JP5885632B2 - Method for producing toner for developing electrostatic latent image - Google Patents

Description

  The present invention relates to a method for producing a toner for developing an electrostatic latent image.

  In general, in electrophotography, the surface of a photosensitive drum is charged by corona discharge or the like and then exposed by a laser or the like to form an electrostatic latent image. The formed electrostatic latent image is developed with toner to form a toner image. Further, the formed toner image is transferred to a recording medium, and a high quality image is obtained. Usually, a toner used for forming a toner image is mixed with a binder resin such as a thermoplastic resin and components such as a colorant, a charge control agent, a release agent, and a magnetic material, and then kneaded and pulverized. In addition, toner particles (toner mother particles) having an average particle diameter of 5 μm or more and 10 μm or less obtained through a classification step are used. Such a method for producing a toner including kneading of materials contained in the toner, pulverization of the kneaded material, and classification of the pulverized material is generally called a pulverization method. For the purpose of imparting fluidity to the toner, imparting suitable charging performance to the toner, and improving the cleaning property of the toner from the photosensitive drum, an inorganic fine powder such as silica or titanium oxide is used. Externally added to the base particles.

  With respect to such a toner, from the viewpoint of energy saving and apparatus miniaturization, a toner having excellent low-temperature fixability that can be fixed satisfactorily without heating the fixing roller as much as possible is desired. However, toners excellent in low-temperature fixability often use a binder resin having a low melting point or glass transition point or a low melting point release agent. For this reason, a toner having excellent low-temperature fixability easily causes aggregation (blocking) when the toner is stored at a high temperature, and causes image defects due to toner components adhering to members such as a developing roller and a photosensitive drum. It is easy.

  Therefore, in order to obtain a toner capable of suppressing blocking that occurs when the toner is stored at a high temperature, an aggregate of these fine particles is formed in a solvent in which fine particles of the binder resin and fine particles of the colorant are dispersed and heated. A method for producing a toner by a fine particle agglomeration method in which fine particle agglomerates are united is proposed (see Patent Document 1).

JP-A-6-0250439

  In such a fine particle aggregation method, the heating temperature for coalescence of the fine particle aggregate is usually a temperature equal to or higher than the glass transition point (Tg) of the binder resin. However, in the toner manufacturing method described in Patent Document 1, depending on the Tg of the binder resin, after the fine particle aggregates are formed, the particles are released from the fine particle aggregates by heating when coalescing the fine particle aggregates. There is a risk of the agent component falling off. In this case, there is a problem that the obtained toner tends to aggregate when the toner is stored at a high temperature.

  The present invention has been made in view of such circumstances, and is capable of producing an electrostatic latent image developing toner that is excellent in storage stability and low-temperature fixability and can suppress the occurrence of offset at high temperatures. It is an object of the present invention to provide a method for producing a latent image developing toner.

The present inventors aggregate fine particles containing a binder resin, fine particles containing a release agent, or fine particles containing a binder resin and a release agent to form a fine particle aggregate in an aqueous medium. The electrostatic latent image developing toner formed by heating the fine particle aggregates in an aqueous medium to coalesce the components contained in the fine particle aggregates is combined in the (II) coalescence step. at a temperature _{(t u),} and the viscosity of the binder resin (pr _u), and a viscosity of the release agent (ρW _u), a predetermined relation, and, the binder resin at the melting point (Tm), sintered It has been found that the above-mentioned problems can be solved by setting the viscosity (ρR _m ) of the resin to a predetermined relationship between the viscosity (ρW _m ) of the release agent, and the present invention has been completed. Specifically, the present invention provides the following.

The present invention includes the following steps (I) and (II):
(I) The fine particles of the binder resin and the fine particles of the release agent are aggregated in an aqueous medium to form a fine particle aggregate, or the fine particles containing the binder resin and the release agent are dispersed in the aqueous medium. A fine particle aggregate forming step of aggregating to form a fine particle aggregate to obtain an aqueous medium dispersion (A) containing the fine particle aggregate; and
(II) The fine particle aggregate is heated in an aqueous medium to a coalescence temperature (t _u ) that is equal to or higher than the glass transition point (Tg) of the binder resin to combine the components contained in the fine particle aggregate. Unitizing step to obtain an aqueous medium dispersion (B) containing toner particles,
Including
Wherein at coalescence temperature _{(t u),} the viscosity of the binder resin (pr _u), the viscosity of the release agent (ρW _u), but satisfy the relationship ρR _u / _{ρW u} ≦ 1,
At the melting point (Tm) of the said binder resin, wherein the viscosity of the binder resin (pr _m), wherein the viscosity of the release agent (ρW _m), but satisfy the relationship ρR _m / _{ρW m} ≧ 5,
The present invention relates to a method for producing a toner for developing an electrostatic latent image.

  According to the present invention, there is provided a method for producing an electrostatic latent image developing toner capable of producing an electrostatic latent image developing toner that is excellent in storage stability and low-temperature fixability and can suppress the occurrence of offset at a high temperature. be able to.

It is a figure explaining the measuring method of melting | fusing point by a Koka flow tester.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. . In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the summary of invention is not limited.

The present invention relates to a method for producing an electrostatic latent image developing toner (hereinafter also referred to as toner) including the following steps (I) and (II):
The method for producing the toner of the present invention includes:
(I) The fine particles of the binder resin and the fine particles of the release agent are aggregated in an aqueous medium to form a fine particle aggregate, or the fine particles containing the binder resin and the release agent are dispersed in the aqueous medium. A fine particle aggregate forming step of aggregating to form a fine particle aggregate to obtain an aqueous medium dispersion (A) containing the fine particle aggregate; and
(II) The fine particle aggregate is heated in an aqueous medium to a coalescence temperature (t _u ) that is equal to or higher than the glass transition point (Tg) of the binder resin, and the components contained in the fine particle aggregate are coalesced. Obtaining an aqueous medium dispersion (B) containing toner particles,
including.
Then, at coalescence temperature _{(t u),} and the viscosity of the binder resin (pr _u), the viscosity of the release agent and (ρW _u), but the relationship ρR _u / _{ρW u} ≦ 1 meet,
At the melting point (Tm) of the binder resin, the viscosity of the binder resin (pr _m), and the viscosity of the release agent (ρW _m), but satisfy the relationship ρR _m / _{ρW m} ≧ 5.
Hereinafter, the toner material used in the method for producing a toner for developing an electrostatic latent image of the present invention and the method for producing the toner for developing an electrostatic latent image will be described in order.

≪Toner material≫
The toner obtained by the method for producing a toner of the present invention essentially contains a binder resin and a release agent, and the viscosity (ρR _u ) of the binder resin at the coalescence temperature (t _u ) the viscosity of the mold agent (ρW _u), but satisfy the relationship ρR _u / _{ρW u} ≦ 1, and, at the melting point (Tm) of the binder resin, the viscosity of the binder resin (pr _m), release agent the viscosity (ρW _m), but satisfy the relationship ρR _m / _{ρW m} ≧ 5. Further, the toner obtained by the method for producing a toner of the present invention may contain components such as a colorant, a charge control agent, and magnetic powder, if necessary.

  The toner obtained by the method for producing a toner of the present invention may have an external additive attached to the surface thereof, if necessary. Further, the toner obtained by the toner production method of the present invention can be mixed with a desired carrier and used as a two-component developer. Hereinafter, a binder resin and a release agent, which are essential materials used in the production of toner, a viscosity of the binder resin, a viscosity of the release agent, and a colorant that is an arbitrary material used in the production of toner The charge control agent, the magnetic powder, and the external additive, and the carrier used when the toner is used as the two-component developer will be described in order.

[Binder resin]
Binder resin contained in the toner, in (II) coalescence temperature in the coalescence step (t _u), and the viscosity of the binder resin (pr _u), and the viscosity of the release agent (ρW _u) but The resin satisfying the predetermined relationship and the viscosity (ρR _m ) of the binder resin at the melting point (Tm) of the binder resin and the viscosity of the release agent (ρW _m ) satisfy the predetermined relationship. If there is, there is no particular limitation. Specific examples of the binder resin include styrene resin, acrylic resin, styrene acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether. And thermoplastic resins such as styrene resins, N-vinyl resins, and styrene-butadiene resins. Among these resins, styrene acrylic resins and polyester resins are preferable from the viewpoint of chargeability of toner and fixability to paper. Hereinafter, the styrene acrylic resin and the polyester resin will be described.

  The styrene acrylic resin is a copolymer of a styrene monomer and an acrylic monomer. Specific examples of the styrene monomer include styrene, α-methylstyrene, vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-ethylstyrene. Specific examples of the acrylic monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, meta Examples include (meth) acrylic acid alkyl esters such as methyl acrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate.

  As the polyester resin, those obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component can be used. Examples of the components used when synthesizing the polyester resin include the following divalent or trivalent or higher alcohol components and divalent or trivalent or higher carboxylic acid components.

  Specific examples of the divalent or trivalent or higher alcohol component include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1 Diols such as 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenol A Bisphenols such as hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sol Tan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2, Examples include trivalent or higher alcohols such as 4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

  Specific examples of the divalent or trivalent or higher carboxylic acid component include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, Sebacic acid, azelaic acid, malonic acid, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid Acid, alkyl such as isododecyl succinic acid, isododecenyl succinic acid, or divalent carboxylic acid such as alkenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5 -Benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4 Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid , A trivalent or higher carboxylic acid such as tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid. These divalent or trivalent or higher carboxylic acid components may be used as ester-forming derivatives such as acid halides, acid anhydrides, and lower alkyl esters. Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  When the binder resin includes a polyester resin, the acid value of the polyester resin is preferably 10 mgKOH / g or more and 40 mgKOH / g or less. When the acid value of the polyester resin is too low, the aggregation of the fine particles tends not to proceed well depending on the formulation of the step (II) included in the toner manufacturing method according to the second embodiment described later. When the acid value of the polyester resin is too high, various performances of the toner are easily affected by humidity under high humidity conditions. The acid value of the polyester resin can be adjusted by adjusting the balance between the hydroxyl group of the alcohol component used for the synthesis of the polyester resin and the carboxyl group of the carboxylic acid component.

  As the binder resin, it is preferable to use a thermoplastic resin because the toner has good fixability to paper. However, the binder resin is not only used alone, but also used as a crosslinking agent or a thermosetting resin. Can be added. By introducing a partially crosslinked structure into the binder resin, it is possible to improve properties such as the storage stability, form retention, and durability of the toner without deteriorating the fixability of the toner to the paper.

  As the thermosetting resin that can be used together with the thermoplastic resin, an epoxy resin or a cyanate resin is preferable. Specific examples of suitable thermosetting resins include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins, cycloaliphatic type epoxy resins, and cyanate resins. . These thermosetting resins can be used in combination of two or more.

  The glass transition point (Tg) of the binder resin is preferably 45 ° C. or higher and 60 ° C. or lower, and more preferably 50 ° C. or higher and 65 ° C. or lower. If the glass transition point of the binder resin is too low, the toners may be fused inside the developing unit of the image forming apparatus, or the storage stability may be reduced. May be partly fused. Further, when the glass transition point is too high, the strength of the binder resin is lowered, and the toner is likely to adhere to the latent image carrier (image carrier: photoconductor). If the glass transition point is too high, the toner tends to be difficult to fix well at low temperatures.

  The glass transition point of the binder resin can be obtained from the change point of the specific heat of the binder resin using a differential scanning calorimeter (DSC). More specifically, the glass transition point of the binder resin can be obtained by measuring the endothermic curve of the binder resin using a differential scanning calorimeter DSC-6200 manufactured by Seiko Instruments Inc. as a measuring device. 10 mg of a measurement sample is put in an aluminum pan, and an empty aluminum pan is used as a reference. The glass transition point of the binder resin can be obtained from the endothermic curve of the binder resin obtained by measurement under normal temperature and humidity under the measurement temperature range of 25 to 200 ° C. and the temperature increase rate of 10 ° C./min.

The melting point (Tm) of the binder resin is preferably 80 ° C. or higher and 115 ° C. or lower, and more preferably 80 ° C. or higher and 100 ° C. or lower. When the melting point of the binder resin is too low, the toners are fused inside the developing portion of the image forming apparatus or the storage stability is lowered, so that the toners are kept at the same time when the toner container is transported or stored in a warehouse. Some parts may be fused. On the other hand, when the melting point is too high, the strength of the binder resin is reduced, and the toner tends to adhere to the latent image carrier (image carrier: photoconductor). If the melting point is too high, the toner tends to be difficult to fix well at low temperatures. The melting point of the binder resin can be measured according to the following method.

<Measuring method of melting point>
The melting point of the binder resin (toner) is measured using a Koka flow tester (CFT-500D (manufactured by Shimadzu Corporation)). Specifically, the melting point of the binder resin is measured as follows. Using 1.5 g of toner as a sample, a die having a height of 1.0 mm and a diameter of 0.5 mm is used. Then, the measurement is performed under the conditions of a heating rate of 1 ° C./min, a preheating time of 300 seconds, a load of 10 kg, and a measurement temperature range of 35 ° C. to 200 ° C. The melting point of the binder resin is read from an S-shaped curve relating to temperature (° C.) and stroke (mm) obtained by measuring the binder resin using a flow tester.

How to read the melting point will be described with reference to FIG. The maximum value of the stroke and S _1, the stroke value of the low-temperature side of the base line and S _2. In the S curve, the temperature at which the stroke value is (S ₁ + S ₂ ) / 2 is defined as the melting point of the binder resin.

  The number average molecular weight (Mn) of the binder resin is not particularly limited as long as the object of the present invention is not impaired, but is preferably 2,000 or more and 4,000 or less. By setting the number average molecular weight (Mn) of the binder resin in such a range, it becomes easy to obtain a toner having excellent low-temperature fixability. Further, the molecular weight distribution (Mw / Mn) represented by the ratio of the number average molecular weight (Mn) to the mass average molecular weight (Mw) is preferably 2 or more and 15 or less. By setting the molecular weight distribution of the binder resin in such a range, it is possible to obtain a toner that can realize good fixability in a wide temperature range. The number average molecular weight (Mn) and the mass average molecular weight (Mw) of the polyester resin can be measured by gel permeation chromatography.

〔Release agent〕
The toner for developing an electrostatic latent image of the present invention contains a release agent for the purpose of improving the fixability and offset resistance. Type of release agent, (II) at coalescence temperature in the coalescence step (t _u), and the viscosity of the binder resin (ρR _u), the viscosity of the release agent (ρW _u) and is given satisfies the relationship, and, at the melting point (Tm) of the binder resin, the viscosity of the binder resin (pr _m), and the viscosity of the release agent (ρW _m), but as long as it is a resin satisfying a predetermined relationship, There is no particular limitation.

  Suitable mold release agents include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymers, polyolefin waxes, microcrystalline waxes, paraffin waxes, and aliphatic hydrocarbon waxes such as Fischer-Tropsch wax; oxidized polyethylene waxes, and Oxides of aliphatic hydrocarbon waxes such as block copolymers of oxidized polyethylene waxes; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax, and rice wax; beeswax, lanolin, and whale Animal waxes such as waxes; mineral waxes such as ozokerite, ceresin, and vetrolactam; waxes based on fatty acid esters such as montanate ester wax and castor wax; Some fatty acid esters such as acid carnauba wax, or wax deoxidizing the like all.

  Suitable release agents further include saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, and long-chain alkyl carboxylic acids having a long-chain alkyl group; brassic acid, eleostearic acid And unsaturated fatty acids such as valinalic acid; saturated alcohols such as stearyl alcohol, eicosyl alcohol, behenyl alcohol, carnauvyl alcohol, seryl alcohol, melyl alcohol, and long chain alkyl alcohols having long chain alkyl groups Polyhydric alcohols such as sorbitol; fatty acid amides such as linoleic acid amide, oleic acid amide, and lauric acid amide; methylene bis stearic acid amide, ethylene biscapric acid amide, ethylene bis lauric acid amide, and hexamethylene vinyl Saturated fatty acid bisamides such as stearic acid amides; Unsaturated fatty acids such as ethylene bisoleic acid amides, hexamethylene bisoleic acid amides, N, N′-dioleyl adipic acid amides, N, N′-dioleyl sebacic acid amides Aromatic bisamides such as amides, m-xylene bis-stearic amide, and N, N′-distearylisophthalic amide; fatty acid metal salts such as calcium stearate, calcium laurate, zinc stearate, and magnesium stearate A wax obtained by grafting a vinyl monomer such as styrene or acrylic acid to an aliphatic hydrocarbon wax; a partially esterified product of a fatty acid such as behenic monoglyceride and a polyhydric alcohol; hydrogenating vegetable oils and fats; Hydro obtained by And methyl ester compounds having a sill group.

  The amount of the release agent used is not particularly limited as long as the object of the present invention is not impaired. Specifically, the amount of the release agent used is preferably 8% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less with respect to the mass of the toner. If the amount of the release agent used is too small, the desired effect may not be obtained in terms of suppressing the occurrence of offset and image smearing in the formed image. If the amount of release agent used is excessive, In some cases, the storage stability of the toner may be reduced due to the fusing. According to the method for producing a toner for developing an electrostatic latent image of the present invention, which will be described later, even when a large amount of the release agent is used, the release agent is removed from the toner surface or the release agent from the inside of the toner. Therefore, it is easy to obtain a toner having both low-temperature fixability and heat-resistant storage stability.

[Binder resin viscosity and release agent viscosity]
The binder resin and the release agent used in the toner production method of the present invention are (II) the viscosity (ρR _u ) of the binder resin at the coalescence temperature (t _u ) in the coalescence process, The viscosity (ρW _u ) of the release agent satisfies the relationship of ρR _u / ρW _u ≦ 1, and
At the melting point (Tm) of the binder resin, the viscosity of the binder resin (pr _m), and the viscosity of the release agent (ρW _m), but satisfy the relationship ρR _m / _{ρW m} ≧ 5.

In (II) coalescence temperature in the coalescence step _{(t u),} and the viscosity of the binder resin (pr _u), the viscosity of the release agent and (ρW _u), but the ρR _u / _{ρW u} ≦ 1 By satisfying the relationship, in the (II) coalescence step, the release agent charged when the toner is produced can be favorably dispersed in the toner. On the other hand, when ρR _u / ρW _u > 1, the viscosity (ρW _u ) of the release agent is lower than the viscosity (ρR _u ) of the binder resin at the coalescence temperature (t _u ). II) The fine particles of the release agent incorporated into the fine particle aggregate in the coalescing step easily fall off from the fine particle aggregate. In this case, the content of the release agent in the produced toner tends to be smaller than the amount of the release agent charged when the toner is produced, and a desired effect can be obtained for suppressing the occurrence of offset in the formed image. It may not be possible.

At the melting point (Tm) of the binder resin, the viscosity of the binder resin (pr _m), and the viscosity of the release agent (ρW _m), but by satisfying the relation of ρR _m / _{ρW m} ≧ 5, the toner When fixing on the recording medium, the releasability between the fixing roller and the recording medium on which the image is formed is excellent, and the occurrence of offset at a high temperature can be suppressed. On the other hand, if ρR _m / ρW _m <5, because in the binder resin melting point (Tm), the viscosity of the release agent (ρW _u) is not sufficiently low relative to the viscosity of the binder resin (pr _u), When fixing the toner to the recording medium, it is difficult to obtain a good effect of the release agent in the toner. Therefore, the releasability between the fixing roller and the recording medium on which the image is formed is inferior, and it may be difficult to suppress the occurrence of offset at a high temperature.

  In addition, the measuring method of the viscosity of binder resin and the viscosity of a mold release agent can be measured using a Koka type flow tester (CFT-500D (made by Shimadzu Corporation)). Specifically, 1.5 g of toner is used as a sample, and a die having a height of 1.0 mm and a diameter of 0.5 mm is used. Then, the measurement is performed under the conditions of a heating rate of 1 ° C./min, a preheating time of 300 seconds, a load of 10 kg, and a measurement temperature range of 35 ° C. to 200 ° C.

[Colorant]
As the colorant contained in the toner for developing an electrostatic latent image of the present invention, a known pigment or dye can be used according to the color of the toner particles. Specific examples of suitable colorants that can be added to the toner include the following colorants.

  Examples of the black colorant include carbon black. Further, as the black colorant, a colorant that is toned to black using a colorant such as a yellow colorant, a magenta colorant, and a cyan colorant, which will be described later, can also be used. Examples of the color toner colorant include yellow colorants, magenta colorants, and cyan colorants.

  Examples of yellow colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 191 and 194.

  Examples of the magenta colorant include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177, 184, 185, 202, 206, 220, 221 and 254.

  Examples of cyan colorants include copper phthalocyanine compounds, copper phthalocyanine derivatives, anthraquinone compounds, and basic dye lake compounds. Specifically, C.I. I. Pigment blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66.

  Each color of these colorants can be used alone or in combination. The amount of the colorant used is not particularly limited as long as the object of the present invention is not impaired. Specifically, the content is preferably 3% by mass or more and 15% by mass or less with respect to the mass of the toner.

(Charge control agent)
The electrostatic latent image developing toner of the present invention may contain a charge control agent as required. The charge control agent improves the stability of the charge level of the toner and the charge rise characteristic that is an indicator of whether the toner can be charged to a predetermined charge level in a short time. Used for gaining purposes. When developing with positively charged toner, a positively chargeable charge control agent is used. When developing with negatively charged toner, a negatively chargeable charge control agent is used.

  The type of the charge control agent is not particularly limited as long as the object of the present invention is not impaired, and can be appropriately selected from charge control agents conventionally used in toners. Specific examples of the positively chargeable charge control agent include pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1, 2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, Azine compounds such as phthalazine, quinazoline and quinoxaline; Azin Fast Red FC, Azin Fast Red 12BK, Azine Violet BO, Azine Direct dyes composed of azine compounds such as N-Brown 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Deep Black EW, and Azin Deep Black 3RL; Nigrosine such as Nigrosine, Nigrosine Salt, Nigrosine Derivative Compounds; Acid dyes consisting of nigrosine compounds such as nigrosine BK, nigrosine NB, nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; 4 such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride A class ammonium salt is mentioned. Among these positively chargeable charge control agents, a nigrosine compound is particularly preferable in that a more rapid start-up property can be obtained. These positively chargeable charge control agents can be used in combination of two or more.

  A resin having a quaternary ammonium salt, carboxylate, or carboxyl group as a functional group can also be used as a positively chargeable charge control agent. More specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, and a carboxylate Styrene resin having carboxylate, acrylic resin having carboxylate, styrene acrylic resin having carboxylate, polyester resin having carboxylate, styrene resin having carboxyl group, acrylic resin having carboxyl group, carboxyl group Styrene acrylic resin having a carboxyl group and polyester resin having a carboxyl group. The molecular weight of these resins is not particularly limited as long as the object of the present invention is not impaired, and may be an oligomer or a polymer.

  Among the resins that can be used as positively chargeable charge control agents, styrene acrylic resins having a quaternary ammonium salt as a functional group are more preferable because the charge amount can be easily adjusted to a value within a desired range. preferable. Specific examples of preferred acrylic comonomers that are copolymerized with styrene units in styrene acrylic resins having a quaternary ammonium salt as a functional group include methyl acrylate, ethyl acrylate, n-propyl acrylate, and iso-propyl acrylate. (Meth) acrylic acid, such as n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate Examples include alkyl esters.

  As the quaternary ammonium salt, a unit derived from a dialkylaminoalkyl (meth) acrylate, dialkylamino (meth) acrylamide, or dialkylaminoalkyl (meth) acrylamide through a quaternization step is used. Specific examples of the dialkylaminoalkyl (meth) acrylate include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, and dibutylaminoethyl (meth) acrylate. A specific example of dialkyl (meth) acrylamide is dimethylmethacrylamide. Specific examples of the dialkylaminoalkyl (meth) acrylamide include dimethylaminopropyl methacrylamide. Further, a hydroxy group-containing polymerizable monomer such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, or N-methylol (meth) acrylamide can be used in combination during polymerization.

  Specific examples of the negatively chargeable charge control agent include organometallic complexes and chelate compounds. Examples of organometallic complexes and chelate compounds include acetylacetone metal complexes such as aluminum acetylacetonate and iron (II) acetylacetonate, and salicylic acid metal complexes such as chromium 3,5-di-tert-butylsalicylate. A salicylic acid metal salt is preferable, and a salicylic acid metal complex or a salicylic acid metal salt is more preferable. These negatively chargeable charge control agents can be used in combination of two or more.

  The amount of the positively or negatively chargeable charge control agent used is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the positively or negatively chargeable charge control agent used is preferably 0.5 parts by mass or more and 15 parts by mass or less, and 1.0 part by mass when the total amount of toner is 100 parts by mass. More preferred is 8.0 parts by mass or less. When the amount of charge control agent used is too small, it is difficult to stably charge the toner to a predetermined polarity, so that the image density of the formed image falls below a desired value, or it is difficult to maintain the image density over a long period of time. There are things to do. In such a case, the charge control agent is difficult to uniformly disperse in the toner, so that the formed image is likely to be fogged or the latent image carrier is easily contaminated by the toner component. When the amount of the charge control agent used is excessive, image defects in the formed image due to poor charging under high temperature and high humidity due to deterioration of environmental resistance, and contamination by the toner component of the latent image carrier are likely to occur. .

[Magnetic powder]
The electrostatic latent image developing toner obtained by the method of the present invention can be blended with magnetic powder as desired. The kind of magnetic powder is not particularly limited as long as the object of the present invention is not impaired. Examples of suitable magnetic powders include irons such as ferrite and magnetite; ferromagnetic metals such as cobalt and nickel; alloys containing iron and / or ferromagnetic metals; compounds containing iron and / or ferromagnetic metals A ferromagnetic alloy subjected to a ferromagnetization treatment such as heat treatment; chromium dioxide.

  The particle size of the magnetic powder is not limited as long as the object of the present invention is not impaired. The particle diameter of the specific magnetic powder is preferably 0.1 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. When magnetic powder having a particle diameter in such a range is used, it is easy to uniformly disperse the magnetic powder in the binder resin.

  The magnetic powder can be used that has been surface-treated with a surface treatment agent such as a titanium coupling agent or a silane coupling agent for the purpose of improving dispersibility in the toner.

  The usage-amount of magnetic powder is not specifically limited in the range which does not inhibit the objective of this invention. The specific amount of magnetic powder used is preferably 35 parts by weight or more and 60 parts by weight or less, and 40 parts by weight or more and 60 parts by weight or less when the toner is used as a one-component developer and the total amount of toner is 100 parts by weight. The following is more preferable. If the amount of magnetic powder used is excessive, the image density may not be maintained at a desired value over a long period of time, or the fixability may be extremely reduced. If the amount of magnetic powder used is too low, formation may occur. The durability of the image density may be lowered due to the occurrence of fog in the image. When the toner is used as a two-component developer, the amount of magnetic powder used is preferably 20% by mass or less and more preferably 15% by mass or less when the total amount of toner is 100 parts by mass.

(External additive)
The surface of the electrostatic latent image developing toner obtained by the method of the present invention may be optionally treated with an external additive. The type of external additive is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected from external additives conventionally used for toners. Specific examples of suitable external additives include silica and metal oxides such as alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. These external additives can be used in combination of two or more. These external additives can also be used after being hydrophobized with a hydrophobizing agent such as an aminosilane coupling agent or silicone oil. In the case of using a hydrophobized external additive, it is easy to suppress a decrease in charge amount of the toner under high temperature and high humidity, and it is easy to obtain a toner excellent in fluidity.

  The particle diameter of the external additive is not particularly limited as long as it does not impair the object of the present invention, and is typically 0.01 μm or more and 1.0 μm or less.

  The amount of the external additive used is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the external additive used is preferably 0.1 parts by mass or more and 10 parts by mass or less, and 0.2 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the toner particles before the external addition process. More preferred.

[Carrier]
The electrostatic latent image developing toner obtained by the method of the present invention can be mixed with a desired carrier and used as a two-component developer. When preparing a two-component developer, it is preferable to use a magnetic carrier.

  Suitable carriers when the toner for developing an electrostatic latent image obtained by the method of the present invention is used as a two-component developer include those in which a carrier core material is coated with a resin. Specific examples of the carrier core material include particles such as iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, and cobalt, and these materials and metals such as manganese, zinc, and aluminum. Alloy particles, particles such as iron-nickel alloy, iron-cobalt alloy, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, titanate Ceramic particles such as lithium, lead titanate, lead zirconate and lithium niobate, particles of high dielectric constant materials such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, Rochelle salt, and the above magnetic particles in resin And a resin carrier in which is dispersed.

  Specific examples of the resin covering the carrier core material include (meth) acrylic polymers, styrene polymers, styrene- (meth) acrylic copolymers, olefin polymers (polyethylene, chlorinated polyethylene, polypropylene, etc. ), Polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, polyfluoride) Vinylidene chloride), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, amino resin. These resins can be used in combination of two or more.

  The particle size of the carrier is not particularly limited as long as the object of the present invention is not impaired, but the particle size measured using an electron microscope is preferably 20 μm or more and 120 μm or less, and more preferably 25 μm or more and 80 μm or less.

  When the toner produced by the method of the present invention is used as a two-component developer, the toner content is preferably 3% by mass or more and 20% by mass or less, and preferably 5% by mass or more and 15% by mass or less with respect to the mass of the two-component developer. The mass% or less is preferable. By setting the toner content in the two-component developer in such a range, an appropriate image density is maintained in the formed image, and toner contamination inside the image forming apparatus and transfer paper are suppressed by suppressing toner scattering from the developing apparatus. Toner adhesion to the toner can be suppressed.

  Using the materials described above, an electrostatic latent image developing toner is prepared by the method described below.

<Method for producing toner for developing electrostatic latent image>
The method for producing a toner for developing an electrostatic latent image of the present invention includes at least the following steps (I) and (II).
(I) The fine particles of the binder resin and the fine particles of the release agent are aggregated in an aqueous medium to form a fine particle aggregate, or the fine particles containing the binder resin and the release agent are dispersed in the aqueous medium. A fine particle aggregate forming step of aggregating to form a fine particle aggregate to obtain an aqueous medium dispersion (A) containing the fine particle aggregate; and
(II) The fine particle aggregate is heated in the aqueous medium dispersion to a coalescence temperature (t _u ) that is equal to or higher than the glass transition point (Tg) of the binder resin, and the components contained in the fine particle aggregate are coalesced. A coalescing step for obtaining an aqueous medium dispersion (B) containing toner particles.

  Since the method for producing a toner for developing an electrostatic latent image of the present invention includes the above steps (I) and (II), the image density becomes lower than a desired value when images are formed continuously over a long period of time. And the occurrence of fogging in the formed image can be suppressed, excellent in storage stability, low-temperature fixability, and releasability between the fixing roller and the recording medium on which the image is formed, and the occurrence of offset at high temperatures. An electrostatic latent image developing toner that can be suppressed can be produced.

In addition to the above steps (I) to (V), the method for producing a toner for developing an electrostatic latent image of the present invention may include the following steps (III) to (V) as necessary.
Step (III): A washing step for washing the toner obtained in step (II).
Step (IV): A drying step of drying the toner obtained in step (II).
Step (V): an external addition step of attaching an external additive to the surface of the toner obtained in the step (II).

  Hereinafter, the steps (I) to (V) will be described in order.

[Step (I): Fine Particle Aggregate Formation Step]
In step (I), fine particles of the binder resin and fine particles of the release agent are aggregated in an aqueous medium to form fine particle aggregates, or fine particles containing the binder resin and the release agent are aqueous. By agglomerating in a medium to form a fine particle aggregate, an aqueous medium dispersion (A) containing the fine particle aggregate is obtained.
The method for forming the fine particle aggregate is not particularly limited, and can be appropriately selected from conventionally known methods. The binder resin fine particles, the release agent fine particles, and the fine particles containing the binder resin and the release agent are obtained by finely dividing these components or a composition containing these components into a desired size. It is preferably prepared as an aqueous medium dispersion. Further, when the fine particles are aggregated, if necessary, the fine particles of the colorant are used together with the fine particles of the binder resin, the fine particles of the release agent, and the fine particles containing the binder resin and the release agent. It is also preferable.

  Hereinafter, a method for preparing an aqueous medium dispersion of binder resin fine particles, a method for preparing an aqueous medium dispersion of fine particles of a release agent, a method of preparing an aqueous medium dispersion of fine particles including a binder resin and a release agent, A method for preparing an aqueous medium dispersion of colorant fine particles and a method for agglomerating fine particles will be described in this order.

[Preparation method of aqueous dispersion of binder resin fine particles]
First, the binder resin is heated to a temperature equal to or higher than its melting point to obtain a binder resin melt. The temperature at which the binder resin is melted is not particularly limited as long as the binder resin melts uniformly, but a temperature of the melting point of the binder resin + 10 ° C. to the melting point + 40 ° C. is preferred.

  When a polyester resin is used as the binder resin, a basic substance may be added to the molten binder resin in order to neutralize the acid groups contained in the polyester resin. The basic substance is not particularly limited as long as it can neutralize acid groups contained in the polyester resin and does not impair the object of the present invention. Suitable basic materials include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, alkali metal carbonates such as sodium carbonate, and potassium carbonate, sodium bicarbonate, and hydrogen carbonate. Alkali metal hydrogen carbonate such as potassium, N, N-dimethylethanolamine, N, N-diethylethanolamine, triethanolamine, tripropanolamine, tributanolamine, triethylamine, n-propylamine, n-butylamine, isopropyl Examples thereof include nitrogen-containing organic bases such as amine, monomethanolamine, morpholine, methoxypropylamine, pyridine, and vinylpyridine. These basic compounds may be used individually by 1 type, and may be used in combination of 2 or more types.

  The usage-amount of a basic compound is not specifically limited in the range which does not inhibit the objective of this invention, 1 mass part or more and 20 mass parts or less are preferable with respect to 100 mass parts of binder resin, and 5 mass parts or more and 15 mass parts. The following is more preferable.

  Further, a surfactant can be added to the binder resin melt. When a surfactant is added to the binder resin melt, fine particles of the binder resin can be stably dispersed in an aqueous medium.

  The surfactant that can be added to the binder resin melt is not particularly limited, and can be appropriately selected from the group consisting of an anionic surfactant, a cationic surfactant, and a nonionic surfactant. Examples of anionic surfactants include sulfate ester type surfactants, sulfonate type surfactants, phosphate ester type surfactants, and soaps. Examples of the cationic surfactant include an amine salt type activator and a quaternary ammonium salt type activator. Examples of nonionic surfactants include polyethylene glycol type activators, alkylphenol ethylene oxide adduct type activators, and polyhydric alcohol type activators that are derivatives of polyhydric alcohols such as glycerin, sorbitol, and sorbitan. . Among these surfactants, it is preferable to use at least one of an anionic surfactant and a nonionic surfactant. These surfactants may be used alone or in combination of two or more.

As the anionic surfactant, polyoxyethylene alkyl ether sulfate is preferable. Among the polyoxyethylene alkyl ether sulfates, those represented by the following formula (1) are preferable.
R ¹ —O— (CH ₂ CH ₂ O) _p —SO ₃ M (1)
(In Formula (1), R ¹ is an alkyl group, M is a monovalent cation, and p is an integer of 1 to 50.)

R ¹ may be a linear alkyl group or a branched alkyl group, and is preferably a linear alkyl group. R ¹ may have an unsaturated bond. The number of carbon atoms in R ¹ is preferably 10 to 20, 12 to 18 is more preferable. p is an integer of 1-50. Since it is easy to control the particle diameter of the fine particles within a suitable range, p is preferably an integer of 1 to 30, and more preferably an integer of 2 to 20. M is a monovalent cation. M is preferably a sodium ion, a potassium ion, or an ammonium ion, more preferably a sodium ion or an ammonium ion, and particularly preferably a sodium ion because the particle diameter of the fine particles can be easily controlled within a suitable range.

  In addition, it is preferable to use said polyoxyethylene alkyl ether sulfate together with a nonionic surfactant. As the nonionic surfactant used in this case, polyoxyethylene alkyl ether is preferable.

  The amount of the surfactant used is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the surfactant used is preferably 1% by mass or more and 10% by mass or less with respect to the mass of the binder resin.

  In this way, an aqueous medium dispersion of binder resin fine particles can be prepared by adding water to the prepared binder resin melt and further stirring and mixing. As a device for stirring the binder resin melt and water, a stirring device having a function of maintaining the temperature of the contents is preferable in order to hold the binder resin in a molten state. As a suitable method for maintaining the temperature of the contents in the stirring device, there is a method of using a stirring device equipped with a jacket and circulating hot water, water vapor, or heat medium oil at a predetermined temperature in the jacket. As a specific example of a suitable stirring apparatus, a heating kneading apparatus (TK Hibis Disper Mix HM-3D-5 (manufactured by PRIMIX Corporation)) may be mentioned.

The particle diameter of the binder resin fine particles contained in the aqueous dispersion of the binder resin fine particles obtained by stirring the melt of the binder resin and water is the same as that of the binder resin melt and water. It can adjust by adjusting the stirring speed at the time of confusion. The volume average particle diameter (D ₅₀ ) of the fine particles of the binder resin is preferably 1 μm or less, and more preferably 50 nm or more and 500 nm or less. When the particle size of the fine particles of the binder resin is in such a range, the particle size distribution is sharp and it is easy to obtain a toner having a uniform shape, so that variations in toner performance and productivity are reduced. The volume average particle diameter (D ₅₀ ) of the fine particles of the binder resin can be measured using, for example, a laser diffraction / scattering particle diameter distribution measuring apparatus (LA-950 (manufactured by Horiba, Ltd.)).

[Method of preparing aqueous medium dispersion of release agent fine particles]
Hereinafter, a preferred example of a method for preparing an aqueous medium dispersion of release agent fine particles will be described. The method for preparing the aqueous medium dispersion of the release agent fine particles is not limited to the method described below.

  First, the release agent is pulverized to about 100 μm or less in advance to obtain a release agent powder. A release agent powder is added to an aqueous medium containing a surfactant to prepare a slurry. The resulting slurry is then heated to a temperature above the melting point of the release agent. A strong shearing force is applied to the heated slurry using a homogenizer or a pressure discharge type disperser to prepare an aqueous dispersion of release agent fine particles.

  As a device for applying a strong shearing force to the dispersion, NANO3000 (manufactured by Miki Co., Ltd.), nanomizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.), micro full dither (manufactured by MFI), gorin homogenizer (manufactured by Manton Gorin) Clare mix W motion (M Technique Co., Ltd.) is listed.

The volume average particle diameter (D ₅₀ ) of the fine particles of the release agent contained in the aqueous dispersion of the fine particles of the release agent is preferably 1 μm or less, and more preferably 100 nm to 700 nm. By using fine particles of a release agent having a particle diameter in such a range, it is easy to obtain a toner in which the release agent is uniformly dispersed in the binder resin. The volume average particle size of the fine particles of the release agent (D ₅₀₎ can be measured in the same manner as the volume average particle diameter of the binder resin (D _50).

[Preparation Method of Aqueous Medium Dispersion of Fine Particles Containing Binder Resin and Release Agent]
Hereinafter, a preferred example of a method for preparing an aqueous medium dispersion of fine particles containing a binder resin and a release agent will be described. The method for preparing the fine particles containing the binder resin and the release agent is not limited to the method described below.

  The fine particles containing the binder resin and the release agent are the same as those described above except that the release resin is contained in the binder resin melt with respect to the preferred method for preparing the fine particles of the binder resin. It can be prepared by a method similar to a suitable method for preparing fine particles of the resin.

  The method for incorporating a release agent into the binder resin melt is not particularly limited. As a preferred method of incorporating a release agent into the binder resin melt, (a) a method of melting the resulting mixture after mixing the solid state binder resin and the release agent, and (b) release. After the mold is heated and melted, the binder resin is added to the melted release agent and both are melted by heating; and (c) the binder resin is heated and melted and then melted An example is a method in which a release agent is added to the binder resin and both are heated and melted.

[Preparation Method of Aqueous Medium Dispersion of Colorant Fine Particles]
Hereinafter, a preferred example of a method for preparing an aqueous medium dispersion of colorant fine particles will be described. The method for preparing the fine particles of the colorant is not limited to the method described below.

  Fine particles containing a colorant are obtained by dispersing the colorant and, if necessary, a component such as a colorant dispersant in an aqueous medium containing a surfactant by a known disperser. The type of the surfactant is not particularly limited, and any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant can be used. The amount of the surfactant used is not particularly limited, but is preferably not less than the critical micelle concentration (CMC).

  Dispersers used for dispersion treatment are not particularly limited, and pressure dispersers such as ultrasonic dispersers, mechanical homogenizers, manton gourins, and pressure homogenizers, sand grinders, horizontal and vertical bead mills, and ultra apex mills. Media type dispersers such as (manufactured by Kotobuki Industries Co., Ltd.), dyno mill (manufactured by WAB Co., Ltd.), and MSC mill (manufactured by Nippon Coke Industries, Ltd.) can be used.

The volume average particle diameter (D ₅₀ ) of the fine particles of the colorant is preferably 0.05 μm or more and 0.7 μm or less.

[Method of agglomerating fine particles]
An aqueous medium dispersion of fine particles containing fine particles of a binder resin and fine particles of a release agent using the various fine particles described above, or an aqueous medium dispersion of fine particles containing a binder resin and a release agent Then, the fine particles contained in the aqueous medium dispersion of fine particles are aggregated to form fine particle aggregates to obtain an aqueous medium dispersion (A) containing the fine particle aggregates. The fine particle aggregate may further contain fine particles of a colorant as required.

  The method for aggregating the fine particles is not particularly limited as long as the object of the present invention is not impaired. A suitable method for aggregating the fine particles includes a method of adding an aggregating agent to the aqueous dispersion of fine particles.

  Examples of the flocculant include inorganic metal salts, inorganic ammonium salts, and divalent or higher metal complexes. Inorganic metal salts include metal salts such as sodium sulfate, sodium chloride, calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, and polyaluminum chloride and polyaluminum hydroxide. An inorganic metal salt polymer is mentioned. Examples of inorganic ammonium salts include ammonium sulfate, ammonium chloride, and ammonium nitrate. Further, a quaternary ammonium salt type cationic surfactant, polyethyleneimine can also be used as a flocculant.

  As the flocculant, a divalent metal salt or a monovalent metal salt is preferably used. In addition, the aggregation rate of fine particles when a monovalent metal salt is used is slower than the aggregation rate of fine particles when a divalent metal salt is used. For this reason, the aggregation speed | rate of microparticles | fine-particles can be adjusted later using a monovalent metal salt using a divalent metal salt as an aggregating agent. As described above, since the divalent metal salt and the monovalent metal salt have different fine particle aggregation rates, the combined use of these salts allows the fine particle agglomeration while controlling the particle diameter of the obtained fine particle aggregate. It is easy to make the particle size distribution of the aggregate sharp.

  The addition amount of the flocculant is not particularly limited as long as the object of the present invention is not impaired, and is preferably 0.1 mmol / g or more and 10 mmol / g or less with respect to the solid content of the fine particle dispersion. Further, the addition amount of the flocculant is preferably adjusted as appropriate according to the type and amount of the surfactant contained in the fine particle dispersion.

  The flocculant is added at a temperature not higher than the glass transition point of the binder resin after adjusting the pH of the fine particle dispersion. In particular, when the binder resin is a polyester resin, the flocculant is added after adjusting the pH of the fine particle dispersion to the alkali side, preferably pH 8 or higher. Thereby, uniform fine particle aggregation can be performed, and the particle size distribution of the fine particle aggregate can be sharpened. The flocculant may be added at one time or may be added sequentially.

  After the aggregation has progressed until the fine particle aggregate has a desired particle size, an aggregation terminator is preferably added. Examples of the aggregation terminator include sodium chloride and sodium hydroxide. In this way, an aqueous medium dispersion (A) containing fine particle aggregates can be obtained.

[Step (II): Fine particle coalescence step]
In the coalescence process of the fine particles, the fine particle aggregate obtained in the step (I) is heated in an aqueous medium to a coalescence temperature (t _u ) that is equal to or higher than the glass transition point (Tg) of the binder resin. The components contained in the fine particle aggregate are united to obtain an aqueous medium dispersion (B) containing toner particles. In the coalescence process, the shape of the fine particle aggregate gradually approaches a spherical shape by heating the fine particle aggregate. This is because the melt viscosity of the binder resin decreases due to the temperature rise, and the shape of the fine particle aggregate changes in the direction of spheroidization due to the surface tension. By controlling the temperature and time during heating, the circularity of the obtained toner particles can be controlled to a desired value.

The coalescence temperature (t _u ) for heating the fine particle aggregate in the fine particle coalescence step is equal to or higher than the glass transition point (Tg) of the binder resin, and the glass transition temperature (Tg) of the binder resin. More preferably, the temperature is 10 ° C. or more higher than the melting point (Tm) of the binder resin. By heating the fine particle aggregate to a temperature in such a range, the coalescence of the components contained in the fine particle aggregate can be favorably progressed, and a toner having a suitable circularity can be easily prepared.

[Step (III): Cleaning step]
The toner particles obtained in the step (II) are washed with water as necessary. The cleaning method is not particularly limited, and examples include the following methods. That is, toner particles are recovered as a wet cake by solid-liquid separation from a dispersion of toner particles, and the resulting wet cake is washed with water, or the toner particles in the dispersion of toner particles are precipitated to obtain a supernatant liquid. Is replaced with water, and after the replacement, the toner particles are redispersed in water. Among these, cleaning using a filter press device is preferable.

[Step (IV): Drying step]
The toner particles obtained in step (II) are dried as necessary. The method for drying the toner particles is not particularly limited. Suitable drying methods include methods using a dryer such as a spray dryer, fluidized bed dryer, vacuum freeze dryer, and vacuum dryer. Among these methods, a method using a spray dryer is more preferable because aggregation of toner particles during drying is easily suppressed. In the case of using a spray dryer, the external additive can be attached to the surface of the toner particles by spraying a dispersion of the external additive such as silica together with the dispersion of the toner particles.

[Process (V): External addition process]
The electrostatic latent image developing toner produced by the method of the present invention may be one having an external additive attached to the surface thereof as necessary. The method for attaching the external additive to the surface of the toner particles is not particularly limited. As a preferred method, a method of mixing the toner particles and the external additive by using a mixer such as a Henschel mixer or a Nauter mixer so that the external additive is not buried in the toner surface.

  According to the method of the present invention described above, when images are continuously formed over a long period of time, the storage stability and the low-temperature fixability are excellent, and the occurrence of offset at a high temperature can be suppressed. For this reason, the electrostatic latent image developing toner produced by the method of the present invention has the above-described excellent properties, and is therefore suitably used in various image forming apparatuses.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

[Examples 1-8 and Comparative Examples 1-3]
[Step (I): Fine Particle Aggregate Formation Step]
(Method for preparing aqueous dispersion of binder resin fine particles)
Using binder resins r-1 to r-4 described later, aqueous medium dispersions R-1 to R-4 of binder resin fine particles having an average particle diameter shown in Table 1 were prepared.
1000 g of the binder resin of the type shown in Table 1 was put into a heating kneading apparatus (TK Hibis Dispermix HM-3D-5 (manufactured by PRIMIX Corporation)) equipped with a temperature adjusting jacket. When charging the binder resin, the temperature of the heating kneader was adjusted to 25 ° C. The binder resin was heated to 120 ° C. while being stirred at a revolution of 20 rpm and a rotation of 48 rpm, and was melted. Thereafter, 80 g of triethanolamine (basic compound) and 80 g of an aqueous solution having a concentration of 25% by mass of sodium lauryl sulfate (surfactant, Emar 0 (manufactured by Kao Corporation)) were added to the melt, Stirring was continued at 97 rpm for 15 minutes (hereinafter, stirring at the same speed). Thereafter, 2870 g of 98 ° C. ion-exchanged water was added to the melt at a rate of 50 g / min to obtain a resin emulsion. Thereafter, the emulsion was cooled to 50 ° C. at a rate of 5 ° C./min to obtain an aqueous medium dispersion of binder resin fine particles. The solid content concentration of the resulting aqueous dispersion of the binder resin fine particles was 25% by mass. The average particle size of the resin fine particles was measured using a particle size measuring device (LA-950 (manufactured by Horiba, Ltd.)).

<Binder resin r-1>
The following polyester resin powder was used as the binder resin r-1.
Number average molecular weight (Mn): 2,600
Mass average molecular weight (Mw): 12,000
Molecular weight distribution (Mw / Mn): 4.6
Glass transition point (Tg): 52 ° C
Melting point (Tm): 90 ° C
Acid value: 20.5mgKOH / g

<Binder resin r-2>
The following polyester resin powder was used as the binder resin r-2.
Number average molecular weight (Mn): 2,400
Mass average molecular weight (Mw): 11,500
Molecular weight distribution (Mw / Mn): 4.79
Glass transition point (Tg): 47 ° C
Melting point (Tm): 90 ° C
Acid value: 22.5 mgKOH / g

<Binder resin r-3>
The following polyester resin powder was used as the binder resin r-3.
Number average molecular weight (Mn): 3,100
Mass average molecular weight (Mw): 24,000
Molecular weight distribution (Mw / Mn): 7.74
Glass transition point (Tg): 58 ° C
Melting point (Tm): 110 ° C.
Acid value: 15.5 mg KOH / g

<Binder resin r-4>
The following styrene acrylic resin powder was used as the binder resin r-4.
Number average molecular weight (Mn): 4,000
Mass average molecular weight (Mw): 17,000
Molecular weight distribution (Mw / Mn): 4.25
Glass transition point (Tg): 50 ° C
Melting point (Tm): 90 ° C

(Method for Preparing Aqueous Medium Dispersions W-1 to W-3 of Release Agent Fine Particles)
Using the release agents of the type described in Table 2, aqueous medium dispersions W-1 to W-3 of release agent fine particles having an average particle size described in Table 2 were prepared.
After mixing 200 g of the mold release agent of the type shown in Table 2, 20 g of sodium lauryl sulfate (Emal 0 (manufactured by Kao Corporation)) and 780 g of ion-exchanged water, and heating the mixture to 90 ° C., a homogenizer (Ultra Emulsification was carried out for 5 minutes using Tarax T50 (manufactured by IKA) to obtain an emulsion. Thereafter, the emulsion is put into a high-pressure homogenizer (NV-200 (manufactured by Yoshida Kikai Kogyo Co., Ltd.)) having a temperature adjusting function, and is subjected to shear emulsification at a temperature condition of 100 ° C. and a discharge pressure of 100 Pa. An aqueous medium dispersion of fine particles was obtained. The solid content concentration of the obtained aqueous medium dispersion of the release agent fine particles was 10% by mass. The particle size of the release agent fine particles was measured by the same method as the particle size of the binder resin fine particles.

(Preparation method of aqueous medium dispersion of colorant fine particles)
As a colorant, 100 g of a pigment (cyan pigment, CI Pigment Blue 15: 3 (copper phthalocyanine)), 20 g of polyoxyethylene sodium lauryl sulfate (Emar E27C (manufactured by Kao Corporation)), and 380 g of ion-exchanged water The mixture was mixed and subjected to a dispersion treatment for 2 hours using an ultra apex mill (manufactured by Kotobuki Industries Co., Ltd.) to obtain a colorant fine particle dispersion. The solid content concentration of the obtained aqueous medium dispersion of colorant fine particles was 20% by mass. The average particle diameter of the colorant fine particles contained in the colorant fine particle dispersion was 113 nm. The particle diameter of the colorant fine particles was measured by the same method as the particle diameter of the binder resin fine particles.

  In a 2 L round bottom flask made of stainless steel, 320 g of an aqueous medium dispersion of resin fine particles of the type shown in Tables 3 to 5 prepared by the above method, and separation of types and amounts shown in Tables 3 to 5 were used. An aqueous medium dispersion of mold fine particles, 25 g of an aqueous medium dispersion of pigment fine particles, and 505 g of ion-exchanged water were added. Next, while stirring the mixture in the flask at 200 rpm with a stirring blade (stirring blade No. 430 (manufactured by ASONE CORPORATION)) (hereinafter, stirring at the same speed until the end of the coalescence process), the flask The pH of the mixture was adjusted to 10 with an aqueous sodium hydroxide solution, and the mixture was stirred for 10 minutes. Thereafter, 10 g of a magnesium chloride hexahydrate aqueous solution (flocculating agent) having a concentration of 50% by mass was dropped into the flask over 5 minutes. Next, the mixture in the flask was heated at a rate of 0.2 ° C./min to start aggregation of fine particles. After stopping the temperature rise at 50 ° C., the mixture in the flask was kept at 50 ° C. for 30 minutes to advance the aggregation of the fine particles. Thereafter, 50 g of a sodium chloride aqueous solution having a concentration of 20% by mass was added to the flask all at once to stop the progress of the aggregation of the fine particles, thereby obtaining an aqueous medium dispersion of the fine particle aggregates.

[Process (II): Unification process]
100 g of an aqueous solution of sodium lauryl sulfate (Emal 0 (manufactured by Kao Corporation)) having a concentration of 5% by mass was added to the obtained aqueous medium dispersion of fine particle aggregates at once. Next, the aqueous dispersion of the fine particle aggregate was heated to 68 ° C. at a temperature rising rate of 0.2 ° C./min. After the temperature was raised to 68 ° C., the mixture was stirred at the same temperature for 1 hour to coalesce the toner components contained in the fine particle aggregate and to control the shape of the fine particle aggregate to be spherical. Thereafter, the aqueous medium dispersion of the fine particle aggregate was cooled to 25 ° C. at a rate of 10 ° C./minute, and an aqueous medium dispersion containing the shape-controlled fine particle aggregate as toner particles was obtained. The average particle diameter of the toner particles in the aqueous medium dispersion containing toner particles obtained in Example 1 was 5.5 μm, and the circularity was 0.980. The particle diameter of the toner particles is measured by the same method as the particle diameter of the binder resin fine particles, and the circularity of the toner particles is measured using a flow type particle image analyzer (FPIA-3000 (manufactured by Sysmex Corporation)). Measured.

[Step (III): Cleaning step]
Using a Buchner funnel, the toner wet cake was filtered from the aqueous medium dispersion containing the toner particles. The toner wet cake was again dispersed in ion exchange water to wash the toner. The same washing with the ion exchange water of the toner was repeated 6 times.

[Step (IV): Drying step]
A slurry was prepared by dispersing a wet cake of toner in an aqueous ethanol solution having a concentration of 50% by mass. The obtained slurry was supplied to a continuous surface reformer (Coat Mizer (Freund Sangyo Co., Ltd.)) to dry the toner particles in the slurry, thereby obtaining a toner. Drying conditions by the coatizer were a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min.

[Process (V): External addition process]
100 parts by mass of toner and 2 parts by mass of an external additive (RA200H (manufactured by Nippon Aerosil Co., Ltd.)) were mixed using a Henschel 10B (manufactured by Nippon Coke Industry Co., Ltd.) at a stirring speed of 3,000 rpm for 5 minutes. An external additive was adhered.

≪Evaluation 1≫
The toners obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were evaluated for heat resistant storage stability and release agent content according to the following methods. Tables 6 to 8 show the evaluation results of the heat resistant storage stability and the release agent content of the toners of Examples 1 to 8 and Comparative Examples 1 to 3, respectively.

<Method for evaluating heat-resistant storage stability>
3 g of toner is weighed into a 20 ml capacity plastic container, left in a thermostat set at 50 ° C. for 3 hours, and then left in an environment of 25 ° C. and 65% RH for 30 minutes to evaluate heat resistant storage stability. No toner was obtained. Thereafter, sieves having openings of 105 μm, 63 μm, and 45 μm are used in an overlapping manner in order from the smallest openings, and a toner for heat-resistant storage stability evaluation is placed on the sieve having openings of 105 μm, and a powder tester (Hosokawa Micron Corporation) is used. The product was screened for 30 seconds on the vibration scale 5. After sieving, the mass of the toner remaining on the sieve having an opening of 105 μm (T ₁ (g)), the mass of the toner remaining on the 63 μm sieve (T ₂ (g)), and the toner remaining on the 45 μm sieve Each mass (T ₃ (g)) was weighed, and the degree of aggregation of the toner was measured by the following formula.
_{T 1/3 × 100 = C} 1
_{T 2/3 × 100 × 3} /5 = C 2
_{T 3/3 × 100 × 1} /5 = C 3
Toner cohesion (%) = C ₁ + C ₂ + C ₃
Evaluation of heat-resistant storage stability was evaluated according to the following criteria, and evaluations of “◯” and “Δ” were accepted, and evaluation of “x” was rejected.
○: The degree of aggregation of the toner is less than 5%.
Δ: The degree of aggregation of the toner is 5% or more and less than 15%.
X: The degree of aggregation of the toner is 15% or more.

<Releasing agent content>
A differential scanning calorimeter (DSC-6200 (manufactured by Seiko Instruments Inc.)) was used as a measuring device, and the endothermic curve of the toner was measured in accordance with ASTM D3418-8. 10 mg of a measurement sample was put in an aluminum pan, and an empty aluminum pan was used as a reference. The release agent content (% by mass) was determined from the endothermic curve of the toner obtained by measurement at a measurement temperature range of 40 to 200 ° C. and a temperature increase rate of 10 ° C./min at normal temperature and humidity.

≪Evaluation 2≫
In addition, using the toners obtained in Examples 1 to 8 and Comparative Examples 1 to 3, the initial toner charge amount, image density, and fog density, and toner charge amount after continuous image formation were performed according to the following method. The image density and the fog density were evaluated. A color printer (FS-C5300DN (manufactured by Kyocera Document Solutions Inc.)) was used as an evaluation machine. Plain paper (C2 (manufactured by Fuji Xerox Co., Ltd.)) was used as the recording medium. The evaluation was performed using a two-component developer prepared according to the following method. The evaluation results of the toners of Examples 1 to 8 and Comparative Examples 1 to 3 are shown in Tables 6 to 8.

[Preparation Example 1]
(Preparation of carrier)
A developer carrier (FS-C5300DN carrier) and a toner of 8% by mass based on the mass of the carrier using a rocking mixer (RM-10 (manufactured by Aichi Electric Co., Ltd.)) under normal temperature and normal humidity conditions And mixing at 30 rpm for 30 minutes to obtain a two-component developer.

<Image density>
With an evaluator, an image evaluation pattern was formed on the recording medium in an environment of 28 ° C. and 80% RH to obtain an initial image. Thereafter, after continuous printing of 10,000 sheets at a printing rate of 4% in an environment of 28 ° C. and 80% RH, an image evaluation pattern is formed on the recording medium to form an image after continuous image formation (hereinafter referred to as “image after durability evaluation”). Obtained). The image density of the solid image in the image evaluation pattern of the initial image and the post-durability evaluation image was measured with a reflection densitometer (RD914 (manufactured by Gretag Macbeth)). The image density was evaluated according to the following criteria. ○ and Δ were accepted, and x was rejected.
○: 1.40 or more.
Δ: 1.20 or more and less than 1.40.
X: Less than 1.20

<Fog density>
The image density of the non-image portion of the recording medium on which the initial image and the post-durability evaluation image obtained in the image density evaluation were measured with a reflection densitometer (RD914 (manufactured by Gretag Macbeth)). The value obtained by subtracting the image density of the blank paper before image output from the image density of the non-image area was defined as the fog density. The fog density was evaluated according to the following criteria. ○ and Δ were accepted, and x was rejected.
○: 0.003 or less.
Δ: More than 0.003 and 0.007 or less.
X: Over 0.007.

<Evaluation of toner charge amount>
The toner charge amount of the two-component developer prepared in Preparation Example 1 was measured in an environment of 28 ° C. and 80% RH. Next, the charge amount of the toner collected from the surface of the developing sleeve of the developing device of the color printer after continuous image formation was measured. The charge amount was measured using a QM meter (MODEL 210HS-1 (manufactured by TREK)).

≪Evaluation 3≫
Further, using the toners obtained in Examples 1 to 8 and Comparative Examples 1 to 3, low temperature fixability and high temperature offset resistance were evaluated according to the following methods. As an evaluation machine, a color multifunction machine (TASKalfa 550ci (manufactured by Kyocera Document Solutions Co., Ltd.)) with the fixing device removed is used. Further, a fixing tester in which an external driving device and a fixing temperature control device are installed in the fixing device removed from the evaluation machine was used. Plain paper (C2 (manufactured by Fuji Xerox Co., Ltd.)) was used as the recording medium. The evaluation was performed using a two-component developer prepared according to the above method. The evaluation results of the toners of Examples 1 to 8 and Comparative Examples 1 to 3 are shown in Tables 6 to 8.

<Low temperature fixability>
An unfixed solid image having a size of 2 cm × 3 cm and an applied toner amount of 1.8 g / cm ² was formed on a recording medium (C2 (manufactured by Fuji Xerox Co., Ltd.)) using an evaluation machine. The obtained unfixed image was fixed by a fixing tester set at a predetermined temperature under the condition of a linear speed of 275 mm / sec. The image after fixing was folded in half so that the image portion was inside, and the bottom surface was rubbed 5 times on the crease with a 1 kg weight covered with a fabric. Next, the paper was spread and the image portion was rubbed 5 times with a weight. The toner peeling at the bent portion was determined to be acceptable within 1 mm, and over 1 mm was determined to be unacceptable. Evaluation was performed by increasing the fixing temperature from 90 ° C. in increments of 5 ° C., and the lowest fixing temperature at which the toner peeling was determined to be acceptable was set as the minimum fixing temperature, and the low temperature fixing property was evaluated according to the following evaluation criteria. ○ and Δ were accepted, and x was rejected.
○: The minimum fixing temperature is less than 110 ° C.
(Triangle | delta): The minimum fixing temperature is 110 degreeC or more and less than 125 degreeC.
X: The minimum fixing temperature is 125 ° C. or higher.

<High temperature offset resistance>
An evaluation image (solid image) formed under the same conditions as in the low-temperature fixability evaluation, except that the same evaluation machine, fixing tester and recording medium as in the low-temperature fixability evaluation were used and the linear velocity was 49 mm / sec. ) Was evaluated.
The fixing temperature was increased from 110 ° C. in increments of 5 ° C., and the highest temperature at which no offset occurred was defined as the high temperature offset non-occurrence temperature, and the high temperature offset resistance was evaluated according to the following evaluation criteria. ○ and Δ were accepted, and x was rejected.
○: High temperature offset occurrence temperature is 140 ° C. or higher.
(Triangle | delta): High temperature offset non-occurrence | production temperature is 115 degreeC or more and less than 140 degreeC.
X: High temperature offset non-occurrence | production temperature is less than 115 degreeC.

According to Examples 1 to 8, for the electrostatic latent image developing toner obtained by aggregating and coalescing the fine particles of the toner material by a predetermined method, (II) the coalescence temperature in the coalescence process at _{(t u),} and the viscosity of the binder resin (pr _u), and the viscosity of the release agent (ρW _u), but satisfies a predetermined relation, and, the binder resin at the melting point (Tm), sintered viscosity of Chakujushi (pr _m), and the viscosity of the release agent (ρW _m), but if a predetermined relationship, storage stability, and excellent low-temperature fixability, can suppress the occurrence of offset at high temperatures I understand. In such a case, when images are continuously formed over a long period of time, it is possible to prevent the image density from being lower than a desired value and the occurrence of fogging in the formed image, and the fixing roller and the image are formed. It can also be seen that it is excellent in releasability from the recording medium.

Comparative Example 1, and according to 2, and (II) at coalescence temperature _{(t u)} in coalescence step, the viscosity of the binder resin (pr _u), the viscosity of the release agent (ρW _u) However, when ρR _u / ρW _u > 1, when forming images continuously over a long period of time, it is difficult to prevent fogging from occurring in the formed image, and a toner having poor storage stability is obtained. I understand. This is presumably because the fine particles of the release agent incorporated into the fine particle aggregates easily fall off from the fine particle aggregates in the coalescence process.

According to Comparative Example 3, in the melting point (Tm) of the binder resin, the viscosity of the binder resin (pr _m), viscosity of the release agent (ρW _m) and it is the ρR _m / _{ρW m} <5 In this case, it is difficult to suppress the occurrence of offset at a high temperature. When this is the binder resin melting point (Tm), relative to the viscosity of the binder resin (pr _u), the viscosity of the release agent (ρW _u) is not sufficiently low, to fix the toner to the recording medium In addition, it is presumed that the effect of the release agent in the toner is hardly exhibited.

Claims (3)

The following steps (I) and (II):
(I) The fine particles of the binder resin and the fine particles of the release agent are aggregated in an aqueous medium to form a fine particle aggregate, or the fine particles containing the binder resin and the release agent are dispersed in the aqueous medium. A fine particle aggregate forming step of aggregating to form a fine particle aggregate to obtain an aqueous medium dispersion (A) containing the fine particle aggregate; and
(II) The fine particle aggregate is heated in an aqueous medium to a coalescence temperature (t _u ) that is equal to or higher than the glass transition point (Tg) of the binder resin to combine the components contained in the fine particle aggregate. Unitizing step to obtain an aqueous medium dispersion (B) containing toner particles,
Including
Wherein at coalescence temperature _{(t u),} the viscosity of the binder resin (pr _u), the viscosity of the release agent (ρW _u), but satisfy the relationship ρR _u / _{ρW u} ≦ 1,
At the melting point (Tm) of the said binder resin, and a viscosity (pr _m) of the binder resin, the viscosity of the releasing agent (ρW _m), but satisfy the relationship ρR _m / _{ρW m} ≧ 5,
The binder resin is a polyester resin;
In the fine particle aggregate forming step, an aqueous medium dispersion containing fine particles of the binder resin, fine particles of the release agent, or an aqueous medium dispersion containing fine particles containing the binder resin and a release agent. With the pH adjusted to 8 or more, the flocculant is added,
A method for producing a toner for developing an electrostatic latent image, wherein the content of the releasing agent is 14.5 % by mass or more and 27.8 % by mass or less based on the mass of the toner for developing an electrostatic latent image.   The method for producing a toner for developing an electrostatic latent image according to claim 1, wherein the binder resin has a glass transition point (Tg) of 50 ° C. or more and 65 ° C. or less.   The method for producing a toner for developing an electrostatic latent image according to claim 1, wherein the binder resin has a melting point (Tm) of 80 ° C. or more and 100 ° C. or less.

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