JP4334293B2 - Thermal recording material - Google Patents

Description

  The present invention relates to a heat-sensitive recording material having a cured film layer of an energy ray-curable resin composition as an overcoat layer on a heat-sensitive color forming layer. More specifically, it is excellent in recording runability, preservability of the thermal recording material before and after color development, suitable for producing a high-quality thermal recording material with gloss, and excellent in workability and environmental security. The present invention relates to an energy ray-curable aqueous resin composition and a heat-sensitive recording material using the cured film as an overcoat layer.

Conventionally, a heat-sensitive recording material that obtains a recorded image by reacting a colorless or light leuco dye with an organic or inorganic developer by heat is relatively inexpensive, and the apparatus is compact and maintenance-free. In recent years, the use field of POS labels, overhead projectors (OHP), second original drawings, cards, and the like has also expanded.
However, conventional heat-sensitive recording materials have problems in storage stability (particularly, fading due to plasticizer, oil, and water in a color image) and have drawbacks such as background fogging. As a method for solving this problem, a method of providing an energy ray curable resin layer on the heat sensitive layer or an energy ray curable resin layer via an intermediate layer on the heat sensitive color developing layer without causing fogging. A method for obtaining a heat-sensitive recording material excellent in storability and recording characteristics has been proposed.

However, with the recent diversification and higher performance of thermal recording systems, hardware such as thermal printers and facsimiles have made significant progress. For high-speed printing and video printer printing, energy beam curable resins are overcoated. However, there are problems such as adhesion of debris to the thermal head and generation of sound during printing (sticking sound), and a good thermal recording material has not yet been obtained. In addition, a method using an energy ray curable resin having a Tg point (glass transition point) of 200 ° C. or higher, a method of adding a pigment of 15 μm or less to the resin, and the like have been proposed. However, the object of obtaining a heat-sensitive recording material excellent in high-speed recording characteristics, high gloss, heat-sensitive recording material itself, and excellent storability of color images has not yet been achieved.
Energy beam curable resins are used in many fields because of their simple curing equipment and good productivity. However, reactive diluents and organic solvents are used for handling and coating problems. In many cases, the composition has problems in workability and safety in terms of skin irritation, odor, and toxicity. As a means for solving this problem, there is emulsification of an energy beam curable resin.

However, when an ordinary emulsifier is used for emulsification, there is a problem that the preservability of the thermal recording material such as water resistance and the recording characteristics at the time of printing deteriorate due to the effect of the emulsifier remaining in the cured film. In addition, when used for printing on high-speed printers, etc., the recording properties are insufficient even when overcoated with a coating solution in which only an energy ray curable resin is emulsified. It is necessary to impart a function. In such a case, addition of an inorganic or organic filler is necessary. As the method, prior to emulsifying the energy beam curable resin, an inorganic or organic filler is dispersed in advance in the resin, and this is emulsified and dispersed in water to produce an energy beam curable resin emulsion. There is a way. However, in such a case, if an inorganic or organic filler is filled, the stability of the oil-in-water emulsion is reduced, which makes it difficult to produce the emulsion, and the gloss of the coating film of the overcoat layer using such an emulsion is reduced. This causes problems. As a method for solving such a problem, the present inventors have previously proposed an oil-in-water type radiation curable resin emulsion composition suitable for a protective layer of a thermosensitive recording material (Patent Document 1). However, these methods also have insufficient points for the stability of the emulsion and the printing performance corresponding to the recent high performance of printers. In the case of such an oil-in-water emulsion, it is difficult to dilute with a solvent such as alcohol in consideration of the stability of the emulsion, and it is difficult to increase the drying rate during coating.
Japanese Patent No. 2772359

  It can be diluted with an organic solvent to increase the drying speed during coating, and can be used as an overcoat agent for thermal recording media to match the thermal head when printing at high energy (sticking properties) Development of an aqueous radiation-curable resin composition for an overcoat agent that gives a heat-sensitive recording material having a high gloss and a high-class feeling, with a good degree of adhesion to the head).

