JP2006346893A - Thermosensitive recording body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosensitive recording body, in which especially print fading due to contact with oils, chemicals or the like is little, which is excellent in the storage stability and, at the same time, heat resistance and recording sensitivity of a recording part. <P>SOLUTION: In the thermosensitive recording body, in which a thermosensitive recording layer including at least a leuco dye and a colorant is provided on a support, the thermosensitive recording layer includes 4-hydroxy-4'-isopropoxy diphenyl sulfone and a specified fluorene compound as the colorant under the condition that the fluorene compound occupies 10-100 mass% of the whole leuco dye solids. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  A heat-sensitive recording material that utilizes a color reaction between a leuco dye and a color former to obtain a recorded image by heat is well known. Such a thermal recording medium is relatively inexpensive, and the recording device is compact and easy to maintain. Therefore, it is not only used as a recording medium for output of facsimiles and various computers, printers of scientific measurement devices, etc. It is widely used as a recording medium for various printers such as labels, ATMs, CAD, handy terminals, and various ticket sheets.

  However, since the heat-sensitive recording material is a reversible reaction that develops color when the leuco dye and the colorant are melted and brought into contact with heat, contact with a chemical or the like causes the color to fade or disappear. Information such as bar code information cannot be confirmed.

  In order to solve these problems of printing fading, many methods using a plurality of colorants or using an anti-fading agent have been proposed. As one of the techniques, a method of adding a fluorene compound has been proposed. (See Patent Documents 1 to 3)

Since the fluorene compound has a high melting point and low coloration ability, it is difficult to obtain a sufficient color density, and many cases are used in combination with 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A). However, the thermosensitive recording material using bisphenol A has a problem that the storage stability of the recorded contents is not sufficient and the background fogging with respect to heat.
Furthermore, in thermosensitive recording media using bisphenol A, there are cases where a large amount of fluorene compound is used in order to improve the storage stability of the recorded contents, but this time a sufficient color density is obtained due to the low coloring ability. There is a high possibility that such a problem will occur (see Patent Document 1).
In addition, a method of melt-mixing a fluorene compound with a colorant and / or a sensitizer has also been proposed, but this method also has a problem that a sufficient color density cannot be obtained and the background fogging with respect to heat deteriorates. (See Patent Document 2).

JP-A-3-140289 JP-A-6-40155 JP-A-5-193267

  An object of the present invention is to provide a heat-sensitive recording material that has less printing discoloration due to contact with oils, chemicals, and the like, is excellent in storage stability of a recording portion, and is excellent in heat resistance and recording sensitivity.

  As a result of intensive studies, the present inventors have used a specific compound and a specific fluorene compound as a colorant in the heat-sensitive recording layer, and control the blending amount of the fluorene compound, so that oils, chemicals, etc. The present inventors have found that a heat-sensitive recording material can be obtained which has less printing discoloration due to contact with the toner, excellent storage stability of the recording portion, heat resistance and recording sensitivity, and has completed the present invention.

  That is, the present invention provides the following thermal recording material.

  Item 1: In a heat-sensitive recording material provided with a heat-sensitive recording layer containing at least a leuco dye and a colorant on a support, 4-hydroxy-4'-isopropoxydiphenylsulfone as a colorant in the heat-sensitive recording layer And a fluorene compound represented by the following general formula (1), wherein the fluorene compound is 10 to 100% by mass relative to the total solid content of the leuco dye.

（式中、Ｒ１は、水素原子、炭素数１〜５のアルキル基を表し、Ｒ２は、ヒドロキシ基、アミノ基または−ＯＣＨ_２ＣＨ_２ＯＨを表し、これらは同一であっても、異なってもよい）

(In the formula, R1 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R2 represents a hydroxy group, an amino group or —OCH ₂ CH ₂ OH, which may be the same or different. Good)

  Item 2: The thermal recording material according to Item 1, wherein the amount of the fluorene compound represented by the general formula (1) is 5 to 80% by mass with respect to the total solid content of the 4-hydroxy-4'-isopropoxydiphenylsulfone.

  Item 3: The fluorene compound is 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxyphenyl) fluorene, or 9,9-bis (4-phenoxyethanol) fluorene. Item 3. The thermal recording material according to Item 1 or 2, which is at least one selected.

  According to the present invention, there is provided a heat-sensitive recording material that has less printing discoloration due to contact with oils, chemicals, and the like, is excellent in storage stability of a recording portion, and is excellent in heat resistance and recording sensitivity.

Hereinafter, the present invention will be described in detail.
The present invention relates to a heat-sensitive recording material provided with a heat-sensitive recording layer containing at least a leuco dye and a colorant on a support, and 4-hydroxy-4′-isopropoxydiphenyl sulfone as a colorant in the heat-sensitive recording layer. And a specific fluorene compound, and the fluorene compound is 10 to 100% by mass with respect to the total solid content of the leuco dye.

  In the heat-sensitive recording layer of the present invention, by using 4-hydroxy-4′-isopropoxydiphenylsulfone and a specific fluorene compound as a colorant, a practically sufficient color density can be obtained, and the storage stability of recorded contents is excellent. In addition, a heat-sensitive recording material in which background fogging against heat is suppressed can be obtained. Furthermore, by controlling the blending amount of the fluorene compound to 10 to 100% by mass with respect to the total solid content of the leuco dye, a thermal recording material capable of obtaining a sufficient color density without being influenced by the fluorene compound having a low coloration ability. Is obtained.

  Examples of the fluorene compound include 9,9-bis (4-hydroxyphenyl) fluorene, and 9,9-bis (3-alkyl-4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxy). Phenyl) fluorene, 9,9-bis (3-ethyl-4-hydroxyphenyl) fluorene, 9,9-bis (3-propyl-4-hydroxyphenyl) fluorene, 9,9-bis (3-butyl-4-) 1-9 carbon atoms of hydroxyphenyl) fluorene and 9,9-bis (3-pentyl-4-hydroxyphenyl) fluorene are exemplified, and 9,9-bis (2-alkyl-4-hydroxyphenyl) fluorene is exemplified. 9,9-bis (2-methyl-4-hydroxyphenyl) fluorene, 9,9-bis (2-ethyl-4-hydro) Ciphenyl) fluorene, 9,9-bis (2-propyl-4-hydroxyphenyl) fluorene, 9,9-bis (2-butyl-4-hydroxyphenyl) fluorene, 9,9-bis (2-pentyl-4- Hydroxyphenyl) fluorene alkyl having 1 to 5 carbon atoms. Among them, preferred fluorene compounds include 9,9-bis (4-hydroxyphenyl) fluorene and 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, and 9,9-bis (3-methyl- 4-hydroxyphenyl) fluorene is more preferred because of its low cost.

  Furthermore, as the fluorene compound, 9,9-bis (4-anilino) fluorene and 9,9-bis (3-alkyl-4-anilino) fluorene as 9,9-bis (3-methyl-4-anilino) fluorene 9,9-bis (3-ethyl-4-anilino) fluorene, 9,9-bis (3-propyl-4-anilino) fluorene, 9,9-bis (3-butyl-4-anilino) fluorene, 9 9,9-bis (3-pentyl-4-anilino) fluorene, and 9,9-bis (2-alkyl-4-anilino) fluorene as 9,9-bis (2-methyl-4-anilino) fluorene, 9,9-bis (2-ethyl-4-anilino) fluorene, 9,9-bis (2-propyl-4-anilino) fluorene, 9,9-bis (2-butyl-4-anilino) fluorene Ren, 9,9-bis (2-pentyl-4-anilino) fluorene and the like.

  Furthermore, as the fluorene compound, 9,9-bis (4-phenoxyethanol) fluorene and 9,9-bis (3-alkyl-4-phenoxyethanol) fluorene as 9,9-bis (3-methyl-4-phenoxyethanol) Fluorene, 9,9-bis (3-ethyl-4-phenoxyethanol) fluorene, 9,9-bis (3-propyl-4-phenoxyethanol) fluorene, 9,9-bis (3-butyl-4-phenoxyethanol) fluorene, Examples include 9,9-bis (3-pentyl-4-phenoxyethanol) fluorene having 1 to 5 carbon atoms, and 9,9-bis (2-alkyl-4-phenoxyethanol) fluorene includes 9,9-bis ( 2-methyl-4-phenoxyethanol) fluorene, 9,9-bis ( -Ethyl-4-phenoxyethanol) fluorene, 9,9-bis (2-propyl-4-phenoxyethanol) fluorene, 9,9-bis (2-butyl-4-phenoxyethanol) fluorene, 9,9-bis (2-pentyl) -4-phenoxyethanol) fluorene alkyl having 1 to 5 carbon atoms. Among them, 9,9-bis (4-phenoxyethanol) fluorene is a preferable fluorene compound.

  The compounding quantity of the fluorene compound used by this invention is 10-100 mass% with respect to the total leuco dye solid content, Preferably it is 20-80 mass%, More preferably, it is 30-50 mass%. If it is less than 10% by mass, the preservability of the recording part is inferior, and if it exceeds 100% by mass, the coloring ability may be impaired and the recording sensitivity may be lowered.

  Moreover, it is preferable that the compounding quantity of the said fluorene compound is 5-80 mass% with respect to 4-hydroxy-4'-isopropoxy diphenyl sulfone total solid, 7-60 mass% is more preferable, 10-40 mass % Is particularly preferred. If it is less than 5% by mass, the preservability of the recording part is inferior, and if it exceeds 80% by mass, the coloring ability may be impaired and the recording sensitivity may be lowered.

  The fluorene compound used in the present invention may be dispersed using mechanical means such as ultrasonic waves, high-speed rotary mills, roller mills, container drive medium mills, medium agitation mills, jet mills, sand grinders, and nanomizers. preferable. In addition to single dispersion of a fluorene compound alone, it can be dispersed together with 4-hydroxy-4'-isopropoxydiphenyl sulfone, leuco dye, sensitizer and the like.

  The particle size of the fluorene compound single dispersion or the composite dispersion containing the fluorene compound is 0.8 to 2.0 μm, more preferably 1.0 to 1.7 μm. If the thickness is less than 0.8 μm, the whiteness may be lowered, or the composite dispersion with 4-hydroxy-4′-isopropoxydiphenylsulfone may cause quality deterioration due to hydration. If it exceeds 2.0 μm, the color developing ability may be hindered and the recording sensitivity may be lowered, or the preservability effect of recorded contents may be saturated.

  Other known pigments can be added to the heat-sensitive recording layer as long as the desired effects of the present invention are not lost. For example, kaolin, light calcium carbonate, heavy calcium carbonate, calcined kaolin, titanium oxide, carbonic acid Examples thereof include magnesium, aluminum hydroxide, colloidal silica, urea-formalin resin filler, and plastic pigment. Among these, basic pigments are preferable, and magnesium carbonate, light calcium carbonate, and heavy calcium carbonate are particularly preferably used because they have an effect of suppressing background fog.

In addition, various known adhesives, leuco dyes, sensitizers, various auxiliaries and the like can be used for the heat-sensitive recording layer of the present invention.
Examples of the adhesive used in the heat-sensitive recording layer include various molecular weight polyvinyl alcohols, modified polyvinyl alcohols, starches and derivatives thereof, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, Polyvinylpyrrolidone, acrylic acid amide-acrylic acid ester copolymer, acrylic acid amide-acrylic acid ester-methacrylic acid terpolymer, styrene-maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and Water-soluble polymer materials such as casein, polyvinyl acetate, polyurethane, styrene-butadiene copolymer, polyacrylic acid, polyacrylate ester, vinyl chloride-vinyl acetate copolymer, poly Chill methacrylate, ethylene - vinyl acetate copolymer, and styrene - butadiene - such as latex of a hydrophobic polymer such as an acrylic copolymer can be mentioned, can be used in combination with one kind or two or more kinds.

Among them, use of polyvinyl alcohol or modified polyvinyl alcohol having various molecular weights is preferable because the coating layer strength is excellent and the recording sensitivity is improved.
The content of the adhesive in the heat-sensitive recording layer is preferably 3 to 20% by weight, more preferably 5 to 18% by weight, based on the total solid content of the heat-sensitive recording layer. If it is less than 3% by mass, the strength of the coating layer may be insufficient. On the other hand, if it exceeds 20% by mass, the recording sensitivity may be lowered.

  The leuco dye can be used alone or in combination of two or more. For example, leuco dyes such as triphenylmethane, fluorane, phenothiazine, auramine, spiropyran, and indolylphthalide are preferably used. Specific examples of leuco dyes include, for example, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, crystal violet lactone, 3- (N -Ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (o, p -Dimethylanilino) fluorane, 3- (N-ethyl-Np-toluidino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-di (N-butyl) amino-6-methyl-7-anilinofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluora 3-diethylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6 -Methylfluorane, 3-cyclohexylamino-6-chlorofluorane, and 3- (N-ethyl-N-hexylamino) -6-methyl-7- (p-chloroanilino) fluorane. -(N-ethyl-Np-toluidino) -6-methyl-7-anilinofluorane and 3-di (N-butyl) amino-6-methyl-7-anilinofluorane are preferred.

  As a sensitizer, it can use individually or in combination of 2 or more types. Specific examples of the sensitizer include, for example, stearamide, stearic acid methylenebisamide, stearic acid ethylenebisamide, 4-benzylbiphenyl, p-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, 1,2- Diphenoxyethane, 1- (4-methoxyphenoxy) -2- (3-methylphenoxy) ethane, 2-naphthylbenzyl ether, 1- (2-naphthyloxy) -2-phenoxyethane, 1,3-di (naphthyl) Oxy) propane, dibenzyl oxalate, di-p-methyl-benzyl oxalate, di-p-oxalate Rubenjiru, dibutyl terephthalate, dibenzyl terephthalate, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole.

  In addition, as the various auxiliary agents, known agents such as a lubricant, an antifoaming agent, a wetting agent, an antiseptic, a fluorescent brightening agent, a dispersing agent, a thickening agent, a coloring agent, and an antistatic agent can be used.

  In the thermosensitive recording layer of the present invention, the content of the leuco dye in the thermosensitive coloring layer is generally 5 to 20% by mass, and the content of the colorant 4-hydroxy-4′-isopropoxydiphenyl sulfone is generally 5 to 5. 40% by mass. When a sensitizer is included, the content of the sensitizer is preferably 10 to 40% by mass. It is preferable that various adjuvants are contained at a content of 5 to 20% by mass.

  The support used in the heat-sensitive recording material of the present invention includes paper, coated paper coated with pigment, latex, etc. on the surface, synthetic paper having a multilayer structure made of polyolefin resin, plastic film, or a composite thereof. You can choose from body sheets. In the present invention, an undercoat layer can be provided between the support and the heat-sensitive recording layer as necessary. In this case, as a component constituting the undercoat layer, known pigments, adhesives, various auxiliaries and the like can be used. Further, a protective layer can be provided on the thermosensitive recording layer. Also in this case, known pigments, adhesives, various auxiliaries and the like can be used as components constituting the protective layer. A back layer may be provided on the back surface of the support.

  The heat-sensitive recording material of the present invention can be produced by a generally known method. For example, the coating solution for the heat-sensitive recording layer is prepared by pulverizing and dispersing leuco dye, 4-hydroxy-4'-isopropoxydiphenylsulfone and fluorene derivative monomer together with an aqueous adhesive solution with a dispersing machine such as a ball mill, and then bonding as necessary. It is prepared by mixing and stirring an agent, a sensitizer and various auxiliary agents. Next, the thermal recording layer coating solution may be coated and dried on the support by a known method.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Further, “parts” and “%” in the examples indicate “parts by mass” and “% by mass”, respectively, unless otherwise specified.

Example 1
(Preparation of coating solution for undercoat layer)
A dispersion obtained by dispersing 85 parts of calcined clay (trade name: Ansilex, Engelhard) in 320 parts of water, 40 parts of a styrene-butadiene copolymer emulsion (solid content 50%), and oxidized starch An undercoat layer coating solution was obtained by mixing and stirring 50 parts of a 10% aqueous solution.

(Preparation of leuco dye dispersion and preparation of solution A)
A composition comprising 10 parts of 3-di (N-butyl) amino-6-methyl-7-anilinofluorane, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water was averaged to 1.5 μm by a sand mill. The resulting mixture was pulverized until a leuco dye dispersion liquid A was obtained.

(Preparation of colorant dispersion and preparation of solution B)
A composition comprising 10 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water is pulverized with a sand mill until the average particle size becomes 1.5 μm, and a colorant dispersion -B liquid was obtained.

(Preparation of colorant dispersion / C liquid preparation)
A composition comprising 10 parts of 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water was pulverized with a sand mill until the average particle size was 1.5 μm. Thus, a colorant dispersion liquid / C liquid was obtained.

(Preparation of sensitizer dispersion / D 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 is pulverized with a sand mill until the average particle size becomes 1.5 μm, and the sensitizer. A dispersion / liquid D was obtained.

(Preparation of thermal recording layer coating solution)
Composition comprising 25 parts of A liquid, 50 parts of B liquid, 10 parts of C liquid, 50 parts of D liquid, 50 parts of 50% light calcium carbonate, and 50 parts of 20% polyvinyl alcohol (trade name: PVA-205, manufactured by Kuraray Co., Ltd.) The product was mixed and stirred to obtain a thermal recording layer coating solution.

(Preparation of coating solution for protective layer)
To a dispersion obtained by dispersing 50 parts of kaolin (trade name: UW-90, manufactured by Engelhard) in 100 parts of water, acetoacetyl-modified polyvinyl alcohol (trade name: Goosefimmer Z-200, Nippon Synthetic Chemical) 600 parts of a 10% aqueous solution of Kogyo Kogyo Co., Ltd. and 25 parts of zinc stearate (trade name: Hydrin Z-8-36, solid content 36%, manufactured by Chukyo Yushi Co., Ltd.) are mixed and stirred to obtain a coating solution for a protective layer. It was.

(Preparation of thermal recording material)
An undercoat layer coating solution is applied and dried on one side of a 48 g / m ² base paper so that the applied amount after drying is 7.0 g / m ^2, and the applied amount after drying is further 3 on the undercoat layer. The thermal recording layer coating solution was applied and dried so as to have a viscosity of 0.5 g / m ² . Further, the protective layer coating solution was applied and dried on the heat-sensitive recording layer so that the coating amount after drying was 2.5 g / m ² . Thereafter, it was treated with a super calender to obtain a heat-sensitive recording material having a surface smoothness of 1000 to 4000 seconds with a Oken type smoothness meter.

Example 2
In the same manner as in Example 1, except that 9,9-bis (4-hydroxyphenyl) fluorene was used instead of 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene in the liquid C of Example 1. A heat-sensitive recording material was obtained.

Example 3
In the same manner as in Example 1, except that 9,9-bis (4-phenoxyethanol) fluorene was used instead of 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene in the liquid C of Example 1. A heat-sensitive recording material was obtained.

Comparative Example 1
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the liquid C was removed in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

Comparative Example 2
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 2 parts of C solution was used in the preparation of the thermosensitive recording layer coating solution of Example 1.

Comparative Example 3
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 30 parts of solution C was used in the preparation of the heat-sensitive recording layer coating liquid of Example 1.

Comparative Example 4
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that 2,2-bis (4-hydroxyphenyl) propane was used in place of 4-hydroxy-4′-isopropoxydiphenylsulfone in the preparation of Liquid B of Example 1. Got.

Comparative Example 5
In the preparation of the liquid C of Example 1, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) was used instead of 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene. ) A heat-sensitive recording material was obtained in the same manner as in Example 1 except that butane was used.

Comparative Example 6
In the preparation of the liquid C of Example 1, 1,1,5-tris (4-t-butyl-3-hydroxy-2, instead of 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 6-dimethylbenzyl) isocyanuric acid was used.

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

(Recording density)
Using a thermal evaluation machine (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.), each thermal recording medium was colored at 0.40 mJ / dot, and the density of the recording part was measured using a Macbeth densitometer (trade name: RD-914, Macbeth). Measured in visual mode.

(Heat-resistant)
Each blank paper sample was allowed to stand for 16 hours in an environment of 80 ° C., and then the density of the background portion was measured in a visual mode of Macbeth densitometer trade name: RD-914, manufactured by Macbeth Co.).

(Plasticizer resistance)
A wrap film (trade name: High Wrap KMA-W, manufactured by Mitsui Chemicals) is wrapped on a polycarbonate pipe (40 mmΦ) in a triple layer, and each color-recorded thermal recording material is placed on the wrap film. After wrapping three times and allowing to stand at 40 ° C. for 24 hours, the density of the recording portion was measured in a visual mode of a Macbeth densitometer (trade name: RD-914, manufactured by Macbeth).

(Oil resistance)
Cone oil is hung on the surface of each color-recorded thermal recording medium and allowed to stand for 24 hours, and then the corn oil is wiped off with gauze. Measured in mode.

Claims (3)

In a heat-sensitive recording material provided with a heat-sensitive recording layer containing at least a leuco dye and a colorant on a support, 4-hydroxy-4′-isopropoxydiphenylsulfone and the following general colorant are used as the colorant in the heat-sensitive recording layer. A heat-sensitive recording material comprising a fluorene compound represented by the formula (1), wherein the fluorene compound is 10 to 100% by mass relative to the total content of leuco dye.

(In the formula, R1 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R2 represents a hydroxy group, an amino group or —OCH ₂ CH ₂ OH, which may be the same or different. Good)   The heat-sensitive recording material according to claim 1, wherein the amount of the fluorene compound represented by the general formula (1) is 5 to 80% by mass with respect to the total solid content of the 4-hydroxy-4'-isopropoxydiphenylsulfone.   The fluorene compound was selected from 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxyphenyl) fluorene, and 9,9-bis (4-phenoxyethanol) fluorene. The heat-sensitive recording material according to claim 1 or 2, which is at least one kind.