JPS62162595A - Direct drawing type planographic plate material - Google Patents

Abstract

PURPOSE:To enhance hydrophilicity and prevent ground contamination from occurring, without requiring a pre-etching step, by using an inorganic pigment based on a mixture of alumina, silica, zinc oxide and acetic acid or acetic anhydride or an inorganic pigment based on a mixture of said mixture with kaolinite in providing an image-receiving layer. CONSTITUTION:A coating liquid comprising a pigment based on a mixture of alumina, silica, kaolinite and zinc oxide, acetic acid or acetic anhydride, a water-soluble binder and a water-resisting agent is applied to a base, followed by drying to provide an image-receiving layer. A water-resistant intermediate layer may be further provided between the base and the image-receiving layer. By this method, it is possible to enhance hydrophilicity while maintaining the high sensitivity of the image-receiving layer, to ensure excellent plate wear, and to provide water resistance without using a potential catalyst or a special PVA.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a direct plate lithographic printing original plate whose surface is directly plated.

The original plate for direct-drawing type lithographic printing, whose surface is directly plated using a zero-phase pencil, ballpoint pen, PPC (plain paper copier), typewriter, wire tod printer, thermal transfer printer, etc., is generally made of wet-strengthened paper. An image-receiving layer is provided by coating a support with a water-based paint containing fine inorganic pigment particles, a water-soluble resin binder, and a water-resistant agent. After plate making, the surface is treated with a desensitizing liquid containing a phosphoric acid compound. used as a printing plate. Alkaline pigments such as calcium carbonate and zinc oxide are often used as inorganic pigments in the image-receiving layer of such direct-drawing planographic printing original plates. However, when alkaline pigments are used alone, they also require a latent catalyst such as ammonium chloride to crosslink the water-soluble binder and make it waterproof.
Moreover, when this latent catalyst is used, a crosslinking reaction may occur in a part of the coating solution for the image-receiving layer, increasing the viscosity or forming a gel, making it unusable as a coating solution. In addition, in general, image-receiving layers that use not only alkaline pigments but also ordinary inorganic pigments such as clay and silica have poor oil sensitivity. Ink produces a blurred plate image with poor ink receptivity.
Cannot withstand continuous use. For example, JP-A-48-9802
Zn○~clay (kaolinite) as described in the issue
When mixed pigments are used, plate making with low oil-sensitivity inks produces only blurry images, and JP-A-68-2
Even when a kaolinite-silica mixed pigment as described in No. 3097 is used, only a faint image is similarly obtained in plate making using a low oil-sensitive ink. Moreover, in the latter case, special PVA (acetoacetylated P'
It was necessary to use V A ). Furthermore, conventionally, in order to prevent background smearing, it has been necessary to perform etching treatment (hereinafter referred to as pre-etching) before using the printing plate for printing.

Therefore, the present inventors previously proposed the use of a mixture of alumina and silica, each of which is neutral or acidic, or a mixture of these and kaolinite as an inorganic pigment. Since the image-receiving layer using such a mixed type pigment is highly oil-sensitive, it has good receptivity to low oil-sensitivity inks and therefore print durability, but it is somewhat lacking in hydrophilicity. There are disadvantages in that pre-etching is required, and when printing at high temperatures, as the number of prints increases, ink also adheres to the background of the printing plate, causing background smudges and thick letters.

Purpose 1 The purpose of the present invention is to improve the hydrophilicity of an aluminal-silica mixed image-receiving layer without reducing its high oil sensitivity, and to improve its ink receptivity and
Therefore, it has excellent printing durability, and also contains latent catalysts and special P.
To provide a surface structure type lithographic printing original plate which can obtain water resistance without using VA and can also prevent scumming even during printing at high temperatures without a pre-etching step.

Purchasing - The surface structure type lithographic printing original plate of the present invention contains an inorganic pigment,
In a planographic printing original plate provided with an image-receiving layer containing a water-soluble binder and a water-resistant agent as main components, the inorganic pigments include a mixture of neutral to acidic aluminium, neutral to acidic silica, zinc oxide, or It is characterized by using a mixed system of these and kaolinite, and further adding acetic acid or acetic anhydride.

The lithographic printing original plate of the present invention has improved hydrophilicity of the previously proposed original plate by adding zinc oxide and acetic acid or its anhydride.

Among the mixed inorganic pigments used in the image-receiving layer of the present invention, alumina must be neutral or acidic in an aqueous liquid, but it is preferably cationic and in the form of a sol or colloid. . Examples of such preferred alumina include basic chlorinated alumina sol such as An2(○H)3CQ; α-AQ20.・Alumina made of colloidal boehmite like H2O; Gibsite (α
-AQ203・3H20), barialite (β-AQ
203・3H20), norstrandite (new β
-All, ○, -3H, ○), diaspore (β-AQ
203・3H20), Nordite (5AR203・H2
O), sol or colloid of crystalline alumina such as ρ-alumina, γ-alumina, η-alumina, δ-alumina, χ-alumina, ni-alumina, 0-alumina, and α-alumina.

