High speed negative working thermal printing plates

A printing plate precursor, comprising:

• a substrate;
• and
• coated on said substrate an IR-sensitive composition comprising:
• a polymeric binder;
• and a free radical polymerizable system consisting of:
• at least one component selected from unsaturated free radical polymerizable monomers, oligomers which are free radical polymerizable and polymers containing C═C bonds in the backbone and/or in the side chain groups;
• and an initiator system comprising:
• (a) at least one compound capable of absorbing IR radiation;
• (b) at least one compound capable of producing radicals;
• and (c) at least one carboxylic acid represented by the formula:
• 13
• wherein each of R5, R6, R7, R8 and R9 is independently selected from the group consisting of:
• hydrogen, alkyl, aryl, halogen, alkoxy, hydroxyalkyl, carboxyalkyl, alkylthio, alkylsulfonyl, sulfonic, alkylsulfonate, dialkylamino, acyl, alkoxycarbonyl, cyano and nitro;
• wherein R5 and R6, R6 and R7, R7 and R8, or R8 and R9 together optionally form an aromatic or aliphatic ring;
• wherein R10 is selected from the group consisting of:
• hydrogen, alkyl, aryl, hydroxyalkyl, carboxyalkyl, acyl, alkoxycarbonyl, alkylsulfonyl and alkylsulfonate;
• or R10 and its bond together optionally form an electron pair;
• or R9 and R11 together optionally form a ring;
• wherein R11 is an alkylene group of C1-C6 carbon atoms;
• and wherein R10 and R11 together optionally form an aliphatic ring;
• wherein A is a heteroatom selected from the group consisting of:
• N, O and S;
• with the proviso that the total acid number of said polymeric binder is 70 mg KOH/g or less.

A process for preparing a printing plate, comprising:

• imagewise exposing a printing plate precursor to IR radiation, said printing plate precursor comprising:
• a substrate;
• and coated on said substrate an IR-sensitive composition comprising:
• a polymeric binder;
• and a free radical polymerizable system consisting of:
• at least one component selected from unsaturated free radical polymerizable monomers, oligomers which are free radical polymerizable and polymers containing C═C bonds in the backbone and/or in the side chain groups;
• and an initiator system comprising:
• (a) at least one compound capable of absorbing IR radiation;
• (b) at least one compound capable of producing radicals;
• and (c) at least one carboxylic acid represented by the formula:
• 14
• wherein each of R5, R6, R7, R8 and R9 is independently selected from the group consisting of:
• hydrogen, alkyl, aryl, halogen, alkoxy, hydroxyalkyl, carboxyalkyl, alkylthio, alkylsulfonyl, sulfonic, alkylsulfonate, dialkylamino, acyl, alkoxycarbonyl, cyano and nitro;
• wherein R5 and R6, R6 and R7, R7 and R8, or R8 and R9 together optionally form an aromatic or aliphatic ring;
• wherein R10 is selected from the group consisting of:
• hydrogen, alkyl, aryl, hydroxyalkyl, carboxyalkyl, acyl, alkoxycarbonyl, alkylsulfonyl and alkylsulfonate;
• or R10 and its bond together optionally form an electron pair;
• or R9 and R11 together optionally form a ring;
• wherein R11 is an alkylene group of C1-C6 carbon atoms;
• and wherein R10 and R11 together optionally form an aliphatic ring;
• wherein A is a heteroatom selected from the group consisting of:
• N, O and S;
• with the proviso that the total acid number of said polymeric binder is 70 mg KOH/g or less;
• and thereafter
• developing with a developer solution to produce the printing plate.

A method for producing an image, comprising:

