JP2009113346A - Thermosensible recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensible recording medium and its manufacturing method having a high degree of luster and high density in recording, excellent in the recorded picture quality and record storing property, and free of generation of cracks at the recorded surface. <P>SOLUTION: The thermosensible recording medium is structured so that an intermediate layer, a thermosensible recording layer containing an electron giving compound and an electron receiving compound, a protection layer containing aqueous resin, and an outermost layer are formed on one surface of a support in this order, wherein the intermediate layer and the outermost layer are formed from an ultraviolet ray or an electron beam hardening resin which is hardened by irradiating with ultraviolet rays or electron beams, and the outermost layer has a surface transcribed onto the support from the base material having a flat surface, and the protection layer contains polyvinyl alcohol having a degree of polymerization of 200-600. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material using a color reaction by heat of a leuco dye and a colorant and a method for producing the same, and particularly has high glossiness and recording density, excellent recording image quality and recording storability, and has a recording surface. The present invention relates to a heat-sensitive recording material that does not crack and a method for producing the same.

  2. Description of the Related Art Conventionally, a heat-sensitive recording material using a color development reaction caused by heat between a leuco dye and a color former is well known. Such a thermal recording medium is relatively inexpensive, and the recording apparatus is compact and relatively easy to maintain, so that it can be used not only as a facsimile, various labels, or other output recording media, It is also widely used as a recording medium used in printers of medical diagnostic apparatuses such as line image diagnosis.

  Among them, in a printer of a medical diagnostic apparatus that requires uniformity of recorded images and high resolution, a synthetic paper having a multilayer structure and a biaxially stretched resin film containing an inorganic pigment as necessary are used as a support. A thermal recording medium is used. In recent years, there has been an increasing demand for a thermal recording material that is excellent in gradation reproducibility from low density to high density and that can obtain a high-quality and high-gloss recording image comparable to silver salt photography.

  As such a heat-sensitive recording material, a heat-sensitive recording material in which the surface of the protective layer is a cast surface has been proposed (see Patent Document 1). In order to make the surface of the protective layer a cast surface, the first member in which a part or all of the layers including the overcoat layer are formed on the smooth surface of the film, and the remaining layers not formed in the first member There has been proposed a method of peeling a film after laminating a second member made of a base material on which a film is formed (see Patent Document 2). Further, a method has been proposed in which a protective layer and a thermosensitive recording layer are provided on a mirror drum, and then the protective layer and the thermosensitive recording layer are transferred from the mirror drum onto a support (see Patent Document 3). However, in the method of forming a layer on a substrate having such a smooth surface, the recording surface is liable to crack in the process of applying and drying and laminating on a highly smooth substrate, and the glossiness is lowered. However, since not only the unrecorded portion but also the recorded portion is cracked and the recording density and the recording image quality are inferior, further improvement is desired. Further, there is a problem of recording storability, in particular, fading due to plasticizer, oil, water, solvent, etc. and background fogging, and satisfactory ones are not obtained.

JP-A-63-205278 Japanese Patent Laid-Open No. 11-321111 JP 2002-234251 A

  An object of the present invention is to provide a heat-sensitive recording material having high glossiness and recording density, excellent recording image quality and recording storability, and free from cracks on the recording surface, and a method for producing the same.

  As a result of intensive studies in view of the above prior art, the present inventors have found that the outermost layer is a layer cured by irradiating ultraviolet ray or electron beam curable resin with ultraviolet ray or electron beam, and has a smooth surface. The above-mentioned problems are solved by containing a polyvinyl alcohol (hereinafter sometimes referred to as specific PVA) having a surface transferred from the substrate to the support and having a polymerization degree of 200 to 600. It came to. That is, the present invention relates to the following thermal recording material and a method for producing the same.

  Item 1: A heat-sensitive recording material having an intermediate layer, a heat-sensitive recording layer containing an electron-donating compound and an electron-accepting compound, a protective layer containing an aqueous resin, and an outermost layer in this order on one surface of the support. The intermediate layer and the outermost layer are layers cured by irradiating the ultraviolet ray or electron beam curable resin with ultraviolet rays or an electron beam, and the outermost layer was transferred onto a support having a smooth surface. A heat-sensitive recording material comprising a surface and a protective layer containing polyvinyl alcohol having a polymerization degree of 200 to 600.

  Item 2: The support is either synthetic paper, a resin film, or a laminate of resin film and paper, and the substrate having a smooth surface is either a resin film, a mirror-plated metal drum, or an endless belt Item 2. The heat-sensitive recording material according to item 1.

  Item 3: The heat-sensitive recording material according to Item 1 or 2, wherein the ultraviolet or electron beam curable resin in the outermost layer is an aqueous resin.

  Item 4: The heat-sensitive recording material according to any one of Items 1 to 3, wherein a barrier layer containing an aqueous resin is provided between the intermediate layer and the heat-sensitive recording layer.

