Presensitised lithographic printing plate with light-sensitive ester coating - comprises naphthoquinone-di:azide-sulphonate of poly-4-hydroxyphenyl-alkane and alkali-soluble resin, for hydrofluoride free soln. mark removal

摘要

The plate comprises a roughened and anodised Al with a light-sensitive coating contg. an alkali-soluble resin (I) and, as light-sensitive substance, a 1,2 (and/or 2,1)-naphthoquinone-diazide-5- (and/or -4-)-sulphonate ester (II) of a polyhydroxy cpd., which is a poly(4-hydroxyphenyl)-alkane of the formula Q-(CH2)a-C(Q)2-(CH2)b-C(R5)(R6)-(CH2)c-Q (III); Q = a 4-hydroxyphenyl gp. of formula (IV); R1-4 is H, OH, halogen, alk(en)yl or alkoxy; R5-6 is H, alkyl or Q: a and c are o or 1; and b is 0-4. More specifically, R1-4 = H, OH, Cl, Br, I, 1-4C alk(en)yl or 1-4C alkoxy; and R5-6 = H, 1-4C alkyl or Q. The coating contains 5-100, (10-50) (wt.) pts. (III) w.r.t (I) and max. 80% (I). It may also contain 0.1-5% cyclic anhydride, phenol and/or organic acid, 0.1-5% nonionic or amphoteric surfactant, 0.05-0.5% fluorinated surfactant and/or a print-out agent to produce a visible image immediately after exposure, a dyestuff to colour the image and/or a filler. ADVANTAGE - Sticky marks formed by half-exposed area at the edge of the plate may be removed with a soln. free from HF and ink is unstuck to the areas, even if the plate is baked.