JPH11227335A - Heat sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording medium having an excellent recording sensitivity and recording feedability by reducing a texture fog in a high temperature environment. SOLUTION: In the heat sensitive recording medium comprising an undercoating layer and a heat sensitive recording layer containing a leuco dye and a colorant sequentially provided on a support; the undercoating layer contains an organic pigment having a through hole, and the recording layer contains as a leuco dye, at least one type of a fluoran derivative represented by a formula (wherein R1 , R2 , are each a 1-6C alkyl group, a 5-6C cycloalkyl group or a tolyl group, R1 , R2 may form a hetero ring together with an adjacent nitrogen atom, R3 , R4 are each a 1-6C alkyl group or a phenyl group, R3 , R4 may form a 5-6C cycloalkyl ring together with adjacent carbon atom) such as 2,2-bis 4-[6'-N-ethyl-N-p-tolylamino-3'-methylspiro(phthalide-3,9'-xanthene)-2'- ilamino]phenyl}propane or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color-forming reaction between a colorless or light-colored leuco dye and a color former, and more particularly to a heat-resistant recording material having excellent heat-resistant storage stability in a recorded portion and an unrecorded portion.
In addition, it is an object of the present invention to provide a thermosensitive recording medium having excellent recording sensitivity and recording running property.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known which utilizes a color reaction between a leuco dye and a coloring agent to obtain a recorded image by bringing both substances into contact with heat. Such a thermosensitive recording medium is relatively inexpensive, and its recording equipment is compact and its repair is relatively easy. Therefore, it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

For example, POS (Point of Sa)
les) Label systems have been introduced in various manufacturing processes, and thermal recording media for POS labels may be used under high temperature conditions. Generally, the temperature of the thermal recording medium is 70 ° C.
When used under high-temperature conditions, the background fog occurs, and there is a problem that bar codes cannot be read.

JP-A-63-315290 discloses a heat-sensitive recording material using a dimer of a fluoran compound which is a leuco dye having excellent heat stability (unground fog resistance) or chemical resistance in an unrecorded portion. And JP-A-4-62091 and JP-A-7-314894, but have the disadvantage of low recording sensitivity.

Japanese Patent Application Laid-Open No. Sho 59-17168 discloses a thermosensitive recording medium in which an undercoat layer containing hollow particles made of a thermoplastic resin is provided between a support and a thermosensitive recording layer in order to increase recording sensitivity.
No. 5, JP-A-59-225987, etc., since these compounds have low oil-absorbing properties as compared with inorganic pigments, these hollow particles adhere to the heat-sensitive head during recording (head residue). ) Is liable to occur.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermosensitive recording medium which is excellent in heat stability of a recorded portion and an unrecorded portion, and is excellent in recording sensitivity and recording running property.

[0007]

[MEANS FOR SOLVING THE PROBLEMS] An undercoat layer,
And a thermosensitive recording medium having a thermosensitive recording layer sequentially containing a leuco dye and a color former, as one means for solving the above-described problem, the present invention includes an organic pigment having a through-hole in an undercoat layer. The heat-sensitive recording layer contains at least one fluoran derivative represented by the following general formula (1) as a leuco dye.

[0008]

Embedded image

(Wherein R ₁ and R ₂ each represent C ₁ -C ₆
Alkyl group, a cycloalkyl group or a tolyl group _{C 5 ~C 6, R 1,} R 2 may form a heterocyclic ring together with the adjacent nitrogen atom. R ₃ and R ₄ each represent a C ₁ -C ₆ alkyl group or a phenyl group;
_3, R ₄ may form a cycloalkyl ring of C ₅ -C ₆ together with the adjacent carbon atoms. )

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a heat-sensitive recording material having a support layer and a heat-sensitive recording layer containing a leuco dye and a colorant on a support, in which an organic pigment having through-holes is contained in the undercoat layer. The heat-sensitive recording layer contains at least one fluoran derivative represented by the above general formula (1) (hereinafter, referred to as a specific leuco dye) as a leuco dye. The volume average particle size of the pigment (hereinafter, referred to as a specific pigment) is particularly 0.1
The oil absorption is preferably 100 ml / 100 g / m ² or more. If the specific pigment has a volume average particle diameter of less than 0.1 μm or an oil absorption of less than 100 ml / 100 g, the effect of improving the recording sensitivity is small, and the recording runnability may be reduced due to the adhesion of the residue to the therma head. If it exceeds 5.0 μm, the recording image quality may be degraded, more preferably about 0.2 to 2.0 μm.

