US3476025A - Cathode ray tube and method of manufacture - Google Patents

Cathode ray tube and method of manufacture Download PDF

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US3476025A
US3476025A US557663A US3476025DA US3476025A US 3476025 A US3476025 A US 3476025A US 557663 A US557663 A US 557663A US 3476025D A US3476025D A US 3476025DA US 3476025 A US3476025 A US 3476025A
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screen
lens
misregister
mask
phosphor
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Fred Herzfeld
Frans Van Hekken
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RCA Corp
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RCA Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/20—Manufacture of screens on or from which an image or pattern is formed, picked up, converted or stored; Applying coatings to the vessel
    • H01J9/22—Applying luminescent coatings
    • H01J9/227—Applying luminescent coatings with luminescent material discontinuously arranged, e.g. in dots or lines
    • H01J9/2271—Applying luminescent coatings with luminescent material discontinuously arranged, e.g. in dots or lines by photographic processes
    • H01J9/2272—Devices for carrying out the processes, e.g. light houses

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  • a shadow mask type color picture tube mosaic screen pattern is laid down by means of a lighthouse including a light refracting element or lens having an analytical surface approximating the theoretical lens surface required to provide misregister compensation at each of -a multiplicity of points distributed over the entire surface of the screen as determined from misregister measurements ⁇ at those points on the screen of an uncompensated color tube.
  • the lens may be formed by sagging a plate of glass onto a mold fabricated by numerical control milling techniques. The lens surface has no symmetry.
  • This invention relates to cathode ray tubes, and to the manufacture thereof, and particularly to shadow mask type color cathode ray tubes comprising a plurality of electron guns, a multi-apertured shadow mask, and a mosaic screen of systematically arrayed color phosphor deposits, or dots.
  • the phosphor dots of the screen of such a tube may be laid down in trios (groups of three dots of different coloremitting phosphors) by a direct photographic printing technique wherein a photosensitive coating on the faceplate panel of the tube is exposed through the apertures of the mask by a point source of light, and the coating is then developed, as by washing off the unhardened unexposed portions, leaving the desired pattern of exposed hardened dots. This process is repeated for each color.
  • the shadow mask is preferably detachably mounted on the faceplate panel so that it can be easily removed and replaced in exactly the same position every time.
  • Phosphor powder may, e.g., be mixed directly with each photosensitive coating before application to the faceplate, or else applied to the coating after the latter has been eX- posed.
  • the electron beams are subjected to forces such as scanning (i.e. horizontal and vertical deflection) and dynamic convergence (to maintain convergence of the beams near the screen at various angles of deflection), which affect the electron beam paths (and hence, the landing points or spots of the beams on the screen) in ways that the screen-printing light rays are not affected.
  • forces such as scanning (i.e. horizontal and vertical deflection) and dynamic convergence (to maintain convergence of the beams near the screen at various angles of deflection), which affect the electron beam paths (and hence, the landing points or spots of the beams on the screen) in ways that the screen-printing light rays are not affected.
  • scanning i.e. horizontal and vertical deflection
  • dynamic convergence to maintain convergence of the beams near the screen at various angles of deflection
  • radial misregister of the type wherein a trio of beam spots is shifted as a unit radially outward from its associated dot trio, caused by an axial shift of the deflection centers of the beams toward the screen with increasing angles of deection, is termed radial misregister.
  • degrouping misregister of the type wherein the individual spots of a spot trio are all three moved away from each other, caused primarily by dynamic convergence forces, is termed degrouping misregister.
  • misregister of the type wherein the beam spots of a spot trio are distorted away from equilateralism because of nonuniformities of the raster scanning deflection fields and/ or the phosphor dots of atrio are distorted away from equilateralism because of inherent characteristics of the dot printing system, is termed astigmatic misregister.
  • Misregister of the type wherein a phosphor dot and its associated beam spot are individually moved different distances relative to the centers of their respective trios due to an apparent decrease of the spacing of the dot printing light sources and of the electron beams from the central axis at increasing angles of deflection, is termed foreshortening misregister.
  • misregister of the spots and dots include the effect of the earths magnetic field upon the paths of the electron beams, and the effect of distortion of the faceplate when the tube is evacuated.
