JP6915598B2 - Positively charged hydrophobic spherical silica particles, a method for producing the same, and a positively charged toner composition using the same. - Google Patents

Description

The present invention relates to positively charged hydrophobic spherical silica particles, a method for producing the same, and a positively charged toner composition using the same.

In the electrophotographic development method, a high-quality image is obtained by visualizing an electrostatic latent image or visualizing an electrostatic latent image by inversion development. Toner suitable for the electrophotographic development method is obtained by mixing a thermoplastic resin as a binder with a dye or pigment as a colorant, a charge control agent, a wax as a release agent, and a magnetic material, and kneading, pulverizing, and classifying the toner. , Toner particles. Further, in order to impart fluidity to the toner particles and improve the cleanability, it is common to add an external additive composed of inorganic fine powder such as silica, titanium oxide, or alumina to the toner particles. be.
However, these inorganic fine powders are generally highly hydrophilic, and the fluidity and charge rising property of the toner may change depending on the surrounding environmental conditions (humidity).

Therefore, in order to prevent the influence of such environmental conditions, a method of treating the surface of these inorganic fine powders with a hydrophobic agent or introducing a charging polar group on the surface of the inorganic fine powders has been carried out.
Among these methods, a method of using a metal oxide such as silica fine powder surface-treated with an aminosilane coupling agent or the like as an external additive for a positively charged toner is described in Patent Document 1 (Japanese Patent Laid-Open No. 52-135739). No. 5) and Patent Document 2 (Japanese Unexamined Patent Publication No. 56-123550). According to this silane treatment method, a developer exhibiting strong positive chargeability can be obtained by the terminal amino group of the aminosilane coupling agent.

Further, a method in which hydrophobic silica particles are surface-treated with both a positive charge control agent and a hydrophobic agent and used as an external additive for a developer is described in Patent Document 3 (Japanese Patent Laid-Open No. 58-216252). A method of treating fine silicic acid powder with a predetermined amount of a nitrogen-containing silane coupling agent and a silicone oil having a nitrogen atom, and using it as an external additive for a developer. Is disclosed in Patent Document 4 (Japanese Patent Laid-Open No. 63-73271) and Patent Document 5 (Japanese Patent Laid-Open No. 63-73272). According to these methods, a developer exhibiting strong positive charge property can be obtained by the action of the positive charge control agent.

Further, a method of using inorganic particles in which both polar groups of negatively charged polar groups and positively charged polar groups are bonded to the surface as an external agent for a non-magnetic one-component developing toner is described in, for example, Patent Document 6 (Japanese Patent Laid-Open No. It is disclosed in Japanese Patent Publication No. 2-66564).
According to this method, a non-magnetic one-component developing toner having excellent charge level improving property, charging rising property, and fluidity can be obtained.

Further, in Patent Document 7 (Japanese Unexamined Patent Publication No. 11-160907), a dry silica fine powder having a positively charged polar group and a hydrophobic group is provided in order to increase charging, improve durability, and obtain environmental stability. And, it is disclosed that the combined use with the wet silica fine powder in which a positively charged polar group is introduced and hydrophobized with silicone oil is effective.
Further, Patent Document 8 (Japanese Unexamined Patent Publication No. 11-143111) describes a dry silica fine powder having a positively charged polar group and a hydrophobic group in order to obtain rising charge, improvement of durability, and environmental stability. , It is disclosed that the combined use with a wet silica fine powder containing a positively charged polar group and a fluorine-containing polar group is effective.
Further, Patent Document 9 (Japanese Unexamined Patent Publication No. 2007-108801) has a positively charged polar group and a hydrophobic group in order to obtain good image density and fog resistance for a long period of time even when printing with a low printing rate is performed. It is disclosed that a positively charged toner containing a dry silica fine powder and a wet silica fine powder having a fluorine-containing negatively charged polar group and surface-treated with a quaternary ammonium salt type silane compound as an external additive is effective. Has been done.

Japanese Unexamined Patent Publication No. 52-135739 Japanese Unexamined Patent Publication No. 56-123550 Japanese Unexamined Patent Publication No. 58-216252 Japanese Unexamined Patent Publication No. 63-73271 Japanese Unexamined Patent Publication No. 63-73272 Japanese Unexamined Patent Publication No. 2-66564 Japanese Unexamined Patent Publication No. 11-160907 Japanese Unexamined Patent Publication No. 11-143111 JP-A-2007-108801

As seen in the above literature, the external additive for positively charged toner is generally treated with an aminosilane coupling agent such as aminotrialkoxysilane, and these positively charged hydrophobic spherical silica particles are used. When used as a toner external additive, there is a problem that the aminosilane component is peeled off from the silica surface due to long-term contact with the carrier, the original negative charge property of silica is developed, and the positive charge property is lowered. This is because the amino group of aminosilane is quasi-bonded to the silanol group on the silica surface by a hydrogen bond or the like before the silanol group on the silica surface reacts with the alkoxy group of aminosilane such as aminotrialkoxysilane. It is presumed that there are many aminosilanes that simply adhere to the silica surface without forming a Si—O—Si bond with the group.
Therefore, the present invention includes silica particles for a toner external additive, which can impart a desired positive charge polarity to the toner and can stably maintain the positive charge polarity for a long period of time, that is, have excellent positive charge retention. It is an object of the present invention to provide a toner composition.

As a result of diligent research in view of such circumstances, the present inventor has found that the following positively charged hydrophobic spherical silica particles can solve the above-mentioned problems, and completed the present invention.

That is, the present invention provides the following positively charged hydrophobic spherical silica particles, a method for producing the silica particles, and a positively charged toner composition containing the silica particles.

（式中、Ｒ¹及びＲ²は、独立に、水素原子、又は、炭素原子数１〜１０の直鎖状、分岐状もしくは環状のアルキル基を表す。ｎは０または１である。） [1]
A positively charged hydrophobic sphere having a median diameter (D50) of 5 to 250 nm, a D90 / D10 ratio of 3 or less, and an average circularity of 0.8 to 1 in a volume-based particle size distribution. Silica particles
Positively charged hydrophobic spherical silica particles having an organosilicon compound represented by the following formula (I) bonded to the surface.

(In the formula, R ¹ and R ² independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms. N is 0 or 1.)

[2]
The positively charged hydrophobic sphere according to claim 1, further surface-treated with a silica compound represented by the following formula (III), a monofunctional silane compound represented by the following formula (IV), or a mixture thereof. Silica particles.
R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
R ⁴ ₃ SiX (IV)
(In the formula, R ⁴ represents a monovalent hydrocarbon group having the same or different substituted or unsubstituted carbon atoms 1 to 6, and X represents a hydroxyl group or a hydrolyzable group.)

（式中、Ｒ¹及びＲ²は、独立に、水素原子、又は、炭素原子数１〜１０の直鎖状、分岐状もしくは環状のアルキル基を表す。ｎは０または１である。） [3]
The method for producing positively charged hydrophobic spherical silica particles according to [1] or [2], which comprises the following steps (A2) to (A4).

Step (A2): A hydrophilic spherical silica particle dispersion is mixed with a silazane compound represented by the following formula (III), a monofunctional silane compound represented by the following formula (IV), or a mixture thereof. 0.01 to 0.1 mol is added to 1 mol of Si atom of the particle dispersion, and _1/2 ^{unit of R 4} ₃ SiO is introduced on the surface of the hydrophilic spherical silica particles to obtain a hydrophobic spherical silica particle dispersion. Step R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
R ⁴ ₃ SiX (IV)
(In the formula, R ⁴ represents a monovalent hydrocarbon group having the same or different substituted or unsubstituted carbon atoms 1 to 6, and X represents a hydroxyl group or a hydrolyzable group.)

Step (A3): A step of substituting the dispersion medium of the hydrophobic spherical silica particle dispersion obtained in the step (A2) with a ketone solvent to obtain a ketone solvent dispersion of the hydrophobic spherical silica particles.

Step (A4): An organosilicon compound represented by the following formula (I) is added to the ketone solvent dispersion of the hydrophobic spherical silica particles obtained in the step (A3), and the surface of the hydrophobic spherical silica particles is surfaced. Step of phenylaminoing silanol groups

(In the formula, R ¹ and R ² independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms. N is 0 or 1.)

[4]
The method for producing positively charged hydrophobic spherical silica particles according to [3], wherein the hydrophilic spherical silica particle dispersion is produced by the following step (A1).

Step (A1): A tetrafunctional silane compound represented by the following formula (II), a partially hydrolyzed condensate thereof, or a mixture thereof is placed in a mixed solution containing a hydrophilic solvent and water in the presence of a basic substance. Step of obtaining hydrophilic spherical silica particle dispersion by hydrolysis and condensation Si (OR ³ ) ₄ (II)
(In the formula, R ³ represents a monovalent hydrocarbon group having the same or different carbon atoms 1 to 6).

[5]
Further, the method for producing positively charged hydrophobic spherical silica particles according to [3] or [4], which comprises the following step (A5).

Step (A5): The silazan compound represented by the following formula (III), the monofunctional silane compound represented by the following formula (IV), or the monofunctional silane compound represented by the following formula (IV) is added to the phenylaminoized spherical silica particle dispersion obtained in the step (A4). A step of adding 0.01 to 0.3 mol of these mixtures to 1 mol of Si atoms of the phenylaminoized spherical silica particles and reacting them with the silanol groups remaining on the surface of the phenylaminoized spherical silica particles R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
R ⁴ ₃ SiX (IV)
(In the formula, R ⁴ represents a monovalent hydrocarbon group having the same or different substituted or unsubstituted carbon atoms 1 to 6, and X represents a hydroxyl group or a hydrolyzable group.)

[6]
A positively charged toner composition containing the positively charged hydrophobic spherical silica particles according to [1] or [2].

The positively charged hydrophobic spherical silica particles of the present invention have a rapid rise in charging and are also excellent in maintaining positive charging over time. Further, the toner composition containing the positively charged hydrophobic spherical silica particles of the present invention is excellent in fluidity and printing characteristics, and these characteristics are less affected by changes in surrounding environmental conditions.

（式中、Ｒ¹及びＲ²は、独立に、水素原子、又は、炭素原子数１〜１０の直鎖状、分岐状もしくは環状のアルキル基を表す。ｎは０または１である。） Hereinafter, the positively charged hydrophobic spherical silica particles of the present invention will be described in detail.
In the positively charged hydrophobic spherical silica particles of the present invention, the median diameter (D50) of the primary particles in the volume-based particle size distribution is 5 to 250 nm, the D90 / D10 ratio is 3 or less, and the average circularity is Positively charged hydrophobic spherical silica particles having a size of 0.8 to 1 and having an organosilicon compound represented by the following formula (I) bonded to the surface thereof.

(In the formula, R ¹ and R ² independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms. N is 0 or 1.)

R ¹ and R ² are independently hydrogen atoms, linear alkyl groups having 1 to 10 carbon atoms, branched alkyl groups having 3 to 10 carbon atoms, or cyclic alkyl groups having 3 to 10 carbon atoms. Represents the alkyl group of. Specific examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, cyclopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group and decyl. Groups and the like are exemplified. Among these, a hydrogen atom and a methyl group having less steric hindrance are particularly preferable because they do not inhibit the reaction with the silica surface.

Specific examples of the organic silicon compound represented by the formula (I) include 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane and 2-methoxy-2-methyl-1-phenyl-1. -Aza-2-silacyclopentane, 2,2-diethoxy-1-phenyl-1-aza-2-silacyclopentane, 2-ethoxy-2-methyl-1-phenyl-1-aza-2-silacyclopentane And so on. Particularly preferred as the organosilicon compound represented by the formula (I) is 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane.

The positively charged hydrophobic spherical silica particles of the present invention preferably have a median diameter (D50: particle diameter that accumulates 50% from the smaller particle size side) of the primary particles in a volume-based particle size distribution of 5 to 250 nm. Is 10 to 200 nm. If D50 is smaller than 5 nm, the particles agglomerate violently, causing gelation of the whole and adhesion to the inside of the manufacturing apparatus, and it may not be taken out well. Further, if D50 is larger than 250 nm, good positive chargeability may not be imparted, which is not preferable.

In the volume-based particle size distribution, the positively charged hydrophobic spherical silica particles of the present invention are D90, where D10 is the particle size that is cumulative 10% from the smaller particle size side, and D90 is the particle size that is 90% cumulative. Since the / D10 ratio is 3 or less, the particle size distribution is narrow. It is preferable that the particles have such a narrow particle size distribution because the fluidity can be easily controlled. The D90 / D10 ratio is more preferably 2.9 or less.
In the present invention, the volume-based particle size distribution is measured by a dynamic light scattering method using a laser beam.

Further, in the present invention, the circularity refers to (perimeter of a circle equal to the particle area) / (perimeter of particles), and specifically is based on a shape obtained by an electron microscope (magnification: 100,000 times). The average circularity of 10 silica particles is defined as "average circularity".
The average circularity of the positively charged hydrophobic spherical silica particles of the present invention is 0.8 to 1, and 0.92 to 1 is particularly preferable. Further, in the present invention, the "sphere" includes not only a true sphere but also a slightly distorted sphere. The shape of such particles is evaluated by the circularity when the particles are projected two-dimensionally.

The positively charged hydrophobic spherical silica particles of the present invention were further surface-treated with a silazane compound represented by the following formula (III), a monofunctional silane compound represented by the following formula (IV), or a mixture thereof. It is preferable that the material is one.
R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
R ⁴ ₃ SiX (IV)
(In the formula, R ⁴ represents a monovalent hydrocarbon group having the same or different substituted or unsubstituted carbon atoms 1 to 6, and X represents a hydroxyl group or a hydrolyzable group.)

In the above formulas (III) and (IV), R ⁴ is preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ⁴ include an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group and a butyl group, and preferably a methyl group, an ethyl group and a propyl group. It is particularly preferable that it is a methyl group and an ethyl group. Further, a part or all of hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atom, chlorine atom and bromine atom, preferably fluorine atom.

Examples of the hydrolyzable group represented by X include a hydroxy group, a chlorine atom, an alkoxy group, an amino group, an acyloxy group and the like, preferably an alkoxy group and an amino group, and more preferably an alkoxy group. Yes, methoxy and ethoxy groups are particularly preferred.

Examples of the silazane compound represented by the above formula (III) include hexamethyldisilazane and hexaethyldisilazane, and hexamethyldisilazane is preferable. Examples of the monofunctional silane compound represented by the above formula (IV) include monosilanol compounds such as trimethylsilanol and triethylsilanol; monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane; and monos such as trimethylmethoxysilane and trimethylethoxysilane. Alkoxysilanes; monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; monoacyloxysilanes such as trimethylacetoxysilanes, preferably trimethylsilanol, trimethylmethoxysilane and trimethylsilyldiethylamine, and particularly preferably trimethylsilanol and trimethyl. It is methoxysilane.

The method for evaluating the hydrophobicity of the positively charged hydrophobic spherical silica particles of the present invention is not particularly limited, but for example, the degree of hydrophobicity (methanol wettability) can be preferably used. The positively charged hydrophobic spherical silica particles of the present invention preferably have a degree of hydrophobicity of 60% or more, more preferably 65% or more, as measured by the following procedure. When this value is 60% or more, good environmental resistance can be imparted to the obtained silica particles, and when the silica particles are applied as a toner for electrostatic charge development, good charge stability can be obtained.

Here, the degree of hydrophobicity can be determined by the following procedure.
1) Weigh 0.2 g of the sample into a 200 ml beaker and add 50 ml of pure water.
2) Add methanol below the liquid surface while stirring electromagnetically.
3) The end point is the point where no sample is found on the liquid surface.
4) Calculate the degree of hydrophobization from the required amount of methanol by the following formula.

Degree of hydrophobization (%) = [x / (50 + x)] x 100
x: Amount of methanol (ml)

Next, the method for producing the positively charged hydrophobic spherical silica particles of the present invention will be described in detail.

The positively charged hydrophobic spherical silica particles of the present invention can be obtained, for example, by going through the following steps (A2) to (A4). Further, the hydrophilic spherical silica particle dispersion which is the raw material of the step (A2) can be obtained by, for example, the step (A1).
Step (A1): Synthesis step to obtain hydrophilic spherical silica particle dispersion Step (A2): Surface treatment step with 1 functional silane compound Step (A3): Dispersion medium replacement step Step (A4): Hydrophobic spherical silica particles Step to phenylaminoize the surface

Hereinafter, each step will be described in order.

Step (A1): Synthesis step to obtain a hydrophilic spherical silica particle dispersion In this step, a tetrafunctional silane compound represented by the following formula (II), a partially hydrolyzed condensate thereof, or a mixture thereof is used as a basic substance. This is a synthetic step of obtaining a hydrophilic spherical silica particle dispersion by hydrolyzing and condensing in a mixed solution containing a hydrophilic solvent and water in the presence of.
Si (OR ³ ) ₄ (II)
(In the formula, R ³ represents a monovalent hydrocarbon group having the same or different carbon atoms 1 to 6).

In the above formula (II), R ³ is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably one having 1 to 4 carbon atoms, and particularly preferably one having 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ³ include a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group and the like, and preferably a methyl group, an ethyl group, a propyl group and a butyl group. Yes, particularly preferably a methyl group and an ethyl group.

Examples of the tetrafunctional silane compound represented by the above formula (II) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, and tetraphenoxysilanes, which are preferable. , Tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane and tetrabutoxysilane, with particular preference being tetramethoxysilane and tetraethoxysilane. Examples of the hydrolyzed condensate of the tetrafunctional silane compound represented by the above formula (II) include methyl silicate and ethyl silicate.

Examples of the basic substance include ammonia, dimethylamine, diethylamine and the like, preferably ammonia and diethylamine, and particularly preferably ammonia. As these basic substances, those in which the required amount is dissolved in water can be used.

Examples of the hydrophilic solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol and t-butanol; ethers such as tetrahydrofuran and dioxane; glycols such as diethylene glycol and dipropylene glycol. ..

The amount of water used in this step is 0.5 to 5 with respect to a total of 1 mol of hydrocarbyloxy groups of the tetrafunctional silane compound represented by the general formula (II) and / or its partially hydrolyzed condensate. It is preferably mol, more preferably 0.6 to 2 mol, and particularly preferably 0.7 to 1 mol.
The ratio of the hydrophilic solvent to water is preferably 0.5 to 10 by mass ratio from the viewpoint of the affinity between the hydrophobic spherical silica particles and the mixed solvent and the ease of production, and is preferably 3 to 9. It is more preferable to have it, and it is particularly preferable to have 5 to 8.
The amount of the basic substance is 0.01 to 2 mol with respect to 1 mol of the total of the hydrocarbyloxy groups of the tetrafunctional silane compound represented by the general formula (II) and / or its partially hydrolyzed condensation product. It is preferably 0.02 to 0.5 mol, more preferably 0.04 to 0.12 mol, and particularly preferably 0.04 to 0.12 mol.

The reaction conditions for hydrolysis condensation in this step are preferably a reaction temperature of 20 to 120 ° C. and a reaction time of 1 to 8 hours, more preferably a reaction temperature of 20 to 100 ° C. and a reaction time of 1 to 6 hours.

The concentration of silica particles in the hydrophilic spherical silica particle dispersion obtained in the step (A1) is preferably 2 to 20% by mass, particularly preferably 3 to 10% by mass.

Further, instead of the above-mentioned step (A1), a commercially available product may be used as the hydrophilic spherical silica particle dispersion to be subjected to the step (A2). As a commercially available product, a hydrophilic spherical silica particle dispersion in which hydrophilic spherical silica particles are dispersed in a hydrophilic solvent such as the above-mentioned alcohols can be used. When a commercially available product is used, a hydrophilic solvent is added or distilled off so that the silica particle concentration becomes appropriate when the product is subjected to the step (A2), and the commercially available hydrophilic spherical silica particle dispersion is diluted or concentrated. May be used. In this case, the silica particle concentration is preferably 2 to 20% by mass, which is the same as the silica particle concentration in the hydrophilic spherical silica particle dispersion obtained in the above-mentioned step (A1).

Step (A2): Surface treatment step with one functional silane compound In this step, the hydrophilic spherical silica particle dispersion obtained in step (A1) is mixed with the silazane compound represented by the following formula (III) and the following formula (IV). ) Is added to 1 mol of Si atom of the hydrophilic spherical silica particle dispersion, and 0.01 to 0.1 mol of the monofunctional silane compound represented by) is added to the surface of the hydrophilic spherical silica particles. This is a step of introducing at least a part of R ⁴ ₃ SiO _1/2 unit to obtain a hydrophobic spherical silica particle dispersion.

R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
R ⁴ ₃ SiX (IV)
(In the formula, R ⁴ represents a monovalent hydrocarbon group having the same or different substituted or unsubstituted carbon atoms 1 to 6, and X represents a hydroxyl group or a hydrolyzable group.)

In the above formulas (III) and (IV), R ⁴ is preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ⁴ include an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group and a butyl group, and preferably a methyl group, an ethyl group and a propyl group. It is particularly preferable that it is a methyl group and an ethyl group. Further, a part or all of hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atom, chlorine atom and bromine atom, preferably fluorine atom.

Examples of the hydrolyzable group represented by X include a hydroxy group, a chlorine atom, an alkoxy group, an amino group, an acyloxy group and the like, preferably an alkoxy group and an amino group, and more preferably an alkoxy group. Yes, methoxy and ethoxy groups are particularly preferred.

Examples of the silazane compound represented by the above formula (III) include hexamethyldisilazane and hexaethyldisilazane, and hexamethyldisilazane is preferable. Examples of the monofunctional silane compound represented by the above formula (IV) include monosilanol compounds such as trimethylsilanol and triethylsilanol; monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane; and monos such as trimethylmethoxysilane and trimethylethoxysilane. Alkoxysilanes; monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; monoacyloxysilanes such as trimethylacetoxysilanes, preferably trimethylsilanol, trimethylmethoxysilane and trimethylsilyldiethylamine, and particularly preferably trimethylsilanol and trimethyl. It is methoxysilane.

The amount of the compounds represented by the above formulas (III) and (IV) to be used is the above formula (II) when the Si atom of the hydrophilic spherical silica particles (when the hydrophilic spherical silica particle dispersion is obtained by the step (A1)). It is 0.01 to 0.1 mol, preferably 0.03 to 0.08 mol, per 1 mol of the derived Si atom). If the amount used is less than 0.01 mol, water is distilled off from the dispersion medium, and when the silica particles are replaced with a ketone solvent system, the silica particles do not disperse well and may precipitate, which is not preferable. Further, if the amount used is more than 0.1 mol, the aminosilane treatment in the subsequent step may not be successful, which is not preferable.

In this step (A2), a silazane compound represented by the above formula (III), a monofunctional silane compound represented by the above formula (IV), or a mixture thereof is added to the hydrophilic spherical silica particle dispersion. A surface treatment reaction with a monofunctional silane compound is carried out under the following reaction conditions. The reaction conditions for the surface treatment in this step (A2) are preferably a reaction temperature of 40 to 60 ° C. and a reaction time of 1 to 10 hours, more preferably a reaction temperature of 50 to 60 ° C. and a reaction time of 2 to 8 hours.

Step (A3): Dispersion medium replacement step This step includes water in the hydrophobic spherical silica particle dispersion obtained in step (A2), a hydrophilic organic solvent, and volatile by-products such as alcohol generated by condensation. This is a step of replacing the dispersion medium composed of the above with a ketone solvent.

Specific examples of the ketone solvent include methyl ethyl ketone, methyl isobutyl ketone, acetylacetone and the like, and methyl isobutyl ketone is preferable.

The amount of the ketone solvent added is preferably 0 by weight with respect to the hydrophobic spherical silica particles obtained in the step (A2) from the viewpoint of suppressing aggregation of the silica particles and the concentration of the reaction system in the aminosilane treatment in the next step. It is preferable to use 5 to 5 times the amount, more preferably 1 to 2 times the amount.

As a method for replacing volatile by-products such as hydrophilic organic solvent, water, and alcohol produced by condensation in the hydrophobic spherical silica particle dispersion with a ketone solvent, concentration (atmospheric pressure or reduced pressure) and a filter are used. Examples include the method used for ultrafiltration. The hydrophilic organic solvent contained in the hydrophobic spherical silica particle dispersion obtained in the step (A2) and the ketone solvent having a boiling point higher than that of water are added to the hydrophobic spherical silica particle dispersion obtained in the step (A2). The method of concentrating is preferable.

（式中、Ｒ¹及びＲ²は、独立に、水素原子、又は、炭素原子数１〜１０の直鎖状、分岐状もしくは環状のアルキル基を表す。ｎは０または１である。） Step (A4): Step of phenylaminoizing the surface of the hydrophobic spherical silica particles This step is represented by the following formula (I) in the ketone solvent dispersion of the hydrophobic spherical silica particles obtained in the step (A3). This is a step of adding an organosilicon compound to phenylaminoify at least a part of silanol groups on the surface of the hydrophobic spherical silica particles.

(In the formula, R ¹ and R ² independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms. N is 0 or 1.)

R ¹ and R ² are independently hydrogen atoms, linear alkyl groups having 1 to 10 carbon atoms, branched alkyl groups having 3 to 10 carbon atoms, or cyclic alkyl groups having 3 to 10 carbon atoms. Represents the alkyl group of. Specific examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, cyclopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group and decyl. Groups and the like are exemplified. Among these, a hydrogen atom and a methyl group having less steric hindrance are particularly preferable because they do not inhibit the reaction with the silica surface.

Specific examples of the organic silicon compound represented by the formula (I) include 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane and 2-methoxy-2-methyl-1-phenyl-1. -Aza-2-silacyclopentane, 2,2-diethoxy-1-phenyl-1-aza-2-silacyclopentane, 2-ethoxy-2-methyl-1-phenyl-1-aza-2-silacyclopentane And so on. Particularly preferred is 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane.

By treating the surface of the hydrophobic spherical silica with the organosilicon compound represented by the above formula (I), positively charged hydrophobic spherical silica particles can be obtained.

The surface treatment step is preferably a method of adding the organosilicon compound represented by the above formula (I) to the treatment in which the hydrophobic spherical silica particles are dispersed in the ketone solvent. The organosilicon compound represented by the above formula (I) may be used as it is, or may be added in a diluted form to the above-mentioned ketone solvent.

The amount of the organosilicon compound represented by the above formula (I) added is preferably 1 to 30% by mass, particularly preferably 5 to 20% by mass, based on the hydrophobic spherical silica particles. Within such a range, good positive chargeability can be obtained for the silica particles.

After adding the organosilicon compound represented by the above formula (I), the reaction is preferably carried out at a reaction temperature of 20 to 120 ° C. and a reaction time of 1 to 8 hours, preferably at a reaction temperature of 20 to 100 ° C. and a reaction time of 1 to 6 hours. It is more preferable to react.

The positively charged hydrophobic spherical silica particles of the present invention are preferably produced through the following step (A5).
Step (A5): The silazan compound represented by the following formula (III), the monofunctional silane compound represented by the following formula (IV), or the monofunctional silane compound represented by the following formula (IV) is added to the phenylaminoized spherical silica particle dispersion obtained in the step (A4). A step of adding 0.01 to 0.3 mol of these mixtures to 1 mol of Si atoms of the phenylaminoized spherical silica particles and reacting them with silanol groups remaining on the surface of the phenylaminoized spherical silica particles R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
R ⁴ ₃ SiX (IV)
(In the formula, R ⁴ represents a monovalent hydrocarbon group having the same or different substituted or unsubstituted carbon atoms 1 to 6, and X represents a hydroxyl group or a hydrolyzable group.)

The compounds represented by the above formulas (III) and (IV) in the step (A5) are the same as those described in the above step (A2). In this step, the silanol groups remaining on the surface of the silica particles after the above step (A4) are further triorganosilylated to make the obtained silica particles highly hydrophobic and improve the fluidity, and the residual silanol groups form protons. The formation of silica anion due to release can be suppressed.

The amount of the compound represented by the above formulas (III) and (IV) to be used is preferably 0.01 to 0.3 with respect to 1 mol of Si atom of the phenylaminoized spherical silica particles obtained in the above step (A4). It is mol, more preferably 0.03 to 0.2 mol. Within such a range, good positive chargeability, environmental chargeability, and fluidity can be obtained.

In this step (A5), the phenylaminoized spherical silica particle dispersion obtained in step (A4) is mixed with the silazane compound represented by the above formula (III) and the monofunctional silane represented by the above formula (IV). A compound or a mixture thereof is added, and a surface treatment reaction with a monofunctional silane compound is carried out under the following reaction conditions. The reaction conditions for the surface treatment in this step (A5) are preferably a reaction temperature of 40 to 110 ° C. and a reaction time of 1 to 10 hours, more preferably a reaction temperature of 60 to 100 ° C. and a reaction time of 2 to 5 hours.

After the reaction, positively charged hydrophobic spherical silica particles can be obtained by appropriately removing volatile by-products such as a dispersion medium and alcohol from the dispersion of positively charged hydrophobic spherical silica particles.

Next, the positively charged toner composition of the present invention will be described in detail.
The positively charged toner composition of the present invention contains the above-mentioned positively charged hydrophobic spherical silica particles of the present invention as a toner external agent. When the positively charged hydrophobic spherical silica particles are used as a toner external additive, the blending amount is usually preferably 0.1 to 3 parts by mass, more preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the toner. 2 parts by mass. Within such a range, positive chargeability can be stably imparted to the toner.

As the toner particles contained in the positively charged toner composition of the present invention, known toner particles composed mainly of a binder resin and a colorant can be used. In addition, other external additives may be added as needed.

The positively charged toner composition of the present invention can be produced by a general method for producing a toner composition. For example, a method of mixing the positively charged hydrophobic spherical silica particles of the present invention with the toner particles obtained by melt-mixing, pulverizing, and classifying a binder resin, a colorant, and other additives can be mentioned. ..

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The following examples do not limit the present invention in any way. The particle size distribution measurement and particle shape observation of the silica particles obtained in Examples and Comparative Examples were performed under the following conditions, and the results are shown in Table 1.

[Particle size distribution]
The particle size distribution when the silica particle dispersion is diluted with methanol so that the silica particles are 0.5% by mass and irradiated with ultrasonic waves for 10 minutes is measured by the dynamic light scattering method / laser Doppler method nanotrack particle size distribution measuring device. (UPA-EX150, manufactured by Nikkiso Co., Ltd.) was measured, and the median diameter and the D90 / D10 ratio were calculated based on the obtained volume-based particle size distribution.

[Particle shape]
The shape of the silica particles was confirmed by observing the silica particles using an electron microscope (manufactured by Hitachi, Ltd., S-4700 type, magnification: 100,000 times). The circularity when the particles were projected two-dimensionally was determined as (perimeter of a circle equal to the particle area) / (perimeter of the particles), and the average value of the circularity of 10 silica particles was defined as the average circularity.

[Synthesis Example 1] Synthesis of 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane N-phenyl-3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd.) in a distillation pot. Product name KBM-573) 255 g (1.0 mol) and 2.0 g of a methanol solution of sodium methoxide (28 mass% sodium methoxide) are added, and distillation is performed while distilling off the generated alcohol to obtain a boiling point of 173. 156 g of a colorless transparent distillate at ~ 175 ° C./0.4 kPa was obtained (yield 70%).

From the results of measuring the mass spectrum of the obtained fraction, ¹ H-NMR spectrum (deuterated chloroform solvent) and IR spectrum, the obtained compound was 2,2-dimethoxy-1-phenyl-1-aza-2-sila. It was confirmed to be cyclopentane.

[Example 1]
Step (A1): Synthesis step to obtain hydrophilic spherical silica particle dispersion In a 3 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer, 793.0 g of methanol, 32.1 g of water and 28% aqueous ammonia. 40.6 g was added and mixed. The solution was adjusted to 34 ° C., and 466.5 g (4.25 mol) of tetramethoxysilane and 160.9 g of 5.4% aqueous ammonia were simultaneously started to be added dropwise with stirring, and both were added dropwise over 3 hours. did. After completion of the dropping, the mixture was further stirred for 0.5 hours to carry out hydrolysis condensation to obtain 1,662 g of a dispersion of hydrophilic spherical silica particles.

Step (A2): Surface Treatment Step with 1 Functional Silane Compound 600 g (silica content 15% by mass, 90 g (1.5 mol)) of the dispersion of hydrophilic spherical silica particles obtained in the above step (A1). The mixture was placed in a 3 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer, and 12.8 g (0.08 mol) of hexamethyldisilazane was added and mixed at 25 ° C. This solution was heated to 60 ° C. and reacted for 3 hours to silylate the surface of hydrophilic spherical silica particles.

-Step (A3): Dispersion medium replacement step 1,200 g of methyl isobutyl ketone was added to the reaction vessel after the above step (A2). An ester adapter and a cooling tube are attached to a glass reaction vessel, heated to 80 to 110 ° C., and 1,210 g of a mixture of methanol and water is removed by concentration over 5 hours to remove 592 g of a hydrophobic spherical silica particle ketone solvent dispersion. (Silica content 15.2% by mass, 90 g (1.5 mol)) was obtained.

Step (A4): Step of phenylaminoizing the surface of the hydrophobic spherical silica particles 200 g of the hydrophobic spherical silica particles ketone solvent dispersion obtained in the above step (A3) (silica content 30.4 g, 0.51). (Mol) was placed in a 0.5 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer, and 1.52 g (0.) of 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane. 007 mol, 5% by mass (based on silica mass)) was added dropwise from the dropping funnel. The mixture was heated to 100 ° C. and reacted for 3 hours. Gas chromatography analysis of the reaction solution after the reaction for 3 hours confirmed the disappearance of the peak of 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane.

Step (A5): Resurface treatment step with 1 functional silane compound To the phenylaminoized spherical silica particle dispersion obtained in the above step (A4), 16.1 g (0.10) of hexamethyldisilazane from the dropping funnel was further added. Mol) was added and the reaction was carried out at a reaction temperature of 100 ° C. for 3 hours to silylate the surface of the phenylaminoized spherical silica particles. Then, the dispersion medium was distilled off under reduced pressure to obtain 32 g of phenylaminated hydrophobic spherical silica particles.

[Example 2]
In the step (A4) of Example 1, the amount of 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane was reduced to 3.1 g (0.014 mol, 10% by mass (based on silica mass)). The same procedure as in Example 1 was carried out except for the change, and 33 g of phenylaminoated hydrophobic spherical silica particles were obtained.

[Example 3]
Step (A1): Synthesis step to obtain hydrophilic spherical silica particle dispersion In a 3 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer, 623.7 g of methanol, 41.4 g of water and 28% aqueous ammonia 49. 8.8 g was added and mixed. The solution was adjusted to 35 ° C. and the dropping of 1163.7 g (7.66 mol) of tetramethoxysilane and 418.1 g of 5.4% aqueous ammonia was started simultaneously with stirring, the former for 6 hours, and then. The latter was added dropwise over 4 hours. After completion of the dropping, the mixture was further hydrolyzed for 0.5 hour to obtain 2,295 g of a dispersion of hydrophilic spherical silica particles.

Step (A2): Surface treatment step with 1 functional silane compound 600 g (silica content 20% by mass, 120 g (2 mol)) of the dispersion obtained in the above (A1) is provided with a stirrer, a dropping funnel and a thermometer. The mixture was placed in a 5 liter glass reactor, and 9.7 g (0.06 mol) of hexamethyldisilazane was added and mixed at 25 ° C. This solution was heated to 60 ° C. and reacted for 3 hours to silylate the surface of hydrophilic spherical silica particles.

-Step (A3): Dispersion medium replacement step 1,600 g of methyl isobutyl ketone was added to the reaction vessel after the above step (A2). An ester adapter and a cooling tube are attached to a glass reaction vessel, heated to 80 to 110 ° C., and 1,457 g of a mixture of methanol and water is removed by concentration over 5 hours to remove 751 g of a hydrophobic spherical silica particle ketone solvent dispersion. (Silica content 16% by mass, 120 g (2 mol)) was obtained.

Step (A4): Step of phenylaminoizing the surface of the hydrophobic spherical silica particles 200 g of the hydrophobic spherical silica particles ketone solvent dispersion obtained in the above step (A3) (silica content 32 g, 0.53 mol). Into a 0.5 liter glass reactor equipped with a stirrer, dropping funnel and thermometer, 1.60 g (0.007 mol) of 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane. 5, 5% by mass (mass with respect to silica)) was added dropwise from the dropping funnel. The mixture was heated to 100 ° C. and reacted for 3 hours. Gas chromatography analysis of the reaction solution after the reaction for 3 hours confirmed the disappearance of the peak of 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane.

Step (A5): Resurface treatment step with 1 functional silane compound To the phenylaminoized spherical silica particle dispersion obtained in the above step (A4), 12.9 g (0.08) of hexamethyldisilazane from the dropping funnel was further added. Mol) was added and the reaction was carried out at a reaction temperature of 100 ° C. for 3 hours to silylate the surface of the phenylaminoized spherical silica particles. Then, the dispersion medium was distilled off under reduced pressure to obtain 33 g of phenylaminated hydrophobic spherical silica particles.

[Example 4]
In Example 1, the step (A5) was not performed, and after the step (A4) was completed, the dispersion medium was distilled off under reduced pressure to obtain 29 g of phenylaminoated hydrophobic spherical silica particles.

[Example 5]
Instead of the step (A1), a commercially available hydrophilic spherical silica particle dispersion (IPA-ST-L manufactured by Nissan Chemical Industry Co., Ltd., particle diameter 45 nm, 30 mass% isopropyl alcohol dispersion) was used.

Step (A2): Surface treatment step with 1 functional silane compound 350 g (silica content 30% by mass, 90 g (1.5 mol)) of IPA-ST-L and 250 g of isopropyl alcohol with a stirrer, dropping funnel and temperature. The mixture was placed in a 3 liter glass reactor equipped with a meter, and 12.8 g (0.08 mol) of hexamethyldisilazane was added and mixed at 25 ° C. This solution was heated to 60 ° C. and reacted for 3 hours to silylate the surface of hydrophilic spherical silica particles.

-Step (A3): Dispersion medium replacement step 1,200 g of methyl isobutyl ketone was added to the reaction vessel after the above step (A2). An ester adapter and a cooling tube are attached to a glass reaction vessel, heated to 80 to 110 ° C., 1,220 g of isopropyl alcohol is removed by concentration over 5 hours, and 575 g (silica-containing) of a hydrophobic spherical silica particle ketone solvent dispersion is added. Amount of 15.6% by mass, 90 g (1.5 mol)) was obtained.

Step (A4): Step of phenylaminoizing the surface of the hydrophobic spherical silica particles 200 g of the hydrophobic spherical silica particles ketone solvent dispersion obtained in the above step (A3) (silica content 30.4 g, 0.51). Mol) was placed in a 0.5 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer, and 1.52 g (0. 007 mol, 5% by mass (based on silica mass)) was added dropwise from the dropping funnel. The mixture was heated to 100 ° C. and reacted for 3 hours. Gas chromatography analysis of the reaction solution after the reaction for 3 hours confirmed the disappearance of the peak of 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane.

Step (A5): Resurface treatment step with 1 functional silane compound To the phenylaminoized spherical silica particle dispersion obtained in the above step (A4), 16.1 g (0.10) of hexamethyldisilazane from the dropping funnel was further added. Mol) was added and the reaction was carried out at a reaction temperature of 100 ° C. for 3 hours to silylate the surface of the phenylaminoized spherical silica particles. Then, the dispersion medium was distilled off under reduced pressure to obtain 33 g of phenylaminated hydrophobic spherical silica particles.

[Comparative Example 1]
In the step (A4) of Example 1, 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane was added to N-phenyl-3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd.). Synthetic spherical silica particles were synthesized in the same manner as in Steps (A1) to (A4) of Example 1 except that the product name was KBM-573) 1.8 g (0.007 mol, 5% by mass (% by mass of silica)). went. After the reaction at 100 ° C. for 3 hours in the step (A4), gas chromatography analysis of the reaction solution revealed that residual (13%) of N-phenyl-3-aminopropyltrimethoxysilane was observed. Then, a resurface treatment step was carried out in the same manner as in the step (A5) of Example 1, and finally, the dispersion medium was distilled off under reduced pressure to obtain 32 g of phenylaminoated hydrophobic spherical silica particles.

[Comparative Example 2]
In the step (A4) of Example 1, 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane was added to 3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-). 903) Spherical silica particles were synthesized in the same manner as in Steps (A1) to (A4) of Example 1 except that 1.2 g (0.007 mol, 5% by mass (based on silica mass)) was used. In the step (A4), the disappearance of the peak of 3-aminopropyltrimethoxysilane was confirmed by gas chromatography analysis of the reaction solution after the reaction at 100 ° C. for 3 hours. Then, a resurface treatment step was carried out in the same manner as in the step (A5) of Example 1, and finally the dispersion medium was distilled off under reduced pressure to obtain 33 g of aminoated hydrophobic spherical silica particles.

Toner was prepared using the silica particles synthesized in the above Examples and Comparative Examples, and the toner charge amount was measured, the image characteristics and the image flow (fog property) were evaluated.
[Toner charge amount]
1 g of model toner having an average particle size of 8.2 μm obtained by pulverizing and classifying styrene / acrylic resin, 19 g of standard carrier P-01 (distributed by the Imaging Society of Japan), and positively charged hydrophobic spheres produced in the above Examples and Comparative Examples. 0.01 g of each silica particle was weighed. When the sample prepared in this way was humidity-controlled and mixed according to the standard toner charge measurement standard of the Imaging Society of Japan (Journal of the Imaging Society of Japan, 37, 461 (1998)) and the mixing time was changed. The amount of toner charged was measured. A paint conditioner (manufactured by Toyo Seiki Co., Ltd.) was used for mixing, and a blow-off charge amount measuring device (manufactured by Toshiba Chemical Co., Ltd., trade name: TB203) was used for measuring the toner charge amount. Humidity control and measurement were performed at a temperature of 23 ± 3 ° C. and a humidity of 55 ± 10%. The results are shown in Table 2.

Further, the styrene / acrylic resin, the magnetic powder, the charge control agent, and the wax were melt-kneaded by a twin-screw extruder so as to have the following compounding composition. After cooling this, it was pulverized and classified to obtain toner particles having an average particle diameter of 8 μm.
Toner composition 100 parts by mass of styrene / acrylic resin Magnetic powder (BL-200; manufactured by Titanium Kogyo Co., Ltd.) 75 parts by mass Charge control agent (TP-415; manufactured by Hodogaya Chemical Co., Ltd.) 4 parts by mass Wax (Viscol TS) -200; manufactured by Sanyo Kasei Kogyo Co., Ltd. 4 parts by mass In addition, the particle size distribution of the obtained toner particles was measured, and 80% by mass or more of the total was distributed within the particle size range of 5 to 13 μm. It was confirmed.
0.5 parts by mass of the positively charged hydrophobic spherical silica particles (Examples 1 to 5 and Comparative Examples 1 and 2) were externally added to 100 parts by mass of the toner to prepare a positively charged toner. Then, using a Kyocera page printer (FS-3750), the image characteristics and image flow (fog property) of the positively charged toner were evaluated. A 2% printed original was used as the print-resistant printing pattern.
The results are shown in Table 3.

[Image characteristics]
Using the obtained positively charged toner, 200,000 sheets were actually printed by a Kyocera page printer (FS-3750), and based on the following criteria, the initial image characteristics, the image characteristics after printing, and the image under high temperature and high humidity conditions. The characteristics were evaluated.
The initial image characteristics (denoted as "initial" in Table 3) are the initial image by printing an image evaluation pattern in a normal environment (20 ° C., 65% RH), and the solid image density which is the image evaluation pattern is set to Macbeth. It was measured and evaluated using a reflection densitometer.
For the image characteristics after printing (denoted as "200,000 sheets" in Table 3), the image characteristics after printing 200,000 sheets are measured in the same manner as the initial image characteristics in a normal environment (20 ° C., 65% RH). And evaluated.
Further, for the image characteristics under high temperature and high humidity conditions (denoted as "high temperature and high humidity" in Table 3), the image evaluation pattern is printed under the high temperature and high humidity conditions (33 ° C., 85% RH) to initialize the image characteristics. It was measured and evaluated in the same manner as the image characteristics.

Evaluation Criteria ⊚: The image density is a value of 1.35 or more.
◯: The image density is a value of 1.3 or more and less than 1.35.
Δ: The image density is a value of 1.2 or more and less than 1.3.
X: The image density is a value less than 1.2.

[Fog]
Using the obtained positively charged toner, 200,000 sheets were actually printed by a Kyocera page printer (FS-3750) in the same manner as in the evaluation of image characteristics. And the fog property (skin fog) under high temperature and high humidity conditions was evaluated.

Evaluation criteria ○: No fog has occurred.
Δ: Slight fog has occurred.
X: Significant fog is occurring.

From the above results, it was found that by using the positively charged hydrophobic spherical silica particles of the present invention, the desired positively charged polarity and the amount of charge can be imparted to the toner, and this can be stably maintained for a long period of time.

Claims (6)

A positively charged hydrophobic sphere having a median diameter (D50) of 5 to 250 nm, a D90 / D10 ratio of 3 or less, and an average circularity of 0.8 to 1 in a volume-based particle size distribution. Silica particles
Positively charged hydrophobic spherical silica particles having an organosilicon compound represented by the following formula (I) bonded to the surface.

(In the formula, R ¹ and R ² independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms. N is 0 or 1.) The positively charged hydrophobic sphere according to claim 1, further surface-treated with a silica compound represented by the following formula (III), a monofunctional silane compound represented by the following formula (IV), or a mixture thereof. Silica particles.
R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
R ⁴ ₃ SiX (IV)
(In the formula, R ⁴ represents a monovalent hydrocarbon group having the same or different substituted or unsubstituted carbon atoms 1 to 6, and X represents a hydroxyl group or a hydrolyzable group.) The method for producing positively charged hydrophobic spherical silica particles according to claim 1 or 2, which comprises the following steps (A2) to (A4).
Step (A2): A hydrophilic spherical silica particle dispersion is mixed with a silazane compound represented by the following formula (III), a monofunctional silane compound represented by the following formula (IV), or a mixture thereof. 0.01 to 0.1 mol is added to 1 mol of Si atom of the particle dispersion, and _1/2 ^{unit of R 4} ₃ SiO is introduced on the surface of the hydrophilic spherical silica particles to obtain a hydrophobic spherical silica particle dispersion. Step R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
R ⁴ ₃ SiX (IV)
(In the formula, R ⁴ represents a monovalent hydrocarbon group having the same or different substituted or unsubstituted carbon atoms 1 to 6, and X represents a hydroxyl group or a hydrolyzable group.)

Step (A3): A step of substituting the dispersion medium of the hydrophobic spherical silica particle dispersion obtained in the step (A2) with a ketone solvent to obtain a ketone solvent dispersion of the hydrophobic spherical silica particles.

Step (A4): An organosilicon compound represented by the following formula (I) is added to the ketone solvent dispersion of the hydrophobic spherical silica particles obtained in the step (A3), and the surface of the hydrophobic spherical silica particles is surfaced. Step of phenylaminoing silanol groups

(In the formula, R ¹ and R ² independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms. N is 0 or 1.) The method for producing positively charged hydrophobic spherical silica particles according to claim 3, wherein the hydrophilic spherical silica particle dispersion is produced by the following step (A1).

Step (A1): A tetrafunctional silane compound represented by the following formula (II), a partially hydrolyzed condensate thereof, or a mixture thereof is placed in a mixed solution containing a hydrophilic solvent and water in the presence of a basic substance. Step of obtaining hydrophilic spherical silica particle dispersion by hydrolysis and condensation Si (OR ³ ) ₄ (II)
(In the formula, R ³ represents a monovalent hydrocarbon group having the same or different carbon atoms 1 to 6). The method for producing positively charged hydrophobic spherical silica particles according to claim 3 or 4, further comprising the following step (A5).

Step (A5): The silazan compound represented by the following formula (III), the monofunctional silane compound represented by the following formula (IV), or the monofunctional silane compound represented by the following formula (IV) is added to the phenylaminoized spherical silica particle dispersion obtained in the step (A4). A step of adding 0.01 to 0.3 mol of these mixtures to 1 mol of Si atoms of the phenylaminoized spherical silica particles and reacting them with silanol groups remaining on the surface of the phenylaminoized spherical silica particles R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
R ⁴ ₃ SiX (IV)
(In the formula, R ⁴ represents a monovalent hydrocarbon group having the same or different substituted or unsubstituted carbon atoms 1 to 6, and X represents a hydroxyl group or a hydrolyzable group.) A positively charged toner composition containing the positively charged hydrophobic spherical silica particles according to claim 1 or 2.