• coating an optionally pretreated substrate with an IR-sensitive composition comprising:
• a polymeric binder;
• and a free radical polymerizable system consisting of:
• at least one component selected from unsaturated free radical polymerizable monomers, oligomers which are free radical polymerizable and polymers containing C═C bonds in the backbone and/or in the side chain groups;
• and an initiator system comprising:
• (a) at least one compound capable of absorbing IR radiation;
• (b) at least one compound capable of producing radicals;
• and (c) at least one carboxylic acid represented by the formula:
• 15
• wherein each of R5, R6, R7, R8 and R9 is independently selected from the group consisting of:
• hydrogen, alkyl, aryl, halogen, alkoxy, hydroxyalkyl, carboxyalkyl, alkylthio, alkylsulfonyl, sulfonic, alkylsulfonate, dialkylamino, acyl, alkoxycarbonyl, cyano and nitro;
• wherein R5 and R6, R6 and R7, R7 and R8, or R8 and R9 together optionally form an aromatic or aliphatic ring;
• wherein R10 is selected from the group consisting of:
• hydrogen, alkyl, aryl, hydroxyalkyl, carboxyalkyl, acyl, alkoxycarbonyl, alkylsulfonyl and alkylsulfonate;
• or R10 and its bond together optionally form an electron pair;
• or R9 and R11 together optionally form a ring;
• wherein R11 is an alkylene group of C1-C6 carbon atoms;
• and wherein R10 and R11 together optionally form an aliphatic ring;
• wherein A is a heteroatom selected from the group consisting of:
• N, O and S;
• with the proviso that the total acid number of said polymeric binder is 70 mg KOH/g or less to produce a printing plate precursor;
• imagewise exposing said printing plate precursor to IR radiation to produce an imagewise exposed printing plate precursor;
• and thereafter
• developing the precursor with an aqueous developer to obtain a printing plate having thereon a printable lithographic image.

An IR-sensitive composition comprising:

• a polymeric binder;
• and
• a free radical polymerizable system consisting of:
• at least one component selected from unsaturated free radical polymerizable monomers, oligomers which are free radical polymerizable and polymers containing C═C bonds in the backbone and/or in the side chain groups;
• and an initiator system comprising:
• (a) at least one compound capable of absorbing IR radiation;
• (b) at least one compound capable of producing radicals;
• and (c) at least one polycarboxylic acid having an aromatic moiety substituted with a heteroatom selected from N, O and S and further having at least two carboxyl groups wherein at least one of said carboxyl groups is bonded to said heteroatom via a methylene group;
• with the proviso that the total acid number of said polymeric binder is 70 mg KOH/g or less.

A printing plate precursor, comprising:

• a substrate;
• and
• coated on said substrate an IR-sensitive composition comprising:
• a polymeric binder;
• and a free radical polymerizable system consisting of:
• at least one component selected from unsaturated free radical polymerizable monomers, oligomers which are free radical polymerizable and polymers containing C═C bonds in the backbone and/or in the side chain groups;
• and an initiator system comprising:
• (a) at least one compound capable of absorbing IR radiation;
• (b) at least one compound capable of producing radicals;
• and (c) at least one polycarboxylic acid having an aromatic moiety substituted with a heteroatom selected from N, O and S and further having at least two carboxyl groups wherein at least one of said carboxyl groups is bonded to said heteroatom via a methylene group;
• with the proviso that the total acid number of said polymeric binder is 70 mg KOH/g or less.

A process for preparing a printing plate, comprising:

• imagewise exposing a printing plate precursor to IR radiation, said printing plate precursor comprising:
• a substrate;
• and coated on said substrate an IR-sensitive composition comprising:
• a polymeric binder;
• and a free radical polymerizable system consisting of:
• at least one component selected from unsaturated free radical polymerizable monomers, oligomers which are free radical polymerizable and polymers containing C═C bonds in the backbone and/or in the side chain groups;
• and an initiator system comprising:
• (a) at least one compound capable of absorbing IR radiation;
• (b) at least one compound capable of producing radicals;
• and (c) at least one polycarboxylic acid having an aromatic moiety substituted with a heteroatom selected from N, O and S and further having at least two carboxyl groups wherein at least one of said carboxyl groups is bonded to said heteroatom via a methylene group;
• with the proviso that the total acid number of said polymeric binder is 70 mg KOH/g or less;
• and thereafter
• developing with a developer solution to produce the printing plate.

A method for producing an image, comprising:

• coating an optionally pretreated substrate with an IR-sensitive composition comprising:
• a polymeric binder;
• and a free radical polymerizable system consisting of:
• at least one component selected from unsaturated free radical polymerizable monomers, oligomers which are free radical polymerizable and polymers containing C═C bonds in the backbone and/or in the side chain groups;
• and an initiator system comprising:
• (a) at least one compound capable of absorbing IR radiation;
• (b) at least one compound capable of producing radicals;
• and (c) at least one polycarboxylic acid having an aromatic moiety substituted with a heteroatom selected from N, O and S and further having at least two carboxyl groups wherein at least one of said carboxyl groups is bonded to said heteroatom via a methylene group;
• with the proviso that the total acid number of said polymeric binder is 70 mg KOH/g or less to produce a printing plate precursor;
• imagewise exposing said printing plate precursor to IR radiation to produce an imagewise exposed printing plate precursor;
• and thereafter
• developing the precursor with an aqueous developer to obtain a printing plate having thereon a printable lithographic image.