JPH02307787A - Thermally sensitive lithography plate - Google Patents

Abstract

PURPOSE:To ensure that ink builds up satisfactorily during printing, the reproduction of a single-dot image formed by printing and printed matter is not contaminated by providing a thermally sensitive recording layer consisting of inorganic pigment, thermoplastic resin and thermally melting material with a specific HLB value. CONSTITUTION:A thermally sensitive recording layer consists mainly of inorganic pigment, thermoplastic resin and thermally melting material at HLB value of 4 or less. The preferable inorganic pigment should be zinc oxide from the viewpoint of coloring effect and application sensitivity. The thermoplastic resin should preferably have a softening point or a melting point of 150 deg.C or less using a cyclic technique. For example, the use of polystyrene or styrene- ester acrylate copolymer is recommended. The thermally melting material of at HLB value of 4 or less is sorbitan fatty acid ester such as sorbitantrioleic ester or glycol fatty acid ester such as ethyleneglycol fatty acid ester. The use ratio of inorganic pigment and thermoplastic resin is 0.5/1 to 10/1 in terms of weight ratio. The addition amount of thermally melting material at HLB value of 4 or less is 0.1 to 20 wt.% for the total amount of the inorganic pigment and thermoplastic resin.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the improvement of a thermal lithographic printing original plate, and more specifically, to a digital type 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 thermal lithographic printing original plates.

[Conventional technology]

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-56-6215, JP-A-56-1); (No. 13456) (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-59-76)
260) (3) Those using an organic photoconductor (JP-A-60-239762) (4) Those using a dispersion system of phthalocyanine and zinc oxide (JP-A-60-240106)
No. 0) (5) Plate making by discharge destruction (Unexamined Japanese Patent Publication No. 54
-6602, JP-A No. 50-591.13, JP-A-6
0-194467) (6) Method of removing parent wood layer and hydrophobic layer with laser light (JP-A-50-113307) and method of plate making in heat mode (JP-A-50-158405)
No.) (7) Method using a thermal printing device such as a thermal head (Japanese Patent Application Laid-Open No. 58-199153, JP-A No. 59-1743)
No. 95) (8) A method of curing the surface recording layer with a laser beam, a thermal head, etc. and cleaning and removing the uncured portion (Japanese Patent Application Laid-open No. 1986-
164049, JP-A-62-164596), etc. are known.

However, all of these methods had the following drawbacks and were not satisfactory.

For 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 them hydrophilic, and Since a developing step is also required in order to utilize a photographic process, the plate-making cost is high and the sensitivity is also low. Furthermore, the method (5) that utilizes discharge destruction causes significant wear on the electrode needles.

It cannot be said that it is an industrially advantageous manufacturing method, and (6)
This method requires a larger device and is not suitable for office printing. Since method (7) contains a hydrophilic resin such as polyvinyl acetate, it is not possible to impart sufficient lipophilicity to the recording layer, and printed materials printed with these printing plates cannot produce clear printed images. There are drawbacks. Further, the method (8) has the disadvantage that a cleaning step is required like the method (4).

In addition, the present inventors have previously filed an application for a lithographic printing plate having a recording layer with a defined carbon number;
According to subsequent research, insufficient ink adhesion (particularly 1.
This resulted in a fine pattern (such as a dot reproduction area), causing image blurring, and it was found that it was still insufficient from the viewpoint of printing suitability.

[Problem to be solved by the invention]

An object of the present invention is to provide a heat-sensitive lithographic printing original plate which has excellent ink receptivity in the image area, has no image unevenness, and provides a clear printed image without background smudge.

[Means to solve the problem]

According to the present invention, in a heat-sensitive lithographic printing original plate in which a heat-sensitive recording layer mainly composed of an inorganic pigment, a thermoplastic resin, and a heat-fusible substance is provided on a water-resistant support, the HLB value of the heat-fusible substance is 4 or less. A thermal lithographic printing original plate is provided.

The heat-sensitive lithographic printing original plate of the present invention has an inorganic pigment thermoplastic resin and a heat-fusible substance with an HLB value of 4 or less as the main components as a heat-sensitive recording layer, so it forms a good printed image during thermal printing. When a lithographic printing plate obtained from this material is used for printing, it is possible to obtain a printed matter that has excellent ink receptivity in the image area, has no image unevenness, and has a clear printed image without background smearing.

The present invention will be explained in more detail below.

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 thermoplastic resin used in the present invention preferably has a softening point or melting point of 150° C. or less by the cyclic method, and such resins include, for example, polystyrene, styrene-
Acrylic ester copolymer, styrene resin such as poly-t-butylstyrene, low melting point polyamide resin, polyacrylic ester/polymethacrylic ester, acrylic ester/acrylic ester copolymer, polyester resin, ethylene -Vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, vinylidene chloride resin, butyral resin, acetal resin, polyvinyltoluene, etc., but in order to impart particularly excellent lipophilicity to the printing plate, polystyrene, It is preferable to use styrene/acrylic ester copolymers, polyacrylic esters, polymethacrylic esters, acrylic ester/acrylic ester copolymers, and low-melting 4-point polyamide resins.

The thermoplastic resins may be used alone or in combination of two or more.

The heat-fusible substances with a B value of 4 or less used in the present invention include sorbitan fatty acid esters such as sorbitan trioleate, sorbitan tristearate, and sorbitan monostearate, ethylene glycol fatty acid esters, and propylene glycol. In addition to glycol fatty acid esters such as fatty acid esters, glycerin fatty acid esters such as glycerin heptanostearate ester, glycerin monooleate, etc., straight chain saturated fatty acids such as arachidic acid, behenic acid, cerotanoic acid, montanic acid, and melisic acid are listed. It will be done. If the HLB value of the heat-melting substance exceeds 4, the ink colorability during printing will be poor, the reproducibility of the one-dot image forming area in printing will be poor, and background smear will occur, which will interfere with the purpose of the present invention. unable to achieve its purpose.

The ratio of the inorganic pigment and thermoplastic resin used in the present invention is 0.5/1 to 1071, preferably 1/1 to 1071 by weight.
5/1 is appropriate. If this usage ratio is less than 0.5/1, the hydrophilicity will be insufficient and the background 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 a decrease in image density. This is not preferable because it may cause unevenness or image unevenness.

Further, the added amount of the heat-melting substance having a B value of 4 or less used in the present invention is 0 to the total amount of the inorganic pigment and thermoplastic resin.
．． It is 1 to 20% by weight. If the amount added is less than 0.1% by weight, the density of the printed image will not be sufficient;
Exceeding this is not preferable as it will cause stains on the printed matter.

The water-resistant support used in the present invention includes, for example, paper moist-strengthened with melamine-formaldehyde resin, urea-formaldehyde resin, etc., polyethylene terephthalate 1 to
Examples include synthetic resin films such as , and metal-deposited paper coated with aluminum or the like. In the present invention, a lubricating mold release agent such as alcohol-modified silicone oil or polyether-modified silicone oil may also be added to prevent the head from sticking.

The lithographic printing original plate of the present invention can be produced by the method shown below, but is not limited to these methods. First, an inorganic pigment, a thermoplastic resin, and the above-mentioned HL8
4 or less heat-melting substances and furthermore modified silicone oil are mixed at the same time. This is dispersed using a dispersing machine such as a ball mill, attritor, homomixer, green mill or sand mill to prepare a heat-sensitive recording layer coating solution, which is then coated on a water-resistant support using a wire bar, roll coater or other conventional method. After applying it using the method described above, it is dried and calendered.

There are no particular restrictions on the amount of the heat-sensitive recording layer coating solution applied to the water-resistant support, but it is generally 5 g/rr? ~30
It is preferable to set it in the range of g/m.

When the lithographic printing original plate obtained according to the present invention is thermally printed using a printing device equipped with a thermal head with a recording density of 16 dots/+ nm, the thermally printed portion is melted by a heat-fusible substance having an I-3 value of 4 or less. , the printing plate has excellent lipophilicity and ink receptivity. One-way valve printing area (non-image area)
is coated with a hydrophilic inorganic pigment and becomes printable by desensitization treatment after image formation.

〔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 Zinc oxide 50 parts Toluene 50 parts The above mixed solution was dispersed in a crane mill for 30 minutes to obtain a 40% by weight coating solution. The obtained coating liquid was applied to synthetic paper (YUPO base paper FPG-1).
, 50 manufactured by Oji Yuka Co., Ltd.) with a dry weight of 20 g/m
The coated surface was calendered to obtain a thermal lithographic printing original plate. Next, the thermal printing original plate was thermally printed using a printing test device equipped with a line-type thermal head having a recording density of 16 tots/square to obtain a planographic printing plate having a good printed image. When this product was printed using an offset printing machine AP3700 manufactured by Ricoh Co., Ltd., more than 1,000 sheets of clear printed matter with no fading in the image area, especially in the fine line area, good ink receptivity, and no scumming were obtained.

Examples 2 to 5 Thermal printing original plates were prepared in the same manner as in Example except that the heat-melting substances shown in Table 1 were used instead of behenic acid in Example 1, and printing was performed after thermal printing. . The results are shown in Table -].

Comparative Examples 1 to 2 A thermal printing original plate was prepared in the same manner as in Example except that a heat-melting substance shown in Table 1 was used instead of behenic acid in Example 1, and printing was performed after thermal printing. .

The results are shown in Table -].

Table-1 Evaluation 1) One-dot reproducibility: Evaluation of ink adhesion at the initial stage of printing.

Good: No smearing or unevenness, slightly poor: Slight smearing or unevenness, poor:
・・Many stains and unevenness 2) Print density ・・Measurement value using Macbeth densitometer 3)
Printing stains: No stains ○, Slight stains Δ, Stains × [Effects of the invention] The thermal lithographic printing original plate of the present invention contains an inorganic pigment, a thermoplastic resin, and a heat-fusible material with an annular B value of 4 or less. Since the heat-sensitive recording layer made of the substance is provided, the ink receptivity during printing is improved, the reproducibility of the 11-cut image forming area during printing is also improved, and printed matter without background smearing can be obtained.

Claims (1)

[Claims] (1) In a heat-sensitive lithographic printing original plate in which a heat-sensitive recording layer mainly composed of an inorganic pigment, a thermoplastic resin, and a heat-fusible substance is provided on a water-resistant support, the HLB value of the heat-fusible substance is 4 or less. A thermal lithographic printing original plate characterized by: