JP2015150760A - Thermosensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording medium having high recording characteristics for an optical character (or a mark) reading device having a reading wavelength range over the near-infrared region and excellent preservability of an unrecorded part and a recorded part over the near-infrared region.SOLUTION: There is provided a thermosensitive recording medium comprising a thermosensitive recording layer containing a leuco dye and a coloring agent on a support body, where the thermosensitive recording medium contains a specific leuco dye which reacts with the coloring agent to form a dye having absorbency in the near infrared region and contains a specific urea urethane compound as the coloring agent. The urea urethane compound is preferably incorporated in an amount of 0.1 to 4 pts.mass based on 1 pt.mass of the specific leuco dye.

Description

  The present invention relates to a heat-sensitive recording material utilizing a color reaction between a leuco dye and a colorant, and more specifically, high recording for an optical character (or mark) reader having a reading wavelength region in the near infrared region. The present invention relates to a heat-sensitive recording material having characteristics and excellent plasticizer resistance of a recording portion.

  A heat-sensitive recording material is preferred in which a recording image is obtained by reacting heat with a color precursor capable of acting as an electron acceptor of a dye precursor such as a colorless to light leuco dye and an electron acceptor of the dye precursor. Are known.

  Examples of the application field include cash register sheets and ticket sheets for POS (point of sales) systems. In particular, POS systems that collect and process information such as product information necessary for business management and sales management are very popular in large mass retailers and restaurants such as supermarkets and department stores, and rational delivery and shipment in the home delivery industry. Adopt system to do. As one of these systems, a method of displaying a barcode or a two-dimensional code mark on a product and optically reading it has been put into practical use, and is currently used for a wide range of applications.

  Conventionally, a He-Ne gas laser (633 nm) has been used for reading a barcode or the like by a color image, but recently, a semiconductor laser (near infrared light) has become widespread. This is because the semiconductor laser is small and light, easy to handle, low in price, and the oscillation wavelength is in the near infrared region (700 to 1600 nm). This is due to the advantage of less.

  Since a color image formed on a general thermal recording paper has an absorption wavelength in the visible region (400 to 700 nm), it can be read with a He—Ne gas laser, but cannot be read with a semiconductor laser. Accordingly, it is desired to provide a thermal recording material that forms a near infrared absorption image that can be read by a semiconductor laser.

  As a thermosensitive recording material capable of forming a near-infrared absorption image, an electron acceptor such as a phenolic organic compound is used as a color former for coloring the dye precursor, and the dye precursor has a lactone ring in the molecule. The use of a specific vinyl-containing color-forming compound (see Patent Document 1) and the use of a specific fluorene compound (see Patent Document 2) have been proposed. However, near-infrared absorption images obtained by coloring these dye precursors with a colorant have a problem of fading over time or being decolored in a short time by contact with oil or a plasticizer.

  In order to improve water resistance and plasticizer resistance, it has been proposed to provide a thermosensitive coloring layer containing a specific coloring compound and 3,4-dihydroxyphenyl-p-tolylsulfone as a colorant (patent) Reference 3). However, at present, satisfactory results are not always obtained with respect to the storage stability of color images.

JP-A-55-115448 JP 59-199775 A Japanese Patent Laid-Open No. 7-179055

  The present invention has a high recording characteristic for an optical character (or mark) reading device having a reading wavelength region in the near infrared region, and is excellent in preservability of unrecorded and recorded portions in the near infrared region. The main purpose is to provide a body.

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

  Item 1: In a heat-sensitive recording material comprising a heat-sensitive recording layer containing a leuco dye and a colorant on a support, the heat-sensitive recording layer contains a leuco dye represented by the following general formula (1), A heat-sensitive recording material comprising a urea urethane compound represented by the following general formula (2) as a color former.

（１）

（式中、Ｒ^１及びＲ^２は、炭素数が１〜６個の直鎖又は分枝状のアルキル基を表す。）

(1)

(Wherein, R ¹ and R ² has a carbon number represents 1-6 straight-chain or branched alkyl group.)

