JPH0195098A - Original plate for lithographic printing - Google Patents

Abstract

PURPOSE:To form an original plate at relatively low energy whereby an image can be printed with superior quality, by interpositioning a layer containing an organic additive material between a supporting member and an image receiving layer the surface of which changes from hydrophilic to oleophilic. CONSTITUTION:For a supporting member, a sheet of paper, a plastic sheet, a composite sheet or a compound of these materials is employed. For an image receiving layer, a water paint or an oil paint which is obtained by dissolving or diffusing a hydrophilic paint, a resin and a wax in the water or in an organic solvent is used. An organic additive material containing layer is obtained by diffusing an organic additive material composed of fine particles of e.g., epoxy resin, polyethylene, urea resin, melamine resin, etc. into a resin binder. The ratio of the resin binder in solid with respect to the organic additive material 1 by weight part is suitable to be 0.2-0.8pts.wt., and the adhering amount of the organic additive material containing layer onto the supporting member is preferably 1-10g/m<2>. Generally, a thermal head is used for applying a thermal energy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a lithographic printing original plate, particularly a lithographic printing original plate that can be made by applying thermal energy.

[Prior art] There are two methods for creating a lithographic printing plate: 1. As with PS plates, a transparent positive or negative film is created using a silver halide photographic process, and the plate is made by contact printing. 2. Direct plate making, such as with Silver Master However, there are two methods: 3. A method of making a plate using a direct electrophotographic process like a fax master, 4. A method of transferring a toner image using an indirect electrophotographic process like a direct drawing master, Alternatively, a method of making a plate by transferring a wax ink image by a wire dot method or a thermal transfer method is known.

Above 1. Method 2 uses silver salt, which increases the cost, method 3 requires a slightly larger plate-making device, and method 4 requires the use of toner and wax ink ribbon, which require their management.

[Purpose] The present invention solves the above-mentioned drawbacks of the conventional method, and extremely simply uses a small device such as a thermal head without using consumables such as silver salt, chemicals, toner, or wax ink ribbon. The purpose is to provide a lithographic printing plate for creating a printing plate on which an image is drawn.

A further object of the present invention is to provide a printing original plate having high thermal sensitivity and excellent print image quality.

[Configuration] The configuration of the present invention for achieving the above object includes a support,
This is a lithographic printing original plate in which an organic filler-containing layer is interposed between an image-receiving layer whose surface changes from hydrophilic to lipophilic by application of thermal energy.

As the support, paper, plastic sheet, synthetic paper, or a composite thereof can be used.

The image-receiving layer is composed of (1) a water-based paint made of a hydrophilic pigment, a resin, and a wax dissolved or dispersed in water; (2) a water-based paint made of a hydrophilic pigment, a resin, and a wax dissolved or dispersed in an organic solvent; There are oil-based paints made of dissolved or dispersed materials, but in both (1) and (2), a substance that can develop or change color by thermal printing may be further added.

Although the above objective can be achieved by laminating the above-mentioned image-receiving layer on the support, the present inventors believe that by providing an organic filler-containing layer between the support and the image-receiving layer, , were found to increase thermal sensitivity and also improve printed image quality.

The organic filler-containing layer is made of a so-called organic filler made of fine particles of epoxy resin, polyethylene, urea resin, melamine resin, etc., dispersed in a resin binder.

As the resin binder, common ones such as polyvinyl alcohol, starch, casein, synthetic resin emulsion, or those to which a crosslinking agent is added are used. The ratio of resin binder to 1 part by weight of organic filler is 0.2 to 0 in terms of solid content.
．． 8 parts by weight is suitable.

The amount of organic filler-containing layer deposited on the support is 1 to 10 g/■
If the amount is less than 1 g/ls2, the effect cannot be exhibited, and if it is more than 10 g/m, the effect will not be improved and the cost will simply increase.

Although it is unclear why the provision of organic filler content increases thermal sensitivity and improves printed image quality, it is thought that it improves the heat insulation effect and smoothness. Note that a precoat layer made of an inorganic pigment and a resin binder such as a synthetic resin emulsion may be provided between the organic filler-containing layer and the image-receiving layer.

Thermal energy can be applied using any method such as a thermal pen, a thermal head, or an infrared laser, but a thermal head is usually used.

The present invention will be explained below with reference to Examples. However, all amounts (parts) of each component in the text are parts by weight.

Example 1 An organic filler was applied to both sides of a moisture-resistant high-quality paper with a weight of 60 g/a+': An aqueous dispersion of fine particles of urea resin with a non-volatile content of 22 wt% (manufactured by Mitsui Toatsu Kagaku KK, trade name: Nie Pearl S-122) 10 parts Resin binder: 8 parts of a 10wt% aqueous solution of polyvinyl alcohol Crosslinking agent: 1.6 parts of an 80vt% aqueous solution of melamine resin Crosslinking accelerator: 1.6 parts of a 10vt% aqueous solution of NH4Cl A dispersion consisting of 1.6 parts was coated with a wire bar coater. After drying, an organic filler-containing layer of 5g10+2 per side was applied.

Next, an image-receiving layer was formed on one side of this material by the following method.

