US3764366A - Method and apparatus for making color cathode ray tube - Google Patents

Method and apparatus for making color cathode ray tube Download PDF

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Publication number
US3764366A
US3764366A US00085413A US3764366DA US3764366A US 3764366 A US3764366 A US 3764366A US 00085413 A US00085413 A US 00085413A US 3764366D A US3764366D A US 3764366DA US 3764366 A US3764366 A US 3764366A
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United States
Prior art keywords
phosphor
color
light
ray tube
cathode ray
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Expired - Lifetime
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US00085413A
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English (en)
Inventor
M Okamoto
C Ninagawa
S Ashizaki
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Panasonic Holdings Corp
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Matsushita Electronics Corp
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Publication date
Application filed by Matsushita Electronics Corp filed Critical Matsushita Electronics 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
    • H01J9/2274—Light sources particularly adapted therefor

Definitions

  • This invention relates to an improvement in a method and apparatus for forming phosphor dots on the screen of a color cathode ray tube for use in a color television set.
  • phosphor dots have been fixed in a particular array on the face of the tube by means of the photo-chemical fixing method, wherein an emulsion containng phosphor and photo-fixing agent is irradiated by ultraviolet ray beams transmitted through apertures in the shadow mask, as explained in U.S. Pat. No. 285,935 to D. W. Epstein et al.
  • the phosphor dot is inevitably formed with a diameter larger than that of the aperture in the shadow mask through which ultraviolet rays strike the screen to fix said dot.
  • the phosphor dots are of sufiicient size to be tangent to each other.
  • even a slight drifting of the path of the electron beam may cause undesirable striking of adjacent color dots, resulting in lack of color disparity or inaccurate color expression.
  • each color dot it is preferable to limit the diameter of each color dot so that the color dots are arranged with suitable spaces therebetween.
  • limiting of the diameter of these very small dots is very difiicult, especially with presently known methods of fabrication.
  • a light source having a hemispherical light-emitting surface is employed to emit photo-chemical rays, such as ultraviolet rays, onto a screen coated with a phosphor slurry. Details of such process are described referring to FIG. 1 and FIG. 2, wherein a phosphor-containing emulsion 9 applied on the inside face of the face plate 8 of a color cathode ray tube is struck by photo-chemical rays, such as ultraviolet rays 4', which are generated by an ultraviolet lamp 2 in a light box 1. The ultraviolet rays are then transmitted through the transparent light conduit 3 in the light box 1 and are Patented Oct.
  • the emulsion 9 is struck by the ultraviolet rays 4' coming through each aperture 7, and the energy of the received rays is distributed in the form of a circular truncated cone, which cone is composed of a central part 10 and a surrounding outskirt part 10', the latter having an outer diameter larger than that of the aperture 7.
  • the parts of the emulsion 9 thus exposed to the ultraviolet rays 4 are hardened by known photo-chemical reaction, and such hardness depends on the energy of the received rays. Accordingly, the central part of the exposed area acquires the greatest hardness and the hardness gradually diminishes towards the outskirt part of the dot until it becomes zero at the outmost boundary.
  • the exposed emulsion is then developed by being washed with a hot spray or a shower of washing liquid so as to retain dots at the exposed areas.
  • a hot spray or a shower of washing liquid so as to retain dots at the exposed areas.
  • attempts have been made to remove the portion at the outskirt of each exposed area, where the hardness is comparable low, by applying a rather strong hot shower or spray thereto.
  • the portion at the outskirt of the exposed area has no critical zone where the hardness of the exposed emulsion changes abruptly, only the outermost part of the portion at the outskirt can be removed through the developing process, and in addition, the dots sometimes acquire a non-circular shape during such a process.
  • the principal object of the invention is to provide an improved color cathode ray tube, wherein picture dots are arranged with suitable spaces therebetween, in order to avoid undesirable loss of color disparity, due to undesirable drifting of the electron beam path while in use, and to assure more accurate color expression.
  • Another object of the present invention is to provide an improved color cathode ray tube having a wider tolerance in dynamic convergence of a set of electron beams.
  • a specially shaped light emitting source is employed in order to limit the diameter of each phosphor dot to a size no larger than that of each aperture in the mask through which ultraviolet rays strike the screen to fix the phosphor dot.
  • FIG. 1 is an elevation, in section, of a photographic lighthouse having an optical system for use in making color cathode ray tube, and a shadow mask and a screen plate of a color cathode ray tube set up thereon;
  • FIG. 2 is a partially schematic sectional view of the aforementioned prior art optical arrangement including a face plate, phosphor-containing emulsion, shadow mask, hemispherical faced light source top, together with a curve showing the distribution of the rays received by the emulsion;
  • FIG. 3(a) is a sectional view of a light conduit for a light source in accordance with the present invention.
  • FIG. 3(b) is a perspective view of the light conduit shown in FIG. 3 (a).
  • FIG. 4 is a schematic view of the present invention, in section, including a face plate, phosphor-containing emulsion, shadow mask and a specially designed light-source, together with a curve showing the distribution of the rays received by the emulsion.
  • FIGS. 2 and 4 the dimensions of the parts and arra-ngement thereof are not shown in exact proportion, but are exaggerated for the sake of easy understanding, and the correction lens is omitted since it has no substantial influence over the distribution of received rays.
  • the light conduit 11 of the light source of the present invention is made of a heatresistive, transparent material of comparatively high refractive index, for instance, quartz glass, and is so shaped to provide a ring-shaped light-emitting face 12 on the top of a generally cylindrical or frusto-conical part and a light-intake face 13 at the bottom thereof.
  • the ring-shaped light-emitting face 12 is positioned substantially in parallel with the inner face of the face plate 8 which is substantially in parallel with the shadow mask 6.
  • the concave inner conical depression 11' in the ring-shaped light-emitting face 12 is formed by a surface having a suitable conical angle so as to exclude emission of light therefrom.
  • a face plate 8 and a shadow mask 6 are mounted in a lighthouse 1' which contains a correction lens and a light box 1 comprising a lamp 2 and a light conduit 3.
  • Phosphor-containing emulsion 9 applied on the inside face of the face plate 8 is struck by photo-chemical rays, such as ultraviolet rays 12', which are generated by the lamp 2 in the light box 1, and then are conducted through the transparent light conduit 11 in the light box 1, so as to be emitted from the emitting face 12.
  • the rays are suitably refracted by the correcting lens 5, and finally pass through aperture 7 in the shadow mask 6 located inside the face plate 8.
  • the photo-chemical rays such as ultraviolet rays 12'
  • the emulsion 9 is struck by the ultraviolet rays 12' coming through each aperture 7, and the energy of the received rays is distributed in a pattern resembling a two-storied circular truncated cone, which cone is composed of a higher central part 14 and a surrounding lower outskirt part 14'. It is a feature of the present process that there is a considerable difference between the light energy level of the central part 14 and that of the outskirt part 14, separated by a distinctive circular edge 14" inbetween.
  • the higher central part 14 has a diameter considerably smaller than that of the lower outskirt part 14'. Moreover, the diameter of the central part 14 is made smaller when the diameter of the ring-shaped emitting face is made larger.
  • the parts of the emulsion 9 thus exposed to the ultraviolet rays 12' are hardened by known photochemical reaction, and such hardness depends on the energy of the received rays. Accordingly, the central part of the exposed area acquires the greater hardness and the hardness of the outskirt part of the dot is distinctly less than that of the central area.
  • the exposed emulsion 9 is then developed by being washed with a hot spray or shower of washing liquid so as to retain dots at the exposed areas. During such de- 4 1 velopment, the less-hardened outskirt part of the exposed dot on the emulsion-9 is selectively removed.
  • the diameter of the phosphor dots can be made smaller than that of the aperture of the shadow mask, according to the present invention, it is possible to make the aperture larger than the conventional ones so as to make the picture on the screen face brighter without creating a crowding between adjacent phosphor dots and consquent undesirable loss of color disparity and unwanted mixing of the emitted colors.
  • Method of making a color screen for a cathode ray tube comprising the steps of:

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
US00085413A 1969-10-30 1970-10-30 Method and apparatus for making color cathode ray tube Expired - Lifetime US3764366A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP8736269 1969-10-30

Publications (1)

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US3764366A true US3764366A (en) 1973-10-09

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US00085413A Expired - Lifetime US3764366A (en) 1969-10-30 1970-10-30 Method and apparatus for making color cathode ray tube

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US (1) US3764366A (fr)
CA (1) CA923352A (fr)
DE (1) DE2053422B2 (fr)
FR (1) FR2066749A5 (fr)
GB (1) GB1267000A (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3936302A (en) * 1972-02-07 1976-02-03 Hitachi, Ltd. Method for manufacturing fluorescent screens for use in colour picture tubes
US3948660A (en) * 1972-08-05 1976-04-06 Agfa-Gevaert, A.G. Method for the manufacture of fresnel lenses using light-sensitive materials
US3993487A (en) * 1969-01-03 1976-11-23 Matsushita Electronics Corporation Method for manufacture of color television picture tubes using rotating light source
US4013467A (en) * 1971-06-18 1977-03-22 Matsushita Electronics Corporation Method of manufacturing color picture tubes using rotating light attenuator
US4020191A (en) * 1974-09-13 1977-04-26 Hitachi, Ltd. Method for forming flat display panel phosphor dots
US4049451A (en) * 1972-01-14 1977-09-20 Rca Corporation Method for forming a color television picture tube screen
US4223083A (en) * 1977-12-27 1980-09-16 Tektronix, Inc. Virtual mask exposure system for CRT screen manufacture

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3993487A (en) * 1969-01-03 1976-11-23 Matsushita Electronics Corporation Method for manufacture of color television picture tubes using rotating light source
US4013467A (en) * 1971-06-18 1977-03-22 Matsushita Electronics Corporation Method of manufacturing color picture tubes using rotating light attenuator
US4049451A (en) * 1972-01-14 1977-09-20 Rca Corporation Method for forming a color television picture tube screen
US3936302A (en) * 1972-02-07 1976-02-03 Hitachi, Ltd. Method for manufacturing fluorescent screens for use in colour picture tubes
US3948660A (en) * 1972-08-05 1976-04-06 Agfa-Gevaert, A.G. Method for the manufacture of fresnel lenses using light-sensitive materials
US4020191A (en) * 1974-09-13 1977-04-26 Hitachi, Ltd. Method for forming flat display panel phosphor dots
US4223083A (en) * 1977-12-27 1980-09-16 Tektronix, Inc. Virtual mask exposure system for CRT screen manufacture

Also Published As

Publication number Publication date
CA923352A (en) 1973-03-27
GB1267000A (fr) 1972-03-15
FR2066749A5 (fr) 1971-08-06
DE2053422B2 (de) 1973-08-30
DE2053422A1 (de) 1971-05-06

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