Electrophotographic lithographic printing plate precursor

Details Electrophotographic lithographic printing plate precursor Electrophotographic lithographic printing plate precursor

1993-04-21

1995-06-13

Goodrow, John

Radiation imagery chemistry: process, composition, or product th

Electric or magnetic imagery, e.g., xerography,...

To produce printing surface

G03G 1328

Patent

active

054241553

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to an electrophotographic lithographic printing plate precursor and more particularly, it is concerned with an electrophotographic lithographic printing plate precursor excellent in printing adaptability as well as printing efficiency and capable of giving a high image quality print.


BACKGROUND TECHNIQUE

Up to the present time, there has generally been employed an electrophotographic process for the production of a lithographic printing plate precursor comprising subjecting the photoconductive layer of an electrophotographic lithographic printing plate precursor to uniform static charge, to imagewise exposure and then to liquid development with a liquid toner to obtain a toner image, then fixing this toner image and processing with an oil-desensitizing solution (etching solution) to render hydrophilic a non-image area free from the toner image.
As a base for the lithographic printing plate precursor, a paper which has previously been rendered electroconductive, etc. is used, but this paper base is penetrated with water, resulting in bad influences on the printing durability or photographic properties. That is, the paper base is penetrated with the above described etching solution or dampening water during printing and expanded so that the photoconductive layer sometimes separates from the paper base to lower the printing durability, sad the moisture content of the paper base is varied with the temperature and humidity conditions in carrying out the above described static charge or imagewise exposure so that the electric conductivity is varied to affect unfavorably the photographic performances. Furthermore, if the water resistance is insufficient, wrinkles occur during printing.
In order to solve these problems, it has been proposed to coat the one or both surfaces of a support with, for example, an epoxy resin or ethylene-acrylic acid copolymer having water resisting property (Japanese Patent Laid-Open Publication Nos. 138904/1975, 105580/1980 and 68753/1984) or to provide with a laminated layer of polyethylene or the like (Japanese Patent Laid-Open Publication Nos. 57994/1983).
Furthermore, a layer provided as a back coated layer on the opposite surface to a surface of a support having a photoconductive layer (also called "top layer" or "printing surface") is called a back layer, and various improvements have been made as to a composition for forming the back layer for the purpose of not only imparting water resistance thereto, but also maintaining various functions.
The inventors have developed and proposed, as a process for developing an electrophotographic lithographic printing plate precursor, a liquid development method by the so-called direct electron injection system, as disclosed in Japanese Patent Laid-Open Publication No. 26043/1989, which method comprises using a conductor instead of an electrode at the opposite side of a printing surface and effecting development while directly feeding electrons to the back side of a base from this conductor, whereby the prior art system of passing a master through a developing liquid flowed between electrodes is substituted.
As an improved technique, the inventors have further proposed a precursor comprising a base having polyolefin laminated layers on both the surfaces of the base, provided with, as a back layer, a layer having a surface electric resistance of at most 1.times.10.sup.10 .OMEGA. and a larger friction resistance than the polyolefin laminated layers, whereby to render correct winding and fixing of the printing plate, to prevent slipping in printing, to carry out favorably electrophotographic printing plate making and to render possible developemnt by the direct electron injection system (Japanese Patent Laid-Open Publication No. 84665/1990).
In addition, the inventor have proposed a precursor comprising an under layer and a photoconductive layer provided on the surface of a base and a back layer on the back surface thereof, the under layer having a surface resistivity of 1.times.10.sup.8 to 1.ti

REFERENCES:
patent: 3658538 (1972-04-01), Hilhorst
patent: 4272569 (1981-06-01), Shaw et al.
patent: 4400440 (1983-08-01), Shaw

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