JPH0367255B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an offset printing original plate, and more particularly to a direct printing type offset printing original plate that does not require desensitization treatment.

Currently, offset printing original plates used in office printing have (1) a printing layer (image-receiving layer) on the substrate;
(2) Electrophotographic type with a photoconductive layer (image-receiving layer) provided on the base paper; (3) Silver salt photographic type with a silver halide emulsion layer provided on the base paper. It can be cited as a representative example. Above all,
In order to create a printing plate by forming an image on the original plate (1), it is necessary to handwrite it on the printing layer with lipophilic ink, type it, or print it with a wire dot type or thermal transfer printer. , or can be easily done using the xerography method, etc.
It has advantages compared to the other original plates mentioned in (2) and (3) above.

By the way, the image-receiving layer in this direct-printing type offset printing original plate, like that of other types of offset printing original plates, is desensitized and has a hydrophilicity sufficient to repel ink during printing by an offset printing machine. At the same time, it must also have enough water resistance to withstand the repeated application of dampening water during printing.

In order to satisfy both hydrophilicity and water resistance, conventional direct printing offset printing plates have the following properties:
It is known that an image-receiving layer is provided on a support by adding a melamine formaldehyde resin as a crosslinking agent to a water-soluble resin such as polyvinyl alcohol, and further adding an inorganic pigment (U.S. Pat. No. 2,532,865). There is. However, in such original plates, either the hydrophilicity or the water resistance of this layer may be insufficient due to the mixing ratio of the water-soluble resin and the crosslinking agent, or due to slight fluctuations in the drying conditions after forming the image-receiving layer. The selection range of conditions for simultaneously achieving both printing and water resistance was narrow, and the quality of the products (direct printing type offset printing original plates) tended to vary widely.

Therefore, the inventor of the present invention has developed an image-receiving layer that has stable hydrophilicity and water resistance, has small variations in quality, prevents background smudges during printing, improves printing durability, and provides clear images at all times. It was proposed that an image-receiving layer containing an inorganic pigment and acetoacetylated polyvinyl alcohol as a binder as a main component be provided on a support as a direct printing type offset printing original plate from which sheets of printed matter can be obtained.

However, when a water-resistant agent such as melamine resin is added after coating the image-receiving layer for the purpose of further improving printing durability, there is a problem in that the coating solution thickens and becomes a gel within a short period of time, making coating impossible.

In addition, in the above-described printing method, it takes time to desensitize the offset printing original plate, and special equipment for desensitization is required. In addition, the dampening water used in offset printing machines is a desensitizing solution diluted several times, and since this dampening water is acidic, it can alter the surface of the metal parts of the machine and cause dampening. Among the solute components in the dampening water, those that are solid at room temperature precipitate out as the dampening water evaporates, resulting in an unfavorable effect on printing.

An object of the present invention is to provide a patternable offset printing original plate obtained by coating an image-receiving layer coating liquid containing acetoacetylated polyvinyl alcohol and a water-resistant agent that is stable for a long time. Another object of the present invention is to provide a direct printing type offset printing original plate that does not require desensitizing treatment during printing. Another object of the present invention is to provide a direct printing type offset printing original plate which is free from scumming during printing and has excellent printing durability. A further object of the present invention is to provide an offset printing method in which printing can be carried out using water other than the dilution water of the desensitizing treatment liquid that has been commonly used as dampening water.

That is, the direct printing type offset printing original plate of the present invention has an image-receiving layer containing an inorganic pigment, acetoacetylated polyvinyl alcohol, and a water-resistant agent on a support, and a mesoinositohexalic acid ester and its It is characterized by the presence of one or more desensitizing agents selected from derivatives, and an image is formed directly on the image-receiving layer of the original plate using an oil-based ink, a typewriter, a printer, etc., or Offset printing involves forming an image by transferring a toner image onto the image-receiving layer using a plain paper copying machine using dry toner or wet toner, and then applying water to the non-image area of the image-receiving layer for printing. The present invention provides a printing method.

Here, specific examples of mesoinositohexalic acid ester and its derivatives include mesoinositohexalic acid ester, mesoinositohexalic acid ester trizinc salt, mesoinositohexalic acid ester dimagnesium salt, and mesoinositohexalic acid ester. There are hexaphosphate monocalcium salts, etc. By adding these desensitizing agents to the image-receiving layer coating solution, the coating solution can be kept stable for a long time without weakening the crosslinking reaction between the acetoacetylated polyvinyl alcohol and the water-resistant agent. Further, during formation of the image-receiving layer, the desensitizing agent reacts with acetoacetylated polyvinyl alcohol to form a strong bond, resulting in an image-receiving layer that does not require desensitizing treatment.

The acetoacetylated polyvinyl alcohol constituting the image-receiving layer in the original plate of the present invention can be obtained by adding liquid diketene to polyvinyl alcohol powder and reacting it. ) made)
It is commercially available as such and can be easily obtained.

Water resistance agents include aldehydes, amines, melamine resin, hydrazides, persulfates, Ni ²⁺ ,
Cu ²⁺ , Al ³ , Fe ³ , Sb ²⁺ , NH ₄ ⁺ , Mg ²⁺ , Ca ²⁺ ,
One or more salts containing cations such as Zn ²⁺ can be added in an amount of 50% by weight or less based on the amount of acetoacetylated polyvinyl alcohol.

As inorganic pigments, clay, calcium carbonate, zinc oxide, silica, aluminum oxide, barium sulfate, titanium oxide, and all other inorganic pigments used in conventional direct-drawing offset printing plates can be used. These pigments may be used alone or in combination of two or more. The appropriate ratio of pigment to acetoacetylated polyvinyl alcohol is 2 to 10 parts by weight of pigment to 1 part by weight of acetoacetylated polyvinyl alcohol.

As mentioned above, the original plate of the present invention has a form in which an image-receiving layer is provided on a support, and the support used here includes a paper base, a melamine resin, a urea resin, and a polyamide epichlorohydrin resin. Examples include paper substrates, resin-coated papers, plastic films, etc., which have been wet-strengthened using, for example, inorganic pigments, acetoacetylated polyvinyl alcohol, An image-receiving layer coating solution containing a water-resistant agent and mesoinositohexaphosphate or its derivatives is coated on the support and heated at 80 to 150°C.
An image-receiving layer having a thickness of about 5 to 20 μm may be formed by drying.

In this case, a water-resistant intermediate layer may be provided between the support and the image-receiving layer to further improve printing durability, and a back coat layer may be provided on the back of the support to prevent curling. It may also be provided.

For the intermediate layer (1 to 20 μm thick), use an emulsion type resin such as acrylic resin, SBR, MBR, NBR, vinyl acetate-ethylene copolymer, or a solvent such as epoxy resin, polyvinyl butyral, polyvinyl acetate, or polyvinyl chloride. Soluble resins may be used alone or in combination of two or more. Also, a suitable amount of pigment may be added to this intermediate layer.

The pack coat layer (5 to 20 μm thick) may be starch or starch derivatives, cellulose derivatives such as CMC or HEC, polyvinyl alcohol, casein, vinyl acetate-crotonic acid copolymer, water-soluble resin such as ammonium polyacrylate, or acrylic resin. , SBR, MBR, emulsion type resins such as vinyl acetate-ethylene copolymer, etc. may be used alone or in combination of two or more. Also, a suitable amount of pigment may be added to this backcoat layer.

As described above, the offset printing original plate according to the present invention contains mesoinositohexaphosphate or its derivative in the image-receiving layer coating solution, which delays the crosslinking reaction between acetoacetylated polyvinyl alcohol and water resistance. Since a stable coating liquid is used, workability during manufacturing is good, and in addition, when the image-receiving layer is formed, the acetoacetylated polyvinyl alcohol is made water-resistant by a water-resisting agent.
In addition, the acetoacetylated polyvinyl alcohol and mesoinositohexalic acid ester or its derivatives are strongly bonded to each other, resulting in an original plate that does not require desensitization treatment. During offset printing, the excellent surface strength and hydrophilicity of acetoacetylated polyvinyl alcohol make it possible to obtain many clear prints without background smearing from printing plates made using this, which do not require desensitization treatment. become.

Next, examples will be shown. Note that all parts are parts by weight.

Example 1 An image-receiving layer coating solution having the following composition was coated on the surface of a support and dried at 130°C for 3 minutes to form a coating solution of about 20g/
An image-receiving layer of m ² was formed. It should be noted that even if this coating liquid was allowed to stand for a day and night, the viscosity of the liquid increased only slightly.

[Image-receiving layer coating liquid]

10% of acetoacetylated polyvinyl alcohol
Aqueous solution (trade name: Gocephaimer Z-200, manufactured by Nippon Gosei Kagaku Co., Ltd.) 200 parts 50% aqueous solution of mesoinositohexaphosphate 1 part 80% aqueous solution of melamine-formalin resin (trade name: Sumirezu Resin-613, Sumitomo Chemical Co., Ltd.) ) 2.5 parts of a 10% aqueous solution of ammonium chloride 2 parts of a 50% aqueous dispersion of clay 200 parts of water 150 parts of water Next, a back coat layer coating solution having the following composition was applied to the back side of this support, and heated at 130°C for 3 minutes. After drying, a back coat layer of approximately 10 g/m ² was formed, and this was supercalendered to produce a direct printing type offset printing original plate that did not require desensitization treatment.

[Back coat layer coating liquid]

SBR latex (50% solids) 10 parts 10% aqueous solution of polyvinyl alcohol (product name
(PVA-117, manufactured by Kuraray Co., Ltd.) 50 parts 50% aqueous dispersion of clay 100 parts 80% aqueous solution of melamine-formalin resin 2 parts 10% aqueous solution of ammonium chloride 1.6 parts Water 50 parts Image image with a thermal transfer printer using this original plate When this was printed directly on an offset printing machine (Toko Model 810), more than 2,000 sheets of brightly colored prints with no background smudges were obtained. Note that water was used as a dampening solution during printing.

Comparative Example 1 When an offset printing original plate was obtained and printed in the same manner as in Example 1 except that the meso-inositohexalic acid ester in the image-receiving layer coating liquid of Example 1 was removed, scumming was observed from about the 100th sheet. Ta. In addition, when the above image-receiving layer coating solution was left for about 30 minutes
Within minutes, it became gel-like and could no longer be applied.

Example 2 An intermediate coating solution having the following composition was coated on the surface of a support (100 g/m ² wet reinforced paper) and dried at 130° C. for 3 minutes to form an intermediate layer 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 solution of clay 200 parts 80% aqueous solution of melamine-formalin resin (trade name: Violet Resin-613, manufactured by Sumitomo Chemical Co., Ltd.) 12 parts 35% aqueous solution of curing catalyst (Product name Accelerator
ACX (manufactured by Sumitomo Chemical Co., Ltd.) 1.2 parts Furthermore, an image-receiving layer coating solution having the following composition was coated thereon and dried at 130° C. for 3 minutes to form an image-receiving layer of about 15 g/m ² . Note that even if this coating liquid was allowed to stand for a day and night, the increase in liquid viscosity was slight.

[Image-receiving layer coating liquid]

10% of acetoacetylated polyvinyl alcohol
Aqueous solution (trade name: Gocephaimer Z-200, manufactured by Nippon Gosei Kagaku Co., Ltd.) 200 parts 30% aqueous solution of mesoinositohexaphosphate dicalcium salt 2 parts 50% aqueous solution of melamine formalin resin (trade name: Violet Resin-607, Sumitomo) (manufactured by Kagaku Co., Ltd.) 4 parts 10% aqueous solution of ammonium chloride 2 parts 50% aqueous dispersion of clay 200 parts Water 150 parts Next, the same back coat layer as in Example 1 was provided on the back side of this support to make it desensitized. We have created a direct printing type offset printing plate that does not require any processing.

This master plate was made into a plate in the same manner as in Example 1,
After printing, more than 3,000 clear prints were obtained. Note that water was used as a dampening solution during printing.

Claims (1)

[Claims] 1. An image-receiving layer containing an inorganic pigment, acetoacetylated polyvinyl alcohol, and a water-resistant agent is provided on a support, and one or more desensitizing agents selected from mesoinositohexalic acid esters and derivatives thereof are included in the layer. Offset printing original plate with the presence of.