WO2025244088A1 - Thermal recording material - Google Patents

Abstract

Disclosed is a thermal recording material characterized by including at least one compound represented by general formula (1). (In formula (1), R¹ to R¹⁰, R²¹, and R²² each independently represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, a hydroxy group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.) In formula (1), two or more of R¹ to R⁵ may be hydrogen atoms and two or more of R⁶ to R¹⁰ may be hydrogen atoms. In formula (1), R⁴ and R⁵ may be hydrogen atoms and R⁹ and R¹⁰ may be hydrogen atoms.

Description

Thermal recording materials

The present invention relates to a heat-sensitive recording material that utilizes color development caused by the reaction between a color-forming dye and a color-developing compound, and to a compound that is suitably used in the heat-sensitive recording material.
In particular, the present invention relates to a heat-sensitive recording material that preferably has excellent heat resistance in the background and excellent water resistance and/or plasticizer resistance and/or oil resistance in the printed portion, and to a compound that is suitably used for the heat-sensitive recording material.

Thermal recording materials are generally made by dispersing a leuco dye and a color-developing compound such as a phenolic compound separately into fine particles, mixing the two, and adding additives such as binders, sensitizers, fillers, and lubricants to obtain a coating liquid, which is then applied to paper, film, synthetic paper, etc. With thermal recording materials, the leuco dye and/or the color-developing compound melt when heated and come into contact, resulting in a chemical reaction that produces a colored record. To produce color in such thermal recording materials, thermal printers with built-in thermal heads are typically used. Compared to other recording methods, this thermal recording method has the following advantages: (1) no noise during recording, (2) no need for development or fixing, (3) no maintenance, and (4) relatively inexpensive equipment. For these reasons, it is widely used in fields such as facsimiles, computer output, printers for calculators, medical measurement recorders, automatic ticket vending machines, and thermal recording labels.

In recent years, as the uses of thermal recording materials have expanded, there has been an ever-increasing demand for high-speed recording to improve productivity. Therefore, there is a strong demand for the development of thermal recording materials with excellent thermal response that can adequately accommodate high-speed recording. In this case, a color-developing compound with a low melting point and low heat of fusion is required. However, this property can easily cause the unrecorded areas (background) of the thermal recording material to deteriorate during manufacturing, use, or storage, resulting in the drawback of background fogging (unwanted background color development). Therefore, there is a demand for improved stability as well as high whiteness for the background of thermal recording materials.

In general, color-developing compounds containing phenolic hydroxyl groups have high color-developing ability. Among these, many bisphenol-based color-developing compounds have been reported due to their high color density, including 2,2-bis(4-hydroxyphenylpropane) (bisphenol A) shown in Patent Document 1 and 4,4'-dihydroxydiphenyl sulfone (bisphenol S) shown in Patent Document 2. However, these color-developing compounds containing phenolic hydroxyl groups have drawbacks, such as poor thermal response due to their high melting points and poor water resistance of printed areas. Furthermore, the use of phenolic compounds such as bisphenol A has been problematic due to endocrine problems, and there is a demand for non-phenolic color-developing compounds that do not contain a phenol structure.

Various non-phenolic color-developing compounds, such as diphenylurea and sulfonylurea compounds, have been proposed (Patent Documents 3 to 6). However, thermal recording materials using these color-developing compounds have poor thermal stability of the background and low plasticizer resistance in the printed area. These compounds have the drawback of causing the colored recording to fade or disappear when exposed to heat for a relatively short period of time or when used as food labels, placing certain limitations on expanding their applications. Therefore, no color-developing compounds have yet been found that can satisfy the market's demands in a balanced manner. In particular, there is a strong demand for the development of thermal recording materials that offer excellent heat resistance in the background and plasticizer resistance in the printed area.

U.S. Patent No. 3,539,375 Japanese Unexamined Patent Publication No. 57-11088 Japanese Patent Application Publication No. 8-59603 Japanese Patent Application Publication No. 8-156426 International Publication No. 2014/080615 International Publication No. 2019/044462

An object of the present invention is to provide a heat-sensitive recording material which has excellent heat resistance in the background and excellent water resistance and/or plasticizer resistance and/or oil resistance in the printed area.
Another object of the present invention is to provide a thermosensitive recording layer containing such a thermosensitive recording material, and a thermosensitive recording paper or a thermosensitive film containing this thermosensitive recording layer.
It is still another object of the present invention to provide novel compounds which can be used as color-developing compounds.

As a result of extensive research into achieving the above-mentioned objectives, the inventors have newly discovered that a compound with a specific structure can solve the above-mentioned problems, and that a thermal recording material using this compound as a color-developing compound has excellent heat resistance in the background and excellent water resistance, plasticizer resistance, and/or oil resistance in the printed area, preferably all of these properties, and have thus completed the present invention.

Aspects and embodiments of the present invention relate to the following items [1] to [7].
[1]
A heat-sensitive recording material comprising at least one compound represented by the following general formula (1):

(In the formula, R ¹ to R ¹⁰ , R ²¹ , and R ²² each independently represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, a hydroxy group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.)
[2]
The heat-sensitive recording material according to the above [1], wherein in the formula (1), two or more of R ¹ to R ⁵ are hydrogen atoms, and two or more of R ⁶ to R ¹⁰ are hydrogen atoms.
[3]
The heat-sensitive recording material according to the above [1], wherein in the formula (1), R ⁴ and R ⁵ are hydrogen atoms, and R ⁹ and R ¹⁰ are hydrogen atoms, and R ¹ to R ³ , R ⁶ to R ⁸ , R ²¹ and R ²² are as defined above.
[4]
In the formula (1), R ³ and R ⁸ are each independently a hydrogen atom or an alkyl group, and R ¹ , R ² , R ⁴ to R ⁷ , R ⁹ , R ¹⁰ , R ²¹ and R ²² are each a hydrogen atom.
[5]
A thermosensitive recording layer comprising the thermosensitive recording material according to any one of the above [1] to [4].
[6]
A thermosensitive recording paper or a thermosensitive film comprising the thermosensitive recording layer according to the above item [5].
[7]
A compound represented by the following general formula (2):

(In the formula, R ¹ to R ¹⁰ , R ²¹ , and R ²² each independently represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, a hydroxy group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.)

According to one aspect of the present invention, by using at least one compound represented by general formula (1) as a color-developing compound, it is possible to provide a thermal recording material that has excellent heat resistance in the background and excellent water resistance and/or plasticizer resistance and/or oil resistance in the printed area.
Because of the excellent properties described above, such a thermosensitive recording material can be suitably used for a thermosensitive recording layer, and for thermosensitive recording paper or thermosensitive film containing a thermosensitive recording layer.
According to another aspect of the present invention, there is provided a novel compound represented by general formula (2) which can be used as a color-developing compound.

The present invention will now be described in detail.
The present invention relates to a heat-sensitive recording material which contains a color-forming compound which is usually colorless or pale in color, and a color-developing compound represented by the above formula (1), and optionally contains other color-developing compounds, sensitizers, storage stability improvers, and further contains the binders shown below, and optionally fillers, other additives, etc.

[Compound represented by formula (1)]
Examples of the halogen atom in R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) include a fluorine atom, a chlorine atom, and a bromine atom, with a fluorine atom and a chlorine atom being preferred.

The alkyl groups represented by R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) include linear, branched, and cyclic alkyl groups. Among these, linear or branched groups are preferred, and linear groups are even more preferred. The carbon number range is usually C1 to C12, preferably C1 to C8, more preferably C1 to C6, and even more preferably C1 to C4. Specific examples of the alkyl group include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl; branched alkyl groups such as isopropyl, isobutyl, sec-butyl, t-butyl, isopentyl, isohexyl, and isooctyl; and cyclic alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Among these, preferred are methyl, ethyl, and n-propyl, more preferred are methyl and ethyl, and particularly preferred is methyl.

The alkoxy groups in R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) include linear, branched, and cyclic alkoxy groups. Of these, linear or branched alkoxy groups are preferred, and linear alkoxy groups are more preferred. The carbon number range is usually C1 to C12, preferably C1 to C8, more preferably C1 to C6, and even more preferably C1 to C4. Specific examples of the alkoxy group include straight-chain alkoxy groups such as methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexyloxy, n-heptoxy, n-octyloxy, n-nonyloxy, and n-decyloxy; branched-chain (preferably C3 to C10) alkoxy groups such as isopropoxy, isobutoxy, sec-butoxy, t-butoxy, isoamyloxy, t-amyloxy, isohexyloxy, t-hexyloxy, isoheptoxy, t-heptoxy, isooctyloxy, t-octyloxy, 2-ethylhexyloxy, isononyloxy, and isodecyloxy; and cyclic (preferably C3 to C7) alkoxy groups such as cyclopropoxy, cyclobutoxy, cyclopentoxy, cyclohexyloxy, and cycloheptoxy. Of these, methoxy, ethoxy and n-propoxy are preferred, methoxy and ethoxy are more preferred, and methoxy is particularly preferred.

The aryloxy group in R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) is not particularly limited as long as it has a structure in which an aromatic hydrocarbon is bonded via an oxygen atom. The aromatic hydrocarbon can be arbitrarily selected from, for example, a monocyclic structure, a polycyclic structure, a fused ring structure, a heterocyclic structure, and the like. Examples of aromatic hydrocarbons constituting the aryloxy group include benzene, pyrrole, thiophene, furan, naphthalene, anthracene, biphenyl, indole, and the like. These aromatic hydrocarbons may further have a substituent. The aryloxy group in R ¹ may be, for example, phenoxy, naphthyloxy, anthracenoxy, halogenated phenoxy, alkylphenoxy, biphenoxy, and the like. Preferably, it may be a C6 to C12 aryloxy group, and specific examples include phenoxy, naphthyloxy, biphenoxy, and the like.

The alkylcarbonyloxy group in R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) may be a linear, branched, or cyclic alkylcarbonyloxy group, and may be preferably a C1 to C10 alkylcarbonyloxy group. Specific examples of the alkylcarbonyloxy group include linear ones such as methylcarbonyloxy, ethylcarbonyloxy, n-propylcarbonyloxy, n-butylcarbonyloxy, n-pentylcarbonyloxy, n-hexylcarbonyloxy, n-heptylcarbonyloxy, n-octylcarbonyloxy, n-nonylcarbonyloxy, and n-decylcarbonyloxy; isopropylcarbonyloxy, isobutylcarbonyloxy, sec-butylcarbonyloxy, t-butylcarbonyloxy, isoamylcarbonyloxy, t-amylcarbonyloxy, and iso Branched chain (preferably C3 to C10) alkylcarbonyloxy groups such as hexylcarbonyloxy, t-hexylcarbonyloxy, isoheptylcarbonyloxy, t-heptylcarbonyloxy, isooctylcarbonyloxy, t-octylcarbonyloxy, 2-ethylhexylcarbonyloxy, isononylcarbonyloxy, and isodecylcarbonyloxy; and cyclic (preferably C3 to C7) alkylcarbonyloxy groups such as cyclopropylcarbonyloxy, cyclobutylcarbonyloxy, cyclopentylcarbonyloxy, cyclohexylcarbonyloxy, and cycloheptylcarbonyloxy. Of these, linear or branched alkylcarbonyloxy groups are preferred, and linear alkylcarbonyloxy groups are more preferred.

The arylcarbonyloxy groups represented by R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) may preferably be C6 to C12 arylcarbonyloxy groups. Specific examples of the arylcarbonyloxy groups include phenylcarbonyloxy, naphthylcarbonyloxy, and biphenylcarbonyloxy. Of these, the phenylcarbonyloxy group is preferred.

The alkylcarbonylamino group in R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) includes a linear, branched, or cyclic alkylcarbonylamino group, and is preferably a C1 to C10 alkylcarbonylamino group. Specific examples of the alkylcarbonylamino group include linear ones such as methylcarbonylamino, ethylcarbonylamino, n-propylcarbonylamino, n-butylcarbonylamino, n-pentylcarbonylamino, n-hexylcarbonylamino, n-heptylcarbonylamino, n-octylcarbonylamino, n-nonylcarbonylamino, and n-decylcarbonylamino; isopropylcarbonylamino, isobutylcarbonylamino, sec-butylcarbonylamino, t-butylcarbonylamino, isoamylcarbonylamino, t-amylcarbonylamino, and iso Examples of the alkylcarbonylamino group include branched (preferably C3 to C10) groups such as hexylcarbonylamino, t-hexylcarbonylamino, isoheptylcarbonylamino, t-heptylcarbonylamino, isooctylcarbonylamino, t-octylcarbonylamino, 2-ethylhexylcarbonylamino, isononylcarbonylamino, and isodecylcarbonylamino; and cyclic (preferably C3 to C7) groups such as cyclopropylcarbonylamino, cyclobutylcarbonylamino, cyclopentylcarbonylamino, cyclohexylcarbonylamino, and cycloheptylcarbonylamino. Preferred are linear or branched alkylcarbonylamino groups, more preferably linear alkylcarbonylamino groups. Of the linear alkylcarbonylamino groups, preferred are methylcarbonylamino, ethylcarbonylamino, and n-propylcarbonylamino groups, more preferably methylcarbonylamino and ethylcarbonylamino groups, and particularly preferably methylcarbonylamino groups.

