Process for preparing a lithographic printing plate

A process for preparing a lithographic priming plate which comprises the steps of providing a presensitized plate comprised of a substrate having a hydrophilic surface provided thereon with a light-sensitive layer containing an alkaline water-soluble or swellable photocrosslinkable polymer having photodimerizable unsaturated double bonds wherein the light-sensitive layer contains a copolycondensed diazo resin having, as structural units, units derived from an aromatic compound having at least one carboxyl group and units derived from an aromatic diazonium compound represented by the following general formula (I):

• ##STR9## wherein R.sup.1 represents a hydrogen atom, an alkyl group, an alkoxy group, a hydroxy group, a carboxy ester group or a carboxyl group;
• R.sup.2 and R.sup.3 each represents a hydrogen atom, an alkyl group or an alkoxy group;
• X.sup.- represents an anion;
• and Y represents --NH--, --O-- or --S-- wherein the light-sensitive layer is composed so as to be capable of being developed in an aqueous alkaline solution free from an organic solvent;
• imagewise exposing the presensitized plate and developing the presensitized plate with an aqueous alkaline solution free from an organic solvent so as to remove non-image areas of the light-sensitive layer.