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
2000-04-20
2002-07-16
Baxter, Janet (Department: 2854)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S138000, C430S302000, C430S944000, C430S945000, C101S453000, C101S463100
Reexamination Certificate
active
06420083
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a planographic printing plate precursor. More specifically, the present invention relates to a planographic printing plate precursor which has excellent sensitivity and can be used to manufacture a planographic printing plate directly by heating by a heating device such as a thermal head or by laser scanning on the basis of digital signals of a computer or the like. In addition, the present invention relates to a planographic printing plate precursor requiring no development processing, and a process for manufacturing a planographic printing plate which enables direct image formation by heat.
2. Description of the Related Art
In recent years, owing to the progress in technologies related to solid-state lasers and semiconductor lasers which emit rays in regions ranging from a near infrared region to an infrared region, systems, which use these infrared lasers, have been drawing attention as systems for direct planographic printing plate manufacturing in accordance with digital data of a computer.
Processes conventionally known as direct planographic printing plate manufacturing processes in which plates are manufactured from digitized image data without using a lithographic film include (1) an electrophotographic process; (2) a process using a high-sensitivity photopolymer which can be written with a blue-light or green-light-emitting laser of a relatively small output power; (3) a process using a silver salt or a combination of a silver salt and another system; and (4) a process in which heat-cured images are obtained by a post-heating process in the presence of an acid which is generated by heat mode laser exposure and acts as a catalyst.
Although these conventional processes are very useful in efficiently realizing the printing process, these conventional processes have not yet reached a completely satisfactory level and present the following problems.
First, image formation requires a huge amount of energy and a laser of a high output power because the materials used in the above-mentioned heat mode processes generally have low sensitivity. In addition, the processes are complicated because an additional thermal treatment is necessary after laser irradiation.
Secondly, despite their extreme usefulness in efficiently realizing the printing process, in addition to the problem that these processes are complicated or require large-scale equipment, these processes also have the following problems. Namely, these processes include a wet development step in which the recording layer formed on substrate surface is removed image-wise after an exposure step, and include a post-treatment step in which the printing plate which has been subjected to development is washed with water or is treated with a rinsing solution containing a surfactant or with a desensitizing solution containing gum arabic or a starch derivative. Therefore, a need exists for a planographic printing plate precursor which does not require the above-mentioned wet developing treatment and can be used directly for printing after exposure.
In view of the foregoing needs, in recent years, planographic printing plate precursors, which do not require complicated wet development processing and can be used directly in printing after exposure, have been developed.
As an example of a planographic printing plate precursor which does not require wet development processing, U.S. Pat. No. 5,258,263 discloses a planographic printing plate having a photosensitive hydrophilic layer whose curing or insolubilization is promoted in exposed regions, and a photosensitive hydrophobic layer, and both layers are laminated on a substrate.
This plate, however, is a so-called on-printer development type printing plate whose unexposed regions of the photosensitive layer are removed in a printing process. This plate has the drawback that dampening water and printing ink are contaminated at the time of manufacturing a planographic printing plate.
Japanese Patent Application Laid-Open (JP-A) No. 7-186,562 (EP 652,483) discloses a planographic printing plate precursor containing a polymer, which generates a carboxylic acid by the action of heat and acid, and a dye capable of absorbing infrared rays. This planographic printing plate precursor does not require a development step because the plate precursor by itself is a hydrophobic recording layer which generates an acid by being heated to thereby hydrophilize the heated areas so that images are formed. However, this planographic printing plate precursor presents a problem in that stains are formed at the time of printing because the hydrophilized regions are not sufficiently hyrophilic.
On the other hand, JP-A No. 10-329,443 discloses a planographic printing plate precursor for imaging comprising a substrate having a hydrophilic surface and having thereon a photosensitive layer containing a metal chelate compound as a crosslinking agent. However, the sensitivity of this plate is insufficient, and therefore, an improvement of the sensitivity is required.
SUMMARY OF THE INVENTION
The first aspect of the present invention is a planographic printing plate precursor comprising a substrate having thereon an image recording layer containing a metal compound (I-a) which causes a decarboxylation reaction by heat and releases a polyvalent metal cation, and a hydrophilic polymer (I-b) which has at least two hydrophilic groups within the molecule and can coordinate with the polyvalent cation.
The second aspect of the present invention is a planographic printing plate precursor comprising a substrate having thereon an image recording layer containing a metal complex compound (II-a) and a hydrophilic polymer (II-b) which can coordinate with the metal generated from the metal complex compound by the action of heat and which has at least two hydrophilic groups within the molecule and whose main chains are crosslinked.
The third aspect of the present invention is a process for manufacturing a planographic printing plate, said process comprising the step of exposing a planographic printing plate precursor image-wise to infrared laser light so as to form a hydrophobic region on a surface of a planographic printing plate precursor, the planographic printing plate precursor being comprised of a substrate having thereon an image recording layer containing a metal complex compound (II-a) a hydrophilic polymer (II-b), which can coordinate with the metal generated from the metal complex compound by the action of heat and which has at least two hydrophilic groups within the molecule and whose main chains are crosslinked, and a substance (c) capable of converting light to heat.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is described in detail herein after.
The planographic printing plate precursor, which is the first aspect of the present invention, is explained.
The task of the present invention is to solve the above-mentioned existent problems and to achieve the following objects. That is, the first object of the present invention is to provide a planographic printing plate precursor which can be used to manufacture a planographic printing plate directly with excellent high sensitivity by heat generated either by a heating device or by a light-to-heat conversion action of laser light according to digital signals of a computer or the like.
After studies for the first object, the present inventors have found that the sensitivity of a planographic printing plate precursor can be further improved by use of a thermal decarboxylation-type metal compound which releases a polyvalent metal cation by causing a decarboxylation reaction when heated. Based on this discovery, they have established the first aspect of the present invention.
The planographic printing plate precursor as the first aspect of the present invention comprises a substrate having at least an image recording layer provided thereon, wherein the image recording layer contains a metal compound (I-a), which causes a decarboxylation reaction by heat and releases a
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Gilmore Barbara
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