The oil absorption of a specific pigment is 500 ml / 100
When the amount exceeds g, it is necessary to increase the volume ratio occupied by the through-hole portion with respect to the total volume of the specific pigment (the sum of the volume of the solid portion and the volume of the through-hole portion).
There is a risk that certain pigments will be destroyed and the recording sensitivity will decrease,
The oil absorption is more preferably about 100 to 200 ml / 100 g. In the specific pigment particles, the volume ratio occupied by the through holes is about 10 to 80%.

The material of the specific pigment is not particularly limited as long as it is a hydrophobic organic polymer, and examples thereof include polystyrene, ethylene, propylene, polymethyl (meth) acrylate, polyethyl (meth) acrylate, polyvinyl chloride, polyurethane, and polyurethane. Examples include resins such as vinylidene chloride and poly (meth) acrylonitrile, and copolymers having these resin components. Among them, styrene and acrylate copolymers are preferred because they have excellent heat stability in the recorded and unrecorded areas.

The specific pigment particles may have at least one through hole. The specific pigment is dissolved in an alkaline water such as sodium hydroxide, ammonium hydroxide, potassium hydroxide or triethylamine. It is obtained by eluting the core substance with alkaline water while synthesizing the above-mentioned hydrophobic organic polymer which is not dissolved in alkaline water around the resin particles as the core substance.

Examples of the resin dissolved in alkaline water include ethylenically unsaturated carboxylic acid monomers such as maleic anhydride, acrylic acid, methacrylic acid and fumaric acid and hydrophobic monomers such as styrene, methyl (meth) acrylate and ethylene. And copolymers thereof.

The shape of the specific pigment particles is not particularly limited. However, a structure in which the particles are dense when the undercoat layer is formed improves the strength of the coating film, and is therefore preferably spherical. The volume average particle size is not particularly limited, either, but is preferably 0.1 to 5.0 μm, more preferably 0.1 to 1.2 μm in consideration of the thickness of the undercoat layer and the strength of the coating film.
m.

The use amount of the specific pigment is not particularly limited, but is preferably about 10% by weight based on the total solid content of the undercoat layer. If the amount is less than 10% by weight, the recording sensitivity may decrease. If the amount exceeds 95% by weight, the surface strength of the undercoat layer may decrease and the heat-sensitive recording layer may not be uniformly formed. The degree is more preferred.

Other known inorganic or organic pigments can be used in combination as long as the desired effects of the present invention are not impaired. Specific examples of such pigments include, for example, calcium carbonate, magnesium carbonate, kaolin, calcined kaolin,
Inorganic pigments such as talc, aluminum hydroxide amorphous silica and titanium oxide, and organic pigments having a solid structure or a hollow structure composed of polystyrene, polymethyl acrylate, polyvinyl chloride, polyvinylidene chloride, and urea-formaldehyde resin. .

The undercoat layer is prepared, for example, by mixing and stirring an adhesive in an aqueous dispersion containing a specific pigment, and then coating the undercoat layer with a high-quality paper (neutral paper, acidic paper), plastic film, synthetic film, or the like. The coated amount after drying on a support such as paper is 2 to 10 g
/ M ² by coating and drying.

Examples of the adhesive contained in the coating solution for the undercoat layer include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and the like.
Gelatin, casein, gum arabic, partially (completely) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol,
Silicon-modified polyvinyl alcohol, diisobutylene / maleic acid copolymer salt, styrene / maleic acid copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene latex, polyester Polyurethane-based latex and the like can be mentioned. The amount of the adhesive used is about 5 to 35% by weight based on the total solid content of the undercoat layer.

