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
2000-12-05
2003-03-25
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
C430S281100, C430S302000, C430S944000, C430S945000, C430S964000
Reexamination Certificate
active
06537725
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a plate for planographic printing with which direct plate formation, in which a plate can be formed directly by scanning an infrared laser based on digital signals from a computer or the like, is possible. Specifically, the present invention relates to an infrared-sensitive planographic printing plate suitable for alkali developing processing.
2. Description of the Related Art
High-output, compact solid-state lasers, semiconductor lasers, and gas lasers, which emit ultraviolet light, visible light, and infrared light having wavelengths ranging from 300 nm to 1200 nm, have become readily available. These lasers are very useful as a recording light source for making a printing plate directly from digital data of computers or the like.
Various studies concerning recording materials sensitive to these various types of laser have been made. Typical examples of recording materials that can be recorded by an infrared laser beam having a wavelength of 760 nm or greater include the positive-type recording material described in U.S. Pat. No. 4,708,925, and the negative-type recording material that is crosslinkable by an acid catalyst and described in Japanese Patent Application Laid-Open (JP-A) No. 8-276558.
Examples of recording materials responsive to an ultraviolet or visible light laser having a wavelength of 300 nm to 700 nm are numerous, and include the radical polymerizable, negative-type recording materials disclosed in U.S. Pat. No. 2,850,445 and Japanese Patent Application Bulletin (JP-B) No. 44-20189.
In the greater part of such image recording materials that use various kinds of laser beams, particularly in drawing techniques which use an infrared laser having a wavelength of 760 nm or greater, an image is formed by using high heat generated at portions irradiated with the infrared laser. Because the high heat used in this manner is utilized not as an optical mode but as a heat mode, a threshold property appears in image formation and a very contrasty image quality is obtained, so that such image recording materials are preferable as printing materials. To briefly describe threshold property in image formation, in the optical mode, when unexposed portions are irradiated only with weak light leaked at the exposure apparatus, photochemical reactions and the like corresponding to the amount of leaked light are generated, whereby fogging is produced. By contrast, in the heat mode, because a high temperature is not generated unless an amount of light greater than a given value is irradiated, a thermal reaction is not generated (threshold property) and fogging at weakly exposed regions is not produced. On the other hand, at exposed portions irradiated with a strong light, a high temperature is generated and a sufficient image is formed, even in the heat mode. The result is a contrasty image.
Ordinarily, when used as a heat mode characteristic, and in particular when used as material for a printing plate, a support made of metal such as aluminum is used from the standpoint of printability, smoothness and processing ease. However, there is the drawback that heat diffuses from the support and exposure energy is not used effectively for recording, thus leading to a considerable drop in sensitivity.
For this reason, the use of an insulated support or the provision of a heat-insulating material on a support are effective when an image is formed in the heat mode. Because sensitivity is greatly improved by the effect of preventing heat diffusion caused by a reduction in heat conductivity, various insulation methods have been explored.
However, one of the large characteristics of a printing plate is that it is structured by an image portion (a region that is highly hydrophobic and whose affinity to ink is high) and a non-image portion ( a region that is highly hydrophilic and ink-repellant). Here, when a highly hydrophobic material is used as a heat insulating material, the non-image portion (highly hydrophilic portion) must be formed by exposure in order to actually function as a printing plate. When the hydrophilic portion is not formed sufficiently, it becomes easy for ink to adhere to areas whose hydrophilicity has been lowered by abrasion at the time of printing, and there emerges the possibility for contamination in printing to occur.
Conversely, when a highly hydrophilic material is used as a heat insulating material, when the image portion (highly hydrophobic portion) is formed by exposure, problems arise in that damping water at the time of printing penetrates the surface of the heat insulating material along the hydrophilic portion thereof, whereby the photosensitive layer is stripped away by surface destruction, thus leading to a deterioration in printability.
As examples of a structure in which such problems originating in heat insulating materials are few, systems which utilize a heat insulating material at the support or in the vicinity thereof and which carry out recording by ablation, which are systems without alkali developing processing (hydrophilic processing), and systems in which a hydrophilic region and a hydrophobic region are formed in the surface by a polar-transformable material have been investigated. When recording is conducted using ablation, recording layer material is scattered within the exposure apparatus, whereby particularly delicate lenses in a laser transmission section are contaminated. For that reason, there has been the need to additionally furnish a device to remove the ablated materials. The apparatus thus grows complex and is not desirable in terms of costs. Raising printability is therefore substantially difficult in view of the present circumstances.
There are no problems associated with contamination of optical systems when polar-transformable materials are used. However, because the hydrophobic and hydrophilic regions are formed by utilizing only polar variations in the vicinity of the surface of the printing plate, repeated printings of 300,000 plates or more cannot possibly be withstood, printability is low, and there is the fear that contamination in printing caused by a deterioration in the hydrophilicity of the non-image portion will occur.
Accordingly, attempts have been made to develop a heat insulating technology that will eliminate problems associated with heat loss, without adversely effecting other characteristics required of a planographic printing plate, such as compatibility with ink used in printing, printability, adhesion to the recording layer, and the like.
SUMMARY OF THE INVENTION
An object of the present invention is to improve the loss of exposure energy and to form an image in which the on-off thereof in the irradiated and non-irradiated portions is enlarged in an infrared-sensitive planographic printing plate and to provide an aqueous alkali developing type planographic printing plate having high sensitivity and high printing durability.
The inventors of the present invention have conducted various studies to solve the aforementioned problem and, as a result, found that the drop of the heat of a recording layer is prevented and a hydrophilic/hydrophobic region is formed without decreasing adhesion between a support and a recording layer, for example, by using a material having low thermal conductivity and by providing a layer having the ability to make the surface thereof hydrophilic by using an alkali developing solution or by using a support which itself has such an ability. The present invention was thus completed.
Accordingly, the planographic printing plate of the present invention comprises forming a first layer which is made of an heat-insulating material having a low thermal conductivity and is made hydrophilic by treating using an alkali or a silicate in an alkali developing solution after being exposed and a second layer which is an infrared ray-sensitive recording layer to be changed in alkali developing ability without being abraded by irradiation with infrared rays in this order on a support.
Also, in one embodiment, the plan
Kawamura Koichi
Kunita Kazuto
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
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