .on' the dielectric by dusting, evaporatiornsettling or the like.

I have discovered that in order to produce the high field necessary for electron extraction from the metallic base under the conditions of cold emission (about a million volts per centimeter), the thickness of the dielectric layer is ofimportance. A- voltage due to secondary electron emission of more than a few thousand volts is not obtained in practice. The-thickness should preferably not exceed 0.03 millimeter, and in any case the thickness of the layer should notexceed 1.6 0.1 millimeter. No. limiton-thinness is necessary provided the dielectric functions.

The invention-is operative in its broader phases provided the metallic base, phosphor dielectric layer and secondary-electron-emitting layer are as described, without further precautions to avoid time lag, but for best results, special precautions should be taken-to assure that the phosphor is' a semiconductor and thus avoid time lag. There are several-ways of overcoming this trouble which have been discovered by me.

One method of overcoming time lag isto deposit the dielectric layer deliberately with considerable porosity. This can be-done if the-dielectric is applied by the established technique of settling from a liquid, controlling the fineness of grinding of the particles. Particles with a diameter of the order of ten microns have been found-to be satisfactory in obtaining porosity. If difliculty is encounteredwith colloidal. properties an electrolyte may be added to cause .dispersion and hence-aid settling.

A suspensionis made of a semiconductor phosphor in a suitable liquid, for example water. The electrolyte frequently added is lithium .hydroxide or barium acetate in the proportion of a fraction of a-percent. Thesuspension of phosphor settles. slowly upon the surface which is to be coated, after which the supernatant liquid is drained oil bytilting orsyphoning and the coating is allowed to dry.

The-same effect may be obtained'by spraying the phosphor on the surface in a suitable medium, for example cellulose nitrate lacquer. The porous phosphor layer is then coated with secondary electron emitter, using any desired technique, after which the multiplier element suitably. in the tube is heat treated in a vacuum at a temperature from 500 C. up to the softening point of the glass and other components, for a time of at least an hour at the lower temperature, diminishing with increase in temperature. This heat treatment enables molecules of the secondary electron emitting layer to penetrate the phosphor dielectric, thus assisting in preventing time lag by conducting electrons to the surface and neutralizing the charge.

As explained above, the field intensity which produces cold emission will fall too low if any individual dielectric layer is allowed to become thicker thanabout 0.1 mm., preferably 0.03 mm. If for any other reason the dielectric layer must be thicker, this can be accomplished by several alternate layers of a phosphor dielectric and secondary electron emitter, each dielectric layer of optimum thickness and not exceeding 0.1 mm.

Where the secondary electron emitter is beryllium it has been successfully applied to the tube element by evaporation in vacuo by electrically heated tantalum spires which serve as supports and heaters. It does not matter whether the beryllium is oxidized or not, since the metal and oxide are equally good as secondary electron emitters.

Where magnesium .is used as a secondary electron emitter the oxidation is essential, as the unoxidized magnesium is not a good emitter. The metal will, however, oxidize readily in air. The effectiveness of .magnesium (oxidized) as a secondary electron emitter is greatly improved by the step of baking in vacuo at a temperature of 600 to 800 C.

The secondary-electron-emitting layer should be free from poisoning ingredients such as metallic nickel or less importantly cobalt.

It will be evident that by the invention it is possible to scan slightly'difierent line elements at intervals separated by a few micro seconds and energize phosphors of different colors. The elimination of the difiiculty due to time lag thus makes it practical to obtain color television re ception in a manner similar to the C. B. S. or C. T." I. systems without the difficulties incident to a mechanical color filter.

It will further be evident that by the invention improved brightness in the color television images is produced to make it more nearly comparable to the brightness of black-and-white reception.

When reference is made herewith to a D. C. voltage which is maintained on the conducting layer for the purpose of deflection of the electron beam, it will be understood that the voltage need be efiectively constant only for a time of the order of a microsecond before it changes to another momentarily constant value.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the process and apparatus shown, and I, therefore. claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a color television cathode ray tube having an electron gun directing an electron beam upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the tube on the plate, a conducting grid extending across the tube between the electron gun and the conducting layer adjacent the conducting layer and having slits parallel to one another which pass the electron beam toward the conducting layer, insulating baflies extending along one side of individual slits from the grid and in at least some places touching the conducting layer, a semi-conducting layer on one side of each bafiie, semi-conducting phosphors of a plurality of diiferent colors arranged in strips parallel to the slits selectively in the path of the electron beam on the conducting layer with the phosphors of a particular color in the same geometrical relationship to each slit, semi-conducting phosphor of a different color arranged in strips along the semi-conducting layer on each bathe in the same geometrical relationship to each slit, the phosphors of the different colors being selectively in the path of the electron beam through the slits, and means for deflecting the electron beam into difierent angular relationships to energize phosphors of different colors.

2. In a color television cathode ray tube having an electron gun directing an electron beam upon a face plate, a transparent conducting layer on the inside of the face plate, a conducting grid extending across the tube between the electron gun and the conducting layer, adjacent the conducting layer, and having openings which pass the electron beam toward the conducting layer, a plurality of semiconducting phosphor areas engaging the conducting layer on the opposite side from the side of the conducting layer engaging the face plate, with phosphor of a plurality of diiferent colors arranged in different areas in the path of the electron beam between the grid and the conducting layer beyond the respective openings, with phosphor of a particular color selectively in the path of the electron beam only at the same deflection of the electron beam, means for maintaining the grid at a particular setting of D. C. voltage and means for maintaining the conducting layer at diiferent D. C. voltages at least all but one of which are difierent from the voltage of the grid.

3. In a color television cathode ray tube having an electron gun directing an electron beam upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the tube on the plate, a conducting grid extending across the tube between the electron gun and the conducting layer, adjacent the conducting layer, and having openings which pass the electron beam toward the conducting layer, baffles at one side of the grid openings extending toward the conducting layer and. limiting deflection of the electron beam passing through the openings, semi-conducting phosphors of a plurality of different colors arranged in different areas in the path of the electron beam beyond the respective grid openings between the grid and the conducting layer in electrical contact with the conducting layer, with the phosphor of a particular color selectively in the path of the beam only at the same deflection, means for maintaining the grid at a particular setting of D. C. voltage and means for maintaining the conducting layer selectively at different D. C. voltages at least all but one of which are different from the voltage of the grid.

4. In a color television cathode ray tube having an electron gun directing an electron beam upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the tube on the plate, a conducting grid extending across the tube between the electron gun and the conducting layer adjacent the conducting layer and having openings which pass the electron beam toward the conducting layer, electrically insulating bafiles extending from the grid at the side of individual openings toward the conducting layer, a semiconducting layer on one side of each baflle, semiconducting phosphors of a plurality of difierent colors arranged in different areas selectively in the path of the electron beam between the grid and the conducting layer beyond the respective openings distributed on and in electrical contact with the conducting layer with a phosphor of a. particular color in the path of the beam only at the same deflection, semiconducting phosphor of a difierent color on the semiconducting layer on each baffle, means for maintaining the grid at a particular setting of D. C. voltage and means for maintaining the conducting layer selectively at different D. C. voltages, at least all but one of which are different from the voltage of the grid.

5. In a color television cathode ray tube having an electron gun directing an electron beam upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the tube on the plate, a conducting grid extending across the tube between the electron gun and the conducting layer adjacent the conducting layer and having openings which pass the electron beam toward the conducting layer, semiconductor phosphor of a plurality of different colors arranged in different areas in the path of the electron beam between the grid and the conducting layer beyond the respective openings in electrical contact with the conducting layer, with the phosphor of a particular color selectively in the path of the beam only at the same 19 deflection, means for hi'aintaining the-grid at a particular setting of D. C. voltage and'means f o r maintainingl'the conducting layerl'selective ly at difierent voltages atiesstan but one of which are negative with respect to the grid voltage and different from the'grid voltage.

