JPH0469079B2 - - Google Patents

Description

[Detailed description of the invention] (A) Industrial application field The present invention relates to a direct printing type offset printing original plate,
More specifically, the present invention relates to a direct plate for offset printing that can be directly plate-made using an impact type printer such as a type printer or a wire dot printer.

Offset printing master 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 original printing plate mentioned in (1) above is
This is advantageous compared to the other printing master plates mentioned in (2) and (3) above because it can be handwritten with oil-based ink on the image-receiving layer or plate-made directly using a PPC copying machine.

Recently, with the spread of office automation equipment, particularly word processors, there has been a demand for direct plate printing type offset printing plates that can be used to directly make plates and print. When making plates using a word processor, an impact printer such as a type printer or a wire dot printer is often used, and colorants such as pigments and oil-soluble dyes, mineral oil,
Printing is performed directly on the original plate for direct-drawing offset printing via a cloth ink ribbon impregnated with printer ink whose main component is a solvent such as vegetable oil. The printer ink transferred by printing is fixed on the image-receiving layer and exhibits lipophilicity, forming an image area during printing. In order to obtain clear printed matter, it is important that the image-receiving layer of the direct plate-type offset printing original plate has good fixing properties for the transferred printer ink.

(B) Prior art Conventional direct-printing offset printing plates generally consist of inorganic pigments such as kaolin clay, zinc oxide, and synthetic silica, polyvinyl alcohol, and polyvinyl alcohol on a water-resistant support.
An image-receiving layer whose main component is a binder made of a water-soluble polymer compound such as starch or carboxymethylcellulose is provided.
In general, it is required to have hydrophilicity and water resistance, as well as fixability to printer ink and the like. However, hydrophilicity and water resistance have a contradictory relationship with each other; increasing the water resistance will result in a lack of hydrophilicity, making it more likely to cause scumming, and conversely, increasing the hydrophilicity will result in a lack of water resistance, making the image-receiving layer more likely to peel off. There was a problem. Therefore, in order to obtain an image-receiving layer that has both hydrophilicity and water resistance, for example, in JP-A-57-1791, a mixture of carboxymethyl cellulose and polyamide epichlorohydrin resin or
No. 59-135190 proposes using a mixture of two water-soluble polymer compounds, such as a mixture of carboxymethyl cellulose and a polyglycidyl ether compound, as a binder.

However, in these cases, although the toner of a PPC copying machine exhibits good fixing properties, the fixing properties of printer ink are very poor, and clear printed matter cannot be obtained by plate making using this method. That is, conventional direct-printing type offset printing original plates that have both hydrophilicity and water resistance have a drawback in that they do not have good fixing properties for printer ink.

(C) Purpose of the invention The purpose of the present invention is to have both water resistance and hydrophilicity,
The present invention also provides an original plate for direct-drawing type offset printing, which has an image-receiving layer that has good fixing properties for printer ink and also has good fixing properties for toner of a PPC copying machine.

(D) Structure of the Invention The direct-printing type offset printing original plate of the present invention has an image-receiving layer mainly composed of an inorganic pigment, a binder, and a microencapsulated lipophilic substance on a water-resistant support. It is characterized by:

A detailed observation of the reason why conventional direct printing offset printing plates, which have an image-receiving layer that is both water resistant and hydrophilic, does not have the ability to fix printer ink, revealed that it is used as a binder. It has been found that the solvent resistance of water-soluble polymer compounds, that is, their strong barrier properties against solvents, greatly inhibits the fixation of printer inks based on solvents such as mineral oil. Therefore, in order to weaken the barrier performance, we investigated ways to reduce the amount of a binder made of a water-soluble polymer compound.
Although this considerably improves printer ink fixing properties, it is still necessary to promote fixing with the aid of a heating device such as a human user. Furthermore, if the amount of binder is reduced, the adhesion with PPC toner will be significantly reduced, and simply reducing the amount of binder in the image-receiving layer will not result in a well-balanced direct-coating offset printing method. It was not possible to obtain the original version. Therefore, an attempt was made to improve the image-receiving layer by adding a material having good affinity for printer ink (ie, a lipophilic substance) to the image-receiving layer. In other words, when an aqueous dispersion of wax or the like is added to the image-receiving layer, printer ink fixing properties are improved due to its lipophilic property, but on the other hand, it causes a decrease in the hydrophilicity of the image-receiving layer, resulting in background smearing and other problems during printing. However, it was not possible to obtain the desired original plate for offset printing.

