Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2002-06-24
2004-04-13
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S176000, C430S270100, C430S281100, C430S302000, C430S944000, C101S456000, C101S465000
Reexamination Certificate
active
06720125
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image recording material which can be used as a planographic printing plate precursor, a color proof, a photoresist and a color filter. More specifically, the invention relates to a heat mode-usable negative-type image recording material which can be used as a planographic printing plate precursor capable of a so-called direct plate-making, by which a plate can directly be made by scanning with an infrared laser based on digital signals from a computer or the like.
2. Description of the Related Art
Conventionally, as systems for direct plate-making based on digital data from a computer, proposals have included: (1) a system using an electrophotographic method, (2) a system using a photopolymer, which is exposed by a laser emitting blue or green light, (3) a system in which silver salts are deposited on a photosensitive resin, and (4) a system in which silver salts are made to diffuse and transfer.
However, the system using an electrophotographic method (1) involves intricate processes for forming images, such as electrification, exposure, development and the like, and requires a large scale and complicated apparatus. In the system using photopolymerization (2), handling the recording material in a light room is difficult since a plate material exhibiting high sensitivity to blue or green light is used. The systems (3) and (4) use silver salts, therefore, they have the drawbacks that developing is complicated and processing waste liquids include the silver salts.
In recent years, with the remarkable development of laser, high output and portable solid lasers or semiconductor lasers emitting infrared rays, particularly of wavelengths from 760 nm to 1200 nm, are readily available. These lasers are very useful as a recording light source for directly making a plate based on digital data from a computer, or the like. However, using an infrared laser, images cannot be recorded on most types of practically usable photosensitive recording materials since photosensitive wavelengths thereof lie within a visible ray region of 760 nm or less. Therefore, there is a demand for materials on which images can be recorded using an infrared laser.
As this image recording material on which images can be recorded using an infrared laser, a recording material containing an onium salt, a phenol resin and a spectral sensitizer is described in U.S. Pat. No. 4,708,925. This image recording material is a positive-type image recording material which utilizes an effect of inhibiting solubility in a developer using an onium salt and a phenol resin; that is, this recording material is not of a negative-type as disclosed in the present invention. As the negative-type image recording material, a recording material containing an infrared absorbent, an acid generator, a resol resin and a novolak resin is described in U.S. Pat. No. 5,340,699. However, this negative-type image recording material requires heat treatment after laser exposure to form images. Accordingly, there has been a demand for a negative-type image recording material which does not require heat treatment after exposure.
For example, Japanese Patent Application Publication (JP-B) No. 7-103171 describes a recording material which does not require heat treatment after imagewise exposure, and contains a cyanine dye having a specific structure, an iodonium salt and an addition-polymerizable compound having an ethylenically unsaturated double bond. However, when used as a planographic printing plate, this image recording material is low in strength at formed image areas and has a problem in that the number of sheets that can be printed is small.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a negative-type image recording material onto which images can directly be recorded based on digital data from a computer or the like using a solid laser or a semiconductor laser emitting infrared ray, and which, when used as a planographic printing plate, has high sensitivity, and even under low exposure conditions, has excellent hardening properties at image areas and printing durability.
The inventors conducted extensive research of components constituting the negative-type image recording material, to find that the aforementioned object can be achieved by using, as an infrared absorbent, a cyanine dye having a specific moiety in its molecule, and finally accomplished the present invention.
That is, according to the present invention, there is provided an image recording material onto which images can be recorded by irradiation with an infrared ray, and which contains an infrared absorbent (A), wherein the infrared absorbent (A) is a cyanine dye in which at least one substituent on a nitrogen atom in a heterocyclic ring at each end forms a cyclic ring which includes a methine chain. In a preferred embodiment, the present invention provides a negative-type image recording material which further contains a radical-generating agent (B) represented by onium salts and a radically polymerizable compound (C), in addition to the above-mentioned specific infrared absorbent (A).
Although the functional mechanism of the present invention is not elucidated, the following is hypothesized. When a cyanine dye containing the cyclic ring introduced into at least one of both ends in the molecule is used as the infrared absorbent, a methine chain in the cyanine dye is prevented from being rotated in an excited state while the absorbent is under light exposure. Consequently, thermal deactivation from the excited state, due to molecular movement, decreases and the life span of the excited state is elongated correspondingly, which leads to high sensitivity and sufficient progress of hardening reaction under low exposure conditions. In a photosensitive material system in which a dye is irradiated with a large excess amount of light in heat mode exposure, highly excited state occurs besides ordinal singly excited state, and this state potentially participates in decomposition of a radical-generating agent or the like, whereas because of elongation of the life span of the excited state due to suppressed rotation of a methine chain, the probability of highly excited state to be produced is presumably increased, whereby production of the desired radicals increases, with achieving high sensitivity and rapid progress of polymerizing radically polymerizable compound, thereby leading to formation of a tough recording layer as well as enhancement of printing durability.
Incidentally, “heat mode-usable” in the present invention means that recording by heat-mode exposure is possible. The definition of the heat-mode exposure in the present invention is describe in detail. As stated in Hans-Joachim Timpe, IS & Ts NIP 15:1999 International Conference on Digital Printing Technologies, p.209, there are known two modes in a process starting from photo-excitation of a light absorbing material (for example, dyes) effected in a photosensitive material to a chemical or physical change, in the case where photo-excitation is caused in the material resulting in a chemical or physical change to finally form an image. One is a so-called photon mode in which a photo-excited light absorbing material is deactivated by creating some photochemical interaction (for example, energy transfer or electron transfer) with other reactants in a photosensitive material so that the activated reactants induce a chemical or physical change required for the image-forming. Another is a so-called heat mode in which a photo-excited light absorbing material is deactivated by generating heat and, by utilizing the generated heat, reactants induce a chemical or physical change required for the image-forming. There are known additional specific modes, such as abrasion in which a substance is exploded and scattered by an action of energy of light gathered locally or multi-photon absorption in which one molecule absorbs a large number of photons at a time. However, description of these specific modes is omit
Fujimaki Kazuhiro
Nakamura Ippei
Chu John S.
Fuji Photo Film Co. , Ltd.
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