JP2001305804A - Coating agent for carrier for developing electrostatic image and carrier for developing electrostatic image thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for realizing a improved carrier for electrophotography which resists destruction such as wear, peeling, crack, and rarely suffers from a spent phenomenon, so it excels in long-term durability and electrostatic stability. SOLUTION: The present invention provides a coating agent for the carrier which is characteristically composed of spherical hydrophobic fine silica particles having primary particles having an average particle diameter of from 0.01 to 5. μm and an organic resin. Those fine silica particles fulfill the following conditions (i) and (ii). (i) When an organic compound which is liquid at room temperature and has a dielectric constant of from 1 to 40 F/m and fine silica particles are mixed in a weight ratio of 5:1 and shaken, the fine silica particles disperse uniformly in the organic compound. (ii) The quantity of primary particles remaining as primary particles when methanol is evaporated under heating by means of an evaporator from a dispersion prepared by dispersing the fine silica particles in methanol and thereafter the particles are held at 100 deg.C for 2 hours, represents at least 20% of the quantity of primary particles originally present.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating agent for an electrostatic image developing carrier used for developing an electrostatic image in electrophotography, electrostatic recording and the like, and a carrier for developing an electrostatic image using the same. About. In particular, the present invention relates to a coating agent for an electrostatic image developing carrier having excellent copy durability and excellent stability of charging characteristics, and an electrostatic image developing carrier using the same.

[0002]

2. Description of the Related Art Two-component developers comprising a carrier and a toner are widely used in copying machines utilizing electrophotography.
As the carrier in this case, oxidized or unoxidized iron powder is usually used. However, if this is mixed with the toner as it is and used, the triboelectric charging characteristics for the toner are insufficient and the Among them, there is a disadvantage that the toner is fixed to the carrier surface to form a toner film (spent phenomenon), and the charging characteristics of the carrier change with time, and eventually the life of the developer is shortened. Further, there is a disadvantage that the difference in the charging characteristics of the carrier is large between when dry and when wet.

[0003] In order to prevent such defects, the carrier surface is coated with a resin such as a fluororesin, an acrylic resin, a styrene-acryl copolymer, a silicone resin, a polyester resin, and a polyolefin resin.

Further, a method of using fine particles for reducing the surface energy of the carrier to reduce the spent phenomenon is also known. A method of coating a carrier with a resin obtained by adding inorganic solid particles to a silicone resin (Japanese Patent Application Laid-Open No. 54-2173)
No. 0), a method of coating a carrier with mechanical impact force using silicone resin fine particles and styrene and / or acrylic resin fine particles or copolymer resin fine particles thereof.
(JP-A-5-45936), a method of immobilizing resin fine particles on the surface of a carrier coated with polyolefin (JP-A-9-30497)
There is 4).

[0005]

However, in recent years, as the particle size of the developer has been rapidly reduced in recent years in order to improve the quality of an image, stress on the developer and maintenance of the developer characteristics are very problematic. It has become. That is, as the particle size of the developer has been reduced in order to improve the image quality, the speed of the copying machine has been increased, and the load on the developer during the development process appears extremely in the image quality, and the toner is spent on the carrier. It became easy to do. Since the spent causes charging failure, the toner scatters in the copying machine and contaminates the image, and in addition, disadvantages such as a failure to obtain a desired image density are caused.

[0006] In addition, the carrier coating such as abrasion, peeling, and cracking of the carrier coated with the passage of time also occurs, and the carrier is damaged at the same time, and the damaged carrier adheres to the photoconductor and damages the photoconductor. Insufficient durability as a developer has been a problem. On the other hand, Japanese Patent Application Laid-Open No. 2000-44226 describes an organic resin composition comprising an organic resin and hydrophobic silica fine particles, but does not disclose any coating agent, particularly no coating agent for an electrostatic image developing carrier. Therefore, an object of the present invention is to improve an electrophotographic carrier, and it is difficult for destruction such as abrasion, peeling, and cracks to occur, and it is also unlikely that a spent phenomenon occurs. Therefore, long-term durability and stability of carrier charging characteristics are improved. It is to provide a means for realizing an excellent carrier.

[0007]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that spherical hydrophobic particles satisfying the following conditions (i) and (ii) have an average primary particle size of 0.01 to 5 μm. It has been found that a coating agent for a carrier for developing an electrostatic charge image characterized by comprising silica fine particles and an organic resin solves the above problems. (i) When an organic compound which is liquid at room temperature and has a dielectric constant of 1 to 40 F / m and silica fine particles are mixed at a weight ratio of 5: 1 and shaken, the silica fine particles are contained in the organic compound. Disperse evenly. (ii) After the methanol was distilled off from the dispersion in which the silica fine particles were dispersed in methanol by heating with an evaporator, 100 ° C
At a temperature of 2 hours, the ratio of the amount of primary particles remaining as primary particles to the amount of primary particles initially present is 20%.
% Or more.

[0008] By coating a carrier substrate with this coating agent, a carrier free of the above problems can be obtained. Accordingly, the present invention provides a carrier for developing an electrostatic image, which is further coated with a carrier substrate with the above-mentioned coating agent.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments.

[Coating Agent for Electrostatic Image Developing Carrier] The coating agent for an electrostatic image developing carrier of the present invention comprises the following hydrophobic silica fine particles and an organic resin. -Hydrophobic silica fine particles-The silica fine particles used in the present invention are spherical, the surface is highly hydrophobic, and no reactive groups such as silanol groups remain,
It has high dispersibility, low cohesion, good lubricity, and low surface energy, so that good results can be obtained for the objects and effects of the present invention.

The hydrophobic silica fine particles used in the present invention are Si
R ² SiO _3/2 units on the surface of hydrophilic silica fine particles composed of O ₂ units
(Wherein, R ² is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) in the obtained hydrophobic silica fine particle surface by introducing the R ¹ ₃ SiO _1/2 units (Here, R ¹ is the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms) has an average particle diameter of 0.0
These are spherical hydrophobic silica fine particles of 1 to 5 μm.

One example of a method for producing the above-mentioned hydrophobic silica fine particles is as follows. General formula (I): Si (OR ³ ) ₄ (where R ³ is the same or different 1 to 6 carbon atoms)
Or a compound selected from the group consisting of a silane compound represented by the formula (I) and a hydrolytic condensate thereof: a hydrophilic solvent such as methanol or ethanol; water; and a basic compound such as ammonia or an organic amine. A step of obtaining a dispersion of hydrophilic silica fine particles by hydrolysis and condensation in a mixed solution of water; adding water to the obtained dispersion of hydrophilic silica fine particles, distilling off the hydrophilic solvent, and converting the dispersion to an aqueous dispersion. Completely hydrolyzing the alkoxy groups remaining on the surface of the fine particles;

The aqueous dispersion of hydrophilic silica fine particles treated as described above has the general formula (II): R ² Si (OR ⁴ ) ₃ (where R ² is a monovalent hydrocarbon having 1 to 20 carbon atoms) Group,
R ⁴ is the same or different and is a monovalent hydrocarbon group having 1 to 6 carbon atoms), and one or more compounds selected from hydrolytic condensates thereof, and hydrophilic silica fine particles are added. A step of coating the surface to obtain hydrophobic silica fine particles; a step of adding a ketone-based solvent to the hydrophobic silica fine-particle aqueous dispersion and distilling off water to convert to a hydrophobic silica fine-particle ketone-based solvent dispersion; the hydrophobic silica fine particles ketone solvent dispersion, the general formula _{^{(III): R 1 3 SiNHSiR}} 1 3 ( where, R ¹ is 1 of the same carbon atoms or heterologous 1-6
Silazane compound represented by the valence hydrocarbon group), and the general formula _{^{(IV): R 1 3 SiX}} ( where, R ¹ is the general formula (III) silane same .X in represented by OH or hydrolysable groups) A compound selected from the compounds is added and reacted to obtain a silanol group remaining on the surface of the silica fine particles by trialkylsilylation and further highly hydrophobicizing.

Specific examples of the tetrafunctional silane compound represented by the general formula (I) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane. Specific examples of the partially hydrolyzed condensate of the tetrafunctional silane compound represented by the general formula (I) include methyl silicate and ethyl silicate.

The hydrophilic organic solvent is not particularly limited as long as it dissolves the compound of the formula (I) or its partially hydrolyzed condensate and water. Alcohols, methyl cellosolve, ethyl cellosolve, butyl cellosolve, cellosolve acetate, etc. And ketones such as acetone and methyl ethyl ketone, and ethers such as dioxane and tetrahydrofuran. Alcohols are preferable. Examples of the alcohol include an alcohol solvent represented by the general formula (V): R ⁶ OH (V) (where R ⁶ is a monovalent hydrocarbon group having 1 to 6 carbon atoms).
Examples include methanol, ethanol, isopropanol, butanol and the like. As the number of carbon atoms in the alcohol increases, the particle size of the silica fine particles formed increases. Therefore, it is desirable to select the type of alcohol according to the target particle size of the silica fine particles.

The basic compound includes ammonia, dimethylamine, diethylamine and the like.
Preferably it is ammonia. After dissolving a required amount of these basic compounds in water, the resulting aqueous solution (basic water)
May be mixed with a hydrophilic organic solvent.

The amount of water used at this time is represented by the general formula (I)
Is preferably 0.5 to 5 mol with respect to 1 mol of the alkoxy group of the silane compound or the partial hydrolysis condensate thereof, and the ratio of water to the hydrophilic organic solvent is preferably 0.5 to 10 by weight, and The amount of the acidic compound is preferably from 0.01 to 1 mol based on 1 mol of the alkoxy group of the silane compound of the general formula (I) or the partial hydrolysis condensate thereof.

For hydrolysis and condensation of the tetrafunctional silane compound of the general formula (I), the tetrafunctional silane compound of the general formula (I) is dropped into a mixture of water and a hydrophilic organic solvent containing a basic compound. This is performed by a known method. In order to convert the dispersion medium of the silica fine particle mixed solution dispersion into water, for example, an operation of adding water to the dispersion and distilling off the hydrophilic organic solvent (if necessary, repeating this operation) can be performed. .
The amount of water added at this time is 0.5 to 2 times, preferably almost 1 time, in terms of the weight ratio of the total amount of the used hydrophilic organic solvent and the generated alcohol.

Specific examples of the trifunctional silane compound represented by the general formula (II) include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane,
Ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, trifluoro Examples include trialkoxysilanes such as propyltrimethoxysilane and heptadecafluorodecyltrimethoxysilane, and a partially hydrolyzed condensate thereof may be used.

The amount of the trifunctional silane compound represented by the general formula (II) is determined by the amount of SiO _{2 of} the hydrophilic fine silica particles used.
1 to 0.001 mol, preferably 0.1 to 1 mol per unit mol
It is preferable to use 0.01 to 0.01 mol.

In the step of converting the dispersion medium of the aqueous dispersion of hydrophobic silica fine particles into a ketone-based solvent, an operation of adding a ketone-based solvent to the dispersion and distilling off water (this operation is repeated as necessary) is performed. Done. The amount of the ketone solvent added at this time is 0.5 to 5 times, preferably 1 to 2 times the weight ratio of the hydrophilic silica fine particles used. Specific examples of the ketone solvent used here include:
Methyl ethyl ketone, methyl isobutyl ketone, acetylacetone and the like are mentioned, and methyl isobutyl ketone is preferable.

Specific examples of the silazane compound represented by the general formula (III) include hexamethyldisilazane. Specific examples of the monofunctional silane compound represented by the general formula (IV) include trimethylsilanol and triethyl. Monosilanol compounds such as silanol, trichlorochlorosilane, monochlorosilane such as triethylchlorosilane,
Monoalkoxysilanes such as trimethylmethoxysilane and trimethylethoxysilane; monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; and monoacyloxysilanes such as trimethylacetoxysilane are exemplified.

These are used in an amount of 0.1 to 0.5 mol per mol of SiO ₂ unit of the hydrophilic silica fine particles used,
Preferably, 0.2 to 0.3 mol is used.

The hydrophobic silica-based fine particles thus produced can be obtained as a powder by a conventional method.

The particle diameter of the hydrophobic silica fine particles used in the present invention is usually from 0.01 to 0.01 from the viewpoints of preventing the toner from being spent on the carrier and the strength of the coating film coated on the carrier.
It is 5 μm, preferably 0.05 to 0.5 μm. If the particle size is too small, the surface energy of the carrier cannot be reduced and the toner will be spent on the carrier.If the particle size is too large, the film coated on the carrier will be worn, peeled off, cracked, and the damaged carrier will damage the photoconductor. Disadvantage.

The compounding amount of the hydrophobic silica fine particles may be generally in the range of 1 to 50 parts by weight, preferably 10 to 25 parts by weight, based on 100 parts by weight of the organic resin described later. If the compounding amount is too small, the surface energy of the carrier cannot be reduced and the toner will be spent on the carrier.If the compounding amount is too large, the film strength will be weakened and the film will peel off, making it impossible to impart charge to the toner and economically. Disadvantageous.

-Organic resin- The organic resin which is the other essential component of the coating agent of the present invention is not particularly limited, and various resins can be used. Specifically, for example, styrene-based resin, acrylic-based resin, styrene-acryl-based resin, vinyl-based resin, ethylene-based resin, rosin-modified resin, polyamide resin, polyester resin, silicone resin, acryl-modified silicone resin, polyester-modified silicone resin And a resin such as a fluorine-based resin. Of these, silicone resins, acryl-modified silicone resins, polyester-modified silicone resins, and fluorine-based resins are preferred in terms of preventing toner from being spent on a carrier. These resins may be used alone or in combination of two or more.

These resins may be used in organic solvents (for example,
It is preferably dissolved in a hydrocarbon solvent such as toluene, xylene, or volatile oil, alcohol, or ester. The amount of the organic solvent is preferably such that the solid content of the organic resin is 1 to 30% by weight. If necessary, a cross-linking agent or a curing catalyst may be added.

[Electrostatic Image Developing Carrier] The electrostatic image developing carrier of the present invention is obtained by coating a carrier substrate with the above-described electrostatic image developing carrier coating agent.

Typical carrier base particles to be used are iron powder and ferrite powder, and other magnetic metals such as nickel and cobalt or oxides thereof, copper, carborundum, glass beads and silicon dioxide. The carrier base particles can be appropriately selected from known materials as carrier base particles. The particle size of the carrier base particles is 10
1,0001,000 μm, preferably 20-200 μm. The method for producing the carrier of the present invention is not particularly limited, and a known coating method can be applied.

Specifically, the above-mentioned coating agent containing hydrophobic silica fine particles and an organic resin is applied to carrier base particles by, for example, a fluidized bed method, an immersion method, a spray method, etc., and then dried and cured. A method in which a carrier in which only an organic resin is coated by the above method and hydrophobic fine particles are mixed in a required amount, and resin fine particles are adhered and arranged on the surface of the coated carrier, and then mechanically or mechanically applied to the carrier surface. A method of performing a process of applying thermal stress and firmly fixing the hydrophobic fine particles on the carrier surface can be used.

The thickness of the coating layer is preferably 0.1 to 20 μm. It is also possible to apply multiple layers if necessary,
Depending on the purpose, it is also possible to change the components of each layer and apply them repeatedly.

As the toner used when preparing the developer using the carrier of the present invention, a known toner can be used without any particular limitation. Specifically, it is a toner comprising at least a binder resin and a colorant, and may be a toner to which a release agent, a charge control agent, a fluidizing agent, and a magnetic substance are added as necessary. Known materials can be used for the constituent materials. The particle size of the toner is preferably in the range of 1/4 to 1/20 of the weight average particle size of the carrier used.

[0034]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following, the viscosity indicates a value measured at 25 ° C.

Example 1 [Synthesis of spherical hydrophobic silica fine particles] (Step 1) In a 3 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer, 623.7 g of methanol, 41.4 g of water, 2
49.8 g of 8% aqueous ammonia was added and mixed. This solution
Adjust to 35 ° C and stir with tetramethoxysilane 1163.7
g and 5.4% ammonia water 418.1 g were added at the same time,
The former drip over 6 hours and the latter over 4 hours. After the dropwise addition of tetramethoxysilane, stirring was continued for 0.5 hour to carry out hydrolysis to obtain a suspension of silica fine particles. Attach an ester adapter and a cooling tube to the glass reactor, heat to 60 to 70 ° C and distill off 1132 g of methanol.Add 1200 g of water, and then further heat to 70 to 90 ° C to distill off 273 g of methanol. An aqueous suspension of fine silica particles was obtained.

(Step 2) To this aqueous suspension, 11.6 g of methyltrimethoxysilane (equivalent to a molar ratio of 0.01 to tetramethoxysilane) was dropped at room temperature over 0.5 hours, and the mixture was stirred for 12 hours after dropping. The surface of the silica fine particles was treated. (Step 3) After adding 1440 g of methyl isobutyl ketone to the dispersion thus obtained, the mixture was heated to 80 to 110 ° C. and 1163 g of aqueous methanol was distilled off over 7 hours. 357.6 g of hexamethyldisilazane was added to the obtained dispersion at room temperature, and the mixture was heated to 120 ° C. and reacted for 3 hours to trimethylsilyl fine particles. After that, the solvent was distilled off under reduced pressure, and the average particle diameter was 0.12μ.
Thus, 477 g of spherical hydrophobic silica fine particles of m were obtained. The following tests were performed on the obtained hydrophobic silica fine particles.

[Dispersibility test] Fine particles were added to a liquid organic compound at room temperature in a weight ratio of 5: 1, and the mixture was shaken for 30 minutes using a shaker, and the dispersion state of the fine particles was visually observed. I do.を: uniform when the whole amount of the fine particles is dispersed to form a slurry, and ；: when the whole amount of the fine particles is wet with the organic compound but is not partially dispersed in the organic compound, and △; when the fine particles are not wet with the organic compound. The results are shown in Table 1 as x when the two do not mix.

[Aggregation Acceleration Test] (1) Fine particles are added to methanol at a weight ratio of 5: 1, and shaken using a shaker for 30 minutes. The particle size distribution of the fine particles treated as described above is measured by a laser diffraction scattering type particle size distribution analyzer (LA910, Horiba, Ltd.). (2) Next, methanol is distilled off from the fine particle dispersion obtained in (1) by heating using an evaporator, and then the mixture is kept at 100 ° C. for 2 hours. After adding the fine particles thus treated to methanol and shaking for 30 minutes using a shaker, the particle size distribution is measured in the same manner as described above. The ratio of the residual amount of the primary particles is determined based on the particle size distribution obtained in (1). The primary particle diameter is confirmed in advance by observation with an electron microscope. The results are shown in Table 1.

[Preparation of Silicone Resin Liquid] In a 1-liter glass reactor equipped with a stirrer, a cooler, a dropping funnel and a thermometer, an average composition formula is CH ₃ (CH ₃ O) ₂ SiOSi (OCH ₃ ). compounds represented by _{2 CH 3 96.0g, (CH 3} ) 2 Si (OCH 3) a compound represented by _{2 12.0g, HO (CH 3)} 2 SiO [SiO (CH 3) 2] 8 Si (CH 3) 2 After charging 3.7 g of the compound represented by 0H and 135 g of toluene and adding 3.8 g of methanesulfonic acid with stirring, 21.5 g of water was further added to the mixture.
The mixture was added dropwise over time, and aged at 30 ° C. for 12 hours. The obtained solution was neutralized, the by-produced alcohol was distilled off, and the residue was washed with water, dehydrated and filtered, and then diluted with toluene so as to have a nonvolatile content of 40% by weight. An amount of 1.3% by weight of silicone resin was obtained. The obtained silicone resin
100 parts by weight methyl tris (methyl ethyl ketoxime)
After mixing 12 parts by weight of silane and 0.4 part by weight of a xylene solution containing 50% by weight of dibutyltin dioctate, a volatile oil is further added and mixed so that the non-volatile content becomes 25% by weight.
A 1.5 cSt curable silicone resin liquid was obtained. Further, the above silicone resin solution was diluted with toluene to obtain a 4% by weight solution.

[Preparation of Coating Agent] A coating agent was prepared by mixing 100 parts by weight of the above silicone resin solution, 37.5 parts by weight of hydrophobic silica fine particles, and 525 parts by weight of toluene.

[Preparation of Carrier] 1 kg of ferrite having an average particle diameter of 50 μm as carrier base particles was placed in a fluidized bed apparatus.
After spraying 500 g of the above coating agent using (Spilar Flow Mini: trade name, manufactured by Freund Corporation), the silicone component was cured by heating at 150 ° C. for 10 minutes.

[Preparation of Developer] 96 parts by weight of a polyester resin having a Tg of 60 ° C. and a softening point of 110 ° C., and 4 parts by weight of Carmine 6BC (manufactured by Sumitomo Color Co., Ltd.) as a coloring agent were melt-kneaded, pulverized, classified, and averaged. A toner having a diameter of 7 μm was obtained. A developer was prepared by mixing 4 parts by weight of the toner with 96 parts by weight of the treated carrier powder. Using this, the following method evaluated.

[Evaluation of Charging Stability] After the above developer was charged with shaking for 5 minutes or 30 minutes, the toner was charged by a blow-off powder charge amount measuring device (TB-200, manufactured by Toshiba Chemical Co., Ltd.). The amount was measured. If the difference in charge amount due to the shaking time was within 3 μC / g, it was considered stable. The results are shown in Table 1.

[Print Evaluation] The above developer was put into a two-component modified developing machine equipped with an organic photoreceptor, and a print test of 30,000 sheets was performed. Toner spent on the carrier
Observation and evaluation were performed using an electron microscope. The toner scattering was visually evaluated for the degree of contamination inside the copying machine and around the developing device. Carrier destruction was observed and evaluated with an electron microscope. The results are shown in Table 1.

Example 2 In the same manner as in Example 1 except that the hydrolysis temperature of tetramethoxysilane was changed to 20 ° C. instead of 35 ° C. in the synthesis of the spherical hydrophobic silica fine particles, a spherical hydrophobic silica having an average particle diameter of 0.30 μm was used. 467 g of functional silica fine particles were obtained. Using this, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Example 3 A spherical hydrophobic silica having an average particle diameter of 0.09 μm was prepared in the same manner as in Example 1 except that the hydrolysis temperature of tetramethoxysilane was changed to 40 ° C. instead of 35 ° C. in the synthesis of the spherical hydrophobic silica fine particles. 469 g of functional silica fine particles were obtained. Using this, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 451 g of spherical silica fine particles having an average particle size of 0.12 μm in the same manner as in Example 1 except that the step of trimethylsilylating silica fine particles using hexamethyldisilazane in (Step 3) in Example 1 was omitted. I got Using this, evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 2 1200 g of water used for solvent replacement in (Step 1) of Example 1
In the same manner as in Example 1 except that a mixture of 1000 g of water and 1000 g of methyl isobutyl ketone was used in place of
468 g of spherical hydrophobic silica fine particles of μm were obtained. Using this, evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 3 Nipsil SS50F prepared by treating the surface of a precipitated silica with an organosilicon compound instead of the spherical hydrophobic silica fine particles of Example 1.
(Nippon Silica Co., Ltd.) was evaluated in the same manner as in Example 1.

Comparative Example 4 Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.) obtained by hydrophobizing fumed silica in place of the spherical hydrophobic silica fine particles of Example 1 was evaluated in the same manner as in Example 1.

Comparative Example 5 A carrier was obtained in the same manner as in Example 1 except that the spherical hydrophobic silica fine particles of Example 1 were not added. This was evaluated in the same manner as in Example 1.

[0052]

[Table 1]

Note: MIBK: methyl isobutyl ketone, THF: tetrahydrofuran, D ₅ : decamethylcyclopentasiloxane

[0054]

[Table 2]

[0055]

As described above in detail, the carrier coated with the coating agent for an electrophotographic carrier of the present invention has abrasion and wear.
Peeling, cracking and the like are hardly generated, and spent phenomenon is hardly generated. Therefore, it can withstand use for a long time and is excellent in stability of carrier charging characteristics.

Claims (3)

[Claims] An electrostatic charge image comprising spherical hydrophobic silica fine particles having an average primary particle size of 0.01 to 5 μm and an organic resin satisfying the following conditions (i) and (ii): Coating agent for development carrier. (i) When an organic compound which is liquid at room temperature and has a dielectric constant of 1 to 40 F / m and silica fine particles are mixed at a weight ratio of 5: 1 and shaken, the silica fine particles are contained in the organic compound. Disperse evenly. (ii) After the methanol was distilled off from the dispersion in which the silica fine particles were dispersed in methanol by heating with an evaporator, 100 ° C
At a temperature of 2 hours, the ratio of the amount of primary particles remaining as primary particles to the amount of primary particles initially present is 20%.
% Or more. Wherein the hydrophobic silica fine particles are made of SiO ₂ units hydrophilic silica fine particle surface in the R ² SiO _3/2 units (wherein, monovalent R ² is a substituted or unsubstituted 1 to 20 carbon atoms carbide Hydrogen group)
Hydrophobic silica fine particle surface in R ¹ ₃ SiO _1/2 units obtained by introducing a (however, monovalent hydrocarbon group of R ¹ may be the same or a substituted or unsubstituted 1-6 carbon atoms heterologous) 2. The coating agent for an electrostatic image developing carrier according to claim 1, wherein the coating agent is a spherical hydrophobic silica fine particle having an average particle size of 0.01 to 5 [mu] m obtained by introducing the compound. 3. An electrostatic image developing carrier comprising carrier substrate particles coated with the electrostatic image developing carrier coating agent according to claim 1 or 2.