Chunghwa Picture Tubes, Ltd.

Chung Picture Tubes, Ltd.

Yu-Chung Yu

Hua-Sou Tong

Chun-Min Hu

Kuo-Chu Wang

Chung-Min Hu

Ming-Yu Hsu

The inner surface of a video display panel such as cathode ray tube (CRT) glass faceplate is initially coated with a mixture of one of the primary color phosphors, an organic binder such as polyvinyl alcohol (PVA) diluted with water, and a photoresist agent. The organic binder overcomes the poor adhesion to the glass faceplate of the photoresist which typically includes polyvinyl pyrrolidone (PVP) and reduces the oxygen which decreases phosphor exposure time. To overcome PVA and PVP incompatibilities which give rise to nonuniform film thickness, a vinyl pyrrolidone-vinyl alcohol (VP-VA) copolymer is added to the phosphor, organic binder and photoresist mixture in the range of 0.1-30 wt %. The copolymer with both the VP and VA functioning groups serves as a coupling agent between the PVA and PVP and eliminates incompatibilities between these components. The VP-VA copolymer preferably has a VP/VA mole ratio in the range of 20/80 to 80/20. The photoresist further includes a photosensitive tetraalkylammonium salt and water. By substituting the sodium disulfonate group in the prior an disodium salt with a di-tetraalkylammonium group, the water solubility of the salt is substantially increased permitting increased concentrations of the tetraalkylammonium salt to be used in the photoresist for improved video image contrast. The tetraalkylammonium salt also serves as a linking, or bonding, agent between VP-VA and PVP to prevent the VP-VA from being wiped away during CRT manufacture and for improved application of the photoresist to the glass faceplate.

Photoresist for cathode ray tubes that includes vinyl

An antistatic coating for the outer surface of a video display panel such as of a cathode ray tube (CRT), and a method of applying this type of surface coating, employs a conventional antistatic material such as antimony doped tin oxide to which is added a solvent which is (1) soluble in water and alcohol, (2) has an evaporation point higher than that of water, and (3) has greater solubility for oil-based contaminants than for water. Solvents having these characteristics and which are adapted for use in the antistatic coating include ethylene glycol and dimethyl-based solvents, and their derivatives. The antistatic coating has reduced susceptibility to picking up surface contaminants such as dust and wiping residues such as applied in cleaning the display panel, particularly during manufacture, while affording a high degree of static charge dissipation.

Antistatic coating for video display screen

The outer surface of the glass display panel of a cathode ray tube (CRT) is first coated with an antistatic conductive metal salt solution. A water or organic solvent soluble antireflective coating is then applied by conventional means such as spinning, spraying or dipping to the glass display panel over the first coating. The antireflective coating is comprised of either an organic or an inorganic salt, or a polymer. The coated display panel is then baked, followed by thorough washing with either water in the case of an organic or inorganic salt or water soluble polymer antireflective coating, or toluene in the case of a non-water soluble polymer antireflective coating. Washing the display panel partially dissolves the salt or polymer in the antireflective coating more on the outer surface of the coating than on the inner portion of the coat adjacent the glass facelate. Dissolution of a portion of the salt or polymer in the coating produces pores in the coating and variations in coating thickness, thus changing the light refractive index of the coating. A continuous decreasing dissolution rate determined by the extent of washing of the coated display panel provides the coating with a continuous decreasing light refractive index and broadband antireflection (400-700 nm) with a minimum reflectance of 1.0% in the range of 560-650 nm. Knowing the light refractive index of the glass substrate and that of air (typically 1.0), the refractive index of the salt or polymer coating may be established by the extent of dissolution of the coating during washing.

Broadband antireflective and antistatic coating for CRT

The inner surface of a video display panel such as cathode ray tube (CRT) glass faceplate is initially coated with a mixture of one of the primary color phosphors, an organic binder such as polyvinyl alcohol (PVA) diluted with water, and a photoresist agent. The organic binder overcomes the poor adhesion to the glass faceplate of the photoresist which typically includes polyvinyl pyrrolidone (PVP) and reduces the oxygen which decreases phosphor exposure time. To overcome PVA and PVP incompatibilities which give rise to nonuniform film thickness, a vinyl pyrrolidone-vinyl alcohol (VP-VA) copolymer is added to the phosphor, organic binder and photoresist mixture in the range of 0.1-30 wt %. The copolymer with both the VP and VA functioning groups serves as a coupling agent between the PVA and PVP and eliminates incompatibilities between these components. The VP-VA copolymer preferably has a VP/VA mole ratio in the range of 20/80 to 80/20.

Photoresist for cathode ray tubes

For use in a self-emitting color display device such as a cathode ray tube (CRT) having a display screen with a phosphor coating on its inner surface, a surface coating disposed on the display screen's outer surface affords improved color purity, or contrast, by reducing overlap in the color spectrum between two adjacent primary colors, i.e., between red and green and/or between green and blue. An organic dye is added to either an inner antistatic layer or an outer antireflective layer of an antireflective/antistatic outer coating on the display screen, where both of the aforementioned layers contain silane. The dye functions as a color filter absorbing only light within the frequency range between adjacent primary colors, such as between the red and green color phosphors, i.e., in the range of 460-500 nm, and/or between the green and blue color phosphors, i.e., in the range of 560-600 nm. A silane coupling agent is also added to serve as a binding agent bridging the organic dye and silane together. In this manner, the organic dye is bonded to the silane in either the antistatic layer or the antireflective layer to prevent separation and escape of the organic dye filter from either of these layers of the outer coating on the display screen.

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Chungli, Taiwan

Yu-Chung Yu