JPH0453425B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a lithographic printing original plate that is applied to electrophotographic plate making, and particularly relates to a lithographic printing original plate that is sensitive to a semiconductor laser wavelength range. <Prior Art> With the recent streamlining of office processes, a method using laser light has been considered as a method for producing printing plates from electrical signals recorded in the memory of a word processor. Among laser recording methods, semiconductor lasers are
Compared to argon and helium-neon lasers, it is ultra-small, has low voltage, low power consumption, high efficiency, can be modulated at high speed, and has excellent compatibility with semiconductor circuits. However, on the other hand, since the output wavelength is a high wavelength of 760 to 880 nm, special consideration must be given to the sensitivity characteristics of the material constituting the photoreceptor. Phthalocyanine has been known as a photoreceptor sensitive to these wavelength ranges. The phthalocyanine is an excellent material in terms of toxicity and cost, but when used as a lithographic printing plate, it does not have sufficient water retention during plate making, and the surface is too smooth, resulting in poor toner adhesion. Therefore, a method in which zinc oxide and phthalocyanine pigments are dispersed in a binder resin has been proposed (Japanese Patent Laid-Open No. 116760/1983). However, since these are phthalocyanine pigments, they must be used with positive charge, which is insufficient to provide a satisfactory saturation potential and sensitivity. In addition, phthalocyanine pigments have low resistance, and in addition, it is necessary to increase the zinc oxide/binder resin ratio in order to obtain sufficient water retention, so the potential retention is poor, and in the above plate-making system, word processing There was a drawback that the electric potential was attenuated during the laser processing, making it difficult to ensure sufficient plate-making density. This tendency was particularly noticeable in a high humidity atmosphere. <Problems to be Solved by the Invention> The present invention has been made in view of the above circumstances, and aims to improve the potential buildup and attenuation in a binder resin dispersion system of phthalocyanine pigment and zinc oxide, and further improve the sensitivity. This is the purpose. <Means for Solving the Problems> The present invention provides a lithographic printing plate comprising a photosensitive layer containing zinc oxide, a phthalocyanine pigment, and a binder resin on a conductive support, wherein the binder resin is (a) styrene. (2) unsaturated carboxylic acid and unsaturated dicarboxylic acid monoalkyl ester At least one ethylenically unsaturated monomer selected from
(3) at least one selected from aminoalkyl esters, aminoalkylamides, aminoalkyl vinyl ethers, and vinylpyridine compounds of ethylenically unsaturated carboxylic acids;
The present invention is a lithographic printing original plate characterized in that it is a copolymer of various ethylenically unsaturated amine monomers (hereinafter referred to as the third monomer component). The materials of the photosensitive layer constituting the lithographic printing original plate of the present invention are as follows. [Binder Resin] The copolymer applied to the present invention is a so-called amphoteric synthetic polymer copolymer, and the general formula when using an acrylic ester as the first monomer component is shown below. show. First monomer component Second monomer component Third monomer component The details of each substitution are as follows. X: H, _CH3R1 : _{C1 to C12} alkyl group Y: H, _CH3 , COOH, _COOR1 , _CH2COOH ,
CH ₂ COOR ₁ Z:H, CH ₃ A:

【formula】 [Electrically conductive support]

As the conductive support used in the present invention, a metal plate such as aluminum or copper, a plastic plate, a conductive treated paper, or a metal oxide plate can be used. [Zinc oxide] Zinc oxide has an average flow diameter of about 0.2 to 0.5μ,
Powdered materials commonly used for electrophotography can be used. Furthermore, zinc oxide sensitized with N-type and P-type dyes such as rose bengal, uranine, and crystal violet can also be applied. Also, as a photoconductive zinc oxide, the US patent
3060134, in which zinc oxide, which is heat-treated in hydrogen sulfide and has both positive and negative charges, is used instead of ordinary zinc oxide, or mixed with ordinary zinc oxide. Applicable. [Phthalocyanine pigment] As the phthalocyanine pigment, ε-type copper phthalocyanine, α-type copper phthalocyanine, β-type copper phthalocyanine, α-type metal-free phthalocyanine, β-type metal-free phthalocyanine, chlorindium phthalocyanine, magnesium phthalocyanine, etc. can be used. Although the ratio of phthalocyanine to zinc oxide is not particularly limited, it is preferable that the ratio of phthalocyanine pigment/zinc oxide is about 1/5 to 1/2 from the viewpoint of sensitivity when using laser light or water retention during planographic printing. Furthermore, the ratio of phthalocyanine, zinc oxide and binder resin does not matter, but in order to maintain a balance between surface strength, adhesion and water retention, the ratio of adhesive resin to the total weight of phthalocyanine and zinc oxide should be 20 to 40%. It is preferably about % by weight. <Examples> The present invention will be explained in detail below using examples. Note that the number of parts representing the compounded components indicates parts by weight. Monomers and solvents are blended (solid content ratio) as shown in Table 1 below, and polymerized by heating in a nitrogen atmosphere using a reaction initiator to obtain a binder resin constituting the photosensitive layer of the lithographic printing original plate of the present invention. Synthesized.

【table】

[Table] Using the binder resins for Examples 1 to 5 and Comparative Examples 1 to 3 obtained from Table 1, compositions for photosensitive layers were prepared according to the following compositions. α-Copper phthalocyanine (manufactured by Toyo Ink Mfg. Co., Ltd.) 2.2g Binder resin 17g Cellosolve acetate 24g Methyl ethyl ketone 24g After dispersing the above composition in a ball mill for 3 hours, photoconductive zinc oxide (manufactured by Sakai Chemical Co., Ltd., SAZEX
After adding 11 g of #2000), the dispersed paint was further coated on a conductive support for 1 hour to prepare a lithographic printing original plate of the present invention. This lithographic printing original plate was charged with +6KV corona treatment at a speed of 167mm/sec using an Electro Paper Analyzer manufactured by Kawaguchi Electric Co., Ltd., and then subjected to dark decay (DD) until the potential reached 1/2 of the saturation potential (V ₀ ). _1/2 ) was measured. The sensitivity was determined by exposing the sample to 780 nm monochromatic light at 2 μJ/cm ² and measuring the amount of light (E _1/2 ) required to reduce the potential to 1/2. Further, the residual potential (Vres) is expressed as the potential when twice the amount of light of E _1/2 is applied. The results obtained are shown in Table 2 below.

[Table] As is clear from the results in Table 2, the lithographic printing original plate of the present invention has saturation potential, dark decay characteristics, sensitivity, and residual potential that are sufficiently high for practical use. confirmed. On the other hand, in Comparative Example 1, which does not contain the second monomer component and the third monomer component constituting the binder resin, both V ₀ and DD _1/2 are extremely poor, and the second monomer component In the case of Comparative Examples 2 and 3 in which only the components were excluded, DD _1/2 improved, but E _1/2 decreased and Vres increased, resulting in problems. In addition, when the prepared lithographic printing original plate was plate-made using a regular commercial electrophotographic plate-making machine and printed using an offset printing machine, good printing results were obtained in terms of water retention, printing durability, etc. I got it. <Effects of the Invention> Since the present invention has the above-described structure, it has become possible to obtain sufficient charging characteristics and photosensitivity even when a phthalocyanine pigment sensitive to semiconductor lasers is blended with zinc oxide as a composition of the photosensitive layer. .
Furthermore, it has sufficient water retention, which is essential as a lithographic printing original plate, making it possible to provide printing materials of unprecedented quality.

Claims (1)

[Scope of Claims] 1. A lithographic printing original plate comprising a photosensitive layer containing zinc oxide, a phthalocyanine pigment, and a binder resin on a conductive support, wherein the binder resin is (a) styrenes, acrylic esters, etc. and at least one monomer selected from methacrylic acid esters, (b) at least one ethylenically unsaturated monomer selected from unsaturated carboxylic acids and unsaturated dicarboxylic acid monoalkyl esters, ( c) At least one ethylenically unsaturated amine monomer selected from aminoalkyl esters of ethylenically unsaturated carboxylic acids, aminoalkylamides, aminoalkyl vinyl ethers, and vinylpyridine compounds. An original plate for lithographic printing.