Desensitizing using dry reverse lithographic plate

Claim 1

A process for producing a locally desensitized color developer sheet which comprises printing a desensitizor or desensitizor composition for color developer on a color developer sheet using a lithographic printing plate having hydrophilic image areas and hydrophobic non-image areas, wherein said desensitizor composition consists essentially of a desensitizor and water or consists essentially of a desensitizor and an organic solvent having a dielectric constant (at 20° C) of not less than about 5.0 and a surface tension (at 20° C) of not less than about 15 dyne/cm, said desensitizor composition being hydrophilic in nature so as to wet said hydrophilic image and be repelled by said hydrophobic non-image areas said densitizor being selected from polyethylene glycol, polyalkylene polyamines represented by the following general formula: ##STR7## wherein n represents an integer of 2 - 5, m represents an integer of 0 - 6, a, b, c, d and e each represents an integer other than 0 and a + b + c + d + e are about 5 - 200; amine derivatives represented by the following general formula: ##STR8## wherein R 1 represents a C 2 -C 10 alkyl group, an aryl group, preferably with up to 18 carbon atoms, an aralkyl group, preferably of from 7 to 18 carbon atoms, or (CH 2 CH 2 O) z H, x + y being about 3 - 100 and x + y + z are about 5 - 100; spiroacetal diamines represented by the following general formula: ##STR9## wherein R 2 represents a hydrogen atom or an alkyl group, and R 3 and R 4 each represents a C 1 -C 6 straight or branched chain alkylene group; reaction products between the above-described spiroacetal diamine and a compound containing in its molecule one or more oxirane groups; diazabicycloalkenes represented by the following general formula: ##STR10## wherein q represents 2 - 6, and p represents 2 - 11; and compounds between the above described diazabicycloalkene and water or an acid.