Thermal recording materials

Abstract

To provide a thermal recording material whereby, when forming an image part, it is possible to prevent fogging from occurring in a non-image part adjacent to the image part.SOLUTION: A thermal recording material has, on a light transmitting support, an infrared absorption layer comprising an infrared absorption dye, a thermal recording layer comprising a non-photosensitive organic silver salt and a reductant, and a protective layer comprising fine particles, in this order from the side close to the light transmitting support. The fine particles are spherical particles mainly composed of a substance with a thermal conductivity of 6.5 W / (m K) or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a heat-sensitive recording material capable of forming an image by irradiation with an infrared laser, and more particularly to a heat-sensitive recording material suitable for producing a plate material. [Background technology]

[0002] As a high-quality image recording method used for preparing a plate material, a wet-process image forming method using a silver halide photosensitive material has been generally used for a long time. However, since the image forming method involving wet processing requires waste liquid treatment such as developer and fixer, which places a large burden on the environment, various dry image forming methods that do not require wet processing have been investigated. As a dry image forming method that can obtain a high contrast equivalent to the wet-process image forming method using a silver halide photosensitive material, there is a method of forming an image using a thermal head or an infrared laser on a thermal recording material having a thermal recording layer on a support. Among them, the thermal recording method using an infrared laser is advantageous from the viewpoint of high density recording and high quality recording.

[0003] As an example of a heat-sensitive recording material that forms an image by irradiation with an infrared laser, JP-A-6-194781 (Patent Document 1) discloses a heat-sensitive recording material that can record high-density images and contains a thermally reducible silver source, a reducing agent for silver ions, a dye that absorbs laser light in the wavelength range of approximately 500 to 1100 nm, and a polymerizable binder.

[0004] When such a thermal recording material is used as a plate material, it is known that the effect of facilitating vacuum contact with a photosensitive material (improving vacuum properties) can be obtained by using a thermal recording material with a roughened surface on the image recording layer side. A typical roughened thermal recording material is a thermal recording material containing fine particles in the outermost layer on the image recording layer side, and for example, the above-mentioned Patent Document 1 describes that an adhesion prevention layer containing wax or silica particles can be used on the image forming layer. JP-A-1998-29377 (Patent Document 2) describes an infrared laser thermal recording material having a thermal layer containing an organic silver salt, an organic silver salt developer, an infrared absorbing dye, and a water-soluble binder on a support, and describes that a protective layer containing a pigment can be used on the thermal layer. Also, JP-A-2002-311535 (Patent Document 3) describes that a barrier layer containing amorphous silica fine particles as a matting agent can be used.

[0005] However, when an image is formed by irradiating an infrared laser onto a heat-sensitive recording material that contains fine particles in the outermost layer and uses a thermally reducible silver source, unintended black spots (spots), so-called fogging, may occur in the non-image area adjacent to the image area. In addition, in a heat-sensitive recording material that contains fine particles in the outermost layer and also contains an infrared absorbing dye or a heat converting dye in the image recording layer, the above-mentioned fogging may become even more noticeable. In a plate material, image reproducibility is of utmost importance, and improvements were required.

[0006] On the other hand, JP-A-59-174389 (Patent Document 4) describes a heat-sensitive recording material having high dynamic color development sensitivity, which is used to form images using a thermal head, and which has a protective layer containing a filler having a specific heat conductivity and a water-soluble polymer binder. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-194781 [Patent Document 2] JP 1998-29377 A [Patent Document 3] JP 2002-311535 A [Patent Document 4] Japanese Patent Application Publication No. 59-174389 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a heat-sensitive recording material which, when an image area is formed, suppresses fogging occurring in a non-image area adjacent to the image area. [Means for solving the problem]

[0009] The above-mentioned problems are solved by the following invention. A thermal recording material comprising, on a light-transmitting support, an infrared-absorbing layer containing an infrared-absorbing dye, a thermal recording layer containing a non-photosensitive organic silver salt and a reducing agent, and a protective layer containing fine particles, in that order from the side closest to the light-transmitting support, wherein the fine particles are spherical fine particles mainly containing a substance having a thermal conductivity of 6.5 W / (m K) or less. Effect of the Invention

[0010] According to the present invention, it is possible to provide a heat-sensitive recording material in which, when an image area is formed, fogging occurring in a non-image area adjacent to the image area is suppressed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below.

[0012] The heat-sensitive recording material of the present invention has, on a light-transmitting support described later, an infrared absorbing layer containing an infrared absorbing dye, a heat-sensitive recording layer containing a non-photosensitive organic silver salt and a reducing agent, and a protective layer containing fine particles, in this order from the side closer to the light-transmitting support. As a result, compared with a heat-sensitive recording material containing an infrared absorbing dye in a heat-sensitive recording layer as described in Patent Document 2, for example, the heat-sensitive recording material of the present invention can suppress fogging occurring in a non-image area adjacent to an image area when an image area is formed.

[0013] Examples of the light-transmitting support of the heat-sensitive recording material of the present invention include resin films such as polyethylene terephthalate, polyethylene naphthalate, cellulose nitrate, and polycarbonate, and inorganic materials such as glass. In the present invention, the light-transmitting support means a support having a total light transmittance of 60% or more, and more preferably 70% or more. The haze value of the light-transmitting support is preferably 10% or less. The light-transmitting support may have known layers such as an easy-adhesion layer, a hard coat layer, and an antistatic layer. The thickness of the light-transmitting support of the present invention is not particularly specified, but is preferably 50 to 300 μm from the viewpoint of handling.

[0014] In the present invention, the infrared absorbing layer of the thermal recording material contains an infrared absorbing dye. The infrared absorbing dye in the present invention means a known compound that absorbs infrared rays. Among them, a dye having absorption in the wavelength region of 600 to 1500 nm is preferable, a dye having an absorption maximum in the wavelength region of 650 to 1100 nm is more preferable, and a dye having an absorption maximum in the wavelength region of 750 to 1100 nm is even more preferable. In addition, since the infrared absorbing dye in the present invention can obtain a thermal recording material capable of forming a high-contrast image suitable for preparing a copybook, it is preferable that the absorption in the wavelength region of 350 to 450 nm, where the emission peak in the ultraviolet region of a high-pressure mercury lamp or a chemical lamp exists, is as small as possible compared with the absorption in the wavelength region of 600 to 1500 nm described above. Specifically, it is preferable that the ratio ε1 / ε2 of the absorbance ε1 at the absorption maximum in the wavelength region of 600 to 1500 nm and the absorbance ε2 at the absorption maximum in the wavelength region of 350 to 450 nm is 4.0 or more. Examples of such dyes include compounds having a polymethine skeleton, such as squarylium, cyanine, merocyanine, and bis(aminoaryl)polymethine. Specific examples of such dyes include compounds represented by the following general formulas (1) to (3), but are not limited to these.

[0015] [ka]

[0016] In general formulas (1) to (3), R 1 ~R 10 is a substituent, and examples thereof include a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an acyl group, an ester group, an amide group, a halogen atom, a hydroxyl group, a thiol group, a thioether group, and a sulfonyl group. These may be the same or different substituents, and may be bonded to other substituents to form a ring structure. X -represents an atom or atomic group having a negative charge, and examples thereof include halogen ions, oxoacids such as perchlorate ions, tetrafluoroborate, hexafluorophosphate, alkyl and aryl sulfonates, etc. Specific examples thereof include, but are not limited to, the following exemplary compounds (1) to (7).

[0017] [ka]

[0018] [ka]

[0019] An example of a method for measuring ε1 and ε2 is to prepare a 2-butanone solution of an infrared absorbing dye and measure the absorption spectrum of the solution using a UV-2600 ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation) in a quartz cell with an optical path length of 1 cm.

[0020] The content of the infrared absorbing dye in the infrared absorbing layer is preferably from 0.05 to 50% by mass, and more preferably from 0.1 to 20% by mass, based on the total solid content of the infrared absorbing layer.

[0021] In the present invention, the infrared absorbing layer preferably contains a binder component together with the infrared absorbing dye. Such a binder component is preferably a thermoplastic resin, and examples thereof include cellulose derivatives such as hydroxyethyl cellulose and hydroxypropyl cellulose, acrylic resins, polyester resins, polyurethane resins, vinyl chloride resins, vinyl acetate resins, polyolefin resins, polyvinyl acetal resins, and polyvinyl alcohol resins. These binder components may be used by dissolving them in water or an organic solvent, or may be used as latex in which hydrophobic polymer solids are dispersed in the form of fine particles, or as polymer molecules dispersed in the form of micelles. In the present invention, the above-mentioned binder components are preferably those which form a light-transmitting coating after drying. Furthermore, these binder components may be used in combination of two or more resins which are compatible with each other as necessary.

[0022] The infrared absorbing layer may contain, in addition to the above-mentioned infrared absorbing dye and binder component, known additives such as a reducing agent, an ultraviolet absorbing agent, an antioxidant, a silane coupling agent, a pigment, a dye, a pH adjuster, a surfactant, an antifoaming agent, a thickener, a softener, a lubricant, an antistatic agent, and an antiblocking agent.

[0023] In the present invention, the infrared absorbing layer of the heat-sensitive recording material is preferably formed by preparing an infrared absorbing layer coating liquid containing the above-mentioned infrared absorbing dye, binder component, additives that can be contained in the infrared absorbing layer, and further a known solvent, and coating the infrared absorbing layer coating liquid on the above-mentioned light-transmitting support and drying the same. The coating amount of the infrared absorbing layer is 0.01 to 8.0 g / m2 in terms of dry mass. 2 is preferably 0.05 to 5.0 g / m 2 is more preferred.

