JP2007101864A - Charging component and electrophotographic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent charging component and an electrophotographic system which can reduce the amount of used materials without using expensive materials and maintain uniform charging over a long time even when applying a dc voltage only. <P>SOLUTION: This charging component has a conductive support, a conductive elastic layer formed on this conductive support, an underlayer formed on this conductive elastic layer, and a surface layer having resin particles and formed on this underlayer. When the thickness of this surface layer is represented by A, the mean particle diameter of the resin particles by B, and the average of the surface roughness (Rz) measured at ten points on this underlayer by C, they satisfy relations C<A<B and B<2A. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a charging member for charging a latent image holding member such as a photosensitive member used in an electrostatic latent image process, such as a copying machine or a printer, and an electrophotographic apparatus using the charging member.

  Conventionally, the charging process in the electrophotographic process is such that the surface of the electrophotographic photosensitive member as a charged body is uniformly set to a predetermined polarity and potential by a corona shower generated by applying a high voltage (DC voltage 6 to 8 kV) to a metal wire. Corona chargers for charging have been widely used. However, there are problems such as requiring a high-voltage power supply and generating a relatively large amount of ozone.

  On the other hand, a contact charging method in which a voltage is applied while a conductive member is in contact with the photosensitive member to charge the surface of the photosensitive member has been put into practical use. In this method, a conductive member (charging member) such as a roller type, a blade type, a brush type, or a magnetic brush type is brought into contact with the photosensitive member as a charge supply member, and a predetermined charging bias is applied to the contact charging member. The photosensitive member surface is uniformly charged to a predetermined polarity and potential.

  This charging method has the advantages of lowering the voltage of the power supply and generating less ozone. In particular, a roller charging method using a conductive roller as a contact charging member is preferably used from the viewpoint of charging stability. However, the uniformity of charging is slightly disadvantageous compared to the corona charger.

  In order to improve the charging uniformity, an AC voltage component (AC voltage component) having a peak-to-peak voltage more than twice the charging start voltage (Vth) is superimposed on a direct current corresponding to the desired charged object surface potential Vd. An “AC charging method” is used in which a voltage (pulsating voltage; a voltage whose voltage value periodically changes with time) is applied to the contact charging member.

  This is intended to equalize the potential by the AC voltage, and the potential of the charged object converges to the potential Vd which is the center of the peak of the AC voltage, and is not affected by disturbances such as the environment. It is an excellent method as a contact charging method.

  However, the AC charging method superimposes a high-voltage AC voltage that is a peak-to-peak voltage more than twice the discharge start voltage (Vth) when a DC voltage is applied, so an AC power supply is required separately from the DC power supply, and the device itself Incurs an increase in costs. Further, the AC charging method has a problem that durability of the charging roller and the photosensitive member is liable to be reduced by consuming a large amount of alternating current.

  Although these problems can be solved by applying only a DC voltage to the charging roller and charging, there is a problem as shown below when only the DC voltage is applied to the charging roller.

  That is, when only a DC voltage is applied to a conventional charging member, uneven charging occurs when the surface of a charged body such as a photoconductor is charged to a desired charging potential or more or when the potential is insufficient. In particular, in an electrophotographic process in which pre-exposure for erasing the potential on the photoreceptor before primary charging is not performed, uneven charging tends to occur in the potential portion of the halftone image area.

  As described above, when a halftone image is output by a reversal development method using a conventional charging roller, for example, the above-described charging unevenness is partially white streaks, white spots, black streaks or black spots on the image. , Appearing as a half-tone image surface, and there is a problem that the image quality deteriorates.

  As means for suppressing this charging unevenness, uniform resistance distribution and surface property improvement have been studied. For example, as for the former, a technique for improving the dispersibility of the conductive substance in the surface layer or using a resin having a relatively low volume resistance value for the surface layer has been proposed. For the latter, methods such as adding a leveling agent to the surface layer and improving the surface property of the elastic layer have been proposed.

  Among these, regarding surface properties, it is proposed to apply a direct current voltage to uniformly charge the object to be charged using a charging member in which two types of particles having a large particle size and a small particle size are added to the surface layer. (See Patent Document 1). However, since two types of particles having a large particle size and a small particle size are added, management (handling, lot difference, etc.) becomes difficult in production, and problems such as an increase in cost occur. In consideration of actual mass production, there is a need for a charging member that can maintain charging uniformity over a long period of time with as few types of materials as possible rather than including many types of materials.

In addition, as a means of controlling the surface property, it is proposed that an insoluble fluororesin having a particle diameter of 30 μm is arranged near the surface of the outermost layer, thereby ensuring both surface roughness and prevention of contamination due to large surface roughness. (See Patent Document 2). However, since this means generally uses an expensive insoluble fluororesin, it is disadvantageous in terms of cost compared to the case where resin particles of other materials are used. In addition, when a fluororesin is used, the familiarity with the paint deteriorates, and appearance defects such as a dirty skin tend to occur. It is necessary to use a material that is as inexpensive as possible, stably produce at low cost, and satisfy the performance as a charging member.
JP 2003-316111 A JP-A-8-123143

  The present invention has been made in view of the above-mentioned problems, and without using an expensive material, reduces the amount of material used, and is excellent in charging uniformity over a long period even when only a DC voltage is applied. It is an object of the present invention to provide a charging member and an electrophotographic apparatus including the charging member.

The charging member according to the present invention is:
A conductive support member; a conductive elastic layer formed on the conductive support member; a base layer formed on the conductive elastic layer; and a surface layer formed on the base layer and having resin particles; A charging member comprising:
When the film thickness of the surface layer is A, the average particle diameter of the resin particles is B, and the ten-point average surface roughness (Rz) of the base layer is C,
C <A <B and B <2A.

  In addition, an electrophotographic apparatus according to the present invention includes the above-described charging member.

  According to the present invention, it is possible to reduce the amount of material used without using an expensive material, and to obtain excellent charging uniformity over a long period even when only a DC voltage is applied.

  Hereinafter, embodiments of the present invention will be described in detail.

(Charging member according to the present invention)
The present inventors have found that the charging uniformity when only a DC voltage is applied can be sufficiently improved by incorporating resin particles having an average particle diameter equal to or greater than this film thickness into the outermost surface layer. It was. That is, the charging member according to the present invention includes a conductive support member, a conductive elastic layer formed on the conductive support member, a base layer formed on the conductive elastic layer, and a base layer on the base layer. A charging member having a surface layer formed with resin particles, wherein the film thickness of the surface layer is A, the average particle diameter of the resin particles is B, and the ten-point average surface roughness (Rz) of the base layer When C is C, C <A <B and B <2A.

  In the present invention, the film thickness of the surface layer is a position other than the position (mountain portion) where the shape in the vicinity of the surface formed by the resin particles contained in the surface layer is changed, that is, 1c in FIG. The average value obtained by arbitrarily measuring 10 points at the film thickness measurement position of the surface layer indicated by.

  FIG. 1 is a conceptual cross-sectional view of the configuration of a charging member according to the present invention. In the charging member according to the present invention, since the average particle diameter of the resin particles is larger than the film thickness of the surface layer 1a, the resin particles are uniformly arranged in the surface layer one by one as shown in FIG. This is thought to be due to the fact that it is possible to control the surface roughness appropriately with the blending amount.

  The charging member according to the present invention relates to the film thickness A of the surface layer, the average particle diameter B of the resin particles, and the ten-point average surface roughness (Rz) C of the base layer, C <A <B and B <2A. Satisfy the relationship. In a general charging member, a surface layer having a film thickness larger than the average particle diameter of resin particles is employed. In this case, it is considered that the surface layer is in a state as shown in FIG. It will be difficult to control. That is, when A ≧ B, it is difficult to control the surface property uniformly, and stable charging uniformity cannot be exhibited. In addition, if the existence form of the resin particles is as shown in FIG. 2, it is considered that the resin particles are arranged in a very wasteful manner, which is disadvantageous in terms of cost.

  In addition, in the charging member according to the present invention, if the surface layer 1a contains resin particles having an average particle diameter that is twice or more the film thickness of the surface layer, the phenomenon that the resin particles fall off during the operation of the charging member, As a result, adhesion of dirt due to the formation of surface irregularities more than necessary occurs. That is, when B ≧ 2A, the resin particles fall off with long-term use, leading to deterioration of performance.

  Further, in the charging member according to the present invention, when the ten-point average surface roughness (Rz) of the underlayer is larger than the film thickness of the surface layer, it is influenced by the shape of the underlayer, and the resin particles as shown in FIG. It becomes difficult to control the uniform surface property, and the charging uniformity cannot be sufficiently improved. That is, when C ≧ A, it becomes difficult to control the surface properties by the resin particles, and the charging uniformity cannot be sufficiently improved.

  Next, a specific configuration example of the charging member according to the present invention is shown in FIGS. FIG. 3 is a cross-sectional view showing the configuration of the charging member according to the present invention, and FIG. 4 is a vertical cross-sectional view showing the configuration of the charging member according to the present invention. The charging member according to the present invention is formed on the conductive support member 2a, the conductive elastic layer 2b formed on the outer periphery thereof, the base layer 2c formed on the outer periphery thereof, and the base layer 2c, and forms the outermost layer. And a surface layer 2d.

  The conductive support member 2a used in the present invention is not particularly limited as long as it has conductivity. For example, metals such as iron, aluminum, titanium, copper and nickel, stainless steel containing these metals, duralumin, There are known materials showing rigidity and conductivity, such as alloys such as brass and bronze, and composite materials in which carbon black and carbon fibers are hardened with plastic. In addition to the columnar shape, the conductive support member 2a may have a cylindrical shape having a hollow central portion. In addition, the surface of the conductive support member 2a may be subjected to a surface treatment such as plating for the purpose of providing rust prevention or scratch resistance.

  In the charging member according to the present invention, the conductive elastic layer 2b is not particularly limited as long as it is a material having conductivity and elastic characteristics. For example, as the elastic material, natural rubber, chloroprene rubber (CR), isoprene rubber ( IR), ethylene propylene rubber (EPDM), styrene butadiene rubber (SBR), urethane rubber, epichlorohydrin rubber, epoxy rubber and butyl rubber, or sponges. The conductive elastic layer 2b is a conductive agent having an electronic conductivity such as carbon black, graphite, and conductive metal oxide, or a conductive material having an ion conductive mechanism such as an alkali metal salt or a quaternary ammonium salt. What is necessary is just to add an agent suitably.

  In the charging member according to the present invention, the base layer 2c includes olefin (TPO), styrene (TPS), urethane (TPU), ester (TPEE), amide (TPA), vinyl chloride (PVC), and the like. These thermoplastic elastomers can be mentioned.

  As a manufacturing method of the foundation layer 2c, first, the above-mentioned thermoplastic elastomer and a conductive agent such as carbon black are kneaded together with necessary additives, and then pelletized. Next, the obtained pellet is formed into an underlayer member having a desired shape such as a seamless tube by an extrusion molding machine. And the method etc. etc. which coat | cover and manufacture the member for base layers, such as a molded seamless tube, on an electroconductive support member, etc. are mentioned. The underlayer 2c may be a simultaneously formed tube having multiple layers.

