JP2006235240A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing a charging sound and forming a high definition image and a process cartridge attachable and detachable to and from the image forming apparatus. <P>SOLUTION: Regarding the image forming apparatus, a photoreceptor 11 has a first region successively laminated with at least an under coating layer, a charge generating layer and a charge transfer layer on a conductive support and a second region provided with an under coating layer on the conductive support. The photoreceptor and a charging member 12 are disposed to face each other apart a distance of ≥20 to ≤100 μm. A spacer member 5 for holding the distance between the photoreceptor and the charging member is made to abut on the second region and is disposed in a main part section. The charging bias applied to the charging member is a DC voltage superposed with an AC voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus and a process cartridge.

  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, development, Each means such as transfer, separation, cleaning, and static elimination is 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 V by charging means. There are two types of voltage applied to the charging means: a DC voltage and a DC voltage on which an AC voltage is superimposed. Normally, image formation with no practical problem is possible with only a DC voltage, but by superimposing an AC voltage on the DC voltage, it becomes less susceptible to environmental conditions. In addition, it is possible to reduce the potential unevenness caused by the charging member, the unevenness of the photosensitive member, the minute unevenness of the member, and the like, which are generated when the contact charging method is used.

The charging method generally used 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 with a diameter of 40 to 80 μm that is mounted in a shield case, and a photoreceptor. A corona charging method for charging a roller member having a resistance of about 10 ² to 10 ⁸ Ω · cm, a brush shape charging member, etc., a direct current voltage of −1200 to −2000 V or a direct current voltage of −500 to −900 V to 1000 A contact charging method in which the photosensitive member is charged while applying a voltage in which an alternating voltage of 500 to 4500 Hz is superimposed at 2500 V, or the charging member and the photosensitive member are arranged close to each other by about 30 to 250 μm, and a voltage similar to the above is applied. There is a non-contact charging method in which the photosensitive member is charged by applying it.

  In the corona charging method, since a high voltage is applied, ozone having a high concentration of around 10 ppm is generated. Therefore, there is an environmental problem due to ozone odor. For this reason, in recent years, a contact charging method capable of being charged 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 that applies a DC voltage on which an AC voltage is superimposed on a charging member.

  However, when a DC voltage superimposed with an AC voltage is applied to the charging means, in addition to the generation of ozone and nitrogen oxides that are the cause of image quality deterioration, an irritating charging noise is generated during charging. There's a problem. This charging sound is hardly a problem with a DC voltage, and is a phenomenon peculiar to an AC voltage because it is called an oscillating current. The larger the amplitude, the more easily the material that the support of the photoreceptor is susceptible to, Charging noise increases. Therefore, it is desirable to set the conditions for low charging noise, but there is a problem that charging noise increases when charging stability is increased.

  As means for improving this phenomenon, methods such as insertion of a damping material (filler) into the inside of the drum-shaped photoconductor, increase of the film thickness of the support of the photoconductor, and improvement of the charging member 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 for the ears to be felt, 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 method of press-fitting a buffer material inside the photosensitive drum (see Patent Document 1), photosensitive A method of filling a body with a viscoelastic material (see Patent Document 2), a method of inserting a rigid body having a density of 2.0 g / cm ³ or more into the interior of a photoreceptor (see Patent Document 3), and two or more elastic bodies ( A method of inserting a member composed of an O-ring) and a cylindrical member (polybutylene terephthalate resin containing 20% or more of glass fiber having a specific gravity of 1.5 or more) into a photoreceptor (see Patent Document 4) and metal A method of inserting a resin cylindrical member with a built-in spring and fixing it to the wall of the photosensitive body with a pressing force is known (see Patent Document 5).

Further, as a method of increasing the vibration damping effect by increasing the film thickness of the photoconductor support, the photoconductor support has an inlay, and the thickness other than the inlay is 1.9 mm or more. A method for obtaining an effect (see Patent Document 6) and a method for obtaining 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 (see Patent Document 7) are known. It has been.

  Further, as a method of improving the charging member to achieve charging noise suppression, 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 core metal is inserted through the elastic body. There is known a method (see Patent Document 8) for improving the charging sound by adopting a structure that supports the structure. The countermeasure method for charging sound differs 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.

Even if the above method is improved by the contact charging method, it may be difficult to obtain the effect by the non-contact charging method in which the charging member is disposed in close proximity to the photosensitive member. 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 charging noise by inserting a filler inside the support of the photosensitive member is easy to obtain the effect, but even if it is simply inserted, there is a gap between the support and the insert. In such a case, it is difficult to obtain an effect when the weight is small. 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.
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)

  SUMMARY OF THE INVENTION In view of the above-described problems of the prior art, the present invention provides an image forming apparatus capable of suppressing charging noise and forming a high-quality image, and a process cartridge that is detachable from the image forming apparatus. Objective.

  The invention according to claim 1 is an image forming apparatus having at least a photosensitive member and a charging member whose shaft portion is covered with a main body portion made of a resin containing a conductive agent, wherein the photosensitive member has a conductive support. At least a first region in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on the body, and a second region in which the undercoat layer is provided on the conductive support. The photosensitive member and the charging member are provided to face each other with a distance of 20 μm or more and 100 μm or less, and the spacer member that holds the distance between the photosensitive member and the charging member is the second region. And the charging bias applied to the charging member is a DC voltage on which an AC voltage is superimposed.

  According to the first aspect of the present invention, the photoconductor includes at least a first region in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive support; A second region in which the undercoat layer is provided on a conductive support, and the photoconductor and the charging member are provided to face each other with a distance of 20 μm to 100 μm. A spacer member that maintains a distance between the charging member and the charging member is in contact with the second region and is provided in the main body, and an AC voltage is superimposed on the charging bias applied to the charging member. Therefore, it is possible to provide an image forming apparatus capable of suppressing charging noise and forming a high-quality image.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the second region further includes the charge generation layer.

  According to the second aspect of the present invention, since the second region further includes the charge generation layer, charging noise can be suppressed and a high-quality image can be formed.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the frequency of the AC voltage is 100 Hz to 2.5 kHz.

  According to the invention described in claim 3, since the frequency of the AC voltage is 100 Hz or more and 2.5 kHz or less, it is possible to suppress the occurrence of uneven charging and background contamination.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the AC voltage has an amplitude of 1.0 kV to 3.0 kV.

  According to the fourth aspect of the invention, since the amplitude of the AC voltage is 1.0 kV or more and 3.0 kV or less, a stable charged potential of the photosensitive member can be obtained.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the volume resistivity of the main body portion is 1 × 10 ⁵ Ω · cm or more and 1 × 10 ¹⁰ Ω · It is characterized by being cm or less.

According to the invention described in claim 5, since the volume resistivity of the main body is 1 × 10 ⁵ Ω · cm or more and 1 × 10 ¹⁰ Ω · cm or less, the abnormal discharge is suppressed and the photosensitive member is charged. Can be made.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the photosensitive member has a cylindrical shape and a shaft, and the bearing member that receives the shaft is It is provided in openings at both ends of the photoconductor.

  According to the sixth aspect of the present invention, the photoconductor has a cylindrical shape and a shaft, and the bearing members that receive the shaft are provided in the openings at both ends of the photoconductor. The outer diameter deflection accuracy of the body can be improved.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the photoconductor has a cylindrical shape, and the charging member is used to charge the photoconductor. The rotational speed of the photosensitive member is 30 rpm or more and 200 rpm or less.

  According to the invention of claim 7, the photoconductor has a cylindrical shape, and the rotation speed of the photoconductor when the charging member charges the photoconductor is 30 rpm or more and 200 rpm or less, Uneven charging can be suppressed.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the second region has a distance from both ends of the photoconductor. It is characterized by being provided in a region that is within 10% of the above.

  According to the invention described in claim 8, the second region is provided in a region where the distance from both ends of the photoconductor is within 10% of the distance between both ends of the photoconductor. An image can be formed.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the image forming apparatus further includes a developing unit having a toner containing inorganic particles having an average particle diameter of 70 nm to 300 nm. It is characterized by that.

  According to the ninth aspect of the present invention, the image forming apparatus further includes a developing unit having a toner containing inorganic particles having an average particle diameter of 70 nm or more and 300 nm or less, so that a good image can be formed.

  A tenth aspect of the present invention is the process cartridge according to any one of the first to ninth aspects, wherein the process cartridge includes at least one of a charging unit having a charging member, an exposure unit, a developing unit, and a transfer unit, and a photosensitive member. The image forming apparatus is detachable.

  According to the tenth aspect of the present invention, since it is detachable from the image forming apparatus according to any one of the first to ninth aspects, it is possible to suppress charging noise and form a high-quality image. A process cartridge can be provided.

  According to an eleventh aspect of the present invention, an image forming apparatus includes the process cartridge according to the tenth aspect.

  According to the eleventh aspect of the present invention, since the process cartridge according to the tenth aspect is provided, an image forming apparatus capable of suppressing charging noise and forming a high quality image can be provided.

  According to the present invention, it is possible to provide an image forming apparatus capable of suppressing charging noise and forming a high-quality image, and a process cartridge that can be attached to and detached from the image forming apparatus.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing an example of an image forming apparatus according to the present invention, and modifications as will be described later also belong to the category of the present invention.

  The photoconductor 11 may be a sheet shape or a belt shape, but in order to improve the accuracy of the photoconductor, a cylindrical shape (drum shape) is preferable. As the charging member 12, a charging roller is used, and the charging member 12 is disposed to face the photosensitive member 11 with a distance G therebetween.

  The transfer means 16 can generally use the above-mentioned charging roller or wire charger as a transfer member, but a combination of a transfer charger and a separation charger is effective.

  Further, as a light source used for the exposure means 13, the charge removal means 20, etc., a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), an electroluminescence (EL), etc. Listed are all luminescent materials. At this time, various 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 photosensitive member by the developing unit 14 is transferred to the image receiving medium 18, but toner remaining on the photosensitive member without being transferred is also generated. Such toner is removed from the photoreceptor using the cleaning means 17. Examples of the cleaning means 17 include rubber cleaning blades, fur brushes, and mag fur brushes.

  By using at least toner containing inorganic particles having an average particle diameter of 70 nm or more and 300 nm or less in the developing unit 14, a high-quality image can be output.

  When the photoreceptor 11 is positively (or negatively) charged and image exposure is performed, an electrostatic latent image is formed on the surface of the photoreceptor 11. If this is developed with negative (or positive) charged toner, a positive image can be obtained. Further, if the toner is developed with positive (or negative) charged toner, a negative image can be obtained. As the developing unit 14 and the charge eliminating unit 20, known ones can be used.

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

  The image forming apparatus of the present invention may be fixedly incorporated in a copying machine, a facsimile machine, or a printer. On the other hand, a process cartridge may be incorporated in the image forming apparatus of the present invention. The process cartridge is an apparatus (part) that contains the photoconductor 11 and includes at least one of a charging unit 12, an exposure unit 13, a developing unit 14, a transfer unit 16, a cleaning unit 17, and a charge eliminating unit 20. . FIG. 2 shows an example of the process cartridge of the present invention.

  FIG. 3 shows another example of the image forming apparatus of the present invention. The image forming apparatus includes a charging member 12, an exposure unit 13, black (Bk), cyan (C), magenta (M), and yellow (Y) toner developing units 14 Bk, 14 C, and 14 M around a photosensitive member 11. 14Y, an intermediate transfer belt 23 as an intermediate transfer member, and a cleaning unit 17 are arranged in this order.

  The developing means 14Bk, 14C, 14M and 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 23 by the first transfer means 21 disposed inside the intermediate transfer belt 23. The first transfer means 21 is arranged so as to be able to come into contact with and separate from the photoconductor 11 and causes the intermediate transfer belt 23 to contact the photoconductor 11 only during the transfer operation. The image of each color is sequentially formed, and the toner images superimposed on the intermediate transfer belt 23 are collectively transferred to the image receiving medium 18 by the second transfer unit 22 and then fixed by the fixing unit 19 to form an image. The The second transfer means 22 is also arranged so as to be able to contact and separate from the intermediate transfer belt 23 and contacts the intermediate transfer belt 23 only during the transfer operation.

  In the transfer drum type image forming apparatus as shown in FIG. 1, since the toner images of the respective colors are sequentially transferred onto the image receiving medium 18 electrostatically attracted to the transfer drum, there is a limitation that transfer onto a cardboard is difficult. On the other hand, the image forming apparatus of the intermediate transfer system as shown in FIG. 3 has a feature that the toner image of each color is superimposed on the intermediate transfer member 23 and thus is not limited by the image receiving medium 18. Such an intermediate transfer method can be applied not only to the image forming apparatus shown in FIG. 3 but also to the image forming apparatus shown in FIG. 1 and the process cartridge shown in FIG.

FIG. 4 is an example of a cross-sectional view of the charging member 12 used in the present invention. The charging member 12 has a shaft portion 12a at the center and a main body portion 12b on the outside thereof. The material of the shaft portion 12a is a metal having high rigidity and conductivity, such as stainless steel or aluminum, and has high rigidity with a volume resistivity of 1 × 10 ³ Ω · cm or less, preferably 1 × 10 ² Ω · cm or less. Examples thereof include conductive resins. Moreover, it is preferable that the diameter of the axial part 12a is 8-20 mm. The volume resistivity of the main body portion 12b is preferably 1 × 10 ⁵ to 1 × 10 ¹⁰ Ω · cm. If the volume resistivity exceeds 1 × 10 ¹⁰ Ω · cm, the discharge becomes insufficient and the surface of the photoreceptor 11 cannot be sufficiently charged. Further, when the volume resistivity is smaller than 1 × 10 ⁵ Ω · cm, 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, and abnormal discharge occurs. Overcurrent enlarges the pinhole and causes an abnormal image to be output. Moreover, it is preferable that the film thickness of the main-body part 12b is about 1-2 mm.

  The main body 12b shown in FIG. 4 has a single-layer structure, but is not limited to this structure, and may have two or more layers.

  Although rubber such as hydrin rubber may be used for the main body portion 12b, it is preferable to use a material whose electric resistance is adjusted by mixing a conductive agent with a resin having a lower expansion coefficient than rubber. 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. If rubber is used, the dimensional accuracy of the rubber may change due to heat or humidity, which may affect the distance G between the charging member and the photoreceptor (hereinafter referred to as distance G).

