JP2019184794A - Electrostatic charge image developing toner and two component developer for electrostatic charge image development - Google Patents

Abstract

To provide an electrostatic charge image developing toner capable of suppressing excessive electrification, improving cleanability and forming a high definition image even during continuous printing, and a two component developer for electrostatic charge image development using the same.SOLUTION: An electrostatic charge image developing toner comprises: toner base particles including a binder resin; and toner particles including an external additive including strontium titanate fine particles (A) having 20 nm or more and 60 nm or less of the particle size Rof a peak top in number particle size distribution and strontium titanate fine particles (B) having more than 300 nm and 2000 nm or less of the particle size Rof a peak top in number particle size distribution and having a volume standard median size of 3.0 μm or more and 5.0 μm or less. The two component developer for electrostatic charge image development uses the electrostatic charge image developing toner.SELECTED DRAWING: None

Description

  The present invention relates to an electrostatic charge image developing toner and an electrostatic charge image developing two-component developer.

  In recent years, image forming apparatuses are required to have higher speed, higher image quality, and higher durability. Further, while the speed of each process for forming an image is accelerated, the life of each component constituting the apparatus is required to be extended from the viewpoint of high definition of the image and cost reduction.

  As means for achieving high image quality, reduction in the particle size of toner particles has been studied. The smaller the particle diameter of the toner particles, the better the reproducibility of the fine latent image. Further, since it is possible to conceal paper with a small amount of toner, it is possible to reduce energy required for fixing without lowering the image density.

  Also, in a general electrophotographic image forming system using a two-component developer, carrier particles and toner particles are mixed in a developing machine, and the toner particles are charged by friction to form a toner image on an image carrier. To do. That is, in the two-component developer, the function of the toner particles and the function of the carrier particles are separated. Therefore, the two-component developer is superior to the one-component developer containing the toner alone in that the controllability is high and a high-quality image can be easily obtained.

  However, since the specific surface area increases when the particle size of the toner particles is reduced, the contact area with the carrier particles tends to increase in the two-component developer, and the toner particles tend to be overcharged. Particularly in a low-temperature and low-humidity environment, the toner is difficult to develop on the image carrier due to overcharging, and is also difficult to transfer during transfer from the toner on the image carrier to the transfer material. May decrease.

  Further, the toner remaining on the image carrier without being transferred to the transfer material must be removed from the image carrier. As a method of cleaning the toner remaining on the image carrier, a method of bringing the edge of a cleaning blade made of an elastic material such as urethane rubber into contact with the surface of the image carrier is widely used. At this time, the cleaning blade is generally used with one edge thereof being pressed against the running direction of the image carrier in the counter direction. At this time, since the toner having a small particle diameter is likely to pass through the cleaning blade as described above, cleaning becomes very difficult.

  The phenomenon that toner particles having a small particle diameter pass through the cleaning blade is generally considered as follows. The toner particles having a small particle size collected at the edge (nip portion) of the cleaning blade have a large contact area with each other and have the same particle size, so that it is difficult to move over each other. As a result, it is likely to be in the closest packing state (a state in which there is no gap). Further, it is considered that the contact area with the surface of the image carrier increases, so that the adhesion force also increases, and the force that pushes up the cleaning blade as if it is one aggregate is exhibited, and the cleaning blade slips through. .

  As a method for improving the cleaning properties of the toner, Patent Document 1 describes a toner in which abrasive particles such as strontium titanate particles are added together with lubricant particles.

JP, 2006-186547, A

  However, even if the pressure contact force of the cleaning blade is increased by using abrasive particles as in Patent Document 1, the effect on cleaning cannot be expected so much. Rather, it is considered that defects such as the abrasive particles damaging the surface of the image carrier and reducing its life are likely to occur. Therefore, an electrostatic charge image developing toner and a developer having a small particle diameter, in which overcharging is suppressed, the image carrier is highly cleanable, and a high quality image can be formed even during continuous printing. Not yet reported.

  The present invention relates to a toner for developing an electrostatic charge image capable of suppressing excessive charging, improving cleaning properties, and forming a high-quality image even during continuous printing, and a two-component development for developing an electrostatic charge image using the same. It is an object to provide an agent.

The present invention provides, as a first means for solving the above problems, an electrostatic charge image developing toner including toner base particles including at least a binder resin and toner particles including an external additive including strontium titanate fine particles. The toner particles have a volume-based median diameter of 3.0 μm or more and 5.0 μm or less, and the strontium titanate fine particles have a peak top particle size _RA in a number particle size distribution of 20 nm or more and 60 nm or less. and strontium particles (a), the number particle size diameter R _B of the peak top in the distribution and a strontium titanate fine particles (B) is less than 2000nm exceed 300 nm, to provide a toner for developing electrostatic images.

  Furthermore, the present invention provides, as a second means for solving the above problems, a two-component developer for developing an electrostatic charge image, which contains the toner for developing an electrostatic charge image of the present invention and carrier particles.

  According to the present invention, toner for developing an electrostatic charge image capable of suppressing excessive charging, improving cleaning properties, and forming a high-quality image even during continuous printing, and two-component development for developing an electrostatic charge image using the same. An agent can be provided.

The toner of the present invention contains toner base particles containing at least a binder resin and an external additive containing strontium titanate fine particles. In the present invention, the strontium titanate fine particles contained in the external additive are the strontium titanate fine particles (A) having a peak top particle size _RA in the number particle size distribution of 20 nm to 60 nm, and the peak tops in the number particle size distribution. by the particle diameter R _B comprising at least two strontium titanate fine particles of strontium titanate fine particles is less than 2000nm exceed 300 nm (B), the excessive charging is suppressed, improved cleanability, during continuous printing In addition, it is possible to provide a toner for developing an electrostatic image capable of forming a high-quality image, and a two-component developer for developing an electrostatic image using the same. The mechanism is not clear, but is presumed as follows.

When the external additive contains strontium titanate fine particles (A) having a particle diameter _RA of 20 nm to 60 nm and having a small particle diameter, excessive charging of the toner is suppressed even when the toner particles are reduced in size. I found out that it could be done. This is presumably because a compound called strontium titanate has characteristics of low resistance and high positive chargeability. Further, since the particle diameter R _A strontium titanate fine particles (A) as small as 20nm or 60nm or less, increasing the contact area between the toner particles and carrier particles, the rise of charging would also be improved. Furthermore, since strontium titanate has a high positive chargeability, it is possible to improve the charge rise even with a small content. Therefore, problems such as an increase in toner fluidity due to the inclusion of many external additive particles having a small particle diameter (about 20 nm to 60 nm) and a corresponding decrease in the cleaning property are caused by the use of strontium titanate fine particles (A). Can be suppressed.

The particle diameter R _B to the external additive is less than 2000nm exceeded 300 nm, the include strontium titanate fine particles of the large particle diameter (B), to the toner base particles of strontium titanate small particle diameter (A) Can be suppressed, and a stable charge amount can be maintained even during continuous printing.

  Furthermore, it is considered that the strontium titanate fine particles (B) can improve the cleaning property and exhibit a polishing effect for removing deposits adhering to the surface of the image bearing member, thereby enabling the formation of a good image. Since the strontium titanate fine particles (B) having a large particle diameter are present in the outermost layer of the toner particles, a certain amount of particles are detached by the rubbing of the toner particles in the development process. The detached strontium titanate fine particles (B) retain the polarity (positive chargeability) opposite to that of the toner particles due to friction with the toner particles, and are developed in the non-image area in the developing process. The strontium titanate fine particles (B) developed in the non-image area remain on the electrostatic latent image carrier and are collected in the cleaning process, and selectively are in contact with the cleaning member and the electrostatic latent image carrier. accumulate. For the image portion, the strontium titanate fine particles (B) in the transfer residual toner particles remaining in the vicinity of the cleaning blade accumulate in the contact portion as described above. The strontium titanate fine particles (B) remaining in the non-image area and the image area and accumulated in the contact portion of the cleaning member and the electrostatic latent image carrier form a blocking layer that blocks toner leakage from the cleaning member. It is considered that the toner cleaning property can be improved by preventing the toner from slipping through.

  Further, the strontium titanate fine particles (B) accumulated as described above can also exhibit a polishing effect for removing filming and fusing by the toner adhering to the image carrier. This is considered to be because the Mohs hardness of strontium titanate has an appropriate hardness of 5-6. Since the accumulated strontium titanate fine particles (B) are present in both the image area and the non-image area, the image carrier can be uniformly polished.

  Therefore, by using at least two types of strontium titanates having different particle diameters, overcharge is suppressed, cleaning properties are improved, and an electrostatic charge image developing toner capable of forming a high-quality image even during continuous printing. And a two-component developer for developing an electrostatic image using the same.

  Embodiments of the present invention will be described below.

1. Toner for Developing an Electrostatic Charge Image The toner according to the exemplary embodiment contains toner base particles containing at least a binder resin and an external additive containing strontium titanate fine particles. The toner base particles are particles mainly composed of a binder resin and containing various additives such as a colorant, a release agent, an electric control agent, and a surfactant as necessary. First, the binder resin will be described.

1-1. Binder Resin As the binder resin constituting the toner base particles, it is preferable to use a thermoplastic resin.

  As such a binder resin, those generally used as the binder resin constituting the toner can be used without any particular limitation. Specific examples include styrene resins, acrylic resins, styrene acrylic copolymer resins, polyester resins, silicone resins, olefin resins, amide resins, and epoxy resins.

  Furthermore, in the present invention, the binder resin preferably contains an amorphous resin and a crystalline resin.

[Amorphous resin]
The amorphous resin that can be contained in the toner of the present invention constitutes a binder resin together with the crystalline resin. An amorphous resin is a resin that does not have a melting point and has a relatively high glass transition temperature (Tg) when differential scanning calorimetry (DSC) is performed on the resin.

  The glass transition temperature (Tg) of the resin can be measured using, for example, “Diamond DSC” (manufactured by Perkin Elmer). Enclose 3.0 mg of measurement sample (resin) in an aluminum pan, and set it in a sample holder of “Diamond DSC”. The reference uses an empty aluminum pan. Then, a first temperature raising process for raising the temperature from 0 ° C. to 200 ° C. at a temperature raising rate of 10 ° C./min, a cooling process for cooling from 200 ° C. to 0 ° C. at a cooling rate of 10 ° C./min, A DSC curve is obtained by the measurement conditions (temperature increase / cooling conditions) in which the second temperature increase process in which the temperature is increased from 0 ° C. to 200 ° C. in this order is performed in this order. Based on the DSC curve obtained by this measurement, the maximum between the rising line of the first peak and the peak peak before the rising of the first endothermic peak in the second temperature rising process and the peak peak. A tangent line indicating an inclination is drawn, and the intersection is defined as a glass transition temperature (Tg).

In DSC measurement, when the glass transition temperature in the _first temperature raising process is Tg ₁ and the glass transition temperature in the _second temperature raising process is Tg ₂ , fixing properties such as low-temperature fixability and heat-resistant storage stability From the viewpoint of reliably obtaining heat resistance, Tg ₁ of the amorphous resin is preferably 35 ° C. or higher and 80 ° C. or lower, and particularly preferably 45 ° C. or higher and 65 ° C. or lower. Further, from the same viewpoint as described above, Tg ₂ of the amorphous resin is preferably 20 ° C. or higher and 70 ° C. or lower, and particularly preferably 30 ° C. or higher and 55 ° C. or lower.

  The content of the amorphous resin is not particularly limited, but is preferably 20% by mass or more and 99% by mass or less with respect to the total amount of the toner base particles from the viewpoint of image strength. Further, the content of the amorphous resin is more preferably 30% by mass or more and 95% by mass or less, and particularly preferably 40% by mass or more and 90% by mass or less with respect to the total amount of the toner base particles. When two or more kinds of resins are included as the amorphous resin, the total amount thereof is preferably within the above-mentioned content range with respect to the total amount of the toner base particles. When an amorphous resin containing a release agent is used, the release agent in the amorphous resin is included in the content of the release agent constituting the toner.

  The amorphous resin used for the toner base particles according to the present invention is not particularly limited, and any conventionally known amorphous resin in this technical field can be used. Specific examples include styrene resins, vinyl resins, olefin resins, epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and the like. These resins may be used alone or in combination of two or more. As the amorphous resin, a polyester resin or a vinyl resin is preferable.

