JP3290963B2 - Erasable image forming material and image erasing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an erasable image forming material and a method for erasing an image formed using the image forming material.

[0002]

2. Description of the Related Art In recent years, with the spread of OA, the data amount of various types of information has been steadily increasing, and the output of information has also increased accordingly. The output of information is represented by a display output and a hard copy output to paper by a printer. However, display output requires a large-scale circuit board in the display unit, and thus poses a problem in terms of portability and cost. In addition, in the hard copy output, when information increases, a large amount of paper is used as a recording medium, which is problematic in terms of resource protection. In addition, recycling paper printed by a printer or copier requires a large amount of bleach and water, and thus the recycling cost is high. Therefore, information is printed on paper using an erasable image forming material, and the formed paper is erased and the paper returned to a blank state is reused (reused) to reduce the actual amount of paper used. It is considered to reduce.

Conventionally, an image forming material which can be erased by applying heat is disclosed, for example, in Japanese Patent Application Laid-Open No. 7-81236. This image forming material contains a coloring compound such as a leuco dye, a developer, and an organic phosphoric acid compound having an erasing action.

However, when an image forming material comprising such components is used, erasing is insufficient and it is difficult to return the paper to a blank state. For this reason, erasable image forming materials have not yet been put to practical use.

Accordingly, the present inventors have been developing a new image forming material and an image erasing method capable of obtaining a good erasing state, but in the process, depending on the binder used for the image forming material, good erasing is possible. It has been found that the state may not be obtained or the stability of the erased state may be deteriorated.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming material which can obtain a good erased state without depending on the binder used and which has a stable erased state. An object of the present invention is to provide a method capable of satisfactorily erasing a formed image.

[0007]

According to the image erasing method of the present invention, the image forming material contains a color former, a color developer and an erasing agent. Is brought into contact with a solvent.

In this method, the image forming material may further contain a basic compound. Further, the image forming material may further contain a binder. On the other hand, the solvent may further contain an erasing agent. In this method, it is preferable to remove the solvent from the recording medium after bringing the image forming material into contact with the solvent.

The image-forming material of the present invention comprises a color-forming compound,
It is characterized by containing polystyrene or a styrene-acrylic copolymer as a developer, an erasing agent, and a binder.

Another image forming material of the present invention is characterized by containing a color developing compound, a color developer, an erasing agent, and a polyester or epoxy resin as a binder.

Still another image-forming material of the present invention is an image-forming material comprising a color former, a developer, an erasing agent, a polyester or epoxy resin as a binder, and a basic compound. In this case, it is preferable that the basic compound is encapsulated in the microcapsules.

In any of the above image forming materials, the content of the binder is preferably 30% by weight or more.
Such an image forming material is used, for example, as a toner for electrophotography.

Another image erasing method according to the present invention is a method for erasing an image formed of an image forming material containing a polyester or epoxy resin as a color former, a developer, an erasing agent, and a binder. It is characterized in that a solvent containing a basic compound is brought into contact with the material.

Still another image erasing method of the present invention is a method for erasing an image formed of an image forming material containing a polyester or epoxy resin as a color former, a developer, an erasing agent, and a binder. It is characterized in that the forming material is heated.

Still another image erasing method of the present invention is a method for erasing an image formed of an image forming material containing a polyester or an epoxy resin as a color former, a developer, an erasing agent, and a binder. The method is characterized by heating after contacting a basic compound with a forming material.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The image forming material according to the present invention can form an image by using a color former, a developer and an erasing agent.
Erasing is enabled. First, the operation of the basic components constituting the erasable image forming material will be schematically described. A color-forming compound is a precursor compound of a dye that forms a color image such as a character or a figure, and a color developer is a color-forming compound that interacts with a color-forming compound (mainly exchanges electrons or protons). A compound that develops a color. The erasing agent is a compound that is preferentially compatible with one of the developer and the coloring compound.

The composition system of the image forming material comprising these components can take the following two states when solidified. That is, (1) the erasing agent is mixed with an amount of the coloring compound and the developing agent in an amount corresponding to the equilibrium solubility, and an excess of the coloring compound and the developing agent exceeding the equilibrium solubility in the erasing agent is added to the erasing agent. (2) a state in which the color developing compound and the color developing agent form a color due to the interaction, and (2) the erasing agent takes in the developing agent or the color developing compound in a large amount exceeding the equilibrium solubility, and the color is formed. In this state, the interaction between the coloring compound and the developer is reduced and the color is erased.

In the present invention, in order to erase an image formed on a basically white recording medium, for example, paper, using an image forming material containing the above-mentioned components, the image forming material is erased by an erasing agent. Or a method in which the image forming material is brought into contact with a solvent.

The state change between the colored state and the decolored state is performed according to the following principle. Here, it is assumed that the erasing agent preferentially dissolves the color developer when the composition system is in a molten state and is in a fluidized state, and the case of erasing by heating will be described first. At room temperature, the state in which the phase of the coloring compound and the developer and the phase of the erasing agent are phase-separated is close to the equilibrium state. In this case, the color-forming compound and the 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 erasing agent in the fluid state, and loses the interaction with the color-forming compound, so that the state becomes the decolored state. When the composition in the molten state is forcibly solidified by cooling, the erasing agent becomes amorphous by incorporating an amount of the developer exceeding the equilibrium solubility and becomes colorless at room temperature. The amorphous composition system is in a relatively non-equilibrium state, but has a sufficiently long life at a temperature lower than the glass transition point Tg, and easily equilibrates from the amorphous state if Tg is higher than room temperature. It does not move to the state.

In the method in which the image forming material is brought into contact with a solvent, erasing is performed in the same manner as in the heating method, according to the following principle. That is, when an image forming material in a colored state on paper is brought into contact with a solvent, the solvent swells or partially dissolves the binder. As a result, the developer and the erasing agent can move relatively freely, the developer mixes with the erasing agent, and the interaction between the developer and the coloring compound is lost, so that the image forming material is erased. To color. Then, when the solvent is removed from the paper, the erasing agent becomes amorphous in a state in which the developing agent has taken in an amount of the developer exceeding the equilibrium solubility, so that the erasing state of the image forming material is fixed. This erased state is very stable at room temperature.

