JP4279206B2 - External toner additive - Google Patents

Description

  The present invention relates to a novel external additive used for a dry toner for electrophotography. More specifically, the present invention provides an external additive for toner that uses silica as a base material, has chargeability controlled while maintaining its excellent fluidity-providing characteristics, and has excellent charge rising characteristics.

  The dry toner in the developer used in electrophotographic technology, which is indispensable for image forming apparatuses such as copying machines and printers, is intended to provide fluidity, improve toner charging efficiency, and control the amount of charge. External additives are widely used. As such an external additive, fine-particle silica, titania, alumina and the like are generally used, and among them, silica excellent in fluidity imparting characteristics is widely used.

  In recent years, with the expansion of the use of color toners and the finer particle size of toners for the purpose of forming high-definition images, the negative effects of toners on silica used as an external additive can be reduced without impairing the fluidity imparting characteristics. There has been a strong demand for a charge control technique that suppresses the charge amount to a smaller value. That is, when the charge amount of the toner is large, the toner composed of fine particles tends to have a larger variation in the surface charge amount of the individual particles than the toner composed of large particles, When using toner with such a wide charge distribution, the electrophotographic process that handles toner particles with a constant electric field is less accurate when moving individual toner particles to a specific position. It becomes difficult to achieve fine image formation. Therefore, as the toner particle size becomes smaller, control to a lower charge amount that enables a relatively narrow charge amount distribution is required.

  Conventionally, as a technique for suppressing the negative chargeability of silica, hydrophobic silica that has been surface-treated with an amino group-containing silane coupling agent has been proposed (see Patent Document 1).

  However, when hydrophobic silica surface-treated with an amino group-containing silane coupling agent is used for the toner, although there is an effect of suppressing the negative charge amount, the rising speed when frictionally charging the toner is small, There was a problem that the charge amount changed with time, and stable image formation could not be performed.

  On the other hand, as in the case of the amino group-containing silane coupling agent, for the purpose of controlling the negative charge amount, a proposal has been made to use hydrophobic silica particles whose surface is coated with aqueous titanium oxide, aluminum oxide, etc. as an external additive. (See Patent Document 2).

  However, the silica in which titanium oxide or the like is adhered to the particle surface by the wet method as described above has been found to have a certain effect of suppressing the negative charge amount, but has no effect of improving the charge rising speed.

  Not only that, it is due to the fact that the attachment of titanium oxide or the like to the surface of the silica particles is carried out in water, that is, “treatment under wet conditions” in which fumed silica is dispersed in an aqueous solvent. There is a problem that coarse particles in which silica particles are aggregated are generated, and the fluidity imparting characteristics inherent in silica are remarkably lowered. Moreover, about the process state, the titanium oxide etc. coarsened and the state which was mixed with the silica particle nonuniformly was observed.

Japanese Patent No. 2140389 JP 2002-29730 A

  Therefore, an object of the present invention is to control the toner charge to a moderately low charge amount, to improve the charge rising characteristics and the toner charge amount stability over time, and to have a high fluidity imparting effect. It is to provide an agent.

  As a result of extensive research, the inventors of the present invention have made the metal oxide adhere to the surface of the silica particles by bringing the silica into contact with the vapor or mist of the metal alkoxide and then bringing it into contact with the water vapor. Silica deposited by treatment under a dry process exhibits a significant improvement in the charge rise rate when silica is mixed with resin particles, which was not manifested by the conventional treatment by metal oxide deposition under wet conditions. I found out. In addition to the above treatment, a treatment agent having a basic group such as an amino group-containing silane coupling agent is brought into contact with silica in a vapor or mist form, that is, the treatment agent is applied to the surface of the silica particles by a dry treatment. It has been found that, by adhering, the charge level of the silica can be suitably controlled to an appropriate low charge amount without hindering the effect of improving the charge rising speed due to the adhesion of the metal oxide. Furthermore, it was confirmed that the fluidity imparting characteristics inherent to silica can be maintained at a high level through such a series of treatments under dry conditions, and the present invention has been completed.

That is, the present invention includes the following steps (A), (B) and (C), and is performed in the order of step (C) after the steps (A) and (B) at the same time. After that, by carrying out the steps (B) and (C) in the same order, or by sequentially carrying out the steps (A), (B) and (C), a metal other than silica alone is formed on the surface of the silica particles. An external additive for toner, comprising a surface-treated silica to which an oxide, a treatment agent having a basic group, and a hydrophobizing agent are attached.
Step (A) The silica is brought into contact with a metal alkoxide vapor or mist to adhere the metal alkoxide to the silica surface, and then brought into contact with water vapor to hydrolyze the metal alkoxide attached to the silica surface to thereby convert the metal oxide into the metal alkoxide. A process of adhering to the surface of silica particles.
Process (B) The process which makes a silica contact the vapor | steam or mist of the processing agent which has a basic group, and makes a processing agent adhere to the silica particle surface.
Step (C) A step of bringing silica into contact with the hydrophobizing agent vapor or mist to adhere the hydrophobizing agent to the surface of the silica particles.

  As described above, the toner external additive obtained by the series of dry production methods of the present invention has an appropriate low chargeability and an excellent charge rising property, and also has an excellent fluidity imparting property. Have.

  Further, the toner using the external additive for toner of the present invention has remarkably stable charging performance against changes in environmental atmosphere such as temperature and humidity. That is, the external additive for toner of the present invention is silica that provides excellent environmental stability.

  When the effect of imparting fluidity to particles such as toner is high as in the toner external additive of the present invention, when the toner is frictionally charged, carrier particles are used in the two-component development method, and rubber is used in the one-component system. Since the contact efficiency with a friction probe for charging such as a metal blade or a metal blade is improved, it is presumed that a quick rise of charging is achieved.

Since the external additive for toner of the present invention is a silica having a uniform surface coating using a combination of a basic processing agent and a metal oxide,
(1) The negative charge amount can be controlled to an arbitrary charge level on the positive charge side.
(2) Charging rise characteristics are greatly improved.
(3) Does not impair the fluidity-imparting properties of the toner with silica. (4) It also has the characteristics of excellent charging environmental stability, and solves the problems that cannot be achieved with conventional external additives. Can do.

  In the external additive for toner of the present invention, each characteristic value obtained by a measurement method described later has an index representing a charge level of −85 or more, a charge rising coefficient of 0.80 or more, and an M value indicating hydrophobicity. 35 to 80, in particular, high performance is exhibited such that the index representing the charge level is −80 or more, the rising coefficient of charge is 0.85 or more, and the M value indicating hydrophobicity is 40 to 75.

  Hereinafter, the present invention will be described in more detail and specifically.

(Silica as the base material)
The silica used as the base material for the toner external additive of the present invention is not particularly limited, and is obtained by a known method such as a dry method such as a flame hydrolysis method or a melting method, a wet method such as a precipitation method or a sol-gel method. Of these, “fumed silica” produced by a dry method is preferred because of its excellent fluidity-providing properties for toner.

  The fumed silica can be produced by burning a silicon compound, in particular a silicon halide, generally a silicon chloride, usually purified silicon tetrachloride, in an oxyhydrogen flame. Such silica is sometimes referred to as “dry silica” or “vapor phase silica” in order to distinguish it from silica produced by a wet method such as precipitated silica.

There is no particular limitation on the physical properties of the silica, if illustrate preferred range, for example, in the case of fumed silica, a specific surface area of 10 to 400 m ² / g, in particular, available as general-purpose products 50 to 380 m ² / g Are preferred.

  The primary particle diameter of the silica particles is generally 5 nm to 1 μm, preferably 10 nm to 500 nm.

  In addition, in the present invention, in addition to a mode in which a single type of silica is used, a mode in which a plurality of types of silica, for example, a plurality of silicas having different specific surface areas are mixed and used in an appropriate amount is also employed. can do.

  In the present invention, the silica adsorbed water serving as the base material is less than 0.1% in advance and preferably 0.05% before the metal oxide and the treatment agent having a basic group are adhered. In order to improve the fluidity-imparting property of the toner external additive of the present invention, it is preferable to reduce the content to less than 0.01%, more preferably less than 0.01%. The adsorbed water in this case generally refers to water called physical adsorbed water, and is measured by weight loss due to drying at 105 ° C. for 2 hours.

  As a method for reducing the adsorbed water of silica as described above, for example, silica as a base material is put in a reaction vessel heated to 100 to 400 ° C., preferably 120 to 350 ° C., and dehydrated nitrogen or the like is used. The inert gas can be achieved by sufficiently circulating, for example, over 2 hours. It is also possible to reduce the amount of adsorbed water by partially treating the hydrophilic silica used as the base material with a hydrophobizing agent in advance to make a part of the silica particle surface hydrophobic to give a slight water repellency. This is an effective technique.

(Metal oxide adhesion to the surface of silica particles)
The external additive for toner of the present invention is characterized in that a metal oxide is adhered to the surface of silica particles as a base material by treatment under a dry process.

  In the present invention, “treatment under a dry process” is an expression for distinguishing from “treatment under a wet process” in which silica is dispersed in a solvent such as water or an organic compound and contacted with a treatment agent. All aspects of contacting the silica with the treatment agent while maintaining the state are included. For example, the aspect which sprays a processing agent and makes it contact in mist form other than the aspect which uses a processing agent as a vapor | steam is mentioned.

  Silica having a metal oxide attached to the surface by the above-described treatment under the dry process maintains the fluidity imparting characteristics inherent to silica at a high level, and, as described above, the toner to which the silica is externally added is rubbed. The effect of increasing the rising speed of charging when charged is exhibited.

  On the other hand, silica, which is a conventional method, in which silica is dispersed in a solvent such as water or an organic compound and processed, and the metal oxide is attached by processing under wet conditions, imparts the fluidity inherent to silica. The characteristics are significantly deteriorated, and the rising speed of charging is not improved.

  About the difference of the said effect, it estimates as follows.

  In conventional wet processing, silica particles aggregate in the drying process to remove the solvent and coarse particles are generated. Therefore, when externally added to the toner, the silica is uniformly dispersed on the toner particle surface. Therefore, it is presumed that the fluidity-imparting property is remarkably deteriorated. On the other hand, in the treatment under the dry method of the present invention, silica is not immersed in a liquid solvent, so that aggregated particles are not generated, and it is estimated that the original fluidity imparting characteristics are maintained. .

  In the case of treatment under wet conditions, before the metal alkoxide of the treatment agent reacts with the surface of the silica particles, it self-reacts in a solvent to form a domain, and then adheres to the silica surface. Since oxide particles and silica are mixed, it is presumed that the rising speed of charging is not improved. On the other hand, in the treatment under the dry process of the present invention, the metal alkoxide adheres to the surface of the silica particles in the form of vapor or mist, and is hydrolyzed with water vapor, so that it is an extremely fine metal of several to several tens nm level. It is presumed that the rising speed of charging is improved because the oxide adheres uniformly and densely on the surface of the silica particles.

  As a result of observing the external additive for toner of the present invention with a transmission electron microscope, the metal oxide adhering to the silica was not observed as a lump or as an independent particle. Even in the result of mapping the Si element and the attached metal element by TEM-EELS, there was no bias in the distribution of both elements, so that uniform adhesion of the metal oxide could be confirmed. That is, the fine and uniform adhesion of the metal oxide is a feature of the toner external additive of the present invention, and has excellent charge rise characteristics and fluidity that could not be achieved with conventional silica. It is considered that favorable effects such as property imparting characteristics are exhibited.

  Therefore, the surface-treated silica as an external additive for toner of the present invention is substantially composed of a metal oxide lump, specifically, a coarse portion of metal oxide exceeding 20 nm, preferably a large lump exceeding 10 nm. It is also mentioned as a feature that it does not exist.

  Although the mechanism by which the above-described metal oxide is uniformly and densely adhered to significantly improve the charge rising speed is not clear, the present inventors presume as follows.

  That is, since the surface of the silica particles is uniformly coated with a different type of metal oxide by surface treatment under a dry process, charge transfer is facilitated at the interface between the silica and the metal oxide. It is considered that the charge rising speed is increased as a result of the charge moving to the whole particle quickly through the interface and being homogenized.

  In addition, a method in which a metal halide such as silicon tetrachloride and a metal halide compound as a metal oxide raw material are simultaneously fed into a flame as particles in which a metal oxide is uniformly dispersed in silica particles, that is, flame There is a method for producing a composite oxide or mixed oxide containing silica by a hydrolysis method. However, such composite oxide particles or mixed oxide particles cannot achieve a state in which the surface of the silica particles is uniformly coated with the metal oxide due to the difference in melting point and crystallization temperature between silica and other metal oxides. As in the case of the wet processing, the effect of improving the charge rising speed is not expected.

  In the present invention, the metal oxide is not particularly limited as long as it is a metal oxide other than silica alone. It may be a metal oxide of a single metal species, a composite oxide composed of a plurality of metal species, or a mixed oxide. In particular, when the metal element constituting the metal oxide is one or more selected from Al, Ti, Zr, Sn, Zn, and Mg, it is preferable because the surface-coated metal oxide is not colored. is there.

  The metal oxide may be a complex oxide with Si.

  Further, among the above metals, Al or Ti is preferable because it can be easily treated in a dry process with a metal alkoxide, which will be described later, and has a large effect of improving the rising speed of charging.

  In the present invention, the adhesion amount of the metal oxide to the silica is not particularly limited, but a particularly effective amount is exemplified by M / Si (M is a metal element derived from a metal alkoxide) in terms of an element molar ratio. Si is silicon derived from silica as a base material.) 0.001 to 0.5, preferably 0.01 to 0.3. It is preferable for imparting moderately low chargeability and excellent charge rise characteristics to the silica.

  Specifically, the amount of metal oxide deposited can be determined by a known method such as X-ray fluorescence analysis or ICP emission analysis after dissolving the toner external additive of the present invention with a mixed acid of hydrofluoric acid and nitric acid. Can be measured.

  The amount of metal oxide adhesion measured by such a method cannot be generally specified because the optimum value varies depending on the type of metal element, the properties of the added toner, and the electrophotographic system used. Specifically, the standard is 0.1 to 30% by weight, preferably 0.5 to 20% by weight in terms of metal oxide in the toner external additive.

  In the present invention, the method of attaching the metal oxide to the surface of the silica particles by the treatment under the dry method is to contact the silica and the metal alkoxide under the dry method to attach the metal alkoxide to the surface of the silica particles, and then apply it. It can be suitably carried out by a method (step (A)) in which metal alkoxide adhering to the particle surface is brought into contact with water vapor and hydrolyzed.

  In the present invention, the method of bringing silica and metal alkoxide into contact with each other under a dry method is not particularly limited as long as silica is not immersed in a solvent such as water or an organic compound.

  Specific methods for contact treatment under a dry method include a method in which a metal alkoxide vapor transported with a carrier gas such as nitrogen is circulated to and contacted with silica in a fluidized bed or a liquid metal alkoxide stock solution or solution is sprayed. For example, there is a method of making it into a mist form by contact with silica under stirring. Among these, the embodiment in which the metal alkoxide is contacted in the form of mist can be easily carried out, and the reaction efficiency between the metal alkoxide and silica is high, which is preferable.

  In the embodiment in which the above metal alkoxide is contacted in a mist form, the liquid metal alkoxide remains as a stock solution, and a highly viscous liquid or solid liquid is a hydrocarbon solvent such as alcohol, ether, hexane or toluene. It is preferable to dilute or dissolve with a non-aqueous solvent such as silicone oil, and supply it into the reactor in the form of a mist with a spray nozzle or the like.

  The particle size of the mist is not particularly limited because it varies depending on the type and concentration of the metal alkoxide, the viscosity of the liquid, and the form and size of the spraying device and the size and shape of the reaction device, but is generally several μm to several hundreds. The smaller one is preferable. As a spraying method, a commonly used spray nozzle, atomizer, or the like can be used, and a one-fluid nozzle that forms a mist by pressurizing and passing through a small-diameter orifice is particularly suitable.

  As the metal alkoxide used in the present invention, a compound represented by the following general formula (1) is used without particular limitation.

M (OR) _n (1)
(However, M represents a metal element, R represents an alkyl group, and n represents an integer. When n is 2 or more, R may be the same alkyl group or a plurality of alkyl groups having different carbon numbers and structures. Good.)
The metal element (M) in the general formula is not particularly limited, but Al, Si, Ti, Zr, Sn, Zn, and Mg are preferable. Further, the alkoxy group (RO) is not particularly limited, but methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group and the like are common. Is preferred.

  Specific examples of the metal alkoxide used in the present invention include trimethoxyaluminum, triethoxyaluminum, tri-iso-propoxyaluminum, tri-n-butoxyaluminum, tri-sec-butoxyaluminum, tri-tert-butoxyaluminum. , Mono-sec-butoxydi-iso-propylaluminum, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetramethoxytitanium, tetraethoxytitanium, tetra-iso-propoxytitanium, tetra-n-propoxytitanium, tetra -N-butoxy titanium, tetra-sec-butoxy titanium, tetra-tert-butoxy titanium, tetraethoxy zirconium, tetra-iso-propoxy zirconium, tetra-n Butoxyzirconium, dimethoxytin, diethoxytin, di-n-butoxytin, tetraethoxytin, tetra-iso-propoxytin, tetra-n-butoxytin, diethoxyzinc, magnesium methoxide, magnesium ethoxide, magnesium isopropoxide, Examples include magnesium methoxyethoxide. Of these, mono-sec-butoxydi-iso-propylaluminum, tetra-iso-propoxytitanium, and tetra-n-butoxyzirconium are easily available and particularly preferred.

  Furthermore, there is no problem as a metal alkoxide defined in the present invention even when a combination of compounds that react to produce a metal alkoxide, for example, a metal halide dissolved in an alcohol is used.

  However, for the purpose of attaching a metal oxide, it is conceivable to use a metal halide represented by a metal chloride such as titanium tetrachloride or aluminum chloride directly as a treatment agent instead of a metal alkoxide. The halide has an acidity that prevents a sufficient amount of metal oxide from adhering to the silica, and tends to make the charge control unstable due to halogen remaining in the resulting toner external additive.

  In addition, in order to increase the reactivity of the metal halide, the treatment temperature is set to a high temperature of, for example, 500 ° C. or higher, the adsorbed water, for example, 1% or more of the physical adsorbed water is applied to the base silica in advance, or the reaction is performed. If a method of adding a similar amount of water vapor to the system is employed, the fluidity imparting characteristics of the surface-treated silica particles obtained tend to deteriorate.

  This is because the metal halide is thermally decomposed at a high temperature or hydrolyzed by water vapor before the base silica and the metal halide come into contact with each other. This is probably because the oxide layer cannot be formed.

  In the present invention, the treatment can be carried out by using one kind of the metal alkoxide alone, mixing a plurality of kinds, or using them step by step.

  In addition, a preferred embodiment for contacting a metal alkoxide with silica under a dry process will be described in more detail.

  When the contact treatment between the metal alkoxide and silica is carried out in a closed container, the silica surface reacts sufficiently with the metal alkoxide, and the silica surface can be efficiently coated with the metal oxide by the subsequent hydrolysis treatment. Therefore, it is preferable.

  Further, by carrying out the treatment at a temperature of 100 to 400 ° C., preferably 120 to 350 ° C., the reaction between silica and the metal alkoxide is promoted, and the partial pressure of the metal alkoxide vapor is increased, thereby increasing the amount of the metal oxide. A uniform coating state is easily achieved, and further, there are advantages such as easy removal of a solvent in which alcohol or metal alkoxide generated in the reaction is dissolved out of the system. At a high temperature exceeding 400 ° C., the metal alkoxide is likely to be thermally decomposed before coming into contact with the silica of the base material, which tends to be a factor that inhibits the adhesion of fine and uniform metal oxides.

  Further, the treatment time is not particularly limited because it varies depending on conditions such as the properties of silica, the type of metal alkoxide, the treatment temperature, etc. Generally, it is preferably 5 minutes to 3 hours.

  The silica having the metal alkoxide attached to the particle surface by the above treatment is brought into contact with water vapor to hydrolyze the metal alkoxide attached to the surface to form a metal oxide coating layer on the base silica.

  Also in this case, as described above, when hydrolyzed by immersion in a solvent such as water or an organic compound containing water, that is, when the treatment is performed under a wet condition, the fluidity of the surface-coated silica obtained as described above is imparted. The characteristics deteriorate and the object of the present invention cannot be achieved.

  In addition, when hydrolysis is not performed, a large amount of undecomposed alkoxy groups remain in the metal alkoxide attached to the base material, and the hydrophobization efficiency in the next step tends to be low. Further, when it is used as an external additive for toner, the charging characteristics fluctuate with time depending on the environmental atmosphere such as humidity and temperature, which is not preferable.

  The hydrolysis method is not particularly limited as long as it is a method in which the base silica after the metal alkoxide is dry-treated is brought into contact with water vapor in a dry manner and is not immersed in a solvent such as water or an organic compound.

  As a specific hydrolysis method, the silica after the metal alkoxide is dry-treated is stirred or in a fluidized bed, water vapor is directly circulated, water vapor is introduced by adjusting the partial pressure together with a carrier gas such as nitrogen. Examples thereof include a method and a method of introducing water vapor to a reactor and introducing water vapor. Hydrolysis with water vapor may be carried out in either a closed system or an open system. An acid-base catalyst such as ammonia may be added to the water vapor for the purpose of increasing the hydrolysis efficiency.

  In addition, the temperature of the hydrolysis treatment is not particularly limited as long as it is a temperature at which water vapor and the silica to which the metal alkoxide is attached can be contacted. Generally, the conditions are selected from the temperature range of 50 to 350 ° C. do it. In particular, the treatment is preferably performed at a temperature exceeding the dew point of water vapor.

(Adhesion of treatment agent having basic group to silica particle surface)
In the present invention, the purpose of attaching the treatment agent having a basic group is to exhibit a function of suppressing the negative charge amount when the toner is frictionally charged when silica is used as an external additive, Such a treatment agent is made of a compound that has a functional group that reacts with water to exhibit alkalinity or an electron-donating functional group in the molecule and that can be chemically or physically attached to the surface of the silica particles. If it is a thing, it will not restrict | limit in particular.

  The charge level is controlled by the basic strength and amount of the treating agent. For example, in a silane coupling agent containing an amino group, the basic strength is in the order of a tertiary amino group, a secondary amino group, a primary amino group, and an aromatic amino group. The effect of suppressing the amount is great.

  In the present invention, preferred basic groups include primary amino groups, secondary amino groups, tertiary amino groups, aromatic amino groups, quaternary ammonium bases and the like.

  Specific treating agents include N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl). -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, N-phenyl-3 -Aminopropyltrimethoxysilane, N-ethyl-3-aminopropyltrimethoxysilane, N-butyl-3-aminopropyltrimethoxysilane, N, N-diethyl-3-aminopropyltrimethoxysilane, N, N-dibutyl -3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -3-amino Propyltrimethoxysilane hydrochloride, octadecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride, tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride, N-trimethoxysilylpropyl-N, N, N-tri-n Primary amino groups such as -butylammonium bromide, N-trimethoxysilylpropyl-N, N, N-tri-n-butylammonium chloride, N-trimethoxysilylpropyl-N, N, N-trimethylammonium chloride, One or more silane coupling agents containing a secondary amino group, a tertiary amino group, an aromatic amino group, or a quaternary ammonium base, or a treating agent such as an amino-modified silicone oil can be used.

  Further, amines represented by the following general formula (2) can also be used as the treating agent having a basic group.

NR ₁ R ₂ R ₃ (2)
(However, N represents nitrogen, R ₁ , R ₂ , R ₃ represent hydrogen or a hydrocarbon group. R ₁ , R ₂ , R ₃ may be the same hydrogen or hydrocarbon group, carbon (It may be a hydrogen or hydrocarbon group having a different number or structure, including the case where the hydrocarbon chain contains nitrogen.)
Among such amines, those having a total carbon number of 3 to 30 of hydrogen or hydrocarbon groups of R ₁ , R ₂ , and R ₃ are preferable because the treatment under a dry process described later can be easily performed. Further, the basic strength of these amines varies depending on the combination of R ₁ , R ₂ and R ₃ , and thus cannot be defined unconditionally. In general, however, tertiary amines, secondary amines, primary amines, The order is aromatic amine.

  Examples of specific amines are isopropylamine, cyclobutylamine, n-butylamine, tert-butylamine, n-pentylamine, isopentylamine, tert-amylamine, cyclohexylamine, n-hexylamine, n-heptylamine, n -Primary amines such as octylamine, 2-ethylhexylamine, 1,1,3,3-tetramethylbutylamine, diethylamine, diisopropylamine, di-n-butylamine, diisobutylamine, dipentylamine, N-methylhexylamine, Secondary amines such as dicyclohexylamine, dihexylamine, di-n-octylamine, Nn-butylaniline, triethylamine, N, N-dimethylcyclohexylamine, N, N-diethylcyclohexylamine, -Tertiary amines such as n-butylamine, trihexylamine and trioctylamine, polyamines such as ethylenediamine, diethylenetriamine, hexamethylenetetramine and tetraethylenepentamine, and cyclic amines such as pyrrolidine, piperidine, piperazine, pyrazolidine and pyrrole And derivatives thereof.

  Further, pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2-propylpyridine, 3-propylpyridine, 4-propylpyridine, 2 , 3-dimethylpyridine, 2,4-dimethylpyridine, 2,5-dimethylpyridine, 2,6-dimethylpyridine, 3,4-dimethylpyridine, 3,5-dimethylpyridine, 2-ethyl-4-methylpyridine, 2-ethyl-6-methylpyridine, 3-ethyl-4-methylpyridine, 3-ethyl-6-methylpyridine, 4-ethyl-2-methylpyridine, 2,3,4,5-tetramethylpyridine, 2, Pyridines such as 3,4,6-tetramethylpyridine and 2,3,5,6-tetramethylpyridine, pyrazines and pyrimidines , Pyrimidazole, 1- (2-pyridyl) pyrrole, 2- (2-pyridyl) pyrrole, 2- (3-pyridyl) pyrrole, pyridylmethylamine, β-2-pyridylstyrene, β-4-pyridylstyrene, 3- Consists of conjugated heterocycles containing nitrogen atoms such as (2-pyridyl) piperidine, 2- (2-pyridyl) pyrrolidine, 2- (3-pyridyl) pyrrolidine, cytosine, uracil, thymine, 5-methylcytosine, oxymethylcytosine, etc. A compound having a basic group is also exemplified as the treating agent.

  Of these, a silane coupling agent containing an amino group in the molecule is particularly preferable because it is easy to handle and has high processing efficiency.

  Further, the amount of the treatment agent having a basic group cannot be generally limited because the charge level required for the toner differs depending on the electrophotographic system, but it is 0.1 to 20 weights with respect to 100 parts by weight of silica. Part, preferably 0.5 to 15 parts by weight is suitable when the cost such as reaction efficiency and treatment agent price is compared with the effect of low charging.

  The adhesion of the treatment agent having a basic group to the surface of the silica particles is performed by a treatment under a dry process, as in the case of the adhesion of the metal oxide, while maintaining the effect due to the adhesion of the metal oxide. This is necessary for fully exhibiting the effect of the treating agent having a basic group and maintaining high fluidity-imparting characteristics of silica.

  On the other hand, in the case of a treatment under a wet process in which it is dispersed in a solvent such as water or an organic compound, the silica particles aggregate in a drying process for removing the solvent, and coarse particles are generated. There arises a problem that the fluidity-imparting property is lowered.

  In wet processing, it is presumed that processing agents form domains, for example, silane coupling agents containing amino groups may react with silica after forming oligomers in a solvent. The Therefore, the surface of the silica particles is unevenly coated with amino groups, and the charge amount of the individual silica particles can be varied, thereby causing a wide distribution in the charge amount of the toner and hindering high-precision image formation. End up.

  In the present invention, the treatment under a dry process with a treating agent having a basic group is specifically preferably carried out by a method (step (B)) in which the treating agent is brought into contact with silica in a vapor or mist form. be able to. The said contact can be implemented by a fluidized bed, a stirrer, etc. similarly to adhesion of the said metal oxide.

(Adhesion of hydrophobizing agent to silica particle surface)
The toner external additive of the present invention is further preferably, as a preferred embodiment, a hydrophobizing agent attached by a dry process.

  Generally, the toner is required to exhibit a stable charging behavior regardless of the environmental atmosphere such as the temperature and humidity used. In order to obtain such environmental stability, the external additive for toner is generally hydrophobized for the purpose of minimizing the influence of humidity.

  In the present invention, by attaching a hydrophobizing agent, the function of suppressing the negative charge amount when externally added to the toner resin caused by the adhesion of the treatment agent having the metal oxide and the basic group, and rapid charging It is possible to exhibit a stable rise characteristic extremely stably regardless of the environmental atmosphere.

  The amount of the hydrophobizing agent used is not particularly limited because the degree of hydrophobization varies depending on the type of hydrophobizing agent, but the hydrophobizing degree is an M value described later, and is in the range of 35 to 80, particularly 40 to 75. It is preferable to adjust the adhesion amount so that the external additive for toner has high charging stability with respect to the environment and is easy to handle.

  The surface treatment of silica with the hydrophobizing agent can be suitably performed by a step (step (C)) of bringing silica and the hydrophobizing agent into contact with each other in a dry manner and attaching the hydrophobizing agent to the surface of the silica particles. .

  Specifically, a method in which silica is brought into contact with the hydrophobizing agent vapor under stirring, a method in which the hydrophobizing agent is sprayed into a mist form, and the like are preferably employed. Such a contact operation is the same as the above-described operation. In addition, it can be carried out in a fluidized bed or a stirring device.

  The said hydrophobizing agent can be used without restrict | limiting a well-known processing agent at all. Specifically, as a silylating agent, chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tert-butyldimethylchlorosilane, vinyltrichlorosilane, tetramethoxysilane, methyl Trimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltrimethoxysilane, iso-butyltrimethoxysilane, hexyltrimethoxy Silane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysila , Dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, iso-butyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxy Alkoxysilanes such as silane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexa Butyldisilazane, hexapentyldisilazane, hexahexyldisilazane, hexacyclohexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, dimethyltetrabini There is silazanes such as disilazane. Also, dimethyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil, alkyl modified silicone oil, chloroalkyl modified silicone oil, chlorophenyl modified silicone oil, fatty acid modified silicone oil, polyether modified silicone oil, alkoxy modified silicone oil, Silicone oil such as diol-modified silicone oil, fluorine-modified silicone oil, and terminal-reactive silicone oil, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, octamethyltrisiloxane Siloxanes such as are also preferred as hydrophobizing agents. Of these, silylating agents are the most common, and alkoxysilanes and silazanes are preferred because they can be easily hydrophobized. In the present invention, one type of such a hydrophobizing agent is used alone, or in the case of two or more types, mixed, or sequentially processed step by step, which is required according to individual electrophotographic systems. Hydrophobicity can be achieved.

  The hydrophobized silica obtained by the above method has excellent water repellency in addition to the characteristics of the silica produced by the steps (A) and (B), and the toner charging performance against humidity change. Becomes remarkably stable.

(Silica surface treatment order)
In addition, description is added about the implementation order of the said process (A)-(C).

The order of the steps (A) to (C) is the same as the steps (A) and (B), followed by the step (C), after the step (A), and the steps (B) and (C). The steps (A), (B), and (C) are sequentially performed in the same order. Step allowed to adhere step allowed to adhere to the metal oxide (A) and a basic group-containing treatment agent (B) may be carried stepped on sequential stage or step (A) and (B) at the same time However, it is preferable that the step (A) is performed first, the metal oxide is uniformly coated on the surface of the base material, and then the step (B) is performed.

The step regard (B) a hydrophobic treatment step (C), may be carried out sequential processing or, although step (B) and (C) may be carried out simultaneously, the step (B) It is better to carry out the step (C) after first carrying out the process and sufficiently attaching the basic group-containing treatment agent to the surface.

(Application as an external additive for toner)
The present invention is an external additive for an electrophotographic toner comprising such surface-coated silica. Below, the application to this use is demonstrated.

  As a toner to which the external additive for toner of the present invention can be applied, any of black toner and color toner can be used, and any electrophotographic system such as magnetic one component, non-magnetic one component, two component, etc. Can also be used. The binder resin for the toner can also be applied without particular limitation, such as commonly used styrene / acrylic copolymer resins, polyester resins, epoxy resins and the like. In addition, the toner production method can be applied without problems even to a so-called chemical toner obtained by a polymerization method such as suspension polymerization or emulsion polymerization or a dissolution suspension method as well as a mainstream pulverization / kneading method.

  The toner external additive of the present invention can also be applied to toners that are arbitrarily blended with other toner constituent materials. Black colorants, color colorants such as cyan, magenta, and yellow, positive and negative charge control agents, and release agents such as wax can be used without any limitation in materials normally used in this field.

  The amount of the external additive of the present invention added to the toner is not particularly limited as long as the obtained toner has desired characteristics, but is usually 0.05 to 5% by weight, preferably 0.1 to 0.1%. The amount is preferably 4% by weight and can be added to the toner by a known method.

  Further, when the toner is produced, the external additive of the present invention is not necessarily used alone, and if necessary, a hydrophobic silica other than the external additive of the present invention may be combined, titania, alumina, etc. Other additives such as oxide fine particles other than silica, lubricants such as Teflon (registered trademark), zinc stearate, and polyvinylidene fluoride, or fixing aids such as polyethylene and polypropylene may be used in combination as necessary. Is possible.

  EXAMPLES Hereinafter, examples and comparative examples will be shown to specifically describe the present invention, but the present invention is not limited only to these examples.

  A method for measuring physical properties of the toner external additive of the present invention is as follows.

(Measurement of charge amount)
A pseudo toner was prepared by mixing a polyethylene resin (PEW-2000 manufactured by Seishin Enterprise Co., Ltd., average particle size: 8 μm) so that the sample was 2% by weight. 1 g of this pseudo toner and 99 g of ferrite carrier were placed in a sample bottle and conditioned for 24 hours in a constant temperature and humidity chamber at 25 ° C. and 50% relative humidity. The sample bottle is rotated and mixed at 100 rpm using a desktop roller mill, and charged with a blow-off powder charge measuring device TB-200 manufactured by Toshiba Chemical Corporation under conditions of a blow gas pressure of 0.1 MPa and a blow time of 30 seconds. The amount was measured.

  The value at the time of mixing for 60 minutes was adopted as the charge amount. The charge amount was displayed as a relative value with the value of the sample of Comparative Example 1 described later as “−100”, and this was used as an “index indicating the charge level”. When this value is larger than −100 (a value on the positive side from −100), it is determined that the negative charge amount suppressing effect of the present invention is effective. Depending on the electrophotographic system, the surface-treated silica may be produced to have a positive value.

  The rising speed of charging is expressed as a ratio of the charging amount at the time of mixing for 5 minutes / mixing for 60 minutes, and this is referred to as “charging rising coefficient”. The coefficient is evaluated to be better as the rising property of charging is closer to 1. However, if this value exceeds 1, there is a return of charge amount (a phenomenon in which a large charge amount is taken and then changes to a low charge amount over time), which is not preferable.

(Evaluation of fluidity imparting characteristics)
A silica sample was added to a crosslinked acrylic resin powder (MX-1000 manufactured by Soken Chemical Co., Ltd., average particle size 10 μm) so as to be 1% by weight, and the mixture was sufficiently mixed with a mixer. This was conditioned at 25 ° C. and 50% relative humidity. The fluidity of the mixed powder sample was evaluated by measuring the degree of compression with a powder tester (manufactured by Hosokawa Micron Corporation, PT-R type). The degree of compression is expressed by the following equation (3).

上記圧縮度の値は、小さいほど流動性付与特性が良好と判定する。

The smaller the value of the degree of compression, the better the fluidity imparting characteristics.

(Measurement of hydrophobicity (M value))
0.2 g of sample was added to 50 ml of water in a 250 ml beaker and stirred with a magnetic stirrer. To this, methanol was added using a burette, and titration was performed with the end point when the entire amount of the sample powder was wetted and suspended in the solvent in the beaker. At this time, the tube was introduced into the solution by a tube so that the sample did not directly touch the sample. The volume% of methanol in the methanol-water mixed solvent at the end point was defined as the degree of hydrophobicity (M value).

(Quantification of metal oxides by ICP emission spectrometry)
A 1.0 g sample was weighed and immersed in 10 ml of a mixed acid in which 50% hydrofluoric acid and 69% nitric acid were mixed at a volume ratio of 1: 1. The solids were completely dissolved with occasional shaking. 1 ml was taken from this solution, placed in a platinum crucible, 1 ml of concentrated sulfuric acid was added, and the mixture was heated on a hot plate heated to 200 ° C. until white smoke appeared. After cooling, it was transferred to a volumetric flask and pure water was added to make up a total volume of 100 ml. This prepared solution was applied to an ICP emission analyzer (Plasma emission spectroscopic analyzer SPS1500VR manufactured by Seiko Denshi Kogyo Co., Ltd.), and the metal concentration in the prepared solution was measured. The detected metal concentration was converted to oxide and calculated as the weight percent per sample.
(Environmental stability)
A pseudo toner sample was prepared that was allowed to stand for 2 days at 35 ° C. and 85% relative humidity as a high temperature and high humidity condition (HH condition), and at 10 ° C. and 15% relative humidity as a low temperature and low humidity condition (LL condition). After mixing for 60 minutes under humidity, the charge amount was measured in the same manner as described above. The smaller the difference in charge amount between the HH condition and the LL condition, the better the environmental stability.

  In the following examples and comparative examples, the treatment amounts of the basic group-containing treatment agent, metal alkoxide, and hydrophobizing agent are expressed in parts by weight with respect to 100 parts by weight of silica as the base material.

Example 1
100 parts by weight of fumed silica having a specific surface area of 200 m ² / g (Reokusil QS-102 manufactured by Tokuyama Corporation) was placed in a mixer, stirred, and replaced with a nitrogen atmosphere, and simultaneously heated to 250 ° C. While continuing the stirring and the flow of nitrogen gas, the temperature was maintained at 250 ° C. for 2 hours. By this operation, the adsorbed water of fumed silica became less than 0.05%.

  Steps (A) and (B) The mixer was sealed, and 25 parts by weight of tetra-iso-propoxytitanium and 1.1 parts by weight of 3-aminopropyltriethoxysilane were sprayed with a one-fluid nozzle. Stirring was continued for 60 minutes after spraying. Subsequently, the mixer was opened, and 120 parts by weight of water vapor was passed over 60 minutes while maintaining stirring at 250 ° C. to carry out hydrolysis.

  Step (C) The mixer was sealed while maintaining stirring of the mixer, sprayed with 30 parts by weight of hexamethyldisilazane, and subjected to hydrophobic treatment by stirring for 30 minutes.

Example 2
The same treatment as in Example 1 was carried out except that the amount of 3-aminopropyltriethoxysilane in step (B) was 2.1 parts by weight.

Example 3
The same treatment as in Example 1 was carried out except that 8.3 parts by weight of 3-aminopropyltriethoxysilane in the step (B) was changed.

Example 4
Except for changing the processing order, the same processing as in Example 2 was performed. That is, step (A) 25 parts by weight of tetra-iso-propoxytitanium was sprayed with a one-fluid nozzle. Stirring was continued for 60 minutes as it was after spraying, and then the mixer was opened to perform hydrolysis with water vapor.

  Steps (B) and (C) While maintaining stirring of the mixer, the mixer was sealed, and 2.1 parts by weight of 3-aminopropyltriethoxysilane and 30 parts by weight of hexamethyldisilazane were sprayed. The mixture was stirred for 60 minutes.

Example 5
The same treatment as in Example 2 was performed except that 50 parts by weight of tetra-iso-propoxytitanium and 240 parts by weight of water vapor for 120 minutes were used in step (A).

Example 6
In the step (B), the same treatment as in Example 2 was carried out except that 2.2 parts by weight of N, N-diethyl-3-aminopropyltrimethoxysilane was used instead of 3-aminopropyltriethoxysilane.

Example 7
In step (A), 9 parts by weight of mono-sec-butoxydi-iso-propylaluminum instead of tetra-iso-propoxytitanium was doubled with silicone oil (KF-96L-1CS manufactured by Shin-Etsu Chemical Co., Ltd.). The same treatment as in Example 4 was carried out except that the solution was diluted in

Example 8
The spraying of mono-sec-butoxydi-iso-propylaluminum in the step (A) and the spraying of 3-aminopropyltriethoxysilane in the step (B) are carried out at the same time. The same treatment as in Example 7 was carried out except that the amount was 3 parts by weight.

Example 9
The same treatment as in Example 1 was performed except that the step (A) and the step (B) were sequentially performed as follows.

  Step (A) After substituting the base silica with nitrogen, heating, and dehydrating, the mixer was sealed, and 25 parts by weight of tetra-iso-propoxy titanium was sprayed with a one-fluid nozzle. Stirring was continued for 60 minutes after spraying. Subsequently, the mixer was opened, and 120 parts by weight of water vapor was passed over 60 minutes while maintaining stirring at 250 ° C. to carry out hydrolysis.

  Step (B) Thereafter, the mixer was sealed again, and 5.3 parts by weight of N, N-dimethylcyclohexylamine was sprayed with a one-fluid nozzle, and stirring was continued for 60 minutes.

Example 10
The same treatment as in Example 1 was carried out except that the amount of 3-aminopropyltriethoxysilane in step (B) was 1.5 parts by weight.

Example 11
The same treatment as in Example 10 was carried out except that the silica used as the base material was fumed silica having a specific surface area of 300 m ² / g (Reokuro QS-30 manufactured by Tokuyama Corporation).

Comparative Example 1
A commercial product, Toroyama Leolosil HM-20S, which was hydrophobized with a specific surface area of 200 m ² / g of fumed silica was subjected to physical property measurement. This sample was used as a reference in the measurement of the charge amount.

Comparative Example 2
A fumed silica having a specific surface area of 200 m ² / g (Leosil QS-102 manufactured by Tokuyama Co., Ltd.) was placed in a mixer, stirred, and replaced with a nitrogen atmosphere, and simultaneously heated to 250 ° C. Next, the mixer was sealed, 2.1 parts by weight of 3-aminopropyltriethoxysilane was sprayed, and stirring was continued for 60 minutes as it was (step (B)). Further, steam was introduced into the mixer to replace about 60% of nitrogen, the mixer was sealed, 30 parts by weight of hexamethyldisilazane was sprayed, and the mixture was stirred as it was for 30 minutes (step (C)).

Comparative Example 3
In the step (B), the same treatment as in Comparative Example 2 was performed except that 2.4 parts by weight of N-phenyl-3-aminopropyltrimethoxysilane was used instead of 3-aminopropyltriethoxysilane.

Comparative Example 4
The step (B) and the step (C) are carried out at the same time, and the treating agent in the step (B) is replaced with N, N-diethyl-3-aminopropyltrimethoxysilane 2.2 instead of 3-aminopropyltriethoxysilane. Except for the parts by weight, the same treatment as in Comparative Example 2 was performed.

Comparative Example 5
Comparative Example 4 except that the treating agent in step (B) was 2.1 parts by weight of 3-aminopropyltriethoxysilane and 0.6 parts by weight of N, N-diethyl-3-aminopropyltrimethoxysilane. A similar process was performed.

Comparative Example 6
A fumed silica having a specific surface area of 200 m ² / g (Leosil QS-102 manufactured by Tokuyama Co., Ltd.) is dispersed in 2,000 parts by weight of water, heated to a temperature of 70 ° C., and 30% titanium sulfate. 100 parts by weight of the solution and 5N aqueous sodium hydroxide solution were simultaneously added dropwise so that the pH was 5.7 to 6.3. After the dropping, the liquid temperature was cooled to 40 ° C., the pH was adjusted to 6.5, and stirring was continued for 1 hour, and the product was filtered and washed with water. The cake after filtration and washing with water was dried in a drier kept at 140 ° C. and then pulverized with an air jet pulverizer.

  The obtained silica was subjected to the same hydrophobizing treatment as in Step (C) of Comparative Example 2.

Comparative Example 7
In the same manner as in Comparative Example 6, treatment with a titanium sulfate solution in water was performed, and silica obtained by drying and pulverization was charged into a mixer, steam was introduced to replace about 60% of nitrogen, and the mixer was After sealing, 2.1 parts by weight of 3-aminopropyltriethoxysilane and 30 parts by weight of hexamethyldisilazane were sprayed and stirred as they were for 60 minutes (steps (B) and (C)).

  About the sample manufactured by the above Example and the comparative example, each manufacturing condition is put together as a list in Table 1 and Table 2, and the result of having measured various physical properties, such as charge amount and a fluid provision property, is put together in Table 3. Show.

また、図１に、比較例１、２、及び、実施例１で作製した試料について、擬似トナーとフェライトキャリアとの混合時間による帯電量の経時変化を示す。

In addition, FIG. 1 shows changes with time in the charge amount of the samples prepared in Comparative Examples 1 and 2 and Example 1 depending on the mixing time of the pseudo toner and the ferrite carrier.

  From Table 3, it can be seen that the index representing the charge level of the example is a value on the positive charge side of −85 or more with respect to Comparative Example 1. In addition, it can be seen that the rising coefficient of charging is remarkably improved.

  In particular, as can be seen from FIG. 1 regarding the charge rising characteristics, the surface-coated silica of the present invention achieves quick charge rising as compared with conventional silica.

  Since the compression degree showing the fluidity imparting characteristics is a value equivalent to or better than the example in which the treatment was performed under the dry method, and Comparative Examples 2 to 5 were compared with Comparative Example 1 of a commercial product, It can be seen that the fluidity-imparting property of silica is not deteriorated by the surface coating treatment of the present invention, and the original good properties of silica are maintained. Moreover, it is also confirmed that the fluidity imparting characteristics of Comparative Examples 6 and 7 subjected to the treatment under wet conditions are remarkably deteriorated.

  In addition, as a cause of the difference in the effect between the dry treatment of the present invention and the wet treatment of the comparative example, the surface-treated silica obtained by the dry treatment of the above-described example is a metal as a result of observing the surface. In contrast to the fact that the oxide bulky mass could not be confirmed, it was confirmed that the metal oxide obtained by wet processing had a coarse mass of 20 nm or more of the metal oxide. The difference is considered.

  Table 4 shows the results of measuring the environmental stability of the surface-treated silica of Examples 8 to 11 and Comparative Example 1.

このように、本発明のトナー用外添剤は、比較例１に比較して温度、湿度が違う環境下においても帯電量の差が小さいことがわかる。

Thus, it can be seen that the external additive for toner of the present invention has a small difference in charge amount even in an environment with different temperature and humidity as compared with Comparative Example 1.

  As described above, the surface-treated silica of the present invention is a silica having negative chargeability suppressed without impairing the good fluidity imparting characteristics inherent in silica, and having excellent charge rising characteristics, Excellent performance as an external additive for photographic toners.

The graph which shows the time-dependent change of the charge amount by the mixing time of a pseudo toner and a ferrite carrier about the sample produced in Comparative Examples 1 and 2 and Example 1.

Claims (6)

It includes the following steps (A), (B), and (C), and is performed in the order of step (C) after the steps (A) and (B) at the same time. After step (A), step (B ), (C) It is carried out in the same order, or step (A), step (B) and step (C) are carried out in sequence, so that a metal oxide other than silica alone, a basic group is formed on the silica particle surface. An external additive for toner, comprising: a treatment agent having a surface treatment silica to which a treatment agent and a hydrophobizing agent are attached.
Step (A) The silica is brought into contact with a metal alkoxide vapor or mist to adhere the metal alkoxide to the silica surface, and then brought into contact with water vapor to hydrolyze the metal alkoxide attached to the silica surface to thereby convert the metal oxide into the metal alkoxide. A process of adhering to the surface of silica particles.
Process (B) The process which makes a silica contact the vapor | steam or mist of the processing agent which has a basic group, and makes a processing agent adhere to the silica particle surface.
Step (C) A step of bringing silica into contact with the hydrophobizing agent vapor or mist to adhere the hydrophobizing agent to the surface of the silica particles. 2. The external additive for toner according to claim 1, wherein the amount of silica adsorbed water used in step (A) is less than 0.1%. The external additive for toner according to claim 1, wherein the silica is fumed silica. Metal element forming the metal oxide is Al, Si, Ti, Zr, Sn, Zn, outside toner according to one or any one of claims 1 to 3, which is a more selected from among Mg Additive. The toner external additive according to any one of claims 1 to 4 , wherein the treating agent having a basic group is an amino group-containing silane coupling agent. The external additive for toner according to any one of claims 1 to 5 , wherein an index representing a charge level is -85 or more, a rising coefficient of charge is 0.80 or more, and an M value indicating hydrophobicity is 35 to 80. Agent.

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