Electrophotographic lithograph printing plate material

Claim 1

An electrophotographic lithograph printing plate material comprising: (A) an electroconductive and water-resistant support; and (B) an electrophotographic layer formed on a surface of the support and comprising at least finely divided photoconductive zinc oxide, a binder resin and a sensitizing dye material comprising: (a) 30 to 99% by weight of a sensitizing dye consisting of at least one member selected from the group consisting of the compounds of the formulae (I), (II), and (V) to (VII): ##STR5## and capable of being adsorbed by the zinc oxide at an adsorption rate of less than 90%, and (b) 1 to 70% by weight of another sensitizing dye consisting of at least one member selected from the group consisting of the compounds of the formulae (III), (IV) and (VIII) to (X): ##STR6## and capable of being adsorbed by the zinc oxide at an adsorption rate of 90% or more, said adsorption being determined in such a manner that a dye solution having a total weight of 50 g and a concentration of methyl alcohol of 15% by weight is prepared from a sensitizing dye in an absolute weight of 1 mg and a mixed solvent consisting of toluene and methyl alcohol, 2 g of finely divided zinc oxide are dispersed in the dye solution, the resultant dispersion is stirred and then left to stand at a temperature of 25° C. for one hour, to allow the resultant dye-adsorbed zinc oxide to be precipitated to provide a clear supernatant dye solution, a spectral absorption of the original dye solution and the resultant clear supernatant dye solution are measured at a wave length at which the dye exhibits a highest absorption, and the adsorption of the sensitizing dye by the finely divided zinc oxide is calculated in accordance with the equation: ##EQU3## wherein A represents a maximum spectral absorption of the original dye solution at the above-mentioned wave length and B represents a maximum spectral absorption of the supernatant dye solution at the same wave length as mentioned above.