JPH0592676A - Lithographic printing plate material and its manufacture - Google Patents

Abstract

PURPOSE:To provide a technique to manufacture an offset printing plate which can be directly made based on a digital such as of a computer using a compact device and a dry process as well as a lithographic printing plate material used for the offset printing plate. CONSTITUTION:A lithographic printing plate material consists of a hydrophilic layer in which at least, an inorganic pigment and a binder resin are contained and dispersed, formed on a support. In addition, the binder resin contains at least, a copolymer composed of ester methacrylate and ester acrylate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic printing plate capable of plate making in a heat mode and a method for producing the same, and more particularly to a so-called direct plate making material which can be made directly from a computer.

[0002]

2. Description of the Related Art Conventionally, as a system for making a plate directly from digital data of a computer, (a) a combination of a laser scanning exposure and an electrophotographic method,
(A) A method in which a resin layer or the like is changed by scanning with a high-power laser such as CO ₂ ; (c) A method in which a photosensitive resin and a silver salt sensitive material are laminated and scanning exposure is performed with an Ar laser; (d) There is a silver master type that is exposed by a semiconductor or HeNe laser.

In the method (a), since the electrophotographic method is used, the steps of charging, exposing and developing are required, and the apparatus is complicated and large-scale. Further, the dry developing method has a poor image quality and is not suitable for printing, while the wet developing method is not preferable from the viewpoint of occupational health and danger. Further, the method of using the toner image as a resist to remove the non-image portion is not preferable because the wet process is further increased.

In the system (a), a large output laser itself such as a CO ₂ or YAG laser is large, and the apparatus becomes huge,
Energy consumption also increases. Moreover, the reliability of the life of these lasers was not sufficient.

In the method (c), the silver salt photosensitive material is exposed to Ar laser, the exposed portion is blackened by wet development, and UV is further applied.
However, not only the process is complicated but also the cost of the plate material is high. The method (d) has a drawback that it is a wet development because the cost is high because a silver salt is used.

On the other hand, JP-A-58-193154,
JP-A-59-76260, JP-A-63-2228
No. 57, etc., using a support having a hydrophilic surface, a wire dot type or a heat-sensitive melt transfer method for making a plate by thermal transfer is a dry type and the process is simple. Therefore, the apparatus is compact and maintenance is not required. Therefore, it is widely used in printer applications. However, these have a drawback in that the binder resin has insufficient hydrophilicity, which causes background stains such that ink adheres to the non-image areas during printing.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an offset printing plate which can be directly plate-formed from a digital signal of a computer or the like by a small-sized apparatus and a dry process, and a planographic printing plate material used therefor. That is.

[0008]

Means for Solving the Problems The present invention, which achieves the above object, provides a hydrophilic layer comprising a support and at least an inorganic pigment and a binder resin which are dispersed in the support. A plate material for lithographic printing wherein the binder resin contains a copolymer containing at least a methacrylic acid ester and an acrylic acid ester.

In the present invention, the binder resin may be a copolymer containing, in addition to the methacrylic acid ester and the acrylic acid ester, an acrylic acid ester having a hydroxyl group or a methacrylic acid ester having a hydroxyl group. it can.

In producing the lithographic printing plate of the present invention,
On a support, a plate sheet having a hydrophilic layer formed by containing and dispersing at least an inorganic pigment, a methacrylic acid ester, and a binder resin using a copolymer containing an acrylic acid ester, Transfer sheets provided with at least a non-hydrophilic transfer layer are superposed together, and imagewise heated from the transfer sheet side to partially transfer the transfer layer onto the plate sheet to form a lipophilic layer. ..

The printing plate thus obtained is provided with a hydrophilic layer formed by containing and dispersing a binder resin containing at least an inorganic pigment and a copolymer containing methacrylic acid ester and acrylic acid ester. A lithographic printing plate in which a lipophilic transfer layer is partially transferred onto a printing plate sheet.

[0012]

The hydrophilic layer of the printing plate of the present invention can be easily formed by a general method. Further, since the heat-sensitive recording method is used for the plate making method, the plate can be directly made from digital data, and a wet process such as development is not included. The binder resin of the hydrophilic layer is methacrylic acid ester,
Since it contains a copolymer containing an acrylic ester, it has high strength and high printing durability. Moreover, it is a hydrophilic group-
Since it has OH and> C = O, it is excellent in water retention when used as a printing plate, and a high-quality printed matter with no background stain can be obtained.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The present invention is described in detail below. The lithographic printing plate material of the present invention generally comprises a support and a hydrophilic layer on which at least an inorganic pigment is dispersed in a binder resin. As a support for the plate sheet, paper, a metal plate such as aluminum, a polyester sheet or a plastic sheet such as polyvinyl chloride can be used.

Examples of the inorganic pigment include silica particles, zeolite, alumina, titanium oxide, zinc oxide, talc, barium sulfate, calcium carbonate, and the like.
Zinc oxide having wide grade selectivity and high hydrophilicity is preferable. The binder resin is a copolymer containing an acrylic acid ester and a methacrylic acid ester. Furthermore, a resin containing a acrylic acid ester having a hydroxyl group or a methacrylic acid ester having a hydroxyl group to form a copolymer is used. Good.

As the methacrylic acid ester, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate and the like are used.
Acrylic acid esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, acrylic acid i
So-propyl, n-butyl acrylate, i-acrylic acid
So-butyl or the like is used.

Further, as the acrylic acid ester having a hydroxyl group or the methacrylic acid ester having a hydroxyl group, 2-hydroxyethyl acrylate and 2-acrylic acid acrylate can be used.
Examples thereof include hydroxypropyl, 2-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate and the like.

The copolymerization ratio is shown below. If the content of methacrylic acid ester is too high, it becomes brittle, and if it is too low, the mechanical strength deteriorates, so that it is 30% by weight to 60% by weight.
Is preferred. If the content of the acrylate ester is too high, the mechanical strength will be insufficient, and if it is too low, the flexibility will be insufficient, so that the content is preferably 30% by weight to 70% by weight.

If the content of the acrylic acid ester having a hydroxyl group or the methacrylic acid ester having a hydroxyl group is too large, the plate surface becomes soft, resulting in poor printing durability. If the content is too small, the water retention property of the plate surface is insufficient. Therefore, 5
% To 25% by weight is preferred.

This copolymer can be easily produced. That is, a plurality of corresponding monomers may be solution polymerized in the presence of a reaction initiator such as azobisisobutyronitrile or benzoyl peroxide using an organic solvent such as an aromatic hydrocarbon, a ketone, an ester or cellosolve.

The value of the ratio of the inorganic pigment / binder resin is preferably 60/40 or more in weight ratio in order to secure water retention during printing.
Particularly, 75/25 or more is preferable.

As the transfer sheet, a heat melting transfer recording sheet using a generally used wax as a binder can be used. Further, a heat-softening type transfer recording sheet containing a thermoplastic resin as a binder can also be used.

The method for producing the lithographic printing plate of the present invention will be described below. First, a mixture of an inorganic pigment, an adhesive resin, and a suitable organic solvent such as toluene is dispersed with a dispersing machine such as a ball mill, a paint shaker, an ultrasonic homogenizer, and a sand mill. The obtained mixed liquid is applied onto a support by a conventionally known applicator such as an applicator, a spray coater, a bar coater, a dip coater and a doctor blade, followed by heating and drying to provide a hydrophilic layer to obtain a plate sheet. The thickness of the hydrophilic layer can be arbitrarily set, but is preferably 2 μm or more.

A lithographic printing plate is obtained by superposing both the plate sheet and the transfer sheet with the support on the outside and heating them imagewise from the transfer sheet side to partially transfer the transfer layer to the plate sheet. At this time, the pressure is 0.1 to 10 kg / cm
^{2. The} temperature is preferably 70 ° C or higher. Further, an offset printing plate can be manufactured directly from a computer by scanning imagewise heating using a thermal head according to digital information. Further, as a heating method, in addition to a thermal head, laser scanning or photothermal conversion by flash can be used.

[0024]

【Example】

<Example 1> Monomers, a solvent and a reaction initiator were mixed in the following blending ratio, and the mixture was stirred and heated in a nitrogen atmosphere to synthesize a binder resin. N-butyl methacrylate 60 g n-butyl acrylate 40 g 2-butanone 150 g benzoyl peroxide 0.5 g

Next, as a composition, a coating liquid of 90 g of zinc oxide, 10 g of binder resin, and 230 g of toluene was dispersed with 100 g of 4 mmφ glass beads for 30 minutes with a paint conditioner to obtain a coating liquid for the hydrophilic layer. A 100 μm polyester film that had been subjected to a chemical matting treatment was coated with a bar coater to a dry film thickness of 10 μm to obtain a plate sheet.

A thermal simulator (printing conditions: applied voltage 4.5 w / applied voltage) was used so that a commercially available heat-meltable transfer recording sheet was placed on the obtained plate sheet, and the support sheet was placed on the outer side of the superposed transfer sheet. dot, pulse width 2.
5 msec ON / OFF) to partially thermally transfer the heat-melted layer to the plate sheet. As a result, a lithographic printing plate having a good printed image on the plate sheet was prepared.

This was printed on a commercially available offset printing machine (AD-80 manufactured by Ryobi Imagix Co., Ltd.) using an ink trade name "Mark V" manufactured by Toyo Ink Mfg. Co., Ltd. As a result, the area ratio of the background stain of the printed matter is 0.1% or less (trade name "Viewback III" manufactured by Toyo Ink Mfg. Co., Ltd.).
The printed image density of the image area after printing 3000 sheets was 1.2 or more (measured by Macbeth reflection densitometer RD914), and a very high-quality printed matter was obtained.

Example 2 The same procedure as in Example 1 was repeated except that the binder resin was synthesized by mixing the monomers, the solvent and the reaction initiator in the following mixing ratios, stirring and heating in a nitrogen atmosphere. A lithographic printing plate was created. Methyl methacrylate 80 g n-butyl acrylate 64 g 2-hydroxyethyl methacrylate 16 g z-butanone 240 g Benzoyl peroxide 0.3 g

Next, a printing plate was prepared by thermal printing with a thermal printer, and after surface etching treatment, printing was carried out, and the area ratio of the background stain of the imprint was 0.03% or less, and 3000 sheets were printed. The print image density of the subsequent image area is 1.0
As described above, a very high-quality printed matter similar to that of Example 1 was obtained.

<Comparative Example> A lithographic printing plate was prepared in the same procedure as in Example 1 except that an epoxy resin (Epicoat 807, manufactured by Shell Chemical Co., Ltd.) was used as the binder resin. Next, a printing plate was prepared by thermal printing with a thermal printer, and after performing surface etching treatment, printing was carried out. The entire plate surface was stained with ink, and the background area ratio of the non-image area was 35% or more. A low-quality printed matter with severe background stain was obtained.

[0031]

[Effect] As described above, according to the plate material for a lithographic printing plate and the method for manufacturing a lithographic printing plate of the present invention, an offset printing plate can be easily produced from digital data by a dry process by a heat-sensitive plate making method. In addition, the obtained image quality is good, and the printing durability is also good.

In addition, if a copolymer further containing a hydroxyl group-containing acrylate ester or a hydroxyl group-containing methacrylic acid ester is used as the binder resin, the water retention property of the plate surface is improved and the scumming is eliminated. At the same time, there is an effect that the heat resistance of the plate itself is increased.

Claims (4)

[Claims] 1. A lithographic printing plate material comprising a support and a hydrophilic layer comprising at least an inorganic pigment and a binder resin dispersed therein, wherein the binder resin is at least methacrylic acid ester and acrylic. A lithographic printing plate material comprising a copolymer containing an acid ester. 2. The lithographic printing plate material according to claim 1, wherein the binder resin is a copolymer further containing an acrylic acid ester having a hydroxyl group or a methacrylic acid ester having a hydroxyl group. 3. A plate sheet comprising a support and a hydrophilic layer formed by containing and dispersing at least an inorganic pigment and a binder resin using a copolymer containing methacrylic acid ester and acrylic acid ester. And a transfer sheet provided with at least a non-hydrophilic transfer layer on the substrate are superposed together and heated imagewise from the transfer sheet side to partially transfer the transfer layer onto the plate sheet to form a lipophilic layer. A method for producing a lithographic printing plate, which comprises forming. 4. A copolymer comprising at least an inorganic pigment and a methacrylic acid ester or an acrylic acid ester, and having a hydroxyl group-containing acrylic acid ester or a hydroxyl group-containing acrylic acid ester-methacrylic acid ester on a support. The binder resin, which was contained, was provided with a plate sheet provided with a hydrophilic layer formed by dispersion, and a transfer sheet provided with at least a non-hydrophilic transition layer on the substrate were superposed together,
A method for producing a lithographic printing plate, which comprises imagewise heating from a transfer sheet side to partially transfer the transfer layer onto a plate sheet to form a lipophilic layer.