US 2961314 A
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Description (OCR text may contain errors)
N 1 M. E. AMDURSKY ETAL 2,961,314
METHOD OF MANUFACTURING COLOR IMAGE REPRODUCER Original Filed June 24, 1955 2 Sheets-Sheet 1 FIG. 5
MARK E. AMDURSKY 4 JOSEPH P. Flo
Nov- 2, 9 M. E. AMDURSKY ETAL 2,961,314
METHOD OF MANUFACTURING COLOR IMAGE; REPRODUCER 2 Sheets-Sheet 2 Original Filed June 24, 1955 FIG 2 MARK E. AMDURSKY JOSEPH F? FloRE mmvrons.
Unite METHOD OF MANUFACTURING COLOR IMAGE REPRODUCER Original application June 24, 1955, Ser. No. 517,864. Divided and this application Dec. 11, 1956, Ser. No. 627,700
2 Claims. (Cl. 96-38) This'invention is directed to a new and improved method of manufacturing color image reproducers of the post-deflection-acceleration type and is particularly concerned with an improved process for manufacturing the image screen and color-selection barrier in a device of this type. This application is a division of copending application Serial No. 517,864, filed June 24, 1955, for Color Image Reproducer, and assigned to the same assignee as the present application.
At present, there are a wide variety of known types of cathode-ray color image reproducers in which color selection is achieved by means of a barrier structure interposed between a multi-color image screen and the electron gun or guns of the device. For example, some of these color-selection barriers operate to restrict an electron beam or beams to impinge upon phosphors which emit a selected color depending upon the angle of incidence of the beam with respect to the barrier. Other types of barriers comprise deflection grids which establish electric fields to direct an electron beam or beams to impinge upon selected colors. In many of these devices, particularly the direction-sensitive barrier types, the apertures in the barrier through which the electron beam passes to reach the image screen are of approximately the same size as the elementary color phosphor areas of that screen; In other .color tubes, however, the color-selection barrier is maintained at a substantially lower potential than the image screen so that a focusing field comprising a multiplicity of minute convergent lenses is established between the barrier and the screen. The present invention is particularly concerned with the manufacture of the latter type of image reproducer, commonly referred to as a post-deflectionaccelcration or post-deflection-focus tube.
One of the principal advantages of post-deflectionacceleration color tubesresults from the fact that the electron beam is subjected to a substantial focusing action as it traverses the space between the color selection barrier and the image screen. Consequently, the barrier apertures may be made substantially larger in area than the individual color phosphor areas of the screen without permitting the beam to spread over an inordinately large portion of the screen to create color contamination. However, because virtually all of these color image reproducers require substantial correspondence between the distribution patterns of the barrier apertures and individual color phosphors on the screen, fabrication of post-deflection-acceleration tubes is considerably more difiicult than the manufacture of tubes in which the color selection barrier is maintained at the same potential as therscreen. The principal difiiculty results from the fact that the mask or barrier apertures are so large that this structure cannot conveniently be used as a master pattern in laying down the image screen. Thus, the most effective means known for maintaining accurate correspondence between the distribution patterns of the mask s stem 2,961,314 Patented Nov. 22, 1960 apertures and the screen phosphor areas is not available using conventional techniques. The problem thus presented becomes particularly acute in the case of tubes in which the image screen and/or the color-selection barrier are substantially spherical or otherwise curved in configuration, since printing techniques cannot be readily applied to the manufacture of these tubes and photographic techniques are made extremely difficult because of the substantial differences in size between the mask apertures and the individual screen phosphor areas.
One proposed method for avoiding this difficulty has been to fabricate the color-selection barrier with apertures equal in size to the desired operating apertures. The barrier structure is then plated or otherwise coated with some material to reduce the size of the apertures so that the barrier may be employed as a master pattern in a photographic process for fabricating the image screen of the picture tube. Subsequently, the plating or coating material is removed by etching or some similar process to restore the color-selection barrier to its desired operating configuration. This process in general has proven quite unsatisfactory, however, because the plating or coating step requires deposition of very substantial amounts of material on the color-selection mask and because it is difficult to maintain the requisite uniformity in aperture size.
It is a general object of this invention, therefore, to provide a new and improved, efficient and economical, method of manufacturing a color image reproducer of the type comprising an image screen including a multiplicity of minute areas of color phosphor material and a color-selection barrier having an aperture pattern representative of the distribution pattern of one color group of the image screen areas.
