JP2007264050A - Toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide toner having small tackiness, causing no filming and capable of good image formation. <P>SOLUTION: The toner is obtained as follows; a mixture comprising a synthetic resin, a release agent, a colorant and an organic solvent is emulsified in an aqueous solvent to form fine particles, the fine particles are aggregated by adding an electrolyte to prepare toner base particles containing 4-20 mass% of the release agent, and 0.5-2 pts.wt. of hydrophobed negative charge type silica fine particles having an average particle diameter of 10-50 nm and 0.5-2 pts.wt. of strontium titanate fine particles having an average particle diameter of 100-250 nm are externally added to 100 pts.wt. of the toner base particles. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a toner used for developing an electrostatic latent image on a latent image carrier in an electrophotographic apparatus, an electrostatic recording apparatus, and the like.

  In electrophotographic copiers, printers, fax machines, etc., due to demands for print image quality, for toner, the resolution of the print image is increased, the gradation is improved, the amount of waste toner is reduced, and the fixing temperature is lowered. In view of demands for reduction in energy consumption due to the above, improvement in image characteristics in full-color images, and the like, a method using a polymerization method, emulsification dispersion, or the like is used instead of a pulverization method that reduces the particle size by pulverization.

In the toner manufacturing method by the polymerization method, since the binder resin is limited to the vinyl polymer capable of radical polymerization, it is not possible to manufacture the toner from the polyester resin. In addition, the polymerization method has a problem that volatile organic compounds composed of unreacted monomers remain.
On the other hand, an emulsification dispersion method has been proposed in which particles are formed after a mixture of a binder resin and a colorant is mixed with an aqueous medium and emulsified.
The emulsification dispersion method is a method of obtaining toner particles by mixing and emulsifying a mixture of a binder resin and a colorant with an aqueous medium, so that it is difficult to recover and reuse the solvent because a mixed solvent is used. At the same time, there is a problem that the yield of the toner is reduced because fine particles are generated.

Therefore, a method has been proposed in which a polyester resin or the like is emulsified and dispersed as a binder resin, and then the obtained fine particles are aggregated and further heated and fused to form an aggregate. Therefore, there is a problem that it is necessary to stir at high temperature for a long time.
In addition, a method has been proposed in which fine particles are produced by emulsification and dispersion, and then the step of aggregating the fine particles and the step of fusing the agglomerated fine particles are performed at the same time. Since coalescence is performed by collision between particles under force, coalescence is likely to be non-uniform, and agglomeration is unavoidable. On the other hand, emulsification dispersion is performed under shear force, Since the particles are aggregated, crushing occurs competitively with coalescence, so that the generation of fine particles increases, and there is a limit to narrowing the distribution of toner particles to be generated.

In contrast to these methods, phase inversion emulsification in which a binder resin such as a polyester resin, a release agent, a colorant, and the like are dissolved or dispersed in an organic solution, and the resulting oil phase component is dispersed and granulated in an aqueous medium. A toner manufacturing method called “method” has been proposed.
In this method, in order to reduce emulsification loss and obtain a sharp particle size distribution, an oil phase component is emulsified in an aqueous medium to form fine particles of the mixture in the aqueous medium, followed by dispersion stabilization. A toner is manufactured through a coalescing step in which the fine particles are coalesced by adding an agent and sequentially adding an electrolyte (for example, Patent Documents 1 and 2).

However, when an image is formed with the obtained toner, there is a problem that the tackiness is large and filming is likely to occur on the developing roller, etc. In order to reduce the tackiness, silica fine particles having high fluidity are removed. Even if it was added as an additive, it could not be improved sufficiently.
When the toner produced by the phase inversion emulsification method was analyzed by a particle shape analyzer, it was found that there are many particles not containing a colorant, as well as resin particles containing a colorant. Particles that do not contain a colorant are particles composed only of a release agent, and even if silica fine particles are added as external additives, fine silica fine particles are incorporated into the soft release agent-only particles. In other words, since the function as an external additive cannot be exhibited, tackiness is increased, and filming or the like occurs on the developing roller.
Japanese Patent No. 3063269 JP 2004-198598 A

  The present invention relates to a toner produced by dissolving or dispersing a binder resin such as a polyester resin, a release agent, a colorant and the like in an organic solution and dispersing and granulating the obtained component in an aqueous medium. It is an object of the present invention to provide a toner capable of reducing the tackiness caused by the release agent particles that are not taken in and released, preventing the occurrence of filming, and capable of forming a good image.

An object of the present invention is to form a fine particle by emulsifying a mixture of a synthetic resin, a release agent, a colorant, and an organic solvent in an aqueous medium in a toner, and then adding the electrolyte to unite the fine particle. 100 parts by weight of toner base particles containing 4 to 20% by mass of the release agent obtained in the above are 0.5 to 2 parts by weight of hydrophobically charged negatively charged silica fine particles having an average particle size of 10 to 50 nm. And a toner externally added with 0.5 to 2 parts by weight of strontium titanate fine particles having an average particle diameter of 100 to 250 nm.
Further, in the toner described above, the negatively charged silica fine particles and the strontium titanate fine particles subjected to the hydrophobic treatment are externally added in the order of the negatively charged silica fine particles and the strontium titanate fine particles subjected to the hydrophobic treatment.
In the above toner, the toner base particles use a polyester resin as a binder resin.
In the above toner, the release agent is an ester-based natural wax.

  In the toner of the present invention, fine particles are formed by emulsifying a mixture of a synthetic resin such as polyester resin, a release agent, a colorant, and an organic solvent in an aqueous medium, and then adding the electrolyte to combine the fine particles. The toner base particles having a release agent content of 4 to 20% by mass, which are produced by the same process, are subjected to hydrophobization-treated negatively-charged silica fine particles having an average particle size of 10 to 50 nm and an average particle size of 100 to Since the external addition treatment was performed with strontium titanate fine particles of 250 nm, even when the negatively-charged silica fine particles added as an external additive were embedded in the surface of the released release agent particles, the external additive did not perform its function sufficiently. As a result of electrostatic adsorption of the strontium titanate fine particles with a large dielectric constant and particle size on the surface of the released release agent particles, tackiness is reduced, filming is avoided, Excellent images can provide a toner capable of forming a.

In the present invention, a mixture comprising a synthetic resin such as a polyester resin, a release agent, a colorant, and an organic solvent is emulsified in an aqueous medium to form fine particles, and then an electrolyte is added to coalesce the fine particles. Focusing on the fact that the toner produced by the phase emulsification method has problems such as tackiness and filming due to the presence of a large number of free release agent particles, an external additive having a large particle size and a large polarizability. It has been found that problems such as tackiness and filming properties can be solved by allowing the agent to be present on the surface of the release agent particles.
In the case where strontium titanate fine particles having a large particle size and a large dielectric constant are used as external additives in addition to the silica fine particles as in the present invention, a portion in which fine negative chargeable silica fine particles are embedded to become negative charges Tackiness is improved by covering the surface of the release agent released by electrostatic adsorption of strontium titanate with large particle size and large polarizability in any part where the negatively chargeable silica particles are not embedded. It is presumed that

A method for producing toner base particles of the present invention will be described.
The toner base particles are prepared by emulsifying a resin solution containing a binder resin, a release agent and an organic solvent in an aqueous medium to form fine particles, and then combining the fine particles to produce an aggregate of the fine particles, The organic solvent contained in the aggregate is removed, and then the aggregate of fine particles is separated from the aqueous medium, washed, and dried to obtain toner base particles.
A mixture containing the binder resin and the organic solvent can be prepared by introducing the binder resin into an organic solvent and dissolving or dispersing the binder resin. The mixture obtained by melting and kneading the charge control agent is preferably dispersed in an organic solvent.

In the case of emulsifying a mixture containing a binder resin and an organic solvent in an aqueous medium, in the case of a polyester resin having an acidic group, the mixture is emulsified by mixing with an aqueous medium in the presence of a basic neutralizing agent. Is preferred. Then, by gradually adding water to the oil phase of the mixture, a discontinuous phase of the water phase is generated in the oil phase, and by adding additional water, the oil phase is discontinuous in the water phase. The phase is reversed and the mixture is suspended and suspended as particles in an aqueous medium.
Accordingly, the binder resin used preferably has an acidic group, and a polyester resin that becomes self-water dispersible by neutralizing the acidic group is preferable.
Such a polyester resin preferably has an acid value of 1 to 20. The resin having self-water dispersibility becomes an anionic type by neutralizing an acidic group with a basic neutralizing agent. As a result, the hydrophilicity of the resin is increased, and the resin can be stably dispersed in the aqueous medium without using a dispersion stabilizer or a surfactant.

Examples of the acidic group include an acidic group such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group. Among these, a carboxyl group is preferable from the viewpoint of toner charging characteristics. Moreover, as a basic substance for neutralization, inorganic bases, such as sodium hydroxide, potassium hydroxide, and ammonia, and organic bases, such as diethylamine, triethylamine, and isopropylamine, are used.
Of these, inorganic bases such as ammonia, sodium hydroxide and potassium hydroxide are preferred. In order to disperse the polyester resin in the aqueous medium, there is a method of adding a dispersion stabilizer such as a suspension stabilizer or a surfactant. However, the suspension stabilizer or the surfactant is added and emulsified. The method requires high shear forces. As a result, the generation of coarse particles and the particle size distribution become broad, which is not preferable. Therefore, it is preferable to use a self-water dispersible resin and neutralize the acidic group of the resin with a basic compound.

  Examples of a method for neutralizing an acidic group of a polyester resin with a base include, for example, a method of producing a mixture containing a polyester resin having an acidic group, a colorant, a wax and an organic solvent, and then neutralizing with a base, or an aqueous medium There is a method in which a basic neutralizing agent is mixed in advance and the acidic groups of the polyester resin contained in the mixture are neutralized when phase inversion emulsification is performed.

  For the dispersion of the binder resin, a mixture containing various additives such as a binder resin, a colorant, a release agent, and a charge control agent is used using a pressure kneader, a heated two-roll, two-screw extrusion kneader, etc. The binder resin to be used is kneaded by heating to a temperature above the softening point. At this time, the colorant or the like may be added directly or as a master batch and kneaded. The obtained kneaded chips can be prepared by dissolving or dispersing in an organic solvent with a stirrer such as a desper.

Further, various additives such as a binder resin, a colorant, a release agent, and a charge control agent may be mixed with an organic solvent, and this may be wet-kneaded by a ball mill or the like. The colorant, the release agent and the like may be mixed after preliminary dispersion separately in advance. Specifically, in a mixing / dispersing machine using media such as a ball mill, a bead mill, a sand mill, or a continuous bead mill, a resin solution in which a binder resin is dissolved in an organic solvent, a colorant, and a release agent are added and stirred. A resin solution in which a coloring agent, a release agent, and the like are finely dispersed in an organic solvent can be produced by mixing a binder resin for dilution and an additional organic solvent by dispersing the mixture into a master batch.
Also, rather than putting the colorant, release agent, etc. untreated directly into a mixing / dispersing machine such as a ball mill, a low-viscosity binder resin, colorant, release agent, etc. are pre-pressurized and heated. It is preferable to use a master batch obtained by kneading and dispersing with two rolls.

  Examples of the organic solvent for dissolving or dispersing the binder resin, the colorant, the release agent and the like include hydrocarbons such as pentane, hexane, heptane, benzene, toluene, xylene, cyclohexane, petroleum ether, methylene chloride, Halogenated hydrocarbons such as chloroform and dichloroethane, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, and esters such as ethyl acetate and butyl acetate are used. These solvents can be used in combination of two or more.

The binder resin can be dissolved in the water-insoluble organic solvent used, and is insoluble in water or hardly soluble in water. Conventionally, a polyester resin, a styrene resin, ( One or more of (meth) acrylic resin, styrene- (meth) acrylic copolymer resin, olefin resin, polyamide resin, carbonate resin, polyether resin, polyvinyl acetate resin, polysulfone, epoxy resin, polyurethane resin, etc. Can be used.
Of these, polyester resins having good solubility at fixing and excellent flexibility are preferred, and acidic group-containing polyester resins are preferred.

The polyester resin that can be used in the present invention can be obtained by condensation polymerization of a carboxylic acid component and an alcohol component.
The carboxylic acid component includes terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid, maleic anhydride, fumaric acid, succinic acid, alkenyl succinic anhydride, adipic acid, cyclohexanedicarboxylic acid And divalent or higher carboxylic acids. These carboxylic acids can be used alone or in combination of two or more. Among these, it is preferable to use an aromatic carboxylic acid.

As alcohol components, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, bisphenol A The ethylene oxide adduct of bisphenol A, the propylene oxide adduct of bisphenol A and the like can be used. These alcohol components can be used alone or in combination of two or more.
Among these alcohol components, aromatic diols and alicyclic diols are preferable, and aromatic diols are more preferable.

  The polyester resin obtained by condensation polymerization of carboxylic acid component and alcohol component is further added with monocarboxylic acid, monoalcohol, etc. to esterify the hydroxyl group, carboxyl group, etc. at the polymerization terminal, and adjust the acid value of the polyester resin can do. Examples of the monocarboxylic acid used for such purpose include acetic acid, acetic anhydride, benzoic acid, trichloroacetic acid, trifluoroacetic acid, and propionic anhydride. Examples of the monoalcohol include methanol, ethanol, propanol, octanol, 2-ethylhexanol, trifluoroethanol, trichloroethanol, hexafluoroisopropanol, and phenol.

Examples of the release agent added to the toner base particles include carnauba wax, beeswax, montan wax, and other ester-based natural waxes, paraffin waxes, polyolefin waxes, modified waxes having aromatic groups, and alicyclic groups. And hydrocarbon compounds having 12 or more carbon atoms or esters thereof, long-chain fatty acid metal salts, fatty acid amides, fatty acid bisamides, and the like. Of these, natural ester waxes such as carnauba wax are preferred.
Further, the release agent in the toner base particles is preferably 4 to 20% by mass. When the content is less than 4% by mass, the releasability is not sufficient, and when the content is more than 20% by mass, the effect of the external addition treatment with the external additive cannot be sufficiently obtained.
These release agents can be used alone or in combination. The softening point is 40 to 130 ° C, preferably 50 to 120 ° C. The softening point is represented by an endothermic peak value in differential scanning calorimetry.

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.
As yellow pigments, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navelous yellow, naphthol yellow S, banza yellow, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake, etc. are used. .

As the orange pigment, 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.
Examples of red pigments include Bengala, Permanent Red 4R, Resol Red, Pyrozolone Red, Watching Red, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, and the like.
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, pigment green B, malachite green lake, final yellow green G, or the like is 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.

In the case of a translucent color toner, the following various pigments and dyes are used as the colorant.
Examples of yellow pigments include C.I. I. 10316 (Naphthol Yellow S), C.I. I. 11710 (Hansaero 10G), C.I. I. 11660 (Hansaero 5G), C.I. I. 11670 (Hansaero 3G), C.I. I. 11680 (Hansaero G), C.I. I. 11730 (Hansa GR), C.I. I. 11735 (Hansaero A), C.I. I. 11740 (Hansaero NR), C.I. I. 12710 (Hansaero R), C.I. I. 12720 (Pigment Yellow L), C.I. I. 21090 (benzidine yellow), C.I. I. 21095 (Benzidine Yellow G), C.I. I. 21100 (Benzidine Yellow GR), C.I. I. 20040 (Permanent Aero NCG), C.I. I. 21220 (Vulcan Fast Yellow 5), C.I. I. 21135 (Vulcan Fast Yellow R) or the like is used.

Examples of red pigments include C.I. I. 12055 (Starlin I), C.I. I. 12075 (permanent orange), C.I. I. 12175 (Risor Fast Orange 3GL), C.I. I. 12305 (permanent orange GTR), C.I. I. 11725 (Hansaero 3R), C.I. I. 21165 (Vulcan Fast Orange GG), C.I. I. 21110 (Benzidine Orange G), C.I. I. 12120 (Permanent Red 4R), C.I. I. 1270 (Para Red), C.I. I. 12085 (Fire Red), C.I. I. 12315 (Brilliant Fast Scarlet), C.I. I. 12310 (Permanent Red F2R), C.I. I. 12335 (Permanent Red F4R), C.I. I. 12440 (Permanent Red FRL), C.I. I. 12460 (Permanent Red FRLL), C.I. I. 12420 (Permanent Red F4RH), C.I. I. 12450 (Light Fast Red Toner B), C.I. I. 12490 (Permanent Carmine FB), C.I. I. 15850 (brilliant carmine 6B) or the like is used.
Examples of blue pigments include C.I. I. 74100 (metal-free phthalocyanine blue), C.I. I. 74160 (phthalocyanine blue), C.I. 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 preferable to use 1 to 20 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the binder resin. When the amount is more than 20 parts by weight, the fixing property and transparency of the toner are deteriorated.

  An organic charge control agent or an inorganic charge control agent is used to adjust the charging characteristics of the toner. Examples of the positive charge control agent include nigrosine base EX (manufactured by Orient Chemical Industries), quaternary ammonium salt P-51 (manufactured by Orient Chemical Industries), nigrosine bontron N-01 (manufactured by Orient Chemical Industries), Sudan Chief Schwartz BB (Solvent Black 3: Color Index 26150), Fettschwarz HBN (C.I.NO. 26150), Brilliant Spirits Schwarz TN (manufactured by Bayer), Zavon Schwartz X (manufactured by Hoechst). Of these, the quaternary ammonium salt P-51 is preferable. 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.

  Examples of the negative charge control agent include oil black (Color Index 26150), oil black BY (manufactured by Orient Chemical Industries), Bontron S-22 (manufactured by Orient Chemical Industries), and salicylic acid metal complex E-81 (manufactured by Orient Chemical Industries). Thioindigo pigments, sulfonylamine derivatives of copper phthalocyanine, Spiron Black TRH (Hodogaya Chemical Co., Ltd.), Bontron S-34 (Orient Chemical Industries Co., Ltd.), Nigrosine SO (Orient Chemical Industries Co., Ltd.), Ceres Schwartz ( R) G (manufactured by Bayer), Chromogen Schwarz ETOO (CI NO. 14645), azo oil black (R) (manufactured by National Aniline) and the like. Of these, salicylic acid metal complex E-81 is preferably used. These positive charge control agents can be used alone or in combination.

  The number average particle size of the toner in the present invention is preferably 9 μm or less, and more preferably 8 μm to 4.5 μm. For toners larger than 9 μm, even if a latent image is formed at a high resolution of 1200 dpi or higher, the reproducibility of the resolution is lower than that of a toner having a small particle diameter. In addition, the amount of the external additive used to increase the fluidity increases, and as a result, the fixing performance tends to decrease.

By adding negatively chargeable silica fine particles as an external additive to the toner base particles of the present invention, the fluidity of the toner particles can be improved and the charging characteristics during development can be improved.
The negatively chargeable silica fine particles preferably have a volume average particle diameter of 10 to 50 nm, particularly preferably 15 to 30 nm.
When the average particle size of the negatively chargeable silica fine particles is larger than 50 nm, the toner fluidity is lowered. On the other hand, when the particle size is smaller than 10 nm, the secondary aggregation of the silica fine particles is increased, and it is difficult to adhere the silica fine particles to the surface of the release agent particles that are separated from the toner base particles.
The addition amount of the negatively chargeable silica fine particles is preferably 0.5 to 2 parts by weight, and more preferably 0.7 to 1.5 parts by weight. When the addition amount is 0.5 parts by weight or less, the silica fine particles cannot be attached to the surface of the released release agent. On the other hand, when the amount is 2 parts by weight or more, the coverage by the external additive is increased, which adversely affects the fixing characteristics.
In the present invention, the average particle diameter is indicated by a volume distribution D50 measured by an electric resistance method particle size distribution measuring apparatus (Multisizer III manufactured by Beckman Coulter, Inc.).

  The negatively chargeable silica fine particles are preferably hydrophobized. By subjecting the surface of the negatively chargeable silica fine particles to a hydrophobic treatment, the fluidity and chargeability of the toner are further improved. Hydrophobization of silica fine particles can be achieved by using silane compounds such as hexamethyldisilazane and dimethyldichlorosilane, or silicones such as dimethyl silicone, methylphenyl silicone, fluorine-modified silicone oil, alkyl-modified silicone oil, amino-modified silicone oil, and epoxy-modified silicone oil. Using oil, it can be carried out by a method such as a wet method or a dry method.

  Specifically, as negatively chargeable silica fine particles, RX200 manufactured by Nippon Aerosil: average particle size of 10 nm, hexamethyldisilazane treatment. RY200: average particle size 10 nm, silicone oil treatment. RX50: Average particle diameter 50 nm, hexamethyldisilazane treatment. TG-811F manufactured by Cabot Corporation: average particle size 10 nm, hexamethyldisilazane treatment. TG-308F: Average particle diameter of 15 nm, silicone oil treatment and the like can be mentioned.

Further, the toner of the present invention is characterized in that strontium titanate fine particles having a large dielectric constant and a large average particle size are added together with the above-described hydrophobically charged negatively charged silica fine particles.
The volume average particle diameter of the strontium titanate fine particles is preferably 100 to 250 nm, and more preferably 120 to 200 nm. If it is smaller than 100 nm, it is buried in the release agent particles which are present in the same manner as the negatively chargeable silica fine particles, so that the effect of addition cannot be exhibited.
Moreover, when larger than 250 nm, since it becomes difficult to fully coat | cover the released mold release agent surface, it is unpreferable.

The amount of strontium titanate fine particles added is preferably 0.5 to 2 parts by weight, more preferably 0.7 to 1.5 parts by weight, based on 100 parts by weight of the toner base particles. When the added amount is less than 0.5 parts by weight, it is not preferable because it is insufficient to cover the surface of the released release agent. On the other hand, if it exceeds 2 parts by weight, the charge distribution of the toner is adversely affected by the dielectric effect of the strontium titanate fine particles, which is not preferable.
Specific examples of the strontium titanate fine particles include SW-320C manufactured by Titanium Industry Co., Ltd. and a particle size of 200 nm.

  In the external addition treatment of the negatively chargeable silica fine particles and the strontium titanate fine particles to the toner base particles, it is preferable to externally add the strontium titanate fine particles after the external charge treatment of the negatively chargeable silica fine particles. By externally adding negatively-charged silica fine particles and strontium titanate fine particles in this order, even if the silica fine particles are buried in the surface of the release agent, the silica fine particles are Since it is electrostatically adsorbed to either the unattached portion or the portion where the silica fine particles are buried, the effect of the external addition treatment can be enhanced.

The external addition treatment with the negatively chargeable silica fine particles and strontium titanate fine particles on the toner base particles can be performed using a high-speed fluid mixer such as a Henschel mixer or Perpenmeier, a mixer using a mechanochemical method, or the like.
The toner base particles and the negatively chargeable silica fine particles are obtained by stirring for a predetermined time at a predetermined stirring speed with a mixer as shown above, and then adding strontium titanate fine particles and stirring for a predetermined time at a predetermined stirring speed. It is done.

(Preparation of toner base particles)
70 parts by weight of polyester resin (Toughton NE-1110 JIS K2207, softening point 130 ° C by Kao) and 30 parts by weight of Carnauba No. 1 (manufactured by Toa Kasei) as a mold release agent using a twin screw extruder (Ikegai Iron Works PCM-30) A kneaded product was prepared by melt-kneading, and 30 parts by weight of the obtained kneaded product and 100 parts by weight of methyl ethyl ketone were put into a ball mill and pulverized for 12 hours to obtain a release agent dispersion.

  50 parts by weight of a polyester resin (Tafton NE-1110 JIS K2207, softening point 130 ° C.) and 50 parts by weight of a pigment (Daiichi Seika Kogyo phthalocyanine copper: P.B.15; 3) are mixed into a twin screw extruder (Ikekai Tekko) 30 parts by weight of the resulting kneaded product and 100 parts by weight of methyl ethyl ketone were put into a ball mill and pulverized for 12 hours to obtain a fine pigment dispersion.

The same polyester resin as that used in the preparation of the release agent dispersion and the pigment dispersion is added to 48 parts by weight of the release agent dispersion and 36 parts by weight of the pigment dispersion, and the solid content concentration becomes 60% by mass. In this manner, methyl ethyl ketone was added and stirred and mixed with a universal mixer to prepare a dispersion described as dispersion 1 in Table 1.
In Table 1, as for the release agent, C-WAX means carnauba wax, and C-WAX means rice wax. The release agent dispersion is expressed in parts by weight, and the release agent ratio indicates the content in the release agent dispersion in mass%.

Table 1
Release agent dispersion Pigment dispersion Release agent type Release agent ratio
Dispersion 1 48 36 C-WAX 8%
Dispersion 2 48 36 R-WAX 8%
Dispersion 3 52 33 C-WAX 10%
Dispersion 4 49 30 C-WAX 6%
Dispersion 5 39 57 C-WAX 3%
Dispersion 6 39 52 C-WAX 3%
Dispersion 7 69 29 R-WAX 22%
Dispersion 8 72 20 R-WAX 22%

30 parts by weight of 1N ammonia water was added to 120 parts by weight of the obtained dispersion 1, and after stirring at 350 rpm with a stirrer, 100 parts by weight of water was added and further stirred to adjust the temperature to 30 ° C. Thereafter, 150 parts by weight of water was added dropwise to perform phase inversion emulsification to produce a fine particle dispersion, and then 150 parts by weight of water was added to adjust the amount of solvent.
Subsequently, 0.8 part by weight of a nonionic surfactant (Newcol 506: manufactured by Nippon Emulsifier) was diluted with water and added, and then the temperature was set to 70 ° C. and the rotation speed of the stirrer was set to 300 rpm. 100 parts by weight of a 0% by weight aqueous ammonium sulfate solution was added dropwise to adjust the amount of solvent in the dispersion to 30% by weight.
Further, after the stirring was continued for 70 minutes, the coalescence process was completed.
Next, the particles obtained after the solid-liquid separation were washed with water and vacuum-dried at 45 ° C. for 10 hours to prepare toner base particles having a volume average particle size of 7.0 μm. The obtained toner had an average circularity of 0.97.
The circularity is a ratio of the circumference of the projected image of the toner particles to be measured to the circumference of a perfect circle equal to the area of the projected image of the toner particles to be measured.

  Next, as shown in Table 2, 1 part by weight of RX200 (produced by Nippon Aerosil, average particle size 10 nm, hexamethyldisilazane treatment) is added to 100 parts by weight of the obtained toner base particles. Then, using a stirrer (Hitchel mixer FM20B type, manufactured by Mitsui Mining Co., Ltd.), the treatment was performed under the mixing conditions of a stirring blade peripheral speed of 30 m / sec and a stirring time of 5 minutes. A toner of Sample 1 was prepared by treating with 1 weight of SW-320C (Titanium Industry average particle size 200 nm) as strontium fine particles.

The obtained toner of Sample 1 was evaluated by the following evaluation method, and the results are shown in Table 2.
In Table 2, the release agent means C-WAX means carnauba wax, the content in the toner base particles is expressed by mass%, and the free release agent is the free release agent in the observed particles. The number of molds is shown. Silica fine particles and SrTiO ₃ are trade names of negatively chargeable silica fine particles and strontium titanate fine particles used as external additives, respectively, and the blending amount with respect to 100 parts by weight of toner base particles in parts by weight. .

(Evaluation of toner characteristics)
1. Measurement of released mold release agent Using a flow type particle shape analyzer (FPIA-2100 manufactured by Sysmex), class 4 (20-40 μm), class 5 (10-20 μm), class 6 (5-10 μm), class 7 ( The determination was made based on the number of uncolored particles observed at 0 to 5 μm). The release agent released without being taken into the toner base particles is observed as non-colored particles. Moreover, since it is a mold release agent component, it has an irregular shape. In the table, it is expressed as the ratio of the released release agent particles to the observed toner.
2. Filming evaluation Each sample toner was filled in a color laser printer (LP9000C manufactured by Seiko Epson Corporation), and a continuous image formation test was performed every 3000 sheets with a 5% toner consumption pattern in A4 size. Microscopic observation was performed at a magnification, and the case where there were less than 5 streaks due to toner filming was judged good, and the case where 5 or more streaks were observed was judged as bad.

  The composition of Dispersion 1 was changed to the composition indicated by Dispersion 2 in Table 1, and Carnauba wax was changed to Rice Wax (manufactured by Toa Kasei). Dispersion in the same manner as in Example 1 except that 1.5 parts by weight of methyldisilazane treatment and 1.2 parts by weight of SW-320C (average particle diameter of 200 nm manufactured by Titanium Industry) were used as strontium titanate fine particles. No. 2 was prepared, and the toner of sample 2 was prepared by changing the types and amounts of external additives shown in Table 2 in terms of parts by weight. Table 2 shows the results.

Comparative Example 1
The composition of Dispersion 1 was changed to the composition indicated by Dispersion 3 in Table 1, carnauba wax was changed to the amount shown in Table 2, and the same procedure as in Example 1 was performed except that strontium titanate fine particles were not added. Thus, a toner of Comparative Sample 1 was prepared, and the result is shown as Comparative 1 in Table 2.

Comparative Example 2
The composition of Dispersion 1 was changed to the composition indicated by Dispersion 4 in Table 1, carnauba wax was changed to the amount of rice wax (manufactured by Toa Kasei) in Table 2, and the external additive was listed in Table 2. Thus, the negative chargeable silica fine particles were changed to 0.8 parts by weight of RX50 (Nippon Aerosil average particle diameter 50 nm) and SW-200C (titanium industry average particle diameter 300 nm) 1 part by weight as strontium titanate fine particles. A toner of Comparative Sample 2 was prepared in the same manner as in Example 1 except that the external addition treatment with the chargeable silica fine particles was performed last, and the result is shown as Comparative Example 2 in Table 2.

Comparative Example 3
The composition of Dispersion 1 was changed to the composition indicated by Dispersion 5 in Table 1, and the toners of Example 1 and Comparative Sample 3 were prepared except that the external additives were simultaneously externally treated as shown in Table 2. The results are shown as Comparative 3 in Table 2.

Comparative Example 4
The composition of Dispersion 1 was changed to the composition indicated by Dispersion 6 in Table 1, and a toner of Comparative Sample 4 was prepared in the same manner as in Example 1 except that the strontium titanate fine particles were not added. 2 as comparison 4.

Comparative Example 5
The composition of Dispersion 1 was changed to the composition indicated by Dispersion 7 in Table 1, the mold release agent was changed to rice wax, and the external additive was added at the same time, and the same treatment as in Example 1 was performed. Thus, a toner of comparative sample 5 was prepared, and the result is shown as comparative 5 in Table 2.

Comparative Example 6
The composition of Dispersion 1 was changed to the composition indicated by Dispersion 8 in Table 1, Carnauba wax was changed to Rice wax, and strontium titanate fine particles were not added. Toners were prepared and the results are shown as Comparative 6 in Table 2.

Comparative Example 7
Using dispersion 1, as shown in Table 2, 1 part by weight of RX300 (Nippon Aerosil Co., Ltd.) treated with hexamethyldisilazane having an average particle diameter of 7 nm was used as negatively chargeable silica fine particles, and strontium titanate. A toner of Sample 7 was prepared in the same manner as in Example 1 except that fine particles were not added, and the result is shown as Comparative Example 7 in Table 2.

Comparative Example 8
Using dispersion 1, as shown in Table 2, 1 part by weight of ES-650 (manufactured by Titanium Industry) treated with hexamethyldisilazane having an average particle size of 300 nm as negatively chargeable silica fine particles was used, and titanic acid. A toner of Sample 8 was prepared in the same manner as in Example 1 except that no strontium fine particles were added, and the result is shown as Comparative Example 8 in Table 2.

Comparative Example 9
As shown in Table 2, the dispersion 1 was used as in Example 1 except that 1 part by weight of SW-50C (manufactured by Titanium Industry) having an average particle diameter of 50 nm was used as strontium titanate fine particles. In Table 2, the toner of Sample 9 was prepared, and the result is shown as Comparative 9 in Table 2.

Comparative Example 10
As shown in Table 2, the dispersion 1 was used as in Example 1, except that 1 part by weight of SW-100C (manufactured by Titanium Industry) having an average particle diameter of 75 nm was used as strontium titanate fine particles. The toner of Sample 10 was prepared, and the result is shown as Comparative 10 in Table 2.

Table 2
Release agent Free release agent Silica SrTiO ₃ External addition order Filming
Sample 1 C-WAX / 8% 5/26 RX200: 1 SW-320C: 1 Silica first good sample 2 R-WAX / 8% 4/22 RX50: 1.5 SW-320C: 1.2 Silica first Good comparison 1 C- WAX / 10% 4/25 RX200: 1---Defect comparison 2 R-WAX / 6% 7/33 RX50: 0.8 SW-200C: 1 After silica Defect comparison 3 C-WAX / 3% 1/12 RX200: 1 SW-320C: 1 Simultaneous addition Defect comparison 4 C-WAX / 3% 1/19 RX200: 1 − − Defect comparison 5 R-WAX / 22% 20/30 RX200: 1 SW-320C: 1 Simultaneous addition Defect comparison 6 R-WAX / 22% 20/26 RX200: 1 − − Defect comparison 7 C-WAX / 8% 8/23 RX300: 1 − − Defect comparison 8 C-WAX / 8% 6/11 ES-650: 1 − − Defect comparison 9 C-WAX / 8% 9/16 RX200: 1 SW-50C: 1 Silica first defect
Comparison 10 C-WAX / 8% 17/26 RX200: 1 SW-100C: 1 Silica first

In Table 2,
Negatively chargeable silica fine particles RX50: manufactured by Nippon Aerosil Co., Ltd., average particle diameter of 50 nm, hexamethyldisilazane treatment.
RX200: Nippon Aerosil Co., Ltd. average particle diameter 10 nm, hexamethyldisilazane treatment.
RX300: Nippon Aerosil Co., Ltd. average particle diameter 7 nm, hexamethyldisilazane treatment.
ES-650: Titanium Kogyo average particle size 300 nm, hexamethyldisilazane treatment.
Strontium titanate fine particles SW-50C: Titanium industry average particle size 50 nm
SW-100C: Titanium industry average particle size 75nm
SW-200C: Titanium industry average particle size 300nm
SW-320C: Titanium industry average particle size 200nm
Moreover,% shows the mass% and the number described after the name of each external additive means a weight part.

  The toner of the present invention is formed by emulsifying a mixture of a synthetic resin such as a polyester resin, a release agent, a colorant, and an organic solvent in an aqueous medium to form fine particles, and then adding the electrolyte to combine the fine particles. Negatively charged silica fine particles having an average particle size of 10 to 50 nm and an average particle size of toner base particles containing 4 to 20% by mass of a release agent produced by a phase inversion emulsification method. Was externally treated with strontium titanate fine particles of 100 to 250 nm, so that the negatively chargeable silica fine particles added as external additives were embedded in the surface of the released release agent particles to sufficiently function as external additives. Even if it does not work, the strontium titanate fine particles with large dielectric constant and particle size are electrostatically adsorbed on the surface of the released release agent particles, resulting in reduced tackiness and filming. Avoiding, it is possible to provide a possible form toner excellent image characteristics.

Claims (4)

In a toner, a mixture of a synthetic resin, a release agent, a colorant, and an organic solvent is emulsified in an aqueous medium to form fine particles, and then added to an electrolyte to combine the fine particles. 100 parts by weight of toner base particles containing 4 to 20% by weight of the mold agent are 0.5 to 2 parts by weight of hydrophobically charged negatively charged silica fine particles having an average particle diameter of 10 to 50 nm, and an average particle diameter Is a toner that has been externally added with 0.5 to 2 parts by weight of 100 to 250 nm strontium titanate fine particles. The hydrophobized negatively chargeable silica fine particles and strontium titanate fine particles are externally added in the order of hydrophobized negatively chargeable silica fine particles and strontium titanate fine particles. toner. The toner according to claim 1, wherein the toner base particles are made of a polyester resin as a binder resin. 4. The toner according to claim 1, wherein the release agent is an ester-based natural wax.