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
2002-02-25
2003-11-25
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
C430S284100, C430S286100, C430S288100, C430S944000, C430S945000, C430S964000
Reexamination Certificate
active
06653050
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image-recording material, and particularly to a negative image-recording material, which corresponds to heat-mode exposure which are able to form images by heat-mode exposure with an IR laser. Moreover, the present invention relates to a negative type image-recording material which is able to form planographic printing plates which have excellent resistance to printing and recording layers with high strength image areas.
2. Description of the Related Art
The recent development of laser technology has been remarkable; increases to output and miniaturization of solid lasers and semiconductor lasers which emit near-IR and IR rays (hereinafter referred to as IR lasers) are progressing. Such IR lasers are extremely useful as light sources in directly processing printing plate precursors from the digital data of computers or the like.
Negative type planographic printing plates which can be exposed by IR lasers use a negative type image recording material as an image recording layer, which image-recording material comprises an IR absorbent, a polymerization initiator, which generates a radical by light or heat, and a polymerizable compound. An ordinary recording system for the negative image-recording material of the type is as follows: The recording layer of the material is exposed to light or heat, and the radical initiator therein generates a radical. The radical acts on the polymerizable compound to initiate the polymerization of the compound, and the exposed area of the recording layer of the material is thereby cured to form an image area.
The image formability of the negative type image-forming materials of this type is low, as compared with that of positive type image-forming materials in which the recording layer is solubilized by laser energy when exposed by an IR laser. Before being developed, therefore, the negative type image-forming material is generally heated to promote the polymerization to cure the exposed area of the recording layer. Thus heated, the strength of the image area of the recorded layer of the material may be enhanced.
For printing plates the recording layer of which is made of the image-recording material of the type mentioned above, a technique of using a photopolymerizable or thermopolymerizable composition for the recording layer (photosensitive layer), for example, as in JP-A 8-108621 and 9-34110 is known. The recording layer disclosed is good, as its sensitivity is high and its image formability is good. However, when a hydrophilicated support is used for the recording layer, there have been problems in that the interfacial adhesiveness between the support and the layer is low and therefore the printing durability of the printing plates having the layer is low.
To increase the sensitivity of the image-recording material, using high-power IR lasers to expose the material to light has been studied. However, there have been problems in that the recording layer often undergoes ablation, when scanned with such high-power lasers, and stains the optical system used.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the problems noted above, and more specifically, an object of the present invention is to provide a negative type image-recording material which can form a planograpic printing plate having excellent resistance to printing and formed with high strength image areas.
We, the present inventors have assiduously studied the object, and, as a result, have found that, when a polyurethane resin having a specific unsaturated group in its side-chain branches and soluble in an alkaline aqueous solution is added to an image-recording material, then it enables good image recording on the material and an image area strength of the material is thereby enhanced.
Specifically, the object of the present invention is attained as follows.
In its first aspect, the present invention provides a negative image-recording material for heat-mode exposure, which is able to form images by heat-mode exposure, comprises a polyurethane resin having at least one or more side-chain branches of the following general formulae (1) to (3), which polyurethane resin is soluble in an alkaline aqueous solution; a photo-thermal converting agent; and a compound which generates a radical through heat-mode exposure to light of a wavelength which wavelength can be absorbed by the photo-thermal converting agent.
wherein R
1
to R
11
each independently represents a monovalent organic group; X and Y each independently represents an oxygen atom, a sulfur atom, or —N(R
12
)—; Z represents one of an oxygen atom, a sulfur atom, —N(R
13
)—, and an optionally-substituted phenylene group; R
12
represents a hydrogen atom or a monovalent organic group; and R
13
represents a hydrogen atom or a monovalent organic group.
A second embodiment of the negative type image-recording material for heat-mode exposure of the present invention is a negative type image-recording material for heat-mode exposure of the first embodiment, which further comprises a radical polymerizing compound.
Effects of the negative type image-recording material for heat-mode exposure of the present invention are unclear. By using the polyurethane resin as a polymer compound, which is soluble in alkali aqueous solution, it is possible to form a high-strength film, which is formed by hydrogen bonding of the principle-chain urethane group. Accordingly, when the image-recording material is used in the recording layer of planographic printing plate precursors for heat-mode exposure, it is believed that the recording layer will be prevented from ablating while being IR laser scan exposured, and therefore the negative image area will be prevented from being damaged and the optical system, such as the spinner mirror of the laser scanner used will be prevented from being stained.
In addition, since the polyurethane resin has good film formability, the dissolved oxygen content of the resin film is low. Further, as the barrier property of the polyurethane resin to oxygen from outside is good, polymerization inhibition of the radical polymerizing compounds by oxygen is suppressed. Through polymerization, therefore, the cured resin forms a hard film. Accordingly, when the polyurethane resin is used in the recording layer of planographic printing plate precursors, the image area formed in the layer is sufficiently cured, and, as a result, the printing plates from the precursors can have high printing durability.
Moreover, since the polyurethane resin for use in the present invention has a polar urethane group in its principle chain, it has good affinity for high-polar media such as water. Accordingly, the polyurethane resin is easily dispersible in water, as compared with alkali-soluble acrylic resins that are generally used in ordinary image-recording materials. Another advantage of the polyurethane resin is that, when it is used in the recording layer of planographic printing plate precursors, it is difficult for contaminants to form during development. Contaminants, if formed during development, interfere with smooth development.
In cases where the polyurethane resin of the present invention has an acidic hydrogen atom in the structure of the side-chain branches, it may form a high strength film by the hydrogen-bonding property of the atom. Therefore, it is thought that the polyurethane resin will contribute to the effect of improving the hardness of the image areas along with the effect of the functional groups, which are expressed by the formulae (1)-(3). When the polyurethane resin is used in the recording layer of planographic printing plate precursors, the molecules of the binder polymer are kept firmly bonding to each other via the hydrogen bonding between them in the step of developing the precursors with an alkaline developer. In this step, therefore, it is believed that the developer used will be prevented from penetrating into the precursors to lower the strength of the image area formed in the processed precur
Fujimaki Kazuhiro
Sorori Tadahiro
Baxter Janet
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
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