MANUFACTURE OF SUPPORT FOR LITHOGRAPHIC PLATE

摘要

PURPOSE:To improve the performance as support for lithographic plate by applying an alternating waveform current to an aluminum plate in a solution contaning an electrolyte comprising hydrochloric acid, nitric acid or the combination thereof so that the ratio of the quantity of electricity at the time of positive to that at the time of negative is as specified to effect an electrolytic roughening treatment after the surface thereof is roughened mechanically. CONSTITUTION:After the surface of an aluminum plate is roughened mechanically, an alternating waveform current is applied thereto in a solution containing an electrolyte comprising hydrochloric acid, nitric acid or the combination thereof so that the ratio of the quantity of electricity at the time of positive to that at the time of negative is 1.0-2.5 to effect an electrolytic roughenening treatment. The brush graining method is preferable for the mechanical roughening of the aluminum plate. The aluminum plate undergoes a chemical etching on the surface thereof before doing the electrochemical roughening. Then, the aluminum plate is treated in the solution containing the electrolyte comprising hydrochloric acid, nitric acid or the combination thereof by running such an alternating waveform current that the quantity Qa of electricity at the time of positive to that Qc at the time of negative is 1.0-2.5 between the aluminum plate and an opposed electrode made of a graphite material or an aluminum plate. In this case, the value Qa preferably exceeds 300 Coulomb/dm2.