Processless lithographic printing plate precursor

Abstract

A radiation-sensitive medium comprises hydrophilic polymer particles, the particles comprising a thermally softenable hydrophobic polymer, a hydrophilic polymer and a bonding compound capable of chemically bonding to the hydrophobic polymer and to the hydrophilic polymer. The radiation-sensitive medium further may comprise a substance capable of converting radiation into heat. The radiation-sensitive medium is aqueous-ineluable when coated and dried, and becomes hydrophobic under the action of heat. The polymer particles are made by polymerization of at least one hydrophobic monomer and at least one bonding compound in the presence of the hydrophilic polymer. The radiation-sensitive medium may be provided as a coatable composition to be applied to substrates to form a processless radiation-imageable lithographic printing precursor, which may further be provided with an aqueous eluable hydrophilic overcoat. The processless radiation-imageable lithographic printing precursor so created may be imaged using absorbed radiation that is imagewise converted to heat, resulting in areas of hydrophobic property, while unimaged areas retain their hydrophilic property. This allows the latent image so formed to be employed in creating a negative-working lithographic printing master. The negative-working lithographic printing master so created is irreversible, does not require a substrate of controlled hydrophilicity and provides great toughness in the exposed areas. The radiation-sensitive medium may be coated on-platesetter or on-press onto a suitable substrate, including the drum of the press. It may also be coated off-press on a suitable substrate to create a precoated processless radiation-imageable lithographic printing precursor.

1 . A processless radiation-imageable lithographic printing precursor comprising a substrate, a dried and aqueous-ineluable coating of a radiation-sensitive medium on the substrate and an aqueous eluable hydrophilic overcoat over the coating of a radiation-sensitive medium, the radiation-sensitive medium comprising:
 a. a substance capable of converting radiation into heat; and   b. hydrophilic polymer particles comprising:
 i. at least one thermally softenable hydrophobic polymer, 
 ii. at least one hydrophilic polymer and 
 iii. at least one bonding compound capable of chemically bonding to the hydrophobic polymer and to the hydrophilic polymer. 
   
   
   
       2 . The precursor of  claim 1 , wherein the aqueous eluable hydrophilic overcoat comprises a water-soluble organic polymer. 
   
   
       3 . The precursor of  claim 2 , wherein the water-soluble organic polymer is at least one of polyvinylalcohol, polyvinylacetate, polyacrylic acid, poly(meth)acrylic acid, an alkali metal salt of poly(meth)acrylic acid, an amine salt of poly(meth)acrylic acid, poly 2-hydroxyethyl(meth)acrylate, poly(meth)acrylamide, polyvinyl methyl ether, polyvinyl methyl ether/maleic anhydride copolymer, polyvinylpyrolidone, poly-2-acrylamide-2-methylpropane sulfonic acid, an alkali metal salt of poly-2-acrylamide-2-methylpropane sulfonic acid, an amine salt of poly-2-acrylamide-2-methylpropane sulfonic acid, alginic acid, a salt of alginic acid, protan jelly, carageenin, tragacanth, laminarin sulfate, starch, animal glues, vegetable mucilages, gum arabic, cellulose, a modification product of cellulose and a polysaccharide. 
   
   
       4 . The precursor of  claim 3 , wherein the overcoat further comprises at least one of a light-to-heat converting agent, a water-soluble dye, a colorant and a surfactant. 
   
   
       5 . The precursor of  claim 2 , wherein the coating is capable of becoming hydrophobic under the action of heat. 
   
   
       6 . The precursor of  claim 5 , wherein the substance capable of converting radiation into heat is hydrophobic. 
   
   
       7 . The precursor of  claim 5 , wherein the radiation is infrared radiation. 
   
   
       8 . The precursor of  claim 7 , wherein the infrared radiation has wavelength between 700 nm and 1200 nm n. 
   
   
       9 . The precursor of  claim 5 , wherein the hydrophilic polymer has a primary amine group. 
   
