Positive working thermal imaging assembly or structure, method for the manufacture thereof and products used as lithographic printing plates and the like

A process for preparing a positive working thermal imaging assembly comprising

• A—a substrate;
• and
• B—a thermally sensitive imaging element of a composite layer structure;
• the process comprising
• (i) applying on a substrate a first layer of a first polymeric material soluble in aqueous alkali solution, optionally containing a compound that absorbs and converts light to heat and/or a colored dye or pigment;
• the first layer being oleophilic;
• (ii) treating the said first layer on a surface thereof with a solution at an elevated temperature that contains an active compound or compounds capable of rendering said first polymeric material less soluble in an aqueous alkali developer at the point of contact, wherein the first layer is treated by contact with solution for 1 to 120 seconds at a temperature of from 50 to 120° C., and wherein said active compound or compounds are polymeric amines, polyacetals, polyethylene glycol, butylated urea formaldehyde, copolymers of vinyl pirrolidone and vinyl acetate, methylated melamine formaldehyde, cellulose esters, or mixtures thereof;
• optionally, and before step (i) applying a first intermediate layer between the substrate and the first layer of a polymeric material which is soluble or dispersible in an aqueous solution and that optionally contains a compound that absorbs and converts light or radiation to heat and/or a colored dye or pigment coated from a solvent that does not substantially dissolve the first layer;
• and
• optionally, applying a third or top layer over the treated first layer from step (ii);
• the third or top layer being composed of a polymeric material which is soluble or dispersible in an aqueous solution and that optionally contains a compound that absorbs and converts light or radiation to heat and/or a colored dye or pigment;
• the first intermediate layer and the third layer being applied with a solvent that does not substantially dissolve the treated or converted first layer.

A positive working thermal imaging assembly comprising

• A—a substrate;
• and
• B—a thermally sensitive imaging element of a composite layer structure comprising
• a first layer on the substrate of a polymeric material soluble in an aqueous alkali solution, optionally containing a compound that absorbs and converts light to heat and/or a colored dye or pigment;
• said first layer being converted on a surface thereof by treatment with a solution at an elevated temperature that contains an active compound capable of rendering said first polymeric material less soluble in an aqueous alkali developer at the point of contact;
• the first layer being oleophilic, wherein the first layer is treated by contact with said solution for 1 to 120 seconds at a temperature of from 50 to 120° C., and wherein said active compound or compounds are polymeric amines, polyacetals, polyethylene glycol, butylated urea formaldehyde, copolymers of vinyl pirrolidone and vinyl acetate, methylated melamine formaldehyde, cellulose esters, or mixtures thereof;
• a first intermediate layer between the substrate and the first layer of a polymeric material selected from the group consisting of polyvinylalcohol, polyvinylpyrrolidone, polyvinylmethyl ether and polyvinylethyl ether which is soluble or dispersible in an aqueous solution and that optionally contains a compound that absorbs and converts light or radiation to heat and/or a colored dye or pigment coated from a solvent that does not substantially dissolve the first layer;
• and
• a third or top layer over the converted first layer and composed of a polymeric material selected from the group consisting of polyvinylalcohol, polyvinylpyrrolidone, polyvinylmethyl ether and polyvinylethyl ether which is soluble or dispersible in an aqueous solution and that optionally contains a compound that absorbs and converts light or radiation to heat and/or a colored dye or pigment;
• the first intermediate layer and the third layer being applied with a solvent that does not substantially dissolve the converted first layer.

A positive working thermal imaging assembly comprising

• A—a substrate;
• and
• B—a thermally sensitive imaging element of a composite layer structure comprising
• a first layer on the substrate of a polymeric material soluble in an aqueous alkali solution, optionally containing a compound that absorbs and converts light to heat and/or a colored dye or pigment;
• said first layer being converted on a surface thereof by treatment with a solution at an elevated temperature that contains an active compound or compounds capable of rendering said first polymeric material less soluble in an aqueous alkali developer at the point of contact;
• the first layer being oleophilic, wherein the first layer is treated by contact with said solution for 1 to 120 seconds at a temperature of from 50 to 120° C., and wherein said active compound or compounds are polymeric amines, polyacetals, polyethylene glycol, butylated urea formaldehyde, copolymers of vinyl pirrolidone and vinyl acetate, methylated melamine formaldehyde, cellulose esters, or mixtures thereof;
• a first intermediate layer between the substrate and the first layer of a polymeric material which is soluble or dispersible in an aqueous solution and that optionally contains a compound that absorbs and converts light or radiation to heat and/or a colored dye or pigment coated from a solvent that does not substantially dissolve the first layer;
• and
• a third or top layer over the converted first layer and composed of a polymeric material which is soluble or dispersible in an aqueous solution and that optionally contains a compound that absorbs and converts light or radiation to heat and/or a colored dye or pigment;
• the first intermediate layer and the third layer being applied with a solvent that does not substantially dissolve the converted first layer.