JP2000103170A - Reversible thermal coloring composition and reversible thermal recording medium employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the stabilization and decoloring property of a coloring state by containing a compound expressed by a specific formula as a coloring and decoloring inhibitor in a reversible thermal coloring composition. SOLUTION: Compounds expressed by formulas I, II, III are contained in a reversible thermal coloring composition as a coloring and decoloring inhibitor. In the formula, R is hydrogen, a lower alkyl group, a lower alkoxy group, halogen, and a nitro group, R1 is a 1-20C bivalent hydrocarbon residue R2, R3 is 1-5C bivalent hydrocarbon radicals, and l, m and n are each 0 or 1. The reversible thermal coloring composition is fundamentally formed by combining a developing agent with a coloring agent, and such a coloring agent exhibits an electron donative property. The developing agent employs one having, e.g. an acid group such as a phenolic hydroxyl group, a carboxylic group, and a phosphoric acid group. A radio between the coloring agent and the developing agent is made approximately 0.1-20 parts of a developing agent to one of a coloring agent at a mol ratio. When the composition is formed into a reversible thermal recording medium, its support body employs paper, a resin film, synthetic paper, metallic foil, glass, and the like.

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 relates to a reversible thermosensitive recording medium capable of forming and erasing.

[0002]

2. Description of the Related Art Conventionally, an electron-donating color-forming compound (hereinafter, referred to as an electron-donating 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, a recording medium using a combination of gallic acid and phloroglucinol as a color developing agent (Japanese Patent Laid-Open Publication No. H11-163191). Japanese Patent Application Laid-Open (JP-A) No. 60-193691) and a compound using a compound such as phenolphthalein or thymolphthalein as a color developer.
No. 84, a recording layer containing a homogeneous solution of a color former, a developer and a carboxylic acid ester (Japanese Patent Laid-Open No. 62-13 / 1987).
No. 8556, JP-A-62-138568 and JP-A-62-140881) and those using an ascorbic acid derivative as a color developer (JP-A-63-1736).
No. 84), and those using bis (hydroxyphenyl) acetic acid or a salt of gallic acid and a higher aliphatic amine as a color developing agent (JP-A-2-188293 and JP-A-2-2-1).
No. 88294) and the like. However, the conventional reversible thermosensitive recording medium described above has a problem in that it is compatible with stability of color development and decoloration, or stability in color density and repetition,
It is not satisfactory as a practical recording medium.

Further, the present inventors have disclosed in Japanese Patent Laid-Open No.
No. 4360, 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 developer, and the color is developed and decolored by combining this with a leuco dye as a color former. Can be easily performed by heating and cooling conditions, and its color development and decoloration can be stably maintained at room temperature. A thermochromic 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 was proposed (Japanese Patent Application Laid-Open No. 6-210954), but this also had a similar problem.

As described above, a reversible thermosensitive recording medium capable of repeating coloring and decoloring has been proposed. This type of recording medium has storage characteristics (with respect to temperature, humidity, and light), Although high-speed erasing characteristics are required, a reversible thermosensitive recording medium satisfying this has not been obtained.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reversible thermosensitive coloring composition and a reversible thermosensitive recording medium which have high storage stability in a color-developing state and also have excellent decoloring properties.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by using a coloring / decoloring controlling agent having a specific structure (a specific phthalimide), a thermal elimination control agent has been proposed. It has been found that the storage stability of the color-developed state can be improved, and at the same time, the decoloring property is excellent and good high-speed erasing characteristics can be obtained. The reason that the storage stability against heat is improved is that, in the color-developed state, the color-decoloring control agent mainly enters the color-aggregated structure constituted by the dye and the developer having a long-chain alkyl to form a more stable structure. It is considered that the coloring structure at high temperature is stably maintained. Also, in the decoloring process, it is considered that a residual structure at the time of decoloring is reduced in order to promote crystallization to a decolored state, because the flocculant has a cohesive structure stronger than the cohesive force of only the developers.

[0008] That is, the above object is achieved by (1) the present invention.
"Using an electron-donating color-forming compound and an electron-accepting compound,
A reversible thermochromic composition capable of forming a relatively colored state and a decolored state depending on a difference in a heating temperature and / or a cooling rate after heating. A reversible thermosensitive color-forming composition, characterized by containing a compound represented by the following general formula (1):

[0009]

Embedded image Achieved by

Further, (2) a reversible thermosensitive recording medium characterized in that a recording layer containing the reversible thermosensitive coloring composition according to the above (1) as a main component is provided on a support. Achieved.

