JP2011128574A - Method for producing developing agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a developing agent having a sharper particle size distribution. <P>SOLUTION: In a method for producing the developing agent, in the formation of aggregated particles, particles in a dispersion liquid have a volume average particle size of 2 μm or less when the pH of the dispersion liquid is 7, and also the pH of the dispersion liquid is from 3.0 to 6.9 when the zeta potential of the particles is -30 mV. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a developer for developing an electrostatic charge image and a magnetic latent image in electrophotography, electrostatic printing, and magnetic recording.

  In electrophotography, an electrical latent image is formed on an image carrier, and then the latent image is developed with toner to form a toner image. The toner image is transferred to a transfer material such as paper, and then heated and heated. An image is formed by fixing by means such as pressure. In order to form a full-color image, an image is formed using not only black toner but also a plurality of colors of toner.

  The toner includes a two-component developer used by mixing with carrier particles and a one-component developer used as a magnetic toner or a non-magnetic toner. These toners are usually produced by a kneading and pulverizing method. This kneading and pulverizing method is a method for producing desired toner particles by melt-kneading a binder resin, a release agent such as a pigment and wax, a charge control agent and the like, finely pulverizing them after cooling, and classifying them. Depending on the purpose, inorganic and / or organic fine particles are added to the surface of the toner particles produced by the kneading and pulverization method to obtain a toner.

  In the case of toner particles produced by a kneading and pulverizing method, the shape thereof is usually indeterminate and the surface composition thereof is not uniform. Although the shape and surface composition of the toner particles vary slightly depending on the pulverization properties of the materials used and the conditions of the pulverization process, it is difficult to intentionally control the shape.

  In particular, when a material with high pulverization properties is used, it is further pulverized or changed in shape due to various stresses in the developing machine. As a result, in the two-component developer, the pulverized toner is Adhering to the surface of the carrier accelerates the charging deterioration of the developer, and in the case of a one-component developer, the particle size distribution expands, the finely divided toner scatters, and the developability decreases with changes in the toner shape. However, there may be a problem that the image quality deteriorates.

  Further, when the toner contains a release agent such as wax, pulverization is likely to occur at the interface between the binder resin and the release agent, so that the release agent may be exposed on the surface of the toner. In particular, in the case of a toner composed of a highly elastic resin that is not easily pulverized and a brittle wax such as polyethylene, polyethylene is often exposed on the surface of the toner. Although such toner is advantageous for releasability at the time of fixing and cleaning of untransferred toner from the photoreceptor, the toner on the surface of the toner is subjected to mechanical force such as shearing force in the developing machine. And can be easily transferred to a developing roll, an image carrier, a carrier, and the like. For this reason, the developing roll, the image carrier, the carrier and the like are easily contaminated by wax, and the reliability as a developer may be lowered.

  Under such circumstances, in recent years, an emulsion polymerization aggregation method has been proposed as a toner production method in which the shape and surface composition of toner particles are intentionally controlled (see, for example, Patent Document 1 and Patent Document 2).

  In the emulsion polymerization aggregation method, a resin dispersion is prepared by emulsion polymerization, while a colorant dispersion in which a colorant is dispersed in a solvent is prepared and mixed to form aggregated particles corresponding to the toner particle size. Thereafter, the toner particles are obtained by fusing to obtain toner particles. According to this emulsion polymerization aggregation method, the toner shape can be arbitrarily controlled from an indeterminate shape to a spherical shape by selecting the heating temperature condition.

  In the emulsion polymerization aggregation method, it can be obtained by aggregating and fusing at least a dispersion of resin fine particles and a dispersion of a colorant under predetermined conditions. However, the emulsion polymerization aggregation method has limitations on the types of resins that can be synthesized and is suitable for the production of styrene acrylic copolymers, but it is possible to apply polyester resins that are known to have good fixability. Can not.

  On the other hand, there is a phase inversion emulsification method in which a pigment dispersion or the like is added to a solution dissolved in an organic solvent and water is added to the solution dissolved in an organic solvent as a toner manufacturing method using a polyester resin, but the organic solvent is removed and recovered. There is a need. A method of producing fine particles by mechanical shearing in an aqueous medium without using an organic solvent has been proposed (see, for example, Patent Document 3), but it is necessary to supply a molten resin or the like to a stirring device, It is difficult to handle. Further, when this method is used, the degree of freedom in shape control is low, and the toner shape cannot be arbitrarily controlled from an indeterminate shape to a spherical shape. Furthermore, when the polyester resin is refined by mechanical shearing in an aqueous medium, hydrolysis may occur and the molecular weight of the polyester resin may be reduced. A developer containing a polyester resin having a reduced molecular weight is likely to aggregate and storage stability is reduced. Furthermore, the softening point of the polyester resin changes with a decrease in molecular weight, and the fixability deteriorates.

  In view of this, a method has been proposed in which particles containing a polyester resin are made finer and grown to a toner particle size (see, for example, Patent Document 4). Since the viscosity increases, it is difficult to obtain a desired toner particle size.

  An object of the present invention is to obtain a developer having a sharper particle size distribution.

The developer producing method of the present invention comprises a step of preparing a toner material dispersion by mixing a granular mixture containing a binder resin and a colorant, and an aqueous medium,
Subjecting the toner material dispersion to mechanical shearing, atomizing the granular mixture to prepare a dispersion containing fine particles having a particle size smaller than the particle size of the granular mixture; and A developer manufacturing method comprising a step of aggregating the fine particles by adjusting the pH of the dispersion liquid to form aggregated particles, wherein the particles in the dispersion include: When the pH is 7, it has a volume average particle diameter of 2 μm or less, and when the zeta potential of the particles is −30 mV, the pH in the dispersion is 3.0 to 6.9.

  By using the present invention, it is possible to obtain a developer having a sharper particle size distribution by controlling aggregation of fine particles containing a toner material.

It is a flow showing an example of the method of this invention. 6 is a graph showing the relationship between the pH of a dispersion and the ζ potential of aggregated particles in the method for producing a developer of the present invention. It is a graph showing the relationship between the pH of the dispersion liquid and the volume average particle diameter of aggregated particles in the method for producing a developer of the present invention.

  Hereinafter, the present invention will be described in more detail with reference to the drawings.

  FIG. 1 shows a flow representing an example of the method of the present invention.

  First, in the developer production method of the present invention, a particulate mixture containing a binder resin and a colorant and an aqueous medium are mixed to prepare a toner material dispersion (Act 1).

  At this time, the pH can be arbitrarily adjusted with a basic compound or the like.

  Moreover, a surfactant etc. can be added and a granular mixture dispersibility can be adjusted.

  Next, the toner material dispersion is subjected to mechanical shearing to atomize the granular mixture to prepare a dispersion containing fine particles having a particle size smaller than the particle size of the granular mixture (Act 2).

  Thereafter, by adjusting the pH of the dispersion liquid containing fine particles, the fine particles are aggregated to form aggregated particles (Act 3).

  In the present invention, in the step of forming aggregated particles (Act 3), the particles in the dispersion have a volume average particle size of 2 μm or less, preferably 0.5 μm to 2 μm when the pH is 7, When the zeta potential is −30 mV, the pH in the dispersion is 3.0 to 6.9.

  Further, the agglomerated particles are fused by arbitrarily heating, and then toner particles are obtained by washing (Act 4) and drying (Act 5).

  The zeta (ζ) potential measurement method used in the present invention is as follows.

  1. Hydrochloric acid is added dropwise to the colored fine particle dispersion to adjust the pH (the pH at this time is defined as pH (A)).

  2. The solid content concentration of the colored fine particles of pH (A) is adjusted to 5 ppm with ion exchange water.

  3. Hydrochloric acid is added dropwise to the diluted fine particle dispersion, and the pH is adjusted to be the same as pH (A).

  4). The ζ potential of the atomized dispersion after pH adjustment is measured under the following conditions.

