Thermal recording materials

Abstract

To provide a thermal recording material that allows reduction in ejecta from the surface of the thermal recording material irradiated with an infrared laser, giving a high-contrast image.SOLUTION: A thermal recording material includes, on a light transmitting support, an image formation layer including an infrared absorption dye with the ratio of a molar extinction coefficient ε(830) at 830 nm to a molar extinction coefficient ε(365) at 365 nm, ε(830) / ε(365), of 4.0 or more, a non-photosensitive organic silver salt, and a reductant, wherein the total light transmittance based on JIS K7361-1: 1997 is 55% or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a heat-sensitive recording material which reduces ejections from the surface of the heat-sensitive recording material upon irradiation with an infrared laser, and which is capable of producing a high-contrast image. [Background technology]

[0002] As a high-quality image forming 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, the wet-process image forming method requires waste liquid treatment such as developer and fixer, which places a large burden on the environment, so various dry image forming methods that do not require wet processing have been studied. Currently, image forming systems such as inkjet printers, electrophotography, and dye thermal transfer systems are in practical use. However, these dry image forming methods have difficulty in obtaining a so-called high-contrast plate material that has excellent light shielding properties in the image area and excellent light transmittance in the non-image area.

[0003] As a dry image forming method capable of obtaining a high contrast equivalent to that of a wet processing image forming method using a silver halide photosensitive material, there is a method of forming an image on a thermal recording material having a thermal recording layer on a support using a thermal head or an infrared laser. Among them, a thermal recording method using an infrared laser is advantageous from the viewpoint of high density recording and high image quality recording. As a thermal recording material that can be imaged by an infrared laser, for example, JP-A-6-194781 (Patent Document 1) discloses a thermal recording material containing a thermally reducible silver source, a reducing agent for silver ions, a dye that absorbs laser light in the wavelength range of about 500 to 1100 nm, and a polymeric binder, and JP-A-10-29377 (Patent Document 2) discloses a thermal recording material having a thermal layer containing an organic silver salt, a developer for the organic silver salt, a merocyanine infrared absorbing dye having a specific structure, and a water-soluble binder. Furthermore, JP-A No. 2001-10229 (Patent Document 3) discloses a thermal color image forming material containing a non-photosensitive organic silver salt, a reducing agent for silver ions, a binder, a color tone adjusting agent, and an absorbent that absorbs radiation in the wavelength range of 750 to 1100 nm.

[0004] In thermal recording methods using infrared lasers, infrared lasers are used to locally heat a thermal recording material, causing the thermal recording layer to develop color and create an image. However, because infrared lasers have high energy, the components contained in the thermal recording material and by-products produced during the color development process of the thermal recording layer volatilize or explode as ejection from the surface of the thermal recording material, contaminating the surface of the thermal recording material and the infrared laser irradiation device.

[0005] As a method for solving the above problems, it is known to provide another layer on the thermal recording layer. For example, JP-A-2002-311535 (Patent Document 4) discloses a thermally developable material having a thermally developable image forming layer on a support and a barrier layer containing a specific water-insoluble aromatic polyester, and it is described that the barrier layer effectively prevents the diffusion of fatty acids and other chemical substances from the thermally developable material. JP-A-2004-9583 (Patent Document 5) discloses an image forming material in which an image forming layer containing a non-photosensitive organic silver salt and a reducing agent, and a protective layer are laminated in this order on a support, and the farther from the support the layer is, the more crosslinking agent is contained, and it is described that the image forming material can reduce the amount of compounds that emerge to the surface when the latent image after imagewise heating or exposure is heat-developed. However, there has been a demand for further improvement in the effect of reducing the ejection generated from the surface of the thermal recording material by irradiation with an infrared laser.

[0006] On the other hand, JP-A-11-34495 (Patent Document 6) discloses a thermosensitive recording material having a thermosensitive recording layer and an undercoat layer containing a specific gelatin and a layered inorganic compound on a support, and the publication states that a light transmittance adjusting layer can be provided. Also, JP-A-2003-1937 (Patent Document 7) discloses a thermosensitive recording material having a first thermosensitive coloring layer and a light reflecting layer having a total light transmittance of 30% or less, in that order, on one side of a transparent support, and a second thermosensitive coloring layer on the other side of the transparent support. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-194781 [Patent Document 2] Japanese Patent Application Publication No. 10-29377 [Patent Document 3] JP 2001-10229 A [Patent Document 4] JP 2002-311535 A [Patent Document 5] JP 2004-9583 A [Patent Document 6] Japanese Patent Application Publication No. 11-34495 [Patent Document 7] JP 2003-1937 A 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 reduces ejections from the surface of the heat-sensitive recording material upon irradiation with an infrared laser and which allows a high-contrast image to be obtained. [Means for solving the problem]

[0009] The above-mentioned problems are solved by the following invention. A thermal recording material having an image forming layer on a light-transmitting support, the image forming layer containing an infrared absorbing dye having a ratio of the molar absorption coefficient ε(830) at 830 nm to the molar absorption coefficient ε(365) at 365 nm, ε(830) / ε(365), of 4.0 or more, a non-photosensitive organic silver salt, and a reducing agent, and having a total light transmittance of 55% or more based on JIS K7361-1:1997. Effect of the Invention

[0010] According to the present invention, it is possible to provide a heat-sensitive recording material which reduces ejections from the surface of the heat-sensitive recording material upon irradiation with an infrared laser and which provides a high-contrast image. 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 a light-transmitting support. Examples of such light-transmitting supports 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 in the present invention is not particularly specified, but is preferably 50 to 300 μm from the viewpoint of handling.

[0013] The heat-sensitive recording material of the present invention has an image-forming layer on a light-transmitting support. In the present invention, the image-forming layer means a system capable of forming a light-shielding image by developing color in a portion irradiated with an infrared laser.

[0014] The image forming layer of the thermal recording material of the present invention contains an infrared absorbing dye having a ratio of the molar absorption coefficient ε(830) at 830 nm to the molar absorption coefficient ε(365) at 365 nm, ε(830) / ε(365), of 4.0 or more. The infrared absorbing dye in the present invention is preferably a dye having absorption in the wavelength region of 600 to 1500 nm, more preferably having an absorption maximum in the wavelength region of 650 to 1200 nm, and even more preferably having an absorption maximum in the wavelength region of 750 to 1100 nm. The infrared absorbing dye in the present invention has low absorption in the wavelength region of 350 to 450 nm, where the emission peak in the ultraviolet region of high pressure mercury lamps and chemical lamps exists, that is, the above-mentioned ε(830) / ε(365) value is 4.0 or more, so that the thermal recording material can obtain a high contrast image by irradiation with an infrared laser. The upper limit of ε(830) / ε(365) is not particularly limited. Examples of such infrared absorbing 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 the present invention is not limited to these.

[0015] [ka]

[0016] In general formulas (1) to (3), R 1 ~R 10 is a substituent, and examples of the substituent 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. In addition, in the general formulas (1) to (3), 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 the molar extinction coefficients (ε(830) and ε(365)) described above 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] In the present invention, a high contrast image means that the difference Dmax-Dmin between the maximum ultraviolet light transmission density (Dmax) of the image area and the ultraviolet light transmission density (Dmin) of the non-image area is 3.0 or more, and more preferably 3.5 or more. The ultraviolet light transmission density can be measured, for example, by using X-Rite (registered trademark) 361T manufactured by Videojet X-Rite Inc. in ultraviolet light mode.

[0021] The content of the infrared absorbing dye is not particularly limited, but is preferably from 0.01 to 25% by mass, and more preferably from 0.02 to 15% by mass, based on the total solid content of the image forming layer.

[0022] In the present invention, the image forming layer may contain a single infrared absorbing dye or may contain two or more kinds of infrared absorbing dyes.

[0023] The image forming layer of the thermal 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, the silver salt may be a silver salt of an organic acid such as gallic acid, oxalic acid, behenic acid, stearic acid, palmitic acid, or lauric acid, as described in Research Disclosure No. 17029(II) or No. 29963(XVI) relating to thermally developable photosensitive materials; a silver salt of a carboxyalkylthiourea such as 1-(3-carboxypropyl)thiourea or 1-(3-carboxypropyl)-3,3-dimethylthiourea; a silver salt of an aldehyde such as formaldehyde, acetaldehyde, or butylaldehyde, or an aromatic amine such as salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, or 5,5-thiodisalicylic acid. Examples of the silver salt include a complex of a polymer reaction product with a carboxylic acid and silver; a silver salt or complex of thiones such as 3-(2-carboxyethyl)-4-hydroxymethyl-4-thiazoline-2-thione and 3-carboxymethyl-4-methyl-4-thiazoline-2-thione; a silver salt or complex of a nitrogen-containing heterocycle selected from imidazole, pyrazole, urazole, 1,2,4-triazole, 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benzotriazole; a silver salt of saccharin, 5-chlorosalicylaldoxime, etc.; and a silver salt of a mercaptide. Among these, a silver salt of a fatty acid having 10 or more carbon atoms is preferred, and silver stearate and silver behenate are particularly preferred.

[0024] In the present invention, the content of the non-photosensitive organic silver salt contained in the image forming layer can be appropriately adjusted according to the ultraviolet light transmittance density 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.

[0025] The image forming layer of the heat-sensitive recording material of the present invention preferably does not substantially contain photosensitive silver halide. Here, "substantially does not contain" means that the amount of photosensitive silver halide contained in the image forming layer is less than 1% by mass based on the total solid content of the image forming layer, which suppresses the increase in transmission density in non-image areas during storage and normal use of the heat-sensitive recording material of the present invention, and provides a heat-sensitive recording material capable of forming high-contrast images.

[0026] The image forming layer of the thermal recording material of 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-6-317870, and dihydroxybenzoic acid derivatives described in JP-A-2001-328357. Among the above-mentioned reducing agents, polyhydroxybenzene compounds and polyhydroxybenzoic acid compounds are preferred from the viewpoint of obtaining a high-contrast image.

[0027] The content of the reducing agent in the image forming 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] The image forming layer of the thermal recording material of the present invention 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 Thermally Developable Photosensitive 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, two or more of the above color toning agents may be used in combination.

[0029] The image forming layer of the thermal recording material of the present invention 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 thermal 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, etc., which are known as photographic additives. In addition, for various purposes, the above-mentioned accelerators, stabilizers and precursors thereof may be used in combination of two or more kinds.

[0030] The image-forming layer of the heat-sensitive recording material of the present invention preferably contains a binder component for the purpose of holding the infrared absorbing dye, the non-photosensitive organic silver salt, and the reducing agent. 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 such as polyvinyl butyral 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 latexes 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 image-forming layer of 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.

[0031] The image forming layer of the heat-sensitive recording material of the present invention may contain, in addition to the above-mentioned infrared absorbing dye, non-photosensitive organic silver salt, reducing agent, and binder component, known additives such as ultraviolet absorbers, antioxidants, silane coupling agents, pigments, dyes, pH adjusters, surfactants, defoamers, thickeners, softeners, lubricants, antistatic agents, and antiblocking agents depending on various purposes.

