JP2006119528A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method for obtaining a stable image over a long period under any environment including an environment of low temperature and low humidity. <P>SOLUTION: Regarding the image forming method having at least a cleaning process of cleaning an electrifying member while bringing a cleaning member in contact with the electrifying member, the electrifying member contains composite particle having a base particle whose surface is covered with conductive material in the outermost layer on the outer periphery of the supporting body, and the cleaning member for the electrifying member is provided with a freely deformable flexible member, and the flexible member is brought into surface-contact with the surface of the electrifying member by the repulsive force generated by flexing the flexible member, and the inroad quantity of the flexible member coming in contact with the electrifying member is set to be 0.1 to 6.0mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming method using a charging member and an apparatus having a cleaning member for cleaning the surface of the charging member, and is applied to an image forming method using an image forming apparatus such as a copying machine or a printer. Is.

  Conventionally, a corona charger has been used as a charging device for an electrophotographic image forming apparatus, but in recent years, a contact charging device has been put to practical use instead. This is intended for low ozone and low power, and in particular, a roller charging method using a conductive roller as a charging member is preferable and widely used in terms of charging stability. In the roller charging method, a conductive elastic roller is brought into pressure contact with a member to be charged, and a voltage is applied thereto to charge the member to be charged by discharge.

  Specifically, the required photoreceptor surface potential Vd is added to the discharge start voltage (about 550 V when the charging roller is pressed against the OPC photoreceptor (organic photoreceptor)). For the purpose of improving the potential fluctuation due to the environment / endurance fluctuation or the like, the DC voltage corresponding to the required photoreceptor surface potential Vd is set to the DC voltage which performs charging by applying the DC voltage, or the discharge start voltage There is an AC charging method in which charging is performed by applying a voltage in which an AC component having a peak-to-peak voltage more than twice is applied to a contact charging member.

  However, in such a contact roller charging system, the surface of the charging roller is contaminated by fine powder toner, external additives, etc. that pass through the cleaning blade due to the property of contacting with the photosensitive drum. In some cases, charging failure occurs due to resistance increase, and density unevenness (spots, stripes, and strips) or toner adhesion (fogging) on the white part may occur in the image.

Therefore, as a countermeasure against the surface contamination of the charging roller, a flexible member that can be bent and deformed is provided, and the flexible member is moved against the surface of the charging member by a repulsive force caused by bending the flexible member. Thus, the surface of the charging member is cleaned while sliding the surface contact portion between the flexible member and the charging member to improve the image output to a level that does not cause a problem (for example, Patent Document 1). See).
Japanese Patent Laid-Open No. 11-288150

  However, in recent years, due to the demand for higher image quality in the market, the toner has become smaller in particle size, the proportion of fine toner has increased, and the degree of contamination of the charging roller has increased accordingly. In addition, due to demands for longer life and color, the target durability life value (time) of the unit including the charging roller and photosensitive drum has been greatly increased (the operation time for obtaining one output by colorization is As a result, the amount of deposits increases, and image defects that did not occur with the previous number of durable sheets become apparent in the latter half of the durability.

  In addition, since the adhering matter on the surface of the charging roller is removed by contacting a flexible member fixedly arranged on the surface of the charging roller, a minute rubbing scratch is formed on the surface of the charging roller in the second half of the endurance when used for a long time. Occasionally, vertical stripes may occur.

  The present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to provide a long-lasting image without causing image defects due to dirt or scratches on the charging roller in any environment including low temperature and low humidity environments. An object of the present invention is to provide an image forming method for obtaining a stable image over a period of time.

  In order to achieve the above object, in the present invention, as a result of intensive studies, it has been found that the above object can be achieved by the following means.

  That is, the present invention relates to a charging step in which a rotatable charging member is brought into contact with an electrophotographic photosensitive member having at least a photosensitive layer on a conductive support to charge the electrostatic latent image on the charged photosensitive member. An electrostatic latent image forming step to be formed; a developing step of transferring the toner carried on the toner carrying member to the electrostatic latent image for visualization; and transferring the toner image formed on the photoconductor to a transfer material And a cleaning step for removing residual toner remaining on the photoconductor after transfer from the photoconductor, and a cleaning member is brought into contact with the charging member to In the image forming method having a cleaning step of cleaning, the charging member contains composite particles in which at least the surface of the mother particle is coated with a conductive material on the outermost layer of the outer periphery of the support, and the charging member is cleaned The member is flexibly deformable The intrusion amount of the flexible member in contact with the charging member at the time when the flexible member is brought into surface contact with the surface of the charging member by a repulsive force caused by bending the flexible member Is an image forming method characterized by being 0.1 to 6.0 mm.

The present invention is the image forming method, wherein the composite particles have a volume resistivity of 10 ¹ to 10 ⁴ Ω · cm.

  In the image forming method, the composite particles may have an average particle size of 10 to 500 nm.

  Further, the present invention is the image forming method, wherein the base particle of the composite particle is silica.

  Further, the present invention is the image forming method, wherein the conductive material of the composite particles is carbon black.

  In the image forming method, the outermost layer of the charging member may have a thickness of 3 to 30 μm.

  Further, the present invention is the image forming method, wherein the cleaning member is made of a resin selected from polyimide, polyamide, polycarbonate, and polyester.

  According to the present invention, a stable image can be obtained over a long period of time without any image defect due to dirt or scratches on the charging roller in any environment including low temperature and low humidity environment by the above achievement means.