  • That patent teaches that best correction for degrouping and radial misregister can be obtained by (a) using a mask-to-screen assembly such that the spacing between the mask and screen varies in a particular manner from a maximum at the central axis to a minimum at a given radius near the edge of the assembly, and (b) interposing, in the path of light from the light source to the mask in the screen printing apparatus, or lighthouse, a special light refracting device, or lens, having a single central plane of symmetry.
  • the contour of the lens along the diametrical section perpendicular to this plane is determined by measuring the average radial misregister of the spots and dots on the screen of an evacuated tube, calculating the rate of change in thickness of a lens along this section necessary to correct or compensate for the measured misregister and fitting an odd power polynomial to the rate of change values.
  • the contour of the lens at all other points is calculated by multiplying the odd powers of the polynomial by the cosine of the azimuthal angle with respect to the plane of symmetry and adding the even powers of the polynomial thereto. The result is a lens that is relatively simple to fabricate by known grinding methods.
  • such a lens provides acceptable compensation for beam path distortion, and hence acceptable register of the beam spots and phosphor dots in color tubes having a maximum beam defiection angle of 70, only along said line of symmetry.
  • maximum deflection angles e.g. and non-circular shape, e.g. rectangular
  • the amount of misregister produced in regions not on the line of symmetry in tubes made with such lenses exceeds desirable tolerances.
  • an object of the present invention is to provide an improved cathode ray tube of the shadow mask type wherein the phosphor dots are laid down by a light printing process in which acceptable register of the beam spots and phosphor dots is obtained over the entire screen of the tube.
  • Another object of the invention is to provide an improved method of photographically printing the phosphor dot screen of a shadow mask type cathode ray tube which will exhibit acceptable register of the beam spots and phosphor dots over the entire surface of the screen.
  • Still another object is to provide an improved method of making an improved corrective lens to be used in the manufacture of phosphor dot screens of shadow mask type cathode ray tubes.
  • the phosphor dot screen of the tube by means of a light house including one or more special lenses designed to produce acceptable correction or compensation for all of the causes of misregister over the entire surface of the screen.
  • a different lens is used to print the dot pattern for each color.
  • the invention could be used to make a dot screen for a tube having only one beam and one kind of phosphor dot.
  • the improved lens for use in printing one color dot pattern on the screenplate of a tube of given kind as, for example, a 19" rectangular color kinescope with 90 deflection may be made by the following steps:
  • a phosphor dot pattern is printed on the faceplate according to prior art techniques, by applying a photosensitive layer to the faceplate, assembling the screenplate and mask in predetermined spaced relation on a lighthouse, exposing the photosensitive layer to light rays passing through the mask aperatures, and developing the layer to remove the unexposed portions;
  • the tube is operated, with an electron beam scanning the printed dot pattern, and the direction and amount of misregister of the beam spots and corresponding phosphor dots is measured at each of a multiplicity of points distributed over the entire surface of the screen;
  • the total number of data points may be multiplied, e.g. to 250-300 points, by interpolating additional data points located between the measured points;
  • step (7 The theoretical lens surface of step (7 is approximated by fitting a bivariant polynomial to the calculated slopes or normal vectors to obtain a description of a continuous surface of the lens to be made;
  • Tme bi-variant polynomial surface description of step 8) is converted to one or more tapes for controlling a numerical-control (NC) milling machine;
  • a lens mold is fabricated by the NC machine and tape to the desired lens surface
  • the printing step (3) could be carried out with no lens used in the lighthouse, in which case the lens produced could be used alone in a lighthouse to print the phosphor screen (one color) for a commercial tube.
  • the method is preferably practiced by using at least one lens of known configuration in step (3), in which case the description of this lens is incorporated in step (7), and the resulting new lens is used in combination with the first lens to make commercial tubes.
  • one or more lenses could be used in step (3) Vand a new lens could be fabricated to be substituted for one or more of the first lenses in manufacturing tubes, which new lens would incorporate the refractive properties of the original lens of step (3).
  • step (3) is repeated to print each color dot patem prior to step (4), and the misregister measurements of step are preferably made simultaneously for all three colors.
