JP2009061631A - Thermosensitive recording body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensitive recording body excellent in water resistance, resistance to plasticizer and thermal resistance even under severe environments. <P>SOLUTION: In the thermosensitive recording body, the support of which is provided with a thermosensitive color developing layer including colorless or light-colored electron donative leuco dye and electron acceptive developer and a protective layer, the protective layer includes carboxyl group including resin, epichlorohydrin base resin and denatured polyamine/amide base resin and the thermosensitive color developing layer includes 4-hydroxy-4'-n-propoxydiphenylsulfone and 4-hydroxy-4'-allyloxydiphenylsulfone as the electron acceptive developer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material utilizing a color development reaction between a basic colorless dye and an electron-accepting developer, and more particularly to a heat-sensitive recording material excellent in water resistance, plasticizer resistance and heat resistance.

In general, a thermosensitive color development mainly composed of a colorless or light-colored electron-donating leuco dye (hereinafter referred to as a dye) and an electron-accepting color developer (hereinafter referred to as a developer) that reacts with the dye when heated to develop a color. Thermal recording materials having layers have been widely put into practical use. In order to perform recording on this thermal recording medium, a thermal printer or the like with a built-in thermal head is used. Compared to other recording methods that have been put to practical use, this thermal recording method is free from noise during recording, does not require development and fixing, is maintenance-free, is relatively inexpensive, and is compact. The developed color is very clear, and it is widely used for facsimiles, computer terminal printers, automatic ticket vending machines, measuring recorders, handy terminals, and so on.
In addition to the output sheets of various devices described above, the thermal recording medium is used in fields where high storage stability is required. In particular, when heat-sensitive recording materials are used for various tickets, receipts, labels, bank ATMs, gas and electricity meter readings, and car bills, etc. Plasticizer resistance that does not cause problems with the readability of the printed part even when stored in a clean state, heat resistance that does not cause the white paper to develop color even when stored in a hot place, and water resistance against moisture and moisture such as rain Is required.

  As a method for improving these qualities, it is generally proposed to provide a protective layer on the thermosensitive coloring layer. Patent Documents 1 and 2 disclose a technique relating to a protective layer using a water-soluble polymer such as polyvinyl alcohol and starch and a crosslinking agent such as glyoxal, but the effect is still insufficient. In particular, Patent Document 2 uses carboxyl-modified polyvinyl alcohol as the binder of the protective layer, epichlorohydrin and glyoxal as the cross-linking agent, but this technique simply uses epichlorohydrin as the carboxyl group of the carboxyl-modified polyvinyl alcohol. Water resistance is imparted by crosslinking reaction of glyoxal with a hydroxyl group. However, since the crosslinking reaction rate of epichlorohydrin is slow, water resistance is not immediately developed, and sufficient effects cannot be exhibited immediately after coating and drying. For this reason, when epichlorohydrin is used for the crosslinking agent, heat treatment for a long time, that is, curing is required, but there are problems of operability such as the covering of the ground and the inability to produce a product immediately after production. Further, the water resistance under severe conditions is not satisfactory because the crosslinking reaction site is easily hydrolyzed.

JP-A-8-230324 JP-A-9-164863

  In addition to this, a specific developer or a specific stabilizer is used (Patent Documents 3 and 4), and a specific sensitizer and a specific stabilizer are used in combination (Patent Document 5). A technique for improving storage stability is disclosed.

JP2003-154760 JP 2001-347757 A WO2004-002748

However, as thermal recording media are increasingly used for applications that are used in harsh environments such as cash vouchers, image storability with higher quality than before has been required. In the current state of the art, sufficient quality is not obtained.
Accordingly, an object of the present invention is to provide a heat-sensitive recording material excellent in water resistance, plasticizer resistance and heat resistance even in a harsh environment.

As a result of intensive studies, the present inventors have found that the above problems can be solved by using a specific protective layer and two specific electron-accepting color developers, and have completed the present invention.
That is, the present invention is a thermosensitive recording medium comprising a thermosensitive color-developing layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer and a protective layer on a support, wherein the protective layer comprises Containing a carboxyl group-containing resin, an epichlorohydrin-based resin and a modified polyamine / amide-based resin, wherein the thermosensitive coloring layer is 4-hydroxy-4′-n-propoxydiphenylsulfone and 4-hydroxy as an electron-accepting developer. A heat-sensitive recording material comprising -4'-allyloxydiphenyl sulfone.

