JP3453473B2 - Foamed conductive roller, method of manufacturing the same, and electrophotographic apparatus using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to charging, transfer, paper conveyance, and image forming apparatus using an electrophotographic process.
The present invention relates to a foamed conductive roller used for development, cleaning, etc., a manufacturing method thereof, and an electrophotographic apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic process, a charging / transferring process has been performed by using corona discharge. However, ozone is generated at the time of corona discharge, and ozone or the like causes deterioration of the surface of the photoconductor. The dirt of the wire affects the image, and there are problems such as white spots and black streaks in the image.

In order to make up for such drawbacks, many methods of contact charging and transfer have been conventionally studied.

Conventionally, a solid charging roller using a conductive rubber has been mainly used as a member used in the contact charging system. This is because the presence of surface defects such as irregularities on the surface of the charging member causes partial unevenness of charging. However, if a solid rubber roller or the like is used as the charging member, it is difficult to reduce the hardness of the roller, which causes problems such as generation of charging noise.

On the other hand, in the transfer roller, it is necessary to adjust the nip region formed by the pressure contact surface between the transfer roller surface and the photosensitive drum surface at the time of transfer by using one having an appropriate hardness.

Therefore, instead of the solid rubber roller as the conductive roller, a foam in which conductive powder is dispersed is used.
Those with reduced hardness have come into use.

In the foamed conductive roller, a tube made of foamed rubber in which conductive powder is dispersed is inserted into a core metal, the surface of the tube is polished with a polishing grindstone, and finally the polishing powder is removed by air, a brush or the like. Some are manufactured by removing in.

In some of the rollers thus produced, the roller resistance is adjusted by applying a conductive paint to the surface layer depending on the application.

However, in the conventional foamed conductive roller, when it was attempted to lower the roller hardness depending on the degree of foaming, it was necessary to increase the diameter of the pores of the foamed body. As a result, the diameter of the pores of the foam appearing on the surface of the roller after polishing becomes large, and the contact with the photosensitive drum or the like is not uniform, so that stable conductivity cannot be obtained.

Further, the above-mentioned conventional method, particularly the cleaning method after polishing has the following drawbacks. In pressurized air cleaning and brush cleaning, the smoothness of the surface of the foamed conductive roller is impaired due to variations in the cleaning state after polishing, so the resistance on the medium that the roller contacts is not stable, and Even when the coating is applied, there is a problem that the surface smoothness and electric resistance are not uniform.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a foamed conductive roller which has excellent surface averaging property and uniform surface electric resistance.

Another object of the present invention is to provide a method for manufacturing such a foamed conductive roller.

Still another object of the present invention is to provide an electrophotographic apparatus using such a foamed conductive roller.

The foamed conductive roller according to the present invention is characterized in that it has a conductive powder filled in the pores of the foam on the surface.

In the foamed conductive roller according to the present invention, the surface of the foamed conductive roller is smoothed by filling the pores of the foam on the surface with the conductive powder, and the pores are also conductive. And has an electrically uniform surface property.

[0016]

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

FIG. 3 is a diagram schematically showing a cross section of the foamed conductive roller according to the present invention. Reference numeral 30 is a hole filled with the conductive powder 32. Reference numeral 31 is a hole portion inside which is not filled with the conductive powder. Reference numeral 33 is a non-void portion of the foam conductive roller. The foamed conductive roller is formed by kneading a binder component, a conductive material and a foaming agent into a roller shape, performing vulcanization and foaming treatment.

As the binder component, synthetic rubber such as natural rubber, butadiene rubber, isoprene rubber, butyl rubber, nitrile rubber, styrene butadiene rubber, chloroprene rubber, acrylo rubber, ethylene propylene rubber, urethane rubber, silicone rubber, fluorine rubber and chlorine rubber. Alternatively, either resin or the like may be used.

Examples of the conductive material include carbons such as carbon black and conductive carbon powder, metal powder and conductive fibers, and semiconductive powder such as metal oxides such as tin oxide, zinc oxide and titanium oxide. However, any mixture thereof may be used.

Although various foaming agents are used, more preferably, an organic decomposition type foaming agent has a good foaming temperature rise and a uniform cell diameter.

The above-mentioned conductive material can be used as the conductive powder filled in the pores on the surface of the foamed conductive roller.
A powder formed of a conductive material dispersed in an elastic body is suitable so as not to reduce the elasticity of the foamed conductive roller. At this time, the hardness of the conductive powder is preferably about the same as the hardness of the non-hole portion of the foamed conductive roller.

The electrically conductive powder has an electric resistance value of 1
Those having a resistivity of 0 ⁵ to 10 ⁹ Ω · cm are generally suitable. This resistance value is 100 V under a pressure of 500 g / cm ² by placing conductive powder in an insulating (eg, alumina) cylindrical cell.
Is the volume resistance measured at the applied voltage of. In particular, from the viewpoint of equalizing the electric resistances of the pores and the non-pores, those having substantially the same resistance value as the conductive foam powder as the conductive powder, or the conductive composition having the same composition as the conductive foam roller. Powder is preferred.

In order to increase the filling rate, a conductive elastic powder having a smaller particle size is preferable, and an elastic body to be dispersed having a high hardness can be used.

As for the form of filling the voids with the conductive powder, it is optimal that the voids and the non-voids have substantially the same surface as shown in FIG. However, the distance A from the top of the edge around the hole to the bottom of the hole is 50 μm or more without being filled with the conductive powder, and the top of the edge around the hole is From the above, the distance from the uppermost portion of the conductive powder with which the pores are filled is preferably 1/2 or less, particularly 1/3 or less of the distance A.

In the production of the foamed conductive roller according to the present invention, after filling the pores with the conductive powder, the pressure-sensitive adhesive sheet is adhered to the roller surface and peeled off so that the conductive particles attached to the non-pores are electrically conductive. It is effective to remove the powder.

As the foamed conductive roller, in use such as charging, transfer, paper conveyance, development and cleaning,
The cell diameter of the pores is preferably 500 μm or less from the viewpoint of uniformity of contact property, and when the surface is coated and used, the cell diameter is preferably 200 μm or less because of the problem of large dents after coating.

Further, as a foamed conductive roller, after polishing and cleaning, the surface of the roller is coated to form a surface layer, and in the roller exhibiting electrical characteristics, the polishing powder adhered to the surface may become convex during coating. The polishing powder stains the coating liquid to cause defective projections, which easily causes defects in electrical characteristics. For this reason, it is preferable to remove the deposits of the polishing powder on the surface. The electric resistance of the surface layer is 10
⁵ to 10 ⁹ Ω · cm is preferable.

As a method for filling the voids with the conductive powder, a conductive foam roller is placed in the conductive powder, and the conductive powder is foamed with the other roller or the like to be pressed. The method of pushing into the pores of the, the method of applying a voltage to the foamed conductive roller, and attracting the conductive powder to the pores by the electric force, the abrasive powder generated by polishing the foamed conductive roller is made conductive. There is a method of using the powder as a powder and pressing the powder into the pores simultaneously with polishing. In the method of pushing into the pores at the same time as polishing, the surface of the foamed conductive roller is activated by polishing, and the polishing powder can be efficiently filled in the pores.

A method for manufacturing a foamed conductive roller by polishing the roller and then peeling the surface of the roller with an adhesive sheet will be described.

This method can be realized by using a device as schematically shown in FIG. In the vicinity of the polishing position on the surface of the foamed conductive roller 42 polished by the polishing grindstone 41, by rotating the pressure contact roller 44 in the reverse direction,
The polishing powder adhered to the surface is pushed in to fill the inside of the pores of the foam with the polishing powder. Foamed conductive roller 4
2 covers the cored bar 43.

As the polishing grindstone, for example, white alumina,
It can be used in various abrasive grain size combinations such as green silicon carbide. More preferably, finer abrasive grains can reduce the polishing powder and improve the filling property. In this way, when the roller surface is expanded after polishing under the condition that the conductive powder is filled in the pores, the non-void portion of the roller surface and the polishing powder are adhered or filled inside the pores. Although it can be seen that in pressurized air cleaning and brush cleaning,
Since it is not possible to remove only the polishing powder that has adhered to the non-holes, and the polishing powder that has been filled in the holes is also dug out at the same time,
The pores on the roller surface tend to be larger than before cleaning, and the surface smoothness deteriorates due to re-adhesion of polishing powder to the non-pores.Therefore, the contact area between the roller and the medium changes. , It causes the electric resistance to vary. In contrast, the surface of the foaming roller washed with the adhesive sheet, the adhesive sheet adheres only to the convex portion of the surface, it is possible to peel and clean the polishing powder of only the roller non-void portion, the roller non-void portion There is no polishing powder in the inside, and the state in which the polishing powder is filled inside the pores is maintained. As a result, the surface of the foamed conductive roller is smoothed, and the electric resistance on the medium with which the roller is in contact and the electric resistance after coating are stabilized, and the smoothness of the surface is improved.

As the adhesive sheet, urethane-based adhesive components, natural rubber-based adhesives, epoxy-based adhesives, acrylic-based adhesives having various adhesive strengths defined in JIS Z1528 can be used. If the adhesive strength is too small, the deposit cannot be peeled off. On the other hand, if it is too large, it will not be used because the pillars and the like of the holes will peel off and break. It is preferable that the peeling adhesive force is 600 g / 20 mm width or more and 1800 g / 20 mm width or less.

FIG. 1 shows an example of an electrophotographic apparatus using the foamed conductive roller according to the present invention as a contact charging member.

In the figure, reference numeral 1 is a photosensitive member as a member to be charged, and this example is a conductive support 1 such as aluminum.
b and a photosensitive layer 1a formed on the outer peripheral surface thereof as a basic constituent layer. It is rotationally driven around the support shaft 1d in the clockwise direction in the drawing at a predetermined peripheral speed.

Numeral 2 is a roller type charging member which is in contact with the surface of the photoconductor 1 to uniformly perform a primary charging process on the photoconductor surface to a predetermined polarity and potential. The charging member 2 is composed of a cored bar 2c, a foamed conductive roller 2b formed on the outer periphery thereof, and a surface layer 2a formed on the outer periphery thereof, and both ends of the cored bar 2c are rotatably supported by bearing members (not shown). Then, the drum type photoconductor 1 is arranged in parallel with the photoconductor 1 and is pressed against the surface of the photoconductor 1 with a predetermined pressing force by a pressing means (not shown) such as a spring.
The photoconductor 1 is driven to rotate as it rotates.

Then, a predetermined direct current (DC) bias or direct current + alternating current (DC + AC) is applied to the core metal 2c by the power source 3.
By applying the bias, the peripheral surface of the rotating photoconductor 1 is contact-charged with a predetermined polarity and potential.

The surface of the photosensitive member 1 which has been uniformly charged by the charging member 2 is then subjected to exposure of the target image information (laser beam scanning exposure, slit exposure of the original image, etc.) by the exposure means 10, and the peripheral surface thereof. An electrostatic latent image corresponding to the target image information is formed on.

The latent image is then sequentially visualized as a toner image by the developing means 11.

This toner image is then transferred to the transfer means 12
Is sequentially transferred to the surface of the transfer material 14 that is conveyed from the sheet feeding means (not shown) to the transfer portion between the photosensitive body 1 and the transfer means 12 at an appropriate timing in synchronism with the rotation of the photosensitive body 1. To go. The transfer unit 12 of the present example is a transfer roller, and the toner image on the surface of the photoreceptor 1 is transferred to the surface of the transfer material 14 by charging the reverse polarity of the toner from the back of the transfer material 14.

The transfer material 14 to which the toner image has been transferred is separated from the surface of the photosensitive member 1 and is forwarded to an image fixing means (not shown) to be subjected to image fixing and output as an image-formed product.

After the image is transferred, the surface of the photosensitive member 1 is cleaned by the cleaning means 13 to remove adhered contaminants such as transfer residual toner, and is repeatedly used for image formation.

In the present invention, as shown in FIG. 1, a plurality of elements of the electrophotographic apparatus such as a photoconductor, a charging member, a developing means and a cleaning means can be integrally incorporated in a process cartridge. By doing so, the process cartridge can be attached to and detached from the apparatus main body. For example, the foamed conductive roller of the present invention used as a charging member and, if necessary, at least one of a developing unit and a cleaning unit are integrally incorporated in a process cartridge together with a photoconductor, and a guide unit such as a rail of an apparatus main body is installed. It can be configured to be removable using.

The foamed conductive roller of the present invention is for transfer,
In addition to primary charging and static elimination, it can be used for transporting a paper feed roller and the like.

Examples of the electrophotographic apparatus which can use the foamed conductive roller of the present invention include electrophotographic application apparatuses such as a copying machine, a laser beam printer, an LED printer, and an electrophotographic plate making system.

[0045]

DETAILED DESCRIPTION OF THE INVENTION 【Example】

Example 1 A charging roller was manufactured by the following method. EPDM
Knead Ketjen black and an organic foam material, and extrude the obtained rubber into a tube,
It is vulcanized and simultaneously foamed. Finally, a cored bar was inserted into the center of the tube to obtain a foamed charging roller in which the pores of the foam had an average diameter of 100 μm and a resistance of 10 ⁶ Ω. The charging roller was polished by using the apparatus shown in FIG. 4, and at the same time, polishing powder was filled. The results are shown in Table 1.

The rollers thus obtained were evaluated as follows.

In order to measure the conductive resistance unevenness of this charging roller, a method as schematically shown in FIG. 2 was used.
The resistance was measured. The charging roller 18 is pressed against a cylindrical aluminum drum 19, and then, in a rotated state, a DC voltage of 100 V is applied to the core of the charging roller using a power source 20, and the charging roller 18 is connected to the aluminum drum 19 in series. The variation in resistance in the circumferential direction of the charging roller was obtained from the voltage applied to the resistance 21. Maximum resistance (M
The ratio of ax) to the minimum value (Min) is shown as an average of 10 rollers. The surface condition was evaluated by microscopic observation when the abrasive powder adhesion area was 10% or less of the whole, ◯: 10% or more and 30% or less was Δ, and 30% or more was ×.

Example 2 The charging roller manufactured in the same manner as in Example 1 was polished with a polishing machine. After the polishing, a roller having a smooth surface was pressed against the rotating sponge charging roller, and the polishing powder was sprinkled in the vicinity of the contact portion to fill the polishing powder.

In the same manner as in Example 1, the ratio of the maximum resistance value to the minimum resistance value is shown in Table 1 as an average for 10 rollers.

Example 3 The charging roller manufactured in the same manner as in Example 1 was polished with a polishing machine. After the polishing, a roller having a smooth surface was pressed against a rotating sponge charging roller, Ketjen black was dispersed in SBR in the vicinity of the contact portion, and a finely divided product was sprinkled and filled.

In the same manner as in Example 1, the ratio of the maximum resistance value to the minimum resistance value is shown in Table 1 as an average for 10 rollers.

Comparative Example 1 A charging roller manufactured in the same manner as in Example 1 was manufactured by polishing with a polishing machine and not filled with polishing powder, and the polishing powder was removed by blowing air.

In the same manner as in Example 1, the ratio of the maximum resistance value to the minimum resistance value is shown in Table 1 as an average and a variance for 10 rollers. Compared to the other examples, the average value is significantly worse.

In Table 1, the distance from the top of the edge around the hole to the bottom of the hole (hereinafter referred to as distance A) is about 10 holes which are arbitrarily selected by cutting the roller. It is measured and is the average value. For the distance from the top of the edge around the hole to the top of the conductive powder filled in the hole (hereinafter referred to as distance B), a laser microscope (Lasertec, 1LM21) is used. Then, the non-contact measurement of the three-dimensional shape is performed on 10 arbitrarily selected holes, and the average value is the distance between the polishing powder uppermost part filled in the holes and the polishing surface.

[0055]

[Table 1]

Example 4 EPDM having azodicarbonamide foaming agent and conductive carbon dispersed as a conductive material is extruded into a tube by an extruder. Insert the core metal into the tube foamed by heating,
The tube surface is polished with a polishing grindstone WA320, the polishing conditions are a rotation speed of 200 RPM and a feed rate of 500 m / min.
At the same time, polishing powder was filled in to obtain a powder having a resistance value of 10 ⁶ Ω and a pore diameter of 100 μm. Peel off the foam roller, adhesive strength 550g / 20mm width, shear adhesive strength 5kg
Adhesive peeling cleaning was performed with a sheet of / cm ² . The surface condition was evaluated by microscopic observation and electric resistance (Table 2).

Example 5 Adhesive strength of 550 g / 20 mm width in Example 4
Breaking adhesive force 5kg / cm ² 60 sheets instead of the sheet
0g / 20mm width, shear adhesive strength 5.2kg / cm² of
Peel off the foam roller with a sheet and clean it with adhesive peeling.
It was Surface condition was evaluated by microscopic observation and electrical resistance
(Table-2).

Example 6 Adhesive strength of 550 g / 20 mm width in Example 4
Breaking adhesive force 5kg / cm ² Adhesive strength of 18 instead of sheet
00g / 20mm width, shear adhesive strength 7.6kg / cm² 
Peel off the foam roller with a sheet of
It was Surface condition was evaluated by microscopic observation and electrical resistance
The results are shown in Table-2.

Example 7 Adhesive strength of 550 g / 20 mm width in Example 4
Breaking adhesive force 5kg / cm ² Adhesive strength of 20 instead of
00g / 20mm width, shear adhesive strength 15kg / cm² of
Peel off the foam roller with a sheet and clean it with adhesive peeling.
It was Surface condition was evaluated by microscopic observation and electrical resistance
The results are shown in Table-2.

Reference Example 1 Adhesive strength of 550 g / 20 mm width in Example 4
Breaking adhesive force 5kg / cm ² Instead of the seat of
The foaming roller was washed more. Surface condition with microscope
Table 2 shows the results of observation and evaluation by electric resistance.

Reference Example 2 Adhesive strength of 550 g / 20 mm width in Example 4
Breaking adhesive force 5kg / cm ² Brush instead of the sheet
The foam roller was washed. Microscopic view of surface condition
Table-2 shows the results of evaluation based on observation and electric resistance.

[0062]

[Table 2]

Example 8 A foamed conductive roller prepared under the conditions of Example 4 was coated with a paint in which tin oxide was dispersed in a water-soluble urethane resin so that the volume resistance was 10 ⁸ Ω · cm, and resistance was applied. Value is 10
^{A 6} Ω roller was obtained. Table 3 shows the results of evaluation of the surface condition of this by microscopic observation and electric resistance.

Example 9 A foamed conductive roller prepared under the conditions of Example 5 was coated with a paint in which tin oxide was dispersed in a water-soluble urethane resin so that the volume resistance was 10 ⁸ Ω · cm, and the resistance was changed. Value is 10
^{A 6} Ω roller was obtained. Table 3 shows the results of evaluation of the surface condition of this by microscopic observation and electric resistance.

Example 10 A conductive foam roller made under the conditions of Example 6 was coated with a paint in which tin oxide was dispersed in a water-soluble urethane resin so that the volume resistance was 10 ⁸ Ω · cm, and the resistance was adjusted. Value is 10
^{A 6} Ω roller was obtained. Table 3 shows the results of evaluation of the surface condition of this by microscopic observation and electric resistance.

Example 11 A foamed conductive roller prepared under the conditions of Example 7 was coated with a paint in which tin oxide was dispersed in a water-soluble urethane resin so that the volume resistance was 10 ⁸ Ω · cm, and the resistance was adjusted. Value is 10
^{A 6} Ω roller was obtained. Table 3 shows the results of evaluation of the surface condition of this by microscopic observation and electric resistance.

Reference Example 3 A foamed conductive roller prepared under the conditions of Reference Example 1 was coated with a paint in which tin oxide was dispersed in a water-soluble urethane resin so that the volume resistance was 10 ⁸ Ω · cm, and resistance was applied. Value is 10
^{A 6} Ω roller was obtained. Table 3 shows the results of evaluation of the surface condition of this by microscopic observation and electric resistance.

Reference Example 4 A foamed conductive roller prepared under the conditions of Reference Example 2 was coated with a paint in which tin oxide was dispersed in a water-soluble urethane resin so that the volume resistance was 10 ⁸ Ω · cm, and the resistance was adjusted. Value is 10
^{A 6} Ω roller was obtained. Table 3 shows the results of evaluation of the surface condition of this by microscopic observation and electric resistance.

As is clear from Table 2, those washed with the adhesive sheet showed good results both in appearance and resistance.

As is clear from Table 3, the product washed with the adhesive sheet showed good results both in appearance and resistance.

[0071]

[Table 3]

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an electrophotographic apparatus using a contact charging / transfer member.

FIG. 2 is a diagram schematically showing a method for measuring resistance of a foamed conductive roller used in the present invention.

FIG. 3 is a diagram schematically showing a state in which the polishing powder of the present invention is filled inside the pores of a foam.

FIG. 4 is a schematic diagram showing the structure of a polishing machine according to the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Nishimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inori Noriyuki Nagata 3-30-2 Shimomaruko, Ota-ku, Tokyo Ki Canon Inc. (72) Inventor Nobutoshi Hayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-6-320554 (JP, A) JP-A-6-149097 ( JP, A) JP 7-92776 (JP, A) JP 5-303257 (JP, A) JP 5-11636 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/02 G03G 13/14-13/16 G03G 15/00 G03G 15/00 550 G03G 15/02-15/02 103 G03G 15/14-15/16 103 G03G 21/16-21/18 F16C 13/00-15/00

Claims (17)

(57) [Claims] 1. A foamed conductive roller comprising a conductive powder filled in pores of a foamed body on the surface of the foamed conductive roller. 2. The foamed conductive roller according to claim 1, wherein the conductive resistance of the conductive powder is substantially the same as that of the foamed conductive roller. 3. The foamed conductive roller according to claim 2, wherein the conductive powder is a conductive powder having the same composition as the foamed conductive roller. 4. The foamed conductive roller according to claim 3, wherein the conductive powder is abrasive powder generated by polishing the foamed conductive roller. 5. The foamed conductive roller according to claim 1, wherein the foamed conductive roller is a charging roller. 6. The foamed conductive roller according to claim 1, wherein the foamed conductive roller is a transfer roller. 7. The electric resistance value of the conductive powder is from 10 ⁵ to 10 ^5.
The foamed conductive roller according to claim 1, which has a resistance of ⁹ Ω · cm. 8. The distance A from the top of the edge around the hole to the bottom of the hole is 50 μm or more when the conductive powder is not filled, and the distance A around the edge of the hole is The foamed conductive roller according to claim 1, wherein the distance from the uppermost portion to the uppermost portion of the conductive powder filled in the pores is ½ or less of the distance A. 9. The distance from the uppermost part of the edge around the hole to the uppermost part of the conductive powder with which the hole is filled is 1/3 or less of the distance A. Foamed conductive roller. 10. The foamed conductive roller according to claim 1, further comprising a surface layer on the foamed conductive roller. 11. The electric resistance of the surface layer is from 10 ⁵ to 10 ⁹ Ω.
The foamed conductive roller according to claim 10, wherein the conductive foamed roller is cm. 12. A foamed electroconductive roller, characterized in that after a process for filling voids of a foamed body on the surface of the foamed electroconductive roller with a conductive powder, an adhesive sheet is adhered to the surface of the foamed electroconductive roller and peeled off. Roller manufacturing method. 13. The peeling adhesive force of the adhesive sheet is 60.
13. An adhesive sheet having a width of 0 g / 20 mm or more and 1800 g / 20 mm or less is used.
7. The method for producing a foamed conductive roller according to. 14. An electrophotographic apparatus having a charging roller and an electrophotographic photosensitive member, wherein the charging roller is a foamed conductive roller, and has a conductive powder filled in the pores of the foamed material on the surface thereof. An electrophotographic device characterized in that 15. The electrophotographic apparatus according to claim 14, further comprising a surface layer on the foamed conductive roller. 16. A process cartridge in which an electrophotographic photosensitive member and a charging roller are integrally formed into a cartridge, and which is detachable from an image forming apparatus main body, wherein the charging roller is a foam conductive roller, and a foam on the surface thereof. A process cartridge, characterized in that it has a conductive powder filled in the holes of the process cartridge. 17. The process cartridge according to claim 16, further comprising a surface layer on the foamed conductive roller.