JP2001296701A - Granular decolorable coloring agent and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a granular decolorable coloring agent which is good and stable in color developing state as an image forming device, easily decolored by heating and decoloration processing to bring the agent into contact with an organic solvent, etc., after being used for printing and printing characters, and stably maintained in its decoloring state. SOLUTION: The decoloring agent of the granular decolorable coloring agent consisting of at least a matrix material, color developing agent color developable compound, and decoloring agent exists in the granular decolorable coloring agent as a particulate and microphase separation state of the size at which the average diameter when the shape of the decoloring agent is approximated by a ball does not exceed the diameter of the granular decolorable coloring agent. The color developing agent, in a color developing state, exists by being adsorbed on the decoloring agent particulate surfaces in a decoloring process step by intermolecular interaction with a color developable compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particulate color-erasable colorant capable of changing a color-forming compound in a color-developing state to a colorless color-erasable state, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, with the spread of computers, printers, copiers, facsimiles, and the like, the output of information on paper has increased. Although there is a call for "paperlessness by digitizing information" in order to reduce output on paper, hard copy to paper is required because of its features such as good visibility, high portability, and ease of information search by turning pages. Demands are endless. As a result, protection of natural resources as a raw material for paper, reduction of waste disposal amount, and reduction of carbon dioxide emission have become issues to be solved. “Recycling and reuse of paper” is a very contemporary issue in each aspect of protecting natural resources, reducing the amount of waste disposal, and reducing carbon dioxide emissions.

Under these circumstances, the technology of making image forming materials (various printing inks, toners, jet inks, etc.) for printing and printing on paper colorless after printing and printing promotes the recycling and reuse of paper. It is extremely important in doing so. That is, in the conventional paper recycling method, a method in which the recovered paper is deflocculated with water and then the ink portion is floated and separated in a so-called "deinking step" or a method of decolorizing using a bleaching agent is used. However, these are factors that make the process cost higher than in the case of newly producing paper.

Accordingly, paper printed with an image forming material using an erasable colorant capable of changing a color developing compound into a colorless and erasable state requires a time-consuming decompression as in the prior art. It is expected that it can be reused or recycled without going through the black ink process.

In recent years, various studies have been made on erasable colorants, and erasable colorants which can be erased by applying heat are disclosed in, for example, JP-A-7-81236 and JP-A-Hei.
No. 0-88046. The former publication discloses a coloring compound such as a leuco dye, a developer,
An erasable colorant containing an organic phosphoric acid compound having a decolorizing action, and the latter publication discloses that a combination of a color former such as a leuco dye and a developer is heat-sensitive. A discolorable colorant using a sterol compound such as cholic acid, lithocholic acid, testosterone, cortisone, etc. as a decoloring agent exhibiting a decolorizing effect by adding a colorant is disclosed.

An erasable colorant that can be erased by contact with an organic solvent is disclosed in, for example, JP-A-11-2122.
No. 95 discloses this. This erasable colorant is
It is composed of a coloring compound such as a leuco dye, a developer, and a decoloring agent. As the decoloring agent, a highly amorphous phase separation inhibitor (for example, a cyclic sugar alcohol) and an amorphous It is characterized in that a phase separation inhibitor having low reactivity (for example, a non-aromatic cyclic compound having a hydroxyl group other than a cyclic sugar alcohol and a 5- or more-membered ring or a derivative of a cyclic sugar alcohol) is used in combination. Further, JP-A-11-212296 discloses a biodegradable sterol compound and a cyclic sugar alcohol extracted from animals, plants or fungi as a decoloring agent exhibiting a decoloring effect upon contact with an organic solvent. Derivatives thereof are disclosed.

[0007]

While such conventional erasable colorants have their respective features, it is not easy to achieve both good coloring and good erasing properties, or as a printed matter. However, there are drawbacks such as poor durability under actual use conditions and high cost, and further improvement in performance is desired for full-scale practical use.

Accordingly, it is an object of the present invention to provide a decolorizable, good and stable color-forming state under actual use conditions as a printed material, and to use an organic solvent after printing or printing as an image forming material. An object of the present invention is to provide a particulate erasable colorant which can be easily erased by an erasing treatment such as contact with the toner and can maintain the erased state stably.

The present inventor has conducted various investigations on the causes of insufficient coloring and decoloring of the erasable colorant in the prior art. Further, the inventors have found that the intermolecular interaction with the color developer is an important controlling factor, and have completed the present invention based on this finding.

[0010]

The above object is achieved by the present invention described below. That is, the present invention provides at least a matrix material, a color developer, a color-forming compound which develops a color by an intermolecular interaction with the color developer, and an intermolecular interaction between the color developer and the color former. Stronger, a particulate erasable colorant comprising a decolorant that interacts with the developer and intermolecularly, in the particulate erasable colorant,
The decoloring agent always exists as a fine particle or a microphase separated state whose average diameter when its shape is approximated by a sphere does not exceed the diameter of the particulate decolorable colorant, and in a color developing state. The developer is present in the matrix material in an intermolecular interaction with the color former, and in the decolored state, the developer does not interact with the color former in the molecule. A particulate decolorizable colorant which is adsorbed on the surface of the decolorant existing in a state of fine particles or microphase separation and is present in a molecular interaction with the decolorant, and a method for producing the same. It is.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention. As the size of the particulate erasable colorant of the present invention, an optimal size is selected depending on the use as the colorant. For example, when a poster color is used for writing characters of several cm to several tens of cm or is coated on the entire surface of the poster, the average diameter of the shape approximated by a sphere is several tens μm to 100 μm. Even a relatively large size of several tens of μm can be used. When the particulate erasable colorant of the present invention is used as a toner for copying machines and printers, the average diameter of the particles when approximated by a sphere is about 10 μm to 7 μm.
A size of about m is preferred. When the particulate erasable colorant of the present invention is dispersed and used as an ink for an ink jet printer or an aqueous ink for a writing implement, the average diameter of the particles when approximated by a sphere should be 2 to 1 μm or less. Is preferred.

The particulate erasable colorant of the present invention comprises at least a matrix material, a color former, a color developer, and a crystalline decolorant. Is the same as the colorable colorant, but the average diameter of the decolorizable agent in the particulate erasable colorant when the shape is approximated by a sphere is a predetermined size, irrespective of the state of color development or decolorization. It is characterized in that the particles have a size not exceeding the diameter of the particulate erasable colorant and are dispersed in the form of fine particles or microphase separated.

Hereinafter, a matrix material, a coloring compound,
The developer and the decoloring agent will be sequentially described in detail. [Matrix Material] As a matrix material used for the particulate erasable colorant of the present invention, an organic high molecular compound or a low molecular compound can be used. Hereinafter, a matrix material composed of an organic polymer compound will be referred to as a polymer matrix material, and a matrix material composed of a low molecular compound will be referred to as a low molecular matrix material, as necessary.

The polymer matrix material used in the particulate colorable / colorable colorant of the present invention is a binder which is usually additionally used when the particulate colorable / colorable colorant is used as an image forming material. The resin may be the same or different. For example, jet ink (ink for ink jet printer)
In the case of an image forming material in which a particulate erasable colorant is directly dispersed in a solvent (water or an organic solvent) as in the above, a binder additionally used when used as an image forming material The resin or dispersant is soluble in the solvent, while the matrix material used for the particulate erasable colorant must be insoluble and swellable in the solvent.

For example, when a particulate erasable colorant is used by dispersing it in a varnish such as an offset ink, the matrix material used for the particulate erasable colorant is a solvent for the varnish. Linseed oil, soybean oil, high boiling petroleum solvents, etc.

Further, for example, when the particulate erasable colorant of the present invention is used in a crayon, a craper, a thermal transfer ink, or a toner for a copying machine, the matrix material used for the particulate erasable colorant is Alternatively, it may be the same as the binder resin additionally used when the present particulate erasable colorant is used as an image forming material.

The polymer matrix material may be selected from known thermoplastic resins and thermosetting resins in accordance with the form of use of the particulate erasable colorant of the present invention, such as jet ink or printing ink. In the temperature range in which the decolorable colorant is used as a dye in a color-developing state, the color former and the developer can be solid-solved (dissolve and molecularly dispersed), and A resin that can be dispersed as fine particles or microphase separated in the above size and that can maintain the form as particles can be appropriately selected and used, and is not particularly limited.

Specifically, for example, when a leuco dye is used as the color-forming compound, a phenol compound is used as the color developer, and starch is used as the decolorant, the following organic polymer compound is preferably used as the matrix material. be able to. That is, for example, ketone resin, norbornene resin, polystyrene, poly (α-methylstyrene), polyindene, poly (4-methyl-1-pentene), polyvinylpyridine, polyacetal, polyvinylformal, polyvinylacetal, polyvinylbutyral, and polyvinyl acetate , Poly (vinyl propionate), polyvinyl alcohol, polyethylene, polypropylene, polybutadiene,
Polymethylpentene, polyvinyl chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, chlorinated polypropylene,
Polyvinylidene chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl benzyl ether, polyvinyl methyl ketone, poly (N-vinylcarbazole), poly (N-
Vinylpyrrolidone), polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polyacrylonitrile, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polybenzyl methacrylate, polyhexyl methacrylate, polymethacrylic acid, Polymethacrylamide, polymethacrylonitrile, polyacetaldehyde, polychloral, polyethylene oxide, polypropylene oxide, polyethylene terephthalate, polybutylene terephthalate, polycarbonates (bisphenols + carbonic acid), polysulfone, polyether sulfone, polyphenylene sulfide, poly ( Diethylene glycol / bisallyl carbonate), 6-nylon, 6,6-nylon, 12-nylon, 6,12-ny Down, ethyl polyaspartic acid, ethyl polyglutamic acid, polylysine, polyproline, poly (.gamma.-benzyl -L- glutamate), methyl cellulose, ethyl cellulose, benzyl cellulose,
Hydroxyethyl cellulose, hydroxypropyl cellulose, acetyl cellulose, cellulose triacetate, cellulose tributyrate, alkyd resin (phthalic anhydride + glycerin), fatty acid modified alkyd resin (fatty acid + phthalic anhydride + glycerin), unsaturated polyester resin (maleic anhydride) + Phthalic anhydride + propylene glycol), epoxy resin (bisphenols + epichlorohydrin), epoxy resin (cresol novolak +
Epichlorohydrin), polyurethane resin, phenolic resin, urea resin, melamine resin, xylene resin, toluene resin, furan resin, guanamine resin, resin such as diallyl phthalate resin, organic polysilane such as poly (phenylmethylsilane), organic polygermane and the like. Can be suitably used.

Further, for example, the particulate decolorizable colorant of the present invention obtained by using a leuco dye as a color-forming compound, a phenol compound as a color developer, and starch as a decolorant is used for a copier or printer. When used in the toner of (1), as the matrix material of the particulate erasable colorant and the binder resin of the image forming material, for example, polystyrene, a blend polymer of polystyrene and an acrylic resin, a styrene-acrylic copolymer , Polyester, epoxy resin and the like can be particularly preferably used. Here, 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. The proportion of styrene in the copolymer is preferably at least 50% by weight. 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. Here, when a blend polymer of polystyrene and an acrylic resin is used as the matrix, one or more of the acrylic resins exemplified in the above copolymerization can be used. In addition, a copolymer containing butadiene, maleic acid ester, chloroprene or the like at a ratio of 10% by weight or less may be used. The proportion of polystyrene in the matrix is preferably at least 50% by weight.

Further, a polyester synthesized from a carboxylic acid and a polyhydric alcohol can also be used. As the carboxylic acid, for example, terephthalic acid, fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,
Suberic acid, azelaic acid, sebacic acid, brassic acid,
Examples include pyromellitic acid, citraconic acid, glutaconic acid, mesaconic acid, itaconic acid, terraconic acid, phthalic acid, isophthalic acid, hemimellitic acid, melophanic acid, trimesic acid, planitic acid, trimellitic acid, and the like. One or more of these can be used. Examples of the polyhydric alcohol include bisphenol A, hydrogenated bisphenol A, ethylene glycol, propylene glycol, butanediol, neopentyldiol, hexamethylenediol, heptanediol, octanediol, pentaglycerol, pentaerythritol, cyclohexanediol, and cyclopentane Examples thereof include diol, pinacol, glycerin, etherified diphenol, catechol, resorcinol, pyrogallol, benzenetriol, phloroglucinol, benzenetetraol and the like. One or more of these can be used. Further, a blend polymer of two or more polyesters may be used.

An epoxy resin synthesized from a compound having epichlorohydrin and a polyvalent phenolic hydroxyl group can also be used. 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. Further, a phenol resin, a urea resin, a melanin resin, an alkyd resin, an acrylic resin, a polyester, a polyamide, a polyurethane, or the like may be blended with the epoxy resin at a ratio of 15% by weight or less.

As the low-molecular matrix material, low-molecular compounds such as low-molecular plasticizers, low-molecular lubricants, and low-molecular waxes can be used. That is, in the temperature range where the particulate erasable colorant is used as a dye in a color-developing state, the color former and the developer can be solid-solved (dissolved and molecularly dispersed), and the color can be erased. The agent can be dispersed as fine particles or microphase separated, and a low molecular compound capable of maintaining the form as particles can be appropriately selected and used as a low molecular matrix material.

Specifically, for example, when a crayon is prepared using a leuco dye as a color former, a phenol compound as a developer, and starch as a decolorizer, a low molecular weight compound (wax) such as 1 -Docosanol can be suitably used.

[Color-forming compound] Examples of the color-forming compound used in the present invention include leuco auramines, diaryl phthalides, polyaryl carbinols, acyl auramines, aryl auramines, and rhodamines. B
Organic compounds such as lactams, indolines, spiropyrans, and fluorans can be given.

Specific examples of the color-forming compound include, for example, 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-methyl Indole-3-yl) -4-azaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3-diethylamino-7
-Chloroanilinofluoran, 3-diethylamino-
7,8-benzofluoran, 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide,
3,6-dimethylethoxyfluoran, 3-diethylamino-6-methoxy-7-aminofluoran, 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- (phenyliminoethanedilidene)
-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-methylfluorane and the like can be suitably used. These can be used alone or in combination of two or more. Needless to say, if a color-forming compound is appropriately selected, a color-developed state of various colors can be obtained, and multicoloring can be realized. These color-forming compounds are, for example, tautomeric compounds that can take both a colorless form and a color-forming form, as shown by a chemical formula below.

[0027]

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[Developer] It is known that in the chemical formulas showing the tautomerism as described above, the chemical structure of the inner salt type shown at the lower side corresponds to the "colored type". A compound capable of stabilizing the chromogenic type by stabilizing such an ionic inner molecular salt type structure by transfer of protons or formation of hydrogen bonds or formation of a metal complex salt is a so-called color developing compound. Agent.

Examples of the color developer used in the present invention include phenol and phenol derivatives, metal salts of phenol derivatives, metal salts of carboxylic acid derivatives, salicylic acid and salicylic acid metal salts, benzophenone and benzophenone derivatives, sulfonic acids, and sulfonic acids. Salts, phosphoric acids,
Examples thereof include metal phosphates, acid phosphates, acid phosphate metal salts, phosphorous acid, metal phosphites, and zinc halides. These can be used alone or in combination of two or more. Specific examples of phenol derivatives that can be used as a color developer are shown below by chemical formulas.

[0030]

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These phenol derivatives, for example, interact with the carboxylic acid residues of the color-forming color-forming compound between the molecules to form hydrogen bonds, as shown by the following chemical formula, thereby stabilizing the color-forming state. Can be Such an intermolecular interaction between the color-forming compound and the developer can occur even when both are solid-solved (dissolved and molecularly dispersed) in the matrix material.

[0032]

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As exemplified by the above chemical formula, in a system in which a color-forming compound and a color developer interact with each other in a matrix material and the color-forming compound becomes a color-forming type, as described later, Decoloring agent ”is (1) amorphous (amorphous)
In the case where the particles are present in the form of microphase-separated fine particles in the matrix material, and (2) when they are crystalline and are dispersed as fine crystals in the matrix material, the activity due to heating or decolorizing aid treatment If the coloration is not performed, the intermolecular interaction between the color developer and the decolorant (which is stronger in chemical equilibrium than the interaction between the color former and the color developer) is controlled by kinetic control. It is virtually impossible to "freeze" and the color developing compound is stabilized by the color developer.

[Decoloring Agent] The decoloring agent in the particulate erasable coloring agent of the present invention is stronger than the intermolecular interaction between the coloring compound and the developing agent, and may be between the coloring agent and the developing agent. Fine particles (decolorized) in a matrix material in the color-developed state of the particulate decolorizable colorant in a matrix material, and in a molten, swollen or dissolved mixture in the decolored state It is a compound that can be dispersed and present as a micro phase separated state (when the agent is in a crystalline state) or a micro phase separated state (when the decoloring agent is in an amorphous state).

As the intermolecular interaction that can act between the decoloring agent and the color developing agent, a hydrogen bond, an ionic bond, a hydrophobic bond, a stereochemical inclusion phenomenon, or the like can be used. That is, from among compounds having one or more alcoholic hydroxyl groups, free carboxylic acid groups, carboxylate residues, cyclic saturated hydrocarbon residues, etc. in the molecule, the solubility in the matrix material used and Based on the temperature dependence, a material usable as a decoloring agent can be selected.

As specific examples of the decoloring agent used in the present invention, for example, starch such as corn starch and tapioca starch, hydrophobized starch, dextrin, cyclodextrin and the like can be suitably used.

The particulate erasable colorant of the present invention comprises at least a matrix material, a coloring compound, a color developer,
It is composed of a decolorizing agent having a controlled particle size. The preferred compounding ratio is as follows. The matrix material is
0.1 to 1000 for 1 part by weight of the coloring compound
Parts by weight, preferably 0.5 to 100 parts by weight, more preferably 1 to 20 parts by weight. The developer is usually 0.1 to 10 parts by weight based on 1 part by weight of the coloring compound,
Preferably, the ratio is 1 to 2 parts by weight. The developer is 0.
When the amount is less than 1 part by weight, the coloring of the particulate erasable colorant due to the interaction between the color former and the 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 decoloring agent is used in an amount of usually 1 to 200 parts by weight, preferably 10 to 100 parts by weight, based on 1 part by weight of the coloring compound. When the amount of the decoloring agent is less than 1 part by weight, it is difficult to cause a change in the state between the colored state and the decolored state of the particulate erasable colorant. When the amount of the decoloring agent exceeds 200 parts by weight, the coloring of the particulate decolorizable colorant becomes insufficient.

In the particulate decolorizable colorant of the present invention, the decolorant is always in a state of fine particles or microphase separation in the particulate decolorable colorant regardless of the state of color development or decoloration. Exists in a distributed manner. The size of the fine particles or the microphase-separated state of the decoloring agent is such that the average diameter when its shape is approximated by a sphere does not exceed the diameter of the particulate decolorizable colorant having a predetermined size. It is necessary to be.

If the size of the decolorizable agent in the particulate colorable / colorable colorant in the state of fine particles or microphase separation is assumed to be the average diameter when its shape is approximated by a sphere, the particle size of the colorable / colorable colorant If the diameter of the agent is exceeded, the particles are substantially composed of only the decoloring agent. That is, in producing the particulate decolorizable colorant, the matrix material, the color forming compound, the color developer, and the coarse particulate decolorant are used without considering the size of the particles of the decolorant. , Kneading, pulverization and classification alone result in "particles comprising a matrix material, a color former, and a developer and substantially free of a decolorant" and "substantially decolorized". A mixture of "particles consisting solely of colorant" is obtained. The erasable colorant composed of such a particle mixture has no problem in terms of the color density in the color-developed state, but compared to the particulate erasable colorant of the present invention, when used as an image forming material. The resolution is inferior, the decoloring property is inferior, and a problem occurs in long-term storage stability when used as an ink.

The particulate erasable colorant of the present invention includes:
As long as the function is not impaired, if necessary, a plasticizer composed of a low-molecular compound, a wax, a lubricant, a release agent,
An appropriate amount of additives such as a light stabilizer, an antioxidant, and a charge control agent can be contained.

[Production Method of Particulate Colorable Colorant] The method of producing the particulate colorable colorant of the present invention comprises at least a matrix material, a color developer, and an intermolecular interaction with the color developer. A color developing compound that develops a color, and a decoloring agent that is stronger than the intermolecular interaction between the color developing agent and the color developing compound and that is in the form of fine particles or a microphase separated state that interacts with the color developing agent. In producing a particulate erasable colorant of a predetermined size by using, the average diameter when the shape of the decolorizable agent is approximated by a sphere exceeds the diameter of the particulate erasable colorant. The above-mentioned decolorizing agent in the state of fine particles or microphase-separated state that has been previously pulverized or refined to a size that is not a matrix material,
After being dispersed in a mixture of the color developer and the color former, the particulate erasable colorant is formed.

A well-known pulverizing method for previously pulverizing or pulverizing the decolorizable agent to a size not exceeding the diameter of the particulate decolorable colorant when the shape of the decolorant is approximated by a sphere is known. Any method can be used. In addition, any known method other than the mechanical pulverization method can be applied as a method of miniaturization.

Examples of the dry pulverization method include a method using a pulverizer such as a circulation air jet pulverizer equipped with a cyclone classifier, a hammer rotary pulverizer, a cutter blade rotary pulverizer, and a semi-dry pulverization method. For example, using a method such as a milling method using a kneader, a vibration mill, a ball mill, or a planetary rotary mill using a salt and a small amount of a solvent as a grinding aid, a decolorizing agent in a state of fine particles or microphase separation is predetermined. Can be crushed to size. Needless to say, when a grinding aid is used, it must be washed with an appropriate solvent and dried before use.

As a finer method other than the mechanical pulverization method, for example, a material obtained by heating and melting a decolorizing agent is ultrasonically dispersed in a non-soluble solvent to form a colloid, then cooled, filtered, and filtered. A method of washing and drying, a method of injecting a good solvent solution of a decoloring agent into a non-soluble solvent (poor solvent) under ultrasonic irradiation to precipitate, filtering, washing and drying can be exemplified. When such a miniaturization method is used, it is effective to add a suitable auxiliary agent in order to prevent the decoloring agent once miniaturized from growing crystals or growing particles due to fusion. . For example, a part of the matrix material used in a later step can be added for such a purpose.

After dispersing a fine particle or a microphase-separated decoloring agent which has been pulverized or fined in advance to a predetermined size in a mixture of the matrix material, the color developer, and the color former, In forming the particulate erasable colorant, a known method used for producing fine particles of a matrix material such that a plurality of low-molecular compound components are present as a solid solution and dispersed therein is used. It can be applied as appropriate. However, it is needless to say that various conditions need to be set so that the decoloring effect frozen in the middle of the manufacturing process does not appear.

For example, a matrix material,
A color former, a color developer, and a decolorizer having an adjusted particle size are sufficiently kneaded at a temperature lower than the melting point or softening point of the decolorant to develop a color. Particle erasable colorants of a size can be produced. This method is suitable for efficiently producing the particulate erasable colorant of the present invention with good color development and color development stability.
The method and method of the kneading device and the device for fine pulverization are not particularly limited.

The presence of the decoloring agent in the particulate erasable colorant in the form of fine particles having the above-mentioned size or in a microphase-separated state can be confirmed by various analytical means as described below. it can. For example, by processing the decolorizable dye composition as it is into a thin film and observing the thin film with an optical microscope or a confocal laser microscope, etc., to confirm the size of the fine particles or the microphase separated state of the erasing agent. Can be. At this time, the fact that the observed “fine particle or microphase separated state” is attributed to the decoloring agent means that the coloring compound / matrix material, the developing agent / matrix material, the coloring compound and the color developing compound The composition of the combination of the agent / matrix material, the decolorant / matrix material, and the other additive / matrix material when other additives are used is processed into a thin film under the same conditions as above. Can be confirmed by comparative observation with an optical microscope or a confocal laser microscope.
Whether the decoloring agent exists as fine particles (crystal) or in a microphase separated state (amorphous)
It can be confirmed by the X-ray diffraction method.

When the size of the main component of the decoloring agent dispersed and present in the state of fine particles or micro phase separation is less than 0.1 μm as the average diameter of the fine particles or micro phase separation state approximated by a sphere. (1) small-angle X-ray scattering method, (2) transmission electron microscopy observation of a thin film sample (using osmium tetroxide staining, if necessary, in order to clarify the image), or (3) The size of fine particles or microphase separated state can be confirmed by scanning electron microscope observation of the thin film sample surface (also using a method such as dissolving only the decolorant from the sample surface using an appropriate solvent). it can. Also in this case, the attribution of the observed fine particles or microphase separation state can be confirmed by comparison with a sample containing no decoloring agent.

[Color erasing method] In order to make the particulate color-erasable colorant in a color-developing state into a color-erasable state, that is, to erase the color, the particulate color-erasable colorant is heated and melted to decolor. And a method in which a part or all of the particulate erasable colorant is dissolved or swelled by contacting it with a liquid or gaseous erasing aid.

By heating and melting the particulate erasable colorant, the molecular motion of the developer which has been kinetically frozen becomes active, and moves in the molten mixture of the composition. Adsorbed on the surface of the particulate colorable / colorable colorant present in the state of fine particles or microphase separation, stronger than the intermolecular interaction between the color developing compound and the color developer, and A strong intermolecular interaction occurs between the two, and as a result, the coloring state of the color former becomes unstable and becomes a decolored state. Since the decolored state as described above is stable in terms of equilibrium, it continues even if the heating is stopped.

The heating means for decolorizing the particulate erasable colorant may be in any form, for example, a thermal printer head (TPH), a thermal bar, a hot stamp, a heat roller, etc. . or,
It may be heated by an infrared lamp or hot air. When a large amount of decoloring processing is performed on the paper on which characters and images are formed by the image forming material using the particulate decolorable colorant of the present invention at a time, a box-shaped warm air dryer or a blown thermostat is used. Can be suitably used.

The heating temperature at the time of decolorizing the particulate colorable / colorable colorant by heating is the temperature at which the particulate colorable / colorable colorant becomes a mixed and molten state as the composition (the “melting point drop by mixing”). Depending on the phenomenon, the temperature is lower than the melting point or softening point of the particulate erasable colorant component alone). The upper limit of the heating temperature at the time of decolorizing the particulate erasable colorant by heating is the lowest temperature among the thermal decomposition starting temperatures of the particulate erasable colorant component. Note that, depending on the type or combination of the color-forming compound, the color developer, the decoloring agent, and the matrix material, the component thermally decomposes by heating, or causes an undesired side reaction to produce a non-decolorable colored compound. Or may form. In such a case, it is preferable to apply a method using a color erasing aid described below as the color erasing method.

When decoloring is performed by contacting a part of or all of the colored decolorizable colorant in a colored state with a liquid decoloring aid (organic solvent) for dissolving or swelling, The molecular motion of the frozen developer is activated by the color erasing aid, and moves through the dissolved or swollen composition to form a particulate erasable color that exists in a state of fine particles or micro phase separation. Adsorbs on the surface of the coloring agent and causes stronger intermolecular interaction between the color developing compound and the color erasing agent than the color developing compound and the color developing agent. The coloring state of the coloring compound is destabilized and becomes a decolored state. Since the decoloring state as described above is equilibrium-stable, it continues even if the liquid decoloring aid is removed. As is apparent from such a decoloring mechanism, the temperature is higher than room temperature, for example, 50 ° C. to 8 ° C.
Performing this method at 0 ° C. is very effective.

Even when decoloring is carried out by contacting a gaseous decolorizing auxiliary (organic gas) which swells the colored particulate decolorizable colorant, the developer which has been kinetically frozen is also used. Is activated by the decolorizing auxiliary, moves through the swollen or dissolved composition, and is adsorbed on the surface of the particulate decolorable colorant existing in a state of fine particles or microphase separation, The interaction between the color former and the color developer is stronger than that between the color developer and the color developer, and a stronger molecular interaction between the color developer and the color erasing agent occurs. As a result, the color development state of the color former is not good. Stabilize,
The color is erased. Since the decoloring state as described above is equilibrium-stable, it continues even after the gas decoloring aid is removed and the swelling state is removed. As is apparent from such a decoloring mechanism, the temperature is higher than room temperature, for example, 50 ° C. to 80 ° C.
It is extremely effective to carry out this method.

The gas used as the color erasing aid in the method of erasing by contacting the gas with the color erasing aid which swells the color developing particulate erasable colorant is a particulate erasable colorant. It must have the property of easily penetrating into the inside of the agent and swelling. Specifically, organic compounds that are gaseous at normal temperature and normal pressure, such as ethylene, acetylene, and dimethyl ether, and organic compounds that sublimate at normal temperature and normal pressure, such as naphthalene and p-dichlorobenzene, can be suitably used.

The organic solvent used as a color erasing aid in the method of erasing by contacting a liquid color erasing aid which swells or dissolves the colored particulate erasable colorant in a colored state includes:
(A) It is preferable to have the property of assisting the formation of hydrogen bonds between the color developer and the decolorant, and (B) the inside of the particulate decolorable colorant has a high affinity with the matrix material. It is preferable to have a property that easily penetrates to. 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.

The first type of solvent, ie, the solvent having both the properties (A) and (B), includes ether,
Examples include ketones and esters. Specifically, for example, ethyl ether, ethyl propyl ether, ethyl isopropyl ether, isopentyl methyl ether,
Saturated ethers such as butyl ethyl ether, dipropyl ether, diisopropyl ether, ethyl isopentyl ether, dibutyl ether, dipentyl ether, diisopentyl ether, and dihexyl ether; Saturated ethers; ethers of dihydric alcohols such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane; oxetane; Cyclic ethers such as tetrahydrofuran, tetrahydropyran, dioxolan, dioxane, trioxane;
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 Saturated ketones such as methyl ketone, heptyl methyl ketone and dibutyl ketone; unsaturated ketones such as ethylidene acetone, allyl acetone and mesityl oxide; cyclic ketones such as cyclopentanone, cyclohexanone, cycloheptanone and cyclooctanone; ethyl formate , Propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, isoacetate Tyl, 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, acetic acid 2
-Ethoxypropyl, 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, ethyl valerate,
Propyl valerate, isopropyl valerate, butyl valerate,
Esters such as methyl hexanoate, ethyl hexanoate, propyl hexanoate, and isopropyl hexanoate. Other solvents other than the above include dichloromethane, γ-butyrolactone, β-propiolactone, N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylisoindolinone,
And dimethyl sulfoxide. 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.

Examples of the second type of solvent, ie, a solvent having the above-mentioned property (A) but having a low affinity for the matrix, include, for example, water, methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and the like. 1-pentanol, 2-pentanol, 3
-Pentanol, isopentyl alcohol, 1-hexanol, 2-hexanol, 3-hexanol, cyclopentanol, cyclohexanol, ethylene glycol, propylene glycol, butylene glycol, glycerin and the like.

Examples of the third type of solvent, ie, a solvent which does not have the property of the above (A) but has high affinity for the matrix, include, for example, toluene, ethylbenzene, propylbenzene, cumene, butylbenzene, isobutylbenzene, and the like.
sec-butylbenzene, pentylbenzene, diethylbenzene, mesitylene, xylene, cresol, ethylphenol, dimethoxybenzene, dimethoxytoluene, benzyl alcohol, tolyl carbinol, cumyl alcohol, acetophenone, propiophenone, hexane, pentane, heptane, octane, Examples thereof include cyclohexane, cyclopentane, cycloheptane, cyclooctane, petroleum fractions (petroleum ether, benzine, etc.).

As mentioned above, the first class of solvents can be used successfully alone. The second type of solvent may be used alone or may be mixed with the first type of solvent. In this case, any kind of solvent has a decoloring ability, so that it can be used at an arbitrary mixing ratio. When a mixed solvent of the second type solvent and the third type solvent is used, the mixing ratio of the two is not particularly limited as long as sufficient decoloring ability is obtained. Is preferred. The third type of solvent may be used as a mixture with the first type of solvent. In this case, the content of the third type solvent may be 90% by weight or less. or,
A mixture of the first to third solvents may be used. In this case, the content of the third type solvent is preferably set to 80% by weight or less.

In order to efficiently decolor the erasable colorant, the solvent may be heated in advance. In this case, the temperature of the solvent is preferably heated to 40 ° C. or higher within a range not exceeding the boiling point of the solvent. When a decoloring method using a solvent is used, a decoloring agent can be added to the solvent.

[0062]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. Example 1 The starch used as a decolorizing agent was obtained by pulverizing and classifying commercially available corn starch (particle outer diameter of about 10 to 20 μm) with a circulating air jet pulverizer equipped with a cyclone classifier.
The particles having a number average particle diameter of 4 μm and a volume average particle diameter of 6 μm were used. The particle size of starch was determined by measuring a sample obtained by ultrasonically dispersing in water containing an electrolyte using sodium dodecylbenzenesulfonate as a dispersant with a Coulter Counter TA-II (manufactured by Coulter Corporation).

A heat-sensitive dye PSD-18 is used as a color-forming compound.
4 (manufactured by Nippon Soda Co., Ltd.), 1 part by weight of propyl gallate as a color developer, 17 parts by weight of starch (number average particle diameter 4 μm and volume average particle diameter 6 μm) as a decolorizer,
79 parts by weight of polystyrene as a matrix material and 1 part by weight of LR-147 (manufactured by Nippon Carlit Co., Ltd.) as a charge controlling agent are mixed in advance, and 1 part is mixed using a kneader.
After sufficiently kneading at a temperature not exceeding 00 ° C., the mixture was cooled to obtain a kneaded product of Example 1. This kneaded material is roughly pulverized to a particle outer diameter of 1 mm by a cutter blade rotary pulverizer, and then pulverized to a maximum particle diameter of 20 μm or less by a circulating air jet pulverizer equipped with a cyclone classifier. Was classified using another cyclone classifier, and the number average particle diameter was 8
Example 1 of the present invention as fine particles having a volume average particle diameter of 12 μm (size larger than the raw starch fine particles)
Was obtained, for example, in a yield of 81%.
The particle size of the particulate erasable colorant of the present invention was determined by ultrasonically dispersing a sample in water containing an electrolyte using sodium dodecylbenzenesulfonate as a dispersant. Manufactured). In addition, the yield of the pulverization / classification process is
The above value is an example because it is affected by the part that stays in the apparatus and cannot be removed (constant regardless of the charged amount) and the part that cannot be collected by the cyclone classifier (proportional to the charged amount). Reasonable values can be achieved for the yield of the classification process.

About 10 m of the particulate erasable colorant of Example 1
g was placed on a slide glass heated to 100 ° C. on a hot plate, another slide glass heated to 100 ° C. was overlaid and pressed, then cooled and cooled to a thickness of about 20 μm sandwiched between glass plates. A thin film sample was prepared. 10
When melted at 0 ° C., it was confirmed that the erasable colorant of Example 1 kept black. FIG. 1 shows the result of microscopic observation of a molten thin film of the particulate erasable colorant of Example 1. Incidentally, one scale of the scale inserted in FIG. 1 is 10 μm.

For comparison, the finely powdered starch used as a raw material (number average particle diameter 4 μm and volume average particle diameter 6 μm)
m) About 10 m of a well-mixed mixture of 17 parts by weight and 79 parts by weight of finely divided polystyrene (matrix material)
g was placed on a slide glass heated to 100 ° C. on a hot plate, another slide glass heated to 100 ° C. was overlaid and pressed, then cooled and cooled to a thickness of about 20 μm sandwiched between glass plates. A thin film sample was prepared. The result of observing this with an optical microscope is shown in FIG. Incidentally, one scale of the scale inserted in FIG. 2 is 10 μm.

As a result of comparative observation, colorless and transparent fine particles (white particles in FIG. 1; the largest one having a diameter of about 8 μm) observed in the thin film obtained by melting the particulate erasable colorant of Example 1; (The smallest one of about 2 μm) was confirmed to be fine particles of starch as a decolorizing agent.
In addition, in the case of this example, it was found that no difference was observed between FIGS. 1 and 2 in the size of the observed starch particles. This is due to the fact that the particulate decolorizable colorant of Example 1 was produced using raw starch fine particles having a particle diameter smaller than that of the particulate decolorable colorant to be obtained by classification. The light non-transmitting fine particles (particles that appear black in FIG. 1) observed in a small number in the thin film obtained by melting the particulate erasable colorant of Example 1 were compared with the samples separately prepared for comparison. As a result,
It was attributed to the fine particles of the charge control agent.

Next, in order to perform decoloration by heating, the particulate decolorizable colorant of this example and a thin film sample of the decolorant (the finely ground starch) / matrix material mixture for comparison were used. When each was heated at 200 ° C. for 10 minutes and cooled to room temperature, the black color of the particulate erasable colorant in the colored state was erased, and it became milky cloudy. When an optical microscope observation was performed on these decolored thin films,
In each case, it was confirmed that the particulate decolorizing agent (starch) observed with an optical microscope was present without change. That is, it was found that the reason why the decolored thin film did not become transparent and appeared in a milky cloudy state was that the starch fine particles were dispersed in the matrix material.

The particulate erasable colorant of Example 1 was further analyzed by powder X-ray diffraction. For the measurement, a JDX-8020 type X-ray diffractometer manufactured by JEOL Ltd. was used. As a result, no clear diffraction line was observed in the particulate erasable colorant of Example 1 regardless of the presence or absence of the heat treatment at 200 ° C. FIG. 5 shows an X-ray diffraction pattern of the particulate erasable colorant (colored state) of Example 1. In addition, when the starch is analyzed by powder X-ray alone, a weak diffraction line is observed as shown in FIG. That is, in the particulate erasable colorant of the present example, it is presumed that a very small part of the starch is crystallized and the majority is present as amorphous fine particles. The fact that the starch fine particles are colorless and transparent when observed with an optical microscope also supports the fact that they are in an amorphous state.

From the above observations, the mechanism of decoloring when starch is used as the decoloring agent is that the developer, which has been hydrogen-bonded to the color former, moves through the matrix material by heating and is thus decolorized. It is presumed that the particles reach the surface of the starch fine particles, which are adsorbed there, and interact with each other. As a result, the coloring state of the coloring compound is destabilized and the color is erased. The particulate erasable colorant of Example 1 produced and analyzed as described above (number-average particle diameter 8 μm and volume-average particle diameter 12 μm; inner starch particles have a number-average particle diameter 4 μm and a volume-average particle diameter 6 μm 1) 100 parts by weight of 1 part by weight of hydrophobic silica was added to prepare a toner as an application example.

The obtained toner was placed in a toner cartridge of an electrophotographic copying machine, and a test image (test chart) was copied on neutral paper for a copying machine (reflectance 0.08). The obtained copy image has a sufficient image density, the resolution is standard as a toner image having the above-mentioned particle size, exhibits high durability under ordinary use conditions, and has a temperature of 100 ° C.
The image was maintained after heating for 30 minutes. Since the heat fixing process of the particulate colorable / colorable toner is performed at a speed on the order of seconds including the completion of the cooling, the substance of the decolorant or the developer in the particulate colorable / colorable colorant is used. The migration and the intermolecular interaction between the color erasing agent and the color developer are kinetically suppressed, and as a result, an image having a sufficient density can be formed. This copy image is heated to 190 ° C or higher, or
The color can be erased by contact with a liquid or gaseous color erasing aid.

100 sheets of paper on which a copy image was formed with the toner comprising the particulate erasable colorant of Example 1,
In a bundled state, it was put into a ventilation thermostat (Model DN83, manufactured by Yamato Scientific Co., Ltd.) whose temperature was adjusted to 190 ° C., left at the same temperature for 12 hours, and then taken out. As a result, all the copy images formed on 100 sheets of paper were erased, and could not be confirmed with the naked eye. The reflection density of each of the erasable image recording papers after erasing was measured and found to be 0.10. That is, it was confirmed that excellent decoloring characteristics were exhibited. The paper on which the copy image had been erased by heating was erased and left at 60 ° C. for 300 hours, but the image did not reappear.

The paper on which a copy image was formed with the toner comprising the particulate erasable colorant of Example 1 was immersed in, for example, methyl isobutyl ketone (MIBK). As a result, the image copied on the paper was erased and could not be confirmed with the naked eye. The measured reflection density of the paper after erasing was 0.08. That is, it was confirmed that excellent decoloring characteristics were exhibited. When the numerical values of the reflection density of the paper after erasing were compared between the erasing by heating and the erasing by solvent treatment, the values in the case of solvent treatment were slightly better. This is because, in the case of decoloring by solvent treatment, the erasable colorant is erased and simultaneously penetrates the paper and disappears from the surface of the paper. This is because the agent melt remains on the paper surface and slightly affects the reflection density measurement, so that there is no problem in reusing the decolored paper.

To confirm the decoloring process by the solvent treatment,
When the toner was brought into contact with MIBK, it swelled and dissolved instantaneously. Apply this liquid thinly on a glass plate and at room temperature,
Evaporate the solvent and add a vacuum of 0.001 Pa
The solvent was completely removed by heating at 00 ° C. for 24 hours.
The decolored state was maintained even when the solvent was removed. When this sample was observed with an optical microscope, fine particles belonging to the decoloring agent starch were observed.

From the above observations, even when the color was erased by using a solvent, the developer which had been hydrogen-bonded to the color-forming compound was activated by the solvent and moved in the dissolved or swelled mixture to form a decolorant. It is presumed that the particles reach the surface of the starch fine particles, which are adsorbed there, and interact with each other. As a result, the coloring state of the color former is destabilized and the color is erased. The paper whose copy image has been erased by the solvent treatment is heated at 60 ° C for 3 hours.
After leaving for 00 hours, the image did not reappear. Thereafter, a process of transferring another image to a paper whose image was erased by the solvent treatment and erasing the image by the solvent treatment was repeated 9 times. The tenth image transferred thereafter was of the same quality as the first image. Further, copying and decoloring were repeated up to 50 times. As a result, the paper was mechanically damaged, but the quality of the copied image and the quality of the erased state were good.

Comparative Example 1 Instead of the finely powdered starch (number-average particle diameter 4 μm and volume-average particle diameter 6 μm) in Example 1, unground starch (outer diameter of particles: about 10 to 20 μm; commercially available corn starch itself) The kneaded product was roughly pulverized to a particle outer diameter of 1 mm in the same manner as in Example 1 except that
Was obtained. This is pulverized to a maximum particle diameter of 20 μm or less by a circulating air jet pulverizer equipped with a cyclone type classifier, and further classified using another cyclone type classifier to obtain a number average particle diameter of 8 μm and a volume average particle size of 8 μm. Diameter 12μ
m (Comparative Example 1B) was obtained with a yield of 80%. The particle diameter was determined by measuring with a Coulter counter in the same manner as in Example 1. FIGS. 3 and 4 show the results of microscopic observation of the kneaded product of Comparative Example 1A (before pulverization) and the molten thin film of the particulate erasable colorant of Comparative Example 1B, which were prepared in the same manner as in Example 1. Shown in Incidentally, one scale of the scale inserted in FIGS. 3 and 4 is 10 μm.

For comparison, 17 parts by weight of unground starch (particle outer diameter: about 10 to 20 μm) used as a raw material and finely powdered polystyrene (matrix material) 79
About 10 mg of a mixture obtained by mixing well with the other parts by weight is placed on a slide glass heated to 100 ° C. on a hot plate, another slide glass heated to 100 ° C. is stacked and pressed, and then cooled, and cooled between glass plates. A thin film sample having a thickness of about 20 μm sandwiched between the samples was prepared. As a result of observing this with an optical microscope (not shown), colorless and transparent particles (particles that appear white in FIG. 3) observed in a thin film obtained by melting the kneaded material (before pulverization) of Comparative Example 1A; (A diameter of about 20 μm and a minimum of about 2 μm) was confirmed to be fine particles of starch as a decolorizing agent.
Further, it was found that there was no difference in the observed size of the starch particles only by the kneading operation.

The colorless and transparent particles (FIG. 4) which are observed in the thin film obtained by pulverizing and classifying the kneaded product containing such coarse starch particles and melting the particulate erasable colorant of Comparative Example 1B. The largest particle has a diameter of about 20 μm, but the number is smaller than that of FIG. 3, and the diameter is mainly 10 to 15 μm, and the smallest particle is about 2 μm. No doubt,
Interestingly, the particle diameter was found to correspond to the classification range of the particulate erasable colorant of Comparative Example 1B. That is, a part of the particulate erasable colorant of Comparative Example 1B is:
It is presumed to consist essentially of only the decolorizing agent starch. The existence of such particles consisting essentially of the decolorizing agent deviates from the gist of the particulate erasable colorant of the present invention. Further, the presence of particles composed of only the decolorizing agent and having a particle size corresponding to the classification range as the particulate decolorizable colorant of Comparative Example 1B means that the particles of Comparative Example 1B Among the erasable colorants, those having a smaller ratio of the decolorant component than the composition ratio set at the time of preparation (the particles alone have poor erasing characteristics),
It means that many are included.

Comparative Example 1B manufactured and analyzed as described above
1 part by weight of hydrophobic silica is added to 100 parts by weight of a particulate erasable colorant (number average particle diameter 8 μm and volume average particle diameter 12 μm; including particles substantially consisting of starch). A toner was prepared. The obtained toner is placed in a toner cartridge of an electrophotographic copying machine, and a test image (test chart) is printed on neutral paper for a copying machine (with a reflectance of 0.0).
8). Although the density of the obtained copy image was the same as that of Example 1, the resolution was inferior to that of the toner image having the above-mentioned particle diameter, and blurring was observed in places of fine lines. In addition, when heat decoloring was performed, it was clear that Example 1 was obtained.
The result was inferior to the case of. That is, 100 sheets of paper on which a copy image was formed with the toner composed of the particulate erasable colorant of Comparative Example 1B were used as in Example 1 for 1 sheet.
After heating at 90 ° C. for 12 hours, it was taken out. as a result,
All the copied images formed on 100 sheets of paper were erased, but afterimages were confirmed with the naked eye. When the reflection density of each of the erasable image recording paper after erasing was measured, it was about 0.25. That is, it was found that the decoloring characteristics due to heating were remarkably poor as compared with the copy image formed by the toner composed of the particulate decolorable colorant of Example 1. The reason for this is that, as described above, the particulate erasable colorant of Comparative Example 1B was produced using coarse starch particles, and thus contained particles consisting essentially of starch, and was more decolorized than the designed value. This is presumed to be due to the inclusion of a particulate erasable colorant having a low colorant content.

Example 2 1 part by weight of crystal violet lactone (manufactured by Tokyo Chemical Industry Co., Ltd.) as a color-forming compound, 1 part by weight of propyl gallate as a color developer, and a fine colorant as in Example 1 18 parts by weight of powdered starch (number average particle diameter 4 μm and volume average particle diameter 6 μm), 79 parts by weight of polystyrene as a matrix material, and 1 part by weight of LR-147 (manufactured by Nippon Carlit Co., Ltd.) as a charge control agent Other than the above, the number average particle diameter was 8 in the same manner as in Example 1.
Example 2 as particles having a volume average particle diameter of 12 μm
Was produced. The yield was equivalent to that of Example 1. The particle diameter was determined in the same manner as in Example 1 by measuring with a Coulter counter.

A thin film sample was prepared in the same manner as in Example 1 by using the particulate erasable colorant of this example.
When it was melted at 0 ° C., it remained blue-violet, while when it was heated to 200 ° C., it disappeared and became milky. As a result of observing these with an optical microscope (not shown; equivalent to FIG. 1), 200
Regardless of the presence or absence of the heat treatment at ℃, it was confirmed that the starch was present as fine particles (clear X-ray diffraction lines were not shown). Particulate erasable colorant of Example 2C (having a number average particle diameter of 8 μm and a volume average particle diameter of 12 μm) 100
As an application example, a toner was prepared by adding 1 part by weight of hydrophobic silica to part by weight.

The obtained toner was put into a toner cartridge of an electrophotographic copying machine, and a test image (test chart) was transferred to neutral paper for copying machine (reflectance 0.08).
The resulting blue-violet image had a sufficient image density, exhibited high durability under normal use conditions, and maintained the image even after heating at 100 ° C. for 30 minutes. This image can be decolorized by heating to 190 ° C. or higher, or by contact with a liquid or gas decolorizing aid. When the paper on which the image was copied was immersed in, for example, methyl isobutyl ketone (MIBK), the image copied on the paper was erased and could not be visually confirmed. The measured reflection density of the paper after erasing was 0.08. That is, it was confirmed that excellent decoloring characteristics were exhibited.

Example 3 A starch used as a decolorizing agent was obtained by pulverizing and classifying commercially available corn starch (particle outer diameter of about 10 to 20 μm) with a circulating air jet pulverizer equipped with a cyclone classifier.
Number average particle diameter 0.6 μm and volume average particle diameter 1.2 μm
Was used. The particle size was determined by measuring a sample obtained by ultrasonically dispersing in purified water using sodium dodecylbenzenesulfonate as a dispersant with a laser light scattering type particle size distribution analyzer (manufactured by Coulter Inc.).

The heat-sensitive dye PSD-18 is used as a color-forming compound.
4 (manufactured by Nippon Soda Co., Ltd.) 2 parts by weight, propyl gallate 1 part by weight as a color developer, starch (a number average particle diameter 0.6 μm and a volume average particle diameter 1.2 μm) 17 as a decolorizer
Parts by weight, 79 parts by weight of polystyrene as a matrix material, and 1 part by weight of LR-147 (manufactured by Nippon Carlit Co., Ltd.) as a charge controlling agent are mixed in advance and sufficiently kneaded at a temperature not exceeding 100 ° C. using a kneader. After cooling, the kneaded material of Example 3 was obtained. This kneaded material is roughly pulverized to a particle outer diameter of 1 mm by a cutter blade rotary pulverizer, and then pulverized to a maximum particle diameter of 4 μm or less by a circulating air jet pulverizer equipped with a cyclone classifier.
This was classified using another cyclone classifier to obtain fine particles having a number average particle diameter of 1.0 μm and a volume average particle diameter of 2.0 μm (larger than the raw starch fine particles).
A particulate erasable colorant of Example 3 of the present invention was obtained. The particle size of the particulate erasable colorant was measured using a laser light scattering type particle size distribution analyzer (manufactured by Coulter, Inc.) by ultrasonically dispersing a sample in purified water using sodium dodecylbenzenesulfonate as a dispersant. Measured.

Using 20 parts of the particulate erasable colorant of Example 3 as a binder, methyl methacrylate-butyl acrylate-
To a binder solution containing 20 parts by weight of an acrylic acid (ammonium salt) copolymer, 2 parts by weight of a nonionic dispersant, 10 parts by weight of propylene glycol, and 48 parts by weight of water, using a three-roll mill To disperse, thereby producing an erasable aqueous colorant as an application example. This erasable aqueous colorant was applied to the entire surface of one side of neutral paper for a copying machine (reflectance 0.08) using a bar coater, and dried. This paper was dipped in, for example, methyl isobutyl ketone (MIBK). As a result, the decolorizable aqueous colorant was decolorized and the color could not be confirmed with the naked eye. The measured reflection density of the paper after erasing was 0.08. That is, it was confirmed that excellent decoloring characteristics were exhibited. It consists of an aluminum cylinder fitted with a pen body holder that fixes a pen body made by binding fiber bundles with resin via a valve mechanism, and presses the pen tip against the paper surface during marking to open the valve. A pen body of a marking pen of a type in which the ink inside was drawn out to a pen tip was prepared, and the above-mentioned erasable water-based colorant was filled into the pen body, and a writing implement was prepared as an application example. Using this writing instrument, writing was performed on neutral paper for a copying machine (reflectance 0.08). The drawn lines had a sufficient concentration, exhibited high durability under ordinary use conditions, and were maintained even after heating at 100 ° C. for 30 minutes. This drawing line could be erased by heating it to 190 ° C. or higher, or by contacting it with a decolorizing aid.

For example, paper written with this writing instrument was immersed in, for example, methyl isobutyl ketone (MIBK). As a result, the drawn line drawn with the erasable aqueous colorant using the particulate erasable colorant of Example 3 was erased and could not be confirmed with the naked eye. The paper with the erasable aqueous colorant using the particulate erasable colorant of Example 3 decolorized by the solvent treatment was left at 60 ° C. for 300 hours, but the line did not appear again. Was. After that, on the paper where the strokes were erased,
The process of writing a line with the above-mentioned writing instrument and erasing by solvent treatment was repeated 9 times. The tenth stroke drawn thereafter was of the same quality as the first stroke, and was not broken on the erased stroke. Further, writing and decoloring were repeated up to 50 times. As a result, the quality of the drawn drawing line and the quality of the decolored state were good.

In order to test the storage stability of the aqueous erasable colorant using the particulate erasable colorant of Example 3 of the present invention, (a) in a glass bottle and (b) Example 1 , A long-term storage test at 50 ° C. was performed in a closed state. As a result, even after storage at 50 ° C. for 6 months, no change was observed in the color development state and dispersion state, and no deterioration was observed in the decoloring characteristics after coating or drawing on paper. .

Comparative Application Example 1 In order to prepare a pigment composition particle having no composition containing a decoloring agent for comparison, a leuco dye PSD-18 was used as a coloring compound.
4 (manufactured by Nippon Soda Co., Ltd.), 2 parts by weight of propyl gallate as a color developer, and 79 parts by weight of polystyrene as a matrix material are mixed in advance, and a temperature of not more than 100 ° C. is sufficiently determined using a kneader. After kneading, the mixture was cooled to produce a dye composition that developed a black color. This kneaded material is roughly pulverized to a particle outer diameter of 1 mm by a cutter blade rotary pulverizer, and then pulverized to a maximum particle diameter of 4 μm or less by a circulating air jet pulverizer equipped with a cyclone classifier. Was classified using another cyclone classifier, and the number average particle diameter was 1.0 μm and the volume average particle diameter was 2.0.
μm dye composition particles were obtained.

A mixture of 83% by weight of this pigment composition and 17% by weight of finely ground starch (number average particle diameter 0.6 μm and volume average particle diameter 1.2 μm) as a decolorizing agent (leuco dye) The components of the developer, the developer and the decolorant are the same as those of the erasable aqueous colorant of Example 3.
20 parts by weight of a methyl methacrylate-butyl acrylate-acrylic acid (ammonium salt) copolymer as a binder, 2 parts by weight of a nonionic dispersant, 10 parts by weight of propylene glycol, and 48 parts by weight of water Comparative Example 1 was dispersed in a binder solution containing parts by weight using three rolls.
Was prepared. Further, this is described in Example 3.
Comparative application example 1 by filling the same pen body as in the case of application example 1
Writing implements.

When the erasable water-based colorant of Comparative Application Example 1 was applied to paper and the drawing written on paper using the writing implement of Comparative Application Example 1 was tested immediately after preparation, Decoloring characteristics equivalent to those of the third application example were exhibited. However, in order to test the storage stability of the erasable aqueous colorant of Comparative Application Example 1, 50 ° C. was sealed in a glass bottle (a) and in the writing implement of Comparative Application Example 1 (b). Long-term storage test. As a result, the starch microparticles aggregate only after storage at 50 ° C. for one week, and it becomes difficult to apply the erasable aqueous colorant of Comparative Application Example 1,
On the other hand, the writing implement of Comparative Application Example 1 was no longer writable. It is presumed that the cause of such an inconvenience is that the fine particles of starch as the decoloring agent are not protected by the matrix material.

[0090]

As described above in detail, the use of the particulate erasable colorant of the present invention forms a stable image on paper and erases the formed image with excellent erasing characteristics. Can be colored. Further, the decolored state can be stably maintained, and the paper after the decoloration can be effectively reused.

[Brief description of the drawings]

FIG. 1 is a diagram obtained by processing a particulate erasable colorant of Example 1 into a thin film and observing it with an optical microscope. One scale of the scale inserted in the figure is 10 μm.

FIG. 2 is a diagram obtained by processing a mixture of finely powdered starch (number average particle diameter of 4 μm and volume average particle diameter of 6 μm) and polystyrene into a thin film and observing it with an optical microscope. One scale of the scale inserted in the figure is 10 μm.

FIG. 3 is a diagram obtained by processing a kneaded product (before pulverization) of Comparative Example 1A into a thin film and observing it with an optical microscope. One scale of the scale inserted in the figure is 10 μm.

FIG. 4 is a diagram obtained by processing the particulate erasable colorant of Comparative Example 1B into a thin film and observing it with an optical microscope. One scale of the scale inserted in the figure is 10 μm.

FIG. 5 is a diagram showing an X-ray diffraction pattern of the particulate erasable colorant (colored state) of Example 1.

FIG. 6 shows the X of the micronized starch used in Example 1.
It is a figure showing a line diffraction pattern.

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[Procedure amendment]

[Submission date] September 1, 2000 (2009.1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Particulate erasable colorant and method for producing the same

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particulate color-erasable colorant capable of changing a color-forming compound in a color-developing state to a colorless color-erasable state, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, with the spread of computers, printers, copiers, facsimiles, and the like, the output of information on paper has increased. Although there is a call for "paperlessness by digitizing information" in order to reduce output on paper, hard copy to paper is required because of its features such as good visibility, high portability, and ease of information search by turning pages. Demands are endless. As a result, protection of natural resources as a raw material for paper, reduction of waste disposal amount, and reduction of carbon dioxide emission have become issues to be solved. “Recycling and reuse of paper” is a very contemporary issue in each aspect of protecting natural resources, reducing the amount of waste disposal, and reducing carbon dioxide emissions.