[0024] The heat-sensitive recording layer of the heat-sensitive recording material of the present invention contains a non-photosensitive organic silver salt. The organic silver salt is reduced by heating together with a reducing agent described later to form a silver image. Specifically, silver salts of organic acids such as gallic acid, oxalic acid, behenic acid, stearic acid, palmitic acid, and lauric acid as described in Research Disclosure No. 17029(II) and No. 29963(XVI) related to heat-developable photosensitive materials; silver salts of carboxyalkylthioureas such as 1-(3-carboxypropyl)thiourea and 1-(3-carboxypropyl)-3,3-dimethylthiourea; silver salts of aldehydes such as formaldehyde, acetaldehyde, and butylaldehyde, and aromatic compounds such as salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, and 5,5-thiodisalicylic acid; complexes of silver with polymeric reaction products with aromatic carboxylic acids; silver salts or complexes of thiones such as 3-(2-carboxyethyl)-4-hydroxymethyl-4-thiazoline-2-thione, 3-carboxymethyl-4-methyl-4-thiazoline-2-thione; silver salts or complexes of nitrogen-containing heterocycles selected from imidazole, pyrazole, urazole, 1,2,4-triazole, 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benzotriazole; silver salts of saccharin, 5-chlorosalicylaldoxime, etc.; silver salts of mercaptides, etc. Among these, silver salts of fatty acids having 10 or more carbon atoms are preferred, and silver stearate and silver behenate are more preferred.

[0025] In the present invention, the content of the non-photosensitive organic silver salt contained in the heat-sensitive recording layer can be appropriately adjusted according to the ultraviolet light transmittance required for use as a plate material, and is 0.2 to 3.0 g / m in terms of silver. 2 is preferably 0.5 to 2.0 g / m 2 is more preferred.

[0026] The heat-sensitive recording layer of the heat-sensitive recording material in the present invention contains a reducing agent. Examples of such reducing agents include polyhydroxybenzene compounds such as hydroquinone, catechol, 4-methylcatechol, 4-tert-butylcatechol, chlorohydroquinone, and pyrogallol, polyhydroxybenzoic acid compounds such as gallic acid, methyl gallate, propyl gallate, stearyl gallate, 2,5-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, and ethyl 3,4-dihydroxybenzoate, aminophenol compounds such as 2-aminophenol, 3-aminophenol, and 4-aminophenol, 1-phenyl-3-pyrazolidone and its derivatives, hydroxylamines, polyhydroxyindanes described in JP-A-06-317870, and dihydroxybenzoic acid derivatives described in JP-A-2001-328357. Among the above-mentioned reducing agents, polyhydroxybenzene compounds and polyhydroxybenzoic acid compounds are preferred.

[0027] The content of the reducing agent in the thermal recording layer can vary widely depending on the type of reducing agent and the type of organic silver salt, but is preferably 0.1 to 3.0 mol, more preferably 0.5 to 2.0 mol, per mol of organic silver salt. For various purposes, two or more of the above-mentioned reducing agents may be used in combination.

[0028] In the present invention, the heat-sensitive recording layer of the heat-sensitive recording material preferably contains a so-called color toning agent known in the field of thermography or photothermography. Examples of color toning agents are known in the above-mentioned Research Disclosure on Photothermographic Materials, items 17029(V) and 29963(XXII), and specifically include imides such as phthalimide, mercapto compounds such as 3-mercapto-1,2,4-triazole, phthalazine, phthalazone, 4-methylphthalic acid, tetrachlorophthalic acid and their anhydrides, and benzoxazine derivatives such as 1,3-benzoxazine-2,4-dione. For various purposes, the above-mentioned color toning agents may be used in combination of two or more kinds.

[0029] In the present invention, the heat-sensitive recording layer of the heat-sensitive recording material may contain various accelerators, stabilizers, and precursors thereof for the purpose of suppressing or promoting the formation of image silver, improving the storage stability of the heat-sensitive recording material before and after image formation, etc. Specifically, they may be selected from benzotriazole, 5-methylbenzotriazole, 5-chlorobenzotriazole, 2-mercaptobenzotriazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene, 1-phenyl-5-mercaptotetrazole, 2-amino-5-mercapto-1,3,4-thiadiazole, 3-mercapto-5-phenyl-1,2,4-triazole, 4-benzamido-3-mercapto-5-phenyl-1,2,4-triazole, and the like, which are known as photographic additives. In addition, the above-mentioned accelerators, stabilizers, and precursors thereof may contain two or more kinds for various purposes.

[0030] In the present invention, the heat-sensitive recording layer of the heat-sensitive recording material preferably contains a binder component. Such a binder component is preferably a thermoplastic resin, and for example, the same thermoplastic resin as the binder component of the infrared absorbing layer described above can be preferably contained. Furthermore, the binder component may contain two or more resins that are compatible with each other as necessary.

[0031] The content of the binder component contained in the thermosensitive recording layer is preferably 10 to 70% by mass based on the total solid content of the thermosensitive recording layer.

[0032] The binder component described above preferably does not contain free halide ions such as chloride ions or bromide ions. Halide ions react with the silver ions of the organic silver salt to form photosensitive silver halide, which causes a decrease in the light resistance of the heat-sensitive recording material of the present invention. Specifically, the content of the free halide ions is preferably 500 ppm or less, more preferably 300 ppm or less, and even more preferably 100 ppm or less, relative to the content of the binder component.

[0033] In addition to the above-mentioned components, the heat-sensitive recording layer may contain known additives such as ultraviolet absorbers, antioxidants, silane coupling agents, pigments, dyes, pH adjusters, surfactants, defoamers, thickeners, softeners, lubricants, antistatic agents, and antiblocking agents.

[0034] In the present invention, the thermosensitive recording layer is preferably adjacent to the infrared absorbing layer, which makes it possible to efficiently form an image by irradiating an infrared laser, and to obtain a high-definition image. As a method for forming the thermosensitive recording layer, it is preferable to prepare a thermosensitive recording layer coating liquid containing the above-mentioned organic silver salt, reducing agent, color toner, binder component, and additives that can be contained in the thermosensitive recording layer, and further a known solvent, and to coat the thermosensitive recording layer coating liquid on the above-mentioned infrared absorbing layer and dry it to form the layer. In addition, the coating amount of the thermosensitive recording layer coating liquid is 2.0 to 30.0 g / m2 in terms of dry mass. 2 is preferable, and 5.0 to 20.0 g / m 2 More preferably, 8.0 to 20.0 g / m 2 This makes it possible to more effectively prevent fogging in adjacent non-image areas when an image area is formed.

[0035] The thermal recording material of the present invention has a protective layer containing spherical fine particles mainly containing a substance having a thermal conductivity of 6.5 W / (m K) or less. By containing the spherical fine particles in the protective layer, the vacuum property of the thermal recording material can be improved, and a thermal recording material suitable as a plate material can be prepared.

[0036] Furthermore, by mainly containing a substance having a thermal conductivity of 6.5 W / (m K) or less, the spherical fine particles described above can suppress fogging in adjacent non-image areas when an image area is formed. In the present invention, "mainly containing" means that 50% by mass or more of the fine particles are made up of the substance, preferably 60% by mass or more, and particularly preferably 70% by mass or more. Among substances having a thermal conductivity of 6.5 W / (m·K) or less, examples of organic fine particles include silicone resin (thermal conductivity 0.16 W / (m·K)), polymethyl methacrylate (thermal conductivity 0.21 W / (m·K)), low-density polyethylene (thermal conductivity 0.33 W / (m·K)), high-density polyethylene (thermal conductivity 0.48 W / (m·K)), and polystyrene (thermal conductivity 0.12 W / (m·K)). Examples of inorganic fine particles include, but are not limited to, titania (thermal conductivity 4.0 W / (m·K)), zirconia (thermal conductivity 3.0 W / (m·K)), amorphous silica (thermal conductivity 1.35 W / (m·K)), and mica (thermal conductivity 0.5 W / (m·K)).

[0037] Since fogging of adjacent non-image areas can be more effectively suppressed when an image area is formed, the thermal conductivity of a material having a thermal conductivity of 6.5 W / (m·K) or less is preferably 2.2 W / (m·K) or less. The lower limit of the thermal conductivity of a material having a thermal conductivity of 6.5 W / (m·K) or less is preferably 0.06 W / (m·K) or more. If it is less than 0.06 W / (m·K), there may be cases where the image is missing when an image is formed by irradiating an infrared laser. Therefore, in the present invention, it is particularly preferable that the thermal conductivity of a material having a thermal conductivity of 6.5 W / (m·K) or less is 0.06 to 2.2 W / (m·K).

[0038] Examples of methods for measuring the thermal conductivity of a substance with a thermal conductivity of 6.5 W / (m K) or less include the heat flow meter method described in ASTM E1530: 2006 and the laser flash method described in JIS R1611: 2010. In addition, the thermal conductivity of a substance contained in fine particles can be a known value described in literature such as "Chemical Handbook: Basics, Revised Fourth Edition" (edited by the Chemical Society of Japan) or "Measurement and Evaluation Techniques for Increasing Thermal Conductivity and Thermal Conductivity of Heat Dissipating Materials for Electronic Devices and Parts" (edited by the Technical Information Association, Inc.).

[0039] The above-mentioned fine particles contained in the protective layer in the present invention are spherical fine particles. By the fact that the fine particles are spherical, it is possible to effectively suppress fogging occurring in the adjacent non-image area when the image area is formed. Examples of commercially available fine particles as described above include the Tospearl (registered trademark) series (manufactured by Momentive Performance Materials Japan LLC), which are fine particles of silicone resin, the Flow Beads (registered trademark) series (manufactured by Sumitomo Seika Chemicals Co., Ltd.), which are fine particles of low-density polyethylene, the SX series (manufactured by Soken Chemical Industries, Ltd.), which are fine particles of polystyrene, and the Sunsphere (registered trademark) series (manufactured by AGC Si-Tech Co., Ltd.), which are fine particles of amorphous silica. In addition, spherical fine particles mainly containing zirconia can be obtained by a known synthesis method, for example, the sol-gel method described in JP-A-03-232724. Although these are single fine particles, the form of the fine particles may be either a single fine particle or a fine particle aggregate particle in which fine particles are aggregated.

[0040] The average particle size of the fine particles contained in the protective layer is not particularly limited, but is preferably 2.0 to 20 μm, and more preferably 2.0 to 16 μm. This makes it possible to suppress fogging of adjacent non-image areas when an image area is formed. The average particle size can be calculated based on volume and determined by laser diffraction / scattering particle size distribution measurement. Specifically, a method of measurement using a laser diffraction / scattering particle size distribution measurement instrument MT3000II manufactured by Microtrack Bell Co., Ltd. can be exemplified.

[0041] The content of the fine particles in the protective layer is preferably 0.5% by mass or more, more preferably 1% by mass or more, based on the total solid content of the protective layer in order to improve the vacuum property. Also, from the viewpoint of suppressing fogging of the adjacent non-image area when the image area is formed, the content of the fine particles is preferably 15% by mass or less, based on the total solid content of the protective layer. Therefore, it is particularly preferable that the content of the fine particles is 1 to 15% by mass, based on the total solid content of the protective layer.

[0042] When forming the protective layer, it is preferable to use fine particles dispersed in a protective layer coating liquid described below, and a high-speed stirrer such as a homodisper is suitable for dispersing the fine particles.

[0043] The components other than the above-mentioned fine particles contained in the protective layer and the method of forming the protective layer are not particularly limited, but from the viewpoint of chemical resistance, it is preferable to form by applying a protective layer coating liquid containing a polyisocyanate compound.The above-mentioned polyisocyanate compound is preferably a compound having two or more isocyanate groups in the molecule, and examples thereof include aliphatic polyisocyanate compounds such as dimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, decane diisocyanate, and isophorone diisocyanate, aromatic polyisocyanate compounds such as tolylene diisocyanate, 1,3-phenylene diisocyanate, 1,3-dimethylbenzene-2,6-diisocyanate, and naphthalene-1,4-diisocyanate, and adducts formed by forming dimers or trimers from one or more of these polyisocyanate compounds, or adducts formed by reacting these polyisocyanate compounds with divalent or trivalent polyols. Among these, hexamethylene diisocyanate and its adduct are preferred as the aliphatic polyisocyanate compound, and tolylene diisocyanate and its adduct are preferred as the aromatic polyisocyanate compound. These polyisocyanate compounds may be used alone or in combination of two or more types depending on various purposes. As such polyisocyanate compounds, products that are generally sold as isocyanate-based crosslinking agents can be used as they are, and specific product names include the Takenate (registered trademark) series manufactured by Mitsui Chemicals, Inc., the Burnock (registered trademark) series manufactured by DIC Corporation, and the Coronate (registered trademark) series manufactured by Tosoh Corporation.

[0044] The content of the polyvalent isocyanate compound that can be contained in the protective layer coating liquid in the present invention is preferably 50 to 95 mass % based on the total solids content of the protective layer coating liquid in order to provide excellent alcohol resistance on the surface of the thermal recording material, more preferably 55 to 90 mass %, and even more preferably 59 to 80 mass %.

[0045] The protective layer in the present invention preferably contains a polymeric compound as a binder component together with the polyvalent isocyanate compound. The polymeric compound preferably has two or more hydroxyl groups in the molecule, and examples thereof include polyvinyl alcohol derivatives such as polyvinyl alcohol and polyvinyl acetal, cellulose derivatives such as cellulose acetate, hydroxyethyl cellulose, and hydroxypropyl cellulose, and copolymers of polyhydric alcohols and various monomers, such as acrylic polyol, polyether polyol, polyester polyol, and polycarbonate polyol. These polymeric compounds may be used alone or in combination of two or more kinds depending on various purposes. Among these, it is more preferable to use an acrylic polyol, and examples of commercially available acrylic polyols include the ACRYDIC (registered trademark) series (manufactured by DIC Corporation) and the #6000 series (manufactured by Taisei Fine Chemical Co., Ltd.). Therefore, the protective layer in the present invention can preferably contain an acrylic urethane resin in which an acrylic polyol and a polyvalent isocyanate are reacted.

[0046] In the present invention, the protective layer may contain, in addition to the above-mentioned polyvalent isocyanate compound, polymer compound, and fine particles, known additives such as reducing agents, ultraviolet absorbers, antioxidants, silane coupling agents, pigments, dyes, pH adjusters, surfactants, defoamers, thickeners, softeners, lubricants, antistatic agents, antiblocking agents, and reducing agents.

[0047] In the present invention, the protective layer of the thermal recording material is preferably formed by preparing a protective layer coating liquid containing the above-mentioned polyisocyanate compound, polymer compound, fine particles, additives, and a known solvent, coating the protective layer coating liquid on the thermal recording layer, and drying the coating liquid. The coating amount of the protective layer in the present invention can vary widely depending on the type of polymer compound used and the desired thermal sensitivity, but is preferably 0.5 to 10 g / m2 in terms of dry mass. 2 is preferable, and 1.0 to 8.0 g / m 2It is more preferable that the dry thickness of the protective layer is in the range of 0.7 to 1.4 times the average particle diameter of the spherical fine particles mainly containing a substance with a thermal conductivity of 6.5 W / (m K) or less, because this provides excellent vacuum properties and suppresses the loss of fine particles during handling. Note that the dry thickness of the protective layer in the present invention does not include the height of the fine particles protruding from the protective layer.

