JPH0971055A - Erasable thermal record medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve recording and erasing speeds and heat stability of record by forming a developer out of a polycyclic structure selected from a non- condensation polycyclic structure of a specified structure and a condensation polycyclic structure and forming molecular skeletons, in which specified substituents are led, in cyclic structures at both ends of the polycyclic structure. SOLUTION: As a liquid crystal compound to be used as a developer, a plurality of cyclic structures have molecular skeletons wherein substituents are led into cyclic structures at both ends of a non-condensation polycyclic structure or a condensation polycyclic structure bonded through any bond out of single bond, vinylene bond, and ethynylene bond. Further, at least one of the substituents is made to be an organic group having a hydrocarbon chain. The developer is made to have an acid group when it is used corresponding to an electron donating coloring compound and is made to have a basic group when the developer is used corresponding to an electron accepting coloring compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable thermal recording medium.

[0002]

2. Description of the Related Art In recent years, the amount of various types of information has increased remarkably as office automation has increased, and the number of opportunities for outputting information has increased as the amount of information has increased. Generally, the output of information includes hard copy output on paper by a printer and display output. However, hard copy output will use a large amount of paper as a recording medium as the amount of information increases, and thus will become a problem from the viewpoint of resource protection in the future. Further, the display output requires a large-scale circuit board for the display unit, which is problematic from the viewpoint of portability and cost. Therefore, a rewritable recording medium without these problems is expected as the third recording medium.

Conventionally, a recording material for such a rewritable recording medium contains a color-developing compound such as a leuco dye and a color developer such as various acids, and develops and decolors depending on the interaction between them. The composition has been widely studied. For example, JP-A-4-50290 contains a leuco dye, an acid as a color developer, and a long-chain amine as a decoloring agent, and it is possible to repeat coloring and decoloring chemically by supplying heat energy. Recording materials are disclosed. In the 42nd Polymer Symposium Proceedings, 1993, p. 2736, a composition system in which a leuco dye and a long-chain phosphonic acid are mixed is reversible by controlling the thermal energy supplied and changing the crystal form. It has been reported that coloring and decoloring occur in the. Further Ja
pan Hardcopy '93 p. 413-41
No. 6 contains a leuco dye having high amorphousness and a long-chain 4-hydroxyanilide compound having high crystallinity, and the thermal energy is controlled to reversibly drive the crystalline-amorphous transition of the entire composition system. Recording materials capable of producing coloring and decoloring are shown.

However, these recording materials are
There is a problem that the activation energy required for repeating erasing is very large and it is generally difficult to increase the recording / erasing speed. For example, when reversible color development / decolorization is repeated based on the crystalline-amorphous transition of a composition system containing a color developable compound and a color developing agent, a metastable non-equilibrium state, amorphous to stable Since it usually takes a long time to change the state of the system to a crystalline state, which is in an equilibrium state, it is not easy to increase the recording / erasing speed. On the other hand, merely preparing a composition system in which the state change from amorphous to crystalline is carried out quickly makes it difficult for this composition system to form a long-lifetime amorphous. That is, when an attempt is made to increase the recording / erasing speed for a recording material of a composition type containing a conventional color developable compound and a color developing agent, a state corresponding to a metastable non-equilibrium state among the colored / decolored states is found. There is a problem that the thermal stability of the recording is deteriorated such that the recording becomes unstable and the state changes gradually from the non-equilibrium state to the equilibrium state even if the heat energy is not supplied from the outside.

[0005]

As described above, various types of rewritable heat-sensitive recording media have been studied, which use a composition system containing a color developable compound and a color developer as a recording material.
However, in the conventional thermal recording medium, the increase in recording / erasing speed and the improvement in thermal stability of recording are in a mutually contradictory relationship, and it is difficult to satisfy these requirements at the same time, so that they have not yet been put to practical use. .

An object of the present invention is to solve the above problems and to provide a rewritable thermosensitive recording medium having a high recording / erasing speed and having sufficient thermal stability of recording.

[0007]

The present invention is a rewritable thermosensitive recording medium comprising a recording material containing a composition system containing at least a color-developing compound and a developer, wherein the developer is composed of a plurality of rings. One kind of polycyclic structure selected from a non-condensed polycyclic structure and a condensed polycyclic structure whose structures are bonded via a single bond, a vinylene bond, or an ethynylene bond, and ring structures at both ends of this polycyclic structure A rewritable heat-sensitive recording medium having a molecular skeleton having a substituent introduced into each of the above and at least one of the substituents is an organic group having a hydrocarbon chain. The developer is preferably a compound capable of forming a liquid crystal phase.

The present invention also provides at least a color-forming compound,
A rewritable thermal recording medium comprising a recording material of a composition system containing a color developer and a matrix agent, wherein the matrix agent is a compound capable of forming a liquid crystal phase. .

Furthermore, the present invention is a reversible phase separation state of a composition system containing at least a color-developing compound, a color developer, a phase separation control agent having an effect of increasing the phase separation rate, and optionally a matrix agent. Is a rewritable heat-sensitive recording medium in which information is recorded / erased based on the change of the above, and the phase separation controlling agent is a compound capable of forming a liquid crystal phase.

That is, the basic principle of the present invention is to control the magnitude of the interaction between the color-developing compound and the color-developing agent by the reversible crystalline-amorphous transition or change in phase separation state of the system. The rewritable heat-sensitive recording medium is based on the use of a compound capable of forming a liquid crystal phase as a developer, a matrix agent or a phase separation control agent.

[0011]

First, the basic principle of the rewritable thermal recording medium of the present invention will be described.

Generally, the color-developing compound is a compound corresponding to a precursor of a dye showing a colored state, and the color-developing agent is a color-developing compound which exchanges electrons and protons with the color-developing compound. Is a compound that develops a color. In the composition system containing the color developing compound and the color developing agent, the coloring state changes depending on the magnitude of the interaction between the color developing compound and the color developing agent. For example, when the interaction between the color-developing compound and the color-developing agent increases, the color-developing state is established, and when the interaction between the color-developing compound and the color-developing agent decreases, the color-erasing state occurs. The rewritable heat-sensitive recording medium of the present invention has a crystallographic or thermodynamic state change of a composition system containing at least a color-developing compound and a developer, specifically, a reversible crystalline-amorphous transition. Or based on the change in phase separation state,
Information is recorded / erased by controlling the interaction between the color developable compound and the color developer.

Here, referring to the thermal characteristic diagram shown in FIG.
The crystalline-amorphous transition of the composition system will be described. This composition system forms a metastable amorphous at room temperature. If this composition system is heated from an amorphous state to a temperature not lower than the crystallization temperature Tc and lower than the melting point Tm and then cooled, the system has a glass transition temperature T.
It forms stable crystals at temperatures below g. When this composition system is heated from a crystalline material to a melting point Tm or higher to be melted and then rapidly cooled or naturally cooled to a room temperature below a glass transition temperature Tg, the system returns to an amorphous state. That is, in the composition system having the thermal characteristics shown in FIG. 1, two kinds of thermal energy of different sizes capable of heating the composition system to a temperature not lower than the crystallization temperature Tc and lower than the melting point Tm and not lower than the melting point Tm. When supplied, the crystalline-amorphous transition can be reversibly repeated.

For example, in a composition system containing a color-developing compound and a color-developing agent, in the amorphous state, the color-developing compound and the color-developing agent are uniformly mixed, the interaction between the two increases, and color develops to form a crystal. In terms of quality, the color-developing compound and the color-developing agent are phase-separated, the interaction between the two is reduced, and the color disappears.

In the present invention, a composition system in which, in addition to the color developable compound and the color developer, a matrix agent is further mixed may be used as a recording material. The matrix agent in the present invention is a compound having a property of affecting a reversible change in the state of the composition system. Specifically, the composition system containing the color-developing compound, the developer and the matrix agent is more preferable than the composition system containing only the color-developing compound and the developer without the matrix agent. Reversible changes are likely to occur. The matrix agent preferably has a property of preferentially dissolving the color developer (or the color developing compound). Due to such a property of the matrix agent, it is possible to easily change the interaction between the color-developing compound and the color-developing agent, which causes coloration and decolorization.

In a composition system containing a color-developing compound, a color developer and a matrix agent, the recording / erasing mode is often reverse to that in the composition system containing no matrix agent. That is, in the amorphous state, the color-developing compound and the color-developing agent are uniformly present in the matrix agent, so that the interaction between the two decreases and the color disappears. On the other hand, in the crystalline state, the color-developing compound and the color-developing agent segregate at the grain boundaries of the crystallized matrix agent, so that the interaction between the two increases and color develops. On the other hand, although not generally, in the crystalline state, one of the color-developing compound and the color-developing agent forms a mixed crystal with the matrix agent, and the phase-separation from the other of the color-developing compound and the color-developing agent is almost complete. In some cases, the interaction between the color-developing compound and the color-developing agent is reduced, resulting in a decolored state.

As described above, binary thermal energy is supplied to a composition system containing a color-developing compound, a color developer and, if necessary, a matrix agent, and each composition system has a crystallization temperature Tc or higher and a melting point Tm. By heating below the temperature and above the melting point Tm, information can be recorded / erased based on the crystalline-amorphous transition of the system. In this case, the crystalline state corresponds to a stable equilibrium state, and the amorphous state corresponds to a metastable non-equilibrium state.

Here, whether the composition system is crystalline or amorphous is analyzed by appropriately using a general method such as X-ray diffraction, electron diffraction or light transmission measurement, if necessary. You can For example, according to X-ray diffraction and electron beam diffraction, sharp peaks and spots are observed when the composition system is crystalline, but sharp peaks and spots are not observed when the composition system is amorphous. On the other hand, it is possible to evaluate the light scattering of the composition system by the light transmission measurement, and in the case of a polycrystalline material, the shorter the light wavelength is, the more strongly scattered and the light transmittance is reduced. The wavelength dependence can be distinguished from the decrease in light transmission due to absorption, and the crystal grain size can also be estimated.

In the heat-sensitive recording medium of the present invention, the crystalline-amorphous transition may be repeated in whole or part of the composition system when recording / erasing information. In addition, each of the components included in the composition system may individually form a crystal, or a plurality of components may integrally form a crystal. In such a case, whether the repeated crystalline-amorphous transition is the whole or a part of the composition system can be detected by the same measurement as above. The patterns of peaks and spots of X-ray diffraction and electron diffraction are peculiar to each component in the composition system. Therefore, by analyzing the obtained pattern, crystalline-amorphous in the composition system It is also possible to identify components that repeat the transition.

Next, referring to FIG. 2, the state change of the composition system in the case where information is recorded and erased based on the change of the phase separation state of the composition system consisting of the color developing compound and the color developing agent. Will be explained. In the figure, A and B respectively represent a color-developing compound and a color developing agent, ":" represents an interaction between these components, and "*" represents that the components are in a fluid state. Also,
In this figure, the process of state change of the system is shown by a straight line,
The solid, dashed and dotted lines represent that the system is a solid phase, a supercooled liquid phase and a liquid phase, respectively.

In this composition system, the state in which the phase of the color developing compound A and the phase of the color developing agent B are phase separated is an equilibrium state at room temperature,
At this time, the interaction between the color developing compound A and the color developing agent B is small. When this composition system is heated from its equilibrium state to its melting point Tm or higher to be melted, the fluidized color-forming compound A and developer B
There is a large interaction between and. When the composition system is cooled from this state to room temperature, preferably rapidly cooled, the system is forcibly fixed while a large interaction between the color-developing compound A and the developer B occurs, and becomes a metastable non-equilibrium state. . Such a non-equilibrium state has a long life below the glass transition temperature Tg of the system. Therefore, if the glass transition temperature Tg of the system is room temperature or higher, the non-equilibrium state is maintained for a sufficiently long period.

Next, when the composition system in the non-equilibrium state is heated above the glass transition temperature Tg, the diffusion rate of the color-developing compound A and the developer B rapidly increases, and the system is in the most stable equilibrium state. Phase separation between the color-forming compound A and the developer B is promoted. The heating temperature at this time is preferably set appropriately in consideration of the diffusion rate of the components, the heat source used, and the like, but in general, it may be higher than the crystallization temperature Tc of the composition system and lower than the melting point Tm. In this way, when the color-developing compound A and the color-developing agent B are sufficiently phase-separated and then cooled to room temperature, the system returns to an equilibrium state in which the interaction between the color-developing compound A and the color-developing agent B is small. .

Further, referring to FIG. 3, the color-forming compound A,
The state change of the composition system in the case where information is recorded / erased based on the change of the phase separation state of the composition system including the color developer B and the matrix agent C will be described. In this figure, the matrix agent C is used in the molten state of the composition system.
It is assumed that the solubility of the color developer B with respect to is extremely high as compared with the solubility of the color developable compound A.

In this composition system, the state in which the phases of the color-developing compound A and the developer B and the phase of the matrix agent C are phase-separated is an equilibrium state at room temperature. At this time, a large interaction occurs between the color developable compound A and the color developer B to develop a color. When the composition system is heated from the equilibrium state to the melting point Tm or higher to be melted, the developer B is dissolved in the matrix agent C, but the color developable compound A is not so dissolved. When the composition system is cooled from this state to room temperature, preferably rapidly cooled and forcibly fixed, the developer B exceeds the equilibrium solubility and is incorporated into the matrix agent C. As a result, the color developing compound A and the color developing agent B
It becomes a metastable nonequilibrium state in which the interaction with and is substantially lost, and the color disappears. Such a non-equilibrium state has a long life at a temperature below the glass transition temperature Tg of the system. Therefore, if the glass transition temperature Tg of the system is room temperature or higher, the non-equilibrium state is maintained for a sufficiently long time.

Next, when the composition system in the non-equilibrium state is heated above the glass transition temperature Tg, the diffusion rate of the developer B taken into the matrix agent C rapidly increases, and the system is most stable. Phase separation between the developer B and the matrix agent C is promoted in an attempt to return to the equilibrium state. The heating temperature at this time is preferably set appropriately in consideration of the solubility of the developer B in the matrix agent C, the heat source used, and the like, but in general, the crystallization temperature Tc of the composition system or higher and the melting point T are used.
It may be less than m. Thus, after the developer B and the matrix agent C are sufficiently phase-separated, if they are cooled to room temperature,
The system returns to equilibrium. As a result, a large interaction occurs again between the color developable compound A and the color developing agent B to develop a color. In the present invention, when the composition system is heated to its melting point Tm or higher and melted, the solubility of the color developing compound in the matrix agent is higher than the solubility of the color developing agent, and the color developing compound is cooled to room temperature. May exceed the equilibrium solubility and be incorporated into the matrix agent.

Further, in the rewritable thermosensitive recording medium of the present invention, when information is recorded / erased based on the change of the phase separation state of the composition system, a phase separation control agent for further increasing the phase separation rate of the composition system is blended. Is effective. Such a phase separation controlling agent has a melting point lower than that of a composition comprising a color-developing compound and a developer or a composition comprising a color-developing compound, a developer and a matrix agent, and the melting point or less It is preferable to use a compound capable of dissolving at least one of the color developable compound and the color developer. Here, the case where the phase separation controlling agent is further added to the composition system shown in FIG.

FIG. 4 shows changes in the system state when information is recorded / erased based on changes in the phase separation state of a composition system containing a color developable compound, a color developer, a matrix agent and a phase separation control agent. FIG. 3 is a characteristic diagram showing that, D in the figure is a phase separation control agent. In this composition system, the equilibrium state at room temperature is the state in which the phases of the color developable compound A and the color developing agent B, the phase of the matrix agent C and the phase of the phase separation controlling agent D are phase separated. At this time, a large interaction occurs between the color developable compound A and the color developer B to develop a color. A composition system in equilibrium has its melting point T
When heated to m or more to be melted, the color developer B is dissolved in the matrix agent C, but the color developable compound A is not so dissolved. From this state, when the composition system is cooled to room temperature and forcibly fixed, the developer B exceeds the equilibrium solubility and is incorporated into the matrix agent C. As a result, the color-forming compound A
And the developer B are substantially lost, resulting in a metastable non-equilibrium state and decoloring. In particular, the composition of the phase separation controlling agent D becomes supercoolable, and the compatible material of the matrix agent C and the phase separation controlling agent D maintains the fluidity even at the melting point Tm or lower, so that even if slowly cooled. The system can be in a metastable non-equilibrium state. Such a non-equilibrium state has a long life at a temperature below the glass transition temperature Tg of the system. Therefore, if the glass transition temperature Tg of the system is room temperature or higher, the non-equilibrium state can be maintained for a sufficiently long time.

Next, when the composition system in the non-equilibrium state is heated above the glass transition temperature Tg, the diffusion speed of the developer B rapidly increases, and the system tries to return to the most stable equilibrium state. The phase separation between the colorant B and the matrix agent C is promoted. Further, when the melting point TmD of the phase separation controlling agent D is exceeded, the liquefied phase separation controlling agent D dissolves the color developing agent B and a part of the matrix agent C, so that the diffusion speed of the color developing agent B increases dramatically. Thus, the phase separation between the color developer B and the matrix agent C is significantly promoted. When the developer B and the matrix agent C are sufficiently phase-separated in this way and then cooled to room temperature, the system returns to an equilibrium state. As a result, a large interaction occurs again between the color developable compound A and the color developing agent B to develop a color.

Thus, in the composition system containing the color-developing compound, the color developer, the matrix agent and the phase separation controlling agent, for example, the color developing agent B and the matrix agent C are mixed by adding the phase separation controlling agent. And the phase separation rate with 2 to 4 digits near the glass transition temperature Tg of the system, the melting point TmD of the phase separation control agent D
It is further increased by 3 to 4 digits in the vicinity.

Further, when a phase separation controlling agent is added to the composition system consisting of the color developable compound and the color developer shown in FIG.
Similarly to the above, the phase separation rate between the color-developing compound and the color developer can be increased.

As described above, in the rewritable thermosensitive recording medium of the present invention, binary thermal energies of different magnitudes are appropriately supplied to reversibly repeat the state change between two phase-separated states. Consequently, information can be recorded / erased by changing the magnitude of the interaction between the color developable compound and the color developing agent. Changes in the phase separation state of the above composition system,
This can be explained as a phenomenon generally known as spinodal decomposition or microphase separation.

In the present invention, the state change that occurs when thermal energy is supplied to the composition system is either a crystalline-amorphous transition or a change in the phase separation state. It depends not only on the types of the color developer and the matrix agent and their combinations, but also on the compounding ratio of these components. It should be noted that the type of state change of the composition system is that when the composition system in the metastable non-equilibrium state is heated to the glass transition temperature Tg or higher to cause the state change of the system to the equilibrium state, the system is colored. It can be estimated by obtaining the time dependence of the change in state. Specifically, when the time dependence of the change in the coloring state of the system obtained by measuring the time change of the reflection density or the light transmittance of the system is in accordance with the Arrhenius equation, the thermally activated crystalline- Amorphous transition, Vog
When the formula of el-Fulcher is followed, it is considered that the change of the phase separation state occurs preferentially. However, only one of the crystalline-amorphous transition and the change in the phase separation state of such a system does not always occur alone, but these may sometimes proceed simultaneously.

In the present invention, two kinds of thermal histories having different cooling rates after being heated to the melting point Tm or more are given instead of supplying binary thermal energies of different magnitudes to the composition system, thereby reversible It is also possible to record / erase information based on a typical crystalline-amorphous transition or a change in phase separation state. That is, in the heat-sensitive recording medium of the present invention, when the composition system is heated to the melting point Tm or higher by supplying thermal energy and then rapidly cooled to room temperature, the system may be in a metastable non-equilibrium state, and if slowly cooled, the system may be in an equilibrium state. Therefore,
By appropriately selecting either quenching or gradual cooling during cooling, the crystalline-amorphous transition or the state change between two phase-separated states can be reversibly repeated, and the color-developing compound and the color-developing agent can be separated. The magnitude of the interaction can be changed. Further, in the process of bringing a composition system in a metastable non-equilibrium state into an equilibrium state, stress may be applied instead of supplying thermal energy to the system.

Next, in the present invention, each component to be added to the composition system of the recording material will be illustrated. First, a color developing compound, a color developing agent, a matrix agent and a phase separation controlling agent which are generally used are generally shown, and a color developing agent, a matrix agent or a phase separation controlling agent capable of forming a liquid crystal phase according to the present invention. Will be described later.

The color-forming compounds that can be used in the present invention include electron-donating organic substances such as leuco auramines, diaryl phthalides, polyaryl carbinols, acyl auramines, aryl auramines and rhodamines. B lactams, indolines, spiropyrans,
Examples thereof include fluorans, cyanine dyes, crystal violet, and electron-accepting organic substances such as phenolphthalein.

Specific examples of the electron-donating organic substance include crystal violet lactone, malachite green lactone, crystal violet carbinol, malachite green carbinol, N- (2,3-dichlorophenyl) leuco auramine, N-benzoyl auramine, rhodamine. B lactam, N-acetyl auramine, N-phenyl auramine, 2- (phenyliminoethanedilidene) -3,3-dimethylindoline, N-3,3-trimethylindolinobenzospiropyran, 8'-methoxy-N -3,3-Trimethylindolinobenzospiropyran, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-6-benzyloxyfluorane, 1,2-benz − 6-diethylaminofluorane,
3,6-di-p-toluidino-4,5-dimethylfluorane-phenylhydrazide-γ-lactam, 3-amino-5-methylfluorane, 2-anilino-6- (N-cyclohexyl-N-methylamino) ) -3-Methylfluorane, 2-anilino-3-methyl-6- (N-methyl-
N-propylamino) fluorane, 3- [4- (4-phenylaminophenyl) aminophenyl] amino-6-
Methyl-7-chlorofluorane, 2-anilino-6-
(N-methyl-N-isobutylamino) -3-methylfluorane, 2-anilino-6- (dibutylamino) -3
-Methylfluorane, 3-chloro-6- (cyclohexylamino) fluorane, 2-chloro-6- (dibutylamino) fluorane, 7- (N, N-dibenzylamino)
-3- (N, N-diethylamino) fluorane, 3,6
Examples thereof include -bis (diethylamino) fluorane-γ- (4'-nitroanilino) lactam and 3-diethylaminobenzo [a] -fluorane. Specific examples of the electron-accepting organic substance include phenolphthalein, tetrabromophenolphthalein, phenanolphthalein ethyl ester, tetrabromophenolphthalein ethyl ester and the like. These can be used alone or in combination of two or more. At this time, since a colored state of various colors can be obtained by appropriately selecting a color-forming compound, multicolor compatibility is possible.

In the present invention, a color-developing compound and a color-developing agent may be used in combination in which the color-developing compound is in a decolored state when the interaction is increased, and is in a color-developed state when the interaction is decreased. For example, among the compounds described above, cyanine dyes and crystal violet may be in a decolored state when the interaction with the developer is increased, and may be in a colored state when the interaction is decreased.

In the present invention, as the color developing agent, when the color developing compound is an electron donating organic substance, phenols, phenol metal salts, carboxylic acid metal salts, sulfonic acids, sulfonates, phosphoric acids, When the phosphoric acid metal salt, acidic phosphoric acid ester, acidic phosphoric acid ester metal salt, phosphorous acid, acidic compound such as phosphorous metal salt, or the color-forming compound is an electron-accepting organic substance, amines, etc. Basic compounds are mentioned. Among these, phenols,
The use of a phenol metal salt is particularly preferable because the coloring density and stability in the coloring state are high, and the coloring and decoloring can be easily repeated. Further, as a color developing agent used in combination with cyanine dyes and crystal violet, a sulfone that forms a decolored state by an increase in interaction with a color-forming compound and a colored state by a decrease in interaction is a sulfone. Examples thereof include acids, sulfonates, phosphoric acids, phosphoric acid metal salts, acidic phosphoric acid esters, acidic phosphoric acid ester metal salts, phosphorous acids, and phosphorous metal salts. These color developers can be used alone or in combination of two or more.

It is desirable that the matrix agent used in the present invention can easily form an amorphous material having good colorlessness. The more amorphous and colorless the matrix agent is, the higher the contrast ratio between the printed portion and the background can be. The matrix agent which requires such properties has a large molecular weight and a small change in melting enthalpy ΔH of the crystal per weight, and therefore the maximum crystal growth rate M.
A compound having a small CV is preferable. Further, if the melting enthalpy change ΔH of the crystal of the matrix agent is small, the amount of heat energy required for melting the crystal is small, which is also preferable from the viewpoint of energy saving. From the above viewpoints, a compound having a bulky molecular skeleton, such as a steroid skeleton, is suitable as the matrix agent.

On the contrary, a low molecular weight compound having a molecular weight of less than 100, or a linear long-chain alkyl derivative or a planar aromatic compound having a molecular weight of 100 or more has a large change in crystal enthalpy ΔH and is amorphous. Is difficult to form,
Not suitable as a matrix agent. However, a compound having a plurality of sites capable of forming hydrogen bonds between molecules has a small molecular weight or has a change in crystal melting enthalpy ΔH.
However, even if it is large to some extent, the substantial molecular weight increases, so that it is easy to form an amorphous substance and it can be applied as a matrix agent. Specifically, a substituent capable of forming a hydrogen bond between molecules, for example, hydroxyl group, primary and secondary amino group, primary and secondary amide bond, urethane bond, urea bond, hydrazone bond, hydrazine group, carboxyl group Examples thereof include compounds having a plurality of the like in the molecule. on the other hand,
Even if it has a plurality of sites capable of forming hydrogen bonds, compounds that form hydrogen bonds in the molecule are not suitable.

From the above viewpoints, a steroidal alcohol (sterol) is preferred as the matrix agent.
Can be used. Specific examples of sterols include:
Cholesterol, stegmasterol, pregnenolone, methylandrostenediol, estradiol benzoate, epiandrostene, stenolone, β-
Sitosterol, pregnenolone acetate, β-cholestanol, 5,16-pregnadien-3β-ol-20-one, 5-α-pregnene-3β-ol-
20-one, 5-pregnene-3β, 17-diol-
20-one 21-acetate, 5-pregnene-3
β, 17-diol-20-one 17-acetate,
5-pregnene-3β, 21-diol-20-one
Examples thereof include 21-acetate, 5-pregnene-3β, 17-diol diacetate, locogenin, tigogenin, esmiragenin, hecogenin, diosgenin and derivatives thereof. These matrix agents can be used alone or in combination of two or more.

In the rewritable thermosensitive recording medium of the present invention,
When recording / erasing is performed based on the reversible crystalline-amorphous transition of the composition system, the matrix agent itself is a component capable of reversibly repeating the crystalline-amorphous transition by supplying binary thermal energy. Preferably there is. However, if the matrix agent is a component capable of reversibly repeating the crystalline-amorphous transition when combined with the color-forming compound and the color-developing agent, the matrix agent does not necessarily reversibly repeat the crystalline-amorphous transition. You don't have to get it. That is, in the present invention, the maximum crystal growth rate MCV and the maximum crystal growth temperature Tc as a composition system are selected by appropriately selecting the color-developing compound and the color developer used in combination with the matrix agent.
You can also adjust max. Moreover, a plurality of compounds that function as a matrix agent only when two or more kinds thereof coexist may be mixed and used.

As described above, the matrix agent in the present invention contains one of the color-developing compound and the color developing agent when melted,
For example, it is preferable to preferentially dissolve the color developer. When the matrix agent preferentially dissolves the color developer, the interaction between the color developing compound and the color developer can be further reduced when the composition system is cooled to be amorphized, and the decoloring concentration Can be reduced. As a result, the contrast ratio between the printing portion and the background can be increased. Further, when the colorless and transparent property in the amorphous state is good, the printing on the underlayer can be used as a background. In order to increase the solubility of the color developer in the matrix agent, it is preferable to use a matrix agent having a high affinity with the color developer. Examples of such a matrix agent include a compound that forms a hydrogen bond with the developer. Specifically, for example, alcohols, thiols, carboxylic acids, carboxylic acid esters, phosphoric acid esters, sulfonic acid esters, ethers, sulfides, disulfides, sulfoxides, sulfones, carbonic acid esters, etc. The compound which has a polar group is mentioned. These can be used alone or in combination of two or more.

The phase-separation controlling agent that is optionally used in the present invention is a crystalline compound having a hydrocarbon group having 8 or more carbon atoms and a polar group such as a hydroxyl group, a carbonyl group, an ester group or a carboxyl group in the molecule. Organic low molecular weight compounds having a high molecular weight are preferable. For example, straight chain higher alcohols, straight chain higher polyhydric alcohols, straight chain higher fatty acids, straight chain higher polyvalent fatty acids, esters and ethers thereof, straight chain higher ketones, straight chain higher fatty acid amides, straight chain higher polyvalent fatty acid amides. Is mentioned. Specifically, linear higher monohydric alcohols such as 1-docosanol, 1-tetracosanol, 1-hexacosanol and 1-octacosanol; 1,12-dodecanediol, 1,14-tetradecanediol, 1,15 −
Pentadecanediol, 1,16-hexadecanediol, 1,17-heptadecanediol, 1,18-octadecanediol, 1,19-nonadecanediol,
1,20-eicosanediol, 1,21-heneicosanediol, 1,22-docosanediol, 1,23
-Linear higher polyhydric alcohols such as tricosane diol, 1,24-tetracosane diol, 1,12-octadecane diol, 1,2-tetradecane diol, 1,2-hexadecane diol; behenic acid, 1-docosanoic acid, 1
-Straight chain higher fatty acids such as tetracosanoic acid, 1-hexacosanoic acid, 1-octacosanoic acid; dodecane diacid, 1,12-
Linear higher polyvalent fatty acids such as dodecanedicarboxylic acid; linear higher ketones such as stearone; linear higher fatty acid alcohol amides such as stearic acid isopropanolamide, behenic acid isopropanolamide, behenic acid hexanolamide; ethylene glycol lauric acid diester, Examples include linear higher fatty acid diol diesters such as catechol lauric acid diester and cyclohexanediol lauric acid diester. These can be used alone or in combination of two or more. Also, among ester waxes, alcohol waxes, and urethane waxes, there are some that can be used as a phase separation control agent.

It is preferable that the phase separation controlling agent as described above itself exhibits supercooling property from the viewpoint of increasing the recording / erasing speed. That is, the phase separation controlling agent preferably has a difference between the melting point and the freezing point of 10 ° C. or more. From the viewpoint of thermal stability of recording in the thermal recording medium of the present invention, the melting point of the phase separation controlling agent is preferably 60 ° C or higher.

The general color-forming compound, the color-developing agent, the matrix agent and the phase-separation controlling agent have been described above. Further, a developer, a matrix agent and a phase separation controlling agent, which are used in the composition system constituting the rewritable thermosensitive recording medium of the present invention and which are composed of a compound capable of forming a liquid crystal phase (hereinafter referred to as a liquid crystal compound), will be described. .

When the composition system according to the present invention contains a liquid crystal compound, the state change of the system from the metastable non-equilibrium state to the equilibrium state can be caused in a short time. That is, recording of information based on the crystalline-amorphous transition of the composition system
When erasing is performed, when a composition system containing a liquid crystal compound is heated from a metastable non-equilibrium amorphous state to a temperature higher than the crystallization temperature Tc, a highly ordered state such as a liquid crystal phase is easily formed. To form. Therefore, the potential energy for crystallization from this state can be reduced,
Crystallization is possible in a short time. Also, in the case where information is recorded / erased based on the change in the phase separation state of the composition system, the liquid crystal compound has a high degree of order when the composition system is heated to the crystallization temperature Tc or higher as described above. With the formation of the state, the diffusion speed of the color-developing compound or the color developer is increased, so that the phase separation speed of the composition system is increased. As a result, the potential energy between the two phase-separated states can be reduced, and the state change between them can be caused in a short time. Moreover, since the liquid crystal compound has a large intermolecular attractive force and high thermal stability,
A composition system containing such a liquid crystal compound has sufficient thermal stability even if it is amorphous.

Further, in the present invention, in order to increase the recording / erasing speed, the liquid crystal compound used as the developer, matrix agent or phase separation control agent forms a liquid crystal phase with a supercooled liquid having a melting point or lower. Is particularly preferable.
The reason for this is that the state change between the liquid crystal phase and the crystalline substance takes place within an extremely short time. From the viewpoint of thermal stability of the composition system in the non-equilibrium state, the temperature range in which the liquid crystal compound forms a liquid crystal phase is preferably 25 ° C. or higher, and more preferably 60 ° C. or higher. However, this is not the case when a recording material for a special purpose intended to be used in a temperature range below room temperature is targeted.

In the present invention, the liquid crystal compound does not necessarily need to form a liquid crystal phase in the process of causing the system to change from a metastable non-equilibrium state to an equilibrium state, and a state with a high degree of ordering is obtained. By forming the, it is possible to increase the recording / erasing speed. However, when the temperature at which the liquid crystal compound forms a liquid crystal phase exceeds 200 ° C., it is necessary to heat the composition system to a temperature at which the liquid crystal compound can sufficiently flow in recording and erasing information. A large amount of heat energy is required, which is disadvantageous in terms of energy saving. When a liquid crystal phase is formed when the composition system is heated, the recording / erasing speed can be further increased by supplying heat energy and applying an electric field or magnetic field.

Next, a liquid crystal compound which can be preferably used as a developer, a matrix agent or a phase separation controlling agent in the present invention will be specifically described.

The liquid crystal compound used as a color developer in the present invention includes a non-condensed polycyclic structure or a condensed polycyclic structure in which a plurality of ring structures are bonded via a single bond, a vinylene bond or an ethynylene bond. A compound having a molecular skeleton in which a substituent is introduced into each of the ring structures at both ends of, and at least one of the substituents is an organic group having a hydrocarbon chain can be mentioned. Further, in the case of the color developing agent used corresponding to the electron-donating color developing compound, this color developing agent is an acidic group, and the color developing agent used corresponding to the electron accepting color developing compound. In some cases it has a basic group.

In the above compound, the non-condensed polycyclic structure or condensed polycyclic structure in which a plurality of ring structures are bonded via a single bond, a vinylene bond or an ethynylene bond is used as a mesogen group of liquid crystal molecules. It is known. Therefore, by appropriately selecting the substituents to be introduced at both ends of the mesogen group and designing the molecule, a liquid crystal compound optimal as a developer can be obtained. In the vinylene bond, a hydrogen atom may be replaced with a halogen atom or an alkyl group. In addition, a liquid crystal compound having a polycyclic structure in which a plurality of ring structures are linked by an ethynylene bond is particularly preferable because it has a high thermal stability and gives a liquid crystal phase having low viscosity. On the other hand, a linking group other than a single bond, a vinylene bond or an ethynylene bond is not preferable. For example, a rigid mesogen group cannot be obtained when a linking group, such as an alkylene bond, which easily causes a conformational change is used. Moreover, if a linking group that is easily hydrolyzed, such as an azo group, an azomethine group, or an ester group, is used, the thermal stability becomes insufficient.

The liquid crystal compound as described above has a large enthalpy change ΔH between a metastable non-equilibrium state and an equilibrium state due to a large interaction between mesogenic groups of adjacent molecules, and both ends of the mesogenic group. Since a substituent is introduced into, a highly ordered state is easily and stably formed. Moreover, since the mesogen group is extremely rigid and its conformational change is small, entropy change is small when the order of the molecule increases, and activation is particularly large when the system changes from a non-equilibrium state to an equilibrium state. Free energy is not required. In other words, the use of a developer having such a molecular structure makes it possible to reduce the potential barrier between an amorphous state and a crystalline state or between two phase-separated states. The state change of can be generated in a short time.

In the present invention, the liquid crystalline compound used as the color developer is represented by the following general formula (1).
In the formula, Y and R correspond to the substituents respectively introduced into the ring structures at both ends of the polycyclic structure.

[0055]

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(In the formula, Ar is a non-condensed polycyclic structure or a condensed polycyclic structure in which a plurality of ring structures are bonded through a single bond, a vinylene bond or an ethynylene bond, X is an ether bond, a thioether bond, Ester bond or amide bond, Y is an acidic group, R is a substituted or unsubstituted alkyl group,
An alkenyl group or an alkynyl group, m is an integer from 1 to 3,
n is an integer of 0 or 1. The ring structure in the compound represented by the general formula (1) may be an aromatic ring or a saturated ring. Moreover, it does not matter even if it contains a hetero atom. In the case of a heterocycle, a large interaction occurs between the molecules, and it becomes possible to easily form a highly ordered state when the compound is heated.
Specifically, as Ar in the formula, an aromatic ring such as a benzene ring or a saturated ring represented by the following chemical formula is a single bond, a non-condensed polycyclic structure in which a vinylene bond or an ethynylene bond is bonded, or a naphthalene ring, Examples thereof include fused polycyclic structures such as an azulene ring, an indene ring, a biphenylene ring, an anthracene ring, a fluorene ring and a phenanthrene ring.

[0057]

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A liquid crystal compound containing a saturated ring is generally advantageous in forming a liquid crystal phase having low viscosity, and when a developer made of such a liquid crystal compound is used, diffusion of the color developing compound This is preferable in that the speed is increased and the phase separation speed of both is increased. In particular, a liquid crystal compound having a cyclohexane ring is preferable because it can form a liquid crystal phase having low viscosity. On the other hand, other liquid crystal compounds having a saturated ring are preferable because they give good heat resistance.

In the present invention, the developer represented by the general formula (1) contains a non-condensed polycyclic structure or a condensed polycyclic structure having high crystallinity in the molecular skeleton and has a sufficiently high melting point. , Contributes to improvement of thermal stability of recording. Among these polycyclic structures, a non-condensed polycyclic structure is preferable because a liquid crystal compound can be easily obtained. Further, from the viewpoint of obtaining a compound having a high melting point, a non-fused polycyclic structure having at least one aromatic ring is desired. In particular, a non-fused polycyclic structure having at least one paraphenylene ring that is highly linear and has a small polarization is extremely preferable in that it is extremely easy to obtain a liquid crystal compound. Specifically, a plurality of paraphenylene rings, or a polycyclic structure in which at least one paraphenylene ring and a saturated ring represented by the above chemical formula are bonded via a single bond, a vinylene bond, or an ethynylene bond. Is mentioned. The condensed polycyclic structure that forms a rigid mesogen group is effective for improving heat resistance.

X in the general formula (1) is particularly preferably an ether bond or a thioether bond which is thermally stable and hardly decomposed by moisture or the like. However, even if an ester bond or an amide bond is used, there is almost no problem depending on the application, and it is advantageous in that a liquid crystal compound can be synthesized easily and inexpensively. Y in the general formula (1) is an acidic group. As described above, since the color developer in the present invention is preferably phenols, Y is preferably a hydroxyl group. Further, as Y, phenol may be linked to the polycyclic structure via a linking group such as an ester group. Other than the above, examples of Y include a phosphoric acid group and a sulfonic acid group.

R in the general formula (1) has 1 to 30 carbon atoms,
It is desirable that the hydrocarbon chain is preferably 4 to 22. If the hydrocarbon chain is too long, entropy change increases in the process of increasing the order of the molecule, and a large activation free energy is required to change the state of the system from the nonequilibrium state to the equilibrium state. The straight-chain alkyl derivative tends to have a lower melting point as the hydrocarbon chain is shorter. Therefore, when a straight chain alkyl derivative having a short hydrocarbon chain and a low melting point is added to the composition as a recording material, the thermal stability is generally lowered. However, since the compound represented by the general formula (1) has a non-condensed polycyclic structure or a condensed polycyclic structure in the molecular skeleton, it has a sufficiently high melting point even if R has 10 or less carbon atoms. Therefore, a thermal recording medium composed of a composition containing such a compound has sufficiently high thermal stability of recording. When R is a perfluoroalkyl group or a perfluoroalkylene group, it is effective in increasing the rigidity of the molecule and easily and stably forming a highly ordered state when the compound is heated. is there. Further, R may be a branched hydrocarbon group. For example, a developer having a branched R having a bifurcated long-chain alkyl group is preferable because the thermal stability of the amorphous state is increased due to the entanglement of the alkyl chains and the crystallization rate is high.

In the present invention, the molecular arrangement of the liquid crystal phase formed by the above liquid crystal compound is not particularly limited. For example, when a liquid crystal compound is used as the color developer,
When the smectic phase is formed, the degree of order is high, and thus phase separation of the composition system is likely to proceed, and the contrast ratio between the colored and decolored states is increased. Further, when a nematic phase is formed, the viscosity is low, so that the diffusion speed of the color-developing compound in the developer is increased and the phase separation speed of these compounds is increased.

In the present invention, examples of the liquid crystal compound suitable as a matrix agent include, for example, a steroid derivative forming a cholesteric phase, a compound in which a plurality of alkyl groups are introduced into a rigid aromatic ring forming a discotic phase, and a smectic phase. Any of a compound having a rigid mesogen group forming a nematic phase and a flexible hydrocarbon chain may be used. Also in this case, if the formed liquid crystal phase is a smectic phase or a discotic phase having a high degree of order, phase separation of the composition system is likely to proceed, the contrast ratio between the colored and decolored states is high, and the nematic phase having a low viscosity is used. In the case of a cholesteric phase or a cholesteric phase, the color-developing compound has a large diffusion rate in the developer, and the phase separation rate of these can be further increased.

Examples of the steroid derivative forming the cholesteric phase include cholesterol halide, monocarboxylic acid cholesterol ester, monocarboxylic acid sitosterol ester, and benzoic acid derivative cholestanol ester. More specifically, for example, cholesteryl chloride, cholesteryl acetate, cholesteryl nonanate, methyl cholesterol carbonate, ethyl cholesterol carbonate, cholesteryl.
Examples include p-methoxybenzoate, sitosteroyl benzoate, sitosteroyl p-methylbenzoate, and cholestanyl benzoate.

Examples of the compound in which a plurality of alkyl groups are introduced into the rigid aromatic ring forming the discotic phase include those represented by the following chemical formula.

[0066]

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In the present invention, examples of the liquid crystal compound suitable as the phase separation controlling agent include those represented by the following chemical formula.

[0068]

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(In the formula, Ar is a non-condensed polycyclic structure or condensed polycyclic structure in which a plurality of ring structures are bonded via a single bond, a vinylene bond, an ethynylene bond, or an ester bond, X is an ether bond, Thioether bond, ester bond or amide bond, Z is a neutral polar group, R is a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group or aryl group, m is an integer of 1 to 3, n is an integer of 0 or 1. In the rewritable heat-sensitive recording medium of the present invention, when the glass transition temperature Tg of the composition system is low and close to room temperature, a slight increase in the environmental temperature causes phase separation or system diffusion due to the diffusion of the color developable compound or the color developer. Crystallization tends to proceed, and the thermal stability of recording tends to decrease. Therefore, in the present invention, the glass transition temperature Tg when all or part of the composition system is amorphous
Is preferably 25 ° C. or higher, more preferably 50 ° C. or higher. Considering this point, the color-forming compound also has a large molecular weight and a small melting enthalpy ΔH, for example, a compound having a bulky molecular skeleton close to a sphere, or a plurality of compounds capable of forming hydrogen bonds between molecules. It is preferable to use a compound having a site.

Contrary to the above, if a composition system having a glass transition temperature Tg close to room temperature is used, for example, a rewritable thermosensitive recording medium in which recorded information is naturally erased after being stored for a desired period. It is also possible to realize Furthermore, for special applications, a composition system having a glass transition temperature Tg lower than room temperature can be used. As such a special use, when the temperature of a refrigerator that stores a substance that needs to be refrigerated temporarily rises due to failure or transportation, it is possible to display the change in the coloring state due to crystallization of the composition system. Conceivable.

On the other hand, in the present invention, if the glass transition temperature Tg of the composition system is too high, in recording and erasing information, the crystallization temperature is not lower than Tc and lower than melting point Tm or melting point Tm.
When heating the composition system to a temperature of m or higher, a large amount of heat energy is required, which is disadvantageous in terms of energy saving.
Therefore, the glass transition temperature Tg of the composition system in the present invention is preferably 150 ° C. or lower.

Here, the glass transition temperature Tg of the mixture is
In general, it is known that the glass transition temperature Tg of each compounded component shows a weight average value. Therefore, in order to set the glass transition temperature Tg of the composition system of the present invention to a desired value, it is effective to control the glass transition temperature Tg of each component in the composition system. In other words, in the rewritable thermal recording medium of the present invention, the glass transition temperature Tg is 25 ° C. or more, and further 50 ° C., respectively, as the color-developing compound, the color developer and the matrix agent to be incorporated in the composition system.
It is preferable to use the above compounds. Considering the thermal stability of recording, the melting point of the matrix agent is 1
It is desirable that the temperature is 00 ° C or higher.

Regarding the composition system and the glass transition temperature Tg of each component contained in the composition system in the thermal recording medium of the present invention, for example, a differential scanning calorimeter (DSC) is used to determine the entire composition system or one of the composition systems. It can be measured for each part and each component in the composition system.

On the other hand, in a component which easily forms an amorphous material having a clear glass transition temperature Tg, Tg = a.Tm (a is 0.65 to 0.55) is generally between the glass transition temperature Tg and the melting point Tm.
0.8; however, Tg and Tm are absolute temperatures. Therefore, the glass transition temperature T of the composition system and each component in the composition system
When g is set to be high, the melting point Tm of the composition system also becomes high as a result. In this case, although the thermal stability of the recording can be improved, it is necessary to heat the composition to a very high temperature when melting the composition. Along with this, for example, a substrate having excellent heat resistance is required, and the practicability decreases. In order to avoid this problem, it is effective to use a composition system that forms a plurality of crystal forms. In order to specifically prepare a composition system that forms a plurality of crystal forms, for example, a component capable of forming a plurality of crystal forms may be used for the developer and the matrix agent in the composition system.

In the present invention, in the composition system containing the color-developing compound and the color developing agent but not the matrix agent, the compounding ratio of the color-developing compound and the color developing agent is 1 part by weight of the color-developing compound. 0.1 to 100 parts by weight of developer, and further 1 to 1
It is preferably set to 0 parts by weight. When the amount of the developer is less than 0.1 part by weight, it is difficult to sufficiently increase the interaction between the color developing compound and the developer at the time of recording or erasing.
On the other hand, when the amount of the developer exceeds 100 parts by weight, the color density in the color-developed state tends to decrease.

In the composition system containing the color-developing compound, the color-developing agent and the matrix agent, the compounding ratio of the color-developing compound and the color-developing agent is 0. 1-1
It is preferably set to 0 parts by weight, more preferably 1 to 2 parts by weight. When the amount of the developer is less than 0.1 part by weight, it is difficult to sufficiently increase the interaction between the color developing compound and the developer at the time of recording or erasing. On the other hand, when the amount of the color developer exceeds 10 parts by weight, it becomes difficult to sufficiently reduce the interaction between the color developing compound and the color developer during recording or erasing. Further, the mixing ratio of the matrix agent is 1 to 1 part by weight of the color-forming compound.
It is preferably set to ˜200 parts by weight, more preferably 10 to 100 parts by weight. If the amount of the matrix agent is less than 1 part by weight, it becomes difficult to cause the crystalline-amorphous transition of the composition system or the change of the phase separation state. When the amount of the matrix agent exceeds 200 parts by weight, the color density in the color-developed state tends to decrease.

The compounding ratio of the phase separation controlling agent in the present invention is
The amount is preferably 0.1 to 100 parts by weight, more preferably 1 to 50 parts by weight, based on 1 part by weight of the color developable compound. If the amount of the phase separation controlling agent is less than 0.1 part by weight, the effect of increasing the phase separation rate of the composition system is hardly obtained. Phase separation control agent is 100
If it exceeds the weight part, the non-equilibrium state of the composition system becomes unstable, and the thermal stability of recording may be deteriorated.

In the rewritable heat-sensitive recording medium of the present invention, components other than the color-developing compound, the color developer, the matrix agent and the phase-separation controlling agent are used as coloring dyes, fluorescent dyes, ultraviolet absorbers, heat insulating agents, heat storage agents. You may mix | blend etc. suitably. At this time, if a color dye or the like is appropriately selected according to the color-forming compound contained in the composition system, any desired colored state can be obtained in any of the color-developed state and the decolored state. .

To use the rewritable heat-sensitive recording medium of the present invention in a bulk form, for example, the composition comprising the above-mentioned components is melted and mixed without a solvent, and then rapidly cooled or naturally cooled and fixed. . At this time, if the melt is molded in a mold, a desired shape can be obtained. It is also possible to thin the melt to form a thin film. On the other hand, the composition may be dissolved in an appropriate solvent and cast to form a thin film. The thickness of the thin film thus formed is preferably 0.5 μm or more and 50 μm or less. If the thickness of the thin film is too thin, the resulting thermosensitive recording medium may have insufficient color density in a color developing state. On the other hand, if the thin film is too thick, a large amount of heat energy is required during recording / erasing, which makes it difficult to perform recording / erasing at high speed.

In the present invention, from the viewpoint of improving the strength of the thermosensitive recording medium, the above-mentioned composition as a recording material may be supported in an appropriate medium. Specifically, impregnation into a polymer sheet, dispersion in a binder polymer,
Examples include dispersion in an inorganic glass, impregnation in a porous substrate, intercalation in a layered material, and microencapsulation.

In order to specifically impregnate the polymer sheet with the composition, a polymer sheet having a sufficient space for holding the composition is used, and the composition is dissolved in a solvent-free melt or a suitable solvent. Impregnated solution. Considering the uniformity of the surface of the heat-sensitive recording medium, the polymer used at this time is preferably as high as the wettability of the composition with the melt or solution. Specific examples include polyether ether ketones; polycarbonates; polyarylates; polysulfones; tetrafluoroethylene resins; tetrafluoroethylene / perfluoroalkoxyethylene copolymers, tetrafluoroethylene / perfluoroalkyl vinyl ethers. Ethylene tetrafluoride copolymers such as copolymers, tetrafluoroethylene / hexafluoropropylene copolymers, tetrafluoroethylene / ethylene copolymers; trifluoroethylene chloride resins; vinylidene fluoride resins; Fluorine-containing polybenzoxazoles; polypropylenes; polyvinyl alcohols; polyvinylidene chlorides; polyesters such as polyethylene terephthalate, polybrylene terephthalate, polyethylene naphthalate; polystyrenes; polyamides such as nylon 66; polyimides; Imidoamido like; polyether sulfones; polymethyl pentene like; polyetherimides; polyurethanes; polybutadienes; methyl cellulose, ethyl cellulose, cellulose acetate, cellulose such as nitrocellulose; gelatin;
Gum arabic; various papers such as neutral paper and acid paper are listed. In particular, celluloses and neutral papers are preferred because the melt or solution of the composition easily penetrates and the resulting thermosensitive recording medium has a high coloring density and a low erasing density.

When the composition is dispersed in the binder polymer, a melt or solution of the composition is prepared, and if necessary, other components are added and dispersed with the binder polymer by various dispersion methods. The resulting product may be coated on a suitable substrate. Examples of the binder polymer include polyethylenes; chlorinated polyethylenes; ethylene copolymers such as ethylene / vinyl acetate copolymers, ethylene / acrylic acid / maleic anhydride copolymers; polybutadienes; polyethylene terephthalate, polybutylene terephthalate, polyethylene. Polyesters such as naphthalate; polypropylenes; polyisobutylenes; polyvinyl chlorides; polyvinylidene chlorides; polyvinyl acetates; polyvinyl alcohols; polyvinyl acetals; polyvinyl butyrals; tetrafluoroethylene resins; trifluoride Chlorinated ethylene resins; fluorinated ethylene / propylene resins; vinylidene fluoride resins; vinyl fluoride resins; tetrafluoroethylene / perfluoroalkoxyethylene copolymers, tetrafluoroethylene / perfluoro Ethylene tetrafluoride copolymers such as alkyl vinyl ether copolymers, tetrafluoroethylene / hexafluoropropylene copolymers, tetrafluoroethylene / ethylene copolymers; Fluorine-containing polybenzoxazole and other fluororesins; Acrylics Resins; methacrylic resins such as polymethylmethacrylate; polyacrylonitriles; acrylonitrile copolymers such as acrylonitrile-butadiene-styrene copolymers; polystyrenes; halogenated polystyrenes; styrene
Styrene copolymers such as methacrylic acid copolymers and styrene-acrylonitrile copolymers; acetal resins; polyamides such as nylon 66; gelatin; gum arabic;
Polycarbonates; Polyester carbonates; Cellulosic resins; Phenolic resins; Urea resins;
Epoxy resins; Unsaturated polyester resins; Alkyd resins; Melamine resins; Polyurethanes; Diarylphthalate resins; Polyphenylene oxides; Polyphenylene sulfides; Polysulfones; Polyphenylsulfones; Silicone resins; Polyimides ;
Bismaleimide triazine resins; polyimide amides; polyether sulfones; polymethylpentenes; polyether ether ketones; polyether imides; polyvinyl carbazoles; norbornene-based amorphous polyolefins and other thermoplastic resins You can

Examples of the above dispersion method include a mixer method, a sand mill method, a ball mill method, an impeller mill method, a colloid mill method, a three roll mill method, a kneader method, a two roll method, a Banbury mixer method, a homogenizer method and a nanomizer method. Can be mentioned. These dispersion methods are:
It may be appropriately selected according to the viscosity of the melt or the solution, the use and form of the heat-sensitive recording medium, and the like. Furthermore, regarding the coating method on the substrate, etc., spin coating method, pull-up coating method, air doctor coating method, blade coating method, rod coating method, knife coating method, squeeze coating method, impregnation coating method, reverse roll coating method It is possible to use a transfer coating method, a gravure coating method, a kiss roll coating method, a cast coating method, a spray coating method, a curtain coating method, a calendar coating method, an extrusion coating method, an electrostatic coating method, and the like. These coating methods can be appropriately selected according to the use, form, and the like of the thermosensitive recording medium.

In the present invention, when the composition as the recording material is dispersed in the binder polymer, the compounding ratio of the binder polymer is 0.01 per part by weight of the matrix agent.
˜100 parts by weight, more preferably 0.05 to 20 parts by weight. This is because if the amount of the binder polymer is less than 0.01 parts by weight, the strength of the heat-sensitive recording medium is not improved so much, and if it exceeds 100 parts by weight, the color density in the color-developed state tends to decrease.

In the present invention, when the composition to be the recording material is supported on the inorganic glass, it is preferable to use the inorganic glass which can be produced by the so-called sol-gel method. At that time, it is desired that the gelling temperature is not so high. Examples of the porous substrate include various inorganic compounds, and examples of the layered material include mica, clay mineral, talc, chlorite, and the like.

In order to prepare microcapsules in which the composition is encapsulated in the coating, interfacial polymerization method, in-situ method is used.
A polymerization method, a liquid hardening coating method, a phase separation method from an aqueous solution system, a phase separation method from an organic solution system, a melt dispersion cooling method, an air suspension method, a spray drying method and the like can be used. These methods can be appropriately selected according to the use and form of the thermosensitive recording medium. As the coating of the microcapsule, a condensation polymer such as melamine resin, epoxy resin, urea resin, phenol resin, furan resin; styrene-
A thermosetting resin such as a three-dimensional crosslinked vinyl polymer such as a divinylbenzene copolymer or a methyl methacrylate-vinyl acrylate copolymer, or a thermoplastic resin exemplified as a binder polymer in which the composition is dispersed can be appropriately used. Moreover, you may form the multilayer coating film which comprises a microcapsule by using 2 or more types selected from the above-mentioned thermosetting resin and thermoplastic resin. In this case, from the viewpoint of improving the thermal stability of the microcapsules, it is preferable to use a thermosetting resin for the outermost shell of the coating. Also,
The microcapsules thus obtained may be dispersed in a binder polymer or inorganic glass. In this case, even when the composition itself has insufficient dispersibility in a medium, a good dispersion state can be obtained by forming and dispersing the microcapsules.

The use form of the heat-sensitive recording medium of the present invention is not particularly limited, and it may be used as a bulk, or may be used in the form of being compounded with various media or fibers as described above, and more suitable. You may use it in the form which formed the recording layer which consists of a thin film of a composition on such a base material. As such a substrate, a plastic film such as a polyethylene terephthalate film, a plastic plate, a metal plate, a semiconductor substrate, a glass plate, a wood plate, paper, an OHP sheet, or the like can be used. In addition, after preparing the microcapsules, the microcapsules may be applied as a paint or an ink on a base material, and then dried if necessary before use. In this case, color compatibility is easy by using different color-forming compounds for each microcapsule. In addition, a plurality of types of microcapsules containing different color compounds and different types of compositions having different crystallization temperatures Tc and melting points Tm, and a plurality of different types of non-equilibrium states that are colored or colorless are used. If you prepare microcapsules and mix them at the desired blending ratio,
The coloring state can be controlled by the amount of heat energy supplied. Therefore, for example, full-color correspondence is possible by using color-forming compounds of cyan, magenta, and yellow.

In the thermosensitive recording medium of the present invention, the durability of the recording layer made of a thin film of the composition is improved, and sticking to a thermal printer head (TPH) for supplying thermal energy to the recording layer is prevented. From the viewpoint, a protective layer may be provided on the recording layer. Examples of the material for the protective layer include wax, thermoplastic resin, thermosetting resin, photocurable resin, water-soluble resin, latex, and the like. The thickness of the protective layer is preferably about 0.1 to 100 μm. Furthermore, in such a protective layer, a thermal release agent, a lubricant,
A heat resistant material, an antistatic material and the like may be appropriately mixed. Specifically, a protective layer can be formed by applying a solution obtained by dissolving or dispersing the above-described components in a solvent onto a recording layer and then drying the solution. Alternatively, a protective layer may be formed by bonding a heat-resistant film, to which an adhesive has been applied in advance, to the recording layer by a dry lamination method. On the other hand, in order to improve the adhesion between the base material and the recording layer, the solvent resistance, etc.,
An undercoat layer may be provided between the base material and the recording layer.

The above heat resistant film is not particularly limited as long as it has a heat distortion temperature higher than the melting point of the composition used as the recording material. For example, polyether ether ketones; polycarbonates; polyarylates; polysulfones; ethylene tetrafluoride resins; tetrafluoroethylene / perfluoroalkoxyethylene copolymers, tetrafluoroethylene / perfluoroalkylvinyl ether copolymers , Ethylene tetrafluoride / propylene hexafluoride copolymer,
Ethylene tetrafluoride copolymers such as tetrafluoroethylene / ethylene copolymers; trifluoroethylene chloride resins; vinylidene fluoride resins; fluorine-containing polybenzoxazoles;
Polypropylenes; polyvinyl alcohols; polyvinylidene chlorides; polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate; polystyrenes; polyamides such as nylon 66; polyimides; polyimide amides; polyether sulfones; poly Sheets of polymer compounds such as methylpentenes; polyetherimides; polyurethanes; polybutadienes can be used. These can be appropriately selected and used depending on the use, form, and the like of the heat source and the heat-sensitive recording medium. As the adhesive, acrylic resins generally used in the dry lamination method; phenoxy resins; ionomer resins; ethylene / vinyl acetate copolymers, ethylene / acrylic acid / maleic anhydride copolymers and the like Copolymers; polyvinyl ethers; polyvinyl formals; polyvinyl butyral; gelatin; gum arabic; polyesters; polystyrenes; styrene copolymers such as styrene-acrylic acid copolymers; vinyl acetate resins; polyurethanes; xylene Examples are resins; epoxy resins; phenol resins; urea resins.

In the heat-sensitive recording medium of the present invention, crystalline-
In order to perform the recording / erasing based on the amorphous transition or the change of the phase separation state, the binary thermal energies having different magnitudes are supplied as described above, or the melting point Tm.
Two types of thermal history having different cooling rates after the above heating are supplied.

To supply heat energy during recording, it is preferable to use a heat source such as a thermal head (for example, TPH) or laser light. Among them, the thermal head is not so large in resolution but can heat the thermal recording medium over a large area and is advantageous in miniaturizing the apparatus. On the other hand, a laser beam is preferable because the spot diameter can be reduced to facilitate high-density recording and the recording / erasing speed can be increased. However,
In the case of using laser light, a light-absorbing layer having an absorption band at the wavelength of laser light is provided, in order to efficiently absorb laser light even for an amorphous composition having a good light-transmitting property, or It is desirable to incorporate a compound having an absorption band at the wavelength of laser light into the composition. To supply heat energy during erasing, it is preferable to use a heat source such as a hot stamper method or a heat roll method capable of heating the entire thermosensitive recording medium at once. When the heated thermosensitive recording medium is cooled, it may be naturally cooled, but it is preferable to cool it rapidly by using a cold stamper, a cold roll, a cold air flow or a Peltier element. Further, in the thermal recording medium of the present invention, overwrite recording can be realized by using a plurality of thermal heads having different energies or a plurality of laser beams having different spot diameters.

[0092]

Embodiments of the present invention will be described below.

Example 1 1.0 part by weight of CVL (Crystal Violet Lactone) as a color developing compound and the following chemical formula (2) as a color developer.
Each 1.0 parts by weight of the phenolic compound represented by the above formula was blended and then dissolved in chloroform to obtain a uniform solution. This solution was cast on a glass substrate having a thickness of 1.5 mm to form an amorphous thin film having a thickness of about 10 μm. A photocurable epoxy resin was applied on the amorphous thin film and then photocured to form a protective film having a film thickness of 1 μm. After pressing a hot roll over the entire surface of this protective film, the amorphous thin film was crystallized to white by allowing it to cool naturally at room temperature.

[0094]

[Chemical 6]

FIG. 5 shows a vertical sectional view of the obtained thermal recording medium. This thermal recording medium has a form in which a thin recording layer 2 is formed on a glass substrate 1 and a protective film 3 is further formed on the recording layer 2.

A thermal head (6 dots / mm, 380Ω) manufactured by Toshiba was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 12 V and a pulse width of 0.8 msec. As a result, the printed portion became amorphous and was colored blue, and positive type recording was performed. Next, the same thermal head was used for the heat-sensitive recording medium after recording, and the entire surface thereof was sequentially heated with an applied voltage of 10 V and a pulse width of 1.5 msec. It was Separately from this, when a hot stamper was pressed against the entire surface of the thermosensitive recording medium after recording for 0.1 seconds and left at room temperature, the printed portion returned to white crystalline and erasing could be performed. Recording / erasing the same as above 1
The display did not deteriorate even after performing 00 cycles.
In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

Examples 2 to 21 Each thermosensitive recording medium was obtained in exactly the same manner as in Example 1 except that the color developable compound and the color developing agent shown in Table 1 were used. PSD-V and PSD-2 used as color developing compounds
90, PSG-3G, and PSD-150 are all fluoran-based leuco compounds manufactured by Nippon Soda Co., Ltd., and IR (Indolyl Red) is a fluoran-based leuco compound manufactured by Yamamoto Kasei Co., Ltd. Chemical formulas (3) to (1 used as a developer
The structures of the compounds of 7) are shown below.

[0098]

[Chemical 7]

[0099]

Embedded image

Example 1 was applied to each of the obtained thermal recording media.
The same recording as in Example 1 was performed using the same thermal head as
I tried to erase it. As a result, positive type recording can be performed with a pulse width of 0.8 msec and a pulse width of 1.5 m.
It was possible to erase in sec. The voltages applied to the thermal head during recording and erasing on each thermal recording medium are also shown in Table 1. Also in these thermosensitive recording media, the display was not deteriorated even after the same recording / erasing was performed for 100 cycles. Also, 1 at 30 ° C
No change was observed in the printed state even after left for a year.

[0101]

[Table 1]

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the phenol compound represented by the chemical formula (18) below was used as the color developer. Next, using the same thermal head as in Example 1 with respect to the obtained thermal recording medium, applied voltage 13V,
As a result of printing by heating with a pulse width of 0.8 msec, the printing portion became amorphous and was colored blue, and positive type recording was performed. However, when the hot stamper was pressed against the entire surface of the heat-sensitive recording medium for 1 second and then left at room temperature, the printed part partially returned to crystalline and turned white. As described above, it was found that the erasing was incomplete when the developer not forming the liquid crystal phase was used.

[0103]

Embedded image

Example 22 1.0 part by weight of CVL as a color-developing compound and 2.0 of a phenolic compound represented by the above chemical formula (3) as a developer.
After mixing each part by weight, the mixture was heated and melted to obtain a uniform composition. An optically polished glass substrate having a thickness of 1.2 mm, which was vacuum-deposited with 100 nm of Cr as a light absorbing layer, and another glass plate were prepared. A small amount of the above composition,
It melted on the light absorption layer on the glass substrate, a glass plate was placed on this melt, and the melt was sandwiched in a spread state. afterwards,
The glass substrate was gradually cooled to form a crystalline thin film having a film thickness of about 10 μm to be a recording layer. Thus, a thermosensitive recording medium composed of the glass substrate, the light absorbing layer, the recording layer and the glass plate was obtained.

Next, the obtained heat-sensitive recording medium was set to 900 RP.
While rotating at M, wavelength 830n focused on 1 μm diameter
m semiconductor laser light has an intensity of 6 m on the surface of the thermal recording medium.
Irradiation was performed so as to attain W, and writing to the recording layer was performed. Observation with a polarization microscope confirmed that the writing portion irradiated with laser light was amorphized with a clear contrast ratio, and it was found that line-shaped recording with a width of about 1 μm was performed. 900 thermal recording media after recording
While rotating at RPM, wavelength 83 focused on 2 μm diameter
A semiconductor laser beam of 0 nm was irradiated so that the intensity on the surface of the thermal recording medium would be 3 mW. Observation with a polarization microscope confirmed that the original writing portion was crystalline in the region irradiated with the laser beam having the intensity of 3 mW, and the erasing was performed. It should be noted that no change was observed in the written state even after being left at 30 ° C. for one year.

Example 23 1.0 part by weight of CVL as a color-developing compound and 2.0 of a phenolic compound represented by the above chemical formula (3) as a developer.
After mixing each part by weight, the mixture was heated and melted to obtain a uniform composition. 30 g of this composition was mixed with 0.5 g of melamine prepolymer and heated and melted. 5 wt% of this melt
Add dropwise to 200 g of gelatin aqueous solution and continue stirring to form fine droplets. Adjust the pH to 2 with hydrochloric acid and adjust to about 8
Stirring was continued at 0 ° C. for 5 hours. By this operation, a suspension of microcapsules in which the cured melamine resin was coated with the composition containing the color-developing compound and the developer was produced. This suspension of microcapsules was applied to copy paper and dried. A heat roll was pressed against the entire surface of this copy paper and naturally cooled at room temperature to form a recording layer mainly containing microcapsules containing a crystalline composition on the paper surface. The microcapsules may be used after being extracted from the suspension by a method such as filtration, centrifugation, drying or the like.

Next, the same thermal head as in Example 1 was used for the obtained thermal recording medium (copy paper),
Thermal printing was performed with an applied voltage of 13 V and a pulse width of 1 msec. As a result, the printed part becomes amorphous and colored blue,
Positive type recordings were made. Then, after the hot stamper was pressed for 0.2 seconds on the entire surface of the copy paper after recording, it was allowed to stand at room temperature, and the printed part returned to crystalline and was erased. It should be noted that no change was observed in the printed state even after left at 30 ° C. for one year.

Example 24 C.I. I. Basic Blue 3 1.
0 parts by weight and 4.0 parts by weight of a benzenesulfonic acid derivative represented by the following chemical formula (19) as a color developer were added respectively, and then heated and melted to obtain a uniform composition. These color-developing compounds and color developers are in a decolored state when their interaction is increased, and are in a colored state when their interaction is decreased.
A small amount of the composition is melted on a glass substrate having a thickness of 1.5 mm, and a glass plate having a thickness of 1 mm on which a small amount of a gap agent made of silica particles having a diameter of 10 μm is attached is placed on the melt, and the melt is melted. After sandwiching it in the opened state, it was naturally cooled at room temperature. When the glass plate was peeled off, a transparent amorphous thin film with a film thickness of about 10 μm was formed on the glass substrate.
A photocurable epoxy resin was applied on this amorphous thin film and then photocured to form a protective layer having a film thickness of 1 μm. Further, a heating roll was pressed on the entire surface of the protective layer and then naturally cooled at room temperature to crystallize the amorphous thin film to form a blue recording layer.

[0109]

Embedded image

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 13 V and a pulse width of 1 msec. As a result, the printed part became amorphous and became colorless, and negative type recording was performed. After the hot stamper method was pressed on the entire surface of the thermosensitive recording medium after recording for 0.2 seconds and left at room temperature, the printed portion returned to blue crystalline and was erased. Similar record
The display did not deteriorate even after 100 cycles of erasing. In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

Example 25 The same as Example 24 except that 1.0 part by weight of cyanine was used as the color developing compound and 2.0 parts by weight of the phosphoric acid compound represented by the following chemical formula (20) was used as the developer. A thermosensitive recording medium was obtained. The color-developing compound and the color-developing agent used in this example are also in a decolored state when their interaction increases,
When the interaction is reduced, it becomes a colored state.

[0112]

Embedded image

Example 1 was applied to the obtained thermosensitive recording medium.
Using the same thermal head as above, heating printing was performed with an applied voltage of 13 V and a pulse width of 0.8 msec. When a hot stamper was pressed for 0.2 seconds on the entire surface of the thermosensitive recording medium after recording and left at room temperature, the printed part returned to blue crystalline and was erased. Same recording / erasing 1
The display was not deteriorated even after performing 00 cycles. In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

Example 26 1.0 part by weight of CVL as a color-developing compound and 1.0 of a phenolic compound represented by the above chemical formula (2) as a developer.
Parts by weight, stearyl alcohol as a phase separation control agent.
After blending 5 parts by weight respectively, a thermal recording medium was obtained in the same manner as in Example 1. The same thermal head as in Example 1 was used for the obtained thermal recording medium, and the applied voltage was 12
As a result of carrying out heating printing with V and a pulse width of 0.8 msec, the printed part became amorphous and was colored blue, and positive type recording was carried out. The same thermal head was used for the thermal recording medium after recording, applied voltage 9V, pulse width 1.
When the entire surface was sequentially heated for 2 msec, the printed part returned to white crystalline and was erased. Even if the same recording / erasing was performed for 100 cycles, the display did not deteriorate.
In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

Example 27 1.0 part by weight of CVL as a color developing compound and a phenolic compound represented by the following chemical formula (21) as a color developing agent 1.
After blending 0 parts by weight of each, it was dissolved in chloroform to obtain a uniform solution. The color developer used in this example is 92
It has been confirmed that a liquid crystal phase (smectic phase) is formed by a supercooled liquid at ˜110 ° C. by a combination of differential scanning calorimetry and polarization microscope measurement. Thick this solution to a thickness of 1.5
It was cast on a glass substrate having a thickness of 10 mm to form an amorphous thin film having a thickness of about 10 μm. A photocurable epoxy resin was applied on the amorphous thin film and then photocured to form a protective film having a film thickness of 1 μm. A hot roll was pressed on the entire surface of this protective film, and then naturally cooled at room temperature to crystallize the amorphous thin film to white.

[0116]

[Chemical 12]

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 12 V and a pulse width of 0.8 msec. As a result, the printed part became amorphous and became blue. Colored and positive type recorded. When the same thermal head was used for the heat-sensitive recording medium after recording and the entire surface was sequentially heated with an applied voltage of 9 V and a pulse width of 1 msec, the printed portion returned to white crystalline and was erased. Even if the same recording / erasing was performed for 100 cycles, the display did not deteriorate. Also, 1 at 30 ° C
No change was observed in the printed state even after left for a year.

Example 28 A thermosensitive recording medium was obtained in the same manner as in Example 27 except that a phenolic compound represented by the following chemical formula (22) was used as a color developer. The color developer used in this example is 63 to 8
It has been confirmed that a liquid crystal phase (nematic phase) is formed by a supercooled liquid at 7 ° C. by a combination of differential scanning calorimetry and polarization microscope measurement.

[0119]

Embedded image

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 11 V and a pulse width of 0.8 msec. Colored and positive type recorded. When the same thermal head was used for the heat-sensitive recording medium after recording and the entire surface was sequentially heated with an applied voltage of 9 V and a pulse width of 1 msec, the printed portion returned to white crystalline and was erased. Even if the same recording / erasing was performed for 100 cycles, the display did not deteriorate. Also, 1 at 30 ° C
No change was observed in the printed state even after left for a year.

Example 29 A thermosensitive recording medium was obtained in the same manner as in Example 27 except that a phenolic compound represented by the following chemical formula (23) was used as a color developing agent. The color developer used in this example is 165-
It has been confirmed that a liquid crystal phase (nematic phase) is formed by a supercooled liquid at 180 ° C. by a combination of differential scanning calorimetry and polarization microscope measurement.

[0122]

Embedded image

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 15 V and a pulse width of 0.8 msec. As a result, the printed portion became amorphous and turned blue. Colored and positive type recorded. The same thermal head was used for the heat-sensitive recording medium after recording, and the entire surface was sequentially heated with an applied voltage of 11 V and a pulse width of 1 msec. The printed part returned to white crystalline and was erased. Even if the same recording / erasing was performed for 100 cycles, the display did not deteriorate. In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

Example 30 1.0 part by weight of CVL as a color developing compound, and a phenolic compound represented by the following chemical formula (24) as a color developing agent 1.
0 parts by weight and 10 parts by weight of a β-sitosterol derivative represented by the following chemical formula (25) were mixed as a matrix agent, and then dissolved in chloroform to obtain a uniform solution. The color developer is not included in the general formula (1). The matrix agent used in this example is confirmed to form a liquid crystal phase (cholesteric phase) in a supercooled liquid by a combination of differential scanning calorimetry and polarization microscope measurement. This solution was cast on a glass substrate having a thickness of 1.5 mm to form an amorphous thin film having a thickness of about 10 μm. After applying a photocurable epoxy resin on this amorphous thin film,
It was photocured to form a protective film having a thickness of 1 μm. A hot roll was pressed on the entire surface of this protective film, and then naturally cooled at room temperature to crystallize the amorphous thin film to white.

