JP2925605B2 - Magnetic brush development - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic brush developing method using a so-called two-component developer in electrophotography.

(Prior art and its problems) In electrostatography, a two-component developer composed of a visible toner and a magnetic carrier is used, and the developer is supplied onto a magnet sleeve to form a magnetic brush. A magnetic brush developing method for rubbing the surface of the photosensitive drum on which the electrostatic latent image is formed to obtain a toner image obtained by visualizing the latent image has been widely used.

However, in this magnetic brush developing method, the peripheral speed of the photosensitive drum, the peripheral speed of the magnet sleeve,
There are various mechanical conditions such as the distance between the drum and the sleeve, the magnetic strength of the magnet, and the length of the head of the magnetic brush.
Setting conditions for obtaining an optimum image is extremely complicated.

In addition, the optimum image means an image having both good image density and resolution. However, since the conditions for obtaining an image with high image density and the conditions for obtaining an image with excellent resolution generally do not match, the development conditions Was extremely difficult to set.

In particular, recently, high-speed copying has been desired, and when the rotational speed of the photosensitive drum is set to be significantly higher than that of the conventional electrophotographic apparatus, other developing conditions also need to be changed significantly. Therefore, the above-mentioned inconvenience becomes a serious problem.

Furthermore, even if the developing conditions are set such that a good image can be formed in the initial stage, if the developer or the sleeve is deteriorated by continuous copying of a large number of sheets, the agitating property and the fluidity of the developer, especially the spike forming property fluctuate. Therefore, it is difficult to form an optimum magnetic brush, and image quality often decreases. This was particularly remarkable under a bad environment of high temperature and high humidity.

(Means for Solving the Problems) The present invention provides a method for controlling the peripheral speed ratio of the magnet sleeve to the photosensitive drum according to the average particle diameter of the magnetic carrier used for the two-component developer, the saturation magnetization, and the dynamic friction coefficient of the magnetic brush. By performing the development while setting it within a certain range, it is possible to obtain an image with high image density and good resolution.

That is, according to the present invention, a two-component developer composed of a visible toner and a magnetic carrier is used, and the developer is supplied onto a magnet sleeve to form a magnetic brush. In a developing method in electrophotography in which development is performed by rubbing the surface of the formed photosensitive drum, the average particle diameter of the magnetic carrier of the developer is dμm, the saturation magnetization is x emu / g, and the dynamic friction coefficient of the magnetic brush is To μ
, The peripheral speed ratio K of the magnet sleeve to the photosensitive drum is expressed by the following equation: The magnetic brush developing method is characterized in that development is performed under conditions that satisfy the following conditions.

In the present invention, it is particularly desirable to use a toner composition in which the acrylic polymer fine powder and the silica fine powder are mixed with the visible toner as the visible toner.

The apparent density of magnetic carriers is 2.4 to 3.0 g / cm
^It is desirable to use one in the range of ³ .

Further, as the particle size distribution of the magnetic carrier,
0.5 times or less of the particles are less than 0.1% by weight and 0.7
It is preferable to use a magnetic carrier having a particle size distribution in which 2 to 1.4 times the particles are 90% by weight or more.

Furthermore, a magnetic carrier coated with a resin can be used as the magnetic carrier.

(Function) In the present invention, in a magnetic brush developing method using a two-component developer, mechanical development conditions for obtaining an optimum image are as follows:
It depends greatly on the peripheral speed ratio of the magnet sleeve for conveying the magnetic brush to the photosensitive drum, and this peripheral speed ratio is appropriately determined by the particle diameter (μm), dynamic friction coefficient and saturation magnetization (emu / g) of the magnetic carrier used. It is based on knowledge.

For example, when the peripheral speed ratio K is larger than 1.25 d / μ ^1/2 ×, the obtained image has poor resolution, and
When the density is smaller than 0.75 / μ ¹ / 2x, even if the resolution is satisfactory, the density of the obtained image is low,
Improper.

The general formula (1) that defines the above-described development conditions is a formula obtained experimentally. The reason why an optimum image can be obtained by performing development within the range defined by the general formula (1) is as follows. Although it is not clear, the present inventors presume as follows.

That is, in order to obtain an optimal image, it is considered necessary that the electric resistance value of the magnetic brush in the developing area be within a certain range, and this electric resistance value is determined by the average particle diameter and saturation magnetization of the magnetic carrier, the dynamic friction of the magnetic brush. This is probably because it is expressed as a function of the coefficient and the peripheral speed ratio of the magnet sleeve to the photosensitive drum.

For example, an optimum image can be obtained as a result of maintaining an appropriate electric resistance value under development conditions satisfying the general formula (1).

In other words, when the peripheral speed ratio K is larger than 1.25 d / μ1 / ² · x, the electric resistance of the magnetic brush is small, and the resolution is reduced even if the image density is increased, and 0.75 / μ
If it is smaller than ¹ / 2x, the electrical resistance will be large,
Even if the resolution is good, the image density will be reduced.

The dynamic friction coefficient μ of the magnetic brush is a constant determined by the combination of the developer and the photoconductor used, and is calculated by, for example, the following method.

That is, a torque meter is provided on a rotating shaft of a photosensitive drum of an electrophotographic apparatus to be used, and a developing operation is performed in this state, whereby a change in torque when the magnetic brush comes into contact with the surface of the drum (photosensitive member surface) is used. to calculate the force F _1.

On the other hand, according to the measurement method disclosed in Japanese Patent Application Sho 62-299795, it calculates the developing pressure F ₂ in similar conditions, the following formula, Is calculated from the equation.

In a preferred embodiment of the present invention, a toner composition in which an acrylic polymer fine powder and a silica fine powder are externally added to a visible toner as a developer is used, as shown in Example 2, which will be described later. The fluidity, transportability and dispersibility of the developer on the sleeve and on the sleeve from the stirring section can be maintained stably, and the state of the magnetic brush formed fluctuates even in repeated image formation. Not
As a result, fluctuations in the electrical characteristics of the magnetic brush in a dynamic state are reduced, and high-quality image formation can be performed for a long period of time.

Further, in the developing method of the present invention, it is desirable that the apparent density of the magnetic carrier used is in the range of 2.4 to 3.0 g / cm ³ as a condition for satisfying the general formula (1).

That is, in order to satisfy the general formula (1) for a long period of time, it is necessary that the electric resistance value of the magnetic brush is always stably set within a certain range. By setting within, the electric resistance value of the magnetic brush can be set within a certain range for a long time, and a good image can be obtained stably for a long time.

Therefore, if the apparent density of the magnetic carrier is outside the above range, the electrical resistance of the magnetic brush will not be kept within a certain range while image formation is repeated for a long period of time, and the general formula tends not to be satisfied.

Further, when the apparent density of the magnetic carrier is outside the above range, if image formation is repeated for a long time and the developer deteriorates,
The image density tends to be unstable, fogging tends to occur, and good images cannot be obtained.

Furthermore, in the developing method of the present invention, the particle size distribution of the magnetic carrier used is 0.1% by weight or less of particles having an average particle size of 0.5 or less.
90% by weight of particles less than 0.7 to 1.4 times the average particle size
The above is desirable as a condition for satisfying the general formula (1).

That is, in order to satisfy the above general formula (1) for a long period of time, it is necessary that the electric resistance value of the magnetic brush is always stable and set within a certain range. By setting, the electric resistance value of the magnetic brush can be maintained within a certain range for a long time, and a good image can be obtained stably for a long time.

Therefore, when the particle size distribution of the magnetic carrier does not satisfy the above condition, the electric resistance value of the magnetic brush is not kept within a certain range during the long-term image formation, and the general formula (1) is not satisfied. Tend.

Further, when the particle size distribution of the magnetic carrier does not satisfy the above conditions, if image formation is repeated for a long period of time, the carrier is scattered due to the deterioration of the developer, and there is a tendency that a good image cannot be obtained.

Furthermore, in the developing method of the present invention, it is desirable to use a magnetic carrier whose surface is coated with a resin. Generally, in a magnetic brush developing method using a two-component developer, a magnetic brush is formed by stirring and mixing a mixture of a toner and a carrier in a developing device. Therefore, when image formation is repeated for a long period of time, the toner and the carrier in the developing device or the collision between the developing device and the carrier causes fusion of the toner to the carrier surface. When the toner is fused to the carrier surface in this manner, the electric resistance of the magnetic brush changes, and the correlation between the electric resistance of the carrier and the electric resistance of the magnetic brush is lost. No longer holds.

Therefore, in order to satisfy the above general formula (1) for a long period of time, it is necessary to prevent the toner from being fused to the carrier. However, the fusion of the toner to the carrier is performed by coating the carrier surface with a resin. Can be effectively prevented.
That is, by coating the surface of the carrier with the resin, the general formula (1) can be satisfied even when image formation is repeated for a long time.

(Preferred Embodiment of the Invention) Developer As the two-component magnetic developer used in the developing method of the present invention, any of those known per se comprising a visible toner and a magnetic carrier can be used.

For example, as the toner, a colored toner having a visualizing property and a fixing property is used. In general, the colored toner has a particle diameter of 5% in which a coloring pigment, a charge control agent, and the like are dispersed in a binder resin. Consists of a granular composition of ~ 30 microns.

As the binder resin, which is a toner component, a thermoplastic resin or a thermosetting resin of an uncured or initial condensate is used. Suitable examples are, in the order of importance, vinyl aromatic resin such as polystyrene, acrylic resin, polyvinyl acetal resin, polyester resin, epoxy resin,
Phenol resin, petroleum resin, olefin resin and the like.

Examples of color pigments include, for example, carbon black, cadmium yellow, molybdenum orange, pyrazolone red,
Fast violet B, phthalocyanine blue, etc.
Species or two or more are used.

As the charge control agent, for example, nigrosine base (CI 5
0415), oil-soluble dyes such as oil black (CI 26150) and spiron black, metal naphthenates, fatty acid metal soaps, resin acid soaps and the like are used as required.

For the toner, the acrylic polymer fine powder to be mixed includes emulsion polymerization, soap-free polymerization, dispersion polymerization,
Spherical resin particle powder produced by suspension polymerization or the like,
A powder obtained by pulverizing the polymerized mass may be used, and a powder having a particle size of generally 0.1 to 1 μm, particularly 0.3 to 0.6 μm is preferably used.

The monomer constituting the polymer is represented by the following formula.

formula, In the formula, R ₃ is a hydrogen atom or a lower alkyl group, and R ₄ is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, or a vinyl ester group.

Acrylic monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate,
2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-hydroxyacrylate,
One or more of σ-butyl acrylate, β-hydroxy methacrylate, ethylene glycol methacrylate, tetramethylene glycol dimethacrylate and the like are used in combination.

Other radically polymerizable monomers can be used together with the acrylic monomer. For example, styrene, α
Styrene monomers such as methyl styrene, o-methyl styrene, ρ-methyl styrene, ρ-methoxy styrene, and ρ-chloro styrene, and unsaturated diesters such as maleic acid, crotonic acid, itaconic acid, and alkyl esters thereof. A carboxylic acid having a heavy bond or an alkyl ester thereof;
Olefinic monomers such as ethylene, propylene and butadiene, vinyl acetate, vinyl chloride, vinylidene chloride; vinyl pyrrolidone; vinyl naphthalene and the like can be exemplified.

The silica fine powder used together with the acrylic polymer fine powder is preferably a hydrophobic one,
Generally, the diameter of the primary particles is 0.01 to 1 μm, preferably 0.02 μm.
A thickness of about 0.5 μm is used. AEROS is a specific example
IL R-927, AEROSIL R-812, and AEROSIL R-805 (all manufactured by Nippon Aerosil Co., Ltd., trade names) can be mentioned.

The mixing amount of the acrylic polymer fine powder and the silica fine powder is such that the acrylic polymer fine powder is used in an amount of 0.01 to 0.2 part by weight, preferably 0.03 to 0.1 part by weight, based on 100 parts by weight of the toner. The powder is in a weight ratio to the acrylic polymer fine powder of 1: 1 to 1: 5, preferably 1: 2.
It is good to use in the range of 5 to 1: 3.5.

When the usage amount of the acrylic polymer fine powder is out of the above range, it is difficult to stably maintain the state of formation of the magnetic brush on the developing sleeve, resulting in deterioration of image quality. Then, it is important to add a specific amount of silica fine powder to the acrylic polymer fine powder, whereby the developer can be transported on the sleeve from the stirring section in the developing device, and on the sleeve. Since the dispersibility is improved, the optimum state of the magnetic brush can be repeatedly formed for a long period of time without being affected by environmental changes and the like, and the number of printings can be dramatically improved.

If the amount of the silica fine powder is less than the above range, the dispersion state (amount) of the developer on the sleeve tends to be non-uniform, and if it is more than the above range, the toner in the magnetic brush migrates to the photoreceptor. It becomes difficult.

As the magnetic carrier used in combination with the toner, any known carrier such as triiron tetroxide, ferrite, and iron powder can be used.

The average particle size of the magnetic carrier is generally 20 to 200μ.
m, preferably in the range of 40 to 130 μm, and it is preferable that the saturation magnetization measured at 50 KOe is in the range of 30 to 70 emu / g, particularly 40 to 50 emu / g.

In one preferred embodiment of the present invention, a magnetic carrier having an apparent density set in the range of 2.4 to 3.0 g / cm ³ is used. According to another preferred embodiment, the particle size distribution of the magnetic carrier is such that particles having an average particle size of 0.5 or less are less than 0.1% by weight of the entire carrier and particles having an average particle size of 0.7 to 1.4 times the entire carrier. Use the one set to 90% by weight or more.

In still another embodiment of the present invention, the surface of the magnetic carrier is coated with a resin. By coating the resin,
The optimum state of the magnetic brush can be repeatedly formed for a long time, and the number of printings can be dramatically improved.

As a resin for coating the magnetic carrier, acrylic resin, styrene-acrylic resin, acrylic-modified silicone resin, silicone resin, epoxy resin, rosin-modified phenol resin, formalin resin, cellulose resin,
Polyether resin, polyvinyl butyral resin, polyester resin, styrene-butadiene resin, polyurethane resin, polyvinyl formal resin, melamine resin, polycarbonate resin, fluororesin such as tetrafluoroethylene alone or a mixture of two or more resins Can be used.

In particular, when a resin obtained by curing and reacting a melamine resin and a thermoplastic resin having an unreacted hydroxyl group or alkoxyl group is used, the mechanical strength of the coating further increases, the life of the carrier can be extended, and over a long period of time. This is preferable because an optimum image can be maintained. As a thermoplastic resin having a hydroxyl group or an alkoxyl group, for example,
Epoxy resin, hydroxyl or alkoxyl group-containing acrylic resin, hydroxyl or alkoxyl group-containing styrene-acrylic resin, acryl-modified silicone resin, phenoxy resin, polyester resin, butyral resin, formal resin, silicone resin, alkoxyl group-containing fluororesin and the like Can be

And the resin component is based on 100 parts by weight of the carrier core material.
It is preferably used in the range of 0.1 to 10 parts by weight, particularly 0.2 to 5 parts by weight.

In the developer, the toner concentration is such that the specific surface area ratio of the carrier and the toner is 1: 0.7 to 1: 1.3, particularly 1: 0.9 to 1:
It is set to be in the range of 1.1.

1. Electrophotographic Apparatus In FIG. 1 showing an electrophotographic apparatus for suitably implementing the magnetic brush developing method of the present invention, a photoconductor layer 2 is provided on the surface of a metal drum 1 which is driven and rotated.

The photoconductor layer 2 is made of, for example, Se, ZnO, CdS, amorphous silicon, or a function-separated organic photoconductor.

Around this drum is a main charging corona charger 3;
An image exposing mechanism comprising a lamp 4, a document supporting transparent plate 5 and an optical system 6; a developing mechanism 8 having a developer 7; a corona charger 9 for toner transfer; a corona charger 10 for separating paper; a discharging lamp 11; They are provided in this order.

The image forming process of this electrophotographic apparatus is briefly described as follows.

First, the photoconductor layer 2 is charged by the corona charger 3 with a charge having a fixed polarity. Next, the original 13 to be copied is illuminated by the lamp 4 and the photoconductor layer 2 is exposed to a light image of the original through the optical system 6 to form an electrostatic latent image corresponding to the original image. This electrostatic latent image is visualized by the developing mechanism 8 to form a toner image. Transfer paper 14 to toner transfer charger 9
Feed the drum surface at the position
The same polarity corona charger as the electrostatic image from the back of the
The toner image is transferred to the transfer paper 14. The transfer paper 14 onto which the toner image has been transferred is electrostatically peeled off from the drum by the charge removal of the separating corona charger 10, and is sent to a processing area such as a fixing area (not shown).

After the toner transfer, the photoconductor layer 2 is erased of residual charges by the entire surface exposure by the charge removing lamp 11, and then the cleaning mechanism is used.
12 removes residual toner.

Developing Apparatus and Developing Method In the above electrophotographic apparatus, an enlarged view of the developing apparatus 8 is shown in FIG.

That is, the developing device 8 includes a cylindrical developer conveying sleeve 21 having a built-in magnet 20 in which N poles and S poles are alternately arranged.

The developing method of the present invention is applied to a type in which the magnet sleeve 20 is fixed and the sleeve 21 rotates in the forward direction with the drum 1 to carry the magnetic brush 7 of the developer.

The magnetic intensity of the main pole of the magnet 20 is 600 to 1000 Gauss, the angle θ between the center of the main pole and the line connecting the centers of the drum and the sleeve is in the range of 0 to 10 degrees, and the photoconductor layer 2 and the sleeve The distance 1 from 21 is set in the range of 0.8 to 1.5 mm.

Further, an upstream cutting mechanism 22 is provided on the upstream side of the developing area, and the magnetic brush 7 is supplied to the developing area with the width of the cutting edge adjusted to 0.8 to 1.2 mm to perform development.

In the present invention, as described above, the two-component developer including the toner and the magnetic carrier is used, and the metal drum 1 is used.
The peripheral speed ratio K of the sleeve to the general formula (1) In the formula, d is the average particle diameter (μm) of the magnetic carrier, x is the saturation magnetization of the magnetic carrier, and μ is the dynamic friction coefficient of the magnetic brush. This makes it possible to obtain an image excellent in high image density and resolution.

(Effects of the Invention) According to the present invention, the photosensitive drum and the magnet are adjusted according to the average particle size and saturation magnetization of the magnetic carrier used for the developer, and the dynamic friction coefficient of the developer (magnetic brush) with respect to the used photosensitive member. An optimum image can be obtained only by appropriately adjusting the peripheral speed ratio with the sleeve.

Therefore, it is extremely easy to set the optimum developing conditions without changing design of various mechanical conditions such as the distance between the drum and the sleeve, the position of the magnetic pole, and the length of the cutting edge each time according to the toner to be used. Became possible.

The present invention is particularly advantageously applied to a case where mechanical development conditions are greatly changed, for example, in high-speed copying.

Further, an optimal image can be obtained over a long period of time by using a toner obtained by adding a specific combination of external additives to a visible toner and by using a magnetic carrier having a specific physical property and a coating structure. It becomes possible.

 The present invention will be described more specifically with the following examples.

(Example) Example 1 Using a copying machine (DC-112C) manufactured by Mita Kogyo Co., Ltd. and employing the following developing conditions, the peripheral speed ratio K of the sleeve to the metal drum and the physical properties of the carrier of the two-component developer (particle diameter, saturation magnetization) ) Were changed in various ways, and copying was performed to evaluate the image quality.

Developing condition Houkiri: 1.0mm Drum-sleeve distance: 1.1mm Sleeve: Main pole position +3.5 ゜ Main pole strength 800 Gauss Surface potential: + 700V Bias potential: + 180V Photoconductor drum: Selenium drum Developer Carrier, ferrite carrier Toner , A toner with an average particle size of 1 / μm for negative charging. The toner concentration is such that the specific surface area ratio of carrier to toner is 1: 1.
It was set to be.

 The evaluation results are shown in Table 1.

The image quality was evaluated as follows: 1st copy ID (reflection density) was 1.
3 or more and the resolution of the 2nd copy is 2.8mm /
Goods (0) and more were rated (X).

Also in Table 1, rubbing force F ₁ is the torque meter provided on the rotary shaft of the drum was calculated from the torque change.

Drag F ₂ was calculated from the surface pressure of the developing zone measured by the method described in Japanese Patent Application No. Sho 62-299795.

From the results in Table 1 above, it is understood that a good image can be obtained when the sleeve peripheral speed ratio K to the tram satisfies the general formula (1).

Example 2 PMMA polymer fine powder having a particle size of 0.5 μm with respect to 100 parts by weight of the toner with respect to 100 parts by weight of the negative toner having an average particle size of 11 μm
0.03 parts by weight were mixed and uniformly dispersed on the surface of the toner particles, and then 0.03 μm of hydrophobic silica having an average primary particle size of 0.03 μm was added.
The toner components were obtained by adding and mixing parts by weight. This was designated as Component-A, and the PMMA polymer powder 0.03
Composition-B containing only parts by weight, Composition-C containing only hydrophobic silica with respect to the toner, and particle size
Composition-D was prepared by adding 0.03 parts by weight of 0.02 μm aluminum oxide and 0.03 parts by weight of hydrophobic silica.

The printing durability test was performed by applying the toner composition to the development conditions of NO1, 3, 10, and 11 in Example 1.

The image evaluation was performed in the same manner as in Example 1, and the number of sheets on which image formation was possible in a range satisfying the evaluation value was defined as the number of printings.

 The results are shown in Table 2 below.

From the above results, when a developer using a toner composition in which an acrylic polymer fine powder and a silica fine powder are mixed is used, the state of formation of the magnetic brush is maintained for a long time without change, and the durability is dramatically improved. It can be seen that the printing performance is improved.

Example 3 In Example 2, 0.04 parts by weight of the PMMA polymer fine powder of the toner composition was added to 100 parts by weight of the toner under the development conditions of NO and 1, and the amount of the hydrophobic silica added was as shown in Table 3. The printing durability test was performed under the high temperature and high humidity conditions (35 ° C., 85%) with the following changes. Table 3 shows the results.

As a result, it is understood that a composition containing 1 to 5 times the amount of silica with respect to the fine acrylic polymer powder is suitable.

Example 4 A printing durability test was carried out in the same manner as in Example 1 except that the carriers used in the experiment No. 11 in Example 1 were used with different apparent densities.

The image evaluation was performed in the same manner as in Example 1, and the number of sheets on which image formation was possible in a range satisfying the evaluation value was defined as the number of printings.

 Table 4 shows the results.

From the above results, when the carrier A having an apparent density satisfying 2.4 to 3.0 g / cm ³ is used, the state of formation of the magnetic brush is higher than when the carriers B and C which do not satisfy are used. Is maintained for a long time without fluctuation, and the printing durability is dramatically improved.

Example 5 A printing endurance test was carried out in the same manner as in Example 1 except that the carrier (average particle size: 80 μm) used in the experiment of No. 11 in Example 1 having a different particle size distribution was used, and development conditions were the same as in Example 1. Was. The image evaluation was performed in the same manner as in Example 1, and the number of printing presses satisfying the evaluation value was measured.

The image evaluation was performed in the same manner as in Example 1, and the number of sheets on which image formation was possible in a range satisfying the evaluation value was defined as the number of printings.

 Table 5 shows the results.

From the above results, the case where the carrier of A whose particle size distribution is 0.5% or less of the average particle size is less than 0.1% by weight and the particles of 0.7 to 1.4 times the average particle size satisfies 90% by weight or more is used. Showed that the number of printing presses was improved and good image quality was obtained over a long period of time as compared with the case where the unsatisfactory B, C and D carriers were used.

Example 6 A printing durability test was performed in the same manner as in Example 1 except that the carrier shown in Table 6 below was used to coat No. 11 carrier surface in Example 1.

The image evaluation was performed in the same manner as in Example 1, and the number of sheets on which image formation was possible in a range satisfying the evaluation value was defined as the number of printings.

 Table 7 shows the results.

From the above results, when the carriers A to E whose surfaces are coated with the resin are used, the formation state of the magnetic brush is maintained for a long time without change compared to the case where the carrier of the uncoated F is used. It can be seen that the printing durability is dramatically improved.

[Brief description of the drawings]

FIG. 1 is a view showing an electrophotographic apparatus which can suitably carry out a developing method of the present invention. FIG. 2 is an explanatory diagram showing a main part of the developing device in an enlarged manner. DESCRIPTION OF SYMBOLS 1 ... Metal drum, 2 ... Photoconductor layer 3 ... Corona charger for main charging 8 ... Developing mechanism, 12 ... Cleaning mechanism 20 ... Magnet, 21 ... Developing / conveying sleeve 22 ... Hot cutting mechanism

──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 1-82929 (32) Priority date Hei 1 (1989) March 31 (33) Priority claim country Japan (JP) (31) Priority Claim No. Japanese Patent Application No. 1-82932 (32) Priority Date Hei 1 (1989) March 31 (33) Priority Country Japan (JP) (72) Inventor Koichi Tsuyama 1-2-2 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka No. 28, Mita Kogyo Co., Ltd. (72) Yoshii Shimizu, Inventor 1-2-28 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka 2-28 Inside Mita Kogyo Co., Ltd. 2-28 Inside Mita Kogyo Co., Ltd. (72) Junko Mizuno, Inventor, 1-chome, Tamazo, Chuo-ku, Osaka-shi, Osaka 2-28 Inside Mita Kogyo Co., Ltd. No. 28 from Mita Kogyo Co., Ltd. (72) Person Hideaki Kawada 1-2-2, Tamazo, Chuo-ku, Osaka-shi, Osaka Inside Mita Kogyo Co., Ltd. (72) Inventor Koji Honda 1-2-28, Tamazo, Chuo-ku, Osaka-shi, Osaka Mita Kogyo Co., Ltd. (56) Reference Reference JP-A-63-212947 (JP, A) JP-A-62-142005 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/08-15/09

Claims (10)

(57) [Claims] A two-component developer comprising a visible toner and a magnetic carrier is used, and the developer is supplied onto a magnet sleeve to form a magnetic brush, which is used to form an electrostatic latent image. The electrophotographic method of developing by rubbing against the surface of the photosensitive drum, wherein the average particle diameter of the magnetic carrier of the developer is dμm, the saturation magnetization is x emu / g, and the dynamic friction coefficient of the magnetic brush is μ. , The peripheral speed ratio K of the magnet sleeve to the photosensitive drum is expressed by the following equation: A magnetic brush development method, wherein development is performed under conditions that satisfy the following conditions. 2. The magnetic carrier has an average particle size of 20 to 200 μm.
2. The developing method according to claim 1, wherein the saturation magnetization is in the range of 30 to 70 emu / g. 3. The developing method according to claim 1, wherein the visible toner is a mixture of the visible toner and an acrylic polymer fine powder and a silica fine powder. 4. An acrylic polymer fine powder of 0.01 to 1 μm
Having a primary particle size of 0.01 to 1 μm
The developing method according to claim 3, which has a primary particle diameter of: 5. The finely divided acrylic polymer powder comprises
The amount of 0.01 to 0.2 parts by weight per 0 parts by weight and the silica fine powder is in a weight ratio of 1: 1 to 1: 5 with respect to the acrylic polymer fine powder.
The developing method according to claim 3, wherein 6. The developing method according to claim 1, wherein the magnetic carrier has an apparent density in the range of 2.4 to 3.0 g / cm ³ . 7. The magnetic carrier according to claim 1, wherein the magnetic carrier contains particles having an average particle size of 0.5 times or less in an amount of less than 0.1% by weight of the entire carrier and 0.7 to 1.4 times the average particle size of 90% by weight of the entire carrier. The developing method according to claim 1, which has a particle size distribution contained in an amount of at least%. 8. The developing method according to claim 1, wherein the magnetic carrier is a magnetic carrier coated with a resin. 9. The developing method according to claim 8, wherein the coating resin is a composition containing a melamine resin and a thermoplastic resin containing a hydroxy group or an alkoxy group. 10. The method according to claim 8, wherein the resin coating is present in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the core of the magnetic carrier.