JPS6354287A - Direct type lithographic plate - Google Patents

Abstract

PURPOSE:To enhance oil sensitivity and hydrophilic properties, by incorporating an alumina in a part of inorganic pigments and a high-water absorption resin in an image receiving layer. CONSTITUTION:A coating liquid containing an alumina (to which other inorganic pigments can be added, if necessary), a water-soluble binder, a water-resisting agent, and a high-water absorption resin is prepared; the coating liquid is coated on a substrate and dried at a temperature of 80-150 deg.C to form an image receiving layer of 2-20g/m<2> coating build-up. All neutral or acid aluminas may be used. A commercially available high-water absorption resin may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a drawing-type lithographic printing original plate, and more specifically, by forming a specific image-receiving layer on a support, it is possible to obtain a printing plate of high quality even under high humidity. The present invention relates to an original plate for drawing-type lithographic printing, which is capable of obtaining the following.

[Prior art]

Most of the office printing is done by offset printing machines, and offset printing plates have an image-receiving layer on the support because they are easy to make and can produce printing plates that are faithful to the original. Type lithographic printing plates are widely used.

This drawing-type lithographic printing original plate (hereinafter sometimes abbreviated as "original plate") is generally a water-based paint containing inorganic pigment fine particles, a water-soluble binder, and a water-resistant agent on a support such as wet reinforcement paper. An image-receiving layer is provided by coating.

By the way, most of these original plates are made using an RPC (plain paper copying machine), but they are also made using mail pens, typewriters, thermal transfer printers for word processors, wire tod printers, and the like. However, printing plates made using PPC platemaking tend to peel off the image area from the image-receiving layer during printing.
After being fixed in a copying machine, the toner image must be further irradiated with infrared rays to completely fix the toner image, which is a hassle. In addition, r
The hydrophilicity of the image-receiving layer is somewhat insufficient for use in PC plate making, and some staining is observed at the initial stage of printing. In addition, it has been pointed out that printing plates made by one-stroke printing using Lepen, Typewriter Lean, etc. have poor ink receptivity due to poor oil sensitivity. Furthermore, when a printing plate made with a word processor printer (wire tod printer in %) was used, there was a tendency for blurring of printed areas, detachment of characters, thickening of characters, background stains, etc. to occur easily.

〔the purpose〕

An object of the present invention is to provide an original plate for direct drawing type lithographic printing which has improved oil sensitivity of an image-receiving layer and also has excellent hydrophilicity. Another object of the present invention is to obtain good water resistance and printing durability without pre-etching. An object of the present invention is to provide a direct drawing type lithographic printing original plate that can prevent printing stains even when printing at high humidity. Still another object of the present invention is to provide a direct-drawing type lithographic printing original plate that allows a printing plate of good quality to be obtained even in plate making with a wire tod printer.

[Structure] The present invention provides 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 as main components is provided on a support, at least a portion of the inorganic pigment. is alumina, and.

The image-receiving layer is characterized in that the image-receiving layer further contains a super absorbent resin.

Incidentally, the present inventors have found that when alumina is used as part of the inorganic pigment in the image-receiving layer, the ink receptivity (oil-sensitivity) is improved, and that the image-receiving layer is coated with a superabsorbent resin. It was confirmed that the addition of this compound improves hydrophilicity. The present invention has been made based on such knowledge.

Inorganic pigments include alumina.

Examples include permanent soluble hydrophilic pigments such as calcium carbonate, barium oxalate, silica, kaolinite, titanium dioxide, and zinc oxide.

△ Here, any alumina can be used as long as it is neutral or acidic, but it must be cationic.

In addition, a sol or colloid is preferable.

A preferred example of such alumina is AJs (O
H) Basic alumina chloride sol such as scl; α-Al
, Os” Hlo-like boehmite colloidalized alumina; Jibsite (α-AJ! 03 @3Ht
O), paraiarite (β-J, o, @3Ht
O), norstrandite (newβ-AIlxOs
” 3 Hlo) -Diaspore (β-/5120.-
H, O) , / f I) (5U*Om ”Hlo
), θ-alumina, r-alumina, η-alumina, δ-
Examples include sols or colloids of crystalline alumina such as alumina, χ-alumina, dew-alumina, θ-alumina, and α-alumina.

The silica may be neutral or acidic, but it should have an oil absorption of 100 mq/100, an F or more, and an average particle size of 2.
It is preferable to have a particle size of 0μ or less. Examples of such preferred silica include thermal decomposition of silicon tetrachloride, acid of sodium silicate, and carbon dioxide.

So-called white carmen obtained by metathesis with ammonium salts, etc.; silica sol obtained by metathesis of sodium silicate with acid, alkali, etc., or by passing it through an ion exchange resin layer; colloidal silica obtained by thermal decomposition of the silica sol; A silica sol consisting of three-dimensional secondary particles in which primary particles with a particle size of several microns to several tens of microns are bonded with siloxane; the primary particle or F′i secondary particle type silica sol, sodium silicate, aluminium. It is obtained by heating sodium chloride as a starting material to 80 to 120°C. Examples include synthetic silica compounds mainly composed of silicic acid, such as so-called synthetic molecular sheep.

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

In the present invention, these inorganic pigments may be used alone or in combination of two or more. Alumina is used when used alone, but when two or more types are used in combination, it is desirable that alumina accounts for 10% by weight or more of the total inorganic pigment.

Examples of water-soluble binders include P'/A, starch or its derivatives, CMC5 methylcellulose, hydroxynibble cellulose, casein, gelatin, gum arabic, sodium alginate, polyvinylpyrrolidone, vinyl acetate-crotonic acid copolymer, etc. Ru. Others include epoxy resin, polyvinyl butyral, polyvinyl acetate, polyvinyl chloride, styrene-butadiene copolymer, acrylic resin, ethylene-vinyl acetate copolymer, methyl methacrylate ~
Citadiene copolymer (MBR).

An organic solvent-soluble or emulsion binder such as an acrylonitrile-citadiene copolymer can also be used in combination.

Waterproofing agents are used to make water-soluble binders waterproof by crosslinking, and include, for example, aldehydes.

Amines, polyamide resin, melamine resin initial charge,
Examples include urea resin precondensation products, hydrazides, persulfates, and the like.

The super absorbent resin used in the present invention has a high water absorption capacity.

It is a resin that has particularly excellent water absorption speed and water retention capacity under pressure, and is generally used in absorbent materials such as disposable diapers, sanitary products, and medical underwear, as well as water retention materials for forestry and gardening, as well as various industrial uses. It is widely used as a dehydrating material.

These superabsorbent resins are therefore manufactured and marketed by several companies. For example, the product name "Sunwet" manufactured by Sanyo Kasei Co., Ltd. is made of starch-acrylic monomer graft and has a granular or spherical shape.

It is said that the water absorption capacity of this substance is 700 to 1000 times its own weight, and the sodium salt in the absorption liquid.

It is lowered by electrolytes such as potassium salts, but is not affected at all by non-electrolytes such as urea. Further, the water absorption ability of this material decreases if the absorbing liquid is strongly acidic or alkaline, but it is hardly adversely affected when the pH is in the range of 4 to 10.

The super-absorbent resin manufactured by Seitetsu Kagaku Co., Ltd. under the trade name ``Aqua Keep'' is cross-linked with acrylic monomers, has poor long-term stability, and has a jelly-like appearance.

Sumikagel, a product manufactured by Sumitomo Chemical Co., Ltd., has high water absorption properties.It is made of acrylic acid-vinyl alcohol copolymer and has a spherical shape with a particle diameter of several ioμ to 300μ, and when it comes into contact with water, it expands while remaining spherical. belongs to.

In any case, such a superabsorbent resin can be said to be an optimal auxiliary agent for improving the hydrophilicity of the image-receiving layer.

The proportion of each component in the image-receiving layer is 50 to 50% of the inorganic pigment.
90% by weight, preferably 75-82% by weight.

Water-soluble resin 8-40% by weight, preferably 21-31% by weight
, water resistance agent 2 to 10% by weight, preferably 5 to 8% by weight, super absorbent resin 5 to 50% by weight, preferably 10 to 30% by weight
The degree is appropriate.

In addition, in consideration of the relationship between superabsorbent resin and alumina on printing quality, the blending ratio of these may be changed depending on the degree of oil sensitivity of the printer for the roadbus setter, but the amount of superabsorbent resin If the amount of alumina, which is a highly fat-sensitizing agent, is increased, the hydrophilicity of the image-receiving layer becomes too high, causing problems such as faded letters and detachment of one letter. On the other hand, if the amount of alumina is increased and the amount of superabsorbent resin is decreased, the characters become thicker and print stains occur in the printing percentage at room temperature and high humidity, which is still unsatisfactory. Therefore, it is desirable that alumina be contained in a range of 10 to 50% by weight, preferably 20 to 40% by weight of the entire image-receiving layer, and further, the weight ratio of alumina/water absorbent resin is 1/1 to 7/1. Preferably a range of 1/3 to 1/6 is advantageous. In addition, the 211 ratio of water-soluble binder/water resistant agent is 100/1 to Zoo
/40 or so, preferably 100/10 to 100/20.

Paper as support; paper wet-strengthened with addition of melamine resin, urea resin, polyamide epichlorohydrin resin;
Paper coated with these resins; plastic films:
Synthetic paper; metal plate, etc. are used.

To make the original plate for direct seeding planographic printing of the present invention.

A working solution containing alumina (other inorganic pigments may be added with alumina if necessary), a water-soluble binder, a water-resistant agent, and a superabsorbent resin is prepared, and this is applied onto a support. It is sufficient to form an image-receiving layer having an adhesion amount of 2 to 20117' by drying at 80 to 150°C.

In order to improve printing durability, a water-resistant intermediate layer may be provided between the image-receiving layer and the support with a coating weight of about 5 to 20,117 mm. This water-resistant intermediate layer is composed of the organic solvent-soluble or emulsion resin, or these resins to which various inorganic pigments are added.

Also, on the side of the support opposite to the image-receiving layer.

To prevent curling, apply a back coat layer with an adhesion amount of 5 to 20.
It may be provided at about i/lel. This back coat layer is composed of the above-mentioned water-soluble binder, but if necessary, it can also be composed of a composition similar to that of the above-mentioned water-resistant intermediate layer.

Next, examples will be shown. All parts and parts here are based on the amount of X.

Example: P was applied to the surface of the paper support (basis weight approximately 80 I/Zeno wet reinforced paper).
VA (Kuraray's Popal 117) 10% aqueous solution and 88R emulsion (Mitsui Toatsu #!-Riratsuku 750) mixed at a ratio of 1:1 o3i was applied and dried to a solid content of approximately 101 A water-resistant intermediate layer of /d was provided. Furthermore, a 47% aqueous solution of MBR (Polylac 530 manufactured by Mitsui Toatsu Co., Ltd.) 2 was added to the back side of this paper support.
10 parts aqueous solution of 0 parts PVA (Popal 117 manufactured by Kuraray Co., Ltd.) SOO part is 92%,
A mixed solution consisting of 120 parts of 50% aqueous solution (pH = 6.2) was diluted with water to make a 25% aqueous coating solution, and dried at 130°C for 3 minutes to reduce the solid content to approx. 51
A back coat layer of /wl was provided.

On the other hand, prepare a mixture of 39 (A, B, and C) in Table 1 below and dilute each of these with water to obtain 15% aqueous coating solution (image-receiving layer forming solution A', B/ and C/). was prepared.

Table 1 These image-receiving layer forming liquids were applied onto the pre-coat layer, and dried at 120'C for 3 minutes to form an image-receiving layer with a solid content of about 511/ze0. Then, super calendering was applied to create three types of direct-distributed lithographic printing plates.

Next, print these originals using a wire tod printer (DP-43 manufactured by Su;- Inc.) that comes with the word processor.
20F printer) and made a plate. These were printed using a lithographic printing machine (Ricoh AP-1600) without pre-etching.
), the results shown in Table 2 below were obtained.

Table-2 In addition to plate making using the wire tod printer mentioned above, p.
Pcm plate making, plate making using a thermal transfer printer, direct seeding plate making using /-reubene, etc. were performed, and when these were subjected to similar printing without pre-etching, good results were obtained in all cases.

〔effect〕

As is clear from the description of the examples, the original plate of the present invention has high oil sensitivity due to the inclusion of alumina in its image-receiving layer, and increased hydrophilicity due to the inclusion of a super absorbent resin. This led to the production of high-quality printing plates.

Claims (1)

[Claims] 1. In a printing original plate having an image-receiving layer mainly composed of an inorganic pigment, a water-soluble binder, and a water-resistant agent on a support, at least a part of the inorganic pigment is alumina, and the image-receiving layer A direct drawing type lithographic printing original plate characterized by further adding a super absorbent resin therein.