[0032] The method for forming the image forming layer of the heat-sensitive recording material of the present invention can be exemplified by preparing an image forming layer coating liquid containing the above-mentioned infrared absorbing dye, non-photosensitive organic silver salt, reducing agent, binder component, additives that can be contained in the heat-sensitive recording layer, and further a known solvent, and coating the image forming layer coating liquid on the above-mentioned light-transmitting support and drying the image forming layer. The coating amount of the image forming layer coating liquid is 3.0 to 50.0 g / m2 in terms of dry mass. 2 is preferable, and 5.0 to 40.0 g / m 2 More preferably, 8.0 to 30.0 g / m 2 is more preferred.

[0033] As long as the above-mentioned elements are provided, the composition of the image-forming layer of the heat-sensitive recording material of the present invention is not particularly limited, but since a high-contrast image can be obtained by irradiation with an infrared laser, the image-forming layer preferably has an infrared absorbing layer containing an infrared absorbing dye on a light-transmitting support, and a heat-sensitive recording layer containing a non-photosensitive organic silver salt and a reducing agent on the infrared absorbing layer separately. In addition, since it can effectively reduce the ejection during irradiation with an infrared laser, it is preferable that the image-forming layer has a protective layer on the outermost surface. Therefore, a particularly preferred embodiment of the heat-sensitive recording material of the present invention has an infrared absorbing layer, a heat-sensitive recording layer, and a protective layer on a light-transmitting support in this order from the side closer to the light-transmitting support.

[0034] When the image forming layer has an infrared absorbing layer, the infrared absorbing layer preferably contains a binder for the purpose of holding the infrared absorbing dye. Examples of such binders include binders that can be preferably contained in the image forming layer. The content of the infrared absorbing dye in the infrared absorbing layer is not particularly limited, but is preferably 0.05 to 50 mass %, more preferably 0.1 to 20 mass %, based on the total solid content of the infrared absorbing layer.

[0035] In one preferred embodiment, the infrared absorbing layer contains a reducing agent in addition to the infrared absorbing dye and binder component. An example of such a reducing agent is the reducing agent contained in the image forming layer. The reducing agents contained in the infrared absorbing layer and the thermosensitive recording layer may be the same or different, or two or more types may be contained.

[0036] The infrared absorbing layer is preferably formed by preparing an infrared absorbing layer coating liquid containing the above-mentioned infrared absorbing dye, binder component, reducing agent, and additives that can be contained in the image forming layer, and further a known solvent, and coating the infrared absorbing layer coating liquid on the above-mentioned light-transmitting support and drying it. The coating amount of the infrared absorbing layer coating liquid 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.

[0037] When the image forming layer has a thermosensitive recording layer, the thermosensitive recording layer preferably contains a binder for the purpose of holding the non-photosensitive organic silver salt and the reducing agent. Examples of such binders include binders that can be preferably contained in the image forming layer. The binder component of the thermosensitive recording layer preferably does not contain free halide ions such as chloride ions and bromide ions. Halide ions react with silver ions of the organic silver salt to form photosensitive silver halide, which causes a decrease in the light resistance of the thermosensitive recording material of the present invention. Specifically, the content of the binder component is preferably 100 ppm or less.

[0038] In the present invention, when the image forming layer has an infrared absorbing layer and a thermosensitive recording layer, it is preferable that the infrared absorbing layer and the thermosensitive recording layer are adjacent to each other, which makes it possible to efficiently form an image by irradiating an infrared laser, and to obtain an image with a particularly high contrast. As a method for forming a 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 image forming 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, 7.0 to 15.0 g / m 2 is more preferred.

[0039] When the image forming layer has a protective layer, it is preferable that the protective layer contains at least hydrophilic particles and a hydrophobic resin, which can effectively reduce ejection of material during irradiation with an infrared laser.

