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
1997-12-23
2003-02-04
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
C430S285100, C430S287100, C430S283100, C430S284100, C101S453000, C101S454000, C101S457000
Reexamination Certificate
active
06514668
ABSTRACT:
The present invention relates to a photosensitive lithographic printing plate. Particularly, it relates to a photosensitive lithographic printing plate which is highly sensitive to light rays in a visible light region and which is excellent in developability and adhesion to a support.
In recent years, highly sensitive sensitized materials employing photopolymerizable photosensitive materials have been studied in various application fields. Among them, as a prospective system for practical application in near future, development of a highly sensitive photopolymer system which is useful for direct plate making by laser and which is suitable for exposure with a light having a wavelength of laser, such as 488 nm of argon ion laser or 532 nm of YAG laser, is desired, and various proposals for such system have been made.
However, such a photopolymer is poor in adhesion to an aluminum support, whereby there has been a problem that the image is likely to peel during development, or the printing resistance tends to be extremely low during printing.
Various studies have been made with respect to the support in order to improve the adhesion of the photosensitive layer. An aluminum support which has been commonly used as a support for a photosensitive lithographic printing plate, is usually subjected to surface roughening (graining) by e.g. mechanical polishing, chemical etching or electrolytic etching to improve the water holding property for wetting water during printing or to improve the adhesion to a photosensitive layer to be formed thereon. The surface structure of the grained aluminum plate contributes substantially to the plate making performance or the printing performance as a printing plate, and it is very important to control the surface structure. For example, for a support of a printing plate for a correction machine for which excellent image reproducibility and resolution are required, a grain structure is suitable wherein relatively fine shallow dents (pits) are densely present. On the other hand, for a support of a printing plate for the main printing machine for which excellent water holding property and high printing resistance are required, a grain structure is suitable wherein pits are uniform (microscopically uniform) in their diameters and relatively deep.
As grain treatment, an electrolytic etching treatment has been mainly used in recent years, since it is thereby possible to form a wide range of grain structures ranging from a relatively fine shallow grain structure to a deep uniform grain structure, as compared with a mechanical polishing method (such as ball polishing or brush polishing) or a chemical etching method. In an electrolytic etching method, graining is usually carried out by dipping an aluminum plate in a proper electrolyte solution and electrolyzing it by alternate current or direct current.
As the electrolyte, hydrochloric acid has been most commonly employed. However, if electrolytic etching is carried out by using hydrochloric acid as an electrolyte, it is hardly possible to obtain a grain which is deep and uniform in the microscopic structure (the structure as observed with a magnification of from 1,000 to 1,200 times by e.g. a microscope). Accordingly, when used as a support for a printing plate for the main printing machine, it has not been necessarily satisfactory with respect to the printing resistance or the adhesion of the photosensitive layer at the image portion, although the water holding property, and removability of the photosensitive layer at a portion which corresponds to a non-image portion, at the time of development, may be excellent.
On the other hand, JP-A-53-67507 discloses a method for electrolytic surface roughening treatment in an electrolytic bath of nitric acid type. By this method, a deep grain structure with a uniform pit diameter can be obtained, and it is possible to obtain a support excellent in adhesion of a photosensitive layer.
However, when a photopolymer is coated as a photosensitive layer on the support thus obtained, removability of the photosensitive layer at a non-image portion tends to be extremely low, although the adhesion of the photosensitive layer to the support may be improved. Accordingly, a residual film remains, and when such a plate is used as a printing plate, the non-image portion is likely to be inked, thus leading to a stain on a paper.
On the other hand, as an attempt to improve the adhesion from the photosensitive layer side, JP-A-50-100120 discloses that an addition-polymerizable unsaturated bond-containing phosphate such as 2-methacryloyloxyethyldihydrodiene phosphate, adheres well to a metal such as aluminum, iron or antimony. However, with such a phosphate monomer alone, the density of the cured film tends to be relatively small, so that the image portion is likely to be readily eroded, for example, by alkaline water, and fine lines or dots are likely to be eroded during development, whereby the image reproducibility tends to be poor. Further, at a non-image portion, the adhesion of the phosphate to the metal is rather high, whereby a residual film tends to remain, thus leading to a stain.
Further, JP-A-5-25232 discloses an example of a photosensitive lithographic printing plate having coated on hydrochloric acid EE grain (grain formed by electrolytic etching in a hydrochloric acid solution), a photopolymerizable composition comprising a phosphate compound having at least one unsaturated bond and a compound having a part of carboxyl groups of a polymer binder reacted with glycidyl methacrylate. However, also in this case, the printing resistance and the image reproducibility are not yet adequate.
It is an object of the present invention to provide a photosensitive lithographic printing plate which is excellent in various printing properties such as printing resistance, sensitivity, image reproducibility and removability of a non-image portion.
The present inventors have conducted an extensive study to solve the above problems of the prior art and as a result, have unexpectedly found that by a combination of nitric acid EE grain (an aluminum support subjected to electrolytic surface roughening in nitric acid or in an electrolyte composed mainly of nitric acid) and a polymerizable composition containing a phosphate compound, both of which have been believed to be inferior in the removability of a non-image portion, it is possible to obtain a photosensitive lithographic printing plate excellent in all of printing resistance, sensitivity, image reproducibility and removability of a non-image portion. The present invention has been accomplished on the basis of this discovery.
That is, the present invention provides a photosensitive lithographic printing plate having a photosensitive resin layer formed on an aluminum substrate subjected to electrolytic surface roughening in nitric acid or in an electrolyte composed mainly of nitric acid and further to anodic oxidation treatment, wherein the photosensitive resin layer is made of a photopolymerizable composition comprising (A) an addition-polymerizable ethylenically unsaturated bond-containing monomer, (B) a photopolymerization initiator, and (C) a polymer binder, wherein the addition-polymerizable ethylenically unsaturated bond-containing monomer (A) contains a phosphate compound having at least one (meth)acryloyl group.
Now, the present invention will be described in detail with reference to the preferred embodiments.
The addition-polymerizable ethylenically unsaturated bond-containing monomer (A) (hereinafter referred to simply as “an ethylenic monomer”) contained as a first essential component in the photopolymerizable composition of the present invention, is a monomer having an ethylenically unsaturated bond which undergoes addition polymerization and cures by an action of a photopolymerization initiator as a second essential component when the photopolymerizable composition is irradiated with active light rays. In the present invention, the term “monomer” is meant for a concept as opposed to a so-called polymer, and accordingly, it includ
Okamoto Hideaki
Tsuji Shigeo
Baxter Janet
Clarke Yvette M.
Mitsubishi Chemical Corporation
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