JP2012078794A - Electrophotographic toner and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology of achieving a decolorizable electrophotographic toner capable of improving picture qualities.SOLUTION: The decolorizable electrophotographic toner contains at least a binder resin and a colorant encapsulated by a shell material. In a measurement of the toner by using a flow particle image analyzer after the toner is dispersed by 0.08 wt.% in an aqueous medium and subjected to a stirring treatment in which stirring is carried out at 5000 rpm for 30 minutes by using a homogenizer (T-25 digital ULTRA-TURRAX (manufactured by IKA Japan K.K., provided with a shaft generator S25N-10G)), the proportion of particles having a circle-equivalent diameter of 0.6 μm or more and 2.5 μm or less is 30% by number or less.

Description

  Embodiments described herein relate generally to an electrophotographic toner and a method for producing the same.

  Conventionally, a toner containing a color developable compound and a developer and capable of erasing an image formed by erasing by heating is known. In this technique, a color developable compound and a developer are melt-kneaded together with a binder resin by a kneading pulverization method, and taken into the toner. With this toner, the printed paper can be erased by heating the printed paper at 100 to 200 ° C. for about 1 to 3 hours, and the erased paper can be reused. It is an excellent technology that can contribute to reducing environmental impact by reducing paper consumption.

  In a decolorable toner, some colorants (color developing compound and developer) are encapsulated in a capsule, and such a capsule has a size of about several μm. On the other hand, the toner has only a size of several μm to 20 μm. Therefore, when the capsule-like colorant is not sufficiently taken in, the colorant is largely exposed from the binder resin.

  When such a toner is used in an image forming apparatus such as an MFP, it is easily crushed at the interface between the binder resin and the capsule-like colorant due to stress such as stirring, and causes the generation of fine powder of the binder resin. It is easy to become.

  For fine powder measurement, use a flow particle image analyzer to measure the amount of fine powder (small particle size) toner (maximum number particle size is 2 to 4 μm or less), and after irradiating the dispersion liquid in which the toner is dispersed with ultrasonic waves A technique for measuring particles of 0.5 μm to 2 μm using a flow particle image analyzer has been proposed.

  However, in these techniques, only the amount of fine powder of toner after production is measured. In addition, the amount of fine powder tends to be larger than that of toner after production by ultrasonic irradiation, but the amount of fine powder during actual use cannot be reproduced because the toner cannot be stressed to the same extent as in the developing device. For this reason, depending on the conventional technology, the image quality such as fogging and the effect of the machine contamination due to toner scattering are not sufficiently improved.

  This specification has been made to solve the above-described problems, and provides a technique capable of suppressing the occurrence of fogging and toner scattering in a decolorizable toner containing an encapsulated colorant. Objective.

  This specification includes a binder resin and a colorant containing at least a color developing compound and a developer and having a capsule structure covered with an outer shell, and is 0.08% by weight in an aqueous medium. A flow type particle image measuring device for the toner subjected to a stirring process at 5000 rpm for 30 minutes using a homogenizer (T 25 Digital ULTRA-TURRAX (manufactured by IKA: Shaft Generator; S25N-10G)) The present invention relates to a decolorable electrophotographic toner in which particles having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less are 30% by number or less.

6 is a table showing the relationship between toner density, homogenizer rotation speed, stirring time and amount of fine powder generated. 6 is a table showing the amount of fine powder generated after stirring the toner under a certain condition. 6 is a table showing measurement results of toners of examples and comparative examples.

  The electrophotographic toner of the present embodiment (hereinafter also simply referred to as toner) contains at least a binder resin and a colorant. In the toner of this embodiment, the toner is dispersed in an aqueous medium at a ratio of 0.08% by weight, and is used at 5000 rpm using a homogenizer (T 25 Digital ULTRA-TURRAX (IKA: Shaft Generator; S25N-10G)). After being subjected to a stirring process for 30 minutes (hereinafter, also simply referred to as a stirring process or a homogenizer process), particles having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less are 30% by number or less in the flow type particle image analyzer. Furthermore, it is more preferably 20% by number or less.

In this embodiment, the colorant has an encapsulated structure covered with an outer shell. The present inventor has found that a erasable toner containing a colorant having an encapsulated structure, particularly a toner containing a colorant having a volume average particle size (volume D50) of 0.5 to 3.5 μm, It has been found that the cause of toner scattering is that the binder resin tends to break at the interface between the binder resin and the colorant due to stress applied to the toner during operation of the image forming apparatus. When the toner breaks, fine powder of the binder resin is generated. It was also found that such a crushing phenomenon easily occurs particularly when the colorant is largely exposed from the toner.
Among the fine powders, particles having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less in the flow type particle image analyzer described later deteriorate the charging characteristics and seriously affect the image quality. As a result of earnest research, it is possible to give the toner the same stress as that used in the image forming apparatus by subjecting the toner to the above-described stirring process, and after performing the stirring process, a flow type particle image analyzer In the measurement using the toner, toner having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less of 30% by number or less can suppress generation of fine powder when used in an image forming apparatus, and fog and toner scattering. The toner of this embodiment was completed. In the description of the toner of the present exemplary embodiment, particles having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less are referred to as fine powder.
The toner of the present embodiment is based on the finding that image fogging and toner scattering can be suppressed when the amount of fine powder generated after the stirring treatment is a specific numerical value (30% by number) or less. Therefore, it does not specifically limit about the lower limit of the generation amount of the fine powder after the stirring treatment.

  Here, the toner of the present exemplary embodiment is specified by using a flow particle image analyzer (Flow Particle Image Analyzer) and measuring distribution based on the number. In this specification, a flow-type particle image analyzer is an apparatus that takes a particle image and calculates the diameter of a circle having the same area as the equivalent circle diameter from the area of a two-dimensional image of each particle.

  The toner particle can be measured by a flow type particle image analyzer, for example, using a flow type particle image analyzer FPIA2100 manufactured by Sysmex Corporation.

Here, an example of a method for measuring the proportion of fine toner particles using a flow particle image analyzer will be described.
In the measurement, a surfactant and a sample are added to an aqueous medium in which the number of particles in the measurement range contained in a predetermined volume is reduced to 20 or less using a filter or the like, and an ultrasonic disperser or the like is added. To perform distributed processing. By this dispersion treatment, the particle concentration of the sample dispersion is 1000 × 10 ³ -15000 × 10 ³ particles / mL, preferably 6000 × 10 ³ -15000 × 10 ³ particles / mL (for particles in the measurement circle equivalent diameter range) As)). The dispersion is subjected to measurement using a flow particle image analyzer, 2000 or more toner particles are measured, and the particle size distribution of particles having a circle-equivalent diameter in the range of 0.6 μm or more and less than 400 μm is measured to obtain 0.6. A value of the ratio (number%) of particles of μm or more and 2.5 μm or less is obtained.

  The inventors have a ratio (number%) of particles having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less, for example, when produced through an aggregation treatment and a fusion treatment of a binder resin and a colorant described later, It has also been found that there is a relationship with the circularity of the particles obtained after the fusion treatment.

In the toner according to the exemplary embodiment, the number of particles having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less obtained by measurement using the above-described flow type particle image measuring device for toner that has not been subjected to the stirring treatment. Ratio (A) and the ratio of the number of particles having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less (B) obtained by measurement using the above-described flow type particle image measuring device of the toner subjected to the stirring treatment Preferably satisfy the relationship of (B) / (A) ≦ 2.0. By satisfying the relationship of (B) / (A) ≦ 2.0, it is possible to further suppress the generation of fine powder due to toner cracking in the image forming apparatus and further improve the charging characteristics. Therefore, contamination inside the machine due to fogging and toner scattering can be further suppressed.
As described above, the lower limit value of the amount of fine powder generated after the stirring treatment is not particularly limited, and therefore the lower limit value is not particularly limited for (B) / (A).

Furthermore, in the toner of this embodiment, the volume average particle diameter (D) of the toner subjected to the stirring treatment and the volume average particle diameter (C) of the toner measured without being subjected to the stirring treatment are 0.85. It is preferable that the relationship of ≦ (D) / (C) is satisfied. By satisfying this relationship, it is possible to further suppress the toner cracking and further improve the charging characteristics. Therefore, contamination inside the machine due to fogging and toner scattering can be further suppressed.
The upper limit of (D) / (C) is not particularly limited, but the range of (D) / (C) is, for example, 0.85 ≦ (D) / (C) due to the influence on the toner by the stirring process. <1.

  In this specification, the volume average particle diameter is obtained from the volume sum of individual particles calculated from the particle diameter, and when the total volume sum of these is 50%, the corresponding particle diameter (volume) D50). The volume average particle diameter can be measured using, for example, Maltisizer 3 (manufactured by Beckman Coulter, Inc .: aperture diameter 100 μm).

Subsequently, the components of the toner of this embodiment will be described.
The toner according to the exemplary embodiment includes a colorant and a binder resin. In the present specification, the colorant refers to one compound or composition that imparts color to the toner. In the present embodiment, the colorant has a color developable compound and a developer.

  The material of the toner used in this embodiment is not particularly limited as long as it contains a binder resin and a colorant and the manufactured toner can be decolored. For example, as other components contained or held on the outer surface as necessary, there may be mentioned a release agent, a charge control agent, a flocculant, a neutralizing agent, an external additive, and the like.

In the present embodiment, the binder resin includes, for example, polystyrene, styrene resins such as styrene / butadiene copolymer and styrene / acrylic copolymer, polyethylene, polyethylene / vinyl acetate copolymer, polyethylene / norbornene copolymer, polyethylene / Examples thereof include ethylene resins such as vinyl alcohol copolymers, polyester resins, acrylic resins, phenol resins, epoxy resins, allyl phthalate resins, polyamide resins, and maleic resins. These resins may be used alone or in combination of two or more.
The binder resin preferably has an acid value of 1 or more.
Further, the above polyester component may be made into a crosslinked structure by using a trivalent or higher polyvalent carboxylic acid such as 1,2,4-benzenetricarboxylic acid (trimellitic acid) or glycerin or a polyhydric alcohol component. .
In the toner of the exemplary embodiment, two or more kinds of polyester resins having different compositions may be mixed and used.
In the toner of this embodiment, the polyester resin may be amorphous or crystalline.
Moreover, as a polystyrene-type resin, what copolymerized the aromatic vinyl component and the (meth) acrylic acid ester component is preferable. Examples of the aromatic vinyl component include styrene, α-methylstyrene, o-methylstyrene, and p-chlorostyrene. Examples of the acrylic ester component include ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, ethyl methacrylate, and methyl methacrylate. Of these, butyl acrylate is generally used. As a polymerization method, an emulsion polymerization method is generally employed, and it is obtained by radical polymerization of monomers of respective components in an aqueous phase containing an emulsifier.
The glass transition temperature of the polyester resin and the polystyrene resin is preferably 35 ° C. or higher and 80 ° C. or lower, and more preferably 40 ° C. or higher and 75 ° C. or lower. When the glass transition temperature is lower than 35 ° C., the storage stability is worse than when the glass transition temperature is within the range, and blocking occurs in the developing machine. On the other hand, when the glass transition temperature is higher than 75 ° C., it is impossible to ensure sufficient fixability than within the range.
The weight average molecular weight Mw of the polyester resin is preferably 5000 or more and 30000 or less. On the other hand, the weight average molecular weight Mw of the polystyrene-based resin is more preferably 10,000 or more and 70,000 or less. When the weight average molecular weight Mw is less than 5000 (10000 in the case of polystyrene resin), the heat resistant storage stability of the toner is lower than that within the range. Further, when the weight average molecular weight Mw is larger than 30000 (70,000 in the case of polystyrene resin), the fixing temperature becomes higher than that within the range, which is not preferable from the viewpoint of suppressing power consumption in the fixing process.

The color developable compound is typically a leuco dye and is an electron donating compound capable of developing color with a developer. Examples thereof include diphenylmethane phthalides, phenyl indolyl phthalides, indolyl phthalides, diphenyl methane azaphthalides, phenyl indolyl azaphthalides, fluorans, styrinoquinolines, diazarhodamine lactones, and the like.
Specifically, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) Phthalide, 3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide, 3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3- (2- Ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- [2-ethoxy-4- (N-ethylanilino) phenyl] -3- (1 -Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3,6-diphenylaminofluorane, 3,6-dimethoxyfluorane, 3,6-di-n-butoxy Luolan, 2-methyl-6- (N-ethyl-Np-tolylamino) fluorane, 2-N, N-dibenzylamino-6-diethylaminofluorane, 3-chloro-6-cyclohexylaminofluorane, 2- Methyl-6-cyclohexylaminofluorane, 2- (2-chloroanilino) -6-di-n-butylaminofluorane, 2- (3-trifluoromethylanilino) -6-diethylaminofluorane, 2- (N -Methylanilino) -6- (N-ethyl-Np-tolylamino) fluorane, 1,3-dimethyl-6-diethylaminofluorane, 2-chloro-3-methyl-6-diethylaminofluorane, 2-anilino-3 -Methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-di-n-butylaminofluorane, -Xylidino-3-methyl-6-diethylaminofluorane, 1,2-benz-6-diethylaminofluorane, 1,2-benz-6- (N-ethyl-N-isobutylamino) fluorane, 1,2-benz -6- (N-ethyl-N-isoamylamino) fluorane, 2- (3-methoxy-4-dodecoxystyryl) quinoline, spiro [5H- (1) benzopyrano (2,3-d) pyrimidine-5, 1 '(3'H) isobenzofuran] -3'-one, 2- (diethylamino) -8- (diethylamino) -4-methyl-, spiro [5H- (1) benzopyrano (2,3-d) pyrimidine- 5,1 ′ (3′H) isobenzofuran] -3′-one, 2- (di-n-butylamino) -8- (di-n-butylamino) -4-methyl-, spiro [5H- ( 1) Be Nzopyrano (2,3-d) pyrimidine-5,1 '(3'H) isobenzofuran] -3'-one, 2-di-n-butylamino) -8- (diethylamino) -4-methyl-, spiro [5H- (1) benzopyrano (2,3-d) pyrimidine-5,1 '(3'H) isobenzofuran] -3'-one, 2- (di-n-butylamino) -8- (N- Ethyl-Ni-amylamino) -4-methyl-, spiro [5H- (1) benzopyrano (2,3-d) pyrimidine-5,1 '(3'H) isobenzofuran] -3'-one, 2 -(Di-n-butylamino) -8- (di-n-butylamino) -4-phenyl, 3- (2-methoxy-4-dimethylaminophenyl) -3- (1-butyl-2-methylindole) -3-yl) -4,5,6,7-tetrachlorophthalide 3- (2-Ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4,5,6,7-tetrachlorophthalide, 3- (2-ethoxy- 4-diethylaminophenyl) -3- (1-pentyl-2-methylindol-3-yl) -4,5,6,7-tetrachlorophthalide. Furthermore, a pyridine type, a quinazoline type, a bisquinazoline type compound, etc. can be mentioned. You may use these in mixture of 2 or more types.

