Radiation imagery chemistry: process – composition – or product th – Producing cathode-ray tube or element thereof – Using specified radiation-sensitive composition other than a...
Patent
1998-07-28
2000-02-22
Rodee, Christopher D.
Radiation imagery chemistry: process, composition, or product th
Producing cathode-ray tube or element thereof
Using specified radiation-sensitive composition other than a...
430 70, 430 77, 2525011, G03G 1306
Patent
active
060278404
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a solution for making a photoconductive layer and a method of electrophotographically manufacturing a viewing screen for a cathode ray tube(CRT) using the solution, and more particularly to a photoconductive solution which does not cause cancer and facilitates performing all the processes under a visible light environment with safety in work operations.
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 FIG. 2, 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 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.
To solve or alleviate the above problems, the improved process of electrophotographically manufacturing the screen utilizing dry-powdered phosphor particles is developed. U.S. Pat. No. 4,921,767, issued to Datta at al. on May 1, 1990, describes one method of electrophotographically manufacturing the phosphor screen assembly using dry-powdered phosphor particles through the repetition of a series of steps represented in FIGS. 3A to 3E, as is briefly explained in the following.
Prior to the electrophotographic screening process, foreign substance is clearly removed from an inner surface of a panel by several conventional methods. Then, 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-diazaundecamethylene polymethobromide, hexadimethrine bromide), available from Aldrich Chemical Co., Milwaukee Wis., or another quaternary ammonium salt. The polybren
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patent: 5405722 (1995-04-01), Datta et al.
patent: 5413885 (1995-05-01), Datta et al.
patent: 5501928 (1996-03-01), Datta et al.
Orion Electric Co. Ltd.
Rodee Christopher D.
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