US2842697A - Beam-intercepting structure for cathode ray tube - Google Patents

Description

F. J. BINGLEY 2,842,697

BEAM-INTERCEPTING STRUCTURE FOR CATHODE RAY TUBE July 8, 1958 Fild Dec. 7, 1955 0 2 it n 6 a! 7 Z 2 2 Z a M W m M W M7 0 INVENTOR. AMA Km AVA 02f) BEAM INTERCEPTlNGSTRUCTURE FOR I CATHODE RAY TUBE Frank J. Bingiey, l t leadowbrook,'lai, assignorto Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application December 7, 1955, Serial N0.'551,'648 28 Claims. (at. 313-92) modulated by signals representative of the colors of the U i d States Patents TO scanned elements of a televised scene, is caused to scan said structure in a manner such that, at a time when it is modulated in intensity by a signal representative of, say the redcolored elements of the scene, it will impinge only on 'a phosphor'strip 'emissive of red. An indexing system for coordinating the intensity modulation of the beam with its position on the beam-intercepting screen may be 'employed so that the colors of the reproduced image are faithful to those of the original televised scene.

If the phosphor strips'are disposed contiguous to one another,-the area of impingement' ofthe beam, having a finite width, may overlap 'two adjacent strips. Consequently the redemissive phosphor strip, for example,

' m'ay be impinged upon by the beam not only during the intervals when the beam is modulated in intensity by signals corresponding to the red color of the scanned element of the televised scene, but also during intervals when it is modulated by blue or green representative signals.

7 Furthermore, even if the width of the area of impinge mentof the'beam is very small, the faithful rendition of colors is extremely diflicult to achieve since there are generally non-linearities in the performance of the beam deflection circuits and components, irregularities in the .geometrical disposition of the elements of the beamintercepting structure, and other practical problems which make exact coordination of beam position and beam modulation very diflicult to achieve. An indexing system is extremely helpful in coordinating the modulation of the beamintensity with the position thereof, but even it may be subject to aberrations and inherent limitations which prevent it from being completely effective. -As a result of the fact that, in practice, coordination of the 'bearn modulation and position is not always perfectly achieved, the purity of the colors reproduced is adversely affected.

To a certain extent deficiencies in the rendition of colors due to the various factors mentioned above maybe overcome by making the individual phosphor strips narrower and spacing them from one another instead of disposing them contiguous to one another so that the scanning beam is less likely to overlap any two adjacent ones of the phosphor strips. The space between any two adjacent phosphor strips also helps to prevent the production of light of any color in the intervals in which Patented Jut s, less the beam intensity is undergoing a transition from modulations by signals corresponding to the intensity, of one color of a televised scene to modulation by signals corresponding to the intensity of a different .color. 'In making the strips narrower and spacing them from one another it becomes possible to increase thev brightness of the reproduced image since the'scanning beam spot size may be made larger, provided, of course, that it is not wider than the total width ofa phosphor strip and the spaces adjacent it on either side.' The use of. larger beam spots also tends to simplify display tube construction and reduce the costs thereof.

An electron-permeable, light-reflecting, and electrically conductive materialis often deposited on the rear (facing the electron-gun) surface of the phosphor strips in order to increase further the brightness of a screen so constructed. This layer increases the brightness of the reproduced image by reflecting back toward the viewer light initially emitted from the fluorescent beam fspot toward the rear of the tube. It also assistsin preventing damage caused by the impact on the phosphor screen of ions which have a much greatermass. than the electrons. It is also of use in establishing a desired potential on the rear surface of the phosphor strips. J

While the addition of the light-reflecting layer increases brightness, it also introduces some unwantedeffects. In addition to reflecting toward the viewer light from the spot emitted in a backward direction, it unfortunately also reflects backto the observer ambientlight striking it. For example, if there is a source of illumination in the viewing area, some of its rays will fall on the portions of the light reflecting layer situated in the spacesbetween the phosphor strips and a mirror image of-the source can be seen by the viewer. If daylight enters the viewing area the colored image will be 'somewhat obscured by. the

glare from the reflective coating and the colors of the image on the display tube will bedesaturated to a certain extent. i. v

Another disadvantageof spaced phosphor strips backed by a layer of. light=refiecting material is that the adverse elfects of halation' are multiplied. Halation occurs because, as the phosphor stripsernissive of. the

various colors arecaused to emit light by the electron beam impinging thereupon, the light from the red phosphor strip, for example, will be reflected bythe "front internal surface of the glass faceplate. of the tube back toward phosphor strips emissive of green and blue light, thereby causing the latter colors to be desaturated.

Halation may also cause fuzziness in the reproduction of sharp transitions from one color to another in the reproduced image.

