JPH1016389A - Reversible thermal recording medium and coating solution for forming reversible thermal recording layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible thermal recording medium, which hords stable color forming properties and color erasing properties and can correspond to a wide use condition and a wide environmental condition, and a coating soln, for forming a reversible thermal recording layer. SOLUTION: A reversible thermal recording medium is obtained by providing a recording layer containing a color forming agent being an electron donating color forming compd., a coupler being an electron acceptive compd., and a matrix polymer as main components and capable of relatively forming a developed color state and an erased color state by the difference between heating temp. and/or a cooling speed after heating on a support. In this case, in the medium and the coating soln. forming the same, the electron acceptive compd. and the matrix polymer is a combination of the electron acceptive compd. represented by formula δA-δP<=1, wherein δA is a solubility parameter of the electron acceptive compd. and δP is a solubility parameter of the matrix polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording medium and a coating solution for forming a reversible thermosensitive recording layer utilizing a color development reaction between an electron-donating color-forming compound and an electron-accepting compound. Specifically, the present invention relates to a reversible thermosensitive recording medium capable of forming and erasing a color image by controlling thermal energy, and a coating liquid for forming a reversible thermosensitive recording layer.

[0002]

2. Description of the Related Art Conventionally, an electron-accepting color-forming compound (hereinafter, referred to as an electron-accepting color-forming compound)
Thermal recording media utilizing a color development reaction between a color former or a leuco dye and an electron-accepting compound (hereinafter also referred to as a developer) are widely known, such as facsimile machines, word processors, and scientific measuring instruments. Used in printers. However, these conventional recording media that have been put into practical use all have irreversible color development, and once recorded images cannot be erased and used repeatedly.

On the other hand, according to the patent publication, a recording medium capable of reversibly developing and erasing colors has been proposed. For example, Japanese Patent Application Laid-Open No. 60-1985 discloses a method using a combination of gallic acid and phloroglucinol as a color developer. No. 193691, JP-A No. 61-237684 using a compound such as phenolphthalein or thymolphthalein as a developer, and a recording layer containing a homogeneous solution of a color former, a developer and a carboxylic acid ester in a recording layer. JP-A-62-138556, JP-A-62-138
568 and JP-A-62-140881, and JP-A-63-173 using an ascorbic acid derivative as a developer.
No. 684,684, JP-A-2-188293 and JP-A-2-1882 using a salt of bis (hydroxyphenyl) acetic acid or gallic acid and a higher aliphatic amine as a developer.
No. 94 is disclosed. However, the conventional reversible thermosensitive recording medium described above has a problem in terms of compatibility between color stability and decoloration, or stability in color density and repetition, and practical recording. It is not satisfactory as a medium.

[0004] The present applicant has previously disclosed in Japanese Patent Laid-Open No. 5-124360.
In the publication, an organic phosphoric acid compound having a long-chain aliphatic hydrocarbon group, an aliphatic carboxylic acid compound or a phenol compound is used as a color developer, and by combining this with a leuco dye as a color former, color development and decoloration are performed. Reversible color development that can be easily performed by heating and cooling conditions, and that its color development and decoloration states can be stably maintained at room temperature, and that color development and decoloration can be repeated stably A composition and a reversible thermosensitive recording medium using the same in a recording layer were proposed. This has practical performance in terms of the balance between color stability and color erasure and color density, but it is also improved in terms of compatibility with a wider range of usage environments and the range of application of color erasure conditions. There was room to be. Thereafter, use of a specific structure for a phenol compound having a long-chain aliphatic hydrocarbon group has been proposed (Japanese Patent Application Laid-Open No.
210954), which also had a similar problem.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reversible color-forming composition, a reversible thermosensitive recording medium and a reversible thermosensitive recording medium which maintain stable coloring and decoloring properties and can be used in a wide range of use conditions and environmental conditions. Another object of the present invention is to provide a coating liquid for forming a thermosensitive recording layer.

[0006]

As a result of intensive studies, the present inventors have found that the interaction between the main components constituting the reversible thermosensitive recording medium affects the above-mentioned various properties of the medium, and arrived at the present invention. That is, the present invention includes the following (I) to (IV).

(I) It contains a color former, which is an electron-donating color-forming compound, a developer, which is an electron-accepting compound, and a matrix polymer as main components. The relative temperature varies depending on the heating temperature and / or the cooling rate after heating. In a reversible thermosensitive recording medium provided on a support with a recording layer capable of forming a colored state and a decolored state, the electron-accepting compound and the matrix polymer satisfy the following formula (1): And a matrix polymer. | Δ _A −δ _p | ≦ 1 (1) (where δ _A is the solubility parameter of the electron-accepting compound, and δ _p is the solubility parameter of the matrix polymer.) (II) The electron-accepting compound is electron-donating The reversible thermosensitive recording medium according to the above (I), wherein the reversible thermosensitive recording medium is present in a dispersed state in a matrix polymer in which a coloring compound is dissolved.

(III) It contains a color former as an electron-donating color-forming compound, a developer as an electron-accepting compound, a matrix polymer and a solvent as main components, and is different in a heating temperature and / or a cooling rate after heating. In the coating liquid for forming a recording layer capable of forming a relatively colored state and a decolored state, the coating liquid for forming a recording layer is formed of a solvent, an electron-accepting agent satisfying the following formulas (1) and (2). A coating liquid for forming a reversible thermosensitive recording layer, which is a combination of a hydrophilic compound and a matrix polymer. | Δ _A −δ _p | ≦ 1 (1) | δ _A −δ _s | ≦ 0.5 (2) (where δ _A is the solubility parameter of the electron-accepting compound, δ _p is the solubility parameter of the matrix polymer, δ _s is a solubility parameter of the solvent.) (IV) The above-mentioned (III), wherein the electron-accepting compound is present in a dispersed state in a vehicle containing the electron-donating color-forming compound and the matrix polymer. The coating liquid for forming a reversible heat-sensitive recording layer according to the above (2).