In the heat-sensitive recording material of the present invention, the reason why it is excellent in water resistance, plasticizer resistance and heat resistance has not been clearly clarified, but by the coexistence of two types of diphenylsulfone compounds having similar structures in the heat-sensitive color developing layer, One reason is that the stability of the electron transfer complex, which is a reaction product of the developer and the basic dye, is increased.
In the protective layer of the heat-sensitive recording material, a crosslinking reaction (first water resistance) occurs between the carboxyl group of the carboxyl group-containing resin and the amine or amide portion of the epichlorohydrin resin as the crosslinking agent. Next, since the hydrophilic cross-linking site formed of the carboxyl group-containing resin and epichlorohydrin resin attracts the hydrophilic site of the modified polyamine / amide resin, this cross-linking site is the same as that of the modified polyamine / amide resin. It is in a state of being wrapped with the hydrophobic group on the outside, that is, in a state where the hydrophilic crosslinking site is protected from water by the hydrophobic group (second water resistance). Thus, it is presumed that good water resistance and moisture resistance can be obtained by imparting higher hydrophobicity to the reaction site between the resin used in the protective layer and the crosslinking agent.

In particular, when the carboxyl group-containing resin is carboxyl-modified polyvinyl alcohol, the hydrophilic part of the modified polyamine / polyamide resin and the carboxyl-modified polyvinyl alcohol are attracted, and the carboxyl-modified polyvinyl alcohol has the hydrophobic group of the modified polyamine / amide resin on the outside. When the cationic part of the modified polyamine / amide resin is cross-linked with the carboxyl group of the carboxyl-modified polyvinyl alcohol, high water resistance is exhibited and heat resistance is also improved. it is conceivable that.
Also, a modified polyamine / amide resin that has a three-dimensional structure by a crosslinking reaction of carboxyl-modified polyvinyl alcohol and epichlorohydrin resin, and is cationic when a pigment is contained in the protective layer. Is considered to be a porous layer compared to the prior art because it exhibits a dispersion effect on anionic pigments. For this reason, since the melt of the material with low heat resistance in the coating layer is adsorbed in the voids in the protective layer, excellent print running properties (head debris resistance, sticking resistance) can be exhibited.

  In the protective layer of the present invention, it is necessary to use an epichlorohydrin resin and a modified polyamine / amide resin in combination. When the epichlorohydrin resin and the modified polyamine / amide resin are used alone, sufficient water resistance cannot be obtained, and problems such as blocking occur. In addition, sufficient water resistance cannot be obtained even when other general crosslinking agents such as glyoxal and epichlorohydrin resin or modified polyamine / amide resin are used in combination.

Hereinafter, the present invention will be described in more detail.
The heat-sensitive recording material of the present invention comprises a heat-sensitive color-developing layer and a protective layer provided on a support, and this protective layer comprises a carboxyl group-containing resin, particularly a carboxyl-modified polyvinyl alcohol, an epichlorohydrin resin, and a modified polyamine / amide system. It contains a resin, and the thermosensitive coloring layer contains two specific types of electron-accepting color developers.

  In the present invention, the carboxyl group-containing resin used as the binder of the protective layer may be any resin having mainly a carboxyl group, such as methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate. , A resin containing a monofunctional acrylic monomer having a carboxyl group such as dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, oxidized starch, carboxymethylcellulose, Examples include carboxyl-modified polyvinyl alcohol in which a carboxyl group is introduced into polyvinyl alcohol. Particularly, carboxyl-modified polyvinyl alcohol having excellent heat resistance and solvent resistance. Preferably used Le.

The carboxyl-modified polyvinyl alcohol used in the present invention is a product in which a carboxyl group is introduced for the purpose of enhancing reactivity to a water-soluble polymer, such as polyvinyl alcohol and fumaric acid, phthalic anhydride, melittic anhydride, itaconic anhydride, etc. A reaction product of a polycarboxylic acid, or an esterified product of these reaction products, and an ethylenically unsaturated dicarboxylic acid such as vinyl acetate and maleic acid, fumaric acid, itaconic acid, crotonic acid, acrylic acid or methacrylic acid As a saponified product of Specific examples include the production methods exemplified in JP-A-53-91995.
Furthermore, the carboxyl-modified polyvinyl alcohol used in the present invention has a low Hercules viscosity, that is, a high fluidity in a state where a rotational force (share) is applied, and is easily immobilized at a low share. For this reason, it is considered that the coating liquid extends smoothly during coating and solidifies immediately after coating to form a coating layer that is homogeneous and has no unevenness, thereby improving the image quality and sensitivity of the printed image. In addition, since carboxyl-modified polyvinyl alcohol has high water retention, the penetration of the binder into the support can be suppressed, and this effect also improves the image quality and sensitivity because a coating layer without unevenness is formed. It is guessed.
The degree of polymerization and the degree of saponification of the carboxyl-modified polyvinyl alcohol used in the present invention can be appropriately selected and used from the viewpoint of the water retention of the paint and the surface strength of the coating layer.

  Specific examples of the epichlorohydrin-based resin used in the present invention include polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and the like, and they can be used alone or in combination. Moreover, as an amine which exists in the principal chain of an epichlorohydrin-type resin, the thing from a primary to a quaternary can be used, and there is no restriction | limiting in particular. Further, the degree of cationization and molecular weight are preferably water cation resistance, so that the degree of cationization is 5 meq / g · Solid (measured value at pH 7) and the molecular weight is 500,000 or more. Specific examples include Sumire's Resin 650 (30) (manufactured by Sumitomo Chemical), Sumire's Resin 675A (manufactured by Sumitomo Chemical), Sumire's Resin 6615 (manufactured by Sumitomo Chemical), WS4002 (manufactured by Seiko PMC), WS4020. (Made by Starlight PMC), WS4024 (made by Starlight PMC), WS4030 (made by Starlight PMC), WS4046 (made by Starlight PMC), WS4010 (made by Starlight PMC), CP8970 (made by Starlight PMC), and the like. .

  In the present invention, the modified polyamine / amide resin is a polyamide urea resin, polyethylene imine resin, polyalkylene polyamine resin, polyalkylene polyamide resin, polyamine polyurea resin, modified polyamine resin, modified polyamide resin, polyalkylene polyamine urea formalin. Resin, polyalkylene polyamine polyamide polyurea resin, and the like are listed. Specific examples include Sumire Resin 302 (manufactured by Sumitomo Chemical Co., Ltd .: polyamine polyurea resin) and Sumire Resin 712 (manufactured by Sumitomo Chemical Co., Ltd .: polyamine polyurea resin). ), Sumire Resin 703 (manufactured by Sumitomo Chemical: polyamine polyurea resin), Sumire Resin 636 (manufactured by Sumitomo Chemical: polyamine polyurea resin), Sumire Resin SPI-100 (manufactured by Sumitomo Chemical: modified polyamine) Tree ), Sumire Resin SPI-102A (Sumitomo Chemical Co .: modified polyamine resin), Sumire Resin SPI-106N (Sumitomo Chemical Co .: modified polyamide resin), Sumire Resin SPI-203 (50) (Sumitomo Chemical Co., Ltd.) : Polyamide resin), Sumirez resin SPI-198 (manufactured by Sumitomo Chemical Co., Ltd .: polyamide resin), printable A-700 (manufactured by Asahi Kasei), printable A-600 (manufactured by Asahi Kasei), PA6500 (manufactured by Seiko PMC): Polyalkylene polyamine urea formalin resin), PA6504 (manufactured by Starlight PMC: polyalkylene polyamine urea formalin resin), PA6664, PA6638, PA6640, PA6664, PA6664, PA6654, PA6702, PA6704 (above, manufactured by Starlight PMC: polyalkylenepolyamide) Polyamide polyurea resin), CP8994 (manufactured by Seiko PMC: polyethyleneimine resin), and the like. Although not particularly limited, polyamine resins (polyalkylene polyamine resins, polyamine polyurea resins) are considered in terms of color development sensitivity. It is desirable to use a modified polyamine resin, polyalkylene polyamine urea formalin resin, polyalkylene polyamine polyamide polyurea resin).

  The content of the epichlorohydrin resin and the modified polyamine / amide resin used in the present invention is preferably 1 to 100 parts by weight, more preferably 5 to 100 parts by weight with respect to 100 parts by weight of the carboxyl-modified polyvinyl alcohol. 50 parts by weight. If the content is too small, the crosslinking reaction becomes insufficient and good water resistance cannot be obtained. If the content is too large, there arises a problem in operability due to an increase in viscosity of the coating liquid or gelation. Moreover, since epichlorohydrin resin cross-links at pH 6.0 or higher, it is desirable to adjust the pH of the protective layer coating to 6.0 or higher.

  The types and amounts of various components used in the protective layer of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. Usually, polyvinyl alcohol is 10 to 500 parts per 100 parts by weight of the pigment. It is preferable to use 1 to 100 parts by weight of the crosslinking agent component with respect to 100 parts by weight of polyvinyl alcohol.

  The pigments that can be used in the protective layer in the present invention include kaolin, (calcined) kaolin, calcium carbonate, aluminum oxide, titanium oxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, diatomaceous earth, talc and the like. It is possible. In the present invention, the content of the pigment and the binder in the protective layer is about 30 to 300 parts by weight in solid content of the binder with respect to 100 parts by weight of the pigment.

  The electron-accepting color developers used in the heat-sensitive layer in the present invention are 4-hydroxy-4'-n-propoxydiphenyl sulfone and 4-hydroxy-4'-allyloxydiphenyl sulfone. 4-Hydroxy-4′-allyloxydiphenyl sulfone is preferably used at a ratio of 0.01 to 10.0 parts by weight per 1 part by weight of 4-hydroxy-4′-n-propoxydiphenyl sulfone. It is more preferable to use it at a ratio of ˜5.0 parts by weight. If it is less than 0.01 part by weight, it is difficult to obtain sufficient plasticizer resistance. On the other hand, if it exceeds 10.0 parts by weight, the sensitivity and image quality of the heat-sensitive recording material (heat-sensitive color forming layer) tend to be lowered.

  It is desirable that the heat-sensitive recording layer of the heat-sensitive recording material of the present invention contains a carboxyl group-containing resin and / or an epichlorohydrin resin. By including it in the heat-sensitive recording layer, the adhesion between the heat-sensitive recording layer and the protective layer is improved, and the immersion water resistance is improved. The carboxyl group-containing resin is desirably contained in an amount of 30% by weight or more based on the total binder of the heat-sensitive recording layer, and the epichlorohydrin resin is 0.2 to 5.0 parts by weight ( (Dry weight) is desirable. When the amount of the epichlorohydrin resin added increases, the stability of the paint decreases. In view of color development sensitivity, the carboxyl group-containing resin is preferably carboxy-modified polyvinyl alcohol.

  Examples of various materials used in the heat-sensitive color former of the present invention include a developer, a stabilizer, a binder, a cross-linking agent, etc., which are used in the heat-sensitive recording layer as long as the desired effects on the above problems are not inhibited. Binders, crosslinking agents, pigments, and the like can be used in the protective layer as long as the desired effects on the above-described problems are not impaired. Moreover, these materials can be used also for each coating layer provided as needed other than the thermosensitive coloring layer and the protective layer.

As the electron-donating leuco dye used in the heat-sensitive recording material of the present invention, any of those conventionally known in the field of pressure-sensitive or heat-sensitive recording paper can be used, and is not particularly limited. Compounds, fluoran compounds, fluorene compounds, divinyl compounds and the like are preferable. Specific examples of typical colorless or light-colored dyes (dye precursors) are shown below. These dye precursors may be used alone or in combination of two or more.
<Triphenylmethane leuco dye>
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone); 3,3-bis (p-dimethylaminophenyl) phthalide (also known as malachite green lactone)

<Fluoran leuco dye>
3-diethylamino-6-methylfluorane; 3-diethylamino-6-methyl-7-anilinofluorane; 3-diethylamino-6-methyl-7- (o, p-dimethylanilino) fluorane; 3-diethylamino- 6-methyl-7-chlorofluorane; 3-diethylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane; 3-diethylamino-6-methyl-7- (o-chloroanilino) fluorane; Diethylamino-6-methyl-7- (p-chloroanilino) fluorane; 3-diethylamino-6-methyl-7- (o-fluoroanilino) fluorane; 3-diethylamino-6-methyl-7- (m-methylanilino) fluorane 3-diethylamino-6-methyl-7-n-octylanilinofluorane; 3-diethylamino-6-methyl-7-n-octylaminofluorane; 3-diethylamino-6-methyl-7-benzylaminofluorane; 3-diethylamino-6-methyl-7-dibenzylaminofluorane;
3-diethylamino-6-chloro-7-methylfluorane; 3-diethylamino-6-chloro-7-anilinofluorane; 3-diethylamino-6-chloro-7-p-methylanilinofluorane; 3-diethylamino -6-ethoxyethyl-7-anilinofluorane; 3-diethylamino-7-methylfluorane; 3-diethylamino-7-chlorofluorane; 3-diethylamino-7- (m-trifluoromethylanilino) fluorane; 3-diethylamino-7- (o-chloroanilino) fluorane; 3-diethylamino-7- (p-chloroanilino) fluorane; 3-diethylamino-7- (o-fluoroanilino) fluorane; 3-diethylamino-benzo [a] fluorane ;
3-dibutylamino-6-methyl-7- (o); 3-dibutylamino-6-methyl-7- (o; 3-dibutylamino-6-methyl-7- (o , P-dimethylanilino) fluorane; 3-dibutylamino-6-methyl-7- (o-chloroanilino) fluorane; 3-dibutylamino-6-methyl-7- (p-chloroanilino) fluorane; 3-dibutylamino- 6-methyl-7- (o-fluoroanilino) fluorane; 3-dibutylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane; 3-dibutylamino-6-methyl-chlorofluorane; 3-dibutylamino-6-ethoxyethyl-7-anilinofluorane; 3-dibutylamino-6-chloro- 7-anilinofluorane; 3-dibutylamino-6-methyl-7-p-methylanilinofluorane; 3-dibutylamino-7- (o-chloroanilino) fluorane; 3-dibutylamino-7- (o- 3-di-n-pentylamino-6-methyl-7-anilinofluorane; 3-di-n-pentylamino-6-methyl-7- (p-chloroanilino) fluorane; Di-n-pentylamino-7- (m-trifluoromethylanilino) fluorane; 3-di-n-pentylamino-6-chloro-7-anilinofluorane; 3-di-n-pentylamino-7 -(P-chloroanilino) fluorane; 3-pyrrolidino-6-methyl-7-anilinofluorane; 3-piperidino-6-methyl-7-anilinofluorane 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluorane; 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane; -(N-ethyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-xylamino) -6-methyl-7- (p-chloroanilino) fluorane; (N-ethyl-p-toludino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane; 3- (N- Ethyl (N-isoamylamino) -6-chloro-7-anilinofluorane; 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane; Til-N-isobutylamino) -6-methyl-7-anilinofluorane; 3- (N-ethyl-N-ethoxypropylamino) -6-methyl-7-anilinofluorane; 3-cyclohexylamino-6 -Chlorofluorane; 2- (4-oxahexyl) -3-dimethylamino-6-methyl-7-anilinofluorane; 2- (4-oxahexyl) -3-diethylamino-6-methyl-7-ani Linofluorane; 2- (4-oxahexyl) -3-dipropylamino-6-methyl-7-anilinofluorane; 2-methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane 2-methoxy-6-p- (p-dimethylaminophenyl) aminoanilinofluorane; 2-chloro-3-methyl-6-p- (p-phenylaminophenyl); 2-chloro-6-p- (p-dimethylaminophenyl) aminoanilinofluorane; 2-nitro-6-p- (p-diethylaminophenyl) aminoanilinofluorane; -Amino-6-p- (p-diethylaminophenyl) aminoanilinofluorane; 2-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane; 2-phenyl-6-methyl-6-p -(P-phenylaminophenyl) aminoanilinofluorane; 2-benzyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane; 2-hydroxy-6-p- (p-phenylaminophenyl) Aminoanilinofluorane; 3-methyl-6-p- (p-dimethylaminophenyl) aminoanilinov Oran; 3-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane; 3-diethylamino-6-p- (p-dibutylaminophenyl) aminoanilinofluorane; 2,4-dimethyl-6 -[(4-Dimethylamino) anilino] -fluorane

<Fluorene leuco dye>
3,6,6′-tris (dimethylamino) spiro [fluorene-9,3′-phthalide]; 3,6,6′-tris (diethylamino) spiro [fluorene-9,3′-phthalide]
<Divinyl leuco dye>
3,3-bis- [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrabromophthalide; 3,3-bis- [2- (P-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide; 3,3-bis- [1,1-bis (4-pyrrolidinophenyl) ) Ethylene-2-yl] -4,5,6,7-tetrabromophthalide; 3,3-bis- [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2- Yl] -4,5,6,7-tetrachlorophthalide

<Others>
3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide; 3- (4-diethylamino-2-ethoxyphenyl) -3- ( 1-octyl-2-methylindol-3-yl) -4-azaphthalide; 3- (4-cyclohexylethylamino-2-methoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl)- 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide; 3,6-bis (diethylamino) fluorane-γ- (3′-nitro) anilinolactam; -Bis (diethylamino) fluorane-γ- (4'-nitro) anilinolactam; 1,1-bis- [2 ', 2', 2 ", 2" -tetrakis- (p-dimethyla Nophenyl) -ethenyl] -2,2-dinitrileethane; 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2- β-naphthoylethane; 1,1-bis- [2 ′, 2 ′, 2 ″, 2 ″ -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,2-diacetylethane; bis- [2, 2,2 ′, 2′-Tetrakis- (p-dimethylaminophenyl) -ethenyl] -methylmalonic acid dimethyl ester

  As the electron-accepting developer that can be used together in the heat-sensitive recording material of the present invention, all those known in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used and are not particularly limited. Are, for example, inorganic clays such as activated clay, attapulgite, colloidal silica, aluminum silicate, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4 -Hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4, -Hydroxy-4'-isopropoxydiphenyl sulfone, -Hydroxy-4'-n-propoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 3 , 4-dihydroxyphenyl-4′-methylphenylsulfone, aminobenzenesulfonamide derivatives described in JP-A-8-59603, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) ) -3-oxapentane, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [ α-methyl-α- (4′-hydroxyphenyl) ethyl] , 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-tert-octylphenol) ), 2,2′-thiobis (4-tert-octylphenol), compounds described in International Publication WO 02/081229 or JP-A 2002-301873, and thioureas such as N, N′-di-m-chlorophenylthiourea Compound, p-chlorobenzoic acid, stearyl gallate, zinc bis [4- (n-octyloxycarbonylamino) salicylate] dihydrate, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [ 3- (p-Tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxy) Toxi) cumyl] aromatic carboxylic acids of salicylic acid, and salts of these aromatic carboxylic acids with polyvalent metal salts such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, and further zinc thiocyanate Antipyrine complex, complex zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid, etc. are mentioned. These developers can be used alone or in combination of two or more. A metal chelate color-developing component such as a higher fatty acid metal double salt and a polyvalent hydroxyaromatic compound described in JP-A No. 10-258577 can also be contained.

  In the heat-sensitive recording material of the present invention, a conventionally known sensitizer can be used as the sensitizer to be used. Examples of such sensitizers include fatty acid amides such as stearamide and palmitic acid amide, ethylene bisamide, montanic acid wax, polyethylene wax, 1,2-di- (3-methylphenoxy) ethane, p-benzylbiphenyl, β- Benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di (p-chlorobenzyl) oxalate, di (p-methylbenzyl) oxalate, Dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, o-xylene-bis -(Phenyl ether), 4- (m-methyl) Ruphenoxymethyl) biphenyl, 4,4′-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di (3-methylphenoxy) ethylene, bis [2- (4-methoxy- Examples thereof include, but are not limited to, phenoxy) ethyl] ether, methyl p-nitrobenzoate and phenyl p-toluenesulfonate. These sensitizers may be used alone or in combination of two or more.

  In the present invention, 4,4′-butylidene (6-tert-butyl-3-methylphenol), 2 as a stabilizer exhibiting the oil resistance effect of the recorded image and the like within a range not impairing the desired effect on the above problems. 2,2'-di-t-butyl-5,5'-dimethyl-4,4'-sulfonyldiphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane and the like.

  In the heat-sensitive recording material of the present invention, as a binder to be used, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl Alcohol, olefin modified polyvinyl alcohol, nitrile modified polyvinyl alcohol, pyrrolidone modified polyvinyl alcohol, silicone modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene Copolymer and ethyl cellulose, acetyl cell Cellulose derivatives such as sugar, casein, arabic gum, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyvinyl butyral, polystyrose and the like Examples of such a copolymer include polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, and coumaro resin. These polymer substances are used by dissolving them in solvents such as water, alcohol, ketones, esters, hydrocarbons, etc., and are used in the state of being emulsified or pasted in water or other media to achieve the required quality. It can also be used in combination.

In the heat-sensitive recording material of the present invention, the crosslinking agent used is glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, potassium persulfate, ammonium persulfate, persulfate. Examples thereof include sodium sulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, and ammonium chloride.
In the heat-sensitive recording material of the present invention, examples of the pigment used include inorganic or organic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, and aluminum hydroxide.
In the heat-sensitive recording material of the present invention, examples of the lubricant used include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, silicone resins and the like.
In addition, benzophenone and triazole ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

The type and amount of the dye, developer, and other various components used in the heat-sensitive color developing layer of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. On the other hand, 0.5 to 10 parts of developer, 0.5 to 10 parts of sensitizer, 0.01 to 10 parts by weight of stabilizer, and 0.01 to 10 parts by weight of other components are used.
Dye, developer, and materials to be added as necessary are finely pulverized to a particle size of several microns or less by a pulverizer such as a ball mill, an attritor, a sand glider, or an appropriate emulsifier, and depending on the binder and purpose. Various additive materials are added to form a coating solution. As the solvent used in the coating solution, water or alcohol can be used, and the solid content is about 20 to 40% by weight.

The following examples illustrate the invention but are not intended to limit the invention.
In the following examples and comparative examples, an under layer, a thermosensitive coloring layer (recording layer) and a protective layer were formed on one side of the support.
The coating liquid used for each coating layer of the heat-sensitive recording material was prepared as follows.
In the description, parts and% indicate parts by weight and% by weight, respectively.