  The amorphous polyester resin is obtained by a polycondensation reaction between a divalent or higher carboxylic acid (polyvalent carboxylic acid) and a divalent or higher alcohol (polyhydric alcohol). There is no limitation in particular in the example of the polyhydric carboxylic acid and polyhydric alcohol used for preparation of an amorphous polyester resin. For example, as the polyvalent carboxylic acid, it is preferable to use unsaturated aliphatic polyvalent carboxylic acid, aromatic polyvalent carboxylic acid, and derivatives thereof. A saturated aliphatic polyvalent carboxylic acid may be used in combination as long as an amorphous resin can be formed. Moreover, polyvalent carboxylic acid may be used individually or in mixture of 2 or more types.

  As the polyhydric alcohol, it is preferable to use an unsaturated aliphatic polyhydric alcohol, an aromatic polyhydric alcohol, and derivatives thereof from the viewpoint of chargeability and toner strength, and if an amorphous resin can be formed, A saturated aliphatic polyhydric alcohol may be used in combination. The polyhydric alcohols may be used alone or in admixture of two or more.

  There is no particular limitation on the method for producing the amorphous polyester resin, and the resin is produced by polycondensation (esterification) of the polyvalent carboxylic acid and the polyhydric alcohol using a known esterification catalyst. Can do. About a reaction catalyst and reaction conditions, it is equivalent to the reaction conditions which can be used for manufacture of the crystalline polyester resin mentioned later.

  Moreover, it is preferable that an amorphous vinyl resin is included with an amorphous polyester resin. When the amorphous vinyl resin is contained in an amount of 0.1% by mass to 20% by mass with respect to the total mass of the binder resin, the surface of the toner particles has an appropriate hardness. Therefore, the toner base of the strontium titanate fine particles (A) It becomes difficult for the particles to be buried. Further, during continuous printing, the charge rising property is improved, and the image quality of the formed image is easily improved. Further, when the content of the amorphous vinyl resin is less than 20% by mass, the low-temperature fixability tends to be good.

  The amorphous vinyl resin may include the amorphous vinyl resin itself in the binder resin or may be included as a composite resin in which the amorphous vinyl resin component is hybridized.

  Examples of the amorphous vinyl resin include 1,8-octanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, and 1,11-undecane. Diol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate, 1,13-tridecanediol di (meth) acrylate, 1,14-tetradecanediol di (meth) acrylate, 1,15-pentadecanediol Di (meth) acrylate, 1,16-hexadecanediol di (meth) acrylate, 1,17-heptadecanediol di (meth) acrylate, 1,18-octadecanediol di (meth) acrylate, 1,19-nonadecanediol Di (meth) acrylate, 1,20-eicosane All di (meth) acrylate, 1,21-heneicosanediol di (meth) acrylate, 1,22-docosanediol di (meth) acrylate, 1,23-tricosanediol di (meth) acrylate, 1,24 Toteracosanediol di (meth) acrylate, 1,25-pentacosanediol di (meth) acrylate, 1,26-hexacosanediol di (meth) acrylate, 1,27-heptacosanediol di (meth) acrylate, 1, A polymer having structural units derived from monomers such as 28-octacosanediol di (meth) acrylate, 1,29-nonacosanediol di (meth) acrylate, and 1,30-triacontanediol di (meth) acrylate. is there. These monomers can be used alone or in combination of two or more. In the present specification, “(meth) acrylate” means “acrylate and / or methacrylate”.

  In addition to the above monomers, styrene monomers, (meth) acrylic acid ester monomers, vinyl esters, vinyl ethers, vinyl ketones, N-vinyl compounds, vinyl compounds, acrylic acid or methacrylic acid One or more acid derivatives may be used.

  The method for producing the amorphous vinyl resin is not particularly limited, and an arbitrary polymerization initiator such as a peroxide, a persulfide, a persulfate, an azo compound or the like usually used for the polymerization of the above monomer is used to form a lump. Examples of the polymerization method include a polymerization method, a solution polymerization method, an emulsion polymerization method, a miniemulsion method, and a dispersion polymerization method. A known chain transfer agent can be used for the purpose of adjusting the molecular weight. Examples of the chain transfer agent include alkyl mercaptans such as n-octyl mercaptan, mercapto fatty acid esters, and the like.

  The amorphous vinyl resin preferably has a glass transition temperature (Tg) of 25 to 70 ° C, more preferably 35 to 65 ° C. In addition, the glass transition temperature (Tg) of vinyl resin can be measured by the method mentioned above.

[Crystalline resin]
In the present invention, the toner particles preferably contain at least a crystalline polyester resin in order to increase the flexibility of the toner base particles and to easily fix the strontium titanate fine particles contained in the external additive. In addition, since the toner particles are easily dissolved by containing a crystalline polyester resin, it is preferable from the viewpoint of low-temperature fixability.

  In the present specification, “crystalline polyester resin” refers to a polyester resin having a clear endothermic peak in DSC rather than a stepwise endothermic change. Specifically, the clear endothermic peak means a peak in which the half-value width of the endothermic peak is within 15 ° C. when measured at a heating rate of 10 ° C./min in DSC. The melting point of the crystalline resin is an endothermic peak derived from the crystalline resin in the second temperature raising step based on the DSC curve obtained in the same manner as the glass transition temperature (Tg) of the amorphous resin. The temperature at the peak top of (an endothermic peak whose half width is within 15 ° C.) is defined as the melting point (Tc).

  The crystalline polyester resin can also be synthesized from a polyvalent carboxylic acid component and a polyhydric alcohol component.

  Examples of the polyvalent carboxylic acid component include oxalic acid, succinic acid, glutaric acid, adipic acid, speric acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, and dodecanedioic acid. (1,12-dodecanedicarboxylic acid), 1,14-tetradecanedicarboxylic acid, aliphatic dicarboxylic acid such as 1,18-octadecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid And aromatic dicarboxylic acids such as dibasic acids such as malonic acid and mesaconic acid. Furthermore, although these anhydrides and these lower alkyl esters are also mentioned, it is not limited to these. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and the like, and anhydrides thereof. And lower alkyl esters. These may be used individually by 1 type and may use 2 or more types together. Furthermore, in addition to the polyvalent carboxylic acid component, a dicarboxylic acid component having a double bond may be used. Examples of the dicarboxylic acid having a double bond include, but are not limited to, maleic acid, fumaric acid, 3-hexenedioic acid, and 3-octenedioic acid. In addition, these lower esters, acid anhydrides and the like are also included.

  On the other hand, the polyhydric alcohol component is preferably an aliphatic diol, and more preferably a linear aliphatic diol having a main chain portion having 7 to 20 carbon atoms. When the aliphatic diol is a linear type, the crystallinity of the polyester resin is maintained, and the decrease in the melting temperature is suppressed, so that the toner blocking resistance, the image storage stability, and the low-temperature fixability are excellent. Moreover, when the carbon number is 7 or more and 20 or less, the melting point when polycondensation with the polyvalent carboxylic acid component is kept low, and low-temperature fixing is realized, but the material is practically easily available. The number of carbon atoms in the main chain portion is more preferably 7 or more and 14 or less.

  Examples of the aliphatic diol suitably used for the synthesis of the crystalline polyester resin include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1, 7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1, Examples thereof include, but are not limited to, 14-tetradecanediol and 1,18-octadecanediol. These may be used individually by 1 type and may use 2 or more types together. Among these, considering availability, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferable. Examples of the trihydric or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. These may be used individually by 1 type and may use 2 or more types together.

  The crystalline polyester resin can be synthesized by a polycondensation reaction between a polyvalent carboxylic acid component and a polyhydric alcohol component in the presence of a polymerization catalyst such as dibutyltin oxide or tetrabutoxy titanate according to a conventional method.

  The reaction temperature in the polycondensation reaction is preferably 180 ° C. or higher and 230 ° C. or lower. If necessary, the reaction system is depressurized and reacted while removing water and alcohol generated by polycondensation. When the monomer is not dissolved or compatible at the reaction temperature, a solvent having a high boiling point may be added as a solubilizer and dissolved. In the polycondensation reaction, the dissolution auxiliary solvent is distilled off. In the case where a monomer having poor compatibility exists in the copolymerization reaction, it is preferable that the monomer having poor compatibility and the monomer and the acid or alcohol to be polycondensed are condensed in advance and then polycondensed together with the main component.

  The weight average molecular weight of the crystalline polyester resin is preferably 5,000 to 50,000. In addition, in this specification, the weight average molecular weight of crystalline polyester resin is a value measured by GPC, for example, can be measured with the following method.

  Using “HLC-8120GPC” (manufactured by Tosoh Corporation) as an apparatus and “TSKguardcolumn + TSKgelSuperHZ-M3 series” (manufactured by Tosoh Corporation) as a column, while maintaining the column temperature at 40 ° C., tetrahydrofuran (THF) is used as a carrier solvent at a flow rate. Run at 0.2 mL / min. As the measurement sample (resin), a solution dissolved in tetrahydrofuran so as to have a concentration of 1 mg / ml is used. The solution can be obtained by treating with an ultrasonic disperser at room temperature for 5 minutes and then treating with a membrane filter having a pore size of 0.2 μm. 10 μL of this sample solution is injected into the apparatus together with the above carrier solvent and detected using a refractive index detector (RI detector). The molecular weight distribution of the measurement sample is calculated based on a calibration curve created using monodisperse polystyrene standard particles.

<Other components (internal additives)>
The toner base particles used in the present invention may contain an internal additive such as a colorant, a release agent (wax), and a charge control agent in addition to the binder resin.

<Colorant>
As the colorant contained in the toner of the present invention, a known inorganic or organic colorant can be used. As the colorant, various organic or inorganic pigments and dyes can be used in addition to carbon black and magnetic powder.

  Examples of yellow colorants for yellow toner include C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, etc., and C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, etc. can be used, and mixtures thereof can also be used.

  As a magenta colorant for magenta toner, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, etc. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 122, 139, 144, 149, 166, 177, 178, 222, etc. can be used. Mixtures can also be used.

  As a cyan colorant for cyan toner, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc. I. Pigment Blue 1, 7, 7, 15: 3, 18: 3, 60, 62, 66, 76, etc. can be used.

  As a green colorant for green, C.I. I. Solvent Green 3, 5, 28, etc., C.I. I. Pigment Green 7 or the like can be used.

  As an orange colorant for orange toner, C.I. I. Solvent Orange 63, 68, 71, 72, 78, etc. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71, etc. can be used.

  As the colorant for black toner, carbon black, magnetic material, iron / titanium composite oxide black, etc. can be used, and as carbon black, channel black, furnace black, acetylene black, thermal black, lamp black, etc. It can be used. Moreover, ferrite, magnetite, etc. can be used as the magnetic material.

  The content ratio of the colorant is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 10% by mass or less with respect to the total mass of the toner. Within such a range, color reproducibility of the image can be ensured.

  The size of the colorant is preferably 10 nm to 1000 nm, 50 nm to 500 nm, and more preferably 80 nm to 300 nm in terms of volume average particle size (volume-based median diameter). The volume average particle diameter may be a catalog value. For example, the volume average particle diameter (volume-based median diameter) of the colorant is measured by “UPA-150” (manufactured by Microtrack Bell Co., Ltd.). can do.

<Release agent>
A release agent can be added to the toner according to the present invention. Examples of the release agent include polyethylene wax, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, dialkyl ketone wax such as distearyl ketone, carnauba wax, montan wax, behenyl behenate, behenate behenate, trimethylolpropane. Tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, Ester waxes such as tristearyl trimellitic acid and distearyl maleate, ethylenediamine dibehenylamide, tristearic acid trimester Such as amide-based waxes such as Ruamido the like. These can be used alone or in combination of two or more.

  The content of the release agent in the toner is preferably 2% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less with respect to the total mass of the toner.

<Charge control agent>
In addition, a charge control agent can be added (internally added) to the toner according to the present invention as necessary. Various known materials can be used as the charge control agent.

  As the charge control agent, various known compounds that can be dispersed in an aqueous medium can be used. Specific examples include nigrosine dyes, naphthenic acid or higher fatty acid metal salts, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts or metal complexes thereof.

  The content ratio of the charge control agent is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 5% by mass or less with respect to the total amount of the binder resin.

<Structure of toner base particles>
In addition, the structure of the toner base particles according to the present embodiment may be a single-layer structure including only the toner base particles described above, or the core particles and the surface thereof are covered using the toner base particles described above as core particles. A multilayer structure such as a core-shell structure including a shell layer may be used. The shell layer may not cover the entire surface of the core particle, and the core particle may be partially exposed. The cross section of the core-shell structure can be confirmed by known observation means such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM).

  In the case of the core / shell structure, the core particles and the shell layer can have different properties such as glass transition point, melting point, and hardness, and toner base particles can be designed according to the purpose. For example, a shell layer is formed by aggregating and fusing a resin with a relatively high glass transition point on the surface of core particles that contain a binder resin, a colorant, a release agent, etc., and a relatively low glass transition point. can do.

  In the toner of the present invention, it is preferable that the release agent is present in the vicinity of the toner particle surface in a state where it is not exposed on the toner particle surface from the viewpoint of suppressing fogging. For example, when the toner base particles contain a vinyl resin and the release agent contains an ester wax, the release agent is present in the vicinity of the vinyl resin, so the vinyl resin is also present in the vicinity of the surface of the toner particles. It is preferable. That is, the toner includes toner base particles having a laminated structure of at least two layers (inner layer and outer surface layer) and the outer layer (surface layer) includes a vinyl resin and a release agent including an ester wax. It is preferable. In this aspect, the outer layer may further contain an amorphous polyester resin as a main component. In order to further enhance the effects of the present invention, the vinyl resin domains are preferably dispersed in a matrix of an amorphous polyester resin.

  The average circularity of the toner base particles is preferably 0.935 to 0.995, more preferably 0.945 to 0.990, and still more preferably 0.955 to 0.980. If the average circularity is in such a range, the individual toner particles are not easily crushed, the charge amount is stable, and the image quality tends to be high. The average circularity can be measured using, for example, a flow particle image analyzer “FPIA-3000” (manufactured by Sysmex).

Specifically, the toner base particles are moistened in an aqueous surfactant solution and dispersed by performing ultrasonic dispersion for 1 minute, and then using “FPIA-2100” in the measurement condition HPF (high magnification imaging) mode. Measurement is performed at an appropriate concentration of 4000 HPF detections. The circularity is calculated by the following formula.
Circularity = (perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)
The average circularity is an arithmetic average value obtained by adding the circularity of each particle and dividing by the total number of particles measured.

1-2. External Additive The toner according to the present invention contains an external additive containing strontium titanate fine particles.

[Strontium titanate fine particles]
The strontium titanate fine particles used in the present invention include small strontium titanate fine particles (A) and large strontium titanate fine particles (B).

The peak top particle size _RA in the number particle size distribution of the strontium titanate fine particles (A) is 20 nm or more and 60 nm or less, and preferably 30 nm or more and 50 nm or less. If the particle diameter R _A strontium titanate fine particles (A) is 20nm or more, the fluidity of the toner is not too high, the cleaning property tends to be improved. Moreover, if the particle diameter _RA is 60 nm or less, the effect of suppressing excessive charging is easily exhibited.

Particle diameter _{R B} of a peak top in the number particle size distribution of strontium titanate fine particles (B) is 2000nm exceed 300nm or less, preferably 1500nm or less than 310 nm, and more preferably 350nm or more 1200nm or less. If the particle diameter R _B of strontium titanate fine particles (B) is more than 300 nm, by protecting the strontium titanate fine particles (A), it may improve image quality (density) in the endurance conditions. On the other hand, when the thickness is 2000 nm or less, the image carrier is not excessively worn, so that deterioration of the image quality under the durability condition is easily suppressed.

  In the present invention, the measurement method of the particle diameter of the strontium titanate fine particles varies depending on the shape.

The particle diameter of cubic or rectangular parallelepiped strontium titanate particles can be measured by the following method.
Using a scanning electron microscope (SEM) (for example, “JSM-7401F” manufactured by JEOL Ltd.), the external additive on the toner particle surface is observed at a magnification of 40000 times. The longest diameter and the shortest diameter of each particle are measured by image analysis of the primary particles of the external additive, and the intermediate value is set as the equivalent sphere diameter. Then, the number particle size distribution is obtained based on the measured particle diameter and number of 100 primary particles. Of the peaks present in the distribution, select the two largest peaks, the smaller peak value is the peak of the strontium titanate fine particles (A), and the larger peak is the peak of the strontium titanate fine particles (B). The particle diameter of the peak top is defined as the particle diameter of the strontium titanate particles.

The peak top particle diameter of amorphous strontium titanate particles can be measured by the following method.
Using a scanning electron microscope (SEM), a toner image is taken at a magnification of 5000 times. Next, energy dispersive X-ray analysis (EDS analysis) in the visual field is performed. At that time, elemental analysis of strontium and titanium is performed to determine strontium titanate particles. The SEM image in which strontium titanate is determined is binarized by an image processing analyzer (for example, “LUZEX AP” (manufactured by Nireco)). In a plurality of photographs, a horizontal ferret diameter for 100 strontium titanates is calculated, and a particle size distribution is obtained based on the horizontal ferret diameter and the number. Of the peaks present in the distribution, select the two largest peaks, the smaller peak value is the peak of the strontium titanate fine particles (A), and the larger peak is the peak of the strontium titanate fine particles (B). The horizontal ferret diameter at the peak top is defined as the particle diameter of the strontium titanate particles. Here, the horizontal ferret diameter is the length of a side parallel to the x axis of the circumscribed rectangle when the image of the external additive is binarized.
When the number average primary particle diameter of strontium titanate is small and exists as an aggregate on the toner surface, the particle diameter of the primary particles forming the aggregate is measured.

The particle diameter R _A strontium titanate fine particles (A) is not less 60nm or less, than the particle size R _B is 300nm strontium titanate fine particles (B), contains other strontium titanate fine particles as described further below In the embodiment, the particle diameter of 100 primary particles measured as described above is defined as strontium titanate fine particles (A) having a particle size of less than 200 nm and strontium titanate fine particles (B) having a particle size of 200 nm or more. the number average particle size are the respective average values, may be used in place of the particle diameter R _a and R _B is a peak top particle size.

  The shapes of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) used in the present invention are not limited, and may be any of a cubic shape, a rectangular parallelepiped shape, or an indefinite shape. However, it is preferable that one of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) has a cubic shape and / or a rectangular parallelepiped shape. If the particle shape of the strontium titanate fine particles (A) or strontium titanate fine particles (B) is a cubic shape and / or a rectangular parallelepiped shape, and the other is an indeterminate shape, further improvement in toner cleaning properties and polishing power is expected. .

  The shapes of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) can be confirmed by observation with a scanning electron microscope (SEM).

  In addition, when a plurality of types of strontium titanate fine particles having different shapes are present in one type of strontium titanate fine particles, the shape of the strontium titanate fine particles is the most abundant shape (for example, 100 confirmed particles The shape occupying more than 50 of them is the particle shape.

  The particle diameter and shape of the strontium titanate fine particles can be controlled by the production method. Next, the relationship between the manufacturing method and the shape will be described.

(Method for producing cubic and / or cuboid strontium titanate fine particles)
Cubic and / or cuboid strontium titanate fine particles are obtained by adding strontium hydroxide to a titania sol dispersion obtained by adjusting the pH of a hydrous titanium oxide slurry obtained by hydrolyzing a titanyl sulfate aqueous solution. It can be synthesized by heating to the reaction temperature. By setting the hydrous titanium oxide slurry to a pH of 0.5 or more and 1.0 or less, a titania sol having a good crystallinity and particle size can be obtained. For the purpose of removing ions adsorbed on the titania sol particles, it is preferable to add an alkaline substance such as sodium hydroxide to the titania sol dispersion. At this time, in order not to allow alkali metal ions or the like to be adsorbed on the surface of the hydrous titanium oxide, the slurry is preferably not adjusted to pH 7 or more. The reaction temperature is preferably 60 ° C. or more and 100 ° C. or less. In order to obtain a desired particle size distribution, the temperature rising rate is preferably 30 ° C./hour or less, and the reaction time is 3 hours or more and 7 hours or less. It is preferable.

As an example of the production method, a hydrous titanium oxide slurry obtained by hydrolysis from titanyl sulfate is washed with an alkaline aqueous solution. Next, hydrochloric acid is added to the resulting hydrous titanium oxide slurry to obtain a titania sol dispersion. NaOH is added to the titania sol dispersion to obtain hydrous titanium oxide. Sr (OH) ₂ .8H ₂ O is added to hydrous titanium oxide, nitrogen gas replacement is performed, and distilled water is added. The slurry is heated to 80 ° C. in a nitrogen atmosphere and reacted at 80 ° C. for 6 hours. After the reaction, the reaction mixture is cooled to room temperature, washed repeatedly, and then filtered and dried to obtain strontium titanate fine particles not passing through the sintering step. In this way, cubic and / or cuboid strontium titanate can be obtained by using a production method (wet method) that does not go through the firing step.

(Method for producing amorphous strontium titanate fine particles)
The amorphous strontium titanate fine particles can be obtained by a firing method through a firing step. For example, it can be produced by taking approximately equimolar amounts of strontium carbonate and titanium oxide, mixing them with a ball mill, etc., pressure forming, firing at 1000 ° C. or more and 1500 ° C. or less, and then classifying after mechanical pulverization. In addition, a shape, a particle size, etc. can be adjusted by changing suitably a raw material, raw material composition, a molding pressure, a calcination temperature, a grinding | pulverization, and a classification.

  Moreover, it is preferable that at least one of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) are lanthanum-containing strontium titanate fine particles. By doping strontium titanate fine particles with lanthanum, cubic and rectangular parallelepiped corners can be taken and the strontium titanate fine particles can be adjusted in sphere diameter. By using lanthanum-containing strontium titanate fine particles as an external additive, excessive wear and scratches on the surface of the electrostatic latent image carrier can be prevented.

  The lanthanum-containing strontium titanate fine particles can be produced, for example, using an aqueous lanthanum chloride solution or the like, as in the examples of the present application.

  Note that whether or not the strontium titanate fine particles contain lanthanum can be confirmed by fluorescent X-ray analysis (XRF). Specifically, the sample 3g can be pressurized and pelletized, and measurement can be performed by qualitative analysis using an X-ray fluorescence analyzer “XRF-1700” (manufactured by Shimadzu Corporation). The Kα peak angle of the element measured from the 2θ table can be determined and used for measurement.

  The content of the strontium titanate fine particles (A) is preferably 0.3 parts by mass or more and 3.0 parts by mass or less, and 0.5 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the toner base particles. More preferably. When the content of the strontium titanate fine particles (A) is 0.3 parts by mass or more, a sufficient excessive charge suppressing effect is easily achieved. Further, when the content is 3.0 parts by mass or less, there is little detachment from the toner base particles, and the effect of suppressing excessive charging under durable conditions is easily exhibited.

  The content of the strontium titanate fine particles (B) is preferably 0.3 parts by mass or more and 3.0 parts by mass or less, and 0.5 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the toner base particles. More preferably. When the content of the strontium titanate fine particles (B) is 0.3 parts by mass or more, the protective effect and cleaning properties for the strontium titanate fine particles (A) under the durability conditions are easily exhibited, and the abrasiveness of the image carrier Is good and the image quality is easily improved. Further, when the content is 3.0 parts by mass or less, the image carrier is appropriately polished, so that the durability of the image carrier tends to increase.

  As long as the effect of the use of the strontium titanate particles (A) and (B) is not impaired, the strontium titanate fine particles (A) and other strontium titanate particles having a particle diameter different from that of (B) are used as the external additive. 1 or more types may be included. The particle size of the peak top in the number particle size distribution of such other strontium titanate fine particles is not particularly limited, and may be smaller than the strontium titanate fine particles (A) or larger than the strontium titanate fine particles (B). The particle diameter may be that between the strontium titanate fine particles (A) and (B).

  Further, the external additive may contain inorganic fine particles, organic fine particles, and a lubricant other than the strontium titanate particles as long as the effect of the use of the strontium titanate fine particles (A) and (B) is not impaired.

