JP2008180882A - Electrifying member and electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrifying member capable of preventing contamination of a body to be electrified while holding uniformity of electrification, and restraining noise from being made during electrification such as electrification sound while maintaining an excellent image even in long-term use, and an electrophotographic device having the electrifying member. <P>SOLUTION: The electrifying member has a conductive support member, a foaming rubber layer provided on the conductive support member, a non-foaming rubber layer provided on the foaming rubber layer, and a surface layer formed on the non-foaming rubber layer. In the electrifying member, a difference between the ASKER C hardness of the foaming rubber layer and the ASKER C hardness of the non-foaming rubber layer is 20 or more and 50 or less, the thickness of the non-foaming rubber layer is 100 μm or more and 2 mm or less, and the surface layer is cross-linked resin layer having thickness of 5 μm to 50 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a charging member and an electrophotographic apparatus using the charging member, and in particular, a charging member that charges a charged body by bringing the charging member to which a voltage is applied into contact with the charged body (photosensitive drum), And an electrophotographic apparatus using the same.

  Many methods are known as an electrophotographic apparatus, but generally, a method of attaching a charged toner to an electrostatic latent image is widely used. In other words, in this method, first, an electric latent image is formed on the photosensitive drum by various means using a photoconductive substance. Next, development is performed by attaching toner to the latent image to form a visible image, and after transferring the toner image to a transfer material such as paper as necessary, the toner image is formed on the transfer material by heat, pressure, or the like. Is fixed to obtain a copy. In addition, toner particles that are not transferred onto the transfer material and remain on the photosensitive member are removed from the photosensitive drum by a cleaning process.

  Conventionally, a corona charger has been used as a charging processing device of an electrophotographic apparatus used to form the above-described electric latent image. In recent years, contact charging devices have been put to practical use instead. The contact charging device aims to achieve low ozone and low power consumption. Among these, the roller charging method using a conductive roller is preferably used as a charging member from the viewpoint of charging stability. In the roller charging method, first, a conductive elastic roller (charging roller) is brought into pressure contact with a member to be charged (photosensitive drum). Next, a DC voltage and an oscillating electric field having a peak-to-peak voltage more than twice the charging start voltage when the DC voltage is applied to the charging roller are formed between the charging roller and the photosensitive drum. Thereby, the charging uniformity of the photosensitive drum can be achieved. However, the application of an oscillating electric field causes a problem that the charging roller and the photosensitive drum vibrate in contact with each other and a charging sound is generated. This charging sound becomes annoying noise at a high frequency particularly when the frequency of the AC voltage applied to the charging roller is large. Further, when the roundness of the charging roller is low, the noise of the charging sound is swelled in a form corresponding to the shaking of the charging roller, which is very disturbing.

  Conventionally, it has been effective to reduce the hardness of the charging roller in order to suppress the noise level of the charging sound. As a method for reducing the hardness of the charging roller, it is conceivable to increase the amount of additive such as softening oil or plasticizer contained in the elastic layer. However, there is a problem that the plasticizer oozes out from the charging member and contaminates the photosensitive drum.

  In addition, for the purpose of imparting a desired electrical resistance characteristic to the surface of the conductive roller, a technique of providing a resistance layer by coating is employed. However, when this technique is employed, it is easily affected by unevenness of the underlying surface. Therefore, it is difficult to finish the surface after forming the resistance layer smoothly. In particular, when the foam is used for the elastic layer, it is very difficult to finish the resistance layer surface smoothly because the surface of the foam has large irregularities. If the surface smoothness is poor, there is a problem that unevenness due to unevenness occurs when a plurality of images are continuously printed, resulting in an image defect.

On the other hand, in recent years, as a charging roller, a conductive foam layer is provided on a conductive shaft body, and a conductive non-foam layer is further provided on the conductive foam layer. A charging roller having a protective layer coated on the layer is disclosed (see Patent Document 1). As a method of manufacturing the charging roller, there is a method of forming by vulcanization foaming using a cylindrical molding die. When the state where the charging roller and the photosensitive drum are in pressure contact continues for a long time, the charging roller Compression permanent distortion occurs at the contact portion with the photosensitive drum. As a result, there has been a problem that the compression set part deteriorates the undulation of the charged sound.
JP-A-6-186824

  The present invention has been made in view of the above-mentioned problems, and while maintaining charging uniformity, prevents contamination of an object to be charged, maintains a good image even in long-term use, It is an object of the present invention to provide a charging member capable of suppressing generation of noise during charging and an electrophotographic apparatus having the charging member.

