Patent ID: 6136889
Filing Date: 2000-10-24
Classification: B41C,C09D,G03G

Abstract:
A method for preparing a printing plate by an ink jet process comprising:discharging dropwise an oily ink using an electrostatic field on an image receiving layer of a lithographic printing plate precursor from a head having a discharge electrode to form an image on the image receiving layer, and thendesensitizing a non-image area of the image receiving layer by a chemical reaction to prepare a lithographic printing plate,wherein the lithographic printing plate precursor comprises a water-resistant support having provided thereon the image receiving layer, wherein the image receiving layer contains zinc oxide and a binder resin, wherein the surface of the image receiving layer has a contact angle with water of 50.degree. or more, and wherein the oily ink comprises resin particles dispersed in a nonaqueous carrier liquid having an electric resistance of 10.sup.9 .OMEGA.cm or more and a dielectric constant of 3.5 or less,wherein said resin particles dispersed are polymer particles obtained by polymerization granulation of a solution comprising (i), (ii) and (iii):(i) at least one monofunctional monomer (A) which is soluble in a nonaqueous solvent which is at least miscible with the nonaqueous carrier liquid and becomes insoluble therein by polymerization;(ii) (ii-a) at least one monomer (B) represented by the following formula (I-A) which is copolymerizable with the monomer (A), or(ii-b) at least one monofunctional macromonomer (MA) having a weight average molecular weight of 1.times.10.sup.3 to 2.times.10.sup.4 obtained by combining a polymerizable double bond group represented by the following formula (II-B) with only one end of a main chain of a polymer comprising a repeating unit corresponding to a monomer represented by the following formula (I-B); and(iii) at least one resin for dispersion stabilization (P) which is a polymer comprising a repeating unit represented by the following formula (III), wherein the polymer is crosslinked at a part of its main chain thereof, and the resin (P) is soluble in the nonaqueous solvent: ##STR44## wherein E.sup.1 represents an aliphatic group having 8 or more carbon atoms or a substituent having a total number of atoms of 8 or more, provided that hydrogen atoms directly attached to a carbon or nitrogen atom are excluded from the number, represented by the following formula (IV-A): ##STR45## wherein R.sup.21 represents a hydrogen atom or an aliphatic group having 1 to 18 carbon atoms;B.sup.1 and B.sup.2 are the same or different and each represents --O--, --S--, --CO--, --CO.sub.2 --, --OCO--, --SO.sub.2 --, --N(R.sup.22)--, --CON(R.sup.22)--, --N(R.sup.22)CO--, --N(R.sup.22)SO.sub.2 --, --SO.sub.2 N(R.sup.22)--, --NHCO.sub.2 --, or --NHCONH--, in which R.sup.22 has the same meaning as R.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 (IV-Aa) 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 (IV-Aa) 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 (IV-Aa), (2) a combination of at least one group represented by formula (IV-Aa) 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: ##STR46## wherein 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;R.sup.3 has the same meaning as R.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;U.sup.1 represents --COO--, --CONH--, --CON(R.sup.11)--, --OCO--, --CONHCOO--, --CH.sub.2 COO--, --(CH.sub.2).sub.k OCO--, --O--, --C.sub.6 H.sub.4 --, or --C.sub.6 H.sub.4 --COO--, in which R.sup.11 represents an aliphatic group or a substituent represented by formula (IV-A) described above, and k represents an integer of 1 to 4; anda.sup.1 and a.sup.2 are the same or different and each represents a hydrogen atom, an alkyl group, a halogen atom, a cyano group, --COO--R.sup.12 or --CH.sub.2 COO--R.sup.12, in which R.sup.12 represents an aliphatic group: ##STR47## wherein V.sup.0 represents --COO--, --OCO--, --(CH.sub.2).sub.r COO--, --(CH.sub.2)OCO--, --O--, --SO.sub.2 --, --CONHCOO--, --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.11 and a.sup.12 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 group 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 (IV-B): ##STR48## wherein D.sup.21 represents a hydrogen atom or an aliphatic group having 1 to 22 carbon atoms;B.sup.11 and B.sup.12 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 D.sup.21 ;A.sup.11 and A.sup.12 are the same or different and each represents at least one group selected from a group represented by the following formula (IV-Ba) and a hydrocarbon group having 1 to 18 carbon atoms, which each may be substituted, provided that, in the case where A.sup.11 or A.sup.12 represents two or more groups selected from a group represented by the following formula (IV-Ba) and a hydrocarbon group having 1 to 18 carbon atoms, A.sup.11 or A.sup.12 represents (1) two or more groups represented by formula (IV-Ba), (2) a combination of at least one group represented by formula (IV-Ba) 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: ##STR49## wherein B.sup.13 and B.sup.14 are the same or different and each has the same meaning as B.sup.11 and B.sup.12 ;A.sup.14 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.sup.0, n.sup.0 and p.sup.0 are the same or different and each represents an integer of 0 to 4, provided that m.sup.0, n.sup.0 and p.sup.0 are not 0 at the same time; ##STR50## wherein V.sup.1 represents --COO--, --CONHCOO--, --CONHCONH--, --CONH-- or a phenylene group; andb.sup.11 and b.sup.12 are the same or different and each has the same meaning as a.sup.11 and a.sup.12 in formula (I-B); ##STR51## wherein X.sup.1 represents --COO--, --OCO--, --(CH.sub.2).sub.x OCO--, --(CH.sub.2).sub.x COO--, --O-- or --SO.sub.2 --, in which x represents an integer of 1 to 3;Y.sup.1 represents an aliphatic group having 6 or more carbon atoms; andd.sup.1 and d.sup.2 are the same or different and have the same meaning as a.sup.1 and a.sup.2 in formula (I-A) or a.sup.11 and a.sup.12 in formula (I-B);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 surface of the image receiving layer faces the discharge electrode and a counter electrode is provided on the opposite side thereof.