JP2007047607A - Method for manufacturing electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic toner capable of maintaining a large charge quantity and reducing fogging even in a one-component development system; and also to provide a method for manufacturing the same. <P>SOLUTION: The method for manufacturing the electrophotographic toner using a toner material composition containing a binder resin, a colorant and a charge control agent includes: (I) a step of mixing 10-40 wt.% of the binder resin, ≥70 wt.% of the colorant and ≥70 wt.% of the charge control agent, and subjecting the mixture to melt kneading and pulverization; (II) a step of mixing pulverized powder obtained at the step (I) and the remaining toner material composition, and subjecting the mixture to melt kneading, pulverization and classification to obtain toner base particles; and (III) a step of mixing the toner base particles obtained at the step (II) and external additives, wherein alumina having a number average particle diameter of 100-400 nm and silica having a number average particle diameter of 8-30 nm are used as the external additives. An electrophotographic toner obtained by the manufacturing method is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

Along with the development of electrophotographic technology, miniaturization of machines is progressing, and a non-magnetic one-component development method that does not use a carrier for charging a toner has become mainstream. In this method, the toner is charged not by frictional charging by the carrier but by friction with the blade, so that the toner charging performance is important. Therefore, a toner whose surface is treated with silica or alumina with an external additive on the toner surface is disclosed (see Patent Documents 1 and 2).
JP-A-6-118690 JP-A-7-301944

  However, with the increase in machine speed, the one-component development method has a heavy load on the toner, and problems such as image quality deterioration such as fog are likely to occur due to insufficient charge amount and poor fluidity due to embedding external additives.

  An object of the present invention is to provide an electrophotographic toner capable of maintaining a high charge amount and reducing fog even in a one-component development system, and a method for producing the same.

The present invention
[1] A method for producing an electrophotographic toner using a toner raw material composition containing a binder resin, a colorant, and a charge control agent, comprising steps (I) to (III):
(I): a step of mixing 10-40% by weight of the binder resin, 70% by weight or more of the colorant and 70% by weight or more of the charge control agent in the toner raw material composition, melt-kneading, and pulverizing;
(II): a step of mixing the pulverized product obtained in step (I) with the remaining toner raw material composition, melt-kneading, pulverizing and classifying to obtain toner mother particles, and
(III): A step of mixing the toner base particles obtained in the step (II) and an external additive, wherein the external additive is alumina having a number average particle diameter of 100 to 400 nm and the number average particle diameter. Relates to a method for producing an electrophotographic toner using silica having a diameter of 8 to 30 nm, and [2] an electrophotographic toner obtained by the production method.

  The toner for electrophotography of the present invention has an excellent effect that it can maintain a high charge amount and can reduce fog even in the one-component development system.

  In the present invention, a part of a toner raw material composition used for toner production is mixed in advance, melt-kneaded and pulverized, and the obtained pulverized product is further mixed with the remaining toner raw material composition to be melt-kneaded. It has a great feature in that the toner base particles are surface-treated with a specific external additive. That is, although the detailed reason is unclear, a part of the toner raw material composition is previously melt-kneaded, then mixed with the remaining toner raw material composition, and melt-kneaded to improve the chargeability and durability of the toner base particles. Furthermore, the electrical balance can be achieved by surface-treating the toner base particles with a specific external additive.

  In the present invention, the toner raw material composition contains at least a binder resin, a colorant, and a charge control agent.

  In the present invention, examples of the binder resin include vinyl resins such as polyester and styrene-acrylic resins, epoxy resins, polycarbonates, polyurethanes, hybrid resins having two or more resin components, and the like. Among these, polyester is preferable from the viewpoint of durability and fixability. Since the toner of the present invention is excellent in charging performance and generally has an ester group, a positively chargeable toner can be used even if a polyester which is considered disadvantageous as a binder resin for a positively chargeable toner is used as the binder resin. Can be suitably used. The polyester content is preferably 50 to 100% by weight in the binder resin, more preferably 70 to 100% by weight, and still more preferably 100% by weight.

  The raw material monomer of the polyester is not particularly limited, and a known alcohol component and a known carboxylic acid component such as carboxylic acid, carboxylic acid anhydride, or carboxylic acid ester are used.

  Alcohol components include alkylenes of bisphenol A such as polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane (Carbon number 2 to 3) Oxide (average added mole number 1 to 16) adduct, ethylene glycol, propylene glycol, glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or alkylene thereof (carbon number 2 -4) Oxide (average added mole number 1-16) adduct and the like.

  The carboxylic acid component includes dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, adipic acid and succinic acid, alkyl groups having 1 to 20 carbon atoms such as dodecenyl succinic acid and octenyl succinic acid, or carbon. Trivalent or higher polyvalent carboxylic acids such as succinic acid, trimellitic acid and pyromellitic acid substituted with alkenyl groups having 2 to 20 carbon atoms, anhydrides of these acids and alkyls of these acids (1 to 3 carbon atoms) ) Esters and the like.

  The polyester can be produced, for example, by subjecting an alcohol component and a carboxylic acid component to condensation polymerization at a temperature of 180 to 250 ° C. in an inert gas atmosphere, if necessary, using an esterification catalyst.

  The softening point of the polyester is preferably 110 to 160 ° C, and more preferably 110 to 140 ° C from the viewpoint of low-temperature fixability. The glass transition point is preferably 45 to 80 ° C, and more preferably 50 to 65 ° C from the viewpoint of durability and fixability.

  The acid value of the polyester is preferably 0.5 to 60 mgKOH / g from the viewpoint of environmental resistance, raw material dispersibility, etc., and in the case of a positively charged toner, preferably 10 mgKOH / g or less, more preferably 0 to 6 mgKOH / g. . The hydroxyl value is preferably 1 to 60 mgKOH / g, more preferably 1 to 50 mgKOH / g.

  As the colorant, dyes and pigments used as toner colorants can be used. Carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, solvent red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Disazo Yellow, etc., and these can be used alone or in admixture of two or more. Either toner or full color toner may be used. The blending amount of the colorant used in the present invention is preferably 1 to 40 parts by weight and more preferably 3 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As the charge control agent, a conventionally known charge control agent for an electrophotographic toner can be used without any particular limitation, but in the present invention, from the viewpoint of chargeability, a positively chargeable charge control agent can be used. Use is preferred. Specifically, nigrosine dyes such as “Bontron N-07”, “Bontron N-09”, “Bontron N-04” (manufactured by Orient Chemical Co., Ltd.), etc .; triphenyl containing amine in the side chain Methane dyes such as “COPY BLUE PR” (Hoechst); quaternary ammonium salts such as “TP-415” (Hodogaya Chemical Co.), “COPY CHARGE PSY” (Hoechst), “Bontron P- 51 "(produced by Orient Chemical Co., Ltd.), cetyltrimethylammonium bromide, etc .; polyamine resins such as" Bontron P-52 "(produced by Orient Chemical Co., Ltd.), etc., are used alone or in combination of two or more. Can be used. Furthermore, in the present invention, a charge control resin can also be used as the charge control agent, and in particular, from the viewpoint of the dispersibility in the binder resin and the balance between the chargeability of alumina and silica used as an external additive, A polymer having a functional group involved in charging, such as an ammonium salt, and further having a conjugated electron in the molecule capable of holding a charge is preferable. In the present invention, examples of commercially available charge control resins that can be suitably used include FCA-201-PS manufactured by Fujikura Kasei Co., Ltd., which is a copolymer of styrene-acrylic resin.

  The amount of the charge control agent used in the present invention is preferably 5 to 20 parts by weight and more preferably 6 to 15 parts by weight with respect to 100 parts by weight of the binder resin.

  In the present invention, in addition to the binder resin, the colorant and the charge control agent, a release agent, a fluidity improver, a conductivity modifier, an extender pigment, a reinforcing filler such as a fibrous substance, an antioxidant, Additives such as anti-aging agents and cleaning improvers may be used as toner raw materials.

  Examples of mold release agents include polypropylene wax, polyethylene wax, synthetic wax such as Fischer Tropu, coal wax such as montan wax, petroleum wax such as paraffin wax, and wax such as alcohol wax. Or a mixture of two or more thereof. The content of the release agent used in the present invention is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  Hereinafter, steps (I) to (III) for producing the toner for electrophotography of the present invention using the toner raw material composition will be described.

  Step (I) is a step in which a part of the toner raw material composition is mixed, melt-kneaded, and pulverized.

  The binder resin used in the step (I) is 10 to 40% by weight, more preferably 15 to 35% by weight, and more preferably 18 to 30% by weight in the total amount of the binder resin used in the present invention.

  The colorant used in the step (I) is 70% by weight or more, preferably 80% by weight or more, and more preferably 90% by weight or more in the total amount of the colorant used in the present invention.

  The charge control agent used in the step (I) is 70% by weight or more, preferably 80% by weight or more, and more preferably 90% by weight or more in the total amount of the charge control agent used in the present invention.

  In a more preferred embodiment, in the step (I), in the toner raw material composition, 10 to 40% by weight of the binder resin and all of the toner raw materials other than the binder resin such as the colorant and the charge control agent (100% by weight). %) And the remaining binder resin in the step (II) and the pulverized product obtained in the step (I) are preferably mixed.

  In the step (I), as a mixer for mixing the toner raw material composition, Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), super mixer (manufactured by Kawata Co., Ltd.), high speed mixer (manufactured by Fukae Kogyo Co., Ltd.), Various mixers such as a mixer (manufactured by Matsubo) can be used without particular limitation.

  For melt kneading of the obtained mixture, a known kneader such as a closed kneader, a uniaxial or biaxial extruder, and an open roll type kneader can be used.

  The kneading temperature is not particularly limited as long as the raw materials are mixed.

  After the melt-kneading, the melt-kneaded product is appropriately cooled and pulverized until reaching a grindable hardness.

  An atomizer, a rotoplex, etc. can be used for the grinding | pulverization of the cooled melt-kneaded material.

  The pulverized product obtained in the step (I) is preferably pulverized to a particle size that passes through a screen of 5 mmφ or less, and the size of the screen is more preferably 3 mmφ or less, and further preferably 2 mmφ or less.

  Step (II) is a step in which the pulverized product obtained in Step (I) and the remaining toner raw material composition are mixed, melt-kneaded, pulverized, and classified.

  Examples of the mixer and kneader used in step (II) include the same devices as in step (I).

  The pulverization of the cooled melt-kneaded product in the step (II) may be performed once or divided into a plurality of times, but from the viewpoint of pulverization efficiency and production efficiency, it may include coarse pulverization and fine pulverization. Preferably, after coarsely pulverizing in advance to a particle size passing through a screen of preferably 5 mmφ or less, more preferably 3 mmφ or less, and even more preferably 2 mmφ or less, the obtained coarsely pulverized product is further taken into account the target toner particle size. Then, it is preferable to pulverize.

  As a pulverizer used for coarse pulverization, a cutter mill, an atomizer, a rotoplex, or the like can be used.

  For fine pulverization, a jet pulverizer such as a collision plate jet mill, a fluidized bed jet mill or an airflow jet mill, a mechanical pulverizer such as a turbo mill, or the like can be used.

  Examples of the classifier used for classification include an air classifier, an inertia classifier, and a sieve classifier.

  Step (III) is a step of mixing the toner base particles obtained in step (II) and an external additive.

  In the present invention, alumina and silica having a specific particle diameter are used as external additives. The function of the external additive includes durability and fluidity. These are contradictory physical properties, but in the present invention, particles having a large particle size (alumina having a number average particle size of 100 to 400 nm) and particles having a small particle size (silica having a number average particle size of 8 to 30 nm) are used in combination. By doing so, both of these can be achieved. It is presumed that the durability is ensured by the large particle size particles and the fluidity is secured by the small particle size particles. In addition, there is concern about the effect of charging characteristics on the toner due to external additives. By using alumina as the large particle size and silica as the small particle size, the durability, fluidity and chargeability can be balanced. Toner.

The number average particle diameter of the alumina used in the present invention is 100 to 400 nm, preferably 200 to 300 nm. Further, BET specific surface area is preferably 6~15m ² / g, more preferably 7~12m ² / g, more preferably 8~10m ² / g.

  Alumina is preferably treated with a hydrophobizing agent containing aminosilane, and more preferably treated with a hydrophobizing agent containing aminosilane and silicone oil, from the viewpoint of chargeability.

The number average particle diameter of the silica used in the present invention is 8 to 30 nm, preferably 10 to 20 nm. The BET specific surface area is preferably 180 to 220 m ² / g.

  Silica is preferably treated with a hydrophobizing agent containing silicone oil from the viewpoint of fluidity and environmental resistance.

  The weight ratio of alumina to silica (alumina / silica) is preferably 0.9 to 3.9, more preferably 1.0 to 2.9.

  The total amount of alumina and silica is preferably 0.5 to 3 parts by weight, more preferably 0.5 to 2 parts by weight, and still more preferably 0.5 to 1 part by weight with respect to 100 parts by weight of the toner base particles.

  Furthermore, in the range not impairing the effect of the present invention, external additives other than the above alumina and silica, for example, resin fine particles such as polytetrafluoroethylene, titania, zinc oxide, magnesium oxide, cerium oxide, iron oxide, copper oxide, You may use together inorganic oxides, such as a tin oxide.

  As an external additive used in combination with alumina and silica in the present invention, the negative charge amount of the fine particles themselves due to frictional charging is large, and mixing of the toner before passing through the charging blade and passing through the charging blade makes the toner more charged. From the viewpoint of good performance, polytetrafluoroethylene is preferred.

  The average particle diameter of the primary particles of the polytetrafluoroethylene fine particles is preferably from 0.05 μm to less than 0.5 μm, more preferably from 0.1 to 0.45 μm, and more preferably from 0.15 to 0.4 μm, from the viewpoint of embedding and releasing into the toner base particles. Further preferred. Here, the average particle diameter of the primary particles of the fine particles is calculated by averaging the particle diameters of the primary particles measured from the electron micrograph.

  More specific examples of such polytetrafluoroethylene fine particles include those having a shape close to a sphere produced by emulsion polymerization. These are commercially available, for example, “KTL-500F” (manufactured by Kitamura, average particle size of primary particles 0.3 μm), “Lublon L2” (manufactured by Daikin Industries, Ltd., average particle size of primary particles 0.3 μm), “ "Lublon L5" (Daikin Kogyo Co., Ltd., primary particle average particle size 0.2μm), "Fullon Lubricant L170J" (Asahi IC Fluoropolymers Co., Ltd. average particle size 0.1μm), "Fullon Lubricant L172J" (Asahi IC Fluoropolymers, average particle size of primary particles 0.1μm), “MP-1100” (Mitsui / DuPont Fluorochemicals, average particle size of primary particles 0.2μm), “MP-1200” (Mitsui / DuPont Fluorochemical Co., Ltd., average particle size of primary particle 0.3 μm), “TLP-10F-1” (Mitsui / DuPont Fluorochemical Co., Ltd., primary particle average particle size 0.2 μm), etc. .

  The addition amount of the polytetrafluoroethylene fine particles is preferably 0.01 to 1.5 parts by weight, more preferably 0.05 to 1.0 parts by weight with respect to 100 parts by weight of the toner base particles.

  The mixing of the toner base particles and the external additive is preferably carried out by dry mixing using a high-speed stirrer such as a Henschel mixer or a super mixer, or a V-type blender, whereby the toner base particle surface is coated with the external additive. Surface treatment can be performed. The external additives may be mixed in advance and added to a high-speed stirrer or a V-type blender, or may be added separately.

The volume median particle size (D ₅₀ ) of the toner of the present invention is preferably 3 to 12 μm, more preferably 4 to 10 μm. In the present specification, the volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size.

  The electrophotographic toner of the present invention can be used for both one-component and two-component development methods, but is excellent in chargeability and durability, so that it is a one-component development method, particularly a non-magnetic one-component development method. The effect of the present invention is more remarkable when used in

[Softening point]
Using a flow tester (manufactured by Shimadzu Corporation, CFT-500D), a 1 g sample was heated at a heating rate of 6 ° C / min, a load of 1.96 MPa was applied by a plunger, and it was extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. did. The amount of plunger drop of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[Glass transition point]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210C), the temperature was raised to 100 ° C at a rate of temperature increase of 10 ° C / min, and the sample cooled to -10 ° C at a rate of temperature decrease of 100 ° C / min was left for 3 minutes. Then, the temperature is raised to 25 ° C. at a heating rate of 60 ° C./min, held for 2 minutes, and measurement is started at a heating rate of 10 ° C./min. The glass transition point is defined as the temperature at the intersection of the base line extension below the glass transition point and the tangent that indicates the maximum slope from the peak rising portion to the peak apex.

[Acid value and hydroxyl value]
Measured by the method of JIS K0070.

[Number average particle diameter of external additives]
The number average particle diameter of the external additive is determined from a photograph obtained with a scanning electron microscope or a transmission electron microscope.

[Volume-median particle diameter of toner (D ₅₀ )]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 100 μm
Measurement particle size range: 2-60μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) 5% electrolyte dispersion condition: 10 mg of measurement sample is added to 5 ml of dispersion, and dispersed for 1 minute with an ultrasonic disperser. Then, 25 ml of the electrolytic solution is added, and further dispersed with an ultrasonic disperser for 1 minute.
Measurement conditions: Add 100 ml of electrolyte and dispersion in a beaker, measure 30,000 particles at a concentration that can measure the particle size of 30,000 particles in 20 seconds, and determine the volume-median particle size ( determine the D _50).

Resin production example 1
70 mol parts of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 30 mol parts of polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 58 mol of terephthalic acid Part, 12 mol parts of isooctenyl succinic acid and 15.5 mol parts of trimellitic acid and dibutyltin oxide as a catalyst were mixed and reacted at 210 ° C. with stirring. The degree of polymerization was tracked according to the softening point, and when the softening point reached 148 ° C., the reaction was terminated to obtain polyester A. Polyester A had a softening point of 148 ° C., a glass transition point of 63 ° C., an acid value of 6 mgKOH / g, and a hydroxyl value of 35 mgKOH / g.

Resin production example 2
70 mol parts of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 30 mol parts of polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 58 mol of terephthalic acid Part B, 12 parts by mole of isooctenyl succinic acid and 14 parts by mole of trimellitic acid, and polyester B was obtained in the same manner as in Resin Production Example 2. Polyester B had a softening point of 136 ° C, a glass transition point of 63 ° C, an acid value of 3 mgKOH / g, and a hydroxyl value of 40 mgKOH / g.

Example 1
[Process (I)]
8 parts by weight of polyester resin A and 12 parts by weight of polyester B as binder resin, 4 parts by weight of carbon black (trade name: REGL 330R, Cabot Specialty Chemicals) as colorant, and nigrosine dye (trade name: Bontron) as charge control agent N-04, manufactured by Orient Chemical Industry Co., Ltd.) 4 parts by weight, quaternary ammonium salt compound (trade name: Bontron P-51, manufactured by Orient Chemical Industry Co., Ltd.) 0.6 part by weight, charge control resin (FCA-201- PS, manufactured by Fujikura Kasei Co., Ltd.) 7 parts by weight, polypropylene wax (HIWAX NP-055, manufactured by Mitsui Chemicals Co., Ltd.) 1 part by weight and polyethylene wax (Paraflint SP105, manufactured by Hiroyuki Kato) 1 part by weight of the mixture was mixed for 3 minutes using a Henschel mixer (capacity 20 liters) in which the blade rotation speed was set to 1500 r / min.

  The resulting mixture was melt kneaded with a twin screw extruder. The operating conditions when using the twin screw extruder were as follows: the barrel (kneading extruder outer cylinder) set temperature was 90 ° C, and the kneading temperature was 90 ° C. The obtained melt-kneaded product was cooled with a cooling belt and then pulverized with a cutter mill having a 2 mmφ screen.

[Process (II)]
Using a Henschel mixer (capacity 20 liters) with a mixture of 37.6 parts by weight of the pulverized product, 56 parts by weight of polyester resin A and 24 parts by weight of polyester B as binder resins, and the blade rotation speed set to 1500 r / min, Mix for 3 minutes.

  The resulting mixture was melt kneaded with a twin screw extruder. The operating conditions when using the twin screw extruder were as follows: the barrel (kneading extruder outer cylinder) set temperature was 90 ° C, and the kneading temperature was 90 ° C. The obtained melt-kneaded product was cooled with a cooling belt, coarsely pulverized with a mill having a 2 mmφ screen, and then pulverized with an impact plate jet mill.

Further, coarse powder and fine powder were removed by a cyclone type air classifier to obtain toner base particles having a volume median particle size (D ₅₀ ) of 9.5 μm.

[Process (III)]
Positively chargeable alumina (number average particle diameter: 200 nm, BET specific surface area: 9 m ² / g) hydrophobized with silane / silane coupling agent as aminosilane with respect to 100 parts by weight of the obtained toner base particles. 0.53 parts by weight, silica (Caboseal TS-720, manufactured by Cabot Specialty Chemicals, (number average particle size: 12 nm, BET specific surface area: 200 m ² / g), 0.21 parts by weight, and polytetrafluoroethylene (KTL-500F, ( Made by Kitamura Co., Ltd., average particle size: 0.3 μm) Adds 0.25 parts by weight of external additive, mixes using a Henschel mixer, and externally adds silica to the toner surface. A component developing toner was obtained.

Comparative Example 1
In step (III), 0.53 parts by weight of silica (RY-50, manufactured by Nippon Aerosil Co., Ltd., number average particle size: 40 nm, BET specific surface area: 50 m ² / g) and silica (Caboseal TS-720, Cabot) were used as external additives.・ Specialty Chemicals, number average particle size: 12 nm, BET specific surface area: 200 m ² / g) 0.21 parts by weight, and polytetrafluoroethylene (KTL-500F, manufactured by Kitamura Co., Ltd., average particle size: 0.3 μm) A positively chargeable nonmagnetic one-component toner was obtained in the same manner as in Example 1 except that 0.25 parts by weight were mixed using a Henschel mixer.

Comparative Example 2
64 parts by weight of polyester resin A and 36 parts by weight of polyester B as binder resin, 4 parts by weight of carbon black (trade name: REGAL 330R, Cabot Specialty Chemicals) as colorant, and nigrosine dye (trade name: Bontron) as charge control agent N-04, manufactured by Orient Chemical Industry Co., Ltd.) 4 parts by weight, quaternary ammonium salt compound (trade name: Bontron P-51, manufactured by Orient Chemical Industry Co., Ltd.) 0.6 part by weight, charge control resin (FCA-201- PS, manufactured by Fujikura Kasei Co., Ltd.) 7 parts by weight, polypropylene wax (HIWAX NP-055, manufactured by Mitsui Chemicals Co., Ltd.) 1 part by weight and polyethylene wax (Paraflint SP105, manufactured by Hiroyuki Kato) 1 part by weight of the mixture was mixed for 3 minutes using a Henschel mixer (capacity 20 liters) in which the blade rotation speed was set to 1500 r / min.

  The resulting mixture was melt kneaded with a twin screw extruder. The operating conditions when using the twin screw extruder were as follows: the barrel (kneading extruder outer cylinder) set temperature was 90 ° C, and the kneading temperature was 90 ° C. The obtained melt-kneaded product was cooled with a cooling belt, coarsely pulverized with a mill having a 2 mmφ screen, and then pulverized with an impact plate jet mill.

Further, coarse powder and fine powder were removed by a cyclone type air classifier to obtain toner base particles having a volume median particle size (D ₅₀ ) of 9.5 μm.

  Thereafter, step (III) was carried out in the same manner as in Example 1 to obtain a positively chargeable non-magnetic one-component toner.

Test example 1 [Measurement of charge amount and transport amount]
Toner was mounted on a commercially available non-magnetic one-component developing printer, and 5000 images with a printing rate of 1% were printed continuously. At the time of continuous printing, after every 1000 sheets were printed, 3 solid white images were printed, and then a 1 cm × 2 cm metal frame was attached to 3 arbitrarily selected locations on the developing roller. Use a Q / M meter (MODEL 210HS, manufactured by TREK) to absorb toner on the developing roller for a total of 6 cm ² , and calculate the charge amount (μC / g) by dividing the charge amount by the absorbed toner amount. It was. The results are shown in Table 1.

Test Example 2 [Evaluation of fog]
In Test Example 1, the machine was stopped in the middle of printing a white solid image, and a transparent mending tape was attached to the surface of the photoreceptor before transfer. The tape peeled off from the surface of the photoreceptor is pasted on unused paper, and the difference ΔY (Y ₀ −Y) between the whiteness Y and the whiteness Y ₀ of the reference mending tape is measured. According to the following evaluation criteria The fog was evaluated. The results are shown in Table 2. A smaller ΔY indicates a higher transfer rate and better fog.

〔Evaluation criteria〕
A: ΔY <0.5
○: 0.5 ≦ ΔY <1.0
Δ: 1.0 ≦ ΔY <2.0
×: 2.0 ≦ ΔY

  From the above results, the toner of the example can maintain a high charge amount and suppress fogging even in the continuous printing by the non-magnetic one-component development method, as compared with the toner of the comparative example. I understand.

  The toner for electrophotography obtained by the present invention is suitably used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (5)

A method for producing an electrophotographic toner using a toner raw material composition containing a binder resin, a colorant and a charge control agent, comprising steps (I) to (III):
(I): a step of mixing 10-40% by weight of the binder resin, 70% by weight or more of the colorant and 70% by weight or more of the charge control agent in the toner raw material composition, melt-kneading, and pulverizing;
(II): a step of mixing the pulverized product obtained in step (I) with the remaining toner raw material composition, melt-kneading, pulverizing and classifying to obtain toner mother particles, and
(III): A step of mixing the toner base particles obtained in the step (II) and an external additive, wherein the external additive is alumina having a number average particle diameter of 100 to 400 nm and the number average particle diameter. For producing a toner for electrophotography using silica having a diameter of 8 to 30 nm.   The production method according to claim 1, wherein the alumina is treated with a hydrophobizing agent containing aminosilane.   The method according to claim 1 or 2, wherein the charge control agent is a charge control resin.   In the obtained toner, the weight ratio of alumina to silica (alumina / silica) is 0.9 to 3.9, and the content of the charge control agent is 5 to 20 parts by weight with respect to 100 parts by weight of the binder resin. 3. The production method according to any one of 3.   An electrophotographic toner obtained by the production method according to claim 1.