6. In a skew-neck color television cathode ray tube having an electron directed diagona ly upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the tube on the 'plate, a conducting grid extending across the tube' between the electron gun and the conducting layer adjacent the conducting layer and having openings which pass the electron beam toward the conducting layer, semiconducting phospho'r'of a plurality of different colors arranged in different areas in the path of the diagonal electron beam between the grid and the conducting layer beyond the respective openings in electrical contact with the conducting layer, with the'phosphor of a particular color in the path of the diagonal beam only at the same deflection, means for maintaining the grid at a particular setting of D. C. voltage and means for maintaining the conducting layer selectively at different 'D. C. voltages at least all'but one of which are difierent from the voltage of the grid.

7. In a color television'cathode ray tube having an electron gun directing an electron beam diagonally upon'a plate adjacent to and across the face of the tubefa transparent conducting layer across the inside of the tube on the plate, a conducting grid extending across the tube'between the electron gun and the conducting layer adjacent the conducting layer and having parallel slits which pass'the electron beam toward the plate, bafiles extending diagonally from one side of individual slits toward the conducting layer in the direction of the diagonal beam, a semiconducting layer on each bafiie on the side on which the electron beam may impinge on the battle, semiconducting phosphor multipher elements each having a dielectric phosphor layer and a secondary-electron-emitting layer, the thickness of the phosphor layer plus the secondary-electron-emitting layer being between 2 and 20 microns, the phosphor layer being of a plurality of different colors, the multiplier elements having phosphor layers of one of the colors being mounted on the semiconducting layers on the bafiles and the multiplier elements having phosphor layers of a plurality of different colors being mounted on the conducting layer, the respective multiplier elements being selectively in the path of the electron beam between the grid and the conducting layer beyond the respective slits with the phosphor of a particular color extending as a strip in the path of the beam only at the same deflect-ion of the electron beam, means for maintaining the grid at a particular setting of D. C. voltage and means for deflecting the diagonal electron beam with respect to the major plane of the grid to energize difierent phosphor colors.

8. In a color television cathode ray tube having an electron gun directing a diagonal electron beam upon a plate adjacent to and across the face of the tube, a. transparent conducting layer across the inside of the tube 'on the plate, a conducting grid extending across the tube between the electron gun and the conducting layer adjacent the conducting layer and having parallel slits which pass the electron beam toward the plate, supports between the grid and the conducting layer electrically connected to the conducting layer, semiconductor phosphor of a plurality of different colors in strips on the conducting layer and in strips on the supports, the phosphor strips on the conducting layer being spaced and the phosphor strips on the support being disposed behind the space between the phosphor strips on the conducting layer, the respective phosphor strips'being selectively in the path of the electron beam between the grid and the conducting layer beyond the respective shts with the phosphor of a particular color extending as a strip in the path of the beam only at the same deflection of the electron beam, means for maintaining the grid at a particular setting of D. C. voltage and means for deflecting the diagonal electron beam with respect to the major plane of the grid to energize different phosphor colors.

9. The process of producing color images inside the face plate of a color television cathode ray tube, which comprises introducing a transparent conducting layer across the inside of the tube adjacent the face plate, distributing phosphor areas over the tube adjacent and in electrical contact with the conducting layer in a geometrical pattern having a plurahty of phosphor colors at each locality, projecting an electron beam in the tube toward the phosphor, screening the beam away from'the phosphor at spaces between individual localities and passing the beam through to the phosphor at spaces corresponding to individual localities, scanning the phosphor of a particular color with the electron beam, while maintaining a particular voltage relationship between the position of shielding and the conducting layer so that the conducting layer is more negative in potential and shifting the voltage relationship between the position of shielding and the conducting layer and thereby shifting the scanning beam to encounter another color of phosphor.