Underlayer coating liquid -calcined kaolin (Ansilex 90 manufactured by BASF) 90.0 parts-styrene-butadiene copolymer latex (solid content 50%) 10.0 parts-water 50.0 parts A mixture comprising the above composition was mixed. The under layer coating solution was prepared by stirring.

Thermosensitive coloring layer coating solution The following solutions A to D were separately wet-ground with a sand grinder until the average particle size became 0.5 μm.
Liquid A (first developer dispersion)
4-hydroxy-4′-n-propoxydiphenylsulfone (manufactured by API Corporation, trade name: JKY146) 6.0 parts -carboxyl-modified polyvinyl alcohol (trade name: KL318, degree of polymerization: about 1700, saponification) Degree: 85-90 mol%) 10% aqueous solution 5.0 parts-water 1.5 parts

Liquid B (second developer dispersion)
4-hydroxy-4'-allyloxydiphenyl sulfone (manufactured by Nikka Chemical Co., Ltd., trade name: BPS-MAE) 6.0 parts -carboxy-modified polyvinyl alcohol (KL318) 10% aqueous solution 5.0 parts -water 1.5 parts Liquid C (basic colorless dye dispersion)
-3-dibutylamino-6-methyl-7-anilinofluorane (manufactured by Yamamoto Kasei Co., Ltd., trade name: ODB-2) 6.0 parts -carboxy-modified polyvinyl alcohol (KL318) 10% aqueous solution 5.0 parts -water 1.5 parts D liquid (sensitizer dispersion)
-1,2-bis (3-methylphenoxy) ethane (manufactured by Sanko Co., Ltd., trade name: KS232)
6.0 parts -Carboxy modified polyvinyl alcohol (KL318) 10% aqueous solution 5.0 parts -Water 1.5 parts

Next, the dispersions were mixed at the following ratio to obtain a thermosensitive coloring layer coating solution.
Liquid A (first developer dispersion) 36.0 parts Liquid B (second developer dispersion) 36.0 parts Liquid C (basic colorless dye dispersion) 18.0 parts Liquid D (sensitizer) Dispersion) 36.0 parts Silica (manufactured by Mizusawa Chemical Co., Ltd., trade name: P537 25% dispersion) 7.5 parts Carboxy-modified polyvinyl alcohol (KL318) 10% aqueous solution 25.0 parts Polyamide epichlorohydrin resin (Starlight PMC) (Product name: WS4030, solid content 25%, degree of cationization: 2.7, molecular weight: 2.2 million, quaternary amine) 4.0 parts

Protective layer coating solution- Aluminum hydroxide 50% dispersion (trade name: Martinfin OL, manufactured by Martinsberg) 9.0 parts-Carboxyl-modified polyvinyl alcohol (KL318) 10% aqueous solution 30.0 parts-Polyamide epichlorohydride Phosphoric resin (WS4030) 4.0 parts-Modified polyamine-based resin (trade name, Sumirez Resin SPI-102A, solid content 45%) 2.2 parts-Zinc stearate (trade name, manufactured by Chukyo Yushi Co., Ltd.) Hydrin Z-7-30, solid content 30%)
2.0 parts

[Example 1]
Apply and dry the under layer coating solution on one side of high-quality paper (47 g / m ² base paper) with a Meyer bar to 10.0 g / m ² (fan dryer, 60 ° C., 2 minutes) Coated paper was obtained. The thermosensitive coloring layer coating solution was applied and dried (fan drying at 60 ° C. for 2 minutes) so that the coating amount was 6.0 g / m ² on the under layer of the under-coated paper. On this thermosensitive coloring layer, the protective layer coating solution was applied and dried (blow dryer, 60 ° C., 2 minutes) so that the coating amount was 3 g / m 2. This sheet was processed with a super calendar so as to have a smoothness of 500 to 1000 seconds to obtain a heat-sensitive recording material.

[Example 2]
Except for changing D liquid (sensitizer dispersion) to stearic acid amide / paltimic acid amide mixture (mixing ratio: 7/3, Nippon Kasei Co., Ltd., trade name: AP-1), the same procedure as in Example 1 was performed. A heat-sensitive recording material was produced.
[Example 3]
The same as Example 2 except that the liquid C (dye dispersion) was changed to 3-N-di-n-pentylamino-6-methyl-7-anilinofluorane (manufactured by Yamada Chemical Co., Ltd., trade name: BLACK305). Thus, a heat-sensitive recording material was produced.

