Dry lithographic printing plate prodn. from presensitised plate - by exposure, development and dyeing in aq. dye-bath contg. little organic solvent

摘要

Prodn. of a dry lithographic printing plate from a presensitised (PS) plate involves (a) selective exposure of a Ps plate with a substrate habing a light-sensitive coat covered by a silicone rubber layer; (b) rubbing the exposed plate with a brush whilst the plate is immersed in a liquid developer (I) contg. max. 4 (wt.)% water-insol. organic solvent (II) to remove the silicone rubber layer in the unexposed areas; and (c) immersing the plate in a coloured liq. (III) contg. water as main component and max. 20% organic solvent (IV) to dye the image areas selectively. Pref. (II) is propylene glycol, diethylene glycol mono-n-hexyl ether, n-butyl lactate, isoamyl alcohol, n-hexanol, diethyl oxalate, diethyl succinate, ethylene glycol monobutyl ether acetate ethylene glycol mono-n-hexyl ether, tri-n-butyl phosphate, toluene or `Exxsol D100' (RTM) (I) may also contain a water-soluble organic solvent, pref. glycerol, (di)ethylene glycol, mono-, di- or tri-propylene glycol, diethylene glycol mono-(m)ethyl or -n-butyl ether, lactic acid, acetic acid, triethyl phosphate or (m) ethyl lactate. ADVANTAGE - The process prevents the dyestuff diffusing into the nonimage areas in the course of many days, with loss of plate test properties.