JPWO2013035700A1 - Thermal recording material - Google Patents

Abstract

A thermosensitive recording material is disclosed that includes a support, a thermosensitive coloring layer provided on one side of the support, and an intermediate layer provided between the thermosensitive coloring layer and the support. The intermediate layer is a foam, contains hollow particles, or is a foam containing hollow particles. The thermosensitive coloring layer contains a leuco dye and a bisphenol compound represented by the following formula (1). [Wherein, R represents a methyl group or an ethyl group. ]

Description

  The present invention relates to a heat-sensitive recording material. The present invention also relates to a method for producing a bisphenol compound that can be used to obtain such a heat-sensitive recording material.

  The heat-sensitive recording material generally has a structure in which a heat-sensitive coloring layer containing a colorless or light-colored dye and a developer as main components is formed on a support such as paper, film or synthetic paper. The heat-sensitive color forming layer develops color by a chemical reaction that occurs when the dye and the developer are melted and brought into contact with heating to obtain a color record. For the color recording of the heat-sensitive recording material, a thermal printer with a built-in thermal head is used. Compared with other recording methods, such a thermal recording method is (1) no development, fixing, etc., (2) maintenance-free, (3) no noise during recording, (4) machine And the system is relatively inexpensive. Thermal recording methods are widely used in communication fields such as facsimiles, ticketing fields such as ticket machines, receipts and receipts, POS system label fields in convenience stores and supermarkets, industrial and medical measurement recorder fields, etc. It is used.

  In recent years, the use of heat-sensitive recording materials for labels, tickets, coupon tickets, etc. has become widespread along with POS systemization at retail stores, convenience stores, supermarkets, etc., and automation systems at transportation facilities. In these applications, high storage stability of the thermosensitive recording material is desired. The demand for high-speed recording has further increased, and development of a heat-sensitive recording material that can sufficiently cope with high-speed recording is strongly desired. In addition, for receipts of cash register sheets, labels attached to convenience foods or frozen foods, cards for long-term use, tickets, etc. Alternatively, there is a demand for a heat-sensitive recording material in which the undeveloped portion is less colored due to heat and wet heat exposed during storage.

  In the past, studies have been made on color developers and the like of heat-sensitive recording materials (for example, Patent Documents 1 to 4). A thermal recording material having a foam layer has also been proposed (Patent Document 5).

JP 60-127190 A Japanese Patent Laid-Open No. 7-156558 Japanese Patent Laid-Open No. 10-166740 JP 2001-260540 A Japanese Patent Publication No. 4-77673

  In general, when the color development sensitivity of a heat-sensitive recording material is increased in order to improve the thermal response, the background (uncolored portion) tends to develop during manufacture, use, or storage, so that a so-called background fog tends to occur. . In addition, the storage stability of a printed image that has been color-recorded is also required to be excellent.

  Accordingly, an object of the present invention is to provide a heat-sensitive recording material having good color development sensitivity, little color development in an uncolored portion, and excellent image storage stability. Another object of the present invention is to provide a method capable of obtaining a bisphenol compound that can be used for obtaining such a heat-sensitive recording material with high purity.

  As a result of various studies, the present inventors have solved the above problem by combining a thermosensitive coloring layer containing a specific color developing compound and a specific intermediate layer provided between the thermosensitive coloring layer and the support. The present invention has been completed.

  The present invention relates to a thermosensitive recording material comprising a support, a thermosensitive coloring layer provided on one side of the support, and an intermediate layer provided between the thermosensitive coloring layer and the support. The intermediate layer is a foam, contains hollow particles, or is a foam containing hollow particles. The thermosensitive coloring layer contains a leuco dye and a bisphenol compound represented by the following formula (1). In the formula (1), R represents a methyl group or an ethyl group.

  The heat-sensitive recording material according to the present invention has good color development sensitivity, little color development in uncolored portions, and excellent image storage stability. Usually, the color development sensitivity is improved by using a heat fusible compound as a sensitizer. In this case, however, color development due to environmental temperature is likely to occur at the same time. In contrast, the heat-sensitive recording material of the present invention is provided with a heat-insulating intermediate layer between the support and the heat-sensitive color-developing layer as a means for increasing the color-development sensitivity, and as a color developing compound for coloring the leuco dye. A bisphenol compound of the formula (1) is used. Thereby, although the color development sensitivity is high, the color development of the uncolored portion is small, and the storage stability of the image area is sufficiently enhanced without using other stabilizers or the like.

  The thermosensitive recording material according to the present invention may further include an overcoat layer provided on the opposite side of the thermochromic layer from the intermediate layer.

  In another aspect, the present invention relates to a method for producing a bisphenol compound represented by the above formula (1). The method according to the present invention is obtained by reacting phenol and glyoxylic acid in an acidic reaction solution to produce a hydroxycarboxylic acid compound represented by the following formula (1A), and mixing the reaction solution with water. Adjusting the aqueous liquid to alkaline, extracting impurities from the aqueous liquid with an organic solvent, adjusting the aqueous liquid to acidic, extracting the hydroxycarboxylic acid compound from the aqueous liquid with an organic solvent, and from the aqueous liquid. A step of esterifying the extracted hydroxycarboxylic acid compound to produce a bisphenol compound represented by the formula (1) in this order.

  According to the present invention, there is provided a heat-sensitive recording material having good color development sensitivity, little color development in an uncolored portion, and excellent image storage stability. Furthermore, according to the present invention, there is also provided a method capable of obtaining a bisphenol compound that can be used for obtaining such a heat-sensitive recording material with high purity.

It is sectional drawing which shows one Embodiment of a thermosensitive recording material.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a cross-sectional view showing an embodiment of a heat-sensitive recording material. A thermosensitive recording material 10 according to the present embodiment shown in FIG. 1 mainly includes a sheet-like support 1, a thermosensitive coloring layer 3 provided on one surface side of the support 1, a thermosensitive coloring layer 3, and a support. 1 and an intermediate layer 5 provided between the two.

As the support, paper, plastic sheet, synthetic paper or the like is used. The mass of the support may be, for example, 10 to 300 g / m ² .

  The intermediate layer may be a foam or may contain minute hollow particles dispersed in the intermediate layer. The intermediate layer may be a foam containing hollow particles.

  Hollow particles (fine hollow fillers) are particles in which voids are formed, and are formed of, for example, plastic, glass, or ceramic. The material forming the hollow particles may be plastic, and among them, may be a thermoplastic resin.

  The hollow particles may be spherical. The average particle diameter of the hollow particles is usually 0.2 to 10 μm, or 0.5 to 3 μm. As the hollow ratio of hollow particles (the ratio of internal voids to the apparent volume) increases, the heat insulation effect increases. However, the hollow ratio may be limited depending on the particle diameter. The hollow ratio of the hollow particles may be 30 to 90% by volume, or 50 to 90% by volume.

  The amount of the hollow particles contained in the intermediate layer is usually 10 to 90% by mass and may be 40 to 80% by mass based on the mass of the intermediate layer.

  The foam as the intermediate layer is formed, for example, by foaming foamable hollow particles having a shell made of a thermoplastic resin and containing therein a low boiling point solvent as a foaming agent.

  The intermediate layer may contain other components selected from binders, fillers, stabilizers, dispersants, antifoaming agents and other additives. These components can be appropriately selected from those generally used for pressure-sensitive recording paper and heat-sensitive recording paper. For example, the same materials as those for a heat-sensitive coloring layer described later are used.

  Usually, the amount of binder is 10-50% by weight and the amount of filler is 10-50% by weight. Stabilizers, surfactants, and other additives that are added as necessary are added to the intermediate layer in arbitrary proportions, for example, usually in the range of 0 to 30% by mass.

The intermediate layer is prepared by, for example, mixing and dispersing hollow particles, a binder and a filler, and if necessary, a surfactant and other additives in water to prepare a coating solution for the intermediate layer. Is formed on the support and the coating film is dried. The dry mass of the intermediate layer is usually ² to 20 g / m ² and may be 5 to 10 g / m ² . The coating solution for the intermediate layer can be applied using a bar coater, a doctor blade, a gravure coater or the like.

  The intermediate layer which is a foam is prepared by mixing and dispersing, for example, expandable hollow particles, a binder and a filler, and, if necessary, a surfactant and other additives in water to form a coating solution for the intermediate layer. Prepare. The coating liquid is applied onto a support, the coating film is dried, and further foamed to form. The foaming treatment is performed, for example, by bringing the coating film into close contact with the surface of a drum dryer having a heater and heating to a temperature (100 to 150 ° C.) at which the thermoplastic resin forming the foamed hollow particle shell is softened. Done.

  The thermosensitive coloring layer contains a leuco dye as a color forming compound and a bisphenol compound represented by the following formula (1) as a color developing compound. In the formula (1), R represents a methyl group or an ethyl group. R may be a methyl group.

  The bisphenol compound of formula (1) can be obtained, for example, by the method described in Japanese Patent No. 1639499. A step of reacting phenol and glyoxylic acid in an acidic reaction solution to produce a hydroxycarboxylic acid compound represented by the following formula (1A), and adjusting the aqueous solution obtained by mixing the reaction solution with water to be alkaline Extracting the impurities from the aqueous liquid with an organic solvent, adjusting the aqueous liquid to acidic, extracting the hydroxycarboxylic acid compound from the aqueous liquid with an organic solvent, and extracting the hydroxycarboxylic acid compound extracted from the aqueous liquid with The compound represented by the formula (1) having a high purity can be obtained by a method comprising esterification to produce a compound represented by the formula (1) in this order.

  The reaction between phenol and glyoxylic acid can be performed, for example, in a reaction solution containing an inorganic acid such as sulfuric acid. The reaction conditions are appropriately set within the range usually employed.

  Water is added to the reaction solution containing the hydroxycarboxylic acid of the formula (1A) to be generated, and an alkali such as sodium hydroxide is added to the obtained aqueous solution to make the aqueous solution alkaline, for example, pH 7.5 to 9.0. adjust. Impurities including unreacted phenol and the like are extracted from the aqueous liquid adjusted to alkaline with an organic solvent. For example, ethyl acetate is used as the organic solvent.

  After extraction of the impurities, the aqueous liquid is adjusted to an acidity of 3.0 to 5.0 or pH 3 to 3.7, and then the reaction product containing the hydroxycarboxylic acid compound is extracted with an organic solvent. For example, ethyl acetate is used as the organic solvent. In the extraction, by setting the pH of the aqueous liquid to 3 to 3.7, a particularly high purity bisphenol compound can be obtained in a high yield. When the pH increases, the hydroxycarboxylic acid compound tends to remain on the water layer side, and the yield tends to decrease.

  The organic layer containing the hydroxycarboxylic acid compound is concentrated if necessary, and then the bisphenol compound is esterified to produce the bisphenol compound of formula (1). The esterification reaction can be carried out by appropriately employing ordinary reactions and conditions. For example, the hydroxycarboxylic acid compound can be esterified by a method of reacting the hydroxycarboxylic acid compound of the formula (1A) with an alcohol in an acidic reaction solution with heating as necessary. For example, methanol or ethanol is used as the alcohol.

  The product bisphenol compound is purified by a usual method such as recrystallization, if necessary, and then used to form the exothermic photosensitive layer.

  The thermosensitive coloring layer may contain other color developing compounds in addition to the bisphenol compound of formula (1). As the color developing compound, various electron-accepting compounds such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids and metal salts thereof can be used. Specific examples of the color developing compound that can be used in combination with the compound of the formula (1) 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, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (3 -Phenyl-4-hydroxyphenyl) propane, 4,4'-thiobisphenol, 4,4'-cyclohexylidene Phenol, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane (also known as tetrabromobisphenol A), 4,4′-isopropylidenebis (2-t-butylphenol), 2,2′- Methylene bis (4-chlorophenol), 4,4′-isopropylidene bis (o-methylphenol), 4,4′-secondary butylidene bisphenol, 4,4′-isopropylidene bis (2-chlorophenol), 4 , 4′-butylidenebis (6-tertiarybutyl-2-methylphenol), 4,4′-thiobis (6-tertiarybutyl-2-methylphenol), 4,4′-dihydroxydiphenylsulfone, 2,4 ′ -Dihydroxydiphenyl sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-hydroxy-4′-allyloxydiphenyl sulfone, 4-benzyloxy-4′-hydroxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4,4′-diphenol sulfoxide, p-hydroxybenzoic acid Ethyl acetate, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, 5-hydroxy Ethyl isophthalate, 1,3-bis (4-hydroxyphenylthio) -propane, 1,8-bis (4-hydroxyphenylthio) -2-hydroxypropane, N, N′-diphenylthiourea, N, N ′ -Di (m-chlorophenyl) thi Urea, salicylanilide, 5-chloro-salicylanilide, bis- (4-hydroxydiphenyl) acetic acid butyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis (4-hydroxycumyl) benzene, 1,4-bis (4-hydroxychloro) benzene, 2,4′-diphenylsulfone, 3,4-dihydroxy-4′-methyldiphenylsulfone, zinc 1-acetyloxy-2-naphthoate, 2-acetyloxy- 1, zinc naphthoate, zinc 2-acetyloxy-3-naphthoate, α, α-bis (4-hydroxydiphenyl) -α-methyltoluene, zinc thiocyanate antipyrine complex, 3,5-di (α-methyl) Benzyl) salicylic acid zinc salt, a phenylsulfone cross-linking compound represented by the following formula (2), and the following formula (3) ) And the urethane urethane derivative compound. These compounds are used alone or in combination of two or more.

  The leuco dye used as the color forming compound can be appropriately selected from compounds generally used for pressure-sensitive recording paper or heat-sensitive recording paper. The leuco dye (color-forming compound) is, for example, at least one selected from the group consisting of a fluorane compound, a triarylmethane compound, a spiro compound, a diphenylmethane compound, a thiazine compound, a lactam compound, and a fluorene compound. It is this compound.

  Examples of the fluorane compound include 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-dipentylamino-6-methyl-7-aniline. Linofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilino Fluorane, 3- (N-ethyl-N-isobutylamino) -6-methyl-7-anilinofluorane, 3- [N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7 -Anilinofluorane, 3- (N-ethyl-N-hexylamino) -6-methyl-7-anilinofluorane, 3- (N-methyl-N-propylamino) -6-methyl-7 Anilinofluorane, 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- [N-ethyl-N- (p-tolyl) amino] -6-methyl-7-anilinofluorane, 3-diethylamino-6- Methyl-5- (p-toluidino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (o-fluoro) Anilino) fluorane, 3-dibutylamino-7- (o-fluoroanilino) fluorane, 3-diethylamino-7- (3,4 Dichloroanilino) fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-ethoxyethylaminofluorane, 3-diethylamino-6-chloro-7-anilinofluor Oran, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7-octylfluorane, and 3- [N-ethyl-N- (p-tolyl) amino]- 6-methyl-7-phenethylfluorane is 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, and 3,3- (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1 -Methylpyrrol-2-yl) -6-dimethylaminophthalide.

  Examples of the spiro compound include 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-propylspirodinaphthopyran, 3 -Methylnaphtho- (3-methoxybenzo) spiropyran and 1,3,3-trimethyl-6-nitro-8'-methoxyspiro (indoline-2,2'-benzopyran).

  Examples of the diphenylmethane compound include N-halophenyl-leucooramine, 4,4-bis-dimethylaminophenylbenzhydrylbenzyl ether, and N-2,4,5-trichlorophenylleucooramine.

  Examples of thiazine compounds include benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue.

  Examples of the lactam 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 and 3,6-bis (dimethylamino) fluorene spiro (9,3 ′). -6'-pyrrolidinophthalide and 3-dimethylamino-6-diethylaminofluorene spiro (9,3 ')-6'-pyrrolidinophthalide.

  The chromogenic compounds listed above can be used alone or in combination.

  The thermosensitive coloring layer may further contain a binder. As the binder, a water-soluble compound, a water-dispersible compound or an emulsion is used. Examples of the water-soluble compound include methyl cellulose, ethyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, acetyl cellulose, polyvinyl alcohol (PVA), carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, silyl group-modified polyvinyl alcohol, and polyvinylpyrrolidone. , Polyacrylamide, polyacrylic acid, starch and derivatives thereof, casein, gelatin, water-soluble isoprene rubber, styrene / maleic anhydride copolymer, and iso (or diiso) butylene / maleic anhydride copolymer. Water dispersible compounds or emulsions include, for example, styrene / butadiene latex, carboxylated styrene / butadiene latex, acrylic acid ester copolymers, styrene / acrylic acid copolymers, ethylene / vinyl acetate copolymers, acrylic / It is selected from urethane copolymers, acrylic / polyester copolymers, and acrylic / silicon copolymers.

  Based on the mass of the thermosensitive coloring layer, the amount of the color forming compound is usually 1 to 50% by mass, and may be 5 to 30% by mass. The amount of the color developing compound of the formula (1) is usually 1 to 70% by mass and may be 10 to 50% by mass. The amount of the binder is usually 1 to 90% by mass. The mass ratio of the color developing compound of formula (1) to the color developing compound (leuco dye) is usually 0.5 to 20 times, and may be 1 to 5 times.

  The heat-sensitive color forming layer may contain a sensitizer, a stabilizer, a filler, a surfactant, and other additives as necessary. The amount of the sensitizer, stabilizer and filler is usually 0 to 80% by mass. The surfactant and other additives are each added to the thermosensitive coloring layer in an arbitrary ratio, for example, usually in the range of 0 to 30% by mass.

  The sensitizer is solid at room temperature and may have a melting point. The melting point of the sensitizer may be about 70 ° C. or higher. Examples of the sensitizer include waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, naphthalene derivatives, aromatic ethers, aromatic carboxylic acid derivatives, aromatic sulfonic acid ester derivatives, carbonic acid derivatives. Alternatively, oxalic acid diester derivatives, biphenyl derivatives, terphenyl derivatives, and sulfone derivatives are used.

  Examples of waxes include wood wax, carnauba wax, shellac, paraffin, montan wax, oxidized paraffin, polyethylene wax, and oxidized polyethylene. Examples of higher fatty acids include stearic acid and behenic acid. Examples of the higher fatty acid amide include stearic acid amide, oleic acid amide, N-methyl stearic acid amide, erucic acid amide, methylol behenic acid amide, methylene bis stearic acid amide, and ethylene bis stearic acid amide. Examples of the higher fatty acid anilide include stearic acid anilide and linoleic acid anilide. Specific examples of naphthalene derivatives include 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, and the like. Examples of the aromatic ether include 1,2-diphenoxyethane, 1,4-diphenoxybutane, 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-methoxyphenoxy) ethane, 1,2-diphenoxymethylbenzene Is mentioned. Examples of the aromatic carboxylic acid derivative include p-benzyloxybenzoic acid benzyl ester and terephthalic acid dibenzyl ester. Examples of the aromatic sulfonic acid ester derivative include p-toluenesulfonic acid phenyl ester, phenyl mesitylene sulfonate, and 4-methylphenyl mesitylene sulfonate. Examples of the carbonic acid or oxalic acid diester derivative include diphenyl carbonate, dibenzyl oxalate, di (4-chlorobenzyl) oxalate, and di (4-methylbenzyl) oxalate. Examples of the biphenyl derivative include p-benzylbiphenyl, p-acetylbiphenyl, and p-allyloxybiphenyl. Examples of the terphenyl derivative include m-terphenyl and a terphenyl isomer mixture. Examples of the sulfone derivative include diphenyl sulfone, 4-methyldiphenyl sulfone, and chlorinated diphenyl sulfone. These sensitizers are appropriately used by selecting one or two or more of these sensitizers.

  As the stabilizer, for example, a phenol derivative and an amine derivative imparting an antioxidant or antiaging effect, or a benzotriazole compound and a benzophenone compound as an ultraviolet absorber can be used.

  Examples of phenol derivatives and amine derivatives include 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 4,4 ′. -Butylidenebis (6-t-butyl-2-methylphenol), 4,4'-thiobis (6-t-butyl-2-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-) 5-t-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, tetramethylbisphenol S, tetrabromobisphenol S, 4,4′-thiobis (2 -Methylphenol), 4,4′-thiobis (2-chlorophenol), bis (2,2,6,6-tetramethyl-4-sebacate) Peridinyl), tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, tetrakis (1,2,2,6,6-tetramethyl-) 4-piperidyl) -1,2,3,4-butanetetracarboxylate.

  Examples of the benzotriazole compounds include 2- (2′-hydroxy-5′-methyl-phenyl) -benzotriazole and 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5. -Chlorobenzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl)- Benzotriazole, 2- (2′-hydroxy-4′-octoxyphenyl) -benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -benzotriazole, 2- ( 2′-hydroxy-3 ′, 5′-di-t-amylphenyl) -benzotriazole, methylene-bis [2- (2′-hydroxy-5′-dodecanyl phen Le) benzotriazole], and the like.

  Examples of the benzophenone compounds include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone. Bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane).

  Examples of the filler include calcium carbonate, silica, white carbon, talc, clay, alumina, titanium oxide, zinc oxide, aluminum hydroxide, aluminum oxide, magnesium carbonate, magnesium oxide, magnesium hydroxide, barium sulfate, polystyrene resin, urea -Formalin resin, hollow plastic pigment, foamable hollow plastic pigment.

  Surfactants include, for example, fatty acid metal soaps, polycarboxylic acid type polymer activators, sulfates of higher alcohols, sulfates of alkyl polyethers, ethylene oxide adducts of higher alcohols, alkylaryls. Sulfonates, alkyl sulfonic acids, aryl sulfonic acids, phosphate esters, aliphatic phosphate esters, aromatic phosphate esters, polyoxyethylene alkyl sulfate esters, polyoxyethylene aryl sulfate esters, polyoxyethylene Alkylaryl sulfates, dialkylsulfosuccinates, alkylbenzenesulfonates, polyoxyalkylene alkyl ether phosphates, polyoxyalkylene aryl ether phosphates, polyoxyalkylenes Alkyl aryl ether phosphate, sodium alkyl sulfate, dioctyl sulfosuccinate sodium salt, polyalkylene glycol 9 (eg, polyoxyethylene nonylphenyl ether), acetylene glycol, ethylene oxide adduct of acetylene glycol, propylene oxide addition of acetylene glycol Products, ethylene oxide and propylene oxide adducts of acetylene glycol, and the like.

  Other additives include lubricants (for example, higher fatty acid metal salts such as zinc stearate and calcium stearate), water resistance agents (for example, glyoxal, glutaraldehyde, dialdehyde, ethylenediamine, urea-formaldehyde resin, melamine-formaldehyde resin, polyamide) Resin, polyamidoamine-epichlorohydrin resin, adipic acid dihydrazide, phthalic acid dihydrazide, boric acid, borax, titanium lactate, ammonium zirconium carbonate and potassium zirconium carbonate), thickener (eg xanthan gum, carboxymethylcellulose), Foaming agents and antifoaming agents (for example, silicon oil, mineral oil), fluorescent whitening agents, fluorescent dyes, colored dyes, colored pigments and the like can be used.

For example, the thermosensitive coloring layer is composed of a leuco dye and a color developing compound containing the bisphenol compound of formula (1) separately from each other, and a binder and, if necessary, a sensitizer, a stabilizer, a filler, and other additives. And the like, a step of preparing a dispersion in which each component is dispersed by wet pulverization using a medium such as water, a step of preparing a coating solution by mixing each dispersion, and this coating solution on the intermediate layer It can form by the method including the process of apply | coating and drying the apply | coated coating liquid. The wet dispersion for obtaining the dispersion liquid can be performed using a disperser such as a ball mill, an attritor or a sand mill. The dry mass of the thermosensitive coloring layer is usually ² to 20 g / m ² and may be 4 to 10 g / m ² .

  The thermosensitive recording material 10 according to the present embodiment may further include a layer other than the intermediate layer 5 and the thermosensitive coloring layer 3 as necessary. For example, another intermediate layer may be provided between the intermediate layer 5 and the thermosensitive coloring layer 3, or the overcoat layer 7 may be provided on the thermosensitive coloring layer 3. Another intermediate layer and overcoat layer contain, for example, binders and fillers as described above, and other additives added as needed. These additional layers can be formed by applying a coating solution containing each component and drying it, as in the case of the intermediate layer and the thermosensitive coloring layer.

The overcoat layer includes, for example, a binder, a filler, and a lubricant, and a surfactant, a water resistant agent and other additives which are added as necessary. The dry mass of the overcoat layer is usually 1 to 10 g / m ² .

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” represents parts by weight and “%” represents mass%.

1. Synthesis of Bisphenol Compound Represented by Formula (1) According to the following reaction formulas (A) and (B), a compound represented by formula (10) in which R in formula (1) is a methyl group was produced.

Production Example 1
A reaction solution was prepared by charging 118.5 g (0.8 mol) of a 50% aqueous solution of glyoxylic acid, 165 g (1.753 mol) of phenol, and 98 g (1 mol) of 39.3% sulfuric acid in a reaction vessel. The reaction solution was heated to 45 ° C. for 18 hours to allow the reaction of formula (A) to proceed. Thereafter, water was added to the reaction solution, and the pH of the reaction solution was adjusted to 8.3 with 25% NaOH. The extraction operation was performed twice with ethyl acetate, and then the pH of the aqueous layer was adjusted to 3.5 with 35% hydrochloric acid. Ethyl acetate was added thereto, and the ethyl acetate layer was collected by liquid separation and concentrated to obtain an oily reaction product. Methanol and sulfuric acid were added to the reaction product, and the mixture was refluxed for 10 hours to promote esterification of the formula (B). Thereafter, methanol was distilled off, and water was added to precipitate crystals. The crystals were filtered off while cooling to 4 ° C, and the crystals were washed twice with 25% methanol and dried to obtain 109 g of the compound represented by the formula (10). The yield was 52%. When the obtained compound represented by the formula (10) was analyzed by HPLC, the purity was 97.16%. In the product, the concentration of the compound represented by formula (1A) is 0.59%, the concentration of phenol is 0.07%, and the concentration of ethyl ester of the compound represented by formula (1A) is 0.55%. The impurity concentration was sufficiently low. Moreover, melting | fusing point calculated | required by DSC measurement of the compound shown by Formula (10) was 151.8 degreeC.

Production Example 2
A reaction vessel was charged with 53.5 kg (0.361 kg) of a 50% aqueous solution of glyoxylic acid, 74.6 kg (0.793 kg) of phenol, and 44.3 kg (0.177 kg) of 39.2% sulfuric acid. Was prepared. Others were the same as in Production Example 1, and 49.7 kg of the compound represented by the formula (10) was obtained. The yield was 53%. When the obtained compound represented by the formula (10) was analyzed by HPLC, the purity was 98.86%. In the product, the concentration of the compound represented by the formula (1A) is 0.59%, the concentration of the phenol is below the detection limit, and the concentration of the ethyl ester of the compound represented by the formula (1A) is 0.16%. The impurity concentration was sufficiently low. Moreover, melting | fusing point calculated | required by DSC measurement of the compound shown by Formula (10) was 152.3 degreeC.

Comparative production example 1
A reaction solution was prepared by charging 28.1 g (0.2 mol) of a 50% aqueous solution of glyoxylic acid, 41.4 g (0.44 mol) of phenol, and 20 mL (0.1 mol) of 10N sulfuric acid in a reaction vessel. The reaction solution was heated to 45 ° C. for 18 hours to allow the reaction of formula (A) to proceed. Then, water was added to the reaction liquid, and extraction operation was performed twice with ethyl acetate. After concentrating the ethyl acetate layer, methanol and sulfuric acid were added to carry out the esterification reaction of formula (B). After completion of the reaction, methanol was distilled off, and 40% methanol was added to the residue to recrystallize the product. The precipitated crystals were collected by filtration, washed twice with 25% methanol and then dried to obtain 16.54 g of a compound represented by the formula (10). The yield was 34%. When the obtained compound represented by the formula (10) was analyzed by HPLC, the purity was 92.5%, which was lower than Production Examples 1 and 2.

Comparative production example 2
A reaction solution was prepared by charging 28.1 g (0.2 mol) of a 50% aqueous solution of glyoxylic acid, 41.4 g (0.44 mol) of phenol, and 20 mL (0.1 mol) of 10N sulfuric acid in a reaction vessel. The reaction was heated to 45 ° C. for 18 hours to allow the reaction to proceed. Thereafter, 100 mL of water was added to the reaction solution, and extraction operation was performed twice with 100 mL of ethyl acetate. The compound represented by the formula (1A) was extracted from the ethyl acetate layer to the aqueous layer side with a saturated aqueous NaHCO 3 solution. After adjusting the pH of the obtained aqueous layer to 1.8 with sulfuric acid, extraction operation was performed twice with ethyl acetate. The ethyl acetate layer was concentrated to obtain an oily reaction product. Methanol and sulfuric acid were added thereto and refluxed for 4 hours. After completion of the reaction, methanol was distilled off, and 30% methanol was added to the residue to recrystallize the product. The precipitated crystals were collected by filtration, washed with 30% methanol and dried to obtain 27.3 g of a compound represented by the formula (10). The yield was 56%. When the obtained compound represented by the formula (10) was analyzed by HPLC, the purity was 90.7%, which was lower than Production Examples 1 and 2.

Example 1 (Formation of an intermediate layer)
The following materials were mixed to prepare a coating solution for the intermediate layer. This coating solution was applied onto fine paper having a basis weight of 64 g / m ² , and the coating film was dried to form an intermediate layer of 7 g / m ² .
30% hollow fine particle aqueous dispersion (material = styrene / acrylic acid ester copolymer, average particle size = 1 μm, hollow ratio = 54%) 640 parts 60% calcium carbonate aqueous dispersion 50 parts 48% carboxyl group-modified SBR latex 85 225 parts water

(Formation of thermosensitive coloring layer)
The solids in the three kinds of mixture containing the following materials were dispersed while being pulverized using a bead mill until the average particle size became 1 μm to obtain [A] liquid, [B] liquid and [C] liquid. It was.
[A] Liquid 3-dibutylamino-6-methyl-7-anilinofluorane 30 parts PVA 5 parts water 65 parts [B] Compound represented by liquid formula (10) (Production Example 1) 30 parts PVA 5 parts water 65 parts [C] liquid CVL (crystal violet lactone) 30 parts PVA 5 parts water 65 parts

Next, a coating solution for the thermosensitive coloring layer having the following composition containing the [A] solution and the [B] solution was prepared. The coating solution is applied onto the intermediate layer, and the coating film is dried to form a thermosensitive coloring layer of 6 g / m ² , and a thermosensitive recording material composed of fine paper, the intermediate layer, and the thermosensitive coloring layer is obtained. Obtained.
[A] Liquid 50 parts [B] Liquid 100 parts 60% calcium carbonate aqueous dispersion 83 parts 20% silica aqueous dispersion 250 parts 36% zinc stearate aqueous dispersion 61 parts 10% fully saponified PVA aqueous solution 200 parts water 156 Part

Example 2
[A] 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane is used instead of 3-dibutylamino-6-methyl-7-anilinofluorane in the solution A heat-sensitive recording material was obtained in the same manner as Example 1 except for the above.

Example 3
[A] A thermosensitive recording material was obtained in the same manner as in Example 1 except that CVL was used instead of 3-dibutylamino-6-methyl-7-anilinofluorane in the solution.

Example 4
A thermosensitive recording material was prepared in the same manner as in Example 1 except that the compound represented by the formula (10) obtained in Production Example 2 was used instead of the compound represented by the formula (10) obtained in Production Example 1. Obtained.

Example 5
A heat-sensitive recording material was obtained in the same manner as in Example 1, except that the weight of the intermediate layer when dried was 10 g / m ² .

Example 6
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the intermediate layer was dried at a mass of 5 g / m ² .

Comparative Example 1
A heat-sensitive color-developing layer (6 g / m ² ) similar to that in Example 1 was formed on high-quality paper having a basis weight of 64 g / m ² without forming an intermediate layer, thereby obtaining a heat-sensitive recording material for comparison.

Comparative Example 2
A heat-sensitive color-developing layer (6 g / m ² ) similar to that of Example 2 was formed on high-quality paper having a basis weight of 64 g / m ² without forming an intermediate layer, thereby obtaining a heat-sensitive recording material for comparison.

Comparative Example 3
A coating solution for the thermosensitive coloring layer having the following composition was prepared. This coating solution was applied onto a high-quality paper having a basis weight of 64 g / m ² without forming an intermediate layer, and the coating film was dried to obtain a comparative thermosensitive recording material having a thermosensitive coloring layer of 7 g / m ^2. It was.
[C] Liquid 50 parts [B] Liquid 100 parts 25% aqueous stearamide dispersion 120 parts 60% calcium carbonate aqueous dispersion 83 parts 20% silica aqueous dispersion 250 parts 36% zinc stearate aqueous dispersion 61 parts 10 % Fully saponified PVA aqueous solution 200 parts water 36 parts

Comparative Example 4
[B] Instead of the compound represented by the formula (10) in the liquid, bis- (4-hydroxydiphenyl) acetic acid butyl ester having a substituted alkyl group different from that of the compound represented by the formula (10) was used. Other than this, a heat-sensitive recording material for comparison was obtained in the same manner as in Example 1.

Comparative Example 5
[B] A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that bisphenol A was used instead of the compound represented by formula (10) in the liquid.

  The heat-sensitive recording material obtained as described above was evaluated by the following quality performance test. Tables 1 and 2 show the evaluation results.

1) Background The reflection density (Macbeth reflection density) of the uncolored portion (background) of the sample was measured using a Macbeth reflection densitometer (SpectroEyeLT, manufactured by Sakata Engineering Co., Ltd.).
2) Color density Using a commercially available thermal printer (Ishida BP-4000, Ishida Co., Ltd.), the sample was developed with a printing energy of 75% or 95%. It measured similarly.
3) Moisture resistance A sample colored in the same manner as in “2) Color density” was left in a humidity chamber at 40 ° C. and 90% relative humidity for 24 hours. The reflection density of the uncolored portion after the moisture resistance test and the image residual ratio of the image portion (= reflection density after test / reflection density (%) before test) were measured.
4) Heat resistance A sample colored in the same manner as in “2) Color density” was left in a thermostat at 60 ° C. for 24 hours. The reflection density of the uncolored portion after the heat resistance test and the image residual ratio of the image portion (= reflection density after test / reflection density (%) before test) were measured.
5) Heat resistance A sample colored in the same manner as in “2) Color density” was left in an incubator at 80 ° C. for 24 hours. The reflection density of the uncolored portion after the heat resistance test and the image residual ratio of the image portion (= reflection density after test / reflection density (%) before test) were measured.
6) Heat resistance A sample colored in the same manner as in “2) Color density” was left in an incubator at 100 ° C. for 1 hour. The reflection density of the uncolored portion after the heat resistance test and the image remaining ratio of the image portion (= reflection density after test / reflection density (%) before test).

  Example 1 and Example 2 have higher color development while suppressing background fogging (coloration of the uncolored portion) after the heat resistance test, as compared with Comparative Example 1 and Comparative Example 2 in which no corresponding intermediate layer is provided. The concentration has been reached. Compared with Comparative Example 3 using stearamide as a sensitizer for improving sensitivity, Example 3 has a middle layer provided without using a sensitizer. A color density exceeding the effect of the sensitizer has been reached at a low level of printing energy. Further, Example 3 showed smaller undeveloped color development and a higher image residual ratio after the moisture resistance test and the heat resistance test at 80 ° C. or 100 ° C. as compared with Comparative Example 3.

  In Comparative Example 4 in which bis- (4-hydroxydiphenyl) acetic acid butyl ester having a substituted alkyl group different from the compound represented by the formula (10) is used, the color development density is satisfactory, but a heat resistance test at 100 ° C. in particular. It is clearly inferior in terms of coloration of the later uncolored part. In Comparative Example 5 using general-purpose bisphenol A (BPA), although an intermediate layer was provided, it was inferior to Examples in terms of coloring in the uncolored portion after the heat resistance test. Thus, the thermosensitive recording material having an intermediate layer and using the compound represented by the formula (10) is thermosensitive using bis- (4-hydroxydiphenyl) acetic acid butyl ester or bisphenol A having different substituted alkyl groups. Compared to the recording material, the coloring of the uncolored portion due to heat is small.

  From the above experimental results, it was confirmed that the heat-sensitive recording material of the present invention has good color development sensitivity, little color development in the uncolored portion, and excellent image storage stability.

  DESCRIPTION OF SYMBOLS 1 ... Support body, 3 ... Thermal coloring layer, 5 ... Intermediate | middle layer, 7 ... Overcoat layer, 10 ... Thermal recording material.

Claims (3)

A support, a thermosensitive coloring layer provided on one side of the support, and an intermediate layer provided between the thermosensitive coloring layer and the support,
The intermediate layer is a foam, contains hollow particles, or is a foam containing hollow particles,
A heat-sensitive recording material, wherein the heat-sensitive coloring layer contains a leuco dye and a bisphenol compound represented by the following formula (1).

[Wherein, R represents a methyl group or an ethyl group. ]   The thermosensitive recording material according to claim 1, further comprising an overcoat layer provided on a side of the thermosensitive coloring layer opposite to the intermediate layer. A step of reacting phenol and glyoxylic acid in an acidic reaction solution to produce a hydroxycarboxylic acid compound represented by the following formula (1A);
Adjusting the aqueous liquid obtained by mixing the reaction liquid with water to be alkaline, and extracting impurities from the aqueous liquid with an organic solvent;
Adjusting the aqueous liquid to acid, and extracting the hydroxycarboxylic acid compound from the aqueous liquid with an organic solvent;
Esterifying the hydroxycarboxylic acid compound extracted from the aqueous liquid to produce a bisphenol compound represented by the following formula (1);
Are prepared in this order.

[Wherein, R represents a methyl group or an ethyl group. ]

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