Developer and thermosensitive recording material

Abstract

Provided is a developer capable of yielding a thermosensitive recording material that has excellent color developing sensitivity and printing part preservability. The developer contains a compound represented by formula (1). (R1, R2, R3 are groups represented by formula (2), which may be the same or independently different from each other.) (In formula (2), m is 0 or 1, A is a linking group selected from the group consisting of -C(=O)-, -C(=S)-, -C(=O)-NH-, -C(=S)-NH-, -C(=O)-NH-SO2-, -C(=S)-NH-SO2-, -SO2-, -SO2-NH- and -C(=O)-O-, and B is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, or an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.)

Description

Color developer and thermal recording material

[0001] The present invention relates to a color developer capable of providing a heat-sensitive recording material excellent in color development sensitivity and print storage stability, and to a heat-sensitive recording material obtained by using the color developer.

[0002] In general, heat-sensitive recording materials having a heat-sensitive recording layer mainly composed of a colorless or pale-colored basic (electron-donating) leuco dye (hereinafter sometimes abbreviated as "dye") and an electron-accepting developer (hereinafter sometimes abbreviated as "developer") that reacts with the dye to develop color when heated have been widely put to practical use.

[0003] Many of the compounds used as such color developers are compounds that mainly contain a phenol structure, such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), bis(4-hydroxyphenyl)sulfone (bisphenol S), etc. However, due to concerns about environmental impact, studies are also being conducted to use compounds that do not have a phenol structure as color developers.

[0004] As a compound not having a phenol structure, for example, a color developer having a sulfonylurea structure compound having a p-toluenesulfonyloxyphenyl moiety is useful, but since the sulfonylurea skeleton is used, there are concerns about safety to the human body, and color developers utilizing safer raw materials are desired. For example, Patent Documents 1 to 6 disclose methods using ascorbic acid or an ascorbic acid derivative as a color developer.

[0005] JP 4-270683 JP 2-117890 JP 63-256488 JP 2018-103469 JP 63-179787 JP 60-101171

[0006] According to the investigations of the present inventors, when ascorbic acid or an ascorbic acid derivative shown in Patent Documents 1 to 6 is used as a color developer, it has not necessarily been possible to obtain a thermal recording material that satisfies both sufficient color development sensitivity and print area preservation properties such as heat resistance, plasticizer resistance, moisture resistance, water resistance, alcohol resistance, oil resistance, and grease resistance. That is, an object of the present invention is to provide a color developer that can provide a thermal recording material that is even more excellent in terms of color development sensitivity and print area preservation properties, and a thermal recording material obtained using the color developer.

[0007] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by using an ascorbic acid derivative, which is a compound represented by formula (1), as a color developer.

[0008] <1> A color developer containing a compound represented by the following formula (1): (In the formula (1), R1, R2, and R3 may be the same or different independently and represent a group represented by the following formula (2).) (In the formula (2), m is 0 or 1; A is a linking group selected from the group consisting of -C(=O)-, -C(=S)-, -C(=O)-NH-, -C(=S)-NH-, -C(=O)-NH-SO2-, -C(=S)-NH-SO2-, -SO2-, -SO2-NH-, and -C(=O)-O-; and B is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.) <2> The color developer according to <1>, wherein in formula (2), m is 1 and A is any one selected from the group consisting of -C(=O)-, -C(=O)-NH-, -SO2-, and -C(=O)-NH-SO2-. <3> The color developer according to <1> or <2>, wherein in formula (2), B is an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, or an arylalkyl group having 7 to 48 carbon atoms which may have a substituent. <4> The color developer according to any one of <1> to <3>, wherein in formula (2), m is 1, A is any one selected from the group consisting of -C(=O)-, -C(=O)-NH-, and -SO2-, and B is an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, or an aryl group having 6 to 18 carbon atoms which may have a substituent. <5> The color developer according to any one of <1> to <4>, wherein in formula (2), m is 1, A is -C(=O)- or -C(=O)-NH-, and B is an aliphatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent. <6> The color developer according to any one of <1> to <5>, wherein R1, R2, and R3 are the same in formula (1). <7> The color developer according to any one of <1> to <6>, wherein the compound represented by formula (1) is at least one of a compound represented by the following formula (1-1) or a compound represented by the following formula (1-2): (In formula (1-1), R1 to R3 have the same meanings as R1 to R3 in formula (1), respectively.) (In formula (1-2), R1 to R3 have the same meanings as R1 to R3 in formula (1), respectively.) <8> A thermosensitive recording material having a support and a thermosensitive recording layer provided on the support, wherein the thermosensitive recording layer contains the developer described in any one of <1> to <7> above. <9> The thermosensitive recording material according to <8> above, further containing at least one of a compound represented by the following formula (3) or a compound represented by the following formula (5): (In the formula (3), R 1a , R 2a , R 3a are the same or different independently, and are a hydrogen atom or a group represented by the following formula (4), and R 1a , R 2a , or R 3a At least one of these is a hydrogen atom.) (In the above formula (4), m a is 0 or 1, and A a is any linking group selected from the group consisting of -C(=O)-, -C(=S)-, -C(=O)-NH-, -C(=S)-NH-, -C(=O)-NH-SO2-, -C(=S)-NH-SO2-, -SO2-, -SO2-NH-, and -C(=O)-O-; B a is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent. (In the formula (5), R 31 , R 32are each independently any one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.) <10> The thermosensitive recording material according to <8> or <9>, wherein the thermosensitive recording layer contains a leuco dye. <11> The thermosensitive recording material according to any one of <8> to <10>, wherein the thermosensitive recording layer contains a sensitizer. <12> The thermosensitive recording material according to any one of <8> to <11>, wherein the thermosensitive recording layer contains a stabilizer.

[0009] According to the present invention, there are provided a color developer capable of providing a heat-sensitive recording material excellent in color development sensitivity and print storage stability, and a heat-sensitive recording material obtained by using the color developer.

[0010] The present invention will be described in detail below, but the present invention is not limited to the following description and can be modified as desired without departing from the gist of the present invention. In the present invention, when an expression using "~" is used with a numerical value or physical property value before and after it, the value before and after it is included in the expression.

[0011] In this disclosure, the term "substituent" refers not only to the usual meaning of a substituent, but also to the terminal end of a molecule among multiple chemical structural moieties when a single chemical structural moiety cannot be expressed. For example, the structure "-CH2-CH2-CH3" can be expressed as a single chemical structural moiety as a whole, namely, a propyl group, and is therefore interpreted as having no substituent. The propyl group is not interpreted as "removing one hydrogen atom from the methyl group to further bond an ethyl group as a substituent at the molecular end" or "removing one hydrogen atom from the ethyl group to further bond a methyl group as a substituent at the molecular end." Furthermore, for example, the structure "-CH2-CH2-F" is interpreted as a fluoroethyl group, but since it is expressed as a combination of fluoro and ethyl groups, it is interpreted as a case in which a single chemical structural moiety cannot be expressed, i.e., as multiple chemical structural moieties exist. Specifically, among the multiple chemical structural moieties, it is interpreted as "removing one hydrogen atom from the ethyl group to further bond a fluorine atom, a type of halogen substituent." Therefore, since the center of the molecule can be interpreted as an "ethyl group" and the terminal end of the molecule as fluorine, it can be said that fluorine is the substituent in this case. If multiple interpretations of the molecular center and molecular terminal are possible, the option with the largest number of carbon atoms at the molecular center is used to interpret the substituent. If the number of carbon atoms at the molecular center and the molecular terminal are the same, the option with the largest molecular weight at the molecular center is used to interpret the substituent.

[0012] In the present disclosure, the "substituent" is not particularly limited, and is, for example, one group selected from a hydroxy group, a carboxy group, a halogen atom, a nitro group, a cyano group, an amino group, an aliphatic hydrocarbon group, an alkoxy group, an alkenyloxy group, an aryl group, an aryloxy group, and an arylalkyl group, or a combination thereof. Examples of the halogen atom include fluorine, chlorine, bromine, iodine, astatine, and tennessine, and are preferably fluorine, chlorine, bromine, and iodine, more preferably fluorine, chlorine, and bromine, even more preferably fluorine and chlorine, and particularly preferably fluorine. Examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, and an alkynyl group, and are preferably an alkyl group or an alkenyl group. There is no particular limit to the number of carbon atoms in the aliphatic hydrocarbon group, but it is usually 1 to 8. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an i-propyl group, a butyl group, an i-butyl group, a t-butyl group, a pentyl group, an i-pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, and a 2-ethylhexyl group, and preferably a methyl group or an ethyl group. The number of carbon atoms in the alkenyl group is not particularly limited, but is usually 2 to 4. Examples of the alkenyl group include a vinyl group, an allyl group, a propenyl group, and a butenyl group, and preferably a vinyl group or an allyl group. The number of carbon atoms in the alkynyl group is not particularly limited, but is usually 2 to 4. Examples of the alkynyl group include an ethynyl group and a prop-2-yn-1-yl group. The number of carbon atoms in the alkoxy group is not particularly limited, but is typically 1 to 8. Examples include methoxy, ethoxy, propoxy, i-propoxy, butoxy, i-butoxy, t-butoxy, pentyloxy, i-pentyloxy, hexyloxy, cyclohexyloxy, heptyloxy, octyloxy, and 2-ethylhexyloxy groups, with methoxy and ethoxy being preferred. The number of carbon atoms in the alkenyloxy group is not particularly limited, but is typically 2 to 4. Examples include vinyloxy, allyloxy, 1-propenyloxy, and 2-propenyloxy groups, with vinyloxy and allyloxy being preferred. The number of carbon atoms in the aryl group is not particularly limited, but is typically 6 to 18. Examples of aryl groups include phenyl, naphthyl, and anthracenyl groups, with phenyl and naphthyl being preferred.The number of carbon atoms in the aryloxy group is not particularly limited, but is usually 6 to 18. Examples of the aryloxy group include a phenyloxy group, a naphthyloxy group, and an anthracenyloxy group, with the phenyloxy group being preferred. The number of carbon atoms in the arylalkyl group is not particularly limited, but is usually 7 to 20. An arylalkyl group is a group in which one hydrogen atom is removed from the above alkyl group and the above aryl group is bonded to it. Examples of the arylalkyl group include a benzyl group, a phenylethyl group, a phenylpropyl group, a naphthylmethyl group, a naphthylethyl group, a naphthylpropyl group, an anthracenylmethyl group, and an anthracenylethyl group, with the benzyl group, a phenylethyl group, a naphthylmethyl group, and an anthracenylmethyl group being preferred.

[0013] The phrase "may have a substituent" means that the group may have a substituent, but preferably does not have a substituent.

[0014] [Color Developer] The color developer of the present invention contains a compound represented by the following formula (1): In the present invention, the compound represented by formula (1) may be referred to as "compound (I)."

[0015]

[0016] The color developer of the present invention exhibits remarkable effects, such as excellent color development sensitivity and print storage stability, including heat resistance, plasticizer resistance, moisture resistance, water resistance, alcohol resistance, oil resistance, and grease resistance. The reason why the present invention exhibits such excellent effects is presumably due to the following reasons: The introduction of a highly hydrophobic functional group into ascorbic acid increases compatibility with the leuco dye, facilitating reaction with the leuco dye, thereby improving color development sensitivity, and at the same time, stabilizing the color development state and improving storage stability. Furthermore, the presence of a hydrophobic moiety in the molecule resulting from the group represented by formula (2) of compound (I) is thought to enhance resistance to heat, moisture, water, alcohol, etc., while the presence of a hydrophilic moiety resulting from the highly polar ascorbic acid skeleton is thought to simultaneously enhance resistance to plasticizers, oil, grease, etc., to a high level.

[0017] Furthermore, the compound represented by formula (1) contained in the developer of the present invention has three functional groups introduced into the 2,5,6-O site of ascorbic acid, which increases its molecular weight, and is therefore thought to prevent exudation into plasticizers, oils, greases, etc., thereby improving the storage stability of the printed area.

[0018] [R1, R2, R3 in Formula (1)] In Formula (1), R1, R2, and R3 are groups represented by the following Formula (2), and R1, R2, and R3 may be the same or different independently from one another. However, it is preferable that two of R1, R2, and R3 are the same, and more preferably that all three are the same. When two or three are the same, it is thought that uniform compatibility with the leuco dye is achieved, improving color development performance.

[0019]

[0020] [m in formula (2)] In formula (2), m is 0 or 1. However, m is preferably 1 from the viewpoint of appropriate compatibility with the leuco dye.

[0021] [A in Formula (2)] In Formula (2), A is any linking group selected from the group consisting of -C(=O)-, -C(=S)-, -C(=O)-NH-, -C(=S)-NH-, -C(=O)-NH-SO2-, -C(=S)-NH-SO2-, -SO2-, -SO2-NH-, and -C(=O)-O-. However, from the viewpoint of appropriate compatibility with the leuco dye, A is preferably any one selected from the group consisting of -C(=O)-, -C(=S)-, -C(=O)-NH-, -C(=O)-NH-SO-, and -SO-, more preferably any one selected from the group consisting of -C(=O)-, -C(=O)-NH-, -SO-, and -C(=O)-NH-SO-, and even more preferably any one selected from the group consisting of -C(=O)-, -C(=O)-NH-, and -SO-. Furthermore, A may be any linking group selected from the group consisting of -C(=O)-, -C(=O)-NH-, and -C(=O)-NH-SO-.

[0022] [B in Formula (2)] In Formula (2), B is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.

[0023] However, since thermal motion of the molecules is suppressed and storage stability is likely to be improved, B is preferably any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent, and more preferably at least one of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, or an aryl group having 6 to 18 carbon atoms which may have a substituent. B may also be at least one of an aryl group having 6 to 18 carbon atoms which may have a substituent, or an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.

[0024] Examples of the aliphatic hydrocarbon group having 1 to 30 carbon atoms include an alkyl group, an alkenyl group, and an alkynyl group, preferably an alkyl group or an alkenyl group, and more preferably an alkyl group. The aliphatic hydrocarbon group may be linear, branched, or cyclic. From the viewpoints of suppressing thermal motion of molecules and thus easily improving storage stability, and compatibility with the leuco dye, the number of carbon atoms in the aliphatic hydrocarbon group having 1 to 30 carbon atoms, which may have a substituent, is preferably 2 to 18, more preferably 4 to 18, and even more preferably 6 to 18. In the case of an alkenyl group or alkynyl group, the number of carbon atoms is 2 or more.

[0025] Specific examples of the aliphatic hydrocarbon group include a methyl group, an ethyl group, a propyl group, an i-propyl group, a butyl group, an i-butyl group, a t-butyl group, a pentyl group, an i-pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a dodecyl group, a tetradecyl group, a palmityl group, a stearyl group, a behenyl group, a vinyl group, an allyl group, a propenyl group, a butenyl group, an ethynyl group, and a prop-2-yn-1-yl group. Among these, any one of an ethyl group, a propyl group, an i-propyl group, a butyl group, an i-butyl group, a t-butyl group, a pentyl group, an i-pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, a tetradecyl group, a palmityl group, a stearyl group, a vinyl group, an allyl group, and a propenyl group is preferred, a butyl group, a t-butyl group, a pentyl group, a hexyl group, a cyclohexyl group, an octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, a tetradecyl group, a palmityl group, and a stearyl group is more preferred, and a hexyl group, a cyclohexyl group, an octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, a tetradecyl group, a palmityl group, and a stearyl group is even more preferred.

[0026] Examples of the alkoxy group having 1 to 30 carbon atoms include the following. From the viewpoints of suppressing thermal motion of molecules and easily improving storage stability, and compatibility with the leuco dye, an alkoxy group having 2 to 18 carbon atoms is preferred, an alkoxy group having 4 to 18 carbon atoms is more preferred, and an alkoxy group having 6 to 18 carbon atoms is even more preferred.

[0027] Specific examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an i-propoxy group, a butoxy group, an i-butoxy group, a t-butoxy group, a pentyloxy group, an i-pentyloxy group, a hexyloxy group, a cyclohexyloxy group, a heptyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a nonyloxy group, a decyloxy group, a dodecyloxy group, a tetradecyloxy group, a palmityloxy group, a stearyloxy group, and a behenyloxy group. Among these, any one of ethoxy group, propoxy group, i-propoxy group, butoxy group, i-butoxy group, t-butoxy group, pentyloxy group, i-pentyloxy group, hexyloxy group, cyclohexyloxy group, heptyloxy group, octyloxy group, 2-ethylhexyloxy group, decyloxy group, dodecyloxy group, tetradecyloxy group, palmityloxy group, and stearyloxy group is preferable, and butoxy group, i-butoxy group, t-butoxy group, pentyloxy group, i-pentyloxy group, hexyloxy group, cyclohexyloxy group, heptyloxy group, octyloxy group, 2-ethylhexyloxy group, decyloxy group, dodecyloxy group, tetradecyloxy group, palmityloxy group, and stearyloxy group is preferable. More preferably, the group is any one of a hexyloxy group, a cyclohexyloxy group, a heptyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a decyloxy group, a dodecyloxy group, a tetradecyloxy group, a palmityloxy group, or a stearyloxy group, and even more preferably any one of a hexyloxy group, a cyclohexyloxy group, a heptyloxy group, an octyloxy group, a 2-ethylhexyloxy group, a decyloxy group, a dodecyloxy group, a tetradecyloxy group, a palmityloxy group, or a stearyloxy group.

[0028] Examples of aryl groups having 6 to 18 carbon atoms include the following. From the viewpoint of compatibility with the leuco dye, aryl groups having 6 to 12 carbon atoms are preferred, and aryl groups having 6 carbon atoms are more preferred. Specific examples of unsubstituted aryl groups having 6 to 18 carbon atoms include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, and an anthracenyl group. Of these, a phenyl group, a 1-naphthyl group, or a 2-naphthyl group is preferred, and a phenyl group is more preferred.

[0029] Examples of substituted aryl groups having 6 to 18 carbon atoms include o-tolyl, m-tolyl, p-tolyl, 2,3-xylyl, 2,4-xylyl, 2,5-xylyl, 2,6-xylyl, 3,4-xylyl, 3,5-xylyl, 2,4,6-mesityl, o-ethylphenyl, m-ethylphenyl, p-ethylphenyl, o-propylphenyl, m-propylphenyl, p-propylphenyl, o-i-propylphenyl, m-i-propylphenyl, p-i-propylphenyl, o-butylphenyl, m-propylphenyl, m-propylphenyl, p ... -butylphenyl group, p-butylphenyl group, o-i-butylphenyl group, mi-i-butylphenyl group, p-i-butylphenyl group, o-t-butylphenyl group, m-t-butylphenyl group, p-t-butylphenyl group, o-pentylphenyl group, m-pentylphenyl group, p-pentylphenyl group, o-i-pentylphenyl group, mi-i-pentylphenyl group, p-i-pentylphenyl group, o-hexylphenyl group, m-hexylphenyl group, p-hexylphenyl group, o-cyclohexylphenyl group, m-cyclohexylphenyl group, p-cyclo hexylphenyl group, o-heptylphenyl group, m-heptylphenyl group, p-heptylphenyl group, o-octylphenyl group, m-octylphenyl group, p-octylphenyl group, o-2-ethylhexylphenyl group, m-2-ethylhexylphenyl group, p-2-ethylhexylphenyl group, o-vinylphenyl group, m-vinylphenyl group, p-vinylphenyl group, o-allylphenyl group, m-allylphenyl group, p-allylphenyl group, o-methoxyphenyl group, m-methoxyphenyl group, p-methoxyphenyl group, o-ethoxyphenyl group, m -ethoxyphenyl group, p-ethoxyphenyl group, o-propoxyphenyl group, m-propoxyphenyl group, p-propoxyphenyl group, o-i-propoxyphenyl group, m-i-propoxyphenyl group, p-i-propoxyphenyl group, o-vinyloxyphenyl group, m-vinyloxyphenyl group, p-vinyloxyphenyl group, o-allyloxyphenyl group, m-allyloxyphenyl group, p-allyloxyphenyl group, o-phenoxyphenyl group, m-phenoxyphenyl group, p-phenoxyphenyl group, o-biphenyl group, m-biphenyl group,p-biphenyl group, o-cumylphenyl group, m-cumylphenyl group, p-cumylphenyl group, 2-methyl-1-naphthyl group, 3-methyl-1-naphthyl group, 4-methyl-1-naphthyl group, 5-methyl-1-naphthyl group, 6-methyl-1-naphthyl group, 7-methyl-1-naphthyl group, 8-methyl-1-naphthyl group, 2-ethyl-1-naphthyl group, 3-ethyl-1-naphthyl group, 4-ethyl-1-naphthyl group, 5-ethyl-1-naphthyl group, 6-ethyl-1-naphthyl group, 7-ethyl-1-naphthyl group, 8-ethyl-1-naphthyl group, 2-vinyl-1-naphthyl group, a vinyl group, a 3-vinyl-1-naphthyl group, a 4-vinyl-1-naphthyl group, a 5-vinyl-1-naphthyl group, a 6-vinyl-1-naphthyl group, a 7-vinyl-1-naphthyl group, a 8-vinyl-1-naphthyl group, a 2-allyl-1-naphthyl group, a 3-allyl-1-naphthyl group, a 4-allyl-1-naphthyl group, a 5-allyl-1-naphthyl group, a 6-allyl-1-naphthyl group, a 7-allyl-1-naphthyl group, a 8-allyl-1-naphthyl group, a 2-methoxy-1-naphthyl group, a 3-methoxy-1-naphthyl group, a 4-methoxy-1-naphthyl group, a 5-methoxy-1-naphthyl group, a 6-methyl-1-naphthyl group, a 2 ... ethoxy-1-naphthyl group, 7-methoxy-1-naphthyl group, 8-methoxy-1-naphthyl group, 2-ethoxy-1-naphthyl group, 3-ethoxy-1-naphthyl group, 4-ethoxy-1-naphthyl group, 5-ethoxy-1-naphthyl group, 6-ethoxy-1-naphthyl group, 7-ethoxy-1-naphthyl group, 8-ethoxy-1-naphthyl group, 2-vinyloxy-1-naphthyl group, 3-vinyloxy-1-naphthyl group, 4-vinyloxy-1-naphthyl group, 5-vinyloxy-1-naphthyl group, 6-vinyloxy-1-naphthyl group, 7-vinyloxy-1-naphthyl group, 8-vinyloxy-1-naphthyl group, 2-allyloxy-1-naphthyl group, 3-allyloxy-1-naphthyl group, 4-allyloxy-1-naphthyl group, 5-allyloxy-1-naphthyl group, 6-allyloxy-1-naphthyl group, 7-allyloxy-1-naphthyl group, 8-allyloxy-1-naphthyl group, 1-methyl-2-naphthyl group, 3-methyl-2-naphthyl group, 4-methyl-2-naphthyl group, 5-methyl-2-naphthyl group, 6-methyl-2-naphthyl group, 7-methyl-2-naphthyl group, 8-methyl-2-naphthyl group, 1-ethyl-2-naphthyl group,3-ethyl-2-naphthyl group, 4-ethyl-2-naphthyl group, 5-ethyl-2-naphthyl group, 6-ethyl-2-naphthyl group, 7-ethyl-2-naphthyl group, 8-ethyl-2-naphthyl group, 1-vinyl-2-naphthyl group, 3-vinyl-2-naphthyl group, 4-vinyl-2-naphthyl group, 5-vinyl-2-naphthyl group, 6-vinyl-2-naphthyl group, 7-vinyl-2-naphthyl group, 8-vinyl-2-naphthyl group, 1- Allyl-2-naphthyl group, 3-allyl-2-naphthyl group, 4-allyl-2-naphthyl group, 5-allyl-2-naphthyl group, 6-allyl-2-naphthyl group, 7-allyl-2-naphthyl group, 8-allyl-2-naphthyl group, 1-methoxy-2-naphthyl group, 3-methoxy-2-naphthyl group, 4-methoxy-2-naphthyl group, 5-methoxy-2-naphthyl group, 6-methoxy-2-naphthyl group, 7-methoxy-2-naphthyl group group, 8-methoxy-2-naphthyl group, 1-ethoxy-2-naphthyl group, 3-ethoxy-2-naphthyl group, 4-ethoxy-2-naphthyl group, 5-ethoxy-2-naphthyl group, 6-ethoxy-2-naphthyl group, 7-ethoxy-2-naphthyl group, 8-ethoxy-2-naphthyl group, 1-vinyloxy-2-naphthyl group, 3-vinyloxy-2-naphthyl group, 4-vinyloxy-2-naphthyl group, 5-vinyloxy-2- naphthyl group, a 6-vinyloxy-2-naphthyl group, a 7-vinyloxy-2-naphthyl group, an 8-vinyloxy-2-naphthyl group, a 1-allyloxy-2-naphthyl group, a 3-allyloxy-2-naphthyl group, a 4-allyloxy-2-naphthyl group, a 5-allyloxy-2-naphthyl group, a 6-allyloxy-2-naphthyl group, a 7-allyloxy-2-naphthyl group, and an 8-allyloxy-2-naphthyl group.

[0030] From the viewpoint of compatibility with the leuco dye, examples of the aryl group having 6 to 18 carbon atoms and having a substituent include an o-tolyl group, an m-tolyl group, a p-tolyl group, a 2,3-xylyl group, a 2,4-xylyl group, a 2,5-xylyl group, a 2,6-xylyl group, a 3,4-xylyl group, a 3,5-xylyl group, a 2,4,6-mesityl group, an o-ethylphenyl group, an m-ethylphenyl group, a p-ethylphenyl group, an o-propylphenyl group, an m-propylphenyl group, a p-propylphenyl group, an o-i-propylphenyl group, an m-i-propylphenyl group, and a p-i-propylphenyl group. , o-butylphenyl group, m-butylphenyl group, p-butylphenyl group, o-i-butylphenyl group, m-i-butylphenyl group, p-i-butylphenyl group, o-t-butylphenyl group, m-t-butylphenyl group, p-t-butylphenyl group, o-hexylphenyl group, m-hexylphenyl group, p-hexylphenyl group, o-cyclohexylphenyl group, m-cyclohexylphenyl group, p-cyclohexylphenyl group, o-octylphenyl group, m-octylphenyl group, p-octylphenyl group, o-2-ethylhexylphenyl group, m 2-ethylhexylphenyl group, p-2-ethylhexylphenyl group, o-vinylphenyl group, m-vinylphenyl group, p-vinylphenyl group, o-allylphenyl group, m-allylphenyl group, p-allylphenyl group, o-methoxyphenyl group, m-methoxyphenyl group, p-methoxyphenyl group, o-ethoxyphenyl group, m-ethoxyphenyl group, p-ethoxyphenyl group, o-vinyloxyphenyl group, m-vinyloxyphenyl group, p-vinyloxyphenyl group, o-allyloxyphenyl group, m-allyloxyphenyl group, p-allylo an o-phenoxyphenyl group, an m-phenoxyphenyl group, a p-phenoxyphenyl group, an o-biphenyl group, an m-biphenyl group, a p-biphenyl group, an o-cumylphenyl group, an m-cumylphenyl group, a p-cumylphenyl group, a 2-methyl-1-naphthyl group, a 3-methyl-1-naphthyl group, a 4-methyl-1-naphthyl group, a 5-methyl-1-naphthyl group, a 6-methyl-1-naphthyl group, a 7-methyl-1-naphthyl group, an 8-methyl-1-naphthyl group, a 2-ethyl-1-naphthyl group, a 3-ethyl-1-naphthyl group, a 4-ethyl-1-naphthyl group,5-ethyl-1-naphthyl group, 6-ethyl-1-naphthyl group, 7-ethyl-1-naphthyl group, 8-ethyl-1-naphthyl group, 2-methoxy-1-naphthyl group, 3-methoxy-1-naphthyl group, 4-methoxy-1-naphthyl group, 5-methoxy-1-naphthyl group, 6-methoxy-1-naphthyl group, 7-methoxy-1-naphthyl group, 8-methoxy-1-naphthyl group, 2-ethoxy-1-naphthyl group, 3-ethoxy-1-naphthyl group, 4-ethoxy-1-naphthyl group, 5-ethoxy-1-naphthyl group, 6-ethoxy-1-naphthyl group, 7-ethoxy-1-naphthyl group a 1-methoxy-2-naphthyl group, a 3-methoxy-2-naphthyl group, a 4-methoxy-2-naphthyl group, a 5-ethoxy-1-naphthyl group, a 2-methyl-2-naphthyl group, a 3-methyl-2-naphthyl group, a 4-methyl-2-naphthyl group, a 5-methyl-2-naphthyl group, a 6-methyl-2-naphthyl group, a 7-methyl-2-naphthyl group, a 8-methyl-2-naphthyl group, a 1-ethyl-2-naphthyl group, a 3-ethyl-2-naphthyl group, a 4-ethyl-2-naphthyl group, a 5-ethyl-2-naphthyl group, a 6-ethyl-2-naphthyl group, a 7-ethyl-2-naphthyl group, a 8-ethyl-2-naphthyl group, a 1-methoxy-2-naphthyl group, a 3-methoxy-2-naphthyl group, a 4-methoxy ...7-ethyl-2-naphthyl group, a 8-ethyl-2-naphthyl group, a 1-methoxy-2-naphthyl group, a 3-methoxy-2-naphthyl group, a 4-methoxy-2-naphthyl group, a 5-ethyl- Preferably, the alkyl group is any one of 1-ethoxy-2-naphthyl, 2-ethoxy-2-naphthyl, 3-ethoxy-2-naphthyl, 4-ethoxy-2-naphthyl, 5-ethoxy-2-naphthyl, 6-ethoxy-2-naphthyl, 7-ethoxy-2-naphthyl, and 8-ethoxy-2-naphthyl groups, and more preferably any one of o-tolyl, m-tolyl, p-tolyl, 2,3-xylyl, 2,4-xylyl, 2,5-xylyl, and 2,6-xylyl. an aryl group, a 3,4-xylyl group, a 3,5-xylyl group, a 2,4,6-mesityl group, an o-ethylphenyl group, an m-ethylphenyl group, a p-ethylphenyl group, an o-vinylphenyl group, an m-vinylphenyl group, a p-vinylphenyl group, an o-allylphenyl group, an m-allylphenyl group, a p-allylphenyl group, an o-methoxyphenyl group, an m-methoxyphenyl group, a p-methoxyphenyl group, an o-ethoxyphenyl group, an m-ethoxyphenyl group, a p-ethoxyphenyl group, an o-vinyloxyphenyl group, an m-vinyloxyphenyl group, a p-vinyloxyphenyl group,More preferably, it is any one of an o-allyloxyphenyl group, an m-allyloxyphenyl group, a p-allyloxyphenyl group, an o-phenoxyphenyl group, an o-phenoxyphenyl group, an m-phenoxyphenyl group, a p-phenoxyphenyl group, an o-biphenyl group, an m-biphenyl group, a p-biphenyl group, an o-cumylphenyl group, an m-cumylphenyl group, and a p-cumylphenyl group.

[0031] The arylalkyl group having 7 to 48 carbon atoms is a group in which one hydrogen atom is removed from the alkyl group described above and the aryl group described above is bonded to the alkyl group described above. From the viewpoint of compatibility with the leuco dye, an arylalkyl group having 7 to 30 carbon atoms is preferred, and an arylalkyl group having 7 to 18 carbon atoms is more preferred.

[0032] Examples of unsubstituted arylalkyl groups having 7 to 48 carbon atoms include benzyl, 1-phenylethyl, 2-phenylethyl, 1-phenylpropyl, 2-phenylpropyl, 3-phenylpropyl, 1-phenylbutyl, 2-phenylbutyl, 3-phenylbutyl, 4-phenylbutyl, cumyl, naphthylmethyl, 1-naphthylethyl, 2-naphthylethyl, 1-naphthylpropyl, 2-naphthylpropyl, 3-naphthylpropyl, 1-naphthylbutyl, 2-naphthylbutyl, 3-naphthylbutyl, and 4-naphthylbutyl groups. Among these, any one of benzyl group, 1-phenylethyl group, 2-phenylethyl group, 1-phenylpropyl group, 2-phenylpropyl group, 3-phenylpropyl group, cumyl group, naphthylmethyl group, 1-naphthylethyl group, 2-naphthylethyl group, 1-naphthylpropyl group, 2-naphthylpropyl group, and 3-naphthylpropyl group is preferred, and any one of benzyl group, 1-phenylethyl group, 2-phenylethyl group, cumyl group, naphthylmethyl group, 1-naphthylethyl group, and 2-naphthylethyl group is more preferred.

[0033] Examples of the substituted arylalkyl group having 7 to 48 carbon atoms include an o-methylbenzyl group, an m-methylbenzyl group, a p-methylbenzyl group, an o-vinylbenzyl group, an m-vinylbenzyl group, a p-vinylbenzyl group, an o-methoxybenzyl group, an m-methoxybenzyl group, a p-methoxybenzyl group, an o-vinyloxybenzyl group, an m-vinyloxybenzyl group, a p-vinyloxybenzyl group, an o-allyloxybenzyl group, an m-allyloxybenzyl group, a p-allyloxybenzyl group, an o-methylcumyl group, an m-methylcumyl group, a p-methylcumyl group, an o-methoxycumyl group, an m-methoxycumyl group, and a p-methoxycumyl group. Among these, any one of an o-methylbenzyl group, an m-methylbenzyl group, a p-methylbenzyl group, an o-vinylbenzyl group, an m-vinylbenzyl group, a p-vinylbenzyl group, an o-methoxybenzyl group, an m-methoxybenzyl group, a p-methoxybenzyl group, an o-vinyloxybenzyl group, an m-vinyloxybenzyl group, a p-vinyloxybenzyl group, an o-allyloxybenzyl group, an m-allyloxybenzyl group, and a p-allyloxybenzyl group is preferred, and any one of an o-methylbenzyl group, an m-methylbenzyl group, a p-methylbenzyl group, an o-vinylbenzyl group, an m-vinylbenzyl group, a p-vinylbenzyl group, an o-methoxybenzyl group, an m-methoxybenzyl group, and a p-methoxybenzyl group is more preferred.

[0034] From the viewpoints of compatibility with the leuco dye, molecular weight, and melting point, the formula (2) is preferably the following (2A), more preferably the following (2B), even more preferably the following (2C), and still more preferably the following (2D):

[0035] (2A): m is 1, A is any one selected from the group consisting of -C(=O)-, -C(=S)-, -C(=O)-NH-, -C(=O)-NH-SO2-, and -SO2-, and B is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.

[0036] (2B): m is 1, A is any one selected from the group consisting of -C(=O)-, -C(=O)-NH-, -C(=O)-NH-SO2-, and -SO2-, and B is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.

[0037] (2C): m is 1, A is any one selected from the group consisting of -C(=O)-, -C(=O)-NH-, and -SO2-, and B is an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, or an aryl group having 6 to 18 carbon atoms which may have a substituent.

[0038] (2D): m is 1, A is -C(=O)- or -C(=O)-NH-, and B is an aliphatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent.

[0039] From the viewpoints of compatibility with the leuco dye, molecular weight, and melting point, R, R, and R in formula (1) are the same group represented by formula (2), and formula (2) is preferably (2A) above, more preferably (2B) above, even more preferably (2C) above, and even more preferably (2D) above.

[0040] The compound represented by formula (1) has isomers, and there are compounds represented by the following formulas (1-1), (1-2), (1-3), and (1-4). From the viewpoint of structural stability in consideration of steric hindrance, at least one of the compounds represented by formula (1-1) and formula (1-2) is preferred.

[0041]

[0042]

[0043]

[0044]

[0045] In formulas (1-1) to (1-4), R1 to R3 have the same meanings as R1 to R3 in formula (1), respectively.

[0046] [Thermal Recording Material] The thermal recording material of the present invention is a thermal recording material having a support and a thermal recording layer provided on the support, and the thermal recording layer contains the color developer of the present invention. In the present invention, the "thermal recording material" refers to any material having a thermal recording layer on a support, and the material may be in the form of paper, film, synthetic paper, card, etc. The thermal recording material of the present invention has a thermal recording layer on a support, but may also have a protective layer, under layer, back layer, intermediate layer, etc., as described below, if necessary. Here, "on the support" refers to at least one side of the support, and typically refers to one side. Furthermore, "on the support" means that the layer is present on at least a portion of the support.

[0047] [Thermosensitive Recording Layer] The thermosensitive recording material of the present invention has a thermosensitive recording layer containing the color developer of the present invention. The thermosensitive recording layer may contain, in addition to the color developer of the present invention, a leuco dye, a color developer other than the compound represented by formula (1), compound (II) described below, a sensitizer, a stabilizer, a binder, a crosslinking agent, a pigment, a lubricant, and other additives.

[0048] <Leuco Dye> In the present invention, the thermosensitive recording layer preferably contains a leuco dye. Leuco dyes are typically basic, and any leuco dyes known in the art for pressure-sensitive or thermosensitive recording paper can be used. Specific examples of leuco dyes include triphenylmethane-based leuco dyes, fluoran-based leuco dyes, fluorene-based leuco dyes, and divinyl-based leuco dyes. Specific examples of representative colorless or pale-colored dyes (dye precursors) are shown below. These leuco dyes (leuco dye precursors) may be used alone or in combination of two or more. The leuco dye is preferably used in an amount of 10 to 200 parts by weight, more preferably 15 to 150 parts by weight, and even more preferably 20 to 100 parts by weight, per 100 parts by weight of the developer.

[0049] Examples of triphenylmethane leuco dyes include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone); 3,3-bis(p-dimethylaminophenyl)phthalide (also known as malachite green lactone); and the like.

[0050] Examples of fluoran leuco dyes include 3-diethylamino-6-methylfluoran; 3-diethylamino-6-methyl-7-anilinofluoran; 3-diethylamino-6-methyl-7-(o,p-dimethylanilino)fluoran; 3-diethylamino-6-methyl-7-chlorofluoran; 3-diethylamino-6-methyl-7-(m-trifluoromethylanilino)fluoran; 3-diethylamino-6-methyl-7-(o-chloroanilino)fluoran; and 3-diethylamino-6-methyl-7-(p-chloroanilino)fluoran. ; 3-diethylamino-6-methyl-7-(o-fluoroanilino)fluoran; 3-diethylamino-6-methyl-7-(m-methylanilino)fluoran; 3-diethylamino-6-methyl-7-octylanilinofluoran; 3-diethylamino-6-methyl-7-octylaminofluoran; 3-diethylamino-6-methyl-7-benzylaminofluoran; 3-diethylamino-6-methyl-7-dibenzylaminofluoran; 3-diethylamino-6-chloro-7-methylfluoran; 3-diethylamino-6-chloro -7-anilinofluoran; 3-diethylamino-6-chloro-7-p-methylanilinofluoran; 3-diethylamino-6-ethoxyethyl-7-anilinofluoran; 3-diethylamino-7-methylfluoran; 3-diethylamino-7-chlorofluoran; 3-diethylamino-7-(m-trifluoromethylanilino)fluoran; 3-diethylamino-7-(o-chloroanilino)fluoran; 3-diethylamino-7-(p-chloroanilino)fluoran; 3-diethylamino-7-(o-fluoroanilino)fluoran fluoran; 3-diethylamino-benzo[a]fluoran; 3-diethylamino-benzo[c]fluoran; 3-dibutylamino-6-methyl-fluoran; 3-dibutylamino-6-methyl-7-anilinofluoran; 3-dibutylamino-6-methyl-7-(o,p-dimethylanilino)fluoran; 3-dibutylamino-6-methyl-7-(o-chloroanilino)fluoran; 3-dibutylamino-6-methyl-7-(p-chloroanilino)fluoran; 3-dibutylamino-6-methyl-7-(o-fluoroanilino)fluoran;3-dibutylamino-6-methyl-7-(m-trifluoromethylanilino)fluoran; 3-dibutylamino-6-methyl-chlorofluoran; 3-dibutylamino-6-ethoxyethyl-7-anilinofluoran; 3-dibutylamino-6-chloro-7-anilinofluoran; 3-dibutylamino-6-methyl-7-p-methylanilinofluoran; 3-dibutylamino-7-(o-chloroanilino)fluoran; 3-dibutylamino-7-(o-fluoroanilino)fluoran; 3-di-pentylamino-6-methyl-7-anilinofluoran ; 3-di-pentylamino-6-methyl-7-(p-chloroanilino)fluoran; 3-di-pentylamino-7-(m-trifluoromethylanilino)fluoran; 3-di-pentylamino-6-chloro-7-anilinofluoran; 3-di-pentylamino-7-(p-chloroanilino)fluoran; 3-pyrrolidino-6-methyl-7-anilinofluoran; 3-piperidino-6-methyl-7-anilinofluoran; 3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluoran; 3-(N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluoran; 3-(N-ethyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran; 3-(N-ethyl-N-xylamino)-6-methyl-7-(p-chloroanilino)fluoran; 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran; 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran; 3-(N-ethyl-N-isoamylamino)-6-chloro-7-anilinofluoran; 3-(N-ethyl-N-tetrahydrofurfurylamino)-6- Methyl-7-anilinofluoran; 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluoran; 3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluoran; 3-cyclohexylamino-6-chlorofluoran; 2-(4-oxahexyl)-3-dimethylamino-6-methyl-7-anilinofluoran; 2-(4-oxahexyl)-3-diethylamino-6-methyl-7-anilinofluoran; 2-(4-oxahexyl)-3-dipropylamino-6-methyl-7-anilinofluoran;2-Methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran; 2-Methoxy-6-p-(p-dimethylaminophenyl)aminoanilinofluoran; 2-Chloro-3-methyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran; 2-Chloro-6-p-(p-dimethylaminophenyl)aminoanilinofluoran; 2-Nitro-6-p-(p-diethylaminophenyl)aminoanilinofluoran; 2-Amino-6-p-(p-diethylaminophenyl)aminoanilinofluoran; 2-Diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluoran; 2-Phenyl Examples thereof include 2-benzyl-6-p-(p-phenylaminophenyl)aminoanilinofluoran; 2-hydroxy-6-p-(p-phenylaminophenyl)aminoanilinofluoran; 3-methyl-6-p-(p-dimethylaminophenyl)aminoanilinofluoran; 3-diethylamino-6-p-(p-diethylaminophenyl)aminoanilinofluoran; 3-diethylamino-6-p-(p-dibutylaminophenyl)aminoanilinofluoran; 2,4-dimethyl-6-[(4-dimethylamino)anilino]fluoran, and the like.

[0051] Examples of fluorene-based leuco dyes include 3,6,6'-tris(dimethylamino)spiro[fluorene-9,3'-phthalide]; 3,6,6'-tris(diethylamino)spiro[fluorene-9,3'-phthalide]; and the like.

[0052] Examples of divinyl leuco dyes include 3,3-bis[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl]-4,5,6,7-tetrabromophthalide; 3,3-bis[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl]-4,5,6,7-tetrachlorophthalide; 3,3-bis[1,1-bis(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrabromophthalide; and 3,3-bis[1-(4-methoxyphenyl)-1-(4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide.

[0053] Other leuco dyes include 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide; 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindol-3-yl)-4-azaphthalide; 3-(4-cyclohexylethylamino-2-methoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide; 3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide; 3,6-bis(diethylamino)fluoran-γ-(3′-nitro)anilinolactam; 3, Examples include 6-bis(diethylamino)fluoran-γ-(4′-nitro)anilinolactam; 1,1-bis[2′,2′,2″,2″-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2,2-dinitrileethane; 1,1-bis[2′,2′,2″,2″-tetrakis-(p-dimethylaminophenyl)-ethenyl]-2-β-naphthoylethane; 1,1-bis[2′,2′,2″,2″-tetrakis(p-dimethylaminophenyl)ethenyl]-2,2-diacetylethane; and bis[2,2,2′,2′-tetrakis(p-dimethylaminophenyl)ethenyl]-methylmalonic acid dimethyl ester. Among these, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide [also known as crystal violet lactone], 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-octylaminofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, and 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran are preferred.

[0054] <Other Color Developers> The thermosensitive recording layer may contain a color developer other than Compound (I) of the present invention (hereinafter referred to as "other color developers") within a range that does not impair the effects of the present invention. Any other color developer known in the field of conventional pressure-sensitive or thermosensitive recording paper can be used as the other color developer, and there are no particular limitations, but an electron-accepting color developer is preferred. One type of other color developer may be used alone, or two or more types may be used in combination. When other color developers are used, the amounts used are preferably Compound (I):other color developer = 99:1 to 30:70 parts by mass, more preferably Compound (I):other color developer = 99:1 to 50:50 parts by mass, and even more preferably Compound (I):other color developer = 99:1 to 60:40 parts by mass, based on 100 parts by mass of the total amount of color developers.

[0055] By using other color developers, it is possible to obtain an excellent heat-sensitive recording material that maintains high color development sensitivity and further improves image preservation properties such as heat resistance, moisture resistance, and water resistance.

[0056] Examples of other color developers include bisphenol compounds, urea compounds, novolak-type phenol compounds, and amino acid derivative compounds. Compound (II), which will be described later, may also be used as the other color developer.

[0057] Examples of bisphenol compounds include 4,4'-isopropylidenediphenol, 2,2'-bis(4-hydroxy-3-methylphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, di(4-hydroxy-3-methylphenyl)sulfide, 2,2'-thiobis(3-tert-octylphenol), 2,2'-thiobis(4-tert-octylphenol), 4,4'-dihydroxydiphenyl sulfone, and 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-propoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 3,4-dihydroxyphenyl-4'-methylphenyl sulfone, 2,4-bis(phenylsulfonyl)phenol, bisphenol sulfone crosslinked compounds described in Japanese Patent No. 3913820, and bisphenol sulfone derivatives described in Japanese Patent No. 4004289.

[0058] Examples of urea compounds include 4,4'-bis(3-(phenoxycarbonylamino)methylphenylureido)diphenyl sulfone, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)urea described in Japanese Patent No. 4601174, 4,4'-bis(3-tosylureido)diphenylmethane described in JP-A-2011-105638, N-[2-(3-phenylureido)phenyl]benzenesulfonamide described in JP-A-2016-165835, N-[2-(acetoxy)phenyl]-N'-phenylurea, N-[3-(acetoxy)phenyl]-N'-phenylurea, N-[2-(benzoyloxy)phenyl]-N'-phenylurea, and N-[3-(benzoyloxy)phenyl]- N'-phenylurea, [3- (3-phenylureido) phenyl] = 4-methylbenzenesulfonate described in Japanese Patent Application No. 2023-515875, 4-methylphenyl = [3- [ [ (phenylamino) carbonyl] amino] benzenesulfonate] described in WO2022 / 045287, N, N'-bis (3- [ {4-methylphenyl} sulfonylamino] phenyl) urea described in Japanese Patent Application No. 2021-131277, N, N'-di - [3- (p- toluenesulfonyloxy) phenyl] urea described in Japanese Patent Application No. 2019-539154, 3- [ (phenylcarbamoyl) amino] phenyl-4-methylbenzenesulfonate described in Japanese Patent Application No. 2015-254099, N, N'-di [3- (p- toluenesulfonyl) oxy] phenyl urea described in Japanese Patent Application No. 2017-167444, and the like.

[0059] Examples of novolak-type phenolic compounds include phenol-formalin condensates described in WO 02 / 098674.

[0060] Examples of the amino acid derivative compounds include N-(m-tolylaminocarbonyl)-phenylalanine, N-(p-toluenesulfonyl)-phenylalanine, N-(benzyloxycarbonyl)-valine, N-(m-tolylaminocarbonyl)-methionine, N-(m-tolylaminocarbonyl)-tyrosine, N-(m-tolylaminocarbonyl)-phenylglycine, N-(m-tolylaminocarbonyl)-valine, and N-( and amino acid derivatives such as N-(m-tolylaminocarbonyl)-cysteine-S-benzyl, N-(m-tolylaminocarbonyl)-β-alanine, N-phenylaminothiocarbonyl-glycylglycine, N-(p-toluenesulfonylaminocarbonyl)-phenylalanine-methyl ester, N-(p-toluenesulfonyl)-β-alanine, N-(p-tolylaminocarbonyl)-methionine, and N-(phenylaminocarbonyl)-methionine.

[0061] In addition to the compounds listed above, inorganic acidic substances such as activated clay, attapulgite, colloidal silica, and aluminum silicate, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, aminobenzenesulfonamide derivatives described in JP-A-8-59603, bis(4-hydroxyphenylthioethoxy)methane, 1,5-di(4-hydroxyphenylthio)-3-oxapentane, butyl bis(p-hydroxyphenyl)acetate, methyl bis(p-hydroxyphenyl)acetate, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,4-bis[α-methyl-α-(4'-hydroxyphenyl)ethyl]benzene, 1,3-bis[α-methyl-α-(4'-hydroxyphenyl)ethyl]benzene, and compounds disclosed in WO 02 / 081229 are also usable. and the compounds described in JP-A-2002-301873, thiourea compounds such as N,N'-di-m-chlorophenylthiourea, aromatic carboxylic acids such as p-chlorobenzoic acid, stearyl gallate, zinc bis[4-(octyloxycarbonylamino)salicylate] dihydrate, 4-[2-(p-methoxyphenoxy)ethyloxy]salicylic acid, 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid, and 5-[p-(2-p-methoxyphenoxyethoxy)cumyl]salicylic acid, and salts of these aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, as well as antipyrine complexes of zinc thiocyanate and complex zinc salts of terephthalaldehyde acid and other aromatic carboxylic acids. Examples include metal chelate complexes of higher fatty acid metal double salts and polyvalent hydroxy aromatic compounds, etc., as described in JP-A-10-258577.

[0062] Among the above-mentioned other color developers, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-propoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 4,4'-isopropylidenediphenol, 2,2'-bis(4-hydroxy-3-methylphenyl)propane, diphenyl sulfone crosslinked compounds described in Japanese Patent No. 3913820, diphenyl sulfone derivatives described in Japanese Patent No. 4004289, phenol-formalin condensates described in International Publication No. 02 / 098674, 4,4'-bis(3-(phenoxycarbonylamino)methylphenylureido)diphenyl sulfone, N-(p-toluenesulfonyl)-N'-( 3-p-toluenesulfonyloxyphenyl)urea, 4,4'-bis(3-tosylureido)diphenylmethane described in JP 2011-105638 A, N-[2-(3-phenylureido)phenyl]benzenesulfonamide described in JP 2016-165835 A, N-(m-tolylaminocarbonyl)-phenylalanine and N-(m-tolylaminocarbonyl)-methionine described in WO 2017 / 047572 A N,N'-bis(3-[{4-methylphenyl}sulfonylamino]phenyl)urea described in Japanese Patent Application No. 2021-131277, N,N'-bis(3-[{4-methylphenyl}sulfonylamino]phenyl)urea described in Japanese Patent Application No. 2019-539154, N,N'-bis(3-[{4-methylphenyl}sulfonylamino]phenyl)urea described in Japanese Patent Application No. 2023-515875, N,N'-bis(3-[{4-methylphenyl}sulfonylamino]phenyl)urea described in Japanese Patent Application No. 2019-539154,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N-(m-tolylaminocarbonyl)-phenylalanine described in WO 2017 / 047572, N-(p-toluenesulfonyl)-phenylalanine, N-(benzyloxycarbonyl)-valine, N-(m-tolylaminocarbonyl)-methionine, N-(m-tolylaminocarbonyl)-tyrosine, N-(m-tolylaminocarbonyl)-phenylglycine, N-(m-tolylaminocarbonyl)-valine, N-(m-tolylamino carbonyl)-cysteine-S-benzyl, N-(m-tolylaminocarbonyl)-β-alanine, N-phenylaminothiocarbonyl-glycylglycine, N-(p-toluenesulfonylaminocarbonyl)-phenylalanine-methyl ester, N-(p-toluenesulfonyl)-β-alanine, N-(p-tolylaminocarbonyl)-methionine, N-(phenylaminocarbonyl)-methionine, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzene described in Japanese Patent Application No. 2015-254099 Sulfonates, and N,N'-di[3-(p-toluenesulfonyl)oxy]phenylurea described in Japanese Patent Application No. 2017-167444 are preferred, as well as 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-propoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-allyloxydiphenyl sulfone, bis(3-allyl-4-hydroxyphenyl) sulfone, 2,2'-bis(4-hydroxy-3-methyl) diphenyl)propane, diphenyl sulfone bridged compounds described in Japanese Patent No. 3913820, diphenyl sulfone derivatives described in Japanese Patent No. 4004289, phenol-formalin condensates described in International Publication No. 02 / 098674, 4,4'-bis(3-(phenoxycarbonylamino)methylphenylureido)diphenyl sulfone, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)urea described in Japanese Patent No. 4601174, 4,4'-bis(3-(phenoxycarbonylamino)methylphenylureido)diphenyl sulfone, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)urea described in Japanese Patent No. 2011-105638,4'-bis(3-tosylureido)diphenylmethane, N-[2-(3-phenylureido)phenyl]benzenesulfonamide described in JP 2016-165835 A, N-(m-tolylaminocarbonyl)-phenylalanine and N-(m-tolylaminocarbonyl)-methionine described in WO 2017 / 047572, [3-(3-phenylureido)phenyl]=4-methylbenzenesulfonate described in Japanese Patent Application No. 2023-515875, 4-methylphenyl=[3-[[(phenylamino) )carbonyl]amino]benzenesulfonate], N,N'-bis(3-[{4-methylphenyl}sulfonylamino]phenyl)urea described in Japanese Patent Application No. 2021-131277, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea described in Japanese Patent Application No. 2019-539154, 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate described in Japanese Patent Application No. 2015-254099, and N,N'-di[3-(p-toluenesulfonyl)oxy]phenylurea described in Japanese Patent Application No. 2017-167444 are more preferred. By using these, it is possible to improve the image storage stability (heat resistance, plasticizer resistance, humidity resistance, water resistance, grease resistance) while maintaining the color development sensitivity of the thermal recording material.

[0063] <Compound (II)> The thermosensitive recording layer may contain compound (II), which is at least one of a compound represented by the following formula (3) and a compound represented by the following formula (5), within a range that does not impair the effects of the present invention. Compound (II) may be used alone or in combination of two or more types. That is, compound (II) may be only a compound represented by formula (3), only a compound represented by formula (5), or a compound represented by formula (3) and a compound represented by formula (5). In each case, the compound represented by formula (3) may be one or two or more types, and the compound represented by formula (5) may be one or two or more types.

[0064] The amount of compound (II) used is preferably compound (I):compound (II)=99:1 to 30:70 parts by mass, more preferably compound (I):compound (II)=99:1 to 50:50 parts by mass, and even more preferably compound (I):compound (II)=99:1 to 60:40 parts by mass, where the total of compound (I) and compound (II) is 100 parts by mass.

[0065] (Compound represented by formula (3))

[0066] In the formula (3), R 1a , R 2a , R 3a are the same or different independently, and are a hydrogen atom or a group represented by the following formula (4), and R 1a , R 2a , or R 3a At least one of the groups is a hydrogen atom.

[0067]

[0068] In the formula (4), m a is 0 or 1, and A a is any linking group selected from the group consisting of -C(=O)-, -C(=S)-, -C(=O)-NH-, -C(=S)-NH-, -C(=O)-NH-SO2-, -C(=S)-NH-SO2-, -SO2-, -SO2-NH-, and -C(=O)-O-; B a is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.

[0069] The compound represented by formula (3) is R 1a , R 2a , or R 3a is the same as the compound represented by formula (1) except that at least one of R 1a is a group represented by formula (4), R 1a is the same as R in formula (1), and R in formula (3) 2ais a group represented by formula (4), R 2a is the same as R in formula (1), and R in formula (3) 3a is a group represented by formula (4), R 3a has the same meaning as R3 in formula (1).

[0070] The compound represented by formula (3) is R 1a , R 2a , or R 3a Among these, one, two, or three may be a hydrogen atom. 1a , R 2a , or R 3a Among these, it is preferred that one or two of them are hydrogen atoms, and it is more preferred that two of them are hydrogen atoms.

[0071] The compound represented by formula (3) is R 1a is a hydrogen atom, and R 2a and R 3a is a group represented by formula (4), R 2a is a hydrogen atom, and R 1a and R 3a is a group represented by formula (4), R 3a is a hydrogen atom, and R 1a and R 2a is a group represented by formula (4), R 1a and R 2a is a hydrogen atom, and R 3a is a group represented by formula (4), R 1a and R 3a is a hydrogen atom, and R 2a is a group represented by formula (4), R 2a and R 3a is a hydrogen atom, and R 1a is a group represented by formula (4), R 1a , R 2a and R 3a may be a hydrogen atom. 1a is a hydrogen atom, and R 2a and R 3a is preferably a group represented by formula (4), and R 1a and R 3a is a hydrogen atom, and R 2ais more preferably a group represented by formula (4).

[0072] From the viewpoints of compatibility with the leuco dye, molecular weight, and melting point, the formula (3) is preferably the following (3A), more preferably the following (3B), and even more preferably the following (3C).

[0073] (3A): m a is 1, and A a is any one selected from the group consisting of —C(═O)—, —C(═S)—, —C(═O)—NH—, —C(═O)—NH—SO—, and —SO—; B a is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.

[0074] (3B): m a is 1, and A a is any one selected from the group consisting of —C(═O)—, —C(═O)—NH—, —C(═O)—NH—SO—, and —SO—; B a is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.

[0075] (3C): m a is 1, and A a is any one selected from the group consisting of —C(═O)—, —C(═O)—NH—, and —SO2, and B a is an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, or an aryl group having 6 to 18 carbon atoms which may have a substituent.

[0076] The compound represented by formula (3), like the compound represented by formula (1), exists in four isomers depending on the positions of the hydrogen atom bonded to the carbon atom corresponding to the 4-position of ascorbic acid and the oxygen atom bonded to the carbon atom corresponding to the 5-position of ascorbic acid, and at least one of the compounds represented by formula (3-1) or formula (3-2) is preferred.

[0077]

[0078]

[0079]

[0080]

[0081] (Compound represented by formula (5))

[0082] In the formula (5), R 31 , R 32 are each independently any one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent. Specific examples of the aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, the alkoxy group having 1 to 30 carbon atoms which may have a substituent, the aryl group having 6 to 18 carbon atoms which may have a substituent, and the arylalkyl group having 7 to 48 carbon atoms which may have a substituent are the same as those for B in formula (2).

[0083] From the viewpoint of compatibility with leuco dyes and melting point, R 31 , R 32are each preferably independently any one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent, and more preferably any one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 18 carbon atoms which may have a substituent.

[0084] Also, R 31 , R 32 It is preferable that either or both of are other than a hydrogen atom.

[0085] The compound represented by formula (5), like the compound represented by formula (1), exists in four isomers depending on the positions of the hydrogen atom bonded to the carbon atom corresponding to the 4-position of ascorbic acid and the oxygen atom bonded to the carbon atom corresponding to the 5-position of ascorbic acid, and at least one of the compounds represented by formula (5-1) or formula (5-2) is preferred.

[0086]

[0087]

[0088]

[0089]

[0090] <Sensitizer> In the thermal recording material of the present invention, a known sensitizer may be used in the thermal recording layer. From the viewpoint of enabling color development with lower energy, it is preferable that the thermal recording layer contains a sensitizer. There are no particular limitations on the sensitizer, but examples thereof include 1,2-di-(3-methylphenoxy)ethane, 2-benzyloxynaphthalene, fatty acid amides having 10 to 21 carbon atoms (e.g., stearic acid amide, palmitic acid amide, etc.), ethylene bisamide, montanic acid wax, polyethylene wax, p-benzylbiphenyl, diphenyl sulfone, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di(p-chlorobenzyl oxalate), di(p-methylbenzyl oxalate), dibenzyl terephthalate, and p-benzyloxybenzoate. Examples of suitable benzoates that can be used include benzyl benzoate, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, o-xylene-bis-(phenyl ether), 4-(m-methylphenoxymethyl)biphenyl, 4,4′-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di(3-methylphenoxy)ethylene, bis[2-(4-methoxy-phenoxy)ethyl]ether, methyl p-nitrobenzoate, and phenyl p-toluenesulfonate. Among these, 1,2-di-(3-methylphenoxy)ethane, 1,2-diphenoxyethane, fatty acid amides having 10 to 21 carbon atoms (e.g., stearic acid amide, palmitic acid amide, etc.), 2-benzyloxynaphthalene, diphenyl sulfone, p-toluenesulfonamide, and oxalic acid-di-p-methylbenzyl ester are preferred, and 1,2-di-(3-methylphenoxy)ethane, 1,2-diphenoxyethane, and 2-benzyloxynaphthalene, which exhibit high color-developing sensitivity even at low energy, are particularly preferred. These sensitizers may be used alone or in combination of two or more. When a sensitizer is used, the amount used is preferably 25 to 250 parts by mass, more preferably 50 to 150 parts by mass, per 100 parts by mass of Compound (I).

[0091] <Stabilizer> In the present invention, a stabilizer may be used in the thermosensitive recording layer to improve the image storage stability of the thermosensitive recording material. A stabilizer refers to a substance that has the effect of improving the image storage stability. Examples of stabilizers include hindered phenol compounds, ultraviolet absorbers (e.g., benzophenone compounds, triazole compounds), antioxidants, etc. Among these, hindered phenol compounds are preferred in terms of improving the image storage stability (heat resistance, moisture resistance, water resistance, plasticizer resistance, etc.) of the recorded area.

[0092] The hindered phenol compound is a compound having typically 1 to 15, preferably 2 to 6, hydroxyphenyl groups per molecule. The molecular weight of the hindered phenol compound is typically 200 to 2,000, preferably 250 to 1,800, more preferably 300 to 1,500. The melting point of the hindered phenol compound is preferably 100° C. to 300° C.

[0093] Furthermore, in at least one of the hydroxyphenyl groups contained in the hindered phenol compound, when the position of the phenolic hydroxyl group is taken as the 1st position, it is preferable that the carbon atom at either the 2nd or 6th position is bonded to a hydrogen atom (i.e., there is no substituent at the 2nd or 6th position).

[0094] Specific examples of the hindered phenol compound include tris(hydroxyphenyl)alkanes and 1,1,3-tris-substituted butane compounds described in JP-B No. 39-4469 or JP-A No. 56-40629, and these may be used in combination of two or more.

[0095] The hindered phenol compounds may be used alone or in combination of two or more. When a hindered phenol compound is used in the heat-sensitive recording material of the present invention, the content thereof is preferably 1 to 100 parts by mass, more preferably 1 to 70 parts by mass, and even more preferably 1 to 50 parts by mass, per 100 parts by mass of compound (I). If the content of the hindered phenol compound is less than this range, the moisture resistance, water resistance, and heat resistance of the recorded area may be reduced, and color development in blank areas due to heating may not be suppressed. If the content is greater than this range, the color development sensitivity may be reduced, and the plasticizer resistance of the recorded area may be reduced.

[0096] <Binder> It is preferable to use a binder to form the thermal recording layer. Examples of the binder include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, polystyrene, styrene copolymers such as styrene-maleic anhydride copolymer and styrene-butadiene copolymer, cellulose derivatives such as ethyl cellulose and acetyl cellulose, casein, gum arabic, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid ester, polyvinyl butyral, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, and coumarone resin. The amount of binder used is suitably about 5 to 25% by mass of the solid content of the heat-sensitive recording layer.

[0097] The binder is generally used as a solution, emulsion, dispersion, paste, or a combination thereof. Examples of the solvent for the solution, emulsion, or dispersion, or the medium for the paste, include water, alcohol, ketones, esters, and hydrocarbons.

[0098] <Crosslinking Agent> In the heat-sensitive recording material of the present invention, a crosslinking agent may be used in the heat-sensitive recording layer. Examples of crosslinking agents include glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, borax, boric acid, alum, and ammonium chloride. When a crosslinking agent is used, the amount used is preferably 0.5 to 500 parts by mass per 100 parts by mass of compound (I).

[0099] <Pigment> In the heat-sensitive recording material of the present invention, a pigment may be used in the heat-sensitive recording layer. Examples of the pigment include inorganic or organic pigments such as silica (excluding colloidal silica), calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, and aluminum hydroxide. When a pigment is used, the amount used is preferably 25 to 1,000 parts by mass per 100 parts by mass of compound (I).

[0100] <Lubricant> In the heat-sensitive recording material of the present invention, a lubricant may be used in the heat-sensitive recording layer. Examples of lubricants include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins. When a lubricant is used, the amount thereof is preferably 0.5 to 500 parts by mass per 100 parts by mass of compound (I).

[0101] <Other Additives> In the heat-sensitive recording material of the present invention, other additives may be used in the heat-sensitive recording layer. Examples of other additives include dispersants, antifoaming agents, fluorescent dyes, etc. When other additives are used, the amount used is preferably 0.5 to 500 parts by mass per 100 parts by mass of Compound (I).

[0102] From the viewpoints of the color development, image preservation, and mechanical performance of the thermal paper against printing devices, the thermal recording layer preferably contains a color developer, a leuco dye, a binder, a pigment, and a lubricant, more preferably 25 to 75 parts by mass of the leuco dye, 5 to 40 parts by mass of the binder, 100 to 500 parts by mass of the pigment, and 5 to 30 parts by mass of the lubricant, relative to 100 parts by mass of the color developer. Furthermore, from the viewpoints of improving the color development and image preservation of the thermal paper, the thermal recording layer preferably contains a color developer, a leuco dye, a binder, a pigment, a lubricant, a sensitizer, and a stabilizer, more preferably 25 to 75 parts by mass of the leuco dye, 5 to 30 parts by mass of the binder, 100 to 500 parts by mass of the pigment, 5 to 40 parts by mass of the lubricant, 25 to 200 parts by mass of the sensitizer, and 5 to 100 parts by mass of the stabilizer, relative to 100 parts by mass of the color developer.

[0103] [Support] The shape, structure, size, material, etc. of the support used in the thermal recording material of the present invention are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the support include sheet, roll, and flat plate. The support may have a single-layer structure or a laminated structure. The size of the support can be appropriately selected depending on the intended use of the thermal recording material. Examples of support materials include plastic film, synthetic paper, high-quality paper, waste paper pulp, recycled paper, one-side gloss paper, greaseproof paper, coated paper, art paper, cast-coated paper, lightly coated paper, resin-laminated paper, and release paper. A composite sheet combining these materials may also be used as the support.

[0104] The thickness of the support is not particularly limited and can be appropriately selected depending on the purpose, and is preferably 30 to 2,000 μm, more preferably 50 to 1,000 μm.

[0105] [Protective Layer] In the thermosensitive recording material of the present invention, a protective layer may be provided on the thermosensitive recording layer. Generally, providing a protective layer on the thermosensitive recording layer to improve the image storage stability of the thermosensitive recording material reduces the color development sensitivity. However, in the thermosensitive recording material of the present invention, since the highly sensitive compound (I) is used as a color developer, the sensitivity required for thermal paper can be maintained even when a protective layer is provided on the thermosensitive recording layer. The types and amounts of various components used in the protective layer are determined according to the required performance and recording suitability and are not particularly limited.

[0106] [Underlayer, Back Layer, and Intermediate Layer] In the thermosensitive recording material of the present invention, an underlayer mainly composed of a pigment and a binder may be provided between the support and the thermosensitive recording layer in order to further enhance color development sensitivity. Furthermore, in order to correct curling of the thermosensitive recording material of the present invention, a back layer may be provided on the side of the support opposite to the side on which the thermosensitive recording layer is located. One embodiment of the layers in the thermosensitive recording material of the present invention includes, but is not limited to, a layered configuration in the order of protective layer / thermosensitive recording layer / underlayer / support / back layer.

[0107] Furthermore, an intermediate layer may be formed between the support and the under layer, between the under layer and the thermosensitive recording layer, between the thermosensitive recording layer and the protective layer, and / or between the support and the back layer.

[0108] [Method for producing a thermal recording material] The thermal recording material of the present invention can be produced by, for example, applying a coating liquid containing a basic leuco dye and a color developer, and optionally a hindered phenol compound, a sensitizer, etc., to at least a portion of at least one surface of a support, and drying the coating liquid to form a thermal recording layer. This coating liquid can be applied according to well-known conventional techniques. There are no particular limitations on the coating means, and for example, an off-machine or on-machine coater equipped with various coaters such as an air knife coater, a rod blade coater, a bent blade coater, a bevel blade coater, a roll coater, or a curtain coater can be used.

[0109] The coating liquid for forming the thermosensitive recording layer can be prepared by blending, for example, a color developer and, if necessary, a leuco dye, a hindered phenol compound, a sensitizer, etc., and then atomizing the mixture to a particle size of several microns or less using a grinder such as a ball mill, attritor, or sand grinder, or an appropriate emulsifying device, and then adding a binder, etc. to the resulting mixture. Examples of solvents that can be used in this coating liquid include water and alcohol. The solid content of the coating liquid is usually 20 to 40% by mass. The coating amount of the thermosensitive recording layer can be appropriately selected depending on the composition and the application of the thermosensitive recording material, but is usually 1 to 20 g / m2 in dry mass. 2 , preferably 2 to 12 g / m 2 The range is.

[0110] From the viewpoint of the color development, image preservation, and mechanical performance of the thermal paper against printing devices, the coating liquid preferably contains a color developer, a leuco dye, a binder, a pigment, a lubricant, and water, and more preferably contains 25 to 75 parts by mass of the leuco dye, 5 to 40 parts by mass of the binder, 100 to 500 parts by mass of the pigment, and 5 to 30 parts by mass of the lubricant, relative to 100 parts by mass of the color developer, and the solids content is 14 to 25% by mass. Furthermore, from the viewpoint of improving the color development and image preservation properties of the thermal paper, it is preferable that the coating liquid contains a color developer, a leuco dye, a binder, a pigment, a lubricant, a sensitizer, a stabilizer, and water, and that the amounts of the leuco dye, binder, pigment, lubricant, sensitizer, stabilizer, and water are 25 to 75 parts by mass, 5 to 30 parts by mass, 100 to 500 parts by mass, lubricant, 5 to 40 parts by mass, sensitizer, 25 to 200 parts by mass, and stabilizer, relative to 100 parts by mass of the color developer, and that the solids content is 14 to 25% by mass.

[0111] Similarly to the above-mentioned thermosensitive recording layer, the protective layer, under layer, back layer, and intermediate layer can also be formed by applying and drying a coating liquid containing the constituent components thereof. Furthermore, the thermosensitive recording material of the present invention having each layer formed thereon may be subjected to a treatment known in the art (for example, smoothing treatment by supercalendering, etc.).

[0112] [Uses of the Thermal Recording Material] The thermal recording material of the present invention can be suitably used for applications such as paper, film, IC cards, and friction ballpoint pens.

[0113] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not changed.

[0114] In the following examples and comparative examples, Hakugin paper manufactured by Nippon Paper Industries Co., Ltd. was used as a support, and a thermosensitive recording layer (thermosensitive coloring layer) was formed on one side (smooth side) of the paper. In the following examples and comparative examples, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0115] Comparative Synthesis Example 1: Synthesis of 2,6-O-dibenzoyl-L-ascorbic acid

[0116]

[0117] 20 g of L-ascorbic acid was placed in a three-neck flask equipped with a dropping funnel, thermometer, and reflux condenser and dissolved in 89.8 g of pyridine and 79.0 g of acetone. While stirring the reaction solution with a magnetic stirrer in an ice bath, 31.9 g of benzoyl chloride was added dropwise via the dropping funnel and stirred for 1 hour. The precipitated solid was removed by filtration. The filtrate was concentrated under reduced pressure, adjusted to strong acidity with dilute hydrochloric acid, extracted with ethyl acetate, and the solvent was evaporated to obtain an orange adhesive. The resulting adhesive was dissolved in ethyl acetate and subjected to silica gel chromatography with heptane / ethyl acetate / formic acid. The solvent was evaporated to obtain 5.1 g of the target white crystals.

[0118] The chemical shifts (σ ppm) in the proton NMR spectrum (400 MHz) measured in deuterated DMSO solvent were as follows: σ: 4.23-4.26 (t, 1H, J = 6.0 Hz), 4.30-4.44 (m, 2H), 5.18 (d, 1H, J = 1.6 Hz), 7.53-8.09 (m, 10H).

[0119] Synthesis Example 1: Synthesis of 2,5,6-O-tribenzoyl-L-ascorbic acid

[0120]

[0121] 11.0 g of L-ascorbic acid was placed in a three-neck flask equipped with a dropping funnel, thermometer, and reflux condenser and dissolved in 77.4 g of pyridine and 55.0 g of acetone. While stirring the reaction solution with a magnetic stirrer in an ice bath, 25.5 g of benzoyl chloride was added dropwise using a dropping funnel and stirred for 1 hour. The precipitated solid was removed by filtration, and the filtrate was concentrated under reduced pressure and then added dropwise to dilute sulfuric acid to neutralize it, followed by extraction with ethyl acetate and washing with water. A pale brown oily substance was obtained by distilling off the solvent. The resulting crystals were dissolved in a small amount of ethyl acetate, and the resulting solution was subjected to silica gel chromatography using heptane / ethyl acetate / formic acid to elute and isolate each component of the composition. The solvent in the eluate containing the target product was distilled off, and the concentrated solution was added dropwise to toluene to obtain crude crystals. The resulting crude crystals were repeatedly recrystallized using heptane / ethyl acetate to obtain 7.6 g of the target white crystals.

[0122] The chemical shifts (σ ppm) in the proton NMR spectrum (400 MHz) measured in deuterated chloroform were as follows: σ: 4.71-4.80 (m, 2H), 5.25 (d, 1H, J=2.4 Hz), 5.94-5.98 (m, 1H), 7.34-8.16 (m, 15H).

[0123] Synthesis Example 2: Synthesis of 2,5,6-O-tritoyl-L-ascorbic acid

[0124]

[0125] The target product was obtained by the same procedure as in Synthesis Example 1, except that 28 g of p-toluoyl chloride was used instead of benzoyl chloride.

[0126] The chemical shifts (σ ppm) in the proton NMR spectrum (400 MHz) measured in deuterated chloroform were as follows: σ: 2.35-2.5 (t, 9H), 4.65-4.78 (m, 2H), 5.2-5.29 (d, 1H), 5.87-6.0 (m, 1H), 7.16-8.13 (m, 11H).

[0127] Synthesis Example 3: Synthesis of 2,6-O-dibenzoyl-5-O-toluoyl-L-ascorbic acid

[0128]

[0129] 6.5 g of the 2,6-dibenzoyl compound was placed in a three-neck flask equipped with a dropping funnel, thermometer, and reflux condenser and dissolved in 1.3 g of pyridine and 7.9 g of acetone. While stirring the reaction solution with a magnetic stirrer in a water bath, 2.6 g of paratoluoyl chloride was added dropwise using a dropping funnel, and the mixture was stirred for 3 hours. Hydrochloric acid was added to the reaction solution to neutralize it, followed by extraction with ethyl acetate and washing with water. The reaction solution was neutralized with hydrochloric acid, followed by extraction with ethyl acetate and washing with water. A pale yellow oily substance was obtained by distilling off the solvent. This substance was subjected to silica gel chromatography using hexane / ethyl acetate, and each component of the composition was eluted and isolated. The eluate containing the target product was distilled off, and the resulting white solid was repeatedly recrystallized using hexane / ethyl acetate to obtain 3.6 g of the target white crystal.

[0130] The chemical shifts (σ ppm) in the proton NMR spectrum (400 MHz) measured in deuterated chloroform were as follows: σ: 2.35 (s, 3H), 4.68-4.78 (m, 2H), 5.23 (d, 1H, J=1.6 Hz), 5.91-5.96 (m, 1H), 7.16-8.16 (m, 14H).

[0131] Synthesis Example 4: Synthesis of 2,5,6-O-tribenzoyl-D-isoascorbic acid

[0132]

[0133] The target product was obtained by the same procedure as in Synthesis Example 1, except that the same amount of D-isoascorbic acid was used instead of ascorbic acid.

[0134] The chemical shifts (σ ppm) in the proton NMR spectrum (400 MHz) measured in deuterated chloroform were as follows: σ: 4.58-4.82 (m, 2H), 5.25 (d, 1H, J = 3.6 Hz), 5.85-5.97 (m, 1H), 7.32-7.72 (m, 9H), 7.93-8.21 (m, 6H).

[0135] Synthesis Example 5: Synthesis of 2,5,6-phenylcarbamate-L-ascorbic acid

[0136]

[0137] 1.0 g of L-ascorbic acid was placed in a three-neck flask equipped with a dropping funnel, thermometer, and reflux condenser, and 5.0 g of THF, 1.7 g of triethylamine, and 2.0 g of phenyl isocyanate were added and stirred at room temperature for 5 hours. Hydrochloric acid was added to the reaction solution to neutralize it, followed by extraction with chloroform and washing with water. The solvent was evaporated, and the resulting light brown crude product was subjected to silica gel chromatography using hexane / ethyl acetate to elute and isolate each component of the composition. The eluate containing the target product was evaporated, and the resulting white solid was repeatedly recrystallized using hexane / ethyl acetate to obtain 0.5 g of the target white crystal.

[0138] The chemical shifts (σ ppm) in the proton NMR spectrum (400 MHz) measured in deuterated dimethyl sulfoxide were as follows: σ: 4.26-4.58 (m, 2H), 4.91 (d, 1H, J = 1.2 Hz), 5.54-5.61 (m, 1H), 6.92-7.52 (m, 15H), 9.70-9.86 (br, 2H), 10.20 (br, 1H).

[0139] <Coating liquid for thermosensitive recording layer> The following liquids A to E were prepared. Liquids A and B were wet-milled using a ready mill (RMB-02) manufactured by Imex Co., Ltd. until the average particle size of each component reached 0.5 μm. The average particle size here is the average size in a volume-based distribution, and was measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac MT3000II) manufactured by Nikkiso Co., Ltd.

[0140] <Solution A> Compound of Synthesis Example 1: 9.0 parts Polyvinyl alcohol (10% aqueous solution): 10.0 parts Water: 81.0 parts

[0141] <Solution B> 3-dibutylamino-6-methyl-7-anilinofluoran (manufactured by Yamamoto Chemical Industries, Ltd., trade name "ODB-2"): 36.5 parts Polyvinyl alcohol (10% aqueous solution): 60.0 parts Water: 3.5 parts

[0142] <Liquid C> Calcium carbonate dispersion with 60% solids (manufactured by Okutama Kogyo Co., Ltd., product name "Tama Pearl (registered trademark) TP-123CS")

[0143] <Solution D> 36% zinc stearate dispersion (manufactured by Chukyo Yushi Co., Ltd., product name "Hydrin Z-8-36")

[0144] <Solution E> 10% aqueous solution of polyvinyl alcohol (10% aqueous solution of "GOHSENOL (registered trademark) NH-18", manufactured by Nippon Synthetic Co., Ltd.)

[0145] [Example 1] A coating liquid for a thermosensitive recording layer was prepared by mixing the respective liquids in the following proportions: Liquid A: 85.00 parts Liquid B: 10.00 parts Liquid C: 17.87 parts Liquid D: 6.00 parts Liquid E: 19.62 parts Next, a coating liquid for a thermosensitive recording layer having a dry mass of 4 to 6 g / m2 was applied to one side (smooth side) of a paper support. 2 The coating liquid for the thermosensitive recording layer was applied and dried (air blower, 60°C, 2 minutes) so that the thermosensitive recording layer was formed. The support on which the thermosensitive recording layer had been formed was then treated with a supercalender to a smoothness of 500 to 1000 seconds, to obtain a thermosensitive recording material. This was then treated with a supercalender at 1 kgf / cm 2 The film was smoothed by applying a pressure of 1000 psi to obtain a heat-sensitive recording material.

[0146] [Example 2] A thermal recording material was produced in the same manner as in Example 1, except that the compound in Synthesis Example 1 in Solution A was changed to the compound in Synthesis Example 2, and the components of Solution A were prepared by stirring, mixing, and dissolving them.

[0147] [Example 3] A thermal recording material was produced in the same manner as in Example 1, except that the compound in Synthesis Example 1 in Solution A was changed to the compound in Synthesis Example 3, and the components of Solution A were prepared by stirring, mixing, and dissolving them.

[0148] Example 4 A thermal recording material was produced in the same manner as in Example 1, except that the compound in Synthesis Example 1 in Solution A was changed to the compound in Synthesis Example 4, and the components of Solution A were prepared by stirring, mixing, and dissolving them.

[0149] Example 5 A thermal recording material was produced in the same manner as in Example 1, except that the amount of the compound in Synthesis Example 1 in Solution A was changed to 7.2 parts, 1.8 parts of 6-O-palmitoyl-L-ascorbic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the components of Solution A were mixed and dissolved by stirring to prepare Solution A.

[0150] Example 6 A thermal recording material was produced in the same manner as in Example 1, except that the amount of the compound in Synthesis Example 1 in Solution A was changed to 5.4 parts, 3.6 parts of 6-O-palmitoyl-L-ascorbic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the components of Solution A were mixed and dissolved by stirring to prepare Solution A.

[0151] Example 7 A thermal recording material was produced in the same manner as in Example 1, except that the amount of the compound in Synthesis Example 1 in Solution A was changed to 5.4 parts, 3.6 parts of 6-O-stearoyl-L-ascorbic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the components of Solution A were mixed and dissolved by stirring to prepare Solution A.

[0152] [Example 8] A thermal recording material was produced in the same manner as in Example 1, except that the compound in Synthesis Example 1 in Solution A was changed to the compound in Synthesis Example 5, and the components of Solution A were prepared by stirring, mixing, and dissolving them.

[0153] Comparative Example 1 A thermal recording material was produced in the same manner as in Example 1, except that the compound in Synthesis Example 1 for Solution A was changed to 2-O-α-D-glucopyranosyl-L-ascorbic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and the components of Solution A were mixed and dissolved by stirring to prepare Solution A.

[0154] Comparative Example 2 A heat-sensitive recording material was produced in the same manner as in Example 1, except that the compound in Synthesis Example 1 of Solution A was changed to 6-O-stearoyl-L-ascorbic acid (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0155] Comparative Example 3 A heat-sensitive recording material was produced in the same manner as in Example 1, except that the compound in Synthesis Example 1 of Solution A was changed to the compound in Comparative Synthesis Example 1.

[0156] [Color development sensitivity] Gradation patterns were printed using a thermal printer (TH-M2 / PX) manufactured by Okura Electric Co., Ltd., and the image density at an applied energy of 0.396 mJ / dot was measured using an eXact densitometer manufactured by X-Rite Corporation. The results are shown in Table 1. Note that in this test, a higher image density value indicates better color development sensitivity.

[0157] [Printed section storage stability] In order to evaluate the printed section storage stability under various storage conditions, the heat resistance, plasticizer resistance, moisture resistance, water resistance, alcohol resistance, oil resistance, and grease resistance were evaluated by the following methods.

[0158] <Heat Resistance> A checkerboard pattern was printed on a thermal recording material using an Okura Electric thermal printer (TH-M2 / PS) with an applied energy of 0.396 mJ / dot, and the material was left in an environment at a temperature of 60°C for 24 hours, after which the image density was measured using an X-Rite eXact densitometer. Table 1 shows the image densities after the test. Note that a higher image density value in this test indicates better heat resistance.

[0159] <Plasticizer Resistance> A checkerboard pattern was printed on both sides of a thermal recording material using a thermal printer (TH-M2 / PX) manufactured by Ohkura Electric Co., Ltd. at an applied energy of 0.396 mJ / dot. DiaWrap (registered trademark) i-GSW manufactured by Mitsubishi Chemical Corporation was then brought into contact with the front and back of the thermal recording material, and the material was left at 20°C for 2 hours, after which the image density was measured using an eXact densitometer manufactured by X-Rite. Table 1 shows the image densities after the test. Note that a higher image density value in this test indicates better plasticizer resistance.

[0160] <Moisture Resistance> A checkerboard pattern was printed on a thermal recording material using an Okura Electric thermal printer (TH-M2 / PS) with an applied energy of 0.396 mJ / dot. The material was then left for 24 hours in an environment of 40°C temperature and 90% humidity, and the image density was measured using an X-Rite eXact densitometer. Table 1 shows the image densities after the test. Note that a higher image density value in this test indicates better moisture resistance.

[0161] <Water Resistance> A thermal recording material was printed in a checkerboard pattern using an Okura Electric thermal printer (TH-M2 / PS) with an applied energy of 0.396 mJ / dot, and then immersed in tap water at 20°C for 24 hours. After air drying, the image density was measured using an X-Rite eXact densitometer. Table 1 shows the image densities after the test. Note that a higher image density value in this test indicates better water resistance.

[0162] <Alcohol Resistance> A thermal recording material was printed in a checkerboard pattern using an Okura Electric thermal printer (TH-M2 / PS) with an applied energy of 0.396 mJ / dot, and then immersed in 25% aqueous ethanol for 20 minutes, removed, and left at room temperature for 24 hours. The image density was then measured using an X-Rite eXact densitometer. Table 1 shows the image densities after the test. Note that a higher image density value in this test indicates better alcohol resistance.

[0163] <Oil Resistance> A drop of Nissin salad oil (manufactured by The Nissin Oillio Group, Inc.) was dropped onto the printed portion of a thermal recording material in which a checkerboard pattern had been printed using an Okura Electric thermal printer (TH-M2 / PS) with an applied energy of 0.396 mJ / dot, and the material was lightly wiped clean and left to stand at 20°C for 24 hours, after which the print density of the printed portion was measured using an X-Rite eXact densitometer. Table 1 shows the image density after the test. Note that a higher image density value in this test indicates better oil resistance.

[0164] <Grease Resistance> A drop of Skin Milk (manufactured by Nivea-Kao Corporation) was dropped onto the printed area of ​​a thermal recording material that had been printed in a checkerboard pattern using an Okura Electric thermal printer (TH-M2 / PS) with an applied energy of 0.396 mJ / dot, and the material was lightly wiped clean and left to stand at 20°C for 24 hours, after which the print density of the printed area was measured using an X-Rite eXact densitometer. Table 1 shows the image density after the test. Note that a higher image density value in this test indicates better grease resistance.

[0165]

[0166] As is clear from the results in Table 1, Examples 1 to 8, in which the compounds of the present invention were used as color developers, showed improved color development sensitivity as well as improved print storage stability, such as heat resistance, plasticizer resistance, moisture resistance, water resistance, alcohol resistance, oil resistance, and grease resistance, compared to Comparative Examples 1 to 3, in which conventional color developers were used.

[0167] As described above, by using a compound represented by formula (1), it is possible to provide a well-balanced heat-sensitive recording material that is excellent in both color development sensitivity and print storage stability.

Claims

1. A color developer comprising a compound represented by the following formula (1): (In the formula (1), R1, R2, and R3 may be the same or different independently and represent a group represented by the following formula (2).) (In the formula (2), m is 0 or 1; A is a linking group selected from the group consisting of -C(=O)-, -C(=S)-, -C(=O)-NH-, -C(=S)-NH-, -C(=O)-NH-SO2-, -C(=S)-NH-SO2-, -SO2-, -SO2-NH-, and -C(=O)-O-; and B is any group selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.) 2. The color developer according to claim 1, wherein in formula (2), m is 1 and A is any one selected from the group consisting of -C(=O)-, -C(=O)-NH-, -SO2- and -C(=O)-NH-SO2-.

3. The color developer according to claim 1, wherein in formula (2), B is an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, or an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.

4. The color developer according to claim 1, wherein in formula (2), m is 1, A is any one selected from the group consisting of -C(=O)-, -C(=O)-NH- and -SO2-, and B is an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, or an aryl group having 6 to 18 carbon atoms which may have a substituent.

5. The color developer according to claim 1, wherein in formula (2), m is 1, A is -C(=O)- or -C(=O)-NH-, and B is an aliphatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent.

6. The color developer according to claim 1, wherein R1, R2 and R3 in formula (1) are the same.

7. The color developer according to claim 1, wherein the compound represented by formula (1) is at least one of a compound represented by the following formula (1-1) and a compound represented by the following formula (1-2): (In formula (1-1), R1 to R3 have the same meanings as R1 to R3 in formula (1), respectively.) (In formula (1-2), R1 to R3 have the same meanings as R1 to R3 in formula (1), respectively.) 8. A heat-sensitive recording material having a support and a heat-sensitive recording layer provided on the support, wherein the heat-sensitive recording layer contains the color developer according to any one of claims 1 to 7.

9. The heat-sensitive recording material according to claim 8, further comprising at least one of a compound represented by the following formula (3) and a compound represented by the following formula (5): (In the formula (3), R 1a , R 2a , R 3a are the same or different independently, and are a hydrogen atom or a group represented by the following formula (4), and R 1a , R 2a , or R 3a At least one of these is a hydrogen atom.) (In the above formula (4), m a is 0 or 1, and A a is any linking group selected from the group consisting of -C(=O)-, -C(=S)-, -C(=O)-NH-, -C(=S)-NH-, -C(=O)-NH-SO2-, -C(=S)-NH-SO2-, -SO2-, -SO2-NH-, and -C(=O)-O-; B a is any one selected from the group consisting of an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent. (In the formula (5), R 31 , R 32 are each independently any one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, an alkoxy group having 1 to 30 carbon atoms which may have a substituent, an aryl group having 6 to 18 carbon atoms which may have a substituent, and an arylalkyl group having 7 to 48 carbon atoms which may have a substituent.

10. The heat-sensitive recording material according to claim 8, wherein the heat-sensitive recording layer contains a leuco dye.

11. The heat-sensitive recording material according to claim 8, wherein the heat-sensitive recording layer contains a sensitizer.

12. The thermosensitive recording material according to claim 8, wherein the thermosensitive recording layer contains a stabilizer.

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