[0125]

[Chemical 15]

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 12 V and a pulse width of 0.8 msec. It became colorless and a negative type record was made. When the same thermal head was used for the heat-sensitive recording medium after recording and the entire surface was sequentially heated with an applied voltage of 8.5 V and a pulse width of 1 msec, the printed part returned to blue crystalline and was erased. Even if the same recording / erasing was performed for 100 cycles, the display did not deteriorate. Also, 30 ℃
No change was observed in the printing state even after being left for 1 year.

Example 31 A thermosensitive recording medium was obtained in the same manner as in Example 30 except that the compound represented by the following chemical formula (26) was used as the matrix agent. The matrix agent used in this example is confirmed to form a liquid crystal phase (smectic phase) with a supercooled liquid by a combination of differential scanning calorimetry and polarization microscope measurement.

[0128]

Embedded image

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 13 V and a pulse width of 0.8 msec. The negative type was recorded. When the same thermal head was used for the heat-sensitive recording medium after recording and the entire surface was sequentially heated with an applied voltage of 9 V and a pulse width of 1 msec, the printed portion returned to a blue crystalline state and was erased. The same recording / erasing was performed for 100 cycles, but no display deterioration occurred. In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

Example 32 1.0 part by weight of CVL as a color developing compound, and a phenolic compound represented by the above chemical formula (24) as a color developing agent 1.
After blending 0 part by weight, 10 parts by weight of the β-sitosterol derivative represented by the above chemical formula (25) as a matrix agent, and 5 parts by weight of eicosanol as a phase separation controlling agent, a thermosensitive recording medium was prepared in the same manner as in Example 30. Obtained.

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 11 V and a pulse width of 0.8 msec. As a result, the printed portion became amorphous. It became colorless and a negative type record was made. When the same thermal head was used for the heat-sensitive recording medium after recording and the entire surface was sequentially heated with an applied voltage of 8 V and a pulse width of 0.8 msec, the printed portion returned to a blue crystalline state and was erased. Even if the same recording / erasing was performed for 100 cycles, the display did not deteriorate. Also, 30 ℃
No change was observed in the printing state even after being left for 1 year.

Example 33 10 parts by weight of cholesterol as a matrix agent, and a compound 7 represented by the following chemical formula (27) as a phase separation controlling agent
A thermosensitive recording medium was obtained in the same manner as in Example 32 except that the parts by weight were used. It has been confirmed by the combination of differential scanning calorimetry and polarization microscope measurement that the phase separation controlling agent used in this example can form a smectic phase and a nematic phase as a liquid crystal phase.

[0133]

Embedded image

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 11 V and a pulse width of 0.8 msec. The negative type was recorded. When the same thermal head was used for the heat-sensitive recording medium after recording and the entire surface was sequentially heated with an applied voltage of 8.5 V and a pulse width of 1 msec, the printed part returned to blue crystalline and was erased. Even if the same recording / erasing was performed for 100 cycles, the display did not deteriorate. In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

Example 34 A thermosensitive recording medium was obtained in the same manner as in Example 33 except that the compound represented by the following chemical formula (28) was used as the phase separation controlling agent. It has been confirmed by the combination of the differential scanning calorimetry and the polarization microscope measurement that the phase separation controlling agent used in this example can also form a smectic phase and a nematic phase as the liquid crystal phase.

[0136]

Embedded image

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out at an applied voltage of 11 V and a pulse width of 0.8 msec. The negative type was recorded. When the same thermal head was used for the heat-sensitive recording medium after recording and the entire surface was sequentially heated with an applied voltage of 8.2 V and a pulse width of 1 msec, the printed part returned to blue crystalline and was erased. Even if the same recording / erasing was performed for 100 cycles, the display did not deteriorate. In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

Example 35 1.0 part by weight of phenolphthalein as a color-developing compound and 1.0 part by weight of an amino compound represented by the following chemical formula (29) as a color developing agent were blended and dissolved in chloroform. To give a uniform solution. Thick this solution to a thickness of 1.5
It was cast on a glass substrate having a thickness of mm to form an amorphous film having a thickness of about 10 μm. A photocurable epoxy resin was applied on the amorphous film and then photocured to form a protective film having a thickness of 1 μm. After pressing the heat roll on the entire surface of this protective film,
The amorphous thin film was crystallized to white by spontaneous cooling at room temperature.

[0139]

Embedded image

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out with an applied voltage of 12 V and a pulse width of 0.8 msec. As a result, the printed portion was colored red and positive type recording was performed.
Next, the same thermal head was used for the heat-sensitive recording medium after recording, the applied voltage was 10 V, and the pulse width was 1.5 msec.
When the entire surface was heated in sequence, the printed area returned to white crystalline and was erased. 10 similar recording / erasing
The display did not deteriorate even after 0 cycles. In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

Example 36 1.0 part by weight of CVL as a color developing compound, 1.0 part by weight of a phenolic compound of the above chemical formula (18) as a color developer, and the following chemical formula (3) as a phase separation controlling material having liquid crystallinity.
0.3 parts by weight of the compound represented by 0) was blended and dissolved in chloroform to obtain a uniform solution. This solution was cast on a glass substrate having a thickness of 1.5 mm,
An amorphous film having a film thickness of about 10 μm was formed. A photocurable epoxy resin was applied on the amorphous film and then photocured to form a protective film having a thickness of 1 μm. After pressing a hot roll over the entire surface of this protective film, the amorphous thin film was crystallized to white by allowing it to cool naturally at room temperature.

[0142]

Embedded image

The same thermal head as in Example 1 was used for the obtained thermal recording medium, and heating printing was carried out with an applied voltage of 12 V and a pulse width of 0.8 msec. As a result, the printed portion was colored blue and positive type recording was performed.
Next, the same thermal head was used for the heat-sensitive recording medium after recording, the applied voltage was 10 V, and the pulse width was 1.5 msec.
When the entire surface was heated in sequence, the printed area returned to white crystalline and was erased. Separately from this, a hot stamper is applied to the entire surface of the thermal recording medium after recording by 0.1
When pressed for two seconds and left at room temperature, the printed part again returned to white crystalline and was erased. Even if the same recording / erasing was performed for 100 cycles, the display did not deteriorate. In addition, no change was observed in the printed state even after left at 30 ° C. for 1 year.

[0144]

As described above in detail, according to the present invention, it is possible to provide a rewritable thermal recording medium which has a high recording / erasing speed and has sufficient thermal stability of recording. Such a rewritable thermal recording medium of the present invention can be applied to rewritable recording media such as thermal paper and cards,
Its industrial value is immense.

[Brief description of drawings]

FIG. 1 is a thermal characteristic diagram of a composition system in a rewritable thermal recording medium of the present invention.

FIG. 2 is a characteristic diagram showing a state change of a composition system in the rewritable thermal recording medium of the present invention.

FIG. 3 is a characteristic diagram showing a state change of another composition system in the rewritable thermal recording medium of the present invention.

FIG. 4 is a characteristic diagram showing a state change of still another composition system in the rewritable thermosensitive recording medium of the present invention.

FIG. 5 is a longitudinal sectional view showing an example of a rewritable thermal recording medium of the present invention.

[Explanation of symbols]

 1 ... Glass substrate 2 ... Recording layer 3 ... Protective film

Claims (15)

[Claims] 1. A rewritable thermosensitive recording medium comprising a recording material comprising a composition system containing at least a color-developing compound and a color developer, wherein the color developer has a plurality of ring structures each having a single bond, a vinylene bond, One kind of polycyclic structure selected from a non-condensed polycyclic structure and a condensed polycyclic structure bonded via any of ethynylene bonds, and substituents respectively introduced into the ring structures at both ends of the polycyclic structure A rewritable heat-sensitive recording medium having a molecular skeleton provided with and at least one of the substituents is an organic group having a hydrocarbon chain. 2. The rewritable heat-sensitive recording medium according to claim 1, wherein the substituent introduced into the color developer has an acidic group or a basic group. 3. The rewritable heat-sensitive recording medium according to claim 1, wherein the developer is a compound represented by the following general formula (1). Embedded image (In the formula, Ar is a single bond having a plurality of ring structures, a vinylene bond,
A non-fused polycyclic structure or a fused polycyclic structure bonded through any of ethynylene bonds, X is an ether bond, a thioether bond, an ester bond or an amide bond, Y is an acidic group, R is a substituted or unsubstituted alkyl group, Alkenyl group or alkynyl group, m is an integer from 1 to 3, n is 0 or 1
Is an integer. ) 4. The rewritable thermal recording medium according to claim 3, wherein the compound represented by the general formula (1) is a compound capable of forming a liquid crystal phase. 5. R of the compound represented by the above general formula (1)
Is a branched hydrocarbon group, and the rewritable thermosensitive recording medium according to claim 3. 6. A rewritable thermosensitive recording medium comprising a recording material containing a composition system containing at least a color-developing compound and a color developer, wherein the color developer is a compound capable of forming a liquid crystal phase. Rewritable thermal recording medium. 7. The rewritable thermosensitive recording medium according to claim 6, wherein the developer is a compound that forms a liquid crystal phase at 25 ° C. or higher. 8. A rewritable thermosensitive recording medium comprising a recording material comprising a composition system containing at least a color-forming compound, a color developer and a matrix agent, wherein the matrix agent is a compound capable of forming a liquid crystal phase. A rewritable thermosensitive recording medium characterized by: 9. The rewritable thermal recording medium according to claim 8, wherein the matrix agent is a compound capable of forming a liquid crystal phase at 25 ° C. or higher. 10. The rewritable thermosensitive recording medium according to claim 9, wherein the matrix agent is a compound capable of forming a liquid crystal phase at 60 to 200 ° C. 11. The rewritable thermosensitive recording medium according to claim 8, wherein the matrix agent is a compound having a steroid skeleton. 12. The recording / erasing of information is performed based on at least one of reversible crystalline-amorphous transition of composition system and change of phase separation state. The rewritable thermosensitive recording medium according to claim 8. 13. Information is recorded / erased based on a reversible change in the phase separation state of a composition system containing at least a color-developing compound, a color developer and a phase separation control agent having an action of increasing the phase separation rate. A rewritable heat-sensitive recording medium, wherein the phase separation controlling agent is a compound capable of forming a liquid crystal phase. 14. Recording of information based on a reversible change in phase separation state of a composition system containing at least a color-developing compound, a color developer, a matrix agent and a phase separation controlling agent having an action of increasing the phase separation rate. A rewritable heat-sensitive recording medium which is erased, wherein the phase separation control agent is a compound capable of forming a liquid crystal phase. 15. The rewritable thermosensitive recording medium according to claim 13, wherein the phase separation controlling agent is a compound which forms a liquid crystal phase at 25 ° C. or higher.