JPS62199444A - Method for photoengraving of planographic printing base plate - Google Patents

Abstract

PURPOSE:To enable photoengraving only by light irradiation, by a method wherein the thermal transfer layer on a thermal transfer medium and the hydrophilic surface of an image receiving body are superposed to be heated imagewise before the thermal transfer medium is released to form an image on the image receiving body. CONSTITUTION:A thermal transfer layer containing a polymer curable by isocyanate and block isocyanate is provided on a substrate to form a thermal transfer medium. The thermal transfer layer of this thermal transfer medium and the hydrophilic surface of an image receiving body of which the surface is made hydrophilic are superposed to be heated imagewise and, thereafter, the thermal transfer medium is released to form a thermal transfer image on the image receiving body. As a means for the aforementioned imagewise heating, a thermal head is used in a facsimile or a printer, however, a means using a heat pen can be employed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a simple plate-making method for a 1,000-plate printing original plate using a thermal transfer recording method.

<Prior Art> As a lithographic printing original plate, a PS plate using a photosensitizer, an electrophotographic master using zinc oxide, etc. are conventionally used. However, these printing plates and plate-making methods had some problems that needed improvement.

For example, PS plates require sufficient care in storage and handling before use due to their photosensitivity. In plate making, it is not possible to print a pattern directly from an original onto a printing plate, so a lithographic film is used as an intermediate layer. The process of treating this lithium film is complicated, and some of the chemicals used are polluting, causing problems in handling. On the other hand, although the electrophotographic method is easier to make than the PS plate, it requires an expensive device called an electrophotographic engraving machine, so it cannot necessarily be said to be a simple plate-making method.

<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned circumstances, and provides a novel plate-making method for a lithographic printing original plate with simple plate-making operations and steps.

More specifically, instead of the conventional plate-making method that requires equipment with an expensive optical system, it has made it possible to use the thermal head used in the thermal recording method, which has recently become popular in printers such as word processors, personal computers, and facsimile machines. The present invention provides a novel plate-making method for a lithographic printing original plate.

Means for Solving the Problems> The present invention provides a thermal transfer medium in which a thermal transfer layer containing an isocyanate-curable polymer and a blocked isocyanate is provided on a substrate, and a hydrophilic surface. A method for making a lithographic printing original plate, which comprises superimposing the hydrophilic surface of an image receptor and heating the image in an image-like manner, and then peeling off the heat-sensitive transfer medium to form a heat-sensitive transfer image on the image receptor. It provides:

The thermal transfer recording method has been put into practical use mainly in printers and the like, and the present invention utilizes this method to make a lithographic printing original plate. The heat-sensitive transfer layer in conventional heat-sensitive transfer recording systems consists of colored pigments, dyes, wax components, and polymers, and the mechanical strength of the transferred image itself and the adhesive force between the transferred image and the image receptor are not necessarily strong. The inventors of the present invention believe that by solving these problems, the thermal transfer recording method can be applied to the plate making of lithographic printing original plates, and as a result of intensive study on the material of the thermal transfer layer that constitutes the thermal transfer medium, we found that The thermal transfer layer contains a combination of an isocyanate-curable polymer and a block isocyanate.

Blocked isocyanate, which is the biggest feature of the present invention, is
It can be obtained by placing an isocyanate compound and a blocking agent as described below in a predetermined mixing ratio in a reaction vessel and heating. In this case, a solvent and a catalyst for promoting the reaction can be used as necessary.

That is, as the isocyanate compound, compounds known as curing agents for epoxy resins and polyester resins can be applied to the present invention. For example, ■, 6-hexamethylene diisocyanate, 1,8-octamethylene diisocyanate, 2
．． 2.4-Trimethylhexamethylene diisocyanate and other alkylene diisocyanates, 3.3'-diisocyanate dipropyl ether, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, transvinylene diisocyanate and other unsaturated isocyanates, toluene diisocyanate , aromatic isocyanates such as xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, phenyl isocyanate, 4,4'-biphenyl diisocyanate,
Furthermore, prepolymers having isocyanate at the terminals may be mentioned, but are not limited to these compounds.

On the other hand, blocking agents for the above isocyanates include phenol-based, alcohol-based, active methylene-based, mercaptan-based, acid amide-based, imide-based, amine-based, guanidine-based,
Compounds such as imidazole-based, urea-based, carbamate-based, imine-based, oxime-based, and sulfite-based compounds can be used.

Suitable blocking agents for synthesizing the blocked isocyanate referred to in the present invention include phenol-based, alcohol-based,
These are amine-based, guanidine-based, imidazole-based, and urea-based compounds. Specifically, phenol as a phenolic type,
Cresol, xylenol, p-ethylphenol, 0
-Isopropylphenol, p-tert-butylphenol, p-tert-octylphenol, thymol, p-naphthol, p-nitrophenol, p-chlorophenol, etc.; alcohols include methanol, ethanol, propatool, butanol, ethylene; Glycol, methyl cellosolve, butyl cellosolve, methylcarpitol, benzyl alcohol, phenyl cellosolve, furfuryl alcohol, cyclohexanol, etc. are used as amines, diphenylamine, phenylnaphthylamine, aniline, carbazole, etc., and guanidines are guanidine, methylguanidine, etc. , ■, 3-dimethylguanidine, stearylguanidine, acetylguanidine, phenylguanidine, ■, 3-diphenylguanidine, ■, 3-di-o-tolylguanidine, 1-dimethyl-3-methoxyphenylguanidine, 1-benzoyl-3- Phenylguanidine, o-tolylbiguanide, imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-
Medylimidazole, 2-undecylimidazole, 2
-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 2,4-diamino-6(2'-methylimidazolyl(1')l-ethyl- Examples of s-triazine and urea include urea, thiourea, ethyleneurea, and phenylurea.

In the present invention, as the polymer constituting the heat-sensitive transfer layer together with the block isocyanate, there is used a polymer having active hydrogen that can be cured by reacting with isocyanate generated from the block isocyanate during heating. Isocyanate reacts with many functional groups, but in the present invention, it is particularly preferable to use a polymer having one kind of functional group among hydroxyl groups or carboxylic acid groups. Prepolymers or oligomers of molecular weight are also included as constituents of the present invention.Those containing hydroxyl groups include polyether polyols, polyester polyols,
Examples include polyol prepolymers and oligomers for polyurethane resins such as acrylic polyols and epoxy polyols. Further, examples containing carboxylic acid groups include isobutylene-maleic anhydride copolymers, acrylic acid copolymers, methacrylic acid copolymers, and the like. Other polymers and oligomers containing ethyleneimine groups or amino groups can also be used. Incidentally, in the present invention, a single polymer may be used, but it is also possible to use two or more kinds in combination.

In the present invention, various catalysts can be contained in the heat-sensitive layer in order to promote isocyanate dissociation during heating of the aforementioned blocked isocyanate, and to promote the curing reaction between the isocyanate and the polymer containing active hydrogen. Specific examples include triethylamine, triethylenediamine, tin octoate, dibutyltin (2-ethylhexoate), lead 2-ethylhexoate, bismuth nitrate, titanic acid, 2-ethylhexyl, bismuth nitrate, antimony trioxide, etc. It will be done.

The heat-sensitive transfer layer of the present invention contains inorganic pigments such as calcium carbonate, silica, and aluminum hydroxide, crosslinked styrene fine particles, urea-formalin resin fine particles, and benzoguanamine resin fine particles in order to improve ink receptivity and transfer efficiency. organic pigments such as stearamide, methylolstearoamide, paraffin wax,
microcrystalline wax, montan acid wax,
Wax-like substances such as higher alcohols can be added. In addition, so that the transfer status of the image can be easily determined,
A coloring pigment such as carbon black or a heat-sensitive color forming material can also be contained in the heat-sensitive transfer layer.

As the substrate of the heat-sensitive transfer medium, one having heat-resistant strength, high dimensional stability, and high surface smoothness is used. For example, papers such as plain paper, condenser paper, glassine paper, laminated paper, coated paper, resin films such as polyethylene, polyethylene terephthalate, polystyrene, polypropylene, polyimide, paper-resin film composites, metal sheets such as aluminum foil, etc. etc. are preferably used. The thickness of the substrate is preferably 60 μm or less, particularly 2 to 20 μm, in order to obtain good thermal conductivity. In addition, in order to improve transferability, a layer having mold releasability may be provided between the substrate and the heat-sensitive transfer layer. Further, a layer for improving the matching property with the thermal head may be provided on the opposite side of the substrate to the side on which the thermal transfer layer is provided.

The thermal transfer medium is prepared by mixing a solution or dispersion of a polymer curable with isocyanate, a solution or dispersion of blocked isocyanate, and various additives as necessary, and applying the mixture onto a substrate using a wire bar or other suitable method. It is produced by drying at a relatively low temperature.

In the present invention, the image receptor having a hydrophilic surface includes a desensitized aluminum plate, a metal plate made of zinc, etc.
Paper, resin-impregnated paper, or plastic film laminated with desensitized metal foil, or vapor-deposited metal such as aluminum are used. In addition, hydrophilic fine powders such as kaolin clay and silica can be mixed with PVA,
#It is also possible to use a product coated on paper or plastic film together with a hydrophilic binder such as powder and a crosslinking agent for the binder.

To perform plate making of a lithographic printing original plate using the heat-sensitive transfer medium prepared as described above, the heat-sensitive transfer layer and the hydrophilic surface of the image receptor are overlapped and heated in an image-like manner, and then the heat-sensitive transfer medium is heated. This can be done by peeling off the image and forming a lipophilic heat-sensitive transfer image on the image receptor.

The heat-sensitive transfer layer of the present invention is transferred to an image receptor by heating, and at the same time, the transferred heat-sensitive layer is cured by heating between isocyanate generated from the block isocyanate and the isocyanate and a curable polymer. As the reaction progresses, a lipophilic transferred image is formed that firmly adheres to the image receptor, and a lithographic printing original plate having excellent printing durability can be obtained.

As a means of heating in the form of an image, there are methods such as using a thermal head that has recently become popular in facsimiles and printers, using a thermal pen, or pressing a heated pixel-shaped mold, or by using a method that is easy to operate. In this respect, a method using a thermal head is preferable. In addition, the thermal transfer layer, the substrate,
It is also possible to contain a light-to-heat converting substance such as carbon black in at least one part of the image receptor, and perform thermal transfer by imagewise exposure to laser light or flash light.

Although heating can basically be performed from both the thermal transfer medium and the image receptor, it is generally preferable to heat from the thinner thermal transfer medium side from the viewpoint of thermal efficiency.

In addition, when the mechanical strength of the image area of the image receptor obtained by the above method and the adhesive strength with the image receptor are insufficient, it is preferable to further heat the entire surface to advance the curing of the image area.

<Example> Next, the method for making a lithographic printing original plate of the present invention will be described with reference to Examples.

Synthesis Example-1 125 g of 2-methylimidazole and 125 g of 1.6-hexamethylene diisocyanate were charged into a three-piece flask equipped with a stirrer, a thermometer, and a condenser, and the reaction temperature was raised from room temperature to 75°C. The reaction was carried out until no free isocyanate was observed to obtain blocked isocyanate.

Synthesis Example-2 53g of guanidine was added to MEK in a four-way flask with a stirrer.
240 g of phenyl isocyanate was slowly added dropwise thereto at an internal system temperature of 60 to 70° C. After the dropwise addition was completed in about 3 hours, MEK was distilled off to obtain about 290 g of proisocyanate.

Example 1 A heat-sensitive transfer paint having the following formulation was applied onto a 18 μl thick condenser paper using a wire bar, and dried with warm air at 60°C to form a heat-sensitive transfer layer with a coating amount of 3.0 g/+J in 1 Synthesis Example-1. Synthesized block 35g Next, thickness 125μm
The aluminum-deposited surface of the image receptor, which is formed by providing an aluminum-deposited layer on a polyester film, and the heat-sensitive transfer layer of the above-mentioned heat-sensitive transfer medium are superimposed, and a thermal recording facsimile machine MI Panafax U is attached from the thermal transfer medium side.
Images were heated in the copy mode of the F-920. Thereafter, the heat-sensitive transfer medium was peeled off to obtain a lithographic printing original plate having a heat-sensitive transfer image on the image receptor.

This printing plate was printed on a small offset printing machine (Ryobi 2700).
After printing 5,000 sheets under normal printing conditions, there was no background smearing in the non-image area, no falling off of the image area, and no wear on the plate surface (and prints with excellent clarity were obtained. .

Example 2 A heat-sensitive transfer layer coating having the following formulation was applied onto a 25-um-thick polyester film using a wire bar, and dried with warm air at 6°C to obtain a heat-sensitive transfer layer with a coating weight of 3.5 g/J. Got the medium.

an aluminum vapor-deposited surface of an image receptor formed by providing an aluminum vapor-deposited layer on a polyester film having a thickness of 125 um;
The heat-sensitive transfer layer of the above-mentioned heat-sensitive transfer medium is overlapped, and a wavelength of 4880A is applied from the heat-sensitive transfer medium side.

Using an argon laser with output IW, main scanning speed 1.5
Image recording was performed under conditions of 111/sec and a cotton density of 15 pus/pus. Thereafter, the heat-sensitive transfer medium was peeled off, and the image receptor bearing the heat-sensitive transfer image was heat-treated in a dryer at 100° C. for 3 minutes to obtain a lithographic printing original plate.

When this printing plate was printed in the same manner as in Example 1, the same excellent results were obtained.

<Effects of the Invention> Since the present invention has the above configuration, it does not require an expensive and complicated plate-making device like the conventional lithographic printing original plate (or a contact heating means such as a thermal head or a simple light source such as laser light irradiation). It was possible to easily make a plate using only irradiation means, and its printing characteristics were also excellent.

Claims (1)

[Claims] The heat-sensitive transfer layer of a heat-sensitive transfer medium comprising a heat-sensitive transfer layer containing an isocyanate-curable polymer and a blocked isocyanate provided on a substrate and the hydrophilic surface of an image receptor having a hydrophilic surface are superimposed. 1. A method for making a lithographic printing original plate, which comprises forming a heat-sensitive transfer image on an image receptor by heating image-wise and then peeling off a heat-sensitive transfer medium.