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
2001-08-10
2004-02-10
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
C430S281100, C430S283100, C430S302000, C430S303000
Reexamination Certificate
active
06689534
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image recording material to be used as an offset printing master. In particular, the present invention relates to a positive-type planographic printing original plate for an infrared laser for so-called direct plate-making, to be produced directly from digital signals of a computer or the like.
2. Description of the Related Art
Recently, development of lasers has been remarkable. In particular, solid lasers and semiconductor lasers having a near-infrared to infrared light emission area can be obtained with a high output and a small size. These lasers are extremely useful as an exposure light source at the time of producing a plate directly from digital data of a computer, or the like.
A positive-type planographic printing plate material for an infrared laser includes an alkaline aqueous solution-soluble binder resin and an IR dye that absorbs light and generates heat or the like as essential components. The IR dye or the like functions as a dissolution inhibiting agent for substantially lowering the solubility of the binder resin by interaction with a binder resin in an unexposed part (image part). In an exposed part (non-image part), the interaction between the IR dye or the like and the binder resin is weakened by the generated heat such that the binder resin is dissolved in an alkaline developing solution so as to provide a planographic printing plate.
However, such a positive-type planographic printing plate material for an infrared laser involves a problem in that the difference between dissolution resistance of the unexposed part (image part) with respect to a developing solution and the solubility of the exposed part (non-image part) is not sufficient in various use conditions, and thus excessive development and developing failures can easily be generated due to fluctuations of use conditions. Moreover, in a case where the surface state is changed slightly due to contact on the surface in handling or the like, a problem arises in that the unexposed part (image part) is dissolved at the time of development, forming flaws and causing printing durability deterioration and poor adherence.
These problems are derived from the inherent difference between a positive-type planographic printing plate material for an infrared laser and a positive-type planographic printing plate material produced by UV exposure. That is, the positive-type planographic printing plate material produced by the UV exposure includes an alkaline aqueous solution-soluble binder resin, an onium salt, and a quinonediazide compound as essential components. The onium salt and the quinonediazide compound perform two roles, not only as a dissolution inhibiting agent in the unexposed part (image part), by interaction with the binder resin, but also as a dissolution promoting agent in the exposed part (non-image part), by decomposition by light so as to generate an acid.
In contrast, the IR dye or the like in the positive-type planographic printing plate material for an infrared laser functions only as a dissolution inhibiting agent for the unexposed part (image part), without a function of promoting the dissolution of the exposed part (non-image part). Therefore, in the positive-type planographic printing plate material for an infrared laser, in order to provide solubility difference between the unexposed part and the exposed part, as the binder resin, a resin having high solubility with respect to an alkaline developing solution must be used, and thus a state before development is unstable.
In order to improve the dissolution resistance of the unexposed part (image part) with respect to the developing solution, without lowering the developing property of the exposed part (non-image part), for example, Japanese Patent Application Laid Open (JP-A) No. 11-288093 discloses a method of using a copolymer including a fluorine-containing monomer capable of addition polymerization with a fluoro aliphatic group with a hydrogen atom on a carbon atom substituted by a fluorine atom at a side chain. Moreover, EP950517 discloses a method of using a siloxane based surfactant. Although these methods to some extent contribute to improvement of the developing resistance of the recording layer image part, the solubility difference between the unexposed part and the exposed part cannot be provided sufficiently for forming a sharp and good image regardless of developing solution activity fluctuations.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a positive-type planographic printing original plate for an infrared laser which has a recording layer with excellent latitude in forming an image by development, and excellent flaw resistance.
As a result of detailed studies by the present inventors, it was found that a planographic printing plate having excellent developing latitude and excellent flaw resistance can be obtained by using a positive-type photosensitive composition for an infrared laser that includes a fluorine-containing alkali-soluble resin as a recording layer. Thus, the present invention has been completed.
That is, a planographic printing original plate according to the present invention includes: a support; and on the support, a positive-type recording layer comprising an infrared absorbing agent and a water-insoluble, alkali-soluble resin which has a fluorine atom in a molecule thereof, solubility in an alkaline aqueous solution of the recording layer being increasable by infrared laser exposure.
As a water-insoluble, alkali-soluble resin having a fluorine atom in the molecule to be used herein, a polymer compound having a phenol hydroxyl group or a novolak compound is preferable.
In the present invention, the reason why the developing latitude and flaw resistance of an obtained positive-type planographic printing original plate can be made excellent by use of the above-mentioned fluorine-containing alkali-soluble resin is not clear. However, it is thought that a functional group having a fluorine atom in a molecule of the above-mentioned alkali-soluble resin forms an outermost part by being oriented and being present locally on the recording layer surface during a drying step in applying and drying a recording layer coating liquid containing the alkali-soluble resin molecules so that resistance with respect to the developing solution and external stresses is improved in an image part, and further, since the fluorine atom-containing functional group does not inhibit the stability or solubility inherent to the alkali-soluble resin in a non-image part, a recording layer with excellent developing latitude can be formed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the present invention will be explained in detail.
According to a planographic printing original plate according to the present invention, an alkali-soluble resin having a fluorine atom in a molecule and a infrared absorbing agent should be contained in a recording layer. Hereafter, components comprising the recording layer will be explained successively.
Water-insoluble, Alkali-soluble Resin Having a Fluorine Atom in the Molecule
As a water-insoluble, alkali-soluble resin having a fluorine atom in the molecule (hereinafter optionally referred to as a fluorine-containing alkali-soluble resin) to be used in the present invention, any of conventionally known water-insoluble, alkaline aqueous solution-soluble polymer compounds with at least one kind of substituent having a fluorine atom introduced therein can be used.
As a water-insoluble, alkaline aqueous soluble polymer compound (hereinafter optionally referred to as an alkali-soluble polymer) to serve as a base, a polymer compound having in the molecule any functional group selected from (1) a phenol hydroxyl group, (2) a sulfonamide group, and (3) an active imide group is preferable. Although a polymer compound having (1) the phenol hydroxyl group in the molecule is particularly preferable, the present invention is not limited thereto.
As a fluorine-containing alkali-sol
Nakamura Ippei
Oda Akio
Tsuchimura Tomotaka
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Walke Amanda C.
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