JP3315360B2 - Erasable image forming material 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 a method for erasing an image formed using an erasable 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 image 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 novel image forming material and an image erasing method capable of obtaining a good erased state, and various image prepared by combining various components in the process. It has been found that it is not always easy to erase all of the forming materials at a high erase speed and to obtain a good erased state.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image erasing method capable of erasing an image at a high erasing speed and obtaining a good erasing state irrespective of the components of the image forming material. It is in.

[0007]

An image erasing method according to one embodiment of the present invention erases an image formed using an image forming material containing a color developing compound and a color developing material. In the image forming material , (a) a sterol compound,
(B) cholic acid, lithocholic acid, testosterone and
Cortisone and derivatives thereof, and (c)
(C1) cyclic sugar alcohol and (c2) cyclic sugar alcohol
5-membered or more non-aromatic having a hydroxyl group other than
Aromatic compounds or derivatives of cyclic sugar alcohols
Selected from the group consisting of (a), (b) and (c)
The image is erased by contacting a solvent in which at least one erasing agent is dissolved.

In the method of the present invention, since the solvent in which the erasing agent is dissolved is brought into contact with the image forming material, the image can be erased at a high erasing speed by selecting the optimum erasing agent and solvent according to the image forming material. In addition, a good erased state can be obtained.

[0009]

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. In the method of the present invention, the erasing agent is used in a state of being dissolved in an erasing solvent.

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.

The state change between the colored state and the decolored state is performed according to the following principle. Here, the case where the image forming material is erased by heating will be described for convenience. It is also assumed that the erasing agent preferentially dissolves the developer when the composition system is molten and in a fluid state. 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
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.

In the method of bringing the image forming material into contact with a solvent, the erasure is performed in the same manner as in the heating method, according to the following principle. Here, it is assumed that the image forming material contains a binder. 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.

In the present invention, since the image is erased by bringing the solvent in which the erasing agent is dissolved into contact with the image forming material, an optimum erasing agent can be selected according to the image forming material, and a high erasing speed can be realized. This method is particularly advantageous when erasing a large amount of paper containing various image forming materials.

When an image is erased using a solvent,
The quality of the paper in the erased state can be 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.

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. 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 it is in an 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.

In the case where these erasing agents are used, when the composition in the 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 the 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, a rewritable recording medium using 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, except for special uses,
Essentially no reversibility is required.

(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) A 5- or more-membered non-aromatic cyclic compound 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), 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 a 5- or more-membered ring 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.

The preferred compounding ratio of the color former and the developer in the image forming material of the present invention is as follows. The mixing ratio of the developer is 0.1 to 1 with respect to 1 part by weight of the coloring compound.
It is preferably set to 0 parts by weight, more preferably 1 to 2 parts by weight. 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 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, a wax and the like and applying the mixture to a plastic sheet. The ink of the ink jet printer is used by dispersing a color former, a color developer and the like in a solvent. The toner is prepared by pulverizing a composition containing a color former, a developer, 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. Average molecular weight 1,00
In the case of 0 to 200,000, 30 to 90 wt%. 30 to 8 when the average molecular weight is 200,000 to 600,000
0 wt%. Average molecular weight 600,000-1000,00
In the case of 0, it is 30 to 70 wt%.

The 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%. Average molecular weight 200,000-400,00
In the case of 0, it is 30 to 85 wt%. Average molecular weight 400,00
In the case of 0 to 1,000,000, it is 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. Average molecular weight 1,000-20
In the case of 0.000, it is 30 to 95 wt%. Average molecular weight 20
30-85 wt for 000-400,000
%. 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.

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 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 of the above (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 successfully alone. 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.

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.

In the present invention, a basic compound may be used in order to prevent unreacted carboxylic acid or phenol from affecting the image erasure. 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. 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 compounds include
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 azido group, a nitrile group, a diazoamino group, an imino group, a urea bond, a thiourea bond, an amide bond, a urethane bond, and a carbonyldioxy group May be substituted with a group.

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

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

Other 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, the basic compound may be mixed with other components of the image forming material in a state of being encapsulated in the microcapsules. In this case, a step of heating the image forming material when erasing the image is performed.

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.

In the present invention, when an image is formed from an image forming material containing a color former, a color developer, and a polyester or an epoxy resin as a binder, and the image is erased, an erasing agent is added to the image forming material. And a solvent in which a basic compound is dissolved. The erasing agent solution and the basic compound solution may be separately prepared, and the image forming material may be separately contacted with the erasing agent and the basic compound. To bring these solutions into contact with the imaging material,
A method of spraying the solution on the paper or dipping the paper in the solution is used. After contacting the image forming material with a solvent in which the erasing agent and the basic compound are dissolved, heating may be performed.

The solvent that can be used for preparing the solution of the basic compound is not particularly limited. 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 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 immersing the paper in the solvent contained in a 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 uses a gravure roller 12 as a means for bringing a solvent into contact with an image forming material on paper.
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 the 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 examples 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-scale 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.

[0065]

Embodiments of the present invention will be described below.

In the following embodiment, Neus, which is a standard paper used in Europe as an image forming paper, is used.
Iedler neutral paper (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 coloring compound and propyl gallate 1 as a color developing material
Parts by weight, 70 parts by weight of polystyrene having an average molecular weight of 45,000 as a binder, and LR- as a charge control agent.
147 (manufactured by Nippon Carlit Co., Ltd.) were mixed and sufficiently kneaded using a kneader. The kneaded material was pulverized with a pulverizer to obtain a powder having an average particle size of 10 μm. The resulting powder 100
Toner was prepared by adding 1 wt% of hydrophobic silica to wt%. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

On the other hand, 5% by weight of cholesterol and 5% by weight of D-glucose were used as scavengers in the organic solvents shown in Table 1.
Was dissolved to prepare an erasing solution. The erasing solution was put into the image erasing apparatus shown in FIG. 2, and the paper on which the image was formed was brought into contact with the erasing solution for 30 seconds to erase the image, and then dried. Table 1 shows the results of measuring the reflection density of the paper from which the image was erased.
Shown in 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 in each case, the image was successfully erased.

[0069]

[Table 1]

The paper from which the image has been erased is heated 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.

On the other hand, 3% by weight of cholesterol and D-
3% by weight of glucose was dissolved to prepare an erasing solution.
The erasing solution was put into the image erasing apparatus shown in FIG. 1, and the paper on which the image was formed was immersed in the solution 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. Polystyrene content is 20-25w
When t% of the toner 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.

[0073]

[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.

On the other hand, 3% by weight of cholesterol and D-
3% by weight of glucose was dissolved to prepare an erasing solution.
The erasing solution was put into the image erasing device shown in FIG. 3, and the solution was sprayed on the paper on which the image was formed to erase the image, and then dried. Table 3 shows the results of measuring the reflection density of the paper from which the image was erased.
Shown in 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.

[0076]

[Table 3]

Example 4 A toner was prepared in the same manner as in Example 1 except that 70 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. did. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

On the other hand, 5 wt% of cholesterol and 5 wt% of D-glucose were added to the organic solvents shown in Table 4 as scavengers.
Was dissolved to prepare an erasing solution. The erasing solution was placed in a container, and the paper on which the image was formed was immersed in the solution 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 successfully erased in any case. The same results as in Example 1 were obtained for the stability of the erased state.

[0079]

[Table 4]

Example 5 Styrene having a molecular weight of 130,000 / n 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.

On the other hand, 3% by weight of cholesterol and D-
3% by weight of glucose was dissolved to prepare an erasing solution.
The erasing solution was placed in a container, and the paper on which the image was formed was immersed in the solution 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. The same results as in Example 1 were obtained for the stability of the erased state.

[0082]

[Table 5]

Example 6 As shown in Table 6, styrene / n-butyl methacrylate copolymers (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.

On the other hand, 3% by weight of cholesterol and 3% by weight of D-glucose as an erasing agent were dissolved in ethylene glycol diethyl ether to prepare an erasing solution. The erasing solution was put into 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 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.

[0085]

[Table 6]

Example 7 As shown in Table 7, the binder had an average molecular weight of 13
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.

On the other hand, 5% by weight of cholesterol and 5% by weight of D-glucose as an erasing agent were dissolved in ethylene glycol diethyl ether to prepare an erasing solution. The erasing solution was put into 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 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.

[0088]

[Table 7]

Example 8 In the same manner as in Example 1 except that 70 parts by weight of a styrene-acrylic copolymer having an average molecular weight of 130,000 and an acrylate monomer content of 10% by weight as shown in Table 8 was added as a binder. A toner was prepared. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

On the other hand, 7% by weight of cholesterol and 7% by weight of D-glucose were dissolved as disinfectants in ethylene glycol diethyl ether to prepare an erasing solution. The erasing solution was put into the image erasing device shown in FIG. 3, and the solution was sprayed on the paper on which the image was formed to erase the image, and then dried. Table 8 shows the results of measuring the reflection density of the paper from which the image was erased.
Shown in 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.

[0091]

[Table 8]

Example 9 As shown in Table 9, an average molecular weight of 13 was used as a binder.
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 0 part by weight was added. The obtained toner was placed in a toner cartridge of a copying machine, and the image was transferred to paper.

On the other hand, 7% by weight of cholesterol and 7% by weight of D-glucose were dissolved as disinfectants in ethylene glycol diethyl ether to prepare an erasing solution. The erasing solution was placed in a container, and the paper on which the image was formed was immersed in the solution 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 erasing the image was almost the same as the initial reflection density, and the image could be satisfactorily erased using any of the toners containing the binder. The same results as in Example 1 were obtained for the stability of the erased state.

[0094]

[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, 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 controlling agent and 5 parts by weight of a basic compound shown in Table 10 were mixed and kneaded by a kneader. The kneaded product was pulverized with a pulverizer to obtain a powder having an average particle size of 10 μm. Hydrophobic silica 1w with respect to this powder 100wt%
t% was added to prepare a toner. Put the obtained toner in the toner cartridge of the laser beam printer,
The image was transferred to paper.

Separately, 7% by weight of cholesterol and 7% by weight of D-glucose were dissolved in toluene as an erasing agent to prepare an erasing solution. Put this erasing solution in a container,
The paper on which the image was formed was immersed in the solution for 30 seconds to erase the image, and then dried. Further, the paper was brought into contact with a heat roller heated to 200 ° C. for 30 seconds. Table 10 shows the measurement results of the reflection density of the paper from which the image was erased. Table 10
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 with any of the basic compounds.

[0097]

[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 To a solution (37 ° C.) of 4 g of gelatin dissolved in 40 mL of water was added 4 g of a basic compound shown in Table 11, and 45 mL (37 ° C.) of a solution of 11 g of sodium sulfate were 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, 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. 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.

On the other hand, 7% by weight of cholesterol and 7% by weight of D-glucose as an erasing agent were dissolved in toluene to prepare an erasing solution. Put this erasing solution in a container,
The paper on which the image was formed was immersed in the solution for 30 seconds to erase the image, and then dried. Further, the paper was brought into contact with a heat roller heated to 200 ° C. for 30 seconds. Table 11 shows the measurement results of the reflection density of the paper from which the image was erased. Table 11
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 with any of the basic compounds. The same results as in Example 10 were obtained for the stability of the erased state.

[0102]

[Table 11]

Example 12 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, 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 5 parts by weight of calcium chloride were mixed and kneaded by 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.

On the other hand, 7 wt% of cholesterol and 7 wt% of D-glucose were added to the organic solvents shown in Table 12 as scavengers.
% Was dissolved to prepare an erasing solution. The erasing solution was put into the image erasing device shown in FIG. 2, and the solution 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 the image was erased was almost the same as the initial reflection density, and the images could be erased favorably by using any of the solutions. The same results as in Example 10 were obtained for the stability of the erased state.

[0105]

[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 color developer, and a molecular weight of 2,500 as a binder
Was mixed with 3 parts by weight of pyromellitic acid / ethylene glycol-based polyester and 15 parts by weight of paraffin and kneaded sufficiently with a kneader. This kneaded material was applied to a thickness of about 2 μm on a 4.5 μm thick PET sheet using a hot melt coater 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. Also, 3% by weight of 1,2,5,6-diisopropylidene-D-mannitol and 3% by weight of D-fructose were dissolved in toluene as an erasing agent to prepare an erasing solution.

The solution of the basic compound and the solution for erasing were placed in two separate containers. The paper on which the image was formed was immersed in a solution of a basic compound for 1 minute and dried. Next, the image was erased by immersing the paper in an erasing solution for 30 seconds. afterwards,
200 ° C warm air was blown for 30 seconds. Table 13 shows the measurement results of the reflection density of the paper from which the image was erased. As shown in Table 13, 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 in any case. The same results as in Example 10 were obtained for the stability of the erased state.

[0109]

[Table 13]

Example 14 The thermal transfer sheet prepared in Example 13 was set on a thermal printer by superimposing it on paper, and an image was printed.

On the other hand, 3% by weight of pyridine as a basic compound and 3% by weight of 1,2,5,6-diisopropylidene-D-mannitol and 3% by weight of D-fructose are dissolved in toluene to prepare an erasing solution. did. The erasing solution was placed in a container, and the paper on which the image was formed was immersed in the solution for 30 seconds to erase the image.
Of hot air. The reflection density of the paper from which the image was erased was 0.08. The same results as in Example 10 were obtained for the stability of the erased state.

Example 15 1 part by weight of crystal violet lactone (CVL) as a coloring compound, 1 part by weight of propyl gallate as a color developing material, and an average molecular weight of 11,500 as a binder
Was mixed with 72 parts by weight of a fumaric acid / etherified diphenol-based polyester and 1 part by weight of a charge control agent, 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.

On the other hand, 3% by weight of pyridine as a basic compound and 3% by weight of 1,2,5,6-diisopropylidene-D-mannitol and 3% by weight of D-fructose as an erasing agent are dissolved in diethylene glycol diethyl ether to obtain an erasing solution. Was prepared. The erasing solution was placed in a container, and the paper on which the image was formed was immersed in the solution for 30 seconds to erase the image, and then dried. The reflection density of the paper from which the image was erased was 0.08. The same results as in Example 10 were obtained for the stability of the erased state.

Example 16 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 the 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.

On the other hand, 7% by weight of cholesterol and 7% by weight of D-glucose were dissolved in toluene as an erasing agent to prepare an erasing solution. Put this erasing solution in a container,
The paper on which the image was formed was immersed in the solution for 30 seconds to erase the image, and then dried. Further, the paper was brought into contact with a heat roller heated to 200 ° C. for 30 seconds. Table 14 shows the measurement results of the reflection density of the paper from which the image was erased. Table 14
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 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.

[0116]

[Table 14]

Example 17 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.

On the other hand, 7% by weight of cholesterol and 7% by weight of D-glucose were dissolved in toluene as an erasing agent to prepare an erasing solution. Put this erasing solution in a container,
The paper on which the image was formed was immersed in the solution for 30 seconds to erase the image, and then dried. Further, the paper was brought into contact with a heat roller heated to 200 ° C. for 30 seconds. Table 15 shows the measurement results of the reflection density of the paper from which the image was erased. Table 15
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 with any of the basic compounds. The same results as in Example 10 were obtained for the stability of the erased state.

[0119]

[Table 15]

Example 18 1 part by weight of crystal violet lactone (CVL) as a coloring compound and propyl gallate 1 as a color developing material
Parts by weight, 72 parts by weight of a bisphenol A epoxy resin having an average molecular weight of 5,500 as a binder, 1 part by weight of a charge controlling agent, and 5 parts by weight of pyridine as a basic compound were mixed and kneaded by 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.

On the other hand, 5 wt% of cholesterol and 5 wt% of D-glucose were used as scavengers in the organic solvents shown in Table 16.
% Was dissolved to prepare an erasing solution. This erasing solution was put into the image erasing apparatus shown in FIG. 1, and the solution 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 images could be erased favorably by using any of the solutions. The same results as in Example 10 were obtained for the stability of the erased state.

[0122]

[Table 16]

[0123]

As described above, by using the method of the present invention, an image can be erased at a high erasing speed and a good erased state can be obtained irrespective of the components of the image forming material.

[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-4-356087 (JP, A) JP-A-7-81236 (JP, A) JP-A-1-102489 (JP, A) JP-A-4- 108197 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 21/00 G03G 21/00 570-578 G03G 9/00-9/18

Claims (5)

(57) [Claims] When erasing an image formed using an image forming material containing a color former and a color developing material, the image forming material contains (a) a sterol compound,
(B) cholic acid, lithocholic acid, testosterone and
Cortisone and derivatives thereof, and (c)
(C1) cyclic sugar alcohol and (c2) cyclic sugar alcohol
5-membered or more non-aromatic having a hydroxyl group other than
Aromatic compounds or derivatives of cyclic sugar alcohols
Selected from the group consisting of (a), (b) and (c)
An image erasing method comprising erasing an image by contacting a solvent in which at least one erasing agent is dissolved. 2. The image erasing method according to claim 1, wherein said image forming material contains said color developing compound, said color developing material, polyester or epoxy resin as a binder, and a basic compound. 3. An image erasing method according to claim 2, wherein said basic compound is encapsulated in a microcapsule. Wherein said image forming material, the color former compound, wherein the Akirairozai, and contains a polyester or epoxy resin as a binder, wherein said solvent contains said scavenger and the basic compound The image erasing method according to claim 1, wherein To wherein said image forming material, after contacting the solvent, the 4 claims 1, characterized in that heating
Image erasing method described .