  A charging member according to the present invention is formed on a conductive support member, a foamed rubber layer provided on the conductive support member, a non-foamed rubber layer provided on the foamed rubber layer, and the non-foamed rubber layer. The difference between the Asker C hardness of the foamed rubber layer and the Asker C hardness of the non-foamed rubber layer is 20 degrees or more and 50 degrees or less, and the thickness of the non-foamed rubber layer is: The surface layer is a cross-linked resin layer having a thickness of 5 μm or more and 50 μm or less.

  The electrophotographic apparatus according to the present invention is characterized in that in the electrophotographic apparatus, the charging means is the above-described charging member.

  According to the present invention, even when a plurality of images are continuously printed out with a smooth surface, image defects due to dirt unevenness do not occur. Further, there is no contamination of the member to be charged due to the plasticizer exuding from the member to the member to be charged. Further, the compression set is small, the noise level of the charging sound is low when an AC electric field is applied, and the undulation of the noise of the charging sound is also low.

  Hereinafter, preferred embodiments of the present invention will be described.

(Charging member according to the present invention)
A charging member according to the present invention is formed on a conductive support member, a foamed rubber layer provided on the conductive support member, a non-foamed rubber layer provided on the foamed rubber layer, and the non-foamed rubber layer. In the charging member having the surface layer formed, the difference between the Asker C hardness of the foamed rubber layer and the Asker C hardness of the non-foamed rubber layer is 20 degrees or more and 50 degrees or less, and the thickness of the non-foamed rubber layer is The surface layer is a cross-linked resin layer having a thickness of 5 μm or more and 50 μm or less.

  A specific configuration example of the charging member according to the present invention is shown in FIGS. FIG. 1 is a schematic cross-sectional view showing the structure of a charging member according to the present invention, and FIG. 2 is a schematic vertical cross-sectional view showing the structure of a charging member according to the present invention. The charging member according to the present invention is a charging member having at least a conductive support member 1a, a foamed rubber layer 1b formed on the outer periphery thereof, a non-foamed rubber layer 1c formed on the outer periphery thereof, and an outermost surface layer 1d. It is a member.

  Examples of the conductive support member 1a used in the present invention include metals such as iron, aluminum, titanium, copper and nickel, and alloys such as stainless steel, duralumin, brass and bronze containing these metals. In addition to the above, the conductive support member 1a may be a known material that is rigid and exhibits conductivity, such as a composite material in which carbon black or carbon fiber is solidified with plastic. In addition to the columnar shape, the conductive support member 1a may have a cylindrical shape having a hollow central portion. In addition, these surfaces may be plated for the purpose of providing rust prevention and scratch resistance.

  Examples of materials for the foamed rubber layer 1b and the non-foamed rubber layer 1c (hereinafter collectively referred to as “conductive elastic body layer”) used in the present invention include the following various rubbers.

Natural rubber Chloroprene rubber (CR)
Isoprene rubber (IR)
Ethylene propylene rubber (EPDM)
Styrene butadiene rubber (SBR)
Urethane rubber Epichlorohydrin rubber Epoxy rubber Butyl rubber

  The foamed rubber layer 1b and the non-foamed rubber layer 1c may be formed by forming these materials into rubber or sponge. The foamed rubber layer 1b and the non-foamed rubber layer 1c may be obtained by appropriately adding a conductive agent having an electronic conductive mechanism such as carbon black, graphite, and conductive metal oxide to these rubbers. Moreover, what added suitably the electrically conductive agent which has an ionic conductive mechanism like an alkali metal salt and a quaternary ammonium salt may be used.

  In addition to the above, a known foaming agent may be used as the material of the foamed rubber layer 1b of the conductive elastic body layer. Examples of blowing agents include azodicarbonamide (ADCA), p, p'-oxybis (benzenesulfonylhydrazide) (OBSH), N, N'-dinitropentamethylenetetramine (DPT), and sodium bicarbonate. Of these, azodicarbonamide (ADCA) and p-p′oxybisbenzenesulfonyl hydrazide (OBSH) are preferable from the viewpoint that the vulcanization rate is difficult to increase. For the purpose of assisting foaming, a known foaming aid such as urea may be added.

  In the charging member according to the present invention, the difference between the Asker C hardness of the foamed rubber layer of the conductive elastic layer and the Asker C hardness of the non-foamed rubber layer is 20 degrees or more and 50 degrees or less. When this difference is less than 20 degrees, the non-foamed rubber layer does not absorb pressure deformation only by deformation of the foamed rubber layer when the charging member is in pressure contact with the member to be charged for a long time. Will be deformed. Then, compression set is generated at the contact portion between the charging member and the member to be charged, and the compression set part deteriorates the undulation of the charged sound. If this difference is greater than 50 degrees, the smoothness of the non-foamed rubber layer of the conductive elastic layer after polishing becomes poor. As a result, when a plurality of images are continuously printed, the unevenness of the unevenness occurs, resulting in an image defect.

  In the charging member according to the present invention, the non-foamed rubber layer of the conductive elastic layer has a thickness of 100 μm or more and 2 mm or less. If the thickness is less than 100 μm, the original characteristics (hardness / strength) of the non-foamed rubber layer are not fully exhibited, and it deforms in the same way as the foamed rubber layer when pressed against a charged body. End up. In this case, if the state where the charging member is in pressure contact with the member to be charged continues for a long period of time, compression permanent distortion occurs at the contact portion between the charging member and the member to be charged, and the portion of the compression permanent distortion is charged with the charged sound. Will make the swell worse. On the other hand, when the thickness exceeds 2 mm, the hardness of the charging member increases, and the noise level of the charging sound is deteriorated.

  The method for forming the conductive elastic layer having the foamed rubber layer and the non-foamed rubber layer is not particularly limited as long as it satisfies the above-described configuration, and a known method may be appropriately used. For example, this forming method may be a method in which a composition comprising the above-described various rubber components and other components is mixed, and then extruded and vulcanized simultaneously and integrally by a extruder, and then polished and formed. Good. Man-hours can be simplified by simultaneously extruding and forming a plurality of layers. Further, since vulcanization / foaming is not performed in the mold, continuous production is possible.

  In the charging member according to the present invention, the surface layer 1d formed on the non-foamed rubber layer is a crosslinked resin layer having a thickness of 5 μm or more and 50 μm or less.

  When the thickness of the surface layer is less than 5 μm, components such as softening oil, plasticizer, and ionic conductive agent contained in the conductive elastic body layer that is a rubber composition ooze out and contaminate the object to be charged. Problems arise. When the thickness of the surface layer is larger than 50 μm, the hardness of the charging member is increased and the noise level of the charging sound is deteriorated.

  The cross-linked resin layer constituting the surface layer is not particularly limited as long as the cross-linked resin layer is made of a resin capable of charging the surface of the charged body by contact with the charged body such as a photosensitive drum. It is preferable to have a crosslinked urethane resin or a urethane resin containing fluorine.

  Specific examples of the polyol include the following various polyether polyols, polycaprolactone, and derivatives thereof (acrylic modification).

Polyoxytetraethylene glycol Polyoxytetramethylene glycol Polyoxypropylene glycol

  The isocyanate is not particularly limited as long as it is a compound having an isocyanate group in the molecule. Among these, polyisocyanates such as MDI (diphenylmethane-4,4′-diisocyanate) and HDI (hexamethylene diisocyanate) having two or more isocyanate groups in the molecule are easy to handle and provide a high-quality coating film. Is preferable. Moreover, you may use the derivative of these isocyanate, or these in combination.

  Further, the surface layer 1d can be imparted with antifouling property, and an additive capable of reacting with the above-mentioned isocyanate compound and chemically bonded as an additive for preventing contamination of a charged body such as a photosensitive drum. You may have. Illustrative examples include polymers having substituents such as hydroxyl groups, alkyl groups, and carboxyl groups. Specific examples include block copolymers of methacrylic acid esters and fluorinated alkyl acrylates and acrylic fluoropolymers that are derivatives thereof. It is done.

  Various conductive agents may be added to the surface layer 1d for the purpose of imparting conductivity. Although it does not specifically limit as this electrically conductive agent, The following components are illustrated.

Conductive carbon such as ketjen black EC, acetylene black Carbon for rubber such as SAF, ISAF, HAF, FEP, GPF, SRF, FT, MT Carbon for color ink subjected to oxidation treatment Pyrolytic carbon, natural graphite, Artificial graphite Antimony-doped metals such as tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, germanium or metal oxides

  The surface of the conductive agent may be treated with various surface treatment agents. Examples of the surface treatment agent include the following components. These components may be used in combination.

Coupling agent such as titanium coupling agent or alkoxysilane coupling agent Coupling agent such as fluoroalkylalkoxysilane coupling agent (the center metal such as silicon, titanium, aluminum and zirconium is not particularly selected)
Oil, varnish, organic compound

  Moreover, the addition amount of the said electrically conductive agent can be suitably adjusted so that desired resistance may be obtained.