The arylcarbonylamino groups represented by R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) may preferably be C6 to C12 arylcarbonylamino groups. Specific examples of the arylcarbonylamino group include a phenylcarbonylamino group, a naphthylcarbonylamino group, and a biphenylcarbonylamino group. Of these, the phenylcarbonylamino group is preferred.

The alkylsulfonylamino groups in R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) may be linear, branched, or cyclic alkylsulfonylamino groups, and may preferably be C1 to C10 alkylsulfonylamino groups. Specific examples of the alkylsulfonylamino group include linear ones such as methylsulfonylamino, ethylsulfonylamino, n-propylsulfonylamino, n-butylsulfonylamino, n-pentylsulfonylamino, n-hexylsulfonylamino, n-heptylsulfonylamino, n-octylsulfonylamino, n-nonylsulfonylamino, and n-decylsulfonylamino; branched-chain (preferably C3 to C10) sulfonylamino groups such as 2-ethylhexylsulfonylamino, t-hexylsulfonylamino, isoheptylsulfonylamino, t-heptylsulfonylamino, isooctylsulfonylamino, t-octylsulfonylamino, 2-ethylhexylsulfonylamino, isononylsulfonylamino, and isodecylsulfonylamino; and cyclic (preferably C3 to C7) sulfonylamino groups such as cyclopropylsulfonylamino, cyclobutylsulfonylamino, cyclopentylsulfonylamino, cyclohexylsulfonylamino, and cycloheptylsulfonylamino. Of these, preferred are linear or branched-chain alkylsulfonylamino groups, and more preferred are linear alkylsulfonylamino groups.

The arylsulfonylamino groups represented by R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) may preferably be C6 to C12 arylsulfonylamino groups. Specific examples of the arylsulfonylamino group include phenylsulfonylamino, toluenesulfonylamino, naphthylsulfonylamino, and biphenylsulfonylamino.

The monoalkylamino group in R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) may be a linear, branched, or cyclic monoalkylamino group, and is preferably a mono C1 to C10 alkylamino group. Specific examples of monoalkylamino groups include straight-chain ones such as methylamino, ethylamino, n-propylamino, n-butylamino, n-pentylamino, n-hexylamino, n-heptylamino, n-octylamino, n-nonylamino, and n-decylamino; branched-chain (preferably C3 to C10) ones such as isopropylamino, isobutylamino, sec-butylamino, t-butylamino, isoamylamino, t-amylamino, isohexylamino, t-hexylamino, isoheptylamino, t-heptylamino, isooctylamino, t-octylamino, 2-ethylhexylamino, isononylamino, and isodecylamino; and cyclic (preferably C3 to C7) ones such as cyclopropylamino, cyclobutylamino, cyclopentylamino, cyclohexylamino, and cycloheptylamino. Straight-chain or branched-chain ones are preferred, and straight-chain ones are more preferred.

The dialkylamino groups in R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) may be linear, branched, or cyclic dialkylamino groups, and are preferably C1 to C10 dialkylamino groups. Specific examples of dialkylamino groups include linear ones such as dimethylamino, diethylamino, di-n-propylamino, di-n-butylamino, di-n-pentylamino, di-n-hexylamino, di-n-heptylamino, di-n-octylamino, di-n-nonylamino, and di-n-decylamino; diisopropylamino, diisobutylamino, di-sec-butylamino, di-t-butylamino, diisoamylamino, di-t-amylamino, diisohexylamino, and di-t-heptylamino; Examples of the alkylamino group include branched amino groups (preferably having two C3 to C10 branched chains) such as dicyclopropylamino, dicyclobutylamino, dicyclopentylamino, dicyclohexylamino, dicycloheptylamino, and dicycloheptylamino. These alkylamino groups are preferably straight-chain or branched, and more preferably straight-chain.

The arylamino groups in R ¹ to R ¹⁰ , R ²¹ , and R ²² in formula (1) may be monoarylamino groups or diarylamino groups, and are preferably mono- or di-C6 to C12 arylamino groups. Specific examples of the arylamino group include phenylamino (anilino), naphthylamino, biphenylamino, diphenylamino, dinaphthylamino, and di(biphenyl)amino.

In the present invention, the substituents R ¹ to R ¹⁰ are particularly preferably a hydrogen atom, a methyl group, or a phenyl group.

Preferred examples of the compound represented by formula (1) are listed below.
i) A compound in which two or more of R ¹ to R ⁵ are hydrogen atoms and two or more of R ⁶ to R ¹⁰ are hydrogen atoms.
ii) A compound in which two of R ¹ to R ⁵ are hydrogen atoms and two of R ⁶ to R ¹⁰ are hydrogen atoms.
iii) Compounds in which R ⁴ and R ⁵ are hydrogen atoms, and R ⁹ and R ¹⁰ are hydrogen atoms.
iv) Compounds in which R ¹ , R ² , R ⁴ to R ⁷ , R ⁹ and R ¹⁰ are hydrogen atoms.
v) Compounds in which R ³ and R ⁸ are each independently a hydrogen atom or an alkyl group, and R ¹ , R ² , R ⁴ to R ⁷ , R ⁹ and R ¹⁰ are each a hydrogen atom.
vi) Compounds in which R ³ and R ⁸ are hydrogen atoms or methyl groups, and R ¹ , R ² , R ⁴ to R ⁷ , R ⁹ and R ¹⁰ are hydrogen atoms.
vii) Compounds in which R ¹ to R ¹⁰ are all hydrogen atoms.

The compound represented by formula (1) according to the present invention may be any of the compounds listed as specific examples in Tables 1 to 6 below, but is not limited to these.

[Method for producing the compound represented by formula (1)]
The compound represented by the above formula (1) can be synthesized by any of the following four methods, although there is no particular limitation.
<Manufacturing method 1>
The compound represented by the above formula (1) can be synthesized according to the following reaction route.

R ¹ to R ¹⁰ , R ²¹ , and R ²² in the above formulas [1-1] to [1-3] have the same meanings as R ¹ to R ¹⁰ , R ²¹ , and R ²² in the above formula (1).

Compounds of general formula [1-2] can be produced by reacting compounds of general formula [1-1] with phosgene or triphosgene, urea, or chloroformate, in the presence or absence of a base. The compound of formula [1-1] is available, for example, as sulfanilic acid from Tokyo Chemical Industry Co., Ltd. (see Chemical Communications (Cambridge, United Kingdom) (2020), 56(18), 2735-2738; Communications (2018), 48(3), 247-254).

The solvent used in this reaction is not particularly limited, so long as it does not affect the reaction. Examples of solvents include amides such as N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone; halogenated hydrocarbons such as methylene chloride or chloroform; aromatic hydrocarbons such as toluene, xylene, or mesitylene; ethers such as dioxane, tetrahydrofuran, anisole, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, or diethylene glycol diethyl ether; nitriles such as acetonitrile; ketones such as acetone or 2-butanone; esters such as ethyl acetate or butyl acetate; sulfones such as sulfolane; sulfoxides such as dimethyl sulfoxide; and water. Two or more of these solvents may be used in combination.

The amount of phosgene or triphosgene, urea, or chloroformate used in this reaction is typically 0.1 to 50 times the molar amount of the compound of general formula [1-1], preferably 0.2 to 20 times the molar amount, and more preferably 0.4 to 1.3 times the molar amount.

The base optionally used in this reaction includes, for example, inorganic bases such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, or cesium carbonate; and organic bases such as triethylamine or diisopropylethylamine. The amount of these bases used may be 0.01 to 50 times the molar amount of the compound of general formula [1-1], and preferably 0.1 to 2 times the molar amount.

The reaction temperature for this reaction may typically be -10 to 250°C, with 0 to 200°C being preferred. The reaction may be carried out for, for example, 10 minutes to 48 hours.

The compound of the formula [1-3] can be produced by reacting the compound of the general formula [1-2] with phosphorus oxychloride, thionyl chloride, chlorosulfonic acid, oxalyl chloride, phosphorus pentachloride, or the like in the presence or absence of a base to obtain a sulfonyl chloride, which is then reacted with a phenol, or by a method of reacting the compound of the general formula [1-2] with a phenol by direct dehydration condensation.
The solvent used in this reaction is not particularly limited as long as it does not affect the reaction. Examples of the solvent include amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; halogenated hydrocarbons such as methylene chloride and chloroform; aromatic hydrocarbons such as benzene, toluene, and xylene; ethers such as dioxane, tetrahydrofuran, anisole, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, and diethylene glycol diethyl ether; nitriles such as acetonitrile; ketones such as acetone and 2-butanone, esters such as ethyl acetate and butyl acetate; sulfones such as sulfolane; sulfoxides such as dimethyl sulfoxide; and water. Two or more of these solvents may be used in combination.

The amount of the phenol used in this reaction may be 0.1 to 50 times by mole, preferably 0.7 to 3 times by mole, relative to the compound of the general formula [1-2].
The reaction temperature for this reaction may usually be −78 to 200° C., preferably −20 to 120° C. The reaction may be carried out for, for example, 10 minutes to 24 hours.

<Manufacturing method 2>
The compound represented by the above formula (1) can be synthesized according to the following reaction route.

R ¹ to R ¹⁰ , R ²¹ , and R ²² in the above formulas [2-1] and [2-2] have the same meanings as R ¹ to R ¹⁰ , R ²¹ , and R ²² in the above formula (1).

The compound of general formula [2-2] can be produced by reacting the compound of general formula [2-1] with phosgene, triphosgene, urea, a chloroformate, or the like in the presence or absence of a base. The compound of formula [2-1] can be synthesized by a known method using aminobenzenesulfonic acid (obtained from Tokyo Chemical Industry Co., Ltd.) and a phenolic compound as starting materials.
The solvent used in this reaction is not particularly limited as long as it does not affect the reaction. Examples of the solvent include amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; halogenated hydrocarbons such as methylene chloride and chloroform; aromatic hydrocarbons such as toluene, xylene, and mesitylene; ethers such as dioxane, tetrahydrofuran, anisole, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, and diethylene glycol diethyl ether; nitriles such as acetonitrile; ketones such as acetone and 2-butanone; esters such as ethyl acetate and butyl acetate; sulfones such as sulfolane; sulfoxides such as dimethyl sulfoxide; and water. Two or more of these solvents may be mixed and used.

The base optionally used in this reaction includes, for example, inorganic bases such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, or cesium carbonate; and organic bases such as triethylamine or diisopropylethylamine. The amount of these bases used may be 0.01 to 50 times the molar amount of the compound of general formula [2-1], and preferably 0.1 to 2 times the molar amount.

The reaction temperature for this reaction may typically be -10 to 250°C, with 0 to 200°C being preferred. The reaction may be carried out for, for example, 10 minutes to 48 hours.

<Manufacturing method 3>
The compound represented by the above formula (1) can be synthesized according to the following reaction route.

R ¹ to R ¹⁰ , R ²¹ , and R ²² in the above formulas [3-1] to [3-3] have the same meanings as R ¹ to R ¹⁰ , R ²¹ , and R ²² in the above formula (1).

The compound of general formula [3-3] can be produced by reacting the compound of general formula [3-1] with the compound of general formula [3-2] in the presence or absence of a base. The compound of formula [3-1] can be synthesized by a known method using the compound of formula [2-1] as a starting material.
The solvent used in this reaction is not particularly limited as long as it does not affect the reaction. Examples of the solvent include amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; halogenated hydrocarbons such as methylene chloride and chloroform; aromatic hydrocarbons such as toluene, xylene, and mesitylene; ethers such as dioxane, tetrahydrofuran, anisole, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, and diethylene glycol diethyl ether; nitriles such as acetonitrile; ketones such as acetone and 2-butanone; esters such as ethyl acetate and butyl acetate; sulfones such as sulfolane; sulfoxides such as dimethyl sulfoxide; and water. Two or more of these solvents may be mixed and used.

The base optionally used in this reaction includes, for example, inorganic bases such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, or cesium carbonate; and organic bases such as triethylamine or diisopropylethylamine. The amount of these bases used may be 0.01 to 50 times the molar amount of the compound of general formula [3-1], and preferably 0.1 to 2 times the molar amount.

The reaction temperature for this reaction may typically be between -10 and 200°C, with 0 to 120°C being preferred. The reaction may be carried out for, for example, 10 minutes to 24 hours.

