JPH07186549A - Electron accepting developer, thermal color developing composition using the same, recording medium containing the same composition and reversibly recording method - Google Patents

Abstract

PURPOSE:To obtain a reversible thermal color developing composition which can be used as solvent type coating fluid and be recorded at a high speed when a thermal color developing layer is formed by using specific compound as elec tron accepting developer. CONSTITUTION:A reversible thermal recording medium has a recording layer formed of reversible thermal color developing composition containing developer and color developing agent. As the developer, i.e., electron accepting developer, CH2 n+1-X-PO(OH)2 is used. In the formula, X is -OCH2-, -SCH2-, -CH(NH2)-, -CH(COOH)-, -CONHCH2-, -C6H4-, and n is integer of 6-23. When such a composition is heated to a melting temperature or higher, the composition instantaneously develops a color, and its color developing state is stably existed at the ambient temperature. However, the composition of the developed state is decolored when heated to a temperature lower than the developing temperature, and its decolored state is stably existed at the ambient temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron-accepting color developer used in a color-forming reaction between an electron-donating color developing compound and an electron-accepting color developer, and a reversible thermochromic composition using the same. And a reversible thermosensitive recording medium using the composition.

[0002]

2. Description of the Related Art Conventionally, a color-forming reaction between an electron-donating color-forming compound (hereinafter also referred to as a color-developing agent) and an electron-accepting color-developing agent (hereinafter also referred to as a color-developing agent) has been used. Thermosensitive recording medium (in this specification, the recording medium includes a display medium)
Is widely known for computer output, facsimile,
Widely applied to vending machines, printers for scientific measuring machines, printers for CRT medical measurement, etc. However, all the conventional products have irreversible color development, and it is not possible to repeat the color development and the color erasing alternately.

On the other hand, according to the patent publication, there is also proposed one that reversibly performs coloring and erasing, for example, 1. Japanese Patent Application Laid-Open No. 60-193691, in which a developer in which gallic acid and phloroglucinol are combined is used. 2. JP-A-61-237684, wherein a compound such as phenolphthalein or thymolphthalein is used as a developer. Incorporating a homogenous solution of a color former, a developer and a carboxylic acid ester into the recording layer is disclosed in JP-A-62-138556 and JP-A-62.
-138568 gazette and JP-A-62-140881, 4. 4. JP-A-2-188294 in which a salt of gallic acid and a higher aliphatic amine is used as a developer. JP-A-2-188293, which uses a salt of bis (hydroxyphenyl) acetic acid or butyric acid and a higher aliphatic amine as a developer, is disclosed. However, various problems remain in the conventional reversible thermosensitive recording medium described above, and it is not yet satisfactory.

[0004]

DISCLOSURE OF THE INVENTION The present invention, in a reversible thermochromic composition utilizing the reaction between a color former and a color developer, solves various problems found in the prior art and at the same time, develops and erases the color. Coloring can be easily performed only by heating, and the coloring and decoloring states can be maintained at room temperature, and the decoloring temperature is lower than the coloring temperature. The first object is to provide a developer capable of forming a reversible thermochromic composition that can be repeated many times. In particular, it is intended to provide a composition which can be used as a solution type coating solution when forming a thermosensitive color developing layer and which enables high speed recording. It is also intended to provide a reversible thermochromic composition containing the developer and a recording medium containing the composition in a recording layer, and to provide a reversible thermosensitive recording method using the recording medium. The second issue.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present invention has been completed.
That is, according to the present invention, an electron-accepting developer represented by the following general formula is provided. General formula _{I C n H 2n + 1 -X} -PO (OH) 2 ( wherein, X is _{-OCH 2 -, - SCH 2 -} , - CH (NH
_{2) -, - CH (COOH} ) -, - CONHCH 2 -, -
C ₆ H ₄ −, and n represents an integer of 6 to 23) Further, according to the present invention, a reversible thermochromic composition containing the developer and the color former and the composition are recorded. A reversible thermosensitive recording medium containing layers is provided. Furthermore, according to the present invention, a color recording step comprising heating to a temperature above the melting temperature of the reversible thermochromic composition, and heating the composition in a colored state to a temperature lower than the melting temperature. A reversible thermosensitive recording method is provided, which comprises a recording and erasing step comprising

It is no exaggeration to say that the thermal characteristics of the reversible thermochromic composition of the present invention are determined by the color developer. As will be described later, the color developer develops the leuco dye in a molten state, and The color developer, which is combined with the leuco dye to form a colored state, is decolored by separating and crystallizing from the composition in the colored state at a temperature lower than the coloring temperature. Therefore, the developer can be said to be a key material in the reversible thermochromic composition of the present invention, and the present invention uses a compound represented by the following general formula as the developer. General formula _{I C n H 2n + 1 -X} -PO (OH) 2 ( wherein, X is _{-OCH 2 -, - SCH 2 -} , - CH (NH
_{2) -, - CH (COOH} ) -, - CONHCH 2 -, -
C ₆ H ₄ −, n represents an integer of 6 to 23) In the general formula I, R represents an aliphatic group having 12 or more carbon atoms,
n represents an integer of 1 or 2, but the aliphatic group represented by R includes a linear or branched alkyl group and an alkenyl group, and a substituent such as a halogen atom, an alkoxy group, or an ester group. You may have a base. Specific examples of the developer of the present invention include the following compounds, but the present invention is not limited thereto.

[0007] Specific examples of the electron-accepting color developer represented by the general formula _{C n H 2n + 1 -X-} PO (OH) 2 X = -OCH 2 - CH 3 (CH 2) 11 OCH 2 PO (OH ) ₂ CH ₃ (CH ₂ ) ₁₃ OCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₁₅ OCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₁₇ OCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) _{19 OCH 2 PO (OH) 2} CH 3 (CH 2) 21 OCH 2 PO (OH) 2 X = -SCH 2 - CH 3 (CH 2) 7 SCH 2 PO (OH) 2 CH 3 (CH 2) 9 SCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₁₁ SCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₁₃ SCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₁₅ SCH ₂ PO (OH) ₂ -CH _{(NH 2) - CH 3 (} CH 2) 9 CH (NH 2) PO (OH) 2 CH 3 (CH 2) 11 CH (NH 2) PO (OH _{) 2 CH 3 (CH 2)} 13 CH (NH 2) PO (OH) 2 CH 3 (CH 2) 15 CH (NH 2) PO (OH) 2 X = -CH (COOH) - CH 3 (CH 2) _{9 CH (COOH) PO (OH} ) 2 CH 3 (CH 2) 11 CH (COOH) PO (OH) 2 CH 3 (CH 2) 13 CH (COOH) PO (OH) 2 CH 3 (CH 2) 15 CH _{(COOH) PO (OH) 2} CH 3 (CH 2) 19 CH (COOH) PO (OH) 2 X = -CONH- CH 3 (CH 2) 10 CONHCH 2 PO (OH) 2 CH 3 (CH 2) 12 CONHCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₁₄ CONHCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₁₆ CONHCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₁₈ CONHCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₂₀ CONHCH ₂ PO (OH) ₂ CH ₃ (CH ₂ ) ₂₂ CONHCH ₂ PO (OH) ₂

[0008]

[Chemical 1]

The reversible thermochromic composition of the present invention instantly develops a color when heated to a temperature higher than the melting temperature, and the color development state thereof is stable even at room temperature, but the composition in the color development state is heated to a temperature lower than the color development temperature. Then, the color is erased, and the decolorized state is stable even at room temperature. The coloring and decoloring of the reversible thermochromic composition of the present invention will be described with reference to a reversible thermosensitive recording medium having the composition in a recording layer. That is, the principle of image formation and image deletion will be described with reference to the graph shown in FIG.
The vertical axis of the graph represents the color density and the horizontal axis represents the temperature. The solid line 1 represents the image forming process by heating and the dotted line 3 represents the image erasing process by heating. A is the concentration in the completely erased state, B is the concentration in the saturated coloring state when heated to a temperature of T ₁ or higher, C is the concentration at the temperature of T ₀ or lower in the saturated coloring state, and D is T _0. ~ T
_It shows the density when recording is erased by heating at a temperature between _{1 and} .

The recording medium containing the reversible thermochromic composition of the present invention in the recording layer is in a colorless state (A) at a temperature of T ₀ or lower. To record, use a thermal head
_It may be heated to a temperature of ₁ or more, and color development (B) is performed to form a recorded image. Even if the recorded image is returned to the temperature of T ₀ or less according to the solid line 2, the state (C) is maintained as it is, and the recording memory property is not lost. Next, in order to erase the recorded image, the formed recorded image may be heated to a temperature between T _{0 and} T _{1, which} is lower than the coloring temperature, and the state becomes colorless (D). This state is maintained as it is even if the temperature is returned to T ₀ or lower (A). That is, the formation process of the recorded image reaches C by the path of the solid line ABC and the recording is held. During the process of erasing the recorded image, the erased state is maintained up to A by the path of the broken line CDA. The behavioral characteristics of forming and erasing the recorded image are reversible and can be repeated many times.

FIG. 2 is an explanatory view showing an example of image formation and image erasure. 1 is a support, 2 is a reversible thermosensitive recording layer, and 3 is
Is a colored image. In the image forming process (A) → (B), the image forming heat source, for example, the thermal head 4 is used to perform the T of FIG.
Recording and printing may be performed at a temperature of ₁ or higher. The image erasing step (B) → (A) is achieved by heating the image erasing heat source, for example, the heating roller 5 to a temperature between T _{0 and} T ₁ . The reversible thermochromic composition of the present invention contains a color former and a developer as essential components. The color of the composition is obtained by cooling the color body formed by heating and melting the color developer and the color developer to room temperature. Since this color-forming material composition has an erasing temperature region on the lower temperature side than the melting temperature, rapid cooling is preferable when cooling from the melt-colored state to room temperature while maintaining the color development. In the case of gradual cases, some color disappears when passing through the color-erasing temperature region, and the density often decreases.

It is considered that in the color former composition, the molecules of the color former and the developer interact with each other to open the lactone ring of the color former to develop a color. The composition in the melted state and the rapidly cooled state contains, in addition to the color former molecules, the color former molecules and the developer molecules not directly involved in the formation of the color former. In the reversible thermochromic composition of the present invention, the colorant composition at room temperature is in a solidified state due to the cohesive force between these molecules. Further, although the aggregate structure of the color former composition shows some regularity, it may be very regular or not very regular. This depends on the combination and amount ratio of the color-developing agent and the color-developing agent, cooling conditions and the like. Such an aggregation structure acts between the long-chain structure portion of the developer molecule forming the chromophore and the excess long-chain structure portion of the developer molecule not forming the chromophore. It is presumed that force is the basis of formation. The formation of such an aggregate structure is associated with the decoloring phenomenon of the color former composition.

The color-forming material composition can be decolored by heating its color-developed state to a specific temperature range.
In this decoloring process, the aggregate structure of the color developing state changes, and eventually the developer molecules are separated and crystallized from the color former composition to form crystals of the developer alone, resulting in a stable decolored state. X
Confirmed by lines. As described above, in the reversible thermochromic composition of the present invention, it is clear that the long-chain portion of the color developer plays a large role in the formation of the color-developed state and the decoloring process thereof. This is a characteristic of the color-forming material composition formed in the composition. Therefore, the decolorization temperature can be controlled by the length of the long chain portion of the color developer, and the longer the chain length, the more often the color development and decolorization temperature shift to the high temperature side. This is because the cohesiveness and motility of the developer molecules change depending on the length of this portion.

The reversible thermochromic composition of the present invention is basically a composition in which the above-mentioned color developer having a long chain structure and a color developer are combined, and a preferable color development for each color developer. There is an agent. The combination of the color-developing agent and the color-developing agent used in this composition is the ease of decoloring that occurs when the color-developed state composition obtained by heating both of them to a temperature lower than the melting temperature is heated. (Decoloring property) and characteristics such as color tone of the color-developed state are appropriately selected. Among these, the decoloring property can be judged by the presence or absence of an exothermic peak appearing in the temperature rising process in the differential thermal analysis (DTA) or the differential scanning calorimetry (DSC) of the color-developed state composition obtained by the combination. This exothermic peak corresponds to the decoloring phenomenon that characterizes the composition, and serves as a criterion for selecting a combination having a good decoloring property. The third substance may be present in the reversible thermochromic composition of the present invention. For example, even if a eutectic agent (heat sensitizer) polymer compound or a decolorization accelerator is present, its reversibility is improved. It is possible to maintain the typical erasing and coloring behavior.

The reversible thermochromic composition of the present invention is basically constituted by combining a color former with the color developer. The color-forming agent used in the present invention is one that exhibits an electron-donating property and is a colorless or light-colored dye precursor itself, and is not particularly limited, and conventionally known triphenylmethanephthalide-based compounds, fluoran-based compounds, phenothiazine-based compounds are known. A compound, a leuco auramine-based compound, an indolinophtalide-based compound, or the like is used. Specific examples of the color former are shown below. Preferred color formers for use in the present invention include compounds represented by the following formula II or III.

[0016]

[Chemical 2]

However, R ₁ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ₂ represents an alkyl group having 1 to 6 carbon atoms, a cyclohexyl group or an optionally substituted phenyl group.
Examples of the substituent for the phenyl 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, and a halogen atom. R ₃ represents hydrogen, an alkyl group having 1 to 2 carbon atoms, an alkoxy group or halogen. R ₄ represents hydrogen, a methyl group, a halogen or an optionally substituted amino group. The substituent for the amino group is
Examples thereof include an alkyl group, an optionally substituted aryl group, an aralkyl group, and the like, and the substituent here is an alkyl group, a halogen, an alkoxy group, or the like.

Specific examples of such a color former include the following compounds. 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-
Methyl-6- (di-n-butylamino) fluorane, 2
-Anilino-3-methyl-6- (Nn-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- (Nn-amyl-N-
Ethylamino) fluorane, 2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) fluorane, 2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino) ) Fluoran, 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-diethylaminofluorane, 2- (m-trifluoromethylanilino) -3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane, 2- (2,4-
Dimethylanilino) -3-methyl-6-diethylaminofluorane, 2- (N-ethyl-p-toluidino) -3
-Methyl-6- (N-ethylanilino) fluorane, 2
-(N-methyl-p-toluidino) -3-methyl-6-
(N-propyl-p-toluidino) fluorane, 2-anilino-6- (Nn-hexyl-N-ethylamino)
Fluorane, 2- (o-chloroanilino) -6-diethylaminofluorane, 2- (o-bromoanilino) -6
-Diethylaminofluorane, 2- (o-chloroanilino) -6-dibutylaminofluorane, 2- (o-floranilino) -6-dibutylaminofluorane, 2-
(M-Trifluoromethylanilino) -6-diethylaminofluorane, 2- (p-acetylanilino) -6-
(Nn-amyl-Nn-butylamino) fluorane, 2-benzylamino-6- (N-ethyl-p-toluidino) fluorane, 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)
Fluoran, 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) fluorane, 2-amino-6- (N-ethyl-p-chloranilino) fluorane, 2-amino-6
-(N-propyl-p-chloroanilino) fluorane,
2,3-dimethyl-6-dimethylaminofluorane, 3
-Methyl-6- (N-ethyl-p-toluidino) fluorane, 2-chloro-6-diethylaminofluorane, 2
-Bromo-6-diethylaminofluorane, 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-chloro-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) fluorane,
1,2-benzo-6-dibutylaminofluorane, 1,
2-benzo-6- (N-methyl-N-cyclohexylamino) fluorane, 1,2-benzo-6- (N-ethyl-p-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) fluorane, 2-benzoylamino-6- (N-ethyl-p-toluidino) fluorane, 2- (o-methoxybenzoylamino) -6-
(N-methyl-p-toluidino) fluorane, 2-dibenzylamino-4-methyl-6-diethylaminofluorane, 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) fluorane, 2- (o-methoxycarbonylanilino) -6-diethylaminofluorane, 2-acetylamino-6- ( N-methyl-p-toluidino) fluorane, 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-morpholinofluorane , 2-
(Di-Np-chlorophenyl-methylamino) -6-
Pyrrolidinofluorane, 2- (N-n-propyl-m-
Trifluoromethylanilino) -6-morpholinofluorane, 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) xanthyl lactam benzoate, 3,3-bis (p-dimethylanilino)-
Phthalide, 3,3-bis (p-dimethylanilino) -6
-Dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylanilino)
-6-Diethylaminophthalide, 3,3-bis (p-dimethylanilino) -6-chlorophthalide, 3,3-bis (p-dibutylanilino) phthalide, 3- (2-methoxy-4-dimethylanilino) ) -3- (2-Hydroxy-
4,5-dichlorophenyl) phthalide, 3- (2-hydroxy-4-dimethylanilino) -3- (2-methoxy-5-chlorophenyl) phthalide, 3- (2-hydroxy-4-dimethoxyanilino) ) -3- (2-Methoxy-
5-chlorophenyl) phthalide, 3- (2-hydroxy-4-dimethylanilino) -3- (2-methoxy-5-
Nitrophenyl) phthalide, 3- (2-hydroxy-4)
-Diethylanilino) -3- (2-methoxy-5-tolyl) phthalide, 3- (2-methoxy-4-dimethylanilino) -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-benzoin Dorino-spiropyran and others.

In the reversible thermochromic composition of the present invention, it is necessary that the ratio of the color former to the color developer is appropriately adjusted depending on the physical properties of the compound used. The range is generally in the range of 1 to 20 and preferably 2 to 10 with respect to the color former 1 in terms of molar ratio. If the amount of the color developer is less or more than this range, the density of the color-developed state becomes low, which is a practical problem. Further, even in the above preferable range, the decoloring property changes depending on the ratio of the color developing agent and the color developing agent. When the color developing agent is relatively large, the decoloring start temperature is low, and when it is relatively small. Decolorization becomes sharp with respect to temperature. Therefore,
This ratio must be appropriately selected according to the application and purpose. When a eutectic agent (heat sensitizer) is contained as a component of the thermochromic composition of the present invention, the color develops faster, and when heated to a temperature higher than the melting temperature, the color develops instantly.

Specific examples of the eutectic agent used in the present invention include the following. Palmitic acid amide, stearic acid amide, behenic acid amide, palmitic acid anilide, stearic acid anilide, benzoic acid stearyl amide, paraoctyl sulfonic acid amide, 4-octanoylbiphenyl, 2-palmityl imidazole,
2-stearyl imidazole and the like, and further, betanaphthol benzyl ether, oxalic acid benzyl ester, oxalic acid paramethyl benzyl ester and the like, which are generally used in the heat-sensitive recording field, can be used.

The reversible thermosensitive recording medium of the present invention has a recording layer containing the above-mentioned composition provided on a support, and the basic constitution of the recording medium is that the lowermost layer has a support, and The recording layer and the protective layer are sequentially laminated, and an undercoat layer for preventing the developer of the recording layer from penetrating into the support is provided between the support and the recording layer, and the recording layer and the protective layer. It is more preferable to provide an intermediate layer between the layers for the purpose of improving adhesiveness. The support used here is paper, synthetic paper, a plastic film or a composite thereof, a glass plate, and the like, as long as it can hold the recording layer.

The recording layer may be in any form as long as the above-mentioned reversible thermochromic composition is present, but normally, the recording layer is prepared by sufficiently well dispersing the color former and the developer in the binder resin. And a reversible thermosensitive recording medium having a long life can be obtained by this method. The color former and the color developer can be used as they are or by being encapsulated in microcapsules. Microencapsulation of the color former and the color developer can be carried out by a known method such as a coacervation method, an interfacial polymerization method or an in situ polymerization method. The color former and the color developer may be used alone or as a mixture of two or more kinds.

In the reversible thermosensitive recording medium of the present invention, various additives, such as dispersants and surfactants, which are used in ordinary thermosensitive recording paper, are used for the purpose of improving coating properties or recording properties, if necessary. Further, a polymeric cationic conductive agent, a filler, a color image stabilizer, an antioxidant, a light stabilizer, a lubricant and the like can be added to the recording layer. The recording layer may be formed by a known method in which a color former and a developer are uniformly dispersed or dissolved in water or an organic solvent together with a binder resin, and this is applied onto a support and dried, and the thickness thereof is Is 0.5 to 50 μm,
The thickness is preferably 1 to 20 μm. The main role of the binder resin in the recording layer is to prevent the reversible thermochromic composition from aggregating due to repeated coloring and decoloring, and to maintain the composition in a uniformly dispersed state. Since the composition often agglomerates when heat is applied during color development, it is preferable to use a binder resin having high heat resistance.

Examples of such binder resins include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, ethyl cellulose, polystyrene, styrene copolymers, phenoxy resins, polyesters, aromatic polyesters, polyurethanes, polycarbonates. , Polyacrylic acid esters, polymethacrylic acid esters, acrylic acid copolymers, maleic acid copolymers, polyvinyl alcohol, chlorinated vinyl chloride resins, mixtures of the binder resins and the like are used. Since the protective layer prevents the surface from being deformed or discolored by heat and pressure when heat is applied, it is preferable to install the protective layer when used many times.

For the protective layer, conventionally known resins such as polyvinyl alcohol, styrene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer, carboxy-modified polyethylene, melamine-formaldehyde resin and urea-formaldehyde resin are used. used. These may be used alone or in combination of two or more, but it is also possible to add a curing agent to the resin for forming the protective layer to form a layer, and to cure the layer after the layer is formed. In addition to the above, conventionally known ultraviolet curable resins are also preferably used. Further, as the solvent when using the ultraviolet curable resin, an organic solvent such as tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, toluene, benzene is used. . A photopolymerizable monomer effective as a reactive diluent may be used in place of these organic solvents.

