Method for manufacturing surface-treated sol-gel silica particles, surface-treated sol-gel silica particles, and toner additive for electrostatic charge development

Abstract

The present invention comprises: (A1) a process of obtaining hydrophilic sol-gel silica particles having silanol groups on a surface and substantially composed of SiO2 units; (A2) a process of adding a compound having (C2H5)3Si- group or R1R22Si- group (where R1 is an alkyl group or alkenyl group having 2 to 8 carbon atoms or an aryl group having 6 to 8 carbon atoms, and R2 is an identical or heterogeneous substituted or unsubstituted alkyl group having 1 to 4 carbon atoms) and introducing (C2H5)3SiO1 / 2 units or R1R22SiO1 / 2 units onto the surface of the hydrophilic sol-gel silica particles to obtain pretreated silica particles; and (A3) a process of adding a compound having R33Si- group (where R3 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms) and additionally introducing R33SiO1 / 2 units onto the surface of the pretreated silica particles to perform surface treatment. A method for manufacturing surface-treated sol-gel silica particles is provided, comprising a process for obtaining sol-gel silica particles. Accordingly, surface-treated sol-gel silica particles capable of imparting good fluidity when added to toner and having minimal charge change upon environmental change, a method for manufacturing the same, and an external additive for toner comprising the surface-treated sol-gel silica particles are provided.

Description

Technology Field

[0001] The present invention relates to surface-treated sol-gel silica particles, a method for manufacturing the same, and an external additive for toner used to develop electrostatic images in electrophotography, electrostatic recording, etc. Background Technology

[0002] Dry developers used in electrophotography and the like can be broadly classified into one-component developers, which use toner itself in which a colorant is dispersed in a binding resin, and two-component developers, which mix a carrier with the toner. When performing copy operations using these developers, in order to have process suitability, the developer must have excellent fluidity, anti-caking properties, fixing properties, antistatic properties, and cleaning properties. In particular, in order to improve fluidity, anti-caking properties, fixing properties, and cleaning properties, inorganic fine particles are often used as toner additives.

[0003] However, the dispersibility of inorganic microparticles has a significant impact on toner characteristics, and if the dispersibility is non-uniform, desired characteristics such as fluidity, anti-caking properties, and fixation properties may not be obtained, or cleaning properties may become insufficient, leading to toner adhesion on the photoresist and causing black spot-like image bonding. To improve these issues, various methods have been proposed to hydrophobize the surface of inorganic microparticles.

[0004] In addition, recently, there has been a demand for faster photocopiers and lower energy consumption, and higher degradation resistance than that of conventional toners has become required. If the degradation resistance of the toner is not high, the transfer efficiency of the toner cannot be maintained at a high level from the start of use until the end of use. As one of the countermeasures, a toner degradation suppression technology utilizing the spacer effect of a large particle size toner additive has been proposed (Patent Documents 1, 2).

[0005] In addition, as toner additives, it is common practice to use both small-particle and large-particle toner additives in combination. Due to the presence of large-particle toner additives attached to the surface of toner particles, the frequency with which small-particle toner additives attached to the surface of nearby toner particles are directly subjected to external forces, such as shear or impact forces, is reduced. Since this prevents the small-particle toner additives from being buried in the toner particle surface by such external forces (spacer effect), it becomes possible to suppress toner degradation.

[0006] In addition, it is believed that the large-diameter toner additive functions as a transfer aid, as the addition of the large-diameter toner additive facilitates the separation of toner from the photosensitive material and allows the toner carried on the photosensitive material to be rapidly transferred onto the paper, thereby maintaining a high transfer efficiency.

[0007] The small-particle silica used at this time is often used primarily as a fluidizing agent, and until now, fumed silica particles produced by the combustion method have been mainly used. However, while conventional fumed silica particles certainly improve fluidity, the amount added tended to be large to improve the fluidity of the current quench-hardened toner. Furthermore, as high resolution progresses, transferability and cleanability are required more strictly, and there has been a demand for particles that are free of agglomerates and have excellent dispersibility.

[0008] Meanwhile, fumed silica particles as described above are used for the purpose of improving electrostatic characteristics, etc., but generally, surface hydrophobization is insufficient and silanol groups remain on the surface, so there is a problem that it is difficult to control electrostatic charge, especially when the environment changes, so there was a demand for small-sized silica particles that have good electrostatic control along with fluidity. Prior art literature

[0009] Japanese Patent Publication No. H06-027718 Japanese Patent Publication No. H11-143118 The problem to be solved

[0010] The present invention, made in consideration of the above circumstances, aims to provide surface-treated sol-gel silica particles capable of imparting good fluidity when added to toner and having minimal charge change upon environmental changes, a method for manufacturing the same, and an external additive for toner composed of said surface-treated sol-gel silica particles. means of solving the problem

[0011] To solve the above problem, the present invention,

[0012] A method for manufacturing surface-treated sol-gel silica particles,

[0013] (A1) A process of obtaining hydrophilic sol-gel silica particles having silanol groups on the surface and substantially composed of SiO2 units by hydrolyzing and condensing a tetrafunctional silane compound, its partial hydrolysis condensation product, or a mixture thereof.

[0014] (A2) (C2H5)3Si- groups or R on the hydrophilic sol-gel silica particles 1 R 2 2Si-group(in the formula, R 1 is an alkyl group or alkenyl group having 2 to 8 carbon atoms, or an aryl group having 6 to 8 carbon atoms, and R 2 A compound having (which is an identical or heterogeneous substituted or unsubstituted alkyl group having 1 to 4 carbon atoms) is added, and (C2H5)3SiO is applied to the surface of the hydrophilic sol-gel silica particles. 1 / 2 Unit or R 1 R 2 2SiO 1 / 2 Unit (in the formula, R 1 and R 2 A process for obtaining pretreated silica particles by introducing (as described above), and

[0015] (A3) R to the above pre-treated silica particles 3 3Si-group(in the formula, R 3 A compound having (which is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms) is added, and additionally R on the surface of the pretreated silica particles 3 3SiO 1 / 2Unit (in the formula, R 3 The process includes obtaining surface-treated sol-gel silica particles by introducing (as described above), and also,

[0016] The unit introduced to the surface of the hydrophilic sol-gel silica particle in the above process (A2) and the unit introduced to the surface of the pre-treated silica particle in the above process (A3) each provide a method for manufacturing surface-treated sol-gel silica particles that are different.

[0017] With this method of manufacturing surface-treated sol-gel silica particles, it is possible to produce surface-treated sol-gel silica particles that provide good fluidity when added to toner and have minimal charge change when the environment changes.

[0018] In addition, the above process (A1) is general formula (i):

[0019] Si(OR 4 )4(i)

[0020] (among the food, each R 4 is a monovalent hydrocarbon group having 1 to 6 carbon atoms of the same or different type.

[0021] A process for obtaining a mixed solvent dispersion of hydrophilic sol-gel silica particles having silanol groups on the surface and substantially composed of SiO2 units by hydrolyzing and condensing a tetrafunctional silane compound represented by, its partial hydrolysis condensation product, or a mixture thereof in a mixture of a hydrophilic organic solvent and water in the presence of a basic substance.

[0022] The above process (A2) is applied to the mixed solvent dispersion of the obtained hydrophilic sol-gel silica particles, with the general formula (ii):

[0023] R 1 R 2 2SiNHSiR 1 R 2 2(ii)

[0024] (during food, R 1 and R 2 is as above)

[0025] Silazane compounds represented by, hexaethyldisilazane, general formula (iii-1):

[0026] R 1 R 2 2SiX (iii-1)

[0027] (during food, R 1 and R 2 is as above, and X is an OH group or a hydrolytic group)

[0028] A monofunctional silane compound represented by, general formula (iii-2):

[0029] (C2H5)3SiX (iii-2)

[0030] (In the formula, X is as above)

[0031] A monofunctional silane compound represented by, or a mixture thereof, is added in an amount of 0.001 to 1 mole per mole of SiO2 unit in the hydrophilic sol-gel silica particles, and (C2H5)3SiO is applied to the surface of the hydrophilic sol-gel silica particles. 1 / 2 Unit or R 1 R 2 2SiO 1 / 2 Unit (R 1 and R 2 The process is to obtain a mixed solvent dispersion of pretreated silica particles by introducing (as described above), and

[0032] The above process (A3) is applied to the mixed solvent dispersion of the obtained pre-treated silica particles, with the general formula (iv):

[0033] R 3 3SiNHSiR 3 3(iv)

[0034] (during food, R 3 (It is as above)

[0035] Silazane compounds represented by , general formula (v):

[0036] R 3 3SiX (v)

[0037] (during food, R 3 and X are as above)

[0038] A monofunctional silane compound represented by, or a mixture thereof, is added in an amount of 5 to 50 moles per mole of SiO2 unit in the pretreated silica particles, and R on the surface of the pretreated silica particles 3 3SiO 1 / 2 Unit (R 3 It is preferable to use a process to obtain surface-treated sol-gel silica particles by introducing the above-mentioned method.

[0039] The method for manufacturing the surface-treated sol-gel silica particles of the present invention can be done using this manufacturing method.

[0040] In addition, the above R 1 is an alkyl group having 6 to 8 carbon atoms, a phenyl group, or a vinyl group, and the above R 2 is a methyl group, ethyl group, propyl group, or isopropyl group, and the R 3 It is preferable to make it a methyl group or an ethyl group.

[0041] In the present invention, it is preferable to perform surface treatment of hydrophilic sol-gel silica particles, particularly using such a compound.

[0042] In addition, in the present invention,

[0043] R on the surface 1 R 2 2SiO 1 / 2 Unit (in the formula, R 1 is an alkyl group, an aryl group, or a vinyl group having 6 to 8 carbon atoms, and R 2 is an identical or different alkyl group having 1 to 4 carbon atoms) and R 3 3SiO 1 / 2 Unit (in the formula, R 3 A surface-treated sol-gel silica particle having a monovalent hydrocarbon group having 1 to 6 carbon atoms, which is identical or heterogeneous substituted or unsubstituted.

[0044] In dynamic light scattering, the median diameter is 5 nm to 99 nm, and

[0045] The average circularity is 0.8 to 1.0, and

[0046] The refractive index is 1.38–1.42, and

[0047] True density is 1.7 g / cm³ 3 Above 1.9 g / cm³ 3 Less than,

[0048] The ratio expressed as water vapor adsorption specific surface area / nitrogen adsorption specific surface area is 0.4 to 1.9, and

[0049] Methanol hydrophobicity of 67% or more and 75% or less

[0050] Provides surface-treated sol-gel silica particles.

[0051] In the present invention, surface-treated sol-gel silica particles having these characteristics can be used.

[0052] At this time, the above R 1 This is an alkyl group, a phenyl group, or a vinyl group having 6 to 8 carbon atoms, and the above R 2 ga is a methyl group, ethyl group, propyl group, or isopropyl group, and R 3 It is preferable that this be a methyl group or an ethyl group.

[0053] It is particularly preferable that the surface-treated sol-gel silica particles of the present invention undergo such surface treatment.

[0054] In addition, the present invention provides a toner additive for electrostatic phase development containing the above-mentioned surface-treated sol-gel silica particles.

[0055] When the surface-treated sol-gel silica particles of the present invention are used as toner additives, they can impart good fluidity and printing characteristics to the toner. Effects of the invention

[0056] As explained above, according to the present invention, surface-treated sol-gel silica particles capable of improving electrostatic abnormalities or toner flowability caused by environmental changes that occurred when conventional small-particle fumed silica was used as an external additive, an external additive for electrostatic charge development made of the same, and a toner for electrostatic charge development can be provided. Specific details for implementing the invention

[0057] As described above, there was a need for an external additive for toner that could provide good fluidity when added to the toner and also have minimal change in charge amount during environmental changes.

[0058] The inventors, having conducted careful examinations to achieve the above objective, discovered that by surface-treating spherical silica particles obtained from the sol-gel method with a specific organosilicon compound, surface-treated sol-gel silica particles can be obtained that provide good fluidity when added to toner and exhibit minimal change in charge amount during environmental changes, thereby completing the present invention.

[0059] That is, the present invention is,

[0060] A method for manufacturing surface-treated sol-gel silica particles,

[0061] (A1) A process of obtaining hydrophilic sol-gel silica particles having silanol groups on the surface and substantially composed of SiO2 units by hydrolyzing and condensing a tetrafunctional silane compound, its partial hydrolysis condensation product, or a mixture thereof.

[0062] (A2) (C2H5)3Si- groups or R on the hydrophilic sol-gel silica particles 1 R 2 2Si-group(in the formula, R 1 is an alkyl group or alkenyl group having 2 to 8 carbon atoms, or an aryl group having 6 to 8 carbon atoms, and R 2 A compound having (which is an identical or heterogeneous substituted or unsubstituted alkyl group having 1 to 4 carbon atoms) is added, and (C2H5)3SiO is applied to the surface of the hydrophilic sol-gel silica particles. 1 / 2 Unit or R 1 R 2 2SiO 1 / 2 Unit (in the formula, R 1 and R 2 A process for obtaining pretreated silica particles by introducing (as described above), and

[0063] (A3) R to the above pre-treated silica particles 3 3Si-group(in the formula, R 3A compound having (which is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms) is added, and additionally R on the surface of the pretreated silica particles 3 3SiO 1 / 2 Unit (in the formula, R 3 The process includes obtaining surface-treated sol-gel silica particles by introducing (as described above), and also,

[0064] The unit introduced to the surface of the hydrophilic sol-gel silica particle in the above process (A2) and the unit introduced to the surface of the pre-treated silica particle in the above process (A3) are each different methods for manufacturing surface-treated sol-gel silica particles.

[0065] The present invention will be described in detail below, but the invention is not limited to these.

[0066] (Method for manufacturing surface-treated sol-gel silica particles)

[0067] · Process (A1): Synthesis process of hydrophilic sol-gel silica particles

[0068] Process (A1) is a process of obtaining hydrophilic sol-gel silica particles having silanol groups on the surface and substantially composed of SiO2 units by hydrolyzing and condensing a tetrafunctional silane compound, its partial hydrolysis condensation product, or a mixture thereof.

[0069] In process (A1), the statement that the hydrophilic sol-gel silica particles are “substantially composed of SiO2 units” means that the particles are basically composed of SiO2 units, but are not composed only of SiO2 units, and may have a number of silanol groups on at least the surface as is commonly known. In addition, in some cases, it means that hydrolyzable groups (hydrocarbyloxy groups) derived from the raw material tetrafunctional silane compound and / or its partial hydrolysis condensation product may remain on the surface or inside the particles in small amounts without being converted into some silanol groups.

[0070] In the present invention, small-sized sol-gel silica particles obtained by hydrolysis of a tetrafunctional silane compound such as tetraalkoxysilane in process (A1) are used as the silica source (silica particles before hydrophobization treatment), and by performing a specific surface treatment on this, when obtained as a powder, the particle size after hydrophobization treatment maintains the primary particle size of the silica source, is not aggregated, is small-sized, and is a good surface-treated sol-gel silica particle for use as an external additive for toner.

[0071] Process (A1) is, general formula (i):

[0072] Si(OR 4 )4(i)

[0073] (among the food, each R 4 is a monovalent hydrocarbon group having 1 to 6 carbon atoms of the same or different type.

[0074] It is preferable that the process be to obtain a mixed solvent dispersion of hydrophilic sol-gel silica particles by hydrolyzing and condensing a tetrafunctional silane compound represented by, its partial hydrolysis condensation product, or a mixture thereof, in a mixture of a hydrophilic organic solvent and water in the presence of a basic substance.

[0075] Among the above general formula (i), R 4 is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and particularly preferably 1 to 2 carbon atoms. 4 Examples of monovalent hydrocarbon groups represented by α include alkyl groups such as methyl, ethyl, propyl, and butyl groups; aryl groups such as phenyl groups, preferably methyl, ethyl, propyl, or butyl groups, particularly preferably methyl or ethyl groups.

[0076] Examples of tetrafunctional silane compounds represented by the above general formula (i) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; and tetraphenoxysilane, preferably tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, particularly preferably tetramethoxysilane and tetraethoxysilane. In addition, examples of partial hydrolysis condensation products of the tetrafunctional silane compound represented by the above general formula (i) include alkyl silicates such as methyl silicate and ethyl silicate.

[0077] The above hydrophilic organic solvent is not particularly limited as long as it dissolves a tetrafunctional silane compound represented by general formula (i), its partial hydrolysis condensation product, and water. Examples include alcohols; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and acetic acid cellosolve; ketones such as acetone and methyl ethyl ketone; and ethers such as dioxane and tetrahydrofuran. Preferably, it is an alcohol or a cellosolve, and particularly preferably, an alcohol. Examples of such alcohols include general formula (vi):

[0078] R 5 OH (vi)

[0079] (during food, R 5 is a monovalent hydrocarbon group with 1 to 6 carbon atoms.

[0080] Examples of alcohols indicated by [this] include [this].

[0081] Among the above general formula (vi), R 5 is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and particularly preferably 1 to 2 carbon atoms. 5Examples of monovalent hydrocarbon groups represented by α include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and t-butyl groups, preferably methyl, ethyl, propyl, and isopropyl groups, more preferably methyl and ethyl groups. Examples of alcohols represented by general formula (vi) include methanol, ethanol, propanol, isopropanol, butanol, and preferably methanol and ethanol. As the number of carbon atoms in the alcohol increases, the particle size of the hydrophilic sol-gel silica particles produced increases. Therefore, methanol is preferred to obtain silica particles of small particle size.

[0082] Examples of the above basic substances include ammonia, dimethylamine, diethylamine, etc., preferably ammonia, diethylamine, and particularly preferably ammonia. These basic substances can be prepared by dissolving the required amount in water and then mixing the resulting aqueous solution (basic) with the above hydrophilic organic solvent.

[0083] The amount of basic substance used is preferably 0.01 to 2 moles per 1 mole of the total hydrocarbyloxy groups of the tetrafunctional silane compound represented by general formula (i) and / or its partial hydrolysis condensation product, more preferably 0.02 to 0.5 moles, and particularly preferably 0.04 to 0.12 moles. At this time, the smaller the amount of basic substance, the smaller the particle size of the silica particles.

[0084] The amount of water used in the above hydrolysis and condensation is preferably 0.1 to 2 moles per 1 mole of the total hydrocarbyloxy groups of the tetrafunctional silane compound represented by general formula (i) and / or its partial hydrolysis condensation product, and more preferably 0.1 to 1 mole. The ratio of the hydrophilic organic solvent to water (amount of hydrophilic organic solvent / amount of water) is preferably 0.2 to 10 by mass ratio, and more preferably 0.3 to 5. The greater the amount of hydrophilic organic solvent, the smaller the particle size of the silica particles obtained.

[0085] Hydrolysis and condensation of tetrafunctional silane compounds, etc., can be carried out by a well-known method, namely by adding a tetrafunctional silane compound and a basic substance to a mixture of a hydrophilic organic solvent and water.

[0086] The temperature during hydrolysis and condensation is preferably 20 to 50°C, and the higher the temperature, the smaller the particle size of the silica particles obtained.

[0087] The concentration of hydrophilic sol-gel silica particles obtained in this process (A1) in the mixed solvent dispersion is generally 3 to 15 mass%, and preferably 5 to 10 mass%.

[0088] · Process (A2): Process for obtaining pre-treated silica particles

[0089] Process (A2) involves (C2H5)3Si- groups or R in the hydrophilic sol-gel silica particles obtained in the above process (A1). 1 R 2 2Si-group(in the formula, R 1 is an alkyl group or alkenyl group having 2 to 8 carbon atoms, or an aryl group having 6 to 8 carbon atoms, and R 2 A compound having (which is an identical or heterogeneous substituted or unsubstituted alkyl group having 1 to 4 carbon atoms) is added, and (C2H5)3SiO is applied to the surface of hydrophilic sol-gel silica particles. 1 / 2 Unit or R 1 R 2 2SiO 1 / 2 Unit (in the formula, R 1 and R 2 This is a process for obtaining pre-treated silica particles by introducing the above-mentioned method. Through this process, the surface treatment in the following process (A3) is more uniform and also proceeds to a higher degree.

[0090] Process (A2) involves a mixed solvent dispersion of the obtained hydrophilic sol-gel silica particles, with the general formula (ii):

[0091] R 1 R 2 2SiNHSiR 1 R 2 2(ii)

[0092] (during food, R1 and R 2 is as above)

[0093] Silazane compounds represented by, hexaethyldisilazane, general formula (iii-1):

[0094] R 1 R 2 2SiX (iii-1)

[0095] (during food, R 1 and R 2 is as above, and X is an OH group or a hydrolytic group)

[0096] A monofunctional silane compound represented by, general formula (iii-2):

[0097] (C2H5)3SiX (iii-2)

[0098] (In the formula, X is as above)

[0099] A monofunctional silane compound represented by, or a mixture thereof, is added, and the surface of hydrophilic sol-gel silica particles is treated with the silazane compound, the monofunctional silane compound, or a mixture thereof, thereby (C2H5)3SiO₂ on the surface of the hydrophilic sol-gel silica particles 1 / 2 Unit or R 1 R 2 2SiO 1 / 2 Unit (R 1 and R 2 It is preferable that the process be one that obtains a mixed solvent dispersion of pretreated silica particles by introducing (as described above).

[0100] R 1Examples of alkyl groups having 2 to 8 carbon atoms include ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, t-butyl groups, n-hexyl groups, cyclohexyl groups, n-octyl groups, cyclooctyl groups, etc. Examples of alkenyl groups having 2 to 8 carbon atoms include vinyl groups, allyl groups, n-butenyl groups, n-hexenyl groups, n-octenyl groups, etc. Examples of aryl groups having 6 to 8 carbon atoms include phenyl groups, 2-methylphenyl groups, 3-methylphenyl groups, 4-methylphenyl groups, 2,3-dimethylphenyl groups, 2,4-dimethylphenyl groups, 2,6-dimethylphenyl groups, etc. R 1 Silver, an alkyl group having 6 to 8 carbon atoms, a phenyl group, and a vinyl group are preferred, and an n-octyl group, a phenyl group, and a vinyl group are particularly preferred.

[0101] R 2 Examples of alkyl groups having 1 to 4 carbon atoms represented by α include methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, t-butyl groups, etc., preferably methyl groups, ethyl groups, propyl groups, and isopropyl groups, more preferably methyl groups and ethyl groups. In these alkyl groups, some or all of their hydrogen atoms may be substituted with halogen atoms such as fluorine atoms, chlorine atoms, or bromine atoms, preferably fluorine atoms. Meanwhile, R 2 is the above R 1 It is a different kind of energy.

[0102] Examples of hydrolytic groups represented by X include a chlorine atom, an alkoxy group, an amino group, and an acyloxy group, preferably an alkoxy group or an amino group, particularly preferably an alkoxy group.

[0103] Silazane compounds represented by general formula (ii) include 1,3-diethyltetramethyldisilazane, 1,3-di-n-propyltetramethyldisilazane, 1,3-di-n-butyltetramethyldisilazane, 1,3-di-n-hexyltetramethyldisilazane, 1,3-di-n-octyltetramethyldisilazane, 1,3-diphenyltetramethyldisilazane, 1,3-divinyltetramethyldisilazane, 1,3-diallyltetramethyldisilazane, etc.

[0104] Examples of monofunctional silane compounds represented by general formula (iii-1) include monoalkoxysilanes such as ethyldimethylmethoxysilane, n-propyldimethylmethoxysilane, isopropyldimethylmethoxysilane, n-butyldimethylmethoxysilane, n-hexyldimethylmethoxysilane, n-octyldimethylmethoxysilane, phenyldimethylmethoxysilane, vinyldimethylmethoxysilane, etc., or their silanol bodies or monochloro bodies.

[0105] Examples of monofunctional silane compounds represented by general formula (iii-2) include monoalkoxysilanes such as triethylmethoxysilane, their silanol bodies, and monochloro bodies.

[0106] The total amount of the silazane compound represented by general formula (ii), hexaethyldisilazane, and monofunctional silane compounds represented by general formulas (iii-1) and (iii-2) added is preferably 0.001 to 1 mole per mole of SiO2 unit in hydrophilic sol-gel silica particles, more preferably 0.02 to 0.5 moles, and particularly preferably 0.05 to 0.3 moles. Within this range, the surface treatment efficiency in process (A3) can be improved.

[0107] In addition, the reaction temperature of the surface treatment in process (A2) is not particularly limited, but is preferably 20 to 80°C, more preferably 40 to 60°C.

[0108] · Process (A3): Process for obtaining surface-treated sol-gel silica particles

[0109] Process (A3) involves R to the pretreated silica particles obtained in process (A2). 3 3Si-group(in the formula, R 3 A compound having (which is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms) is added, and R on the surface of the pretreated silica particles 3 3SiO 1 / 2 Unit (in the formula, R 3 This is a process for obtaining surface-treated sol-gel silica particles by introducing (as described above). In this process, R is formed by triorganosilylating the silanol groups remaining on the surface of the pre-treated silica particles.3 3SiO 1 / 2 A unit is introduced to obtain more highly surface-treated sol-gel silica particles.

[0110] Process (A3) involves a mixed solvent dispersion of the obtained pretreated silica particles, with the general formula (iv):

[0111] R 3 3SiNHSiR 3 3(iv)

[0112] (during food, R 3 (It is as above)

[0113] Silazane compounds represented by , general formula (v):

[0114] R 3 3SiX (v)

[0115] (during food, R 3 and X are as above)

[0116] A monofunctional silane compound represented by, or a mixture thereof, is added, and the surface of the pretreated silica particles is treated with the silazane compound, the monofunctional silane compound, or a mixture thereof, and R on the surface of the pretreated silica particles 3 3SiO 1 / 2 Unit (R 3 It is preferable that the process be one that obtains surface-treated sol-gel silica particles by introducing (as described above).

[0117] R 3 It is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and particularly preferably 1 to 2 carbon atoms. R 3 Examples of monovalent hydrocarbon groups represented by are alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and t-butyl groups; alkenyl groups such as vinyl and allyl groups; and phenyl groups, and preferably methyl and ethyl groups, more preferably methyl groups. In addition, some or all of the hydrogen atoms of these groups may be substituted with halogen atoms such as fluorine, chlorine, and bromine atoms, preferably fluorine atoms.

[0118] X can be the same as that described in the process (A2) section.

[0119] Examples of silazane compounds represented by general formula (iv) include hexamethyldisilazane, hexaethyldisilazane, etc., and hexamethyldisilazane is preferred.

[0120] Examples of monofunctional silane compounds represented by the general formula (v) include monosilanol compounds such as trimethylsilanol and triethylsilanol; monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane; monoalkoxysilanes such as trimethylmethoxysilane and trimethylethoxysilane; monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; and monoacyloxysilanes such as trimethylacetoxysilane. Preferably, trimethylsilanol, trimethylmethoxysilane, or trimethylsilyldiethylamine may be used, and particularly preferably, trimethylsilanol or trimethylmethoxysilane may be used.

[0121] The total amount of the silazane compound represented by general formula (iv) and the monofunctional silane compound represented by general formula (v) added is preferably 5 to 50 moles, more preferably 10 to 30 moles, per mole of SiO2 unit in the pretreated silica particles. Within this range, surface-treated sol-gel silica particles with excellent dispersibility in toner and less aggregation of particles is obtained. Meanwhile, the number of SiO2 units in the pretreated silica particles is the same as the number of SiO2 units in the hydrophilic sol-gel silica particles that served as the raw material.

[0122] In addition, the reaction temperature of the surface treatment in process (A3) is not particularly limited, but is preferably 20 to 80°C, more preferably 50 to 70°C.

[0123] In addition, the unit introduced to the surface of the hydrophilic sol-gel silica particles in process (A2) and the unit introduced to the surface of the pre-treated silica particles in process (A3) are different. That is, (C2H5)3SiO on the surface of the hydrophilic sol-gel silica particles in process (A2) 1 / 2 In the case where the unit is introduced, in process (A3), (C2H5)3SiO on the surface of the pretreated silica 1 / 2 Introduce units other than the unit.

[0124] The above-mentioned surface-treated sol-gel silica particles are obtained as a powder by conventional methods such as atmospheric pressure drying and reduced pressure drying.

[0125] (Surface-treated sol-gel silica particles)

[0126] The surface-treated sol-gel silica particles obtained by the method for manufacturing surface-treated sol-gel silica particles of the present invention are,

[0127] R on the surface 1 R 2 2SiO 1 / 2 Unit (in the formula, R 1 is an alkyl group, an aryl group, or a vinyl group having 6 to 8 carbon atoms, and R 2 is an identical or different alkyl group having 1 to 4 carbon atoms) and R 3 3SiO 1 / 2 Unit (in the formula, R 3 A surface-treated sol-gel silica particle having a monovalent hydrocarbon group having 1 to 6 carbon atoms, which is identical or heterogeneous substituted or unsubstituted.

[0128] (1) In dynamic light scattering, the median diameter is 5 nm to 99 nm, and

[0129] (2) The average circularity is 0.8 to 1.0, and

[0130] (3) The refractive index is 1.38 to 1.42, and

[0131] (4) True density is 1.7 g / cm³ 3 Above 1.9 g / cm³ 3 Less than,

[0132] (5) The ratio expressed as water vapor adsorption specific surface area / nitrogen adsorption specific surface area is 0.4 to 1.9, and

[0133] (6) Methanol hydrophobicity of 67% or more and 75% or less

[0134] It is a surface-treated sol-gel silica particle.

[0135] R 1 ~R 3 Specific examples of this include those identical to those described above.

[0136] By combining the above physical properties (1) to (6), when used as an external additive to toner, good fluidity and printing characteristics are imparted to the toner.

[0137] (1) Median diameter in dynamic light scattering method

[0138] In the dynamic light scattering method of the surface-treated sol-gel silica particles of the present invention, the median diameter is preferably 10 nm to 70 nm. If the median diameter is less than 5 nm, the number of silica particles embedded in the toner particles increases, and when used as an external additive to the toner, the required amount of additive increases, which is undesirable. In addition, if the median diameter exceeds 99 nm, it is undesirable, such as a decrease in fluidity, a decrease in charge amount due to a decrease in surface area, and a decrease in adhesion to the toner particles.

[0139] The median diameter can be determined from the particle size distribution of surface-treated sol-gel silica particles measured by the dynamic light scattering method. The dynamic light scattering method is a method for determining the particle size distribution obtained from scattering intensity by utilizing the fact that the scattering intensity of scattered light obtained by irradiating a dispersion of silica particles with laser light using a dynamic light scattering particle size distribution measuring device (e.g., NanotracWave II-Ex150 manufactured by Microtrackbell) changes according to the particle size of the silica-based fine particles.

[0140] (2) Average circularity

[0141] The sphericity of the surface-treated sol-gel silica particles of the present invention is defined as (periphery of a circle with an area equal to the particle area / particle periphery) when the particles are projected in two dimensions, and it is preferable that the average is 0.92 to 1. If the average sphericity is lower than 0.8, the proportion of irregularly shaped particles increases, and it is easy to cause toner contamination, so it is not desirable.

[0142] (3) Refractive index

[0143] The refractive index indicates the voids inside the surface-treated sol-gel silica particles, and if the refractive index is less than 1.38, it is undesirable because it implies that there are many voids and the cross-linking structure of the sol-gel silica particles is weak. In addition, if the refractive index exceeds 1.42, the voids are small and the specific gravity increases, which may result in a decrease in the charge capacity or a decrease in the adhesion to the toner particles, so it is undesirable.

[0144] In the present invention, the refractive index of the surface-treated sol-gel silica particles is determined by adding and dispersing the surface-treated sol-gel silica particles in a mixed solvent of toluene (refractive index 1.4962) and methyl isobutyl ketone (refractive index 1.3958), adjusting the refractive index according to the mixing ratio of the solvents, and taking the refractive index of the mixed solvent at the point where the dispersion becomes transparent at 25°C (the point where the refractive indices of the mixed solvent and the surface-treated silica microparticles match).

[0145] (4) True density

[0146] The true density is, preferably, 1.75 g / cm³ 3 ~1.85g / cm 3 Its true density is 1.7 g / cm³. 3 If it is less than, it is undesirable because the strength of the surface-treated sol-gel silica particles may decrease. In addition, the true density is 1.9 g / cm³ 3 The above is undesirable because, as the weight per silica particle increases, the impact on the toner particles increases when used as an additive to toner.

[0147] (5) Ratio of water vapor adsorption specific surface area to nitrogen adsorption specific surface area

[0148] The ratio of the water vapor adsorption specific surface area to the nitrogen adsorption specific surface area is a measure of hygroscopicity, and the adsorption specific surface area of ​​each gas can be determined by the BET method. Since water molecules (about 2 Å) are smaller than nitrogen molecules (about 3 Å), a small ratio of the water vapor adsorption specific surface area to the nitrogen adsorption specific surface area indicates that there are pores that are difficult for water molecules to pass through but allow nitrogen to pass through.

[0149] The ratio of the water vapor adsorption specific surface area to the nitrogen adsorption specific surface area is preferably 0.5 to 1.5. If this specific surface area ratio is greater than 1.9, the hygroscopicity is excessively high, and the charge of the toner is greatly affected by humidity, so it is undesirable.

[0150] (6) Methanol hydrophobicity

[0151] The methanol hydrophobicity indicates the hydrophobicity of surface-treated sol-gel silica particles. If the methanol hydrophobicity is less than 67%, it is undesirable because, due to residual silanol groups on the silica surface, when added to toner as an external additive for electrostatic charge development, the amount of charge in the toner is significantly affected by humidity. Furthermore, aggregation of silica microparticles is prone to occur, and dispersibility in the toner is inferior, resulting in poor toner fluidity and print quality. If the methanol hydrophobicity exceeds 75%, when added to toner, the amount of charge in the toner may become excessively high. Meanwhile, the methanol hydrophobicity in the present invention refers to the value measured under the following conditions.

[0152] Method for Measuring Methanol Hydrophobicity

[0153] 0.2 g of surface-treated sol-gel silica particles are added to 60 ml of a methanol aqueous solution with a volume concentration of 50% (temperature 25°C) and stirred with a stirrer. Then, while adding methanol dropwise to the solution in which the silica particles are suspended on the surface, light with a wavelength of 780 nm is irradiated onto the methanol aqueous solution to measure the transmittance. The volume concentration (%) of methanol in the methanol aqueous solution at which the silica particles are suspended and settle and the transmittance becomes 80% is defined as the degree of methanol hydrophobization.

[0154] (Toner additive for electrostatic charge phenomenon)

[0155] In addition, the present invention provides a toner additive for electrostatic phase development containing the above-described surface-treated sol-gel silica particles. When the surface-treated sol-gel silica particles of the present invention are used as a toner additive, they impart good fluidity and printing characteristics to the toner.

[0156] Examples

[0157] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited thereto.

[0158] (Preparation of Surface-Treated Sol-Gel Silica Particles)

[0159] [Example 1-1]

[0160] Process (A1): 793.0 g of methanol, 32.1 g of water, and 40.6 g of 28% ammonia solution were added and mixed in a 3-liter glass reactor equipped with a stirrer, a dropping funnel, and a thermometer. The solution was adjusted to 45°C, and while stirring, 160.9 g of 5.5% ammonia solution and 646.5 g of tetramethoxysilane were simultaneously added dropwise, with the former added over 4 hours and the latter over 6 hours. After the addition of tetramethoxysilane was completed, stirring was continued for an additional 0.5 hours to carry out hydrolysis, thereby obtaining a suspension of hydrophilic sol-gel silica particles.

[0161] Process (A2): 2.0 g of 1,3-divinyl-1,1,3,3-tetramethyldisilazane (equivalent to 0.26 mol per 1 mol of SiO2) was added to the suspension obtained in the above process (A1) at 25°C, and then stirred at 50°C for 1 hour to obtain a dispersion of pre-treated silica particles with a surface dimethylvinylsilylated.

[0162] Process (A3): 205.3 g of hexamethyldisilazane (equivalent to 30 moles per 1 mole of SiO2) was added dropwise to the dispersion obtained in the above process (A2) at 25°C over a period of 0.5 hours, and then reacted at 60°C for 8 hours to obtain a dispersion of surface-treated sol-gel silica particles with a surface further trimethylsilylated. Next, the dispersion medium in this dispersion was removed at 130°C under reduced pressure (6650 Pa) to obtain 271 g of white powder of surface-treated sol-gel silica particles (I).

[0163] [Examples 1-2]

[0164] In Example 1-1, the process was carried out in the same manner as Example 1-1 except that the reaction temperature of the process (A1) was set to 35℃, and 272g of white powder of surface-treated sol-gel silica particles (II) was obtained.

[0165] [Examples 1-3]

[0166] In Example 1-1, the process was carried out in the same manner as Example 1-1 except that the reaction temperature of the process (A1) was set to 27°C, and 269g of white powder of surface-treated sol-gel silica particles (III) was obtained.

[0167] [Examples 1-4]

[0168] In Example 1-1, the process was carried out in the same manner as Example 1-1 except that the reaction temperature of the process (A1) was set to 25°C, and 273g of white powder of surface-treated sol-gel silica particles (IV) was obtained.

[0169] [Examples 1-5]

[0170] In Example 1-1, 3.1 g of 1,3-diphenyl-1,1,3,3-tetramethyldisilazane (equivalent to 0.26 mol per 1 mol of SiO2) was used instead of 1,3-divinyl-1,1,3,3-tetramethyldisilazane in process (A2), and the process was carried out in the same manner as in Example 1-1 to obtain 274 g of white powder of surface-treated sol-gel silica particles (V).

[0171] [Examples 1-6]

[0172] In Example 1-1, 275 g of white powder of surface-treated sol-gel silica particles (VI) was obtained by performing the same procedure as in Example 1-1, except that 3.9 g of 1,3-di-n-octyl-1,1,3,3-tetramethyldisilazane (equivalent to 0.26 mol per 1 mol of SiO2) was used instead of 1,3-divinyl-1,1,3,3-tetramethyldisilazane of process (A2).

[0173] [Comparative Example 1-1]

[0174] In Example 1-1, process (A1) was performed, process (A2) was not performed, and as process (A3), 205.3 g of hexamethyldisilazane (equivalent to 30 molar amount relative to 1 molar of SiO2) was added dropwise over 0.5 hours at 25°C to the suspension obtained in process (A1), and then reacted at 60°C for 8 hours to obtain a dispersion of surface-treated sol-gel silica particles with a surface trimethylsilylated. Subsequently, the dispersion medium in this dispersion was removed at 130°C under reduced pressure (6650 Pa) to obtain 268 g of white powder of surface-treated sol-gel silica particles (VII).

[0175] [Comparative Example 1-2]

[0176] In Examples 1-3, process (A1) was performed, process (A2) was not performed, and as process (A3), 205.3 g of hexamethyldisilazane (equivalent to 30 molar amount relative to 1 molar of SiO2) was added dropwise over 0.5 hours at 25°C to the suspension obtained in process (A1), and then reacted at 60°C for 8 hours to obtain a dispersion of surface-treated sol-gel silica particles with a surface trimethylsilylated. Subsequently, the dispersion medium in this dispersion was removed at 130°C under reduced pressure (6650 Pa) to obtain 268 g of white powder of surface-treated sol-gel silica particles (VIII).

[0177] Table 1 shows the results of measurements taken according to the following measurement methods (1) to (6) for the surface-treated sol-gel silica particles (I) to (VIII) obtained by the above process.

[0178] [measurement method]

[0179] (1) Median diameter in dynamic light scattering method

[0180] 0.1 g of surface-treated sol-gel silica particles and 19.9 g of methanol were placed in a glass bottle, placed in an ultrasonic cleaner, and irradiated with ultrasound at an output of 30 W / L for 10 minutes to disperse the silica particles in the methanol. The median diameter of the dispersion was measured using a dynamic light scattering particle size distribution analyzer (MicroTracWave II-Ex150).

[0181] (2)Circular drawing

[0182] Surface-treated sol-gel silica particles were photographed using an electron microscope (Hitachi, S-4700, magnification: 100,000x), and the circularity (periphery of a circle with an area equal to the particle area / particle periphery) when the particles were projected in two dimensions was evaluated using image analysis particle size distribution measurement software (Mountec Co., Ltd. Mac-View Ver. 5). Meanwhile, the average value of 100 primary particles was used for the circularity.

[0183] (3) Refractive index

[0184] Surface-treated sol-gel silica particles were added and dispersed in a mixed solvent of toluene (refractive index 1.4962) and methyl isobutyl ketone (refractive index 1.3958), and the refractive index was adjusted according to the mixing ratio of the solvents. The refractive index of the mixed solvent at the point where the dispersion becomes transparent (the point where the refractive indices of the mixed solvent and the surface-treated silica microparticles match) was defined as the refractive index of the surface-treated sol-gel silica particles. Meanwhile, the refractive index of the mixed solvent is the value at 25°C measured using a digital refractometer (RX-9000α manufactured by Atago Co., Ltd.).

[0185] (4) True density

[0186] The true density of surface-treated sol-gel silica particles was measured using an automatic true density measuring device (Auto True Denser MAT-7000 manufactured by Seishin Corporation) utilizing the liquid phase displacement method.

[0187] (5) Ratio of water vapor adsorption specific surface area / nitrogen adsorption specific surface area

[0188] Using a high-precision gas adsorption measuring device (Microtrack Bell BELSORP MAXII), the specific surface area of ​​surface-treated sol-gel silica particles for each of the water vapor medium and nitrogen medium was measured according to the BET 1-point method, and the ratio of the water vapor adsorption specific surface area to the nitrogen adsorption specific surface area was calculated.

[0189] (6) Methanol hydrophobicity

[0190] Using a powder wettability tester (WET101P manufactured by Resca Co., Ltd.), 0.2 g of surface-treated sol-gel silica particles were added to 60 ml of a methanol aqueous solution with a volume concentration of 50% (temperature 25°C) and stirred with a stirrer. Subsequently, while adding methanol dropwise to the liquid in which the silica particles were suspended on the surface, light with a wavelength of 780 nm was irradiated onto the methanol aqueous solution to measure the transmittance. The methanol volume concentration (%) in the methanol aqueous solution at which the surface-treated sol-gel silica particles were suspended and settled, and the transmittance reached 80%, was defined as the degree of methanol hydrophobization.

[0191] [Table 1]

[0192]

[0193] As shown in Table 1, the surface-treated sol-gel silica particles of Examples 1-1 to 1-6 exhibited a high degree of methanol hydrophobicity, and their surfaces were highly hydrophobic. On the other hand, in Comparative Examples 1-1 and 1-2, the surface hydrophobicity was insufficient.

[0194] (Manufacture of external additive mixed toner)

[0195] [Examples 2-1 to 2-6, Comparative Examples 2-1, 2-2]

[0196] 96 parts by weight of polyester resin with a Tg of 60°C and a softening point of 110°C and 4 parts by weight of carmine 6BC (manufactured by Sumika Color Co., Ltd.) as a colorant were melt-kneaded, ground, and classified to obtain a toner with a volume median diameter of 7 μm. 10 g of this toner and 0.2 g of surface-treated sol-gel silica particles obtained in Examples 1-1 to 1-6 and Comparative Examples 1-1 and 1-2 were mixed in a sample mill to obtain an external additive mixed toner. These were evaluated by the method of (7) below.

[0197] (7) Toner cohesion

[0198] 10g of toner mixed with external additives was placed in a 20ml polyethylene container, and after being exposed to constant temperature and humidity conditions of 60℃ and 30%RH for 100 hours with the container lid open, 5g of toner was subjected to a powder characteristic evaluation device (Powder Tester PT-X manufactured by Hosokawa Micron Co., Ltd.) and vibrated for 60 seconds with sieve opening diameters of 150μm, 75μm, and 45μm from the top, a vibration amplitude of 1mm, and a vibration frequency of 1Hz. The amount remaining on the sieve was then measured, and the degree of aggregation was calculated using the following formula. The results are shown in Table 2.

[0199] Cohesion (%) = (W1 + 0.6 × W2 + 0.2 × W3) / 5 × 100

[0200] W1: Residual amount (g) on ​​a sieve with an opening diameter of 150 μm

[0201] W2: Residual amount (g) on ​​a sieve with an opening diameter of 75 μm

[0202] W3: Residual amount (g) on ​​a 45μm aperture diameter sieve

[0203] [Table 2]

[0204]

[0205] As shown in Table 2, the external additive mixed toners of Examples 2-1 to 2-6 have low agglomeration, and it can be seen that the surface-treated sol-gel silica particles of the present invention are suitablely used as toner external additives. On the other hand, in Comparative Examples 2-1 and 2-2, the surface treatment of the silica particles was insufficient, resulting in high agglomeration.

[0206] (Manufacture of two-component developer)

[0207] [Examples 3-1 to 3-6, Comparative Examples 3-1, 3-2]

[0208] A two-component developer was prepared by mixing 3 parts by mass of the external additive mixed toner of Examples 2-1 to 2-6 and Comparative Examples 2-1 and 2-2 with 97 parts by mass of the carrier, standard ferrite L (Japan Society of Imaging Science). The results of measurements taken according to the following methods (8) to (12) on the two-component developer obtained by the above process are shown in Table 3.

[0209] (8) Toner charge

[0210] After exposing the above two-component developer to high temperature and high humidity (30℃, 90%RH), medium temperature and medium humidity (25℃, 55%RH), and low temperature and low humidity (10℃, 15%RH) for one day, the amount of charge when each sample was tribocharged under the same conditions was measured using a blow-off powder charge amount measuring device (Toshiba Chemical Co., Ltd., TB-200).

[0211] (9) Toner attachment to photosensitive material

[0212] The above two-component developer was placed in a developer equipped with an organic photosensitive material, and a print test of 30,000 sheets was performed under conditions of 25°C and 50% RH. At this time, the adhesion of toner to the photosensitive material can be detected as whitening of the entire solid image. Here, the degree of whitening is 1 cm 2 The number of white spots was rated as "many" for 10 or more, "few" for 1 to 9, and "none" for 0.

[0213] (10) Photosensitive material wear

[0214] In the print test of (9) above, photosensitive material wear detected as image distortion was evaluated according to the following criteria.

[0215] A: The absence of image distortion

[0216] B: No distortion in the large image

[0217] C: Image distortion

[0218] (11) Evaluation of image defects (white spots)

[0219] The above two-component developer was exposed to an environment of 30°C and 90% RH for one day, and subsequently, 5,000 continuous solid prints (image density 100%) of 20cm x 20cm were produced, after which the above two-component developer was again left to stand under an environment of 30°C and 90% RH. This process was repeated 60 times to produce a total of 300,000 prints. The 10th print from the first day was designated as Print 1, and the final print from the last day was designated as Print 2.

[0220] The presence or absence of image defects (white dots) based on image observation of Printed Material 2 obtained above was evaluated according to the following criteria.

[0221] A: No visible image defects (no white spots)

[0222] B: 1 to 4 white spots (grainy white areas) visible to the naked eye

[0223] C: 5 to 9 white spots visible to the naked eye

[0224] D: 10 or more white spots visible to the naked eye

[0225] (12) Evaluation of change in concentration (ΔE)

[0226] Regarding the change in density of Print 2 relative to Print 1 above, a reflectance meter X-rite 938 (manufactured by X-rite) was used to measure the color difference (ΔE) in the CIE 1976 (L*a*b*) color space in accordance with JIS Z 8781-5, and evaluated according to the following criteria.

[0227] A: ΔE difference is less than 1

[0228] B: ΔE difference is 1 or greater and less than 2.5

[0229] C: ΔE difference is 2.5 or greater and less than 3.0

[0230] D: ΔE difference is 3.0 or greater

[0231] [Table 3]

[0232]

[0233] As shown in Table 3, the two-component developer using the surface-treated sol-gel silica particles obtained in Examples 1-1 to 1-6 as toner additives had small variations in toner charge amount depending on the environment and was free of printing image defects. On the other hand, the one using the surface-treated sol-gel silica particles obtained in Comparative Examples 1-1 and 1-2 had large variations in toner charge amount depending on the environment and had inferior printing characteristics.

[0234] Meanwhile, the present invention is not limited to the above embodiments. The above embodiments are examples, and any configuration that is substantially identical to the technical concept described in the claims of the present invention and exhibits the same functional effects is included within the technical scope of the present invention.

Claims

Claim 1 A method for preparing surface-treated sol-gel silica particles, (A1) general formula (i): Si(OR 4 )4(i)(of the equation, each R 4 A process of obtaining a mixed solvent dispersion of hydrophilic sol-gel silica particles having silanol groups on the surface and substantially composed of SiO2 units by hydrolyzing and condensing a tetrafunctional silane compound represented by (which is a monovalent hydrocarbon group having 1 to 6 carbon atoms of the same or different type), its partial hydrolysis condensation product, or a mixture thereof, in a mixture of a hydrophilic organic solvent and water in the presence of a basic substance; (A2) to the obtained mixed solvent dispersion of hydrophilic sol-gel silica particles, general formula (ii): R 1 R 2 2SiNHSiR 1 R 2 2(ii)(of the formula, R 1 is an alkyl group or alkenyl group having 2 to 8 carbon atoms, or an aryl group having 6 to 8 carbon atoms, and R 2 Silazane compounds represented by (where is an identical or heterogeneous substituted or unsubstituted alkyl group having 1 to 4 carbon atoms), hexaethyldisilazane, general formula (iii-1):R 1 R 2 2SiX (iii-1)(wherein, R 1 and R 2 A monofunctional silane compound represented by the formula (wherein X is an OH group or a hydrolyzable group), a monofunctional silane compound represented by the general formula (iii-2): (C2H5)3SiX (iii-2) (wherein X is as above), or a mixture thereof, is added in an amount of 0.001 to 1 mole per mole of SiO2 unit in the hydrophilic sol-gel silica particles, and (C2H5)3SiO is applied to the surface of the hydrophilic sol-gel silica particles. 1 / 2 Unit or R 1 R 2 2SiO 1 / 2 Unit (R 1 and R 2 A process for obtaining a mixed solvent dispersion of pretreated silica particles by introducing (as described above), and (A3) to the obtained mixed solvent dispersion of pretreated silica particles, general formula (iv): R 3 3SiNHSiR 3 3(iv)(among the formula, R 3 Silazane compounds represented by (which is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms), general formula (v): R 3 3SiX (v)(in the formula, R 3 A monofunctional silane compound represented by (and X is as above) or a mixture thereof is added in an amount of 5 to 50 moles per mole of SiO2 unit in the pretreated silica particles, and R on the surface of the pretreated silica particles 3 3SiO 1 / 2 Unit (R 3 A method for manufacturing surface-treated sol-gel silica particles, comprising a process for obtaining surface-treated sol-gel silica particles by introducing a unit (as described above), wherein the unit introduced to the surface of the hydrophilic sol-gel silica particles in the process (A2) and the unit introduced to the surface of the pre-treated silica particles in the process (A3) are different, and furthermore, the reaction temperature of the surface treatment in the process (A2) is 40 to 80°C, and the reaction temperature of the surface treatment in the process (A3) is 50 to 80°C. Claim 2 delete Claim 3 In paragraph 1, the above R 1 is an alkyl group having 6 to 8 carbon atoms, a phenyl group, or a vinyl group, and the above R 2 is a methyl group, ethyl group, propyl group, or isopropyl group, and the R 3 A method for producing surface-treated sol-gel silica particles characterized by using a methyl group or an ethyl group. Claim 4 R on the surface 1 R 2 2SiO 1 / 2 Unit (in the formula, R 1 is an alkyl group, an aryl group, or a vinyl group having 6 to 8 carbon atoms, and R 2 is an identical or different alkyl group having 1 to 4 carbon atoms) and R 3 3SiO 1 / 2 Unit (in the formula, R 3 Surface-treated sol-gel silica particles having a (which is an identical or heterogeneous substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms), wherein the median diameter in dynamic light scattering is 5 nm to 99 nm, the average circularity is 0.8 to 1.0, the refractive index is 1.38 to 1.42, and the true density is 1.7 g / cm³ 3 Above 1.9 g / cm³ 3 Surface-treated sol-gel silica particles characterized by having a ratio of water vapor adsorption specific surface area to nitrogen adsorption specific surface area of ​​0.4 to 1.9, and a methanol hydrophobization degree of 67% or more and 75% or less. Claim 5 In paragraph 4, the above R 1 This is an alkyl group, a phenyl group, or a vinyl group having 6 to 8 carbon atoms, and the above R 2 ga is a methyl group, ethyl group, propyl group, or isopropyl group, and R 3 Surface-treated sol-gel silica particles characterized by having a methyl group or an ethyl group. Claim 6 An external additive for electrostatic charge development, characterized by containing surface-treated sol-gel silica particles as described in claim 4 or 5.

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