Patent ID: 6127452
Filing Date: 2000-10-03
Classification: C09D

Abstract:
A method for preparing a printing plate by an ink jet process consisting essentially of discharging an oily ink using an electrostatic field on a water-resistant support having provided thereon an image receiving layer having a lithographically printable hydrophilic surface dropwise from a head having a discharge electrode to form an image on the lithographically printable hydrophilic surface, wherein the oily ink comprises resin particles dispersed in a nonaqueous solvent having an electric resistance of 10.sup.9 .OMEGA.cm or more and a dielectric constant of 3.5 or less, and said resin particles dispersed are copolymer resin particles obtained by polymerization of a solution comprising:(i) at least one monofunctional monomer (A) which is soluble in the nonaqueous solvent and becomes insoluble therein by polymerization;(ii) at least one monofunctional macromonomer (MA) having a weight average molecular weight of 2.times.10.sup.4 or less in which a polymerizable double bond group represented by the following formula (II) is combined with only one end of a main chain of a polymer comprising a repeating unit represented by the following formula (I): ##STR24## wherein, in formula (I), X.sup.0 represents --COO--, --OCO--, --(CH.sub.2).sub.r COO--, --(CH.sub.2).sub.r OCO--, --O--, --SO.sub.2 --, --CONHCONH--, --CONHCONH--, --CON(D.sup.11)-, --SO.sub.2 N(D.sup.11)- or a phenylene group, in which D.sup.11 represents a hydrogen atom or a hydrocarbon group having 1 to 22 carbon atoms, and r represents an integer of 1 to 4;a.sup.1 and a.sup.2 are the same or different, and each represents a hydrogen atom, a halogen atom, a cyano group, a hydrocarbon group, --COO-D.sup.12, or --COO-D.sup.12 linked through a hydrocarbon group, in which D.sup.12 represents a hydrogen atom or a hydrocarbon group which may be substituted;D.sup.0 represents a hydrocarbon group having 8 to 22 carbon atoms or a substituent having a total number of atoms of 8 or more, provided that hydrogen atoms attached to a carbon or nitrogen atom are excluded from the number, represented by the following formula (I'):-(A.sup.1 -B.sup.1).sub.m -(A.sup.2 -B.sup.2).sub.n -D.sup.21 (I')wherein, in formula (I'),D.sup.21 represents a hydrogen atom or an aliphatic group having 1 to 22 carbon atoms;B.sup.1 and B.sup.2 are the same or different, and each represents --O--, --CO--, --CO.sub.2 --, --OCO--, --SO.sub.2 --, --N(D.sup.22)-, --CON(D.sup.22)-, or --N(D.sup.22)CO--, in which D.sup.22 has the same meaning as D.sup.21 ;A.sup.1 and A.sup.2 are the same or different, and each represents at least one group selected from a group represented by the following formula (I"") and a hydrocarbon group having 1 to 18 carbon atoms, which each may be substituted, provided that, in the case where A.sup.1 or A.sup.2 represents two or more groups selected from a group represented by the following formula (I"") and a hydrocarbon group having 1 to 18 carbon atoms, A.sup.1 or A.sup.2 represents (1) two or more groups represented by formula (I""), (2) a combination of at least one group represented by formula (I"") and at least one hydrocarbon group having 1 to 18 carbon atoms, or (3) two or more hydrocarbon groups having 1 to 18 carbon atoms: ##STR25## wherein, in formula (I""), B.sup.3 and B.sup.4 are the same or different, and each has the same meaning as B.sup.1 and B.sup.2 ;A.sup.4 represents a hydrocarbon group having 1 to 18 carbon atoms which may be substituted;D.sup.23 has the same meaning as D.sup.21 ; andm, n and p are the same or different, and each represents an integer of 0 to 4, provided that m, n and p are not 0 at the same time;wherein, in formula (II),V.sup.1 represents --COO--, --CONHCOO--, --CONHCONH--, --CONH--, or a phenylene group; andb.sup.1 and b.sup.2 are the same or different, and each has the same meaning as a.sup.1 and a.sup.2 in formula (I); and(iii) at least one resin (P) for dispersion stabilization which is colloidally dispersed in the nonaqueous solvent and contains(iiia) at least one macromonomer (MM) having a weight average molecular weight of 1.times.10.sup.3 to 2.times.10.sup.4 in which a polymerizable double bond group which is selected from the polymerizable double bond groups represented by the above formula (II) is combined with only one end of a main chain of a polymer comprising a repeating unit represented by the following formula (III): ##STR26## wherein, in formula (III), X.sup.1 has the same meaning as X.sup.0 in formula (I);d.sup.1 and d.sup.2 are the same or different, and each has the same meaning as a.sup.1 and a.sup.2 in formula (I); andQ.sup.1 represents an alkyl or alkenyl group having 10 to 22 carbon atoms; and(iiib) at least one monofunctional monomer (M) which is soluble in the nonaqueous solvent and becomes insoluble therein by polymerization;wherein the water-resistant support has a specific electric resistance of 10.sup.10 .OMEGA.cm or less at least at an area directly under the image receiving layer;wherein the resin particles dispersed in the oily ink are electrically detectable particles positively or negatively charged;wherein the lithographically printable hydrophilic surface faces the discharge electrode and a counter electrode is provided on the opposite side thereof;wherein said resin (P) for dispersion stabilization is dispersed colloidally into the nonaqueous solvent to have an average particle diameter of 0.13 .mu.m or less.