Information signal record medium of the capacitance type

Abstract

An improvement is provided in and relating to a capacitance-type record medium wherein an information signal is recorded as a variation in the geometrical shape of its surface area, and is played back by the variation of the capacitance between its surface and an electrode of a reproducing stylus scanning the surface of the record medium relatively which occurs according to a variation in the geometrical shape of its surface area. The improvement consists in the fact that at least the surface area of the record medium is formed of (1) a material composed of an electrically conductive substance and a copolymer consisting of 98 to 65% by weight of vinyl chloride, 2 to 20% by weight of an alkyl vinyl ether with the alkyl group having 4 to 18 carbon atoms and/or a vinyl ester of a fatty acid in which the fatty acid residue has 4 to 18 carbon atoms and 0 to 15% by weight of another monomer copolymerizable with these compounds, or (2) a material composed of an electrically conductive substance and a polymer mixture consisting of at least two polymers in which the proportions of the constituent monomers are the same as in the aforesaid copolymer.