JP3464959B2 - Image erasing method for erasable image forming material - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to erasable image formation.
A method for erasing an image of a material .

[0002]

2. Description of the Related Art In recent years, due to the spread of OA, the data amount of various information has been expanding, and the output of information has also increased accordingly. The output of information is represented by a display output and a hard copy output on paper by a printer. However, the display output requires a large-scale circuit board for the display unit, which is problematic in terms of portability and cost. Further, in hard copy output, a large amount of paper is used as a recording medium when the amount of information increases, which is problematic in terms of resource protection. Moreover, in order to recycle (recycle) the paper printed by a printer or a copying machine, a large amount of bleaching agent and water are required, so that the recycle cost becomes high. Therefore, information is printed on paper using an erasable image forming material, the formed image is erased, and the paper is returned to a blank state for reuse (reuse).
However, it is considered that the amount of paper used is substantially reduced by recycling (recycling) when the paper becomes so damaged that it cannot be reused.

Recently, special paper rewritable paper for the purpose of reusing hard copy paper has been proposed. However, since rewritable paper uses special paper, it has the drawback that it can be reused but not recycled, and that it cannot be imaged by means other than a thermal method.

Conventionally, an image forming material which can be erased by applying heat is disclosed in, for example, JP-A-7-81236. This image-forming material contains a color-forming compound such as a leuco dye, a color developer, and an organic phosphoric acid compound having an erasing effect. However, when an image forming material composed of such components is used, erasing is insufficient and it is difficult to return the paper to a blank state.

Therefore, the present inventors have proceeded with the development of an erasable image-forming material in which a color developable compound, a developer, and an erasing agent having a high affinity for the developer are dispersed in a binder resin. In many material systems, a good erased state can be obtained by heating or contact with a solvent. However, some erasing agents exhibiting good performance are relatively expensive, so it is desirable to reduce the amount of erasing agent used.

When erasing an erasable image forming material,
It has been found that the amount of erasing agent required to obtain a good erasing state is smaller in solvent erasing than in heat erasing. For this reason, the content of the erasing agent in the erasable image forming material is designed based on the amount required for heat erasing. However, if the content of the erasing agent in the image forming material is too high, the color density may vary depending on the production lot due to a decrease in dispersibility of each material,
Poor image fixing may occur due to lack of matrix material.

Further, considering the reuse of paper in an office where paper consumption is high, it is not preferable to use a solvent from the viewpoint of odor and the like. Moreover, it is preferable that a large amount of paper can be heat-treated at once in a bundle. However, since such processing conditions and an erasable image forming material suitable therefor have not been studied so far, it has been found that a good erasing state may not be obtained in some cases.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to remove paper
Those who can erase a large number of images by heating them in a bundle
To provide the law.

[0009]

[0010]

[0011]

The image erasing method of the present invention comprises a color forming compound, a color developing agent having a molecular weight of 120 to 210, a matrix material and a erasing agent. Bunch of paper with 100 to 140 ℃
And a step of cooling the heated paper to room temperature.

[0012]

[0013]

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.

The inventors of the present invention have explained the reason why the amount of the erasing agent required for obtaining a good erasing state in erasing the erasable image forming material is smaller in the solvent erasing than in the heat erasing. I considered. As a result, the following conclusions were reached. That is, in the case of erasing the solvent, it is considered that a part of the color developer that can freely diffuse by the solvent is captured and fixed on the paper. On the other hand, in the case of heat erasing, since the diffusion of the color developing agent is almost restricted to the inside of the image forming material, it is considered that a sufficient erasing agent is necessary to capture all the color developing agent.

Next, the present inventor examined the heating conditions for erasing by heating the paper on which the image forming material is attached. First, in consideration of the efficiency of heat treatment, the decolored state was examined by heating at high temperature. As a result, if the paper on which the image forming material is attached is kept at a high temperature in the air for a long time, the color-forming compound undergoes a chemical reaction to change its color and complete decoloring becomes impossible, and the paper itself is gradually carbonized. There was also the problem of turning brown. As a countermeasure, it was considered that the paper on which the image forming material is attached is kept at high temperature for a short time to prevent discoloration of the paper and the color-developing compound. But such a condition
It has been found that it is suitable for processing paper one by one, but not for erasing a large amount of paper in a bundle at a time. This is because it takes some time to transfer the heat to the center of the bundle of paper. From these results, it has been found that a method of holding at a relatively low temperature for a certain period of time is desirable for collectively erasing the bundle of paper by heat treatment.

The inventor of the present invention puts a bundle of papers to be erased in a high temperature box before returning home in the office, takes out the bundle of papers the next morning, and reuses the image forming material in a heating time of several hours. It was considered suitable if the color could be erased.

Next, the present inventor investigated the temperature dependence of the color of the paper and the color-developing compound in order to determine the upper limit of the heating temperature in the heat erasing for several hours. First, 100 sheets of paper to which the image forming material was attached were bundled and placed in a constant temperature bath, heated at a predetermined temperature for 5 hours, and then the color of the paper was examined. The color value of the paper was measured using a colorimeter (CR-300, manufactured by Minolta) and expressed in the La ^* b ^* color system. Table 1 shows the results.

[0019]

[Table 1]

From Table 1, it can be judged that the heating temperature must be 170 ° C. or lower in order not to significantly reduce the reflection density of the paper. In order to suppress the color change of the paper, especially the increase of the b ^* value showing the change to the red direction, heat treatment at a lower temperature is necessary. From these results, it was determined that the upper limit of the heat treatment temperature was 155 ° C. at which the quality of the paper did not deteriorate when visually observed.

Next, the present inventor examined the discoloration of the color-forming compound. Leuco dye Blu as a color-forming compound
A sample of an image forming material was prepared by kneading with e63, ethyl gallate as a color developer, starch as a decolorizer, and a binder resin. In this sample, the color-developing compound and the developing agent were mixed at a molar ratio of 1: 1 and the content of the developing agent in the binder resin was 1 wt%. A color-developed pattern of the image-forming material was formed on the paper, and the color change of the pattern of the image-forming material was examined when the paper was kept at a temperature of 155 ° C. or lower for a predetermined time. In the same manner as above, the color value was measured using a colorimeter and expressed in the La ^* b ^* color system. Table 2
The results are shown in. Note that BG in Table 2 is the value of the background paper.

[0022]

[Table 2]

From Table 2, holding at 142 ° C. for several hours,
There was an increase in the b ^* value indicating a non-negligible color change of the color-developing compound, especially towards the red. From this, it can be seen that the color-developing compound discolors at a temperature lower than that of paper.
Table 2 shows data for an example of the color-forming compound, but similar data was obtained for other color-forming compounds. Therefore, it is desirable that the heating temperature at the time of erasing is 140 ° C. or lower.

On the other hand, it is important to avoid a decrease in color density when preparing the image forming material. The image forming material according to the present invention is prepared by kneading a color developable compound, a color developing agent, a decoloring agent, and a binder resin, and the kneading temperature at that time is set to 80 ° C to 100 ° C. Therefore, the heating temperature at the time of erasing must be 100 ° C. or higher.

As described above, when the image forming material according to the present invention is heated to be erased, the heating temperature is 100 to 140.
It is desirable to set the temperature in the range of ° C.

In the case of erasing the color of the image forming material in the above temperature range, a good erasing state can be obtained when the content of the color developable compound is as low as about 1 wt%. However, it has been found that as the content of the color-developing compound increases, the remaining color remains depending on the type of the color developer.

The present inventor has found that when a developer having a slow diffusion rate in the binder resin is used in the above temperature range, the unerased residue easily occurs. In the erasable image forming material of the present invention, a developer having a small molecular weight and easily diffusing in the binder resin even at the above decoloring temperature is used. In the image forming material containing such a color developer,
Since the developer easily diffuses even at a low temperature, the interaction between the developer and the color-forming compound disappears, and a good decolored state can be obtained. However, when the molecular weight of the developer is too small, the developer is vaporized and desorbed during kneading at 80 to 100 ° C. during the preparation of the image forming material, resulting in a decrease in color density.

Therefore, in the image forming material of the present invention,
In order to prevent erasing at a erasing temperature of 100 to 140 ° C. for several hours, and not to erase in a kneading step at 100 ° C. or less,
A developer having a molecular weight in the appropriate range is used. A suitable range of the molecular weight of the color developer in the present invention is 120 to 210.

It is known that an image forming material containing no erasing agent can be decolored by heating by using a volatile developer (JP-A-1-138275). However, when the volatility of the color developer is too high, there is a problem that the color density is lowered as described above and the vaporized color developer has an unfavorable environmental influence. Therefore, it is necessary to select a developing agent that remains inside the image forming material and the paper even when heated.

Various materials used in the image forming material of the present invention will be described below. Examples of the color-forming compound used in the present invention include leuco auramines, diaryl phthalides, polyaryl carbinols, acyl auramines, aryl auramines, rhodamine B lactams, indolines, spiropyrans, and fluoran. Examples thereof include electron-donating organic substances.

Specific color-forming compounds include crystal violet lactone (CVL), malachite green lactone, 2-anilino-6- (N-cyclohexyl-
N-methylamino) -3-methylfluorane, 2-anilino-3-methyl-6- (N-methyl-N-propylamino) fluorane, 3- [4- (4-phenylaminophenyl) aminophenyl] amino -6-Methyl-7-chlorofluorane, 2-anilino-6- (N-methyl-N
-Isobutylamino) -3-methylfluorane, 2-anilino-6- (dibutylamino) -3-methylfluorane, 3-chloro-6- (cyclohexylamino) fluorane, 2-chloro-6- (diethylamino) fluorane , 7- (N, N-dibenzylamino) -3- (N, N
-Diethylamino) fluorane, 3,6-bis (diethylamino) fluorane-γ- (4'-nitroanilino)
Lactam, 3-diethylaminobenzo [a] -fluorane, 3-diethylamino-6-methyl-7-aminofluorane, 3-diethylamino-7-xylidinofluorane, 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-chloroanilinofluorane, 3-diethylamino- 7,8-
Benzofluorane, 3,3-bis (1-n-butyl-2)
-Methylindol-3-yl) phthalide, 3,6-dimethylethoxyfluorane, 3-diethylamino-6-
Methoxy-7-aminofluorane, DEPM, ATP,
ETAC, 2- (2-chloroanilino) -6-dibutylaminofluorane, crystal violet carbinol, malachite green carbinol, N- (2,3-
Dichlorophenyl) leuco auramine, N-benzoyl auramine, rhodamine B lactam, N-acetyl auramine, N-phenyl auramine, 2- (phenyliminoethanedilidene) -3,3-dimethylindoline,
N, 3,3-Trimethylindolinobenzospiropyran, 8'-methoxy-N, 3,3-trimethylindolinobenzospiropyran, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-
Methoxyfluorane, 3-diethylamino-6-benzyloxyfluorane, 1,2-benzo-6-diethylaminofluorane, 3,6-di-p-toluidino-4,5.
-Dimethylfluorane, phenylhydrazide-γ-lactam, 3-amino-5-methylfluorane and the like. These may be used alone or in combination of two or more. Since a colored state of various colors can be obtained by appropriately selecting a color-developing compound, multi-color compatibility is possible.

As the color developer used in the present invention, phenols, phenol metal salts, carboxylic acid metal salts,
Examples thereof include benzophenones, sulfonic acids, sulfonates, phosphoric acids, phosphoric acid metal salts, acidic phosphoric acid esters, acidic phosphoric acid ester metal salts, phosphorous acids, and phosphorous metal salts. Particularly, a phenolic compound containing two or more hydroxyl groups is desirable. In the present invention, it is important that the color density is high at the time of preparation of the image forming material, and that a good decolored state can be obtained under the heating condition of 100 to 140 ° C. which is adopted when collectively erasing a bundle of paper. is there. For this purpose, as described above, the molecular weight is 120 to 210.
Is used. One or two of these developers
Used as a mixture of two or more species.

Particularly suitable developers include biphenol (molecular weight 186), methyl gallate (molecular weight 184),
Ethyl gallate (molecular weight 198), 4,4'-oxybisphenol (molecular weight 202), methylenebisphenol (molecular weight 202), phenylmethylbenzenediol (molecular weight 200), 2,4-dihydroxyacetophenone (molecular weight 152), 2,3 , 4-trihydroxyacetophenone (molecular weight 168), methyl 2,3-dihydroxybenzoate (molecular weight 164), methyl 2,6-dihydroxybenzoate (molecular weight 164), ethyl 2,3-dihydroxybenzoate (molecular weight 180), Ethyl 3,5-dihydroxybenzoate (molecular weight 180), ethyl 2,6-dihydroxybenzoate (molecular weight 180), propyl 2,3-dihydroxybenzoate (molecular weight 196) and the like can be mentioned.

Examples of the scavenger used in the present invention include sterol compounds such as animal sterin, plant sterin and fungal sterin, and their derivatives. Animal sterins include cholesterol, lanosterol,
Examples include lanostadier, agnosterol, cholestanol, coprostanol, ostreasterol, actinia sterol, spongosterol, and clionasterol. Examples of bile acids include colanic acid, cholic acid, hyodeoxycholic acid, lithocholic acid and the like. Examples of the plant sterin include stigmasterol, α-sitosterol, β-sitosterol, γ-sitosterol, brassicasterol, vitamin D and the like. Examples of the fungal sterin include ergosterol. One or more of these may be used. A plurality of these may be mixed and used. Alternatively, a material that is originally a mixture such as lanolin alcohol may be used. Cholesterol, which is an animal sterin, is also used as a shrimp feed, and its safety is guaranteed. On the other hand, even for biological sterols, it is unsuitable to use highly toxic materials such as diquiranide, dicoxigen, digitoxin, digitoxigenin, bufotalin, bufotoxin, strophanthin, strophantidine and psilalen.

Cyclic sugar alcohols and their derivatives are also mentioned as scavengers which show good scavenging ability when mixed with a steroid scavenger. 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, ertruvic acid, trehalose, saccharose, maltose, cellobiose, gentiobiose, lactose, melibiose, raffinose, gentianose, melezitose, stachyose, methyl = α-glucopyranoside, salicin, amygdalin, Examples include euxanthic acid, 1,2,5,6-diisopropylidene-D-mannitol and the like. One or more of these may be used. Sugars are widely used for food and their safety is high.

As the scavenger showing good scavenging ability when mixed with a steroidal scavenger, a non-aromatic cyclic compound having a hydroxyl group of 5 or more members other than the cyclic sugar alcohol or a cyclic sugar alcohol is used. Derivatives are also included. 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-menthen-4-ol, isopulegol, dihydrocarbeol, carveol;
Alicyclic polyhydric alcohols such as 1,4-cyclohexanediol, t-1,2-cyclohexanediol, phloroglucitol, quercitol, inositol,
1,2-cyclododecandiol, 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 may be mentioned.
In particular, in order to improve temperature stability, it is effective to synthesize a plurality of compounds having a cyclic structure and design the molecule so that the molecular structure has a larger steric hindrance.

In the present invention, it is particularly preferable to use a polymer eliminator. As the polymer eliminator, a polymer having a sugar skeleton, a polyamino acid, a polymer having a hydroxyl group, a polymer having an amino group, polyvinyl acetal, polyacrylonitrile, or a derivative thereof,
And mixtures thereof.

Specific polymers having a sugar skeleton include:
Starch (α-starch, β-starch, corn starch, potato starch, starch starch, etc.) and starch-based grain powder (flour, barley flour, rye flour, rice flour, etc.); methylated starch, ethylated starch, Acetylated starch, starch derivatives typified by nitrated starch; cellulose, cellulose acetate, methylated cellulose, ethylated cellulose, cellulose derivatives typified by nitrated cellulose; dextrin, dextran, mannan, amylopectin, Examples thereof include polysaccharides such as amylose, xylan, glycogen, inulin, lichenin, chitin, hemicellulose, pectin, vegetable gum, agarose, carrageenin and saponin, and their derivatives.

When a polymer having a sugar skeleton is used as a polymer erasing agent for toner, the anti-offset property is remarkably improved. It is considered that this is because such a polymer erasing agent has a high affinity with the fibers of the paper, and thus enhances the adhesion between the matrix material and the paper. This effect is particularly remarkable for starch and its derivatives. Further, if the matrix material is damaged due to offset or the like, the image forming material flows out quickly during the image erasing operation, and the erasing agent cannot sufficiently adsorb the color developer, which causes erasing failure. Therefore, the improvement of the offset resistance property also leads to the improvement of the erasing property. By substituting a part of the hydroxyl groups contained in the sugar skeleton with a substituent such as an acetyl group, the moisture resistance of the image forming material can be controlled. The substitution ratio is appropriately determined depending on the ratio of the polymer erasing agent contained in the image forming material.

Examples of the polyamino acid include amino acids having a hydroxyl group or amino group such as threonine, serine, cysteine, hydroxyproline, tryptophan, aspartic acid, glutamic acid, arginine, lysine, ornithine and histidine, and derivatives thereof. Or a copolymer containing 5% by weight or more of these amino acids and their derivatives.

Glycoprotein in which sugar and protein are bound also functions as a polymer eliminator. Examples thereof include collagen, takaamylase A, casein, embryo glycoprotein, ovalbumin and the like.

The polymer having a hydroxyl group may be any polymer as long as it can donate an electron from a lone pair of oxygen atoms and can physically or chemically adsorb a developer. From this point of view, phenolic resins having a phenolic hydroxyl group, which has a strong developing effect, do not fall into this category. A typical example is polyvinyl alcohol. By protecting a part of the side chain hydroxyl groups with an acetyl group, an alkyl group or the like, the moisture resistance of the image forming material can be controlled. The substitution ratio is determined by the ratio of the polymeric erasing agent contained in the image forming material.

The polymer having an amino group has an aromatic amino group as long as it can donate an electron from a lone pair of nitrogen atoms to physically or chemically adsorb a developer. It may be a polymer or a polymer having a non-aromatic amino group. Preferably, polyvinyl pyridine, polyvinyl pyrazine, polyvinyl pyrimidine, polyvinyl imidazole, polyvinyl pyrrole, polyvinyl carbazole, polyvinyl pyrrolidine,
Examples thereof include homopolymers such as polyvinylpiperidine, polyvinylpiperazine, and polyvinylmorpholine, and copolymers containing 5% by weight or more of the above-mentioned amino group-containing monomer. Further, a polymer in which an amino group is introduced into the benzene ring of polystyrene can also be used as the polymer eliminator. Examples thereof include polyvinyl aniline and a quaternary ammonium salt substitution product used as an anion exchange resin, a substitution product with an amino group having an ethylenediamine skeleton, and derivatives thereof. The substitution rate of the amino group may be arbitrary, but is preferably 5% or more.

Here, in FIG. 1, crystal violet lactone (CVL) which is a color developing compound, propyl gallate which is a color developing agent, pregnenolone which is an erasing agent, and a mixture thereof (color developing compound: color developing agent). : Erasing agent = 1:
The TGA curve of 1:10) is shown. From this figure, the weight of propyl gallate has begun to decrease from around 190 ° C,
It is considered that propyl gallate is volatilized at a temperature higher than this temperature. However, as described above, the image forming material of the present invention can be erased at a temperature much lower than 190 ° C. From this, decolorization does not occur due to volatilization of the developer,
It is considered that when the color developer diffuses in the matrix agent, the interaction between the color developer and the color-forming compound disappears and the color disappears.

In the present invention, the matrix material means a binder resin for holding each component of the image forming material and a wax component added for adjusting the physical properties. The binder resin that can be used in the invention is not particularly limited as long as it is a resin used in ordinary electrophotographic toners, liquid inks, ink ribbons, writing tools, and the like. In the case of the binder resin for toner, a resin having a glass transition point Tg of 40 ° C. or higher is preferably used in view of temperature stability. Examples of the binder resin for toner include polystyrene, polystyrene-acrylate copolymer, polystyrene-acrylic acid copolymer, polystyrene-methacrylate copolymer, polystyrene-methacrylic acid copolymer, polyester, epoxy resin, styrene-
Butadiene copolymer, styrene-propylene copolymer,
Styrene-butadiene rubber, styrene-maleic acid ester copolymers, styrene-maleic anhydride copolymers and the like fall into this category. These binder resins may be used alone or in a blend. For binder resin for thermal transfer ink ribbon, Tg
A resin having a temperature of 70 ° C. or lower is preferably used. Examples thereof include ethylene-vinyl acetate and polyester resins.
You may blend 2 or more types of these.

As the waxes, higher alcohols, higher ketones, higher aliphatic esters, low molecular weight polypropylenes, low molecular weight polyethylenes, low molecular weight polybutylenes, low molecular weight polyalkanes, natural waxes such as rice wax and the like can be used. 10 if specified by acid value
The following waxes are preferred. The weight average molecular weight of these is preferably 10 ² to 10 ⁵ , and more preferably 10 ² to 10 ⁴ .

To erase the image-forming material of the present invention, a colored image-forming material containing a color-developing compound, a color developer having a molecular weight of 120 to 210, a matrix material and an erasing agent is used. The attached paper is bundled and 100 to 14
A method having a step of heating to 0 ° C. to erase the color of the image forming material and a step of cooling the heated bundle of paper to room temperature is used. The heating time in the erasing step is preferably 3 to 12 hours. This method is suitable for processing and erasing a large amount of paper in an office that consumes a lot of paper.

The image forming material of the present invention can be erased by using a solvent. The erasing solvent used for erasing the image forming material of the present invention is required to have the following characteristics. (1) The erasing agent physically or chemically adsorbs and takes in and retains the color developing agent acting on the color-forming compound. (2) It has a high affinity with the binder resin, can penetrate into the inside of the image forming material on paper, and does not dissolve the binder resin and the erasing agent on the time scale until volatilization.

Suitable erasing solvents include ethyl ether, ethylpropyl ether, tetrahydrofuran, tetrahydropyran, ethers represented by dioxane, 2-methoxyethanol, 2-ethoxyethanol, 1,2-dimethoxyethane, 1,2. -Cellosolves such as diethoxyethane, acetone, methyl ethyl ketone, methyl propyl ketone, diethyl ketone, cyclopentanone, ketones such as cyclohexanone, ethyl acetate, ethyl lactate, methyl propionate, esters such as ethyl butyrate, methylene chloride, Examples thereof include N-methylpyrrolidinone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like. These solvents may be used alone or in combination of two or more. In this case, the mixing ratio can be arbitrarily selected.

Further, depending on the matrix material, there is a solvent capable of exhibiting the erasing property. As such a solvent,
Examples thereof include alcohols typified by methyl alcohol, ethyl alcohol, propyl alcohol, and isopropyl alcohol, water, and basic aqueous solutions. These solvents are particularly effective for image forming materials such as crayons having a large proportion of wax components. Further, when such a solvent is used by adding it to the above-mentioned erasing solvent, the efficiency of image erasing may increase.

Further, toluene, xylene, cresol,
A solvent such as dimethoxybenzene, hexane, cyclohexane, cyclopentane, petroleum ether, and benzine, which has a high affinity for a binder resin represented by petroleum fractions, may be mixed with the above-mentioned erasing solvent.

[0052]

EXAMPLES Examples of the present invention will be described below. In the following examples, as a paper for forming an image, unless otherwise specified, 500BLATT manufactured by NEUSIEDER was used.

Example 1 4 parts by weight of 3- (4-dimethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azafuralide as a color developing compound, 2 parts by weight of ethyl gallate (molecular weight 198.17) as a coloring agent, 1 part by weight of polypropylene wax as a wax component, 8 parts by weight of hydrophobized starch as a polymer erasing agent, and polystyrene 84 having a molecular weight of 45,000 as a binder resin.
Parts by weight, charge control agent (LR-14, Nippon Carlit Co., Ltd.)
7) 1 part by weight was mixed and kneaded with a kneader. This kneaded material was pulverized with a pulverizer to obtain a powder having an average particle size of 10 μm.
1 wt% of hydrophobic silica was externally added to this powder to prepare a blue electrophotographic toner. The obtained toner was put in a toner cartridge of a copying machine (Toshiba, Plimage 38), and a standard pattern image for evaluation was transferred onto paper. The reflection density of the standard pattern image measured by a Macbeth densitometer was about 1.0, and it was found that an image with sufficient density can be formed.

This paper was placed in a constant temperature bath and heated to 130 ± 2 ° C. to erase the color. Resin is present on the surface of the decolorized paper,
Depending on the viewing angle, traces of imaging material were visible to the naked eye due to light reflection. However, when the trace of the image forming material was compared with the background, the difference in reflection density was about 0.05, and the afterimage was hardly noticeable. The reflection density did not change even after the paper was stored at 55 ° C. for 1000 hours.

Comparative Example 1 For blue electrophotography in the same manner as in Example 1 except that stearyl gallate (molecular weight 422.6) was used in place of the ethyl gallate used as the developer in Example 1. A toner was prepared. The obtained toner was put in a toner cartridge of a copying machine (Toshiba, Plimage 38), and a standard pattern image for evaluation was transferred onto paper. The reflection density of the standard pattern image measured by a Macbeth densitometer was about 0.8.

This paper was placed in a constant temperature bath and heated to 130 ± 2 ° C. In this case, when the trace of the image forming material was compared with the background, the difference in reflection density was about 0.2. A bluish afterimage was observed with the naked eye, and the image forming material was not completely decolored. 1000 this paper at 55 ℃
The reflection density did not change even after storage for a period of time.

Example 2 Crystal Violet Lactone 4 as a color developing compound
Parts by weight, 2 parts by weight of methyl 3,5-dihydroxybenzoate (molecular weight 154.12) as a developer, 1 part by weight of polypropylene wax as a wax component, 10 parts by weight of methyl cholate as an erasing agent, and 82 parts by weight of polystyrene as a binder resin. Part, charge control agent (Japan Carlit Co., L
1 part by weight of R-147) was mixed and kneaded with a kneader.
This kneaded material was pulverized with a pulverizer to obtain a powder having an average particle size of 10 μm. 1 wt% of hydrophobic silica was externally added to this powder to prepare a blue electrophotographic toner. The obtained toner was put in a toner cartridge of a copying machine, and a standard pattern image for evaluation was transferred onto paper. The reflection density of the standard pattern image measured by a Macbeth densitometer was about 0.8, and it was found that an image with sufficient density can be formed.

This paper was placed in a constant temperature bath and heated to 130 ± 2 ° C. to erase the color. Resin is present on the surface of the decolorized paper,
Depending on the viewing angle, traces of imaging material were visible to the naked eye due to light reflection. However, when the trace of the image forming material was compared with the background, the difference in reflection density was about 0.05, and the afterimage was hardly noticeable. The reflection density did not change even after the paper was stored at 55 ° C. for 1000 hours.

Comparative Example 2 Instead of the methyl 3,5-dihydroxybenzoate used as the developer in Example 2, 2,2'-methylenebis [6-
[(2-hydroxy-5-methylenephenyl) methyl]
-4-Methylphenol] (molecular weight 468) was used to prepare a blue electrophotographic toner in the same manner as in Example 2. The obtained toner was put in a toner cartridge of a copying machine, and a standard pattern image for evaluation was transferred onto paper. The reflection density of the standard pattern image measured by a Macbeth densitometer was about 0.6.

This paper was placed in a constant temperature bath and heated to 130 ± 2 ° C. In this case, when the trace of the image forming material was compared with the background, the difference in reflection density was about 0.2. A bluish afterimage was observed with the naked eye, and the image forming material was not completely decolored. 1000 this paper at 55 ℃
The reflection density did not change even after storage for a period of time.

Example 3 4 parts by weight of 3- (4-dimethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azafuralide as a color developing compound, 2,3,4-trihydroxyacetophenone 2 as a colorant
Parts by weight, polypropylene wax 2 as a wax component
Parts by weight, 8 parts by weight of cellulose acetate fine particles having a degree of acetylation of 52% as a polymer erasing agent, and a styrene-acrylate copolymer 8 having an acrylate content of 5 wt% as a binder resin.
3 parts by weight and 1 part by weight of a charge control agent (Bontron E-88, Oriental Chemical Co., Ltd.) were mixed and kneaded with a kneader.
This kneaded material was pulverized with a pulverizer to obtain a powder having an average particle size of 10 μm. 1 wt% of hydrophobic silica was externally added to this powder to prepare a blue electrophotographic toner. The obtained toner was put in a toner cartridge of a copying machine, and a standard pattern image for evaluation was transferred onto paper. The reflection density of the standard pattern image measured by a Macbeth densitometer was about 0.7.

This paper was placed in a constant temperature bath and heated to 130 ± 2 ° C. to erase the color. Resin is present on the surface of the decolorized paper,
Depending on the viewing angle, traces of imaging material were visible to the naked eye due to light reflection. However, when the trace of the image forming material was compared with the background, the difference in reflection density was about 0.04, and the afterimage was hardly noticeable. The reflection density did not change even after the paper was stored at 55 ° C. for 1000 hours.

Example 4 51 g of leuco dye (RED520 manufactured by Yamada Chemical Co., Ltd.), 33 g of ethyl gallate, 100 g of waxy corn starch,
916 g of styrene-butyl acrylate copolymer having a butyl acrylate content of 6 wt% was weighed, kneaded in advance with a pressure kneader to develop color, and then pulverized with a pulverizer and classified by a wind classifier to obtain an average particle size. A powder of 0.8 μm was obtained. Limonene (35 g) was added to the powder (15 g) and dispersed for 1 hour using a paint shaker to prepare a liquid ink. This liquid ink is used for stationery parts (I & J
A writing pen was prepared by putting it in FIS-02 (FISNER). 1cm x 1c on copy paper with this writing pen
I drew a solid image of m. The reflection density of the image measured by a Macbeth densitometer was 0.8.

This paper was placed in a constant temperature bath and heated to 130 ± 2 ° C. to erase the color. Resin is present on the surface of the decolorized paper,
Depending on the viewing angle, traces of imaging material were visible to the naked eye due to light reflection. However, when the trace of the image forming material was compared with the background, the difference in reflection density was about 0.05, and the afterimage was hardly noticeable. The reflection density did not change even after the paper was stored at 55 ° C. for 1000 hours.

Example 5 Ethyl gallate and polypropylene wax were mixed at a weight ratio of 1:10 and stirred well while heating at 130 ° C. This mixture was spread on a vat, rapidly cooled and solidified, and then finely ground in a mortar to prepare a masterbatch.
To this masterbatch, leuco dye RED520 (manufactured by Yamada Chemical Co., Ltd.) as a color developing compound and hydrophobized starch as a decoloring agent were added. At this time, the molar ratio of ethyl gallate to the leuco dye and the ratio of hydrophobized starch to the leuco dye were adjusted to 5 times and 5 times, respectively. The composition obtained is at 100 ° C.
After stirring while heating to, it was poured into a mold to prepare a crayon. 1cm x 1c on copy paper with this crayon
I drew a solid image of m. The reflection density of the image measured with a Macbeth densitometer was 1.0.

This paper was placed in a constant temperature bath and heated to 130 ± 2 ° C. to erase the color. Wax was present on the surface of the decolorized paper, and depending on the viewing angle, the traces of the image-forming material were visible to the naked eye due to the reflection of light. However, when the trace of the image forming material is compared with the background, the difference in reflection density is about 0.05.
The afterimage was almost unnoticed.

Example 6 2 parts by weight of leuco dye Blue 220 (manufactured by Yamada Chemical Co., Ltd.) as a color developing compound, 1 part by weight of methyl 3,5-dihydroxybenzoate as a color developer, and ethylene-vinyl acetate copolymer (as a binder resin ( 17 parts by weight of Mitsui DuPont Polychemical, ELVAX500W), 70 parts by weight of polyethylene wax, and 10 parts by weight of corn starch as a polymer erasing agent were mixed and kneaded with a three-roll mill. This kneaded product was applied on a base film of an ink ribbon with a coating amount of about 5 g / m ² using a hot melt coater to prepare a blue thermal transfer ink ribbon. This ink ribbon was set on a barcode printer (manufactured by TEC, B-30) and transferred onto a thermal transfer paper (JW-Z103). As a result, a bar code image with a reflection density of about 0.7 could be obtained.

This paper was placed in a constant temperature bath and heated to 130 ± 2 ° C. to erase the color. Resin is present on the surface of the decolorized paper,
Depending on the viewing angle, traces of imaging material were visible to the naked eye due to light reflection. However, when the trace of the image forming material was compared with the background, the difference in reflection density was about 0.05, and the afterimage was hardly noticeable. The reflection density did not change even after the paper was stored at 55 ° C. for 1000 hours.

[0069]

As described in detail above, according to the present invention, a clear image can be formed even when the amount of the erasing agent used is small, and the image can be satisfactorily erased. An image forming material capable of erasing an image by heat treatment in a large amount, and such a method can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing TGA curves of a color developing compound, a color developing agent, an erasing agent, and a mixture thereof.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI G03G 9/08 361

Claims (4)

(57) [Claims] 1. A color-forming compound having a molecular weight of 120 to 21.
A bundle of paper to which a colored image forming material containing a color developing agent of 0, a matrix material and an erasing agent is attached is set to 100.
Heating to ~ 140 ° C to erase the color of the image forming material;
And a step of cooling the heated paper to room temperature. 2. The developer is biphenol, methyl gallate, ethyl gallate, 4,4′-oxybisphenol, methylenebisphenol, phenylmethylbenzenediol, 2,4-dihydroxyacetophenone,
2,3,4-trihydroxyacetophenone, 2,3-
Methyl dihydroxybenzoate, Methyl 2,6-dihydroxybenzoate, Ethyl 2,3-dihydroxybenzoate,
A contract characterized in that it is selected from the group consisting of ethyl 3,5-dihydroxybenzoate, ethyl 2,6-dihydroxybenzoate and propyl 2,3-dihydroxybenzoate.
The image erasing method according to claim 1 . 3. The erasing agent is a polymer having a sugar skeleton,
A contract characterized in that it is selected from the group consisting of polyamino acids, polymers having hydroxyl groups, polymers having amino groups, polyvinyl acetals, polyacrylonitriles, copolymers thereof, and mixtures thereof.
The image erasing method according to claim 1 . 4. The image erasing method according to claim 1 , wherein the heating time is 3 to 12 hours.