It is therefore an object of the-present invention to provide systems for improving the quality of luminous images produced by certain types ofcathode ray tubes.

Another object of the invention is to provide a screen structure'for improving the color fidelity of images reproduced by certain types of color television display tubes In the manufacture of the beam-intercepting structures of display tubes such as those previously described, the :sets 'of phosphor strips are frequent' ly 'depositedupon the inner surface of the faceplate of the cathode ray tube by photographic means. Formerly, in order to maintain color'purity,'it was imperative to lay down the phosphor strips on the inner surface of the faceplate so that the width :of each strip was essentially uniformthroughout its entire length. The attainment of this objective is difiicult because the particles of the respective phosphor "materials used for the strips. have different average. 7 I

sizes. "The strips of phosphor materialswhose'pa'rti'cles are relatively large generally have edges whose contour 'is' characterized by large variations, whereas the strips cient phosphors such as the red phosphor.

composed of relatively small phosphor particles tend to have edges whose contour is characterized by relatively small variations. In the present state of the art phosphors emissive of the colors desired cannot be obtained which all have uniformly dimensioned particles of the desired fineness.

Accordingly it is another object of the invention to provide a system for manufacturing beam-intercepting structures of cathode ray tubes of the type described in which the edges of all the phosphor strips are made so that their contour is subject to only very small variations.

It is a further object of the invention to provide a method for manufacturing fluorescent screens in cathode ray tubes of the type desired in which the visible or effective width of the fluorescent strips is maintained uniform despite variations in the particle sizes of the particular fluorescent materials used therein.

Previously also, in the manufacture of screens having spaced phosphor strips some of the phosphor materials inadvertently became lodged in the spaces between adjacent ones of the phosphor strips. Consequently, when 'the beam traversed these spaces, light of one or more colors was emitted with a resulting loss of color fidelity in the image. It also happened in the manufacture of such screens that, because of inaccuracies in the successive steps of laying down the different sets of phosphor strips, the strips were not displaced laterally from one another according to the specifications. This adversely afiected the desired coordination between the beam position and the modulation thereof, with a concomitant loss of color purity. In cases of extreme misplacement of the strips, some particles of the phosphor material of one strip overlapped those of another set so that, toward the edges of the strips, a mixture of colors was produced, with a resulting loss of color purity.

Another object of the invention is to overcome the adverse effects of misplaced phosphor particles on the color quality of the reproduced image.

Still another object of the invention is to simplify the fabrication of such screens by reducing the precision required in depositing the strips in successive steps.

In cathode ray tubes of the type described it is customary to decrease the efficiencies of the naturally more eificient phosphor materials emissive of green and blue light, for example, so as to equalize the light output therefrom with respect to the light output from the less efficedure naturally results in a reduced efiiciency of light output with respect to electrical input to the display tube for a given area of phosphor material.

It is, accordingly, another object of the invention to preserve the advantages of using phosphors which are naturally more eflicient while compensating for the phosphors which are less eflicient in order to achieve greater image brightness and proper color balance.

These objects, as well as others which will appear, are achieved according to my invention by an improved beam-intercepting structure for cathode ray tubes of the type described, in which a plurality of substantially opaque and non-reflecting guard elements are deposited in a predetermined pattern on an appropriate transparent substrate and a plurality of electron-sensitive elements are deposited in a predetermined pattern in the spaces between the opaque and non-reflecting elements. In accordance with one form of the invention as used in color television display apparatus, a plurality of opaque, nonrefiecting and elongated elements are deposited on a transparent substrate in a definite pattern and a plurality of elongated phosphor elements which emit light of selected colors in response to electrons impingent thereupon are deposited in the spaces between, and in contact with, the adjacent opaque elements. Preferably, the phosphor elements are so deposited that they overlap on the rear surfaces of the opaque elements. This helps to insure th t the spaces between the guard elements are completely This profilled by the phosphor elements, yet permits the latter to be deposited with less precision than has heretofore been customary. If an electron-permeable and light-reflecting layer is deposited on the rear surfaces of the phosphor strips and the opaque elements, ambient light falling on the face of the tube will not be reflected back into the observers line of vision from those portions of the reflective layer situated between the phosphor strips. Halation is also reduced because a considerable portion of the light reflected back onto the screen from the front internal surface of the faceplate is absorbed by the opaque and non-reflective elements.

