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
2001-07-06
2004-08-03
Huff, Mark F. (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
C430S287100, C430S302000, C430S309000, C430S434000, C430S348000, C430S944000
Reexamination Certificate
active
06770422
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image-recording material usable for lithographic printing plates, color proofs, photoresists and color filters. In particular, the present invention relates to a negative image-recording material for heat-mode exposure, which can be directly processed by scanning thereon an IR laser on the basis of digital signals from a computer or the like, and which is therefore usable for directly-processable recording layers for lithographic printing plates, and relates to a method of forming an image on the recording material.
2. Description of the Related Art
As a system for directly processing a recording material from digital data of a computer, heretofore proposed have been <1> electrophotography, <2> exposure of photopolymerization materials to blue or green-emitting lasers, <3> silver salt lamination on photosensitive resin, and <4> silver salt diffusion transfer photography.
However, these all have some drawbacks. Specifically, the image-forming process of electrophotography <1> is troublesome, in comprising complicated steps of electric charging, exposure to light and development, and this requires a complicated large-scale apparatus. Photopolymerizable plates for <2> are highly sensitive to blue and green light, and are difficult to handle in light rooms. In the processes for <3> and <4> using silver salts, development is troublesome and, in addition, wastes contain silver.
On the other hand, the recent development of laser technology is remarkable, and high-power and small-sized solid lasers and semiconductor lasers for emitting IR radiation within a wavelength range of from 760 nm to 1200 nm are easily available. For a light source for directly processing a recording material from the digital data of a computer or the like, these lasers are extremely useful. However, many practicable photosensitive recording materials are sensitive to visible light falling within a wavelength range of at most 760 nm, to which, therefore, these IR lasers are not applicable for recording images thereon. Accordingly, recording materials capable of being processed with IR lasers are desired.
An image-recording material capable of being processed with an IR laser is described in U.S. Pat. No. 4,708,925, which comprises an onium salt, a phenolic resin and a color sensitizer. This is a positive image-recording material, in which the onium salt and the phenolic resin express dissolution resistance to developers, and this is not a negative image-recording material as in the present invention. On the other hand, a negative image-recording material is disclosed in U.S. Pat. No. 5,340,699, which comprises an IR absorber, an acid generator, a resol resin and a novolak resin. For image formation thereon, however, this requires heat treatment after exposure to a laser. Therefore, a negative image-recording material not requiring heat treatment after exposure to light is desired.
For example, Japanese Patent Application Publication (JP-B) No. 7-103171 discloses a recording material that comprises a cyanine dye having a specific structure, an iodonium salt, and an ethylenically unsaturated double bond-containing, addition-polymerizable compound. This does not require heat treatment after imagewise exposure to light. However, the strength of the image area of this material is low. Therefore, this is unfavorable to lithographic printing plates, as the number of prints from a lithographic printing plate using this material is small.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a negative image-recording material which can be imagewise exposed to IR radiation from an IR-emitting solid laser or semiconductor laser and which enables direct image formation thereon from digital data of a computer or the like, and which, when used in a lithographic printing plate, ensures good hardenability in an image area and exhibits good printing durability, even if not heated for image formation thereon, and ensures a large number of good prints from the printing plate.
Having specifically noted the constituent components of negative image-recording materials and having assiduously studied them, the present inventors have found that the above-mentioned object can be attained when an IR absorber having a specific oxidation potential is used. On the basis of this finding, the present invention has been completed.
The present invention provides a negative image-recording material, which comprises (A) an IR absorber, (B) a thermal radical generator such as typically an onium salt and (C) a radical-polymerizing compound, and is imagewise exposed to IR radiation for image formation thereon, and in which the IR absorber (A) has an oxidation potential of at most 0.45 V (vs. SCE).
Though not clear, the advantages of the negative image-recording material of the present invention may result from the IR absorber having a low oxidation potential in the material. In the recording material, the IR absorber having a low oxidation potential will promote decomposition of the thermal radical generator, and will therefore promote polymerization of the radical-polymerizing compound therein, to thereby enhance the mechanical strength of the image-recorded layer of the material, and, as a result, the printing durability of the material when used in printing plates may be enhanced. The reason for this may be that the donor property of the IR absorber having a low oxidation potential is good. Therefore, in the material, the radical generator is readily decomposed through ordinary light-heat conversion, and, in addition, it will easily react with the IR absorber having such a good donor property to form an intermediate of the radical generator and the IR absorber (this intermediate will participate in the decomposition of the radical generator).
The recording material of the present invention is for “heat-mode exposure”, and this means that the recording material is subjected to heat-mode exposure for image formation thereon. The definition of heat-mode exposure is described in detail below. As in Hans-Joachim Timpe, IS & Ts NIP 15:1999
International Conference on Digital Printing Technologies
, page 209, it is known that, with regard to a process comprising photo-excitation of a light-absorbing substance (e.g., dye) in a photographic material followed by chemical or physical change thereof for image formation in a layer of the material, the process of image formation comprising photo-excitation of the light-absorbing substance followed by chemical or physical change thereof includes two major modes. Specifically, one is a photon mode in which the photo-excited light-absorbing substance in a photographic material is inactivated through some photo-chemical interaction (for example, energy transfer or electron transfer) with the other reactive substance in the material, and the reactive substance having been thus activated as a result of the interaction undergoes chemical or physical change necessary for image formation in a layer of the material; and the other is a heat mode in which the photo-excited light-absorbing substance in a photographic material generates heat and is thus inactivated through the heat generation, and the other reactive substance in the material receives the heat and undergoes chemical or physical change necessary for image formation in a layer of the material. Other minor modes of the process are omitted herein; for example, ablation, in which the substances in a photographic material are explosively scattered by some locally focused light energy, and multiphoton absorption, in which one molecule in a photographic material absorbs a number of photons all at a time.
The modes of the exposure process are referred to as photon-mode exposure and heat-mode exposure. The technical difference between photon-mode exposure and heat-mode exposure is whether or not energy quantities from a plurality of photons for exposure can be added up for the intended reaction. For example,
Nakamura Ippei
Sorori Tadahiro
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
Huff Mark F.
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