JP3344169B2 - Electrostatic image developing toner and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic image for developing an electrostatic latent image formed by an electrophotographic method or an electrostatic recording method, and a method for producing the same.

[0002]

2. Description of the Related Art Methods for visualizing image information via an electrostatic image, such as electrophotography, are currently used in various fields. In the electrophotographic method, an electrostatic latent image is formed on a photoconductor by a charging and exposing process, developed with a developer containing a toner, and visualized through a transfer and fixing process of a 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 production of the toner is usually performed using a thermoplastic resin. Is kneaded with a pigment, a charge controlling agent, a releasing agent such as wax, and the like, and then cooled, finely pulverized, and then classified to obtain a kneading and pulverizing method. To these toners, inorganic and organic fine particles for improving fluidity and cleaning properties are added as necessary, and adhere to the surface of the toner particles.

In the ordinary kneading and pulverizing method, the shape of the toner and the surface structure of the toner are indefinite, and vary slightly depending on the pulverizability of the materials used and the conditions of the pulverizing process. Control is difficult. In particular, in the case of a toner using a material having high pulverizability, the toner is often pulverized due to mechanical force in a developing machine or the like, often causing generation of fine powder or change in toner shape. Due to these effects, in the case of a two-component developer, fine powder adheres to the surface of the carrier to accelerate the deterioration of the charge of the developer. , The image quality is likely to be degraded due to a decrease in developability due to the change in the image quality. In addition, when a toner such as a wax is internally added to form a toner, depending on the combination with a thermoplastic resin, the release agent is exposed on the surface and often has various effects upon development. In particular, in the case of a combination of a resin which is imparted with elasticity by a high molecular weight component and is hardly pulverized and a polyethylene wax, polyethylene is often exposed on the toner surface. Although these are advantageous in terms of releasability at the time of fixing and cleaning properties for removing untransferred toner from the photoreceptor, since the polyethylene wax on the surface is easily transferred by mechanical force, the developing roll, the photoreceptor and Carrier surface contamination is likely to occur, leading to lower reliability.

Further, since the toner has an irregular shape, the fluidity is not sufficient even by adding a fluidity aid.
During use, the fine particles on the toner surface move to the toner concave portion due to mechanical force, and the fluidity decreases over time, and the developability, transferability, and cleaning performance deteriorate. Further, when the toner collected by cleaning is returned to the developing machine and used again, the image quality is further likely to be deteriorated. If the flow aid is further increased in order to prevent these problems, there arises a problem that black spots are generated on the photoreceptor and the aid particles are scattered.

On the other hand, when the kneaded and pulverized toner is formed into a spherical shape, a change in shape due to mechanical force is less likely to occur, and the influence of the movement of the fluidity aid to the concave portions on the toner surface is reduced, so that the durability is increased. Further, usually, since the particle size selectivity in the development and transfer steps is relaxed, the maintainability of the developer is enhanced, and in particular, in toner recycling development in which the transfer residual toner on the photoreceptor is returned to the developing machine and reused, The effect of improving the durability of the developer is high. Also, even if you do not completely spherical,
Smoothing the surface of the toner obtained by the pulverization method,
Similar effects are often obtained even when the protrusions are deformed so as to be rounded. Examples of the sphering or deformation treatment of the toner include a method using mechanical force by a hybridizer or the like and a dry processing method such as a hot air treatment. However, the former has a problem that the processing time per unit weight is too long, and the spheroidization does not proceed sufficiently depending on the type of thermoplastic resin. Is necessary, and the chargeability tends to be abnormal due to decomposition and oxidation of the resin.
In order to increase the processing efficiency, there is a problem that coalescence between toner particles proceeds, and the particle size distribution largely moves to the large particle size side.

Another method of obtaining a spherical toner is to obtain a spherical toner by incorporating a toner component in a volatile solvent, mixing with water containing a dispersion stabilizer and emulsifying the mixture (Japanese Patent Laid-Open No. Sho 63-2).
No. 5664), a method in which a monomer composition containing a colorant is dispersed in water using a poorly water-soluble inorganic compound powder as a dispersion stabilizer, and then subjected to suspension polymerization (JP-A-4-19515).
Various methods have been proposed. However, these methods have problems in controllability of the shape and controllability of the particle size distribution, and are not yet satisfactory.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the toner obtained by the kneading and pulverizing method and the above-mentioned problems caused by the toner spheroidization. That is, an object of the present invention is to control the toner shape and the surface composition structure when used as a two-component developer to achieve good developing properties, transfer properties, fixing properties, and cleaning properties, and to reduce contamination of carriers and photoconductors. It realizes stable chargeability and, when used as a one-component developer, prevents contamination of the developing roll and photoreceptor by controlling the toner shape and surface composition structure. Stable image maintenance is achieved by fixing and cleaning properties, and even when toner collected by cleaning is returned to the developing machine and reused, a high-quality copy image can be formed stably. An object of the present invention is to provide a toner for developing an electrostatic image and a method for manufacturing the same.

[0008]

According to a first aspect of the present invention, there is provided a method for producing a toner for developing an electrostatic image, comprising the steps of mixing a binder resin and a colorant in a water-immiscible solvent. BET coated with a polymer having a carboxyl group
A step of dispersing in a water-based medium in the presence of a hydrophilic inorganic dispersant having a specific surface area of 10 to 50 m ² / g, and a step of removing a solvent from the obtained suspension by heating and / or reducing pressure. And A second method for producing a toner for developing an electrostatic image according to the present invention comprises a step of mixing a binder resin and a colorant in a solvent that is immiscible with water, and a step of mixing the obtained composition with a polymer having a carboxyl group. B coated with
Dispersing in an aqueous medium in the presence of a hydrophilic inorganic dispersant having an ET specific surface area of 10 to 50 m ² / g, diluting the obtained suspension with an aqueous medium, and heating the obtained suspension And / or a step of removing the solvent by reduced pressure. A third method of producing a toner for developing an electrostatic image according to the present invention comprises a step of mixing a binder resin and a colorant in a solvent that is immiscible with water, and a step of mixing the obtained composition with a polymer having a carboxyl group. Dispersing in an aqueous medium in the presence of a hydrophilic inorganic dispersant having a BET specific surface area of 10 to 50 m ² / g and a viscosity modifier coated with
It is characterized by comprising a step of diluting the obtained suspension with an aqueous medium and a step of removing a solvent from the obtained suspension by heating and / or reducing pressure.

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

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

Hereinafter, the present invention will be described in detail. In the present invention, in the first step, the binder resin and the colorant are mixed, but the mixing must be performed in a solvent that is immiscible with water. This is because, for example, Japanese Patent Application Laid-Open No. 52-9 / 1982
When mixed with a water-miscible organic solvent such as an alcohol disclosed in JP-A-435-435, it is advantageous for dispersion and the like when hydrophobic silica is used in combination, but the toner softened by heating. This is because coalescence of particles occurs, so that toner aggregation cannot be prevented unless the toner concentration in the medium is considerably reduced.

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

In the present invention, any known binder resin can be used. Specifically, thermoplastic resins, for example, styrene, parachlorostyrene, styrenes such as α-methylstyrene, methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, Esters having an unsaturated bond such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, acrylonitrile, nitriles having an unsaturated bond such as methacrylonitrile, vinyl methyl ether,
Vinyl ethers such as vinyl isobutyl ether, vinyl methyl ketone, vinyl ethyl ketone, vinyl ketones such as vinyl isopropenyl ketone, ethylene, propylene, a polymer or copolymer using monomers such as olefins such as butadiene, or These mixtures and the like, furthermore, epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, non-vinyl condensed resins such as polyether resins, these condensed resins mixed with the vinyl resin, these A graft polymer or the like obtained by polymerizing a vinyl monomer in the presence of the polymer can be used.

Examples of the coloring agent include carbon black, chrome yellow, Hansa yellow, benzidine yellow, slen yellow, quinoline yellow, permanent orange GRT, pyrazolone orange, vulcan orange, watching red, permanent red, brilliant carmine 3B, and brilliant carmine 6B. , Dupont Oil Red, Pyrazolone Red, Risor Red, Rhodamine B Lake, Lake Red C, Rose Bengal,
Examples include aniline blue, ultramarine blue, calcoil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, and malachite green oxalate.

In the present invention, the binder resin may contain a magnetic material, a charge controlling agent, a release agent, and the like as an internal additive, if necessary. Examples of the magnetic substance include metals such as ferrite, magnetite, reduced iron, cobalt, nickel, and manganese, alloys thereof, and compounds containing such metals. As the charge control agent, a quaternary ammonium salt compound, a nigrosine compound,
Known dyes such as dyes comprising complexes of aluminum, iron, chromium and the like, and triphenylmethane pigments can be used.

Examples of the releasing agent include low molecular weight polyolefins such as polyethylene, polypropylene and polybutene, silicone resins which are softened by heating, and fatty acid amides such as oleamide, erucamide, ricinoleamide and stearamide. , Carnauba wax,
Mineral / petroleum waxes such as rice wax, candelilla wax, vegetable wax such as wood wax, jojoba oil, animal wax such as beeswax, montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, And their modifications. When these release agents are used, generally, in the case of a wax containing a highly polar wax ester such as carnauba wax or candelilla wax, the amount of exposure of the wax on the surface of the toner particles is large, and conversely, polyethylene 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 to the surface of the toner particles decreases. The increase / decrease in the amount of the release agent on the toner surface can be qualitatively observed with a scanning electron microscope, and the Annual Conference of Japan Hard Copy f
or the Society of Electrophotography of Japan, p3
X-ray electron spectroscopy (X
PS) can be quantitatively confirmed.

The above components are added to a water-immiscible solvent,
For example, after mixing with a mixer such as a ball mill, the obtained composition is dispersed in an aqueous medium in the next step in the presence of a hydrophilic inorganic dispersant coated with a polymer having a carboxyl group. Although water is used as the aqueous medium, a solvent miscible with water or a dispersant may be added. Examples of such miscible solvents include alcohols such as methanol and ethanol, and ketones such as acetone. The hydrophilic inorganic dispersant used at that time is BET
It is necessary that the specific surface area is in the range of 10 to 50 m ² / g. When the BET specific surface area is smaller than 10 m ² / g, the primary particles of the hydrophilic inorganic dispersant become too large, and the dispersion stabilizing effect is reduced, causing agglomeration or a marked particle size distribution of the toner. Easy to spread.
If it is larger than 50 m ² / g, the hydrophilic inorganic dispersant is easily buried in the binder resin of the granulated particles, and after the operation of dissolving and removing the hydrophilic inorganic dispersant with acid, alkali or the like. Also remain in the suspended granulated particles, so that the charging property and the fixing property are likely to deteriorate.

The hydrophilic inorganic dispersant used in the present invention includes silica, alumina, titania, calcium carbonate, magnesium carbonate, tricalcium phosphate, clay,
Diatomaceous earth, bentonite and the like can be used, but calcium carbonate, magnesium carbonate and tricalcium phosphate are particularly preferred.

In the present invention, it is necessary that the surface of these hydrophilic inorganic dispersants 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. As a result, the particle size distribution of the toner can be narrowed. it can.

Examples of the polymer having a carboxyl group include:
1000 to 20,000 in number average molecular weight by VPO method etc.
About 0 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. If the molecular weight is too low, the contribution to the dispersibility is reduced. Specific examples of the polymer having a carboxyl group used in the present invention include, as typical examples, acrylic resin, methacrylic resin, fumaric resin, maleic resin, and the like. Not only homopolymers such as acrylic acid, methacrylic acid, fumaric acid, and maleic acid, 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, and a magnesium salt. As a method of coating the particle surface of the above-mentioned hydrophilic inorganic dispersant with a polymer having these carboxyl groups, a method of dissolving these polymers in water, adding a hydrophilic inorganic dispersant, mixing, drying and grinding is used. Alternatively, 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 from 0.01% by weight to 5.0% by weight, preferably from 0.03% by weight to
It is in the range of 3.0% by weight.

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

In the present invention, the dispersion treatment is carried out by adding the surface-coated hydrophilic inorganic dispersant to an aqueous medium in an amount of 0.05% by weight to 5.0% by weight, more preferably 0.2% by weight to 0.2% by weight.
What is necessary is just to make it contain so that it may become the density | concentration of the range of 3.0 weight%, and to stir. The addition of the hydrophilic inorganic dispersant may be previously added to the aqueous medium,
It may be added successively during the dispersion treatment to control the particle size distribution. The stirring can be performed by a known means such as a homomixer or the like, whereby a suspension in which the composition is suspended in fine particles can be obtained.

The suspension obtained as described above is diluted with an aqueous medium as required. Pure water is preferred as the aqueous medium. For dilution, the toner concentration after dilution is 2 to 4
It is desirable to carry out so as to be in the range of 0% by weight. Thereby, coalescence of toner particles can be effectively prevented.

Next, in a final step, the obtained suspension is heated and / or reduced in pressure to remove the solvent.
The heating is preferably carried out by holding the film in a moderate state, generally at a temperature of 50 ° C. to 90 ° C. for 1 to 6 hours. Further, the pressure reduction is preferably up to 6.1 × 10 ⁴ Pa (460 mmHg). After the solvent is removed by evaporation, the suspension is cooled, filtered, washed with water, and, if necessary, crushed and sieved to obtain a desired toner. In addition, as a hydrophilic inorganic dispersant, for example, when calcium carbonate or tricalcium phosphate is used,
It is preferable to add hydrochloric acid or sodium hydroxide to the suspension to dissolve the hydrophilic inorganic dispersant attached to the surface of the toner particles formed.

In the present invention, the obtained toner has a spherical shape with a controlled particle diameter, and particularly preferably a toner whose volume average particle diameter is controlled in the range of 3 to 9 μm.

[0026]

EXAMPLES The present invention will be described below in more detail 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 measurement of the particle size and its distribution was performed using a Coulter Counter TA2 (manufactured by Coulter). Example 1 85 g of styrene-n-butyl methacrylate resin (copolymerization ratio: 80:20, manufactured by Sanyo Chemical Co., Ltd.) (Mn = 9000, Mw = 120,000, Tg = 62 ° C.) 5 g of polyethylene wax fine powder (molecular weight 8000) (trade name) : 800P, manufactured by Mitsui Petrochemical Co., Ltd.) Carbon black (BPL, manufactured by Cabot) 10 g Polymer dispersant for pigment (trade name: Solsperse, manufactured by ICI) 2 g Ethyl acetate 300 g The above components were mixed and dispersed by a ball mill for 10 hours. I let it. The obtained dispersion was mixed with polyethylene glycol (#
BET specific surface area 18 m ² / g calcium carbonate (manufactured by Maruo Calcium Co.) 0.3% coated with 20% of 1000, Wako Pure Chemical Industries, Ltd. and 1% of acrylic acid-maleic acid copolymer (number average molecular weight 4000) Was added to an aqueous solution containing 1500 g, and subjected to a dispersion treatment for 3 minutes by a homomixer. Thereafter, the temperature was kept at 70 ° C. in a water bath and kept for 6 hours while stirring with a three-one motor. Thereby, particles having a volume average particle diameter of 7.5 μm were formed.
The particles in the obtained suspension had a percentage of 8.5% or less of 8.5% or less and a volume percentage of 20 μm or more of 0.1%.
% Having a very narrow particle size distribution. The shape was observed with a scanning electron microscope. As a result, it was confirmed that the shape showed a spherical shape having a slight concave portion and having no regularity.

Then, water is put into the water bath,
Cooled to 35 ° C. in 2 hours. 500 g of 1N hydrochloric acid was added, and the pure water washing treatment by suction filtration was repeated 5 times. Next, after drying with a vacuum dryer and crushing, 43 μm
Sieve with a net to obtain toner. In the obtained spherical toner,
0.6% of hydrophobic silica (diameter in terms of specific surface area: 12 nm) was added and mixed with a ferrite carrier having an average particle diameter of 65 μm at a weight ratio of 5:95 to obtain a developer. The transfer efficiency of this developer was evaluated by a copying machine equipped with a brush cleaning mechanism (Vivace 500 modified machine, manufactured by Fuji Xerox Co., Ltd.). As a result, this spherical toner showed a transfer efficiency of 99%. In addition, a continuous running test was performed by repeatedly using the spherical toner.
The image quality was good even after 50,000 copies were made, and the amount of toner destruction fine powder in the developer was quantified. As a result, there was almost no difference from the initial state, and no change was observed.

Comparative Example 1 Calcium carbonate in Example 1 was replaced with a BET specific surface area of 8
A toner was prepared under the same conditions except that the toner was changed to m ² / g. The volume average particle diameter of the obtained toner was 12.5 μm, and the percentage of 5 μm or less was 17.5 μm.
%, The volume percentage of 20 μm or more was 5.2%, and had a broad particle size distribution. When a continuous copying test was carried out using this toner in the same manner, a background stain and a decrease in density were observed after copying 50,000 sheets, and the amount of toner fine powder in the developer had increased to 38%.

Comparative Example 2 A toner was prepared under the same conditions as in Example 1 by using calcium carbonate having a BET specific surface area of 18 m ² / g and not subjected to surface coating treatment, under the same conditions as in Example 1. The diameter is 14.5 μm, the few percent below 5 μm is 13.5% and the volume percentage above 20 μm is 7.
4%, and had a broad particle size distribution. After crushing, 40% or more remained on the 43 μm net, and the yield was significantly reduced.

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

After that, water is poured into the water bath,
Cooled to 35 ° C. in 2 hours. 800 g of 1N hydrochloric acid was added, and the pure water washing treatment by suction filtration was repeated 5 times. Next, after drying with a vacuum dryer and crushing, 43 μm
Sieve with a net to obtain toner. In the obtained spherical toner,
0.8% of hydrophobic silica (diameter: 12 nm in terms of specific surface area) was added and mixed with a ferrite carrier having an average particle diameter 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 (Vivace 500 modified machine, manufactured by Fuji Xerox Co., Ltd.), this spherical toner showed a transfer efficiency of 98.0%.
When a continuous running test was performed using the spherical toner repeatedly, the image quality was good even after 100,000 copies were made.

Comparative Example 3 A toner was prepared under the same conditions except that the tricalcium phosphate in Example 2 was changed to a BET specific surface area of 55 m ² / g. The volume average particle diameter of the obtained toner was Was 4.5 μm, but as a result of cross-sectional observation with an electron microscope, it was found that tricalcium phosphate particles remained in the toner even after washing with addition of hydrochloric acid. 0.8% of hydrophobic silica (specific surface area converted diameter: 12 nm) was added to the toner, and mixed with a ferrite carrier having an average particle diameter of 50 μm to obtain a developer. As a result of a copy test, a slight decrease in image density was observed in 70,000 copies.

Example 3 Polyester resin (bisphenol resin, manufactured by Kao Corporation) 180 g (Mn = 4000, Mw = 30000, Tg = 62 ° C.) Carbon black (BP1300, manufactured by Cabot Corporation) 10 g Polymer dispersant for pigment (commercially available) (Name: Solsperse, manufactured by ICI) 1 g 300 g ethyl acetate The components having the above composition were mixed and dispersed by a ball mill for 10 hours. The resulting dispersion was coated with polymethacrylic acid (number average molecular weight 3000) and had a BET specific surface area of 30 m.
Aqueous solution 4 containing 0.6% ² / g tricalcium phosphate (prepared from sodium phosphate and calcium chloride)
Then, the mixture was dispersed for 7 minutes by a homomixer. Thereafter, the mixture 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. Thereby, substantially spherical particles having a volume average particle diameter of 8.2 μm were formed. The particles in the resulting suspension have a percentage of less than 4 μm of 1%.
It was 4.5%, the volume percentage of 20 μm or more was 0%, and the particle size distribution was slightly wider than that of Example 2, but within a range without any problem.

