Toner for developing electrostatic charge image and its production

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a toner for developing an electrostatic charge image for developing an electrostatic latent image formed by an electrophotographic method, an electrostatic recording method, or the like, and a method for producing the same.

【0002】

[Conventional technology]

Methods for visualizing image information via electrostatic charge images, such as electrophotographic methods, are currently used in various fields. In the electrophotographic method, an electrostatic latent image is formed on a photoconductor by a charging and exposure process, developed with a developing agent containing toner, and visualized through a transfer and fixing process of the toner image. The developer used here includes a two-component developer composed of a toner and a carrier, and a one-component developer using a magnetic toner or a non-magnetic toner alone. The toner is usually produced by a thermoplastic resin. Is melt-kneaded together with a mold release agent such as a pigment, a charge control agent, and a wax, cooled, finely pulverized, and further classified by a kneading pulverization method. Inorganic and organic fine particles for improving fluidity and cleanability are added to these toners and adhere to the surface of the toner particles, if necessary.

【0003】

In the usual kneading and crushing method, the shape of the toner and the surface structure of the toner are irregular, and although they change slightly depending on the crushability of the material used and the conditions of the crushing process, it is difficult to intentionally control the shape and surface structure of the toner. Is. Further, in the case of a toner using a material having a particularly high pulverizability, it is often further pulverized due to mechanical force in a developing machine or the like, which causes the generation of fine powder or the change of the toner shape. Due to these effects, in the two-component developer, fine powder adheres to the carrier surface and the charge deterioration of the developer is accelerated, and in the one-component developer, the toner scatters due to the expansion of the particle size distribution, and the toner shape. Deterioration of image quality is likely to occur due to deterioration of developability due to changes in. Further, when a mold release agent such as wax is internally added to form a toner, the mold release agent is often exposed on the surface and has various effects on development depending on the combination with the thermoplastic resin. In particular, in the combination of polyethylene wax and a resin that is slightly hard to crush and has elasticity imparted by a high molecular weight component, polyethylene is often exposed on the toner surface. Although these are advantageous in terms of releasability at the time of fixing and cleaning property for removing untransferred toner from the photoconductor, the polyethylene wax on the surface is easily transferred by mechanical force, so that the developing roll, the photoconductor and the photoconductor The surface of the carrier is likely to be contaminated, leading to a decrease in reliability.

【0004】

In addition, since the toner shape is irregular, the fluidity is not sufficient even with the addition of a fluidity aid, and the fine particles on the toner surface move to the toner recesses due to mechanical force during use, resulting in fluidity over time. Deteriorates, and developability, transferability, and cleanability deteriorate. Further, when the toner recovered by cleaning is returned to the developing machine and used, the image quality is likely to be further deteriorated. If the amount of the fluidity aid is further increased in order to prevent these, there arises a problem that black spots are generated on the photoconductor and the auxiliary agent particles are scattered.

【0005】

On the other hand, when the kneaded and pulverized toner is made spherical, the shape change due to mechanical force is less likely to occur, and the influence of the movement of the fluidity aid to the toner surface recess is reduced, so that the durability is improved. In addition, since the particle size selectivity in the development and transfer steps is usually relaxed, the maintainability of the developer is improved, and particularly in toner recycling development in which the transfer residual toner on the photoconductor is returned to the developing machine and reused. It has a high effect of improving the durability of the developer. Further, even if the toner is not completely spherical, a similar effect can often be obtained by smoothing the surface of the toner obtained by the pulverization method or deforming the protrusions so as to be rounded. As an example of the spherical or deforming treatment of the toner, a mechanical force using a hybridizer or the like or a dry treatment method such as hot air treatment is generally used. However, the former has problems such as taking too much processing time per unit weight and insufficient spheroidization depending on the type of thermoplastic resin, and the latter usually has a temperature of 300 ° C or higher during processing. High temperature is required, and the resin is decomposed and oxidized, so that the chargeability tends to be abnormal. Also, when trying to improve the processing efficiency, the coalescence between the toner particles progresses and the particle size distribution is wide. There is a problem such as moving to the particle size side.