In another form of the invention, the. disparities in the etficiencies of the phosphor materials of the several sets of phosphor strips are equalized by making the widths of the strips of each set vary inversely with the relative efficiency of the phosphor material of which it is composed. Thus, the width of a relatively inefficient phosphor strip, such as the red emissive strip for example, is made large with respect to the width of a relatively efiicient phosphor strip such as the green emissive strip. In'order to permit the beam intensity to be modulated at a single frequency, the center-to-center distance between any two adjacent phosphor strips, regardless of their width, may be made equal. In some cases, however, it may be desirable to vary the center-to-center distance between adjacent phosphor strips because of other considerations which are not pertinent to the present invention.

In accordance with still another form of the invention an effective method is provided for expediting the production of improved screen structures with a concomitant relaxation of some of the manufacturing tolerances required therein. This system involves the process of first depositing the opaque and non-reflective elements on one surface of an appropriate transparent substrate, and next depositing each of the sets of phosphor strips in turn in the spaces between the opaque strips. Even if each deposited phosphor strip overlaps somewhat on the rear surfaces of the adjacent opaque strips because it is wider than the space therefor, there is no loss of uniformity of the visible width of the phosphor strips or loss of color purity since the opaque strips block light from those portions of the phosphor strips which do overlap and prevent it from reaching the viewer. Thus the phosphor strip deposition process can be performed with less precision than heretofore has been required.

It has previously been stated with respect to previous types of screen structures that the particle sizes of the various phosphors employed are relatively large and thus the edges of the phosphor strips have contours which are subject to rather large variations. In one particularly advantageous form of our invention the particle size of the material of which the opaque guard strips are constituted is very line in comparison with the particle size of the phosphors. If the guard strips are laid down first, and the phosphor strips next, it is the edges of the guard strips which define the visible edges of the phosphor strips contiguous therewith. Since the material of the guard strips is very fine, their edges have contours which are marked by relatively small variations so that the width of each one can be made very uniform. Thus the visible edges of the phosphor strips defined thereby have contours marked by relatively small variations, and the visible or efiective width of each of the phosphor strips is rendered more uniform so that light emitted therefrom is confined with greater precision than has hitherto been possible.

Figure l is a sectional perspective view of one form of beam-intercepting structure in accordance with my invention;

Figure 2 is a sectional plan view of the structure shown in Figure l; and

assess? Figure 3' is a sectional plan View of another form of screen structure in accordance withthe invention.

Referring to Figure l, a beam-intercepting structure for a cathode ray tube used to reproduce images of televised scenes in color is' shown.- It consists of a transparent substrate 20 which may be the faceplate of the cathode ray tube, for example, or an essentially planar transparent membe'r mounted in proximity thereto. De-

sed of ferrous oxide which has heenflewed ontd the facelate; in the term or a slurry aswiii be ex lained belov'vg-or-rnay be of graphite. These materials are recited solely as" eiramples which have proved effective in making a screen; structure according to the invention. It is referablethat the material be substantially non-reflective but irisoine cases the material may reflect light of low visibility, as for example, the characteristio'da'rk' red of ferrous oxide'whioh may have other desirable properties in addition to good opacity and substantial non-reflectivity.

Onv the rear surface of the strips 21, 22 and 23 and the strips 27 a conventional electron-1'5errheable andlightreflecting layer 26 is deposited. This layer 26, which may be of aluminum for example, increases the bright- ,ness of the' rfepr6duced ifriage by; reflecting-toward the "observer those rays of light' e itted in the direction of the electron un from the po t'where the electron beam impinges on the phosiphor' strips.

On the r'ear surface of the layer 26 and coincident with I the strips 21, for exampieg'antimber of iiidexin strips 28 maybe deposited which may be composedof a material such as MgO, for example, which hash secondary emission ratio different from that of the layer26, or may be composed of a light emissivephosphor. Indexing signals in the form of a secondary electrori current or light variation's, as the ease may be, are generated in re'sponseto: the scanning of the-electron beam thereupon.

7 These signalsmay beus'e'cl in" an iride'xingsystem (not shown)- for coordinating the beans position with the intensity modulation thereof. I r if The'istrips 21; 22 arid-L23 are e arated by strips 27 of an opaque and non-reflective 'materialfor a number of reasons' The strips 27 assist in preventing, the simultaneous: impingement of the electron beam upon two wadjacent phosphor strips. The strips 27, beiiig opaque and V non reflective, also prevent'arhb'ient light from the view.- ing'; area from being reflected b'ack to the viewer by the reflective layer 26. This is more readily apparent from inspection of Figure 2 wherein the beam-intercepting 1 structure 19 is shown in a plan and sectional view. Parts in Figure 2 similar to those of Figure 1 are similarly numbered. A ray of ambient light 36 is seen passing through the'substrate' 2'0 and striking one of. the opaque strips 27. Were t'he strip 27 on whichfit falls absent, the.

ray 36 wouldbe reflected back to the viewer by a portioh of therefle'cting'layer' 26. Since the rays of ambient light are largely absorbed by" th'e strips 27 on which they 'fall, the saturation of the colors of the image as viewed by an observer is' im-pr'ove'd since they" are not diluted by reflected ambient light. 1

Fig. 2 also depicts 'how the opaque strips 27 serve to reduce the amount of hal-ation caused by the impingefment of ambient light on' the novel screen. Another ray 30' of'ambi'en't light is'reflected from a point 31 adjacent one of" th'e blue color emissive strips 26in response to the ray '30 incident thereuponxontothe front internal i surface 3.5: of; the faceplate 20' whence part ss' of-it is" T able .ayerZ causing that por'tion of theblue emissive strip 22 through which it passes to emit light of thatv once again reflected back onto one of the stiips' 27 where it is absorbed. Were it not for the presence of the latter strip 27, it would be reflected once again toward the observer by the reflective coating 26.

color. Most of the blue light rays 42 and 43 pass through the substrate and out to the viewer, but-part of the ray 42 is reflected back onto, and absorbed by, oneof the opaque strips 27. The ray 44 from the spot is refiected by the front internal surface back onto the green emissive phosphor 21 at point 48 where at least part of it is again reflected as indicated by the rays emanating from that point. A ray from the luminous spot at point 41 is also reflected in part from internal surface 35 back onto one of the opaque strips 27 where it is absorbed. It is seen that, absent the strips 27 between the phosphor strips, the color purity of the image produced would be subject to considerable deterioration because of the desaturating effect of the halation efiects arising from the reflection of the blue light of the spot, onto the adjacent green and red emissive phosphor strips, for example.

Figure 3 illustrates another form of the invention in which the opaque strips 27 intermediate the phosphor strips are of varying width thus masking ofI' part of the phosphor strips from the view of the observer and cansing the visible width of the several phosphor strips to differ. These diiierences are introduced for the express purpose of compensating for the diflerences in the efiiciencies of the various phosphors employed. The best phosphor materials presently known, which emit red in response to the impingement of electrons thereupon, have a much lower efliciency than the available blue and green light-emissive phosphors. It has been common practice heretofore to adulterate or dilute, deliberately the green and blue phosphors so that their elfective ef ficiencies are lowered to correspond to the efliciencyrof the red emissive phosphors; This obviously reduces the total light output of the image and therebyadversely aifect's the visibility thereof in the pr'esence of ambient light. p

By employing the form of my inventionshown in Fig. 3, the maximum natural efliciency ratios of the available phosphor materials emissive of red, blue and green light may be exploited without affecting the balance of colors as viewed by an observer. In this form of theinvention the opaque strips may be uniformly wide and the P1108? phor strips may be of different widths, or both the opaque strips and the phosphor strips may-be of difiierent Widths. In the particular embodiment shown in Fig. 3 the opaque strips 27' and the phosphor strips 21', 22', and 23 both have different widths. The widths of the opaque strips optionally may be selected so as to achieve asubstantially uniform center-to-center spacing at between any two adjacent phosphor strips so that the beam intensity may be modulated at a single frequency. Thus', for example, the distance x may be made equal to the corresponding distance y of Fig. 2. If the center-to-center distance between the phosphor strips is made to vary the beam intensity would be modulated by a signal wave having a complex frequency. In certain other applications the width of the respective phosphor strips may be adjusted arbitrarily to over-emphasize one or more. of the colors of the reproduced image or display. 7 a

To improve the reproduction of the colored image for the reasons stated previously it is only necessary that e the opaque elements 27- be located between adjacent ones of the color emissive phosphor strips. senin Fig. 3,.

however, the phosphor strips are located not just between the opaque elements 27' but may also overlap them to some extent on their rear surfaces. While the deposition of the phosphor strips in the manner shown in Fig. 3 may appear somewhat wasteful of phosphor material, this possible disadvantage is greatly outweighed by the resultant simplification in the process of manufacturing such structures and the considerable improvement in screen structures provided thereby, which makes possible the reproduction of superior colored images. These advantages will become clearer from the following explanation of some of the factors involved in the manufacture of such tubes.

Previously each set of phosphor strips was deposited upon the substrate 20 by the use of photographic techniques involving the projection of a grill of vertical lines onto a layer of a photo-sensitive material deposited on the inner surface of the faceplate of such a tube. After exposure the photo-sensitive layer was covered with one of the phosphor materials and then the inner surface of the faceplate was washed. Those portions of the photosensitive layer which had been exposed to light became hardened and the phosphor material adhered closely there to, whereas the unexposed portions remained relatively soft so that they, and the particles of the phosphor material deposited thereupon, were washed away. This process is explained in more detail in the co-pending application of P. D. Payne, Jr., Serial No. 376,345, filed August 25, 1953. a

The other sets of phosphor strips were deposited in a similar manner, i. e., other grills for the respective sets of phosphor strips were projected upon photo-sensitive materials on the screen and the phosphor materials were deposited in the same fashion. The grills had to be precisely placed so as to fulfill the requirements of extremely precise spacing between the strips to yield a tube capable of reproducing good color images.

In accordance with the present invention, the beamintercepting structure of such tubes are preferably made by first depositing the opaque elements on the substrate, and then depositing thereupon the electron sensitive phosphor elements whose edges visible to the viewer are defined by the edges of the opaque elements. This has several advantages over former methods, among which are: (l) the positioning of the respective grills after the deposition of each set of phosphor strips is not so critical since, if the phosphor strips are not displaced from one another exactly as specified, they will overlap on the backs of the adjacent opaque elements to a certain extent. tions that do overlap will not be visible to the observer; (2) the visible width of the phosphor strips may be made more uniform. This is due to the fact that the opaque strips may be composed of particles Which are much finer and more nearly homogeneous than those of available phosphor strips. Therefore the edges or" the opaque strips may have a contour subject to only small variations. Thus the visible edges of the phosphor strips are defined by the more invariant edges of the opaque strips and the effective widths of the phosphor strips are thereby made more uniform, (3) the possibility that some of the phosphors deposited in subsequent processing steps may become lodged in the spaces between adjacent phosphor strips, causing color contamination, is eliminated since the opaque elements are deposited first. Even if some phosphor particles in later steps inadvertently adhere to the rear surfaces of the opaque elements, no color contamination will be caused since the light of the color emitted by the phosphor in response to electron impingement will be blocked from the viewer by the opaque elements.

As stated above, a photographic method of depositing the opaque strips and the sets of phosphor strips may be used which accords with the method explained in the Payne application previously referred to. However, it

However, since the latter are opaque, those porshould be understood that other methods may be used, provided, however, that the opaque elements are deposited first. For example, the process for depositing the elements of the beam-intercepting structure disclosed in the co-pending application of C. H. Pool, Serial No. 333,726, filed January 28, 1953, may be employed. In that application an improved method of laying down some of the screen elements is set forth, in which the elements are deposited not once but twice in order to improve the characteristic responses of those elements to the scanning thereof by an electron beam.

In practice, the fabrication of the beam-intercepting structure according to the principles disclosed herein, has been very successfully achieved by using the following process:

(1) Coat the inner surface of the faceplate with a photo-sensitive material comprising, for example, water, polyvinyl alcohol, and a denatured alcohol such as that designated by the trademark Solox manufactured by the Industrial Solvents Division of the Union Carbide and Chemical Company.

(2) Dry the emulsion.

(3) Project the image of a grill on the coated inner surface of the faceplate.

(4) Flow on a slurry of grams unactivated willemite, cc. Solox, and 60 cc. water.

(5) Dry.

(6) Wash with water.

(7) Dry.

(8) Deposit another layer of the photo-sensitive ma terial mentioned in step number 1.

(9) Dry.

(10) Project grill image again as in step three.

(11) Flow on a slurry of 30 grams Fe O 20 cc. water, and cc. Solox. This slurry differs from the slurry described in step four and helps to produce the desired width of the opaque lines. (Alternatively, two slurries of Fe 0 may be applied.)

(12) Dry.

(13) Wash with water.

(14) Dry.

(15) Coat faceplate as in steps number 1 and 8.

(16) Dry.

(17) Project the image of another grill corresponding to the position of one of the sets of phosphor strips on the inner surface of the faceplate.

(18) Flow on a slurry comprising water, Solox and the phosphor material emissive of the color desired. Repeat steps 5-14 using a slurry of the phosphor desired instead of the Fe O called for in step 11.

(19) After the phosphor strips of one color have been deposited, deposit the strips of the other colors in a similar fashion.

(20) Deposit the reflecting layer 26 on the rear surfaces of the phosphor strips and of the intermediate opaque guard lines.

(21) Deposit the indexing strips 28 on the rear surface of the layer 26 by a process similar to the process by which the guard lines and the phosphor strips are deposited.