  Item 5: A heat-sensitive recording material having an intermediate layer, a heat-sensitive recording layer containing an electron-donating compound and an electron-accepting compound, a protective layer containing an aqueous resin, and an outermost layer in this order on one surface of the support. The intermediate layer and the outermost layer are layers cured by irradiating the ultraviolet ray or electron beam curable resin with ultraviolet rays or an electron beam, and the outermost layer was transferred onto a support having a smooth surface. A method for producing a heat-sensitive recording material having a surface and a protective layer containing polyvinyl alcohol having a polymerization degree of 200 to 600, on a substrate having a smooth surface in advance, an uncured outermost layer, a protective layer, A thermal recording layer and, if necessary, a barrier layer containing an aqueous resin are provided in this order, and one surface of the support and the surface of the thermal recording layer or barrier layer are bonded via an uncured intermediate layer, Or irradiate with electron beam Method for producing a thermosensitive recording material, characterized in that curing the layers and the intermediate layer is peeled between the surface and the outermost layer of the substrate having a smooth surface.

  Item 6: The method for producing a heat-sensitive recording material according to Item 5, wherein at least a heat-sensitive recording layer and a protective layer are simultaneously applied on a substrate having a smooth surface.

  According to the present invention, it is possible to provide a thermal recording material having high glossiness and recording density, excellent recording image quality and recording storability, and no cracking on the recording surface, and a method for producing the same.

The support used in the present invention is preferably either synthetic paper, a resin film, or a laminate of a resin film and paper. As the support, for example, a thermoplastic polyolefin resin and a white inorganic pigment are heat-kneaded, extruded from a die, and stretched in the longitudinal direction. Laminated layers are stretched in the transverse direction to make them translucent or opaque, and thermoplastic paper such as synthetic paper, polyethylene, polypropylene, polystyrene, polyester, etc. or a mixture of them is heated and kneaded, extruded from a die and biaxially stretched. In addition to resin films obtained by mixing these resins with white inorganic pigments and biaxially stretched opaque films or unstretched resin films, high-quality paper, medium-quality paper, neutral paper, recycled A laminate or the like in which resin is coated on one side or both sides of paper manufactured from pulp fibers such as paper and coated paper can be used. The basis weight of such supports, the order of 30 to 200 g / ^{m 2} is preferred.

  The base material having a smooth surface used in the present invention preferably has a high gloss and a high smooth surface, and the base material having a smooth surface has a glossiness of 90% or higher by setting the 75 ° specular gloss to 90% or more. Therefore, a more excellent thermal recording material can be obtained. Moreover, peelability can be improved by having apply | coated the release agent on the base-material surface. Examples of the substrate include polyester films (PET films), polypropylene films, polystyrene films, polycarbonate films, nylon films, and other resin films, mirror-plated metal drums, and endless belts. . Especially, a resin film is preferable and the thickness is preferably about 10 to 500 μm. In particular, a polyester film with less expansion and contraction during drying is more preferable.

  The outermost layer in the present invention is a layer cured by irradiating ultraviolet ray or electron beam curable resin with ultraviolet ray or electron beam, and has a surface transferred from a substrate having a smooth surface onto a support. ing. As a result, a heat-sensitive recording material having high glossiness and recording density and excellent recording image quality and recording storability can be obtained.

  Examples of the ultraviolet or electron beam curable resin include the following prepolymers and monomers. Prepolymers include epoxy (meth) acrylate, urethane (meth) acrylate, saturated polyester / styrene, polyethylene (meth) acrylate, polyether (meth) acrylate, silicon (meth) acrylate, polybutadiene (meth) acrylate, and polyene / thiol. , Polystyrylethyl (meth) acrylate, polyamide (meth) acrylate, and the like. As monomers, styrene, vinyl acetate, vinyl monomers such as N-vinylpyrrolidone, butyl acrylate, 2-ethylhexyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-decyl acrylate isobornyl acrylate, dicyclopentenyloxyethyl acrylate, Monofunctional monomers such as phenoxyethyl acrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol 400 diacrylate, tripropylene glycol diacrylate, bisphenol A diethoxydiacrylate, tetraethylene glycol diacrylate, hydroxypivalate neope Chill glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, polyfunctional monomers such as dipentaerythritol hexaacrylate. These can be used singly or in combination of two or more.

  In the present invention, the ultraviolet or electron beam curable resin in the outermost layer is preferably an aqueous resin. As the aqueous resin, any of water-dispersible and water-soluble aqueous resins can be used. Thereby, when applying the outermost layer on the substrate having a smooth surface, simultaneous multi-layer application with a protective layer, a heat-sensitive recording layer, etc. is facilitated, and productivity can be improved. Here, water-dispersible or water-soluble means a state in which precipitation does not occur using water as a medium. Specifically, it is a state in which it is uniformly emulsified and dispersed in water, and forms micelles in water. It means the state of being dissolved or dissolved in water.