  Item 2: The urea urethane compound represented by the general formula (2) is contained in an amount of 0.1 to 4 parts by mass with respect to 1 part by mass of the leuco dye represented by the general formula (1). The heat-sensitive recording material according to 1.

  Item 3: 2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone as a colorant One type selected from the group consisting of 4-allyloxy-4′-hydroxydiphenylsulfone and Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea is represented by the general formula (2). Item 3. The heat-sensitive recording material according to Item 1 or 2, which is contained in an amount of 0.3 to 25 parts by mass with respect to 1 part by mass of the urea urethane compound.

  Item 4: The urea urethane compound represented by the general formula (2) as the colorant is heat-treated in the same liquid as the basic inorganic pigment, according to any one of Items 1 to 3. Thermal recording material.

  Item 5: Any one of Items 1 to 4, wherein the basic inorganic pigment is at least one selected from the group consisting of a magnesium compound, an aluminum compound, a calcium compound, a titanium compound, magnesium silicate, magnesium phosphate, and talc. The heat-sensitive recording material according to item 1.

  Item 6: The heat-sensitive recording material according to any one of Items 1 to 5, further comprising an undercoat layer containing plastic hollow particles between the support and the heat-sensitive recording layer.

  The heat-sensitive recording material of the present invention has high recording characteristics compared to an optical character (or mark) reader having a reading wavelength region in the near infrared region, and is excellent in storability of an unrecorded portion and a recorded portion in the near infrared region. Are better.

  The support in the present invention is not particularly limited, and examples thereof include neutral or acidic high-quality paper, synthetic paper, transparent or translucent plastic film, and white plastic film. Although the thickness of a support body is not specifically limited, Usually, it is about 20-300 micrometers.

  The heat-sensitive recording layer in the present invention is formed on a support. The heat-sensitive recording layer contains a leuco dye represented by the general formula (1) (hereinafter also referred to as a specific leuco dye). The specific leuco dye reacts with a colorant to form a dye having absorbency in the near infrared region. As a result, it has excellent absorption capability in the near infrared region (700 to 1100 nm), enhances recording characteristics for optical character (or mark) readers having a reading wavelength region in the near infrared region, and has excellent readability. It can be demonstrated.

  Examples of the specific leuco dye include 3,3-bis [2- (4-dimethylaminophenyl) -2- (4-methoxyphenyl) vinyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [2- (4-diethylaminophenyl) -2- (4-ethoxyphenyl) vinyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [2- (4- Dimethylaminophenyl) -2- (4-ethoxyphenyl) vinyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [2- (4-diethylaminophenyl) -2- (4-methoxy Phenyl) vinyl] -4,5,6,7-tetrachlorophthalide and the like. Among these, 3,3-bis [2- (4-dimethylaminophenyl) -2- (4-methoxyphenyl) vinyl] -4,5,6,7-tetrachlorophthalide is preferable.

  Although the content rate of the said specific leuco dye is not specifically limited, 0.5-20 mass% is preferable in the total solid of a heat-sensitive recording layer, 1-15 mass% is more preferable, 3-10 mass% is still more preferable.

  The heat-sensitive recording layer can contain various other known leuco dyes as long as the desired effects of the present invention are not impaired. Other leuco dyes include, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) ) -6-dimethylaminophthalide, blue coloring dyes such as fluoran, 3- (N-ethyl-Np-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilino Green coloring dyes such as fluorane, 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- ( -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-anilinofluorane 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- 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] phenyl } Black coloring dyes such as propane, 3-diethylamino-7- (3′-trifluoromethylphenyl) aminofluorane, 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidino Phenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3-p- (p-dimethylaminoanilino) anilino-6-methyl-7-chlorofluorane, 3 Near-infrared such as p- (p-chloroanilino) anilino-6-methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide Examples include dyes having an absorption wavelength in the region. 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, 3- (N- Ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane and 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane have excellent recording sensitivity and print storage stability. Therefore, it is preferably used. The content of the leuco dye is about 2 to 15% by mass, preferably 3 to 10% by mass in the total solid content of the heat-sensitive recording layer. By setting the content to 2% by mass or more, the color development ability can be improved and the printing density can be improved. Heat resistance can be improved by setting it as 15 mass% or less.

  The heat-sensitive recording layer in the present invention contains at least one urea urethane compound represented by the general formula (2) (hereinafter also referred to as a specific urea urethane compound) as a colorant. As a result, a thermal recording material having high recording characteristics with respect to an optical character (or mark) reader having a reading wavelength region in the near infrared region and excellent in plasticizer resistance of the recording portion in the near infrared region is obtained. be able to.

  Specific examples of the specific urea urethane compound include, for example, 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4′-bis [(2-methyl-5 -Phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4- (2-methyl-3-phenoxycarbonylaminophenyl) ureido-4 '-(4-methyl-5-phenoxycarbonylaminophenyl) ureidodiphenylsulfone, and the like. These specific urea urethane compounds can be used singly or in combination of two or more.

  In this invention, it is preferable that the specific urea urethane compound represented by the said General formula (2) is heat-processed in the same liquid as a basic inorganic pigment as a colorant. For example, when the heat-sensitive recording layer is formed using a heat-sensitive recording layer coating liquid containing 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, 4,4′- -Bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone was previously heat-treated in the same liquid as the basic inorganic pigment in the temperature range of 50 to 90 ° C., preferably 60 to 80 ° C. It can be blended in the thermal recording layer coating liquid as a dispersion. Thereby, after the thermal recording layer coating liquid is applied and dried to form the thermal recording layer, it is possible to suppress the occurrence of extra color development (background fogging) as the thermal recording body. The treatment time is appropriately adjusted depending on the heating temperature, but it is generally preferable to perform the heat treatment for 2 to 24 hours. The dispersion prior to the heat treatment is prepared by dispersing 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone to a predetermined particle size and then mixing a basic inorganic pigment. It can also be obtained by mixing them and then dispersing them to a predetermined particle size.

  The basic inorganic pigment is preferably at least one selected from the group consisting of magnesium compounds, aluminum compounds, calcium compounds, titanium compounds, magnesium oxide, magnesium phosphate, and talc. Of these, magnesium silicate, magnesium phosphate, and talc are preferably used from the viewpoint of the stability of the coating liquid and the coating suitability.

  Although the usage-amount of a basic inorganic pigment is not specifically limited, It is about 0.5-20 mass parts with respect to 100 mass parts of specific urea urethane compounds, Preferably it is about 1-10 mass parts.

  Although content of the specific urea urethane compound in a thermosensitive recording layer is not specifically limited, 0.1-4 mass parts is preferable with respect to 1 mass part of specific leuco dyes, and about 0.2-3 mass parts is more. Preferably, about 0.5-3 mass parts is further more preferable, about 0.8-3 mass parts is especially preferable, and 0.8-2.0 mass parts is the most preferable. By setting it as 0.1 mass part or more, the plasticizer resistance in the near infrared region of a recording part can be improved. On the other hand, the light resistance in the near-infrared region of a recording part can be improved by setting it as 4 mass parts or less.

As long as the desired effect of the present invention is not impaired, the heat-sensitive recording layer can contain various other known colorants having coloration ability. Examples of other colorants include inorganic acidic substances such as activated clay, attapulgite, colloidal silica, and 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) Phenolic compounds such as lufone, 4-hydroxy-4′-methyldiphenylsulfone, 4-allyloxy-4′-hydroxydiphenylsulfone, 3,4-dihydroxyphenyl-4′-methylphenylsulfone, N, N′-di- Thiourea compounds such as m-chlorophenylthiourea, N- (p-toluenesulfonyl) carbamoyl acid p-cumylphenyl ester, N- (p-toluenesulfonyl) carbamoyl acid p-benzyloxyphenyl ester, N- (o-toluoyl) ) -P-toluenesulfoamide and other organic compounds having a —SO ₂ NH— bond, p-chlorobenzoic acid, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- ( p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p- Toxiphenoxyethoxy) cumyl] aromatic carboxylic acids such as salicylic acid, and salts of these aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, and zinc thiocyanate Antipyrine complex, organic acidic substance such as complex zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid, 4,4′-bis (3-tosylureido) diphenylmethane, 1,5- (3-oxapentylene)- Bis (3- (3 ′-(p-toluenesulfonyl) ureido) benzoate, 1- (4-butoxycarbonylphenyl) -3-tosylurea, Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) ) Phenylurea, N- (p-toluenesulfonyl) -N′-phenylurea, N- ( -Toluenesulfonyl) -N′-p-tolylurea, sulfonylurea compounds such as 4,4′-bis (3- (tosyl) ureido) diphenyl ether, 4,4′-bis (3-tosylureido) diphenylsulfone, the following general formula ( And a diphenylsulfone derivative represented by 3). Of course, it is not limited to these, Moreover, 2 or more types can also be used together as needed. Among them, 2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-allyloxy- The combined use with one selected from the group consisting of 4′-hydroxydiphenylsulfone and Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea is a synergistic effect in the near infrared region. It is preferably used because it improves color developability and is excellent in print storage stability.

（式中、ｎ＝１〜６の整数を表す。）

(In the formula, n represents an integer of 1 to 6.)

  2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-allyloxy-4′- The content of one kind selected from the group consisting of hydroxydiphenylsulfone and Np-toluenesulfonyl-N′-3- (p-toluenesulfonyloxy) phenylurea is not particularly limited, but specific urea urethane compound 1 0.3-25 mass parts is preferable with respect to mass parts, 0.5-21 mass parts is more preferable, and 0.5-5 mass parts is still more preferable. By setting it as 0.3 mass part or more, the reflectance in the near-infrared area | region of a background part can be improved, the contrast at the time of a reading can be improved, and print preservation property can be improved. By setting the content to 25 parts by mass or less, the reflectance in the near-infrared region after storage of the recording unit can be suppressed, and the contrast at the time of reading can be increased.

  The heat-sensitive recording layer in the present invention may contain a sensitizer. Thereby, the recording sensitivity can be increased. Examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoyl stearic acid amide, 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- Benzylbiphenyl, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, p-tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylpheno) B) 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-methylthiophenyl benzyl ether, 1,4-di (phenylthio) butane, p-acetoluidide, p-acetophenetide, N- Examples include acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, and the like.

  The content ratio of the sensitizer is not particularly limited, and may be an amount effective for sensitization. Usually, about 2 to 40% by mass is preferable in the total solid amount of the heat-sensitive recording layer, About 25% by mass is more preferable.

  In the heat-sensitive recording layer of the present invention, a storability improving agent can be contained. 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 0.01 to 20% by mass, more preferably about 0.1 to 10% by mass in the total solid amount of the heat-sensitive recording layer, and 0.2 to 0.2%. About 10 mass% is further more preferable.

The heat-sensitive recording layer uses, for example, water as a dispersion medium, and a specific leuco dye and a colorant together with a sensitizer and a storage stability improver, if necessary, using a stirrer / crusher such as a ball mill, an attritor, or a sand mill. Alternatively, using a dispersion obtained by dispersing separately, a thermal recording layer coating solution prepared by mixing adhesives, auxiliaries, etc., if necessary, is coated on a support and dried. Is done. The coating amount of the heat-sensitive recording layer coating composition is preferably about 2~12g / ^{m 2} by dry weight, about 3 to 10 g / ^{m 2} is more preferable.

  As the adhesive used in the heat-sensitive recording layer coating liquid, any of a water-soluble adhesive and a water-dispersible adhesive can be used. Examples of water-soluble adhesives include, for example, fully saponified or partially saponified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol and silicon-modified polyvinyl alcohol, modified polyvinyl alcohol, starch and derivatives thereof, methoxycellulose , Cellulose derivatives such as carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose and ethylcellulose, polyacrylic acid soda, polyvinylpyrrolidone, acrylic acid amide-acrylic acid ester copolymer, acrylic acid amide-acrylic acid ester-methacrylic acid copolymer, styrene -Maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, etc. It is. Water dispersible adhesives include polyvinyl acetate, polyurethane, styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride-acetic acid Examples thereof include latex of hydrophobic polymers such as vinyl copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, silylated urethane, acrylic-silicon composite, and acrylic-silicon-urethane composite.