The invention is also applicable to other forms of display devices for the production of images in color. For example, it is applicable to the conventional socalled aperture mask type of color television display tube which comprises a screen containing a plurality of sets of phosphor dots emissive of light in selected colors, said dots being arranged in a number of triads, i. e., triangular patterns containing three different color emissive phosphor dots displaced equally from one another, a plurality of electron guns for producing a plurality of beams whose respective intensities are modulated to correspond to the intensities of the colors of the elements of the scene televised, and a perforated mask interposed between the electron guns and the phosphors on the screen to assist in assuring that the respective beams Inpractice the pattern of opaque 9 impinge only on the corresponding sets of phosphors. '..,..l,n conventional aperture mask tubes up to ninety "percent ofthe electron beam current may be dissipated back surface of the screen of such a tube the intensity of; the luminous image maybe considerably increased.

n wever. the presence. of .areflective material in the interstices.betweenadjacent ones of phosphor dots causes serious desaturation of the image due to reflected ambient light which is. themore marked becauseof the fact that'the image actually producedtisof very low brightness. The reflective layer also produces a multiplication'of, halation effects for reasons explained above in connection withJFig. 2. 7

It is possible; employingthe principles of my inventien, to expedite'the production of phosphor screens of aperture mask tubestby reducing to a certain extent, the preciSitJnrequired in depositing the successive sets of phosphor dots according to the rigid manufacturing tolerances specified therefor. 7 I l A tube of the aperture mask type constructed accordingto the; present; invention can be made in the following; way, First, an opaque and non-reflective material is deposited; on an, appropriatesubstrate, such asthe inner surface of the faceplate of the tube, or on a separate Bl'slllltfiubstrate, in a pattern corresponding to the intersti cesbetween thephosphor does of the completed screen, Second, the respective sets of phosphor dots are deposited inthe spaces in the deposited. pattern of opaque ma ri l.

material, can bendeposited in several ways. One way is to project the image of the aperture mask to be-v built into a particular tube,

d g the image of a master aperture plate, onto a photo- 'se itive layer which has. been deposited upon the substrate-ofthe tube under construction. This photo-sensitiye-layer; should have properties such that those portioufiwhichg are exposed to light are'easily removable in a subsequent washing or dissolving process. After exposure of the-photosensitive layer, an opaque and substantially non-reflecting material such as ferrous oxide is'flowed onto the photo-sensitive layer. and is dried. Subsequently, the entire screen: is washed with water and the exposed portions of'thephoto-sensitive material, on which, rest the particles of the opaque oxide material, are Washedy V Alternatively-one can project the image of a negative mask; that is one which is; opaque where theprojected phosphor dots are to fall andwhich is transparent where the interstices between the phosphor dots are to be lgc ed. Th6 lg ptqi-scnsitive layer. deposited upon the substrate in; this casehas characteristics opposite those employed in the first method, i; e., those portions which are exposedtolight become-hardened and insoluble. in water,- After exposure of this photo-sensitive layer, the ferroustoxideis. deposited thereupon, dried, and,.theentire. screen is; then washed with; water, leaving a: pattern atopague material corresponding tot-he: interstices be t Ween -the locations where; the phosphor dots, are. sub,- sequently to be placed. This photo-sensitive material maybe the same as: the one. used in the manufacture of;screenssuchasshown ;-in.-Fig. 1, ashaspreviously been explained.-

. The sets of phosphor dots; may then be, deposited in successivestepsas has been: heretofore customary in thenmanufacture, of, such tubes. Previously the phos-- phor v dots were laid. downby means of appropriate silk screenprocessesior by-purely photographic processes) inwhich asilk-screen mask. (or its photographicv equiv V alent) is rotated clockwise by approximately 120- after the nfirst set of; dots, :is laid down and. the second; set of '10 dots is deposited. The mask is then rotated 120 counter clockwise with respect to its first position and thethird set of dots is deposited. Since the opaque pattern is deposited first it is not necessary that the-phosphors dots actually deposited have exactly circular contours or that they have a configuration which is congruous with ,the spaces in the pattern of opaque areas which has been previously deposited. The phosphor dots may be slightly larger than the spaces in the opaque patternyin fact they may overlap onto the rear surface of the pattfcrn' of opaque areas provided that the overlap is not-so great that the phosphor dotmaterial falls into 'a space in'the pattern to which a phosphor dot emissive of a different color is to be located. Thus, even if the precise spacing of the respective sets of dots is not exactly achieved, the pattern of opaque material masks the actual pattern of phosphor dots from the viewer, those portions of the phosphor dots. which are not properly alignedbbeing blocked from sight by the opaquematerial. H 7

If desired, an' electron-permeable and light-reflecting layer may be deposited on the rear surfacesof the phosphor strips and of the opaque areas to enhance the brightness of the'reproduced image. "It is evident that then. the pattern of opaque material will preventambient light from being reflected back into the eyes of the viewer from those portions of the light-reflecting layer which would. normally be located in the interstices-be tween adjacent phosphor dots. a

Other types of tubes used-for color televisionrecep-' tionsuch. as the so-called Chromatron described in the January 1954 issue of Proceedings of the I. .R. E.' at

page 309 may also profit by embodying the principles of my invention as explained herein. The post-deflection focussing: tube: described in the December 1955 issue of Radio-Electronics at page would be improved b the application of. the instant invention thereto.

