JP2002072813A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic device which can precisely detect the joint part of a seam belt photoreceptor without requiring a detection hole or a reflection mark and position an image formation area. SOLUTION: The electrophotographic device has at least an electrostatic charging means, the seam belt photoreceptor, and a detecting means which detects the surface potential of the photoreceptor; and the photoreceptor is formed in an endless belt shape by joining both the ends of a conductive sheet type base provided with a photosensitive layer, has at least one or more image areas in one round of the belt, and is provided with a resin layer 24 on the surface of the joint part. This electrophotographic device includes at least once a process wherein the voltage applied to the electrostatic charging means when an image area of the photoreceptor passes by the electrostatic charging means becomes equal to the voltage applied to the electrostatic charging means when the joint part of the photoreceptor passes by the electrostatic charging means and the joint part is detected by the potential detecting means to control the positioning of the image formation area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus which uses a seam belt photoreceptor and controls the position of an image forming area by detecting a belt joint.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, the Carlson process and various deformation processes thereof have been known, and are widely used in copiers and printers. Electrophotographic photosensitive members used in such an electrophotographic method include those using an organic photosensitive material and those using an inorganic photosensitive material.

On the other hand, electrophotographic photoreceptors include a drum-shaped photoreceptor having a photosensitive layer formed on a metallic hollow drum, a seamless belt photoreceptor, and a seam belt photoreceptor.
Since there are various advantages in terms of cost, design form, etc., at present, the shape of the electrophotographic apparatus is properly used according to the characteristics of the electrophotographic apparatus to be developed.

[0004] The seam belt photoreceptor uses, for example, an aluminum-evaporated polyethylene terephthalate (PET) sheet as a support, and continuously applies a photosensitive layer on the support to form a photoreceptor-coated sheet. The sheet-shaped photosensitive member is cut and punched, and both ends of the obtained sheet-shaped photosensitive member are fused to each other by a method such as ultrasonic bonding to form a belt-shaped photosensitive member.

The seam belt photoreceptor has a seam portion (fusion bonding portion) as described above, and the seam portion does not function as a photoreceptor. Therefore, an image forming area must be formed in a region other than the seam portion. For use in an electrophotographic apparatus, it is necessary to use a belt having a circumference equal to or longer than the output paper length. That is, for example, in the case of an A3 size electrophotographic apparatus, the circumference of the seam belt photoreceptor needs to be at least 42 cm, which is a large object corresponding to a large-diameter drum having a diameter of 130 mm or more in terms of a drum diameter. However, a general black-and-white electrophotographic apparatus is not used much because it is a great design constraint.

However, in recent years, colorization of electrophotographic apparatuses has been advanced, and high image quality, low cost, high speed, and the like have been required. In such a flow, the seam belt photoreceptor can be used in a desired form because of (1) the belt outer shape is large, but its flexibility, and (2) the application of the photosensitive layer is performed by nozzle coating and mass production is possible. In addition to being possible,
Low loss of coating liquid and low cost; (3)
Since there are advantages such as being able to be designed in a form that is convenient for opposing the four color developing machines, they are being reviewed for use in color electrophotographic apparatuses.

However, as described above, the seam belt photoreceptor cannot control the belt drive so that the seam portion cannot be used for image formation and the seam portion is outside the image forming area. Therefore, conventionally, a seam portion has been detected by attaching a detection sensor to a belt end outside the image forming area. As a detection method, a method of making a detection hole, detecting a change in the pattern of light when light passes through the hole with a transmission type sensor or a reflection type sensor,
There is a method of measuring a change in reflectance by attaching a reflection mark.However, in the method of forming a detection hole, there is a problem that the photosensitive layer peels off from the detection hole portion during image formation, and furthermore, the detection hole There is also a problem that processing is difficult due to the required precision, and that the photosensitive layer is scratched by a punched piece formed in a hole at the time of processing. Further, in the method of detecting the reflectance of the reflection mark, there is a problem that the reflection mark portion is stained in the image forming apparatus during a long-term use, the reflectance changes, and a malfunction occurs. .

In a color electrophotographic apparatus, fluctuations in each electrophotographic process tend to appear as an image defect. For example, in order to suppress the influence on the image due to fluctuations in the potential of the photosensitive member, a potential detector is used between exposure and development. In some cases, a method of optimizing charging, exposure, and development conditions according to potential fluctuations is used.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is possible to accurately detect a joint portion of a seam belt photoconductor without detecting holes or reflection marks. It is another object of the present invention to provide an electrophotographic apparatus capable of positioning an image forming area.

[0010]

The above object of the present invention is attained by the following 1) to 4). 1) In an electrophotographic apparatus having at least a charging unit, a seam belt photoreceptor, and a detection unit for detecting a surface potential of the photoreceptor, the photoreceptor is formed by joining both ends of a conductive sheet-like support provided with a photosensitive layer. Endless belt-shaped, and has at least one or more image areas between one belt circumference, a resin layer is provided on the surface of the joint portion, the photosensitive member At least one process in which the voltage applied to the charging means when the image area passes through the charging means is equal to the voltage applied to the charging means when the junction of the photoconductor passes through the charging means. An electrophotographic apparatus, wherein positioning control of an image forming area is performed by detecting the joint by the potential detecting means. 2) The electrophotographic apparatus according to 1), wherein the potential detecting unit is located between an exposing unit that forms a latent image on the seam belt photoconductor and a developing unit that develops the latent image. 3) The electrophotographic apparatus according to 1) or 2), wherein a thickness of the resin layer covering the joint is 3 to 20 μm. 4) The electrophotographic apparatus according to 3), wherein the width of the resin layer covering the joint is 3 mm or more.

Hereinafter, the present invention will be described in detail. FIG. 1 is a sectional view of a general seam belt photoconductor. This seam belt photoreceptor is manufactured as follows. First,
An aluminum electrode 18 is deposited to a thickness of 0.1 μm on a PET substrate 19 having a thickness of 100 μm to form a support for a photoreceptor, and a subbing layer 17 of 1 μm, a charge generation layer 16 of 0.2 μm, and a 20 μm The charge transport layer 15 is formed by nozzle coating to produce a sheet-shaped photoconductor. Next, this sheet-shaped photoreceptor is cut and punched into a desired size and shape by a mold (the shape is generally a rectangular sheet or a parallelogram sheet). ~
It is completed by overlapping about 1 mm and fusing and joining the overlapped portion with an ultrasonic horn. Further, a resin layer is provided at the joint portion in order to prevent occurrence of abnormal discharge by the contact charger.

FIG. 2 shows a conventional seam belt photosensitive member having a detection mark. Detection hole 20 in the figure
Is usually formed outside the image forming area at the end of the seam belt photoreceptor at the time of punching by a mold, but may be formed before the formation of the photosensitive layer or after the superposition. The shape of the hole may be any shape such as a circle, an ellipse, a square, and a rectangle, and the size is not particularly limited as long as it can be detected. For example, a circle having a diameter of about 1 to 10 mm is preferable. Also,
There is also known one provided with a metal evaporated film or the like having a high reflectance at a position corresponding to the detection hole 20 in FIG.

Referring now to FIG. 3, a detection hole according to the present invention,
An example of a seam belt photoreceptor that does not have a reflection mark or the like and has only a joint resin layer 24 is shown. The joint resin layer is one of the essential components for the operation of the electrophotographic apparatus of the present invention.

As the binder resin used in the resin layer, polycarbonate (bisphenol A type,
Bisphenol Z type, etc.), polyester, methacrylic resin, acrylic resin, polyethylene, polyvinyl chloride, polyvinyl acetate, polystyrene, phenolic resin,
Examples include epoxy resin, polyurethane, polyvinylidene chloride, alkyd resin, silicon resin, polyvinyl carbazole, polyvinyl butyral, polyvinyl formal, polyacrylate, polyacrylamide, and phenoxy resin. These binder resins can be used alone or as a mixture of two or more.

In the resin layer, in addition to the binder resin described above, for example, resin particles for a lubricant such as polytetrafluoroethylene (PTFE) may be contained to lower the surface friction coefficient, and to contain an inorganic pigment (such as titanium oxide). It is also possible to reduce the amount of abrasion and improve the durability by dispersing it.

The thickness of the resin layer is preferably 3 to 20 μm.
When the film thickness is less than 3 μm, the durability becomes insufficient, and the resin layer is scraped by a rubbing object, for example, a blade, a brush, a sealing material, a roller member, or the like, and the resin layer is easily worn or peeled. . Further, in order to increase the potential difference between the resin layer and the photosensitive layer in the image area and to improve the detection accuracy of the joint, a film thickness of 3 μm or more is required. If the film thickness exceeds 20 μm, the thickness of all layers at the boundary between the resin layer end portion and the resin layer-free portion at the edge of the resin layer becomes significantly different from the boundary, and the photoconductor is bent. In the case where the photosensitive layer is used, cracks in the photosensitive layer occur at the boundary portion, and in some cases, peeling of the photosensitive layer is induced, which is not preferable. In the case where the resin layer of the joining portion is composed of two layers separated in function, the combined thickness of the two layers is preferably in the range of 3 to 20 μm.

The width of the resin layer is preferably at least 3 mm. By setting the distance to 3 mm or more, the accuracy of temporal detection of the junction potential by the potential detection means can be further increased, and erroneous detection can be prevented. Although there is no particular upper limit on the width, it is preferable that the width is as narrow as possible because the wider the width, the smaller the image forming area. As a method of providing a resin layer at the joint, for example, the above-mentioned polycarbonate resin or the like is dissolved in an appropriate solvent, and this resin solution is applied onto the joint of the seam belt photoreceptor by a method such as nozzle or brush painting. do it.

In the photoreceptor used in the electrophotographic apparatus of the present invention, conventionally known techniques can be used for the structure of the support, the photosensitive layer, and the like other than the bonding resin layer. As the support, those exhibiting a conductivity of 1 × 10 ³ Ωcm or less, for example, a metal oxide such as tin oxide or indium oxide formed on a film by vapor deposition or sputtering, or polyethylene vapor-deposited with aluminum A terephthalate sheet and the like can be mentioned.

The photosensitive layer may be a single-layer type photosensitive layer containing a charge generating agent and one or more charge transporting agents in the same layer, or a charge generating layer containing a charge generating material and a charge containing a charge transporting material. Any of a stacked photosensitive layer in which a transport layer is stacked may be used. Further, in the electrophotographic photoreceptor of the present invention,
In order to improve environmental resistance, an antioxidant can be added, particularly for the purpose of preventing a decrease in sensitivity and an increase in residual potential. The antioxidant may be added to any layer as long as it is a layer containing an organic substance, but a particularly good effect can be obtained by adding it to a layer containing a charge transporting substance.

FIG. 4 shows an example of a process form and an arrangement of the electrophotographic apparatus according to the present invention. In the apparatus shown in FIG. 4, the potential detector 14 is located between the exposure unit 3 for forming a latent image on the seam belt photoreceptor and the developing unit 4 for developing the latent image. The latent image formation potential and the junction can be detected, but if it is not necessary to detect the fluctuation of the photoconductor potential, the photoconductor can be installed at any position in the electrophotographic process. If only detection and charging control are performed, a potential detecting means can be provided between charging and exposure. In any case, the present invention is not limited to the form and arrangement of each process shown in FIG.

In general, in a photosensitive layer in an image area, a charging means is designed so that a charging potential before a latent image is formed does not fluctuate much, and a charging correction mechanism is provided in some cases (a charging potential of the photosensitive layer is usually 500 V to 500 V). 800V). Since the joining resin layer has very low dark attenuation and hardly any light attenuation as compared with the photosensitive layer, when charged under the same conditions, the potential becomes significantly higher than the charged potential of the photosensitive layer (1200 V in the embodiment of the present invention). that's all). Therefore, when the electrophotographic apparatus is stopped and the photosensitive layer joint is at any position in the process, the voltage applied to the charging means when the image area of the seam belt photoreceptor passes through the charging means, At least once, the process of equalizing the voltage applied to the charging means when the joining portion of the belt photoreceptor passes through the charging means (that is, applying the voltage to the charger and rotating the photoreceptor at least one rotation) Then, the junction can be detected from the potential difference by the potential detector.

In the image forming method of the present invention, the step of forming an electrostatic charge image on the photoreceptor can employ a known exposure system for forming an electrostatic latent image, and forms a visible image by development. In the step of performing the development, a known development process for visualizing a latent image can be adopted. Further, a transfer step of transferring the developed visible image to a print medium, a charge removal step of initializing an electrostatic latent image as needed, and a cleaning step of removing deposits on the photoconductor surface may be provided. For each of these steps, various known techniques recognized as a general electrophotographic process can be employed.

[0023]

The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

Example 1 28 parts by weight of titanium oxide (CR-EL, manufactured by Ishihara Sangyo), 12 parts by weight of alcohol-soluble polyamide (CM-8000, manufactured by Toray Industries, Inc.), methanol / n-butanol = 8/2
A mixture consisting of 200 parts by weight of a mixed solvent (volume ratio) was dispersed and mixed in a ball mill for 72 hours to prepare a coating liquid for an undercoat layer. This coating solution was applied on an aluminum-deposited PET sheet having a thickness of 75 μm, a width of 500 mm, and a length of 500 mm, and dried at 130 ° C. for 20 minutes to form a 1 μm-thick undercoat layer. Next, 10 parts by weight of a trisazo pigment having the following structural formula [Formula 1] was added to a resin solution obtained by dissolving 4 parts by weight of a polyvinyl butyral resin (BM-2: manufactured by Sekisui Chemical Co., Ltd.) in 150 parts by weight of cyclohexanone. The mixture was dispersed and mixed in a ball mill for 72 hours. Thereafter, 210 parts by weight of cyclohexanone was further added, and the mixture was dispersed and mixed for 3 hours.
A coating solution for a charge generation layer was prepared.

[0025]

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This coating solution is applied on the undercoat layer,
After drying at 30 ° C. for 10 minutes, a charge generation layer having a thickness of 0.2 μm was formed. Next, 7 parts by weight of a compound having the following structural formula [Formula 2] and a polycarbonate resin (Iupilon Z20)
0: 10 parts by weight of Mitsubishi Gas Chemical Co., Ltd.) and 0.002 parts by weight of silicone oil (KF-50: Shin-Etsu Chemical Co., Ltd.) were dissolved in 100 parts by weight of tetrahydrofuran to prepare a coating solution for a charge transport layer.

[0027]

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The above coating solution is applied on the charge generation layer,
The resultant was dried at 30 ° C. for 20 minutes to form a charge transport layer having an average film thickness of 20 μm, thereby obtaining an electrophotographic photosensitive member sheet. After cutting the electrophotographic photoreceptor sheet, the width was 340 mm and the length was 42.
A 1 mm rectangle was punched out, and the short sides of the rectangle were overlapped by about 1 mm so that the photosensitive layer was on the surface side, and the bonding speed was 20 mm.
mm / s, horn gap 80μm, horn load 100
Ultrasonic fusion was performed under the condition of 0 g to produce a seam belt photoreceptor having a circumference of 420 mm and a length (length in the width direction) of 340 mm.

A polyurethane resin [N-2302] was placed on the joint of the seam belt photoreceptor obtained as described above.
(Nippon Polyurethane Industry Co., Ltd.)] A seam belt photoreceptor having the structure of the present invention was prepared by applying a resin solution obtained by dissolving 16 parts by weight in 84 parts of tetrahydrofuran using a nozzle.
The thickness of the joint resin layer after drying is 10 μm, and the coating width is 5 m.
m. Obtained seam belt photoreceptor and exposure
Using an image forming apparatus (SP-10PS modified by Ricoh Co., Ltd.) modified so that a potential sensor can be attached during development, continuous output of 50,000 halftone images was performed.

Comparative Example 1 When punching a photosensitive sheet, a circular hole having a diameter of 3 mm was simultaneously punched at a position corresponding to the belt end outside the image forming area, and no resin layer was provided at the joint. A seam belt photoreceptor was manufactured in the same manner as in Example 1 except for the above. Using the obtained seam belt photoreceptor and an image forming apparatus (SP-10PS remodeled by Ricoh Co., Ltd.) modified so that the transmission type sensor for seam detection can be mounted, 50,000 continuous halftone images Output was implemented.

Comparative Example 2 A seam was formed in the same manner as in Example 1 except that a circular reflective mark having a diameter of 3 mm was attached to the end of the photoreceptor belt outside the image forming area, and no resin layer was provided at the joint. Create a belt photoreceptor, obtained seam belt photoreceptor,
Image forming apparatus (SP-10 manufactured by Ricoh Co., Ltd.) which is improved so that a reflection type sensor for seam detection can be mounted.
50,000 of a halftone image using a PS modified machine)
Continuous output was performed.

By the continuous output (repeated image output) of the 50,000 sheets, a detecting portion (a detecting hole or a resin layer of a bonding portion) is obtained.
The number of the photosensitive layers peeled off from the sample was confirmed, and whether the detection of the joint functioned well was evaluated. Table 1 shows Example 1
Also, the device configurations and evaluation results of Comparative Examples 1 and 2 are shown. Table 1
As can be seen from the graph, in the electrophotographic apparatus of Example 1, no peeling of the resin layer and the photosensitive layer from the bonding portion occurred, no false detection of the bonding portion occurred, and high reliability was maintained. It was confirmed that the device was an excellent electrophotographic device. On the other hand, in Comparative Example 1, the photosensitive layer peeled from the detection hole occurred on 32500 consecutive images, and in Comparative Example 2, although the photosensitive layer did not peel, the reflectance of the reflective mark was reduced due to dirt. Erroneous detection of the joints occurred frequently with more than one sheet.

Example 2 In the same manner as in Example 1, a seam belt photoreceptor was prepared, and the obtained seam belt photoreceptor was improved so that a potential sensor could be mounted between exposure and development, and the charging means was contacted. Image forming apparatus changed to charging roller (SP manufactured by Ricoh Co., Ltd.)
-10PS remodeling machine), 50
A continuous output of 000 sheets was performed.

Comparative Example 3 A seam belt photoreceptor was produced in the same manner as in Comparative Example 1, and was evaluated using the same image forming apparatus as in Example 2.

Comparative Example 4 A seam belt photoreceptor was produced in the same manner as in Comparative Example 2, and was evaluated using the same image forming apparatus as in Example 2. Table 1 summarizes the device configurations and evaluation results of Example 2 and Comparative Examples 3 and 4. As shown in the table, from the evaluation results, in the case of Example 2, even if a contact charging roller was used as a charging unit,
No peeling of the resin layer and the photosensitive layer from the joined portion occurred, and no erroneous detection of the joined portion occurred, confirming that the electrophotographic apparatus was an excellent electrophotographic apparatus capable of maintaining high reliability. On the other hand, in Comparative Example 3, peeling of the photosensitive layer from the detection hole occurred on 29850 continuous images, and in Comparative Example 4, although the photosensitive layer did not peel off, the reflectance of the reflective mark decreased due to dirt. Therefore, erroneous detection of the joint portion occurred frequently when the number of sheets was 3,050 or more.

Examples 3 to 7 A seam belt photoreceptor was produced in the same manner as in Example 1 except that the thickness of the resin layer of the bonding portion was changed to the thickness shown in Table 1, and image formation was conducted in the same manner as in Example 1. The evaluation was performed using an apparatus. The results are as shown in Table 1, and the film thickness was 2 μm or 25 μm.
In the case of (3), the effect was slightly inferior to the example of the case of 3 μm to 20 μ, but it was found that it was superior to the comparative example.

Examples 8 to 11 A seam belt photoreceptor was prepared in the same manner as in Example 1 except that the width of the resin layer in the joint portion was changed to the width shown in Table 1.
The evaluation was performed using the same image forming apparatus as that described above. The results, as shown in Table 1, show that when the width is 2 mm, the effect is slightly inferior to the example in which the width is 3 mm or more, but it is superior to the comparative example.

Examples 12 to 15 A seam belt photoreceptor was produced in the same manner as in Example 1 except that the resin for the joint resin layer was changed to the resin shown in Table 1, and an image forming apparatus similar to that in Example 1 was used. The evaluation was carried out. As shown in Table 1, it was found that good results were obtained even when the type of resin was changed.

[0039]

[Table 1]

In summary, by providing the resin layer at the joint of the seam belt photoreceptor, the durability of the detecting portion against peeling and the reliability of detecting the joined portion are improved.
It can be seen that the effect is somewhat insufficient in some cases. However, if the thickness and width of the joint resin layer are appropriately selected,
It can be seen that no exfoliation of the resin layer and the photosensitive layer from the detection bonding portion occurs, no erroneous detection of the bonding portion occurs, and an excellent electrophotographic apparatus that can maintain high reliability can be obtained.

[0041]

According to the present invention, since there is no detection hole or reflection mark at the end of the photoreceptor for detecting a joint portion, it is not necessary to form a hole in the belt or attach a reflection mark. Thus, an electrophotographic apparatus can be obtained which does not cause erroneous detection of a joint due to occurrence of film peeling from a portion or a change in reflectance of a reflection mark. Also, since a resin layer is provided at the joint of the photoconductor,
Prevent the occurrence of abnormal discharge from the charging means to the joint, and
An electrophotographic apparatus capable of preventing the photosensitive layer from peeling off from the joint and forming a good image over a long period of time can be obtained. Further, a compact electrophotographic apparatus capable of detecting the latent image forming potential of the photoreceptor and the bonding portion with only one potential detecting means and optimizing the latent image forming conditions and controlling the positioning of the image forming area can be obtained. In addition, by setting the thickness of the resin layer of the joint portion of the seam belt photoreceptor to 3 to 20 μm, an electrophotographic apparatus that is durable, does not cause erroneous detection of the joint portion, and can form a good image for a long time can be obtained. Can be Further, by setting the width of the resin layer to 3 mm or more, the accuracy of the temporal detection of the junction potential in the detection means is further improved, and an electrophotographic apparatus capable of forming a good image without erroneous detection of the junction is obtained. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a general seam belt photoconductor.

FIG. 2 is a view showing a conventional seam belt photoconductor having a detection mark.

FIG. 3 is a view showing an example of a seam belt photoreceptor according to the present invention, which does not have a detection hole, a reflection mark, or the like, and has only a joint resin layer.

FIG. 4 is a diagram showing an example of a process form and an arrangement of the electrophotographic apparatus according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Seam belt photoreceptor 2 Charger 3 Exposure unit 4 Developing unit 5 Feeding unit 6 Registration roller 7 Transfer unit 8 Fixing unit 9 Cleaning 10 Static elimination unit 11 Driving roller 12 Follower roller 13 Tension roller 14 Potential detector 15 Charge transport layer 16 Charge generation layer 17 Undercoat layer 18 Al electrode 19 PET base 20 Detection hole 21 Joint 22 Photosensitive layer 23 Grounding conductive layer 24 Joint resin layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshi Taniguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Toshiyuki Kabata 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Naohiro Toda 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Katsuichi Ota 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. F-term (reference) 2H027 DA02 DE10 ED03 EE02 2H035 CA02 CB06 CG01

Claims (4)

[Claims] 1. An electrophotographic apparatus having at least a charging unit, a seam belt photoreceptor, and a detection unit for detecting a surface potential of the photoreceptor, wherein the photoreceptor is provided at both ends of a conductive sheet-like support provided with a photosensitive layer. Are formed in the form of an endless belt by joining, and at least one or more image areas between the circumference of the belt, and a resin layer is provided on the surface of the joining portion, At least a process in which the voltage applied to the charging unit when the image area of the photoconductor passes through the charging unit and the voltage applied to the charging unit when the bonding portion of the photoconductor passes through the charging unit is performed. An electrophotographic apparatus, wherein the control is performed once, and the positioning of the image forming area is controlled by detecting the joint by the potential detecting means. 2. The electrophotographic apparatus according to claim 1, wherein said potential detecting means is located between an exposing means for forming a latent image on the seam belt photoreceptor and a developing means for developing the latent image. 3. The resin layer covering the joining portion has a thickness of 3 to 2.
3. The electrophotographic apparatus according to claim 1, wherein the thickness is 0 μm. 4. The electrophotographic apparatus according to claim 3, wherein the width of the resin layer covering the joint is 3 mm or more.