  The content ratio of the adhesive in the heat-sensitive recording layer is not particularly limited, and is preferably about 3 to 40% by mass, and more preferably about 5 to 30% by mass in the total solid content of the heat-sensitive recording layer.

  The auxiliary agent used in the thermal recording layer coating liquid can be appropriately selected from those conventionally used. Auxiliary agents include, for example, surfactants, waxes, lubricants, pigments, water resistance agents, antifoaming agents (for example, natural fat-based antifoaming agents such as glycerin ester emulsion type antifoaming agents), fluorescent whitening Agents, colored dyes and the like. Examples of the surfactant include fatty acid alkali metal salts such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate and sodium stearate, and fluorine-based surfactants. Examples of waxes include carnauba wax, paraffin wax, ester wax, polyethylene wax, and the like. Examples of lubricants include fatty acid metal salts such as zinc stearate and calcium stearate, alkyl phosphates such as stearyl phosphate potassium salt, and the like. Examples of the pigment include inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined kaolin, titanium oxide, amorphous silica, aluminum hydroxide, styrene resin filler, nylon resin filler, urea-formalin resin filler, poly (meth) Examples thereof include organic pigments such as acrylic ester resin fillers and raw starch particles. Examples of water-proofing agents include glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, dialdehyde starch, melamine resin, polyamide resin, polyamide polyamine-epichlorohydrin resin, ketone-aldehyde resin, borax, boric acid, Examples include ammonium zirconium carbonate, epoxy compounds, hydrazine compounds, oxazoline group-containing compounds, sodium glyoxylate, di (calcium glyoxylate), ammonium glyoxylate and the like.

  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 readability in the near-infrared region can be improved and even more excellent plasticizer resistance can be exhibited. Not only does the undercoat layer improve recording sensitivity with organic hollow particles, it also has the function of increasing the reflectance of the background in the near-infrared region through the heat-sensitive recording layer, so that the recorded portion and the unrecorded portion (background portion) It is conceivable that the identification is clear and the readability is improved.

  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.

  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 preferably 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 The total solid amount 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 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, with water as a medium, on a support, and drying. It is formed. The coating amount of the undercoat layer 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 in the total solid amount of an undercoat layer, and about 10-20 mass% is more preferable.

  In the present invention, a protective layer may be provided on the thermosensitive recording layer. The protective layer can be formed, for example, by applying a protective layer coating liquid on the heat-sensitive recording layer and drying it. Thereby, the preservation | save property of the recording image with respect to chemicals, such as a plasticizer and oil, can be improved further. Also, the recording aptitude can be improved.

  The coating liquid for the protective layer is not particularly limited and is generally prepared by mixing and stirring water, a dispersion medium, and an adhesive, pigment, auxiliary agent, water-soluble polyvalent metal salt such as potassium alum and aluminum acetate, and the like. can do. Adhesives, pigments, auxiliaries, and the like used in the protective layer coating liquid can be appropriately selected from those that can be used in the heat-sensitive recording layer. Of these, acetoacetyl-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and the like are preferably used as the adhesive from the viewpoint of improving plasticizer resistance and water resistance.

  The content ratio of the adhesive in the protective layer is not particularly limited and can be appropriately selected from a wide range. In general, the total solid content of the protective layer is preferably about 1 to 95% by mass, 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. In general, the pigment content is preferably about 1 to 95% by mass and more preferably about 2 to 90% by mass in the total solid content of the protective layer.

  In the present invention, the protective layer may contain microcapsules encapsulating a UV absorber that is liquid at room temperature, such as 2- (2′-hydroxy-3′-dodecyl-5′-methylphenyl) benzotriazole. preferable. Thereby, yellowing of the background portion and fading of the recorded image can be effectively suppressed against light exposure. The content ratio of the ultraviolet absorber is preferably about 3 to 30% by mass, more preferably about 5 to 25% by mass, and still more preferably about 7 to 20% by mass in the total solid content of the protective layer.

The coating amount of the protective layer coating solution is not particularly limited, but is adjusted in the range of about 0.5 to 15 g / m ² , preferably about 1.0 to 8 g / m ² in terms of dry weight.

  The method for forming the undercoat layer, the heat-sensitive recording layer and the protective layer is not particularly limited. For example, an appropriate method such as air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. An undercoat layer coating solution is applied and dried on a support by a coating method, and then a thermal recording layer coating solution and further a protective layer coating solution are applied and dried on the undercoat layer.

  If necessary, a protective layer can also be provided on the back side of the heat-sensitive recording material to further improve the storage stability or to give the recording surface a strong gloss. A smoothing process using a super calender may be performed in an arbitrary process after forming each layer or after forming all the layers. In the heat-sensitive recording material of the present invention, the back surface of the heat-sensitive recording material is subjected to a pressure-sensitive adhesive treatment to be processed into a pressure-sensitive adhesive label, ink jet recording suitability, a magnetic recording layer, a printing coating layer, and further a thermal transfer recording. Various known techniques in the heat-sensitive recording material manufacturing field, such as providing a layer, can be added as necessary.

  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) And a composition comprising 20 parts of 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 and stirred to obtain an undercoat layer coating solution.

-Preparation of liquid A (leuco dye dispersion) 3,3-bis [2- (4-dimethylaminophenyl) -2- (4-methoxyphenyl) vinyl] -4,5 represented by the general formula (1) , 6,7-tetrachlorophthalide, 100 parts of a sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.), 50 parts of a 5% emulsion of a natural fat / oil defoamer. And the composition which consists of 90 parts of water was grind | pulverized with the sand mill until the median diameter by the laser diffraction type particle size distribution analyzer SALD2200 (made by Shimadzu Corp.) became 1.5 micrometers, and A liquid was obtained.

-Preparation of liquid B (leuco dye dispersion) 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 100 parts, sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, Nippon Synthetic Chemical Co., Ltd.) The composition comprising 50 parts of a 20% aqueous solution, 10 parts of a 5% emulsion of a natural fat and oil-based antifoaming agent, and 90 parts of water is subjected to a median by a sand mill using a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation). The liquid B was obtained by pulverizing until the diameter became 0.5 μm.

-Preparation of liquid C (coloring agent dispersion) 100 parts of bis (3-allyl-4-hydroxyphenyl) sulfone, 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.) Part of the composition, 10 parts of a 5% emulsion of natural fat and oil-based antifoaming agent, and 90 parts of water, a median diameter by a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation) is 1.0 μm by a sand mill. C liquid was obtained.

-Preparation of liquid D (coloring agent dispersion) 4,4'-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenyl sulfone 100 parts, sulfone-modified polyvinyl alcohol (trade name: Gogo) 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 a liquid D.

-Preparation of solution E (sensitizer dispersion) 100 parts of di-p-methylbenzyl oxalate, 50 parts of a 20% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Gocelan L-3266, manufactured by Nippon Gosei Kagaku), natural A composition comprising 10 parts of a 5% emulsion of a fat and oil-based antifoaming agent (trade name: Nopco 1407H, manufactured by San Nopco) and 90 parts of water was obtained by a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation) using a sand mill. The liquid E was obtained by pulverizing until the median diameter became 1.0 μm.

-Preparation of coating solution for heat-sensitive recording layer A part 15 parts, B part 15 parts, C part 45 parts, D part 30 parts, E part 50 parts, light calcium carbonate (trade name: Brilliant 15, manufactured by Shiraishi Kogyo Co., Ltd.) 14 For a thermosensitive recording layer by mixing 120 parts of a 10% aqueous solution of a completely saponified polyvinyl alcohol (trade name: PVA110, manufactured by Kuraray Co., Ltd.), 20 parts of a 5% aqueous solution of adipic dihydrazide and 20 parts of water. A coating solution was obtained.

-Preparation of coating solution for protective layer 250 parts of 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Gohsephimer Z-200, polymerization degree: 1000, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), aqueous urethane binder (trade name: Hydran AM-1, solid content concentration 20%, manufactured by DIC) 50 parts, aluminum hydroxide (trade name: Hygielite H-42M, average particle size 1.0 μm, Showa Denko) 50 parts, fine powder amorphous silica (Product name: Mizukasil P-527, average particle size 2.0 μm, manufactured by Mizusawa Chemical Industry Co., Ltd.) 10 parts, zinc stearate dispersion (product name: Hydrin Z-8-36, solid content concentration 36%, Chukyo Yushi Co., Ltd.) (Product) A composition comprising 15 parts was mixed to obtain a coating solution for a protective layer.

・ Preparation of thermosensitive recording material On one surface of 120 g / m ² high-quality paper (acidic paper), an undercoat layer coating solution was applied so that the weight after drying was 7 g / m ^2, and dried to form an undercoat layer. The heat-sensitive recording layer coating liquid is applied onto the undercoat layer so that the weight after drying is 4.5 g / m ² , dried to form a heat-sensitive recording layer, and further dried onto the heat-sensitive recording layer. A protective layer coating solution was applied so that the subsequent coating amount was 3.0 g / m ² and dried to form a protective layer, followed by supercalendering to obtain a thermal recording material.

Example 2
-Preparation of liquid F (coloring agent dispersion) 4,4'-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone 100 parts, magnesium silicate 5 parts, sulfone-modified polyvinyl alcohol ( Brand name: Go-Selan L-3266, manufactured by Nippon Synthetic Chemical Co., Ltd.) 50% 20% aqueous solution, natural fat-based antifoaming agent (trade name: Nopco 1407H, San Nopco) 10% 5% emulsion, and water 90 The composition consisting of parts was pulverized by a sand mill with a laser diffraction particle size distribution analyzer SALD2200 (manufactured by Shimadzu Corporation) until the median diameter became 1.0 μm to obtain a dispersion. Further, the dispersion was subjected to a heat treatment at 70 ° C. for 4 hours to obtain a liquid F.

  A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the liquid F was used instead of the liquid D in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

Example 3
In the preparation of the heat-sensitive recording layer coating liquid of Example 2, the amount of liquid C was changed to 71.5 parts instead of 45 parts, and the amount of liquid F was changed to 3.5 parts instead of 30 parts. A heat-sensitive recording material was obtained in the same manner as in Example 2.

Example 4
In the preparation of the thermal recording layer coating liquid of Example 2, the same as Example 2 except that the amount of liquid C was changed to 45 parts instead of 45 parts and the amount of liquid F was changed to 45 parts instead of 30 parts. A heat-sensitive recording material was obtained.

Example 5
In the preparation of the heat-sensitive recording layer coating liquid of Example 2, the same as Example 2 except that the amount of liquid C was changed to 45 parts instead of 45 parts and the amount of liquid F was changed to 30 parts instead of 30 parts. A heat-sensitive recording material was obtained.

Comparative Example 1
In preparation of solution A in Example 1, instead of 3,3-bis [2- (4-dimethylaminophenyl) -2- (4-methoxyphenyl) vinyl] -4,5,6,7-tetrachlorophthalide In addition, a thermosensitive recording material was obtained in the same manner as in Example 1 except that 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane was used.

Comparative Example 2
In the preparation of the heat-sensitive recording layer coating liquid of Example 1, a heat-sensitive recording material was obtained in the same manner as in Example 1 except that the amount of liquid C was changed to 45 parts instead of 45 parts and liquid D was not used. It was.

Comparative Example 3
Instead of 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone in the preparation of solution D of Example 1, 4-hydroxybenzoic acid and 2,2-bis (hydroxymethyl) were used. ) -1,3-propanediol polycondensate dehydration condensate (trade name: Adeka Arcles K-5, manufactured by Adeka) was used in the same manner as in Example 1 to obtain a heat-sensitive recording material. .

  The following evaluation was performed on the heat-sensitive recording material thus obtained. The results were as shown in Table 1.

(Color development in the near infrared region)
Using a thermal recording evaluation machine (trade name: TH-PMH, manufactured by Okura Electric Co., Ltd.), each thermal recording medium is printed at an applied energy of 0.28 mJ / dot, and the vicinity of the recorded and unrecorded areas (background area). The reflectance in the infrared region was measured with a D filter (about 905 nm) of a micro-reflectance meter (trade name: MR-12, manufactured by Sakata Engineering Co., Ltd.), and a PCS value was calculated. Here, the PCS value in the present invention is obtained from the following equation. The higher the PCS value, the clearer the discrimination between the recorded part and the unrecorded part (background part), and the better the readability. The smaller the numerical value of the reflectance of the recording part and the larger the numerical value of the reflectance of the unrecorded part, the higher the PCS value.
PCS value (%) = [(reflectance of background portion−reflectance of recording portion) / reflectance of background portion] × 100

(Moisture and heat resistance)
Each heat-sensitive recording material developed for color development measurement was allowed to stand for 24 hours in an atmosphere of 40 ° C. and 90% RH, and then the reflectance of the recorded part and the unrecorded part (background part) was measured using a micro-reflectance meter ( Measurement was made with a D filter (about 905 nm) of a trade name: MR-12, manufactured by Sakata Engineering Co., Ltd., and a PCS value was calculated.

(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 manner, and each heat-sensitive recording material colored for the color development measurement is placed on the wrap film. A wrap film is wound on the wrapping film three times and allowed to stand at 40 ° C. for 24 hours, and then the reflectance of the recorded portion and the unrecorded portion (background portion) is measured by a micro-reflectance meter (trade name: MR-12, Sakata Engineering Co., Ltd.). PCS value was calculated using a D filter (about 905 nm).

(Light resistance)
Each heat-sensitive recording material developed for color development measurement is allowed to stand under a 5000 Lux fluorescent lamp for 24 hours, and the reflectance of a recorded portion and an unrecorded portion (background portion) is measured using a micro-reflectance meter (trade name: Measurement was performed with a D filter (about 905 nm) of MR-12, manufactured by Sakata Engineering Co., Ltd., and a PCS value was calculated.

  The heat-sensitive recording material of the present invention has a high recording characteristic with respect to an optical character (or mark) reader having a reading wavelength region in the near-infrared region and is excellent in the plasticizer resistance of the recording part. It is suitable for ticket papers.

Claims (6)

A heat-sensitive recording material comprising a heat-sensitive recording layer containing a leuco dye and a colorant on a support, the colorant containing a leuco dye represented by the following general formula (1) in the heat-sensitive recording layer: And a urea urethane compound represented by the following general formula (2).

(Wherein, R ¹ and R ² has a carbon number represents 1-6 straight-chain or branched alkyl group.)

  The urea urethane compound represented by the general formula (2) is contained in 0.1 to 4 parts by mass with respect to 1 part by mass of the leuco dye represented by the general formula (1). The heat-sensitive recording material described.   2,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-allyloxy as colorants One selected from the group consisting of -4'-hydroxydiphenylsulfone and Np-toluenesulfonyl-N'-3- (p-toluenesulfonyloxy) phenylurea is represented by the general formula (2) The heat-sensitive recording material according to claim 1, which is contained in an amount of 0.3 to 25 parts by mass with respect to 1 part by mass of the urethane compound.   The heat-sensitive composition according to any one of claims 1 to 3, wherein the urea urethane compound represented by the general formula (2) as the color former is heat-treated in the same liquid as the basic inorganic pigment. Recorded body.   The basic inorganic pigment is at least one selected from the group consisting of a magnesium compound, an aluminum compound, a calcium compound, a titanium compound, magnesium silicate, magnesium phosphate, and talc. A heat-sensitive recording material according to 1. The heat-sensitive recording material according to claim 1, further comprising an undercoat layer containing plastic hollow particles between the support and the heat-sensitive recording layer.