Negative-working photosensitive composition and negative-working photosensitive planographic printing plate
A negative-working photosensitive composition comprises (a) an alkali-soluble resin, (b) a compound which causes a crosslinking reaction by an acid, (c) a compound which generates an acid by heating, and (d) a photothermal converting agent, wherein the compound (c) which generates an acid by heating described above is an onium salt of an acidic dye having a sulfonic group in a molecule. A negative-working photosensitive planographic printing plate is provided with a photosensitive layer comprising the negative-working photosensitive composition, on a surface of a support.
1 . A negative-working photosensitive composition comprising
(a) an alkali-soluble resin,
(b) a crosslinking agent crosslinkable by an acid,
(c) a compound that generates an acid upon heating, wherein the compound is an onium salt of an acidic dye having a sulfonic group within the molecule, and
(d) a photothermal converting agent.
2 . (canceled)
3 . (canceled)
4 . The composition of claim 1 , wherein the alkali-soluble resin comprises a novolak resin.
5 . The composition of claim 1 , wherein the composition comprises from 40 to 95 percent, by mass, of the alkali-soluble resin.
6 . The composition of claim 1 , wherein the crosslinking agent comprises a resol resin.
7 . The composition of claim 1 , wherein the composition comprises from 5 to 70 percent, by mass, of the crosslinking agent.
8 . The composition of claim 1 , wherein the acidic dye having the sulfonic group has 21 or more carbon atoms in the molecule.
9 . The composition of claim 1 , wherein the onium salt is a diazonium, iodonium, or sulfonium salt.
10 . The composition of claim 1 , wherein the composition comprises from 0.01 to 50 percent, by mass, of the compound that generates an acid upon heating.
11 . The composition of claim 1 , wherein the composition comprises from 0.1 to 20 percent, by mass, of the compound that generates an acid upon heating.
12 . The composition of claim 1 , comprising a mixture of compounds that generate acid upon heating.
13 . The composition of claim 1 , wherein the photothermal converting agent absorbs light in the near infrared to infrared region.
14 . The composition of claim 1 , wherein the composition comprises from 3 to 50 percent, by mass, of a pigment as the photothermal converting agent.
15 . The composition of claim 1 , wherein the composition comprises from 0.5 to 20 percent, by mass, of a dye as the photothermal converting agent.
16 . A printing plate precursor comprising:
a substrate; and
a photosensitive layer on the substrate, the photosensitive layer comprising
(a) an alkali-soluble resin,
(b) a crosslinking agent crosslinkable by an acid,
(c) a compound that generates an acid upon heating, wherein the compound is an onium salt of an acidic dye having a sulfonic group within the molecule, and
(d) a photothermal converting agent.
17 . The printing plate precursor of claim 16 , wherein the precursor is sensitive to light in the near infrared to infrared region.
18 . The printing plate precursor of claim 16 , wherein the alkali-soluble resin comprises a novolak resin.
19 . The printing plate precursor of claim 16 , wherein the crosslinking agent comprises a resol resin.
20 . The printing plate precursor of claim 16 , wherein the acidic dye having the sulfonic group has 21 or more carbon atoms in the molecule.
21 . A method for making a printing plate precursor having a photosensitive layer on a substrate, the method comprising:
(i) providing a substrate; and
(ii) applying to a surface of the substrate a composition comprising
(a) an organic solvent,
(b) an alkali-soluble resin,
(c) a crosslinking agent crosslinkable by an acid,
(d) a compound that generates an acid upon heating, wherein the compound is an onium salt of an acidic dye having a sulfonic group within the molecule, and
(e) a photothermal converting agent; and
(iii) drying the composition to form a photosensitive layer on the substrate.
22 . The method of claim 21 , wherein the acidic dye having the sulfonic group has 21 or more carbon atoms in the molecule.