Heat-sensitive imaging element

A heat-sensitive lithographic printing plate precursor comprising:

• a support having a hydrophilic surface or which is provided with a hydrophilic layer;
• and
• on the support, a coating which includes thermoplastic polymer particles dispersed in a hydrophilic binder and an IR dye having a structure according to Formula I:
• wherein
• +Y1═ is represented by one of the following structures:
• Y2— is represented by one of the following structures:
• n is 0, 1, 2, or 3;
• each of p and q is 0, 1, or 2;
• R1 and R2 are independently an optionally substituted hydrocarbon group, or wherein two of the R1, R2, Rd, or Ra groups together include the necessary atoms to form a cyclic structure:
• at least one of the Rd groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-donor than the Rd;
• or
• at least one of the Ra groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-acceptor than the Ra;
• the other Rd and Ra groups are independently represented by a group selected from the list consisting of a hydrogen atom, a halogen atom, —Re, —ORf, —SRg, and —NRuRv;
• wherein Re, Rf, Rg, Ru, and Rv independently are an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group;
• and
• the transformation provides an increase of the integrated light absorption of the dye between 400 nm and 700 nm.

A heat-sensitive lithographic printing plate precursor comprising:

• a support having a hydrophilic surface or which is provided with a hydrophilic layer;
• and
• on the support, a coating which includes a switchable polymer which is capable of changing a polarity of a surface of the coating upon IR-radiation or heating from hydrophilic to hydrophobic or from hydrophobic to hydrophilic and an IR dye having a structure according to Formula I:
• wherein
• +Y1═ is represented by one of the following structures:
• Y2— is represented by one of the following structures:
• n is 0, 1, 2, or 3;
• each of p and q is 0, 1, or 2;
• R1 and R2 are independently an optionally substituted hydrocarbon group, or wherein two of the R1, R2, Rd, or Ra groups together include the necessary atoms to form a cyclic structure:
• at least one of the Rd groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-donor than the Rd;
• or
• at least one of the Ra groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-acceptor than the Ra;
• the other Rd and Ra groups are independently represented by a group selected from the list consisting of a hydrogen atom, a halogen atom, —Re, —ORf, —SRg, and —NRuRv;
• wherein Re, Rf, Rg, Ru, and Rv independently are an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group;
• and
• the transformation provides an increase of the integrated light absorption of the dye between 400 nm and 700 nm.

A heat-sensitive lithographic printing plate precursor comprising:

• a support having a hydrophilic surface or which is provided with a hydrophilic layer;
• and
• on the support, a coating which includes a polymer soluble in an alkaline solution, a solubility inhibiting compound which reduces the solubility of the coating in the alkaline solution, and wherein, upon IR-radiation or heating, the coating has an increased solubility in the alkaline solution, and an IR dye having a structure according to Formula I:
• wherein
• +Y═ is represented by one of the following structures:
• Y2— is represented by one of the following structures:
• n is 0, 1, 2, or 3;
• each of p and q is 0, 1, or 2;
• R1 and R2 are independently an optionally substituted hydrocarbon group, or wherein two of the R1, R2, Rd, or Ra groups together include the necessary atoms to form a cyclic structure:
• at least one of the Rd groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-donor than the Rd;
• or
• at least one of the Ra groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-acceptor than the Ra;
• the other Rd and Ra groups are independently represented by a group selected from the list consisting of a hydrogen atom, a halogen atom, —Re, —ORf, —SRg, and —NRuRv;
• wherein Re, Rf, Rg, Ru, and Rv independently are an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group;
• and
• the transformation provides an increase of the integrated light absorption of the dye between 400 nm and 700 nm.

A method for making a lithographic printing plate comprising the steps of:

• (i) providing a heat-sensitive lithographic printing plate precursor including a support having a hydrophilic surface or which is provided with a hydrophilic layer and on the support, a coating which includes an IR dye having a structure according to Formula I:
• wherein
• +Y1═ is represented by one of the following structures:
• Y2— is represented by one of the following structures:
• n is 0, 1, 2, or 3;
• each of p and g is 0, 1, or 2;
• R1 and R2 are independently an optionally substituted hydrocarbon group, or wherein two of the R1, R2, Rd, or Ra groups together include the necessary atoms to form a cyclic structure;
• at least one of the Rd groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-donor than the Rd;
• or
• at least one of the Ra groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-acceptor than the Ra;
• the other Rd and Ra groups are independently represented by a group selected from the list consisting of a hydrogen atom, a halogen atom, —Re, —ORf, —SRg, and —NRuRv;
• wherein Re, Rf, Rg, Ru, and Rv independently are an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group;
• and
• the transformation provides an increase of the integrated light absorption of the dye between 400 nm and 700 nm;
• (ii) image-wise exposing the coating of the precursor to IR-radiation or heat thereby inducing the transformation of the IR dye and forming a print-out image;
• and
• (iii) optionally developing the image-wise exposed precursor.

A method for obtaining a print-out image by exposing a lithographic printing plate precursor comprising an IR dye having a structure according to Formula I to IR-radiation or heat:

• wherein
• +Y1═ is represented by one of the following structures:
• Y2— is represented by one of the following structures:
• n is 0, 1, 2, or 3;
• each of p and g is 0, 1, or 2;
• R1 and R2 are independently an optionally substituted hydrocarbon group, or wherein two of the R1, R2, Rd, or Ra groups together include the necessary atoms to form a cyclic structure;
• at least one of the Rd groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-donor than the Rd;
• or
• at least one of the Ra groups is a group which is transformed by a chemical reaction, induced by exposure to IR-radiation or heat, into a group which is a stronger electron-acceptor than the Ra;
• the other Rd and Ra groups are independently represented by a group selected from the list consisting of a hydrogen atom, a halogen atom, —Re, —ORf, —SRg, and —NRuRv;
• wherein Re, Rf, Rg, Ru, and Rv independently are an optionally substituted aliphatic hydrocarbon group or an optionally substituted (hetero)aryl group;
• and
• the transformation provides an increase of the integrated light absorption of the dye between 400 nm and 700 nm.