Under these circumstances, the technology of making image forming materials (various printing inks, toners, jet inks, etc.) for printing and printing on paper colorless after printing and printing promotes the recycling and reuse of paper. It is extremely important in doing so. That is, in the conventional paper recycling method, a method in which the recovered paper is deflocculated with water and then the ink portion is floated and separated in a so-called "deinking step" or a method of decolorizing using a bleaching agent is used. However, these are factors that make the process cost higher than in the case of newly producing paper.

Accordingly, paper printed with an image forming material using an erasable colorant capable of changing a color developing compound into a colorless and erasable state requires a time-consuming decompression as in the prior art. It is expected that it can be reused or recycled without going through the black ink process.

In recent years, various studies have been made on erasable colorants, and erasable colorants which can be erased by applying heat are disclosed in, for example, JP-A-7-81236 and JP-A-Hei.
No. 0-88046. The former publication discloses a coloring compound such as a leuco dye, a developer,
An erasable colorant containing an organic phosphoric acid compound having a decolorizing action, and the latter publication discloses that a combination of a color former such as a leuco dye and a developer is heat-sensitive. A discolorable colorant using a sterol compound such as cholic acid, lithocholic acid, testosterone, cortisone, etc. as a decoloring agent exhibiting a decolorizing effect by adding a colorant is disclosed.

An erasable colorant that can be erased by contact with an organic solvent is disclosed in, for example, JP-A-11-2122.
No. 95 discloses this. This erasable colorant is
It is composed of a coloring compound such as a leuco dye, a developer, and a decoloring agent. As the decoloring agent, a highly amorphous phase separation inhibitor (for example, a cyclic sugar alcohol) and an amorphous It is characterized in that a phase separation inhibitor having low reactivity (for example, a non-aromatic cyclic compound having a hydroxyl group other than a cyclic sugar alcohol and a 5- or more-membered ring or a derivative of a cyclic sugar alcohol) is used in combination. Further, JP-A-11-212296 discloses a biodegradable sterol compound and a cyclic sugar alcohol extracted from animals, plants or fungi as a decoloring agent exhibiting a decoloring effect upon contact with an organic solvent. Derivatives thereof are disclosed.

[0007]

While such conventional erasable colorants have their respective features, it is not easy to achieve both good coloring and good erasing properties, or as a printed matter. However, there are drawbacks such as poor durability under actual use conditions and high cost, and further improvement in performance is desired for full-scale practical use.

Accordingly, it is an object of the present invention to provide a decolorizable, good and stable color-forming state under actual use conditions as a printed material, and to use an organic solvent after printing or printing as an image forming material. An object of the present invention is to provide a particulate erasable colorant which can be easily erased by an erasing treatment such as contact with the toner and can maintain the erased state stably.

The present inventor has conducted various investigations on the causes of insufficient coloring and decoloring of the erasable colorant in the prior art. Further, the inventors have found that the intermolecular interaction with the color developer is an important controlling factor, and have completed the present invention based on this finding.

[0010]

The above object is achieved by the present invention described below. That is, the present invention provides at least a matrix material, a color developer, a color-forming compound which develops a color by an intermolecular interaction with the color developer, and an intermolecular interaction between the color developer and the color former. Stronger, a particulate erasable colorant comprising a decolorant that interacts with the developer and intermolecularly, in the particulate erasable colorant,
The decoloring agent always exists as a fine particle or a microphase separated state whose average diameter when its shape is approximated by a sphere does not exceed the diameter of the particulate decolorable colorant, and in a color developing state. The developer is present in the matrix material in an intermolecular interaction with the color former, and in the decolored state, the developer does not interact with the color former in the molecule. A particulate decolorizable colorant which is adsorbed on the surface of the decolorant existing in a state of fine particles or microphase separation and is present in a molecular interaction with the decolorant, and a method for producing the same. It is.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention. As the size of the particulate erasable colorant of the present invention, an optimal size is selected depending on the use as the colorant. For example, when a poster color is used for writing characters of several cm to several tens of cm or is coated on the entire surface of the poster, the average diameter of the shape approximated by a sphere is several tens μm to 100 μm. Even a relatively large size of several tens of μm can be used. When the particulate erasable colorant of the present invention is used as a toner for copying machines and printers, the average diameter of the particles when approximated by a sphere is about 10 μm to 7 μm.
A size of about m is preferred. When the particulate erasable colorant of the present invention is dispersed and used as an ink for an ink jet printer or an aqueous ink for a writing implement, the average diameter of the particles when approximated by a sphere should be 2 to 1 μm or less. Is preferred.

[0012] Particulate friendly decolorable colorant of the present invention, at least the matrix material, color former and the developer, the point consisting及beauty erasing <br/> colorant, like conventional particles in the composition surface Same as the erasable colorant, but the average diameter when the shape of the erasable colorant in the particulate erasable colorant is approximated by a sphere is predetermined regardless of the state of color development or decoloration. The particle size is not larger than the diameter of the particulate erasable colorant, and is dispersed in the form of fine particles or microphase separated.

Hereinafter, a matrix material, a coloring compound,
The developer and the decoloring agent will be sequentially described in detail. [Matrix Material] As a matrix material used for the particulate erasable colorant of the present invention, an organic high molecular compound or a low molecular compound can be used. Hereinafter, a matrix material composed of an organic polymer compound will be referred to as a polymer matrix material, and a matrix material composed of a low molecular compound will be referred to as a low molecular matrix material, as necessary.

The polymer matrix material used in the particulate colorable / colorable colorant of the present invention is a binder which is usually additionally used when the particulate colorable / colorable colorant is used as an image forming material. The resin may be the same or different. For example, jet ink (ink for ink jet printer)
In the case of an image forming material in which a particulate erasable colorant is directly dispersed in a solvent (water or an organic solvent ) as described above, a binder is additionally used when used as an image forming material The resin or dispersant is soluble in the solvent, while the matrix material used for the particulate erasable colorant must be insoluble and swellable in the solvent.

For example, when a particulate erasable colorant is used by dispersing it in a varnish such as an offset ink, the matrix material used for the particulate erasable colorant is a solvent for the varnish. Linseed oil, soybean oil, high boiling petroleum solvents, etc.

Further, for example, when the particulate erasable colorant of the present invention is used in a crayon, a craper, a thermal transfer ink, or a toner for a copying machine, the matrix material used for the particulate erasable colorant is Alternatively, it may be the same as the binder resin additionally used when the present particulate erasable colorant is used as an image forming material.

The polymer matrix material may be selected from known thermoplastic resins and thermosetting resins in accordance with the form of use of the particulate erasable colorant of the present invention, such as jet ink or printing ink. In the temperature range in which the decolorable colorant is used as a dye in a color-developing state, the color former and the developer can be solid-solved (dissolve and molecularly dispersed), and A resin that can be dispersed as fine particles or microphase separated in the above size and that can maintain the form as particles can be appropriately selected and used, and is not particularly limited.

Specifically, for example, when a leuco dye is used as the color-forming compound, a phenol compound is used as the color developer, and starch is used as the decolorant, the following organic polymer compound is preferably used as the matrix material. be able to. That is, for example, ketone resin, norbornene resin, polystyrene, poly (α-methylstyrene), polyindene, poly (4-methyl-1-pentene), polyvinylpyridine, polyacetal, polyvinylformal, polyvinylacetal, polyvinylbutyral, and polyvinyl acetate , Poly (vinyl propionate), polyvinyl alcohol, polyethylene, polypropylene, polybutadiene,
Polymethylpentene, polyvinyl chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, chlorinated polypropylene,
Polyvinylidene chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl benzyl ether, polyvinyl methyl ketone, poly (N-vinylcarbazole), poly (N-
Vinylpyrrolidone), polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polyacrylonitrile, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polybenzyl methacrylate, polyhexyl methacrylate, polymethacrylic acid, Polymethacrylamide, polymethacrylonitrile, polyacetaldehyde, polychloral, polyethylene oxide, polypropylene oxide, polyethylene terephthalate, polybutylene terephthalate, polycarbonates (bisphenols + carbonic acid), polysulfone, polyether sulfone, polyphenylene sulfide, poly ( Diethylene glycol / bisallyl carbonate), 6-nylon, 6,6-nylon, 12-nylon, 6,12-ny Down, ethyl polyaspartic acid, ethyl polyglutamic acid, polylysine, polyproline, poly (.gamma.-benzyl -L- glutamate), methyl cellulose, ethyl cellulose, benzyl cellulose,
Hydroxyethyl cellulose, hydroxypropyl cellulose, acetyl cellulose, cellulose triacetate, cellulose tributyrate, alkyd resin (phthalic anhydride + glycerin), fatty acid modified alkyd resin (fatty acid + phthalic anhydride + glycerin), unsaturated polyester resin (maleic anhydride) + Phthalic anhydride + propylene glycol), epoxy resin (bisphenols + epichlorohydrin), epoxy resin (cresol novolak +
Epichlorohydrin), polyurethane resin, phenolic resin, urea resin, melamine resin, xylene resin, toluene resin, furan resin, guanamine resin, resin such as diallyl phthalate resin, organic polysilane such as poly (phenylmethylsilane), organic polygermane and the like. Can be suitably used.

Further, for example, the particulate decolorizable colorant of the present invention obtained by using a leuco dye as a color-forming compound, a phenol compound as a color developer, and starch as a decolorant is used for a copier or printer. When used in the toner of (1), as the matrix material of the particulate erasable colorant and the binder resin of the image forming material, for example, polystyrene, a blend polymer of polystyrene and an acrylic resin, a styrene-acrylic copolymer , Polyester, epoxy resin and the like can be particularly preferably used. Here, 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. The proportion of styrene in the copolymer is preferably at least 50% by weight. 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. Here, when a blend polymer of polystyrene and an acrylic resin is used as the matrix, one or more of the acrylic resins exemplified in the above copolymerization can be used. In addition, a copolymer containing butadiene, maleic acid ester, chloroprene or the like at a ratio of 10% by weight or less may be used. The proportion of polystyrene in the matrix is preferably at least 50% by weight.

Further, a polyester synthesized from a carboxylic acid and a polyhydric alcohol can also be used. As the carboxylic acid, for example, terephthalic acid, fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,
Suberic acid, azelaic acid, sebacic acid, brassic acid,
Examples include pyromellitic acid, citraconic acid, glutaconic acid, mesaconic acid, itaconic acid, terraconic acid, phthalic acid, isophthalic acid, hemimellitic acid, melophanic acid, trimesic acid, planitic acid, trimellitic acid, and the like. One or more of these can be used. Examples of the polyhydric alcohol include bisphenol A, hydrogenated bisphenol A, ethylene glycol, propylene glycol, butanediol, neopentyldiol, hexamethylenediol, heptanediol, octanediol, pentaglycerol, pentaerythritol, cyclohexanediol, and cyclopentane Examples thereof include diol, pinacol, glycerin, etherified diphenol, catechol, resorcinol, pyrogallol, benzenetriol, phloroglucinol, benzenetetraol and the like. One or more of these can be used. Further, a blend polymer of two or more polyesters may be used.

An epoxy resin synthesized from a compound having epichlorohydrin and a polyvalent phenolic hydroxyl group can also be used. 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. Further, a phenol resin, a urea resin, a melanin resin, an alkyd resin, an acrylic resin, a polyester, a polyamide, a polyurethane, or the like may be blended with the epoxy resin at a ratio of 15% by weight or less.

As the low-molecular matrix material, low-molecular compounds such as low-molecular plasticizers, low-molecular lubricants, and low-molecular waxes can be used. That is, in the temperature range where the particulate erasable colorant is used as a dye in a color-developing state, the color former and the developer can be solid-solved (dissolved and molecularly dispersed), and the color can be erased. The agent can be dispersed as fine particles or microphase separated, and a low molecular compound capable of maintaining the form as particles can be appropriately selected and used as a low molecular matrix material.

Specifically, for example, when a crayon is prepared using a leuco dye as a color former, a phenol compound as a developer, and starch as a decolorizer, a low molecular weight compound (wax) such as 1 -Docosanol can be suitably used.

[Color-forming compound] Examples of the color-forming compound used in the present invention include leuco auramines, diaryl phthalides, polyaryl carbinols, acyl auramines, aryl auramines, and rhodamines. B
Organic compounds such as lactams, indolines, spiropyrans, and fluorans can be given.

Specific examples of the color-forming compound include, for example, 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-methyl Indole-3-yl) -4-azaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3-diethylamino-7
-Chloroanilinofluoran, 3-diethylamino-
7,8-benzofluoran, 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide,
3,6-dimethylethoxyfluoran, 3-diethylamino-6-methoxy-7-aminofluoran, 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- (phenyliminoethanedilidene)
-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-methylfluorane and the like can be suitably used. These can be used alone or in combination of two or more. Needless to say, if a color-forming compound is appropriately selected, a color-developed state of various colors can be obtained, and multicoloring can be realized. These color-forming compounds are, for example, tautomeric compounds that can take both a colorless form and a color-forming form, as shown by a chemical formula below.

[0027]

Embedded image

[Developer] It is known that in the chemical formulas showing the tautomerism as described above, the chemical structure of the inner salt type shown at the lower side corresponds to the "colored type". A compound capable of stabilizing the chromogenic type by stabilizing such an ionic inner molecular salt type structure by transfer of protons or formation of hydrogen bonds or formation of a metal complex salt is a so-called color developing compound. Agent.

Examples of the color developer used in the present invention include phenol and phenol derivatives, metal salts of phenol derivatives, metal salts of carboxylic acid derivatives, salicylic acid and salicylic acid metal salts, benzophenone and benzophenone derivatives, sulfonic acids, and sulfonic acids. Salts, phosphoric acids,
Examples thereof include metal phosphates, acid phosphates, acid phosphate metal salts, phosphorous acid, metal phosphites, and zinc halides. These can be used alone or in combination of two or more. Specific examples of phenol derivatives that can be used as a color developer are shown below by chemical formulas.

[0030]

Embedded image

These phenol derivatives, for example, interact with the carboxylic acid residues of the color-forming color-forming compound between the molecules to form hydrogen bonds, as shown by the following chemical formula, thereby stabilizing the color-forming state. Can be Such an intermolecular interaction between the color-forming compound and the developer can occur even when both are solid-solved (dissolved and molecularly dispersed) in the matrix material.

[0032]

Embedded image

As exemplified by the above chemical formula, in a system in which a color-forming compound and a color developer interact with each other in a matrix material and the color-forming compound becomes a color-forming type, as described later, Decoloring agent ”is (1) amorphous (amorphous)
In the case where the particles are present in the form of microphase-separated fine particles in the matrix material, and (2) when they are crystalline and are dispersed as fine crystals in the matrix material, the activity due to heating or decolorizing aid treatment If the coloration is not performed, the intermolecular interaction between the color developer and the decolorant (which is stronger in chemical equilibrium than the interaction between the color former and the color developer) is controlled by kinetic control. It is virtually impossible to "freeze" and the color developing compound is stabilized by the color developer.

[Decoloring Agent] The decoloring agent in the particulate erasable coloring agent of the present invention is stronger than the intermolecular interaction between the coloring compound and the developing agent, and may be between the coloring agent and the developing agent. Fine particles (decolorized) in a matrix material in the color-developed state of the particulate decolorizable colorant in a matrix material, and in a molten, swollen or dissolved mixture in the decolored state It is a compound that can be dispersed and present as a micro phase separated state (when the agent is in a crystalline state) or a micro phase separated state (when the decoloring agent is in an amorphous state).

As the intermolecular interaction that can act between the decoloring agent and the color developing agent, a hydrogen bond, an ionic bond, a hydrophobic bond, a stereochemical inclusion phenomenon, or the like can be used. That is, from among compounds having one or more alcoholic hydroxyl groups, free carboxylic acid groups, carboxylate residues, cyclic saturated hydrocarbon residues, etc. in the molecule, the solubility in the matrix material used and Based on the temperature dependence, a material usable as a decoloring agent can be selected.

As specific examples of the decoloring agent used in the present invention, for example, starch such as corn starch and tapioca starch, hydrophobized starch, dextrin, cyclodextrin and the like can be suitably used.

The particulate erasable colorant of the present invention comprises at least a matrix material, a coloring compound, a color developer,
It is composed of a decolorizing agent having a controlled particle size. The preferred compounding ratio is as follows. The matrix material is
0.1 to 1000 for 1 part by weight of the coloring compound
Parts by weight, preferably 0.5 to 100 parts by weight, more preferably 1 to 20 parts by weight. The developer is usually 0.1 to 10 parts by weight based on 1 part by weight of the coloring compound,
Preferably, the ratio is 1 to 2 parts by weight. The developer is 0.
When the amount is less than 1 part by weight, the coloring of the particulate erasable colorant due to the interaction between the color former and the 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 decoloring agent is used in an amount of usually 1 to 200 parts by weight, preferably 10 to 100 parts by weight, based on 1 part by weight of the coloring compound. When the amount of the decoloring agent is less than 1 part by weight, it is difficult to cause a change in the state between the colored state and the decolored state of the particulate erasable colorant. When the amount of the decoloring agent exceeds 200 parts by weight, the coloring of the particulate decolorizable colorant becomes insufficient.

In the particulate decolorizable colorant of the present invention, the decolorant is always in a state of fine particles or microphase separation in the particulate decolorable colorant regardless of the state of color development or decoloration. Exists in a distributed manner. The size of the fine particles or the microphase-separated state of the decoloring agent is such that the average diameter when its shape is approximated by a sphere does not exceed the diameter of the particulate decolorizable colorant having a predetermined size. It is necessary to be.

If the size of the decolorizable agent in the particulate colorable / colorable colorant in the state of fine particles or microphase separation is assumed to be the average diameter when its shape is approximated by a sphere, the particle size of the colorable / colorable colorant If the diameter of the agent is exceeded, the particles are substantially composed of only the decoloring agent. That is, in producing the particulate decolorizable colorant, the matrix material, the color forming compound, the color developer, and the coarse particulate decolorant are used without considering the size of the particles of the decolorant. , Kneading, pulverization and classification alone result in "particles comprising a matrix material, a color former, and a developer and substantially free of a decolorant" and "substantially decolorized". A mixture of "particles consisting solely of colorant" is obtained. The erasable colorant composed of such a particle mixture has no problem in terms of the color density in the color-developed state, but compared to the particulate erasable colorant of the present invention, when used as an image forming material. The resolution is inferior, the decoloring property is inferior, and a problem occurs in long-term storage stability when used as an ink.

The particulate erasable colorant of the present invention includes:
As long as the function is not impaired, if necessary, a plasticizer composed of a low-molecular compound, a wax, a lubricant, a release agent,
An appropriate amount of additives such as a light stabilizer, an antioxidant, and a charge control agent can be contained.

[Production Method of Particulate Colorable Colorant] The method of producing the particulate colorable colorant of the present invention comprises at least a matrix material, a color developer, and an intermolecular interaction with the color developer. A color developing compound that develops a color, and a decoloring agent that is stronger than the intermolecular interaction between the color developing agent and the color developing compound and that is in the form of fine particles or a microphase separated state that interacts with the color developing agent. In producing a particulate erasable colorant of a predetermined size by using, the average diameter when the shape of the decolorizable agent is approximated by a sphere exceeds the diameter of the particulate erasable colorant. The above-mentioned decolorizing agent in the state of fine particles or microphase-separated state that has been previously pulverized or refined to a size that is not a matrix material,
After being dispersed in a mixture of the color developer and the color former, the particulate erasable colorant is formed.

A well-known pulverizing method for previously pulverizing or pulverizing the decolorizable agent to a size not exceeding the diameter of the particulate decolorable colorant when the shape of the decolorant is approximated by a sphere is known. Any method can be used. In addition, any known method other than the mechanical pulverization method can be applied as a method of miniaturization.

Examples of the dry pulverization method include a method using a pulverizer such as a circulation air jet pulverizer equipped with a cyclone classifier, a hammer rotary pulverizer, a cutter blade rotary pulverizer, and a semi-dry pulverization method. For example, using a method such as a milling method using a kneader, a vibration mill, a ball mill, or a planetary rotary mill using a salt and a small amount of a solvent as a grinding aid, a decolorizing agent in a state of fine particles or microphase separation is predetermined. Can be crushed to size. Needless to say, when a grinding aid is used, it must be washed with an appropriate solvent and dried before use.

As a finer method other than the mechanical pulverization method, for example, a material obtained by heating and melting a decolorizing agent is ultrasonically dispersed in a non-soluble solvent to form a colloid, then cooled, filtered, and filtered. A method of washing and drying, a method of injecting a good solvent solution of a decoloring agent into a non-soluble solvent (poor solvent) under ultrasonic irradiation to precipitate, filtering, washing and drying can be exemplified. When such a miniaturization method is used, it is effective to add a suitable auxiliary agent in order to prevent the decoloring agent once miniaturized from growing crystals or growing particles due to fusion. . For example, a part of the matrix material used in a later step can be added for such a purpose.

After dispersing a fine particle or a microphase-separated decoloring agent which has been pulverized or fined in advance to a predetermined size in a mixture of the matrix material, the color developer, and the color former, In forming the particulate erasable colorant, a known method used for producing fine particles of a matrix material such that a plurality of low-molecular compound components are present as a solid solution and dispersed therein is used. It can be applied as appropriate. However, it is needless to say that various conditions need to be set so that the decoloring effect frozen in the middle of the manufacturing process does not appear.

For example, a matrix material,
A color former, a color developer, and a decolorizer having an adjusted particle size are sufficiently kneaded at a temperature lower than the melting point or softening point of the decolorant to develop a color. Particle erasable colorants of a size can be produced. This method is suitable for efficiently producing the particulate erasable colorant of the present invention with good color development and color development stability.
The method and method of the kneading device and the device for fine pulverization are not particularly limited.

The presence of the decoloring agent in the particulate erasable colorant in the form of fine particles having the above-mentioned size or in a microphase-separated state can be confirmed by various analytical means as described below. it can. For example, by processing the decolorizable dye composition as it is into a thin film and observing the thin film with an optical microscope or a confocal laser microscope, etc., to confirm the size of the fine particles or the microphase separated state of the erasing agent. Can be. At this time, the fact that the observed “fine particle or microphase separated state” is attributed to the decoloring agent means that the coloring compound / matrix material, the developing agent / matrix material, the coloring compound and the color developing compound The composition of the combination of the agent / matrix material, the decolorant / matrix material, and the other additive / matrix material when other additives are used is processed into a thin film under the same conditions as above. Can be confirmed by comparative observation with an optical microscope or a confocal laser microscope.
Whether the decoloring agent exists as fine particles (crystal) or in a microphase separated state (amorphous)
It can be confirmed by the X-ray diffraction method.

When the size of the main component of the decoloring agent dispersed and present in the state of fine particles or micro phase separation is less than 0.1 μm as the average diameter of the fine particles or micro phase separation state approximated by a sphere. (1) small-angle X-ray scattering method, (2) transmission electron microscopy observation of a thin film sample (using osmium tetroxide staining, if necessary, in order to clarify the image), or (3) The size of fine particles or microphase separated state can be confirmed by scanning electron microscope observation of the thin film sample surface (also using a method such as dissolving only the decolorant from the sample surface using an appropriate solvent). it can. Also in this case, the attribution of the observed fine particles or microphase separation state can be confirmed by comparison with a sample containing no decoloring agent.

[Color erasing method] In order to make the particulate color-erasable colorant in a color-developing state into a color-erasable state, that is, to erase the color, the particulate color-erasable colorant is heated and melted to decolor. And a method in which a part or all of the particulate erasable colorant is dissolved or swelled by contacting it with a liquid or gaseous erasing aid.

By heating and melting the particulate erasable colorant, the molecular motion of the developer which has been kinetically frozen becomes active, and moves in the molten mixture of the composition. Adsorbed on the surface of the particulate colorable / colorable colorant present in the state of fine particles or microphase separation, stronger than the intermolecular interaction between the color developing compound and the color developer, and A strong intermolecular interaction occurs between the two, and as a result, the coloring state of the color former becomes unstable and becomes a decolored state. Since the decolored state as described above is stable in terms of equilibrium, it continues even if the heating is stopped.

The heating means for decolorizing the particulate erasable colorant may be in any form, for example, a thermal printer head (TPH), a thermal bar, a hot stamp, a heat roller, etc. . or,
It may be heated by an infrared lamp or hot air. When a large amount of decoloring processing is performed on the paper on which characters and images are formed by the image forming material using the particulate decolorable colorant of the present invention at a time, a box-shaped warm air dryer or a blown thermostat is used. Can be suitably used.

The heating temperature at the time of decolorizing the particulate colorable / colorable colorant by heating is the temperature at which the particulate colorable / colorable colorant becomes a mixed and molten state as the composition (the “melting point drop by mixing”). Depending on the phenomenon, the temperature is lower than the melting point or softening point of the particulate erasable colorant component alone). The upper limit of the heating temperature at the time of decolorizing the particulate erasable colorant by heating is the lowest temperature among the thermal decomposition starting temperatures of the particulate erasable colorant component. Note that, depending on the type or combination of the color-forming compound, the color developer, the decoloring agent, and the matrix material, the component thermally decomposes by heating, or causes an undesired side reaction to produce a non-decolorable colored compound. Or may form. In such a case, it is preferable to apply a method using a color erasing aid described below as the color erasing method.

When decoloring is performed by contacting a part of or all of the colored decolorizable colorant in a colored state with a liquid decoloring aid (organic solvent) for dissolving or swelling, The molecular motion of the frozen developer is activated by the color erasing aid, and moves through the dissolved or swollen composition to form a particulate erasable color that exists in a state of fine particles or micro phase separation. Adsorbs on the surface of the coloring agent and causes stronger intermolecular interaction between the color developing compound and the color erasing agent than the color developing compound and the color developing agent. The coloring state of the coloring compound is destabilized and becomes a decolored state. Since the decoloring state as described above is equilibrium-stable, it continues even if the liquid decoloring aid is removed. As is apparent from such a decoloring mechanism, the temperature is higher than room temperature, for example, 50 ° C. to 8 ° C.
Performing this method at 0 ° C. is very effective.

Even when decoloring is carried out by contacting a gaseous decolorizing auxiliary (organic gas) which swells the colored particulate decolorizable colorant, the developer which has been kinetically frozen is also used. Is activated by the decolorizing auxiliary, moves through the swollen or dissolved composition, and is adsorbed on the surface of the particulate decolorable colorant existing in a state of fine particles or microphase separation, The interaction between the color former and the color developer is stronger than that between the color developer and the color developer, and a stronger molecular interaction between the color developer and the color erasing agent occurs. As a result, the color development state of the color former is not good. Stabilize,
The color is erased. Since the decoloring state as described above is equilibrium-stable, it continues even after the gas decoloring aid is removed and the swelling state is removed. As is apparent from such a decoloring mechanism, the temperature is higher than room temperature, for example, 50 ° C. to 80 ° C.
It is extremely effective to carry out this method.

The gas used as the color erasing aid in the method of erasing by contacting the gas with the color erasing aid which swells the color developing particulate erasable colorant is a particulate erasable colorant. It must have the property of easily penetrating into the inside of the agent and swelling. Specifically, organic compounds that are gaseous at normal temperature and normal pressure, such as ethylene, acetylene, and dimethyl ether, and organic compounds that sublimate at normal temperature and normal pressure, such as naphthalene and p-dichlorobenzene, can be suitably used.

The organic solvent used as a color erasing aid in the method of erasing by contacting a liquid color erasing aid which swells or dissolves the colored particulate erasable colorant in a colored state includes:
(A) It is preferable to have the property of assisting the formation of hydrogen bonds between the color developer and the decolorant, and (B) the inside of the particulate decolorable colorant has a high affinity with the matrix material. It is preferable to have a property that easily penetrates to. 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.

The first type of solvent, ie, the solvent having both the properties (A) and (B), includes ether,
Examples include ketones and esters. Specifically, for example, ethyl ether, ethyl propyl ether, ethyl isopropyl ether, isopentyl methyl ether,
Saturated ethers such as butyl ethyl ether, dipropyl ether, diisopropyl ether, ethyl isopentyl ether, dibutyl ether, dipentyl ether, diisopentyl ether, and dihexyl ether; Saturated ethers; ethers of dihydric alcohols such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane; oxetane; Cyclic ethers such as tetrahydrofuran, tetrahydropyran, dioxolan, dioxane, trioxane;
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 Saturated ketones such as methyl ketone, heptyl methyl ketone and dibutyl ketone; unsaturated ketones such as ethylidene acetone, allyl acetone and mesityl oxide; cyclic ketones such as cyclopentanone, cyclohexanone, cycloheptanone and cyclooctanone; ethyl formate , Propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, isoacetate Tyl, 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, acetic acid 2
-Ethoxypropyl, 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, ethyl valerate,
Propyl valerate, isopropyl valerate, butyl valerate,
Esters such as methyl hexanoate, ethyl hexanoate, propyl hexanoate, and isopropyl hexanoate. Other solvents other than the above include dichloromethane, γ-butyrolactone, β-propiolactone, N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylisoindolinone,
And dimethyl sulfoxide. 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.

Examples of the second type of solvent, ie, a solvent having the above-mentioned property (A) but having a low affinity for the matrix, include, for example, water, methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and the like. 1-pentanol, 2-pentanol, 3
-Pentanol, isopentyl alcohol, 1-hexanol, 2-hexanol, 3-hexanol, cyclopentanol, cyclohexanol, ethylene glycol, propylene glycol, butylene glycol, glycerin and the like.

Examples of the third type of solvent, ie, a solvent which does not have the property of the above (A) but has high affinity for the matrix, include, for example, toluene, ethylbenzene, propylbenzene, cumene, butylbenzene, isobutylbenzene, and the like.
sec-butylbenzene, pentylbenzene, diethylbenzene, mesitylene, xylene, cresol, ethylphenol, dimethoxybenzene, dimethoxytoluene, benzyl alcohol, tolyl carbinol, cumyl alcohol, acetophenone, propiophenone, hexane, pentane, heptane, octane, Examples thereof include cyclohexane, cyclopentane, cycloheptane, cyclooctane, petroleum fractions (petroleum ether, benzine, etc.).

As mentioned above, the first class of solvents can be used successfully alone. The second type of solvent may be used alone or may be mixed with the first type of solvent. In this case, any kind of solvent has a decoloring ability, so that it can be used at an arbitrary mixing ratio. When a mixed solvent of the second type solvent and the third type solvent is used, the mixing ratio of the two is not particularly limited as long as sufficient decoloring ability is obtained. Is preferred. The third type of solvent may be used as a mixture with the first type of solvent. In this case, the content of the third type solvent may be 90% by weight or less. or,
A mixture of the first to third solvents may be used. In this case, the content of the third type solvent is preferably set to 80% by weight or less.

In order to efficiently decolor the erasable colorant, the solvent may be heated in advance. In this case, the temperature of the solvent is preferably heated to 40 ° C. or higher within a range not exceeding the boiling point of the solvent. When a decoloring method using a solvent is used, a decoloring agent can be added to the solvent.

[0062]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. Example 1 The starch used as a decolorizing agent was obtained by pulverizing and classifying commercially available corn starch (particle outer diameter of about 10 to 20 μm) with a circulating air jet pulverizer equipped with a cyclone classifier.
The particles having a number average particle diameter of 4 μm and a volume average particle diameter of 6 μm were used. The particle size of starch was determined by measuring a sample ultrasonically dispersed in water containing an electrolyte using sodium dodecylbenzenesulfonate as a dispersant, using a Coulter Counter TA-II (manufactured by Coulter Inc.).

A heat-sensitive dye PSD-18 is used as a color-forming compound.
4 (manufactured by Nippon Soda Co., Ltd.), 1 part by weight of propyl gallate as a color developer, 17 parts by weight of starch (number average particle diameter 4 μm and volume average particle diameter 6 μm) as a decolorizer,
79 parts by weight of polystyrene as a matrix material and 1 part by weight of LR-147 (manufactured by Nippon Carlit Co., Ltd.) as a charge controlling agent are mixed in advance, and 1 part is mixed using a kneader.
After sufficiently kneading at a temperature not exceeding 00 ° C., the mixture was cooled to obtain a kneaded product of Example 1. This kneaded material is roughly pulverized to a particle outer diameter of 1 mm by a cutter blade rotary pulverizer, and then pulverized to a maximum particle diameter of 20 μm or less by a circulating air jet pulverizer equipped with a cyclone classifier. Was classified using another cyclone classifier, and the number average particle diameter was 8
Example 1 of the present invention as fine particles having a volume average particle diameter of 12 μm (size larger than the raw starch fine particles)
Was obtained, for example, in a yield of 81%.
The particle size of the particulate erasable colorant of the present invention was determined by ultrasonically dispersing a sample in water containing an electrolyte using sodium dodecylbenzenesulfonate as a dispersant. Manufactured). In addition, the yield of the pulverization / classification process is affected by the loss of the part that remains in the equipment and cannot be removed (constant regardless of the charged amount) and the part that cannot be collected by the cyclone classifier (proportional to the charged amount). Therefore, the above value is an example, but a reasonable value can be achieved as the yield in the pulverizing / classifying step.

About 10 m of the particulate erasable colorant of Example 1
g was placed on a slide glass heated to 100 ° C. on a hot plate, another slide glass heated to 100 ° C. was overlaid and pressed, then cooled and cooled to a thickness of about 20 μm sandwiched between glass plates. A thin film sample was prepared. 10
When melted at 0 ° C., it was confirmed that the erasable colorant of Example 1 kept black. FIG. 1 shows the result of microscopic observation of a molten thin film of the particulate erasable colorant of Example 1. Incidentally, one scale of the scale inserted in FIG. 1 is 10 μm.

For comparison, the finely powdered starch used as a raw material (number average particle diameter 4 μm and volume average particle diameter 6 μm)
m) About 10 m of a well-mixed mixture of 17 parts by weight and 79 parts by weight of finely divided polystyrene (matrix material)
g was placed on a slide glass heated to 100 ° C. on a hot plate, another slide glass heated to 100 ° C. was overlaid and pressed, then cooled and cooled to a thickness of about 20 μm sandwiched between glass plates. A thin film sample was prepared. The result of observing this with an optical microscope is shown in FIG. Incidentally, one scale of the scale inserted in FIG. 2 is 10 μm.

As a result of comparative observation, colorless and transparent fine particles (white particles in FIG. 1; the largest one having a diameter of about 8 μm) observed in the thin film obtained by melting the particulate erasable colorant of Example 1; (The smallest one of about 2 μm) was confirmed to be fine particles of starch as a decolorizing agent.
In addition, in the case of this example, it was found that no difference was observed between FIGS. 1 and 2 in the size of the observed starch particles. This is due to the fact that the particulate decolorizable colorant of Example 1 was produced using raw starch fine particles having a particle diameter smaller than that of the particulate decolorable colorant to be obtained by classification. The light non-transmitting fine particles (particles that appear black in FIG. 1) observed in a small number in the thin film obtained by melting the particulate erasable colorant of Example 1 were compared with the samples separately prepared for comparison. As a result,
It was attributed to the fine particles of the charge control agent.

Next, in order to perform decoloration by heating, the particulate decolorizable colorant of this example and a thin film sample of the decolorant (the finely ground starch) / matrix material mixture for comparison were used. When each was heated at 200 ° C. for 10 minutes and cooled to room temperature, the black color of the particulate erasable colorant in the colored state was erased, and it became milky cloudy. When an optical microscope observation was performed on these decolored thin films,
In each case, it was confirmed that the particulate decolorizing agent (starch) observed with an optical microscope was present without change. That is, it was found that the reason why the decolored thin film did not become transparent and appeared in a milky cloudy state was that the starch fine particles were dispersed in the matrix material.

The particulate erasable colorant of Example 1 was further analyzed by powder X-ray diffraction. For the measurement, a JDX-8020 type X-ray diffractometer manufactured by JEOL Ltd. was used. As a result, no clear diffraction line was observed in the particulate erasable colorant of Example 1 regardless of the presence or absence of the heat treatment at 200 ° C. FIG. 5 shows an X-ray diffraction pattern of the particulate erasable colorant (colored state) of Example 1. In addition, when the starch is analyzed by powder X-ray alone, a weak diffraction line is observed as shown in FIG. That is, in the particulate erasable colorant of the present example, it is presumed that a very small part of the starch is crystallized and the majority is present as amorphous fine particles. The fact that the starch fine particles are colorless and transparent when observed with an optical microscope also supports the fact that they are in an amorphous state.

From the above observations, the mechanism of decoloring when starch is used as the decoloring agent is that the developer, which has been hydrogen-bonded to the color former, moves through the matrix material by heating and is thus decolorized. It is presumed that the particles reach the surface of the starch fine particles, which are adsorbed there, and interact with each other. As a result, the coloring state of the coloring compound is destabilized and the color is erased. The particulate erasable colorant of Example 1 produced and analyzed as described above (number-average particle diameter 8 μm and volume-average particle diameter 12 μm; inner starch particles have a number-average particle diameter 4 μm and a volume-average particle diameter 6 μm 1) 100 parts by weight of 1 part by weight of hydrophobic silica was added to prepare a toner as an application example.

The obtained toner was placed in a toner cartridge of an electrophotographic copying machine, and a test image (test chart) was copied on neutral paper for a copying machine (reflectance 0.08). The obtained copy image has a sufficient image density, the resolution is standard as a toner image having the above-mentioned particle size, exhibits high durability under ordinary use conditions, and has a temperature of 100 ° C.
The image was maintained after heating for 30 minutes. Since the heat fixing process of the particulate colorable / colorable toner is performed at a speed on the order of seconds including the completion of the cooling, the substance of the decolorant or the developer in the particulate colorable / colorable colorant is used. The migration and the intermolecular interaction between the color erasing agent and the color developer are kinetically suppressed, and as a result, an image having a sufficient density can be formed. This copy image is heated to 190 ° C or higher, or
The color can be erased by contact with a liquid or gaseous color erasing aid.

100 sheets of paper on which a copy image was formed with the toner comprising the particulate erasable colorant of Example 1,
In a bundled state, it was put into a ventilation thermostat (Model DN83, manufactured by Yamato Scientific Co., Ltd.) whose temperature was adjusted to 190 ° C., left at the same temperature for 12 hours, and then taken out. As a result, all the copy images formed on 100 sheets of paper were erased, and could not be confirmed with the naked eye. The reflection density of each of the erasable image recording papers after erasing was measured and found to be 0.10. That is, it was confirmed that excellent decoloring characteristics were exhibited. The paper on which the copy image had been erased by heating was erased and left at 60 ° C. for 300 hours, but the image did not reappear.

The paper on which a copy image was formed with the toner comprising the particulate erasable colorant of Example 1 was immersed in, for example, methyl isobutyl ketone (MIBK). As a result, the image copied on the paper was erased and could not be confirmed with the naked eye. The measured reflection density of the paper after erasing was 0.08. That is, it was confirmed that excellent decoloring characteristics were exhibited. When the numerical values of the reflection density of the paper after erasing were compared between the erasing by heating and the erasing by solvent treatment, the values in the case of solvent treatment were slightly better. This is because, in the case of decoloring by solvent treatment, the erasable colorant is erased and simultaneously penetrates the paper and disappears from the surface of the paper. This is because the agent melt remains on the paper surface and slightly affects the reflection density measurement, so that there is no problem in reusing the decolored paper.

To confirm the decoloring process by the solvent treatment,
When the toner was brought into contact with MIBK, it swelled and dissolved instantaneously. Apply this liquid thinly on a glass plate and at room temperature,
Evaporate the solvent and add a vacuum of 0.001 Pa
The solvent was completely removed by heating at 00 ° C. for 24 hours.
The decolored state was maintained even when the solvent was removed. When this sample was observed with an optical microscope, fine particles belonging to the decoloring agent starch were observed.

From the above observations, even when the color was erased by using a solvent, the developer which had been hydrogen-bonded to the color-forming compound was activated by the solvent and moved in the dissolved or swelled mixture to form a decolorant. It is presumed that the particles reach the surface of the starch fine particles, which are adsorbed there, and interact with each other. As a result, the coloring state of the color former is destabilized and the color is erased. The paper whose copy image has been erased by the solvent treatment is heated at 60 ° C for 3 hours.
After leaving for 00 hours, the image did not reappear. Thereafter, a process of transferring another image to a paper whose image was erased by the solvent treatment and erasing the image by the solvent treatment was repeated 9 times. The tenth image transferred thereafter was of the same quality as the first image. Further, copying and decoloring were repeated up to 50 times. As a result, the paper was mechanically damaged, but the quality of the copied image and the quality of the erased state were good.

Comparative Example 1 Instead of the finely powdered starch (number-average particle diameter 4 μm and volume-average particle diameter 6 μm) in Example 1, unground starch (outer diameter of particles: about 10 to 20 μm; commercially available corn starch itself) The kneaded product was roughly pulverized to a particle outer diameter of 1 mm in the same manner as in Example 1 except that
Was obtained. This is pulverized to a maximum particle diameter of 20 μm or less by a circulating air jet pulverizer equipped with a cyclone type classifier, and further classified using another cyclone type classifier to obtain a number average particle diameter of 8 μm and a volume average particle size of 8 μm. Diameter 12μ
m (Comparative Example 1B) was obtained with a yield of 80%. The particle diameter was determined by measuring with a Coulter counter in the same manner as in Example 1. FIGS. 3 and 4 show the results of microscopic observation of the kneaded product of Comparative Example 1A (before pulverization) and the molten thin film of the particulate erasable colorant of Comparative Example 1B, which were prepared in the same manner as in Example 1. Shown in Incidentally, one scale of the scale inserted in FIGS. 3 and 4 is 10 μm.

For comparison, 17 parts by weight of unground starch (particle outer diameter: about 10 to 20 μm) used as a raw material and finely powdered polystyrene (matrix material) 79
About 10 mg of a mixture obtained by mixing well with the other parts by weight is placed on a slide glass heated to 100 ° C. on a hot plate, another slide glass heated to 100 ° C. is stacked and pressed, and then cooled, and cooled between glass plates. A thin film sample having a thickness of about 20 μm sandwiched between the samples was prepared. As a result of observing this with an optical microscope (not shown), colorless and transparent particles (particles that appear white in FIG. 3) observed in a thin film obtained by melting the kneaded material (before pulverization) of Comparative Example 1A; (A diameter of about 20 μm and a minimum of about 2 μm) was confirmed to be fine particles of starch as a decolorizing agent.
Further, it was found that there was no difference in the observed size of the starch particles only by the kneading operation.

The colorless and transparent particles (FIG. 4) which are observed in the thin film obtained by pulverizing and classifying the kneaded product containing such coarse starch particles and melting the particulate erasable colorant of Comparative Example 1B. The largest particle has a diameter of about 20 μm, but the number is smaller than that of FIG. 3, and the diameter is mainly 10 to 15 μm, and the smallest particle is about 2 μm. No doubt,
Interestingly, the particle diameter was found to correspond to the classification range of the particulate erasable colorant of Comparative Example 1B. That is, a part of the particulate erasable colorant of Comparative Example 1B is:
It is presumed to consist essentially of only the decolorizing agent starch. The existence of such particles consisting essentially of the decolorizing agent deviates from the gist of the particulate erasable colorant of the present invention. Further, the presence of particles composed of only the decolorizing agent and having a particle size corresponding to the classification range as the particulate decolorizable colorant of Comparative Example 1B means that the particles of Comparative Example 1B Among the erasable colorants, those having a smaller ratio of the decolorant component than the composition ratio set at the time of preparation (the particles alone have poor erasing characteristics),
It means that many are included.

Comparative Example 1B manufactured and analyzed as described above
1 part by weight of hydrophobic silica is added to 100 parts by weight of a particulate erasable colorant (number average particle diameter 8 μm and volume average particle diameter 12 μm; including particles substantially consisting of starch). A toner was prepared. The obtained toner is placed in a toner cartridge of an electrophotographic copying machine, and a test image (test chart) is printed on neutral paper for a copying machine (with a reflectance of 0.0).
8). Although the density of the obtained copy image was the same as that of Example 1, the resolution was inferior to that of the toner image having the above-mentioned particle diameter, and blurring was observed in places of fine lines. In addition, when heat decoloring was performed, it was clear that Example 1 was obtained.
The result was inferior to the case of. That is, 100 sheets of paper on which a copy image was formed with the toner composed of the particulate erasable colorant of Comparative Example 1B were used as in Example 1 for 1 sheet.
After heating at 90 ° C. for 12 hours, it was taken out. as a result,
All the copied images formed on 100 sheets of paper were erased, but afterimages were confirmed with the naked eye. When the reflection density of each of the erasable image recording paper after erasing was measured, it was about 0.25. That is, it was found that the decoloring characteristics due to heating were remarkably poor as compared with the copy image formed by the toner composed of the particulate decolorable colorant of Example 1. The reason for this is that, as described above, the particulate erasable colorant of Comparative Example 1B was produced using coarse starch particles, and thus contained particles consisting essentially of starch, and was more decolorized than the designed value. This is presumed to be due to the inclusion of a particulate erasable colorant having a low colorant content.

Example 2 1 part by weight of crystal violet lactone (manufactured by Tokyo Chemical Industry Co., Ltd.) as a color-forming compound, 1 part by weight of propyl gallate as a color developer, and a fine colorant as in Example 1 18 parts by weight of powdered starch (number average particle diameter 4 μm and volume average particle diameter 6 μm), 79 parts by weight of polystyrene as a matrix material, and 1 part by weight of LR-147 (manufactured by Nippon Carlit Co., Ltd.) as a charge control agent Other than the above, the number average particle diameter was 8 in the same manner as in Example 1.
Example 2 as particles having a volume average particle diameter of 12 μm
Was produced. The yield was equivalent to that of Example 1. The particle diameter was determined in the same manner as in Example 1 by measuring with a Coulter counter.

A thin film sample was prepared in the same manner as in Example 1 by using the particulate erasable colorant of this example.
When it was melted at 0 ° C., it remained blue-violet, while when it was heated to 200 ° C., it disappeared and became milky. As a result of observing these with an optical microscope (not shown; equivalent to FIG. 1), 200
Regardless of the presence or absence of the heat treatment at ℃, it was confirmed that the starch was present as fine particles (clear X-ray diffraction lines were not shown). Particulate erasable colorant of Example 2C (having a number average particle diameter of 8 μm and a volume average particle diameter of 12 μm) 100
As an application example, a toner was prepared by adding 1 part by weight of hydrophobic silica to part by weight.

The obtained toner was put into a toner cartridge of an electrophotographic copying machine, and a test image (test chart) was transferred to neutral paper for copying machine (reflectance 0.08).
The resulting blue-violet image had a sufficient image density, exhibited high durability under normal use conditions, and maintained the image even after heating at 100 ° C. for 30 minutes. This image can be decolorized by heating to 190 ° C. or higher, or by contact with a liquid or gas decolorizing aid. When the paper on which the image was copied was immersed in, for example, methyl isobutyl ketone (MIBK), the image copied on the paper was erased and could not be visually confirmed. The measured reflection density of the paper after erasing was 0.08. That is, it was confirmed that excellent decoloring characteristics were exhibited.

Example 3 A starch used as a decolorizing agent was obtained by pulverizing and classifying commercially available corn starch (particle outer diameter of about 10 to 20 μm) with a circulating air jet pulverizer equipped with a cyclone classifier.
Number average particle diameter 0.6 μm and volume average particle diameter 1.2 μm
Was used. The particle size was determined by measuring a sample obtained by ultrasonically dispersing in purified water using sodium dodecylbenzenesulfonate as a dispersant with a laser light scattering type particle size distribution analyzer (manufactured by Coulter Inc.).

The heat-sensitive dye PSD-18 is used as a color-forming compound.
4 (manufactured by Nippon Soda Co., Ltd.) 2 parts by weight, propyl gallate 1 part by weight as a color developer, starch (a number average particle diameter 0.6 μm and a volume average particle diameter 1.2 μm) 17 as a decolorizer
Parts by weight, 79 parts by weight of polystyrene as a matrix material, and 1 part by weight of LR-147 (manufactured by Nippon Carlit Co., Ltd.) as a charge controlling agent are mixed in advance and sufficiently kneaded at a temperature not exceeding 100 ° C. using a kneader. After cooling, the kneaded material of Example 3 was obtained. This kneaded material is roughly pulverized to a particle outer diameter of 1 mm by a cutter blade rotary pulverizer, and then pulverized to a maximum particle diameter of 4 μm or less by a circulating air jet pulverizer equipped with a cyclone classifier.
This was classified using another cyclone classifier to obtain fine particles having a number average particle diameter of 1.0 μm and a volume average particle diameter of 2.0 μm (larger than the raw starch fine particles).
A particulate erasable colorant of Example 3 of the present invention was obtained. The particle size of the particulate erasable colorant was measured using a laser light scattering type particle size distribution analyzer (manufactured by Coulter, Inc.) by ultrasonically dispersing a sample in purified water using sodium dodecylbenzenesulfonate as a dispersant. Measured.

Using 20 parts of the particulate erasable colorant of Example 3 as a binder, methyl methacrylate-butyl acrylate-
To a binder solution containing 20 parts by weight of an acrylic acid (ammonium salt) copolymer, 2 parts by weight of a nonionic dispersant, 10 parts by weight of propylene glycol, and 48 parts by weight of water, using a three-roll mill To disperse, thereby producing an erasable aqueous colorant as an application example. This erasable aqueous colorant was applied to the entire surface of one side of neutral paper for a copying machine (reflectance 0.08) using a bar coater, and dried. This paper was dipped in, for example, methyl isobutyl ketone (MIBK). As a result, the decolorizable aqueous colorant was decolorized and the color could not be confirmed with the naked eye. The measured reflection density of the paper after erasing was 0.08. That is, it was confirmed that excellent decoloring characteristics were exhibited. It consists of an aluminum cylinder fitted with a pen body holder that fixes a pen body made by binding fiber bundles with resin via a valve mechanism, and presses the pen tip against the paper surface during marking to open the valve. A pen body of a marking pen of a type in which the ink inside was drawn out to a pen tip was prepared, and the above-mentioned erasable water-based colorant was filled into the pen body, and a writing implement was prepared as an application example. Using this writing instrument, writing was performed on neutral paper for a copying machine (reflectance 0.08). The drawn lines had a sufficient concentration, exhibited high durability under ordinary use conditions, and were maintained even after heating at 100 ° C. for 30 minutes. This drawing line could be erased by heating it to 190 ° C. or higher, or by contacting it with a decolorizing aid.

For example, paper written with this writing instrument was immersed in, for example, methyl isobutyl ketone (MIBK). As a result, the drawn line drawn with the erasable aqueous colorant using the particulate erasable colorant of Example 3 was erased and could not be confirmed with the naked eye. The paper with the erasable aqueous colorant using the particulate erasable colorant of Example 3 decolorized by the solvent treatment was left at 60 ° C. for 300 hours, but the line did not appear again. Was. After that, on the paper where the strokes were erased,
The process of writing a line with the above-mentioned writing instrument and erasing by solvent treatment was repeated 9 times. The tenth stroke drawn thereafter was of the same quality as the first stroke, and was not broken on the erased stroke. Further, writing and decoloring were repeated up to 50 times. As a result, the quality of the drawn drawing line and the quality of the decolored state were good.

In order to test the storage stability of the aqueous erasable colorant using the particulate erasable colorant of Example 3 of the present invention, (a) in a glass bottle and (b) Example 1 , A long-term storage test at 50 ° C. was performed in a closed state. As a result, even after storage at 50 ° C. for 6 months, no change was observed in the color development state and dispersion state, and no deterioration was observed in the decoloring characteristics after coating or drawing on paper. .

Comparative Application Example 1 In order to prepare a pigment composition particle having no composition containing a decoloring agent for comparison, a leuco dye PSD-18 was used as a coloring compound.
4 (manufactured by Nippon Soda Co., Ltd.), 2 parts by weight of propyl gallate as a color developer, and 79 parts by weight of polystyrene as a matrix material are mixed in advance, and a temperature of not more than 100 ° C. is sufficiently determined using a kneader. After kneading, the mixture was cooled to produce a dye composition that developed a black color. This kneaded material is roughly pulverized to a particle outer diameter of 1 mm by a cutter blade rotary pulverizer, and then pulverized to a maximum particle diameter of 4 μm or less by a circulating air jet pulverizer equipped with a cyclone classifier. Was classified using another cyclone classifier, and the number average particle diameter was 1.0 μm and the volume average particle diameter was 2.0.
μm dye composition particles were obtained.

A mixture of 83% by weight of this pigment composition and 17% by weight of finely ground starch (number average particle diameter 0.6 μm and volume average particle diameter 1.2 μm) as a decolorizing agent (leuco dye) The components of the developer, the developer and the decolorant are the same as those of the erasable aqueous colorant of Example 3.
20 parts by weight of a methyl methacrylate-butyl acrylate-acrylic acid (ammonium salt) copolymer as a binder, 2 parts by weight of a nonionic dispersant, 10 parts by weight of propylene glycol, and 48 parts by weight of water Comparative Example 1 was dispersed in a binder solution containing parts by weight using three rolls.
Was prepared. Further, this is described in Example 3.
Comparative application example 1 by filling the same pen body as in the case of application example 1
Writing implements.

When the erasable water-based colorant of Comparative Application Example 1 was applied to paper and the drawing written on paper using the writing implement of Comparative Application Example 1 was tested immediately after preparation, Decoloring characteristics equivalent to those of the third application example were exhibited. However, in order to test the storage stability of the erasable aqueous colorant of Comparative Application Example 1, 50 ° C. was sealed in a glass bottle (a) and in the writing implement of Comparative Application Example 1 (b). Long-term storage test. As a result, the starch microparticles aggregate only after storage at 50 ° C. for one week, and it becomes difficult to apply the erasable aqueous colorant of Comparative Application Example 1,
On the other hand, the writing implement of Comparative Application Example 1 was no longer writable. It is presumed that the cause of such an inconvenience is that the fine particles of starch as the decoloring agent are not protected by the matrix material.

[0090]

As described above in detail, the use of the particulate erasable colorant of the present invention forms a stable image on paper and erases the formed image with excellent erasing characteristics. Can be colored. Further, the decolored state can be stably maintained, and the paper after the decoloration can be effectively reused.

[Brief description of the drawings]

FIG. 1 is a diagram obtained by processing a particulate erasable colorant of Example 1 into a thin film and observing it with an optical microscope. One scale of the scale inserted in the figure is 10 μm.

FIG. 2 is a diagram obtained by processing a mixture of finely powdered starch (number average particle diameter of 4 μm and volume average particle diameter of 6 μm) and polystyrene into a thin film and observing it with an optical microscope. One scale of the scale inserted in the figure is 10 μm.

FIG. 3 is a diagram obtained by processing a kneaded product (before pulverization) of Comparative Example 1A into a thin film and observing it with an optical microscope. One scale of the scale inserted in the figure is 10 μm.

FIG. 4 is a diagram obtained by processing the particulate erasable colorant of Comparative Example 1B into a thin film and observing it with an optical microscope. One scale of the scale inserted in the figure is 10 μm.

FIG. 5 is a diagram showing an X-ray diffraction pattern of the particulate erasable colorant (colored state) of Example 1.

FIG. 6 shows the X of the micronized starch used in Example 1.
It is a figure showing a line diffraction pattern.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Yoshifumi Sugito, Inventor 1-7-6, Bakurocho, Nihonbashi, Chuo-ku, Tokyo Dainichi Seika Kogyo Co., Ltd. F-term (reference) 2H005 AA06 AA08 AA11 AA21 AA25 AA27 CA20 DA04 DA10 2H086 BA55 4J039 BC29 BE01 BE02

Claims (3)

[Claims] 1. At least a matrix material, a developer,
A color developing compound that develops a color by an intermolecular interaction with the color developing agent, and an inter molecular interaction with the color developing agent that is stronger than the inter molecular interaction between the color developing compound and the color developing compound. A particulate decolorizable colorant comprising a decolorant, wherein in the particulate decolorizable colorant, the decolorant is always
An average diameter when the shape is approximated by a sphere exists as fine particles or a microphase separated state having a size not exceeding the diameter of the particulate erasable colorant. In the matrix material, the color former is present in a molecular interaction with the color former, and in the decolored state, the developer does not interact with the color former in the form of fine particles or micro phase separated. A particulate decolorizable colorant, which is adsorbed on the surface of the decolorant and exists in a molecular interaction with the decolorant. 2. At least a matrix material, a color developer,
A color developing compound that develops a color by an intermolecular interaction with the color developing agent, and an inter molecular interaction with the color developing agent that is stronger than the inter molecular interaction between the color developing compound and the color developing compound. In producing a particulate erasable colorant of a predetermined size using the erasing agent in the state of fine particles or microphase separation, the average diameter of the erasing agent when the shape of the erasing agent is approximated by a sphere is the particle size. The decolorizing agent in the form of fine particles or microphase-separated in advance in a state not exceeding the diameter of the decolorable colorant is obtained by mixing the matrix material, the developer, and the coloring compound. A method for producing a particulate erasable colorant, the method comprising forming the particulate erasable colorant after dispersing in the mixture. 3. The method for producing a particulate erasable colorant according to claim 2, wherein the shape of the erasable agent approximates a sphere, and the average diameter of the erasable particles is a predetermined size. A mixture of the matrix material, the color developer, and the color former, wherein the decoloring agent in the form of fine particles or micro phase separated, which has been previously pulverized or refined to a size not exceeding the diameter of the colorant, is mixed. A method for producing a particulate erasable colorant, the method comprising kneading and dispersing the mixture therein, followed by pulverization and classification to form the particulate erasable colorant having a predetermined size.