As a result of extensive research, the inventors of the present invention have worked on an improvement by a method in which a lipophilic substance is microencapsulated with a hydrophilic wall material and added to the image-receiving layer. In other words, when making a plate with an impact printer, the microcapsules in the printed area are destroyed and the lipophilic substance wrapped in the wall material adheres to the image-receiving layer, and at the same time the printer ink overlaps.
The lipophilicity of the printed area is doubled. For this reason, it has been found that even immediately after plate making using printer ink, ink fixability and printing durability can be greatly improved.
On the other hand, since the microcapsules in the non-image area that remain undestructed are hydrophilic in the wall material, they do not cause scumming during printing.

Methods for microencapsulating lipophilic substances include chemical methods such as interfacial polymerization, in-situ methods, and in-liquid curing methods, coacervation methods, phase separation methods, in-liquid drying methods, and melting and dispersion methods. Physical and chemical methods such as cooling methods, air suspension methods, spray drying methods,
Mechanical methods such as electrostatic coalescence can be used, but in order to enhance the effects of the present invention, it is desirable to use a method that creates a hydrophilic wall material. That is, it is desirable to use a hydrophilic polymer compound as the main component of the wall material. For example, microcapsules using gelatin as a wall material produced by the coacervation method, microcapsules using urea formaldehyde resin as a wall material produced by the in-situ method, and the like are suitable for the present invention.

As lipophilic substances to be microencapsulated,
Parafine wax, microcrystalline wax, beeswax, spermaceti wax, ceramic wax, carnauba wax, candelilla wax, montan wax, low molecular weight polyethylene wax, stearamide, linolenic amide, laurylamide, myristeramide, methylene bis stearamide,
Heat-melting lipophilic substances such as waxes such as ethylene bisstearamide, coumaron-indene resins, rosin-modified phenolic resins, terpene-modified phenolic resins, xylene resins, ketone resins, and other resins are suitable. Grinding or dispersing a single substance or a mixture of two or more to a size of several μm,
Alternatively, it is dissolved in synthetic oils such as alkylnaphthalene, alkylated biphenyl, and alkylated diphenyl, petroleum distillates such as kerosene and naphtha, vegetable oils such as cottonseed oil, soybean oil, and linseed oil, and then emulsified and dispersed to a size of several μm. The material may be made into microcapsules by the above-mentioned microencapsulation method using a hydrophilic polymer compound as the main component of the wall material.

As the binder for the image-receiving layer, polyvinyl alcohol, modified polyvinyl alcohol, starch, oxidized starch, carboxymethyl cellulose, hydroxyethyl cellulose, casein, gelatin, polyacrylate, polyvinylpyrrolidone, polyvinyl ether-maleic anhydride copolymer, Water-soluble polymer compounds such as polyamide and polyacrylamide can be used.

As inorganic pigments for the image-receiving layer, kaolin clay, zinc oxide, synthetic silica, barium sulfate, aluminum oxide, calcium carbonate, titanium oxide, etc. can be used. In order to further improve fixing properties, it is preferable to use a synthetic silica-colloidal silica mixed pigment previously proposed by the present inventor.

Furthermore, crosslinking agents such as aldehydes, amines, melamine formaldehyde resin, urea formaldehyde resin, hydrazides, and various inorganic acids and metal salts are added to the image-receiving layer to improve hydrophilicity and promote crosslinking. It's okay.

