US3790839A - Rectangular grade black surround screen - Google Patents

Rectangular grade black surround screen Download PDF

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Publication number
US3790839A
US3790839A US00240931A US3790839DA US3790839A US 3790839 A US3790839 A US 3790839A US 00240931 A US00240931 A US 00240931A US 3790839D A US3790839D A US 3790839DA US 3790839 A US3790839 A US 3790839A
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United States
Prior art keywords
faceplate
black surround
area
center
phosphor
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Expired - Lifetime
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US00240931A
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English (en)
Inventor
L Dietch
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Zenith Electronics LLC
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Zenith Radio Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/30—Luminescent screens with luminescent material discontinuously arranged, e.g. in dots, in lines
    • H01J29/32—Luminescent screens with luminescent material discontinuously arranged, e.g. in dots, in lines with adjacent dots or lines of different luminescent material, e.g. for colour television
    • H01J29/327—Black matrix materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/187—Luminescent screens screens with more than one luminescent material (as mixtures for the treatment of the screens)
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/30—Luminescent screens with luminescent material discontinuously arranged, e.g. in dots, in lines
    • H01J29/32—Luminescent screens with luminescent material discontinuously arranged, e.g. in dots, in lines with adjacent dots or lines of different luminescent material, e.g. for colour television
    • H01J29/322—Luminescent screens with luminescent material discontinuously arranged, e.g. in dots, in lines with adjacent dots or lines of different luminescent material, e.g. for colour television with adjacent dots

Definitions

  • ABSTRACT The screen structure of a black surround type rectangular color cathode ray tube has a plurality of viewable image elements which decrease in area from the center of the faceplate to the periphery. However, instead of having a uniform grade in all radial directions from the center, the viewable image elements of similar area are located along a substantially rectangular locus centered with respect to the face plate.
  • the present invention concerns the grade pattern of viewable image elements on phosphur deposits on the faceplate of a color television picture tube.
  • the image elements in a conventional tri-gun shadow mask color cathode ray tube comprise deposits of light emitting phosphors having different color responses.
  • the term viewable indicates the maximum area of light emitting surface, which is normally limited by the area of the electron beam impinging thereon.
  • the concept of grading the apertures of a shadow mask is quite old.
  • the purpose of grading the apertures is to preserve purity in spite of the fact that the electron beam triangle suffersdistortion with scanning so that its registration with the phosphor dot triangles tends to become imperfect with increase in deflection angle.
  • a condition of misregistration is encountered and a change of white field color, e.g. a tinting of the white field, is suffered whenever any one of the three beams rides off its assigned phosphor dot whether or not'the misregistration is so extreme that the beam impinges upon a non-assigned phosphor dot.
  • color television picture tubes having elemental phosphor deposits separated from one another over the faceplate, with the spaces between phosphor deposits filled with a light absorptive material, have found widespread commercial acceptance.
  • This type of color television picture tube commonly referred to as a black surround tube, is fully described in US. Pat. No. 3,146,368 issued Aug. 25, 1964 in the name of Joseph P. Fiore et al. and assigned to the assignee of the present invention.
  • a matrix of opaque In one method of manufacturing a black surround tube, a matrix of opaque,
  • non-reflective material is initially deposited on the inner surface of the faceplate.
  • the matrix defines a plurality of phosphor receiving holes arranged in triads, which holes determine the viewable area of the latter applied phosphor deposits since the black surround matrix is opaque.
  • the maximum light emitting area is restricted by the matrix hole area even though the cross-sectional area of the electron beam impinging on the phosphor deposit maybe greater than that of the deposit.
  • the purity tolerance or guard band may be reversed with numerous advantages in brightness and contrast characteristics as fully set out in the above-mentioned Fiore et al. patent.
  • a negative tolerance or guardband means that the electron beam area is larger than the effective phosphor dot area.
  • the negative tolerance may be photographically achieved as set out in the Fiore et al. patent or may be attained by enlarging the shadow mask apertures after screening has been performed.
  • the present invention is an improvement in that a specifically different grading pattern of viewableimage elements defined by apertures in a black matrix is taught to further increase the total area of viewable image elements over the tube faceplate, thus increasing the brightness capability of the tube without loss of guard band. In fact, the guard band can actually be increased.
  • the screen assembly of a color cathode ray tube constructed in accordance with the invention, comprises a plurality of viewable image elements distributed throughout a rectangular field with an area grade characterized in that the viewable image element areas decrease in a predetermined manner with distance from the center of the field and further characterized by the fact that viewable image elements having the same area are disposed along a substantially rectangular locus centered in the field.
  • the screen assembly has a light emission characteristic comprising a concentric series of substantially rectangularly shaped patterns of equal light emission in contradistinction-to devices of the prior art wherein the light emission characteristic is a concentric series of circular patterns of equal light emission.
  • FIG. 1 is a fragmentary showing of a color tube screen structure including a shadow mask and a black surround grille having a hole size grade pattern in accordance with the invention
  • FIG. 2 is a plot used in explaining typical conditions of registration between the phosphor dot and beam triads
  • FIG. 3 represents essentially the iso-transmission patterns of a black surround grille embodying the invention.
  • FIG. 4 is a plot showing an illustration hole size grade for the black surround grille.
  • Shadow mask types of color cathode ray tubes are well known in the art and comprise a screen having in-.
  • the electron beams are developed in a triangular gun cluster in the neck of the picture tube opposite the screen which is on the inner surface of the tube faceplate.
  • a shadow mask having a multiplicity of small apertures is interposed in the electron beam paths close to the screen and the apertures thereof are arranged in a pattern essentially the same as the pattern of phosphor deposits on the screen.
  • the shadow mask may be termed a color-selection electrode because the arrangement is such that each of the three beams, in passing through a given aperture of the mask, is angularly disposed to excite only that one of the three phosphors that is assigned to the particular beam.
  • the usual deflection yoke and beam convergence arrangement provided so that the beams may scan a rectangular raster and in all positions thereof impinge on the screen with the angular relation required to maintain color selectivity.
  • the screen is a mosaic structure defined by a multiplicity of phosphor triads each of which has a dot of green, a dot of blue and a dot of red phosphor.
  • the phosphor dots in the early introduction of commercial television were sized to be in essentially tangential contact with one another over the screen area with the electron beams of smaller diameter. The difference in the dot and beam diameters provided a positive guard band or tolerance which permitted some migration of the beam over its assigned dot before a loss of purity was suffered.
  • the area of the phosphor dots may be smaller than the area of the electron beams and provide an equally large negative guard band or tolerance range for purity.
  • a major advantage of small sized dots, separated from one another, is that a light-absorbing material may be placed on the faceplate areas separating the phosphor dots, which leads to enhanced brightness and contrast.
  • FIG. 1 discloses this screen arrangement wherein a screen 10 has phosphor dots 11 separated from each other on the faceplate and varying in area in accordance with the invention.
  • the phosphor deposits are arranged to define triads, some of which are delineated by the characters r,,, b,,, g,,, r,, b etc.
  • the shadow mask 12 which is spaced from but substantially parallel to the screen, is a foraminous or perforated member having a multiplicity of circular apertures with the apertures of the mask in alignment with corresponding phosphor dot triads in the conventional manner.
  • the mask apertures are larger than the phosphor deposits.
  • the apertures are of the same area A, although this is not essential to the invention.
  • Certain series of phosphor triads are designated by reference characters Y Y Y Y and Y.,.
  • a common subscript indicates triads of dots of approximately the same diameter and the series are graded from the largest value Y at the center of the screen. The particulars of the grading will be discussed hereafter.
  • FIG. 2 depicts the manner in which misregistration is usually encountered in a conventional color tube of the three-gun shadow mask type.
  • FIG. 2 indicates a portion of the upper right quadrant of a tube screen and the clear circles designate assumed tangent components g, b and r of phosphor triads while the fitted-in smaller circles represent electron beams with each beam shown impinging upon or exciting its assigned phosphor dot. Since the screen is rectangular, it has both a minor and a major axis with the latter usually disposed in the direction of horizontal scan while the other is disposed in the direction of the vertical scan. These axes intersect at the center of the screen where, as illustrated in FIG. 2, perfect registration is obtained.
  • a condition of perfect registration is one wherein the beam triangle is in precise registration with the phosphor triangle, that is to say, each beam is concentric with its assigned phosphor dot.
  • both the phosphor dots and the beams define equilateral triangles which, being in proper registration, establish the desired condition of color purity.
  • This ideal geometrical relation holds only in the central portion of the screen and, because of such factors as astigmatism of the yoke, suffers deterioration and a loss of registration as well as purity tolerance with deflection angle.
  • the red and green beams tends to become grouped, that is to say, they tend to be closer to one another while the blue beam experiences a displacement in the opposite or in the degrouping sense; that is, the blue beam tends to be further displaced vertically from the remaining two beams than is the case at the center of the screen, as indicated in FIG. 2.
  • This is the most serious condition of beam triad distortion and results in the least purity tolerance because, comparing the conditions at the center and at the end of the major axis, less movement of the beam is permissable at the 3 and 9 oclock positions before suffering loss of purity than is true at the center of the screen.
  • red and green beams tend to be separated or degrouped while the blue beam shifts in a grouping sense. This is apparent from comparison ofthe 12 oclock and center positions in FIG. 2. It again represents a condition of imperfect beam-phosphor registration where purity loss is apt to be encountered.
  • Other screen locations of particular interest are those which occur at the ends of the diagonal axes of the screen; one such location is also indicated in FIG. 2.
  • the mask apertures are of uniform diameter, there is obviopsly a much greater likelihood of color distortiori ends of the riiajoi and minor axes than is the case at the center of the screen simply because of the influence of yoke astigmatism and other tube parameters responsible for th'eloss' of registration with deflection angle. It is to minimize thatpossibility and to provide a guard band or purity tolerance that the art has adopted the technique of a graded mask. In prior art tubes, however, the grading is such that the aperture diameter decreases uniformly along all radial directions from the center of the screen toward the periphery. That, of course, means that there is a severe brightness loss at the ends of the diagonal axes which gives rise to .what was known as a hot center or dark corner screen effect.
  • the central hole in the black surround grille is designated Y and one series of holes Y, having a substantially common but smaller area is disposed along the rectangular path bearing the same designation.
  • the rectangles Y and Y; of FIG. 3 are similarly loci of holes having a common area although the area decreases from one rectangle to the next in the direction of the edge of the screen.
  • the grille may be said to' have an area characteristic comprisinga concentric series of rectangularly shaped isotransmission patterns or equal brightness patterns on the face of the tube, assuming the electron beams are always larger than the holes and the gun currents match to provide white light of a given color temperature.
  • the transmission or brightness at the center of the screen may be I and the iso-transmission patterns Y, to Y have the following percentages of the transmission or brightness at Y namely, 95, 84, 68 and 50, respectively.
  • the hole area grade of black' surround grille 20 in accordance with the invention is such that equal brightness patterns are disposed at the same percentages of distance from thecenter of the screen.
  • the broken-construction rectangles of FIG. 1 are also an effort. to represent these patterns and, while shown over only a part of the screen, it will be understood that the grade continues in this fashion throughout'the entirety of the screen.
  • a screen assembly having a black surround grille may be fabricated in at least two distinct ways.
  • the preferred form of fabrication is to initially deposit on the clear faceplate of the picture tube a black surround grille with its pattern of hole areas varying in accor dance with the teachings of the invention. Thereafter, appropriate phosphors are deposited in corresponding holes in the black surround grille. In this technique the physical dimensions of the phosphor materials are not critical in that the black surround grille holes determine the viewable phosphor areas.
  • Such a screen assembly may be prepared by initially forming clear dots of polyvinyl alcohol (pva), sensitized with ammonium dichromate, over the elemental areas of the faceplate which are to receive phosphor deposits. This is accomplished by photoexposure of the sensitized pva coating from all three lighthouse positions, which results in insolubilizing the pva in areas where the phosphor deposits are to be.
  • the faceplate is then developed by washing away the soluble areas of pva in the spaces intervening the insoluble dots. Thereafter a light-absorbing material such as an aqueous solutionof graphite mixed with an inorganic binder is coated over the faceplate and dried. The inorganic binder causes the graphite to adhere to both the glass and insoluble dots of pva.
  • the pva dots are then caused to swell and break the graphite coating thereover by application of hydrogen peroxide to the faceplate. Then a water wash is used to remove the pva and adherent graphite to leave a black grille with a plurality of holes in appropriate locations for reception of proper phosphors. Screening with appropriate phosphor materials is then carried out in accordance with conventional techniques.
  • a different method of applying a black surround grille is to initially screen the faceplate with appropriate color phosphor materials. Thereafter the spaces intervening the phosphor deposits are filled with a black, light absorbing material.
  • One technique is to photoexpose, through the front of the faceplate, with a photosensitized solution of such material, for example, causing insolubilization thereof in the intervening spaces. Subsequent washing removes the material in .the areas protected from the solubilizing radiation, namely over the deposited phosphor materials.
  • the phosphor deposits themselves would initially be graded in area in accordance with the invention.
  • the viewable image elements are the areas of phosphor available for light emitting purposes.
  • the available phosphor is determined by the area of the holes in the black surround grille, whereas in the latter case the phosphor deposit itself determines the available area since the grille merely fills in the spaces between such deposits.
  • shader plates comprise glass plates which have deposited thereon a light attenuating medium, such as metal, which varies in intensity in accordance with the light distribution pattern desired. The deposited metal is of micro thickness and introduces very little refraction to the exposure rays passing therethrough.
  • the coating is put on a surface of the lens usually associated with lighthouses.
  • a shader plate in lighthouses used to expose faceplates for forming a black surround grille in accordance with the instant invention can facilitate obtaining the desired rectangular grade pattern for the hole areas.
  • a shader plate may be fabricated to produce an exposure intensity across the faceplate which will yield appropriate size deposits of insoluble pva (with or without phosphor material added) in accordance with the desired graded area pattern.
  • a black surround color television picture tube having a substantially rectangular faceplate and a screen assembly including an aperture mask spaced from a plurality of viewable image elements distributed in a rectangular field over the faceplate and characterized in that said viewable image elements diminish gradually in area from the center to the edge of the faceplate such that elements having the same area are disposed on concentric loci which are centered in said field and which have a substantially rectangular geometry.
  • a rectangular screen assembly for a color television picture tube including a matrix of light absorbing material on said faceplate, said matrix having holes arranged in a rectangular field over said faceplate coextensive with the maximum viewable areas of light emitting phosphors, said holes having areas diminishing in accordance with distance from the center of said faceplate and arranged in a pattern characterized in that lines of holes of substantially the same areas occur at the same percentages of distance from said center.
  • a screen assembly for a color cathode ray tube having a faceplate with a black surround grille including a multiplicity of holes, each defining the viewable area of an associated deposit of light emitting phosphor, distributed throughout said faceplate with an area grade characterized in that the hole areas decrease in a predetermined manner with distance from the center of the faceplate and further characterized in that holes having substantially the same areas are disposed along a substantially rectangular locus centered in said faceplate so that the screen assembly, when incorporated into a tube, will have a viewable phosphor area characteristic comprising a concentric series of substantially rectangularly shaped patterns of equal brightness.
  • a black surround color television picture tube having a substantially rectangular faceplate and a screen assembly including an aperture mask spaced from a plurality of viewable image elements distributed in a rectangular field over the faceplate and characterized in that in at least one common coordinate direction said viewable image elements diminish gradually in dimension from the center to the edge of the faceplate such that elements having the same value of said dimension in said common coordinate direction are disposed on concentric loci which are centered in said field and which have a non-circular geometry.

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US00240931A 1972-04-04 1972-04-04 Rectangular grade black surround screen Expired - Lifetime US3790839A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3866082A (en) * 1972-10-17 1975-02-11 Philips Corp Cathode ray tube for displaying coloured pictures
US3889145A (en) * 1972-08-30 1975-06-10 Tokyo Shibaura Electric Co Color cathode ray tube with phosphor strips concave toward vertical center line
US3890527A (en) * 1973-04-26 1975-06-17 Westinghouse Electric Corp Triad color screen having elements larger than mask apertures near screen center and smaller near periphery
US3904912A (en) * 1972-08-26 1975-09-09 Philips Corp Cathode ray tube display screen having overlapping triad elements and separated triads
US6534907B1 (en) * 1998-01-30 2003-03-18 Hitachi, Ltd. Cathode ray tube faceplate having particular black matrix hole transmittivity in the peripheral areas

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2755402A (en) * 1953-09-28 1956-07-17 Rca Corp Color kinescopes of the masked-target dot-screen variety
US2947899A (en) * 1958-01-23 1960-08-02 Zenith Radio Corp Color image reproducers
US3146368A (en) * 1961-04-04 1964-08-25 Rauland Corp Cathode-ray tube with color dots spaced by light absorbing areas

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2755402A (en) * 1953-09-28 1956-07-17 Rca Corp Color kinescopes of the masked-target dot-screen variety
US2947899A (en) * 1958-01-23 1960-08-02 Zenith Radio Corp Color image reproducers
US3146368A (en) * 1961-04-04 1964-08-25 Rauland Corp Cathode-ray tube with color dots spaced by light absorbing areas

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3904912A (en) * 1972-08-26 1975-09-09 Philips Corp Cathode ray tube display screen having overlapping triad elements and separated triads
US3889145A (en) * 1972-08-30 1975-06-10 Tokyo Shibaura Electric Co Color cathode ray tube with phosphor strips concave toward vertical center line
US3866082A (en) * 1972-10-17 1975-02-11 Philips Corp Cathode ray tube for displaying coloured pictures
US3890527A (en) * 1973-04-26 1975-06-17 Westinghouse Electric Corp Triad color screen having elements larger than mask apertures near screen center and smaller near periphery
US6534907B1 (en) * 1998-01-30 2003-03-18 Hitachi, Ltd. Cathode ray tube faceplate having particular black matrix hole transmittivity in the peripheral areas
US20030164672A1 (en) * 1998-01-30 2003-09-04 Haruhiko Yoshida Cathode ray tube
US6765344B2 (en) 1998-01-30 2004-07-20 Hitachi, Ltd. Cathode ray tube having specific radius of curvatures for inner and outer surface of the panel

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