Abstract: A lithographic printing plate is produced by the steps of forming a latent electrostatic image on a photoconductive zinc oxide insulating layer and developing this layer with a toner which forms an imagewise deposit on the recording layer. Applicants' invention relates to contacting the portions of the recording layer which are not covered with the hydrophobic deposit with a hydrophilizing composition (commonly called a conversion wash) comprising the reaction product of (1) phosphoric acid or one of the anions derived from such acid, (2) an organic amine compound, and (3) a hydrophilic metal cation, to form a reaction product with zinc ions from the zinc oxide which reaction product of zinc ions with said composition is substantially insoluble in said composition and is preferentially wetted by water thereby repelling lithographic inks. The plate produced by this process is especially useful for use on a lithographic offset press to produce multiple copies of an original.

Abstract: A lithographic printing plate is produced by the steps of forming a latent electrostatic image on a photoconductive zinc oxide insulating layer and developing this layer with a toner which forms an imagewise deposit on the recording layer. Applicants' invention relates to contacting the portions of the recording layer which are not covered with the hydrophobic deposit with a hydrophilizing composition (commonly called a conversion wash) comprising the reaction product of (1) phosphoric acid or one of the anions derived from such acid, (2) an organic amine compound, and (3) a hydrophilic metal cation, to form a reaction product with zinc ions from the zinc oxide which reaction product of zinc ions with said composition is substantially insoluble in said composition and is preferentially wetted by water thereby repelling lithographic inks. The plate produced by this process is especially useful for use on a lithographic offset press to produce multiple copies of an original.