JP2014199306A - Manufacturing method of toner for electrostatic latent image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a toner for electrostatic latent image development with which a toner for electrostatic latent image development can be manufactured including a desired amount of mold release agent, in attaching positively-charged resin fine particles onto the surface of toner core particles including a negatively-charged binder resin to form a toner of a core-shell structure, by suppressing drop-off of mold release agent fine particles from the toner core particles.SOLUTION: A manufacturing method of a toner for electrostatic latent image development includes: mixing an aqueous medium dispersion (X) including negatively-charged toner core particles containing a binder resin and mold release agent and an aqueous medium dispersion (Y) including positively-charged resin fine particles; and stirring subsequently the mixture to form a shell layer comprising the resin fine particles on the surface of the toner core particles to obtain a toner for electrostatic latent image development, in which the toner core particles are obtained by aggregating binder resin fine particles and mold release agent fine particles having a predetermined particle diameter in an aqueous medium.

Description

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

  Concerning toner, toner core particles using low melting binder resin and low melting point release agent for the purpose of obtaining good fixability in a wide range of low temperatures and improving storage stability at high temperatures. A core-shell structure toner is used in which the toner is coated with a resin having a Tg higher than the glass transition point (Tg) of the binder resin of the toner core particles.

  In addition, since such a toner is easy to obtain a toner excellent in color developability and low-temperature fixability, a negatively charged binder having a negatively charged functional group such as a polyester resin, a styrene-acrylic resin, or an acrylic resin. It is often prepared using a resin.

As a method for producing such a core-shell toner using a negatively chargeable binder resin, mechanical shearing force is applied in an aqueous medium to a granular mixture containing the binder resin and a colorant. A step of preparing a dispersion containing fine particles and a step of aggregating the fine particles in the dispersion to form aggregated particles by adjusting the pH of the dispersion, and the pH of the dispersion is 7 When a toner is produced by a method in which the volume average particle diameter of the fine particles in the dispersion liquid is 2 μm or less and the pH of the dispersion liquid is 3.0 to 6.9 when the zeta potential of the fine particles is −30 mV In addition, a method has been proposed in which a dispersion liquid containing additional fine particles containing a resin is added to a dispersion liquid of aggregated particles in the step of forming aggregated particles (see Patent Document 1).
When such a method is used, a shell layer composed of fine particles containing the added resin can be formed on the surface of the aggregated particles, and a toner having a core-shell structure can be obtained.

JP 2011-128574 A

  When obtaining a positively chargeable toner having desired charging performance using a negatively chargeable binder resin, in order to make it less susceptible to the negative chargeability of the binder resin, positively chargeable resin fine particles are used. It is effective to form a shell layer on the surface of the toner core particles. However, when a toner having a core-shell structure is produced using positively chargeable resin fine particles by the method described in Patent Document 1, after adding positively chargeable resin fine particles to a dispersion of aggregated particles (toner core particles), The positively chargeable resin fine particles and the release agent fine particles in the aggregated particles are aggregated, so that the release agent fine particles easily fall off the aggregated particles.

  If the release agent fine particles fall off from the aggregated particles, a toner containing a desired amount of the release agent may not be obtained. When an image is formed using toner having a release agent content less than the desired amount, image defects due to poor fixing of the toner tend to occur in the formed image.

  The present invention has been made in view of the above circumstances, and forms a core-shell structure toner by attaching positively chargeable resin fine particles to the surface of toner core particles containing a negatively chargeable binder resin. In the electrostatic latent image developing toner, it is possible to produce a toner for developing an electrostatic latent image containing a desired amount of the release agent by suppressing the dropping of the release agent fine particles from the toner core particles. An object is to provide a manufacturing method.

  The present inventors have prepared an aqueous medium dispersion (X) containing negatively chargeable toner core particles containing a binder resin and a release agent, and an aqueous medium dispersion (Y) containing positively charged resin fine particles. Is mixed, and then the mixture is stirred to form a shell layer made of resin fine particles on the surface of the toner core particles to obtain an electrostatic latent image developing toner. The present inventors have found that the above problems can be solved by aggregating binder resin fine particles and release agent fine particles having a predetermined particle diameter in an aqueous medium to form toner core particles, and have completed the present invention. Specifically, the present invention provides the following.

In the present invention, an aqueous medium dispersion (X) containing negatively chargeable toner core particles containing a binder resin and a release agent is mixed with an aqueous medium dispersion (Y) containing positively charged resin fine particles. Then, the mixed liquid is stirred to form a shell layer made of resin fine particles on the surface of the toner core particles to obtain a toner for developing an electrostatic latent image.
The toner core particles are obtained by aggregating binder resin fine particles containing the binder resin and release agent fine particles containing the release agent in an aqueous medium,
The present invention relates to a method for producing a toner for developing an electrostatic latent image, wherein the release agent fine particles have a particle size of 280 nm to 550 nm.

  According to the present invention, a release agent from a toner core particle when a toner having a core-shell structure is formed by attaching positively chargeable resin fine particles to the surface of a toner core particle containing a negatively chargeable binder resin. By suppressing the omission of the fine particles, it is possible to provide a method for producing a toner for developing an electrostatic latent image, which can produce a toner for developing an electrostatic latent image containing a desired amount of a release agent.

It is a figure explaining the measuring method of the softening point using the 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.

  In the present invention, the electrostatic latent image developing toner (hereinafter also referred to as toner) includes an aqueous medium dispersion (X) containing negatively chargeable toner core particles containing a binder resin and a release agent, and a positively chargeable property. After mixing with the aqueous medium dispersion (Y) containing resin fine particles, the mixture is stirred to form a shell layer made of resin fine particles on the surface of the toner core particles. The toner core particles are obtained by aggregating binder resin fine particles containing a binder resin and release agent fine particles containing a release agent in an aqueous medium. Hereinafter, a toner material used for manufacturing the electrostatic latent image developing toner and a method of manufacturing the electrostatic latent image developing toner will be described in order.

≪Toner material≫
In the method for producing a toner of the present invention, the surface of the negatively chargeable toner core particles containing a binder resin, a release agent, and, if necessary, an optional component such as a colorant, a charge control agent, and magnetic powder is applied. Then, it is coated with a shell layer made of positively chargeable resin fine particles. The toner obtained by using the production method of the present invention may further have an external additive attached to the surface thereof. The toner obtained using the production method of the present invention can be mixed with a carrier and used as a two-component developer, if necessary. Hereinafter, the toner core particles, the shell layer, and the external additive, and the carrier used when the toner obtained by using the production method of the present invention is used as a two-component developer will be described in order.

[Toner core particles]
In the toner manufacturing method of the present invention, negatively chargeable toner core particles and positively chargeable resin fine particles are used. When negatively charged toner core particles are dispersed in water, the polarity of the zeta potential of the toner core particles becomes negative. When positively charged resin fine particles are dispersed in water, the polarity of the zeta potential of the resin fine particles becomes positive.

  The polarity of the zeta potential of the toner core particles is determined by the material constituting the toner core particles. In order to make the polarity of the zeta potential of the toner core particles in water negative, a material having a negatively charged functional group such as a carboxyl group or a sulfonic acid group may be added to the toner core particles. As a material having a negatively chargeable functional group, a binder resin described later is usually used. The zeta potential of the dispersion can be measured using a measuring device such as an ultrasonic particle size distribution / zeta potential measuring device (DT-1200 (manufactured by Dispersion Technology)).

  The toner core particles may contain an optional component such as a colorant, a charge control agent, and magnetic powder, if necessary, in addition to the binder resin and the release agent. Hereinafter, regarding the components contained in the toner core particles, the binder resin, the release agent, the colorant, the charge control agent, and the magnetic powder will be described in order.

[Binder resin]
The type of the binder resin is not particularly limited as long as negatively chargeable toner core particles can be prepared. Specific examples of the binder resin include styrene resin, (meth) acrylic resin, styrene- (meth) acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin. And thermoplastic resins such as polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. As the binder resin, a negatively chargeable toner core particle can be easily prepared. Therefore, a resin having an acidic group such as a carboxyl group or a sulfonic acid group in a part of the molecular chain (terminal, side chain) is used. preferable. Examples of the resin having such an acidic group include (meth) acrylic resins, styrene- (meth) acrylic resins, and polyester resins. Among these, a polyester resin is more preferable because it can be favorably fixed at a low temperature and a toner excellent in color developability can be easily prepared.

  When the binder resin is a resin having an acidic group, the acid value of the binder resin is preferably 5 mgKOH / g or more and 40 mgKOH / g or less. If the acid value is too low, when an aqueous medium dispersion containing toner core particles is prepared using the aggregation method described later, the aggregation of the fine particles may not proceed well depending on the formulation during aggregation. On the other hand, if the acid value is too high, various performances of the toner produced using such a resin may be impaired under the influence of humidity under high humidity conditions.

  Hereinafter, (meth) acrylic resin, styrene- (meth) acrylic resin, and polyester resin, which are preferable binder resins, will be described in order.

<(Meth) acrylic resin>
The (meth) acrylic resin is a resin obtained by copolymerizing at least a monomer containing a (meth) acrylic monomer. The content of the unit derived from the (meth) acrylic monomer contained in the (meth) acrylic resin is preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, and 100% by mass. % Is most preferred.

  (Meth) acrylic monomers used for the preparation of (meth) acrylic resins include (meth) acrylic acid; alkyls such as methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate ( (Meth) acrylates; such as (meth) acrylamide, N-alkyl (meth) acrylamide, N-aryl (meth) acrylamide, N, N-dialkyl (meth) acrylamide, and N, N-diaryl (meth) acrylamide (meta) ) Acrylamide compounds. The (meth) acrylic resin preferably contains a carboxyl group contained in a unit derived from (meth) acrylic acid as an acidic group. In this case, the acid value of the (meth) acrylic resin can be adjusted by increasing or decreasing the amount of (meth) acrylic acid used when preparing the (meth) acrylic resin.

  When the (meth) acrylic resin is a resin obtained by copolymerizing a monomer other than the (meth) acrylic monomer and the (meth) acrylic monomer, the other monomers include ethylene, propylene, butene-1, and pentene. Olefins such as -1, hexene-1, heptene-1 and octene-1; allyl esters such as allyl acetate, allyl benzoate, allyl acetoacetate and allyl lactate; hexyl vinyl ether, octyl vinyl ether, ethyl hexyl vinyl ether , Methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether, 2-ethylbutyl vinyl ether, dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether, benzyl vinyl ether, vinyl phenyl ether, Vinyl ethers such as nyltolyl ether, vinyl chlorophenyl ether, vinyl-2,4-dichlorophenyl ether, and vinyl naphthyl ether; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl diethyl acetate, Examples include vinyl esters such as vinyl chloroacetate, vinyl methoxyacetate, vinyl butoxyacetate, vinyl phenylacetate, vinyl acetoacetate, vinyl lactate, vinyl benzoate, vinyl salicylate, vinyl chlorobenzoate, and vinyl naphthoate.

<Styrene- (meth) acrylic resin>
The styrene- (meth) acrylic resin is a resin obtained by copolymerizing at least a monomer containing a styrene monomer and a (meth) acrylic monomer. The total content of units derived from styrene monomers and units derived from (meth) acrylic monomers contained in the styrene- (meth) acrylic resin is preferably 70% by mass or more, more preferably 80% by mass or more. More preferably, 90% by mass or more is particularly preferable, and 100% by mass is most preferable.

  Styrene monomers used for the preparation of styrene- (meth) acrylic resins include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2, 4-dimethylstyrene, pn-butylstyrene, p-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, and p-chlorostyrene.

  The (meth) acrylic monomer used for the preparation of the styrene- (meth) acrylic resin is the same as the (meth) acrylic monomer used for the preparation of the (meth) acrylic resin.

  Moreover, it is preferable that styrene- (meth) acrylic-type resin contains the carboxyl group contained in the unit derived from (meth) acrylic acid as an acidic group. In this case, the acid value of the styrene- (meth) acrylic resin can be adjusted by increasing or decreasing the amount of (meth) acrylic acid used when preparing the styrene- (meth) acrylic resin.

  When the styrene- (meth) acrylic resin is a resin obtained by copolymerizing a styrene monomer, a (meth) acrylic monomer, a styrene monomer, and another monomer other than the (meth) acrylic monomer, Examples of the monomer are the same as other monomers other than the (meth) acrylic monomer in the (meth) acrylic resin.

<Polyester resin>
As the polyester resin, those obtained by condensation polymerization or cocondensation polymerization of a divalent or trivalent or higher alcohol component and a divalent or trivalent or higher 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, 1,10-decanedicarboxylic 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 Divalent carboxylic acids such as alkyl or alkenyl succinic acids such as dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid ), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalene Recarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, Trivalent or higher carboxylic acids such as 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid. It is done. 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.

  The acid value of the polyester resin can be adjusted by adjusting the balance of the functional groups of the hydroxyl group of the alcohol component used for the synthesis of the polyester resin and the carboxyl group of the carboxylic acid component.

  The glass transition point (Tg) of the binder resin is preferably 30 ° C. or higher and 60 ° C. or lower. When the Tg of the binder resin is too low, the toner particles are likely to be fused when the toner is washed and dried. When the Tg of the binder resin is too high, it is necessary to increase the temperature at which the fine particles containing the binder resin are aggregated, and the energy required for aggregation is increased.

(Method for measuring glass transition point (Tg))
The glass transition point of the binder resin can be determined using a measuring method based on JIS K7121. More specifically, it can be determined 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, an empty aluminum pan is used as a reference, a measurement temperature range is 25 ° C. or more and 200 ° C. or less, a temperature rising rate is 10 ° C./min, and the measurement ambient environment is measured at normal temperature and humidity The glass transition point of the binder resin can be determined from the endothermic curve of the obtained binder resin.

  The softening point of the binder resin is preferably 80 ° C. or higher and 150 ° C. or lower, and more preferably 90 ° C. or higher and 140 ° C. or lower. If the softening point of the binder resin is too high, the toner may be difficult to fix on the recording medium at low temperatures. If the softening point of the binder resin is too low, resin fine particles are likely to be buried in the toner core particles in the (II) shell layer forming step of the toner production method described later. If the resin fine particles are easily embedded in the toner core particles, the toner may agglomerate during storage at a high temperature, and the heat resistant storage stability of the toner may be impaired. The softening point of the binder resin can be measured according to the following method.

(Softening point measurement method)
The softening point of the resin (toner) is measured using an elevated flow tester (for example, CFT-500D (manufactured by Shimadzu Corporation)). Using 1.5 g of toner as a sample, using a die having a height of 1.0 mm and a diameter of 1.0 mm, a heating rate of 4 ° C./min, a preheating time of 300 seconds, a load of 5 kg, a measurement temperature range of 60 ° C. to 200 ° C. Measurement is performed under the following conditions. The softening point is read from an S-shaped curve relating to temperature (° C.) and stroke (mm) obtained by the flow tester measurement.

How to read the softening 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. The temperature at which the stroke value is (S ₁ + S ₂ ) / 2 on the S-curve is defined as the softening point of the measurement sample.

  The number average molecular weight (Mn) of the binder resin is preferably 2,000 or more and 20,000 or less. The molecular weight distribution (Mw / Mn) represented by the ratio between the number average molecular weight (Mn) and the mass average molecular weight (Mw) is preferably 2 or more and 60 or less, and more preferably 2 or more and 10 or less. By setting the molecular weight distribution of the resin in such a range, the particle size distribution of the aggregated particles tends to be sharper. The number average molecular weight (Mn) and the mass average molecular weight (Mw) of the resin can be measured using gel permeation chromatography.

〔Release agent〕
The release agent is used for the purpose of improving the fixing property of the toner to the paper and the anti-offset property. 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 petrolactam; waxes based on fatty acid esters such as montanate ester waxes and castor waxes; 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; Hydroxyl obtained in And methyl ester compounds having the like.

  The amount of the release agent used is preferably 0.1 part by mass or more and 30 parts by mass or less, and more preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

[Colorant]
A well-known thing can be used for a coloring agent. Specific examples of suitable colorants include the following colorants.

  Examples of yellow colorants include colorants such as condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds. Specifically, C.I. I. Pigment Yellow 3, 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, 194; Nephthol Yellow S, Hansa Yellow G, and C.I. I. Coloring agents such as vat yellow can be mentioned.

  Examples of magenta colorants include colorants such as 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, Colorants such as 184, 185, 202, 206, 220, 221 and 254 may be mentioned.

  Examples of cyan colorants include colorants such as 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; phthalocyanine blue, C.I. I. Bat Blue, and C.I. I. Coloring agents such as Acid Blue are listed.

  The amount of the colorant used is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

(Charge control agent)
The toner core particles may contain a charge control agent as required. The charge control agent is used in such a range that the polarity of the zeta potential of the toner core particles becomes negative when the toner core particles are dispersed in water. 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.

  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 quicker charge rising 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 A styrene resin having a carboxylate, an acrylic resin having a carboxylate, a styrene-acrylic resin having a carboxylate, a polyester resin having a carboxylate, a styrene resin having a carboxyl group, an acrylic resin having a carboxyl group, Examples thereof include styrene-acrylic resins having a carboxyl group and polyester resins having a carboxyl group. The molecular weight of these resins may be an oligomer or a polymer.

  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 use amount of the positively or negatively chargeable charge control agent is preferably 1.5 parts by mass or more and 15 parts by mass or less, and 2.0 parts by mass or more and 8.0 parts by mass when the total amount of the toner is 100 parts by mass. Is more preferably 3.0 parts by mass or more and 7.0 parts by mass or less.

[Magnetic powder]
Suitable types of magnetic powder 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 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 resin.

  The amount of magnetic powder used is preferably 35 parts by weight or more and 60 parts by weight or less, more preferably 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. preferable. When toner is used as a two-component developer, the amount of magnetic powder used is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less when the total amount of toner is 100 parts by mass.

[Shell layer]
In the toner obtained using the production method of the present invention, a shell layer made of positively chargeable resin fine particles is formed on the surface of toner core particles. As described above, when positively charged resin fine particles are dispersed in water, the polarity of the zeta potential of the resin fine particles becomes positive. The polarity of the zeta potential of the resin fine particles is determined by the material constituting the resin fine particles. In order to make the zeta potential polarity of the resin fine particles in water positive, the resin fine particles may contain a material having a positively charged functional group such as a quaternary ammonium salt functional group. The positively chargeable resin fine particles can be prepared by making fine particles of a resin composition containing a positively chargeable functional group or a positively chargeable charge control agent. As the resin constituting the resin fine particles, a monomer polymer having an unsaturated bond is preferable because fine particles having a uniform particle diameter can be easily prepared and a shell layer having excellent strength can be easily formed.

  As a material constituting the resin fine particles, a resin having a positively chargeable functional group is preferable, and a resin that is a polymer of a monomer having a positively chargeable functional group and having an unsaturated bond is more preferable. As a suitable example of a resin that is a polymer of a monomer having a positively chargeable functional group and an unsaturated bond, the quaternary ammonium salt described above as a resin that can be used as a positively chargeable charge control agent is used. Styrenic resin having, acryl resin having quaternary ammonium salt, styrene-acrylic resin having quaternary ammonium salt, polyester resin having quaternary ammonium salt. Among these resins, from the viewpoint of the strength of the shell layer, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, and a styrene-acrylic resin having a quaternary ammonium salt are preferable.

  The glass transition point (Tg) of the resin constituting the resin fine particles is preferably 45 ° C. or higher and 75 ° C. or lower, more preferably 50 ° C. or higher and 70 ° C. or lower, and particularly preferably 55 ° C. or higher and 65 ° C. or lower. If the Tg of the resin constituting the resin fine particles is too low, toner particles may aggregate in a high temperature and high humidity environment. If the Tg of the resin constituting the resin fine particles is too high, it may be difficult to fix the toner satisfactorily at a low temperature. The glass transition point of the resin constituting the resin fine particles can be measured by the same method as the method for measuring the glass transition point of the binder resin.

  The number average molecular weight (Mn) of the resin constituting the resin fine particles is preferably 10,000 or more and 100,000 or less, and more preferably 10,000 or more and 40,000 or less. 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 from 1 to 5, and more preferably from 1 to 3. The number average molecular weight (Mn) and the mass average molecular weight (Mw) of the resin constituting the resin fine particles can be measured using gel permeation chromatography.

  The mass of the shell layer is preferably 5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the toner core particles.

[External additive]
The toner obtained using the production method of the present invention may have an external additive attached to the surface thereof as necessary. In the specification and claims of the present application, the particles before being treated with the external additive may be referred to as toner base particles.

  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.

  The particle diameter of the external additive is preferably 0.01 μm or more and 1.0 μm or less. The amount of the external additive used is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 2 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the toner base particles.

[Career]
The toner obtained using the production 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 include those in which a carrier core material is coated with a resin. Specific examples of carrier core materials include iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, and cobalt particles, and these materials and metals such as manganese, zinc, and aluminum. Alloy particles, iron-nickel alloy, iron-cobalt alloy particles, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, titanium Disperse the magnetic particles in ceramic particles such as lead oxide, lead zirconate and lithium niobate, particles of high dielectric constant materials such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate and Rochelle salt, and resin. Resin carriers.

  Specific examples of the resin for coating the carrier core material include (meth) acrylic polymers, styrene polymers, styrene- (meth) acrylic copolymers, olefin polymers (polyethylene, chlorinated polyethylene, polypropylene). ), 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, and amino resin. These resins can be used in combination of two or more.

  The particle diameter of the carrier is a particle diameter measured using an electron microscope, 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 obtained using the production 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 with respect to the mass of the two-component developer. The content is preferably 15% by mass or less.

<Method for producing toner for developing electrostatic latent image>
In the method for producing a toner for developing an electrostatic latent image of the present invention,
After mixing an aqueous medium dispersion (X) containing negatively chargeable toner core particles containing a binder resin and a release agent and an aqueous medium dispersion (Y) containing positively charged resin fine particles, mixing The liquid is stirred to form a shell layer made of resin fine particles on the surface of the toner core particles.

More specifically, the method for producing a toner for developing an electrostatic latent image of the present invention includes the following steps (I) and (II):
(I) An aqueous medium dispersion (X) containing negatively chargeable toner core particles containing a binder resin and a release agent, and an aqueous medium dispersion (Y) containing positively charged resin fine particles are mixed. Obtaining a mixed liquid containing toner core particles and resin fine particles, and
(II) a shell layer forming step of stirring a mixed liquid containing toner core particles and resin fine particles to form a shell layer made of resin fine particles on the surface of the toner core particles;
including.

The method for producing a toner for developing an electrostatic latent image of the present invention may include the following steps (III) to (V) in addition to the steps (I) and (II).
(III) A cleaning step of cleaning the toner particles or toner base particles.
(IV) A drying step of drying the washed toner particles or toner mother particles.
(V) An external addition step of attaching an external additive to the surface of the toner base particles.
Hereinafter, steps (I) to (V) will be described.

[(I) Mixing step]
In step (I), an aqueous medium dispersion (X) containing negatively chargeable toner core particles and an aqueous medium dispersion (Y) containing positively chargeable resin fine particles are mixed to obtain toner core particles and resin fine particles. A liquid mixture containing is obtained. Hereinafter, a method for preparing an aqueous medium dispersion (X) containing toner core particles and a method for preparing an aqueous medium dispersion (Y) containing resin fine particles will be described.

[Preparation of aqueous medium dispersion (X)]
In the production method of the present invention, the toner core particles contained in the aqueous medium dispersion (X) are agglomerated by aggregating the binder resin fine particles containing the binder resin and the release agent fine particles containing the release agent in the aqueous medium. Obtained using the method. A method for producing an aqueous medium dispersion (X) containing toner core particles using an agglomeration method includes the following steps (i) and (ii):
(I) an aggregation step in which the binder resin fine particles containing the binder resin and the release agent fine particles containing the release agent are aggregated in an aqueous medium to form a fine particle aggregate; and (ii) the fine particle aggregation. A coalescence process in which the components contained in the aggregate are coalesced in an aqueous medium to form toner core particles;
Is preferably included.
Hereinafter, (i) the aggregation process and (ii) the coalescence process will be described.

((I) Aggregation step)
In the aggregation process, binder resin fine particles containing a binder resin and release agent fine particles containing a release agent are used. (I) In the aggregation step, fine particles other than the binder resin fine particles and the release agent fine particles may be contained in the aqueous medium when forming the fine particle aggregates. Examples of the fine particles other than the binder resin fine particles and the release agent fine particles include colorant fine particles containing a colorant. Hereinafter, the method for preparing the binder resin fine particles, the method for preparing the release agent fine particles, and the method for preparing the colorant fine particles will be described in order. The fine particles containing components different from the fine particles described here can be prepared by appropriately selecting the method for producing these fine particles.

Preparation of Fine Particles Containing Binder Resin A resin composition containing the binder resin or the binder resin and optional components that may be contained in the toner core particles is roughly pulverized using a pulverizer such as a turbo mill. The coarsely pulverized product is heated to a temperature 10 ° C. higher than the softening point of the binder resin measured by a flow tester (at a temperature up to about 200 ° C.) in a state dispersed in an aqueous medium such as ion exchange water. To do. Dispersion of aqueous binder resin containing fine particles including binder resin by applying high shearing force to the heated binder resin dispersion using a high-speed shearing emulsifier such as Claremix (M Technique Co., Ltd.) A liquid is obtained.

The volume average particle diameter (D ₅₀ ) of the fine particles containing the binder resin is preferably 1 μm or less, and more preferably 0.05 μm or more and 0.5 μm or less. When the particle diameter of the fine particles containing the binder resin is in such a range, it is easy to prepare toner-core particles having a sharp particle size distribution and a uniform shape. The volume average particle diameter (D ₅₀ ) of the fine particles containing the binder resin can be measured using a device such as a laser diffraction particle size distribution measuring device (SALD-2200 (manufactured by Shimadzu Corporation)).

  The aqueous medium dispersion containing fine particles containing a binder resin preferably contains a surfactant. When the surfactant is contained in the aqueous medium dispersion liquid containing the fine particles containing the binder resin, the fine particles containing the binder resin can be stably dispersed in the aqueous medium.

  The surfactant that can be contained in the aqueous medium dispersion containing fine particles including the binder resin can be appropriately selected from the group consisting of an anionic surfactant, a cationic surfactant, and a nonionic surfactant. As an anionic surfactant, the same thing as the above-mentioned anionic surfactant is mentioned. Examples of the cationic surfactant include amine salt type surfactants and quaternary ammonium salt type surfactants. Examples of nonionic surfactants include polyethylene glycol type surfactants, alkylphenol ethylene oxide adduct type surfactants, and polyhydric alcohol type surfactants that are derivatives of polyhydric alcohols such as glycerin, sorbitol, and sorbitan. Is mentioned. Of these surfactants, anionic surfactants are preferred. These surfactants may be used alone or in combination of two or more.

  The amount of the surfactant used is preferably 0.01% by mass to 10% by mass with respect to the mass of the binder resin.

  As described above, the toner core particles are preferably prepared using a resin having an acidic group such as a carboxyl group. When a resin having an acidic group is used as the binder resin, the specific surface area of the binder resin increases when the binder resin is directly atomized in an aqueous medium, so the acidic groups exposed on the surface of the fine particles including the binder resin are increased. The pH of an aqueous medium may fall to about 3-4 by the influence of. In this case, the binder resin may be hydrolyzed, or the particle diameter of the obtained fine particles may be difficult to reduce to a desired particle diameter.

  In order to suppress such a problem, a basic substance may be added to the aqueous medium when preparing the fat fine particles containing the binding tree. The basic substance may be any substance that can suppress the above-mentioned problems, and alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, alkali metal carbonates such as sodium carbonate, and potassium carbonate. Alkali metal hydrogen carbonates such as sodium hydrogen carbonate and potassium hydrogen carbonate, N, N-dimethylethanolamine, N, N-diethylethanolamine, triethanolamine, tripropanolamine, tributanolamine, triethylamine, n- Examples thereof include nitrogen-containing organic bases such as propylamine, n-butylamine, isopropylamine, monomethanolamine, morpholine, methoxypropylamine, pyridine, and vinylpyridine.

-Method for preparing release agent fine particles The method for preparing the release agent fine particles may be any method capable of preparing release agent fine particles having an average particle diameter of 280 nm or more and 550 nm or less. Examples of the method for preparing the release agent fine particles include the methods described below.

  The release agent is pulverized to about 100 μm or less in advance to obtain a release agent powder. For preparing the release agent fine particles, it is preferable to add a release agent powder to an aqueous medium containing a surfactant to prepare a slurry. The amount of the surfactant used is preferably 0.01% by mass or more and 10% by mass or less with respect to the mass of the release agent.

  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 (Ultra Turrax T50 (manufactured by IKA)) or a pressure discharge type disperser to prepare an aqueous dispersion containing 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 dizer (manufactured by MFI), gorin homogenizer (manufactured by Manton Gorin), and A device such as Claremix W Motion (M Technique Co., Ltd.) can be mentioned.

The volume average particle diameter (D ₅₀ ) of the release agent fine particles contained in the aqueous medium dispersion is 280 nm or more and 550 nm or less. By using release agent fine particles having a particle diameter in such a range, a predetermined type of fine particles are aggregated to form a fine particle aggregate, and when components contained in the obtained fine particle aggregate are united, It is possible to suppress the release agent fine particles from dropping from the fine particle aggregates. Therefore, a toner containing a desired amount of the release agent in the binder resin can be obtained by preparing the toner using the release agent fine particles having a volume average particle diameter (D ₅₀ ) within the above-mentioned range. Can do. The volume average particle diameter of the releasing agent particles (D ₅₀₎ can be measured in the same manner as the volume average particle diameter of the binder resin particles (D _50).

-Preparation method of colorant microparticles Hereinafter, a suitable example of a method for preparing colorant microparticles will be described.
Fine particles containing a colorant are prepared by dispersing a colorant and, if necessary, a component such as a colorant dispersant in an aqueous medium containing a surfactant, using a known disperser. It is preferable to do this. As the type of the surfactant, the surfactant used in the preparation of the binder resin fine particles described above can be used. The amount of the surfactant used is preferably 0.01% by mass or more and 10% by mass or less.

  Dispersers used for dispersion processing are pressure dispersers such as ultrasonic dispersers, mechanical homogenizers, manton gourins, pressure homogenizers, and high pressure homogenizers (manufactured by Yoshida Kikai Kogyo Co., Ltd.), sand grinders, horizontal types Moreover, a medium type disperser such as a vertical bead mill, an ultra apex mill (manufactured by Kotobuki Industries Co., Ltd.), a dyno mill (manufactured by WAB Co., Ltd.), and an MSC mill (manufactured by Nippon Coke Industries, Ltd.) can be used.

The volume average particle diameter (D ₅₀ ) of the colorant fine particles is preferably 0.05 μm or more and 0.2 μm or less. The volume average particle diameter of the colorant fine particles (D ₅₀₎ can be measured by the volume average particle size (D ₅₀₎ In the same manner as the binder resin fine particles.

  An aqueous medium dispersion containing fine particles containing a binder resin and an aqueous medium dispersion containing release agent fine particles, and an aqueous medium dispersion containing colorant fine particles as necessary, and toner core particles containing predetermined components The aqueous medium dispersion containing the fine particle aggregate can be obtained by aggregating the fine particles after the combination. As a preferred method for aggregating the fine particles, the pH of the aqueous medium dispersion containing fine particles containing the binder resin is adjusted, and then the flocculant is added to the aqueous medium dispersion, and then the temperature of the aqueous medium dispersion is set to a predetermined value. A method of agglomerating fine particles by adjusting the temperature can be mentioned.

  Suitable flocculants 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 and a nitrogen-containing compound such as polyethyleneimine can also be used as an aggregating agent.

  As the flocculant, a divalent metal salt and a monovalent metal salt are preferably used. A flocculant may be used individually by 1 type and may be used in combination of 2 or more type. When two or more kinds of flocculants are used in combination, it is preferable to use a divalent metal salt and a monovalent metal salt in combination. The aggregation rate of fine particles differs between a divalent metal salt and a monovalent metal salt. Therefore, by using these together, it is easy to make the particle size distribution of the fine particle aggregate sharp while controlling the increase in the particle size of the obtained fine particle aggregate.

  The flocculant is preferably added after adjusting the pH of the fine particle dispersion. The pH of the aqueous medium dispersion when adding the flocculant is preferably 8 or more. The flocculant may be added at one time or may be added sequentially.

  The addition amount of the flocculant is preferably 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the solid content of the aqueous medium dispersion. The addition amount of the flocculant is preferably adjusted as appropriate according to the type and amount of the anionic or nonionic surfactant contained in the fine particle dispersion.

  The temperature of the aqueous medium dispersion when agglomerating the fine particles is preferably a temperature not lower than the glass transition point (Tg) of the binder resin and lower than Tg + 10 ° C. of the binder resin. By heating the aqueous medium dispersion containing fine particles of the binder resin to a temperature in such a range, aggregation of the fine particles contained in the aqueous medium dispersion can be favorably progressed.

  After the aggregation has progressed until the fine particle aggregate has a desired particle diameter, an aggregation terminator may be added. Examples of the aggregation terminator include sodium chloride, potassium chloride, and magnesium chloride. In this way, an aqueous medium dispersion containing fine particle aggregates can be obtained.

((Ii) coalescence process)
(Ii) In the coalescing step, the aqueous medium dispersion containing the fine particle aggregate obtained as described above is heated to coalesce the components contained in the fine particle aggregate to obtain toner core particles having a desired particle size. An aqueous medium dispersion (X) containing is obtained. The temperature at which the aqueous medium dispersion containing fine particle aggregates is heated is preferably a glass transition point (Tg) of the binder resin + 10 ° C. or higher and a melting point of the binder resin or lower. By heating the aqueous medium dispersion containing the fine particle aggregate to a temperature within such a range, the coalescence of the components contained in the fine particle aggregate can be favorably progressed.

[Preparation of aqueous medium dispersion (Y)]
As a method for preparing the aqueous medium dispersion (Y), a resin, which is a material of resin fine particles, can be formed into fine particles in an aqueous medium using the same method as the method for producing fine particles containing the binder resin described above. And a method of polymerizing a monomer having a predetermined composition in an aqueous medium using a known method to form resin fine particles.

  The aqueous medium dispersion (Y) preferably contains fine resin particles that have been agitated with an anionic surfactant. In this case, when the shell layer made of resin fine particles is formed on the surface of the toner core particles, aggregation of the resin fine particles is particularly easily suppressed. When the aqueous medium dispersion (Y) contains an anionic surfactant, the concentration of the anionic surfactant in the aqueous medium dispersion (Y) is preferably 0.01% by mass or more and 10% by mass or less.

The volume average particle diameter (D ₅₀ ) of the resin fine particles contained in the aqueous medium dispersion (Y) is preferably 0.03 μm or more and 0.50 μm or less, and more preferably 0.05 μm or more and 0.30 μm or less. When the volume average particle diameter (D ₅₀ ) of the resin fine particles covering the toner core particles is within such a range, the toner core particles can be easily coated uniformly. The volume average particle diameter of the resin fine particles covering the toner core particles can be measured using an apparatus such as an electrophoretic light scattering photometer (LA-950V2 (manufactured by Horiba, Ltd.)).

[(II) Shell layer forming step]
In step (II), as described above, after preparing a mixed solution containing toner core particles and resin fine particles, the mixture is stirred to form a shell layer made of resin fine particles on the surface of the toner core particles. Toner particles (toner mother particles) are obtained. After preparing the mixed solution, the resin fine particles, which are the material of the shell layer in the mixed solution, are in a state of being easily aggregated. For this reason, it is preferable to start stirring the mixed solution immediately after preparing the mixed solution.

  After the shell layer made of resin fine particles is formed on the surface of the toner core particles, the aqueous medium dispersion may be heated. The heating temperature at this time is preferably not less than the glass transition point (Tg) of the resin constituting the resin fine particles and not more than 90 ° C. By heating the aqueous medium dispersion at a temperature within such a range, the formation of the resin fine particle layer covering the toner core particles can be favorably progressed, and the toner core particles can be satisfactorily covered with the shell layer formed as a film. it can.

  Examples of the stirring device used for stirring the mixed solution include T.I. K. Stirring devices such as Filmix (manufactured by Primix Co., Ltd.), Robomix (Primix Co., Ltd.), and Cavitron (Eurotech Co., Ltd.) may be mentioned.

  The core-shell structured particles formed through the above-described (I) mixing step and (II) shell layer forming step are recovered from the mixed liquid as toner particles or toner base particles.

[(III) Cleaning step]
(III) In the washing step, the toner particles or toner base particles formed by the above method are washed with water. As a washing method, a method of recovering toner particles or toner mother particles as a wet cake from a mixed liquid containing toner particles or toner mother particles using solid-liquid separation, and washing the obtained wet cake with water In addition, there is a method in which toner particles or toner base particles in a mixed solution are precipitated, the supernatant liquid is replaced with water, and the toner particles or toner base particles are redispersed in water after the replacement.

[(IV) Drying step]
The toner particles or toner base particles obtained through the step (II) or (III) are preferably dried in the (IV) drying step. 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 or toner base particles during drying is easily suppressed.

[(V) External addition process]
The toner for developing an electrostatic latent image may be one having an external additive attached to the surface thereof as necessary. When the core-shell structured particles formed through the steps (I) and (II) are recovered as toner base particles, (V) a suitable external agent is attached to the surface of the toner base particles in the external addition step. As a method, using a mixer such as a Henschel mixer or a Nauter mixer, adjusting the conditions so that the external additive is not buried in the toner surface, the toner base particles and the external additive are mixed. It is done.

  When the method for producing a toner for developing an electrostatic latent image according to the present invention described above is used, a core-shell structure is formed by attaching positively chargeable resin fine particles to the surface of a toner core particle containing a negatively chargeable binder resin. The toner for developing an electrostatic latent image containing a desired amount of the release agent can be produced by suppressing the dropout of the release agent fine particles from the toner core particles when forming the toner.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the scope of the examples.

[Preparation Example 1]
(Preparation of binder resin fine particle dispersion)
A fine particle dispersion containing a binder resin was prepared according to the following method.
The following polyester resins were used as binder resins.
Monomer composition: polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane / polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane / fumar Acid / trimellitic acid = 25/25/46/4 (molar ratio)
Number average molecular weight (Mn): 2,500
Mass average molecular weight (Mw): 6,500
Molecular weight distribution (Mw / Mn): 2.6
Softening point (Tm): 91 ° C
Glass transition point (Tg): 51 ° C
Acid value: 15.5 mg KOH / g

  100 g of a coarsely pulverized polyester resin having an average particle size of about 10 μm, coarsely pulverized using Turbomill T250 (manufactured by Turbo Kogyo Co., Ltd.), and dispersant A (anionic surfactant, Emar E-27C (Kao Corporation) ), 2 g of sodium polyoxyethylene lauryl ether sulfate) and 50 g of a 0.1N sodium hydroxide aqueous solution (basic substance) were mixed, and ion-exchanged water was added as an aqueous medium to prepare a total slurry of 500 g. .

  The obtained slurry was put into a pressure-resistant round bottom stainless steel container. Next, using a high-speed shearing emulsifier CLEARMIX (CLM-2.2S (manufactured by M Technique Co., Ltd.)), with the slurry heated and pressurized to 145 ° C. and a pressure of 0.5 MPa (G), the rotor rotational speed 20 Shear dispersion was performed at 1,000 rpm for 30 minutes. After the shear dispersion, the slurry was continuously stirred at a rotor rotational speed of 15,000 rpm while the slurry was cooled at a rate of 5 ° C./min until the temperature inside the stainless steel container reached 50 ° C. Thereafter, the slurry was cooled to room temperature at a rate of 5 ° C./min. Binder resin fine particles in which fine particles of polyester resin having an average particle size of about 140 nm are dispersed by adding ion-exchanged water to a slurry cooled to room temperature so that the solid content with respect to the mass of the dispersion is 5% by mass. A dispersion was obtained. The average particle size of the fine particles in the dispersion was measured using a particle size distribution measuring device (Microtrac UPA150 (manufactured by Nikkiso Co., Ltd.)).

[Preparation Example 2]
(Preparation of release agent fine particle dispersions A to D)
Release agent fine particle dispersions A to D were prepared according to the following method.
200 g of a mold release agent of the type shown in Table 1, 2 g of dispersant A, and 800 g of ion-exchanged water were mixed. After the mixture is heated to 100 ° C. to melt the release agent, the time emulsification treatment described in Table 1 is performed using an emulsification apparatus A (double motion type CLEARMIX (M Technique Co., Ltd., laboratory)). And the mixture was emulsified. In this way, release agent fine particle dispersions A to D containing release agent fine particles having a volume average particle diameter shown in Table 1 and having a solid content concentration of 20% by mass were obtained.
The following release agents A and B were used as release agents.
Release agent A: ester wax (WEP-5 (manufactured by NOF Corporation), pentaerythritol behenate ester wax, melting temperature 84 ° C.)
Release agent B: Fischer-Tropsch wax (HNP-51 (manufactured by Nippon Seiwa Co., Ltd.), melting temperature 77 ° C.)

(Partner fine particle dispersions E and F)
Release agent fine particle dispersions E and F were prepared according to the following method.
Release agent A200g, dispersing agent A2g, and ion-exchange water 800g were mixed. After the mixture is heated to 100 ° C. and the release agent is melted, the emulsification apparatus B (homogenizer (Ultra Turrax T50 (manufactured by IKA)) is used to perform the emulsification treatment for the time shown in Table 1 and mixing. The liquid was emulsified. Subsequently, the emulsification process was performed at 100 degreeC using the gorin homogenizer (made by Manton Gorin). In this way, release agent fine particle dispersions E and F containing release agent fine particles having a volume average particle diameter shown in Table 1 and having a solid content concentration of 20% by mass were obtained.

[Preparation Example 3]
(Preparation of colorant fine particle dispersion)
A dispersion of colorant fine particles was prepared according to the following method.
90 g of a cyan colorant (CI Pigment Blue 15: 3 (copper phthalocyanine)), 10 g of a dispersant B (anionic surfactant, Emar 0 (manufactured by Kao Corporation), sodium lauryl sulfate), and 400 g of ion-exchanged water Were mixed. The mixture was emulsified and dispersed for 1 hour using a high-pressure impact disperser Ultimateizer (HJP30006 (manufactured by Sugino Machine Co., Ltd.)) to obtain a colorant fine particle dispersion having a solid content concentration of 18% by mass.

  The particle size distribution of the colorant fine particles contained in the obtained colorant dispersion was measured using a particle size distribution measuring device (Microtrac UPA150 (manufactured by Nikkiso Co., Ltd.)). The volume average particle size (MV) of the colorant fine particles contained in the obtained colorant dispersion was 160 nm, and the Cv value of the particle size distribution was 25%. From the TEM image of the colorant fine particles, it was confirmed that the circularity was 0.800.

[Preparation Example 4]
(Preparation of resin fine particle dispersion)
A 2-liter four-necked flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet tube was used as a reaction vessel. To the reaction vessel, 180 g of isobutanol was added, and further 16 g of diethylaminoethyl methacrylate and 16 g of methyl paratoluenesulfonate were added. Under a nitrogen atmosphere, the flask contents were stirred for 1 hour under the conditions of 80 ° C. and a stirring speed of 230 rpm (until the end of the polymerization reaction), to carry out a quaternization reaction. Next, under a nitrogen stream, 214 g of styrene, 72 g of butyl acrylate, and 12 g of t-butylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd.) as a peroxide initiator were added to the reaction vessel. . After raising the internal temperature of the reaction vessel to 95 ° C. (polymerization temperature), the contents of the reaction vessel were stirred at the same temperature for 3 hours. Next, 6 g of t-butylperoxy-2-ethylhexanoate was further added to the reaction vessel. Thereafter, the contents of the reaction vessel were stirred at 95 ° C. for 3 hours to complete the polymerization reaction. The contents of the reaction vessel were repeatedly filtered and washed to obtain a styrene-acrylic resin.

  The obtained styrene acrylic resin was coarsely pulverized using a turbo mill T250 (manufactured by Turbo Kogyo Co., Ltd.) to obtain a coarsely pulverized product having a particle size of about 30 μm to 50 μm. 200 g of the coarsely pulverized styrene acrylic resin obtained, 20 g of dispersant B (anionic surfactant, EMAL 0 (manufactured by Kao Corporation), sodium lauryl sulfate) and 780 g of ion-exchanged water are mixed and heated. Using a high-pressure homogenizer (NV-200 (manufactured by Yoshida Kikai Kogyo Co., Ltd.)) equipped with a system, emulsification was performed once at 170 ° C. and a discharge pressure of 150 MPa, and the volume average particle size was 250 nm and the solid content concentration A 20% by mass resin fine particle dispersion was obtained. The zeta potential of the resin fine particles in the obtained resin fine particle dispersion was +60 mV. The zeta potential of the dispersion was measured using an ultrasonic particle size distribution / zeta potential measuring device (DT-1200 (manufactured by Dispersion Technology)).

[Examples 1 to 4, Comparative Example 1 and Comparative Example 2]
[Preparation of toner core particle dispersion]
Toner core particle dispersions were prepared by mixing the following amounts of binder resin fine particle dispersion, release agent fine particle dispersion, and colorant fine particle dispersion obtained in Preparation Examples 1 to 3.
(Fine particle dispersion mixing ratio)
Binder resin fine particle dispersion (solid content concentration 5 mass%): 425 g
Release agent fine particle dispersion of the type described in Table 2 and Table 3 (solid content concentration 20% by mass): 12.5 g
Colorant fine particle dispersion (solid concentration: 18% by mass): 7 g

  Specifically, a dispersion of toner core particles was prepared according to the following method. Into a 1 L four-necked flask equipped with a thermometer, a condenser, and a stirrer, the above three kinds of fine particle dispersions, 0.4 g of dispersant B, and 43.5 g of ion-exchanged water are added and stirred at 200 rpm. Stir at speed. Next, triethanolamine was added to the flask to adjust the pH of the flask contents to 9. After pH adjustment, an aqueous solution in which 6.0 g of a flocculant (magnesium chloride hexahydrate) was dissolved in 6.0 g of ion-exchanged water was added to the flask. After allowing the dispersion in the flask to stand for 5 minutes, the temperature of the contents of the flask was raised to 50 ° C. at a rate of 5 ° C./min. Thereafter, the temperature of the contents of the flask was raised to 73 ° C. at a rate of 0.5 ° C./min. The temperature of the dispersion liquid was maintained at 73 ° C., and when the volume average particle diameter of the aggregated particles in the dispersion liquid became 6.5 μm, the dispersion liquid was stirred at a stirring speed of 350 rpm for 10 minutes. After stirring, the dispersion is cooled to room temperature at a rate of 5 ° C./minute, and toner core particles having a volume average particle size (MV) of 6.6 μm, a number average particle size (MN) of 5.7 μm, and an average circularity of 0.93. A toner core particle dispersion liquid was obtained. At this time, a part of the obtained toner core particle dispersion was taken out and used for evaluation of the toner release agent uptake rate. With respect to the toner core particle dispersion from which a part was taken out, the toner core particles were recovered from the dispersion according to the following method.

[Toner core particle recovery method]
A wet cake of toner core particles was filtered from the toner core particle dispersion using a filter cloth having a 1-um opening. The toner core particle wet cake was again dispersed in ion exchange water to wash the toner core particles. Washing of the toner core particles with ion-exchanged water was repeated 5 times. The wet cake of toner core particles after washing was vacuum dried at 40 ° C. to obtain toner core particles used for evaluation of the release agent uptake rate of the toner.

  Next, the toner core particle dispersion was allowed to stand for 24 hours to precipitate the toner core particles. Thereafter, the supernatant was removed from the container by decantation. After the removal of the supernatant liquid, the same amount of ion-exchanged water as that removed was added to the settled toner core particles. Thereafter, the toner core particles were redispersed in ion exchange water.

[Formation of shell layer]
30 g of the re-dispersed toner core particle dispersion and 0.3 g of the resin fine particle dispersion obtained in Preparation Example 4 K. It put into the stirring tank of a film mix (made by Primix Co., Ltd.). Thereafter, T.W. K. The stirring speed of the film mix is set to 30 m / s (the average flow rate of the contents in the stirring tank is 20 m / s), and the contents in the stirring tank are stirred at 30 ° C. for 20 minutes to disperse the toner particles. A liquid was obtained. With respect to the obtained toner particle dispersion, toner particles were recovered from the toner particle dispersion using a method similar to the method for recovering toner core particles.

≪Evaluation≫
With respect to the toners obtained in Examples 1 to 4, Comparative Example 1 and Comparative Example 2, the release agent uptake rate was evaluated. The evaluation results are shown in Tables 2 and 3.

<Evaluation of release agent uptake rate>
According to the following method, the release agent content (Pa) in the solid content contained in the toner core particle dispersion and the release agent content (Pb) in the obtained toner particles are measured, and the following formula is used. The toner particle release agent uptake rate was calculated.
Release agent uptake rate (%) = (Pb / Pa) × 100
From the calculation result of the release agent uptake rate, the amount of release agent uptake of the toner particles was evaluated according to the following criteria, and the evaluation of “、” or “◯” was evaluated as acceptable.
A: The release agent uptake rate is 90% or more.
○: The release agent uptake rate is 85% or more and less than 90%.
X: The release agent uptake rate is less than 85%.

(Method for measuring release 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 measurement sample 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. Measurement was performed under the conditions of a measurement temperature range of 40 to 200 ° C., a temperature increase rate of 10 ° C./min, and a measurement ambient environment at normal temperature and humidity. The endothermic amount (W ₀ ) per unit mass of the release agent was calculated in advance from the endothermic curve measured with the release agent alone. From the endothermic curve of the measurement sample, the endothermic amount (Q _W ) due to the release agent was measured, and the release agent content (% by mass) in the measurement sample was determined using the following formula.
Release agent content (% by mass) in the measurement sample = ((Q _W / W ₀ ) / 10) × 100

  According to Examples 1 to 4, an aqueous medium dispersion liquid (X) containing negatively chargeable toner core particles containing a binder resin and a release agent, and an aqueous medium dispersion liquid containing positively chargeable resin fine particles ( Y), and then the mixture is stirred to form a shell layer made of resin fine particles on the surface of the toner core particles to obtain an electrostatic latent image developing toner. Regarding the method, toner for developing an electrostatic latent image containing a desired amount of a release agent by aggregating toner core particles, binder resin fine particles, and release agent fine particles having a predetermined particle diameter in an aqueous medium It can be seen that can be manufactured.

Claims (1)

After mixing an aqueous medium dispersion (X) containing negatively chargeable toner core particles containing a binder resin and a release agent and an aqueous medium dispersion (Y) containing positively charged resin fine particles, mixing A method for producing an electrostatic latent image developing toner, comprising stirring a liquid to form a shell layer composed of resin fine particles on the surface of toner core particles to obtain an electrostatic latent image developing toner,
The toner core particles are obtained by aggregating binder resin fine particles containing the binder resin and release agent fine particles containing the release agent in an aqueous medium,
A method for producing a toner for developing an electrostatic latent image, wherein the release agent fine particles have an average particle diameter of 280 nm or more and 550 nm or less.

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