Radiation imagery chemistry: process – composition – or product th – Producing cathode-ray tube or element thereof
Patent
1997-03-31
1998-12-01
Martin, Roland
Radiation imagery chemistry: process, composition, or product th
Producing cathode-ray tube or element thereof
430 26, G03C 500
Patent
active
058436014
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a shadow mask of a cathode ray tube, and more particularly to a shadow mask, a cathode ray tube having the shadow mask and a method for manufacturing a screen using the shadow mask, in which electron beams are concentrated during the passing through electron passing holes of the shadow mask.
Referring to FIG. 1, a color cathode-ray tube (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 or a color selection electrode 16 removably mounted to a sidewall of the panel 12. A three color phosphor screen 20 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 accelerated by a high potential 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 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 fluorescent elements or the phosphor elements R, G and B.
An aluminum thin film 22 which is an electroconductive film overlies the screen 20 in order to provide a means for applying the uniform potential to the screen 20. The aluminum thin film 22 increases the brightness of the phosphor screen and prevents the phosphor screen from being burned due to ions and the potential of the phosphor screen from decreasing. And also, a film of resin such as lacquer(not shown) may be applied between the aluminum thin film 22 and the phosphor screen 20 to enhance the flatness and reflectivity of the aluminum thin film 22.
In a wet photolithographic 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.
To solve or alleviate the above problems of the wet photolithographic process, an eletrophotographical process for manufacturing the phosphor screen has been developed. The eletrophotographical process can be also classified as a wet-type and a dry-type, of which the dry eletrophotographical process utilizing dry-powdered phosphor particles fairly overcomes the above problems while the wet eletrophotographical process cannot.
U.S. Pat. No. 4,921,767, issued to Datta at al. on May 1, 1990, describes one dry-type method of electrophotographically manufacturing the phosphor screen assembly, as shown in FIGS. 3A to 3E and as is briefly explained in the following.
Prior to the screen process, the panel 12 is washed by various methods. Thereafter, a conductive layer 32, as shown in FIG. 3A, is formed by conventionally coating the inner surface of the viewing faceplate 18 with a suitable conductive solution comprising an electrically conductive material which provides an electrode for an overlying photoconductive layer 34. The conductive layer 32 can be an inorganic conductive material such as tin oxide or indium oxide, or their mixture or, preferably, a volatilizable organic conductive material consisting of a polyelectrolyte commercially known as polybrene(1,5-dimethyl-1,5-diazaun
REFERENCES:
patent: 3956526 (1976-05-01), Ohshima et al.
patent: 5229234 (1993-07-01), Riddle et al.
patent: 5240798 (1993-08-01), Ebemann
Martin Roland
Orion Electric Co. Ltd.
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