JPH0519480B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to a method for producing a direct-printing type offset printing plate, and particularly to a method for producing a direct-printing type offset printing plate, in particular a direct-printing type plate having an extremely flat image-receiving layer without minute coarse particles on the surface of the plate. The present invention relates to a method for producing a mold offset printing original plate.

Offset printing plates currently used in the light printing field include (1) direct-printing types with an image-receiving layer on a water-resistant support, and (2) those with a photoconductive layer on a water-resistant support. (3) A silver salt photographic type in which a silver halide emulsion layer is provided on a water-resistant support. Among them, the printing manuscript board mentioned in (1) above is
Hand-write with oleophilic ink on the image-receiving layer, or
Printing can be done directly with a printer or plate-making can be done directly with a PPC copying machine, so other
There are some advantages compared to the original printing plates (2) and (3).

Recently, with the spread of office automation equipment, especially Japanese word processors, it has become more common to use them to directly print on offset printing plates. When using this Japanese word processor, wire dot or thermal transfer printers are often used, and are made of nylon or polyester impregnated with or coated with ink made of oil-soluble dyes, mineral oils, resins, wax, etc. Printing is performed directly on the surface of the image-receiving layer of a direct-printing type offset printing original plate via an ink ribbon. In this case, since the ink ribbon comes into direct contact with the surface of the image-receiving layer, the surface needs to be highly flat so that only the printed areas receive ink and no ink adheres to the non-printed areas.

In particular, when word processing and printing are frequently performed in an office, corrections are not usually made, so no ink should adhere to non-printing areas.

That is, if there are minute coarse particles protruding on the surface of the image-receiving layer of this type of offset original plate, scumming will occur, so the surface of the image-receiving layer must be extremely flat.

(B) Prior art The direct drawing type offset printing original was published in Tokuko Publication No. 40-23581.
Many publications have been published, such as JP-A No. 48-9802 and JP-A No. 57-205196, and generally, an image-receiving layer coating solution containing an inorganic pigment, a hydrophilic binder, and a water-resistant agent as main components is coated on a water-resistant support. A material that is coated to form a hydrophilic and water-resistant image-receiving layer is used. To prepare this coating solution, generally, an inorganic pigment is first dispersed in water, and then a hydrophilic binder etc. dissolved in water is mixed therein. At this time, fine agglomerated particles may often be generated due to poor dispersion of the pigment or agglomeration of the pigment due to shock during mixing with the hydrophilic binder.
It is extremely difficult to remove or eliminate this from the coating solution. If it is applied as is, many protruding fine coarse particles appear on the surface of the image-receiving layer. If this happens, when making a plate with a word processor, etc., the protruding microscopic grains will catch ink in spots even on areas that should originally be plain.
This caused scumming on the printed surface.

(C) Purpose of the Invention The purpose of the present invention is to eliminate agglomerated particles in the image-receiving layer coating liquid that cause such minute coarse particles on the surface of the image-receiving layer when producing a direct printing type offset printing original plate. There is a particular thing.

(D) Structure of the Invention The present inventors have carefully observed the phenomenon of agglomerated particles occurring during the preparation of an image-receiving layer coating solution to be coated on a water-resistant support. It is very difficult to disperse the particles to a state where there are no aggregated particles, and the shock when mixing a hydrophilic binder tends to make the aggregated particles even larger. It has been discovered that when used, it tends to produce larger shocks, that is, it tends to produce agglomerated particles, than other hydrophilic binders.

In response to this, the present inventor attempted various improvements, and as a result,
It has been found that sand milling the image-receiving layer coating solution is extremely effective in eliminating agglomerated particles. That is, by performing a sand milling effect at the stage of an aqueous dispersion of an inorganic pigment, or by sand milling agglomerated particles produced by mixing an inorganic pigment and a hydrophilic binder, polyvinyl is added as a hydrophilic binder. Even when alcohol is used, no agglomerated particles are generated in the coating liquid, and it has become possible to obtain an image-receiving layer without fine coarse particles on the surface.

The sand mill used in the present invention is a container filled with microparticles (hard beads) such as natural or synthetic mineral microsand, hard glass microsand, metal microparticles, etc. ) refers to a device that processes the dispersed coating liquid to be treated in a batch or continuous manner while mechanically stirring it using a stirring blade such as a screw. Equipment is commercially available. Naturally, a disperser with general turbine blades is
They are clearly distinguished by their dispersion or crushing ability.

As a sand mill, for example, a Visco mill dispersion machine
CVM-30 (continuous type, manufactured by Igarashi Machinery Co., Ltd.; diameter 1.5~
When using 2.0 mm glass beads), it depends on the concentration of the coating solution, but in general, to get the desired amount of coarse particles on the image-receiving layer (30 particles or less per 100 ^cm2 as described later). It is desirable to run the water through this at a flow rate of about 10 to 40 per minute. At this time, the aggregated particles or undispersed particles present in the coating liquid are gradually pulverized into individual primary particles by receiving a strong shearing force at the bead-to-bead contact points. If the flow rate is less than this, it is not preferable because the production efficiency decreases or the pigment changes in quality. Moreover, if the amount is more than this, the effect of crushing the aggregated particles will be reduced, which is also not preferable.

If the coating liquid is treated, it can be applied directly onto a water-resistant support, or if a pigment dispersion has been treated, it can be coated as a coating liquid on a water-resistant support by adding a hydrophilic binder and a water-resistant agent. Even after coating, it is possible to obtain an offset original plate with almost no problematic coarse particles on the surface of the resulting image-receiving layer.

The size of the minute coarse particles that are a problem here is about 100 μm or more in diameter, and the frequency is
30 or more pieces per 100cm ² (10cm square). Anything less than that is practically acceptable.

To prepare the direct-printing type offset printing original plate used in the present invention, an image-receiving layer coating solution containing an inorganic pigment, a hydrophilic binder, and a water-resistant agent as main components is coated on a water-resistant support at a coating temperature of 80 to 150%. It is sufficient to form an image-receiving layer having a thickness of about 3 to 20 .mu. by drying at .degree. In this case, a water-resistant intermediate layer is provided between the support and the image-receiving layer,
The printing durability may be further improved, and a back coat layer may be provided to prevent curling on the back surface of the support.

As the inorganic pigment for the image-receiving layer, kaolin alone or a mixture of kaolin and other inorganic pigments can be used, and a mixture of kaolin and synthetic silica is particularly preferred. Kaolin that is generally used for paper coating can be used. Synthetic silica includes white carbon, silica gel, colloidal silica,
There are synthetic silicon compounds based on silicic acid, such as silica gel and synthetic molecular sieves.

Hydrophilic binders include starch or starch derivatives,
Examples include cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, polyvinyl alcohol, modified polyvinyl alcohol, casein, vinyl acetate-crotonic acid copolymer, and ammonium polyacrylate.

Water resistance agents include aldehydes, amines,
Melamine formalin resin, urea formalin resin,
Examples include hydrazides and persulfates, and furthermore, dispersants, antifoaming agents, etc. may be added to the image-receiving layer as necessary.

As the water-resistant support, high-quality paper moisture-strengthened using melamine-formalin resin, urea-formalin resin, polyamide epichlorohydrin resin, etc.
Examples include resin coated paper and plastic film.

The intermediate layer (1 to 20μ thick) is acrylic resin,
Emulsion type resins such as SBR, MBR, NBR, vinyl acetate-ethylene copolymer, or solvent-soluble resins such as epoxy resin, polyvinyl butyral, polyvinyl acetate, and polyvinyl chloride are used alone or in combination of two or more. . Also, a suitable amount of pigment may be added to this intermediate layer.

The back coat layer (1 to 20μ thick) may be starch or starch derivatives, cellulose derivatives such as carboxymethyl cellulose or hydroxyethyl cellulose, water-soluble resins such as polyvinyl alcohol, casein, vinyl acetate-crotonic acid copolymer, or ammonium polyacrylate. Emulsion type resins such as acrylic resins, SBR, MBR, and vinyl acetate-ethylene copolymers are used alone or in combination of two or more. Also, a suitable amount of pigment may be added to this backcoat layer.

(E) Examples The present invention will be explained in more detail with examples.

Example 1 An intermediate layer coating solution having the following composition was coated on the surface of wet reinforced paper with a basis weight of 100 g/m ² and dried to form an intermediate layer with a weight of about 15 g/m ² .

[Intermediate layer coating liquid]

Carboxyl-modified SBR latex (solid content 50%) 120 parts 10% aqueous solution of oxidized starch 100 parts 50% aqueous dispersion of Siegrite (sericite content
35% inorganic pigment, manufactured by Zeeklite Chemical Co., Ltd.) 200 parts 80% aqueous solution of melamine resin (product name: Violet Resin-613, manufactured by Sumitomo Chemical Co., Ltd.) 12 parts 35% aqueous solution of curing catalyst (product name: Accelerator)
ACX-P (manufactured by Sumitomo Chemical Co., Ltd.) 1.2 parts Next, a back coat layer coating solution having the following composition was applied to the back side of this wet reinforced paper and dried to give approximately 15 g/
A water-resistant support was obtained by providing a back coat layer of ^m2 .

[Back coat layer coating liquid]

SBR latex (solid content 50%) 10 parts 10% aqueous polyvinyl alcohol (product name Kuraray Poval 117, manufactured by Kuraray Co., Ltd.) 50 parts 50% aqueous dispersion of kaolin 100 parts 80% aqueous solution of melamine resin 2 parts Chloride 10% aqueous solution of ammonium 2 parts water 50 parts Furthermore, in order to coat an image-receiving layer coating solution with the following composition on top of this, a mixed system of a 50% dispersion of kaolin and a 20% dispersion of synthetic silica was mixed with Viscomil (Igarashi). After continuous processing at a flow rate of 20 per minute (manufactured by Kikai Co., Ltd.), a 10% aqueous solution of polyvinyl alcohol or less was sequentially added and mixed, and the mixture was applied to a smearer to obtain an offset printing original plate.

[Image-receiving layer coating liquid]

50% dispersion of kaolin (trade name Ultra White-90, manufactured by Engelhard) 100 parts 20% dispersion of synthetic silica (trade name Thyroid 308,
Fuji Davison Chemical Co., Ltd.) 250 parts 10% aqueous solution of polyvinyl alcohol (trade name Kuraray Poval 117, manufactured by Kuraray Co., Ltd.) 200 parts 80% aqueous solution of melanin resin (trade name Sumirezu Resin-613, manufactured by Sumitomo Chemical Co., Ltd.) ) 2.5 parts 10% aqueous solution of ammonium chloride 2 parts water 60 parts Coarse particles of 100μ or more on the surface of the resulting image-receiving layer
There were about 15 pieces per ^100cm2 . This is a Japanese word processor Tosword JW-8S (manufactured by Toshiba Corporation)
Printing is done using a wire dot printer,
This was installed on an offset printing machine (Gestettner 339,
When I printed it using the Gestettner
There were no spots of dirt on the plain area, and the print finish was extremely good.

Example 2 When coating an image-receiving layer coating solution with the same formulation on the water-resistant support of Example 1, a polyvinyl alcohol aqueous solution, a polyvinyl alcohol aqueous solution,
and a waterproofing agent and other raw materials were added and mixed. A large number of aggregated particles were observed in this subsequent coating solution. This coating liquid was treated with a Viscomill at a flow rate of 15 per minute, and then applied to a smearer to obtain an offset printing original plate.

The number of coarse particles of 100 μm or more on the surface of the image-receiving layer was about 5 per 100 cm ² . This is a Japanese word processor Tosword JW-8S (manufactured by Toshiba Corporation)
Printing is done using a wire dot printer,
This was installed on an offset printing machine (Gestettner 339,
When printed on a paper (manufactured by Gestettner), no endless spots were observed at all, and the print finish was extremely good.

Comparative Example 1 An image-receiving layer coating solution having the same composition as in Example 1 was coated on the water-resistant support using a smearer without performing Viscomill treatment to obtain an offset printing original plate.

Coarse particles of 100μ or more on the surface of the image-receiving layer obtained are 100
There were about 100 pieces per ^cm2 . When this was printed using a wire dot printer of the Japanese word processor Tosward W-8S (manufactured by Toshiba Corporation) and then printed using an offset printing machine (Gestettner 339, manufactured by Gestettner), dots appeared on the plain area. The print finish was not good due to the occurrence of dirt.

Example 3 Acetoacetylated polyvinyl alcohol (Gosefheimer Z200 manufactured by Nippon Gosei Kagaku Co., Ltd.) was used instead of polyvinyl alcohol in the image-receiving layer coating solution of Example 1, and the method was completely the same as in Example 1. A direct printing type offset printing original plate was obtained by Viscomill treatment. 100μ of the surface of the resulting image-receiving layer
There were approximately 10 coarse particles per 100 ^cm2 . This includes Japanese word processor Canon Word 45S
When printing plates were made using a thermal transfer printer (manufactured by Canon Inc.) and then printed using an offset printing machine (Gestettner 339, manufactured by Gestettner), there were no spots of dirt on the plain areas, and the print finish was excellent. It was in extremely good condition.

Comparative Example 2 In obtaining a direct printing type offset printing original plate by the method of Example 3, the Viscomill treatment was not performed.
Coarse particles of 100μ or more on the surface of the image-receiving layer obtained are 100
There were about 60 pieces per ^cm2 . When this was printed using a thermal transfer printer using a Japanese word processor, Cano Word 45S (manufactured by Canon Inc.), and then printed on an offset printing machine (Gestettner 339, manufactured by Gestettner Inc.), there were some spots on the plain area. The print quality was not good.

(F) Effects of the invention As is clear from the examples, by carrying out the manufacturing method of the present invention, there are no minute coarse particles protruding on the image-receiving layer, and therefore, during plate making with a word processor etc. It has now become possible to supply an offset original plate for direct printing that has no risk of staining and has an excellent printing finish. This will greatly contribute to the spread of light printing in offices, and it can be said that the effects of the invention are extremely large.

Claims (1)

[Claims] 1. Inorganic pigment, hydrophilic binder,
In a direct printing type offset printing original plate provided with an image-receiving layer containing a water-resistance agent as a main component, after applying and drying a sand-milled image-receiving layer coating liquid, coarse particles (agglomerates with a diameter of 100 μm or more) on the surface of the image-receiving layer are removed. 1. A method for producing a direct-printing type offset printing original plate, characterized in that the number of particles (referring to particles obtained by printing) is 30 or less per 100 cm ² . 2. The manufacturing method according to claim 1, wherein the hydrophilic binder in the image-receiving layer coating liquid is polyvinyl alcohol.