As the ultraviolet curable resin used for forming the protective layer, all of monomers or oligomers (or prepolymers) which are polymerized and cured by irradiation with ultraviolet rays can be used. Examples of such low molecular weight compounds include (poly) ester acrylate, (poly) urethane acrylate,
Epoxy acrylate, polybutadiene acrylate,
Examples include silicon acrylate and melamine acrylate. The (poly) ester acrylate is 1,6-
A polyhydric alcohol such as hexanediol, propylene glycol or diethylene glycol, a polybasic acid such as adipic acid, maleic anhydride or trimellitic acid, and acrylic acid are reacted. By forming such a protective layer, it is possible to obtain a recording medium in which the formation and deletion of an image due to a temperature change can be repeated without problems even when contacted with an organic solvent, a plasticizer, oil, sweat, water and the like. Further, by containing a light stabilizer in the protective layer, it is possible to obtain a recording medium in which the light resistance of the image and the background are remarkably improved, and further by containing an organic or inorganic filler and a lubricant in the protective layer, It is possible to obtain a reversible thermosensitive recording medium having excellent reliability and head matching properties without causing a problem such as sticking caused by contact with a thermal head or the like.

The coating method and coating amount of the protective layer are not particularly limited, but the coating amount is preferably in the range of 0.1 to 20 μm on the recording medium from the viewpoint of performance and economical efficiency as the protective layer. Is preferably in the range of 0.5 to 10 μm. The undercoat layer is provided for the purpose of improving heat insulation, improving the adhesion between the support and the recording layer, and improving the resistance of the support to the solvent when the recording layer is formed. One of the important roles of the layer is to improve the heat insulating property so that the applied heat energy can be useful for forming or erasing the recording without waste, and the color development and the color erasing can be sharply performed by installing the heat insulating undercoat layer. You can The layer may be installed by coating fine hollow particles of an organic or inorganic material on a support, and specifically, a particle size of 10 to 50 formed of glass or ceramics, plastic, or the like.
It is sufficient to finely disperse the micro hollow body of μm in a solvent together with the binder resin, and uniformly coat and dry it on the support.
A heat insulating support may be used instead of the heat insulating undercoat layer to improve the heat insulating property. Besides the above,
The undercoat layer prevents the color developer in the recording layer from penetrating into the support, and thus prevents the color erasing defect due to the color developer being adsorbed by the cellulose or pigment of the support during the color erasing. The installation of the undercoat layer has many advantages in terms of improving the decoloring ability and the degree of freedom in selecting a support. The coating thickness of the undercoat layer is 0.1 to 50 μm, preferably 0.2 to 20 μm.

The intermediate layer is provided for various purposes such as improving the adhesion between the recording layer and the protective layer and preventing the color-forming composition of the recording layer from migrating to the protective layer. Since a curable resin having high abrasion resistance is often used, the provision of the intermediate layer for improving the adhesiveness has many advantages, and the durability of the recording medium is often improved by the provision of the layer. Since the intermediate layer is often used for the purpose of improving the adhesiveness, it is desirable that the coating thickness be thin, and the general thickness is 0.1 to 10 μm.
m, preferably 0.5-5 μm. The binder resin for forming the undercoat layer and the intermediate layer, in addition to the binder resin for forming the recording layer, methyl cellulose, methoxycellulose, hydroxyethyl cellulose, carboxymethyl cellulose, cellulose acetate, nitrocellulose, polyvinylpyrrolidone, gelatin, casein,
Starch is used. The method for forming and erasing a recorded image is not particularly limited as long as the temperature conditions for coloring and erasing are given, and a thermal head, laser heating, a hot pen, etc. may be used for image formation, and a heating roller or surface may be used for image erasing. A heating element, a heating lamp, etc. are generally used. It is also possible to erase a recorded image with the thermal head set to the erasing temperature and simultaneously form the recorded image with another thermal head set to the recording temperature.

[0030]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. All parts shown below are based on weight. i. Thermochromic composition: Each of the following compounds pulverized in a mortar was thoroughly mixed to obtain a thermochromic composition. 2-anilino-3-methyl-6-dibutylaminofluorane 1.0 part 4-n-decylphenylphosphonic acid (mp 86-88 ° C) 2.5 parts ii. Thermal recording medium: The following composition was ball-milled for 30 hours to prepare a thermal recording layer forming liquid. The thermochromic composition 1.0 part Polyvinyl butyral resin (Denka # 3000-2, manufactured by Denki Kagaku Kogyo Co., Ltd.) 2.5 parts Toluene / methyl ethyl ketone (volume ratio 1: 1) mixed liquid 10.5 parts This liquid is 100 μm thick 0.6 on transparent PET film
Apply with mm type wire bar, dry at room temperature, then 55 ℃
And dried for 3 minutes to prepare a thermosensitive recording sheet.

Then, a 55% ethyl acetate solution of the UV-curable resin Unidic C7-157 was added to the recording layer in an amount of 0.1 m.
A transparent thermosensitive recording sheet was prepared by coating with a m-diameter wire bar, drying at 55 ° C. and curing by UV irradiation to provide a thin film protective layer. The thermal recording sheet thus obtained was processed with a word processor (manufactured by Ricoh Co., Ltd., My Report NL-3).
A printout of Ai) was performed and a clear black print was obtained. Image density of a small solid part is Macbeth reflection densitometer RD-9
It was 1.93 when measured at 14, and 0.07 in the non-image area. This could be seen as a clear black image as a projected image of OHP.

Example 2 i. Thermochromic composition: The following compounds were thoroughly mixed and dispersed in a mortar to obtain a thermochromic composition. 3,6-di-NN-diphenylaminofluorane 1.0 part Lauric acid acid methanephosphonic acid (mp 114-117 ° C.) 3.0 parts Polyvinyl alcohol 10% aqueous solution 6.0 parts ii. Thermosensitive recording medium: The above thermochromic composition was added to ion-exchanged water 1
Along with 5 parts, the mixture was stirred and diluted to obtain a heat-sensitive layer forming liquid.
This solution was mixed with white synthetic paper (VIF-92, 92 manufactured by Oji Yuka Co., Ltd.).
(μm thickness) was applied with a wire bar and dried at 60 ° C.
A recording sheet having a coating amount of 4.7 g / m ² after drying was obtained. When a received image was obtained using this recording sheet as a recording sheet of RIFAX-600 (GIII FAX machine manufactured by Ricoh Co., Ltd.), a clear blue image was recorded against a white background.

Example 3 i. Reversible thermochromic composition: Each of the following compounds was ground in a mortar and mixed well to obtain a reversible thermochromic composition. 2- (o-chloroanilino) -6-dibutylaminofluorane 1.0 part n-hexadecylmercaptomethylphosphonic acid (mp86.0-86.5 ° C) 2.5 parts Reversible thermosensitive recording medium: dissolve the following composition To obtain a thermosensitive recording layer forming liquid. The reversible thermochromic composition 1.0 part Polyurethane resin (Mylactone P26S, manufactured by Nippon Polyurethane Company) 2.5 parts Tetrahydrofuran 10.0 parts Toluene 0.5 parts This solution was coated on a transparent PET film having a thickness of 100 μm with a wire bar. After coating to a film thickness of about 10 μm,
The sheet that was dried at 0 ° C for 3 minutes and developed a black color on the whole surface was taken out and naturally cooled, and then dried in a dryer at 70 ° C for 2 minutes.
A recording sheet was prepared by heating for a minute to erase the entire surface. A CUVAX-MC50 (a thermal copying machine manufactured by Ricoh Co., Ltd.) was used to copy a newspaper article to this sheet, and a copy was obtained with a black character image. The density of the solid part was measured by a Macbeth densitometer, and 1.68 was obtained, and the non-image part was 0.09. When this recorded sheet was heated in a dryer at 70 ° C. for 1 minute and taken out, the copy character image was erased. Further, when this operation was repeated 5 times, it was possible to obtain a rewritable recording medium that reversibly reproduced copying and erasing.

Example 4 i. Reversible thermochromic composition: each of the following compounds in Example 3
A reversible thermochromic composition was obtained by the same treatment as described above. 2- (N-methyl-N-o-chloroanilino) -3-methyl-6-dibutylaminofluorane 1.0 part n-octadecanoxymethylphosphonic acid (mp67-68 ° C) 2.5 parts Vinyl chloride-acetic acid Vinyl copolymer powder (VYHH, Union Carbide Co., Ltd.) 7.0 parts ii. Reversible thermosensitive recording medium: The following composition was heated and dissolved to obtain a reversible thermosensitive recording layer forming liquid. Reversible thermochromic composition 1.0 part Tetrahydrofuran / tetrahydropyran (weight ratio 1: 1 mixture solution) 3.8 parts This solution was spread on the white synthetic paper used in Example 2 with a wire bar to about 10 μm. And apply at 40 ℃ for 1
A recording sheet was prepared by drying for 5 minutes.

Next, when the recording sheet thus obtained was used to print out a word processor, a dark green character image was recorded. When this recorded sheet was put in a dryer at 55 ° C., the character image immediately disappeared. Then, the print recording and the record erasing could be reproduced many times.

