JP2000075644A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve stable layer formation by using a developer subjected to a mechanical impact force or a sphering treatment by heating in a manufacturing process, and to achieve high-quality image formation over a long period of time. An object of the present invention is to provide a developing device with a low page-per cost. SOLUTION: A developer 3d, a developer carrier 5d provided to face the electrostatic latent image carrier, and carrying the developer, and a developer urged toward the developer carrier, and Developing device 4 having developer regulating member 6d for regulating the amount of developer
In d, the developer has a particle size of 0.6 μm or more and 1.0 μm
The following particles occupy less than 5.0% of the whole on a number basis, the number average particle diameter is 4 to 10 μm, and the developer regulating member has a wear index that forms a nip with the developer carrier. It has an elastic body of 0.03 to 0.15, and the contact pressure P (g / cm) of the elastic body is 15 ≦ P ≦ 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for an image forming apparatus such as an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, one-component toner (developer) is widely used in an image forming apparatus such as a copying machine or a printer of an electrophotographic type or an electrostatic recording type, and an image forming apparatus capable of obtaining a full-color image. Has also been applied.

As a full-color image forming apparatus, an intermediate transfer member system as shown in FIG. 4 has been proposed. This image forming apparatus forms toner images by sequentially performing charging, exposing, and developing steps for each color based on image information decomposed into four colors of yellow, magenta, cyan, and black, and forms them on an intermediate transfer member. After superimposition (primary transfer), collective transfer (secondary transfer) to a medium such as paper is performed to obtain a full-color image.

Each developing unit is disposed in a rotary, and sequentially develops an electrostatic latent image formed on an adjacent photosensitive drum by a rotation switching method. By adopting the rotation switching method, it is not necessary to make the shapes of the developing devices different from each other, and there is an advantage that the size of the apparatus can be reduced compared to a method in which the developing devices are arranged in parallel and can be switched.

The advantages of the use of the intermediate transfer member system include the absence of color misregistration and the improvement of media flexibility irrespective of paper size and thickness. However, since the transfer step is performed twice as described later, more excellent transferability and charge characteristics are required as the toner characteristics.

[0006] Each color toner is a non-magnetic toner produced by a polymerization method. Since the toner becomes a substantially spherical toner due to its manufacturing method, the above-mentioned toner characteristics can be satisfied.

[0007]

However, in the market, the consumption of black toner is generally much higher than that of color toner. Therefore, a large capacity and durability of the black developing device are required, and it is important to reduce the page cost.

Therefore, the black developing device is detached from the rotary and is fixed so as to increase the capacity of the black toner container. Further, a pulverized magnetic toner which is inexpensive and has a proven durability is used. The use of a magnetic toner eliminates the need for a toner supply / recovery roller, which is essential in the configuration of a developing device using a non-magnetic toner, but also causes deterioration of the durability of the developer. Is brought into contact with the developing sleeve to apply a tribo to the toner on the sleeve while regulating the coating amount, thereby satisfying the durability and cost of the developing device.

However, in the conventional pulverized magnetic toner, the transfer efficiency required in the intermediate transfer member system is low, and the chargeability is low.

[0010] As a solution to this, the pulverized magnetic toner is subjected to a mechanical impact force or a sphering treatment by heating as post-processing. It has been found that this spherical magnetic toner can achieve the same transferability and charge characteristics as the spherical nonmagnetic toner produced by the polymerization method.

However, the magnetic toner which has been subjected to a mechanical impact or a spheroidizing treatment by heating cannot maintain the durability with a conventional developing device using a urethane blade. This is because the toner is liable to be deteriorated, and the problem of fusion of the toner at the contact nip portion of the urethane blade occurs. Further, since the magnetic toner which has been subjected to the sphering treatment is spherical, it is difficult to regulate the coating amount by the developing blade. In order to achieve satisfactory image quality, it is necessary to increase the regulating force of the developing blade.

