Negative photosensitive composition and negative photosensitive lithographic printing plate
There are provided a negative-working photosensitive composition which can be cured by infrared rays and is less likely to suffer polymerization inhibition by oxygen during radical polymerization, and also exhibits high adhesion with a metal, and a negative-working photosensitive lithographic printing plate which is capable of directly forming images by irradiation with infrared rays from a solid or semiconductor laser based on digital signals, and also has high sensitivity and excellent printing durability. The negative-working photosensitive composition contains an infrared absorber (A), an organoboron compound (B) which functions as a polymerization initiator by using in combination with the infrared absorber (A), a compound having a polymerizable unsaturated group (C) and a diazo resin (D), and the negative-working photosensitive lithographic printing plate comprises a support, and a photosensitive layer containing the negative-working photosensitive composition formed on the support.
1. A negative-working photosensitive composition comprising:
(A) an infrared absorber,
(B) an organoboron compound which functions as a polymerization initiator by using in combination with the infrared absorber (A),
(C) a compound having a polymerizable unsaturated group, and
(D) a diazo resin.
2. The negative-working photosensitive composition according to claim 1 , wherein the infrared absorber (A) is a near infrared absorbable cationic dye represented by the following formula (1):
D + A − (1)
wherein D + represents a cationic dye having an absorption within a near infrared range, and A − represents an anion.
3. The negative-working photosensitive composition according to claim 1 , wherein the organoboron compound (B) is an ammonium salt of a quaternary boron anion represented by the following formula (2):
wherein R 1 , R 2 , R 3 and R 4 each independently represents an alkyl group, an aryl group, an alkaryl group, an allyl group, an aralkyl group, an alkenyl group, an alkynyl group, an alicyclic group, or a saturated or unsaturated heterocyclic group, and at least one of R 1 , R 2 , R 3 and R 4 is an alkyl group having 1 to 8 carbon atoms, and R 5 , R 6 , R 7 and R 8 each independently represents a hydrogen atom, an alkyl group, an aryl group, an allyl group, an alkaryl group, an aralkyl group, an alkenyl group, an alkynyl group, an alicyclic group, or a saturated or unsaturated heterocyclic group.
4. The negative-working photosensitive composition according to claim 1 , further comprising a binder resin (E).
5. The negative-working photosensitive composition according to claim 4 , wherein the binder resin (E) is an alkali-soluble resin.
6. The negative-working photosensitive composition according to claim 1 wherein the compound having a polymerizable unsaturated group is a monomer or oligomer having at least one addition-polymerizable ethylenically unsaturated group, and comprises 5 to 60% weight based on the solid content of the composition.
7. A negative-working photosensitive lithographic printing plate comprising a support and a photosensitive layer containing the negative-working photosensitive composition according to claim 1 formed on the support.
8. The printing plate of claim 7 wherein the support is an electrolytically etched and anodized aluminum support.
9. The printing plate further comprising an oxygen-impermeable protective layer.
10. A method of imaging comprising direct computer to plate imaging of the printing plate of claim 7 .