US3484269A

US3484269A - Process for the manufacture of a display screen of a cathode ray tube for reproducing color images employing phosphor strips luminescing in different colors and an indexing strip

Info

Publication number: US3484269A
Application number: US582882A
Authority: US
Inventors: Johannes Josephus Anto Jonkers; Hendrik Groendijk
Original assignee: US Philips Corp
Current assignee: US Philips Corp
Priority date: 1965-10-02
Filing date: 1966-09-29
Publication date: 1969-12-16
Anticipated expiration: 1986-12-16
Also published as: GB1150927A; DE1462853B2; SE325297B; FR1501085A; JPS4939306B1; DE1462853A1; NL6512812A

Description

Dec.'1-6. 1969 J. J. A. JON-KERS ETAL 3,484,269 PROCESS FOR THE MANUFACTURE OF A DISPLAY SCREEN OF A CATHODE" RAY TUBE FOR REPRODUCING- COLOR IMAGES EMPLOYING PHOSPHOR STRIPS LUMINESCING IN DIFFERENT COLORS AND AN INDEXING STRIP Filed septv 29, 1966 2 SheetsSheet 1 INVENTORJ .mnmnss J. A. JON KERS BY HENDRIK GROENDIJK AGENT Dec. 16. 1969 J, J, A, JONKERQ ET AL PROCESS FOR THE MANUFACTURE 01" 3,484,269 A DISPLAY SCREEN OF A CATHODE RAY TUBE FOR REPRODUCING COLOR IMAGES EMPLOYING PHOSPHOR STRIPS LUMINESCING IN DIFFERENT COLORS AND AN INDEXING STRIP 2 Sheets-Sheet 2 Filed Sept. 29, 1966 INV JOHANNES J. A. SWfis HENDRIK GROENDIJK AGENT United States Patent 3,484,269 PROCESS FOR THE MANUFACTURE OF A DIS- PLAY SCREEN OF A CATHODE RAY TUBE FOR REPRODUCING COLOR IMAGES EM- PLOYING PHOSPHOR STRIPS LUMINESCING IN DIFFERENT COLORS AND AN INDEXING STRIP Johannes Josephus Antonius Jonkers, and Hendrik Groendijk, Emmasingel, Eindhoven, Nether-lands, assignors, by mesne assignments, to US. Philips Corporation, New York, N.Y., a corporation of Delaware Filed Sept. 29, 1966, Ser. No. 582,882 Claims priority, application Netherlands, Oct. 2, 1965, 6512812 Int. Cl. B44d 5/00; C09k 1/00; C03c 17/00 US. Cl. 117-38 2 Claims ABSTRACT OF THE DISCLOSURE A method of manufacturing a display screen for a cathode ray tube for reproducing color images in which phosphor strips luminescing in three different colors separated by non-luminescent strips are successively deposited on a window of the tube by first exposing portions of the window covered with a light-hardenable binder through a mask which blocks the hardening radiation from striking those portions which are to be exposed and at a later time exposing intermediate strips through a lens, and a plane-parallel glass plate which can be rotated to refract radiation passing through it. After the phosphor strips and the non-luminescing strips are applied, a thin reflecting metal film is applied over the strips. Strips of indexing material are then applied over the metal layer but only on those portions covering the non-luminescing strips beneath the metal layer.

The invention relates to a method of manufacturing a picture screen for a cathode ray tube for reproducing color pictures. In this method a luminescent layer is provided on the screen by using a photosensitive binder, the layer consisting of at least two substances present in substantially strip-shaped surfaces which, on excitation by electrons, luminesce in different colors. These luminescent strips are separated by substantially strip-shaped surfaces of a substance which, on excitation by electrons, does not luminesce in visible light and passes no light. A metal layer which is permeable to electrons is then provided on it. This layer is provided, by using a photosensitive binder, with substantially strip-shaped surfaces of a substance which, on excitation by electrons, provides an indexing signal. The latter surfaces take the position of a part of the surfaces of the substance which, on excitation by electrons, does not luminesce in visible light and passes no light.

The manufacture of the various surfaces is carried out by using a photosensitive binder, i.e., a substance which, after exposure to so-called hardening radiation no longer dissolves in a particular solvent, each time those parts being exposed where the substance in question must be present. This may be carried out in several manners.

On the one hand the substance to be provided may be suspended in a solution of the photosensitive binder which solution also usually contains a sensitizer. The suspension is spread on the support and dried. Subsequently, those places where the surfaces of the substance in question have to be provided are exposed to the hardening radiation as a result of which the binder at those places becomes insoluble in a solvent which need not be the same as the solvent in which the binder was first dissolved. The binder and the substance are then removed from the un- ICC operations a support which is covered with particular surfaces of the substance is obtained. exposed places by washing with a solvent. After these On the other hand, the substance to be provided may not be suspended in the solution of the photosensitive binder. So in this case only the layer of binder is exposed. At the exposed places the binder becomes insoluble and, at least if the exposure is not continued too long, it becomes somewhat sticky as soon as it is wetted with a solvent. For providing the substance in question two methods are possible. In one case the unexposed parts of the binder layer are washed away with a solvent, the exposed parts becoming somewhat sticky. Then a suspension of the substance to be provided in some suitable medium or other is spread on the sticky parts of the binder. Grains of the substance then adhere to the sticky parts. By rinsing the grains may be removed everywhere else. In the other case a suspension of the substance to be provided in some suitable medium or other which makes the exposed parts of the binder layer somewhat sticky is spread over the locally exposed binder layer and dried. By rinsing with a solvent for the unexposed binder all the unexposed binder and the grains present on it are simultaneously removed while the grains adhere to the exposed and sticky parts. Although in these two cases the grains of the substance to be provided adhere to the sticky hinder, the resulting layer of grains often is not dense enough so that it is usually desirable to repeat the whole operation.

In all these cases the desired distribution of the substantially strip-shaped surfaces is obtained, for example, by using a punctiform source of radiation and providing between that source and the layer to be exposed a mask comprising parts which are permeable to the radiation through which the desired surfaces are exposed. Another possibility of obtaining the desired distribution is to reproduce on the layer to be exposed an illuminated mask by means of a system of lenses.

In the case of the above-described picture tube usually first the substantially strip-shaped surfaces are provided of the substance which, on excitation by electrons, does not luminesce in visible light and passes no light, which surfaces will hereinafter simply be termed intermediate strips. The intermediate strips usually have also the prop erty of being non-reflective. In view of these properties of the substance a suspension of the substance in a solution of the photosensitive binder does not or substantially not pass the hardening radiation. If, as is usually the case, exposure takes place from the side remote from the support, in providing said surfaces the method should be used in which the layer of binder is made sticky at particular places on which the grains of the substance are provided. In order to ensure that said surfaces indeed pass no light, it is desirable for a suflicient covering to repeat the operation.

After providing said substantially strip-shaped surfaces the intermediate spaces are successively provided with the substances which luminesce in different colors when being excited by electrons. It is common practice to provide three substances which emit red, green, and blue light, respectively. Since these substances usually pass the hardening radiation to a sulficient extent, the luminescent substance in these cases may be suspended in a solution of the photosensitive binder. The hardening of the binder need not be restricted in each of these cases to exactly the space between the surf-aces of the intermediate strips already present, but viewed from the window, it may also extend partly behind said surfaces and this is done more in particular to be sure that the intermediate space is indeed filled.

Also the substantially strip-shaped surfaces of the substance which, on excitation by electrons, provides an indexing signal, which surfaces will hereinafter simply be termed indexing strips, are provided with the use of a photosensitive binder. The indexing signal may be obtained in several manners. If the substance consists of secondary emitting material, an electron current is formed on excitation by electrons which is received on a collector electrode. In another case the substance has the property of emitting radiation on excitation by electrons which is received in a photoelectric cell. The resulting signals are used for the coordination of the instantaneous modulation of the electron beam. Since these substances usually pass the hardening radiation to a sufficient extent, the substance to be provided in this case may be suspended in a solution of the photosensitive binder. These surfaces take the position of a part of the surfaces of the substance which, on excitation by electrons, does not luminesce in visible light and passes no light. This is to be understood to mean that the indexing strips are located exactly on the other side of the metal layer permeable to electrons than a part of the intermediate strips. The width of the indexing strips is maximally equal to that of the intermediate strips; otherwise, in fact, the electron current would not reach a part of the luminescent strips or at least not with sufficient energy. The Width may be smaller if it is ensured that sufiicient substance which, on excitation by electrons, provides an indexing signal is present for producing the required signal.

In these various operations a number of masks are used, namely a mask having a pattern which corresponds to the intermediate strips, masks having patterns which correspond to the parts of the binder to be hardened for each of the luminescent substances or, if required, one such mask which each time assumes a different position relative to the window, and a mask having a pattern which corresponds to the indexing strips. The difficulty in this case is that the masks must accurately be adapted to one another and, during exposure, must always assure a very defined place with respect to the window and the system of lenses, if any. In connection with the electron optical system it is usually desirable that the luminescent strips at some places are not straight but are somewhat curved and that the width of the luminescent strips is not the same everywhere. This has for its result that the masks have a very complicated structure.

The invention now provides a method which mitigates these drawbacks because always the same mask is present. According to the invention, in providing the substantially strip-shaped surfaces of the substance which, on excitation by electrons, luminesce in different colors, and, in providing the substantially strip-shaped surfaces of the substance which, on excitation by electrons, provides an indexing signal, the radiation which hardens the photosensitive binder each time passes the partly covered mask which is used in providing the substantially strip-shaped surfaces of the substance which, on excitation by electrons, does not luminesce in visible light and passes no light.

The covering of the mask is adapted to the surfaces to be provided. If the picture screen comprises three luminescent substances, then in providing the substantially strip-shaped surfaces of each of the said substances, each time two out of three successive radiation-passing parts of the mask passing the radiation are covered. This may be done, for example, with an additional mask. In this additional mask the parts which pass the radiation need not be provided with great accuracy, since it is sufficient that the additional mask is constructed so that on the one hand only radiation is passed which passes one of three successive radiation-passing parts of the mask always present passing radiation and, on the other hand, no parts of said radiation are retained. An analogous reasoning holds, of course, in the case of a different num ber of luminescent substances. For covering during providing the indexing strips a corresponding reasoning holds good. In a particular case the indexing strips, not counting a comparatively narrow region which extends substantially parallel to the edge of the efiiective picture screen, are present at every other intermediate strip to which the additional mask is adapted. In this case also no high requirements as to accuracy need be imposed upon the additional mask.

Since the indexing strips take the position of a part of the intermediate strips, the mask always present may take the same place with respect to the Window and the systems of lenses, if any, during the exposure for the indexing strips as during the exposure for the intermediate strips. This is not possible as such during the exposure for the various luminescent strips since the hardening radiation must exactly harden those parts of the layer of binder present between the intermediate strips on the window. The required adaptation may be carried out in various manners. It is possible to displace the window relative to the mask always present over a distance which is equal to the distance from the center of an intermediate strip and that of an adjacent intermediate space. Alternatively it is possible to displace the mask over that distance. If the illuminated mask is re-pr duced by means of a system of lenses it is also possible, however, to effect an optical displacement in which the arrangement remains unaltered mechanically which, of course, is to be preferred. For this purpose a plane-parallel glass or quartz plate is used which during providing the intermediate strips and the indexing strips extends parallel to the mask but during providing the phosphor strips is rotated over a small angle about an axis which extends parallel to the radiation-passing line in the center of the mask. The thickness of the plane and the angle through which it is rotated during providing the phosphor strips depends upon the required displacement at the area of the window. Therefore, in general the hardening radiation preferably always passes a plane-parallel plate which, during providing the substantially strip-shaped surfaces of the substance which, on excitation by electrons, does not luminesce in visible light and passes no light and, during providing the substantially strip shaped surfaces of the substance which, on excitation by electrons, provides an indexing signal, takes the same position and, during providing the substantially strip-shaped surfaces of the substances which, on excitation by electrons, luminesce in different colors, is rotated relative to that position over a small angle about an axis parallel to the radiation passing line in the center of the mask.

When the phosphor strips of the first color are provided, the arrangement in providing the following phosphor strips must be altered so that the hardening radiation impinges upon other parts located between the intermediate strips. This may be effected by displacing the window relative to the mask always present and the additional mask. However, it is recommended that the place of the window be left unaltered. Then there are two more possibilities. In one case the additional mask is displaced relative to the mask always present in such manner that the hardening radiation passes parts of the mask always present which parts were covered by the additional mask in the preceding case or in the preceding cases. In the other case a separate additional mask is present for providing the strips of each luminescent substance.

Since it is permissible that the luminescent strips are partly located behind the intermediate strips and usually will be located behind said strips, on the one hand the radiatlon-passing parts of the mask passing radiation, whlch mask is used in providing all the strip-shaped surfaces of the picture screen, are decisive of the position, the shape, and the width of the intermediate strips and of the indexing strips and, on the other hand, the radiatron-passing parts of that mask not passing radiation are decisive of the position, the shape, and the width of the parts of the phosphor Strips which are in contact with the Wll'ldOW. This must be taken into account in constructing the mask. The width of the hardened parts of each of the layers of binder is determined, besides by the parts of the mask passing radiation, also by the way in which the substance to be provided is applied, namely, whether this substance is suspended in a solution of the photosensitive binder or whether only the layer of binder is ex posed and the substance to be provided is adhered in a later stage to the parts which have become sticky, and, although to a lesser extent, by the exposure time. If the substance to be provided is suspended in a solution of the photosensitive binder, the particles of that substance cause a certain spreading of the hardening radiation which has for its result that the hardened part of the layer of binder is widened as compared with the case in which the substance is not suspended in the solution. The influence of the exposure time is larger if the illuminated mask is reproduced on the layer to be exposed 'by means of a system of lenses than if in the arrangement the mask is located close to the layer of binder. If the illuminated mask is reproduced on the layer to be exposed by means of a system of lenses and if the parts of the radiationpassing mask are equally wide as the parts which do not pass radiation, the exposed parts of the layer of binder, in the case the substance to be pr vided is suspended in the solution of the photosensitive binder, are always wider than the unexposed parts; how much wider depends upon the exposure time. In the case of the substance to be provided is not suspended in the solution, the exposed parts of the layer of binder are usually s meWhat wider than the unexposed parts; by the choice of the exposure time they may also be equally wide and, if required, even somewhat narrower. As already noted, the binder at the exposed places becomes insoluble and, if at least the exposure is not continued too long, it becomes somewhat sticky as soon as it is wetted with a solvent. If, to obtain the desired width, a longer exposure time must be used all the same, a thicker layer of binder will have to be used.

The method will now be described as an example with reference to the exposure arrangement shown diagrammatically in the drawing in cross-sectional views and not to scale, of which FIGURE 1 relates to the provision of the intermediate strips, FIGURE 2 to the provision of the strips of the first phosphor, FIGURE 3 to the provision of the strips of the second phosphor and FIGURE 4 to the provision of the indexing strips. In these figures, 1 is a part of the window, 2 is the mask always present and which is exposed by a source of radiation not shown, 3 is a system of lenses shown diagrammatically by means of which the illuminated mask is reproduced on the layer to be exposed on the window, and 4V is a plane-parallel glass plate having a thickness of 2 cm. which passes the hardening radiation. The mask 2 consists of a glass plate 5 having provided on it substantially strip-shaped

surfaces

11, 13, 15, 17, 19, 21, 23, 25, 27, 29 and 31 which do provided is suspended in the solution of the photosensitive binder, are always wider than the unexposed parts; how much wider depends upon the exposure time. For the case the substance to be provided is not suspended in the solution, the exposed parts of the layer of binder are usually somewhat wider than the unexposed parts; by the choice of the exposure time they may also be equally wide and, if required, even somewhat narrower. As already noted, the binder at the exposed places becomes insoluble and, if at least the exposure is not continued too long, it becomes somewhat sticky as soon as it is wetted with a solvent. If, to obtain the desired width, a longer exposure time must be used all the same, a thicker layer of binder will have to be used.

The method will now be described as an example with reference to the exposure arrangements shown diagrammatically in the drawing in cross-sectional views and not to scale, of which FIGURE 1 relates to the provision of the intermediate strips, FIGURE 2 to the provision of the strips of the first phosphor, FIGURE 3 to the provision of the strips of the second phosphor and FIGURE 4 to the provision of the indexing strips. In these figure, 1 is a part of the window, 2 is the mask always present and which is exposed by a source of radiation not shown, 3 is a system of lenses shown diagrammatically by means of which the illuminated mask is reproduced on the layer to be exposed on the window, and 4 is a plane-parallel glass plate having a thickness of 2 cm. which passes the hardening radiation. The mask 2 consists of a glass plate 5 having provided on it substantially strip-shaped

surfaces

11, 13, 15, 17, 19, 21, 23, 25, 27, 29 and 31 which do not pass the hardening radiation. These surfaces, in the centre of the mask, have a width of slightly more than 37 microns. During reproduction the radiation-passing

parts

12, 14, 16, 18, 20, 22, 24, 26, 28 and 30 having a width, in the centre of the mask, of slightly under 37 microns, serve as objects.

The inside of the glass window 1 is first of all covered with an aqueous solution of polyvinyl alcohol which contains a bichromate, for example, ammonium bichromate, as a sensitizer. After drying said layer is subjected to the influence of hardening radiation namely in accordance with the arrangement shown in FIGURE 1 in which the source of radiation not shown, the mask 2 and the system 3 of lenses are rigidly arranged relative to one another and the window 1 is arranged so that it can assume the same position with respect to said rigidly arranged members in a subsequent operation. To avoid drawing complexity only the

hardened parts

41, 42, 43, 44, 45, 46, 47, 48, 49 and 50 of the layer of binder are shown. It is clear, however, that the window 1 with the said hardened parts is formed only after washing away the unexposed parts with a solvent which operation, of course, is carried out outside the exposure arrangement so that in fact the figure does not represent a stage during the method. The same holds good for FIGURES 2, 3 and 4. The hardening radiation passes the plane-parallel glass plate 4 which is placed parallel to the mask 2. Optically the arrangement is such that a magnification of 200/37 occurs. In addition the exposure time is chosen to be such that, in spite of the fact that the radiation-passing parts of the mask passing radiation are narrower in the center than the parts which do not pass radiation, as a result of the widening occurring the hardened parts of the layer of binder on the window in the center is substantially equally wide as the non-hardened parts so that the hardened parts in the center of the window have a width of 200 microns. After the unexposed parts of the layer of binder have been washed away, in which the exposed parts have become somewhat sticky, a suspension of iron oxide powder in a dilute solution of polyvinyl alcohol in water is provided in the window. These black powder particles adhere to the substantially strip-shaped, sticky parts of the layer of binder. This entire process is repeated to be sure that the intermediate strips indeed pass no light.

Then the inside of the glass window 1 with the black strips of

binder

41, 42, 43, 44, 45, '46, 47, 48, 49 and 50 provided on it is covered with an aqueous solution of polyvinyl alcohol which contains a bichromate, for example ammonium bichromate, as a sensitizer and in which the first luminescent substance, for example, green luminescent silver-activated zinc cadmium sulphide, is suspended. After drying this layer is subjected to the influ' ence of hardening radiation and that in accordance with the arrangement shown in FIGURE 2. As compared with the arrangement shown in FIGURE 1 the mask 6 is placed on the side of the mask 2 facing the source of radiation not shown. The mask 6 consists of a glass plate 60 having provided on it substantially strip-shaped

surfaces

61, 62, 63, and 64 which do not pass the hardening radiation. The surface 61 ensures that the hardening radiation cannot reach the

parts

12 and 14 passing the radiation of the mask 5; the analogous situation holds good for the surface 62 relative to the

parts

18 and 20, for the surface 63 relative to the

parts

24 and 26 and for the surface 64 relative to the part 30. On the other hand the mask 6 does not impede the passage of radiation directed to the

parts

16, 22 and 28 passing radiation of the mask 2. In the reproduction which takes place in the arrangement shown in FIGURE 2 the

parts

16, 22 and 28 passing the radiation serve as objects. The plane-parallel plate 4 is rotated through an angle of 310 with respect to the position shown in FIGURE 1 to ensure that with the same arrangement of the window 1 relative to the source of radiation not shown, the mask 2, and the system 3 of lenses as in FIGURE 1, parts of the layer of binder which are located between the intermediate strips are exposed. To avoid complexity of the drawing again only the

hardened parts

65, 66, 67 and 68 of the layer of binder are shown. As stated, the intermediate strips in the center of the window are substantially equally wide as the parts located between the intermediate strips and they have a width of 200 microns. In the reproduction of the

parts

16, 22 and 28 passing radiation widening of the hardened parts occurs in the layer of binder because the luminescent substance is present in the layer of binder. Although the

parts

16, 22 and 28 passing radiation have a width in the center of the mask which is slightly under 37 microns and the magnification of the arrangement is 200/37, the

hardened parts

65, 66, 67 and 68 have a width, also as a result of the exposure time chosen, of slightly more than 200 microns and the edges thereof are located on the adjacent intermediate strips. Subsequently the unexposed parts of the layer of binder with the luminescent substance present therein are washed away.

The inside of the glass window 1 with the

strips

41, 42, 43, 44, 45, 46, 47, 48, 49 and 50 of binder with black substance present thereon and with the

strips

65, 66, 67, 68 of binder with the first luminescent substance present thereon is then covered with an aqueous solution of polyvinyl alcohol which contains a bichromate, for example, ammonium bichromate, as a sensitizer and in which the second luminescent substance, for example, blue luminescent silveractivated zinc sulphide, is suspended. After drying said layer is subjected to the influence of hardening radiation and that in accordance with the arrangement shown in FIGURE 3. On the side of the mask 2 facing the source of radiation not shown the mask 7 is placed. The mask 7 comprises a glass plate 70 having provided thereon substantially strip-shaped

surfaces

71, 72, 73 and 74 which do not pass the hardening radiation. The surface 71 ensures that the hardening radiation cannot reach the part 12 passing the radiation of the mask 2; the analogous situation holds good for the surface 72 relative to the

parts

16 and 18, for the surface 73 relative to the parts 22 and 24, and for the surface 74 relative to the

parts

28 and 30. On the other hand the mask 7 does not impede the passage of the radiation which is directed to the

parts

14, and 26 passing radiation of the mask 2. In the reproduction which takes place in the arrangement shown in FIGURE 3, the

parts

14, 20 and 26 passing the radiation serve as objects. For the rest the arrangement is similar to that shown in FIGURE 2. The mask 7 may be a separate mask but alternatively the mask 6 may be used for this purpose and be displaced over the relative distance, in the case described 74 microns, for the arrangement shown in FIG- URE 3. Again to avoid complexity of the drawing only the

hardened parts

75, 76 and 77 of the layer of binder are shown. For the same reason as described with reference to FIGURE 2, the edges of the

hardened parts

75, 76 and 77 are located on the adjacent intermediate strips. The unexposed parts of the layer of binder with the luminescent substance present therein are then washed away.

In an analogous manner the binder with the third luminescent substance is then provided. On the cover thus formed of the window 1 a metal layer which is permeable to electrons is provided in known manner, for example, by evaporating aluminum on an organic skin provided. The hardened parts of binder with the third luminescent substance are denoted in FIGURE 4 by 101, 102. 103 and 104 and the aluminum layer is denoted by 105. The organic skin is not shown.

The aluminum layer 185 is covered with an aqueous solution of polyvinyl alcohol which contains a bichromate, for example, ammonium bichromate, as a sensi tizer and in which a substance is suspended which, on excitation by electrons, provides an indexing signal, for example, calcium aluminum silicate activated with cerium which, on excitation by electrons, emits ultraviolet radiation with a peak at 3900 A. After drying said layer is subjected to the influence of hardening radiation namely in accordance with the arrangement shown in FIGURE 4. On the side of the mask 2 facing the source of radiation not shown this time the mask 8 is placed. The mask 8 consists of a glass plate 80 having provided thereon substantially strip-shaped

surfaces

81, 82, 83, 84 and which do not pass the hardening radiation. The surface 81 ensures that the hardening radiation cannot reach the part 14 passing the radiation of the mask 2; the analogous situation holds good for the surface 82 relative to the part 18, for this surface 83 relative to the part 22, for the surface 84 relative to the part 26 and for the surface 85 relative to the part 30. On the other hand the mask 9 does not impede the passage of the radiation which is directed to the

parts

12, 16, 20, 24 and 28 passing radiation of the mask 2. In the reproduction which take place in the arrangement shown in FIGURE 4 the

parts

12, 16, 20, 24 and 28 passing radiation serve as objects. The plane-parallel plate 4 in this case is again placed parallel to the mask 2 exactly as in the arrangement shown in FIGURE 1. The parts of the layer of binder hardened by the radiation thus assume the same position relative to the window 1 as a part of the intermediate strips. Again for avoiding drawing complexity only the

hardened parts

111, 112, 113, 114 and 115 of the layer of binder are shown. In this reproduction of the

parts

12, 16, 20, 24 and 28 passing radiation widening of the hardened part occurs in the layer of binder because the substance to be provided is present in the layer of binder. The

parts

12, 16, 20, 24 and 28 passing radiation have a width in the center of the screen of slightly under 37 microns and the magnification of the arrangement is 200/ 37. The exposure time is now chosen to be so that the width of the

hardened parts

111, 112, 113, 114 and 115 in the center of the screen is 200 microns. The unexposed parts of the layer of binder are subsequently washed away.

Finally the screen thus formed is heated, the organic substance present, namely the binders and the organic skin, being fired out.

What is claimed is:

1. A process for the manufacture of a picture screen of a cathode ray tube for reproducing color pictures comprising, positioning the screen substrate in spaced relation to a radiation source, placing between the substrate and radiation source a mask having multiple strip-shaped apertures, placing between the substrate and mask a transparent plate having plane parallel surfaces with the surface intersecting to the path of radiation passing through the center aperture of the mask, providing the substrate with strip-shaped layers of a material which on excitation by electrons does not visibly luminesce and passes no light by coating the substrate with a photosensitive binder and exposing the strip-shaped areas to hardening radiation from the radiation source through all apertures of the mask and removing unexposed binder from the substrate, rotating the transparent plate through a small angle to refract the radiation passing through the mask apertures sufiiciently to cause the radiation passing through the mask apertures and plate to strike the substrate in the strip-shaped areas between the first applied stripshaped layers, sequentially applying strip-shaped layers of at least two substances which on excitation by elec trons luminesce in diiferent colors by partially covering the mask to block all apertures except those corresponding to areas of one color, coating the substrate with a photosensitive binder and exposing the strip-shaped areas to be of that color to hardening radiation from the radiation source through the partially covered mask and remaining unexposed binder, repeating the steps of partially covering the mask, coating the substrate, exposing and removing unexposed binder for each diiferent color, applying a layer of a metal which is permeable to electrons over the various strip-shaped layers, repositioning the transparent plate to its original position with its surfaces intersecting to the path of radiation passing through the center aperture of the mask, applying over the metal layer and only in areas overlaying the strip-shaped layers of material which do not visibly luminesce strip-shaped layers of a substance which on excitation by electrons provides an indexing signal by applying to the metal layer a coating of a photo-sensitive binder and exposing the strip-shaped areas to hardening radiation from the radiation source through at least some of the apertures of the mask and removing unexposed binder.

2. A process for the manufacture of a picture screen of a cathode ray tube for reproducing color pictures comprising, positioning the screen substrate in spaced relation to a radiation source, placing between the substrate and radiation source a mask having multiple strip-shaped apertures, providing the substrate with strip-shaped layers of a material which on excitation by electrons does not visibly luminesce and passes no light by coating the substrate with a photosensitive binder and exposing the stripshaped areas to hardening radiation from the radiation source through all apertures of the mask and removing unexposed binder from the substrate, sequentially applying strip-shaped layers of at least two substances which on excitation by electrons luminesce in difiFerent colors by partially covering the mask to block all apertures except those corresponding to areas of one color, coating the substrate with a photosensitive binder and exposing the strip-shaped areas to be of that color to hardening radiation from the radiation source through the partially covered mask and remaining unexposed binder, repeating the steps of partially covering the mask, coating the substrate, exposing and removing unexposed binder for each different color, applying a layer of a metal which is permeable to electrons over the various strip-shaped layers, applying over the metal layer and only in areas overlaying the strip-shaped layers of material which do not visibly luminesce strip-shaped layers of a substance which on excitation by electrons provides an indexing signal by applying to the metal layer a coating of a photosensitive binder and exposing the strip-shaped areas to hardening radiation from the radiation source through at least some of the apertures of the mask and removing unexposed binder.

References Cited UNITED STATES PATENTS 2,756,167 7/1956 Barnett 11733.5 X 2,792,741 5/1957 Mazzon 35026 X 2,950,193 8/1960 Payne 9636.1 X 3,005,125 10/1961 Evans et a1.

RALPH S. KENDALL, Primary Examiner M. F. ESPOSITO, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3484369 Dated December 16, 1969 Invent0r(S) J. J. A. JONKERS ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, before line 1 insert line 3 Column 3, line 37 "assure" should read -assume-- Column 5, omit lines 55 through 75 Column 6, omit lines 1 through 9 Signed and sealed this 3th day of Segtember 1970 (SEAL) e Anew Edward M. Fletcher, 11''. Atleating Offioer WILLIAM E- sum, JR.

Oomissioner of Patents