As mentioned above, the direct-printing type offset printing original plate of the present invention has a structure in which an image-receiving layer is provided on a water-resistant support.The water-resistant support used here is melamine formaldehyde. Examples include high-quality paper, resin-coated paper, plastic film, etc., which are wet-strengthened using resin, urea-formaldehyde resin, polyamide epichlorohydrin resin, and the like.

In order to produce the original plate for direct printing type offset printing of the present invention, an image-receiving layer coating solution containing an inorganic pigment, a binder, and a microencapsulated lipophilic substance as main components is coated on a water-resistant support. Dry at ~130℃,
It is sufficient to form an image-receiving layer with an adhesion amount of about 2 to 30 g/m ² .

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

The intermediate layer (adhesion amount 1 to 20 g/m ² ) may be the water-soluble polymer compound mentioned above, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer,
Synthetic rubber latex such as methyl methacrylate-butadiene copolymer, vinyl acetate (vinyl acetate,
Synthetic resin emulsion such as vinyl acetate to acrylic, ethylene to vinyl acetate), acrylic (Racrylic, styrene to acrylic), vinyl chloride, or solvent-soluble resin such as epoxy resin, polyvinyl butyral resin, vinyl acetate resin, vinyl chloride resin etc. may be used alone or in combination of two or more. A suitable amount of pigment may also be added to this intermediate layer.

The back coat layer (coating amount: 1 to 20 g/m ² ) may be made of the aforementioned water-soluble polymer compounds, synthetic rubber latex, synthetic resin emulsion, etc. alone or in combination.
More than one species is used in combination. Appropriate amounts of pigments may also be added to this backcoat layer.

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

Example 1 A microcapsule liquid having gelatin as a wall material was prepared in the following manner.

[Microcapsule liquid]

Heat and melt 50g of parafine wax (melting point 50℃) and 50g of carnauba wax, add to 100g of 7% acidic gelatin aqueous solution at 55℃, and add it to the oil droplet size of 3.
It was emulsified and dispersed until it reached ~5 μm. 5% methyl vinyl ether - maleic anhydride copolymer aqueous solution
Add 5.7g, 2% gum arabic 238g, and 115g water.
Warmed to 55°C. After adjusting the pH of the system to 4.5 with acetic acid, the system was cooled to 10°C. 3.6 g of a 25% aqueous glutaraldehyde solution was added, followed by 6.7 g of a 5% methyl vinyl ether-maleic anhydride copolymer. PH
was adjusted to 10 to obtain a microcapsule liquid with a solid content of approximately 20%.

Next, an intermediate layer coating solution having the following composition was applied to the surface of the support (100 g/m ² wet reinforced paper) and dried at about 120° C. to form an intermediate layer of about 15 g/m ² . [Intermediate layer coating solution] Carboxyl-modified styrene-butadiene latex (solid content 50%) 120 parts 10% aqueous solution of oxidized starch 100 parts 50% aqueous dispersion of Zeeklite (inorganic pigment manufactured by Zeeklite Chemical Co., Ltd.) 200 parts 80% aqueous solution of melamine formaldehyde resin (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.) 3 parts water 80 parts Next, a back coat layer coating solution having the following composition was applied to the back of this support and dried at about 120°C to form a back coat of about 15 g/m ² A layer was provided and then calendered to obtain a water-resistant support.

[Back coat layer coating liquid]

Styrene to butadiene latex (solid content 50
%) 80 parts 10% aqueous solution of polyvinyl alcohol (product name PVA117, manufactured by Kuraray Co., Ltd.) 100 parts 50% aqueous dispersion of kaolin clay 200 parts 80% aqueous solution of melamine formaldehyde resin
10 parts 10% aqueous solution of ammonium chloride 8 parts Water 50 parts An image-receiving layer coating solution having the following composition was coated on the intermediate layer and dried at about 120°C to form an image-receiving layer of about 8 g/m ² .

[Image-receiving layer coating liquid]

Synthetic silica (trade name Thyroid 308, manufactured by Fuji Davison Chemical Co., Ltd.) 20 parts Colloidal silica 20% aqueous dispersion (trade name Snowtex C, manufactured by Nissan Chemical Co., Ltd.) 100 parts 50% aqueous dispersion of kaolin clay 120 10% aqueous solution of polyvinyl alcohol (product name
PVA117, manufactured by Kuraray Co., Ltd.) 120 parts of the above microcapsule liquid 57 parts 80% aqueous solution of melamine formaldehyde resin
1.2 parts 10% aqueous solution of ammonium chloride 1 part water 100 parts This original plate for direct drawing type planographic printing was manufactured by Mitsubishi Japanese Word Processor Office Ace 200 (manufactured by Mitsubishi Electric Corporation).
A printing plate was created by directly printing and plate making using a dot printer. Immediately print this using a fully automatic offset printing machine (Gestettner 339, manufactured by Gestettner).
When I printed it, there was no background smear from the beginning.
Over 500 clear prints were obtained. In addition, the above original version was used as a PPC copier Ubitkus 2500MR (Roku Konishi).
Co., Ltd.) to make printing plates. When this was printed using the above-mentioned printing machine, more than 500 clear prints with no background smudges were obtained from the beginning.

Comparative Example 1 A direct plate offset printing original plate was obtained in the same manner as in Example 1 except that the microcapsules were removed from the image-receiving layer coating solution in Example 1. When this original plate was made using the dot printer of Example 1 and immediately printed using the offset printing machine of Example 1, the printer ink did not fix well and only unclear prints were obtained.

Comparative Example 2 Instead of the microcapsule liquid of Example 1, 3~
A direct printing type offset printing original plate was obtained in the same manner as in Example 1 except that 50 parts of a 20% aqueous dispersion of a 1:1 mixture of paraffin wax and carnauba wax having a size of 5 μm was used. When this original plate was made using the dot printer of Example 1 and immediately printed using the offset printing machine of Example 1, the printer ink fixability was good, but only prints with background stains were obtained.

Example 2 A direct printing type offset printing original plate was obtained in the same manner as in Example 1 except that the microcapsule liquid in Example 1 was replaced with 44 parts of the following microcapsule liquid. When this original plate was made using the dot printer of Example 1 and immediately printed using the offset printing machine of Example 1, more than 500 clear prints without background smear were obtained from the beginning. Further, when the plates were made using the PPC copying machine of Example 1 and printed using a printing machine, more than 500 clear prints with no background smear were obtained from the beginning.

[Microcapsule liquid]

After mixing 200 parts of a 10% aqueous solution of ethylene-maleic anhydride copolymer, 20 parts of urea, 2 parts of resorcinol, and 400 parts of water, heating the mixture to 55°C and adjusting the pH to 3.5, add 100 parts of diisopropylnaphthalene. A solution containing 100 parts of rosin resin was added to each part, and emulsified and dispersed until the size of oil droplets became 3 to 5 μm. Fifty parts of a 37% formaldehyde aqueous solution was added, and the temperature of the system was kept at 55° C. After 2 hours, the pH was adjusted to 9.5 to obtain a microcapsule liquid with a solid content of about 30%.

(F) Effects of the invention As is clear from the examples, the direct drawing type lithographic printing original plate of the present invention can be used immediately after printing with a word processor printer.
Even when plate-making and printing using a PPC copying machine, hundreds of clear prints with no background smudges can now be obtained from the beginning. This greatly contributed 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. In a direct printing type offset printing original plate having an image-receiving layer provided on a water-resistant support, a lipophilic substance is micro-encapsulated in the image-receiving layer with a wall material mainly composed of a hydrophilic polymer compound. An original plate for direct printing type offset printing, characterized by comprising: