JP7497672B2 - Toner manufacturing method - Google Patents

Description

The present invention relates to a method for producing a toner, such as a toner for developing an electrostatic image, which is used to develop an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing, etc.

In image forming devices such as electrophotographic devices, electrostatic recording devices, and electrostatic printing devices, a method of forming a desired image by developing an electrostatic latent image formed on a photoconductor with toner is widely used, and is applied to copiers, printers, facsimiles, and multifunction machines that combine these.

In such toners, a method of adhering an external additive such as inorganic fine particles to the surface of the colored resin particles is generally used to impart the desired chargeability and fluidity. As disclosed in Patent Document 1, a method of adhering an external additive such as inorganic fine particles to the surface of the colored resin particles involves mixing the colored resin particles with an external additive such as inorganic fine particles using a mixing device including a mixing tank and a rotatable stirring blade.

Japanese Patent Application Laid-Open No. 11-216347

On the other hand, in the method of mixing colored resin particles and external additives such as inorganic fine particles using a mixing device including a mixing tank and a rotatable stirring blade, as in the technology of Patent Document 1, when these are mixed, the toner particles may fuse together to generate coarse particles, which may cause vertical streaks, or the inorganic fine particles may not be dispersed sufficiently, causing photoreceptor filming due to poorly dispersed inorganic fine particles. Therefore, there has been a demand for a method of manufacturing a toner that effectively suppresses the occurrence of vertical streaks and photoreceptor filming while achieving high productivity.

The object of the present invention is to provide a method for producing toner with high productivity that effectively suppresses the occurrence of vertical streaks and photoreceptor filming.

The inventors conducted research to solve the above problems, and discovered that when mixing colored resin particles containing a binder resin and a colorant with inorganic fine particles, the above problems can be solved by using a mixing device in which the stirring blades constituting the mixing device have a main body and a protruding portion formed along the longitudinal direction of the main body and protruding from the bottom surface of the mixing tank, and the protruding height of the protruding portion is 1.0 mm or more, and by setting the width L of the protruding portion of the stirring blade, the number of rotations per second R of the stirring blade, and the number N of stirring blades included in the mixing device within specific ranges, thereby completing the present invention.

That is, according to the present invention, there is provided a method for producing a toner, comprising a mixing step of mixing colored resin particles containing a binder resin and a colorant with inorganic fine particles, the method comprising the steps of:
the mixing step is a step of mixing the colored resin particles and the inorganic fine particles by rotating the stirring blade in a mixing device including a mixing tank and a rotatable stirring blade in the mixing tank, thereby fixing the inorganic fine particles to the colored resin particles;
The mixing device is a device in which the stirring blade constituting the mixing device has a main body and a protruding portion formed along the longitudinal direction of the main body and protruding from the bottom surface of the mixing tank, and the protruding height of the protruding portion is 1.0 mm or more,
The toner production method includes the steps of: mixing the mixture under conditions represented by the following formula (1);
900≦L×R×N≦5000 (1)
(In the above formula (1), L is the width [mm] of the protruding part of the agitating blade, R is the rotation speed per second [rpm/60] of the agitating blade, and N is the number of agitating blades included in the mixing device.)

In the toner production method of the present invention, it is preferable that the distance between the protruding portion of the stirring blade and the bottom surface of the mixing tank is 0.5 to 6 mm.
In the toner production method of the present invention, it is preferable that the colored resin particles have a circularity of 0.980 or more.
In the toner production method of the present invention, it is preferable that the colored resin particles are obtained by a suspension polymerization method.
In the toner manufacturing method of the present invention, it is preferable that the colored resin particles have a volume average particle size of 3 to 11 μm, and the inorganic fine particles have a specific surface area of 1 to 400 m ² /g.
In the toner production method of the present invention, it is preferable to use two or more types of inorganic fine particles as the inorganic fine particles.

The present invention provides a method for producing toner that can produce toner with high productivity and effectively suppresses the occurrence of vertical streaks and photoreceptor filming.

FIG. 1 is a diagram showing a mixing device according to one embodiment used in the production method of the present invention. FIG. 2(A) is a bottom view of a lower rotating body constituting a mixing device according to one embodiment used in the manufacturing method of the present invention, and FIG. 2(B) is a cross-sectional view taken along line IIb-IIb of the lower rotating body constituting a mixing device according to one embodiment used in the manufacturing method of the present invention.

The toner manufacturing method of the present invention includes a mixing step in which colored resin particles containing a binder resin and a colorant are mixed with inorganic fine particles, and the mixing device and mixing conditions used in the mixing step are the specific device and conditions described below.

First, we will explain the method for producing the colored resin particles that make up the toner of the present invention.

The methods for producing the colored resin particles that constitute the toner of the present invention are broadly divided into dry methods such as pulverization and wet methods such as emulsion polymerization aggregation, dispersion polymerization, suspension polymerization, and dissolution suspension. Wet methods are preferred because they are more likely to produce toner with excellent printing characteristics such as image reproducibility. Among the wet methods, polymerization methods such as emulsion polymerization aggregation, dispersion polymerization, and suspension polymerization are more preferred because they are more likely to produce toner with a relatively small particle size distribution on the order of microns, and of these, suspension polymerization is more preferred.

The emulsion polymerization aggregation method is a method in which an emulsified polymerizable monomer is polymerized to obtain resin fine particles, which are then aggregated with a colorant or the like to produce colored resin particles. The dissolution suspension method is a method in which a solution in which toner components such as a binder resin and a colorant are dissolved or dispersed in an organic solvent is dripped into an aqueous medium to form droplets, and then the organic solvent is removed to produce colored resin particles. Both of these methods can be known.

The colored resin particles constituting the toner of the present invention can be produced by either a wet method or a dry method. When the colored resin particles are produced by adopting (A) the suspension polymerization method, which is preferred among the wet methods, or (B) the pulverization method, which is representative among the dry methods, the process is as follows. First, (A) the suspension polymerization method will be described.

(A) Suspension Polymerization Method (A-1) Preparation Step of Polymerizable Monomer Composition In the suspension polymerization method, first, a polymerizable monomer, a colorant, and other additives such as a charge control agent, which are used as necessary, are mixed and dissolved to prepare a polymerizable monomer composition. Mixing when preparing the polymerizable monomer composition is performed, for example, using a media type disperser.

In the present invention, the polymerizable monomer refers to a compound that can be polymerized, and the polymerizable monomer becomes a binder resin by polymerization. As the polymerizable monomer, it is preferable to use a monovinyl monomer as the main component constituting the polymerizable monomer. Examples of the monovinyl monomer include styrene-based monomers such as styrene, vinyl toluene, α-methylstyrene, and ethylstyrene; (meth)acrylate-based monomers such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and dimethylaminoethyl methacrylate; acrylic acid and methacrylic acid; nitrile compounds such as acrylonitrile and methacrylonitrile; amide compounds such as acrylamide and methacrylamide; and olefins such as ethylene, propylene, and butylene. These monovinyl monomers can be used alone or in combination of two or more. Of these, styrene-based monomers and (meth)acrylate-based monomers are preferred, with styrene and butyl acrylate being more preferred.

In order to improve hot offset and storage stability, it is preferable to use any crosslinkable polymerizable monomer together with the monovinyl monomer. A crosslinkable polymerizable monomer refers to a monomer having two or more polymerizable functional groups. Examples of crosslinkable polymerizable monomers include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; ester compounds in which two or more carboxylic acids are ester-bonded to an alcohol having two or more hydroxyl groups, such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; other divinyl compounds such as N,N-divinylaniline and divinyl ether; and compounds having three or more vinyl groups. These crosslinkable polymerizable monomers can be used alone or in combination of two or more. The amount of the crosslinkable polymerizable monomer used is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 2 parts by mass, and even more preferably 0.4 to 1 part by mass, relative to 100 parts by mass of the monovinyl monomer.

A macromonomer can also be used as part of the polymerizable monomer. Using any macromonomer is preferable because it provides a good balance between the storage stability and low-temperature fixability of the resulting toner. A macromonomer is a reactive oligomer or polymer having a polymerizable carbon-carbon unsaturated bond at the end of the molecular chain, and usually has a number average molecular weight (Mn) of 1,000 to 30,000. It is preferable that the macromonomer gives a polymer having a higher Tg (glass transition temperature) than the Tg of a polymer obtained without polymerizing the macromonomer. The amount of the macromonomer used is preferably 0.03 to 5 parts by mass, more preferably 0.05 to 1 part by mass, based on 100 parts by mass of the monovinyl monomer.

Examples of macromonomers include polyacrylic acid ester macromonomers, polymethacrylic acid ester macromonomers, polystyrene macromonomers, polyacrylonitrile macromonomers, silicone macromonomers, and copolymers of these macromonomers. Among these, polyacrylic acid ester macromonomers and polymethacrylic acid ester macromonomers are preferred.

In the present invention, colorants are used, but when producing color toners, black colorants, cyan colorants, yellow colorants, and magenta colorants can be used.

Black colorants that can be used include pigments and dyes such as carbon black, titanium black, and magnetic powders such as zinc iron oxide and nickel iron oxide.

Cyan colorants include, for example, copper phthalocyanine pigments, their derivatives, and compounds such as anthraquinone pigments and dyes. Specific examples include C.I. Pigment Blue 2, 3, 6, 15, 15:1, 15:2, 15:3, 15:4, 16, 17:1, and 60.

As yellow colorants, for example, compounds such as monoazo pigments, azo pigments such as disazo pigments, condensed polycyclic pigments, and dyes are used. Specific examples include C.I. Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 93, 97, 120, 138, 151, 155, 180, 181, 185, 186, 214, 219, C.I. Solvent Yellow 98, 162, etc.

As magenta colorants, for example, compounds such as monoazo pigments, azo pigments such as disazo pigments, condensed polycyclic pigments, dyes, etc. are used. Specific examples include C.I. Pigment Red 31, 48, 57:1, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 150, 163, 170, 184, 185, 187, 202, 206, 207, 209, 251, C.I. Solvent Violet 31, 47, 59, and C.I. Pigment Violet 19.

In the present invention, each colorant may be used alone or in combination of two or more kinds, and the amount of colorant used is preferably 1 to 10 parts by mass per 100 parts by mass of binder resin (100 parts by mass of polymerizable monomer for obtaining binder resin).

From the viewpoint of improving the releasability of the toner from the fixing roll during fixing, it is preferable to add a release agent to the polymerizable monomer composition. As the release agent, any agent generally used as a toner release agent can be used without any particular restrictions.

It is preferable that the release agent contains at least one of an ester wax and a hydrocarbon wax. By using these waxes as the release agent, it is possible to achieve a good balance between low-temperature fixability and storage stability.

Examples of ester waxes suitable for use as release agents include monoester compounds such as stearyl stearate, behenyl behenate, behenyl stearate, and stearyl behenate; pentaerythritol ester compounds such as pentaerythritol tetrapalmitate, pentaerythritol tetrabehenate, and pentaerythritol tetrastearate; glycerin ester compounds such as hexaglycerin tetrabehenate tetrapalmitate, hexaglycerin octabehenate, pentaglycerin heptabehenate, tetraglycerin hexabehenate, triglycerin pentabehenate, diglycerin tetrabehenate, and glycerin tribehenate; and dipentaerythritol ester compounds such as dipentaerythritol hexamyristate and dipentaerythritol hexapalmitate. Of these, monoester compounds are preferred.

Examples of hydrocarbon waxes suitable for use as release agents include polyethylene wax, polypropylene wax, Fischer-Tropsch wax, paraffin wax, microcrystalline wax, and petroleum wax. Of these, Fischer-Tropsch wax and petroleum wax are preferred, and petroleum wax is more preferred. The number average molecular weight of the hydrocarbon wax is preferably 300 to 800, and more preferably 400 to 600. The penetration of the hydrocarbon wax measured according to JIS K2235 5.4 is preferably 1 to 10, and more preferably 2 to 7.

In addition to the above release agents, other waxes that can be used include natural waxes such as jojoba, mineral waxes such as ozokerite, etc.

It is preferable to use one or more of the above-mentioned waxes in combination as the release agent. The amount of release agent used is preferably 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of binder resin (100 parts by mass of polymerizable monomer for obtaining binder resin).

As other additives, positively or negatively charged charge control agents can be used to improve the chargeability of the toner. There are no particular limitations on the charge control agents as long as they are generally used as charge control agents for toners, but among charge control agents, positively or negatively charged charge control resins are preferred because they have high compatibility with polymerizable monomers and can impart stable chargeability (charge stability) to toner particles, and from the viewpoint of obtaining a positively charged toner, positively charged charge control resins are more preferably used.

Positively charged charge control agents include nigrosine dyes, quaternary ammonium salts, triaminotriphenylmethane compounds, and imidazole compounds, as well as polyamine resins, quaternary ammonium-containing copolymers, and quaternary ammonium salt-containing copolymers, which are preferably used as charge control resins.

Negatively chargeable charge control agents include azo dyes containing metals such as Cr, Co, Al, and Fe, metal salicylate compounds, and metal alkylsalicylate compounds, as well as sulfonic acid-containing copolymers, sulfonate-containing copolymers, carboxylic acid-containing copolymers, and carboxylate-containing copolymers, which are preferably used as charge control resins.

The amount of charge control agent used is preferably 0.01 to 10 parts by weight, and more preferably 0.03 to 8 parts by weight, per 100 parts by weight of binder resin (100 parts by weight of polymerizable monomer for obtaining binder resin). By keeping the amount of charge control agent used within the above range, the occurrence of fog and print smears can be effectively suppressed.

As another additive, it is preferable to use a molecular weight regulator when polymerizing the polymerizable monomer that becomes the binder resin. The molecular weight regulator is not particularly limited as long as it is one that is generally used as a molecular weight regulator for toners, and examples thereof include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2,4,6,6-pentamethylheptane-4-thiol; thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N,N'-dimethyl-N,N'-diphenylthiuram disulfide, and N,N'-dioctadecyl-N,N'-diisopropylthiuram disulfide; and the like. These molecular weight regulators may be used alone or in combination of two or more kinds.

The amount of molecular weight regulator used is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of binder resin (100 parts by mass of polymerizable monomer for obtaining binder resin).

(A-2) Suspension step for obtaining a suspension (droplet formation step)
Next, the polymerizable monomer composition containing the polymerizable monomer and the colorant obtained in the above (A-1) preparation step of the polymerizable monomer composition is dispersed in an aqueous dispersion medium, a polymerization initiator is added, and then droplets of the polymerizable monomer composition are formed. Here, "suspension" means that droplets of the polymerizable monomer composition are formed in an aqueous dispersion medium. The dispersion treatment for forming droplets can be performed using, for example, an apparatus capable of strong stirring, such as an in-line type emulsifying and dispersing machine (manufactured by Pacific Machinery Works, product name: Milder) or a high-speed emulsifying and dispersing machine (manufactured by Primix Corporation, product name: T.K. Homomixer MARK II type).

Examples of polymerization initiators include persulfates such as potassium persulfate and ammonium persulfate; azo compounds such as 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobisisobutyronitrile; and organic peroxides such as di-t-butyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylbutanoate, diisopropyl peroxydicarbonate, di-t-butylperoxyisophthalate, and t-butylperoxyisobutyrate. These can be used alone or in combination of two or more. Of these, it is preferable to use organic peroxides because they can reduce residual polymerizable monomers and have excellent print durability. Among organic peroxides, peroxyesters are preferred because they have good initiator efficiency and can reduce the amount of residual polymerizable monomers, and non-aromatic peroxyesters, i.e., peroxyesters that do not have an aromatic ring, are more preferred.

As described above, the polymerization initiator may be added after the polymerizable monomer composition is dispersed in an aqueous medium and before droplets are formed, but it may also be added to the polymerizable monomer composition before it is dispersed in an aqueous medium (a medium whose main component is water).

The amount of polymerization initiator used in the polymerization of the polymerizable monomer composition is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 15 parts by mass, and even more preferably 1 to 10 parts by mass, per 100 parts by mass of binder resin (100 parts by mass of polymerizable monomer to obtain binder resin).

In the present invention, it is preferable to add a dispersion stabilizer to the aqueous medium. Examples of the dispersion stabilizer include inorganic compounds such as sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate, and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; and organic compounds such as water-soluble polymers such as polyvinyl alcohol, methyl cellulose, and gelatin; anionic surfactants; nonionic surfactants; and amphoteric surfactants. The above dispersion stabilizers can be used alone or in combination of two or more. The amount of the dispersion stabilizer added is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 10 parts by mass, relative to 100 parts by mass of the binder resin (100 parts by mass of the polymerizable monomer for obtaining the binder resin).

Among the above dispersion stabilizers, inorganic compounds, particularly colloids of poorly water-soluble metal hydroxides, are preferred. By using inorganic compounds, particularly colloids of poorly water-soluble metal hydroxides, the particle size distribution of the colored resin particles can be narrowed, and the amount of dispersion stabilizer remaining after washing can be reduced, so that the image reproduction by the resulting toner can be made clearer without deteriorating the environmental stability.

(A-3) Polymerization Step The desired suspension (aqueous dispersion medium containing droplets of the polymerizable monomer composition) obtained in the above (A-2) step of obtaining a suspension (droplet forming step) is heated to initiate polymerization, thereby obtaining an aqueous dispersion of colored resin particles containing a binder resin and a colorant.

The polymerization temperature in the present invention is preferably 50°C or higher, and more preferably 60 to 95°C. The polymerization time in the present invention is preferably 1 to 20 hours, and more preferably 2 to 15 hours.

In addition, from the viewpoint of carrying out polymerization in a state in which droplets of the polymerizable monomer composition are stably dispersed, in the polymerization process, following the step of obtaining the suspension (A-2) (droplet formation step), the polymerization reaction may be allowed to proceed while carrying out a dispersion treatment by stirring.

In the present invention, the colored resin particles thus obtained may be mixed with inorganic fine particles in a mixing step described below and used as a toner as is, but they may also be so-called core-shell type (also called "capsule type") colored resin particles, which are obtained by forming a core layer of colored resin particles obtained by a polymerization step and creating a shell layer different from the core layer on the outside. Core-shell type colored resin particles can further improve the storage stability and low-temperature fixability of the resulting toner by covering a core layer made of a material with a low softening point with a material with a higher softening point.

The method for producing the core-shell type colored resin particles is not particularly limited and can be produced by a conventionally known method, but in situ polymerization method and phase separation method are preferred from the viewpoint of production efficiency.

A method for producing core-shell type colored resin particles by in situ polymerization will be described below.
In the in situ polymerization method, a polymerizable monomer for forming a shell layer (polymerizable monomer for shell) and a polymerization initiator for shell are added to an aqueous dispersion medium in which colored resin particles are dispersed, and polymerization is carried out to obtain core-shell type colored resin particles.

As the polymerizable monomer for the shell, the same polymerizable monomers as those described above can be used. Among them, it is preferable to use a monomer that can give a polymer with a Tg of more than 80°C, such as styrene or methyl methacrylate, either alone or in combination of two or more kinds.

Examples of the shell polymerization initiator used in the polymerization of the shell polymerizable monomer include metal persulfates such as potassium persulfate and ammonium persulfate; water-soluble azo compounds such as 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide) and 2,2'-azobis-(2-methyl-N-(1,1-bis(hydroxymethyl)2-hydroxyethyl)propionamide); and the like. The amount of the shell polymerization initiator used is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, based on 100 parts by mass of the shell polymerizable monomer.

The polymerization temperature of the shell layer is preferably 50°C or higher, and more preferably 60 to 95°C. The polymerization time of the shell layer is preferably 1 to 20 hours, and more preferably 2 to 15 hours.

(A-4) Washing, Filtration, Dehydration, and Drying Steps After the polymerization is completed, the aqueous dispersion of the colored resin particles obtained by the polymerization step (A-3) is preferably subjected to a series of operations of washing, filtration, dehydration, and drying in a conventional manner, which are repeated several times as necessary.

First, in order to remove the dispersion stabilizer remaining in the aqueous dispersion of colored resin particles, it is preferable to add an acid or an alkali to the aqueous dispersion of colored resin particles and wash it. If the dispersion stabilizer used is an inorganic compound that is soluble in acid, it is preferable to add an acid to the aqueous dispersion of colored resin particles and wash it, while if the dispersion stabilizer used is an inorganic compound that is soluble in alkali, it is preferable to add an alkali to the aqueous dispersion of colored resin particles and wash it.

When an acid-soluble inorganic compound is used as the dispersion stabilizer, it is preferable to add an acid to the aqueous dispersion of colored resin particles to adjust the pH to preferably 6.5 or less, more preferably 6 or less. The acid to be added may be an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, or an organic acid such as formic acid or acetic acid, but sulfuric acid is particularly preferable because it has a high efficiency of removing the dispersion stabilizer and places a small burden on the manufacturing equipment.

The dehydration and filtration methods can be any of a variety of known methods, and are not particularly limited. Examples include centrifugal filtration, vacuum filtration, and pressure filtration. The drying method is also not particularly limited, and a variety of methods can be used.

(B) Pulverization Method When the pulverization method is used to produce colored resin particles, the process is as follows.
First, the binder resin, the colorant, and other additives such as a charge control agent, which are added as necessary, are mixed using a mixer, such as a ball mill, a V-type mixer, a Henschel mixer (trade name), a high-speed dissolver, an internal mixer, a Forberg, etc. Next, the mixture obtained above is kneaded while being heated using a pressure kneader, a twin-screw extrusion kneader, a roller, etc. The kneaded product obtained is coarsely pulverized using a pulverizer such as a hammer mill, a cutter mill, a roller mill, etc. Furthermore, after finely pulverizing using a pulverizer such as a jet mill or a high-speed rotary pulverizer, the particles are classified into the desired particle size using a classifier such as an air classifier or an airflow classifier, and colored resin particles can be obtained by a pulverization method.

The binder resin, colorant, charge control agent, and release agent used in the pulverization method, as well as other additives added as necessary, may be the same as those listed in the suspension polymerization method (A) above. The colored resin particles obtained by the pulverization method may also be made into core-shell type colored resin particles by a method such as in situ polymerization, like the colored resin particles obtained by the suspension polymerization method (A) above.

In addition to the above-mentioned binder resins, resins that have been widely used in toners can also be used as the binder resin. Specific examples of binder resins used in the pulverization method include polystyrene, styrene-butyl acrylate copolymers, polyester resins, and epoxy resins.

(Colored resin particles)
The colored resin particles can be obtained by the above-mentioned (A) suspension polymerization method or (B) pulverization method.
The colored resin particles will be described below. The colored resin particles described below include both core-shell type and non-core-shell type particles.

From the viewpoint of image reproducibility, the volume average particle diameter (Dv) of the colored resin particles is preferably 3 to 11 μm, more preferably 5 to 10 μm, even more preferably 6 to 9 μm, and particularly preferably 6.5 to 8 μm. By setting the volume average particle diameter (Dv) of the colored resin particles within the above range, it is possible to effectively suppress the decrease in toner fluidity and the resulting deterioration in image quality due to fogging, etc., while further increasing the resolution of the obtained image.

In addition, the particle size distribution (Dv/Dp), which is the ratio of the volume average particle size (Dv) to the number average particle size (Dp) of the colored resin particles, is preferably 1.0 to 1.3, and more preferably 1.0 to 1.2, from the viewpoint of image reproducibility. By setting the particle size distribution (Dv/Dp) of the colored resin particles in the above range, it is possible to more effectively suppress the decrease in the fluidity of the toner and the resulting deterioration in image quality due to fogging, etc., while further increasing the resolution of the obtained image. The volume average particle size (Dv) and number average particle size (Dp) of the colored resin particles can be measured, for example, using a particle size analyzer (manufactured by Beckman Coulter, product name: Multisizer) or the like.

In addition, from the viewpoint of image reproducibility, the average circularity of the above-mentioned colored resin particles is preferably 0.980 or more, more preferably 0.980 to 1.000, and even more preferably 0.985 to 1.000.

(Inorganic fine particles)
The inorganic fine particles used in the present invention can be any of those used as external additives for forming toner, including silica, titanium oxide, aluminum oxide, zinc oxide, tin oxide, calcium carbonate, calcium phosphate, and cerium oxide. Among these, silica is preferred. In addition, the inorganic fine particles may be used in a mixture of two or more types, for example, a mixture of different compounds such as silica and titanium oxide, or two types of silica with different particle sizes may be used in a mixture.

From the viewpoint of increasing the fluidity of the toner, it is preferable to use inorganic fine particles having a specific surface area of 1 to 400 m ² /g, more preferably 2 to 300 m ² /g, and even more preferably 3 to 200 m ² /g. The specific surface area can be measured by a nitrogen adsorption method (BET method) using a BET specific surface area measuring device.

The particle size of the inorganic fine particles is not particularly limited, but it is preferable to use two or more types of inorganic fine particles with different number average particle sizes, and more preferably a combination of small and large inorganic fine particles. Specifically, the number average particle size of the small particle side is preferably 5 to 35 nm, more preferably 7 to 30 nm, and even more preferably 10 to 25 nm. The number average particle size of the large particle side is preferably 40 to 200 nm, more preferably 45 to 150 nm, and even more preferably 48 to 100 nm. The number average particle size of the inorganic fine particles can be measured, for example, using a particle size analyzer (Horiba, product name: Partica LA-960) or the like.

(Organic fine particles)
In the present invention, organic fine particles may be used in addition to the inorganic fine particles described above.
Examples of organic fine particles include fatty acid metal salt particles such as zinc stearate and magnesium stearate, methacrylic acid ester polymer particles, acrylic acid ester polymer particles, styrene-methacrylic acid ester copolymer particles, styrene-acrylic acid ester copolymer particles, core-shell particles in which the core is made of a styrene polymer and the shell is made of a methacrylic acid ester polymer, melamine resin particles, and silicone resin particles.
The particle size of the organic fine particles is not particularly limited, but the number average particle size is preferably 0.1 to 2 μm, more preferably 0.3 to 1.5 μm, and even more preferably 0.3 to 1.0 μm. The number average particle size of the organic fine particles can be measured, for example, using a particle size analyzer (Horiba, Ltd., product name: Partica LA-960) or the like.

(Toner Manufacturing Method)
The toner production method of the present invention includes a mixing step of mixing the above-mentioned colored resin particles and the above-mentioned inorganic fine particles,
the mixing step is a step of mixing the colored resin particles and the inorganic fine particles by rotating the stirring blade in a mixing device including a mixing tank and a rotatable stirring blade in the mixing tank, thereby fixing the inorganic fine particles to the colored resin particles;
The mixing device is a device in which the stirring blade constituting the mixing device has a main body and a protruding portion formed along the longitudinal direction of the main body and protruding from the bottom surface of the mixing tank, and the protruding height of the protruding portion is 1.0 mm or more,
The mixing conditions in the mixing step are as shown in the following formula (1).
900≦L×R×N≦5000 (1)
(In the above formula (1), L is the width [mm] of the protruding part of the agitating blade, R is the rotation speed per second [rpm/60] of the agitating blade, and N is the number of agitating blades included in the mixing device.)

Here, FIG. 1 is a diagram showing a mixing device according to one embodiment used in the manufacturing method of the present invention. Below, the manufacturing method of the toner of the present invention will be explained using the mixing device shown in FIG. 1 as an example, but the present invention is not particularly limited to the embodiment shown in FIG. 1.

As shown in FIG. 1, a mixing device 10 according to one embodiment includes a mixing tank 20, a lower rotor 30, an upper rotor 40, a rotating shaft 50, and a deflector 60. In the mixing device 10, the rotating shaft 50 is rotated by a motor (not shown) located below the mixing tank 20, thereby allowing the lower rotor 30 and the upper rotor 40 to rotate.

In the manufacturing method of the present invention, the colored resin particles and the inorganic fine particles are mixed by rotating the lower rotor 30 and the upper rotor 40 located above the lower rotor 30 in the mixing tank 20, and the inorganic fine particles are fixed to the colored resin particles, thereby producing a toner. In other words, the colored resin particles are mixed with the inorganic fine particles, and the inorganic fine particles are fixed to the colored resin particles as an external additive, thereby performing an external addition process on the colored resin particles, and a toner is produced in which the inorganic fine particles are fixed to the surfaces of the colored resin particles.

2(A) shows a bottom view of the lower rotor 30 constituting the mixing device 10 (viewed from the bottom of the mixing tank 20 in the positive Z-axis direction), and FIG. 2(B) shows a cross-sectional view of the lower rotor 30 along line IIb-IIb in FIG. 2(A). As shown in FIG. 2(A) and FIG. 2(B), the lower rotor 30 has two stirring blades 30a, 30b symmetrically arranged around the rotation axis, and the two stirring blades 30a, 30b each have a main body 31a, 31b and a protruding portion 32a, 32b (hatched portion in FIG. 2(A) and FIG. 2(B)) that is formed along the longitudinal direction of the main body 31a, 31b and protrudes from the main body 31a, 31b toward the bottom side of the mixing tank 20. That is, when viewed from the bottom surface of the mixing vessel 20, the two stirring blades 30a, 30b have a portion where the protrusions 32a, 32b are formed, and a portion where the protrusions 32a, 32b are not formed (non-protrusion portion).

In the manufacturing method of the present invention, the lower rotating body 30 having such a configuration is rotated in the direction of the arrow shown in Figure 2 (A) (i.e., clockwise), and as a result, friction is generated between the colored resin particles and the inorganic fine particles due to the clearance C formed between the protruding surfaces of the protruding portions 32a, 32b of the two stirring blades 30a, 30b and the bottom surface of the mixing tank 20, and the inorganic fine particles are fixed to the surfaces of the colored resin particles while breaking down the agglomerations of the inorganic fine particles, thereby performing an external addition treatment on the colored resin particles. In this case, by setting the protruding height H of the protruding portions 32a, 32b to 1.0 mm or more, and by setting the width L [mm] of the protruding portions 32a, 32b, the number of rotations per second R [rpm/60] of the lower rotor 30, and the number N of the stirring blades to satisfy the following formula (1), it is possible to sufficiently break down the aggregation of the inorganic fine particles while suppressing the fusion of the toner particles, and further to ensure sufficient adhesion of the inorganic fine particles to the surfaces of the colored resin particles. This makes it possible to manufacture toner in which the occurrence of vertical streaks and photoreceptor filming is effectively suppressed with high productivity.
900≦L×R×N≦5000 (1)

The width L of the protrusions 32a, 32b, the number of rotations per second R of the lower rotating body 30, and the number N of the stirring blades may satisfy the above formula (1), but in order to make the effects of the present invention even more pronounced, it is more preferable that they satisfy the following formula (2), even more preferable that they satisfy the following formula (3), and particularly preferable that they satisfy the following formula (4).
925≦L×R×N≦4000 (2)
950≦L×R×N≦3000 (3)
975≦L×R×N≦2500 (4)

If the value of L x R x N is too small, the inorganic particles will not be dispersed sufficiently, and the poorly dispersed inorganic particles will be the cause of photoreceptor filming. On the other hand, if the value of L x R x N is too large, the toner particles will fuse together, generating coarse particles, which will result in vertical streaks.

As shown in FIG. 2(A), the width L of the protrusions 32a and 32b is the width in the direction perpendicular to the longitudinal direction of the protrusions 32a and 32b. If the width of the protrusions 32a and 32b in the direction perpendicular to the longitudinal direction is not uniform, the average value of the overall width of the protrusions 32a and 32b is calculated, and this is taken as the width L of the protrusions 32a and 32b. The width L of the protrusions 32a and 32b should satisfy the above formula (1) in relation to the number of rotations per second R of the lower rotor 30 and the number N of the stirring blades, and the width L of the protrusions 32a and 32b is preferably 10 to 100 mm, more preferably 12 to 70 mm, and even more preferably 15 to 50 mm.

The rotation speed R [rpm/60] per second of the lower rotor 30 (i.e., the value obtained by dividing the rotation speed [rpm] per minute by 60 seconds) should satisfy the above formula (1) in relation to the width L of the protrusions 32a, 32b and the number N of the stirring blades, and is preferably 16.67 to 83.33 rpm/60, more preferably 20 to 75 rpm/60, and even more preferably 21.67 to 66.67 rpm/60. The rotation speed [rpm] per minute of the lower rotor 30 is preferably 1000 to 5000 rpm, more preferably 1200 to 4500 rpm, and even more preferably 1300 to 4000 rpm.

The embodiment shown in FIG. 2(A) has two agitating blades, agitating blade 30a and agitating blade 30b, so the number N is 2. The number N of the agitating blades is not particularly limited to the embodiment shown in FIG. 2(A) where N=2, and may be 3 or more. The number N of the agitating blades may be one that satisfies the above formula (1) in relation to the width L of the protrusions 32a, 32b and the number of rotations per second R of the lower rotor 30, but is preferably 2 to 6, and more preferably 2 to 4.

In addition, in the two agitating blades 30a, 30b, the protruding height H of the protrusions 32a, 32b (i.e., the height of the protrusions 32a, 32b relative to the portion where the protrusions 32a, 32b are not formed (non-protrusion portion)) is 1.0 mm or more, preferably 1.2 to 12 mm, and more preferably 1.5 to 10 mm. According to the present invention, by setting L×R×N within the above range and setting the protruding height H of the protrusions 32a, 32b to 1.0 mm or more, deterioration due to wear of the agitating blades 30a, 30b can be appropriately suppressed, and thus toner in which the occurrence of vertical streaks and photoconductor filming is effectively suppressed can be produced with high productivity. On the other hand, if the protruding height H of the protruding parts 32a, 32b is too small or if the protruding parts 32a, 32b are not formed, the agitating blades 30a, 30b are likely to deteriorate due to wear, and the agitating blades 30a, 30b will need to be replaced more frequently, resulting in reduced productivity.

The mixing time T in the mixing step is not particularly limited, and generally the shorter the better, but it is preferably less than 1200 seconds, more preferably 60 to 1000 seconds, and even more preferably 60 to 600 seconds.

The distance between the protruding surfaces of the protruding portions 32a, 32b and the bottom surface of the mixing tank 20, i.e., the clearance C formed by the protruding surfaces of the protruding portions 32a, 32b and the bottom surface of the mixing tank 20, may be adjusted as appropriate depending on the size of the colored resin particles and inorganic fine particles used, but is preferably 0.5 to 6 mm, more preferably 1.0 to 5 mm, and even more preferably 1.5 to 4 mm. By setting the distance (clearance C) between the protruding surfaces of the protruding portions 32a, 32b and the bottom surface of the mixing tank 20 within the above range, it is possible to effectively suppress wear of the lower rotating body 30 while shortening the time required for external addition processing, thereby enabling further improvement in productivity.

In addition, the location of the protrusions 32a, 32b in the agitating blades 30a, 30b is not particularly limited, but from the viewpoint of further enhancing the effects of the present invention, it is preferable to form the protrusions 32a, 32b along the longitudinal direction of the agitating blades 30a, 30b at a position on the forward side with respect to the rotation direction, as shown in Fig. 2 (A). In addition, the length _Lp of the protrusions 32a, 32b formed in the longitudinal direction of the agitating blades 30a, 30b is not particularly limited, but from the viewpoint of further enhancing the effects of the present invention, when the length from the rotation center of the agitating blades 30a, 30b to the tip position (the position farthest from the rotation center) is the length _Lw of the agitating blades 30a, 30b, the length _Lp of the protrusions 32a, 32b is preferably 50% or more, more preferably 60% or more, and more preferably 70% or more, of the length _Lw of the agitating blades 30a, 30b. Moreover, it is preferable that the protrusions 32a, 32b are formed with a length _Lp extending from the tip position of the agitating blades 30a, 30b toward the center.

The protrusions 32a, 32b can be formed, for example, by spraying the same material as the main body parts 31a, 31b or a different material onto the main body parts 31a, 31b that constitute the agitating blades 30a, 30b.

In the mixing step, the amount of inorganic fine particles used is preferably 0.5 to 5 parts by weight, more preferably 0.6 to 4.5 parts by weight, and even more preferably 0.8 to 4 parts by weight, per 100 parts by weight of the colored resin particles. By using inorganic fine particles in the amount within the above range, it is possible to obtain a toner that has stable chargeability and flowability over time while suppressing adverse effects on the printing performance of the toner.

When silica is used as the inorganic fine particles, a surface treatment agent such as a silane coupling agent, silicone oil, fatty acid, or fatty acid metal soap may be used in combination to make the silica surface hydrophobic.

Examples of silane coupling agents include disilazanes such as hexamethyldisilazane; cyclic silazanes; trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane, and alkylsilane compounds such as silane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and vinyltriacetoxysilane; aminosilane compounds such as γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane, and N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane; and the like.

Examples of silicone oils include dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane, and amino-modified silicone oil.

The amount of the surface treatment agent used is preferably 0.5 to 5 parts by mass, more preferably 0.8 to 4 parts by mass, and even more preferably 1.0 to 3 parts by mass, per 100 parts by mass of inorganic fine particles.

When organic fine particles are used in the mixing step, the amount used is preferably 0.05 to 2 parts by weight, more preferably 0.07 to 1.5 parts by weight, and even more preferably 0.1 to 1.2 parts by weight, per 100 parts by weight of the colored resin particles. By keeping the amount of organic fine particles used within the above range, it is possible to provide the resulting toner with stable chargeability and fluidity over time while suppressing adverse effects on the printing performance of the toner.

The toner can be obtained by the manufacturing method of the present invention obtained as described above, and the manufacturing method of the present invention can produce a toner that effectively suppresses the occurrence of vertical streaks and photoreceptor filming with high productivity.

From the viewpoint of image reproducibility, the volume average particle diameter of the toner obtained by the manufacturing method of the present invention is preferably 3 to 11 μm, more preferably 5 to 10 μm, even more preferably 6 to 9 μm, and particularly preferably 6.5 to 8 μm. By setting the volume average particle diameter of the colored resin particles within the above range, it is possible to effectively suppress the decrease in the fluidity of the toner and the resulting deterioration in image quality due to fogging, etc., while further increasing the resolution of the obtained image. The volume average particle diameter of the toner can be measured, for example, using a particle size analyzer (manufactured by Beckman Coulter, product name: Multisizer) or the like.

The average circularity of the toner obtained by the manufacturing method of the present invention is preferably 0.980 or more, more preferably 0.980 to 1.000, and even more preferably 0.985 to 1.000, from the viewpoint of image reproducibility.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Note that "parts" and "%" are by mass unless otherwise specified.
The test methods used in the present examples and comparative examples are as follows.

(1) BET Specific Surface Area of Toner The BET specific surface area of the toner was measured by a nitrogen adsorption method (BET method) using a fully automatic BET specific surface area measuring device (manufactured by Mountec Co., Ltd., product name: Macsorb HM model-1208).

(2) Shear stress of toner (5 kPa)
The toner was subjected to shear stress measurement using a powder fluidity analyzer (manufactured by Freeman Technology, product name: Powder Rheometer FT-4) to determine the internal friction angle of the toner. Specifically, a 50 mm x 85 mm vessel was assembled with the powder fluidity analyzer, and 15 g of toner was uniformly placed in the vessel using a sieve. After the toner was placed, shear stress measurement was performed using a 48 mm shear stress measurement blade dedicated to the powder fluidity analyzer. At this time, the vertical load was changed from 1 kPa to 2 KPa to 4 KPa to 8 KPa to 10 kPa, and the shear load at each vertical load was measured. Then, for the obtained measurement results, an approximation line passing through the origin (X, Y = 0, 0) was obtained with the horizontal axis representing the vertical load and the vertical axis representing the shear load, and the shear load at 5 kPa of the obtained approximation line was taken as the shear stress (5 kPa).

(3) Blow-off charge amount of toner 9.5 g of carrier (manufactured by Powder Tech Co., Ltd., product name: NZ-3) and 0.5 g of toner were weighed, placed in a glass bottle with a volume of 100 cc, and rotated at a rotation speed of 150 rpm for 30 minutes. Next, using a blow-off meter (manufactured by Kyocera Chemical Co., Ltd., product name: TB-203), nitrogen gas was blown at a pressure of 4.5 kPa and sucked in at a pressure of 9.5 kPa to measure the blow-off charge amount (μQ/g) of the toner. The measurement was performed at a temperature of 23° C. and a relative humidity of 50%.

(4) Toner storage stability (59°C)
10 g of toner was placed in a container, which was then sealed and submerged in a thermostatic water bath at 59° C. for 5 hours before being taken out. The toner was transferred from the container onto a 42 mesh sieve with as little vibration as possible, and set in a powder measuring instrument (manufactured by Hosokawa Micron Corporation, product name: Powder Tester PT-R). The sieve was set to have an amplitude of 1.0 mm, and after 30 seconds of vibration, the weight of the toner remaining on the sieve was measured, which was taken as the weight of the aggregated toner. The high-temperature storage stability (%) of the toner was calculated from the ratio (weight %) of the weight of the toner remaining on the sieve (corresponding to the weight of the aggregated toner) to the measured weight of the toner (20 g). The smaller the value of the high-temperature storage stability (%) of the toner, the less the aggregated toner and the better the high-temperature storage stability.

(4) Volume average particle size and amount of coarse particles of toner The volume average particle size of the toner was measured by a particle size distribution measuring instrument (manufactured by Beckman Coulter, Inc., product name: Multisizer). The measurement by this Multisizer was performed under the conditions of aperture diameter: 100 μm, dispersion medium: Isoton II (product name), concentration: 10%, and number of particles measured: 100,000. Specifically, 0.2 g of a toner sample was placed in a beaker, and a surfactant aqueous solution (manufactured by Fuji Film Corporation, product name: Drywell) was added as a dispersant. 2 ml of the dispersion medium was further added thereto to wet the toner, and then 10 ml of the dispersion medium was added, and the mixture was dispersed by an ultrasonic disperser for 1 minute, and then the measurement was performed by the above particle size measuring instrument.
The particle diameter measured in the above manner was regarded as the volume average particle diameter of the toner, and the ratio of particles having a size of 20 μm or more in the volume average was regarded as the amount of coarse particles.

(5) Average circularity of toner 10 ml of ion-exchanged water was placed in a container, 0.2 g of a surfactant aqueous solution (manufactured by Fujifilm Corporation, product name: Drywell) was added as a dispersant, and 0.2 g of toner was further added, followed by dispersion treatment for 3 minutes at 60 W using an ultrasonic disperser. The toner concentration at the time of measurement was adjusted to 3,000 to 10,000 particles/μL, and 1,000 to 10,000 toner particles with a circle equivalent diameter of 0.4 μm or more were measured using a flow type particle image analyzer (manufactured by Sysmex Corporation, product name: FPIA-2100). The average circularity was calculated from the measured values. The circularity is expressed by the following formula, and the average circularity is the average of the formulas.
(Circularity) = (perimeter of a circle equal to the projected area of a particle) / (perimeter of a projected image of a particle)

(6) Amount of silica aggregates in toner Approximately 10 mg of toner was dropped onto a sieve with 45 μm openings, and the toner was sieved by sucking it up from the other side with a vacuum cleaner for powder. After removing the toner, the number of silica aggregates clogging the 45 μm openings was visually counted with a microscope, and the number counted was divided by the amount of toner weighed in mg to determine the number of silica aggregates per 1 mg.

(7) Number of sheets with vertical streaks and number of sheets with photoconductor filming A commercially available non-magnetic single-component development printer (resolution 600 dpi, print speed 28 sheets/min) was used, with printing paper set and toner put into the development device. After leaving the printer for 24 hours under normal temperature and humidity (N/N) environments of 23°C temperature and 50% RH humidity, continuous printing was performed up to 10,000 sheets at 5% print density in the same environment. Every 1,000 sheets, solid white printing (0% print density) and solid white printing (100% print density) were alternately performed three times, and the condition of the development roll was checked.
At this time, if streaks occurred on two or more sheets of solid white print (0% print density) or solid print (100% print density), it was determined that vertical streaks had occurred, and the number of printed sheets at that point was counted as the number of sheets with vertical streaks.
At the same time, the surface of the photoreceptor was also illuminated with light and visually observed. When it was confirmed that silica used as an external additive had adhered to the surface of the photoreceptor, it was determined that photoreceptor filming due to the external additive had occurred, and the number of printed sheets at that point was recorded as the number of sheets with photoreceptor filming.
In this test, it can be judged as good when the number of sheets on which vertical streaks occurred and the number of sheets on which photoconductor filming occurred are both 5,000 or more. The test was also terminated when the maximum number of printed sheets, 10,000, was reached.

[Production Example 1]
78 parts of styrene and 22 parts of n-butyl acrylate as polymerizable monomers, and 5 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, product name: #25B) as a black colorant were dispersed using an in-line type emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., product name: Milder) to obtain a polymerizable monomer mixture. Next, 1.0 part of a charge control resin (quaternary ammonium group-containing styrene acrylic resin) as a charge control agent, 5.0 parts of a fatty acid ester wax (behenyl behenate) as a mold release agent, 0.3 parts of a polymethacrylic acid ester macromonomer (manufactured by Toa Gosei Chemical Industry Co., Ltd., product name: AA6) as a macromonomer, 0.6 parts of divinylbenzene as a crosslinkable polymerizable monomer, and 1.6 parts of t-dodecyl mercaptan as a molecular weight regulator were added to the obtained polymerizable monomer mixture, mixed, and dissolved to prepare a polymerizable monomer composition.

On the other hand, at room temperature, an aqueous solution of 9.3 parts of sodium hydroxide (alkali metal hydroxide) in 50 parts of ion-exchanged water was gradually added to an aqueous solution of 15.2 parts of magnesium chloride (a water-soluble polyvalent metal salt) in 250 parts of ion-exchanged water while stirring to prepare a magnesium hydroxide colloid (poorly water-soluble metal hydroxide colloid) dispersion.

The suspension in which droplets of the polymerizable monomer composition were dispersed (polymerizable monomer composition dispersion) was placed in a reactor equipped with an agitator, and the temperature was raised to 90°C to initiate the polymerization reaction. When the polymerization conversion rate reached nearly 100%, 1 part of methyl methacrylate as a shell polymerizable monomer and 0.3 parts of 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)-propionamide) (manufactured by Wako Pure Chemical Industries, Ltd., trade name: VA-086, water-soluble) as a shell polymerization initiator dissolved in 10 parts of ion-exchanged water were added, and the reaction was continued at 90°C for 4 hours, and then the reaction was stopped by cooling with water to obtain an aqueous medium dispersion containing colored resin particles having a core-shell structure. The colored resin particles at this time had an average volumetric particle size of 7.0 μm and a circularity of 0.988. The average volumetric particle size and circularity were measured using the same methods as in (4) and (5) above.

Sulfuric acid was added dropwise to the aqueous dispersion of the colored resin particles while stirring at room temperature, and acid washing was performed until the pH reached 6.5 or less. Next, filtration and separation were performed, and 500 parts of ion-exchanged water was added to the obtained solid matter to reslurry it, and the water washing treatment (washing, filtration, dehydration) was repeated several times. Next, filtration and separation were performed, and the obtained solid matter was placed in the container of a dryer and dried at 45°C for 48 hours to obtain dried colored resin particles.

[Example 1]
To 100 parts of the colored resin particles obtained in Production Example 1, two types of inorganic fine particles as external additives: 0.90 parts of silica having a number average particle size of 20 nm (manufactured by Cabot Corporation, product name: TG-7120, BET specific surface area: 140 m ² /g) and 1.1 parts of silica having a number average particle size of 50 nm (manufactured by Wacker, product name: HDKH05TA, BET specific surface area: 50 m ² /g), and 0.20 parts of zinc stearate (manufactured by Sakai Chemical Industry Co., Ltd., product name: SPZ-100F) were added, and mixed using the stirrer shown in FIG. 1 (a stirrer using a high-speed stirrer (manufactured by Nippon Coke Company, product name: 150L FM Mixer) with protrusions 32a and 32b as shown in FIG. 2(A) and FIG. 2(B) as the stirring blades 30a and 30b). Thus, a toner was obtained. In Example 1, as shown in Figures 2(A) and 2(B), the lower rotor 30 is composed of two stirring blades 30a, 30b (the number of stirring blades N = 2), and has protruding parts 32a, 32b in the manner shown in Figure 2(A) (the formation length _Lp of the protruding parts 32a, 32b is about 80% of the length _LW of the stirring blades 30a, 30b), the width L of the protruding parts 32a, 32b is 19 mm, and the protruding height H of the protruding parts 32a, 32b is 8 mm. The mixing time T was 480 seconds, the rotation speed of the lower rotor 30 was 1540 rpm (the rotation speed per second R = 25.67 rpm/60), and the distance (clearance C) between the protruding parts 32a, 32b of the two stirring blades 30a, 30b and the mixing tank 20 was 2 mm.
The toner thus obtained was subjected to the respective measurements according to the above-mentioned methods. When the same mixing process was repeated, it was possible to produce toner at a production rate of 300 kg/h, and the replacement frequency of the lower rotating body 30 due to wear was 700 h/times.

[Example 2]
Except for changing the rotation speed of the lower rotating body 30 to 1440 rpm (rotation speed per second R=24 rpm/60), toner was produced and evaluated in the same manner as in Example 1. In Example 2, when the same mixing process was repeated, toner could be produced at a production rate of 300 kg/h, and the replacement frequency of the lower rotating body 30 due to wear was 700 h/times.

[Example 3]
A toner was produced and evaluated in the same manner as in Example 1, except that a lower rotor 30 having four stirring blades (each stirring blade having the same configuration as in Example 1, and each stirring blade was arranged at 90° intervals) was used. In Example 3, when the same mixing process was repeated, toner could be produced at a production rate of 300 kg/h, and the replacement frequency of the lower rotor 30 due to wear was 700 h/times.

[Example 4]
A toner was produced and evaluated in the same manner as in Example 1, except that the distance (clearance C) between the protruding parts 32a, 32b of the two stirring blades 30a, 30b and the mixing tank 20 was set to 5 mm. In Example 3, when the same mixing process was repeated, toner could be produced at a production rate of 300 kg/h, and the replacement frequency of the lower rotor 30 due to wear was 700 h/times.

[Example 5]
Except for changing the mixing time T to 960 seconds, toner was produced and evaluated in the same manner as in Example 1. In Example 5, when the same mixing process was repeated, toner could be produced at a production rate of 150 kg/h, and the replacement frequency of the lower rotating body 30 due to wear was 700 h/times.

[Comparative Example 1]
A toner was produced and evaluated in the same manner as in Example 1, except that the two stirring blades 30a, 30b constituting the lower rotor 30 did not have the protrusions 32a, 32b. In Comparative Example 1, except that the distance (clearance C) between the main bodies 31a, 31b of the two stirring blades 30a, 30b and the mixing tank 20 was set to 2 mm, a similar mixing process was also repeatedly performed in Comparative Example 1, and toner could be produced at a production rate of 300 kg/h, but the replacement frequency of the lower rotor 30 due to wear was 100 h/times.

[Comparative Example 2]
Except for using two stirring blades 30a, 30b with a width L of 10 mm for the protruding portions 32a, 32b, toner was produced and evaluated in the same manner as in Example 1. In Comparative Example 2, when the same mixing process was repeated, toner could be produced at a production rate of 300 kg/h, and the replacement frequency of the lower rotating body 30 due to wear was 700 h/times.

[Comparative Example 3]
Except for setting the rotation speed of the lower rotating body 30 to 1240 rpm (rotation speed per second R=20.67 rpm/60), toner was produced and evaluated in the same manner as in Example 1. In Comparative Example 3, when the same mixing process was repeated, toner could be produced at a production rate of 300 kg/h, and the replacement frequency of the lower rotating body 30 due to wear was 1000 h/times.

[Comparative Example 4]
A toner was produced and evaluated in the same manner as in Comparative Example 1, except that a lower rotor 30 having four stirring blades (each stirring blade having the same configuration as in Comparative Example 1, and each stirring blade was arranged at 90° intervals) was used. In Comparative Example 4, when the same mixing process was repeated, toner could be produced at a production rate of 300 kg/h, but the replacement frequency of the lower rotor 30 due to wear was 100 h/times.

表１中、比較例１，４は、撹拌羽根として突出部を有しないものを用いたため、本体部の幅を突出部の幅Ｌとした。

In Table 1, in Comparative Examples 1 and 4, stirring blades without protrusions were used, and therefore the width of the main body was taken as the width L of the protrusions.

As shown in Table 1, the stirring blades constituting the mixing device were equipped with protruding portions having a protruding height H of 1.0 mm or more, and the width L [mm] of the protruding portions of the stirring blades, the rotation speed R [rpm/60] of the stirring blades per second, and the number N of the stirring blades were set within the range of 900≦L×R×N≦5000. As a result, the number of sheets on which vertical streaks occurred and the number of sheets on which photoreceptor filming occurred were both 5,000 or more, and the occurrence of vertical streaks and photoreceptor filming was effectively suppressed. In addition, the production rate was high and the frequency of replacement of the stirring blades was low, resulting in excellent productivity (Examples 1 to 5).
On the other hand, when a stirring blade not having a protruding portion was used as a stirring blade constituting the mixer, the stirring blade had to be replaced frequently, and the productivity was poor (Comparative Examples 1 and 4).
Furthermore, when the value of L×R×N was less than 900, the amount of silica aggregates increased, resulting in significant occurrence of filming on the photoreceptor (Comparative Examples 2 and 3).
Furthermore, when the value of L×R×N exceeds 5000, the amount of coarse particles in the toner increases, resulting in noticeable occurrence of vertical streaks (Comparative Example 4).

Claims (6)

A method for producing a toner, comprising a mixing step of mixing colored resin particles containing a binder resin and a colorant with inorganic fine particles,
the mixing step is a step of mixing the colored resin particles and the inorganic fine particles by rotating the stirring blade in a mixing device including a mixing tank and a rotatable stirring blade in the mixing tank, thereby fixing the inorganic fine particles to the colored resin particles;
The mixing device is a device in which the stirring blade constituting the mixing device has a main body and a protruding portion formed along the longitudinal direction of the main body and protruding from the bottom surface of the mixing tank, and the protruding height of the protruding portion is 1.0 mm or more,
The method for producing a toner, wherein the mixing condition in the mixing step satisfies the condition shown in the following formula (1):
900≦L×R×N≦5000 (1)
(In the above formula (1), L is the width [mm] of the protruding part of the agitating blade, R is the rotation speed per second [rpm/60] of the agitating blade, and N is the number of agitating blades included in the mixing device.) The method for producing toner according to claim 1, wherein the distance between the protruding portion of the stirring blade and the bottom surface of the mixing tank is 0.5 to 6 mm. The method for producing a toner according to claim 1 or 2, wherein the circularity of the colored resin particles is 0.980 or more. The method for producing a toner according to any one of claims 1 to 3, wherein the colored resin particles are obtained by a suspension polymerization method. The colored resin particles have a volume average particle size of 3 to 11 μm,
The method for producing a toner according to any one of claims 1 to 4, wherein the inorganic fine particles have a specific surface area of 1 to 400 m ² /g. The method for producing a toner according to any one of claims 1 to 5, wherein two or more types of inorganic fine particles are used as the inorganic fine particles.

Images