US3745398A - Cathode ray tube screen having contiguous,overlapping color areas - Google Patents

Cathode ray tube screen having contiguous,overlapping color areas Download PDF

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Publication number
US3745398A
US3745398A US00051438A US3745398DA US3745398A US 3745398 A US3745398 A US 3745398A US 00051438 A US00051438 A US 00051438A US 3745398D A US3745398D A US 3745398DA US 3745398 A US3745398 A US 3745398A
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Prior art keywords
color
screen
picture tube
areas
phosphor
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Expired - Lifetime
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US00051438A
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English (en)
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M Oikawa
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Hitachi Ltd
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Hitachi Ltd
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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
    • H01J29/187—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
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
    • H01J31/20—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours
    • H01J31/201—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours using a colour-selection electrode
    • H01J31/203—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours using a colour-selection electrode with more than one electron beam
    • H01J31/206—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours using a colour-selection electrode with more than one electron beam with three coplanar electron beams

Definitions

  • This invention relates to a color picture tube and more particularly to such a color picture tube in which a light absorbing material is coated on each of the overlapping border portions of the tri-color phosphor dots.
  • the fluorescent screen of a conventional color picture tube is formed by coating tri-color phosphor materials of red (R), green (G) and blue (B) in the form of dots, in such a manner that the centers of the adjoining phosphor dots are located at the apices of a regular triangle and the dots are substatnailly in contact with each other at the peripheral edges thereof. Therefore, a shadow mask having beam passage apertures perforated therein is provided in front of the fluorescent screen to ensure that electron beams modulated by R, G and B chrominance signals for the respective dots will not impinge upon the phosphor dots of other colors to emit a light or, in other words, the color purity will not be degraded.
  • the diameter of the phosphor dots is, for example, 0.4 mm, whereas the diameter of the beam passage apertures in the shadow mask is, for example, 0.28 mm. It will, therefore, be seen that only about 49 percent of the total area of the phosphor dot (or about 70 percent of the diameter of the phosphor dot) is effectively used for the emission of light. This is for the purpose of providing an allowance for deviation of the electron beam and thereby improving the color SUMMARY OF THE INVENTION
  • An object of the present invention is to' provide a color picture tube which is excellent inbrightness as well as in color purity.
  • Another object of the invention is to provided a color picture tube in which the electron beam utility is high.
  • one form of the color picture tube according to the invention comprises an electron gun to generate electron beams, a shadow mask and a fluorescent screen which undergoes bombardment of the electron beams through said shadow mask, said fluorescent screen comprising tri-color phosphor dotsluminous in red, green and blue colors respectively and arranged in such a manner that the centers of the adjoiningthree dots are located at the apices of a regular triangle and the adjoining two dots partially overlap each other, and a light absorbing material layer is coated at least on said overlapping area.
  • FIG. 1 is a side view of a color picture tube, partially shown in cross-section.
  • FIG. 2 is an enlarged view of a portion of a conventional fluorescent screen.
  • FIG. 3 is an elarged view of a portion of a fluorescent screen according to this invention.
  • a color picture tube which generally comprises a glass bulb 1 which is sealed air-tight, an electron gun 2 for generating electron beams 3, a screen 4 comprising a tri-color coating layer, an anode electrode 5 simultaneously serving as a metal back layer, a shadow mask 6 having electron beam passage apertures perforated therein, a terminal 7 for impressing an anode voltage on the shadow mask and the anode electrode, and a deflection coil 8 for deflecting the electron beams.
  • the screen 4 comprising a coating layer of tri-color fluorescent materials has heretofore been formed as shown in FIG. 2. Namely, the centers of the adjoining R, G and B phosphor dots are located at the apices of a regular triangle and these phosphor dots are in contact with each other at their peripheral edges. The radius of the phosphor dots is represented by r.
  • the conventional color picture tube has the disadvantages as described previously, because of such a structure.
  • FIG. 3 shows the structure of a screen according to the present invention, in which R (red), G (green) and B (blue) are tri-color phosphor dots of a substantially polygonal shape having inwardly concaved, sides respectively and arranged with the centers thereof located at the apices of a regular triangle, and the circumscribed circles of the respective dotshave such a radius as will enable said circumscribed circles to overlap each other,
  • R red
  • G green
  • B blue
  • the tri-color phosphor dots of the present invention have such a size that the circumscribed circles of the phosphor dots R, G and B pass the center of gravity c of a regular triangle, each side of which is 2r in length and on the apices of which the centers of said phosphor dots are located respectively.
  • the area defined by the circumscribed circle, which is generally larger than the phosphor element, will hereinafter be referred to briefly as an area in which the phosphor element is positioned.
  • the portion of each phosphor dot of the invention which emits a light is not circular in shape, and the overlapping portion of the circumscribed circles of the adjacent phosphor dots (the hatched portion in FIG. 3) is coated with a non luminous substance (e.g.
  • the above-described portion of the phosphor dot has a unique polygonal shape (a hexagonal shape in the illustration) which is inscribed within a circle having a radius of r (1.16 r,,) and the sides of which are concaved inwardly.
  • the diameter of the beam spots are selected to be about percent of the diameter of the tri-color phosphor dots, so as to provide an allowance for deviation of the electron beams.
  • the diameter of the beam spots is similarly selected to be about 70 percent of the diameter of the circumscribed circles (the radius is r,) of the phosphor dots in the present invention
  • the size S, of the beam spot is represented by the following formula:
  • the size S of the beam spot (which is 49 percent of the area of the phosphor dot) in the conventional color picture tube is represented by the following formula:
  • the light emitting area ratio L between the present invention and the prior art is:
  • the area of each of the beam passage apertures in the shadow mask can be increased to about 1.3 times that of the beam passage aperture in the prior art shadow mask and the present transmission of the beam can be increased accordingly, i.e. the brightness of the picture image can be increased.
  • the radius r and the area S; of the inscribed circle of the phosphor dot (unique hexagonal shape) according to the invention are respectively represented by the following formulas:
  • the ratio L of the effective light emitting area of the total area of the phosphor dot is:
  • the diameter of the beam spot is set at about 70 percent of the diameter of the circumscribed circle of the phosphor dot, similar to the prior art screen, the color purity is not degraded, even through the area of the beam spot is increased to 1.3 times that of the beam spot on the prior art screen, but is rather improved because the area overlapping the area in which the adjacent phosphor dot is positioned, is coated with a non-luminous substance.
  • the ultraviolet ray exposure method can be used which has been used heretofore for the production of color cathoderay tubes.
  • a powder of a non-luminous substance e.g. powdered carbon
  • a polyvinyl alcohol solution with ammonium dichromate (photosensitive material) added thereto e.g., a polyvinyl alcohol solution with ammonium dichromate (photosensitive material) added thereto.
  • the coating layer of the non-luminous substance thus formed is exposed to ultraviolet rays through a shadow mask, as has been practiced heretofore.
  • the shadow mask used has apertures which are larger than those in a shadow mask previously used (e.g.
  • a condensing lens which makes it possible to produce a circular spot exposed to ultraviolet rays through the shadow mask which has a radius of 2r,,/ ⁇ 3 wherein r represents the radius of the prior art dot.
  • the exposure is effected by irradiating concurrently the entire area of the coating layer from three light sources which are set in the position of the electron gun within the cathode-ray tube and arranged at the apices of a regular triangle respectively, and which, as a whole, approximate a point source of light. By so doing, the hatched portions in FIG. 3 are exposed dually.
  • the intensity of light from the three light sources and the time of exposure are so suitably adjusted that the portions only of the coating layer which have been dually exposed may be sensitized and become soluble in water, with the other portions remaining unsensitized, or, for example, the overlapping portions may be exposed to an exposure of 6 KLM (wherein KL is an abbreviation of kilolux and M stands for minute) and the other portions may be exposed to a half of said exposure.
  • KLM an abbreviation of kilolux and M stands for minute
  • a screen can be formed in which the overlapping portion of two of the circumscribed circles of the three adjacent R (red), G
  • a shadow mask is used for exposure which, similar to that mentioned above, has apertures of a diameter about 1.6 times that of the apertures in the conventionally used shadow mask. Therefore, it will be understood that two types of fluorescent materials will be coated on each of the non-luminous coating layer one on top of another and hence said coating layer will emit a light under bombardment of the electron beams. However, the light emitted by the fluorescent material on top of the non-luminous coating layer projects toward the electron gun and does not project toward a viewer by reason of being intecepted by the nonluminous coating layer.
  • r representing the radius of the phosphor dot to be coated
  • said radius may be selected within the range of r 5 R r
  • the diameter of the apertures in the shadow mask, which was used for exposure in the formation of the non-luminous coating layers is reduced, for example, to about 1.3 times that of the apertures in the conventionally used shadow mask, by forming on the peripheral surface of each aperture a layer of plating of such material as aluminum or nickel with which a plating can easily be obtained.
  • the shadow mask (having apertures of a size about 1.6 times that of the apertures in the conventionally used shadow mask) which was used in the formation of the non-luminous coating layers, is used as his, as a shadow mask to be incorporated in the cathode-ray tube, the diameter of the beam spots will become undesirably large, degrading the colorimetric purity. Therefore, a shadow mask is used whose aperture size has been reduced (to about 1.3 times that of the conventionally used one) as by plating, or a postfocusing method, well known in the art, is employed.
  • the exposure is effected by the use of a shadow mask having circular apertures therein, it is to be understood that the exposure may similarly be effected by the use of a shadow mask having hexagonal apertures.
  • the non-luminous coating layer is formed in the shape of a hexagonal ring and the phosphor element is also of a hexagonal shape.
  • a three-gun type color picture tube having a triad-type fluorescent screen, said screen being subdivided into a plurality of contiguous generally hexagonal areas each assigned to one of the three different primary colors, the respective generally hexagonal areas being arranged in zones of three areas each assigned to a different primary color and each of the generally hexagonal areas being located within a circle circumscribed thereabout, which circles are positioned at the apices of a regular triangle and have respectively a radius of r, that is defined by r r 5 1.16m, where r is one half of a side of said regular triangle, whereby the respective adjacent circles circumscribed about said generally hexagonal areas partially overlap each other to from therebetween an overlapped region, respectively;
  • said screen comprising:
  • each of said generally hexagonal areas has an inscribed circle therein whose radius is not less than 0.84r
  • each of the phosphor elements is formed within a circumscribed circle and has a circular shape whose radius r; is limited within the range of 0.84r o 5 r 5 l 1 67'0- 5.
  • a three-gun type color picture tube having a triad-type fluorescent screen subdivided into a plurality of contiguous circular areas of equal size entirely covering said screen, the centers of said circular areas being spaced by a distance less than the diameter of the circular areas so as to provide linked overlapped zones surrounding non-overlapped generally hexagonal zones, said screen comprising a non-luminous substance entirely covering said overlapped zones, and
  • said circular areas each have a radius r and the distance between the centers of said circular areas is r.,, wherein r r 5 l.l6r

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  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
US00051438A 1969-07-04 1970-07-01 Cathode ray tube screen having contiguous,overlapping color areas Expired - Lifetime US3745398A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP44052481A JPS4814499B1 (zh) 1969-07-04 1969-07-04

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3856518A (en) * 1972-03-04 1974-12-24 Philips Corp Method of electrophotographically manufacturing a television screen using hygroscopic material
US4458175A (en) * 1977-04-13 1984-07-03 Weekley Robert R Mosaic additive reflectance color display screen
US4701789A (en) * 1985-03-13 1987-10-20 Rank Electronic Tubes Limited Cathode ray tube
TWI577570B (zh) * 2013-11-04 2017-04-11 三緯國際立體列印科技股份有限公司 立體列印裝置

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05187217A (ja) * 1992-01-13 1993-07-27 Suzuki Motor Corp 排気マフラ

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3856518A (en) * 1972-03-04 1974-12-24 Philips Corp Method of electrophotographically manufacturing a television screen using hygroscopic material
US4458175A (en) * 1977-04-13 1984-07-03 Weekley Robert R Mosaic additive reflectance color display screen
US4701789A (en) * 1985-03-13 1987-10-20 Rank Electronic Tubes Limited Cathode ray tube
TWI577570B (zh) * 2013-11-04 2017-04-11 三緯國際立體列印科技股份有限公司 立體列印裝置

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Publication number Publication date
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