Metal based lithographic printing plates - electroplated with cobalt to provide bonding layer for the organic light sensitive layer

摘要

Lithographic printing plates comprise a support with at least one metallic surface which is electroplated with cobalt and coated directly with an organic light sensitive layer without using an intermediate adhesion layer. The substrate is e.g. of aluminium; or steel which has been successively copper- and chrome plated before applicn. of the cobalt plating layer. The Co layer is pref. applied from an electrolytic bath at 20-60 deg.C, contg. 15-100 g/l CoC12.6H2O, 5-25 g/l boric acid and 4-25 ml 37.8% HCl, at a potential of 3-16 V and a current density of 1.4-8.7 amps/dm2. The cobalt layer gives excellent adhesion of the light-sensitive layer, whilst obviating the need to use an intermediate adhesion layer, thus giving more economical prodn. of the plates.