JPS63166592A - Lithographic original plate - Google Patents

Abstract

PURPOSE:To impart a sharp printing image superior in image density and free from the irregularities of image and scummings and to prevent the occurrence of sticking to a thermal head, by providing an intermediate layer mainly composed of a water-soluble resin or an emulsion resin between a water resistant substrate and a thermal recording layer. CONSTITUTION:As a material for an intermediate layer provided between a water-resistant substrate and a thermal recording layer, a water-soluble resin or an emulsion resin is used. As an inorganic pigment to be used in the thermal recording layer, zinc oxide is preferably used for displaying effects and obtaining operating sensitivity. As a binder, a material having a softening point measured by a ring and ball method or a melting point of 150 deg.C or below is preferably used by adding an appropriate quantity of a hot melt substance. When the obtained lithographic original plate is subjected to a thermal printing, the thermal printed portion has superior hydrophilic properties on the plate surface thereof because of the hot melt substance and the binder melt therein, thus having ink-accepting properties. On the other hand, the non-printed portion is coated with a hydrophilic inorganic pigment and made to be printable by being desensitized after an image-forming.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to the improvement of a lithographic printing original plate, and more specifically, to a digital lithographic plate that does not require a light source or processing such as development and fixation, and can be easily recorded with a thermal printing device. Regarding original printing plates.

[Prior art]

Methods for preparing lithographic printing plates include (1) a method of applying inkjet onto a support having a hydrophilic surface (JP-A-51-84303, JP-A-FJf-15B-6215, JP-A-56-113456; ) (2) Method of plate making by wire tod method or thermal transfer using a support having a hydrophilic surface (JP-A-58-193154, JP-A-59-
76260) (3) Those using an organic photoconductor (JP-A-60-239762) (4) Those using a dispersion system of phthalocyanine and zinc oxide (JP-A-60-2401)
(No. 060) (5) Plate making by electric discharge destruction (JP-A-54-6602, JP-A-50-59113, JP-A-60-194467) (6) Laser light to remove parent wood layer and hydrophobic layer The removal method (Japanese Patent Application Laid-Open No. 113307-1982) and the method of plate making in heat mode (Japanese Patent Application Laid-open No. 15840-1982)
No. 5) etc. are known.

However, all of these methods involved various problems and were not industrially satisfactory.8For example,
Methods (1) and (2) require the use of special inks and transfer ribbons, and methods (3) and (4) require a cleaning process to make the image hydrophilic. To take advantage of the process, l! Because it also requires an image (toner) process.

It has the disadvantages of high plate-making cost and low sensitivity. Furthermore, the method (5) that uses discharge breakdown causes significant wear on the electrode needles and cannot be considered an industrially advantageous manufacturing method, and the method (6) requires larger equipment and is not suitable for office printing. Not suitable.

Incidentally, recently, a method using a thermal printing device such as a thermal head has been proposed as a method to overcome the drawbacks of these conventional lithographic printing plate manufacturing methods (Japanese Patent Application Laid-Open No. 58-19
No. 9153, JP-A-59-174395).

These methods are used to prepare a material with a melting point of 60 to 180 on a water-resistant support.
Using a lithographic printing original plate provided with a heat-sensitive recording layer containing a wax, a hydrophilic binder such as polyvinyl alcohol or acetoacetylated polyvinyl alcohol, and a pigment with a particle size of 0.1 to 10μ, the surface of the heat-sensitive recording layer is thermally heated. An offset printing plate is manufactured by thermal printing with a head, and has the advantage that an offset printing plate can be obtained with a simple device without requiring a light source or developing and fixing as in the past.

However, this method uses a lithographic printing original plate containing a hydrophilic resin such as polyvinyl alcohol or acetoacetylated polyvinyl alcohol in the thermal printing layer, which causes sticking during thermal printing and It is not possible to impart sufficient lipophilicity to the printing layer (recording layer), which causes problems such as low image density of printed matter printed with these offset printing plates and image unevenness, There was a drawback that a clear printed image could not be obtained.

〔the purpose〕

An object of the present invention is to provide a lithographic printing original plate that has excellent image density, provides a clear printed image without image unevenness, and is free from background smear, and does not cause sticking to a thermal head.

