JP2006091495A - Electrification roll, processing cartridge having the same, and electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrification roll obtaining stable and excellent uniform electrification characteristics and output image quality by preventing adhesion of toner and an external additive to the surface of the roll; and to provide a processing cartridge having the electrification roll, and an electrophotographic device. <P>SOLUTION: In the electrification roll having at least a support member and a conductive covering member, surface free energy of the conductive covering member is 30 mN/m or more, and an organic or inorganic particulate layer in which particle diameters are 3.0 μm or less on the whole face of the surface. The electrification roll, the processing cartridge using it, and the electrophotographic device, are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a conductive member, a process cartridge having the conductive member, and an electrophotographic apparatus. More specifically, the surface of the electrophotographic photosensitive member is predetermined by applying a voltage to a charging roll disposed in contact with the electrophotographic photosensitive member. The present invention relates to a charging roll that is charged to a predetermined potential, a process cartridge having the charging roll, and an electrophotographic apparatus.

  Conventionally, a number of methods are known as electrophotographic methods. In general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the latent image is formed with toner. Development is performed to obtain a visible image, and a toner image is transferred to a transfer material such as paper as necessary, and then the toner image is fixed on the transfer material by heat, pressure or the like to obtain a copy. In addition, toner particles that are not transferred onto the transfer material but remain on the photoconductor are removed from the photoconductor by a cleaning process.

  Conventionally, a corona charger has been used as a charging device for electrophotography. In recent years, contact charging devices have been put to practical use instead. This is intended for low ozone and low power consumption, and among these, a roll charging method using a conductive roll as a charging member is particularly preferably used from the viewpoint of charging stability.

  In roll charging, a conductive elastic roll is brought into pressure contact with a member to be charged, and a voltage is applied thereto to charge the member to be charged.

  Specifically, since charging is performed by discharging from a charging member to an object to be charged, charging is started by applying a voltage higher than a certain threshold voltage. For example, when a charging roll is brought into pressure contact with an organic photoconductor (OPC photoconductor) having a photosensitive layer having a thickness of 25 μm, the photosensitivity can be obtained by applying a voltage of about 640 V or more in absolute value. The surface potential of the body starts to rise, and thereafter, the photoreceptor surface potential increases linearly with a slope of 1 with respect to the applied voltage. Hereinafter, this threshold voltage is defined as the charging start voltage Vth.

  That is, in order to obtain the photoreceptor surface potential Vd required for electrophotography, the charging roll needs a DC voltage higher than that required for image formation itself, that is, Vd + Vth. A method of charging by applying only the DC voltage to the contact charging member in this way is called DC charging.

  However, in DC charging, the resistance value of the contact charging member tends to fluctuate due to environmental fluctuations, etc., and Vth fluctuates when the film thickness changes due to the photoconductor being scraped, so the potential of the photoconductor is set to a desired value. It was difficult to do.

  For this reason, in order to further uniform charge, there is an AC + DC charging method in which a voltage obtained by superimposing an AC component having a peak-to-peak voltage of 2 × Vth or more on a DC voltage corresponding to a desired Vd is applied to the contact charging member. Used. This is for the purpose of smoothing the potential due to AC, and the potential of the charged object converges to Vd, which is the center of the peak of the AC voltage, and is hardly affected by disturbances such as the environment.

  As a conductive member for charging, there is an example in which a surface layer is formed by a conductive seamless tube on a conductive support member (see, for example, Patent Document 1). Furthermore, a seamless tube made of a fluororesin is disclosed, and a multi-layer tube having a layer structure with different conductivity is also disclosed. As a method related to manufacture as a charging member, a method of forming by insertion is mentioned as the conventional technique. A surface forming method using a crosshead extruder has also been proposed.

  In such a method of forming a charging roll with a seamless tube, even if a foam is used as the elastic layer on the substrate, a uniform surface can be formed by further covering it with the seamless tube. Uniform charging is easy.

  To cover the support member with a seamless tube, the inner diameter of the seamless tube must be larger than the outer diameter of the support member to be covered, and the tube is shrunk and fitted by physical or chemical means, such as heat, or the seamless tube inner diameter The outer diameter of the support member to be coated is made smaller than that of the support member, and physical or chemical means such as air pressure is used to expand and fit the tube. Since the present invention can provide a seamless tube that is preferable for manufacturing as described above, a conductive member having extremely excellent characteristics can be provided as a result. Moreover, it can also be set as a multilayer simultaneous forming tube (for example, refer patent document 2).

  As a method for imparting conductivity to the seamless tube, there are generally an ion conduction method using a salt as a conductive agent and an electron conduction method using carbon black, a conductive metal oxide, a metal powder or the like as a conductive agent. When conductivity is provided by ionic conduction, there are problems that the environmental fluctuation of the resistance value is likely to increase, and that the salt is liable to contaminate the photoconductor because it contacts the electrophotographic photoconductor. Therefore, in the present invention, carbon black is used as a conductive agent.

  Furthermore, with regard to contact-type charging rolls, if toner and external additives are likely to adhere to the roll surface, the resistance value changes and variations due to adhesion to the roll surface, resulting in stable and good uniform charging characteristics and output images. It has been difficult to provide a charging roll that achieves quality. As means for solving this problem, a method of reducing the surface roughness (Rz; ten-point average roughness) and smoothing it has been proposed (see, for example, Patent Document 3).

  In addition, means for adhering a toner external additive to the surface of the charging roll in advance has been proposed (see, for example, Patent Document 4).

However, as described above, since it has been a necessary physical property to reduce adhesion, it has been difficult to intentionally deposit any substance in the subsequent process.
US Pat. No. 4,967,231 Japanese Patent Laid-Open No. 11-125952 JP 2000-137369 A JP 2000-81759 A

  The present invention relates to a contact-type charging roll, and relates to a charging roll that prevents the toner and external additives from adhering to the roll surface, and that provides stable and good uniform charging characteristics and output image quality, and a process cartridge having the charging roll. And an electrophotographic apparatus.

  That is, according to the present invention, in a charging roll having at least a support member and a conductive coating member, the surface free energy of the conductive coating member is 30 mN / m (millinewton / meter) or more, and the particle diameter is formed on the entire surface. Is a charging roll in which a layer of organic or inorganic fine particles having a thickness of 3.0 μm or less is formed.

  Furthermore, the present invention is the charging roll according to claim 1, wherein the conductive coating agent is composed of a seamless tube containing a thermoplastic elastomer.

  Further, in the process cartridge which integrally supports the electrophotographic photosensitive member and the charging member and one or both of the developing unit and the cleaning unit and is detachable from the main body of the electrophotographic apparatus, the charging member includes the electrophotographic unit. A process member that is disposed in contact with a photoconductor and charges the electrophotographic photoconductor when a voltage is applied thereto, and is a process cartridge using the charging roll.

  Furthermore, the present invention provides an electrophotographic apparatus having an electrophotographic photosensitive member, a charging member, an exposure unit, a developing unit, and a transfer unit, wherein the charging member is disposed in contact with the electrophotographic photosensitive member and a voltage is applied thereto. The electrophotographic apparatus is a charging member for charging the electrophotographic photosensitive member by using the charging roll.

  The present invention provides a charging roll which prevents toner and external additives from adhering to the roll surface, and provides stable and good uniform charging characteristics and output image quality, and a process cartridge and an electrophotographic apparatus having the charging roll. can do.

  Hereinafter, the present invention will be described in more detail.

  In the present invention, the fine particles applied to the surface of the conductive coating member in order to prevent adhesion of the toner and its external additives have an average particle diameter of 3.0 μm or less, and there is no gap between the particle layer and the charging roll. In order to fix the fine particles uniformly, thinly and firmly, it is necessary to adjust the surface free energy of the conductive covering member as a base to 30 mN / m or more. More preferably, it is 35 mN / m.

  The particle diameter of the fine particles applied to the surface of the conductive coating member needs to be 3.0 μm or less, preferably 1.0 μm or less. If the particle diameter exceeds 3.0 μm, it is not preferred because problems such as non-fixing on the roll surface and the effect of preventing adhesion and the occurrence of image unevenness occur.

  Further, the particles that shape the layer need to be formed without any gaps on the entire roll surface. If there is a gap or a portion where powder is not attached, when a charging voltage is applied in the process cartridge, excessive discharge occurs from that portion, and uniform charging is not performed, resulting in an image defect. Alternatively, it is not preferable because an external toner additive or the like is easily attached, and an image defect due to the attached matter is likely to occur.

  Specifically, fine particles to be applied include various metal oxides such as hydrophobic or hydrophilic silica, titania, ceria, alumina, zinc oxide and magnesium oxide, composite metal oxides such as strontium titanate and barium titanate, hydrotal Examples thereof include layered inorganic fine particles such as site, zeolite and montmorillonite, and fluorine-based fine particles such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF).

  As the layer formation method of the fine particles on the surface of the charging roll, direct coating such as electrostatic powder coating method, fluidized dip coating method, electrostatic fluidized dip coating method, sprayed powder coating method, acetone, methanol, Fine particles dispersed in a solvent such as N-hexane and applied to the surface of the charging roll by spray coating, etc., then rubbed on the surface of a paper wiper or the like, and fine particles that were not completely adsorbed on the surface To uniformly form a fine particle layer. Moreover, although the timing of fine particle application can be variously selected, it is preferably applied in the final step after the production of the conductive roll.

  On the other hand, the material used for the conductive covering member is not particularly limited as long as the surface free energy is 30 mN / m or more, but in order to fix the fine particle layer more firmly, the thermoplastic elastomer It is preferable that it is a seamless tube containing.

  Specific examples of thermoplastic elastomers include olefin (TPO), styrene (TPS), urethane (TPU), ester (TPEE), amide (TPA), and vinyl chloride (PVC). Can be mentioned.

  Next, as a method for producing a seamless tube for forming the conductive coating layer of the present invention, first, a conductive pigment such as a thermoplastic elastomer and carbon black is kneaded together with necessary additives, and then pelletized. Next, the obtained pellet is made into a seamless tube by an extrusion molding machine. Then, the formed seamless tube is covered with a support member to form a conductive member.

  Although there is no restriction | limiting in particular in the thickness of the seamless tube in this invention, Preferably it is 100-600 micrometers. Moreover, it does not restrict | limit at all to set it as a multilayer simultaneous forming tube.

  The structure, material, or manufacturing method as a supporting member used in the present invention is exemplified.

  As its form, an elastic roll is used. As the material, a conductive substrate such as a metal such as iron, copper, and stainless steel, a carbon dispersion resin, a metal or metal oxide dispersion resin, and the like can be used. For example, the elastic roll has a structure in which an elastic layer is provided on a conductive substrate and a conductive layer or a resistance layer is further provided. The elastic layer includes chloroprene rubber, isoprene rubber, EPDM rubber, polyurethane rubber. Further, it can be formed of rubber or sponge such as epoxy rubber and butyl rubber, or thermoplastic resin such as styrene butadiene, polyurethane, polyester and ethylene-vinyl acetate. These rubbers and resins may contain a conductive agent such as carbon black, metal and metal oxide particles.

  As the charging roll, the structure of the present invention having a support member and a seamless tube is excellent in manufacturing stability, and can stably produce a medium resistance region which has been conventionally difficult to produce stably.

  An example of the configuration of the charging roll 1 'of the present invention is shown in FIG. FIG. 1 shows a case where there are two conductive coating layers. In the figure, 1 is a conductive substrate, 2 is an elastic layer, 3 is a conductive coating layer, 3 (i) is an inner layer, and 3 (o) is a conductive layer. It is a surface layer.

  The electrophotographic photoreceptor, exposure means, development means, transfer means and cleaning means used in the present invention are not particularly limited.

  FIG. 2 shows an example of the configuration of an electrophotographic apparatus provided with a process cartridge having the charging roll of the present invention as primary charging means.

  In FIG. 2, reference numeral 13 denotes an electrophotographic photosensitive member, which is rotationally driven at a predetermined peripheral speed in the direction of the arrow. In the rotation process, the photosensitive member 13 receives a uniform charge of positive or negative predetermined potential on its peripheral surface by the conductive member 1 ′ of the present invention as a primary charging unit to which a voltage is applied from the power source 12, Image exposure 14 is received from image exposure means (not shown) such as slit exposure or laser beam scanning exposure. In this way, electrostatic latent images are sequentially formed on the peripheral surface of the photoreceptor 13.

  The formed electrostatic latent image is then developed with toner by the developing unit 15, and the developed toner developed image is rotated between the photosensitive member 13 and the transfer unit 16 from a sheet feeding unit (not shown). The image is sequentially transferred by the transfer device 16 to the transfer material 17 that is fed in synchronization.

  The transfer material 17 that has received the image transfer is separated from the surface of the photosensitive member, introduced into the image fixing means 18, and subjected to image fixing, thereby being printed out as a copy (copy).

  The surface of the photoreceptor 13 after the image transfer is cleaned by the removal of the transfer residual toner by the cleaning means 19 and is repeatedly used for image formation.

  The process cartridge 21 is only required to integrally support the electrophotographic photosensitive member and the charging member, and one or both of the developing unit and the cleaning unit, and be detachable from the main body of the electrophotographic apparatus. Both means are incorporated in the illustrated process cartridge. Reference numeral 20 denotes an apparatus main body rail for mounting the process cartridge.

  FIG. 3 shows an example in which a two-layer co-formed tube is produced as a conductive coating layer.

  As shown in FIG. 3, the die 4 used for molding is provided with inner and outer double annular extrusion channels 6 and 7 around a central through hole 5 for air introduction. The material for the inner layer from the first extruder 8 and the material for the surface layer from the second extruder 9 are pressure-injected into the outer channel 7 respectively, and the inner layer 3 (i) and the surface layer 3 (o) are injected. It is cooled by a water cooling ring 10 provided on the outer periphery of the two-layer simultaneous forming tube 3 obtained by superimposing and extruding, and this is pulled by a tube feeding device and sequentially cut to a predetermined length to be seamless for a charging roll. As a tube, the foamed elastic layer having the core 1 is coated in the next step. In FIG. 3, 22 is a tube take-up device.

  Thus, by forming the seamless tube 3 by multilayer coextrusion molding, it is possible to easily produce a multilayered tube including a thin layer that is difficult to cover as a tube alone.

  Hereinafter, although an example is given and explained, the present invention is not limited to an example. In addition, "part" in a present Example shows a mass part.

[Seamless tube creation example 1]
For the tube surface layer, 60 parts of styrene-hydrogenated butadiene-crystalline olefin block copolymer elastomer (SEBC) (styrene content 20% by mass), 40 parts of impact-resistant polystyrene (HIPS), carbon black EC (primary Particle size 30 nm, specific surface area 800 m ² / g, DBP oil absorption 360 units, pH 9.0) 10 parts, calcium stearate 1 part was added, kneaded at 180 ° C. for 15 minutes using a pressure kneader, and cooled and crushed. Pelletized by a grain extruder.

For the tube inner layer, carbon black (primary particle size 30 nm, specific surface area 800 m ² / g, DBP oil absorption 360, pH 9.0) 16 parts and calcium stearate 1 part are added to 100 parts of thermoplastic polyurethane elastomer (TPU). The mixture was kneaded at 180 ° C. for 15 minutes using a pressure kneader, cooled and pulverized, and pelletized by a granulating extruder.

  Using the above pellets, after extrusion molding with a two-color extruder equipped with a die with an inner diameter of φ16.5 mm and a point with an outer diameter of φ18.5 mm, through a sizing and cooling process, the inner diameter φ11.1 mm, the thickness of the surface layer It was molded into a seamless tube having a thickness of 100 μm and an inner layer thickness of 400 μm (used as a tube in Example 1).

[Seamless tube creation example 2]
For tube surface layer, 100 parts of thermoplastic polyamide elastomer (PAE), 10 parts of carbon black (primary particle size 30 nm, specific surface area 800 m ² / g, DBP oil absorption 360, pH 9.0) and 1 part of calcium stearate are added. The mixture was kneaded at 180 ° C. for 15 minutes using a pressure kneader, cooled and pulverized, and pelletized by a granulating extruder. The tube inner layer and the subsequent steps were processed into a seamless tube having an inner diameter of 11.1 mm, a surface layer thickness of 100 μm, and an inner layer thickness of 400 μm through the same manufacturing process as seamless tube preparation example 1 (Example) 2 as a tube).

[Seamless tube creation example 3]
For the tube surface layer, 100 parts of thermoplastic polyurethane elastomer (TPU), 10 parts of carbon black (primary particle size 30 nm, specific surface area 800 m ² / g, DBP oil absorption 360, pH 9.0) and 1 part of calcium stearate are added. The mixture was kneaded at 180 ° C. for 15 minutes using a pressure kneader, cooled and pulverized, and pelletized by a granulating extruder. The tube inner layer and the subsequent steps were processed into a seamless tube having an inner diameter of 11.1 mm, a surface layer thickness of 100 μm, and an inner layer thickness of 400 μm through the same manufacturing process as seamless tube preparation example 1 (Example) 3 as a tube).

[Seamless tube creation example 4]
For tube surface layer, 60 parts of SEBC (styrene content 20%), 40 parts of silicone grafted polyethylene (silicone 40 wt%), carbon black (primary particle size 30 nm, specific surface area 800 m ² / g, DBP oil absorption 360, pH 9 0.0) 10 parts and 1 part of calcium stearate were added, kneaded at 180 ° C. for 15 minutes using a pressure kneader, cooled and pulverized, and pelletized by a granulating extruder. The tube inner layer and subsequent steps were processed into a seamless tube having an inner diameter of 11.1 mm, a surface layer thickness of 100 μm, and an inner layer thickness of 400 μm through the same manufacturing process as seamless tube creation example 1 (comparative example) 1 tube).

[Seamless tube creation example 5]
For the tube surface layer, 100 parts of thermoplastic fluoroelastomer, 5 parts of carbon black (primary particle size 30 nm, specific surface area 800 m ² / g, DBP oil absorption 360, pH 9.0) and 1 part of calcium stearate are added and pressurized. It knead | mixed for 15 minutes at 180 degreeC using the kneader, and pelletized with the extruder for granulation after cooling grinding | pulverization. The tube inner layer and subsequent steps were processed into a seamless tube having an inner diameter of 11.1 mm, a surface layer thickness of 100 μm, and an inner layer thickness of 400 μm through the same manufacturing process as seamless tube creation example 1 (comparative example) 2 as a tube).

  The obtained seamless tube was coated on the foamed elastic layer to produce a conductive roll 1 'as shown in FIG. In FIG. 1, the inner layer 3 (i) and the surface layer 3 (o) are the seamless tubes created as described above.

  The surface free energy of the charging roll prepared above was measured with a wet tension test mixture.

  Subsequently, various fine particles shown in Table 1 were applied to the charging roll prepared above.

  In the examples of the present invention, the various powders were applied to the rolls in such a manner that the designated powders were adhered to the adhesive rolls in advance, and the rolls were rubbed while being counter-rotated.

  The adhesion state of the powder was judged by visual observation. When visual judgment was difficult, it was judged by observing with a microscope or the like.

  The evaluation of the toner adhesion was incorporated in the process cartridge shown in FIG. 2, and images were continuously printed on 1000 sheets, and the surface of the roll after the image was printed was observed and evaluated in four stages. Further, using the same roll, 10,000 images were continuously printed, and it was confirmed whether or not an image defect due to toner adhesion occurred. The results are shown in Table 1.

A: Almost no toner adhesion B: Slight toner adhesion is confirmed C: Toner adhesion is confirmed D: A large amount of toner component is adhered ◎: Image defect due to toner adhesion on the image is not confirmed at all ○: Almost no defect due to toner adhesion is observed on the image. Δ: Slightly black stripe due to toner adhesion is confirmed. X: Image defect due to toner adhesion (black stripe) is clearly observed.

  By adjusting the surface free energy of the conductive coating member of the charging roll to 30 mN / m or more and crushing organic or inorganic fine particles having a particle diameter of 3.0 μm or less on the entire surface to form a layer of particles. As a result, toner adhesion was reduced, and image defects due to toner adhesion were less likely to occur.

The figure which shows schematic structure of a charging roll. 1 is a diagram illustrating a schematic configuration of an electrophotographic apparatus including a process cartridge. The figure which shows schematic structure of a double layer tube shaping | molding apparatus.

Explanation of symbols

1. Conductive substrate 1 '. 1. Charging roll Elastic layer 2. Conductive coating layer 3 (i). Inner layer 3 (o). Outer layer 4. Dice 5. Central through hole (for air introduction)
6). Inner channel 7. Outer channel 8. 8. Inner layer extruder Extruder for outer layer 10. Water cooling ring 12. Power supply 13. Photoconductor 14. Image exposure 15. Developing machine 16. Transfer device 17. Transfer material 18. Fixing device 19. Cleaning device 20. Equipment main body rail for mounting process cartridge 21. Process cartridge 22. Tube take-up device

Claims (4)

  In a charging roll having at least a support member and a conductive coating member, a layer of organic or inorganic fine particles having a surface free energy of 30 mN / m or more and a particle diameter of 3.0 μm or less over the entire surface of the conductive coating member A charging roll characterized in that is formed.   The charging roll according to claim 1, wherein the conductive coating member is formed of a seamless tube containing a thermoplastic elastomer.   In a process cartridge that integrally supports an electrophotographic photosensitive member and a charging member and one or both of a developing unit and a cleaning unit and is detachable from the main body of the electrophotographic apparatus, the charging member includes the electrophotographic photosensitive member A process cartridge comprising a charging roll according to claim 1, wherein the charging roller is a charging member that is placed in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member when a voltage is applied thereto. In an electrophotographic apparatus having an electrophotographic photosensitive member, a charging member, an exposing unit, a developing unit, and a transferring unit, the charging member is disposed in contact with the electrophotographic photosensitive member, and a voltage is applied to the electrophotographic photosensitive member. An electrophotographic apparatus using the charging roll according to claim 1, wherein the charging roll is a charging member for charging a charging member.