In the undercoat layer coating liquid, if necessary, various auxiliaries such as a dispersant, an antifoaming agent, a coloring dye, a fluorescent dye, and a curing agent can be appropriately added.

The heat-sensitive recording layer provided on the undercoat layer contains the specific leuco dye represented by the above general formula (1). Specific examples of such a specific leuco dye include:
For example, 2,2-bis {4- [6'-N, N-diethylamino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} propane,
2,2-bis {4- [6'-N, N-di-n-pentylamino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} propane;
2,2-bis {4- [6'-N-cyclohexyl-N-
Methylamino-3′-methylspiro (phthalide-3,
9'-xanthen) -2'-ylamino] phenyl} propane, 2,2-bis {4- [6'-N-ethyl-N-
Cyclohexylamino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} propane, 2,2-bis {4- [6'-pyrrolidino-3'-methylspiro (phthalide-3, 9'-xanthen) -2'-ylamino] phenyl} propane, 2,2
-Bis {4- [6'-N-ethyl-N-p-tolylamino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} propane;
2-bis {4- [6'-N, N-di-n-butylamino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} butane, 2,2-
Bis {4- [6′-N-ethyl-N-isoamylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2′-ylamino] phenyl} butane, 2,2-
Bis {4- [6'-N-methyl-NN-propylamino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} butane, 2,2
-Bis {4- [6'-N-cyclohexyl-N-methylamino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} butane;
2,2-bis {4- [6'-pyrrolidino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} butane, 2,2-bis {4-
[6′-N-ethyl-Np-tolylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2 ′
-Ylamino] phenyl} butane, 1,1-bis {4-
[6′-N, N-di-n-butylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2′-ylamino] phenyl} cyclohexane, 1,1-bis {4- [6 ′ —N-ethyl-N-cyclohexylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2′-ylamino] phenyl} cyclohexane,
1,1-bis {4- [6'-N-ethyl-N-p-tolylamino-3'-methylspiro (phthalide-3,9'-
Xanthene) -2'-ylamino] phenyl} cyclopentane, α, α-bis {4- [6′-N, N-di-n-
Butylamino-3′-methylspiro (phthalide-3,
9′-xanthen) -2′-ylamino] phenyl} ethylbenzene, α, α-bis {4- [6′-N-cyclohexyl-N-methylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2'-ylamino]
Phenyl @ ethylbenzene, 2,2-bis @ 4- [6 '
—N-ethyl-Np-tolylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2′-ylamino] phenyl} -4-methylpentane.

Among them, 2,2-bis @ 4- [6'-N
-Ethyl-N-p-tolylamino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} propane and 2,2-bis {4-
[6′-N-ethyl-Np-tolylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2 ′
[-Ylamino] phenyldibutane is particularly excellent in heat resistance. The amount of the specific leuco dye used is about 5 to 35% by weight based on the total solid content of the heat-sensitive recording layer.

As long as the desired effects of the present invention are not impaired, various known leuco dyes may be used in addition to the specific leuco dye.

As the colorant contained in the heat-sensitive recording layer together with the specific leuco dye, various known colorants can be used. Specific examples of such a color former include, for example, 2,2′-
Dihydroxydiphenol, 4,4′-isopropylidenediphenol, 4,4′-isopropylidenebis (2-
tert-butylphenol), 4,4'-sec-butylidenediphenol, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-cyclohexylidenediphenol, 2,4'-dihydroxydiphenyl Sulfone, 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 3,4 '-Dihydroxy-4'-methyldiphenylsulfone,3,3'-diallyl-4,4'
-Dihydroxydiphenyl sulfone, hydroquinone monobenzyl ether, 4-hydroxybenzophenone,
1-[(4-hydroxyphenyl) isopropyl] -4
-[2,2-di- (4-hydroxyphenyl) ethyl]
Benzene, benzyl 4-hydroxybenzoate, p-methoxybenzyl 4-hydroxybenzoate, novolak-type phenolic resin, phenolic polymer, zinc 3-cyclohexyl-4-hydroxybenzoate, 4- [2- (p-methoxyphenoxy) ) Ethyloxy] zinc salicylate, 4
-[3- (p-Tolylsulfonyl) propyloxy] zinc salicylate, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] zinc salicylate, 4,4'-bis (p-tolylsulfonylaminocarbonylamino) Diphenylmethane, Np-tolylsulfonyl-N'-phenylurea and the like. Among them, 1-[(4-hydroxyphenyl) isopropyl] -4- [2,2-di- (4-hydroxyphenyl) ethyl] benzene is preferable because of excellent ground fog resistance.

