JP2006047716A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing charging sound occurring when an charging member superposes an AC voltage upon a DC voltage to electrify an electrophotographic photoreceptor in a non-contact state up to a practically non-problem level, and to provide a process cartridge which can be attached to and detached from the image forming apparatus. <P>SOLUTION: In the electrophotographic image forming apparatus, the charging member used in the charging means is composed of a shaft part and a main body part with which the shaft part is covered, the main body part is formed of resin including conductive material and the charging member is arranged opposite to the electrophotographic photoreceptor in the non-contact state. Further, the charging member superposes an alternate voltage upon a direct voltage and the application charging of an electrophotographic photoreceptor is performed in the non-contact state and there is the part in which the thickness d (mm) of a conductive substrate of the electrophotographic photoreceptor satisfies the relation of d≥0.9. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a laser printer, and a facsimile, and more particularly to a charging unit for an electrophotographic photosensitive member disposed in the image forming apparatus and a process cartridge for the image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus that forms an image using indirect electrophotography, such as a facsimile, a laser beam printer, a copying machine, etc., an electrophotographic photosensitive member (hereinafter simply referred to as a “photosensitive member”) is charged. Means such as exposure, development, transfer, separation, cleaning, and charge removal are disposed, and image formation is performed on the photosensitive member in such a manner that each means operates in order.

  First, the photosensitive member is charged (charged) at −400 to −800 volts by charging means. There are two methods for applying a voltage to the charging means: a case where a DC voltage is applied and a case where a DC voltage superimposed with an AC voltage is applied. Normally, it is possible to create an image with no problem in practice using only a DC voltage, but by superimposing an AC voltage on the DC voltage, it becomes less susceptible to environmental conditions, and charging that occurs when using the contact charging method. It is possible to reduce potential unevenness caused by unevenness of the member, the photosensitive member, minute unevenness of the member, and the like.

On the other hand, a charging method that is generally employed at present is that a high voltage of about −4000 to −6000 V is applied to a metal wire such as a tungsten wire or a nickel wire having a diameter of 40 to 80 μm that is built in a shield case. A corona charging method for charging a photosensitive member. A DC voltage of -1200 to -2000 V or a DC voltage of -500 to -900 V is applied to a charging member such as a roller or brush having a resistance of about 10 ² to 10 ⁸ Ω · cm. In addition, a contact charging method in which the photosensitive member is charged while applying an alternating voltage of 1000 to 2500 V / 500 to 4500 Hz, or the charging member and the photosensitive member are arranged close to each other at a distance of about 30 to 250 μm. There is a non-contact charging method in which the voltage is applied to charge the photoreceptor.

  Since a high voltage is applied in the corona charging method, ozone with a high concentration of around 10 ppm is generated. Therefore, there is an environmental problem due to ozone odor. Therefore, in recent years, a contact charging method capable of charging with a low applied voltage has been performed, and the generation of ozone is extremely low at 0.1 ppm or less. Therefore, in recent years, there are an increasing number of image forming apparatuses that use a contact charging method that generates a small amount of ozone and applies an alternating voltage superimposed DC voltage to the charging member.

  However, when applied to a charging means in which an AC voltage is superimposed on a DC voltage, there is a noise problem that an irritating charging sound is generated during charging, in addition to the generation of ozone and nitrogen oxides that cause image quality degradation. There is. This charging sound is hardly a problem with a DC voltage, and is a phenomenon peculiar to alternating current because it is called an oscillating current. The larger the amplitude, the more easily the material that the electroconductive photoconductive support material is likely to resonate with. , Charging noise increases. Therefore, it is desirable to set the conditions as low as possible. However, if the charging stability is increased, the conditions become inevitably severe and the charging noise increases, so it is essential to take measures.

  As means for improving this phenomenon, there are methods such as increasing the thickness of the electrophotographic photosensitive member conductive support, inserting a damping material (filler) inside the drum-shaped photosensitive member, and improving the charging member side. Proposed. These methods are aimed at suppressing the resonance of the photosensitive member and shifting the resonance frequency to a direction where it is difficult to be felt by the ear, and the following examples have been proposed.

As a method for improving the generation of a charging sound (high frequency sound) during charging by inserting a damping material inside the drum-shaped photoconductor, a buffer material is press-fitted inside the photosensitive drum (see, for example, Patent Document 1). ), Filling the photoconductor with a viscoelastic material (see, for example, Patent Document 2), and inserting a rigid body with a density of 2.0 g / cm ³ or more into the photoconductor (for example, see Patent Document 3). ) Inserting a member composed of two or more elastic bodies (O-rings) and a cylindrical member (plastic having a specific gravity of 1.5 or more (polybutylene terephthalate resin containing 20% or more glass fibers) into the photoreceptor. (For example, refer to Patent Document 4), it has been proposed to insert a resin cylindrical member with a built-in metal spring and fix it to the wall of the photosensitive body with a pressing force (for example, refer to Patent Document 5). .

Further, as a method for increasing the thickness of the photoreceptor substrate to enhance the vibration damping effect, the vibration damping effect is obtained by setting the substrate of the photoreceptor body to have an inlay and the thickness other than the inlay to be 1.9 mm or more. (For example, refer to Patent Document 6), it is possible to obtain a damping effect by setting the deposition density of the photosensitive member to 0.6 g / cm ³ or more and 2.0 g / cm ³ or less (for example, refer to Patent Document 7). )Proposed.

Furthermore, as a method for achieving suppression of charging noise from the charging member, a coating layer is provided on the surface of the hollow charging member (roller), an elastic body is inserted into the charging member, and the cored bar is supported via the elastic body. It has been proposed to improve the charging sound by using a structure (see, for example, Patent Document 8). The countermeasure method for charging sound varies depending on whether the vibration frequency of the photosensitive member is shifted to an audible range that does not cause an irritating effect or whether the vibration itself is suppressed.
Japanese Unexamined Patent Publication No. 63-60481 JP-A-3-105348 JP-A-5-197321 JP 11-184308 A JP 2000-321929 A JP 2000-19761 A JP 2000-155500 A Japanese Patent Laid-Open No. 9-230671

  Each of the above methods has a greater or lesser effect. However, even if the contact charging method is improved, the non-contact charging method in which the charging member is disposed in close proximity to the photosensitive member may not be effective. For example, it may be difficult to obtain a sufficient effect only by a method of suppressing charging noise with a charging member or by simply increasing the thickness of a conductive support of an electrophotographic photosensitive member. The method of increasing the weight and suppressing the sound (squeal) by inserting a filler inside the support is easy to obtain, but if there is a gap between the support and the insert even if it is simply inserted, When the weight is small, it is difficult to obtain the expected effect. In addition, the effect may be reduced when it is composed of a single member. Furthermore, in recent years, there is an environmental problem that needs to be recycled, reused, etc., so this point needs to be considered.

  The present invention has been made in consideration of the above-described circumstances, and charging noise generated when a charging member superimposes an AC voltage on a DC voltage to apply and charge the electrophotographic photosensitive member in a non-contact manner is a problem in practical use. It is an object of the present invention to provide an image forming apparatus that can be suppressed to a level that is not present, and a process cartridge that is detachable from the image forming apparatus.

  In order to solve the above problems, the invention described in claim 1 includes an electrophotographic photosensitive member, a charging unit that uniformly charges the electrophotographic photosensitive member, an image exposure unit, a developing unit, and a transfer unit. In the image forming apparatus, the charging member used in the charging unit includes a shaft portion and a main body portion that covers the shaft portion, and the main body portion is formed of a resin containing a conductive material. The charging member is disposed so as to face the photographic photosensitive member in a non-contact manner, and the charging member superimposes an alternating voltage on a DC voltage to apply and charge the electrophotographic photosensitive member in a non-contact manner. The image forming apparatus is characterized in that there exists a portion that satisfies a relationship in which the thickness d (mm) of the support satisfies d ≧ 0.9.

  According to a second aspect of the present invention, the charging member is provided with a spacer member in a main body portion of the charging member that is located outside the image forming area of the electrophotographic photosensitive member arranged to face the charging member, so that the charging member and the image carrier are supported. The image forming apparatus according to claim 1, wherein non-contact charging is performed by forming a gap between the bodies.

  According to a third aspect of the present invention, a gap member is formed between the charging member and the image carrier by providing spacer members at both ends of the electrophotographic photoreceptor outside the image forming area of the electrophotographic photoreceptor. The image forming apparatus according to claim 1, wherein non-contact charging is performed by the method described above.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the AC voltage frequency supplied for charging the electrophotographic photosensitive member by the charging member is 100 Hz or more and 2.5 kHz or less. The image forming apparatus described above is characterized.

  According to a fifth aspect of the present invention, the vibration amplitude (Vpp) of the AC voltage frequency supplied for charging the electrophotographic photosensitive member by the charging member is 1.0 kV or more and 3.0 kV or less. 5. The image forming apparatus according to any one of items 1 to 4 is characterized.

  According to a sixth aspect of the present invention, there is a portion satisfying a relationship in which a thickness d (mm) of the conductive support of the electrophotographic photosensitive member satisfies 0.9 ≦ d ≦ 5. The image forming apparatus described in any one of the above is characterized.

According to a seventh aspect of the present invention, the volume resistivity of the main body of the charging member relative to the electrophotographic photosensitive member is 1 × 10 ⁵ Ω · cm to 1 × 10 ¹⁰ Ω · cm. The image forming apparatus described in 1. is characterized.

  In the invention according to claim 8, the electrophotographic photosensitive member has a photosensitive layer, a charge transport layer as an outermost surface layer, and the thickness of the charge transport layer is 10 to 35 μm. 8. An image forming apparatus according to any one of items 7 to 7.

  According to a ninth aspect of the present invention, in the electrophotographic photosensitive member according to any one of the first to eighth aspects, a bearing member is attached to openings at both ends, and a shaft that penetrates the inside of the photosensitive member is provided. The image forming apparatus is characterized.

  According to a tenth aspect of the present invention, the electrophotographic photosensitive member operates along with the charging member during operation, and the electrophotographic photosensitive member rotates and charges at 200 rpm or less when applied by the charging member. Item 10. The image forming apparatus according to any one of Items 1 to 9.

  The invention according to claim 11 is the image forming apparatus according to claim 1, wherein the toner used in the developing unit contains inorganic fine particles having an average particle diameter of 70 nm or more and 300 nm or less.

  The invention according to claim 12 comprises at least one of charging means, exposure means, developing means, transfer means and an electrophotographic photosensitive member, and according to any one of claims 1 to 11. It is a process cartridge that is used in an image forming apparatus and is detachable.

  According to a thirteenth aspect of the invention, there is provided an image forming apparatus including a plurality of process cartridges according to the twelfth aspect.

  Further, in the invention described in claim 14, after the image forming apparatus primarily transfers the toner image developed on the electrophotographic photosensitive member onto the intermediate transfer member, the toner image on the intermediate transfer member is transferred to the recording material. 14. An image forming apparatus having intermediate transfer means for secondary transfer thereon, wherein a plurality of color toner images are secondarily transferred collectively onto a recording material. It is characterized by.

  According to the present invention, at least an electrophotographic photosensitive member, a charging unit that uniformly charges the electrophotographic photosensitive member, an image exposing unit that performs image exposure after uniform charging and forms an electrostatic latent image, and In an image forming apparatus comprising: a developing unit that develops toner on an electrostatic latent image; a unit that transfers a developed image; and a cleaning unit that cleans residual transfer toner on the electrophotographic photosensitive member. A charging member used in the charging unit is It is composed of a shaft portion and a main body portion covering the shaft portion, the main body portion is formed of a resin containing a conductive material, and the charging member is disposed so as to face the electrophotographic photoreceptor in a non-contact manner, The charging member superimposes an AC voltage on a DC voltage to apply and charge the electrophotographic photosensitive member in a non-contact manner, and a thickness d (mm) of a conductive support of the electrophotographic photosensitive member is d ≧ 0. There is a site that satisfies the relationship of 9 The image forming apparatus can be suppressed to a level no practical problem charging noise in the image forming apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view for explaining an image forming apparatus of the present invention, and modifications as described later also belong to the category of the present invention.

In FIG. 1, a photoconductor 11 is an electrophotographic photoconductor that satisfies the requirements of the present invention.
The photoconductor 11 has a drum shape, but may have a sheet shape or an endless belt shape. The charging member 12 is a charging roller. The charging roller includes a shaft portion and a main body portion that covers the shaft portion, and the main body portion is formed of a resin containing a conductive material. The charging member 12 has a minute gap G and the photosensitive member 11 so as to face each other in a non-contact manner. The gap G between the charging member 12 and the photoreceptor 11 is adjusted by providing a spacer member having a certain thickness in the non-image forming area of the charging member 12.

  The transfer means 16 is generally effective in combination with a transfer charger and a separation charger. Examples of the light source used for the exposure means 13 and the charge removal means 1A include a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), and an electroluminescence (EL). Listed are all luminescent materials. Various types of filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used to irradiate only light in a desired wavelength range.

  The toner 15 developed on the photoconductor by the developing means 14 is transferred to the image receiving medium 18, but not all is transferred, and some toner remains on the photoconductor. Such toner is removed from the photoreceptor by the cleaning means 17. As the cleaning means, a rubber cleaning blade, a brush such as a fur brush, a mag fur brush, or the like can be used.

  The toner used in the developing means can output a high-quality image by containing inorganic fine particles having an average particle size of 70 nm or more and 300 nm or less. When a positive (negative) charge is applied to the electrophotographic photosensitive member and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the photosensitive member. When this is developed with negative (positive) polarity toner (electrodetection fine particles), a positive image can be obtained, and when developed with positive (negative) polarity toner, a negative image can be obtained. A known method is applied to the developing unit, and a known method is also used for the charge eliminating unit.

  The above electrophotographic process exemplifies an embodiment of the present invention, and other embodiments are of course possible.

  Further, the image forming means as described above may be fixedly incorporated in a copying machine, a facsimile, or a printer, but may be incorporated in these apparatuses in the form of a process cartridge. A process cartridge is an apparatus (part) that contains an electrophotographic photosensitive member and includes at least one of charging means, exposure means, developing means, transfer means, cleaning means, and static elimination means. There are many shapes and the like of the process cartridge. Although not described in detail, a general example is shown in FIG.

  FIG. 3 shows another example of the image forming apparatus according to the present invention. In this electrophotographic apparatus, charging means 12, exposure means 13, black Bk, cyan C, magenta M, and yellow Y developing means 14Bk, 14C, 14M, 14Y, and an intermediate transfer member are provided around the photoreceptor 11. The intermediate transfer belt 1F and the cleaning means 17 are arranged in this order. Here, the subscripts Bk, C, M, and Y shown in the figure correspond to the color of the toner, and are added or omitted as appropriate.

  Each color developing means 14Bk, 14C, 14M, 14Y can be controlled independently, and only the color developing means for image formation is driven. The toner image formed on the photoconductor 11 is transferred onto the intermediate transfer belt 1F by the first transfer unit 1D disposed inside the intermediate transfer belt 1F. The first transfer unit 1D is disposed so as to be able to come into contact with and separate from the photoconductor 11, and the intermediate transfer belt 1F is brought into contact with the photoconductor 11 only during the transfer operation. Image formation of each color is sequentially performed, and the toner images superimposed on the intermediate transfer belt 1F are collectively transferred to the image receiving medium 18 by the second transfer unit 1E and then fixed by the fixing unit 19 to form an image. . The second transfer means 1E is also arranged so as to be able to contact and separate from the intermediate transfer belt 1F, and contacts the intermediate transfer belt 1F only during the transfer operation.

  In the transfer drum type image forming apparatus, since the toner images of the respective colors are sequentially transferred onto the transfer material electrostatically attracted to the transfer drum, there is a restriction on the transfer material that cannot be printed on thick paper, as shown in FIG. Such an intermediate transfer type electrophotographic apparatus is characterized in that the toner images of the respective colors are superimposed on the intermediate transfer body 1F, so that the transfer material is not limited. Such an intermediate transfer system is not limited to the apparatus shown in FIG. 3, and can be applied to the image forming apparatus shown in FIGS.

FIG. 4 is a radial cross-sectional view of a charging member provided in the charging unit. The charging member 12 has a structure including a shaft portion 12a made of a metal core at the center and a main body portion 12b on the outside thereof. The shaft portion 12a is made of, for example, stainless steel having a diameter of 8 to 20 mm, aluminum having high rigidity and conductivity, or 1 × 10 ³ Ω · cm or less, preferably 1 × 10 ² Ω · cm or less. It is made of conductive resin having high rigidity.

The main body 12b preferably has a volume resistivity of 1 × 10 ⁵ Ω · cm to 1 × 10 ¹⁰ Ω · cm and a thickness of about 1 to 2 mm. When the volume resistivity of the main body portion 12b is 1 × 10 ¹⁰ Ω · cm or more, the discharge becomes insufficient and the surface of the photoconductor 11 may not be sufficiently charged. Conversely, this resistivity is 1 × 10. ^{If it is 5} Ω · cm or less, if there is a defect such as a pinhole in the photosensitive layer of the photoconductor 11, the discharge current is concentrated on the pinhole, causing an abnormal discharge, and the overcurrent further enlarges the pinhole, The photosensitive layer is destroyed and an abnormal image is output.

  Here, the main body portion 12b is shown in a single layer structure, but is not particularly limited to this structure. If one or more layers of the main body portion are made of a conductive resin or the like, the main body portion 12b has two or more layers. Also good. Conventionally, rubber such as hydrin rubber has been used for the main body portion 12b, but here, a resin having a lower expansion coefficient than that of rubber is used to adjust the electrical resistance by mixing a conductive agent. Usually, the linear expansion coefficient of resin is about 1/2 or less than that of rubber, and the volume expansion coefficient of resin is about 1/6 or less of rubber when isotropic. Conventionally, when rubber is used, the dimensional accuracy of the rubber greatly changes due to heat and humidity, so that when the gap G between the charging member 12 and the photosensitive member 11 is small, the charging member and the electrophotographic photosensitive member are in contact with each other. As a result, the charging noise may increase, or charging unevenness due to abnormal discharge may occur.

  Here, as the resin of the main body portion 12b, olefin resins such as polyethylene and polypropylene, styrene resins such as polystyrene and copolymers thereof, acrylic resins such as polymethyl methacrylate, and the like can be used. In addition to the conductive agent, the resin can be mixed with ceramics such as carbon fiber, glass fiber, carbide and boride in order to improve strength and improve dimensional accuracy, thereby reducing the expansion coefficient.

  Examples of the conductive agent include alkali metal salts such as lithium peroxide, perchlorates such as sodium perchlorate, quaternary ammonium salts such as tetrabutylammonium salts, ionic conductive agents such as polymer conductive agents, carbon black, Metal powder such as silver powder and copper powder, and ceramic powder such as ITO can be used.

  FIG. 5 is a schematic view of a charging member used in the image forming apparatus according to the present invention. The charging member includes spacer members at both ends of the main body. The gap G between the charging member 12 and the image carrier 11 (see FIG. 1) is preferably 100 μm or less, particularly 20 to 50 μm, depending on the spacer member. Thereby, formation of an abnormal image at the time of operation of charging device 100 can be suppressed. When the gap G is 100 μm or more, the image quality of the output image may be degraded, for example, the output image may be easily soiled due to a decrease in the charged potential on the surface of the photoconductor 11. If the gap G is small, the photosensitive member surface deposit that has not been removed by the cleaning member on the photosensitive member surface comes into contact with the charging member, so that a part of it is transferred to the charging member, and charging during charging of the photosensitive member is performed. May cause unevenness.

  As the spacer member 30 shown in FIG. 5, an olefin resin such as polyethylene or polyolefin, a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, or a fluorine resin such as polytetrafluoroethylene can be used. The spacer member 30 can be made of elastic metal or rubber. As the metal, aluminum, iron, copper, titanium, or an alloy mainly composed of these can be used. Furthermore, it is preferable to coat these surfaces with an oxide to make them electrically insulating. Since the metallic space member 30 is harder than the photosensitive layer made of the resin of the photoreceptor 11, it is preferable to cover the surface with the resin. As a result, the hardness of the photosensitive layer of the photoconductor 11 can be made lower and the wear of the photoconductor 11 can be reduced.

  As the rubber, natural rubber, polyurethane rubber, chloroprene rubber, nitrile-butadiene rubber, silicone rubber, and fluorine rubber can be used. JIS-A: The rubber hardness is preferably 70 Hs or higher, and further, those obtained by adding silica, alumina, glass fiber or the like and curing them are preferable. Thereby, the fluctuation | variation of the gap | interval G can be prevented.

  The spacer member can be provided at both ends of the electrophotographic photosensitive member instead of being provided in the charging member, whereby the gap G can be formed. At this time, the same spacer member as the charging member can be used.

  When the photosensitive member is charged by the charging member 12 disposed opposite to the electrophotographic photosensitive member 11, the voltage applied to the charging member 12 is only a DC voltage when the electrophotographic photosensitive member 11 and the charging member 12 are in contact with each other. Therefore, it is possible to provide sufficient practicality, and it is difficult to produce a level of charged sound that causes a practical problem. However, in the case of non-contact, when charging is performed only with a DC voltage, uneven charging tends to occur. Therefore, it is effective to superimpose an AC voltage on a DC voltage and compensate by the AC voltage in order to suppress the occurrence of uneven charging.

  The AC voltage is preferably a sine wave, and the frequency is preferably set to 100 Hz or more and 2.5 KHz or less. When the frequency is 100 Hz or less, the AC voltage does not sufficiently act on the photoconductor, so that uneven charging tends to occur and abnormal images are likely to occur. Above 2.5 kHz, abnormal discharge is likely to occur, and electric charges trapped in the photosensitive layer of the photosensitive member lower the charging potential, destabilize the repeating characteristics of the charging potential, and cause background staining. .

  Although the official value of the frequency of the AC voltage applied to the charging member varies depending on the linear velocity of the photosensitive member, there is no practical problem if it is set to 800 Hz or more and 2 kHz or less. The vibration amplitude (Vpp) of the AC voltage frequency is preferably 1 kV or more and 3.0 kV or more. Within this range, it is possible to moderately suppress the stable charge potential of the photoconductor and the residual potential of the photoconductor due to repeated use. However, the higher the Vpp, the greater the charging noise. Is desired. On the other hand, if the voltage is 1.3 kV or less, the photosensitive member may be partially insufficiently charged, resulting in uneven charging, and an abnormal image is likely to occur.

  It is desirable to increase the AC voltage frequency and Vpp in order to charge the photosensitive member to a potential to be uniformly charged as the rotational speed at the time of charging becomes faster and more uniform. However, as described above, since there are suitable ranges for the AC voltage frequency and Vpp, it is preferable that the photosensitive member is rotated and charged at a rotation speed of 200 rpm or less.

  A bearing member may be attached to the openings at both ends of the photoconductor 11, and a shaft that penetrates the inside of the photoconductor may be provided. For example, by providing a precision bearing member made of resin with a metal precision shaft penetrating the inside of the photosensitive member, it is possible to improve the outer diameter deflection accuracy and contribute to the improvement of the output image quality.

  FIG. 6 is a cross-sectional view of an example of an electrophotosensitive material used in the image forming apparatus of the present invention, taken along a plane including the cylinder central axis. In order to suppress the charging sound when the electrophotographic photosensitive member is charged by the opposing charging member, the thickness d of the conductive support of the photosensitive member is preferably 0.9 mm ≦ d ≦ 5 mm. If the thickness is less than 0.9 mm, the charging sound of the photoconductor becomes loud and causes practical problems. On the other hand, if the thickness exceeds 5 mm, the weight of the photoconductor increases, making it difficult to handle the photoconductor alone, and in an image forming apparatus having a plurality of drums, the increase in weight is significant and becomes a size that cannot be ignored. Further, it is not preferable because a large load is applied to the driving device during driving in the image forming apparatus. More preferably, the thickness d is preferably 0.9 mm ≦ d ≦ 2 mm.

  FIG. 7 is a schematic cross-sectional view of an electrophotographic photoreceptor provided in the image forming apparatus of the present invention, and shows an electrophotographic photoreceptor having a configuration in which a photosensitive layer 21 is provided on a conductive substrate 20. FIG. 8 and FIG. 9 each show a configuration example of another electrophotographic photosensitive member provided in the image forming apparatus of the present invention. FIG. 8 shows a function separation type electrophotographic photosensitive member in which the photosensitive layer 21 is composed of a charge generation layer 22 (CGL) and a charge transport layer 23 (CTL), and FIG. 9 shows a function separation from the conductive substrate 20. An electrophotographic photosensitive member is shown in which an undercoat layer 24 is inserted between the CGL22 and CTL23 of the type-type photosensitive layer. The electrophotographic photoreceptor according to the present invention has at least a photosensitive layer on a conductive support, and if the outermost surface layer is a charge transport layer, other layers other than the above are formed. It doesn't matter.

As the conductive support 20 used for the electrophotographic photosensitive member in the present invention, a conductor or an insulator subjected to a conductive treatment, for example, a metal such as Al, Ni, Fe, Cu, Au, or an alloy thereof, A thin film of a metal such as Al, Ag, Au or a conductive material such as In ₂ O ₃ or SnO ₂ formed on an insulating substrate such as polyester, polycarbonate, polyimide, glass, etc., carbon black, graphite, aluminum in the resin , A metal base such as copper and nickel, a conductive glass powder, etc., and a resin substrate obtained by imparting conductivity to the resin, paper subjected to conductive treatment, and the like can be used.

  The shape of the conductive support 20 is not particularly limited, and any of a plate shape, a drum shape, or a belt shape can be used. However, when a belt-shaped conductive support is used, a driving roller and a driven roller are provided inside. There is a merit that the equipment becomes complicated and large in size, but the degree of freedom in layout is increased. However, when forming a protective layer, there is a possibility that cracks called cracks may occur on the surface due to insufficient flexibility of the protective layer, which may cause granular background stains. It is done. For this reason, a drum-like member having high rigidity is preferably used as the support.

  An undercoat layer 24 may be provided between the conductive support and the photosensitive layer 21 as necessary. The undercoat layer 24 is provided for the purpose of improving adhesiveness, preventing moire, improving the coatability of the upper layer, and reducing the residual potential. The undercoat layer generally comprises a resin as a main component, but these resins are resins having a high solubility resistance to general organic solvents in consideration of applying a photosensitive layer thereon using a solvent. It is desirable that

  Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resins, alkyd-melamine resins, and epoxy resins. Examples thereof include curable resins that form a three-dimensional network structure. Further, fine powders such as metal oxides exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like, or metal sulfides and metal nitrides may be added. These undercoat layers can be formed by a common coating method using an appropriate solvent.

Further, as the undercoat layer, a metal oxide layer formed by using, for example, a sol-gel method using a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like is also useful. In addition, as the undercoat layer, an anodized layer of Al ₂ O ₃ , an organic material such as polyparaxylylene (parylene), or an inorganic material such as SnO ₂ , TiO ₂ , ITO, or CeO ₂ is used. It may be provided by a vacuum thin film manufacturing method. The thickness of the undercoat layer 24 is suitably about 0.1 to 5 μm.

  The charge generation layer 22 is a layer mainly composed of a charge generation material, and a binder resin may be used as necessary. As the charge generation material, inorganic materials and organic materials can be used. Examples of inorganic materials include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, and selenium-arsenic compounds.

  On the other hand, a known material can be used as the organic material. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having fluorenone skeleton, azo pigments having oxadiazole skeleton, azo pigments having bis-stilbene skeleton, azo pigments having distyryl oxadiazole skeleton, azo pigments having distyrylcarbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Goido based pigments, and bisbenzimidazole pigments. These charge generation materials can be used alone or as a mixture of two or more.

  The binder resin used as necessary for the charge generation layer 21 is polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-vinylcarbazole. Polyacrylamide is used. These binder resins can be used alone or as a mixture of two or more. Moreover, you may add a charge transport substance as needed. In addition to the binder resin described above, a polymer charge transporting material is also preferably used as the binder resin for the charge generation layer.

As a method for forming the charge generation layer, a vacuum thin film preparation method and a casting method from a solution dispersion system can be largely mentioned. Examples of the former method include a glow discharge polymerization method, a vacuum deposition method, a CVD method, a sputtering method, a reactive sputtering method, an ion plating method, and an accelerated ion injection method. This vacuum thin film manufacturing method can satisfactorily form the inorganic material or organic material described above. Further, in order to provide the charge generation layer by the latter casting method, a ball mill using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone together with a binder resin, if necessary, the inorganic or organic charge generation material described above, It can be formed by dispersing with an attritor, sand mill or the like, and applying the solution after diluting the dispersion appropriately. The application can be performed using a commonly used method such as a dip coating method, spray coating, or bead coating.
The thickness of the charge generation layer provided as described above is suitably about 0.01 to 5 μm, preferably 0.05 to 2 μm.

  The charge transport layer 23 is a layer intended to hold a charged charge and to couple the charge generated and separated in the charge generation layer by exposure to the charged charge that has been held. In order to achieve the purpose of holding the charged charge, it is required that the electric resistance is high. Further, in order to achieve the purpose of obtaining a high surface potential with the charged charge that has been held, it is required that the dielectric constant is small and the charge mobility is good.

  The charge transport layer 23 for satisfying these requirements is composed of a charge transport material and a binder resin used as necessary. Such a charge transport layer can be formed by dissolving or dispersing these charge transport materials and a binder resin in an appropriate solvent, and applying and drying them. If necessary, an appropriate amount of additives such as a plasticizer, an antioxidant, and a leveling agent can be added to the charge transport layer in addition to the charge transport material and the binder resin. Examples of the charge transport material include a hole transport material and an electron transport material.

  Examples of the electron transport material include chloroanil, bromanyl, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2, 4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4-one, 1,3,7-tri Examples thereof include electron accepting substances such as nitrodibenzothiophene-5,5-dioxide. These electron transport materials can be used alone or as a mixture of two or more.

  Examples of the hole transporting material include the electron donating materials shown below and are used favorably. For example, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline , Phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like. These hole transport materials can be used alone or as a mixture of two or more.

Further, the polymer charge transporting material may have the following structure.
(A) Polymer having a carbazole ring, for example, poly-N-vinylcarbazole, JP-A-50-82056, JP-A-54-9632, JP-A-54-11737, JP-A-4-175337 And the compounds described in JP-A-4-183719 and JP-A-6-234841.

(B) Polymers having a hydrazone structure For example, JP-A-57-78402, JP-A-61-20953, JP-A-61-296358, JP-A-1-134456, JP-A-1- 179164, JP-A-3-180851, JP-A-3-180852, JP-A-3-50555, JP-A-5-310904, JP-A-6-234840, etc. Is done.

(C) Polysilylene polymers For example, JP-A 63-285552, JP-A-1-88461, JP-A-4-264130, JP-A-4-264131, JP-A-4-264132, Examples thereof include compounds described in Kaihei 4-264133 and JP-A-4-289867.

(D) Polymer having a triarylamine structure, for example, N, N-bis (4-methylphenyl) -4-aminopolystyrene, JP-A-1-134457, JP-A-2-282264, JP-A-2- Examples include compounds described in JP-A-304456, JP-A-4-133605, JP-A-4-133066, JP-A-5-40350, and JP-A-5-202135.

(E) Other polymers, for example, formaldehyde condensation polymer of nitropyrene, JP-A-51-73888, JP-A-56-150749, JP-A-6-234836, JP-A-6-234837 The described compounds and the like are exemplified.
The polymer having an electron donating group used in the present invention is not limited to the above-mentioned polymer, but also a copolymer of a known monomer, a block polymer, a graft polymer, a star polymer, It is also possible to use a cross-linked polymer having an electron donating group as disclosed in JP-A-3-109406.

  Further, examples of polycarbonates, polyurethanes, polyesters, and polyethers having a triarylamine structure that are further useful as the polymer charge transporting material used in the present invention include, for example, JP-A 64-1728 and JP-A 64- 13061, JP 64-19049, JP 4-11627, JP 4-225014, JP 4-230767, JP 4-320420, JP 5-232727 JP, 7-56374, JP 9-127713, JP 9-222740, JP 9-265197, JP 9-211877, JP 9-304956. And the like.

  Furthermore, as a binder resin that can be used in combination with the charge transport layer, for example, polycarbonate, polyester, methacrylic resin, acrylic resin, polyethylene, vinyl chloride, vinyl acetate, polystyrene, phenol resin, epoxy resin, polyurethane, polyvinylidene chloride, alkyd resin, Silicone resin, polyvinyl carbazole, polyvinyl butyral, polyvinyl formal, polyacrylate, polyacrylamide, phenoxy resin, and the like are used. These binder resins can be used alone or as a mixture of two or more.

  The film thickness of the charge transport layer is suitably about 5 to 100 μm. However, due to the recent demand for higher image quality, it has been attempted to make the charge transport layer thinner and achieve higher image quality of 1200 dpi or more. For this purpose, a thickness of about 10 to 35 μm is more preferable.

  Additives such as other antioxidants and plasticizers used for rubbers, plastics, fats and the like may be added to the charge transport layer in the present invention. Furthermore, a leveling agent may be added in the charge transport layer. Examples of such leveling agents include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain, and the amount used is 100 parts by weight of binder resin. From 0 to 1 part by weight is appropriate.

  As the coating method, a conventional method such as a dip coating method, spray coating, or bead coating method can be used.

  Examples of the present invention and comparative examples will be described below.

Example 1
An electrophotographic photoreceptor 11 and a charging member 12 having the following conditions were mounted on a modified Ricoh Ipsio Color 8100. The toner contained inorganic fine particles having an average particle diameter of 70 nm or more and 300 nm or less and having an average particle diameter of 5.9 μm.

  Print a mixed image of rectangular patches and characters with an image density of 5%, measure the volume at 30 cm in front of the modified Ipsio Color 8100, average the magnitude of 1 to 4 harmonics of the charged sound, and set it as the charged volume .

(Electrophotographic photoreceptor)
15 parts by weight of alkyd resin (Beckolite M6401-50 (manufactured by Dainippon Ink and Chemicals)), 10 parts by weight of melamine resin (Super Becamine G-821-60 (manufactured by Dainippon Ink and Chemicals)) and 150 parts by weight of methyl ethyl ketone 90 parts by weight of titanium oxide powder (Typer CR-EL (manufactured by Ishihara Sangyo Co., Ltd.)) was added thereto and dispersed with a ball mill for 12 hours to prepare an undercoat layer coating solution.

This was coated on a cylindrical aluminum substrate having a thickness of 1 mm and a diameter of 30 mm by a dip coating method and dried at 130 ° C. for 20 minutes to form an undercoat layer having a thickness of 4.5 μm.
Next, 4 parts by weight of polyvinyl butyral resin (XYHL (manufactured by UCC)) was dissolved in 150 parts by weight of cyclohexanone, which is represented by the following structural formula (1).

  10 parts by weight was added to the bisazo pigment and dispersed for 48 hours by a ball mill, and further 210 parts by weight of cyclohexanone was added and dispersed for 3 hours. This was taken out into a container and diluted with cyclohexanone so that the solid content was 1.5% by weight. The charge generation layer coating solution thus obtained was applied onto the intermediate layer and dried at 130 ° C. for 20 minutes to form a charge generation layer having a thickness of 0.2 μm.

  Next, in 100 parts by weight of tetrahydrofuran, 10 parts by weight of bisphenol Z-type polycarbonate resin and 0.002 parts by weight of silicone oil (KF-50 (manufactured by Shin-Etsu Chemical Co., Ltd.)) are dissolved. A charge transport layer coating solution was prepared by adding 10 parts by weight of the charge transport material. The charge transport layer coating solution thus obtained was applied onto the charge generation layer by a dip coating method and then dried at 110 ° C. for 20 minutes to form a charge transport layer having a thickness of 31 μm.

  The electrophotographic photosensitive member was charged at an image portion potential of −40 V, a non-image portion potential of −500 V, and the photosensitive member linear velocity was 155 mm / sec.

(Charging member)
A charging roller having a structure shown in FIG. 4 in which a stainless steel core shaft (φ6 mm conductive support) was coated with a resin as a main body was manufactured. A composition prepared by blending 0.5 parts by weight of ether amide as a conductive agent with 100 parts by weight of ABS resin as a resin material and adjusting the volume resistivity to 1 × 10 ⁸ Ω · cm to 1 × 10 ⁹ Ω · cm. This material was molded by an extrusion molding machine to cover the core shaft to obtain a charging roller having a diameter of 14 mm. A heat-shrinkable fluororesin was used for the spacer member. The applied voltage conditions were AC voltage frequency 1.1 kHz, Vpp 2.0 kV, and DC voltage −450V.

(Example 2)
Evaluation was conducted in the same manner as in Example 1 except that the thickness d of the conductive support of the electrophotographic photosensitive member was set to 2 mm in Example 1 using a remodeled Ipsio Color 8100 manufactured by Ricoh.

(Example 3)
Evaluation was performed in the same manner as in Example 1 on a modified Ricoh Ipsio Color 8100 machine except that Vpp was changed to 1.7 kV in Example 1.

Example 4
Evaluation was conducted in the same manner as in Example 1 on a modified Ricoh Ipsio Color 8100 machine except that Vpp was set to 2.5 kV in Example 1.

(Example 5)
Evaluations were made in the same manner as in Example 1 except that the thickness of the charge transport layer (CTL) of the photoreceptor was 20 μm in Example 1 using a modified Ricoh Ipsio Color 8100 machine.

(Example 6)
Evaluations were made in the same manner as in Example 1 on a Ricoh Ipsio Color 8100 modified machine except that the linear velocity of the photosensitive member was 77.5 mm / sec in Example 1.

(Comparative Example 1)
Evaluation was performed in the same manner as in Example 1 on the Ricoh Ipsio Color 8100 modified machine except that the conditions of the charging member mounted on the Ricoh Ipsio Color 8100 modified machine were as follows.

(Charging member)
A charging roller having a structure shown in FIG. 4 in which a stainless steel core shaft (φ6 mm conductive support) was coated with a semiconductive elastic layer as a main body was manufactured. As a resin material, 100 parts by weight of a thermoplastic elastomer containing a polyester component is blended with 0.5 parts by weight of lithium perchlorate, resulting in a volume resistivity of 1 × 10 ⁸ Ω · cm to 1 × 10 ⁹ Ω · cm. Using the composition prepared as described above, this material was molded by an extruder and the core shaft was covered to obtain a charging roller having a diameter of 14 mm.

(Comparative Example 2)
Evaluation was made in the same manner as in Comparative Example 1 except that the thickness d of the electroconductive photosensitive member of the electrophotographic photosensitive member was 2 mm in Comparative Example 1, using a remodeled Ipsio Color 8100 manufactured by Ricoh.

(Comparative Example 3)
Evaluation was conducted in the same manner as in Example 1, except that the thickness d of the electroconductive photosensitive member of the electrophotographic photosensitive member was changed to 0.7 mm in Example 1, using a remodeled Ipsio Color 8100 manufactured by Ricoh.
Table 1 shows the evaluation results of Examples 1 to 6 and Comparative Examples 1 to 3.

  From Table 1, it was confirmed that in the examples satisfying the constituent requirements of the present invention, the volume of the charged sound was small and practically no problem. In all of the comparative examples that did not satisfy the requirements of the present invention, the volume of the charged sound was large, which was a problem in practical use.

(Example 7)
The electrophotographic photosensitive member and the charging member used in Example 1 in the Ricoh imgio Neo 270 remodeled machine in which the light source for image exposure was remodeled to 655 nm and the LED irradiation mechanism, which is a neutralizing means, was removed. Mounted under conditions, prints a mixed image of rectangular patches and characters with an image density of 5%, measures the volume at the front 30 cm of imgio Neo 270 remodeling machine, averages the size of 1 to 4 harmonics of the charged sound The charging volume was used.

(Example 8)
The electrophotographic photosensitive member and charging member used in Example 2 were mounted on a remodeled imgio Neo 270 manufactured by Ricoh under the conditions of Example 2 and evaluated in the same manner as in Example 7.

Example 9
The electrophotographic photosensitive member and the charging member used in Example 3 were mounted on a modified Ricoh imgio Neo 270 machine under the conditions of Example 3 and evaluated in the same manner as in Example 7.

(Example 10)
The electrophotographic photosensitive member and the charging member used in Example 4 were mounted on a remodeled imgio Neo 270 manufactured by Ricoh under the conditions of Example 4 and evaluated in the same manner as in Example 7.

(Example 11)
The electrophotographic photosensitive member and charging member used in Example 5 were mounted on a remodeled imgio Neo 270 manufactured by Ricoh under the conditions of Example 5 and evaluated in the same manner as in Example 7.

(Example 12)
The electrophotographic photosensitive member and the charging member used in Example 6 were mounted on a modified Ricoh imgio Neo 270 machine under the conditions of Example 6 and evaluated in the same manner as in Example 7.

(Comparative Example 4)
The electrophotographic photosensitive member and charging member used in Comparative Example 1 were mounted on a remodeled imgio Neo 270 manufactured by Ricoh under the conditions of Comparative Example 1 and evaluated in the same manner as in Example 7.

(Comparative Example 5)
The electrophotographic photosensitive member and charging member used in Comparative Example 2 were mounted on a Ricoh imago Neo Neo 270 modified machine under the conditions of Comparative Example 2 and evaluated in the same manner as in Example 7.

(Comparative Example 6)
The electrophotographic photosensitive member and the charging member used in Comparative Example 3 were mounted on a modified Ricoh imagio Neo 270 machine under the conditions of Comparative Example 3 and evaluated in the same manner as in Example 7.
Table 2 shows the evaluation results of Examples 7 to 12 and Comparative Examples 4 to 6.

  From Table 2, it was confirmed that in the examples satisfying the constituent requirements of the present invention, the volume of the charging sound was small and practically no problem. In all of the comparative examples that did not satisfy the requirements of the present invention, the volume of the charged sound was large, which was a problem in practical use.

  The reason why the charging noise can be suppressed is as follows. By forming the main body of the charging member from a resin containing a conductive material, the formation accuracy is higher than that of a charging member made of rubber, and the resin is less deformable than rubber, so image formation It is difficult to cause a change in the size of the gap between the electrophotographic photosensitive member and the charging member, such as deformation during operation in the apparatus. From this, it is considered that the resin charging member can stably charge the electrophotographic photosensitive member without contact. Furthermore, it is considered that the conductive support is less likely to vibrate by setting the thickness d (mm) of the conductive support of the electrophotographic photosensitive member to d ≧ 0.9. It is presumed that the effects of these are combined in combination, and the effect of reducing the charging sound will appear greatly.

1 is a configuration diagram showing an outline of an image forming apparatus of the present invention. It is a schematic block diagram which shows an example of the process cartridge of this invention. It is a block diagram showing an example of color development of the image forming apparatus of the present invention. It is a section lineblock diagram showing the section of the charging member radial direction of the present invention. 2 is a schematic view of a charging member used in the image forming apparatus of the present invention. FIG. FIG. 3 is a cross-sectional view in the cylinder axis direction of the photoconductor of the image forming apparatus of the present invention. 1 is a schematic cross-sectional view of a photoreceptor provided in an image forming apparatus of the present invention. 1 is a configuration diagram of an example of a photoreceptor provided in an image forming apparatus of the present invention. FIG. 6 is a configuration diagram of another example of a photoreceptor provided in the image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Electrophotographic photosensitive member 12 Charging means 12a Shaft part by metal core 12b Outer body part 13 Exposure means 14 Developing means 14Bk Black developing means 14C Cyan developing means 14M Magenta M developing means 14Y Yellow developing means 15 Toner 16 Transfer means 17 Cleaning Means 18 Image receiving medium 19 Fixing means 1A Neutralizing means 1B Pre-cleaning exposure means 1C Driving means 1D First transfer means 1E Second transfer means 1F Intermediate transfer body G Gap 20 Conductive support 22 Charge generation layer 23 Charge transport layer 24 Undercoat layer 30 Spacer member

Claims (14)

In an image forming apparatus comprising an electrophotographic photosensitive member, a charging unit that uniformly charges the electrophotographic photosensitive member, an image exposing unit, a developing unit, and a transferring unit.
The charging member used in the charging means is composed of a shaft portion and a main body portion covering the shaft portion,
The main body is formed of a resin containing a conductive material, and the charging member is disposed to face the electrophotographic photosensitive member in a non-contact manner, and the charging member superimposes an AC voltage on a DC voltage and The photographic photosensitive member is applied and charged in a non-contact manner, and there is a portion satisfying a relationship in which the thickness d (mm) of the conductive support of the electrophotographic photosensitive member satisfies d ≧ 0.9. Image forming apparatus.   The charging member includes a spacer member in the main body of the charging member that is located outside the image forming area of the electrophotographic photosensitive member arranged opposite to the charging member, thereby forming a gap between the charging member and the image carrier. The image forming apparatus according to claim 1, wherein charging is performed.   Non-contact charging is performed by forming a gap between the charging member and the image bearing member by providing spacer members at both ends of the electrophotographic photosensitive member that are outside the image forming area of the electrophotographic photosensitive member. The image forming apparatus according to claim 1.   4. The image forming apparatus according to claim 1, wherein an AC voltage frequency supplied by the charging member to charge the electrophotographic photosensitive member is 100 Hz or more and 2.5 kHz or less. 5.   5. The vibration amplitude (Vpp) of the AC voltage frequency supplied by the charging member to charge the electrophotographic photosensitive member is 1.0 kV or more and 3.0 kV or less. The image forming apparatus described in the item.   6. The electrophotographic photosensitive member according to claim 1, wherein there is a portion satisfying a relationship in which a thickness d (mm) of the conductive support of the electrophotographic photosensitive member satisfies 0.9 ≦ d ≦ 5. The image forming apparatus described. 3. The image forming apparatus according to claim 1, wherein a volume resistivity of a main body portion of the charging member with respect to the electrophotographic photosensitive member is 1 × 10 ⁵ Ω · cm to 1 × 10 ¹⁰ Ω · cm. .   The electrophotographic photosensitive member has a photosensitive layer, has a charge transport layer as an outermost surface layer, and the thickness of the charge transport layer is 10 to 35 μm. The image forming apparatus described.   9. The image forming apparatus according to claim 1, wherein the electrophotographic photosensitive member includes a shaft that has bearing members attached to openings at both ends and penetrates the inside of the photosensitive member.   10. The electrophotographic photosensitive member operates in conjunction with the charging member during operation, and the electrophotographic photosensitive member rotates at 200 rpm or less to be charged when applied by the charging member. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the toner used in the developing unit contains inorganic fine particles having an average particle diameter of 70 nm or more and 300 nm or less.   13. The image forming apparatus according to claim 1, further comprising at least one of a charging unit, an exposure unit, a developing unit, a transfer unit, and an electrophotographic photosensitive member, and a detachable process cartridge. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 12, wherein the image forming apparatus includes a plurality of the process cartridges.   The image forming apparatus includes an intermediate transfer unit that primarily transfers a toner image developed on an electrophotographic photosensitive member onto an intermediate transfer member and then secondary-transfers the toner image on the intermediate transfer member onto a recording material. The image forming apparatus according to claim 1, wherein the toner images of a plurality of colors are secondarily transferred collectively onto a recording material.

Images