(composition〕 According to the invention, an inorganic pigment on a water-resistant support.

In a lithographic printing original plate provided with a heat-sensitive recording layer containing a binder and a heat-melting substance as main components, an intermediate layer made of a water-soluble resin or an emulsion resin is provided between the water-resistant support and the heat-sensitive recording layer. A lithographic printing original plate is provided.

The lithographic printing original plate of the present invention has an intermediate layer made of a water-soluble resin or an emulsion resin between the water-resistant support and the heat-sensitive recording layer, so that it does not stick to the thermal head during thermal printing. Gives a good printed image without
Furthermore, when printing using the lithographic printing plate obtained from Konomono 1, it is possible to obtain printed matter that has excellent image density, excellent resolution, and clear printed images without background smudges.

Next, one aspect of the present invention will be explained in more detail.

In the present invention, an intermediate layer is provided between the water-resistant support and the heat-sensitive recording layer, and a water-soluble resin or an emulsion resin is preferably used as the material for forming this intermediate layer.

Examples of these resins include acrylic acid.

Examples include unsaturated carboxylic acid resins such as methacrylic acid, vinyl chloride resins, SBR, methyl methacrylate-butadiene copolymers, alkyd resins, phenol resins, epoxy resins, ethylene ionomer resins, and the like.

The amount of the intermediate layer attached to the water-resistant support varies depending on the type of resin used, but it has excellent film-forming properties.

For materials with good solvent resistance, it is sufficient to use 1 to 15 g/%, but for materials with relatively poor film-forming properties and solvent resistance, it is necessary to use more than the above, for example, 10 g/%. A deposition amount of about 30 g/rd' gives desirable results.

Examples of inorganic pigments used in the heat-sensitive recording layer of the present invention include clay, silica, zinc oxide, titanium oxide, aluminum oxide, calcium carbonate, barium carbonate, barium sulfate, etc. In view of this, it is preferable to use zinc oxide.

The binder used in the blade of the present invention preferably has a softening point or melting point of 150° C. or less as determined by the ring and ball method, and specific examples of such a binder include, for example.

Styrenic resins such as polystyrene, styrene-acrylic acid ester copolymer, poly-t-butylstyrene,
Low melting point polyamide resin, polyacrylic acid Tomoe ester, acrylic ester/acrylic ester copolymer, polyester resin, ethylene-vinyl acetate copolymer pentavinyl chloride-vinyl acetate copolymer, vinylidene chloride resin, butyral resin, acetal resin , polyvinyltoluene, etc., but in order to impart particularly excellent lipophilicity to the plate surface, polystyrene, styrene-acrylic ester copolymer, polyacrylic ester, acrylic ester
It is preferable to use an acrylic ester copolymer and a low melting point polyamide resin.

In the present invention, the binders may be used alone or in combination of two or more.

Further, the heat-melting substance preferably melts at a temperature of 50 to 200°C. Examples include carnauba wax, auricule wax, microcrystalline wax, paraffin wax, ceresin wax, montan wax,
Examples include waxes such as candelilla wax, shellac wax, wax wax, beeswax, Japanese wax, low-volume polyethylene, fatty acids such as stearic acid, and polyethylene glycol stearate.

The ratio of the inorganic pigment and binder used in the present invention is 0.5/1 to 10/1 in terms of heavy electric ratio. Preferably 1/1 to 5/
1 is appropriate.

If the usage ratio is less than 0.5/1, the hydrophilicity will be insufficient and the background part of the printed matter will be easily smudged, and if it exceeds 10/1, the lipophilicity of the printing plate will not be sufficient when thermal printing is performed, resulting in poor image density. This is not preferable because it causes deterioration and image unevenness. If it is less than 0.1 weight 2, the printing density will be insufficient.

Moreover, if it exceeds 20% by weight, it is not preferable because the printed matter will become smudged.

Further, the amount of the heat-melting substance used in the present invention is 0.1 to 20% by weight based on the total solid content, and in the case of solvent-based
．． 3 to 10 weight 2 is preferable, and in the case of water-soluble type, 3 to 20
Heavy stones are suitable.

Examples of the water-resistant support used in the present invention include paper moisture-strengthened with melamine-formaldehyde resin, urea-formaldehyde resin, etc., synthetic resin film such as polyethylene terephthalate, and metal-deposited paper coated with aluminum or the like. It will be done.

