JP2006205423A - Thermal direct drawing-type lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal direct drawing-type lithographic printing plate which can stably inhibit a texture smear in a non-imaging part throughout the entirety of numerous printing sheets and secure ink spreading properties, in the thermal direct drawing-type lithographic printing plate which has at least an intermediate layer and a hydrophilic layer as a top layer, formed on a support, and also can form an imaging part as possessing ink-receptivity through a process to deteriorate hydrophilic nature by heating. <P>SOLUTION: This thermal plate-making lithographic printing plate comprises at least the intermediate layer and the hydrophilic layer as a top layer, formed on the support, and can form the imaging part as possessing ink-receptivity through a process to deteriorate hydrophilic nature by heating. In this printing plate, a colloidal silica composite synthetic polymer emulsion is added to the intermediate layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-sensitive direct-drawing lithographic printing plate that is used for offset printing by making a plate using a thermal laser and a thermal printing printer.

  The lithographic printing plate is composed of an oleophilic image portion that accepts oil-based ink and an oleophobic non-image portion that does not accept ink, and the non-image portion is generally composed of a hydrophilic portion that accepts water. In normal lithographic printing, both water and ink are supplied to the printing plate, ink is selectively received in the image area, and water is selectively received in the non-image area, and the ink on the image area is transferred to a printing medium such as paper. By doing so, printing is performed.

  Currently, a lithographic printing plate is produced by providing an oleophilic ink-receiving layer on a substrate such as an aluminum plate, a zinc plate, or paper whose surface has been hydrophilized. Among these, a photosensitive material such as a diazo compound or a photopolymer is used on a metal support having a hydrophilic surface treated as a PS plate, or silver halide is used as a photosensitive material on a paper or plastic support. In general, an image is formed using a silver complex diffusion transfer method (DTR method).

  In order to form an ink receiving layer (hereinafter referred to as an image layer) with a diazo compound or a photopolymer, first, a photosensitive material such as a diazo compound or a photopolymer is coated on a substrate such as a metal plate, paper, laminated plate, or insulating substrate. To do. Next, light is irradiated to cause a chemical change in the photosensitive material, thereby changing the solubility in the developer. Photosensitive materials are classified into two types depending on the type of chemical change. The negative part that becomes polymerized and hardened when irradiated with light and becomes insoluble in the developer, and conversely the functional group of the part that is irradiated with light changes to have solubility in the developer. It is a positive type. In any case, the photosensitive material insoluble in the developer that remains on the substrate after processing with the developer becomes the image layer.

  On the other hand, a lithographic printing plate using the DTR method, particularly a lithographic printing plate having a physical development nucleus layer on a silver halide emulsion layer is disclosed in, for example, US Pat. Nos. 3,728,114 and 4,134,769. No. 4,160,670, No. 4,336,321, No. 4,501,811, No. 4,510,228, No. 4,621,041, etc. As described, the exposed silver halide crystals undergo chemical development by DTR development to form black silver to form hydrophilic non-image areas, while unexposed silver halide crystals are contained in the developer. A silver salt complex is formed by the complexing agent and diffused to the physical development nucleus layer on the surface, and the physical development is caused by the presence of the nucleus to form an image portion mainly composed of ink-accepting physical development silver.

  When forming an image layer using the photosensitive material as described above, the exposure method is one of the important factors that determine the resolution. Conventionally, it has been the mainstream to produce a film for exposure and then perform a contact exposure method using ultraviolet light or white light. However, with the advancement of computers, a laser direct writing method in which a digital signal from computer information is transmitted to an exposure apparatus (computer-to-plate) and a photosensitive material is directly exposed using a laser has been performed. ing. The laser direct writing method has advantages such as low cost, high speed, and high productivity with many kinds and small lots.

In order to cope with this laser direct writing method, the optical sensitivity of the photosensitive material must be increased. Since diazo compounds and photopolymers involve a photochemical reaction, the optical sensitivity is low, being several to several hundred mJ / cm ² . For this reason, the laser output device must have a high output, which causes problems such as an increase in the size of the device and an increase in cost.

In addition, in the case of forming an image by the DTR method using silver halide, the sensitivity is several μJ / cm ² and it can be sufficiently exposed with a simple semiconductor laser or the like, but conversely, it is stored before performing the exposure process. In addition, there has been a drawback that the efficiency of manufacturing and plate making operations is remarkably deteriorated, in that the coating process to the substrate must be performed in the dark or under a safety light. In addition, in diazo compounds and photopolymers, the reaction proceeds even under room light or sunlight, and the reactivity changes even at high temperatures. In addition, the presence of oxygen becomes an inhibitor of the reaction. Therefore, before exposure and development, it is necessary to store in a dark room treatment or in a low oxygen state.

  Further, in the above-described image forming method, it is common to perform liquid processing such as using a developing solution, and naturally, waste liquid processing is necessary, which causes a load from the viewpoint of cost increase and ecology.

  On the other hand, recently, the technology of semiconductor lasers and solid-state lasers has progressed, and it has become available at a low price. By irradiating high-power, high-power lasers and efficiently converting the light energy into heat, A plurality of processless CTPs are disclosed as a thermal mode in which a chemical change, a phase change, and a structural change are caused to form an image on a lithographic plate, and no chemical development process is required.

  The plate material of the type that makes the plate in the heat mode is a type in which the image portion or the non-image portion is removed by ablation (Japanese Patent Laid-Open Nos. 6-199064, 2001-54985, etc.), and is peeled off by pre-dampening on a printing press. Type (Japanese Patent Laid-Open No. 9-136395), phase conversion type for converting hydrophilic / hydrophobic properties of the surface (Japanese Patent Laid-Open Nos. 07-1849, 10-24547, and 2003-43674) Etc.) have been proposed (Patent Documents 1 to 6).

  However, these plate materials do not necessarily have sufficient non-image performance, and have problems such as generation of background stains and insufficient printing durability depending on printing conditions such as a printing machine, ink, and dampening water used.

In particular, in the case of a plate material having an intermediate layer on the support, the outermost layer being hydrophilic, and making the hydrophilic surface an ink receptive surface by thermal drawing, the ink receptivity and non-image of the image portion The key points are to continuously maintain the hydrophilicity of the printing part during printing and to secure the printing durability by the adhesion between the support and the upper layer.
Japanese Patent Laid-Open No. 06-199064 JP 2001-54985 A JP 09-136395 A Japanese Patent Application Laid-Open No. 07-1849 Japanese Patent Laid-Open No. 10-24547 JP 2003-43674 A

  Accordingly, an object of the present invention is to provide a heat-sensitive direct-drawing lithographic printing plate in which at least an intermediate layer and a hydrophilic layer as the outermost layer are provided on a support, and the image portion is formed to have ink acceptability by reducing hydrophilicity by heating. The present invention provides a heat-sensitive direct-drawing lithographic printing plate that can stably suppress background stains in a non-image area over a large number of sheets and can ensure ink transportability.

The above object of the present invention has been achieved by the following invention.
1) In a thermosensitive lithographic printing plate in which at least an intermediate layer and a hydrophilic layer as an outermost layer are provided on a support, and the image portion is heated to lower the hydrophilicity and formed as ink acceptability, the intermediate layer is made of colloidal silica composite A heat-sensitive direct-drawing lithographic printing plate comprising a synthetic polymer emulsion.
2) The heat-sensitive direct-drawing lithographic printing plate as described in 1) above, wherein the intermediate layer further contains hydrophobic hot-melt fine particles.

  According to the present invention, it is possible to provide a heat-sensitive direct-drawing lithographic printing plate that can stably perform plate-making for a long period of time and can improve production efficiency at low cost. Since it is possible to stably suppress background stains in the non-image area over a large number of printed sheets and to ensure ink transportability, there are excellent effects such as improvement in productivity.

  The configuration of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a heat-sensitive direct drawing type lithographic printing plate. The heat-sensitive direct-drawing lithographic printing (a) according to the present invention is provided so that a hydrophobic resin 12 is coated on the front and back surfaces of a paper base 11 of a support 1, and an intermediate layer 3 and its upper layer are provided on one side. The hydrophilic layer 4 is provided as (outermost layer). In the lithographic printing plate making method of the present invention, first, the lithographic printing plate (a) is subjected to printing heating with a thermal head or irradiation heating to a desired image by a thermal laser. Here, the hydrophilic layer 3 in the heated portion is thermally melted and / or thermally decomposed, and the hydrophilicity of the surface is lowered, so that the ink is accepted and the plate making is completed. After that, if it is mounted on a lithographic printing machine, ink is received in the heated part and water is received in the hydrophilic layer 4 in the non-heated part, and offset printing becomes possible.

  The intermediate layer of the lithographic printing plate of the present invention has an upper layer that is thermally melted and / or thermally decomposed by heating, and finally the intermediate layer is exposed to make the ink receptive. It is also necessary to secure the adhesive strength of the film and use a film-forming polymer that is less hydrophilic (higher hydrophobicity) than the upper layer. May occur. Further, if the hydrophobicity is low, the ink loading is poor and the contrast with the non-image portion is low, so it is necessary to ensure the balance. For this reason, it is necessary to contain a colloidal silica composite synthetic polymer emulsion.

  The colloidal silica composite synthetic polymer emulsion according to the present invention is a dispersion medium in which water is the main dispersion medium, the surface of which is coated with colloidal silica particles as a solid content, and other dispersion stability as required It is composed of additives such as preservatives and preservatives. The coating of the colloidal silica on the polymer fine particles can be immobilized on the synthetic polymer fine particles using a silane coupling agent. Moreover, it can coat | cover easily by mixing with colloidal silica after superposing | polymerizing and granulating from the monomer which has a silane group in the step which synthesize | combines a synthetic polymer fine particle previously.

  Examples of the synthetic polymer fine particles include emulsion polymerization of ethylenic monomers such as acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, styrene, acrylonitrile, crotonic acid ester, maleic acid ester, vinyl acetate, Those having a silane group in advance include ethylenic monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxy-ethoxy) silane, vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxy. Those obtained by emulsion polymerization of acrylic silane or vinyl silane such as silane, vinyltrichlorosilane, etc., ethylenic monomers and unsaturated carboxylic acids or unsaturated polycarboxylic esters, unsaturated carboxylic amides, Reactions such as aminosilanes and epoxysilanes to those obtained by emulsion polymerization of ethylenic monomers having functional groups such as carboxyl groups, glycidyl groups, amino groups such as glycidyl compounds and alkylolated unsaturated compounds What reacted the reactive silane compound can be used suitably.

  The colloidal silica is ultrafine silica sol or ultrafine powder silica dispersed in water in a colloidal form, and preferably has an average primary particle size of 100 nm or less.

  The colloidal silica composite synthetic polymer emulsion described above generates pores in the formed film. For this reason, the dampening liquid during printing enters through the outermost hydrophilic layer and is retained in the pores by capillary action, resulting in improved soil resistance. Regarding the mechanism by which pores are formed in this polymer film, the colloidal silica particles that cover the synthetic polymer particles inhibit the fusion of the synthetic polymers during the film formation process and are surrounded by the colloidal silica particles. It is presumed that a fine pore is formed. Accordingly, the size of the pores can also be controlled by the particle diameter of the synthetic polymer fine particles and colloidal silica used.

  In addition, the heat-printed image portion is highly hydrophobic due to the formed synthetic polymer, and the pores are covered and concealed with the received ink, so that the ink acceptability is stable even when printing a large number of sheets.

  Further, the intermediate layer of the lithographic printing plate of the present invention preferably contains a substance whose hydrophilicity is lowered (hydrophobicity is increased) by heating, and if hydrophobic heat-soluble fused fine particles are present. When heated and mixed with and / or mixed with the synthetic polymer that forms the above-described film, the hydrophilicity of the formed film is further lowered (hydrophobicity is further increased).

  The heat-meltable fine particles according to the present invention are in the form of fine particles at room temperature and have a property of forming a dense film structure by being melted and fixed by heating. As an example of a material for forming such a heat-meltable fine particle layer, (Meth) acrylic resin, vinyl acetate resin, polyethylene resin, polypropylene resin, polybutadiene resin, vinyl chloride resin, vinyl acetal resin, vinylidene chloride resin, styrene resin, polyester resin, polyamide resin, phenol resin, xylene resin, alkyd resin , Gelatin, cellulose, wax, wax and the like. Only one kind of heat-meltable fine particles in the image forming layer may be selected or a plurality of fine particles may be selected. Further, fine particles having different inner core and outer shell components, so-called core-shell type heat-meltable fine particles, can also be suitably used. Furthermore, it is preferable that at least one component having a glass transition temperature of 50 ° C. or higher is contained for the purpose of improving the storage stability. When two or more kinds of heat-meltable fine particles are mixed and used, or when one particle such as a core-shell type is composed of a plurality of components, one of them has a glass transition temperature of 50 ° C. It may be above.

  In addition, the intermediate layer of the lithographic printing plate of the present invention has a hydrophilic resin such as gelatin, polyvinyl alcohol resin, polyvinyl pyrrolidone resin, carboxymethyl cellulose resin, titanium oxide, silicon dioxide, oxide for the purpose of further improving printing stain resistance. An inorganic substance such as aluminum can be contained. The ratio to be contained is appropriately determined in a desired range depending on various conditions such as printing ink, dampening water, printing speed, and printing pressure used for printing.

  Further, the intermediate layer of the lithographic printing plate of the present invention may contain coloring materials such as dyes and pigments and various surfactants and preservatives for improving coating properties in order to improve visibility and sensitivity by a thermal laser. I can do it.

Next, the hydrophilic layer of the lithographic printing original plate according to the present invention will be described. The hydrophilic layer is mainly composed of a hydrophilic polymer having a film forming ability, and is coated so that at least the outermost layer is a hydrophilic layer. There may be a plurality of hydrophilic layers. And it may be in the range of 0.5 to 10 g / m ² as the amount of the hydrophilic polymer constituting the hydrophilic layer.

  Examples of the hydrophilic polymer that forms such a hydrophilic layer include the following examples, and these can be used in combination of two or more in view of printing performance such as soiling and printing durability.

  Natural products include starches, seaweed mannan, agar, and algae such as sodium alginate, mannan, pectin, tragacanth gum, karaya gum, xanthine gum, guarbin gum, locust bin gum, gum arabic, and other plant mucus, dextran, glucan , Such as homopolysaccharides such as xanthan gum and levan, microbial mucilage such as heteropolysaccharides such as succinoglucan, pullulan, curdlan and xanthan gum, glue, proteins such as gelatin, casein and collagen, chitin and its derivatives, etc. It is done.

  Semi-natural products (semi-synthetic products) include cellulose derivatives, modified gums such as carboxymethyl guar gum, cultured starches such as dextrin, processed starches such as oxidized starches and esterified starches. .

  Synthetic products include polyvinyl alcohol, partially acetalized polyvinyl alcohol, allyl-modified polyvinyl alcohol, modified polyvinyl alcohol such as polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl isobutyl ether, polyacrylate, polyacrylic ester partial saponified product, poly Methacrylates and polyacrylic acid derivatives and polymethacrylic acid derivatives such as polyacrylamide, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, vinylpyrrolidone / vinyl acetate copolymer, carboxyvinyl polymer, styrene / maleic acid copolymer, Examples thereof include styrene / crotonic acid copolymers.

  Among these, gelatin, modified and non-modified polyvinyl alcohol, and cellulose derivatives can be advantageously used.

  As the gelatin used in the hydrophilic layer related to the lithographic printing plate of the present invention, any gelatin can be used as long as it is made from animal collagen, but gelatin made from collagen obtained from pig skin, cow skin, and cow bones. Is preferred. The type of gelatin is not particularly limited, but in addition to lime-processed gelatin and acid-processed gelatin, JP-B-38-4854, JP-A-39-5514, JP-A-40-12237, and JP-A-42-26345, US Patent No. 2,525,753, No. 2,594,293, No. 2,614,928, No. 2,763,639, No. 3,118,766, No. 3,132 No. 3,945, No. 3,186,846, No. 3,312,553, British Patent No. 1,033,189, and the like. Alternatively, two or more kinds can be used in combination.

  When gelatin is used for the hydrophilic layer, it can be hardened with a gelatin hardener. Gelatin hardeners include, for example, inorganic compounds such as chromium alum, aldehydes such as formalin, glyoxal, malealdehyde, glutaraldehyde, N-methylal compounds such as urea and ethylene urea, mucochloric acid, 2, 3 Aldehyde-related compounds such as dihydroxy-1,4-dioxane, active halogens such as 2,4-dichloro-6-hydroxy-S-triazine salt and 2,4-dihydroxy-6-chloro-S-triazine salt , Divinyl sulfone, divinyl ketone, N, N, N-triacryloyl hexahydrotriazine, compounds having two or more active three-membered ethyleneimino groups and epoxy groups in the molecule, and polymer dura mater Use one or more of various compounds such as dialdehyde starch as an agent. Can.

In particular, a copolymer of acrylamide and vinylimidazole is preferably used because it has an excellent balance between film strength and hydrophilicity, and can provide high plate-making sensitivity and soil resistance. The content of the copolymer polymer in the hydrophilic layer is preferably 300 mg / m ² or less, more preferably in the range of ^{2 to} 150 mg / m ² , and the molecular weight is 10,000 in consideration of coating solution stability and coatability. ˜500,000, more preferably in the range of 50,000 to 300,000.

  The hydrophilic layer of the lithographic printing plate according to the present invention may contain an inorganic substance such as titanium oxide, silicon dioxide, aluminum oxide or the like for the purpose of preventing printing stains. The ratio to be contained is appropriately determined in a desired range depending on various conditions such as printing ink, dampening water, printing speed, and printing pressure used for printing.

  In order to coat the hydrophilic layer of the lithographic printing plate precursor according to the present invention, an anionic, cationic or nonionic surfactant may be used as an auxiliary agent, a matting agent, a thickening agent. An antistatic agent or the like can also be used. Dyes and pigments can also be included for sensitivity to thermal lasers.

  The support relating to the lithographic printing plate of the present invention will be described. The support may be a resin-coated paper, synthetic paper, a synthetic or semi-synthetic polymer film such as polyethylene terephthalate, or a metal plate such as aluminum or iron that can withstand offset printing. In addition, the surface of these supports can be subjected to a surface treatment for improving adhesion with a layer to be coated as an upper layer, or can be subjected to a dyeing treatment to improve laser light absorption.

Hereinafter, the present invention will be described in detail with reference to examples.
A matted layer containing silicon dioxide particles having an average particle size of 5 μm is provided on one side of a 135 g / m ² double-sided polyethylene-coated paper (RC paper), and an intermediate layer and a hydrophilic layer comprising the following components are arranged in this order on the opposite side. Painted.
[Middle layer]
1) Carbon black 2 parts by mass 2) Silicon dioxide particles having an average particle size of 7 μm 2 parts by mass 3) Aqueous emulsion: emulsion polymerization using butyl acrylate, methyl methacrylate, acrylic acid, and γ-methacryloxypropyltrimethoxysilane as raw materials What was obtained by adding colloidal silica having a particle diameter of 10 nm to the obtained polymer fine particles having a particle diameter of 0.5 μm. 90 parts by mass 4) Gelatin Water was added to 6 parts by mass or more to prepare a coating solution, which was applied and dried so that the solid content coating amount was 3 g / m ² .
[Hydrophilic layer]
A copolymer of N-vinylimidazole and acrylamide (with a polymerization ratio of 2:98) was applied and dried at 20 mg / m ² .

  Next, laser irradiation of a portion corresponding to an image portion was performed on the lithographic printing plate (surface having a hydrophilic layer as the outermost layer) with a semiconductor laser irradiation apparatus (830 nm) to obtain a printing plate. Using this printing plate, printing was performed using purple ink (New Champion F gloss purple, manufactured by Dainippon Ink & Chemicals, Inc.) on an offset printing machine (3200MCD manufactured by Ryobi Imagics Co., Ltd.). From the initial stage, the ink was satisfactorily applied to the image area, and up to 3,000 sheets, a good printed matter with no non-image area smearing could be obtained.

  In addition, when the above lithographic printing plate was printed using a commercially available thermal printer and printed in the same manner, the ink was satisfactorily adhered to the image area from the initial stage of printing, and up to 3,000 non-image areas were printed. It was possible to obtain a good printed matter in which no smearing or the like occurred and a stable ink transfer was ensured in the image area.

  The same procedure as in Example 1 was conducted except that 20 parts by mass of a styrene fine particle emulsion (glass transition temperature 100 ° C.) was further added to the intermediate layer of Example 1. As a result, the non-image area was not stained up to 8,000 sheets, and a good printed matter in which the image area was secured with a stable ink transfer could be obtained.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that 3) of the intermediate layer components in Example 1 were all replaced with a styrene fine particle emulsion (glass transition temperature 100 ° C.). Although the ink was satisfactorily satisfactorily, the non-image area stain started to occur from about 300 sheets, and a good printed matter could not be obtained.

[Comparative Example 2]
Of the intermediate layer components of Example 1, 3) was replaced with a styrene fine particle emulsion (glass transition temperature 100 ° C.) in total amount, and 10 parts by mass of colloidal silica (Snowtex C manufactured by Nissan Chemical Industries, Ltd.) was added. The same operation as in Example 1 was performed. Although the ink was satisfactorily deposited on the image area from the initial stage of printing, the non-image area contamination started to occur from about 500 sheets, and a good printed matter could not be obtained.

Schematic cross-section of a heat-sensitive direct-drawing planographic printing plate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support body 11 Paper base 12 Resin 3 Intermediate layer 4 Hydrophilic layer

Claims (2)

  In a thermosensitive lithographic printing plate in which at least an intermediate layer and a hydrophilic layer as an outermost layer are provided on a support and the image portion is formed by heating to reduce hydrophilicity and accept ink, the intermediate layer has a colloidal silica composite composition A heat-sensitive direct-drawing lithographic printing plate comprising a molecular emulsion.   The heat-sensitive direct-drawing lithographic printing plate according to claim 1, wherein the intermediate layer further contains hydrophobic hot-melt fine particles.

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