The color developer for coloring the color former is an electron accepting compound that gives protons to the leuco dye. For example, phenols, phenol metal salts, carboxylic acid metal salts, aromatic carboxylic acids and aliphatic carboxylic acids having 2 to 5 carbon atoms, sulfonic acids, sulfonates, phosphates, phosphate metal salts, acidic phosphate esters, There are acidic phosphoric acid ester metal salts, phosphorous acids, phosphite metal salts, monophenols, polyphenols, 1,2,3-triazole and derivatives thereof, and further substituents thereof are alkyl groups, aryl groups, acyls Groups, alkoxycarbonyl groups, carboxy groups and esters or amide groups thereof, halogen groups, and the like, bis-type, tris-type phenols, phenol-aldehyde condensation resins, and the like, and metal salts thereof. You may use these in mixture of 2 or more types.
Specifically, phenol, o-cresol, tertiary butylcatechol, nonylphenol, n-octylphenol, n-dodecylphenol, n-stearylphenol, p-chlorophenol, p-bromophenol, o-phenylphenol, p-hydroxy N-butyl benzoate, n-octyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, dihydroxybenzoic acid or its esters such as 2,3-dihydroxybenzoic acid, methyl 3,5-dihydroxybenzoate, resorcin, gallic Acid, dodecyl gallate, ethyl gallate, butyl gallate, propyl gallate, 2,2-bis (4-hydroxyphenyl) propane, 4,4-dihydroxydiphenyl sulfone, 1,1-bis (4-hydroxyphenyl) Eta 2,2-bis (4-hydroxy-3-methylphenyl) propane, bis (4-hydroxyphenyl) sulfide, 1-phenyl-1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis ( 4-hydroxyphenyl) -3-methylbutane, 1,1-bis (4-hydroxyphenyl) -2-methylpropane, 1,1-bis (4-hydroxyphenyl) n-hexane, 1,1-bis (4- Hydroxyphenyl) n-heptane, 1,1-bis (4-hydroxyphenyl) n-octane, 1,1-bis (4-hydroxyphenyl) n-nonane, 1,1-bis (4-hydroxyphenyl) n- Decane, 1,1-bis (4-hydroxyphenyl) n-dodecane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxy) Enyl) ethyl propionate, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 2,2-bis (4-hydroxyphenyl) n-heptane, 2,2-bis (4-hydroxyphenyl) n-nonane, 2,4-dihydroxyacetophenone, 2,5-dihydroxyacetophenone, 2,6-dihydroxyacetophenone, 3,5-dihydroxyacetophenone, 2,3 , 4-trihydroxyacetophenone, 2,4-dihydroxybenzophenone, 4,4'-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,2 ', 4 4′-tetrahydroxybenzophenone, 2,3,4,4′-te Lahydroxybenzophenone, 2,4′-biphenol, 4,4′-biphenol, 4-[(4-hydroxyphenyl) methyl] -1,2,3-benzenetriol, 4-[(3,5-dimethyl-4 -Hydroxyphenyl) methyl] -1,2,3-benzenetriol, 4,6-bis [(3,5-dimethyl-4-hydroxyphenyl) methyl] -1,2,3-benzenetriol, 4,4 ′ -[1,4-phenylenebis (1-methylethylidene) bis (benzene-1,2,3-triol)], 4,4 ′-[1,4-phenylenebis (1-methylethylidene) bis (1, 2-benzenediol)], 4,4 ′, 4 ″ -ethylidenetrisphenol, 4,4 ′-(1-methylethylidene) bisphenol, methylenetris-p-cresol, and the like.

  The encapsulating agent (shell material) that forms the outer shell of the colorant is not particularly limited, and can be appropriately set by those skilled in the art.

Furthermore, in this embodiment, a decoloring agent is contained as necessary. The color erasing agent is known in the three-component system of a color developing compound, a color developing agent, and a color erasing agent, as long as it can inhibit the color development reaction caused by the leuco dye and the color developer by heat and can be made colorless. Can be used.
The color erasing agent is particularly excellent in the instantaneous erasing property due to the color erasing mechanism utilizing the temperature hysteresis of the color erasing agent known in JP-A-60-264285, JP-A-2005-1369, JP-A-2008-280523, etc. ing. When this colored three-component mixture is heated to a specific decoloring temperature Th or higher, it can be decolored. Furthermore, even if the decolored mixture is cooled to a temperature equal to or lower than Th, the decolored state is maintained. When the temperature is further lowered, the color development reaction by the leuco dye and the developer is restored again at a specific recoloring temperature Tc or less, and a reversible color erasing reaction that returns to the color development state can be caused. In particular, the decolorizer used in the present invention preferably satisfies the relationship Th>Tr> Tc when the room temperature is Tr.
Examples of the color erasing agent capable of causing this temperature hysteresis include alcohols, esters, ketones, ethers, and acid amides.
Particularly preferred are esters. Specifically, a carboxylic acid ester containing a substituted aromatic ring, an ester of a carboxylic acid and an aliphatic alcohol containing an unsubstituted aromatic ring, a carboxylic acid ester containing a cyclohexyl group in the molecule, a fatty acid and an unsubstituted aromatic alcohol or Ester of phenol, fatty acid and branched fatty alcohol, dicarboxylic acid and aromatic alcohol or branched fatty alcohol, dibenzyl cinnamate, heptyl stearate, didecyl adipate, dilauryl adipate, dimyristyl adipate, adipic acid Examples include dicetyl, distearyl adipate, trilaurin, trimyristin, tristearin, dimyristin, distearin and the like. You may use these in mixture of 2 or more types.

  Examples of release agents include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymers, polyolefin wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, and aliphatics such as acid value polyethylene wax. Oxides of hydrocarbon waxes or block copolymers thereof, plant waxes such as wax wax, jojoba wax, rice wax, animal waxes such as beeswax, lanolin, spermaceti, Mineral waxes such as ozokerite, ceresin and petrolactam, waxes based on fatty acid esters such as montanic ester wax and castor wax, and fatty acid esters such as deoxidized carnauba wax. The other is exemplified such as those de-oxidation all. Further, saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, or long-chain alkyl carboxylic acids having a long-chain alkyl group, unsaturated fatty acids such as brassic acid, eleostearic acid, valinalic acid, stearyl alcohol , Saturated alcohols such as eicosyl alcohol, behenyl alcohol, carnauvir alcohol, seryl alcohol, melyl alcohol, or long chain alkyl alcohols having a long chain alkyl group, polyhydric alcohols such as sorbitol, linoleic acid amide, oleic acid Amide, fatty acid amide such as lauric acid amide, methylene bis stearic acid amide, ethylene biscapric acid amide, ethylene bis lauric acid amide, saturated fatty acid bis amide such as hexamethylene bis stearic acid amide, Unsaturated fatty acid amides such as lenbis oleic acid amide, hexamethylene bis oleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide, m-xylene bis stearic acid amide, Aromatic bisamides such as N, N'-distearylisophthalic amide, fatty acid metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (generally referred to as metal soap), aliphatic Hydroxyl obtained by hydrogenating waxes grafted to hydrocarbon waxes using vinyl monomers such as styrene and acrylic acid, partially esterified products of fatty acids and polyhydric alcohols such as behenic acid monoglycerides, and vegetable oils and fats. Methyl Este Having a Group Compounds.

