JPH0740664A - Electron-accepting developer, reversible thermochromic composition using the same, recording medium containing the composition, and reversible thermosensitive recording method using the recording medium - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] A color developer that can easily perform color development and decolorization only by heating, and can repeat image formation and erasure many times by temperature change, Also provided are a reversible thermochromic composition containing the developer, a recording medium having the composition in a recording layer, and a method for forming and erasing a record using the recording medium. [Structure] An electron-accepting developer represented by the general formula (1). (In the formula, R represents an aliphatic group having 12 or more carbon atoms, and n is 1
Or 2), a reversible thermochromic composition comprising a developer and a color former, and a recording layer containing the composition provided on a support. A color recording step comprising heating to a temperature above the melting temperature of the reversible thermochromic composition, and recording erasing comprising heating the reversible thermochromic composition in the colored state to a temperature below its melting temperature. A reversible thermosensitive recording method comprising the steps of:

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a reversible thermochromic composition utilizing a color reaction between an electron-donating color developing compound and an electron-accepting developer, and a reversible thermosensitive composition using the composition. The present invention relates to a recording medium.

[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 and is widely applied to the output of electronic calculators, facsimiles, automatic ticket vending machines, printers of scientific measuring machines, printers for CRT medical measurement, and the like. 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 a reversible color developing and decoloring method. For example, a combination of a color developer with gallic acid and phloroglucinol is used. No. 193691, JP-A-61-237684 in which a compound such as phenolphthalein or thymolphthalein is used as a developer, and a recording layer contains a homogeneous compatible solution of a color former, a developer and a carboxylic acid ester. JP-A-62-138556 and JP-A-62-13
No. 8568 and JP-A No. 62-140881.
JP-A-2-188294 which uses a salt of gallic acid and a higher aliphatic amine as a developer, and JP-A-2-188294 which uses a salt of bis (hydroxyphenyl) acetic acid or butyric acid and a higher aliphatic amine as a developer. Japanese Patent No. 188293 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. Colors can be easily heated 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. A first object is to provide a developer capable of forming a reversible thermochromic composition that can be repeated many times. 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]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, an electron-accepting developer represented by the following general formula (1) is provided.

[Chemical 1] (In the formula, R represents an aliphatic group having 12 or more carbon atoms, and n is 1
Or 2) Further, according to the present invention, a reversible thermochromic composition containing the developer and the color former and a reversible thermosensitive recording medium containing the composition in a recording layer are 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 can be used as a developer by the following general formula (1).
A monohydric or dihydric phenol having a long chain aliphatic group represented by is used. In addition, according to the results of extensive investigations conducted by the present inventors, there is no example in which the phenol represented by the general formula (1) is used as a developer for a reversible thermochromic composition.

[Chemical 1] In the general formula (1), R represents an aliphatic group having 12 or more carbon atoms, and n represents an integer of 1 or 2, and the aliphatic group represented by R is a linear or branched alkyl group. Groups and alkenyl groups are included and may have a substituent such as a halogen atom, an alkoxy group and an ester group.

Specific examples of the developer of the present invention include the following compounds, but the present invention is not limited thereto. 1-hydroxy-3-pentadecylbenzene, 5-tridecyl-1,3-benzenediol, 3-pentadecyl-1,2-benzenediol, 5-pentadecyl-1,
3-benzenediol, 2-hexadecyl-1,4-benzenediol, 3-heptadecyl-1,2-benzenediol, 4-heptadecyl-1,2-benzenediol, 2-octadecyl-1,3-benzenediol, 5
-Nonadecyl-1,3-benzenediol, 5-heneicosyl-1,3-benzenediol and the like.

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 broken line 3 represents the image erasing process by heating. A is the density in the completely erased state, B is the density in the saturated coloring state when heated to a temperature of T ₁ or higher, C is the density 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 process of forming 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 cooling, some bleaching occurs when passing through the erasing temperature range, 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 former composition can be decolored by heating its color development 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, which is the reversible thermochromic composition. 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, the reversible decoloring / coloring behavior should be maintained even if a polymer compound or a decoloring accelerator is present. You can

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 used in the present invention include compounds represented by the following general formula (2) or (3).

[Chemical 2]

[0015]

[Chemical 3] However, R ₁ is hydrogen or an alkyl group having 1 to 4 carbon atoms, R ₂
Represents an alkyl group having 1 to 6 carbon atoms, a cyclohexyl group or 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 is hydrogen,
It represents a methyl group, a halogen or an amino group which may be substituted. The substituent for the amino group is an alkyl group, an optionally substituted aryl group, an aralkyl group, or the like,
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- (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-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) ) Fluoran, 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-Chloranilino) -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) 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) Fluoran,

2-amino-6- (N-methylanilino)
Fluoran, 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-chloroanilino) fluorane, 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) 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- (N-n-
Palmitylamino) fluorane, 2- (p-chloroanilino) -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-trifluoromethylani) Reno) -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-pyrrolidino Fluoran, 2-
(Α-Naphtylamino) -3,4-benzo-4′-bromo-6- (N-benzyl-N-cyclohexylamino)
Fluoran, 2-piperidino-6-diethylaminofluorane, 2- (Nn-propyl-p-trifluoromethylanilino) -6-morpholinofluorane, 2- (di-Np-chlorophenyl-methyl) Amino) -6-pyrrolidinofluorane, 2- (Nn-propyl-m-trifluoromethylanilino) -6-morpholinofluorane, 1,2-benzo-6- (N-ethyl-N- n-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-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-benzoindolino-spiropyran, etc.

In the reversible thermochromic composition of the present invention, it is necessary that the ratio of the color-developing agent to the color-developing agent is adjusted to an appropriate ratio 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. The reversible thermosensitive recording medium of the present invention is one in which a recording layer containing the above-mentioned composition is provided on a support, and the basic constitution of the recording medium is that the lowermost layer is provided with a support, and the recording layer is provided thereon. The protective layer and the protective layer are sequentially laminated, but an undercoat layer is provided between the support and the recording layer to prevent the developer of the recording layer from penetrating into the support. It is more preferable that an intermediate layer for the purpose of improving adhesiveness be present. 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. Usually, the coloring agent and the color developer are sufficiently well dispersed 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 a dispersant and a surfactant, which are used in ordinary thermosensitive recording paper, are used for the purpose of improving coating properties or recording properties, if necessary.
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 color developer together with a binder resin are uniformly dispersed or dissolved in water or an organic solvent, and this is coated on a support and dried. The thickness is 0.5 to 50 μm, 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 a binder resin include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylic. Acid esters,
Polymethacrylic acid esters, acrylic acid copolymers, maleic acid copolymers, polyvinyl alcohol, chlorinated vinyl chloride resins, mixtures of the above 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. The protective layer, polyvinyl alcohol,
Styrene-maleic anhydride copolymer, diisobutylene-
Conventionally known resins such as maleic anhydride copolymer, carboxy-modified polyethylene, melamine-formaldehyde resin and urea-formaldehyde resin are 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, tetrahydrofuran,
Organic solvents such as methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, toluene and benzene are 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, preferably 0. The range is preferably 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 formed by coating fine hollow particles of an organic or inorganic material on a support, specifically, fine hollow particles having a particle size of 10 to 50 μm formed of glass, ceramics, plastic, or the like. The body may be well dispersed in a solvent together with a binder resin, and uniformly applied and dried on the support. A heat insulating support may be used instead of the heat insulating undercoat layer to improve the heat insulating property. In addition to the above, the undercoat layer prevents the color developer in the recording layer from penetrating into the support, so that the color erasing caused by the color developer being adsorbed by the cellulose or pigment of the support during the color erasing Defects are prevented, and 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 0.1-5.
The thickness is 0 μm, preferably 0.2 to 20 μm.

The intermediate layer is provided for various purposes such as improving the adhesiveness between the recording layer and the protective layer and preventing the coloring 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 the recorded image is not particularly limited as long as temperature conditions for coloring and erasing are given, and a thermal head, laser heating, a hot pen or the like is used for image formation, and a heating is used for image erasing. Rollers, sheet heating elements, heating lamps and the like 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.

[0033]

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.

Example 1 i: Reversible thermochromic composition: Each of the following compounds was pulverized in a mortar and well mixed to obtain a reversible thermochromic composition. 2- (o-chloroanilino) -6-dibutylaminofluorane 1.0 part 5-nonadecyl-1,3-benzenediol 2.5 parts ii: Reversible thermosensitive recording medium: thermosensitive recording layer by dissolving the following composition This was the forming liquid. Reversible thermochromic composition 1.0 part Vinyl chloride-vinyl acetate copolymer powder (trade name: VYHH: Union Carbide Co., Ltd.) 2.5 parts Tetrahydropyran (tetrahydropyran) (volume ratio 2: 1 mixture) ) 10.0 parts Toluene 0.5 parts This solution was applied onto a 100 μm thick polyester film with a wire bar to a film thickness of about 10 μm, and then 6 parts
A reversible thermosensitive recording sheet was prepared by drying at 5 to 75 ° C. Then, a newspaper article was copied onto the reversible thermosensitive recording sheet thus obtained using a CUVAX-MC-50 (a thermal copying machine manufactured by Ricoh Co., Ltd.), and a copy was obtained with a black character image. The solid image density of the copy was 1.16 as measured by a Macbeth densitometer. This copy could be viewed as a projected image on an OHP (overhead projector). When this recording sheet was heated and held for 2 minutes in a constant temperature bath at 65 to 75 ° C., almost all of the character image disappeared. Furthermore, when this operation was repeated, copying and erasing could be reversibly reproduced.

Example 2 i: Reversible thermochromic composition: Each of the following compounds was treated in the same manner as in Example 1 to obtain a reversible thermochromic composition. 2- (N-methyl-N-o-chloroanilino) -3-methyl-6-dibutylaminofluorane 1.0 part 4-heptadecyl-1,2-benzenediol 2.5 parts ii: Reversible thermosensitive recording medium: A reversible thermosensitive recording sheet was prepared by using the following composition and treating in the same manner as in Example 1. The reversible thermochromic composition 1.0 part Polyvinyl butyral (trade name: S-Rex BX-1, manufactured by Sekisui Chemical Co., Ltd.) 2.3 parts Tetrahydrofuran / tetrahydropyran (mixed solution with a weight ratio of 1: 1) 15.0 Part Then, the recording sheet thus obtained was used to print out a word processor to obtain a green character image. This was visible on OHP as a projected image of the same color. When the recorded sheet was heated on a hot plate at 65 to 70 ° C, the image disappeared promptly. Then, the printing and the erasing of the record could be repeatedly reproduced many times.

Example 3 i: Reversible thermochromic composition: The following compositions [A] and [B] were milled separately in a glass ball mill for 30 hours. [A]: Crystal violet lactone 1.0 part 10% aqueous solution of polyvinyl alcohol 1.0 part water 3.0 parts [B]: 2-octadecyl-1,4-benzenediol 1.0 part 10% aqueous solution of polyvinyl alcohol 2.0 parts Water 3.0 parts [A] 1.0 parts and [B] 3.0 parts were mixed to prepare a thermochromic composition solution. ii: Reversible thermosensitive recording medium: white synthetic paper (trade name: VI
F-92: made by Oji Yuka Co., Ltd., 92 μm thick) was coated with the above-mentioned thermochromic composition solution with a wire bar and dried at about 60 ° C. to prepare a reversible thermosensitive recording sheet. When this recording sheet was used as a recording sheet of RIFAX-600 (GIII FAX machine manufactured by Ricoh Co., Ltd.) and a received image was obtained, a clear blue image was recorded against a white background. When this recorded sheet was passed between heating rollers at about 80 ° C., the blue image disappeared.
This printing and erasing could be repeated many times.

[0037]

EFFECTS OF THE INVENTION The color developer according to claim 1 can be easily colored and decolored only by heating, and the coloring and decoloring states can be maintained at room temperature and the decoloring temperature can be developed. It is a developer capable of forming a reversible thermochromic composition which is lower than the temperature and therefore can repeatedly perform color development and decolorization by changing the temperature. The reversible thermochromic composition according to claim 2 is a composition comprising the color developer and the color developer, and the color development and the color erasure can be easily performed only by heating. It is a reversible thermochromic composition that can be retained at room temperature and has a decolorization temperature lower than the color development temperature, and for that reason color development and decolorization can be repeated many times by temperature changes.

The reversible thermosensitive recording medium or display medium according to claim 3 is a recording medium or a display medium having a recording layer containing the reversible thermochromic composition on a support, and recording and erasing can be performed. It is a reversible thermosensitive recording medium or display medium that can be repeated many times according to temperature changes and can stably maintain a recorded state and a recorded erased state at room temperature. Claim 4
The reversible thermosensitive recording method is a recording method for the reversible thermochromic composition or the reversible thermosensitive recording medium and the display medium, and the reversible thermosensitive recording medium contained in the composition or the recording medium. In this method, heat is applied at a temperature equal to or higher than the melting temperature of the color forming composition to form a color recorded state, and heating to a temperature lower than the melting temperature forms a recorded erased state.

[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 Thermosensitive Recording Layer 3 Colored Image 4 Thermal Head 5 Heating Roller

Claims (4)

[Claims] 1. An electron-accepting developer represented by the following general formula (1). [Chemical 1] (In the formula, R represents an aliphatic group having 12 or more carbon atoms, and n is 1
Or 2) 2. A reversible thermochromic composition comprising the compound according to claim 1 and an electron-donating color-developing compound. 3. A reversible thermosensitive recording medium and a display medium, wherein a recording layer containing the reversible thermochromic composition of claim 2 is provided on a support. 4. The reversible thermochromic composition according to claim 2 or the reversible thermosensitive recording medium and display medium according to claim 3 at a temperature not lower than the melting temperature of the reversible thermochromic composition contained therein. A reversible recording step comprising heating the reversible thermochromic composition in a colored state to a temperature lower than its melting temperature. Thermal recording method.