[0040] In the present invention, hydrophilic particles refer to particles whose surface is easily wetted by water. Specifically, inorganic particles whose surface is easily wetted by water, such as metals such as gold, silver, copper, metal oxides such as silica, alumina, zirconia, layered silicates, or composites thereof, organic particles whose surface is easily wetted by water, such as acrylic particles, styrene particles, melamine particles, and organic-inorganic composite particles whose surface is easily wetted by water, can be used. As a method for determining whether a particle is hydrophilic or not, a method can be exemplified in which 10 mL of pure water is measured in a glass beaker, 0.1 g of particles are added thereto, stirred, and left to stand for 10 minutes, and if the particles remain floating on the water surface and do not separate, they are judged to be hydrophilic. The hydrophilic particles may be subjected to a known surface treatment. Two or more types of hydrophilic particles may be used in combination.

[0041] Among the above-mentioned hydrophilic particles, hydrophilic inorganic particles are preferred because they are highly effective in reducing ejections that occur from the surface of a heat-sensitive recording material upon irradiation with an infrared laser.

[0042] The lower limit of the average particle size of the hydrophilic particles is not particularly limited, but it is preferably 1 μm or more since it can effectively reduce the ejection generated from the surface of the thermal recording material by irradiation with an infrared laser. The upper limit of the average particle size of the hydrophilic particles is not particularly limited, but it is preferably 10 μm or less since it can obtain a high-contrast image. The average particle size can be calculated based on the volume obtained 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.

[0043] The hydrophilic particles that the protective layer of the present invention can contain can be commercially available. For example, silica particles include the Seahoster (registered trademark) KE series sold by Nippon Shokubai Co., Ltd., the Sunsphere (registered trademark) series sold by AGC Silysia Chemical Co., Ltd., and the Silica (registered trademark) series sold by Fuji Silysia Chemical Co., Ltd.; alumina particles include the fine alumina SA30 series, SA40 series, and SMM series sold by Nippon Light Metal Co., Ltd.; acrylic particles include the Chemisnow (registered trademark) MX series sold by Soken Chemical Co., Ltd., and the Techpolymer (registered trademark) AQS series sold by Sekisui Chemical Co., Ltd.; melamine particles include the Optobeads (registered trademark) series sold by Nissan Chemical Co., Ltd., and the Eposter (registered trademark) series sold by Nippon Shokubai Co., Ltd., and all of them can be preferably used.

[0044] The content of hydrophilic particles that the protective layer can contain is not particularly limited, but is preferably 1.2 to 40% by mass, and more preferably 1.6 to 30% by mass, based on the total solid content of the protective layer.

[0045] The hydrophobic resin that the protective layer can contain is not particularly limited, and may contain known hydrophobic resins such as acrylic resins, urethane resins, silicone resins, acrylic urethane resins, polyester resins, cellulose acetate resins, and epoxy resins. In the present invention, the hydrophobic resin means a resin having a solubility of less than 1 g in 100 g of water at 25° C. Two or more types of hydrophobic resins may be used in combination.

[0046] Although the components contained in the protective layer and the method for forming the protective layer are not particularly limited, it is preferable to form the protective layer by applying a protective layer coating liquid containing hydrophilic particles, a polyvalent isocyanate compound, and a polyol compound, since this provides a protective layer that can effectively reduce ejections generated from the surface of the thermal recording material by irradiation with an infrared laser. The polyvalent isocyanate compound and the polyol compound crosslink to generate various urethane resins, which are hydrophobic resins. The 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 in which one or more of these polyisocyanate compounds form a dimer or trimer; and adducts in which these polyisocyanate compounds react with a divalent or trivalent polyol. 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 Burnock (registered trademark) series manufactured by DIC Corporation and the Coronate (registered trademark) series manufactured by Tosoh Corporation.

[0047] The content of the polyvalent isocyanate compound that can be contained in the protective layer coating liquid in the present invention is preferably 59 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 59 to 90 mass %, and even more preferably 59 to 80 mass %.

[0048] Examples of polyol compounds that can be contained in the protective layer coating solution of the present invention include 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 polymer compounds may be used alone or in combination of two or more depending on various purposes. Among these, it is more preferable to use 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 of the present invention preferably contains an acrylic urethane resin in which an acrylic polyol and a polyvalent isocyanate are reacted.

[0049] In the present invention, the method for forming the protective layer is preferably to prepare a protective layer coating liquid containing the above-mentioned hydrophilic particles, hydrophobic resin, additives that can be contained in the image forming layer, and further a known solvent, and to coat the protective layer coating liquid on the above-mentioned thermosensitive recording layer and dry it to form the protective layer. The coating amount of the protective layer coating liquid is preferably 1.5 to 10 g / m2 in terms of dry mass. 2 is preferable, and 2 to 8 g / m 2 is more preferred.

[0050] 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 in terms of improving productivity to simultaneously coat multiple layers by a slide coating method using a slit-type die coater or a tandem coating method in which coating and drying are repeated by combining the same or different types of coater devices.

[0051] In addition to the above-mentioned infrared absorbing layer, thermosensitive recording layer, and protective layer, the thermosensitive recording material of the present invention may further include, if necessary, an easy-adhesion layer or a heat-insulating layer between the light-transmitting support and the infrared absorbing layer, an intermediate layer between each of the infrared absorbing layer, the thermosensitive recording layer, and the protective layer, an easy-peel layer on the protective layer, or an antistatic layer on the surface of the light-transmitting support opposite to the surface having the infrared absorbing layer, the thermosensitive recording layer, and the protective layer. However, from the viewpoint of obtaining a high-contrast image as described above, it is preferable that the infrared absorbing layer and the thermosensitive recording layer are adjacent to each other.

[0052] The thermal recording material of the present invention has a total light transmittance of 55% or more based on JIS K7361-1:1997. By achieving such a total light transmittance, ejections generated from the surface of the thermal recording material due to irradiation with an infrared laser are reduced. Since ejections are effectively reduced, the total light transmittance is preferably 59% or more, and particularly preferably 64% or more. A specific method for measuring the total light transmittance can be, for example, a method of measuring with a haze meter HZ-V3 (manufactured by Suga Test Instruments Co., Ltd.) under a D65 light source.

[0053] The upper limit of the total light transmittance of the heat-sensitive recording material of the present invention is not particularly limited, and can vary widely depending on the absorption in the visible light wavelength region of the infrared absorbing dye contained in the image forming layer. However, since a high contrast image can be obtained, it is preferably 86% or less.

[0054] The method for controlling the total light transmittance to 55% or more is not particularly limited, and examples thereof include a method for adjusting the content of the infrared absorbing dye in the image forming layer, a method for adjusting the film thickness of the image forming layer, and a method for incorporating a dye or pigment (such as carbon black) other than the infrared absorbing dye in the image forming layer.

[0055] Using the above-mentioned thermal recording material, an image can be obtained by irradiating an infrared laser imagewise from the image forming 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 part by changing the energy and exposure time of the infrared laser to be irradiated. As a method of irradiating an infrared laser, a thermal CTP setter used for plate making of 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.).

[0056] As a method for measuring the ultraviolet light transmission density of the image part obtained by irradiating the above-mentioned thermal recording material with an infrared laser using a thermal CTP setter or the like, a method using a transmission densitometer can be exemplified. When measuring the ultraviolet light transmission density, it is preferable to measure a filled-in part of a size suitable for the light receiving part of the transmission densitometer, rather than a part of the image part where image parts and non-image parts are mixed in a narrow range, such as halftone dots or thin lines, in order to obtain stability of the measured value. As an example of a transmission densitometer that can measure the ultraviolet light transmission density, the above-mentioned X-Rite361T can be exemplified.

[0057] 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

[0058] The present invention will be described below using examples, but the present invention is not limited to these examples. In the description, "%" is based on mass.

[0059] <Example 1>

[0060] <Preparation of Thermal Recording Material 1> <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., ε(830) / ε(365)=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 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.

[0061] <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.

[0062] <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, and 1.9 g of phthalazone 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 at a concentration of 1.1 g / m2 in terms of silver. 2 The mixture was then dried at 80° C. for 3 minutes to form a heat-sensitive recording layer.

[0063] <Preparation and Application of Protective Layer Coating Solution> To 25.7 g of toluene, 15.2 g of ACRYDIC WBU-1218 (DIC Corporation; acrylic polyol solution, solid content 30% by mass) and 0.35 g of SEAHOSTAR KE-P250 (Nippon Shokubai Co., Ltd.; hydrophilic silica particles, average particle size 2.5 μm) were added, and the whole was homogenized by stirring. Then, 12 g of CORONATE 2715 (Tosoh Corporation; polyisocyanate modified solution, solid content 90% by mass) was added with stirring to obtain a protective layer coating solution. This protective layer coating solution was applied to the above-mentioned thermal recording layer to a dry mass of 4.5 g / m 2 The coating was applied using a wire bar so that the coating became as follows: After drying at 80°C for 3 minutes, the coating was heated at 40°C for 5 days to form a protective layer. In this way, a thermal recording material 1 was obtained. The total light transmittance of the thermal recording material 1 was 71.3%.

[0064] <Preparation of Thermal Recording Material 2> A thermal recording material 2 was obtained in the same manner as in the thermal recording material 1, except that 0.60 g of the exemplary compound (5) was added as an infrared absorbing dye to the infrared absorbing layer coating liquid. The total light transmittance of the thermal recording material 2 was 66.4%.

[0065] <Preparation of Thermal Recording Material 3> A thermal recording material 3 was obtained in the same manner as in the thermal recording material 1, except that 0.80 g of the exemplary compound (5) was added as an infrared absorbing dye to the infrared absorbing layer coating liquid. The total light transmittance of the thermal recording material 3 was 61.7%.

[0066] <Preparation of Thermal Recording Material 4> A thermal recording material 4 was obtained in the same manner as in the thermal recording material 1, except that 1.0 g of exemplary compound (5) was added as an infrared absorbing dye to the infrared absorbing layer coating liquid. The total light transmittance of the thermal recording material 4 was 56.4%.

[0067] <Preparation of Thermal Recording Material 5> A thermal recording material 5 was obtained in the same manner as in the thermal recording material 1, except that 1.2 g of exemplary compound (5) was added as an infrared absorbing dye to the infrared absorbing layer coating liquid. The total light transmittance of the thermal recording material 5 was 53.2%.

[0068] <Preparation of Thermal Recording Material 6> A thermosensitive recording material 6 was obtained in the same manner as in the thermosensitive recording material 1, except that 0.45 g of exemplary compound (1) (ε(830) / ε(365)=18.5) was added as an infrared absorbing dye to the infrared absorbing layer coating liquid. The total light transmittance of the thermosensitive recording material 6 was 85.1%.

[0069] <Preparation of Thermal Recording Material 7> Except for adding 0.20 g of the exemplary compound (1) as an infrared absorbing dye to the infrared absorbing layer coating liquid, the same procedure as for the thermal recording material 1 was followed to obtain thermal recording material 7. The total light transmittance of thermal recording material 7 was 87.0%.

[0070] <Preparation of Thermal Recording Material 8> A thermal recording material 8 was obtained in the same manner as in thermal recording material 1, except that 0.07 g of IX-2-IR-14 (manufactured by Nippon Shokubai Co., Ltd., ε(830) / ε(365)=2.6) was used as the infrared absorbing dye in the infrared absorbing layer coating solution. The total light transmittance of thermal recording material 8 was 80.8%.

[0071] <Formation of a fill image> The thus obtained thermal recording materials 1 to 8 were exposed to an infrared laser using a thermal CTP setter (AURA600E, manufactured by Guangzhou Amsky Technology Co., Ltd.) to obtain a 4000 dpi filled-in image (20 mm (width) × 200 mm (length)). The drum rotation speed of the thermal CTP setter was fixed at 300 rpm, and the laser output was 350 mW.

[0072] <UV light transmittance evaluation> After obtaining the images as described above, the ultraviolet light transmission density of the image area and the non-image area of ​​the thermal recording materials 1 to 8 were measured in the ultraviolet light mode of X-Rite361T (manufactured by Videojet X-Rite Co., Ltd.), and the maximum ultraviolet light transmission density of the image area (Dmax) and the ultraviolet light transmission density of the non-image area (Dmin) were obtained. The calculation results of Dmax-Dmin are shown in Table 1.

[0073] [Table 1]

[0074] <Ejecta evaluation> After obtaining the images as described above, the periphery of the image area in the thermal recording materials 1 to 8 was observed visually and under a microscope to check whether or not the periphery of the image area was stained by the ejected area. The results are shown in Table 1, which is based on the following criteria.

[0075] <Ejecta standards> Excellent: No visible contamination from ejecta Good: A very small amount of ejection can be seen around the image area (not visible to the naked eye, but visible under a microscope). Acceptable: The ejection is visible around the image area, but does not pose any practical problems. Not possible: A large amount of ejecta has fallen and accumulated around the image area, making it impossible to use.

[0076] <Example 2>

[0077] <Preparation of Thermal Recording Material 9> A thermal recording material 9 was obtained in the same manner as in thermal recording material 1, except that 0.15 g of a carbon black dispersion (manufactured by Taisei Kako Co., Ltd., TSBK-007, pigment concentration 12%) was added as a solid content to the infrared absorbing layer coating liquid. The total light transmittance of thermal recording material 9 was 62.0%.

[0078] <Preparation of Thermal Recording Material 10> A thermal recording material 10 was obtained in the same manner as in thermal recording material 1, except that 0.28 g of a carbon black dispersion (manufactured by Taisei Kako Co., Ltd., TSBK-007, pigment concentration 12%) was added as a solid content to the infrared absorbing layer coating liquid. The total light transmittance of thermal recording material 10 was 52.0%.

[0079] <Formation of a fill image> The thus obtained thermal recording materials 9 and 10 were exposed to an infrared laser using a thermal CTP setter (AURA600E, manufactured by Guangzhou Amsky Technology Co Ltd) to obtain a 4000 dpi filled-in image (20 mm (width) x 200 mm (length)). The drum rotation speed of the thermal CTP setter was fixed at 300 rpm, and the laser output was 350 mW.

[0080] <UV light transmittance evaluation> After obtaining the images as described above, the ultraviolet light transmission densities of the image and non-image areas of the thermal recording materials 9 and 10 were measured in the same manner as in the thermal recording materials 1 to 8, and the maximum ultraviolet light transmission density (Dmax) of the image area and the ultraviolet light transmission density (Dmin) of the non-image area were obtained. The calculation results of Dmax-Dmin are shown in Table 2.

[0081] <Ejecta evaluation> After obtaining the images as described above, the periphery of the image area in the thermal recording materials 9 and 10 was observed visually and under a microscope to check whether or not there was any contamination around the image area due to the ejected area. The results, which were judged based on the same criteria as for the thermal recording materials 1 to 8, are shown in Table 2.

[0082] [Table 2]

[0083] As is clear from the results in Tables 1 and 2, the present invention reduces ejections from the surface of a thermal recording material upon irradiation with an infrared laser, and provides a thermal recording material that can provide high-contrast images.

Claims

[Claim 1] A heat-sensitive recording material having an image-forming layer on a light-transmitting support, the image-forming layer containing an infrared absorbing dye, a non-photosensitive organic silver salt, and a reducing agent, the ratio of which, ε(830) at 830 nm to the molar absorption coefficient ε(365) at 365 nm, ε(830) / ε(365), is 4.0 or more, and the total light transmittance based on JIS K7361-1:1997 is 55% or more.

Images