JP2006247857A - Lithographic printing plate material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing plate material which requires no development process after light exposure, can allow an exposed image to be easily checked and can keep high sensitivity without deteriorating production efficiency in a printing process. <P>SOLUTION: The lithographic printing plate material comprises an imaging layer which cannot be removed by water after heating, formed on a base material with a hydrophilic surface, wherein the image layer comprises a thermoplastic resin fine particle having 120 to 200°C minimum film-forming temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lithographic printing plate material (hereinafter also referred to as a printing plate material), and more particularly to a lithographic printing plate material that can form an image by a computer-to-plate (CTP) method and does not require development processing.

  Along with the digitization of print data, there is a need for CTPs that are inexpensive, easy to handle, and have the same printability as PS plates. In particular, in recent years, a development process using a special chemical agent is unnecessary, and it can be applied to a printing machine having a direct imaging (DI) function, and is a general-purpose type thermal processless plate having the same usability as a PS plate. Expectations are growing. An example of the thermal processless plate for DI is Thermo Lite manufactured by Agfa.

  A thermal laser recording system having a wavelength of near infrared to infrared is mainly used for image formation of a thermal processless plate. Thermal processless plates capable of image formation by this method are broadly classified into an ablation type, a thermal fusion image forming layer on-machine development type, and a phase change type, which will be described later.

  Examples of the ablation type are described in JP-A-8-507727, JP-A-6-186750, JP-A-6-199064, JP-A-7-314934, JP-A-10-58636, and JP-A-10-244773. The thing that is.

Development type on heat-bonding image forming layer, and phase change type includes hydrophobized precursor particles in a hydrophilic layer that is not removed during printing, and changes the exposed area from hydrophilic to oleophilic. Is mentioned. (For example, see Patent Documents 1 to 3)
Among the above-mentioned technologies, in the case of the development type on the heat fusion image forming layer machine, the stability to the drying temperature in the coating process at the time of manufacture and the outside temperature at the time of storage is required. However, there is a problem that the image recording sensitivity must be lowered. Further, in order to increase the sensitivity of image recording, it is necessary to lower the coating process drying temperature at the time of production and lengthen the drying time, thereby reducing the production efficiency. Moreover, since the stability is low with respect to the environmental temperature change at the time of storage after manufacture, temperature management is required.

Further, although a resin having relatively high heat sensitivity was used, on-press developability was impaired after storage under high temperature conditions before exposure. In addition, a water-soluble component is included in order to improve storage stability and developability, but this causes a decrease in printing durability.
Japanese Patent No. 2938397 Japanese Patent No. 2938398 JP-A-11-240270

  An object of the present invention is to provide a printing plate material that does not require development processing after exposure, allows easy confirmation of an exposed image, and has high sensitivity without reducing production efficiency in a printing process.

  The above object of the present invention has been achieved by the following constitution.

(Claim 1)
In a lithographic printing plate material having an image forming layer that cannot be removed with water by heating on a substrate having a hydrophilic surface, the minimum film-forming temperature in the image forming layer is 120 ° C. to 200 ° C. A lithographic printing plate material comprising resin fine particles.

(Claim 2)
2. The lithographic printing plate material according to claim 1, wherein the content of the thermoplastic resin fine particles is 50% by mass to 95% by mass of the entire image forming layer.

  The printing plate material according to the present invention does not require a development process after exposure, allows easy confirmation of an exposed image, and has a high sensitivity and an excellent effect in the printing process without lowering the production efficiency.

  Hereinafter, the present invention will be described in detail.

(substrate)
As the substrate of the printing plate material of the present invention, a known material used as a printing plate substrate can be used. For example, a metal plate, a plastic film, paper treated with polyolefin, a composite substrate on which the above materials are appropriately bonded, and the like can be given. The thickness of the substrate is not particularly limited as long as it can be attached to a printing press, but a substrate having a thickness of 50 to 500 μm is generally easy to handle.

Examples of the metal plate include iron, stainless steel, and aluminum. Aluminum is particularly preferable from the relationship between specific gravity and rigidity. The aluminum plate is usually used after degreasing with an alkali, an acid, a solvent or the like in order to remove oil used in rolling and winding existing on the surface. As the degreasing treatment, degreasing with an alkaline aqueous solution is particularly preferable. Moreover, in order to improve adhesiveness with a coating layer, it is preferable to perform an easy adhesion process or undercoat layer application | coating to an application surface. For example, a method of dipping in a liquid containing a coupling agent such as a silicate or a silane coupling agent or applying a liquid, followed by sufficient drying can be used. Anodizing treatment is also considered as a kind of easy adhesion treatment and can be used. Moreover, it can also use combining an anodizing process and the said immersion or application | coating process. Further, an aluminum substrate roughened by a known method, so-called aluminum grain, can also be used as a substrate having a hydrophilic surface. The aluminum substrate used in the printing plate material of the present invention includes pure aluminum and A substrate made of an aluminum alloy is included. Various aluminum alloys can be used. For example, an alloy of aluminum such as silicon, copper, manganese, magnesium, chromium, zinc, lead, bismuth, nickel, titanium, sodium, and iron is used.

  Prior to the roughening treatment, the aluminum substrate is preferably subjected to a degreasing treatment in order to remove the rolling oil on the aluminum surface. As the degreasing treatment, a degreasing treatment using a solvent such as trichlene or thinner, an emulsion degreasing treatment using an emulsion such as kesilon or triethanol, or the like is used. In addition, an alkaline aqueous solution such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate or the like can also be used for the degreasing treatment. When an alkaline aqueous solution is used for the degreasing treatment, dirt and oxide film that cannot be removed only by the degreasing treatment can be removed. When an alkaline aqueous solution is used for the degreasing treatment, it is preferable to perform a neutralization treatment by immersing in an acid such as phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid, chromic acid, or a mixed acid thereof. When electrolytic surface roughening is performed after the neutralization treatment, it is particularly preferable to match the acid used for neutralization with the acid used for electrolytic surface roughening.

  As the roughening of the substrate, an electrolytic surface roughening treatment is performed by a known method, and as a pretreatment, a roughening treatment appropriately combining chemical roughening and mechanical roughening of an appropriate amount of processing is performed. You may do.

  Chemical roughening uses an aqueous solution of an alkali such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate as in the degreasing treatment. After the treatment, it is preferable to carry out a neutralization treatment by dipping in an acid such as phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid, chromic acid, or a mixed acid thereof. When electrolytic surface roughening is performed after the neutralization treatment, it is particularly preferable to match the acid used for neutralization with the acid used for electrolytic surface roughening.

  The mechanical surface roughening treatment method is not particularly limited, but brush polishing and honing polishing are preferable. A mechanically roughened substrate is immersed in an acid or alkaline aqueous solution to remove abrasives, aluminum debris, etc. that have digged into the surface of the substrate, or to control the pit shape. Etching is preferred. Examples of the acid include sulfuric acid, persulfuric acid, hydrofluoric acid, phosphoric acid, nitric acid, and hydrochloric acid. Examples of the base include sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium phosphate. Among these, it is preferable to use an alkaline aqueous solution.

  When the above is immersed in an alkaline aqueous solution, it is preferably immersed in an acid such as phosphoric acid, nitric acid, sulfuric acid, chromic acid, or a mixed acid thereof for neutralization. When the electrolytic surface-roughening treatment is performed after the neutralization treatment, it is particularly preferable that the acid used for neutralization is matched with the acid used for the electrolytic surface-roughening treatment.

  The electrolytic surface roughening treatment is generally a surface roughening using an alternating current in an acidic electrolyte. As the acidic electrolytic solution, those used in a general electrolytic surface roughening method can be used, but a hydrochloric acid-based or nitric acid-based electrolytic solution is preferably used, and in the present invention, a hydrochloric acid-based electrolytic solution is particularly preferable. Various waveforms such as a rectangular wave, a trapezoidal wave, and a sawtooth wave can be used as the power supply waveform used for electrolysis, and a sine wave is particularly preferable. Further, a divided electrolytic surface roughening treatment as disclosed in JP-A-10-869 can also be preferably used.

  In the present invention, the substrate subjected to electrolytic surface roughening is etched by immersing it in an alkaline aqueous solution in order to remove surface smut or the like or to control the pit shape. Examples of the alkaline aqueous solution include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate and the like. By performing the etching treatment with an alkaline aqueous solution, the printability and background stain when the image forming layer according to the present invention is provided are very good.

  As a known method of electrolytic surface roughening treatment, a method of performing etching treatment after electrolytic surface roughening treatment with an acid such as sulfuric acid, persulfuric acid, hydrofluoric acid, phosphoric acid, nitric acid, hydrochloric acid or the like is also known. In the case of using an acid, the printing when the image forming layer is provided is deteriorated and the background is stained.

Following the roughening treatment, an anodizing treatment is performed. There is no restriction | limiting in particular in the method of the anodizing process used by this invention, A well-known method can be used. An oxide film is formed on the substrate by anodizing treatment. In the present invention, for the anodizing treatment, a method of electrolyzing at an electric current density of 1 to 10 A / dm ² using an aqueous solution containing sulfuric acid and / or phosphoric acid at a concentration of 10 to 50% is preferably used. In US Pat. No. 1,412,768, a method of electrolysis using a high current density in sulfuric acid, or phosphoric acid described in US Pat. No. 3,511,661 is used. The method of electrolyzing using can be used.

  The anodized substrate may be sealed as necessary. These sealing treatments can be performed using known methods such as hot water treatment, boiling water treatment, water vapor treatment, dichromate aqueous solution treatment, nitrite treatment, ammonium acetate treatment. Further, the anodized substrate can be appropriately subjected to a surface treatment other than the sealing treatment. Examples of the surface treatment include known treatments such as silicate treatment, phosphate treatment, various organic acid treatments, PVPA treatment, and boehmite treatment. In addition, an organic acid treatment such as citric acid may be performed following the treatment with an aqueous solution containing a bicarbonate described in JP-A-8-314157 or the treatment with an aqueous solution containing a bicarbonate.

  Examples of the plastic film include polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polycarbonate, polysulfone, polyphenylene oxide, and cellulose esters.

  A substrate provided with a back coat layer can also be preferably used for the purpose of controlling the slipperiness of the back surface (for example, reducing the friction coefficient with the plate cylinder surface).

(Hydrophilic layer)
In the printing plate material of the present invention, a hydrophilic layer is preferably provided on the substrate surface so as to be adjacent to an image forming layer described later. As the hydrophilic material used for the hydrophilic layer, a metal oxide is preferable. The metal oxide preferably contains metal oxide fine particles. Examples thereof include colloidal silica, alumina sol, titania sol, and other metal oxide sols. The form of the metal oxide fine particles may be spherical, needle-like, feather-like, or any other form. The average particle diameter is preferably 3 to 100 nm, and several kinds of metal oxide fine particles having different average particle diameters can be used in combination. Further, the surface of the particles may be subjected to surface treatment. The metal oxide fine particles can be used as a binder by utilizing the film forming property. The decrease in hydrophilicity is less than when an organic binder is used, and it is suitable for use in a hydrophilic layer.

  Among the above, colloidal silica can be preferably used in the present invention. Colloidal silica has the advantage of high film-forming properties even under relatively low temperature drying conditions, and can provide good strength.

  The colloidal silica preferably includes necklace-like colloidal silica, which will be described later, and fine particle colloidal silica having an average particle size of 20 nm or less, and the colloidal silica preferably exhibits alkalinity as a colloidal solution.

  The hydrophilic layer of the printing plate material of the present invention preferably contains porous metal oxide particles as a metal oxide. As the porous metal oxide particles, porous silica, porous aluminosilicate particles, or zeolite particles described later can be preferably used.

A silicate aqueous solution can also be used as another additive material in the hydrophilic layer according to the present invention. Alkali metal silicates such as silicate Na, silicate K, and silicate Li are preferred, and the SiO ₂ / M ₂ O ratio is in a range where the pH of the entire coating solution does not exceed 13 when silicate is added. It is preferable to select such that the inorganic particles are not dissolved.

  Further, an inorganic polymer or an organic-inorganic hybrid polymer using a metal alkoxide by a so-called sol-gel method can also be used. The formation of an inorganic polymer or an organic-inorganic hybrid polymer by the sol-gel method is described in, for example, “Application of the sol-gel method” (Sakuo Sakuo / Agne Jofusha) or is described in this document. Known methods described in the cited documents can be used.

  Examples of the hydrophilic organic resin include polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyethylene glycol (PEG), polyvinyl ether, styrene-butadiene copolymer, conjugated diene polymer latex of methyl methacrylate-butadiene copolymer, and acrylic. Examples thereof include resins such as polymer polymer latex, vinyl polymer latex, polyacrylamide, and polyvinylpyrrolidone.

  Further, it may contain a cationic resin, and as the cationic resin, polyalkylene polyamines such as polyethylene amine and polypropylene polyamine or derivatives thereof, and acrylic resins having a tertiary amino group or a quaternary ammonium group. , Diacrylamine and the like. The cationic resin may be added in the form of fine particles. Examples thereof include a cationic microgel described in JP-A-6-161101.

  As polysaccharides, starches, celluloses, polyuronic acids, pullulans and the like can be used, but cellulose derivatives such as methyl cellulose salts, carboxymethyl cellulose salts, hydroxyethyl cellulose salts are particularly preferable, and sodium salts and ammonium salts of carboxymethyl cellulose are preferable. More preferred.

  This is because an effect of forming the surface shape of the hydrophilic layer in a preferable state can be obtained by including the polysaccharide in the hydrophilic layer. This effect has also the raw material A which is a polysaccharide.

  The surface of the hydrophilic layer preferably has a concavo-convex structure with a pitch of 0.1 to 50 μm like the aluminum grain of the PS plate, and this concavo-convex improves water retention and image area retention.

  Such a concavo-convex structure can be formed by containing an appropriate amount of a filler having an appropriate particle size in the hydrophilic layer, but the above-mentioned alkaline colloidal silica and the above-mentioned water-soluble substance are used in the hydrophilic layer coating solution. It is preferable that a structure having better printing performance can be obtained by containing a polysaccharide and forming a phase separation when the hydrophilic layer is applied and dried.

  The shape of the concavo-convex structure (such as pitch and surface roughness) is the type and amount of alkaline colloidal silica, the type and amount of water-soluble polysaccharides, the type and amount of other additives, the solid content concentration of the coating solution, and the wet film. The thickness and drying conditions can be appropriately controlled.

  The pitch of the concavo-convex structure is more preferably 0.2 to 30 μm, and further preferably 0.5 to 20 μm. Further, a concavo-convex structure having a multiple structure in which a concavo-convex structure having a smaller pitch is formed on the concavo-convex structure having a large pitch may be formed. The surface roughness Ra is preferably 100 to 1000 nm, and more preferably 150 to 600 nm.

  Moreover, as a film thickness of a hydrophilic layer, it is 0.01-50 micrometers, Preferably it is 0.2-10 micrometers, More preferably, it is 0.5-3 micrometers.

  Further, the hydrophilic layer (coating solution) according to the present invention may contain a water-soluble surfactant for the purpose of improving the coating property. As the surfactant, it is preferable to use a surfactant such as Si, F, or acetylene glycol. The content of the surfactant is preferably 0.01 to 3% by mass, more preferably 0.03 to 1% by mass, based on the entire hydrophilic layer (solid content as the coating solution).

  In addition, the hydrophilic layer in the present invention can contain a phosphate. In the present invention, since the hydrophilic layer coating solution is preferably alkaline, the phosphate is preferably added as trisodium phosphate or disodium hydrogen phosphate. By adding phosphate, the effect of improving the mesh opening at the time of printing can be obtained. The addition amount of phosphate is preferably 0.1 to 5% by mass, and more preferably 0.5 to 2% by mass as an effective amount excluding hydrate.

  As a preferred embodiment of the present invention, the hydrophilic layer can contain a photothermal conversion material described later. Examples of photothermal conversion materials include the following materials.

  General infrared absorbing dyes such as cyanine dyes, croconium dyes, polymethine dyes, azurenium dyes, squalium dyes, thiopyrylium dyes, naphthoquinone dyes, anthraquinone dyes, organic compounds such as phthalocyanine dyes and naphthalocyanine dyes , Azo-based, thioamide-based, dithiol-based, and indoaniline-based organometallic complexes. Examples of the pigment include carbon, graphite, metal, metal oxide and the like.

  As the metal, any metal can be used as long as the particle diameter is 0.5 μm or less, preferably 100 nm or less, more preferably 50 nm or less. The shape may be any shape such as a spherical shape, a piece shape, or a needle shape. Colloidal metal fine particles (Ag, Au, etc.) are particularly preferable.

As the metal oxide, a material that is black in the visible light region, or a material that has conductivity or is a semiconductor can be used. Examples of the former include black iron oxide and black composite metal oxides containing two or more metals. Examples of the latter include SnO ₂ doped with Sb (ATO), In ₂ O ₃ doped with Sn (ITO), TiO ₂ , TiO ₂ with reduced TiO ₂ (titanium oxynitride, generally titanium black), etc. Is mentioned.

  As a preferred embodiment of the printing plate material of the present invention, an image forming layer described later is provided on an aluminum substrate whose surface has been hydrophilized, or a hydrophilic layer provided on the substrate. A printing plate material containing a photothermal conversion material to be described later in any of the constituent layers on the substrate. A printing plate material that can be developed on-press can be obtained by adopting a configuration in which the image-forming layer can be removed using dampening water or ink on a printing press as described later.

  In the printing plate material of the present invention, it is necessary to provide an image forming layer as a layer that develops ink fillability in the exposed area. In the printing plate material of the present invention, the image forming layer contains a heat-sensitive material that causes changes such as deformation, melting, and softening due to heat.

  Examples of usable materials include natural or synthetic waxes, polyester, polystyrene, polyacryl, polyurethane-based resins or copolymer resins thereof, and thermally reactive materials such as blocked isocyanate. Among them, the heat-sensitive material according to the present invention is preferably a blocked isocyanate, a urethane resin, a polyester resin particle or the like in terms of printing durability, on-press developability, and the like.

  As a preferable physical property of these resins, the glass transition point (Tg) is 40 ° C. or higher. The heat-sensitive material is preferably thermoplastic resin fine particles, and the average particle size is preferably 0.01 to 2 μm, more preferably 0.1 to 1 μm. When the average particle size is smaller than 0.01 μm, when the coating liquid for the layer containing the thermoplastic resin fine particles is applied on the porous hydrophilic layer described later, the thermoplastic resin fine particles are pores of the hydrophilic layer. It becomes easy to enter inside or into the gaps between fine irregularities on the surface of the hydrophilic layer, and the on-press development becomes insufficient, which may cause scumming. When the average particle size of the thermoplastic resin fine particles is larger than 10 μm, the resolution is lowered.

As a method for forming an image forming layer of the present invention, it is preferable that the image forming layer coating solution is applied on a substrate and then dried at a temperature lower than the glass transition temperature (Tg) of the thermoplastic resin fine particles.
The addition amount of the heat-sensitive material is preferably 50% by mass or less based on the entire image forming layer.

  The image forming layer of the present invention contains thermoplastic resin fine particles having a minimum film forming temperature of 120 ° C. or higher and 200 ° C. or lower. When the temperature is 120 ° C. or lower, the effect of the present invention cannot be obtained. When the temperature exceeds 200 ° C., it becomes difficult to make the image layer unremovable due to heat during image exposure. Preferably, the content of the thermoplastic resin fine particles is 50% by mass or more and 95% by mass or less of the entire image forming layer.

  Usable materials include natural or synthetic waxes, polyester, polystyrene, polyacryl, polyurethane resins or copolymer resins thereof, or thermally reactive materials such as blocked isocyanates, as in the above heat-sensitive materials. Is mentioned. In particular, the thermoplastic fine particles used in the present invention have a minimum film-forming temperature that is the same as or higher than that of the heat-sensitive material. In the image forming layer of the present invention, it is also a preferable aspect that the heat-sensitive material and the thermoplastic fine particles are also used as the same if the minimum film-forming temperature is 120 ° C. or higher. The average particle diameter of the thermoplastic resin fine particles is 0.01 to 2 μm. In the image forming layer of the present invention, the thermoplastic resin fine particles are dispersed in the layer, so that unnecessary film formation occurs due to heat received outside the image forming process. Can be prevented.

  Further, since the thermoplastic resin fine particles are insoluble in water, it is possible to maintain the water resistance of the portion heated by image exposure. Moreover, since the part which does not receive image exposure is not formed into a film, on-machine developability is securable.

(Other materials that can be included in the image forming layer)
The image forming layer used in the present invention may further contain the following materials.

  The image forming layer can contain a water-soluble resin or a water-dispersible resin. Examples of water-soluble resins and water-dispersible resins include oligosaccharides, polysaccharides, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyethylene glycol (PEG), polyvinyl ether, styrene-butadiene copolymers, and methyl methacrylate-butadiene copolymers. Examples thereof include resins such as conjugated diene polymer latex, acrylic polymer latex, vinyl polymer latex, polyacrylic acid, polyacrylate, polyacrylamide, and polyvinylpyrrolidone.

  Examples of the oligosaccharide include raffinose, trehalose, maltose, galactose, sucrose, and lactose, and trehalose is particularly preferable. As polysaccharides, starches, celluloses, polyuronic acids, pullulans and the like can be used, but cellulose derivatives such as methyl cellulose salts, carboxymethyl cellulose salts, hydroxyethyl cellulose salts are particularly preferable, and sodium salts and ammonium salts of carboxymethyl cellulose are preferable. More preferred. The polyacrylic acid, polyacrylic acid, polyacrylate (Na salt, etc.), and polyacrylamide preferably have a molecular weight of 3,000 to 5,000,000, and more preferably 5,000 to 1,000,000.

  Water-soluble resins and water-dispersible resins may be added to improve background stains and heat resistance after storage of printing plate materials over time, and on-press developability. In some cases, the amount of addition is preferably the minimum necessary, usually 30% or less, more preferably 10% or less. .

  By using thermoplastic resin fine particles that are in a non-film-forming state in the image forming layer used in the present invention, it is possible to improve background stains and heat resistance after storage over time, so that the water-soluble resin and water-dispersible resin are contained. The amount can be reduced.

  The image forming layer can contain a water-soluble surfactant. Surfactants such as Si, F, and acetylene glycol can be used. Furthermore, it may contain an acid (phosphoric acid, acetic acid, etc.) or an alkali (sodium hydroxide, silicate, phosphate, etc.) for pH adjustment.

The amount with the image forming layer, a 0.01 to 10 g / m ^2, preferably from 0.1 to 3 g / m ^2, more preferably from 0.2 to 2 g / m ^2.

  In addition, metal oxide particles can be included for the purpose of improving the heat resistance of the image forming layer or imparting resistance to scratches.

  Examples thereof include colloidal silica, alumina sol, titania sol, and other metal oxide sols.

  The form of the metal oxide particles may be spherical, needle-like, feather-like, or any other form. The average particle size is preferably 3 to 2000 nm, and several types of metal oxide particles having different average particle sizes can be used in combination. The surface of the particles may be surface treated.

  In addition, it is preferable that porous metal oxide particles are included as the metal oxide. As the porous metal oxide particles, porous silica, porous aluminosilicate particles, or zeolite particles described later can be preferably used.

(Porous silica porous silica or porous aluminosilicate particles)
The porous silica particles are generally produced by a wet method or a dry method. In the wet method, it can be obtained by drying and pulverizing a gel obtained by neutralizing an aqueous silicate solution, or by pulverizing a precipitate deposited after neutralization. In the dry method, silicon tetrachloride is burned together with hydrogen and oxygen to obtain silica. These particles can be controlled in porosity and particle size by adjusting the production conditions.

(Zeolite particles)
Zeolite is a crystalline aluminosilicate and is a porous body having regular three-dimensional network voids having a pore diameter of 0.3 to 1 nm.

  The particle diameter of the porous inorganic particles is preferably substantially 1 μm or less, and more preferably 0.5 μm or less.

  Further, in the visible image imparting layer of the printing plate material of the present invention, layered mineral particles are preferably used as a metal oxide.

  The layered mineral particles include kaolinite, halloysite, talc, smectite (montmorillonite, beidellite, hectorite, saponite, etc.), vermiculite, mica (mica), chlorite, and hydrotalcite, layered polysilicate ( Kanemite, macatite, ialite, magadiite, kenyaite, etc.). Among them, it is considered that the higher the charge density of the unit layer (unit layer), the higher the polarity and the higher the hydrophilicity. The charge density is preferably 0.25 or more, more preferably 0.6 or more. Examples of the layered mineral having such a charge density include smectite (charge density 0.25 to 0.6; negative charge), vermiculite (charge density 0.6 to 0.9; negative charge) and the like. In particular, synthetic fluoromica is preferable because it can be obtained with stable quality such as particle size. Among the synthetic fluorine mica, those that are swellable are preferable, and those that are free swell are more preferable.

  Also, intercalation compounds of the above-mentioned layered mineral particles (pillar crystals, etc.), those subjected to ion exchange treatment, and those subjected to surface treatment (silane coupling treatment, compounding treatment with organic binder, etc.) Can be used.

  As for the size of the layered mineral particles, the average particle size (maximum length of the particles) is 20 μm or less in the state of being contained in the layer (including the case where it has undergone the swelling process and dispersion peeling process), and the average aspect The ratio (maximum particle length / particle thickness) is preferably a thin layer of 20 or more, the average particle size is 5 μm or less, the average aspect ratio is more preferably 50 or more, and the average particle size is More preferably, it is 1 μm or less and the average aspect ratio is 50 or more. When the particle size is in the above range, the continuity and flexibility in the planar direction, which are the characteristics of the thin layered particles, are imparted to the coating film, and it is difficult for cracks to occur, and a tough coating film can be obtained in a dry state. Moreover, in the coating liquid containing many particulate matters, sedimentation of particulate matter can be suppressed by the thickening effect of the layered clay mineral.

  In particular, swellable synthetic fluorinated mica and smectite are preferable because they are effective even when added in a small amount. The layered mineral particles may be added as a powder to the coating solution, but in order to obtain a good degree of dispersion even with a simple preparation method (no need for a dispersion step such as media dispersion), the layered mineral particles are used alone. After the gel swollen in water is prepared, it is preferably added to the coating solution.

  Further, an inorganic polymer or an organic-inorganic hybrid polymer using a metal alkoxide by a so-called sol-gel method can also be used. The formation of an inorganic polymer or an organic-inorganic hybrid polymer by the sol-gel method is described in, for example, “Application of the sol-gel method” (Sakuo Sakuo / Published by Agne Jofusha) or cited in this book. Known methods described in the published literature can be used.

  The addition amount of metal oxide particles is usually 0 to 30%, preferably 10 or less. When the addition amount of the metal oxide particles is more than necessary, the printing durability may be deteriorated because the cohesive force with the heat-sensitive material and the thermoplastic thermoplastic resin fine particles in the image exposure portion cannot be mentioned.

(Protective layer)
A protective layer may be provided as an upper layer of the image forming layer of the present invention. As a material used for the protective layer, a water-soluble resin or a water-dispersible resin can be preferably used. Moreover, the hydrophilic overcoat layer described in Unexamined-Japanese-Patent No. 2002-19318 and 2002-86948 can also be used preferably. The amount with the protective layer is 0.01 to 10 g / m ^2, preferably from 0.1 to 3 g / m ^2, more preferably from 0.2 to 2 g / m ^2. In the present invention, the protective layer can also function as a visible image providing layer.

(On-press development method)
The image forming layer of the printing plate material of the infrared laser heat melting / fusion method, which is a preferred embodiment of the printing plate material of the present invention, has an infrared laser exposed portion becomes an oleophilic image portion, and an unexposed portion layer is removed. It becomes a non-image part. The unexposed portion can be removed by washing with water, but it is sufficiently possible to perform so-called on-press development in which the unexposed portion is removed using dampening water and / or ink on a printing press.

  The removal of the unexposed portion of the image forming layer on the printing press can be performed by contacting a watering roller or an ink roller while rotating the plate cylinder. It can be performed by various sequences. In that case, the water amount may be adjusted by increasing or decreasing the amount of dampening water required for printing, and the water amount adjustment may be divided into multiple stages or steplessly. You may change it.

  (1) As a sequence for starting printing, a watering roller is brought into contact with the plate cylinder to make one to several dozen rotations, then an ink roller is brought into contact with the plate cylinder to make one to several dozen rotations, and then printing is started. To do.

  (2) As a sequence for starting printing, an ink roller is brought into contact with the plate cylinder to make one to several tens of turns, then a watering roller is brought into contact with the plate cylinder to make one to several tens of turns, and then printing is started. To do.

  (3) As a sequence for starting printing, the water roller and the ink roller are brought into contact with each other substantially simultaneously to rotate the plate cylinder one to several tens of times, and then printing is started.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

Example 1
[Roughened substrate 1]
An aluminum plate (material 1050, tempered H16) having a thickness of 0.24 mm was immersed in a 1% by mass sodium hydroxide aqueous solution at 50 ° C., dissolved so that the dissolved amount became 2 g / m ² , and washed with water. Then, it was immersed in 0.1 mass% hydrochloric acid aqueous solution at 25 ° C. for 30 seconds, neutralized, and then washed with water.

Next, this aluminum plate was subjected to electrolytic surface roughening treatment with an electrolytic solution containing hydrochloric acid 10 g / L and aluminum 0.5 g / L using a sine wave alternating current and a peak current density of 50 A / dm ^2. It was. The distance between the electrode and the sample surface at this time was 10 mm. Perform electrolytic graining treatment is divided into 12 times, and the quantity of electricity used in one treatment (at a positive polarity) as the 40C / dm ^2, treatment quantity of electricity 480C / dm ² in total (at a positive polarity). In addition, a rest period of 5 seconds was provided between each surface roughening treatment.

After electrolytic surface roughening, it is immersed in a 1% by weight sodium hydroxide aqueous solution maintained at 50 ° C. and etched so that the amount of dissolution including the smut of the roughened surface becomes 1.2 g / m ^2. Then, it was washed with water, then immersed in a 10% aqueous sulfuric acid solution maintained at 25 ° C. for 10 seconds, neutralized, and then washed with water. Next, anodization was performed in a 20% sulfuric acid aqueous solution so that the amount of electricity was 150 C / dm ² under a constant voltage condition of 20 V, followed by washing with water.

  Next, after squeezing the surface water after washing with water, it was immersed in a 1% by mass sodium dihydrogen phosphate aqueous solution maintained at 70 ° C. for 30 seconds, washed with water, dried at 80 ° C. for 5 minutes, and roughened. The obtained substrate 1 was obtained. Ra of the substrate 1 was 460 nm (measured at 40 times using RST Plus manufactured by WYKO).

[Preparation of printing plate materials 1 to 13]
A material having the following composition was sufficiently stirred and mixed using a homogenizer, followed by filtration to prepare a coating solution for the hydrophilic layer (1) having a solid content of 15% by mass.

On the roughened substrate 1, the coating solution for the hydrophilic layer (1) is applied using a wire bar so that the applied amount after drying is 1.5 g / m ^2, and is applied at 100 ° C. 3 Dried for minutes. Next, an aging treatment at 60 ° C. for 72 hours was performed to produce a substrate 1 having a hydrophilic layer.

Hydrophilic layer colloidal silica (alkaline): Snowtex-S (manufactured by Nissan Chemical Co., Ltd., solid content 30% by mass) 12.86 parts by mass Necklace-shaped colloidal silica (alkaline): Snowtex-PSM (manufactured by Nissan Chemical Co., Ltd., 35.83 parts by mass Infrared absorbing dye: ADS830WS (manufactured by American-Dye-Source) 0.45 parts by mass Layered mineral particles Montmorillonite: colloidal mineral MO (manufactured by Southern-Clay-Products, average particle diameter) 0.1 μm) was vigorously stirred with a homogenizer to form a 5% by mass water-swelling gel 6.00 parts by mass Sodium carboxymethylcellulose: 4% by mass aqueous solution of CMC1220 (manufactured by Daicel Chemical Industries) 3.75 parts by mass phosphoric acid Of trisodium and 12 water (reagent manufactured by Kanto Chemical Co., Inc.) 0% by weight aqueous solution
0.75 parts by mass Porous metal oxide particles: Silton AMT08 (manufactured by Mizusawa Chemical Co., Ltd., porous aluminosilicate particles, average particle size 0.6 μm) 1.50 parts by mass Porous metal oxide particles: Shilton JC-30 ( Made by Mizusawa Chemical Co., Ltd., porous aluminosilicate particles, average particle size 3 μm) 1.50 parts by mass Pure water 37.36 parts by mass Next, the materials having the following composition were sufficiently stirred and mixed, and then the concentration was appropriately diluted with pure water It adjusted and filtered and obtained the coating liquid of image forming layer (1)-(7) of 8 mass% of solid content. Subsequently, the coating liquid of the image forming layers (1) to (7) having thermoplastic fine particles having different minimum film-forming temperatures (MFT) shown in Table 1 is dried on the substrate 1 having a hydrophilic layer using a wire bar. It applied so that a later application amount might be 0.6 g / m < ² >, and the printing plate materials 1-7 were obtained on the following two conditions.

[Condition 1]
The coated sample was dried at a temperature of 45 ° C. for 3 minutes. Next, heat treatment was performed at 45 ° C. for 24 hours.

[Condition 2]
The coated sample was dried at a temperature of 80 ° C. for 30 seconds. Next, heat treatment was performed at 55 ° C. for 24 hours.

  The mass part ratio in the following table represents the mass ratio in the solid content after drying.

Image forming layers (1) to (7) Composition of coating solution Thermosensitive material and thermoplastic fine particles:
The material in the table below is 88% by mass after drying
Water-soluble resin: Sodium polyacrylate, Aquaric DL522 (manufactured by Nippon Shokubai Co., Ltd.), solid content 2% by mass
(Solid content ratio after drying: 2% by mass)
Layered mineral particles: 5% aqueous solution of hydrophilic smectite SWN manufactured by Coop Chemical Co., Ltd. (solid content ratio after drying: 10% by mass)

[Image formation by infrared laser exposure]
The printing plate material was wound around the exposure drum and fixed. For exposure, a laser beam having a wavelength of 830 nm and a spot diameter of about 18 μm was used, exposure energy was 350 mJ / cm ² , 2400 dpi (dpi represents the number of dots per inch, that is, 2.54 cm), and 175 lines. Formed. The exposed image includes a solid image and a 1 to 99% halftone dot image.

(Printing method)
Printing machine: DAIYA1F-1 manufactured by Mitsubishi Heavy Industries, Ltd., coated paper, dampening water: 2% by mass of Astro Mark 3 (manufactured by Nikken Chemical Laboratory), ink (TK High Unity Red manufactured by Toyo Ink Co., Ltd.) Used to print. The printing plate material was attached to the plate cylinder as it was after exposure, and printed using the same printing sequence as the PS plate.

[Printing evaluation]
(On-press developability)
For each printing plate material, the number of sheets printed from the start of printing was determined for completion of on-press development. The on-machine development end index is that there is no stain on the non-image area on the printed matter, the density of the solid image area is 1.6 or more (measured in the M mode using Macbeth RD918), and 95% halftone dot The image is open. The table shows the number of damaged papers until good printing is obtained.

(Dirt)
The non-image area density of the 200th printed material printed with each printing plate material was measured, and the difference ΔD from the density of the unprinted paper was measured as the background stain density. The measurement was performed using X-Rite 528 manufactured by X-Rite, and the magenta concentration was measured under filter condition status-T. Furthermore, the surface of the non-image portion of the printed material was observed with a magnifying glass 100 times for the stains that were not observed as the density.

ΔD value: Loupe observation 5: Less than 0.01: No stain observed 4: 0.01 to less than 0.03: No spot-like spot stain was observed 3: Less than 0.03 to 0.05: Dot-like Slight spot stains are observed 2: 0.05 to less than 0.07: Spot spot stains are frequently observed 1: 007 or more: Spot spot stains are frequently observed

  From the results of Table 2 above, it can be seen that the printing plate material of the present invention does not impair the printing quality even after it is placed in a condition with good production efficiency (time) and in a high temperature environment.

Example 2
The water-soluble resin of the image forming layer coating solution used in the printing plate material 5 of Example 1 is omitted, and a part of the thermoplastic fine particle vironal PMD-1500 is replaced with the following heat-sensitive material as shown in Table 3, Printing plate materials 8 to 13 were prepared under condition 2.
AVECIA NeoCryl; BT-44, styrene-acrylic resin, minimum film-forming temperature (MFT) 97 ° C
Image forming layers (8) to (13) Coating liquid composition

(Print life)
The number of times until a dot of 3% or more was broken by 10% or more was obtained and used as a printing durability index.

  As is apparent from the table, it is understood that the printing plate material of the present invention is excellent in printing durability and printing quality by adding thermoplastic fine particles.

Claims (2)

In a lithographic printing plate material having an image forming layer that cannot be removed with water by heating on a substrate having a hydrophilic surface, the minimum film-forming temperature in the image forming layer is 120 ° C. to 200 ° C. A lithographic printing plate material comprising resin fine particles. 2. The lithographic printing plate material according to claim 1, wherein the content of the thermoplastic resin fine particles is 50% by mass to 95% by mass of the entire image forming layer.