JP7040240B2 - Toner for static charge image development and two-component developer for static charge image development - Google Patents

Description

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

In recent years, there has been a demand for higher speed, higher image quality and higher durability in an image forming apparatus. Toners for static charge image development used for electrophotographic image formation (hereinafter often referred to as "toners" or "toner particles") are usually external to the surface in order to achieve good image formation. Inorganic particles and organic particles called additives are added, and it is designed to maintain toner performance such as chargeability and fluidity by the action of the external additive. Therefore, it is very important to control the chargeability and the cleaning property by the external additive from the viewpoint of high image quality and high durability.

For example, when image formation is performed in a high temperature and high humidity environment, it is important to retain the charge because the charge tends to leak from the toner due to the influence of moisture in the air. On the other hand, when image formation is performed in a low-temperature and low-humidity environment, the amount of water in the air is reduced, which tends to cause deterioration of charge rise and excessive increase in the saturated charge amount of toner, resulting in fog in the image. , There is a concern about problems such as toner scattering in the image forming apparatus. Further, in continuous printing over a long period of time, the filming phenomenon in which paper dust and a fluidizing agent adhere to the surface of the photoconductor and NOx generated by the reaction between ozone generated from the charging device and nitrogen in the air are in the air. The image flow phenomenon due to the charge product generated by adsorbing to the moisture of the above can also be a problem.

In view of the above-mentioned problems, it has been studied to use a metal titanate salt typified by calcium titanate or strontium titanate as an external additive for the toner. Strontium titanate is a compound having excellent charge controllability, because the dielectric constant at room temperature is as high as about 300 and the temperature change of the dielectric constant is small, so that the charge level does not easily change even in environments with different temperatures. Moreover, since the chargeability is almost neutral, it is easy to adjust the chargeability. Further, the Mohs hardness is 5 to 6, and it is considered that there is an excellent polishing effect of preventing the occurrence of filming on the surface of the photoconductor at the time of image formation and image streaks.

For example, Patent Document 1 discloses a toner containing at least one metal oxide fine particle selected from silica fine particles, titania fine particles, and alumina fine particles, and strontium titanate fine particles. Further, Patent Document 2 discloses a developer containing toner and carrier particles, and further containing particles A having behavior with toner and particles B having behavior with carrier particles. Patent Document 2 describes strontium titanate particles as a specific example of the particles A.

Japanese Unexamined Patent Publication No. 2013-156614 Japanese Unexamined Patent Publication No. 2008-23316

As described above, strontium titanate has excellent characteristics such as charge controllability, but has a relatively high resistance, and therefore has a problem that charge rise is slow, especially in a low temperature and low humidity environment. For example, during continuous printing over a long period of time, the toner having a high charge amount that has been sufficiently mixed and agitated is replenished with the toner having a low charge amount, so that the distribution of the charge amount becomes wide. As a result, fog of the image, scattering of toner into the image forming apparatus, reduction of image density, and the like are likely to occur. Further, since strontium titanate has low fluidity, it may be difficult for toner to be discharged from the toner bottle.

The present invention is a toner for static charge image development, which is excellent in charge rising property, charge stability, fluidity, and cleaning property, and can continuously form a high-quality image without fog or white spots, and a toner thereof. It is an object of the present invention to provide a two-component developer for developing a static charge image using the above.

The present invention contains, as a first means for solving the above-mentioned problems, at least toner matrix particles containing a binder resin and an external additive containing strontium titanate fine particles and titanium oxide fine particles, and the strontium titanate fine particles contain the strontium titanate fine particles. , The strontium titanate fine particles (A) and the strontium titanate fine particles (B) are contained, and the peak top particle size RA in the number particle size distribution of the strontium titanate fine particles ( _A ) is 10 nm or more and 100 nm or less, and the titanium acid. The peak top particle size RB in the number particle size distribution of the strontium fine particles ( _B ) is larger than the peak top particle size RA of the strontium titanate fine particles ( _A ), and the particle size _RB and the particle size _RA Provided are an electrostatic charge image developing toner having a difference of 200 nm or more and 3000 nm or less.

Further, in the present invention, as a second means for solving the above problems, the toner for developing an electrostatic charge image of the present invention, the core material particles, and the carrier particles containing the coating resin for coating the surface of the core material particles are provided. Provided is a two-component developer for developing an electrostatic charge image, which is contained therein.

INDUSTRIAL APPLICABILITY According to the present invention, a toner for static charge image development, which is excellent in charge rising property, charge stability, fluidity, and cleaning property, and capable of continuously forming a high-quality image without fog or white spots, and a toner thereof. It is possible to provide a two-component developer for developing an electrostatic charge image using the above.

The toner of the present invention contains at least toner matrix particles containing a binder resin and an external additive containing strontium titanate fine particles and titanium oxide fine particles. In the present invention, the external additive includes titanium oxide fine particles, strontium titanate fine particles (A), and 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 10 nm or more and 100 nm or less, and the peak top particle size RB in the number particle size distribution of the strontium titanate fine particles ( _B ) is The particle size RA of the peak top of the strontium titanate fine particles ( _A ) is larger than that of RA, and the difference between _RB and _RA is 200 nm or more and 3000 nm or less. To provide a toner for static charge image development and a two-component developer for static charge image development using the toner, which has excellent properties and can continuously form a high-quality image without fog or white spots. Can be done. The mechanism is not clear, but it is speculated as follows.

The present inventors have a charge rising property, a charge stability, a fluidity, and a cleaning due to the presence of at least three components, titanium oxide fine particles and strontium titanate fine particles (A) and (B), in the toner external additive. It was found that the sex etc. are improved. First, since the strontium titanate fine particles (A) have a peak top particle diameter _RA of 100 nm or less and a small particle diameter, many contact points can be obtained with the carrier particles contained in the two-component developer. Further, the titanium oxide fine particles have lower resistance than the silica fine particles generally used as an external additive and the strontium titanate fine particles. Therefore, due to the synergistic effect of the strontium titanate fine particles (A) and the titanium oxide fine particles, the toner can be charged more quickly than in either case. Further, since the particle diameter RA of the peak top of the strontium titanate fine particles ( _A ) is 10 nm or more, the strontium titanate fine particles (A) are difficult to be embedded in the toner matrix particles and function as an external additive for a long period of time. obtain. Further, it is considered that the presence of titanium oxide having high fluidity improves the fluidity of the toner as compared with the case of the strontium titanate fine particles (A) alone, so that the toner bottle dischargeability is also improved.

Furthermore, by using the small particle size strontium titanate fine particles (A) and the large particle size strontium titanate fine particles (B) in combination, excellent charge stability and fluidity can be obtained even during long-term continuous printing. It will be possible to maintain. The large particle size strontium titanate fine particles (B) present in the toner act as a spacer, protect the small particle size strontium titanate fine particles (A) from the impact with the carrier particles, and protect the small particle size strontium titanate fine particles (A). Can be suppressed from being buried in the toner matrix. In addition, since at least two types of strontium titanate fine particles having different particle sizes are contained in the external additive, excessive desorption of the strontium titanate fine particles from the toner matrix particles is prevented, so that charge stability and electrostatic charge are prevented. It is possible to improve the cleaning property on the latent image carrier. Therefore, it is possible to maintain excellent charge stability and fluidity even during continuous printing over a long period of time.

Further, it is considered that the cleaning property is improved by the combined use of the strontium titanate fine particles (A) and (B). Since the strontium titanate fine particles (B) having a large particle size are present on the outermost surface layer of the toner, some components are desorbed by rubbing between the toners in the developing process. Since the desorbed strontium titanate fine particles (B) are charged on the positively charged side with respect to the negatively charged toner, they are developed on the non-image portion in the developing step. The strontium titanate fine particles (B) developed in the non-image portion remain on the electrostatic latent image carrier, are recovered in the cleaning step, and are selectively formed on the contact portion between the cleaning member and the electrostatic latent image carrier. accumulate. With respect to the image portion, the strontium titanate fine particles (B) in the transfer residual toner particles remaining in the vicinity of the cleaning blade are accumulated in the contact portion in the same manner as described above. The strontium titanate fine particles (B) remaining in the non-image portion and the image portion and accumulated in the contact portion of the cleaning member and the electrostatic latent image carrier form a blocking layer for blocking the leakage of toner from the cleaning member. It is considered that the cleaning property of the toner can be improved by preventing the toner from slipping through.

Therefore, in the present invention, by using at least two kinds of strontium titanate fine particles having different particle diameters together with the titanium oxide fine particles as the external additive, the charge rising property, the charge stability, the fluidity, and the cleaning property are excellent, and fog. It is possible to provide a static charge image developing toner capable of continuously forming a high-quality image without white spots and a two-component developer for static charge image developing using the same.

Hereinafter, embodiments of the present invention will be described.

1. 1. Toner for static charge image development The toner according to the present embodiment contains at least toner matrix particles containing a binder resin and an external additive containing strontium titanate fine particles and titanium oxide fine particles. The toner matrix particles are particles mainly composed of a binder resin and containing various additives such as a colorant, a mold release agent, an electric control agent, and a surfactant, if necessary. First, the binder resin will be described.

1-1. Bundling resin It is preferable to use a thermoplastic resin as the binding resin constituting the toner matrix particles.

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

Further, 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. The 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 PerkinElmer). Enclose 3.0 mg of the measurement sample (resin) in an aluminum pan and set it in the sample holder of "Diamond DSC". The reference uses an empty aluminum pan. Then, the first heating process of raising the temperature from 0 ° C. to 200 ° C. at a heating rate of 10 ° C./min, the cooling process of cooling from 200 ° C. to 0 ° C. at a cooling rate of 10 ° C./min, and the heating rate of 10 ° C./min. A DSC curve is obtained according to the measurement conditions (heating / cooling conditions) in which the temperature is raised from 0 ° C. to 200 ° C. in minutes in this order. Based on the DSC curve obtained by this measurement, the extension of the baseline before the rise of the first heat absorption peak in the second temperature rise process and the maximum between the rising portion of the first peak and the peak peak. A tangent line indicating the inclination is drawn, and the intersection is defined as the glass transition temperature (Tg).

When the glass transition temperature in the _first temperature rise process is Tg1 and the glass transition temperature in the _second temperature rise process is Tg2 in the DSC measurement, the fixing property such as low temperature fixability and the heat resistant storage property are exhibited. From the viewpoint of reliably obtaining heat resistance, the 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. From the same viewpoint as above, the 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 matrix particles from the viewpoint of image intensity. 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, based on the total amount of the toner matrix particles. When two or more kinds of resins are contained as the amorphous resin, it is preferable that the total amount thereof is within the above range with respect to the total amount of the toner matrix particles. When an amorphous resin containing a mold release agent is used, the mold release agent in the amorphous resin is included in the content of the mold release agent constituting the toner.

The amorphous resin used for the toner matrix particles according to the present invention is not particularly limited, and conventionally known amorphous resins in the present technical field can be used. Specific examples thereof include styrene resin, vinyl resin, olefin resin, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin and the like. These resins may be used alone or in combination of two or more. Further, 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). The examples of the multivalent carboxylic acid and the polyhydric alcohol used for preparing the amorphous polyester resin are not particularly limited. For example, as the polyvalent carboxylic acid, it is preferable to use an unsaturated aliphatic polyvalent carboxylic acid, an aromatic polyvalent carboxylic acid, and derivatives thereof. A saturated aliphatic polyvalent carboxylic acid may be used in combination as long as it can form an amorphous resin. Further, the polyvalent carboxylic acid may be used alone or in combination of two or more.

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, it is preferable. Saturated aliphatic polyhydric alcohol may be used in combination. The polyhydric alcohol may be used alone or in combination of two or more.

The method for producing the amorphous polyester resin is not particularly limited, and the resin can be produced by polycondensing (esterifying) the polyvalent carboxylic acid and the polyhydric alcohol using a known esterification catalyst. Can be done. The reaction catalyst and reaction conditions are the same as the reaction conditions that can be used for producing the above-mentioned crystalline polyester resin.

Further, it is preferable to contain an amorphous vinyl resin together with the 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 becomes moderately hard. Therefore, the toner base of the strontium titanate fine particles (A) Buried in particles is less likely to occur. Further, in the case of continuous printing, the charge rising property is improved, and the image quality of the formed image is likely to be improved. Further, when the content of the amorphous vinyl resin is less than 20% by mass, the low temperature fixability tends to be good.

As the amorphous vinyl resin, the amorphous vinyl resin itself may be contained in the binder resin, or the amorphous vinyl resin component may be contained as a hybrid composite resin.

The amorphous vinyl resin is, for example, 1,8-octanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 1,11-undecane. Didioldi (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-nonadecandiol Di (meth) acrylate, 1,20-eikosandiol di (meth) acrylate, 1,21-heneicosanediol di (meth) acrylate, 1,22-docosanediol di (meth) acrylate, 1,23- Tricosane diol di (meth) acrylate, 1,24-toteracosane diol di (meth) acrylate, 1,25-pentacosane diol di (meth) acrylate, 1,26-hexacosane diol di (meth) acrylate, 1, 27-Heptacosane diol di (meth) acrylate, 1,28-octacosane diol di (meth) acrylate, 1,29-nonacosan diol di (meth) acrylate, 1,30-triacontane diol di (meth) acrylate, etc. It is a polymer having a structural unit derived from the monomer of. These monomers can be used alone or in combination of two or more. In addition, in this 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. It is also possible to use one kind or two or more kinds of acid derivatives and the like.

The method for producing the amorphous vinyl resin is not particularly limited, and a bulk polymerization initiator such as a peroxide, a persulfide, a persulfate, or an azo compound usually used for the polymerization of the above-mentioned monomer is used. Examples thereof include a method of polymerizing by a known polymerization method such as polymerization, solution polymerization, emulsion polymerization method, miniemulsion method, and dispersion polymerization method. Further, 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 and mercapto fatty acid esters.

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

[Crystalline resin]
In the present invention, it is preferable that the toner particles contain at least a crystalline polyester resin because the flexibility of the toner matrix particles is increased and the strontium titanate fine particles and the titanium oxide fine particles contained in the external additive are easily adhered. Further, since the toner particles are easily melted by containing the crystalline polyester resin, it is preferable from the viewpoint of low temperature fixability.

In the present specification, the "crystalline polyester resin" refers to a polyester resin having a clear endothermic peak instead of a stepwise endothermic change in DSC. Specifically, the endothermic peak means a peak in which the half 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 a heat absorption peak derived from the crystalline resin in the second temperature raising process based on the DSC curve obtained in the same manner as the glass transition temperature (Tg) of the amorphous resin described above. The melting point (Tc) is defined as the temperature at the top of the peak (heat absorption peak whose half price width is within 15 ° C.).

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-nonandicarboxylic acid, 1,10-decandicarboxylic acid, and dodecanedioic acid. An aliphatic dicarboxylic acid such as (1,12-dodecanedicarboxylic acid), 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid. , Aromatic dicarboxylic acids such as dibasic acids such as malonic acid and mesaconic acid. Further, examples thereof include, but are not limited to, these anhydrides and their lower alkyl esters. These may be used alone or in combination of two or more.

Examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and their anhydrides and their anhydrides. Examples thereof include lower alkyl esters. These may be used alone or in combination of two or more. Further, 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-hexendioic acid, 3-octendioic acid and the like. Moreover, these lower esters, acid anhydrides and the like are also mentioned.

On the other hand, as the polyhydric alcohol component, an aliphatic diol is preferable, and a linear aliphatic diol having a main chain portion having 7 or more and 20 or less carbon atoms is more preferable. When the aliphatic diol is a linear type, the crystallinity of the polyester resin is maintained and the decrease in melting temperature is suppressed, so that the toner blocking resistance, the image storage property, and the low temperature fixing property are excellent. Further, when the number of carbon atoms is 7 or more and 20 or less, the melting point at the time of polycondensation with the polyvalent carboxylic acid component is suppressed to a low level, and low-temperature fixing is realized, but the material is practically easy to obtain. 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 preferably used for the synthesis of the crystalline polyester resin include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 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 alone or in combination of two or more. Of these, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferable in consideration of availability. Examples of the trihydric or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. These may be used alone or in combination of two or more.

The crystalline polyester resin can be synthesized by carrying out 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 tetrabutoxytitanate 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 pressure inside the reaction system is reduced, and the reaction is carried out while removing water and alcohol generated by polycondensation. If the monomer dissolves or does not dissolve at the reaction temperature, a solvent having a high boiling point may be added as a dissolution aid to dissolve the monomer. The polycondensation reaction is carried out while distilling off the dissolution auxiliary solvent. When a monomer having poor compatibility is present in the copolymerization reaction, it is advisable to condense the monomer having poor compatibility with the monomer and an acid or alcohol to be polycondensed in advance, and then polycondensate the monomer together with the main component.

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

Using "HLC-8120GPC" (manufactured by Tosoh Corporation) as an apparatus and "TSKguardcolum + TSKgelSuperHZ-M3 series" (manufactured by Tosoh Corporation) as a column, while maintaining the column temperature at 40 ° C., a flow rate of tetrahydrofuran (THF) as a carrier solvent was used. Run at 0.2 mL / min. As the measurement sample (resin), a solution dissolved in tetrahydrofuran is used so as to have a concentration of 1 mg / ml. The solution can be obtained by treating at room temperature for 5 minutes using an ultrasonic disperser 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 detection is performed using a refractive index detector (RI detector). The molecular weight distribution of the measurement sample is calculated based on the calibration curve prepared using monodisperse polystyrene standard particles.

<Other constituents (internal additives)>
The toner matrix particles used in the present invention may contain an internal additive such as a colorant, a mold 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, carbon black, magnetic powder, various organic or inorganic pigments and dyes can be used.

As a yellow colorant for yellow toner, 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 and the like can be used, and a mixture 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. as pigments. 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., as pigments of C.I. I. Pigment Blue 1, 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., as a pigment, C.I. I. Pigment Green 7 and the like can be used.

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

As a 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. can be used. It can be used. Further, as the magnetic material, ferrite, magnetite and the like can be used.

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, the color reproducibility of the image can be ensured.

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

<Release agent>
A mold release agent can be added to the toner according to the present invention. Examples of the release agent include dialkylketone waxes such as polyethylene wax, paraffin wax, microcrysterin wax, Fishertropsh wax, and distearyl ketone, carnauba wax, Montan wax, behenyl behenate, behenic acid behenate, and trimethyl propane. Tribehenate, pentaerythritol tetramillistate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, Examples thereof include ester waxes such as tristealyl trimellitic acid and distealyl maleate, and amide waxes such as ethylenediamine dibehenylamide and tristealyl amide trimellitic acid. These can be used alone or in combination of two or more.

The content ratio 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>
Further, a charge control agent can be added (internally added) to the toner according to the present invention, if necessary. As the charge control agent, various known ones can be used.

As the charge control agent, various known compounds that can be dispersed in an aqueous medium can be used. Specific examples thereof include niglocin-based dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo-based 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 matrix particles]
The structure of the toner matrix particles according to the present embodiment may be a single-layer structure of only the toner matrix particles described above, or the above-mentioned toner matrix particles may be used as core particles to cover the core particles and the surface thereof. It may be a multi-layered structure such as a core-shell structure including. The shell layer may not cover the entire surface of the core particles, or the core particles may be partially exposed. The cross section of the core-shell structure can be confirmed by a known observation means such as a transmission electron microscope (TEM) and a scanning probe microscope (SPM).

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

Further, in the toner of the present invention, from the viewpoint of suppressing fog, it is preferable that the release agent is not exposed on the surface of the toner particles and is present in the vicinity of the surface of the toner particles. For example, when the toner matrix particles contain a vinyl resin and the mold release agent contains an ester wax, the mold release agent is present in the vicinity of the vinyl resin, so that the vinyl resin is also present in the vicinity of the surface of the toner particles. Is preferable. That is, the toner contains toner matrix particles having a laminated structure of at least two layers (inner layer and outer surface layer), and the outer layer (surface layer) contains a vinyl resin and a mold release agent containing an ester wax. It is preferable to have it. In this embodiment, the outer layer may further contain an amorphous polyester resin as a main component. Further, in order to further enhance the effect of the present invention, it is preferable that the domain of the vinyl resin is dispersed in the matrix of the amorphous polyester resin.

The average circularity of the toner matrix particles is preferably 0.935 to 0.995, more preferably 0.945 to 0.990, and even more preferably 0.955 to 0.980. With an average circularity in such a range, individual toner particles are less likely to be crushed, the amount of charge is stable, and the image quality tends to be high. The average circularity can be measured using, for example, a flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation).

Specifically, the toner matrix particles are moistened with an aqueous surfactant solution, ultrasonically dispersed for 1 minute, and then dispersed, and then HPF is used in the measurement condition HPF (high magnification imaging) mode using "FPIA-2100". The measurement is performed at an appropriate concentration of 4000 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 mean value obtained by summing the circularity of each particle and dividing by the total number of measured particles.

The volume average particle diameter of the toner matrix particles is a volume-based median diameter (D50), and is preferably 3 to 10 μm. By setting the volume-based median diameter within the above range, reproducibility of fine lines and high image quality can be achieved, and toner consumption can be reduced compared to the case of using large particle size toner. Can be done. In addition, toner fluidity can be ensured. Here, the toner volume-based median diameter (D50) is measured and calculated, for example, by using a device in which a computer system for data processing is connected to "Multisizer 3 (manufactured by Beckman Coulter Co., Ltd.)". Can be done.

The median diameter based on the volume of the toner can be controlled by the concentration of the agglutinant in the coagulation / fusion step at the time of manufacturing the toner, the amount of the solvent added, the fusion time, the composition of the resin component, and the like, which will be described later. ..

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

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

The particle size RA of the peak top in the number particle size distribution of the strontium titanate fine particles ( _A ) is preferably 10 nm or more and 100 nm or less, preferably 20 nm or more and 60 nm or less, and more preferably 30 nm or more and 50 nm or less. When the particle size RA of the strontium titanate fine particles ( _A ) is 10 nm or more, the strontium titanate fine particles (A) are less likely to be embedded in the toner matrix particles, and thus function as an external additive. Further, when the particle diameter _RA is 100 nm or less, it is considered that a sufficient contact point between the toner and the carrier particles is obtained, and the charge rising property and the toner bottle discharge property are improved.

The peak-top particle size RB in the number particle size distribution of the strontium titanate fine particles ( _B ) is larger than the peak _- top particle size RA of the strontium titanate fine particles ( _A ), and the particle size RB and the particle size _RA The difference from the above is 200 nm or more and 3000 nm or less. When the difference between the particle size RB and the particle size _RA (that is, the particle size difference _{RB - RA} ) is 200 nm or more, the effect of using two types of strontium titanate fine particles having different particle sizes is exhibited. .. Further, if the particle size RB of the strontium titanate fine particles ( _B ) is so large that the particle size difference RB _{- RA} exceeds 3000 nm, it is difficult to coat the toner matrix particles together with the strontium titanate fine particles (A). ..

The peak top particle size RB in the number particle size distribution of the strontium titanate fine particles ( _B ) is not particularly limited as long as the above conditions are satisfied, but the particle size RA of the strontium titanate fine particles ( _A ) is 10 nm or more and 100 nm or less. Therefore, the particle size _RB is in the range of 210 nm or more and 2100 nm or less. The particle size RB of the strontium titanate fine particles ( _B ) is preferably more than 300 nm and 2000 nm or less, more preferably 310 nm or more and 1500 nm or less, and further preferably 350 nm or more and 1200 nm or less. When the particle size RB of the strontium titanate fine particles ( _B ) exceeds 300 nm, the strontium titanate fine particles (A) can be protected from the impact with the carrier particles, and the burial of the strontium titanate fine particles (A) in the toner matrix particles can be suppressed. In addition, it is considered that the strontium titanate fine particles (B) are easily desorbed from the surface of the toner matrix particles appropriately, and the cleaning property and the polishing property are improved. Further, if it is 2000 nm or less, the strontium titanate fine particles (B) do not excessively desorb from the toner matrix particles, and it is considered that the charge stability and the cleaning property on the electrostatic latent image carrier are improved.

In the present invention, the measuring method of the particle size of the strontium titanate fine particles differs depending on the shape thereof.

The particle size 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 surface of the toner particles is observed at a magnification of 40,000 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 thereof is defined as the equivalent sphere diameter. Then, the number particle size distribution is obtained based on the particle size and the number of the measured 100 primary particles. Two of the largest peaks existing in the distribution are selected, the one with the smaller peak value is the peak of the strontium titanate fine particles (A), and the one with the larger peak value is the peak of the strontium titanate fine particles (B). The particle size of the peak top is defined as the particle size of the strontium titanate particles.

The peak top particle size of the amorphous strontium titanate particles can be measured by the following method.
An image of the toner is taken at a magnification of 5000 times using a scanning electron microscope (SEM). Next, energy dispersive X-ray analysis (EDS analysis) is performed in that field of view. At that time, elemental analysis of strontium and titanium is performed to determine strontium titanate particles. The SEM image in which strontium titanate is confirmed is binarized by an image processing analysis device (for example, "LUZEX AP" (manufactured by Nireco Corporation)). In a plurality of photographs, the horizontal ferret diameter for 100 strontium titanate is calculated, and the particle size distribution is obtained based on the horizontal ferret diameter and the number of the horizontal ferret diameter. Two of the largest peaks existing in the distribution are selected, the one with the smaller peak value is the peak of the strontium titanate fine particles (A), and the one with the larger peak value is the peak of the strontium titanate fine particles (B). The horizontal ferret diameter of the peak top is defined as the particle diameter of the strontium titanate particles. Here, the horizontal ferret diameter is the length of the 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 on the toner surface as an aggregate, the particle diameter of the primary particles forming the aggregate shall be measured.

Further, the particle size RA of the strontium titanate fine particles ( _A ) is 100 nm or less, the particle size RB of the strontium titanate fine particles ( _B ) exceeds 300 nm, and other strontium titanate fine particles as described later are contained. In other embodiments, the particle size of the 100 primary particles measured as described above is defined as strontium titanate fine particles (A) with a particle size of less than 200 nm and strontium titanate fine particles (B) with a particle size of 200 nm or more. , The number average particle diameter, which is the average value of each, can be used instead of the particle diameters _RA and _RB , which are the peak top particle diameters.

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 cubic, rectangular parallelepiped, or amorphous. However, it is preferable that one of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) is cubic and / or rectangular parallelepiped. When the particle shape of the strontium titanate fine particles (A) or the strontium titanate fine particles (B) is cubic and / or rectangular, and the other is amorphous, the contact area between the strontium titanate fine particles and the toner matrix particles becomes large. As the amount increases, the desorption from the toner matrix particles is suppressed, and the effect of lowering the charge amount becomes easier to be exhibited. In particular, it is preferable that the strontium titanate fine particles (A) are cubic and / or rectangular parallelepiped, and the strontium titanate fine particles (B) are amorphous. Since the cubic and / or rectangular strontium titanate fine particles (A) have a large contact area with the toner matrix particles, desorption from the toner matrix particles is suppressed, and the shape of the strontium titanate fine particles (B) is further formed. When the shape is irregular, the fluidity of the toner can be ensured, and excessive wear and scratches on the surface of the electrostatic latent image carrier can be prevented.

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).

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 has the largest abundance (for example, 100 confirmed particles). The shape that occupies more than 50 of them) is the shape of the particles.

Further, it is preferable that at least one of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) is the lanthanum-containing strontium titanate fine particles. By doping the strontium titanate fine particles with lanthanum, it is possible to take cubic and rectangular parallelepiped corners and adjust the degree of spheroidization of the strontium titanate fine particles. Therefore, by using the strontium titanate fine particles containing lanthanum as an external additive, it is possible to prevent excessive wear and scratches on the surface of the electrostatic latent image carrier.

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

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

Regarding the content of the strontium titanate fine particles (A) and the strontium titanate fine particles (B), it is preferable that the content mass ratio (A) / (B) satisfies the relationship of the following formula (1).
Equation (1): 0.5 ≤ (A) / (B) ≤ 2.5
It is more preferable that the content mass ratio (A) / (B) further satisfies the relationship of the following formula (2).
Equation (2): 0.7 ≤ (A) / (B) ≤ 2.0
When the content mass ratio (A) / (B) of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) is 0.5 or more, it is continuous due to the presence of the strontium titanate fine particles (A) that are difficult to desorb. It is possible to maintain excellent charge rising property, charge stability, and fluidity at the time of printing. Further, when the content mass ratio is 2.5 or less, the presence of the desorbed strontium titanate fine particles (B) can suppress the occurrence of filming and maintain good cleaning properties.

The external additive is another strontium titanate fine particle having a particle size different from that of the strontium titanate fine particles (A) and (B), as long as the effect of using the strontium titanate particles (A) and (B) is not impaired. May be contained in one or more kinds. 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). It may be one, or it may be a particle size between the strontium titanate fine particles (A) and (B).

[Titanium oxide fine particles]
Further, the external additive contains titanium oxide fine particles.

The titanium oxide fine particles contained as an external additive in the toner of the present invention are not particularly limited, and the number average particle diameter thereof is preferably 10 nm or more and 50 nm or less, and more preferably 20 nm or more and 40 nm or less. When the number average particle size of the titanium oxide fine particles is within the above range, the burial in the toner matrix particles is less likely to occur, a sufficient contact point is obtained with the carrier particles, and further, the transfer to the carrier particles is possible. It is thought to be suppressed. It is important that the titanium oxide fine particles are present on the surface of the toner matrix particles and do not migrate to the carrier particles in order to maintain the chargeability of the developer. Further, when the average particle size of the number of titanium oxide fine particles is 50 nm or less, the large particle size strontium titanate fine particles (B) contained in the external additive act as a spacer, whereby the toner of the titanium oxide fine particles is used. It is considered that desorption from the parent particles is less likely to occur. Therefore, excellent charge rising property and charge stability at the time of continuous printing can be achieved.

The number average particle size of the hydrophobic titanium oxide fine particles can be measured by the following method.
An image of the toner is taken at a magnification of 40,000 times using a scanning electron microscope (SEM). Next, energy dispersive X-ray analysis (EDS analysis) is performed in that field of view. At that time, elemental analysis of strontium and titanium is performed to determine particles in which only titanium is detected, that is, titanium oxide particles. Similar to the method for measuring amorphous strontium titanate particles, the SEM image in which titanium oxide is confirmed is binarized and the particle size is measured. The number particle size distribution is obtained based on the particle size and number of the measured 100 primary particles.

The type of titanium oxide is not particularly limited, but hydrophobic titanium oxide that has been surface-treated with a surface treatment agent is preferable. Hydrophobic titanium oxide is preferable because it can reduce the amount of water adsorbed and is effective in reducing the difference in the charging environment by suppressing the decrease in the charging amount in a high temperature and high humidity environment.

As the surface treatment agent, a general silane coupling agent, silicone oil, fatty acid, fatty acid metal salt and the like can be used.

Examples of the silane coupling agent include chlorosilane, alkoxysilane, silazane, and a special silylating agent. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N-bis (Trimethylsilyl) urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ -Glysidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane can be exemplified as representatives.

Specific examples of the silicone oil include, for example, an organosiloxane oligomer, octamethylcyclotetrasiloxane, a cyclic compound such as decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, and tetravinyltetramethylcyclotetrasiloxane, or linear or linear or cyclic compounds. Branched organosiloxanes can be mentioned. Further, a highly reactive silicone oil having a modifying group introduced into one end, both ends, one end of the side chain, both ends of the side chain, or the like may be used. Examples of the type of the modifying group include, but are not limited to, alkoxy, carboxyl, carbinol, higher fatty acid modification, phenol, epoxy, methacrylic, amino and the like. Further, for example, a silicone oil having several kinds of modifying groups such as amino / alkoxy modification may be used. Further, dimethyl silicone oil, these modified silicone oils, and other surface treatment agents may be mixed or used in combination.

As the surface treatment method, for example, a dry method such as a spray-drying method in which a treatment agent or a solution containing the treatment agent is sprayed on the particles suspended in the gas phase, or the particles are immersed in the solution containing the treatment agent. Examples thereof include a wet method of drying the particles and a mixing method of mixing the treatment agent and the particles with a mixer.

The content of titanium oxide is preferably 0.01 parts by mass or more and less than 1.0 part by mass, more preferably 0.1 parts by mass or more and less than 1.0 parts by mass, and 0.2 parts by mass with respect to 100 parts by mass of the toner. More than parts and less than 0.9 parts by mass are more preferable. When the content of titanium oxide is 0.01 part by mass or more, it can contribute to the improvement of charge rising property and fluidity. Further, since titanium oxide has a large specific gravity, it is easily desorbed from the surface of the toner matrix particles, but if it is less than 1.0 part by mass with respect to 100 parts by mass of the toner, the chargeability is lowered due to the transfer of titanium oxide to the carrier particles. It can be suppressed. In addition, excellent charge stability can be exhibited even in continuous printing with high coverage. In addition, deterioration of cleaning property due to excessive fluidity can be suppressed.
The "toner" means "the entire toner" including the toner matrix particles and the external additive.

Further, the external additive is an inorganic fine particle or an organic fine particle other than the strontium titanate fine particles and the titanium oxide fine particles, as long as the effect of using the strontium titanate fine particles (A) and (B) and the titanium oxide fine particles is not impaired. Lubricant may be included.

Examples of strontium titanate particles and inorganic fine particles other than titanium oxide 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, and oxidation. Includes tellurium particles, manganese oxide particles, boron oxide particles, and the like. If necessary, the inorganic fine particles may be hydrophobized with a surface treatment agent such as the above-mentioned silane coupling agent or silicone oil. The size of the inorganic fine particles is preferably in the range of 20 to 500 nm in terms of number average primary particle diameter, and more preferably in the range of 70 to 300 nm.

As the organic fine particles, homopolymers such as styrene and methylmethacrylate and organic fine particles obtained from these copolymers can be used. The size of the organic fine particles is about 10 to 2000 nm in terms of the number average primary particle diameter, and the particle shape is, for example, spherical.

The lubricant is used for the purpose of further improving the cleaning property and the transferability. Examples of the lubricant include metal salts of higher fatty acids, more specifically salts of zinc stearate, aluminum, copper, magnesium, calcium and the like; zinc oleate, manganese, iron, copper and magnesium. Salts such as; salts such as zinc, copper, magnesium, calcium of palmitate; salts such as zinc of linoleic acid, calcium; salts such as zinc of lysynolic acid, calcium, etc. are included.

The total amount of the external additive contained in the toner (that is, the total content of the strontium titanate particles (A) and (B), the titanium oxide fine particles, other inorganic fine particles, the organic fine particles, and the lubricant) is the external additive. It is preferably 0.05 parts by mass to 5 parts by mass, and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the contained toner.

1-3. Toner particles [particle size of toner particles]
The volume-based median diameter of the toner particles according to the present embodiment is preferably 3.0 μm or more and 5.0 μm or less, and preferably 3.5 μm or more and 4.5 μm or less. It is preferable that the median diameter based on the volume of the toner is 3.0 μm or more from the viewpoints of charge rising property, cleaning property, and toner bottle discharge property. When the median diameter based on the volume of the toner is 5.0 μm or less, the low temperature fixability is likely to be improved. In addition, since the toner dot reproducibility of a fine latent image is also excellent, it becomes easy to obtain a high-quality image having excellent graininess at the initial stage and after continuous printing.

The volume-based median diameter can be controlled by the concentration of the flocculant used at the time of production, the amount of the organic solvent added, the fusion time, the composition of the binder resin, and the like.

The volume-based median diameter can be measured using a measuring device 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) is diluted 10-fold with pure water, for example, a neutral detergent containing a surfactant component for the purpose of dispersing 20 mL of a surfactant solution (surfactant particles). After adding to the agent solution) and allowing it to blend in, ultrasonic dispersion treatment is performed for 1 minute to prepare a dispersion of toner particles. The dispersion of toner particles is pipetted into a beaker containing ISOTONII (manufactured by Beckman Coulter) in a sample stand until the indicated concentration of the measuring device reaches 8%. By setting this concentration, a reproducible measured value can be obtained. Then, in the measuring device, the number of measured particles is 25,000, the aperture diameter is 100 μm, the measurement range of 2 to 60 μm is divided into 256, and the frequency value is calculated. The particle size of is calculated as the volume-based median size.

[Manufacturing method of toner particles]
The methods for producing toner particles are a step of producing toner matrix particles (hereinafter, also referred to as “toner matrix particle manufacturing step”) and a step of adding an external additive to the surface of the toner matrix particles (hereinafter, “external addition”). Also referred to as "agent addition step"). The method for producing the toner matrix 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.

Further, the external additive addition step can be performed before the drying step, but it is preferably performed on the toner matrix particles that have undergone the drying step. The addition of the external additive is performed by mixing the toner matrix 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.

When the toner particles produced as described above are used as a one-component magnetic toner by containing a magnetic substance, or when mixed with a so-called carrier and used as a toner as a two-component developer, the non-magnetic toner is used alone. However, it is preferable to use it as a two-component developer.

2. 2. Two-component developer for static charge image development The two-component developer for static charge image development according to the present embodiment contains a toner for static charge image development and carrier particles.

2-1. Toner for developing an electrostatic charge image The toner according to the present invention is the above-mentioned toner for developing an electrostatic charge image of the present invention. That is, it is a toner containing at least toner matrix particles containing a binder resin and an external additive containing at least two types of strontium titanate fine particles and titanium oxide fine particles having a specific particle size.

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 surface of the core material particles is coated with a coating resin because the image density stability in continuous printing is high. The coating includes a state in which the carrier particles are partially covered with a coating resin.

The exposed area ratio of the core material particles on the surface of the carrier particles (hereinafter, also simply referred to as the exposed area ratio) is preferably 10.0% or more and 18.0% or less with respect to the surface area of the core material particles. 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 at the initial stage and after continuous printing. When the exposed area ratio is 18.0% or less, it is possible to suppress the adhesion of carrier particles to the electrostatic latent image carrier (electrophotographic photosensitive member), and the deterioration of image quality in continuous printing is suppressed.

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

Hereinafter, the case where the core material particles are iron oxide-based will be described. 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) was determined, and the obtained carbon, oxygen, and iron were obtained. Based on the following formula, the iron content ratio of the core material particles alone and the core material particles after being coated with the coating layer (carrier) is obtained from the element number ratio of, and then the coating ratio is obtained by the following formula.

The exposed area ratio (%) of the core material particles = 100-covering ratio (%).

When a material other than iron oxide is used as the core material particles, the spectra of the metal elements constituting the core material particles are measured in addition to oxygen, and the same calculation is performed according to the above formula to cover the core material particles. The rate is required.

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

The volume average particle size of the carrier particles can be measured by a wet method using a laser diffraction type particle size distribution measuring device "HEROS KA" (manufactured by Nippon Laser Co., Ltd.). Specifically, first, an optical system having a focal position of 200 mm is selected, and the measurement time is set to 5 seconds. Then, the magnetic particles for measurement are added to a 0.2 mass% sodium dodecyl sulfate aqueous solution and dispersed for 3 minutes using an ultrasonic cleaner "US-1" (manufactured by asone) to prepare a sample dispersion for measurement. Then, a few drops of this are supplied to "HEROS KA", and the measurement is started when the sample concentration gauge reaches the measurable range. A cumulative distribution was created from the small diameter side of the obtained particle size distribution with respect to the particle size range (channel), and the particle size with a cumulative total of 50% was defined as the volume average particle size (D50).

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

[Core particle]
Examples of the core material particles include magnetic metals such as iron, copper, nickel and cobalt, and magnetic metal oxides such as ferrite. Above all, from the viewpoint of durability, it is preferable that the core material particles are 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 is easy to obtain desired magnetization, it has an advantage that carrier particles in which carrier particles are less likely to adhere to each other can be produced. Examples of M in the general formula include manganese (Mn), magnesium (Mg), strontium (Sr), calcium (Ca), titanium (Ti), copper (Cu), zinc (Zn), nickel (Ni), and the like. Metals such as aluminum (Al), silicon (Si), zirconium (Zr), bismuth (Bi), cobalt (Co), lithium (Li) can be adopted. These metal atoms can be used alone or in combination of two or more. Of 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 suitable magnetic properties. That is, the core material particles according to the present invention are preferably ferrite particles containing at least one of manganese and magnesium. More preferably, the core material particles according to the present invention are ferrite particles 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 MnO content ratio is preferably 20 to 40 mol% with respect to the ferrite, and the MgO content ratio is 7 to 7 to. It is preferably 30 mol%.

Commercially available products or synthetic products may be used as the core material particles.

[Coating resin]
As the structural unit contained in the coating resin, it is preferable to include a structural unit derived from an alicyclic (meth) acrylic acid ester. By including a structural unit derived from an alicyclic (meth) acrylic acid ester compound, the hydrophobicity of the resin is increased, the amount of water adsorbed on the carrier particles is reduced, and the difference in chargeability is reduced, especially in a high temperature and high humidity environment. The decrease in the amount of charge underneath is suppressed. Further, the resin containing a structural unit derived from an alicyclic (meth) acrylic acid ester compound has an advantage that it has an appropriate mechanical strength and the surface of carrier particles is refreshed by being appropriately worn as a coating material. Also have.

Examples of the alicyclic (meth) acrylic acid ester include (meth) cyclopropyl acrylate, (meth) cyclobutyl acrylate, (meth) cyclopentyl acrylate, (meth) cyclohexyl acrylate, (meth) cycloheptyl acrylate, (meth). Dicyclopentanyl acrylate, cyclododecyl (meth) acrylate, methylcyclohexyl (meth) acrylate, trimethylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, adamantyl (meth) acrylate, etc. Can be mentioned. Among them, the alicyclic (meth) acrylic acid ester is preferably a (meth) acrylic acid ester having a cycloalkyl ring having 3 to 8 carbon atoms because the above effect can be more easily obtained. Cyclopentyl acid and cyclopentyl (meth) acrylate are more preferable, and cyclohexyl methacrylate is further preferable from the viewpoint of mechanical strength and environmental stability of the amount of charge. 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, another monomer copolymerizable with the alicyclic (meth) acrylic acid ester may be used. Examples of other monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p. -Ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene 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, methacrylic Methacrylate compounds such as lauryl acid, phenyl methacrylate, benzyl methacrylate, isobornyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, Acrylic acid ester compounds such as t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, benzyl acrylate; ethylene, propylene, isobutylene, etc. Olefin compounds; vinyl halide compounds such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, vinylidene fluoride; vinyl ester compounds such as vinyl propionate, vinyl acetate, vinyl benzoate; vinyl methyl ether, vinyl ethyl Vinyl ether compounds such as ether; Vinyl ketone compounds such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone; N-vinyl compounds such as N-vinylcarbazole, N-vinylindole and N-vinylpyrrolidone; Vinyl compounds; examples include 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 them, from the viewpoint of mechanical strength and environmental stability of the amount of charge, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, (meth). It is preferable to use a chain (meth) acrylic acid ester such as hexyl acrylate, octyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, or a chain (meth) acrylic acid ester. More preferred. The alkyl group of the chain (meth) acrylic acid ester preferably has 1 to 8 carbon atoms. A copolymer of an alicyclic (meth) acrylic acid ester and a chain type (meth) acrylic acid ester is preferable because the carrier surface is easily refreshed and the stress resistance in the developing machine is excellent.

At this time, the content mass ratio between the alicyclic (meth) acrylic acid ester and the chain type (meth) acrylic acid ester is not particularly limited, but the alicyclic (meth) acrylic acid ester: chain type ( Meta) Acrylic acid ester = 10:90 to 90:10 (mass ratio) is preferable, and 30:70 to 70:30 is more preferable.

The method for producing the coating resin is not particularly limited, and a conventionally known polymerization method can be appropriately used. For example, 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 can be mentioned. In particular, from the viewpoint of controlling the particle size, it is preferable to synthesize by an emulsion polymerization method.

The polymerization initiators and surfactants other than the above-mentioned monomers used in the emulsion polymerization method, the chain transfer agent used as necessary, and the polymerization conditions such as the polymerization temperature are not particularly limited, and are conventionally known polymerization. An initiator, a surfactant, a chain transfer agent, or the like can be used, and the polymerization conditions such as the 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-mentioned monomer) is not particularly limited, but is preferably in the range of 200,000 to 800,000, more preferably 300,000 to 700,000. When 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 excessively promoted, and the carrier particles are unlikely to adhere. Are better. When the weight average molecular weight of the coating resin is 800,000 or less, a good charge amount can be maintained for a long period of time without causing a decrease in the charge amount due to the transfer of the external additive from the toner particles to the surface of the carrier particles.

The weight average molecular weight of the coating resin is a value measured by the above-mentioned method by gel permeation chromatography (GPC) described above.

[Manufacturing method of carrier particles]
Examples of the method of coating the surface of the core material particles with the coating resin include known wet coating methods and dry coating methods, and any of these methods can provide the resin coating layer. Further, from the viewpoint that no solvent is used, the environmental load is small, and the surface of the core material particles can be uniformly coated with the coating resin, the above-mentioned dry coating method is preferable.

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 attached to the core material particles, and the fat is spread and formed by stirring and mixing under heating. However, as the time is lengthened, the spreading progresses and the resin becomes thinner, so the exposed area increases. It becomes the direction. In order to make the exposed area of the core material particles on the surface of the carrier particles 10% or more and 18% or less, the stirring time during heating is preferably 30 to 70 minutes, more preferably 40 to 60 minutes.

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

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 the resin addition, the amount of the coating resin added to the core material particles, and the like. If the mixing time under heating after adding the resin is lengthened, the exposed area ratio tends to increase, and if the amount of resin added increases, the exposed area ratio tends to decrease.

2-3. Method for Producing a Two-Component Developer for Electrostatic Image Development A 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 amount of charge of the toner becomes appropriate, and the image quality at the initial stage and after 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 device include a Henschel mixer, a Nauter mixer, and a V-type mixer.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

1. 1. Preparation of Amorphous Polyester Resin Particle Dispersion [Preparation of Amorphous Polyester Resin]
Bisphenol A ethylene oxide 2.2 mol Addendum: 40 mol parts Bisphenol A propylene oxide 2.2 mol Addendum: 60 mol part Dimethyl terephthalate: 60 mol part Dimethyl fumarate: 15 mol part Dodecenyl succinic anhydride: 20 mol part Trimellitic acid anhydride: 5 mol parts In a reaction vessel equipped with a stirrer, thermometer, condenser and nitrogen gas introduction tube, the above monomers other than dimethyl fumarate and trimellitic acid anhydride and tin dioctylate are placed. 0.25 parts by mass was added to a total of 100 parts by mass of the above monomers. After reacting at 235 ° C. for 6 hours under a nitrogen gas stream, the temperature was lowered to 200 ° C., dimethyl fumarate and trimellitic acid anhydride were added, and the reaction was carried out for 1 hour. The temperature was raised to 220 ° C. over 5 hours and polymerized under a pressure of 10 kPa to obtain a pale yellow transparent amorphous polyester resin.

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 mass% aqueous ammonia solution were placed in a separable flask and mixed sufficiently. Dissolved. Next, ion-exchanged water was dropped at a liquid feeding rate of 8 g / min using a liquid feeding pump while heating and stirring at 40 ° C., and the dropping was stopped when the liquid feeding amount reached 580 parts by mass. Then, the solvent was removed under reduced pressure to obtain an amorphous polyester resin particle dispersion. Ion-exchanged water was added to the above dispersion to adjust the solid content to 25% by mass to prepare an amorphous polyester resin particle dispersion.

2. 2. Preparation of amorphous vinyl resin particle dispersion liquid Anionic surfactant (Dowfax, manufactured by Dow Chemical Co., Ltd.) 5.0 mass in a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube and a nitrogen introduction device. A portion 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. Next, a solution prepared by dissolving 18.0 parts by mass of potassium persulfate (KPS) in 342 parts by mass of ion-exchanged water was added, and the liquid temperature was adjusted to 75 ° C. Further, 903.0 parts by mass of styrene (St), 282.0 parts by mass of n-butyl acrylate (BA) and 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 dropping, the mixture was polymerized by heating and stirring at 75 ° C. for 2 hours to obtain an amorphous vinyl resin dispersion. Ion-exchanged water was added to the above 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. 3. Preparation of Crystalline Polyester Resin Particle Dispersion [Preparation of Crystalline Polyester Resin]
Dodecane diic 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 to a total of 100 parts by mass of the above-mentioned 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 temperature inside the reaction vessel was reduced to 3 kPa, and the reaction was stirred and reacted under reduced pressure for 13 hours. , 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, which are sufficiently mixed and dissolved at 60 ° C., and then a 10% by mass aqueous ammonia solution is used. Was dropped in an amount of 8 parts by mass. The heating temperature was lowered to 67 ° C., and the mixture was dropped at a liquid feeding rate of 8 g / min using an ion-exchanged water feeding pump while stirring, and when the feeding amount reached 580 parts by mass, the dropping of ion-exchanged water was stopped. .. Then, the solvent was removed under reduced pressure to obtain a crystalline polyester resin particle dispersion. Ion-exchanged 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 by 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 the device "HLC-8120GPC" (manufactured by Tosoh Corporation) and the column "TSKguardcolum + TSKgelSuperHZ-M3 series" (manufactured by Tosoh Corporation), the flow rate of tetrahydrofuran (THF) as a carrier solvent was 0 while maintaining the column temperature at 40 ° C. It was flushed at 2 mL / min. The measurement sample (resin) was dissolved in tetrahydrofuran so as to have a concentration of 1 mg / ml. The solution was prepared by treating at room temperature for 5 minutes using an ultrasonic disperser. Next, a sample solution was obtained by treating with a membrane filter having a pore size of 0.2 μm, and 10 μL of this sample solution was 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 was calculated based on the calibration curve prepared using monodisperse polystyrene standard particles. Ten points were used as the polystyrene 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" (manufactured by PerkinElmer). First, 3.0 mg of the measurement sample (resin) was sealed in an aluminum pan and set in the sample holder of "Diamond DSC". The reference used was an empty aluminum pan. Then, the first heating process of raising the temperature from 0 ° C. to 200 ° C. at a heating rate of 10 ° C./min, the cooling process of cooling from 200 ° C. to 0 ° C. at a cooling rate of 10 ° C./min, and the heating rate of 10 ° C./min. A DSC curve was obtained under the measurement conditions (heating / cooling conditions) through the second heating process in which the temperature was raised from 0 ° C. to 200 ° C. in minutes. Based on the DSC curve obtained by this measurement, the extension of the baseline before the rise of the first heat absorption peak in the second temperature rise process and the maximum between the rising portion of the first peak and the peak peak. A tangent line indicating the inclination was drawn, and the intersection was defined as the glass transition temperature (Tg).
Further, the melting point of the crystalline resin is an endothermic peak derived from the crystalline resin in the second temperature raising process (heat absorption peak having a half width within 15 ° C.) based on the DSC curve obtained in the same manner as above. The temperature at the top of the peak was defined as the melting point (Tc).

4. Preparation of mold 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 Dai-ichi Kogyo Seiyaku Co., Ltd.): 13.5 parts by mass ( Active ingredient 60%, 3% for mold release agent)
Ion-exchanged water: 21.6 parts by mass Mix the above materials, dissolve the paraffin wax at an internal liquid temperature of 120 ° C. with a pressure discharge homogenizer (Gorlin homogenizer, manufactured by Gorlin), and then 120 at a dispersion pressure of 5 MPa. The dispersion treatment was carried out at 40 MPa for 360 minutes and then cooled to obtain a dispersion liquid. Ion-exchanged 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 liquid Preparation of black colorant particle dispersion liquid Carbon black (Regal (registered trademark) 330, manufactured by Cabot): 100 parts by mass Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 15 Parts by mass Ion-exchanged water: 400 parts by mass After mixing the above components and pre-dispersing them with a homogenizer (Ultratarax, manufactured by IKA) for 10 minutes, a high-pressure impact disperser Ultimizer (manufactured by Sugino Machine) is used to pressure 245 MPa. After 30 minutes of dispersion treatment, an aqueous dispersion of black colorant particles was obtained. Ion-exchanged water was further added to the obtained dispersion to adjust the solid content to 15% by mass to obtain 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 Mother Particles [Preparation of Toner Mother Particles 1]
(Agglomeration / fusion process and aging process)
Acrystalline polyester resin particle dispersion (i): 1008 parts by mass Aspherical vinyl resin dispersion: 32 parts by mass Crystalline polyester resin particle dispersion: 160 parts by mass Release agent Particle dispersion: 160 parts by mass Black colorant Dispersion: 187 parts by mass Anionic surfactant (Doufax2A1 20% aqueous solution): 40 parts by mass Ion exchanged water: 1500 parts by mass Place the above initial raw materials in a 4 liter reaction vessel equipped with a thermometer, pH meter and stirrer. The temperature was adjusted to 25 ° C., and 1.0% nitric acid was added to adjust the pH to 3.0. Then, 100 parts by mass of an aqueous solution of aluminum sulfate (aggregator) having a concentration of 2% was added dropwise over 30 minutes while dispersing the above mixture at 3,000 rpm using a homogenizer (Ultratalax T50, manufactured by IKA). After completion of the dropping, the mixture was stirred for 10 minutes to thoroughly mix the raw material and the flocculant.

Next, a stirrer and a mantle heater are installed in the reaction vessel, and the temperature rise 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 agitated. After exceeding 40 ° C, the temperature is raised at a heating rate of 0.05 ° C / min, and the particles in the reaction vessel are used every 10 minutes with a Coulter Multisizer 3 (aperture diameter 100 μm, manufactured by Beckman Coulter). The diameter was measured. The temperature was maintained when the volume-based median diameter reached 3.9 μm, and the mixed solution of the following additional raw materials prepared in advance was added over 20 minutes.
Atypical polyester resin particle dispersion (ii): 400 parts by mass Anionic surfactant (Doufax2A1 20% aqueous solution): 15 parts by mass

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

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

(Filtration / cleaning process and drying process)
The toner matrix particle dispersion was filtered to recover the toner matrix particles, and the toner matrix particles were thoroughly washed with ion-exchanged water. Then, it was dried at 40 ° C. to obtain toner matrix particles 1. The obtained toner matrix particles 1 had a volume-based median diameter of 4.0 μm and an average circularity of 0.971.

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

The average circularity was measured using a flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation). Specifically, the toner is moistened with an aqueous surfactant solution, ultrasonically dispersed for 1 minute, and then dispersed, and then the number of HPFs detected in the measurement condition HPF (high magnification imaging) mode using "FPIA-2100". It was measured at an appropriate concentration of 4000 pieces. The circularity was 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 mean value obtained by adding the circularity of each particle and dividing by the total number of measured particles.

[Preparation of toner matrix particles 2]
In the preparation of the toner matrix particles 1, the temperature was maintained when the volume-based median diameter of the particles in the reaction vessel reached 2.4 μm, and a mixed solution of additional raw materials prepared in advance was added. The toner matrix particles 2 were produced in the same manner as the toner matrix particles 1.
The obtained toner matrix particles 2 had a volume-based median diameter of 2.5 μm and an average circularity of 0.970.

[Preparation of toner matrix particles 3]
In the preparation of the toner matrix 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 mixed solution of additional raw materials prepared in advance was added. The toner matrix particles 3 were produced in the same manner as the toner matrix particles 1.
The obtained toner matrix particles 3 had a volume-based median diameter of 3.0 μm and an average circularity of 0.969.

[Preparation of toner matrix particles 4]
In the preparation of the toner matrix 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 mixed solution of additional raw materials prepared in advance was added. The toner matrix particles 4 were produced in the same manner as the toner matrix particles 1.
The obtained toner matrix particles 4 had a volume-based median diameter of 5.0 μm and an average circularity of 0.970.

[Preparation of toner matrix particles 5]
In the preparation of the toner matrix particles 1, the temperature was maintained when the volume-based median diameter of the particles in the reaction vessel reached 5.4 μm, and a mixed solution of additional raw materials prepared in advance was added. The toner matrix particles 5 were produced in the same manner as the toner matrix particles 1.
The obtained toner matrix particles 5 had a volume-based median diameter of 5.5 μm and an average circularity of 0.971.

[Preparation of toner matrix particles 6]
In the production of the toner matrix particles 1, the toner matrix particles 6 were produced in the same manner as the toner matrix particles 1 except that the initial raw materials were changed as follows.
Atypical polyester resin particle dispersion: 1040 parts by mass Crystalline polyester resin particle dispersion: 160 parts by mass Release agent particle dispersion: 160 parts by mass Black colorant dispersion: 187 parts by mass Anionic surfactant (Dowfax2A1 20) % Aqueous solution): 40 parts by mass Ion-exchanged water: 1500 parts by mass The obtained toner matrix particles 6 had a volume-based median diameter of 4.0 μm and an average circularity of 0.972.

The composition of the binder resin of the toner matrix particles 1 to 6, the content of each resin, the volume-based median diameter and the average circularity are summarized in Table 1 below.

7. Preparation of strontium titanate fine particles [Preparation of strontium titanate fine particles A1]
The hydroxide-containing titanium slurry obtained by hydrolyzing an aqueous solution of titanyl sulfate was washed with an aqueous alkaline solution. Next, the pH of the washed titanium hydroxide-containing slurry was adjusted to 1.0 with hydrochloric acid to obtain a titania sol dispersion. NaOH was added to the obtained titania sol dispersion, and the pH of the dispersion was adjusted to 5.0. After repeated washing until the electrical conductivity of the supernatant becomes 74 μS / cm, 0.98 times the molar amount of Sr (OH) _{2.8H 2 O} is added to the titanium hydroxide-containing titanium hydroxide to the SUS reaction vessel. And replaced with nitrogen gas. Further, distilled water was added so as to be 0.47 mol / liter in terms of SrTiO ₃ . The slurry in the reaction vessel was heated to 84 ° C. at 10 ° C./hour in a nitrogen atmosphere, and the reaction was carried out for 4.1 hours after reaching 84 ° C. After the reaction, the mixture was cooled to room temperature, the supernatant was removed, washing with pure water was repeated, and then filtration was performed with Nuche. The obtained cake was dried to obtain strontium titanate fine particles having a peak top particle diameter _RA of 35 nm.

A solution of normal paraffin wax (Mw: 500) dissolved in isopropanol and n-octyltriethoxysilane were added to the strontium titanate fine particles obtained above, and the temperature was raised to 60 ° C. over 1 hour. 3.0 parts by mass of n-octyltriethoxysilane and 9.0 parts by mass of normal paraffin wax were coated on 100 parts by mass of strontium titanate fine particles. Then, it was filtered and washed to obtain a wet cake, which was heat-treated at 60 ° C. for 24 hours and dried to obtain surface-treated strontium titanate fine particles A1.

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

The peak top particle diameter of the cubic or rectangular parallelepiped strontium titanate fine particles was measured by the following method.
Using a scanning electron microscope (SEM) (“JSM-7401F” manufactured by JEOL Ltd.), observe the strontium titanate fine particles at a magnification of 40,000 times, and by image analysis of the primary particles, the longest diameter of each particle and The shortest diameter was measured, and the intermediate value was taken as the equivalent diameter of the sphere. Then, the number particle size distribution was obtained based on the particle size and the number of the measured 100 primary particles. The particle size of the peak top of the peak existing in the distribution was defined as the particle size of the strontium titanate particles.

[Preparation of strontium titanate fine particles A2-A5, A8, A9 and B8]
In the preparation of strontium titanate fine particles A1, the peak top shown in Table 3 is controlled by controlling the pH of the dispersion, the amount of Sr (OH) _2.8H2O added, the reaction temperature, and the reaction time as shown in Table ₂ . Cubic or rectangular strontium titanate fine particles A2 _- A5, A8, A9 and B8 having a particle size _RA or RB were prepared.

[Preparation of strontium titanate fine particles A6]
600 g of strontium carbonate and 350 g of titanium oxide were wet-mixed in a ball mill for 8 hours, then filtered and dried, and the mixture was formed at a pressure of 10 kg / cm ² and sintered at 1200 ° C. for 7 hours. This was mechanically pulverized to obtain strontium titanate having a peak top particle diameter _RA of 42 nm via a sintering step. As a result of observing the shape of this strontium titanate by SEM, it had an irregular shape.

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 analysis device (“LUZEX AP” (manufactured by Nireco Corporation)). In a plurality of photographs, the horizontal ferret diameter for 100 strontium titanate was calculated, and the particle size distribution was obtained based on the horizontal ferret diameter and the number of the horizontal ferret diameter. The horizontal ferret diameter of the peak top of the peak existing in the distribution was defined as the particle diameter of the strontium titanate particles. Here, the horizontal ferret diameter is the length of the 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 A7]
After the metatitanic acid obtained by the sulfuric acid method was subjected to iron bleaching treatment, an aqueous sodium hydroxide solution was added to adjust the pH to 9.0, and then desulfurization treatment was performed. Then, it was neutralized to pH 5.8 with hydrochloric acid 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 , and then hydrochloric acid was added to adjust the pH to 1.0 and deflocculated to obtain metatitanium acid. 0.625 mol of TiO ₂ was collected from this metatitanium acid and charged into a 3 L reaction vessel. After adding 0.719 mol of strontium chloride aqueous solution and lanthanum chloride aqueous solution so that the SrO / LaО / TiO ₂ mol ratio is 1.00 / 0.18 / 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 sodium hydroxide aqueous solution was added over 12.5 hours, and then stirring was continued at 95 ° C. for 1 hour to complete the reaction.

The reaction slurry was cooled to 50 ° C., hydrochloric acid was added until the pH reached 5.0, and stirring was continued for 1 hour. The obtained precipitate was decantated and washed, 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 stirring and holding was continued for 1 hour. .. Then, filtration and washing were performed, and the obtained cake was dried in the air at 120 ° C. for 8 hours to obtain strontium titanate fine particles A7 containing lanthanum. The peak top particle diameter _RA of the obtained lanthanum-containing strontium titanate fine particles A7 was calculated by the above-mentioned method and found to be 38 nm.

[Preparation of strontium titanate B1-B7, B10, B11]
In the preparation of the strontium titanate fine particles A6, the classification conditions were changed to prepare strontium titanate fine particles B1 to B7, B10, and _B11 having an amorphous shape and having a peak top particle diameter RB shown in Table 3.

[Preparation of strontium titanate B9]
In the preparation of the strontium titanate fine particles A9, the lanthanate _- containing strontium titanate fine particles having the peak top particle diameter RB shown in Table 3 were adjusted by adjusting the SrO / LaО / TiO ₂ molar ratio and the addition rate of the 5N sodium hydroxide aqueous solution. B9 was produced.

8. Titanium Oxide Fine Particles Anatase-type titanium oxide having an average primary particle size of 30 nm was surface-treated with isobutyltrimethoxysilane, which is a hydrophobic agent, in an aqueous wet system to obtain hydrophobic titanium oxide. The obtained hydrophobic titanium oxide was used as titanium oxide fine particles.

9. Silica particles The silica having an average primary particle size of 20 nm was surface-treated with hexamethyldisilazane (HMDS), which is a hydrophobic agent, to obtain hydrophobic silica. The obtained hydrophobic silica was used as silica particles.

[Preparation of toner particles 1]
As shown in Table 3 below, 1.0 part by mass of strontium titanate fine particles A1 (peak top particle size _RA : 40 nm) with respect to 100 parts by weight of toner matrix particles 1 (volume-based median diameter: 4.0 μm). Add 0.7 parts by mass of strontium titanate fine particles B1 (peak top particle size _RB : 1000 nm), 0.5 parts by mass of titanium oxide fine particles (number average particle size: 30 nm), and 0.7 parts by mass of silica particles. Toner particles 1 were prepared by mixing with a mixer for 20 minutes.

[Preparation of toner particles 2-37]
In the preparation of the toner particles 1, the types of toner matrix particles, the types and content ratios (A) / (B) of the strontium titanate fine particles (A) and (B), and the contents of the titanium oxide fine particles and silica particles are shown in Table 3. Toner particles 2 to 37 were prepared in the same manner as the toner particles 1 except that the changes were made as shown.

[Preparation of two-component developer]
(Preparation of core material particles 1)
Weigh the raw materials so that MnO: 35 mol%, MgO: 14.5 mol%, Fe ₂ O ₃ : 50 mol% and SrO: 0.5 mol%, mix with water, and grind for 5 hours with a wet media mill. A slurry was obtained.

The obtained slurry was dried with a spray dryer to obtain spherical particles. After adjusting the particle size of the particles, the particles were heated at 950 ° C. for 2 hours and calcined in a rotary kiln. The stainless beads having a diameter of 0.3 cm were pulverized in a dry ball mill for 1 hour. Next, 0.8% by mass of PVA was added as a binder with respect to the solid content, water and a dispersant were further added, and the mixture was pulverized for 25 hours using zirconia beads having a diameter of 0.5 cm. Then, it was granulated and dried by a spray dryer, kept at a temperature of 1050 ° C. for 20 hours in an electric furnace, and main-baked 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 dressing to obtain core material particles 1. The volume average particle size of the core material particles 1 was 28.0 μm.

(Preparation of coating resin 1)
100 parts by mass of cyclohexylmethacrylate monomer and 1 part by mass of dodecanethiol were mixed and dissolved, and 0.5 parts by mass of anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) in a flask was added to 400 parts by mass of ion-exchanged water. It was emulsion-polymerized by adding it to the aqueous solution dissolved in the part. Specifically, 50 parts by mass of ion-exchanged water in which 0.5 part by mass of ammonium persulfate was dissolved was added as a reaction initiator while slowly mixing for 10 minutes. After nitrogen substitution, the inside of the flask was stirred and heated in an oil bath until the contents reached 70 ° C., and emulsion polymerization was continued as it was for 5 hours to obtain a resin dispersion. Then, the resin dispersion was spray-dried to obtain a coating resin 1. When the weight average molecular weight of the coating resin was measured in the same manner as above, it was 350,000.

(Preparation of carrier particle 1)
100 parts by mass of core material particles 1 and 4.5 parts by mass of coating resin 1 are put into a high-speed stirring mixer with horizontal stirring blades, and the temperature is 22 ° C. under the condition that the peripheral speed of the horizontal rotary blade is 8 m / sec. Was mixed and stirred for 15 minutes. Then, the mixture was mixed at 120 ° C. for 50 minutes to coat the surface of the core material particles with a coating material by the action of a mechanical impact force (mechanochemical method), and cooled to room temperature to obtain "carrier particles 1". The volume average particle diameter of the carrier particle 1 was 28.0 μm.

(Preparation of carrier particles 2)
In the production of the carrier particles 1, the carrier particles 2 were produced in the same manner except that the coating resin 1 was changed to 5.5 parts by mass and the mixing time at 120 ° C. was changed to 20 minutes. The volume average particle diameter of the carrier particles 2 was 28.0 μm.

(Preparation of carrier particles 3)
In the production of the carrier particles 1, the carrier particles 3 were produced in the same manner except that the coating resin 1 was changed to 5.5 parts by mass and the mixing time at 120 ° C. was changed to 40 minutes. The volume average particle diameter of the carrier particles 3 was 28.0 μm.

(Preparation of carrier particles 4)
In the production of the carrier particles 1, the carrier particles 4 were produced in the same manner except that the coating resin 1 was changed to 3.5 parts by mass and the mixing time at 120 ° C. was changed to 70 minutes. The volume average particle diameter of the carrier particles 4 was 28.0 μm.

(Preparation of carrier particles 5)
In the production of the carrier particles 1, the carrier particles 5 were produced in the same manner except that the coating resin 1 was changed to 3.5 parts by mass and the mixing time at 120 ° C. was changed to 90 minutes. The volume average particle diameter of the carrier particles 5 was 28.0 μm.

Table 4 shows the conditions for producing carrier particles 1 to 5.

The exposed area of the core material particles in the carrier particles 1 to 5 was determined by measuring the coverage of the coating layer on the core material particles by XPS measurement (X-ray photoelectron spectroscopy measurement). K-Alpha manufactured by Thermo Fisher Scientific is used as the XPS measuring device, and Al monochromatic X-rays are used as the X-ray source, and the acceleration voltage is set to 7 kV and the emission current is set to 6 mV. , The main element (carbon) constituting the coating layer, the main element (iron) constituting the core material particles, and oxygen were measured. Based on the obtained C1s spectrum of carbon, Fe2p3 / 2 spectrum of iron, and O1s spectrum of oxygen, the number of elements of carbon, oxygen, and iron (represented as "AC", "AO", and "AFe", respectively). Based on the following formula, the iron content ratio of the core material particles alone and the core material particles after being coated with the coating layer (carrier) was obtained from the obtained element number ratios of carbon, oxygen, and iron. Subsequently, the coverage was calculated by the following formula.

The exposure area ratio (%) of the core material particles was 100-covering ratio (%).

The exposed area ratio of the core material particles in the carrier particles 1 to 5 is shown in Table 5 below.

(Preparation of developer 1)
The toner particles 1 and the carrier particles 1 prepared above were mixed so that the toner concentration was 9% by mass to prepare a developer 1. Mixing was carried out at 25 ° C. for 30 minutes using a V-type mixer (manufactured by Tokuju Kosakusho Co., Ltd.).

<Preparation of developer 2-37>
Developers 2 to 37 were prepared in the same manner as in the above-mentioned preparation of the developer 1 except that the combination of the toner particles and the carrier particles was changed as shown in Table 5.

For each of the prepared developeres 1 to 37, the fog, the bottle discharge property, the cleanability, and the occurrence of filming of the photoconductor were evaluated.
In all the evaluations, a multifunction device "bizhub PRESS (registered trademark) C1070" (manufactured by Konica Minolta Co., Ltd.) was used as the image forming apparatus.

(1) Fog The density of fog on the image was evaluated in order to evaluate the charge rising property and the charge stability.
In a low temperature and low humidity environment (temperature 10 ° C, humidity 15% RH), 5000 sheets of images with a pixel ratio of 45% are printed on A4 size woodfree paper (64 g / m ² ), then blank paper is printed, and blank paper for the transfer material is printed. The concentration was evaluated. Specifically, the blank paper density was measured at 20 places of A4 size high-quality paper as a transfer material, and the average value was taken as the fog density. The density was measured using a reflection densitometer "RD-918" (manufactured by Macbeth).
The fog was evaluated based on the following evaluation criteria.
⊚: Good level when the fog concentration is less than 0.003 ○: Level where there is no practical problem when the fog concentration is 0.003 or more and less than 0.005 Δ: The fog concentration is 0.005 or more and less than 0.010 Level that is not practically problematic ×: Level that is practically problematic when the fog concentration is 0.010 or more

(2) Toner bottle discharge property A toner bottle is filled with 1,100 g of a developer, and A4 size plain paper is used as an image support, and printing is performed in a normal temperature and humidity environment (temperature 20 ° C., humidity 55% RH). 1,000 sheets were printed under the printing rate conditions of 100%, 90%, 80%, and 70%. It was confirmed whether or not the toner empty display was lit at the time of printing, and the bottle dischargeability was evaluated based on the following evaluation criteria.
⊚: The empty display does not light even if 1,000 sheets are printed at a printing rate of 100%. 〇: The empty display lights when 1,000 sheets are printed at a printing rate of 90%.
Does not light at a print rate of 80% Δ: The empty display lights when 1,000 sheets are printed at a print rate of 80%.
Does not light at a print rate of 70% ×: The empty display lights when 1,000 sheets are printed at a print rate of 70%.

(3) Cleanability After forming 500,000 images, scratches on the photoconductor caused by slipping through the external additive and image defects in the halftone image were observed and visually evaluated based on the following evaluation criteria. ..
⊚: There are no visible scratches on the surface of the photoconductor, and no defects are observed in the halftone image. ○: There are no noticeable scratches on the surface of the photoconductor, and the halftone image also has no defects. No image defects corresponding to scratches on the photoconductor are observed. Δ: Minor scratches are visually observed on the surface of the photoconductor, but image defects corresponding to scratches on the photoconductor are not observed in the halftone image. Not observed ×: Scratches are clearly observed on the surface of the photoconductor, and image defects corresponding to the scratches are also observed in the halftone image.

(4) Filming of the photoconductor The polishability of the toner was evaluated by the white spots on the image due to the filming of the photoconductor.
Under an environment of a temperature of 33 ° C. and 80% RH (relative humidity), 100,000 printed images with 5% coverage were continuously printed, and then 20,000 black images with 20% coverage were continuously printed. Then, a solid black image of A3 was created with toner, and the state of white spots caused by photoconductor filming was evaluated based on the following evaluation criteria.
⊚: Filming on the photoconductor is 0 to 5, and white spots on the image are 0 to 2. ○: Filming on the photoconductor is 6 to 10 and white spots on the image are 3. 6 to 6 Δ: 11 to 30 filming on the photoconductor, 7 to 10 white spots on the image ×: 31 or more filming on the photoconductor, white on the image 11 or more omissions

The evaluation results of the developing agents 1 to 37 are summarized in Table 5 below together with the types of toner particles and carrier particles constituting the developing agent.

As is clear from the results in Table 5, the external additive contains strontium titanate fine particles and titanium oxide fine particles, and the strontium titanate fine particles have a peak top particle diameter _RA of 10 nm or more and 100 nm or less (strontium titanate fine particles). _A ) and static charge image development including strontium titanate fine particles ( _B ) having a peak top particle diameter RB larger than the peak top particle diameter _RA and a difference between RB and _RA of 200 nm or more and 3000 nm or less. Since the developers 1 to 30 using the toner for particles all have less fog, they have good charge rising property and charge stability, and have sufficient fluidity to achieve good toner bottle discharge. It was possible to continuously form a high-quality image without white spots, with excellent cleaning properties and good filming properties.

Further, the developers 3 and 4 in which the particle size RA of the strontium titanate fine particles ( _A ) is in the range of 20 nm or more and 60 nm or less are the developer 2 in which the particle size _RA of the strontium titanate fine particles (A) is less than 20 nm. In particular, the evaluation results of fog and cleanability were improved. Further, as compared with the developer 5 having a particle diameter _RA of more than 60 nm, the evaluation results of fog and toner bottle dischargeability were particularly improved.

The developers 8 to 10 in which the particle size RB of the strontium titanate fine particles ( _B ) is in the range of more than 300 nm and 2000 nm or less are the toner particles 6 having the particle size RB of the strontium titanate fine particles ( _B ) of 300 nm or less. Compared with 7, the evaluation results of fog and filming were improved. Further, as compared with the toner particles 11 in which the particle diameter RB of the strontium titanate fine particles ( _B ) exceeds 2000 nm, the fog and the toner bottle dischargeability are improved. When the particle size of the strontium titanate fine particles (B) exceeds 300 nm, the strontium titanate fine particles (A) are protected from the impact with the carrier particles and the burial of the strontium titanate fine particles (A) is suppressed, so that the fog is evaluated. It is considered to have improved. In addition, it is considered that the polishability of the toner is improved and the evaluation result of filming is also improved. Further, when the particle size of the strontium titanate fine particles (B) is 2000 nm or less, the desorption of the strontium titanate fine particles (B) from the toner matrix particles is unlikely to be excessive, and the toner matrix particles of the strontium titanate fine particles (A) are less likely to be detached. It is considered that the fog and toner bottle dischargeability were improved because the burial in the particles was suppressed.

The developing agents 14 and 15 having a content of titanium oxide fine particles of 0.1 parts by mass or more and less than 1.0 part by mass with respect to 100 parts by mass of the toner base particles have a content of titanium oxide fine particles of 0.1 parts by mass. Compared with the developer 13 which is less than a part, the evaluation result of the fog and the toner bottle discharge property was particularly improved. Further, as compared with Example 16 in which the content of the titanium oxide fine particles was 1.0 part by mass or more, the evaluation results of the fog and the cleaning property were improved.

The developer 1 in which the strontium titanate fine particles (A) are rectangular parallelepipeds has an evaluation result of cleaning property and filming property as compared with the developer 22 in which both the strontium titanate fine particles (A) and (B) are amorphous. Has improved. This is because one of the strontium titanate fine particles (A) and (B) has a rectangular shape and the other has an amorphous shape, so that the contact area between the strontium titanate fine particles and the toner matrix particles increases, and the toner It is considered that the desorption of the strontium titanate fine particles from the mother particles was suppressed, and the effect of lowering the charge amount became easier to be exhibited. Further, the developer 25, in which the strontium titanate fine particles (A) are rectangular parallelepiped lanthanum-containing fine particles, has a fog and filming property as compared with the developer 1 using the strontium titanate fine particles (A), which does not contain lanthanum. The evaluation result was further improved. It is considered that this is because the cube-shaped and rectangular parallelepiped-shaped corners were removed by doping the strontium titanate fine particles with lanthanum, and excessive wear and scratches on the surface of the electrostatic latent image carrier were suppressed. However, as the developer 26 in which both the strontium titanate fine particles (A) and (B) are rectangular parallelepiped strontium-containing fine particles, the rectangular parallelepiped strontium titanate fine particles (A) and (B) containing no lanthanum were used. Although the evaluation results of fog and toner bottle dischargeability were better than those of the developer 23, the evaluation results of the toner bottle dischargeability were lower than those of the developer 25. It is considered that this is because a part of the effect of doping the strontium titanate fine particles with lanthanum was offset by the demerit of using two kinds of rectangular parallelepiped particles.

Further, the developing agents 28 and 29 in which the exposed area ratio of the core material particles in the carrier particles is 10.0% or more and 18.0% or less are compared with the developing agent 27 in which the exposed area ratio is less than 10.0%. , The evaluation result of fog and filming property was improved. Further, as compared with the developer 30 having an exposed area ratio of more than 18.0%, all the evaluation items, particularly the evaluation results of the fog and the toner bottle dischargeability, were improved. When the exposure area ratio of the carrier particles is within the above range, the resistance value of the carrier particles does not become too high, and the adhesion of the carrier particles to the electrophotographic photosensitive member can be suppressed, so that a high-quality image can be output. It is thought that it was.

On the other hand, the developer 31 of Comparative Example 1 in which the peak top particle diameter RA of the strontium titanate fine particles ( _A ) was less than 10 nm was at a level at which the evaluation results of fog and cleanability were impractical. Further, the developer 32 of Comparative Example 2 in which the peak top particle diameter RA of the strontium titanate fine particles ( _A ) exceeds 100 nm was at a level at which the evaluation results of fog and toner bottle dischargeability were impractical. This is because when the particle size RA of the strontium titanate fine particles ( _A ) is less than 10 nm, it is easily buried in the toner matrix particles, the function as an external additive is deteriorated, and when the particle size _RA exceeds 100 nm. It is considered that the contact points between the toner and the carrier particles became insufficient, and the fog and the toner bottle dischargeability decreased.

Further, the development of Comparative Example 3 in which the difference (particle size difference) between the peak top particle size RA of the strontium titanate fine particles ( _A ) and the peak top particle size RB of the strontium titanate fine particles ( _B ) is less than 200 nm. The evaluation results of the cleaning property and the filming property of the agent 33 were at a level that was impractical. Further, the developer 34 of Comparative Example 4 having a particle size difference of more than 3000 nm had a level at which the evaluation results of fog and filming property were impractical.

The toner particles 35 containing only the strontium titanate fine particles (B) having a large particle diameter as the strontium titanate fine particles had a level at which the evaluation results of fog and toner bottle dischargeability were impractical. Further, the developer 36 containing only the strontium titanate fine particles (A) having a small particle size as the strontium titanate fine particles and the developer 37 containing no titanium oxide fine particles have a level at which the evaluation result of fog and cleaning property is impractical. Met. From these results, it can be seen that it is difficult to obtain a practical toner and developer with only one type of strontium titanate fine particles.

According to the present invention, a toner for static charge image development, which is excellent in charge rising property, charge stability, fluidity, and cleaning property, and can continuously form a high-quality image without fog or white spots. And a two-component developer for developing an electrostatic charge image using the same can be provided. Therefore, according to the present invention, further speedup, higher performance, labor saving and diversification of recording media are expected in the electrophotographic image forming apparatus, and further widespread use of the image forming apparatus is expected.

Claims (10)

Toner matrix particles containing at least a binder resin,
Contains strontium titanate fine particles and an external additive containing titanium oxide fine particles,
The binder resin contains an amorphous vinyl resin in an amount of 0.1% by mass or more and 20% by mass or less based on the total mass of the binder resin.
The strontium titanate fine particles include strontium titanate fine particles (A) and strontium titanate fine particles (B), and the peak top particle size RA in the number particle size distribution of the strontium titanate fine particles ( _A ) is 10 nm or more and 100 nm or less. The peak top particle size RB in the number particle size distribution of the strontium titanate fine particles ( _B ) is larger than the peak top particle size RA of the strontium titanate fine particles ( _A ), and the particle size _RB and the like. The difference from the particle size _RA is 200 nm or more and 3000 nm or less, which is a toner for static charge image development. The toner for static charge image development according to claim 1, wherein the particle diameter RA of the strontium titanate fine particles ( _A ) is 20 nm or more and 60 nm or less. The toner for static charge image development according to claim 1 or 2, wherein the particle diameter RB of the strontium titanate fine particles ( _B ) is more than 300 nm and 2000 nm or less. The toner for static charge image development according to claim 3, wherein the particle diameter RB of the strontium titanate fine particles ( _B ) is 310 nm or more and 1500 nm or less. The static charge image development according to any one of claims 1 to 4, wherein the content of the titanium oxide fine particles is 0.1 part by mass or more and less than 1.0 part by mass with respect to 100 parts by mass of the toner. toner. The toner for static charge image development according to any one of claims 1 to 5, wherein the median diameter based on the volume of the toner matrix particles is 3.0 μm or more and 5.0 μm or less. The electrostatic charge image development according to any one of claims 1 to 6, wherein one of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) contains cubic and / or rectangular parallelepiped fine particles. Toner for. The toner for static charge image development according to any one of claims 1 to 7, wherein at least one of the strontium titanate fine particles (A) and the strontium titanate fine particles (B) is a lanthanum-containing strontium titanate fine particles. .. The toner for developing an electrostatic charge image according to any one of claims 1 to 8 and the toner for developing an electrostatic charge image.
A two-component developer for developing an electrostatic charge image, which contains core material particles and carrier particles containing a coating resin that covers the surface of the core material particles. The two-component developer for static charge image development according to claim 9, wherein the exposed area of the core material particles in the carrier particles is 10.0% or more and 18.0% or less with respect to the surface area of the core material particles. ..