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 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. The coloring agent is shown below. Preferred color formers for use in the present invention include compounds of the following general formula.

[0012]

Embedded image

[0013]

Embedded image (However, 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 cycloalkyl group, or an optionally substituted phenyl group. As a substituent for the phenyl group, , .R ₄ represents an alkyl group, a methoxy group, .R ₃ alkoxy group or a halogen or the like, such as ethoxy groups is indicated hydrogen, an alkyl group having 1 to 2 carbon atoms, an alkoxy group or a halogen such as a methyl group, an ethyl group Represents a hydrogen, a methyl group, a halogen or an optionally substituted amino group, and 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, an alkoxy group, etc.) Specific examples of such a color former include, for example, the following compounds. It is below.

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-methylamino) 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- (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-trichloromethylanilino ) -3-Methyl-6- (N-cyclohexyl-N-methylamino) fluoran, 2- (2,4-dimethylanilino) -3-methyl- - 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-benzylamino-6- (N
-Methyl-p-toluidino) fluoran, 2-benzylamino-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-methylanilino) fluoran, 2-dipropylamino-6- (N -Ethylanilino) 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- 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-methyl-N
-Cyclohexylamino) fluoran, 1,2-benzo-6- (N-ethyl-N-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-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-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-morpholinofluoran , 2-
(Di-N-p-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,

Benzoleucomethylene blue, 2- [3,
6-bis (diethylamino)]-7- (o-chloroanilino) xanthyl] lactam benzoate, 2- [3,6-
Bis (diethylamino)]-9- (o-chloroanilino) xanthyl] lactam benzoate, 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-methylindol-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-methylindole-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.

Next, a developer used in combination with a color former in the reversible thermosensitive recording medium of the present invention will be described. As disclosed in Japanese Patent Application Laid-Open No. 5-124360, a color former can be developed in a molecule as disclosed in the Japanese Patent Application Laid-Open No. 5-124360 together with typical examples of a phosphoric acid compound and a fatty acid compound having a long chain hydrocarbon group. A compound having both a structure having color developing ability and a structure controlling cohesion between molecules is used. As a structure having a color developing ability, for example, a structure having an acidic group such as a phenolic hydroxyl group, a carboxyl group, and a phosphoric acid group is used in the same manner as a general thermal recording medium. What is necessary is just to have the group which can be performed. These include, for example, thiourea groups, metal carboxylate and the like. A typical structure for controlling cohesion between molecules includes a hydrocarbon group such as a long-chain alkyl group. Generally, the number of carbon atoms of the hydrocarbon group is preferably 8 or more from the viewpoint of obtaining good color-developing and decoloring characteristics. The hydrocarbon group may contain an unsaturated bond, and also includes a branched hydrocarbon group. Also in this case, the main chain portion preferably has 8 or more carbon atoms. The hydrocarbon group may be substituted with, for example, a group such as a halogen atom, a hydroxyl group, or an alkoxy group.

As described above, the color developer has a structure in which a structure having a color developing ability and a structure controlling a cohesive force represented by a hydrocarbon group are connected. A divalent group containing a hetero atom as described below or a group obtained by combining a plurality of these groups may be bonded to the linking portion. In addition, an aromatic ring or a heterocyclic ring such as phenylene and naphthylene may be bonded, or both may be bonded. The hydrocarbon group may have a divalent group similar to the above in its chain structure, that is, a divalent group containing an aromatic ring or a hetero atom.

Hereinafter, the developer used in the present invention will be specifically exemplified. -Organic phosphoric acid developer The following compounds can be exemplified as the organic phosphoric acid developer. Dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, ditetradecyl phosphate,
Dihexadecyl phosphate, dioctadecyl phosphate, dieicosyl phosphate, dibehenyl phosphate, and the like.

-Aliphatic carboxylic compounds Examples of the aliphatic carboxylic compounds include the following compounds. 2-hydroxytetradecanoic acid, 2-hydroxyhexadecanoic acid, 2-hydroxyoctadecanoic acid,
2-hydroxyeicosanoic acid, 2-hydroxydocosanoic acid, 2-bromohexadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid, 2-bromodocosanoic acid, 3-bromooctadecanoic acid, 3-bromodocosanoic acid, 2 , 3-dibromooctadecanoic acid, 2-fluorodecanoic 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, perfluoctadecanoic acid, and the like.

Aliphatic dicarboxylic acid and tricarboxylic acid compounds Examples of the aliphatic dicarboxylic acid and tricarboxylic acid compounds include the following compounds. 2-dodecyloxysuccinic acid, 2-tetradecyloxysuccinic acid, 2-hexadecyloxysuccinic acid, 2-octadecyloxysuccinic acid, 2-eicosyloxysuccinic acid, 2-dodecyloxysuccinic acid, 2-dodecylthiosuccinic acid 2-hexadecylthiosuccinic acid, 2-tetradecylthiosuccinic acid,
2-octadecylthiosuccinic acid, 2-eicosylthiosuccinic acid, 2-docosylthiosuccinic acid, 2-tetracosylthiosuccinic acid, 2-hexadecylthiosuccinic acid, 2-octadecyldithiosuccinic acid, 2-eicosyldithiosuccinic acid, dodecylsuccinic acid , Tetradecyl succinic acid, pentadecyl succinic acid, hexadecyl succinic acid, octadecyl succinic acid, eicosyl succinic acid, docosyl succinic acid,
2,3-dihexadecylsuccinic acid, 2,3-dioctadecylsuccinic acid, 2-methyl-3-hexadecylsuccinic acid, 2-methyl-3-octadecylsuccinic acid, 2-octadecyl-3-hexadecylsuccinic acid, hexadecylmalon Acid, octadecylmalonic acid, eicosylmalonic acid,
Docosylmalonic acid, dihexadecylmalonic acid, dioctadecylmalonic acid, didocosylmalonic acid, methyloctadecylmalonic acid, 2-hexadecylglutaric acid, 2-octadecylglutaric acid, 2-eicosylglutaric acid, docosylglutaric acid, 2-pentane Decyl adipic acid, 2-octadecyl adipic acid, 2-eicosyl adipic acid, 2
-Docosyladipic acid, 2-hexadecanoyloxypropane-1,2,3-tricarboxylic acid, 2-octadecanoyloxypropane-1,2,3-tricarboxylic acid and the like.

As the color developer, a phenol compound having a structure for controlling intermolecular cohesion is also preferably used. For example, a phenol compound represented by the following general formula (2) can be exemplified.

[0025]

Embedded image (In the formula, A represents a phenylene group or a naphthylene group. X, Y, and Z are each independently -NHCO-, -C
ONH-, -NHCONH-, -CONHNHCO-,
-COO-, -SCO-, -COS-, -NHCOCO
NH-, -OCONH-, -NHCOO-, -NHSO
_{2 -, - NHSOO -, -} SO 2 -, - CONHCO-,
-CONHCONH-, -CH = N-, -S-, -O
-, - OCOO -, - SO 2 NH -, - NHSONH
-, -N = CH-, -CO-, -OCO-, -SCOO
-, - SCONH -, - NH -, - NHSO 2 -, - N
HCONHNHCO -, - NHCSNH -, - SO 2 N
HCONH-, -OCONH-, -NHNHCONH
-, -NHCONHNH-, -NHCONHCO-,-
A divalent group of CONHNHCONH- or -NHCONH- or a divalent group generated by further bonding of the same or different divalent groups. p is an integer of 0 to 6, and q is 0
R, s, and v are 0 or 1, and t is 0 to 10.
And w represents an integer of 10 to 22. )

Specific examples of the phenol compound represented by the general formula (2) are shown in Table 1 below as p, q, r, s, t, v, w,
It is indicated by the number or structure of X, A, Y, Z. However, in each of these specific examples, n of the phenol moiety is 1 to 3, and for example, 4-hydroxyphenyl, 3-hydroxyphenyl, 2-hydroxyphenyl, 2,4-dihydroxyphenyl, 3,4-dihydroxyphenyl or It is a phenyl group having at least one hydroxyl group, such as 3,4,5-trihydroxyphenyl. This phenyl group may have a substituent other than a hydroxyl group. Also, if it has a phenolic hydroxyl group,
It may be another aromatic ring.

[0027]

[Table 1-1]

[0028]

[Table 1-2]

[0029]

[Table 1-3]

[0030]

[Table 1-4]

[0031]

[Table 1-5]

[0032]

[Table 1-6]

[0033]

[Table 1-7]

[0034]

[Table 1-8] In the present invention, the developer is not limited to the compounds described above, and various other compounds having an electron accepting property can be used.

