Патент USA US3043985код для вставки
July 10, 1962 G. A. BURDICK 3,043,975 IMAGE DISPLAY DEVICE Filed Aug. 5, 1957 4 Sheets-Sheet 1 5m INVENTOR Y _ GLEN A; BURDICK BY ATTORNEY _ July 10, 1962 3,043,975 G. A. BURDICK IMAGE DISPLAY DEVICE Filed Aug. 5, 1957 4 Sheets-Sheet 2 Cu mm Urn INVENTOR GLEN A. BURDKIK BY ATTORNEY July 10, 1962 G. A. BURDlCK 3,043,975 IMAGE DISPLAY DEVICE Filed Aug. 5, 1957 4 Sheets-Sheet 3 TANGEIL H6. 5. INVENTOR GLEN A. BURDICK BY ATTORNEY July 10, 1962 G. A. BURDICK 3,043,975 IMAGE DISPLAY DEVICE Filed Aug. 5, 195'? 4 Sheets-Sheet 4 UGHT AX\S TUBE AX\S \ RADIAL NVENTOR TANG'ENTIAL 4 ' F \G.7. GLEN A.'suR-mc\< - .?jaktim ATTORNEY 3,043,975 United States Patent ice Patented July 10, 1962 1 , 2 tern has a prescribed relationship relative to the distance , 3,043,975 , IMAGE DISPLAY DEVICE ' between the center of the associated spot pattern and ad I joining spot patterns. An exposure device and manufac 7 Glen A. Burdick, Waterloo, N.Y., assignor, by mesne a_s turing process are providedto produce a screen having a plurality of discrete display areas‘, the location of each discrete area being positioned in a prescribed relationship to the impinging beam positions vfora given de?ection ' s'ignments, to Sylvania Electric Products Inc., Wil ming'ton, Del., a corporation of. Delaware _' Filed Aug. 5, 1957, Ser. No. 676,331 2 Claims. (Cl. 313-92) angle. ". , <1 . For a better understanding of the-invention, reference This invention relates to image display devices and more particularly to cathode ray tubes of the type adapted 10 is made to the following description, taken in conjunction with the accompanying drawings in which: ' to be employed in color television apparatus. 1, FIG. 1 is a plan view of a typical cathode ray tube One of the chief problems encountered in the produc adapted for the reproduction of color images; ' tion of screens for image display color tubes such as those FIG. 2 illustrates the manner in which the electron used in television apparatus involves “matching” of the light optics employed in the screen forming process with 15 beams are dynamically converged in the-tube; . FIG. 3 shows a portion of an image-display structure the electron optics existent in the ?nished tube. Unless the discrete image display elements on the screen are posi- ' illustrating one embodiment ofthe invention; 1 ‘FIG. '4 illustrates the spatial relationship between beam tioned so that the scanning electron beam or beams will correctly register therewith, an impure or otherwise un acceptable color image will result. Some of these reg impinging spot patterns formed in accordancexwith one 20 aspect of the invention; , ‘ - ' ~ I FIG. 5 shows a portion of acathode ray tube screen; . FIG. 6 illustrates the optical system employed in the istration problems and their solutions, along with light optical structures and processes for forming the screen, are discussed in detail in the co-pending application, S.N. screen forming process; ' ' ' I ' FIG. 7 is an enlarged view of a portion of. the discrete 595,144, entitled “Cathode Ray Tube Structure and Proc ess,” Glen A. Burdick, which is assigned to the same 25 image display con?gurationsvshowing the beam imping ing spots located thereon; and , FIG. 8 illustrates the relationship between the image assignee as the present invention. This invention is con cerned in part, with that portion of the registration prob lem createdby dynamic convergence of the electron beams employed in the tube. _ . It is the present practice in television art to use a con display areas and the electron vbeam impinging positions; Referring to the drawings, FIG. 1 shows a typical plural 30 beam shadow mask type cathode ray tube. Disposed with in envelope 11 are three electron emitters 12 positioned approximately 120° apart to provide three electron‘ beams . with a multiple beam color tube so that the beams can 13 which may be de?ected by coils 15 over the raster be moved relative to each other in the de?ection region area and converged at mask 17 to impingeiupon screen in’accordance with the de?ection angle and direction of the beam or beams at a given instant. The mask or grid 35 19. The screen comprises a large number of triads, each rtriad consisting of, discrete areas or elements of red, utilized in the tube generally has a spacing from the screen green and blue color ?uorescing ‘materials which are posi such that the electron beams will cross one another at the tioned at the intercepting points‘of', the appropriate one mask and impinge upon the screen without overlap. This of the electron beams 13‘ employed