JPH1195480A - Developer and developing device using that - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developer having stable electrification property and enough fluidity by incorporating specified toner particles and a silicate fine powder the surface of which is treated with hexamethylsilazane and which is deposited on the surface of the toner particles, and by controlling the coating rate of the toner particles with the silicate fine powder to a specified value. SOLUTION: This developer contains toner particles containing a coloring agent, a binder resin and a charge controlling agent, and a silicate fine powder depositing on the toner particle surface. The coating rate of the toner particles with the silicate fine powder is controlled to 60 to 100%. Since the toner particles of the developer are coated with the silicate fine powder treated with hexamethylsilazane by 60 to 100% coating rate, the developer has good fluidity and stable electrification property even at high temp. and high humidity. By using this developer, a good image can be obtd. without causing decrease in the image density, or without fog or splashing of a toner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used for electrophotography, electrostatic recording, and the like, and a developing device using such a developer.

[0002]

2. Description of the Related Art Generally, in an electrophotographic method or an electrostatic recording method, a developing method is used to develop an electrostatic latent image formed on a latent image carrier made of a photoconductive photoreceptor or a dielectric. After the toner image is transferred to a transfer material such as paper after development, if necessary, the toner is thinned by a blade or the like on a sleeve or a toner supply roller, and is appropriately charged and finely powdered. , Fixed by solvent vapor, etc.
A copy is obtained.

The developing methods applied to the electrophotographic method and the like are roughly classified into a dry developing method and a wet developing method.
The former is further divided into a method using a two-component developer and a method using a one-component developer.

Among the two-component developing methods, there are a magnet brush method using an iron powder or a ferrite carrier, a cascade method using a bead carrier, a fur brush method using a fur, and the like, depending on the type of the carrier for conveying the toner.

Further, those belonging to the one-component developing method include:
Powder cloud method in which toner particles are sprayed, contact development method (contact development or toner development) in which toner particles are brought into direct contact with the electrostatic latent image surface and developed, and toner particles are directly in contact with the electrostatic latent image surface A jumping development method in which the toner particles are charged without contact and fly toward the latent image surface by an electric field of the electrostatic latent image, and a magneless developing method in which a magnetic conductive toner is brought into contact with the electrostatic latent image surface and developed. There is a law.

[0006] As a toner applied to these developing methods, fine powders in which dyes and pigments are dispersed in natural or synthetic resins have been used. For example, a dispersion of a colorant in a binder resin such as polystyrene is
Particles pulverized to about μm are used as toner.

In the case of a system using a so-called two-component developer, the toner is usually used by being mixed with carrier particles such as glass beads, iron powder and ferrite.

The charge controlling agent used in such a toner for dry development includes, for example, amino compounds, quaternary ammonium compounds, metal complex salts of Co, Cr, Fe and the like, and organic dyes.

However, these dyes as charge control agents have complicated structures, are not fixed, and have poor stability. In addition, decomposition or deterioration due to decomposition during heat kneading, mechanical shock, friction, changes in temperature and humidity conditions, and the like may cause a phenomenon in which charge controllability is reduced. Therefore, when a toner containing these dyes as a charge controlling agent is developed in a copying machine, the dyes are decomposed or deteriorated with an increase in the number of copies, and the toner is liable to deteriorate.

In addition, many charge controlling dyes are hydrophilic, and due to poor dispersion in these resins, the dye is exposed on the toner surface when pulverized after melt-kneading. When the toner is used under a high humidity condition, there is a disadvantage that a high quality image cannot be obtained because these dyes are hydrophilic.

As described above, when a conventional dye having charge controllability is used for a toner, the dye is generated on the surface of the toner particles between toner particles, between a toner and a carrier, or between a toner and a carrier such as a sleeve. Variations occurred in the charge amount, and failures such as development fog, toner scattering, and carrier contamination were likely to occur.

Further, in many conventional toners, under high-humidity conditions, the fluidity of the toner is reduced, the transfer efficiency of the toner image is significantly reduced, and the toner cannot be used.

[0013] In order to overcome the various deficiencies associated with the conventional toner as described above, a method of adhering various external additives to the toner surface has been often used. As the external additive, those having a property of providing positive or negative chargeability to the toner, such as fine silica powder and metal oxide, are often used.

