JP2015085520A - Thermosensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording medium which has high recording density and is excellent in plasticizer resistance of a recording part.SOLUTION: There is provided a thermosensitive recording medium which has a thermosensitive recording layer containing at least a leuco dye and a coloring agent on a support. The thermosensitive recording medium contains at least one selected from diphenylsulfone crosslinked type compounds represented by a general formula and N-[2-(3-phenylureido)phenyl]benzenesulfonamide as a coloring agent. The diphenylsulfone crosslinked type compound is preferably contained in a ratio of 0.1 to 2.5 pts.mass based on 1 pt.mass of N-[2-(3-phenylureido)phenyl]benzenesulfonamide.

Description

  The present invention relates to a heat-sensitive recording material utilizing a color development reaction between a leuco dye and a colorant.

  A heat-sensitive recording material is known in which a recording image is obtained by reacting a colorless or light-colored leuco dye and a color former capable of acting as an electron acceptor of the leuco dye with heat to cause color development.

  The fields of use include, for example, cash register sheets and ticket sheets for POS (Point of Sales) systems. With the expansion of the system, the use environment and use methods are diversified, and use under severe conditions is also possible. It is increasing. Furthermore, since it is also used as a receipt in the same application, it is necessary to have good storage stability and sealability for various chemicals such as oil in the recording section, plasticizer, office supplies, and hand cream.

  It is known that in a heat-sensitive recording material provided with a heat-sensitive recording layer mainly composed of a leuco dye and a colorant on a support, the color-development reaction is reversible, so that the color-development image disappears with time. It has been. This decolorization reaction is accelerated in a high temperature and high humidity environment, and further proceeds rapidly by contact with oil, plasticizer, etc., and the recorded image may be decolored until it cannot be read. On the other hand, in order to improve the storability of the recording part, it has been proposed to add an epoxy compound in the heat-sensitive recording layer (see Patent Document 1). However, it has a sufficient effect on oil and plasticizer. Is not obtained. Further, in recent years, development of a colorant having high storage stability has progressed, and it has been proposed to add a urea urethane compound to the heat-sensitive recording layer (see Patent Document 2), and the above problems are being solved. There is a problem that is low. In order to increase the stability (heat resistant background fogging property) of the non-printing portion, it is effective to use a colorant having a high melting point, but this also has a problem that the recording sensitivity is lowered. However, it is difficult to cope with recent high-speed printers and battery-powered handy terminal printers.

  In order to solve this problem, it has been proposed to use at least one diphenylsulfone cross-linking compound and at least one specific hydroxydiphenylsulfone derivative as a color former (see Patent Document 3). However, in the heat-sensitive recording material described in Patent Document 3, the storage stability of the recording portion with respect to oil or plasticizer is improved, but the stability (heat resistant background fogging property) of the non-printing portion is insufficient.

  Further, high-quality paper is generally used as a support for the thermal recording medium. In acid papermaking, rosin-based sizing agents and fillers such as clay and talc are internally added for papermaking. A sulfuric acid band is generally used as a fixing agent for this rosin-based sizing agent, but the pH of the paper surface becomes acidic due to the sulfate radical remaining in the paper, and the color-forming substance constituting the thermal recording paper is There is a problem in that it reacts with acidic ions on the surface of the paper and easily causes background fogging during a long-term storage period. For this reason, neutral paper containing an alkali filler such as calcium carbonate may be used as a support for the thermal recording medium for the purpose of preventing background fogging or reducing papermaking costs.

  However, if neutral paper is used as the support for the thermal recording medium, the color developing ability may be reduced before recording, for example, less than one year during storage of the thermal recording medium, or after recording. If so, there is a problem that the color fading occurs and the print is faint, unclear, or in some cases, almost invisible. In particular, if the color developing ability is lowered before recording, the print density of the heat-sensitive recording medium is lowered, making it difficult to read and the original function as a heat-sensitive recording body is lost. The reason why the color developing ability is lowered is not clear, but it is presumed that the color forming agent forms a salt with an alkali filler contained in the neutral paper and causes a change in form, thereby reducing the performance of the color developing agent.

JP-A-4-286855 JP 2002-144746 A Japanese Patent No. 3664840

  The main object of the present invention is to provide a heat-sensitive recording material having a high recording density and excellent plasticizer resistance in the recording area.

  As a result of intensive studies in view of the above-described conventional technology, the present inventors have solved the above-described problems. That is, the present invention relates to the following thermal recording material.

  Item 1: In a heat-sensitive recording material having a heat-sensitive recording layer containing at least a leuco dye and a colorant on a support, as the colorant, a diphenylsulfone cross-linked compound represented by the following general formula (1) A heat-sensitive recording material comprising at least one selected from N- [2- (3-phenylureido) phenyl] benzenesulfonamide.

（式中、ｎは１〜１０の整数を表す。）

(In the formula, n represents an integer of 1 to 10.)

  Item 2: The diphenylsulfone crosslinking compound is contained at a ratio of 0.1 to 2.5 parts by mass with respect to 1 part by mass of the N- [2- (3-phenylureido) phenyl] benzenesulfonamide. The heat-sensitive recording material according to 1.

  Item 3: The diphenylsulfone crosslinking compound is contained in a ratio of 0.2 to 3 parts by mass with respect to 1 part by mass of the leuco dye, and the N- [2- (3-phenylureido) phenyl] benzenesulfonamide Item 3. The heat-sensitive recording material according to Item 1 or 2, comprising 0.5 to 5 parts by mass.

  Item 4: The heat-sensitive recording material according to any one of Items 1 to 3, further comprising an undercoat layer containing plastic hollow particles between the support and the heat-sensitive recording layer.

  Item 5: The heat-sensitive recording material according to any one of Items 1 to 4, which has an undercoat layer formed by a blade coating method between the support and the heat-sensitive recording layer.

  Item 6: The heat-sensitive recording material according to any one of Items 1 to 5, wherein at least one layer formed on the support is formed by a curtain coating method.

  The heat-sensitive recording material of the present invention has a high recording density and excellent plasticizer resistance in the recording area. Moreover, it is excellent in the heat-resistant surface fogging property in a high temperature environment.

  The present invention provides a heat-sensitive recording material having a heat-sensitive recording layer containing at least a leuco dye and a colorant on the support, and the layer structure of the heat-sensitive recording material is that of the support and the heat-sensitive recording layer. The structure is not limited to the above, the structure having an undercoat layer between the support and the heat-sensitive recording layer, the structure having a protective layer on the heat-sensitive recording layer, and the surface of the support opposite to the surface having the heat-sensitive recording layer. Includes a configuration having a back layer.

  Although it does not specifically limit as a support body in this invention, For example, neutral or acidic quality paper (neutral paper, acidic paper), a synthetic paper, a transparent or translucent plastic film, a white plastic film etc. are mentioned. . Although the thickness of a support body is not specifically limited, Usually, it is about 20-200 micrometers.

  In the present invention, it is preferable that the support is neutral paper or acidic paper obtained by making a pulp slurry containing pulp fibers, a filler, and a sizing agent, because the effects of the present invention can be fully exhibited. That is, in either neutral paper or acidic paper, it exerts an excellent effect on plasticizer resistance after storage of white paper, and has excellent storage stability of white paper with potentially high recording density while having heat resistance on the background. A heat-sensitive recording material can be obtained. Although the reason for this is not clear, the colorant generally forms a salt with an alkali filler contained in the neutral paper while the thermal recording material is stored in a blank state before recording. It is estimated that N- [2- (3-phenylureido) phenyl] benzenesulfonamide does not cause a morphological change regardless of whether it is neutral paper or acidic paper.

  The type of neutral paper and production method are not particularly limited, but pulp fibers and generally fillers such as calcium carbonate, sizing agents such as alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), etc., and polyamides as fixing agents, A pulp slurry containing acrylic amide, cationic starch and the like can be obtained by paper making. As such neutral paper, the hot water extraction pH (based on JIS P 8133) is preferably in the range of 6.5 to 10, and more preferably in the range of 7.5 to 10. By setting the pH of the neutral paper to 6.5 or more, background fogging during storage of white paper can be effectively suppressed. On the other hand, aggregation of pulp slurry itself can be suppressed by setting pH to 10 or less. Moreover, as long as pH does not become smaller than 6.5, a pH can be adjusted using a sulfuric acid band as needed, and papermaking property can also be improved.

  Kinds of acid paper and production method are not particularly limited, but pulp fibers and fillers such as kaolin, talc, chlorite, rosin sizing agents such as reinforced rosin soap and reinforced rosin emulsion, alkenyl succinic acid soap, etc. A so-called synthetic sizing agent, etc., and a pulp slurry containing a sulfuric acid band and the like can be obtained by papermaking. Such acidic paper has a hot water extraction pH (based on JIS P 8133) in the range of about 2-6.

  Kinds of pulp fibers used in the present invention, production method and the like are not particularly limited. For example, various high-yield pulps in addition to chemical pulp and SCP such as softwood pulp and hardwood pulp obtained by KP, SP, AP method, and the like, Or a waste paper pulp etc. are mentioned.

  It should be noted that internal additives for papermaking such as dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents, slime control agents can be added to the pulp slurry as appropriate depending on the use of the paper. . Moreover, starch etc. can also be apply | coated in a size press. As the paper machine, a long net paper machine, a twin wire type paper machine, a circular net paper machine, a Yankee dryer paper machine and the like can be used as appropriate.

  The heat-sensitive recording layer in the present invention can contain various known leuco dyes of colorless or light color. Specific examples of such leuco dyes include, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylamino) Phenyl) -6-dimethylaminophthalide, blue coloring dyes such as fluoran, 3- (N-ethyl-Np-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-ani Green chromogenic dyes such as linofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3 -Red coloring dyes such as diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3 (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino- 6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilino Fluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) ) -6-methyl-7- (p-toluidino) fluorane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino No-6-chloro-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6 Methyl-7-anilinofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] ] Black} color developing dye such as phenyl} propane, 3-diethylamino-7- (3′-trifluoromethylphenyl) aminofluorane, 3,3-bis [1- (4-methoxyphenyl) -1- (4- Dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) e Len-2-yl] -4,5,6,7-tetrachlorophthalide, 3-p- (p-dimethylaminoanilino) anilino-6-methyl-7-chlorofluorane, 3-p- (p -Chloroanilino) anilino-6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, etc. And the like. Of course, it is not limited to these, Moreover, 2 or more types can also be used together as needed. Among them, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, and 3- (N -Ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane is preferably used because it is excellent in color development sensitivity and print storage stability. The content ratio of the leuco dye is about 5 to 25% by mass, preferably 7 to 20% by mass, of the total solid content of the heat-sensitive recording layer. By setting the content to 5% by mass or more, the coloring ability can be improved and the printing density can be improved. Heat resistance can be improved by setting it as 25 mass% or less.

  The heat-sensitive recording layer in the invention has at least one selected from diphenylsulfone cross-linked compounds represented by the following general formula (1) as a colorant (hereinafter also referred to as a specific diphenyl sulfone cross-linked compound), and N- Contains [2- (3-phenylureido) phenyl] benzenesulfonamide. As a result, the recording density is high and the plasticizer resistance of the recording part is excellent. In addition, it exhibits an excellent heat-resistant background fogging effect even in a high temperature environment. Moreover, the plasticizer resistance after storage of white paper can be improved. A specific diphenyl sulfone bridge type compound can be used individually by 1 type or in combination of 2 or more types.

（式中、ｎは１〜１０の整数を表す。）

(In the formula, n represents an integer of 1 to 10.)

  N- [2- (3-phenylureido) phenyl] benzenesulfonamide has a high recording density and a low background fogging property in a high temperature environment, but has a problem that the plasticizer resistance of the recording portion is inferior. However, in the present invention, excellent recording density, oil resistance of the recording area, and plasticizer resistance can be secured by using in combination with a specific diphenylsulfone crosslinking type compound. Moreover, in general, the background fog is remarkably deteriorated when a colorant is used in combination, but the combination of the specific diphenylsulfone cross-linking compound and N- [2- (3-phenylureido) phenyl] benzenesulfonamide in the present invention. The synergistic effect is excellent in that not only the background fog is not deteriorated but also the background fog is not generated even in a high temperature environment of 80 ° C.

  The content of the specific diphenylsulfone crosslinking compound in the heat-sensitive recording layer is about 0.1 to 2.5 parts by mass with respect to 1 part by mass of N- [2- (3-phenylureido) phenyl] benzenesulfonamide. Preferably, about 0.2-2 mass parts is more preferable, about 0.5-1.8 mass parts is further more preferable, and about 1.0-1.8 mass parts is especially preferable. By setting it as 0.1 mass part or more, the plasticizer resistance of a recording part can be improved. On the other hand, by setting it to 2.5 parts by mass or less, the heat resistant background fogging property under a high temperature environment can be improved.

  The content of the specific diphenylsulfone crosslinking type compound in the heat-sensitive recording layer is preferably 0.2 to 3 parts by mass, and 0.4 to 2 with respect to 1 part by mass of the leuco dye, from the viewpoint of improving the plasticizer resistance. Mass parts are more preferable, 0.8 to 1.8 parts by mass are further preferable, and 1.1 to 1.8 parts by mass are particularly preferable.

  The content of N- [2- (3-phenylureido) phenyl] benzenesulfonamide in the thermosensitive recording layer is 0.5 to 5 masses with respect to 1 mass part of the leuco dye from the viewpoint of improving plasticizer resistance. Part, preferably 0.8 to 3 parts by weight, more preferably 0.8 to 1.8 parts by weight, and particularly preferably 0.8 to 1.4 parts by weight.

The colorant in the present invention uses a specific diphenylsulfone cross-linking compound and N- [2- (3-phenylureido) phenyl] benzenesulfonamide. Known materials can be used in combination. Specific examples include inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1 , 1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl sulfide, hydroquinone monobenzyl Ether, 4-hydroxy-4′-benzyloxydiphenylsulfone, benzyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, bis (3-allyl-4- Hydroxyphenyl) sulfone, -Hydroxy-4'-methyldiphenylsulfone, 4-allyloxy-4'-hydroxydiphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, 1- [4- (4-hydroxyphenylsulfone) phenoxy]- Phenolic compounds such as 2- [4- (4-isopropoxyphenylsulfone) phenoxy] butane, thiourea compounds such as N, N′-di-m-chlorophenylthiourea, N- (p-toluenesulfonyl) carbamoyl acid p - organic having cumyl phenyl ester, N- (p- toluenesulfonyl) carbamoyl acid p- benzyloxyphenyl ester, N- and _{(o-toluoyl)-p--SO} 2 NH- bond in the molecule such as toluene sulfonamide Compound, p-chlorobenzoic acid, 4- [2- (p-methoxyphene) Aromatic carboxylic acids such as xyl) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and these aromatics Salts of carboxylic acids with zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, and other polyvalent metals, as well as antipyrine complexes of zinc thiocyanate, complex zinc of terephthalaldehyde acid and other aromatic carboxylic acids Organic acidic substances such as salts, 4,4′-bis (3-tosylureido) diphenylmethane, 1,5- (3-oxopentylene) -bis (3- (3 ′-(p-toluenesulfonyl) ureido) benzoate, 1- (4-butoxycarbonylphenyl) -3-tosylurea, Np-toluenesulfonyl- '-3- (p-toluenesulfonyloxy) phenylurea, N- (p-toluenesulfonyl) -N'-phenylurea, N- (p-toluenesulfonyl) -N'-p-tolylurea, 4,4'- Sulfonylurea compounds such as bis (3- (tosyl) ureido) diphenyl ether and 4,4′-bis (3- (tosyl) ureido) diphenylsulfone, and 4,4′-bis [( 4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4′-bis [(2-methyl-5-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4- (2-methyl-3-phenoxy) Carbonylaminophenyl) ureido-4 '-(4-methyl-5-phenoxycarbonylaminophenyl) ureidodi Examples include urea urethane compounds such as phenylsulfone.

  If necessary, the thermosensitive recording layer may contain a preservability improver. Thereby, the preservability of a recording part can be improved. Examples of the preservability improver include 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,2′-ethylidene. Bis (4,6-di-tert-butylphenol), 4,4′-thiobis (2-methyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 1 -[Α-methyl-α- (4'-hydroxyphenyl) ethyl] -4- [α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-methyl -4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, (2,6-dimethyl-4-tertiarybutyl-3-hydroxybenzyl) isocyanurate, 4,4'-thiobis (3-methylphenol), 4,4'-dihydroxy-3,3 ', 5,5 '-Tetrabromodiphenylsulfone, 4,4'-dihydroxy-3,3', 5,5'-tetramethyldiphenylsulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2, Hindered phenol compounds such as 2-bis (4-hydroxy-3,5-dichlorophenyl) propane and 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane; 1,4-diglycidyloxybenzene; 4,4′-diglycidyloxydiphenylsulfone, 4-benzyloxy-4 ′-(2-methylglycidyloxy) diphenylsulfur Hong, diglycidyl terephthalate, cresol novolac epoxy resin, phenol novolac epoxy resin, epoxy compound such as bisphenol A epoxy resin, N, N′-di-2-naphthyl-p-phenylenediamine, 2,2′-methylenebis Examples include sodium salt or polyvalent metal salt of (4,6-di-tert-butylphenyl) phosphate, bis (4-ethyleneiminocarbonylaminophenyl) methane, etc. The content ratio of the preservability improver is improved preservability. In general, the amount is preferably about 1 to 30% by mass, and more preferably about 5 to 20% by mass in the total solid content of the heat-sensitive recording layer.

  If necessary, the heat-sensitive recording layer may contain a sensitizer. Thereby, the recording sensitivity can be increased. Examples of the sensitizer include stearamide, methoxycarbonyl-N-stearic acid benzamyl, N-benzoyl stearamide, N-eicosanoic acid amide, ethylene bis stearic acid amide, behenic acid amide, methylene bis stearic acid amide, N -Methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, p-benzyl Biphenyl, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, oxalic acid dibenzyl ester, p-tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, , 2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (3-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetoluidide, p -Acetophenetide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, diphenylsulfone, etc. . These can be used in combination as long as there is no hindrance. Among them, stearic acid amide, 2-naphthylbenzyl ether, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, 1,2-di (3-methylphenoxy) ethane, 1,2- Diphenoxyethane and diphenylsulfone are preferably used because of their excellent sensitizing effect. The content of the sensitizer may be an amount effective for sensitization, but is usually preferably about 2 to 40% by mass, more preferably 5 to 5% of the total solid content of the heat-sensitive recording layer. It is about 25 mass%, More preferably, it is about 8-20 mass%.

The heat-sensitive recording layer is, for example, water as a dispersion medium, a leuco dye, a specific colorant, if necessary, a sensitizer, a preservability improver, etc., or separately, a stirrer / crusher such as a ball mill, attritor, sand mill, etc. A coating solution for heat-sensitive recording layer prepared by mixing and stirring a dispersion liquid finely dispersed so that the average particle diameter becomes 2 μm or less, if necessary, a pigment, a binder, an auxiliary agent, etc., in a dry weight. preferably 2~12g / ^{m 2,} more preferably about so that 3 to 10 g / ^{m 2} approximately, is formed by coating and drying on a support.

  Various resins can be used as binders in the thermal recording layer coating liquid. Examples of such binders include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl modified polyvinyl alcohol, diacetone modified polyvinyl alcohol, silicon modified polyvinyl alcohol, diisobutylene. -Maleic anhydride copolymer salt, styrene-maleic anhydride copolymer salt, ethylene-acrylic acid copolymer salt, styrene-acrylic acid copolymer salt, styrene-butadiene copolymer, urea resin, melamine resin, Examples include amide resins and polyurethane resins. At least one of these is preferably blended in the range of about 5 to 50% by mass, more preferably about 10 to 40% by mass, of the total solid content of the thermosensitive recording layer. When the medium for the thermal recording layer coating liquid is water, the hydrophobic resin is used in the form of latex.

  Examples of the auxiliary agent include sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salt and the like, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and the like. Waxes, hydrazide compounds such as adipic acid dihydrazide, water resistant agents such as glyoxal, boric acid, dialdehyde starch, methylol urea, glyoxylate, epoxy compounds, antifoaming agents, colored dyes, fluorescent dyes, and pigments It is done.

  In the present invention, in order to improve the whiteness of the heat-sensitive recording layer and improve the uniformity of the image, a fine particle pigment having a high whiteness and an average particle size of 10 μm or less can be contained in the heat-sensitive recording layer. Specific examples include, for example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined kaolin, amorphous silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated carbonate. Inorganic pigments such as calcium and silica, and organic pigments such as urea-formalin resin, styrene-methacrylic acid copolymer resin, polystyrene resin and raw starch particles can be used. The content of the pigment is preferably 50% by mass or less of the amount that does not decrease the color density, that is, the total solid content of the heat-sensitive recording layer.

  In the present invention, it is preferable to have an undercoat layer containing plastic hollow particles between the support and the thermosensitive recording layer. Thereby, the recording sensitivity can be further increased. In addition, the barrier property is improved by the plastic hollow particles staying on the support to form a uniform undercoat layer, preventing the colorant from coming into contact with the alkali filler contained in the plasticizer or neutral paper, A decrease in coloring ability can be suppressed. Examples of the plastic hollow particles include conventionally known particles, for example, particles having a hollow ratio of about 50 to 99% in which the film material is made of an acrylic resin, a styrene resin, a vinylidene chloride resin, or the like. Here, the hollowness is a value obtained by the following formula (d / D) × 100. In the formula, d represents the inner diameter of the organic hollow particles, and D represents the outer diameter of the organic hollow particles. The average particle size of the plastic hollow particles is preferably about 0.5 to 10 μm, more preferably about 1 to 3 μm. By setting the average particle size to 10 μm or less, when the undercoat layer coating solution is applied by a blade coating method, troubles such as streaks and scratches are not caused, and good coating suitability can be obtained.

  In the present invention, by applying the undercoat layer by the blade coating method, the surface smoothness of the undercoat layer can be further enhanced in terms of quality, so that the coating uniformity of the heat-sensitive recording layer coating liquid can be improved and curtain coating can be performed. It is possible to improve the barrier property of the protective layer provided if necessary. The content ratio of the plastic hollow particles can be selected from a wide range, but is generally preferably about 2 to 90% by mass in the total solid content of the undercoat layer. From the viewpoint of improving the color development effect and enhancing the barrier property, the lower limit is more preferably 5% by mass or more, and further preferably 10% by mass or more. On the other hand, from the viewpoint of suppressing wrinkle adhesion to the thermal head, the upper limit is more preferably 80% by mass or less, further preferably 70% by mass or less, particularly preferably 60% by mass or less, and most preferably 50% by mass or less.

  From the viewpoint of improving the effect of suppressing wrinkle adhesion to the thermal head, the undercoat layer preferably contains an oil-absorbing pigment having an oil absorption amount of 70 ml / 100 g or more, particularly about 80 to 150 ml / 100 g. Moreover, a thermally expansible particle can also be contained. Here, the oil absorption is a value determined according to the method described in JIS K 5101.

  Various oil-absorbing pigments can be used, and specific examples include inorganic pigments such as calcined kaolin, amorphous silica, light calcium carbonate, and talc. The average particle diameter of the primary particles of these oil-absorbing pigments is preferably about 0.01 to 5 μm, particularly about 0.02 to 3 μm. The content of the oil-absorbing pigment can be selected from a wide range, but is generally preferably about 2 to 95% by mass and more preferably about 5 to 90% by mass in the total solid content of the undercoat layer.

  When the oil-absorbing inorganic pigment is used in combination with the plastic hollow particles, the oil-absorbing inorganic pigment and the plastic hollow particles are used within the above-mentioned content ratio, and the total amount of the oil-absorbing inorganic pigment and the plastic hollow particles is Of the total solid amount, it is preferably about 5 to 90% by mass, more preferably about 10 to 90% by mass, and still more preferably about 10 to 80% by mass.

The undercoat layer is generally obtained by applying and drying a coating solution for an undercoat layer prepared by mixing and stirring plastic hollow particles, an oil-absorbing pigment, a binder, an auxiliary agent, and the like on a support using water as a medium. It is formed. The coating amount of the undercoat layer coating solution is not particularly limited, but is preferably about 3 to 20 g / m ² , more preferably about 5 to 12 g / m ² in terms of dry weight.

  The binder can be appropriately selected from those usable in the heat-sensitive recording layer. In particular, from the viewpoint of improving the coating film strength, oxidized starch, starch-vinyl acetate graft copolymer, polyvinyl alcohol, styrene-butadiene latex and the like are preferable. Although the content rate of a binder can be selected in a wide range, generally about 5-30 mass% is preferable among the total solid content of an undercoat layer, and about 10-20 mass% is more preferable.

  The heat-sensitive recording material of the present invention preferably comprises a protective layer on the heat-sensitive recording layer for the purpose of improving the preservability of the recorded image with respect to chemicals such as plasticizers and oils, or recording suitability.

The protective layer is, for example, a coating solution for the protective layer prepared by mixing and stirring a binder, a water resistant agent, a pigment, an auxiliary agent, etc., using water as a dispersion medium, and the coating amount is preferably 0.5 wt%. to 15 g / ^{m 2,} more preferably about so that 1.0~8g / ^{m 2} approximately, it is formed by applying and drying a heat-sensitive recording layer.

  Specific examples of the binder include, for example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl modified polyvinyl alcohol, diacetone modified polyvinyl alcohol, silicon modified polyvinyl alcohol, Examples include ionomer type urethane resin latex.

  Examples of the pigment contained in the protective layer include pigments such as kaolin, aluminum hydroxide, light calcium carbonate, and fine particle silica. Of these, kaolin and aluminum hydroxide are preferably used because they have a small decrease in barrier properties against chemicals such as plasticizers and oils and a small decrease in recording density.

  The protective layer may be formed using one or more of a binder and various auxiliary agents without using a pigment, or may be formed using a binder and a pigment in combination. When used in combination, the content ratio of the binder is not particularly limited and can be appropriately selected from a wide range, but in general, about 1 to 95% by mass is preferable in the total solid content of the protective layer, and about 2 to 80% by mass. More preferred. Further, the content ratio of the pigment is not particularly limited and can be appropriately selected from a wide range. Generally, about 1 to 95% by mass is preferable and about 2 to 90% by mass is more preferable in the total solid content of the protective layer. .

  In the protective layer coating solution, surfactants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and surfactants (dispersants, wetting agents) such as sodium dioctylsulfosuccinate are used as necessary. Various auxiliary agents such as water-soluble polyvalent metal salts such as antifoaming agents, potassium alum and aluminum acetate can also be added as appropriate. In order to further improve the water resistance, water resistance agents such as glyoxal, boric acid, glyoxylate, dialdehyde starch, hydrazide compound, and epoxy compound can be used in combination.

  In the protective layer, microcapsules encapsulating an ultraviolet absorber that is liquid at room temperature, such as 2- (2′-hydroxy-3′-dodecyl-5′-methylphenyl) benzotriazole, are included in the total solid content of the protective layer. When the UV absorber is used in an amount of preferably about 2 to 40% by mass, more preferably about 2 to 35% by mass, and still more preferably about 3 to 30% by mass, the yellow color of the background portion is exposed to light exposure. Discoloration and fading of recorded images can be remarkably suppressed.

  In the present invention, a back layer comprising a pigment and a binder as main components can be provided on the surface of the support opposite to the thermosensitive recording layer, if necessary. As a result, the storage stability can be further improved, and the curl aptitude and the printer runnability can be improved. In addition, various processes in the field of thermal recording material production such as processing the pressure-sensitive adhesive label on the back surface, forming a magnetic recording layer, a coating layer for printing, and further providing a thermal transfer recording layer and an inkjet recording layer, etc. Known techniques can be added as necessary.

  There are no particular limitations on the method of forming the heat-sensitive recording layer and, if necessary, the undercoat layer, the protective layer and the back layer. For example, bar coating, air knife coating, varivar blade coating, pure blade coating, rod blade coating, short dwell coating, After applying and drying the undercoat layer coating solution on the support by an appropriate coating method such as curtain coating or die coating, apply and dry the thermal recording layer coating solution and further the protective layer coating solution on the undercoat layer. And the like.

  The undercoat layer is preferably a layer formed by a blade coating method. Thereby, the unevenness | corrugation of a support body is eliminated, the heat-sensitive recording layer of uniform thickness can be formed, and recording sensitivity can be improved. The blade coating method is not limited to a coating method using a blade represented by a bevel type or a vent type, and includes a rod blade method, a bill blade method, and the like.

  In the present invention, it is preferable that at least one layer formed on the support is a layer formed by a curtain coating method. Thereby, a layer having a uniform thickness can be formed, and the recording sensitivity can be increased, and the barrier property against oil, plasticizer, alcohol, etc. can be increased. The curtain coating method is a method in which the coating liquid is allowed to flow and fall freely, and is applied to the support in a non-contact manner, and known methods such as a slide curtain method, a couple curtain method, and a twin curtain method can be employed. There is no particular limitation. In the curtain coating method, a layer having a more uniform thickness can be formed by simultaneous multilayer coating. In simultaneous multi-layer coating, each coating solution is laminated and then applied, and then dried to form each layer. After applying a coating solution that forms the lower layer, the lower surface coating surface is wet without drying. In a state, you may apply | coat the coating liquid which forms an upper layer on a lower layer coating surface, and it may be made to dry after that, and may form each layer. In the present invention, an embodiment in which a heat-sensitive recording layer and a protective layer are simultaneously applied in multiple layers is preferable from the viewpoint of improving barrier properties.

  In the present invention, from the viewpoint of increasing the recording sensitivity and improving the image uniformity, after completing the formation of each layer or after completing the formation of all the layers, a super calendar, a soft calendar, etc. It is preferable to perform a smoothing process using a known method.

  In the present invention, in order to further increase the added value of the product, a multicolor thermosensitive recording material can be used. In general, multicolor thermal recording materials are an attempt to utilize the difference in heating temperature or thermal energy, and are generally constructed by sequentially laminating a high-temperature coloring layer and a low-temperature coloring layer that develop colors in different colors on a support. When these are roughly classified, a multicolor thermosensitive recording material is produced using two types, a decoloring type and a color adding type, a method using a microcapsule, and composite particles comprising an organic polymer and a leuco dye. There is a way.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “part” and “%” indicate “part by mass” and “% by mass”, respectively.

Example 1
-Preparation of coating solution for undercoat layer Plastic hollow particle dispersion (trade name: Ropaque SN-1055, hollow ratio: 55%, average particle size: 1.0 μm, manufactured by Dow Chemical Co., Ltd., solid content concentration 26.5% by mass) 120 parts, 110 parts of a 50% aqueous dispersion (average particle size: 0.6 μm) of calcined kaolin (trade name: Ansilex, manufactured by BASF), styrene-butadiene latex (trade name: L-1571, Asahi Kasei Chemicals) A composition comprising 20 parts of a manufactured product, a solid content concentration of 48% by mass), 50 parts of a 10% aqueous solution of oxidized starch, and 20 parts of water was mixed to obtain a coating solution for an undercoat layer.

-Preparation of liquid A (leuco dye dispersion) 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 100 parts, sulfone-modified polyvinyl alcohol (trade name: Goceran L-3266, Nippon Synthetic Chemical A composition comprising 50 parts of a 20% aqueous solution, 10 parts of a 5% emulsion of a natural fat and oil-based antifoaming agent (trade name: Nopco 1407H, manufactured by San Nopco), and 80 parts of water is obtained by a laser diffraction particle size using a sand mill. A liquid A was obtained by pulverizing until the median diameter was 0.5 μm using a distribution measuring apparatus SALD2200 (manufactured by Shimadzu Corporation).

-Preparation of Liquid B (Coloring Agent Dispersion) 100 parts of N- [2- (3-phenylureido) phenyl] benzenesulfonamide, sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.) A composition comprising 50 parts of a 20% aqueous solution of oil, 10 parts of a 5% emulsion of a natural fat and oil-based antifoaming agent (trade name: Nopco 1407H, manufactured by San Nopco), and 90 parts of water, a laser diffraction particle size distribution analyzer using a sand mill The liquid B was obtained by pulverization until the median diameter by SALD2200 (manufactured by Shimadzu Corporation) was 1.0 μm.

-Preparation of liquid C (colorant dispersion) 100 parts of the compound represented by the general formula (1) (prototype name: X-8213, manufactured by Nikka Chemical Co., Ltd.), sulfone-modified polyvinyl alcohol (trade name: gold) A composition comprising 50 parts of a 20% aqueous solution of Selan L-3266 (manufactured by Nippon Synthetic Chemical Co., Ltd.), 10 parts of a 5% emulsion of a natural fat and oil defoaming agent (trade name: Nopco 1407H, manufactured by San Nopco), and 90 parts of water. Was pulverized with a sand mill using a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation) until the median diameter became 1.0 μm to obtain liquid C.

-Preparation of liquid D (sensitizer dispersion) 1,2-di (3-methylphenoxy) ethane 100 parts, sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, supra) 50 parts of an aqueous solution, A composition consisting of 2 parts of a 5% emulsion of a natural fat and oil-based antifoaming agent (trade name: Nopco 1407H, manufactured by San Nopco) and 98 parts of water is subjected to a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation) using a sand mill. The liquid D was obtained by pulverizing until the median diameter was 1.0 μm.

-Preparation of coating solution for heat-sensitive recording layer A part 23 parts, B part 30 parts, C part 33 parts, D part 30 parts, aluminum hydroxide (trade name: Hijilite H-42, average particle size 1.0 μm, Showa 20 parts by Denko Co., Ltd., fine powder amorphous silica (trade name: Mizukasil P-605, average particle size 3.0 μm, made by Mizusawa Chemical Co., Ltd.), starch-vinyl acetate graft copolymer (trade name: Petrocoat) 120 parts of a 10% aqueous solution of C-8 (manufactured by Nippon Star Chemical Co., Ltd.), 20 parts of a 10% aqueous solution of fully saponified polyvinyl alcohol (trade name: GOHSENOL NМ-11, manufactured by Nippon Gosei Kagaku Co., Ltd.), zinc stearate dispersion ( A composition comprising 15 parts of a trade name: Hydrin Z-8-36, solid concentration 36%, manufactured by Chukyo Yushi Co., Ltd.) and 20 parts of water was mixed to prepare a thermal recording layer coating solution.

-Preparation of thermosensitive recording material On one side of a high-quality paper (basic paper with hot water extraction pH 5.3) having a basis weight of 53 g / m ² as a support, the weight after drying the coating liquid for the undercoat layer was 5.5 g / The undercoat layer is formed by applying and drying by a blade coating method using a blade coater so as to be m ^2, and the weight after drying the thermal recording layer coating liquid on the undercoat layer is 3.5 g / m ^2. Thus, after applying and drying by a curtain coating method using a slide hopper type curtain coating apparatus, a super calendar process was performed to obtain a heat-sensitive recording material.

Example 2
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, the same as Example 1 except that the amount of B liquid was 23 parts instead of 30 parts and the amount of C liquid was 40 parts instead of 33 parts A heat-sensitive recording material was obtained.

Example 3
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, the same as Example 1 except that the amount of B liquid was 40 parts instead of 30 parts and the amount of C liquid was 23 parts instead of 33 parts A heat-sensitive recording material was obtained.

Comparative Example 1
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, the heat-sensitive recording material was obtained in the same manner as in Example 1 except that the amount of liquid B was changed to 30 parts and replaced with 63 parts, and liquid C was not used. It was.

Comparative Example 2
A thermosensitive recording material was obtained in the same manner as in Example 1 except that, in the preparation of the thermal recording layer coating liquid of Example 1, the B liquid was not used and the amount of the C liquid was changed to 63 parts instead of 30 parts. It was.

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

(Recording density)
Using a thermal recording evaluation machine (trade name: TH-PMH, manufactured by Okura Electric Co., Ltd.), each thermal recording body is printed at an applied energy of 0.28 mJ / dot, and the optical properties of the recorded area and the unrecorded area (background part). The density was measured in a visual mode of a reflection densitometer (trade name: Macbeth densitometer RD-918, manufactured by Gretag Macbeth). The larger the numerical value, the higher the density of printing, and the recording portion is preferably 1.20 or more practically. On the other hand, it is preferable that the numerical value of the background portion is smaller. When the value exceeds 0.2, background fogging becomes a problem.

(Heat-resistant)
The optical density of the unrecorded part (background part) after leaving each thermosensitive recording medium before recording for 2 hours in a high temperature environment of 80 ° C. is measured by a reflection densitometer (trade name: Macbeth densitometer RD-918, Gredagg Macbeth Co., Ltd.) ) And the visual mode. The smaller the value, the more preferable.

(Plasticizer resistance)
A wrap film (trade name: HiES Soft, manufactured by Nippon Carbide Industries Co., Ltd.) is wrapped on a polycarbonate pipe (40 mmΦ) in a triple layer, and each thermosensitive recording medium colored for recording density measurement is placed on it. Wrapping film is wrapped in three layers, and the optical density of the recording part after being left for 24 hours in an environment of 23 ° C. and 50% RH is measured by a reflection densitometer (trade name: Macbeth densitometer RD-918, Gretag Macbeth Measured in visual mode. Further, the storage ratio of the recording part was obtained by the following formula. After processing, the recording density is preferably 1.0 or more and the storage rate is 60% or more.
Storage rate (%) = (recording density after processing / recording density before processing) × 100

  The heat-sensitive recording material obtained by the present invention has a high recording density, does not cause background fogging even under high-temperature storage, and is excellent in plasticizer resistance of the recording part, so it is a label for receipts, food and test tubes. It is suitable for such as.

Claims (6)

In the heat-sensitive recording material having a heat-sensitive recording layer containing at least a leuco dye and a colorant on the support, the colorant is at least selected from diphenylsulfone cross-linked compounds represented by the following general formula (1). A heat-sensitive recording material comprising one kind and N- [2- (3-phenylureido) phenyl] benzenesulfonamide.

(In the formula, n represents an integer of 1 to 10.)   The diphenylsulfone cross-linking compound is contained at a ratio of 0.1 to 2.5 parts by mass with respect to 1 part by mass of the N- [2- (3-phenylureido) phenyl] benzenesulfonamide. The heat-sensitive recording material described.   The diphenylsulfone cross-linking compound is contained in a ratio of 0.2 to 3 parts by mass with respect to 1 part by mass of the leuco dye, and the N- [2- (3-phenylureido) phenyl] benzenesulfonamide is added in an amount of 0. The heat-sensitive recording material according to claim 1, which is contained at a ratio of 5 to 5 parts by mass.   The thermal recording body according to any one of claims 1 to 3, further comprising an undercoat layer containing hollow plastic particles between the support and the thermal recording layer.   The thermal recording body according to claim 1, further comprising an undercoat layer formed by a blade coating method between the support and the thermal recording layer.   The heat-sensitive recording material according to claim 1, wherein at least one layer formed on the support is formed by a curtain coating method.