US3703374A - Method of manufacturing color picture tube - Google Patents

Method of manufacturing color picture tube Download PDF

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Publication number
US3703374A
US3703374A US78372A US7837270A US3703374A US 3703374 A US3703374 A US 3703374A US 78372 A US78372 A US 78372A US 7837270 A US7837270 A US 7837270A US 3703374 A US3703374 A US 3703374A
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US
United States
Prior art keywords
hardened
shadow mask
film
aperture
permeating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US78372A
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English (en)
Inventor
Tadao Okabe
Mitsuru Oikawa
Makoto Tanaka
Waichi Nagashiro
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
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Hitachi Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP8079369A external-priority patent/JPS4834350B1/ja
Priority claimed from JP4404070A external-priority patent/JPS5029915B1/ja
Priority claimed from JP4404170A external-priority patent/JPS4932629B1/ja
Application filed by Hitachi Ltd filed Critical Hitachi Ltd
Application granted granted Critical
Publication of US3703374A publication Critical patent/US3703374A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • 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

Definitions

  • This invention relates to a method of manufacturing color picture tubes, and more particularly to a method of manufacturing a color picture tube comprising a plurality of three primary-color phosphor dots smaller than the beam-permeating apertures of a shadow mask.
  • a shadow-mask type color picture tube which has a phosphor screen constructed in such a way that phosphor dots of the three primary colors of red (R), green (G) and Blue (B) are applied in a size smaller than that of the electron-beam permeating apertures of the shadow mask and that a non-luminous and light-absorbing material such as carbon is applied in the interstices of the respective adjacent phosphor dots.
  • the shadow mask is also used for exposure purposes in the step of applying phosphor dots to the screen and that for purposes of precision this mask should be the very same as that used in the finished picture tube, it is extremely difficult to apply phosphor dots smaller than the size of the shadow-mask beam-permeating apertures.
  • An object of this invention is to provide a method of manufacturing color picture tubes, which makes it possible to easily and inexpensively form phosphor dots smaller than the beam-permeating apertures of a shadow mask.
  • Another object of this invention is to provide a method of manufacturing color picture tubes, which makes it possible to uniformly form over the entire picture screen, phosphor dots smaller than the beam-permeating apertures of the shadow mask.
  • a hardened layer of the 'tine particles is formed in the peripheral portion of each beampermeating aperture of a shadow mask thereby to prepare an exposure shadow mask which apparently has lighttransmitting apertures smaller than the shadow-mask beam-permeating apertures.
  • a phosphor screen is produced which is provided with phosphor dots smaller than the shadowmask beam-permeating apertures.
  • FIGS. 1a and 1b are views showing an embodiment of the method of manufacturing a shadow mask for exposure as is used in accordance with the invention, respectively;
  • FIGS. 2a to 2c show enlarged views of a part of the exposure shadow mask in FIG. l, respectively;
  • FIGS. 3a and 3b are views showing a further embodiment of the method of manufacturing an exposure shadow mask employed in the invention, respectively.
  • FIGS. 4a, 4b, 5 and 6 are views for illustrating still another embodiment of the method of manufacturing an exposure shadow mask employed in the invention, respectively.
  • numeral 1 designates an enlarged section of a part of a shadow mask
  • numeral 2 represents electron-beam permeating apertures.
  • Shown at 3 are applied tilms, which are formed in such a way that a liquid consisting of a transparent dispersing agent, e.g. an aqeuous solution of polyvinyl alcohol (PVA) with a ne powder of a usable material (hereinafter described) such as titanium dioxide (for example, TiOz) and carbon (C) incorporated thereinto, is applied on one or both sides of the shadow mask 1 by means of a brush, sprayer, etc.
  • a transparent dispersing agent e.g. an aqeuous solution of polyvinyl alcohol (PVA) with a ne powder of a usable material (hereinafter described) such as titanium dioxide (for example, TiOz) and carbon (C) incorporated thereinto.
  • PVA polyvinyl alcohol
  • C carbon
  • a method for the application includes the step of irnmersing the shadow mask into the liquid with the line powder mixed therein, or applying the liquid onto the shadow mask. Thereafter, the shadow mask is rotated to thereby permit application in a uniform thickness. Under such conditions the shadow mask 1 is subjected to drying treatment. Then, as shown in FIG. 1b, a hardened layer 4 of fine powder (in this embodiment, a hardened layer of TiOQ or C) is formed in the peripheral portion of each beam-permeating aperture 2 of the shadow mask 1, whereas a hardened film 5 of the dispersing medium (in this embodiment, a transparent film of PVA) is formed in the central portion of each aperture.
  • a hardened layer 4 of fine powder in this embodiment, a hardened layer of TiOQ or C
  • a hardened film 5 of the dispersing medium in this embodiment, a transparent film of PVA
  • Fine powder exhibiting such phenomenon is not restricted to the powdery titanium oxides or carbon, but may be made of a variety of substances. Therefore, the general term, fine powder of usable material" is herein given to th'ese substances in powdery form.
  • the size of the hardened film 5 of the dispersing medium may be suitably varied dependent upon the concentration of the dispersant, the amount of ⁇ the fine powder of the usable material to be incorporated, the drying speed of the applied liquid, etc.
  • the portion 5 of the hardened dispersant film may be made small with a short drying time, whereas large with a long drying time.
  • the portion 5 of the hardened film is sometimes torn to become voided at a low concentration of the dispersing agent or at a high drying rate, the objects of the invention may be accomplished in similar manner to the case of untorn films 5.
  • the diameter d of the hardened dispersant film is smaller than the diameter D of the electron-beam permeating aperture of the shadow mask, as illustrated in FIG. 2a. Accordingly, when the exposure shadow mask is used to form the three-primary-color phosphor dots on the screen by the process of ultraviolet-ray exposure, they will be smaller in size than the beam-permeating apertures of the shadow mask.
  • the process of depositing the three-primary-color phosphor dots by ultraviolet-ray exposure is quite identical to that of the prior art, so description thereof is omitted.
  • the process of applying a non-luminous and light-absorptive material, such as carbon, in the interstices of the three-primary-color phosphor dots has been suggested in various forms. Furthermore, such a process of application is not directly related to the invention, so description thereof is also omitted.
  • the exposure shadow mask After the three-primary-color phosphor dots smaller than the shadow-mask beam-permeable apertures are applied by ultraviolet-ray exposure as described above, the exposure shadow mask has the portions of the hardened layers of the fine powder as well as the hardened films of the dispersant removed therefrom by means of rinsing, for example. Then, the original shadow mask may be easily recovered. Accordingly, assemblage of this shadow mask in the picture tube with the three-primarycolor phosphors deposited on the screen, makes it possible to easily manufacture a color picture tube having a screen on which three-primary-color phosphors smaller than the beam-permeating apertures of the shadow mask are applied.
  • the exposure shadow mask prepared as set forth in the foregoing description has exactly circular hardened films of the dispersant formed in the beam-permeable apertures, the three-primary-color phosphor dots provided by use thereby will be in regular form.
  • the exposure shadow mask provided in accordance with the above method that not only the hardened dispersant film 5 formed by drying has an irregular, complicatedly curved configuration at its periphery, but also some particles of the fine powder of the usable material often remain in the film without being moved to the peripheral edge of the shadow-mask aperture.
  • the dispersant film can be torn due to a tension exerted thereon in the step of drying the film for effecting hardening thereof, whereby an opening 6 of abnormal configuration as shown in FIG. 2c appears.
  • the hardened dispersant film is not exactly circular, but is irregular in shape, or the fine powder remains in the hardened film of the dispersing medium, a uniform deposition of phosphor dots is not achieved in the step of forming the phosphor dots by means of this shadow mask and according to the ultraviolet-ray exposing process, which is very undesirable.
  • FIGS. 3a and 3b description will be made of a further embodiment of the invention which eliminates the above-mentioned inconvenience.
  • the irregular bent which existed before the dissolving treatment is smoothed while the dissolved matter is absorbed by the hardened circumferential lm 4, with the result that a regular and circular opening 6 as shown in FIG. 3b is obtained.
  • the size of the hardened film 4 containing the ne powder in a large amount is determined by the quantity of and the material for the tine powder incorporated in the dispersing agent, the viscosity of the dispersing agent, the rate of drying the applied film (3 in FIG. la), etc. Therefore, suitable selection of these factors controls the size of the voids or openings 6 to a desired value, thus making it possible to apply phosphor dots of a desired diameter to the screen.
  • a fine powder of carbon was employed as that of the usable material, and was mixed into an aqueous solution of PVA.
  • the mixed liquid was uniformly applied to at least one side of a shadow mask by means of a brush, sprayer or the like, and was thereafter dried. In this way a transparent PVA film was formed in the central portion of each beam-permeating aperture of the shadow mask, whereas a hardened film containing a large amount of carbon powder was provided in the peripheral edge portion.
  • the mixed ratio between water and alcohol may be suitably varied since the dissolution of the PVA film is influenced by the type as well as the amount of the fine powder, the drying speed, or the like film-forming conditions.
  • the solvent for use in dissolving the hardened dispersant film is not restricted to the liquid mixture consisting of water and ethyl alcohol, but it may be optionally selected from materials capable of dissolving the hardened dispersant film at an appropriate dissolving speed. Still further, the method of applying such solvents is not restricted to one using a brush, sprayer, etc. as in the above embodiment, but a uniform contact of a vapor of the solvent may attain a similar effect.
  • the hardened film formed in the peripheral portion of each beam-permeating aperture of the shadow mask as described in the foregoing embodiments is required to shield light for use in exposure.
  • any hardened film having such a function may attain the objects of this invention.
  • a light-impermeable dispersant may be employed if the tine powder is made of a light-permeable substance such as glass.
  • the light-impermeable dispersing agent may be obtained by, for example, coloring the transparent PVA with a black dyestuff.
  • burst the applied film bursts so as to become scattered and a hardened film is not formed at all
  • radial portions 7 in which the fine powder is not sufficiently applied appear on the shadow mask l as is shown in FIG. 6. Since the portions formed by the spokes have an insufficient amount of the fine powder, the concentration of the fine powder is low in these areas. As a result, the diameter d of the hardened dispersant film (represented in FIG. 2a) becomes larger than in portions where no spoke occurs, thereby lowering the reduction percentage of the beam-permeating aperture.
  • This embodiment has been suggested in order to eliminate such inconveniences. It employs as the usable material a combination between a substance which has a relatively high cohesiveness and a substance which has a relatively high dispersibility, thereby to manufacture an exposure shadow mask having substantially uniform lighttransmitting apertures. With this shadow mask, phosphor dots are deposited by the ultraviolet-ray exposure process.
  • a hardened film was formed in each beam-permeating aperture of a shadow mask. Then, since graphite has a small surface area and is easily dispersed, the fine graphite powder was rapidly concentrated into the peripheral edge portion of the beam-transmitting aperture 2 during drying. Thus, as shown in FIGS. 4a and 4b, a hardened film 4 which is high in its graphite content was formed, along with a hardened PVA film S having a good regular circular shape and being composed of a very small residual amount of graphite.
