Liquid developer for electrostatic photography

A liquid developer useful for developing a latent image having been electrophotographically formed on a printing plate precursor into a toner image during manufacture of a printing plate, said printing plate precursor comprising an electrically conductive substrate having a hydrophilic surface and a layer containing an organic photoconductive compound on said hydrophillic surface, said toner image being fixed, and a non-image area of said layer other than said toner image area being removed by etching with an alkaline etching solution to provide said printing plate said liquid developer comprising resin particles dispersed in a non-aqueous solvent having a volume resistivity of at least 10.sup.9 .OMEGA.cm and having a dielectric constant less than 3, said dispersed resin particles being obtained by polymerizing:

• (a) at least one monomer selected from the group consisting of methyl methacrylate and ethyl methacrylate soluble in said nonaqueous solvent;
• and
• (b) at least one monomer selected from the group consisting of alkyl acrylate wherein the alkyl group has up to 4 carbon atoms and butyl methacrylate, said alkyl acrylate and butyl methacrylate being soluble in said non-aqueous solvent, but being made insolubilized by polymerization;
• said monomer (a) and said monomer (b) being polymerized in the presence of a dispersion stabilizing resin, said dispersion stabilizing resin being soluble in said non-aqueous solvent, said dispersion stabilizing resin comprising a graft copolymer formed by polymerizing:
• (i) at least one macromonomer having a weight-average molecular weight of 1.times.10.sup.3 to 4.times.10.sup.4, said macromonomer having a polymerizable double bond and containing a group represented by the following formula (I) bonded to one terminal of a main polymer chain of said macromonomer, said macromonomer containing at least one moiety represented by the following formula (II) in said main polymer chain of said macromonomer;
• and
• (ii) at least one monomer represented by the following formula (III),
• wherein said monomers (a) and (b) are made insoluble by polymerization:
• ##STR22## wherein V represents --COO--, --OCO--, --(CH.sub.2).sub.k --OCO--, --(CH.sub.2).sub.k --COO--, --O--, --CONHCOO--, --CONHNCO--, --SO.sub.2 --, --CO--, --CONZ.sub.1 --, --SO.sub.2 NZ.sub.1 -- or a phenylene group;
• Z.sub.1 represents a hydrogen atom or a hydrocarbon group;
• k represents an integer of 1 to 3;
• a.sub.1 and a.sub.2 may be the same or different and each represents a hydrogen atom, a halogen atom, a cyano group, a hydrocarbon group, --COO--Z.sub.2 or --COO--Z.sub.2 bonded through a hydrocarbon group;
• and
• Z.sub.2 represents a hydrogen atom or a hydrocarbon group which may be substituted;
• ##STR23## wherein X.sub.0 represents --COO--, --OCO--, --(CH.sub.2).sub.k --OCO--, --(CH.sub.2).sub.k --COO--, --O--, --CONHCOO--, --COHNCO--, --SO.sub.2, --CO--, --CONZ.sub.1 --, or --SO.sub.2 NZ.sub.1 -- or a bonding group comprising at least two combinations thereof;
• Z1 has the same meaning as in formula (I);
• b.sub.1 and b.sub.2 may be the same or different and each has the same meaning as a.sub.1 and a.sub.2 in formula (I);
• k represents an integer of 1 to 3;
• and
• Q.sub.0 represents an aliphatic group having 4 to 22 carbon groups;
• ##STR24## wherein X.sub.1 has the same meaning as V in formula (I);
• Q.sub.1 represents a hydrogen atom, an aliphatic group having 1 to 22 carbon atoms or an aromatic group having 6 to 12 carbon atoms;
• and
• c.sub.1 and c.sub.2 may be the same or different and each has the same meaning as a.sub.1 and a.sub.2 in formula (I).