Composition of image-receiving layer forming liquid Hydrophilic pigment: 50vt% water dispersion of No. 3 zinc white 10 parts Resin: Acrylic resin O/V type emulsion Resin content 50wt% 2.5 parts Wax: Polyethylene O/V type Emulsion resin content 30νt% 0.25 parts water
A two-part dispersion was applied using a wire bar coater and dried with warm air at 50°C to form an image-receiving layer with a coating weight of 8 g/m 2 , and the surface smoothness of the wave layer was 120 according to the Ohken method.
The surface was treated with a super calender until it reached 0 seconds.

The thus obtained lithographic printing original plate was subjected to a plate making test using a plate making tester equipped with a rectangular thin film thermal head of te dot/■, and the application of thermal energy of 0.13 mJ/dot was sufficient to convert hydrophilicity to lipophilicity. was carried out, and prints with good image quality were obtained in printing tests.

Here, the hydrophilicity and lipophilicity of the surface of the image-receiving layer are observed by placing minute water droplets on the surface and observing how well the water droplets fit with the surface, or by measuring the contact angle. Generally, when the contact angle is less than 60'', it is said to be hydrophilic, and when it is larger than 90'', it is said to be hydrophobic or lipophilic.

The printing test was carried out using a commercially available lithographic printing machine (trade name: AP-1700,
Ricoh Co., Ltd.) was used as the desensitizing liquid, and Ricoh Co., Ltd. Fax Etch Liquid Type U was used as the desensitizing liquid, and Ricoh Co., Ltd. LK was used as the ink.
The 800 chrome standard test was carried out using 55k high quality paper as the printing paper.

Example 2 An organic filler was applied to one side of a support made of moisture-resistant high-quality paper with a weight of 55 g/m'.

Acrylic resin fine particles (trade name M P-1000 manufactured by KK Ryoken) 10 parts Resin binder: Aqueous solution of water-soluble isoprene rubber (trade name KL-7N manufactured by Kuraray Sobrene Chemical KK) 20 parts Powder: Sodium polyphosphate 0.03 parts water
A dispersion of 15 parts was applied with a wire bar and dried to provide an organic filler-containing layer with a coverage of 8 g/sr 2 .

Next, this layer was coated with the following precoat forming liquid: Composition of precoat forming liquid Inorganic pigment: 50 wt% aqueous dispersion of clay 10 parts Binder: 50 wt% o/w emulsion of styrene-butadiene copolymer 5 parts water
A dispersion consisting of 10 parts was coated with a wire bar coater and dried to form a precoat layer with a coating weight of 6 g/llI2, and the same dispersion was further coated on the opposite side of the support and dried to give a coating weight of 7 g. /a
A layer of berry ivy of +' was provided.

Next, this material was subjected to a super calendering process to smooth the surface. Next, the following image-receiving layer forming liquid: Composition of image-receiving layer forming liquid Hydrophilic pigment: No. 3 zinc white 10 parts Resin: 40 vt% toluene solution of poly-N-butyl methacrylate (acrylic acid 1 mol% copolymerization) 5 parts wax : Stearic acid 0.3 parts toluene
A dispersion consisting of 10 parts was coated on the precoat layer and dried with warm air at 50°C to form an image receiving layer with a coating weight of 10 g/a+2, and the surface smoothness of the wave layer was 1200 seconds using the Ohken method. The surface was treated with a super calender until it became .

Example 3 Composition of organic filler-containing layer forming liquid A dispersion consisting of 45 parts of organic filler Newvar S-122 (22vt%) and 20 parts of resin binder KL-7N (20vt%) was applied using a wire bar coater.
A lithographic printing original plate was prepared in the same manner as in Example 2 except that an organic filler-containing layer having a dry adhesion amount of 8 g/m 2 was provided.

Example 4 Composition of organic filler-containing layer forming liquid Organic filler: 40 parts of a 20 wt% dispersion of polypropylene fine particles in water (manufactured by Technology Resources KK) Resin binder: A dispersion consisting of 20 parts of KL-7N (20 wt%) Apply with wire bar coater,
A lithographic printing original plate was prepared in the same manner as in Example 2 except that the organic filler content was set such that the amount of adhesion after drying was 5 g/s 2 .

Comparative Example A plain printing original plate was prepared in the same manner as in Example 2 except that the organic filler-containing layer was not provided.

Using these lithographic printing original plates, plate making and printing tests similar to those in Example 1 were conducted, and it was found that in Examples 2 to 4, the conversion from hydrophilicity to lipophilicity on the image-receiving surface was sufficiently performed, and the results were good. Printed matter with good image quality was obtained.

On the other hand, in the comparative examples, the conversion from hydrophilicity to lipophilicity was insufficient, the image quality of the printed matter was low density, there were many missing parts (missing lines), and the quality was low, and the thermal energy was not sufficient. 0
．． Even if the thermal energy was increased to 16 mJ/dot, it was still insufficient, and it was impossible to apply more thermal energy than this in terms of the lifespan of the thermal head.

[Effects] As explained above, the lithographic printing original plate of the present invention allows a printing original plate to be produced with relatively low energy, and can be used to print with excellent image quality.

Claims (1)

[Claims] A lithographic printing original plate characterized in that an organic filler-containing layer is interposed between a support and an image-receiving layer whose surface changes from hydrophilicity to lipophilicity upon application of thermal energy.