JP2013210574A - Toner for electrostatic charge image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic charge image development that has heat-resistance storability of not impairing performance even under a severe environment of high temperature and high humidity, and a good cleaning property.SOLUTION: A toner for electrostatic charge image development contains at least a binder resin and colorant, and includes at least core-shell type composite particles satisfying the following conditions (A) to (C): (A) a structure that uses resin in a core part, and has an outer shell covered with inorganic particles, (B) the water content of 2.8 mass% or less, and (C) the true specific gravity of 0.7 or more and 2.0 or less.

Description

  The present invention relates to an electrostatic charge image developing toner used in electrophotography, electrostatic photography and the like.

  In general, an electrophotographic method forms an electrostatic latent image on a photoconductive photoreceptor by various methods, and then visualizes the latent image using an electrostatic charge image developing toner (hereinafter abbreviated as “toner”). After that, there is a step of transferring the toner visible image onto a transfer material such as paper and fixing the toner image by heating or pressurizing. Various methods are known as these steps, and those suitable for each image forming process are employed.

  One of the typical toner manufacturing methods is a pulverization method that melts and mixes various materials such as binder resins, colorants, and charge control agents, and then pulverizes and classifies them into fine powders. In general, it is widely used regardless of color, monochrome, and various development methods. In addition, research and development of polymerized toners are actively conducted to meet the demand for higher speed and higher image quality in recent electrophotography. Since the particle size of the polymerized toner is easier to control than the pulverized toner, it is possible to obtain toner mother particles having a small particle size suitable for high image quality.

Further, since the toner can be encapsulated by controlling the particle structure, there is an advantage that a toner excellent in heat resistance and low-temperature fixability can be obtained.
In addition to reducing the particle size of the toner as described above, various studies have been made to achieve durability and fluidity to obtain a stable high image quality and to control the chargeability.
For example, in order to obtain the fluidity and chargeability of the toner, the latter technology, in which the technology for externally adding small particle size silica and the technology for externally adding spherical silica of submicron size are known, in order to increase the durability, Spherical silica present on the outermost surface of the toner particles exerts a spacer effect, preventing filming on the photoconductor drum, which is a problem during printing durability, and embedding of small particle size external additives in the toner base particles. It becomes.

JP 2001-109185 A JP 2001-66820 A JP 2002-108001 A JP 2010-266804 A

  In some cases, silica produced by a dry method is used in the toner in order to stabilize the chargeability (Patent Document 1). However, since the silica produced by the conventional dry method has a small primary particle size, not only the spacer effect is insufficient, but also the provision of excessive fluidity causes defects due to slipping through cleaning. There is a technique to reduce the amount of external additives added in the conventional dry method in order to prevent excessive fluidity from being imparted, but at the same time, the coverage of the surface of the mother particles is reduced, so that the wax tends to be exposed on the surface. , The caking property (heat resistant storage stability) of the toner is deteriorated.

As the sub-micron sized spherical silica, silica prepared by a wet method is often used (Patent Documents 2 and 3). However, since these silicas contain a large amount of moisture from the manufacturing method, The electrification also becomes low, and there is a concern about the deterioration of the fog. In addition, when the same number of parts as the dry small particle size silica is added, the coverage of the surface of the mother particles is lowered, and there is a possibility that the caking property (heat resistant storage property) of the storable toner is deteriorated. . On the other hand, it is preferable to increase the number of added parts to improve the coverage ratio because the particle size is large, so that detachment from the toner surface is promoted, which causes adverse effects such as filming on the photosensitive drum and contamination on the charging member. Absent.

As a means for solving the above-mentioned problems of silica, core / shell type composite particles (having an organic substance in the inner shell and a silica compound in the outer shell layer) are added to the toner base particles instead of silica. Has been proposed (Patent Document 4), however, there is no quantitative description of thermal properties such as fixing properties and caking properties, which are the most important properties of toner, and the performance difference from silica is unclear. . In addition, the silica described in the preamble indicates a single silica particle and does not include a silica compound in the outer shell layer of the composite particle.

In other words, a technology that appropriately controls the fluidity / chargeability of the toner and achieves both cleaning properties, caking properties, and fixing properties has not yet been provided.
The present invention has been made in view of such a background art, and its problem is that it has heat-resistant storage stability that does not impair the performance even in a severe environment of high temperature and humidity, and has a static property that also provides good cleaning properties and fixing properties to paper. An object is to provide a toner for developing a charge image.

The present inventor has repeatedly studied to solve the above problems, and has found that the above problems can be solved by using a toner having particles having a specific structure and physical properties. That is, the gist of the present invention is as follows.
1. A toner for developing electrostatic images, comprising at least a binder resin and a colorant, wherein the toner has core / shell type composite particles satisfying at least the following (A) to (C).
(A) Structure in which resin is used for the core and the outer shell is covered with inorganic particles
(B) Moisture content 2.8% by mass or less
(C) True specific gravity 0.7 or more and 2.0 or less The electrostatic image developing toner has toner base particles and external additives, and when n kinds of external additives are added, the coverage of the toner base particles by the external additive represented by the following formula (1) The toner for developing an electrostatic charge image according to the above 1., wherein the toner is 20% or more and 60% or less.

[In the above formula,
Dt represents the particle size (μm) of the toner base particles,
ρt represents the true specific gravity of the toner base particles,
D represents the maximum particle size (μm) of the external additive,
ρ represents the true specific gravity of the external additive,
W represents the number of added parts (parts by mass) of the external additive. ]

  The composite particles used in the present invention are used as a toner external additive in a state of adhering or adhering to the toner surface. The average primary particle size of the composite particles is 30 nm or more and 150 nm or less. Among these, 70 nm or more is preferable, and 75 nm or more is particularly preferable. Moreover, 140 nm or less is preferable and 120 nm or less is especially preferable. If the average primary particle size is too small, a sufficient spacer effect cannot be obtained, causing OPC filming and embedding of the small particle size external additive in the toner base particles, resulting in fogging and scumming after printing. Etc. may occur. On the other hand, if it is too large, it may be difficult to adhere to the toner base particles, and member contamination due to detachment may occur. The average primary particle size of the composite particles or silica particles is measured by the method described in the examples.

  The composite particles used in the present invention are required to have a water content of 2.8% by mass or less. Among these, 2.7% by mass or less is preferable, and 2.6% by mass or less is particularly preferable. If the amount of water is too high, the composite particles are less charged due to excess water, and thus the charge of the externally added toner is also lowered, so fog may occur. Furthermore, the electrostatic charge to the toner base particles is reduced by reducing the charge amount of the composite particles themselves, and when the composite particles are externally added in combination with particles having a reverse polarity, The toner may be easily peeled off from the toner base particles. In addition, when the silica particles contain adsorbed water, the affinity with the particles having the opposite polarity to the silica particles increases, so that the physical adhesion with the particles increases, and the silica particles are easily peeled off. There is a case. The amount of water is measured by the method described in the examples.

