JPS61152490A - Lithographic printing plate for electronic photograph - Google Patents

Abstract

PURPOSE:To obtain excellent printing durability and desensitizing property as well as prevent ground staining and spot staining by subjecting the surface of a photo conductive layer to a flame treatment. CONSTITUTION:The surface of the photo conductive layer of a lithographic printing plate is treated by flame to partly decompose the resin binder in the surface of the photo conductive layer by oxidation, thereby obtaining the photo conductive layer of a low resin binder ratio and having improved desensitizing property. As a supporter used, a metal such as conductive zinc, iron, copper, etc., or a base paper may be cited. The photo conductive layer on the supporter is composed of a binder (e.g., silicone resin) and a photo conductive substance (e.g., zinc oxide, titanium oxide, etc.) in a photo conductive substance to binder ratio of 3:1-20:1 by weight. The flame treatment is made immediately after coating and drying of photo conductive layer on the conductive supporter or in separate process after being dried, using a combustion gas of paraffinic series or of paraffinic hydrocarbonoxygen mixed gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic lithographic printing plate, and more particularly to a lithographic printing plate with improved printing smear.

[Conventional technology]

A method of preparing a lithographic printing plate by electrophotography is well known, and generally involves uniformly electrolyzing a photoconductive layer of an electrophotographic plate material and imagewise exposing it. A toner image is obtained by wet or dry development, and then, after this toner image is fixed, it is treated with a desensitizing liquid (etching liquid) to make the non-image area where there is no toner image hydrophilic, and it is used as a lithographic printing plate. It is something.
'Although it is essential for a printing plate to have little background staining and high printing durability, conventional electrophotographic lithographic printing plates have not yet fully satisfied these conditions. For example, if the ratio of resin binder to zinc oxide particles in the photoconductive layer is reduced, the desensitization property of the surface of the photoconductive layer will be improved and scumming will be reduced, but on the other hand, the internal cohesive force of the photoconductive layer itself will be reduced. In other words, the mechanical strength is insufficient and the printing durability is reduced. On the other hand, if the proportion of the resin binder is increased, the printing durability will improve, but the scumming will increase.

It goes without saying that scumming is a phenomenon related to the desensitization property of the photoconductive layer surface, but the desensitization property of the photoconductive layer surface is determined by the ratio of zinc oxide and resin/ingu in the photoconductive layer. For example, it is not only influenced by
0-31011, JP-A-49-126406, JP-A-5
4-20735 and Japanese Unexamined Patent Publication No. 58-68046,
It is also stated that the resin binder, which is a resin binder, is effective in improving desensitization properties.

[Problem that the invention seeks to solve]

However, even with these resin binders, when strictly evaluated, they are still unsatisfactory, such as background stains, dotted stains, clogging of halftone dots, and insufficient printing durability for rainbows. In particular, when printing with colored inks that have become popular in recent years, background smudges are noticeable, and furthermore, when a large amount of plates are desensitized using an etching processor, the desensitization ability of the etching solution deteriorates. Staining may occur due to fatigue.

Conventionally, as a method for relieving background stains, there is a so-called two-pass method in which a plate that has been processed once with an etching processor is processed again with an etching processor, but this double-pass method is also effective in relieving dotted background stains. The double pass method is often used when it is known from experience that dotted background stains greatly affect the value of printed materials.

However, the etching processor cannot be operated independently.
It is good if the circulation method is possible, but automatic plate-making and printing systems that integrate a plate-making machine and an etching processor, or an etching processor and a printing machine, or a plate-making machine, an etching processor, and a printing machine are becoming popular. In this system, it is practically difficult to run the etching processor twice.

The present invention has been developed in view of these circumstances, and even with one pass through an etching processor, it does not generate uniform stains or dotted stains on the entire surface, and is also resistant to fatigue of colored inks or etching liquids. Insensitivity 0
This is the primary purpose of providing nine electrophotographic printing plates.

A second object of the present invention is to provide a lithographic printing plate that is resistant to friction and scratches on the plate and is easy to handle without scratches or stains caused by carelessness in handling or poor conveyance of an automatic plate-making machine. .

A third objective is to provide a high quality lithographic printing plate with high printing durability and good halftone reproducibility.

[Failure to solve the problem]

As a result of various studies, the present inventors have discovered that in an electrophotographic lithographic printing plate in which a photoconductive layer mainly composed of a photoconductive substance and a resin inder is provided on a conductive support, the photoconductive It has been found that flame treatment of the layer surface significantly improves the desensitization property and achieves the above objectives.

