JPH11105433A - Reversible thermosensible coloring composite and reversible thermosensible recording medium employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To retain a stable coloring property and discoloring property, and correspond to high speed erasing by the use of a phenol compound indicated by a specific formulas as an electron acceptable compound. SOLUTION: A phenol compound indicated y a formula I or formula II is used as an electron acceptable compound. In the formula, X shows a single combination of -CH2 -, -C2 H4 -, -CH=CH- or -NHCH2 -, Y shows -NHCO-,-NHSO2 -, -N=CH-,-NH-CO-NH- or-NH-CS-NH-, and R shows at least 6c alkyl group. Also, (n) is an integer of 1-3, and (l), (m), (p), (q), (s) respectively is an integer of 1-4. In the formula I and formula II, if R has at most 5c, a coloring stability or discoloring property lowers, so that carbon numbers are preferably 5 or more, and they are more preferably 10 or more. A recording medium employing the electron acceptable compound can perform high speed erasing, or iterate printing and erasing stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive coloring composition utilizing a coloring reaction between an electron-donating color-forming compound and an electron-accepting compound. The present invention also relates to a reversible thermosensitive recording medium capable of forming and erasing a color image by controlling the thermal energy using the reversible thermosensitive coloring composition.

[0002]

2. Description of the Related Art Conventionally, an electron-donating color-forming compound (hereinafter, referred to as an electron donating color compound)
Heat-sensitive recording media utilizing a color-forming 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 a facsimile, a word processor, and a scientific measuring instrument. 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.

However, according to the patent publication, a recording medium capable of reversibly developing and decoloring has also been proposed. For example, Japanese Patent Application Laid-Open No. 60-1985 uses a combination of gallic acid and phloroglucinol as a color developer. JP-A-1936991, JP-A-61-237684 using a compound such as phenolphthalein or thymolphthalein as a developer, and a recording layer containing a homogeneous compatibilizer of a color former, a developer and a carboxylic acid ester. JP-A-62-138556, JP-A-62-1
38568 and JP-A-62-140881, and JP-A-63-63163 using an ascorbic acid derivative as a developer.
JP-A-173684, JP-A-2-188293 and JP-A-2-18 using a salt of bis (hydroxyphenyl) acetic acid or gallic acid with a higher aliphatic amine as a developer
No. 8,294, each publication 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,
It is not satisfactory as a practical recording medium.

[0004] The present inventors have previously described Japanese Patent Application Laid-Open No. Hei 5-12436.
In Japanese Patent Publication No. 0, 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 a color is formed by combining this with a leuco dye as a color former. Decoloring can be easily performed by heating and cooling conditions, and the color development and decoloration can be stably maintained at room temperature, and the color development and decoloration can be repeated stably. We proposed a reversible thermosensitive coloring composition and a reversible thermosensitive recording medium using the same in the recording layer. 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. After that, use of a specific structure for a phenol compound having a long-chain aliphatic hydrocarbon group was proposed (Japanese Patent Laid-Open No. 6-210954), but this also had the same problem.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a reversible thermosensitive coloring composition and a reversible thermosensitive recording medium which can maintain stable coloring and decoloring properties and can cope with high-speed erasure. It is.

[0006]

SUMMARY OF THE INVENTION The inventors of the present invention have studied the reversible color-decoloring phenomenon of a composition of a color former and a color developer by using a color developer of a color developer having a long-chain aliphatic group. Considering that the balance between the ability to develop color and the cohesive force between molecules is important, compounds having various structures were examined. As a result, they have found that the above problem can be solved by using a phenol compound having a specific structure as a color developer.

That is, a reversible thermosensitive coloring composition utilizing a coloring reaction of an electron-donating coloring compound with an electron-accepting compound and a reversible thermosensitive recording medium provided with a recording layer containing the coloring composition. In the invention, a phenol compound represented by the following general formula (1) or (2) is used as the electron accepting compound.

Embedded image

Embedded image (In the above formulas, X represents a single _{bond, -CH 2 -, - C 2} H 4 -, - C
H represents CH— or —NHCH ₂ —, and Y represents —NHCO
_{-, - NHSO 2 -, -} N = CH -, - NH-CO-N
Represents H- or -NH-CS-NH-, and R represents an alkyl group having 6 or more carbon atoms. N is an integer of 1 to 3,
l, m, p, q, and s each represent an integer of 1 to 4. )

In the compounds represented by the above general formulas (1) and (2), when the number of carbon atoms of R is 5 or less, the stability of color development and the decoloring property are deteriorated.
More preferably, it is 0 or more.