An object of the present invention is to form a stable layer by using a developer subjected to a mechanical impact force or a spheroidizing treatment by heating in the manufacturing process, thereby achieving high-quality image formation over a long period of time. An object of the present invention is to provide an inexpensive developing device with a low page-per-cost.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first invention of the present application is a developer, a developer carrying member provided opposite to the electrostatic latent image carrier and carrying the developer, A developer regulating member that is urged toward the carrier and regulates the amount of developer on the developer carrier, wherein the developer has a particle size distribution according to a circle equivalent diameter of the developer particles. The ratio of particles having a diameter of 0.6 μm or more and 1.0 μm or less is less than 5.0% of the total number on a number basis, and the number average particle diameter is 4 to 10 μm. Index is 0.03 to form a nip
0.15 elastic body, and the contact pressure P (g / g
cm) is 15 ≦ P ≦ 40.

In the second invention of the present application, the elastic material has a rubber hardness of 10 ° or more and 55 ° or less according to JIS and a filler of 5 to 2%.
It is characterized by being made of silicone rubber containing 0% by weight.

According to a third aspect of the present invention, the elastic member has a free end upstream in the moving direction of the developer carrying member, and a position between the free end and the most upstream contact position between the elastic member and the developer carrying member. Distance NE
(Mm) is 0.25 ≦ NE ≦ 2.25 and 5.0 × NE + 12.5 ≦ P ≦ 6.6 × NE + 28.3.

According to a fourth invention of the present application, the developer has a circularity a of 3 μm or more obtained by the following formula (1).
Is 90% or more on a number basis, and the ratio of particles having a circularity a of 0.98 or more is less than 30% on a number basis. .

Circularity a = L _O / L (1) (L _O ; Perimeter of a circle having the same projected area as the particle image, L;
Perimeter of particle image)

According to a fifth aspect of the present invention, the developing device is a cartridge detachably mountable to the image forming apparatus.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an image forming apparatus using the developing device of the present invention, and is a schematic configuration diagram of an electrophotographic full-color laser beam printer.

A yellow, magenta, and cyan color developing device containing a non-magnetic spherical toner disposed in a photosensitive drum and a rotary, and a black developing device containing a fixed spherical magnetic toner are included in an image forming apparatus. The cartridge is detachable from the forming apparatus. The cartridge is replaced when the life of the photosensitive drum becomes full, when the waste toner is full, and when the toner is used up in the developing device.

The image forming apparatus 20 is connected to a host such as a personal computer and a workstation. In response to a print request from the host 21, image data is received via the video interface. This image data is divided into four colors of yellow, magenta, cyan, and black.
The toner image is decomposed into colors, and the steps of charging, exposing, and developing are sequentially performed for each color to form a toner image. The toner images are superimposed on the intermediate transfer member 7 (primary transfer), and then collectively transferred to a medium such as paper (secondary transfer). ) To obtain a full-color image.

Image formation is described in detail below.

Reference numeral 1 denotes a photosensitive drum, which comprises an OPC photosensitive member. The rotation speed of the photosensitive drum (hereinafter, process speed) is 117 mm / sec.

The developing units for yellow, magenta, cyan, and black are 4a to 4d, respectively.

A yellow toner image is formed for the first color. Uniform charging is performed on the photosensitive drum 1 by the roller charger 2. Next, exposure is performed by the laser scanner 3 in accordance with the image signal. The laser scanner 3 scans the blinking of the semiconductor laser with a polygon scanner and forms an image on the photosensitive drum 1 by an optical system. This creates an electrostatic image. The electrostatic image is developed and visualized by a yellow developing device arranged in the rotary 6. At this time, a jumping development is performed by applying a developing bias in which a DC voltage and an AC voltage are superimposed on the developing sleeve 5a (5b and 5c are not shown).

The visualized toner image is pressed against the photosensitive drum with a predetermined pressing force, and is transferred (primary transfer) onto the surface of the intermediate transfer member 7 rotating at a constant speed at the process speed. At this time, a transfer voltage having a polarity opposite to the charge polarity of the toner is applied.

The toner remaining on the photosensitive drum without being primary-transferred is scraped off by the cleaning blade 8 and collected in the cleaner container 9.

The above process is repeated for the remaining three colors (magenta, cyan,
Black) is repeated in the same manner, and each time, a toner image of the toner included in the developing device of each color is sequentially transferred to the surface of the intermediate transfer body to form a full-color toner image.

To the full-color toner image on the intermediate transfer member, a transfer voltage having a polarity opposite to the charging polarity of the toner is applied, and the medium 12 fed from a paper cassette or a multi-feeder is applied.
At the same time (secondary transfer).

Therefore, it is desired that the non-magnetic toner, which is a color toner, and the magnetic toner, which is a black toner, have comparable transferability and charge characteristics.

The toner remaining on the intermediate transfer member without being transferred during the secondary transfer is charged by the cleaning roller 10 to a polarity opposite to the charging polarity of the toner. Next, the toner image is re-transferred onto the photosensitive drum with the rotation of the intermediate transfer member, and is collected by the cleaning blade 8 into the cleaner container 9.

The full-color toner image transferred to the medium is permanently fixed by the fixing unit 11, and is discharged from the paper discharge unit to the outside of the apparatus. Therefore, a desired print image is obtained.

Next, the black developing device according to the embodiment of the present invention will be described.

FIG. 2 is a sectional view of the black developing device according to the embodiment of the present invention.

An elastic developing blade 6d serving as a developer regulating member is attached to a developing sleeve 5d serving as a developer carrying member.
To form a nip for regulating the amount of developer.

The developing sleeve 5d is a non-magnetic aluminum sleeve having a diameter of 20.0 mm, and its surface is coated with a resin layer containing resin particles as a roughening agent and conductive particles.

A magnet roll 1d is fixedly arranged in the developing sleeve 5d. The one-component magnetic toner 3d is contained in the developing container, is sent to the vicinity of the developing sleeve by stirring 2d, is supplied to the developing sleeve by the action of a magnetic field formed by a magnet roll, and is conveyed with the rotation of the sleeve. Thereafter, the toner is conveyed to the developing area under the application of a tribo at the contact portion with the developing blade and the regulation of the layer thickness.

An alternating voltage in which a direct current and an alternating current are superimposed is applied to the developing sleeve 5d to form a developing electric field with the photosensitive drum, and the electrostatic latent image is developed according to the electric field. A DC voltage is applied to the developing sleeve; an AC voltage at Vdc = -400 V; a rectangular wave Vpp = 1600 V, a frequency f = 2300 H
A developing bias on which z is superimposed is applied. The sleeve and the photosensitive drum face each other with a gap of 300 μm at the closest position. The photosensitive drum has a charging potential Vd = -600 V
And is exposed by a laser according to an image signal, and the portion becomes V1 = −200 V. V1 part is reverse developed with negatively charged toner.

Since a toner having excellent transferability and charge characteristics is essential due to the use of the intermediate transfer member, the pulverized magnetic toner is subjected to a mechanical impact force or a sphering treatment by heating as post-processing. The conditions for the spheroidization treatment are as follows. In the particle size distribution of the toner particles according to the circle-equivalent diameter, the ratio of particles having a particle size of 0.6 μm to 1.0 μm is less than 5.0% of the total number and the number average particle size. It is necessary that the diameter is 4 to 10 μm, and the circularity a = L _O / L (L _O ; perimeter of a circle having the same projected area as the particle image; L; perimeter of the particle image for toner particles of 3 μm or more It is desirable that the proportion of particles having a length (length) of 0.90 or more is 90% or more on a number basis, and the proportion of particles having a circularity a of 0.98 or more is less than 30% on a number basis.

The equivalent circle diameter and particle size distribution of the toner are as follows:
Specifically, it can be measured using a flow-type particle image analyzer FPIA-1000 manufactured by Toa Medical Electronics Co., Ltd.

As a measuring procedure, a surfactant (preferably alkylbenzene sulfone) is used as a dispersant in about 50 ml of water (the number of particles in 10 ⁻³ cm ³ is 20 or less) from which fine dust has been removed by passing through a filter or the like. Acid drops), about 2 to 20 mg of the measurement sample is further added, and a dispersion treatment is performed for about 1 to 3 minutes with an ultrasonic disperser, and the particle concentration of the measurement sample is increased to 4000 to 8000 particles / 10 ^-3 cm ³ . Using the adjusted sample liquid, the flow type particle image analyzer FPI
Measured at A-1000 to determine the particle size distribution of the circle equivalent diameter,
The number basis% and the number average particle diameter of the particles having a particle diameter of 0.6 to 1.0 μm are calculated.

The circularity is determined by using the same measuring device and measuring method.

A method for producing the developer 3d will be described. 100 parts by weight of styrene-butyl acrylate-butyl maleate-half ester copolymer as binder resin, 100 parts by weight of magnetite, 2 parts by weight of iron complex of monoazo dye, and 4 parts by weight of low molecular weight polyethylene as wax were premixed. Thereafter, melt kneading is performed by a twin-screw kneading extruder set at 130 ° C. After cooling the kneaded material, coarsely pulverize, finely pulverize with a pulverizer using a jet stream, further cut a little finer than before using a wind classifier, then use mechanical impact force or heating as post-processing A sphering process is performed. As a result, in the particle size distribution based on the circle equivalent diameter of the toner particles, the ratio of the particles having a particle diameter of 0.6 μm to 1.0 μm is 0.7% of the total on a number basis, and the classified powder having a number average particle diameter of 6.4 μm. Get.

As the sphering treatment by mechanical impact or heating, the toner is centrifugally applied to the inside of the casing by a high-speed rotating blade such as a mechanofusion system manufactured by Hosokawa Micron Corporation or a hybridization system manufactured by Nara Machinery Works. And a method of applying a mechanical impact force to the toner by the force of compression force / frictional force, or a method of melting the toner surface as in a surffusion system manufactured by Nippon Pneumatic.

In the particles of 3 μm or more of the classified powder,
The ratio of particles having a circularity a = L _O / L (L _O ; peripheral length of a circle having the same projected area as the particle image, L; peripheral length of the particle image) of 0.90 or more is 95.2% based on the number. And the ratio of particles having a circularity a of 0.98 or more is 24.0% based on the number.
Met. Further, the classified powder 100 having an average particle size of 6.4 μm is used.
The developer is obtained by mixing 1.2 parts by weight of the hydrophobic silica fine powder with the parts by weight.

The developing blade 5d will be described in detail.

In the conventional urethane blade, when the developer subjected to the spheroidizing treatment is used, toner fusion occurs at the blade nip. Therefore, the occurrence of toner fusion to the blade was examined by changing the material and hardness of the blade.
The rubber hardness of each blade was made by changing the rubber material.

The experiment used the developing device of this embodiment.
The sleeve contact condition of the blade is as follows: the contact pressure P (the linear pressure (g / cm) per cm in the longitudinal direction of the sleeve (g / cm)) is 30 g / cm; NE which is the distance to 2mm
And In order to make the situation of the occurrence of toner fusion easier to understand, the sleeve of the developing device was idly rotated in a high-temperature and high-humidity environment, and the time of occurrence of toner fusion was compared. Taking the correspondence between idle rotation and printing, 15000 prints using the image forming apparatus and the developing device of the present embodiment were OK unless fusing occurred for 20 hours in idle rotation.

Table 1 shows the results.

[0051]

[Table 1]

From the evaluation results, it was found that silicone as a blade rubber material did not cause toner fusion to the blade. It is considered that the reason for this is that silicone is worn away and scraped off, and that the releasability is better than urethane. However, as a problem peculiar to the silicone blade, toner coat streaks occurred. This coating streak was also found to be related to the blade rubber hardness. That is, when the rubber hardness is high, coat streaks are generated, and when the rubber hardness is low, coat streaks are unlikely to occur. Inspection of this coat streak revealed that toner aggregates were formed at the blade nip. For silicone blades, the pressure and frictional heat at the blade nip,
It is considered that the toner aggregates instead of fusing to the blade.

The reason why the low hardness silicone rubber hardly causes streaks is that the low hardness silicone rubber is liable to wear, and the lower the rubber hardness, the larger the nip width. It is considered that the pressure is small, and the toner easily slips through the blade nip portion, so that the toner hardly forms an aggregate.

Then, using silicone rubbers having different physical properties, the wear index was varied as the rubber physical properties, and the influence on the coating streaks was examined. The hardness was changed by changing the weight ratio of silica as the filler to the rubber and the number of crosslinking points of the rubber. The blade contact conditions are the same as those described above. 15000 using the image forming apparatus and the developing apparatus of the present embodiment.
A printout test was performed on each sheet to check the occurrence of streaks. Table 2 shows the results.

[0055]

[Table 2]

The wear index was measured by a test according to JIS K6464. The amount of wear and nip width of the blade in durability is
The cross section of the blade after the printout test of 15,000 sheets was completed was measured by a surface roughness meter.

There are two types of coat streaks appearing in the image.
We could distinguish by cause. One is a streak due to aggregates,
This is for the reason described above. The other is a line due to blade shaving unevenness. This is because the nip width is unevenly scraped, and toner coat unevenness appears as a streak image.

From the evaluation results, it is understood that when the silicone rubber hardness is large, the wear index is small, and the nip and the wear amount are small. For this reason, the pressure per area of the blade contact surface increases, and the toner does not fuse to the silicone blade. However, an aggregate of the toner is generated in the nip portion to form a streak image. Conversely, those having a low rubber hardness have a large amount of wear, so that streaks due to aggregates are unlikely to occur. In addition, it was found that when the amount of the filler in the rubber was large, unevenness in blade shaving resulted in uneven toner coating, resulting in streaks.

Further, as a result of experiments on various rubbers, it was found that a rubber having a wear index in the range of 0.03 to 0.15 was effective for suppressing streaks.

Therefore, when the toner subjected to the spheroidizing treatment is used, as a material of the developing blade, the content of the filler is 5 to 20% as a rubber prescription, and the rubber hardness is 10 to 55 °. It was found that a silicone rubber in which the number of crosslinking points was adjusted to be as good as possible.

Accordingly, a silicone rubber blade having a rubber hardness of 38 ° and a filler content of 18% is used as the developing blade of this embodiment. The manufacturing method is as follows: a silicone primer is coated in a pre-heated mold to a thickness of 60 μm.
m stainless steel is placed, and LTV silicone rubber is injected by a LIM injection molding machine and heated at 150 ° C. for 5 minutes. Then, it is taken out of the mold and heat-treated at 200 ° C. for 4 hours.

Further, in order to realize higher quality image using the toner subjected to the spheroidizing treatment and the silicone rubber blade, the contact pressure P of the blade (the linear pressure per 1 cm in the longitudinal direction of the sleeve (g / g) cm)) and NE, which is the distance from the most upstream contact position (upstream in the sleeve rotation direction) to the free end of the blade.

Since the magnetic toner that has been subjected to the sphering treatment is spherical, it is difficult to regulate the coating amount by the developing blade. This is because, in order to achieve satisfactory image quality, it is necessary to increase the regulating force of the developing blade.

FIG. 3 shows the results.

From this evaluation result, the range of NE is as follows:
It was found that 0.5 ≦ NE ≦ 2.0 was good. If the NE is less than 0.5 mm, edge contact may occur, and the coating amount is reduced, resulting in low density and image white spots. On the other hand, when the thickness exceeds 2.0 mm, the toner coating amount is large and the formation of the toner layer becomes unstable.

It was also found that the contact pressure P is preferably 15 ≦ P ≦ 40. When P is less than 15 g / cm, the charge amount of the toner is insufficient, and the image quality is deteriorated and the density is low. Conversely, if it exceeds 40 g / cm, the toner coating amount is reduced, and the line is scattered due to durability.

Further, it was found that P and NE had the following relationship.

That is, when P is small, the toner regulating force is small, and unless NE is shortened, the coating amount becomes large and the image deteriorates. Since the regulating force of the toner increases as P increases, the toner coat becomes more stable and the image quality improves when NE is increased.

This experimental result can be expressed by the following relational expression.

5.0 × NE + 12.5 ≦ P ≦ 6.6 × NE + 28.3

Therefore, 0.5 ≦ NE ≦ 2.0, 15 ≦ P ≦ 40 and 5.0 × NE + 12.5 ≦ P ≦
By contacting the silicone rubber blade in the range of 6.6 × NE + 28.3, a stable toner layer could be formed using the spheroidized toner, and the image quality was satisfied.

In this embodiment, the contact pressure P (the linear pressure (g / cm) per cm in the longitudinal direction of the sleeve) is set in the developing container so as to contact the developing sleeve at 25 g / cm. I have. The nip, which is the contact width between the sleeve and the blade, is 1.5 mm, and the NE, which is the distance from the most upstream contact position (upstream in the sleeve rotation direction) to the free end of the blade, is 1.0 mm.

With the above settings, normal temperature and normal humidity (25 ° C., 60%
RH), low-temperature low-humidity (15 ° C, 10% RH), high-temperature high-humidity (30 ° C, 80% RH), 15,000 printout test results, high quality images can be stably obtained. Was.

In summary, when a developer subjected to a mechanical impact force or a spheroidizing treatment by heating is used, the silicone rubber is used as a developer regulating member, and the rubber is worn, so that the blade is fused. Is suppressed, and the nip of the blade contact portion is widened to reduce the local pressure, thereby making it possible to eliminate the occurrence of streaks. In addition, by defining the blade contact conditions, it is possible to form a high-quality image through durability.

In this embodiment, the case where the blade abuts in the counter direction has been described, but the present invention can be applied to the case where the blade abuts in the forward direction in the sleeve rotation direction. Also, it goes without saying that a sleeve obtained by roughening a non-magnetic metal such as aluminum or a sleeve coated with a resin layer has the same effect.

[0076]

As described above, according to the present invention,
Even in the manufacturing process, even if a developer subjected to a mechanical impact force or a spheroidizing treatment by heating is used, blade fusion can be prevented by abrasion of the rubber material of the elastic blade.

The rubber hardness is 10 ° or more according to JIS
By using the silicone rubber of 5 ° or less, the nip at the blade contact portion is widened, the local pressure is reduced, and streaks are less likely to occur.

In addition, the contact condition of the blade is determined by the contact pressure P
(G / cm) is 15 ≦ P ≦ 40, and the distance NE (mm) between the most upstream contact position with the developer carrier and the free end is 0.5 ≦ N.
E ≦ 2.0, and P and NE are 5.0 × NE + 1
When the range of 2.5 ≦ P ≦ 6.6 × NE + 28.3 is satisfied, a stable layer can be formed, and high-quality image can be realized for a long time.

Therefore, in the manufacturing process, a stable layer is formed by using a developer subjected to mechanical impact or a spheroidizing treatment by heating, and a page-per-cost which can achieve high-quality image formation for a long period of time. Inexpensive developing device can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an image forming apparatus including a developing device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a developing device according to the embodiment of the present invention.

FIG. 3 is a diagram showing experimental results according to the embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional image forming apparatus using an intermediate transfer member system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (electrostatic latent image carrier) 2 Charging roller 3 Laser scanner 4 Developing device 5 Developing sleeve (developer carrier) 6 Rotary 7 Intermediate transfer member 8 Cleaning blade 9 Cleaner container 10 Cleaning roller 11 Fixing means 12 Media 20 Image forming apparatus 21 Host 1d Magnet roller 2d Stirring 3d Toner (developer) 4d Developing device 5d Developing sleeve (developer carrier) 6d Developing blade (developer regulating member)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H005 AB04 AB09 CA04 CA14 CA21 CB03 EA05 FA06 FA07 2H077 AD06 AD13 AD17 AD23 AD36 BA07 EA13 EA14 EA16 GA13

Claims (5)

[Claims] A developer, a developer carrier provided to face an electrostatic latent image carrier, and carrying the developer, and a developer on the developer carrier urged toward the developer carrier. In the developing device having a developer regulating member that regulates the amount of the developer, the developer occupies a ratio of particles having a particle diameter of 0.6 μm or more and 1.0 μm or less in a particle size distribution according to a circle equivalent diameter of the developer particles. The number is less than 5.0% of the whole, the number average particle diameter is 4 to 10 μm, and the developer regulating member has a wear index of 0.03 to 0.15 for forming a nip with the developer carrier. And a contact pressure P (g / cm) of the elastic body is 15 ≦ P ≦ 40. 2. The elastic body has a rubber hardness of 1 according to JISA.
2. A silicone rubber containing 0 to 55 [deg.] And containing 5 to 20% by weight of a filler.
3. The developing device according to claim 1. 3. The elastic body has a free end on the upstream side in the moving direction of the developer carrier, and a distance NE (mm) between the free-most end and the most upstream contact position with the developer carrier. The developing device according to claim 1, wherein 5 ≦ NE ≦ 2.0 and 5.0 × NE + 12.5 ≦ P ≦ 6.6 × NE + 28.3. 4. The developer according to claim 1, wherein the proportion of particles having a circularity a of 0.90 or more determined by the following formula (1) in the particles of 3 μm or more is 90% or more based on the number, and the circularity a Is 30% based on the number of particles with a particle size of 0.98 or more
The developing device according to any one of claims 1 to 3, wherein Circularity a = L _O / L (1) (L _O ; perimeter of a circle having the same projected area as the particle image, L;
Perimeter of particle image) 5. The developing device according to claim 1, wherein the developing device is a cartridge detachable from the image forming apparatus.