JP4239778B2 - Toner for electrophotography and image forming apparatus using the toner - Google Patents

Description

  The present invention relates to a toner used for developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing, etc., and forming an image by thermal fixing, a method for producing the toner, and image formation using the toner Relates to the device.

  Generally, toner for electrostatic image formation uses toner fine particles made of a binder resin containing a coloring component such as a pigment or dye and, if necessary, a charge control agent, as a toner mother particle, and the outside (surface) of the toner mother particle. In addition, for the purpose of imparting fluidity or controlling chargeability, it is manufactured by a method of adding an external additive. As the external additive, positively chargeable silica fine particles, negatively chargeable silica fine particles, inorganic fine particles other than silica (such as titanium oxide fine particles), metal soap (fatty acid metal salt) and the like are used.

  Among these, metal soaps are attracting attention for their binding properties, and are often used as external additives in toners as disclosed in, for example, Patent Documents 1 to 7. Patent Document 1 discloses a hydrophobic silica fine particle or hydrophobic titania as a first component, a hydrophobic silica fine particle or hydrophobic titania having a particle size larger than the first component as a second component, an inorganic fine particle as a third component, and a fatty acid metal. A method is disclosed in which salt is used as the fourth component, and these first to fourth components are externally added to the toner base particles at the same time, or the first component is finally added externally. In Patent Document 1, a fatty acid metal salt is added from the viewpoint of preventing sticking of the surface of the photoreceptor and prevention of black spot generation, and thereafter, hydrophobic silica or hydrophobic titania is added. However, hydrophobic silica or hydrophobic titania, which is an external additive, is easily released from the toner surface, and the charging stability over a long period of time cannot be maintained and the fluidity of the toner is reduced. There is a problem that a decrease, a decrease in image density, and the like occur.

In Patent Document 2, silica having an amino group on the surface and a fatty acid metal salt are simultaneously added to obtain a toner by one external addition treatment. In the toner obtained by this method, the liberation rate of hydrophobic silica is slightly improved, but there remains a problem that the charge amount of the toner cannot be stably maintained. Patent Documents 3 to 7 also describe that a fatty acid metal salt is externally added when preparing a toner. In these Patent Documents 3 to 7, as in Patent Document 2, the fatty acid metal salt is added simultaneously with other external additives, and the toner is obtained by one external addition process. The toners described in Patent Documents 3 to 7 still have a problem that the charge amount of the toner cannot be stably maintained.
JP 2001-100452 A Japanese Patent No. 2502353 Japanese Patent Publication No. 8-33681 Japanese Patent No. 2759510 Japanese Patent Laid-Open No. 9-114129 JP-A-11-323396 JP 2001-296688 A JP 2002-202622 A

  An object of the present invention is to provide a toner that is excellent in charge uniformity, maintains charge stability for a long period of time even in repeated use, has high fluidity and transfer efficiency, and does not decrease image density.

The present invention relates to a toner obtained by adding two or more external additives to toner base particles containing a binder resin and a colorant, wherein the external additives are added by multi-stage treatment, and in the final stage of the multi-stage treatment. And a toner obtained by adding an external additive containing a metal salt of a long-chain fatty acid at a temperature 10 to 15 ° C. higher than the addition temperature of the external additive in another stage.

In a preferred embodiment, in the final stage of the multistage treatment, an external additive containing a metal salt of a long-chain fatty acid is added at a temperature higher than the addition temperature of the external additive in the other stage, and more than in the other stage. In addition, a toner added with a high share is provided.

In a preferred embodiment, the external additive is added using a mixer having rotor blades, and the external additive containing a metal salt of a long-chain fatty acid in the final stage has a higher temperature in the mixer than in the other stages. By increasing the rotational speed of the rotor blade and increasing the share, the share is increased.

In another preferred embodiment, the external additive is added using a mixer having a rotor blade, and the external additive containing a metal salt of a long-chain fatty acid is added in the mixer more than the other stages in the final stage. And increasing the shear rate by reducing the distance between the rotor blades and the mixer wall.

In a preferred embodiment, negatively-chargeable silica fine particles, at least one of the external additive is selected from the group consisting of titanium oxide fine particles and positively chargeable silica fine particles are added to the toner mother particles, at the final stage of a long chain fatty acid An external additive containing a metal salt is added.

In another preferred embodiment, in the multi-stage treatment, negatively chargeable silica fine particles are first added to the toner base particles, and an external additive containing a metal salt of a long-chain fatty acid is added in the final stage.

In still another preferred embodiment, in the multi-stage treatment, negatively chargeable silica fine particles are added first, then titanium oxide fine particles are added, and an external additive containing a metal salt of a long-chain fatty acid is added in the final step. The

In another preferred embodiment, in the multi-stage treatment, titanium oxide fine particles are added first, and an external additive containing a metal salt of a long-chain fatty acid is added in the final stage.

In another preferred embodiment, in the multi-stage treatment, at least one external additive selected from the group consisting of negatively chargeable silica fine particles and titanium oxide fine particles is added,
Next, positively-charged silica fine particles are added, and a metal salt of a long-chain fatty acid is added at the final stage.

In still another preferred embodiment, in the multi-stage treatment, at least one external additive selected from the group consisting of negatively chargeable silica fine particles and titanium oxide fine particles is first added, and positively chargeable silica fine particles are added in the final stage. And metal salts of long chain fatty acids are added.

The present invention also provides a toner manufacturing method including a step of externally adding two or more external additives to toner base particles containing a binder resin and a colorant in a multistage process, and in the final stage of the multistage process There is provided a method comprising a step of adding an external additive containing a metal salt of a long-chain fatty acid at a temperature 10 to 15 ° C. higher than the addition temperature of the external additive in another stage.

In a preferred embodiment, in the final stage of the multistage treatment, an external additive containing a metal salt of a long-chain fatty acid is added at a temperature higher than the addition temperature of the external additive in the other stage, and more than in the other stage. Is a process with a high share.

In a preferred embodiment, the addition of the external additive is performed using a mixer having a rotor blade, and the final stage includes adding an external additive containing a metal salt of a long-chain fatty acid in the mixer more than the other stages. This is a process of increasing the share by increasing the temperature and increasing the rotational speed of the rotor blade.

In another preferred embodiment, the addition of the external additive is performed using a mixer having a rotor blade, and the final stage mixes the external additive containing a metal salt of a long-chain fatty acid more than the other stages. This is a step of increasing the share and increasing the temperature by increasing the temperature in the machine and reducing the distance between the rotor blade and the mixer wall.

In a preferred embodiment, a step of adding at least one external additive selected from the group consisting of negatively chargeable silica fine particles, titanium oxide fine particles and positively chargeable silica fine particles to the toner base particles, and a long chain in the final stage A step of adding an external additive containing a metal salt of a fatty acid.

In another preferred embodiment, the method includes a step of first adding the negatively chargeable silica fine particles to the toner base particles and a step of adding an external additive containing a metal salt of a long-chain fatty acid in the final step.

In still another preferred embodiment, the step of first adding the negatively chargeable silica fine particles to the toner base particles, the step of adding titanium oxide fine particles, and the external additive comprising a metal salt of a long-chain fatty acid at the final stage The process of adding.

In another preferred embodiment, the method includes a step of adding the titanium oxide fine particles first and a step of adding an external additive containing a metal salt of a long-chain fatty acid in the final step.

In another preferred embodiment, the step of first adding at least one external additive selected from the group consisting of the negatively chargeable silica fine particles and the titanium oxide fine particles, and then the step of adding positively chargeable silica fine particles. And adding a metal salt of a long-chain fatty acid in the final stage.

In yet another preferred embodiment, first adding at least one external additive selected from the group consisting of the negatively chargeable silica fine particles and the titanium oxide fine particles, and
In the final stage, a step of adding positively charged silica fine particles and a metal salt of a long chain fatty acid is included.

  The present invention further provides an image forming apparatus comprising any one of the above toners.

  In a preferred embodiment, the image forming apparatus includes a latent image carrier on which an electrostatic latent image is formed; and transports toner to the latent image carrier to develop the electrostatic latent image on the latent image carrier. A toner carrying member; and a developer having a toner regulating member that regulates the amount of toner conveyed to the latent image carrying member by the toner carrying member.

The toner of the present invention undergoes a multi-stage treatment when the external additive is added to the toner base particles. In the final stage of the multi-stage treatment, the metal salt of the long-chain fatty acid is 10 times higher than the temperature at which the other external additive is added. It is obtained by adding at a temperature higher by -15 ° C. Finally, the metal salt of the long chain fatty acid can be firmly bonded to the toner base particles by adding the metal salt of the long chain fatty acid at a temperature 10 to 15 ° C. higher than that in the other stages. Therefore, long-chain fatty acid metal salts act as binders for external additives such as negatively-charged silica fine particles, titanium oxide fine particles, and positively-charged silica fine particles, and suppress the release of these external additives from the toner surface. obtain. Further, by adding a metal salt of a long chain fatty acid to the toner base particles at a higher temperature and a higher share than in other stages, the metal salt of the long chain fatty acid is uniformly and firmly added onto the toner base particles. . As a result, it not only functions as a binder for the external additive, but also exhibits an effect as a toner lubricant, prevents toner aggregation, and causes the external additive to be contained in the toner base particles by friction between the toners. It is possible to maintain the uniformity of charging. Furthermore, the charging stability can be maintained even when the toner is used repeatedly. Further, in the developing device, due to the contact between the toner and the photoconductor, the metal salt of the long chain fatty acid migrates from the toner surface to the photoconductor surface, lubricates the photoconductor surface, and the surface of the photoconductor surface by the external additive on the toner surface. Polishing can be prevented.

  In the present specification, an external additive or an external additive is a material that is externally added to toner base particles such as particles of long chain fatty acid or a salt thereof, negatively charged silica particles, titanium oxide particles, and positively charged silica particles. The addition of these external additives (external additives) to the outside (surface) of the toner base particles is called external addition.

  First, (i) toner base particles and materials constituting the toner base particles (binder resin and colorant, release agent, dispersant, charge control agent, magnetic agent, etc.), which are materials used in the present invention. Internal additives), (ii) long chain fatty acids or salts thereof, (iii) negatively chargeable silica fine particles, (iv) titanium oxide fine particles, (v) positively chargeable silica fine particles, and added as needed (vi ) Inorganic fine particles will be described, and then the toner of the present invention will be described.

(I) Materials used in the present invention (i) Toner base particles The toner base particles include a binder resin and a colorant, and include a release agent, a dispersant, a charge control agent, a magnetic agent, etc. as necessary. Contains additives. The toner base particles are positively or negatively charged, and preferably negatively charged. There are several methods for charging the toner base particles so as to have a negative charge amount in an appropriate range. For example, a negative charge control agent is blended with a positively chargeable binder resin, and if the chargeability of the negatively chargeable resin is insufficient, a negative charge control agent is further blended, or the binder resin itself is negatively charged. For example, there is a method of making a functional resin. Hereinafter, the material constituting the toner base particles and the method for producing the toner base particles will be sequentially described.

(i-1) Material composing toner mother particles (binder resin)
As the binder resin, a resin generally used as a toner is used. Examples of such binder resins include polystyrene resins, acrylate resins or methacrylate resins (hereinafter referred to as (meth) acrylate resins), styrene-acrylic resins, polyester resins, polyethylene resins, epoxy resins, Silicone resin, polypropylene resin, fluororesin, polyamide resin, polyvinyl alcohol resin, polyurethane resin, polyvinyl butyral resin, and a copolymer containing components of these resins are used.

  Of these, polystyrene resins and styrene- (meth) acrylate resin copolymers are preferably used.

  Examples of polystyrene resins include hydrogenated styrene resins, styrene-isobutylene copolymers, acrylonitrile-butadiene-styrene copolymers (ABS resins), acrylonitrile-styrene copolymers (AS resins), acrylonitrile-polyethylene chloride-styrene. Copolymer (ACS resin), styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene crosslinked polymer, styrene-butadiene-chlorinated paraffin copolymer, styrene-allyl alcohol copolymer, Examples thereof include styrene-butadiene rubber, styrene-maleic ester copolymer, styrene-isobutylene copolymer, and styrene-maleic anhydride copolymer.

  Examples of the styrene- (meth) acrylate resin copolymer include acrylate-styrene-acrylonitrile copolymer (ASA resin), styrene-diethylamino-ethyl methacrylate copolymer, styrene-methyl methacrylate copolymer, styrene. -N-butyl methacrylate copolymer, styrene-methyl methacrylate-n-butyl acrylate copolymer, styrene-methyl methacrylate-butyl allylate-N- (ethoxymethyl) acrylamide copolymer, styrene-glycidyl methacrylate copolymer Polymer, styrene-butadiene-dimethylaminoethyl methacrylate copolymer, styrene-acrylic acid ester-maleic acid ester copolymer, styrene-methyl methacrylate-acrylic acid 2-ethylhexyl Copolymer, styrene-n-butylarylate-ethyl glycol methacrylate copolymer, styrene-n-butyl methacrylate-acrylic acid copolymer, styrene-n-butyl methacrylate-maleic anhydride copolymer, styrene- Examples thereof include butyl acrylate-isobutyl maleic acid half ester-divinylbenzene copolymer, styrene-butadiene-acrylate copolymer, and styrene-acrylate copolymer.

  The mass average molecular weight of the binder resin used in the present invention is not particularly limited, but is usually preferably 2,000 to 30,000, more preferably 4,000 to 25,000, and 6,000 to 20,000. More preferably, it is 000. When the molecular weight is less than 2,000, the viscosity at the time of kneading is lowered, and there is a possibility that the colorant cannot be sufficiently dispersed. Therefore, the saturation or transparency of the obtained toner may be reduced. When the molecular weight is larger than 30,000, the viscosity becomes too high, and the colorant cannot be sufficiently dispersed, and the saturation or transparency of the toner may be lowered. The binder resin may be a mixture of a plurality of resins having a molecular weight within the above range.

  The molecular weight of the binder resin is measured by gel permeation chromatography (GPC).

  When fixing the toner in image formation by the thermal fixing method, the flow softening point (Tm) of the binder resin is preferably low. For example, Tm is preferably 85 to 140 ° C, more preferably 90 to 120 ° C, and further preferably 100 to 110 ° C. The glass transition temperature (Tg) of the binder resin is preferably 40 to 90 ° C, more preferably 50 to 80 ° C. In addition, the flow softening point (Tm) was measured under the following conditions using “Flow Tester CFT-500D” manufactured by Shimadzu Corporation as a sample by pressure-molding 1.0 g of a binder resin into a pellet. To do. Temperature rising rate 5 ° C./min; cylinder pressure 2.0 MPa; die hole diameter 1.0 mm; die hole length 1.0 mm; Tm calculation method 1/2 method. Further, the glass transition temperature (Tg) of the binder resin is measured under the following conditions using 10 mg of the binder resin packed in an aluminum cell and using “DSC120” manufactured by Seiko Instruments Inc. Measurement temperature 0 to 200 ° C .; temperature increase rate 10 ° C./min: Read from DSC curve at the second temperature increase.

  When the toner is fixed by the pressure fixing method, a wax-like resin is preferably used as the binder resin. Examples of the wax-like resin include polyethylene resins, polyethylene-vinyl acetate copolymers, and natural waxes among the above binder resins.

  The binder resin is produced by a polymerization method such as emulsion polymerization, dispersion polymerization, suspension polymerization, or a pulverization method including kneading, pulverization, and classification steps. Considering the uniformity or fluidity of the finally obtained toner particles, the binder resin is preferably a resin obtained by a polymerization method.

  Moreover, the said binder resin may be used independently and may blend and use 2 or more types. Needless to say, the binder resin is an example, and is not limited thereto.

(Coloring agent)
As the colorant, organic pigments, inorganic pigments, and dyes as shown below can be used. Among organic and inorganic pigments, carbon black, copper oxide, iron tetroxide, manganese dioxide, aniline black, activated carbon, etc. are used as the black pigment.

  Yellow pigments include chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, hansa yellow, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow. NCG, tartrazine lake, etc. are used.

  As the orange pigment, red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GKM and the like are used.

  Red pigments include Bengala, Cadmium Red, Red Plum, Mercury Sulfide, Cadmium, Permanent Red 4R, Risor Red, Pyrozolone Red, Watching Red, Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B Alizarin lake, Brilliant Carmine 3B, etc. are used.

  As the purple pigment, manganese purple, fast violet B, methyl violet lake and the like are used. As the blue pigment, bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated product, first sky blue, indanthrene blue BC, and the like are used.

  As the green pigment, chrome green, chromium oxide, pigment green B, malachite green lake, final yellow green G, or the like is used.

  As the white pigment, zinc white, titanium oxide, antimony white, zinc sulfide and the like are used.

  Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white.

  As the dye, basic dyes, acid dyes, disperse dyes, direct dyes, and the like are used. Examples of such dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue.

  When the present invention is a translucent color toner, the following various pigments and dyes are used as the colorant.

  Examples of yellow pigments include CI10316 (Naphthol Yellow S), CI11710 (Hansa Yellow 10G), CI11660 (Hansa Yellow 5G), CI11670 (Hansa Yellow 3G), CI11680 (Hansa Yellow G), CI11730 (Hansa Yellow GR), CI11735 (Hansa Yellow A), CI11740 (Hansa Yellow NR), CI12710 (Hansa Yellow R), CI12720 (Pigment Yellow L), CI21090 (Benzidine Yellow), CI21095 (Benzidine Yellow G), CI21100 (Benzidine Yellow GR), CI20040 (Permanent Yellow NCG), CI21220 (Vulcan Fast Yellow 5), CI21135 (Vulcan Fast Yellow R), etc. are used.

  Red pigments include CI12055 (Starlin I), CI12075 (Permanent Orange), CI12175 (Risor Fast Orange 3GL), CI12305 (Permanent Orange GTR), CI11725 (Hansaero 3R), CI21165 (Vulcan Fast Orange GG) ), CI21110 (Benzidine Orange G), CI12120 (Permanent Red 4R), CI1270 (Paral Red), CI12085 (Fire Red), CI12315 (Brilliant Fast Scarlet), CI12310 (Permanent Red F2R), CI12335 ( Permanent Red F4R), CI12440 (Permanent Red FRL), CI12460 (Permanent Red FRLL), CI12420 (Permanent Red F4RH), CI12450 (Light Fast Red Toner B), CI12490 (Permanent Carmine FB), CI15850 ( Brilliantka Min 6B) and the like can be used.

  As the blue pigment, C.I.74100 (metal-free phthalocyanine blue), C.I.74160 (phthalocyanine blue), C.I.74180 (first sky blue), or the like is used.

  These colorants can be used alone or in combination of two or more, but it is desirable to use 1 to 20 parts by mass, preferably 2 to 10 parts by mass with respect to 100 parts by mass of the binder resin. When the amount is more than 20 parts by mass, the toner fixing property and transparency are deteriorated. On the other hand, when the amount is less than 1 part by mass, a desired image density may not be obtained.

(Release agent)
Release agents include paraffin wax, polyolefin wax, modified wax having aromatic group, hydrocarbon compound having alicyclic group, natural wax, long chain fatty acid having 12 or more carbon atoms or ester thereof, long chain fatty acid metal Salts (metal soaps), fatty acid amides, fatty acid bisamides and the like are used. Of the release agents, paraffin wax, polyolefin wax and metal soap are preferably used.

  Examples of the paraffin wax include paraffin wax (manufactured by Nippon Oil Co., Ltd. or Nippon Seiwa Co., Ltd.), micro wax (manufactured by Nippon Oil Co., Ltd.), and microcrystalline wax (manufactured by Nippon Seiwa Co., Ltd.). , Hard paraffin wax (manufactured by Nippon Seiwa Co., Ltd.), PE-130 (manufactured by Hoechst), Mitsui High Wax 110P (manufactured by Mitsui Petrochemical Co., Ltd.), Mitsui High Wax 220P (manufactured by Mitsui Petrochemical Co., Ltd.), Mitsui High Wax 660P (Mitsui Petrochemical Co., Ltd.), Mitsui High Wax 210P (Mitsui Petrochemical Co., Ltd.), Mitsui High Wax 320P (Mitsui Petrochemical Co., Ltd.), Mitsui High Wax 410P (Mitsui Petrochemical) ), Mitsui High Wax 420P (Mitsui Petrochemical Co., Ltd.), modified wax JC-1141 (Mitsui Petrochemical Co., Ltd.), modified wax JC-2130 (Mitsui Petrochemical Co., Ltd.), Modified wack JC-4020 (Mitsui Petrochemical Co., Ltd.), modified wax JC-1142 (Mitsui Petrochemical Co., Ltd.), modified wax JC-5020 (Mitsui Petrochemical Co., Ltd.), beeswax, carnauba wax, Montan A wax etc. can be mentioned.

  Examples of the polyolefin wax include low molecular weight polypropylene, low molecular weight polyethylene, oxidized polypropylene, oxidized polyethylene, and the like. Specific examples of polyolefin waxes include, for example, Hoechst Wax PE520, Hoechst Wax PE130, Hoechst Wax PE190 (manufactured by Hoechst), Mitsui High Wax 200, Mitsui High Wax 210, Mitsui High Wax 210M, Mitsui High Wax 220, Mitsui High Wax Non-oxidized polyethylene wax such as 220M (Mitsui Petrochemical Industries), Sun Wax 131-P, Sun Wax 151-P, Sun Wax 161-P (Sanyo Chemical Industries), Hoechst Wax PED121, Hoechst Wax PED153, Hoechst Wax PED521, Hoechst Wax PED522, Ceridust 3620, Ceridust VP130, Ceridust VP5905, Ceridust VP9615A, Ceridust TM9610F, Ceridust 3715 (manufactured by Hoechst), Mitsui High Wax 420M Koe Industries Co., Ltd.), Sun Wax E-300, Sun Wax E-250P (Sanyo Kasei Kogyo Co., Ltd.) and other oxidized polyethylene waxes, Hoechi Non-oxidized polypropylene wax such as st Wachs PP230 (Hoechst), Viscol 330-P, Biscol 550-P, Biscol 660P (Sanyo Chemical Industries), and Biscol TS-200 (Sanyo Chemical Industries, Ltd.) Oxidized polypropylene wax, such as

  As the long chain fatty acid metal salt (metal soap), zinc stearate, calcium stearate, magnesium stearate, zinc oleate, zinc palmitate, magnesium palmitate and the like are preferably used.

  These release agents can be used alone or in combination. As the release agent, a compound having a low softening point (melting point) is preferable, and those having a softening point of 40 to 130 ° C, preferably 50 to 120 ° C are preferably used. The softening point is represented by an endothermic main peak value in a DSC endothermic curve measured by “DSC120” manufactured by Seiko Instruments Inc.

(Dispersant)
As the dispersant, metal soap, polyethylene glycol, or the like is used.

(Charge control agent)
The charge control agent is used as necessary to control the chargeability of the toner base particles. When the negative chargeability of the binder resin itself is low, or when the binder resin itself is positively charged, a negative charge control agent is used to make the entire toner base particles have a desired level of negative chargeability. To have.

  Examples of the negative charge control agent include metal salts or metal complexes of salicylic acid derivatives, metal salts of benzylic acid derivatives, and phenylborate quaternary ammonium salts. As the metal salts of salicylic acid derivatives or benzylic acid derivatives, these zinc salts, nickel salts, copper salts, chromium salts and the like are preferably used.

  Examples of commercially available negative charge control agents include oil black (Color Index 26150), oil black BY (manufactured by Orient Chemical Co., Ltd.), Bontron S-22 (manufactured by Orient Chemical Co., Ltd.), and salicylic acid metal complex E. -81 (produced by Orient Chemical Co., Ltd.), thioindigo pigment, sulfonylamine derivative of copper phthalocyanine, Spiron Black TRH (produced by Hodogaya Chemical Co., Ltd.), Bontron S-34 (produced by Orient Chemical Co., Ltd.) ), Nigrosine SO (manufactured by Orient Chemical Industry Co., Ltd.), Ceres Schwartz (R) G (manufactured by Farben Fabricen Bayer), Chromogen Schwarz ETOO (CINO.14645), Azo Oil Black (R) (National Aniline). Among these, salicylic acid metal complex E-81 is preferably used. These negative charge control agents can be used alone or in combination.

  The negative charge control agent is preferably blended in the binder resin so that the charge amount of the toner base particles is −5 to −60 μC / g. Therefore, although the addition amount with respect to binder resin is determined by the binder resin to be used, generally it mix | blends in 0.1-5 mass parts with respect to 100 mass parts of binder resin.

  The positive charge control agent is internally added to the negative charge resin as necessary to adjust the negative charge amount of the toner base particles. A commercially available positive charge control agent is used as the positive charge control agent. For example, Nigrosine Base EX (manufactured by Orient Chemical Industries, Ltd.), quaternary ammonium salt P-51 (manufactured by Orient Chemical Industries, Ltd.), Nigrosine Bontron N-01 (manufactured by Orient Chemical Industries, Ltd.), Sudan Chief Examples include Schwartz BB (Solvent Black 3: Color Index 26150), Fett Schwartz HBN (CI NO. 26150), Brilliant Spirits Schwarz TN (manufactured by Farben Fabricken Bayer), and Zabon Schwartz X (manufactured by Farberge Hoechst). Of these, the quaternary ammonium salt P-51 is preferably used. In addition to the above, alkoxylated amines, alkylamides, molybdate chelate pigments and the like are also used as positive charge control agents. These positive charge control agents can be used alone or in combination.

(Magnetic agent)
Examples of the magnetic agent include metal powders such as Fe, Co, Ni, Cr, Mn, and Zn, metal oxides such as Fe ₃ O ₄ , Fe ₂ O ₃ , Cr ₂ O ₃ , and ferrite, and manganese and acid. Examples include alloys that exhibit ferromagnetism by heat treatment of the alloys. These may be pretreated with a coupling agent or the like.

(i-2) Manufacture of toner base particles Toner base particles are added to the binder resin with the colorant and, if necessary, internal additives such as a release agent, a dispersant, a charge control agent, and a magnetic agent. And manufactured. For example, a method for producing toner base particles by a pulverization method including a kneading, pulverization, and classification process will be described. First, a predetermined amount of additives such as a binder resin, a colorant, and a release agent are charged into a mixer such as a Henschel mixer 20B (Mitsui Mining Co., Ltd.) and mixed uniformly. The mixing ratio of additives such as a binder resin, a colorant, a charge control agent, and a release agent is appropriately determined in consideration of the color of the toner, chargeability, and the like.

  Next, the above mixture is put into a twin-screw kneading extruder (PCM-30 manufactured by Ikekai Kasei Co., Ltd.) and uniformly melt-kneaded. Other melt kneading means include batch-types such as continuous kneaders such as “TEM-37” (Toshiba Machine Co., Ltd.), “KRC Kneader” (Kurimoto Iron Works Co., Ltd.), and heating / pressure kneaders. Examples thereof include a kneader. The obtained melt-kneaded product is finely pulverized using a pulverizing means to obtain toner mother particles having a desired average particle size. The pulverization may be performed by, for example, a mechanical pulverizer turbo mill (Kawasaki Heavy Industries, Ltd.) in addition to collision pulverization using jet air using a jet pulverizer 200AFG (Hosokawa Micron Corporation) or IDS-2 (Nippon Pneumatic Industrial Co., Ltd.). )), Super Rotor (Nisshin Engineering Co., Ltd.), etc.

  Next, the particle size of the obtained toner base particles is adjusted using, for example, wind power or rotor rotation. For example, when the air classifier 100ATP (Hosokawa Micron Co., Ltd.), DSX-2 (Nippon Pneumatic Industrial Co., Ltd.), Elbow Jet (Nittetsu Mining Co., Ltd.) or the like is used, a sharp particle size distribution is obtained.

  The toner base particles are also a method in which an internal additive such as a resin and a colorant constituting the toner base particles is dissolved in an organic solvent, dispersed and granulated with a classifier and an emulsifier in an aqueous solvent, and separated and dried. You may produce by.

  The charge amount of the toner base particles is preferably −5 to −60 μC / g. When the charge amount is smaller than this range, toner leakage from the developing device becomes severe, and when it is larger than −60 μC / g, it is necessary to apply an excessive development bias in order to obtain a sufficient image density. Problem arises.

The charge amount of the toner base particles is measured as follows, for example. In an environment of 25 ° C. and 45% RH, 0.03 g of toner base particles and 0.97 g of ferrite carrier are mixed in a 20 ml polyethylene container and stirred at 100 rpm for 15 minutes to charge the toner base particles. Thereafter, 0.3 g of this mixture is sampled, and nitrogen gas having a pressure of 0.3 kg / cm ² is blown onto the mixture of the toner base particles and the carrier to separate the toner base particles and the ferrite carrier. Next, the charge amount (Q / m) for each toner is measured to measure the charge amount of the toner base particles. For the measurement of the charge amount, for example, an E-SPART analyzer manufactured by Hosokawa Micron Corporation is used.

(Ii) long chain fatty acids or salts thereof,
There is no restriction | limiting in particular in the long chain fatty acid used for this invention, or its salt. As the long chain fatty acid, a long chain fatty acid having preferably 10 to 30 carbon atoms, more preferably 12 to 28 carbon atoms, and still more preferably 12 to 18 carbon atoms is used. Examples of long chain fatty acids include long chain saturated fatty acids and long chain unsaturated fatty acids. Long chain saturated fatty acids are preferably used. The long-chain fatty acid may have a branch, but a linear saturated fatty acid such as stearic acid is preferably used.

  The long chain fatty acid is preferably used in the form of a salt, and more preferably in the form of a metal salt (so-called metal soap). Although there is no restriction | limiting in particular as a metal salt of a long chain fatty acid, For example, calcium salt, zinc salt, magnesium salt, aluminum salt, lithium salt etc. are mentioned. Examples of the metal soap include magnesium stearate, calcium stearate, zinc stearate and the like, and these particles are preferably used. The particles comprising a long-chain saturated fatty acid or a salt thereof may be used alone or in combination of two or more.

  The long-chain fatty acid or a salt thereof, particularly a long-chain fatty acid metal salt (metal soap), preferably has a volume average particle diameter or major axis diameter of 0.5 to 10 μm, and more preferably 1 to 5 μm. If the average particle diameter or the major axis diameter is out of this range, the effect as a binder, lubricant, flow aid, or toner aggregation preventing effect tends to be insufficient.

  The long-chain fatty acid or salt thereof, particularly metal soap, preferably has a melting point of about 100 to 150 ° C. from the viewpoint of heat resistance and lubricity. When the melting point is lower than 100 ° C., the heat resistance of the toner is lowered, and the toner may aggregate when stored in a high temperature environment. If it is higher than 150 ° C, the lubricating action may be reduced.

  As metal soaps, metal soaps manufactured by the direct method and metal soaps manufactured by the double decomposition method are known. It is preferable to adjust the particle size so that

  The particles comprising a long-chain saturated fatty acid or a salt thereof are added in an amount of 0.1 to 1.0 parts by weight, preferably 0.1 to 0.5 parts by weight, based on 100 parts by weight of toner base particles. When the addition amount is less than 0.1% by mass, the effects as the binder, the aggregation preventing effect, the flow aid, the lubricant and the like may not be sufficiently exhibited. On the other hand, when the addition amount is more than 1.0% by mass, the fluidity is inferior, the charge rising property is remarkably deteriorated, and noise such as fog may be generated.

(Iii) Negatively chargeable silica fine particles The negatively chargeable silica fine particles used in the present invention are not particularly limited. As the negatively chargeable silica fine particles, generally, negatively chargeable silica fine particles having an average particle diameter of 4 to 120 nm, preferably 5 to 50 nm, and more preferably 6 to 40 nm are used. The smaller the average particle size of the negatively chargeable silica fine particles, the higher the fluidity of the obtained toner. If it is smaller than 4 nm, the toner may be buried in the toner base particles. If it exceeds 120 nm, the fluidity may be extremely deteriorated. In this specification, the average particle diameter of fine particles such as negatively chargeable silica, toner base particles, and toner particles means a volume average particle diameter unless otherwise specified.

  In the present invention, negatively chargeable silica fine particles having a uniform particle diameter may be used alone, or two or more negatively chargeable silica fine particles having different average particle diameters may be used in combination. In general, negatively chargeable silica fine particles having a small average particle diameter (silica having a small particle diameter) are used alone. However, by using a small particle size silica and a negatively charged silica fine particle having a large average particle size (a large particle size silica) in combination, the absolute value of the charge amount is smaller than when only a small particle size silica is used. In addition, the large particle size silica becomes resistance, and the small particle size silica can be prevented from being embedded in the toner base particles, so that long-term charging stability is excellent. Furthermore, it is possible to improve the fluidity of the toner, exhibit a blocking effect against heat, and improve the storage stability of the toner.

  When the negatively chargeable silica fine particles are used alone, in general, negatively chargeable silica fine particles having a small average particle diameter are preferably used. The average particle diameter of the negatively chargeable silica fine particles is preferably 5 to 20 nm, and more preferably 6 to 15 nm.

  When two or more negatively chargeable silica fine particles having different average particle diameters are used in combination, the average particle diameter is 5 to 20 nm, preferably 6 to 15 nm, and the average particle diameter is 20 to 50 nm. It is preferable to use silica having a large particle diameter of 20 to 40 nm. The difference in average particle size between the large particle size silica and the small particle size silica is preferably 10 nm or more, and more preferably 20 nm or more.

  The addition ratio of the large particle size silica to the small particle size silica is 1: 3 to 3: 1, preferably 1: 2 to 2: 1, more preferably 1: 1.5 to 1.5: by mass ratio. 1 is preferable. Within this range, fluidity is imparted to the toner, and long-term charging stability can be obtained.

  In the case of using large particle size silica and small particle size silica, these may be mixed and added at the same time during the production described below, either one may be added first, and then the other may be added. .

  The addition amount of the negatively chargeable silica fine particles can vary depending on the particle size distribution or fluidity of the toner base particles, or the particle size distribution of the external additive, the desired charge amount, and the like. For example, in the case of silica having the small particle diameter, 0.5 to 2.0 parts by mass, preferably 0.7 to 1.5 parts by mass are added to 100 parts by mass of the toner base particles. In the case of a large particle size silica, 0.2 to 2.0 parts by mass, preferably 0.3 to 1.5 parts by mass is added. When the large particle size silica and the small particle size silica are used in combination, the total amount is 0.5 to 3.0 parts by mass, preferably 0.7 with respect to 100 parts by mass of the toner base particles, taking the above mixing ratio into consideration. Add ~ 2.5 parts by weight.

  The negatively chargeable silica fine particles are preferably hydrophobized. By making the surface of the negatively chargeable silica fine particles hydrophobic, the fluidity and chargeability of the toner are further improved. Hydrophobization of silica fine particles can be achieved by using silane compounds such as aminosilane, hexamethyldisilazane and dimethyldichlorosilane; or dimethylsilicone, methylphenylsilicone, fluorine-modified silicone oil, alkyl-modified silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, etc. This silicone oil is used, for example, by a method commonly used by those skilled in the art, such as a wet method or a dry method.

  As the hydrophobic negatively chargeable silica fine particles, commercially available RX200 and RX50 manufactured by Nippon Aerosil Co., Ltd., TG811F, TG810G and TG308F manufactured by Cabot Corp. are used.

(Iv) Titanium oxide fine particles In the present invention, titanium oxide (titania) fine particles are used as needed for the purpose of adjusting the charge of the toner. Like the positively chargeable silica fine particles, the titanium oxide fine particles can be added after the addition of the negatively chargeable silica fine particles and before the addition of the particles of the long chain fatty acid or a salt thereof. It is preferable in terms of binding to the mother particles and exhibiting the effect of a long chain fatty acid or a salt thereof as a binder and the effect of a lubricant.

  There is no restriction | limiting in particular in the titanium oxide fine particle used by this invention. Fine particles of titanium oxide having a relatively low electrical resistivity are preferably used. Titanium oxide can take crystal forms such as rutile, anatase, and rutile-anatase. Any crystalline titanium oxide may be used, but the rutile-anatase type titanium oxide is easy to adjust the charge, and even if the number of printed sheets increases, the titanium oxide particles are not easily embedded in the toner base particles. It is preferably used in terms of

  Although there is no restriction | limiting in particular in the magnitude | size of a titanium oxide microparticle, It is preferable that a particle size or the magnitude | size of a major axis is a magnitude | size of 10-30 nm. In the case of rutile-anatase type titanium oxide, titanium oxide fine particles having a major axis of about 10 to 30 nm are preferable.

  The titanium oxide fine particles are added in an amount of 0.2 to 2.0 parts by weight, preferably 0.3 to 1.5 parts by weight, based on 100 parts by weight of the toner base particles. The addition of the titanium oxide fine particles and the positively chargeable silica fine particles in a mass ratio of 1: 3 to 3: 1 can adjust the charge without causing an extreme decrease in the electric resistance of the toner. In terms, it is preferable.

  The surface of the fine particles of titanium oxide is hydrophobic in order to reduce the change in chargeability with respect to changes in the external environment of the toner (that is, maintain stable chargeability) and improve the fluidity of the toner. It is preferable. Hydrophobization of the titanium oxide fine particles is carried out by the same method as that of the negatively chargeable silica fine particles.