  While the degree of contamination of the charging roller is increased by reducing the particle size of the toner particles for the purpose of improving the image quality, the target of the unit including the charging roller and the photosensitive drum is required due to demands for longer life and coloration. The endurance life value has increased significantly. Under such circumstances, the present invention proposes means for effectively cleaning the charging roller for a long period of time.

  That is, in order to effectively clean the charging roller dirt, it can be achieved to some extent by bringing a cleaning member such as a cleaning film into contact with the surface of the charging member. This increases the number of image defects. Further, since the cleaning film has been in contact for a long time, the surface of the charging roller is gradually scraped by the pressure applied to the contact surface, and streak-like image defects that may be caused by minute scratches occur in the second half of the endurance.

  Since the charging member containing composite particles in which the surface of the mother particles used in the present invention is coated with a conductive material is composed of different components, between the mother particles to be coated and the conductive material that is the coating, Since there is a difference in electrostatic attraction, the electrical electrostatic attraction between the conductive material particles in the system is weakened, preventing aggregation as in the case of only ordinary conductive particles and excellent in dispersibility. As a result, since it can be uniformly distributed on the surface of the charging member, there is no partial unevenness of hardness, and the pressing force of the cleaning member is evenly applied to the contact of the cleaning member, so that the surface of the charging roller is hardly damaged. In addition, since it is uniformly dispersed, there is no bias in the frictional force on the surface of the charging roller, and dirt does not easily accumulate in places where the frictional force is partially high, so that good releasability can be maintained. .

  On the other hand, the cleaning member for cleaning the surface is arranged in parallel to the longitudinal direction (axial direction) of the charging roller, and a cleaning film as a flexible member arranged so as to form a contact nip with the charging roller is used as the charging member. It is possible to contact the charging member uniformly while sliding the surface contact portion between the flexible member and the charging member while making surface contact with the surface, and the contact area with respect to the charging member is also reduced. It is effective.

  The range of the intrusion amount δ of this cleaning member (see FIG. 5; defined by the maximum value δ of the distance between the surface of the charging roller 102 and the straight line of the free state of the contact surface of the flexible member 122) is 0.1-6. Must be 0 mm. This is because when the intrusion amount δ is less than 0.1 mm, the applied pressure becomes low and it becomes difficult to remove dirt, and an image defect occurs in the second half of the durability. Further, since the applied pressure increases when the intrusion amount exceeds 6 mm, even when the charging member containing the composite particles in which the surface of the mother particle is coated with the conductive material is used, the charging roller is scratched in the latter half of the durability. It becomes intense and the image gets worse. That is, it is necessary to apply a certain amount of pressure in order to remove dirt, and the range of the penetration amount δ that does not damage the charging roller used in the present invention must be 0.1 to 6.0 mm. The penetration amount δ is preferably in the range of 0.5 to 4.0 mm.

  For these reasons, the charging member containing composite particles whose surfaces are coated with a conductive material and the cleaning film as a flexible member are brought into surface contact with the surface of the charging member to charge the flexible member. It is considered that excellent charging uniformity can be maintained for a long time by combining with a cleaning member that cleans the surface of the charging member while sliding the surface contact portion with the member.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

(1) Image Forming Apparatus A charging member, a charging member cleaning apparatus, an image forming apparatus, and a process cartridge used in the first embodiment of the present invention will be described with reference to FIGS.

  In this embodiment, a laser printer is described as an example of an image forming apparatus.

  First, the entire image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic sectional view of an image forming apparatus (laser printer) used in the embodiment of the present invention.

  An image forming apparatus (laser printer) used in this embodiment is connected to a host such as a personal computer or a workstation (not shown), and receives image data via a video interface in response to a print request from the host.

  On the basis of this image data, the image forming apparatus (laser printer) used in the present embodiment, in the same way as in the prior art, sequentially selects each color from the image data separated into four colors of yellow Y, magenta M, cyan C, and black K. Are formed on the intermediate transfer body and transferred onto a transfer material such as paper to obtain a full color image.

  Reference numeral 101 denotes an electrophotographic photosensitive member (photosensitive member) to be charged as a first image carrier that is driven and rotated in a direction indicated by an arrow (an arrow A in FIGS. 2 and 4) with a predetermined peripheral speed (80 mm / s). Drum) [one having a photosensitive layer made of an organic photosensitive material formed on a conductive support (aluminum cylinder) having an outer diameter of 100 mm]. First, the surface is a charging means, and an arrow (in FIG. The charging roller 102 that is driven to rotate in the direction C) is uniformly charged (to about −600 V).

  Next, scanning is performed by an exposure unit (electrostatic latent image forming unit) 103 that is ON / OFF controlled in accordance with image data of the first color (Y), and an electrostatic latent image of the first color is formed ( (Exposure part potential is about -100V).

  The electrostatic latent image of the first color is developed and visualized by the first developing means 104 including the first color Y toner (polarity).

The visualized first toner image is pressed against the photosensitive drum 101 with a predetermined pressing force, and is driven to rotate in the direction of the arrow at a speed equal to the peripheral speed of the photosensitive drum 101 (80 mm / s). An intermediate transfer member 105 (for example, a surface layer made of urethane resin in which carbon, fluorine resin, etc. are dispersed on the surface of a conductive elastic layer made of NBR rubber or the like on an aluminum cylinder. Formed and transferred to the surface of the intermediate transfer member 105 by the primary transfer roller 108 (primary transfer) at a nip portion with a resistance value of about 10 ⁵ to 10 ¹⁰ Ω · cm and an outer diameter of 153 mm. Is done.

  At this time, a voltage VItr (+100 V) that is uniquely set in advance and has a polarity opposite to the charging polarity (−) of the toner is applied to the intermediate transfer member 105.

  Toner remaining on the photosensitive drum without being transferred during the primary transfer is scraped off by a cleaning blade which is a cleaning means pressed against the photosensitive drum and collected in a waste toner container 107.

  The above steps are repeated in the same manner for the remaining three colors (M, C, K), and each time, the colors contained in the second developing means, the third developing means, and the fourth developing means are different. A color image is formed by electrostatically transferring and laminating a toner image with a developer onto the surface of the intermediate transfer member 105 in sequence.

  This color image is contacted with the intermediate transfer member 105 at a predetermined timing, and a secondary transfer roller 106 serving as a contactable / separable transfer unit that rotates at a speed approximately equal to the peripheral speed of the intermediate transfer member. Are transferred onto the surface of the transfer material P conveyed from the paper feeding unit (secondary transfer).

  At this time, a voltage Vtr (+1000 V) that is uniquely set in advance and has a polarity opposite to the charging polarity of the toner is applied to the transfer roller 106.

  Thereafter, the transfer material is conveyed to a fixing means (not shown), and the four color toner images are permanently fixed, and are discharged out of the apparatus from the paper discharge unit to obtain a desired print image.

  The toner remaining on the intermediate transfer member 105 without being transferred during the secondary transfer is controlled in charge polarity by a toner charge control member (not shown), and then the potential difference between the intermediate transfer member 105 and the photosensitive drum. Is returned to the photosensitive drum side, scraped off by a cleaning blade disposed on the photosensitive drum, and collected in the waste toner container 107.

  The photosensitive drum 101, the charging roller 102, the cleaning blade, the waste toner container 107, and the charging roller cleaning member 120 described later are configured to be detachable from the image forming apparatus as one process cartridge (photosensitive drum cartridge). Yes.

  Further, each developing unit of yellow Y, magenta M, cyan C, and black K can be replaced separately as one process cartridge (developing cartridge) depending on the degree of wear.

(2) Charging Member Cleaning Device Next, a charging roller cleaning device, which is a feature of the embodiment of the present invention, will be described with reference to FIGS. 2 to 5 are explanatory views of the charging roller cleaning device used in the first embodiment of the present invention. FIGS. 2, 4 and 5 show the relationship between the charging roller and the charging roller cleaning device. FIG. 3 is a schematic perspective view of a charging roller cleaning device. In the figure, 101 is a photosensitive drum, 102 is a charging roller, 120 is a cleaning member, 121 is a support member, 122 is a flexible member, A is the rotation direction of the photosensitive drum, C is the rotation direction of the charging roller, and δ is the cleaning member. The amount of intrusion.

  The charging roller 102 includes a conductive support body (core metal) 102a, an elastic layer 102b, and an outermost layer (surface layer) 102c. The charging roller 102 is pressed by a bearing (not shown) and a pressure spring and is brought into pressure contact with the photosensitive drum 101 so as to be photosensitive. The drum 101 is driven to rotate as the drum 101 rotates. Details of the charging roller 102 will be described later.

  In the vicinity of the charging roller 102, there is a charging roller cleaning member 120 that constitutes a charging roller cleaning device that cleans and removes contaminants that contaminate the surface of the charging roller (fine powder toner that passes through the cleaning blade, external additives, etc.). It is arranged.

  The charging roller cleaning member 120 used in this embodiment is arranged in parallel to the longitudinal direction (axial direction) of the charging roller 102 and is a support member 121 and a flexible film-like member. For example, the cleaning film 122 is a flexible member that is fixed so that one end is fixed and a contact nip with the charging roller 102 is formed on the film surface near the free end.

  As the cleaning film 122, for example, a resin film having a film thickness of 50 μm is used. The cleaning film is brought into surface contact with the surface of the charging member, and the surface of the charging member is slid at the surface contact portion. to clean up. Due to the repulsive force caused by bending the cleaning film, the flexible member is brought into surface contact with the charging member, so that the pressure member can be contacted with light pressure and uniformly, and the contact area with respect to the charging member can also be reduced. It was found that the surface contact portion could be effectively cleaned by sliding. As described above, the range of the intrusion amount δ of this cleaning film must also be 0.1 to 6.0 mm. This penetration amount δ is also preferably in the range of 0.5 to 4.0 mm.

  The film thickness is preferably in the range of 10 to 1000 μm, but is not limited. The optimum film thickness is selected according to the life of the charging roller, the characteristics of the toner used, the performance of the means for cleaning the photosensitive drum, and the like. do it.

  Further, since the contact force is obtained by the repulsive force obtained by bending the flexible member (cleaning film), the contact nip can be suppressed to about 0.5 mm, and the contact can be made uniformly in the entire charging roller. Further, the contaminants scraped off by the cleaning member of the charging roller are less likely to stay in the contact nip, and the contamination on the roller surface can be kept to an extent that does not affect the image.

  Further, the precision of the parts constituting the cleaning member is not required to be so high as compared with the conventional one.

  The cleaning member for the charging roller may be one in which the resin film is appropriately roughened by a grinder method, a sand blast method, a chemical etching method, a fine particle dispersion method or the like in addition to the resin film used as it is as described above.

  Film materials include polyimide, polyamide, polycarbonate, polyester, polyarylate, phenolic resin, diallyl phthalate resin, polyethylene, polypropylene, epoxy resin, polyphenylene sulfide, polyetherimide, polystyrene, polymethylmethacrylate, PTFE, PVDF, etc. Of these, polyimide, polyamide, polycarbonate, and polyester are preferable, and the friction coefficient is relatively low, the mechanical strength is excellent, and the friction charging characteristics are favorable. Polyimide is particularly preferred.

(3) Charging roller For example, the charging member has a roller shape as shown in FIG. 2, and is formed on the outer periphery of the conductive support 102a, the elastic layer 102b integrally formed on the outer periphery thereof, and the elastic layer. It is composed of a surface layer 102c.

  In addition, the charging member may have a single-layer structure including only the elastic layer 102a, or may include two layers including the elastic layer 102b and the surface layer 102c. Furthermore, three layers may be provided in which a resistance layer (not shown) is provided between the elastic layer 102b and the surface layer 102c. Furthermore, a structure in which a second resistance layer (not shown) is provided between the resistance layer and the surface layer 102c and four or more layers are formed on the conductive support may be employed.

  The conductive metal core 102a used in the present invention can be a round bar made of a metal material such as iron, copper, stainless steel, aluminum, or nickel. Furthermore, the metal surface may be plated for the purpose of providing rust prevention and scratch resistance, but it is necessary that the conductivity is not impaired.

  In the charging roller 102, the elastic layer 102b has a suitable conductivity for supplying power to the electrophotographic photosensitive member 101 as a member to be charged and ensuring good uniform adhesion of the charging roller 102 to the electrophotographic photosensitive member 101. It has sex and elasticity. In addition, in order to ensure uniform adhesion between the charging roller 102 and the electrophotographic photosensitive member 101, the elastic layer 102b may be polished so as to have a thickest central portion and a so-called crown shape that becomes thinner toward both ends. Many. Since the charging roller 102 that is generally used is in contact with the electrophotographic photosensitive member 101 by applying a predetermined pressing force to both ends of the support 102a, the pressing force in the central portion is small and increases toward both ends. For this reason, there is no problem if the straightness of the charging roller 102 is sufficient, but if it is not sufficient, density unevenness may occur in the images corresponding to the central portion and both end portions. The crown shape is formed to prevent this.

The conductivity of the elastic layer 102b is a conductive agent having an electron conduction mechanism such as carbon black, graphite and conductive metal oxide in an elastic material such as rubber, and an ion conduction mechanism such as an alkali metal salt or a quaternary ammonium salt. It is preferable to adjust to less than 10 ¹⁰ Ωcm by appropriately adding a conductive agent having Specific elastic materials for the elastic layer 102b include, for example, natural rubber, EPDM, SBR, silicone rubber, urethane rubber, epichlorohydrin rubber, synthetic rubber such as IR, BR, NBR and CR, and further polyamide resin, polyurethane resin, silicone Resins etc. are also mentioned.

In a charging member that applies only a direct current voltage to charge the object to be charged, in order to achieve charging uniformity, particularly a moderate resistance polar rubber (for example, epichlorohydrin rubber, NBR, CR, urethane rubber, etc.) It is preferable to use polyurethane resin as an elastic material. These polar rubbers and polyurethane resins are considered to have a slight conductivity due to moisture and impurities in the rubber and resin as carriers, and these conduction mechanisms are considered to be ionic conduction. However, an elastic layer was prepared without adding a conductive agent to these polar rubbers and polyurethane resins, and the obtained charging member had a high resistance value in a low temperature and low humidity environment (L / L) and exceeded 10 ¹⁰ Ωcm. Some will end up. Therefore, it is necessary to apply a high voltage to the charging member.

Therefore, the above-described conductive agent having an electron conduction mechanism or a conductive agent having an ionic conduction mechanism is appropriately added and adjusted so that the resistance value of the charging member is less than 10 ¹⁰ Ωcm in a low-pitched low-humidity environment (L / L). Is preferred. However, a conductive agent having an ionic conduction mechanism has a small effect of lowering the resistance value, and particularly in a low temperature and low humidity environment (L / L). Therefore, resistance adjustment may be performed by adding a conductive agent having an electron conduction mechanism in addition to the addition of a conductive agent having an ionic conduction mechanism.

  The elastic layer 102b may be a foam obtained by foaming these elastic materials.

  In the case of a three-layer structure, the resistance layer is formed at a position in contact with the elastic layer, so that it prevents the bleeding out of the surface of the charging member such as softening oil and plasticizer contained in the elastic layer, It is provided for the purpose of adjusting the electrical resistance of the entire member.

  Examples of the material constituting the resistance layer include epichlorohydrin rubber, NBR, polyolefin-based thermoplastic elastomer, urethane-based thermoplastic elastomer, polystyrene-based thermoplastic elastomer, fluororubber-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and polyamide-based heat. Examples thereof include a plastic elastomer, a polybutadiene-based thermoplastic elastomer, an ethylene vinyl acetate-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer, and a chlorinated polyethylene-based thermoplastic elastomer. These materials may be used alone or in combination of two or more, and may be a copolymer.

  The resistance layer used in the present invention needs to have conductivity or semiconductivity.

For the purpose of imparting releasability to these binder resins, solid lubricants such as graphite, mica, molybdenum disulfide and fluororesin powder, or fluorosurfactants, wax, and silicone oil are added. Also good. Conductive agents with various electron conduction mechanisms (carbon black, graphite, conductive metal oxides, copper, aluminum, nickel, iron powder, alkali metal salts, ammonium salts, etc.) for the development of conductivity and semiconductivity Alternatively, an ionic conductive agent can be used as appropriate. In this case, in order to obtain a desired electric resistance, two or more kinds of the various conductive agents may be used in combination.
In the present invention, composite particles in which the surface of the mother particle is coated with a conductive material are used for the outermost layer (surface layer).

  Since such composite particles are composed of different components, there is a difference in electrostatic attraction between the coated mother particles and the conductive material that is the coating, and the electrical conductivity between the conductive material particles in the system. Reduces electrostatic attraction and excels in dispersibility. Therefore, partial unevenness of hardness is eliminated, and the pressure applied to the cleaning member is evenly applied to the contact of the cleaning member, so that the surface of the charging roller is hardly damaged. In addition, the frictional force on the surface of the charging roller is not biased, and dirt does not easily accumulate in a part where the frictional force is partially high, so that good releasability can be maintained.

  In the case of an ordinary conductive agent such as carbon black in which the base particles are not coated with the conductive agent in this way, for example, carbon black is aggregated, and uniform dispersion becomes difficult. For this reason, a partial hardness deviation occurs on the surface of the charging member, and the charging roller is damaged. Further, a portion where dirt is accumulated is generated due to a difference in partial frictional force on the surface, and the degree of image defect becomes serious in the second half of the durability.

Further, the volume resistivity of the composite particles is preferably 10 ¹ to 10 ⁴ Ω · cm. When the volume resistance of the composite particles is lower than 10 ¹ Ω · cm, if the roller surface is damaged over time, the leak resistance deteriorates, which is not preferable. On the other hand, if it is higher than 10 ⁴ Ω · cm, a large amount of composite particles are required to obtain a desired resistance as a charging member, which is not preferable because it tends to aggregate. Composite particles satisfying such a volume resistivity range can be easily selected by adjusting the amount of conductive agent coated on the matrix. The mother particles of the composite particles should have low conductivity, and preferably have a volume resistance of 10 ⁵ Ω · cm or more. By using such core particles, it becomes easy to adjust the resistance of the composite particles within the above range. The volume resistance of the composite particles of the present invention was calculated from the resistance measured using Loresta-GP MCP-T600 (manufactured by Mitsubishi Chemical Corporation). The applied pressure was 10 MPa.

  Further, the size of the composite particles is preferably in the range of 10 nm to 500 nm. If the composite particles are larger than 500 nm, the unevenness of the insulating portion and the conductive portion in the resin layer becomes large, so that the charging uniformity is deteriorated. If it is smaller than 10 nm, aggregation is likely to occur due to an increase in intermolecular force due to finer particles, and thus dispersion becomes difficult. The primary particle diameter of the composite particles of the present invention was observed with 100 transmission particles (TEM) only for the primary particles excluding the secondary aggregated composite particles, and the projected area was obtained. The equivalent diameter was calculated to determine the volume average particle diameter, and the average was taken as the primary particle diameter. The composite particles satisfying such a particle size range can be selected by covering the base particles having a particle size of 1 nm to 500 nm with a conductive agent of 1 nm to 100 nm.

  The covering layer of the mother particles preferably has electronic conductivity because the developed conductivity is less affected by the environment. Examples of the conductive agent for developing electron conductivity include metals or alloys such as carbon black, graphite, aluminum, nickel, and copper alloys, tin oxide, zinc oxide, potassium titanate, tin oxide-indium oxide, and tin oxide. -Metal oxides such as antimony oxide composite oxides are mentioned, among which carbon blacks such as furnace black, ketjen black and channel black having a reinforcing effect are preferably used. In the present invention, in order to fix these conductive materials to the mother particles, surface treatment of the mother particles is performed using an organosilane compound or polysiloxane generated from alkoxysilane as a surface treatment agent for the mother particles. Is preferred. That is, the mother particles are surface-treated with a silane compound, and the surface thereof is coated with a conductive material in order to impart electron conductivity. Specific examples of the alkoxysilane include methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, isobutyltrimethoxysilane. Examples include methoxysilane and decyltrimethoxysilane.

  As the base particles of the composite particles described so far, silica powder, white carbon, fine silica silica powder, barium sulfate particle powder, alumina particle powder, clay, calcium carbonate particle powder, talc, transparent titanium oxide, titanium dioxide particles Inorganic particles such as powders, iron oxide particles, and zinc oxide particle powders can be mentioned. Among them, silica that enhances adhesion to alkoxysilane and suppresses detachment of the coated carbon black is particularly preferable.

  The composite particles used in the present invention are obtained by mixing mother particles and a surface treatment agent, coating the surfaces of the mother particles with alkoxysilane, and then mixing the alkoxysilane-coated mother particles with carbon black. be able to.

  In the present invention, the mother particles are coated on the particle surface by mechanically mixing and stirring the mother particles and the surface treatment agent or the solution of the surface treatment agent, or by spraying the surface treatment agent or the solution of the surface treatment agent. And mixing and stirring. Almost all of the added surface treatment agent is coated on the surface of the mother particles.

  In addition, when alkoxysilane is used as the surface treating agent, the coated alkoxysilane may be coated as an organosilane compound generated from alkoxysilane, a part of which is generated through a coating process. Even in this case, the subsequent adhesion of carbon black is not affected.

  In order to uniformly coat the surface of the base particle with the surface treatment agent, it is preferable that the agglomeration of the base particle is unraveled in advance using a pulverizer.

  As a device for mixing and stirring the mother particles and the surface treatment agent and mixing and stirring the mother particles whose surface is coated with the surface treatment agent and the conductive material, a shear force is applied to the powder layer. A device capable of simultaneously performing shearing, spatula and compression, for example, a wheel-type kneader, a ball-type kneader, a blade-type kneader, a roll-type kneader, and a wheel can be used. A mold kneader can be used more effectively.

Examples of the wheel-type kneader include an edge runner (synonymous with “mix muller”, “simpson mill”, “sand mill”), multi-mal, stotz mill, wet pan mill, conner mill, ring muller, etc., preferably edge Runners, multi-mals, stocks mills, wet pan mills and ring mullers, more preferably edge runners. Examples of the ball kneader include a vibration mill. Examples of the blade-type kneader include a Henschel mixer, a planetary mixer, and a nauter mixer. Examples of the roll-type kneader include an extruder.
The film thickness of the outermost layer when a roller is formed is preferably 3 to 30 μm, particularly preferably 5 to 20 μm. If the thickness is less than 3 μm, the roller surface tends to be damaged, and if it is thicker than 30 μm, a large amount of conductive particles are required to obtain a desired resistance as a charging member, which is not preferable because it tends to aggregate.

  Further, unevenness may be formed on the surface of the charging member. For example, as a method for forming irregularities, there are a method in which resin particles, carbon particles, silicon acid particles, metal oxide particles and the like are included in the surface layer, and a method in which the surface of the charging member is treated by mechanical polishing or the like.

  The surface roughness of the charging member of the present invention is preferably controlled such that the 10-point average surface roughness (Rz) is 3 to 30 μm and the average interval (Sm) is 10 to 500 μm. Further, the 10-point average surface roughness (Rz) is more preferably 3 to 15 μm, and the average interval (Sm) is more preferably 20 to 200 μm.

  In the case of a process without a cleaning member, if the surface of the conductive member is rough (the surface roughness of the conductive member exceeds 10 μm), the developer may enter the recesses on the surface and cause contamination of the surface of the conductive member. It was. However, in the present invention, the contamination of the charging member can be reduced to a problem-free level by the combination with the cleaning means as described above.

  Further, various particles or powders may be used alone or in combination of two or more for improving the image in the surface layer. Specifically, zinc oxide, tin oxide, indium oxide, titanium oxide (titanium dioxide, titanium monoxide, etc.), iron oxide, silica, alumina, magnesium oxide, zirconium oxide, strontium titanate, calcium titanate, magnesium titanate , Particles of barium titanate and calcium zirconate, carbon black, tin oxide, titanium oxide, zinc oxide, barium sulfate, copper, aluminum, nickel, etc., polyamide resin, silicone resin, fluororesin, (meth) acrylic resin, styrene Resin, phenol resin, polyester resin, melamine resin, urethane resin, olefin resin, epoxy resin, resin particles such as copolymers, modified products and derivatives thereof, barium sulfate, molybdenum disulfide, calcium carbonate, carbonic acid Magnesium, doloma Talc, kaolin clay, mica, aluminum hydroxide, magnesium hydroxide, zeolite, wollastonite, diatomaceous earth, glass beads, bentonite, montmorillonite, asbestos, hollow glass sphere, graphite, rice husk, organometallic compound, organic There may be mentioned particles such as metal salts.

  Hereinafter, the present invention will be described in more detail with reference to examples.

"Durability test for continuous multiple image output when only DC voltage is applied to the charging roller (initial, after 30000 sheets)"
The charging roller obtained above is attached to the electrophotographic image forming apparatus shown in FIG. 1, and environment 1 (temperature 23 ° C., humidity 55% N / N environment), environment 2 (temperature 32.5 ° C., humidity 80 % H / H environment) and environment 3 (temperature 15 ° C., humidity 10% L / L environment). Mono-color halftone printing was performed every 5000 sheets. The obtained image was visually observed and evaluated. The results are shown in Table 1.

  A, B, C, D, and E in the table rank image quality in five stages with respect to the occurrence of image density unevenness and streaks due to dirt on the charging roller surface and scratches on the charging roller. Note that A is a level at which there is no image defect, B is a level at which a slight defect can be seen at the edge of the image, C is a level at which some image defect is observed but there is no problem, and D is mostly an image defect. The problem level, E, is a level at which defects can be seen in the entire image.

Example 1
A charging roller as a charging member of the present invention was prepared in the following manner.

<Manufacture of elastic layer>
Epichlorohydrin rubber terpolymer (ethylene oxide content 56 mol%) 100 parts by mass quaternary ammonium salt 2 parts by weight light calcium carbonate 50 parts by mass zinc oxide 5 parts by mass fatty acid 3 parts by mass

  After kneading the above materials for 10 minutes with a closed mixer adjusted to 60 ° C., add 5 parts by mass of sebacic acid polyester plasticizer to 100 parts by mass of epichlorohydrin rubber, and further knead for 10 minutes to adjust the raw material compound. To do. To this compound, 100 parts by mass of raw material epichlorohydrin rubber was added 1 part by mass of sulfur as a vulcanizing agent, 1 part by mass of Noxeller DM as a vulcanization accelerator, and 0.5 parts by mass of Noxeller TS, and cooled to 20 ° C. Knead for 10 minutes in a two-roll mill.

The obtained compound was molded by an extruder so as to form a roller around a φ6 mm stainless steel core, heated and vulcanized, and then polished so as to have an outer diameter of φ12 mm. Obtained.
<Production of composite particles>
To 7.0 kg of silica fine particles (average particle diameter 14 nm, volume resistivity 7.7 × 10 ⁸ Ω · cm), 140 g of methyl hydrogen polysiloxane is added to the silica particle powder while operating the edge runner, and the stirring speed is increased. Were mixed and stirred for 1 hour at a linear load of 588 N / cm (60 Kg / cm) at 22 rpm to obtain carbon black coating particles.

Next, 3.5 kg of carbon black particle powder (particle shape: granular, particle diameter 20 nm, volume specific resistance value 2.0 × 10 ² Ω · cm) is added over 10 minutes while operating the edge runner. The stirring speed was 22 rpm and a linear load of 588 N / cm (60 Kg / cm) for 1 hour, and after adhering carbon black to the methylhydrogenpolysiloxane coating, drying was performed at 80 ° C. for 1 hour using a dryer. To obtain composite particles.

The obtained composite particles had an average particle diameter of 30 nm and a volume resistivity of 1.7 × 10 ² Ω · cm.
<Manufacture of outermost layer (surface layer)>
As a material of the surface layer 102c,
Acrylic polyol solution (active ingredient 70% by weight) 100 parts by weight isocyanate A (IPDI) (active ingredient 60% by weight) 40 parts by weight isocyanate B (HDI) (active ingredient 80% by weight) 30 parts by weight composite particles (conductive particles) 20 parts by mass of polymethyl methacrylate (PMMA) resin particles 50 parts by mass of methyl isobutyl ketone (MIBK) solvent 300 parts by mass was stirred using a mixer to prepare a mixed solution. Subsequently, the mixed solution was subjected to dispersion treatment (treatment speed 500 ml / min) using a circulation type bead mill disperser to prepare a dipping paint. The coating material for dipping is applied onto the elastic layer by dipping method, air-dried for 10 minutes, and then dried with a heating dryer at 160 ° C. for 1 hour to coat the surface layer and form a roller-shaped charging member. Got. At this time, the film thickness of the roller was 15 μm.

  Note that glass beads of φ0.8 mm were used as the media for the bead mill disperser.

The electric resistance of the charging roller was measured by applying a DC voltage of −250 V using a resistance measuring machine under environment 1 (temperature 23 ° C., humidity 55%), and found to be 1.0 × 10 ⁵ Ω. The pressing force between them is the same as in the image forming apparatus used, and the resistance value when -250 V is applied from the external power source S3 is measured.

<Cleaning member>
As the cleaning film, a resin film mainly composed of polyimide having a film thickness of 50 μm is used. At a position of 1 = about 6 mm from the fixed end of the support member 121 (FIG. 2), the nip width n = about 0.5 mm. Touch. At this time, the penetration amount with respect to the charging roller was set to 1.5 mm. These evaluation results are summarized in Table 1.

(Example 2)
Image evaluation was performed with the same configuration as in Example 1 except that the amount of penetration of the cleaning member in Example 1 was 0.3 mm. At this time, a spot-like image that was considered to be caused by dirt was obtained in the image evaluation after endurance, but it was slight. The evaluation results are summarized in Table 1.

(Example 3)
Image evaluation was performed with the same configuration as in Example 1 except that the amount of penetration of the cleaning member in Example 1 was 4.5 mm. At this time, streak-like images that were considered to be caused by scratches on the rollers were obtained in the image evaluation after endurance, but they were slight. The evaluation results are summarized in Table 1.

Example 4
As a result of producing the composite particles by increasing the amount of the carbon black particle powder to 6.8 kg, the volume resistivity of the composite particles was 5 Ωcm. Image evaluation was performed with the same configuration as in Example 1 except that the composite particles were used. The evaluation results are summarized in Table 1.

(Example 5)
As a result of producing the composite particles by reducing the amount of the carbon black particle powder to 1.9 kg, the volume resistivity of the composite particles was 2.0 × 10 ⁴ Ωcm. Image evaluation was performed with the same configuration as in Example 1 except that the composite particles were used. At this time, white spots occurred but were slight. The evaluation results are summarized in Table 1.

(Example 6)
When the composite particles were produced, silica particles having a particle size of 3 nm were coated with 2 nm of carbon black powder. As a result, the average particle size of the composite particles (conductive particles) contained in the surface layer of Example 1 was 8 nm. Became. Image evaluation was performed with the same configuration as in Example 1 except that the composite particles were used. At this time, white spots were generated due to a slightly poor dispersion, but were slight. The evaluation results are summarized in Table 1.

(Example 7)
During production of the composite particles, silica particles having a particle size of 300 nm were coated with 150 nm of carbon black powder, resulting in an average particle size of 600 nm. Image evaluation was performed with the same configuration as in Example 1 except that the composite particles were used. At this time, density unevenness occurred but was slight. The evaluation results are summarized in Table 1.

(Example 8)
When the surface layer was formed, the amount of MIBK to be mixed was 1100 parts by mass. As a result, the roller film thickness was 2 μm. Image evaluation was performed with the same configuration as in Example 1 except that this roller was used. At this time, streak-like images that were considered to be caused by scratches on the rollers were obtained in the image evaluation after endurance, but they were slight. The evaluation results are summarized in Table 1.

Example 9
At the time of creating the surface layer, the roller was coated four times and thickly coated, resulting in a roller film thickness of 40 μm. Image evaluation was performed with the same configuration as in Example 1 except that this roller was used. At this time, white spots were generated due to a slightly poor dispersion, but were slight. The evaluation results are summarized in Table 1.

(Example 10)
When the elastic layer (base layer) was prepared, image evaluation was performed with the same configuration as in Example 1 except that an epichlorohydrin rubber terpolymer having an ethylene oxide content of 73 mol% was used. The evaluation results are summarized in Table 1.

(Example 11)
Image evaluation was performed with the same configuration as in Example 1 except that 25 parts by mass of titanium oxide whose surface was treated was added to the surface layer material. The evaluation results are summarized in Table 1.

(Comparative Example 1)
Image evaluation was performed with the same configuration as in Example 1 except that the amount of penetration of the cleaning member in Example 1 was 0.05 mm.

  At this time, in the image evaluation after endurance, image defects that appear to be caused by dirt appeared in the form of spots. The evaluation results are summarized in Table 1.

(Comparative Example 2)
Image evaluation was performed with the same configuration as in Example 1 except that the amount of penetration of the cleaning member in Example 1 was 6.3 mm. A streak-like image, which seems to be caused by the scratches on the rollers, was obtained. The evaluation results are summarized in Table 1.

(Comparative Example 3)
Image evaluation was performed with the same configuration as in Example 1 except that single carbon black was used without producing composite particles. Since the dispersibility was poor, the image was poor from the beginning, and in the image evaluation after the endurance, a streak-like image that was considered to be caused by a scratch on the roller was obtained. The evaluation results are summarized in Table 1.

(Comparative Example 4)
Image evaluation was performed with the same configuration as Comparative Example 1 except that the composite particles were not manufactured and a single carbon black was used. Since the dispersibility was poor, the image was poor from the beginning, and in image evaluation after durability, image defects that appeared to be caused by dirt appeared in the form of spots. The evaluation results are summarized in Table 1.

1 is a schematic sectional view of an image forming apparatus used in the present invention. It is sectional drawing which shows the relationship between the charging roller used for this invention, its cleaning apparatus, and an electrophotographic photoreceptor. It is a perspective view of the cleaning device for the charging roller used in the present invention. It is a perspective view showing the relationship between the charging roller used in the present invention, its cleaning device, and the electrophotographic photosensitive member. It is explanatory drawing of the penetration | invasion amount of the cleaning apparatus of the charging roller used for this invention.

Explanation of symbols

101 Electrophotographic photosensitive member (photosensitive drum which is a member to be charged as an image carrier)
102 Charging means (charging roller)
102a Conductive support (core metal)
102b Elastic layer 102c Outermost layer (surface layer)
103. Electrostatic latent image forming means (exposure means)
104 Developing means (Y, M, C, Bk)
105 Intermediate transfer member 106 Secondary transfer roller 107 Waste toner container 108 Primary transfer roller 110 Electrophotographic photosensitive member (photosensitive drum)
120 Charging Roller Cleaning Member 121 Support Member 122 Flexible Member (Cleaning Film)

Claims (7)

  A charging process in which a rotatable charging member is brought into contact with an electrophotographic photosensitive member having at least a photosensitive layer on a conductive support, and an electrostatic latent image for forming an electrostatic latent image on the charged photosensitive member A forming step, a developing step for transferring the toner carried on the toner carrying member to the electrostatic latent image for visualization, a transferring step for transferring the toner image formed on the photosensitive member to a transfer material, and a transfer step And a cleaning step for removing transfer residual toner remaining on the photoconductor from the photoconductor, and cleaning the charging member by bringing the cleaning member into contact with the charging member. In the image forming method, the charging member includes composite particles in which at least the surface of the mother particle is coated with a conductive material in the outermost layer on the outer periphery of the support, and the cleaning member of the charging member is flexibly deformable Flexible member, and the flexible part The flexible member is brought into surface contact with the surface of the charging member by a repulsive force caused by bending, and the amount of penetration of the flexible member in contact with the charging member is 0.1 to 6.0 mm. An image forming method characterized by that. 2. The image forming method according to claim 1, wherein the composite particles have a volume resistivity of 10 ¹ to 10 ⁴ Ω · cm.   The image forming method according to claim 1, wherein the composite particles have an average particle size of 10 to 500 nm.   The image forming method according to claim 1, wherein a base particle of the composite particle is silica.   The image forming method according to claim 1, wherein the conductive material of the composite particles is carbon black.   6. The image forming method according to claim 1, wherein the outermost layer of the charging member has a thickness of 3 to 30 [mu] m.   The image forming method according to claim 1, wherein the cleaning member is made of a resin selected from polyimide, polyamide, polycarbonate, and polyester.

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