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that an aqueous radiation-curable resin composition having a specific composition solves the above-mentioned problems, and completed the present invention. I let you.
That is, the present invention
(1) In a thermosensitive recording medium having a thermosensitive coloring layer and an overcoat layer on a support, the overcoat layer has one or more ethylenically unsaturated groups in the molecule and has a water miscibility of 5% by weight or more. The thermosensitive recording medium, which is a cured film of an energy ray-curable aqueous resin composition containing a resin (A) and a filler (B);
(2) The thermosensitive recording according to (1), wherein the water-soluble resin (A) having one or more ethylenically unsaturated groups in the molecule and having a water miscibility of 5% by weight or more is an acrylate of a glycidyl ether of a polyhydric alcohol. body,
(3) A water-soluble resin (A) having one or more ethylenically unsaturated groups in the molecule and having a water miscibility of 5% by weight or more is composed of a polyoxyethylene chain and two or more (meth) acryloyl groups in the molecule. The heat-sensitive recording material according to (1), which is a polyfunctional (meth) acrylate having
(4) The thermal recording according to any one of (1) to (3), wherein the filler (B) is an inorganic filler and the content thereof is 0.5 to 50% by weight in the energy ray curable resin composition. body,
About.

  The energy ray curable aqueous resin composition of the energy ray curable resin composition of the present invention can be diluted with water without using an organic solvent that is stable over time and adversely affects the human body and the environment, and further has a drying rate. If desired, alcohols can be added to increase the viscosity. By using this as an overcoat material for thermal recording media, it has good matching with the thermal head (sticking, degree of adhesion to the head) when printing with high energy, high gloss, high quality A sensitive thermal recording material is obtained.

The present invention relates to a heat-sensitive recording material having a cured film layer of an energy beam curable resin composition as an overcoat layer.
The water-soluble resin (A) having one or more ethylenically unsaturated groups in the molecule and having a water miscibility of 5% by weight or more used in the present invention is a vinyl monomer that is liquid at room temperature, N-methoxymethylacrylamide. And (meth) acrylates are preferable, and (meth) acrylates are preferable, and the structure has a hydrophilic group such as a hydroxyl group, a carboxyl group, a sulfone group, an ethylene oxide chain, and the water miscibility is 5% by weight or more. Are used for the purposes of the present invention. (Here, the water miscibility represents the part by weight of water that can be uniformly added to 100 parts by weight of the resin. Is the water miscibility uniformly dissolved and transparent at room temperature (25 ° C.))? In the case of having a carboxyl group, the group may be neutralized with an amine or alkali, and a water miscibility of 5% by weight or more may be used for the application of the present invention. it can. Those in which water and resin are completely miscible can also be used.

Among these, glycidyl ether acrylate of polyhydric alcohol and polyfunctional (meth) acrylate having a polyoxyethylene chain and two or more (meth) acryloyl groups are particularly preferable for the use of the present invention. The content of the water-soluble resin (A) having at least one ethylenically unsaturated group in the molecule and having a water miscibility of 5% by weight or more is the total weight of the energy ray-curable aqueous resin composition (the energy ray in the following). The total weight of the curable aqueous resin composition refers to the total weight of the components excluding water from the energy ray curable aqueous resin composition of the present invention.) In general, 40 to 95% by weight, preferably 50 to 80% by weight. % Range. If the content is too low, sufficient performance will not be obtained, and if it is too high, a problem of the strength of the coating film may occur.

  The acrylates are roughly classified into monofunctional monomers having one acrylate group, bifunctional monomers having two acrylate groups, oligomers having acrylate groups, and polyfunctional monomers having three or four or more acrylate groups. For example, from the viewpoint of film forming ability, film hardness, odor, etc., a bifunctional monomer having two acrylate groups and a polyfunctional oligomer or polyfunctional monomer which is liquid at room temperature having three or four or more acrylate groups are preferable, The monofunctional monomer is mainly used for the purpose of adjusting the viscosity of the energy beam curable resin composition.

  Examples of the water-soluble resin (A) having one or more ethylenically unsaturated groups in the molecule include, for example, hydroxyethyl (meth) acrylate, hydroxy (meth) acrylate, hydroxypropyl (meth) acrylate, ethylene glycol di (meth) ) Acrylate, ethylene glycol diglycidyl ether (meth) acrylate, polyethylene glycol di (meth) acrylate, glycerin polyethoxy (meth) acrylate, glycerin diepoxy (meth) acrylate, glycerin triepoxy (meth) acrylate, 1,4-butane Diol diepoxy (meth) acrylate, 1,6-hexanediol diepoxy (meth) acrylate, polyethylene glycol diepoxy (meth) acrylate, neopentyl glycol diepoxy ( T) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane polyethoxytri (meth) acrylate, trimethylolpropane polypropoxypolyethoxytri (meth) acrylate, pentaerythritol polyethoxytri (meth) acrylate, pentaerythritol polyethoxy Tetra (meth) acrylate, ditrimethylolpropane polyethoxytetra (meth) acrylate, dipentaerythritol polyethoxytetra (meth) acrylate, dipentaerythritol polyethoxypenta (meth) acrylate, dipentaerythritol polyethoxyhexa (meth) acrylate, Polyether (meth) acrylate, polyester (meth) acrylate, silicone (meth) acrylate Among the monomers such as polybutadiene (meth) acrylate, polyamide (meth) acrylate, polyurethane (meth) acrylate, acryloylmorpholine, those having a water miscibility of 5% by weight or more, carboxyl group-containing epoxy acrylate oligomers and carboxyl group-containing urethane acrylates Examples include oligomers obtained by neutralizing carboxyl groups such as oligomers and carboxyl group-containing polyester acrylate oligomers with ammonia, triethylamine, or an alkaline solution and having a water miscibility of 5% by weight or more.

  Among these, in consideration of performance such as odor, gloss and heat resistance, polyfunctional (meth) acrylate monomers and oligomers having two or more (meth) acrylate groups in the molecule are preferable. In addition, (meth) acrylates of polyglycol glycidyl ether and polyfunctional (meth) acrylates having an ethylene chain and two or more (meth) acryloyl groups in the molecule are water-soluble, heat-resistant, and glossy. Particularly suitable for this application.

  Examples of the filler (B) used in the present invention include inorganic fillers and organic fillers, and inorganic fillers are preferable. Examples of the inorganic filler include inorganic powders such as aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, aluminum oxide, silicon dioxide, titanium dioxide, talc, clay, kaolin, colloidal silica, metal powder, and the like. The filler etc. which surface-treated inorganic powder are mentioned. Examples of the organic filler include styrene microballs, polystyrene resin beads, acrylic resin beads, urethane resin beads, polycarbonate resin beads, benzoguanamine-formalin condensate resin powder, benzoguanamine-melamine-formalin condensate resin powder, urea -Formalin condensate resin powder, aspartic acid ester derivative, zinc stearate, stearic acid amide, epoxy resin powder, polyethylene powder, tetrabromobisphenol A, decabromodiphenyl oxide, tricresyl phosphate, triethyl phosphate, aromatic polyester, etc. Is mentioned.

  These fillers (B) are added mainly for the purpose of preventing the adherence to the head and the sticking in high-speed printing, and these are used alone or in combination of two or more. The particle size is preferably smaller than the film thickness of the overcoat layer, more preferably about 0.01 to 5 μm as the average particle size (measurement is finer, for example, 1 μm or less, BET method, The larger one is by sedimentation). Moreover, the content is 0 to 50% by weight, more preferably, based on the total weight of the energy ray-curable aqueous resin composition, considering the stability of the energy ray-curable aqueous resin composition and the gloss of the coating film. It is in the range of 0.5 to 30% by weight.

  The energy ray curable aqueous resin composition used in the present invention includes a tetrafluoride resin, a stearic acid-modified silicone oil, an aspartic acid ester derivative, a dye for the purpose of improving the slipperiness of the surface of the heat-sensitive recording material, if necessary. M16 A-1212 (manufactured by Ajinomoto Co., Inc.), carnauba wax, etc., straight chain such as zinc stearate, magnesium stearate, calcium stearate, stearic acid amide, polyoxyethylene stearamide, polyoxyethylene sorbite stearate, C16 A compound having a long chain alkyl group of ˜C18, liquid paraffin, paraffin wax, synthetic wax, vegetable oil, animal oil, sorbitan ester, polyoxyethylene sorbite fatty acid ester, polyglycerin fatty acid ester can be added. In addition to the slipperiness, acrylic copolymer, silicone oil, alkyl group, amino group, epoxy group, fluorine group, carboxyl group, hydroxyl group, mercapto group, acrylic group, methacrylic group, etc. Silicone oil modified with a group or the like, a fluorosurfactant, or the like can be added. These can be contained alone or in combination.

  The blending ratio of these components is usually 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the total weight of the energy ray-curable aqueous resin composition.

  The energy ray curable aqueous resin composition used in the present invention may not be used when cured with an electron beam, but when cured with ultraviolet rays, it is a photopolymerization initiator, and if necessary, photopolymerization acceleration. Use the agent. Examples of the photopolymerization initiator that can be used include acetophenone, benzophenone, benzoin ether, chloroacetophenone, diethoxyacetophenone, hydroxyacetophenone, α-aminoacetophenone, benzylmethyl ketal, thioxanthone, α-acyloxime ester, acylphosphine oxide, glycine. Examples include oxyester, 3-ketocoumarin, 2-ethylanthraquinone, camphorquinone, and benzyl. Examples of photopolymerization accelerators include amine compounds such as N-methyldiethanolamine, triethanolamon, diethanolamine, P-dimethylaminobenzoic acid isoamyl ester, N, N-diethyl-P-aminobenzonitrile, and tri-n. -Phosphorus compounds such as butylphosphine, chlorine compounds such as hexachloroethane, Michler's ketone and the like can be used alone or in combination of two or more. The blending ratio of these polymerization initiators and accelerators is usually 0.1 to 15% by weight, preferably 0.5 to 10% by weight, based on the total weight of the energy ray-curable aqueous resin composition.

