JPH0256231B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to offset printing plates. More specifically, the present invention relates to an offset printing plate using a thermal printing device that does not require a light source or development process.

Methods of obtaining offset printing plates used in offset printing include (1) direct printing method, (2) negative and positive base method,
There are (3) camera plate making method and (4) direct plate making method.
The direct plate-making method, which can complete the process from setting the block to starting printing in a few tens of seconds, is widely used in in-house printing and light printing where the number of copies to be printed is not very large due to its low cost.

Direct plate making methods include silver halide photography represented by the Beriris method, silver method, and electrophotography represented by the electrofax wet method, and direct plate making machines using these methods have been commercialized.

However, the direct plate-making method requires a large plate-making machine because it forms an image using light and develops it to obtain a printing plate, and there are problems with using it in an office, such as getting your hands dirty when handling the developer. . Therefore, as a result of intensive research, the present inventors have discovered a method of directly obtaining a printing plate using a thermal printer or thermal facsimile, which is maintenance-free, has a relatively simple device, and is compact.

That is, a film with a melting point of 60 to 180°C and a particle size of 0.1 to 0.1 is deposited on a water resistant support such as water resistant paper, film, synthetic paper, metallized paper, or synthetic resin laminated paper.
By providing a 10-micron layer containing a thermofusible material and thermally printing this surface with a thermal head, an offset printing plate that does not require a light source or development process and can be made with a simple device is provided. It is.

The offset printing plate of the present invention is prepared by coating a normally colorless basic dye on a water-resistant support, a color developer that reacts with the basic dye when heated to develop a color, and a heat treatment having a melting point of 60 to 180°C and a particle size of 0.1 to 10 microns. A layer containing a fusible substance, acetoacetylated polyvinyl alcohol, and a pigment is provided, and this surface is thermally printed using a thermal head.The heat-melting substance in the printed area is melted to make it lipophilic, and an offset printing plate is created. There is a characteristic in obtaining. Furthermore, it is also possible to develop a positive image on the printing plate by causing the layer containing the thermofusible substance to develop color through the reaction of a fine powder of leuco dye and a color developer.

The acetoacetylated polyvinyl alcohol used in the present invention includes polyvinyl alcohol, diketene,
It is obtained by reacting acetoacetic acid, acetoacetic ester, etc. In the case of acetoacetylation with diketene, polyvinyl alcohol is dispersed in acetic acid, and diketene is added thereto.
There are known methods such as dissolving polyvinyl alcohol in advance in a solvent such as dimethylformamide or dioxane and adding diketene thereto, and a method of directly bringing diketene into contact with polyvinyl alcohol to react.

The polyvinyl alcohol used for acetoacetylated polyvinyl alcohol is polyvinyl alcohol obtained by saponifying polyvinyl acetate (polymerization degree
200-3000, degree of saponification 30-100 mol%), derivatives thereof, and saponified copolymers of vinyl acetate and monomers that are copolymerizable.

Examples of the monomer include unsaturated carboxylic acids such as maleic anhydride, fumaric acid, crotonic acid, itaconic acid, and (meth)acrylic acid, and their esters;
α-olefins such as ethylene and propylene;
(meth)allylsulfonic acid (soda), sodium sulfonate (monoalkyl maleate), sodium disulfonate alkyl maleate, N-methylol acrylamide, alkali salt of acrylamide alkyl sulfonate, N-vinylpyrrolidone, N-vinylpyrrolidone derivatives, etc. These can be used alone or in combination of two or more.

The thermofusible substance used in the present invention has a melting point of 60
There are paraffin, polyolefin, micro wax with a melting point of ~120℃, and fatty acid wax with a melting point of 60~180℃. For the former wax, 60-73℃
Paraffin waxes with various melting points of 60~
Examples include microwaxes having various melting points (or softening points) of 120°C, and polyolefin waxes such as polyethylene wax and polypropylene wax. This polyethylene wax or polypropylene wax usually has a molecular weight of
1,000 to 10,000, commonly known as polyolefin waxes, these polyolefins are usually produced by high-pressure and low-pressure polymerization methods (i.e., low-density and high-density polyolefins).
Alternatively, it can be obtained by thermal decomposition of a high molecular weight polyolefin. Furthermore, in order to facilitate emulsification, these waxes can be oxidized to introduce polar groups such as hydroxyl groups, ester groups, carboxyl groups, aldehyde groups, and peroxide groups. Further, in order to lower the softening point and improve workability, it is also possible to use these waxes together. The latter include stearamide, linoleamide, laurylamide, myristeramide, hydrogenated tallow acid amide, palmitamide,
Examples include oleic acid amide, rice sugar fatty acid amide, coconut fatty acid amide, methylolated products of these fatty acid amides, methylene bis stearamide, ethylene bis stearamide, etc., and combinations of these are also possible.

Further, thermofusible substances such as coumaron-indene resin, rosin-modified phenolic resin, terpene-modified phenolic resin, xylene resin, and ketone resin having a melting point of 60 to 180°C can also be used.

The thermofusible substance is dispersed in acetoacetylated polyvinyl alcohol, and these dispersed particles are crushed by a grinder such as a ball mill to a particle size of 0.1 to
It is preferable to grind to a particle size of 10 microns. Further, the thermofusible substance may be dispersed as described above, or may be added in the form of an emulsion using an emulsifier.

Further, in order to further strengthen the water resistance of the layer containing the thermofusible substance, crosslinking agents such as melamine formaldehyde resin, urea formaldehyde resin, glyoxal, and others may be added.

