Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Patent
1997-03-31
1998-08-25
Ramsey, Kenneth J.
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
H01J 918
Patent
active
057977810
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a triple-layered shadow mask for a cathode ray tube(CRT), and more particularly to a triple-layered shadow mask having enlarged apertures or slits and concentrating electron beams, and a method of manufacturing it.
BACKGROUND OF THE INVENTION
Referring to FIG. 1, a color CRT 10 generally comprises an evacuated glass envelope consisting of a panel 12, a funnel 13 sealed to the panel 12 and a tubular neck 14 connected by the funnel 13, an electron gun 11 centrally mounted within the neck 14 and a shadow mask 16 removably mounted to a sidewall of the panel 12. A three color phosphor screen is formed on the inner surface of a display window or faceplate 18 of the panel 12. The electron gun 11 generates three electron beams 19a or 19b, said beams being directed along convergent paths through the shadow mask 16 to the screen 20 by means of several lenses of the gun and a high positive voltage applied through an anode button 15 and being deflected by a deflection yoke 17 so as to scan over the screen 20 through apertures or slits 16a formed in the shadow mask 16.
In the color CRT 10, the phosphor screen 20, as shown in FIGS. 2A and 2B, comprises an array of three fluorescent or phosphor elements R, G and B of three different emission colors arranged in a cyclic order of a predetermined structure of multiple-stripe or multiple-dot shape and a matrix of light-absorptive material surrounding the phosphor elements R, G and B. A thin film of aluminum 22 overlies the screen 20 in order to provide a means for applying the uniform potential applied through the anode button 15 to the screen 20, increase the brightness of the phosphor screen and prevent from degrading ions in the phosphor screen and decreasing the potential of the phosphor screen. And also, a film of resin such as lacquer (not shown) may be applied between the aluminum thin film 22 and the phosphor screen to enhance the flatness and reflectivity of the aluminum thin film 22.
In a photolithographic wet process, which is well known as a prior art process for forming the phosphor screen, a slurry of a photosensitive binder and phosphor particles is coated on the inner surface of the faceplate. It does not meet the higher resolution demands and requires a lot of complicated processing steps and a lot of manufacturing equipments, thereby necessitating a high cost in manufacturing the phosphor screen. And also, it discharges a large quantity of effluent such as waste water, phosphor elements, 6th chrome sensitizer, etc., with the use of a large quantity of clean water.
According to application Ser. No. 817,598, filed Mar. 31, 1997 filed on the same date under the title of "HIGH-LUMINANCE-LOW-TEMPERATURE MASK, CRT HAVING THE MASK AND METHOD OF MANUFACTURING A SCREEN USING THE MASK" by the applicant, a shadow mask 50 as shown in FIG. 3 has been disclosed. The shadow mask 50 comprises a first thin metal plate 51, a dielectric layer 52 and a second thin metal plate 53, being formed in a shape nearly corresponding to a faceplate 18 of a CRT. A multiple electron beam holes 50a shaped in minute apertures or slots are formed on the shadow mask 50 in a regular pattern so as to allow the passage of electron beams 19.
In FIG. 2A, the width W of electron beam holes 50a is greater than one third of screen pitch SP in case of the stripe-type screen and, in case of V1 and the second DC voltage V2 are supplied to said first thin metal plate 51 and the second thin metal plate 53 respectively, so that the electron beams 19 passing through the electron beam holes 50a may be concentrated in a dimension less than one third of screen pitch SP or difference .DELTA.V between said V1 and V2, and the thickness of the shadow mask 50. For the formation of a focusing lens on the electron beam holes 50a, the first thin metal plate 51 and the second thin metal plate 53 are electrically insulated and supplied with two different DC voltages having the voltage difference .DELTA.V respectively, when a dielectric layer 52 is used as an in
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Orion Electric Co. Ltd.
Ramsey Kenneth J.
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