10. The process of producing color image inside the face plate of a color television cathode ray tube, which comprises introducing a transparent conducting layer across the inside of the tube adjacent the face plate, distributing phosphor areas over the tube adjacent and in electrical contact with the conducting layer in a geometrical pattern having a plurality of phosphor colors at each locality, projecting an electron beam in the tube toward the phosphor, shielding the beam away from the phosphor at spaces between individual localities by applying a voltage difference between the localities and the conducting layer and passing the beam through to the phosphor at spaces corresponding to individual localities, scanning the phosphor of a particular color with the electron beam, while maintaining a particular voltage relationship between the localities of shielding and the conducting layer and rendering the conducting layer more negative in potential with respect to the locality of shielding and thereby deflecting the electron beam to encounter a difierent color of phosphor.

11. The process of producing color images inside the face plate of a color television cathode ray tube, which comprises introducing a transparent conducting layer across the inside of the tube adjacent the face plate, distributing phosphor areas over the tube adjacent and in electrical contact with the conducting layer in a geometrical pattern having a plurahty of phosphor color at each locality, projecting an elec-- tron beam diagonally in the tube on to the phosphor of a particular color, scanning the phosphor of that color with the electron beam by 21 applying a potential to the transparentconducting layer and deflecting the electron beam and scanning the phosphor of a different color.

12. The process of producing color images inside the face plate of a color television cathode ray tube, which comprises introducing a transparent conducting layer across the inside of the tube adjacent the face plate, distributing phosphor strips over the tube in parallel relationship adjacent to the conducting layer with a plurality of phosphor colors at each of a plurality of positions, laterally separating the positions from one another to minimize cross reflection of the electron beam, scanning the successive positions with an electron beam impinging on the phosphor of a particular color, and deflecting the scanning beam by applying a potential to the transparent coating which retards the electron beam so that it will encounter phosphor of a different color.

13. In a color television cathode ray tube having an electron gun directing an electron beam upon a plate adjacent to and across the face of thetube, a transparent conducting layer across the inside of the tube on the plate, a conducting grid extending across the tube between the electron gun and the conducting layer, adjacent the conducting layer and having slits parallel to one another which pass the electron beam toward the conducting layer, conducting baflies extending along one side of individual slits from the grid and in at least some places supported on the conducting layer, phosphors of a plurality of different colors arranged in strips parallel to the slits selectively in the path of the electron beam on the conducting layer with the phosphors of a particular color in the same geometrical relationship to each slit, phosphors of a diiferent color arranged in strips on each baflle in the same geometrical relationship to each slit, the phosphors of the difierent colors being selectively in the path of the electron beam through the slits and means for deflecting the electron beam into different angular relationships to energize phosphors of difierent colors.

14. In a color television cathode ray tube having an electron gun directing an electron beam upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the tube on the plate, a conducting grid extending across the tube between the electron gun and the conducting layer, adjacent the conducting layer, and having openings which pass the electron beam toward the conducting layer, baffles on one side of the grid openings extending toward the conducting layer and limitin deflection of the electron beam passing through the openings, phosphors of a plurality of difierent colors arranged in different areas in the path of the electron beam beyond the respective grid openings between the grid and the conducting layer in electrical contact with the conducting layer, with the phosphor of a particular color selectively in the path of the beam only at the same deflection, means for maintainin the grid at a particular setting of D. C. voltage and means for maintaining the conducting layer selectively at different D. C. voltages at least all but one of which are different from the voltage of the grid.

15. In a color television cathode ray tube having an electron gun directing an electron beam upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the tube on the plate, a conductin grid extending across the tube between the electron gun and the conducting layer, adjacent the conducting layer, and having openings which pass the electron beam toward the conducting layer, baflies'on one side of the grid openings extending toward the conducting layer and limiting deflection of the electron beam passing through the openings, phosphors of a plurality of difierent colors arranged in different areas in the path of the electron beambeyond the respective grid openings between the grid and the conducting layer in electrical contact with the conducting layer, with the phosphor of a particular color selectively in the path of the beam only at the same deflection, means for maintaining the grid at a particular setting of D. C. voltage and means for maintaining the conducting layer selectively at different D. C. voltages at least all but one of which are diiferent from the voltage of the grid and negative with respect to the voltage of the grid.