  When used as a water-dispersible aqueous resin, water may be used as a medium, and an emulsifying / dispersing agent may be added to ultraviolet or electron beam curable resin, followed by forced emulsification to use in a stable emulsion state. Examples of the emulsifier / dispersant include polyoxyethylene alkyl ether, polyoxyethylene alcohol ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene derivatives, oxyethylene / oxypropylene block copolymer, polyoxyethylene sorbitan fatty acid ester, polyethylene glycol Nonionic surfactant such as fatty acid ester, fatty acid salt, alkyl sulfate ester salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfosuccinate, alkyl diphenyl ether disulfonate, alkyl phosphate, polyoxyethylenal Kill sulfate ester salt, naphthalene sulfonic acid formalin condensate, special polycarboxylic acid type polymer surfactant, polyoxyethylene alkyl phosphate ester Various emulsification and dispersion agents that are commonly commercialized, such as anionic surface active agents such as Le like. These may be used alone or in combination of two or more depending on the type of ultraviolet or electron beam curable resin to be emulsified and dispersed. If necessary, it can also be used by mixing with emulsifying / dispersing agents other than those described above.

  The amount of the emulsifying / dispersing agent is usually 0.5 to 30% by mass, more preferably 1 to 20% by mass, based on the total solid content of the outermost layer. By setting the content to 0.5% by mass or more, a stable emulsion is obtained, and by setting the content to 30% by mass or less, adhesion of residue to the thermal head and storage stability are improved.

  When used as a water-soluble aqueous resin, the structure of the ultraviolet ray or electron beam curable resin has, for example, a hydrophilic group such as a hydroxyl group, a carboxyl group, a sulfone group, an ethylene oxide group, and a carboxyl group. Can be obtained by neutralizing the group with an amine or alkali.

  When the ultraviolet ray or the electron beam curable resin is cured by irradiating the ultraviolet ray, curing can be promoted by containing a photopolymerization initiator. The photopolymerization initiator is not limited and various known ones can be used. For example, methyl benzoylbenzoate, benzoin, benzyldimethyl ketal, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-methyl-1- [4- (methylthio) phenyl] -2- Morpholino-1-propanone, 1-hydroxycyclohexyl phenyl ketone, 2,4-diethylthioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, camphorquinone , Anthracene, benzyl, phenylmethylglyoxylate and the like. Each of these photopolymerization initiators can be used alone or in combination of two or more.

  The content of the photopolymerization initiator is preferably about 0.05 to 10 parts by mass, more preferably about 0.1 to 5 parts by mass with respect to 100 parts by mass of the ultraviolet ray or electron beam curable resin. By setting the content to 0.05 parts by mass or more, curing can be effectively promoted. On the other hand, if it exceeds 10 parts by mass, the curability will be saturated, so the production cost can be reduced by setting it to 10 parts by mass or less.

  The outermost layer can also contain additives such as pigments, lubricants, waxes, cross-linking agents, and surfactants for the purpose of improving head matching properties such as coating suitability, sticking prevention during recording, and head scratching properties. . Examples of additives include kaolin, clay, aluminum hydroxide, calcined clay, colloidal silica, calcium carbonate, zinc oxide, aluminum oxide, titanium oxide, diatomaceous earth, amorphous silica, barium sulfate, talc, styrene resin filler, and nylon resin. Fillers, pigments such as urea / formalin resin filler, lubricants such as alkyl phosphate, stearamide, zinc stearate, calcium stearate, waxes such as carnauba wax, paraffin wax, boric acid, borax, glyoxal, di Dialdehyde compounds such as aldehyde starch, polyamide / epichlorohydrin resin, melamine resin, dimethylol urea compound, cross-linking agents such as adipic acid dihydrazide, dialkyl sulfosuccinate, alkyl sulfonate, alkyl carbo Salts, surfactants such as alkyl ethylene oxides, fluorine-based surfactants, defoamers, optical brighteners, coloring dyes and the like.

The outermost layer is mixed and stirred together with additives such as water-soluble or water-dispersible ultraviolet or electron beam curable resins and, if necessary, photopolymerization initiators, pigments, lubricants, crosslinking agents, surfactants, etc. the outermost layer coating solution prepared by the coating amount after drying of 0.5-4 g / ^{m 2} approximately, and preferably no greater 0.5 to 2 g / ^{m 2} approximately, a group having a pre-smooth surface It is formed by applying and drying on a material. By setting it as 0.5 g / m ² or more, the barrier property is improved, and the recording storability can be improved. By setting it to 4 g / m ² or less, the recording sensitivity and the recording density can be improved.

  In the present invention, the outermost layer has a surface transferred from a substrate having a smooth surface onto a support. Thereby, a heat-sensitive recording material having a high glossiness can be obtained.

  The method of providing the outermost layer transferred from the substrate having a smooth surface onto the support is as follows: (1) a substrate having a smooth surface in a wet state in which the outermost layer is not dried or rewet after drying. Bonding with material surface, drying while bonded, peeling from substrate having smooth surface after drying, (2) (a) Adhering at least outermost layer provided on substrate having smooth surface in advance (2) (b) a smooth surface in advance, which is bonded to a layer including a heat-sensitive recording layer provided on one surface of a support and peeled from a substrate having a smooth surface There is a method in which a layer including at least an outermost layer and a heat-sensitive recording layer provided on a substrate having a surface is bonded to one surface of a support via an adhesive substance and peeled from a substrate having a smooth surface. Can be mentioned.

  The substance having adhesiveness may be applied to at least one of the surface of the layer to be joined and the surface of the support or contained in any of the layers to be joined. If it is necessary to dry the substance having adhesiveness or a layer containing the same, it may be dried while being bonded, and the outermost layer may be peeled off from the substrate having a smooth surface after drying. The adhesive material in the present invention is preferably applied or contained on the side closer to the heat-sensitive recording layer as viewed from the support, from the viewpoint of further improving the recording image quality. Furthermore, in the heat-sensitive recording material of the present invention, an embodiment in which an adhesive substance is contained as a resin in the intermediate layer is preferable because the effects of the present invention can be fully exhibited. Thereby, at least the heat-sensitive recording layer and the protective layer can be applied at the same time, and the productivity can be remarkably improved.

  The protective layer in the present invention contains polyvinyl alcohol having a polymerization degree of 200 to 600. As a result, since no cracks are generated on the recording surface, it is possible to obtain a thermal recording material having high glossiness and recording density and excellent recording image quality. By setting the degree of polymerization to 200 or more, the coating suitability of the protective layer can be improved. If the degree of polymerization exceeds 600, the water-based resin swollen by moisture dries and shrinks during the transition of the protective layer from the wet state to the dry state, causing cracks on the recording surface of the thermal recording medium. By setting it to 600 or less, it is possible to obtain a heat-sensitive recording material in which no cracks occur on the recording surface. The degree of polymerization referred to in the present invention is the average degree of polymerization determined by the method described in JIS K6726-1994.

  The specific PVA is not particularly limited, and examples thereof include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol. Can be mentioned. Of these, acetoacetyl-modified polyvinyl alcohol is preferable from the viewpoint of water resistance. As content of specific PVA, about 20-95 mass% is preferable with respect to the total solid in a protective layer, and 30-95 mass% is more preferable. By setting the content to 20% by mass or more, cracks on the recording surface can be more effectively suppressed. By making it 95% by mass or less, the coating suitability of the protective layer can be improved.

  The protective layer can contain other aqueous resins as long as the effects of the present invention are not impaired. The other aqueous resin is preferably an aqueous resin having a high barrier property in order to prevent the resin component of the outermost layer from moving to the heat-sensitive recording layer. Thereby, background fogging of the heat-sensitive recording layer due to ultraviolet rays or electron beam curable resin contained in the outermost layer can be effectively prevented.

  As the aqueous resin, either a water-soluble resin or a water-dispersible resin can be used. Examples of water-soluble resins include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, arabic gum, other polyvinyl alcohols other than specific PVA, diisobutylene / maleic anhydride copolymer salts, styrene / maleic anhydride Copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, methyl vinyl ether / maleic anhydride copolymer salt, isopropylene / maleic anhydride copolymer salt, polyacrylamide, etc. Can be mentioned. Examples of the water-dispersible resin include vinyl acetate latex, styrene / butadiene latex, acrylic latex, urethane latex, and the like. The proportion of the other aqueous resin is preferably 50% by mass or less with respect to the specific PVA in order not to impair the effects of the present invention.

For example, the protective layer is prepared by mixing and stirring an aqueous resin containing specific PVA and an additive such as dioctyl sulfosuccinic acid sodium salt using water as a medium. It is formed by applying and drying the outermost layer and the protective layer in this order on a substrate having a smooth surface in advance so as to be about 5 to 4 g / m ² , preferably about 0.5 to ² g / m ² . When the coating amount of the protective layer is 0.5 g / m ² or more, the barrier property is improved, and when it is 4 g / m ² or less, the recording sensitivity and the recording density can be improved.

  The heat-sensitive recording layer of the present invention may be any material that can form a recorded image by heating, and can contain various known electron-donating compounds and electron-accepting compounds as color forming components. Moreover, you may contain a preservability improving agent, a sensitizer, etc. as needed. Examples of the color forming component include a combination of a leuco dye and a colorant, a combination of an imino compound and an isocyanate compound, a combination of a long-chain fatty acid metal salt and a polyhydric phenol, a chelate with a transition element such as iron, cobalt, or copper. Examples include combinations with compounds. Hereinafter, a combination of a leuco dye having a characteristic excellent in recording sensitivity and recording density and a colorant will be described in detail.

  Examples of leuco dyes include 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, and 3-di (n-pentyl). ) Amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilino Fluorane, 3-diethylamino-7- (m-trifluoromethyl) anilinofluorane, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilinofluorane, 3- ( N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-7- (o-chloroanilino) fluorane, 3- (N-ethyl) -p- toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl--p- toluidino) -6-methyl-7- (p-toluidino) fluoran, and the like. Of course, it is not limited to these, Two or more types can also be used together as needed.

  The content of the leuco dye is not particularly limited, but is preferably about 5 to 40% by mass with respect to the total solid content in the heat-sensitive recording layer.

  Examples of the colorant include 4,4′-isopropylidene diphenol, 4,4′-cyclohexylidene diphenol, 4-hydroxybenzoic acid benzyl ester, 4,4′-dihydroxydiphenyl sulfone, and 4-hydroxy-4. '-Allyloxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone, 1,1-bis ( 4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 2,2 ′-[4- (4-hydroxyphenylsulfonyl) phenoxy ] Phenolic compounds such as diethyl ether, Np-tolylsulfonyl- N′-phenylurea, 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4′-bis (Np-tolylsulfonylaminocarbonylamino) diphenylmethane, N Compounds having a sulfonyl group and a ureido group in the molecule such as-(p-tolylsulfonyl) -N'-p-butoxyphenylurea, 4- [2- (p-methoxyphenoxy) ethyloxy] zinc salicylate, 4- [3 Examples include zinc salts of aromatic carboxylic acids such as zinc (p-tolylsulfonyl) propyloxy] salicylate and zinc 5- [p- (2- (p-methoxyphenoxyethoxy) cumyl] salicylate. It is not limited to these, and two or more kinds may be used in combination as required.

  The content of the colorant is not particularly limited, and may be appropriately selected according to the type of the leuco dye and the colorant to be used. Usually, about 1 to 10 parts by mass is preferable with respect to 1 part by mass of the leuco dye. More preferably, it is about 1 to 5 parts by mass.

The heat-sensitive recording layer is, for example, water as a medium, a leuco dye, a colorant, and, if necessary, various known preservability improvers and sensitizers, pigments, additives, etc., with an agitator / crusher such as a sand mill, attritor, or ball mill. A coating solution for a heat-sensitive recording layer prepared by mixing and stirring an adhesive together with a dispersion obtained by pulverizing together or separately, and a coating amount after drying of about 3 to 20 g / m ² The outermost layer, the protective layer, and the heat-sensitive recording layer are applied and dried in this order on a substrate having a smooth surface in advance. Examples of the adhesive include an aqueous resin contained in the protective layer. The content of the adhesive is preferably about 8 to 35% by mass with respect to the total solid content in the heat-sensitive recording layer.

  The intermediate layer in the present invention is a layer cured by irradiating ultraviolet rays or electron beams to ultraviolet rays or electron beam curable resins. As a result, it is possible to obtain a heat-sensitive recording material having a high glossiness by imparting to the outermost layer a surface which is excellent in adhesiveness to the support and is transferred onto the support from a substrate having a smooth surface. UV or electron beam curable resin can also be contained in the form of an emulsion, but it is not necessary to dry after joining the support side and the substrate side having a smooth surface via an intermediate layer, and is moisture permeable as a support. From the viewpoint that synthetic paper or resin film having a low viscosity can be used, a solventless ultraviolet or electron beam curable resin is preferable. The ultraviolet ray or electron beam curable resin can be appropriately selected from those used for the outermost layer.

The intermediate layer includes, for example, ultraviolet or electron beam curable resin, if necessary, photopolymerization initiator, pigment, additive, etc., three roll mill, two roll mill, cowless dissolver, homomixer, sand mill, paint conditioner and ultrasonic dispersion. the intermediate layer coating liquid obtained by mixing and stirring using a machine or the like, about the coating weight of 1 to 6 g / ^{m 2} after drying, and preferably 1.5 to 4.0 g / ^{m 2} approximately Thus, it is applied to at least one of the surface of the thermal recording layer provided on the one side of the support and the substrate side having a smooth surface, or the surface of a barrier layer described later if necessary, and uncured intermediate The substrate side surface having a smooth surface is bonded to the support side through the layer application surface, and irradiated with ultraviolet rays or an electron beam to be cured together with the outermost layer.

  When ultraviolet rays are used, examples of the ultraviolet light source include 1 to 50 ultraviolet lamps, xenon lamps, tungsten lamps, and the like. Thereby, the ultraviolet-ray which has the intensity | strength of about 40-240 W / cm, Preferably about 60-180 W / cm can be irradiated. On the other hand, when an electron beam is used, the absorbed dose of the irradiated electron beam is preferably 150 kGy or less. More preferably, it is 100 kGy or less. Excessive irradiation exceeding 150 kGy may cause discoloration and strength reduction of the thermal recording medium. Although the minimum of the electron beam to irradiate is not limited, 10 kGy or more is preferable when obtaining a desired effect. More preferably, it is 20 kGy or more. The acceleration voltage upon irradiation is preferably about 30 to 300 kV, more preferably about 70 to 200 kV. As an electron beam irradiation method, a curtain beam method, a scanning method, a broad beam method, or the like can be used. The ultraviolet rays or the electron beam may be irradiated from either side of the support or the substrate having a smooth surface, and the irradiation conditions may be appropriately selected according to the type and the application amount of the ultraviolet ray or the electron beam curable resin. .

  In the present invention, a barrier layer containing an aqueous resin can be provided between the intermediate layer and the thermosensitive recording layer. Accordingly, it is possible to prevent the ultraviolet ray or the electron beam curable resin from penetrating into the heat-sensitive recording layer to cause background fogging, the recording sensitivity to be lowered, and the storability of the heat-sensitive recording layer to be lowered. As the aqueous resin, an aqueous resin having a barrier property is preferable, and examples thereof include an aqueous resin contained in the protective layer.

The barrier layer is, for example, a coating solution for a barrier layer prepared by mixing and stirring an aqueous resin and, if necessary, a surfactant such as sodium dioctylsulfosuccinate, using water as a medium, and the coating amount after drying is 0.5. to 5.0 g / ^{m 2,} preferably about so that 0.5 to 2.0 g / ^{m 2} approximately, the outermost layer on a substrate having a pre-smooth surface, a protective layer, the heat-sensitive recording layer, the barrier layer It is formed by applying and drying in order.

  Each of the above coating liquids may be applied and dried one layer at a time, or the same coating liquid may be applied in two or more layers. Two or more layers can be applied simultaneously. As a coating method, for example, a slot die, a slide bead, a curtain, an air knife, a blade, a Mayer bar, a rod, a roll coater, or the like is used.

  In the present invention, from the viewpoint of improving productivity, an embodiment in which at least a heat-sensitive recording layer and an adjacent protective layer are applied simultaneously is preferable. Cracks on the recording surface due to drying shrinkage are likely to occur in the process of simultaneous multi-layer coating and drying on a substrate having a smooth surface, but the protective layer adjacent to the heat-sensitive recording layer contains the specific PVA. The effect of can be demonstrated without regret. As a method for simultaneous multilayer coating, a bead coating method such as a slide die or a multilayer slot die or a curtain coating method such as a slide curtain is preferably used.

  In simultaneous multi-layer coating, even when the wet coating amount of each layer is small, a uniform coating surface can be obtained by applying the multi-layers in layers, and even better recording image quality can be obtained. . In particular, since the outermost layer and the barrier layer can obtain an effect with a small coating amount as compared with the heat-sensitive recording layer, a uniform coated surface can be obtained by simultaneously applying the heat-sensitive recording layer and the adjacent protective layer. . Furthermore, by increasing the solid content concentration of each coating liquid, it is possible to reduce the drying load and improve productivity.

  The thermal recording material of the present invention preferably has an image clarity (based on JIS K7105-1981) of an unrecorded portion of 75% (value at a slit width of 2 mm) or more. The image sharpness is one of the optical properties of the recording surface. The image sharpness is measured by measuring the light reflected by the sample through a moving optical comb and calculating it. By setting the image definition of the unrecorded portion to 75% or more, the recording image quality can be further improved. It is more preferable that the image definition is 80% or more.

  The image clarity of the unrecorded portion can be 75% or more by various methods. In the present invention, the protective layer adjacent to the heat-sensitive recording layer contains polyvinyl alcohol having a polymerization degree of 200 to 600. Since a uniform protective layer coating surface is formed and no cracks occur on the recording surface, the image definition can be improved.

  The heat-sensitive recording material of the present invention has a heat-sensitive recording layer containing an intermediate layer, an electron-donating compound and an electron-accepting compound, a protective layer containing an aqueous resin, and an outermost layer in this order on one side of the support. A recording medium in which an intermediate layer and an outermost layer are layers cured by irradiating ultraviolet rays or an electron beam curable resin with ultraviolet rays or an electron beam, and the outermost layer is formed on a substrate having a smooth surface. A non-cured outermost layer on a substrate having a smooth surface in advance, which is a method for producing a thermosensitive recording material having a surface transferred to a protective layer and containing a polyvinyl alcohol having a polymerization degree of 200 to 600. A protective layer, a heat-sensitive recording layer, and, if necessary, a barrier layer containing an aqueous resin are provided in this order, and one surface of the support and the surface of the heat-sensitive recording layer or the barrier layer are provided via an uncured intermediate layer. Bond UV and electron beam It shines and curing the outermost layer and the intermediate layer is produced by a method characterized by peeling between the surface and the outermost layer of the substrate having a smooth surface.

  A method for joining one surface of the support to the heat-sensitive recording layer or the barrier layer through the intermediate layer is not particularly limited, but it is preferable that the surface is brought into close contact with a pressure nip composed of a metal roll and an elastic roll. . At that time, it is preferable that the support side is in contact with the metal roll surface, and the base material side having a smooth surface is in contact with the elastic roll surface. As a result, the adhesive substance exhibits a more excellent anchoring effect, and it becomes easy to peel off the surface of the base material having a smooth surface and the outermost layer, thereby obtaining a heat-sensitive recording material with high glossiness. be able to.

  Examples of the surface material of the elastic roll used in the present invention include urethane rubber, nitrile rubber (NBR), chloroprene rubber (CR), styrene / butadiene rubber (SBR), ethylene / propylene rubber (EPDM) and the like. In addition, by finishing the surface of the elastic roll to a desired surface roughness, air entrainment during nip can be suppressed and a uniform intermediate layer can be provided. The surface roughness of the elastic roll is not particularly limited, but is preferably Rmax 10 μm or less (according to JIS B0601).

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, it is not limited to these. Unless otherwise specified, “part” and “%” represent “part by mass” and “% by mass”, respectively. The average particle size was measured using a laser diffraction particle size distribution analyzer SALD2000 (manufactured by Shimadzu Corporation).

Example 1
Preparation of leuco dye dispersion (liquid A) Composition comprising 20 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 10 parts of a 10% aqueous solution of polyvinyl alcohol, and 20 parts of water. The product was dispersed with a sand mill so that the average particle size was 1.0 μm to obtain liquid A.

-Preparation of Colorant Dispersion Liquid (Liquid B) An average particle size of a composition comprising 50 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, 20 parts of a 10% aqueous solution of polyvinyl alcohol, and 60 parts of water using a sand mill. Liquid B was obtained by dispersion so as to be 1.2 μm.

-Preparation of coating solution for heat-sensitive recording layer A part 70 parts, B part 75 parts, silica (trade name: Nipseal E-743, manufactured by Nippon Silica Co.) 25% slurry 40 parts, polyvinyl alcohol 10% aqueous solution 50 parts, 30 parts of styrene / butadiene latex (trade name: L-1571, solid concentration 48%, manufactured by Asahi Kasei), stearamide (trade name: Hi-micron L-271, solid content concentration 25%, manufactured by Chukyo Yushi Co., Ltd.) A composition comprising 20 parts, 4 parts of a 10% aqueous solution of dioctyl sulfosuccinate sodium salt, and 35 parts of water was mixed and stirred to obtain a thermal recording layer coating solution.

-Preparation of coating solution for protective layer 165 parts of a 6% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Goosephimer Z-100, polymerization degree 500, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 10% of sodium dioctylsulfosuccinate A composition comprising 5 parts of an aqueous solution was mixed and stirred to obtain a coating solution for a protective layer.

-Preparation of coating solution for outermost layer Aqueous urethane-based resin (trade name: Nikka Coat UV-800, solid content concentration 41%, manufactured by Nippon Kako Co., Ltd.) 140 parts, Kaolin (trade name: UW-90, manufactured by Engelhard) ) 60 parts slurry, zinc stearate (trade name: Himicron L-111, solid content 20%, manufactured by Chukyo Yushi Co., Ltd.), stearyl phosphate ester potassium salt (trade name: Wopole 1800, solid content) A composition comprising 2 parts (concentration 35%, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), 1 part of a 10% aqueous solution of sodium dioctylsulfosuccinate and 250 parts of water was mixed and stirred to obtain a coating solution for the outermost layer.

-Preparation of coating solution for intermediate layer 80 parts of acrylate of ε-caprolactone-modified dipentaerythritol (trade name: Kayrad DPCA-60, manufactured by Nippon Kayaku Co., Ltd.) as an electron beam curable resin and 1,6-hexane modified with ethylene oxide 20 parts of diol diacrylate (trade name: Kayarad R-167, manufactured by Nippon Kayaku Co., Ltd.) was mixed and stirred with a cowless dissolver to obtain an intermediate layer coating solution.

-Preparation of thermosensitive recording material On the PET (polyethylene terephthalate) film (trade name: Teijin Tetron Film S, thickness 25 μm, manufactured by Teijin DuPont Films) as a substrate having a smooth surface, the outermost layer coating solution, protection layer coating solution, a thermal recording layer coating solution in this order, as the coating amount after drying, ^{respectively, 2.0g / m 2, 1.5g /} m 2, a 7.0 g / ^{m 2,} the slide die Were simultaneously coated and dried. On the other hand, the coating amount after curing the intermediate layer coating solution on one surface of a synthetic paper (trade name: YUPO FPG-80, manufactured by YUPO Corporation) as a support is 3.0 g / m ^2. The surface of the heat-sensitive recording layer is bonded to one surface of the support through the intermediate layer coating surface, and an acceleration voltage of 175 kV is applied from the support by an electrocurtain type electron beam accelerator (manufactured by ESI). The intermediate layer and the outermost layer were cured by irradiating an electron beam with an absorbed dose of 45 kGy, and then the surface of the PET film and the outermost layer were peeled to obtain a heat-sensitive recording material.

Example 2
-Preparation of barrier layer coating solution A composition comprising 250 parts of an 8% aqueous solution of partially saponified polyvinyl alcohol (trade name: PVA-217EE, manufactured by Kuraray Co., Ltd.) and 4 parts of a 10% aqueous solution of dioctylsulfosuccinic acid sodium salt was mixed and stirred. Thus, a barrier layer coating solution was obtained.

In the production of the heat-sensitive recording material of Example 1, the outermost layer was formed on a PET (polyethylene terephthalate) film (trade name: Teijin Tetron Film S, thickness 25 μm, manufactured by Teijin DuPont Films) as a substrate having a smooth surface. The coating amounts for the coating solution, the protective layer coating solution, the thermal recording layer coating solution and the barrier layer coating solution in this order were 2.0 g / m ² , 1.5 g / m ² and 7 respectively. .0g ^/ m 2, except that simultaneous multilayer coating and drying so that 1.0 g / ^{m 2,} thereby obtaining the heat-sensitive recording layer in example 1.

Example 3
In the preparation of the coating solution for the outermost layer of Example 2, in place of 140 parts of an aqueous urethane resin (trade name: Nikka Coat UV-800, solid content concentration 41%, manufactured by Nippon Kakko Paint Co., Ltd.) A heat-sensitive recording material was obtained in the same manner as in Example 2 except that 167 parts of a 30% emulsion of Aronix M-8060 (manufactured by Toagosei Co., Ltd.) was used.

Example 4
The same procedure as in Example 1 was performed except that partially saponified polyvinyl alcohol (trade name: PVA203, polymerization degree 300, manufactured by Kuraray Co., Ltd.) was used instead of the polyvinyl alcohol used in the preparation of the coating solution for the protective layer of Example 1. A heat-sensitive recording material was obtained.

Comparative Example 1
Instead of the polyvinyl alcohol used for the preparation of the coating liquid for the protective layer of Example 1, acetoacetyl-modified polyvinyl alcohol (trade name: Goosefimer Z-200, polymerization degree 1000, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used. Except for the above, a heat-sensitive recording material was obtained in the same manner as in Example 1.

Comparative Example 2
In the production of the heat-sensitive recording material of Example 2, a PET (polyethylene terephthalate) film (trade name: Teijin Tetron Film S, thickness 25 μm, manufactured by Teijin DuPont Films Ltd.) as a substrate having a smooth surface was used as follows. outermost coating liquid for a thermal recording layer coating solution and the barrier layer coating solution in this order, the coating amount after drying, ^{respectively, 3.5g / m 2, 7.0g /} m 2, 1.0g / m 2 A heat-sensitive recording material was obtained in the same manner as in Example 2 except that simultaneous multilayer coating and drying were performed. That is, as an outermost layer coating solution, 330 parts of a 12% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Gohsephimer Z-100, polymerization degree 500, manufactured by Nippon Synthetic Chemical Co., Ltd.), kaolin (trade name: UW-90) 85 parts of a 60% slurry of Engelhard, Inc., zinc stearate (trade name: Himicron L-111, solid content concentration 20%, manufactured by Chukyo Yushi Co., Ltd.), stearyl phosphate ester potassium salt (trade name: A composition comprising 2 parts of Wopol 1800, solid content 35%, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), 3 parts of a 10% aqueous solution of dioctylsulfosuccinic acid sodium salt, and 200 parts of water was used by mixing and stirring.

  The thermosensitive recording material thus obtained was evaluated as follows. The results are shown in Table 1.

[Glossiness]
The 75 degree and 20 degree glossiness was measured with a gloss meter (trade name: GM-26D, Murakami Color Research Laboratory).

[Recording density]
The 17 gradations of the built-in pattern were recorded with a thermal recording printer (trade name: UP-880, manufactured by Sony Corporation), and the 17 gradation density was measured with a Macbeth densitometer (trade name: RD918, manufactured by Gretag Macbeth Co.).

[Plasticizer resistance]
The recording material after measuring the recording density was sandwiched between two vinyl chloride wrap films, and the recording density after treatment at 40 ° C. for 24 hours was measured.

[Crack of recording surface]
The degree of cracking on the recording surface (unrecorded portion) of the thermal recording material was visually evaluated with a loupe.
A: There is no crack at all.
○: There are some cracks.
Δ: There are many cracks.
X: There are many cracks.

Claims (6)

  A thermosensitive recording medium comprising, on one side of the support, an intermediate layer, a thermosensitive recording layer containing an electron donating compound and an electron accepting compound, a protective layer containing an aqueous resin, and an outermost layer in this order, The outermost layer and the outermost layer are layers cured by irradiating an ultraviolet ray or electron beam curable resin with ultraviolet rays or an electron beam, and the outermost layer has a surface transferred from a substrate having a smooth surface onto a support. And a protective layer containing polyvinyl alcohol having a polymerization degree of 200 to 600.   The support is either synthetic paper, a resin film or a laminate of resin film and paper, and the substrate having a smooth surface is either a resin film, a mirror-plated metal drum or an endless belt. Item 2. The thermosensitive recording material according to item 1.   The heat-sensitive recording material according to claim 1 or 2, wherein the ultraviolet or electron beam curable resin in the outermost layer is an aqueous resin.   The heat-sensitive recording material according to claim 1, wherein a barrier layer containing an aqueous resin is provided between the intermediate layer and the heat-sensitive recording layer.   A thermosensitive recording medium comprising, on one side of the support, an intermediate layer, a thermosensitive recording layer containing an electron donating compound and an electron accepting compound, a protective layer containing an aqueous resin, and an outermost layer in this order, The outermost layer and the outermost layer are layers cured by irradiating an ultraviolet ray or electron beam curable resin with ultraviolet rays or an electron beam, and the outermost layer has a surface transferred from a substrate having a smooth surface onto a support. And a protective layer comprising a polyvinyl alcohol having a polymerization degree of 200 to 600, wherein the uncured outermost layer, protective layer, and thermal recording layer are formed on a substrate having a smooth surface in advance. And, if necessary, a barrier layer containing an aqueous resin is provided in this order, and one surface of the support and the surface of the thermosensitive recording layer or barrier layer are bonded via an uncured intermediate layer, and an ultraviolet ray or an electron beam Irradiate the outermost layer Curing the fine intermediate layer, the manufacturing method of the heat-sensitive recording material, characterized in that peeling between the surface and the outermost layer of the substrate having a smooth surface.   The method for producing a heat-sensitive recording material according to claim 5, wherein at least a heat-sensitive recording layer and a protective layer are simultaneously applied on a substrate having a smooth surface.