in the tube. Although mask is constructed so that the spacing from the center of the‘ mask to the screen is less than the spacing between 40 a tri-gun shadow mask tube is shown in FIG. *1, it will be apparent that the invention described herein is also these structures along their edges. However, with such a tinuously varying beam convergence ?eld in conjunction applicable to other plural beam types of image reproduc construction, the beam impinging spots for any given pattern are separated by agreater distance over certain tion devices. " ' In order to have the electron beams 13 ‘converge at the apertures in grid 17 over the entire screen, dynamic con tain a reasonable semblance of color purity in the tube, vergence magnets 21 are conventionally employed. Two the discrete image display elements or areas are so posi of the three beams used in a shadow mask cathode ray tioned that at least a small portion of each display area tube are shown in FIG. 2 to illustrate the dynamic con‘ will cover the associated electron beam impinging spot on the screen. The image display so produced is not 50 vergence e?ect-s. The static convergence beam paths pass through points ‘a and b in the de?e'ction‘region and pro’; uniform in appearance nor does it give good'color uni lceed toward mask 17 and screen :19 at an angle. to the formity. Due to the critical design, manufacturing tol tube axis to converge at point g: ‘When the beams 13 erances are extremely rigid and the tube operational set are de?ected to some-angle alpha (ix) withoutthe aid'of up requires a variety of controls and is very costly ‘and areas of the screen than over other areas. In order to ob 45 65 dynamic convergence ?elds supplied by-coils 21, the beams appear to ‘originate from- p'oints a" and b’ and intersect at point c. ‘This situation is highly‘ unsatisfactory. In prac@ tice, the coils 21 provide'rna-gnetic' ?elds which move tirnum display area with good electron beam registration, . improved color uniformity, and a uniform'appearing - the beams 13‘ radially outward inlthede?ection region to time consuming. ' , Accordingly, an object of. this invention is to reduce the aforementioned disadvantages and to-provide an op screen for an image display device. I A further object is to reduce the necessityv for critical control of manufacturing tolerances in the fabrication of 60 cause beams 13 to appear to come fromzpoints' e and f to provide the desired convergence at point gf ‘within an aperture in mask 17. The points ve and f designate posi image displays and to increase the operational set-up e?i tions which-are approximately on‘the locus of motion of ciency for such devices. the apparent center of de?ection for each beam 13 as more I . . Another object is to fabricate improved image display 65 fully described in the above mentioned Burdick applica screens and tubes. 1 tion;v ‘ ‘Q ' . . . ' ' It has been the practice to use a mask' 17 which has a The foregoing objects are achieved in one aspect of the invention by the provision of an image display tube spacing dllat the center/of the mask betweenjthe mask and screen 19 which is less than the‘ spacing d; at the in which the electron beam impinging spot pattern asso ciated with a given image display pattern is such that 70 edge of the mask. This construction, in conjunction with the average distance between the center of a given beam impingingspot and the center of the associated spot pat dynamic convergence,'may produce an electron beam and ?uorescent dot registration of the type shown in FIG. '2' 3,043,975 ' displaced from the screen. The electron beams 13' may be separated by a considerable distance at the edges of less than the radial dimension, it is used as a basis for the the screen,_as shown, or they may be separated or pulled triad pattern should “?t” into the smallest beam triad pattern so that there will not be an overlap of phosphor entire mask toward'orraway from the screen in a manner well understood inthe art. In any event, a tube having this'type of structure produces a-beam pattern» which dots on the screen. beam spot and phosphor dot patterns. The phosphor dot together at other lpreésele'ctedvpositions vby moving the ' FIG. 5 illustrates the derivation of the‘ average beam spots centers, R, B, G, R’, B’, and G" shown in ,FIG. 4. has given areas’ wherein the beams are undesirably sep arated‘ or pulled’ together.- This situationtcauses the Three locations on screen 19 are indicated at 3 o’clock, 7 o’clock and 11 o’clock for a de?ection angle of 33 beams to impinge upon ther?uorescent dots very close to 10 degrees. The sum of 12 numbers of B-O distances, i.e. their borderseat those locations on the screen where the beams.v are adversely affected to the greatest extent. by. n. is +B3-—O3 approximately + . . .equal Brr-f-oq to one-third + . . the B11——011' tangential dis _ tance between the centers of adjoining triads, e.g. dimen i In order'to improve the beam landing position pattern uniformity over the“ screen and the spacing between the sion O7—O7I.' This relationship exists for all R, B and beamimpinging positions in a given triad, it has been 15 G beam spots located on each de?ection radius over the entire screen to provideanimproved beam spot pattern; found that the mask curvature should‘be such that the spacing'sl', FIGJ3, along the tube axis or central portion, It has been found that for a 22 inch 70 degree de?ec-e tion shadow mask color tube, a spacing s1 equal to .530 inch varying to an edge spacing of 52 of .491 inch pro structure takesinto account the non-linearity of the ?elds 20 vides the pattern illustrated in FIG. 5. Such a spacing should be greater than the spacing s2 at the edges or pe riphe‘ral. portions of the grid 17.‘ This grid or mask provided‘ by yoke coils 21, the amount of beam displace mentneededf in the ‘tube for dynamic convergence, and may be ‘achieved by forming the mask 17 with'a radius of curvature substantially equal to the 26‘ inch radius used the geometric con?gurations and spatial relationships of forlthe screen surface. Generally, the center of the mask radius is positioned farther from the screen than the cen-" the gun electrodes 12, screenI19,‘ etc. Since the grid or maskl17>and screen 19 are generally curvilinear in form, 25 ter of the screen radius so that even if the ‘mask and this spacing may be such that the'grid to screen distance screen have the same or a slightly smaller or larger radi measured along the electron beam path varies inversely to us, the peripheral portions of the mask will be- closer'to, the7distance-between' the apparent source of the electron the screen than the central portions. ‘7 beams, e.g. points e and f, and the‘ tube axis. To satisfy An optical exposure device such as that shown in FIG. thiscondition, the structural relationship between the grid and ‘screen should be such that their surfaces will inter 30 6 is used to produce an image display screen wherein the discrete fluorescent dots or areas have maximum cov erage without overlap, i.e. minimumspace between areas, a ' ‘ A grid to screen spacing of the type shown in FIG. 3 l ; while also providing a maximum border of?uorescent material around each beam impinging position or spot will providea unique pattern of'beam spots over'the en sect-if projected. . - the screen. ‘To illustrate this pattern, FIG. 4 shows two 35 when thelspot patternis of the type shown in FIG. 5. Although the above mentioned Burdick application ex-lv adjoining average triads spaced from one another in a ' tangential direction“ The individual average beam po sitions in an'average triad at a given de?ection angle rela 'tive tov the center ,ofthe» triad,'and the relationship be- ' tweeniadjoiuing average triads may be expressed‘in terms 40 plains in detail the method of forming a ?uorescent-screen by a photo-printing process, it will. be discussed here briefly.v In this process, a light hardenable photo-sensi tive material such, as polyvinyl alcohol sensitized with - ammonium dichromate and an appropriate ?uorescent ofv distances measured from the triad centers 0 and 0'. This beam spot pattern is such that for any given triad _. _ material such as the 'red phosphor, zinc phosphate, are de de?ection angle, the average distance from a given beam posited on the glass panel 25. Discrete areas of this coat spot to the center of its associated beam spot triad is ap ing are then exposed to light rays radiated from a point proximately one-third the tangential distance between the 45 source light transmitter 27 through the lens 29 and through‘ apertures in a'negative or grid 17. The areas 23 center of the.‘ associatedtriad and the center of an ad been used to designate the averagecenters of two groups of the ‘sensitized-‘coating which are exposed to light be come hardened and adhere to’ the glass envelope While the of impinging spots provided by the red, green‘ and blue unexposed portions arepremoved by a developing ?uid joining triad. ' In' FIG. 4, the letters R, B and G have > - chroma modulatedbeams representingall locations on 50 such as deionized water. The above process is then re peated using the blue and green phosphors, with proper the screen de?ned by one de?ection angle.‘ For instance, at ca 331degreede?ectioniangle for triad ‘T, the distance - . oif-setting of the transmitterand lens with each exposure‘ B—'—O is: approximately equal to‘ one-third the tangential operation to provide the complete image display screen. distance>'O—,-O’. This ‘relationship is also true for the Zinc ortho-silicate'is one example-of an acceptable green ‘ R-0 and G-O distances in. triad T in additionto the 55 phosphor‘material while zinc sul?de is at present consid; ered to be a satisfactory blue phosphor; FIG. ' " shows an optica-lsystem associated with one ' used Theto tangential de?ne the relative distance triadpositions between beamsince spotit triads is a less is beam position‘ ofa multiple beam tube which is capable constant dimension over jthe*'screen than the radial 'di-‘ of positioning the discrete screen elements 23 at the locai mension and since it-may-be expressed in terms of a 60 tion where the beams 13 will land by substantially supere simple relationship. 1 FIGS. 1, 2 .and 3 illustrate the ' imposing‘ in space the locusrof motion of apparent light manner in which the‘ electron beams are converged at an ' ray origin upon the locus of motion of apparent center aperture in mask 17 to cross one another and impinge upon screen 19 to form a triad of beam spots; The rela-' tive positions of adjoining triads are therefore dependent, 65 in part, upon the relative positions of-the-apertures in mask 17. ‘It is wellfknown that vthe mask "is stretched ' ; ‘of de?ection} of thelelectron beam. This relationship is accomplished‘ by cit-setting light source 27 from the tube non-uniformly in a tangential direction during fabrica ‘utilized in the‘screen forming process is’ located in. space tion, \with the distance‘ ‘between adjoining maskrapertures "axis a distance p and ‘elf-setting lens :29 a distance 'r and an angle beta ( 13) fromthe axis of the transmitter. With this arrangement, "the locus 32 of apparent light ray origin at substantially the same position relative to the screen ,decreasingfpro'gressively ‘toward the mask‘ periphery.‘ 70 and mask as is the locus 33 of the electron beam apparent Consequently, the beam spot triad distances also tend" to center of de?ection in the operating tube. Although the decrease in this direction; However, mask stretch‘ does ' light rays 26 originated from the tip of transmitter 27, not have an appreciable ‘non-uniform, effect upon‘the ra they appear‘to comerfrom apoint on locus 33, when dial dimensions between mask apertures or spot triads,‘ viewedfrom' the screen, since they are refracted by the and, since the tangential distance is usually equal to or 75 plano-concave symmetrical lens 29. The amount of off 3,043,975 6 5 that an increase in o?set will allow a reduction in tilt and vice versa to achieve similar results. In addition, mask con?guration has been illustrated in FIG. 3 to pro vide a more symmetrical and uniform beam impinging spot pattern as illustrated in FIGS. 4 and 5. In addition, although a symmetrical planoconcave lens is shown, other types of lens elements could be employed in conjunction with the correct positioning of transmitter 27 and the 6 is adapted to form a phosphor dot pattern (FIGS. 7 and 8) which registers with the beam spot pattern to duce the improved phosphor dot pattern for this tube. port having discrete light emitting areas arranged thereon ‘by the optical system shown in FIG. 6,‘ when it has the ideal combination of tilt and off-set, that the discrete spaced from one another radially outwardly from the center of said curved support and disposed substantially set and tilt of lens 29 are inter-related in such a manner a process and exposure device such ‘as that shown in FIG. provide a highly satisfactory image display. lens 29 relative to one another and to the mask 17 and Although several embodiments of the invention have the axis of the tube to achieve the desired results. For been shown anddescribed, it will be apparent to those instance, an asymmetrical and/ or an aspherical lens could be used in this system with little or no tilt, if de 10 skilled in the art that various changes and modi?cations may be made therein without departing from the scope sired. It has been found that for a 22 inch shadow of the invention as de?ned by the appended claims. mask tube of the type described above, the application What is claimed is: of a 90 millimeter diameter plano-concave lens 29 with 1. A cathode ray tube of the type adapted to employ a center thickness of .45 centimeter and a radius of curva ture equal to 23.55 centimeters spaced from transmitter 15 a plurality of dynamically converged electron beams directed to'be de?ected over and impinge upon an image 27 a distance of 1.875 inches, offset a distance r of .265 display screen, said screen comprising a curvilinear sup inch and tilted an angle beta (,8) of 3 degrees will pro to form a plurality of patterns located in radial and tan Referring to FIG. 7 it can be seen that the discrete image display phosphor areas or dots 23 are so positioned 20 gential relationships with one another, said patterns being tangent with one another in a tangential direction extend areas are substantially tangent in a tangential direction to provide maximum coverage of the panel 25 in addition ‘ ing normal to the radial direction, said patterns varying to substantially increasing the uniformity of brightness 25 in spacing from each other in said radial direction to locate each discrete area substantially coincident with the and quality of the reproduced image while providing average location of the center of the impinging beam at color pattern uniformity with a minimum amount of color impurity. The relationship between the beam im pinging spots or positions 13 and the discrete phosphor each de?ection angle. 2. A cathode ray tube of the type adapted to employ on the screen located at a given radius from the axis of display screen, said screen comprising a curvilinear sup dots 23 on the screen is clearly shown in FIGS. 7 and 8. 30 a plurality of dynamically converged electron beams ‘directed to be de?ected over and impinge upon an image For any given de?ection angle, i.e. for those positions port having discrete light emitting areas arranged thereon to form a plurality of triad patterns located in radial and substantially coincident with the location of the average centers y of the impinging beam spots \13. The beam 35 tangential relationships with one another, said triad pat terns being spaced from one another radially outwardly positions shown by solid lines in FIG. 8 indicate one from the center of said curved support and disposed sub location on the screen, e.g. a 36 degree de?ection angle stantially tangent with one another in a tangential direc at 3 o’clock. Disposed exactly opposite (in dotted lines) tion extending normal to the radial direction, the radial to the positions shown by the solid lines would be the location of the beam spots ‘13 at a 36 degree de?ection 40 spacing between triad patterns increasing with increased the screen, the centers as of the areas 23 are positioned angle and at 6 o’clock. Therefore, it can be seen that the centers x of discrete phosphor areas 23 are substantially coincident with the average centers y of the spots 13 at all locations on a given screen radius or for a given de ?ection angle. Such an arrangement provides improved 45 registration over the entire screen and minimizes the rescent dots 23 is shown to consist of red, green and blue 50 ?uorescing dot triads which are substantially contiguous in a tangential direction and are separated from one an other in the radial direction for reasons explained more fully in conjunction with FIGS. 4 and 5. That is, if a line is drawn from the center of the screen radially out ‘ye with increasing de?ection angle whereas the adjacent References Cited in the ?le of this patent UNITED STATES PATENTS possibility of color impurity in the reproduced image. Referring particularly to FIG. 7, the pattern of ?uo ward, the successive triads which the line intercepts will be separated from one another by increasing amounts radial distance from the center of said screen, said triad patterns being formed to locate each discrete area sub stantially coincident with the average location of the cen ter of the impinging beam at each de?ection angle. 55 2,416,056 2,745,978 2,795,719 2,795,720 2,801,355 2,817,276 2,823,254 2,855,529 Kallmann ______________ __ Feb. 18, Van Ormer ___________ _.. May 15, Morrell ______________ __ June 11, Epstein ______________ _.. June 11, Nunan ________________ __ July 30, Epstein ______________ __ Dec. 24, 1947 1956 1957 1957 1957 1957 Heuer _______________ __ Feb. 11, 1958 Morrell _______________ __ Oct. 7, 1958 2,885,935 Epstein ______________ __ May 12, 1959 OTHER REFERENCES triads lying along a line tangent to the radial line will be substantially contiguous to one another. This type 60 RCA Publication, Recent Improvements in the of phosphor pattern achieves maximum coverage of face 21AXP22 Color Kinescope, by R. B. J-anes, L. B. Head plate 25 without overlap. It is apparent from the foregoing description that a rick, and J. Evans, printed June 195 6.