[0048] In the present invention, the coating method of the infrared absorbing layer coating liquid, the thermosensitive recording layer coating liquid, and the protective layer coating liquid described above is not particularly limited, and can be selected from various coating methods such as those described in ED Cohen and EB Gutoff, "Modern Coating and Drying Technology", WILEY-VCH, Inc. New York, 1992. Furthermore, it is particularly preferable to simultaneously coat a plurality of layers by a slide coating method using a slit-type die coater or a tandem coating method in which coating and drying treatment are repeated by combining the same or different types of coater devices, in order to improve productivity.

[0049] In the present invention, in addition to the above-mentioned infrared absorbing layer, thermal recording layer, and protective layer, the thermal recording material may further include an easy-adhesion layer or a heat insulating layer between the light-transmitting support and the infrared absorbing layer, an intermediate layer between the infrared absorbing layer, the thermal recording layer, and the protective layer, an easy-peeling layer on the protective layer, or an antistatic layer on the opposite side of the light-transmitting support having the infrared absorbing layer, the thermal recording layer, and the protective layer, as necessary, but as described above, from the viewpoint of obtaining a high-definition image, it is preferable that the infrared absorbing layer and the thermal recording layer are adjacent. In addition, when used as a plate material, in order to suppress refraction or diffusion of light passing through the image recording layer, it is preferable that the thermal recording layer and the protective layer are adjacent, and it is also preferable that the outermost layer on the thermal recording layer side as viewed from the light-transmitting support is a protective layer.

[0050] Using the above-mentioned thermal recording material, an image can be obtained by irradiating an infrared laser imagewise from the protective layer side of the thermal recording material. Examples of the light source of the infrared laser include a semiconductor laser, a He-Ne laser, an Ar laser, a carbon dioxide gas laser, a YAG laser, and a fiber laser. The thermal recording material of the present invention can change the density of the image portion by changing the energy and exposure time of the infrared laser to be irradiated. As a method for irradiating an infrared laser, a thermal CTP setter used in plate making for flexographic printing plates and offset printing plates can be used. Examples of thermal CTP setters include the AURA series (manufactured by Guangzhou Amsky Technology Co Ltd), the Trendsetter (registered trademark) series (manufactured by Eastman Kodak Co.), and the Achieve (registered trademark) series (manufactured by Eastman Kodak Co.).

[0051] After obtaining an image as described above, the heat-sensitive recording material of the present invention can be suitably used as a light-shielding mask material, i.e., a so-called undercoat material, used in making a printing plate such as a flexographic printing plate or a screen printing plate, but can also be used for other purposes, such as a photomask in photolithography. However, the present invention is not limited to this description. EXAMPLES

[0052] The present invention will be described below using examples, but the present invention is not limited to these examples.

[0053] <Example 1>

[0054] <Preparation and Coating of Infrared Absorbing Layer Coating Solution> To 81.0 g of 2-butanone and 24.0 g of methanol, 9.0 g of polyvinyl butyral (Butvar (registered trademark) B-79, manufactured by Eastman Chemical Japan Co., Ltd.) and 0.45 g of exemplary compound (5) (IRT, manufactured by Showa Denko K.K., ε1 / ε2=6.2) as an infrared absorbing dye were added to prepare an infrared absorbing layer coating solution. This infrared absorbing layer coating solution was applied to a polyethylene terephthalate film base having a thickness of 100 μm (total light transmittance 92%, haze value 4%) so that the dry mass was 1.0 g / m 2 The solution was then dried at 60° C. for 1 minute to form an infrared absorbing layer.

[0055] <Preparation of Silver Behenate Dispersion> 20.0 g of silver behenate crystals and 22.0 g of polyvinyl butyral (Butvar B-79) were added to 175 g of 2-butanone, and a silver behenate dispersion (average particle size: 0.8 μm) was obtained using a bead mill (DYNO-MILL KD20B, manufactured by Willy & Bachofen Co.) filled with zirconia beads having a diameter of 0.65 mm.

[0056] <Preparation and Coating of Thermal Recording Layer Coating Solution> To 45.0 g of 2-butanone, 4.2 g of polyvinyl butyral (Butvar B-79), 91.2 g of the above-mentioned silver behenate dispersion, 5.0 g of ethyl 3,4-dihydroxybenzoate, 0.1 g of tetrachlorophthalic anhydride, 1.9 g of phthalazone, and 0.40 g of fumaric acid were added to prepare a thermal recording layer coating solution. This thermal recording layer coating solution was applied to the infrared absorbing layer already obtained as described above so that the dry mass was 13.0 g / m 2 The mixture was then dried at 80° C. for 3 minutes to form a heat-sensitive recording layer.

