JPH0696353B2 - Direct drawing type lithographic printing plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lithographic printing plate precursor, and more particularly to a direct drawing type lithographic printing plate precursor suitable for PPC plate making.

2. Description of the Related Art At present, a direct drawing type lithographic printing plate having an image receiving layer on a support is widely used as an office printing plate. In order to perform plate making, that is, image formation on such a printing plate, generally, an oil-based ink is drawn by hand on the image receiving layer, or
Alternatively, a method of printing with a typewriter is adopted. In addition, a method of transferring and fixing a toner image formed on a photoconductor through a process of charging, exposing and developing using a plain paper electrophotographic copying machine (PPC) to an image receiving layer has also started to be used in recent years. In any case, the printing stock solution after plate making is subjected to surface treatment with a desensitizing solution (so-called etching solution) to desensitize the non-image area, and then subjected to lithographic printing as printing.

A typical example of such a direct drawing type lithographic printing plate precursor is U.S. Pat.
As described in No. 32865, the image-receiving layer was composed mainly of a water-soluble resin binder such as PVA, silica, an inorganic pigment such as calcium carbonate, and a water-proofing agent such as a melamine-formaldehyde resin precondensate. It is a thing.
Here, as the inorganic pigment, in order to obtain an image-receiving layer having a surface as smooth as possible so as to be suitable for plate making by handwriting or type printing, those having a low average particle size of 0.1 to 3 μm are used. As a specific example using a pigment having a particularly small particle size, silica having an average particle size of 0.1 to 0.5 μ is 70 to 90% and an average particle size is 0.01.
An image receiving layer using a mixed system with silica of about 0.02μ is introduced in Japanese Patent Publication No. 6405 / 44-6405.

However, the conventional direct-drawing type lithographic printing plate has a drawback in that when PPC plate-making, the printing plate is stained with ground, which causes the printed matter to be stained. The cause of the background stain is that the toner remaining on the non-image portion of the photosensitive member after development is partially transferred and adhered to the original plate as it is in the transfer step.

The purpose of the present invention is to improve the PP by roughening the image receiving layer.
It is to provide a direct drawing type lithographic printing plate precursor that does not contaminate a printed matter even by C plate making.

Composition The direct drawing type lithographic printing stock solution of the present invention is JIS-B-0 on a support.
It is characterized by having an image receiving layer having a surface roughness Rmax according to 601 of 5 to 20 μm.

As described above, PPC plate making is performed by charging, exposing and developing a photoreceptor and transferring and fixing the obtained toner image to the image receiving layer surface of the original plate. In this case, as the image fixing method, a heating roller, a pressure roller, a flush, a radiant method or the like can be used, but in general, the heating roller method is adopted from the viewpoint of good fixing efficiency such as toner fixing rate and fixing speed. ing. The surface of this heating roller system is 18
This is a system in which an image is fixed by passing an original plate between a pair of rollers composed of a roller heated to 0 to 200 ° C. and a roller pressed against the roller. In this method, as described above, the toner particles directly transferred from the non-image area of the photosensitive pair to the non-image area of the stock solution are softened by the heat of the roller, and at the same time, are crushed by the pressure of the roller to increase the particle size, which causes background stain. Will be noticeable. That is, in this case, the average particle size of the toner particles used in the PPC is about 10 μ, but when crushed by the roller, it increases to about 30 μ.

As a result of various studies on the background stain of the printing original plate thus produced, the present inventors have found that the image receiving layer has a surface roughness Rmax of 5 to 20.
It was found that by roughening the surface to μ, it is possible to reduce the number of toner particles adhering to the stock solution from the non-image area of the photoconductor in the transfer step during PPC plate making, and to prevent the expansion of toner particles at the time of fixing with a heating roller. Was completed.

The image receiving layer of the present invention is mainly composed of a water-soluble binder, an inorganic pigment and a water-proofing agent. As binder, water-soluble PVA, modified PVA such as carboxy PVA, starch and its derivatives, CMC, hydroxyethyl cellulose, casein, gelatin, polyvinylpyrrolidone, vinyl acetate-crotonic acid copolymer, styrene-maleic acid copolymer, etc. Resin is used.

Water-resistant agents include glyoxal, melamine-formaldehyde resin, urea-formaldehyde resin and other aminoplast initial condensates, modified polyamide resins such as methylolated polyamide resins, polyamide / polyamine / epichlorohydrin adducts, polyamide epichlorohydrin resins, modified polyamide polyimide resins. Etc.

As inorganic pigments, kaon wrinkle, calcium carbonate,
Examples thereof include silica, titanium oxide, zinc oxide, barium sulfate, and alumina. Among them, silica is preferable.

In addition, a crosslinking catalyst such as ammonium chloride can be used in combination in the image receiving layer.

The ratio of the binder / pigment / waterproofing agent in the image receiving layer varies depending on the type of material and the particle size of the pigment.
Generally, a weight ratio of 1 / (0.5 to 5) / (0.05 to 2), preferably 1 / (0.8 to 2.5) / (0.1 to 0.7) is suitable.

To set the surface roughness Rmax of the image receiving layer to 5 to 20μ, each Rmax
A pigment having an average particle size (generally about 5 to 20 μm) substantially corresponding to the size is used. The particle size range of particles having an average particle size of 5 μ is preferably 0.1 to 17 μ, and the particle size range of particles having an average particle size of 20 μ is preferably 0.1 to 40 μ. Therefore, in the case of other average particle diameters, the lower limit is preferably 0.1 μ and the upper limit is preferably in the range of 17 to 40 μ. Of course, if the average particle size is in the range of 5 to 20μ for the entire pigment, mix particles with these average particle sizes or mix particles with these average particle sizes and particles with an average particle size outside the previous range. Does not matter. However, in this case, the addition amount of the pigment having an average particle size of less than 5 μ is preferably 50% by weight or less, particularly 30% by weight or less, while the addition amount of the particles having an average particle size of more than 20 μ is 50% by weight or less.
It is preferably not more than 35% by weight, more preferably not more than 35% by weight. In any case, if the surface roughness of the image receiving layer is less than 5μ, the background of the printing plate is stained, and if it exceeds 20μ, the surface roughness is 5 to 20μ.
In case of, the effect is not obtained.

Examples of the support include high quality paper, wet reinforced paper, plastic film such as polyester film, and metal plate such as aluminum plate.

In the present invention, an intermediate layer may be provided between the support and the image receiving layer for the purpose of improving water resistance and interlayer adhesion, and a back coat layer may be provided on the side of the support opposite to the image receiving layer for the purpose of preventing curling. it can.

Here, the intermediate layer is an emulsion resin such as an acrylic resin, styrene-butadiene copolymer, methacrylic acid ester-butadiene copolymer, acrylonitrile-butadiene copolymer, ethylene-vinyl acetate copolymer; epoxy resin, polyvinyl. Solvent-based resin such as butyral, polyvinyl chloride, polyvinyl acetate; composed mainly of at least one of the above-mentioned water-soluble resins, etc., but with addition of an inorganic pigment or water-proofing agent if necessary be able to.

The structure of the back coat layer is almost the same as that of the intermediate layer.

In the present invention, in order to reduce the background stain at the time of PPC plate making, the volume resistivity as a printing original plate becomes 10 ¹⁰ to 10 ¹³ Ωcm, and the image receiving layer, the intermediate layer and / or the back coat layer has a conductive agent. Can be added. The conductive agent may be an inorganic type or an organic type, and as the inorganic type, salts of monovalent or polyvalent metals such as Na, K, Li, Mg, Zn, Co and Ni may be used. Examples thereof include polymeric cation conductive agents such as polyvinylbenzyltrimethylammonium chloride and acrylic resin-modified quaternary ammonium salts, and polymeric anionic conductive agents such as polymeric sulfonates. The amount of the conductive agent added is 3 to 40% by weight, preferably 5 to 20% by weight of the binder layer used in each layer.

In order to prepare the lithographic printing plate precursor of the invention, generally, one surface of a support is coated with a water-soluble material containing an intermediate layer component, if necessary, and dried to form an intermediate layer, and then an aqueous liquid containing an image receiving layer component. May be applied and dried to form an image receiving layer, and if necessary, an aqueous solution containing a backcoat layer component may be applied and dried on the other surface to form a backcoat layer. The amount of each of the image receiving layer, the intermediate layer and the back coat layer is 1 to 30 g / m ² , 5
To 20 g / m ^2, it is appropriate 5 to 20 g / m ^2.

Examples of the present invention will be shown below. All parts and% are based on weight.

Examples 1 to 3 and Comparative Examples 1 to 2 80 g of high-quality paper was coated with an aqueous solution for intermediate layer having the following formulation and dried at 130 ° C. for 2 minutes to form an intermediate layer having an adhesion amount of 10 g / m ² . After that, an aqueous solution for a back coat layer having the following formulation was applied to the opposite surface and dried at 120 ° C. for 2 minutes to form a back coat layer having an adhesion amount of 7 g / m ² .

Intermediate layer formulation: 50% emulsion of styrene-butadiene copolymer 100
Parts clay 50% aqueous dispersion 100 parts water 80 parts backcoat layer formulation: acrylic resin 50% emulsion 100 parts clay 50% aqueous dispersion 100 parts water 100 parts then listed on Table 1 on this intermediate layer Apply an aqueous solution for image processing layer consisting of prescription and dry at 120 ° C for 3 minutes to form an image receiving layer with a coating amount of 3g / m ² , and apply a calendar to make a direct drawing type lithographic printing plate. did.

Next, after measuring the surface roughness of these printing original plates, commercially available PPC
Plate making was carried out, and offset printing was carried out using the obtained printing plate. The results are shown in Table 2.

As can be seen from this table, in Comparative Examples 1 and 2, the stain area of the non-imaging portion of the printing plate was large, and when printing, a considerable amount of fine particle-like stain was generated, whereas in Examples 1 to 3, the stain area ratio was also A clear print which was small and had almost no background stain was obtained. No abnormalities were found on the printing plate even after printing 1000 sheets.

Examples 4 to 6 Direct drawing type lithographic printing plate precursors were prepared in the same manner as in Examples 1 to 3 except that the aqueous liquid for the image receiving layer was changed to that described in Table 3.

Next, after measuring the surface roughness of the above printing stock solution, plate making was carried out in the same manner as in Examples 1 to 3 and printing was carried out to obtain the results shown in Table 4.

As can be seen from this table, there was no print stain and the print was clear, and no abnormality was found on the printing plate even after printing 1000 sheets.

Example 7 An aqueous solution for a back coat layer having the following formulation was applied to one side of 110 g / m ² wet reinforced paper, and dried at 120 ° C. for 3 minutes to give an adhesion amount of 10 g.
After forming a back coat layer of / m ^{2 on} the opposite surface, apply an aqueous solution for the image receiving layer of the following formulation, and dry at 150 ℃ for 3 minutes to form an image receiving layer with an adhesion amount of 20 g / m ² , Further, it was subjected to a calendering process to prepare a direct drawing type lithographic printing plate.

Back coat layer formulation: 50% emulsion of acrylic resin 90 parts 30% aqueous solution of anionic polymer conductive agent (Chemistat 6120 manufactured by Sanyo Kasei Co., Ltd.) 17 parts 50% aqueous dispersion of clay 100 parts water 126 parts Image receiving layer formulation: 3 No. Zinc white (0.5μ) (at solid content) 20 parts Syloid 404 (10μ) (at solid content) 80 parts PVA117 500 parts Epinox-P-9007Y 170 parts Ammonium chloride 20% aqueous solution 4 parts Water 563 parts Next this After measuring the surface roughness of the printing plate, 20 ℃, 65%
Humidity is controlled in an RH atmosphere for 24 hours, the volume resistivity is measured according to the method specified in JIS-C-2122, and the plate is made and printed in the same manner as in Examples 1 to 3. I got the following results.

Surface roughness 7.3μ Volume resistivity 1.8 × 10 ¹¹ Ωcm Image density of printing plate 1.2 Staining area ratio of non-image area of printing plate 0.2% No printing stains. The direct drawing type lithographic printing plate has a rougher image receiving layer than the conventional one.As a result, the amount of toner adhered from the non-image area of the photoconductor to the plate is reduced in the transfer process of PPC plate making Since the crushing by the heating roller is also prevented, there is an advantage that the printing plate does not have a background stain, and therefore a clear printed matter without stain is always obtained.

Claims (1)

[Claims] 1. A direct drawing type lithographic printing plate precursor having an image receiving layer on a support, wherein the image receiving layer has a surface roughness Rmax according to JIS-B-0601 of 5 to 20 μm. Master plate for lithographic printing.