JP2003091136A - Semiconductive roller and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductive roller wherein a conductive agent added to a resistance adjusting layer consisting of a resin tube is modified to reduce variation in resistance, and also, which is favorable in terms of cost, and to provide an electrophotographic device using the semiconductor roller. SOLUTION: The conductive agent previously coated with resin of high attenuation is used as the conductive agent added to a resin tube layer formed on the surface of a roller such as an electrifying roller, a developing roller, a transfer roller, a discharging roller and a toner supply roller, etc., used for an electrophotographic device such as a printer, a copying machine and a facsimile, etc., then, the semiconductive roller having less variance in resistance and also having a stable resistance is manufactured, and also, the semiconductive roller is attached to the electrophotographic device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-conductive roller, which is a resin tube mainly used for a charging roller, a developing roller, a transfer roller, a discharging roller, a toner supply roller, etc., which are members of an electrophotographic apparatus. The present invention relates to a semiconductive roller having a resistance adjusting layer made of, and an electrophotographic apparatus equipped with the semiconductive roller.

[0002]

2. Description of the Related Art Conventionally, as a semiconductive roller used in an electrophotographic apparatus such as a printer, a copying machine, and a FAX,
Examples thereof include a charging roller, a developing roller, a transfer roller, a charge eliminating roller, a toner supply roller and the like. Each roller is required to have a resistance in the semi-conductive region, but it is a fact that it is difficult to control the resistance. Generally, as a method for controlling the resistance of the semiconductive roller, a resistance adjusting layer made of a coating film or the like is provided on an elastic body serving as a base material, and ions, carbon, metal oxides, etc. are provided in the resistance adjusting layer. The method of controlling the amount of the conductive substance added is adopted.

[0003]

However, when ions are used, although a roller having a small variation in resistance can be obtained, it is possible to cover only a relatively high resistance region and the resistance is easily influenced by the environment. There was a problem. In addition, there are problems that the resistance is likely to change due to energization, and that ions easily bleed and become a pollution source. On the other hand, when a conductive material such as carbon or metal oxide is used, the resistance is not easily influenced by the environment,
Although there are many advantages such as a small change in resistance due to energization, a pollution problem is less likely to occur, and a required resistance area can be covered, there are large variations in resistance,
It has problems such as a large voltage dependence of resistance. Therefore, in order to improve the reproducibility and stability of resistance, some attempts have been made to add a dispersant together with the above-mentioned conductive substance, but the above-mentioned additive itself causes a new problem that it easily becomes a pollution source. There is. Further, the resistance adjusting layer may be formed by coating with a paint, forming by powder coating, forming by a resin tube formed by extrusion or the like. Here, in the case of aiming at cost reduction, the method of forming with a resin tube is the most advantageous, but from the viewpoint of resistance control described above, it is a more disadvantageous forming method.

The present invention has been made in view of the problems of the prior art, and is obtained by modifying a conductive agent added to a resistance adjusting layer made of a resin tube, and the variation in resistance is small, and
It is an object of the present invention to provide a semi-conductive roller which is advantageous in terms of cost and an electrophotographic apparatus using the semi-conductive roller.

[0005]

As a result of intensive studies, the present inventors have used a conductive agent pre-coated with a resin having a high charge attenuation property as a conductive agent to be added to a resistance adjusting layer made of a resin tube. As a result, it has been found that a semi-conductive roller with less variation in resistance can be stably obtained, and the present invention has been completed. That is,
The semiconductive roller according to claim 1 is characterized in that a conductive agent previously coated with a resin having a high charge attenuation property is used as the conductive agent added to the resin tube formed on the roller surface. . The semiconductive roller according to claim 2, wherein a voltage of 8 kV is applied to a corona discharger arranged with a distance of 1 mm between the resin and the resin surface to generate corona discharge to charge the resin surface. In this case, the resin has a maximum surface potential of 300 V or less after 0.3 seconds. In the semiconductive roller according to the third aspect, the coating amount of the resin is 0.01 to 50 wt% with respect to the conductive agent. In the semiconductive roller according to the fourth aspect, the conductive agent is at least one of carbon, metal powder, metal oxide, or a mixture thereof. According to a fifth aspect of the present invention, in the semiconductive roller coated with the resin, the solvent insolubility rate of the resin component represented by the following relational expression is 50% or more. Here, the solvent insolubility rate (%) = (B / A) × 100, where A: the weight of the resin component in the resin-coated conductive agent before being immersed in the solvent B; the resin-coated conductive agent in a good solvent, 25
Weight of resin component after immersion at 24 ° C. for 24 hours In the semiconductive roller according to claim 6, the surface roughness of the roller is 4 μm or less. An electrophotographic apparatus according to a seventh aspect is characterized in that the semiconductive roller according to any of the first to sixth aspects is mounted.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. 1 (a) and 1 (b) are diagrams showing a configuration example of a semiconductive roller according to the present invention. The semiconductive roller 10 has an elastic layer 12 formed on the outer circumference of a shaft 11 made of metal or plastic. Further, a resin tube layer 13 which is a resistance adjusting layer is further formed on the surface of the elastic layer 12. In the present invention, the resin tube layer 13 is a resin tube layer to which a conductive agent such as carbon, metal powder, or metal oxide coated with resin in advance is added. That is,
As the conductive agent, by using the conductive agent coated with the resin in advance, the conductive agent which is not coated, compared with the case where the conductive agent such as ordinary carbon or metal oxide is used as it is, The dispersibility can be easily controlled, and the variation in resistance and the voltage dependence of resistance can be reduced. At this time, the coating amount of the resin is 0.01 to 50 wt%, preferably 0.0 to 50 wt% with respect to the original conductive agent to be coated.
1 to 30 wt%, more preferably 0.01 to 20 wt%
Is appropriate. When the coating amount is less than the above range, sufficient effect of improving the dispersibility cannot be obtained, and when it is more than the above range, sufficient conductivity cannot be obtained as described later. By the way, if you just coat the resin,
In the direction of impairing the original conductivity of the conductive agent,
Although the dispersibility can be controlled, it becomes difficult to develop conductivity.
Therefore, in the present invention, a resin having a high volume resistance but a high charge attenuation property (a high charge attenuation property) is selected as the resin with which the conductive agent is coated. Solve a problem.

With respect to the charge decay property, a resin to be coated is formed into a film having a thickness of 3 to 10 μm, and a voltage of 8 kV is applied to a corona discharger arranged at a distance of 1 mm from the film surface to generate corona discharge. Then, the resin surface is charged and the change in the surface potential is measured. In this case, it is important to select, as the resin to be coated, a resin whose maximum surface potential after 0.3 seconds is 300 V or less, preferably 200 V or less. The surface potential is measured, for example, by QEA (Quality Engineering As
sociates, Inc. ) 'S Charge Roller Test System
Measured on CRT2000. FIG. 2 shows a schematic view of the main part. That is, both ends of the shaft 22 of the metallic sample roller 21 having the coating resin disposed on the surface are held by the chucks 23, and the small scorotron discharger 2 is provided.
4 and the surface potentiometer 25 are separated by a predetermined distance, and the measurement unit 20 is installed at a distance of 1 mm from the surface of the subject roller 21.
The measurement roller 20 is moved from one end to the other end of the subject roller 21 at a constant speed while the subject roller 21 is stationary while the subject roller 21 is kept stationary. A method of measuring the surface potential while applying the surface charge is preferably adopted. Since the surface potential depends on temperature and humidity, it is carried out under an atmosphere of normal temperature and normal humidity (20 ° C./50% RH) as standard conditions. The corona charge applied from the scorotron discharger 24 to the subject roller 21 is a negative charge, and the applied voltage is 8 kV. After applying corona discharge to the subject roller 21,
The speed of the measurement unit 20 is adjusted so that the surface potential after 0.3 seconds is measured.

The resin to be coated may be any resin type as long as it satisfies the above-mentioned condition of charge attenuation. Examples of the resin to be coated include urethane resin, acrylic resin, polyester resin, urethane-modified acrylic resin, silicone resin, nylon resin, epoxy resin, styrene resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin. And so on. These resins may be used alone or in combination of two or more, and particularly, urethane resin, fluororesin, silicone resin, acrylic urethane resin are preferable, and further, elastic material described later. It is preferable to include at least one kind of resin that is the same as the above.

The conductive agent to be coated is a so-called conductive substance, and examples thereof include carbon, metal and metal oxide. For example, conductive carbon such as Ketjen black and acetylene black, SAF, ISA
Carbon for rubber such as F, HAF, FEF, GPF, SRF, FT, MT, carbon for ink subjected to oxidation treatment,
Examples thereof include pyrolytic carbon, natural graphite, or a metal or metal oxide such as antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, or germanium.

As a method for coating the above resin, for example, dispa coat, coat mizer, etc. may be mentioned. The disperse coat is provided with a powder supply section provided at the upper part and a multistage disperser capable of supplying liquid in multiple stages from the lateral direction. The above-mentioned powder supply is controlled by controlling the operating conditions of the multistage disperser. Liquid components including coating resin on the surface of the conductive powder supplied from the
The operation of wetting the surface of the conductive powder with a liquid can be carried out in a very short time. The coatmizer supplies the conductive powder to be coated into a jet jet to form a dispersion layer, and then forms a mist-like stream made of fine particles of a droplet containing a coating resin in a position parallel to this. Then, the surface of the conductive powder is coated with a resin by colliding with the conductive powder to be coated.

With respect to the conductive agent coated with the resin, it is preferable that the solvent insolubility rate of the resin component shown by the following relational expression is 50% or more, particularly 70% or more. Solvent insolubility rate (%) = (B / A) × 100 where A: weight of resin component in resin-coated conductive agent before solvent immersion B; resin-coated conductive agent in a good solvent, 25
Weight of resin component after soaking at 24 ° C. for 24 hours When the solvent insolubility ratio is less than 50%, the semiconductive roller of the present invention is mounted on an electrophotographic apparatus such as a printer, a copying machine, or a fax machine, and a developing roller. , Transfer roller,
When used as a semi-conductive roller such as a static elimination roller,
Contamination occurs on the contact portion of the photoconductor such as OPC and causes a problem on the image. As the solvent for measuring the solvent insolubility, methyl ethyl ketone or the like is used for the fluororesin, methanol or the like is used for the polyamide resin, methyl ethyl ketone or toluene is used for the acrylic urethane resin, and melamine resin is used. It is preferable to use acetone, isopanol or the like, and toluene or the like for the silicone resin.

The resin tube layer to which the conductive agent coated with resin is added may be made of any material, and examples thereof include polyamide, polyimide, polycarbonate, polyarylate, polyacetal, polypropylene, polyethylene, polyphenylene ether, Polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyether sulfone,
Polyetherimide, polybutadiene, polyisobutylene, polyvinyl fluoride, polyvinylidene fluoride, acrylic, acrylic acid alkyl ester copolymer, ethylene tetrafluoroethylene copolymer, hexafluoropropylene, perfluoroalkyl vinyl ether copolymer,
One or more of polyester ester copolymers, polyester ether copolymers and polyurethane copolymers can be mixed, and polyamide, polycarbonate, acrylonitrile copolymer and polyvinylidene fluoride are particularly preferable. In addition, if necessary, in addition to the above components, within a range that does not impair the effects of the present invention, for example,
Functional components such as various fillers, coupling agents, antioxidants, lubricants, surface treatment agents, pigments, ultraviolet absorbers, foaming agents, cross-linking agents, compatibilizers and the like may be appropriately blended. Further, the resistance of this resin layer is appropriately selected, but it is 10 ⁶ to 10 ¹³ Ω · c.
It is preferable to adjust to a semiconductive region of m, particularly 10 ⁷ to 10 ¹² Ω · cm. In the semi-conductive region where variations in resistance tend to occur, the variations in resistance can be effectively reduced by adding the conductive agent of the present invention coated with resin in advance. The resin layer may be a single layer or a plurality of layers, and the thickness is appropriately selected, but the range of 5 to 1000 μm is usually used. As a method of forming the resin tube layer, a method of producing the resin tube layer from a molten resin by an extrusion method is exemplified, but the method is not limited to this. Although the resistance of this resin tube layer is appropriately selected, it is 10 ⁴ to 10 ¹⁴
It is preferable to adjust to a semiconductive region of Ω · cm, particularly 10 ⁴ to 10 ⁹ Ω · cm. In the semi-conductive region where variations in resistance tend to occur, the variations in resistance can be effectively reduced by adding the conductive agent of the present invention coated with resin in advance.

The elastic body constituting the elastic body layer provided inside the resin tube layer is not particularly limited as long as it has an elastic function, but examples thereof include urethane rubber, silicone rubber and nitrile. Rubber, ethylene propylene rubber, ethylene propylene diene rubber, styrene butadiene rubber, butadiene rubber, isoprene rubber,
Natural rubber, acrylic rubber, chloroprene rubber, butyl rubber, epichlorohydrin rubber and the like can be mentioned. These may be used alone or in combination of two or more, but urethane rubber, silicone rubber and ethylene propylene rubber are particularly preferable. In addition,
If necessary, a filler such as silica or calcium carbonate, a plasticizer, a crosslinking accelerator, a crosslinking retarder, an antiaging agent, a colorant and the like may be appropriately mixed. The elastic body may be a foam, and in this case, the density is 0.05 to 0.9.
g / cm ³ is suitable. The elastic layer is formed by placing the resin tube on the inner surface of a predetermined molding and injecting the elastic material into it, or by using the resin tube as a mold and injecting the elastic material into it. However, the method is not limited thereto. Moreover, you may form a coating film on the outer surface of the said resin tube layer as needed.

Further, the object of the present invention is to reduce the variation in resistance, and therefore it is desirable that the shape is uniform, and the surface roughness of the roller surface is a ten-point average roughness. It is preferable that Rz is 4 μm or less. The semiconductive roller of the present invention is suitable for use in, for example, a charging roller, a developing roller, a transfer roller, a charge eliminating roller, a toner supply roller and the like used in an electrophotographic apparatus such as a printer, a copying machine and a FAX. Specifically, as shown in FIG. 3, the photosensitive drum (OP
The charging roller 10 which is the semi-conductive roller of the present invention is rotated while being contacted with the C drum) 30, and a DC voltage or a DC voltage is applied between the photosensitive drum 30 and the charging roller 10 by the voltage applying means 40. An example is a charging device of a printer configured to apply a voltage obtained by superimposing an AC voltage on a DC voltage to charge the photosensitive drum 30. The semiconductive roller of the present invention has a small variation in resistance and has stable resistance, and
Since the problem of contamination is unlikely to occur, by mounting this semi-conductive roller, it is possible to stably supply an electrophotographic apparatus capable of obtaining a good image.

<Example> The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following. [Example 1] Nylon 12 (manufactured by Daicel: Daiamide L)
1940), 25 phr of the following resin coating CB type A was added, and the mixture was kneaded with a twin-screw kneader to pelletize it, and then an extruder was used to prepare a conductive resin tube having an outer diameter of 12 mmφ and a thickness of 300 μm. did. next,
After arranging the resin tube and 6 mmφ shaft in the mold, a conductive urethane foam is cast to have an outer diameter of 12
A charging roller of mmφ was manufactured. Resin coating CB
Type A is Denka black carbon (manufactured by Denki Kagaku Kogyo), and acrylic urethane resin EAU65B (manufactured by Asia Industry) / IPDI is used as a resin to be coated in advance.
A system cross-linking agent, Excel Hardener HX (manufactured by Asia Industry Co., Ltd.) was selected. In addition, EAU65B and Excel hardener HX
The ratio of and was adjusted and used so that the solid content weight ratio was 6: 4. The coating method is a spiral flow device (manufactured by Freund), in which Denka black carbon is made to flow, and a solution obtained by mixing the acrylic urethane resin and the cross-linking agent in a MEK solvent is blown in a mist state to form Denka black carbon. Denka black carbon particles were prepared by coating the surface with the resin and heating the resin in advance.

Example 2 In place of the resin coating CB type A used in the above example 1, the resin to be pre-coated in the above resin coating CB type A was replaced by
Urethane resin DP307 (manufactured by Sanyo Chemical Co., Ltd.) / IPDI cross-linking agent Excel Hardener HX (manufactured by Asia Kogyo Co., Ltd.) was used as the resin coating CB type B, and otherwise the charging roller was manufactured in the same manner as in Example 1 above. The ratio of DP307 and Excel hardener HX was adjusted and used so that the solid content weight ratio was 4.5: 1.

Reference Example 1 A charging roller was prepared in the same manner as in Example 1 except that the resin coating CB type C prepared by adjusting the spraying conditions of the coating and increasing the amount of coating resin in Example 1 was used. Was produced. [Reference Example 2] Resin coating C used in Example 1 above
Instead of B type A, resin coating CB type A in which the resin to be pre-coated in the resin coating CB type A is only acrylic urethane resin EAU65B (manufactured by Asia Kogyo Co., Ltd.) is used, and otherwise the same as in Example 1 above. Then, a charging roller was produced.

[Comparative Example 1] Instead of the resin coating CB type A used in the above Example 1, the resin to be pre-coated in the above resin coating CB type A was replaced by
Epoxy resin AER6071 (made by Asahi Kasei) / hardening agent Sumicure M (made by Sumitomo Chemical), resin coating CB
A charging roller was manufactured in the same manner as in Example 1 except that type E was used. In addition, AER6071
And the ratio of Sumikyure M were adjusted to 7 to 2 before use. [Comparative Example 2] A charging roller was produced in the same manner as in Example 1 except that Ketjen black carbon was used as it was in Example 1 without resin coating.

The characteristics of the charging rollers of the examples, reference examples and comparative examples thus manufactured were measured, and the charging roller was mounted on a printer to perform an image output test and a contamination test. The results are shown in the table of FIG. The characteristics were measured and the test results were measured according to the following criteria. (1) Charge potential of resin to be coated in advance A metal roller having the same diameter as the charging roller was coated with only the resin to be coated so as to have a thickness of 5 μm to prepare a subject roller. A CRT2000 device manufactured by QEA is used for this sample roller, a voltage of 8 kV is applied to a scorotron discharger arranged at a distance of 1 mm from the sample roller to generate corona discharge, and the surface of the sample roller is charged. The surface potential after 0.3 seconds was measured. The measurement was performed in an atmosphere of normal temperature and normal humidity (20 ° C./50% RH). (2) Amount of resin coated TGA of resin coated beforehand
Using the apparatus, the temperature rising rate is 20 ° C./min. The temperature was raised to 800 ° C. and the amount of coated resin was calculated from the change in weight. (3) Solvent Insolubility The carbon previously resin-coated was immersed in a MEK solution at 25 ° C. for 24 hours, dried at 100 ° C. for 5 hours, and the weight after drying was measured. The solvent insolubility rate was calculated according to the following formula from the amount of resin before immersion from TGA and the weight change before and after immersion. Solvent insolubility rate (%) = (B / A) × 100 Here, A represents the weight of the resin component in the resin-coated conductive agent before the solvent immersion, and B represents the resin-coated conductive agent in a good solvent, 25 The weight of the resin component after soaking at 24 ° C. for 24 hours is shown. (4) Roller Surface Roughness The surface of the charging roller thus produced was measured with a surface roughness measuring device (Tokyo Seimitsu: Surfcom 120A) to obtain a ten-point average roughness Rz.
Was measured. (5) Roller resistance and variation in resistance The charging roller and the metal drum thus produced were pressed against each other with a load of 500 g and rotated, and then 500 V was applied between the roller and the metal drum to measure the resistance of the roller. The roller resistance was an average value, and the variation of the roller resistance was the difference between the maximum resistance and the minimum resistance within one rotation of the roller. (6) Image Display Test and Contamination Test The charging roller thus prepared was mounted on a commercially available LBP, an image was displayed (white), and the image state was visually judged. The charging roller and the OPC drum thus produced were pressed against each other with a load of 1000 kg and left in an environment of 40 ° C. and 85% RH for 10 days. Then, the OPC drum was mounted on a printer device and 10 images were printed. The state of contamination was judged by the degree of image failure when printing 10 sheets. At this time, if a line-shaped defect occurs at the image position corresponding to the above-mentioned press contact portion,
It was judged to be G.

As is clear from the characteristic measurement results and the test results shown in FIG. 4, the charging rollers of Examples 1 and 2 of the present invention have a small variation in resistance and a stable resistance. Even when mounted, a good image could be obtained and no pollution problem occurred. On the other hand, in Reference Example 1 in which the coating amount of Example 1 was increased, the resistance and the variation in the resistance were increased, the surface roughness was deteriorated, and the image had a slightly sandy pattern. On the other hand, in Reference Example 2 in which the cross-linking agent of Example 1 was omitted, the resistance and the variation in the resistance increased, and further, a pollution problem occurred, resulting in NG. Further, in Comparative Example 1 in which a resin having a slow charge decay was used as the coating resin, the variation in resistance was increased, the surface roughness was significantly deteriorated, and the charging potential was also significantly increased. In addition, a sandy pattern was seen in the image. In Comparative Example 2 in which carbon was used as it was without resin coating, the resistance value could be adjusted,
The dispersibility was poor, the variation in resistance was large, and a sandy pattern was seen in the image.

[0021]

As described above, according to the present invention,
As a conductive agent to be added to the resin tube formed on the roller surface, a conductive agent coated beforehand with a resin having a high charge attenuation property is used, so that there is little variation in resistance and the semiconductive roller has stable resistance. Can be obtained. Further, by using the semiconductive roller as a charging roller, a developing roller, a transfer roller, a charge eliminating roller, a toner supply roller, etc. used in an electrophotographic apparatus such as a printer, a copying machine, and a FAX, a good image can be stabilized. It is possible to provide an electrophotographic apparatus that can be obtained as a result.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a semiconductive roller according to the present invention.

FIG. 2 is a diagram showing a method of measuring a surface potential.

FIG. 3 is a schematic configuration diagram of a charging device of a printer according to the present invention.

FIG. 4 is a diagram showing a result of trial production of a semiconductive roller according to the present invention.

[Explanation of symbols]

10 charging roller, 11 shaft, 12 elastic layer,
13 semi-conductive resin tube layer, 20 measuring unit,
21 sample roller, 22 shaft, 23 chuck, 24 scorotron discharger, 25 surface electrometer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/16 103 G03G 15/16 103 21/06 21/00 340 (72) Inventor Sou Kitano Kodaira, Tokyo City Ogawa Higashimachi 3-5-5 F Term (Reference) 2H035 AA15 2H071 BA43 DA06 DA08 DA09 2H077 AC04 AD06 FA01 FA13 FA25 2H200 GA41 GB01 HA01 HA28 HB12 HB45 HB46 HB47 JA01 JA25 JA26 JA27 MA02 MA12 MA14 A02 A06 A51 A14 A02 BA41 EA02 FA18 GA02 GA57 GA58 GA60 HA04 HA20 HA54

Claims (7)

[Claims] 1. A semi-conductive roller having a resistance adjusting layer made of a resin tube having a conductive agent added to the surface thereof, wherein the conductive agent is previously coated with a resin having a high charge attenuation property. . 2. When the resin is charged on the surface of the resin by applying a voltage of 8 kV to a corona discharger arranged at a distance of 1 mm from the surface of the resin to generate corona discharge, 0.3 Maximum surface potential after 300 seconds is 300
The semiconductive roller according to claim 1, wherein the resin is V or less. 3. The semiconductive roller according to claim 1, wherein the coating amount of the resin is 0.01 to 50 wt% with respect to the conductive agent. 4. The semiconductive roller according to claim 1, wherein the conductive agent is at least one of carbon, metal powder, metal oxide or a mixture thereof. . 5. The conductive agent coated with the resin according to any one of claims 1 to 4, wherein the solvent insolubility of the resin component represented by the following relational expression is 50% or more. The semiconductive roller described. Solvent insolubility rate (%) = (B / A) × 100 where A: weight of resin component in resin-coated conductive agent before solvent immersion B; resin-coated conductive agent in a good solvent, 25
Weight of resin component after immersion for 24 hours at ℃ 6. The semiconductive roller according to claim 1, wherein the surface roughness of the roller is 4 μm or less. 7. An electrophotographic apparatus equipped with the semiconductive roller according to any one of claims 1 to 6.