Clay, zinc oxide, calcium carbonate, aluminum oxide, silica, barium sulfate, etc. are used as pigments.

Next, examples of leuco dyes used when producing a positive image on a printing plate include crystal violet lactone, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-
Chlorofluorane, 2-(N-phenyl-N-methylamino)-6-(N-P-tolyl-N-ethyl)amino-fluorane, 3-(N,N-diethylamino)-5-methyl-7- (N,N-dibenzylamino)-fluorane, malachite green lactone, 3,3-bis(1-ethyl-2-methylindol-3-yl)-phthalide, 3-diethylamino-6-methyl-7-anilino- Fluoran, 2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluoran, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran, 3-pyrrolidino -6
-Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, and other colorless or slightly pale lactones, sultones, lactams, spiropyrans, and other compounds.

As a color developer, a phenolic compound with a melting point of 60°C or higher that can color the leuco dye when heated, particularly a phenolic compound having two or more hydroxyl groups in one molecule, is preferable, and specifically, 4,4-isopropylene Dendiphenol, 4,4-isopropylidenepis (2-tertiarybutylphenol), 4-phenylphenol, 4,4-cyclohexylidenediphenol, 4,4'-cyclohexylidenebis(2-methylphenol), Examples include novolak type phenolic resins.

When adding a leuco dye and a color developer to a layer containing a thermofusible substance, the leuco dye and color developer are separately mixed in a medium containing an appropriate concentration of a water-soluble resin using a pulverizer such as a ball mill. It is necessary to crush and disperse the particles into particles of 10 microns or less.

The water-resistant support used in the present invention is generally water-resistant paper, but films such as PET, synthetic paper, vapor-deposited paper, synthetic resin laminated paper, etc. can also be used.

The offset printing plate of the present invention can be manufactured by the following method, but the present invention is not limited thereto. A coating solution in which a flame-sensitive element, a heat-fusible substance with a melting point of 60 to 180°C and a particle size of 0.1 to 10 microns, and a pigment are dispersed in acetoacetylated polyvinyl alcohol is applied onto a water-resistant support and dried. The coated surface may be calendered if necessary. The obtained offset printing plate precursor is thermally printed using a thermal printing device such as a thermal printer or a thermal facsimile used as a word processor terminal to obtain an image area. The heat-printed area is melted by the thermofusible substance and becomes lipophilic on the plate surface, making it receptive to ink. On the other hand, the thermofusible material in the non-image area is covered with acetoacetylated polyvinyl alcohol, which is a hydrophilic binder, so it exhibits hydrophilicity and acts as a water-retaining surface for dampening water during printing.

In addition, in the present invention, in which a crushed leuco dye and a crushed color developer are added to a layer containing a thermofusible substance, the leuco dye and the color developer react with each other due to thermal printing, resulting in color formation in the printed area. Appears on the printing plate as a positive image. Therefore, typographical errors in printed areas can be easily corrected.

The offset printing plate obtained in this manner is sometimes subjected to a hydrophilic treatment for non-printing areas or a lipophilic treatment for printed areas on the plate surface in order to further improve printing durability. The treatment liquid used for hydrophilic treatment generally contains at least one of hydrophilic resins such as gum arabic and polyvinylpyrrolidone, phosphates, aluminum alum compounds, and acids (organic acids or inorganic acids). , and those mainly composed of ferrocyan compounds or ferrocyan compounds. Examples of the treatment liquid used in the lipophilization treatment include those mainly composed of a polymer having a hydrophilic group or a metal salt thereof.

Next, examples will be described to further specifically explain the present invention.

Example 1 Paint of the following composition was applied to one side of a high-quality paper with a basis weight of 140 g/m ² that was mainly made of long-fiber pulp and had excellent size, water resistance, and smoothness so that the weight after drying would be 12 g/m ² The coated surface was calendered to obtain an offset printing original plate.

(Paint formulation) Clay 20 parts 10% acetoacetylated polyvinyl alcohol aqueous solution (acetoacetylated polyvinyl alcohol with degree of polymerization 500 and degree of saponification 99%) 100 parts stearamide dispersion (solid content 30%, melting point
100°C, average particle size 3 microns) 30 parts 3-diethylamino-6-methyl-7-anilino-fluorane dispersion (40% solids, average particle size 3 microns) 5 parts bisphenol A dispersion (30% solids) , average particle size 3 microns) 25 parts 40% glyoxal aqueous solution 5 parts 10% ammonium chloride aqueous solution 1 part water 20 parts Next, an offset printing plate was obtained by thermally printing the above offset printing plate precursor using a thermal facsimile. At this time, a positive image appeared on the printing plate due to the color development of the leuco dye and developer. When this plate was printed on an offset printing machine (Toko Model 810), more than 1,000 clear prints with no background stains were obtained.

Comparative Example 1 An offset printing plate was obtained in the same manner as in Example 1 except that the acetoacetylated polyvinyl alcohol in the coating solution of Example 1 was replaced with the same amount of polyvinyl alcohol (trade name PVA-117, manufactured by Kuraray Co., Ltd.). When I printed it, I noticed some scuffing from around the 10th page.

Claims (1)

[Claims] 1. A heat-sensitive element usually consisting of a colorless basic dye and a color developer on a water-resistant support, with a melting point of 60 to 180°C and a particle size.
Offset in a lithographic printing plate obtained by thermal printing on a lithographic printing plate made of a thermofusible substance of 0.1 to 10 microns and a hydrophilic binder, characterized in that the hydrophilic binder is acetoacetylated polyvinyl alcohol. Print version.