JP2006084670A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is capable of suppressing a charging sound generated when a charging member subjects an electrophotographic photoreceptor to application charging by superposing an alternating voltage to a direct voltage up to a level of causing no problem in a practical use and has an excellent image quality of an output image, and to provide a process cartridge attachable and detachable for the image forming apparatus. <P>SOLUTION: A spacer member disposed on a main body part of a charging member which comes to a gap holding means between the electrophotographic photoreceptor 11 and the charging member 12 is brought into pressing contact with smoothing parts which are at least 7mm apart from an uppermost layer coating starting point of the electrophotographic photoreceptor 11 and range in 10% distance from both ends of the electrophotographic photoreceptor 11. When the size of a gap formed between the charging member 12 and the electrophotographic photoreceptor 11 is set to be G (μm), the image forming apparatus satisfies the relation; 20≤G≤100. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a laser printer, a facsimile, and the like, and a process cartridge for an image forming apparatus including a charging unit, an electrophotographic photosensitive member, and the like disposed in the image forming apparatus.

In an image forming apparatus that forms an image using indirect electrophotography, such as a facsimile, a laser beam printer, a copying machine, etc., charging, image exposure, focusing on an electrophotographic photoreceptor (hereinafter simply referred to as “photoreceptor”), Each means such as development, transfer, separation, cleaning and static elimination is provided, 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 shape or a brush shape 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 and the more easily the material that the support of the photoconductor resonates, the more the charging sound growing. 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, methods such as increasing the thickness of the support of the photosensitive member, inserting a damping material (filler) inside the drum-shaped photosensitive member, and improving the charging member side have been 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.

For example, 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 into the photosensitive drum (for example, Patent Documents). 1), filling the inside of the photoconductor with a viscoelastic material (for example, see Patent Document 2), and inserting a rigid body with a density of 2.0 g / cm ³ or more into the inside of the photoconductor (for example, Patent Document 2). 3) a member composed of two or more elastic bodies (O-rings) and a cylindrical member (a plastic having a specific gravity of 1.5 or more (polybutylene terephthalate resin containing 20% or more of glass fibers)) to the photoreceptor. Can be inserted (for example, see Patent Document 4), and a resin cylindrical member with a built-in metal spring can be inserted and fixed to the wall of the photosensitive body with a pressing force (for example, see Patent Document 5). Proposed.

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 vibration damping effect by setting the volume density of the photoreceptor 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.
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 is difficult to obtain a sufficient effect only by a method of suppressing charging noise with a charging member or by thickening the support of the photosensitive member. The method of increasing the weight and suppressing the sound (squeal) by inserting a filler inside the photosensitive member support is easy to obtain, but even if it is simply inserted, there is a gap between the support and the insertion material. If 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.
As a method for producing a photoreceptor having a smooth portion start point within 7 mm from the charge transport layer coating start point, there is a method of double coating or multiple coating of the charge transport layer in the vicinity of the charge transport layer coating start point. For example, Patent Document 9 uses a method of double-coating a charge transport layer for the purpose of making the film thickness of the entire coating film uniform. However, it is not described for the purpose of preventing charging noise by making the gap between the charging member and the photosensitive member uniform.

JP-A 63-60481 (pages 2 to 3) Japanese Patent Laid-Open No. 3-105348 (pages 2 to 5) JP-A-5-197321 (Claims, pages 8 to 10) JP 11-184308 A (claims, pages 2 to 3) JP 2000-321929 A (pages 2 to 4) JP 2000-19761 A (pages 2 to 3) JP 2000-155500 A (pages 2 to 3) JP-A-9-230671 (Claims, pages 3 to 10) JP 59-8036 A

  In view of the above problems, the present invention can suppress the charging sound generated when the charging member applies and charges the electrophotographic photosensitive member by superimposing the AC voltage on the DC voltage to a level that does not cause a problem in practice, and the output. An image forming apparatus with good image quality and a process cartridge that can be attached to and detached from the image forming apparatus are provided.

In order to solve the above problems, the present invention is characterized by the following.
1. The present invention relates to an electrophotographic photosensitive member that carries a latent image, a charging unit that uniformly charges the surface of the image carrier, and exposure that writes the latent image by exposing the surface of the charged image carrier based on image data. Means, a developing means for supplying toner to the latent image formed on the surface of the image carrier to make it visible, a transfer means for transferring the visible image on the surface of the image carrier to a transfer medium, and an image after transfer An electrophotographic photosensitive member having at least a conductive support and a photosensitive layer, wherein the electrophotographic photosensitive member includes at least a conductive support and a cleaning unit that cleans the surface of the carrier. The electrophotographic photosensitive member having a smooth portion whose film thickness variation is within 5 μm and the charging means are composed of a shaft portion and a main body portion covering the shaft portion, and the main body portion is formed from a resin containing a conductive agent. An electrophotographic photosensitive member And a charging member that is arranged so as to be opposed to each other in a non-contact manner and superimposes an AC voltage on a DC voltage to apply and charge the electrophotographic photosensitive member in a non-contact manner, and a gap holding unit between the electrophotographic photosensitive member and the charging member The spacer member provided in the main body of the charging member is at least 7 mm or more from the starting point of the outermost surface coating of the electrophotographic photosensitive member, and a smooth portion in the range of 10% from both ends of the electrophotographic photosensitive member. When the size of the gap formed between the charging member and the electrophotographic photosensitive member is G (μm), the relationship of 20 ≦ G ≦ 100 is satisfied.

2. The outermost surface layer of the electrophotographic photosensitive member is a charge transport layer.
3. The charge transport layer is produced by a dip coating method.
4). The solvent of the charge transport layer forming coating solution is tetrahydrofuran.
5. The flat portion of the charge transport layer is coated by double or multiple coating only in the vicinity of the outermost layer coating start point during the dip coating of the charge transport layer.
6). The charge transport layer has a thickness of 10 to 35 μm.
7). The frequency of the AC voltage supplied by the charging member to charge the electrophotographic photosensitive member is 100 Hz or more and 2.5 kHz or less.
8). The charging member is characterized in that the vibration amplitude (Vpp) of the frequency of the AC voltage supplied to charge the electrophotographic photosensitive member is 1.0 kV or more and 3.0 kV or less.
9. The volume resistivity of the main body of the charging member is 1 × 10 ⁵ Ω · cm to 1 × 10 ¹⁰ Ω · cm.

10. The electrophotographic photosensitive member is characterized in that a bearing member is attached to openings at both ends, and a shaft penetrating the inside of the electrophotographic photosensitive member is provided.
11. The electrophotographic photosensitive member operates along with the charging member during operation, and is charged while rotating at 200 rpm or less during application charging by the charging member.
12 12. A detachable process cartridge used in the image forming apparatus according to any one of 1 to 11, further comprising a charging unit and an electrophotographic photosensitive member disposed in the image forming apparatus according to any one of 1 to 11. It is characterized by being.
13. The process cartridge further includes at least one of an exposure unit, a development unit, and a transfer unit disposed in the image forming apparatus according to any one of 1 to 11.
14 The toner used in the developing unit contains inorganic fine particles having an average particle size of 70 nm or more and 300 nm or less.
A plurality of process cartridges according to 15.12 or 13 are provided.

  According to the present invention, the charging sound generated when the charging member superimposes the AC voltage on the DC voltage to apply and charge the electrophotographic photosensitive member can be suppressed to a level that causes no problem in practice, and the image quality of the output image is good. An image forming apparatus and a process cartridge that can be attached to and detached from the image forming apparatus can be provided.

  Embodiments of the present invention will be described below. The following description is an example of the best mode of the present invention, and it is easy for those skilled in the art to make other embodiments within the scope of the claims by making changes and modifications within the scope of the claims. However, this does not limit the scope of the claims.

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 member 12 is disposed to face the photoconductor 11 with a minute gap G therebetween.
The size of the gap G between the charging member 12 and the photosensitive member 11 is such that a spacer member having a certain thickness is provided in the main body of the charging member 12 and the photosensitive member and the non-image forming region are smooth regions. It is adjusted by contact.
As the transfer means 16, the above charger can be generally used, but a combination of a transfer charger and a separation charger is effective.
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. FIG. 2 shows a process cartridge according to the present invention. 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, but a general example is the one shown in FIG.

FIG. 3 is a diagram showing another example of the image forming apparatus according to the present invention. In this electrophotographic apparatus, a charging unit (12), an exposure unit (13), black (Bk), cyan (C), magenta (M), and yellow (Y) are provided for each color toner around the photoreceptor (11). Developing means (14Bk, 14C, 14M, 14Y), an intermediate transfer belt (1F) as an intermediate transfer member, and a 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 photoreceptor 11 is transferred onto the intermediate transfer belt (1F) by the first transfer means (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 has an advantage that the toner images of the respective colors are superimposed on the intermediate transfer body 1F, and thus are not limited by the transfer material. 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. If the volume resistivity of the main body 12b is 1 × 10 ¹⁰ Ω · cm or more, the discharge may be insufficient, and the surface of the photoconductor 11 may not be sufficiently charged. Conversely, this resistivity is 1 × 10. ^{When 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. As in the prior art, when rubber is used, the dimensional accuracy of the rubber changes greatly due to heat and humidity, which may affect the gap G between the charging member 12 and the photoreceptor 11.
If the distance between the charging member and the electrophotographic photosensitive member becomes too close, the charging member and the electrophotographic photosensitive member come into contact with each other, which may increase the charging noise or cause uneven charging due to abnormal discharge. In addition, if the distance between the charging member and the electrophotographic photosensitive member is too long, the charged potential on the surface of the photosensitive member 11 is lowered, and the output image may be deteriorated, for example, the background may be easily soiled.
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 is set to a range of 20 μm or more and 100 μm or less, particularly 20 to 50 μm, by a 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.
The spacer member 30 may be made of 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.
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.

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 no charged sound at a level that causes a practical problem is generated. However, in the case of non-contact, when charging is performed only with a DC voltage, uneven charging tends to occur significantly. From this, it is necessary to suppress the occurrence of charging unevenness by superimposing an AC voltage on a DC voltage and compensating for the AC voltage.
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. In addition, at 2.5 kHz or more, abnormal discharge is likely to occur, and charges trapped in the photosensitive layer of the photosensitive member lower the charging potential, destabilize the charging potential, and cause background stains. .
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, stable charging potential of the photosensitive member and increase in the residual potential of the photosensitive member due to repeated use can be moderately suppressed, but charging noise increases as Vpp increases, so 2.5 kV or less. It is hoped that. 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 without charging unevenness as the rotational speed at the time of charging is increased. However, since there are suitable ranges for the AC voltage frequency and Vpp as described above, it is preferable that the photosensitive member rotate at a rotation speed of 200 rpm or less to be charged.

  The outer diameter deflection accuracy A of the photoconductor 11 is preferably 10 μm or more and 80 μm or less, particularly 50 μm or less. As the outer diameter shake accuracy increases, color misregistration is likely to occur, and the image quality of the output image may be degraded. In order to improve the outer diameter deflection accuracy A, bearing members may be attached to the opening portions at both ends of the photoconductor 11, and a shaft penetrating the inside of the photoconductor may be provided. For example, the outer diameter deflection accuracy A can be improved by providing a resin precision bearing member with a metal precision shaft penetrating the inside of the photoreceptor.

  FIG. 6 and FIG. 7 each show a configuration example of another electrophotographic photosensitive member provided in the image forming apparatus of the present invention. FIG. 6 shows a function separation type electrophotographic photosensitive member in which the photosensitive layer is composed of a charge generation layer (CGL) and a charge transport layer (CTL). FIG. 7 shows a conductive substrate and a function separation type photosensitive member. 2 shows an electrophotographic photosensitive member in which an undercoat layer is inserted between the layers CGL and CTL. The electrophotographic photoreceptor according to the present invention may have other layers other than the above as long as it has at least a photosensitive layer on a conductive support and the outermost surface layer is a charge transport layer. Absent.

The conductive support used in the electrophotographic photosensitive member in the present invention includes 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, polyester In addition, a thin film made of a metal such as Al, Ag, Au or a conductive material such as In ² O ³ or SnO ² is formed on an insulating substrate such as polycarbonate, polyimide, or glass. 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 is not particularly limited, and any of a plate shape, a drum shape, or a belt shape can be used. However, when a belt-like support is used, it is necessary to provide a driving roller and a driven roller inside. While the equipment becomes complicated and large, there are advantages such as increased flexibility in layout. 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 having a high rigidity is preferably used as the support.

If necessary, an undercoat layer may be provided between the conductive support and the photosensitive layer. Such an undercoat layer is provided for the purpose of improving adhesiveness, preventing moire, improving the coatability of the upper layer, and reducing 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 is suitably about 0.1 to 5 μm.

The charge generation layer 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 carbazole skeleton, azo pigments having triphenylamine skeleton, azo pigments having 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.
As a binder resin used as necessary for the charge generation layer, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, Polyacrylamide or the like 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 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 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 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) Polymer having a hydrazone structure For example, JP-A-57-78402, JP-A-61-20953, JP-A-61-296358, JP-A-1-134456, JP-A-1-134456 179164, JP-A-3-180851, JP-A-3-180852, JP-A-3-50555, JP-A-5-310904, JP-A-6-234840, and the like. Is done.
(C) Polysilylene polymer 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 30 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.
In order to suppress the charging noise, when a region where the film thickness variation is within 5 μm from the central portion to the end portion in the axial direction of the photosensitive member is defined as a smooth portion, a gap holding unit between the photosensitive member and the charging member; The spacer member provided in the main body of the charging member is preferably brought into contact with a smooth portion at least 7 mm from the outermost surface coating start point of the photoreceptor and 10% from both ends of the photoreceptor. If it is at least 7 mm or less from the coating start point of the outermost layer, it is difficult to form a smooth portion even if double or multiple coating is used during coating of the charge transport layer. Further, it is often difficult to bring the spacer member into contact with the outside of the image forming area of the photosensitive member within a range of 10% or more from both ends.
FIG. 8 is a view showing one example of the film thickness shape of the upper end portion of the photoreceptor used in the present invention. The film thickness profile from the edge of the photoreceptor and the coating start position is shown. By applying the double coating, the sagging of the coating film can be suppressed, and the portion 7 mm and beyond from the coating start position is used as a smooth portion. If double coating is not performed, the profile becomes a broken line as an example, and the smooth portion is greatly reduced by sagging of the coating film.

In order to suppress charging noise when the spacer member is in contact with at least 7 mm or more from the outermost surface coating start point of the photoreceptor, the charge transporting layer can be applied by using a dip coating method as a charge transporting layer coating method. It is preferable to perform double or multiple coating only in the vicinity of the coating start point. This makes it possible to prevent coating sagging of the smooth portion after the double or multiple coating by increasing the film thickness of the charge transport layer in the vicinity of the coating start point. When coating sagging occurs and the spacer member comes into contact with at least 7 mm or more from the outermost surface coating start point of the photoreceptor, it is impossible to suppress charging noise because it includes a non-smooth range.
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 the front 30 cm of the Ipsio Color 8100 modified machine, and average the size of 1 to 4 harmonics of the charged sound to obtain the charged volume . This volume includes sounds other than charged noise such as background noise. The image quality was evaluated for the presence or absence of background stains.
<< 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 diameter of 30 mm and a longitudinal length of 340 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 (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, 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 in 100 parts by weight of tetrahydrofuran, and the following structural formula (Chemical Formula 2) is dissolved therein. 10 parts by weight of the charge transport material was added to prepare a charge transport layer coating solution. 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. When the charge transport layer is applied, the coating start point is set to 1 mm from the upper end of the conductive support, pulled up from the coating start point to 5 mm, and then dipped back to the coating start point to double it around the coating start point. Coating was performed to obtain a photoreceptor having a smooth portion from 7 mm from the coating start point, and the spacer member was brought into contact with the photoreceptor within a range of 7 mm to 15 mm from the coating start point.

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.
A bearing member is attached to the opening at both ends of the photoconductor, and includes a shaft that penetrates the inside of the photoconductor.
<< Charging member >>
A charging roller having a structure shown in FIG. 4 in which a stainless steel core shaft (φ8 mm conductive support, longitudinal length 348 mm) 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 and covered except for 15 mm on both ends of the core shaft to obtain a charging roller having a diameter of 11 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, DC voltage −450 V, and the gap G between the electrophotographic photosensitive member and the charging member was 50 μm.

<Example 2>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the spacer member was brought into contact with the photosensitive member within a range of 10 mm to 17 mm from the coating start point.
<Example 3>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the gap G was set to 100 μm.
<Example 4>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the gap G was set to 95 μm.
<Example 5>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the gap G was set to 20 μm.
<Example 6>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the gap G was set to 25 μm.
<Example 7>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that Vpp was set to 1.7 kV.
<Example 8>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that Vpp was set to 2.5 kV.
<Example 9>
In Example 1, evaluation was performed in the same manner as in Example 1 except that the film thickness of the charge transport layer (CTL) of the photoreceptor was 20 μm.
<Example 10>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the linear velocity of the photosensitive member was 77.5 mm / sec.

<Comparative Example 1>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the electrophotographic photosensitive member and the charging member were brought into contact with each other because no spacer member was provided.
<Comparative example 2>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the gap G was set to 105 μm.
<Comparative Example 3>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the gap G was set to 15 μm.
<Comparative example 4>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that only the DC voltage was applied to the charging member.
<Comparative Example 5>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the conditions of the charging member mounted on the modified Ricoh Ipsio Color 8100 were as follows.
<< Charging member >>
Using a stainless steel core shaft (φ6 mm conductive support) as a main body, a charging roller having the structure shown in FIG. 4 coated with a semiconductive elastic layer 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 6>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the spacer member was brought into contact with the non-smooth portion of the photosensitive member by not performing double coating when applying the charge transport layer. .
<Comparative Example 7>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the spacer member was brought into contact with the photoconductor within a range of at least 2 mm to 10 mm from the outermost surface coating start point of the photoconductor.
<Comparative Example 8>
In Example 1, the evaluation was performed in the same manner as in Example 1 except that the spacer member was brought into contact with the photoconductor within a range of at least 35 mm to 43 mm from the outermost surface coating start point of the photoconductor.
The evaluation results of Examples 1 to 8 and Comparative Examples 1 to 8 are shown in Table 1.

  From Table 1, it was confirmed that in the examples satisfying the constitutional requirements of the present invention, the volume of the charging sound was reduced, and an extremely high quality image with no background contamination due to charging failure was obtained. In all of the comparative examples not satisfying the requirements of the present invention, an increase in the volume of the charging sound was observed, or an abnormal image was generated due to image flaws and ground contamination due to defective charging.

1 is a schematic view of an image forming apparatus according to the present invention. It is a figure which shows the process cartridge which concerns on this invention. It is a figure which shows another example of the image forming apparatus which concerns on this invention. It is sectional drawing of the radial direction of the charging member with which charging means is equipped. 2 is a schematic view of a charging member used in the image forming apparatus of the present invention. FIG. It is a figure which shows the other structural example of the electrophotographic photosensitive member comprised by the image forming apparatus of this invention. It is a figure which shows the other structural example of the electrophotographic photosensitive member comprised by the image forming apparatus of this invention. It is a figure which shows one example of the film thickness shape of the photoreceptor upper end part used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Electrophotographic photosensitive member 12 Charging means 13 Exposure means 14 Developing means 15 Toner 16 Transfer means 17 Cleaning means 18 Image receiving medium 19 Fixing means 1A Electric discharge means 1B Pre-cleaning exposure means 1C Driving means 1D First transfer means 1E Second transfer Means 1F Intermediate transfer member 1G Image receiving medium carrier 21 Conductive support 22 Charge generation layer 23 Charge transport layer 24 Subbing layer 30 Spacer member

Claims (15)

An electrophotographic photoreceptor carrying a latent image;
Charging means for uniformly charging the surface of the image carrier;
Exposure means for exposing the surface of the charged image carrier based on image data and writing a latent image;
Developing means for supplying a toner to the latent image formed on the surface of the image bearing member to visualize the latent image;
Transfer means for transferring a visible image on the surface of the image carrier to a transfer medium;
In an image forming apparatus comprising a cleaning means for cleaning the surface of an image carrier after transfer,
An electrophotographic photosensitive member having at least a conductive support and a photosensitive layer,
An electrophotographic photosensitive member having a smooth portion with a film thickness variation of 5 μm or less from the axial center to the end of the electrophotographic photosensitive member;
The charging means includes a shaft portion and a main body portion covering the shaft portion, and the main body portion is a charging member formed of a resin containing a conductive agent,
A charging member that is disposed so as to face the electrophotographic photosensitive member in a non-contact manner, and superimposes an alternating voltage on a direct current voltage to apply and charge the electrophotographic photosensitive member in a non-contact manner.
The spacer member provided in the main body of the charging member serving as a gap holding means between the electrophotographic photosensitive member and the charging member is at least 7 mm or more from the starting point of the outermost surface coating of the electrophotographic photosensitive member, and the electrophotographic photosensitive member When the size of the gap formed between the charging member and the electrophotographic photosensitive member is G (μm) with a smooth portion in a range of 10% from both ends of the body,
20 ≦ G ≦ 100
An image forming apparatus characterized by satisfying the following relationship. The image forming apparatus according to claim 1, wherein the outermost surface layer of the electrophotographic photosensitive member is a charge transport layer. The image forming apparatus according to claim 1, wherein the charge transport layer is produced by a dip coating method. The image forming apparatus according to claim 1, wherein a solvent of the charge transport layer forming coating solution is tetrahydrofuran. 5. The coating of the flat portion of the charge transport layer is performed by double or multiple coating only in the vicinity of the outermost layer coating start point at the time of dip coating of the charge transport layer. The image forming apparatus described in 1. The image forming apparatus according to claim 1, wherein the charge transport layer has a thickness of 10 to 35 μm. The image forming apparatus according to any one of claims 1 to 6, wherein a frequency of an AC voltage supplied by the charging member to charge the electrophotographic photosensitive member is 100 Hz or more and 2.5 kHz or less. . The vibration amplitude (Vpp) of the frequency of the AC voltage supplied to charge the electrophotographic photosensitive member by the charging member is 1.0 kV or more and 3.0 kV or less. The image forming apparatus according to any one of the above. The image forming apparatus according to claim 1, wherein a volume resistivity of the main body portion of the charging member is 1 × 10 ⁵ Ω · cm to 1 × 10 ¹⁰ Ω · cm. 11. The image forming apparatus according to claim 1, wherein the electrophotographic photosensitive member includes a shaft having bearing members attached to openings at both ends and penetrating through the inside of the electrophotographic photosensitive member. 11. The electrophotographic photosensitive member operates along with the charging member during operation, and is charged while rotating at 200 rpm or less when applied by the charging member. 11. Image forming apparatus. 12. An attachment / detachment used in the image forming apparatus according to claim 1, comprising at least a charging unit and an electrophotographic photosensitive member disposed in the image forming apparatus according to any one of claims 1 to 11. Free process cartridge. The process cartridge according to claim 12, further comprising at least one of an exposure unit, a development unit, and a transfer unit disposed in the image forming apparatus according to claim 1. 12. 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. An image forming apparatus comprising a plurality of process cartridges according to claim 12 or 13.

Images