  Examples of the resin used for the main body portion 12b include olefin resins such as polyethylene and polypropylene, styrene resins such as polystyrene and copolymers thereof, and acrylic resins such as polymethyl methacrylate. In order to improve strength and dimensional accuracy, the resin may be mixed with ceramics such as carbon fiber, glass fiber, carbide, boride and the like in addition to the conductive agent. Thereby, an expansion coefficient can be made small. 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, Examples thereof include metal powder such as silver powder and copper powder, and ceramic powder such as ITO.

  FIG. 5 shows a schematic diagram of a photoreceptor and a charging member used in the image forming apparatus of the present invention. Spacer members 51 having a certain thickness are provided at both ends of the main body 12 b of the charging member 12. The distance G can be maintained by bringing the spacer member 51 into contact with the contact portion 11a. The distance G can also be adjusted by the thickness of the layer formed above the charge transport layer and the charge transport layer.

  The distance G is maintained at 20 to 100 μm by the spacer member 51, but 20 to 50 μm is preferable. Thereby, formation of an abnormal image at the time of operation of the charging device can be suppressed. When the distance G is greater than 100 μm, the charged potential on the surface of the photoreceptor is lowered, so that the background of the output image is likely to be stained, and the image quality of the output image may be lowered. Further, when the distance G is less than 20 μm, the deposit on the surface of the photosensitive member that has not been removed by the cleaning means comes into contact with the charging member, so that a part thereof is transferred to the charging member and causes uneven charging. There is. Further, the charging noise may increase due to contact between the charging member and the photosensitive member.

  Since the undercoat layer and the charge generation layer are less likely to be scratched by contact with the spacer member than the charge transport layer, variation in the distance G is reduced by using the contact portion 11a as the undercoat layer or the charge generation layer. It is possible to suppress the increase in charging noise and the occurrence of soiling. When the contact portion 11a is a charge generation layer, the charge generation layer is more easily scratched than the undercoat layer. However, the charge generation layer is usually 0.5 μm or less in thickness and is a thin film compared to the undercoat layer. Therefore, it is possible to obtain substantially the same effect as when the spacer member 51 is in contact with the undercoat layer. Note that at least an undercoat layer needs to be formed on the contact portion 11a in order to suppress leakage when charging the photosensitive member.

  By making the contact portion 11a a region where the distance from both ends of the photoreceptor is within 10% of the distance between both ends of the photoreceptor, the spacer member 51 is brought into contact with a region other than the image forming portion 11b of the photoreceptor. This makes it easy to form a good image. In addition, since it is possible to reduce the area other than the image forming unit 11b of the photoconductor, it is possible to contribute to resource saving.

  Examples of the material of the spacer member 51 include olefin resins such as polyethylene and polyolefin, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, and fluorine resins such as polytetrafluoroethylene. In addition, an elastic metal or rubber can be used. Examples of the metal include aluminum, iron, copper, titanium, and alloys mainly composed of these. In addition, it is preferable to coat the surface of the metal spacer member 51 with an oxide to make it insulating. In order to reduce the amount of wear of the photoreceptor, it is preferable to coat the surface of the metal spacer member 51 with a resin. Examples of the rubber include natural rubber, polyurethane rubber, chloroprene rubber, nitrile-butadiene rubber, silicone rubber, and fluorine rubber. The rubber hardness (JIS-A) is preferably 70 Hs or more, and silica, alumina, glass fiber or the like can be added. Thereby, the fluctuation | variation of the distance G can be suppressed.

  When charging the photosensitive member with the charging member disposed opposite to the photosensitive member, the charging bias applied to the charging member is sufficient for practical use with only a DC voltage when the photosensitive member and the charging member are in contact with each other. Therefore, a level of charging sound that causes a problem in practical use does not occur. However, when the photosensitive member and the charging member are not in contact with each other, charging unevenness is likely to occur if only the DC voltage is used for charging. For this reason, 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 100 Hz to 2.5 kHz. When the frequency is less than 100 Hz, the AC voltage does not sufficiently act on the photosensitive member, and thus charging unevenness is likely to occur and abnormal images are likely to occur. If the frequency is higher than 2.5 kHz, abnormal discharge is likely to occur, and the charges trapped in the photosensitive layer of the photosensitive member lower the charging potential, making the repeated characteristics of the charging potential unstable. Dirt is likely to occur.

  A suitable value of the frequency of the AC voltage applied to the charging member varies depending on the linear velocity of the photosensitive member, but the frequency of the AC voltage to be applied may be set to 800 Hz or more and 2 kHz or less.

  The amplitude of the AC voltage is preferably 1.0 to 3.0 kV. As a result, a stable charged potential of the photoreceptor can be obtained, and an increase in the residual potential of the photoreceptor due to repeated use can be suppressed. Note that the amplitude is more preferably 2.5 kV or less because the charged sound is further reduced. Further, since the charging of the photosensitive member may be partially insufficient, the amplitude is more preferably 1.3 kV or more.

  In the present invention, it is preferable that the frequency and amplitude of the AC voltage are large in order to suppress uneven charging of the photosensitive member when the rotational speed of the photosensitive member during charging is high. However, in order to set the frequency and amplitude of the AC voltage within the above range, the rotational speed at the time of charging the photoreceptor is preferably 30 rpm or more and 200 rpm or less.

  The outer diameter fluctuation accuracy of the photoreceptor is preferably 10 to 80 μm, and particularly preferably 10 to 50 μm. As the outer diameter shake accuracy increases, color misregistration is likely to occur, and the image quality of the output image is likely to deteriorate. In order to improve the outer diameter deflection accuracy, it is preferable that bearing members are attached to the openings at both ends of the photoconductor, and a shaft that penetrates the inside of the photoconductor is provided. For example, it is possible to improve the outer diameter deflection accuracy by providing a resin precision bearing member with a metal precision shaft penetrating the inside of the photoreceptor. As a result, the distance G can be stabilized, charging noise can be suppressed, and the quality of the output image can be improved.

  FIG. 6 shows an example of the configuration of the image forming unit in FIG. Here, an undercoat layer 62 is provided between the photosensitive layer composed of the charge generation layer 63 and the charge transport layer 64 and the conductive support 61. The image forming portion of the photoreceptor used in the present invention is formed by applying at least the undercoat layer 62, the charge generation layer 63, and the charge transport layer 64 in this order on the conductive support 61. Any other layer may be formed.

  In the present invention, as the conductive support used for the photoreceptor, a conductor or an insulator subjected to a conductive treatment can be used. Specific examples of the conductive support include metals such as aluminum, nickel, iron, copper, and gold or alloys thereof, polyester resin, polycarbonate resin, polyimide resin, glass and other insulators such as aluminum, silver, and gold. A thin film made of a conductive material such as metal or indium oxide or tin oxide, carbon black, graphite, aluminum, copper, nickel, conductive glass powder or the like dispersed uniformly in a resin, and imparted conductivity, Examples include paper subjected to a conductive treatment. 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-shaped support is used, it is necessary to provide a driving roller and a driven roller inside. However, there is an advantage that the degree of freedom of layout is increased while the apparatus is complicated and enlarged. However, when the protective layer is formed, the protective layer is not flexible enough to cause cracks on the surface, which may cause granular soiling. For this reason, a highly rigid drum shape is preferably used as the conductive support.

  In the present invention, an undercoat layer is provided between the conductive support and the photosensitive layer. The undercoat layer is provided for the purpose of improving adhesiveness, suppressing moire, improving coatability of the photosensitive layer, and reducing residual potential. The undercoat layer generally contains a resin as a main component. However, since the photosensitive layer is applied onto the undercoat layer using a solvent, it is preferable to use a resin having high solvent resistance. 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 resins, melamine resins, alkyd-melamine resins, and epoxy resins. And a curable resin that forms a three-dimensional network structure. Further, fine powders such as metal oxides such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide, metal sulfides, and metal nitrides may be added to the undercoat layer. The undercoat layer can be formed by using a commonly used coating method using an appropriate solvent.

  In addition, 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 an undercoat layer, an aluminum oxide provided by anodizing aluminum, an organic substance such as polyparaxylylene (parylene) provided by using a vacuum thin film preparation method, tin oxide, titanium oxide, ITO And inorganic substances such as cerium oxide.

  The thickness of the undercoat layer is preferably about 0.1 to 5 μm.

  The charge generation layer is a layer mainly composed of a charge generation material, and a binder resin can be used as necessary. An inorganic material and an organic material can be used as the charge generation material.

  Examples of the inorganic material include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, and selenium-arsenic compounds.

  A known material can be used as the organic material. Specifically, 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, An azo pigment having a dibenzothiophene skeleton, an azo pigment having a fluorenone skeleton, an azo pigment having an oxadiazole skeleton, an azo pigment having a bisstilbene skeleton, an azo pigment having a distyryloxadiazole skeleton, an azo having a distyrylcarbazole skeleton Pigments, perylene pigments, anthraquinone and polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, a Jigoido based pigments, bisbenzimidazole pigments. These charge generation materials can be used alone or as a mixture of two or more.

  Binder resins used as necessary for the charge generation layer include polyamide resins, polyurethane resins, epoxy resins, polyketones, polycarbonate resins, silicone resins, acrylic resins, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly (N -Vinylcarbazole), polyacrylamide and the like are used. These binder resins can be used alone or as a mixture of two or more.

  In addition, a charge transport material may be added to the charge generation layer as necessary. In addition to the binder resin described above, a polymer charge transport material is also preferably used as the binder resin for the charge generation layer.

  Examples of the method for forming the charge generation layer include a vacuum thin film preparation method and a casting method from a solution dispersion system.

  Examples of the vacuum thin film preparation 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 be applied to the inorganic material or organic material described above.

  In addition, as a casting method, the above-described inorganic material or organic material may be used together with a binder resin in a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone, if necessary, using a ball mill, an attritor, a sand mill, or the like. The method of apply | coating after diluting the liquid obtained by melt | dissolving or disperse | distributing moderately is mentioned. The coating can be performed using a dip coating method, a spray coating method, a bead coating method, or the like. The thickness of the charge generation layer is usually 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 obtain a good output image, it is required to hold a charged charge, and it is preferable that the electric resistance is high. In addition, in order to obtain a high surface potential with the charged charge held, it is preferable that the dielectric constant is small and the charge mobility is good.

  The charge transport layer is composed of a charge transport material and a binder resin used as necessary. The charge transport layer can be formed by dissolving or dispersing a charge transport material in a suitable solvent together with a binder resin, if necessary, and applying and drying it.

  Examples of the charge transport material include a hole transport material and an electron transport material.

  Electron transport materials include chloroanil, bromoanil, 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] thiophen-4-one, 1,3,7-trinitro Examples thereof include electron accepting substances such as dibenzothiophene-5,5-dioxide. These electron transport materials can be used alone or as a mixture of two or more.

  As hole transport materials, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styryl Examples thereof include electron donating substances such as anthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, and thiophene derivatives. These hole transport materials can be used alone or as a mixture of two or more.

  Examples of the polymer charge transport material include a polymer having a carbazole ring, a polymer having a hydrazone structure, a polysilylene, and a polymer having a triarylamine structure.

  Examples of the polymer having a carbazole ring include poly (N-vinylcarbazole), JP-A-50-82056, JP-A-54-9632, JP-A-54-11737, and JP-A-4-175337. Examples thereof include compounds described in JP-A-4-183719 and JP-A-6-234841.

  Examples of the polymer having a hydrazone structure include JP-A-57-78402, JP-A-61-20953, JP-A-61-296358, JP-A-1-134456, and JP-A-1-179164. Examples thereof include compounds described in JP-A-3-180851, JP-A-3-180852, JP-A-3-50555, JP-A-5-310904, and JP-A-6-234840. .

  Examples of polysilylene include JP-A-63-285552, JP-A-1-88461, JP-A-4-264130, JP-A-4-264131, JP-A-4-264132, and JP-A-4-264133. And the compounds described in JP-A-4-289867.

  Examples of the polymer having a triarylamine structure include N, N-bis (4-methylphenyl) -4-aminopolystyrene, JP-A-1-134457, JP-A-2-282264, and JP-A-2-304456. Examples thereof include compounds described in JP-A-4-133065, JP-A-4-133066, JP-A-5-40350, and JP-A-5-202135. Further, as polycarbonate resins, polyurethane resins, polyester resins, and polyether resins having a triarylamine structure, JP-A 64-1728, JP-A 64-13061, JP-A 64-19049, JP-A-4-11627, JP-A-4-225014, JP-A-4-230767, JP-A-4-320420, JP-A-5-232727, JP-A-7-56374, JP Examples thereof include compounds described in JP-A-9-127713, JP-A-9-222740, JP-A-9-265197, JP-A-9-211877, JP-A-9-30495, and the like.

  Examples of polymers other than those described above include formaldehyde condensation polymers of nitropyrene, JP-A-51-73888, JP-A-56-150749, JP-A-6-234836, and JP-A-6-234837. These compounds are exemplified.

  Examples of the polymer charge transport material used in the present invention include known monomer copolymers, block copolymers, graft copolymers, star polymers, and electron donating properties disclosed in JP-A-3-109406. It is also possible to use a crosslinked polymer having a group.

  As binder resins that can be used for the charge transport layer, polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polyethylene, polyvinyl chloride, polyvinyl acetate, polystyrene, phenol resin, epoxy resin, polyurethane resin, 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 usually about 5 to 100 μm. However, in order to achieve a high image quality of 1200 dpi or more in order to achieve a high image quality of 1200 dpi or more, a reduction in film thickness has been achieved in recent years. About 35 μm is preferable.

  You may add additives, such as antioxidant used for rubber | gum, a plastics, fats and oils, a plasticizer, to a charge transport layer. Further, a leveling agent may be added to the charge transport layer. Examples of the leveling agent include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, resins having a perfluoroalkyl group in the side chain, and the addition amount is usually 0 with respect to 100 parts by weight of the binder resin. -1 part by weight.

Example 1
The photoreceptor 11 was produced as follows.

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

  The undercoat layer coating solution is applied to cylindrical aluminum (conductive support) having an outer diameter of 30 mm and a longitudinal length of 340 mm using a dip coating method, and dried at 130 ° C. for 20 minutes. An undercoat layer having a thickness of 4.5 μm was formed.

  Next, after dissolving 4 parts by weight of polyvinyl butyral resin XYHL (UCC) in 150 parts by weight of cyclohexanone, chemical structural formula

で示されるビスアゾ顔料１０重量部を加え、ボールミルで４８時間分散させた後、さらにシクロヘキサノン２１０重量部を加えて３時間分散させた。これを容器に取り出し、固形分が１．５重量％となるようにシクロヘキサノンで希釈し、電荷発生層用塗工液を作製した。

10 parts by weight of a bisazo pigment represented by the formula (1) was added and dispersed by a ball mill for 48 hours, and then 210 parts by weight of cyclohexanone was further 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 to prepare a charge generation layer coating solution.

  With the contact portion 11a sealed, the charge generation layer coating solution is spray-coated on the undercoat layer and dried at 130 ° C. for 20 minutes to form a charge generation layer having a thickness of 0.2 μm. did.

  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.

で示される電荷輸送物質１０重量部を加えて電荷輸送層用塗工液を作製した。当接部１１ａにシールを施した状態で、電荷発生層上に電荷輸送層用塗工液をスプレー塗工し、１１０℃で２０分間乾燥し、膜厚が３１μｍの電荷輸送層を形成した。

A charge transport layer coating solution was prepared by adding 10 parts by weight of a charge transport material represented by the following formula. With the contact portion 11a sealed, the charge transport layer coating solution was spray-coated on the charge generation layer and dried at 110 ° C. for 20 minutes to form a charge transport layer having a thickness of 31 μm.

  Note that bearing members are attached to openings at both ends of the photoconductor, and include shafts that penetrate the inside of the photoconductor.

  The charging member 12 was produced as follows.

A core shaft made of stainless steel and having a diameter of 6 mm was used as the shaft portion 12a. The main body 12b is 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 and adjusting the volume resistivity to 1 × 10 ⁸ to 1 × 10 ⁹ Ω · cm. Was formed by molding with an extruder, and the core shaft was covered. As a result, a charging roller having a diameter of 14 mm was obtained.

  A heat-shrinkable fluororesin was used for the spacer member.

  The photoreceptor 11 and the charging member 12 described above were mounted on a modified Ipsio Color 8100 (manufactured by Ricoh). As the toner, at least inorganic particles having an average particle size of 70 to 300 nm and an average particle size of 5.9 μm were used.

  The potentials of the image portion and the non-image portion of the image forming portion 11b of the photoconductor 11 were set to −50 V and −500 V, respectively, and the rotation speed of the photoconductor 11 during charging was set to 100 rpm. Further, the charging bias applied to the charging member 12 was set such that the frequency of the AC voltage was 1.1 kHz, the amplitude was 2.0 kV, and the DC voltage was −450 V. The distance G was 50 μm.

Under these conditions, after printing 50,000 sheets of rectangular patch and character mixed images with an image density of 5%, the mixed images are printed, and 30 cm away from the front of the Ipsio Color 8100 remodeling machine. The sound volume was measured, and the magnitude of 1 to 4 harmonics of the charged sound was averaged to obtain the charged sound volume. This volume includes sounds other than the charged sound such as background noise. The image quality was evaluated for the presence or absence of background stains.
(Example 2)
Evaluation was performed in the same manner as in Example 1 except that when the charge generation layer was applied, the contact portion 11a was not sealed and the charge generation layer was formed on the contact portion 11a.
(Example 3)
Evaluation was performed in the same manner as in Example 1 except that the distance G was set to 100 μm.
Example 4
Evaluation was performed in the same manner as in Example 1 except that the distance G was 95 μm.
(Example 5)
Evaluation was performed in the same manner as in Example 1 except that the distance G was 20 μm.
(Example 6)
Evaluation was performed in the same manner as in Example 1 except that the distance G was 25 μm.
(Example 7)
Evaluation was performed in the same manner as in Example 1 except that the amplitude of the AC voltage of the charging bias was 1.7 kV.
(Example 8)
Evaluation was performed in the same manner as in Example 1 except that the amplitude of the AC voltage of the charging bias was 2.5 kV.
Example 9
Evaluation was performed in the same manner as in Example 1 except that the thickness of the charge transport layer of the photoreceptor 11 was 20 μm.
(Example 10)
Evaluation was performed in the same manner as in Example 1 except that the rotation speed of the photoconductor 11 during charging was set to 50 rpm.
(Comparative Example 1)
Evaluation was performed in the same manner as in Example 1 except that the spacer member 51 was not provided and the photosensitive member 11 and the charging member 12 were brought into contact with each other.
(Comparative Example 2)
Evaluation was performed in the same manner as in Example 1 except that the distance G was set to 105 μm.
(Comparative Example 3)
Evaluation was performed in the same manner as in Example 1 except that the distance G was set to 15 μm.
(Comparative Example 4)
Evaluation was performed in the same manner as in Example 1 except that the charging bias was only DC voltage.
(Comparative Example 5)
The charging member 12 was produced as follows.

As the shaft portion 12a, a stainless steel core shaft having a diameter of 6 mm was used. The main body 12b is composed of 100 parts by weight of a thermoplastic elastomer containing a polyester component and 0.5 parts by weight of lithium perchlorate, and has a volume resistivity of 1 × 10 ⁸ Ω · cm to 1 × 10 ⁹ Ω · cm. The composition prepared as described above was formed by molding with an extruder, and the core shaft was covered. As a result, a charging roller having a diameter of 14 mm was obtained.

Evaluation was performed in the same manner as in Example 1 except that the charging member 12 was used.
(Comparative Example 6)
Evaluation was performed in the same manner as in Example 1 except that when the charge generation layer and the charge transport layer were applied, the contact portion 11a was not sealed and the charge generation layer and the charge transport layer were formed on the contact portion 11a. Went.
(Comparative Example 7)
Evaluation was performed in the same manner as in Example 1 except that when the undercoat layer was applied, the contact portion 11a was sealed and the undercoat layer was not formed on the contact portion 11a.
(Evaluation results)
The evaluation results of Examples 1 to 10 and Comparative Examples 1 to 7 are shown in Table 1.

表１から、本発明の構成要件を満たす実施例では帯電音の音量の低減が見られ、帯電不良による地汚れが見られない極めて高画質な画像を得られることが確認された。本発明の要件を満たしていない比較例は、いずれも帯電音の音量の増大が見られるか、帯電不良による地汚れが見られ、異常画像が発生した。

From Table 1, it was confirmed that in the examples satisfying the constitutional requirements of the present invention, the volume of the charged sound was reduced, and it was possible to obtain an extremely high-quality image with no background stain due to charging failure. 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 scumming due to poor charging was observed, and an abnormal image was generated.

It is a figure which shows an example of the image forming apparatus of this invention. It is a figure which shows an example of the process cartridge of this invention. It is a figure which shows another example of the image forming apparatus of this invention. It is a figure which shows an example of the cross section of the charging member used by this invention. It is a figure which shows an example of the photoreceptor and charging member which are used by this invention. FIG. 6 is a diagram illustrating an example of a configuration of an image forming unit in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Photoconductor 11a Contact part 11b Image formation part 12 Charging member 12a Shaft part 12b Main body part 13 Exposure means 14, 14Bk, 14C, 14M, 14Y Developing means 15 Toner 16 Transfer means 17 Cleaning means 18 Image receiving medium 19 Fixing means 20 Static elimination Means 21 First transfer means 22 Second transfer means 23 Intermediate transfer belt 51 Spacer member 61 Conductive support 62 Subbing layer 63 Charge generation layer 64 Charge transport layer

Claims (11)

In an image forming apparatus having at least a photosensitive member and a charging member whose shaft portion is covered with a main body portion made of a resin containing a conductive agent,
The photoreceptor includes a first region in which at least an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive support, and the undercoat layer is provided on the conductive support. Has a second region,
The photoconductor and the charging member are provided facing each other with a distance of 20 μm or more and 100 μm or less,
A spacer member that holds the distance between the photosensitive member and the charging member is in contact with the second region and is provided in the main body.
The image forming apparatus according to claim 1, wherein the charging bias applied to the charging member is a DC voltage on which an AC voltage is superimposed.   The image forming apparatus according to claim 1, wherein the second region further includes the charge generation layer.   The image forming apparatus according to claim 1, wherein the frequency of the AC voltage is 100 Hz to 2.5 kHz.   The image forming apparatus according to claim 1, wherein an amplitude of the AC voltage is 1.0 kV or more and 3.0 kV or less. 5. The image forming apparatus according to claim 1, wherein the main body has a volume resistivity of 1 × 10 ⁵ Ω · cm to 1 × 10 ¹⁰ Ω · cm. The photoreceptor has a cylindrical shape and an axis,
The image forming apparatus according to claim 1, wherein the bearing member that receives the shaft is provided in openings at both ends of the photoconductor. The photoconductor has a cylindrical shape,
The image forming apparatus according to claim 1, wherein a rotation speed of the photoconductor when the charging member charges the photoconductor is 30 rpm or more and 200 rpm or less.   7. The second area is provided in an area where a distance from both ends of the photoconductor is within 10% of a distance between both ends of the photoconductor. The image forming apparatus described in 1.   The image forming apparatus according to claim 1, further comprising a developing unit having a toner containing inorganic particles having an average particle diameter of 70 nm to 300 nm. In a process cartridge having at least one of charging means having a charging member, exposure means, developing means, and transfer means, and a photosensitive member,
A process cartridge which is detachable from the image forming apparatus according to claim 1.   An image forming apparatus comprising the process cartridge according to claim 10.

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