As described above, in order to impart chargeability and fluidity to a toner, it is widely used to add an external additive such as a fine silica powder or a metal oxide.

FIG. 4 is a graph showing the relationship between the number of sheets passed and the amount of charge in the case where the external additive has an appropriate charge providing ability. As shown in the figure, when the charging ability is appropriate, the charging ability is substantially constant regardless of the number of sheets passed.

FIG. 5 is a graph showing the relationship between the number of sheets passed and the amount of charge when the charging ability of the external additive is excessive, and FIG. 6 when the charging ability of the external additive is insufficient. Each figure is shown. As shown in FIG. 5, when the charge providing ability is excessive, the charge amount tends to increase during repeated image formation (continuous paper passing). At this time, the chargeability of the toner is not stable, and image defects such as a decrease in image density occur. Further, as shown in FIG. 6, when the charge providing ability of the external additive is insufficient, the amount of charge is reduced during repeated image formation, and the toner is developed in a non-image area. Further, a phenomenon occurs that the toner is scattered inside the copying machine. It is considered that this charging ability is determined by the amount and type of the external additive.

Such external additives have been treated with a hydrophobizing agent for the purpose of preventing the toner from absorbing moisture and obtaining good fluidity even under high humidity conditions. .

For example, on the surface of silica, a hydrophilic silanol group (Si-OH) and a hydrophobic siloxane (Si-O
-Si) is present. The water molecules are adsorbed on the silanol groups of the silica, so that the silanol groups are made to react with other substances by a chemical reaction to make them hydrophobic.

FIG. 7 is a schematic diagram showing a reaction between silanol groups on the silica surface and dimethyldichlorosilane as an example of hydrophobicizing the silica surface with a general silicone resin. As shown, the silanol groups are hydrophobized by reaction with dimethyldichlorosilane. However, hydrophobized silica using dimethyldichlorosilane has many residual hydrophilic groups, and has a problem that aggregation and deterioration of chargeability under high humidity conditions are inevitable. In particular, when an external additive is excessively added, these problems have become remarkable. In addition, when the degree of hydrophobicity of the surface of the external additive was low, the amount of adsorbed water was increased, and the aggregation and the deterioration of chargeability were large.

On the other hand, if the external additives are insufficient, there is a problem that a sufficient toner fluidity cannot be obtained.

[0021]

As described above, in the conventional developer, a charge control agent is used to improve the chargeability. However, the charge control agent alone has a stable chargeability and a sufficient chargeability. Due to the inability to obtain flowability, various external additives have been used. However, even if these external additives are added, aggregation and deterioration of chargeability are unavoidable, especially under high-humidity conditions. This leads to image defects such as deterioration of so-called fog, and furthermore, phenomena such as toner scattering in which toner scatters inside the copying machine.

The present invention has been made in view of the above circumstances, and provides a developer having stable chargeability and sufficient fluidity to prevent a decrease in image density, fog, toner scattering, and the like. The purpose is to obtain good images.

Also, Another object of the present invention is to provide a developing device that uses a developer having stable charging properties and sufficient fluidity to prevent a decrease in image density, fog, and toner scattering, and to obtain a good image. It is in.

[0024]

The present invention firstly comprises toner particles containing a colorant, a binder resin, and a charge control agent, and fine silica powder adhered to the surface of the toner particles. The coverage of the toner particles with the silica fine powder is 6
0 to 100% of a developer is provided.

The present invention provides, secondly, toner particles containing a colorant, a binder resin, and a charge controlling agent, and fine silica particles adhered to the surface of the toner particles and the surface of which is treated with hexamethyldisilazane. A developer container containing a developer having a coverage of the toner particles of 60 to 100% with the fine silica particles, the developer container being provided opposite to the image carrier, A developer carrying member connected to the developer carrying the developer supplied from the developer container, and supplying the carried developer to the image carrying member to perform development. A developing device is provided.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is to improve a developer in which fine silica powder is attached as an external additive to toner particles.

The developer of the present invention comprises toner particles containing a colorant, a binder resin, and a charge control agent, and fine silica powder which adheres to the surface of the toner particles and whose surface is treated with hexamethyldisilazane. And the coverage of the toner particles with the fine silica powder is 60 to 100%.

The developing device of the present invention refers to a developing device to which the developer of the present invention is applied. The developing device includes toner particles containing a coloring material, a binder resin, and a charge control agent, and adheres to the surface of the toner particles. A developer container containing a developer having a surface coated with fine particles of silicic acid treated with hexamethyldisilazane and having a coverage of 60 to 100% of the toner particles with the fine particles of silicic acid; A developer carrier that is provided to face and is connected to the developer container to carry the developer supplied from the developer container, and supplies the carried developer to the image carrier to perform development; And

In the present invention, fine silica powder is used as an external additive. As the fine silica powder here,
Anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate and zinc silicate can all be applied.

The surface of the fine silicic acid powder used in the present invention is subjected to a hydrophobic treatment with a silicone resin, particularly hexamethyldisilazane.

Of the silicic acid fine powder used as an external additive, anhydrous silicon dioxide (silica) is produced by high-temperature gas-phase hydrolysis in an oxyhydrogen salt of silicon tetrachloride according to the following reaction formula. It is.

[0032]

Embedded image On the other hand, wet silica is produced by adding a mineral acid to an aqueous solution of water glass (Na ₂ SiO ₃ ). The silica produced by this method precipitates in the liquid phase in the form of a hydrosol, which is filtered, washed with water, dried, pulverized and classified to obtain a product.

The silica preferably used in the present invention is silica (dry silica) produced by high-temperature gas phase decomposition,
Compared to wet silica, it is loosely agglomerated and therefore has excellent dispersibility.

In the present invention, the coverage is calculated as follows.

FIG. 1 is a schematic diagram showing a contact state between silica and toner. In the figure, reference numeral 100 indicates silica fine powder, and 200 indicates toner particles.

When the silica concentration is c%, the number n of silica adhering to one toner particle is expressed by the following equation (2).

[0037]

(Equation 3) Where c is the silica concentration (%), ρ _t is the toner density (g / cm ³ ), ρ _s is the silica density (g / cm ³ ), d
_t is the toner average particle diameter (cm), and _ds is the silica average particle diameter (cm). The projected area S of one silica on the toner sphere is represented by the following equation (3).

[0038]

(Equation 4) The area (coverage) where the toner surface is covered with silica is
It is represented by the following equation (1).

[0039]

(Equation 5) In the present invention, the coverage is calculated using the following values.

Toner density: ρ _t = 1.22 (g / cm ³ ) Silica density: ρ _s = 2.2 (g / cm ³ ) In the developer of the present invention, toner particles were treated with hexamethylsilazane. It is coated with silica fine powder at a coverage of 60 to 100%, whereby the fluidity is improved and the chargeability is stable even under high temperature and high humidity. By using such a developer, a good image can be obtained without lowering the image density, fogging, toner scattering and the like.

Further, a carrier whose surface is coated with a silicone resin is preferably mixed with the developer of the present invention. By using such a carrier, the fluidity of the developer becomes better, and the chargeability is further stabilized.

Next, a developing device to which the developer used in the present invention can be applied will be described.

FIG. 2 is a schematic view showing an example of the developing device of the present invention.

As shown in FIG. 2, the developing device 14 is provided to face the photosensitive drum 10 rotatably arranged. The photosensitive drum 10 is rotated in the direction of arrow a by a main motor (not shown).

An electrostatic latent image corresponding to image information to be recorded is formed on the surface of the photosensitive drum 10 by a laser beam from a laser exposure device described later.

A charging device 12 for charging the photosensitive drum 10 to a predetermined potential is formed around the photosensitive drum 10 along its rotation direction (arrow a), and is formed on the photosensitive drum 10 by a laser exposure device described later. Developing device 14 that develops the electrostatic latent image by supplying toner to the formed electrostatic latent image, transfer device 16 that transfers the toner image formed on photosensitive drum 10 by developing device 14 to paper, and photosensitive drum 10
A cleaning device 18 for scraping off toner remaining on the surface, that is, untransferred toner, and a charge removing device 19 for removing charges remaining on the surface of the photosensitive drum 10 are arranged in this order. Note that the static eliminator 19 is disposed integrally with the housing of the cleaning device 18. Further, the cleaning device 18 has a drum holding portion that supports the photosensitive drum 10 when the photosensitive drum 10 is loaded into the image forming apparatus 1, and is also used as a drum holding member.

The charging device 12 includes a corona wire 12a and a grid screen 12b, is connected to a high voltage generating circuit and a grid bias voltage generating device (not shown), and charges the surface of the photosensitive drum 10 to a predetermined surface potential.

The developing device 14 is a two-component developer D in which a toner T containing a binder resin, a coloring material, a charge controlling agent and fine silica powder and a carrier C of a magnetic member are mixed at a predetermined ratio. And a developing roller 14a that holds only the negatively charged toner to the electrostatic latent image formed on the photoconductor drum 10 while holding the toner on the outer periphery. The two-component developer D and the developing roller 14a are housed in a housing 14b.

At both longitudinal ends of the developing roller 14a, the distance between the surface of the non-magnetic sleeve forming the outer peripheral surface of the developing roller 14a and the photosensitive layer on the surface of the photosensitive drum 10 is kept constant. Guide roller 14c is provided. Thus, the distance between the surface of the sleeve and the photosensitive layer of the photosensitive drum 10 is always kept constant.
The sleeve of the developing roller 14a has S
A magnet medium in which a plurality of pole and N pole fixed magnets are arranged at a predetermined angle is provided.

A predetermined developing bias voltage is applied to the developing roller 14a and the carrier C and the toner T, that is, the developer D in the developing device 14 via a developing bias voltage generating circuit (not shown).

When developing the electrostatic latent image formed on the surface of the photosensitive drum 10, the carrier C formed on the sleeve along the lines of magnetic force generated from the main magnetic pole of the magnet medium of the developing roller 14a is developed. The toner adhered to the ears (spikes) by a mirror image force is formed by the potential of the electrostatic latent image on the photosensitive drum 10 and the developing bias voltage in a developing region where the photosensitive drum 10 and the developing roller 14a face each other. The toner is moved by the electric field, and the electrostatic latent image is developed.

The toner T used in the above-described image forming process will be described below.

As the binder resin used in the production of the toner according to the present invention, a copolymer of styrene and its substituent or an acrylic resin which has been conventionally used as a binder resin for a toner can be used.

Examples of the copolymer of styrene and its substituted product include polystyrene homopolymer, hydrogenated styrene resin, styrene-isobutylene copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene terpolymer. Acrylonitrile-styrene-acrylic ester terpolymer, styrene-acrylonitrile copolymer, acrylonitrile-acrylic rubber-styrene terpolymer, acrylonitrile-chlorinated polystyrene-styrene terpolymer, acrylonitrile-EVA- Styrene terpolymer, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer,
Examples thereof include styrene-butadiene rubber, styrene-maleic acid ester copolymer, styrene-isobutylene copolymer, and styrene-maleic anhydride copolymer.

As the acrylic resin, for example,
Polyacrylate, polymethyl methacrylate, polyethyl methacrylate, poly-n-butyl methacrylate, polyglycidyl methacrylate, polyfluorinated acrylate, styrene-methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-ethyl acrylate copolymer And the like.

Other examples of the binder resin include polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, phenol resin, urea resin, polyvinyl butyral, polyacrylic resin, rosin, modified rosin, Terpene resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like can be used alone or in combination.

As the colorant used in the present invention, carbon black, organic or inorganic pigments and dyes, and the like are used. Although there are no special restrictions, carbon black includes acetylene black, furnace black, thermal black, channel black, Ketjen black and the like, and face dyes such as Fast Yellow G,
Benzin Yellow, Indofast Orange, Irgazin Red, Carmin FB, Permanent Bordeaux FR
R, Pigment Orange R, Risor Red 2G, Lake Red C, Rhodamine FB, Rhodamine B Lake, Phthalocyanine Blue, Pigment Blue, Brilliant Green B, Phthalocyanine Green, Quinacridone, and the like. These may be used alone or in combination. Can be used.

Specific examples of the charge control agent used in the present invention include metal-containing azo dyes such as "Varifast Black 3804", "Bontron S-31" and "Bontron S".
-32 "," Bontron S-34 "," Bontron S-
36 (manufactured by Orient Chemical Co., Ltd.), Eizen Spiron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.), and other metal complexes of copper phthalocyanine dyes and alkyl derivatives of salicylic acid, such as Bontron E-82 and Bontron E-
84 "and" Bontron E-85 "(all manufactured by Orient Chemical Co., Ltd.).

[0059]

The present invention will be described below in detail with reference to examples.

Example 1 Raw materials used as an example of the developer of the present invention are prepared in the following ratio.

Polyester resin 94 parts by weight Binder resin Boron complex 1 part by weight Charge control agent Carbon black 5 parts by weight Coloring agent The prepared raw materials were mixed. As the mixing means, for example, a ball mill, a V-type mixer, a Henschel mixer, or the like can be used.

The obtained mixture was melt-kneaded. As the melt-kneading means, for example, a roll, a pressure kneader, an internal mixer, a screw-type extruder or the like can be used.

The obtained kneaded material was cooled. As the cooling means, for example, a cooling conveyor, a cooling drum, or the like can be used.

As a means for coarsely pulverizing, finely pulverizing and classifying the obtained kneaded material, for example, a hammer mill, a cutter mill, a jet mill, a roller mill, a ball mill and the like can be used. Further, as a means for finely pulverizing the coarsely pulverized product, a jet mill, a high-speed rotary pulverizer or the like can be used. As a means for classifying the finely pulverized material, an air flow classifier is preferably used.

External additives were mixed with the obtained toner.
As means for mixing the external additive, for example, it is desirable to use a high-speed fluid mixer. Examples of the high-speed flow type mixing device include a Henschel mixer, a super mixer,
A micro speed mixer and the like can be mentioned.

By coarse pulverization / fine pulverization / classification average, the particle size was 8
Silica having an average particle diameter of 7 nm, which had been subjected to surface hydrophobization treatment with hexamethyldisilazane, was added to the toner adjusted to μm so that the silica concentration was 0.5% by weight. At this time, the ratio of the surface area of the toner assumed as a true sphere to be covered with silica (coverage) was 79.5%. The obtained toner was measured and evaluated for its coverage, charge amount, charge amount stability, image density, fog, and toner scattering. Table 2 shows the results.

The charge amount stability is calculated by the following equation (4) (charge amount after passing 50,000 sheets / initial charge amount) × 100 (%) (4). It is desirable that the range of the charge amount is 90 to 105%.

FIG. 3 is a graph showing the relationship between the silica coverage and the charge stability when the surface of the silica fine powder was hydrophobized with dimethyldichlorosilane and hexamethyldisilazane, respectively. In the figure, 101 is the case of silica surface-treated with hexamethyldisilazane;
Shows the case of silica surface-treated with dimethyldichlorosilane.

As shown in the figure, the silica surface-treated with hexamethyldisilazane has a silica coverage of 60 to 100% showing a charge amount of 90 to 105%, whereas the silica surface coverage with dimethyldichlorosilane is 60 to 100%. In the case of the treated silica, the silica coverage range showing a charge amount of 90 to 105% is narrowed to about 69 to 80%.

Examples 2 to 9 and Comparative Examples 1 to 4 For Examples 2 to 9 and Comparative Examples 1 to 4, the toner particle size, silica particle size, silica surface treating agent, and silica concentration are shown in Table 1 below. A developer was obtained in the same manner as in Example 1 except for the above.

[0071]

[Table 1] The obtained developer was stirred with a ferrite carrier coated with a silicone resin and the above toner for 1 hour using a ball mill to obtain a developer.

However, in Comparative Example 4, a toner similar to that in Example 9 and a ferrite carrier coated with a fluororesin were stirred using a ball mill to obtain a developer.

The obtained developer was introduced into the copying machine shown in FIG. 1 to form an image, and an initial test and a life test after passing 50,000 sheets were conducted. In each test, the image density, charge amount, fogging, and toner scattering were measured.

The image density was measured by obtaining a solid image density using a Macbeth densitometer. Image density is 1.3
Desirably, it is 0 or more.

The measurement of fog was carried out by using a colorimeter (manufactured by Minolta) to determine the color difference between the white background portion of the image and the white paper. The fog is desirably 1.0 or less.

The charge amount was measured using a blow-off powder charge amount measuring device TB-200 manufactured by Toshiba Chemical Corporation.

The evaluation results of Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 2 below.

[0078]

[Table 2] As described above, in Examples 1 to 9, the image density, fog, and toner scattering at the initial stage and after 50,000 sheets were passed were all good.

On the other hand, in Comparative Example 1, since the silica coverage on the toner surface was small, the charge amount was reduced during continuous paper passing, and fog and toner scattering were observed to be worse.

In Comparative Example 2, since the coverage was high,
During continuous paper passing, the charge amount increased, and the image density decreased.

In Comparative Example 3, although the toner particle diameter, the silica particle diameter and the silica concentration were the same as those in Example 9, the charge amount increased during continuous paper feeding, and the image density decreased. on the other hand,
Under a high humidity condition, the charge amount was significantly reduced, and fog was deteriorated. This is because dimethyldichlorosilane-treated silica having a lower hydrophobicity than hexamethyldisilazane-treated silica was used.

In Comparative Example 4, although the same toner as in Example 9 was used, the charge amount increased during continuous paper feeding. This is because the developer was a carrier using a carrier coated with a fluororesin having higher negative chargeability.

[0083]

According to the present invention, a developer having stable chargeability and sufficient fluidity can be obtained. By using such a developer, it is possible to prevent a decrease in image density, fog, toner scattering, and the like, and obtain a good image.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a contact state between silica and a toner.

FIG. 2 is a schematic view illustrating an example of a developing device of the present invention.

FIG. 3 is a graph showing the relationship between silica coverage and charge stability.

FIG. 4 is a graph showing the relationship between the number of sheets passed and the charge amount.

FIG. 5 is a graph showing the relationship between the number of sheets passed and the charge amount.

FIG. 6 is a graph showing the relationship between the number of sheets passed and the charge amount.

FIG. 7 is a schematic diagram showing a reaction between silanol groups on a silica surface and dimethyldichlorosilane.

[Description of sign]

 DESCRIPTION OF SYMBOLS 10 ... Photoreceptor drum 12 ... Charging device 14 ... Developing device 16 ... Transfer device 18 ... Cleaning device 19 ... Static elimination device

Claims (8)

[Claims] Claims: 1. A toner comprising: a toner particle containing a colorant, a binder resin, and a charge controlling agent; and a silica fine powder adhered to the surface of the toner particle, the surface of which is treated with hexamethylsilazane. A developer, wherein the coverage of the toner particles with the acid fine powder is 60 to 100%. 2. A toner particle containing a colorant, a binder resin, and a charge control agent, a fine silica powder adhered to the surface of the toner particle, and the surface of which is treated with hexamethylsilazane; A carrier which is mixed with toner particles coated with a body and whose surface is coated with a silicone resin, wherein the coverage of the toner particles with the fine silica powder is 60 to 100%. Agent. 3. The silicate fine powder is selected from the group consisting of anhydrous silicon dioxide, aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate. 3. The developer according to 1 or 2. 4. The coverage is calculated by the following equation (1). The developer according to claim 1, wherein the developer is represented by the following formula. 5. A toner comprising a colorant, a binder resin, and a charge control agent, and fine silica particles adhered to the surface of the toner particles. The coverage of the fine silica particles with the fine toner particles is A developer container that contains a 60 to 100% developer, and a developer container that is provided to face the image carrier;
While carrying the developer supplied from the developer container connected to the developer container, the image carrier,
A developer carrying member that supplies the carried developer to perform development. 6. A toner particle containing a colorant, a binder resin, and a charge controlling agent, a fine silica powder adhered to the surface of the toner particle, and the surface of which is treated with hexamethylsilazane; A carrier containing a developer mixed with the toner particles coated with the body and having a surface coated with a silicone resin, wherein the coverage of the toner particles with the fine silica particles is 60 to 100%. A developer container, provided opposite to the image carrier, connected to the developer container to carry the developer supplied from the developer container, and a developer carried by the image carrier; And a developer carrier that supplies the developer to perform development. 7. The silicate fine powder is selected from the group consisting of anhydrous silicon dioxide, aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate. 7. The developing device according to 5 or 6. 8. The coverage is calculated by the following equation (1). The developing device according to any one of claims 5 to 7, wherein: