JP2000019769A - Erasable image forming material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve dispersion failure and obtain an excellent erased state even in the case of using an achromatic agent low in compatibility by containing a colored compound, a developer and a precursor of an achromatic agent with a functional group protected by a protective group. SOLUTION: A colored compound, a developer and a precursor of an achromatic agent with a protective group led in are combined to make image forming material erasable after printing. The compounding ratio of the developer is 0.1-10 pts.wt., preferably 1-2 pts.wt., to 1 pts.wt. of the colored compound. The compounding ratio of the precursor of the achromatic agent is set to 1-200 pts.wt., preferably 10-100 pts.wt., to 1 pts.wt. of the colored compound. As the colored compound, there is an electron donative organic substance such as leucoauramines or diarylphthalides. As the developer, there is an acid compound such as phenol, phenol metal salt or carboxylic acid metal salt. The achromatic agent with the protective group displays notable achromatic action when the protective group is dissociated, and a storol compound or the like is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for electrophotography of a printer, a copying machine, a facsimile, etc., and thermal transfer recording.
The present invention relates to an image forming material that can be erased after forming an image.

[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, the reuse (recycling) of paper resources is
It is carried out by treating paper on which an image forming material is printed with a large amount of bleach and water, and remaking the paper fibers to produce recycled paper of poor paper quality. 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, the present inventors have proposed a method for forming an image in the same manner as a normal image forming material, which contains a color former, a color developer and a decolorant compatible with these compounds. The development of an image forming material capable of erasing an image by processing with heat or a solvent is being promoted.
When such an erasable image forming material is used, the paper whose image has been erased and returned to a blank state can be reused (reused) many times while minimizing deterioration of the paper quality. Since the paper may be recycled when the quality of the paper due to reuse becomes remarkable, the utilization efficiency of the paper resources is dramatically improved. In this manner, substantial paper usage can be reduced, and logging of timber can be minimized. In addition, the high cost of recycled paper and the environmental pollution caused by waste liquid treatment, which are problems in the current recycling system, can be avoided as much as possible.

According to the study of the present inventors, in an erasable image forming material containing a color former, a color developer, a decolorant, a binder, etc., the phase of the decolorant and the binder is particularly high. If the solubility is poor, the dispersion of the decoloring agent will be poor,
It has been found that this may cause uneven erase. For example, when erasing is performed using a solvent, traces of the flow of the image forming material and uneven peeling may occur, and the image may not be erased well. Conversely, depending on the usage environment, the density of the formed image may be reduced and the image may not be stably maintained.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of poor dispersion even when using a decoloring agent having poor compatibility with other materials constituting the image forming material. An object of the present invention is to provide an erasable image forming material capable of obtaining an erased state.

[0007]

The erasable image-forming material of the present invention contains a color former, a developer, and a precursor of a decolorant whose functional group is protected by a protecting group. It is characterized by the following. Another erasable image forming material of the present invention is a color developing compound, a developer, a decoloring agent, and a functional compound protected with a protecting group, and a polymer compound acting as a decolorizing aid. And a precursor. In this case, a polymer compound acting as a decolorizing aid may be copolymerized with a binder, and its functional group may be protected by a protecting group.

In the present invention, it is preferable that the protecting group introduced into the decoloring agent or the decolorizing auxiliary is dissociated by heating, light irradiation, or contact with a basic substance. In the present invention, even a decoloring agent or a decoloring aid having poor compatibility with other components such as a binder exhibits good compatibility by introducing a protective group. The dispersibility of the color assistant is improved. When the protective group is dissociated, such a decoloring agent or a precursor of the decoloring aid develops a decoloring action while maintaining a good dispersion state. Therefore, it is possible to prevent erasure unevenness due to dispersion failure in the image erasing process.
Further, since the decoloring agent or the precursor of the decoloring aid does not exhibit the decoloring effect until the protective group is dissociated, the image can be stably maintained even in a relatively severe use environment.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The erasable image-forming material of the present invention comprises a combination of a color former, a color developer, and a precursor of a decolorizer having a protective group introduced therein, and the erasure is performed after printing. Is what makes it possible.

The image forming material of the present invention can be used in various forms. For example, it can be used as an ink for a thermal printer; an ink for an ink jet printer; a toner for a copier (PPC) and a laser printer; a printing ink for screen printing and printing; a writing ink for a ballpoint pen and a fountain pen. Thermal printer ink is a coloring compound,
A developer, a decolorant precursor, a wax and the like are mixed and applied to a plastic sheet for use. The ink of the inkjet printer is used by dispersing a color former, a color developer, a decolorant precursor, and the like in a solvent. The toner is prepared by pulverizing a composition containing a color former, a developer, a decolorant precursor, a binder, and the like. Use of the image forming material of the present invention enables printing on various papers.

The operation of the basic components constituting the image forming material of the present invention will be schematically described. A color-forming compound is a precursor compound of a dye that forms coloring information such as characters and figures, and a color developer is a compound that develops color by interacting with the color-forming compound (mainly by transferring electrons or protons). It is a compound that colors the compound. The decoloring agent in which the protective group has been removed is a compound having a property that one of the color developer and the color developing compound is preferentially compatible at the time of melting or in the presence of a solvent.

When these three components are solidified, they can take the following two states. That is, (1) the decolorizing agent is mixed with the color developing compound and the developer in an amount corresponding to the equilibrium solubility, and the surplus color developing compound and the developer exceeding the equilibrium solubility in the decoloring agent are obtained. A state in which the color developing compound and the color developing agent are colored by the phase separation with the color erasing agent, and (2) the color erasing agent dissolves the color developing compound or the color developing compound in excess of the equilibrium solubility. This is a state in which the interaction between the uptake and color former and the developer is reduced and the color is erased.

The state change between the colored state and the decolored state is performed according to the following principle. Here, the description will be made on the assumption that the color erasing agent preferentially dissolves the color developer when the above composition system is molten and in a fluid state. At room temperature, the state in which the phase of the color former and the phase of the developer and the phase of the decolorant are phase-separated is close to the equilibrium state. In this case, the color former and the color developer interact with each other to form a color. From this state, when the composition system is heated to a temperature equal to or higher than the melting point, the color developer is preferentially dissolved in the decolorizing agent in the fluid state, and loses the interaction with the color forming compound, so that the color is changed to the decolored state. When the composition in the molten state is forcibly solidified by quenching, the decolorizing agent takes in a developer in an amount exceeding the equilibrium solubility to become amorphous and becomes colorless at room temperature. The amorphous composition system is
Although it is in a relatively non-equilibrium state, it has a sufficiently long life at a temperature lower than the glass transition point Tg, and does not easily transition from an amorphous state to an equilibrium state if Tg is higher than room temperature.

When a solvent is applied to an image forming material containing three components of a color former, a developer and a decolorant, the color is changed from the color-developed state to the decolored state by the same principle as described above. Can be changed.

A coloring compound in the image forming material of the present invention,
The preferred compounding ratio of the color developer and the color erasing agent precursor is as follows. The mixing ratio of the color developer is preferably set to 0.1 to 10 parts by weight, more preferably 1 to 2 parts by weight, based on 1 part by weight of the coloring compound. When the amount of the color developer is less than 0.1 part by weight, the color of the image forming material due to the interaction between the color former and the color developer becomes insufficient. When the amount of the developer exceeds 10 parts by weight, it is difficult to sufficiently reduce the interaction between the two. The compounding ratio of the decoloring agent precursor is 1 to 200 parts by weight, more preferably 10 to 10 parts by weight, per 1 part by weight of the color former.
It is preferably set to 0 parts by weight. Decoloring agent precursor is 1
When the amount is less than the weight part, it is difficult to cause a state change between the color forming state and the color erasing state of the image forming material. When the amount of the decoloring agent precursor exceeds 200 parts by weight, the color of the image forming material becomes insufficient.

Next, specific compounds that can be used as components of the image forming material of the present invention will be described.
Examples of the color-forming compound used in the present invention include leuco auramines, diaryl phthalides, polyaryl carbinols, acyl auramines, aryl auramines, rhodamine B lactams, indolines, spiropyrans, and fluoran And an electron donating organic material such as

As specific color-forming compounds, crystal violet lactone (CVL), malachite green lactone, 2-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-methylindole-3-
Yl) -4-azaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3-diethylamino-7-chloroanilinofluoran, 3-diethylamino- 7,8-
Benzofluorane, 3,3-bis (1-n-butyl-2
-Methylindol-3-yl) phthalide, 3,6-dimethylethoxyfluoran, 3,6-diethylamino-
6-methoxy-7-aminofluoran, DEPM, AT
P, 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 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.

The color developing agent used in the present invention includes phenol, phenol metal salt, carboxylic acid metal salt, benzophenone, sulfonic acid, sulfonate, phosphoric acid, metal phosphate, acid phosphate, acid phosphate. Acid compounds such as ester metal salts, phosphorous acid, and metal phosphites are exemplified. These can be used alone or in combination of two or more.

The decoloring agent having a protecting group used in the present invention exhibits a remarkable decoloring effect when the protecting group is dissociated. The protective group is a functional group such as a hydroxyl group or a carboxyl group, which plays the most important role in causing the decoloring agent to exhibit a decoloring effect by being compatible with a color developer and a color forming compound constituting the image forming material. It is a substituent that protects the group. Here, the decoloring agent not protected by the protecting group will be described first. It is desirable that the decoloring agent has good colorlessness when in the amorphous state. The more the decoloring agent is amorphous and colorless and transparent, the more the paper can be returned to a state close to the original white paper when the image forming material is decolorized. Since such properties are required, the decoloring agent is preferably a compound having a large molecular weight, a small change in enthalpy of melting ΔH per crystal and a small maximum crystal growth rate MCV. If the change in enthalpy of melting ΔH of the crystal of the decoloring agent is small, the amount of heat energy required for melting the crystal becomes small, which is also preferable in terms of energy saving. Further, in order to increase the solubility of the color developer in the color erasing agent, it is preferable that the color erasing agent has a high affinity with the color developing agent, and for example, a compound having an alcoholic hydroxyl group is suitable. From the viewpoint of storage stability of the composition system in the decolored state, the glass transition point Tg of the composition system needs to be at least room temperature (25 ° C.), and more preferably 50 ° C. or higher. In order to satisfy this condition, the glass transition point of the decoloring agent is preferably at least room temperature (25 ° C.), more preferably at least 50 ° C. On the other hand, the crystallization temperature of the decoloring agent is in a temperature range between the glass transition point Tg and the melting point Tm of the composition system. Therefore, in order to speed up the erasing, the glass transition point of the decoloring agent is preferably 150 ° C. or lower. Preferred decoloring agents satisfying these conditions include the following (a) to (a).
Compounds such as (c) are mentioned.

(A) Sterol compound. Specific examples of the sterol compound include cholesterol, stigmasterol, pregnenolone, methylandrostenediol, estradiol benzoate, epiandrostene, stenolone, β-sitosterol, pregnenolone acetate, β-cholesterol, and 5,16-pregnadien-3β -All-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
17-acetate, 5-pregnene-3β, 21-diol-20-one 21-acetate, 5-pregnene-3β, 17-diol diacetate, locogenin,
Tigogenin, esmilagenin, hecogenin, diosgenin and derivatives thereof. These decoloring agents can be used alone or in combination of two or more.

When the decolorizing agent (a) is used, when the composition in the amorphous state is heated to a temperature higher than the glass transition point, the diffusion rate of the color developing agent is sharply increased, and the state of equilibrium is reached. In the returning direction, the phase separation movement between the color developer and the decolorant is accelerated. Then, when the composition system is heated to a temperature equal to or higher than the crystallization temperature and lower than the melting point, and then gradually cooled to room temperature, a more stable phase separation state close to an equilibrium state is returned to the color development state. Therefore,
The composition system using the decoloring agent of (a) can, in principle, reversibly repeat the colored state and the decolored state. In this sense, the decolorizing agent (a) can be said to be a “reversible decoloring agent”. However, the erasable image forming material of the present invention only needs to be erasable after forming an image, and is essentially not required to be reversible.

(B) cholic acid, lithocholic acid, testosterone and cortisone, and derivatives thereof. Specific examples include cholic acid, cholic acid methyl ester, sodium cholate, lithocholic acid, lithocholic acid methyl ester, sodium lithocholic acid, hydroxycholic acid, hydroxycholic acid methyl ester, hyodeoxycholic acid, hyodeoxycholic acid methyl ester , Testosterone, methyltestosterone, 11α-hydroxymethyltestosterone, hydrocortisone, cholesterol methyl carbonate, and α-cholestanol. Among them, those having two or more hydroxyl groups are particularly preferable.

The color erasing agent (b) has a higher affinity with the color developer at the time of melting than the color erasing agent (a), and has very high compatibility. In addition, since the decoloring agent (b) has a high amorphous property, phase separation hardly occurs even after the composition system is solidified. In this sense, the color erasing agent (b) can be said to be a "compatible color erasing agent". Therefore, in the composition system using the decoloring agent of (b), a more stable decolored state can be obtained.

(C) a non-aromatic cyclic compound having at least one 5-membered ring having at least one hydroxyl group. The melting point of these compounds is preferably 50 ° C. or higher. Specific examples include alicyclic monohydric alcohols (eg, cyclododecanol), alicyclic dihydric alcohols (eg, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,2-cyclododecanediol), saccharides And its derivatives (eg, glucose and saccharose) and alcohols having a cyclic structure (eg, 1,2,5,6-diisopropylidene-D-mannitol).

Although the decoloring agent of (c) may be used alone,
It is particularly effective when used together with the decoloring agent (a). That is, the decoloring agent of (c) has a strong affinity with the decoloring agent of (a), and hardly causes phase separation even after being solidified. In this sense, the decolorizing agent (c) may be referred to as a “phase separation suppressing decoloring agent” or a “phase separation suppressing agent”. Even when the decoloring agent of (c) is used, a more stable decolored state can be obtained.

The above-mentioned decolorizing agent (c), that is, a phase separation inhibitor, can be further classified into two types. That is, (c1) a compound having a relatively high melting point and a glass transition point and easily becoming amorphous at ordinary temperature (highly amorphous phase separation inhibitor)
And (c2) a compound which has a relatively low melting point and glass transition point and is unlikely to become amorphous at normal temperature and may form microcrystals, but has a very high compatibility with a color developer in a fluid state ( A low-amorphous phase separation inhibitor).

The change in image density when an image forming material containing a color former, a color developer and a highly amorphous phase separation inhibitor is heated and cooled will be described. When the image forming material in a color developing state at room temperature is heated to a temperature higher than the melting point of the highly amorphous phase separation inhibitor, the developer dissolves in the highly amorphous phase separation inhibitor, and Is lost because of the loss of interaction. When the image forming material in a molten state is cooled and solidified, the highly amorphous phase separation inhibitor takes in a developer in an amount exceeding the equilibrium solubility to become amorphous and lose color at room temperature. Thus, the highly amorphous phase separation inhibitor alone functions as a decoloring agent. In addition, since the highly amorphous phase separation inhibitor tends to become amorphous at room temperature, the colorless state can be maintained for a long time. However, if the compatibility with the color developer is not so good in the flowing state, there is a possibility that a remarkable change in the image density cannot be obtained between the coloring state and the decoloring state.

The change in image density when an image forming material containing a color former, a color developer and a low amorphous phase separation inhibitor is heated and cooled will be described. When an image-forming material that is in a color-developed state at room temperature is heated above the melting point of the low-amorphous phase-separation inhibitor, a considerable amount of the developer is dissolved in the low-amorphous phase-separation inhibitor, and the color is formed. It loses the interaction with the sexual compound and becomes a decolored state. However, even when the image forming material in the molten state is cooled and solidified, the low-amorphous phase separation inhibitor hardly becomes amorphous and may be microcrystallized. Return to the color development state. Thus, the low amorphous phase separation inhibitor alone does not function as a decoloring agent.

As can be seen from the above behavior, if both a highly amorphous phase-separation inhibitor and a low-amorphous phase-separation inhibitor are used as the decolorizing agent, the advantages of both can be utilized. . The change in image density when an image forming material containing a color former, a color developer, and a highly amorphous and low amorphous phase separation inhibitor is heated and cooled will be described. At room temperature, an image is formed in a state where a mixture of a color former, a developer, and a phase separation inhibitor having a low amorphous phase and a phase of a phase separation inhibitor having a high amorphous phase are separated. You. When the composition is heated above the melting point of the low-amorphous phase-separation inhibitor, the developer dissolves in the low-crystalline phase-separation inhibitor in a fluid state and interacts with the color-forming compound. To lose color. further,
When the composition is heated above the melting point of the highly amorphous phase separation inhibitor, the color developer and the low amorphous phase separation inhibitor are dissolved in the highly amorphous phase separation inhibitor. Become. When the composition in the molten state was cooled and solidified, the action of the highly amorphous phase separation inhibitor caused the low amorphous phase separation inhibitor to take in more developer than its equilibrium solubility. The color is erased at room temperature to make it amorphous. Since the highly amorphous phase separation inhibitor has a high amorphous property, it suppresses crystallization of the low amorphous phase separation inhibitor and suppresses phase separation of the composition system. Therefore, the decolored state of the image forming material can be maintained very stably.

A preferred highly amorphous phase separation inhibitor is a cyclic sugar alcohol. Specific examples include D-glucose,
D-mannose, D-galactose, D-fructose, L-sorbose, L-rhamnose, L-fucose,
D-ribodesource, α-D-glucose = pentaacetate, acetoglucose, diacetone-D-glucose, D-glucuronic acid, D-galacturonic acid, D-glucosamine, D-fructosamine, D-isosugaric acid, vitamin C, eltorbin Acid, trehalose, saccharose,
Maltose, cellobiose, gentiobiose, lactose, melibiose, raffinose, gentianose,
Melezitose, stachyose, methyl = α-glucopyranoside, salicin, amygdalin, euxanthinic acid. One or more of these can be used.