The reversible thermosensitive recording medium of the present invention can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. This basic coloring / decoloring phenomenon will be described. FIG. 1 shows the relationship between the color density and the temperature of this composition. Introduction gradually heated a composition in the decolorized state (A), a molten colored state occurs coloration at temperatures T ₁ begins to melt (B). When the color is rapidly cooled from the melted color development state (B), the temperature can be lowered to room temperature while maintaining the color development state, and a solid color development state (C) is obtained. Whether or not this color-developed state is obtained depends on the rate of temperature decrease from the molten state. In the case of slow cooling, decoloration occurs in the process of temperature decrease, and the same decolored state (A) or quenched color state (C) as at the beginning. A) is formed with a relatively lower concentration. On the other hand, rapidly cooled colored state (C) is again raised gradually and discoloring occurs at a lower temperature T ₂ than the coloring temperature (E from D), returns the beginning when the temperature decreases from here to the same decolored state (A). The actual color development temperature and decolorization temperature vary depending on the combination of the color developer and color developer used, and can be selected according to the purpose. In addition, the density in the molten color development state and the color development density after quenching do not always match, and may differ.

The composition comprising the color developer and the color former contained in the recording layer of the present invention has a color development state (C) obtained by quenching from a molten state. They are in a mixed state where possible, which often forms a solid state. This state is a state in which the color developer and the color forming agent aggregate to maintain the color development, and it is considered that the color formation is stabilized by the formation of the aggregate structure. On the other hand, the decolored state is a state where both are phase-separated. This state is a state in which molecules of at least one compound are aggregated to form a domain or crystallized, and it is considered that the color former and the developer are separated and stabilized by aggregation or crystallization. Can be In many cases, the present invention causes more complete decoloration due to phase separation of the two and crystallization of the color developer. In the decoloring by slow cooling from the molten state and the decoloring by raising the temperature from the colored state shown in FIG. 1, the cohesive structure changes at this temperature, resulting in phase separation and development of a color developer.

The formation of color recording on the reversible thermosensitive recording medium of the present invention is carried out by using a thermal head or the like to heat the mixture to a temperature at which the mixture is melted and then rapidly cool the mixture. There are two methods of decoloring: a method of gradually cooling from a heated state and a method of heating to a temperature slightly lower than the color development temperature. But,
These are the same in the sense that the two are phase-separated or temporarily maintained at a temperature at which at least one crystallizes. The quenching in the formation of a colored state is to prevent the phase separation or the crystallization temperature from being maintained. Here, the rapid cooling and the slow cooling are relative to one composition, and the boundary changes depending on the combination of the color former and the developer.

In order to form a color image using the reversible thermosensitive recording medium of the present invention, the color image may be heated once to a color development temperature and then rapidly cooled. Specifically, for example, when the recording layer is heated for a short time by a thermal head or a laser beam, the recording layer is locally heated, so that the heat is immediately diffused, rapid cooling occurs, and the coloring state can be fixed. On the other hand, in order to erase the color, heating may be performed by using an appropriate heat source for a relatively long time to cool, or heating may be temporarily performed to a temperature slightly lower than the coloring temperature. If the recording medium is heated for a long time, the temperature of a wide area of the recording medium rises, and the subsequent cooling is slowed down. As a heating method in this case, a heat roller, a heat stamp, hot air, or the like may be used, or heating may be performed for a long time using a thermal head. In order to heat the recording layer to the decoloring temperature range, the applied energy may be slightly reduced from that at the time of recording, for example, by adjusting the applied voltage and the pulse width to the thermal head. With this method, recording and erasing can be performed only with the thermal head, and so-called overwriting can be performed. Of course, it can be erased by heating to a decoloring temperature range by a heat roller or a heat stamp.

The materials used for the reversible thermosensitive recording medium and the coating solution for forming the reversible thermosensitive recording layer of the present invention are described below. The color former used in the present invention is a compound having an electron donating property, and may be used alone or as a mixture of two or more kinds. However, the color former itself is a colorless or light-colored dye precursor and is not particularly limited. For example, triphenylmethane phthalide, fluoran, phenothidiane, leuco auramine, indolino phthalide and the like can be selected. The coloring agent is shown below. Preferred color formers used in the present invention include compounds represented by the following general formula (a) or (b).

[0014]

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(Provided that R ₁ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, R ₂ represents an alkyl group having 1 to 6 carbon atoms, a cyclohexyl group or a phenyl group which may be substituted. Examples of the group include an alkyl group such as a methyl group and an ethyl group, an alkoxy group such as a methoxy group and an ethoxy group, a halogen, etc. R ₃ represents hydrogen, an alkyl group having 1 to 2 carbon atoms, an alkoxy group, or a halogen. R ₄ represents hydrogen, methyl, halogen, or an amino group which may be substituted, for example, an alkyl group, an aryl group which may be substituted, an aralkyl which may be substituted; Wherein the substituent is an alkyl group, a halogen,
And an alkoxy group. Hereinafter, specific examples of such a color former will be described, but the present invention is not limited thereto.

2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6
(Di-n-butylamino) fluoran, 2-anilino-
3-methyl-6- (Nn-propyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N
-Isopropyl-N-methylamino) fluoran, 2-
Anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluoran, 2-anilino-3-methyl-
6- (Nn-amyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N-sec-butyl-N-ethylamino) fluoran, 2-anilino-
3-methyl-6- (Nn-amyl-N-ethylamino) fluoran, 2-anilino-3-methyl-6- (N
-Iso-amyl-N-ethylamino) fluoran, 2
-Anilino-3-methyl-6- (Nn-propyl-N
-Isopropylamino) fluoran, 2-anilino-3
-Methyl-6- (Nn-propyl-N-isopropylamino) fluoran, 2-anilino-3-methyl-6
(N-cyclohexyl-N-methylamino) fluoran, 2-anilino-3-methyl-6- (N-ethyl-p
-Toluidino) fluoran, 2-anilino-3-methyl-6- (N-methyl-p-toluidino) fluoran, 2
-(M-trichloromethylanilino) -3-methyl-6
-Diethylaminofluoran, 2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluoran, 2- (m-trifluoromethylanilino) -3-
Methyl-6- (N-cyclohexyl-N-methylamino) fluoran, 2- (2,4-dimethylanilino)-
3-methyl-6-diethylaminofluoran, 2- (N
-Ethyl-p-toluidino) -3-methyl-6- (N-
Ethylanilino) fluoran, 2- (N-ethyl-p-
Toluidino) -3-methyl-6- (N-propyl-p-
Toluidino) fluoran, 2-anilino-6- (N-n
-Hexyl-N-ethylamino) fluoran, 2- (o
-Chloroanilino) -6-diethylaminofluoran,
2- (o-bromoanilino) -6-diethylaminofluoran, 2- (o-chloroanilino) -6-dibutylaminofluoran, 2- (o-fluoroanilino) -6-dibutylaminofluoran, 2- (m-toluene) Fluoromethylanilino) -6-diethylaminofluoran, 2-
(P-acetylanilino) -6- (Nn-amyl-N
-N-butylamino) fluoran, 2-benzylamino-6- (N-ethyl-p-toluidino) fluoran, 2
-Benzylamino-6- (N-methyl-2,4-dimethylanilino) fluoran, 2-benzylamino-6-
(N-ethyl-2,4-dimethylanilino) fluoran, 2-dibenzylamino-6- (N-methyl-p-toluidino) fluoran, 2-dibenzylamino-6
(N-ethyl-p-toluidino) fluoran, 2- (di-p-methylbenzylamino) -6- (N-ethyl-p
-Toluidino) fluoran, 2- (α-phenylethylamino) -6- (N-ethyl-p-toluidino) fluoran, 2-methylamino-6- (N-methylanilino)
Fluoran, 2-methylamino-6- (N-ethylanilino) fluoran, 2-methylamino-6- (N-propylanilino) fluoran, 2-ethylamino-6
(N-methyl-p-toluidino) fluoran, 2-methylamino-6- (N-methyl-2,4-dimethylanilino) fluoran, 2-ethylamino-6- (N-methyl-2,4-dimethyl Anilino) fluoran, 2-dimethylamino-6- (N-methylanilino) fluoran, 2
-Dimethylamino-6- (N-ethylanilino) fluoran, 2-diethylamino-6- (N-methyl-p-toluidino) fluoran, 2-diethylamino-6- (N
-Ethyl-p-toluidino) fluoran, 2-dipropylamino-6- (N-methylanilino) fluoran, 2
-Dipropylamino-6- (N-ethylanilino) fluoran, 2-amino-6- (N-methylanilino) fluoran, 2-amino-6- (N-ethylanilino) fluoran, 2-amino-6- (N-propyl Anilino) fluoran, 2-amino-6- (N-methyl-p-toluidino) fluoran, 2-amino-6- (N-ethyl-p
-Toluidino) fluoran, 2-amino-6- (N-propyl-p-toluidino) fluoran, 2-amino-6
-(N-methyl-p-ethylanilino) fluoran, 2
-Amino-6- (N-ethyl-p-ethylanilino) fluoran, 2-amino-6- (N-propyl-p-ethylanilino) fluoran, 2-amino-6- (N-methyl-2,4-dimethylaniline) Rino) fluorane, 2-amino-6- (N-ethyl-2,4-dimethylanilino) fluoran, 2-amino-6- (N-propyl-2,4-
Dimethylanilino) fluoran, 2-amino-6- (N
-Methyl-p-chloroanilino) fluoran, 2-amino-6- (N-ethyl-p-chloroanilino) fluoran, 2-amino-6- (N-propyl-p-chloroanilino) fluoran, 2,3-dimethyl-6 -Dimethylaminofluoran, 3-methyl-6- (N-ethyl-p-
Toluidino) fluoran, 2-chloro-6-diethylaminofluoran, 2-bromo-6-diethylaminofluoran, 2-chloro-6-dipropylaminofluoran, 3-chloro-6-cyclohexylaminofluoran, 3-bromo -6-cyclohexylaminofluoran, 2-chloro-6- (N-ethyl-N-isoamylamino) fluoran, 2-chloro-3-methyl-6-diethylaminofluoran, 2-anilino-3-chloro-6
-Diethylaminofluoran, 2- (o-chloroanilino) -3-chloro-6-cyclohexylaminofluoran, 2- (m-trifluoromethylanilino) -3-chloro-6-diethylaminofluoran, 2- (2 , 3-Dichloroanilino) -3-chloro-6-diethylaminofluoran, 1,2-benzo-6-diethylaminofluoran, 1,2-benzo-6- (N-ethyl-N-isoamylamino) fluoran, 1, 2-benzo-6-dibutylaminofluoran, 1,2-benzo-6- (N-ethyl-N-cyclohexylamino) fluoran, 1,2-
Benzo-6- (N-ethyl-toluidino) fluoran,
Other.

Specific examples of other color formers preferably used in the present invention are as follows.

2-anilino-3-methyl-6- (N-2
-Ethoxypropyl-N-ethylamino) fluoran,
2- (p-chloroanilino) -6- (Nn-octylamino) fluoran, 2- (p-chloroanilino) -6
-(Nn-partimylamino) fluoran, 2- (p
-Chloroanilino) -6- (di-n-octylamino)
Fluoran, 2-benzoylamino-6- (N-ethyl-p-toluidino) fluoran, 2- (o-methoxybenzoylamino) -6- (N-ethyl-p-toluidino) fluoran, 2-dibenzylamino-4 -Methyl-
6-diethylaminofluoran, 2-dibenzylamino-4-methoxy-6- (N-methyl-p-toluidino)
Fluoran, 2-dibenzylamino-4-methyl-6
(N-ethyl-p-toluidino) fluoran, 2- (α
-Phenylethylamino) -4-methyl-6-diethylaminofluoran, 2- (p-toluidino) -3- (t
-Butyl) -6- (N-methyl-p-toluidino) fluoran, 2- (o-methoxycarbonylanilino) -6
-Diethylaminofluoran, 2-acetylamino-6
-(N-methyl-p-toluidino) fluoran, 3-diethylamino-6- (m-trifluoromethylanilino) fluoran, 4-methoxy-6- (N-ethyl-p
-Toluidino) fluoran, 2-ethoxyethylamino-3-chloro-6-dibutylaminofluoran, 2-dibenzylamino-4-chloro-6- (N-ethyl-p-
Toluidino) fluoran, 2- (α-phenylethylamino) -4-chloro-6-diethylaminofluoran,
2- (N-benzyl-p-trifluoromethylanilino)
-4-chloro-6-diethylaminofluoran, 2-anilino-3-methyl-6-pyrrolidinofluoran, 2-
Anilino-3-chloro-6-pyrrolidinofluoran, 2
-Anilino-3-methyl-6- (N-ethyl-N-tetrahydrofurfurylamino) fluoran, 2-mesidino-4 ', 5'-benzo-6-diethylaminofluoran, 2- (m-trifluoromethylani (Lino) -3-methyl-6-pyrrolidinofluoran, 2- (α-naphthylamino) -3,4-benzo-4′-bromo-6- (N-benzyl-N-cyclohexylamino) fluoran, 2-
Piperidino-6-diethylaminofluoran, 2- (N
-N-propyl-p-trifluoromethylanilino) -6
-Morpholinofluoran, 2- (di-N-p-chlorophenyl-methylamino) -6-pyrrolidinofluoran, 2- (Nn-propyl-m-trifluoromethylanilino) -6-morpho Linofluoran, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-
Ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-octyl-2-methylindole-
3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2
-Methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide;
3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3,3-bis (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide, 1,2-benzo-6- (N -Ethyl-Nn-octylamino) fluoran, 1,2-benzo-6-diallylaminofluoran, 1,2-benzo-6- (N-ethoxyethyl-N-ethylamino) fluoran, benzoleucomethylene blue, 2- [3,6-bis (diethylamino)]-6- (o-chloroanilino) xanthylbenzoic acid lactam, 2- [3,6-bis (diethylamino)]-9- (o-chloroanilino) xanthylbenzoic acid lactam, 3,3-bis (p-dimethylaminophenyl) phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethyla Nofutarido (aka crystal violet lactone), 3,3-bis (p- dimethylaminophenyl) -6-diethylamino phthalide, 3,
3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3- (2-methoxy-4-dimethylaminophenyl) -3- (2-hydroxy- 4,5-dichlorophenyl) phthalide, 3- (2-hydroxy-4-dimethylaminophenyl) -3- (2-methoxy-5-chlorophenyl) phthalide, 3- (2-hydroxy-4-
Dimethoxyaminophenyl) -3- (2-methoxy-5
-Chlorophenyl) phthalide, 3- (2-hydroxy-
4-dimethylaminophenyl) -3- (2-methoxy-
5-nitrophenyl) phthalide, 3- (2-hydroxy-4-diethylaminophenyl) -3- (2-methoxy-5-methylphenyl) phthalide, 3,6-bis (dimethylamino) fluorenespiro (9,3 ′ 6) -Dimethylaminophthalide, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-
2'-methoxy-benzoindolino-spiropyran and the like.

Next, the developer used in combination with the color former in the present invention is an electron-accepting compound, and has a structure exhibiting a color developing ability capable of causing the color former to develop a color in the molecule and a cohesive force between the molecules. Is a compound having a long-chain structure portion that controls the following, for example, an organic phosphoric acid compound having an aliphatic group having 12 or more carbon atoms, an aliphatic carboxylic acid compound having 12 or more carbon atoms, and a phenol having an aliphatic group having 12 or more carbon atoms And the like. The aliphatic group includes a linear or branched alkyl group and alkenyl group, and may have a substituent such as a halogen, an alkoxy group, and an ester. Hereinafter, specific examples of the developer will be described. (A) Organophosphate Compound A compound represented by the following general formula (1) is used.

[0020]

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(R ₅ represents a linear alkyl group having 12 or more carbon atoms) Specific examples of the organic phosphoric acid compound represented by the general formula (1) include the following. Dodecylphosphonic acid, tetradecylphosphonic acid,
Hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, hexacosylphosphonic acid, octacosylphosphonic acid and the like.

(B) Aliphatic carboxylic acid compounds α-hydroxy fatty acids represented by the following general formula (2) are preferably used. R ₆ —CH (OH) —COOH (2) (where R ₆ represents an aliphatic group having 12 or more carbon atoms) Examples of the α-hydroxy aliphatic carboxylic acid compound represented by the general formula (2) include The following are mentioned.

Α-hydroxydecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxydecanoic acid
Hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid, α-hydroxytetracosanoic acid, α-hydroxyhexacosanoic acid, α-hydroxyoctacosanoic acid, and the like.

The aliphatic carboxylic acid compound is an aliphatic carboxylic acid compound having an aliphatic group having 12 or more carbon atoms and substituted with a halogen element, at least in the α-position or β-position.
Those having a halogen element at the carbon at the position are also preferably used. Specific examples of such compounds include, for example, the following. 2-bromohexadecanoic acid, 2-bromoheptadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid, 2-bromodocosanoic acid, 2-bromotetracosanoic acid, 3-bromooctadecanoic acid, 3-bromoeicosanoic acid 2,2-dibromooctadecanoic acid, 2-fluorododecanoic acid, 2-fluorotetradecanoic acid, 2-fluorohexadecanoic acid, 2-fluorooctadecanoic acid, 2-fluoroeicosanoic acid, 2-
Fluorodocosanoic acid, 2-iodohexadecanoic acid, 2-
Iodooctadecanoic acid, 3-iodohexadecanoic acid, 3
-Iodooctadecanoic acid, perfluorooctadecanoic acid and the like.

The aliphatic carboxylic acid is an aliphatic carboxylic acid compound having an oxo group in the carbon and having an aliphatic group having 12 or more carbon atoms.
Those having an oxo group at the carbon atom are preferably used. Specific examples of such compounds include, for example, the following.

2-oxododecanoic acid, 2-oxotetradecanoic acid, 2-oxohexadecanoic acid, 2-oxooctadecanoic acid, 2-oxoeicosanoic acid, 2-oxotetracosanoic acid, 3-oxododecanoic acid, 3-oxo Tetradecanoic acid, 3-oxohexadecanoic acid, 3-oxooctadecanoic acid, 3-oxoeicosanoic acid, 3-oxotetracosanoic acid, 4-oxohexadecanoic acid, 4-oxooctadecanoic acid, 4-oxodokosanoic acid and the like. As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (3) is also preferably used.

[0027]

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(Where R ₇ represents an aliphatic group having 12 or more carbon atoms, X represents an oxygen atom or a sulfur atom,
Represents 1 or 2. As specific examples of the dibasic acid represented by the general formula (3),
For example, the following are mentioned.

Dodecyl malate, tetradecyl malate, hexadecyl malate, octadecyl malate, eicosyl malate, docosyl malate, tetracosyl malate, dodecyl thiomalate, tetradecyl thiomalate, hexadecyl thiomalate Acid, octadecylthiomalic acid, eicosylthiomalic acid, docosylthiomalic acid, tetracosylthiomalic acid, dodecyldithiomalic acid, tetradecyldithiomalic acid, eicosyldithiomalic acid, docosyldithiomalic acid, tetracosyl Rudithiomalic acid and the like. As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (4) is also preferably used.

[0030]

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(However, R ₈ , R ₉ , and R ₁₀ represent hydrogen or an aliphatic group, and at least one of them is an aliphatic group having 12 or more carbon atoms.) Specific examples of the basic acid include:
For example, the following are mentioned.

Dodecyl butane diacid, tridecyl butane diacid, tetradecyl butane diacid, pentadecyl butane diacid, octadecyl butane diacid, eicosyl butane diacid,
Docosyl butane diacid, 2,3-dihexadecyl butane diacid, 2,3-dioctadecyl butane diacid, 2-methyl-
3-dodecyl butane diacid, 2-methyl-3-tetradecyl butane diacid, 2-methyl-3-hexadecyl butane diacid, 2-ethyl-3-dodecyl butane diacid, 2-propyl-3-dodecyl butane Diacid, 2-octyl-3-hexadecylbutanedioic acid, 2-tetradecyl-3-octadecylbutanedioic acid and the like. As the aliphatic carboxylic acid compound,
A dibasic acid represented by the following general formula (5) is also preferably used.

[0033]

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(However, R ₁₁ and R ₁₂ represent hydrogen or an aliphatic group, at least one of which is an aliphatic group having 12 or more carbon atoms.) Of the dibasic acid represented by the general formula (5), As a specific example,
For example, the following are mentioned.

Dodecylmalonic acid, tetradecylmalonic acid, hexadecylmalonic acid, octadecylmalonic acid, eicosylmalonic acid, docosylmalonic acid, tetracosylmalonic acid, didetecylmalonic acid, ditetradecylmalonic acid, dihexadecylmalonic acid, Dioctadecylmalonic acid, dieicosylmalonic acid, didocosylmalonic acid, methyloctadecylmalonic acid, methyldocosylmalonic acid, methyltetracosylmalonic acid, ethyloctadecylmalonic acid, ethyleicosylmalonic acid, ethyldocosylmalonic acid, ethyl Tetracosylmalonic acid and the like. As the aliphatic carboxylic acid compound, a dibasic acid represented by the following general formula (6) is also preferably used.

[0036]

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(Where, R ₁₃ represents an aliphatic group having 12 or more carbon atoms, n represents 0 or 1, m represents 1, 2 or 3, and when n is 0, m represents 2 or 3) Yes,
When n is 1, m represents 1 or 2. As specific examples of the dibasic acid represented by the general formula (6),
For example, the following are mentioned.

2-dodecyl-pentanedioic acid, 2-hexadecyl-pentanedioic acid, 2-octadecylpentanedioic acid, 2-eicosyl-pentanedioic acid, 2-docosyl-pentanedioic acid, 2-dodecyl-hexanedioic acid, 2-pentadecyl-hexane diacid, 2-octadecyl-hexane diacid, 2-eicosyl-hexane diacid, 2-docosyl-hexane diacid, and the like. As the aliphatic carboxylic acid compound, a tribasic acid such as citric acid acylated with a long-chain fatty acid is also preferably used. Specific examples include the following.

[0039]

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As the phenol compound, a compound represented by the following general formula (7) is used.

[0041]

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(Where Y is -S-, -O-, -CON
_{H -, - NHSO 2 -,} - CH = CHCONH -, - N
HCO -, - NHCONH-, or -COO- a represents, R ₁₄ represents a number of 12 or more aliphatic group having a carbon, n is an integer of 1, 2 or 3. Specific examples of the phenol compound represented by the general formula (7) include the following. p-
(Dodecylthio) phenol, p- (tetradecylthio) phenol, p- (hexadecylthio) phenol, p- (octadecylthio) phenol, p- (eicosylthio) phenol, p- (docosylthio) phenol, p- (tetracosylthio) phenol Phenol, p- (dodecyloxy) phenol, p- (tetradecyloxy) phenol, p- (hexadecyloxy) phenol, p- (octadecyloxy) phenol, p- (eicosyloxy) phenol, p- (docosyloxy)
Phenol, p- (tetracosyloxy) phenol,
p-dodecylcarbamoylphenol, p-tetradecylcarbamoylphenol, p-hexadecylcarbamoylphenol, p-octadecylcarbamoylphenol, p-eicosylcarbamoylphenol, p-docosylcarbamoylphenol, p-tetracosylcarbamoylphenol, hexagallate Decyl ester,
Octadecyl gallate, eicosyl gallate, docosyl gallate, tetracosyl gallate, N-dodecyl-p-hydroxycinnamamide, N-tetradecyl-p-hydroxycinnamamide, N-octadecyl-p -Hydroxycinnamamide, N-docosyl-p-hydroxycinnamamide, N
-Dodecyl-p-hydroxycinnamamide, N-octacosyl-p-hydroxycinnamamide, 4'-hydroxytridecaneanilide, 4'-hydroxyheptadecaneanilide, 4'-hydroxynonadecaneanilide,
3'-hydroxynonadecaneanilide, 4- (N-docosylsulfonylamino) phenol, 4- (N-octadecylsulfonylamino) phenol, N- (4-hydroxyphenyl) -N'-dodecylurea, N- (4 -Hydroxyphenyl) -N'-octadecylurea, N-
(4-hydroxyphenyl) -N'-docosyl urea and the like.

In the present invention, the color developer is not limited to the compounds described above, and various other electron-accepting compounds can be used. The matrix polymer used in the present invention is a polymer compound having a film forming property, and these are all known. Specific examples of usable polymer compounds are shown below.

Polyolefins such as polyethylene and polypropylene; polymethyl acrylate, polyethyl acrylate, poly (n-butyl acrylate), polymethyl methacrylate, polyethyl methacrylate, poly (isobutyl methacrylate), poly (n-butyl methacrylate), (Sec-butyl methacrylate), poly (tert-butyl methacrylate), poly (isobornyl methacrylate), poly (benzyl methacrylate), poly (2-ethylhexyl methacrylate), polyacrylic acid, polymethacrylic acid and copolymers thereof Acrylic polymers such as polystyrene,
Styrene-based polymers such as styrene-acrylonitrile copolymer; polyvinyl chloride, polyvinyl alcohol,
Polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl formal, vinyl alcohol
Such as vinyl butyral copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer Vinyl polymers; Fluorine polymers such as polytetrafluoroethylene, polytrifluoroethylene, and polyvinylidene fluoride; such as nitrocellulose, cellulose acetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate, ethyl cellulose, and methyl cellulose Cellulosic polymer; isobutylene-maleic anhydride copolymer;
Polyisobutyl ether; Polyethylene oxide; Polypropylene oxide; Polycarbonate, Polyarylate, Polysulfone, Poly (2,6-dimethyl-p-
Engineering plastics such as phenylene oxide), polyimide polyamide imide, polyether imide; polyurethane; nylon 6, nylon 66
Such as polyamide resins; silicone resins; melamine-formaldehyde resins; urea-formaldehyde resins; phenol-formaldehyde resins; alkyd resins, etc., such as xylene resins, furan resins, epoxy resins, unsaturated polyester resins, and maleic anhydride resins. Thermosetting resins, rubber-based polymers such as natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and the like.

The coating solution for forming a reversible thermosensitive recording layer of the present invention contains the above-mentioned developer, color former, and matrix polymer as main components. The coating liquid of the present invention is used in the form of a uniform coating liquid in which the above-mentioned main components are completely dissolved, or a dispersion coating liquid in which a color developing agent and a developer are dispersed in a vehicle in which a matrix polymer is dissolved in a solvent. The vehicle referred to in the present invention is a conventionally known concept in coating science,
Generally, it refers to components other than pigments in a coating solution (for example, Yuji Harazaki: New Edition Coating Engineering, Maki Shoten (1978), p. 183). In the present invention, a solution component obtained by dissolving a color former and a matrix polymer in a solvent is defined as a vehicle. The coating liquid component may contain a soluble additive or the like. Specific examples of the solvent used in the coating liquid of the present invention are shown below.

Water; alcohols such as methanol, ethanol, isopropanol, n-butynol and methyl isocarbinol; acetone, 2-butanone, 3-methyl-2-butanone, diacetone alcohol, isophorone,
Ketones such as cyclohexanone; amides such as N, N-dimethylformamide and N, N-phodimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol and ethylene glycol dimethyl ether; 2-methoxyethyl acetate;
Glycol ether acetates such as ethoxyethyl acetate and 2-butoxyethyl acetate; esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate and ethylene carbonate; aromatic hydrocarbons such as benzene, toluene and xylene Aliphatic hydrocarbons such as hexane, heptane and iso-octanecyclohexane; halogenated hydrocarbons such as methylene chloride, 2,2-dichloroethane, dichloropropane and chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl- 2-pyrrolidone N-octyl-
Examples thereof include pyrrolidones such as 2-pyrrolidone.

The solubility parameter used in the present invention is a concept well known in the coatings industry. The solubility parameter is a physical property value that is a measure of the intermolecular interaction, and can accurately predict the intermolecular interaction such as the solubility of a polymer in a solvent, the compatibility between polymers, or the adsorptivity of a polymer to a pigment. it can. Methods for determining solubility parameters are also known. The values of the solubility parameters used in the present invention are known in the art (Toshinao Okitsu: Journal of the Adhesion Society of Japan, Vol. 29, page 204 (1993); and Yuji Harazaki: Super Technology Revolution, New Technology Development Center (1991), 59 Page) method. In the case of a coating liquid prepared using a main component whose solubility parameter does not satisfy the above-mentioned relational expression (1) and / or (1) and (2) and a recording layer formed using the coating liquid, the image density of a recording medium Is low, and the image density is greatly reduced when used repeatedly. Further, the image density is largely reduced by storage at high temperature.

A recording medium comprising a coating liquid prepared using a main component having a solubility parameter satisfying the above-mentioned relational expression (1) and / or (1) and (2) and a recording layer formed using the coating liquid. When the image density is low and the image is repeatedly used, the image density greatly decreases. Further, the image density is largely reduced by storage at high temperature. The solubility parameter is defined by the relational expression (1) or / and (1)
The reason why the improvement of the characteristics of the recording medium was realized by the coating liquid prepared using the main components satisfying (2) and the recording layer formed using the coating liquid is not necessarily clear, but the coating liquid for forming the recording layer is not clear. It is inferred that the interaction between the main components in the middle and the recording layer is due to the optimized result.

The ratio of the color former to the color developer in the recording layer varies in an appropriate range depending on the combination of the compounds to be used.
And preferably in the range of 0.3 to 10. If the amount of the developer is smaller or larger than this range, the density of the color-developed state is reduced, which is problematic. The ratio of the matrix polymer to the color-forming component (color-forming agent and color-developing agent) varies in an appropriate range depending on the combination of the compounds used. And preferably ranges from 0.1 to 5. The reversible thermosensitive recording medium of the present invention is produced by applying the coating liquid for forming a reversible thermosensitive recording layer prepared above on a suitable support and providing a recording layer. Any type of support can be used, and examples thereof include paper, synthetic paper, plastic films such as polyester, metal films, and composite films obtained by laminating these.

The coating method is not particularly limited, and known methods such as blade coating, Meyer bar coating, spray coating, air knife coating, bead coating, curtain coating, gravure coating, and kiss coating can be used. Can be used. The thickness of the recording layer is preferably in the range of 1 μm to 20 μm, and more preferably in the range of 2 μm to 15 μm. In the reversible thermosensitive recording medium of the present invention, an additive for improving or controlling the coating characteristics and the coloring and decoloring characteristics of the recording layer can be used as necessary. These additives include, for example, dispersants, surfactant conductive agents, fillers, lubricants, antioxidants, light stabilizers, ultraviolet absorbers, color stabilizers, and decolorization accelerators. The reversible thermosensitive recording medium of the present invention is basically provided with the above recording layer on a support, but in order to improve the properties as a recording medium, a protective layer, an adhesive layer, an intermediate layer,
An undercoat layer, a backcoat layer, and the like can be provided.

In printing using a thermal head, the surface of the recording layer may be deformed by heat and pressure, so that a so-called dent may be formed. In order to prevent this, it is preferable to provide a protective layer on the surface. For the protective layer, polyvinyl alcohol, styrene-maleic anhydride copolymer, carboxy-modified polyethylene, melamine-formaldehyde resin, urea-formaldehyde resin, ultraviolet curable resin, electron beam curable resin and the like can be used. Further, additives such as an ultraviolet absorber can be contained in the protective layer. It is also preferable to provide an intermediate layer between the recording layer and the protective layer for the purpose of improving the adhesion between the recording layer and the protective layer, preventing deterioration of the recording layer due to application of the protective layer, and preventing migration of additives in the protective layer to the recording layer. . or,
It is preferable to use a resin having low oxygen permeability for the protective layer and the intermediate layer provided on the recording layer. It is possible to prevent or reduce oxidation of the color former and the developer in the recording layer.

Further, a heat insulating undercoat layer can be provided between the support and the recording layer in order to effectively utilize the applied heat. The heat insulating layer can be formed by applying organic or inorganic fine hollow particles using a binder resin. An undercoat layer may be provided for the purpose of improving the adhesion between the support and the recording layer and preventing the penetration of the recording layer material into the support. The same resin as the above-mentioned resin for the recording layer can be used for the intermediate layer and the undercoat layer.
The protective layer, the intermediate layer, the recording layer, and the undercoat layer can contain fillers such as calcium carbonate, magnesium carbonate, titanium oxide, silicon oxide, aluminum hydroxide, kaolin, and talc. In addition, a lubricant, a surfactant dispersant and the like can be contained.

[0053]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples. In the examples, “parts” and “%” are based on weight. Also, the unit of the solubility parameter value of each material: (cal / c
m ^{3) 1/2} is omitted. Example 1 A) Dokoshiruhosuhon acid (δ _A: 8.4) 10 parts B) poly (tert- butyl methacrylate) (δ _p: 8.0) 15 parts of C) 2-anilino-3-methyl-6 (N-ethyl-p-toluidino) fluoran 3 parts D) N-methyl-2-pyrrolidone (δ _s : 12.7) 85 parts A was completely dissolved in D above while heating first, and then the heated solution Is added and dissolved, and finally, C is added and dissolved to prepare a coating liquid for forming a recording layer of the present invention.

Next, the above coating solution was applied on a 100 μm thick white polyester film using a wire bar,
By heating and drying, a recording layer having a thickness of about 7 μm was provided. After applying a protective layer coating solution having the following composition on the recording layer using a wire bar, the coating solution was cured under a UV lamp having an irradiation energy of 80 W / cm at a transport speed of 9 m / min to be cured to a thickness of 3 μm. A protective layer was provided, and a reversible thermosensitive recording medium of this example was prepared.

(Protective Layer Coating Solution) Urethane acrylate UV curable resin (C7-157, manufactured by Dainippon Ink) 10 parts Ethyl acetate 90 parts Example 2 A) Docosylphosphonic acid (δ _A : 8.4) ) 10 parts B) polyvinyl acetate (δ _p : 9.4) 15 parts C) 2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluoran 3 parts D) dichloroethane (δ _s : 11.7) 85 parts C is first completely dissolved in D, and then B is added and dissolved to prepare a vehicle. Add A to this vehicle,
This mixture was pulverized and dispersed for 96 hours using a paint shaker to obtain a coating liquid for forming a recording layer of the present invention.

Next, the above coating solution was applied on a 100 μm thick white polyester film using a wire bar,
By heating and drying, a recording layer having a thickness of about 7 μm was provided. After applying a protective layer coating liquid having the same composition as that used in Example 1 on the recording layer using a wire bar, the irradiation energy was 80 W.
A protective layer having a thickness of 3 μm was provided by passing under a UV lamp at a conveying speed of 9 m / min to provide a protective layer having a thickness of 3 μm. Thus, a reversible thermosensitive recording medium of this example was prepared.

Example 3 A) 10 parts of N-4-hydroxyphenyl-N'-octadecylurea (δ _A : 10.3) B) 15 parts of poly (benzyl methacrylate) (δ _p : 9.8) C) 2 - anilino-3-methyl -6- (N, N- Jiechiruami Roh) fluoran 3 D) dimethylformamide ([delta] _S: 12.1) recording of the present invention in the same manner as in example 1 with 85 parts of the formulation A coating liquid for forming a layer was prepared and used to prepare a reversible thermosensitive recording medium of this example.

Example 4 A) 10 parts of N-4-hydroxyphenyl-N'-octadecylurea (δ _A : 10.3) B) 15 parts of polycarbonate (δ _p : 10.0) C) 2-anilino-3 - methyl -6- (N, N- Jiechiruami Roh) fluoran 3 D) in tetrahydrofuran (δ _S: 9.2) 85 parts of the recording layer forming coating liquid of the present invention in the same manner as in example 2 using the formulation Was prepared and used to prepare a reversible thermosensitive recording medium of this example.

Example 5 A) 10 parts of p- (docosylthio) phenol (δ _A : 9.4) B) 15 parts of polyethyl methacrylate (δ _p : 8.9) C) 2-anilino-3-methyl-6 - (N, N-Jibuchiruami Roh) fluoran 3 D) 1,4-dioxane (δ _S: 10.2) 85 parts of the recording layer forming coating liquid of the present invention in the same manner as in example 1 using the above formulations Was prepared and used to prepare a reversible thermosensitive recording medium of this example.

Example 6 A) p- (Docosylthio) phenol (δ _A : 9.4) 10 parts B) Vinyl chloride-vinyl acetate copolymer (VYHH, manufactured by Union Carbide, USA) (δ _p : 9.9) ) 15 parts of C) 2-anilino-3-methyl -6- (N, N- Jibuchiruami Roh) fluoran 3 D) 3--methyl-2-butanone ([delta] _S: 8.7) performed using 85 parts of the formulation A coating solution for forming a recording layer of the present invention was prepared in the same procedure as in Example 2, and this was used to prepare a reversible thermosensitive recording medium of this example.

Example 7 A) 10 parts of docosylmalonic acid (δ _A : 8.6) B) 15 parts of polyethyl methacrylate (δ _p : 8.9) C) 2- (o-chloroanilino) -6- (N, N- Jibuchiruami Roh) fluoran 3 D) 2-butanone ([delta] _S: 9.2) the recording layer forming coating liquid of the present invention was prepared in the same manner as in example 2 using 85 parts of the above formulation, it The reversible thermosensitive recording medium of the present example was produced using this.

Example 8 A) 10 parts of docosylthiomalic acid (δ _A : 8.8) B) 15 parts of polyethyl methacrylate (δ _p : 8.9) C) 2- (o-chloroanilino) -6- (N , N- Jibuchiruami Roh) fluoran 3 D) 2-butanone ([delta] _S: 9.2) the recording layer forming coating liquid of the present invention was prepared in the same manner as in example 2 using 85 parts of the above formulation, which Was used to prepare a reversible thermosensitive recording medium of this example.

Comparative Example 1 A) 10 parts of docosylphosphonic acid (δ _A : 8.4) B) 15 parts of polyvinyl chloride (δ _p : 9.5) C) 2-anilino-3-methyl-6- ( N- ethyl -p- Tolui Gino) fluoran 3 D) N- methyl-2-pyrrolidone (δ _S: 12.7) 85 parts of a reversible thermosensitive of this comparative example in the same manner as in example 1 using the above formulations A recording medium was created.

Comparative Example 2 A) 10 parts of docosylphosphonic acid (δ _A : 8.4) B) poly (n-propyl methacrylate) (δ _p : 8.9) 15 parts C) 2-anilino-3-methyl -6-(N-ethyl -p- Tolui Gino) fluoran 3 D) toluene (δ _S: 8.9) 85 parts of a reversible thermosensitive recording medium of this comparative example in the same manner as in example 2 using the formulation It was created.

Comparative Example 3 A) 10 parts of docosylphosphonic acid (δ _A : 8.4) B) 15 parts of nitrocellulose (δ _p : 10.7) C) 2-anilino-3-methyl-6- (N -Ethyl-p-toluidino) fluoran 3 parts D) 2-ethoxyethanol (δ _S : 10.7) 85 parts By using the above composition, a reversible thermosensitive recording medium of this comparative example was prepared in the same procedure as in Example 2. did.

Comparative Example 4 A) 10 parts of N-4-hydroxyphenyl-N'-octadecyl urea (δ _A : 10.3) B) Vinyl chloride-vinyl acetate copolymer (VYHH, manufactured by Union Carbide Co., USA) [delta] _p: 9.9) 15 parts of C) 2-anilino-3-methyl -6- (N, N- Jiechiruami Roh) fluoran 3 D) cyclohexanone ([delta] _S: 10.1) carried with 85 parts of the formulation A reversible thermosensitive recording medium of this comparative example was prepared in the same procedure as in Example 2. The reversible thermosensitive recording media prepared in Examples 1 to 8 and Comparative Examples 1 to 4 were evaluated for the repetition characteristics of image writing and erasing and the heat-resistant storage stability according to the following procedures, and the results shown in Table 1 were obtained. Was.

1) Evaluation method of repetition characteristics: Commercially available thermosensitive facsimile printing tester (TH-PM, manufactured by Okura Electric Co., Ltd.)
Dot density using D): 8 dots / mm, applied voltage:
Image writing is performed under the setting conditions of 13.3 V, pulse width: 0.8 millisecond, and the image density is measured with a reflection densitometer (RD91).
8, Macbeth). Next, the colored image obtained above was erased using a heat stamp under the conditions shown in Table 1, and the density of the erased portion was measured. The above-described image writing and erasing operations were repeated 100 times, and the first and 100th densities were measured.

2) Evaluation method for heat-resistant storage stability: The image written in 1) was stored in a thermostat at 60 ° C. for 24 hours, and the image density after storage was measured. Then, heat resistance storage stability was calculated using the following equation. Heat storage stability (%) = Image density after storage / Image density before storage × 10

[0069]

[Table 1]

[0070]

The reversible thermosensitive composition of the present invention can be repeatedly formed into a stable color-developed state and a good decolored state.
A reversible thermosensitive recording medium using this can be formed by an easy operation of forming and erasing a high-contrast image. In addition, the color image is stable under normal use conditions, has high durability against repeated recording and erasure, and provides a highly practical rewritable recording medium.

[Brief description of the drawings]

FIG. 1 is a view showing the color development / decoloration characteristics of the reversible thermosensitive coloring composition of the present invention.

Claims (4)

[Claims] 1. A color former which is an electron-donating color-forming compound,
Supports a recording layer that contains a developer and a matrix polymer, which are electron-accepting compounds, as main components and can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. A reversible thermosensitive recording medium provided on a body, wherein the electron-accepting compound and the matrix polymer are a combination of an electron-accepting compound and a matrix polymer satisfying the following formula (1). | Δ _A −δ _p | ≦ 1 (1) (where, δ _A is the solubility parameter of the electron-accepting compound, and δ _p is the solubility parameter of the matrix polymer.) 2. The reversible thermosensitive recording medium according to claim 1, wherein the electron-accepting compound is present in a dispersed state in a matrix polymer in which the electron-donating color-forming compound is dissolved. 3. A color former which is an electron-donating color-forming compound,
A recording layer containing a developer, a matrix polymer, and a solvent, which are electron-accepting compounds, as main components and capable of forming a state in which color is relatively developed and a state in which color is erased by a difference in a heating temperature and / or a cooling rate after heating. Wherein the coating liquid for forming a recording layer is a combination of a solvent, an electron-accepting compound, and a matrix polymer satisfying the following formulas (1) and (2): Coating liquid for forming a layer. | Δ _A −δ _p | ≦ 1 (1) | δ _A −δ _s | ≦ 0.5 (2) (where δ _A is the solubility parameter of the electron-accepting compound, δ _p is the solubility parameter of the matrix polymer, δ _s is the solubility parameter of the solvent.) 4. The reversible thermosensitive recording layer according to claim 3, wherein the electron-accepting compound is present in a dispersed state in a vehicle containing the electron-donating color-forming compound and the matrix polymer. Coating liquid.