JPS60107041A - Electrophotographic lithographic plate material - Google Patents

Abstract

PURPOSE:To obtain an interlayer superior in resistance to water and solvents by hardening with UV rays a soln. contg. acrylic oligomer or monomer having >=2 acryloyl groups in the molecule applied on the interlayer or a barrier layer. CONSTITUTION:A printing plate comprises a substrate, a barrier layer having 1X10<8>-1X10<12>OMEGA surface resistivity formed on the substrate, an interlayer formed on it, and a photoconductive layer composed essentially of zinc oxide. The interlayer is formed by coating the barrier layer with acrylic oligomer or monomer having >=2 acryloyl groups in the molecule, and hardening it by UV irradiation. As said acrylic oligomer or monomer, that of polyester acrylate, epoxy acrylate, and polyester urethane acrylate are used. A photopolymn. initiator is contained in an amt. of 1-5wt% of the acrylic oligomer or monomer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a lithographic printing original plate, and more specifically, to an electrophotographic lithographic printing original plate with less printing surface staining and a long print life.

Prior Art In recent years, with the development of small offset printing presses and automatic printing presses, the mainstream of light printing is shifting to offset printing.

Much research and development has been carried out on such offset printing plate materials, and various materials have been put into practical use. Among these materials, electrophotographic printing original plates having a photoconductive layer mainly composed of zinc oxide are the mainstream for light printing plates because they are inexpensive and the plate-making process is simple. occupies .

Electrophotographic lithographic printing plates are usually produced by subjecting the printing plate material to corona charging, exposure, development and fixing processes in a desired master turn using a plate-making machine, thereby imparting a desired color to the photoconductive layer. Obtained by forming a visualization of the turn.

In the above-mentioned development process, there are a dry development method using a mixture of toner and a carrier such as iron powder, and a wet development method using a developer in which toner is dispersed in an organic solvent such as Isopar.

When the plate is made using the above-mentioned wet development method, there are advantages such as good halftone reproducibility), excellent resolution, short plate making time, and no correction of the entire length. In Japan, electrophotographic lithographic printing plates based on a wet development method are widely used.

Electrophotographic lithographic printing plate materials must have various properties required as lithographic printing materials in addition to the image properties generally required as electrophotographic copying materials.

For example, a printing plate that has undergone a development process must be able to desensitize its non-image areas.

In addition, as a plate material for offset printing, non-image areas can be made hydrophilic by treating the surface of the photoconductive layer with an etchant. It is necessary to have excellent water resistance.

In order to improve the water resistance as described above, it has been proposed to form various intermediate layers between the support and the photoconductive layer. In each case, the properties required of the intermediate layer are as follows.

(1) It has excellent adhesion to both the support and the photoconductive layer.

(2) It has excellent barrier properties to prevent the photoconductive layer coating from penetrating into the support.

(3) It should not be damaged by the solvent of the photoconductive layer paint (4) It should have excellent water resistance and be able to prevent the image-receiving layer (photoconductive layer) from peeling even if it comes into contact with water.

(5) It has appropriate conductivity, so that it does not cause poor contrast due to a decrease in image density or an increase in fog when forming an image.

In order to form an intermediate layer that can satisfy the above requirements, combinations of hydrophilic polymeric substances, such as casein, polyvinyl alcohol, or gelatin, and various water-resistant agents have been proposed. However, the intermediate layer mainly composed of a hydrophilic polymer substance has excessive conductivity under high humidity conditions, which causes a decrease in image density and poor image quality. The water resistance is also unsatisfactory, and therefore the number of printing sheets is low, about 500 to 700 sheets, and the plate elongation is very large. For this reason, plate materials having such an intermediate layer cannot satisfy the lithographic printing plate material market, which requires a high level of quality as in recent years.

In order to overcome the drawbacks of the conventional intermediate layers as described above, intermediate layers using various improved synthetic resin aqueous solutions or synthetic resin dispersions as adhesives have been proposed. The use of these improved adhesives has greatly improved the water resistance of the interlayer; however, the solvent of the photoconductive layer paint (toluene, xylene, etc.) remains diffused in the interlayer. The solvent refluxes into the photoconductive layer over time and plasticizes the adhesive, reducing the mechanical strength of the photoconductive layer and causing damage to the photoconductive layer during multiple winding or sheet cutting processes. This results in disadvantages such as the tendency to become sticky. Damage to the photoconductive layer changes its photoconductive properties, making the image susceptible to capping and causing print smear.

As mentioned above, the intermediate layer is required to have excellent water resistance as well as excellent solvent resistance.

However, it has been extremely difficult to obtain an intermediate layer that has both of these two contradictory properties.

For example, in Japanese Patent Publication No. 40-18708, the water resistance and solvent resistance of the intermediate layer is improved by using a resin having reactive hydroxyl or carboxyl groups with an aminoplastic initial condensate such as dimethylolmelamine, dimethyltrimethylolmelamine, or urea-formaldehyde condensate. It has been proposed to solve the problem by cross-linking to make it water-insoluble, and several methods of cross-linking in this way have been reported.

However, even though such an intermediate layer has sufficient water resistance in the sense that it does not dissolve in water, it cannot completely prevent water from penetrating and swelling, and as a countermeasure, acrylic acid,
It is also necessary to use a water-dispersed emulsion obtained by emulsion polymerization of a vinyl group-containing monomer such as vinyl chloride, vinylidene chloride, vinyl acetate, acrylonitrile, butadiene, or styrene.

When using the above emulsions in combination, if the ratio of emulsion used is too low, the water resistance of the resulting intermediate layer may be unsatisfactory, and if the ratio of emulsion used is too large, the water resistance of the resulting intermediate layer may be Although it becomes good, the organic solvent resistance decreases and becomes unsatisfactory. Therefore, an intermediate layer that satisfies both water resistance and organic solvent resistance is desired. Our goal is to provide lithographic printing plates.

Structure of the Invention The electrophotographic printing original plate of the present invention comprises: a support;
a barrier layer having a surface electrical resistance value of 120; an intermediate layer formed on the barrier layer; a photoconductive layer formed on the intermediate layer and containing zinc oxide as a main component; The intermediate layer is formed by applying a coating liquid 'ff:m containing an acrylic oligomer and/or monomer containing two or more acryloyl groups in the molecule on the barrier layer, and curing this coating liquid layer by UV irradiation. It is characterized by:

The electrophotographic lithographic printing original plate of the present invention comprises a support, a barrier layer, an intermediate layer and a photoconductive layer.

As the support, paper, synthetic paper, or plastic film with excellent water resistance is used, and there are no particular limitations on its shape and dimensions, but generally one with a thickness of 50 to 200 microns is used. .

The photoconductive layer generally contains 15 to 3017 m2 of zinc oxide, and also contains a binder.

A barrier layer is formed on one side of the support. This barrier layer is intended to prevent a low-viscosity intermediate layer forming coating solution from penetrating into the support, and a desired barrier forming material layer is formed on the support by size-pressing or an aqueous treatment solution. A layer can be formed by processing. Preferably, the weight of the barrier layer is within the range of 1 to 1017 m2;
It is more preferably within the range of ~1017 m''.

For forming a single barrier layer, at least one aqueous solution selected from ethylene-acrylic/acid co-i1F combination, polyvinyl alcohol, casein, polyvinylpyrrolidone, and water-soluble resins such as gelatin, and/or acrylic resin, Applying an aqueous emulsion containing at least one selected from ethoxy resin, polyurethane resin, and styrene-butadiene copolymer to at least one surface of the support,
This is dried and solidified. The barrier layer formed in this way is 1 x 108 ~ 1 cut o 12 g 2 s ℃, 45% RH)
It has a surface electrical resistance value of 1x108
It is preferable that the electrical resistance is in the range of 1 to 1 XI O"Ω. When the electrical resistance is higher than 10120, when a photoconductive layer is coated, the image formed thereon is likely to have flashing. This development is particularly carried out under low humidity conditions (e.g. 20°C).

This is especially noticeable on the 20'qb Rig. In addition, if the electrical resistance is as small as 1×108Ω, under high humidity conditions (for example, 3
0'C, 851RH), the image density becomes low.

This results in disadvantages such as: A desired amount of conductive agent may be used in the barrier layer to adjust the electrical resistance.

To form the intermediate layer, a coating solution containing an acrylic oligomer and/or monomer containing two or more acryloyl groups in the molecule is applied onto the barrier layer, and this coating solution layer is cured by ultraviolet irradiation. . The acrylic oligomer and monomer include polyester acrylate 1. Oligomers and monomers such as epoxy acrylate and preester urethane acrylate are used. These acrylic oligomers have high viscosity and may be difficult to apply, so in that case, 10 to 40% of the acrylic oligomer weight I should be used. The viscosity may be lowered by diluting with a low-viscosity photopolymerizable monomer. Such photopolymerizable monomers include 2-ethylhexyl acrylate, 2
- Monofunctional monomers such as hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc.; 1,
Difunctional monomers such as 3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol 400 diacrylate, and the like; These include polyfunctional monomers such as trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, and the like.

The intermediate layer forming coating solution contains acrylic oligomer and/or
Or, 1 to 5 photoinitiators are included based on the weight of the monomer, and the initiators include acetophenone, benzophenone, citler ketone, benzyl, inzoin,
Benzoin ether, pendyl dimethyl ether, thioxanthone, and the like can be used.

The weight of the intermediate layer is preferably in the range 1-10117 m'', more preferably 1-5117 m2.

An intermediate layer forming coating solution is applied onto the barrier layer, dried, and then cured by ultraviolet irradiation. There are no particular limitations on the ultraviolet irradiation device; high-pressure mercury lamps, medium-pressure mercury lamps,
An ozone-less lamp or the like can be used.

A conductive paint such as a paint containing sodium styrene sulfonate, a paint containing a pigment/acrylic resin emulsion/styrene sulfonate sorter, etc. is applied to the back side of the support.
It is preferable to apply the coating at a weight of 201 t/m''. Such a back layer is effective for preventing etching curls on the original plate and reducing image fog.

Example 1 Basis weight 1201! A single layer of 4 layers (of the following composition) was formed on a base paper of 211 parts m2 (dry coating weight) by size press treatment on a base paper of 211 parts m2 (dry coating weight).

Polyvinyl alcohol 80 parts (solid content ratio)? Sodium acrylic acid 20 parts (〃) The surface electrical resistance value of this barrier layer was measured using a surface resistance meter (4329A High Resistance Meter) made by Huhle Paracard. ”
(dry weight) and was cured by irradiating ultraviolet rays with a high-pressure mercury lamp to form a coating film.

! Urethane acrylate oligomer 25 parts by weight Polyol acrylate oligomer 25 Trimethylomeruronoctria acrylate 10 IH piece nia (photopolymerization initiator) 3N The following composition was applied to the surface of the obtained intermediate layer; Photoconductive zinc oxide 100 parts (by weight) ) (Sakai Chemical SAZsuooo) Rose Bengal 0.1 parts (〃) Toluene 150 parts (//) Apply a paint with a dry coating amount of 251 parts m2,
A photoconductive layer was formed.

On the back side of the support, a conductive paint with the following composition was applied in a dry coating amount of 8.
11/m".

Clay 40 parts (weight) Polyvinyl alcohol 10 parts (〃) (PVA-11
7K, Clan) Vinyl acetate resin 40 parts (〃) (Sevian A-522, Daicel) Quaternary ammonium type conductive agent 10 parts (〃) (ECR, Uchemika rv) Next, this was heated at 50% RH and 25°C. In a dark place with atmosphere 2
After conditioning the humidity for 4 hours, the plate was made using an Itic 175 electronic plate making machine. This was desensitized using an etchant (product of Itic Co., Ltd.) and then printed using an offset printing machine (Hamada Star 500).
) and conducted a printing durability test.

The printing test results showed that no picking was observed even after printing 5,000 sheets, and there was little staining on the printing surface, which was good. Comparative Example 1 Using base paper with a basis weight of 1,201 parts m'', 5-size paper was used to form a single barrier layer. A printing plate was obtained in exactly the same manner as in Example 1 except that the press treatment was omitted.

The surface electrical resistance value of the base paper is 3. Since the viscosity of the paint was about 150 cps when forming an intermediate layer with OxlO''A, the paint penetrated into the support without a barrier layer, and a uniform coating film could not be obtained.

The ICIC 175 plate had strong image fog and was unusable as a printing plate.

Example 2 A barrier single-layer coating composition having the following composition was applied to a base paper having a basis weight of 1201 parts m" in a dry coating amount of 6.51 parts m".

The surface electrical resistance value of the obtained barrier layer was 4.0×109
0 (25° C. 1.45 cmRH). On top of this, an intermediate layer forming paint f having the following composition mainly composed of urethane-modified oligomers was applied in a coating amount of 1.211 parts m'' and cured by irradiation with ultraviolet rays from a high-pressure mercury lamp.

Coating composition Urethane acrylate oligomer 40 parts by weight Polyester acrylate oligomer 10 〃1.6--,'
A photoconductive layer similar to that described in Example 1 was formed on the obtained intermediate layer, and a photoconductive layer similar to that described in Example 1 was formed on the back side of the support. A conductive layer similar to that described above was entirely formed to create an electronic printing lithographic printing original plate.

According to the printing test results of the printing plate obtained using this original plate, no picking was observed even after printing 5000 sheets.

Comparative Example 2 For comparison, the results were the same except that no intermediate layer was provided (Example 2)
When a lithographic printing plate was used for printing in the same manner as above, picking occurred after 1000 sheets.

Comparative Example 3 For comparison, a lithographic printing plate was produced in the same manner as in Example 1, except that a paint having the composition shown below was used instead of the intermediate layer forming paint.

Clay 35 parts (by weight) SBR emulsion 50 parts (〃) (JSR-0693 Japan Synthetic Rubber) Casein 10 parts (〃) SR-6135 parts (〃) (Melamine resin, Sumitomo Chemical) Printing test results are 3000 sheets Peeling occurred between the intermediate layer and the photoconductive layer. In addition, scattered stains appeared on the printed matter.

Claims (1)

[Scope of Claims] 1. A support, formed on one side of the support, and having a diameter of 1×10 8 to 1×10
a barrier layer having a surface electrical resistance value of f2Ω, an intermediate layer formed on the barrier layer, a photoconductive layer formed on the intermediate layer and containing zinc oxide as a main component, and gold; The layer is obtained by applying a coating liquid containing an acrylic oligomer and/or monomer containing two or more acryloyl foundations in the molecule onto the barrier layer, and curing the coating liquid layer by UV irradiation. An original plate for electrophotographic printing, which is characterized by 2. The barrier layer is an aqueous solution of at least one selected from ethylene-acrylic acid copolymer, vinyl alcohol, casein, polyvinylpyrrolidone, and gelatin, and/or acrylic resin, epoxy resin, and polyurethane. The present invention is formed by applying an aqueous emulsion containing at least one selected from resin and styrene-butane diene copolymer onto at least one surface of the support, and drying and solidifying the emulsion. The original plate for electrophotographic lithography according to item 1. 3. The electrophotographic printing original plate according to claim 1, wherein the intermediate layer-forming acrylic oligomer or monomer is selected from oligomers and monomers of I-lyester acrylate, niboxy acrylate, and polyester urethane acrylate. . 4. The electrophotographic printing original plate according to claim 1, wherein the intermediate layer forming coating liquid contains a photocurable monomer component together with the acrylic oligomer and/or monomer. 5. The photocurable monomer component is 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate-1-12
-Hydroxy-2-ethylhexyl acrylate, 2-
Hydroxyethyl acrylate, 2-hydroxyglobyl acrylate, 1,3-butanediol diacrylate), 1,4-butanediol diacrylate), 1.6-
A small number selected from hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, hard ethylene glycol 400 diacrylate, trimethylol glonomant triacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate. Tomo1
The electrophotographic printing original plate according to claim 4, which contains seeds. 6. The electrophotographic printing original plate according to claim 1, wherein the weight of the barrier layer is within the range of 1 to 1517 m''. 7. The patent, wherein the weight of the intermediate layer is within the range of 1 to 1097 m2. The electrophotographic lithographic printing original plate according to claim 1.