JP2005300667A - Charging member and its manufacture method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging member capable of stably being manufactured with stable charging uniformity and leak resistance even in the case of the change of temperature/humidity avoiding a harmful influence caused by the excessive flow of a current such as overdischarge and also obtaining an excellent image even when it is assembled in an electrophotographic device realizing high-speed operation, high gradation and high definition, and to provide a manufacturing method of the charging member. <P>SOLUTION: In the charging member having a structure where a conductive base substance is covered with a resistance layer or the resistance layer is supported on the conductive base substance, the resistance layer contains conductive material and non-conductive particles, wherein the non-conductive particles are contained much more in the vicinity of the surface side than in the vicinity of the inner surface side near to the conductive base substance. The manufacturing method of the charging member is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charging member used for a copying machine, a laser printer, and the like, and a manufacturing method thereof.

  In a conventional electrophotographic apparatus, as a charging apparatus for uniformly charging the surface of a photoreceptor, a corotron charger using a corona discharge generated as a result of applying a high voltage to a thin wire such as tungsten is generally used. Met. However, the method using corona discharge has drawbacks such as requiring a high-voltage power source and causing adverse effects such as deterioration of the photoreceptor due to the strong oxidizing action by the generated ozone. Therefore, many ozone-less charging methods have been proposed in the past, but they reduce the discharge current as much as possible by supplying electric charge directly from the conductive charging member to the photosensitive member, which is the object to be charged, and as a result At this time, the amount of ozone generated was reduced.

  The forms of ozone-less charging are simply classified into a method using an elastic roller and an elastic blade, a method using a fur brush, a method using a solid discharge element, and the like. As a method for forming the discharge electric field, there are a method in which a DC voltage is applied to the charging member and a method in which an AC voltage and a DC voltage are simultaneously applied.

  As a configuration of a charging member having conductivity, a material in which a resistance layer is coated on a conductive substrate such as iron or stainless steel is widely used. The resistance layer is formed by adding a softening agent such as oil or plasticizer to an elastic body such as rubber or resin in order to make the nip width with the surface to be charged appropriate. Conductive material such as metal powder is added to have conductivity.

  In general, if the volume resistance is too high as the conductive property of the charging member, an abnormal image (sand image) due to uneven charging or poor charging of the photoconductor occurs. On the other hand, if the surface is too low, if a pinhole occurs on the surface of the photoreceptor due to manufacturing or handling, a rhombus-shaped abnormal image is generated on the image corresponding to the pinhole portion during reversal development (leakage) For example, there is an appropriate region for the resistance of the charging member.

  Therefore, if necessary, the resistance layer has a multi-layer structure of two or more layers, and the resistance is adjusted by dispersing a polymer material such as acrylic, urethane, acrylic urethane, hydrin or polyamide, or a conductive material such as conductive carbon black in the coating layer. Attempts have been made to provide a layer to achieve uniformity of charging of the member to be charged and leakage resistance.

  In order to improve the leakage resistance with respect to the object to be charged, Patent Document 1 provides a distribution density difference of the conductive material inside the resistor having a single structure, on the contact side with the object to be contacted such as the object to be charged. It is indicated that the distribution density of the conductive material is smaller or substantially zero than the other parts. In this method, the resistance of the resistor can be increased on the surface side (contact side with the contacted body), so that the leak resistance can be improved. However, the resistance of the conductive material that uniformly covers the surface of the resistor, where the distribution of the conductive agent is small or substantially zero, is high and close to the resistance of the rubber or resin used. Since resistance is greatly affected, the resistance greatly varies depending on temperature and humidity. For this reason, when used as a charging member, there is a problem that it is difficult to obtain uniform charging uniformity and leakage resistance under low temperature / low humidity and high temperature / high humidity. In addition to the rubber and resin used, a small amount of the conductive agent affects the resistance of the resistor, so that the resistance value abruptly fluctuates depending on the content of the conductive agent. There was a problem.

  In order to improve the charging uniformity with respect to the object to be charged, Patent Document 2 describes that the maximum roughness Rmax of the charging member surface is 0.01 to 0.5 mm. Conventionally, a method for improving the uniformity of charging by controlling the surface roughness of the charging member surface within an arbitrary range has been employed. As a method for controlling the surface roughness of the charging member surface, Patent Document 3 describes a charging member in which non-conductive particles having an average particle diameter of 5 to 30 μm are dispersed in a resistance layer so that Rz is 7 to 14 μm. Has been. As described above, in the manufacturing method in which the nonconductive particles are uniformly dispersed in the resistance layer, although the surface roughness of the charging member can be controlled, the nonconductive particles are also present in the resistance layer and on the lower surface side. Since a large amount of non-conductive particles need to be added into the resistance layer, the resistance of the resistance layer increases as a result. Therefore, the amount of conductive material added must be increased in order to set the resistance of the charging member to a predetermined value, and a large amount of conductive material is present in the portion of the resistance layer excluding nonconductive particles. There is a case where an adverse effect due to an excessive current such as discharge occurs. In addition, the surface roughness of the charging member is largely controlled by the particle size of the non-conductive particles to be added, but the particle size of the non-conductive particles that are commercially available is often different from the desired particle size. In the case of producing non-conductive particles, the production cost is increased.

  Patent Document 4 proposes a charging member in which 20 vol% or more non-adhesive fine particles having an average particle diameter of 0.1 μm or more are contained in a region from the surface to 0.5 μm. In this conventional technology, by regulating the existence ratio of non-adhesive particles in the vicinity of the surface, the low molecular weight component oozes out and adheres to the object to be charged. From the standpoint of achieving both, there is no difference from conventional technology.

The current electrophotographic apparatus is in a situation where high-speed gradation and high-definition are rapidly progressing with high speed, and the charging member is required to have both improved charging uniformity and leakage resistance more than the conventional technology. It has been.
JP 2000-39755 A JP-A-7-281507 JP-A-9-258523 Japanese Patent No. 2996453

  The object of the present invention is that there is no adverse effect caused by excessive electric current such as overdischarge, and it is possible to stably manufacture a charging member having stable charging uniformity and leakage resistance against changes in temperature and humidity. It is another object of the present invention to provide a charging member capable of always obtaining a good image even when incorporated in an electrophotographic apparatus with high speed, high gradation, and high definition, and a method for manufacturing the charging member.

  According to the present invention, in a charging member having a structure in which a resistive layer is coated or supported on a conductive substrate, the resistive layer contains a conductive material and non-conductive particles, and the non-conductive particles are close to the conductive substrate. Provided is a charging member characterized by containing more in the vicinity of the surface side than in the vicinity of the inner surface side.

  According to the present invention, in the method of manufacturing a charging member having a resistance layer containing a large amount of nonconductive particles on the surface side, the conductive substrate or the elastic layer covered on the conductive substrate may be formed of a conductive material, a nonconductive material. There is provided a method for producing a charging member, comprising a step of coating the resistance layer composition by moving the resistance layer composition relative to the resistance layer composition containing the conductive particles and the binder material.

  According to the present invention, in a charging member having a structure in which a resistive layer is coated on a conductive substrate, the resistive layer contains a conductive material and non-conductive particles, and the non-conductive particles are close to the conductive substrate. The voltage between the applied voltage that generates an abnormal image due to uneven charging or defective charging and the applied voltage that generates a rhombus-shaped abnormal image when pinholes are present due to inclusion in the vicinity of the surface side more than the vicinity of the side The difference can be widened, and there is little influence on the applied voltage due to temperature and humidity, and a wide range of applied voltage necessary for obtaining a proper image can be secured.

  In addition, the elastic layer is manufactured by a method including a step of coating the resistive layer composition by moving the elastic layer relative to the resistive layer composition containing the conductive material, the nonconductive particles, and the binder material. It is possible to stably supply a conductive member that can obtain an appropriate image.

  In the charging member according to the present invention, the resistance layer provided on the outer periphery of the conductive substrate contains a conductive material and non-conductive particles, and the non-conductive particles are contained in the resistance layer near the surface more than the lower surface side. It is characterized by doing. By containing more non-conductive particles near the surface than on the lower surface side, the charging member can be controlled to the desired surface roughness, so that charging uniformity can be improved and without significantly increasing the resistance value of the resistance layer, The resistance near the surface of the resistance layer can be controlled to improve the leak resistance. Moreover, since a conductive material exists in places other than non-conductive particles, fluctuations in resistance to temperature and humidity can be suppressed.

  The charging member according to the present invention is preferably distributed at a ratio of 1.1 times or more and 5 times or less in the range of 10% thickness from the surface side to the thickness range of 10% from the lower surface side in the resistance layer. . By making the distribution of non-conductive particles on the surface side of the resistance layer 1.1 times or more compared to the lower surface side, even when the resistance layer has a large thickness or the resistance required for the charging member is low, the resistance layer surface side The resistance can be controlled to a desired value, and leakage resistance can be improved. In addition, by making the distribution state of non-conductive particles 5 times or less, there is a conductive material on the surface side so that the charging uniformity can be improved and the resistance is not affected by temperature / humidity and stable characteristics. Can be obtained.

  The charging member according to the present invention preferably has a resistance layer containing non-conductive particles in an inclined manner, and the charging member has a surface roughness Rz of 3 μm or more and 15 μm or less. It has a resistance layer containing more non-conductive particles near the surface than the lower surface side, and by setting the surface roughness Rz of the charging member to 3 μm or more, there are a large number of discharge points and the charging uniformity can be improved. Since the number of contacts with the charged body is reduced and there is a gap between the contacts, the leakage resistance can be improved, and by making the surface roughness 15 μm or less, charging defects caused by the recesses can be suppressed even in long-term use.

  The charging member according to the present invention may satisfy 0.05 × D ≦ d ≦ 1.2 × D, where d is the average particle diameter of the non-conductive particles and D is the average thickness of the outermost layer of the charging member. preferable. By setting the average particle size d of the non-conductive particles to 0.05 × D ≦ d with respect to the average thickness D of the resistance layer, the surface roughness of the charging member is desired without adding excessive non-conductive particles. The value can be controlled. In addition, by setting d ≦ 1.2 × D, the depth and width of the recess can be controlled, so that charging failure can be suppressed even in long-term use.

  In the charging member according to the present invention, the surface state prepared in the initial stage can be maintained for a long period of time even in a long-term use or in a long-term pressure contact state with respect to an object to be charged by constituting the non-conductive particles with a crosslinked polymer compound.

  According to the method for producing a charging member according to the present invention, a resistive layer composition containing a conductive substrate or an elastic layer covered on a conductive substrate as a substrate, a conductive material, non-conductive particles, and a binder material. By applying the resistance layer composition by moving the resist layer relative to the surface, a resistance layer containing more non-conductive particles in the vicinity of the surface side than in the vicinity of the inner surface side can be molded. As an action mechanism in which a large amount of non-conductive particles are contained in the vicinity of the surface, when the conductive layer or the elastic layer coated on the conductive substrate is applied to the resistive layer composition while moving, The distribution of shear stress in the resistance layer composition is different, and the stress is directed in the direction of movement of the substrate on the inner surface side of the resistance layer, and in the direction of movement of the resistance layer composition and the direction of gravity on the surface side. It will be. In the case of a composition containing particles such as the resistance layer composition used in the present invention, the flow is different when stress is applied between the portion excluding the particles inside the composition and the particles, and particularly the non-conductive particles. Such relatively large particles are likely to be affected, and many non-conductive particles are likely to be contained near the surface.

  For that purpose, the viscosity characteristics of the resistance layer composition, the particle size contained, and the resistance layer composition are controlled by appropriately adjusting the moving speed of the conductive substrate or the elastic layer coated on the conductive substrate. I found that I can do it. Thereby, the resistance layer containing a large amount of non-conductive particles in the vicinity of the surface can be coated.

  By the manufacturing method of the present invention, the stress distribution inside the resistance layer and the pulling start side and the end side are made uniform by slowing the moving speed of the pulling end side end compared to the pulling start side end with respect to the base material. be able to.

  The charging member of the present invention is a charging member having a conductive substrate and a resistance layer that covers or is supported by the conductive substrate. Here, the coating is a roller-shaped conductive member that has an inner surface. The term “support” refers to the lamination on the inner layer of the blade-like conductive member.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of the charging member of the present invention, and FIG. 2 is a cross-sectional view showing an example in which the charging member is applied to an image forming apparatus.

  The charging member 2 includes a coating layer 8 containing non-conductive particles 100, a resistance layer 6 including an elastic layer 7, and a conductive substrate 5.

  The charging device 1 includes a charging member 2 and a power source 3, and a drum-shaped electrophotographic photosensitive member 10 includes an OPC, amorphous silicon, selenium, and zinc oxide on a grounded drum base 11 that can rotate in the R direction. The photosensitive layer 12 is covered.

  One embodiment of the charging member to which the present invention is applied will be described below.

As the conductive material used in the present invention, a known conductive material can be used, acetylene black, conductive carbon black and graphite of ketjen black, metal oxide such as metal powder, titanium oxide, tin oxide, and zinc oxide, or Appropriate surface of tin oxide, antimony oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, iron, copper, chromium, cobalt, lead, platinum or rhodium electrolytic treatment, spray coating, mixed shaking It may be attached by. In addition, quaternary alkylammonium salts such as tetraethylammonium and tetrabutylammonium sulfonate, polyethylene oxide modified products thereof, metal salts such as lithium perchlorate and sodium bromate, or ionic properties such as ester plasticizers and surfactants A conductive agent may be used. In addition, the volume resistivity can be adjusted as is known by adjusting the selection and addition amount of an appropriate dopant. The volume resistivity of the conductive material is preferably 1 × 10 ⁻² Ω · cm or more in order to prevent a local excess current. From the viewpoint of preventing deterioration of film properties such as strength by adding a large amount of conductive material, 1 × 10 ⁵ Ω · cm or less is preferable.

  The non-conductive particles used in the present invention are not particularly limited as long as they are not dissolved by a solvent or the like when the resistance layer composition is produced, and polymers such as urethane, acrylic, fluororesin, silica, Alumina, calcium carbonate, precipitated barium sulfate, clay, shirasu balloon, benzoquamine, talc, and other inorganic powders and glass can be used, but the average particle size control and dispersibility are relatively easy. Molecular polymers are preferred. Such high molecular weight polymers are commercially available as Duracon series from Polyplastics Co., Ltd. and as flow beads series from Sumitomo Seika Co., Ltd.

The average particle diameter of the non-conductive particles 100 is preferably 1 μm or more for controlling the surface roughness, and preferably 30 μm or less for making the contact state with the charged body uniform. The addition amount is preferably about 10 parts by mass to 100 parts by mass, and the surface roughness can be controlled and uniform charge to the charged body can be easily obtained. The distribution state of the nonconductive particles in the resistance layer can be observed with an electron microscope. The volume resistance of the non-conductive particles may be conductive so as not to decrease the resistance of the resistance layer, but the resistance may change depending on the temperature and humidity. 1 × 10 ⁸ Ω · cm or more is more preferable.

  The resistance layer may be made of resin or rubber material. Examples of the resin used for the resistance layer include polyurethane, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, polyvinyl butyral, polyvinyl acetal, polyarylate, polycarbonate, polyester, phenoxy resin, polyvinyl acetate, polyamide, polyvinyl pyridine, and cellulose. Based resins and the like. Examples of the rubber material include EPDM, polybutadiene, natural rubber, polyisoprene, SBR (styrene butadiene rubber), CR (chloroprene rubber), NBR (nitrile butadiene rubber), silicone rubber, urethane rubber, and epichlorohydrin rubber. It is done. As a dispersing means, a roll kneader, a Banbury mixer, a ball mill, a sand grinder, a paint shaker, or the like may be used as appropriate.

  When the resistance layer composition contains a relatively large amount of non-conductive particles near the surface of the charging member due to the flow of non-conductive particles, the viscosity is adjusted to 5 mPa · s to 500 mPa · s. preferable.

  The distribution state of the non-conductive particles in the resistance layer can be observed as the occupied area of the particles in the cross section by an electron microscope. Although the average thickness of a resistance layer is not specifically limited, Usually, it is about 1 micrometer-100 micrometers. As for the average thickness, the cut section can be observed with an electron microscope. The average thickness of the surface irregularities was determined from the median value of the apexes of the adjacent concave and convex portions. The range of 10% thickness in the present invention indicates a region from the median value of the concave and convex portions for obtaining the average thickness to the top of the convex portion from 10% of the film thickness in the thickness direction.

The volume resistance value of the resistance layer 8 is preferably 1 × 10 ⁴ Ω · cm or more from the viewpoint of preventing an excessive current to the member to be charged, and 1 × 10 ¹³ Ω · cm for charging the surface of the member to be charged. cm or less is preferable.

  When the charging member is formed of two or more layers, the elastic layer can be made of a material that can be used for the resistance layer, and the form thereof may be solid or foam, and the surface thereof is solid or foam. The polished surface may be a surface to which the inner surface of the mold is transferred or a skin surface, and is not particularly limited.

  Moreover, when manufacturing a foam by using a foaming agent, as a foaming agent, A.I. D. C. A. (Azodicarbonamide) series, D.I. P. T.A. (Di-nitrosopentamethylenetetramine) system, O.D. B. S. H. (4,4'-oxybis-benzenesulfonyl-hydrazide) system, T.I. S. H. (P-trienesulfonyl hydrazide) system, A.I. I. B. N. (Azobisisobutyronitrile) and the like can be used. D. C. A. System, O.D. B. S. H. In the blend system, a dense foam and a vulcanized tight (high crosslink density) foam can be obtained.

  Moreover, you may mix | blend a vulcanizing agent with the elastic layer 7 as needed. As the vulcanizing agent, known vulcanizing agents such as sulfur, peroxide and oxime can be used. In addition, what is necessary is just to determine the compounding quantity of a vulcanizing agent suitably in order to adjust hardness etc. In addition to this, a vulcanization accelerator, an anti-aging agent, a plasticizer, and the like may be added to the elastic layer 7.

  Such an elastic layer 7 may be formed by a known method. Examples thereof include a method of extruding an elastic material mixed with a foaming agent and heating and foaming and vulcanizing and curing, and injection and transfer for injecting the elastic material into a mold.

The volume resistance value of the elastic layer 7 is preferably 1 × 10 ² Ω · cm or more so that an excessive voltage is not applied to the resistance layer, and 1 × 10 ¹³ Ω to charge the surface of the member to be charged. -Cm or less is preferable. The thickness of the elastic layer 7 is not particularly limited, but is usually about 1 mm to 10 mm.

  The conductive substrate 5 (core metal) is not particularly limited, but those having strength as a substrate and exhibiting conductivity are suitable. Examples of these materials include iron, stainless steel, aluminum, and conductive plastic.

  The charging member of the present invention is usually composed of a conductive substrate, an elastic layer, and a resistance layer, but may further be provided with a bleed prevention layer.

  The photosensitive drum 10 is configured as follows. The photosensitive layer 12 is provided on the photosensitive drum base 11. As the photosensitive drum substrate, a substrate having a conductive property such as aluminum, aluminum alloy, stainless steel, nickel or the like can be used. In addition, aluminum, aluminum alloy, indium oxide-tin oxide alloy, etc. are vacuum deposited. It is possible to use a plastic having a layer formed by coating, a substrate obtained by applying conductive particles (for example, carbon black, tin oxide particles, etc.) to a metal or plastic together with an appropriate binder, a plastic having a conductive binder, and the like.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive substrate and the photosensitive layer. The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, etc.), polyurethane, gelatin, aluminum oxide, or the like. The thickness of the undercoat layer is preferably 5 μm or less, more preferably 0.5 μm to 3 μm. The undercoat layer is preferably 1 × 10 ⁷ Ω · cm or more in order to exhibit its function.

  The photosensitive layer 12 can be formed by applying an organic or inorganic photoconductor together with a binder resin as necessary, and can also be formed by vapor deposition. As a form of the photosensitive layer, a function-separated type laminated photosensitive layer of a charge generation layer and a charge transport layer is preferable. The charge generation layer can be formed by depositing a charge generation material such as an azo pigment, a phthalocyanine pigment, a quinone pigment, or a perylene pigment, or by coating with a suitable binder resin (without a binder). The film thickness of the charge generation layer is preferably from 0.01 μm to 5 μm, particularly preferably from 0.05 μm to 2 μm. The charge transport layer can be formed by dissolving a charge transport material such as a hydrazone compound, a styryl compound, an osissazole compound, and a triarylamine compound in a binder resin having a film forming property. The film thickness of the charge transport layer is preferably 5 μm to 50 μm, particularly preferably 10 μm to 30 μm. A protective layer may be provided on the photosensitive layer to prevent deterioration due to ultraviolet rays or the like.

  The photosensitive member 10 is not limited to a drum shape, but may be a belt shape or a sheet shape, and the charging member 2 may be a non-rotating roller, a blade-shaped pad member, or the like. In this embodiment, a roller shape was used.

  The charging member 2 abuts on the photoconductor 10 and is connected to the photoconductor 10 via the power source 3 to constitute an electric circuit. The power supply 3 charges the nip portion 13 between the contact charging device 2 and the photosensitive member 10, and the nip portion 13 moves as the photosensitive member 10 moves, so that the entire surface of the photosensitive member 10 is charged. Thereafter, as shown in FIG. 3, a latent image is formed by exposure with laser light L according to image information, and then developed with toner by a developing device 31, and transferred to a transfer material by a transfer member 32 in a transfer unit, Heat fixing is performed by the fixing device 33. On the other hand, the photoreceptor 10 is cleaned by a post-transfer cleaner 35 to prepare for the next image formation.

  The charging member used in this example was manufactured by the following method.

(Example 1)
100 parts by mass of ethylene-propylene-diene terpolymer (trade name: EPT4045, manufactured by Mitsui Petrochemical Co., Ltd.) as raw rubber, 1 part by mass of stearic acid as processing aid, and 5 parts by mass of zinc oxide as vulcanization accelerator , 50 parts by mass of SRF carbon black (trade name: Asahi # 35, manufactured by Asahi Carbon Co., Ltd.) as a filler, 7 parts by mass of Ketjen black (product name: Ketjen Black EC600JD, manufactured by Ketchen Black International) as a conductive agent, plasticizer As paraffin oil (trade name: PW-380, manufactured by Idemitsu Kosan Co., Ltd.), sulfur as a crosslinking agent, 0.5 part as sulfur, 2-mercaptobenzothiazole (MBT) as 2 parts by weight, tetramethylthiuram disulfide ( TMTD) 1 part, zinc dibutyldithiocarbamate (ZnBDC) 1 part by weight The unvulcanized rubber composition was obtained by mixing with a bun roll. Next, in order to form the unvulcanized rubber composition into a tube shape, the tube was extruded into a tube shape using an extruder in which a mandrel having an outer diameter of φ5.0 mm and a die having an inner diameter of φ12.5 mm were set. Thereafter, a vulcanization reaction was performed at 150 ° C. for 30 minutes with pressurized steam to obtain a vulcanized tube. Next, after applying an olefin-based adhesive (trade name: Super Clon 851L Nippon Paper) to a core metal having a diameter of φ6 mm and a material as a conductive substrate, it is inserted into a vulcanizing tube and heated at 130 ° C. for 30 minutes. Adhesion was performed, and the elastic body was obtained by polishing to a diameter φ11.8 mm and a length 224 mm.

  As a resistance layer paint, 15 parts by mass of conductive titanium oxide (trade name: ET-500W Ishihara Sangyo Co., Ltd.) as a conductive material with respect to 100 parts by mass of polyester polyol (trade name: Nipponporan 131 Nippon Polyurethane Industry Co., Ltd.) In addition, 200 parts by mass of ethyl acetate as a solvent and 75 parts by mass of thermosetting phenol resin particles (trade name: Belpearl R800 Kanebo) having an average particle diameter of 20 μm as non-conductive particles were mixed and dispersed for 10 hours using a paint shaker. . Next, 90 parts by mass of an isocyanate resin (trade name: Coronate L Nippon Polyurethane Industry Co., Ltd.) was added to obtain a resistance layer composition having a viscosity of 18 mPa · s.

The resistance layer composition was applied to the elastic body by dipping and heated at 150 ° C. for 1 hour to carry out a crosslinking reaction, whereby the charging member 1 was produced. The pulling speed (moving speed of the elastic body with respect to the resistance layer composition) was controlled to be 20 mm / s at the upper end and 5 mm / s at the lower end. The resistance value of the charging member 1 was 5 × 10 ⁷ Ω.

  Table 1 shows that the charging member 1 produced as described above is attached to the contact charging device 1, and the lowest AC voltage (sand voltage) that eliminates the occurrence of abnormal images due to poor charging under the initial use conditions and abnormal images due to pinholes are generated. It is the result of having measured the sand ground voltage after passing 10,000 sheets as minimum AC voltage (leakage voltage) and a durability test on the conditions of 15 degreeC / 15% RH. The results of measuring the leakage voltage at the initial use conditions at 35 ° C./90% RH are also shown.

  From Table 1, the charging member 1 has an initial sand ground voltage of 1.7 kV at 15 ° C./15% RH and a leak voltage of 2.6 kV, and the sand ground voltage after passing 10,000 sheets is 2.0 kV, 35 ° C./90. The leak voltage at% RH was 2.6 kV. Although the difference between the sand ground voltage and the leakage voltage is 0.9 kV, it was found that there is no problem in use. Further, there was no change in the surface roughness after the durability test, and there was no problem in use at the sand ground voltage, and no influence on the leakage voltage at 15 ° C./15% and 35 ° C./90% was observed.

  As the resistance value of the charging member, a voltage of DC 100 V was applied between the conductive substrate and the metal drum in a state where the foam was brought into contact with the cylindrical metal drum and rotated, and connected to the metal drum in series. It was determined by measuring the voltage applied to the resistor.

  The contact charging device 1 includes a charging member 1 and a power source 3. A drum-shaped electrophotographic photosensitive member 10 is formed on a photosensitive drum base 11 that can be rotated in the R direction, such as OPC, amorphous silicon, selenium, and zinc oxide. Any structure in which the photosensitive layer is covered may be used. In this embodiment, a photosensitive drum covering the OPC photosensitive layer 12 is used. The shape is not limited to a drum shape, but may be a belt shape or a sheet shape. The charging roller 1 is in contact with the photoconductor 10 and constitutes an electric circuit connected to the photoconductor 10 via the power source 3. In addition, a DC voltage of −670 V superimposed on a 920 Hz alternating voltage was applied, and the peripheral speed of the OPC photosensitive drum was set to 100 mm / sec. When evaluating the occurrence of abnormal images due to pinholes, a pinhole of about 0.3 [mmφ] is artificially provided on the surface of the OPC photoreceptor.

  The average film thickness of the resistance layer, which is the outermost layer, was obtained by observing with an electron microscope and connecting the average heights of adjacent concave and convex. Moreover, the content rate of the particle | grains in 10% from the average height of the surface vicinity and the lower surface vicinity was computed by calculating | requiring the occupation area of the nonelectroconductive particle of a cross section. The viscosity of the resistance layer composition was measured at 60 rpm using a B-type viscometer. For the surface roughness, a 10-point average roughness (Rz) was measured according to JISB0601, using a surface roughness measuring instrument (trade name: Surfcoder SE-30H, manufactured by Kosaka Laboratory).

(Example 2)
Example 1 except that 25 parts by mass of thermoplastic polyethylene particles (trade name: Flow Beads Sumitomo Seika Co., Ltd.) having an average particle diameter of 12 μm were added as non-conductive particles and the viscosity was adjusted to 20 mPa · s with ethyl acetate as a solvent. In the same manner as above, a composition for a resistance layer was produced.

The resistance member composition was applied to the elastic body produced in the same manner as in Example 1 so that the pulling speed at the upper end was 40 mm / s and the lower end was 20 mm / s, and the charging member 2 was produced. The resistance value of the charging member 2 was 5 × 10 ⁶ Ω.

  From Table 1, the charging member 2 has an initial sand ground voltage of 15 kC / 15% at 1.5 kV and a leakage voltage of 2.6 kV, and the sand ground voltage after passing 10,000 sheets is 1.9 kV at 35 ° C./90%. The leakage voltage at 2.6 kV was 2.6 kV.

  The difference between the sand ground voltage and the leak voltage was 1.1 kV, but it was found that there was no problem in use. Further, the surface roughness decreased by 2 μm after the durability test, but the sand voltage had no problem in use, and no influence on the leakage voltage at 15 ° C./15% and 35 ° C./90% was observed.

(Example 3)
Example 1 except that 75 parts by mass of thermosetting acrylic particles (trade name: Evostar Nippon Shokubai Co., Ltd.) having an average particle diameter of 1 μm were added as non-conductive particles and the viscosity was 25 mPa · s with ethyl acetate as a solvent. Similarly, a composition for a resistance layer was produced.

The composition for a resistance layer was applied to the elastic body produced in the same manner as in Example 1 so that the pulling speed at the upper end was 20 mm / s and the lower end was 10 mm / s, and the charging member 3 was produced. The resistance value of the charging member 3 was 7 × 10 ⁷ Ω.

  From Table 1, the charging member 3 has an initial sand ground voltage of 15 kC / 15% at 1.7 kV and a leak voltage of 3.0 kV, and the sand ground voltage after passing 10,000 sheets is 1.9 kV at 35 ° C./90%. The leakage voltage at 3.0 kV was 3.0 kV. Although the difference between the sand ground voltage and the leakage voltage is 1.3 kV, it was found that there is no problem in use. Moreover, the surface roughness did not decrease after the durability test, the sand ground voltage had no problem in use, and no influence on the leakage voltage at 15 ° C./15% and 35 ° C./90% was observed.

Example 4
As in Example 1, except that 50 parts by mass of thermosetting phenol resin (trade name: Belpearl R600 Kanebo) having an average particle size of 10 μm was added as non-conductive particles and the viscosity was adjusted to 10 mPa · s with ethyl acetate as a solvent. Thus, a composition for the resistance layer was produced.

The resistance member composition was applied to the elastic body produced in the same manner as in Example 1 so that the pulling speed at the upper end was 20 mm / s and the lower end was 10 mm / s, and the charging member 4 was produced. The resistance value of the charging member 4 was 8 × 10 ⁶ Ω.

  From Table 1, the charging member 4 has an initial sand voltage of 1.5 kV at 15 ° C./15% and a leak voltage of 2.8 kV, and the sand voltage after passing 10,000 sheets is 1.7 kV, 35 ° C./90%. The leakage voltage at 2.8 kV was 2.8 kV. The difference between the sand ground voltage and the leakage voltage was 1.3 kV, and it was found that there was no problem in use. Moreover, the surface roughness did not decrease after the durability test, the sand ground voltage had no problem in use, and no influence on the leakage voltage at 15 ° C./15% and 35 ° C./90% was observed.

(Example 5)
Except for adding 15 parts by mass of silica particles (trade name: Tospearl 120 GE Toshiba Silicone) having an average particle diameter of 21 μm as non-conductive particles and setting the viscosity to 25 mPa · s with ethyl acetate as a solvent, the same as in Example 1. A composition for a resistance layer was prepared.

The resistance layer composition was applied to the elastic body produced in the same manner as in Example 1 so that the pulling speed at the upper end was 40 mm / s and the lower end was 10 mm / s, and the charging member 5 was produced. The resistance value of the charging member 5 was 1 × 10 ⁷ Ω.

  From Table 1, the charging member 5 has an initial sand voltage of 1.5 kV at 15 ° C./15% and a leak voltage of 3.0 kV. The sand voltage after passing 10,000 sheets is 1.5 kV, 35 ° C./90%. The leakage voltage at 3.0 kV was 3.0 kV. The difference between the sand ground voltage and the leakage voltage was 1.5 kV, and it was found that there was no problem in use. Moreover, the surface roughness did not decrease after the durability test, the sand ground voltage had no problem in use, and no influence on the leakage voltage at 15 ° C./15% and 35 ° C./90% was observed.

(Example 6)
A composition for a resistance layer was prepared in the same manner as in Example 4 except that 30 parts by mass of non-conductive particles were added and the viscosity was 22 mPa · s with a solvent ethyl acetate.

The resistance member composition was applied to the elastic body produced in the same manner as in Example 1 so that the pulling speed at the upper end was 20 mm / s and the lower end was 10 mm / s, and the charging member 6 was produced. The resistance value of the charging member 6 was 3 × 10 ⁷ Ω.

  From Table 1, the charging member 6 has an initial sand ground voltage of 15 kC / 15% at 1.5 kV and a leakage voltage of 3.0 kV, and the sand ground voltage after passing 10,000 sheets is 1.5 kV, 35 ° C./90%. The leakage voltage at 3.0 kV was 3.0 kV. Although the difference between the sand ground voltage and the leakage voltage is 1.5 kV, it was found that there is no problem in use. Moreover, the surface roughness did not decrease after the durability test, the sand ground voltage had no problem in use, and no influence on the leakage voltage at 15 ° C./15% and 35 ° C./90% was observed.

(Comparative Example 1)
A composition for a resistance layer was prepared in the same manner as in Example 4 except that 10 parts by mass of non-conductive particles were added and the viscosity was 20 mPa · s with a solvent ethyl acetate.

The charging member 7 was manufactured by performing dipping coating at a pulling speed of 5 mm / s on the elastic body manufactured in the same manner as in Example 1 four times while turning it upside down once. The resistance value of the charging member 7 was 5 × 10 ⁶ Ω.

  According to Table 1, the charging member 7 has an initial sand ground voltage of 1.7 kV at 15 ° C./15% and a leak voltage of 2.2 kV, and the sand ground voltage after passing 10,000 sheets is 2.0 kV, 35 ° C./90%. The leakage voltage at 2.2 kV was 2.2 kV. The difference between the sand ground voltage and the leak voltage was 0.5 kV, and it was found that the voltage range in use was narrow and problematic.

(Comparative Example 2)
A composition for a resistance layer was prepared in the same manner as in Example 1 except that the viscosity was 200 mPa · s with ethyl acetate as a solvent without adding non-conductive particles. The composition for the resistance layer was injected into a φ100 mm centrifugal molding machine rotated at 3500 rpm, and an uncured film having a thickness of 30 μm was produced by decompression. Subsequently, it was wound around an elastic body produced in the same manner as in Example 1 and heated at 150 ° C. for 1 hour to carry out a crosslinking reaction, whereby a charging member 8 was produced. The resistance value of the charging member 8 was 5 × 10 ⁷ Ω.

  From Table 1, the charging member 8 had an initial sand voltage of 2.0 kV at 15 ° C./15% and a leakage voltage of 3.0 kV, but the leakage voltage at 35 ° C./90% was 2.2 kV, It has been found that there is a difference in characteristics between low temperature and low humidity and high temperature and high humidity, and that the voltage range in use under high temperature and high humidity is narrow.

It is a cross-sectional conceptual diagram of the charging member of the present invention. 1 is a schematic view of a charging portion of an image forming apparatus to which a charging member of the present invention is applied. 1 is a schematic view of an image forming apparatus to which a charging member of the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Contact charging device 2 Charging member 3 Power supply 4 Image forming apparatus 5 Conductive substrate 6 Resistive layer 7 Elastic body 8 Covering layer 10 Photoconductor 11 Photoconductor substrate 12 Photosensitive layer 13 Nip part 100 Nonconductive particle

Claims (7)

  In a charging member having a structure in which a resistance layer is coated or supported on a conductive substrate, the resistance layer contains a conductive material and non-conductive particles, and the non-conductive particles are placed near the inner surface near the conductive substrate. A charging member characterized by containing a larger amount in the vicinity of the surface side than the surface side.   In the resistance layer, the non-conductive particles are distributed at a ratio of 1.1 times to 5 times within the range of 10% of the thickness from the surface side compared to the range of the thickness of 10% on the lower surface side. The charging member according to claim 1.   The charging member according to claim 1, wherein the charging member has a resistance layer containing a large amount of non-conductive particles on the surface side, and the charging member has a surface roughness Rz of 3 μm or more and 15 μm or less. When the average particle diameter of the non-conductive particles is d and the average thickness of the outermost layer of the charging member is D,
0.05 × D ≦ d ≦ 1.2 × D
The charging member according to claim 1, wherein:   The charging member according to claim 1, wherein the nonconductive particles are made of a crosslinked polymer compound.   In the method for producing a charging member according to any one of claims 1 to 5, which has a resistance layer containing a large amount of non-conductive particles on the surface side, an electrically conductive substrate or an elastic layer covered on the electrically conductive substrate, A method for producing a charging member, comprising a step of coating the resistance layer composition by moving the resistance layer composition relative to the resistance layer composition containing the conductive material, the nonconductive particles, and the binder material. .   In the process of moving the conductive substrate or the elastic layer covered on the conductive substrate relative to the resistive layer composition, the coating process is a dipping method, and the moving speed is increased compared to the end of the starting side. The method of manufacturing a charging member according to claim 6, wherein the charging member is delayed at the end on the end side.

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