JP3230004B2 - Negatively chargeable magnetic one-component developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, and the like.

[0002]

2. Description of the Related Art There are many known developing methods in electrophotography. Until now, U.S. Pat.
The cascade developing method described in U.S. Pat. No. 618,552 and the magnetic brush method described in U.S. Pat. No. 2,874,063 have been widely used.

All of these methods are excellent methods for obtaining a good image relatively stably. However, on the other hand, there are common problems concerning the two-component developer such as deterioration of the carrier and fluctuation of the mixing ratio of the toner and the carrier. Have.

In order to avoid such a problem, various developing methods using a one-component developer consisting of toner alone have been proposed. Among them, many excellent methods using a developer consisting of magnetic toner particles are used. .

[0005] US Pat. No. 3,909,258 proposes a method of developing using a magnetic toner having electrical conductivity. This is a technique in which a conductive magnetic developer is supported on a cylindrical conductive toner carrier (sleeve) having magnetism therein, and this is brought into contact with an electrostatic image for development.

At this time, a conductive path is formed between the surface of the recording medium and the surface of the sleeve by the toner particles in the developing device. Due to the Coulomb force, toner particles adhere to the image area and are developed.

The developing method using the conductive magnetic toner is an excellent method which avoids the problems associated with the conventional two-component developing method. However, since the toner is conductive, the developed image can be transferred from a recording medium to plain paper. However, it is difficult to electrostatically transfer to a final supporting member.

As a developing method using a high-resistance magnetic toner capable of electrostatic transfer, there is a developing method utilizing dielectric polarization of toner particles. However, such a method is problematic in that the development speed is essentially low and the density of a developed image cannot be sufficiently obtained, and is practically difficult.

As another developing method using a high-resistance magnetic toner, the toner particles are frictionally charged by friction between the toner particles, friction between the toner particles and a sleeve or the like, and are contacted with the electrostatic image holding member. Methods for developing are known. However, in these methods, the number of times of contact between the toner particles and the friction member is small and triboelectric charging is likely to be insufficient, and the charged toner particles are liable to agglomerate on the sleeve due to an increased Coulomb force between the sleeve and the like. It had problems and was practically difficult.

The applicant has previously proposed a new developing method which has solved the above-mentioned problems in Japanese Patent Application Laid-Open No. 55-42141. It is developed by applying a very thin insulating magnetic toner on a sleeve, triboelectrically charging it, and then facing the electrostatic image very close to the electrostatic image under the action of a magnetic field and causing the toner to fly. It is.

According to this method, the degree of contact between the sleeve and the toner is increased by applying the magnetic toner extremely thinly on the sleeve, and sufficient frictional charging is enabled.
The toner is supported by the magnetic force, and the magnet and the toner are relatively moved to dissolve the aggregation of the toner particles and sufficiently rub against the sleeve.The toner is supported by the magnetic force, and the electrostatic force is applied to the toner. An excellent image can be obtained by, for example, preventing background fog by developing the image without facing the image.

However, also in this method, the triboelectric charge of the toner particles applied on the sleeve is significantly smaller than the triboelectric charge of the toner particles in the ordinary two-component developing method.

When a magnetic toner having only a weak charge amount is used in such a method, low image density, scattering, bleeding, image unevenness, etc. are generated, and the image quality is insufficient.

In particular, the initial image density is low, and several hundred copies are usually required to stabilize it at a good high density. This instability at the start is one of the major problems in one-component development. In order to solve the rising instability, it is conceivable to improve the triboelectric charge amount of the toner, and as a means for adding the triboelectric charge, it is known to add fine silica powder (silicon oxide, silica) to the developer. .

Here, silica is hydrophilic as it is, and may cause agglomeration due to moisture in the air to lower the fluidity, or the charge amount of the developer may deteriorate due to moisture absorption of silica.

In order to solve such a problem, a method of adding a hydrophobized silicic acid fine powder to a developer is disclosed in
No. 5782, JP-A-48-47345, JP-A-48-47346, and the like. This is a method in which a silicic acid fine powder is reacted with a silane coupling agent, and the silanol group on the surface of the silicic acid fine powder is replaced with another organic group to make the silicic acid fine powder hydrophobic. However, in this method, although the fine silica powder is tentatively hydrophobized, the degree of hydrophobicity is not sufficient, so that the charge amount of the developer is often deteriorated when left under high humidity conditions. .

Therefore, Japanese Patent Application Laid-Open No. 63-139367 discloses a developer containing fine silica powder which has been treated with a silane coupling agent and further treated with silicone oil. Certainly, after being treated with a silane coupling agent, silica with a hydrophobicity of 90% or more can be obtained by further treating with a silicone oil.
(10 ° C., 10%) and high temperature and high humidity (32.5 ° C., 90%).

In recent years, there has been a growing demand for higher quality images and higher durability than ever before, and there is a strong demand for developer technology to precisely control the charge amount of the developer and to further enhance environmental stability. In this case, the conventional method of adding silica to the developer makes it difficult to achieve even more precise control of the amount of charge of the developer and to achieve environmental stability. The image deteriorates. Conversely, depending on the amount of silica added to the developer, environmental stability may be destabilized. When a developer is stored for a long period of time, the charge amount of the developer tends to fluctuate. Problems still exist.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer having a stable and uniform chargeability.

Still another object is to provide a durable developer having high image density from the beginning without instability of image density rising.

Still another object of the present invention is to provide a developer having excellent storage stability that maintains initial properties even after long-term storage.

Still another object is to provide a developer which is hardly affected by environmental changes such as high temperature, low temperature, high humidity and low humidity.

Still another object is to provide a developer from which a high quality image can be obtained.

[0024]

According to the present invention, there is provided a process for forming an electric latent image on a latent image holding layer, comprising a negatively chargeable magnetic one-component developer disposed on a toner holding member and at least a latent image. A step of causing the one-component developer to fly and developing the latent image to form a toner image, a step of transferring the obtained toner image to a member to be transferred, and a process speed. Is 90 to 300 mm / sec, the negatively chargeable magnetic one-component developer comprises 100 parts by weight of a binder resin and 20 to 200 parts by weight of a magnetic material. And negative charge control agent 0.
1 to 10 parts by weight of a magnetic toner and 0.01 to 10 parts by weight of silica fine powder hydrophobized with at least hexamethyldisilazane externally added to 100 parts by weight of the magnetic toner. The hydrophobized silica fine powder has a BET specific surface area of 16 due to nitrogen adsorption.
0 m ² / g or less, the degree of hydrophobicity is 95% or more,
The present invention relates to a negatively chargeable magnetic one-component developer, wherein the residual amount of ammonia is 100 ppm or less.

BET by nitrogen adsorption specified in the present invention
By setting the specific surface area to 160 m ² / g or less, the contact area between the silica and the classified particles can be made an appropriate state. Therefore, the silica can sufficiently exhibit the function as spacer particles between the classified product particles, and can impart appropriate fluidity.

Conversely, when the BET specific surface area of silica exceeds 160 m ² / g due to nitrogen adsorption, the contact area between the classified particles and the silica increases, so that the fluidity becomes excessively good and the particles are scattered inside the copying machine. Is concerned.

By setting the degree of hydrophobicity specified in the present invention to 95% or more, it is possible to prevent deterioration of the ability to impart charge to the developer mainly due to moisture absorption of silica in a high-temperature and high-humidity environment. Therefore, by using the silica of the present invention, it is possible to obtain a developer having a stable chargeability under a high temperature and high humidity environment.

When the hydrophobicity of silica is less than 95%, the ability to impart a charge to the developer deteriorates due to the absorption of silica in a high-temperature and high-humidity environment.

The remaining amount of ammonia specified in the present invention is 10
By setting the content to 0 ppm or less, it is possible to prevent the charge amount of silica from excessively increasing under a low-temperature and low-humidity environment. Therefore, by using the silica of the present invention, it is possible to obtain a developer having stable chargeability under a low-temperature and low-humidity environment.

When the residual amount of ammonia in the silica exceeds 100 ppm, the developer to which the silica is applied tends to cause an excessive increase in the charge amount in a low-temperature and low-humidity environment, which causes a decrease in image density. Easier to do.

As described above, according to the present invention, it is possible to obtain a developer which maintains an appropriate fluidity and has stable chargeability under a high-temperature, high-humidity environment and a low-temperature, low-humidity environment. Enables precise control.

In the present invention, the hydrophobized silicic acid having a BET specific surface area of 160 m ² / g or less by nitrogen adsorption, a degree of hydrophobicity of 95% or more, and a residual amount of ammonia of 100 ppm or less is used. By using fine powder (silica), the following effects can be exhibited in addition to the above effects.

By using the silica of the present invention, environmental stability is excellent, and precise control of the charge amount of the developer is made possible.

In particular, the step of forming an electric latent image on the latent image holding layer is performed so that the magnetic one-component developer provided on the toner holding member does not contact at least the non-latent image portion of the latent image holding layer. In an image forming method including a step of developing the latent image in close proximity and a step of transferring the obtained toner image to a member to be transferred, the process speed is 90 to 300 mm.
/ Sec, the following effects can be exhibited.

1. The copied image can have excellent fine line reproducibility.

2. The copied image can have excellent resolution.

3. The amount of silica fine powder scattered in the machine during durability can be reduced, and a clearer image can be obtained.

4. A developer with excellent storage stability is obtained,
The fluctuation in developer charge is small even after long-term storage.

Here, the process speed is 90 mm / s
Below ec, the toner on the sleeve often cannot maintain a good triboelectric charge amount (the toner charge amount on the sleeve is too small).
4 is difficult to obtain.

The process speed is 300 mm / s
When the value exceeds ec, the toner charge amount on the sleeve tends to be excessively increased, and conversely, the image density tends to be reduced. Also in this case, it is difficult to obtain the above-described effects 1 to 4.

As the fine silica powder used in the present invention, fine silica powder produced by a dry method and a wet method can be used. The dry method referred to herein is a method for producing fine silicic acid powder generated by vapor phase oxidation of a silicon halide. On the other hand, various conventionally known methods can be applied to the method for producing the fine silica powder used in the present invention by a wet method.

As the fine silicate powder here, anhydrous silicon dioxide (silica) is a typical example. In addition, aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, zinc silicate and the like can be used. Silicates can be used.

The silicic acid fine powder used in the present invention has been hydrophobized using at least hexamethyldisilazane which reacts or physically adsorbs with the silicic acid fine powder as a hydrophobizing agent.

The hydrophobized silica fine powder used in the present invention is used in an amount of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the classified product. The degree of hydrophobicity of the hydrophobized silica fine powder is measured by the following procedure.

Sample 1.0 was placed in a 200 ml separating funnel.
g is collected, and 100 ml of ion-exchanged water is added using a measuring cylinder.

Set a separating funnel in a turbula shaker mixer.

90r. p. m for 10 minutes.

Remove the separatory funnel from the turbula shaker mixer and let stand for 10 minutes.

After leaving still for 10 minutes, 20-30 ml is withdrawn and then collected in a 10 mm cell.

The transmittance of the ion-exchanged water is measured using a colorimeter with a blank. The transmittance at this time is defined as the degree of hydrophobicity.

The remaining amount of ammonia in the hydrophobized silica fine powder was measured by removing the separatory funnel from the turbula shaker mixer in the procedure for measuring the degree of hydrophobicity, allowing the mixture to stand for 10 minutes, extracting 20-30 ml, Quantify with Nessler's reagent.

As the binder resin for the toner used in the present invention, known resins can be used. For example, homopolymers of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene and a substituted product thereof; Styrene-p
-Chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-
Vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer Styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-
Chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer,
Styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid half ester copolymer, Styrene-based copolymers such as styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, Rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax and the like can be used alone or in combination.

To the binder resin, a negative charge control agent (0.1 to 10 parts by weight based on 100 parts by weight of the binder resin) and, if necessary, a coloring agent (preferably based on 100 parts by weight of the binder resin). 0.1 to 10 parts by weight), a lubricant and the like are contained, and the volume average particle diameter of the toner when the particles are formed is 3 to 30 μm.
Particularly preferably, those having a thickness of 5 to 20 μm are used.

The magnetic substance contained in the magnetic toner of the magnetic one-component developer includes ferromagnetic elements and alloys containing them, and compounds such as iron such as magnetite, hematite and ferrite, cobalt, nickel and manganese. Alloys, compounds and other ferromagnetic alloys can be used as appropriate. The magnetic material also functions as a colorant.

The particle size is 0.1 to 2 μm, preferably 0.1 to 0.5 μm, and 20 to 200 parts by weight, more preferably 40 to 1 part by weight, per 100 parts by weight of the binder resin.
It is preferred to contain 50 parts by weight.

In addition, even if a charge control agent, a flow modifier, a coloring agent, a lubricant, and the like are added and contained as necessary in the magnetic toner, the present invention is not hindered at all.

In the production of the toner of the present invention, the constituent materials are well kneaded by a hot kneader such as a hot roll, kneader, extruder or the like, and then obtained by mechanical pulverization and classification.

Alternatively, a method in which a material such as a magnetic powder is dispersed in a binder resin solution and then spray-dried, or a method in which a predetermined material is mixed with a monomer to constitute the binder resin, and then emulsified suspension is performed. Various methods such as a polymerization method for producing a toner by polymerizing a liquid and a toner production method can be applied.

Further, as a method of adding the inorganic fine powder to the toner, a known mixer, for example, a rotary container type mixer such as a V-type mixer or a turbula mixer, a ribbon type, a screw type, a rotary blade type, etc. Other fixed container type mixers can be appropriately used.

Further, they may be mixed at the same time at the time of mixing, or may be mixed in order in consideration of the properties of the toner. Further, a known fourth substance can be added. For example, polyethylene fluoride, polyvinylidene fluoride, fatty acid metal salt, various abrasives, and the like.

[0061]

EXAMPLES "Parts" in each example means parts by weight.

Example 1 Styrene-butyl acrylate 100 parts Divinylbenzene copolymer Magnetic iron oxide 80 parts Negative charge controller 2 parts Low molecular weight polypropylene 3 parts After the above materials are mixed well in a blender, a biaxial kneading extruder And kneaded. The obtained kneaded material was cooled, coarsely pulverized by a cutter mill, pulverized using a fine pulverizer using a jet stream, and further classified using an air classifier to have a volume average particle size of 8.6 μm. A black fine powder was obtained.

Next, 100 parts of aerosol # 200 silica fine powder (manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g were treated with 20 parts of hexamethyldisilazane (HMDS). ² / g Hydrophobicity 98.5% The remaining amount of ammonia 41 ppm 0.4 part was externally added to 100 parts of the black fine powder to obtain a magnetic toner.

Using this magnetic toner as a one-component developer, a commercially available copy machine Canon NP-1215 modified machine (photosensitive material is made of amorphous silicon), process speed 100
An image-drawing test was performed by applying mm / sec.

Normal temperature and normal humidity (23 ° C., 60%), high temperature and high humidity (32.5 ° C., 60%), low temperature and low humidity (15 ° C., 10%)
Under each of the environmental conditions described above, the image density and the charge amount on the sleeve were stable, and an image excellent in fine line reproducibility and resolution was obtained even after repeated image formation of 100,000 sheets. After leaving this magnetic toner for one year, an image formation test was conducted under environmental conditions of normal temperature and normal humidity. The image density and the charge amount on the sleeve were stable even after repeated image formation of 100,000 sheets. Was.

Table 1 shows the results of an image-drawing test under a low-temperature and low-humidity environment.

The reproducibility of fine lines was measured by the following method. That is, an image obtained by copying an original of a fine line accurately having a width of 100 μm under appropriate copying conditions is used as a measurement sample, and a Luzex 450 particle analyzer is used as a measuring device. Measurement. At this time, since the line width measurement position has irregularities in the width direction of the thin line image of the toner, the average line width of the irregularities is used as the measurement point. From this, the value (%) of the fine line reproducibility is calculated by the following equation.

[0068]

(Equation 1)

The resolution was measured by the following method. That is, a pattern composed of five fine lines having the same line width and the same interval is 2.8, 3.2, 3,.
6,4.0,4.5,5.0,5.6,6.3,7.
Create an original image drawn as if there were 1,8.0,9.0,10.0 lines. An image obtained by copying the original manuscript having these 12 types of line images under appropriate copying conditions is observed with a magnifying glass, and the value of the resolving power is determined based on the number of images (lines / mm) in which fine lines are clearly separated. I do.

The larger this number is, the higher the resolution is.

Example 2 In the same manner as in Example 1, a black fine powder having a volume average particle diameter of 8.7 μm was obtained.

Next, a BET specific surface area of 145 m2 by adsorption of silica nitrogen obtained by treating 100 parts of silica fine powder Aerosil # 200 (manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g with 20 parts of hexamethyldisilazane (HMDS). ² / g Hydrophobicity 99% The remaining amount of ammonia 30 ppm 0.4 part was externally added to 100 parts of the fine black powder to obtain a magnetic toner.

Using this magnetic toner as a one-component developer, a commercially available copy machine Canon NP-2020 modified machine (photosensitive material is made of amorphous silicon), process speed 120
An image-drawing test was performed by applying mm / sec.

As in Example 1, the image density and the amount of charge on the sleeve were stable and the fine line reproducibility and resolution were excellent even under various environmental conditions even when 100,000 sheets were repeatedly printed. An image was obtained. After leaving this magnetic toner for one year, an image formation test was conducted under environmental conditions of normal temperature and normal humidity. The image density and the charge amount on the sleeve were stable even after repeated image formation of 100,000 sheets. Was.

Table 1 shows the results of an image-drawing test under a low-temperature and low-humidity environment.

Example 3 In the same manner as in Example 1, a black fine powder having a volume average particle size of 8.4 μm was obtained.

Next, 100 parts of fine silica silicate powder # 200 (manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g were treated with 20 parts of hexamethyldisilazane (HMDS). ² / g Hydrophobicity 98.5% Remaining amount of ammonia 35 ppm 0.4 part was externally added to 100 parts of the black fine powder to obtain a magnetic toner.

Using this magnetic toner as a one-component developer, a commercially available copy machine Canon NP-4835 modified machine (photosensitive material is made of amorphous silicon), process speed 225
An image-drawing test was performed by applying mm / sec.

As in Example 1, the image density and the amount of charge on the sleeve were stable and the fine line reproducibility and resolution were excellent even under various environmental conditions even when 100,000 sheets were repeatedly printed. An image was obtained. After leaving this magnetic toner for one year, an image formation test was conducted under environmental conditions of normal temperature and normal humidity. The image density and the charge amount on the sleeve were stable even after repeated image formation of 100,000 sheets. Was.

Table 1 shows the results of an image-drawing test under a low-temperature and low-humidity environment.

Comparative Example 1 In the same manner as in Example 1, a black fine powder having a volume average particle size of 8.6 μm was obtained.

Next, 100 parts of fine silica silicate # 200 (manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g were treated with 20 parts of hexamethyldisilazane (HMDS), and the BET specific surface area was 141 m by silica nitrogen adsorption. ² / g Hydrophobicity 98.5% The remaining amount of ammonia 120 ppm 0.4 part was externally added to 100 parts of the black fine powder to obtain a magnetic toner.

Using this magnetic toner as a one-component developer, a commercially available copy machine Canon NP-1215 modified machine (photosensitive material is made of amorphous silicon), process speed 100
An image-drawing test was performed by applying mm / sec.

Under ambient conditions of normal temperature and normal humidity (23 ° C., 60%), the image density and the amount of charge on the sleeve are stable both at the initial stage and after the endurance even after repeated image formation of 100,000 sheets. An image having excellent reproducibility and resolution was obtained.

However, during endurance under low-temperature and low-humidity (15 ° C., 10%) environmental conditions, the initial image density, the charge amount on the sleeve, the fine line reproducibility, and the resolution were good. Since the image density began to decrease and the image density near 7000 sheets became 1.09, the durability was stopped. 70
The charge amount on the sleeve at around 00 sheets is -31.5 μC / g
Met.

Table 1 shows the endurance results under low temperature and low humidity environment conditions.

Reference Example 1 In the same manner as in Example 1, a black fine powder having a volume average particle size of 8.5 μm was obtained.

Next, 100 parts of silica silicate fine powder Aerosil # 200 (manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g was treated with 20 parts of hexamethyldisilazane (HMDS). Silica nitrogen adsorption BET specific surface area of 139 m ² / g Hydrophobicity 98.7% Remaining amount of ammonia 38 ppm 0.4 part was externally added to 100 parts of the black fine powder to obtain a magnetic toner.

This magnetic toner was applied as a one-component developer to a commercially available copying machine, NP-6650 manufactured by Canon Co., Ltd., at a process speed of 324 mm / sec, to perform an image formation test.

Under ambient conditions of normal temperature and normal humidity (23 ° C., 60%), the image density and the charge amount on the sleeve are stable both at the initial stage and after the endurance even after repeated image formation of 100,000 sheets. An image having excellent reproducibility and resolution was obtained.

However, during endurance under low-temperature and low-humidity (15 ° C., 10%) environmental conditions, the initial image density, the charge amount on the sleeve, the fine line reproducibility, and the resolution were good. The image density began to decrease, and the image density near 6000 sheets became 1.04. 600
The charge amount on the sleeve near zero was -28.5 μC / g.

Table 1 shows the results of durability under low temperature and low humidity environment conditions.

[0093]

[Table 1]

[0094]

According to the present invention, a developer excellent in environmental stability and capable of precisely controlling the charge amount can be obtained. Particularly, in a medium-to-low speed machine having a process speed of 90 to 300 mm / sec, the durability is improved. And high quality images can be obtained.

Continued on the front page (72) Inventor Masaaki Taya 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masaki Uchiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-63-139367 (JP, A) JP-A-3-64763 (JP, A) JP-A-61-277964 (JP, A) JP-A-2-259658 (JP, A) JP-A-3-72370 (JP, A) JP-A-2-6985 (JP, A) JP-A-2-47669 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (1)

(57) [Claims] A step of forming an electric latent image on the latent image holding layer; bringing a negatively chargeable magnetic one-component developer disposed on a toner holding member and at least the latent image holding layer into close proximity to each other; A step of developing the latent image by flying the component developer to form a toner image, a step of transferring the obtained toner image to a member to be transferred, and a process speed of 90 to 300 mm / s
In the negatively chargeable magnetic one-component developer for use in an image forming method which is ec, the negatively chargeable magnetic one-component developer, a binder resin 100 weight
Parts, 20 to 200 parts by weight of a magnetic substance, and 0.1
Magnetic toner and the magnetic toner 1 containing 10 parts by weight
0.01 to 10 parts by weight, based on 00 parts by weight, of at least hexamethyldisilazane hydrophobized silica fine powder. Is B by nitrogen adsorption
A negatively chargeable magnetic one-component developer having an ET specific surface area of 160 m ² / g or less, a degree of hydrophobicity of 95% or more, and a residual amount of ammonia of 100 ppm or less.