JP2000085250A - Erasable image forming material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly rewrite and to improve thermal stability of recording or erasing state by incorporating a substituent polymerizable with a developer and preparing an erasable image forming material containing a chromogenic compound and the developer. SOLUTION: The erasable image forming material comprises a chromogenic compound and a developer, thereby becoming a coloring state when an interaction of the compound and the developer is increased or becoming an erasing state when the interaction is decreased. In this case, the developer is contained with a polymerizable substitutent and prepared to perform a rapid rewriting, and the erasing state is irreversibly immobilized. The developer has a monocyclic aromatic ring structure and a ring structure of a non-condensed polycyclic structure in which a plurality of ring structures are bonded via a single bond, a vinylene bond or the like or a condensed polycyclic structure and substituents introduced to both ends of the ring structure in such a manner that the one of the substituents is a polymerizable substituent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming material which is rewritable and irreversibly erasable.

[0002]

2. Description of the Related Art In recent years, as office automation has become widespread, the amount of various types of information has increased remarkably, and the output of information has increased accordingly. The output of information is represented by a display output and a hard copy output to paper by a printer. Display output requires a large-scale circuit board in the display unit, and therefore has a problem in terms of portability and cost. On the other hand, the hard copy output is the most basic information display means and has excellent versatility and storability. However, in the case of hard copy output, as information increases, a large amount of paper is used as a recording medium, which leads to an increase in the cutting of wood used as a raw material for paper. Forest resources are very important in terms of maintaining the global environment and controlling the greenhouse effect of carbon dioxide. For this reason, it has become a major issue to minimize the cutting of new timber and to make efficient use of the existing paper resources. Conventionally, paper resources have been reused by treating paper on which image forming materials have been printed with a large amount of bleach and water, and re-making the paper fibers to produce recycled paper of poor quality. Have been done. Such a method not only increases the cost of recycled paper, but also causes new environmental pollution associated with the treatment of waste liquid.

On the other hand, a medium such as a card coated with a rewritable (rewritable) material has been studied. In such a rewritable medium, information can be rewritten many times on the same medium, so that the consumption of paper resources can be suppressed. As a material for a rewritable recording medium, a composition containing a color former such as a leuco dye and a developer such as various acids, and using a crystalline-amorphous transition to produce a color / decoloration is widely used. Are being considered. However, conventionally known rewritable materials have problems in that it is difficult to increase the recording / erasing speed, and it is difficult to form an amorphous state and maintain a stable state. On the other hand, the present inventors reported in Japanese Patent Application No. 7-37001 that the composition containing a coloring compound and a color developer had a crystalline-amorphous transition or a reversible change in a phase separation state. It has been found that these problems can be solved by using a reversible agent having an effect, for example, a sterol compound or a phase separation controlling agent for controlling a phase separation rate.

[0004] Such a rewritable material is generally used by being applied to a portion of a medium where rewritable characteristics are to be imparted. Further, at places where it is not necessary to rewrite information on the medium, characters and the like are printed with a normal image forming material (ink or toner). For this reason, the number of reuses of such a medium is limited to the number of rewrites of the rewritable material. Further, since an ordinary image forming material and a rewritable material are mixed on a medium, an effective recycling method has not been established. For this reason, most media must be incinerated, which is not preferable in terms of environmental protection. Further, when printing on a medium using a rewritable material as an image forming material instead of applying the rewritable material on the medium, there may be a problem that the rewritable material cannot be completely erased. For example, even if confidential information is printed using a rewritable material and then erased, the color can be changed to a colored state again, which makes it difficult to maintain confidentiality.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming material which can be rewritten at a high speed, has sufficient thermal stability in a recorded or erased state, and can be finally irreversibly erased. Is to do.

[0006]

The erasable image-forming material of the present invention is an erasable image-forming material containing a color former and a color developer, wherein the color developer is a polymerizable substitution material. Having a group.

Another erasable image forming material of the present invention is:
It contains a color former, a color developer, and a reversible agent having an effect of affecting the reversible change of the composition system, and the reversible agent is a compound having a polymerizable substituent.

[0008] Still another erasable image forming material of the present invention comprises a color former, a color developer, and a phase separation controlling agent having an effect of increasing the phase separation speed of the composition system. The agent is a compound having a polymerizable substituent. In the present invention, the developer, the reversible agent or the phase separation controlling agent is preferably a compound capable of forming a liquid crystal phase at room temperature (25 ° C.) or higher.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. First, the basic principle of the erasable image forming material of the present invention will be described. Generally, a color-forming compound is a compound corresponding to a precursor of a coloring matter that exhibits a colored state, and a developer is used to transfer electrons or protons with the color-forming compound to form the color-forming compound. Compound. A composition system containing a color former and a developer becomes a colored state when the interaction between the color former and the developer increases, and disappears when the interaction between the color former and the developer decreases. It becomes a color state.

[0010] The erasable image-forming material of the present invention comprises a crystallographic or thermodynamic state change of a composition system containing a color former and a developer, specifically, a reversible crystalline-non-crystalline material. It exhibits rewritable characteristics that can repeat coloring and decoloring by controlling the interaction between a color former and a color developer based on a change in crystallinity transition or phase separation state.

In the present invention, since the developer, reversible agent or phase separation controlling agent has a polymerizable substituent, if the developer, reversible agent or phase separation controlling agent is polymerized by light or heat, The decolored state can be irreversibly fixed.

The mechanism of coloring and decoloring of the image forming material according to the present invention is as follows. Here, the description will be made in accordance with the combination of the constituent components of the image forming material. (1) Two-Component System Containing a Coloring Compound and a Developer When the two-component system is rapidly cooled from a molten state to an amorphous state, the coloring compound interacts with the developer to form a color. When the temperature is increased from this state and the color developer is crystallized, the color developing compound is three-dimensionally extruded from the color developer, so that the two cannot interact with each other and the color is erased. At this time, even if an attempt is made to erase the color during the heating process, crystallization is extremely slow, which is disadvantageous. On the other hand, it is faster to crystallize by heating once to the melting point of the composition system or higher and then gradually cooling it. This two-component system develops color by the mechanism described above.
Decoloring can be repeated and shows rewritable characteristics.

When the developer is a compound capable of forming a liquid crystal phase, the developer crystallizes via a metastable liquid crystal phase having an ordered structure in a supercooled state. At this time, the coloring compound is hardly dissolved in the developer, and the coloring compound is rapidly diffused, so that the interaction between the two is rapidly lost.
Further, the color developer in the liquid crystal state is liable to undergo a state change, and the molecular orientation of the color developer is not so different between the liquid crystal phase and the crystal phase, so that the transition from the liquid crystal phase to the crystal phase occurs at high speed. Therefore, the change from the color-developed state to the decolored state can be performed at an extremely high speed.

When the liquid crystal phase is a smectic phase or a discotic phase, the interaction is further reduced and the decolorization is more completely achieved. When the liquid crystal phase is a nematic phase, diffusion is fast and the decoloring speed is further increased.

In this case, if the color developer has a polymerizable substituent, the decolorization state is achieved by polymerizing the polymerization site of the color developer by light or heat in a decolorized state in which each component is crystallized. The state can be irreversibly stabilized to eliminate rewritable characteristics.

(2) A ternary reversible agent containing a color-forming compound, a color developer and a reversible agent is a compound having the property of affecting the reversible change in the state of the composition system. Specifically, a three-component system containing a color former, a developer and a reversible agent is more reversible than a two-component system containing only a color former and a developer without a reversible agent. Change of the state is likely to occur. The reversible agent preferably has a property of preferentially dissolving the color developer in a molten state. Due to such properties of the reversible agent, it is possible to easily change the interaction between the color former and the developer, which causes color development and decoloration. As described below, the recording / erasing mode of a three-component system containing a color former, a color developer, and a reversible agent is often opposite to that of a two-component system containing no reversible agent.

When the ternary system is rapidly cooled from a molten state to be amorphous, the color former and the developer are uniformly present in the reversible agent.
After heating from this state to the melting point of the composition system or more and then gradually cooling, crystallization of the reversible agent proceeds, and the color former and the developer are segregated at the grain boundaries of the crystallized reversible agent. Interaction increases and color develops. This three-component system can repeat coloring and decoloring by the mechanism described above,
Shows rewritable characteristics.

When the reversible agent is a compound capable of forming a liquid crystal phase, the reversible agent crystallizes in a supercooled state via a metastable liquid crystal phase having an ordered structure. At this time, the coloring compound and the developing agent are less likely to be dissolved in the reversible agent, and the coloring compound and the developing agent are three-dimensionally extruded, and the two interact rapidly. In addition, a reversible agent in a liquid crystal state is liable to undergo a state change, and the molecular orientation of the reversible agent is not so different between a liquid crystal phase and a crystalline phase. Therefore, the change from the decolored state to the colored state can be performed at an extremely high speed.

In the case where the liquid crystal phase is a smectic phase or discotic phase, the coloring becomes more complete. When the liquid crystal phase is a nematic phase, the color development speed is further increased due to rapid diffusion.

In this case, if the reversible agent has a polymerizable substituent, each component is polymerized by light or heat in a decolorized state in which the components are in an amorphous state, whereby the reversible agent is polymerized. The color state can be irreversibly stabilized to eliminate rewritable characteristics.

(3) A ternary phase separation controlling agent comprising a color former, a color developer and a phase separation controlling agent is a compound having an action of increasing the phase separation speed of a composition system. The phase separation controlling agent has a lower melting point than a composition comprising a color former and a developer, or a composition comprising a color former, a developer and a reversible agent,
It is preferable that the compound be capable of dissolving one of the color former and the developer at a temperature lower than its melting point.

The three-component system includes a color former, a developer,
When the respective components of the phase separation controlling agent separate from each other, the color disappears. In this state, when heated to a temperature higher than the melting point of the composition system, the three components dissolve each other to allow the color former and the developer to interact with each other to develop color. This three-component system can repeat coloring and decoloring by the mechanism described above, and exhibits rewritable characteristics.

When the phase separation controlling agent is a compound capable of forming a liquid crystal phase, the phase separation controlling agent becomes a metastable liquid crystal phase having an ordered structure in a supercooled state, and phase separation of each component occurs. At this time, the phase separation speed of the coloring compound or the developer is promoted, and the respective components self-aggregate and are separated. Further, the phase separation controlling agent in a liquid crystal state is liable to undergo a state change, and the molecular orientation of the phase separation controlling agent is not so different between the liquid crystal phase and the phase separation state, so that phase separation occurs at high speed. Therefore, the change from the color-developed state to the decolored state can be performed at an extremely high speed.

When the liquid crystal phase is a smectic phase or a discotic phase, the interaction is further reduced, and the decoloring is more completely achieved. When the liquid crystal phase is a nematic phase, diffusion is fast and the decoloring speed is further increased.

In this case, if the phase separation controlling agent has a polymerizable substituent, the polymerization site of the phase separation controlling agent is polymerized by light or heat in a decolored state where each component is phase separated, The erasable state can be irreversibly stabilized to eliminate rewritable characteristics.

(4) A four-component system comprising a color-forming compound, a color developer, a reversible agent and a phase separation controlling agent. This four-component system is in a state where the color-forming compound and the color developer are interacting with each other. When the agent and the phase separation controlling agent are mutually phase-separated, a color is formed. When the composition is heated to a temperature equal to or higher than the melting point of the composition in this state, the components dissolve in each other and the color former and the developer are uniformly present. This four-component system can repeat coloring and decoloring by the mechanism described above, and exhibits rewritable characteristics.

For example, when the phase separation controlling agent is a compound capable of forming a liquid crystal phase, the phase separation controlling agent becomes a metastable liquid crystal phase having an ordered structure in a supercooled state, and further, phase separation of each component occurs. . At this time, the phase separation speed of the coloring compound or the developer is promoted, and the respective components self-aggregate and are separated. Further, the phase separation controlling agent in a liquid crystal state is apt to undergo a state change, and its molecular orientation is not so different between the liquid crystal phase and the phase separation state, so that phase separation occurs at high speed.
Therefore, the change from the decolored state to the colored state can be performed at an extremely high speed.

When the liquid crystal phase is a smectic phase or a discotic phase, the color development becomes more complete. When the liquid crystal phase is a nematic phase, the color development speed is further increased due to rapid diffusion.

In this case, if any one of the color developer, the reversible agent and the phase separation controlling agent has a polymerizable substituent, the light or heat is applied in a decolored state where the components are mutually dissolved. By polymerizing the polymerization site, the decolored state can be irreversibly stabilized and the rewritable property can be eliminated.

In any of the above cases, in the process of causing the state change of the composition system, the color developer, the reversible agent or the phase separation controlling agent does not necessarily need to form a liquid crystal phase, but has a high degree of order. By forming the state, the coloring / erasing speed can be increased.

Next, in the present invention, each component to be mixed in the composition system to be the recording material will be exemplified. First, generally used color developing compound, a developer, a reversible agent and a phase separation controlling agent are collectively shown, and the developer, a reversing agent or a phase separation controlling agent suitably used in the present invention is appropriately described. explain.

Examples of the color-forming compound that can be used in the present invention include electron-donating compounds such as leuco auramines, diaryl phthalides, polyaryl carbinols, acyl auramines, aryl auramines, and rhodamines. B-lactams, indolines, spiropyrans,
Fluorans, cyanine dyes and crystal violet.

Specific examples include crystal violet lactone (CVL), malachite green lactone,
-Anilino-6- (N-cyclohexyl-N-methylamino) -3-methylfluoran, 2-anilino-3-methyl-6- (N-methyl-N-propylamino) fluoran, 3- [4- ( 4-phenylaminophenyl) aminophenyl] amino-6-methyl-7-chlorofluoran, 2-anilino-6- (N-methyl-N-isobutylamino) -3-methylfluoran, 2-anilino-6
(Dibutylamino) -3-methylfluoran, 3-chloro-6- (cyclohexylamino) fluoran, 2-chloro-6- (diethylamino) fluoran, 7- (N,
N-dibenzylamino) -3- (N, N-diethylamino) fluoran, 3,6-bis (diethylamino) fluoran-γ- (4′-nitroanilino) lactam, 3-
Diethylaminobenzo [a] -fluoran, 3-diethylamino-6-methyl-7-aminofluoran, 3-diethylamino-7-xylidinofluoran, 3- (4-
Diethylamino-2-ethoxyphenyl) -3- (1-
Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylaminophenyl) -3-
(1-ethyl-2-methylindol-3-yl) phthalide, 3-diethylamino-7-chloroanilinofluoran, 3-diethylamino-7,8-benzofluoran, 3,3-bis (1-n- Butyl-2-methylindol-3-yl) phthalide, 3,6-dimethylethoxyfluoran, 3,6-diethylamino-6-methoxy-
7-aminofluoran, DEPM, ATP, ETAC,
2- (2-chloroanilino) -6-dibutylaminofluoran, 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- (phenyliminoethanedylidene) -3,3-dimethylindoline, N, 3,3
-Trimethylindolinobenzospiropyran, 8'-methoxy-N, 3,3-trimethylindolinobenzospiropyran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-methoxyfluoran, 3- Diethylamino-6-benzyloxyfluoran, 1,2-benzo-6-diethylaminofluoran, 3,6-di-p-toluidino-4,5-dimethylfluoran, phenylhydrazide-γ-lactam, 3-amino-5 -Methylfluoran and the like. These coloring compounds can be used alone or in combination of two or more. By appropriately selecting a color-forming compound, a variety of colors can be obtained, so that it is possible to cope with multi-colors.

In the present invention, the color developing agents include phenols, phenol metal salts, carboxylic acid metal salts, sulfonic acids, sulfonates, phosphoric acids, metal phosphates,
Acidic compounds such as acid phosphates, metal salts of acid phosphates, phosphorous acid, and metal salts of phosphite are exemplified. Of these, phenols and phenol metal salts are particularly preferable because they have high color density and stability in a color-developing state and can easily repeat color development and decoloration.

The developer preferably used in the present invention is a compound having a polymerizable substituent and capable of forming a liquid crystal phase at room temperature or higher. As such a developer,
A monocyclic aromatic ring structure and a ring structure selected from a non-condensed polycyclic structure and a condensed polycyclic structure in which a plurality of ring structures are bonded via a single bond, a vinylene bond, or an ethynylene bond; Compounds having a molecular skeleton having substituents introduced at both ends of the structure, and one of the substituents is a polymerizable substituent. As a more specific developer, the following general formula (1)

[0036]

Embedded image (In the formula, Ar is a non-condensed polycyclic structure or a condensed polycyclic structure in which a monocyclic aromatic ring structure or a plurality of ring structures are bonded via any of a single bond, a vinylene bond, and an ethynylene bond, and X is an ether Bond, thioether bond, ester bond or amide bond, R is a substituted or unsubstituted alkyl group, PL is a substituent having an unsaturated bond or an epoxy group, Y is an acidic group, m is an integer of 1 to 3, n is 0 Or an integer of 1).

The ring structure Ar in the compound represented by the general formula (1) may be an aromatic ring, a saturated ring, or a hetero ring. Examples of the condensed polycyclic structure include a naphthalene ring, an azulene ring, an indene ring, a biphenylene ring, an anthracene ring, a fluorene ring and a phenanthrene ring. The non-fused polycyclic structure refers to a structure in which an aromatic ring or a saturated ring is bonded via any of a single bond, a vinylene bond, and an ethynylene bond. Examples of the saturated ring include those represented by the following chemical formula (2).

[0038]

Embedded image

Such a ring structure is known as a mesogen structure for developing a thermally stable liquid crystal phase or a smectic phase having a high degree of molecular orientation in a liquid crystal compound. In order for the developer to exhibit liquid crystallinity, Ar preferably has a non-condensed polycyclic structure. From the viewpoint of obtaining a compound having a high melting point, a non-fused polycyclic structure having at least one aromatic ring is preferable. In particular, a non-condensed polycyclic structure having at least one paraphenylene ring is very preferable because it has high linearity and low polarization, and thus easily exhibits a highly ordered smectic phase. Specifically, a plurality of paraphenylene rings, or at least one
A polycyclic structure in which two paraphenylene rings and a saturated ring represented by the chemical formula (2) are bonded via any of a single bond, a vinylene bond, and an ethynylene bond. The condensed aromatic ring forms a hard core and gives a liquid crystal phase having high thermal stability. An aromatic ring containing a hetero atom tends to develop a smectic phase. Saturated rings have low thermal stability but tend to develop a liquid crystal phase with low viscosity.

In a color developer having a non-condensed polycyclic structure or a condensed polycyclic structure in which a plurality of ring structures are linked, it is important for the development of liquid crystal properties that substituents are introduced into the ring structures at both ends. . Compounds in which a substituent is introduced only into one end of the ring structure are generally difficult to exhibit liquid crystallinity.

The linking group X is selected from the group consisting of an ether bond, a thioether bond, an ester bond and an amide bond. However, the linking group X may not be present. Of these, an ether bond and a thioether bond, which are thermally stable and are not easily decomposed in the presence of moisture or the like, are particularly preferable. However, there is no particular problem with ester bonds or amide bonds, and compounds having these bonds are advantageous in that they can be easily synthesized.

R is a substituted or unsubstituted alkyl group, and preferably has 8 to 30 carbon atoms. If the hydrocarbon chain is too long, a large activation entropy will be required for the transfer, and the transfer rate will be slow. Note that the use of a perfluoroalkyl group is preferable because the thermal stability of the order of the liquid crystal phase is improved.

PL is a substituent having an unsaturated bond or an epoxy group. PL may be a substituent consisting of a linking group such as an ester bond and an unsaturated bond or an epoxy group. Vinyl group, allyl group, 1-propenyl group, isopropenyl group, 1-butenyl group, 2-methylallyl group, ethynyl group, 2-propynyl group, styryl group, cinnamyl group, benzylidene group, acryloyl group, methacryloyl group, acryloyloxy Group, methacryloyloxy group, crotonoyl group, isocrotonoyl group, sorboyl group, 1,2-epoxyethyl group, 1,2-epoxypropyl group, 1,2
-Epoxybutyl group, 1-methyl-1,2-epoxyethyl group and the like.

Y is an acidic group. Since the color developer in the present invention is preferably a phenol, Y is preferably a phenolic hydroxyl group. Y may be an acidic group consisting of a phenol and a linking group such as an ester bond. Y may be a phosphate group, a sulfonic group, or the like.

Suitable developers having the above structure include hydroxybiphenyl derivatives, gallic acid derivatives, gallic acid ester derivatives, dihydroxyphenyl alkyl ketone derivatives, dihydroxybenzoic acid derivatives, dihydroxybenzoic acid derivatives. Ester derivatives and the like.

It is desirable that the reversible agent used in the present invention can easily form an amorphous material having good colorlessness.
That is, by selecting an appropriate reversible agent, a colorless and transparent amorphous state and a colored and opaque crystalline state can be formed. The more the reversible agent is amorphous and colorless and transparent, the higher the contrast ratio between the printed portion and the background, and the easier it is to use the background display. In this respect, a sterol compound is preferable as the reversible agent. Specifically, cholesterol, stegmasterol, pregnenolone, methylandrostenediol, estradiol benzoate, epiandrostene, stenolone, β-sitosterol, pregnenolone acetate, 5,16-pregnadiene-3β-ol-20-one, 5α-pregnene -3β-ol-20-one, 5-pregnene-3
β, 17-diol-20-one 21-acetate, 5
-Pregnene-3β, 17-diol-20-one 1
7-acetate, 5-pregnene-3β, 21-diol-20-one 21-acetate, 5-pregnene-
3β, 17-diol diacetate, locogenin, tigogenin, esmilagenin, hecogenin, 1,2,5
Sterol compounds having a skeleton such as 6-diisopropylidene-D-mannitol. These reversible agents can be used alone or in combination of two or more. Also, a compound in which a plurality of alkyl groups are introduced into a rigid aromatic ring forming a discotic phase as a reversible agent,
A compound having a rigid mesogen group forming a smectic phase or a nematic phase and a flexible hydrocarbon chain may be used.

The reversible agent suitably used in the present invention is a compound having a polymerizable substituent and capable of forming a liquid crystal phase at room temperature or higher. Specifically, as described in relation to the general formula (1), a sterol compound having cholesteric liquid crystallinity is substituted with a substituted or unsubstituted alkyl group (R) and an unsaturated bond or an epoxy group. And a substituent (PL) having the substituent is introduced.

The phase separation controlling agent used in the present invention includes a hydrocarbon group having 8 or more carbon atoms and a hydroxyl group in the molecule;
An organic low molecular weight compound having high crystallinity and having a polar group such as a carbonyl group, an ester group, and a carboxyl group is preferred. For example, linear higher alcohol, linear higher polyhydric alcohol, linear higher fatty acid, linear higher polyvalent fatty acid, esters and ethers thereof, linear higher ketone, linear higher fatty acid amide, linear higher polyfatty acid amide Is mentioned. Specifically, 1-docosanol, 1-tetracosanol, 1
Linear higher monohydric alcohols such as hexacosanol and 1-octacosanol; 1,12-dodecanediol,
14-tetradecanediol, 1,15-pentadecanediol, 1,16-hexadecanediol, 1,17
-Heptadecanediol, 1,18-octadecanediol, 1,19-nonadecanediol, 1,20-eicosandiol, 1,21-heneicosandiol,
1,22-docosanediol, 1,23-trichosanediol, 1,24-tetracosanediol, 1,12-
Straight-chain higher polyhydric alcohols such as octadecanediol, 1,2-tetradecanediol and 1,2-hexadecanediol; straight-chain polyhydric alcohols such as behenic acid, 1-docosanoic acid, 1-tetracosanoic acid, 1-hexacosanoic acid and 1-octacosanoic acid; Linear higher fatty acids such as dodecane diacid, 1,12-dodecane dicarboxylic acid; linear higher ketones such as stearone; direct fatty acids such as stearic acid isopropanolamide, behenic acid isopropanolamide and behenic acid hexanolamide. Chain higher fatty acid alcohol amides; linear higher fatty acid diol diesters such as ethylene glycol laurate diester, catechol laurate diester, and cyclohexanediol laurate diester. These can be used alone or in combination of two or more. Some of ester waxes, alcohol waxes, and urethane waxes can be used as a phase separation controlling agent.

The phase separation controlling agent suitably used in the present invention is a compound having a polymerizable substituent. Specifically, in the above, the phase separation controlling agent is represented by the general formula (1)
As described in connection with (1), those in which a substituted or unsubstituted alkyl group (R) and a substituent (PL) having an unsaturated bond or an epoxy group are introduced.

The phase separation controlling agent suitably used in the present invention is a compound having a polymerizable substituent and capable of forming a liquid crystal phase at room temperature or higher. As such a phase separation controlling agent, the following general formula (3)

[0051]

Embedded image (In the formula, Ar is a non-condensed polycyclic structure or a condensed polycyclic structure in which a monocyclic aromatic ring structure or a plurality of ring structures are bonded via any of a single bond, a vinylene bond, and an ethynylene bond, and X is an ether Bond, thioether bond, ester bond or amide bond, R is a substituted or unsubstituted alkyl group, PL is a substituent having an unsaturated bond or an epoxy group, Z is a neutral polar group, m is an integer of 1-3, n Is an integer of 0 or 1.).

In the image forming material of the present invention, the crystallization temperature Tc at which the crystallization of the amorphous phase proceeds varies depending on the heating rate, but is in the temperature range between the glass transition temperature Tg and the melting point Tm. When the glass transition temperature Tg is low and close to room temperature,
A slight rise in the environmental temperature tends to promote phase separation and crystallization due to the diffusion of the coloring compound and the developer, and the thermal stability of recording tends to decrease. Therefore, the glass transition temperature Tg of the image forming material of the present invention is preferably 25 ° C. or more, more preferably 50 ° C. or more. On the other hand, if the glass transition temperature Tg of the image forming material is too high, large heat energy is required for recording and erasing information, which is disadvantageous in terms of energy saving. Therefore, the glass transition temperature Tg of the image forming material of the present invention is preferably 150 ° C. or lower. This standard is applied to each component constituting the image forming material of the present invention.

In consideration of the above points, the coloring compound is also
Large molecular weight and change in melting enthalpy per weight Δ
Preferably, H is small. For example, a color-forming compound having a bulky molecular skeleton close to a sphere or a polyvalent hydrogen-bonding low-coloring compound capable of forming a hydrogen bond between molecules is preferable. However, by utilizing this in reverse, for example, if an image forming material having a glass transition temperature Tg close to room temperature is used, the recorded information can be naturally erased after being stored for a desired period. . Further, the glass transition temperature T
By using an image forming material having a low g, for example, when a product requiring refrigeration is refrigerated, a color is generated when the temperature temporarily rises due to a failure of the refrigerator or the like. The rise can be recorded.

In the present invention, in the composition system containing the color former and the developer but not containing the reversible agent, the compounding ratio of the color former to the developer is 1 part by weight of the color former. It is preferable to set the amount of the developer to 0.1 to 100 parts by weight, more preferably 1 to 10 parts by weight. If the developer is less than 0.1 parts by weight, it is difficult to sufficiently increase the interaction between the color former and the developer during recording or erasing. Conversely, when the amount of the developer exceeds 100 parts by weight, the color density in the color-developing state tends to decrease.

In a composition system containing a color former, a developer and a reversible agent, the compounding ratio of the color former to the developer is as follows:
It is preferable to set the color developer to 0.1 to 10 parts by weight, more preferably 1 to 2 parts by weight, per 1 part by weight of the color former.
If the developer is less than 0.1 parts by weight, it is difficult to sufficiently increase the interaction between the color former and the developer during recording or erasing. Conversely, if the developer exceeds 10 parts by weight,
It becomes difficult to sufficiently reduce the interaction between the color former and the developer during recording or erasing. The mixing ratio of the reversible agent is preferably set to 1 to 200 parts by weight, more preferably 10 to 100 parts by weight, based on 1 part by weight of the coloring compound. When the amount of the reversible agent is less than 1 part by weight, it is difficult to cause a crystalline-amorphous transition or a change in a phase separation state of the composition system. When the amount of the reversible agent exceeds 200 parts by weight, the color density in the color-developing state tends to decrease.

The mixing ratio of the phase separation controlling agent in the present invention is as follows:
It is preferably 0.1 to 100 parts by weight, more preferably 1 to 50 parts by weight, per 1 part by weight of the coloring compound. When the amount of the phase separation controlling agent is less than 0.1 part by weight, the effect of increasing the phase separation speed of the composition system is hardly obtained. 100 phase separation controlling agent
If the amount exceeds the weight part, the non-equilibrium state of the composition system becomes unstable, and the thermal stability of recording may decrease.

In the erasable image forming material of the present invention, a polymerization initiator, a wax, a binder and the like may be appropriately compounded as components other than the color former, the developer, the reversible agent and the phase separation controlling agent. Good.

In the present invention, in order to eliminate the rewritable property of the image forming material and completely erase the image, the temperature is raised to a temperature at which the image forming material is erased, and then the polymerizable substituent is polymerized to erase the image. Stabilizes the state irreversibly. At this time, the polymerizable substituent does not polymerize in the color-developed state,
It is necessary to control the polymerization in the decolored state. From the mechanism described above, the temperature at which the polymerizable substituent is polymerized is, in the composition system (1), not less than the crystallization temperature of the color developer and not more than the melting point, in the composition system (2), not less than the melting point of the reversible agent, and (3) In the composition system of (1), the temperature is higher than the temperature at which each component is phase-separated and lower than the temperature at which each component is compatible.

In the composition system of (2) or (4), a compound which has catalytic activity at a temperature higher than the melting point of the reversible agent or at a temperature higher than the temperature at which each component is compatible as a polymerization initiator and does not make the composition system acidic is used. Preferred polymerization initiators include inorganic or organic basic compounds and organic phosphine compounds.

Suitable inorganic basic compounds include calcium chloride, potassium hydroxide, calcium hydroxide, sodium hydroxide, barium hydroxide, magnesium hydroxide, ammonium carbonate, potassium carbonate, calcium carbonate, sodium carbonate, magnesium carbonate, Examples include ammonium bicarbonate, potassium bicarbonate, sodium bicarbonate, borates of alkali metals, tripotassium phosphate, dipotassium hydrogenphosphate, calcium phosphate, trisodium phosphate and disodium hydrogenphosphate.

Suitable organic basic compounds include primary to tertiary amines and quaternary ammonium salts.
Examples of the counter ion of the quaternary ammonium salt include a hydroxyl ion, a halogen ion, and an alkoxide ion.

The non-aromatic organic basic compound includes
An aliphatic hydrocarbon group having 1 to 50 carbon atoms or 1 carbon atom;
Those having from 50 to 50 alicyclic hydrocarbon groups are exemplified.
These hydrocarbon groups include vinyl, ethynylene, ethynyl, oxy, oxycarbonyl, thiocarbonyl, dithiocarbonyl, thio, sulfinyl,
At least one substitution selected from a sulfonyl group, a carbonyl group, a hydrazo group, an azo group, an azide group, a nitrile group, a diazoamino group, an imino group, a urea bond, a thiourea bond, an amide bond, a urethane bond, and a carbonyldioxy group May be substituted with a group.

Examples of the aromatic organic basic compound include a benzene ring, a biphenyl ring, a naphthalene ring, a tetralone ring, an anthracene ring, a phenanthrene ring, an indene ring,
Those having an aromatic ring such as an indane ring, a pentalene ring, an azulene ring, a heptalene ring and a fluorene ring are exemplified. These aromatic rings may be substituted with an aliphatic hydrocarbon group having 1 to 50 carbon atoms or an alicyclic hydrocarbon group having 1 to 50 carbon atoms. Further, these hydrocarbon groups may be substituted with the substituents described above.

As the cyclic amine, aziridine, azetidine, pyrroline, pyrrolidine, indoline, pyridine,
Piperidine, hydropyridine, quinoline, isoquinoline, tetrahydroquinoline, tetrahydroisoquinoline, acridine, phenanthridine, phenanthroline, pyrazole, benzimidazole, pyridazine, pyrimidine, pyrazine, imidazole, histamine, decahydroquinoline, pyrazoline, imidazoline, imidazolidine, piperazine , Cinnoline, phthalazine, quinazoline, quinosaline, dihydrophenazine, triazole, benzotriazole, triazine, tetrazole,
Pentamethylenetetrazole, tetrazine, purine, pteridine, carboline, naphthyridine, indolizine,
Quinolidine, quinuclidine, oxazole, oxazolidine, benzoxazole, isoxazole, anthranyl, oxazine, oxazoline, thiazole, thiazolidine, benzothiazole, benzothiazoline, isothiazole, thiazine, azoxime, furazane, oxadiazine, thiadiazole, benzothiadiazole, thiadiazine, dithiazine, Examples include morpholine, hexamethylenetetramine, diazabicycloundecene and the like.

Other basic compounds that can be used include alkali metal salts of alcohols, alkaline earth metal salts of alcohols, amidine, guanidine, aminoguanidine, urea, thiourea, semicarbazide, thiosemicarbazide, carbonohydrazide. Is mentioned.

Examples of the organic phosphine compound include trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenyl) phosphine, methyldiphenylphosphine, dibutylphenylphosphine, tricyclohexylphosphine, and the like. Examples thereof include 1,2-bis (diphenylphosphine) ethane and bis (diphenylphosphine) methane.

These polymerization initiators may be directly mixed with other components of the image forming material. Further, the polymerization initiator may be mixed with other components of the image forming material while being encapsulated in the microcapsules.

As the shell material of the microcapsule,
Polyether sulfone, polyether ketone, epoxy resin, polyethylene, polypropylene, polyphenylene ether, polyphenylene sulfite, polyalkylene oxide, polystyrene, polyphenol ether, nylon, polyamide, polyurethane, gelatin,
Polymethacrylic acid, polyimide, melamine resin, polyester, polyacrylic acid, polyvinyl alcohol, polyacrylonitrile, polymethacrylonitrile, polysiloxane, polysulfide, polyvinyl acetate, nitrocellulose, methylcellulose, acetylcellulose, ethylcellulose, gum arabic, polyvinylpyrrolidone, Polycarbonate, polysulfone, polyisocyanate, polypyrrole, chitosan, collagen, polyamino acid and the like can be mentioned. These may be used alone or as a mixture. Further, these copolymers may be used.

The physical properties required of the microcapsule material are that when heated to a temperature higher than the temperature at which the image forming material loses color, the microcapsule material is broken and releases the encapsulated polymerization initiator. The temperature at which microcapsules break is 12
The temperature is preferably from 0 to 200 ° C. The particle size of the microcapsules varies depending on the use of the image forming material, but in the case of toner, printing ink, heat transfer material,
5 μm, in the case of ink for an ink jet printer,
Since it is necessary to reduce the size of the nozzle to 100 or less,
000 nm. The addition amount of microcapsules is 1 to
It is preferably 30 wt%, more preferably 1 to 15 wt%.

In the composition system (1) or (3) described above, the temperature at which the image forming material develops a color is higher than the temperature at which the color is erased. Polymerization may proceed and lose rewritable properties. Therefore, in the case of these composition systems, it is preferable to use a photopolymerization initiator which exhibits catalytic activity by light. Since the photopolymerization initiator is thermally stable and does not show catalytic activity (shows potential) before irradiation with light, the rewritable characteristics are not impaired.

The photopolymerization initiator is not particularly limited as long as it does not involve acid generation. Specifically, acetophenone, trichloroacetophenone, 2,2-diethoxyacetophenone, α, α-dimethoxy-α-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4′-isopropyl-2 −
Methyl propiophenone, α, α-dimethoxy-α-morpholino-methylthiophenylacetone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoylphosphine oxide, diethoxyacetophenone, 2-hydroxy-2-methyl-1 -Phenylpropan-1-one, benzophenone, Michler's ketone analog, o-benzoyl-methylbenzoate, chlorine-substituted benzophenone, halogen-substituted alkyl-aryl ketone, xanthone, thioxanthon, chlorothioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, -Methylthioxanthone, 2-ethylthioxanthone, quinone, thioacridone, benzoin, benzyl, isobutyl benzoin ether, isopropyl benzoin ether Le, benzoin ethyl ether, benzoin methyl ether, 1-phenyl-1,2
-Propanedione-2- (o-ethoxycarbonyl) oxime, 2-ethylanthraquinone, methylbenzoyl formate and analogs thereof.

Other than the above, there is a combination of a radical generator and a sensitizer. For example, a combination of a peroxyacid ester with a sensitizer such as an aromatic amine, a xanthene dye, a merocyanine dye, a quinoline dye, a coumarin dye, or a ketocoumarin dye is exemplified. Bisimidazole also generates active radicals in combination with a sensitizer. Further, a combination of a tris (trichloromethyl) -s-triazine derivative and an aromatic amine such as a dimethylaniline derivative also shows an efficient catalytic action. These photopolymerization initiators can also be used in the composition system of (2) or (4). The addition amount of the photopolymerization initiator is 0.2 to 20 wt%, and further 1 to 10 w
It is preferably t%.

The wax that can be used in the present invention is not particularly limited as long as it has an acid value of 10 or less, more preferably 5 or less. For example, a long-chain aliphatic alcohol having 10 or more carbon atoms, a long-chain aliphatic ketone having 10 or more carbon atoms, low-molecular-weight polypropylene, low-molecular-weight polyethylene, low-molecular-weight polybutylene, low-molecular-weight polyalkane, or a modified product thereof is used as it is. be able to.
These waxes may be used alone or as a mixture of a plurality of waxes. The weight average molecular weight of the wax is 10
^{2-10 5,} more preferably a 10 ² to 10 ^4.

Aliphatic carboxylic acid wax represented by stearic acid wax, carnauba wax containing fatty acid,
Rice wax containing free carboxylic acid as ester of higher fatty acid and higher alcohol, montan wax containing polymer wax acid in coal-based synthetic wax, acid amide,
Liquid paraffin, sasol wax, castor wax, chlorinated paraffin and the like have an acid value, but these can be used if the saponified acid value is lowered with calcium hydroxide. The acid value may be adjusted by adding a basic compound.

The binder resin that can be used in the present invention includes a copolymer of styrene and its derivatives and an acrylic resin. As a copolymer of styrene and its derivatives, polystyrene homopolymer,
Hydrogenated styrene resin, styrene-isobutylene copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene terpolymer, acrylonitrile-styrene-acrylic ester terpolymer, styrene-acrylonitrile copolymer, Acrylonitrile
Acrylic rubber-styrene terpolymer, acrylonitrile-chlorinated styrene-styrene terpolymer, acrylonitrile-EVA-styrene terpolymer, styrene-
p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene rubber, styrene-maleic acid ester copolymer, styrene-maleic anhydride copolymer and the like. As the acrylic resin, polyacrylate, polymethyl methacrylate, polyethyl methacrylate, poly-n-butyl methacrylate, polyglycidyl methacrylate, polyfluorinated acrylate, styrene-methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-acryl Ethyl acid copolymer and the like.

In addition, chlorinated polyethylene, polyvinyl acetate, ethylene-vinyl acetate copolymer, ethylene-acrylic acid-maleic anhydride copolymer, polyethylene, polypropylene, polybutadiene, polyester (polyethylene terephthalate, polybutylene terephthalate, polyethylene na Phthalate), polyisobutylene, polyurethane, polyamide, polyvinyl chloride, natural rubber, polyvinylidene chloride, epoxy resin, urea resin, polyvinyl butyral, rosin, modified rosin, terpene resin, aliphatic or alicyclic hydrocarbon resin, aromatic Petroleum resins, chlorinated paraffins, paraffin waxes and the like can be used alone or as a mixture. In some cases, the oxidized resin interacts with the color-forming compound to form a color, so that the basic compound is reduced to reduce the acid value, so that the pH value of the material as a whole becomes 7 or more. It is desirable to adjust to.

The image forming material of the present invention can be printed on a medium such as paper in the same manner as a usual image forming material. In this case, a method is considered in which a part that does not need to be rewritten and a part that requires a relable characteristic are used separately. Characters and the like are printed with a color-developed image forming material in places where rewriting is not necessary. An image forming material is printed on the entire surface where the relability property is required, and coloring and decoloring are repeated by a heating means such as a thermal head. Further, any portion of the image forming material can be completely erased by polymerizing a polymerizable substituent. Such a medium exhibits rewritable characteristics and can be completely erased with only one type of image forming material, and thus can be easily reused and recycled.

The image forming material of the present invention can be used as a recording medium by coating on an arbitrary medium. In this case, a recording medium can be produced by a method in which a composition containing a predetermined component is melted without solvent, mixed and applied onto a medium, and then quenched or allowed to cool. At this time, a desired shape can be obtained by molding the melt in a mold, and a thin film can be obtained by stretching the melt thinly. Alternatively, the composition can be formed into a thin film by dissolving the composition in an appropriate solvent and casting. The thickness of the thin film is preferably 0.5 to 50 μm. If the thickness of the thin film is too thin, the image density of the recording medium in the color developing state may be insufficient. If the thickness of the thin film is too large, large heat energy is required at the time of coloring and decoloring, making it difficult to form and decolor at high speed.

As the substrate of the recording medium, polyvinyl alcohol, polyvinyl acetal, polyvinyl butyral, ethylene tetrafluoride copolymer (for example, ethylene tetrafluoride resin, ethylene trifluoride resin, ethylene / propylene resin, vinylidene fluoride) Resin, vinyl fluoride resin, tetrafluoroethylene / perfluoroalkoxyethylene copolymer, ethylene tetrafluoride / perfluoroalkyl vinyl ether copolymer, ethylene tetrafluoride / propylene hexafluoro copolymer, tetrafluoroethylene・ Ethylene copolymer, etc., fluororesin (eg, fluorine-containing polybenzoxazole), acrylic resin, methacrylic resin, polyacrylonitrile, acrylonitrile copolymer (eg, acrylonitrile / butadiene / styrene copolymer), polystyrene, Len-acrylonitrile copolymer, acetal resin, polyamide (for example, nylon 66), polycarbonate, polyester carbonate, cellulose resin, phenol resin, urea resin, epoxy resin, unsaturated polyester resin, alkyd resin, melamine resin, polyurethane, diaryl phthalate resin , Polyphenylene oxide, polyphenylene sulfide, polysulfone, polyphenylsulfone, silicone resin, polyimide, bismaleimide triazine resin, polyimide amide, polyetherimide, polyvinyl carbazole, norbornene-based amorphous polyolefin, and the like. In addition, celluloses and neutral paper can easily penetrate a composition comprising a relatively large number of color-forming compounds, a developer and a reversible agent, and have a high image density during color development and a high reflection density during decoloration. It is preferable because of its low point.

Among the above-mentioned substrate materials, those having an acid value may interact with a color-forming compound to develop an irreversible color in some cases. Therefore, a basic compound is added to reduce the acid value. It is preferable to adjust the pH value of the whole material to be 7 or more before use.

In the present invention, from the viewpoint of improving strength,
The image forming material may be carried on a suitable medium. Specifically, microencapsulation, impregnation in a porous medium composed of a polymer or an inorganic compound, dispersion in a binder polymer, dispersion in an inorganic glass, layered material (mica, clay mineral,
Talc, green stone, etc.). In a form in which microcapsules are prepared and applied on a substrate as an ink or a paint, it is easy to handle colors by using different coloring compounds for each microcapsule.
As the material for the microcapsules, the above-described materials can be used. The particle size of the microcapsules is also adjusted based on the same criteria as described above. Sol-based inorganic glass
There is no particular limitation as long as it can be produced by the gel method,
Those having a gelling temperature not so high are preferred.

In order to develop and decolor a recording medium using the image forming material of the present invention as a rewritable material, it is necessary to supply binary thermal energy having different magnitudes from each other.
Alternatively, two types of heat histories having different cooling rates after heating to a temperature equal to or higher than the melting point Tm are supplied. In order to supply thermal energy at the time of color development, it is preferable to use a heat source such as a thermal head (for example, TPH) or a laser beam. Among them, the thermal head is not so high in resolution, but can heat the image forming material over a large area, and is advantageous in miniaturizing the apparatus. On the other hand, laser light
By reducing the spot diameter, it is preferable because it is easy to cope with high-density recording, and furthermore, the coloring and decoloring speed can be increased. However, when laser light is used, a light absorbing layer having an absorption band at the wavelength of the laser light may be provided in order to efficiently absorb the laser light even for an amorphous composition having a good light-transmitting property. Alternatively, it is desirable to compound a compound having an absorption band at the wavelength of laser light into the composition. In the recording medium using the image forming material of the present invention, a protective film may be provided as necessary. The thickness of the protective film is 0.1
It is preferably about 100 μm. As the material of the protective film, wax, thermoplastic resin, thermosetting resin, photocurable resin, or the like is used. On the other hand, at the time of decoloring, it is preferable to use a heat source such as a hot stamper or a heat roll that can heat the entire recording medium at once. When the heated recording medium is cooled, the recording medium may be naturally cooled, but is preferably rapidly cooled using a cold stamper, a cold roll, a cold air flow, or a Peltier element. Further, in the recording medium of the present invention, overwrite recording is also possible by using a plurality of thermal heads having different energies or a plurality of laser beams having different spot diameters.

[0083]

Embodiments of the present invention will be described below. Example 1 A recording layer, a gelatin layer, a protective layer, and a lubricating layer were formed on a glass substrate in the following manner to produce a recording medium. Each of these layers was formed by casting a solution or dispersion and then drying.

1.0 part by weight of crystal violet lactone (CVL) as a color-forming compound and 2.0 parts by weight of a biphenyl derivative represented by the chemical formula (3) as a color developer were mixed, and 5 wt% of diethoxyacetophenone was added. After the addition, it was dissolved in methylene chloride to prepare a homogeneous solution.

[0085]

Embedded image

This solution was cast on a glass substrate having a thickness of 1.5 mm to form a recording layer having a thickness of about 10 μm. Next, gelatin / polyvinyl alcohol (weight ratio: 6:
4) A 10 wt% aqueous solution of the mixture was prepared. This solution was applied on the recording layer and dried to form a gelatin layer having a thickness of 0.2 μm. Next, the polyether sulfide was dissolved in a mixed solution of methyl ethyl ketone / dimethylformamide (1: 4), and mica was added to prepare a dispersion. This dispersion was coated on the above gelatin layer and dried to form a film having a thickness of 0.
A 2 μm protective layer was formed. Further, a silicone acrylate resin was dissolved in methyl ethyl ketone to prepare a solution. This solution was applied onto the above-mentioned protective layer and dried to form a slippery layer having a thickness of 0.2 μm.

This recording medium was heated to 150 ° C., which is higher than the melting point of the recording layer material, rapidly cooled, and then annealed at 80 ° C. to a colorless state. Printing was performed on this recording medium using a thermal head (6 dots / mm, 380Ω) manufactured by Toshiba under the conditions of an applied voltage of 13 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 could be performed. This recording medium was heated again to 150 ° C. and then gradually cooled. In this case, the recording layer crystallizes at high speed via the liquid crystal phase. For this reason, compared with the case of annealing at 80 ° C. after rapid cooling as described above, the time required for colorlessization is shorter. This operation was repeated 100 times, but there was no change in the image density in the color-developed state and no coloring in the colorless state.

The recording medium was kept at 80 ° C. to make it colorless, and an i-line of 10 mW / cm ² was applied using a high-pressure mercury lamp.
Irradiated for 0 seconds. Thereafter, when the mixture was heated to 150 ° C. and cooled, no coloring was observed. This is because the polymerizable substituent was polymerized by light irradiation, the molecular orientation was fixed, and the decolored state was irreversibly stabilized. When this recording medium was left at 60 ° C. for 300 hours, there was no change in the erased state.

Example 2 A biphenyl derivative represented by the chemical formula (3), in which n is 18, and PL is an acroyloxy group was used as a developer.
Further, as a photopolymerization initiator, α, α-dimethoxy-α-
Phenylacetophenone, 2-hydroxy-2-methylpropiophenone, α, α-dimethoxy-α-morpholino-methylthiophenylacetone, thioxanthone,
-Isopropylthioxanthone, 2-methylthioxanthone, isobutyl benzoin ether or isopropyl benzoin ether was added. Using these materials, a recording medium was produced in the same manner as in Example 1.

When the same operation as in Example 1 was repeated for this recording medium, good rewritable characteristics were exhibited. The recording medium is kept at 80 ° C. to be colorless,
Irradiation with i-ray of 10 mW / cm ² was performed for 20 seconds using a high-pressure mercury lamp. Thereafter, when the mixture was heated to 150 ° C. and cooled, no coloring was observed. When this recording medium was left at 60 ° C. for 300 hours, there was no change in the erased state.

Example 3 4 g of imidazole as a basic compound was dissolved in a solution (37 ° C.) of 4 g of gelatin dissolved in 40 mL of water. Coacervation was induced by adding 11 g of sodium sulfate to 45 mL of this solution. This dispersion was cooled to 30 ° C., left to stand, and then decanted to separate microcapsules. To the obtained microcapsules, an equal volume of formaldehyde was added and stirred for 5 minutes. Further, ethanol twice the amount of formaldehyde was added and stirred for 5 minutes, and then the microcapsules were filtered. The obtained microcapsules were washed with cold water and then dried.

1 part by weight of crystal violet lactone (CVL) as a coloring compound, 1 part by weight of propyl gallate as a color developer, 18 parts by weight of a hecogenin derivative represented by the chemical formula (4) as a reversible agent, and a molecular weight of 4 as a binder resin , 700 parts by weight of polystyrene, 1 part by weight of a charge control agent (LR-147, Nippon Carlit Co., Ltd.), and 5 parts by weight of microcapsules containing a basic compound were sufficiently kneaded using a kneader. The kneaded material was pulverized by a pulverizer to obtain a powder having an average particle diameter of 10 μm. Toner was prepared by adding 1 wt% of hydrophobic silica to 100 wt% of this powder.

[0093]

Embedded image

This toner is put into a toner cartridge of a laser beam printer (Laser Shot LBP-730), and plain paper (manufactured by Neusiedler, pH =
In 9.4), the information colored blue was printed. At this time, as shown in FIG. 1, toner was printed on the entire surface to make the central portion 1 of the paper a place where rewritable recording was possible. on the other hand,
Characters and the like were printed on the upper part 2 and the lower part 3 of the paper as in the case of using normal toner.

In this state, printing was performed on the central portion 1 using a thermal head (6 dots / mm, 380Ω) manufactured by Toshiba under the conditions of an applied voltage of 13 V and a pulse width of 0.8 msec. As a result, the printed portion became amorphous and became colorless, and negative type recording could be performed. Next, the central portion 1 was heated to 200 ° C., which is higher than the melting point of the reversible agent, and then gradually cooled.
In this case, since the image forming material is crystallized at a high speed via the liquid crystal phase, the time required for colorlessization is short. This operation was repeated 100 times, but there was no change in the image density in the color-developed state and no coloring in the colorless state.

Next, when the temperature was raised to 250 ° C., the color became colorless, and no rewritable characteristics were exhibited. This is because the microcapsules are broken, the basic compound is diffused into the material, and even when any of the reversible agents represented by the chemical formula (4) is used, polymerization of the polymerizable substituent occurs, and the decolored state occurs. This is due to irreversible stabilization.

This paper was left at 60 ° C. for 300 hours.
There was no change in the decolored state. After another pattern was formed on the erased paper, the process of completely erasing was repeated nine times. As a result, it was confirmed that the quality of the tenth image was equivalent to that of the first image. Further, when the test was repeated up to 50 times, the paper was physically damaged, but both the color-developed state and the decolored state were good.

The same results as above can be obtained when potassium carbonate, pyridine, piperidine, pyrazine, piperazine, triazole, oxazole, morpholine, or diazabicycloundecene is used as the basic compound instead of imidazole. Was.

Example 4 1.0 part by weight of crystal violet lactone (CVL) as a color-forming compound, 1.0 part by weight of propyl gallate as a color developer, and a compound represented by the chemical formula (5) as a phase separation controlling agent 20 parts by weight were added, and 10% by weight of α, α-dimethoxy-α-morpholino-methylthiophenylacetone was added as a photopolymerization initiator and dissolved in methylene chloride to prepare a uniform solution.

[0100]

Embedded image

This solution was cast on a glass substrate having a thickness of 1.5 mm to form a recording layer having a thickness of about 10 μm on the glass substrate. Next, a 10 wt% aqueous solution of a gelatin / polyvinyl alcohol (weight ratio of 6: 4) mixture was prepared. This solution was applied on the recording layer and dried to a film thickness of 0.2
A μm gelatin layer was formed. Next, the polyether sulfide was dissolved in a mixed solution of methyl ethyl ketone / dimethylformamide (1: 4), and mica was added to prepare a dispersion. This dispersion was coated on the above gelatin layer and dried to form a protective layer having a thickness of 0.2 μm. further,
A solution was prepared by dissolving the silicone acrylate resin in methyl ethyl ketone. This solution was applied onto the above-mentioned protective layer and dried to form a slippery layer having a thickness of 0.2 μm.

An applied voltage of 11 was applied to this recording medium using a thermal head (6 dots / mm, 380Ω) manufactured by Toshiba.
The printing was performed under the conditions of V, pulse width 0.8 msec. As a result, the printed portion was colored blue. Next, the recording medium was heated using a thermal head under the conditions of an applied voltage of 7.5 V and a pulse width of 1 msec. As a result, the printed portion was erased.

The recording medium was made colorless and irradiated with i-ray of 10 mW / cm ² for 20 seconds using a high-pressure mercury lamp.
Thereafter, when the mixture was heated to 150 ° C. and cooled, no coloring was observed. This is because the polymerizable substituent was polymerized by light irradiation, the molecular orientation was fixed, and the decolored state was irreversibly stabilized. This recording medium is heated at 60 ° C. for 3 hours.
After leaving for 00 hours, the erased state did not change.

[0104]

As described in detail above, the erasable image forming material of the present invention can be rewritten at a high speed, has a sufficient thermal stability in a recorded or erased state, and finally has an optical or thermal property. Can be irreversibly erased. Like this one
Since rewritable characteristics can be obtained and complete erasing is possible with various kinds of image forming materials, paper can be reused and recycled efficiently.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state where an image forming material is printed on paper in Example 3 of the present invention.

[Explanation of symbols]

 1 Central part 2 Upper part 3 Lower part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katsuyuki Naito 1st address, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term (Reference) 2H026 AA09 BB02 BB24 DD45 DD53 4H027 BA02 BA13 BB07 BE06 CD02 DM02

Claims (9)

[Claims] 1. An erasable image forming material comprising a color developing compound and a color developing agent, wherein said color developing agent has a polymerizable substituent. 2. A non-condensed polycyclic structure and a condensed polycyclic structure in which the color developer has a monocyclic aromatic ring structure and a plurality of ring structures bonded via any one of a single bond, a vinylene bond and an ethynylene bond. 2. The erasable composition according to claim 1, having a ring structure selected from the structures and substituents respectively introduced at both ends of the ring structure, and one of the substituents is a polymerizable substituent. Image forming materials. 3. The developer according to claim 1, wherein the developer is represented by the following general formula (1). (In the formula, Ar is a non-condensed polycyclic structure or a condensed polycyclic structure in which a monocyclic aromatic ring structure or a plurality of ring structures are bonded via any of a single bond, a vinylene bond, and an ethynylene bond, and X is an ether Bond, thioether bond, ester bond or amide bond, R is a substituted or unsubstituted alkyl group, PL is a substituent having an unsaturated bond or an epoxy group, Y is an acidic group, m is an integer of 1 to 3, n is 0 Or an integer of 1). 2. The erasable image forming material according to claim 1, wherein 4. The erasable image forming material according to claim 1, wherein the developer is a compound that forms a liquid crystal phase at 25 ° C. or higher. 5. A color-forming compound, a color developer, and a reversible agent having an effect of affecting a reversible change of a composition system, wherein the reversible agent is a compound having a polymerizable substituent. An erasable image forming material characterized by the following. 6. The erasable image forming material according to claim 5, wherein the reversible agent is a sterol compound having a polymerizable substituent. 7. The erasable image forming material according to claim 5, wherein the reversible agent is a compound that forms a liquid crystal phase at 25 ° C. or higher. 8. A compound comprising a color former, a color developer, and a phase separation controlling agent having an effect of increasing the phase separation rate of the composition system, wherein the phase separation controlling agent is a compound having a polymerizable substituent. An erasable image forming material, characterized in that: 9. The erasable image forming material according to claim 8, wherein the phase separation controlling agent is a compound which forms a liquid crystal phase at 25 ° C. or higher.