JPS61255899A - Plate for direct lithography - Google Patents

Abstract

PURPOSE:To obtain a plate for lithography having superior water resistance and printing durability without the need for a latent catalyst causing the increase in coating liquid viscosity or its gelation, by using inorganic pigments each consisting of a mixture of neutral or acid alumina with silica or a mixture thereof with kaolinite. CONSTITUTION:In a plate for direct lithography wherein an image receptive layer containing inorganic pigments, a binding agent and a water-resisting agent is formed on a substrate, the inorganic pigments each consists of a mix ture of neutral or acid alumina with silica or a mixture thereof with kaolinite. The cationic alumina of sol-form or colloid-form is preferably used. It is also preferably that the silica has an oil absorption not less than 100mg/100g and an average particle size of not more than 20mum and the kaolinite, e.g. a finely divided aluminum silicate of hexagon plate form, has the particle size distribu tion of not less than 50% with respect to the particle having a size of not more than 2mum. In addition, the individual pigment may be neutral or acid, but the mixed pigment must be acid as a whole mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a direct plate lithographic printing plate whose surface is directly engraved.

Prior Art Pencils, Reuben, PP, O (Santsu Paper Copying Machine), typewriters, wire tod printers, thermal transfer printers, etc. are used to directly plate the surface for direct drawing type lithographic printing, generally made of wet-strengthened paper. An image-receiving layer is provided by coating a water-based paint containing inorganic pigment fine particles, a water-soluble resin binder, and a water-resistant agent on a support such as the following: Inorganic pigments include alkaline pigments such as calcium carbonate and zinc oxide. is often used. However, the use of alkaline pigments also requires a latent catalyst, such as ammonium chloride, to crosslink the water-soluble binder and make it waterproof; In some cases, a crosslinking reaction occurred in the solution, resulting in increased viscosity and gel formation, making it unusable as a coating solution. In general, image-receiving layers using not only alkaline pigments but also ordinary inorganic pigments have poor oil sensitivity, so they cannot be attached to low oil-sensitive inks such as those used in typewriter adhesives and wire tod printers' multi-strike cleans. The printed image is blurred and has poor quality9, making it unusable. For example, □ Japanese Patent Publication No. 4
When a ZnO-clay (kaolinite) mixed pigment as described in JP-A No. 8-9802 is used, only a faint image can be obtained by plate making with a low oil-sensitivity ink; When a kaolinite-silica mixed pigment is used, as there is no alumina sol used, platemaking using a low-lipidity ink similarly produces a faint image. Another disadvantage was that it required the use of special PVA (acetoacetylated PVA). Furthermore, in order to prevent printing stains, polyvalent metal salts have conventionally been added to coating solutions, but this also increases the viscosity of the solution, making coating difficult. In plate making using ink, characters came off immediately after printing started, and an image that could withstand use on the bottom could not be obtained. Furthermore, even when a polyvalent metal salt is used, it has conventionally been necessary to perform etching treatment (hereinafter referred to as pre-etching) before the printing plate is used for printing in order to prevent scumming.

Purpose The purpose of the present invention is to prepare latent catalysts, polyvalent metal salts, special PVA
The water resistance and printing durability of the image-receiving layer can be obtained without the addition of other additives, and printing stains can be prevented without the need for a pre-etching process. Another object of the present invention is to provide an excellent original plate for direct drawing type lithographic printing.

Structure The lithographic printing original plate of the present invention is a direct drawing type lithographic printing original plate in which an image-receiving layer containing an inorganic pigment, a binder, and a water-resistant agent is provided on a support. It is characterized by being composed of a mixed system of alumina and silica or a mixed system of these and kaolinite.

The inorganic pigments used in the image-receiving layer of the present invention are, as described above, from the alumna-silica mixed system or the alumina-silica-kaolinite mixed system, and each pigment exhibits neutrality to acidity in an aqueous liquid. .

Among these inorganic pigments, any alumina that is neutral or acidic can be used, but cationic alumina and sol-like or colloid-like alumina are preferred. As such preferable alumina, for example, Ajs(OH)
, basic alumina chloride sol such as Q7; α-kl*0
．．・Alumina made by colloidizing boehmite such as H,0; gibbsite (α-1,0m・3H snow O), no9ryalite (β-A is Os・3 H2O), norstrandite (newβ-AJhOs)・3H,0),
Diasuia (β-Aj*Os・H2O), Nordite (5°i/!os・HsO), ρ-alumina, r-alumina, η-alumina, δ-alumina, 2-alumina,
Examples include sols or colloids of crystalline alumina such as -alumina, θ-alumina, and α-alumina.

The silica may be neutral or acidic, but it must have an oil absorption of 100μ/100.9 or more and an average particle size of 20μ.
The following are preferred. Examples of such preferable silica include so-called white carbon obtained by thermal decomposition of silicon tetrachloride or metathesis of sodium silicate with acids, carbon dioxide, ammonium salts, etc.; metathesis of sodium silicate with acids, alkalis, etc.; Silica sol obtained by passing through an ion-exchange resin layer; Kotetraid silica obtained by thermal decomposition of the silica sol; Particle size from several mμ to several tens of m, obtained by gelling the silica sol.
A silica sol consisting of three-dimensional secondary particles in which μ primary particles are bonded with siloxane; the above-mentioned primary particle or secondary particle type silica sol, sodium silicate, sodium aluminium, etc. are used as starting materials and heated to 80 to 120 G. Synthetic silicon compounds mainly composed of silicic acid, such as so-called synthetic sorechierase, which can be obtained by

Kaolinite may be neutral or acidic, such as fine hexagonal aluminum silicate used for paper coating, but the particle size distribution must be 50% or more of particles of 2μ or less. is preferred.

As mentioned above, each individual pigment may be neutral or acidic, but in the case of a mixed system, the mixed system as a whole must be acidic. The alkaline components of night act additively to improve ink adhesion (oil sensitivity) to low oil-sensitive inks and also improve printing durability, and silica is present on the particle surface. The silanol groups and the oil absorbing properties of the particles improve etching properties due to the interaction with the OH groups in the hydrophilic alumina, and have the effect of preventing background staining during printing even without pre-etching.

In any case, in the mixed inorganic pigment of the present invention, the ratio of alumina and silical kaolinite mixture in parts by weight is usually 0.5/99.5 to 90/10, preferably 5/9.
It is in the range of 5 to 70/30. If the amount of alumina is less than 0.5 parts by weight, the oil sensitivity or ink receptivity and etching properties will be reduced, and if it exceeds 90 parts by weight, the oil sensitivity or ink receptivity will be too strong, causing printing stains and water resistance. In addition, the original plate may curl. The silica/kaolinite ratio varies depending on the plate making machine or printing machine used, but is usually in the range of 5/95 to 100 parts by weight. Silica amount is 5T
If the amount is less than L, poor etching will occur and printing stains will occur. Naori Olinite is particularly effective when using a low oil-sensitivity ink at a maximum of 95 parts, and when using a relatively high oil-sensitivity ink, sufficient oil-sensitivity can be obtained without using kaolinite. .

The other materials used for the image-receiving layer are exactly the same as before.

That is, examples of water-soluble binders include PTA, starch or its derivatives, OMO, methylcellulose, hydroxyethylcellulose, casein, gelatin, gum arabic, sodium alginate, polyvinylzerolidone, vinyl acetate-crotonic acid copolymer, and the like. Others, epoxy resin, /
IJ vinyl butyral, I-vinyl acetate, pre-vinyl chloride, styrene-butadiene copolymer, acrylic resin,
Ethylene - vinyl acetate copolymer, methyl methacrylate-butadiene copolymer (MBR), acrylonitrile -
An organic solvent soluble or emulsion binder such as a butadiene copolymer can also be used in combination.

Water-resistant agents are used to make water-soluble binders water-resistant by crosslinking, such as aldehydes, amines, etc. Examples include lyamide resin, melamine resin initial condensate, urea resin initial condensate, hydrazides, persulfates, and the like.

The ratio of the water-soluble binder, the mixed inorganic pigment, and the water-resistant agent in the image-receiving layer depends on the type of material and, in the case of pigments, the particle size, but is generally 1/(0.5 to 5). )/(0,0
5 to 2) is appropriate.

The support is paper; melamine resin, urea resin, and polyamide epichlorohydrin resin are added to moisten and strengthen the paper;
Paper coated with these resins; plastic films;
Synthetic paper; metal plate, etc. are used.

To make the lithographic printing original plate of the present invention, a coating solution containing an aluminal silica mixed pigment or an aluminal silical kaolinite mixed pigment, a water-soluble binder, and a water resistant agent is coated on a support, and Dry at ~150C to achieve a coating weight of 2~20
What is necessary is to provide an image-receiving layer of g/d. In this case, in order to improve printing durability', a water-resistant intermediate layer may be further provided between the support and the image-receiving layer with a coating amount of about 1 to 2011/rIl, or to prevent curling, The coating amount of Notuku Coat layer is 5 to 25 on the side of the support opposite to the receiving layer.
It may be provided at about i/P/.

Such an intermediate layer is composed of the organic solvent-soluble or emulsion binder resin described above and, if necessary, various inorganic pigments.

On the other hand, the Nokko coat layer is composed of the above-mentioned water-soluble binder resin, if necessary, the organic solvent-soluble or emulsion binder resin, and further, if necessary, various inorganic pigments.

The present invention will be explained in detail below using examples. In addition,
Both parts and percentages are based on weight.

Example 1 A 15% aqueous coating solution (pH
=5. Q5), apply this to one side of 80777 wet reinforcement paper, dry it at 120C for 3 minutes, and dry it for about s77/
The image receiving layer of 1 is set to 9. The better mixture was then diluted with water to give a 25% aqueous coating, which was coated on the side of the support opposite the image-receiving layer and dried at 130 m:' for 3 minutes to form a 25% aqueous coating. After forming the layer, apply a suit calendar to the layer to produce a master plate for direct-drawing planographic printing.

Example 2 An aqueous coating solution for the image-receiving layer was prepared by diluting a mixture of the following with water to a concentration IS% (pl
A lithographic printing original plate was produced in the same manner as in Example 1, except that the material (=4.90) was used.

Next, each of the printing original plates described above was set in a wire tod printer and a thermal transfer printer that were attached to two types of word processors, respectively, and wire tod plate making and thermal transfer plate making were performed to obtain printing plates, and the plates were set in a lithographic printing machine without pre-etching. I printed it. In addition, each printing plate has PPO
A printing plate was prepared by transferring the toner image from the electrophotographic photoreceptor using a printing plate, and printing was carried out in the same manner without pre-etching. Furthermore, each printing original plate was handwritten with an I-lepen to form a printing plate, and it was set in a lithographic printing machine without pre-etching.
I printed it.

The above results are shown in the table below.

(Margins below) As described above, the product of the present invention does not cause blurred or printed images even without the pre-etching process, and has excellent water resistance, so it has long printing durability ( Printing durability) is also sufficient. Incidentally, no phenomenon such as viscosity increase or gelation was observed in the coating liquid for image receiving reservoir of the present invention.

Effects As described above, in the present invention, since a neutral or acidic inorganic pigment is used, there is no need for a potential catalyst that would increase the viscosity of the coating solution or cause gelation, and furthermore, the crosslinking reaction by the water resistant agent can be carried out easily. Since this is carried out sufficiently during the drying process of the receiving layer, a lithographic printing original plate having excellent water resistance and printing durability can be obtained. In addition, in the present invention, since the inorganic pigment is composed of an aluminal silica mixed system or an aluminal silical kaolinite mixed system, the alumina system improves oil sensitivity and ink receptivity, which eliminates blurring of printed images and Printing stains can be prevented without the need for polyvalent metal salts or special PVA, which have the same drawbacks as standard catalysts, and without pre-etching. Furthermore, since there is no pre-etching process for the printing plate, the printing process is simplified.

Claims (1)

[Claims] 1. In a direct drawing type lithographic printing original plate in which an image-receiving layer containing an inorganic pigment, a water-soluble binder, and a water-resistant agent is provided on a support, the inorganic pigment is a mixture of neutral or acidic alumina and silica. A direct drawing type lithographic printing original plate characterized by comprising a mixed system or a mixed system of these and kaolinite.