| 摘要 |
A sheet suitable for use as an electrostatic writing medium comprises a paper base sheet having substantially uniformly distributed throughout a polyhydric alcohol and ammonium chloride, said paper base sheet having a continuous dielectric insulating coating thereon. The weight of polyhydric alcohol and ammonium chloride may be within the range of 2 to 12 pounds per 3000 square feet of paper base sheet. The ammonium chloride may be present in an amount within the range of 0.1 to 25 per cent by weight of the paper base sheet and in which the polyhydric alcohol is present in an amount within the range of 0.1 to 35 per cent by weight of the paper base sheet. The polyhydric alcohol and ammonium chloride may be present in the ratio of 1 part by weight of ammonium chloride to 1 to 4 parts by weight of the polyhydric alcohol. The polyhydric alcohol may be glycerol, ethylene, glycol, diethylene glycol, triethylene glycol, propylene glycol, pentaerythritol or sorbitol. The dielectric coating may be polyvinyl chloride or acetate, polyvinylidene chloride, polyethylene, a polyacrylic acid ester, a vinyl acetate-crotonic acid copolymer or other vinyl acetate copolymer, polyesters an alkyd resin, an oil-modified alkyd resin, shellac, microcrystalline wax, a petroleum hydrocarbon resin, a butadiene-styrene copolymer, nitrocellulose, cellulose acetate, or an epoxy resin. The sheet may be produced by applying the polyhydric alcohol-ammonium chloride composition to the paper base sheet preferably after coating with a dielectric material if the ammonium chloride is soluble in the coating, or if insoluble in the coating, or of a barrier coating is employed between the dielectric coating and the paper, the composition can be applied before coating. |