   
       10 . The precursor of  claim 5 , wherein the at least one hydrophilic polymer is at least one of a saccharide, a chitosan polymer, a polyethyleneimine polymer, a polyamine polymer, a polyvinylamine polymer, a polyallylamine polymer, a polydiallylamine polymer, an amino(meth)acrylate polymer, a polyamide polymer, a polyamide-epichlorohydrin polymer, a polyamine-epichlorohydrin polymer, a polyamidepolyamine-epichlorohydrin polymer, a dicyandiamide-polycondensation product polymer and a copolymer thereof. 
   
   
       11 . A method for making a negative-working lithographic printing master, the method consisting essentially of, in the order stated, imagewise irradiating the processless radiation-imageable lithographic printing precursor of  claim 10  with imaging radiation and treating the precursor with an aqueous medium. 
   
   
       12 . A processless radiation-imageable lithographic printing precursor comprising a substrate, a dried and aqueous-ineluable coating of a radiation-sensitive medium on the substrate and an aqueous eluable hydrophilic overcoat over the coating of a radiation-sensitive medium, the radiation-sensitive medium comprising:
 a. a substance capable of converting radiation into heat; and   b. a hydrophilic polymer; and   c at least one copolymer of a hydrophobic monomer and a bonding monomer, the bonding monomer being capable of chemically bonding to the hydrophilic polymer and to the hydrophobic monomer.   
   
   
       13 . The precursor of  claim 12 , wherein the aqueous eluable hydrophilic overcoat comprises a water-soluble organic polymer. 
   
   
       14 . The precursor of  claim 13 , wherein the water-soluble organic polymer is at least one of polyvinylalcohol, polyvinylacetate, polyacrylic acid, poly(meth)acrylic acid, an alkali metal salt of poly(meth)acrylic acid, an amine salt of poly(meth)acrylic acid, poly 2-hydroxyethyl(meth)acrylate, poly(meth)acrylamide, polyvinyl methyl ether, polyvinyl methyl ether/maleic anhydride copolymer, polyvinylpyrollidone, poly-2-acrylamide-2-methylpropane sulfonic acid, an alkali metal salt of poly-2-acrylamide-2-methylpropane sulfonic acid, an amine salt of poly-2-acrylamide-2-methylpropane sulfonic acid, alginic acid, a salt of alginic acid, protan jelly, carageenin, tragacanth, laminarin sulfate, starch, animal glues, vegetable mucilages, gum arabic, cellulose, a modification product of cellulose and a polysaccharide. 
   
   
       15 . The precursor of  claim 12 , wherein the overcoat further comprises at least one of a light-to-heat converting agent, a water-soluble dye, a colorant and a surfactant. 
   
   
       16 . The precursor of  claim 13 , wherein the coating is capable of becoming hydrophobic under the action of heat. 
   
   
       17 . The precursor of  claim 16 , wherein the substance capable of converting radiation into heat is hydrophobic. 
   
   
       18 . The precursor of  claim 17 , wherein the radiation is infrared radiation. 
   
   
       19 . The precursor of  claim 18 , wherein the infrared radiation has wavelength between 700 nm and 1200 nm. 
   
   
       20 . The precursor of  claim 16 , wherein the hydrophilic polymer has a primary amine group. 
   
   
       21 . The precursor of  claim 16 , wherein the at least one hydrophilic polymer is at least one of a saccharide, a chitosan polymer, a polyethyleneimine polymer, a polyamine polymer, a polyvinylamine polymer, a polyallylamine polymer, a polydiallylamine polymer, an amino(meth)acrylate polymer, a polyamide polymer, a polyamide-epichlorohydrin polymer, a polyamine-epichlorohydrin polymer, a polyamidepolyamine-epichlorohydrin polymer, a dicyandiamide-polycondensation product polymer and a copolymer thereof. 
   
   
       22 . A method for making a negative-working lithographic printing master, the method consisting essentially of, in the order stated, imagewise irradiating the processless radiation-imageable lithographic printing precursor of  claim 21  with imaging radiation and treating the precursor with an aqueous medium. 
   
   
       23 .- 44 . (canceled) 
   
   
       45 . A processless radiation-imageable lithographic printing precursor comprising a substrate, a dried and aqueous-ineluable hydrophilic coating of a radiation-sensitive medium on the substrate and an aqueous eluable hydrophilic overcoat over the coating of a radiation-sensitive medium, the radiation-sensitive medium comprising hydrophilic polymer particles, the particles comprising chitosan and at least one thermally softenable hydrophobic polymer, the coating capable of becoming hydrophobic under the action of heat. 
   
   
       46 . The precursor of  claim 45 , wherein the aqueous eluable hydrophilic overcoat comprises a water-soluble organic polymer. 
   
   
       47 . The precursor of  claim 46 , wherein the water-soluble organic polymer is at least one of polyvinylalcohol, polyvinylacetate, polyacrylic acid, poly(meth)acrylic acid, an alkali metal salt of poly(meth)acrylic acid, an amine salt of poly(meth)acrylic acid, poly 2-hydroxyethyl(meth)acrylate, poly(meth)acrylamide, polyvinyl methyl ether, polyvinyl methyl ether/maleic anhydride copolymer, polyvinylpyrollidone, poly-2-acrylamide-2-methylpropane sulfonic acid, an alkali metal salt of poly-2-acrylamide-2-methylpropane sulfonic acid, an amine salt of poly-2-acrylamide-2-methylpropane sulfonic acid, alginic acid, a salt of alginic acid, protan jelly, carageenin, tragacanth, laminarin sulfate, starch, animal glues, vegetable mucilages, gum arabic, cellulose, a modification product of cellulose and a polysaccharide. 
   
   
       48 . The precursor of  claim 47 , wherein the overcoat further comprises at least one of a light-to-heat converting agent, a water-soluble dye, a colorant and a surfactant. 
   
   
       49 . A method for making a negative-working lithographic printing master, the method comprising the steps of:
 a. providing a precursor comprising a dried and aqueous-ineluable coating of a radiation-sensitive medium on a substrate and an aqueous eluable hydrophilic overcoat over the coating of a radiation-sensitive medium, the radiation-sensitive medium comprising hydrophilic polymer particles, the particles comprising chitosan and at least one thermally softenable hydrophobic polymer, the coating being hydrophilic and capable of becoming hydrophobic under the action of heat,   b. imagewise irradiating the precursor with infrared imaging radiation of wavelength between 700 nm and 1200 nm and   c treating the precursor with an aqueous medium.   
   
   
       50 . The method of  claim 49 , wherein the aqueous eluable hydrophilic overcoat comprises a water-soluble organic polymer. 
   
   
       51 . The method of  claim 50 , wherein the water-soluble organic polymer is at least one of polyvinylalcohol, polyvinylacetate, polyacrylic acid, poly(meth)acrylic acid, an alkali metal salt of poly(meth)acrylic acid, an amine salt of poly(meth)acrylic acid, poly 2-hydroxyethyl(meth)acrylate, poly(meth)acrylamide, polyvinyl methyl ether, polyvinyl methyl ether/maleic anhydride copolymer, polyvinylpyrollidone, poly-2-acrylamide-2-methylpropane sulfonic acid, an alkali metal salt of poly-2-acrylamide-2-methylpropane sulfonic acid, an amine salt of poly-2-acrylamide-2-methylpropane sulfonic acid, alginic acid, a salt of alginic acid, protan jelly, carageenin, tragacanth, laminarin sulfate, starch, animal glues, vegetable mucilages, gum arabic, cellulose, a modification product of cellulose and a polysaccharide. 
   
   
       52 . The method of  claim 51 , wherein the overcoat further comprises at least one of a light-to-heat converting agent, a water-soluble dye, a colorant and a surfactant.