JPH08240962A - Electrifying roller, process cartridge and image forming device - Google Patents

Abstract

PURPOSE: To reduce electrifying noise and to prevent filming and toner melt- sticking by providing a top layer and a bottom layer consisting of a sponge layer, having specific characteristics respectively in a roller main body. CONSTITUTION: A process cartridge 17 is constituted in such a manner that a photoreceptor 1, an electrifying roller 2 being an electrifier, a developing device 7 and a cleaning device 14 are integrally incorporated in a cartridge container. Then the electrifying roller 2 is provided with the sponge layer as a base layer (bottom layer) on a core metal and the top layer thereon and the level of the electrifying noise depends on both characteristics of the sponge layer and the top layer. At this time, sponge used as the bottom layer has 60-150μm averaged faam diameter, so that the top layer having excellent surface layer can be obtained while the electrifying noise is prevented. Moreover, the micro hardness of the top layer is set <=80 deg., to weaken the rubbing force of the electrifying roller against the surface of an image carrier and prevent the melt-sticking to the image carrier and the filming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roller, a process cartridge and an image forming apparatus used in an image forming apparatus such as an electrophotographic copying machine and a laser beam printer.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, a contact charging device is known as a device for charging a photoconductor as an image carrier. In this contact charging device, the drawbacks of the corona charging device which is a representative of the non-contact charging device, that is, the high applied voltage and the large amount of ozone generated are improved.

When a charging roller is used as the contact charging member in the contact charging device, the charging roller is
The following conditions are required to ensure uniform charging of the surface of the photoconductor. The roller body must have uniform resistance.
That is, the roller shape and the surface property are good in order to form a predetermined nip portion with the surface of the photoconductor.

When a superposed voltage in which an AC bias is superposed on a DC bias is used as the voltage applied to the charging roller (hereinafter referred to as "AC charging"), the photosensitive body is exposed due to uneven resistance of the roller body and insufficient surface property. It is possible to eliminate uneven charging on the body surface. However, on the other hand, charging noise tends to occur.

As described in Japanese Unexamined Patent Publication No. 5-210281, the generation of the charging sound causes the surface of the charging roller to vibrate at the cycle of twice the frequency of the applied voltage due to an oscillating electric field, so that the surface of the photosensitive member is vibrated. It is generated by hitting.

As one measure to prevent this,
The above-mentioned publication proposes a sponge roller. That is, the roller body has a two-layer structure, a sponge layer is provided as a lower layer, and a solid surface layer (charging layer) having a thickness of 5 to 10000 μm is provided thereon. As a result, charging noise is prevented and charging without uneven charging is realized.

[0007]

However, as described above, the applicant of the present application has confirmed that the charging sound is greatly affected by the foaming state of the sponge layer only by providing the solid surface layer on the sponge layer. did. As a measure against this, as proposed in Japanese Patent Laid-Open No. 5-224506, the sponge has a porosity of 50% or more, a surface layer thickness of 500 μm or less, and a surface cell diameter of 200 μm.
Below.

As a result, the charging noise could be reduced to a level at which there was almost no problem, but it was found that the charging noise was still a little annoying depending on the foaming conditions of the sponge layer. . Also, sponge layer (lower layer)
When the above-mentioned AC charging is performed on the roller having a solid surface layer on the top, the charging noise is dramatically improved as compared with a charging roller (for example, a rubber roller) in which all layers are solid. It has been found that there is a strong tendency to cause filming and to fuse the toner onto the photoconductor.

Therefore, it is an object of the present invention to provide a charging roller, a process cartridge, and an image forming apparatus that reduce charging noise and prevent filming and toner fusion.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in a charging roller which is disposed in contact with the surface of an image carrier to charge or discharge the surface of the image carrier, And a roller body disposed around the core and having at least two layers, and the roller body has a surface that directly contacts the surface of the image carrier. Having a micro hardness of 80 degrees or less, and a lower layer which is arranged inside the surface layer to support the surface layer and which is constituted by a sponge layer having an average foam diameter of 60 to 150 μm. Is characterized by.

In this case, the thickness of the surface layer is 50 to 250.
μm or the surface roughness Rz of the surface layer is 20
It is recommended to set it to less than μm.

It is preferable that the surface layer is made of at least a mixture of urethane and acrylic, and the mixing ratio of these is 2: 8 to 8: 2.

Next, in a process cartridge detachably attached to the main body of the image forming apparatus, at least the image carrier and any one of the above-mentioned charging rollers are integrated into a cartridge container. To do.

Next, the image forming apparatus forms an latent image on the surface of the image carrier after charging, an image carrier, any one of the charging rollers described above, a power source for applying an oscillating voltage to the charging roller. Latent image forming means, a developing means for forming a toner image by adhering toner to the latent image, and a transfer means for transferring the toner image on the image carrier onto a transfer material. .

[0015]

According to the above construction, by setting the average foam diameter of the sponge layer to 60 to 150 μm, a good surface layer can be obtained while reducing the charging noise.

Further, by setting the micro hardness of the surface layer to 80 degrees or less, it is possible to weaken the force with which the roller body of the charging roller rubs the surface of the image carrier, thereby preventing filming and toner fusion. can do.

By setting the thickness of the surface layer to 50 μm or more,
It is possible to form a surface layer having a good surface property that is not affected by the lower sponge layer. Further, by setting the film thickness to 250 μm or less, it is possible to realize the above-described micro hardness of 80 or less. Further, by setting the range of the film thickness in this way, the level of the charging sound can be made substantially the same level as in the case where the roller body is composed of a single layer of sponge.

Filming can be prevented by setting the surface roughness Rz of the surface layer to 20 μm or less.

When the surface layer is made of a mixture of at least urethane and acryl and the mixing ratio is set as described above, the surface layer is in close contact with the surface of the image bearing member and a charging roller mark is formed on the surface of the image bearing member. The surface fragility of the surface layer can be improved.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to the present invention.

This image forming apparatus is of a type in which the process cartridge 17 is removably attached to an image forming apparatus main body (not shown).

The process cartridge 17 includes the photoconductor 1,
The charging roller 2 of the charging device (charging means), the developing device (developing means) 7, and the cleaning device 14 are integrally incorporated in a cartridge container.

On the other hand, laser scanner (exposure means) power supplies 12 and 16, a transfer roller (transfer means) 13, and a fixing device 15 are arranged on the main body side of the image forming apparatus.

First, the outline of this image formation will be described.

Photoreceptor 1 as charged body (image bearing body)
Is a photoconductive layer 1a having a photoconductive property laminated on the surface of a cylindrical conductive substrate 1b made of aluminum, and has a drum shape with a diameter of 30 mm as a whole. The photoconductor 1 is rotationally driven in the direction of arrow A in the figure at a peripheral speed of 36 mm / sec.

Further, the photosensitive member 1 is uniformly charged with a negative polarity by the charging roller 2, and then converted into an image information time-series electric digital image signal output from the video controller (not shown) output by the laser scanner 4. Scanning exposure is performed with a resolution of 600 dpi by the corresponding laser exposure 5, and an electrostatic latent image is formed on the surface via a mirror 6 installed in the main body of the image forming apparatus.

The electrostatic latent image on the photosensitive member 1 is reversely developed by the toner 8 carried on the developing sleeve 11 in the developing device 7 and visualized as a toner image.

The toner image is transferred onto the transfer material P such as paper by the transfer roller 13. Then, the transfer material P, which has received the transfer of the toner image, is separated from the photoconductor 1 and is fixed in the fixing device 1.
5, the toner image is fixed there, and then discharged from the main body of the image forming apparatus. After the transfer process, the residual toner on the surface of the photoconductor 1 is removed by the cleaning device 14 and is used for the next image formation.

Next, each member will be described in detail in order.

The above-mentioned developing device 7 adopts a non-contact developing system, and carries toner 8 and carries it.
Rotating developing sleeve (toner carrier)
11, a magnet (fixed magnetic field generating means) 10 fixed in the developing sleeve 11, and a toner storage chamber 3. The developing sleeve 11 is connected to a power source 16 to which an AC + DC bias can be applied, and in this embodiment, a DC component of −400V is superimposed and applied to a rectangular wave having a peak-to-peak voltage of 1200V. The doctor blade 9 for regulating the layer thickness of the toner 8 on the developing sleeve 11 is made of urethane rubber so as to have a thickness of 1.1 mm, and its hardness is 67 ° according to JIS A. When the above-described developing bias is applied to the developing sleeve 11, the toner 8 applied in a thin layer on the developing sleeve 11 is attached to the photoconductor 1 at a portion facing the photoconductor 1. In this embodiment, the toner 8 is a magnetic one-component toner and is stored in the toner storage chamber 3.

Next, the charging roller 2 which is a feature of the present invention will be described.

The charging roller 2 has a cored bar 2a and a roller main body, and the roller main body has a two-layer structure including a sponge layer (lower layer) 2b and a surface layer 2c. Core metal 2a has a diameter of 6 m
m, roller outer diameter is 12 mm, roller length is about 220
mm.

Further, both ends of the cored bar 2a are indicated by an arrow C in the figure.
The pressure is applied by 500 gf in each direction, and is in contact with the back surface of the photoconductor 1 with a nip width of about 1.5 mm. The charging roller 2 is not driven, and is driven to rotate with respect to the photoconductor 1. Further, the charging roller 2 is a core metal 2a.
Is connected to the bias applying power supply 12 via the AC bias (peak voltage 1600).
V, sine wave of frequency 370 Hz) DC bias -60
0V is superimposed and applied. With this bias,
The surface of the photoconductor 1 is uniformly charged to about -580V.

Next, various characteristics of the charging roller according to the embodiment of the present invention will be described.

The charging roller 2 has a sponge layer 2b as a base layer (lower layer) on the core metal 2a, and a surface layer 2c on the sponge layer 2b. The magnitude of the charging sound depends on the characteristics of the sponge layer 2b and the surface layer 2c. First, the surface layer 2c
The relationship between the characteristics of the sponge layer 2b and the loudness of the charging sound was examined without the provision of the. In most cases, the sound pressure level is often discussed in the measurement of charged sound, but in order to perform more precise measurement, the FFT analysis is performed on the frequency component twice the applied frequency, which is the main component of the charged sound. And extracted for comparison.

The measuring method and the evaluating method of the charging noise will be described below.

(Charging Sound Measuring Method and Evaluation Method) As shown in FIG. 2, a charging roller (e.g., C container, with the cleaning blade and the squeeze sheet removed) of a Canon LBP EP-L GRG cartridge cartridge is used. Set the C roller) and the photoconductor (photosensitive drum), and set them in the cartridge idler. The rotation speed of idle rotation was adjusted so that the drum peripheral speed was 36 mm / sec. The applied bias at this time is V _dc = −580V, V _pp
= 2000 V and f = 370 Hz.

The charging noise is measured by a sound level meter (ordinary sound level meter NL-0.
2 type, manufactured by Rion Co., Ltd., and the AC output (analog output) is converted into an A / D converter (ADN-1400,
Personal computer (PC-98) through Canopus Co., Ltd.
01 NC-A340, manufactured by NEC). The signal sent to the personal computer is a time change of voltage that represents the amplitude of sound. Therefore, as shown in FIG. 2A, the horizontal axis: time t,
Vertical axis: voltage V, which represents the amplitude of sound.

By subjecting this signal to FFT (using the data conversion software for the arbitrary waveform generator AG1200, Yokogawa Electric Co., Ltd.), the magnitude of the frequency component for each frequency can be obtained, and the charged sound A graph as shown in FIG. 2B is obtained as the frequency analysis result. The magnitude of the charging sound will be discussed by comparing the magnitudes of the portions corresponding to the charging sound in this graph (a component having a frequency twice the applied frequency, hereinafter referred to as “2f component”).

Prior to this, the correlation between the sound pressure of the charging sound and the magnitude of the 2f component was measured and shown in FIG. From FIG. 3, the sound pressure of the charging sound and the magnitude of the 2f component have a good correspondence,
By extracting the 2f component, it is possible to remove the fluctuation factors such as the noise of the measurement environment and the noise of the idler, so that more accurate measurement is possible.

FIG. 4 shows the average foam diameter of the sponge roller and 2f.
The relationship with the size of the components is shown. The average foam diameter was measured from the average value of 10 bubbles (30 in total) by measuring the charging sound at 3 points on both ends of the roller and the center, cutting the roller, and observing the cross section with an optical microscope. I asked. FIG.
It can be seen that the larger the average foam diameter, the smaller the size of the 2f component. As a level that is not noisy in practice,
As a result of the sensory test, the size of the 2f component as the charging roller is required to be 0.25 or less in the measurement system of this experiment. Although details will be described later, the size of the 2f component may be increased by about 0.1 by providing the surface layer on the sponge layer. Considering this, the size of the 2f component needs to be about 0.15 in the state of only the sponge layer. Therefore, from FIG. 4, the average foam diameter of the sponge is 60.
μm or more is desirable.

However, when the average foam diameter exceeds 150 μm, it is difficult to coat the surface layer. That is, in order to obtain a smooth surface property, a very large thickness, for example, 5
There is no choice but to obtain a surface layer of 00 μm or more by repeating coating a plurality of times or to cover a tube. As will be described later in detail, the thickness of the surface layer is 2 from the viewpoint other than the surface property.
If it is not less than 50 μm, the surface hardness of the roller is increased to cause an adverse effect on the image such as filming, or the charging noise is increased. Further, when a tube having a small film thickness is covered, the rigidity of the tube is insufficient, and the bubble portion of the underlying sponge cannot be completely covered, resulting in a dent in the surface layer. Therefore, when a sponge layer having an average foam diameter of more than 150 μm is polished, it is difficult to absorb the dent on the sponge surface and thin the surface layer as described above.

It is also possible to provide a skin layer on the surface of the sponge layer by in-mold foaming. In this case, since the surface of the sponge layer has the skin layer, the smoothness of the surface is easily obtained. However, it is very difficult to obtain an average foam diameter of 150 μm by in-mold foaming because of providing a skin layer.
This is because when the foam diameter is increased, the variation in foaming becomes large and the average foam diameter becomes rather small. Further, defects such as large dents are likely to occur on the surface. Therefore, the average foam diameter of the sponge layer is preferably 150 μm or less regardless of the presence or absence of the skin layer.

As described above, the average foam diameter of the sponge layer is 60 μm including the viewpoint of the volume of the charging sound.
To 150 μm is desirable.

Next, FIG. 6 shows various characteristics of the roller manufactured by changing the surface layer material and thickness.

In the figure, the surface layer materials A to C are those prepared by dispersing carbon or tin oxide in acrylic resin, urethane elastomer or a mixture thereof to adjust the resistance value to about 10 ⁵ to 10 ⁷ Ω. .

Of course, the type of material is not limited to this.

The surface layer has a thickness of 100 μm to 250 μm.
I made a prototype of a degree.

The lower layer sponge has an average foam diameter of 120 μm.
It is a urethane foam of about m and all rollers are the same. Carbon is dispersed in urethane foam to make it electrically conductive. The conductivity may be imparted by a metal oxide other than carbon (tin oxide, titanium oxide, etc.).

As for the lower sponge layer, in the case of the present prototype roller, one having a skin layer on the surface layer was used by foaming in the mold. Needless to say, the shape may be adjusted by free foaming and polishing the outer diameter.

Under the condition of the lower sponge layer before dipping the surface layer and after the dipping of the surface layer into the final dry roller state, a roller hardness is measured with an Asker C hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) under a load of 500 gf. Was measured. Also,
In the final roller state, the micro hardness of the surface layer was also measured with a macro rubber hardness meter MD-1 (manufactured by Kobunshi Keiki Co., Ltd.).

The film thickness of the roller was obtained by cutting after the durability test and observing the cut surface with an optical microscope.

Next, image evaluation was carried out by using the above-mentioned image forming apparatus for the various charging rollers shown in FIG.
At 5 ° C. and 10%), an endurance test of 10000 prints was performed at an image ratio of 4%, and the results are shown in the same table.

Toner fusion did not occur for all the rollers (indicated by "O" in the table).

Regarding filming in the image evaluation items in the table, those which did not occur at all were marked with "◯", those which were not visible on the image but were slightly generated on the drum were marked with "△",
What was generated on the image was "X", and what was severely generated on the image was "XX".

It can be seen from FIG. 6 that the film hardness of the roller N may be 49 ° or less. However, since the roller hardness measurement error is about 1 to 2 °, the roller N
O. 5 and NO. It can be said that there is almost no difference in roller hardness between No. 6 and 6. On the other hand, the surface hardness (micro hardness) of the roller is NO. 6 and NO. It is 5 ° different from 7 and it can be said that there is a significant difference. Further, there is a good correspondence between the degree of filming and the surface hardness, and if the surface hardness is 70 ° or less, filming does not occur even on the drum. Further, if it is 80 ° or less, it does not cause a problem because it is slightly generated on the drum but does not appear on the image.
Therefore, in order to obtain an image without filming by using the sponge roller for AC charging, the surface hardness has a great influence, not the entire hardness (Asuka C) of the roller. By suppressing the hardness to 80 ° or less, it is possible to obtain a roller having no problem in terms of image. The measured value of Micro Rubber Hardness Meter MD-1 (manufactured by Kobunshi Keiki Co., Ltd.) is JIS A (JIS K 6301).
It corresponds well with the value of (A type). Therefore, if a surface layer material having a JIS A hardness of 80 ° or less (for example, a general rubber) is selected, the surface layer thickness can be freely selected, and a surface layer material having a JIS A hardness of 80 ° or more can be selected. By selecting (for example, a material closer to resin than an elastomer), the surface layer hardness can be set to 80 ° or less by appropriately reducing the surface layer thickness.

Even if the material such as C in FIG. 6 is considerably soft, if the thickness of the surface layer is about 250 μm, the micro hardness of the surface layer exceeds 80 °. Therefore, the thickness of the surface layer is preferably 250 μm or less.

The surface roughness of the roller shown in FIG. 6 is almost R.
z was about 5 μm to 15 μm, but the surface roughness was 2
If it exceeds 0 μm, even if the micro hardness of the surface layer is 80 °
Since filming may occur on the image even if it is below, the surface roughness Rz of the surface layer is preferably 20 μm or less.

Next, it was examined how much the size of the charging sound changed when the surface layer was provided.

First, the size of the 2f component was measured in the state of the sponge (before coating the surface layer) with the above-mentioned measuring system. Then, the film thickness of the surface layer was changed and two types of surface layers were provided.

For each roller, the magnitude of the 2f component of the charging sound was measured again by the above-mentioned measuring system.

The difference between the size of the 2f component in the sponge state and the size of the 2f component after coating the surface layer was determined.
If this difference is negative, it means that the charging noise is reduced by providing the surface layer, and if this difference is positive, it means that the charging noise is increased by providing the surface layer. FIG. 5 shows the results of a graph in which the horizontal axis represents the thickness of the surface layer and the vertical axis represents the difference in the 2f component. From the figure, it can be seen that the magnitude of the charging noise may increase or decrease from the sponge state by changing the thickness and material of the surface layer.

It can be seen that when the material is fixed, the magnitude of the charging sound has a minimum value with respect to the thickness of the surface layer. This minimum value is approximately 50 μm, although it depends on the material and the frequency of the AC component of the charging bias applied.
To a minimum of 250 μm. The size of the 2f component is about 0.15 at maximum with only the sponge,
The level at which it is determined that the roller as a whole is quiet after the surface layer is provided is about 0.25. Therefore, the size of the 2f component increased by adding the surface layer needs to be within 0.1. In order to keep the 2f component difference (Δ2f) within 0.1 in FIG. 5, the coat B has a surface layer thickness of 7
It is desirable that the thickness is 0 μm to 180 μm, and more desirably 80 μm to 170 μm so that Δ2f becomes negative. Similarly, in the coat C, the thickness of the surface layer is 100
μm to 250 μm, and more preferably 80 μm to 170 μm so that Δ2f becomes negative. From the above, the thickness of the sponge layer also affects the charging sound, so it is necessary to optimize it depending on the frequency and material actually used.

Generally, it is desirable to select the optimum film thickness within the film thickness of 50 μm to 250 μm. If the surface layer is too thin, it is difficult to obtain a smooth surface having good surface properties, but if the surface layer has a thickness of 50 μm or more, sufficient surface smoothness can be obtained.

Next, as a material for the surface layer, a mixture of acrylic and urethane was used, and a roller was manufactured by changing the mixing ratio of the acrylic and urethane. Fig. 7 shows the types of prototype rollers. In the same figure, as the roller evaluation, the results of the adhesion test with the photosensitive drum and the surface cracking test when the roller is pressed against the photosensitive drum and rotated for a long time are also shown. In the adhesion test of the photosensitive drum, both ends of the core metal of the roller were pressed at 500 gf on each side and a total pressure of 1 kgf, and after leaving for 1 month in an environment of a temperature of 50 ° C. and a humidity of 90%, a transferred substance was found on the photosensitive drum. I decided whether or not there was. Those that did not exist were marked with "○", and those that had a slight transition were marked with "△".

With regard to cracks and cracks on the surface layer, both ends of the core metal of the roller were moved onto the photosensitive drum by 1 kg on each side.
f, a total pressure of 2 kgf was applied, and driven rotation was performed at a peripheral speed of 50 mm / sec in an environment of 32.5 ° C. and 85% for 48 hours, and it was confirmed whether the surface layer was cracked or cracked.

When the surface layer was free from cracks or cracks, "○" was given, and when the edge of the roller was slightly cracked, "△" was given.

As shown in FIG. 7, since urethane is softer than acrylic, it is effective in lowering the microhardness of the surface layer. However, when it is made of 100% urethane, there are transitions on the drum, and in extreme cases, the surface layer on the drum is There is a risk of sticking. Acrylic has a lower adhesion to the drum than urethane, but is very hard, so the microhardness of the surface layer becomes high. In addition, if it is made of 100% acrylic, the surface layer is hard and brittle, and cracks occur. . By mixing the two, it is possible to combine the flexibility of urethane and the non-adhesiveness of acrylic, and to complement the drawbacks of both materials. The mixing ratio of urethane: acrylic is preferably from 2: 8 to 8: 2.

[0069]

As described above, according to the present invention,
By setting the average foam diameter of the sponge to be 60 to 150 μm, it is possible to obtain a surface layer having good surface property while preventing charging noise.

Further, by setting the micro hardness of the surface layer to 80 ° or less, it is possible to weaken the force with which the charging roller slides on the surface of the image carrier (photosensitive drum) and prevent the image carrier from being fused and filming.

By setting the surface roughness Rz of the surface layer to 20 μm or less, filming can be prevented.

By setting the film thickness to 50 μm or more,
A surface layer having a good surface property is obtained without being affected by the sponge of the base layer, and by setting it to 250 μm or less, the micro hardness of the surface layer can be set to 80 ° or less. Further, by selecting this film thickness range, the charging noise can be made smaller than the roller having a single layer of sponge, and can be reduced in some cases.

By using a composite material of urethane and acrylic as the material for the surface layer and setting the mixing ratio to 2: 8 to 8: 2, adhesion to the image carrier / roller marks can be prevented and the brittleness of the surface layer can be reduced. It can be resolved.

By using the above charging roller, it is possible to realize an image forming apparatus with a small charging noise even in AC charging, and it is not necessary to take extra cost as a countermeasure against charging noise. In addition, it is possible to output a stable image without image defects such as drum fusion and filming over a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus showing an embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram of a charging sound measuring system.

FIG. 3 is a correlation diagram between the magnitude of the 2f component of the charging sound and the conventional sound pressure value.

FIG. 4 is a correlation diagram between the foam diameter of a single sponge roller and the magnitude of the 2f component of the charging sound.

FIG. 5 is a correlation diagram between the thickness of the surface layer and the difference in the 2f component of the charging sound before and after the surface coating.

FIG. 6 is a table showing various characteristics of a roller according to the present embodiment and an image durability result.

FIG. 7 is a diagram showing a list of various characteristics of the roller of the present embodiment and an image durability result.

[Explanation of symbols]

 1 image carrier (photoreceptor, photosensitive drum) 2 charging roller 2a core metal 2b lower layer (sponge layer) 2c surface layer 3 toner storage chamber 4 exposure means (laser scanner) 5 laser light 6 mirror 7 developing means (developing device) 8 toner 9 Doctor Blade 10 Fixed Magnetic Field Generating Means (Magnet) 11 Developing Sleeve 12, 16 Power Supply 13 Transfer Means (Transfer Roller) 14 Cleaning Device 14a Cleaning Blade 15 Fixing Device 17 Process Cartridge

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yusuke Nakazono 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Hiroyuki Adachi Inventor Hiroyuki Adachi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (6)

[Claims] 1. A charging roller, which is disposed in contact with the surface of an image carrier to charge or remove the surface of the image carrier, a core metal to which a voltage is applied, and at least 2 cores disposed around the core metal. A roller main body constituted by more than one layer, wherein the roller main body has a surface layer having a micro hardness of 80 degrees or less on a contact surface which is in direct contact with the surface of the image carrier, and an inner side of the surface layer. A charging roller, which is arranged and supports the surface layer, and has a lower layer constituted by a sponge layer having an average foam diameter of 60 to 150 μm. 2. The charging roller according to claim 1, wherein the thickness of the surface layer is set to 50 to 250 μm. 3. The charging roller according to claim 1, wherein the surface roughness Rz of the surface layer is set to 20 μm or less. 4. The surface layer is made of a mixture of at least urethane and acrylic, and the mixing ratio of these is 2: 8 to 8: 2. The charging roller according to any one of the above. 5. A process cartridge detachably attached to an image forming apparatus main body, wherein at least an image carrier and the charging roller according to any one of claims 1 to 4 are integrally formed in a cartridge container. A process cartridge that is characterized by being incorporated. 6. An image carrier, the charging roller according to claim 1, a power supply for applying an oscillating voltage to the charging roller, and a latent image on the surface of the image carrier after charging. A latent image forming means for forming the latent image, a developing means for forming a toner image by adhering toner to the latent image, and a transfer means for transferring the toner image on the image carrier onto a transfer material. A characteristic image forming apparatus.