  The composite particles used in the present invention usually have a true specific gravity of 0.7 or more and 2.0 or less. Above all, it is preferably 0.9 or more. Moreover, 1.9 or less is preferable and 1.4 or less is especially preferable. If the true specific gravity is too small, the composite particles tend to adsorb moisture on the surface, so that charge reduction occurs and fogging may occur. On the other hand, if it is too large, embedding on the surface of the toner becomes remarkable, which may also cause deterioration of the fog. In addition, when the approach distance between the toners is shortened, the wax in the vicinity of the surface is fused, and the caking property (heat resistant storage stability) in a high temperature and high humidity environment may be lowered. The true specific gravity is measured by the method described in the examples.

  In the toner of the present invention, the toner base particle coverage by the external additive is not particularly limited, but the lower limit is usually 20% or more, preferably 25% or more, and particularly preferably 30% or more. On the other hand, the upper limit is usually 60% or less, preferably 55% or less, and particularly preferably 45% or less. If the coverage is too low, the wax tends to be exposed on the surface, and the solidification property (heat resistant storage stability) of the toner may be deteriorated. On the other hand, if the coverage is too high, the heat transfer to the resin is hindered by the external additive, and the toner may be peeled off without sufficiently soaking into the paper, and a cold offset may occur. The base particle coverage of the external additive is calculated by the above formula (1).

  The structure of the composite particles used in the present invention has a core / shell structure, the core material contains a resin, and the shell material contains inorganic particles. The resin used for the core may be any organic material as long as atomization is easy, and the method for polymerizing the resin is not particularly limited. Examples of the resin production method include a pulverization method, a suspension polymerization method, an emulsion polymerization aggregation method, a dissolution suspension method, and an ester extension method. Examples of the resin include polystyrene, a styrene-substituted homopolymer, a styrene copolymer, acrylic acid, methacrylic acid, a polyester resin, a polyamide resin, an epoxy resin, a xylene resin, and a silicone resin. These resins may be used alone or in combination. Silicon compounds used for the shell include, for example, tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, alkylalkoxysilane compounds, phenylalkoxysilane compounds, amino group-containing silane compounds, vinyl Examples thereof include silicates such as a group-containing silane compound, a glycidyl group-containing silane compound, an acrylic group-containing silane compound, sodium silicate, and potassium silicate.

The production method of the composite particles used in the present invention is not particularly limited, and can be prepared by a known method. For example, it is manufactured by the method described in JP 2010-266804 A.
The volume median diameter of the toner base particles of the present invention is not particularly limited, but is usually 3 μm or more, preferably 4 μm or more, more preferably 5 μm or more, and usually 10 μm or less. Yes, it is preferably 8 μm or less, and more preferably 7 μm or less If the volume median diameter of the toner is too large, the charge amount per unit weight tends to decrease, and fogging and toner scattering occur. If the amount is too small, the amount of charge per unit weight tends to be excessive, and problems such as extreme reduction in image density may occur. It is measured by the method described.

  The average circularity of the toner base particles of the present invention is usually 0.955 or more and preferably 0.960 or more. Moreover, it is 0.985 or less normally, and it is preferable that it is 0.980 or less. If the circularity is too large, slipping in the cleaning part is likely to occur, and the image may be defective. On the other hand, if the circularity is too small, when the inorganic particles roll on the surface of the mother particles due to agitation by printing durability, the mother particles The effect of the present invention may not be maintained until the end. The circularity of the toner base particles of the present invention is measured by the method described in the examples.

The constituent material of the toner of the present invention is not particularly limited, and includes at least a binder resin and a colorant, and includes a charge control agent, a wax, and other additives as necessary.
The production method of the toner base particles of the present invention is not limited, and a conventionally used method such as a pulverization method, a wet method, a method of spheroidizing the toner by a mechanical impact force, heat treatment or the like can be used. Examples of the wet method include a suspension polymerization method, an emulsion polymerization aggregation method, a dissolution suspension method, and an ester extension method.

The pulverization method will be described later. In the case of the pulverization method, a predetermined amount of a binder resin, a colorant, and other components as required are mixed and mixed. Examples of the mixing apparatus include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, and a Nauter mixer.
Next, the blended and mixed toner raw materials are melt-kneaded to melt the resins and disperse the colorant and the like therein. In the melt-kneading step, for example, a batch kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used. For the kneading machine, a single-screw or twin-screw extruder is used. For example, KTK type twin screw extruder manufactured by Kobe Steel, TEM type twin screw extruder manufactured by Toshiba Machine Co., Ltd., twin screw extruder manufactured by K.C.K. , Bus Co., Ltd. co-kneader. Further, the colored resin composition obtained by melt-kneading the toner raw material is rolled by a two-roll roll after melt-kneading and becomes a cooled product through a process of cooling by water cooling or the like.

  The cooled product of the colored resin composition obtained above is then pulverized to a desired particle size in a pulverization step. In the pulverization step, first, coarse pulverization is performed with a crusher, a hammer mill, a feather mill or the like, and further, pulverization is performed with a kryptron system manufactured by Kawasaki Heavy Industries, Ltd., a super rotor manufactured by Nisshin Engineering Co., Ltd. or the like. After that, if necessary, the particles are classified using a classifier such as an inertia classification type elbow jet (manufactured by Nippon Steel Mining Co., Ltd.) or a centrifugal classification type turboplex (manufactured by Hosokawa Micron Co., Ltd.). obtain. Further, the toner may be spheroidized using a conventionally used method.

After obtaining the toner base particles, the toner can be obtained through a processing step of adding an external additive and, if necessary, other processing steps.
Examples of the wet method include a suspension polymerization method, an emulsion polymerization aggregation method, a dissolution suspension method, and the like, and any method may be used without any particular limitation.
In the present invention, as a method for producing a suspension polymerization toner, a coloring agent, a polymerization initiator, and, if necessary, a wax, a polar resin, a charge control agent, a crosslinking agent, etc. in the above-mentioned binder resin monomer. An additive is added to prepare a monomer composition that is uniformly dissolved or dispersed. This monomer composition is dispersed in an aqueous medium containing a dispersion stabilizer and the like. Preferably, granulation is performed by adjusting the stirring speed and time so that the droplets of the monomer composition have a desired toner particle size. Thereafter, polymerization is performed by stirring to such an extent that the particle state is maintained and the sedimentation of the particles is prevented by the action of the dispersion stabilizer. These are collected by washing and filtration, and dried to obtain toner mother particles. After obtaining the toner base particles, the toner can be obtained through a processing step of adding an external additive and, if necessary, other processing steps.

  In the production method of the emulsion polymerization aggregation method, polymer primary particles of a binder resin monomer obtained by the emulsion polymerization step, a colorant dispersion, a wax dispersion, etc. are prepared, and these are put in an aqueous medium. By dispersing and heating, it undergoes an agglomeration step and an aging step. These are collected by washing and filtration, and dried to obtain toner mother particles. After obtaining the toner base particles, the toner can be obtained through a processing step of adding an external additive and, if necessary, other processing steps.

In the present invention, as the binder resin contained in the toner, resins conventionally used as the binder resin for toner can be appropriately used.
The binder resin used when the toner base particles are produced by a pulverization method includes polystyrene, a styrene-substituted homopolymer, a styrene copolymer, acrylic acid, methacrylic acid, polyester resin, polyamide resin, epoxy resin, Examples include xylene resins and silicone resins. These resins may be used alone or in combination.

Examples of the binder resin used when the toner base particles are produced by a polymerization method include vinyl polymerizable monomers capable of radical polymerization. Examples include styrene, styrene derivatives, acrylic polymerizable monomers, methacrylic polymerizable monomers, vinyl esters, vinyl ethers, vinyl ketones, and the like. These resins may be used alone or in combination of two or more.

As the monomer, a polymerizable monomer having an acidic group (hereinafter sometimes simply referred to as an acidic monomer), a polymerizable monomer having a basic group (hereinafter simply referred to as a basic monomer) Any polymerizable monomer having no acidic group or basic group (hereinafter sometimes referred to as other monomer) can be used.
Among the above-described polymerization methods, when the toner mother particles are produced using the emulsion polymerization aggregation method, in the emulsion polymerization step, the polymerizable monomer is usually polymerized in an aqueous medium in the presence of an emulsifier. At this time, when supplying the polymerizable monomer to the reaction system, each monomer may be added separately, or a plurality of types of monomers may be mixed in advance and added simultaneously. The monomer may be added as it is, or may be added as an emulsion mixed and adjusted in advance with water or an emulsifier.

  As the acidic monomer, a polymerizable monomer having a carboxyl group such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, cinnamic acid, a polymerizable monomer having a sulfonic acid group such as sulfonated styrene, Examples thereof include polymerizable monomers having a sulfonamide group such as vinylbenzenesulfonamide. Examples of the basic monomer include aromatic vinyl compounds having an amino group such as aminostyrene, nitrogen-containing heterocyclic-containing polymerizable monomers such as vinylpyridine and vinylpyrrolidone, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, etc. And (meth) acrylic acid ester having an amino group. These acidic monomers and basic monomers may be used singly or as a mixture of a plurality of types, and may exist as a salt with a counter ion. Among these, it is preferable to use an acidic monomer, more preferably acrylic acid and / or methacrylic acid.

The total amount of the acidic monomer and the basic monomer in 100 parts by mass of the total polymerizable monomer constituting the binder resin is usually 0.05 parts by mass or more, preferably 0.5 parts by mass or more. Especially preferably, it is 1.0 mass part or more. Further, it is usually 10 parts by mass or less, preferably 5 parts by mass or less.
Examples of other polymerizable monomers include styrenes such as styrene, methylstyrene, chlorostyrene, dichlorostyrene, p-tert-butylstyrene, pn-butylstyrene, and pn-nonylstyrene, methyl acrylate, Acrylic esters such as ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n methacrylate -Methacrylic acid esters such as butyl, isobutyl methacrylate, hydroxyethyl methacrylate, 2-ethylhexyl methacrylate, acrylamide, N-propylacrylamide, N, N-dimethylacrylamide, N, N-dipropylacrylic De, N, N-dibutyl acrylamide, and the like, the polymerizable monomer may be used singly, or may be used in combination.

  Furthermore, when the binder resin is a cross-linked resin, a polyfunctional monomer having radical polymerizability is used together with the above polymerizable monomer, for example, divinylbenzene, hexanediol diacrylate, ethylene glycol dimethacrylate, Examples include diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, and diallyl phthalate. It is also possible to use a polymerizable monomer having a reactive group in a pendant group, such as glycidyl methacrylate, methylol acrylamide, acrolein and the like. Among these, radically polymerizable bifunctional polymerizable monomers are preferable, and divinylbenzene and hexanediol diacrylate are particularly preferable. These polyfunctional polymerizable monomers may be used alone or as a mixture of plural kinds.

When the binder resin is polymerized by an emulsion polymerization aggregation method, a known surfactant can be used as an emulsifier. As the surfactant, one or more surfactants selected from cationic surfactants, anionic surfactants, and nonionic surfactants can be used in combination.
Examples of the cationic surfactant include dodecyl ammonium chloride, dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, hexadecyl trimethyl ammonium bromide, and examples of the anionic surfactant include And fatty acid soap such as sodium stearate and sodium dodecanoate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate and the like. Nonionic surfactants include, for example, polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene sorbitan monooleate ether, monodecanoyl sucrose, etc. Is mentioned.

  The amount of the emulsifier used in the production of the toner base particles using the emulsion polymerization aggregation method is not particularly limited, but is preferably 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the polymerizable monomer. . In addition, these emulsifiers can be used as protective colloids, for example, one or more of partially or completely saponified polyvinyl alcohols such as polyvinyl alcohol and cellulose derivatives such as hydroxyethyl cellulose.

The volume average particle diameter of the polymer primary particles obtained by the emulsion polymerization aggregation method is usually 0.02 μm or more, preferably 0.05 μm or more, particularly preferably 0.1 μm or more. Further, it is usually 3 μm or less, preferably 2 μm or less, particularly preferably 1 μm or less. If the particle size is too small, it may be difficult to control the aggregation rate in the aggregation process. If it is too large, the particle size of the toner particles obtained by aggregation tends to be large, and a toner having the target particle size is obtained. May be difficult.

  When the toner base particles are produced using the emulsion polymerization aggregation method, a known polymerization initiator can be used as necessary, and the polymerization initiators can be used alone or in combination of two or more. For example, persulfates such as potassium persulfate, sodium persulfate, ammonium persulfate, and the like, and redox initiators combining these persulfates as a component with a reducing agent such as acidic sodium sulfite, hydrogen peroxide, 4,4 Water-soluble polymerization initiators such as' -azobiscyanovaleric acid, t-butyl hydroperoxide, cumene hydropeoxide, etc., and these water-soluble polymerization initiators as a component combined with a reducing agent such as ferrous salt Redox initiator systems, benzoyl peroxide, 2,2′-azobis-isobutyronitrile, and the like are used. These polymerization initiators may be added to the polymerization system before, simultaneously with the addition of the monomer, or after the addition, and these addition methods may be combined as necessary.

  In the case of producing toner base particles using the emulsion polymerization aggregation method, a known chain transfer agent can be used as necessary. Specific examples include t-dodecyl mercaptan, 2-mercaptoethanol, diisopropylxanthogen. , Carbon tetrachloride, trichlorobromomethane and the like. The chain transfer agent may be used alone or in combination of two or more, and is used in an amount of 0 to 5% by mass based on the polymerizable monomer.

  In the case of producing toner base particles using an emulsion polymerization aggregation method, a known suspension stabilizer can be used as necessary. Specific examples of the suspension stabilizer include calcium phosphate, magnesium phosphate calcium hydroxide, magnesium hydroxide and the like. These may be used alone or in combination of two or more. The suspension stabilizer is usually used in an amount of 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the polymerizable monomer.

Both the polymerization initiator and the suspension stabilizer may be added to the polymerization system at any time before, simultaneously with, or after the addition of the polymerizable monomer. You may combine.
In addition, a pH adjuster, a polymerization degree adjuster, an antifoaming agent, and the like can be appropriately added to the reaction system.

The toner of the present invention may contain wax for imparting releasability. Any wax can be used as long as it has releasability.
Specifically, for example, olefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene and copolymer polyethylene, paraffin waxes, ester waxes having a long chain aliphatic group such as behenyl behenate, montanate ester, stearyl stearate, etc. , Plant waxes such as hydrogenated castor oil, carnauba wax, ketones having long chain alkyl groups such as distearyl ketone, silicones having alkyl groups, higher fatty acids such as stearic acid, long chain aliphatic alcohols such as eicosanol, glycerin, Examples thereof include carboxylic acid esters of polyhydric alcohols obtained from polyhydric alcohols such as pentaerythritol and long chain fatty acids, or higher fatty acid amides such as partial esters, oleic acid amides and stearic acid amides, and low molecular weight polyesters.

  Among these waxes, in order to improve fixability, the melting point of the wax is usually 30 ° C. or higher, preferably 40 ° C. or higher, and particularly preferably 50 ° C. or higher. Moreover, it is 100 degrees C or less normally, 90 degrees C or less is more preferable, and 80 degrees C or less is especially preferable. If the melting point is too low, the wax may be exposed on the surface after fixing, and stickiness may occur. On the other hand, if the melting point is too high, the fixability at low temperatures may be poor.

  As the wax compound species, higher fatty acid ester waxes are preferable. Specific examples of higher fatty acid ester waxes include behenyl behenate, stearyl stearate, stearates of pentaerythritol, montanic acid glycerides, etc. Esters are preferred. Moreover, as an alcohol component which comprises ester, a C1-C30 thing is preferable in the case of monohydric alcohol, and a C3-C10 thing is preferable in the case of a polyhydric alcohol.

The above waxes may be used alone or in combination. Further, the melting point of the wax compound can be appropriately selected depending on the fixing temperature for fixing the toner.
In the present invention, when the wax is contained, the amount of the wax is not particularly limited, but is usually 1 part by mass or more, preferably 2 parts by mass or more, particularly preferably 5 parts by mass with respect to 100 parts by mass of the toner. Or more. Moreover, it is 40 mass parts or less normally, Preferably it is 35 mass parts or less, Most preferably, it is 30 mass parts or less. If the wax content in the toner is too low, performance such as high-temperature offset may not be sufficient, while if it is too high, the blocking resistance may not be sufficient, or the wax may leak from the toner and contaminate the device. Sometimes.

  A known colorant can be arbitrarily used as the colorant of the present invention. Specific examples of colorants include carbon black, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa yellow, rhodamine dyes, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallylmethane dye, monoazo, Any known dyes and pigments such as disazo dyes and condensed azo dyes can be used alone or in combination. In the case of a full color toner, it is preferable to use benzidine yellow for yellow, monoazo and condensed azo dyes, magenta for quinacridone and monoazo dyes, and cyan for phthalocyanine blue. The colorant is preferably used so as to be 3 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the polymer primary particles.

  The blending of the colorant in the emulsion polymerization aggregation method is usually performed in an aggregation step. A dispersion of polymer primary particles and a dispersion of colorant particles are mixed to form a mixed dispersion, which is then aggregated to form a particle aggregate. The colorant is preferably used in the state of being dispersed in water in the presence of an emulsifier, and the volume average particle size of the colorant particles is usually 0.01 μm or more, preferably 0.05 μm or more. Further, it is usually 3 μm or less, preferably 1 μm.

  In the present invention, a charge control agent may be used as necessary. When the charge control agent is used, any known one can be used alone or in combination. For example, azine series such as quaternary ammonium salt, nigrosine, processed nigrosine, and alkyl nigrosine as a positive charge control agent. Examples include black dyes, processed nigrosine compounds, guanidine compounds, triphenylsulfonium compounds, resin-based charge control agents, amide group-containing compounds, and basic / electron-donating metal substances. Aromatic oxycarboxylics as negatively chargeable charge control agents Acid-based, aromatic dicarboxylic acid metal chelates, monoazo metal-containing complex compounds, organic acid metal salts, metal-containing dyes, diphenylhydroxy complex compounds, iron-containing azo compounds, home appliance control agents for emulsion polymerization, various metal oxycarboxylic acids Complex compounds, calixarene compounds, phenolic compounds, resin-based charge control agents, naphtha Lumpur compounds and their metal salts, urethane compounds, and acidic or electron-withdrawing organic substances.

In addition, when the toner of the present invention is used as a toner other than a black toner in a color toner or a full color toner, it is preferable to use a charge control agent that is colorless or light-colored and does not impair the color tone of the toner. As a charge control agent, a quaternary ammonium salt compound, as a negative charge control agent, a metal salt with zinc or aluminum of salicylic acid or alkylsalicylic acid, a metal complex, a metal salt of benzylic acid, a metal complex, an amide compound, Preference is given to hydroxynaphthalene compounds such as phenolic compounds, naphthol compounds, phenolamide compounds, and 4,4′-methylenebis [2- [N- (4-chlorophenyl) amide] -3-hydroxynaphthalene].

  In the toner of the present invention, when a charge control agent is contained in the toner using an emulsion polymerization aggregation method, the charge control agent is added together with a polymerizable monomer or the like at the time of emulsion polymerization, or polymer primary particles and a colorant. Or the like in the agglomeration step, or after the polymer primary particles and the colorant are agglomerated to almost the target particle size. Among these, it is preferable to disperse the charge control agent in water using a surfactant and add it to the aggregation step as a dispersion having a volume average particle size of 0.01 μm or more and 3 μm or less.

In the emulsion polymerization aggregation method, the aggregation is usually carried out in a tank equipped with a stirrer, but there are a heating method, a method of adding an electrolyte, and a method of combining them. When polymer primary particles are agglomerated with stirring to obtain particle aggregates of the desired size, the particle size of the particle aggregates is controlled based on the balance between the agglomeration force between the particles and the shearing force due to agitation. However, the cohesive force can be increased by heating or adding an electrolyte. In the present invention, the electrolyte in the case where the electrolyte is added and agglomerated may be either an organic salt or an inorganic salt. Specifically, NaCl, KCl, LiCl, Na2SO4, K2SO4, Li2SO4, MgC
l2, CaCl2, MgSO4, CaSO4, ZnSO4, Al2 (SO4) 3, Fe2 (SO4) 3, CH3COONa, C6H5SO3Na and the like. Of these, inorganic salts having a divalent or higher polyvalent metal cation are preferred.

  In the toner of the present invention, the amount of electrolyte added varies depending on the type of electrolyte, target particle size, etc., but is usually 0.05 parts by mass or more with respect to 100 parts by mass of the solid component of the mixed dispersion. .1 part by mass or more is preferable. Moreover, it is 25 mass parts or less normally, 15 mass parts or less are preferable, and especially 10 mass parts or less are preferable. If the addition amount is too small, the progress of the agglutination reaction is delayed, and fine powders of 1 μm or less remain even after the agglomeration reaction, and the average particle size of the obtained particle aggregate may not reach the target particle size. On the other hand, if the amount is too large, rapid aggregation tends to occur and it is difficult to control the particle size, and the resulting aggregated particles may include problems such as inclusion of coarse powder or irregular shapes. The aggregation temperature in the case of performing aggregation by adding an electrolyte is usually 20 ° C. or higher, preferably 30 ° C. or higher. Moreover, it is 70 degrees C or less normally, Preferably it is 60 degrees C or less.

The aggregation temperature in the case of performing aggregation only by heating without using an electrolyte is usually (Tg-20) ° C. or higher, preferably (Tg-10) ° C. or higher, where Tg is the glass transition temperature of the polymer primary particles. . Moreover, it is below Tg normally and is below (Tg-5) degreeC.
The time required for agglomeration is optimized depending on the shape of the apparatus and the processing scale, but in order for the toner particle size to reach the target particle size, it is usually held at the predetermined temperature for at least 30 minutes. desirable. The temperature rise until reaching the predetermined temperature may be raised at a constant rate, or may be raised stepwise.

If necessary, particles having adhered or fixed resin particles may be formed on the surface of the particle aggregate after the above-described aggregation treatment. In some cases, the chargeability and heat resistance of the obtained toner can be improved by attaching or fixing the resin particles whose properties are controlled to the surface of the particle aggregate, and the effect of the present invention can be further enhanced. .
When resin particles having a glass transition temperature higher than that of the polymer primary particles are used as the resin particles, it is preferable because blocking resistance can be further improved without impairing fixing properties. The volume average particle diameter of the resin particles is usually 0.02 μm or more, preferably 0.05 μm or more. Moreover, it is 3 micrometers or less normally, and 1.5 micrometers or less are preferable. As the resin particles, those obtained by emulsion polymerization of monomers similar to the polymerizable monomers used for the above-mentioned polymer primary particles can be used.

Resin particles are usually used as a dispersion dispersed in water or a liquid mainly composed of water with a surfactant. However, when a charge control agent is added after the aggregation treatment, charge control is performed on the dispersion containing particle aggregates. It is preferable to add the resin particles after adding the agent.
In order to increase the stability of the particle aggregate obtained in the aggregation step, it is preferable to perform fusion in the aggregated particles in the aging step after the aggregation step. The temperature of the aging step is usually at least Tg of the polymer primary particles, preferably at least 5 ° C higher than Tg, and usually at most 80 ° C higher than Tg, preferably at most 50 ° C higher than Tg. The time required for the aging step varies depending on the shape of the target toner, but after reaching the glass transition temperature or higher of the polymer primary particles, it is usually held for 0.1 to 10 hours, preferably 1 to 6 hours. Is desirable.

  In addition, it is preferable to add a surfactant or raise the pH value after the aggregation process, preferably before the aging process or during the aging process. As the surfactant used here, one or more emulsifiers can be selected from the emulsifiers that can be used when producing the polymer primary particles. In particular, the emulsifiers used when producing the polymer primary particles. It is preferable to use the same. The addition amount in the case of adding the surfactant is not limited, but is usually 0.1 parts by mass or more, preferably 1 part by mass or more, particularly preferably 3 parts by mass or more with respect to 100 parts by mass of the solid component of the mixed dispersion. It is. Moreover, it is 20 mass parts or less normally, Preferably it is 15 mass parts or less, Most preferably, it is 10 mass parts or less. After the aggregation process, before the completion of the ripening process, by adding a surfactant or raising the pH value, it is possible to suppress aggregation of the particle aggregates aggregated in the aggregation process, In some cases, the generation of coarse particles can be suppressed.

  By heat treatment in the aging step, the polymer primary particles in the aggregate are fused and integrated, and the toner particle shape as the aggregate becomes close to a spherical shape. The particle aggregate before the aging step is considered to be an aggregate due to electrostatic or physical aggregation of the polymer primary particles, but after the aging step, the polymer primary particles constituting the particle aggregate are fused to each other. In addition, the shape of the toner particles can be made nearly spherical. According to such an aging process, by controlling the temperature and time of the aging process, the shape of the polymer primary particles is agglomerated, a potato type with advanced fusion, a spherical form with further fusion For example, various shapes of toner can be manufactured according to the purpose.

The obtained particles are subjected to solid-liquid separation by a known method, the particles are collected, and washed and dried as necessary to obtain target toner mother particles.
<External addition process>
The toner of the present invention can be obtained by externally adding at least composite particles to the surface of the toner mother particles. May be used together and added to the toner base particles to adhere to or adhere to the surface of the toner base particles.

  Examples of the “other particles” include inorganic particles such as silica, titanium oxide, aluminum oxide (alumina), zinc oxide, tin oxide, barium titanate, strontium titanate, hydrotalcite, and the like. Organic acid salt particles such as zinc stearate and calcium stearate, methacrylate polymer particles, acrylate polymer particles, styrene-methacrylate copolymer particles, styrene-acrylate copolymer particles, etc. Examples thereof include resin particles.

The silica mentioned above as “other particles” will be described in detail.
At present, commercially available silica particles are difficult to control to a true specific gravity of 1.8 or less even with particles produced by a wet method without a firing step, and silica particles satisfying a true specific gravity of 1.9 or less were obtained. In some cases, the amount of water becomes high, and fogging may occur because the charge of the silica itself and the charge of the externally added toner become low due to excessive water.

  Even if the water content of silica particles at room temperature and normal humidity is 1% by mass or less, silica particles having a low true specific gravity and an internal surface area tend to absorb moisture in a high temperature and high humidity environment. In addition to lowering the charge of the silica particles themselves, the toner charge amount may change depending on the environment, so that there may be a problem of fogging in a high-temperature and high-humidity environment and image contamination due to charge-up in a low-temperature and low-humidity environment.

The method for producing the silica particles used in the present invention is not particularly limited and can be prepared by a known method, but from the viewpoint of the water content, those produced by a dry method are preferable. The dry method here refers to the entire production method by reaction in the gas phase, such as flame hydrolysis of a silicon compound, oxidation by a flame combustion method, or a combination of these reactions.
The silica particles used in the present invention are not particularly limited, but silica particles that have been subjected to a hydrophobic treatment on the surface are preferred from the viewpoint of environmental stability. The treatment agent and the treatment method are not particularly limited, and known ones are used. However, since higher hydrophobicity can be imparted, treatment with a silicone compound or a silicone treatment agent is performed, for example, hexamethyldisilazane, dimethylpolysiloxane. Examples include siloxane, dimethyldichlorosilane, methyltriethoxysilane, and octylsilane. Hexamethyldisilazane and dimethylpolysiloxane are preferred because higher hydrophobicity can be imparted, and dimethylpolysiloxane is particularly preferred.

  The blending ratio of the composite particles and “other particles” used in the present invention is not particularly limited, and the amount of all external additives composed of the composite particles and “other particles” is not particularly limited, but the toner base is not limited. The amount of all external additives used is usually 1.0 part by mass or more, preferably 1.1 parts by mass or more and 2.4 parts by mass or less, and more preferably 2.3 parts by mass or less with respect to 100 parts by mass of the particles. . If the amount used is too small, the coverage on the surface of the toner base particles decreases, and the wax in the vicinity of the surface may be fused to reduce the caking property (heat resistant storage stability) in a high temperature and high humidity environment. On the other hand, if the amount is too large, it may cause image defects due to missing of the cleaning blade due to excessive fluidity, and poor fixability due to suppression of exudation of wax from the toner inside. The coverage of the mother particle surface with the external additive is measured by the method described in the examples.

Regarding the “other particles” other than the composite particles used in the present invention, the order of adhering or fixing to the surface of the toner base particles is not particularly limited, but they may be used in combination with the composite particles or may be used together. It may be added.
In the present invention, the method for adhering or fixing the composite particles and “other particles” to the surface of the toner base particles is not particularly limited, and a mixer generally used for toner production can be used. Specifically, it is made by stirring and mixing with a mixer such as a Henschel mixer, a V-type blender, a Redige mixer, or a Q-mixer.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the following examples, “part” means “part by mass”, and “%” means “% by mass”.

<Measurement method of average particle diameter of polymer primary particles>
Nikkiso Co., Ltd., Model: Microtrac Nanotrac 150 (hereinafter abbreviated as “Nanotrack”), according to the instruction manual of NanoTrack, using its analysis software Microtrac Particle Analyzer Ver10.1.2.-019EE Using ion-exchanged water having a degree of 0.5 μS / cm as a dispersion medium, the measurement was performed by the method described in the instruction manual under the following conditions or by inputting the following conditions.
Solvent refractive index: 1.333
・ Measurement time: 100 seconds
・ Number of measurements: 1 time
-Particle refractive index: 1.59
・ Transparency: Transmission
・ Shape: Spherical shape
Density: 1.04

<Method for Measuring Volume Median Diameter (Dv50) of Toner Particles>
Use Beckman Coulter's Multisizer III (aperture diameter 100 μm) (hereinafter abbreviated as “Multisizer”), use the company's Isoton II as the dispersion medium, and disperse so that the dispersoid concentration is 0.03% by mass. And measured. The measurement particle diameter range is from 2.00 to 64.00 μm, and this range is discretized into 256 divisions so as to be equidistant on a logarithmic scale, and the volume calculated based on the statistical values on the basis of the volume is the volume. The median diameter (Dv50) was used.

<Measurement method of circularity>
In the present invention, the “average circularity” is determined by dispersing toner base particles in a dispersion medium (Isoton II, manufactured by Beckman Coulter, Inc.) so as to be in the range of 5720 to 7140 particles / μL. The measurement is performed under the following apparatus conditions using a company (former Toa Medical Electronics Co., Ltd., FPIA 3000), and the value is defined as “average circularity”. In the present invention, the same measurement is performed three times, and an arithmetic average value of three “average circularity” is adopted as the “average circularity”.
・ Mode: HPF
-HPF analysis amount: 0.35 μL
-Number of detected HPFs: 2000 to 2500 The following are measured by the above apparatus and automatically calculated and displayed in the above apparatus, but "circularity" is defined by the following equation.
[Circularity] = [Perimeter of a circle with the same area as the projected particle area] / [Perimeter of projected particle image]
And 2000-2500 which is the number of HPF detection is measured, and the arithmetic average (arithmetic mean) of the circularity of each individual particle is displayed on the apparatus as “average circularity”.

<Measuring method of average primary particle size of composite particles and silica particles>
In the present invention, the average primary particle size of the silica particles is determined by measuring the particle size of 2500 random particles from the silica fine particles and the inorganic particle sample on the transmission electron microscope image, and obtaining the average primary particle size by the number average. It was.

<Method for measuring average primary particle diameter of titanium oxide>
In the present invention, the average primary particle diameter of titanium oxide is a sphere equivalent diameter obtained from a measured BET specific surface area.

<Measurement method of charge amount>
In the present invention, the charge amount of the inorganic particles is measured under the following conditions.
Carrier at temperature 23 ° C and humidity 55%: F-150 core (Powdertech) 19.8g
Inorganic particles: 0.2g
Is placed in a 20 ml glass bottle and left for 12 hours or longer. Thereafter, the mixture is mixed 50 times by hand shaking and stirred for 1 minute at an amplitude of 1.0 cm and a shaking speed of 500 rpm.
0.2 g is taken out from the glass bottle and measured with the blow-off TB-200 apparatus manufactured by Toshiba Chemical under the following settings.
N2 pressure gauge: 1.0Kg / cm ²
SET TIME: 20.0sec
Wire mesh set on Faraday gauge (Stainless steel: 400 mesh)
The charge amount Q / M (μC / g) per unit mass can be obtained by calculating the read value Q (μC) by the following formula.
Q / M (μC / g) = − (Q (μC) / (measured mass (g)) × 100

<Method for measuring moisture content>
The moisture content is measured using Mitsubishi Chemical Analytech Co., Ltd.'s Quantitative Moisture Analyzers VA-100 and CA-100, using Aquamicron AX as the generation tank and Aquamicron CXU as the counter electrode tank. went. (Carrier gas: N ₂ 250 ml / min)
1.0 g of a sample was weighed on a medicine wrapping paper and placed in a glass container for a sample. The glass container was inserted into the heater of the apparatus and heated at 150 ° C. for 30 minutes, and the gas phase was introduced into the liquid tank to measure the amount of water.

<Measurement method of true specific gravity>
The true specific gravity was measured according to JIS-K-0061 5-2-1 using a Le Chatelier specific gravity bottle. The operation was performed as follows.
(1) About 250 ml of ethyl alcohol is put into a Lechatelier specific gravity bottle and adjusted so that the meniscus is at the position of the scale.
(2) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle. (Accuracy 0.025ml)
(3) About 100 g of a sample is weighed and its mass is set to W.
(4) Put the weighed sample in a specific gravity bottle to remove bubbles.
(5) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature becomes 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle. (Accuracy 0.025ml)
(6) The true specific gravity is calculated by the following formula.
D = W / (L2-L1)
S = D / 0.9982
In the formula, D is the density of the sample (20 ° C.) (g / cm ³ ), S is the true specific gravity of the sample (20 ° C.), W is the apparent mass of the sample (g), and L1 is before the sample is placed in the specific gravity bottle. Meniscus reading (20 ° C.) (ml), L2 is the meniscus reading (20 ° C.) (ml) after the sample is placed in the density bottle, 0.9982 is the density of water at 20 ° C. (g / cm ³ ) It is.

<Measurement of loose apparent density>
The loose apparent density is a density in a state where the toner is sieved off with a sieve and represents the fluidity of the toner. In the toner used in the present invention, the toner 15 [g] is put in a 50 [ml] graduated cylinder, the lid is put on, the hand is shaken 20 times, the lid is opened and the scale is read and measured for 10 minutes. The ratio to the amount of toner that was used was taken as the measured value of the loose apparent density. Note that the loose apparent density may not be measured under the above-mentioned conditions as long as it is obtained by the same principle.

[Manufacture of mother particle A]
<Preparation of wax / long-chain polymerizable monomer dispersion A1>
Paraffin wax (Nippon Seiki Co., Ltd., HNP-9) 27 parts, stearyl acrylate (Tokyo Kasei Co., Ltd.) 2.8 parts, 20% sodium dodecylbenzenesulfonate aqueous solution (Daiichi Kogyo Seiyaku Co., Ltd., Neogen S20D) 1.9 parts (abbreviated as “20% DBS aqueous solution”) and 68.3 parts of demineralized water were heated to 90 ° C. and stirred for 10 minutes using a homomixer (Mark IIf model manufactured by Tokushu Kika Kogyo Co., Ltd.). Next, this dispersion was heated to 90 ° C., and circulation emulsification was started under a pressure condition of 25 MPa using a homogenizer (manufactured by Gorin, 15-M-8PA type). A wax / long-chain polymerizable monomer dispersion A1 (emulsion solid content concentration = 30.2%) was prepared by dispersing until the diameter (MV) reached 250 nm.

<Preparation of silicone wax dispersion A2>
27 parts of alkyl-modified silicone wax (melting point: 77 ° C.), 1.9 parts of 20% DBS aqueous solution and 71.1 parts of demineralized water are placed in a stainless steel container and heated to 90 ° C. and homomixer (Mark IIf model, manufactured by Special Machine Industries Co., Ltd.) ) For 10 minutes. Next, this dispersion was heated to 99 ° C., and circulation emulsification was started under a pressure of 45 MPa using a homogenizer (manufactured by Gorin Co., Ltd., 15-M-8PA type). MV) was dispersed to 240 nm to prepare a silicone wax dispersion A2 (emulsion solid content concentration = 27.4%).

<Preparation of polymer primary particle dispersion A1>
35.6 parts of wax / long chain polymerizable monomer dispersion A1 and 259 parts of demineralized water are added to a reactor equipped with a stirrer (three blades), a heating / cooling device, a concentrating device, and each raw material / auxiliary charging device. Was heated to 90 ° C. under a nitrogen stream while stirring.
Thereafter, the following mixture of monomers and an aqueous emulsifier solution was added over 5 hours from the start of polymerization while stirring was continued. The time when the mixture of the monomers and the emulsifier aqueous solution was started to be dropped was set as the polymerization start, and the following initiator aqueous solution was added over 4.5 hours from 30 minutes after the start of the polymerization. The aqueous solution of the agent was added over 2 hours, and the internal temperature was maintained at 90 ° C. for 1 hour while continuing stirring.

[Monomers]
Styrene 76.8 parts Butyl acrylate 23.2 parts Acrylic acid 1.5 parts Trichlorobromomethane 1.0 part Hexanediol diacrylate 0.7 part
[Emulsifier aqueous solution]
20% DBS aqueous solution 1.0 part demineralized water 67.1 parts
[Initiator aqueous solution]
8% aqueous hydrogen peroxide solution 15.5 parts 8% L (+)-ascorbic acid aqueous solution 15.5 parts
[Additional initiator aqueous solution]
8% L (+)-ascorbic acid aqueous solution 14.2 parts After the completion of the polymerization reaction, the mixture was cooled to obtain a milky white primary polymer particle dispersion A1. The volume average particle diameter (MV) measured using a nanotrack was 280 nm, and the solid content concentration was 21.1%.

<Preparation of polymer primary particle dispersion A2>
In a reactor equipped with a stirrer (three blades), a heating / cooling device, a concentrating device, and a raw material / auxiliary charging device, 23.6 parts of silicone wax dispersion A2, 1.5 parts of 20% DBS aqueous solution, demineralized water 324 parts were charged, the temperature was raised to 90 ° C. under a nitrogen stream, and 3.2 parts of an 8% aqueous hydrogen peroxide solution and 3.2 parts of an 8% L (+)-ascorbic acid aqueous solution were added all at once with stirring.
5 minutes later, polymerization of the following mixture of monomers and emulsifier aqueous solution was started (from the time when 3.2 parts of 8% hydrogen peroxide aqueous solution and 3.2 parts of 8% L (+)-ascorbic acid aqueous solution were added all at once. After 5 minutes), the following initiator aqueous solution was added over 6 hours from the start of polymerization, and the internal temperature was maintained at 90 ° C. for 1 hour with further stirring.

[Monomers]
Styrene 92.5 parts Butyl acrylate 7.5 parts Acrylic acid 1.5 parts Trichlorobromomethane 0.6 parts
[Emulsifier aqueous solution]
20% DBS aqueous solution 1.5 parts demineralized water 66.2 parts
[Initiator aqueous solution]
8% aqueous hydrogen peroxide solution 18.9 parts 8% L (+)-ascorbic acid aqueous solution 18.9 parts After completion of the polymerization reaction, the mixture was cooled to obtain a milky white primary polymer particle dispersion A2. The volume average particle diameter (MV) measured using a nanotrack was 290 nm, and the solid content concentration was 19.0%.

<Preparation of Colorant Dispersion A>
In a container equipped with a stirrer (propeller blade), carbon black (Mitsubishi Chemical Corporation, Mitsubishi Carbon Black MA100S) 20 parts, 20% DBS aqueous solution 1 part, nonionic surfactant (Kao Corporation, Emulgen 120) 4 parts, 75 parts of ion-exchanged water having an electric conductivity of 2 μS / cm was added and predispersed to obtain a premix solution. The volume average diameter (Mv) of carbon black in the premix solution was 90 μm.
The premix solution was supplied to a wet bead mill and subjected to one-pass dispersion. The black colorant dispersion A is obtained by continuously supplying the premix slurry from the supply port at a constant supply speed by a non-pulsating metering pump and continuously discharging from the discharge port, with the rotation speed of the rotor being constant. Obtained. The volume average diameter (Mv) of the colorant in the colorant dispersion was 150 nm.

<Manufacture of mother particle A>
Polymer primary particle dispersion A1 95 parts as a solid content Polymer primary particle dispersion A2 5 parts as a solid content Colorant fine particle dispersion A 6 parts as a colorant solid content 20% DBS aqueous solution 0.1 parts as a solid content Using each component, mother particles were produced by the following procedure.

Polymer primary particle dispersion A1 and 20% DBS aqueous solution were charged into a mixer equipped with a stirrer (double helical blade), heating / cooling device, concentrating device, and each raw material / auxiliary charging device, and the internal temperature was 12 ° C. Mix evenly for minutes. Subsequently, while continuing stirring at an internal temperature of 12 ° C., 0.52 parts of 5% aqueous solution of ferrous sulfate as FeSO ₄ · 7H ₂ O was added over 5 minutes, and then the colorant fine particle dispersion A was added over 5 minutes. The mixture was uniformly mixed at an internal temperature of 12 ° C., and a 0.5% aqueous solution of aluminum sulfate was added dropwise under the same conditions (the solid content with respect to the resin solid content was 0.10 parts). Thereafter, the temperature was raised to 53 ° C. over 75 minutes, and further raised to 56 ° C. over 90 minutes. Here, when the volume median diameter was measured using a multisizer, it was 5.2 μm. Thereafter, the polymer primary particle dispersion A2 was added over 3 minutes and held for 60 minutes, followed by addition of 20% DBS aqueous solution (6 parts as solids) over 10 minutes and then over 90 minutes over 90 minutes. The temperature was raised to 0 ° C. and held for 75 minutes.

  Thereafter, the slurry obtained by cooling to 30 ° C. over 20 minutes was extracted, and suction filtration was performed with an aspirator using 5 types C (No5C manufactured by Toyo Roshi Kaisha, Ltd.) filter paper. The cake remaining on the filter paper was transferred to a stainless steel container equipped with a stirrer (propeller blade), and ion-exchanged water having an electric conductivity of 1 μS / cm was added and stirred to uniformly disperse, and then stirred for 30 minutes. .

  Then, suction filtration is performed with an aspirator again using filter paper of 5 types C (Toyo Filter Paper Co., Ltd. No5C), and the solid matter remaining on the filter paper is again equipped with a stirrer (propeller blade) and has an electric conductivity of 1 μS / cm. It moved to the container containing ion-exchange water, and it was made to disperse | distribute uniformly by stirring and was stirred for 30 minutes. When this process was repeated 5 times, the electrical conductivity of the filtrate was 2 μS / cm.

The cake obtained here was spread on a stainless pad so as to have a height of 20 mm, and dried in a blow dryer set at 40 ° C. for 48 hours to obtain mother particles A. The resulting toner base particle A had a volume median diameter of 5.7 μm and an average circularity of 0.972.
In Examples and Comparative Examples, the following silica particles A and B or composite particles A were used.
Silica particle A: The raw material is prepared by a wet method, and the surface is treated with hexamethyldisilazane. (Average primary particle size 30 nm, BET: 42.95 m ² / g, moisture content 0.04%, true specific gravity 2.2, negative chargeability)
Silica particle B: The raw material is prepared by a wet method, and the surface is treated with hexamethyldisilazane. (Average primary particle size 110 nm, BET: 27.81 m ² / g, moisture content 2.82%, true specific gravity 1.8, negative chargeability)
Composite particle A: Structure in which the surface of the core resin is reacted with silica in an aqueous solution (average primary particle size 100 nm, BET: 28.35 m ² / g, moisture content 2.51%, true specific gravity 1.2, Negative charging)

[Example 1]
<Manufacture of toner A>
0.5 parts of the silica particles A with respect to the base particles A (100 parts), titanium oxide (average primary particle diameter: 15 nm, BET: 91.0 m ² / g, charge amount: −30.4 μC / g) ) 0.6 parts, positively chargeable silica (average primary particle size 8 nm, BET: 118.8 m ² / g, charge amount: +509.
Toner A was obtained by adding 0.15 part of 3 μC / g) and further stirring and mixing with a Henschel mixer at 3000 rpm for 30 minutes and sieving.

[Example 2]
<Manufacture of toner B>
In Example 1, a toner B was obtained in the same manner as in Example 1 except that the addition amount of silica particles A, titanium oxide and positively charged silica was doubled.
[Comparative Example 1]
<Manufacture of toner C>
A toner C was obtained in the same manner as in Example 1 except that the silica particles B were used instead of the silica particles A in Example 1.

[Comparative Example 2]
<Manufacture of toner D>
In Example 1, a toner D was obtained in the same manner as in Example 1 except that the composite particle A was used instead of the silica particle A.
The details of the external additive formulations of Examples and Comparative Examples are shown in Table 1.

<Evaluation method>
The obtained toner was evaluated as follows.
Image quality (cleaning property) evaluation by live-action test Heat resistance evaluation by caking property (heat resistance storage) test was performed.
3. Evaluation of Fixability by External Fixing Tester Table 2 shows the evaluation results of 1-3.

<Evaluation method for cleaning properties>
For real-life tests, a full-color printer using a non-magnetic two-component contact development method, using an organic photoreceptor (OPC), roller charging, process speed 230 mm / second, tandem method, intermediate transfer method, thermal fixing method, blade drum cleaning method Was used.
After printing several sheets under an environment of 25 ° C. and 50%, printing was performed up to a total of 1,000 sheets of a total of 960 sheets of a 5% printing rate chart and 40 sheets of a 20% printing chart. A solid image was printed before the 1,000 sheets were printed, and the presence or absence of image defects such as white spots and streaks due to toner fluidity and chargeability was visually confirmed. Judgment criteria were as follows.
○: No image defect
Δ: Minor image defects are observed, but there is no problem in actual use. ×: Obvious image defects are observed, causing problems in actual use.

<Cover on printed matter>
The fog on the printed matter was evaluated as follows. That is, standard paper before and after printing (lightness 98, paper thickness 0.09mm, size A4)
The whiteness difference △ of Nippon Denshoku SE-6000 (standard light / viewing angle): C / 2, UV cut filt
er (with 420 nm)) was calculated. The paper cover was the average of two sheets.
Δ = delta Wb
Judgment criteria are as follows.
○: Paper fog less than 0.2 △: Paper fog 0.2 or more, less than 0.3 ×: Paper fog 0.3 or more

<Method of caking (heat resistance storage) test>
10 g of developing toner is put into a cylindrical container, a load of 20 g is put on it, left in an environment with a temperature of 50 ° C. and a humidity of 40% for 24 hours, the toner is taken out of the container, and a certain amount of load is applied from above to the cylinder. It was confirmed whether or not the shape of the formed toner collapsed. That is, as the material breaks down at a lower load, the caking property (heat resistant storage stability) becomes better.
Judgment criteria are as follows.
A: Less than 50 g when the toner collapses ○: Less than 110 g when the toner collapses ×: 110 g or more when the toner collapses

<Fixability test method>
a. Acquisition of Unfixed Image An unfixed image was acquired using a full-color printer using a non-magnetic one-component development method, an organic photoreceptor (OPC), roller charging, a tandem method, and a blade drum cleaning method. (Print area: 4.0 cm × 20.0 cm, adhesion amount: 26 to 30 mg / cm ² ). Note that letter paper (lightness 92, paper thickness 20 lb) was used as the fixing paper.

b. Image fixing and evaluation of fixability
For the unfixed image obtained in a., the fixing temperature is gradually decreased from 180 ° C to 130 ° C in 5 ° C increments using an external fixing device (fixing speed: 229mm / sec) equipped with a heat roll type fixing device. However, it was fixed on the paper at 162 rpm. The occurrence of offset was visually observed, and the temperature region where cold offset did not occur was examined.
Judgment criteria are as follows.
○: No offset occurs up to 130 ° C ×: Offset occurs in the region above 135 ° C

Claims (2)

A toner for developing electrostatic images, comprising at least a binder resin and a colorant, wherein the toner has core / shell type composite particles satisfying at least the following (A) to (C).
(A) Structure in which resin is used for the core and the outer shell is covered with inorganic particles
(B) Moisture content 2.8% by mass or less
(C) True specific gravity 0.7 or more and 2.0 or less The electrostatic image developing toner has toner base particles and external additives, and when n kinds of external additives are added, the coverage of the toner base particles by the external additive represented by the following formula (1) The electrostatic image developing toner according to claim 1, wherein the toner is 20% or more and 60% or less.

[In the above formula,
Dt represents the particle size (μm) of the toner base particles,
ρt represents the true specific gravity of the toner base particles,
D represents the maximum particle size (μm) of the external additive,
ρ represents the true specific gravity of the external additive,
W represents the number of added parts (parts by mass) of the external additive. ]