JPS6255504B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a printing plate by printing, and more particularly to a method for strengthening the image area of a lithographic printing plate having a duplicated hydrophilic non-image area.

Conventionally, the general method of obtaining an offset printing plate is to prepare a negative film or a positive film and then convert it into a negative presensitized plate (hereinafter referred to as
A printing plate is obtained by exposing the printing plate to light in close contact with a PS plate (called a PS plate) or a positive type PS plate, and then developing it with a prescribed developer to dissolve and remove the non-image areas. However, this plate-making method consists of the steps of creating a film, exposing the PS plate, and developing the PS plate, which is unavoidably disadvantageous in terms of time and cost in order to obtain multiple printing plates. That is the reality.

Furthermore, today, with the generalization of computers, electronic editing systems have been put into practical use even in the newspaper printing field, and methods of writing image information converted into electrical signals onto film or photosensitive printing plates using laser beams have been put into practical use. In this electronic editing system, the method of recording on film using a laser is less rapid than the method of directly recording on photosensitive printing plate material because it involves the steps of developing the film and exposing it to the PS plate. Currently, the direct plate making method, in which printing plates are exposed directly to laser beams, is the best method for rapidly manufacturing printing plates. Direct plate making systems have been commercialized by Ecom and LogEtronics, and printing plates are produced without going through a negative. However, when producing multiple printing plates, the method of writing on each printing plate one by one using a laser requires at least several tens of seconds of scanning time per A-2 size page, which reduces the lifespan of the laser tube. There were problems in terms of speed and cost, such as the need for a photosensitive printing plate material that could be sensitive to laser. Under these circumstances, a challenge in the mass printing industry is how to quickly and inexpensively produce a plurality of printing plates with high printing durability from printing plates made by laser recording.

JP-A-53-100005 describes a printing plate manufacturing method in which an ink image-receiving layer is formed by offset printing on an anodized aluminum plate, and a master plate is further formed by laser recording means. JP-A No. 55-46973 describes a duplication method in which a large-scale printing plate is obtained by preparing a lithographic plate and using the same for duplication printing. This method uses special ink on a sheet-like printing plate material such as aluminum to offset print images to reproduce a planographic printing plate, and the ink printed on the aluminum plate is used as the oil-sensitive component of the printing plate. It is used for printing. In general, in offset lithographic printing, when the non-image areas on the surface of the printing plate are moistened with water and then oil-based ink is applied to the surface of the printing plate, the non-image areas moistened with water repel the oil-based ink and become lipophilic. It is based on the principle that oil-based ink adheres only to the printed areas. In order to maintain faithful reproduction and uniformity of lines, it is necessary to skillfully control the balance of ink and dampening water during printing. If the supply of dampening water is too low or too much ink is supplied, ink may adhere to non-image areas, fine areas may be crushed, dots may become thicker, and the reproduction of image areas may be affected. cause problems. For printing plates with these ink image areas as oil-sensitive areas, the printing durability of the printing plate depends on the adhesion between the ink components formed on the aluminum plate and the aluminum plate, the abrasion resistance of the ink composition, and the amount of ink. have a big impact. However, increasing the amount of ink during printing in order to increase the printing durability of the printing plate has a negative effect on the faithful reproduction of images as described above. This method has the above-mentioned drawbacks.

In this way, it is not only possible to apply a large amount of ink to printed matter not only in the offset printing method, but also in the case of copying from a letterpress master plate. In letterpress printing, if a large amount of ink is applied, the ink will be pushed out to the contours of the convex portions, which will have a negative effect on image reproduction, so it is not possible to apply a large amount of ink. Therefore, the oleophilic layer in the image area of an imaged printing plate is thin and therefore easily damaged mechanically, making it unsuitable for high-volume printing.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for producing printing plates with improved printing durability. Other objects will become apparent from the description.

The object of the present invention is achieved by applying toner to an image area of a printing plate on which an image has been formed by printing, and fixing the toner with heat.

In the present invention, in order to produce a printing plate by forming an image by printing, an image formed from printing ink may be produced by printing on a commonly used lithographic printing plate material by a known printing method.

The printing plate material used in the present invention includes paper laminated with plastic (e.g., polyethylene, polypropylene, polystyrene, etc.);
For example, metal plates such as aluminum (including aluminum alloys), zinc, chromium, copper, etc.
For example, plastic films such as cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc., and metals such as those mentioned above are coated on the surface by lamination or vapor deposition. Examples include paper or plastic film.