Another object of the invention is to provide a new and improved method of manufacturing a post-deflectionacceleration color image reproducer in which conventional techniques may be employed to fabricate the image screen, using the color-selection barrier as a master pattern.
A more specific object of the invention is to provide a new and improved post-deflection acceleration color image reproducer manufacturing method utilizing a resistcoated colorselection barrier as a master pattern for depositing a color image screen and which requires but a single etching step to form color-selection apertures in the barrier.
The invention is thus directed to a process for manufacturing a color image reproducer of the type comprising an image screen including a multiplicity of minute areas of color phosphor material and a color-selection barrier having an aperture pattern representative of the distribution pattern of one color group of the image screen areas. In accordance with the invention, an opaque resist coating having a pattern of apertures of predetermined size corresponding to the above-mentioned screen area distribution pattern is applied to a tages thereof, may best be understood by reference tg The organization and manner of operation of the following description taken in conjunction with the accompanying drawings, in which like reference numerals refer to like elements in the several figures, and in which: Figure l is a perspective view of a color-selection barrier at an early stage of the process of the invention;
Figure 2 is an enlarged view of a portion of the colorselection barrier of Figure 1 illustrating the relationship of the barrier apertures to the distribution pattern of the image screen of a color image reproducer;
Figure 3 illustrates a further step which may be employed in the process;
Figure 4 shows the color-selection barrier as used in forming the image screen of the color picture tube; and
Figure 5 illustrates a subsequent step in a related. process.
The inventive process described and claimed in the above-identified copending application contemplates, as an intermediate step, the formation of a color-selection barrier having an effective pattern of apertures substantially equal in area and distribution to the corresponding pattern desired for one color phosphor group in the image reproducer screen. This intermediate form of the color-selection barrier is utilized as a master pattern in laying down the image screen, thereby maintaining maximum correspondence between the screen distribution pattern and the mask aperture pattern. Subsequently, the effective apertures in the mask or barrier structure are substantially enlarged to permit realization of the full advantages of post-deflection operation. At the same time, the process of the invention avoids the deposit of excessive material on the color-selection barrier and effectively precludes distortion which might arise from the use of such deposits as an incident to the manufacture of the image screen.
Figure 1, which illustrates an early step in the process, shows a sheet of conductive material suitable for use as a color-selection barrier in a color image reproducer. Sheet 10, may, for example, comprise a copper-nickel alloy or any other conductive material adapted for use as a color-selection electrode; one type of material which has been found well suited for this use comprises a 95-5 percent copper-nickel alloy approximately 0.0075 inch thick. At the start of the process, sheet 10 is coated on both sides with layers 11 and 12 of a photosensitive resist material such as bichromated glue or shellac. Resist coatings 11 and 12 are then processed photographically to produce a pattern of apertures 13 in each of the coatings; this aperture pattern corresponds to the distribution pattern desired for each color group of phosphor areas in the image screen of a color image reproducer. Moreover, apertures 13 should be of a size approximately equal to or somewhat smaller than the desired color phosphor areas. Because a wide variety of conventional photographic processes may be employed to establish the desired aperture pattern in coatings 11 and 12, and because the methods employed at this stage of the inventive process are not critical, no specific technique for forming apertures 13 need be described. Moreover, it will be understood that the resist coating, comp ete with the desired aperture pattern, may be directly applied to conductive sheet 10 by printing or other techniques well known in the graphic arts.
Figure 2 shows coated sheet 10 and illustrates the relationship between apertures 13 and the image-area pattern of the color picture tube screen. As indicated therein, the screen of the image reproducer comprises a multiplicity of minute color phosphor areas 14 deposited on a suitable substrate 15; substrate 15 is usually formed from glass or similar suitable transparent material and may comprise the faceplate of a cathode-ray tube envelope. Phosphor areas 14 comprises a plurality of distinct color groups; in the usual case, there are three color phosphor groups R, B and G which individually emit light corresponding to the additive primary colors red, blue and green respectively. As indicated in this figure, aperture pattern 13 corresponds to the distribu tion pattern of each of the color groups R, B and G; moreover, apertures 13 are of approximately the same size or slightly smaller than the individual phosphor areas 14.
In accordance with the process described and claimed in the aforesaid parent application, the coated sheet next is immersed in an etching solution and the uncoated portions of sheet 10 are etched away to form apertures corresponding to resist apertures 13 in the coated sheet; this etching step preferably is restricted so that no substantial portion of sheet 10 other than that exposed through apertures 13 is removed. The present inventive process also involves the etching of apertures in the coated sheet, but, as is described more fully below, the size of the apertures formed in this step of the process is markedly different; suflice it to say for the present that the uncoated portions of sheet 10 are etched away in both processes. The etching time, of course, is a function of the etching agent employed and of its concentration in the etching bath but may be readily determined by empirical methods for any given etchant and concentration. In one embodiment of the method claimed in the parent application, in which sheet 10 comprises the aforementioned copper-nickel alloy, a ferric chloride solution, approximately 42 percent Baum or 1.41 specific gravity, has given satisfactory results, the etching time being approximately 10 minutes, depending on the temperature of the etch bath.
In many picture tubes, it is desirable that the image screen substrate and the color-selection barrier be substantially spherical in configuration, since that configuration tends to minimize electron optical problems in the image reproducer. In applying the methods described in this and the parent application to the manufacture of a tube of this type, the resist-coated sheet 10 is placed in a suitable die comprising a pair of die sections 16 and 17, as shown in Figure 3. Die sections 16 and 17 are then forced together as indicated by arrows A to deform conductive sheet 10 to a predetermined configuration substantially similar to the configuration of the screen substrate of the image reproducer. In the usual case, the final configuration for sheet 10 is substantially spherical, although other barrier configurations may be employed if desired. Deformation of the conductive sheet may be accomplished before the sheet is coated with the resist material, although this is not usually desirable since it is ordinarily more convenient to apply the resist coating and to form aperture pattern 13 when conductive sheet 10 is substantially planar in configuration.
After coated sheet 10 has been deformed in die 16, 17, it is utilized as a master pattern to deposit the image screen comprising color phosphor areas 14 (Figure 2) upon a suitable substrate. This step in the process is generally illustrated in Figure 4, in which the substrate 15 is shown as the glass faceplate of a cathode-ray pic ture tube. Screen deposition may be accomp ished by a photographic process in which faceplate 15 is first coated with a layer 18 of photo-sensitive material. The coated and etched conductive sheet 10 is mounted in juxtaposition to the resist-coated faceplate, usually in the same position with respect to the faceplate as the conductive sheet will occupy when utilized as the colorselection barrier in the finished image reproducer. The photo-sensitive coating 18 is exposed from a light source 19, after which the coating is suitably developed and one of the phosphor area groups R, B or G is deposited on the developed resist image. This process is repeated two times to complete formation of the image screen. Because there are a number of different screen-deposition processes known in the art, any of which is quite suitable for use in conjunction with the invention, no specific screen formation techinque will be described.
For the process claimed in the parent application sheet next is mounted on a mold 20, as shown in Figure 5, after disposition of the image screen. Mold 20 has the same configuration as die section 16 and is preferably'formed of plaster or noncorrosive metal. Coated sheet 10 and mold 20 are then immersed in an etching solution 21 to etch away additional portions of the conductive sheet underneath the resist coating and form substantially larger apertures therein. It is usually desirable to stir etching solution 21 continuously, as by an agitator 22, in order to accelerate the etching process and obtain uniform results throughout the area of conductive sheet 10. Mounting of the conductive sheet on mold 20 prevents any distortion of the conductive sheet which might arise from agitation of the etching solution, although the supporting mold may be eliminated if little or no agitation of the etchant is required. For the copper-nickel sheet material noted above, a ferric chloride solution serves very satisfactorily as an etchant. After this second etch, resist coatings 11 and 12 are removed from conductive sheet 10, which may then be mounted in a cathode-ray tube envelope to serve as a color-selection barrier for the image screen formed in the process described in connection with Figure 4. The relative sizes of the apertures in the finished mask and the original apertures in the mask as used in the photographic process described in connection with Figure 4 are illustrated in Figure 2. As indicated in Figure 2, the final aperture size indicated by dash outlines 23 is usually of the order of twice as large as the original apertures 13. In a typical color image reproducer, apertures 13 are approximately 0.01 inch in diameter and image screen phosphor areas 14 have a diameter of approximately 0.014 inch, whereas in the final color-selection barrier apertures 23 have a diameter of approximately 0.019 inch. The second etching step for forming apertures 23 in this mask requires approximately ten minutes immersion in an etching bath comprising a 42 percent Baum ferric chloride solution, depending upon the temperature of the etch bath; spray etching techniques may also be employed in this step and in the original etching step.
The inventive processes provide color-selection barriers in which the apertures exhibit excellent uniformity in distribution and size. At the same time, the processes provide extremely accurate correspondence between the distribution patterns of the apertures and the color phosphor areas of the image screen. Shaping of the etched coated conductive sheet which later becomes the co orselection mask does not affect the quality and efficacy of conventional resist materials, so that there is no undue distortion of the aperture pattern when conductive sheet 10 is formed into the desired spherical shape. Of course, the processes may be utilized in the manufacture of color-selection barriers 'and image screens for picture tubes in which these elements are not of spherical configuration. For example, any other desired curved configuration may be employed without changing the process in any way. On the other hand the processes may be readily adapted to the manufacture of planar masks and screens, in which case the mask-deformation step described in connection with Figure 3 is omitted entirely.
In accordance with the present invention, only a single etching step is utilized in carrying out the complete process; it is not necessary to use two distinct etching steps. Instead, resist-coated sheet 10, which may first be deformed as described in connection with Figure 3, is etched completely to the extent indicated by dash lines 23 in Figure 2; that is, the etched screen apertures in conductive sheet 10 are indicated by the dashed lines 23 although the apertures in the opaque resist remain of the size indicated by solid lines 13. The etched conductive sheet is then employed as a master pattern in forming an image screen, as described in connection with Figure 4, after which it is only necessary to remove the resist coatings from conductive sheet 10. In the method of the present invention, resist coatings 11 and 12 must be substantially completely opaque to the radiation used in the screen-forming steps described in connection with Figure 4. While the resist coatings must be considerably more flexible than with the process claimed in the parent application, since otherwise they may crack or otherwise deform unequally when pressed into the desired spherical shape in die 16, 17, this method is more eincient and economical due to the complete elimination of the second etching step described in connection with the other process. Also eliminated is the need for mold 20 described above in connection with Figure 5. In addition, it is possible to carry out the inventive method by forming apertures 13 in only one of the resist coatings 11 and 12, in which case the unapertured coating is removed during the screen-forming process described in connection with Figure 4.
While a particular embodiment of the present invention has been described in detail, it is apparent that changes and modifications may be made without departing from the invention in its broader aspects. The aim of the appended claims, therefore, is to cover all such changes and modifications as fall within the true spirit and scope of the invention.
1. The method of manufacturing a color image reproducer of the type comprising an image screen including a multiplicity of minute areas of color phosphor material afiixed to a substrate and a color-selection barrier having an aperture pattern representative of the distribution pattern of one color group of said image screen areas, said method comprising the following steps: applying an opaque resist coating, having a first pattern of apertures individually of predetermined size corresponding to said distribution pattern, to a sheet of conductive material suitable for use as said barrier; immersing said coated sheet in an etching solution for a period of time sufiicient to form through said sheet a second pattern of apertures each of a size substantially larger than said predetermined size and individually centered about the apertures of said first pattern, said apertures of said second pattern extending beneath said opaque resist coating; mounting said etched coated sheet in predetermined spaced relation to said substrate; depositing a photographic resist coating on said substrate; exposing said photographic resist coating through said mounted etched coated sheet; dismounting said sheet and removing said opaque resist coating therefrom to expose said second pattern of apertures; afiixing said color phosphor material onto said substrate in a pattern determined by development of the exposed photographic resist; and mounting said sheet in predetermined spaced relation to said substrate and affixed phosphor material to dispose said second aperture pattern in color selecting position.
2. The method of manufacturing a color image reproducer of the type comprising an image screen including a multiplicity of minute areas of color phosphor material aflixed on a non-planar substrate and a color-selection barrier having an aperture pattern representative of the distribution pattern of one color groupof said image screen areas, said method comprising the following steps: applying an opaque resist coating, having a first pattern of apertures individually of predetermined size corresponding to said distribution pattern, to a sheet of conductive material suitable for use as said barrier; immersing said coated sheet in an etching solution for a period of time sufiicient to form through said sheet a second pattern of apertures each of a size substantially larger than said predetermined size and individually centered about the apertures of said first pattern, said apertures of said second pattern extending beneath said opaque resist coating; deforming said coated sheet to a predetermined configuration corresponding substantially to that of said nonplanar substrate; mounting said etched coated sheet in zoo-1,3 14- References Git'ed in the file of this patent UNITED STATES PATENTS Epstein Mar. 30, 1943 Law Jan. 20, 1953 Ramberg Dec. 20; 1955 Braham June 12, 1956 Farnsworth July 10. 1956 Morrell July 17, 1956 FOREIGN PATENTS Great Britain Aug. 18, 1954