Example 5 i. Reversible thermochromic composition: The following composition was treated in the same manner as in Example 3 to obtain a reversible thermochromic composition. 3-chloro-6-cyclohexylaminofluorane 1.0 part α-aminoheptadecylphosphonic acid (mp 250 ° C.) 2.5 parts stearic acid amide (mp 109 ° C.) 1.7 parts ii. Reversible thermosensitive recording medium: The following composition was dissolved by heating to obtain a thermosensitive recording layer forming liquid. The above reversible thermochromic composition 1.5 parts Polystyrene (MW280,000, Aldrich reagent) 2.5 parts Tetrahydrofuran / tetrahydropyran (weight ratio 1: 1 mixture) 6.0 parts This liquid was mixed with 100 μm thick transparent PET. 130 ° C after coating on the film with a wire bar to a film thickness of about 10 μm
The sheet which had been dried in a drier of No. 1 and which had developed an orange color on the entire surface was subsequently heated in a drier at 85 ° C. for 5 minutes to be entirely decolored to produce a reversible thermosensitive recording sheet. This sheet was able to reversibly reproduce the orange color development and the color erasing even after repeating the color development heating and the color erasing heating 20 times in the dryer.

[0037]

As described above, the color developer of the present invention is a new type which has not been known so far, has excellent reaction stability, and when it is combined with a color forming agent to form a thermosensitive color forming layer. Can be used as a solution-type coating liquid. When the developer of the present invention is used, a heat-sensitive recording material having excellent storage stability and suitable for high speed recording can be obtained. The image obtained by the recording material of the present invention is
It is clear and has excellent weather resistance, oil resistance and alcohol resistance, and has good long-term storage stability.

The color developer according to claim 1 can be easily colored and decolored only by heating, the coloring state and the decoloring state can be maintained at room temperature, and the decoloring temperature is higher than the coloring temperature. Therefore, it is a developer capable of forming a reversible thermochromic composition capable of repeatedly performing color development and color erasure by changing temperature. The reversible thermochromic composition of claims 2 and 3 is a composition comprising the developer and a color former,
Coloring and decoloring can be easily performed only by heating, and the decoloring state and decoloring state can be maintained at room temperature, and the decoloring temperature is lower than the coloring temperature. It is a reversible thermochromic composition that can be repeated many times.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between color density and temperature of a reversible thermosensitive recording medium of the present invention.

FIG. 2 is an explanatory diagram of an image forming process and an image erasing process of the reversible thermosensitive recording medium of the present invention.

[Explanation of symbols]

 1 Support 2 Reversible Thermal Recording Layer 3 Colored Image 4 Thermal Head 5 Heating Roller

Claims (13)

[Claims] 1. An electron-accepting developer represented by the following general formula I: General formula _{I C n H 2n + 1 -X} -PO (OH) 2 ( wherein, X is _{-OCH 2 -, - SCH 2 -} , - CH (NH
_{2) -, - CH (COOH} ) -, - CONHCH 2 -, -
C ₆ H ₄ - represents, n is an integer of 6 to 23) 2. A thermochromic composition comprising at least one of the compounds according to claim 1 and an electron-donating color-forming compound. 3. A reversible thermochromic composition comprising at least one compound of n = 12 or more according to claim 1 and an electron donative color developing compound. 4. The reversible thermochromic composition according to claim 2, which contains a eutectic agent. 5. The thermochromic composition according to claim 2, further comprising a binder resin. 6. A polyurethane resin as a binder resin,
A reversible thermochromic composition comprising one or more of a polystyrene resin, a polyacrylic resin and a vinyl chloride-vinyl acetate copolymer resin. 7. A heat-sensitive recording medium comprising a support and a recording layer containing the composition according to any one of claims 2 to 6. 8. A reversible thermosensitive recording medium having a recording layer containing the composition according to claim 3 or 5 on a support. 9. The thermal recording medium according to claim 7, wherein a protective layer is provided on the recording layer. 10. The heat-sensitive recording medium according to claim 7, which has a recording layer on a transparent support and a resin thin film layer on the recording layer, and is transparent as a whole. 11. A heat-sensitive recording method comprising the step of heating the compound according to claim 1 and an electron-donating color-forming compound. 12. The method according to claim 7, wherein after the recording layer is provided, a decoloring state is brought about by heating to a coloring state and subsequent heating to a temperature lower than the coloring temperature. Manufacturing method of reversible thermosensitive recording medium. 13. A recording step of heating the reversible thermosensitive recording medium according to claim 7 to a coloring state, and an erasing step of heating means to a temperature lower than the coloring temperature, if necessary. A reversible thermosensitive recording method comprising: