JP7493973B2 - toner - Google Patents

Description

The present invention relates to a toner for developing electrostatic images used in electrophotography, electrostatic recording, and the like.

In the electrophotographic method, the process of developing an electrostatic latent image is to adhere a toner that has been triboelectrically charged to the electrostatic latent image by utilizing the electrostatic force of the electrostatic latent image, thereby forming a toner image. Toners for developing electrostatic latent images include non-magnetic toners that do not contain magnetic material, and magnetic toners that have magnetic material dispersed in a resin. Among these, non-magnetic toners are classified into one-component systems in which the toner is directly carried on a developer carrier and triboelectrically charged to develop the electrostatic latent image, and two-component systems in which the toner is mixed with a magnetic carrier and carried on a magnetic brush formed on the developer carrier by the magnetic carrier to develop the electrostatic latent image. The latter is preferably used for full-color image forming devices such as full-color copiers and full-color printers that require high image quality.
In the following, a two-component developer using a magnetic carrier will be described.
In response to the trend toward higher image quality in recent years, it has become necessary to use small particle size toner. In other words, it has become necessary to improve image quality by improving the reproducibility of fine lines and dots in images by making the particle size of the toner smaller. However, the smaller the particle size, the more likely it is that the toner will slip through the cleaning blade, which makes cleaning failure more likely to occur and leads to deterioration in image quality. Therefore, when aiming to improve image quality by making the particle size of the toner smaller, it is important to prevent such cleaning failure.
In order to address the problem of poor cleaning, a method has been proposed in the past in which an external additive is retained on the blade edge to form a blocking layer, thereby blocking toner particles and stabilizing cleaning (see Patent Document 1).

JP 2002-318467 A

However, in the method of Patent Document 1, it is necessary to migrate the external additive from the toner particles to form the blocking layer. And, although the toner can be blocked by this blocking layer, the external additive itself that has been migrated to form the blocking layer may slip through the blade and remain on the photoreceptor.
On the other hand, to achieve high image quality, it is necessary to suppress the "fogging" of non-image areas on the photoreceptor caused by toner with a low charge amount. Therefore, it is necessary to design the toner so that it can be given a sufficient charge amount by frictional charging with the carrier. For this purpose, a method is used in which an external additive that is in the negative direction of the triboelectric series with respect to the carrier is added to the toner surface. In particular, silica is often used as an external additive because it is more negatively positioned. Also, a silica external additive with a relatively large particle size is often selected for placement on the toner surface so that the carrier and silica surface can come into contact efficiently and be triboelectrically charged.
In a toner designed in this manner, when an external additive is transferred to the blade edge portion to form a blocking layer in order to prevent the toner from passing through the blade, the above-mentioned silica external additive passes through the blade and remains on the photoreceptor surface, which can cause the following problems.
That is, the silica external additive remaining on the photoreceptor surface may go through the charging process after passing through the blade, and the external additive may be strongly negatively charged due to the strong negativity of the silica external additive. This charge-up may occur locally at the top of the silica external additive remaining on the photoreceptor surface. In this case, when a relatively large particle size silica external additive is used for the above-mentioned reason, a large negative potential is generated at a relatively high position from the photoreceptor surface due to the large particle size of the external additive. Then, due to this locally large negative potential generated at a relatively high position from the photoreceptor surface, a "draw-in electric field" that draws the negatively charged toner toward the photoreceptor surface side may be formed near the photoreceptor surface. Then, this "draw-in electric field" may cause ghosts. That is, when consecutive images are formed, the silica external additive adheres to the photoreceptor in the previous image forming unit. As a result of the silica external additive passing through the blade and being charged, this "draw-in electric field" is generated, and in the next image formation, the toner is developed in the previous image forming unit to which the silica external additive adheres. There is a problem that ghosts may occur in this way.

The present inventors have found that ghosts can be suppressed while suppressing image degradation such as fogging by making silica particles having a primary particle number average particle size of 50 nm to 300 nm present on the surface of toner particles containing a binder resin and a colorant, and by making the zirconium contained in the silica particles have a mass concentration of _ZrO2 of 20 ppm to 1000 ppm when all elements detected in a fluorescent X-ray analysis are considered to be oxides and the mass amount of all oxides is set to 1.
That is, the toner of the present invention is a toner having toner particles containing a binder resin and a colorant, and silica particles on the surfaces of the toner particles,
The number average particle size of the primary particles of the silica particles is 50 nm or more and 300 nm or less,
The toner is characterized in that, in a fluorescent X-ray analysis of the silica particles, all elements detected are considered to be oxides, and the toner contains _ZrO2 at a mass concentration of 20 ppm or more and 1,000 ppm or less when the total mass of all oxides is set to 1.

It is possible to provide a toner that can output image quality with reduced ghosting while suppressing image degradation such as fogging.

FIG. 2 is an explanatory diagram illustrating an example of a toner particle surface treatment device. FIG. 11 is an explanatory diagram of a test chart used for evaluating ghosts. 3A and 3B are explanatory diagrams of areas (a) and (b) shown in FIG. 2 after the test chart is passed. FIG. 3 is an explanatory diagram of a case where a ghost occurs after the test chart shown in FIG. 2 is passed through;

In the present invention, the expressions "xx or more and xx or less" and "xx to xx" that express a numerical range refer to a numerical range including the lower and upper limit endpoints, unless otherwise specified.

The toner of the present invention is a toner having toner particles containing a binder resin and a colorant, and silica particles on the surfaces of the toner particles,
The number average particle size of the primary particles of the silica particles is 50 nm or more and 300 nm or less,
The toner is characterized in that, in a fluorescent X-ray analysis of the silica particles, all elements detected are considered to be oxides, and the toner contains _ZrO2 at a mass concentration of 20 ppm or more and 1,000 ppm or less when the total mass of all oxides is set to 1.

The toner of the present invention has silica particles on the surface of the toner particles, the primary particles having a number-average particle size of 50 nm or more and 300 nm or less.

By making the number-average particle size of the primary particles of the silica particles on the surface of the toner particles 50 nm or more, the carrier and the surface of the silica particles can easily come into contact with each other in the developer, and efficient frictional charging can be achieved, imparting a sufficient amount of charge to the toner and preventing the occurrence of fogging.

At the same time, by making the number-average particle size of the primary particles of the silica particles 300 nm or less and incorporating zirconium on the surface of the silica particles, it is possible to suppress the "pulling electric field" that occurs when the silica particles adhere to the photoreceptor, thereby suppressing ghosting. Since zirconium has a relatively high conductivity even when oxidized, it is possible to suppress the "pulling electric field" by suppressing the localization of negative charge on the silica particle surface even over time, and it is believed that this will continue to contribute to the suppression of ghosting.

In order to achieve this effect, zirconium must be contained in a concentration of 20 ppm or more as _ZrO2 mass concentration when all elements detected by fluorescent X-ray analysis are considered to be oxides and the total mass of all oxides is set to 1.

On the other hand, by keeping the zirconium content at 1000 ppm or less, leakage of toner charge caused by excessive increase in conductivity can be suppressed, and fogging can be prevented.

Furthermore, in order to suppress ghosting, it is preferable for the above-mentioned silica particles contained in the toner of the present invention to contain iron in an amount of 100 ppm or more in terms of mass concentration of _Fe2O3 , assuming that all elements detected by fluorescent X-ray analysis are oxides and the total mass amount of _all oxides is 1.

Among metals, iron is inexpensive and relatively resistant to oxidation, and therefore it is easy to maintain high conductivity on the silica surface. Therefore, by using it in combination with zirconium, it is possible to suppress the localization of negative charges on the silica particle surface over time, thereby suppressing the "pulling electric field," which is thought to continue to contribute to suppressing ghosting.

In addition, by keeping the iron content at 5,000 ppm or less, leakage of toner charge caused by excessive conductivity can be suppressed, and fogging can be prevented.

Furthermore, it is preferable that the above-mentioned silica particles contained in the toner of the present invention contain aluminum as follows. That is, it is preferable for the purpose of suppressing ghosting that aluminum is contained in an amount of 500 ppm or more and 20,000 ppm or less in terms of mass concentration of _Al2O3 when all elements detected in fluorescent X-ray analysis are considered to be oxides and the total mass amount of all _oxides is set to 1. By containing aluminum in the above range, in addition to imparting electrical conductivity, the silica particles are oxidized to alumina and are thereby given an appropriate positive charging property, suppressing excessive negative charging of the silica particles, suppressing the "pulling electric field" and suppressing ghosting while suppressing fogging.

Furthermore, the above-mentioned silica particles contained in the toner of the present invention are preferably silica aggregate particles in which multiple primary silica particles are bonded together, and the number-average density (ψSi) is 0.90 or less and 0.40 or more.

Here, density is an index showing the characteristics of the constricted parts of the shape of silica particles, and the value is small when the silica particles are silica aggregate particles. Specifically, density is the value obtained by dividing the projected area of the external additive when projected onto a two-dimensional image by the area of the external additive surrounded by the envelope. In other words, it is the value obtained by dividing the projected area of the external additive by the convex area of the external additive. Here, the convex area is the area of the part surrounded by the envelope created based on the outline of the target external additive. Density takes a value greater than 0 and less than 1, and the smaller the density, the more or larger the constricted parts are, indicating a complicated shape.

When the number-average density, which is the number average of the density, is within the aforementioned range, the number of contact points with the toner particle surface is likely to increase, adhesion to the toner particle surface becomes stronger, and excessive migration to the drum surface is suppressed, thereby suppressing ghosting.

The number average value of the maximum Feret diameter of the silica-bound particles is preferably 100 nm or more and 500 nm or less. That is, in order to more fully suppress the "pulling electric field" when transferred to the photoreceptor surface and to more easily suppress ghosts, it is preferable to set it to 500 nm or less. In addition, in the toner, in order to make the surface of the silica-bound particles protrude and efficiently triboelectrically charge the carrier, thereby making it possible to obtain a sufficient toner charge amount and to more easily suppress fogging, it is preferable that the number average value of the maximum Feret diameter of the silica-bound particles is 100 nm or more.

The coverage of the toner particle surface with the above-mentioned silica particles contained in the toner of the present invention is preferably 10% or more. By having a coverage of the silica particles of 10% or more, the carrier and the silica particle surface can easily come into contact in the developer, and efficient frictional charging can be achieved, imparting a sufficient amount of charge to the toner and preventing the occurrence of fogging.

Further, it is preferable that the toner of the present invention has _SrTiO3 particles externally added to the surface of the toner particles, and the number average value of the maximum Feret diameter of the _SrTiO3 particles is preferably 30 nm or more and 80 nm or less.

When the number average value of the maximum Feret's diameter of the _SrTiO3 particles is within this range, the particles are easily caught in the constricted portion or complicated shape of the silica-bound particle. As a result, even if the silica-bound particle moves to the drum surface, the _SrTiO3 particles tend to move in close proximity. Since _SrTiO3 has a positive charging polarity, it can reduce the negative charging of the silica-bound particle, suppress the "pulling electric field", and suppress ghosts.

In order to achieve this effect, the coverage of the SrTiO ₃ particles on the surface of the toner particles is preferably 5% or more.

In order to sufficiently charge the toner and further prevent the occurrence of fogging, the coverage of the SrTiO ₃ particles is preferably 50% or less.

In addition, when the _SrTiO3 particles migrate from the toner particles to the photoconductor surface, the above-mentioned "attraction electric field" caused by the silica external additive remaining on the photoconductor surface may be strengthened. In that case, ghosts may easily occur. Therefore, it is preferable that the adhesion rate of the _SrTiO3 particles is 80% or more.

In addition, for the following reasons, it is preferable that the binder resin contained in the toner particles of the present invention contains polyester.

In other words, by including a polyester resin in the binder resin, good low-temperature fixability can be maintained. Furthermore, when silica aggregate particles with a low number-average density are added externally, gaps tend to form between the toner particles and the silica aggregate particles because the silica aggregate particles have a constricted shape. This tends to reduce the efficiency of heat transfer to the toner particles during fixing, but the inclusion of a polyester resin can suppress this disadvantage. For these reasons, it is preferable that the binder resin contained in the toner particles of the present invention contains a polyester.

In addition, in order to achieve better low-temperature fixing properties, it is preferable to incorporate a crystalline polyester into the toner particles of the present invention.

Next, we will describe the preferred aspects.

<Silica particles>
The silica particles used in the present invention are particles primarily composed of silica (i.e., _SiO2 ), and may be particles manufactured using silicon compounds such as water glass or alkoxysilanes as raw materials, or may be particles obtained by crushing quartz.

Specific examples include silica particles produced by the sol-gel method, precipitated silica particles produced by the precipitation method, aqueous colloidal silica particles, fumed silica particles obtained by the gas phase method, fused silica particles, etc. Among these, the precipitation method or sol-gel silica is preferred for controlling the shape to have the aforementioned number average density, and the precipitation method is particularly preferred.

Precipitated silica is produced as follows:

An aqueous solution of water glass, which is an aqueous solution of sodium silicate, is prepared, and this aqueous solution of water glass is brought into contact with a mineral acid. Sulfuric acid is usually used as the mineral acid to be brought into contact with.

There are no limitations on the method of contacting the two, but it is preferable to contact them in small amounts. For example, one solution may be placed in a container and the other solution may be added dropwise to it.

It is also preferable that this contact is carried out so that the two solutions are mixed efficiently, and therefore it is preferable to carry out the contact under stirring. Therefore, it is preferable that the above-mentioned container is capable of stirring. For example, it is preferable to place the above-mentioned aqueous solution of water glass in a container capable of stirring, and drop sulfuric acid into the container while stirring.

It is also preferable to bring the water glass into contact with sulfuric acid at a relatively high temperature, preferably between 50°C and 80°C.

In this way, the water glass is brought into contact with sulfuric acid to cause a reaction. The pH value at which this contact occurs is generally around 7 to 10. The pH value decreases as this contact occurs, and when the pH value falls below 7 to 8, silica is produced and precipitated.

The dripping should end when the pH value reaches 7 or less, and preferably should continue until the pH value reaches the range of 2 to 5.

The silica particles thus produced and grown will precipitate as they grow and aggregate. The water is then separated and removed by filtration, centrifugation or other suitable means, and the precipitated silica is recovered. If necessary, it is washed, and then dried by a method such as heating, and further pulverized to obtain silica particles.

In addition, the precipitated silica produced in this way has the characteristic of being easy to crush, since it forms secondary particles through gentle aggregation. Furthermore, in this method, it is possible to obtain silica particles with different characteristics by changing the reaction conditions and post-treatment process to change physical properties such as surface area, pore size, and dispersed particle size.

In addition, compared to silica particles obtained by other manufacturing methods, the specific surface area is higher, the primary particle aggregate structure is more developed, and the pore volume tends to be higher.

Next, zirconium, and preferably iron and aluminum, are added to the silica particles thus produced.

Methods for incorporating these metals into silica particles include vapor deposition, sputtering, and PVD, but sputtering is preferred for its simplicity.

By using this method, the silica particles used in the present invention can be obtained by incorporating zirconium, and preferably also iron and aluminum, into the surface of the silica particles.

<Strontium titanate particles>
The strontium titanate particles preferably used in the present invention can be produced, for example, by a normal pressure heating reaction method. In this case, it is preferable to use a mineral acid peptized product of a hydrolyzate of a titanium compound as a titanium oxide source, and a water-soluble acidic metal compound as a source of a metal other than titanium. Then, the strontium titanate particles can be produced by reacting the mixture of the raw materials with an aqueous alkali solution at 60° C. or higher, followed by acid treatment.

The atmospheric pressure heating reaction method is explained below.

As the titanium oxide source, a mineral acid peptized product of a hydrolyzate of a titanium compound is used. Preferably, metatitanic acid obtained by a sulfuric acid method and having an _SO3 content of 1.0% by mass or less, more preferably 0.5% by mass or less, is peptized by adjusting the pH to 0.8 to 1.5 with hydrochloric acid.

On the other hand, metal sources other than titanium can include metal nitrates or hydrochlorides.

As the nitrate, for example, strontium nitrate can be used. As the hydrochloride, for example, strontium chloride can be used. The strontium titanate particles obtained here have a perovskite crystal structure, which is preferable in that the environmental stability of charging is further improved.

As the alkaline aqueous solution, caustic alkali can be used, but among them, sodium hydroxide aqueous solution is preferable.

In this manufacturing method, factors that affect the particle size of the resulting metal titanate particles include the pH when metatitanic acid is peptized with hydrochloric acid, the mixing ratio of the titanium oxide source and the metal source other than titanium, and the titanium oxide source concentration at the beginning of the reaction. Further factors include the temperature, addition rate, reaction time, and stirring conditions when the alkaline aqueous solution is added. In particular, if the reaction is stopped by suddenly lowering the temperature of the system after the addition of the alkaline aqueous solution, for example by pouring the system into ice water, the reaction can be stopped forcibly in the middle of the crystal growth saturation, making it easier to obtain a wide particle size distribution. In addition, a wide particle size distribution can be obtained by making the state of the reaction system non-uniform by reducing the stirring speed, changing the stirring method, etc.

These factors can be adjusted as appropriate to obtain metal titanate particles with the desired particle size and particle size distribution. It is preferable to prevent the inclusion of carbon dioxide gas, for example by carrying out the reaction under a nitrogen gas atmosphere to prevent the formation of carbonate during the reaction process.

The mixing ratio of the titanium oxide source and the source of a metal other than titanium during the reaction, where a metal other than titanium is represented by M and its oxide is represented by MXO, is preferably 0.90 or more and 1.40 or less, and more preferably 1.05 or more and 1.20 or less, in terms of the molar ratio MXO/ _TiO2 , where X is 1 when M is an alkaline earth metal and 2 when M is an alkali metal.

When the MXO/ _TiO2 (molar ratio) is 1.00 or less, the reaction product tends to contain not only metal titanate but also unreacted titanium oxide. Since metal sources other than titanium have relatively high solubility in water while titanium oxide sources have low solubility in water, when the MXO/ _TiO2 (molar ratio) is 1.00 or less, the reaction product tends to contain not only metal titanate but also unreacted titanium oxide.

The concentration of the titanium oxide source at the beginning of the reaction is preferably 0.050 mol/L or more and 1.300 mol/L or less, and more preferably 0.080 mol/L or more and 1.200 mol/L or less, in terms of _TiO 2 .

By increasing the concentration of the titanium oxide source at the beginning of the reaction, the number average particle size of the primary particles of the metal titanate particles can be reduced.

When adding the alkaline aqueous solution, if the temperature is over 100°C, a pressure vessel such as an autoclave is required, but for practical purposes, a temperature between 60°C and 100°C is appropriate.

The slower the rate of addition of the alkaline aqueous solution, the larger the particle size of the metal titanate particles obtained, and the faster the rate of addition, the smaller the particle size of the metal titanate particles obtained. The rate of addition of the alkaline aqueous solution is preferably 0.001 equivalents/h or more and 1.2 equivalents/h or less, more preferably 0.002 equivalents/h or more and 1.1 equivalents/h or less, based on the charged raw material. These can be adjusted appropriately depending on the particle size to be obtained.

In this manufacturing method, it is preferable to further treat the metal titanate particles obtained by the normal pressure heating reaction with an acid. When performing normal pressure heating reaction to manufacture metal titanate particles, if the mixing ratio of the titanium oxide source and the metal source other than titanium exceeds 1.00 in terms of MXO/ _TiO2 (molar ratio), the following is likely to occur. That is, the unreacted metal source other than titanium remaining after the reaction is completed is likely to react with carbon dioxide gas in the air to generate impurities such as metal carbonates. In addition, if impurities such as metal carbonates remain on the surface, it becomes difficult to uniformly coat the surface treatment agent when performing surface treatment to impart hydrophobicity due to the influence of the impurities. Therefore, it is recommended to perform acid treatment to remove the unreacted metal source after adding an alkaline aqueous solution.

In the acid treatment, it is preferable to adjust the pH to 2.5 or more and 7.0 or less using hydrochloric acid, and it is more preferable to adjust the pH to 4.5 or more and 6.0 or less. In addition to hydrochloric acid, nitric acid, acetic acid, etc. can be used for the acid treatment. If sulfuric acid is used, metal sulfates that have low solubility in water are likely to be generated.

The strontium titanate preferably used in the present invention is not particularly limited as long as it can be surface-treated and can be made into a cubic or rectangular shape. In addition, a method of performing a dry mechanical treatment may be used as a method for controlling the shape of the metal titanate particles.

The surface treatment agent is not particularly limited, but examples include disilylamine compounds, halogenated silane compounds, silicone compounds, and silane coupling agents.

A disilylamine compound is a compound having a disilylamine (Si-N-Si) moiety. Examples of disilylamine compounds include hexamethyldisilazane (HMDS), N-methyl-hexamethyldisilazane, and hexamethyl-N-propyldisilazane. An example of a halogenated silane compound is dimethyldichlorosilane.

Examples of silicone compounds include silicone oils and silicone resins (varnishes). Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, and fluorine modified silicone oil. Examples of silicone resins (varnishes) include methyl silicone varnish and phenyl methyl silicone varnish.

Examples of silane coupling agents include silane coupling agents having an alkyl group and an alkoxy group, or silane coupling agents having an amino group and an alkoxy group, or fluorine-containing silane coupling agents. More specific examples of silane coupling agents include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, trimethylmethoxysilane, trimethyldiethoxysilane, triethylmethoxysilane, triethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyldimethoxymethylsilane, γ-aminopropyldiethoxymethylsilane, 3,3,3-trifluoropropyldimethoxysilane, 3,3,3-trifluoropropyldiethoxysilane, perfluorooctylethyltriethoxysilane, 1,1.1-trifluorohexyldiethoxysilane, etc.

It is particularly preferable that the material is treated with a fluorine-based silane coupling agent such as trifluoropropyltrimethoxysilane or perfluorooctylethyltriethoxysilane.

The preferred amount of treatment agent is 0.5 parts by mass or more and 20.0 parts by mass or less per 100 parts by mass of strontium titanate particles.

The above-mentioned surface treatment agents may be used alone or in combination of two or more.

<Binder resin>
The toner particles in the present invention must contain a polyester resin as a binder resin from the viewpoint of low-temperature fixability. The toner particles may also be a hybrid resin in which a polyester resin and a vinyl resin are mixed or in which both are partially reacted.

As monomers used in the polyester unit of the polyester resin, polyhydric alcohols (divalent or trivalent or higher alcohols), polyvalent carboxylic acids (divalent or trivalent or higher carboxylic acids), their acid anhydrides or their lower alkyl esters are used. Here, in order to produce a branched polymer in order to express "strain hardening", it is effective to partially crosslink within the molecule of the amorphous resin, and for this purpose, it is preferable to use a polyfunctional compound with a valence of three or more. Therefore, it is preferable to include a trivalent or higher carboxylic acid, its acid anhydride or its lower alkyl ester, and/or a trivalent or higher alcohol as the raw material monomer for the polyester unit.

The following polyhydric alcohol monomers can be used as the polyhydric alcohol monomers for the polyester unit of the polyester resin:

Dihydric alcohol components include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, and bisphenol represented by formula (A) and its derivatives;

（式中、Ｒはエチレンまたはプロピレン基であり、ｘ及びｙはそれぞれ０以上の整数であり、かつ、ｘ＋ｙの平均値は０以上１０以下である。）

(In the formula, R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x+y is 0 or more and 10 or less.)

Diols represented by formula (B);

Examples of trihydric or higher alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene. Of these, glycerol, trimethylolpropane, and pentaerythritol are preferably used. These dihydric alcohols and trihydric or higher alcohols can be used alone or in combination.

The following polycarboxylic acid monomers can be used as polycarboxylic acid monomers in the polyester unit of the polyester resin:

Examples of divalent carboxylic acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, n-octenylsuccinic acid, n-octylsuccinic acid, isooctylsuccinic acid, isooctylsuccinic acid, anhydrides of these acids, and lower alkyl esters of these acids. Of these, maleic acid, fumaric acid, terephthalic acid, and n-dodecenylsuccinic acid are preferably used.

Examples of trivalent or higher carboxylic acids, their anhydrides, or their lower alkyl esters include 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, and their anhydrides or lower alkyl esters. Of these, 1,2,4-benzenetricarboxylic acid, i.e., trimellitic acid or its derivatives, is particularly preferred because it is inexpensive and easy to control the reaction. These divalent carboxylic acids and trivalent or higher carboxylic acids can be used alone or in combination.

The method for producing the polyester unit of the present invention is not particularly limited, and known methods can be used. For example, the above-mentioned alcohol monomer and carboxylic acid monomer are charged at the same time, and polymerized through an esterification reaction or ester exchange reaction and a condensation reaction to produce a polyester resin. The polymerization temperature is not particularly limited, but is preferably in the range of 180°C to 290°C. When polymerizing the polyester unit, for example, a polymerization catalyst such as a titanium-based catalyst, a tin-based catalyst, zinc acetate, antimony trioxide, or germanium dioxide can be used. In particular, the binder resin of the present invention is more preferably a polyester unit polymerized using a tin-based catalyst.

In addition, the acid value of the polyester resin is 5 mgKOH/g or more and 20 mgKOH/g or less, and the hydroxyl value is 20 mgKOH/g or more and 70 mgKOH/g or less, which can suppress the amount of moisture adsorption in a high-temperature and high-humidity environment and can suppress the non-electrostatic adhesion force. Therefore, it is preferable from the viewpoint of fogging suppression.

The binder resin may contain the following, with polyester resin as the main component. Examples of such components include homopolymers of styrene and its substituted derivatives, such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-based copolymers, such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, and styrene-methacrylic acid ester copolymer; styrene-based copolymer resin, polyvinyl chloride, phenolic resin, naturally modified phenolic resin, naturally modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyethylene resin, and polypropylene resin.

The binder resin may be a mixture of low molecular weight resin and high molecular weight resin. From the viewpoint of low temperature fixability and hot offset resistance, it is preferable that the content ratio of high molecular weight resin to low molecular weight resin is 40/60 or more and 85/15 or less by mass.

The toner particles in the present invention may contain a crystalline polyester as necessary. The crystalline polyester is not particularly limited and any known crystalline polyester can be used, but it is preferably a saturated polyester. A crystalline resin is a resin that shows a clear melting point in differential scanning calorimetry.

Furthermore, it is preferable that the crystalline polyester is a condensate of an aliphatic dicarboxylic acid, an aliphatic diol, and an aliphatic monocarboxylic acid. Incorporating an aliphatic monocarboxylic acid as a component of the crystalline polyester is preferable because it makes it easier to adjust the molecular weight and hydroxyl value of the crystalline polyester, and also makes it possible to control the affinity with the wax.

The content of the crystalline polyester is preferably 0.1 parts by mass or more and 10 parts by mass or less, and more preferably 0.2 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the binder resin.

<Coloring Agent>
The toner particles in the present invention may contain a colorant. Examples of the colorant include the following.

Black colorants include carbon black, and those toned to black using yellow, magenta, and cyan colorants. As a colorant, a pigment may be used alone, but it is more preferable to use a dye and a pigment in combination to improve the clarity of the image in terms of the image quality of a full-color image.

Pigments for magenta toner include the following: C.I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48:2, 48:3, 48:4, 49, 50, 51, 52, 53, 54, 55, 57:1, 58, 60, 63, 64, 68, 81:1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269, 282; C.I. Pigment Violet 19; C.I. Bat Red 1, 2, 10, 13, 15, 23, 29, 35.

Dyes for magenta toner include the following: C.I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; C.I. Disperse Red 9; C.I. Solvent Violet 8, 13, 14, 21, 27; C.I. Disperse Violet 1; basic dyes such as C.I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; C.I. Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

Pigments for cyan toner include the following: C.I. Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, 17; C.I. Bat Blue 6; C.I. Acid Blue 45; copper phthalocyanine pigments with 1 to 5 phthalimidomethyl groups substituted on the phthalocyanine skeleton.

An example of a dye for cyan toner is C.I. Solvent Blue 70.

Yellow toner pigments include: C.I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185; C.I. Vat Yellow 1, 3, 20.
Dyes for yellow toner include C.I. Solvent Yellow 162.

These colorants can be used alone or in mixtures, or even in the form of a solid solution. Colorants are selected based on their hue angle, saturation, brightness, light resistance, transparency on overhead projectors, and dispersibility in toner.

The content of the colorant is preferably 0.1 parts by mass or more and 30.0 parts by mass or less per 100 parts by mass of the total amount of the resin components.

<Developer>
The toner of the present invention can be used as a one-component developer, but in order to suppress localization of charge on the toner surface, it can also be mixed with a magnetic carrier and used as a two-component developer.

The magnetic carrier may be any of the commonly known magnetic carriers, such as iron oxide; metal particles such as iron, lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium, and rare earth elements, alloy particles thereof, and oxide particles thereof; magnetic materials such as ferrite; magnetic material-dispersed resin carriers (so-called resin carriers) that contain magnetic materials and binder resins that hold the magnetic materials in a dispersed state; etc.

When the toner is mixed with a magnetic carrier to be used as a two-component developer, the mixing ratio of the magnetic carrier is preferably 2% by mass or more and 15% by mass or less, and more preferably 4.0% by mass or more and 13.0% by mass or less, in terms of the toner concentration in the two-component developer.

<Toner Manufacturing Method>
The method for producing the toner particles is not particularly limited, but a pulverization method is preferred from the viewpoint of dispersion of the toner materials such as pigments.

The procedure for producing toner using the pulverization method is explained below.

In the raw material mixing process, materials constituting the toner particles, such as binder resin, release agent, colorant, and other components such as charge control agent if necessary, are weighed out in predetermined amounts, blended, and mixed. Examples of mixing devices include a double-con mixer, V-type mixer, drum-type mixer, super mixer, Henschel mixer, Nauta mixer, and Mechano Hybrid (manufactured by Nippon Coke and Engineering Co., Ltd.).

Next, the mixed materials are melt-kneaded to disperse the pigments in the binder resin. In the melt-kneading process, a batch kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used, and single-screw or twin-screw extruders are the mainstream due to their advantage of continuous production. Examples include a KTK twin-screw extruder (manufactured by Kobe Steel, Ltd.), a TEM twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), a PCM kneader (manufactured by Ikegai Iron Works), a twin-screw extruder (manufactured by KCK Corporation), a Co-Kneader (manufactured by Buss Co., Ltd.), and a Kneadex (manufactured by Nippon Coke and Engineering Co., Ltd.). Furthermore, the resin composition obtained by melt-kneading may be rolled with a twin roll or the like and cooled with water or the like in a cooling process.

Next, the cooled resin composition is pulverized to the desired particle size in a pulverization process. In the pulverization process, the resin composition is coarsely pulverized using a pulverizer such as a crusher, hammer mill, or feather mill. The resin composition is then finely pulverized using a pulverizer using an air jet system, such as a Kryptron System (Kawasaki Heavy Industries), a Super Rotor (Nisshin Engineering), a Turbo Mill (Turbo Kogyo), or an air jet system. If necessary, the resin composition is classified using a classifier or sieve such as an Elbow Jet, which uses an inertial classification system, or a Turbo Plex, TSP Separator, or Faculty, which uses a centrifugal classification system. The Elbow Jet is manufactured by Nittetsu Mining Co., Ltd., and the Turbo Plex, TSP Separator, and Faculty are manufactured by Hosokawa Micron Corporation. The toner particles are then surface-treated by heating to adhere the external additives to the toner particles.

For example, surface treatment can be performed with hot air using the surface treatment device shown in Figure 1. The mixture supplied by the material supplying means 1 is introduced into the inlet pipe 3, which is installed vertically to the material supplying means, by compressed gas adjusted by the compressed gas adjusting means 2. The mixture that passes through the inlet pipe is uniformly dispersed by the conical protruding member 4 installed in the center of the material supplying means, and is introduced into the eight-way supply pipe 5 that spreads radially, and is introduced into the treatment chamber 6 where the heat treatment is performed. At this time, the flow of the mixture supplied to the treatment chamber is regulated by the regulating means 9 for regulating the flow of the mixture installed in the treatment chamber. Therefore, the mixture supplied to the treatment chamber is heat-treated while swirling in the treatment chamber, and then cooled.

Hot air for heat-treating the supplied mixture is supplied from the hot air supplying means 7, and is introduced into the treatment chamber by spirally swirling the hot air using the swirling member 13 for swirling the hot air. The configuration is such that the swirling member 13 for swirling the hot air has multiple blades, and the swirling of the hot air can be controlled by the number and angle of the blades. The hot air supplied into the treatment chamber preferably has a temperature of 100°C to 300°C at the outlet of the hot air supplying means 7. If the temperature at the outlet of the hot air supplying means is within the above range, it is possible to uniformly spheronize the toner particles while preventing the toner particles from fusing or coalescing due to excessive heating of the mixture.

The heat-treated toner particles are then cooled by cold air supplied from cold air supply means 8, and the temperature of the cold air supplied from cold air supply means 8 is preferably -20°C to 30°C. If the temperature of the cold air is within the above range, the heat-treated toner particles can be efficiently cooled, and the fusion and coalescence of the heat-treated toner particles can be prevented without impeding the uniform spheroidization of the mixture. The absolute moisture content of the cold air is preferably 0.5 g/ ^m3 or more and 15.0 g/ ^m3 or less.

Next, the cooled heat-treated toner particles are collected by the collection means 10 at the bottom of the processing chamber. A blower (not shown) is provided beyond the collection means, which is used to suction and transport the particles.

The powder particle supply port 14 is provided so that the swirling direction of the supplied mixture and the swirling direction of the hot air are the same, and the recovery means 10 of the surface treatment device is provided on the outer periphery of the treatment chamber so as to maintain the swirling direction of the swirled powder particles. Furthermore, the cold air supplied from the cold air supply means 8 is configured to be supplied horizontally and tangentially from the outer periphery of the device to the circumferential surface inside the treatment chamber. The swirling directions of the toner supplied from the powder supply port, the swirling direction of the cold air supplied from the cold air supply means, and the swirling direction of the hot air supplied from the hot air supply means are all the same. Therefore, no turbulence occurs in the treatment chamber, the swirling flow in the device is strengthened, a strong centrifugal force is applied to the toner, and the dispersibility of the toner is further improved, so that a toner with a uniform shape and few coalesced particles can be obtained.

Then, the fine powder side is divided into two parts, the coarse powder side and the fine powder side. For example, an inertial classification method Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.) is used to divide the particles into two. A desired amount of external additives is added to the surface of each of the divided heat-treated toner particles. The method of adding external additives includes stirring and mixing using a mixing device such as a Double Con Mixer, V-type mixer, drum mixer, super mixer, Henschel mixer, or Nauta mixer as an external adder. Alternatively, a mixing device such as Mechano Hybrid (manufactured by Nippon Coke & Engineering Co., Ltd.) or Nobilta (manufactured by Hosokawa Micron Corporation) can be used as an external adder to stir and mix the particles. In this case, if necessary, external additives such as a flow agent can be added.

The methods for measuring various physical properties of toner and raw materials are explained below.

<Water washing treatment method>
In the present invention, the water washing treatment was carried out as follows. 6 cc of Contaminon N, a surfactant, was added to a 30 cc glass vial and thoroughly mixed with an aqueous sucrose solution prepared by dissolving 20.7 g of sucrose (manufactured by Kishida Chemical Co., Ltd.) in 10.3 g of ion-exchanged water to prepare a dispersion. Contaminon N may be, for example, a neutral detergent for cleaning precision measuring instruments with a pH of 7, which is composed of a nonionic surfactant, an anionic surfactant, and an organic builder. The glass vial may be, for example, VCV-30, manufactured by Nichiden Rika Glass Co., Ltd., with an outer diameter of 35 mm and a height of 70 mm. 1.0 g of toner was added to this vial, and the toner was allowed to stand until it naturally settled to prepare a pre-treatment dispersion. This dispersion was shaken for 5 minutes with a shaker (YS-8D type: manufactured by Yayoi Co., Ltd.) at a shaking speed of 200 rpm to separate the inorganic fine particles from the surface of the toner particles. A centrifuge is used to separate the toner with the remaining inorganic fine particles from the separated inorganic fine particles. The centrifugation step was carried out at 3700 rpm for 30 minutes. The toner containing the remaining inorganic fine particles was collected by suction filtration, dried, and washed with water to obtain the toner.

<Method of measuring adhesion rate>
The adhesion rate is measured as follows. First, the amount of strontium titanate particles contained in the toner before the water washing process is quantified. This is done by measuring the Sr element strength in the toner using a wavelength dispersive X-ray fluorescence analyzer Axios advanced (manufactured by PANalytical Corporation). Next, the Sr element strength of the toner after the water washing process is measured in the same manner. The adhesion rate is calculated by (Sr element strength of toner after water washing/Sr element strength in toner)×100(%).

<Method of measuring the coverage of strontium titanate and silica particles>
Twenty toner surface images photographed with a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation) are randomly sampled.

The image information is binarized using the image analysis software Image-Pro Plus ver. 5.0 (Nippon Roper Co., Ltd.) by taking advantage of the difference in brightness between the toner particle surface and the external additive portion. This binarization separates the area of the external additive portion and the area of the toner particle portion (including the area of the external additive portion) STone.

The surface area of the external additive portion is made up of silica-bound particles and strontium titanate, but they can be distinguished by their shapes as follows. That is, silica particles are amorphous or spherical, whereas strontium titanate particles are rectangular or cubic with rounded corners.

By distinguishing based on this shape, the area of the external additive portion occupied by strontium titanate, _SSrTiO3, is calculated.

The coverage (%) of the toner particles with the SrTiO ₃ particles, σSrTiO ₃ , is calculated by the following formula:
σSrTiO ₃ (%) = SSrTiO ₃ /S Toner × 100

Similarly, the area SSi of the silica particles in the area of the external additive portion is calculated by the above-mentioned classification based on the shape. Then, the coverage rate (%) σSi of the toner particles by the silica particles is calculated by the following formula.
σSi (%) = SSi/SToner × 100

<Number average particle diameter RSi of primary particles constituting silica particles, and number average value RCSi of maximum Feret diameter of silica aggregate particles>
A measurement sample is prepared. 1 ml of isopropanol is added to about 5 mg of an external additive, and the mixture is dispersed for 5 minutes using an ultrasonic disperser (ultrasonic cleaner). Next, a drop of the dispersion liquid is placed on a microgrid (150 mesh) with a support film for TEM, and the mixture is dried to prepare a measurement sample.

Next, images are taken using a transmission electron microscope (TEM) at an accelerating voltage of 200 kV at a magnification (e.g., 200k to 1M) that allows sufficient measurement of the length of the silica particles in the field of view, and the number-average particle size is determined from the particle sizes of the primary particles that make up 100 randomly selected silica particles. Furthermore, if the silica particles are silica aggregate particles, the number-average maximum Feret diameter is determined from the maximum Feret diameter of the 100 silica particles. The particle size and maximum Feret diameter of the primary particles of each silica particle may be measured manually or using a measurement tool.

<Method for measuring number average density ψSi of silica particles>
In the image of silica particles obtained by the above-mentioned transmission electron microscope (TEM), silica particle regions and non-silica particle regions are divided by binarization based on the difference in brightness.

The conditions for binarization can be appropriately selected depending on the observation device. Image J image analysis software is used for binarization.

The number-average solidity of the silica particles is calculated from the obtained binary image by performing particle analysis using the image analysis software Image J as follows. That is, in the image analysis software Image J, the solidity is named and a numerical range is specified.

The above is performed for 100 binarized images, and the average value is taken as the number-average density of the silica particles.

<Method for measuring the softening point of resin>
The softening point of the resin is measured using a constant load extrusion type capillary rheometer "Flow characteristic evaluation device Flow Tester CFT-500D" (manufactured by Shimadzu Corporation) according to the manual that comes with the device. With this device, a constant load is applied from above the measurement sample by a piston, while the measurement sample filled in a cylinder is heated and melted, and the molten measurement sample is extruded from a die at the bottom of the cylinder, and a flow curve showing the relationship between the piston descent amount and temperature at this time can be obtained.

In the present invention, the "melting temperature in the 1/2 method" described in the manual attached to the "Flow characteristic evaluation device Flow Tester CFT-500D" is taken as the softening point. The melting temperature in the 1/2 method is calculated as follows. First, find 1/2 of the difference between the piston descent amount Smax at the time when the outflow ends and the piston descent amount Smin at the time when the outflow starts (this is called X. X = (Smax - Smin) / 2). Then, the temperature of the flow curve when the piston descent amount on the flow curve is X is the melting temperature in the 1/2 method.

The measurement sample is prepared by compressing approximately 1.0 g of resin at approximately 10 MPa for approximately 60 seconds using a tablet compression machine (e.g., NT-100H, manufactured by NPA Systems) in an environment of 25°C, and forming it into a cylindrical shape with a diameter of approximately 8 mm.

The measurement conditions for CFT-500D are as follows.
Test mode: Heating method Starting temperature: 40°C
Reached temperature: 200°C
Measurement interval: 1.0°C
Heating rate: 4.0° C./min. Piston cross-sectional area: 1.000 cm ²
Test load (piston load): 10.0 kgf (0.9807 MPa)
Preheat time: 300 seconds Die hole diameter: 1.0 mm
Die length: 1.0 mm

<Method for measuring the content of zirconium, iron, and aluminum in silica particles>
The content of zirconium, iron, and aluminum in the silica particles used in the present invention can be measured by an X-ray fluorescence analyzer. For example, a wavelength dispersive X-ray fluorescence analyzer Axios advanced (manufactured by PANalytical) is used. Then, 2 g of the sample is weighed into a cup recommended by PANalytical for powder measurement with a dedicated PP (polypropylene) film attached to the bottom, a layer of uniform thickness is formed on the bottom, and the lid is put on. Then, elements from Na to U in the silica particles are measured by the FP method under atmospheric pressure He atmosphere. At that time, it is assumed that all the detected elements are oxides, and their total mass is 100%, and the content (mass%) of ZrO ₂ , Fe ₂ O ₃ , and Al ₂ O ₃ relative to the total mass is calculated as an oxide equivalent value using the software SpectraEvaluation (version 5.0L).

The present invention will be described in more detail below using examples and comparative examples, but the aspects of the present invention are not limited to these. Note that the parts and percentages in the examples and comparative examples are all by weight unless otherwise specified.

<Production Example of Strontium Titanate Particles>
Metatitanic acid obtained by the sulfuric acid method was deironized and bleached, then an aqueous solution of sodium hydroxide was added to adjust the pH to 9.0, desulfurized, neutralized to pH 5.8 with hydrochloric acid, filtered, and washed with water. Water was added to the washed cake to make a slurry of 1.85 mol/L in terms of _TiO2 , and hydrochloric acid was added to adjust the pH to 1.4, followed by peptization.

After desulfurization and peptization, 1.88 moles of metatitanic acid was collected as _TiO2 and charged into a 3 L reaction vessel.

To the peptized metatitanic acid slurry, 2.16 moles of an aqueous strontium chloride solution was added so that the SrO/ _TiO2 molar ratio was 1.15. The _TiO2 concentration was adjusted to 1.039 moles/L.

Next, the mixture was heated to 90°C while stirring, and 440 mL of 12 mol/L aqueous sodium hydroxide solution was added over 40 minutes. Stirring was continued at 95°C for 45 minutes to complete the reaction.

The reaction slurry was cooled to 40°C, hydrochloric acid was added until the pH reached 4.9, and stirring was continued for 20 minutes. The resulting precipitate was decanted, filtered, and separated, and then dried in air at 120°C for 8 hours.

300 g of the dried product was then placed in a dry particle composite device (Nobilta NOB-130, manufactured by Hosokawa Micron Corporation). Processing was carried out for 10 minutes at a processing temperature of 30°C with a rotary processing blade speed of 95 m/sec. Hydrochloric acid was then added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation. The slurry containing the precipitate was adjusted to 40°C, and hydrochloric acid was added to adjust the pH to 2.5.

Next, 4.6% by mass of isobutyltrimethoxysilane and 4.6% by mass of trifluoropropyltrimethoxysilane were added to the solid content after stirring and mixing for 1 hour, and stirring was continued for 10 hours. 5 mol/L sodium hydroxide solution was added to adjust the pH to 6.2, and stirring was continued for 1 hour. After filtering and washing, the resulting cake was dried in air at 130°C for 8 hours to obtain strontium titanate particles.

