JPH09290566A - Reversibly thermosensitive coloring composition and reversibly thermosensitive recording medium using this composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversibly thermosensitive coloring composition and a reversibly thermosensitive recording medium which have stably coloring and discharging properties and can deal with rapid erasure. SOLUTION: In a reversibly thermosensitive coloring composition using a coloring reaction between an electron-donative coloring compound and an electron-receptive compound, a carboxylic acid compound expressed by formula is used as the electron-receptive compound. In the formula, X is a divalent group with at least one of hetero atoms, R1 is a hydrocarbon group which can have a substituent, and R2 is an aliphatic hydrocarbon group having a main chain with the number of carbon atoms of 6 of less which can have a directly connecting hand or a substituent. These substituents are a hydroxyl group, a halogen atom or an alkoxy group.

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, electron-donating color-forming compounds (hereinafter referred to as
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.

However, according to the patent publication, a recording medium capable of reversibly developing and erasing colors has been proposed. For example, Japanese Patent Laid-Open No. Sho 60-58 uses a combination of gallic acid and phloroglucinol as a developer. No. 193,691; JP-A-61-237684, wherein a compound such as phenolphthalein or thymolphthalein is used as a color developer. A recording layer contains a homogenous solution of a color developer, a color developer and a carboxylic acid ester. JP-A-62-138556 and JP-A-62-1
38568 and JP-A-62-140881, and JP-A-63-63163 using an ascorbic acid derivative as a developer.
-173684, JP-A-2-188293 and JP-A-2-18 using a salt of bis (hydroxyphenyl) acetic acid or gallic acid and a higher aliphatic amine as a color developer.
No. 8294, etc. are disclosed. However, the conventional reversible thermosensitive recording mediums described above still have problems in terms of compatibility of color development stability and decolorization property, or stability in color density and repetition, and practical recording It is not a satisfactory medium.

[0004] The present inventors have previously described Japanese Patent Application Laid-Open No. Hei 5-12436.
In JP-A-0, No. 0,058,032, an organic phosphoric acid compound, an aliphatic carboxylic acid compound or a phenol compound having a long-chain aliphatic hydrocarbon group is used as a color developing agent, and by combining this with a leuco dye which is a color developing agent, color development is achieved. Decoloring can be easily performed under heating / cooling conditions, and the colored state and decolored state can be maintained stably at room temperature, and the colored state and decolored state can be stably repeated. A reversible thermosensitive color-developing composition and a reversible thermosensitive recording medium using the same for a recording layer have been proposed. This was superior to the conventional recording medium in terms of the balance of color development stability and decoloring property and the color density. However, from the viewpoint of practicality, there is a demand for the development of a reversible thermosensitive recording which is insufficient in terms of erasing speed, maintains the stability of color development, and can be erased at high speed.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a reversible thermosensitive coloring composition and a reversible thermosensitive recording medium which can maintain stable color development and decolorization and can be used for high speed erasing. Is.

[0006]

The present inventors have developed a color-developing agent having a long chain aliphatic group to develop a color-developing agent having a long-chain aliphatic group in the reversible color-decoloring phenomenon of the composition of the color-developing agent and the color-developing agent. We considered that the balance between the ability to induce and the cohesive force between molecules is important, and investigated compounds with various structures. As a result, they have found that the above problems can be solved by using a carboxylic acid compound having a specific structure as a developer.

That is, in a reversible thermosensitive color-forming composition utilizing the color-forming reaction of an electron-donating color-forming compound with an electron-accepting compound, in the present invention, an electron-accepting compound represented by the following formula (1) An acid compound is used.

Embedded image In the formula, X represents a divalent group having at least one hetero atom, R ₁ represents a hydrocarbon group which may have a substituent, and R ₂ represents a direct bond or a substituent. It represents an aliphatic hydrocarbon group having 6 or less carbon atoms in the main chain which may be contained. These substituents are a hydroxyl group, a halogen atom or an alkoxy group.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. First, the compound represented by the general formula (1) will be described in detail. In the above formula, R ₁ represents a hydrocarbon group which may have a substituent, may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and may be a hydrocarbon group composed of both of them. . Further, the aliphatic hydrocarbon group may be linear or branched, and may have an unsaturated bond. Examples of the substituent attached to the hydrocarbon group include a hydroxyl group, a halogen atom, and an alkoxy group. Further, when the carbon number of R ₁ is 7 or less, the stability of color development and the decoloring property decrease,
The carbon number is preferably 8 or more, more preferably 11 or more.

Preferred examples of R ₁ include those shown in Table 1 below.

[Table 1] In the formula, p, p ′, p ″ and p ″ ″ are preferably integers satisfying the above-mentioned carbon number.

R ₂ represents a direct bond or an aliphatic hydrocarbon group having 6 or less carbon atoms in the main chain which may have a substituent, and the aliphatic hydrocarbon group may be straight chain or branched. It may have an unsaturated bond. The substituent attached to the hydrocarbon group includes a hydroxyl group or a halogen atom. Further, when the number of carbon atoms in the main chain of R ₂ is 7 or more, the color developability deteriorates.

Preferred examples of R ₂ include those shown in Table 2 below.

[Table 2] In the formula, q and q'represent integers satisfying the carbon number of R ₂ respectively, and q ″ and q ″ ″ are not particularly limited integers, but are preferably 5 or less.

X represents a divalent group having at least one hetero atom. Examples of X include those shown in Table 3 below, but the present invention is not limited thereto.

[0013]

[Table 3]

Preferred examples of the carboxylic acid compound represented by the general formula (1) used in the present invention include compounds represented by the following general formula (2).

Embedded image In the formula, m represents 8 to 22, and n represents an integer of 0 to 6.

More specific examples of the carboxylic acid compound represented by the general formula (1) of the present invention include the compounds shown in Table 4 by taking the general formula (2) as an example. However, the present invention is not limited to these.

[0016]

[Table 4- (1)]

[0017]

[Table 4- (2)]

[0018]

[Table 4- (3)]

[0019]

[Table 4- (4)]

[0020]

[Table 4- (5)]

[0021]

[Table 4- (6)]

[0022]

[Table 4- (7)]

[0023]

[Table 4- (8)]

[0024]

[Table 4- (9)]

[0025]

[Table 4- (10)]

[0026]

[Table 4- (11)]

[0027]

[Table 4- (12)]

[0028]

[Table 4- (13)]

[0029]

[Table 4- (14)]

The carboxylic acid compound used in the present invention may be a group in which X is a divalent group having one or more hetero atoms via a hydrocarbon group such as alkylene. That is, X is shown as a group of the structure shown below.

Embedded image Here, R ₃ represents a divalent group and a direct bond similar to the above R ₂ , but the carbon number of the main chain is not particularly limited. Moreover, the carbon chain may contain an aromatic ring. Y and Y'represent a divalent group similar to X. Also,
r represents an integer of 1 to 4. At this time, Y ′ and R _{3 which} are repeated may be the same or different.

Specific preferred examples thereof include compounds represented by the following general formulas (3) to (7). R ₁ -YR ₃ -Y'-R ₂ -COOH (3) R ₁ -YR ₃ -Y'-R ₃ '-Y "-R ₂ -COOH (4) R ₁ -YR ₃ -Y'-R ₃ '-Y "-R ₃ "-Y'"-R ₂ -COOH (5) R ₁ -YR ₃ -Y'-R ₃ '-Y" -R ₃ "-Y"'-R ₃ `` '-Y''''-R ₂ -COOH (6) In the formula, R ₃ ', R ₃ "and R ₃ '" are the same as R _3, and Y ",
Y '''andY''''represent the same groups as Y, and these may be the same or different.

Specific examples of these include R ₃ , R ₃ '
When showing the case R ₃ "and R ₃ '''is alkylene Representative include compounds represented by the following general formula (7) ~ (10). CH 3 (CH 2) m-1 -Y -(CH ₂ ) w-Y '-(CH ₂ ) n-COOH (7) CH ₃ (CH ₂ ) _m-1 -Y- (CH ₂ ) w-Y'-(CH ₂ ) xY "-(CH ₂ ) n-COOH (8) CH ₃ (CH ₂ ) _m-1 -Y- (CH ₂ ) w-Y '-(CH ₂ ) xY "-(CH ₂ ) y-Y'''-(CH ₂ ) n-COOH (9) CH ₃ (CH ₂ ) _m-1 -Y- (CH ₂ ) w-Y '-(CH ₂ ) xY "-(CH ₂ ) y-Y'''-(CH ₂ ). z-Y '''' - (CH 2) n -COOH (10) wherein, w, x, y and z is not particularly limited, preferably, 0-8 integer.

More specific examples of the carboxylic acid compounds represented by the above general formulas (7) to (10) of the present invention include:
For example, the compounds shown in Table 5 are mentioned as examples of the general formula (7). Although not shown in the structural formula here,
Also in the case of the compounds represented by the general formulas (8) to (10), the same compounds as those in Table 5 are shown as Y, Y ′, Y ″, Y ′ ″ and Y ″ ″. However, the present invention is not limited to these.

[0034]

[Table 5- (1)]

[0035]

[Table 5- (2)]

[0036]

[Table 5- (3)]

[0037]

[Table 5- (4)]

[0038]

[Table 5- (5)]

The reversible thermosensitive color-forming composition of the present invention is basically constituted by combining the above-mentioned color developer and color-developing agent. The color former used in the present invention has an electron donating property and is itself a colorless or light-colored dye precursor (leuco dye), and is not particularly limited, and may be a conventionally known one such as a phthalide compound or an azaphthalide compound. , A fluoran compound, a phenothiazine compound, a leuco auramine compound, and the like. Specific examples of the color former are shown below.

Preferred color formers for use in the present invention are compounds represented by the following general formula (11) or (12).

Embedded image

Embedded image (However, R ₃ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₄ represents an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group or an optionally substituted phenyl group. Substituent for the phenyl group Examples of the alkyl 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 atom, etc. R ₅ is a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, an alkoxy group or a halogen atom. R ₆ represents a hydrogen atom, a methyl group, a halogen atom or an optionally substituted amino group.
Examples of the substituent for the amino group include an alkyl group, an optionally substituted aryl group, and an optionally substituted aralkyl group. The substituents here are an alkyl group, a halogen atom, an alkoxy group, etc.). Specific examples of such a color former include, for example, the following compounds.

2-anilino-3-methyl-6-diethylaminofluorane 2-anilino-3-methyl-6- (di-n-butylamino) fluorane, 2-anilino-3-methyl-6- (N
-N-propyl-N-methylamino) fluorane, 2-
Anilino-3-methyl-6- (N-isopropyl-N-
Methylamino) fluorane, 2-anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (Nn-amyl-N-methylamino) fluorane , 2-anilino-3-
Methyl-6- (N-sec-butyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (N
-N-amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (N-iso-amyl-N-
Ethylamino) fluorane, 2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino)
Fluorane, 2-anilino-3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane, 2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-anilino-3 -Methyl-6- (N
-Methyl-p-toluidino) fluorane, 2- (m-trichloromethylanilino) -3-methyl-6-diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluor Oran, 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) fluorane, 2- (N-methyl-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-bromoanilino) -6-diethylaminofluoran, 2-
(O-chloroanilino) -6-dibutylaminofluoran, 2- (o-fluoroanilino) -6-dibutylaminofluoran, 2- (m-trifluoromethylanilino)
-6-Diethylaminofluorane, 2- (p-acetylanilino) -6- (Nn-amyl-Nn-butylamino) fluorane, 2-benzylamino-6- (N-ethyl-p-toluidino) ) Fluoran, 2-benzylamino-6- (N-methyl-2,4-dimethylanilino) fluorane, 2-benzylamino-6- (N-ethyl-)
2,4-Dimethylanilino) fluorane, 2-dibenzylamino-6- (N-methyl-p-toluidino) fluorane, 2-dibenzylamino-6- (N-ethyl-p-
Toluidino) fluorane, 2- (di-p-methylbenzylamino) -6- (N-ethyl-p-toluidino) fluorane, 2- (α-phenylethylamino) -6- (N
-Ethyl-p-toluidino) fluorane, 2-methylamino-6- (N-methylanilino) fluorane, 2-methylamino-6- (N-ethylanilino) fluorane,
2-Methylamino-6- (N-propylanilino) fluorane, 2-ethylamino-6- (N-methyl-p-toluidino) fluorane, 2-methylamino-6- (N-
Methyl-2,4, -dimethylanilino) fluorane, 2
-Ethylamino-6- (N-ethyl-2,4, -dimethylanilino) fluorane, 2-dimethylamino-6-
(N-methylanilino) fluorane, 2-dimethylamino-6- (N-ethylanilino) fluorane, 2-diethylamino-6- (N-methyl-p-toluidino) fluorane, 2-diethylamino-6- (N-ethyl-p −
Toluidino) fluorane, 2-dipropylamino-6-
(N-methyl-anilino) fluorane, 2-dipropylamino-6- (N-ethyl-anilino) fluorane, 2
-Amino-6- (N-methylanilino) fluorane, 2
-Amino-6- (N-ethylanilino) fluorane, 2
-Amino-6- (N-propylanilino) fluorane,
2-Amino-6- (N-methyl-p-toluidino) fluorane, 2-amino-6- (N-ethyl-p-toluidino) fluorane, 2-amino-6- (N-propyl-p
-Toluidino) fluorane, 2-amino-6- (N-methyl-p-ethylanilino) fluorane, 2-amino-
6- (N-ethyl-p-ethylanilino) fluorane,
2-Amino-6- (N-propyl-p-ethylanilino) fluorane, 2-amino-6- (N-methyl-2,
4-dimethylanilino) fluorane, 2-amino-6-
(N-Ethyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-propyl-2,4-dimethylanilino) fluorane, 2-amino-6- (N-methyl-p-chloranilino) ) Fluoran, 2-amino-6
-(N-ethyl-p-chloroanilino) fluorane, 2
-Amino-6- (N-propyl-p-chloranilino)
Fluoran,

2,3-Dimethyl-6-dimethylaminofluorane, 3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-chloro-6-diethylaminofluorane, 2-bromo-6-diethylamino Fluoran, 2-chloro-6-dipropylaminofluorane, 3
-Chloro-6-cyclohexylaminofluorane, 3-
Bromo-6-cyclohexylaminofluorane, 2-chloro-6- (N-ethyl-N-isoamylamino) fluorane, 2-chloro-3-methyl-6-diethylaminofluorane, 2-anilino-3-chloro-6. -Diethylaminofluorane, 2- (o-chloroanilino) -3-
Chlor-6-cyclohexylaminofluorane, 2-
(M-Trifluoromethylanilino) -3-chloro-6-
Diethylaminofluorane, 2- (2,3-dichloroanilino) -3-chloro-6-diethylaminofluorane, 1,2-benzo-6-diethylaminofluorane,
1,2-benzo-6- (N-ethyl-N-isoamylamino) fluoran, 1,2-benzo-6-dibutylaminofluoran, 1,2-benzo-6- (N-methyl-N
-Cyclohexylamino) fluorane, 1,2-benzo-6- (N-ethyl-toluidino) fluorane, 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) fluorane, 2- (p-chloroanilino) -6- (Nn-octylamino) fluorane, 2
-(P-chloranilino) -6- (Nn-palmitylamino) fluorane, 2- (p-chloranilino) -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) fluorane, 2-benzylamino-4-methyl-6- (N-ethyl-P-toluidino) fluorane, 2- (α-phenylethylamino)-
4-methyl-6-diethylaminofluorane, 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) fluorane, 4-methoxy-6- (N-ethyl-p-toluidino) fluorane,
2-ethoxyethylamino-3-chloro-6-dibutylaminofluorane, 2-dibenzylamino-4-chloro-6- (N-ethyl-p-toluidino) fluorane, 2
-(Α-phenylethylamino) -4-chloro-6-diethylaminofluorane, 2- (N-benzyl-p-trifluoromethylanilino) -4-chloro-6-diethylaminofluorane, 2-anilino-3 -Methyl-6-pyrrolidinofluorane, 2-anilino-3-chloro-6-
Pyrrolidinofluorane, 2-anilino-3-methyl-6
-(N-ethyl-N-tetrahydrofurfurylamino)
Fluorane, 2-mesidino-4 ', 5'-benzo-6-
Diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-methyl-6-pyrrolidinofluorane, 2- (α-naphthylamino) -3,4-benzo-
4'-Bromo-6- (N-benzyl-N-cyclohexylamino) fluorane, 2-piperidino-6-diethylaminofluorane, 2- (Nn-propyl-p-trifluoromethylanilino) -6-morpho Rinofluorane, 2- (di-Np-chlorophenyl-methylamino) -6-pyrrolidinofluorane, 2- (Nn-propyl-m-trifluoromethylanilino) -6-morpholinoflu Oran, 1,2-benzo-6- (N-ethyl-
Nn-octylamino) fluorane, 1,2-benzo-6-diallylaminofluorane, 1,2-benzo-6
-(N-ethoxyethyl-N-ethylamino) fluorane,

Benzoleucomethylene blue, 2- [3,
6-bis (diethylamino)]-6- (o-chloroanilino) xanthyl benzoate 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) fluorene spiro (9,3 ')-6'-dimethylaminophthalide, 6'-chloro-8 '-Methoxy-benzoindolino-spiropyran, 6'-bromo-2'-methoxy-benzoindolino-spiropyran, 3- (1-ethyl-2)
-Methylindol-3-yl) 3- (2-ethoxy-
4-diethyldiethylaminophenyl) -4-azaphthalide, 3- (1-octyl-2-methylindole-3
-Yl) -3- (2-ethoxy-4-diethyldiethylaminophenyl) -4-azaphthalide, 3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethyldiethylamino) Phenyl) -7-
Azaphthalide, 3,3-bis (2-ethoxy-4-diethyldiethylaminophenyl) -4-azaphthalide,
3,3-bis (2-ethoxy-4-diethyldiethylaminophenyl) -4-azaphthalide and others.

The reversible thermosensitive coloring composition of the present invention is capable of forming a relatively colored state and a relatively 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 the solid color-developed state (C) results. Whether or not this coloring state can be obtained depends on
Depends on the rate of temperature decrease from the molten state, bleaching occurs in the process of temperature decrease during slow cooling, and the state where the concentration is relatively lower than the same color erasing state (A) or rapid cooling color developing state (C) as in the beginning It is formed. On the other hand, when the temperature of the rapidly cooled coloring state (C) is increased again, decoloring occurs at a temperature T ₂ lower than the coloring temperature (D to E), and when the temperature is lowered from here, the same decoloring state (A) as that at the beginning is obtained. Return. The actual color-developing temperature and decoloring temperature vary depending on the combination of the color-developing agent and the color-developing agent 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 color-developing agent and the color-developing agent are mixed in such a state that the molecules can contact with each other to react with each other. 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 crystallize, and it is 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. Color fading from the molten state shown in FIG. 1 by slow cooling and color fading from the colored state by temperature rise are
In both cases, the aggregate structure changes at this temperature, causing phase separation and crystallization of the developer.

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 and then rapidly cooled. 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, these are the same in the sense that both are phase-separated, or at least one is temporarily kept at a temperature at which crystallization occurs. 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 can be varied in an appropriate range depending on the combination of the compounds used.
The range is from 0.2 to 10, preferably from 0.2 to 10. If the amount of the color developing agent is less or more than this range, the density of the color-developed state decreases, which is a problem.

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. In general, 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.

In the reversible thermosensitive recording medium of the present invention, an additive for improving or controlling the coating characteristics of the recording layer and the coloring and decoloring characteristics can be used as necessary. Examples of these additives include a dispersant, a surfactant, a conductive agent, a filler, a lubricant, an antioxidant, a light stabilizer, an ultraviolet absorber, a color development stabilizer, and a decolorization accelerator.

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, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid copolymer, maleic acid Examples thereof include copolymers, polypinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, and starches. 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 characteristics 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, and so-called dents may be formed. In order to prevent this, it is preferable to provide a protective layer on the surface. For the protective layer, in addition to polyvinyl alcohol, styrene maleic anhydride copolymer, carboxy-modified polyethylene, melamine-formaldehyde resin, urea-formaldehyde resin, UV curable resin and electron beam curable resin can be used. 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 the adhesion between the recording layer and the protective layer, preventing deterioration of the recording layer due to the 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.

Further, in order to effectively utilize 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, it is sufficient that the color image is heated once above the 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, it may be heated and cooled for a relatively long time using an appropriate heat source, or may be temporarily heated 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 done only with the thermal head, and so-called overwriting becomes possible. Of course, it can be erased by heating to a decoloring temperature range by a heat roller or a heat stamp.

[0060]

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 A composition of the present invention was prepared by using 2-anilino-3-methyl-6-dibutylaminofluorane as a color former and N'-n-octadecylureidoacetic acid as a developer. Created like. First, a color former and a developer were weighed so as to have a mixing ratio (molar ratio) of 1: 3, and were crushed and mixed in a mortar. A 1.2 mm thick glass plate was heated to a temperature of 190 ° C. on a hot plate. Subsequently, a cover glass was put over the molten mixture, the melt was spread to a uniform thickness, and immediately the whole glass plate was immersed in ice water prepared for rapid cooling. 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 composition sample in the above-mentioned colored state was placed on a hot plate heated to 120 ° C., the color was instantaneously erased. When this decolorized composition sample was heated again to 190 ° C., it 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 same as Example 1 except that 3- (N'-n-octadecylureido) propionic acid was used in place of N'-n-octadecylureidoacetic acid as the developer in Example 1. As a result, it was confirmed that the composition of this example also had the repeating characteristics of color development and decolorization.

Example 3 Example 3 was repeated except that 4- (N'-n-octadecylureido) butyric acid was used in place of N'-n-octadecylureidoacetic acid as the developer in Example 1. As a result, it was confirmed that the composition of this example also had the repeating property of color development and decolorization.

Example 4 Example 4 was repeated except that 4- (N'-n-octadecylureido) -3-hydroxybutyric acid was used in place of N'-n-octadecylureidoacetic acid as the developer in Example 1. When carried out in the same manner as in Example 1, it was confirmed that the composition of the present example also had the repeating property of color development and decolorization.

Example 5 The same as Example 1 except that N ′-(n-octadecylaminocarbonyl) glycylglycine was used in place of N′-n-octadecylureidoacetic acid as the developer in Example 1. As a result, it was confirmed that the composition of this example also had the repeating characteristics of color development and decolorization.

Example 6 Example 1 was repeated except that N ′-(n-octadecylaminocarbonyl) glycylglycylglycine was used in place of N′-n-octadecylureidoacetic acid as the developer in Example 1. When carried out in the same manner, it was confirmed that the composition of this example also had a repeating property of color development and decolorization.

Example 7 The procedure of Example 1 was repeated, except that stearyl thioglycolic acid was used instead of N'-n-octadecylureidoacetic acid as the color developer.
It was confirmed that the composition of this example also had the repeating property of color development and decolorization.

Example 8 The same procedure as in Example 1 was repeated except that stearyl thiopropionic acid was used instead of N'-n-octadecylureidoacetic acid as the developer in Example 1.
It was confirmed that the composition of this example also had the repeating property of color development and decolorization.

Example 9 The procedure of Example 1 was repeated, except that stearoylglycine was used instead of N'-n-octadecylureidoacetic acid as the developer in Example 1, and the composition of this example was obtained. It was confirmed that the product also has a repeating characteristic of color development and decolorization.

Example 10 The procedure of Example 1 was repeated except that stearoylalanine was used in place of N'-n-octadecylureidoacetic acid as the developer in Example 1, and the composition of this example was obtained. It was confirmed that the product also has a repeating characteristic of color development and decolorization.

Example 11 The procedure of Example 1 was repeated except that adipic acid monododecylamide was used in place of N'-n-octadecylureidoacetic acid as the color developer. It was confirmed that the composition of the example also has the repeating property of color development and decolorization.

Example 12 The same procedure as in Example 1 was carried out except that adipic acid monostearylamide was used in place of N'-n-octadecylureidoacetic acid as the developer in Example 1, and this example was carried out. It was confirmed that the composition of the example also has the repeating property of color development and decolorization.

Example 13 The procedure of Example 1 was repeated except that stearylsulfonylpropionic acid was used in place of N'-n-octadecylureidoacetic acid as the color developer. It was confirmed that the composition (1) also had the property of repeating color development and decolorization.

Example 14 The procedure of Example 1 was repeated except that eicosylsulfonylpropionic acid was used in place of N'-n-octadecylureidoacetic acid as the developer in Example 1. It was confirmed that the composition of the example also has the repeating property of color development and decolorization.

Example 15 This example was carried out in the same manner as in Example 1 except that stearylsulfonyl glycolic acid was used in place of N'-n-octadecylureidoacetic acid as the color developer. It was confirmed that the composition (1) also had the property of repeating color development and decolorization.

Example 16 The procedure of Example 1 was repeated, except that eicosylsulfonylglycolic acid was used instead of N'-n-octadecylureidoacetic acid as the color developer. It was confirmed that the composition of the example also has the repeating property of color development and decolorization.

Examples 17 to 32 In Examples 1 to 16, 2-anilino-as a color former was used.
Instead of 3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-
The same procedure as in Example 1 was carried out except that p-tolylaminofluorane was used. As a result, it was confirmed that all the compositions had repeated coloring and decoloring characteristics.

Example 33 A recording layer coating solution was prepared by pulverizing and dispersing the following composition into a particle size of 1 to 4 μm using a ball mill. 2-anilino-3-methyl-6-dibutylaminofluorane 2 parts N'-n-octadecylureidoacetic acid 8 parts vinyl chloride-vinyl acetate copolymer (VYHH manufactured by Union Carbide) 20 parts methyl ethyl ketone 45 parts toluene 45 Parts A recording layer coating solution having the above composition was applied onto a polyester film having a thickness of 100 μm using a wire bar and dried to prepare a reversible thermosensitive recording medium of the present invention having a recording layer having a thickness of about 6.0 μm. .

Example 34 In the same manner as in Example 33 except that 3- (N′-n-octadecylureido) propionic acid was used in place of N′-n-octadecylureidoacetic acid in Example 33, a reversible feeling was obtained. A thermal recording medium was produced.

Example 35 A reversible thermosensitive material was prepared in the same manner as in Example 33 except that 4- (N'-n-octadecylureido) butyric acid was used in place of N'-n-octadecylureidoacetic acid. A recording medium was produced.

Example 36 Example 33 was repeated except that 4- (N'-n-octadecylureido) -3-hydroxybutyric acid was used in place of N'-n-octadecylureidoacetic acid in Example 33.
In the same manner as in the above, a reversible thermosensitive recording medium was produced.

Example 37 The procedure of Example 33 was repeated except that N ′-(n-octadecylaminocarbonyl) glycylglycine was used instead of N′-n-octadecylureidoacetic acid in Example 33. A thermal recording medium was produced.

Example 38 A reversible substance was prepared in the same manner as in Example 33 except that N ′-(n-octadecylaminocarbonyl) glycylglycylglycine was used in place of N′-n-octadecylureidoacetic acid. A thermosensitive recording medium was prepared.

Example 39 In Example 33, except that stearoylglycine was used instead of N'-n-octadecylureidoacetic acid in Example 33,
A reversible thermosensitive recording medium was prepared in the same manner as in Example 33.

Example 40 In Example 33, except that stearoylalanine was used in place of N'-n-octadecylureidoacetic acid,
A reversible thermosensitive recording medium was prepared in the same manner as in Example 33.

Example 41 A reversible thermosensitive recording medium was prepared in the same manner as in Example 33, except that adipic acid monododecylamide was used instead of N'-n-octadecylureidoacetic acid.

Example 42 A reversible thermosensitive recording medium was prepared in the same manner as in Example 33 except that adipic acid monostearylamide was used in place of N'-n-octadecylureidoacetic acid.

Example 43 A reversible thermosensitive recording medium was prepared in the same manner as in Example 33 except that stearylsulfonylpropionic acid was used instead of N'-n-octadecylureidoacetic acid.

Example 44 A reversible thermosensitive recording medium was prepared in the same manner as in Example 33 except that eicosylsulfonylpropionic acid was used instead of N'-n-octadecylureidoacetic acid.

Example 45 In Example 33, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
A reversible thermosensitive recording medium was prepared in the same manner as in Example 33 except that 3-methyl-6-diethylaminofluorane was used.

Example 46 In Example 34, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
A reversible thermosensitive recording medium was prepared in the same manner as in Example 34 except that 3-methyl-6-diethylaminofluorane was used.

Example 47 In Example 35, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
A reversible thermosensitive recording medium was prepared in the same manner as in Example 35 except that 3-methyl-6-diethylaminofluorane was used.

Example 48 In Example 36, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
A reversible thermosensitive recording medium was prepared in the same manner as in Example 36 except that 3-methyl-6-diethylaminofluorane was used.

Example 49 In Example 36, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
A reversible thermosensitive recording medium was prepared in the same manner as in Example 36 except that 3-methyl-6-N-ethyl-Np-tolylaminofluorane was used.

Example 50 In Example 36, 2-anilino-3-methyl-6-
A reversible thermosensitive recording medium was prepared in the same manner as in Example 36 except that 2- (o-chloroanilino) -6-dibutylaminofluorane was used instead of dibutylaminofluorane.

Example 51 In Example 37, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
A reversible thermosensitive recording medium was prepared in the same manner as in Example 37 except that 3-methyl-6-diethylaminofluorane was used.

Example 52 In Example 38, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
A reversible thermosensitive recording medium was prepared in the same manner as in Example 38 except that 3-methyl-6-diethylaminofluorane was used.

Example 53 In Example 33, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
Using 3-methyl-6-N-ethyl-N-p-tolylaminofluorane and using stearyl thioglycolic acid instead of N'-n-octadecyl ureidoacetic acid in the same manner as in Example 33. A reversible thermosensitive recording medium was prepared.

Example 54 In Example 33, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
Example 3 was repeated except that 3-methyl-6-N-ethyl-Np-tolylaminofluorane was used and eicosylsulfonylglycolic acid was used instead of N′-n-octadecylureidoacetic acid. Then, a reversible thermosensitive recording medium was prepared.

Example 55 In Example 33, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
Using 3-methyl-6-N-ethyl-N-p-tolylaminofluorane and using stearyl thioglycolic acid instead of N'-n-octadecyl ureidoacetic acid in the same manner as in Example 33. A reversible thermosensitive recording medium was prepared.

Example 56 In Example 33, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
Using 3-methyl-6-N-ethyl-N-p-tolylaminofluorane and using stearyl thiopropionic acid instead of N'-n-octadecyl ureidoacetic acid were carried out in the same manner as in Example 33. A reversible thermosensitive recording medium was prepared.

Example 57 In Example 33, 2-anilino-3-methyl-6-
2-anilino-instead of dibutylaminofluorane
Example 3 was repeated except that 3-methyl-6-N-ethyl-Np-tolylaminofluorane was used and stearoylaminomethylthiopropionic acid was used instead of N′-n-octadecylureidoacetic acid. Then, a reversible thermosensitive recording medium was prepared.

The recording media prepared in Examples 33 to 57 were printed with a thermal head of 8 dots / mm under the conditions of an applied voltage of 13.3 V and an applied pulse width of 1.2 ms to obtain a colored image. The optical density of this color image was measured using a Macbeth densitometer RD-914. Next, the color-developed recording medium was heated at the erasing temperature shown in Table 6 for 1 second using a thermal gradient tester, and then the density was measured. Table 6 shows the results. From Table 6, the recording medium of the present invention is 1
It can be seen that heating for 2 seconds erases the color to the same level as the background density. 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 1 Eicosylphosphonic acid was used in place of the color developer of the present invention, and 2-anilino-3-methyl-6-as a leuco dye.
A reversible thermosensitive recording medium was prepared in the same manner as in Example 33 except that (N-ethyl-Np-tolylamino) fluorane was used. Printing and erasing were performed on this recording medium in the same manner as in Example 33. As shown in Table 6, this recording medium does not erase to the initial background density by heating for 1 second and remains unerased. 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.

Comparative Example 2 A reversible thermosensitive recording medium was prepared in the same manner as in Example 33 except that 2- (eicosylthio) succinic acid was used instead of the color developing agent of the present invention. Printing and erasing were performed on this recording medium in the same manner as in Example 33. As shown in Table 6, this recording medium does not erase to the initial background density by heating for 1 second and remains unerased. Further, this recording medium that developed color required heating for 10 seconds in order to reduce it to 0.21 which is almost equal to the background density.

Comparative Example 3 A reversible thermosensitive recording medium was prepared in the same manner as in Example 33 except that α-hydroxyoctadecanoic acid was used instead of the color developing agent of the present invention. About this recording medium, Example 3
Printing and erasing were performed in the same manner as in 3. This recording medium is shown in Table 6.
As shown in (1), heating for 1 second does not erase the color to the initial background density, and the erase remains. In addition, this recording medium that developed color required heating for 10 seconds in order to reduce the color density to 0.17, which is almost equal to the background density.

Comparative Example 4 The same as Example 33 except that octadecyl malonic acid was used in place of the color developing agent of the present invention, and 2- (o-chloroanilino) -6-dibutylaminofluorane was used as a leuco dye. Then, a reversible thermosensitive recording medium was prepared.
Printing and erasing were performed on this recording medium in the same manner as in Example 33. As shown in Table 6, this recording medium does not erase to the initial background density by heating for 1 second and remains unerased.
In addition, the color-developed recording medium did not decrease to the background density after heating for 1 minute.

[0108]

[Table 6]

[0109]

The reversible thermosensitive coloring composition of the present invention can be formed by repeating a stable coloring state and a favorable decoloring state.
Therefore, as shown in the examples, the reversible thermosensitive recording medium using the same enables formation and erasing of an image with high contrast by an easy operation. In addition, the color image is stable under normal use conditions and has high-speed erasability,
Further, it is highly durable against repeated recording and erasing, and rewritable recording with high practicality can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing color developing / decoloring characteristics of a reversible thermosensitive color developing composition of the present invention.

Continuation of the front page (31) Priority claim number Japanese Patent Application No. 8-65388 (32) Priority Day Hei 8 (1996) February 26 (33) Country of priority claim Japan (JP) (72) Inventor Hiroaki Matsui Tokyo Ricoh Co., Ltd., 1-3-6 Nakamagome, Ota-ku, Tokyo (72) Inventor Kyoji Tsutsui 1-3-6, Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (72) Masaru Shimada Naka, Ota-ku, Tokyo 1-3-6 Magome In Ricoh Co., Ltd. (72) Inventor Fumio Kawamura 1-3-6 Nakamagome, Ota-ku, Tokyo In-house Ricoh Co., Ltd. (72) Katsuji Maruyama 1-chome, Nakamagome, Ota-ku, Tokyo No. 3-6 In Ricoh Co., Ltd. (72) Inventor Katsuhisa Kamio 4-66-1 Horikiri, Katsushika-ku, Tokyo Within Miyoshi Yushi Co., Ltd. (72) Inventor Katsuyuki Sugiyama 4-6-6 Horikiri, Katsushika-ku, Tokyo No. 1 Miyoshi Oil & Fat Co., Ltd. (72) Inventor Kazuo Hosoda 4-66-1 Horikiri, Katsushika-ku, Tokyo Miyoshi Oil & Fat Co., Ltd. (72) Inventor Masaki Kawashima 4-16-1 Horikiri, Katsushika-ku, Tokyo Within Miyoshi Yushi Co., Ltd. (72) Inventor Masafumi Moriya 4-66-1 Horikiri, Katsushika-ku, Tokyo Within Miyoshi Yushi Co., Ltd.

Claims (2)

[Claims] 1. A reversible sensation capable of forming a relatively colored state and a relatively decolorized state by using an electron-donating color-forming compound and an electron-accepting compound, depending on a difference in heating temperature and / or a cooling rate after heating. A reversible thermosensitive coloring composition, wherein the carboxylic acid compound represented by the following general formula (1) is used as an electron-accepting compound in the thermochromic composition. Embedded image In the formula, X represents a divalent group having at least one hetero atom, R ₁ represents a hydrocarbon group which may have a substituent, and R ₂ represents a direct bond or a substituent. It represents an aliphatic hydrocarbon group having 6 or less carbon atoms in the main chain which may be contained. These substituents are a hydroxyl group, a halogen atom or an alkoxy group. 2. A reversible thermosensitive recording medium characterized in that a recording layer containing the reversible thermosensitive coloring composition of claim 1 as a main component is provided on a support.