The flame treatment referred to in the present invention is a known technique. For example, flame treatment, that is, the surface treatment of the polyolefin, is one of the methods for imparting adhesion with printing ink or various coating materials to a molded product made of polyolefin. U.S. Patent No. 2.63 describes a treatment method involving short-term exposure to high-temperature flames.
No. 2,921, US Pat. No. 2,648,097, Japanese Patent Publication No. 55-33057, etc. The mechanism by which desensitization is improved when the surface of the photoconductive layer of a lithographic printing plate provided with a photoconductive layer mainly composed of the photoconductive substance of the present invention and a resin inder has been fully elucidated. It is thought that a part of the photoconductive layer is oxidized and decomposed, and a photoconductive layer having a substantially low resin noider ratio is obtained, thereby promoting desensitization. Furthermore, although this can be limited depending on the treatment conditions, a short treatment of several seconds or less can treat only a very small surface area, and even in this case, a sufficient improvement in desensitization is observed. The mechanical strength of the entire photoconductive layer is not impaired, and the influence on the adhesion to the toner image or printing durability can be minimized.

The flame treatment of the electrophotographic printing plate according to the present invention has an extremely short treatment time of several seconds or less, and is a dry treatment, so it has excellent manufacturing suitability.

As the support that can be used in the present invention, conductive metals such as aluminum, zinc, iron, copper, etc. or conductive base papers conventionally used in electrophotographic photosensitive materials can be used. For example, ion conductive materials and US Pat. 5.597.272 and French Painting Patent No. 2,277.136, or paper impregnated with electronically conductive substances such as inorganic metal compounds and carzene, or mixed during paper making. What was made, Special Publication No. 52-4239, No. 53-190
Synthetic paper described in Patent Publications No. 31 and No. 56-19654, or polyolefin 2-laminated paper, etc., which is prepared by kneading a conductive substance on one side or the inner surface of the base paper described in JP-A No. 58-57994, are used. can.

Furthermore, polyethylene terephthalate, polyvinyl chloride,
A metal-rich film such as aluminum or a metal oxide such as indium oxide or tin oxide is deposited or laminated on an insulating film such as cellulose acetate.
It may be a laminated polyolefin film kneaded with carzene, etc. described in Publication No. 94, and may be coated with a conductive substance such as CuI to impart conductivity to the film surface. There is no particular limitation as long as it is conductive.

The photoconductive layer provided on the support as described above is composed of a photoconductive substance and a binder. As the photoconductive substance, a photoconductive substance such as zinc oxide, cadmium sulfide, titanium oxide, etc. is used. /9 As the inder, silicone resin, polystyrene, polyacrylic or methacrylic ester,
Polyvinyl acetate, polyvinyl chloride, polyvinyl butyral, derivatives thereof, and the like are used. The ratio of photoconductive material to binder is suitably used in a weight ratio of 3:1 to 20:1. Further, a sensitizer, a coating aid used during coating, etc. can be added as necessary. Such a photoconductive layer is provided on the support described above, but the surface is previously subjected to corona discharge treatment, glow treatment, etc., as described in U.S. Pat. No. 3,411,908. Surface treatments such as discharge treatment, flame treatment, ultraviolet ray treatment, ozone treatment, and plasma treatment are preferred because the adhesive strength with the photoconductive layer is improved. The thickness of the photoconductive layer thus provided is 5~
A range of 60μ is suitable.

In a particularly preferred embodiment of the invention, an intermediate layer may be further provided between the support and the photoconductive layer.

The resin used for the intermediate layer is not particularly limited, and examples include ethylene terephthalate, polyimide,
Polycarbonate, polyacrylate, polymethyl methacrylate, polyvinyl fluoride, polyvinyl chloride F1 polyvinyl acetate, polystyrene, styrene-butadiene copolymer, polymethacrylate, silicone resin, chlorinated rubber, epoxy resin, pure and modified alkyd resin, Polyethyl methacrylate, poly-n-butyl methacrylate, cellulose acetate, ketone resin, polyethylene, I-lipropylene, polyacrylonitrile,
Rosin derivatives, polyvinylidene chloride, nitrocellulose, phenol-formaldehyde resin, metacresol formaldehyde resin, styrene-maleic anhydride copolymer, polyacrylic acid-polyacrylamide copolymer, ethylene glycol fumarate copolymer, methyl Vinyl ether-maleic anhydride copolymer, acryloylglycine-vinyl acetate copolymer, polyvinylpyrrolidone, polyvinyl alcohol, polyamide, halogenated styrene, etc. are used. The amount of coverage of the intermediate layer is 0.01~1Qf
/m” range.