  • the subsequent steps are carried out independently for each color, to produce three different lenses, one for each color.
  • each final lens resulting from the process described briefly above is tested, before being used commercially, by using it to print a dot pattern on the faceplate of an experimental tube, operating the tube, and again measuring the misregister at the same or different points. In most cases, the amount of misregister is within predetermined limits or tolerances, and hence, commercially acceptable. In the event that the residual misregister in this test is not acceptable, the entire process is repeated, using in step (3) the last lens fabricated, to produce a new lens capable of producing tubes with acceptable register over the screen surface.
  • FIG. l is a schematic illustration of a three-beam shadow mask cathode ray tube showing the causes of radial and degrouping spot-dot misregister;
  • FIG. 2 is a partial axial section of a lighthouse apparatus that may be used in practicing the method of the invention
  • FIG. 3 is a plan view of cathode ray tube faceplate showing a distribution of points at which misregister may be measured;
  • FIGS. 4 and 5 are schematic views, partly in section in the plane of FIG. 2, to be used in explaining the dot printing operation;
  • FIG. 6 is a transverse section through a lens mold made according to the invention and a glass plate to be sagged onto the mold;
  • FIG. 7 is a view similar to FIG. 6 after the sagging operation.
  • FIG. 8 is a transverse section of the finished lens.
  • FIG. 1 illustrates a cathode ray tube of the type described which comprises an envelope 10 containing therein three electron guns 11, 12 and 13, which may, for example, be disposed co-planar or in a triangular array, for projecting three electron beams towards a faceplate panel 14.
  • a delta triangular array symmetrically disposed about the central axis A-A of the tube is preferred.
  • a shadow mask 15 is usually formed with a multiplicity of apertures 15a systematically hexagonally arrayed thereover; and a mosaic screen 14a is provided on the faceplate 14 comprising a multiplicity of phosphor dots similarly arrayed, with a trio of three dots, each of a different color emitting phosphor, being provided for each aperture 15a in the mask 15.
  • three separate electron beams are projected from the three guns 11, 12 and 13 and are directed to be converged to a cross-over point near the screen 14a by virtue of the mechanical disposition of the guns and/or convergence forces generated by convergence means 16.
  • the three beams approach the mask 15 and portions thereof pass through the mask apertures 15a and excite the different color-emitting dots of the same dot trio.
  • the numerals 18, 20 and 22 indicate the paths of three beams passing through a central aperture of the mask.
  • the centers of deflection 24, 25 and 26 of the beams 18, 20 and 22 lie in a plane P-P perpendicular to the central tube axis A-A, which is referred to as the plane of deflection of the tube.
  • the beams When the beams are deflected away from the paths 18, 20 and 22 to e.g., the beam paths 28, 29 and 30, the beams would, in the absence of dynamic convergence forces being applied thereto, converge to a cross-over before they reach the screen 14a, because of the greater distances between the centers of deflections and the screen.
  • the beams are spread apart, by dynamic convergence forces established by convergence means 16.
  • the dashed lines 2S and 30' illustrate the spreading of the beams from guns 11 and 13 by convergence means 16 when the beams are deflected to follow paths 28 and 3).
  • the center of deflection is defined as the point of intersection of the beam path through the central aperture and the rearward extension of the beam path in the region beyond the influence of the defleeting field.
  • the deflection centers of the deflected beams following paths 28, 29 and 30 are respectively indicated by points 32, 33 and 34 in FIG. 1.
  • the trio of beam spots will be spread apart, or degrouped, at the outer portions of the screen 14a. Unless compensated for, the trios of beam spots will be larger than the printed phosphor dots at the outer edge of the screen, causing degrouping misregister. Both radial and degrouping misregister increase as a function of increasing distance from the center of the screen.
  • FIG. 2 illustrates a typical lighthouse apparatus of the type normally used for printing a phosphor dot screen of a cathode ray tube.
  • the lighthouse 110 comprises an open-top cabinet 111 having a shoulder 112 on which the bowl-shaped faceplate panel 14 of the cathode ray tube is disposed.