The use ratio of the specific leuco dye to the color former is not particularly limited, but is generally preferably about 1 to 5 parts by weight per 1 part by weight of the specific leuco dye.

Further, the heat-sensitive recording layer may contain a storability improving agent for improving the storability of the recording portion and a sensitizer for improving the recording sensitivity. Specific examples of the preservability improver include, for example, 1,4-diglycidyloxybenzene, 4-benzyloxy-4 ′-(2-methyl-2,3-epoxypropyloxy) diphenylsulfone, and 4,4′- Epoxy compounds such as diglycidyloxydiphenylsulfone, diglycidyl terephthalate, bisphenol A type epoxy resin, 2,2′-methylenebis (4-methyl-6-tert-butylphenol),
2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,2′-ethylidenebis (4,6-di-
tert-butylphenol), 4,4′-thiobis (3-
Methyl-6-tert-butylphenol), 4,4′-thiobis (2-methyl-6-tert-butylphenol),
4,4′-butylidenebis (6-tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane,
1,3-tris (2-methyl-4-hydroxy-5-te
rt-butylphenyl) butane, 4,4′-thiobis (3
-Methylphenol), 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4- Hindered phenol compounds such as hydroxy-3,5-dimethylphenyl) propane,
1- [α-methyl-α- (4′-hydroxyphenyl)
Ethyl] -4- [α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, N, N′-di-2-naphthyl-p-phenylenediamine, 2,2′-methylenebis (4,6 -Di-tert-butylphenyl) sodium phosphate and the like.

Specific examples of the sensitizer include, for example, stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, ethylene bistearic acid amide, methylenebisstearic acid amide, N-methylol Stearic acid amide,
Dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chloro oxalate Benzyl, 2-naphthyl benzyl ether, m-terphenyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy)
Ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane,
2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluizide, p-acetophene Tidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like.

The heat-sensitive recording layer generally uses water as a dispersion medium,
For example, a specific leuco dye, a coloring agent, and if necessary, a preservative improver and a sensitizer together or separately with a dispersing agent together with or separately from a stirrer / pulverizer such as a ball mill, an attritor or a sand mill to have an average particle diameter of 0.1%. After finely dispersing so as to have a thickness of about 2 to 2.0 μm, an adhesive is added thereto, and the solution for the heat-sensitive recording layer prepared by mixing and stirring is dried on the undercoat layer to a coating amount of 3 to 12 g / m ^2. It is formed by coating and drying to a degree.

Examples of the adhesive added to the coating solution for the heat-sensitive recording layer include those added to the coating solution for the undercoat layer. The amount of the adhesive used is about 5 to 40% by weight based on the total solid content of the heat-sensitive recording layer.

Further, pigments such as kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth, amorphous silica, aluminum hydroxide, and urea / formalin resin filler are contained in the coating solution for the heat-sensitive recording layer. , Sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, surfactants such as sodium lauryl alcohol sulfate, alginates, fatty acid metal salts, ultraviolet absorbers, defoamers, fluorescent dyes, coloring dyes, etc. May be added.

The method for forming the undercoat layer and the heat-sensitive recording layer includes, for example, an air knife coating method, a variver blade coating method, a pure blade coating method, a short dwell coating method, and a curtain coating method.

Further, on the heat-sensitive recording layer, an adhesive, a lubricant,
By providing a protective layer composed of a pigment or the like, a thermosensitive recording medium having excellent stick resistance and scratch resistance can be obtained.

Specific examples of the adhesive used for the protective layer include gelatin, casein, partially (completely) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and acrylic latex. ,
Examples include polyester polyurethane-based latex and polyether polyurethane-based latex. These adhesives are used in an amount of 10 to 95% by weight, preferably about 30 to 90% by weight, based on the total solid amount. The coating amount of the protective layer, 0.5 to 10 g / m ² by dry weight, preferably from 1 to 7 g / m ^2.

In particular, microcapsules containing a liquid ultraviolet absorber such as 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole in a protective layer or bis [2- Hydroxy-3- (2′H
-Benzotriazol-2'-yl) -5-t-butylphenyl] methane, etc., significantly improved yellowing of the background and fading of recorded images against light by adding a finely divided ultraviolet absorber. Is done.

In addition, a layer mainly composed of a water-soluble, water-dispersible, electron beam-curable or ultraviolet-curable resin may be provided on the protective layer for the purpose of imparting a high gloss or the like. It is also possible to provide a protective layer on the back surface, and various known techniques in the field of thermal recording medium production can be added.

[0036]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto. Unless otherwise specified, parts and% in examples are parts by weight and% by weight, respectively.

Example 1 Preparation of Coating Solution for Undercoat Layer The volume average particle diameter was 0.6 μm and the oil absorption was 150 ml /
50 g of a 20% dispersion of an organic pigment having 100 g of through-holes
0 parts, styrene / butadiene-based latex having a solid concentration of 48% (trade name: L-1571L, manufactured by Asahi Kasei Corporation)
0 parts, polyvinyl alcohol (trade name: PVA-20)
5, manufactured by Kuraray Co., Ltd.) and mixed with 50 parts of a 20% aqueous solution to obtain an undercoat layer coating solution.

Preparation of solution A 2,2-bis {4- [6'-N-ethyl-Np-tolylamino-3'-methylspiro (phthalide-3,9'-
A composition comprising 20 parts of (xanthene) -2'-ylamino] phenyl} propane, 6 parts of a 5% aqueous solution of methylcellulose, and 54 parts of water was sand-milled to have an average particle size of 0.8.
It grind | pulverized until it became micrometer, and liquid A was obtained.

Preparation of Solution B 1-[(4-hydroxyphenyl) isopropyl] -4
-[2,2-di- (4-hydroxyphenyl) ethyl]
40 parts of benzene, 5% aqueous solution of methylcellulose 10
Part B and 110 parts of water were pulverized with a sand mill until an average particle diameter of 1.2 μm was obtained to obtain a liquid B.

Solution C Preparation A composition comprising 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was pulverized by a sand mill until the average particle diameter became 2 μm. Liquid C was obtained.

Preparation of coating solution for heat-sensitive recording layer 50 parts of solution A, 130 parts of solution B, light calcium carbonate 10
Parts, amorphous silica (oil absorption 180 ml / 100 g, average particle diameter of secondary particles 2.4 μm) 20 parts, 30% dispersion of zinc stearate 15%, and polyvinyl alcohol (trade name: PVA-110, Kuraray Co., Ltd.) Was mixed and stirred to obtain a coating solution for a heat-sensitive recording layer.

Preparation of Thermosensitive Recording Material The coating amount of the undercoat layer coating solution and the thermosensitive recording layer coating solution on one side of a high-quality paper of 50 g / m ² after drying was 7 g / m ^2.
m ^2, 6g / m ² and so as to sequentially applied and dried after the formation of the undercoat layer and the heat-sensitive recording layer to obtain a heat-sensitive recording material by super calendering.

Example 2 In the preparation of a coating liquid for an undercoat layer in Example 1, 500 parts of a 20% dispersion of an organic pigment having a through-hole having a volume average particle diameter of 0.6 μm and an oil absorption of 150 ml / 100 g was added. Instead, the volume average particle diameter is 2.6 μm and the oil absorption is 180
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 500 parts of a 20% dispersion of an organic pigment having a through hole of ml / 100 g was used.

Example 3 In the preparation of the coating liquid for the undercoat layer in Example 1, 500 parts of a 20% dispersion of an organic pigment having a volume average particle diameter of 0.6 μm and an oil absorption of 150 ml / 100 g having through holes was added. Instead, the volume average particle diameter is 0.6 μm and the oil absorption is 150 μm.
200 parts of a 20% dispersion of an organic pigment having through-holes of 100 ml / 100 g and calcined kaolin (trade name: Ansilex, EC) having an oil absorption of 130 ml / 100 g
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 300 parts of the% dispersion was used.

Example 4 In the preparation of solution A of Example 1, 2,2-bis @ 4-
[6′-N-ethyl-Np-tolylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2 ′
-Ylamino] phenyl} propane instead of 2,2-
Example 1 except that bis {4- [6'-N-ethyl-N-p-tolylamino-3'-methylspiro (phthalide-3,9'-xanthen) -2'-ylamino] phenyl} butane was used. In the same manner as in the above, a thermosensitive recording medium was obtained.

Comparative Example 1 Preparation of Coating Solution for Undercoat Layer 20% dispersion 100 of calcined kaolin (trade name: Ansilex, EC) having an oil absorption of 130 ml / 100 g
Parts, styrene / butadiene latex having a solid concentration of 48% (trade name: L-1571L, manufactured by Asahi Chemical Industry Co., Ltd.) 10
Part, polyvinyl alcohol (trade name: PVA-205,
A composition consisting of 50 parts of a 20% aqueous solution of Kuraray Co., Ltd.) was mixed and stirred to obtain a coating liquid for an undercoat layer.

Preparation of a thermosensitive recording medium A thermosensitive recording medium was prepared in the same manner as in Example 1 except that the undercoat layer coating liquid used in the preparation of the thermosensitive recording medium of Example 1 was used. Obtained.

Comparative Example 2 Preparation of Coating Liquid for Undercoat Layer 330 parts of a 30% dispersion of organic hollow particles having a volume average particle diameter of 0.8 μm and a hollowness of 80%, and a styrene / butadiene latex having a solid concentration of 48% ( Product name: L-1571
L, 10 parts of Asahi Kasei Kogyo Co., Ltd.) and 50 parts of a 20% aqueous solution of polyvinyl alcohol (trade name: PVA-205, manufactured by Kuraray Co., Ltd.) were mixed and stirred to obtain a coating solution for an undercoat layer.

Preparation of Thermosensitive Recording Material A thermosensitive recording material was prepared in the same manner as in Example 1 except that the undercoat layer coating solution used in the preparation of the thermosensitive recording material of Example 1 was used. Obtained.

Comparative Example 3 Preparation of Thermosensitive Recording Material In the preparation of solution A of Example 1, 2,2-bis @ 4-
[6′-N-ethyl-Np-tolylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2 ′
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 3-di (n-butyl) amino-6-methyl-7-anilinofluorane was used instead of [-ylamino] phenyl} propane.

Comparative Example 4 In the preparation of Solution A of Example 1, 2,2-bis @ 4-
[6′-N-ethyl-Np-tolylamino-3′-methylspiro (phthalide-3,9′-xanthen) -2 ′
-Ylamino] phenyl} propane instead of 3- (N
-Ethyl-N-p-tolylamino) -6-methyl-7-
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that anilinofluorane was used.

The heat-sensitive recording medium thus obtained was evaluated by the following methods, and the results are shown in Table 1. [Recording density] A thermal label printer [M4800RV type, manufactured by SATO CORPORATION] was used for recording, and the recorded density and unrecorded area of the obtained recording portion were measured by a Macbeth densitometer [Macbeth, RD-914, visual filter] ].

[Heat resistance stability] The unrecorded portion and the recorded portion after contacting the above-described heat-sensitive recording medium with a hot plate at 120 ° C. for 10 seconds were subjected to a Macbeth densitometer (visual filter).
Was measured.

[Recording traveling property]
Twenty bar codes are printed continuously, and the amount of lees attached to the head is visually evaluated. The smaller the amount of lees adhering to the head, the better the recording traveling property.

[0055]

[Table 1]

Example 5 The following coating liquid for a protective layer was applied onto the heat-sensitive recording layer of the heat-sensitive recording medium of Example 1 and dried so that the coating amount after drying was 4 g / m ^2, and the heat-sensitive recording medium was dried. Obtained. Preparation of Coating Solution for Protective Layer 250 parts of a 10% aqueous solution of acetoacetyl-modified polyvinyl alcohol, kaolin (trade name: UW-90, ECM)
(Commercially available), a composition consisting of 70 parts of a 30% aqueous dispersion of zinc stearate and 150 parts of water were mixed and stirred to obtain a coating liquid for a protective layer.

Example 6 A thermosensitive recording medium was prepared in the same manner as in Example 5, except that the thermosensitive recording medium of Example 4 was used in place of the thermosensitive recording medium of Example 1. I got

Comparative Example 5 A thermosensitive recording medium was prepared in the same manner as in Example 5 except that the thermosensitive recording medium of Example 1 was used instead of the thermosensitive recording medium of Example 1. I got

Comparative Example 6 A thermosensitive recording medium was prepared in the same manner as in Example 5, except that the thermosensitive recording medium of Example 1 was used instead of the thermosensitive recording medium of Example 1. I got

Comparative Example 7 Example 1 was used to produce the thermosensitive recording medium used in Example 5.
A thermosensitive recording medium was obtained in the same manner as in Example 5, except that the thermosensitive recording medium of Comparative Example 4 was used instead of the thermosensitive recording medium of Comparative Example 4.

With respect to the thermosensitive recording medium having the protective layer thus obtained, in addition to the above-mentioned recording density and heat stability,
A test was performed according to the following evaluation, and the obtained results are shown in Table 2.

[Plasticizer resistance] A wrap film (trade name: High Wrap KMA-W, manufactured by Mitsui Chemicals, Inc.) was wound three times on a polycarbonate pipe (40 mm diameter).
Each printed thermosensitive recording medium is placed thereon, and a wrap film is further wound three times on the thermosensitive recording medium.
After standing for 4 hours, the optical density of the recording portion was measured with a Macbeth densitometer to evaluate the plasticizer resistance.

[Oil resistance] An edible oil was applied to the surface of each heat-sensitive recording medium on which color printing was performed, left at 24 ° C. for 24 hours, and then wiped off. The optical density of the recording portion was measured with a Macbeth densitometer to evaluate the oil resistance. .

[0064]

[Table 2]

[0065]

As is evident from the results of Tables 1 and 2, the heat-sensitive recording material of the present invention has excellent heat stability of the unrecorded portion under a high temperature environment, excellent recording sensitivity and excellent recording running property,
In addition, it has an excellent effect on the storage stability of the recorded image.

Claims (4)

[Claims] 1. A heat-sensitive recording material comprising a support and an undercoat layer and a heat-sensitive recording layer containing a leuco dye and a colorant in order, wherein the undercoat layer contains an organic pigment having a through-hole. The following general formula (1) is used as a leuco dye in the layer.
A thermosensitive recording medium comprising at least one fluoran derivative represented by the formula: Embedded image (Wherein, R ₁ and R ₂ each represent a C ₁ -C ₆ alkyl group, a C ₅ -C ₆ cycloalkyl group or a tolyl group, and R ₁ and R ₂ form a heterocycle together with an adjacent nitrogen atom. Further, R ₃ and R ₄ may each be C ₁ -C
_{6 represents} an alkyl group or a phenyl group, and R ₃ and R ₄ may form a C ₅ -C ₆ cycloalkyl ring together with adjacent carbon atoms. ) 2. An organic pigment having through-holes having an oil absorption of 100.
The thermosensitive recording medium according to claim 1, wherein the thermosensitive recording medium is at least ml / 100 g (based on JIS K 5101). 3. The thermosensitive recording medium according to claim 1, wherein the organic pigment having a through-hole has a volume average particle diameter of 0.1 to 5.0 μm. 4. The method according to claim 1, wherein the color former is 1-[(4-hydroxyphenyl) isopropyl] -4- [2,2-di- (4-hydroxyphenyl) ethyl] benzene. 2. The heat-sensitive recording material according to item 1.