The silica may also be neutral or acidic, but it is preferably one with an oil absorption of 100 μ/100 g or more and an average particle size of 20 μm or less. Examples of such preferable silica include so-called white carbon obtained by thermal decomposition of silicon tetrachloride, double decomposition of sodium silicate with acids, carbon dioxide, ammonium salts, etc.; double decomposition of sodium silicate with acids, alkalis, etc., or ion exchange resins. Silica sol obtained by passing the silica sol through a layer; Colloidal silica obtained by thermal decomposition of the silica sol; Particle size from several mμ to several tens of mμ obtained by gelling the silica sol.
A silica sol consisting of three-dimensional secondary particles in which primary particles are bonded with siloxane; using the above-mentioned primary particle or secondary particle type silica sol, sodium silicate, sodium aluminate, etc. as a starting material and heating it to 80 to 120 ° C. can be obtained.

Examples include synthetic silicon compounds mainly composed of silicic acid, such as so-called synthetic molecular sieves.

Kaolinite may also be neutral or acidic, such as fine hexagonal plate-shaped aluminum silicate, which is usually used for paper coating, but the particle size distribution should be 50% or more of particles of 2μ or less. preferable.

As mentioned above, for alumina, silica, and kaolinite, each individual pigment may be neutral or acidic, but in the case of a mixed system containing zinc oxide, the mixed system as a whole must be neutral or acidic.

On the other hand, zinc oxide is itself known as an alkaline pigment, and is a pigment that exhibits alkalinity in an aqueous liquid.

In the mixed inorganic pigment of the present invention as described above, the aluminal silica type or aluminal silical kaolinite type is highly oil sensitive as described above, and also exhibits a certain degree of hydrophilicity. This high oil sensitivity is due to the alumina component in alumina and kaolinite, and the hydrophilicity is due to the silanol groups in silica and the ○ in alumina or the alumina component.
I] group. However, these systems alone lack hydrophilicity, and as mentioned above, background smear during high-temperature printing (hereinafter, ``background smear during high-temperature printing'' is simply referred to as ``unless otherwise specified'').
It is called ``ground dirt''. ). Therefore, in the present invention, zinc oxide and acetic acid or anhydride thereof are further added as hydrophilicity improvers. The mechanism by which this addition improves hydrophilicity is that highly hydrophilic zinc acetate is formed through a reaction between these substances, and this is further used during surface treatment of the image-receiving layer.

This is thought to be due to the reaction with the phosphoric acid compound in the desensitizing solution to form highly hydrophilic zinc phosphate. However, such an effect of improving hydrophilicity cannot be obtained even if zinc oxide, acetic acid, or its anhydride is used alone. That is, in the case of zinc oxide, it has low hydrophilicity and also reduces the high oil sensitivity of the aluminal silica type or aluminal silical kaolinite type, thereby deteriorating the ink receptivity and therefore the printing durability. On the other hand, when acetic acid or its anhydride is used alone, although it is highly hydrophilic in itself, it lowers the high oil sensitivity of the system, and thus the printing durability similarly deteriorates.

In any case, in the mixed inorganic pigment of the present invention, the mixing ratio of alumina/silica/kaolinite/zinc oxide is usually 10 to 40/10 to 40/20 to 50/2 in parts by weight.
5-20, preferably 15-25/20-30/30
It is in the range of 40/7.5 to 15. On the other hand, the amount of acetic acid or acetic anhydride is related to the amount of zinc oxide, and is 2 to 10% of the weight of zinc oxide.
, preferably in the range of about 4 to 8%. The amount of acetic anhydride is about 1/3 of the amount of acetic acid.

The other materials used in the image-receiving layer are identical to conventional layers.

That is, as water-soluble binders, PVA, starch or its derivatives,
Examples include CMC, methylcellulose, hydroxyethylcellulose, casein, gelatin, gum arabic, sodium alginate, polyvinylpyrrolidone, and vinyl acetate-crotonic acid copolymer. Others include epoxy resin, polyvinyl butyral, polyvinyl acetate, polyvinyl chloride,
Organic solvent-soluble or emulsion binders such as styrene-butadiene copolymer, acrylic resin, ethylene-vinyl acetate copolymer, methyl methacrylate-butadiene copolymer (MBR), acrylonitrile-butadiene copolymer are also used. can.

Water-resistant agents are used to make water-soluble binders water-resistant by crosslinking, such as aldehydes, amines, polyamide resins, melamine resin initial condensates, urea resin initial fasteners, hydrazides, persulfates, etc. can be mentioned.