  • the panel 14 is adapted to be subsequently sealed at its open end 115 to another member (not shown in FIG. 2) to form a completed cathode ray tube bulb.
  • the panel 14 includes a surface 14b for supporting the phosphor screen 14a of FIG. 1 and a plurality of studs 118 on which the apertured shadow lrnask 1,5 (FTG. 1) can be removably mounted.
  • FSG. 1 apertured shadow lrnask 1,5
  • the surface 14h Prior to mounting the panel 14 on the cabinet 111, the surface 14h is coated with a conventional photoresist material, such as polyvinyl alcohol sensitized with ammonium dichromate.
  • a conventional photoresist material such as polyvinyl alcohol sensitized with ammonium dichromate.
  • bosses 119 On the external surface of the panel 14 are a plurality of bosses 119 which cooperate with mating recesses in the cabinet 111, whereby the panel 14 may be positioned in a prescribed orientation on the lighthouse 110.
  • a housing 120 which contains a lamp 121 and a tapered light conductor or collimator 122.
  • the lamp 21 may, for example, be an ultraviolet light emitting device such as a General Electric Company 1 kilowatt, high pressure, mercury arc lamp, Type BH6.
  • the collimator 122 is positioned above the UV lamp 121 and tapers away therefrom to a small area point 124.
  • the point 124 is positioned in a selected plane of deflection at a predetermined distance d from the central axis A-A of the panel 14.
  • the section of FIG. 2 is taken in the plane passing through the central axis A-A and the point source 124.
  • the housing 120 may, as shown, be mounted on a rotatable table 125 which can be indexed at a plurality of predetermined positions.
  • Means 126 including a spring-loaded plunger is provided which cooperates with mating depressions in the rim of the table 125 to fix the table in these positions.
  • Such indexing of the table 125 and housing 1201 is designed to selectively position the light source 124 at a different location for each of the dot-printing exposures required.
  • a support bracket 127 disposed between the light source 124 and the panel 14 is supported on a plurality of legs 128 from the table 125.
  • the bracket 127 has an opening 129 therein, opposite the light source 124, across which a light refracting element or lens 130 may be disposed.
  • the lens 130 is thus maintained in a fixed angular relationship to the light source 124 when the latter is moved.
  • the table may be omitted, the housing .120 mounted directly on the base of cabinet 111, and the bracket 127 mounted directly on the wall of the cabinet.
  • the light source 124 and lens are fixed.
  • a plurality of such light-houses 110 ⁇ are then provided for making the plurality of required dot printing exposures on a given faceplate panel 14.
  • the light source for each phosphor dot exposure is located substantially at a position termed the first order color center of the beam.
  • the lirst order color center may be defined as the intersection of a line extending through the center of a given phosphor dot and its associated mask aperture with the plane of deflection associated with the given phosphor dot.
  • the term associated aperture refers to the same aperture that the beam passes through to excite the given phosphor dot.
  • the present invention may be used with either first or higher order color center printing.
  • first order color center printing will be used for simplicity.
  • the lens 130 in FIG. 2 could be any known lens which is usable for partial correction or compensation of the various beam or printing errors involved.
  • a lens is selected which is known to produce as much correction as possible, thereby minimizing the additional correction required.
  • lens 130 is a known lens fabricated according to the Epstein et al. Patent 2,885,935 to provide substantial correction for both radial and degrouping errors along its line of symmetry.
  • the first step in the process of developing a new lens for a new tube type is the selection and/or fabrication of a faceplate panel 14 of given contour.
  • the faceplates for the 19 and V15" tubes are nearly spherical, as compared to the complex contour of the earlier 25" tube faceplates.
  • the internal surface 14b may have a spherical radius of 26.812 inches.
  • a shadow mask 15 for use with the chosen faceplate 14 is fabricated.
  • the contour of the mask 15 is made such that when mounted on the panel the spacing q therebetween, as measured along the beam path, varies from a predetermined maximum value, e.g., about .4 inch, at the center to a predetermined smaller value at a given radius near the edge of the screen.
  • the variation in q' is preferably such that, after correction for all errors, the size of the beam spot trios and phosphor dot trios is substantially the same over the entire screen surface.