After that, water is put into the water bath,
Cooled to 35 ° C. in 2 hours. 800 g of 1N hydrochloric acid was added, and the pure water washing treatment by suction filtration was repeated 5 times. Next, after drying with a vacuum dryer and crushing, 43 μm
Sieve with a net to obtain toner. In the obtained spherical toner,
0.8% of hydrophobic silica (diameter: 12 nm in terms of specific surface area) was added and mixed with a ferrite carrier having an average particle diameter 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 (Vivace 500 modified machine, manufactured by Fuji Xerox Co., Ltd.), the spherical toner showed a transfer efficiency of 97.3%.
When the spherical toner was repeatedly used and subjected to a continuous running test, the image quality was good even after 80,000 copies were made.

[0035]

According to the present invention, the binder resin and the colorant are mixed in a solvent immiscible with water, and the resulting composition is coated with a polymer having a carboxyl group to a BET specific surface area of 10 to 50 m. ^{Since the} toner particles are dispersed in an aqueous medium in the presence of ² / g of a hydrophilic inorganic dispersant, coalescence of the formed toner particles is prevented, the particle size distribution is easily controlled, and a narrow particle size distribution is obtained. Spherical toner can be obtained.
Further, when a release agent is internally added to the toner, the exposure of the release agent to the surface of the suspended particles can be effectively controlled. For example, when a hydrophobic release agent such as paraffin wax is used, it can be taken into the inside of the particles at the time of dispersion and finally can be hardly exposed to the surface of the particles. Therefore, the toner for developing an electrostatic image obtained by the method of the present invention realizes good developing property, transfer property, fixing property, cleaning property and reduction of contamination of the carrier and the photoreceptor, and shows stable charging property. Further, even when the toner collected by cleaning is returned to the developing machine and reused, a high-quality copy image can be stably formed.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-161402 (JP, A) JP-A-60-121454 (JP, A) JP-A-7-152202 (JP, A) JP-A-5-152202 11497 (JP, A) JP-A-2-173666 (JP, A) JP-A-5-127422 (JP, A) JP-A-3-216664 (JP, A) JP-A-3-35250 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/087

Claims (4)

(57) [Claims] 1. A step of mixing a binder resin and a colorant in a solvent which is immiscible with water, and mixing the resulting composition with a BET specific surface area of 10 to 50 m ² / g coated with a polymer having a carboxyl group. A step of dispersing the suspension in an aqueous medium in the presence of a hydrophilic inorganic dispersant, and a step of removing a solvent from the obtained suspension by heating and / or reducing pressure. Production method. 2. A step of mixing a binder resin and a colorant in a solvent which is immiscible with water, and mixing the obtained composition with a BET specific surface area of 10 to 50 m ² / g coated with a polymer having a carboxyl group. Dispersing in an aqueous medium in the presence of a hydrophilic inorganic dispersant, diluting the obtained suspension with an aqueous medium, and removing a solvent from the obtained suspension by heating and / or reducing pressure A method for producing an electrostatic image developing toner, comprising: 3. A step of mixing a binder resin and a colorant in a water-immiscible solvent, and mixing the obtained composition with a BET specific surface area of 10 to 50 m ² / g coated with a polymer having a carboxyl group. Dispersing in an aqueous medium in the presence of a hydrophilic inorganic dispersant and a viscosity modifier, diluting the obtained suspension with an aqueous medium, and heating and / or depressurizing the obtained suspension to form a solvent. A process for producing a toner for developing an electrostatic image, characterized by comprising a step of removing toner. 4. A binder resin and a colorant are mixed in a water-immiscible solvent, and the resulting composition is coated with a polymer having a carboxyl group in a BET specific surface area of 10 to 50 m.
^{2. A} toner for developing an electrostatic image, comprising particles produced by dispersing in an aqueous medium in the presence of ² / g of a hydrophilic inorganic dispersant, and then removing the solvent by heating and / or reducing pressure. .