・ Measuring device ZEECOM (manufactured by Microtech Nichion)
・ Cell position 15mm
・ Voltage 70 [V]
Measurement number 50 The production method of the present invention is a method for producing toner for electrophotography in which toner material fine particles are prepared in an aqueous medium and aggregated and grown to a desired toner particle size. The present invention relates to a technique for producing a toner having a sharp particle size distribution by controlling the ζ potential of the toner by adjusting the pH.

  In the method of the present invention, when the granular mixture containing the binder resin and the colorant is atomized, mechanical shearing is used without using an organic solvent. At this time, a pH adjuster is used in order to make finer more easily. As the pH adjuster, those which make the pH of the obtained dispersion liquid basic can be used. The pH of the toner material dispersion can be in the range of 7.2 to 11.5, for example. The ζ potential of the colored fine particles in the dispersion can be −32 mV or less, preferably −30 mV or less in order to prevent coalescence.

  Examples of pH adjusters used to make the pH basic include, for example, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, sec-butylamine, monoethanol Amine, diethanolamine, triethanolamine, triisopropanolamine, isopropanolamine, dimethylethanolamine, diethylethanolamine, N-butyldiethanolamine, N, N-dimethyl-1,3-diaminopropane, N, N-diethyl-1,3 -Organic amine compounds such as diaminopropane, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, and ammonia.

  In the process of agglomerating fine particles and growing the agglomerated particles to a desired toner particle size, if a commonly used water-soluble metal salt is used, the softening point of the toner rises due to metal cross-linking, preventing low-temperature fixing. become. From this, in the method of the present invention, it is possible to agglomerate the colored fine particles only by adjusting the pH with an acid. However, the volume average particle diameter of the aggregated particles when the pH is 7.0 is 2.0 μm or less, preferably 0.5 to 2.0 μm. When the volume average particle size of the aggregated particles when the pH is 7.0 is larger than 2.0 μm, the particle size variation of the colored fine particles with respect to the pH is large, and the particle size becomes larger than 10 μm when the necessary flocculant is dropped. The particle size cannot be controlled intentionally. On the other hand, if the particle size is smaller than 0.5 μm, there is a tendency that aggregate particles cannot be grown to a desired toner particle diameter by pH adjustment with an acid, or fine particles that do not aggregate remain.

  Examples of the acid used for pH adjustment include nitric acid, sulfuric acid, hydrochloric acid, acetic acid, acetic anhydride, phosphoric acid, and citric acid.

  In this aggregated particle forming step, an acid is further added, and the dropping of the acid is stopped when the ζ potential of the colored fine particle dispersion becomes −30 mV. The pH of the colored fine particle dispersion at this time is between 3.0 and 6.9. When the ζ potential does not rise to −30 mV, or when the pH is on the acidic side from 3.0, the dispersion stability of the particles is high, and the aggregation of the colored fine particles cannot be controlled.

  By using such a fine particle dispersion, a toner having a desired particle diameter can be easily obtained.

  In the method for producing a developer of the present invention, first, a coarsely granulated mixture containing at least a binder resin and a colorant is prepared. The coarsely granulated mixture is obtained, for example, by a step of melt-kneading and roughly pulverizing a mixture containing a binder resin and a colorant. Alternatively, it is obtained by granulating a mixture containing a binder resin and a colorant.

  The coarsely granulated mixture preferably has a volume average particle size of 0.012 mm to 0.2 mm. When the volume average particle size is less than 0.012 mm, energy for coarse crushing increases, and productivity decreases. If it exceeds 0.2 mm, it will be clogged inside the piping etc. provided in the miniaturization apparatus, or the particle size distribution obtained will become large.

  Next, the coarsely granulated mixture is dispersed in an aqueous medium to form a dispersion of the coarsely granulated mixture.

  In the step of forming a dispersion of the coarsely granulated mixture, at least one of a surfactant and a pH adjuster can be optionally added to the aqueous medium.