  • a mask having a spherical radius of 27.27 inches may be used with the panel radius given above.
  • the selected panel 14 and mask 15 are mounted in the lighthouse with the lens 130, as in FIG. 2, with a photosensitive coating on the faceplate surface 14b, and a dot pattern is printed and developed in conventional manner on the surface 14b. This may, for example, be the green-emitting dot pattern. Then, the printing process may be repeated to add the red and blue dot patterns.
  • the same lens 130 may be used for each pattern in this step, if desired.
  • the assembly of the printed panel 14 and mask 15 is then combined with the bulb funnel, stem and other parts, and processed to produce an operative, evacuated, shadow mask color tube.
  • the tube is operated in normal manner, scanning the screen with the beam (or beams, if all three colors are screened), and the misregister between the electron spots and phosphor dots is measured at a multiplicity of points or locations distributed over the entire face of the tube.
  • FIG. 3 shows an example of a distribution of points P1, P2, P3, etc., on the faceplate 14 at which the misregister may be measured.
  • the points shown are systematically arranged on circles concentric with the axis A-A of FIGS. 1 and 2, and on radial lines at the various clock positions. At each point, the measurement includes the three-dimensional location of the point in space, and the magnitude and three dimensional direction of the misregister.
  • One method that can be used to measure and record the misregister is as follows. At each of 63 points distributed over the screen, a photomicrograph is taken of a small group of phosphor dots during operation of the tube. The points are recorded by clock positions, which are later converted to azimuthal angles in radians ⁇ from a given axis. Each photograph cover an area of about 6 by 7 rows of dots. First, the centers of three pairs of phosphor dots and electron spots for each color of dots in the central area of each photograph are deter mined. Then, the magnitude and direction of misregister are measured and recorded for each pair of spots and dots, for each color of dots.
  • the misregister measurements are converted to vectors, and the three misregister vectors for each color are averaged (by averaging vector components)
  • the mask to screen spacing q parallel to the beam path is measured at each point to determine the variation, if any, from the desired, or bogie, q'. Then, if necessary, the measured misregister vectors for each color are corrected for the variation ⁇ from bogie q'.
  • Misregister measurements are usually made on live substantially identical tubes printed by the same lens 130, and the corrected misregister vectors for each color at each coresponding point on the live tubes are averaged. In the above example, this results in 63 average misregister vectors for each color. Since the subsequent surface fitting calculations require a larger number of data points, additional data points are obtained by interpolating additional data points located between the measured data points up to a total of about 250 vectors for each color.
  • the next step in the process is the determination of the location in space of the mask aperture associated with the dots and spots at each data point. This is done, as shown in FIG. 4, by first determining the path of a light ray from the position B of the light source 124, through the known lens 130, to the position D of each data point.
  • ray BEFCD enters the lens at point E, at an angle 01 with the normal EG to the lens surface at that point, and is retracted to path EF within the lens, at an angle 02 with the same normal extended (EH).
  • EH normal extended
  • the ray is again refracted from path EF to new path FD. Since the lens 130- is wedge-shaped at the ray path shown, the two paths BE and FD are not parallel.
  • the point of intersection C of the ray path FD with the mask 15 is the location of the corresponding mask aperture.
  • the vector DD' which represents the error due to the straight line approximation, is then subtracted vectorially from the straight line BD, and a second straight line approximation is drawn from B to D and a new corrected ray path through the lens is determined. This series of approximations is continued until the error is not more than 50 microinches tolerance.
  • FIG. 5 shows the lens 130 in the same position relative to the mask 15 and screen 14a as in FIGS. 2 and 4.
  • C and D represent the same aperture and dot, respectively, as in FIG. 4.
  • Point S is the measured center of the electron spot corresponding to dot D, hence DS is the measured misregister therebetween.
  • the object is to determine the elemental slope at a corresponding point on a theoretical lens 132 which, if used in combination with lens 130, would print a dot at point S, instead of D.
  • a straight line is drawn from spot S through aperture C to lens 130, at point I.
  • the path JK of a refracted ray passing through lens 130 is then -retermined, using Snells law.