When a heat treatment or a solvent treatment is performed in a state where the color developing compound and the color developing agent interact with each other to form a color as described above, the color developing compound and the decoloring agent combine to form the color developing compound. Is induced and the erased state is fixed. The interaction between these states will be described with reference to the following chemical formulas, taking a typical color-forming compound and a color developer as examples. As shown in the chemical formula (A), when the color-forming compound binds to the color developer, a double bond is formed at the center of the color-forming compound, and the π-electron conjugate system spreads over the entire molecule to form a color. . On the other hand, as shown in the chemical formula (B), when the color developer and the decolorant are bonded, the carboxylic acid portion of the color forming compound which has been involved in the bond with the color developer becomes free, and the lactone ring is formed. Form and stabilize. As a result, the double bond represented by the chemical formula (A) disappears, and the π-electron conjugated system is cut off, so that the colorless state is obtained. It is also considered that the affinity between the color former and the color developer is lower than the affinity between the color developer and the color erasing agent when the image forming material in the color erasing state is heated or comes into contact with a solvent.

[0023]

Embedded image

Next, specific compounds that can be used as components of the image forming material of the present invention will be described.

The color-forming compounds used in the present invention include leuco auramines, diaryl phthalides, polyaryl carbinols, acyl auramines, aryl auramines, rhodamine B lactams, indolines, spiropyrans Donating organic substances such as benzenes and fluorans.

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-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
-Dimethylfluorane, phenylhydrazide-γ-lactam, 3-amino-5-methylfluoran and the like. These can be used alone or in combination of two or more. A variety of colors can be obtained by appropriately selecting a color-forming compound, so that multi-color support is possible.

The color developing agent used in the present invention includes phenol, phenol metal salt, carboxylic acid metal salt, benzophenone, sulfonic acid, sulfonic acid salt, 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 erasing agent used in the present invention preferably has good colorlessness when in the amorphous state. The more the erasing agent is amorphous and colorless and transparent, the more the paper can return to a state close to the original white paper when the color of the ink is erased. Since such properties are required, the erasing agent is preferably a compound having a large molecular weight, a small crystal melting enthalpy change ΔH per weight, and a small maximum crystal growth rate MCV. If the change in enthalpy of melting ΔH of the crystal of the erasing agent is small, the amount of heat energy required for melting the crystal becomes small, which is also preferable from the viewpoint of energy saving. The melting point of the erasing agent is preferably 50 ° C. or higher. Further, the erasing agent preferably has a high affinity for the color developer, and for example, a compound having an alcoholic hydroxyl group is suitable. Preferred erasing agents include the following compounds (a) to (c).

(A) Sterol compound. Specific examples of the sterol compound include cholesterol, stigmasterol, pregnenolone, methylandrostenediol, estradiol benzoate, epiandrostene, stenolone, β-sitosterol, pregnenolone acetate, β-cholesterol, 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 erasing agents can be used alone or in combination of two or more.
Among these erasing agents, those suitable for obtaining a stable erased state include methylandrostenediol, hecogenin, locogenin, tigogenin, diosgenin, esmilagenin and the like.

When these erasing agents are used, when the composition in an amorphous state is heated to a temperature exceeding the glass transition point, the diffusion rate of the developer rapidly increases, and the developer returns to an equilibrium state. The phase separation movement between the developer and the erasing agent 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 erasing agent (a) can, in principle, reversibly repeat a colored state and a decolored state. In this sense, the erasing agent (a) may be hereinafter referred to as a “reversible erasing agent”. Actually, rewritable paper utilizing such a reversible change has been proposed. However, the image-forming material of the present invention is intended to be erased after an image is formed, and is essentially not required to be reversible except for special uses.

(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, hyodeoxycholic acid, hyodeoxycholic acid methyl ester, testosterone, methyltestosterone, 11α-hydroxymethyl Testosterone, hydrocortisone, cholesterol methyl carbonate, α-cholestanol. Among them, those having two or more hydroxyl groups are particularly preferable.

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

(C) Non-aromatic cyclic compounds having 5 or more membered rings having one or more hydroxyl groups. 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), Examples include formula sugar alcohols (eg, glucose and saccharose) and derivatives of cyclic sugar alcohols (eg, 1,2,5,6-diisopropylidene-D-mannitol).

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

The above phase separation inhibitors can be further classified into two types. That is, (c1) a compound having a relatively high melting point and glass transition point and easily becoming amorphous at ordinary temperature (hereinafter referred to as a highly amorphous phase separation controlling agent), and (c2) a melting point and glass transition point Because it is relatively low, it may be difficult to become amorphous at room temperature and form microcrystals,
A compound having a very high compatibility with a color developer in a fluidized state (hereinafter referred to as a low amorphous phase separation inhibitor). Even when a highly amorphous phase separation controlling agent and a low amorphous phase separation controlling agent are used in combination as the erasing agent, 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 cyclododecanol, 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, isosorbide; derivatives of cyclic sugar alcohols, such as 1,2: 5 , 6-diisopropylidene-D-mannitol. When a material having a large steric hindrance molecular structure obtained by reacting a compound having another cyclic structure with a cyclic alcohol as described above is used, the temperature of the image forming material in a decolored state is used. Stability can be improved. For example, esters of isosorbide and cyclohexanedicarboxylic acid are suitable low amorphous phase separation inhibitors. One or more of these can be used.

A color-forming compound in the image-forming material of the present invention,
Preferred mixing ratios of the developer and the erasing agent are 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 erasing agent is preferably set to 1 to 200 parts by weight, more preferably 10 to 100 parts by weight, per 1 part by weight of the coloring compound. If the erasing agent is less than 1 part by weight,
It becomes 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 erasing agent exceeds 200 parts by weight, the color formation of the image forming material becomes insufficient.

The image forming material according to the present invention can be used in various forms. For example, thermal printer inks; inkjet printer inks; toners for copiers (PPCs), laser beam printers, faxes, etc .; printing inks for screen printing and type printing; inks for writing utensils such as ballpoint pens and fountain pens. it can. The ink of the thermal printer is used by mixing a color former, a developer, an erasing agent, a wax and the like, and applying the mixture to a plastic sheet. The ink of the inkjet printer is used by dispersing a color former, a color developer, an erasing agent, and the like in a solvent. The toner is prepared by pulverizing a composition containing a color former, a developer, an erasing agent, a binder, and the like. In this case, typical binders include polystyrene, styrene-acrylic copolymer, polyester, and epoxy resin.

In the case of an image forming material containing a binder, it is preferable to appropriately adjust the content in the image forming material according to the average molecular weight of the binder. This is because when an image is erased using a solvent, the affinity between the solvent and the binder decreases as the average molecular weight of the binder increases.

When polystyrene is used as the binder, the content in the image forming material is preferably adjusted as follows according to the average molecular weight. When the average molecular weight is 1,000 to 200,000, 30 to
90 wt%. When the average molecular weight is 200,000 to 600,000, 3
0 to 80 wt%. When the average molecular weight is 600,000 to 1,000,000,
30-70 wt%.

Acrylic monomers constituting the styrene-acrylic copolymer include n-butyl methacrylate, isobutyl methacrylate, ethyl acrylate,
n-butyl acrylate, methyl methacrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, diethylaminopropyl acrylate, 2-ethylhexyl acrylate, butyl acrylate-N- (ethoxymethyl) acrylamide, ethylene glycol methacrylate, 4-hexafluorobutyl methacrylate And the like. One or more of these acrylate monomers can be used. Further, in addition to styrene and acrylic monomers, butadiene, maleic ester, chloroprene, and the like may be copolymerized, but the content of these components is preferably 10% by weight or less. The ratio of styrene in the binder is preferably at least 50 wt%. When a styrene-acrylic copolymer is used as the binder, it is preferable to adjust the content in the image forming material according to the average molecular weight as follows. When the average molecular weight is 1,000 to 200,000, 30 to
95 wt%. When the average molecular weight is 200,000 to 400,000, 3
0 to 85 wt%. When the average molecular weight is 400,000 to 1,000,000,
30 to 75 wt%.

A blend polymer of polystyrene and an acrylic resin may be used as a binder. One or more acrylic resins can be used. In addition, butadiene, maleic acid ester, chloroprene, etc.
A copolymer containing 0% or less may be used. The proportion of polystyrene in the binder is preferably at least 50 wt%. When a blend polymer of polystyrene and an acrylic resin is used as a binder, the content in the image forming material is preferably adjusted as follows according to the average molecular weight. When the average molecular weight is 1,000 to 200,000, 30 to
95 wt%. When the average molecular weight is 200,000 to 400,000, 3
0 to 85 wt%. When the average molecular weight is 400,000 to 1,000,000,
30 to 75 wt%.

The carboxylic acid and polyhydric alcohol which are the raw materials of the polyester are not particularly limited. As carboxylic acids, terephthalic acid, fumaric acid, maleic acid, succinic acid,
Glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassic acid, pyromellitic acid, citraconic acid, glutaconic acid, mesaconic acid, itaconic acid, terraconic acid, phthalic acid, isophthalic acid, hemimelitic acid, melophanic acid Acids, trimesic acid, planitic acid, trimellitic acid, and the like. One or more of these can be used. Examples of polyhydric alcohols include bisphenol A, hydrogenated bisphenol A, ethylene glycol, propylene glycol, butanediol, neopentyldiol, hexamethylenediol, heptanediol, octanediol, pentaglycerol, pentaerythritol, cyclohexanediol, cyclopentanediol, Examples include pinacol, glycerin, etherified diphenol, catechol, resorcinol, pyrogallol, benzenetriol, phloroglucinol, and benzenetetraol. One or more of these can be used.
Further, a blend polymer of two or more polyesters may be used. When polyester is used as the binder of the toner, the content in the image forming material is preferably adjusted as follows according to the average molecular weight. 30 to 95 when the average molecular weight is 1,000 to 5,000
wt% When the average molecular weight is 5,000 to 10,000, 30 to 9
0 wt% When the average molecular weight is 10,000 to 20,000, 30 to
87 wt% 30 when the average molecular weight is 20,000 to 100,000
８５85 wt% When the average molecular weight is 100,000 to 1,000,000,
When using 30 to 80 wt% polyester as a binder for the thermal transfer ink, the content of the polyester is preferably 2 to 50 wt% because paraffin is used as a wax component.

The epoxy resin is synthesized using epichlorohydrin and a compound having a polyhydric phenolic hydroxyl group as raw materials. Examples of the polyhydric phenol compound include bisphenol A, hydrogenated bisphenol A, bisphenol S, etherified diphenol, catechol, resorcinol, pyrogallol, benzenetriol, phloroglucinol, benzenetetraol, and the like. One or more of these are used. In addition, 15 wt% of phenol resin, urea resin, melanin resin, alkyd resin, acrylic resin, polyester, polyamide, polyurethane, etc.
% Or less.

When an epoxy resin is used as a binder for the toner, the content in the image forming material is preferably adjusted as follows according to the average molecular weight. 30 to 95 when the average molecular weight is 1,000 to 5,000
wt% When the average molecular weight is 5,000 to 10,000, 30 to 9
0 wt% When the average molecular weight is 10,000 to 20,000, 30 to
87 wt% 30 when the average molecular weight is 20,000 to 100,000
８５85 wt% When the average molecular weight is 100,000 to 1,000,000,
When the epoxy resin is used as the binder of the thermal transfer ink, the content of the polyester is preferably 2 to 50% by weight because paraffin is used as the wax component.

When a polyester or an epoxy resin is used as a binder, an image cannot be erased well or the stability of the erased state is deteriorated due to the effect of unreacted carboxylic acid or phenol remaining in the binder. is there. That is, when these acidic compounds are present in the vicinity of the color-forming compound, they act on the color-forming compound to bring about an irreversible coloring state. On the other hand, if a compound that acts on an acidic compound and neutralizes it is allowed to coexist,
The original coloring and decoloring can be realized by the interaction of the coloring compound, the developer and the erasing agent without the acidic compound acting on the coloring compound. In the present invention, it is preferable to use a basic compound in order to avoid an unreacted carboxylic acid or phenol from affecting the image erasure.

Even when a polymer having no acid value, such as a polystyrene resin, is used as a binder, a poorly dispersed toner may be produced industrially. This causes erasing failure. Even in such a case, if the basic compound is dispersed in the toner or the microcapsules in which the basic compound is encapsulated are dispersed, the effect of the erasing agent in the toner is assisted, and the effect of keeping the erased state in good condition. is there.

Further, when a basic compound is used, even when an image is formed on paper having a pH of less than 8, the influence on image erasure can be avoided. In any case, the basic compound is not particularly limited, and may be an inorganic compound or an organic compound.

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.

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.

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.

Other organic basic compounds that can be used include amidine, guanidine, aminoguanidine, urea, thiourea, semicarbazide, thiosemicarbazide, and carbonohydrazide.

In the present invention, the basic compound may be directly mixed with other components of the image forming material. Further, it is preferable that the basic compound is mixed with other components of the image forming material in a state of being encapsulated in the microcapsules.

As the shell material of the microcapsule,
A material that is broken when the image forming material is heated to erase the image and that releases the enclosed basic compound is selected.
The temperature at which the microcapsules break is preferably from 120 to 200 ° C. Suitable materials include polyether sulfone, polyether ketone, epoxy resin, polyethylene, polypropylene, polyphenylene ether,
Polyphenylene sulfite, polyalkylene oxide, polystyrene, polyphenol ether, nylon, polyamide, polyurethane, gelatin, polymethacrylic acid, polyimide, melanin resin, polyester, polyacrylic acid, polyvinyl alcohol, polyacrylonitrile, polymethacrylonitrile, polysiloxane, Examples thereof include polysulfide, polyvinyl acetate, nitrocellulose, methylcellulose, acetylcellulose, ethylcellulose, gum arabic, polyvinylpyrrolidone, polycarbonate, polysulfone, polyisocyanate, polypyrrole, chitosan, collagen, and polyamino acids. These may be used alone or as a mixture. Further, these copolymers may be used.

The method of erasing an image formed on paper using the image forming material in the present invention is roughly classified into a method of heating the image forming material to a temperature exceeding the melting point of the erasing agent, as described above. Alternatively, a method of contacting the image forming material with a solvent may be used.

In the method of erasing an image by heating an image forming material, a heat roller, a thermal printer head (TPH), a thermal bar, a hot stamp, an infrared lamp, hot air, or the like can be used as a heating means.

In the present invention, when erasing an image formed with an image forming material containing a polyester or an epoxy resin as a color developing compound, a color developer, an erasing agent, and a binder, a basic After contacting the compound, a method of erasing an image by heating may be used.

To contact the basic compound with the image forming material, a method of preparing a solution of the basic compound and spraying it on paper or dipping the paper in the solution is used. The solvent that can be used for preparing the solution is not particularly limited as long as it dissolves the basic compound. Specifically, water, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methylene chloride, ethyl acetate, ethyl lactate, ethyl butyrate, n-pentyl butyrate, ethyl ether,
Tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, cellosolve acetate, γ-butyrolactone, β-propiolactone, n-methylpyrrolidinone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, methyl ethyl ketone, methyl isopropyl ketone, toluene, Examples include xylene, hexane, pentane, heptane, and petroleum fractions (petroleum ether, benzine). The concentration of the solution of the basic compound is preferably 1 to 40% by weight.

In the present invention, the method of contacting the image forming material with a solvent when erasing the image forming material formed on paper, which contains a color developing compound, a color developing agent and an erasing agent, requires a method of thermal erasing. In this case, the quality of the paper in the erased state is improved. The reason is as follows. That is, when the solvent contained in the binder is vaporized after the image forming material is erased by contact with the solvent, the binder becomes porous, and light is scattered on the surface thereof, so that reflection is reduced. Further, since the image forming material spreads as the binder spreads, the boundary between a portion where the image forming material is present and a portion where the image forming material is not present becomes unclear. Therefore, it is impossible to recognize that the image forming material remains with the naked eye or the touch.

In the present invention, an image is formed with an image-forming material containing a color-forming compound, a color developer, an erasing agent, and a polyester or epoxy resin as a binder. May be used in which a solvent containing a basic compound is brought into contact with the solvent.

In order to carry out the image erasing method using a solvent, an image erasing apparatus having means for bringing the image forming material into contact with the solvent and means for removing the solvent from the paper is used.

Means for bringing the image forming material colored on the paper into contact with the solvent include 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, and A gravure roller for supplying paper is used. As a means for removing the 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 that the apparatus of the present invention is provided with a means for collecting the used solvent. 1 to 5 show specific examples of an image erasing apparatus using a solvent.

A solvent container 101 and a solvent tank 103 for supplying a solvent 102 to the solvent container 101 are provided below the image erasing apparatus shown in FIG. The paper is carried into the apparatus one by one by the carry-in roller 104 with the surface on which the image is formed facing down, and is carried by the carrier roller. While the paper is conveyed between the immersion roller 105 and the opposing roller 106, the solvent 1
02 and the image is erased. Thereafter, the paper is conveyed by a carrier roller, dried by applying hot air generated from a radiator of an electronic cooler described later at the upper part of the apparatus, and then heated by the heat roller 107 and the wrinkles are extended. The paper from which the solvent has been removed in this way
The sheet is carried out of the apparatus by the carry-out roller 108 and stored in a stocker.

This apparatus is provided with a solvent recovery mechanism. This recovery mechanism has a recovery device in which the adsorbent 110 and the electronic cooler 111 are sealed, and a circulation pump 114 as main components. The used solvent is stored in the recovery solvent container 109 from the solvent container 101. The solvent vaporized in the recovery solvent container 109 is adsorbed by the adsorbent 110 cooled by an electronic cooler (for example, a Peltier device) 111. The temperature of the electronic cooler 111 is set so that the vapor pressure of the solvent becomes 100 ppm or less. Adsorbent 11
The solvent adsorbed at 0 is drawn by the circulation pump 114 and absorbed by the absorption filter 113. Providing the absorption filter 113 in front of the circulation pump 114 can prevent the pump material from being exposed to the solvent.
A dehumidifier may be provided to prevent the entry of moisture in the atmosphere. The warm air generated from the radiator 112 of the electronic cooler 111 is used for drying the paper immersed in the solvent as described above.

The image erasing apparatus shown in FIG. 2 employs a gravure roller 12
1 has a configuration substantially similar to that of the apparatus shown in FIG. The gravure roller 121 rotates to rotate the solvent container 10.
After being immersed in one solvent 102, the amount of solvent adhering to the surface is adjusted by blade 123. The paper carried into the apparatus is a gravure roller 121 and a counter roller 12.
2, the solvent is supplied to the paper by the gravure roller 121, and the image is erased.

The image erasing apparatus shown in FIG. 3 uses a pump 131 and a spray nozzle 132 as means for bringing a solvent into contact with an image forming material on paper, and uses a lamp heater 133 for removing the solvent. It has almost the same configuration as the device. The image is erased by pumping the solvent 102 from the solvent container 101 onto the paper carried into the apparatus by the pump 131 and spraying it from the nozzle 132. Thereafter, the conveyed paper is dried with warm air and heated by a lamp heater 133 to remove the solvent.

FIGS. 4A to 4C show an example of a batch type image erasing apparatus using a solvent. (A) is a plan view, (B)
And (C) is a side view. A solvent tank 201 is provided below the apparatus and accommodates a solvent 202. A solvent immersion tank 203 is provided above the apparatus. A chemical pump 204 and a liquid feed pipe 205 connected to the chemical pump 204 are provided between the solvent tank 201 and the solvent immersion tank 203. At the lower part of the solvent immersion tank 203, an electronic cooler (for example, a Peltier element) 206 is provided with the heat radiation surface facing upward. Electric power is supplied from a power supply 207 to the electronic cooler 206.

Using this apparatus, an image is erased as follows. The lid of the solvent immersion tank 203 is opened, and a bundle of about 100 sheets is placed therein. Chemical pump 20
In step 4, the solvent 202 is supplied from the solvent tank 201 to the solvent immersion tank 203, and the paper is immersed in the solvent to erase the image.
Thereafter, the solvent tank 201 is operated by the chemical pump 204.
The solvent is discharged to the solvent immersion tank 203 from. Further, the solvent is removed from the paper using the heat radiation of the electronic cooler 206.
Further, the vaporized solvent can be cooled and collected by the electronic cooler 206.

FIG. 5 shows an example of a large in-line plant using a solvent. In this apparatus, an image is erased as follows. A bundle of paper 301 is transferred to a conveyor 302.
Immersed in a solvent 304 to remove the image. The bundle of paper 301 in the solvent processing tank 303 is taken out by the conveyor 305 and sent to the primary drying station. By supplying hot air from the heater 306 and the fan 307 in the primary drying place, the paper is separated and dried, and further sent to the secondary drying place. In the secondary drying station, the paper is completely dried by the infrared heater 309 while being transported by the conveyor 308. The dried paper is stored in the storage 310.

The solvent used in the present invention is (A)
It preferably has a property of assisting the formation of a hydrogen bond between the color developer and the erasing agent, and more preferably has a property of having high affinity with the binder (B) and easily penetrating into the inside of the image forming 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. 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 above 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.

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.).

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.

Further, the above-mentioned erasing agent may be added to these erasing solvents. In this case, the addition rate of the erasing agent is not particularly limited, but is preferably 1 to 40% by weight. When the erasing agent is added to the erasing solvent in this way, the erasing agent in the solvent and the erasing agent in the image forming material work synergistically to obtain an extremely good erased state.

[0079]

Embodiments of the present invention will be described below.

In the following examples, Neus, which is a standard paper used in Europe as an image forming paper, is used.
Iedler (pH = 9.4) was used. The reflection density of this paper is 0.07.

Example 1 1 part by weight of crystal violet lactone (CVL) as a color-forming compound and propyl gallate 1 as a color developer
Parts by weight, 10 parts by weight of cholesterol and 10 parts by weight of D-glucose as an erasing agent, 77 parts by weight of polystyrene having an average molecular weight of 45,000 as a binder, and LR-147 (manufactured by Nippon Carlit Co., Ltd.) 1 as a charge controlling agent
Parts by weight were mixed and kneaded with a kneader. The kneaded product was pulverized with a pulverizer to obtain a powder having an average particle size 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 the image was transferred to paper.

The organic solvent shown in Table 1 was placed in the image erasing apparatus shown in FIG. 2, the solvent was brought into contact with the paper on which the image was formed for 30 seconds to erase the image, and then dried. Table 1 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 1, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image could be satisfactorily erased using any of the organic solvents.

[0083]

[Table 1]

Further, the paper from which the image was erased was removed at 60 ° C. for 30 minutes.
After leaving for 0 hours, the image did not reappear.
Thereafter, the process of transferring another image to the paper from which the image had been erased and erasing it was repeated nine times. Then transferred 10
The second image 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 quality of the erased state were good.

Example 2 A toner was prepared in the same manner as in Example 1 except that polystyrene having a molecular weight of 45,000 was added as a binder at a ratio shown in Table 2. The obtained toner was placed in a toner cartridge of a laser beam printer, and an image was printed on paper.

Ethylene glycol diethyl ether (that is, 1,2-diethoxyethane) was placed in the image erasing apparatus shown in FIG. 1, and the paper on which the image was formed was immersed in a solvent for 30 seconds to erase the image, and then dried. Table 2 shows the measurement results of the reflection density of the paper from which the image was erased. When a toner having a polystyrene content of 20 to 25% by weight was used, the reflection density was not measured because the image forming material flowed out during the immersion in the solvent, leaving traces on the paper surface. When a toner having a polystyrene content of 30% by weight or more was used, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image was successfully erased. The same results as in Example 1 were obtained for the stability of the erased state.

[0087]

[Table 2]

Example 3 As shown in Table 3, a toner was prepared in the same manner as in Example 1 except that polystyrenes having different molecular weights were added at a predetermined ratio as a binder. The resulting toner was placed in a facsimile toner cartridge, and the image was transferred to paper.

Ethylene glycol diethyl ether was placed in the image erasing apparatus shown in FIG. 3, and the solvent was sprayed on the paper on which the image was formed for 30 seconds to erase the image, followed by drying. Table 3 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 3, when polystyrene having a large molecular weight is used, it is understood that it is preferable to reduce the content.

[0090]

[Table 3]

Example 4 A toner was prepared in the same manner as in Example 1 except that 77 parts by weight of a styrene / n-butyl methacrylate copolymer having an average molecular weight of 130,000 (n-butyl methacrylate content: 10 wt%) was added as a binder. Prepared. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

The organic solvent shown in Table 4 was placed in a container, and the paper on which the image was formed was immersed in the solvent for 30 seconds to erase the image, and then dried. Table 4 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 4, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image was satisfactorily erased using any of the organic solvents. The same results as in Example 1 were obtained for the stability of the erased state.

[0093]

[Table 4]

Example 5 Styrene / n having a molecular weight of 130,000 as a binder
A toner was prepared in the same manner as in Example 1 except that a -butyl methacrylate copolymer (n-butyl methacrylate content: 10 wt%) was added at a ratio shown in Table 5.
The obtained toner was placed in a toner cartridge of a laser beam printer, and an image was printed on paper.

Ethylene glycol diethyl ether was placed in a container, and the paper on which the image was formed was immersed in a solvent for 30 seconds to erase the image, and then dried. Table 5 shows the measurement results of the reflection density of the paper from which the image was erased. When a toner having a binder content of 15 to 20% by weight was used, the reflection density was not measured because the image forming material flowed out during the immersion in the solvent, leaving a mark on the paper surface. When a toner having a binder content of 30% by weight or more was used, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image was successfully erased. Example 1 Regarding Stability of Erased State
The same result as was obtained.

[0096]

[Table 5]

Example 6 As shown in Table 6, styrene / n-butyl methacrylate copolymers having different average molecular weights (n-
(Butyl methacrylate content: 10 wt%) was added in a predetermined ratio to prepare a toner in the same manner as in Example 1. The resulting toner was placed in a facsimile toner cartridge, and the image was transferred to paper.

Ethylene glycol diethyl ether was placed in the image erasing apparatus shown in FIG. 1, the paper on which the image was formed was immersed in a solvent for 30 seconds to erase the image, and then dried. Table 6 shows the measurement results of the reflection density of the paper from which the image was erased.
As shown in Table 6, when a binder having a large molecular weight is used, it is found that the content is preferably reduced.

[0099]

[Table 6]

Example 7 As shown in Table 7, as a binder, an average molecular weight of 13 was used.
A toner was prepared in the same manner as in Example 1 except that a styrene / n-butyl methacrylate copolymer having a different content of n-butyl methacrylate at 000 was added at a predetermined ratio. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

Ethylene glycol diethyl ether was put into the image erasing apparatus shown in FIG. 1, the paper on which the image was formed was immersed in a solvent for 30 seconds to erase the image, and then dried. Table 7 shows the measurement results of the reflection density of the paper from which the image was erased.
As shown in Table 7, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image was satisfactorily erased even when the toner containing any binder was used. The same results as in Example 1 were obtained for the stability of the erased state.

[0102]

[Table 7]

Example 8 The procedure of Example 1 was repeated except that 77 parts by weight of a styrene-acrylic copolymer having an average molecular weight of 130,000 and a acrylate monomer content of 10% by weight as shown in Table 8 was added as a binder. To prepare a toner. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

Ethylene glycol diethyl ether was put into the image erasing apparatus shown in FIG. 3, and a solvent was sprayed on the paper on which the image was formed to erase the image, and then dried. Table 8 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 8, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image could be satisfactorily erased using any of the binder-containing toners. The same results as in Example 1 were obtained for the stability of the erased state.

[0105]

[Table 8]

Example 9 As shown in Table 9, the binder had an average molecular weight of 13
000 blended polymer of polystyrene and polyacrylate (polyacrylate content 10% by weight) 7
A toner was prepared in the same manner as in Example 1 except that 7 parts by weight was added. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

Ethylene glycol diethyl ether was placed in a container, the paper on which the image was formed was immersed in a solvent to erase the image, and then dried. Table 9 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 9,
The reflection density of the paper after the image was erased was almost the same as the initial reflection density, and the image could be erased favorably even when the toner containing any binder was used. The same results as in Example 1 were obtained for the stability of the erased state.

[0108]

[Table 9]

Example 10 1 part by weight of crystal violet lactone (CVL) as a color-forming compound and propyl gallate 1 as a color developer
Parts by weight, 10 parts by weight of cholesterol and 10 parts by weight of D-glucose as an erasing agent, 72 parts by weight of a fumaric acid / etherified diphenol-based polyester having an average molecular weight of 11,500 as a binder, 1 part by weight of a charge control agent, and Table 10 5 parts by weight of the basic compound were mixed and kneaded with a kneader. The kneaded product was pulverized with a pulverizer to obtain a powder having an average particle size 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 laser beam printer, and the image was transferred to paper.

The paper on which the image was formed was brought into contact with a heat roller heated to 200 ° C. for 30 seconds to erase the image.
Table 10 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 10, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image could be satisfactorily erased using any of the basic compounds.

[0111]

[Table 10]

Further, the paper from which the image was erased was removed at 60 ° C. for 30 minutes.
After leaving for 0 hours, the image did not reappear.
Thereafter, the process of transferring another image to the paper from which the image had been erased and erasing it was repeated nine times. Then transferred 10
The second image 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 quality of the erased state were good.

Example 11 4 g of a basic compound shown in Table 11 was added to a solution (37 ° C.) of 4 g of gelatin dissolved in 40 mL of water, and 45 mL (37 ° C.) of a solution of 11 g of sodium sulfate was added. Elicitation. This dispersion is added to 30
After cooling to 0 ° C. and standing, the microcapsules were separated by decantation. To 1 mL of the obtained microcapsules, an equal amount 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. Microcapsules encapsulating a basic compound were prepared in such a manner.

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, 10 parts by weight of cholesterol and 10 parts by weight of D-glucose as an erasing agent, and an average molecular weight of 11, as a binder. 67 parts by weight of 500 maleic acid / propylene glycol-based polyester, 1 part by weight of a charge controlling agent, and 10 parts by weight of microcapsules were mixed and kneaded sufficiently using a kneader. This kneaded material is pulverized by a pulverizer,
A powder having an average particle size of 10 μm was obtained. 100% by weight of this powder
Was added with 1 wt% of hydrophobic silica to prepare a toner. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

The paper on which the image was formed was brought into contact with a heat roller heated to 200 ° C. for 30 seconds to erase the image.
Table 11 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 11, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image could be satisfactorily erased using any of the basic compounds. The same results as in Example 10 were obtained for the stability of the erased state.

[0116]

[Table 11]

Example 12 In the same manner as in Example 10 except that 72 parts by weight of maleic acid / etherified diphenol-based polyester having an average molecular weight of 11,500 was used as a binder and 5 parts by weight of dibutylamine was used as a basic compound. A toner was prepared.
The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

The organic solvent shown in Table 12 was placed in the image erasing apparatus shown in FIG. 2, the solvent was brought into contact with the paper on which the image was formed for 30 seconds to erase the image, and then dried. Table 12 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 12, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image was satisfactorily erased using any of the organic solvents. The same results as in Example 10 were obtained for the stability of the erased state.

[0119]

[Table 12]

Example 13 1 part by weight of ODB-2 (manufactured by Yamamoto Kasei) as a color-forming compound, 1 part by weight of 2,4,4'-trihydroxybenzophenone as a developer, and 1,2,5 as an erasing agent 10 parts by weight of 6-diisopropylidene-D-mannitol and D
10 parts by weight of fructose, 3 parts by weight of a pyromellitic acid / ethylene glycol-based polyester having a molecular weight of 2,500 as a binder, and 15 parts by weight of paraffin were mixed and kneaded sufficiently by a kneader. This kneaded material was mixed with a hot melt coater to form a 4.5 μm thick PE.
It was applied to a thickness of about 2 μm on a T sheet to prepare a thermal transfer sheet. An image was printed by placing a thermal transfer sheet on paper and setting it on a thermal printer.

On the other hand, 3 wt.
% Solution was prepared. As shown in Table 13, water, ethanol or acetone was used as the solvent, depending on the basic compound.

The paper on which the image was formed was immersed in a solution of a basic compound shown in Table 13 for 1 minute and dried, and then blown with hot air at 200 ° C. for 30 seconds to erase the image. Table 13 shows the measurement results of the reflection density of the paper from which the image was erased. Table 1
As shown in FIG. 3, 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 in any case. Example 1 Regarding Stability of Erased State
A result similar to 0 was obtained.

[0123]

[Table 13]

Example 14 Example 10 was repeated except that 72 parts by weight of a bisphenol A epoxy resin having an average molecular weight of 5,500 was used as a binder.
In the same manner as in the above, a toner containing a basic compound shown in Table 14 was prepared. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

The paper on which the image was formed was brought into contact with a heat roller heated to 200 ° C. for 30 seconds to erase the image.
Table 14 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 14, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image could be erased well using any of the basic compounds. The same results as in Example 10 were obtained for the stability of the erased state.

[0126]

[Table 14]

Example 15 In the same manner as in Example 11, microcapsules containing the basic compounds shown in Table 15 were prepared. A toner containing microcapsules was prepared in the same manner as in Example 11, except that 67 parts by weight of a bisphenol A epoxy resin having an average molecular weight of 5,500 was used as a binder. The obtained toner was placed in a toner cartridge of a laser beam printer, and the image was transferred to paper.

The paper on which the image was formed was brought into contact with a heat roller heated to 200 ° C. for 30 seconds to erase the image.
Table 15 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 15, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image could be satisfactorily erased using any of the basic compounds. The same results as in Example 10 were obtained for the stability of the erased state.

[0129]

[Table 15]

Example 16 A toner was prepared in the same manner as in Example 10 except that 72 parts by weight of a bisphenol A epoxy resin having an average molecular weight of 5,500 was used as a binder and 10 parts by weight of cyclohexylamine was used as a basic compound. . The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

The organic solvent shown in Table 16 was placed in the image erasing apparatus shown in FIG. 2, the solvent was brought into contact with the paper on which the image was formed for 30 seconds to erase the image, and then dried. Table 16 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 16, the reflection density of the paper after the image was erased was almost the same as the initial reflection density, and the image could be erased well using any of the organic solvents. The same results as in Example 10 were obtained for the stability of the erased state.

[0132]

[Table 16]

Example 17 1 part by weight of crystal violet lactone (CVL) as a color-forming compound and propyl gallate 1 as a color developer
Parts by weight, 17 parts by weight of cholic acid as an erasing agent, 80 parts by weight of polystyrene as a binder, and 1 part by weight of LR-147 (manufactured by Nippon Carlit Co., Ltd.) as a charge control agent were mixed and kneaded with a kneader. The kneaded product was pulverized with a pulverizer to obtain a powder having an average particle size of 10 μm. This powder 10
Toner was prepared by adding 1 wt% of hydrophobic silica to 0 wt%. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper. In this case, as the paper, in addition to Neusiedler (pH = 9.4), neutral paper (P-
50S, pH = 7.5) and recycled paper (TL-RW,
pH = 7.5) was used. The reflection density of these papers is 0.
07.

On the other hand, the basic compounds shown in Table 17
Was prepared at a concentration of 10 wt% in the solvent shown in (1).

The paper on which the image was formed was immersed in the basic compound solution shown in Table 17 for 1 minute and then dried. Table 17 shows the measurement results of the reflection density of the paper from which the image was erased. Table 17
As shown in Table 2, the reflection density of the paper after erasing the image was almost the same as the initial reflection density, and the image was successfully erased irrespective of the pH of the paper. Also, regarding the stability of the erased state,
The same results as in Example 1 were obtained.

[0136]

[Table 17]

Example 18 4 g of a basic compound shown in Table 18 was added to a solution (37 ° C.) of 4 g of gelatin dissolved in 40 mL of water, and 45 mL (37 ° C.) of a solution of 11 g of sodium sulfate was added. Elicitation. This dispersion is added to 30
After cooling to 0 ° C. and standing, the microcapsules were separated by decantation. To 1 mL of the obtained microcapsules, an equal amount 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. After washing the obtained microcapsules with cold water,
Dried. Microcapsules encapsulating a basic compound were prepared in such a manner.

For comparison, microcapsules were prepared in the same manner as described above without using a basic compound.

1 part by weight of crystal violet lactone (CVL) as a coloring compound, 1 part by weight of propyl gallate as a color developer, 19 parts by weight of cholic acid as an erasing agent,
67 parts by weight of polystyrene as a binder, 1 part by weight of propylene wax as a wax component, 1 part by weight of a charge control material, and 10 parts by weight of microcapsules were mixed and kneaded using a kneader. This kneaded material is pulverized by a pulverizer,
A powder having an average particle size of 10 μm was obtained. 100% by weight of this powder
1 wt% of hydrophobic silica was added to the toner to prepare a toner. In this toner, kneading by a kneader was insufficient, so that cholic acid caused poor dispersion.

The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper. After immersing the obtained paper in ethylene glycol diethyl ether for 1 minute,
Dried. Table 18 shows the measurement results of the reflection density of the paper after the image was erased. As shown in Table 18, the reflection density of the paper after erasing the image is almost the same as the initial reflection density.
The image was successfully erased. In addition, the same results as in Example 10 were obtained for the stability of the erased state.

On the other hand, as can be seen from the results when no basic compound is contained, the toner in which cholic acid has a poor dispersion has a high image density after erasing, and it is difficult to completely erase.

[0142]

[Table 18]

Example 19 1 part by weight of crystal violet lactone (CVL) as a color-forming compound and propyl gallate 1 as a color developer
Parts by weight, 17 parts by weight of cholic acid as an erasing agent, 1 part by weight of propylene wax as a wax, 79 parts by weight of polystyrene as a binder resin, and LR-
147 (manufactured by Nippon Carlit Co.) was mixed and kneaded with a kneader. The kneaded product was pulverized with a pulverizer to obtain a powder having an average particle size of 10 μm. Toner was prepared by adding 1 wt% of hydrophobic silica to 100 wt% of this powder. The kneading time of this toner was short, and the dispersion of cholic acid was insufficient. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper. The paper on which the image was formed was immersed in diethoxyethane containing 10 wt% of cholic acid for 1 minute, and then dried. The reflection density of the paper after erasing the image was 0.07, which was the same as the initial reflection density, and the image was successfully erased. In addition, the same result as in Example 1 was obtained for the stability of the erased state.

On the other hand, when immersed in diethoxyethane containing no cholic acid for 1 minute and dried,
The erased state of the image was not uniform, and the reflection density was as high as 0.25.

[0145]

As described above, when the image forming material and the image erasing method of the present invention are used, a good erased state can be obtained without depending on the binder used, and the stability of the erased state can be improved. can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing a solvent-type image erasing apparatus according to the present invention.

FIG. 2 is a view showing a solvent-type image erasing apparatus according to the present invention.

FIG. 3 is a diagram showing a solvent-type image erasing apparatus according to the present invention.

FIG. 4 is a diagram showing a solvent-type image erasing apparatus according to the present invention.

FIG. 5 is a diagram showing a solvent-type image erasing apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Solvent container 102 ... Solvent 103 ... Solvent tank 104 ... Import roller 105 ... Immersion roller 106 ... Opposing roller 107 ... Heat roller 108 ... Export roller 109 ... Recovery solvent container 110 ... Adsorbent 111 ... Electron cooler 112 ... Heat radiator 113 ... absorption filter 114 ... circulation pump 121 ... gravure roller 122 ... opposite roller 123 ... blade 131 ... pump 132 ... spray nozzle 133 ... lamp heater 201 ... solvent tank 202 ... solvent 203 ... solvent immersion tank 204 ... chemical pump 205 ... liquid feed pipe 206: Electronic cooler 207: Power supply 301: Bundle of paper 302, 305, 308: Conveyor 303: Solvent treatment tank 304: Solvent 306: Heater 307: Fan 309: Infrared heater 310: Storage

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-27735 (JP, A) JP-A-2000-191931 (JP, A) JP-A-10-197984 (JP, A) JP-A-9-176627 (JP, A) JP-A-4-108197 (JP, A) JP-A-62-14163 (JP, A) JP-A-5-2356 (JP, A) JP-A-9-152818 (JP, A) JP-A-7-81236 (JP, A) JP-A-49-62230 (JP, A) JP-A-57-90085 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 21 / 00 G03G 21/00 570-578 G03G 9/00-9/18 C09D 11/00-13/00

Claims (14)

(57) [Claims] 1. An image erasing device comprising a color former, a color developer and an erasing agent, wherein the image forming material is brought into contact with a solvent when erasing the image forming material formed on a recording medium. Method. 2. The image erasing method according to claim 1, wherein said image forming material further contains a basic compound. 3. The image erasing method according to claim 1, wherein said image forming material further contains a binder. 4. The image erasing method according to claim 1, wherein said solvent further contains an erasing agent. 5. The image erasing method according to claim 1, wherein the solvent is removed from the recording medium after the image forming material is brought into contact with the solvent. 6. A color former, a developer, and (a)
Roll compound, (b) cholic acid, lithocholic acid, test
Sterone and cortisone and their derivatives,
(C) (c1) cyclic sugar alcohol and (c2)
5-membered ring having hydroxyl group other than cyclic sugar alcohol
Induction of the above non-aromatic cyclic compounds or cyclic sugar alcohols
A group consisting of conductors (a), (b) and (c)
At least one quenching agent selected from
And styrene-acrylic copolymers
An image characterized by containing a selected binder
Forming material. 7. A color developing compound, a color developer, and (a)
Roll compound, (b) cholic acid, lithocholic acid, test
Sterone and cortisone and their derivatives,
(C) (c1) cyclic sugar alcohol and (c2)
5-membered ring having hydroxyl group other than cyclic sugar alcohol
Induction of the above non-aromatic cyclic compounds or cyclic sugar alcohols
A group consisting of conductors (a), (b) and (c)
At least one quenching agent selected from
Binder selected from the group consisting of epoxy and epoxy resin
And an image forming material comprising: 8. A color former, a color developer, and (a)
Roll compound, (b) cholic acid, lithocholic acid, test
Sterone and cortisone and their derivatives,
(C) (c1) cyclic sugar alcohol and (c2)
5-membered ring having hydroxyl group other than cyclic sugar alcohol
Induction of the above non-aromatic cyclic compounds or cyclic sugar alcohols
A group consisting of conductors (a), (b) and (c)
At least one quenching agent selected from
Binder selected from the group consisting of epoxy and epoxy resin
Characterized by containing-and a basic compound
Forming material. 9. The image forming material according to claim 8, wherein the basic compound is encapsulated in a microcapsule. 10. The content of the binder is 30 wt%.
9. The image forming material according to claim 6, wherein the content is at least 95 wt%. 11. The image forming material according to claim 6, which is used as a toner for electrophotography. 12. When erasing an image formed by an image forming material containing a polyester or an epoxy resin as a color developing compound, a color developer, an erasing agent, and a binder, the image forming material contains a basic compound. An image erasing method comprising contacting a solvent. 13. A color-forming compound, a color developer, (a) stero
Compounds, (b) cholic acid, lithocholic acid, testes
Teron and cortisone and their derivatives,
(C) (c1) cyclic sugar alcohol and (c2) ring
5 or more membered rings having a hydroxyl group other than the formula sugar alcohol
Of the above non-aromatic cyclic compounds or cyclic sugar alcohols
From the group consisting of (a), (b) and (c)
An image formed by heating an image forming material for erasing an image formed by the image forming material containing at least one selected erasing agent and a polyester or an epoxy resin as a binder. Erase method. 14. A method for erasing an image formed of an image forming material containing a polyester or an epoxy resin as a color developing compound, a color developer, an erasing agent, and a binder, by bringing a basic compound into contact with the image forming material. And then heating the image.