[Comparative Example 1]
Change A liquid (first developer dispersion) and B liquid (second developer dispersion) to 4-hydroxy-4'-isopropoxydiphenylsulfone (product name: NY-DS, manufactured by API Corporation). A thermosensitive recording material was produced in the same manner as in Example 1 except that.
[Comparative Example 2]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the blending part of the liquid B of Example 1 was 72 parts and the liquid A was not blended.

[Comparative Example 3]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the blending part of the liquid A in Example 1 was 72 parts and the liquid B was not blended.
[Comparative Example 4]
Thermosensitive in the same manner as in Example 1 except that the liquid A (first developer dispersion) was changed to 4-hydroxy-4′-isopropoxydiphenyl sulfone (manufactured by API Corporation, trade name: NY-DS). A recording body was produced.
[Comparative Example 5]
Thermosensitive in the same manner as in Example 1 except that the B liquid (second developer dispersion) was changed to 4-hydroxy-4′-isopropoxydiphenyl sulfone (manufactured by API Corporation, trade name: NY-DS). A recording body was produced.
[Comparative Example 6]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the protective layer was not provided.
[Comparative Example 7]
A heat-sensitive recording material was produced in the same manner as in Example 1 except that the modified polyamine resin was not added to the protective layer and 6.2 parts of polyamide epichlorohydrin resin was added.

  The following evaluations were performed on the heat-sensitive recording materials obtained in the above Examples and Comparative Examples, and the results are shown in Table 1.

<Print density>
A checkerboard pattern was printed with a thermal printer TH-PMD applied energy of 0.35 mJ / dot manufactured by Okura Co., Ltd., and the colored portion was measured with a Macbeth densitometer.
<Water resistance>
50 μl of water was dropped on the recording surface of the heat-sensitive recording material after recording obtained by the recording sensitivity evaluation, and the recording surface was strongly rubbed with a finger to evaluate the degree of water resistance. The evaluation criteria are shown below.
○: There is no slimy feeling and the recording layer does not peel. Δ: There is a slimy feeling, but the recording layer does not peel. ×: The recording layer melts and a part of the recording layer peels off, making it difficult to determine the recording portion.
<Plasticizer resistance>
A dial wrap (manufactured by Mitsui Chemicals) was brought into contact with the front and back of the heat-sensitive recording material printed as described above and allowed to stand in an environment of 40 ° C. and 90% for 24 hours. The survival rate was calculated from
Residual rate = (printed part density after test) / (printed part density before test) × 100 (%)
◎: Residual rate is 90% or more ○: Residual rate is 75% or more and less than 90% Δ: Residual rate is 50% or more and less than 75% ×: Residual rate is less than 50% <Heat resistance>
A blank paper sample was allowed to stand in an 80 ° C. environment for 24 hours, and the color density before and after the test was measured to obtain the ground color development value.
Ground color development value = color density after test−density before test ◎: ground color development value is less than 0.1 ○: ground color development value is 0.1 or more and less than 0.3 Δ: ground color development value is 0. 3 or more and less than 0.5 x: Ground color development value is 0.5 or more

  The results are shown in the table below.

表１から、保護層にカルボキシル基含有樹脂、エピクロロヒドリン系樹脂及び変性ポリアミン／アミド系樹脂を含有し、感熱発色層に４−ヒドロキシ−４'−ｎ−プロポキシジフェニルスルホンおよび４−ヒドロキシ−４'−アリルオキシジフェニルスルホンを含有させた場合には、その感熱記録体が耐水性、耐可塑剤性および耐熱性に優れていることがわかる。

From Table 1, the protective layer contains a carboxyl group-containing resin, an epichlorohydrin resin and a modified polyamine / amide resin, and the thermosensitive coloring layer contains 4-hydroxy-4′-n-propoxydiphenyl sulfone and 4-hydroxy- When 4′-allyloxydiphenyl sulfone is contained, it can be seen that the thermal recording material is excellent in water resistance, plasticizer resistance and heat resistance.

Claims (3)

A heat-sensitive recording material comprising a support and a heat-sensitive color-developing layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, and a protective layer, the protective layer comprising a carboxyl group-containing resin, Containing a chlorohydrin-based resin and a modified polyamine / amide-based resin, wherein the thermosensitive coloring layer is 4-hydroxy-4′-n-propoxydiphenylsulfone and 4-hydroxy-4′-allyloxy as an electron-accepting developer. A heat-sensitive recording material comprising diphenyl sulfone. The heat-sensitive recording material according to claim 1, wherein the modified polyamine / amide resin is a polyamine resin. The heat-sensitive recording layer according to claim 1 or 2, wherein the heat-sensitive recording layer contains a carboxyl group-containing resin and / or an epichlorohydrin-based resin.