  The charge control agent is added to control the triboelectric charge amount. As the charge control agent, for example, a positively chargeable charge control agent such as a nigrosine dye, a quaternary ammonium compound, or a polyamine resin, or a metal-containing azo compound is used, and the metal element is a complex of iron, cobalt, or chromium. , Complex salts, or mixtures thereof, and metal-containing salicylic acid derivative compounds can also be used, and examples include negatively chargeable charge control agents such as complexes, complex salts, or mixtures of zirconium, zinc, chromium, and boron as metal elements.

  Examples of the surfactant include anionic surfactants such as sulfate ester-based, sulfonate-based, phosphate ester-based, and soap-based surfactants, and cationic surfactants such as amine salt type and quaternary ammonium salt type, Nonionic surfactants such as polyethylene glycol, alkylphenol ethylene oxide adducts, and polyhydric alcohols can be mentioned.

  When the toner according to the exemplary embodiment is manufactured through the aggregation and fusing process, an aggregating agent is used for manufacturing the toner according to the exemplary embodiment. Examples of the flocculant include sodium chloride, calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, magnesium sulfate, aluminum chloride, aluminum sulfate, potassium aluminum sulfate and other metal salts, and polyaluminum chloride and polyhydroxide. Inorganic metal salt polymers such as aluminum and calcium polysulfide, polymer flocculants such as polymethacrylate ester, polyacrylate ester, polyacrylamide, sodium acrylamide acrylate copolymer, polyamine, polydiallylammonium halide, melanin formaldehyde Condensates, coagulants such as dicyandiamide, methanol, ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, 2-methoxyethanol, 2-ethoxyethanol, Examples thereof include alcohols such as 2-butoxyethanol, organic solvents such as acetonitrile and 1,4-dioxane, inorganic acids such as hydrochloric acid and nitric acid, and organic acids such as formic acid and acetic acid.

  As the neutralizing agent, inorganic bases and amine compounds can be used. Examples of inorganic bases include sodium hydroxide and potassium hydroxide. Examples of amine compounds include dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, sec-butylamine, monoethanolamine, diethanolamine, triethanolamine, triisopropanolamine. , Isopropanolamine, dimethylethanolamine, diethylethanolamine, N-butyldiethanolamine, N, N-dimethyl-1,3-diaminopropane, N, N-diethyl-1,3-diaminopropane and the like.

  As the external additive, for example, 0.01 to 20% by weight of inorganic fine particles can be externally added and mixed with the toner particles in order to adjust fluidity and chargeability. As such inorganic fine particles, silica, titania, alumina, strontium titanate, tin oxide and the like can be used alone or in admixture of two or more. The inorganic fine particles are preferably surface-treated with a hydrophobizing agent from the viewpoint of improving environmental stability. In addition to such inorganic oxides, resin fine particles having a size of 1 μm or less may be externally added to improve cleaning properties.

  Next, a toner manufacturing method according to this embodiment will be described. The toner of the present exemplary embodiment can be manufactured, for example, by aggregating and fusing encapsulated colorants and binder resin particles.

Methods for forming the encapsulated colorant include interfacial polymerization, coacervation, in situ polymerization, submerged drying, submerged cured coating, and the like.
In particular, an in-situ method using melamine resin as a shell component, an interfacial polymerization method using urethane resin as a shell component, and the like are preferable.
In the case of the In-Situ method, first, the above three components (color developing compound, color developer, and decoloring agent added as necessary) are dissolved and mixed, and emulsified in a water-soluble polymer or surfactant aqueous solution. Let Then, it can encapsulate by adding melamine formalin prepolymer aqueous solution, heating, and superposing | polymerizing.
In the case of the interfacial polymerization method, the above three components and a polyvalent isocyanate prepolymer are dissolved and mixed and emulsified in a water-soluble polymer or a surfactant aqueous solution. Then, it can encapsulate by adding polyvalent bases, such as diamine or diol, and heat-polymerizing.
The volume D50 of the colorant is not particularly limited and can be appropriately set by those skilled in the art. However, when the volume D50 of the colorant is small, the colorant may have poor color developability. Even if a toner containing a colorant having poor properties is produced, a sufficient image density cannot be obtained.
Therefore, from the viewpoint of the color developability of the colorant, the volume D50 of the colorant is preferably 0.5 to 3.5 μm.
Further, it has been experimentally confirmed that when the volume D50 is outside the range of 0.5 to 3.5 μm, the colorant uptake is deteriorated as compared with the case where the volume D50 is within the range. The mechanism by which the incorporation of the small-diameter colorant deteriorates is not exactly known, but when using the encapsulated colorant, the incorporation into the binder resin is worsened when the particle size is less than a certain particle size, The amount of fine powder generated increases. (See FIG. 3 described later).

  Further, the encapsulated colorant depends on the specific color developing compound and the type of the color developer. For example, by placing the colorant at −20 to −30 ° C., the color developing compound and the color developer. To develop color.

  Subsequently, the encapsulated colorant prepared as described above and particles containing a binder resin are aggregated. Specifically, an aggregating agent is added to a dispersion in which a colorant and particles containing a binder resin are dispersed in a dispersion medium, for example, an aqueous dispersion medium such as water, and then heated to be aggregated. A person skilled in the art can appropriately set the type, amount of addition, and heating temperature of the flocculant.

Next, the fluidity of the binder resin is increased by heating, and the aggregated first aggregated particles and resin fine particles are fused.
A person skilled in the art can appropriately set the heating temperature in the fusion process.
In addition, it is preferable that the circularity of the particle | grains obtained by a melt | fusion process is 0.88-0.95, for example. When the circularity is lower than 0.88, the fusion is not sufficient, and the toner strength is small and easily cracked as compared with the case where the circularity is within the range, so that fine powder is easily generated. On the other hand, when the circularity is higher than 0.95, although the toner has strength, the mechanism is not clear, but the colorant is easily separated, and as a result, fine powder is likely to be generated as compared with the case where it is within the range. The circularity can be adjusted, for example, by changing the temperature during the fusion process (target temperature when the temperature is increased after adding the flocculant) and the time during which the fusion process is performed. Further, the size of the particles obtained by the fusing process is not particularly limited, and can be appropriately set by those skilled in the art in consideration of the particle diameter of the toner to be produced.

The circularity can be obtained by measurement using a flow type particle image measuring device.
Specifically, the particle diameter of the equivalent circle diameter is measured for particles in the range of the equivalent circle diameter of 0.60 to 400 μm using a flow type particle image analyzer. And the circularity of the measured particle | grain is calculated | required from following formula (1), and the value which remove | divided the sum total of circularity by the total particle number is made into circularity. Measurement is performed on 1000 to 1500 particles, and the calculated value is defined as the average circularity.

  In equation (1), n is the circularity, l is the circumference of a circle having the same projected area as the particle image, and m is the circumference of the projected image of the particle.

  Subsequently, the particles obtained by the fusing process are washed and dried to produce a toner. An external additive is externally added to the generated toner as necessary. The volume D50 of the electrophotographic toner is not particularly limited, but is preferably 4 to 20 μm from the viewpoint of toner handling and image quality.

  In the toner of the exemplary embodiment, the proportion of the component is not particularly limited, and can be appropriately set by those skilled in the art. The amount of the colorant contained in the electrophotographic toner is 5 to 35% by weight. Is preferred. If it is less than 5% by weight, the uptake is improved, but sufficient color developability cannot be ensured. If the amount is more than 35% by weight, it tends to be deposited on the toner surface, and if the toner is stressed due to an increase in the interface with the binder resin, fine powder is more likely to be generated than in the range.

The toner obtained by the toner manufacturing method of the present embodiment is mixed with a carrier and configured as a developer, like a normal toner, and is mounted on an image forming apparatus such as an MFP (Multi Function Peripheral) and recorded. Used for image formation on a medium.
In the image forming process, the toner image formed by the toner of the present embodiment transferred to the recording medium is heated at the fixing temperature. As a result, the resin melts and penetrates into the recording medium, and then the resin solidifies. An image is formed (fixing process).
The image formed on the recording medium can be erased by performing a toner decoloring process. Specifically, the color erasing treatment is performed by heating the recording medium on which an image is formed at a heating temperature equal to or higher than the color erasing start temperature to dissociate the bonded color former and developer. it can.

  Hereinafter, the toner of the exemplary embodiment will be described in more detail with reference to examples, but the invention is not limited to the examples.

[Preparation of resin / release agent mixed atomization dispersion 1]
After mixing 95 parts by weight of a polyester resin (Tg 52 ° C.) as a binder resin and 5 parts by weight of an ester wax as a release agent, the mixture was melt-kneaded using a biaxial kneader set at 120 ° C. to obtain a kneaded composition. .
The obtained kneaded composition was coarsely pulverized to a volume average particle size of 1.2 mm using a hammer mill manufactured by Nara Machinery Co., Ltd. to obtain coarse particles.
The coarse particles were medium pulverized to a volume average particle size of 0.05 mm using a bantam mill manufactured by Hosokawa Micron Corporation to obtain intermediate crushed particles.
30 parts by weight of ground particles, 1.2 parts by weight of sodium alkylbenzene sulfonate as an anionic surfactant, 1 part by weight of triethylamine as an amine compound, and 67.8 parts by weight of ion-exchanged water are treated and dispersed at 160 MPa and 180 ° C. using NANO3000. A dispersion having a volume average particle diameter of 500 nm was prepared.

[Preparation of resin / release agent mixed atomization dispersion 2]
After mixing 95 parts by weight of a polyester resin (Tg 57 ° C.) as a binder resin and 5 parts by weight of an ester wax as a release agent, the mixture was melt-kneaded using a biaxial kneader set at 120 ° C. to obtain a kneaded composition. .
The obtained kneaded composition was coarsely pulverized to a volume average particle size of 1.2 mm using a hammer mill manufactured by Nara Machinery Co., Ltd. to obtain coarse particles.
The coarse particles were medium pulverized to a volume average particle size of 0.05 mm using a bantam mill manufactured by Hosokawa Micron Corporation to obtain intermediate crushed particles.
30 parts by weight of crushed particles, 1.2 parts by weight of sodium alkylbenzene sulfonate as an anionic surfactant, 1 part by weight of triethylamine as an amine compound, and 67.8 parts by weight of ion-exchanged water were treated with NANO3000 at 160 MPa and 180 ° C., and volume averaged particles A dispersion having a diameter of 350 nm was prepared.

[Preparation of Colorant Dispersion 1]
1 part by weight of 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide as the leuco dye and 2,2-bis ( A component composed of 5 parts by weight of 4-hydroxyphenyl) hexafluoropropane and 50 parts by weight of a diester compound of pimelic acid and 2- (4-benzyloxyphenyl) ethanol as a decolorizer was dissolved by heating. A solution prepared by mixing 20 parts by weight of an aromatic polyvalent isocyanate prepolymer and 40 parts by weight of ethyl acetate as an encapsulating agent was added to 250 parts by weight of an 8% aqueous polyvinyl alcohol solution, and emulsified and dispersed. After stirring at 70 ° C. for about 1 hour, 2 parts by weight of a water-soluble aliphatic modified amine is added as a reactant, and the liquid temperature is kept at 90 ° C. and stirring is continued for about 3 hours to obtain colorless capsule particles. It was. Further, this capsule particle dispersion was put in a freezer (−30 ° C.) to develop a color, and a blue colored particle C1 dispersion was obtained. When the colored particles C1 were measured using SALD7000 manufactured by Shimadzu Corporation, the volume average particle diameter was 2 μm. The complete color erasing temperature Th was 79 ° C., and the complete color development temperature Tc was −20 ° C.

[Preparation of Colorant Dispersion 2]
2 parts by weight of 3- (4-diethylamino-2-hexyloxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide as the leuco dye, 1,1-bis as the developer From 4 parts by weight of (4′-hydroxyphenyl) hexafluoropropane, 4 parts by weight of 1,1-bis (4′-hydroxyphenyl) n-decane, and 50 parts by weight of caprylic acid-4-benzyloxyphenylethyl as a decoloring agent A solution in which 30 parts by weight of an aromatic polyvalent isocyanate prepolymer and 40 parts by weight of ethyl acetate are mixed as an encapsulating agent is mixed with an 8% aqueous solution of polyvinyl alcohol 300. After emulsifying and dispersing in parts by weight and continuing stirring at 70 ° C. for about 1 hour, 2.5 parts of a water-soluble aliphatic modified amine was added as a reactant, and an additional 6 Stirring was continued for between give a colorless capsule particles. Further, this capsule particle dispersion was put in a freezer (−30 ° C.) to develop a color, and a blue colored particle C2 dispersion was obtained. When the colored particles C2 were measured using SALD7000 manufactured by Shimadzu Corporation, the volume average particle diameter was 3.3 μm. The complete color erasing temperature Th was 55 ° C., and the complete color developing temperature Tc was −24 ° C.

[Preparation of Colorant Dispersion 3]
1 part by weight of 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide as the leuco dye and 2,2-bis ( 4-hydroxyphenyl) hexafluoropropane 5 parts by weight, and a component comprising 50 parts by weight of a diester compound of pimelic acid and 2- (4-benzyloxyphenyl) ethanol as a color erasing agent is heated and dissolved. A solution prepared by mixing 20 parts by weight of an aromatic polyvalent isocyanate prepolymer and 40 parts by weight of ethyl acetate as an encapsulating agent is put into 250 parts by weight of an 8% aqueous polyvinyl alcohol solution, and emulsified and dispersed. After continuing stirring for a period of time, 2 parts by weight of a water-soluble aliphatic modified amine was added as a reactant, and the liquid temperature was kept at 90 ° C. for about 1.5 hours. To give a colorless capsule particles continue. Further, this capsule particle dispersion was placed in a freezer to develop color, and a blue colored particle C3 dispersion was obtained. When the colored particles C3 were measured using SALD7000 manufactured by Shimadzu Corporation, the volume average particle diameter was 1.0 μm. The complete color erasing temperature Th was 79 ° C., and the complete color development temperature Tc was −30 ° C.

[Preparation of colorant dispersion 4]
1 part by weight of 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide as the leuco dye and 2,2-bis ( 4-hydroxyphenyl) hexafluoropropane 5 parts by weight, and a component comprising 50 parts by weight of a diester compound of pimelic acid and 2- (4-benzyloxyphenyl) ethanol as a color erasing agent is heated and dissolved. A solution prepared by mixing 20 parts by weight of an aromatic polyvalent isocyanate prepolymer and 40 parts by weight of ethyl acetate as an encapsulating agent is put into 250 parts by weight of an 8% aqueous polyvinyl alcohol solution, and emulsified and dispersed. After stirring for an hour, 2 parts by weight of a water-soluble aliphatic modified amine was added as a reaction agent, and the liquid temperature was kept at 90 ° C. and stirring was continued for about 1 hour. Only to give a colorless capsule particles. Further, this capsule particle dispersion was placed in a freezer to develop color, and blue colored particle C4 dispersion was obtained. When the colored particles C1 were measured using SALD7000 manufactured by Shimadzu Corporation, the volume average particle diameter was 0.4 μm. The complete color erasing temperature Th was 79 ° C., and the complete color development temperature Tc was −35 ° C.

[Preparation of colorant dispersion 5]
2 parts by weight of 3- (4-diethylamino-2-hexyloxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide as the leuco dye, 1,1-bis as the developer From 4 parts by weight of (4′-hydroxyphenyl) hexafluoropropane, 4 parts by weight of 1,1-bis (4′-hydroxyphenyl) n-decane, and 50 parts by weight of caprylic acid-4-benzyloxyphenylethyl as a decoloring agent The resulting ingredients were uniformly heated and dissolved. A solution prepared by mixing 30 parts by weight of an aromatic polyvalent isocyanate prepolymer as an encapsulating agent and 40 parts by weight of ethyl acetate as an encapsulating agent is emulsified and dispersed in 300 parts by weight of an 8% aqueous polyvinyl alcohol solution. After stirring for about 1 hour, 2.5 parts by weight of a water-soluble aliphatic modified amine was added as a reactant, and stirring was further continued for 6.5 hours to obtain colorless capsule particles. Further, this capsule particle dispersion was put in a freezer to cause color development, and blue colored particle C5 dispersion was obtained. When the color-developing particles C5 were measured using a Shimadzu SALD7000, the volume average particle size was 3.6 μm. The complete color erasing temperature Th was 55 ° C., and the complete color developing temperature Tc was −24 ° C.

<Example 1>
15 parts by weight of the resin / release agent dispersion 1, 1.7 parts by weight of the colorant dispersion 1, and 68.5 parts by weight of ion exchange water were added and mixed. As a flocculant, 5 parts by weight of a 5% by weight aqueous aluminum sulfate solution was added at 30 ° C. After the addition of the metal salt, the temperature was raised to 40 ° C. and left for 1 hour. After adding 10 parts by weight of a 10 wt% aqueous sodium polycarboxylate salt solution, the temperature was raised to 70 ° C. and left for 1 hour.
After cooling, the solid content of the obtained dispersion was repeatedly centrifuged using a centrifuge, the supernatant removed, and washed with ion-exchanged water until the supernatant had a conductivity of 50 μS / cm. . Thereafter, the toner was dried by using a vacuum dryer until the water content became 1.0% by weight or less.
After drying, as additives, 2 parts by weight of hydrophobic silica and 0.5 parts by weight of titanium oxide were adhered to the toner particle surface to obtain a desired toner for electrophotography.

<Example 2>
15 parts by weight of resin / release agent dispersion 1, 1.7 parts by weight of colorant dispersion 2, and 68.5 parts by weight of ion-exchanged water were added and mixed. As a flocculant, 5 parts by weight of a 5% by weight aqueous aluminum sulfate solution was added at 30 ° C. After the addition of the metal salt, the temperature was raised to 40 ° C. and left for 1 hour. After adding 10 parts by weight of a 10 wt% aqueous sodium polycarboxylate salt solution, the temperature was raised to 70 ° C. and left for 1 hour.
After cooling, the solid content of the obtained dispersion was repeatedly centrifuged using a centrifuge, the supernatant removed, and washed with ion-exchanged water until the supernatant had a conductivity of 50 μS / cm. . Thereafter, the toner was dried by using a vacuum dryer until the water content became 1.0% by weight or less.
After drying, as additives, 2 parts by weight of hydrophobic silica and 0.5 parts by weight of titanium oxide were adhered to the toner particle surface to obtain a desired toner for electrophotography.

<Example 3>
15 parts by weight of the resin / release agent dispersion 1, 1.7 parts by weight of the colorant dispersion 3, and 68.5 parts by weight of ion exchange water were added and mixed. As a flocculant, 5 parts by weight of a 5% by weight aqueous aluminum sulfate solution was added at 30 ° C. After the addition of the metal salt, the temperature was raised to 40 ° C. and left for 1 hour. After adding 10 parts by weight of a 10 wt% aqueous sodium polycarboxylate salt solution, the temperature was raised to 70 ° C. and left for 1 hour.
After cooling, the solid content of the obtained dispersion was repeatedly centrifuged using a centrifuge, the supernatant removed, and washed with ion-exchanged water until the supernatant had a conductivity of 50 μS / cm. . Thereafter, the toner was dried by using a vacuum dryer until the water content became 1.0% by weight or less.
After drying, as additives, 2 parts by weight of hydrophobic silica and 0.5 parts by weight of titanium oxide were adhered to the toner particle surface to obtain a desired toner for electrophotography.

<Example 4>
15 parts by weight of the resin / release agent dispersion 1, 1.7 parts by weight of the colorant dispersion 1, and 68.5 parts by weight of ion exchange water were added and mixed. As a flocculant, 5 parts by weight of a 5% by weight aqueous aluminum sulfate solution was added at 30 ° C. After the addition of the metal salt, the temperature was raised to 40 ° C. and left for 1 hour. After adding 10 parts by weight of a 10% by weight aqueous solution of sodium polycarboxylate, the temperature was raised to 80 ° C. and left for 1 hour.
After cooling, the solid content of the obtained dispersion was repeatedly centrifuged using a centrifuge, the supernatant removed, and washed with ion-exchanged water until the supernatant had a conductivity of 50 μS / cm. . Thereafter, the toner was dried by using a vacuum dryer until the water content became 1.0% by weight or less.
After drying, as additives, 2 parts by weight of hydrophobic silica and 0.5 parts by weight of titanium oxide were adhered to the toner particle surface to obtain a desired toner for electrophotography.

<Example 5>
15 parts by weight of the resin / release agent dispersion 2, 1.7 parts by weight of the colorant dispersion 1, and 68.5 parts by weight of ion exchange water were added and mixed. As a flocculant, 5 parts by weight of a 5% by weight aqueous aluminum sulfate solution was added at 30 ° C. After the addition of the metal salt, the temperature was raised to 40 ° C. and left for 1 hour, and then 10 parts by weight of a 10% by weight aqueous polycarboxylic acid sodium salt solution was added, and then the temperature was raised to 75 ° C. and left for 1 hour.
After cooling, the solid content of the obtained dispersion was repeatedly centrifuged using a centrifuge, the supernatant removed, and washed with ion-exchanged water until the supernatant had a conductivity of 50 μS / cm. . Thereafter, the toner was dried by using a vacuum dryer until the water content became 1.0% by weight or less.
After drying, as additives, 2 parts by weight of hydrophobic silica and 0.5 parts by weight of titanium oxide were adhered to the toner particle surface to obtain a desired toner for electrophotography.

<Comparative Example 1>
15 parts by weight of the resin / release agent dispersion 1, 1.7 parts by weight of the colorant dispersion 4, and 68.5 parts by weight of ion-exchanged water were added and mixed. As a flocculant, 5 parts by weight of a 5% by weight aqueous aluminum sulfate solution was added at 30 ° C. After the addition of the metal salt, the temperature was raised to 40 ° C. and left for 1 hour. After adding 10 parts by weight of a 10% by weight aqueous solution of sodium polycarboxylate, the temperature was raised to 80 ° C. and left for 1 hour.
After cooling, the solid content of the obtained dispersion was repeatedly centrifuged using a centrifuge, the supernatant removed, and washed with ion-exchanged water until the supernatant had a conductivity of 50 μS / cm. . Thereafter, the toner was dried by using a vacuum dryer until the water content became 1.0% by weight or less.
After drying, as additives, 2 parts by weight of hydrophobic silica and 0.5 parts by weight of titanium oxide were adhered to the toner particle surface to obtain a desired toner for electrophotography.

<Comparative example 2>
15 parts by weight of the resin / release agent dispersion 1, 1.7 parts by weight of the colorant dispersion 5, and 68.5 parts by weight of ion-exchanged water were added and mixed. As a flocculant, 5 parts by weight of a 5% by weight aqueous aluminum sulfate solution was added at 30 ° C. After the addition of the metal salt, the temperature was raised to 40 ° C. and left for 1 hour. After adding 10 parts by weight of a 10% by weight aqueous solution of sodium polycarboxylate, the temperature was raised to 80 ° C. and left for 1 hour.
After cooling, the solid content of the obtained dispersion was repeatedly centrifuged using a centrifuge, the supernatant removed, and washed with ion-exchanged water until the supernatant had a conductivity of 50 μS / cm. . Thereafter, the toner was dried by using a vacuum dryer until the water content became 1.0% by weight or less.
After drying, as additives, 2 parts by weight of hydrophobic silica and 0.5 parts by weight of titanium oxide were adhered to the toner particle surface to obtain a desired toner for electrophotography.

<Comparative Example 3>
15 parts by weight of the resin / release agent dispersion 1, 1.7 parts by weight of the colorant dispersion 1, and 68.5 parts by weight of ion exchange water were added and mixed. As a flocculant, 5 parts by weight of a 5% by weight aqueous aluminum sulfate solution was added at 30 ° C. After adding the metal salt, the temperature was raised to 40 ° C. and left for 1 hour, and then 10 parts by weight of a 10% by weight polycarboxylic acid sodium salt aqueous solution was added, and the temperature was raised to 80 ° C. and left for 2 hours.
After cooling, the solid content of the obtained dispersion was repeatedly centrifuged using a centrifuge, the supernatant removed, and washed with ion-exchanged water until the supernatant had a conductivity of 50 μS / cm. . Thereafter, the toner was dried by using a vacuum dryer until the water content became 1.0% by weight or less.
After drying, as additives, 2 parts by weight of hydrophobic silica and 0.5 parts by weight of titanium oxide were adhered to the toner particle surface to obtain a desired toner for electrophotography.

<Comparative example 4>
15 parts by weight of the resin / release agent dispersion 1, 1.7 parts by weight of the colorant dispersion 1, and 68.5 parts by weight of ion exchange water were added and mixed. As a flocculant, 5 parts by weight of a 5% by weight aqueous aluminum sulfate solution was added at 30 ° C. After the addition of the metal salt, the temperature was raised to 40 ° C. and left for 1 hour, and then 10 parts by weight of a 10% by weight polycarboxylic acid sodium salt aqueous solution was added, and then the temperature was raised to 65 ° C.
After cooling, the solid content of the obtained dispersion was repeatedly centrifuged using a centrifuge, the supernatant removed, and washed with ion-exchanged water until the supernatant had a conductivity of 50 μS / cm. . Thereafter, the toner was dried by using a vacuum dryer until the water content became 1.0% by weight or less.
After drying, as additives, 2 parts by weight of hydrophobic silica and 0.5 parts by weight of titanium oxide were adhered to the toner particle surface to obtain a desired toner for electrophotography.

<Measurement using flow type particle image measuring device>
Measurement of particles of 0.6 μm or more and 2.5 μm or less was performed using a flow type particle image measuring device (FPIA2100, manufactured by Sysmex Corporation).
A toner sample was prepared as follows. First, 40 mg of a toner sample and 2 ml of an alkylbenzene sulfonate (dispersant) were added to a 100 ml beaker and ultrasonically dispersed for 5 minutes. The particle sheath liquid was added to the total amount of 30 ml and ultrasonically dispersed again for 5 minutes to obtain a toner measurement sample.
With respect to this measurement sample, a static image of the toner particles dispersed in the measurement sample is photographed and analyzed using a flow type particle image measuring apparatus, and 2000 or more toner particles are measured, and 0.6 μm or more and less than 400 μm. The particle size distribution of particles having a circle-equivalent diameter in a range was measured to obtain a value of the ratio (number%) of particles of 0.6 μm to 2.5 μm.
In addition, by preparing a sample of particles obtained by fusion so that the circularity of the particles obtained by fusion is 6000 × 10 ³ -15000 × 10 ³ particles / mL at the time of measurement, Obtained using an image measuring device.

<Determination of conditions for homogenizer treatment>
First, using the toner of Example 5, a 5 wt% toner dispersion was prepared. To 0.1 mL of 5 wt% toner dispersion, 0.1 mL of 10 wt% palm soap and 5.8 mL of ion exchange water were added to adjust the toner ratio to 0.08 wt%. Further, the dispersion dispersed at 0.08% by weight was diluted to prepare each dispersion in which the toner was dispersed at the ratio shown in FIG.
The volume D50 (μm) of the toner contained in each dispersion was 10.45 μm. From the measurement results using FPIA2100 (manufactured by Sysmex Corporation), the ratio of particles having a size of 0.6 μm to 2.5 μm was 12.39% by number.
Each dispersion having a different toner ratio was subjected to a stirring process using a T 25 Digital ULTRA-TURRAX (manufactured by IKA: Shaft Generator; S25N-10G) at the rotation speed and stirring time shown in FIG.
Further, the toner of Example 5 was mixed with a ferrite carrier coated with a silicone resin, loaded into a copying machine e-STUDIO4520C manufactured by Toshiba Tec Corporation, and operated for 3000 sheets under aging conditions. Then, the generated fine powder was confirmed by measurement using a flow type particle image measuring device. The said fine powder amount is shown as actual machine evaluation in FIG.
From the results shown in FIG. 1, when the toner is dispersed in water at a rate of 0.08% by weight and stirred for 30 minutes at a rotational speed of 5000 rpm, the stress equivalent to the stress applied to the toner in actual operation It can be appreciated that can be provided to the toner.
Therefore, the toner according to Example 1 is similarly loaded in the TOSHIBA TEC copier e-STUDIO4520C, and the toner is dispersed in water at a rate of 0.08% by weight for 30 minutes at a rotational speed of 5000 rpm. The amount of fine powder generated when the stirring treatment was performed was measured in the same manner. As a result, the amount of fine powder generated when the toner is dispersed in water at a rate of 0.08% by weight and stirred for 30 minutes at a rotational speed of 5000 rpm is very close to the amount of fine powder generated during operation of the actual machine. It was. FIG. 2 shows the amount of fine powder generated when the toner is dispersed in water at a rate of 0.08% by weight and stirred for 30 minutes at a rotational speed of 5000 rpm, and the amount of fine toner powder generated during operation of the actual machine.
Further, for the toners of other examples and comparative examples, the amount of fine powder generated when dispersed in water at a rate of 0.08% by weight and stirred for 30 minutes at a rotational speed of 5000 rpm is the actual machine operation. It was very close to the amount of toner fine powder generated.
From these results, the toner is dispersed in water at a ratio of 0.08% by weight, and the stirring process is performed for 30 minutes at a rotation speed of 5000 rpm, so that the toner is stressed in the same manner as in the actual machine. It is understood that

After determining the stirring conditions in this manner, the toners of the examples and comparative examples were stirred, and the equivalent circle diameter obtained using a flow type particle image measuring device (FPIA2100 manufactured by Sysmex Corporation) was 0.6 μm. The ratio (number%) of particles of 2.5 μm or less is shown in FIG. Similarly, for the toners of Examples and Comparative Examples, the volume average particle diameter D50 was measured using Multisizer 3 (aperture diameter 100 μm) manufactured by Beckman Coulter. In FIG. 2, the ratio (number%) of particles having a particle size of 0.6 μm to 2.5 μm and the volume D50 measured without homogenizer treatment, and the proportion of particles having a particle diameter of 0.6 μm to 2.5 μm after homogenizer treatment ( Number%) and the ratio of the volume average particle diameter D50 measured.
Furthermore, in FIG. 2, the circularity of the particles at the end of the fusion process, measured using a flow particle image measuring device, is also displayed.

<Evaluation of fog and toner scattering>
The toners of Examples and Comparative Examples were evaluated for fogging and toner scattering, and the results are shown in FIG.
Specifically, the fog was evaluated by measuring the reflectance of the first, second, and third sheets of the three sheets using X-Rite 938 and measuring the average value and the reflectance of the untransferred paper ( It was confirmed by the difference in the average value of 2 places / sheet.
In FIG. 3, A is less than 0.20, B is less than 0.30, C is less than 0.40, and D is 0.40 or more.
In addition, the evaluation of toner scattering was confirmed by loading 3000 sheets of paper into a copying machine e-STUDIO4520C manufactured by Toshiba Tec Corporation. In FIG. 3, the case where the scattering amount is less than 10 mg is indicated as A, the case where it is less than 25 mg is indicated as B, the case where it is less than 50 mg is indicated as C, and the case where it is 50 mg or more is indicated as D.

From the results of Examples and Comparative Examples, in the measurement using the flow type particle image measuring apparatus after the homogenizer treatment, particles having a particle size of 0.6 μm or more and 2.5 μm or less were 30% by number or less in fogging and toner scattering. Both obtained results superior to the comparative examples.
Further, in the case where the value of (B) / (A) expressed as the rate of change in the amount of fine powder in FIG. 3 was 2.0 or less, the fog and toner scattering could be further improved. further,
When the value of (D) / (C) expressed as the rate of change of volume D50 in FIG. 2 is 0.85 or more, fogging and toner scattering could be further improved.

<Evaluation of color erasability>
The toner of each example was mixed with a ferrite carrier coated with a silicone resin, and an image was output using an MFP (e-studio 4520c) manufactured by TOSHIBA TEC. Except for the toner according to Comparative Example 1 in which the fixing device temperature is set to 70 ° C. and the paper feed speed is adjusted to 30 mm / sec, the image density of the paper medium is 0. 5 colored images could be formed. For the toner according to Comparative Example 1, a sufficient image density could not be obtained.
In addition, when a paper medium on which a color image is formed with the toner of each embodiment is set at a fixing device temperature of 100 ° C. and conveyed at a paper feed speed of 100 mm / sec, the formed image may become colorless. confirmed.
Furthermore, when the paper medium from which the image was erased was stored in a freezer at −30 ° C., it was confirmed that the image density returned to 0.5 before the color erasure.

The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the scope of claims, and is not restricted by the text of the specification. Further, all modifications, various improvements, alternatives and modifications belonging to the equivalent scope of the claims are all within the scope of the present invention.
As described above in detail, according to the above-described embodiment, it is possible to provide a technique capable of improving the image quality of a decolorizable toner containing an encapsulated colorant.

Japanese Patent No. 4105718 JP 2009-300991 JP 2010-107849 A JP 2009-222940 JP 2005-70760 A JP 2009-294374 A

Claims (7)

A binder resin and a colorant containing at least a color developable compound and a developer and having a capsule structure covered with an outer shell,
The mixture was subjected to a stirring treatment in which the mixture was dispersed in an aqueous medium at a rate of 0.08% by weight and stirred for 30 minutes at 5000 rpm using a homogenizer (T 25 Digital ULTRA-TURRAX (IKA: Shaft Generator; S25N-10G)). A erasable electrophotographic toner in which particles having a circle-equivalent diameter of 0.6 μm or more and 2.5 μm or less are 30% by number or less in a measurement using a flow type particle image measuring apparatus for toner. The toner according to claim 1.
The ratio (A) of the number of particles having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less obtained by measurement using the flow type particle image measuring device of the toner,
The ratio (B) of the number of particles having an equivalent circle diameter of 0.6 μm or more and 2.5 μm or less obtained by measurement using the flow type particle image measuring device of the toner subjected to the stirring treatment is (B) / (A) An erasable electrophotographic toner satisfying the relationship of ≦ 2.0. The toner according to claim 1 or 2,
A decolorizable electrophotographic image in which the volume average particle diameter (C) of the toner and the volume average particle diameter (D) of the toner subjected to the stirring treatment satisfy a relationship of 0.85 ≦ (D) / (C). Toner. The toner according to any one of claims 1 to 3,
A color erasable electrophotographic toner in which the colorant has a volume average particle diameter of 0.5 to 3.5 μm. The toner according to claim 4.
An erasable electrophotographic toner in which the toner has a volume average particle diameter of 4 to 20 μm. Particles containing a binder resin, and a colorant having a volume average particle size of 0.5 to 3.5 μm, containing at least a color developing compound and a developer and having a capsule structure covered with an outer shell; Is dispersed in a dispersion medium,
A method for producing a decolorable electrophotographic toner, in which dispersed particles containing the binder resin and the colorant are aggregated and fused to obtain particles having a circularity of 0.88 to 0.95. In the toner production method according to claim 6,
A method for producing an electrophotographic toner, wherein the circularity value is obtained by measurement using a flow type particle image measuring device.

Images