Moreover, in the present invention, in addition to the above-mentioned essential components.

It is also possible to add a dispersion aid to the coating liquid, if necessary. Examples of such dispersion aids include naphthenic acid metal salts, fatty acids and their metal salts, cationic surfactants, nonionic surfactants, anionic surfactants, etc., and the amount added depends on the coating liquid. The amount is usually 10% by weight or less based on the solid content.

The lithographic printing original plate of the present invention can be produced by the following methods, but is not limited to these methods.

First, an intermediate layer coating solution such as a water-soluble resin or an emulsion resin is applied onto a water-resistant support using a conventionally known method such as a wire bar or a roll coater to form an intermediate layer.

Next, a mixture containing an inorganic pigment, a binder, a heat-melting substance, and, if necessary, the above-mentioned dispersion aid is dispersed and mixed using a dispersing machine such as a ball mill, an attritor, a homomixer, a grain mill, or a sand mill to record heat-sensitive information. A layer coating solution is prepared, and then this is coated on the intermediate layer by a conventionally known method such as a wire bar or a roll coater, and then dried and, if necessary, calendered. There are no particular restrictions on the amount of coating liquid for the recording layer, but
Generally, the range is preferably from 5g/rrr to 30g/rif.

When the lithographic printing original plate obtained according to the present invention is thermally printed using a thermal printing device such as a thermal printer or a thermal facsimile, the thermally printed area has excellent adhesive properties on one plate surface because the heat-melting substance and binder melt. It becomes oily and becomes ink receptive.

On the other hand, the non-printing area (non-image area) is coated with a hydrophilic inorganic pigment, and becomes printable by being desensitized after image formation.

〔effect〕

The lithographic printing original plate of the present invention has the above-mentioned structure, and since an intermediate layer containing a water-soluble resin or an emulsion resin as a main component is provided between the water-resistant support and the heat-sensitive recording layer, the surface of the heat-sensitive recording layer is heated. When printing, a good printed image is formed without causing sticking to the thermal head, so when printing using the obtained lithographic printing plate, it has excellent image density and resolution, and is free from background stains. Printed matter with a clear printed image can be obtained.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. All parts shown below are based on weight.

Example 1 A 3° aqueous solution of acrylic resin (acrylic resin: AP-604, manufactured by Showa Kobunshi Co., Ltd.) was coated on a water-resistant support with a basis weight of 80 g/rrr so that the amount of adhesion after drying was 2 g/rd. It was applied with a bar and an intermediate layer was provided.

Next, a heat-sensitive recording layer coating solution having the following composition was applied onto this intermediate layer using a wire bar so that the coating amount after drying was 10 g/rrr, dried at 100°C for 1 minute, and then supercalendered. A lithographic printing original plate of the present invention was obtained.

[Thermosensitive recording layer coating liquid]

Zn0 (SX-8ND manufactured by Seido Kagakusha > 1
00 parts toluene 13
5 Parts Example 2 to 1O1 Comparative Example 1 Lithographic printing was carried out in the same manner as in Example 1, except that the intermediate layer forming material and its adhesion amount to the water-resistant support were changed to those shown in Table 1. I got the original version.

Next, when each of the planographic printing original plates obtained above was thermally printed using a thermal head device, the one of Example 1-1O produced a good printed image without any sticking sound or stick peeling. A lithographic printing plate having the above-mentioned properties was obtained, but the comparative example produced a loud sticking sound and peeled off the stick during printing.

Next, after etching these printing plates using a normal etching process, ■ Ricoh offset printing machine AP
When printing was carried out using I700, more than 1,000 clear prints with good ink receptivity and no background smudge were obtained in Examples 1-10 from the initial stage of printing.

On the other hand, in the comparative example, only printed matter with poor image quality and a lot of scumming was obtained.

Claims (1)

[Claims] (1) In a lithographic printing original plate in which a heat-sensitive recording layer mainly composed of an inorganic pigment, a binder, and a heat-melting substance is provided on a water-resistant support, there is a space between the water-resistant support and the heat-sensitive recording layer. A lithographic printing original plate characterized by having an intermediate layer made of a water-soluble resin or an emulsion resin.