JP2011240574A - Heat-sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording medium having a protective layer on a heat-sensitive recording layer, which has sufficient water resistance and solvent resistance, and excels in printing concentration, image qualities and scuff resistance.SOLUTION: In the heat sensitive recording medium having a heat sensitive recording layer containing an electron-donating leuco dye and an electron-accepting developer on a support, and a protective layer containing a carboxyl group-containing resin and a cross-linking agent, the protective layer in a wet state is pressed on a heated miller-surfacing drum, and dried.

Description

The present invention relates to a heat-sensitive recording material excellent in printing density, image quality, water resistance, scratch resistance, and plasticizer resistance.

In general, a heat-sensitive recording material is usually a colorless or light-colored electron-donating leuco dye (hereinafter also referred to as “leuco dye”) and an electron-accepting developer (hereinafter also referred to as “developer”) such as a phenolic compound. Are dispersed in fine particles, then mixed together, and a paint obtained by adding a binder, a filler, a sensitivity improver, a lubricant and other auxiliaries to paper, synthetic paper, film, It is coated on a support such as plastic, and develops color by an instantaneous chemical reaction by heating with a thermal head, hot stamp, thermal pen, laser light, etc., and a recorded image is obtained. Thermal recording media are widely used in facsimiles, computer terminal printers, automatic ticket vending machines, measurement recorders, and the like.

In recent years, the application of thermal recording media has been expanded to use for various tickets, receipts, labels, bank ATMs, gas and electricity meter readings, and car tickets, etc. Severe characteristics such as water resistance, which has not been a problem in the past, are beginning to be required for the recording medium. These applications are often used outdoors, and quality performance that can withstand use in harsher environments than before, so that it is not difficult to read the recorded area due to moisture, moisture, and solvents such as rain. Is required.

In response to this requirement, a thermal recording material excellent in water resistance, solvent resistance and the like has been disclosed by including carboxy-modified polyvinyl alcohol, epichlorohydrin resin, and polyamine / amide resin in the protective layer. (Patent Document 1, Patent Document 2).

Japanese Patent No. 3955083 JP 2007-130999 A

However, the heat-sensitive recording material containing carboxy-modified polyvinyl alcohol, epichlorohydrin resin, and polyamine / amide resin in the protective layer has good water resistance and solvent resistance, but it is new to video printers and the like. Print density, image quality,
There is a need for improved scratch-resistant quality.

Accordingly, the present invention provides a thermal recording layer having a thermal recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer on a support, and a protective layer containing a carboxyl group-containing resin and a crosslinking agent. It is an object of the present invention to provide a heat-sensitive recording medium having sufficient water resistance and solvent resistance and excellent print density, image quality, and scratch resistance.

The object is to provide a heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, and a protective layer containing a carboxyl group-containing resin and a crosslinking agent. In this method, the protective layer in a wet state was heated, pressed against a mirror drum, and dried.

According to the present invention, it is an object to provide a heat-sensitive recording material having sufficient water resistance and solvent resistance and excellent print density, image quality, and scratch resistance.

  Embodiments of the present invention will be described below.

The heat-sensitive recording material of the present invention comprises, on a support, a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer, and a protective layer containing a carboxyl group-containing resin and a crosslinking agent. The heat-sensitive recording material has a wet recording layer that is heated, pressed against a mirror drum, and dried.

In the present invention, the reason for having sufficient water resistance and solvent resistance and excellent print density, image quality, and scratch resistance is presumed as follows. Regarding water resistance and solvent resistance, it is considered that excellent performance is exhibited because the entire protective layer is in a film-like state when the carboxyl group-containing resin is firmly bound by the crosslinking agent.

On the other hand, a protective layer containing a carboxy group-containing resin and a crosslinking agent in a wet state is pressed against a heated mirror drum and dried to improve the surface properties of the protective layer, thereby improving the print density and image quality. Become. Moreover, after making the state of loosening the bond between the carboxyl group-containing resin and the cross-linking agent by making it wet, by pressing and drying (pressurizing / heating treatment),
It becomes a kind of recrystallized state. As a result, since the reaction between the carboxyl group-containing resin and the crosslinking agent becomes uniform, the protective layer becomes stronger and denser, so that water resistance and solvent resistance are further improved, and excellent scratch resistance is expected to be developed. Is done.