[0057] <Preparation and Coating of Protective Layer Coating Solution> 11.4 g of ACRYDIC (registered trademark) WFU-289 (DIC Corporation; acrylic polyol resin, solid content 50% by mass) was dissolved in 25.7 g of toluene, and then 0.30 g of Sunsphere H-51 (AGC Si-Tech Corporation; average particle size 5.0 μm), which is a spherical microparticle mainly containing amorphous silica (thermal conductivity 1.35 W / (m K)), was added and stirred to make the whole homogenous. Then, 14 g of Coronate HL (Tosoh Corporation; polyisocyanate, solid content 75% by mass) was added while stirring to obtain a protective layer coating solution. This protective layer coating solution was applied to the above-mentioned thermal recording layer so that the dry mass was 4.0 g / m 2 The coating was applied using a wire bar so that the coating had a thickness of 4 μm, and the coating was dried at 80° C. for 3 minutes, and then heated at 40° C. for 5 days to form a protective layer. In this way, the heat-sensitive recording material of Example 1 was obtained.

[0058] <Example 2> The thermal recording material of Example 2 was obtained in the same manner as in Example 1, except that in the preparation and application of the protective layer coating liquid of Example 1, 0.30 g of Sunsphere H-31 (manufactured by AGC Si-Tech Co., Ltd.; average particle diameter 3.0 μm), which is a spherical microparticle mainly containing amorphous silica, was added instead of Sunsphere H-51 to obtain the protective layer coating liquid.

[0059] <Example 3> The thermal recording material of Example 3 was obtained in the same manner as in Example 1, except that in the preparation and application of the protective layer coating liquid of Example 1, 0.30 g of Sunsphere H-121 (manufactured by AGC Si-Tech Co., Ltd.; average particle diameter 12.0 μm), which is a spherical microparticle mainly containing amorphous silica, was added instead of Sunsphere H-51 to obtain the protective layer coating liquid.

[0060] <Example 4> The thermal recording material of Example 4 was obtained in the same manner as in Example 1, except that in the preparation and application of the protective layer coating solution of Example 1, 0.30 g of Sunsphere H-201 (manufactured by AGC Si-Tech Co., Ltd.; average particle diameter 20.0 μm), which is a spherical microparticle mainly containing amorphous silica, was added instead of Sunsphere H-51 to obtain the protective layer coating solution.

[0061] <Example 5> The thermal recording material of Example 5 was obtained in the same manner as in Example 1, except that in the preparation and application of the protective layer coating solution of Example 1, 0.30 g of Tospearl 145 (manufactured by Momentive Performance Materials Japan, LLC; average particle size: 4.5 μm), which is spherical fine particles mainly containing silicone resin (thermal conductivity: 0.16 W / (m K)), was added instead of Sunsphere H-51 to obtain a protective layer coating solution.

[0062] <Example 6> The thermal recording material of Example 6 was obtained in the same manner as in Example 1, except that in the preparation and coating of the protective layer coating solution of Example 1, 0.30 g of Flow Beads LE-1080 (manufactured by Sumitomo Seika Chemicals Co., Ltd.; average particle size: 6.0 μm), which are spherical fine particles mainly containing low-density polyethylene resin (thermal conductivity: 0.33 W / (m K)), was added instead of Sunsphere H-51 to obtain a protective layer coating solution.

[0063] <Example 7> The thermal recording material of Example 7 was obtained in the same manner as in Example 1, except that in the preparation and coating of the protective layer coating solution of Example 1, 0.30 g of SX-500H (manufactured by Soken Chemical & Engineering Co., Ltd.; average particle size: 5.0 μm), which is spherical fine particles mainly containing polystyrene resin (thermal conductivity: 0.12 W / (m K)), was added instead of Sunsphere H-51 to obtain a protective layer coating solution.

[0064] <Example 8> The thermal recording material of Example 8 was obtained in the same manner as in Example 1, except that in the preparation and coating of the protective layer coating solution in Example 1, spherical fine particles (average particle size 5.1 μm) mainly containing zirconia (thermal conductivity 3.0 W / (m K)) were prepared by the sol-gel method using an aqueous solution of zirconium hydrate instead of Sunsphere H-51, and 0.30 g of this was added to obtain the protective layer coating solution.

[0065] <Example 9> A heat-sensitive recording material of Example 9 was obtained in the same manner as in Example 1, except that in the preparation and coating of the protective layer coating solution in Example 1, the amount of Sunsphere H-51 added was changed to 0.04 g to obtain a protective layer coating solution.

[0066] <Example 10> The heat-sensitive recording material of Example 10 was obtained in the same manner as in Example 1, except that in the preparation and coating of the protective layer coating solution of Example 1, the amount of Sunsphere H-51 added was 0.12 g to obtain a protective layer coating solution.

[0067] <Example 11> A heat-sensitive recording material of Example 11 was obtained in the same manner as in Example 1, except that in the preparation and coating of the protective layer coating solution of Example 1, the amount of Sunsphere H-51 added was changed to 1.8 g to obtain a protective layer coating solution.

[0068] <Example 12> A heat-sensitive recording material of Example 12 was obtained in the same manner as in Example 1, except that in the preparation and coating of the protective layer coating solution of Example 1, the amount of Sunsphere H-51 added was changed to 4.1 g to obtain a protective layer coating solution.

[0069] <Example 13> In the preparation and application of the protective layer coating solution in Example 1, the protective layer coating solution had a dry mass of 8.5 g / m 2 A heat-sensitive recording material of Example 13 was obtained in the same manner as in Example 1, except that the coating was performed using a wire bar so that the coating had a thickness of 8.5 μm.

[0070] <Example 14> In the preparation and application of the protective layer coating solution in Example 1, the protective layer coating solution had a dry mass of 5.5 g / m 2 A heat-sensitive recording material of Example 14 was obtained in the same manner as in Example 1, except that the coating was performed using a wire bar so that the coating had a thickness of 5.5 μm.

[0071] <Example 15> In the preparation and application of the thermosensitive recording layer coating solution in Example 1, the dry mass of the thermosensitive recording layer coating solution was 6.0 g / m 2 A heat-sensitive recording material of Example 15 was obtained in the same manner as in Example 1, except that coating was performed using a wire bar so that the coating liquid was as follows:

[0072] <Example 16> In the preparation and application of the thermosensitive recording layer coating solution in Example 1, the thermosensitive recording layer coating solution was prepared so that the dry mass was 10.0 g / m 2 A heat-sensitive recording material of Example 16 was obtained in the same manner as in Example 1, except that coating was performed using a wire bar so that the coating liquid was as follows:

[0073] <Comparative Example 1> A thermal recording material of Comparative Example 1 was obtained in the same manner as in Example 1, except that in the preparation and coating of the protective layer coating solution of Example 1, 0.30 g of spherical fine particles (average particle size 10.8 μm) mainly containing crystalline silica (thermal conductivity 10 W / (m K)) was added instead of Sunsphere H-51 to obtain a protective layer coating solution.

[0074] <Comparative Example 2> A thermal recording material of Comparative Example 2 was obtained in the same manner as in Example 1, except that in the preparation and application of the protective layer coating solution in Example 1, 0.30 g of Alnabeads (registered trademark) CB-P05 (manufactured by Showa Denko K.K.; average particle size: 4.0 μm), which are spherical fine particles mainly containing alumina (thermal conductivity: 29 W / (m K)), was added instead of Sunsphere H-51 to obtain a protective layer coating solution.

[0075] <Comparative Example 3> A heat-sensitive recording material of Comparative Example 3 was obtained in the same manner as in Example 1, except that in Example 1, no infrared absorbing layer was applied, and 0.12 g of exemplary compound (5) was added to the heat-sensitive recording layer coating solution and coated on the PET base.

[0076] <Comparative Example 4> A thermal recording material of Comparative Example 4 was obtained in the same manner as in Example 1, except that in the preparation and coating of the protective layer coating solution of Example 1, 0.30 g of Syloid (registered trademark) 378 (manufactured by GCP Japan, Ltd.; average particle size: 5.5 μm), which is irregular fine particles mainly containing amorphous silica (thermal conductivity: 1.35 W / (m K)), was added instead of Sunsphere H-51 to obtain a protective layer coating solution.

[0077] The thermal recording materials of Examples 1 to 16 and Comparative Examples 1 to 4 thus obtained were exposed to an infrared laser using a thermal CTP setter (AURA600E, manufactured by Guangzhou Amsky Technology Co Ltd) at a drum rotation speed of 300 rpm and a laser output of 250 mW to obtain a 50 μm thin line (length 200 mm).

[0078] <Evaluation of fogging in non-image areas> After obtaining the image as described above, the number of black spots not present in the image data, i.e., the number of fogs, was counted by observing a visual field of 0.5 mm square on the center line of the image with an optical microscope (magnification 500 times). Fogs with a diameter of 3 to 10 μm were counted, and the results are shown in Table 1 as follows: ◎ indicates that no fog was observed, ◯ indicates that 1 to 2 very thin fogs were observed that do not affect the return characteristics, △ indicates that 3 to 5 very thin fogs were observed that do not affect the return characteristics, and × indicates that fogs that affect the return characteristics were observed. Among these, ◎, ◯, and △ were determined to be thermal recording materials in which fog in non-image areas was suppressed.

[0079] <Vacuum performance evaluation> In the non-image areas of the thermal recording materials of Examples 1 to 16 and Comparative Examples 1 to 4, the Beck smoothness was measured under conditions of 25°C, 50% RH, and an air inflow of 1 cc using a Beck smoothness tester HK type (manufactured by Kumagai Riki Kogyo Co., Ltd.) Beck smoothness of 1 to 100 sec was evaluated as ⊚, 101 to 500 sec was evaluated as ◯, and 501 sec or more was evaluated as △.

[0080] [Table 1]

[0081] As is clear from the results in Table 1, when an image area is formed according to the present invention, a heat-sensitive recording material can be obtained in which fog occurring in the non-image area adjacent to the image area is suppressed.

Claims

[Claim 1] A thermal recording material having, on a light-transmitting support, an infrared absorbing layer containing an infrared absorbing dye, a thermal recording layer containing a non-photosensitive organic silver salt and a reducing agent, and a protective layer containing fine particles, in this order from the side closest to the light-transmitting support, wherein the fine particles are spherical fine particles mainly containing a substance having a thermal conductivity of 6.5 W / (m K) or less.

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