  • the path KL of this ray through lens 132 is determined. If the two lenses are in optical contact and made of the same index of refraction material, path KL will merely be a straight line continuation of path J K. Having determined the location of point L in space, the elemental slope of the surface of lens 132 at that point necessary to refract the ray KL to a ray path passing through the light source at B is determined.
  • Point B may be, but is not necessarily, at the same point as in FIGS. 2 and 4.
  • the elemental slope of the lens 132 at each point x, y, z thereon may be expressed in terms of z/x and z/y, in the coordinate system shown in FIGURE 4, where the Z axis is parallel to the axis A-A, and X and Y are the rectangular coordinates in a plane perpendicular to the Z axis.
  • the slopes of the lens surface are converted to vectors normal to the elemental plane of the surface, with one normal vector at the lens data point corresponding to each screen data point.
  • the next step is to prepare a description of a continuous lens vsurface which approximates as nearly as possible the contour of the surface defined by the multiplicity of normal vectors obtained from the measured misregister data.
  • This continuous lens surface may be expressed as a bi-variant polynomial 2:2'1/1.
  • jxiyj (1) where z is the height of the lens surface at each point (x, y) thereon from the X-Y plane z' and j are the exponents of x and y, respectively, in each term of the polynominal, and 7i, j represents all of the coeicients of the (xiy) terms in the desired polynominal.
  • Equation l may be expressed 2: i.-Pi.i 21,
  • Equation 8 becomes m z z y E nhe/LPM)- m 12ga (Pi, je, a1-Pf; a]
  • Equation 4 for the desired lens surface can now be evaluated to any desired degree, using the key Equations 11, 12, 13a, 13b, and 16, for
  • an RCA-604 computer is programmed to perform the mathematical operations involved in Equations 4, 11, 12, 13a, 13b and 16 from the input data z/x and x/y at the various points (x, y) on the ideal lens determined from the misregister data, up to the desired degree N.
  • the output from the computer is a description of the surface of the desired lens surface on magnetic tape in APT language.
  • APT automated programmed tools
  • APT is the designation given to a known system or series of computer programs that will: (a) read-in APT language statements; (lb) perform the calculations ordered or implied by these statements; calculate cut vectors to machine a part described by the APT statements; and output a punched tape to machine the part on the NC (numerical control) machine specified.
  • the APT language tape output from the computer is then fed into a computer which has been programmed in the APT system, for example, an IBM 7094 cornputer, to convert the surface description to an NC tape for controlling the particular NC milling machine to be used to fabricate the part, which machine may, for example, be a Pratt & Whitney machine with a Bendix controller.
  • a computer which has been programmed in the APT system, for example, an IBM 7094 cornputer, to convert the surface description to an NC tape for controlling the particular NC milling machine to be used to fabricate the part, which machine may, for example, be a Pratt & Whitney machine with a Bendix controller.
  • FIG. 6 shows a transverse section of such a mold 140 with an upper surface 142 cut by the NC machine to the surface contour of the desired lens.
  • the desired lens, as well as the first lens 130 if used, may be made of any suitable transparent optical material, such as glass or clear plastic.
  • the mold 140 can be used to fabricate the desired lens.
  • One way is to use a sagging technique in which the mold surface is suitably treated to prevent glass from sticking to it, and a fiat plate 150 of optical glass is placed on the mold and heated in an oven to the softening temperature of the glass to cause the glass to sag by gravity into intimate contact with the mold surface 142, as shown in FIG. 7.
  • the upper surface of the plate 150 is given a surface contour 162 substantially identical with the surface contour 142 of the mold.
  • the plate 150 is then removed from the mold 140 and formed into the desired lens 160 (shown in FIG. 8) by grinding flat or otherwise removing the bottom side, which was in contact with the mold, along the plane indicated by the dashed line 164 in FIG. 7.
  • lens 160 Since the surface 162 of lens 160 is substantially the surface described by Eq. 4, it is a sufliciently close approximation to the theoretical lens surface defined by the normal vectors (z/x, z/'yL as determined in 14 connection with FIG. 5, that the lens 160 can be used in combination with lens in a lighthouse to print a phosphor dot screen of one color with acceptable spotdot register over the entire surface of the screen.
  • the refractive properties of the two lenses 130 and 160 can be combined in a single lens for use in the lighthouse.
  • three separate lenses one for each color, are designed and fabricated from the misregister data, and the three different color dot patterns. are sequentially printed with the three lenses, each alone or in combination with a lens 130.
  • a cathode ray tube having a mosaic phosphor screen comprising an array of discrete phosphor elements, a multi-apertured shadow mask spaced from said screen, and means for projecting an electron beam through the apertures of said mask and onto said screen; the method of laying down said array of elements onto a screen support by a direct photographic process, said method comprising the steps of:
  • a color picture tube having a mosaic phosphor screen made up of a plurality of arrays of discrete phosphor elements, each array adapted to emit light of a different color, a multi-apertured shadow mask spaced from said screen, and means for projecting a plurality of electron beams, one for each array, through the apertures of said mask and onto said screen; the method of laying down said arrays of elements onto a screen support by a direct photographic process, said method comprising the steps of:
  • a color cathode ray tube having a mosaic phosphor screen made up of a plurality of arrays of discrete phosphor elements, each array adapted when energized by an electron beam to emit light of a different color, a mu-lti-apertured shadow mask spaced from said screen, and means for projecting a plurality of electron beams, one for each array, through the apertures of said mask and onto said screen, and wherein the several electron beams in their transit from separate sources to said screen are subjected to various forces including (1) horizontal and vertical scanning forces, and (2) dynamic convergence forces, all of said forces operating to jointly shift the landing spots of said beams on said screen, and hence, cause misregister of said beam spots 'with their corresponding phosphor elements in the absence of compensation therefor; the method of laying down each of said arrays of phosphor elements onto a screen support by a direct photographic lprocess, said method comprising the steps of (a) applying a photosensitive layer to said screen support; (b) projecting light
  • a cathode ray tube having a mosaic phosphor screen comprising an array of discrete phosphor elements, a multi-apertured shadow mask spaced from said screen, and means for projecting an electron beam through the apertures of said mask and onto said screen; the method of making a corrective light refracting device for use in laying down said array of elements on a screen support by a direct photographic process; said method comprising the steps of (a) fabricating and mounting an apertured shadow mask adjacent to said screen support in predeter mined spaced relation therewith;
  • step (e) fabricating a complete cathode ray tube using the screen resulting from step (d) with the mask of step ta);
  • step (a) The method of claim 10, wherein said mold is fabricated in step (a) by a numerical-control machining process.
  • step (c) comprises the use of a first light refracting element designed to cornpensate for at least one of the conditions which tend to produce misregister of the beam spot and phosphor element
  • step (g) involves the design and fabrication of a second light refracting element to be used in combination with said rst element in said subsequent printing operation to substantially compensate for all other conditions tending to cause misregister.
  • an apparatus for laying down said array of elements onto said faceplate by a direct photographic process comprising:
  • a light refracting device interposed in the path of said light rays for refracting said rays in such manner as to provide acceptable compensation over the entire screen area for all conditions that would otherwise cause misregister between said elements and the impingement spots thereon of the electrons of said beam in the operation of said tube, said light refracting device having an asymmetrical continuous surface described by the bi-variant polynomial:
  • z is the distance of said surface at any point (x, y) thereon from a given X-Y plane
  • P1, (x, y) are orthogonal bi-variant polynomials in x and y
  • am ⁇ are the expansion coefficients of the terms P1,j(x,y)
  • the values of am and Pi,j(x,y) are determined from measurements of misregister at a multiplicity of predetermined points distributed over the screen surface of an uncompensated operating cathode ray tube.
  • a cathode ray tube having a faceplate, a mosaic phosphor 4screen comprising an array of discrete phosphor elements on said faceplate, a multi-apertured shadow mask spaced from said screen, and means for projecting an electron beam through the apertures of said mask and onto said screen: the method of laying down said array of elements onto said faceplate by a direct photographic process, comprising the steps of: (a) supporting said faceplate and mask in the same relative position that the faceplate and mask are to occupy in said tube; (b) projecting light rays from a predetermined point toward said mask and faceplate; and (c) interposing a light refracting device in the path of said light rays for refracting said rays in such manner as to provide acceptable compensation over the entire screen area for all conditions that would otherwise cause misregister between said elements and the impingement spots thereon of the electrons of said beam in the operation of said tube, said light refracting device having an asymmetrical continuous surface described by the
  • z is the distance of said surface at any point (x, y) thereon from a given X-Y plane
  • P1,j(x, y) are orthogonal bi-variant polynomials in x and y
  • am are the expansion coefficients of the terms of Pi, (x, y)
  • the values of am and Pi' j(x, y) are determined from measurements of misregister at a multiplicity of predetermined points distributed over the screen surface of an uncompensated operating cathode ray tube.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
US557663A 1966-06-15 1966-06-15 Cathode ray tube and method of manufacture Expired - Lifetime US3476025A (en)

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JP (1) JPS5428711B1 (xx)
AT (1) AT279683B (xx)
BE (1) BE699947A (xx)
DE (1) DE1614369A1 (xx)
ES (1) ES341726A1 (xx)
GB (1) GB1194023A (xx)
MY (1) MY7300269A (xx)
NL (1) NL168363C (xx)
SE (1) SE338111B (xx)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3559546A (en) * 1967-11-01 1971-02-02 Sylvania Electric Prod Cathode ray tube screen exposure
US3883880A (en) * 1972-12-25 1975-05-13 Hitachi Ltd Exposure apparatus for manufacturing fluorescent screens of colour picture tubes
US4020494A (en) * 1976-03-18 1977-04-26 Gte Sylvania Incorporated CRT screen exposure device having improved optical alignment
US4053906A (en) * 1976-06-23 1977-10-11 Gte Sylvania Incorporated Control system for an optical scanning exposure system for manufacturing cathode ray tubes
US4092651A (en) * 1975-08-27 1978-05-30 International Standard Electric Corporation Device and method for exposing phosphor dots in a color television picture tube
US6491481B1 (en) * 2000-10-31 2002-12-10 Eastman Kodak Company Method of making a precision microlens mold and a microlens mold

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2885935A (en) * 1956-05-16 1959-05-12 Rca Corp Color-kinescopes, etc.
US2986080A (en) * 1956-07-02 1961-05-30 Sylvania Electric Prod Cathode ray tube structure and process
US3279340A (en) * 1964-03-19 1966-10-18 Rca Corp Art of making color-phosphor mosaic screens

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2885935A (en) * 1956-05-16 1959-05-12 Rca Corp Color-kinescopes, etc.
US2986080A (en) * 1956-07-02 1961-05-30 Sylvania Electric Prod Cathode ray tube structure and process
US3279340A (en) * 1964-03-19 1966-10-18 Rca Corp Art of making color-phosphor mosaic screens

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3559546A (en) * 1967-11-01 1971-02-02 Sylvania Electric Prod Cathode ray tube screen exposure
US3883880A (en) * 1972-12-25 1975-05-13 Hitachi Ltd Exposure apparatus for manufacturing fluorescent screens of colour picture tubes
US4092651A (en) * 1975-08-27 1978-05-30 International Standard Electric Corporation Device and method for exposing phosphor dots in a color television picture tube
US4020494A (en) * 1976-03-18 1977-04-26 Gte Sylvania Incorporated CRT screen exposure device having improved optical alignment
US4053906A (en) * 1976-06-23 1977-10-11 Gte Sylvania Incorporated Control system for an optical scanning exposure system for manufacturing cathode ray tubes
US6491481B1 (en) * 2000-10-31 2002-12-10 Eastman Kodak Company Method of making a precision microlens mold and a microlens mold

Also Published As

Publication number Publication date
BE699947A (xx) 1967-11-16
ES341726A1 (es) 1968-07-01
NL168363C (nl) 1982-03-16
NL168363B (nl) 1981-10-16
DE1614369A1 (de) 1972-01-27
JPS5428711B1 (xx) 1979-09-18
GB1194023A (en) 1970-06-10
NL6708246A (xx) 1967-12-18
AT279683B (de) 1970-03-10
MY7300269A (en) 1973-12-31
SE338111B (xx) 1971-08-30

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