6 10 9 u03c9 and accordingly could be called an antistatic coating film next a mixed solution of ch 3 si nco 3 and ch 3 2 si nco 2 o in ethyl acetate was applied onto the surface of the antistatic coating film by a roll coating method and the glass plate was baked at about 250 u00b0 c for about 2 hr as the result a transparent lubricative coating film having a thickness of about 700 u00e5 was formed the glass board produced by the above process exhibited an average transmittance of about 89 for visible light which means only an ignorable change from the transparency of the chemically strengthened glass plate before coating as an indication of lubricity of the coated top surface of the glass board angle of slip of the top surface was measured by placing a weight of 50 g on the glass board and slowly lifting up one edge of the board with the opposite edge as the fulcrum until the weight began to slide down on an average of measurements on five samples the angle of slide was 13 9 degrees the glass board was installed in a copying machine of automatic document feed type and the copying machine was operated until 10000 sheets of paper were carried on the top surface of the glass board which was never cleaned midway the machine operation after that surface potential of the glass board was measured to be 0 8 kv on an average of measurements on five samples and the lubricative coating film.