In the charging member according to the present invention, the surface layer 2d constitutes the surface of the charging member and is in direct contact with the electrophotographic photosensitive member which is a member to be charged. The surface layer 2d is not particularly limited as long as the surface layer 2d is a material that can appropriately impart charge to the member to be charged. For example, polyester resin, acrylic resin, urethane resin, acrylic urethane resin, polyamide resin, epoxy resin, polyvinyl acetal resin, vinylidene chloride resin, fluororesin, and silicone resin can be used. . Furthermore, the surface layer 2d may have an appropriate amount of an additive such as a crosslinking agent, if necessary. In this case, any crosslinking agent may be used as long as a desired crosslinking effect can be obtained. For example, an epoxy type, an oxazoline type, a melanin type, an isocyanate type, and a phenol type crosslinking agent are mentioned. In addition, the surface layer 2d may be imparted or adjusted by adding a conductive agent. In this case, the conductive agent is not particularly limited, but ketjen black EC, acetylene black, etc. Conductive carbon, SAF, ISAF, HAF, FEP, GPF, SRF, FT, MT and other rubber carbon, oxidized color ink carbon, pyrolytic carbon, natural graphite, artificial graphite, antimony-doped oxidation Metals such as tin, titanium oxide, zinc oxide, nickel, copper, silver, germanium, or metal oxides can be used. For the surface of these conductive agents, a coupling agent such as a titanium coupling agent or an alkoxysilane coupling agent, a coupling agent such as a fluoroalkylalkoxysilane coupling agent (a central metal such as silicon, titanium, aluminum, and zirconium is not particularly selected. ), Surface treatment with oil, varnish, organic compound or the like. Moreover, the addition amount of the said electrically conductive agent can be suitably adjusted so that desired resistance may be obtained. In this case, the resistance of the surface layer is preferably 10 ³ to 10 ¹⁵ Ω · cm, more preferably 10 ⁵ to 10 ¹⁴ Ω · cm.

  Examples of the resin particles added to the surface layer 2d include insulative organic particles such as acrylic resin, acrylic / styrene copolymer resin, polyamide resin, silicone rubber resin, and epoxy resin. The particle diameter of the resin particles is preferably 1 μm or more and 50 μm or less, and more preferably 5 μm or more and 30 μm or less. If the particle diameter of the resin particles exceeds 50 μm, rust or black spots occur on the image. Furthermore, if the particle diameter of the resin particles is 50 μm or more, aggregation is likely to occur, which is not preferable.

  In the charging member according to the present invention, the resin particles contained in the surface layer are preferably contained in an amount of 10% by mass to 30% by mass with respect to the mass of the surface layer. When the content is larger than 30% by mass, the resin particle content is excessively large with respect to the surface layer, so that it is difficult to form the presence state of the resin particles in the surface layer as shown in FIG. If it is less than%, the existence interval between the resin particles becomes too large, resulting in poor charging uniformity.

  As a method for forming the surface layer, first, the above-described materials constituting the surface layer are dispersed by a known method using a conventionally known dispersion apparatus using beads such as a sand mill, a paint shaker, a dyno mill, and a pearl mill. The obtained resin coating for forming the surface layer is applied on a base layer such as a conductive seamless tube by dipping or spray coating. As the method for forming the surface layer, the dipping method is preferable from the viewpoint of the utilization efficiency of the surface layer paint. When the dipping method is used for forming the surface layer, the surface layer film thickness is adjusted by adjusting / controlling the amount of resin in the coating material for forming the surface layer and the coating lifting speed. Increasing the amount of resin in the surface layer paint increases the film thickness of the surface layer, and decreasing the amount of resin decreases the film thickness. Further, when the pulling speed is decreased, the film thickness is increased, and when the pulling speed is increased, the film thickness is decreased.

(Electrophotographic apparatus according to the present invention)
Next, an electrophotographic apparatus according to the present invention will be described.

  FIG. 5 is a schematic configuration diagram of an example of an electrophotographic apparatus having a charging member according to the present invention. As long as the electrophotographic apparatus according to the present invention has the above-described charging member, other configurations are not particularly limited. As an example, according to FIG. 5, in the electrophotographic apparatus according to the present invention, the rotating drum type electrophotographic photosensitive member 21 as the image carrier rotates at a predetermined peripheral speed (process speed) in the direction indicated by the arrow in the figure. To drive. The electrophotographic photoreceptor 21 may be, for example, a known photoreceptor having at least a roll-like conductive support and a photosensitive layer containing an inorganic photosensitive material or an organic photosensitive material on the support. The electrophotographic photosensitive member 21 may further include a charge injection layer for charging the surface of the photosensitive member to a predetermined polarity or potential. A charging roller (conductive roller) 22 as a charging member is combined with a charging bias application power source S1 for applying a charging bias to the charging roller 22 to constitute a charging unit. The charging roller 22 is brought into contact with the electrophotographic photosensitive member 21 with a predetermined pressing force, and is driven to rotate with respect to the rotation of the electrophotographic photosensitive member 21. In the example of FIG. 5, the charging roller 22 is shown to be driven to rotate in the forward direction with respect to the rotation of the electrophotographic photosensitive member 21. The charging roller 22 is applied with a predetermined DC voltage (in this example, −1200 V) from the charging bias application power source S1, and the surface of the electrophotographic photosensitive member 21 is predetermined by the DC charging method among the contact charging methods. Is uniformly charged to a polar potential (in this example, a dark portion potential of −600 V). The exposure means 23 may use a known means, and for example, a laser beam scanner or the like is preferable. The exposure means 23 exposes the exposure processing surface of the electrophotographic photosensitive member 21 with the exposure L corresponding to the target image information, and the potential of the exposure bright portion of the charging surface of the electrophotographic photosensitive member (in this example, the bright portion potential −). 350V) is selectively lowered (attenuated) to form an electrostatic latent image on the electrophotographic photosensitive member 21. A known means can be used as the developing means 24. For example, the developing unit 24 includes a toner carrying member 24a that is disposed in an opening of a developing container that contains toner and carries and conveys the toner, a stirring member 24b that stirs the contained toner, and the toner of the toner carrying member 24a. And a toner regulating member 24c that regulates the carrying amount (toner layer thickness). The developing means 24 is a toner (with a developing bias of −350 V in this example) charged to the exposed bright portion of the electrostatic latent image on the surface of the electrophotographic photosensitive member 21 with the same polarity as the charging polarity of the electrophotographic photosensitive member 21 (in this example, the developing bias is −350 V). Negative toner) is selectively attached to visualize the electrostatic latent image as a toner image. There is no particular limitation on the development method, and all existing methods can be used, and examples thereof include a jumping development method, a contact development method, and a magnetic brush method. In particular, in an electrophotographic apparatus that outputs a color image, the contact development method is preferable from the viewpoint of improving toner scattering properties. As the transfer roller 25 which is a transfer means, a known means can be used, for example, a transfer roller formed by coating a conductive support such as metal with an elastic resin layer adjusted to a medium resistance. . The transfer roller 25 is brought into contact with the electrophotographic photosensitive member 21 with a predetermined pressing force to form a transfer nip portion, and is approximately equal to the rotational peripheral speed of the electrophotographic photosensitive member 21 in the forward direction with the rotation of the electrophotographic photosensitive member 21. Rotates at the same peripheral speed. The transfer roller 25 is applied with a transfer voltage having a polarity opposite to the charging characteristics of the toner from the transfer bias application power source S2. The transfer material P is fed to the transfer nip portion at a predetermined timing from a paper feed mechanism portion (not shown). The back surface of the transfer material P is charged to a polarity opposite to the charging polarity of the toner by the transfer roller 25 to which a transfer voltage is applied. As a result, the toner image on the surface of the electrophotographic photosensitive member 21 is electrostatically transferred to the surface side of the transfer material P at the transfer nip portion. The transfer material P that has received the transfer of the toner image at the transfer nip portion is separated from the surface of the electrophotographic photosensitive member and is introduced into a toner image fixing means (not shown). Is output. In the case of the double-sided image forming mode or the multiple image forming mode, this image formed product is introduced into a recirculation conveyance mechanism (not shown) and reintroduced into the transfer nip portion. Residues on the electrophotographic photosensitive member 21 such as transfer residual toner are collected from the photosensitive member by a cleaning means 26 such as a blade type. Further, when residual charge remains on the electrophotographic photosensitive member 21, it is preferable to remove the residual charge of the electrophotographic photosensitive member 21 by the pre-exposure means 27 before performing the primary charging by the charging roller 22.

  Hereinafter, the present invention will be described in more detail by way of specific examples. However, the present invention is not limited to these. In addition, "part" in an Example shows a mass part.

Example 1
[Preparation of conductive elastic layer]
The following components were mixed with two rolls for 20 minutes to produce a compound.
EPDM 100 parts Zinc oxide 5 parts Higher fatty acid 1 part Conductive carbon black 5 parts Paraffin oil 10 parts Sulfur 2 parts Vulcanization accelerator (MBT) 1 part Vulcanization accelerator (TMTD) 1 part Vulcanization accelerator (ZnMDC) 1 .5 parts Foaming agent (sodium bicarbonate) 10 parts This is extruded into a cylindrical shape with an outer diameter of 10 mm and an inner diameter of 5.5 mm using a rubber extruder, cut into a length of 250 mm, and a vulcanized can is used. Then, primary vulcanization was performed in water vapor at 160 ° C. for 40 minutes to obtain a conductive elastic body layer rubber primary vulcanization tube. Next, a thermosetting adhesive (trade name: metal and rubber) is attached to the central portion 231 mm in the axial direction of the cylindrical surface of a cylindrical conductive support member (steel, surface industrial nickel plating) having a diameter of 6 mm and a length of 256 mm. Metalloc U-20 (manufactured by Toyo Chemical Laboratory Co., Ltd.) was applied. After coating, the film was dried at 80 ° C. for 30 minutes and then dried at 120 ° C. for 1 hour. This conductive support member is inserted into the above-described conductive elastic layer rubber primary vulcanization tube, and then subjected to secondary vulcanization and curing of the adhesive in an electric oven at 160 ° C. for 2 hours, An unpolished layer was obtained. In this unpolished layer, both ends of the rubber part are cut off and the length of the rubber part is set to 231 mm, and then the rubber part is polished with a rotating grindstone to form a crown shape having an end diameter of 8.00 mm and a central part diameter of 8.10 mm. A foaming roller having a conductive elastic layer was obtained.

[Creation of underlayer]
For the conductive seamless tube formed on the above-mentioned foaming roller, 16 parts of ketjen black EC, 10 parts of magnesium oxide and 1 part of calcium stearate were added to 100 parts of thermoplastic polyurethane elastomer (TPU). This was kneaded at 180 ° C. for 15 minutes using a pressure kneader, cooled and pulverized, and pelletized by a granulating extruder. The pellets were extruded using an extruder equipped with a point having an outer diameter of φ11.85 mm and a mirror die having an inner diameter of φ12.75 mm. After that, through a sizing and cooling process, a seamless tube having an outer diameter of φ8.5 mm, an inner diameter of φ7.9 mm, and a thickness of 300 μm was formed and cut into a length of 300 mm. The obtained seamless tube was covered with the foaming roller having the conductive elastic body layer described above, both ends were cut off, and the length of the seamless tube portion was 234 mm. As a result, a conductive roller having a crown-shaped underlayer with an end diameter of 8.45 mm and a center diameter of 8.50 mm was obtained.

(Creation of surface layer)
The following surface layer was formed on the conductive roller described above.

As a material for the surface layer, 100 parts of lactone-modified acrylic polyol (trade name “Placcel DC2016” manufactured by Daicel Chemical Industries, Ltd.) was dissolved in 250 parts of methyl isobutyl ketone. The following components were blended and dispersed for 6 hours using a paint shaker to prepare a dip coating paint.
Block isocyanate (IPDI)
(Product name “Duranate MF-K60X”: manufactured by Asahi Kasei Chemicals Corporation)
92.14 parts carbon black (trade name “MA100” manufactured by Mitsubishi Chemical Corporation) 20.02 parts modified dimethyl silicone oil (trade name “SH-28PA” manufactured by Toray Dow Corning Silicone Co., Ltd.)
0.1 part polymethyl methacrylate (PMMA) particles (trade name “Techpolymer” (average particle size 5 μm): Sekisui Plastics Co., Ltd.)
20 parts of this surface layer coating was applied to the surface of the conductive roller by dipping. After air drying for 30 minutes, it was sintered and dried at 110 ° C. for 60 minutes. Thus, a roller-shaped charging member having a surface layer formed thereon was obtained.

<Measurement of 10-point average surface roughness (Rz) of underlayer>
Using the seamless tube obtained as described above, ten-point average surface roughness (Rz) was measured. The measurement is made by Kosaka Laboratory: Surface roughness meter SE-3300H, and the measurement conditions are cut-off 0.8 mm, measurement distance 8 mm, feed rate 0.5 mm / second, and three conductive roller central portions ( The Rz average value of 120 ° increments from any place was determined. The results are shown in Table 1.

<Measurement of surface layer thickness>
Using the charging member obtained as described above, the surface layer thickness was measured. The measurement is performed so that the cross section of the surface layer of the roller center portion can be seen, and using an SEM (scanning electron microscope), as described above, arbitrary 10 points corresponding to the film thickness measurement position 1c of the surface layer are measured and averaged. Asked. The results are shown in Table 1.

<Endurance test for continuous image output when only DC voltage is applied to the charging roller>
The charging member obtained as described above was mounted on a printer, and a continuous plural-sheet image endurance test was performed in an atmosphere of a temperature of 23 ° C. and a humidity of 55%. Monocolor halftone printing was performed on the initial and 20,000 sheets. The obtained image was visually observed and evaluated. The results are shown in Table 1.

  “◎”, “◯”, “Δ”, “×”, and “XX” in the table are the image quality rankings in five levels for the occurrence of charging unevenness. In addition, “」 ”is a level where there is no charging unevenness, and“ ◯ ”is good. “△” and “×” are judged as NG because they have some image problem parts which are inferior as a product. Furthermore, “XX” was determined to be a defective level because of uneven charging. The results are shown in Table 1.

  The charging member of Example 1 did not cause uneven charging before and after endurance, and maintained good charging uniformity even after endurance.

(Example 2)
In the production of the surface layer of Example 1, polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 8 μm were used instead of polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 5 μm. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  The charging member of Example 2 did not cause uneven charging before and after endurance, and maintained good charging uniformity even after endurance.

(Example 3)
In the preparation of the surface layer of Example 1, polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 15 μm were used instead of polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 5 μm. Further, the amount of methyl isobutyl ketone was changed from 250 parts to 200 parts. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  The charging member of Example 3 did not cause uneven charging before and after endurance, and maintained good charging uniformity even after endurance.

Example 4
In the production of the surface layer of Example 1, polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 30 μm were used instead of polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 5 μm. Further, the amount of methyl isobutyl ketone was changed from 250 parts to 150 parts. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  The charging member of Example 4 did not cause uneven charging before and after durability, and maintained good charging uniformity even after durability.

(Example 5)
In preparation of the underlayer of Example 1, a roughing die was used instead of the mirror die. In the preparation of the surface layer, polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 30 μm were used instead of polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 5 μm. Further, the amount of methyl isobutyl ketone was changed from 250 parts to 150 parts. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  The charging member of Example 5 was free from uneven charging before and after endurance and maintained good charging uniformity after endurance.

(Example 6)
In preparation of the underlayer of Example 1, a roughing die was used instead of the mirror die. In the preparation of the surface layer, polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 40 μm were used instead of polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 5 μm. Further, the amount of methyl isobutyl ketone was changed from 250 parts to 150 parts. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  The charging member of Example 6 had no charging unevenness before the endurance, and slight charging unevenness due to the stain occurred after the endurance, but the image quality had no problem in practical use.

(Example 7)
In preparation of the underlayer of Example 1, a roughing die was used instead of the mirror die. In the preparation of the surface layer, polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 50 μm were used instead of polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 5 μm. Further, the amount of methyl isobutyl ketone was changed from 250 parts to 150 parts. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  In the charging member of Example 7, slight charging unevenness that seems to be a factor of the particle diameter occurred before the endurance, and after charging, the slight charging unevenness due to the stain occurred. The image quality was satisfactory.

(Comparative Example 1)
In preparation of the surface layer of Example 1, the amount of methyl isobutyl ketone was changed from 250 parts to 200 parts. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  Since the charging member of Comparative Example 1 had a film thickness larger than the resin particle diameter before endurance, uneven charging occurred, and the endurance deteriorated further after endurance.

(Comparative Example 2)
In preparation of the underlayer of Example 1, a roughing die was used instead of the mirror die. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  The charging member of Comparative Example 2 had charging unevenness that seemed to be a cause of the surface roughness of the underlayer before endurance, and the occurrence of this charging unevenness did not disappear even after endurance.

(Comparative Example 3)
In the preparation of the surface layer of Example 1, polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 15 μm were used instead of polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 5 μm. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  The charging member of Comparative Example 3 had good image quality with no occurrence of charging unevenness before endurance, but after the endurance, charging unevenness that was considered to be a cause of dropping of resin particles occurred.

(Comparative Example 4)
In the production of the surface layer of Example 1, polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 30 μm were used instead of polymethyl methacrylate (PMMA) resin particles having an average particle diameter of 5 μm. Others were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  The charging member of Comparative Example 4 had charging unevenness that seemed to be a factor of the particle diameter with respect to the film thickness before the endurance, and after the endurance, charging unevenness that seemed to be a cause of dropping of the resin particles occurred.

1 is a conceptual cross-sectional view of a configuration of a charging member according to the present invention. It is a conceptual sectional view of the configuration of a conventional charging member. It is a cross-sectional view which shows the structure of the charging member by this invention. It is a longitudinal cross-sectional view which shows the structure of the charging member by this invention. 1 is a schematic configuration diagram of an example of an electrophotographic apparatus having a charging member according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Surface layer 1b Resin particle 1c Surface layer film thickness measurement position 1d Surface layer film thickness measurement position 1e Underlayer 2a Conductive support member 2b Conductive elastic layer 2c Underlayer 2d Surface layer 21 Electrophotographic photosensitive member 22 Charging roller 23 Exposure means 24 Developing means 24a Toner carrier 24b Stirring member 24c Toner regulating member 25 Transfer roller 26 Cleaning means 27 Pre-exposure means P Transfer material L Laser light S1 Bias application power source S2 Bias application power source S3 Bias application power source

Claims (7)

A conductive support member; a conductive elastic layer formed on the conductive support member; a base layer formed on the conductive elastic layer; and a surface layer formed on the base layer and having resin particles; A charging member comprising:
When the film thickness of the surface layer is A, the average particle diameter of the resin particles is B, and the ten-point average surface roughness (Rz) of the base layer is C,
A charging member, wherein C <A <B and B <2A.   The charging member according to claim 1, wherein an average particle diameter of the resin particles is 1 μm or more and 50 μm or less.   The charging member according to claim 1, wherein the surface layer has the resin particles at 10 mass% or more and 30 mass% or less.   The charging member according to claim 1, wherein the underlayer has a ten-point average surface roughness (Rz) of 2 μm or more and 15 μm or less.   The charging member according to claim 1, wherein the underlayer is a seamless tube.   The charging member according to any one of claims 1 to 5, wherein the surface layer is a surface layer mainly composed of an acrylurethane resin in which a lactone-modified acrylic polyol is isocyanate-crosslinked.   An electrophotographic apparatus comprising the charging member according to claim 1.

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