【0006】

As another method for obtaining spherical toner, a method in which a toner component is contained in a volatile solvent, mixed with water containing a dispersion stabilizer and emulsified to obtain spherical toner (Japanese Patent Laid-Open No. 63-25664), a colorant Various methods have been proposed, such as a method of dispersing a monomer composition containing the above in water using a poorly water-soluble inorganic compound powder as a dispersion stabilizer and then suspend polymerization (Japanese Patent Laid-Open No. 4-195153). ing. However, these methods have problems in terms of shape controllability and particle size distribution controllability, and are not yet sufficient.

【0007】

[Problems to be Solved by the Invention]

The present invention has been made for the purpose of solving the above-mentioned drawbacks of the toner by the kneading and pulverizing method and the above-mentioned problems due to the spheroidization of the toner. That is, an object of the present invention is to improve developability, transferability, fixability, cleanability, and reduce contamination of carriers and photoconductors by controlling the toner shape and surface composition structure when used as a two-component developer. It is realized and shows stable chargeability, and when used as a one-component developer, it prevents contamination of the developing roll and photoconductor by controlling the toner shape and surface composition structure, and has good developability and transferability. Stable image retention is achieved by fixability and cleanability, and even when the toner recovered by cleaning is returned to the developing machine and reused, a high-quality copy image can be stably formed. An object of the present invention is to provide a toner for developing an electrostatic charge image and a method for producing the same.

【0008】

[Means for solving problems]

The first method for producing a toner for static charge image development of the present invention is a step of mixing a binder resin and a colorant in a solvent immiscible with water, and the obtained composition is a polymer having a carboxyl group. BET specific surface area covered with 10-50 m²It is characterized by having a step of dispersing in an aqueous medium in the presence of a hydrophilic inorganic dispersant of / g, and a step of removing the solvent from the obtained suspension by heating and / or depressurizing. The second method for producing a toner for static charge image development of the present invention is a step of mixing a binder resin and a colorant in a solvent immiscible with water, and the obtained composition is a polymer having a carboxyl group. BET specific surface area covered with 10-50 m²A step of dispersing in an aqueous medium in the presence of / g of a hydrophilic inorganic dispersant, a step of diluting the resulting suspension with an aqueous medium, and heating and / or depressurizing the solvent from the resulting suspension. It is characterized by having a step of removing. The third method for producing a toner for static charge image development of the present invention is a step of mixing a binder resin and a colorant in a solvent immiscible with water, and the obtained composition is a polymer having a carboxyl group. BET specific surface area covered with 10-50 m²The step of dispersing in an aqueous medium in the presence of / g of hydrophilic inorganic dispersant and viscosity modifier, the step of diluting the resulting suspension with an aqueous medium, and heating and / or from the resulting suspension. It is characterized by having a step of removing the solvent by reducing the pressure.

【0009】

In the present invention, after mixing the binder resin and the colorant in a solvent immiscible with water, the obtained composition is coated with a polymer having a carboxyl group and has a BET specific surface area of 10 to 50 m.²Disperse in an aqueous medium in the presence of / g of a hydrophilic inorganic dispersant and remove the solvent from the resulting suspension by heating and / or depressurization so that the resulting toner is spherical.

【0010】

In this case, in order to effectively suppress the coalescence of particles during solvent evaporation, the binder resin and the colorant are mixed in a solvent that is immiscible with water, and are water-based in the presence of the above-mentioned hydrophilic inorganic dispersant. After dispersion in the medium, it is effective to further dilute the resulting suspension with an aqueous medium and then remove the solvent by heating and / or depressurization. Further, when a viscosity modifier having a high affinity for water is added when dispersing in an aqueous medium in the presence of the above hydrophilic inorganic dispersant, the shear stress at the time of dispersion works effectively and at a high solute concentration. The particle size and particle size distribution can be controlled, and coalescence after dispersion can be prevented. Further, when the suspension obtained by the dispersion treatment is diluted with an aqueous medium, it is more preferable because the influence of the viscosity modifier and the like on the toner can be controlled to the minimum.

【0011】

Hereinafter, the present invention will be described in detail. In the present invention, the binder resin and the colorant are mixed in the first step, but the mixing needs to be performed in a solvent that is immiscible with water. This is because, for example, when mixing with a water-miscible organic solvent such as alcohol as disclosed in Japanese Patent Application Laid-Open No. 52-9435, the dispersion and the like when hydrophobic silica is used in combination, etc. However, since the toner particles softened by heating are coalesced, the toner aggregation cannot be prevented unless the toner concentration in the medium is considerably reduced.

【0012】

In the present invention, the solvent immiscible with water means a solvent having a solubility in water of 30% or less at room temperature, and specifically, an ether solvent such as diethyl ether and isopropyl ether, dichloromethane, chloroform, and carbon tetrachloride. Halogenated hydrocarbon solvents such as ethyl acetate, methyl acetate, n-propyl acetate and other ester solvents, toluene, xylene and other hydrocarbon solvents, methyl ethyl ketone, methyl isobutyl ketone and other ketone solvents, or the like. It can be a mixture or the like.

【0013】

As the binder resin in the present invention, any known binder can be used. Specifically, thermoplastic resins such as styrenes such as styrene, parachlorostyrene, α-methylstyrene, methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, Esters having unsaturated bonds such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, nitriles having unsaturated bonds such as acrylonitrile and methacrylic nitrile, vinyl methyl Polymers or copolymers using monomers such as vinyl ethers such as ether and vinylisobutyl ether, vinylketones such as vinylmethylketone, vinylethylketone and vinylisopropenylketone, and olefins such as ethylene, propylene and butadiene. , Or a mixture thereof, and further, a non-vinyl-based condensed resin such as an epoxy resin, a polyester resin, a polyurethane resin, a polyamide resin, a cellulose resin, or a polyether resin, or a mixture of these condensed resins with the vinyl-based resin. , A graft polymer obtained by polymerizing a vinyl-based monomer in the presence of these polymers can be used.

【0014】

Coloring agents include carbon black, chrome yellow, hanza yellow, benzine yellow, slene yellow, quinoline yellow, permanent orange GRT, pyrazolon orange, vulcan orange, watching red, permanent red, brilliant carmine 3B, brilliant carmin 6B, dupon oil. Examples include red, pyrazolone red, resole red, rhodamine B lake, lake red C, rose bengal, aniline blue, ultramarine blue, calcoyl blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, and malakite green oxalate.

【0015】

In the present invention, the binder resin may contain a magnetic substance, a charge control agent, a mold release agent, or the like as an internal additive, if necessary. Examples of the magnetic material include metals such as ferrite, magnetite, reduced iron, cobalt, nickel and manganese, alloys thereof, and compounds containing such metals. Examples of the charge control agent include known ones such as a quaternary ammonium salt compound, a niglosin compound, a dye composed of a complex of aluminum, iron, chromium and the like, and a triphenylmethane pigment.

【0016】

Examples of the mold release agent include low molecular weight polyolefins such as polyethylene, polypropylene and polybutene, silicone resins softened by heating, fatty acid amides such as oleic acid amide, erucic acid amide, ricinolic acid amide and stearic acid amide, and carnauba. Wax, rice wax, candelilla wax, wood wax, plant wax such as jojoba oil, animal wax such as beeswax, montan wax, ozokerite, selecin, paraffin wax, microcrystallin wax, fisher tropsh wax and other mineral / petroleum wax Wax and other modified products can be used. When these release agents are used, in general, in the case of a wax containing a highly polar wax such as carnauba wax or candelilla wax, the amount of wax exposed on the surface of the toner particles is large, and conversely, polyethylene is used. In the case of a wax having a small polarity such as wax or paraffin wax, the amount of exposure to the surface tends to decrease, but in the present invention, the amount of exposure of these release agents on the surface of the toner particles becomes small. The increase or decrease in the amount of mold release agent on the toner surface can be qualitatively observed with a scanning electron microscope, and the It can be confirmed quantitatively by X-ray electron spectroscopy (XPS) as proposed in the Annual Conference of Japan Hard Copy for the Society of Electrophotography of Japan, p33 (1989).

【0017】

After adding the above components to a solvent immiscible with water and mixing with a mixer such as a ball mill, the obtained composition is a hydrophilic inorganic dispersant coated with a polymer having a carboxyl group in the next step. Disperse in an aqueous medium in the presence of. Water is used as the aqueous medium, but a solvent miscible with water or a dispersant may be added. Examples of such a miscible solvent include alcohols such as methanol and ethanol and ketones such as acetone. The hydrophilic inorganic dispersant used at that time has a BET specific surface area of 10 to 50 m.²Must be in the / g range. BET specific surface area is 10m²When it is smaller than / g, the primary particles of the hydrophilic inorganic dispersant become too large and the dispersion stabilizing effect becomes small, and agglomeration tends to occur or the particle size distribution of the toner tends to be remarkably widened. Also 50m²If it is larger than / g, the hydrophilic inorganic dispersant is easily buried in the binding resin of the granulated particles, and it is suspended even after the operation of dissolving and removing the hydrophilic inorganic dispersant with an acid, alkali, etc. Since it remains in the granulated particles, its chargeability and fixability tend to deteriorate.

【0018】

As the hydrophilic inorganic dispersant used in the present invention, silica, alumina, titania, calcium carbonate, magnesium carbonate, tricalcium phosphate, clay, keiso soil, bentonite and the like can be used, and in particular, calcium carbonate, magnesium carbonate and phosphorus can be used. Tricalcium acid is preferred.

【0019】

In the present invention, these hydrophilic inorganic dispersants need that the surface of the particles thereof is coated with a polymer having a carboxyl group. As a result, the hydrophilic inorganic dispersant tends to become primary particles in water, and the dispersion of the hydrophilic inorganic dispersant on the surface of the suspended particles becomes uniform, and as a result, the particle size distribution of the toner can be narrowed. it can.

【0020】

As the polymer having a carboxyl group, a polymer having a number average molecular weight of about 1000 to 200,000 by the VPO method or the like can be used. If the molecular weight is extremely high, the adhesion to the surface of the suspended particles is too strong and the particles are buried in the particles, and if the molecular weight is too low, the contribution to dispersibility is small. Specific examples of the copolymer having a carboxyl group used in the present invention include acrylic acid-based resin, methacrylic acid-based resin, fumaric acid-based resin, maleic acid-based resin, and the like. Not only homopolymers such as acrylic acid, methacrylic acid, fumaric acid, and maleic acid, which are monomers, but also copolymers obtained by copolymerizing them with other vinyl monomers can be used. Further, the carboxyl group may have a salt structure such as a sodium salt, a potassium salt, or a magnesium salt. As a method of coating the particle surface of the hydrophilic inorganic dispersant with a polymer having these carboxyl groups, a method of dissolving these polymers in water, adding the hydrophilic inorganic dispersant, mixing, drying and pulverizing. , Or a method of mixing in a dry state at the time of crushing the hydrophilic inorganic dispersant can be used. The coating amount of the polymer having a carboxyl group is in the range of 0.01% by weight to 5.0% by weight, preferably 0.03% by weight to 3.0% by weight.

【0021】

In the present invention, a viscosity modifier may be further added to the above-mentioned aqueous medium. Examples of the viscosity modifier include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol and the like, and it is generally preferable to add them in the range of 2 to 40% by weight. It is also possible to use a surfactant in combination in order to enhance the dispersion stability. Examples of the surfactant include anionic surfactants such as sulfate ester type, sulfonate type and phosphoric acid ester type, cationic surfactants such as amine salt type and quaternary ammonium salt type, polyethylene glycol type and alkylphenol ethylene oxide. Nonionic surfactants such as adducts and polyhydric alcohols can be used.

【0022】

In the present invention, the dispersion treatment is carried out so that the surface-coated hydrophilic inorganic dispersant has a concentration in the aqueous medium in the range of 0.05% by weight to 5.0% by weight, more preferably 0.2% by weight to 3.0% by weight. It may be carried out by adding the mixture to the mixture and stirring the mixture. The hydrophilic inorganic dispersant may be added to the aqueous medium in advance, or may be added sequentially during the dispersion treatment in order to control the particle size distribution. Stirring can be performed by a known means such as a homomixer, whereby a suspension in which the composition is suspended in the form of fine particles is obtained.

【0023】

The suspension obtained as described above is diluted with an aqueous medium, if desired. Pure water is preferable as the aqueous medium. It is desirable that the dilution is performed so that the toner concentration after dilution is in the range of 2 to 40% by weight. Thereby, coalescence of toner particles can be effectively prevented.

【0024】

The resulting suspension is then heated and / or reduced in pressure in the final step to remove the solvent. Heating is preferably carried out in a gradual state, generally by holding at a temperature of 50 ° C to 90 ° C for 1 to 6 hours. The decompression is 6.1 x 10⁴Up to Pa (460 mmHg) is preferable. After the solvent has been removed by evaporation, the suspension can be cooled, filtered, washed with water and, if necessary, crushed and sieved to obtain the desired toner. When, for example, calcium carbonate or tricalcium phosphate is used as the hydrophilic inorganic dispersant, it adheres to the surface of the toner particles formed by adding hydrochloric acid, sodium hydroxide, or the like to the suspension. It is preferable to dissolve the hydrophilic inorganic dispersant.

【0025】

In the present invention, the obtained toner has a spherical shape in which the particle size is controlled, and it is particularly preferable that the volume average particle size is controlled in the range of 3 to 9 μm.

【0026】

[Example]

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. In the following description, all "parts" mean "parts by weight". The particle size and its distribution were measured using a Coulter counter TA2 type (manufactured by Coulter). Example 1 Styrene-n-butyl methacrylate resin 85g (Copolymerization ratio 80:20, manufactured by Sanyo Chemical Industries, Ltd.) (Mn = 9000, Mw = 120000, Tg = 62 ° C) Polyethylene wax fine powder (molecular weight 8000) 5g (Product name: 800P, manufactured by Mitsui Petrochemical Co., Ltd.) Carbon black (BPL, manufactured by Cabot) 10g Polymer dispersant for pigments (trade name: Solsparse, manufactured by ICI) 2g Ethyl acetate 300g The above components were mixed and dispersed by a ball mill for 10 hours. The obtained dispersion was coated with 20% polyethylene glycol (# 1000, manufactured by Wako Pure Chemical Industries, Ltd.) and 1% acrylic acid-maleic acid copolymer (number average molecular weight 4000) with a BET specific surface area of 18 m.²It was added to 1500 g of an aqueous solution containing 0.3% of / g calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) and dispersed by a homomixer for 3 minutes. Then, the temperature was maintained at 70 ° C. in a water bath, and the mixture was maintained for 6 hours while stirring with a three-one motor. As a result, particles having a volume average particle diameter of 7.5 μm were formed. The particles in the obtained suspension had a volume percentage of 5 μm or less of 8.5% and a volume percentage of 20 μm or more of 0.1%, and had a very narrow particle size distribution. Moreover, when the shape was observed with a scanning electron microscope, it was confirmed that the shape showed an irregular sphere with a slight recess.

【0027】

After that, water was poured into the water bath and cooled to 35 ° C in 2 hours. 500 g of 1N hydrochloric acid was added, and the pure water cleaning treatment by suction filtration was repeated 5 times. Then, it was dried in a vacuum dryer, crushed, and then sieved with a 43 μm net to obtain toner. Hydrophobic silica (diameter 12 nm in terms of specific surface area) of 0.6% was added to the obtained spherical toner, and the developer was mixed with a ferrite carrier having an average particle size of 65 μm at a weight ratio of 5:95 to obtain a developer. When the transfer efficiency of this developer was evaluated by a copying machine equipped with a brush cleaning mechanism (Vivace500 modified machine, manufactured by Fuji Xerox Co., Ltd.), this spherical toner showed a transfer efficiency of 99%. In addition, when the spherical toner was repeatedly used and a continuous running test was performed, the image quality was good even after copying 150,000 sheets, and when the toner-destroying fine powder in the developer was quantified, it was almost the same as the initial state. There was no difference and no change was observed.

【0028】

Comparative example 1 Calcium carbonate in Example 1 with a BET specific surface area of 8 m²When toner was prepared under the same conditions except that it was changed to / g, the volume average particle size of the obtained toner was 12.5 μm, the percentage of 5 μm or less was 17.5%, and the volume was 20 μm or more. The percentage was 5.2% and it had a wide particle size distribution. When a continuous copying test was carried out in the same manner using this toner, background stains and a decrease in density were observed after copying 50,000 sheets, and the amount of fine toner powder in the developer increased to 38%.

【0029】

Comparative example 2 In addition, BET specific surface area 18m²When a toner was prepared under the same conditions as in Example 1 using calcium carbonate which had not been surface-coated with / g, the volume average particle size of the obtained toner was 14.5 μm, and the percentage of the obtained toner was 5 μm or less. It was 13.5%, had a volume percentage of 20 μm or more of 7.4%, and had a wide particle size distribution. In addition, after crushing, more than 40% remained on the 43 μm network, and the yield was significantly reduced.

【0030】

Example 2 Polyester resin (bisphenol resin, manufactured by Kao Corporation) 180g (Mn = 6000, Mw = 70000, Tg = 64 ° C) Carbon black (BP1300, manufactured by Cabot) 20g Polymer dispersant for pigments (trade name: Solsparse, manufactured by ICI) 2g Ethyl acetate 300g The components having the above composition were mixed and dispersed by a ball mill for 10 hours. The obtained dispersion was coated with 20% glycerin and 1% polymethacrylic acid (number average molecular weight 3000), and had a BET specific surface area of 30 m.²It was added to 400 g of an aqueous solution containing 0.6% of tricalcium phosphate (prepared from sodium phosphate and calcium chloride) of / g, and dispersed for 3 minutes with a homomixer. Then, it was put into 2000 g of pure water, kept at 70 ° C. in a water bath, and kept for 6 hours while stirring with a three-one motor. As a result, almost spherical particles having a volume average particle diameter of 5.2 μm were formed. The particles in the obtained suspension had a volume percentage of 4 μm or less of 12.5% and a volume percentage of 20 μm or more of 0%, and had a very narrow particle size distribution.

【0031】

After that, water was poured into the water bath and cooled to 35 ° C in 2 hours. 800 g of 1N hydrochloric acid was added, and the pure water cleaning treatment by suction filtration was repeated 5 times. Then, it was dried in a vacuum dryer, crushed, and then sieved with a 43 μm net to obtain toner. To the obtained spherical toner, 0.8% of hydrophobic silica (specific surface area equivalent diameter 12 nm) was added, and the developer was mixed with a ferrite carrier having an average particle size of 50 μm at a weight ratio of 5:95 to obtain a developer. When the transfer efficiency of this developer was evaluated by a copying machine (Vivace500 modified machine, manufactured by Fuji Xerox Co., Ltd.), this spherical toner showed a transfer efficiency of 98.0%. Further, when the spherical toner was repeatedly used and a continuous running test was conducted, the image quality was good even after 100,000 copies were made.

【0032】

Comparative example 3 Tricalcium phosphate in Example 2 with a BET specific surface area of 55 m²When toner was prepared under the same conditions except that it was changed to / g, the volume average particle size of the obtained toner was 4.5 μm, but as a result of cross-sectional observation with an electron microscope, even after cleaning with hydrochloric acid addition. It was found that tricalcium phosphate particles remained in the toner. 0.8% of hydrophobic silica (specific surface area equivalent diameter 12 nm) was added to this toner, and the mixture was mixed in the same manner as a ferrite carrier having an average particle size of 50 μm to obtain a developer, and then a continuous copying test similar to that of Example 2 was performed. As a result, a slight decrease in image density was observed in 70,000 copies.

【0033】

Example 3 Polyester resin (bisphenol resin, manufactured by Kao Corporation) 180g (Mn = 4000, Mw = 30000, Tg = 62 ° C) Carbon black (BP1300, manufactured by Cabot) 10g Polymer dispersant for pigments (trade name: Solsparse, manufactured by ICI) 1g Ethyl acetate 300g The components having the above composition were mixed and dispersed by a ball mill for 10 hours. The obtained dispersion was coated with polymethacrylic acid (number average molecular weight 3000) to have a BET specific surface area of 30 m.²It was added to 400 g of an aqueous solution containing 0.6% of tricalcium phosphate (prepared from sodium phosphate and calcium chloride) of / g, and dispersed for 7 minutes with a homomixer. Then, it was put into 2000 g of pure water, kept at 70 ° C. in a water bath, and kept for 6 hours while stirring with a three-one motor. As a result, almost spherical particles having a volume average particle diameter of 8.2 μm were formed. The particles in the obtained suspension had a volume percentage of 4 μm or less of 14.5% and a volume percentage of 20 μm or more of 0%, and had a slightly wider particle size distribution than in Example 2. However, it was within the range where there was no problem.

【0034】

After that, water was poured into the water bath and cooled to 35 ° C in 2 hours. 800 g of 1N hydrochloric acid was added, and the pure water cleaning treatment by suction filtration was repeated 5 times. Then, it was dried in a vacuum dryer, crushed, and then sieved with a 43 μm net to obtain toner. To the obtained spherical toner, 0.8% of hydrophobic silica (specific surface area equivalent diameter 12 nm) was added, and the developer was mixed with a ferrite carrier having an average particle size of 50 μm at a weight ratio of 5:95 to obtain a developer. When the transfer efficiency of this developer was evaluated by a copying machine (Vivace500 modified machine, manufactured by Fuji Xerox Co., Ltd.), this spherical toner showed a transfer efficiency of 97.3%. Further, when the spherical toner was repeatedly used and a continuous running test was conducted, the image quality was good even after 80,000 copies were made.

【0035】

[Effect of the invention]

In the present invention, the binder resin and the colorant are mixed in a solvent immiscible with water, and the obtained composition is coated with a polymer having a carboxyl group to have a BET specific surface area of 10 to 50 m.²Since it is dispersed in the aqueous medium in the presence of the hydrophilic inorganic dispersant of / g, the coalescence of the formed toner particles is prevented, the particle size distribution can be easily controlled, and the particle size distribution is narrow. Spherical toner can be obtained. Further, when the release agent is internally added to the toner, it is possible to effectively control the exposure of the release agent on the surface of the suspended particles. For example, when a hydrophobic mold release agent such as paraffin wax is used, it can be taken into the particles at the time of dispersion and finally exposed to the particle surface can be almost eliminated. Therefore, the toner for static charge image development obtained by the method of the present invention realizes good developability, transferability, fixability, cleanability, reduction of contamination of carriers and photoconductors, and exhibits stable chargeability. Further, even when the toner recovered by cleaning is returned to the developing machine and reused, a high-quality copy image can be stably formed.