The weight ratio of the water-soluble binder, the mixed inorganic pigment containing acetic acid or its anhydride, and the water-resistant agent in the image-receiving layer depends on the type of material and, in the case of a pigment, the particle size. Generally, about 1 to 2/4 to 510.01 to 0.5 is suitable.

Paper as a support; melamine resin, urea resin.

Paper that has been wet-strengthened by adding a resin such as polyamide epichlorohydrin resin; paper coated with these resins; plastic film; synthetic paper; metal plate, etc. are used.

To make the lithographic printing original plate of the present invention, alumina-silica-zinc oxide mixed pigment or alumina-silica-
Applying a coating liquid containing a kaolinite to zinc oxide mixed pigment, acetic acid or its anhydride, a water-soluble binder, and a water-resistant agent,
Dry at 80-150°C with a coating weight of 2-10g/rd
An image receiving layer may be provided. 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 at an adhesion +i of about 5 to 20 g/m, or to prevent curling, a water-resistant intermediate layer may be provided between the support and the image-receiving layer. A back coat layer may be provided on the opposite side of the support with a coating weight of about 5 to 20 g/m.

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 back coat layer is composed of the water-soluble binder resin as described above, the organic solvent-soluble or emulsion binder resin if necessary, and various inorganic pigments if necessary.

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

Example 1 20% aqueous dispersion of white carbon (mite-based amorphous alumina sol) 92%, PH
= 6.2) 50% aqueous dispersion of zinc oxide (manufactured by Sakai Chemical Co., Ltd. 3)
50% aqueous dispersion of No. Zinc White)
30 parts acetic acid
1.5 parts PVA (Poval 117 manufactured by Kuraray Co., Ltd., polymerization degree 1700, saponification degree 98 or higher) 10%
Aqueous solution 150 parts 30% aqueous solution of polyamide resin (Evinox 9887 manufactured by Dick Vercules)
Y) A mixed solution consisting of 6.7 parts was diluted with water to obtain a 15% aqueous coating solution (pH=6.28, viscosity 171
cp/24° C.), and an AOG/I image-receiving layer was provided thereon. Next, a 47% aqueous dispersion of MBR (Mitsui Toatsu Polylac 5)
30) 20 copies P
VA (Poval-117) (7) 10% aqueous solution
500 parts 50% aqueous dispersion of kaolinite (Ultra White 90)
A mixture of 120 parts was diluted with water to give a 25% aqueous coating solution, which was applied to the side of the support opposite to the image-receiving layer and dried at 130° C. for 3 minutes to form a bank of about Log/m. After providing the coating layer, this was subjected to supercalendering to produce a planographic printing original plate.

Example 2 (same as Example 1) 20% aqueous dispersion of white carbon) 50% aqueous dispersion of kaolinite (same as Example 1) 82 parts subtense oxide
50% aqueous dispersion of 'H (same as Example 1) 16 parts acetic acid 1 part 10% PVA
A mixed solution consisting of an aqueous solution (same as in Example 1) was mixed with water to a concentration of 1
Diluted to 5% (pl+=6, 27, viscosity 210
A lithographic printing original plate was prepared in the same manner as in Example 1, except that CP/24°C) 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 the printing plates were made by wire tod plate making and thermal transfer plate making, and then set in a lithographic printing machine without pre-etching. I printed it. Further, in the case of wire tod plate making, the image after plate making was further heat-fixed and printed.

Comparative Example 1 A lithographic printing original plate was prepared in the same manner as in Example 1 except that zinc oxide and acetic acid were removed from the image-receiving layer coating solution, and plate making and printing were performed in the same manner.

Comparative Example 2 A lithographic printing original plate was prepared in the same manner as in Example 2 except that zinc oxide and acetic acid were removed from the image-receiving layer coating solution, and plate making and printing were performed in the same manner.

The above results are shown in the table below.

Effects As can be seen from the above results, the product of the present invention exhibited extremely good performance, except when the image was not fixed by wire tod plate making. This improves hydrophilicity without impairing the high oil sensitivity of the original aluminium-silica mixture system by using a mixture system of alumina-silica zinc oxide - acetic acid or its anhydride, or a mixture system of these and kaolinite in the image-receiving layer. This is because. That is, the improved hydrophilicity eliminates the occurrence of scumming even during high-temperature printing without the need for a pre-etching step, and the high oil sensitivity and excellent water resistance provide sufficient printing durability.

Claims (1)

[Claims] 1. In a direct drawing type lithographic printing original plate in which an image-receiving layer mainly composed of an inorganic pigment, a water-soluble binder, and a water-resistant agent is provided on a support, neutral to acidic alumina to medium is used as the inorganic pigment. 1. A direct drawing type lithographic printing original plate, characterized in that a mixed system of neutral or acidic silica and zinc oxide or a mixed system of these and neutral or acidic kaolinite is used, and further acetic acid or acetic anhydride is added.