  By adding a surfactant, it can be easily dispersed in an aqueous medium by the action of the surfactant adsorbed on the surface of the mixture. Moreover, self-dispersibility can be improved by increasing the dissociation degree of the dissociable functional group on the surface of the mixture or increasing the polarity by adding a pH adjuster.

  Subsequently, the resulting dispersion can be heated to a desired temperature. For atomization, the temperature of the dispersion can be made higher than the glass transition temperature of the binder resin used. There is a need. Further, the higher the temperature, the finer the colored particles, which is advantageous. However, since the hydrolysis is accelerated, the fixing property is deteriorated. The dispersion heated to these desired temperatures is subjected to mechanical shearing, and the coarsely granulated mixture is more finely granulated to produce a dispersion containing fine particles. At this time, the volume average particle diameter of the fine particles is preferably 1.0 μm or less, more preferably 0.05 μm to 1.0 μm.

  Next, these dispersions are cooled to below the glass transition temperature of the resin. At this time, it can cool to the desired temperature which performs aggregation.

  A material that promotes particle growth is added to the cooled dispersion so as to obtain a desired toner particle size. In the step of forming aggregated particles, a plurality of fine particles may be aggregated using at least one process of pH adjustment, addition of a surfactant, addition of a water-soluble metal salt, addition of an organic solvent, and temperature adjustment. However, in the first step of aggregating the particles, it is desirable to agglomerate by controlling the ζ potential of the fine particles by adjusting the pH using an acid. The acid to be used is not particularly limited, but it is desirable to use at least one of nitric acid, sulfuric acid, hydrochloric acid, acetic acid, acetic anhydride, phosphoric acid, and citric acid. In order to further promote the aggregation after the completion of the first stage aggregation, one or more of the above methods can be used. It is possible to control the shape of the aggregated particles obtained by adjusting these processes.

  Subsequently, in order to improve the stability of the agglomerated particles, the agglomerated particles are fused at a constant temperature, but there is no particular limitation as long as the temperature at which the agglomerates are integrated. Is preferably fused at a temperature of about +5 to +80 degrees with respect to the glass transition temperature. Further, the growth and fusion of the particles may be performed simultaneously or individually as described above.

  The agglomerated particles or stabilized agglomerated particles preferably have a volume average particle diameter of 2.5 to 10 μm.

  The agglomerated particles or stabilized agglomerated particles preferably have a circularity of 0.8 to 1.0.

  Subsequently, the toner particles are obtained by cooling the agglomerated particles or the dispersion containing the stabilized agglomerated particles to, for example, 5 ° C. or below the glass transition point, and then washing and drying using, for example, a filter press. Is obtained.

  The binder resin used in the present invention is not particularly limited as long as it is a resin having a dissociable group, but it is desirable to use a polyester resin in consideration of fixing characteristics and the like. These resins can be used alone or in combination of two or more.

  The binder resin preferably has an acid value of 1 or more.

  Examples of the colorant used in the present invention include carbon black, organic or inorganic pigments and dyes. For example, carbon black includes acetylene black, furnace black, thermal black, channel black, ketjen black, and the like. Examples of yellow pigments include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 81, 83, 93, 95, 97, 98, 109, 117, 120, 137, 138, 139, 147, 151, 154, 167, 173, 180, 181, 183, 185, C.I. I. Bat yellow 1, 3, 20, etc. are mentioned. These may be used alone or in combination. Examples of magenta pigments include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 150, 163, 184, 185, 202, 206, 207, 209, 238, C.I. I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35, etc. are mentioned. These may be used alone or in combination. Examples of cyan pigments include C.I. I. Pigment blue 2, 3, 15, 16, 17, C.I. I. Bat Blue 6, C.I. I. Acid Blue 45 and the like. These may be used alone or in combination.

  In the coarsely granulated mixture, at least one of a wax and a charge control agent can be further added.

Examples of waxes include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer polyolefin wax, microcrystalline wax, paraffin wax, and Fischer-Tropschwax, and aliphatic hydrocarbon waxes such as oxidized polyethylene wax. Oxide of wax or block copolymer thereof, candelilla wax, carnauba wax, wood wax, jojoba wax, plant wax such as rice wax, beeswax, animal wax such as lanolin, spermaceti, ozokerite, ceresin Mineral waxes such as petrolatum, montanic acid ester waxes, waxes based on fatty acid esters such as castor waxes, and fatty acid esters such as deoxidized carnauba wax. It can be mentioned such as those de-oxidation all. Further, saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, or long-chain alkyl carboxylic acids having a long-chain alkyl group, unsaturated fatty acids such as brassic acid, eleostearic acid, parinaric acid, stearyl alcohol A saturated alcohol such as eicosyl alcohol, behenyl alcohol, carnauvir alcohol, seryl alcohol, melyl alcohol, or a long chain alkyl alcohol having a long chain alkyl group, a polyhydric alcohol such as sorbitol, linoleic acid amide, Fatty acid amides such as oleic acid amide and lauric acid amide, methylene bis stearic acid amide, ethylene biscapric acid amide, ethylene bis lauric acid amide, saturated fatty acid bisamides such as hexamethylene bis stearic acid amide, Unsaturated fatty acid amides such as lenbis oleic acid amide, hexamethylene bis oleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide, m-xylene bis stearic acid amide, Aromatic bisamides such as N, N'-distearylisophthalic acid amide, fatty acid metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (generally referred to as metal soap), aliphatic hydrocarbons The hydroxyl groups obtained by hydrogenating waxes grafted with vinyl monomers such as styrene and acrylic acid, partially esterified products of fatty acids and polyhydric alcohols such as behenic monoglyceride, and vegetable oils and fats. Having methyl esthetic Compounds.

  As the charge control agent for controlling the triboelectric charge amount, for example, a metal-containing azo compound is used, and the metal element is preferably a complex, complex salt of iron, cobalt, chromium, or a mixture thereof. In addition, a metal-containing salicylic acid derivative compound can be used, and the metal element is preferably a complex, complex salt of zirconium, zinc, chromium, boron, or a mixture thereof.

  Examples of the surfactant that can be used in the present invention include anionic surfactants such as sulfate ester, sulfonate, phosphate, and soap, amine salts, quaternary ammonium salts, and the like. Nonionic surfactants such as cationic surfactants, polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols can be mentioned.

  Examples of the mechanical shearing device used in the present invention include Ultra Tarrax (manufactured by IKA Japan), TK auto homomixer (manufactured by Primix), TK pipeline homomixer (manufactured by Primix), and TK Philmix. (Manufactured by Primemix), Claremix (manufactured by M Technique), Claire SS5 (manufactured by M Technique), Cavitron (manufactured by Eurotech), fine flow mill (manufactured by Taiheiyo Kiko), microfluidizer (Mizuho) Industrial shear), Starburst (manufactured by Sugino Machine), Nanomizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.), Genus PY (manufactured by Hakusui Chemical Co., Ltd.), and NANO3000 (manufactured by Miki Co., Ltd.) Equipment, Viscomill (made by IMEX), Apex Mill (made by Kotobuki Industries), S -Mill (Ashizawa, Finetech), DCP Super Flow (Nippon Eirich), MP Mill (Inoue), Spike Mill (Inoue), Mighty Mill (Inoue), SC Mill (Mitsui) And a mechanical shearing device using a medium such as Mining Co., Ltd.

  In the present invention, in order to prepare a coarsely granulated mixture, a mixture containing at least a binder resin and a colorant can be kneaded.

  The kneader to be used is not particularly limited as long as melt kneading is possible, and examples thereof include a single screw extruder, a twin screw extruder, a pressure kneader, a Banbury mixer, and a Brabender mixer. Specifically, FCM (made by Kobe Steel), NCM (made by Kobe Steel), LCM (made by Kobe Steel), ACM (made by Kobe Steel), KTX (made by Kobe Steel), GT (manufactured by Ikegai Co., Ltd.), PCM (manufactured by Ikegai Co., Ltd.), TEX (manufactured by Nippon Steel Works Co., Ltd.), TEM (manufactured by Toshiba Machine Co., Ltd.), ZSK (manufactured by Warner Company), and Nidex (manufactured by Mitsui Mining Company) It is done.

  In the present invention, it is desirable to use an acid when agglomerating fine particles, but the type of acid is not particularly limited. For example, nitric acid, sulfuric acid, hydrochloric acid, acetic acid, acetic anhydride, and phosphoric acid may be used. I can do it.

  In the present invention, in order to adjust fluidity and chargeability with respect to the toner particles, 0.01 to 20% by weight of inorganic fine particles can be added to and mixed with the toner particle surface with respect to the total weight of the toner. As such inorganic fine particles, silica, titania, alumina, strontium titanate, tin oxide, cerium oxide or the like can be used alone or in admixture of two or more.

  The inorganic fine particles are preferably surface-treated with a hydrophobizing agent from the viewpoint of improving environmental stability. In addition to such inorganic oxides, resin fine particles of 1 μm or less can be externally added to improve the cleaning property.

  As a mixing machine for inorganic fine particles, for example, Henschel mixer (manufactured by Mitsui Mining), super mixer (manufactured by Kawata), ribocorn (manufactured by Okawara Seisakusho), nauter mixer (manufactured by Hosokawa Micron), turbulator (Hosokawa Micron) Co., Ltd.), cyclomixer (manufactured by Hosokawa Micron Corporation), spiral pin mixer (manufactured by Taiheiyo Kiko Co., Ltd.), and Redige mixer (manufactured by Matsubo).

  In the present invention, coarse particles and the like can be further screened. As the sieving equipment used for the sieve, Ultrasonic (manufactured by Sakae Sangyo Co., Ltd.), Gyroshifter (Tokusu Kosakusha Co., Ltd.), Vibrasonic System (manufactured by Dalton), Soniclean (manufactured by Shinto Kogyo Co., Ltd.), Turbo Screener (Manufactured by Turbo Kogyo Co., Ltd.), micro shifter (manufactured by Hadano Sangyo Co., Ltd.), circular vibrating sieve, etc.

  By adopting such a configuration, a toner having a sharp particle size distribution can be easily produced.

Example 1
90 parts by weight of polyester resin as binder resin (glass transition temperature 58 degrees, acid value 6, weight average molecular weight Mw 13,658), 5 parts by weight of cyan pigment as colorant, 4 parts by weight of ester wax, and zirconia as charge control agent After mixing 1 part by weight of the metal complex, the mixture was melt kneaded in a biaxial kneader set at 120 ° C. to obtain a kneaded product.

  The obtained kneaded product was coarsely pulverized to a mean volume particle size of 1.2 mm using a hammer mill manufactured by Nara Machinery Co., Ltd., to obtain coarse particles. Subsequently, the mixture was further pulverized using a pulverizer manufactured by Hosokawa Micron Co., Ltd. to obtain medium crushed particles having an average volume particle diameter of 58 μm.

  30 parts by weight of the crushed particles obtained, 1 part by weight of sodium dodecylbenzenesulfonate as an anionic surfactant, 1 part by weight of triethylamine as an amine compound, and 68 parts by weight of ion-exchanged water were stirred and mixed with a homogenizer manufactured by IKA. Liquid 1 was obtained.

  Next, the obtained mixed liquid 1 is put into a nanomizer (Yoshida Kikai Kogyo Co., Ltd., adding a heating system to the YSNM-2000AR) whose heating system temperature is set to 120 ° C., and is repeatedly treated three times at a processing pressure of 150 MPa. went. As a result of measuring the volume average particle size of the colored fine particles obtained after cooling with SALD7000 (manufactured by Shimadzu Corporation), the pH of the fine particle dispersion which was 0.70 μm was 8.2.

Next, after dilution so that the solid content concentration of the colored fine particles was 18%, 0.1 M hydrochloric acid was added dropwise to adjust the pH. The temperature of the dispersion was controlled to be 30 degrees. When the pH reached 7.0, the particle size was measured and found to be 0.85 μm. Further, 0.1M hydrochloric acid was added dropwise, and the addition was terminated when the ζ potential of the fine particles became −30 mV. The pH at this time was 3.9.

  Next, while stirring the dispersion with a paddle blade (500 rpm), the temperature was raised to 80 ° C. at a rate of 10 ° C./min, and held at 80 ° C. for 1 hour. After cooling, the dispersion was allowed to stand overnight and the state of the supernatant was observed. As a result, the supernatant was transparent and no agglomerated particles were observed. Moreover, as a result of measuring the volume average particle diameter with a Coulter counter (manufactured by Beckman Coulter, Inc .: aperture diameter 100 μm), it was 6.3 μm, and coarse particles of 20 μm or more were not observed.

Examples 2-8, Comparative Examples 1-8
Except that the composition of the liquid mixture 1 of Example 1 was changed as shown in Table 1-1 below, all the conditions were the same as those of Example 1. The characteristics and test results of the colored fine particle dispersion are shown in Tables 1-2 and 1-3 below.

  Further, for Examples 1 and 2 and Comparative Examples 1 and 2, a graph showing the relationship between pH and the ζ potential of the fine particles and the aggregated particles thereof is shown in FIG. 2, pH and the volume average particle size of the fine particles and the aggregated particles thereof. The graph showing the relationship of is shown.

  In the figure, reference numerals 101, 102, 101 ', and 102' denote graphs representing the cases of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, respectively.

  201, 202, 201 ′ 202 ′ indicate graphs representing the cases of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, respectively.

  As shown in the figure, in Example 1, aggregated particles are formed at least in a region where the ζ potential is −30 mV or more. The change in the particle size of the aggregated particles is not abrupt and is stable at a desired size. In Example 2, in the region where the ζ potential is −30 mV, the fine particles are not yet sufficiently aggregated, and in the region where the ζ potential is greater than −30 mV, the aggregation progresses as the ζ potential increases. . Further, the pH when the ζ potential is −30 mV is in the range of 3.0 to 6.9. In either case, aggregation is easily controlled by adjusting the ζ potential by pH.

  In Comparative Example 1, the pH when the ζ potential is −30 mV is in the range of 3.0 to 6.9, but the dispersion stability is too high to cause aggregation.

  In Comparative Example 2, the ζ potential does not become −30 mV or more, and the particle size of the aggregated particles changes abruptly around pH 7, so that large particles are generated and it is difficult to control the particle size. Recognize.

Japanese Patent Laid-Open No. 63-282275 JP-A-6-250439 JP-A-9-311502 JP 2007-323071 A

Claims (6)

A step of preparing a toner material dispersion by mixing a granular mixture containing a binder resin and a colorant, and an aqueous medium;
Subjecting the toner material dispersion to mechanical shearing, atomizing the granular mixture to prepare a dispersion containing fine particles having a particle size smaller than the particle size of the granular mixture; and A developer manufacturing method comprising a step of aggregating the fine particles by adjusting the pH of the dispersion liquid to form aggregated particles, wherein the particles in the dispersion include: When the pH is 7, the developer has a volume average particle diameter of 2 μm or less, and when the zeta potential of the particles is −30 mV, the pH in the dispersion is 3.0 to 6.9. .   The method according to claim 1, wherein the fine particles have a volume average particle diameter of 0.05 to 1.0 μm.   In the step of forming the agglomerated particles, pH adjustment is performed using at least one acid selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, acetic acid, acetic anhydride, phosphoric acid, and citric acid. 2. The method according to 2.   The method according to any one of claims 1 to 3, wherein the binder resin is a polyester resin.   In the step of forming the agglomerated particles, a step of encapsulating the agglomerated particles by adding a dispersion liquid containing additional fine particles containing a resin component and heteroaggregating the fine particles on the surface of the agglomerated particles. 5. The method according to any one of claims 1 to 4, further comprising:   The method according to claim 5, wherein the volume average particle diameter of the additional fine particles is 0.03 to 1 μm.

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