<Manufacturing method 4>
The compound represented by the above formula (1) can be synthesized according to the following reaction route.

R ¹ to R ¹⁰ , R ²¹ , and R ²² in the above formulas [4-1] to [4-3] have the same meanings as R ¹ to R ¹⁰ , R ²¹ , and R ²² in the above formula (1). R ¹¹ represents an alkyl group or an aryl group. Specifically, R ¹¹ may be, for example, a methyl group, an ethyl group, a phenyl group, a chlorophenyl group, a nitrophenyl group, or the like. R ¹¹ is not particularly limited as long as it is a group that does not interfere with the synthesis of the compound [4-3].

The compound of general formula [4-3] can be produced by reacting the compound of general formula [4-1] with the compound of general formula [4-2] in the presence or absence of a base. The compound of formula [4-1] can be synthesized by a known method using the compound of formula [2-1] or [3-1] as a starting material.
The solvent used in this reaction is not particularly limited as long as it does not affect the reaction. Examples of the solvent include amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; halogenated hydrocarbons such as methylene chloride and chloroform; aromatic hydrocarbons such as toluene, xylene, and mesitylene; ethers such as dioxane, tetrahydrofuran, anisole, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, and diethylene glycol diethyl ether; nitriles such as acetonitrile; ketones such as acetone and 2-butanone; esters such as ethyl acetate and butyl acetate; sulfones such as sulfolane; sulfoxides such as dimethyl sulfoxide; and water. Two or more of these solvents may be used in combination.

The base optionally used in this reaction includes, for example, inorganic bases such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, and cesium carbonate; and organic bases such as triethylamine and diisopropylethylamine. The amount of these bases used may be 0.01 to 50 times the molar amount of the compound of general formula [4-1], and preferably 0.1 to 2 times the molar amount.

The reaction temperature for this reaction may typically be between -10 and 200°C, with 0 to 120°C being preferred. The reaction may be carried out for, for example, 10 minutes to 24 hours.

[Thermal recording material]
The heat-sensitive recording material of the present invention usually contains a color-developing compound including the compound shown in (1) above, and a color-forming compound, and may further optionally contain known color-developing compounds other than those mentioned above, sensitizers, binders, storage stability improvers, fillers, and other additives.
In forming the thermosensitive recording material of the present invention, the color-forming compound is typically used in an amount of 1 to 50% by weight, preferably 5 to 30% by weight, the compound represented by formula (1) is typically used in an amount of 1 to 70% by weight, preferably 10 to 50% by weight, the sensitizer is typically used in an amount of 0 to 80% by weight, preferably 1 to 80% by weight, the storage stability improver is typically used in an amount of 0 to 30% by weight, the binder is typically used in an amount of 0 to 90% by weight, preferably 1 to 90% by weight, the filler is typically used in an amount of 0 to 80% by weight, and other lubricants, surfactants, antifoaming agents, and ultraviolet absorbers are each used in an optional proportion, for example, 0 to 30% by weight (here, "% by weight" refers to the weight proportion of each component in the thermosensitive color-forming layer). However, the total content of the color-forming compound, the compound represented by formula (1), and other optional components constituting the thermosensitive recording material is 100% by weight.

In a more preferred embodiment, the compound represented by formula (1) can be used in a mass ratio of typically 0.5 to 20 times, more preferably 1 to 5 times, the mass of the color-forming compound.

<Color-forming compound>
The color-forming compound used in the present invention is not particularly limited, as long as it is generally used in pressure-sensitive recording paper or heat-sensitive recording paper.Examples of the color-forming compound used include fluoran-based compounds, triarylmethane-based compounds, spiro-based compounds, diphenylmethane-based compounds, thiazine-based compounds, lactam-based compounds, and fluorene-based compounds.Among these, fluoran-based compounds are preferred.

Specific examples of fluoran compounds include 3-diethylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran, 3-[N-ethyl-N-(3-ethoxypropyl)amino ]-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-hexylamino)-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-tetrahydrofurylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(p-chloroanilino)fluoran, 3-diethylamino-6-methyl-7- (p-fluoroanilino)fluoran, 3-[N-ethyl-N-(p-tolyl)amino]-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(p-toluidino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-diethylamino-7-(o-fluoroanilino)fluoran, 3-dibutylamino-7-(o-fluoroanilino)fluoran, 3-diethylamino-7 -(3,4-dichloroanilino)fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-ethoxyethylaminofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7-octylfluoran, 3-[N-ethyl-N-(p-tolyl)amino]-6-methyl-7-phenethylfluoran, etc. Among these, 3-dibutylamino-6-methyl-7-anilinofluoran is preferred.

Specific examples of triarylmethane compounds include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone or CVL), 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylaminoindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, and 3-(p-dimethylaminophenyl)-3-(2-phenylindol-3-yl). Examples include 3,3-bis(1,2-dimethylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3-yl)-5-dimethylaminophthalide, 3,3-(2-phenylindol-3-yl)-5-dimethylaminophthalide, and 3-p-dimethylaminophenyl-3-(1-methylpyrrol-2-yl)-6-dimethylaminophthalide.

Specific examples of spiro compounds include 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-propylspirobenzopyran, 3-methylnaphtho-(3-methoxybenzo)spiropyran, 1,3,3-trimethyl-6-nitro-8'-methoxyspiro(indoline-2,2'-benzopyran), and the like.
Specific examples of diphenylmethane compounds include N-halophenyl-leucoauramine, 4,4-bis-dimethylaminophenyl benzhydryl benzyl ether, and N-2,4,5-trichlorophenyl leucoauramine.
Specific examples of thiazine compounds include benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, and the like.
Specific examples of lactam compounds include rhodamine B anilinolactam and rhodamine B p-chloroanilinolactam.
Specific examples of fluorene compounds include 3,6-bis(dimethylamino)fluorene spiro(9,3')-6'-dimethylaminophthalide, 3,6-bis(dimethylamino)fluorene spiro(9,3')-6'-pyrrolidinophthalide, and 3-dimethylamino-6-diethylaminofluorene spiro(9,3')-6'-pyrrolidinophthalide.
These color-forming compounds may be used alone or in combination of two or more.

<Other color-developing compounds>
The thermosensitive recording material of the present invention contains the compound represented by formula (1) as a color-developing compound, but may also use one or a mixture of two or more other color-developing compounds in combination. The color-developing compounds that can be used in combination with the compound represented by formula (1) are not particularly limited, and may be any compounds commonly used in pressure-sensitive recording paper or thermosensitive recording paper. Examples of other color-developing compounds include α-naphthol, β-naphthol, p-octylphenol, 4-t-octylphenol, p-t-butylphenol, p-phenylphenol, 1,1-bis(p-hydroxyphenyl)propane, 2,2-bis(p-hydroxyphenyl)propane (also known as bisphenol A or BPA), 2,2-bis(p-hydroxyphenyl)butane, 1,1-bis(p-hydroxyphenyl)cyclohexane, 4,4'-thiobisphenol, 4,4'- Cyclohexylidene diphenol, 2,2'-bis(2,5-dibromo-4-hydroxyphenyl)propane, 4,4'-isopropylidenebis(2-t-butylphenol), 2,2'-methylenebis(4-chlorophenol), 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-ethoxydiphenyl sulfone phenolic compounds such as 4-hydroxy-4'-butoxydiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, methyl bis(4-hydroxyphenyl)acetate, butyl bis(4-hydroxyphenyl)acetate, benzyl bis(4-hydroxyphenyl)acetate, and 2,4-dihydroxy-2'-methoxybenzanilide; benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, 5-hydroxybenzoic acid, methyl 4-hydroxybenzoate ...phthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, methyl 4-hydroxybenzoate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, methyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, methyl 4-hydroxyphthalate, aromatic carboxylic acid derivatives such as ethyl 4-hydroxyisophthalate, 3,5-di-t-butylsalicylic acid, and 3,5-di-α-methylbenzylsalicylic acid; aromatic carboxylic acids or polyvalent metal salts thereof; and urea compounds such as [3-(3-phenylureido)phenyl]-4-methylbenzenesulfonate, N-[2-(3-phenylureido)phenyl]benzenesulfonamide, N-p-toluenesulfonyl-N'-3-(p-toluenesulfonyloxy)phenylurea and diphenylurea.

<Sensitizer>
Specific examples of sensitizers (heat-fusible compounds) that may be used in the heat-sensitive recording material of the present invention include waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, naphthalene derivatives, aromatic ethers, aromatic carboxylic acid derivatives, aromatic sulfonic acid ester derivatives, carbonic acid or oxalic acid diester derivatives, biphenyl derivatives, terphenyl derivatives, sulfonic acid derivatives, aromatic ketone derivatives, aromatic hydrocarbon compounds, etc. These sensitizers may be used alone or in combination of two or more.

<Waxes>
Specific examples of waxes that may be used in the thermal recording material of the present invention include Japan wax, carnauba wax, shellac, paraffin, montan wax, oxidized paraffin, polyethylene wax, and oxidized polyethylene; higher fatty acids such as stearic acid and behenic acid; higher fatty acid amides such as stearic acid amide, oleic acid amide, N-methylstearic acid amide, erucic acid amide, methylolbehenic acid amide, methylenebisstearic acid amide, and ethylenebisstearic acid amide; and higher fatty acid anilides such as stearic acid anilide and linoleic acid anilide. etc.; naphthalene derivatives include, for example, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, 2,6-diisopropylnaphthalene, etc.; aromatic ethers include, for example, 1,2-diphenoxyethane, 1,4-diphenoxybutane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methoxyphenoxy)ethane, 1,2-bis(3,4-dimethylphenyl)ethane, 1-phenoxy-2-(4-chlorophenoxy)ethane, 1-phenoxy-2-(4-methoxyphenoxy)ethane, 1,2-diphenoxymethyl ethylbenzene, diphenyl glycol, etc.; aromatic carboxylic acid derivatives, for example, p-hydroxybenzoic acid benzyl ester, p-benzyloxybenzoic acid benzyl ester, terephthalic acid dibenzyl ester, etc.; aromatic sulfonic acid ester derivatives, for example, p-toluenesulfonic acid phenyl ester, phenylmesitylenesulfonate, 4-methylphenylmesitylenesulfonate, 4-tolylmesitylenesulfonate, etc.; carbonic acid or oxalic acid diester derivatives, for example, diphenyl carbonate, oxalic acid dibenzyl ester, oxalic acid di(4-chlorobenzyl) ester, Examples of the wax include di(4-methylbenzyl) oxalate esters; biphenyl derivatives such as p-benzylbiphenyl and p-allyloxybiphenyl; terphenyl derivatives such as m-terphenyl; sulfone derivatives such as p-toluenesulfonamide, benzenesulfonanilide, p-toluenesulfonanilide, 4,4'-diallyloxydiphenyl sulfone and diphenyl sulfone; aromatic ketone derivatives such as 4,4'-dimethylbenzophenone and dibenzoylmethane; and aromatic hydrocarbon compounds such as p-acetotoluidine. These waxes may be used alone or in combination of two or more.

<Storability improver>
Specific examples of the storage stability improver that may be used in the heat-sensitive recording material of the present invention include 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis(4,6-di-tert-butylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), 4,4'-butylidenebis(6-tert-butyl-m-cresol), 1-[α-methyl-α-(4'-hydroxyphenyl)ethyl]-4-[ α',α'-bis(4'-hydroxyphenyl)ethyl]benzene, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, tris(2,6-dimethyl-4-tert-butyl-3-hydroxybenzyl)isocyanurate, 4,4'-thiobis(3-methylphenol), 4,4'-dihydroxy-3,3',5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3',5 hindered phenol compounds such as 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4'-(2-methylglycidyloxy)diphenyl sulfone, diglycidyl terephthalate, cresol novolac type olefins, and the like; Examples of suitable preservatives include epoxy compounds such as epoxy resins, phenol novolac epoxy resins, and bisphenol A epoxy resins; N,N'-di-2-naphthyl-p-phenylenediamine, sodium or polyvalent metal salts of 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, bis(4-ethyleneiminocarbonylaminophenyl)methane, urea urethane compounds (such as the color-developing compound "UU" manufactured by Chemipro Chemical Co., Ltd.), and diphenyl sulfone-bridged compounds represented by the following formula (3) or mixtures thereof. These preservatives may be used alone or as a mixture of two or more.

(In the formula, a is an integer of 0 to 6.)