Next, specific examples of the compound according to the present invention are shown in Table 2. However, the present invention is not limited to these.

[0036]

[Table 2-1]

[0037]

[Table 2-2]

The reversible thermosensitive coloring composition of the present invention is capable of forming a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. The basic color development / decolorization development 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 decoloration occurs with a color temperature lower than temperature T ₂ and (E from D), the same colorless state, including when the temperature decreases from which (A)
Return to The actual color forming temperature and color erasing temperature can be selected according to the purpose because they vary depending on the combination of the color developer and the color developing agent used. In addition, the density in the molten color development state and the color development density after quenching do not always match, and may differ.

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 developer and the color-developing agent are mixed in a state where they can be brought into contact with each other. It often forms a 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 aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

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 mixture is 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, 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 varies 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, but the molar ratio of the color developer to the color developer is from 0.1 to 20. It is in the range, 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. The support is paper, resin film, synthetic paper, metal foil, glass or a composite thereof, and may be any as long as it can hold the recording layer.

The recording layer may be of any type as long as the composition of the present invention is present. Generally, a recording layer in which a color former and a color developer are finely and uniformly dispersed in a binder resin is used. Can be The color former and the developer may form particles individually, but are more preferably dispersed 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 characteristics of the recording layer and the coloring and decoloring characteristics. These additives include, for example, dispersants, surfactants, conductive agents, fillers, lubricants, antioxidants, light stabilizers, ultraviolet absorbers, color stabilizers, and decolorization accelerators.

Examples of the binder resin used for forming the recording layer include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, and aromatic polyester. , Polyurethane, polycarbonate, polyacrylate, polymethacrylate, acrylic acid copolymer, maleic acid copolymer, polyvinyl 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 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, 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, besides 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, 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. It becomes possible to prevent or reduce the 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.

For the intermediate layer and the undercoat layer, the same resins as those for the recording layer described above can be used. The protective layer, the intermediate layer, the recording layer, and the undercoat layer may 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. A back coat layer may be provided on the opposite side of the support in order to improve the smoothness and transportability of the support or to prevent curling.

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 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, heating may be performed by using an appropriate heat source for a relatively long time to cool, or the color may be temporarily heated to an erasing temperature slightly lower than the coloring temperature. When 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 and gradually cooled, so that decoloring occurs in the process. 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. Using this method, recording and
Erasing is possible, so-called overwriting becomes possible. Of course, the image can be erased by heating to the decoloring temperature range by a heat roller, a heat stamp, a heating bar or the like.

[0052]

The present invention will be described in more detail with reference to the following examples. “Parts” and “%” in the examples are all based on weight. Example 1 The following composition was ground and mixed in a mortar. [Coloring agent] 2-anilino-3-methyl-6-dibutylaminofluoran 1 part [Developing agent]

[0053]

Embedded image [Coloring / decoloring control agent] Compound 2 of Part 3 An appropriate amount of this mixture was placed on a glass plate having a thickness of 1.2 mm, and heated and mixed at 200 ° C. on a hot plate.
Subsequently, a cover glass was put over the mixed melt mixture to spread the melt to a uniform thickness, and the entire glass plate was immediately immersed in the prepared ice water and rapidly cooled. Immediately after the temperature was lowered, the water adhered was removed to remove the adhering water, thereby obtaining a black-colored composition of the present invention as a thin film. Next, when the above-described composition sample in a color-developed state was placed on a hot plate heated to 110 ° C., the color was instantaneously erased. Again, the decolorized composition sample was 200
When heated to ° 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 following composition was pulverized and dispersed to a particle size of 1 to 4 μm using a ball mill. [Coloring agent] 2-anilino-3-methyl-6-dibutylaminofluoran 2 parts [Developing agent]

[0055]

Embedded image [Coloring / decoloring control agent] 6 parts 3 parts Phenoxy resin (manufactured by Union Carbide Co., Ltd., PKHH) 15% tetrahydrofuran (THF) solution 150 parts

To the resulting dispersion was added 20 parts of Coronate HL (adduct type hexamethylene diisocyanate, 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd., and the mixture was stirred well to prepare a recording layer coating solution. The recording layer coating solution having the above composition was applied onto a 100 μm-thick polyester film using a wire bar, dried at 80 ° C., and then heated at 100 ° C. for 10 minutes and at 60 ° C. for 24 hours to form a film having a thickness of 6. A recording layer of 0 μm was provided. A protective layer solution having the following composition was applied on the recording layer by using a wire bar, and then cured under a UV lamp having an irradiation energy of 80 W / cm at a conveying speed of 9 m / min to cure the recording layer to a thickness of 3 μm. The layer was provided to produce a reversible thermosensitive recording medium of the present invention. [Protective layer liquid] Urethane acrylate ultraviolet curable resin (C7-157, manufactured by Dainippon Ink and Chemicals) 10 parts Ethyl acetate 90 parts

The produced recording medium was printed by a thermal printing apparatus manufactured by Okura Electric Co., Ltd. at a voltage of 13.3 V and a pulse width of 1.2 msec. When the density of the printed portion was measured with a Macbeth densitometer RD914, the image density was 1.00. Next, this printed sample was subjected to a heat gradient tester at 110 ° C. for 0.1 hour.
Heat for 5 seconds to erase. The densities of the erased portion and the background portion were measured in the same manner. The residual density was 0.02. In response to the problem, the color development was evaluated by the image density, the decoloration was evaluated by the remaining density, and the storability was evaluated by the density retention. When the print sample was stored for 24 hours under the drying condition at 50 ° C., the density retention of the image portion was 72%. Here, the density retention is represented by the following equation.

[0058]

(Equation 1) The remaining erase density is the difference between the density after erasure and the background density, and is expressed by the following equation.

## EQU2 ## Remaining erase density = (image density after erasure)-(background density)

Example 3 A reversible thermosensitive recording medium was prepared in the same manner as in Example 2, except that the developer in Example 2 was changed to the following. [Developer]

[0060]

Embedded image When the produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2, the image density was 1.05, the erasing residual density at 110 ° C. for 0.5 second was 0.01, and the image density under the drying condition at 50 ° C. The concentration retention was 70%.

Example 4 In place of the color former 2-anilino-3-methyl-6-dibutylaminofluorane in Example 2, 3,3-bis (2
A reversible thermosensitive recording medium was prepared in the same manner as in Example 2 except that (ethoxy-4-diethylaminophenyl) -4-azaphthalide was used. When the produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2, the image density was 0.9.
The residual density after elimination at 9, 110 ° C. and 0.5 seconds was 0.02, and the concentration retention under the drying condition at 50 ° C. was 68%.

Example 5 The coloring and decoloring controlling agents in Example 2 6 to N
o. A reversible thermosensitive recording medium was produced in the same manner as in Example 2 except that the recording medium was replaced with 13. When the produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2, an image density of 1.0 was obtained.
The residual density after elimination at 1,110 ° C. and 0.5 seconds was 0.01, and the concentration retention under 50 ° C. drying conditions was 70%.

Example 6 The coloring and decoloring control agents in Example 2 6 to N
o. A reversible thermosensitive recording medium was prepared in the same manner as in Example 2 except that the recording medium was replaced with 17. When the produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2, an image density of 1.0 was obtained.
The residual density after erasure at 0, 110 ° C. and 0.5 seconds was 0.02, and the concentration retention under the drying condition at 50 ° C. was 74%.

Comparative Example Except that no coloring / decoloring controlling agent was used in Example 2,
A reversible thermosensitive recording medium was produced in the same manner as in Example 2.
When the produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2, the image density was 1.02, the residual density after erasing at 110 ° C. for 0.5 seconds was 0.05, and the dry density was 50 ° C. The concentration retention was 54%. From the above results, it can be seen that the present invention has a higher color stability (coloring density), a higher storage stability of a colored state, and an excellent decoloring property, as compared with the comparative example.

[0065]

As described above, the reversible thermochromic composition and the reversible thermosensitive recording medium of the present invention are represented by the general formula (1) as a coloring / decoloring controlling agent. Since the compound is used, the storage properties and the erasing properties are good and the practicability is high.

[Brief description of the drawings]

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

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroaki Matsui 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 2H026 AA07 AA09 BB02 BB24 DD46 DD53 FF01

Claims (2)

[Claims] 1. A reversibility capable of forming a relatively colored state and a decolored state by using an electron-donating color-forming compound and an electron-accepting compound depending on a difference in a heating temperature and / or a cooling rate after heating. A reversible thermosensitive coloring composition characterized in that a compound represented by the following general formula (1) is contained in the reversible thermochromic composition as a coloring / decoloring control agent. Embedded image 2. A reversible thermosensitive recording medium comprising a support and a recording layer containing the reversible thermosensitive coloring composition according to claim 1 as a main component.