JP7693307B2 - Method for producing external additive particles - Google Patents

Description

The present invention relates to external additive particles, a method for producing the same, and a toner.

In recent years, there has been a demand for faster speeds and higher image quality in image forming devices that use electrophotography. In response to these demands, toners that have the stress resistance to withstand long periods of friction in the developing device and have excellent fluidity and developability to obtain high image quality even in high-speed printing are being studied.

Patent Document 1 discloses a method for producing organic-inorganic composite particles having an organic polymer skeleton and a polysiloxane skeleton as a toner additive. It discloses that the inclusion of the toner additive in the toner improves the transfer properties of the toner.

Japanese Patent Application Publication No. 9-197706

As a result of the inventors' investigation of a toner to which particles produced by the method described in Patent Document 1 have been externally added, they have recognized that further improvement in the fluidity of the toner is required.

One aspect of the present invention is to provide additive particles and a method for producing the same that provide a toner that has excellent fluidity and is less likely to change in fluidity even when continuous image output is performed.

Another aspect of the present invention is to provide a toner that has excellent fluidity and is less likely to change in fluidity even when continuous image output is performed.

According to one aspect of the present invention, there is provided a method for producing an external additive particle containing a polymer, comprising the steps of:
The manufacturing method comprises:
a radical polymerization step of carrying out a radical polymerization reaction of a monomer raw material containing a compound represented by the following formula (3) using a radical polymerization initiator having a carboxy group under a condition of 6.0≦pH≦8.0; and a condensation step of carrying out a hydrolysis reaction and a polycondensation reaction of the hydrolyzable group X in the following formula (3) after the radical polymerization step to obtain particles containing a polymer.
A method for producing an external additive particle is provided.

R ⁶ _m SiX _4-m ... (3)
(In formula (3), X is a hydrolyzable group, m is an integer of 1 to 3, each R ⁶ is independently an organic group having 1 to 20 carbon atoms, and at least one of R ⁶ is a radical polymerizable group.)
According to another aspect of the present invention, there is provided a method for producing an external additive particle containing a polymer, comprising the steps of:
The manufacturing method comprises:
a radical polymerization step of carrying out a radical polymerization reaction of a monomer raw material containing at least one of a radical polymerizable carboxylic acid and a radical polymerizable carboxylate, and a compound represented by the following formula (3), under a condition of 6.0≦pH≦8.0;
a condensation step in which, after the radical polymerization step, a hydrolysis reaction and a polycondensation reaction of the hydrolyzable group X in the following formula (3) are carried out to obtain particles containing a polymer;
A method for producing an external additive particle is provided.

R ⁶ _m SiX _4-m ... (3)
(In formula (3), X is a hydrolyzable group, m is an integer of 1 to 3, each R ⁶ is independently an organic group having 1 to 20 carbon atoms, and at least one of R ⁶ is a radical polymerizable group.)

According to one aspect of the present invention, it is possible to obtain external additive particles that provide a toner that has excellent fluidity and can maintain excellent fluidity even when continuous image output is performed. According to another aspect of the present invention, it is possible to obtain a toner that can maintain excellent fluidity even when continuous image output is performed.

When a numerical range is expressed as "xx or more and xx or less" or "xx to xx", it means that the numerical range includes the upper and lower limits, which are the endpoints, unless otherwise specified. When a numerical range is stated in stages, the upper and lower limits of each numerical range can be combined in any way.

<Background to the invention>
The present inventors consider the reason why further improvement in the fluidity of the toner to which the particles produced by the production method disclosed in Patent Document 1 are externally added is necessary as follows.

The inventors have discovered that toners to which particles produced by the production method of Patent Document 1 are added may not have sufficient fluidity. In this production method, the hydrolysis and polycondensation of hydrolyzable groups bonded to silicon are carried out, followed by polymerization of vinyl groups, which is thought to result in the formation of particles whose main skeleton is a polysiloxane skeleton. Since the main skeleton of the particles is an inorganic skeleton, the adhesion to toner particles may not be sufficient, and the particles tend to separate from the surface of the toner particles, which the inventors believe is one of the causes of the reduced fluidity of the toner.

The inventors therefore investigated particles whose main skeleton is a vinyl polymer molecular chain, which are obtained by a manufacturing method in which hydrolysis and polycondensation are carried out after vinyl polymerization. The particles were less likely to separate from the toner particles, and a certain degree of improvement in toner fluidity was observed. However, there was room for further improvement in the change in toner fluidity over time when continuous image output is performed, i.e., the ability to maintain toner fluidity.

As a result of intensive research conducted by the inventors based on the above considerations, it was found that a toner to which external additive particles are added, which is manufactured by a manufacturing method having the above-mentioned constituent elements, can have excellent fluidity and is easy to obtain a toner that can maintain excellent fluidity. The estimated mechanism of the effect and each of the constituent elements will be explained in detail below.

<Presumed mechanism by which the effects of the present invention are manifested>
By carrying out radical polymerization using a monomer raw material containing the compound represented by formula (3), followed by hydrolysis and polycondensation, a polymer having a molecular chain of a vinyl polymer as the main skeleton is obtained, and the polymer contains a structure in which the molecular chain is bonded via a siloxane bond.

When the main skeleton of the polymer is a vinyl polymer molecular chain, the adhesive force to the toner particles tends to be strong. In addition, when the vinyl polymer molecular chain has a structure bonded via siloxane bonds, the mechanical strength of the external additive particles tends to be strong, and it is believed that plastic deformation is less likely to occur.

As a result, it is believed that the external additive particles containing the above polymer are less likely to separate from the toner particles and are less likely to undergo plastic deformation, making it easier to obtain a toner with excellent fluidity.

In addition, in the method for producing external additive particles according to the present invention, it is believed that carboxy groups are contained in the surface regions of the produced external additive particles by at least one of the following (i) and (ii).
(i) In the radical polymerization step, a radical polymerization initiator having a carboxy group is used.
(ii) At least one of a radically polymerizable carboxylic acid and a radically polymerizable carboxylate is used as a monomer raw material.

The present inventors speculate that by including carboxyl groups in the surface region of the external additive particles, they are more likely to interact strongly with the areas on the toner particle surface that are capable of electrostatic interaction, making it more difficult for the external additive particles to separate from the surface of the toner particles. As a result, it becomes easier to obtain a toner that can maintain excellent fluidity even when continuous image output is performed.

<Method of manufacturing external additive particles>
The method for producing external additive particles according to the present invention involves carrying out a radical polymerization reaction using a compound represented by the following formula (3), which contains both a radically polymerizable group and a hydrolyzable group that forms a siloxane bond by hydrolysis and polycondensation, and then carrying out a hydrolysis reaction and a polycondensation reaction.

R ⁶ _m SiX _4-m ... (3)
(In formula (3), X is a hydrolyzable group, m is an integer of 1 to 3, each R ⁶ is independently an organic group having 1 to 20 carbon atoms, and at least one of R ⁶ is a radical polymerizable group.)
Before carrying out hydrolysis and polycondensation, a radical polymerization reaction is carried out under neutral conditions to obtain a polymer having a vinyl polymer molecular chain as the main skeleton. After the vinyl polymer molecular chain is formed by the radical polymerization reaction, hydrolysis and polycondensation are carried out to obtain a polymer having a structure in which the vinyl polymer molecular chain is bonded via a siloxane bond. It is also considered that carrying out the hydrolysis reaction and polycondensation reaction later makes it easier for the carboxyl group, which is likely to interact with water molecules, to be contained in the surface region of the external additive particles.

Examples of the hydrolyzable group include, for example, a functional group that is converted to a hydroxy group after hydrolysis of the compound, or a hydroxy group.

The radical polymerizable group means a substituent having a radically reactive double bond in the structure. R ⁶ in the above formula (3) is more preferably an organic group having 1 to 15 carbon ^atoms , and even more preferably an organic group having 1 to 10 carbon atoms.

Here, it is preferable to use a radical polymerization initiator having a carboxy group as the radical polymerization initiator, since the carboxy group can be contained in the surface region of the external additive particles. The radical polymerization initiator is preferably an azo compound.

A suitable example of a radical polymerization initiator having a carboxy group is a compound represented by the following formula (2). An example of a compound used as a radical polymerization initiator represented by the following formula (2) is 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine].

(In formula (2), R ⁵ is an alkylene group having 1 to 12 carbon atoms.)
In addition to using the above-mentioned radical polymerization initiator, a method for incorporating a carboxy group in the surface region of the external additive particles may be to incorporate at least one of a radically polymerizable carboxylic acid and a radically polymerizable carboxylate into the monomer raw material.

Examples of radically polymerizable carboxylates include the following: sodium 4-vinylbenzoate, potassium 4-vinylbenzoate, lithium 4-vinylbenzoate, magnesium 4-vinylbenzoate, calcium 4-vinylbenzoate, ammonium 4-vinylbenzoate, sodium (meth)acrylate, potassium (meth)acrylate, lithium (meth)acrylate, magnesium (meth)acrylate, calcium (meth)acrylate, ammonium (meth)acrylate, etc. These radically polymerizable carboxylates may be used alone or in combination of two or more.

Radically polymerizable carboxylic acids include 4-vinylbenzoic acid and (meth)acrylic acid. These may be used alone or in combination of two or more.

From the viewpoint of maintaining the flowability of the toner, the total mass of the radically polymerizable carboxylic acid and the radically polymerizable carboxylate is preferably 0.4 to 7.0% by mass, more preferably 0.6 to 5.0% by mass, and even more preferably 0.6 to 2.0% by mass, based on the total mass of the monomer raw materials.

<Radical Polymerization Reaction>
The radical polymerization reaction method is preferably an emulsion polymerization method. The emulsion polymerization method is a polymerization method in which a medium such as water, a monomer that is poorly soluble in the medium, and an emulsifier (surfactant) or an ionic comonomer are mixed, and a polymerization initiator that is soluble in the medium is added thereto. The emulsion polymerization method is preferably a soap-free emulsion polymerization method in which polymerization is performed without using a surfactant. The present inventors believe that this is because the soap-free emulsion polymerization method does not leave a surfactant on the surface of the external additive particles, making it easier to control the affinity between the toner particles and the external additive particles.

The hydrolyzable group in the above formula (3) may be, for example, a monovalent group selected from a hydroxy group, a fluoro group, a chloro group, a bromo group, an iodo group, an alkoxy group, and an acyloxy group. Preferred are a methoxy group, an ethoxy group, a propoxy group, and an acetoxy group, and more preferred are a methoxy group and an ethoxy group. These hydrolyzable groups are easily hydrolyzed by water and are likely to undergo a subsequent polycondensation reaction, so it is believed that the polysiloxane skeleton is easily contained in the external additive particles.

From the viewpoint of the fluidity and fluidity maintenance of the toner, the compound represented by the above formula (3) is preferably 50 to 80% by mass, more preferably 60 to 75% by mass, based on the total mass of the monomer raw materials.

Specific examples of compounds represented by the above formula (3), i.e., monomers containing both a radical polymerizable group and a hydrolyzable group, include the following:

Organotrialkoxysilane compounds such as γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropyltriacetoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, 1-hexenyltrimethoxysilane, and 1-octenyltrimethoxysilane, organotriacetoxysilane, bis(γ-acryloxypropyl)dimethoxysilane, bis(γ-methacryloxypropyl)dimethoxysilane, γ-methacryloxypropylethyldimethoxysilane, γ-methacryloxypropylethyldiethoxysilane, and γ-acryloxypropyl Diorganodialkoxysilane compounds such as pylethyldimethoxysilane and gamma-acryloxypropylethyldiethoxysilane; tris(gamma-acryloxypropyl)methoxysilane, tris(gamma-acryloxypropyl)ethoxysilane, tris(gamma-methacryloxypropyl)methoxysilane, tris(gamma-methacryloxypropyl)ethoxysilane, bis(gamma-acryloxypropyl)vinylmethoxysilane, bis(gamma-methacryloxypropyl)vinylmethoxysilane, gamma-acryloxypropyldiethylmethoxysilane, gamma-acryloxypropyldiethylethoxysilane, gamma-methacryloxypropyldiethylmethoxysilane, and triorganoalkoxysilane compounds such as gamma-acryloxypropyldiethylethoxysilane.

Among the above monomers, more preferred are γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropyltriacetoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltriacetoxysilane.

The compound represented by the above formula (3) is preferably a compound represented by the following formula (1):

(In formula (1), R ¹ is an alkylene group having 1 to 10 carbon atoms, R ² , R ³ , and R ⁴ are each independently any of hydrogen, a methyl group, and an ethyl group, and R′ is hydrogen or a methyl group.)
<Radical Polymerization Initiator>
Other than the above-mentioned radical polymerization initiator having a carboxy group, examples of the radical polymerization initiator that can be used include at least one compound selected from persulfates, azo compounds, and peroxides.

Examples of persulfates include potassium persulfate, sodium persulfate, and ammonium persulfate. These may be used alone or in combination of two or more.

The amount of radical polymerization initiator in the radical polymerization step is not particularly limited, but is preferably 0.1 to 10.0% by mass, and more preferably 0.3 to 5.0% by mass, based on the total mass of the raw material monomers. By using a radical polymerization initiator within the above range, the radical polymerization can be sufficiently progressed and the amount of heat generated in the reaction system is less likely to become excessive, which is preferable.

<Radical polymerization reaction conditions>
The temperature during radical polymerization can be appropriately selected depending on the type and amount of the radical polymerization initiator used, and is preferably in the range of 30 to 100°C, more preferably in the range of 50 to 80°C.

The radical polymerization process is a process in which radical polymerization is performed under the condition of 6.0≦pH≦8.0. More preferably, 6.5≦pH≦7.5. When the pH of the reaction system is within the above range, it is considered that hydrolysis of the hydrolyzable group and polycondensation reaction are unlikely to occur during the progress of the radical polymerization reaction. By performing hydrolysis and polycondensation reaction after radical polymerization, it is considered that the ratio of polysiloxane skeletons in the external additive particles is easily controlled, and carboxyl groups having higher polarity are easily contained in the surface region of the external additive particles. Therefore, it is preferable that the radical polymerization reaction is performed in a buffer solution. There are no particular limitations on the buffer solution, and it is sufficient if it is a buffer solution that shows a pH near neutral, such as a phosphate buffer solution or an MES buffer solution.

In addition, when performing radical polymerization, not only monomers containing both radically polymerizable groups and hydrolyzable groups but also other monomers having radically polymerizable groups may be used.

Examples of other monomers include unsaturated carboxylic acids such as acrylic acid and methacrylic acid, unsaturated carboxylic acid esters such as acrylic acid esters, methacrylic acid esters, crotonates, itaconic acid esters, maleic acid esters, and fumaric acid esters, acrylamides, methacrylamides, aromatic vinyl compounds such as styrene, α-styrene, and divinylbenzene, vinyl esters such as vinyl acetate, and vinyl halide compounds such as vinyl chloride. Monomers containing two or more radically polymerizable groups, such as divinylbenzene, trimethylolpropane trimethacrylate, and ethylene glycol dimethacrylate, may also be used. These may be used alone or in combination of two or more.

<Hydrolysis reaction and polycondensation reaction>
The above-mentioned hydrolysis reaction and polycondensation reaction method is not particularly limited, but it is preferable to add a catalyst such as acid or base to the emulsion containing the particles obtained by radical polymerization, and then carry out hydrolysis and polycondensation as it is to obtain particles containing a polymer.That is, it is preferable that the above-mentioned condensation step is a step of carrying out the hydrolysis reaction and polycondensation reaction of the hydrolyzable group X in formula (3) after the above-mentioned radical polymerization step to obtain particles of the condensate.In addition, the particles obtained by radical polymerization may be isolated from the emulsion by performing operations such as filtration, centrifugation, and vacuum concentration, and then a catalyst may be added to carry out hydrolysis and polycondensation.

When carrying out hydrolysis or polycondensation reactions after particle formation by radical polymerization reactions, catalysts such as acetic acid, hydrochloric acid, ammonia, urea, alkanolamines, tetraalkylammonium hydroxides, alkali metal hydroxides, and alkaline earth metal hydroxides may be used.

More preferred catalysts from the viewpoint of further promoting polycondensation include organic titanium compounds such as titanium tetraisopropoxide, titanium tetrabutoxide, and diisopropoxy-bis(acetylacetonate) titanate; organic aluminum compounds such as aluminum triisopropoxide, aluminum trisec-butoxide, aluminum trisacetylacetonate, and aluminum isopropoxide-bisacetylacetonate; organic zirconium compounds such as zirconium tetrabutoxide and tetrakis(acetylacetonate) zirconium; organic tin compounds such as dibutyltin diacetate, dibutyltin diethylhexanoate, and dibutyltin dimaleate; and acidic phosphate esters. These may be used alone or in combination of two or more. Among them, at least one selected from the group consisting of organic tin compounds and acidic phosphate esters is preferred.

The solvent used in the production of the external additive particles may contain an organic solvent other than water or a catalyst. Specific examples of organic solvents include alcohols such as methanol, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, and 1,4-butanediol, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, (cyclo)paraffins such as isooctane and cyclohexane, ethers such as dioxane and diethyl ether, and aromatic hydrocarbons such as benzene and toluene. Two or more of these may be mixed and used.

The hydrolysis reaction and polycondensation reaction can be carried out, for example, by adding an appropriate catalyst to the emulsion produced by the radical polymerization reaction and stirring at 0 to 100°C, preferably 0 to 70°C, for 3 to 24 hours.

<Surface treatment with amine compound>
From the viewpoint of density stability of the output image, it is preferable to perform surface treatment of the particles containing the above polymer with an amine compound. It has been found that by performing the surface treatment, the image density is less likely to vary when the image is output in a low humidity environment. Although the reason for this is unclear, the present inventors speculate as follows.

In the process of toner acquiring charge through frictional charging, negative charges tend to accumulate in the toner due to the influence of negatively charged functional groups, such as carboxyl groups, present on the surfaces of external additive particles and toner particles. By performing surface treatment with an amine compound, the amine moiety derived from the amine compound is more likely to receive a positive charge by receiving hydrogen ions, and it is believed that excessive accumulation of negative charges in the toner as a whole is less likely to occur. As a result, it is believed that even in low-humidity environments where toner is more likely to be overcharged, it is more likely that a toner with less variation in image density can be obtained.

The amine compound used in the surface treatment may or may not be chemically bonded to the particles containing the polymer.