The number-average particle size of the strontium titanate thus obtained was approximately 40 nm.

<Production Example of Silica Particles 1>
Silica particles 1 were produced by the so-called precipitation method as follows.
A 3 L settling vessel equipped with a metallic stirring rod, a dropping nozzle (a Teflon (registered trademark) microtube pump), a heating device, and a thermometer was charged with 12.6 L of water under stirring and heated to 80°C.

Then water glass solution (weight ratio 3.4:1 = 26.8% _SiO2 and 7.85% _Na2O ; density 1.352 g/ml) was added to reach a pH value of 8.5.

Next, while maintaining the solution temperature at 80°C, 56.7 ml/min of water glass (composition as above) and an amount of sulfuric acid (50%) to constantly maintain the pH value at 8.5 were added simultaneously to precipitate the silica for 230 minutes. Sulfuric acid (50%) alone was then added dropwise to acidify the solution to a pH value of 3.5, which was the end point. The precipitated silica was then separated from the suspension and washed with water, then dried at 105°C to 110°C, and then crushed in an experimental pin mill to obtain a crushed silica body.

Then, the obtained silica pulverized body was coated with small amounts of zirconium, aluminum, and iron by magnetron sputtering to obtain silica particles 1 as a silica bond.

The number average particle size of the primary particles of silica particles 1, the number average maximum Feret's diameter, and the number average density of silica particles 1 are shown in Table 1. Table 1 also shows the mass concentrations of _ZrO2 , _Al2O3 , and _Fe2O3 when all elements contained in silica particles 1 and detected by fluorescent X-ray analysis are considered to be oxides _and the total mass of _all oxides is set to 1.

<Production Examples of Silica Particles 2 to 6>
In the manufacturing example of silica particle 1, the number average particle size and the number average particle size of the primary particles were changed. In addition, the amount of trace coating of zirconium, aluminum, and iron by magnetron sputtering was changed. In this way, silica particles 2 to 6 were obtained as silica aggregate particles. The number average particle size of the primary particles of silica particles 2 to 6, the number average value of the maximum Feret's diameter, and the number average particle size of silica particles 2 to 6 are shown in Table 1. In addition, the mass concentrations of ZrO 2 , Al 2 O ₃ , and Fe ₂ O ₃ contained in silica particles 2 to 6 are shown in Table 1 when all elements detected by fluorescent X-ray _analysis contained in silica particles 2 to ₆ are considered to be oxides and the total mass of all oxides is set to 1.

<Production Example of Silica Particles 7>
Silica particles 7 were produced by the so-called sol-gel method as follows.

Preparation of alkaline catalyst solution (1) 640 parts of methanol and 87 parts of 10% aqueous ammonia were placed in a 3 L glass reaction vessel equipped with a metal stirring rod, a dropping nozzle (a Teflon (registered trademark) microtube pump), and a thermometer, and mixed with stirring to obtain alkaline catalyst solution (1). The amount of ammonia catalyst in alkaline catalyst solution (1): the amount of _NH3 ( _NH3 [mol]/(aqueous ammonia + methanol) [L]) was 0.61 mol/L.

Preparation of silica microparticle suspension (1) The alkaline catalyst solution (1) was replaced with nitrogen. Then, while stirring the alkaline catalyst solution (1), 125 parts of tetramethoxysilane (TMOS) and 80 parts of ammonia water with a catalyst ( _NH3 ) concentration of 4.4% were simultaneously added dropwise in the following feed amounts to obtain a suspension of silica microparticles (silica microparticle suspension (1)).

Here, the supply rate of tetramethoxysilane (TMOS) was 13 g/min, i.e., 0.0046 mol/(mol·min), relative to the total moles of methanol in the alkaline catalyst solution (1).

The supply rate of 4.4% ammonia water was 4 g/min, relative to the total supply rate of tetraalkoxysilane per minute (0.0855 mol/min). This corresponds to 0.29 mol/min per 1 mol of the total supply rate of tetraalkoxysilane per minute.

Hydrophobization treatment of silica fine particles 5.59 parts of trimethylsilane was added to 200 parts of the silica fine particle suspension (1) (solid content 13.985%) to perform hydrophobization treatment. After that, the mixture was heated at 65°C using a hot plate and dried to produce silica aggregate particles.

Then, trace amounts of zirconium, aluminum, and iron were coated by magnetron sputtering to obtain silica particles 7 as silica-bound particles coated with these metals.

The number average density, number average particle size of the primary particles, and number average value of the maximum Feret's diameter of the silica particles 7 thus obtained are shown in Table 1. In addition, the mass concentrations of ZrO2, Al2O3, and _Fe2O3 contained in the silica particles ₇ , when all elements detected by fluorescent _{X -} ray analysis contained in the silica particles ₇ are considered to be oxides and the total mass of all oxides is set to 1, are shown in Table 1.

<Production Examples of Silica Particles 8 to 12>
In the manufacturing example of silica particle 7, the number average density and the number average particle diameter of the primary particles were changed. In addition, the amount of trace coating of zirconium, aluminum, and iron by magnetron sputtering was changed. In this way, silica particles 8 to 12 were obtained as silica aggregate particles. The number average particle diameter of the primary particles of silica particles 8 to 12, the number average value of the maximum Feret diameter, and the number average density of silica particles 8 to 12 are shown in Table 1. In addition, the mass concentrations of ZrO 2 , Al 2 O 3 , and Fe ₂ O ₃ contained in silica particles _{8 to 12} are shown in Table 1 when all elements detected by fluorescent X-ray analysis contained in silica particles 8 to 12 are considered to be oxides and the total mass amount of all oxides is set to 1.

<Production Example of Silica Particles 13>
The silica particles 13 were produced by the so-called sol-gel method as follows.

589.8 g of methanol, 42.0 g of water, and 47.2 g of 26% aqueous ammonia were added to a 3-liter glass reactor equipped with a stirrer, dropping funnel, and thermometer and mixed.

The resulting solution was adjusted to 35°C, and 1,100.0 g (7.23 mol) of tetramethoxysilane and 395.4 g of 5.3% by mass aqueous ammonia were added simultaneously while stirring.

Tetramethoxysilane was added dropwise over 6 hours, and ammonia water over 5 hours. After the addition was completed, stirring was continued for an additional 0.5 hours to carry out hydrolysis, yielding a methanol-water dispersion of hydrophilic spherical sol-gel silica microparticles.

Next, an ester adapter and a cooling tube were attached to the glass reactor, and the dispersion was thoroughly dried at 80°C under reduced pressure. The above process was repeated several dozen times, and the resulting silica particles were crushed using a pulverizer (manufactured by Hosokawa Micron Corporation).

500 g of silica particles were then placed in a 1000 ml polytetrafluoroethylene inner cylinder stainless steel autoclave. After replacing the atmosphere inside the autoclave with nitrogen gas, 0.5 g of HMDS (hexamethyldisilazane) and 0.1 g of water were sprayed uniformly onto the silica powder in a mist form using a two-fluid nozzle while rotating the stirring blade attached to the autoclave at 400 rpm. After stirring for 30 minutes, the autoclave was sealed and heated at 200°C for 2 hours. Next, the system was depressurized while still heated to perform deammoniation.

The silica particles thus produced were almost entirely single particles, with almost no bonding between primary particles. The resulting single silica particles were then coated with trace amounts of zirconium, aluminum, and iron by magnetron sputtering to obtain silica particles 13, which are single silica particles coated with these metals.

The number average density and number average particle diameter of the primary particles of the silica particles 13 are shown in Table 1. In addition, the mass concentrations of _ZrO2 , _Al2O3 , and _Fe2O3 contained in the silica particles 13, when all elements detected by fluorescent X-ray analysis are considered to be oxides and the total mass of _all oxides is set to ₁ , are shown in Table 1.

<Production Examples of Silica Particles 14 to 24>
In the production example of silica particles 13, the number average particle size of the primary particles was changed. In addition, the amounts of trace coating of zirconium, aluminum, and iron by magnetron sputtering were changed. Silica particles 14 to 24 were obtained as single silica particles.

At this time, silica particles 17 to 24 were not coated with aluminum, silica particles 19 to 24 were not coated with iron, and silica particles 23 and 24 were not coated with zirconium. The number average compactness and number average particle size of primary particles of each silica particle are shown in Table 1. Furthermore, the mass concentrations of ZrO ₂ , Al ₂ O ₃ , and Fe ₂ O ₃ contained in silica particles 17 to 24, when all elements detected by fluorescent X-ray analysis are considered to be oxides and the total mass of all oxides is set to 1, are shown in Table 1.

<Production Example of Amorphous Polyester Resin>
Polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane: 73.3 parts (0.20 moles; 100.0 mol% based on the total number of moles of polyhydric alcohol)
Terephthalic acid: 22.4 parts (0.13 moles; 82.0 mol% based on the total number of moles of polycarboxylic acids)
Adipic acid: 4.3 parts (0.03 moles; 18.0 mol% based on the total number of moles of polycarboxylic acids)
Titanium tetrabutoxide (esterification catalyst): 0.51 parts The above materials were weighed into a reaction vessel equipped with a cooling tube, a stirrer, a nitrogen inlet tube, and a thermocouple. The flask was then replaced with nitrogen gas, and the temperature was gradually raised while stirring. The mixture was allowed to react for 4.5 hours while stirring at a temperature of 202°C, to obtain an amorphous polyester resin as a binder resin. The softening point of the obtained amorphous polyester resin was 90°C.

<Production Example of Styrene Acrylic Resin>
Into a 2-liter four-necked glass flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser and a nitrogen inlet tube, 850 g of xylene was placed, and the inside of the flask was replaced with nitrogen and then heated to 150°C.

Styrene 1700 parts n-butyl acrylate 250 parts polyoxypropylene (2,2)-2,2-bis (4-hydroxyphenyl) propane 50 parts dicumyl peroxide 80 parts Then, the mixture of the above materials was dropped from a dropping funnel over 4 hours, and aged for 4 hours at 150°C. Then, the temperature was raised to 200°C, and xylene was distilled off under reduced pressure to obtain a styrene acrylic resin as a binder resin. The softening point of the obtained styrene acrylic resin was 108°C.

<Synthesis Example of Crystalline Polyester Resin>
Dodecanediol: 34.5 parts (0.29 moles; 100.0 mol% based on the total number of moles of polyhydric alcohol)
Sebacic acid: 65.5 parts (0.28 moles; 100.0 mol% based on the total number of moles of polycarboxylic acids)
The above materials were weighed and placed in a reaction vessel equipped with a cooling tube, a stirrer, a nitrogen inlet tube, and a thermocouple. Next, the atmosphere in the flask was replaced with nitrogen gas, and the temperature was gradually raised with stirring, and the reaction was carried out for 3 hours at a temperature of 140° C. with stirring.

Tin 2-ethylhexanoate: 0.5 parts by mass The above materials were then added, the pressure in the reaction vessel was lowered to 8.3 kPa, and the reaction was carried out for 4 hours while maintaining the temperature at 200° C. After that, the pressure in the reaction vessel was gradually released to return to normal pressure, and a crystalline polyester resin was obtained. The softening point was 82° C.

(Toner Production Example)
<Production Example of Toner 1>
The type of binder resin is an amorphous polyester resin,
Binder resin 100 parts Crystalline polyester resin 5 parts Fischer-Tropsch wax (melting point: 90 ° C.) 6 parts C.I. Pigment Blue 15:3 4 parts The above materials were premixed in a Henschel mixer (FM-75 type, manufactured by Mitsui Mining Co., Ltd.), and then melt-kneaded at 160 ° C. with a twin-screw kneading extruder (PCM-30 type, manufactured by Ikegai Co., Ltd.).

The resulting kneaded material was cooled and coarsely crushed to 1 mm or less using a hammer mill, and then finely crushed using a mechanical crusher (T-250, manufactured by Turbo Kogyo Co., Ltd.).

The resulting finely pulverized material was classified using a Faculty (F-300, manufactured by Hosokawa Micron Corporation). The operating conditions were a classification rotor rotation speed of 11,000 rpm and a dispersion rotor rotation speed of 7,200 rpm. In this way, toner particles 1 were obtained.

Next,
The raw materials shown in the above recipe were mixed using a Henschel mixer (FM-10C, manufactured by Nippon Coke Co., Ltd.) at a rotation speed ^{of 67} s (4000 rpm) for a rotation time of 2 minutes, and then passed through an ultrasonic vibration sieve with a mesh size of 54 μm to obtain toner 1.

<Production Examples of Toners 2 to 24>
Toners 2 to 24 were obtained by carrying out the same operations as in the production example of toner 1, except that in the production example of toner 1, the type of binder resin, the presence or absence of addition of crystalline polyester, the amount of strontium titanate added, and the type and amount of silica particles added were changed as shown in Table 2.

Table 2 also shows the coverage and adhesion rate of strontium titanate and the coverage rate of silica for toners 1 to 24.

<Production Example of Magnetic Core Particles>
Step 1 (weighing and mixing step):
The ferrite raw materials were weighed so as to obtain the above _composition ratio, and _then crushed _and mixed for 5 hours in _a dry vibration mill using stainless steel beads with a diameter of 1/8 _inch .

Step 2 (pre-firing step):
The obtained pulverized material was made into pellets of about 1 mm square using a roller compactor. The pellets were passed through a vibrating sieve with 3 mm openings to remove coarse powder, and then through a vibrating sieve with 0.5 mm openings to remove fine powder. The pellets were then fired in a burner-type firing furnace at 1000° C. for 4 hours in a nitrogen atmosphere (oxygen concentration 0.01% by volume) to produce calcined ferrite. The composition of the resulting calcined ferrite was as follows:
(MnO)a (MgO)b ( _SrO )c ( _Fe2O3 )d
In the above formula, a = 0.257, b = 0.117, c = 0.007, d = 0.393

Step 3 (grinding step):
The obtained calcined ferrite was crushed to about 0.3 mm with a crusher, and then 30 parts of water was added to 100 parts of the calcined ferrite and the mixture was crushed in a wet ball mill using zirconia beads with a diameter of 1/8 inch for 1 hour. The obtained slurry was crushed in a wet ball mill using alumina beads with a diameter of 1/16 inch for 4 hours to obtain a ferrite slurry (finely crushed calcined ferrite).

Step 4 (granulation step):
To the ferrite slurry, 1.0 part of ammonium polycarboxylate as a dispersant and 2.0 parts of polyvinyl alcohol as a binder were added per 100 parts of the calcined ferrite, and the mixture was granulated into spherical particles using a spray dryer (manufacturer: Okawara Kakoki Co., Ltd.). After adjusting the particle size of the resulting particles, the mixture was heated at 650°C for 2 hours using a rotary kiln to remove the organic components of the dispersant and binder.

Step 5 (firing step):
In order to control the firing atmosphere, the material was heated from room temperature to 1300° C. in a nitrogen atmosphere (oxygen concentration 1.00% by volume) in an electric furnace over a period of 2 hours, and then fired at a temperature of 1150° C. for 4 hours. The temperature was then lowered to 60° C. over a period of 4 hours, and the material was returned from the nitrogen atmosphere to the air and taken out at a temperature of 40° C. or less.

Step 6 (sorting step):
After crushing the agglomerated particles, low magnetic particles were removed by magnetic separation, and coarse particles were removed by sieving through a sieve with 250 μm openings to obtain magnetic core particles having a volume distribution-based 50% particle size (D50) of 37.0 μm.

<Preparation of Coating Resin>
Cyclohexyl methacrylate monomer 26.8% by mass
Methyl methacrylate monomer 0.2% by weight
Methyl methacrylate macromonomer 8.4% by mass
(Macromonomer having a weight average molecular weight of 5000 and a methacryloyl group at one end)
Toluene 31.3% by mass
Methyl ethyl ketone 31.3% by mass
Azobisisobutyronitrile 2.0% by mass
Among the above materials, cyclohexyl methacrylate monomer, methyl methacrylate monomer, methyl methacrylate macromonomer, toluene, and methyl ethyl ketone are placed in the following equipment. That is, they are placed in a four-necked separable flask equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a stirrer. Nitrogen gas is then introduced to create a sufficient nitrogen atmosphere. After that, the mixture is heated to 80°C, azobisisobutyronitrile is added, and the mixture is refluxed for 5 hours to polymerize. Hexane is poured into the resulting reaction product to precipitate a copolymer, and the precipitate is filtered and then vacuum dried to obtain coating resin 1.

Next, 30 parts of coating resin 1 were dissolved in 40 parts of toluene and 30 parts of methyl ethyl ketone to obtain a polymer solution (solid content 30% by mass).

<Preparation of Coating Resin Solution>
Polymer solution (resin solids concentration 30%) 33.3% by mass
Toluene 66.4% by mass
Carbon black Regal 330 (manufactured by Cabot) 0.3% by mass
(Primary particle size: 25 nm, nitrogen adsorption specific surface area: 94 m ² /g, DBP oil absorption: 75 mL/100 g)
The mixture was dispersed for 1 hour using a paint shaker with zirconia beads having a diameter of 0.5 mm. The resulting dispersion was filtered through a 5.0 μm membrane filter to obtain a coating resin solution.

<Magnetic Carrier Manufacturing Example>
(Resin coating process):
The magnetic core particles and the coating resin solution were put into a vacuum degassing kneader maintained at room temperature (the amount of the coating resin solution put in was 2.5 parts as a resin component for 100 parts of the magnetic core particles). After the put-in, the mixture was stirred at a rotation speed of 30 rpm for 15 minutes, and after the solvent had evaporated to a certain extent (80 mass%), the mixture was heated to 80°C while mixing under reduced pressure, and the toluene was distilled off over 2 hours, after which it was cooled. The obtained magnetic carrier was separated into low magnetic products by magnetic separation, passed through a sieve with an opening of 70 μm, and then classified with a wind classifier to obtain a magnetic carrier with a 50% particle size (D50) of 38.2 μm based on the volume distribution.

<Production Example of Developer 1>
92.0 parts of the magnetic carrier and 8.0 parts of the toner 1 were mixed in a V-type mixer (V-20, manufactured by Seishin Enterprise Co., Ltd.) to obtain a developer 1.

<Production Examples of Developers 2 to 24>
Developers 2 to 24 were obtained in the same manner as in the production example of developer 1, except for the changes shown in Table 3.

Example 1
The following evaluations were carried out using a Canon full-color copier ImagePRESS C800 or a modified version thereof.

The image forming device has a photoconductor that forms an electrostatic latent image as an image carrier, and has a development process that develops the electrostatic latent image on the photoconductor into a toner image using a two-component developer.

The developed toner image is then transferred to an intermediate transfer medium in a transfer process, after which the toner image on the intermediate transfer medium is transferred to paper, and the toner image on the paper is then fixed in a fixing process using heat.

Developer 1 was placed in the developing device of the cyan station of this image forming device, and the following evaluations were performed.

<Ghost evaluation>
The ghosting was evaluated as follows.

A modified version of the image forming device described above was used. The modification involved removing the mechanism that discharges excess magnetic carrier from the developing unit.

The amount of toner laid on the paper in the FFH image (solid image) was adjusted to 0.45 mg/ ^cm2 . FFH is a value obtained by expressing 256 gradations in hexadecimal, with 00H being the first gradation (white background) of the 256 gradations and FFH being the 256th gradation (solid area) of the 256 gradations.

Next, 999 sheets of a test chart with a solid black vertical band and solid white except for the vertical band as shown in Figure 2 were passed in succession, and then the 1000th sheet was printed with a full-surface halftone image in the same job. The paper passing direction is shown in Figure 2. On the halftone image, the image density was measured in the area (a) where the solid black vertical band in Figure 3 was passed and the area (b) where the solid white was passed, and the ghost was evaluated based on the difference in density. Figure 4 shows a case where a ghost occurred.

Image density was measured using an X-Rite color reflection densitometer (X-Rite 500 Series, manufactured by X-Rite Corporation).

Measurements were taken in a normal temperature and humidity (NN) environment (temperature 23°C, relative humidity 50% to 60%), a normal temperature and low humidity (NL) environment (temperature 23°C, relative humidity 5%), and a high temperature and high humidity (HH) environment (temperature 30°C, relative humidity 80%). The highest concentration difference was taken as the concentration difference and ranked as follows:

(Evaluation criteria: Ghost)
A: The density difference between the area (a) and the area (b) is less than 0.02 (excellent)
B: The density difference between the area (a) and the area (b) is 0.02 or more and less than 0.04 (slightly superior)
C: The density difference between the area (a) and the area (b) is 0.04 or more and less than 0.06 (the acceptable level in the present invention)
D: The density difference between the region (a) and the region (b) is 0.06 or more and less than 0.10 (a level unacceptable in the present invention)

<Low temperature fixability (lowest fixable temperature)>
A developer containing two-component developer 1 was installed in the cyan station of a modified Canon full-color copier imagePRESS C800, and the machine was modified so that an image could be formed with the fixing unit removed. An unfixed toner image (hereinafter, "unfixed image") was then formed on evaluation paper. For the evaluation, plain paper for color copiers and printers GF-C157 (A4, 157 g/ ^cm2 ) (sold by Canon Marketing Japan Inc.) was used.

In practice, the developing conditions were appropriately adjusted so that the toner loading amount on the paper of the FFH image (hereinafter, solid area) was 1.2 mg/ ^cm2 , and an unfixed image of 2 cm x 10 cm was formed 3 cm from the leading edge of the A4 portrait evaluation paper and at the center of the evaluation paper. The unfixed image was conditioned in a low-humidity and low-temperature environment (15°C/10% Rh) for 24 hours.

Next, the fixing unit was removed from a Canon full-color copier, ImagePRESS C800, and a fixing test jig was prepared so that the process speed and the temperature of the upper and lower fixing members could be controlled independently. The fixing performance evaluation was carried out in a low-temperature, low-humidity environment (15°C/10% Rh), and the fixing test jig was adjusted so that the process speed was 400 mm/sec.

In the actual evaluation, the temperature of the upper belt of the fixing test jig was adjusted in 5°C increments between 100°C and 200°C while an unfixed image was passed through, while the temperature of the lower belt was fixed at 100°C during the evaluation.

The fixed image that had passed through the fixing unit was rubbed five times back and forth with a lens cleaning wiper (Dusper, manufactured by Ozu Sangyo Co., Ltd.) under a load of 4.9 kPa, and the fixing temperature was determined as the point at which the decrease in image density before and after rubbing was 10% or less.

Based on the criterion that a density drop of more than 10% is deemed to be unsuccessful in fixing, the lowest upper belt setting temperature at which the image density drop rate does not exceed 10% was determined as the low-temperature fixing temperature, and evaluation was performed according to the following evaluation criteria.

(Evaluation criteria: low temperature fixability)
A: Less than 130°C (Excellent)
B: 130°C or higher and lower than 150°C (slightly better)
C: 150° C. or higher and lower than 160° C. (acceptable level in the present invention)
D: 160° C. or higher (a level unacceptable in the present invention)

＜Focusing＞
The fog density (%) was measured as follows. Immediately after the 20,000th image was output using plain paper for color copiers and printers GF-C157 (A4, 157 g/cm ² ) (sold by Canon Marketing Japan Inc.), a solid white paper was passed through. Then, using a "REFLECTMETER MODEL TC-6DS" (manufactured by Tokyo Denshoku Co., Ltd.), the fog density (%) was calculated from the difference in whiteness between the white background part of the measured image and the whiteness of the transfer paper. An amber filter was used. The smaller the value, the better the fog level.

(Evaluation criteria)
A: Fog density less than 0.5% (excellent)
B: Fog density 0.5% or more and less than 1.0% (slightly better)
C: Fog density of 1.0% or more and less than 2.0% (acceptable level in the present invention)
D: Fog density of 2.0% or more (a level unacceptable in the present invention)

The results are shown in Table 4.

[Examples 2 to 20, Comparative Examples 1 to 4]
Evaluation was carried out in the same manner as in Example 1, except that developers 2 to 24 were used instead of developer 1. The results are shown in Table 4.

The above results show the following: That is, the number average particle size of the primary particles of the silica particles externally added to the surfaces of the toner particles is 50 nm or more and 300 nm or less. And, the silica particles contain _ZrO2 at a mass concentration of 20 ppm or more and 1000 ppm or less when all elements detected in fluorescent X-ray analysis are considered to be oxides and the total mass amount of all oxides is set to 1. By externally adding silica particles that satisfy these conditions, it is possible to suppress ghosts while suppressing the occurrence of fog, and therefore to provide high-quality images.

1. Means for supplying a fixed amount of raw material, 2. Means for adjusting the flow rate of compressed gas, 3. Introduction pipe, 4. Projection-shaped member, 5. Supply pipe, 6. Processing chamber, 7. Means for supplying hot air, 8. Means for supplying cold air, 9. Regulating means, 10. Recovery means, 11. Hot air supply means outlet, 12. Distribution member, 13. Swirling member, 14. Powder particle supply port

Claims (9)

A toner having toner particles containing a binder resin and a colorant, and silica particles on the surfaces of the toner particles,
The number average particle size of the primary particles of the silica particles is 50 nm or more and 300 nm or less,
The toner is characterized in that, when all elements detected in a fluorescent X-ray analysis of the silica particles are considered to be oxides and the total mass of all oxides is set to 1, the toner contains _ZrO2 at a mass concentration of 20 ppm to 1,000 ppm. 2. The toner according to claim 1, wherein the silica particles contain _Fe2O3 at a mass concentration of 100 ppm to 5,000 _ppm when all elements detected in a fluorescent X-ray analysis are considered to be oxides and the total mass of all oxides is set to 1. 3. The toner according to claim 1, wherein the _silica particles contain _Al2O3 at a mass concentration of 500 ppm to 20,000 ppm when all elements detected in a fluorescent X-ray analysis are regarded as oxides and the total mass of all oxides is taken as 1. The silica particles are toner particles having silica aggregate particles formed by binding primary silica particles, the number average value of the maximum Feret diameter of the silica aggregate particles is 100 nm or more and 500 nm or less, and when the number average density of the silica aggregate particles is ψSi, ψSi satisfies the following condition: 0.40≦ψSi≦0.90.
4. The toner according to claim 1, wherein The toner according to any one of claims 1 to 4, wherein the coverage of the toner particles with the silica particles is 10% or more. 6. The toner according to claim 1, wherein the toner particles have _SrTiO3 particles on their surfaces, and a coverage rate of the toner particles with the _SrTiO3 particles is 5% or more and 50% or less. 7. The toner according to claim 6, wherein the adhesion rate of the _SrTiO3 particles is 80% or more. The toner according to any one of claims 1 to 7, wherein the binder resin contains a polyester resin. The toner according to any one of claims 1 to 8, wherein the toner particles contain a crystalline polyester.

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