JP6750241B2 - Toner for developing electrostatic image, electrostatic image developer, toner cartridge, process cartridge, image forming apparatus, and image forming method - Google Patents

Description

The present invention relates to an electrostatic charge image developing toner, an electrostatic charge image developer, a toner cartridge, a process cartridge, an image forming apparatus, and an image forming method.

A method of visualizing image information through an electrostatic charge image by an electrophotographic method or the like is currently used in various fields. In electrophotography, image information is formed as an electrostatic charge image on the surface of an image carrier (photoreceptor) by a charging and exposure process, and a toner image is developed on the surface of the photoreceptor using a developer containing toner. The toner image is visualized as an image through a transfer process of transferring the toner image to a recording medium such as paper and a fixing process of fixing the toner image on the surface of the recording medium.

For example, in Patent Document 1, "Toner particles containing a binder resin, titanium oxide particles having a number average particle diameter (D1) of primary particles of 10.0 nm or more and 30.0 nm or less as external additives, A toner to which silica particles having a number average particle diameter (D1) of 4.0 nm or more and 15.0 nm or less are externally added."

In addition, in Patent Document 2, "Toner particles prepared by a wet granulation method, a first hydrophobic silica having an average primary particle size of 5 to 18 nm as an external additive and an average primary particle size of Negatively charged with externally added second hydrophobic silica having an average primary particle size of 18 to 50 nm and larger than that of the first hydrophobic silica, and hydrophobic titanium oxide having an average primary particle size of 10 to 40 nm. Toner" is disclosed.

JP, 2005-125258, A JP, 2003-202702, A

As described above, conventional toner particles include inorganic oxide particles (hereinafter referred to as “medium resistance”) having a volume resistivity of 1.0×10 ⁸ Ωcm or more and 1.0×10 ¹⁵ Ωcm or less typified by titanium oxide particles. Particles) and silica particles are externally added to the toner for developing electrostatic images (hereinafter also referred to as “toner”). The reason is that the use of the inorganic oxide particles having a medium resistance makes it possible to suppress high charging at low humidity while maintaining the charge imparting ability under high humidity. This is because even if the image having a low image density is repeatedly formed even in the same high temperature and high humidity environment, the relative humidity in the developing machine decreases and the amount of new toner replenishment also decreases. The electrification becomes remarkable and the density is lowered. On the other hand, in the electrostatic image development including the toner and the carrier, when the medium resistance particles are released from the toner particles and migrate (attach) to the surface of the carrier, the charging ability of the carrier may be reduced. When the charge amount of the toner decreases due to the decrease in the charging ability of the carrier, fogging (a phenomenon in which the toner adheres to the non-image portion) may occur. In particular, when an image having a high image density is repeatedly formed in a high temperature and high humidity environment, the amount of medium resistance particles transferred to the carrier increases, and fogging easily occurs.

Therefore, an object of the present invention is to provide an external additive having a compression aggregation degree of less than 60% or more than 95%, or a particle compression ratio of less than 0.20 or more than 0.40 as an external additive to be externally added to toner particles together with medium resistance particles. It is an object of the present invention to provide a toner for developing an electrostatic charge image, which suppresses the occurrence of fogging that occurs when an image having a high image density is repeatedly formed in a high temperature and high humidity environment as compared with a toner having only silica particles.

The above problem can be solved by the following means.

The invention according to < 1 > is
Toner particles,
Inorganic oxide particles having a volume resistivity of 1.0×10 ⁸ Ωcm or more and 1.0×10 ¹⁵ Ωcm or less, and an average equivalent circle diameter larger than that of the inorganic oxide particles, and a compression cohesion degree of 60% or more and 95% or more. An external additive containing silica particles having a particle compression ratio of 0.20 or more and 0.40 or less,
And a toner for developing an electrostatic charge image.

The invention according to < 2 > is
The inorganic oxide particles are the electrostatic charge image developing toner according to < 1 > , which are titanium oxide particles.

The invention according to < 3 > is
The toner for developing an electrostatic charge image according to < 1 > or < 2 > , wherein the silica particles have an average equivalent circle diameter of 40 nm or more and 200 nm or less.

The invention according to < 4 > is
The electrostatic charge image developing toner according to any one of < 1 > to < 3 > , wherein the particle dispersity of the silica particles is 90% or more and 100% or less.

The invention according to < 5 > is
Any one of < 1 > to < 4 > , wherein the silica particles are surface-treated with a siloxane compound having a viscosity of 1000 cSt or more and 50,000 cSt or less, and the surface adhesion amount of the siloxane compound is 0.01% by mass or more and 5% by mass or less. Or the toner for developing an electrostatic charge image according to item 1.

The invention according to < 6 > is
The siloxane compound is the electrostatic charge image developing toner according to < 5 > , which is a silicone oil.

The invention according to < 7 > is
An electrostatic charge image developer comprising the toner for developing an electrostatic charge image according to any one of < 1 > to < 6 > and a carrier.

The invention according to < 8 > is
< 1 > to < 6 > The toner for developing an electrostatic charge image according to any one of the items < 1 > to < 6 > is contained,
A toner cartridge that is attached to and detached from the image forming apparatus.

The invention according to < 9 > is
< 7 > The electrostatic charge image developer according to < 7 > is contained, and the electrostatic charge image developer is provided with a developing unit that develops the electrostatic charge image formed on the surface of the image carrier as a toner image,
A process cartridge that can be attached to and detached from an image forming apparatus.

The invention according to < 10 > is
An image carrier,
Charging means for charging the surface of the image carrier,
Electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier,
< 7 > A developing means for accommodating the electrostatic charge image developer, and developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer,
Transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium,
A fixing unit that fixes the toner image transferred to the surface of the recording medium;
And an image forming apparatus including.

The invention according to < 11 > is
A charging step of charging the surface of the image carrier,
An electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged image carrier;
A developing step of developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer according to < 6 > ;
A transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium,
A fixing step of fixing the toner image transferred onto the surface of the recording medium,
An image forming method having

According to the invention of < 1 > , < 2 > , or < 3 > , the compression aggregation degree is less than 60% or more than 95%, or the particle compression ratio as an external additive externally added to the toner particles together with the medium resistance particles. Electrostatic charge image development that suppresses the occurrence of fogging that occurs when images with high image density are repeatedly formed in a high temperature and high humidity environment, compared to a toner having only silica particles having a particle size of less than 0.20 or more than 0.40. Toner is provided.
According to the invention of < 4 > , compared to the case where the particle dispersity of the silica particles is less than 90%, the occurrence of fogging that occurs when images with high image density are repeatedly formed in a high temperature and high humidity environment is suppressed. A toner for developing an electrostatic image is provided.
According to the invention of < 5 > or < 6 > , silica particles surface-treated with a siloxane compound having a viscosity of less than 1000 cSt or more than 50,000 cSt as an external additive to be externally added to the toner particles together with the medium resistance particles, or a siloxane compound. Of fog that occurs when images with high image density are repeatedly formed in a high temperature and high humidity environment, compared to the case where only silica particles having a surface adhesion amount of less than 0.01 mass% or more than 5 mass% are applied. A toner for developing an electrostatic charge image that suppresses the above is provided.

According to the invention of < 7 > , the compression aggregation degree is less than 60% or more than 95%, or the particle compression ratio is less than 0.20 or 0.40 as an external additive to be externally added to the toner particles together with the medium resistance particles. Provided is an electrostatic charge image developer that suppresses the occurrence of fogging that occurs when an image having a high image density is repeatedly formed in a high temperature and high humidity environment as compared with the case where a toner having only silica particles exceeding the above amount is applied. ..

According to the invention of < 8 > , < 9 > , < 10 > , or < is 11 > , the compression aggregation degree is less than 60% or more than 95% as an external additive to be externally added to the toner particles together with the medium resistance particles. Fogging that occurs when images with high image density are repeatedly formed in a high temperature and high humidity environment, as compared with the case where toner having only silica particles having a particle compression ratio of less than 0.20 or more than 0.40 is applied. A toner cartridge, a process cartridge, an image forming apparatus, or an image forming method that suppresses the occurrence of

FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to this embodiment. It is a schematic structure figure showing an example of a process cartridge concerning this embodiment.

Hereinafter, an embodiment which is an example of the present invention will be described.

<Toner for developing electrostatic image>
The electrostatic charge image developing toner according to this exemplary embodiment (hereinafter, referred to as “toner”) is a toner including toner particles and an external additive.
The external additive has a volume resistivity of 1.0×10 ⁸ Ωcm or more and 1.0×10 ¹⁵ Ωcm or less, and an average circle equivalent diameter of the inorganic oxide particles (medium resistance particles). It includes large silica particles having a compression aggregation degree of 60% or more and 95% or less and a particle compression ratio of 0.20 or more and 0.40 or less (hereinafter also referred to as "specific silica particles").

Here, conventionally, there is known a toner obtained by externally adding toner particles, medium resistance particles (inorganic oxide particles having a volume resistivity in the above range) represented by titanium oxide particles, and silica particles. ing. The reason is that by using the inorganic oxide particles having a medium resistance, it is possible to suppress the increase in the charge amount at low humidity while maintaining the charge imparting ability under high humidity. This is because even if the image having a low image density is repeatedly formed even in the same high temperature and high humidity environment, the relative humidity in the developing machine decreases and the amount of new toner replenishment also decreases. The amount of charge is remarkably increased, and the density is reduced. On the other hand, in electrostatic image development including a toner and a carrier (hereinafter also referred to as “two-component developer”), when the medium resistance particles are released from the toner particles and migrate (adhere) to the surface of the carrier, the carrier is charged. May reduce ability. This is because that portion becomes a charge leakage site especially under high temperature/high humidity.
If the charge amount of the toner decreases due to the decrease in the charging ability of the carrier, fogging (a phenomenon in which the toner adheres to the non-image portion) may occur.

On the other hand, as a technique for suppressing the release of the medium resistance particles from the toner particles, which causes the deterioration of the charging ability of the carrier, there is a method of externally adding large-diameter silica particles having a larger diameter than the medium resistance particles. When large silica particles are added externally, the large silica particles exert a buffer function (spacer function), making it difficult for the medium resistance particles to be mechanically loaded, and for making it difficult for the carriers to contact the medium resistance particles. The release of the medium resistance particles from the toner particles is easily suppressed.

However, since the large-diameter silica particles generally have high fluidity and move on the toner particles to be unevenly distributed or to be released from the toner particles, the external addition structure of the large-diameter silica particles is likely to change. The buffer function (spacer function) becomes difficult to exert. On the other hand, when externally adding large-diameter silica particles treated with silicone oil, the large-diameter silica particles treated with silicone oil become toner particles in a non-uniform state due to low fluidity and high cohesiveness. It tends to adhere to toner particles in the state of adhesion or aggregation, and it is difficult to achieve the targeted external addition structure (external addition structure in which large-diameter silica particles adhere to the periphery of the area where medium resistance particles adhere). The buffer function (spacer function) of the large-diameter silica particles becomes difficult to exert.

When the buffer function (spacer function) of the large-diameter silica particles becomes difficult to exert, a mechanical load is applied to the medium resistance particles, and the medium resistance particles are easily brought into contact with the carrier. The tendency to be liberated increases.

In particular, when an image having a high image density (for example, an image density of 80% or more) is repeatedly formed under a high temperature and high humidity environment (for example, an environment of a temperature of 30° C. and a humidity of 90% RH), the toner density in the developing unit is reduced. As a result, the mechanical load on the medium resistance particles and the chances of the carrier contacting the medium resistance particles are increased, and the amount of medium resistance particles released from the toner particles is increased. The transfer amount (adhesion amount) also increases. Then, as the charging ability of the carrier is reduced, the charge amount of the toner is reduced, and fogging is likely to occur.

Therefore, in the toner according to the present exemplary embodiment, as the large-diameter silica particles having a larger average circle equivalent diameter than the medium-resistance particles, the specific silica particles are externally added to the toner particles together with the medium-resistance particles. For example, the occurrence of fogging that occurs when an image having a high image density (for example, an image density of 80% or more) is repeatedly formed in an environment of a temperature of 30° C. and a humidity of 90% RH is suppressed. The reason is presumed as follows.

First, the specific silica particles having a degree of compression aggregation and a particle compression ratio satisfying the above ranges are silica particles having high fluidity and high dispersibility in toner particles, and high aggregability and adhesiveness to toner particles. is there.

Here, the silica particles generally have good fluidity, but have low bulk density, and therefore have low adhesion and are unlikely to aggregate.
On the other hand, a technique is known in which the surface of the silica particles is surface-treated with a hydrophobizing agent for the purpose of enhancing the fluidity of the silica particles and the dispersibility in the toner particles. According to this technique, the fluidity of the silica particles and the dispersibility in the toner particles are improved, but the cohesiveness remains low.
Further, a technique is also known in which the surface of the silica particles is surface-treated by using a hydrophobic treatment agent and silicone oil in combination. According to this technique, the adhesion to the toner particles is improved and the cohesiveness is improved. However, conversely, the fluidity and the dispersibility in the toner particles are likely to decrease.
That is, it can be said that, in the silica particles, the fluidity and the dispersibility in the toner particles and the aggregability and the adhesiveness to the toner particles have a contradictory relationship.

On the other hand, as described above, the specific silica particles have the following properties of fluidity, dispersibility in toner particles, cohesiveness and adhesion to toner particles, when the degree of compression aggregation and the particle compression ratio are in the above ranges. Two characteristics become good.

Next, the significance of setting the compression coagulation degree and the particle compression ratio within the above ranges will be described in order.

First, the significance of setting the compression aggregation degree of the specific silica particles to 60% or more and 95% or less will be described.
The degree of compression aggregation is an index showing the cohesiveness of silica particles and the adhesiveness to toner particles. This index is indicated by the degree of unraveling of the molded body when the molded body of silica particles is dropped after the molded body of silica particles is compressed.
Therefore, it is shown that the higher the degree of compression aggregation is, the higher the bulk density of silica particles tends to be, the stronger the cohesive force (intermolecular force) is, and the stronger the adhesive force to the toner particles is. The details of the method of calculating the compression aggregation degree will be described later.
Therefore, the specific silica having a high degree of compression aggregation of 60% or more and 95% or less has good adhesion to toner particles and aggregation. However, from the viewpoint of ensuring good fluidity and dispersibility in toner particles while maintaining good adhesion to toner particles and cohesiveness, the upper limit of the degree of compression aggregation is set to 95%.

Next, the significance that the particle compression ratio of the specific silica particles is 0.20 or more and 0.40 or less will be described.
The particle compression ratio is an index showing the fluidity of silica particles. Specifically, the particle compression ratio is represented by the ratio of the difference between the solid apparent specific gravity and the loose apparent specific gravity of the silica particles and the solid apparent specific gravity ((solid apparent apparent specific gravity-slack apparent specific gravity)/solid apparent apparent specific gravity).
Therefore, the lower the particle compression ratio, the higher the fluidity of the silica particles. Further, when the fluidity is high, the dispersibility in toner particles tends to be enhanced. The details of the method for calculating the particle compression ratio will be described later.
Therefore, the specific silica particles whose particle compression ratio is controlled to be as low as 0.20 or more and 0.40 or less have good fluidity and dispersibility in toner particles. However, the lower limit of the particle compression ratio is 0.20 from the viewpoint of improving the adhesiveness and the cohesiveness to the toner particles while improving the fluidity and the dispersibility to the toner particles.

From the above, the specific silica particles have peculiar properties that they are easy to flow and disperse in the toner particles, and further have high cohesive force and high adhesive force to the toner particles. Therefore, the specific silica particles having a degree of compression aggregation and a particle compression ratio satisfying the above ranges are high in fluidity and dispersibility in toner particles, and also have high aggregability and adhesiveness to toner particles. Become.

Next, the presumed action when externally adding the specific silica particles to the toner particles will be described.
First, since the specific silica particles have high fluidity and dispersibility in the toner particles, when externally added to the toner particles, they are likely to be attached to the surface of the toner particles in a nearly uniform state. Therefore, the specific silica particles are likely to be externally added (adhered) to the toner particles in a targeted external addition structure (an external addition structure in which large-diameter silica particles adhere to the periphery of the portion to which the high resistance particles adhere).
The specific silica particles once attached to the toner particles have high cohesiveness and adhesiveness to the toner particles, so that the high temperature and high humidity environment (for example, an environment of temperature 30° C. and humidity 90% RH) is high. Even if an image having an image density (for example, an image density of 80% or more) is repeatedly formed and the toner concentration in the developing means rises, it is difficult for the toner to move on the toner particles and separate from the toner particles. That is, the change in the externally added structure is unlikely to occur. Thereby, the buffer function (spacer function) of the specific silica particles is exhibited, and the function is easily maintained.

Therefore, the buffering function (spacer function) of the specific silica particles suppresses the release of the medium resistance particles from the toner particles, so that the medium resistance particles to the carrier are also suppressed. Then, the decrease in the chargeability of the carrier and the decrease in the charge amount of the toner are suppressed, and the occurrence of fogging is suppressed.

From the above, the toner according to the present embodiment repeatedly forms an image having a high image density (for example, an image density of 80% or more) under a high temperature and high humidity environment (for example, an environment of a temperature of 30° C. and a humidity of 90% RH). It is presumed that the occurrence of fogging, which sometimes occurs, is suppressed.

In the toner according to this exemplary embodiment, the specific silica particles preferably have a particle dispersity of 90% or more and 100% or less.

Here, the meaning that the particle dispersity of the specific silica particles is 90% or more and 100% or less will be described.
The particle dispersity is an index showing the dispersibility of silica particles. This index is indicated by the degree of ease of dispersion of silica particles in the toner particles in the primary particle state. Specifically, the particle dispersity is calculated by calculating the measured coverage C on the adhered object, where C ₀ is the calculated coverage of the silica particles on the toner particle surface, and C is the measured coverage. It is shown by the ratio with the above-mentioned coverage C ₀ (coverage C actually measured/coverage C ₀ calculated).
Therefore, it is indicated that the higher the particle dispersity, the less likely the silica particles are aggregated, and the more easily they are dispersed in the toner particles in the state of primary particles. The details of the method for calculating the particle dispersity will be described later.

By controlling the degree of particle dispersion of the specific silica particles to 90% or more and 100% or less while controlling the compression coagulation degree and the particle compression ratio within the above ranges, the dispersibility in the toner particles is further improved. Thereby, the fluidity of the toner particles themselves is further increased, and the high fluidity is easily maintained. As a result, even if toner particles that are close to true spheres, whose external additive structure is likely to change, are applied, it is easy to suppress a decrease in charge maintainability.

In the toner according to this exemplary embodiment, as the specific silica particles having the above-described properties of high fluidity and dispersibility in toner particles, and high aggregability and adhesiveness to toner particles, relatively large. Preferable are silica particles having a siloxane compound having a weight average molecular weight attached to the surface thereof. Specifically, silica particles to which a siloxane compound having a viscosity of 1000 cSt or more and 50,000 cSt or less adheres to the surface (preferably adheres at a surface adhesion amount of 0.01% by mass to 5% by mass) are preferable. The specific silica particles are prepared by, for example, using a siloxane compound having a viscosity of 1000 cSt or more and 50,000 cSt or less, and subjecting the surface of the silica particles to a surface treatment so that the surface adhesion amount is 0.01% by mass or more and 5% by mass or less. can get.
Here, the surface adhesion amount is a ratio to the silica particles before the surface treatment of the silica particles (untreated silica particles). Hereinafter, the silica particles before surface treatment (that is, untreated silica particles) are also simply referred to as “silica particles”.

The specific silica particles obtained by surface-treating the surface of the silica particles using a siloxane compound having a viscosity of 1000 cSt or more and 50000 cSt or less so that the surface adhesion amount is 0.01% by mass or more and 5% by mass or less have fluidity and toner particles. In addition to the dispersibility in the toner, the cohesiveness and the adhesiveness to the toner particles are enhanced, and the compression cohesion degree and the particle compression ratio are likely to satisfy the above requirements. The reason for this is not clear, but it is considered that the reason is as follows.

When a small amount of a siloxane compound having a relatively high viscosity in the above range is attached to the surface of the silica particles within the above range, a function derived from the characteristics of the siloxane compound on the surface of the silica particles is exhibited. The mechanism is not clear, but when silica particles are flowing, a small amount of a siloxane compound having a relatively high viscosity adheres within the above range, so that the releasability derived from the siloxane compound is easily expressed. Alternatively, the adhesion between silica particles is reduced by reducing the interparticle force due to the steric hindrance of the siloxane compound. This further improves the fluidity of the silica particles and the dispersibility of the silica particles in the toner particles.
On the other hand, when the silica particles are pressed, long molecular chains of the siloxane compound on the surface of the silica particles are entangled with each other, the close packing property of the silica particles is enhanced, and the aggregation of the silica particles is strengthened. It is considered that the cohesive force of the silica particles due to the entanglement of the long molecular chains of the siloxane compound is canceled when the silica particles are made to flow. In addition to this, the long molecular chain of the siloxane compound on the surface of the silica particles also enhances the adhesion to the toner particles.

From the above, the specific silica particles in which the siloxane compound having a viscosity in the above range is attached to the surface of the silica particles in a small amount in the above range, the compression aggregation degree and the particle compression ratio are likely to satisfy the above requirements, and the particle dispersity is also the above requirements. Will be easier to meet.

Hereinafter, the configuration of the toner will be described in detail.

(Toner particles)
The toner particles include, for example, a binder resin. The toner particles may contain a colorant, a release agent, other additives, etc., if necessary.

-Binder resin-
Examples of the binder resin include styrenes (eg, styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (eg, methyl acrylate, ethyl acrylate, n-propyl acrylate, acrylic acid). n-butyl, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc., ethylenically unsaturated nitriles (eg acrylonitrile, Methacrylonitrile etc.), vinyl ethers (eg vinyl methyl ether, vinyl isobutyl ether etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone etc.), olefins (eg ethylene, propylene, butadiene etc.) etc. Examples of the vinyl resin include homopolymers of the above monomers or copolymers of two or more kinds of these monomers in combination.
As the binder resin, for example, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, non-vinyl resin such as modified rosin, a mixture of these and the vinyl resin, or these A graft polymer obtained by polymerizing a vinyl-based monomer in the coexistence thereof may also be mentioned.
These binder resins may be used alone or in combination of two or more.

A polyester resin is suitable as the binder resin.
Examples of the polyester resin include known polyester resins.

Examples of the polyester resin include polycondensates of polycarboxylic acids and polyhydric alcohols. As the polyester resin, a commercially available product or a synthesized product may be used.

Examples of polycarboxylic acids include aliphatic dicarboxylic acids (eg, oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid, etc.) , Alicyclic dicarboxylic acids (eg, cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acids (eg, terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, etc.), anhydrides thereof, or lower ones thereof (eg, having 1 or more carbon atoms). 5 or less) alkyl ester. Of these, aromatic dicarboxylic acids are preferable as the polycarboxylic acid.
The polyvalent carboxylic acid may be used in combination with a dicarboxylic acid and a trivalent or higher carboxylic acid having a crosslinked structure or a branched structure. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, their anhydrides, and their lower (for example, 1 to 5 carbon atoms) alkyl esters.
The polycarboxylic acids may be used alone or in combination of two or more.

Examples of the polyhydric alcohol include aliphatic diols (eg, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (eg, cyclohexanediol, cyclohexanedimethanol, Hydrogenated bisphenol A) and aromatic diols (for example, bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, etc.). Among these, as the polyhydric alcohol, for example, aromatic diols and alicyclic diols are preferable, and aromatic diols are more preferable.
As the polyhydric alcohol, a trihydric or higher polyhydric alcohol having a crosslinked structure or a branched structure may be used together with the diol. Examples of the trihydric or higher polyhydric alcohol include glycerin, trimethylolpropane, and pentaerythritol.
The polyhydric alcohols may be used alone or in combination of two or more.

The glass transition temperature (Tg) of the polyester resin is preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower.
The glass transition temperature is determined from the DSC curve obtained by differential scanning calorimetry (DSC), and more specifically, it is described in the method for determining the glass transition temperature in JIS K 7121-1987 "Plastic transition temperature measurement method". "Extrapolated glass transition onset temperature".

The weight average molecular weight (Mw) of the polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less.
The number average molecular weight (Mn) of the polyester resin is preferably 2000 or more and 100000 or less.
The molecular weight distribution Mw/Mn of the polyester resin is preferably 1.5 or more and 100 or less, more preferably 2 or more and 60 or less.
The weight average molecular weight and the number average molecular weight are measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is carried out by using a Tosoh GPC HLC-8120GPC as a measuring device, a Tosoh column TSKgel Super HM-M (15 cm), and a THF solvent. The weight average molecular weight and the number average molecular weight are calculated from the measurement results using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample.

The polyester resin is obtained by a known manufacturing method. Specifically, for example, it can be obtained by a method in which the polymerization temperature is 180° C. or higher and 230° C. or lower, the pressure in the reaction system is reduced as necessary, and the reaction is performed while removing water and alcohol generated during the condensation.
When the raw material monomers are insoluble or incompatible at the reaction temperature, a high-boiling point solvent may be added as a solubilizing agent and dissolved. In this case, the polycondensation reaction is carried out while distilling the solubilizing agent. If there is a poorly compatible monomer, it is recommended that the poorly compatible monomer be condensed with the monomer or the acid or alcohol to be polycondensed in advance and then polycondensed with the main component. ..

The content of the binder resin is, for example, preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and 60% by mass or more and 85% by mass or less with respect to the entire toner particles. More preferable.

-Colorant-
Examples of the colorant include carbon black, chrome yellow, Hansa yellow, benzidine yellow, slen yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brilliant carmine 3B, brilliant. Carmine 6B, DuPont Oil Red, Pyrazolone Red, Resole Red, Rhodamine B Lake, Lake Red C, Pigment Red, Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Pigment Blue, Phthalocyanine Green, Various pigments such as malachite green oxalate, or acridine, xanthene, azo, benzoquinone, azine, anthraquinone, thioindico, dioxazine, thiazine, azomethine, indico, phthalocyanine, aniline black Examples include various dyes such as system dyes, polymethine dyes, triphenylmethane dyes, diphenylmethane dyes, and thiazole dyes.
The colorants may be used alone or in combination of two or more.

As the colorant, a surface-treated colorant may be used as necessary, or the colorant may be used in combination with a dispersant. Further, a plurality of kinds of colorants may be used in combination.

The content of the colorant is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less, based on the entire toner particles.

-Release agent-
Examples of the releasing agent include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax and candelilla wax; synthetic waxes such as montan wax and mineral/petroleum waxes; ester waxes such as fatty acid ester and montanic acid ester. ; And the like. The release agent is not limited to this.

The melting temperature of the release agent is preferably 50° C. or higher and 110° C. or lower, and more preferably 60° C. or higher and 100° C. or lower.
The melting temperature is obtained from the DSC curve obtained by differential scanning calorimetry (DSC) according to "melting peak temperature" described in JIS K 7121-1987 "Method for measuring transition temperature of plastics". ..

The content of the release agent is, for example, preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the entire toner particles.

-Other additives-
Examples of other additives include known additives such as magnetic materials, charge control agents, and inorganic powders. These additives are contained in the toner particles as internal additives.

-Characteristics of toner particles-
The toner particles may be toner particles having a single layer structure, or toner particles having a so-called core-shell structure composed of a core portion (core particles) and a coating layer (shell layer) covering the core portion. May be.
Here, the toner particles having a core/shell structure include, for example, a core portion containing a binder resin and, if necessary, other additives such as a colorant and a release agent, and a binder resin. And a coating layer that is configured.

The volume average particle diameter (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, more preferably 4 μm or more and 8 μm or less.

Various average particle diameters and various particle size distribution indexes of the toner particles are measured by using Coulter Multisizer II (manufactured by Beckman Coulter, Inc.) and an electrolyte solution is measured by ISOTON-II (manufactured by Beckman Coulter, Inc.). It
In the measurement, 0.5 mg or more and 50 mg or less of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzenesulfonate) as a dispersant. This is added to 100 ml or more and 150 ml or less of the electrolytic solution.
The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for 1 minute with an ultrasonic disperser, and a Coulter Multisizer II is used to obtain a particle size distribution of particles in a range of 2 μm or more and 60 μm or less using an aperture of 100 μm as an aperture diameter. taking measurement. The number of particles sampled is 50,000.
A cumulative distribution is drawn from the small diameter side for the volume and number for the particle size range (channel) divided based on the measured particle size distribution, and the cumulative particle size is 16% as the volume particle size D16v and the number particle size. D16p, a particle size with a cumulative 50% is defined as a volume average particle size D50v, a cumulative number average particle size D50p, and a particle size with a cumulative 84% is defined as a volume particle size D84v and a number particle size D84p.
Using these, the volume average particle size distribution index (GSDv) is calculated as (D84v/D16v) ^1/2 , and the number average particle size distribution index (GSDp) is calculated as (D84p/D16p) ^1/2 .

The average circularity of the toner particles is preferably 0.94 or more and 1.00 or less, and more preferably 0.95 or more and 0.98 or less.

The average circularity of the toner particles is calculated by (circle equivalent perimeter)/(perimeter) [(perimeter of circle having the same projected area as the particle image)/(perimeter of particle projection image)]. Specifically, it is a value measured by the following method.
First, toner (developer) to be measured is dispersed in water containing a surfactant, and then ultrasonic treatment is performed to obtain toner particles from which external additives have been removed. The obtained toner particles are collected by suction, a flat flow is formed, and a particle image is captured as a still image by instantaneously emitting strobe light, and a flow type particle image analyzer (manufactured by Sysmex Corporation) for image analysis of the particle image is obtained. FPIA-2100). The number of samplings when obtaining the average circularity is 3500.

(External additive)
The external additive contains medium resistance particles (inorganic oxide particles having a volume resistivity in the above range) and specific silica particles. The external additive may include an external additive other than the medium resistance particles and the specific silica particles. That is, in the toner particles, only the medium resistance particles and the specific silica particles may be externally added, or the medium resistance particles and the specific silica particles and other external additives may be externally added.

[Specific silica particles]
-Compression degree-
The degree of compression aggregation of the specific silica particles is 60% or more and 95% or less, but the fluidity and the dispersibility to the toner particles are ensured while improving the cohesiveness and the adhesion to the toner particles in the specific silica particles. From the viewpoint (particularly from the viewpoint of suppressing fogging occurrence), it is preferably 65% or more and 95% or less, and more preferably 70% or more and 95% or less.

The degree of compression aggregation is calculated by the method described below.
A disc-shaped mold having a diameter of 6 cm is filled with 6.0 g of the specific silica particles. Then, the mold was compressed for 60 seconds at a pressure of 5.0 t/cm ² using a compression molding machine (manufactured by Maekawa Test Machine Co., Ltd.) to obtain a compacted disc-shaped specific silica particle compact (hereinafter, referred to as “before falling”). Referred to as a "molded body"). Then, the mass of the molded product before dropping is measured.
Then, the molded product before dropping was placed on a sieve mesh having an opening of 600 μm, and the molded product before falling was subjected to an amplitude of 1 mm and a vibration time of 1 minute by a vibrating sieving machine (manufactured by Tsutsui Rikagaku Kikai KK, product number VIBRATING MVB-1). Drop under the conditions of. As a result, the specific silica particles fall from the molded product before falling through the sieve mesh, and the molded product of the specific silica particles remains on the sieve mesh. Then, the mass of the remaining molded body of the specific silica particles (hereinafter, referred to as “molded body after falling”) is measured.
Then, using the following formula (1), the degree of compression cohesion is calculated from the ratio of the mass of the molded body after the fall to the mass of the molded body before the fall.
-Formula (1): degree of compression aggregation = (mass of molded body after falling/mass of molded body before falling) x 100

-Particle compression ratio-
The particle compression ratio of the specific silica particles is 0.20 or more and 0.40 or less, but the specific silica particles have good fluidity and dispersibility in the toner particles while improving the cohesiveness and the adhesion to the toner particles. From the viewpoint of ensuring (particularly from the viewpoint of suppressing fogging occurrence), it is preferably 0.24 or more and 0.38 or less, more preferably 0.28 or more and 0.36 or less.

The particle compression ratio is calculated by the method described below.
A loose apparent specific gravity and a solid apparent specific gravity of the silica particles are measured using a powder tester (manufactured by Hosokawa Micron, product number PT-S type). Then, using the following formula (2), the particle compression ratio is calculated from the ratio of the difference between the apparent apparent specific gravity and the apparent apparent specific gravity of the silica particles and the apparent apparent specific gravity.
-Formula (2): Particle compression ratio = (consolidated apparent specific gravity-loose apparent specific gravity)/consolidated apparent specific gravity

Note that the "loose apparent specific gravity", capacity of the silica particles were packed into a container of 100 cm ^3, a measurement value derived by weighing, filling density of the state where the free fall the specific silica particles into the vessel Say. The "solidified apparent specific gravity" is degassed by tapping the bottom of the container 180 times repeatedly at a stroke length of 18 mm and a tapping speed of 50 times/min from the state of the loose apparent specific gravity, thereby degassing the specific silica particles. Rearranged and refers to apparently more densely packed apparent specific gravity.

-Particle dispersity-
The particle dispersity of the specific silica particles is preferably 90% or more and 100% or less, and more preferably 95% or more and 100% or less, from the viewpoint of further improving the dispersibility in toner particles (particularly from the viewpoint of suppressing fogging). % Or less.

The particle dispersity is the ratio of the actually measured coverage C to the toner particles and the calculated coverage C _0, and is calculated using the following equation (3).
Formula (3): Particle dispersity=measured coverage C/calculated coverage C ₀

Here, the calculated coverage C ₀ on the surface of the toner particles by the specific silica particles is defined as the volume average particle diameter of the toner particles dt (m), the average equivalent circle diameter of the specific silica particles da (m), and the toner particles. Where ρt is the specific gravity of the toner, ρa is the specific gravity of the specific silica particles, Wt (kg) is the weight of the toner particles, and Wa (kg) is the addition amount of the specific silica particles. it can.
- formula (3-1): computational coverage _{C 0 = √3 / (2π)} × (ρt / ρa) × (dt / da) × (Wa / Wt) × 100 (%)

The actual coverage C of the specific silica particles on the surface of the toner particles was measured by an X-ray photoelectron spectrometer (XPS) (“JPS-9000MX”: manufactured by JEOL Ltd.). For the toner particles coated (attached) with the specific silica particles, the signal intensity of the silicon atoms derived from the specific silica particles can be measured and calculated by the following formula (3-2).

-Equation (3-2): Actual coverage C = (z-x)/(y-x) x 100 (%)
(In the formula (3-2), x represents the signal intensity of the silicon atom derived from the specific silica particles of only the toner particles. y represents the signal intensity of the silicon atom derived from the specific silica particles of only the specific silica particles. (Z represents the signal intensity of silicon atoms derived from the specific silica particles in the toner particles coated (attached) with the specific silica particles.)

-Average circle equivalent diameter-
The average equivalent circle diameter of the specific silica particles is from the viewpoint of improving the fluidity, dispersibility in toner particles, cohesiveness, and adhesion to toner particles (particularly from the viewpoint of suppressing fogging) in the specific silica particles. , 40 nm or more and 200 nm or less are preferable, 50 nm or more and 180 nm or less are more preferable, and 60 nm or more and 160 nm or less are further preferable.

The average equivalent circle diameter D50 of the specific silica particles is obtained by externally adding the specific silica particles to the toner particles, and the primary particles are determined by scanning electron microscope SEM (Scanning Electron Microscope) device (manufactured by Hitachi Ltd.: S-4100). ), an image is taken, the image is taken into an image analyzer (LUZEXIII, manufactured by Nireco Co., Ltd.), the area of each particle is measured by image analysis of primary particles, and the equivalent circle diameter is calculated from this area value. calculate. The 50% diameter (D50) in the volume-based cumulative frequency of the obtained equivalent circle diameters is defined as the average equivalent circle diameter D50 of the specific silica particles. In the electron microscope, the magnification is adjusted so that about 10 or more and 50 or less specific silica particles are imaged in one visual field, and the equivalent circle diameter of the primary particles is obtained by observing the plural visual fields.

-Average circularity-
The shape of the specific silica particles may be spherical or irregular, but the average circularity of the specific silica particles is such that the specific silica particles have fluidity, dispersibility in toner particles, cohesiveness, and toner. From the viewpoint of improving the adhesion to particles (particularly from the viewpoint of suppressing fogging occurrence), 0.85 or more and 0.98 or less are preferable, 0.90 or more and 0.98 or less are more preferable, and 0.93 or more and 0. More preferably, it is 98 or less.

The average circularity of the specific silica particles is measured by the method described below.
First, the circularity of the specific silica particles is calculated by the following formula from the planar image analysis of the primary particles obtained by observing the primary particles after externally adding the silica particles to the toner particles with an SEM device. 100/SF2".
Formula: Circularity (100/SF2)=4π×(A/I ² ).
[In the formula, I represents the perimeter of the primary particles on the image, and A represents the projected area of the primary particles.
Then, the average circularity of the specific silica particles is obtained as 50% circularity in the cumulative frequency of the circularity of 100 primary particles obtained by the planar image analysis.

Here, a method of measuring each characteristic (compressed cohesion degree, particle compression ratio, particle dispersion degree, average circularity) of the specific silica particles from the toner will be described.
First, external additives (specific silica particles, medium resistance particles) are separated from the toner as follows. The external additive can be separated from the toner by putting the toner in methanol to disperse it, stirring and then treating with an ultrasonic bath. The ease of separation is determined by the particle size and specific gravity of the external additive, and large specific silica particles are easy to separate, so it is possible to separate only specific silica particles by setting weak ultrasonic treatment conditions. it can. Next, by changing the ultrasonic treatment to a strong condition, the medium resistance particles can be peeled off from the toner particle surface, and each time, only the methanol in which the external additive is dispersed by precipitating the toner particles by centrifugation is removed. The specific silica particles and the medium resistance particles can be taken out by recovering and then volatilizing the methanol. This ultrasonic treatment condition needs to be adjusted depending on the specific silica particles and the medium resistance particles. Then, each of the above characteristics is measured using the separated specific silica particles.

Hereinafter, the structure of the specific silica particles will be described in detail.

-Specific silica particles-
The specific silica particles are particles containing silica (that is, SiO ₂ ) as a main component, and may be crystalline or amorphous. The specific silica particles may be particles produced from a raw material of a silicon compound such as water glass or alkoxysilane, or particles obtained by crushing quartz.
As the specific silica particles, specifically, silica particles produced by a sol-gel method (hereinafter “sol-gel silica particles”), aqueous colloidal silica particles, alcoholic silica particles, fumed silica particles obtained by a gas phase method, fused silica Examples thereof include particles, and among these, sol-gel silica particles are preferable.

-Surface treatment-
The specific silica particles are preferably surface-treated with a siloxane compound in order to set the compression coagulation degree, the particle compression ratio, and the particle dispersity within the above specific ranges.
As the surface treatment method, it is preferable to use supercritical carbon dioxide and subject the surface of the silica particles to surface treatment in supercritical carbon dioxide. The surface treatment method will be described later.

-Siloxane compound-
The siloxane compound is not particularly limited as long as it has a siloxane skeleton in its molecular structure.
Examples of the siloxane compound include silicone oil and silicone resin. Among these, silicone oil is preferable from the viewpoint of treating the surface of the silica particles in a nearly uniform state.

Examples of the silicone oil include dimethyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, methacryl-modified silicone oil, and mercapto-modified silicone oil. Examples thereof include silicone oil, phenol-modified silicone oil, polyether-modified silicone oil, methylstyryl-modified silicone oil, alkyl-modified silicone oil, higher fatty acid ester-modified silicone oil, higher fatty acid amide-modified silicone oil, and fluorine-modified silicone oil. Of these, dimethyl silicone oil, methyl hydrogen silicone oil, and amino-modified silicone oil are preferable.
The above siloxane compounds may be used alone or in combination of two or more.

-Viscosity-
The viscosity (kinematic viscosity) of the siloxane compound is preferably 1000 cSt or more and 50,000 cSt or less, and 2000 cSt or less from the viewpoint of improving the fluidity, dispersibility in toner particles, cohesiveness, and adhesion to toner particles in the specific silica particles. It is more preferably 30,000 cSt or less and more preferably 3,000 cSt or more and 10,000 cSt or less.
The viscosity of the siloxane compound is obtained by the following procedure. Toluene is added to the specific silica particles and dispersed with an ultrasonic disperser for 30 minutes. Then, the supernatant is collected. At this time, a toluene solution of a siloxane compound having a concentration of 1 g/100 ml is prepared. The specific viscosity [η _sp ] (25° C.) at this time is determined by the following formula (A).

-Formula (A): (eta) _sp =((eta)/(eta) ₀ )-1.
(Η ₀ : viscosity of toluene, η: viscosity of solution)

Next, the specific viscosity [η _sp ] is substituted into the Huggins relational expression shown in the following formula (B) to obtain the intrinsic viscosity [η].
-Formula (B): η _sp =[η]+K'[η] ²
(K': Huggins constant K'=0.3 (when [η]=1 to 3 is applied))

Next, the intrinsic viscosity [η] of the A.V. The molecular weight M is obtained by substituting in the Kollov equation.
- formula (C): [η] = 0.215 × ¹⁰ -4 ^{M 0.65}

The siloxane viscosity [η] is determined by substituting the molecular weight M into the AJ Barry equation shown in the following equation (D).
· Formula (D): logη = 1.00 + 0.0123M 0.5

-Amount of surface adhesion-
The amount of the siloxane compound adhering to the surface of the specific silica particles is determined from the viewpoint of improving the fluidity, dispersibility in toner particles, cohesiveness, and adhesion to toner particles of the specific silica particles. 0.01% by mass or more and 5% by mass or less is more preferable, 0.05% by mass or more and 3% by mass or less is more preferable, and 0.10% by mass or more and 2% by mass or less is more preferable. ..
The surface adhesion amount is measured by the method described below.
100 mg of specific silica particles were dispersed in 1 mL of chloroform, and 1 μL of DMF (N,N-dimethylformamide) was added as an internal standard solution, followed by ultrasonic treatment for 30 minutes with an ultrasonic cleaner, and a siloxane compound in a chloroform solvent. Is extracted. Then, a hydrogen nuclear spectrum is measured with a JNM-AL400 type nuclear magnetic resonance apparatus (manufactured by JEOL Ltd.), and the amount of the siloxane compound is obtained from the ratio of the siloxane compound-derived peak area to the DMF-derived peak area. Then, the surface adhesion amount is obtained from the amount of this siloxane compound.

Here, it is preferable that the specific silica particles are surface-treated with a siloxane compound having a viscosity of 1000 cSt or more and 50,000 cSt or less, and the amount of the siloxane compound attached to the surface of the silica particles is 0.01% by mass or more and 5% by mass or less. ..
By satisfying the above requirements, it becomes easy to obtain specific silica particles having good fluidity and dispersibility in toner particles, and improved cohesiveness and adhesion to toner particles.

-External amount-
The external addition amount (content) of the specific silica particles is preferably 0.1% by mass or more and 6.0% by mass or less with respect to the toner particles from the viewpoints of the charge maintainability of the toner and the suppression of scratch generation on the photoreceptor. , 0.3 mass% or more and 4.0 mass% or less are more preferable, and 0.5 mass% or more and 2.5 mass% or less are still more preferable.

[Method for producing specific silica particles]
The specific silica particles are obtained by subjecting the surface of the silica particles to a surface treatment with a siloxane compound having a viscosity of 1000 cSt or more and 50000 cSt or less so that the amount of surface adhesion is 0.01% by mass or more and 5% by mass or less with respect to the silica particles. can get.
According to the method for producing specific silica particles, silica particles having good fluidity and dispersibility in toner particles as well as improved cohesiveness and adhesion to toner particles can be obtained.

Examples of the surface treatment method include a method of treating the surface of silica particles with a siloxane compound in supercritical carbon dioxide; a method of treating the surface of silica particles with a siloxane compound in the atmosphere.

Specific examples of the surface treatment method include a method in which supercritical carbon dioxide is used to dissolve a siloxane compound in supercritical carbon dioxide to attach the siloxane compound to the surface of silica particles; A method of applying (for example, spraying or coating) a solution containing a siloxane compound and a solvent that dissolves the siloxane compound onto the surface of the silica particle to adhere the siloxane compound to the surface of the silica particle; And a solution containing a solvent for dissolving the siloxane compound are added and held, and then a silica particle dispersion and a mixed solution of the solution are dried.

Above all, as the surface treatment method, a method in which supercritical carbon dioxide is used to deposit a siloxane compound on the surface of silica particles is preferable.
When the surface treatment is performed in supercritical carbon dioxide, the siloxane compound is dissolved in the supercritical carbon dioxide. Since supercritical carbon dioxide has the property of low interfacial tension, the siloxane compound dissolved in supercritical carbon dioxide diffuses with the supercritical carbon dioxide and reaches deep inside the pores of the silica particles. It is considered that the surface treatment with the siloxane compound is performed not only on the surface of the silica particles but also deep inside the pores.
Therefore, silica particles surface-treated with a siloxane compound in supercritical carbon dioxide are silica particles surface-treated with a siloxane compound so that the surface is almost uniform (for example, a thin-film surface treatment layer is formed). It is believed that

In addition, in the method for producing specific silica particles, a surface treatment may be performed to impart hydrophobicity to the surface of silica particles by using a hydrophobizing agent together with a siloxane compound in supercritical carbon dioxide.
In this case, the hydrophobizing agent is dissolved in the supercritical carbon dioxide together with the siloxane compound, and the siloxane compound and the hydrophobizing agent dissolved in the supercritical carbon dioxide together with the supercritical carbon dioxide form silica particles. It is considered that the particles easily diffuse and reach deep inside the pores on the surface, and it is considered that the surface treatment with the siloxane compound and the hydrophobizing agent is performed not only on the surface of the silica particles but also deep inside the pores.
As a result, the silica particles surface-treated with the siloxane compound and the hydrophobizing agent in supercritical carbon dioxide are treated with the siloxane compound and the hydrophobizing agent so that the surface has a nearly uniform surface and high hydrophobicity is imparted. It is easy to be done.

In addition, in the method for producing specific silica particles, supercritical carbon dioxide may be used in another production process of silica particles (for example, a solvent removal step).
As a method for producing specific silica particles using supercritical carbon dioxide in another production process, for example, a step of preparing a silica particle dispersion containing silica particles and a solvent containing alcohol and water by a sol-gel method (hereinafter , "Dispersion preparation step"), a step of circulating supercritical carbon dioxide to remove the solvent from the silica particle dispersion (hereinafter referred to as "solvent removal step"), and in supercritical carbon dioxide, A method for producing silica particles having a step of treating the surface of the silica particles after removing the solvent with a siloxane compound (hereinafter referred to as "surface treatment step") can be mentioned.

When the solvent is removed from the silica particle dispersion by using supercritical carbon dioxide, generation of coarse powder is easily suppressed.
The reason for this is not clear, but 1) when removing the solvent of the silica particle dispersion liquid, because of the property that supercritical carbon dioxide "interfacial tension does not work", the particles are separated from each other by the liquid crosslinking force when removing the solvent. It is considered that the solvent can be removed without coagulation. 2) Supercritical carbon dioxide "It is carbon dioxide in a state of temperature and pressure above the critical point and has both gas diffusibility and liquid solubility. By virtue of the property of "having", it is possible to efficiently contact the supercritical carbon dioxide and dissolve the solvent at a relatively low temperature (for example, 250° C. or lower). Therefore, by removing the supercritical carbon dioxide in which the solvent is dissolved, The reason is considered to be that the solvent in the silica particle dispersion liquid can be removed without producing coarse powder such as secondary aggregates due to condensation of silanol groups.

Here, the solvent removal step and the surface treatment step may be performed individually, but it is preferably performed continuously (that is, each step is performed without being opened under atmospheric pressure). The surface treatment step can be performed in a state where the silica particles do not have an opportunity to adsorb moisture after the solvent removal step and excessive adsorption of moisture to the silica particles is suppressed after the solvent removal step. This eliminates the need to use a large amount of siloxane compound or to perform excessive heating to perform the solvent removal step and the surface treatment step at a high temperature. As a result, the generation of coarse powder can be suppressed more effectively.

Hereinafter, the details of the method for producing the specific silica particles will be described in detail for each step.
The method for producing the specific silica particles is not limited to this, and may be, for example, 1) a mode in which supercritical carbon dioxide is used only in the surface treatment step, or 2) a mode in which each step is performed individually. ..

Hereinafter, each step will be described in detail.

-Dispersion liquid preparation step-
In the dispersion liquid preparation step, for example, a silica particle dispersion liquid containing silica particles and a solvent containing alcohol and water is prepared.
Specifically, in the dispersion liquid preparation step, for example, a silica particle dispersion liquid is prepared by a wet method (for example, a sol-gel method or the like) and prepared. In particular, the silica particle dispersion liquid is a wet sol-gel method, specifically, tetraalkoxysilane is allowed to undergo a reaction (hydrolysis reaction, condensation reaction) in the presence of an alkali catalyst in a solvent of alcohol and water to produce silica particles. To produce a silica particle dispersion.

The preferable range of the average equivalent circular diameter of the silica particles and the preferable range of the average circularity are as described above.
In the dispersion liquid preparation step, for example, when silica particles are obtained by a wet method, the silica particles are obtained in a dispersion liquid state (silica particle dispersion liquid).

Here, when shifting to the solvent removal step, the silica particle dispersion liquid to be prepared may have a mass ratio of water to alcohol of, for example, 0.05 or more and 1.0 or less, preferably 0.07 or more and 0.1. It is 5 or less, more preferably 0.1 or more and 0.3 or less.
When the mass ratio of water to alcohol in the silica particle dispersion is in the above range, the generation of coarse particles of the silica particles after the surface treatment is small, and the silica particles having good electric resistance are easily obtained.
If the mass ratio of water to alcohol is less than 0.05, the condensation of silanol groups on the surface of the silica particles when removing the solvent in the solvent removal step is reduced, so that the water adsorbed on the surface of the silica particles after removal of the solvent is reduced. When the amount of particles increases, the electric resistance of the silica particles after the surface treatment may become too low. Further, when the mass ratio of water exceeds 1.0, a large amount of water remains in the vicinity of the end point of solvent removal in the silica particle dispersion in the solvent removal step, and silica particles are likely to aggregate due to the liquid crosslinking force, May be present as coarse powder after surface treatment.

Further, when shifting to the solvent removal step, the silica particle dispersion liquid to be prepared preferably has a mass ratio of water to the silica particles of, for example, 0.02 or more and 3 or less, and preferably 0.05 or more and 1 or less. It is preferably 0.1 or more and 0.5 or less.
When the mass ratio of water to the silica particles in the silica particle dispersion is within the above range, the generation of coarse particles of the silica particles is small, and silica particles having good electric resistance are easily obtained.
If the mass ratio of water to silica particles is less than 0.02, the condensation of silanol groups on the surface of the silica particles during removal of the solvent in the solvent removal step is extremely reduced, so that the surface of the silica particles after removal of the solvent is removed. When the adsorbed water content increases, the electric resistance of the silica particles may become too low.
Further, when the mass ratio of water exceeds 3, a large amount of water remains in the vicinity of the solvent removal end point in the silica particle dispersion liquid in the solvent removal step, and the silica particles are likely to aggregate due to the liquid crosslinking force. is there.

Further, when shifting to the solvent removal step, the silica particle dispersion liquid to be prepared has a mass ratio of silica particles to the silica particle dispersion liquid of, for example, 0.05 or more and 0.7 or less, preferably 0.2 or more and 0.1. It is 65 or less, more preferably 0.3 or more and 0.6 or less.
If the mass ratio of the silica particles to the silica particle dispersion is less than 0.05, the amount of supercritical carbon dioxide used in the solvent removal step may increase and the productivity may deteriorate.
Further, when the mass ratio of the silica particles to the silica particle dispersion exceeds 0.7, the distance between the silica particles in the silica particle dispersion becomes short, and coarse particles due to aggregation or gelation of the silica particles are likely to occur. There is.

-Solvent removal step-
The solvent removal step is, for example, a step of circulating supercritical carbon dioxide to remove the solvent of the silica particle dispersion liquid.
That is, in the solvent removal step, the supercritical carbon dioxide is caused to come into contact with the silica particle dispersion liquid by circulating the supercritical carbon dioxide to remove the solvent.
Specifically, in the solvent removal step, for example, the silica particle dispersion liquid is put into a closed reactor. Then, liquefied carbon dioxide is added and heated in the closed reactor, and the pressure inside the reactor is increased by a high-pressure pump to bring carbon dioxide into a supercritical state. Then, while supercritical carbon dioxide is introduced into the closed reactor and discharged, the supercritical carbon dioxide is circulated in the closed reactor, that is, the silica particle dispersion liquid.
As a result, the supercritical carbon dioxide dissolves the solvent (alcohol and water) and, together with it, is discharged to the outside of the silica particle dispersion (outside the sealed reactor), and the solvent is removed.

Here, supercritical carbon dioxide is carbon dioxide in a state of being kept at a temperature and pressure higher than the critical point and has both gas diffusibility and liquid solubility.

The temperature condition for solvent removal, that is, the temperature of supercritical carbon dioxide is, for example, 31° C. or higher and 350° C. or lower, preferably 60° C. or higher and 300° C. or lower, and more preferably 80° C. or higher and 250° C. or lower.
If this temperature is lower than the above range, the solvent becomes difficult to dissolve in the supercritical carbon dioxide, so that it may be difficult to remove the solvent. Further, it is considered that coarse powder may be easily generated due to the liquid or cross-linking force of supercritical carbon dioxide. On the other hand, when this temperature exceeds the above range, it is considered that coarse powder such as secondary agglomerates may be easily generated due to condensation of silanol groups on the surface of silica particles.

The pressure condition for solvent removal, that is, the pressure of supercritical carbon dioxide is, for example, 7.38 MPa or more and 40 MPa or less, preferably 10 MPa or more and 35 MPa or less, and more preferably 15 MPa or more and 25 MPa or less.
If this pressure is less than the above range, the solvent tends to be difficult to dissolve in supercritical carbon dioxide, while if the pressure exceeds the above range, the equipment tends to be expensive.

The amount of supercritical carbon dioxide introduced and discharged into the closed reactor is, for example, preferably 15.4 L/min/m ³ or more and 1540 L/min/m ³ or less, and preferably 77 L/min/m. ^{It is 3} or more and 770 L/min/m ³ or less.
If the amount introduced/discharged is less than 15.4 L/min/m ³ , it takes a long time to remove the solvent, and the productivity tends to deteriorate.
On the other hand, if the amount introduced/exhausted exceeds 1540 L/min/m ³ , the supercritical carbon dioxide short-passes, the contact time of the silica particle dispersion becomes short, and it tends to be difficult to efficiently remove the solvent.

-Surface treatment process-
The surface treatment step is, for example, a step in which the surface of the silica particles is surface-treated with a siloxane compound in supercritical carbon dioxide continuously with the solvent removal step.
That is, in the surface treatment step, for example, the surface of the silica particles is surface-treated with the siloxane compound in supercritical carbon dioxide without opening to the atmosphere before shifting from the solvent removal step.
Specifically, in the surface treatment step, for example, after stopping the introduction and discharge of supercritical carbon dioxide into the closed reactor in the solvent removal step, the temperature and pressure inside the closed reactor are adjusted to In the state in which supercritical carbon dioxide exists, a siloxane compound is added at a constant ratio to silica particles. Then, the siloxane compound is reacted in a state where this state is maintained, that is, in supercritical carbon dioxide, to perform the surface treatment of the silica particles.

Here, in the surface treatment step, the reaction of the siloxane compound may be carried out in supercritical carbon dioxide (that is, in the atmosphere of supercritical carbon dioxide), and the supercritical carbon dioxide flows (that is, the supercritical carbon dioxide in the closed reactor is The surface treatment may be carried out while introducing/exhausting the critical carbon dioxide), or the surface treatment may be carried out without distribution.

In the surface treatment step, the amount of silica particles relative to the volume of the reactor (that is, the charged amount) is, for example, 30 g/L or more and 600 g/L or less, preferably 50 g/L or more and 500 g/L or less, and more preferably 80 g/L. L or more and 400 g/L or less.
If this amount is less than the above range, the concentration of the siloxane compound with respect to supercritical carbon dioxide will be low, the contact probability with the silica surface will be lowered, and the reaction may be difficult to proceed. On the other hand, when the amount is more than the above range, the concentration of the siloxane compound with respect to the supercritical carbon dioxide becomes high, the siloxane compound cannot be completely dissolved in the supercritical carbon dioxide, resulting in poor dispersion, and coarse aggregates are easily generated.

The density of supercritical carbon dioxide is, for example, 0.10 g/ml or more and 0.80 g/ml or less, preferably 0.10 g/ml or more and 0.60 g/ml or less, more preferably 0.2 g/ml or more 0. It is less than or equal to 50 g/ml.
If this density is lower than the above range, the solubility of the siloxane compound in supercritical carbon dioxide is lowered, and aggregates tend to be generated. On the other hand, if the density is higher than the above range, the diffusibility into the silica pores decreases, and the surface treatment may become insufficient. In particular, the sol-gel silica particles containing a large amount of silanol groups are preferably surface-treated within the above density range.
The density of supercritical carbon dioxide is adjusted by temperature, pressure and the like.

Specific examples of the siloxane compound are as described above. Moreover, the preferable range of the viscosity of the siloxane compound is as described above.
Among the siloxane compounds, when silicone oil is applied, the silicone oil is likely to adhere to the surface of the silica particles in a nearly uniform state, and the flowability, dispersibility, and handleability of the silica particles are likely to be improved.

The amount of the siloxane compound used is, for example, 0.05% by mass or more and 3% by mass or less with respect to the silica particles, from the viewpoint of easily controlling the surface adhesion amount to the silica particles from 0.01% by mass to 5% by mass. Well, preferably 0.1% by mass or more and 2% by mass or less, more preferably 0.15% by mass or more and 1.5% by mass or less.

The siloxane compound may be used alone or as a mixed solution with a solvent in which the siloxane compound is easily dissolved. Examples of the solvent include toluene, methyl ethyl ketone, methyl isobutyl ketone, and the like.

In the surface treatment step, the silica particles may be surface-treated with a mixture containing a siloxane compound and a hydrophobizing agent.

Examples of the hydrophobizing agent include silane-based hydrophobizing agents. Examples of the silane-based hydrophobizing agent include known silicon compounds having an alkyl group (eg, methyl group, ethyl group, propyl group, butyl group, etc.), and specific examples include, for example, silazane compounds (eg, methyltrimethoxy). Silane compounds such as silane, dimethyldimethoxysilane, trimethylchlorosilane, trimethylmethoxysilane, hexamethyldisilazane, tetramethyldisilazane, etc.) and the like. The hydrophobizing agent may be used alone or in combination of two or more.
Among silane-based hydrophobizing agents, silicon compounds having a trimethyl group such as trimethylmethoxysilane and hexamethyldisilazane (HMDS), particularly hexamethyldisilazane (HMDS), are preferable.

The amount of the silane-based hydrophobizing agent used is not particularly limited, but is, for example, 1% by mass or more and 100% by mass or less, preferably 3% by mass or more and 80% by mass or less, and more preferably, with respect to the silica particles. Is 5% by mass or more and 50% by mass or less.

The silane-based hydrophobizing agent may be used alone, or may be used as a mixed solution with a solvent in which the silane-based hydrophobizing agent is easily dissolved. Examples of the solvent include toluene, methyl ethyl ketone, methyl isobutyl ketone, and the like.

The temperature condition of the surface treatment, that is, the temperature of supercritical carbon dioxide is preferably 80° C. or higher and 300° C. or lower, preferably 100° C. or higher and 250° C. or lower, and more preferably 120° C. or higher and 200° C. or lower.
If this temperature is less than the above range, the surface treatment ability of the siloxane compound may decrease. On the other hand, if the temperature exceeds the above range, the condensation reaction between the silanol groups of the silica particles may proceed and particle aggregation may occur. In particular, the sol-gel silica particles containing a large amount of silanol groups are preferably surface-treated within the above temperature range.

On the other hand, the pressure condition of the surface treatment, that is, the pressure of supercritical carbon dioxide may be a condition that satisfies the above density, for example, 8 MPa or more and 30 MPa or less, preferably 10 MPa or more and 25 MPa or less, more preferably 15 MPa or more. It is 20 MPa or less.

Through the steps described above, the specific silica particles are obtained.

[Medium resistance particles]
The medium resistance particles are inorganic oxide particles having a volume resistivity of 1.0×10 ⁸ Ωcm or more and 1.0×10 ¹⁵ Ωcm or less. The volume resistivity of the medium resistance particles is preferably 1.0×10 ¹⁰ Ωcm or more and 1.0×10 ¹⁵ Ωcm or less from the viewpoint of the balance between charge imparting ability and charge leakage.

The volume resistivity of the medium resistance particles is measured by the method described below. The measurement environment is set to a temperature of 20° C. and a humidity of 50% RH.
Medium resistance particles to be measured are placed on the surface of a circular jig provided with a 20 cm ² electrode plate so as to have a thickness in the range of 1 mm or more and 3 mm or less to form a medium resistance particle layer. An electrode plate of 20 cm ² similar to the above is placed on the medium resistance particle layer, and the medium resistance particle layer is sandwiched. To eliminate voids between the medium resistance particles, a load of 4 kg is applied on the electrode plate placed on the medium resistance particle layer, and then the thickness (cm) of the medium resistance particle layer is measured. The electrodes above and below the medium resistance particle layer are connected to an electrometer and a high-voltage power generator. A high voltage is applied to both electrodes so that the electric field is 6000 V/cm, and the volume electric resistance (Ωcm) of the medium resistance particles is calculated by reading the current value (A) flowing at this time. The formula for calculating the volume resistivity (Ωcm) of the carrier is as shown in the following formula.
· Formula: R = E × 20 / ( I-I 0) / L
In the above formula, R is the volume resistivity (Ω·cm) of the medium resistance particles, E is the applied voltage (V), I is the current value (A), I ₀ is the current value (A) at the applied voltage of 0 V, and L is Each represents the thickness (cm) of the medium resistance particle layer. The coefficient of 20 represents the area (cm ² ) of the electrode plate.

Examples of the medium resistance particles include titanium oxide particles, aluminum oxide particles, zinc oxide particles and the like. Among these, titanium oxide particles (titania particles) that suppress the dependency of the charging environment on the toner (change in the amount of charge under high temperature/high humidity/low temperature/low humidity) are preferable as the medium resistance particles.
Examples of titanium oxide particles include anatase type titanium oxide particles, rutile type titanium oxide particles, metatitanic acid particles, and any of these may be used.

In addition, metatitanic acid means a thing of n=1 among titanic acid hydrate TiO ₂ .nH ₂ O. Then, the metatitanic acid particles are usually purified by a wet method of chemically reacting in a solvent. The wet method is divided into a sulfuric acid method and a hydrochloric acid method. In the sulfuric acid method, TiOSO ₄ is generated by the progress of the reaction between FeTiO ₃ and 2H ₂ SO ₄ in the liquid phase, and metatitanic acid (TiO(OH) ₂ ) particles are obtained by hydrolysis of the generated TiOSO ₄ . On the other hand, in the hydrochloric acid method, first, chlorination is performed by the same method as in the dry method to produce titanium tetrachloride, and then it is dissolved in water and hydrolyzed by adding a strong base thereto, and metatitanic acid (TiO(OH(OH ₂ ) Particles are obtained.

The average circle equivalent diameter of the medium resistance particles is smaller than that of the specific silica particles, and for example, 7 nm or more and 50 nm or less is preferable, and 7 nm or more and 40 nm or less is more preferable.
The average equivalent circle diameter D50 of the medium resistance particles is measured by the same method as the average equivalent circle diameter D50 of the specific silica particles.

Here, a method of measuring each characteristic of the medium resistance particles (volume resistivity, average circle equivalent diameter, etc.) from the toner will be described.
First, the external additive is separated from the toner according to the same method as the method for measuring each characteristic of the specific silica particles. Then, each of the above characteristics (volume resistivity, average equivalent circle diameter, etc.) is measured using the separated medium resistance particles.

The medium resistance particles may be hydrophobized. The hydrophobizing treatment is performed, for example, by immersing the titania particles in a hydrophobizing agent. Examples of the hydrophobic treatment agent used for the hydrophobic treatment include a silane coupling agent and silicone oil.
Examples of the silane coupling agent include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxysilane, and isobutyltrimethoxysilane. , Dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane, vinyltrimethoxy Examples thereof include silane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane and the like.
Examples of the silicone oil include dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane and the like.
In addition, as the hydrophobizing agent, known hydrophobizing agents such as titanate coupling agents and aluminum coupling agents may also be used.
The hydrophobizing agents may be used alone or in combination of two or more.

The external addition amount (addition amount) of the medium resistance particles is preferably 0.1% by mass or more and 4.0% by mass or less, and 0.3% by mass or more and 2.0% by mass or less, based on the total mass of the toner particles. Is more preferable.

[Other external additives]
As another external additive, organic particles such as a cleaning aid may be used if necessary.

(Toner manufacturing method)
Next, a method of manufacturing the toner according to this exemplary embodiment will be described.
The toner according to this exemplary embodiment is obtained by manufacturing toner particles and then externally adding an external additive to the toner particles.

The toner particles may be manufactured by either a dry manufacturing method (for example, a kneading pulverization method or the like) or a wet manufacturing method (for example, an aggregation and coalescence method, a suspension polymerization method, a dissolution suspension method or the like). The production method of toner particles is not particularly limited to these production methods, and well-known production methods are adopted.
Among these, it is preferable to obtain the toner particles by the aggregation and coalescence method.

Specifically, for example, when the toner particles are produced by the aggregation and coalescence method,
A step of preparing a resin particle dispersion liquid in which resin particles serving as a binder resin are dispersed (resin particle dispersion liquid preparing step), and a step in the resin particle dispersion liquid (after mixing other particle dispersion liquids as necessary) (In the dispersion liquid), a step of aggregating the resin particles (other particles as necessary) to form the agglomerated particles (agglomerated particle forming step), and heating the agglomerated particle dispersion liquid in which the agglomerated particles are dispersed. Then, the toner particles are manufactured through the steps of fusing and coalescing the aggregated particles to form toner particles (fusing and coalescing step).

The details of each step will be described below.
In the following description, a method for obtaining toner particles containing a colorant and a release agent will be described, but the colorant and the release agent are used as necessary. Of course, you may use other additives other than a coloring agent and a mold release agent.

-Resin particle dispersion liquid preparation step-
First, together with a resin particle dispersion liquid in which resin particles serving as a binder resin are dispersed, for example, a colorant particle dispersion liquid in which colorant particles are dispersed, a release agent particle dispersion liquid in which release agent particles are dispersed are prepared. To do.

Here, the resin particle dispersion is prepared, for example, by dispersing resin particles in a dispersion medium with a surfactant.

Examples of the dispersion medium used for the resin particle dispersion liquid include an aqueous medium.
Examples of the aqueous medium include water such as distilled water and ion-exchanged water, alcohols and the like. These may be used alone or in combination of two or more.

Examples of the surfactant include anionic surfactants such as sulfate ester type, sulfonate type, phosphate ester type, and soap type; cationic surfactants such as amine salt type and quaternary ammonium salt type; polyethylene glycol. Examples thereof include nonionic surfactants such as compounds, alkylphenol ethylene oxide adducts and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are particularly preferable. The nonionic surfactant may be used in combination with the anionic surfactant or the cationic surfactant.
The surfactants may be used alone or in combination of two or more.

Examples of a method for dispersing the resin particles in the dispersion medium in the resin particle dispersion liquid include general dispersion methods such as a rotary shear homogenizer, a ball mill having a medium, a sand mill, and a dyno mill. Further, depending on the type of resin particles, the resin particles may be dispersed in the resin particle dispersion liquid by using, for example, a phase inversion emulsification method.
The phase inversion emulsification method is to dissolve a resin to be dispersed in a hydrophobic organic solvent in which the resin is soluble, add a base to an organic continuous phase (O phase) to neutralize the resin, and then to form an aqueous medium. A method in which the resin is converted from W/O to O/W (so-called phase inversion) by introducing (W phase) to form a discontinuous phase, and the resin is dispersed in an aqueous medium into particles. Is.

The volume average particle diameter of the resin particles dispersed in the resin particle dispersion liquid is, for example, preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and further preferably 0.1 μm or more and 0.6 μm or less. preferable.
The volume average particle size of the resin particles is the particle size distribution obtained by measurement with a laser diffraction particle size distribution measuring device (for example, LA-700 manufactured by Horiba Ltd.), and is based on the divided particle size range (channel). The cumulative distribution is subtracted from the small particle size side with respect to the volume, and the particle size at which cumulative 50% of all particles is obtained is measured as the volume average particle size D50v. The volume average particle size of the particles in the other dispersions is measured in the same manner.

The content of the resin particles contained in the resin particle dispersion liquid is, for example, preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less.

In addition, for example, a colorant particle dispersion liquid and a release agent particle dispersion liquid are prepared in the same manner as the resin particle dispersion liquid. That is, regarding the volume average particle size of the particles in the resin particle dispersion liquid, the dispersion medium, the dispersion method, and the content of the particles, the colorant particles dispersed in the colorant particle dispersion liquid and the release agent particle dispersion liquid are The same applies to the release agent particles to be dispersed.

-Agglomerated particle formation step-
Next, the colorant particle dispersion and the release agent particle dispersion are mixed together with the resin particle dispersion.
Then, in the mixed dispersion liquid, the resin particles, the colorant particles, and the release agent particles are hetero-aggregated to have a diameter close to the diameter of the intended toner particles. Forming agglomerated particles containing.

Specifically, for example, while adding an aggregating agent to the mixed dispersion, adjusting the pH of the mixed dispersion to acidic (for example, pH is 2 or more and 5 or less), and adding a dispersion stabilizer as necessary, The resin particles are heated to a glass transition temperature (specifically, for example, the glass transition temperature of the resin particles −30° C. or higher and the glass transition temperature −10° C. or lower) to aggregate the particles dispersed in the mixed dispersion liquid. , To form agglomerated particles.
In the aggregated particle forming step, for example, the aggregating agent is added at room temperature (for example, 25° C.) while stirring the mixed dispersion with a rotary shear homogenizer, and the pH of the mixed dispersion is acidic (for example, pH is 2 or more and 5 or less). The above heating may be performed after adjusting to (1) and adding a dispersion stabilizer as needed.

Examples of the aggregating agent include a surfactant having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion liquid, an inorganic metal salt, and a divalent or higher valent metal complex. In particular, when a metal complex is used as the aggregating agent, the amount of the surfactant used is reduced and the charging characteristics are improved.
If necessary, an additive which forms a complex or a similar bond with the metal ion of the aggregating agent may be used. A chelating agent is preferably used as the additive.

Examples of the inorganic metal salt include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride and aluminum sulfate, and inorganic salts such as polyaluminum chloride, polyaluminum hydroxide and calcium polysulfide. Examples thereof include metal salt polymers.
A water-soluble chelating agent may be used as the chelating agent. Examples of the chelating agent include oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, iminodic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA).
The addition amount of the chelating agent is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass with respect to 100 parts by mass of the resin particles.

-Fusion/unification process-
Next, the aggregated particle dispersion liquid in which the aggregated particles are dispersed is heated to, for example, the glass transition temperature of the resin particles or higher (for example, 10 to 30° C. higher than the glass transition temperature of the resin particles) to obtain the aggregated particles. Are fused and united to form toner particles.

Toner particles are obtained through the above steps.
After obtaining the aggregated particle dispersion liquid in which the aggregated particles are dispersed, the aggregated particle dispersion liquid and the resin particle dispersion liquid in which the resin particles are dispersed are further mixed, and further resin particles are formed on the surface of the aggregated particles. A step of forming second agglomerated particles by aggregating so as to adhere, and heating the second agglomerated particle dispersion liquid in which the second agglomerated particles are dispersed to fuse and coalesce the second agglomerated particles. The toner particles may be manufactured through the step of forming toner particles having a core/shell structure.

Here, after the fusion and coalescence step is completed, the toner particles formed in the solution are subjected to a known washing step, solid-liquid separation step, and drying step to obtain dried toner particles.
In the cleaning step, it is preferable to sufficiently perform displacement cleaning with ion-exchanged water from the viewpoint of chargeability. The solid-liquid separation step is not particularly limited, but suction filtration, pressure filtration and the like may be performed from the viewpoint of productivity. The drying step is also not particularly limited in terms of method, but from the viewpoint of productivity, freeze drying, air flow drying, fluidized drying, vibration type fluidized drying and the like are preferably performed.

Then, the toner according to the present exemplary embodiment is manufactured, for example, by adding an external additive to the obtained dry toner particles and mixing them. The mixing may be performed by, for example, a V blender, a Henschel mixer, a Laedige mixer or the like. Further, if necessary, coarse particles of the toner may be removed using a vibration sieving machine, a wind sieving machine or the like.

<Electrostatic image developer>
The electrostatic image developer according to this exemplary embodiment contains at least the toner according to this exemplary embodiment.
The electrostatic image developer according to this exemplary embodiment may be a one-component developer containing only the toner according to this exemplary embodiment or a two-component developer in which the toner and a carrier are mixed.

The carrier is not particularly limited, and known carriers can be used. Examples of the carrier include a coated carrier obtained by coating a surface of a core material made of magnetic powder with a coating resin; a magnetic powder dispersion type carrier in which magnetic powder is dispersed and mixed in a matrix resin; porous magnetic powder is impregnated with resin. And the like.
The magnetic powder-dispersed carrier and the resin-impregnated carrier may be carriers in which the constituent particles of the carrier are used as core materials and which are coated with a coating resin.

Examples of the magnetic powder include magnetic metals such as iron, nickel and cobalt, and magnetic oxides such as ferrite and magnetite.

Examples of the coating resin and the matrix resin include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid ester. Examples thereof include a copolymer, a straight silicone resin containing an organosiloxane bond or a modified product thereof, a fluororesin, a polyester, a polycarbonate, a phenol resin, an epoxy resin and the like.
The coating resin and the matrix resin may contain other additives such as conductive particles.
Examples of the conductive particles include particles of metals such as gold, silver and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate and potassium titanate.

Here, in order to coat the surface of the core material with the coating resin, a method of coating with the coating resin and a coating layer forming solution in which various additives as necessary are dissolved in a suitable solvent can be mentioned. The solvent is not particularly limited, and may be selected in consideration of the coating resin used, coating suitability and the like.
Specific resin coating methods include a dipping method in which the core material is immersed in a coating layer forming solution, a spray method in which the coating layer forming solution is sprayed on the surface of the core material, and a state in which the core material is suspended by flowing air. Examples thereof include a fluidized bed method of spraying a coating layer forming solution and a kneader coater method of removing a solvent by mixing a carrier core material and a coating layer forming solution in a kneader coater.

The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer is preferably toner:carrier=1:100 to 30:100, more preferably 3:100 to 20:100.

<Image forming apparatus/image forming method>
An image forming apparatus/image forming method according to this embodiment will be described.
The image forming apparatus according to the present exemplary embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the charged surface of the image carrier, and an electrostatic charge. A developing unit that contains an image developer and develops the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer, and a toner image formed on the surface of the image carrier as a recording medium. And a fixing unit for fixing the toner image transferred on the surface of the recording medium. Then, as the electrostatic charge image developer, the electrostatic charge image developer according to the exemplary embodiment is applied.

In the image forming apparatus according to the present exemplary embodiment, a charging step of charging the surface of the image holding member, an electrostatic charge image forming step of forming an electrostatic charge image on the charged surface of the image holding member, and an electrostatic charge according to the present embodiment. A developing step of developing an electrostatic charge image formed on the surface of the image carrier as a toner image with the image developer; a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of the recording medium; An image forming method (image forming method according to this embodiment) including a fixing step of fixing the toner image transferred on the surface of the recording medium is performed.

The image forming apparatus according to the present embodiment is a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image carrier to a recording medium; a toner image formed on the surface of the image carrier is an intermediate transfer body. A device of an intermediate transfer system that performs a primary transfer to the surface and secondarily transfers the toner image transferred to the surface of the intermediate transfer member to the surface of the recording medium; after the transfer of the toner image, the surface of the image carrier before charging is cleaned. A well-known image forming apparatus such as a device provided with a cleaning unit; a device provided with a static elimination unit that radiates static elimination light to the surface of the image holding body to discharge the static electricity after transfer of the toner image and before charging.
In the case of the apparatus of the intermediate transfer system, the transfer means includes, for example, an intermediate transfer body on which a toner image is transferred on the surface, and a primary transfer for primarily transferring the toner image formed on the surface of the image carrier to the surface of the intermediate transfer body. And a secondary transfer unit that secondarily transfers the toner image transferred on the surface of the intermediate transfer member to the surface of the recording medium.

In the image forming apparatus according to the present exemplary embodiment, for example, a portion including the developing unit may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including a developing unit containing the electrostatic image developer according to this exemplary embodiment is preferably used.

Hereinafter, an example of the image forming apparatus according to the present exemplary embodiment will be shown, but the invention is not limited to this. The main parts shown in the figure will be described, and the description of other parts will be omitted.

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to this embodiment.
The image forming apparatus shown in FIG. 1 is a first to an electrophotographic system that outputs an image of each color of yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. The fourth image forming unit 10Y, 10M, 10C, 10K (image forming means) is provided. These image forming units (hereinafter, may be simply referred to as “units”) 10Y, 10M, 10C, and 10K are arranged in parallel in the horizontal direction with a predetermined distance therebetween. The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the image forming apparatus.

Above the units 10Y, 10M, 10C, and 10K in the drawing, an intermediate transfer belt 20 as an intermediate transfer member extends through the units. The intermediate transfer belt 20 is provided by being wound around a drive roll 22 and a support roll 24 that are in contact with the inner surface of the intermediate transfer belt 20 and are spaced apart from each other in the left to right direction in the drawing. It is designed to run in the direction toward the unit 10K. A force is applied to the support roll 24 in a direction away from the drive roll 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around the both. An intermediate transfer member cleaning device 30 is provided on the side of the image transfer member of the intermediate transfer belt 20 so as to face the drive roll 22.
Further, the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K respectively include yellow, magenta, cyan, and black stored in toner cartridges 8Y, 8M, 8C, and 8K. The toner including the four color toners is supplied.

Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration, here, the first unit for forming a yellow image is provided on the upstream side in the running direction of the intermediate transfer belt. 10Y will be described as a representative. It should be noted that the same units as the first unit 10Y are provided with reference numerals with magenta (M), cyan (C), and black (K) instead of yellow (Y), so that the second to fourth units are provided. The description of the units 10M, 10C, and 10K will be omitted.

The first unit 10Y has a photoconductor 1Y that functions as an image carrier. Around the photoconductor 1Y, a charging roll (an example of a charging unit) 2Y that charges the surface of the photoconductor 1Y to a predetermined potential, and the charged surface is exposed by a laser beam 3Y based on a color-separated image signal. To form an electrostatic charge image (an example of an electrostatic charge image forming unit) 3, a developing device (an example of a developing unit) 4Y that supplies toner charged in the electrostatic charge image to develop the electrostatic charge image, and develops A primary transfer roll 5Y (an example of a primary transfer unit) that transfers the toner image onto the intermediate transfer belt 20 and a photoconductor cleaning device (an example of a cleaning unit) 6Y that removes the toner remaining on the surface of the photoconductor 1Y after the primary transfer. Are arranged in order.
The primary transfer roll 5Y is arranged inside the intermediate transfer belt 20 and is provided at a position facing the photoconductor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C and 5K. Each bias power source changes the transfer bias applied to each primary transfer roll under the control of a controller (not shown).

The operation of forming a yellow image in the first unit 10Y will be described below.
First, prior to the operation, the surface of the photoconductor 1Y is charged to a potential of −600V to −800V by the charging roll 2Y.
The photoconductor 1Y is formed by laminating a photoconductive layer on a conductive (for example, volume resistivity at 20° C.: 1×10 ⁻⁶ Ωcm or less) substrate. This photosensitive layer usually has high resistance (resistance of general resin), but when irradiated with the laser beam 3Y, the specific resistance of the portion irradiated with the laser beam changes. Therefore, the laser beam 3Y is output to the surface of the charged photoconductor 1Y through the exposure device 3 according to the yellow image data sent from the control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoconductor 1Y, whereby an electrostatic image of a yellow image pattern is formed on the surface of the photoconductor 1Y.

The electrostatic image is an image formed on the surface of the photoconductor 1Y by charging, and the laser beam 3Y reduces the specific resistance of the irradiated portion of the photosensitive layer, and the charged charge on the surface of the photoconductor 1Y flows. On the other hand, it is a so-called negative latent image which is formed by remaining electric charges in a portion which is not irradiated with the laser beam 3Y.
The electrostatic charge image formed on the photoconductor 1Y is rotated to a predetermined developing position as the photoconductor 1Y travels. Then, at this developing position, the electrostatic charge image on the photoconductor 1Y is made into a visible image (developed image) as a toner image by the developing device 4Y.

In the developing device 4Y, for example, an electrostatic charge image developer containing at least a yellow toner and a carrier is stored. The yellow toner is triboelectrically charged by being stirred inside the developing device 4Y, has a charge of the same polarity (negative polarity) as the electrostatic charge charged on the photoconductor 1Y, and has a developer roll (developer holding member). One example) is held on. Then, as the surface of the photoconductor 1Y passes through the developing device 4Y, the yellow toner electrostatically adheres to the neutralized latent image portion on the surface of the photoconductor 1Y, and the latent image is developed by the yellow toner. .. The photoconductor 1Y on which the yellow toner image is formed continues to run at a predetermined speed, and the toner image developed on the photoconductor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photoconductor 1Y is conveyed to the primary transfer, the primary transfer bias is applied to the primary transfer roll 5Y, and the electrostatic force directed from the photoconductor 1Y to the primary transfer roll 5Y acts on the toner image to The toner image on 1Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a polarity (+) opposite to the polarity (−) of the toner, and is controlled to +10 μA by a control unit (not shown) in the first unit 10Y, for example.
On the other hand, the toner remaining on the photoconductor 1Y is removed and collected by the photoconductor cleaning device 6Y.

In addition, the primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K after the second unit 10M is also controlled according to the first unit.
In this way, the intermediate transfer belt 20 to which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner. It

The intermediate transfer belt 20 to which the toner images of four colors are transferred in multiples through the first to fourth units is arranged on the image transfer surface side of the intermediate transfer belt 20, the support roll 24 in contact with the inner surface of the intermediate transfer belt 20. The secondary transfer roll (an example of the secondary transfer means) 26 thus formed reaches the secondary transfer portion. On the other hand, recording paper (an example of a recording medium) P is fed at a predetermined timing into a gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are in contact with each other via a supply mechanism, and the secondary transfer bias is applied to the support roll. 24 is applied. The transfer bias applied at this time has the same polarity (-) as the polarity (-) of the toner, and the electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image to cause the toner image on the intermediate transfer belt 20. Toner image is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by the resistance detecting means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

After that, the recording paper P is sent to the pressure contact portion (nip portion) of the pair of fixing rolls in the fixing device (an example of fixing means) 28, and the toner image is fixed on the recording paper P to form a fixed image.

Examples of the recording paper P onto which the toner image is transferred include plain paper used in electrophotographic copying machines and printers. The recording medium may be an OHP sheet or the like in addition to the recording paper P.
In order to further improve the smoothness of the image surface after fixing, the surface of the recording paper P is also preferably smooth. For example, coated paper obtained by coating the surface of plain paper with resin or the like, art paper for printing, etc. are preferably used. To be done.

The recording paper P on which the fixing of the color image is completed is carried out toward the discharge section, and the series of color image forming operations is completed.

<Process cartridge/Toner cartridge>
The process cartridge according to this embodiment will be described.
The process cartridge according to the present exemplary embodiment stores the electrostatic charge image developer according to the present exemplary embodiment, and develops the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer. And a process cartridge that is attached to and detached from the image forming apparatus.

The process cartridge according to the present embodiment is not limited to the above-described configuration, and the developing device and other means such as an image carrier, a charging unit, an electrostatic charge image forming unit, and a transfer unit, if necessary. The configuration may include at least one selected from

Hereinafter, an example of the process cartridge according to the present embodiment will be shown, but the process cartridge is not limited thereto. The main parts shown in the figure will be described, and the description of other parts will be omitted.

FIG. 2 is a schematic configuration diagram showing the process cartridge according to the present embodiment.
The process cartridge 200 shown in FIG. 2 includes, for example, a photoconductor 107 (an example of an image carrier) and a periphery of the photoconductor 107 by a housing 117 provided with a mounting rail 116 and an opening 118 for exposure. The charging roll 108 (an example of a charging unit), the developing device 111 (an example of a developing unit), and the photoconductor cleaning device 113 (an example of a cleaning unit) that have been formed are integrally combined and held to form a cartridge. There is.
In FIG. 2, 109 is an exposure device (an example of electrostatic charge image forming means), 112 is a transfer device (an example of transfer means), 115 is a fixing device (an example of fixing means), and 300 is recording paper (of a recording medium). One example) is shown.

Next, the toner cartridge according to the present exemplary embodiment will be described.
The toner cartridge according to the present exemplary embodiment is a toner cartridge that contains the toner according to the present exemplary embodiment and is attached to and detached from the image forming apparatus. The toner cartridge contains replenishment toner to be supplied to the developing means provided in the image forming apparatus.

The image forming apparatus shown in FIG. 1 is an image forming apparatus having a configuration in which the toner cartridges 8Y, 8M, 8C, and 8K are attached and detached, and the developing devices 4Y, 4M, 4C, and 4K are the respective developing devices (colors). ) And a toner cartridge corresponding to () are connected by a toner supply pipe (not shown). Further, when the amount of toner contained in the toner cartridge is low, this toner cartridge is replaced.

Hereinafter, the present embodiment will be specifically described by way of examples, but the present embodiment is not limited to these examples. In the following description, all "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified.

[Preparation of toner particles]
(Preparation of Toner Particles (1))
-Styrene-butyl acrylate copolymer (copolymerization ratio (mass ratio) = 80:20, weight average molecular weight Mw = 130,000, glass transition temperature Tg = 59°C) 88 parts-Cyan pigment (CI Pigment Blue) 15:3) 6 parts/low molecular weight polypropylene (softening temperature: 148° C.) 6 parts The above materials were mixed by a Henschel mixer, and this was heat-kneaded by an extruder. After cooling, the kneaded product was roughly pulverized/finely pulverized, and the pulverized product was classified to obtain toner particles (1) having a volume average particle diameter of 6.5 μm.

(Preparation of Toner Particles (2))
-Preparation of polyester resin particle dispersion liquid (1)-
・Ethylene glycol [Wako Pure Chemical Industries, Ltd.]: 37 parts ・Neopentyl glycol [Wako Pure Chemical Industries, Ltd.]: 65 parts ・1,9 Nonanediol [Wako Pure Chemical Industries, Ltd.]: 32 parts terephthalic acid [manufactured by Wako Pure Chemical Industries, Ltd.]: 96 parts The above monomer was charged into a flask and the temperature was raised to 200° C. over 1 hour, and after confirming that the reaction system was stirred, 1.2 parts of dibutyltin oxide was added. Furthermore, while distilling off the produced water, the temperature was raised from that temperature to 240° C. over 6 hours, and the dehydration condensation reaction was continued at 240° C. for an additional 4 hours to obtain an acid value of 9.4 mg KOH/g and a weight average molecular weight. A polyester resin A having a glass transition temperature of 62° C. and 13,000 was obtained.

Next, the polyester resin A was transferred in a molten state to Cavitron CD1010 (manufactured by Eurotech Co., Ltd.) at a rate of 100 parts per minute. Into an aqueous medium tank prepared separately, 0.37% diluted dilute ammonia water prepared by diluting reagent ammonia water with ion-exchanged water was put, and the polyester was heated at a rate of 0.1 liters per minute while heating to 120° C. in a heat exchanger. The resin melt was transferred to the Cavitron. The cavitron is operated under the condition that the rotation speed of the rotor is 60 Hz and the pressure is 5 kg/cm ² .
A polyester resin particle dispersion liquid (1) in which resin particles having a volume average particle diameter of 160 nm, a solid content of 30%, a glass transition temperature of 62° C. and a weight average molecular weight Mw of 13,000 were obtained.

-Preparation of colorant particle dispersion-
-Cyan pigment [Pigment Blue 15:3, manufactured by Dainichiseika Kogyo KK]: 10 parts-Anionic surfactant [Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.]: 2 parts-Ion-exchanged water: 80 parts The above components were mixed and dispersed for 1 hour by a high pressure impact disperser Ultimaizer [HJP30006, manufactured by Sugino Machine Ltd.] to obtain a colorant particle dispersion having a volume average particle diameter of 180 nm and a solid content of 20%.

-Preparation of release agent particle dispersion-
・Carnauba wax [RC-160, melting temperature 84°C, manufactured by Toa Kasei Co., Ltd.]: 50 parts ・Anionic surfactant [Neogen SC, manufactured by Dai-ichi Kogyo Seiyaku]: 2 parts ・Ion-exchanged water: 200 parts The components were heated to 120° C., mixed and dispersed with Ultra Turrax T50 manufactured by IKA, and then dispersed with a pressure discharge type homogenizer to disperse release agent particles having a volume average particle diameter of 200 nm and a solid content of 20%. A liquid was obtained.

-Preparation of Toner Particles (1)-
-Polyester resin particle dispersion liquid (1): 200 parts-Colorant particle dispersion liquid: 25 parts-Release agent particle dispersion liquid: 30 parts-Polyaluminum chloride: 0.4 parts-Ion-exchanged water: 100 parts Was charged into a stainless steel flask, and was mixed and dispersed using an IKA Ultra Turrax, and then the flask was heated to 48° C. with stirring in an oil bath for heating. After holding at 48° C. for 30 minutes, 70 parts of polyester resin particle dispersion liquid (1) was added thereto.

Then, the pH of the system was adjusted to 8.0 using an aqueous solution of sodium hydroxide with a concentration of 0.5 mol/L, the stainless steel flask was sealed, and the stirring shaft was magnetically sealed to continue stirring. Heat to 90° C. and hold for 3 hours. After the reaction was completed, the temperature was lowered at a rate of 2° C./min, and after filtration and washing with ion-exchanged water, solid-liquid separation was carried out by Nutsche suction filtration. This was redispersed using 3 L of ion-exchanged water at 30° C., and stirred and washed at 300 rpm for 15 minutes. This washing operation was repeated 6 times, and when the pH of the filtrate became 7.54 and the electric conductivity became 6.5 μS/cm, the No. type suction filtration was performed to remove No. Solid-liquid separation was performed using 5A filter paper. Then, vacuum drying was continued for 12 hours to obtain toner particles (3).
The volume average particle diameter D50v of the toner particles (2) was 5.8 μm, and the average circularity was 0.967.

[Preparation of external additives]
(Preparation of silica particle dispersion liquid (1))
To a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle, and a thermometer, 300 parts of methanol and 70 parts of 10% ammonia water were added and mixed to obtain an alkali catalyst solution.
After adjusting the alkali catalyst solution to 30° C., 185 parts of tetramethoxysilane and 50 parts of 8.0% ammonia water were simultaneously added dropwise with stirring to obtain a hydrophilic silica particle dispersion liquid (solid content concentration: 12. 0% by weight) was obtained. Here, the dropping time was 30 minutes.
Then, the obtained silica particle dispersion was concentrated to a solid content concentration of 40 mass% with a rotary filter R-fine (manufactured by Kotobuki Kogyo Co., Ltd.). This concentrated product was used as a silica particle dispersion liquid (1).

(Preparation of silica particle dispersions (2) to (8))
In the preparation of the silica particle dispersion liquid (1), according to Table 1, an alkali catalyst solution (methanol amount and 10% ammonia water amount), silica particle generation conditions (tetramethoxysilane (expressed as TMOS) in the alkali catalyst solution) and 8% Silica particle dispersions (2) to (8) were prepared in the same manner as the silica particle dispersion (1) except that the total amount of ammonia water added and the dropping time) were changed.

Hereinafter, Table 1 collectively shows the details of the silica particle dispersions (1) to (8).

(Preparation of surface-treated silica particles (S1))
Using the silica particle dispersion liquid (1), the silica particles were subjected to a surface treatment with a siloxane compound in a supercritical carbon dioxide atmosphere as described below. For the surface treatment, a device equipped with a carbon dioxide cylinder, a carbon dioxide pump, an entrainer pump, an autoclave with a stirrer (capacity 500 ml), and a pressure valve was used.

First, 250 parts of the silica particle dispersion liquid (1) was put into an autoclave with a stirrer (capacity 500 ml), and the stirrer was rotated at 100 rpm. Then, liquefied carbon dioxide was injected into the autoclave, and the temperature was raised by a heater to raise the pressure by a carbon dioxide pump, and the inside of the autoclave was brought to a supercritical state of 150° C. and 15 MPa. While keeping the internal pressure of the autoclave at 15 MPa with a pressure valve, supercritical carbon dioxide was passed through the carbon dioxide pump to remove methanol and water from the silica particle dispersion liquid (1) (solvent removal step), and silica particles (untreated silica particles). ) Got.

Next, the flow of supercritical carbon dioxide was stopped when the flow rate of the supercritical carbon dioxide that had flowed (integrated amount: measured as the flow amount of carbon dioxide in the standard state) reached 900 parts.
Thereafter, with a heater maintaining a temperature of 150° C. and a carbon dioxide pump maintaining a pressure of 15 MPa, while maintaining the supercritical state of carbon dioxide in the autoclave, with respect to 100 parts of the silica particles (untreated silica particles), 20 parts of hexamethyldisilazane (HMDS: manufactured by Organic Synthetic Chemical Industry Co., Ltd.) as a hydrophobic treatment agent, and dimethyl silicone oil having a viscosity of 10,000 cSt as a siloxane compound (DSO: trade name “KF-96 (manufactured by Shin-Etsu Chemical Co., Ltd.) )”) A treating agent solution in which 0.3 part was dissolved was injected into the autoclave by an entrainer pump, and then reacted at 180° C. for 20 minutes while stirring. After that, the supercritical carbon dioxide was passed again to remove the excess processing agent solution. Then, stirring was stopped, the pressure valve was opened, the pressure in the autoclave was released to atmospheric pressure, and the temperature was lowered to room temperature (25° C.).
Thus, the solvent removal step and the surface treatment with the siloxane compound were sequentially performed to obtain surface-treated silica particles (S1).

(Production of surface-treated silica particles (S2) to (S5), (S7) to (S9), (S12) to (S17))
In the preparation of the surface-treated silica particles (S1), the silica particle dispersion liquid, the surface treatment conditions (treatment atmosphere, siloxane compound (seed, viscosity and its addition amount), hydrophobizing agent and its addition amount) were changed according to Table 2. The surface-treated silica particles (S2) to (S5), (S7) to (S9), and (S12) to (S17) were prepared in the same manner as the surface-treated silica particles (S1) except for the above.

(Preparation of surface-treated silica particles (S6))
Using the same dispersion liquid as the silica particle dispersion liquid (1) used in the preparation of the surface-treated silica particles (S1), the silica particles are subjected to a surface treatment with a siloxane compound in the atmosphere as described below. It was
An ester adapter and a cooling tube were attached to the reaction vessel used for preparing the silica particle dispersion liquid (1), the silica particle dispersion liquid (1) was heated to 60 to 70° C., and water was added when methanol was distilled off. The mixture was heated to 70 to 90° C. and methanol was distilled off to obtain an aqueous dispersion of silica particles. To 100 parts of silica particles in this aqueous dispersion, 3 parts of methyltrimethoxysilane (MTMS: manufactured by Shin-Etsu Chemical Co., Ltd.) was added at room temperature and reacted for 2 hours to treat the surface of the silica particles. After adding methyl isobutyl ketone to this surface-treated dispersion, it was heated to 80° C. to 110° C. to distill off methanol water, and 100 parts of silica particles in the obtained dispersion were mixed with hexamethyldisilazane (HMDS) at room temperature. : Organic Synthetic Chemical Industry Co., Ltd.) 80 parts and dimethyl silicone oil having a viscosity of 10,000 cSt as a siloxane compound (DSO: trade name “KF-96 (manufactured by Shin-Etsu Chemical Co., Ltd.)”) 1.0 part, and 120° C. After 3 hours of reaction, the mixture was cooled, and then dried by spray drying (spray drying) to obtain surface-treated silica particles (S6).

(Preparation of surface-treated silica particles (S10))
Surface-treated silica particles (S10) were prepared according to the surface-treated silica particles (S1) except that fumed silica OX50 (AEROSIL OX50, manufactured by Nippon Aergil Co., Ltd.) was used instead of the silica particle dispersion liquid (1). .. That is, 100 parts of OX50 was put into the same autoclave equipped with a stirrer as in the preparation of the surface-treated silica particles (S1), and the stirrer was rotated at 100 rpm. Then, liquefied carbon dioxide was injected into the autoclave, and the temperature was raised with a heater to raise the pressure with a carbon dioxide pump, and the inside of the autoclave was brought to a supercritical state of 180° C. and 15 MPa. While maintaining the internal pressure of the autoclave at 15 MPa with a pressure valve, 20 parts of hexamethyldisilazane (HMDS: manufactured by Organic Synthetic Chemical Industry Co., Ltd.) as a hydrophobizing agent, and dimethyl silicone oil having a viscosity of 10000 cSt as a siloxane compound (DSO: product name) "KF-96 (manufactured by Shin-Etsu Chemical Co., Ltd.)" 0.3 parts of a treating agent solution was injected into the autoclave by an entrainer pump, and then reacted at 180°C for 20 minutes while stirring, and then, Supercritical carbon dioxide was circulated to remove the excess treating agent solution to obtain surface-treated silica particles (S10).

(Preparation of surface-treated silica particles (S11))
Surface-treated silica particles (S11) were prepared according to the surface-treated silica particles (S1) except that fumed silica A50 (AEROSIL A50, manufactured by Nippon Aergil Co., Ltd.) was used instead of the silica particle dispersion liquid (1). .. That is, 100 parts of A50 was put into the same autoclave equipped with a stirrer as in the preparation of the surface-treated silica particles (S1), and the stirrer was rotated at 100 rpm. Then, liquefied carbon dioxide was injected into the autoclave, and the temperature was raised with a heater to raise the pressure with a carbon dioxide pump, and the inside of the autoclave was brought to a supercritical state of 180° C. and 15 MPa. While maintaining the internal pressure of the autoclave at 15 MPa with a pressure valve, 40 parts of hexamethyldisilazane (HMDS: manufactured by Organic Synthetic Chemical Industry Co., Ltd.) as a hydrophobizing agent and dimethyl silicone oil having a viscosity of 10000 cSt as a siloxane compound (DSO: product name) "KF-96 (manufactured by Shin-Etsu Chemical Co., Ltd.)") was dissolved in a treating agent solution in an autoclave by an entrainer pump, and then reacted at 180°C for 20 minutes with stirring. Supercritical carbon dioxide was circulated to remove the excess treating agent solution to obtain surface-treated silica particles (S11).

(Preparation of surface-treated silica particles (SC1))
The surface-treated silica particles (S1) were prepared in the same manner as the surface-treated silica particles (S1) except that the siloxane compound was not added.

(Preparation of surface-treated silica particles (SC2) to (SC4))
In the preparation of the surface-treated silica particles (S1), the silica particle dispersion liquid, surface treatment conditions (treatment atmosphere, siloxane compound (seed, viscosity and addition amount thereof), hydrophobizing treatment agent and addition amount thereof) were changed according to Table 3. Surface-treated silica particles (SC2) to (SC4) were produced in the same manner as the surface-treated silica particles (S1), except that the above-mentioned processes were performed.

(Preparation of surface-treated silica particles (SC5))
In preparation of the surface-treated silica particles (S6), surface-treated silica particles (SC5) were prepared in the same manner as the surface-treated silica particles (S6) except that the siloxane compound was not added.

(Preparation of surface-treated silica particles (SC6))
The silica particle dispersion liquid (8) is filtered, dried at 120° C., put in an electric furnace and fired at 400° C. for 6 hours, and then 10 parts of HMDS is sprayed to 100 parts of silica particles by spray drying, It was dried to prepare surface-treated silica particles (SC6).

(Physical properties of surface-treated silica particles)
Regarding the obtained surface-treated silica particles, the average circle equivalent diameter, the average circularity, the amount of the siloxane compound attached to the untreated silica particles (indicated as "surface attachment amount" in the table), the degree of compression aggregation, the particle compression ratio, and The particle dispersity was measured by the method described above.

Details of the surface-treated silica particles are listed in Tables 2 and 3 below. The abbreviations in Tables 2 to 3 are as follows.
・DSO: Dimethyl silicone oil ・HMDS: Hexamethyldisilazane

(Medium resistance particles)
As the medium resistance particles, inorganic oxide particles having the types, volume resistivity and average equivalent circle diameter shown in Table 3 were prepared. The number of copies shown in the “Type” column in Table 3 indicates the amount of the surface treatment agent to be treated with respect to the particles.

[Examples 1-28, Comparative Examples 1-8]
To 100 parts of the toner particles shown in Table 5, the silica particles and the medium resistance particles shown in Table 5 were added in the numbers shown in Table 5, and mixed with a Henschel mixer at 2000 rpm for 3 minutes to obtain the toner of each example.

Then, the obtained toner and carrier were put in a V blender at a ratio of toner:carrier=5:95 (mass ratio) and stirred for 20 minutes to obtain each developer.

The carrier used was prepared as follows.
・Ferrite particles (volume average particle diameter: 50 μm) 100 parts ・Toluene 14 parts ・Styrene-methyl methacrylate copolymer 2 parts (component ratio: 90/10, Mw=80,000)
Carbon black (R330: manufactured by Cabot Co.) 0.2 part First, the above components except ferrite particles are stirred for 10 minutes with a stirrer to prepare a dispersed coating liquid, and then the coating liquid and ferrite particles are mixed. It was put in a vacuum degassing type kneader, stirred at 60° C. for 30 minutes, depressurized by further heating and degassing, and dried to obtain a carrier.

[Evaluation]
The "density/fog" of the developer obtained in each example was evaluated. The results are shown in Table 5.

(Evaluation of density/fogging)
The developer obtained in each example was filled in a developing device of an image forming apparatus "Focus DouCentre-V C7785 modified machine" manufactured by Fuji Xerox. With this image forming apparatus, in an environment of a temperature of 30° C. and a humidity of 90% RH, 3000 sheets of an image having an image density of 2% were output on A4 paper, then a solid patch was output and the density was measured by X-rite. Based on this image density, density reproducibility was evaluated. Further, an image having an image density of 80% was output on 20,000 sheets of A4 size paper. During that time, after outputting 10,000 sheets, after outputting 15,000 sheets, and after outputting 20,000 sheets, the apparatus is stopped, the non-image portion on the photoconductor is transferred to the tape, and the image density of the tape is measured by Xrite. It was measured. From this image density, the fogging on the photoconductor was evaluated.
On the other hand, the non-image part of the paper output immediately before the stop of each device was visually observed, and the fog on the paper was evaluated according to the following criteria.

The evaluation criteria of the density reproducibility are as follows.
◯: Concentration 1.45 or more ×: Less than 1.40

The evaluation criteria for fogging on the photoconductor and on the paper are as follows.
G7: No fog can be confirmed on the photoconductor or the paper at the end of 20,000 sheets.
G6: Fogging cannot be confirmed on the paper at the end of 20,000 sheets, but it can be confirmed on the photoconductor.
G5: At the end of 15,000 sheets, fog cannot be confirmed on the photoconductor or the paper.
G4: Fogging cannot be confirmed on the sheet at the end of 15,000 sheets, but it can be confirmed on the photoconductor.
G3: Fogging cannot be confirmed on the photoconductor or the paper at the end of 10,000 sheets.
G2: Fogging cannot be confirmed on the sheet at the end of 10,000 sheets, but it can be confirmed on the photoconductor.
G1: Fogging can be confirmed on the paper at the end of 10,000 sheets.
The allowable range was up to G2. Further, when fog was confirmed on the paper at the end of 10,000 sheets, no further evaluation was made.

From the above results, it can be seen that the occurrence of fogging is suppressed in this example as compared with the comparative example. In addition, it can be seen that in the present embodiment, the charge retention property of the toner is high. However, at the time of output, it was confirmed that in Examples 10 and 11, the stain inside the machine was worse than in the other Examples.
In particular, Examples 1 to 5 and 14 in which silica particles having a compression coagulation degree of 70% to 95% and a particle compression ratio of 0.28 to 0.36 are applied as external additives are In comparison, it can be seen that the occurrence of fogging on the photoconductor and the paper is suppressed.

1Y, 1M, 1C, 1K photoconductors (an example of an image carrier)
2Y, 2M, 2C, 2K charging roll (an example of charging means)
3 Exposure device (an example of electrostatic charge image forming means)
3Y, 3M, 3C, 3K Laser beam 4Y, 4M, 4C, 4K Developing device (an example of developing means)
5Y, 5M, 5C, 5K Primary transfer roll (an example of primary transfer means)
6Y, 6M, 6C, 6K Photoconductor cleaning device (an example of cleaning means)
8Y, 8M, 8C, 8K Toner cartridges 10Y, 10M, 10C, 10K Image forming unit 20 Intermediate transfer belt (an example of an intermediate transfer member)
22 drive roll 24 support roll 26 secondary transfer roll (an example of secondary transfer means)
30 Intermediate Transfer Body Cleaning Device 107 Photoconductor (an example of image carrier)
108 charging roll (an example of charging means)
109 exposure device (an example of electrostatic charge image forming means)
111 developing device (an example of developing means)
112 transfer device (an example of transfer means)
113 photoconductor cleaning device (an example of cleaning means)
115 Fixing device (an example of fixing means)
116 Mounting Rail 118 Opening 117 for Exposure 117 Housing 200 Process Cartridge 300 Recording Paper (Example of Recording Medium)
P recording paper (an example of recording medium)

Claims (10)

Toner particles,
Inorganic oxide particles having a volume resistivity of 1.0×10 ⁸ Ωcm or more and 1.0×10 ¹⁵ Ωcm or less, and an average equivalent circle diameter larger than that of the inorganic oxide particles, and a compression cohesion degree of 60% or more and 95% or more. An external additive containing silica particles having a particle compression ratio of 0.20 or more and 0.40 or less,
Have a,
A toner for developing an electrostatic charge image , wherein the silica particles are silica particles to which a siloxane compound having a viscosity of more than 1000 cSt and not more than 50,000 cSt is attached, and the amount of the siloxane compound attached to the surface is 0.01% by mass or more and 5% by mass or less . The electrostatic charge image developing toner according to claim 1, wherein the inorganic oxide particles are titanium oxide particles. The toner for developing an electrostatic charge image according to claim 1 or 2, wherein an average equivalent circle diameter of the silica particles is 40 nm or more and 200 nm or less. The electrostatic charge image developing toner according to claim 1, wherein the silica particles have a particle dispersity of 90% or more and 100% or less. The toner for developing an electrostatic charge image according to claim 1 , wherein the siloxane compound is silicone oil. Electrostatic image developer comprising a toner according, and a carrier in any one of claims 1 to 5. A toner for developing an electrostatic charge image according to any one of claims 1 to 5 is contained,
A toner cartridge that is attached to and detached from the image forming apparatus. A developing means is provided, which stores the electrostatic charge image developer according to claim 6, and develops the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer.
A process cartridge that is attached to and detached from an image forming apparatus. An image carrier,
Charging means for charging the surface of the image carrier,
Electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier,
A developing unit that contains the electrostatic charge image developer according to claim 6, and develops the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer.
Transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium,
A fixing unit that fixes the toner image transferred to the surface of the recording medium;
An image forming apparatus including. A charging step of charging the surface of the image carrier,
An electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged image carrier;
A developing step of developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer according to claim 6 .
A transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium,
A fixing step of fixing the toner image transferred onto the surface of the recording medium,
An image forming method having: