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
2000-05-03
2003-03-18
Baxter, Janet (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
C430S271100, C430S944000, C430S945000
Reexamination Certificate
active
06534237
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a heat-sensitive lithographic printing plate, and particularly to a heat-sensitive lithographic printing plate requiring no development processing after image recording and good in resistance to staining.
BACKGROUND OF THE INVENTION
Conventional methods for directly plate-making printing plates from digitized image data without using lithographic films include (1) electrophotographic methods, (2) methods using high-sensitive photopolymers writable with relatively low-output lasers emitting-blue or green light, (3) methods using silver salts, or composite systems of silver salts and other systems and (4) methods of generating acids by heat mode laser exposure, and conducting after-heating using the acids as catalysts, thereby obtaining thermoset images.
These methods are very useful in respect to rationalization of the printing processes, but they are not necessarily satisfactory in the present circumstances. For example, in the electrophotographic methods of (1), processes of image formation such as electrification, exposure and development are complicated to cause complicated and large-scale apparatus. In the methods using photopolymers of (2), high-sensitive printing plates are used, so that illuminated room processing becomes difficult. The methods using silver salts of (3) have the disadvantages that processing becomes complicated, and that silver is contained in waste liquid. The methods of (4) also necessitate after heating and subsequent development processing, resulting in complicated processing.
Further, the production of these printing plates contains the wet development stage for imagewise removing recording layers provided on surfaces of supports, and the after processing stage that developed printing plates are washed with water or processed with rinsing solutions containing surfactants and desensitizing solutions containing gum arabic and starch derivatives, after the exposure stage.
On the other hand, in the fields of platemaking and printing, plate-making operations have recently been rationalized, and printing plate precursors which necessitate no complicated wet development processing as described above and can be used for printing as such after exposure have been desired.
For example, JP-A-10-282672 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses heat-sensitive lithographic printing plate precursor having layers containing hydrophobic polymers which necessitate no processing and in which side chains are turned hydrophilic by heat. The printing plate precursor is characterized by that the polymer turned hydrophilic by exposure is developed with a fountain solution on a printing machine, which causes no particular need to conduct development processing. However, high heat-conductive aluminum is used as a substrate, so that heat generated by exposure and the action of a light-heat converting agent is diffused in the aluminum substrate. The printing plate precursor therefore has the characteristic that the temperature in the vicinity of a surface of the substrate is hard to increase. Accordingly, the heat reaction of the polymer does not sufficiently proceed in the vicinity of the substrate, and the polymer is not turned hydrophilic. Therefore, the polymer is not completely removed in the on-press development and remains as a residual film, which sometimes causes stains in printing. For completely removing the polymer, therefore, it is necessary to increase the exposure of a laser.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to overcome the above-mentioned disadvantages of the prior art and to provide a heat-sensitive lithographic printing plate in which the occurrence of stains in printing can be prevented without increasing the exposure amount of a laser.
The present inventors have made various studies for improving the resistance to staining of the printing plates. As a result, the inventors have discovered that the temperature of recording layers is prevented from being lowered and the solubility of polymers contained in the recording layers in water can be completely converted by providing materials lower in heat sensitivity than aluminum as crosslinked hydrophilic layers on supports, thus completing the invention.
That is, the embodiments and preferred embodiments are. shown below.
(1) A heat-sensitive lithographic printing plate comprising a support having provided thereon a hydrophilic layer having a crosslinked structure, and a layer containing a polymer having on a side chain a group in which the solubility in water of the polymer can be changed by heat (hereinafter sometimes referred to as simply “a recording layer”), said layer being provided on the hydrophilic layer.
(2) The heat-sensitive lithographic printing plate as described in the above item (1), which comprises a support having provided thereon a hydrophilic layer having a crosslinked structure, and a layer containing a polymer having on a side chain a group in which the solubility in water of the polymer can be increased by heat, said layer being provided on the hydrophilic layer.
(3) A lithographic printing plate precursor comprising a support having provided thereon in order of a hydrophilic insulating layer and a layer containing a hydrophilic polymer in which a side chain changes to hydrophobic by heat.
(4) The lithographic printing plate precursor as described in the above item (3), wherein said hydrophilic insulating layer contains a hydrophilic polymer having a crosslinked structure.
(5) The heat-sensitive lithographic printing plate as described in the above item (1), wherein said hydrophilic layer is bonded to the support via a chemical bond by light.
(6) The lithographic printing plate precursor as described in the above item (3), wherein said hydrophilic insulating layer is bonded to the support via a chemical bond by light.
In the heat-sensitive lithographic printing plate of the invention, the crosslinked hydrophilic layer formed of the material lower in heat sensitivity than aluminum is provided between the support and the recording layer, thereby preventing the temperature of the recording layer from being lowered, and making it possible to completely convert the solubility of the polymer contained in the recording layer in water. Further, the combination of the polymer having on a side chain the group in which the solubility in water of the polymer can be increased by heat and a light-heat converting agent prevents a stain due to a residual film even by low-energy IR laser beam irradiation, that is to say, it provides the effect of increasing sensitivity.
DETAILED DESCRIPTION OF THE INVENTION
The heat-sensitive lithographic printing plates of the invention will be illustrated in detail below.
There is no particular limitation on the hydrophilic layer having the crosslinked structure (hereinafter also briefly referred to as the crosslinked hydrophilic layer) contained in the heat-sensitive lithographic printing plate of the invention, as long as it is extremely lower in heat conductivity than aluminum, and one mainly composed of silica or an organic polymer is preferably used. Silica and the organic polymer used in the crosslinked hydrophilic layer of the heat-sensitive lithographic printing plate of the present invention are each about 180 times lower and 1100 to 1600 times lower, respectively, in heat conductivity than aluminum.
As the crosslinked hydrophilic layer of the heat-sensitive lithographic printing plate of the invention, any of the known crosslinked hydrophilic layers can be used. For example, (1) hydrophilic layers comprising metal colloid-containing crosslinked polymers described in PCT International Publication No. WO98/40212, (2) hydrophilic layers comprising condensates of organic hydrophilic polymers and silane coupling agents described in Japanese Patent No. 2,592,225, and (3) hydrophilic layers comprising crosslinked organic polymers described in JP-A-10-6468 and JP-A-10-58636 can be used.
The respective crosslinked hydrop
Kawamura Koichi
Tashiro Hiroshi
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
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