  Examples of inorganic fine particles other than strontium titanate particles include silica particles, alumina particles, zirconia particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, tungsten oxide particles, tin oxide particles, tellurium oxide particles, Manganese oxide particles and boron oxide particles are included. The inorganic fine particles may be subjected to a hydrophobic treatment with a surface treatment agent such as a silane coupling agent or silicone oil, if necessary. Further, the size of the inorganic fine particles is preferably in the range of 20 to 500 nm, more preferably in the range of 70 to 300 nm in terms of number average primary particle diameter.

  For the organic fine particles, homopolymers such as styrene and methyl methacrylate, and organic fine particles of these copolymers can be used. The organic fine particles have a number average primary particle size of about 10 to 2000 nm, and the particle shape is, for example, spherical.

  The lubricant is used for the purpose of further improving cleaning properties and transfer properties. Examples of the lubricant include metal salts of higher fatty acids. More specifically, salts of zinc stearate such as zinc, aluminum, copper, magnesium, calcium; salts of zinc oleate, manganese, iron, copper, magnesium, etc .; zinc of palmitic acid, copper, magnesium, calcium, etc. Salts: Salts of linoleic acid such as zinc and calcium; Salts of ricinoleic acid such as zinc and calcium are included.

  The total amount of external additives contained in the toner (that is, the total content of strontium titanate particles (A) and (B), other inorganic fine particles, organic fine particles, and lubricant) is 100 parts by weight of toner base particles. It is preferably within the range of 0.05 parts by mass or more and 5.0 parts by mass or less.

1-3. Toner particles [Particle size of toner particles]
The volume-based median diameter of the toner particles according to the exemplary embodiment is 3.0 μm or more and 5.0 μm or less, and preferably 3.5 μm or more and 4.5 μm or less. If the volume-based median diameter of the toner is 3.0 μm or more, the cleaning property tends to be good, and if it is 5.0 μm or less, high image quality tends to be good.

  The volume-based median diameter can be controlled by the concentration of the aggregating agent used in the production, the addition amount of the organic solvent, the fusing time, the composition of the binder resin, and the like.

  The volume-based median diameter can be measured using a measuring apparatus in which a computer system equipped with data processing software Software V3.51 is connected to Multisizer 3 (manufactured by Beckman Coulter). Specifically, 0.02 g of a sample (toner particles) was added to 20 mL of a surfactant solution (for the purpose of dispersing toner particles, for example, a neutral detergent containing a surfactant component was diluted 10 times with pure water to obtain a surface activity. After adding and adhering to the agent solution, ultrasonic dispersion treatment is performed for 1 minute to prepare a dispersion of toner particles. The toner particle dispersion is injected into a beaker containing ISOTON II (manufactured by Beckman Coulter, Inc.) in a sample stand with a pipette until the display density of the measuring device is 8%. By using this concentration, a reproducible measurement value can be obtained. In the measurement apparatus, the measurement particle count is 25000, the aperture diameter is 100 μm, the frequency range is calculated by dividing the measurement range of 2 to 60 μm into 256, and the volume integrated fraction is 50% from the largest. Is determined as a volume-based median diameter.

[Method for producing toner particles]
The method for producing toner particles includes a step of producing toner base particles (hereinafter also referred to as “toner base particle production step”) and a step of adding an external additive to the surface of the toner base particles (hereinafter “external additive”). Also referred to as “agent addition step”). The method for producing the toner base particles is not limited, and examples thereof include known methods such as a kneading and pulverizing method, a suspension polymerization method, an emulsion aggregation method, a dissolution suspension method, a polyester elongation method, and a dispersion polymerization method.

  The external additive addition step can be performed before the drying step, but is preferably performed on the toner base particles that have undergone the drying step. The external additive is added by, for example, mixing the toner base particles and the external additive using various known mixing devices such as a Turbuler mixer, a Henschel mixer, a Nauter mixer, and a V-type mixer. be able to.

  The toner particles produced as described above contain, for example, a magnetic material and are used as a one-component magnetic toner. When the toner particles are mixed with a so-called carrier and used as a toner as a two-component developer, a non-magnetic toner is used alone. However, it is preferably used as a two-component developer.

2. Two-component developer for developing an electrostatic charge image The two-component developer for developing an electrostatic charge image according to this embodiment contains a toner for developing an electrostatic charge image and carrier particles.

2-1. Toner for developing an electrostatic image The toner according to the present invention is the toner for developing an electrostatic image of the present invention described above. That is, it contains toner base particles containing at least a binder resin and an external additive containing at least two types of strontium titanate fine particles having a specific particle diameter, and a volume-based median diameter of 3.0 μm or more and 5.0 μm or less. A toner containing toner particles.

2-2. Carrier particles The carrier particles according to the present invention include core material particles and a coating resin that covers the surface of the core material particles. It is preferable that the core particle surface is coated with a coating resin because of high image density stability in continuous printing. The coating includes a state in which carrier particles are partially coated with a coating resin.

  The exposed area ratio of the core particles on the surface of the carrier particles (hereinafter also simply referred to as the exposed area ratio) is not particularly limited, but is 10.0% or more and 18.0% or less with respect to the surface area of the core particles. Is preferred. When the exposed area ratio is 10.0% or more, the resistance value of the carrier particles does not become too high, and a high-quality image can be output after initial and continuous printing. When the exposed area ratio is 18.0% or less, adhesion of carrier particles to the electrostatic latent image carrier (electrophotographic photosensitive member) can be suppressed, and deterioration of image quality in continuous printing is suppressed.

  Measurement of the exposed portion of the core material particle on the surface of the carrier particle is obtained by measuring the coverage of the coating layer with respect to the core material particle by XPS measurement (X-ray photoelectron spectroscopy measurement) by the following method. As XPS measurement equipment, K-Alpha manufactured by Thermo Fisher Scientific was used, and measurement was performed using Al monochromatic X-ray as an X-ray source, acceleration voltage set to 7 kV, and emission current set to 6 mV. The main element (usually carbon) constituting the coating layer and the main element (usually iron) constituting the core particle are measured.

  Hereinafter, description will be made on the assumption that the core particles are iron oxide-based. Here, the C1s spectrum is measured for carbon, the Fe2p3 / 2 spectrum is measured for iron, and the O1s spectrum is measured for oxygen. Based on the spectrum of each of these elements, the number of elements of carbon, oxygen, and iron (represented as “AC”, “AO”, and “AFe”, respectively) is obtained, and the obtained carbon, oxygen, iron Based on the ratio of the number of elements, the iron content rate after the core material particles and the core material particles are coated with the coating layer (carrier) is obtained based on the following formula, and then the coverage is obtained by the following formula.

  The ratio of the exposed area of the core particles (%) = 100−coverage (%).

  When a material other than iron oxide is used as the core material particle, the spectrum of the metal element that constitutes the core material particle in addition to oxygen is measured, and the same calculation is performed according to the above formula to cover the core particle. A rate is required.

  The volume average particle diameter of the carrier particles is not particularly limited, but is preferably 15.0 μm or more and 28.0 μm or less, more preferably 20.0 μm or more and 25.0 μm or less. The volume average particle diameter of the carrier particles can be measured by the following method.

  The volume average particle diameter of the carrier particles can be measured by a wet method using a laser diffraction particle size distribution measuring device “HEROS KA” (manufactured by Nippon Laser Corporation). Specifically, first, an optical system with a focal position of 200 mm is selected, and the measurement time is set to 5 seconds. And the magnetic substance particle for a measurement is added to 0.2 mass% sodium dodecyl sulfate aqueous solution, and it disperse | distributes for 3 minutes using ultrasonic cleaner "US-1" (made by Asone), and produces the sample dispersion liquid for a measurement. Then, several drops are supplied to “HEROS KA”, and the measurement is started when the sample concentration gauge reaches the measurable region. With respect to the obtained particle size distribution, a cumulative distribution was created from the small diameter side with respect to the particle size range (channel), and the particle size (D50) at which accumulation was 50% was defined as the volume average particle size.

  Hereinafter, the core particles and the coating resin constituting the carrier particles will be described.

[Core particles]
Examples of the core particles include magnetic metals such as iron, copper, nickel, and cobalt, and magnetic metal oxides such as ferrite. Among these, from the viewpoint of durability, the core material particles are preferably ferrite.

Ferrite is a compound represented by the general formula: (MO) _x (Fe ₂ O ₃ ) _y , and the molar ratio y of Fe ₂ O ₃ constituting the ferrite is preferably 30 to 95 mol%. Since ferrite having a molar ratio y in such a range easily obtains desired magnetization, it has an advantage that carrier particles can be produced in which adhesion between carrier particles hardly occurs. Examples of M in the general formula include manganese (Mn), magnesium (Mg), strontium (Sr), calcium (Ca), titanium (Ti), copper (Cu), zinc (Zn), nickel (Ni), Metals such as aluminum (Al), silicon (Si), zirconium (Zr), bismuth (Bi), cobalt (Co), and lithium (Li) can be employed. These metal atoms can be used alone or in combination of two or more. Among these, manganese, magnesium, strontium, lithium, copper, and zinc are preferable, and manganese and magnesium are more preferable from the viewpoint of low residual magnetization and obtaining suitable magnetic characteristics. That is, the core particles according to the present invention are preferably ferrite particles containing at least one of manganese and magnesium. More preferably, the core material particle according to the present invention is a ferrite particle containing both manganese and magnesium. In this case, since it is easy to control the average magnetization of the carrier core material within a desired range, the content ratio of MnO is preferably 20 to 40 mol% with respect to the ferrite, and the content ratio of MgO is 7 to It is preferable to set it as 30 mol%.

  As the core particles, commercially available products may be used, or synthetic products may be used.

[Resin for coating]
As the coating resin, a resin containing a structural unit derived from an alicyclic (meth) acrylic acid ester is preferable. When the coating resin contains a structural unit derived from an alicyclic (meth) acrylic acid ester compound, it is possible to reduce the moisture adsorption amount of the carrier particles and the environmental difference in chargeability. As a result, a decrease in charge amount can be suppressed particularly in a high temperature and high humidity environment. Moreover, since the resin containing a structural unit derived from an alicyclic (meth) acrylic acid ester has an appropriate mechanical strength, the carrier particle surface is refreshed by being appropriately worn as a coating material. Also have.

  The alicyclic (meth) acrylic acid esters include cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, ( Dicyclopentanyl (meth) acrylate, cyclododecyl (meth) acrylate, methyl cyclohexyl (meth) acrylate, trimethyl cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, adamantyl (meth) acrylate, etc. Can be mentioned. Among these, the alicyclic (meth) acrylic acid ester is preferably a (meth) acrylic acid ester having a cycloalkyl ring having 3 to 8 carbon atoms, and (meth) acrylic because the above effects are more easily obtained. Cyclohexyl acid and cyclopentyl (meth) acrylate are more preferable, and cyclohexyl methacrylate is more preferable from the viewpoint of mechanical strength and environmental stability of charge amount. The alicyclic (meth) acrylic acid ester can be used alone or in combination of two or more.

  As the polymerization component, in addition to the alicyclic (meth) acrylic acid ester, other monomers copolymerizable with the alicyclic (meth) acrylic acid ester may be used. Examples of other monomers include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, p-chloro styrene, 3,4-dichloro styrene, p-phenyl styrene, p -Ethyl styrene, 2,4-dimethyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene Styrene compounds such as: methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, methacryl Lauryl acid, phenyl methacrylate, Methacrylic acid ester compounds such as benzyl crylate, isobornyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, acrylic Acrylic acid ester compounds such as isobutyl acid, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate and benzyl acrylate; olefin compounds such as ethylene, propylene and isobutylene; vinyl chloride, Vinyl halide compounds such as vinylidene chloride, vinyl bromide, vinyl fluoride, vinylidene fluoride; vinyl ester compounds such as vinyl propionate, vinyl acetate, vinyl benzoate; vinyl Vinyl ether compounds such as methyl ether and vinyl ethyl ether; Vinyl ketone compounds such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone; N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone; Vinyl naphthalene And vinyl compounds such as vinyl pyridine; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide. These other monomers can be used alone or in combination of two or more. Among these, from the viewpoint of mechanical strength and the environmental stability of the charge amount, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, (meth) It is preferable to use a chain (meth) acrylate such as hexyl acrylate, octyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, or styrene, and a chain (meth) acrylate is used. More preferred. It is preferable that carbon number of the alkyl group of chain | strand-type (meth) acrylic acid ester is 1-8. A copolymer of an alicyclic (meth) acrylic acid ester and a chain (meth) acrylic acid ester is preferable because the carrier surface is easily refreshed and is excellent in stress resistance in a developing machine.