  • activated carbon is employed alone as the usable material, it will be once dispersed in the aqueous solution of PVA but will form a net-like structure to provide a flocculated state with a lapse of time, due to it being very large in surface area and very high in its adsorption power for various substances and ions. For this reason, the movement of the activated carbon towards the circumferential portion of the beampermeating aperture in the step of drying the applied film to harden it, tends to become insutiicient. As a resuit, as shown in FIG.
  • each process using graphite or activated carbon alone as the usable material has its own advantages as well as disadvantages.
  • the disadvantges may be eliminated when, for use, both the substances are mixed in an appropriate ratio and dispersed in the aqueous solution of PVA. It is therefore possible to provide a shadow mask for the ultravioletray exposure process which has hardened IVA films each being reduced iu the spokes and/or the burst to the utmost, having a good circular shape and containing an extremely small amount of residual light-impermeable substances.
  • Activated carbon and graphite both ranging in particle size from in to 5u. were mixed in a variety of proportions and were added to an aqueous solution of PVA, thereby preparing a liquid which contained a mixture of 2% (by weight). Subsequently, this liquid was used to form hardened films on an ultraviolet-ray exposure shadow mask by the above process. Characteristics of the hardened films obtained were compared.
  • the hardened films formed on the ultravioletray exposure shadow mask exhibit different characteristics dependent upon the mixed ratio between activated carbon and graphite.
  • an appropriate selection of the value of the mixed ratio between the two substances removes the disadvantages of activated carbon and graphite as occurring when they are respectively used alone. Hardened films of good characteristics are then attainable.
  • the mixed ratio between activated carbo-n and graphite of approximately 1:20 may provide hardened PVA films which are good in configuration and which are small in any amounts of the residual carbon in said films, the burst and the spokes.
  • the usable material employed in the invention is not restricted to the combination of the two substances but the constituents may be suitably selected from substances which are relatively high in cohesive and dispersive properties, respectively.
  • this embodiment is the process wherein after the applied films are drying-treated to be hardened, only the hardened dispersant films 5 are dissolved and removed with a suitable solvent, e.g. the liquid mixture consisting of water and alcohol as in the foregoing embodiments.
  • a suitable solvent e.g. the liquid mixture consisting of water and alcohol as in the foregoing embodiments.
  • those among the exposure masks provided by the above embodiments in which the hardened layers of the usable material are left in the peripheral portions of shadow-mask apertures but the hardened dispersant lms are removed, may be utilized not only for the ultraviolet-ray exposure process but also for the well-known process of applying phosphor dots with an electron beam.
  • a color phosphor screen made up of a plurality of phosphor dots of the three primary colors on a target surface for use in a cathode ray tube of the shadow mask type which comprises the steps of forming a shadow mask provided with apertures of the ultimate size and pattern of distribution required by the normal operating parameters of said cathode ray tube, forming in the annular peripheral por- A tion of each of said apertures an opaque substance to temporarily reduce the size of the apertures, disposing a radiation sensitive phosphor layer on said target surface, exposing said phosphor layer to radiation through the mask formed by the shadow mask having the opaque substance in the peripheral portions of each aperture, removing the opaque portions from the shadow musk, and assembling said shadow mask into said cathode ray tube to serve as the electron-optical element of said tube; the improvement characterized in that said opaque substance is formed in the peripehal portion of each aperture in the shadow mask by the steps of applying onto at least one side of the shadow mask a slurry containing a
  • a method according to claim l wherein said hardened film is so formed as to have at least a part of a hardened dispersant film in a central portion thereof containing said dispersing agent but little of said tine powder material, said method further comprising, before the step of exposing said phosphor layer, the step of removing oniy said hardened dispersant film with a solution capable of dissolving said dispersant lm.
  • said dispersing agent is polyvinyl alcohol and said tine powder material is selected from the group consisting of carbon and titanium dioxide.
  • said solution for dissolving said hardened dispersant film is a liquid mixture consisting of a first liquid capable of dissolving said hardened dispersant iilm and a second liquid incapable of dissolving said hardened dispersant film.
  • said tine powder material is powder formed of a light-impermeable substance.
  • said lightimpermeable substance is selected from the group consisting of carbon and titanium oxides.
  • said fine powder material is a powdery mixture consisting of powder of a light-impermeable substance which has a high cohesiveness and that of a further light-impermeable substance which has a high dispersibility.
  • An exposure mask usable for forming a phosphor screen having phosphor dots of three primary colors formed by exposure of a phosphor 'layer disposed on the inner surface of the face panel of a color picture tube to a selected radiation comprising:
  • a hardened film formed entirely over each of said beam-permeating apertures, said hardened lm having a center portion permeable with respect to a selected radiation which is usable for formation of said phosphor screen and an annular peripheral portion substantially impermeable to said radiation, said peripheral portion of said hardened film being extended inwardly from the periphery of the aperture of said shadow mask and serving as means for reducing the aperture size of said shadow mask with respect to said radiation.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
US78372A 1969-10-09 1970-10-06 Method of manufacturing color picture tube Expired - Lifetime US3703374A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP8079369A JPS4834350B1 (enrdf_load_stackoverflow) 1969-10-09 1969-10-09
JP4404070A JPS5029915B1 (enrdf_load_stackoverflow) 1970-05-25 1970-05-25
JP4404170A JPS4932629B1 (enrdf_load_stackoverflow) 1970-05-25 1970-05-25

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US3703374A true US3703374A (en) 1972-11-21

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US78372A Expired - Lifetime US3703374A (en) 1969-10-09 1970-10-06 Method of manufacturing color picture tube

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US (1) US3703374A (enrdf_load_stackoverflow)
CA (1) CA918511A (enrdf_load_stackoverflow)
DE (1) DE2049535B2 (enrdf_load_stackoverflow)
FR (1) FR2065211A5 (enrdf_load_stackoverflow)
GB (1) GB1323718A (enrdf_load_stackoverflow)
NL (1) NL7014712A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3822454A (en) * 1972-11-30 1974-07-09 Gte Sylvania Inc Method of fabricating a color cathode ray tube
US3931442A (en) * 1973-03-02 1976-01-06 Gte Sylvania Incorporated Temporary modification of a pattern mask for use in forming a color CRT screen and a process for modifying the same
US3989523A (en) * 1971-09-15 1976-11-02 International Standard Electric Corporation Reducing aperture-size of shadow mask in painting black matrix CRT screen
US4671776A (en) * 1983-09-13 1987-06-09 Kabushiki Kaisha Toshiba Manufacturing method of color picture tube

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3989523A (en) * 1971-09-15 1976-11-02 International Standard Electric Corporation Reducing aperture-size of shadow mask in painting black matrix CRT screen
US3822454A (en) * 1972-11-30 1974-07-09 Gte Sylvania Inc Method of fabricating a color cathode ray tube
US3931442A (en) * 1973-03-02 1976-01-06 Gte Sylvania Incorporated Temporary modification of a pattern mask for use in forming a color CRT screen and a process for modifying the same
US4671776A (en) * 1983-09-13 1987-06-09 Kabushiki Kaisha Toshiba Manufacturing method of color picture tube

Also Published As

Publication number Publication date
DE2049535A1 (de) 1971-04-22
DE2049535B2 (de) 1972-07-13
FR2065211A5 (enrdf_load_stackoverflow) 1971-07-23
NL7014712A (enrdf_load_stackoverflow) 1971-04-14
GB1323718A (en) 1973-07-18
CA918511A (en) 1973-01-09

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