16. In a color television cathode ray tube having an electron gun directing an electron beam upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the-tube on the plate, a conductin grid extending across the tube between the electron gun and conducting layer, adjacent the conducting layer, and having openings which pass the electron beam toward the conducting layer, conducting baflles extending from the grid at the side of individual openings toward the conducting layer, phosphors of a plurality of different colors arranged in different areas selectively in the path of the electron beam between the grid and the conducting layer beyond the respective openings distributed on and in electrical contact with the conducting layer with a phosphor of a particular color in the path of the beam only at the same deflection, phosphor of a difierent color on each baflle, means for maintaining the grid at a particular setting of D. C. voltage and means for maintaining the conducting layer selectively at diiferent D. C. voltages at least all but one of which are different from the voltage of the grid.

17. In a color television cathode ray tube having an electron gun directing a diagonal electron beam upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the tube on the plate, a conducting grid extending across the tube between the electron gun and the conducting layer, adjacent the conducting layer, and having parallel slits which pass the electron beam toward the plate, supports between the grid and the conducting layer, phosphors of a plurality of diiferent colors in strips on the conducting layer and in strips on the supports, the respective phosphor strips behind each slit being in similar geometrical arrangement, the respective phosphor strips being respectively in the path of the electron beam between the grid and the conducting layer beyond the respective slits with a phosphor of a particular color extending as a strip in the path of the beam only in the same deflection of the electron beam, means for maintaining the grid at a particular setting of D. C. voltage and means for deflecting the diagonal electron beam with respect to the major plane of the grid to energize different phosphor colors.

18. A cathode ray tube including an electron gun directing an electron beam upon a face plate with a partially transparent conducting layer on the inside of the face plate, coated with strips of luminescent phosphors on the conducting layer, and a conducting grid in close proximity to the face plate and having two sets of alternating insulated grid elements placed between the electron gun and the face plate, means for maintaining the respective sets of grid elements at somewhat different D. C. potentials, and means for maintaining the conducting layer at a plurality of DC. potentials at least all but one of which aredifierentfrom the respective potentials of the sets of grid elements.

19. A cathode ray tube including a face plate with a partially transparent conducting layer on the inside of the face plate, coated with strips of luminescent phosphor on the conducting layer, and a conducting grid in close proximity to the face plate and having two sets of alternating insulated grid elements placed between the electron gun and the face plate, means for maintaining the respective sets of grid elements at somewhat difierent D. C. potentials, and means for maintaining the conducting layer at a plurality of D. C. potentials at least all but one of which are different from the respective potentials of the sets of grid elements, and negative with respect to the potentials of the sets of grid elements.

20. In a color television cathode ray tube having an electron gun directing an electron beam diagonally upon a plate adjacent to and across the face of the tube, a transparent conducting layer across the inside of the tube on the plate, a conducting grid extending across the tube between the electron gun and the conducting layer, adjacent the conducting layer, and having openings which pass the electron beam toward the conducting layer, baflies on the conducting grid at one side of the .grid openings, phosphor strips of a plurality of diiferent colors in selective paths of the electron beam beyond each slit and at least one strip being on each bafile, means for maintaining the grid at a particular setting of D. C. voltage and means for maintaining the conducting layer selectively at different D. C. voltages at least all but one of which are difierent from the voltage of the grid and negative with respect to the grid.

JENNY BRAMLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,197,625 Teves et al -Apr. 16, 1940 2,312,792 Bamford Mar. 2, 1943 2,343,825 Wilson Mar. 7, 1944 2,446,440 Swedlund Aug. 3, 1948 2,455,710 Szegho Dec. 7, 1948 2,461,515 Bronwell Feb. 15, 1949 2,518,200 Sziklai et a1 Aug. 8, 1950 2,529,485 Chew Nov. 14,1950 2,530,431 Huffman Nov. 21,1950 2,532,511 Okolicsanyi Dec. 5, 1950 2,543,477 Sziklai et al Feb. 27,1951 2,544,690 Koch et al Mar. 13, 1951 FOREIGN" PATENTS Number Country Date 866,065 France 1941

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