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
1999-12-01
2002-06-04
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
C430S138000, C101S453000
Reexamination Certificate
active
06399270
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to supports used for printing plates and printing plates by the use thereof.
BACKGROUND OF THE INVENTION
The surface of a support used for planographic printing plates such as a pre-sensitized plate (hereinafter, also denoted as a PS plate) has been conventionally subjected to a roughening treatment to endow water receptivity and to enhance plate life, and is further subjected to anodic oxidation to endow a hydrophilic property and enhanced resistance to wear by forming an oxide film on the surface thereof.
Generally known roughening treatments include chemical means (e.g., alkali.acid dissolution), mechanical means (e.g., rubbing with an abrasive, sand-blasting, liquid honing, rolling by a roughness-transfer roller, etc.) and electrochemical means (either direct or alternating current electrolytic treatment in an acidic solution). The support surface is subjected to the optimal combination of the treatments described above.
Specifically, electrochemical roughening is indispensable to form pits of 0.1 to a few &mgr;m in diameter to enhance water receptivity, and the acid concentration of an electrolysis solution, the aluminum concentration in the electrolysis solution, the concentration of impurities contaminated in the pre-treatment and the temperature of the electrolysis solution need to be tightly controlled to stably form a uniformly roughened surface, and there are many limitations such that the acceptable composition range of usable aluminum raw plates is limited and the histo-uniformity needs to be superior. The anodic oxidation, in which an aqueous sulfuric acid solution is employed in a high concentration of 20 to 40%, produces safety problems in use of the solution and adverse effects of the effluent on environment.
On the other hand, examples of the surface roughening treatment of a printing plate support, which does not necessarily need the electrochemical roughening treatment nor the anodic oxidation treatment, include a printing plate making method described in Tokuhyohei 9-504241 (WO 95/18019), in which, after being subjected to a mechanical roughening treatment to make the Ra of the substrate 0.3 to 1.5 &mgr;m, oxide particles are thermally sprayed (e.g., by plasma spraying) onto the surface to form a hydrophilic layer; and a method for preparing supports for printing plates described in WO 96/06200, characterized in that a specific substance is formed onto the support surface by a plasma method under low pressure of 1.9984×104 Pa (i.e., 150 torr). However, it was proved that formation of pits of 0.1 to a few &mgr;m in diameter to provide superior water receptivity was not accomplished by such plasma spraying method, and that printing performance was at unacceptable levels, processing stability in the width and longitudinal directions was insufficient when processing was continuously run, and costs were unacceptably high.
A preparation method of printing plate supports is proposed in WO 97/1987, characterized in that inorganic particles dispersed in an aqueous silicate solution were coated on the substrate to form a hydrophilic layer. Thereby, cost reduction may be achieve, however, in this method, multi-layered roughness structure was not added onto the surface so that the dampening water amount latitude during printing was insufficient, and water glass used as a binder was insufficient in flexibility, exhibiting defects such as easily cracking easily which required it to be peeled off and insufficient plate life.
JP-A 9-99662 (hereinafter, the term JP-A means a unexamined, published Japanese Patent Application) proposes a support for offset printing plates, characterized in that an image receiving layer provided on the support has a three-dimensional network structure having 30 to 80% voids and comprising fine inorganic particles of 100 nm or less of an average primary diameter and a water soluble resin. However, it was proved that stain in non-image portions, the dampening water amount latitude and printing life were not at acceptable levels.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a support for a printing plate in which treatment for making the support surface hydrophilic can be performed by coating at a low cost, exhibiting performance as a printing plate (e.g., dampening water amount latitude, resistance to staining in non-image portions or blanket stain, etc.) being superior to the grained aluminum used in conventional presensitized plates and having sufficient plate life.
Further, low-priced, printing plates used for computer to plate making system (hereinafter, also denoted as CTP), which provide easy handlablability and printability at a level equal to conventional presensitized plates (hereinafter, also denoted as PS plates) are desired along with digitalization of printing data. Recently, various types of CTP employing infrared laser recording means have been proposed. Of these, noted is a so-called dry CTP (including development with dampening water in a printing machine), which does not need any specific development, as described in JP-A 8-507727, 6-186750, 6-199064 and 7-314934. However, any type thereof employs laser ablation whereby a layer provided on the substrate is removed, producing problems such as stains occurring in the exposure apparatus. There has been proposed an exposure apparatus in which a suction type cleaner was provided to prevent such staining. However, it was difficult to completely remove ablated substances. There has been proposed a system covering the surface overall with a cover sheet to prevent scattering of the ablated substances, but problems are also produced, such as poor handling in covering with a cover sheet, unacceptable peeling or production of peeled waste.
In cases of printing with using water, there is a problem that the hydrophilicity of a layer constituting a non-image area, and having the function of water receptivity, is insufficient, leading to staining at the time of printing.
Accordingly, it is another object of the invention is to provide a printing plate which is handleable in room light, image formation can be made without need of ablation and therefore without causing any stains in the exposure apparatus, specific developing treatment is not required, there occurs no matter regarding staining of the printing machine, even when being developed in the printing machine and is superior in visualizabity; and an image forming method by the use thereof.
The above objects of the present invention are accomplished by the following constitution:
1. a support for a printing plate comprising a substrate and at least one component layer, wherein the component layer contains porous particles;
2. the support described in 1 above, wherein the component layer is a hydrophilic layer;
3. the support described in 1 above, wherein the porous particles are porous inorganic particles;
4. the support described in 1 above, wherein the porous particles have an average particle size of not more than 1 &mgr;m;
5. the support described in 1 above, wherein the porous particles have a pore volume of not less than 0.5 ml/g;
6. the support described in 3 above, wherein the porous inorganic particles comprise porous silica particles or porous aluminosilicate particles;
7. the support described in 3 above, wherein the porous inorganic particles comprise zeolite particles;
8. the support described in 1 above, wherein the component layer contains flaky inorganic particles;
9. the support described in 8 above, wherein the flaky inorganic particles have an average particle size of not more than 20 &mgr;m and an average aspect ratio of not less than 20;
10. the support described in 8 above, wherein the flaky inorganic particles exhibit not less than 0.7 of a degree of orientation on the substrate surface;
11. the support described in 1 above, wherein the component layer contains metal oxide particles having an average particle size of not more than 100 nm;
12. the support described in 11, wherein the metal oxide particles are col
Hirai Katsura
Mizushima Io
Mori Takahiro
Nishio Kazuyuki
Baxter Janet
Bierman, Muserlian and Lucas
Gilmore Barbara
Konica Corporation
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