JPH0696354B2 - Original plate for lithographic printing - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lithographic printing plate precursor, and more particularly to a direct-drawing lithographic printing plate precursor suitable for plate making in a plain paper copier (PPC).

2. Description of the Related Art At present, a direct drawing type lithographic printing plate precursor in which a water resistant layer is further laminated on a support and a surface recording layer is further laminated thereon is often used for office printing.

The plate making method using this original plate includes handwriting with a lipophilic ink on the surface recording layer, type printing, or a lipophilic toner image on the surface recording layer with a plain paper electrophotographic copying machine (PPC). A method of forming and fixing this is performed.

The lithographic printing original plate (master) after image formation is processed on the surface recording layer with a desensitizing solution also called an etching solution, the non-image area is converted to desensitizing, and then applied to a lithographic printing machine to make many printed matters. Be used for.

Therefore, the surface recording layer is hydrophilic enough to repel the ink in the non-image area during printing and at the same time has enough water resistance to withstand the fountain solution repeatedly supplied during printing. Must have

By the way, as a typical conventional direct-drawing type lithographic printing plate precursor, in order to satisfy both the hydrophilicity and the water resistance, a melamine formaldehyde resin is added as a cross-linking agent to an aqueous solution resin such as polyvinyl alcohol. A surface recording layer containing an inorganic pigment is provided on the support,
The surface is smoothed by super-calendering (US Pat. No. 2532865), or the surface recording layer is made of 0.1-0.5 μm silicic anhydride and 0.01-0.02 μm ultrafine silicic acid sol. There is a pigment formed from a mixture of a water-soluble polymer and a water-proofing agent (Japanese Patent Publication No. 6405/44). In these conventional direct-drawing type lithographic printing plates, the surface recording layer has a surface smoothness (Rmax) of 3 μm or less, and the surface is smooth.

By the way, in recent years, the spread of PPC is remarkable, and instead of plain paper, a direct drawing type lithographic printing plate precursor is used in such a copying machine.
There is a movement to reduce the cost per copy by forming a toner layer on the surface recording layer of the original plate and using it as a printing plate to obtain a large number of copies, that is, printed matter, by a lithographic printing method.

However, when a conventional lithographic printing plate precursor is provided with a PPC plate for printing, there is often a tendency that grain-like background stains occur. This is considered to be because the surface recording layer surface of the lithographic printing original plate was smooth, so that the toner particles attached to the image portion of the electrophotographic photosensitive member were scattered to the non-image portion and transferred to the surface recording layer. . In addition, when the surface recording layer surface is too smooth, when the toner particles forming the image portion on the surface recording layer are fixed by the heat roller, they are flattened, resulting in thickening of characters and images. Was also seen.

The present invention aims to provide a direct-drawing type lithographic printing plate precursor that is less likely to cause toner scattering at the time of plate-making in PPC and has less non-image area grain-like ground stains. Is.

Composition The present invention is a direct drawing type lithographic printing plate precursor in which a water resistant layer and a surface recording layer are sequentially laminated on a support, wherein the water resistant layer is adjusted to have a surface roughness (Rmax) of 5 to 50 μm. To do.

Examples of the support used in the present invention include moisture resistant paper, synthetic paper, synthetic resin film and the like.

Further, as the material of the water resistant layer used in the present invention, styrene-butadiene copolymer emulsion, aqueous emulsion such as acrylic emulsion, coarse particle size silica,
A pigment obtained by dispersing a pigment such as calcium carbonate or cellulose powder and mixing them is suitable. The ratio of the aqueous emulsion to the pigment varies depending on the pigment and the like, but about 0.5 to 3/1 (weight) is suitable. When such a water resistant layer material is applied and dried on a support to form a water resistant layer, the particle diameter of the pigment or cellulose powder in the applied material is coarse, so that the surface of the water resistant layer is roughened. As the surface roughness of the water resistant layer, Rmax defined by JIS-B0601 is 5 to 5.
The range of 50 μm is suitable, and the particle size of the water resistant layer material, especially the pigment is adjusted so that it is preferably in the range of 10 to 30 μm. If Rmax is 5 μm or less, toner scattering, which is the object of the present invention, cannot be prevented, and conversely, if Rmax is 50 μm or more, image uniformity is deteriorated and printing stains due to etching defects occur.

Thus, a surface recording layer is provided on the water resistant layer whose surface roughness (Rmax) is adjusted to 5 to 50 μm. The surface recording layer is mainly composed of a pigment and a hydrophilic binder waterproofing agent,
You can use all the things that you used before.

Known inorganic pigments can be used in the present invention, and examples thereof include ZnO, TiO ₂ , BaSO ₄ , SiO ₂ , Al ₂ O ₃ , CaCO ₃ , kaolin clay, and sericite.

Examples of the hydrophilic binder include hydrophilic polymeric substances such as PVA, modified PVA, casein, protein, CMC, HEC, and vinyl acetate-crotonic acid copolymer. As the water-proofing agent, melamine formalin resin, aminoplast initial condensate such as urea formalin resin, modified polyamide resin, polyamide polyamide, shrimp chlorhydrin adduct glyoxal,
An example is a modified Glioxa monkey.

In addition, in the present invention, a back coat layer can be provided for the purpose of preventing curling. As the back coat layer, starch or starch derivative, cellulose derivative such as CMC, HEC, polyvinyl alcohol, modified PVA, casein, vinyl acetate-crotonic acid derivative, water-soluble resin such as acrylic resin, SBR, MBR, NBR acrylic resin, vinyl acetate -Emulsion such as ethylene copolymer may be used alone or in combination of two or more kinds.

The present invention is configured as described above, the surface roughness (Rmax) of the water resistant layer provided on the support is adjusted to 5 to 50 μm, and the surface recording layer is further provided on the water resistant layer. It acts similarly to roughening, and it is considered that the toner scattering is prevented because the number of toner particles attached to the rough surface of the background portion decreases during toner transfer.

Examples will be shown below.

Example 1 As a support, a styrene-butadiene copolymer (Polylac 750, manufactured by Mitsui Toatsu Chemicals, Inc.) was applied to one side of 80 g / m ² of high-quality paper.
/ A 35% aqueous dispersion of silica (Cyroid 620, manufactured by Fuji Devison Co., Ltd.) having an average particle size of 20 μm (1/1 in weight ratio) was applied and dried to form a water resistant layer having an adhesion amount of 10 g / m ² . Then, a 6% aqueous solution of polyvinyl alcohol was applied to the opposite surface of the water resistant layer and dried to provide a hydrophilic resin layer having an adhesion amount of 2 g / m ² . Next, a 15% aqueous dispersion of the composition of silica (Cyroid 244, manufactured by Fuji Devison Co., Ltd.) / Polyvinyl alcohol-water-proofing agent (1/1 by weight) was applied to the water-resistant layer surface of the obtained support, and 130
A surface recording layer having an adhesion amount of 5 g / m ² was provided by drying and curing at 1 ° C. for 1 minute to obtain a lithographic printing original plate.

Example 2 Example 1 was repeated except that the pigment of the water resistant layer of Example 1 was replaced with calcium carbonate having an average particle size of 8 μm (Whiten # 450, manufactured by Shiraishi Calcium Co., Ltd.) and the ratio with the aqueous emulsion was changed to 2/1. A lithographic printing plate precursor was obtained in exactly the same manner as.

Example 3 The pigment of the water resistant layer of Example 1 was prepared by using 25 mesh pass cellulose powder (KC Floc W-250, manufactured by Sanyo Kokusaku Pulp Co., Ltd.).
Instead of the above, a lithographic printing original plate was obtained in exactly the same manner as in Example 1 except that the ratio with the aqueous emulsion was changed to 3/1.

Comparative Example A lithographic printing plate precursor was obtained in exactly the same manner as in Example 1, except that the pigment of Example 1 was replaced with clay having an average particle size of 0.5 μm (manufactured by VW-90 Engelhard Co., Ltd.).

The lithographic printing plate precursors obtained in Examples 1 to 3 and Comparative Example
Plate-making with FT4080 (dry PPC made by Ricoh Co., Ltd.) AP1600
The results of the plate making transfer density, the printing grain stains and the surface roughness of the water resistant layer when printed by (Ricoh Co., Ltd. offset printing machine) are shown below.

Effect According to the present invention as described above, since the surface roughness Rmax of the water resistant layer provided on the support is set to 5 to 50 μm, the surface recording layer formed on the water resistant layer is also roughened in the same manner. Acting, PP
When the plate is made by C, the toner scattering is prevented, the grain-like background stain in the specific image area is also prevented, and a direct-drawing type lithographic printing plate precursor that gives a good printed matter can be obtained.

Claims (1)

[Claims] 1. A direct drawing type lithographic printing plate precursor in which a water resistant layer and a surface recording layer are sequentially laminated on a support, wherein the water resistant layer is adjusted to have a surface roughness (Rmax) of 5 to 50 μm. An original plate for lithographic printing.