Further, if necessary, a conductive inorganic salt may be mixed into the intermediate layer polymer.

The flame treatment used in the present invention may be performed immediately after coating and drying the photoconductive layer on the conductive support, or the treatment may be performed in a separate step after drying. The combustion gas is preferably a mixed gas of paraffinic or olefinic hydrocarbons and oxygen, and the hydrocarbon gas is methane, ethane, propane, butane, ethylene, and propylene, or two or more of these. A mixture is particularly preferred, and in place of oxygen gas, it is also possible to use a mixture of oxygen and a non-combustible gas such as nitrogen gas, air, or a mixture of air and oxygen gas.

In addition, in the case of flame treatment, in order to suppress excessive temperature rise, it is preferable to carry out the treatment while cooling the support by bringing the back surface of the support into contact with an internal water-cooled ram.

A lithographic printing plate can be prepared using the electrophotographic printing material of the present invention by any conventionally known method. Specifically, the photoconductive layer is uniformly charged using a corona charging method or the like, and then imagewise exposed to form a charged image, and toner is deposited in an inverted image using a wet method or a dry method. is fixed by means such as heating. Next, the non-image area to which toner is not attached is treated with a desensitizing liquid to make it hydrophilic. As a desensitizing liquid, for example, U.S. Pat. No. 4,116,69
A composition containing a ferrocyan compound or a ferricyanide compound as described in U.S. Pat.
, 282,811, and the like can be used. By performing offset printing in a conventional manner using the lithographic printing plate thus prepared, printed matter with excellent pressure resistance, easy handling, and less staining can be obtained.

The present invention will be explained in more detail below with reference to Examples.

It should be noted that "%" and "parts" refer to "% by weight" and "parts by weight", respectively, unless otherwise specified.

<Example 1> The following were mixed and dispersed for 20 minutes using an ultrasonic disperser to obtain a coating material for a photoconductive layer. This paint was applied to water-resistant electrophotographic base paper for lithographic printing plates using a wire parser, and the dry coating amount was 201.
/m'' and dried.This sample was applied at a burner flame-exhaust width of 1cIR, and the consumption rate was 80m/min with a combustion gas of the following composition per hour. The surface was treated with flame while running at high speed.

Combustion gas composition: After dark-adapting this sample in a dark room at 20°C and 60% RH for 24 hours, it was plate-made using an electrophotographic engraving machine ELP404 (manufactured by Fuji Film), and then etching solution (ELP-E, manufactured by Fuji Film) was applied. When the paper was desensitized and printed with red ink (Toyo Ink, LK500 Red), more than 3,000 prints were obtained that were free from background stains and dots and ran well. Furthermore, no plate skipping or other defects were observed.

<Comparative Example 1> After coating and drying in exactly the same manner as in Example 1, without fire pit treatment, after dark adaptation, plate making and etching treatment, and printing with red ink in the same manner, scumming occurred after 500 sheets. did.

<Example 2> An undercoat liquid having the following composition was applied to a 0.15 mm thick aluminum plate at a dry coating amount of 5 t/l and dried.

Composition of Undercoat Next, on the undercoat layer, a photoconductive layer having the same composition as in Example 1 was applied with a dry coating amount of 259/? F! The surface of this sample was treated while running at a speed of 100 Wl/min with a flame composed of combustion gas.

After dark adaptation of the combustion gas composition, printing was performed with red ink in the same manner as in Example 1, and more than 30,000 good prints without stains were obtained.

〔Effect of the invention〕

When the electrophotographic lithographic printing plate according to the present invention is used as a lithographic printing plate, it is possible to obtain a large number of high-quality printed matter free from defects such as scumming and plate skipping.

Claims (1)

[Claims] 1) A lithographic printing plate comprising a photoconductive layer containing a photoconductive substance and a resin binder as main components on a conductive support, characterized in that the surface of the photoconductive layer is subjected to flame treatment. An electrophotographic printing plate. 2) The electrophotographic lithographic printing plate according to claim 2, wherein the photoconductive substance is photoconductive zinc oxide.