<Binder>
Specific examples of binders that may be used in the present invention include water-soluble binders such as methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, cellulose, polyvinyl alcohol (PVA), carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, silyl group-modified polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, starch and its derivatives, casein, gelatin, water-soluble isoprene rubber, alkali salts of styrene/maleic anhydride copolymers, and alkali salts of iso(or diiso)butylene/maleic anhydride copolymers, or (meth)acrylic Examples of binders include acrylic acid ester copolymers, styrene/(meth)acrylic acid ester copolymers, polyurethanes, polyester polyurethanes, polyether polyurethanes, polyvinyl acetate, ethylene/vinyl acetate copolymers, polyvinyl chloride, vinyl chloride/vinyl acetate copolymers, polyvinylidene chloride, polystyrene, styrene/butadiene (SB) copolymers, carboxylated styrene/butadiene (SB) copolymers, styrene/butadiene/acrylic acid copolymers, acrylonitrile/butadiene (NB) copolymers, carboxylated acrylonitrile/butadiene (NB) copolymers, and hydrophobic polymer emulsions such as composite particles of colloidal silica and (meth)acrylic resin. These binders may be used alone or in combination of two or more.

<Filler>
Specific examples of fillers that may be used in the present invention include calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay, alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, urea-formalin resin, etc. These fillers may be used alone or as a mixture of two or more.

In addition, various additives other than those mentioned above can also be used in the present invention. Examples of such additives include higher fatty acid metal salts such as zinc stearate and calcium stearate for purposes such as preventing thermal head wear and sticking, ultraviolet absorbers such as phenol derivatives, benzophenone compounds, and benzotriazole compounds for providing antioxidant or anti-aging effects, various surfactants, and antifoaming agents. These additives may be used alone or in combination.

[Method for preparing a thermal recording material]
A typical example of a method for preparing the thermosensitive recording material of the present invention will now be described. The color-forming compound and the compound represented by formula (1) used in the present invention are separately pulverized and dispersed in a disperser such as a ball mill, attritor, or sand mill together with a binder and, if necessary, other additives to prepare dispersions (usually, water is used as the medium when pulverization or dispersion is carried out wet), and these dispersions are then mixed to prepare a thermosensitive recording material coating solution, which is then coated onto a support such as paper (plain paper, wood-free paper, coated paper, etc.), a plastic sheet, or synthetic paper using a bar coater, blade coater, or the like to a dry weight of 0.1 to 20 g/ ^m2 , and then dried to produce a thermosensitive recording layer containing the thermosensitive recording material of the present invention, and thermosensitive recording paper or thermosensitive recording film having the thermosensitive recording layer.

If necessary, an intermediate layer may be provided between the thermosensitive recording layer and the support, and/or an overcoat layer (protective layer) may be provided on the thermosensitive recording layer. The thermosensitive recording paper or thermosensitive recording film of the present invention can be produced by a process including, for example, pulverizing and dispersing the above-mentioned binder and/or other additives as needed in the same manner as in the preparation of the thermosensitive recording material coating solution to prepare an intermediate layer coating solution or an overcoat layer (protective layer) coating solution, and then coating the resulting coating solution to a dry weight of usually about 0.1 to ¹⁰ g/m2, and drying it.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.
In the examples, "parts" refers to parts by mass, and "%" in the explanation of the solutions refers to % by mass.

Example 1: Synthesis of Compound No. 1 in Table 1 [Step 1]

To 100 parts of DMF, 100.0 parts of 3-aminobenzenesulfonic acid (the above-mentioned compound [1-1]: obtained from Tokyo Chemical Industry Co., Ltd.) and 40 parts of urea were added, and the mixture was stirred at 160°C for 12 hours. Then, the reaction solution was added dropwise to 250 parts of water to precipitate crystals. The crystals were washed successively with methanol and water, and dried, to obtain 70 parts of the above-mentioned compound [1-2] as a pale yellowish white solid.
MS (ESI): [MH] ^- : cal. :371.4, found:371.4.
[Step 2]

30.0 parts of compound [1-2] was added to 100 parts of DMF and stirred, and then 22 parts of thionyl chloride was added dropwise and reacted at room temperature for 2 hours. Next, a DMF solution of 35 parts of phenol was added, and the mixture was stirred at 65°C for 2 hours. The reaction solution was then added dropwise to 250 parts of water to precipitate crystals. The precipitate was separated by filtration, washed with methanol and water, and dried to obtain the compound [1-3] (32 parts) as a pale yellowish white solid.
MS (ESI): [M+H] ⁺ : cal. :525.6, found:525.6.

Example 2: Preparation of thermal recording material Compound No. 1 shown in Table 1, obtained in Example 1, was pulverized and dispersed for 1 hour using a Multi-Beads Shocker (model: PV1001(S)) manufactured by Yasui Kikai Co., Ltd. in the following composition to prepare the following solution [A].

Solution [A]: Compound No. 1 listed in Table 1 15 parts 25% aqueous PVA solution 20 parts Water 65 parts

A mixture of the following composition was pulverized and dispersed using a sand grinder so that the median particle size measured with a laser diffraction/scattering particle size distribution analyzer LA-950 (manufactured by Horiba, Ltd.) was 1 μm, thereby preparing a dispersion liquid [B] of a color-forming compound.
[B] Solution: 3-dibutylamino-6-methyl-7-anilinofluoran 35 parts 15% aqueous PVA solution 40 parts Water 25 parts

Next, the above-obtained solutions and the following chemicals were mixed in the following compositions to prepare a coating solution for a thermal recording material. This was then applied to a fine paper with a basis weight of 50 g/ ^m² so that the dry weight was 5 g/ ^m² , and dried to prepare a thermal recording paper containing the thermal recording layer of the present invention.
Solution [A] 40.0 parts Solution [B] 8.6 parts 67% calcium carbonate aqueous dispersion 9.0 parts 48% modified styrene-butadiene copolymer latex 6.3 parts Water 36.1 parts

(Formation of protective layer)
Next, a protective layer coating solution having the following composition was applied onto the thermosensitive recording layer so that the dry weight was 2 g/m ² , and then dried to prepare a thermosensitive recording layer with a protective layer.
40% styrene/acrylic acid ester copolymer emulsion 115 parts 5% bentonite aqueous dispersion 17 parts 45% styrene-acrylic copolymer aqueous emulsion 44 parts 39% zinc stearate aqueous dispersion 103 parts 67% calcium carbonate aqueous dispersion 15 parts

Comparative Example 1
A mixture of the following composition was ground and dispersed using a sand grinder to a median particle size of 1 μm as measured with a laser diffraction/scattering particle size distribution analyzer LA-950 (manufactured by Horiba, Ltd.) to prepare solution [C]. A comparative thermosensitive recording paper was obtained in the same manner as in Example 1, except that solution [C] was used in place of solution [A] of the thermosensitive recording layer coating solution described in Example 2 above, and mixed in the following composition ratio to prepare a thermosensitive recording material coating solution.
[C] Solution: Bisphenol S (Tokyo Chemical Industry) 25 parts, 25% PVA aqueous solution 20 parts, water 55 parts

[Water resistance evaluation test]
The thermal recording paper samples obtained in Example 2 and Comparative Example 1 were printed using a thermal printer (TH-M2/PP) manufactured by Okura Engineering Co., Ltd. with a pulse width of 1.2 msec, and the samples were immersed in water at 25°C for 24 hours. The Macbeth reflection density of the printed area (colored area) of the samples before and after the test was measured using a colorimeter manufactured by Gretag-Macbeth Co., Ltd., trade name "SpectroEye." Color measurements were performed using Illuminant C as the light source, ANSI A as the density standard, and a viewing angle of 2 degrees. The results are shown in Table 7 below. It can be seen that the higher the retention rate in this test, the better the water resistance. The retention rate was calculated using the following formula (I):
Residual rate (%) = [(Macbeth reflection density of the printed portion of the sample after the test) / (Macbeth reflection density of the printed portion of the sample before the test)] × 100 (I)

As is clear from Table 7 above, Example 2, which used the compound represented by formula (1) above as the color-developing compound, had a higher survival rate in the above test than Comparative Example 1, which used bisphenol S, a color-developing compound described in Patent Document 2. This means that the present invention can be said to provide superior water resistance in printed areas compared to conventional technology.

[Heat resistance of scalp]
The thermal recording paper samples obtained in Example 2 and Comparative Example 1 were kept at 90°C for 1 hour in a constant temperature incubator (DKN402, product name) manufactured by Yamato Scientific Co., Ltd. The ISO brightness of the background before and after the test was measured using a colorimeter (SpectroEye, product name) manufactured by Gretag-Macbeth. All color measurements were performed using Illuminant C as the light source, ANSI A as the density standard, and a viewing angle of 2 degrees. The results are shown in Table 8 below. The smaller the change in ISO brightness before and after the test, the more excellent the heat resistance of the background.

As is clear from Table 8 above, Example 2, in which the compound of the present invention was used as the color-developing compound, showed a smaller change in ISO whiteness in the above test than Comparative Example 1, in which bisphenol S, a color-developing compound described in Patent Document 2, was used. This means that the present invention can be said to have superior heat resistance in the background area compared to conventional technology.

[Plasticizer resistance test of printed area]
A single layer of vinyl chloride film (containing a plasticizer) was wrapped around a glass plate, and each thermal recording paper printed with an applied energy of 0.34 mJ/dot using a thermal printer (TH-M2/PP) manufactured by Okura Engineering Co., Ltd. was placed on top of the film. A single layer of vinyl chloride wrap film was then wrapped around the film and the resulting sheet was then stored in a 40°C environment for 2 hours. The Macbeth reflection density of the printed area of the sample before and after the test was measured using a colorimeter manufactured by GRETAG-MACBETH, trade name "SpectroEye." All color measurements were performed using Illuminant C as the light source, ANSI A as the density standard, and a viewing angle of 2 degrees. The remaining rate of the printed area was calculated using the following formula. The higher the remaining rate in this test, the better the plasticizer resistance of the printed area.
Residual rate (%) = [(reflection density of printed area after test) / (reflection density of printed area before test)] x 100
The results are shown in Table 9 below.

As is clear from Table 9 above, Example 2, in which the compound of the present invention was used as the developer, had a higher retention rate in the above test than Comparative Example 1, in which bisphenol S, a developer compound described in Patent Document 2, was used. It can be said that the present invention provides superior plasticizer resistance in printed areas compared to conventional technology.

[Oil resistance test of printed area]
Three drops of salad oil were placed on the printed area (color-developing area) of each thermal recording paper, which had been printed using a thermal printer (TH-M2/PP) manufactured by Okura Engineering Co., Ltd. with an applied energy of 0.34 mJ/dot, and the paper was left at 40°C for 1 hour. The Macbeth reflection density of the printed area of each sample was measured before and after the test using a colorimeter manufactured by Gretag-Macbeth Co., Ltd., trade name "SpectroEye." All color measurements were performed using Illuminant C as the light source, ANSI A as the density standard, and a viewing angle of 2 degrees. The remaining rate of the printed area was calculated using the following formula. It can be seen that the higher the remaining rate in this test, the better the oil resistance of the printed area.
Residual rate (%) = [(reflection density of printed area after test) / (reflection density of printed area before test)] x 100
The results are shown in Table 10 below.

As is clear from Table 10 above, Example 2, in which the compound of the present invention was used as the color-developing compound, had a higher retention rate in the above test than Comparative Example 1, in which bisphenol S, a color-developing compound described in Patent Document 2, was used. This means that the present invention can be said to provide superior oil resistance in printed areas compared to conventional technology.

The present invention provides a thermal recording material that has excellent heat resistance in the background, as well as water resistance, plasticizer resistance, and oil resistance in the printed area, and overcomes the drawback of color recording fading and disappearance under various conditions. This opens up the possibility of developing a wide range of applications for non-phenolic thermal recording materials, including food labels.

Claims (7)

A heat-sensitive recording material comprising at least one compound represented by the following general formula (1):

(In the formula, R ¹ to R ¹⁰ , R ²¹ , and R ²² each independently represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, a hydroxy group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.) 2. The heat-sensitive recording material according to claim 1, wherein in said formula (1), two or more of R ¹ to R ⁵ are hydrogen atoms, and two or more of R ⁶ to R ¹⁰ are hydrogen atoms. 2. The heat-sensitive recording material according to claim 1, wherein in formula (1), R ⁴ and R ⁵ are hydrogen atoms, and R ⁹ and R ¹⁰ are hydrogen atoms, and R ¹ to R ³ , R ⁶ to R ⁸ , R ²¹ , and R ²² are as defined above. 2. The heat-sensitive recording material according to claim 1, wherein, in formula (1), ^R3 and ^R8 each independently represent a hydrogen atom or an alkyl group, and ^R1 , ^R2 , ^R4 to ^R7 , ^R9 , ^R10 , ^R21 and ^R22 each represent a hydrogen atom. A thermosensitive recording layer comprising the thermosensitive recording material described in any one of claims 1 to 4. A thermal recording paper or thermal film comprising the thermal recording layer described in claim 5. A compound represented by the following general formula (2):

(In the formula, R ¹ to R ¹⁰ , R ²¹ , and R ²² each independently represent a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, a hydroxy group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, or an arylamino group.)