Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2002-08-08
2004-05-04
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
Reexamination Certificate
active
06730455
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of preparing a planographic printing plate, the method comprising the step of developing a presensitized planographic printing plate comprising a photopolymerizable light sensitive layer with a liquid developer to form a negative image on the planographic printing plate.
BACKGROUND OF THE INVENTION
It is generally known that a protective layer (oxygen shielding layer) is provided on a light sensitive layer of a photopolymerizable light sensitive material in order to prevent oxygen from inhibiting polymerization. As a method for providing the oxygen shielding layer, there is a method in which an aqueous solution of a water soluble polymer such as polyvinyl alcohol or polyvinyl pyrrolidone is coated on a light sensitive layer and dried to form a water soluble polymer layer. The water soluble polymer provides an excellent oxygen shielding ability, coatability and solubility to a developer used. However, a planographic printing plate, which is prepared by developing a presensitized planographic printing plate employing the water soluble polymer, has the problem that printing durability as well as ink receptivity are poor.
Use of a developer containing an organic solvent improves the ink receptivity, but results in a new problem such as malorder attributed to the organic solvent or deterioration of working environment.
An increase of pH of the developer makes it possible to eliminate the organic solvent from the developer without lowering developability or ink receptivity, but it has been found that the pH increase of the developer has an adverse effect on printing durability, when printing is carried out employing a specific ink, particularly soybean oil-based ink.
SUMMARY OF THE INVENTION
An object of the invention is to provide a method of developing a presensitized planographic printing plate with high sensitivity and high storage stability, employing a developer, which neither produces malodor nor lowers working environment, to obtain a planographic printing plate with high ink receptivity and high printing durability, wherein the presensitized planographic printing plate comprises a photopolymerizable light sensitive layer and provided thereon, an oxygen shielding layer containing polyvinyl alcohol and polyvinyl pyrrolidone which is firmly adhered to the light sensitive layer with good adhesion.
DETAILED EXPLANATION OF THE INVENTION
The above objects of the invention can be attained by the followings:
1. A method of manufacturing a planographic printing plate, the method comprising the step of developing a presensitized planographic printing plate with a developer with a pH of from 11.5 to less than 12.5, which does not substantially contain an organic solvent, wherein the presensitized planographic printing plate comprises a support having a roughened hydrophilic surface with a center line average surface roughness Ra of from 0.5 to 0.8 &mgr;m, and provided thereon, a photopolymerizable light sensitive layer and an oxygen shielding layer in that order, the photopolymerizable light sensitive layer containing A) an addition polymerizable monomer having an ethylenic double bond, B) a photopolymerization initiator, C) a sensitizing dye, and D) a polymer binder, and the oxygen shielding layer containing E) polyvinyl alcohol and F) polyvinyl pyrrolidone.
2. the method of item 1, wherein the developer is a developer containing no organic solvent or a developer containing an organic solvent in an amount of not more than 2% by weight.
3. the method of item 1, wherein the presensitized planographic printing plate comprises a subbing layer containing a compound having a polyalkoxysilyl group between the support and the photopolymerizable light sensitive layer.
4. the method of item 3, wherein the compound having a polyalkoxysilyl group is a silane coupling agent having a (meth)acryloyl group.
5. the method of item 1, wherein the addition polymerizable monomer having an ethylenic double bond further has a phosphate bond in the molecule.
6. the method of item 1, wherein the photopolymerization initiator is a titanocene compound.
7. the method of item 1, wherein the sensitizing dye is a pyromethene dye.
8. the method of item 1, wherein the polymer binder is a reaction product of a vinyl copolymer having a carboxyl group in the molecule with a compound having a (meth)acryloyl group and an epoxy group in the molecule.
9. the method of item 1, wherein the polymer binder has an acid value of from 10 to 150.
10. the method of item 1, wherein the planographic printing plate is a printing plate used when printing is carried out employing soybean oil-based ink.
11. a method of manufacturing a planographic printing plate, the method comprising the step of developing a presensitized planographic printing plate with a developer with a pH of not less than 11.5 which does not substantially contain an organic solvent, wherein the presensitized planographic printing plate comprises a support having a roughened hydrophilic surface with a center line average surface roughness Ra of from 0.5 to 0.8 &mgr;m, and provided thereon, a photopolymerizable light sensitive layer and an oxygen shielding layer in that order, the photopolymerizable light sensitive layer containing A) an addition polymerizable monomer having an ethylenic double bond, B) a photopolymerization initiator, C) a sensitizing dye, and D) a polymer binder, and the oxygen shielding layer containing E) polyvinyl alcohol and F) polyvinyl pyrrolidone.
12. the method of item 11 above, wherein the pH of the developer is in the range of from 11.5 to less than 12.5.
13. the method of item 11 or 12 above, wherein a subbing layer containing a compound having a polyalkoxysilyl group is provided between the support and the photopolymerizable light sensitive layer.
14. the method of item 13 above, wherein the compound having a polyalkoxysilyl group is a silane coupling agent having a (meth)acryloyl group.
15. the method of any one of items 11 through 14 above, wherein the addition polymerizable monomer having an ethylenic double bond further has a phosphoric acid ester bond in the molecule.
16. the method of any one of items 11 through 15 above, wherein the photopolymerization initiator is a titanocene compound.
17. the method of any one of items 11 through 16 above, wherein the sensitizing dye is a pyrromethene dye.
18. the method of any one of items 11 through 17 above, wherein the polymer binder is a reaction product of a vinyl copolymer having a carboxyl group in the molecule with a compound having a (meth)acryloyl group and an epoxy group in the molecule.
It has been found that a planographic printing plate manufacturing method provides a planographic printing plate with high printing durability even when soybean oil-based ink is employed as a printing ink, the method comprising the step of developing a presensitized planographic printing plate with a developer with a pH of from 11.5 to less than 12.5 which does not substantially contain an organic compound, wherein the presensitized planographic printing plate comprises a support having a roughened surface with a center line average surface roughness Ra (according to JIS B 0601) of from 0.5 to 0.8 &mgr;m, and provided thereon, a light sensitive layer and an oxygen shielding layer containing polyvinyl alcohol and polyvinyl pyrrolidone in that order. In the invention, the center line average surface roughness Ra is measured employing a method as described in JIS B 0601.
The invention will be detailed below.
<Support>
The presensitized planographic printing plate of the invention comprises a support having a hydrophilic surface, which is surface roughened to have a center line average surface roughness of from 0.5 to 0.8 &mgr;m. As a support, a plate of aluminum, stainless steel, chromium, or nickel can be used. Among them, an aluminum plate is preferably used, which may be a pure aluminum plate or an aluminum alloy plate.
As the aluminum alloy, there can be used various ones including an alloy of aluminum and a metal such as silico
Konica Corporation
Le Hoa Van
Squire Sanders & Dempsey LLP
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