Suitable low amorphous phase separation inhibitors are non-aromatic cyclic compounds having 5 or more membered rings having a hydroxyl group other than cyclic sugar alcohols or derivatives of cyclic sugar alcohols. Is terpene alcohol. Specific examples include alicyclic monohydric alcohols such as cyclododeanol, hexahydrosalicylic acid, menthol, isomenthol, neomenthol, neoisomenthol, carbomenthol, α-carbomenthol, piperitol, α-terpineol, β-terpineol. Γ-terpineol, 1-p-menten-4-ol, isopulegol, dihydrocarbeol, carveol; alicyclic polyhydric alcohols such as 1,4-cyclohexanediol, 1,2-cyclohexanediol, phloroglucitol, Quercitol, inositol, 1,2-cyclododecanediol, quinic acid, 1,4-terpine,
1,8-terpine, pinol hydrate, betulin; polycyclic alcohol derivatives such as borneol, isoborneol, adamantanol, norborneol, fenchol, camphor; derivatives of cyclic sugar alcohols;
For example, 1,2,5,6-diisopropylidene-D-mannitol can be mentioned. One or more of these can be used.

Further, a polymer (or oligomer) having a high polarity exhibits a decoloring effect, and functions alone as a decoloring agent or as a decolorizing aid for the above-described low-molecular decoloring agent. Specific examples of the highly polar polymer (or oligomer) include cellulose, for example, nitrocellulose,
Ethylcellulose, methylcellulose, acetylcellulose, etc .; vegetable carbohydrates such as starch; polyacrylic acid, polymethacrylic acid; polybiphenyl acrylate; polyacrylamide, polymethacrylamide; polyvinyl esters, such as polyvinyl acetate; polyphenylene; Polyether ketone; polysulfone; polyamide; polybenzimidazole; polyphenylene ether; polyphenylene sulfide; polycarbonate; polydivinylbenzene; melamine resin;
%, A styrene-acrylate copolymer, a styrene-acrylic acid copolymer, a styrene-methacrylic acid copolymer, a styrene-epoxy-modified styrene copolymer, and the like. The acrylate monomer used in the styrene / acrylate copolymer includes, for example, n
-Butyl methacrylate, isobutyl methacrylate,
Ethyl acrylate, n-butyl acrylate, methyl methacrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-ethylhexyl acrylate, butyl acrylate, N- (ethoxymethyl) acrylamide, ethylene glycol methacrylate, 4-hexafluorobutyl methacrylate, etc. Is mentioned.

In the present invention, a protecting group for protecting the functional group of the above-described color erasing agent or color erasing aid is introduced.
As this protective group, it is preferable to select a component having a property of improving the compatibility with the binder among the components constituting the image forming material. These protecting groups are dissociated by heating, light irradiation, or contact with a basic substance. When the protective group is dissociated, a functional group (for example, a hydroxyl group or a carboxyl group) originally possessed by the decoloring agent or the decoloring aid appears, and the compatibility with the color developing agent or the coloring compound is improved, and the decoloring is performed. It will show its action. In this sense, a decoloring agent having a protecting group (or a decolorizing auxiliary) can be said to be a latent decoloring agent (or a decolorizing auxiliary).

The protecting group for the hydroxyl group includes
Methoxymethyl ether, 2-methoxyethoxymethyl ether, bis (2-chloroethoxy) methyl ether, 2- (trimethylsilyl) ethoxymethyl ether, tetrahydropyranyl ether, 4-methoxytetrahydropyranyl ether, 4-methoxytetrahydrothiopyranyl Ether, tetrahydrofuranyl ether, 1-ethoxyethyl ether, 1-methyl-1-methoxyethyl ether, 1- (isopropyl) ethyl ether, 2- (phenylselenyl) ethyl ether, allyl ether, 5-dibenzosuberyl ether, Triphenylmethyl ether, trimethylsilyl ether, triethylsilyl ether,
Isopropyldimethylsilyl ether, tribenzylsilyl ether, tri-p-xylylsilyl ether, triphenylsilyl ether, formate,
Acetate ester, chloroacetate ester,
Dichloroacetate ester, trichloroacetate ester, methoxyacetate ester, triphenylmethoxyacetate ester, p-chlorophenoxyacetate ester, 2,6-dichloro-4-ester
(1,1,3,3-tetramethylbutyl) phenoxyacetate ester, 2,6-bis- (1,1-dimethylbutyl) phenoxyacetate ester, chlorodiphenylacetate ester, monosuccinoate
Ester, pivaloate ester, adamantoate ester, crotonate ester, 4-methoxycrotonate ester, (E) -2-methyl-2-butenoate ester, benzoate ester, alkyl methyl carbonate, alkyl ethyl carbonate, alkyl vinyl carbonate, alkyl
Examples include p-nitrophenyl carbonate, alkyl N-imidazolyl carbonate, borate ester, nitrate ester, 1,3- (1,1,3,3-tetraisopropyldisiloxanilidene) derivative, cyclic carbonate, cyclic boronate, and the like.

As a protecting group for a carboxyl group,
Trimethylsilyl ester, tert-butyldimethylsilyl ester, methyl ester, propyl ester, tert-butyl ester, N-phthalimidomethyl ester, 2- (trimethylsilyl) ethyl ester, 2-methylthioethyl ester, 2-methylthioethyl ester
(P-toluenesulfonyl) ethyl ester, triphenylmethyl ester, o-nitrobenzyl ester, p-nitrobenzyl ester, 2,4-dinitrophenylsulfenyl ester, and the like.

Of the protecting groups, ether, silyl ether and silyl ester are dissociated when heated and with the aid of a weakly acidic component contained in the image forming material, and deprotection is performed. In addition, these protecting groups may be dissociated by diffusion of a weakly acidic component contained in the image forming material in the course of erasing with a solvent.

Among the protecting groups, esters, borate esters, carbonates, siloxanilidene derivatives and boronates are dissociated under basic conditions and deprotected.
To make the image forming material basic, a basic substance as described later is used.

Of the protecting groups, nitrate ester and o-nitrobenzyl ester are dissociated by light irradiation and deprotected. In this case, a light irradiation step may be added, such as light irradiation in an image erasing step using a solvent or heat.

In the present invention, the decolorizing agent (or decolorizing auxiliary) is encapsulated in a microcapsule which is destroyed by heating and used, whereby the decolorizing agent (or decolorizing auxiliary) having a protective group introduced thereinto is used. ) Can have the same function as the precursor.

The basic substance used to release the protecting group such as an ester as described above will be described.
The basic substance is also used for the purpose of reducing the influence of unreacted carboxylic acid and phenolic hydroxyl group contained in the binder. In addition, if a basic substance is used, even when an image is formed on paper having a pH of less than 8,
The effects of a weakly acidic environment can be avoided. Such a basic substance is not particularly limited, and may be an inorganic compound or an organic compound. Further, the basic substance may be added directly to the image forming material, or may be added in a form encapsulated in microcapsules.

Preferred inorganic compounds include calcium chloride, potassium hydroxide, calcium hydroxide, sodium hydroxide, barium hydroxide, magnesium hydroxide, ammonium carbonate, potassium carbonate, calcium carbonate, sodium carbonate, magnesium carbonate, hydrogen carbonate. Examples include ammonium, potassium bicarbonate, sodium bicarbonate, alkali metal borates, tripotassium phosphate, dipotassium hydrogenphosphate, calcium phosphate, trisodium phosphate, and disodium hydrogenphosphate.

Suitable organic compounds include primary to tertiary
And quaternary ammonium salts 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.

Examples of the non-aromatic amine or ammonium salt include those having an aliphatic hydrocarbon group having 1 to 50 carbon atoms or an alicyclic hydrocarbon group having 1 to 50 carbon atoms. These hydrocarbon groups are vinyl, ethynylene, ethynyl, oxy, oxycarbonyl, thiocarbonyl, dithiocarbonyl, thio, sulfinyl, sulfonyl, carbonyl, hydrazo,
It may be substituted with at least one substituent selected from azo group, azide group, nitrilo group, diazoamino group, imino group, urea bond, thiourea bond, amide bond, urethane bond and carbonyldioxy group.

Examples of the aromatic amine or ammonium salt include benzene ring, biphenyl ring, naphthalene ring, tetralone ring, anthracene ring, phenanthrene ring, indene ring, indane ring, pentalene ring, azulene ring, heptalene ring, fluorene ring and the like. And those having an aromatic ring. 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.

Examples of the cyclic amine include 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.

Organic basic substances which can be used in addition to the above include alkali metal salts of alcohols, alkaline earth metal salts of alcohols, amidines, guanidines, aminoguanidines, ureas, thioureas, semicarbazides, thiosemicarbazides, and carbonocarbonates. Hydrazide.

The following binders can be used in the image forming material of the present invention.
For example, polystyrene homopolymer, polyester,
Epoxy resin, hydrogenated styrene resin, styrene / isobutylene copolymer, styrene / butadiene copolymer, acrylonitrile / butadiene / styrene terpolymer,
Styrene / acrylonitrile copolymer, acrylonitrile / acrylic rubber / styrene terpolymer, acrylonitrile / chlorinated polystyrene / styrene terpolymer,
Acrylonitrile / EVA / styrene terpolymer, styrene / p-chlorostyrene copolymer, styrene / propylene copolymer, styrene / butadiene rubber copolymer,
Styrene / isobutylene copolymer and the like can be mentioned. In addition to these, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyvinyl butyral, rosin, modified rosin, terpene resin, fatty acid or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, Paraffin wax and the like may be mixed.

The above-mentioned polymer (or oligomer) having a high polarity acting as a color erasing aid may be protected with a protecting group for its functional group in a state of being copolymerized with a binder.

When a polyester or epoxy resin is used as a binder, a weakly acidic component such as an unreacted carboxylic acid or a phenolic hydroxyl group is contained. It is preferable to use a basic substance in combination as described above.

In the present invention, a decoloring agent, a decolorizing auxiliary, a basic substance and the like may be mixed with other components of the image forming material in a state of being encapsulated in microcapsules. As the shell material of the microcapsule, a material that is destroyed by heating is selected. The temperature at which the microcapsules break is 120
It is preferable that it is -200 degreeC. Suitable materials include polyetherketone, epoxy resin, polyethylene, polypropylene, polyphenylene ether, polystyrene, gelatin, polyvinyl alcohol, polyacrylonitrile, polymethacrylonitrile, polysiloxane, polyvinyl acetate, gum arabic, polyvinylpyrrolidone, polysulfone, and polysulfone. Examples include isocyanate, polypyrrole, chitosan, collagen, polyamino acid, and the like. These may be used alone or as a mixture. Further, these copolymers may be used.
Suitable particle size of the microcapsules varies depending on the use of the image forming material, but is 1 to 5 μm in the case of toner, thermal transfer ink, writing ink, and 100 to 100 μm or less in the case of ink for ink jet printer. 1000
It is preferably set to nm.

In the present invention, in order to erase the colored image forming material, there are a method of erasing the image forming material by heating and melting, and a method of erasing by contacting the image forming material with a solvent.

In the method of heating the image forming material, any heating means such as a thermal printer head (TP)
H), a laser head, a thermal bar, a hot stamp, a heat roller, a heat gun, a hot air blower, a heating lamp and the like can be applied.

In the method of contacting the image forming material with a solvent, the paper is immersed in the solvent or the solvent is sprayed on the paper. As a means for this, a roller for dipping the paper in the solvent contained in the container, a spray nozzle for spraying the solvent on the paper, a nozzle for dropping the solvent on the paper, a gravure roller for supplying the solvent to the paper, and the like are used. As a means for removing the residual solvent from the paper, hot air, an infrared lamp, a heat roller, a hot press, a thermal printer head (TPH), a thermal bar, or the like is used. When a solvent that easily vaporizes is used, it may be dried naturally. Further, it is preferable to provide a means for collecting the used solvent in these apparatuses.

The solvent used in this method preferably has (A) the property of assisting the formation of hydrogen bonds between the color developing agent and the decoloring agent, and (B) it has a high affinity for the binder and has a high affinity for image formation. It is preferable to have a property that easily penetrates into the inside of the material. The solvent satisfying the above property (A) can be used alone. Further, two or more solvents may be mixed to satisfy the above two properties.

Examples of the solvent having both the properties (A) and (B) include ethers, ketones and esters. Specific examples include saturated ethers such as ethyl ether, ethyl propyl ether, ethyl isopropyl ether, isopentyl methyl ether, butyl ethyl ether, dipropyl ether, diisopropyl ether, ethyl isopentyl ether, dibutyl ether, dipentyl ether, diisopentyl ether. Unsaturated ethers such as ethyl vinyl ether, allyl ethyl ether, diallyl ether, ethyl propargyl ether; ethers of dihydric alcohols such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 1,2-dimethoxy Ethane, 1,2-diethoxyethane, 1,2-dibutoxyethane; cyclic ethers such as oxetane,
Tetrahydrofuran, tetrahydropyran, dioxolan, dioxane, trioxane; saturated ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, diethyl ketone, isopropyl methyl ketone, butyl methyl ketone, ethyl propyl ketone, isobutyl methyl ketone, pinacolone, methyl pentyl ketone, butyl ethyl Ketone, dipropyl ketone, diisopropyl ketone, hexyl methyl ketone, isohexyl methyl ketone, heptyl methyl ketone, dibutyl ketone; unsaturated ketones such as ethylidene acetone, allyl acetone,
Mesityl oxide; cyclic ketone such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone; ester such as ethyl formate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, ethyl acetate, isopropyl acetate, acetic acid Propyl, butyl acetate, isobutyl acetate, pentyl acetate,
Isopentyl acetate, sec-amyl acetate, hexyl acetate, allyl acetate, 2-methoxyethyl acetate, 2-
Ethoxyethyl acetate, 1,2-diacetoxyethane, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, butyl propionate, pentyl propionate, isopentyl propionate, sec-amyl propionate, 2-methoxypropyl Acetate, 2-ethoxypropyl acetate, methyl butyrate, ethyl butyrate, propyl butyrate, isopropyl butyrate, butyl butyrate, pentyl butyrate, isopentyl butyrate, sec-amyl butyrate, methyl isobutyrate, ethyl isobutyrate, propyl isobutyrate, isopropyl isobutyrate, Butyl isobutyrate, pentyl isobutyrate, isopentyl isobutyrate, sec-amyl isobutyrate, methyl valerate, ethyl valerate, propyl valerate, isopropyl valerate, butyl valerate, methyl valerate, Kusasan ethyl, propyl valerate,
Isopropyl valerate, butyl valerate, methyl hexanoate, ethyl hexanoate, propyl hexanoate, isopropyl hexanoate and the like. As a solvent other than the above, methylene chloride, γ-butyrolactone, β-propiolactone, n-methylpyrrolidinone, dimethylformamide,
Examples include dimethylacetamide and dimethylsulfoxide (first group). These may be used alone or as a mixture of two or more. When a mixed solvent is used, the mixing ratio can be set arbitrarily.

Solvents having the property (A) but having low affinity for the binder include, for example, water, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, pentyl alcohol, 2-pentyl. alcohol,
3-pentyl alcohol, isopentyl alcohol, 1
-Hexanol, 2-hexanol, 3-hexanol, cyclopentanol, cyclohexanol, ethylene glycol, propylene glycol, butylene glycol, glycerin and the like (second group).

Solvents which do not have the property (A) but have a high affinity for the binder include, for example, toluene, ethylbenzene, propylbenzene, cumene, butylbenzene, isobutylbenzene, sec-butylbenzene, pentylbenzene, diethylbenzene, Mesitylene, xylene, cresol, ethylphenol, dimethoxybenzene, dimethoxytoluene, benzyl alcohol, tolyl carbinol, cumyl alcohol, acetophenone,
Propiophenone, hexane, pentane, heptane, octane, cyclohexane, cyclopentane, cycloheptane, cyclooctane, petroleum fractions (petroleum ether, benzine, etc.) (Group 3).

As mentioned above, the first group of solvents can be used alone satisfactorily. The second group of solvents may be used alone or may be mixed with the first group of solvents. In this case, since both groups of solvents have erasing ability, they can be used at an arbitrary mixing ratio. When using a mixed solvent of the second group of solvents and the third group of solvents, the mixing ratio of the two is not particularly limited as long as sufficient erasing ability is obtained, but the third group of solvents should be 20 to 80 wt%. Is preferred. The third group of solvents may be used as a mixture with the first group of solvents. In this case, the third group of solvents may be 90 wt% or less. Further, the solvents of the first to third groups may be mixed and used.
In this case, the content of the third group of solvents is preferably set to 80 wt% or less.

In order to efficiently decolor the image forming material, the solvent may be heated in advance. In this case, the temperature of the solvent is preferably in the range of 40 to 150 ° C. In the present invention, when a basic substance is used, the basic substance may be added to the erasing solvent used in the image erasing step with a solvent, or a solution of the basic substance may be sprayed on paper before the image erasing step by heating or paper. May be immersed in a solution of a basic substance. As the solvent used for preparing the solution of the basic substance, any of those exemplified as the erasing solvent that can dissolve the basic substance used can be arbitrarily selected. The concentration of the solution of the basic substance is preferably 1 to 40% by weight.

[0060]

Embodiments of the present invention will be described below. In these examples, the images were formed on NEUSIEDLER paper (pH = 9.4), which is standard in Europe. The reflection density of this paper measured by a Macbeth densitometer was 0.07.

Example 1 As a precursor of a decoloring agent, a precursor in which the hydroxyl group of cholesterol was protected with any of the protecting groups shown in Table 1 was prepared.

1 part by weight of crystal violet lactone (CVL) as a coloring compound, 1 part by weight of propyl gallate as a color developer, 10 parts by weight of a precursor of a decolorizing agent, and 10 parts by weight of D-glucose as a phase separation inhibitor 77 parts by weight of polystyrene having a molecular weight of 45,000 as a binder, and LR-147 (Nippon Carlit Co., Ltd.) as a charge control agent
One part by weight was mixed and 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.

The obtained toner was put into a toner cartridge of a copying machine (manufactured by Toshiba, Premage 3860), and the image was transferred to paper at a fixing temperature of 150 ° C. The paper was immersed in methyl ethyl ketone for 30 seconds and then dried to erase the image. Table 1 shows the measurement results of the reflection density of the paper after the image was erased. As shown in Table 1, the reflection density of the paper after the image was erased was almost the same as the initial reflection density, and the image was successfully erased.

[0064]

[Table 1]

The paper from which the image had been erased was left at 60 ° C. for 300 hours, but the image did not appear again. Thereafter, the process of transferring another image to the paper from which the image had been erased and erasing it was repeated nine times. The tenth image transferred thereafter was of the same quality as the first image. further,
Copying and erasing were repeated up to 50 times. as a result,
The paper was physically damaged, but the quality of the copied image and the erasure were good.

Example 2 A solution obtained by dissolving 4 g of gelatin in 40 mL of water (37 ° C.)
Then, 4 g of potassium carbonate was dissolved as a basic substance. 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.

Further, a precursor of the cholesterol in which the hydroxyl group was protected by any of the protecting groups shown in Table 2 was prepared as a precursor of the decoloring agent. 1 part by weight of crystal violet lactone (CVL) as a coloring compound, 1 part by weight of propyl gallate as a developer, 10 parts by weight of a precursor of a decolorizer, 10 parts by weight of D-glucose as a phase separation inhibitor, 2 parts by weight of the microcapsules thus prepared, 75 parts by weight of polystyrene having a molecular weight of 45,000 as a binder, and 1 part by weight of LR-147 (Nippon Carlit Co., Ltd.) as a charge controlling agent were mixed and kneaded sufficiently 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.

The obtained toner was placed in a toner cartridge of a copying machine, and an image was transferred to paper at a fixing temperature of 150 ° C. The paper was immersed in methyl ethyl ketone for 30 seconds and then dried to erase the image. Table 2 shows the measurement results of the reflection density of the paper after the image was erased. As shown in Table 2, the reflection density of the paper after the image was erased was almost the same as the initial reflection density. The same results as in Example 1 were obtained for the stability of the erased state.

[0069]

[Table 2]

Example 3 As a precursor of the phase separation inhibitor, D
A product in which the hydroxyl group of glucose was protected with any of the protecting groups in Table 3 was prepared.

1 part by weight of crystal violet lactone (CVL) as a coloring compound, 1 part by weight of propyl gallate as a color developer, 10 parts by weight of cholesterol as a decolorizer, 10 parts by weight of a precursor of a phase separation inhibitor, binder 77 parts by weight of polystyrene having a molecular weight of 45000, and LR-147 (Nippon Carlit Co., Ltd.) as a charge control agent
One part by weight was mixed and 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.

The obtained toner was placed in a toner cartridge of a printer (manufactured by Canon, Laser Shot LBP-730), and the image was transferred to paper. Then, add 15 pieces of paper
It was left in a thermostat at 0 ° C. for 1 hour. The paper was immersed in methyl ethyl ketone for 30 seconds and then dried to erase the image. Table 3 shows the results of measuring the reflection density of the paper after erasing the image.
Shown in As shown in Table 3, the reflection density of the paper after the image was erased was almost the same as the initial reflection density except for the case where some precursors of the phase separation inhibitor were used.

[0073]

[Table 3]

Example 4 A solution prepared by dissolving 4 g of gelatin in 40 mL of water (37 ° C.)
4 g of potassium tert-butoxide as a basic substance
Was dissolved. 11 g of sodium sulfate in 45 mL of this solution
Was added to induce coacervation. 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.

As a precursor of the phase separation inhibitor, D-
A product in which the hydroxyl group of glucose was protected by any of the protecting groups in Table 4 was prepared. 1 part by weight of crystal violet lactone (CVL) as a coloring compound, 1 part by weight of propyl gallate as a color developer, 10 parts by weight of cholesterol as a decolorant, 10 parts by weight of a precursor of a phase separation inhibitor, as described above. 2 parts by weight of the prepared microcapsules, 75 parts by weight of polystyrene having a molecular weight of 45,000 as a binder, and 1 part by weight of LR-147 (Nippon Carlit Co., Ltd.) as a charge control agent 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.

The obtained toner was placed in a toner cartridge of a copying machine, and an image was transferred to paper at a fixing temperature of 150 ° C. The paper was immersed in methyl ethyl ketone for 30 seconds and then dried to erase the image. Table 4 shows the results of measuring the reflection density of the paper after image erasure. As shown in Table 4, the reflection density of the paper after image erasure was almost the same as the initial reflection density, except for the case where some precursors of the phase separation inhibitor were used.

[0077]

[Table 4]

Example 5 As a precursor of the decoloring agent, a precursor in which the carboxyl group of cholic acid was protected with any one of the protecting groups shown in Table 5 was prepared.

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 precursor of a decolorizing agent, 79 parts by weight of polystyrene having a molecular weight of 45000 as a binder, and One part by weight of LR-147 (Nihon Carlit Co., Ltd.) was mixed as a charge control agent, kneaded sufficiently using a kneader, and pulverized with 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 this powder.

The obtained toner was placed in a toner cartridge of a copying machine, and an image was transferred to paper at a fixing temperature of 150 ° C. The paper was immersed in methyl ethyl ketone for 30 seconds and then dried to erase the image. Table 5 shows the measurement results of the reflection density of the paper after the image was erased. As shown in Table 5, the reflection density of the paper after the image was erased was almost the same as the initial reflection density.

[0081]

[Table 5]

Example 6 A solution prepared by dissolving 4 g of gelatin in 40 mL of water (37 ° C.)
Then, 4 g of potassium carbonate was dissolved as a basic substance. 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.

Further, a precursor in which the carboxyl group of cholic acid was protected with any of the protecting groups shown in Table 6 was prepared as a precursor of the decoloring agent. 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 precursor of a decolorant, 2 parts by weight of microcapsules prepared as described above, a binder Was mixed with 77 parts by weight of polystyrene having a molecular weight of 45000, and 1 part by weight of LR-147 (Nippon Carlit) as a charge control agent, and kneaded sufficiently using a kneader. This kneaded material is pulverized by a pulverizer to obtain an average particle size of 1
A powder of 0 μm was obtained. Toner was prepared by adding 1 wt% of hydrophobic silica to 100 wt% of this powder.

The obtained toner was placed in a toner cartridge of a copying machine, and an image was transferred to paper at a fixing temperature of 150 ° C. The paper was immersed in diethoxyethane for 30 seconds and then dried to erase the image. Table 6 shows the measurement results of the reflection density of the paper after the image was erased. As shown in Table 6, the reflection density of the paper after the image was erased was almost the same as the initial reflection density. The same results as in Example 1 were obtained for the stability of the erased state.

[0085]

[Table 6]

Example 7 As a precursor of a polymeric decoloring aid, a polyacrylic acid having a molecular weight of 50,000 was prepared by carboxyl groups of tricarboxylic acid.

1 part by weight of crystal violet lactone (CVL) as a color-forming compound, 1 part by weight of propyl gallate as a color developer, 7 parts by weight of cholic acid as a decolorizing agent, 31 parts by weight of a precursor of a polymeric decoloring aid Parts, polystyrene having a molecular weight of 45,000 as a binder, and 57 parts by weight of LR-147 (Nippon Carlit Co., Ltd.) as a charge controlling agent were mixed together, kneaded sufficiently using a kneader, and pulverized using a pulverizer. A powder of 10 μm was obtained. Toner was prepared by adding 1 wt% of hydrophobic silica to this powder.

The obtained toner was placed in a toner cartridge of a printer, and the image was transferred to paper. Thereafter, the paper was passed through a heating roller set at 200 ° C. and heated for 30 seconds to erase the image. As a result, a slight amount of wax was formed (a state in which the wax component and the like soaked in the paper and the paper was glossy), but the reflection density of the paper after the image was erased was 0.07, which was the same as the initial reflection density. The same results as in Example 1 were obtained for the stability of the erased state.

Example 8 As a precursor of a polymeric decolorizing aid also serving as a binder, a trimethylsilylated styrene-acrylate copolymer having a molecular weight of 45,000 (acrylate content 30 w
t%).

1 part by weight of crystal violet lactone (CVL) as a color-forming compound, 1 part by weight of propyl gallate as a color developer, 5 parts by weight of cholic acid as a decolorizer, a precursor (binder) ) 57 parts by weight, and LR-147 (Nippon Carlit Co., Ltd.) as a charge control agent
One part by weight was mixed, sufficiently kneaded using a kneader, and pulverized with 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 this powder.

The obtained toner was placed in a toner cartridge of a printer, and the image was transferred to paper. The paper was sprayed with a 3 wt% aqueous solution of potassium carbonate as a basic substance, immersed in methyl ethyl ketone for 30 seconds, dried, and the image was erased. As a result of measuring the reflection density of the paper after erasing the image, it was 0.10, which was almost the same as the initial reflection density. The same results as in Example 1 were obtained for the stability of the erased state.

Example 9 As a precursor of a polymeric decoloring agent, corn starch having a hydroxyl group protected with methoxymethyl ether was prepared.

1 part by weight of crystal violet lactone (CVL) as a color-forming compound, 1 part by weight of propyl gallate as a color developer, 30 parts by weight of a precursor of a polymer decolorizer,
67 parts by weight of styrene having a molecular weight of 45000 as a binder, and 1 part by weight of LR-147 (Nippon Carlit Co.) as a charge controlling agent are mixed, sufficiently kneaded using a kneader, and pulverized by a pulverizer to obtain an average particle diameter of 10 μm. A powder was obtained. Toner was prepared by adding 1 wt% of hydrophobic silica to this powder.

The obtained toner was placed in a toner cartridge of a copying machine (Primage 3860, manufactured by Toshiba), and the image was transferred to paper at a fixing temperature of 150 ° C. The paper was immersed in methyl ethyl ketone for 30 seconds and then dried to erase the image. As a result of measuring the reflection density of the paper after erasing the image, the reflection density was about 0.10, which is almost the same as the initial reflection density, and the image was successfully erased.

[0095]

As described above in detail, according to the present invention, good compatibility can be obtained by introducing a protective group even in a decoloring agent or a decolorizing auxiliary having poor compatibility with other components such as a binder. As shown in the figure, the dispersibility is improved, and the precursor of the decoloring agent or the decolorizing auxiliary exhibits a decoloring effect while maintaining a good dispersion state when the protective group is dissociated, so that the image is erased. In the process, erasure unevenness due to dispersion failure can be prevented. Further, since the decoloring agent or the precursor of the decoloring aid does not exhibit a decoloring effect until the protective group is dissociated, the image can be stably maintained even in a relatively severe use environment.

Continued on the front page F term (reference) 2H005 AA06 AA21 CA21 4J039 AB02 AD03 AD08 AD09 AD15 AE03 AE05 AE06 AE07 AE08 AE10 AE13 BA10 BA14 BA16 BA18 BA19 BA24 BC07 BC16 BC19 BC29 BC33 BE01 BE02 BE33 EA29 GA06 GA10 GA24 GA27 GA28

Claims (4)

[Claims] 1. An erasable image-forming material comprising a color former, a color developer, and a precursor of a decolorant whose functional group is protected by a protecting group. 2. A color former, a color developer, a decolorant,
An erasable image-forming material, comprising a polymer compound having a functional group protected by a protective group and acting as a decolorizing aid. 3. The erasable image according to claim 2, wherein the polymer compound acting as a color erasing aid is copolymerized with a binder, and the functional group thereof is protected with a protecting group. Forming material. 4. The protecting group is dissociated by heating, light irradiation or contact with a basic substance.
4. The erasable image forming material according to any one of items 1 to 3.