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
1998-12-09
2001-05-08
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
06228559
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a lithographic printing plate precursor for preparing a negative working lithographic printing plate requiring no fountain solution (hereinafter also referred to as a waterless printing plate), and particularly to a negative working waterless lithographic printing plate having good image reproducibility and scratch resistance.
BACKGROUND OF THE INVENTION
As negative working light-sensitive lithographic printing plates requiring no fountain solution in which light-sensitive layers and silicone rubber layers are successively formed on supports, various kinds of plates have been proposed.
For example, the use of compositions in light-sensitive layers have been reported in JP-A-63-88556 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-8-328240, the compositions comprising compounds generating acids by light (light acid generating agents), compounds hydrolyzed by acids to change in solubility and binder resins if necessary. JP-A-8-328240 describes a process comprising adding a compound having two or more enol ether groups or enol thioether groups and a linear polymer having an acid group and a hydroxyl or mercapto group to the above-mentioned light-sensitive layer, thereby forming a three-dimensionally crosslinked resin in coating and drying or by heating after coating and drying, hydrolyzing the crosslinked portion in the presence of an acid generated from a light acid generating agent, for an exposed area, to improve the peeling property of a silicone rubber layer at the exposed area, and effectively removing a solubilized portion of the light-sensitive layer by use of a developing solution.
On the other hand, with the recent rapid progress in prepress systems and output systems such as image setters and laser printers, methods for obtaining printing plates by converting printing images to digital data, and using new prepress processing systems such as computer-to-plate and computer-to-cylinder systems have been proposed. Accordingly, new types of printing materials for these printing systems have been desired, and the development thereof is proceeding.
JP-B-42-21879 (the term “JP-B” as used herein means an “examined Japanese patent publication”), JP-A-50-158405, JP-A-6-55723, JP-A-6-186750, U.S. Pat. No. 5,353,705 and PCT International Publication WO-9401280 describe that ink-repellent silicone rubber layers are formed on light-heat conversion layers containing laser light absorbers such as carbon black and self-oxidizing binders such as nitrocellulose, and that the silicone rubber layers are partially removed by laser beam irradiation to form ink-receiving areas, thereby conducting waterless printing.
In the above, however, the silicone rubber layers are removed by abrasion of the light-heat conversion layers due to laser beam irradiation, and since the adhesion between the light-heat conversion layers and the silicone rubber layers is weak, JP-A-9-146265 reports a process of improving the above-mentioned adhesion by adding an addition polymer having groups reactive to a silicone crosslinking agent on side chains to a light-heat conversion layer, and allowing the polymer to react with the silicone crosslinking agent contained in a silicone rubber layer in coating and drying of the silicone rubber layer.
However, the above-mentioned known negative working light-sensitive lithographic printing plate requiring no fountain solution is insufficient yet in the adhesion between the light-sensitive layer and the silicone rubber layer, and has the problem that the plate is easily scratched in handling the printing plate and in printing, resulting in adhesion of ink on the scratched portion to form an image area. In particular, in the negative working waterless lithographic printing plate, the silicone rubber remains on an unexposed area, so that it is required that the light-sensitive layer is sufficiently adhered with the silicone rubber layer. Insufficient adhesion results in removal of the silicone rubber in a portion where the light-sensitive layer must be adhered with the silicone rubber layer in development, particularly the silicone rubber layer of a nonimage area around the periphery of an image area where the silicone rubber has been removed, which causes a reduction in resolution of an image.
Moreover, the above-mentioned process has the problem that if the crosslinking component in the light-sensitive layer is used in an increased amount for improving the reactivity with the crosslinking agent in the silicone rubber layer to improve the adhesive properties, or if the silicone rubber layer is dried at high temperature for a long period of time in coating for allowing the crosslinking reaction to occur easily, the performance of the light-sensitive layer is deteriorated to cause failure to obtain a good image.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-mentioned problems and provide a negative working waterless lithographic printing plate precursor having good image reproducibility and scratch resistance, in which laser writing is possible.
As a result of intensive investigation, the present inventors have discovered that the above-mentioned problems can be solved by (1) a negative working waterless lithographic printing plate precursor comprising a support having thereon a light-sensitive layer and a silicone rubber layer provided on the light-sensitive layer, the light-sensitive layer being reduced in adhesion to the silicone rubber layer by exposure, wherein the light-sensitive layer comprises a polymer having at least one group selected from the group consisting of a siloxane group and an alkyl fluoride group (hereinafter referred to as a siloxane group and/or an alkyl fluoride group) and at least one group selected from the group consisting of an unsaturated double bond group and a hydroxyl group (hereinafter referred to as an unsaturated double bond group and/or a hydroxyl group); and as a preferred embodiment, (2) the negative working waterless lithographic printing plate precursor described in the above (1), wherein the light-sensitive layer further contains a compound converting a laser beam to heat.
In the present invention, the polymer having a siloxane group and/or an alkyl fluoride group, in addition to an unsaturated double bond group and/or a hydroxyl group having adhesion to the silicone rubber layer, is contained in the light-sensitive layer, whereby the concentrated polymer exists in a surface portion of the light-sensitive layer in coating and drying of the silicone rubber layer. Accordingly, the above-mentioned unsaturated double bond group and/or hydroxyl group effectively reacts with the silicone crosslinking agent of the silicone rubber layer to form a covalent bond, so that even addition of the polymer in a smaller amount results in a very strong bond between the silicone rubber layer and the light-sensitive layer, thereby conceivably showing the great effect of improving the image reproducibility and scratch resistance.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be illustrated in detail below.
The crosslinked silicone rubber layer used in the present invention is a coating formed by hardening the following composition A (condensation type silicone) or composition B (addition type silicone):
Composition A:
(a)
Diorganopolysiloxane
100
parts by weight
(number average molecular
weight: 3,000 to 40,000)
(b)
Condensation Type
3 to 70
parts by weight
Crosslinking Agent
(c)
Catalyst
0.01 to 40
parts by weight
The diorganopolysiloxane of the above-mentioned component (a) is a polymer having repeating units represented by formula (1):
wherein R
1
and R
2
each represents an alkyl group (e.g., methyl, ethyl, propyl, isopropyl, butyl and nonyl) having 1 to 10 carbon atoms, an alkenyl group (preferably, a vinyl group) having 2 to 10 carbon atoms or an aryl group (e.g., phenyl, naphthyl, o-methylphenyl and p-methylphenyl) having 6 to 20 carbon atoms, which may have another appropriate substituen
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilmore Barbara
Le Hoa Van
LandOfFree
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