  Further, the energy ray curable aqueous resin composition used in the present invention may be added with a polymer, an antifoaming agent, an ultraviolet absorber, an antioxidant, a polymerization inhibitor, an antistatic agent, a fluorescent dye, etc., as necessary. The agent can be used in combination by appropriately selecting the type and amount of use.

  In order to produce the energy ray curable aqueous resin composition used in the present invention, for example, the following may be performed. That is, the water-soluble resin (A) having one or more ethylenically unsaturated groups in the molecule to which a photoinitiator, a photopolymerization accelerator, and other additives are added if necessary and having a water miscibility of 5% by weight or more. The filler (B) is dispersed by a dispersing machine such as a ball mill, a roll mill, a sand mill, or a dissolver. At this time, considering the stability of the resulting energy ray-curable aqueous resin composition and the gloss of the coating film, as a dispersant for the filler (B), a polycarboxylic acid-based dispersant, a silane coupling agent, a titanate-based cup It is also possible to use a silicone dispersant such as a ring agent and modified silicone oil, an organic copolymer dispersant, and the like in combination. These compounding ratios can be used in an amount of 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the total weight of the composition.

  The thus obtained energy ray-curable aqueous resin composition of the present invention is stable over time, and diluted with water or alcohol (methanol, ethanol, isopropyl alcohol, etc.) as necessary during coating. be able to. Moreover, even if it does not add an emulsifier, water can also be contained in energy-beam curable aqueous resin composition itself, and the energy-beam curable aqueous resin composition diluted with water is also stable over time.

  As a method of forming a cured film of this energy ray curable aqueous resin composition on the thermosensitive coloring layer, it is known per se by bar coater coating, air knife coating, gravure coating, offset printing, flexographic printing, screen printing, etc. In this way, the energy ray-curable aqueous resin composition of the present invention is coated on paper, synthetic paper or film. When the energy ray-curable aqueous resin composition is diluted with water or alcohol, it is dried as necessary, and then the coating is cured by irradiating energy rays such as ultraviolet rays and electron beams. In that case, when making it harden | cure with an electron beam, the electron beam accelerator which has the energy of 100-500 eV is preferable. On the other hand, in the case of curing with ultraviolet rays, an ultraviolet irradiation device having a xenon lamp, a high-pressure mercury lamp, and a metal halide lamp is used as a light source, and the amount of light and the arrangement of the light source are determined as necessary. It is preferable to cure by irradiating 1 to 4 times with a lamp having a light quantity of ˜120 W / cm at a conveyance speed of 20 to 60 m / min.

  The heat-sensitive recording material of the present invention is obtained by overcoating the above energy ray-curable resin composition on a heat-sensitive color forming layer provided on a support as an overcoat agent.

  In the present invention, the thermosensitive coloring layer usually contains a colorless or light-coloring compound (leuco dye) and a color developing compound capable of developing color when heated, and the following binders and other sensitizing agents as required. Contains additives, fillers and other additives.

In forming the thermosensitive coloring layer in the present invention, the color developing compound is 1 to 50% by weight, the color developing compound is 5 to 80% by weight, the binder is 1 to 90% by weight, the filler and the heat fusible compound. (Sensitizer) is used in an amount of 0 to 80% by weight, and other lubricants, surfactants, antifoaming agents, ultraviolet absorbers and the like are used in an arbitrary ratio, for example, 0 to 30% by weight. The weight% is the weight ratio of each component in the thermosensitive coloring layer.
Examples of the color-forming compound used in the heat-sensitive color developing layer are not particularly limited as long as they are generally used for pressure-sensitive recording paper and heat-sensitive recording paper. Specific examples include fluorane compounds, triarylmethane compounds, spiro compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds, and the like.