  As the hydrophobic titanium oxide fine particles, STT-30S manufactured by Titanium Industry Co., Ltd. is used.

(V) Positively Charged Silica Fine Particles In the present invention, the positively chargeable silica fine particles are used as necessary for adjusting the charge of the toner. The positively chargeable silica fine particles are added after the addition of the negatively chargeable silica fine particles and before the addition of the long chain fatty acid or the salt thereof, so that the negatively chargeable silica fine particles are firmly bonded to the toner base particles. And long-chain fatty acids or salts thereof are preferable for exhibiting the effect as a binder and the effect as a lubricant.

  The positively chargeable silica fine particles used in the present invention are not particularly limited. The volume average particle diameter of the positively chargeable silica fine particles is preferably 10 to 50 nm, more preferably 15 to 40 nm in consideration of fluidity and the like.

  The positively charged silica fine particles are preferably subjected to a hydrophobic treatment. By making the surface of the positively chargeable silica fine particles hydrophobic, the change in the chargeability with respect to the change in the external environment of the toner is reduced (that is, the stable chargeability is maintained) and the fluidity of the toner is improved. Therefore, it is preferable. The hydrophobization of the positively chargeable silica fine particles is performed by the same method as the above-described hydrophobization of the negatively chargeable silica fine particles.

  As the hydrophobic positively chargeable silica fine particles, commercially available NA50H manufactured by Nippon Aerosil Co., Ltd., TG820F manufactured by Cabot Co., Ltd., etc. are used.

  The positively chargeable silica fine particles are added in an amount of 0.1 to 1.0 parts by weight, preferably 0.2 to 0.8 parts by weight, based on 100 parts by weight of the toner base particles, if necessary.

(Vi) Inorganic fine particles Inorganic fine particles other than titanium oxide fine particles can also be externally added for the purpose of controlling the chargeability and improving the fluidity. The inorganic fine particles other than the titanium oxide fine particles can also be added after the addition of the negatively chargeable silica fine particles and before the addition of the particles of the long chain fatty acid or a salt thereof. It is preferable for binding and exhibiting the effect of a long-chain fatty acid or a salt thereof as a binder and the effect of a lubricant.

For example, as inorganic fine particles, fine particles of metal oxides such as aluminum oxide, strontium oxide, tin oxide, zirconia oxide, magnesium oxide and indium oxide; fine particles of nitride such as silicon nitride; fine particles of carbide such as silicon carbide; calcium sulfate And fine particles of metal salts such as barium sulfate and calcium carbonate; and inorganic fine particles such as a composite thereof. Metal oxide fine particles having an electrical resistivity of 10 ⁹ Ωcm or less and a relatively low electrical resistivity are preferably used.

  Although there is no restriction | limiting in particular in the magnitude | size of the inorganic fine particle to add, It is preferable that a particle size is a magnitude | size of 10-30 nm. These inorganic fine particles are preferably subjected to a hydrophobic treatment on the surface for the purpose of stabilizing charging characteristics. For the hydrophobization treatment, the same method as any of the above-described hydrophobic methods for the negatively chargeable silica fine particles and the positively chargeable silica fine particles is employed.

(II) Toner of the Present Invention and Method for Producing the Same As described above, the toner of the present invention adds external additives by multistage treatment, and in the last stage, particles composed of long chain fatty acids or salts thereof are added from other stages. Can also be obtained by adding at a high temperature. The external additive (for example, negatively-charged silica fine particles, titanium oxide fine particles, positively-charged silica fine particles, particles composed of a long chain fatty acid or a salt thereof) is added to the toner base particles such as a Henschel mixer, Perpenmeier, etc. It is carried out using a machine or a method commonly used by those skilled in the art, such as a high-speed fluid mixer and a mixer using a mechanochemical method. The temperature, stirring speed, time, etc. in each step of the multi-stage treatment can be set independently, but the external addition of particles consisting of a long-chain fatty acid or its salt, which is the final stage, makes the temperature higher than the other stages. Done.

  When using a mixer, the external addition of particles comprising a long-chain fatty acid or a salt thereof is performed by increasing the temperature in the mixer. Specifically, if there is a temperature control means in the mixer, it may be used. If there is no such temperature control means, a heating means (for example, a heater) is attached to the mixer, and the temperature in the mixer is increased. It is only necessary to attach a sensor and control the temperature in conjunction with the heater.

  The temperature at the time of external addition of particles comprising a long-chain fatty acid or a salt thereof needs to be higher than the temperature at the time of external addition of other external additives. However, the temperature at the time of external addition must be determined in consideration of the flow softening point (Tm) and glass transition temperature (Tg) of the binder resin used for the toner base particles, and exceeds Tg and Tm. must not. Further, when the melting point of the long-chain fatty acid or salt thereof is exceeded, the long-chain fatty acid or salt thereof may melt and may not be uniformly added to the toner base particles. Therefore, it is necessary to set it lower than the melting point of particles made of long chain fatty acids or salts thereof. Therefore, in the present invention, it is determined in consideration of the Tm and Tg of the binder resin used for the toner base particles and the melting point of the particles made of long chain fatty acid or a salt thereof.

  The temperature at the time of external addition of particles comprising a long-chain fatty acid or a salt thereof is preferably 3 ° C. or more higher than the temperature at the time of external addition of other external additives. It is preferably 5-30 ° C higher, more preferably 5-20 ° C higher, and even more preferably 10-15 ° C higher. In general, the temperature at the time of external addition is preferably 80 ° C. or less, more preferably 60 ° C. or less in consideration of the above-mentioned Tg, Tm and the melting point of the long-chain fatty acid or salt thereof. However, it can be easily understood by those skilled in the art that depending on the type of resin used, the temperature may be higher than these preferable temperatures. As shown in the examples below, when a styrene-acrylic binder resin is used as a toner binder resin and a Henschel mixer is used, an external additive is usually added in the range of 30 to 40 ° C. In this invention, it adds 5-15 degreeC higher than the temperature, for example, 35-55 degreeC.

  Thus, by adding particles comprising a long-chain fatty acid or a salt thereof at a higher temperature than other external additives in the final stage of the multistage treatment, the physical properties of the particles comprising a long-chain fatty acid or a salt thereof (for example, The viscosity changes). As a result, long-chain fatty acids or salts thereof are more likely to adhere (binder) to the toner base particles, so that it acts as a binder for other external additives and prevents these external additives from detaching from the toner surface. Can be suppressed.

  Furthermore, in the present invention, in the final stage of the multi-stage treatment, it is preferable to add particles composed of long-chain fatty acids or salts thereof at a higher temperature than other external additives and at the same time increase the share. As a result, the long-chain fatty acid or a salt thereof is uniformly and firmly added onto the toner, thereby functioning not only as a binder for the external additive but also as a toner lubricant. In addition to preventing toner aggregation, it is possible to prevent the external additive from being embedded in the toner base particles due to friction between the toners, thereby maintaining the uniformity of charging.

  The method of increasing the share (for example, mixing share) at the time of external addition of particles comprising a long-chain fatty acid or a salt thereof may be determined depending on the apparatus for adding the external additive to the toner base particles. Among the above devices, when using a high-speed fluid mixer such as a Henschel mixer having a rotating blade, or Palpenmeier, (1) By increasing the rotating speed of the rotating blade, (2) the distance between the rotating blade and the mixer wall By the method of reducing (gap), the share at the time of mixing the particle | grains which consist of long chain fatty acid or its salt can be raised. When externally adding particles comprising a long-chain fatty acid or a salt thereof, 1.02 times or more, preferably 1.2 times or more, more preferably 1.5 times that of other fine particle external additives. It is preferable to apply the above high share. If a too high share is applied, other fine particles will be affected, so 3 times or less is preferable.

  Specifically, the toner of the present invention includes, for example, at least one external additive selected from the group consisting of negatively-charged silica fine particles, titanium oxide fine particles, and positively-charged silica fine particles added to the toner base particles. It is obtained by adding an external additive comprising particles comprising a long-chain fatty acid or a salt thereof in a stage at a higher temperature than the other stages, and preferably with a higher share. Here, the “external additive containing particles comprising a long-chain fatty acid or a salt thereof” is used in the case of only particles comprising a long-chain fatty acid or a salt thereof, and multistage treatment with particles comprising a long-chain fatty acid or a salt thereof. It may be a combination with an external additive that has not been made.

  Hereinafter, the multi-stage process for obtaining the toner of the present invention will be described with various combinations exemplified. In addition, when the toner base particles are positively to weakly negatively charged during multi-stage processing, first add negatively charged silica fine particles (II-1), and first add negatively charged silica fine particles and titanium oxide fine particles. (II-2) or first adding titanium oxide fine particles (II-3) is performed. When the toner base particles are strongly negatively charged, first, positively charged silica fine particles are added (II-4), and first, positively charged silica fine particles and other external additives are added (II-5). ) Is performed. Hereinafter, these cases will be described.

(II-1) Toner obtained by first adding negatively chargeable silica fine particles When negatively chargeable silica fine particles are added alone, the electrostatic attractive force between the toner base particles and the negatively chargeable silica fine particles is positively charged. The negatively chargeable silica fine particles are strongly adhered to the toner base particles because the work function of the negatively chargeable silica fine particles and the work function of the toner base particles are large. Can do. As a result, the desorption of the negatively chargeable silica fine particles is prevented, the change in chargeability is reduced, and the effect that the chargeability is stabilized in the long term is obtained.

  As the negatively chargeable silica fine particles, it is preferable to use a small particle size silica and a large particle size silica in combination. By using negatively chargeable silica fine particles having different average particle diameters, the absolute value of the charge amount can be increased as compared with the case of using only negatively chargeable silica fine particles having a small particle diameter, and negative particles having a large particle diameter. The chargeable silica fine particles serve as resistance, and silica having a small particle diameter can be prevented from being embedded in the toner base particles, and the long-term charge stability is excellent. Furthermore, it is possible to improve the fluidity of the toner, exhibit a blocking effect against heat, and improve the storage stability of the toner.

  When using a small particle size silica and a large particle size silica in combination, these silicas may be added at the same time, first adding a small particle size silica, then adding a large particle size silica. Good.

  After the negatively chargeable silica fine particles are added first, finally, the particles of the long chain fatty acid or a salt thereof are added at a higher temperature (preferably at a high share at the same time) than the other processing steps, whereby the toner of the present invention is added. Is obtained. In this case, first, a silica having a small particle size and a silica having a large particle size are simultaneously added to the toner base particles, and finally, particles comprising a long-chain fatty acid or a salt thereof are added at a higher temperature (preferably than other processing steps). (With a high share at the same time) or two-stage treatment, or first externally add silica with a small particle size, then externally add silica with a large particle size, and finally add particles consisting of a long-chain fatty acid or a salt thereof. Examples include a three-stage treatment that is added at a higher temperature (preferably at a high share at the same time) than the other treatment stages.

  First, negatively chargeable silica fine particles may be added to toner base particles, and then titanium oxide fine particles and positively chargeable silica fine particles may be added. Although the titanium oxide fine particles and the positively chargeable silica fine particles may be added simultaneously, it is more preferable to add the titanium oxide fine particles first, and then add the positively chargeable silica fine particles. The positively chargeable silica fine particles are positively charged and have a high electric resistance value. Therefore, by adding the titanium oxide fine particles, and then adding the positively chargeable silica fine particles, the positively chargeable silica fine particles function as a charge adjusting agent, and the decrease in the electrical resistivity of the toner is suppressed, and the charge is reduced. It is made uniform. Furthermore, positively-charged silica particles are present in an appropriate ratio in the toner, and the fluidity of the toner is improved, and the positively-charged silica fine particles that are free serve as a carrier, Chargeability becomes more uniform.

  As a multi-stage treatment in which negatively-charged silica fine particles are added first, and finally particles comprising a long-chain saturated fatty acid or a salt thereof are added at a higher temperature (preferably at a high share at the same time) than other treatment steps, The following (a) to (h) are exemplified: (a) Negatively charged silica fine particles-particles composed of long chain saturated fatty acids or salts thereof; (b) Negatively charged silica fine particles-titanium oxide fine particles-long chains. Particles made of saturated fatty acid or salt thereof; (c) Negatively charged silica fine particle-positively charged silica fine particle-particle made of long chain saturated fatty acid or salt thereof; (d) Negatively charged silica fine particle-titanium oxide fine particle-positive charged Silica fine particles-particles composed of long chain saturated fatty acids or salts thereof; (e) Negatively charged silica fine particles-(positively charged silica particles + particles composed of long chain saturated fatty acids or salts thereof); (f) Negatively charged silica Fine particles-Titanium oxide fine particles-(positive (G) Negatively chargeable silica fine particles- (titanium oxide fine particles + long chain saturated fatty acids or particles thereof); (h) Negatively chargeable silica Fine particles— (titanium oxide fine particles + positively charged silica fine particles + particles composed of long-chain saturated fatty acids or salts thereof);

  In addition, in the order of the steps, when adding the small particle size silica alone, the small particle size silica and the large particle size silica are added simultaneously, unless otherwise specified, to the addition of the negatively chargeable silica fine particles. And a case where two-stage treatment is performed in the order of small particle size silica-large particle size silica. For example, (a) particles of negatively charged silica fine particles-long chain saturated fatty acids or salts thereof include (a1) particles of silica-long chain saturated fatty acids or salts thereof having a small particle size; (a2) small particle sizes (A3) (small particle diameter silica + large particle diameter silica) —particles composed of long chain saturated fatty acid or salt thereof; included. In addition, (h) negatively charged silica fine particles- (titanium oxide fine particles + positively charged silica fine particles + long chain saturated fatty acids or particles thereof) include (h1) (small particle size silica + large particle size particles). Silica)-(titanium oxide fine particles + positively charged silica fine particles + long chain saturated fatty acid or a salt thereof).

  As described above, as the multi-stage treatment for obtaining the toner of the present invention by first adding the negatively chargeable silica fine particles, the two-stage treatment, the three-stage treatment, the four-stage treatment, and the above (a2) depending on the combination of the external additives used. In the case of adopting the method of (5), a five-stage process is exemplified. In particular, it is possible to add positively-charged silica fine particles and particles of long-chain fatty acids or salts thereof at a higher temperature (preferably at a high share) at the same time as the other treatment stages, and to perform multistage treatment. The adjustment of the surface charge by the fine particles and the titanium oxide fine particles is preferable in that it can be most efficiently performed without extremely reducing the electric resistance.

(II-2) Toner obtained by first adding negatively chargeable silica fine particles and titanium oxide fine particles When negatively chargeable silica fine particles and titanium oxide fine particles are added simultaneously to the toner base particles, negatively chargeable silica From the relationship between the work function of the fine particles, the work function of the titanium oxide fine particles, and the work function of the toner base particles, the negatively chargeable silica fine particles are relatively strongly attached to the toner base particles, so that the release of the silica fine particles is suppressed. In addition to this, the effect of performing the multistage treatment in which the long-chain fatty acid or a salt thereof is added at a higher temperature (preferably at a high share at the same time) than the other treatment steps is exhibited.

  Such multi-stage treatment includes: (i) (negatively charged silica fine particles + titanium oxide fine particles) —particles composed of long chain saturated fatty acids or salts thereof; (j) (negatively charged silica fine particles + titanium oxide fine particles) —positive Examples include: electrified silica fine particles-long chain saturated fatty acids or salts thereof; (k) (negatively charged silica fine particles + titanium oxide fine particles)-(positive chargeable silica fine particles + long chain saturated fatty acids or salts thereof); When negatively chargeable silica fine particles and titanium oxide fine particles are added simultaneously, (i) (negatively chargeable silica fine particles + titanium oxide fine particles) -long chain saturated fatty acid or a salt thereof includes (i1) ( (Small particle size silica + titanium oxide fine particle) -particles composed of long chain saturated fatty acid or salt thereof; (i2) (Small particle size silica + large particle size silica + titanium oxide fine particle) -long chain saturated fatty acid or salt thereof (I3) silica having a small particle diameter + (silica having a large particle diameter + titanium oxide fine particles) −particles composed of a long-chain saturated fatty acid or a salt thereof; and the like.

(II-3) Toner Obtained by First Adding Titanium Oxide Fine Particles When titanium oxide fine particles are added first, next, particles comprising a long chain fatty acid or a salt thereof may be added. Next to the titanium oxide fine particles, negatively chargeable silica fine particles may be added, and finally particles composed of long-chain fatty acids or salts thereof may be added. If necessary, the positively charged silica fine particles are added before the long-chain fatty acid or salt thereof or simultaneously with the long-chain fatty acid or salt thereof, thereby preventing the charge amount from decreasing sharply. Can be adjusted. In addition to this effect, the effect of the long-chain fatty acid or salt thereof is exhibited.

  Such multi-stage treatment includes (l) particles of titanium oxide fine particles-long chain saturated fatty acids or salts thereof; (m) particles of titanium oxide fine particles-negatively charged silica fine particles-long chain saturated fatty acids or salts thereof; (n) Titanium oxide fine particles-negatively chargeable silica fine particles-positively chargeable silica fine particles-particles composed of long chain saturated fatty acids or salts thereof; (o) Titanium oxide fine particles-negatively chargeable silica fine particles- (positively chargeable silica fine particles + For example, particles composed of a long-chain saturated fatty acid or a salt thereof). In particular, the processing steps (n) and (o) are effective even when the toner base particles are strongly negatively charged.

(II-4) Toner obtained by first adding positively charged silica fine particles When toner base particles are strongly negatively charged, first add positively charged silica fine particles; first positively charged silica fine particles And other external additives are added. Among them, it is most preferable to add positively charged silica fine particles alone first. According to this step, the electrostatic attractive force between the negatively chargeable toner base particles and the positively chargeable silica fine particles is not hindered, and the work function of the positively chargeable silica fine particles and the work function of the toner base particles are Therefore, the positively chargeable silica fine particles are strongly attached to the toner base particles. Therefore, the positively chargeable silica fine particles are prevented from being detached, the change in chargeability is reduced, and the effect that the chargeability is stabilized for a long time is obtained.

  After the addition of the positively chargeable silica fine particles, the titanium oxide fine particles are added alone or together with the particles made of long chain fatty acid or a salt thereof. By externally adding positively-charged silica fine particles having a high electric resistance value in advance, the surface charge when the low-electrical resistance titanium oxide fine particles are externally added is not greatly reduced (that is, positively charged). The chargeable silica fine particles function as a charge adjusting agent), and the decrease in the electrical resistivity of the toner is suppressed, and the charge is made uniform. In addition to these effects, the effect of adding a long-chain fatty acid or a salt thereof at the end is exhibited.

  Examples of such multi-stage treatment include (p) positively charged silica fine particles—long chain fatty acid or salt thereof; (q) positively charged silica fine particles— (titanium oxide fine particles + long chain fatty acid or salt thereof); The

  This multi-stage treatment does not include negatively chargeable silica fine particles as an external additive. A toner containing no negatively chargeable silica fine particles as an external additive has good charging characteristics and fluidity. In addition, the toner fixing temperature can be lowered (the temperature of the fixing device can be set low), and the fixing strength of the image after fixing can be improved. In (p), which is an example of multi-stage treatment, titanium oxide fine particles are not added, but if the charge amount is in an appropriate range, it may not be added.

(II-5) Toner obtained by first adding positively chargeable silica fine particles and other external additives When other external additives are negatively chargeable silica fine particles, the toner base particles are negatively charged. From the viewpoint of charge control, it is preferable to add negatively-charged silica fine particles simultaneously with positively-charged silica fine particles. As an example of multi-stage treatment in which positively charged silica fine particles and negatively chargeable silica are added first, (r) (positively charged silica fine particles + negatively charged silica fine particles) -titanium oxide fine particles-long chain fatty acid or salt thereof) (S) (positively charged silica fine particles + negatively charged silica fine particles + titanium oxide fine particles) -long chain fatty acid or salt thereof; (t) (positively charged silica fine particles + negatively charged silica fine particles) -long chain fatty acid or Examples thereof include salts thereof.

  The order of the multi-stage processes (a) to (t) is merely an example, and is not limited to these. Moreover, you may add the inorganic fine particle of said (vi) for the purpose of charge adjustment, fluidity | liquidity improvement, etc. as needed. The inorganic fine particles may be added at any stage as long as it is before or simultaneously with the addition of the long-chain fatty acid or salt thereof.

  As described above, in the toner of the present invention, the external additive strongly adheres to the toner base particles due to the work function of each external additive and the work function of the toner base particles in multi-stage processing. And, at the last stage, due to the binding action of the long-chain fatty acid or its salt added at a higher temperature than the other stages, and preferably at the same time, effects such as the effect of controlling the release of external additives, Further strengthened. Furthermore, effects such as charging uniformity and long-term charging stability are enhanced, and charging stability is maintained even after repeated use. In addition, the toner has an anti-aggregation effect, a flow aid, a lubricant, etc., and the contact between the toner and the photoconductor causes long-chain fatty acids or salts thereof to migrate to the photoconductor surface, lubricating the photoconductor surface, and It is considered that the effect of preventing the body from being polished by the external additive on the toner surface is further exhibited.

  On the other hand, the conventional toner, for example, the toner described in Patent Document 1 above, is obtained by simultaneously adding positively chargeable silica fine particles and negatively chargeable silica fine particles. By simultaneously adding the silica fine particles and the negatively chargeable silica fine particles, the electrostatic attractive force between the toner base particles and the negatively chargeable silica fine particles is reduced, and the negatively chargeable silica fine particles are easily detached. it is conceivable that. Furthermore, the absence of long-chain fatty acids or salts thereof seems to be a cause of the inability to suppress the release of negatively charged and / or positively charged silica fine particles or titanium oxide fine particles.

  The toner of the present invention can be used in any type of image forming apparatus. An image forming apparatus using a one-component toner or an image forming apparatus using a two-component toner may be used. Further, it may be a contact developing type image forming apparatus or a non-contact type image forming apparatus. A one-component contact-type image forming apparatus that can use the toner of the present invention is described in detail in, for example, Patent Document 8. The image forming apparatus of the present invention includes a latent image carrier on which an electrostatic latent image typified by a photoreceptor is formed; toner is applied to the latent image carrier to develop the electrostatic latent image on the latent image carrier. At least a developing device having a toner carrying member typified by a developing roll to be conveyed; and a toner regulating member for regulating the amount of toner carried to the latent image carrying member by the toner carrying member. The toner of the present invention is accommodated in a toner accommodating portion, conveyed from the toner accommodating portion to a developing roll (toner carrier), and supplied to the photosensitive member (latent image carrier) via the developing roll (toner carrier). And transferred to form an image. The toner regulating member adjusts the toner supply amount so that excessive supply from the developing roll (toner carrier) to the photosensitive member (latent image carrier) is not performed.

Hereinafter, the present invention will be described based on examples. First, the toner evaluation method of the present invention will be described. Evaluation items and evaluation methods are as follows.
(A) Evaluation of Charge Amount and Charge Uniformity The toner charge amount was measured as follows using an E-SPART analyzer manufactured by Hosokawa Micron Corporation. The toner prepared in Examples and Comparative Examples and a carrier (KBN100 ferrite carrier manufactured by Hitachi Metals, Ltd.) were mixed so as to have a toner concentration of 0.1% by mass, and stirred at 100 rpm for 15 minutes to charge the toner. . Thereafter, the toner and the carrier were separated by blowing nitrogen gas onto the mixture of the toner and the carrier. Next, the charge amount (Q / m) for each toner is measured, and the measured toner is measured for at least 100 toner particles having an average particle diameter of ± 0.1 μm obtained by a Coulter counter. Is plotted on the X axis, and the total charge amount represented by the following equation is plotted on the Y axis as the total charge amount.

  Here, if toner particles having the same particle diameter and charge amount are plotted, when the number of toners and the total charge amount are plotted, a straight line passing through the origin with correlation coefficient = 1 should be obtained. The number of toners and the measured value of the total charge amount were plotted, and the deviation from the straight line was evaluated by the correlation coefficient.

(B) Irregular Toner Generation Rate Using the E-SPART analyzer of (1), the number of positively charged toners (reversely charged toners) that are irregular toners was measured to determine the irregular toner generation rate.

(C) Free rate of external additives (silica fine particles, titanium oxide fine particles) The free rate of external additives (silica fine particles, titanium oxide fine particles) was measured using PT1000 particle analyzer (manufactured by Yokogawa Electric Corporation). Was measured. Details of the method for measuring the liberation rate of the external additive are described in Patent Document 8. Briefly, this principle is to determine the liberation rate by introducing toner particles into plasma, exciting and emitting the toner particles, and measuring the intensity and time. For example, the isolation rate of SiO ₂ introduces toner particles SiO ₂ was externally added to the plasma, measuring the emission intensity of the SiO ₂ in the toner particles. From the light emission intensity, the particle diameter (equivalent particle diameter) of the true spherical particles is obtained assuming that the toner particles to which SiO ₂ is externally added are true spherical particles. Liberated SiO _2, similarly to the case of the toner particles, the equivalent diameter of SiO ₂ is determined from the emission intensity. However, since the emission intensity of free SiO ₂ is small, the equivalent particle size is small. Therefore, the toner particles are separated from the free external additive by comparing the equivalent particle diameters. Therefore, when the total number of detected external additives SiO ₂ is obtained and an individual having a small equivalent particle diameter is defined as the number of free external additive particles, the following expression (X) is obtained.

Further, SiO ₂ adhering to the toner particles emits light at the same time in synchronization with the toner particles, but SiO ₂ not adhering to the toner particles does not emit light at the same time as the toner particles and emits light with a time shift (asynchronous). ) To distinguish whether SiO ₂ is attached to or separated from the toner particles. Based on this measured value, the liberation rate is obtained by the following equation (Y).

  In this example, the method represented by the formula (Y) was adopted. In addition, when measuring the liberation rate of the titanium oxide fine particles, the titanium oxide fine particles may be caused to emit light in plasma and measured in the same manner. Further, the volume average particle diameter of the toner base particles can be obtained, for example, by emitting a colorant contained in the toner base particles in plasma and obtaining an equivalent particle diameter.

(D) Durability test The toner is put into a copier (LP-9300 manufactured by Seiko Epson Corporation), and 3000 sheets are printed with a 5% consumption printing pattern. The electrical resistivity was measured.

(Preparation of toner base particles)
100 parts by mass of styrene-acrylic binder resin, 3.5 parts by mass of red pigment CI12055, and 1.0 part by mass of chromium salicylate complex were respectively added to Henschel mixer 20B (Mitsui Mine Co., Ltd.), and uniform. Mixed. This mixture was melt-kneaded using a twin-screw kneading extruder (PCM-30 manufactured by Ikekai Kasei Co., Ltd.), cooled, and then pulverized by jet air using a jet pulverizer 200AFG (Hosokawa Micron Corporation). Next, toner base particles having a volume average particle diameter of 8.5 μm were prepared using an air classifier 100ATP (Hosokawa Micron Corporation).

(External additive)
Table 1 shows external additives that are externally added to the toner base particles in this example.

(External processing)
In the embodiment of the present invention, in the external addition process, a predetermined amount of an external additive is added to 100 parts by mass of the toner base particles, and the Z0S0 type is added using a Henschel mixer FM20B (Mitsui Mining Co., Ltd.). Using a stirring blade, stirring and mixing were performed.

Example 1
100 parts by mass of the toner base particles prepared above were put into a Henschel mixer FM20B, and 1.0 part by mass of hydrophobic negatively chargeable silica RX200 (manufactured by Nippon Aerogel) was added thereto. Minute processing. Next, 0.5 parts by mass of hydrophobic positively charged silica NA50H (manufactured by Nippon Aerogel Co., Ltd.) and 0.2 parts by mass of magnesium stearate are added to this treated product, and a treatment at 3000 rpm for 2 minutes at 45 ° C. And toner A was obtained. Toner A is a toner obtained by a two-stage process. Note that the gap between the rotating blades of the mixer and the mixer wall (hereinafter simply referred to as the gap) at this time was 5 mm in both treatments. The production conditions for Toner A are shown in Table 2.

(Comparative Example 1)
100 parts by mass of the toner base particles prepared above were put into a Henschel mixer FM20B, and 1.0 part by mass of hydrophobic negatively chargeable silica RX200 (manufactured by Nippon Aerogel) was added thereto. To give toner a. Table 2 shows the production conditions of the toner a.

(Examples 2-9, Comparative Examples 2-3)
The toners of Examples 2 to 9 (respectively, toner B to toner I) and the toners of comparative examples 2 to 3 (respectively, toner b to toner c) were prepared according to the toner production conditions shown in Table 2. In Examples 2 to 7, the treatment temperature in the final treatment stage was added higher than other treatment temperatures (35 ° C.) (45 ° C.) and added. Examples 8 and 9 are examples in which the mixture of magnesium stearate and positively-charged silica fine particles in the final stage was added at a higher share while increasing the temperature at the time of addition than other processing temperatures. In Example 8, the share was increased by increasing the rotational speed from 3000 rpm to 4000 rpm. The share at the time of external addition at this time was about 1.3 times the share at the time of adding other external additives. In Example 9, the market share was increased by reducing the gap from 5 mm to 2 mm. The share at the time of external addition at this time was about 1.5 times the share at the time of adding other external additives. Comparative Example 1 is an example in which magnesium stearate is not added, and Comparative Example 2 is an example in which multistage processing is not performed. Comparative Example 3 is an example in which the processing temperature in the final stage is lowered.

  The toner A to toner I of the example and the toner a to toner c of the comparative example were evaluated. The results are shown in FIG. FIG. 1 is a diagram showing the correlation for toner A. FIG. Table 3 shows the correlation coefficient between the number of toners obtained from the plots shown in FIG. 1 (not shown except for toner A) and the total charge amount, and irregularity for each of the toners of Examples and Comparative Examples. The toner generation rate is shown. In addition, with respect to the toner C of Example 3 and the toner c of Comparative Example 3, a 3000 sheet printing durability test was performed, and the correlation coefficient r indicating the uniformity of the charge amount after the durability test, the liberation rate of silica, and the titanium oxide Was determined.

  The results in Table 3 show that the multi-stage treatment was performed, and magnesium stearate alone (Examples 4 to 6) or other external additives (Examples 1 to 3 and 7 to 9) at the final stage. Each of the toners A to I obtained by adding at a higher addition temperature has a higher correlation coefficient r than that of the toner of the comparative example, and the occurrence of positively charged toner (irregular toner) is also low. And the liberation rate of silica and the liberation rate of titanium oxide are also small. That is, it can be seen that the charge amount for each toner is stable, and the charge of the entire toner is uniform.

  On the other hand, Comparative Example 1 in which no magnesium stearate is added and Comparative Example 2 in which no multi-stage treatment is performed have a high generation rate of positively chargeable toner (irregular toner) and the correlation coefficient r is not high. In addition, even when the multi-stage processing was performed, when the temperature was lowered in the final processing, the generation of positively charged toner (irregular toner) was slightly observed. Further, it was confirmed with the toner C of Example 3 that even after the durability test, the correlation function r did not greatly decrease, and the liberation rate of silica and the liberation rate of titanium oxide did not increase greatly. This indicates that the uniformity of charging is maintained even after printing 3000 sheets, and the external additive is firmly added to the toner base particles.

  The toner of the present invention obtained by adding an external additive in a multi-stage treatment and externally adding a long-chain fatty acid or a salt thereof at a higher temperature than other external additives in the final stage is provided for each toner. The charge amount is stable, the charge of the entire toner is uniform, and the charge stability is maintained even after repeated use, and the generation rate of irregular toner is low, so that a stable image can be provided. Therefore, the toner of the present invention is widely used as an electrophotographic toner.

FIG. 6 is a diagram illustrating a relationship between the number of toners and the total charge amount when the toner A of the present invention is charged.

Claims (22)

A toner in which two or more external additives are added to toner base particles containing a binder resin and a colorant, wherein the external additives are added by multi-stage treatment, and in the final stage of the multi-stage treatment, a long-chain fatty acid A toner obtained by adding the external additive containing the metal salt at a temperature higher by 10 to 15 ° C. than the addition temperature of the external additive in another stage. In the final stage of the multi-stage treatment, an external additive containing a metal salt of a long chain fatty acid is added at a temperature higher than the addition temperature of the external additive in the other stage, and is added with a higher share than in the other stage. The toner according to claim 1. The external additive is added using a mixer having a rotor blade, and the external additive containing a metal salt of a long-chain fatty acid in the final stage increases the temperature in the mixer more than the other stages and The toner according to claim 2, wherein the toner is added with an increased share by increasing the number of rotations. The external additive is added using a mixer having a rotor blade, and the external additive containing a metal salt of a long-chain fatty acid increases the temperature in the mixer more than the other stages in the final stage and the rotor blade The toner according to claim 2, wherein the toner is added with a high shear by reducing a distance between the toner and the mixer wall. At least one external additive selected from the group consisting of negatively chargeable silica fine particles, titanium oxide fine particles and positively chargeable silica fine particles is added to the toner base particles, and an external additive containing a metal salt of a long-chain fatty acid in the final stage. The toner according to claim 1, further comprising an agent. 6. The toner according to claim 5, wherein in the multi-stage treatment, negatively chargeable silica fine particles are first added to the toner base particles, and an external additive containing a metal salt of a long-chain fatty acid is added in the final stage. 6. The multistage treatment according to claim 5, wherein in the multi-stage treatment, negatively-charged silica fine particles are added first, then titanium oxide fine particles are added, and an external additive containing a metal salt of a long-chain fatty acid is added in the final step. toner. 6. The toner according to claim 5, wherein in the multistage treatment, titanium oxide fine particles are added first, and an external additive containing a metal salt of a long-chain fatty acid is added in the final stage. In the multi-stage treatment, at least one external additive selected from the group consisting of negatively chargeable silica fine particles and titanium oxide fine particles is added, and then positively chargeable silica fine particles are added,
The toner according to claim 5, wherein a metal salt of a long-chain fatty acid is added in the final stage. In the multistage treatment, at least one external additive selected from the group consisting of negatively charged silica fine particles and titanium oxide fine particles is first added, and positively charged silica fine particles and a metal salt of a long chain fatty acid are added in the final step. The toner according to claim 5. A method for producing a toner comprising a step of externally adding two or more external additives to toner base particles containing a binder resin and a colorant by a multistage treatment, wherein the final stage of the multistage treatment comprises a metal of a long chain fatty acid A method for producing a toner, which is a step of adding an external additive containing salt at a temperature 10 to 15 ° C. higher than the addition temperature of the external additive in another stage. In the final stage of the multi-stage treatment, an external additive containing a metal salt of a long-chain fatty acid is added at a temperature higher than the addition temperature of the external additive in another stage, and is added with a higher share than the other stages. The method of claim 11, which is a process. The addition of the external additive is performed using a mixer having a rotor blade, and the final stage is performed by adding an external additive containing a metal salt of a long-chain fatty acid to increase the temperature in the mixer as compared with other stages and to rotate the rotor blade. The method according to claim 12, wherein the method is a step of increasing the share by increasing the number of revolutions. The addition of the external additive is performed using a mixer having a rotor blade, and the final stage is performed by adding an external additive containing a metal salt of a long-chain fatty acid at a higher temperature in the mixer than in the other stages and performing the rotation. The method according to claim 12, which is a step of adding by increasing the share by reducing the distance between the blade and the mixer wall. A step of adding to the toner base particles at least one external additive selected from the group consisting of negatively chargeable silica fine particles, titanium oxide fine particles and positively chargeable silica fine particles, and a metal salt of a long-chain fatty acid in the final stage The method according to claim 11, comprising a step of adding an external additive.
The method according to claim 15, comprising a step of first adding the negatively chargeable silica fine particles to the toner base particles, and a step of adding an external additive containing a metal salt of a long-chain fatty acid in the final stage. The method includes the step of first adding the negatively chargeable silica fine particles to toner base particles, the step of adding titanium oxide fine particles, and the step of adding an external additive containing a metal salt of a long-chain fatty acid in the final stage. 15. The method according to 15. The method according to claim 15, comprising the step of adding the titanium oxide fine particles first and the step of adding an external additive containing a metal salt of a long-chain fatty acid in the final step. A step of first adding at least one external additive selected from the group consisting of the negatively chargeable silica fine particles and titanium oxide fine particles, then a step of adding positively chargeable silica fine particles, and a metal of a long-chain fatty acid in the final stage 16. The method of claim 15, comprising the step of adding a salt . First adding at least one external additive selected from the group consisting of the negatively chargeable silica fine particles and titanium oxide fine particles, and adding the positively chargeable silica fine particles and the metal salt of the long chain fatty acid in the final stage. The method according to claim 15, comprising a step.   An image forming apparatus comprising the toner according to claim 1. A latent image carrier on which an electrostatic latent image is formed; a toner carrier that transports toner to the latent image carrier to develop the electrostatic latent image on the latent image carrier; and the toner carrier The image forming apparatus according to claim 21, further comprising: a developing unit having a toner regulating member that regulates an amount of toner conveyed to the latent image carrier.

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