The carboxyl group-containing resin contained in the protective layer of the present invention may be any one having a carboxyl group, such as methacrylic acid, 2-hydroxyethyl methacrylate,
A resin containing a monofunctional acrylic monomer having a carboxyl group such as 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, Examples thereof include oxidized starch, carboxymethyl cellulose, and carboxy-modified polyvinyl alcohol in which a carboxyl group is introduced into polyvinyl alcohol, and it is particularly preferable to use carboxy-modified polyvinyl alcohol having excellent heat resistance and solvent resistance.

As the crosslinking agent contained in the protective layer of the present invention, any crosslinking agent may be used as long as it undergoes a crosslinking reaction with the carboxyl group-containing resin contained in the protective layer. Specifically, glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin are used. , Polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, ammonium chloride, etc. However, it is desirable to use an epichlorohydrin resin as a crosslinking agent for carboxy-modified polyvinyl alcohol.

By using an epichlorohydrin-based resin as a crosslinking agent for carboxy-modified polyvinyl alcohol, the carboxyl group or hydroxyl group of carboxy-modified polyvinyl alcohol and the epoxy group of epichlorohydrin-based resin are cross-linked, resulting in water resistance and solvent resistance. To express. In addition, since epichlorohydrin resin exhibits fluidity by heat, surface properties are improved when a wet protective layer is pressurized and heat-treated, so that print density and image quality can be obtained.

In the present invention, the epichlorohydrin-based resin may be any resin having epichlorohydrin as a structural unit, and examples thereof include a polyamide epichlorohydrin resin and a polyamine epichlorohydrin resin. Can be used alone or in combination.
Specific examples include Sumire's Resin 650 (30) (Sumitomo Chemical Co., Ltd.), Sumire Resin 675A (Sumitomo Chemical Co., Ltd.), Sumire Resin 6615 (Sumitomo Chemical Co., Ltd.), WS4002.
(Manufactured by Starlight PMC), WS4020 (manufactured by Starlight PMC), WS4024 (manufactured by Starlight PMC), WS4046 (manufactured by Starlight PMC), WS4010 (manufactured by Starlight PMC), CP8970
(Manufactured by Seiko PMC). In the case of using a polyamide epichlorohydrin resin or a polyamine epichlorohydrin resin, the degree of cationization and the molecular weight are excellent in water resistance, so that the degree of cationization is 5 meq / g · Solid or less (measured value at pH 7). ), Preferably having a molecular weight of 500,000 or more. The amine present in the main chain can be primary to quaternary and is not particularly limited.

In the present invention, it is desirable that the protective layer further contains a polyamine / amide resin (excluding epichlorohydrin resin) from the viewpoint of water resistance and solvent resistance.

When a protective layer containing carboxy-modified polyvinyl alcohol and epichlorohydrin resin contains a polyamine / amide resin (excluding epichlorohydrin resin)
It was excellent in protecting the polar site that had been cross-linked by attracting the amine / amide site in the polyamine / amide resin that had a cross-linked polarity between carboxy-modified polyvinyl alcohol and epichlorohydrin resin. It is thought that water resistance and solvent resistance are expressed.
In addition, since the polyamine / amide resin exhibits fluidity by heat, the surface property is improved when the wet protective layer is pressurized and heat-treated, so that the print density and image quality can be improved. .

In the present invention, polyamine / amide resins (excluding epichlorohydrin resins) include polyamine resins, polyamide resins, polyamide urea resins, polyalkylene polyamine resins, polyalkylene polyamide resins, polyamine polyurea resins, modified resins. Examples include polyamine resins, modified polyamide resins, polyalkylene polyamine urea formalin resins, polyalkylene polyamine polyamide polyurea resins, and specific examples include Sumire Resin 302 (manufactured by Sumitomo Chemical Co., Ltd .: Polyamine Polyurea Resin), Sumire Resin 712. (Sumitomo Chemical Co., Ltd .: polyamine polyurea resin), Sumire Resin 703 (Sumitomo Chemical Co., Ltd .: polyamine polyurea resin), Sumire Resin 636 (Sumitomo Chemical Co., Ltd .: polyamine polyurea resin), Sumire Resin SPI 100 (Sumitomo Chemical Co., Ltd .: modified polyamine resin), Sumire Resin SPI-102A (Sumitomo Chemical Co., Ltd .: modified polyamine resin), Sumire Resin SPI-106N (Sumitomo Chemical Co., Ltd .: modified polyamide resin), Sumire Resin SPI -2
03 (50) (manufactured by Sumitomo Chemical Co., Ltd.), Sumire's Resin SPI-198 (manufactured by Sumitomo Chemical Co., Ltd.), Printive A-700 (manufactured by Asahi Kasei Co., Ltd.), Printive A-600 (manufactured by Asahi Kasei Co., Ltd.), PA6
500, PA6504, PA6634, PA6638, PA6640, PA6664, P
A6646, PA6654, PA6702, PA6704 (above, made by Seiko PMC: polyalkylene polyamine polyamide polyurea resin), CP8994 (made by Seiko PMC: polyethyleneimine resin), and the like, and are not particularly limited. It can be used alone or in combination of two or more, but from the viewpoint of color development sensitivity, polyamine resins (polyalkylene polyamine resins, polyamine polyurea resins, modified polyamine resins, polyalkylene polyamine urea formalin resins, polyalkylene polyamine polyamide polys) It is desirable to use (urea tree).

The content (dry weight) of the carboxyl group-containing polyvinyl alcohol and the crosslinking agent contained in the protective layer of the present invention is not particularly limited, but is 100% by weight of the total protective layer (dry weight). From this point, it is desirable to be 1 to 100 parts by weight. If it is 1 part by weight or less, a sufficient film for protecting the thermosensitive recording layer located in the lower layer cannot be formed, and good water resistance cannot be obtained. Moreover, as for the mixture ratio (dry weight) of carboxyl group-containing resin and a crosslinking agent, it is desirable that a crosslinking agent is 1-100 weight part with respect to 100 weight part of carboxyl group-containing resin. When the blending amount of the crosslinking agent is 1 part by weight or less, a sufficient crosslinking reaction does not proceed and excellent water resistance and solvent resistance cannot be obtained. It becomes a problem.

In the present invention, the method of heating the protective layer in a wet state while being pressed against the mirror drum and drying is not particularly limited, but a cast coating method is usually used. As the cast coating method, (1) a wet casting method (direct method) in which a coating layer is pressed onto a mirror-finished superheated drum while it is wet and dried (2) a wet coating layer is temporarily ( Semi) Rewetting cast method (rewetting method) in which it is swelled and plasticized with a rewetting liquid (rewetting liquid) after drying, and pressed against a heated drum that has been mirror-finished (rewetting method), (3) The coating layer in a wet state is solidified It is generally classified into a dry gelation cast method (coagulation method) that is brought into a gel state and pressed onto a mirror-finished heating drum, and has the following characteristics. Therefore, it is desirable to select and use the best method as appropriate.

In the direct method and the solidification method, the drying load on the mirror drum increases because it is pressed against the mirror drum while the coating layer is in a wet state, but there is a limit to improving the drying ability of the mirror drum,
Forced to operate at low speed. On the other hand, in the rewet method, the coating layer after drying is rewet with the rewet liquid and then pressed against the mirror drum, so that the drying itself can be performed in the previous step, and the mirror drum can have a small drying load. The coating speed is easy to increase compared to the coating method and solidification method.

As an example, in the case of a protective layer containing carboxy-modified polyvinyl alcohol and epichlorohydrin resin, carboxy-modified polyvinyl alcohol and epichlorohydrin resin do not coagulate (gelate) even when mixed. It is desirable to use it.

In addition, the rewetting liquid (rewetting liquid) used in the rewetting cast method is not particularly limited, but is usually a fatty acid such as stearic acid or oleic acid or a salt thereof, or a mold release such as polyethylene wax or lecithin. An aqueous liquid mainly composed of an agent is used. The main effect of the rewetting liquid is to wet plasticize the upper layer of the dry coating layer with the water that accounts for the majority of this liquid. This makes it possible to apply the wet coating layer to the mirror drum by the rewetting cast coating method. Adhere closely and copy the mirror surface to improve the surface properties of the protective layer. In the rewetting liquid, in addition to the above releasing agent, a fluorescent dye, a dye, an ink fixing agent, as long as the effects of the present invention are not impaired.
Colloidal pigments, surfactants and the like may be added. In addition, a pigment dispersant, a water retention agent, a thickening agent, an antifoaming agent, a preservative, a coloring agent, a water resistant agent, a wetting agent, an ultraviolet absorber, a cationic polymer electrolyte, and the like may be appropriately added as necessary. it can.

In the present invention, the temperature of the mirror drum and the pressure to be pressed when the protective layer in a wet state is heated and pressed against the mirror drum and dried are not particularly limited, and it is desirable to adjust appropriately. However, the temperature of the mirror drum is usually 50 to 130 ° C., preferably 60 to 9
The temperature is 0 ° C. and the pressure is 50 to 300 kN / m, preferably 100 to 250 kN / m.
If the drum temperature is too low, the protective layer will be insufficiently dried, and if it is too high, there may be a problem that the white paper portion of the thermosensitive recording medium is colored by heat. On the other hand, if the pressure to be pressed is too low, a heat-sensitive recording material having good surface properties cannot be obtained. If the pressure is too high, the heat-sensitive recording layer of the heat-sensitive recording material may be crushed and color development may be deteriorated.

Next, various materials used in the present invention are exemplified, but binders, cross-linking agents, etc. can be used in the protective layer as long as they do not impair the desired effect on the above-mentioned problems. Can also be used for each coating layer provided as required.

The binder used in the present invention includes fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, and 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 cellulose derivatives such as ethyl cellulose and acetyl cellulose, casein, arabic gum, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate Polyacrylamide, polyacrylic acid ester, polyvinyl butyral, polystyrose and copolymers thereof, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, coumaro resin and the like can be exemplified. 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.

Examples of the crosslinking agent used in the present invention include glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, potassium persulfate, ammonium persulfate, sodium persulfate, chloride chloride Examples include ferric iron, magnesium chloride, borax, boric acid, alum, ammonium chloride and the like.

Examples of the pigment used in the present invention include silica, calcium carbonate, kaolin, calcined kaolin,
Examples thereof include inorganic or organic fillers such as diatomaceous earth, talc, titanium oxide, and aluminum hydroxide. As the pigment used in the protective layer, aluminum hydroxide or kaolin is preferable in consideration of the wearability of the thermal head.

Examples of the lubricant used in the present invention include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins.

Further, in the present invention, 4,4′-butylidene (6-tert-butyl-3) is used as an image stabilizer exhibiting an oil resistance effect of a recorded image within a range that does not impair a desired effect on the above problem.
-Methylphenol), 2,2'-di-t-butyl-5,5'-dimethyl-4,4'-sulfonyldiphenol, 1,1,3-tris (2-methyl-4-hydroxy-5- Cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-t-)
Butylphenyl) butane, 4-benzyloxy-4 ′-(2,3-epoxy-2-methylpropoxy) diphenylsulfone, and the like can also be added.
In addition, benzophenone and triazole ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

As the electron-donating leuco dye used in the present invention, those known in the conventional pressure-sensitive or heat-sensitive recording paper field can be used, and are not particularly limited, but include triphenylmethane compounds, fluorane compounds. 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, 3-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-anilinofluor Oran, 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-diethylamino-benzo [c] fluorane, 3-dibutylamino-6-methyl-fluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 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-7-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-fluoroanilino) fluorane, 3-di -N-pentylamino-6-methyl-7-anilinofluorane, 3-di-n-pentylamino-6-methyl-7- (p-chloroanilino) fluorane, 3-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, 3- (N
-Ethyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane, 3- (
N-ethyl-N-xylamino) -6-methyl-7- (p-chloroanilino) fluorane, 3- (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, 3- (N-ethyl-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-anilinofluorane, 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) aminoanilinofluorane, 2-chloro-
6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 2-nitro-6-
p- (p-diethylaminophenyl) aminoanilinofluorane, 2-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) aminoanilinofluorane, 3-diethylamino-6-p- (p-diethylaminophenyl) aminoanilinofluorane, 3-diethylamino-6-p- (p-dibutylamino) Phenyl) 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)- 4-azaphthalide, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3,6-bis (diethylamino) fluorane-γ- (3′-nitro) anilinolactam, 3,6 -Bis (diethylamino) fluorane-γ- (4'-nitro) anilinolactam, 1,1-bis- [2 ', 2', 2 ", 2"
-Tetrakis- (p-dimethylaminophenyl) -ethenyl] -2,2-dinitrileethane, 1,1-bis- [2 ', 2', 2 ", 2" -tetrakis- (p-dimethylamino) Phenyl) -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 used in the present invention, any known one in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used, and is not particularly limited. , Inorganic acidic substances such as attapulgite, colloidal silica, aluminum silicate,
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′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4
-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-phenyl Ethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 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-te
rt-octylphenol), phenolic compounds such as diphenylsulfone cross-linked compounds described in International Publication No. WO 97/16420, compounds described in International Publication No. WO 02/081229 or JP-A No. 2002-301873, and N, N′-di Thiourea compounds such as -m-chlorophenylthiourea, p-chlorobenzoic acid, stearyl gallate, bis [4-
(N-Octyloxycarbonylamino) zinc salicylate dihydrate, 4- [2- (p-
Methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl)
Propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid aromatic carboxylic acid, and zinc, magnesium, aluminum, calcium, titanium, manganese, tin of these aromatic carboxylic acids, Examples thereof include a salt with a polyvalent metal salt such as nickel, an antipyrine complex of zinc thiocyanate, and a composite zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid.

These developers can be used alone or in combination of two or more. International publication WO
The diphenylsulfone cross-linking compound described in 97/16420 is available as trade name D-90 manufactured by Nippon Soda Co., Ltd. Moreover, the compound as described in international publication WO02 / 081229 etc. is available as Nippon Soda Co., Ltd. brand name NKK-395 and D-100.
In addition, a metal chelate color-developing component such as a higher fatty acid metal double salt and a polyvalent hydroxyaromatic compound described in JP-A-10-258577 can also be contained.

As the sensitizer used in the heat-sensitive recording material of the present invention, a conventionally known sensitizer can be used. Such sensitizers include fatty acid amides such as stearamide, 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, dioxalate (p -Chlorobenzyl), 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-methylphenoxymethyl) biphenyl, 4,4′-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2
Examples include -di (3-methylphenoxy) ethylene, bis [2- (4-methoxy-phenoxy) ethyl] ether, methyl p-nitrobenzoate, phenyl p-toluenesulfonate, and the like. It is not limited. These sensitizers may be used alone or in combination of two or more.

The types and amounts of the electron-donating leuco dye, electron-accepting developer, and other various components used in the heat-sensitive recording material of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. Usually, an electron-accepting developer 0.5 to 10 per 1 part of the electron-donating leuco dye
Part, sensitizer 0.5-10 part is used.

By applying the coating liquid having the above composition to any support such as paper, recycled paper, synthetic paper, film, plastic film, foamed plastic film, non-woven fabric, etc., the desired thermal recording material can be obtained. Moreover, you may use the composite sheet which combined these as a support body.

Electron-donating leuco dye, electron-accepting developer, and materials to be added as necessary are finely divided to a particle size of several microns or less by a pulverizer such as a ball mill, an attritor, or a sand glider, or an appropriate emulsifier. Depending on the binder and purpose, various additive materials are added to form a coating solution. The means for applying is not particularly limited, and can be applied in accordance with a well-known conventional technique. For example, various coaters such as an air knife coater, a rod blade coater, a vent blade coater, a bevel blade coater, a roll coater, and a curtain coater are provided. An off-machine coating machine or an on-machine coating machine is appropriately selected and used.
The coating amount of the heat-sensitive recording layer is not particularly limited and is usually in the range of ² to 12 g / m ^{2 by} dry weight.
Further, the coating amount of the protective layer provided on the thermosensitive recording layer is not particularly limited, and is usually in the range of 1 to 5 g / m ² .

The heat-sensitive recording material of the present invention can further be provided with an undercoat layer such as a polymer material containing a filler under the heat-sensitive recording layer for the purpose of increasing the color development sensitivity. It is also possible to correct the curl by providing a backcoat layer on the opposite side of the support from the thermosensitive recording layer. Further, various known techniques in the heat-sensitive recording material field can be added as appropriate, such as applying a smoothing process such as supercalendering after coating each layer.

The thermal recording material of the present invention will be described below with reference to examples and comparative examples. In the description, parts and% represent parts by weight and% by weight, respectively. Various dispersions or coating solutions were prepared as follows.

[Example 1]
A composition comprising the following composition was stirred and dispersed to prepare an undercoat layer coating solution.
Undercoat layer coating solution calcined kaolin (manufactured by Engelhard: Ansilex 90) 100.0 parts styrene / butadiene copolymer latex (solid content 48%) 40.0 parts fully saponified polyvinyl alcohol (manufactured by Kuraray: PVA117) ) Aqueous solution (10% solids)
) 30.0 parts water 160.0 parts

Subsequently, the coating amount of the undercoat layer coating liquid is solidified on one side of the support (base paper having a basis weight of 60 g / m ² ) as a solid content.
After coating so as to be 0 g / m ² , drying was performed to obtain an undercoat layer-coated paper.

Developer dispersion (A liquid), leuco dye dispersion (B liquid), and sensitizer dispersion (C
The liquids were wet ground with a sand grinder separately until the average particle size became 0.5 microns.
Liquid A (developer dispersion)
4-hydroxy-4'-n-propoxydiphenylsulfone 6.0 parts polyvinyl alcohol aqueous solution (solid content 10%) 18.8 parts water 11.2 parts B liquid (leuco dye dispersion)
3-dibutylamino-6-methyl-7-anilinofluorane (ODB-2) 3.0 parts polyvinyl alcohol aqueous solution (solid content 10%) 6.9 parts water 3.9 parts C liquid (sensitizer dispersion) )
Diphenyl sulfone 6.0 parts aqueous polyvinyl alcohol solution (solid content 10%) 18.8 parts water 11.2 parts

Subsequently, the dispersion liquid was mixed at the following ratio to prepare a thermal recording layer coating liquid.
Thermal recording layer coating liquid A (developer dispersion) 36.0 parts B liquid (leuco dye dispersion) 13.8 parts C liquid (sensitizer dispersion) 36.0 parts fully saponified polyvinyl alcohol ( Kuraray Co., Ltd .: PVA117) aqueous solution (solid content 10%
)
10.0 parts water 25.0 parts

Next, the coating amount of the heat-sensitive recording layer coating solution is 5.0 g / m ² in solid content on the undercoat layer of the undercoat layer-coated paper.
After coating with a blade coater, drying was performed to obtain a heat-sensitive recording layer coated paper.

Subsequently, the mixture which consists of the following ratio was mixed and it was set as the protective layer coating liquid.
<Protective layer coating solution>
Engineered kaolin (Imeris: Conza 1500) dispersion (solid content 50%)
12.0 parts carboxy-modified polyvinyl alcohol (Kuraray Co., Ltd .: KL118, solid content 12%)
26.7 parts polyamide epichlorohydrin resin solution (manufactured by Starlight PMC: WS4030, solid content 25%
3.8 parts modified polyamide resin solution (Sumitomo Chemical Co., Ltd .: Sumirez resin SPI102, solid content 45%
2.1 parts zinc stearate (manufactured by Chukyo Yushi Co., Ltd .: Hydrin L536, solid content 40%) 3.8 parts surfactant (manufactured by Nissin Chemical Co., Ltd .: Surfynol 104P, solid content 50%) 0.1 part

Subsequently, water is added to the protective layer coating solution to adjust the solid content of the protective layer coating solution to 15.0%, and the protective layer coating solution is solidified on the thermal recording layer of the thermal recording layer coated paper. After coating with a blade coater so that the coating amount is 3.0 g / m ^{2 in} minutes, the coating is dried and processed with a super calender so that the smoothness of the coated surface becomes 1000 to 2000 seconds. Was made.

<Rewetting liquid>
A composition comprising the following composition was stirred and dispersed to prepare a 0.6% rewetting liquid (40 to 50 ° C.).
Mold release agent (manufactured by San Nopco: PEM-17, solid content 40%) 0.5%
Surfactant (manufactured by San Nopco: SN-WET-L, solid content 100%) 0.1%

Next, 50.0 g / m ^{2 of the} re-wetting liquid was applied on the coated surface of the heat-sensitive recording material, and the re-wetted coating was applied onto a cast drum having a surface temperature of 70 ° C. while the coated layer was in a wet state. The heat-sensitive recording material of Example 1 was produced by bringing the working surface into contact with the cast drum side, and applying pressure treatment and heating (drying) treatment at a linear pressure of 100 kN / m using a rubber roll. (Rewet cast coating method)

[Example 2]
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the rewetting liquid was not mixed with a release agent and a surfactant, and warm water (40 to 50 ° C.) was used.

[Comparative example]
A heat-sensitive recording material was obtained in the same manner as in the example except that the rewetting cast treatment was not performed.

  The following evaluation tests were performed on the heat-sensitive recording materials obtained in the above examples and comparative examples.

<Print density>
The produced thermosensitive recording medium was solid-printed at an applied energy of 0.41 mJ / dot using a printing tester (manufactured by Okura Electric Co., Ltd .: TH-PMD, equipped with a thermal head manufactured by Kyocera Corporation). Measure the recording density of the recording part with a Macbeth densitometer (RD-914, using amber filter)
The print density was evaluated.

<Image quality>
The produced heat-sensitive recording material was solid-printed at an applied energy of 0.27 mJ / dot using a printing tester (manufactured by Okura Electric Co., Ltd .: TH-PMD, equipped with a thermal head manufactured by Kyocera Corporation). The image quality after printing was visually evaluated according to the following criteria.
○: Unevenness is not seen at all.
Δ: Slight unevenness is observed.
X: Unevenness is observed.

<Water resistance>
The produced thermosensitive recording medium was solid-printed at an applied energy of 0.41 mJ / dot using a printing tester (manufactured by Okura Electric Co., Ltd .: TH-PMD, equipped with a thermal head manufactured by Kyocera Corporation). 2
After water immersion treatment at 3 ° C. and 50% Rh for 24 hours, the recording density of the printed part was measured with a Macbeth densitometer, the residual ratio was calculated from the values before and after the treatment, and the water resistance was evaluated.
Residual rate (%) = (recording density after processing / recording density before processing) × 100

<Abrasion resistance>
About the produced thermal recording body, the coating surface was rubbed with the steel wool which added the load of 1000 gf / cm < ² >, and the color development was evaluated visually according to the following reference | standard.
○: Almost no color △: Light color x: Dark color

<Solvent resistance (plasticizer resistance)>
The produced thermosensitive recording medium was solid-printed at an applied energy of 0.41 mJ / dot using a printing tester (manufactured by Okura Electric Co., Ltd .: TH-PMD, equipped with a thermal head manufactured by Kyocera Corporation). A vinyl chloride wrap (manufactured by Mitsui Toatsu Co., Ltd .: High Wrap KMA) is wrapped around a paper tube in a single layer, and the thermal recording medium is placed on the paper so that the printed part is on the outer surface. Was fixed in a three-fold manner. After processing for 24 hours in an environment of 23 ° C. and 50% RH, the recording density of the printed portion was measured with a Macbeth densitometer, and the residual ratio was calculated from the values before and after the processing.
Residual rate (%) = (recording density after processing / recording density before processing) × 100

Claims (5)

In a heat-sensitive recording medium having a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting developer and a protective layer containing a carboxyl group-containing resin and a crosslinking agent on a support, in a wet state A heat-sensitive recording material, wherein the protective layer is heated and pressed against a mirror drum and dried. The heat-sensitive recording material according to claim 1, wherein the carboxyl group-containing resin is carboxy-modified polyvinyl alcohol. The heat-sensitive recording material according to claim 1, wherein the crosslinking agent is an epichlorohydrin resin. The heat-sensitive recording material according to claim 1, wherein the protective layer contains a polyamine / amide resin (excluding epichlorohydrin resin). The protective layer is treated by a rewet cast coating method.
The thermosensitive recording material according to -4.