While the invention has been described with reference to screens for cathoderay tubes for the reproduction of televised scenes-in color, it should be understood that the advantages of employingscreens constructed accord ing to myinvention are also to be gained in cathode ray tubes for. monochromatic' image production so com structedas to include a plurality of strips of-white'emis sive phosphors backed by a layer of aluminum. In tubes having screens so constructed the eifects of ambient light and halation can be considerably reduced resulting in the production, of aluminous image which is much sharper and whichhas" much better contrast than conventional types. a I s t It will be understood that stillv other embodiments and applications 'ofapparatus constructed according to the diverse forms of the inventiondescribed herein will occur to those skilled in the art'. Consequently, I. desire the-scope of this invention to-be limited only by the appended claims. a 7

What I'cl'aim is: I

1-. An electron beam-intercepting structure. for a: cathode raytube comprisingzza plurality of electron-sensitive elements arranged in: a regular pattern; and a substantially opaque and non-reflecting material. disposed be-' tween-saidielements. r

2.1-An electron beam-intercepting structure' for' a cathode ray tube comprising: a plurality of electron-sensitive elements; arranged in a-regular pattern, and a plurality of substantially opaque and non-reflecting elements disposed infacregular pattern" in the interstices between said electron-sensitive elements.

3.- r Anelectron beam-intercepting: structure for a cathode ray. tube: comprising: a plurality of phosphor elements arrangedlirr a-predetermined pattern, and a plurality'of substantially opaque and non-reflecting elements disposed in apredetermined pattern in the. interstices between said phosphor elements, each of, said opaquelelephosphortelements.

4. An electron beam-intercepting structure for a cathode ray tube comprising: a plurality of electron sensitive elements disposed on a substrate in a predetermined pattern, said elements being emissive of light in response to the impingement of electrons thereupon, and a plurality of substantially opaque and non-reflecting elements disposed in a predetermined pattern in the interstices between said electron-sensitive elements, said non-reflecting elements also being disposed in contiguity to said electronsensitive elements.

5. An electron beam-intercepting structure for a cathode ray tube comprising: a plurality of sets of phosphor elements arranged in a predetermined pattern, each of said sets being emissive of light of a different selected color in response to the impingement of electrons thereupon, and a substantially non-reflecting material intermediate said electron sensitive elements.

6. An electron beam-intercepting structure for a cathode ray tube comprising: a substrate of an essentially transparent material, a plurality of phosphor elements disposed on said substrate in a predetermined pattern, said sets of elements being respectively emissive of light of different selected colors in response to the impingement of electrons thereupon, and a plurality of substantially opaque and non-reflecting elements, each of said opaque elements being disposed intermediate two adjacent ones of said electron sensitive elements.

7. An electron beam-bearing intercepting structure for a cathode ray tube comprising: a plurality of phosphor elements which are emissive of light in response to the impingement of electrons thereupon, a substantially opaque and non-reflecting material intermediate said phosphor elements, and a layer of reflecting material in contact with said phosphor elements and with said opaque elements.

8. The electron beam-intercepting structure according to claim 7 wherein said reflecting material is situated behind said phosphor and opaque elements.

9. An electron beam-intercepting structure for a cathode ray tube comprising: a substrate of an essentially transparent and non-conductive material, a plurality of phosphor elements disposed in a predetermined pattern and in contact with said substrate, said phosphor elements being emissive of light in response to the impingement of electrons thereupon, a plurality of substantially opaque and non-reflecting elements disposed intermediate said phosphor elements and in contact with said substrate, and a layer of a reflecting material disposed in contact with said phosphor and opaque elements.

10. The beam-intercepting structure according to claim 9 wherein said plurality of phosphor elements are emissive of light of difierent selected colors.

11. An electron beam-intercepting structure for a cathode ray tube comprising: a plurality of sets of elongated phosphor elements disposed in a predetermined pattern, each of said sets being emissive of light of a different selected color in response to the impingement of electrons thereupon, and a plurality of elongated and substantially non-reflecting elements disposed intermediate said phosphor elements.

12. The structure according to claim 11 wherein said non-reflecting elements are contiguous with said phosphor elements.

13. The structure according to claim 12 wherein said non-reflecting elements are also opaque.

14. A beam-intercepting structure for a cathode ray tube for reproducing colored images comprising: a plurality of sets of phosphor strips disposed in a predetermined pattern in contact with the inner surface of the faceplate of said cathode ray tube, said sets of phosphors being respectively emissive of light in selected colors in response to the impingement of electrons thereupon, a plurality of substantially opaque and non-reflecting strips, each of said opaque strips being disposed intermediate two adjacent ones of said phosphor strips and in contact 12 therewith, and a layer of a reflecting material disposed in contact with said phosphor strips and said opaque strips.

15. A method for constructing a beam-intercepting structure for a cathode ray tube comprising the steps of: depositing a substantially opaque material in a predetermined pattern on a substrate, said deposited pattern including a plurality of interstices, and depositing an electron-sensitive material in said interstices.

16. The method of constructing a beam-intercepting structure according to claim 15 wherein said electronsensitive material is so deposited in said interstices that 'it overlaps said opaque material.

17. .A method ofv constructing a beam-intercepting structure for a cathode ray tube comprising the steps of: depositing a substantially opaque and non-reflective material in a predetermined pattern on a substrate, said deposited pattern including a plurality of interstices, and depositing a plurality of different phosphor materials in said interstices so that said phosphor materials overlap the rear surface of said opaque material.

18. A method ofmaking a beam-intercepting structure for a cathode ray tube comprising the steps of: depositing a substantially opaque and non-reflective material so that the front surface thereof makes contact with a substrate, said opaque material being deposited in a predetermined pattern having a plurality of interstices therein, depositing a plurality of sets of elements composed of, respectively different electron-sensitive phosphors on the portions of said substrate exposed by said interstices, each of said elements being so deposited as to have a surface which makes contact with a region of the rear surface of said opaque material lying near each of said interstices, and depositing a light-reflecting material on said rear surface of said opaque material and on the rear surfaces of said phosphor elements.

19. 'A beam-intercepting structure for a cathode ray tube comprising: a substantially opaque and non-reflective material deposited in a regular pattern on a substrate, said pattern including a plurality of interstices, and a plurality of different phosphor materials deposited in said interstices so that said phosphor materials overlap the rear surface of said opaque material.

20. A beam-intercepting structure for a cathode ray tube'comprising: a plurality of strips of a substantially opaque and non-reflective material deposited in a regular pattern on a substrate, said pattern including a plurality of intersticesfand a plurality of strips composed of respeetivelydifferent electron-sensitive phosphors on the portions of said substrate exposed by said interstices, each of said strips being so deposited as to make contact with a region of the rear surfaces of said opaque strips near each of said interstices.

21. The structure according to claim 20 and further comprising a light-reflecting material deposited on said rear surfaces of said opaque strips and on the rear surfaces of said phosphor strips.

22. An electron beam-intercepting structure for a cathode ray tube comprising a plurality of mutually spaced strips of opaque material deposited on a substrate and different phosphor material deposited in the spaces between said strips, said spaces having Widths which are a function of the respective efiiciencies of the phosphor materials deposited therein. V

23. An electron beam-intercepting structure for .a cathode ray' tube comprising a plurality of mutually spaced strips of opaque material deposited on a substrate, and phosphor materials deposited in the spaces between said strips, the phosphor material deposited in certain of said spaces having an efliciency differing from that of those deposited in others of said spaces, the spaces occupied by phosphor material of lower efliciency being wider than those occupied by phosphor material of higher efiiciency. V

' 24. The structure according to claim 23 and further 25. The structure accordingto claim 24 wherein said opaque strips have a plurality of different widths.

26. The structure according to claim 25 wherein the center-to-center distance of the phosphor materials deposited in adjacent spaces is substantially the same.

27. A beam-intercepting structure for a cathode ray tube comprising: a substantially opaque and non-reflective material deposited in a regularpattern on a sub- .strate, said pattern including a plurality of interstices,

and phosphor material deposited in said'interstices in a regular pattern, the particles of said phosphor material being larger than the particles of said opaque material.

28. A beam-intercepting structure for a cathode ray tubecomprising: a substantially opaque and non-reflective material havingparticles of a given size'deposited in a regular pattern on a substrate, said pattern having a plurality of interstices, and a plurality of sets of phosphor elements deposited in said interstices, said sets of phosphor elements having respective particle sizes sub-f st-antially larger than said given size.

References Cited in the file of this patent UNITED STATES PATENTS 2,137,118 Schleede Nov. 15, 1938 2,388,203 Zindel Oct. 30, 1945 2,446,440 Swedlund Aug. 3, 1948 2,446,791 Schroeder Aug. 10, 1948 2,687,360 Michaels Aug. 24, 1954

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