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
2000-03-14
2001-12-18
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
C430S926000
Reexamination Certificate
active
06331375
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photosensitive lithographic form plate using an image-forming material, and more particularly, to a photosensitive lithographic form plate which uses an image-forming material, which can be inscribed by light such as a laser light and by heat generated by irradiation of a laser light and is suitable as a material for the lithographic form plate, and which plate can be used for direct preparation of plates from digital signals of a computer or the like by using an infrared laser, i.e., a photosensitive lithographic form plate that can be directly prepared.
DESCRIPTION OF THE RELATED ART
In preparation of a form plate for printing, a developing step and a finishing step must be conducted as wet processes after the step of exposure to light. In the developing step, a portion of an image-recording layer disposed on the surface of a substrate is removed to leave the remaining portion in an image form. In the finishing step, the developed form plate is washed with water and treated with a rinsing liquid containing a surfactant and with a desensitizing liquid containing gum arabic and a starch derivative.
In the field of form plate preparation and printing, a problem of environmental pollution arises because the waste water is alkaline. At the same time, streamlining of operations for preparation of form plates is being promoted. Therefore, a form plate that does not require the complicated wet developing processes described above and can be used as a machine plate for printing directly after exposure to light, i.e., a form plate that can be directly prepared, has been desired.
Progress in laser technology in recent years has been remarkable. In particular, solid lasers and semiconductor lasers, which can emit infrared light of a wavelength in a range of 760 to 1200 nm and which have a high output and are of a small size, are easily available. When a form plate is prepared directly from digital data of a computer or the like, the above laser is very useful as the light source for recording. Instruments for preparation of form plates using a semiconductor laser that generates light of about 830 nm and a YAG laser that generates light of about 1064 nm are commercially available.
However, many photosensitive recording materials of practical use have sensitive wavelengths in the region of visible light, i.e., 760 nm or less, and infrared lasers cannot be used for recording images with such materials. Therefore, developing a material that can be used for recording images with an infrared laser has been desired.
As the image-forming material that can be used for recording by an infrared laser, a positive-type recording material using a tetrahydropyranyl ester as a macromolecular compound soluble in an alkali solution is described in European Patent No. 703499A1. A positive-type recording material based on abrasion by an ultraviolet laser is described in Japanese Patent Application Laid-Open No. (hereinafter, abbreviated as JP-A) 8-310148. However, form plates using the above image-forming materials have a problem in that image-forming property markedly deteriorates when the form plates are kept in a condition of a high temperature and a high humidity.
Heat sensitive positive-type image-forming materials that contain a macromolecular compound soluble in an alkali (solution) and an infrared light absorbing agent and can be inscribed by an infrared laser have also been proposed.
As examples in which the above heat sensitive positive-type image-forming material is used in a positive-type lithographic form plate sensitive to an infrared laser light, a carboxylic ester which can be decomposed with an acid is used with an infrared light absorbing colorant in an example disclosed in JP-A 7-186562 and an abrasion-type polymer and an infrared light absorbing colorant are used in an example disclosed in U.S. Pat. No. 5,605,780.
As examples in which the above material is used in a negative-type lithographic form plate sensitive to an infrared laser light, combinations of resol resins which can be thermally crosslinked, agents that generate an acid and infrared light absorbing agents are used in examples disclosed in JP-A 56-69193, JP-A 7-20629 and JP-A 7-271029.
In the above image-forming materials, images are formed by utilizing a difference in the rate of dissolution of the material in an exposed portion and in an unexposed portion. Therefore, to obtain good positive images, it is necessary that the difference in the rate of dissolution be increased. Particularly, it is necessary that the rate of dissolution in the exposed portion be increased.
However, conventional infrared light absorbing agents have a problem in that the infrared light absorbing agent does not completely lose its ability to suppress the rate of dissolution in the exposed portion because decomposition of the infrared light absorbing agent itself does not proceed so much in the exposed portion, although the infrared light absorbing agent can remarkably suppress the rate of dissolution of an alkali-soluble macromolecular compound into the alkali in the unexposed portion. In other words, the difference in the rate of dissolution in the exposed portion and in the unexposed portion is not large and excellent image formation cannot be achieved.
In short, the conventional lithographic form plates such as those described above do not have a sufficient sensitivity from a practical point of view and further improvement in sensitivity has been desired.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems. An object of the present invention is to provide a photosensitive lithographic form plate which uses an image-forming material having properties suitable for preparing a lithographic form plate for printing (machine plate) by directly writing digital data of a computer or the like using a solid laser or a semiconductor laser emitting infrared light (that is, suitable for direct preparation of a form plate) and which shows excellent image-forming properties (sensitivity and developing latitude) and to provide a photosensitive lithographic form plate that is highly sensitive and forms no stains.
As the result of extensive studies by the present inventors, it was found that the above-mentioned disadvantages of the prior art can be overcome by using a photosensitive layer which is disposed on a (hydrophilic) substrate and which contains an infrared absorbing agent having a hydrophobic functional group which changes to hydrophilic due to heat.
Aspects of the present invention are as follows.
A first aspect of the present invention is a photosensitive lithographic form plate comprising: a substrate; and a photosensitive layer disposed on the substrate, the photosensitive layer containing an infrared light absorbing agent having a hydrophobic functional group which changes to hydrophilic due to heat.
A second aspect of the present invention is a photosensitive lithographic form plate comprising: a hydrophilic substrate; and a photosensitive layer disposed on the substrate, the photosensitive layer containing an infrared light absorbing agent having a hydrophobic functional group which changes to hydrophilic due to heat.
A third aspect of the present invention is a photosensitive lithographic form plate wherein, in the first aspect, the hydrophobic functional group which changes to hydrophilic due to heat is bound to an aromatic ring within the infrared light absorbing agent directly or via a binding group.
A fourth aspect of the present invention is a photosensitive lithographic form plate wherein, in the first aspect, the infrared light absorbing agent is represented by following general formula (1):
wherein A
1
and A
2
each independently represents the hydrophobic functional group which changes to hydrophilic due to heat; Ar
1
and Ar
2
each independently represents an aryl group; B
1
, B
2
, B
3
, B
4
, C
1
, C
2
, C
3
each independently represents hydrogen, a halogen, an alkyl group, an aryl group, an alkenyl group or an alkynyl group, and any
Kawamura Koichi
Oohashi Hidekazu
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilmore Barbara
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