  The amount of the structural unit derived from the alicyclic (meth) acrylic acid ester contained in the coating resin is preferably 50% by mass or more and 90% by mass or less, and 50% by mass with respect to the total mass of the coating resin. More preferably, it is more than 80 mass%. When the amount of the structural unit derived from the alicyclic (meth) acrylic acid ester is 50% by mass or more, the effect of the structural unit derived from the alicyclic (meth) acrylic acid ester compound described above is easily exhibited.

  There is no limitation in particular in the manufacturing method of coating resin, A conventionally well-known polymerization method can be utilized suitably. Examples thereof include a pulverization method, an emulsion dispersion method, a suspension polymerization method, a solution polymerization method, a dispersion polymerization method, an emulsion polymerization method, an emulsion polymerization aggregation method, and other known methods. In particular, from the viewpoint of controlling the particle diameter, it is preferable to synthesize by an emulsion polymerization method.

  There are no particular limitations on polymerization conditions such as polymerization initiators other than the monomers used in the emulsion polymerization method, surfactants, chain transfer agents used as necessary, polymerization temperature, etc., and conventionally known polymerizations An initiator, a surfactant, a chain transfer agent, and the like can be used, and polymerization conditions such as polymerization temperature can be adjusted by appropriately using conventionally known polymerization conditions.

  The weight average molecular weight of the coating resin (polymer obtained by polymerizing the above monomer) is not particularly limited, but is preferably 200,000 to 800,000, more preferably 300,000 to 700,000. If the weight average molecular weight of the coating resin is 200,000 or more, the wear of the resin coating layer formed from the coating resin on the surface of the core material particles is not promoted excessively, and it is difficult to cause adhesion of carrier particles. Are better. If the weight average molecular weight of the coating resin is 800,000 or less, a good charge amount can be maintained for a long time without causing a decrease in charge amount due to the transfer of the external additive from the toner particles to the carrier particle surfaces.

  The weight average molecular weight of the coating resin can be measured by the above-described method by the above-described gel permeation chromatography (GPC).

[Method for producing carrier particles]
Examples of a method for coating the surface of the core particle with a coating resin include a known wet coating method and a dry coating method, and any method can provide a resin coating layer. Moreover, it is preferable to carry out by a dry application method from the viewpoint that a solvent is not used, the environmental load is small, and the surface of the core material particles can be uniformly coated with the coating resin.

In the dry coating method, the exposed area of the core material of the carrier particles can be controlled by the stirring time during heating. The resin particles are adhered to the core material particles, and the mixture is stirred and mixed under heating to spread the fat and form a film. By extending the time, the spread progresses and the resin becomes thin, so that the exposed area increases. Direction. In order to make the exposed area of the core particles on the surface of the carrier particles 10% or more and 18% or less, the stirring time at the time of heating is preferably 30 to 70 minutes, and more preferably 40 to 60 minutes.

  The mixing ratio of the coating resin and the core particles is not particularly limited, but is preferably 1 to 10 parts by mass, and 2 to 6 parts by mass with respect to 100 parts by mass of the core particles. More preferably.

  The exposed area ratio of the core material particles on the carrier surface can be controlled, for example, by controlling the mixing time under heating after addition of the resin, the amount of coating resin added to the core material particles, and the like. If the mixing time under heating after resin addition is lengthened, the exposed area ratio tends to increase, and if the resin addition amount increases, the exposed area ratio tends to decrease.

2-3. Method for producing two-component developer for developing electrostatic image The two-component developer is usually composed of carrier particles and toner particles. The ratio of the toner particles to the total mass of the carrier particles and the toner particles is not particularly limited, but is usually 8.0% by mass or more and 10.0% by mass or less. When the ratio of the toner particles is within this range, the charge amount of the toner becomes appropriate, and the image quality after initial and continuous printing becomes better.

  The two-component developer can be produced by mixing carrier particles and toner particles using a mixing device. Examples of the mixing apparatus include a Henschel mixer, a Nauter mixer, and a V-type mixer.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely using an Example and a comparative example, this invention is not limited to a following example.

1. Preparation of amorphous polyester resin particle dispersion [Preparation of amorphous polyester resin]
Bisphenol A ethylene oxide 2.2 mol adduct: 40 mol parts Bisphenol A propylene oxide 2.2 mol adduct: 60 mol parts Dimethyl terephthalate: 60 mol parts Dimethyl fumarate: 15 mol parts Dodecenyl succinic anhydride: 20 mol parts Trimellitic anhydride: 5 mol part In a reaction vessel equipped with a stirrer, thermometer, condenser and nitrogen gas introduction tube, among the above monomers, monomers other than dimethyl fumarate and trimellitic anhydride, and tin dioctylate 0.25 part by mass was charged with respect to 100 parts by mass in total of the above monomers. After reacting at 235 ° C. for 6 hours under a nitrogen gas stream, the temperature was lowered to 200 ° C., and dimethyl fumarate and trimellitic anhydride were added and reacted for 1 hour. The temperature is raised to 220 ° C. over 5 hours, and polymerized so that the weight average molecular weight is 35,000 and the number average molecular weight is 8,000 under a pressure of 10 kPa, and a light yellow transparent amorphous polyester resin is obtained. Got.

  The amorphous polyester resin had a weight average molecular weight of 35,000, a number average molecular weight of 8,000, and a glass transition temperature (Tg) of 56 ° C.

[Preparation of Amorphous Polyester Resin Particle Dispersion]
200 parts by mass of the amorphous polyester resin obtained above, 100 parts by mass of methyl ethyl ketone, 35 parts by mass of isopropyl alcohol, and 7.0 parts by mass of a 10% by mass aqueous ammonia solution are placed in a separable flask and mixed thoroughly. Dissolved. Next, while heating and stirring at 40 ° C., ion-exchanged water was dropped at a liquid feeding speed of 8 g / min using a liquid feeding pump, and the dropping was stopped when the liquid feeding amount reached 580 parts by mass. Thereafter, the solvent was removed under reduced pressure to obtain an amorphous polyester resin particle dispersion. Ion exchange water was added to the dispersion to adjust the solid content to 25% by mass to prepare an amorphous polyester resin particle dispersion.

The volume-based median diameter (D ₅₀ ) of the amorphous polyester resin particles in the prepared dispersion was measured with Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 156 nm.

2. Preparation of Amorphous Vinyl Resin Particle Dispersion 5.0 mass of anionic surfactant (Dowfax, manufactured by Dow Chemical Co., Ltd.) in a 5 L reaction vessel equipped with a stirrer, temperature sensor, cooling pipe and nitrogen introduction device And 2500 parts by mass of ion-exchanged water were charged, and the internal temperature was raised to 75 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. Subsequently, a solution in which 18.0 parts by mass of potassium persulfate (KPS) was dissolved in 342 parts by mass of ion-exchanged water was added, and the liquid temperature was adjusted to 75 ° C. Furthermore, 903.0 parts by mass of styrene (St), 282.0 parts by mass of n-butyl acrylate (BA), 12.0 parts by mass of acrylic acid (AA), 3.0 parts by mass of 1,10-decanediol diacrylate and A monomer mixed solution consisting of 8.1 parts by mass of dodecanethiol was added dropwise over 2 hours. After completion of the dropwise addition, the mixture was polymerized by heating and stirring at 75 ° C. for 2 hours to obtain an amorphous vinyl resin dispersion. Ion exchange water was added to the dispersion to adjust the solid content to 25% by mass to prepare a dispersion of amorphous vinyl resin particles. The volume-based median diameter (D50) of the amorphous vinyl resin particles in this dispersion was measured with Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 160 nm.

  The amorphous vinyl resin had a glass transition temperature (Tg) of 52 ° C., a weight average molecular weight (Mw) of 38,000, and a number average molecular weight (Mn) of 15,000.

3. Preparation of crystalline polyester resin particle dispersion [Preparation of crystalline polyester resin]
Dodecanedioic acid: 50 mol parts 1,6-hexanediol: 50 mol parts The above monomer was placed in a reaction vessel equipped with a stirrer, thermometer, condenser and nitrogen gas introduction tube, and the inside of the reaction vessel was replaced with dry nitrogen gas. . Next, 0.25 parts by mass of titanium tetrabutoxide (Ti (On-Bu) ₄ ) was added with respect to a total of 100 parts by mass of the above monomers. After stirring and reacting at 170 ° C. for 3 hours under a nitrogen gas stream, the temperature was further raised to 210 ° C. over 1 hour, the pressure inside the reaction vessel was reduced to 3 kPa, and stirring was continued for 13 hours under reduced pressure. A crystalline polyester resin was obtained.

  The crystalline polyester resin had a weight average molecular weight of 25,000, a number average molecular weight of 8,500, and a melting point of 71.8 ° C.

[Preparation of crystalline polyester resin particle dispersion]
200 parts by mass of the crystalline polyester resin obtained above, 120 parts by mass of methyl ethyl ketone, and 30 parts by mass of isopropyl alcohol are placed in a separable flask, and are thoroughly mixed and dissolved at 60 ° C. Was added dropwise in an amount of 8 parts by mass. The heating temperature was lowered to 67 ° C., and the mixture was added dropwise with stirring using an ion exchange water delivery pump at a delivery rate of 8 g / min. When the delivery amount reached 580 parts by mass, the addition of ion exchange water was stopped. . Thereafter, the solvent was removed under reduced pressure to obtain a crystalline polyester resin particle dispersion. Ion exchange water was added to the dispersion to adjust the solid content to 25% by mass to prepare a crystalline polyester resin particle dispersion. The volume-based median diameter (D50) of the crystalline polyester resin particles in this dispersion was measured with Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 198 nm.

  The molecular weight, glass transition temperature (Tg) and melting point of the resin were measured by the following methods.

(Weight average molecular weight and number average molecular weight of resin)
The molecular weight (weight average molecular weight and number average molecular weight) of each resin by GPC was measured as follows. Using an apparatus “HLC-8120GPC” (manufactured by Tosoh Corporation) and a column “TSKguardcolumn + TSKgelSuperHZ-M3 series” (manufactured by Tosoh Corporation), while maintaining the column temperature at 40 ° C., tetrahydrofuran (THF) was used as a carrier solvent at a flow rate of 0. Flowed at 2 mL / min. The measurement sample (resin) was dissolved in tetrahydrofuran to a concentration of 1 mg / ml. The solution was prepared by treatment for 5 minutes at room temperature using an ultrasonic disperser. Next, a sample solution was obtained by processing with a membrane filter having a pore size of 0.2 μm, 10 μL of this sample solution was injected into the apparatus together with the carrier solvent, and detected using a refractive index detector (RI detector). The molecular weight distribution of the measurement sample was calculated based on a calibration curve created using monodisperse polystyrene standard particles. Ten polystyrenes were used for the calibration curve measurement.

(Glass transition temperature (Tg) and melting point)
The glass transition temperature (Tg) of the resin was measured using “Diamond DSC” (Perkin Elmer). First, 3.0 mg of a measurement sample (resin) was sealed in an aluminum pan and set in a sample holder of “Diamond DSC”. The reference used an empty aluminum pan. Then, a first temperature raising process for raising the temperature from 0 ° C. to 200 ° C. at a temperature raising rate of 10 ° C./min, a cooling process for cooling from 200 ° C. to 0 ° C. at a cooling rate of 10 ° C./min, and a temperature raising rate of 10 ° C./min. A DSC curve was obtained under the measurement conditions (temperature increase / cooling conditions) in which the second temperature increase process in which the temperature was increased from 0 ° C. to 200 ° C. per minute in this order. Based on the DSC curve obtained by this measurement, the maximum between the rising line of the first peak and the peak peak before the rising of the first endothermic peak in the second temperature rising process and the peak peak. A tangent line indicating an inclination is drawn, and the intersection is defined as a glass transition temperature (Tg).
The melting point of the crystalline resin is an endothermic peak derived from the crystalline resin in the second temperature raising process based on the DSC curve obtained in the same manner as described above (an endothermic peak having a half-value width of 15 ° C. or less). The peak top temperature of was taken as the melting point (Tc).

4). Preparation of release agent particle dispersion Paraffin wax (HNP0190 manufactured by Nippon Seiwa, melting temperature 85 ° C.): 270 parts by mass Anionic surfactant (Neogen RK manufactured by Daiichi Kogyo Seiyaku): 13.5 parts by mass ( 60% active ingredient, 3% for mold release agent)
Ion-exchanged water: 21.6 parts by mass After mixing the above materials and dissolving the paraffin wax with a pressure discharge type homogenizer (Gorin homogenizer, manufactured by Gorin) at an internal liquid temperature of 120 ° C., 120 at a dispersion pressure of 5 MPa. Dispersion treatment was performed for 360 minutes at 40 MPa, followed by cooling to obtain a dispersion. Ion exchange water was added to adjust the solid content to 20%, and this was used as a release agent particle dispersion (W1). The volume-based median diameter (D50) of the particles in the release agent particle dispersion was measured with Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 215 nm.

5. Preparation of Colorant Particle Dispersion Carbon Black (Regal (registered trademark) 330, manufactured by Cabot Corporation): 100 parts by weight Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku): 15 parts by weight Ion exchange water: 400 parts by weight Part After mixing the above components and pre-dispersing for 10 minutes with a homogenizer (Ultra Turrax, manufactured by IKA), using a high-pressure impact disperser ultimateizer (manufactured by Sugino Machine) for 30 minutes at a pressure of 245 MPa, An aqueous dispersion of black colorant particles was obtained. Ion exchange water was further added to the obtained dispersion to adjust the solid content to 15% by mass, thereby obtaining a black colorant particle dispersion. The volume-based median diameter (D50) of the colorant particles in this dispersion was measured using Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 110 nm.

6). Preparation of toner base particles [Preparation of toner base particles 1]
(Aggregation / fusion process and aging process)
Amorphous polyester resin particle dispersion: 1040 parts by weight Crystalline polyester resin particle dispersion: 160 parts by weight Release agent particle dispersion: 200 parts by weight Black colorant dispersion: 187 parts by weight Anionic surfactant (Dowfax2A1 20 % Aqueous solution): 40 parts by mass Ion-exchanged water: 1500 parts by mass The above initial raw materials are placed in a 4 liter reaction vessel equipped with a thermometer, pH meter and stirrer, the temperature is 25 ° C., and 1.0% nitric acid is added The pH was adjusted to 3.0. Thereafter, 100 parts by mass of a 2% concentration aqueous solution of aluminum sulfate (flocculating agent) was added dropwise over 30 minutes while dispersing the mixture at 3,000 rpm using a homogenizer (Ultra Turrax T50, manufactured by IKA). After completion of dropping, the mixture was stirred for 10 minutes to sufficiently mix the raw material and the flocculant.

Next, a stirrer and a mantle heater are installed in the reaction vessel, and the temperature increase rate is 0.2 ° C./min up to a temperature of 40 ° C. while adjusting the rotation speed of the stirrer so that the slurry is sufficiently stirred. After exceeding 40 ° C., the temperature is increased at a rate of 0.05 ° C./min, and the particles of the particles in the reaction vessel are obtained every 10 minutes using a Coulter Multisizer 3 (aperture diameter 100 μm, manufactured by Beckman Coulter). The diameter was measured. When the volume-based median diameter reached 3.9 μm, the temperature was maintained, and a mixture of the following additional raw materials prepared in advance was added over 20 minutes.
Amorphous polyester resin particle dispersion: 400 parts by weight Anionic surfactant (Dowfax 2A1 20% aqueous solution): 15 parts by weight

  After holding the reaction vessel at 50 ° C. for 30 minutes, 8 parts of EDTA (ethylenediaminetetraacetic acid) 20% solution was added thereto, then 1 mol / L sodium hydroxide aqueous solution was added, and the raw material dispersion liquid in the reaction vessel was added. The pH was adjusted to 9.0. Thereafter, while adjusting the pH to 9.0 every 5 ° C., the temperature was raised to 85 ° C. at a temperature rising rate of 1 ° C./min and held at 85 ° C.

(Cooling process)
About the mixture obtained above, the shape factor was measured using FPIA-3000 (manufactured by Sysmex Corporation), and when the shape factor reached 0.970, the mixture was cooled at a temperature decrease rate of 10 ° C./min. A particle dispersion was obtained.

(Filtering / washing process and drying process)
The toner base particle dispersion was filtered to recover the toner base particles, which were thoroughly washed with ion exchange water. Subsequently, it was dried at 40 ° C. to obtain toner base particles 1. The obtained toner base particles 1 had a volume-based median diameter of 4.0 μm and an average circularity of 0.972.

  The volume-based median diameter of the toner base particles is a value measured with a Coulter Multisizer 3 (aperture diameter 100 μm, manufactured by Beckman Coulter, Inc.).

[Preparation of toner base particles 2]
In the production of the toner base particles 1, the temperature was maintained when the volume-based median diameter of the particles in the reaction vessel reached 2.9 μm, and a mixture of additional raw materials prepared in advance was added. Toner base particles 2 were produced in the same manner as toner base particles 1.
The obtained toner base particles 2 had a volume-based median diameter of 3.0 μm and an average circularity of 0.972.

[Preparation of toner base particles 3]
In the preparation of the toner base particles 1, the temperature was maintained when the volume-based median diameter of the particles in the reaction vessel reached 4.9 μm, and a mixture of additional raw materials prepared in advance was added. Toner base particles 3 were produced in the same manner as toner base particles 1.
The obtained toner base particles 3 had a volume-based median diameter of 5.0 μm and an average circularity of 0.972.

[Preparation of toner base particles 4]
Toner base particles 4 were prepared in the same manner as toner base particles 1 except that the initial raw materials were changed as follows.
Amorphous polyester resin particle dispersion: 1008 parts by weight Amorphous vinyl resin dispersion: 32 parts by weight Crystalline polyester resin particle dispersion: 160 parts by weight Release agent particle dispersion: 200 parts by weight Black colorant dispersion: 187 parts by weight Anionic surfactant (Dowfax 2A1 20% aqueous solution): 40 parts by weight Ion exchange water: 1500 parts by weight The resulting toner base particles 4 have a volume-based median diameter of 4.0 μm and an average circularity of 0.00. 972.

[Preparation of toner base particles 5]
In the preparation of the toner base particles 1, the temperature was maintained when the volume-based median diameter of the particles in the reaction container reached 2.7 μm, and a mixture of additional raw materials prepared in advance was added. Toner base particles 5 were produced in the same manner as toner base particles 1.
The obtained toner base particles 5 had a volume-based median diameter of 2.8 μm and an average circularity of 0.972.

[Preparation of toner base particles 6]
In the preparation of toner base particles 1, the temperature was maintained when the volume-based median diameter of the particles in the reaction vessel reached 5.1 μm, and a mixture of additional raw materials prepared in advance was added. Toner base particles 6 were produced in the same manner as toner base particles 1.
The obtained toner base particles 6 had a volume-based median diameter of 5.2 μm and an average circularity of 0.972.

7). Preparation of strontium titanate fine particles [Preparation of strontium titanate fine particles A1]
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, the pH of the hydrous titanium oxide slurry after washing was adjusted to 0.6 using hydrochloric acid to obtain a titania sol dispersion. NaOH was added to the obtained titania sol dispersion to adjust the pH of the dispersion to 5.0. After repeated washing until the electrical conductivity of the supernatant reaches 50 μS / cm, 0.97-fold molar amount of Sr (OH) ₂ .8H ₂ O is added to the hydrous titanium oxide in a SUS reaction vessel. And replaced with nitrogen gas. Further, distilled water was added so as to be 0.6 mol / liter in terms of SrTiO ₃ . The slurry in the reaction vessel was heated up to 60 ° C. at 10 ° C./hour in a nitrogen atmosphere, and reacted for 8 hours after reaching 60 ° C. After the reaction, the reaction solution was cooled to room temperature, and the supernatant was removed. Then, the washing was repeated with pure water, and then filtered with Nutsche. The obtained cake was dried to obtain strontium titanate fine particles A1 not passing through the sintering step.

As a result of observing the shape of the obtained strontium titanate fine particles A1 by SEM, the particle shape was a rectangular parallelepiped and / or a cube. The peak top particle size _RA was 40 nm.

The peak top particle size of cubic or cuboid strontium titanate fine particles was measured by the following method.
Using a scanning electron microscope (SEM) (“JSM-7401F” manufactured by JEOL Ltd.), the strontium titanate fine particles were observed at a magnification of 40000 times. The shortest diameter was measured, and the intermediate value was taken as the equivalent sphere diameter. And the number particle size distribution was calculated | required based on the measured particle diameter and number of 100 primary particles. The particle diameter of the peak top of the peak existing in the distribution was defined as the particle diameter of the strontium titanate particles.

[Preparation of strontium titanate fine particles A2]
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, the pH of the hydrous titanium oxide slurry after washing was adjusted to 0.6 using hydrochloric acid to obtain a titania sol dispersion. NaOH was added to the obtained titania sol dispersion to adjust the pH of the dispersion to 5.0. After repeated washing until the electrical conductivity of the supernatant reaches 50 μS / cm, 0.97-fold molar amount of Sr (OH) ₂ .8H ₂ O is added to the hydrous titanium oxide in a SUS reaction vessel. And replaced with nitrogen gas. Further, distilled water was added so as to be 0.6 mol / liter in terms of SrTiO ₃ . In a nitrogen atmosphere, the slurry in the reaction vessel was heated up to 50 ° C. at a rate of 10 ° C./hour, and reacted for 6 hours after reaching 50 ° C. After the reaction, the reaction solution was cooled to room temperature, and the supernatant was removed. Then, the washing was repeated with pure water, and then filtered with Nutsche. The obtained cake was dried to obtain strontium titanate fine particles A2 not passing through the sintering step.

As a result of observing the shape of the obtained strontium titanate fine particles A2 by SEM, the particle shape was a rectangular parallelepiped and / or a cube. Moreover, the peak top particle diameter _RA was 20 nm.

[Preparation of strontium titanate fine particles A3]
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, the pH of the hydrous titanium oxide slurry after washing was adjusted to 0.65 using hydrochloric acid to obtain a titania sol dispersion. NaOH was added to the obtained titania sol dispersion to adjust the pH of the dispersion to 4.7. After repeated washing until the electrical conductivity of the supernatant reaches 50 μS / cm, 0.97-fold molar amount of Sr (OH) ₂ .8H ₂ O is added to the hydrous titanium oxide in a SUS reaction vessel. And replaced with nitrogen gas. Further, distilled water was added so as to be 0.6 mol / liter in terms of SrTiO ₃ . The slurry in the reaction vessel was heated to 65 ° C. at 10 ° C./hour in a nitrogen atmosphere, and reacted for 8 hours after reaching 65 ° C. After the reaction, the reaction solution was cooled to room temperature, and the supernatant was removed. Then, the washing was repeated with pure water, and then filtered with Nutsche. The obtained cake was dried to obtain strontium titanate fine particles A3 not passing through the sintering step.

As a result of observing the shape of the obtained strontium titanate fine particles A3 by SEM, the particle shape was a rectangular parallelepiped and / or a cube. The peak top particle size _RA was 60 nm.

[Preparation of strontium titanate fine particles A4]
1500 g of strontium carbonate and 800 g of titanium oxide were wet-mixed in a ball mill for 8 hours and then filtered and dried. The mixture was molded at a pressure of 5 kg / cm ² and sintered at 1300 ° C. for 8 hours. This was mechanically pulverized and classified to obtain strontium titanate fine particles A4.

As a result of observing the shape of the obtained strontium titanate fine particles A4 by SEM, the particle shape was indefinite. The peak top particle size _RA was 40 nm.

The peak top particle size of the amorphous strontium titanate fine particles was measured by the following method.
Using a scanning electron microscope (SEM), images of strontium titanate fine particles were taken at a magnification of 5000 times. The obtained SEM image was binarized by an image processing analyzer (“LUZEX AP” (manufactured by Nireco)). Among a plurality of photographs, the horizontal ferret diameter for 100 strontium titanates was calculated, and the particle size distribution was determined based on the horizontal ferret diameter and number. The horizontal ferret diameter at the peak top of the peak present in the distribution was defined as the particle diameter of the strontium titanate particles. Here, the horizontal ferret diameter is the length of a side parallel to the x-axis of the circumscribed rectangle when the image of the external additive is binarized.

[Preparation of strontium titanate fine particles A5]
The metatitanic acid obtained by the sulfuric acid method was subjected to deiron bleaching treatment, and then an aqueous sodium hydroxide solution was added to adjust the pH to 9.0, followed by desulfurization treatment. Thereafter, the mixture was neutralized with hydrochloric acid to pH 5.8 and washed with filtered water. Water was added to the obtained washed cake to make a slurry of 1.85 mol / L as TiO ₂ , then hydrochloric acid was added to adjust the pH to 1.0, and peptization treatment was performed to obtain metatitanic acid. 0.625 mol of TiO ₂ was collected from this metatitanic acid and charged into a 3 L reaction vessel. After adding 0.663 mol of strontium chloride aqueous solution and lanthanum chloride aqueous solution so that the molar ratio of SrO / LaO / TiO ₂ is 1.00 / 0.06 / 1.00, the TiO ₂ concentration is adjusted to 0.313 mol / L. did. Next, after heating to 90 ° C. with stirring, 296 mL of a 10N aqueous sodium hydroxide solution was added over 11 hours, and then stirring was continued at 95 ° C. for 1.5 hours to complete the reaction.

The reaction slurry was cooled to 50 ° C., hydrochloric acid was added until pH 5.0, and stirring was continued for 1 hour. The obtained precipitate was washed by decantation, hydrochloric acid was added to the slurry containing the precipitate to adjust the pH to 6.5, 9% by weight of isobutyltrimethoxysilane was added to the solid content, and the stirring was continued for 1 hour. . Subsequently, filtration washing was performed, and the obtained cake was dried in the atmosphere at 120 ° C. for 8 hours to obtain lanthanum-containing strontium titanate fine particles A5. The peak top particle diameter _RA of the obtained lanthanum-containing strontium titanate fine particles A5 was calculated by the method described above, and was 40 nm.

[Preparation of strontium titanate fine particles A6]
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, the pH of the hydrous titanium oxide slurry after washing was adjusted to 0.65 using hydrochloric acid to obtain a titania sol dispersion. NaOH was added to the obtained titania sol dispersion to adjust the pH of the dispersion to 4.7. After repeated washing until the electrical conductivity of the supernatant reaches 50 μS / cm, 0.97-fold molar amount of Sr (OH) ₂ .8H ₂ O is added to the hydrous titanium oxide in a SUS reaction vessel. And replaced with nitrogen gas. Further, distilled water was added so as to be 0.6 mol / liter in terms of SrTiO ₃ . In a nitrogen atmosphere, the slurry in the reaction vessel was heated to 55 ° C. at 10 ° C./hour, and reacted for 7 hours after reaching 55 ° C. After the reaction, the reaction solution was cooled to room temperature, and the supernatant was removed. Then, the washing was repeated with pure water, and then filtered with Nutsche. The obtained cake was dried to obtain strontium titanate fine particles A6 not passing through the sintering step.

As a result of observing the shape of the obtained strontium titanate fine particles A6 by SEM, the particle shape was a rectangular parallelepiped and / or a cube. The peak top particle size _RA was 15 nm.

[Preparation of strontium titanate fine particles A7]
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, the pH of the hydrous titanium oxide slurry after washing was adjusted to 0.65 using hydrochloric acid to obtain a titania sol dispersion. NaOH was added to the obtained titania sol dispersion to adjust the pH of the dispersion to 4.7. After repeated washing until the electrical conductivity of the supernatant reaches 50 μS / cm, 0.97-fold molar amount of Sr (OH) ₂ .8H ₂ O is added to the hydrous titanium oxide in a SUS reaction vessel. And replaced with nitrogen gas. Further, distilled water was added so as to be 0.6 mol / liter in terms of SrTiO ₃ . The slurry in the reaction vessel was heated to 75 ° C. at 10 ° C./hour in a nitrogen atmosphere, and reacted for 10 hours after reaching 75 ° C. After the reaction, the reaction solution was cooled to room temperature, and the supernatant was removed. Then, the washing was repeated with pure water, and then filtered with Nutsche. The obtained cake was dried to obtain strontium titanate fine particles A7 not passing through the sintering step.

As a result of observing the shape of the obtained strontium titanate fine particles A7 by SEM, the particle shape was a rectangular parallelepiped and / or a cube. The peak top particle size _RA was 70 nm.

[Preparation of Strontium Titanate Fine Particles B1, B2, B3, B6 and B7]
In the preparation of strontium titanate fine particles A4, using the same classification criteria, peak top particle diameter _{R B} is 1000nm, respectively, 300 nm, 2000 nm, 250 nm, carried out mechanically milling for a time to be 2500 nm, strontium titanate fine particles B1, B2, B3, B6 and B7 were prepared.

[Preparation of strontium titanate fine particles B4]
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, the pH of the hydrous titanium oxide slurry after washing was adjusted to 0.7 using hydrochloric acid to obtain a titania sol dispersion. NaOH was added to the obtained titania sol dispersion to adjust the pH of the dispersion to 4.7. After repeating washing until the electrical conductivity of the supernatant reaches 40 μS / cm, 0.97-fold molar amount of Sr (OH) ₂ .8H ₂ O is added to the hydrous titanium oxide in a SUS reaction vessel. And replaced with nitrogen gas. Further, distilled water was added so as to be 0.6 mol / liter in terms of SrTiO ₃ . The slurry in the reaction vessel was heated to 95 ° C. at 10 ° C./hour in a nitrogen atmosphere, and reacted for 20 hours after reaching 95 ° C. After the reaction, the reaction solution was cooled to room temperature, and the supernatant was removed. Then, the washing was repeated with pure water, and then filtered with Nutsche. The obtained cake was dried to obtain strontium titanate fine particles B4 not passing through the sintering step.

As a result of observing the shape of the obtained strontium titanate fine particles B4 by SEM, the particle shape was a rectangular parallelepiped and / or a cube. The peak top particle size _RA was 1000 nm.

[Preparation of strontium titanate fine particles B5]
The metatitanic acid obtained by the sulfuric acid method was subjected to deiron bleaching treatment, and then an aqueous sodium hydroxide solution was added to adjust the pH to 9.0, followed by desulfurization treatment. Thereafter, the mixture was neutralized with hydrochloric acid to pH 5.8 and washed with filtered water. Water was added to the obtained washed cake to make a slurry of 1.85 mol / L as TiO ₂ , then hydrochloric acid was added to adjust the pH to 1.0, and peptization treatment was performed to obtain metatitanic acid. 0.625 mol of TiO ₂ was collected from this metatitanic acid and charged into a 3 L reaction vessel. After adding 0.663 mol of strontium chloride aqueous solution and lanthanum chloride aqueous solution so that the molar ratio of SrO / LaO / TiO ₂ is 1.00 / 0.06 / 1.00, the TiO ₂ concentration is adjusted to 0.313 mol / L. did. Next, after heating to 90 ° C. with stirring, 296 mL of a 10N aqueous sodium hydroxide solution was added over 11 hours, and then stirring was continued at 95 ° C. for 16 hours to complete the reaction.

The reaction slurry was cooled to 50 ° C., hydrochloric acid was added until pH 5.0, and stirring was continued for 1 hour. The obtained precipitate was washed by decantation, hydrochloric acid was added to the slurry containing the precipitate to adjust the pH to 6.5, 9% by weight of isobutyltrimethoxysilane was added to the solid content, and the stirring was continued for 1 hour. . Next, filtration and washing were performed, and the obtained cake was dried in the atmosphere at 120 ° C. for 8 hours to obtain lanthanum-containing strontium titanate fine particles B5. The resulting peak top particle diameter R _B lanthanum-containing strontium titanate fine particles B5 was calculated by the method described above, was 1000 nm.

8). Production of carrier particles [Carrier particles 1]
(Preparation of core particle 1)
MnO: 35mol%, MgO: 14.5mol %, Fe 2 O 3: 50mol% and SrO: raw materials were weighed so that 0.5 mol%, was mixed with water, and pulverized for 5 hours in a wet media mill A slurry was obtained.

  The obtained slurry was dried with a spray dryer to obtain true spherical particles. After adjusting the particle size, the particles were heated at 950 ° C. for 2 hours and calcined in a rotary kiln. It grind | pulverized for 1 hour with the dry-type ball mill using the stainless steel bead of diameter 0.3cm. Next, 0.8% by mass of PVA as a binder was added to the solid content, water and a dispersant were further added, and the mixture was pulverized for 30 hours using zirconia beads having a diameter of 0.5 cm. Next, the mixture was granulated and dried with a spray dryer, held in an electric furnace at a temperature of 1050 ° C. for 20 hours, and subjected to main firing to obtain a core material.

  The obtained core material was crushed, further classified to adjust the particle size, and then the low magnetic force product was separated by magnetic separation, whereby core particle 1 was obtained. The volume average particle diameter of the core material particles 1 was 22.0 μm.

(Preparation of coating resin 1)
In an aqueous solution of 0.3% by mass sodium benzenesulfonate, cyclohexyl methacrylate (CHMA) and methyl methacrylate (MMA) were added at a “mass ratio = 70: 30” (copolymerization ratio). Thereto, an amount of potassium persulfate corresponding to 0.5% by mass of the total amount of monomers was added and emulsion polymerization was performed to obtain a resin dispersion. Then, the resin 1 for coating was obtained by drying the resin dispersion by spray drying. When the weight average molecular weight of the coating resin was measured by GPC in the same manner as described above, it was 500,000.

(Preparation of carrier particle 1)
In a high-speed stirring mixer equipped with a horizontal stirring blade, 100 parts by mass of core material particles 1 and 4.5 parts by mass of coating resin 1 are charged, and the peripheral speed of the horizontal rotary blade is 8 m / sec. And stirred for 15 minutes. Thereafter, the mixture was mixed at 120 ° C. for 50 minutes, and the coating material was coated on the surface of the core material particles by the action of mechanical impact force (mechanochemical method), and cooled to room temperature to obtain “carrier particles 1”.

[Carrier particle 2]
Carrier particles 2 were produced in the same manner except that the coating resin 1 was changed to the following coating resin 2 in the production of the carrier particles 1.

(Preparation of coating resin 2)
In an aqueous solution of 0.3% by mass sodium benzenesulfonate, cyclohexyl methacrylate and methyl methacrylate were added at a “mass ratio = 50: 50” (copolymerization ratio). Thereto, an amount of potassium persulfate corresponding to 0.5% by mass of the total amount of monomers was added and emulsion polymerization was performed to obtain a resin dispersion. Then, the resin 1 for coating was obtained by drying the resin dispersion by spray drying. The weight average molecular weight of the coating resin was 500,000.

[Carrier particle 3]
A room temperature effect reaction type methyl silicone resin was dissolved in toluene to prepare a coating solution, and the obtained coating solution was applied to the surface of the core material 1. Carrier particles 3 were produced by heating and drying to remove the solvent and cure.

9. Manufacture of two-component developer [Developer 1]
(External additive addition process and developer production)
Toner base particle 1 (volume-based median diameter: 4.0 μm), 0.96 parts by mass of strontium titanate fine particles A1, 0.8 part by mass of strontium titanate fine particles B1, silica (number average particle diameter: 40 nm) The toner was prepared by adding 0.97 parts by mass of the toner and mixing with a Henschel mixer for 20 minutes.

  The toner and carrier particles 1 produced as described above were mixed so that the toner concentration was 9% by mass, and Developer 1 was produced. The mixer used was a V-type mixer (manufactured by Tokuju Kogakusho Co., Ltd.) and mixed at 25 ° C. for 30 minutes.

[Developers 2-5, 8-22]
A toner was prepared in the same manner as Developer 1, except that the toner base particles, strontium titanate fine particles (A) and strontium titanate fine particles (B) shown in Table 1 below were used.
Next, Developers 2 to 5 and 8 to 22 were produced in the same manner as Developer 1 except that the produced toner and carrier particles shown in Table 1 were used.

[Developer 6]
(External additive addition process and developer production)
Toner base particle 2 (volume-based median diameter: 3.0 μm), 1.3 parts by mass of strontium titanate fine particles A1, 0.8 part by mass of strontium titanate fine particles B1, silica (number average particle diameter: 40 nm) Was added, and mixed with a Henschel mixer for 20 minutes to prepare a toner.

  The toner and carrier particles 1 prepared as described above were mixed so that the toner concentration was 9% by mass, and developer 6 was prepared. The mixer used was a V-type mixer (manufactured by Tokuju Kogakusho Co., Ltd.) and mixed at 25 ° C. for 30 minutes.

[Developer 7]
(External additive addition process and developer production)
Toner base particles 3 (volume-based median diameter: 5.0 μm), 0.78 parts by mass of strontium titanate fine particles A1, 0.7 parts by mass of strontium titanate fine particles B1, silica (number average particle diameter: 40 nm) 0.78 parts by mass was added and mixed with a Henschel mixer for 20 minutes to prepare a toner.

  The toner and carrier particles 1 produced as described above were mixed so that the toner concentration was 9% by mass, and developer 7 was produced. The mixer used was a V-type mixer (manufactured by Tokuju Kogakusho Co., Ltd.) and mixed at 25 ° C. for 30 minutes.

[Developer 23]
(External additive addition process and developer production)
Toner base particle 5 (volume-based median diameter: 2.8 μm), 1.38 parts by mass of strontium titanate fine particles A1, 0.9 part by mass of strontium titanate fine particles B1, silica (number average particle diameter: 40 nm) Was added, and mixed for 20 minutes with a Henschel mixer to prepare a toner.

  The toner prepared as described above and the carrier particles 1 were mixed so that the toner concentration was 9% by mass, and a developer 23 was prepared. The mixer used was a V-type mixer (manufactured by Tokuju Kogakusho Co., Ltd.) and mixed at 25 ° C. for 30 minutes.

[Developer 24]
(External additive addition process and developer production)
Toner base particles 6 (volume-based median diameter: 5.3 μm), 0.73 parts by mass of strontium titanate fine particles A1, 0.7 parts by mass of strontium titanate fine particles B1, silica (number average particle diameter: 40 nm) Was added, and mixed for 20 minutes with a Henschel mixer to prepare a toner.

  The toner prepared as described above and the carrier particles 1 were mixed so that the toner concentration was 9% by mass to prepare a developer 24. The mixer used was a V-type mixer (manufactured by Tokuju Kogakusho Co., Ltd.) and mixed at 25 ° C. for 30 minutes.

  The compositions of developers 1 to 24 are shown in Table 1 below.

For each of the produced developers 1 to 24, the cleaning property, the occurrence of image streaks, the image density and the occurrence of fog were evaluated.
For the evaluation, an image forming apparatus “bizhub PRESS C1070” (manufactured by Konica Minolta) was used.

(Cleanability)
In an environment of a temperature of 25 ° C. and a humidity of 50% RH, 500,000 images were formed with an image area ratio of 10%. Next, a halftone image was output. The scratches on the photoreceptor and the image defect of the halftone image were visually observed and evaluated based on the following evaluation criteria.
A: There is no visible scratch on the surface of the photoconductor, and no defect is observed in the halftone image. O: There is no noticeable scratch on the surface of the photoconductor. No occurrence of image defects corresponding to the photoconductor scratches is observed. X: Occurrence of scratches is clearly observed on the surface of the photoconductor, and occurrence of image defects corresponding to the scratches is also observed in the halftone image.

(Image stripe)
A printing durability test 1 was conducted, in which a belt image having an image area ratio of 5% was subjected to continuous printing on both sides of 1 million sheets by A4 horizontal feed in an environment of a temperature of 25 ° C. and a humidity of 50% RH. After the printing durability test, printing durability test 2 was performed in which 500,000 single-sided continuous printing of a character image with an image area ratio of 6% was performed at A4 horizontal feed in an environment of a temperature of 30 ° C. and a humidity of 80% RH. After the printing durability tests 1 and 2, a halftone image was output, and this halftone image was visually observed, and image streaks (FD streaks) due to surface scratches on the photoreceptor were evaluated based on the following evaluation criteria.
A: No image streak defect in the axial direction is observed in the halftone image.
A: Image streak defects in the axial direction having an axial length of less than 1 cm and a paper passing width of less than 1 mm are visually recognized in the number of 1 to 4 in the halftone image.
X: An axial image streak defect having an axial length of less than 1 cm and a paper passage width of less than 1 mm is visually recognized by a number of 5 or more in a halftone image, or an axial length of 1 cm or more or a paper feed width of 1 mm. The axial image streak defect satisfying the above is visually recognized by one or more numbers.

(Image density difference)
In an environment of a temperature of 25 ° C. and a humidity of 50% RH, an image having an image area ratio of 5% was formed on 400,000 A4 quality fine paper (64 g / m ² ).
The same operation was performed under the environment of a temperature of 10 ° C. and a humidity of 15% RH.
The reflection density of the obtained image was all measured by a Macbeth reflection densitometer “RD907” (manufactured by Macbeth Co., Ltd.), and the maximum reflection density difference due to the difference in image formation environment was determined and evaluated based on the following evaluation criteria.
A: Absolute value of the difference in reflection density is 0.03 or less B: Absolute value of the difference in reflection density exceeds 0.03 and 0.06 or less X: The absolute value of the difference in reflection density exceeds 0.06 Since the charge amount is high, the image density is lowered. Therefore, the smaller the absolute value of the reflection density difference, the smaller the occurrence of overcharging.

(Fog)
The fog density was measured. First, with respect to white paper that was not printed, the absolute image density at 20 locations was measured using a Macbeth reflection densitometer “RD-918”, and the average value thereof was defined as the white paper density.
After printing a character image with a printing rate of 5% on 400,000 A4 high-quality paper (64 g / m ² ) in an environment of a temperature of 25 ° C. and a humidity of 50% RH, a solid white image was printed. About the printed solid white image, the absolute image density of 20 places was measured like the said white paper, and the average value was calculated | required. A value obtained by subtracting the white paper density from the average density of the solid white image was defined as a fog density, and evaluation was performed based on the following evaluation criteria.
A: The fog density is less than 0.005. A: The fog density is 0.005 or more and less than 0.010. X: The fog density is 0.010 or more.

  The evaluation results of Developers 1 to 24 are shown in Table 2 below.

As is clear from the results in Table 2, the number particle size and strontium titanate fine particles (A) particle diameter R _A peak top is 20nm or more 60nm or less in the distribution, the particle size of the peak top in the number particle size distribution R _B is 300nm Developers 1 to 16 using toner particles containing an external additive containing strontium titanate fine particles (B) exceeding 2000 nm and having a median diameter on a volume basis of 3.0 μm or more and 5.0 μm or less. In both cases, the cleaning property is good, the occurrence of image streaks and fogging is small, and excessive charging is unlikely to occur, so the density difference due to the difference in image forming environment is small, and a high quality image can be formed. It was.

  The developer 1 in which the strontium titanate fine particles (A) are cuboids has improved cleaning properties compared to the developer 9 in which both of the strontium titanate fine particles (A) and (B) are amorphous. Since one of the strontium titanate fine particles (A) and (B) has a rectangular parallelepiped shape and the other is an indeterminate shape, the contact area between the strontium titanate fine particles and the toner base particles increases, and the toner base particles It is thought that the detachment of strontium titanate fine particles from the iron was suppressed and the cleaning property was improved. Further, the developer 12 in which the strontium titanate fine particles (A) are rectangular parallelepiped lanthanum-containing fine particles had a smaller image density difference than the developer 1 using the strontium titanate fine particles (A) not containing lanthanum. . This is because by doping strontium titanate fine particles with lanthanum, cubic and cuboid corners can be taken, excessive wear and scratches on the surface of the electrostatic latent image carrier are suppressed, and excessive charging is unlikely to occur. Conceivable.

  Furthermore, the developer 1 in which the coating resin contained in the carrier particles contains a structural unit (CHMA) derived from an alicyclic (meth) acrylic acid ester in an amount exceeding 50 mass% is an alicyclic (meth) acrylic. As compared with Developer 15 in which the amount of the structural unit (CHMA) derived from the acid ester is 50% by mass and Developer 16 in which the coating resin is a silicone resin, the occurrence of fogging was small. From these results, it is understood that the structural unit derived from the alicyclic (meth) acrylic acid ester is effective in reducing the environmental difference in chargeability of the carrier particles.

  On the other hand, the developer 21 not containing the strontium titanate fine particles (B) was poor in all evaluation results. Further, the developer 22 that does not contain the strontium titanate fine particles (A) has a large density difference due to a difference in image forming environment, and excessive charging occurs. From these results, it can be seen that the presence of two types of strontium titanate fine particles having different particle diameters is essential to achieve the effects of the present invention.

  Further, the developer 17 in which the particle diameter of the strontium titanate fine particles (A) is less than 20 nm has poor cleaning properties and a large density difference due to the difference in image forming environment. Further, the developer 18 in which the particle diameter of the strontium titanate fine particles (B) was less than 300 nm had poor cleaning properties, generation of streaks in the image, and a large density difference due to the difference in image forming environment. Further, the developer 19 in which the particle diameter of the strontium titanate fine particles (A) exceeds 60 nm and the developer 20 in which the particle diameter of the strontium titanate fine particles (B) exceeds 2000 nm cause streaks in the image and the image forming environment. The concentration difference due to the difference was large. From these results, it can be seen that the particle diameters of the two types of strontium titanate fine particles are important in order to achieve the effects of the present invention.

  In addition, the developer 23 having a toner particle diameter of less than 3.0 μm has poor cleaning properties and a large density difference due to a difference in image forming environment. Further, the developer 24 having a toner particle diameter exceeding 5.0 μm has a large density difference due to a difference in image forming environment, and fogging occurred in the image. From these results, not only the particle size of the strontium titanate fine particles (A) and (B) but also the particle size of the toner particles suppresses overcharging, improves the cleaning property, and provides high image quality even during continuous printing. It can be seen that it is important for obtaining a toner for developing an electrostatic image capable of forming an image and a two-component developer for developing an electrostatic image using the same.

  According to the present invention, toner for developing an electrostatic charge image capable of suppressing excessive charging, improving cleaning properties, and forming a high-quality image even during continuous printing, and an electrostatic charge image developing toner using the same. Component developers can be provided. Therefore, according to the present invention, further increase in speed, performance, labor saving, and diversification of recording media in an electrophotographic image forming apparatus are expected, and further spread of the image forming apparatus is expected.

Claims (7)

Toner base particles containing at least a binder resin;
An electrostatic charge image developing toner comprising toner particles containing an external additive containing strontium titanate fine particles,
The volume-based median diameter of the toner particles is 3.0 μm or more and 5.0 μm or less,
The strontium titanate fine particles, the number particle size and strontium titanate fine particles (A) particle diameter _{R A} peak top is 20nm or more 60nm or less in the distribution, 2000 nm greater than the number particle size diameter _{R B} is 300nm peak top in the distribution An electrostatic charge image developing toner comprising the following strontium titanate fine particles (B):   2. The electrostatic image developing toner according to claim 1, wherein one of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) includes cubic and / or rectangular parallelepiped fine particles.   3. The electrostatic image developing toner according to claim 1, wherein at least one of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) are lanthanum-containing strontium titanate fine particles. Particle diameter _{R B} of the strontium titanate fine particles (B) is 1500nm or less than 310 nm, toner according to any one of claims 1-3. Toner for developing an electrostatic charge image according to any one of claims 1 to 4,
A two-component developer for developing an electrostatic image, comprising carrier particles.   The carrier particles include core material particles and a coating resin that covers a surface of the core material particles, and the coating resin includes a structural unit derived from an alicyclic (meth) acrylic acid ester. The two-component developer according to 5.   The amount of the structural unit derived from the alicyclic (meth) acrylic acid ester contained in the coating resin is 50% by mass or more based on the total mass of the coating resin. Component developer.