The above amine compounds include aminosilanes such as 3-aminopropyltrimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, and 3-(2-aminoethylamino)propyldimethoxydimethylsilane, amino group-containing polymers such as polyallylamine, and polyethyleneimine.

The content of the amine moiety contained in the surface region of the external additive particles by the surface treatment using an amine compound can be confirmed by performing X-ray photoelectron spectroscopy on the surface of the external additive particles. Furthermore, when X-ray photoelectron spectroscopy is performed on the surface of the external additive particles that have been subjected to the surface treatment, it is preferable that the ratio of the number of nitrogen atoms to the total number of carbon atoms, nitrogen atoms, oxygen atoms, and silicon atoms is 1.0% or more and 2.5% or less. It has been found that when the ratio of the number of nitrogen atoms is within the above range, the image density is less likely to vary in a low-humidity environment.

From the viewpoint of the chargeability of the toner, it is preferable to treat the surface of the external additive particles using another surface treatment agent in order to treat the hydroxyl groups remaining on the surface of the external additive particles and to adjust the amount of negative charge. Examples of such other surface treatment agents include silicon compounds such as organoalkoxysilane and hexamethyldisilazane, titanium compounds such as tetrabutyl titanate, or hydrolyzates and condensates of these.

The surface treatment using the other surface treatment agent may be carried out simultaneously with the surface treatment using the above-mentioned amine compound, or may be carried out after the surface treatment using the above-mentioned amine compound.

The method of performing the above surface treatment is not particularly limited as long as it can cover the surface of the particles with the above surface treatment agent. For example, the surface treatment can be performed by putting the particles into a suitable container, then adding the surface treatment agent, and mixing and contacting the particles at room temperature (25°C ± 5°C) to about 100°C while stirring for 3 to 24 hours. In this case, the surface treatment can be more uniformly performed by dissolving the surface treatment agent in a solvent such as methanol and gradually dropping the solution while mixing and contacting the particles. The amount of the surface treatment agent present on the surface of the particles can be adjusted by appropriately selecting the type of surface treatment agent, the time of surface treatment, and the particle size of the external additive particles. The treated object thus surface-treated can be washed with, for example, alcohol, as necessary, to obtain external additive particles from which unnecessary substances have been removed.

<Post-processing>
The particles obtained by carrying out the radical polymerization, hydrolysis/polycondensation, and surface treatment as described above are isolated from the slurry by a method such as filtration, centrifugation, reduced pressure concentration, spray drying, flash vacuum drying, or the like, and then dried at 30 to 100° C., more preferably at 30 to 80° C., and even more preferably at 50 to 70° C. By carrying out the drying, external additive particles having appropriate charging properties and appropriate mechanical strength are easily obtained.

<Physical properties of external additive particles>
<Proportion of the number of silicon atoms to the total number of carbon atoms, oxygen atoms, and silicon atoms>
The ratio of the number of silicon atoms to the total number of carbon atoms, oxygen atoms, and silicon atoms in the external additive particles is preferably 4.0% or more and 25.0% or less.

The inventors believe that the total number of carbon atoms, oxygen atoms, and silicon atoms is an index of how much polymer is present that has a structure in which the molecular chains of the above vinyl polymer are bonded via siloxane bonds. The inventors also believe that the ratio of the number of silicon atoms to the total number of the above atoms is an index of how much siloxane bonds are present.

If the above ratio is 4.0% or more, it is believed that siloxane bonds are sufficiently formed in the polymer, and plastic deformation of the external additive particles is unlikely to occur, so that a toner with excellent fluidity is easily obtained. Also, if the above ratio is 25.0% or less, it is believed that the polymer contains a sufficient amount of vinyl polymer molecular chains as the main skeleton, and the external additive particles are unlikely to separate from the toner particles, so that a toner with excellent fluidity maintenance is easily obtained. Therefore, it is 25.0% or less, preferably 20.0% or less, more preferably 15.0% or less, and even more preferably 10.0% or less. In other words, it is even more preferable that the above ratio is 4.0% or more and 10.0% or less.

In addition, since a toner having excellent fluidity retention is easily obtained, the ratio of the number of carbon atoms in the external additive particles to the number of silicon atoms in the external additive particles is preferably 6.5 or more. More preferably, it is 7.5 or more, and even more preferably, it is 13.5 or more. There is no particular upper limit, but from the viewpoint of toner fluidity, it is preferably 20.0 or less. More preferably, it is 17.0 or less.

The ratio of the above-mentioned atomic numbers can be controlled by adjusting the type and amount of monomer units containing silicon atoms and the type and amount of monomer units not containing silicon atoms when producing the polymer that constitutes the external additive particles.

<D50 of external additive particles>
In order to provide the external additive particles with an appropriate volume average particle size, when the 50% particle size based on the volume distribution of the external additive particles is defined as D50, the D50 is preferably 50 nm or more and 200 nm or less.

<Toner>
The external additive particles according to the present invention are preferably contained on the surface of the toner particles. That is, one aspect of the present invention is a toner containing toner particles and an external additive on the surface of the toner particles, and the external additive is preferably an external additive particle produced by the production method according to the present invention.

The toner particles preferably contain a binder resin. Examples of the binder resin include polyester resins, vinyl resins, epoxy resins, and polyurethane resins.

From the viewpoint of storage stability, it is preferable that the binder resin has a glass transition point (Tg) of 45 to 70°C.

<Method of Manufacturing Toner Particles>
The method for producing the toner particles according to the present invention is not particularly limited, and for example, a pulverization method or a polymerization method such as an emulsion polymerization method, a suspension polymerization method, or a solution suspension method can be used.

The pulverization method will now be described. In the pulverization method, first, the binder resin, colorant, wax, charge control agent, etc. that make up the toner particles are thoroughly mixed using a mixer such as a Henschel mixer or a ball mill. Next, the resulting mixture is melted and kneaded using a thermal kneader such as a twin-screw kneading extruder, a heating roll, a kneader, or an extruder, and then cooled and solidified, after which it is pulverized and classified. This results in the toner particles according to the present invention.

Examples of kneading machines include the following: KRC kneader (manufactured by Kurimoto Iron Works); Buss-Co kneader (manufactured by Buss); TEM type extruder (manufactured by Toshiba Machine); TEX twin-screw kneader (manufactured by Japan Steel Works); PCM kneader (manufactured by Ikegai Iron Works); three-roll mill, mixing roll mill, kneader (manufactured by Inoue Seisakusho); Kneadex (manufactured by Mitsui Mining Co., Ltd.); MS-type pressure kneader, kneader ruder (manufactured by Nippon Spindle); Banbury mixer (manufactured by Kobe Steel, Ltd.).

Examples of pulverizers include the following: Counter Jet Mill, Micron Jet, Innomizer (manufactured by Hosokawa Micron Corporation); IDS type mill, PJM jet pulverizer (manufactured by Nippon Pneumatic Mfg. Co., Ltd.); Cross Jet Mill (manufactured by Kurimoto Iron Works); Urmax (manufactured by Nisso Engineering Co., Ltd.); SK Jet-O-Mill (manufactured by Seishin Enterprise Co., Ltd.); Kryptron (manufactured by Kawasaki Heavy Industries, Ltd.); Turbo Mill (manufactured by Turbo Industrial Co., Ltd.); Super Rotor (manufactured by Nisshin Engineering Co., Ltd.).

Classifiers include the following: Classeal, Micron Classifier, and Spedic Classifier (manufactured by Seishin Enterprises); Turbo Classifier (manufactured by Nisshin Engineering); Micron Separator, Turboplex (ATP), and TSP Separator (manufactured by Hosokawa Micron); Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.), Dispersion Separator (manufactured by Nippon Pneumatic Industry Co., Ltd.); and YM Microcut (manufactured by Yaskawa Shoji Co., Ltd.).

The suspension polymerization method is described below. In the suspension polymerization method, first, a polymerizable monomer capable of producing a binder resin and various additives as necessary are mixed, and the materials are dissolved or dispersed using a disperser to prepare a polymerizable monomer composition. Examples of the various additives include colorants, waxes, charge control agents, polymerization initiators, and chain transfer agents. Examples of the disperser include a homogenizer, a ball mill, a colloid mill, and an ultrasonic disperser. Next, the polymerizable monomer composition is put into an aqueous medium containing poorly water-soluble inorganic fine particles, and droplets of the polymerizable monomer composition are prepared using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser (granulation process). After that, the polymerizable monomer in the droplets is polymerized to obtain toner particles (polymerization process). The polymerization initiator may be mixed when preparing the polymerizable monomer composition, or may be mixed into the polymerizable monomer composition immediately before forming droplets in the aqueous medium. Also, during or after the granulation of the droplets, i.e., immediately before starting the polymerization reaction, it can be added in a dissolved state in a polymerizable monomer or other solvent, as necessary. After the polymerizable monomer is polymerized to obtain a binder resin, a solvent removal process can be performed as necessary to obtain a dispersion of toner particles.

<Method of Adding Additive Particles to Toner Particles>
The toner according to the present invention can be obtained by mixing toner particles and external additive particles with a mixer such as a Henschel mixer.

Examples of mixers include the following: Henschel Mixer (manufactured by Mitsui Mining Co., Ltd.); Super Mixer (manufactured by Kawata Co., Ltd.); Ribocone (manufactured by Okawara Manufacturing Co., Ltd.); Nauta Mixer, Turbulizer, Cyclomix (manufactured by Hosokawa Micron Co., Ltd.); Spiral Pin Mixer (manufactured by Pacific Machinery Co., Ltd.); Lödige Mixer (manufactured by Matsubo Co., Ltd.).

In addition, the toner particles preferably contain the above-mentioned external additive particles on their surfaces, as well as other external additives. Examples of other external additives include the following:

Fluorine-based resin powders such as vinylidene fluoride fine powder and polytetrafluoroethylene fine powder; fine silica powder such as wet-process silica and dry-process silica, fine titanium oxide powder, fine alumina powder, and treated silica obtained by surface-treating these with silane compounds, titanium coupling agents, and silicone oil; oxides such as zinc oxide and tin oxide; double oxides such as strontium titanate, barium titanate, calcium titanate, strontium zirconate, and calcium zirconate; carbonate compounds such as calcium carbonate and magnesium carbonate, etc.

<Various Additives for Toner>
If necessary, the toner may contain one or more additives selected from colorants, waxes, magnetic materials, charge control agents, etc. Various additives used in the toner will be specifically described.

<Magnetic material>
The toner may contain magnetic particles and be used as a magnetic toner. In this case, the magnetic particles may also serve as a colorant.

The magnetic particles contained in magnetic toner include the following:

Iron oxides such as magnetite, hematite, and ferrite, metals such as iron, cobalt, and nickel, or alloys and mixtures of these metals with metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, bismuth, calcium, manganese, titanium, tungsten, and vanadium.

The average particle size of the magnetic particles is preferably 2 μm or less, and more preferably 0.05 μm or more and 0.5 μm or less. The content of the magnetic particles is preferably 20 parts by weight or more and 200 parts by weight or less per 100 parts by weight of the binder resin, and more preferably 40 parts by weight or more and 150 parts by weight or less per 100 parts by weight of the binder resin.

<Coloring Agent>
Examples of colorants include the following:

Black colorants include, for example, carbon black, grafted carbon, and the yellow/magenta/cyan colorants shown below, which are used to tone the color black.

Yellow colorants include compounds such as condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds.

Magenta colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, perylene compounds, etc. Cyan colorants include copper phthalocyanine compounds and their derivatives, anthraquinone compounds, basic dye lake compounds, etc.

The colorants can be used alone or in a mixture or in the form of a solid solution. The colorants are selected based on their hue angle, saturation, brightness, weather resistance, transparency for overhead projectors, and dispersibility in the toner.

The colorant content is preferably 1 part by weight or more and 20 parts by weight or less per 100 parts by weight of the binder resin.

<Wax>
Examples of waxes include the following:

Low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymers, polyolefin wax, microcrystalline wax, paraffin wax, aliphatic hydrocarbon waxes such as Fischer-Tropsch wax, oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, block copolymers of aliphatic hydrocarbon waxes, and oxides thereof.

Ester waxes whose main component is fatty acid esters, such as carnauba wax; partially or completely deoxidized fatty acid esters, such as deoxidized carnauba wax.

<Charge Control Agent>
The charge control agent is not particularly limited, but is preferably an organic metal complex or a chelate compound, such as a monoazo metal complex, an acetylacetone metal complex, or a metal complex or metal salt of an aromatic hydroxycarboxylic acid or an aromatic dicarboxylic acid.

Specific examples that can be used include Spilon Black TRH, T-77, and T-95 (Hodogaya Chemical Co., Ltd.), and BONTRON (registered trademark) S-34, S-44, S-54, E-84, E-88, and E-89 (Orient Chemical Co., Ltd.). Charge control resins can also be used in combination with the charge control agents described above.

<Developer>
The toner can be used as a one-component developer, but in order to further improve dot reproducibility and provide stable images over a long period of time, it may be mixed with a magnetic carrier and used as a two-component developer.

As the magnetic carrier, for example, metals such as iron with an oxidized surface, iron with a non-oxidized surface, nickel, cobalt, manganese, chromium, rare earth elements, and alloys or oxides thereof are preferably used.

It is also preferable that the surface of the magnetic carrier contains or is coated with a styrene-based resin, an acrylic-based resin, a silicone-based resin, a fluorine-based resin, or a polyester.

<Various measurement methods, etc.>
Various measurement methods etc. are described below.

<Method of measuring the ratio of the number of silicon atoms to the total number of carbon atoms, oxygen atoms, and silicon atoms present in external additive particles, and the abundance ratio of carbon atoms and silicon atoms>
Carbon atoms and oxygen atoms The concentrations (atomic %) of carbon atoms and oxygen atoms present in the external additive particles are calculated using elemental analysis by combustion. The device for elemental analysis is shown below.
Device used: PerkinElmer 2400II fully automatic elemental analyzer, silicon atoms The concentration (atomic %) of silicon atoms present in the external additive particles is measured using elemental analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) using alkali fusion. The ICP-AES device is shown below.
Equipment used: Shimadzu ICPS-8100
The obtained composition ratio is converted to mol%, and the converted value is used to calculate the ratio of the number of silicon atoms to the total number of carbon atoms, oxygen atoms, and silicon atoms in the external additive particles. Similarly, the ratio of the number of carbon atoms to the number of silicon atoms in the external additive particles is calculated.

<Method for measuring the ratio of the number of nitrogen atoms to the total number of carbon atoms, nitrogen atoms, oxygen atoms, and silicon atoms in the surface region of an external additive particle>
The ratio of the number of nitrogen atoms present in the surface region of the external additive particles is measured by X-ray photoelectron spectroscopy using the following apparatus and measurement conditions.
Equipment used: ULVAC-PHI PHI Quantera SXM
・X-ray photoelectron spectrometer measurement conditions:
X-ray source Al Kα (1486.6eV) 200μmφ
Pass Energy: 140eV
Charge neutralization: Use of an electron neutralization gun and an Ar ion neutralization gun in combination Sweep number: C 20 times, N 100 times, O 20 times, Si 20 times From the peak intensity of each element measured, the atomic concentrations (all in atomic %) of carbon atoms, nitrogen atoms, oxygen atoms, and silicon atoms present in the surface region of the external additive particle were calculated using a relative sensitivity factor provided by ULVAC-PHI. From this result, the ratio of the number of nitrogen atoms to the total number of carbon atoms, nitrogen atoms, oxygen atoms, and silicon atoms on the surface of the external additive particle was calculated.

<Method for measuring the 50% particle size (D50) based on volume distribution of a fine particle sample>
The 50% particle size (D50) based on the volume distribution of the fine particle sample is measured using a dynamic light scattering particle size distribution meter Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Specifically, the range is set to 0.001 μm to 10 μm, and the measurement is performed according to the following procedure.

To prevent the measurement sample from clumping, a dispersion of the measurement sample is poured into an aqueous solution containing Family Fresh (manufactured by Kao Corporation) and stirred. After stirring, the measurement sample is poured into the above device and two measurements are taken to calculate the average value.

The measurement conditions are: measurement time 30 seconds, sample particle refractive index 1.49, dispersion medium water, dispersion medium refractive index 1.33.

The volumetric particle size distribution of the measurement sample is measured, and the particle size at which the cumulative volume from the small particle size side in the cumulative volume distribution is 50% from the measurement results is taken as the 50% particle size (D50) based on the volume distribution of each microparticle.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass", respectively. Furthermore, the respective measurement results in the examples are the results of measurements performed using the measurement methods described above.

<Production Example of External Additive 1>
The following materials were placed in a glass reactor equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube, and a stirrer.
Phosphate buffer solution (pH = 7.0, prepared using sodium dihydrogen phosphate dihydrate (Kishida Chemical Co., Ltd.) and disodium hydrogen phosphate dodecahydrate (Kishida Chemical Co., Ltd.)) 200 parts 0.1 mol / l sodium hydroxide aqueous solution (Kishida Chemical Co., Ltd.) 1.2 parts Emulsifier: 4-vinyl sodium benzoate (Tokyo Chemical Industry Co., Ltd.) 0.18 parts Monomer having a radical polymerizable group and a hydrolyzable group: 3- (trimethoxysilyl) propyl methacrylate (Tokyo Chemical Industry Co., Ltd.) 11.0 parts Non-hydrolyzable monomer: styrene (Tokyo Chemical Industry Co., Ltd.) 4.7 parts Subsequently, the mixture was heated to 65-70°C while passing nitrogen gas through it, and after stirring for 30 minutes, 1.5 parts of 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] (VA-057, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an initiator, and stirring was continued for 6 hours to obtain an emulsion of particles. To the obtained emulsion of particles, 28% by mass ammonia water (manufactured by Kishida Chemical Co., Ltd.) was added as an ammonia treatment to adjust the pH of the emulsion to 11.0, and then the mixture was stirred at a temperature of 50°C for 3 hours to hydrolyze the hydrolyzable groups contained in the particles and polycondensate. Thereafter, ultrafiltration was performed to remove excess solute, and concentration/filtration was repeated a total of 5 times. Thereafter, 0.13 parts of 3-aminopropyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) as a nitrogen atom source and 27.0 parts of 1,1,1,3,3,3-hexamethyldisilazane (manufactured by Kishida Chemical Co., Ltd.) as a hydrophobizing treatment agent were added, and the mixture was stirred at a temperature of 50° C. for 24 hours. Thereafter, the mixture was dried by spray drying, to obtain external additive 1 having a volume distribution-based 50% particle size (hereinafter also referred to as D50) of 130 nm. The physical properties of external additive 1 are shown in Table 2.

<Production Examples of External Additives 2 to 19>
External Additives 2 to 19 were obtained in the same manner as in the production example of External Additive 1, except that the materials used were changed as shown in Table 1. The physical properties of External Additives 2 to 19 are shown in Table 2.

<Production Example of External Additive 20>
At room temperature, a solution of the following materials was added to a solution of 46.7 parts of 28% by mass ammonia water and 2114 parts of deionized water, and the mixture was stirred for 2 hours to carry out hydrolysis and polycondensation of 3-(trimethoxysilyl)propyl methacrylate.
・3-(trimethoxysilyl)propyl methacrylate 22.1 parts ・Methanol (Kishida Chemical Co., Ltd.) 73.7 parts ・Initiator: 2,2'-azobis(2,4-dimethylvaleronitrile) (V-65, Fujifilm Wako Pure Chemical Industries, Ltd.) 0.12 parts Next, the mixture was heated to 70-75 ° C. while passing nitrogen gas through it, and stirred for 2 hours to carry out radical polymerization. Then, ultrafiltration was carried out to remove excess solute, and concentration/filtration was repeated a total of 5 times. Then, 0.22 parts of 3-aminopropyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd.) and 27.0 parts of 1,1,1,3,3,3-hexamethyldisilazane (Kishida Chemical Co., Ltd.) were added as a hydrophobic treatment agent, and the mixture was stirred at a temperature of 50 ° C. for 24 hours. Then, the mixture was dried by spray drying to obtain an external additive 20. The physical properties of the external additive 20 are shown in Table 2.

<Production Example of External Additive 21>
The following materials were placed in a glass reactor equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube, and a stirrer.
・200 parts of deionized water・1.2 parts of 0.1 mol / l aqueous sodium hydroxide solution (Kishida Chemical Co., Ltd.)・0.18 parts of emulsifier: 4-vinyl sodium benzoate (Tokyo Chemical Industry Co., Ltd.)・6.3 parts of non-hydrolyzable monomer: butyl methacrylate (Tokyo Chemical Industry Co., Ltd.) and 4.7 parts of styrene. Next, the mixture was heated to 65-70 ° C. while passing nitrogen gas through it, and after stirring for 30 minutes, 1.5 parts of 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] (VA-057, Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an initiator, and stirring was continued for 6 hours to obtain an emulsion of particles. Ultrafiltration was performed to remove excess solutes in the obtained emulsion, and concentration / filtration was repeated a total of 5 times. Thereafter, 0.13 parts of 3-aminopropyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) as a nitrogen atom source and 27.0 parts of 1,1,1,3,3,3-hexamethyldisilazane (manufactured by Kishida Chemical Co., Ltd.) as a hydrophobizing agent were added, and the mixture was stirred at a temperature of 50° C. for 24 hours. Thereafter, the mixture was dried by spray drying, thereby obtaining external additive 21. The physical properties of external additive 21 are shown in Table 2.

The abbreviations in Table 1 are as follows.
MA-TMSP: 3-(trimethoxysilyl)propyl methacrylate MA-TESP: 3-(triethoxysilyl)propyl methacrylate AA-TMSP: 3-(trimethoxysilyl)propyl acrylate VTMS: vinyltrimethoxysilane MA-CDMSP: 3-(chlorodimethylsilyl)propyl methacrylate St: styrene MAB: butyl methacrylate Na (4-VBA): sodium 4-vinylbenzoate NaMA: sodium methacrylate NaPSS: sodium p-styrenesulfonate VA-057: 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]
KPS: Potassium peroxodisulfate V-65: 2,2'-azobis(2,4-dimethylvaleronitrile)
AP-TMS: 3-aminopropyltrimethoxysilane (aminosilane having an amino group)
DMAP-TMS: [3-(N,N-dimethylamino)propyl]trimethoxysilane (aminosilane having a dialkylamino group)
IP-TMS: (3-isocyanatopropyl)trimethoxysilane (silane having an isocyanate structure)
PAA-03E: Polyallylamine (weight average molecular weight: 3000)

In Table 2, Si/(C+O+Si) is the ratio of the number of silicon atoms to the total number of carbon atoms, oxygen atoms, and silicon atoms in the external additive particle, and C/Si is the ratio of the number of carbon atoms to the total number of silicon atoms in the external additive particle. Also, N/(C+N+O+Si) is the ratio of the number of nitrogen atoms to the total number of carbon atoms, nitrogen atoms, oxygen atoms, and silicon atoms in the surface region of the external additive particle.

<Production Example of Toner Particle 1>
The following materials were premixed in a Henschel mixer, and then melt-kneaded in a twin-screw extruder (product name: PCM-30, manufactured by Ikegai Iron Works) at a temperature set so that the melt temperature at the discharge port would be 150° C. to obtain a kneaded material.
Amorphous polyester (propylene oxide adduct of bisphenol A/terephthalic acid=50/50, number average molecular weight: 3000, acid value: 12) 100 parts Magnetic iron oxide particles 75 parts Fischer-Tropsch wax (C105 manufactured by Sasol, melting point: 105° C.) 2 parts Charge control agent (T-77 manufactured by Hodogaya Chemical Co., Ltd.) 2 parts The kneaded product obtained was cooled and coarsely pulverized with a hammer mill, and then finely pulverized with a pulverizer (product name: Turbo Mill T250, manufactured by Turbo Kogyo Co., Ltd.) to obtain a finely pulverized powder. The finely pulverized powder obtained was classified with a multi-division classifier utilizing the Coanda effect to obtain toner particles 1 having a weight average particle size of 7.2 μm.

<Production Example of Toner 1>
The external additive was added to the toner particles 1 in a dry manner. 100 parts of the toner particles, 1.3 parts of the external additive 1, and 1.5 parts of fumed silica (BET specific surface area: 200 ^m2 /g) were added to a Henschel mixer and mixed. Then, the mixture was sieved through a mesh with an opening of 150 μm to obtain a toner 1 in which the external additive 1 was added to the toner particles 1.

<Production Examples of Toners 2 to 21>
Toners 2 to 21 were obtained in the same manner as in the production example of toner 1, except that the external additive 1 in the production example of toner 1 was changed to external additives 2 to 21, respectively.

Example 1
The toner 1 was used to carry out the following evaluations.

<Evaluation of Toner Fluidity>
The fluidity of the toner was measured by the following method.

First, 3 g of toner 1 was sieved for 10 seconds using a powder tester (PT-X, manufactured by Hosokawa Micron Corporation) with sieves (plain woven wire mesh, JIS Z8801-1) with openings of 150 μm, 100 μm, and 45 μm, while vibrating the sieves at a strength of 4.0. The fluidity of the toner was evaluated using the fluidity index (%) shown in the following formula, where the amount of toner remaining on the sieve with 150 μm openings is A, the amount of toner remaining on the sieve with 100 μm openings is B, and the amount of toner remaining on the sieve with 45 μm openings is C. The evaluation results are shown in Table 3. It was determined that the effects of the present invention were achieved when the fluidity index was 30% or less.

Fluidity index (%) = [(A + 0.6 x B + 0.2 x C) / measured sample mass] x 100
<Evaluation of Toner Fluidity Maintenance>
The fluidity maintenance property of the toner was evaluated after the above evaluations.

An HP LaserJet Enterprise M609dn (manufactured by HP) was used as the image forming apparatus, toner 1 was placed in a cartridge, and 5,000 images were output under the following conditions.
Paper: GFC-081 (81.0 g/m ² ) (Canon Marketing Japan Inc.)
Toner loading on paper: 0.35 mg/ ^cm2
Process speed: 377 mm/sec. Thereafter, the residual toner in the cartridge was removed, and the above-mentioned fluidity index was calculated for the residual toner, and this value was used as the fluidity index after durability. The fluidity index obtained in the above evaluation of the toner fluidity was used as the fluidity index before durability to calculate the fluctuation rate shown in the following formula, and this value was used to evaluate the fluidity maintenance of the toner.

Fluctuation rate (%) = (fluidity index after durability test - fluidity index before durability test) / fluidity index before durability test x 100
When the fluctuation rate was 100% or less, it was determined that the effect of the present invention was obtained.

<Evaluation of Crushing of External Additive Particles and Detachment from Toner Particles>
The evaluation of crushing of the external additive particles and detachment from the toner particles was carried out after the above-mentioned evaluation of the toner flowability was carried out.

After the above 5,000 images were output, the toner 1 remaining in the cartridge was removed, and the surface of the removed toner 1 was observed using a scanning electron microscope (S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image. In the obtained image, if crushed deposits were observed on the surface of the toner, it was judged that there was crushing, and if depressions from which external additive particles had been detached were observed on the surface of the toner, it was judged that there was detachment.

<Evaluation of Image Density Stability>
Using the image forming apparatus used in the evaluation of toner fluidity maintenance, toner 1 was placed in a cartridge, and 10,000 images were output under the same conditions as those set in the evaluation of toner fluidity maintenance.

Calibration was not performed during the continuous printing of 10,000 sheets, and the set conditions were not changed. The reflection density of all printed images was measured, and the image density stability was evaluated using the standard deviation value. It was determined that the effect of the present invention was achieved when the standard deviation was less than 0.100. An X-Rite color reflection densitometer (500 series: manufactured by X-Rite) was used to measure the reflection density of the images.

<Examples 2 to 19, Comparative Examples 1 and 2>
Using toners 2 to 21, the same evaluation as in Example 1 was carried out. The evaluation results are shown in Table 3. Example 4 is described as a reference example.

Claims (10)

A method for producing an external additive particle containing a polymer, comprising the steps of:
The manufacturing method comprises:
a radical polymerization step of carrying out a radical polymerization reaction of a monomer raw material containing a compound represented by the following formula (3) using a radical polymerization initiator having a carboxy group, which is a compound represented by the following formula (2), in the presence of an emulsifier under the condition of 6.0≦pH≦8.0; and a condensation step of carrying out a hydrolysis reaction and a polycondensation reaction of the hydrolyzable group X in the following formula (3) after the radical polymerization step to obtain particles containing a polymer.
Including,
The method for producing external additive particles is characterized in that the emulsifier is any compound selected from the group consisting of radically polymerizable carboxylic acids, radically polymerizable carboxylates, and sodium p-styrenesulfonate.

(In formula (2), R ⁵ is an alkylene group having 1 to 12 carbon atoms.)
R ⁶ _m SiX _4-m ... (3)
(In formula (3), X is a hydrolyzable group, m is an integer of 1 to 3, each R ⁶ is independently an organic group having 1 to 20 carbon atoms, and at least one of R ⁶ is a radical polymerizable group.) The method for producing external additive particles according to claim 1 , wherein the hydrolyzable group X in the formula (3) is an alkoxy group. 2. The method for producing external additive particles according to claim 1 , wherein the compound represented by formula (3) is a compound represented by the following formula (1):

(In formula (1), R ¹ is an alkylene group having 1 to 10 carbon atoms, R ² , R ³ , and R ⁴ are each independently any of hydrogen, a methyl group, and an ethyl group, and R′ is hydrogen or a methyl group.) the ratio of the number of silicon atoms to the total number of carbon atoms, oxygen atoms, and silicon atoms in the external additive particles is 4.0% or more and 25.0% or less;
The method for producing the external additive particles according to any one of claims 1 to 3 . 5. The method for producing an external additive particle according to claim 1 , wherein the ratio of the number of carbon atoms in the external additive particle to the number of silicon atoms in the external additive particle is 6.5 or more. The method for producing an external additive particle according to any one of claims 1 to 5 , further comprising a step of subjecting the particles containing the polymer to a surface treatment with an amine compound. The method for producing external additive particles according to claim 6 , wherein the amine compound is an aminosilane. When the surface of the external additive particle is subjected to X-ray photoelectron spectroscopy,
the ratio of the number of nitrogen atoms to the total number of carbon atoms, nitrogen atoms, oxygen atoms, and silicon atoms is 1.0% or more and 2.5% or less;
The method for producing the external additive particles according to any one of claims 1 to 7 . When the 50% particle size based on the volume distribution of the external additive particles is defined as D50,
The method for producing external additive particles according to any one of claims 1 to 8 , wherein the D50 is 50 nm or more and 200 nm or less. The method for producing an external additive according to any one of claims 1 to 9 , wherein the emulsifier is sodium 4-vinylbenzoate, sodium methacrylate, or sodium p-styrenesulfonate.