  Examples of the fluorane compound include 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, and 3- (N-methyl-N-cyclohexylamino). -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane, 3-isobutylethylamino-6-methyl-7-ani Linofluorane, 3- [N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-hexylamino) -6-methyl- 7-anilinofluorane, 3-dipentylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluor Lan, 3- (N-ethyl-N-tetrahydrofurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (p-chloroanilino) fluorane, 3-diethylamino-6- Methyl-7- (p-fluoroanilino) fluorane, 3- (p-toluidinoethylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (p-toluidino ) Fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (o-fluoroanilino) fluorane, 3-dibutylamino- 7- (o-fluoroanilino) fluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluor Lan, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-ethoxyethylaminofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- Diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenyl Fluorane, 3- (p-toluidinoethylamino) -6-methyl-7-phenethylfluorane and the like can be mentioned.

  Examples of triarylmethane compounds include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone or CVL), 3,3-bis (p-dimethylaminophenyl). Phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylaminoindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) ) Phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthale 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9- Rucarbazol-3-yl) -5-dimethylaminophthalide, 3,3- (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1- Methylpyrrol-2-yl) -6-dimethylaminophthalide and the like.

  Examples of the spiro compound include 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-propylspirodinaphthopyran, 3 -Methylnaphtho- (3-methoxybenzo) spiropyran, 1,3,3-trimethyl-6-nitro-8'-methoxyspiro (indoline-2,2'-benzopyran) and the like are diphenylmethane compounds such as N- Halophenyl-leucooramine, 4,4-bis-dimethylaminophenylbenzhydrylbenzyl ether, N-2,4,5-trichlorophenylleucooramine and the like include thiazine compounds such as benzoylleucomethylene blue, p- Nitrobenzoyl leucomethylene blue, etc. Examples of the tam compound include rhodamine B anilinolactam and rhodamine Bp-chloroanilinolactam. Examples of the fluorene compound include 3,6-bis (dimethylamino) fluorene spiro (9,3 ')- 6'-dimethylaminophthalide, 3,6-bis (dimethylamino) fluorene spiro (9,3 ')-6'-pyrrolidinophthalide, 3-dimethylamino-6-diethylaminofluorene spiro (9,3') -6'-pyrrolidinophthalide and the like. These color forming compounds are used alone or in combination.

  The color developing compound is not particularly limited as long as it is generally used for pressure-sensitive recording paper and heat-sensitive recording paper. Specific examples include α-naphthol, β-naphthol, p-octylphenol, 4-t-octylphenol, pt-butylphenol, p-phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, 2, 2-bis (p-hydroxyphenyl) propane (also known as bisphenol A or BPA), 2,2-bis (p-hydroxyphenyl) butane, 1,1-bis (p-hydroxyphenyl) cyclohexane, 4,4′- Thiobisphenol, 4,4′-cyclohexylidenediphenol, 2,2 ′-(2,5-dibromo-4-hydroxyphenyl) propane, 4,4-isopropylidenebis (2-t-butylphenol), 2,2 '-Methylenebis (4-chloroenol), 4,4'-dihydroxydiphenylsulfone 2,4′-dihydroxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-methoxydiphenylsulfone, 4-hydroxy-4′-ethoxydiphenylsulfone, 4-hydroxy-4 '-Isopropoxydiphenylsulfone, 4-hydroxy-4'-butoxydiphenylsulfone, methyl bis (4-hydroxyphenyl) acetate, butyl bis (4-hydroxyphenyl) acetate, benzyl bis (4-hydroxyphenyl) acetate, 2, Phenolic compounds such as 4-dihydroxy-2'-methoxybenzanilide, benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate , , 5-di -t- butyl salicylate, 3,5-di -α- aromatic carboxylic acid derivatives such as methyl benzyl salicylate, aromatic carboxylic acid or metal salts thereof.

  Examples of binders that can be used include, for example, methylcellulose, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, cellulose, polyvinyl alcohol (PVA), carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinylpyrrolidone, poly Water-soluble acrylamide, polyacrylic acid, starch and derivatives thereof, casein, gelatin, water-soluble isoprene rubber, alkali salt of styrene / maleic anhydride copolymer, iso (or diiso) butylene / maleic anhydride copolymer salt, etc. Styrene / butadiene (SB) copolymer, carboxylated styrene / butadiene (SB) copolymer, styrene / butadiene / acrylic acid copolymer, Vinyl acetate, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, polystyrene, acrylic resin, acrylic / styrene resin, polyacrylate, polyester, polycarbonate, polyurethane, polybutyral, epoxy resin, furan resin, vinyl toluene resin And hydrophobic polymer compounds such as rosin ester resin, composite particles of colloidal silica and acrylic copolymer, or emulsions thereof.

  Examples of fillers that can be used include calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay, alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, acrylic resin, polyolefin Resins, benzoguanamine resins, melamine resins, urea-formalin resins, and the like.

  Examples of heat-fusible compounds that can be used include waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, acetylated aromatic amines, naphthalene derivatives, aromatic ethers and aromatics. Carboxylic acid derivatives, aromatic sulfonic acid ester derivatives, carbonic acid or oxalic acid diester derivatives, biphenyl derivatives, terphenyl derivatives, and the like that are solid at room temperature and have a melting point of about 70 ° C. or higher can be used. This heat-fusible compound usually acts as a sensitizer that enhances the color development sensitivity.

  As waxes, for example, wood wax, carnauba wax, shellac, paraffin, montan wax, oxidized paraffin, polyethylene wax, polyethylene oxide, etc., higher fatty acids, for example, stearic acid, behenic acid, etc., higher fatty acid amides, For example, stearic acid amide, oleic acid amide, N-methyl stearic acid amide, erucic acid amide, methylol behenic acid amide, methylol stearic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, etc. For example, stearic acid anilide, linoleic acid anilide, etc., acetylated aromatic amines, for example, acetoluizide, etc., and naphthalene derivatives, for example, 1-benzyloxynaphthalene, 2-benzyloxy Examples of aromatic ethers such as phthalene and 1-hydroxynaphthoic acid phenyl ester include 1,2-diphenoxyethane, 1,4-diphenoxyethane, 1,2-bis (3-methylphenoxy) ethane, 1, 2-bis (4-methoxyphenoxy) ethane, 1,2-bis (3,4-dimethylphenyl) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1-phenoxy-2- (4-methoxy) Examples of aromatic carboxylic acid derivatives such as phenoxy) ethane include p-hydroxybenzoic acid benzyl ester, p-benzyloxybenzoic acid benzyl ester, terephthalic acid dibenzyl ester, and aromatic sulfonic acid ester derivatives. p-Toluenesulfonic acid phenyl ester, phenyl mesitylene sulfonate Examples of carbonic acid or oxalic acid diester derivatives such as 4-methylphenylmesitylene sulfonate include diphenyl carbonate, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) ester, and oxalic acid di (4-chlorobenzyl) ester. Examples of the biphenyl derivative include p-benzylbiphenyl and p-allyloxybiphenyl, and examples of the terphenyl derivative include m-terphenyl.

  In addition, lubricants such as zinc stearate, calcium stearate and aluminum stearate, various surfactants, antifoaming agents, ultraviolet absorbers and the like are added as necessary.

Using the material, a thermosensitive coloring layer is prepared on the support by, for example, the following method. That is, after the chromophoric compound and the color developing compound are separately pulverized and dispersed with a binder or other additives as required by a dispersing machine such as a ball mill, an attritor, or a sand mill by a conventional method (pulverization, When the dispersion is carried out in a wet manner, water is usually used as a medium) and mixed to prepare a heat-sensitive color developing layer coating solution, usually on a support such as paper, plastic sheet, synthetic paper, etc. / M ² may be applied by a bar coater, a blade coater, or the like (the ratio of the color developing compound to the color developing compound is usually 2: 1 to 1:10 in terms of dry weight) and dried.

  In the present invention, an intermediate layer may be provided between the thermosensitive coloring layer and the overcoat layer or between the thermosensitive coloring layer and the support. Solvent-soluble materials such as polyvinyl alcohol, starch, hydrophilic or water-dispersible resins such as styrene / butadiene latex / acrylic resin emulsion, and polyester resin, copolymer of acrylic resin and vinyl acetate resin A coating solution containing a mold resin as a main component and adding additives such as calcium carbonate, zinc oxide, talc, kaolin, clay, colloidal silica, and other surfactants as required, is applied in a conventional manner. Can be provided.

As a method of forming the intermediate layer, for example, the hydrophilic resin, water-dispersible resin or solvent-soluble resin is water or other fillers and surfactants together with a ball mill, attritor, sand mill or the like as necessary. After being dispersed by a disperser (usually the resin component is dispersed by adding 5 to 80% by weight of the system used for dispersion), the coating amount is 2 to 2 on the heat-sensitive recording layer obtained as described above. An intermediate layer is provided by coating by bar coater coating, air knife coating, gravure coating, roll coating coating, and the like so as to be 40 g / m ² and drying.

The heat-sensitive recording material of the present invention is coated and cured by the above-mentioned method using the energy ray-curable aqueous resin composition of the present invention as an overcoat agent on the heat-sensitive color developing layer or intermediate layer obtained by the above method. Use. The thickness of the overcoat layer is about 1 to 10 [mu] m (When the weight 1~10g / m ^2), more preferably about 2 to 5 [mu] m (When the weight 2-5 g / m ²⁾ is preferred.

  The present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In addition, a part means a weight part in an Example.

Reference example 1
(1) Formation of heat-sensitive recording layer [A] solution, [B] solution, and [C] solution were prepared by pulverizing and dispersing a mixture having the following composition using a sand grinder so that the average particle size was 2 μm or less. did.
[A] Liquid: 25 parts of 3-dibutylamino-7- (o-chloroanilino) fluorane
20 parts of 25% PVA aqueous solution
Water 55 parts [B] liquid: 2,2-bis (p-hydroxyphenyl) propane 25 parts
20 parts of 25% PVA aqueous solution
55 parts of water

Next, each of the prepared liquids was mixed at the following ratio to prepare a thermosensitive coloring layer coating liquid, which was coated on a fine paper having a basis weight of 50 g / m ² so that the weight when dried was about 10 g / m ² and dried. A thermosensitive coloring layer was obtained.
[A] Liquid 8 parts
[B] Liquid 16 parts
20% 50% calcium carbonate dispersion
6% 50% carboxylated styrene / butadiene copolymer latex
Water 20 parts (2) Formation of an intermediate layer PVA 25 parts Water 74 parts Colloidal oxalate 1 part The above composition was mixed to prepare an intermediate layer coating solution, and the heat-sensitive material obtained in (1) On the recording sheet, a thermal recording sheet having an intermediate layer was obtained by coating and drying so that the dry coating amount was 2 g / m ² .

(3) Formation of overcoat layer TO-1343 (Note 1) 44 parts ACMO (Note 2) 10 parts LR-8765 (Note 3) 20 parts Photoinitiator (Irgacure 184; manufactured by Ciba Specialty Chemicals) 5 parts Calcium carbonate (Average particle diameter: 0.5 μm or less) 20 parts SH28PA (Note 4) 1 part First, calcium carbonate was dispersed and mixed in LR-8765. TO-1343, ACMO, photoinitiator, and SH28PA were dissolved and mixed with a calcium carbonate dispersion to obtain an energy ray curable aqueous resin composition of the present invention. This energy ray-curable aqueous resin composition is diluted with water as necessary to obtain a viscosity suitable for coating, and dried on a heat-sensitive recording sheet having an intermediate layer obtained previously by a bar coater. After coating and drying so that the amount becomes 3 g / m ² (film thickness 3 μm), the conveyor speed is 10 m / min by an ultraviolet irradiation device (GS ASE-20; manufactured by Nihon Battery Co., Ltd.) having an 80 W / cm high-pressure mercury lamp. The energy ray-curable aqueous resin composition was cured by irradiating once with a heat-sensitive recording material of the present invention.

Example 1
Except for using the SR-9035 (Note 5) in place of the TO-1343 in the formation of the overcoat layer of Reference Example 1 to obtain a heat-sensitive recording material of the present invention in the same manner as in Reference Example 1.

Example 2
This except that Reference Example using DPEA-12 (note 6) instead of the TO-1343 in the formation of the first overcoat layer was used SL-140 (Note 7) instead of SH28PA in the same manner as in Reference Example 1 A heat-sensitive recording material of the invention was obtained.

Reference example 2
Except for using the LR-8982 (Note 8) instead of the TO-1343 in the formation of the overcoat layer of Reference Example 1 to obtain a heat-sensitive recording material of the present invention in the same manner as in Reference Example 1.

Comparative Example 1
A comparative energy beam curable resin composition and a heat-sensitive recording material were obtained in the same manner as in Reference Example 1 except that DPHA was used instead of TO-1343 in the formation of the overcoat layer of Reference Example 1.

Comparative Example 2
Except for not using calcium carbonate in the formation of the overcoat layer of Reference Example 1 to obtain a heat-sensitive recording material for comparison and Reference Example 1 in the same manner as the energy ray-curable resin composition.

(Note 1) Aronix TO-1343 (water-soluble polyester acrylate); manufactured by Toa Gosei Co., Ltd. Water miscibility of 50% by weight or more (Note 2) ACMO (acryloylmorpholine); manufactured by Kojin Co., Ltd. (Note 3) LR -8765 (water-soluble epoxy acrylate); BASF Corporation water miscibility 30% by weight or more (Note 4) SH28PA (silicone oil); Toray Dow Corning Silicone
(Note 5) SR-9035 (ethoxylated trimethylolpropane triacrylate); manufactured by Sartomer Co., Ltd. Water miscibility of 50% by weight or more (Note 6) KAYARAD DPEA-12 (ethoxylated dipentaerythritol hexaacrylate) 30% by weight or more (Note 7) Slip aid SL-140 (acrylic polymer wax); Sannopco (Note 8) LR-8982 (water-soluble polyether acrylate); BASF Co., Ltd. Water miscibility 20% by weight more than

  The energy beam curable aqueous resin composition thus obtained and the present invention and a comparative thermal recording material were evaluated. The thermal recording material was printed with a dot line type thermal printer (Teraoka Seiko printer) having a resistance value of 589 Ω to evaluate the recording running property. The results are shown in Table 1. The evaluation criteria described below were adopted. In Comparative Example 1, a coating solution suitable for coating could not be obtained, and evaluation of the thermosensitive recording material with an overcoat layer could not be carried out.

Table 1 Evaluation results
Evaluation of resin composition Stick head
Stability Water dilution IPA dilution King Adhesion
Reference Example 1 ○ ○ ○ ◎ ◎ to ○ 68
Example 1 ○ ○ ○ ◎ to ○ ◎ to ○ 73
Example 2 ○ ○ ○ ○ ◎ to ○ 75
Reference Example 2 ○ ○ ○ ○ ◎ to ○ 88
Comparative Example 1 ○ × ○ (Evaluation test is not possible)
Comparative Example 2 ○ ○ ○ × × 73

(Evaluation criteria)
(1) Evaluation of resin composition Stability: The obtained energy ray-curable aqueous resin composition was allowed to stand at room temperature for 1 month, and the stability was evaluated by observing the liquid state and the gloss of the coating film.
○: There is almost no change in the liquid state and the gloss of the cured film.
Δ: Some separation of the liquid is observed, but the redispersibility is good.
X: Liquid separation and reduction in gloss are large.
2. Dilution with water: 10 parts of water was added to 100 parts of the obtained energy ray-curable aqueous resin composition, and the state of dilution was evaluated.
○: Uniform mixing is possible, there is no decrease in gloss of the coating film, and there is no problem in coating.
X: Uniform mixing is impossible, and the gloss of the coating film is significantly reduced.
3. IPA dilution: 10 parts of IPA was added to 100 parts of the obtained energy ray-curable aqueous resin composition, and the diluted state was evaluated.
○: Uniform mixing is possible, there is no decrease in gloss of the coating film, and there is no problem in coating.
X: Uniform mixing is impossible, and the gloss of the coating film is significantly reduced.

(2) Evaluation of cured film Sticking evaluation criteria A: Smooth recording was possible without any sound during high-speed printing.
○: During high-speed printing, recording was smooth with almost no sound.
Δ: A slight recording failure occurred during high-speed printing.
X: The heat-sensitive recording material did not run smoothly, resulting in recording failure.

2. Evaluation criteria for adhesion of head dust ◎: There was no contamination of the head at the time of high-speed printing.
○: The head was hardly soiled during high-speed printing.
Δ: The head was slightly soiled after high-speed printing.
X: The head was dirty after high-speed printing.
3. Gloss The gloss of the obtained thermal recording material was measured. The gloss was measured using a gloss checker IR-320 (manufactured by Horiba, Ltd.) with a 60-degree specular gloss according to JIS Z8741.

  As is apparent from Table 1, the energy ray-curable aqueous resin composition used in the present invention is stable over time, and can be diluted with water or alcohol as needed during coating. The heat-sensitive recording material of the present invention obtained by using this energy beam curable aqueous resin composition is highly glossy, and has good sticking and adhesion to the head.

Claims (2)

In a thermosensitive recording medium having a thermosensitive coloring layer and an overcoat layer on a support, the overcoat layer is formed of an energy ray curable type water-soluble monomer or oligomer (A) having one or more ethylenically unsaturated groups in the molecule. Curing of the energy beam curable aqueous resin composition containing 40 to 95% by weight of the total weight of the aqueous resin composition and 0.5 to 50% by weight of the filler (B) of the total weight of the energy beam curable aqueous resin composition. A polyfunctional (meth) acrylate having a polyoxyethylene chain and two or more (meth) acryloyl groups in the molecule as the water-soluble monomer or oligomer (A). The heat-sensitive recording material containing acrylate and acryloylmorpholine. The heat-sensitive recording material according to claim 1, wherein the filler (B) is an inorganic filler.