The printing plate material used in the present invention can be subjected to a commonly used surface treatment. Such surface treatments include, for example, chemical treatment, electric discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, activated plasma treatment, laser treatment, etc. in the case of a support having a plastic surface, and aluminum surface treatment. In the case of printing plate materials with Immersion treatment in an aqueous solution such as
Or anodizing treatment, etc., and U.S. patent
As described in No. 2714066, methods include a method in which an aluminum plate is grained and dipped in an aqueous sodium silicate solution, anodized, and then dipped in an aqueous solution of an alkali metal silicate.

Printing inks that can be used to produce the printing plate of the present invention include heat evaporation curing inks, oxidation polymerization curing inks, photocuring inks, thermosetting inks, etc., and in particular, general offset inks can be used. have. Any printing method may be used to form an ink image on the printing plate material regardless of the format. For example, drawing, type printing,
The improvement of the ink image area of the present invention can be applied to an ink image area formed by any method such as letterpress printing, offset printing, gravure printing, screen printing, flat intaglio printing, or inkjet printing.

In the present invention, toner is sprinkled onto a printing plate having an ink image that has tackiness immediately after printing on the surface of the printing plate material, the toner is selectively attached to the ink image, and the toner is removed by heat. By fusing the toner to the image area, a printing plate with high printing durability is produced.

The toner used in the present invention consists of one or more resins, or has one or more resins as a main component,
Colorants such as plasticizers, organic pigments, inorganic pigments, and dyes may be added. Examples of the resin include polyamide resin, polyester resin, polyether resin, polycarbonate resin, polyurethane resin,
Acrylic resins, methacrylic resins, polybutadiene resins, and novolak resins can be used. The primary transition point of the resin used is 50℃~
A range of 240℃ is recommended. More preferably, a resin having a primary transition point of 60°C to 150°C can be used satisfactorily. In addition, resins having a secondary transition point of 25° C. or higher are preferably used. A resin having a low secondary transition point is undesirable because it adversely affects the storage stability of the toner.

The toner can be manufactured by the following method. (1) The necessary ingredients are melted and kneaded using a heated roll or heated kneader, and the uniformly dispersed mixture is cooled and then finely ground. (2) Knead the liquid with a solvent, spread it on a flat plate, dry it, solidify it, and then crush it. (3) Spray dry the mixture of (2). Alternatively, it is stirred and thrown into a large amount of non-solvent that is compatible with the solvent but does not dissolve each component, and is allowed to precipitate as insoluble fine particles. (4) The polymerizable monomer and necessary components are mixed and subjected to suspension polymerization, followed by atomization. (5) Stir the dispersion system in a molten state in a non-solvent to disperse it as spherical particles,
After cooling and solidifying, solid-liquid separation is performed.

If the average particle diameter of the toner is too large, there is a risk that small dots and non-image areas may be covered during fusing, which is undesirable since it has an adverse effect on image reproducibility such as resolution and halftone dot reproduction. On the other hand, if it is too small, image enhancement, which is an important effect of the present invention, will be reduced, and a high printing durability cannot be expected. From the above points, the toner particle size ranges from approximately 0.5μ to 40μ, and the average toner particle size is 1μ.
A range of ~20μ is preferred. To adjust the toner particle size within the above range, a generally known classification method may be used.

The toner may be attached to the ink by a method such as scattering. For example, JJ Sokol,
RC Hendrickson, Plastic Engineers Handbook P.426 (1976) (JJSokol and R.
C. Hendrickson, Plastic Eng. Handbook
In addition to the fluidized bed, electrostatic spray, and electrostatic fluidized head described in (19676), methods using air spray, electrostatic brush, sprinkle, etc. may be used. Toner on non-image areas is removed by blowing air or suctioning air. The steps of scattering the toner and removing the toner from the non-image areas can be performed manually, but are preferably performed automatically in a closed system, and the collected toner can be reused.

In the present invention, in order to fix the toner adhering to the ink image, there is a method of heating with flame;
This can be carried out by blowing heated air, passing it through a heated air chamber, or passing it between hot rolls. These methods may be used alone or in combination of two or more. Further, means for applying pressure to the toner using a roll or the like may be used in combination. When using a roll, a roll whose surface has been treated with silicone resin or Teflon resin in order to prevent the transfer of toner onto the roll can be used particularly well. By fixing the toner, an image area with excellent abrasion resistance, oil sensitivity, and chemical resistance can be formed on the printing plate, and this printing plate can be immediately applied to the printing plate to perform printing.

The printing plate obtained by the manufacturing method of the present invention is a printing plate with excellent printing durability, oil sensitivity, and chemical resistance, and can be suitably used for supplying a large amount of printed matter.

Furthermore, according to the method of the present invention,
It is possible to create a printing plate with good oil sensitivity and high printing durability by using a commonly used oil-based ink for offset lithographic printing without using the special ink described in Publication No. 46973.

Examples of the present invention will be specifically shown below, but the present invention is not limited thereto.

Example 1 m-cresol-formaldehyde novolac resin was ground in a ball mill and classified in a classifier (zigzag classifier manufactured by Albime). The first transition point of this m-cresol-formaldehyde novolak resin is 105℃, and the particle size range is 0.5μ to 8μ.
It was hot. This powder was used as a toner. An aluminum plate with a thickness of 0.3 mm was electrolytically polished and then anodized. (Hereinafter, the term "aluminum plate" refers to this plate.) Images were printed from a master plate on this aluminum plate using an offset proofing machine. did. Sakura PS version SLP was used as the master version, and Toyo King Ultra 70 manufactured by Toyo Ink Co., Ltd. was used as the printing ink.

Immediately after printing, the toner was sufficiently spread over the entire plate surface. The toner on the non-printing lines was removed using an air knife, heat treated in an open environment at 140°C for 2 minutes, and then passed between rolls coated with Teflon at 120°C at a speed of 4 m/min to fix the toner. When we conducted a printing test using this printing plate, we were able to obtain 150,000 good prints.

Comparative Example 1 The same experiment as in Example 1 was conducted except that the image area was not reinforced with toner. As a result, this comparative printing plate had a printing life of only about 3,000 sheets.

Example 2 95 parts by weight of a styrene-methyl methacrylate-acrylic acid (5:5:1) copolymer was kneaded with 5 parts by weight of copper phthalocyanine using a heated roll to be uniformly dispersed. This was ground with a ball mill and classified with the same classifier as in Example 1. The first transition point of this copolymer was 95°C, and the second transition point was 60°C. The particle size of the classified powder was 1μ to 15μ. This powder was used as a toner.

The printing ink is Diatone AK manufactured by Sakata Shokai Co., Ltd.
-Printing was performed from the master plate in the same manner as in Example 1 using SSP.

After printing, the toner was sufficiently spread over the entire plate surface. The toner in the non-image area was removed using an air knife. This was heat-treated in an oven at 200°C for 2 minutes, and then passed between rolls coated with Teflon at 150°C at a speed of 1 m/min to fix the toner. When we conducted a printing test using this printing plate, we were able to obtain 180,000 good prints.

Comparative Example 2 An experiment similar to Example 2 was conducted except that the image area was not reinforced with toner. As a result, this comparative printing plate had a printing life of only about 3,500 sheets.

Example 3 Styrene-methyl methacrylate-butyl acrylate-acrylic acid (3:1:1:2) copolymer
90 parts by weight and 10 parts by weight of copper phthalocyanine were kneaded using a heated roll to uniformly disperse the mixture. The cooled and solidified dispersion was ground with a ball mill and classified with the classifier of Example 1. The first transition point of this copolymer is 100℃
The second transition point was 60°C. The particle size of the classified powder was 0.5μ to 13μ. This powder was used as a toner.

Printing was carried out from a master plate using the method of Example 1 using Toyo King Ultra 70 manufactured by Toyo Ink Co., Ltd. as the printing ink.

After printing, the toner was sufficiently spread over the entire plate surface. The toner in the non-image area was removed using an air knife. This was heat treated in an oven at 200°C for 3 minutes to obtain a printing plate. A printing test was conducted using this printing plate and 120,000 good prints were obtained.

Claims (1)

[Claims] 1. A method for duplicating a lithographic printing plate, which comprises applying toner to an image area of a printing plate on which an image has been formed by printing, and fixing it with heat.