Next, specific examples of the compounds in the present invention are shown in Table 1.
Shown in However, the present invention is not limited to these.

[0010]

[Table 1- (1)]

[0011]

[Table 1- (2)]

[0012]

[Table 1- (3)]

The reversible thermosensitive color-forming composition of the present invention is basically constituted by combining the above-mentioned developer and color former. The color former used in the present invention has an electron donating property, and is itself a colorless or pale color dye precursor (leuco dye), and is not particularly limited. Fluoran compounds, phenothiazine compounds, leuco auramine compounds, indolinophthalide compounds and the like. Specific examples of the coloring agent are shown below.

Preferred color formers for use in the present invention include compounds of the following general formula:

Embedded image

Embedded image (However, R ₁₁ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ₁₂ represents an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group or an optionally substituted phenyl group. R ₁₃ represents a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, an alkoxy group or a halogen atom, for example, an alkyl group such as a methyl group or an ethyl group, an alkoxy group such as a methoxy group or an ethoxy group, or a halogen atom. R ₁₄ represents a hydrogen atom, a methyl group, a halogen atom or an amino group which may be substituted.
Examples of the substituent for the amino group include an alkyl group, an optionally substituted aryl group, and an optionally substituted aralkyl group. The substituent here is an alkyl group, a halogen atom, an alkoxy group or the like).

Specific examples of such a color former include the following compounds. 2-anilino-3-methyl-6-diethylaminofluoran 2-anilino-3-methyl-6- (di-n-butylamino) fluoran, 2-anilino-3-methyl-6- (N
-N-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-methylamino) fluoran, 2-anilino-3-methyl-6- (N
-N-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- (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-diethylaminofluor Oran,
2- (m-trichloromethylanilino) -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- (Nn-hexyl-
N-ethylamino) fluoran, 2- (o-chloroanilino) -6-diethylaminofluoran, 2- (o-chloroanilino) -6-dibutylaminofluoran, 2-
(M-trifluoromethylanilino) -6-diethylaminofluoran, 2- (p-acetylanilino) -6
(Nn-amyl-NNn-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-ethyl-2,4, -dimethylanilino) 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-methyl-anilino) fluoran, 2-dipropylamino-
6- (N-ethyl-anilino) fluoran, 2-amino-6- (N-methylanilino) fluoran, 2-amino-6- (N-ethylanilino) fluoran, 2-amino-6- (N-propylanilino) 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-dimethylanilino) fluoran, 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-diethylamino Fluoran, 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-methyl-N
-Cyclohexylamino) fluoran, 1,2-benzo-6- (N-ethyl-toluidino) fluoran, and others.

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-palmitylamino) fluoran, 2- (p-chloroanilino) -6
-(Di-n-octylamino) fluoran, 2-benzoylamino-6- (N-ethyl-p-toluidino) fluoran, 2- (o-methoxybenzoylamino) -6
(N-methyl-p-toluidino) fluoran, 2-dibenzylamino-4-methyl-6-diethylaminofluoran, 2-dibenzylamino-4-methoxy-6- (N
-Methyl-P-toluidino) fluoran, 2-benzylamino-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-methoxycarbonylamino) -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-trifluoromethylanilino) -3-methyl-6-pyrrolidinofluoran, 2- (α-naphthylamino) -3,4-benzo-
4'-bromo-6- (N-benzyl-N-cyclohexylamino) fluoran, 2-piperidino-6-diethylaminofluoran, 2- (Nn-propyl-p-trifluoromethylanilino) -6-morpho Linofluoran, 2- (di-Np-chlorophenyl-methylamino) -6-pyrrolidinofluoran, 2- (Nn-propyl-m-trifluoromethylanilino) -6-morpholinofluoran , 1,2-benzo-6- (N-ethyl-Nn-octylamino) fluoran, 1,2-benzo-6-diallylaminofluoran, 1,2-benzo-
6- (N-ethoxyethyl-N-ethylamino) fluoran,

Benzolecomethylene blue, 2- [3,
6-bis (diethylamino)]-6- (o-chloroanilino) xanthylbenzoate lactam, 2- [3,6-bis (diethylamino)]-9- (o-chloroanilino)
Lactam xanthylbenzoate, 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-
Dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-
Bis (p-dimethylaminophenyl) -6-diethylaminophthalide, 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- (2-methoxy-4-dimethylaminophenyl)-
3- (2-hydroxy-4-chloro-5-methoxyphenyl) phthalide, 3,6-bis (dimethylamino) fluorenespiro (9,3 ')-6'-dimethylaminophthalide, 3- (1-ethyl -2-methylindole-3-
Yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (1-octyl-2-
Methylindol-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, 6'-chloro-8'-methoxy-
Benzoindolino-spiropyran, 6'-bromo-2 '
-Methoxy-benzoindolino-spiropyran, and others.

The reversible thermosensitive coloring composition 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 coloring density of this composition and the temperature. When the temperature of the composition which is initially in the decolored state (A) is increased, color formation occurs at the temperature T ₁ at which melting starts, and the state changes to the molten color development state (B). When the color is rapidly cooled from the molten color-developed state (B), the temperature can be lowered to room temperature while maintaining the color-developed state, and a solid color-developed state (C) is obtained. Whether or not this coloring state can be obtained depends on
It depends on the rate of temperature drop from the molten state. In slow cooling, decoloration occurs in the process of temperature drop, and the state in which the density is relatively lower than the initial decolored state (A) or rapidly cooled color developing state (C) It is formed. On the other hand, if rapidly cooled colored state (C) is going again heated, discoloring occurs at lower than the coloring temperature the temperature T ₂ (E from D), when the temperature is lowered from this, the same colorless state including (A) Return. 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. Further, the density in the molten color-developing state and the color density after quenching are not always the same, and may be different.

In the composition of the present invention, the color-developed state (C) obtained by quenching from the molten state is a state in which the developer and the color-developing agent are mixed in a state where they can react with each other in a molecule. It 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 a state in which the color former and the developer are separated and stabilized by aggregation or crystallization. Conceivable. In many cases, the present invention causes more complete decoloration due to phase separation of the two and crystallization of the color developer. The decoloring by gradual cooling from the molten state and the decoloring by raising the temperature from the colored state shown in FIG.
In each case, the aggregation structure changes at this temperature, and phase separation and crystallization of the color developer have occurred.

When the composition of the present invention is used as a reversible thermosensitive recording medium, color recording may be formed by heating to a temperature at which the composition is once melted and mixed by a thermal head or the like, followed by rapid cooling. The decoloring is performed by two methods: a method of gradually cooling from a heating state and a method of heating to a temperature slightly lower than a coloring temperature. However, they are the same in the sense that they both phase-separate or temporarily hold at a temperature at which at least one crystallizes. The rapid cooling in the formation of a color-developed state is for preventing the phase separation temperature 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.

The ratio of the color former to the color developer in the composition may vary in an appropriate range depending on the combination of the compounds used.
And preferably in the range of 0.2 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 reversible thermosensitive recording medium of the present invention comprises a support and a recording layer containing the above composition as a main component. Paper, resin film, synthetic paper,
Any material such as metal foil, glass, or a composite thereof, which can hold the recording layer, may be used.

The recording layer may be of any type as long as the composition of the present invention is present. Generally, a state in which a color former and a color developer are finely and uniformly dispersed in a binder resin is used. The color former and the developer may form particles individually, but more preferably form a dispersed state as composite particles. This can be achieved by melting or dissolving the color former and the developer once. To form such a recording layer, a liquid obtained by dispersing and dissolving each material in a solvent, or a liquid obtained by mixing and dispersing or dissolving each material in a solvent is applied to a support and dried. Done by The color former and the developer can be used by being encapsulated in microcapsules.

The reversible thermosensitive recording medium of the present invention may optionally contain additives for improving or controlling the coating properties of the recording layer and the coloring and decoloring properties. These additives include, for example, dispersants, surfactants, conductive agents, fillers, lubricants, antioxidants, light stabilizers, ultraviolet absorbers, color stabilizers, and decolorization accelerators.

As the binder resin used for forming the recording layer, for example, polyvinyl chloride, polyvinyl acetate,
Vinyl chloride vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylate, polymethacrylate, acrylic copolymer, maleic acid System copolymers, polypinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, starches and the like. The role of these binder resins is to maintain a state in which the materials of the composition are uniformly dispersed without bias due to the application of heat for recording and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. For example, the binder resin may be cross-linked by heat, ultraviolet rays, electron beams, or the like.

The reversible thermosensitive recording medium of the present invention basically has the above-mentioned recording layer provided on a support. However, in order to improve the properties as a recording medium, a protective layer, an adhesive layer,
An intermediate layer, an undercoat layer, a back coat layer and the like can be provided.

In printing using a thermal head, the surface of the recording layer may be deformed due to heat and pressure, resulting in so-called dents. In order to prevent this, it is preferable to provide a protective layer on the surface. For the protective layer, a UV-curable resin, an electron beam-curable resin, and the like can be used in addition to polyvinyl alcohol, styrene-maleic anhydride copolymer, carboxy-modified polyethylene, melamine-formaldehyde resin, urea-formaldehyde resin. Further, an additive such as an ultraviolet absorber can be contained in the protective layer.

An intermediate layer is provided between the recording layer and the protective layer for the purpose of improving 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. It is also preferred. Further, it is preferable to use a resin having low oxygen permeability for the protective layer and the intermediate layer provided on the recording layer. This makes it possible to prevent or reduce the oxidation of the color former and the color developer in the recording layer.

In order to effectively use the applied heat,
A heat-insulating undercoat layer can be provided between the support and the recording layer. 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.

For the intermediate layer and the undercoat layer, the same resins as those for the recording layer described above can be used. Further, the protective layer, the intermediate layer, the recording layer and the undercoat layer include calcium carbonate, magnesium carbonate, titanium oxide,
A filler such as silicon oxide, aluminum hydroxide, kaolin, and talc can be contained. In addition, a lubricant, a surfactant, a dispersant and the like can be contained.

In order to form a color image using the reversible thermosensitive recording medium of the present invention, the color image is heated once to a color development temperature and then rapidly cooled. In particular,
For example, when the recording layer is heated for a short time with a thermal head or laser light, the recording layer is locally heated, so that the heat is immediately diffused and rapid cooling occurs, so that 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.

[0034]

The present invention will be described in more detail with reference to the following examples. In the examples, “parts” and “%” are based on weight.

Example 1 As a color former, 2-anilino-3-methyl-6-dibutylaminofluoran was used. Using the 14 compounds, a composition of the present invention was made as follows. First, a color former and a developer were weighed so as to have a mixing ratio (molar ratio) of 1: 2, and were crushed and mixed in a mortar. A glass plate having a thickness of 1.2 mm was heated to a temperature of 210 ° C. on a hot plate. Subsequently, a cover glass was placed over the molten mixture, and the melt was spread to a uniform thickness. Immediately after the temperature was lowered, the composition was removed from the ice water to remove adhering water, thereby obtaining a thin film-shaped composition of the present invention. Next, when the above-described composition sample in a colored state was placed on a hot plate heated to 110 ° C., the color was instantaneously erased. The decolored composition sample was heated to 180 ° C. again and turned black. From this, it was confirmed that the composition of the present invention had a repeating property of coloring and decoloring.

Example 2 The following composition was pulverized and dispersed to a particle size of 1 to 4 μm using a ball mill to prepare a recording layer coating solution. 2-anilino-3-methyl-6-dibutylaminofluoran 2 parts No. Compound No. 22 8 parts Vinyl chloride-vinyl acetate copolymer (VYHH, manufactured by Union Carbide Co., Ltd.) 20 parts Methyl ethyl ketone 45 parts Toluene 45 parts A recording layer coating solution having the above composition was coated on a 100 μm-thick polyester film with a wire bar. The reversible thermosensitive recording medium of the present invention having a recording layer having a thickness of about 6.0 μm was applied and dried.

Embodiment 3 In the embodiment 2, in the case of No. 3 shown in the specific example. Instead of the compound No. 22, No. 22 shown in the specific examples was used. A reversible thermosensitive recording medium of the present invention was prepared in the same manner as in Example 2, except that Compound 26 was used.

Example 4 In Example 2, 2-anilino-3-methyl-6-dibutylaminofluoran was used as a color former instead of 2-anilino-3-methyl-6-dibutylaminofluoran.
Example 2 except that anilino-3-methyl-6- (N-ethyl-Np-toluidinoamino) fluoran was used.
In the same manner as in the above, a reversible thermosensitive recording medium of the present invention was produced.

Example 5 In Example 3, 2-anilino-3-methyl-6-dibutylaminofluorane was used as a color former instead of 2-anilino-3-methyl-6-dibutylaminofluoran.
Example 3 except that anilino-3-methyl-6- (N-ethyl-Np-toluidinoamino) fluoran was used.
In the same manner as in the above, a reversible thermosensitive recording medium of the present invention was produced.

Example 6 In Example 2, 3-anilino-3-methyl-6-dibutylaminofluorane was used as a color former instead of 3-anilino-3-methyl-6-dibutylaminofluoran.
(1-ethyl-2-methylindol-3-yl) -3
-(2-ethoxy-4-diethylaminophenol)-
A reversible thermosensitive recording medium of the present invention was produced in the same manner as in Example 2 except that 4-azaphthalide was used.

Example 7 In Example 3, 3-anilino-3-methyl-6-dibutylaminofluorane was used as a color former instead of 3-anilino-3-methyl-6-dibutylaminofluoran.
(1-ethyl-2-methylindol-3-yl) -3
-(2-ethoxy-4-diethylaminophenol)-
A reversible thermosensitive recording medium of the present invention was produced in the same manner as in Example 3 except that 4-azaphthalide was used.

A color image was printed on each of these recording media using an 8 dot / mm thermal head under the conditions of an applied voltage of 13.3 V and an applied pulse width of 1.2 milliseconds. The optical density of this color image was measured using a Macbeth densitometer RD-914. Next, the recording medium thus colored was heated at an erasing temperature shown in Table 2 for 1 second using a thermal gradient tester, and then the density was measured. Table 2 shows the results. Table 2 shows that the recording medium of the present invention decolors to the same level as the background density by heating for 1 second. Further, it can be seen that printing and erasing are stably repeated. Therefore, it has been clarified that the recording medium of the present invention is a reversible thermosensitive recording medium that can be erased at high speed.

Comparative Example Eicosylphosphonic acid was used in place of the developer in the present invention, and 2-anilino-3-methyl- as a leuco dye was used.
A comparative reversible thermosensitive recording medium was prepared in the same manner as in Example 2 except that 6- (N-ethyl-Np-tolylamino) fluoran was used.

This recording medium was printed and erased in the same manner as in Example 2. In this recording medium, as shown in Table 2, the color was not erased to the initial background density by heating for 1 second, and an unerased portion was left. In addition, this colored recording medium required heating for one minute to reduce it to 0.16, which is almost equal to the background density.

[0045]

[Table 2]

[0046]

Since the reversible thermosensitive coloring composition of the present invention can be repeatedly formed into a stable coloring state and a good decoloring state, the reversible thermosensitive recording medium using the same can form a high-contrast image. Erasing is enabled by an easy operation.
Further, the color image is very stable under ordinary use conditions, has high durability against repeated recording and erasure, and has an extremely excellent effect of obtaining 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 (2)

[Claims] 1. A reversible feeling that can form a relatively colored state and a decolored state by a difference in heating temperature and / or cooling rate after heating using an electron-donating color-forming compound and an electron-accepting compound. A reversible thermosensitive coloring composition, wherein a phenol compound represented by the following general formula (1) or (2) is used as the electron accepting compound in the thermochromic composition. Embedded image Embedded image (In the above formulas, X represents a single _{bond, -CH 2 -, - C 2} H 4 -, - C
H represents CH— or —NHCH ₂ —, and Y represents —NHCO
_{-, - NHSO 2 -, -} N = CH -, - NH-CO-N
Represents H- or -NH-CS-NH-, and R represents an alkyl group having 6 or more carbon atoms. N is an integer of 1 to 3,
l, m, p, q, and s each represent an integer of 1 to 4. ) 2. A reversible thermosensitive recording medium comprising a support and a recording layer containing the reversible thermosensitive coloring composition of claim 1 as a main component.