  The surface layer is made of a coating material in which the material constituting the surface layer is dispersed by a known method using a conventionally known dispersing device using beads such as a sand mill, a paint shaker, a dyno mill, and a pearl mill. What is necessary is just to form so that it may become a layer structure on a foamed rubber layer. Examples of a method for forming a surface layer on a non-foamed rubber layer using this paint include a dipping method, a spray coating method, and a ring coating method. Especially, it is preferable to use a ring coat method for the formation of the surface layer from the viewpoint of the utilization efficiency of the resin paint. Hereinafter, a ring coating method using a cylindrical rubber roller as an object for forming the surface layer will be described.

  FIG. 3 is a schematic view showing an example of an apparatus used for the ring coating method, and FIG. 4 is a schematic view around a ring coating head in the apparatus shown in FIG.

  The rubber roller 2a, which is a target for forming the surface layer, is supported in a vertical state between the upper roller gripping shaft 2b and the lower roller gripping shaft 2c. The ring coating head 2d is arranged in a concentric relationship with the rubber roller 2a. The paint stored in the paint storage tank 2f is supplied to the ring coating head 2d via the syringe pump 2e. The ring coating head 2d has a liquid supply port 3b for introducing the paint into the ring coating head, a liquid distribution chamber 3c arranged concentrically with the ring coating head 2d, and a concentric shape with the ring coating head 2d. It has a discharge port 3a that is disposed and faces the rubber roller at a predetermined distance. The paint stored in the paint storage tank 2f and supplied to the liquid supply port 3b via the syringe pump 2e is introduced into the liquid distribution chamber 3c arranged concentrically around the entire circumference of the ring coating head 2d. This paint is applied to the surface of the rubber roller 2a through the discharge port 3a. When the rubber roller 2a and the ring coating head 2d are moved relative to each other at a predetermined speed in accordance with the amount of paint to be introduced, only an appropriate amount of paint is applied to the surface of the rubber roller 2a uniformly according to the desired coating film thickness. Supplied. In this way, a surface layer is formed on the surface of the rubber roller. In addition, what is necessary is just to adjust suitably the discharge amount to the rubber roller surface by the ratio of the desired coating film thickness and the solid content of the resin coating material.

(Electrophotographic apparatus according to the present invention)
The electrophotographic apparatus according to the present invention has at least the above-described charging member according to the present invention, and other constituent members such as an electrophotographic object, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are particularly limited. It is not something. FIG. 5 is a schematic configuration diagram of an example of an electrophotographic apparatus using the charging member according to the present invention. A rotating drum type electrophotographic charged body (photosensitive drum) 21 as an image carrier is rotationally driven at a predetermined peripheral speed (process speed) in a direction indicated by an arrow in the drawing. As the photosensitive drum 21, for example, a known photosensitive drum 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 may be adopted. The photosensitive drum 21 may further include a charge injection layer for charging the surface of the photosensitive drum to a predetermined polarity or potential. The charging roller 22 as a charging member includes a charging unit including a charging roller and a charging bias application power source S1 that applies a charging bias to the charging roller. The charging roller 22 is brought into contact with the photosensitive drum 21 with a predetermined pressing force, and is rotated in the forward direction with respect to the rotation of the photosensitive drum 21 in this example. A predetermined voltage is applied to the charging roller 22 from the charging bias application power source S1, so that the surface of the photosensitive drum 21 is uniformly charged to a predetermined polarity potential. As the exposure unit 23, a known unit can be used, and a unit such as a laser beam scanner can be preferably exemplified. The exposure means 23 performs an exposure L such as a laser beam corresponding to the target image information on the charging surface of the photosensitive drum 21, whereby the potential of the exposed bright portion of the charging surface of the photosensitive drum is selectively lowered (attenuated). As a result, an electrostatic latent image is formed on the photosensitive drum 21. As the developing unit 24, a known unit can be used. For example, the developing means 24 in this example is composed of the following three members. That is, a toner carrier 24a that is disposed in an opening of a developing container that contains toner and carries and transports toner, an agitating member 24b that stirs the contained toner, and a toner carrying amount ( The toner regulating member 24c regulating the toner layer thickness. The developing unit 24 selectively attaches toner (negative toner) charged to the same polarity as the charged polarity of the photosensitive drum 21 to the exposed bright portion of the electrostatic latent image on the surface of the photosensitive drum 21 to form the electrostatic latent image. Visualize as a toner image. There is no restriction | limiting in particular as a image development system, All the existing methods can be used. Examples of existing methods include a jumping development method, a contact development method, and a magnetic brush method. As the transfer roller 25 as the transfer means, a known means can be used. For example, a transfer roller formed by coating a metal conductive support with an elastic resin layer adjusted to a medium resistance can be exemplified. . The transfer roller 25 is brought into contact with the photosensitive drum 21 with a predetermined pressing force to form a transfer nip portion, and rotates in the forward direction with the rotation speed of the photosensitive drum 21 at substantially the same peripheral speed as the rotation speed of the photosensitive drum 21. . Further, a transfer voltage having a polarity opposite to the charging characteristics of the toner is applied 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). Thereafter, the back surface of the transfer material P is charged to a polarity opposite to the charging polarity of the toner by a transfer roller 25 that applies a transfer voltage. As a result, the toner image on the photosensitive drum 21 surface side is electrostatically transferred to the surface side of the transfer material P in the transfer nip portion. The transfer material P that has received the transfer of the toner image at the transfer nip is separated from the surface of the photosensitive drum, introduced into a toner image fixing means (not shown), and fixed as a toner image and output as an image formed product. Is done. In the case of the double-sided image forming mode or the multiple image forming mode, the image formed product is introduced into a recirculation conveyance mechanism (not shown) and reintroduced into the transfer nip portion. Residue on the photosensitive drum 21 such as transfer residual toner is collected from the photosensitive drum by a cleaning means 26 such as a blade type. In the case where residual charge remains on the photosensitive drum 21, it is preferable to remove the residual charge on the photosensitive drum 21 by the pre-exposure means 27 before the primary charging by the charging roller 22.

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

<Creation of charging member>
-Preparation of a conductive elastic body layer The unvulcanized unfoamed raw material composition for the foamed rubber layer of the conductive elastic body layer used the following components.

[Raw polymer]
Epichlorohydrin rubber (trade name “EPION-301” manufactured by Daiso Corporation)
Epichlorohydrin rubber (trade name “Zeospan 8010” manufactured by Nippon Zeon Co., Ltd.)
[filler]
Carbon black (trade name “Asahi # 15”: manufactured by Asahi Carbon Co., Ltd.)
Calcium carbonate (trade name “Super SS”: manufactured by Maruo Calcium Co., Ltd.)
[Softener]
Sebacic acid-based polyester (P-202) (trade name “Polysizer P-202” manufactured by Dainippon Ink and Chemicals, Inc.)
[Conductive agent]
Quaternary ammonium salt (trade name “Adekasizer LV70” manufactured by Asahi Denka Kogyo Co., Ltd.)
[Vulcanizing agent]
Sulfur (trade name "Salfax PMC": manufactured by Tsurumi Chemical Co., Ltd.)
[Vulcanization accelerator]
2-Mercaptobenzothiazole (M) (Brand name "Noxeller M" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.)
Dibenzothiazyl disulfide (DM) (trade name “Noxeller DM”: Ouchi Shinsei Chemical Co., Ltd.)
Tetraethylthiuram disulfide (TET) (trade name “Noxeller TET”: manufactured by Ouchi Shinsei Chemical Co., Ltd.)
[Vulcanization acceleration aid]
Zinc oxide (trade name “Zinc Hana 2”: manufactured by Hakusui Tech Co., Ltd.)
Stearic acid (trade name “Lunac S” manufactured by Kao Corporation)
[Foaming agent]
Azodicarbonamide (ADCA) (Brand name "Vinihole AC # LQ" manufactured by Eiwa Chemical Co., Ltd.)
p, p'-oxybisbenzenesulfonyl hydrazide (OBSH) (trade name "Neocerbon N1000 # S" manufactured by Eiwa Kasei Co., Ltd.)
[Foaming aid]
Urea ("Cell Paste 101" manufactured by Eiwa Kasei Co., Ltd.)

  The contents (parts by mass) of these components were the values shown in Tables 1 and 2. An open roll was used for kneading to obtain a uniform composition.

Moreover, the following components were used for the unvulcanized non-foamed raw material composition for the non-foamed rubber layer of the conductive elastic layer.
[Raw polymer]
Epichlorohydrin rubber (trade name “EPION-301” manufactured by Daiso Corporation) and epichlorohydrin rubber (trade name “Zeospan 8010” manufactured by ZEON Corporation)
[filler]
Carbon black (trade name “Asahi # 15” manufactured by Asahi Carbon Co., Ltd.) or carbon black (trade name “Thermax N-990” manufactured by Cancarb Co., Ltd.) and calcium carbonate (trade name “Nanox # 30”: Maruo Calcium Co., Ltd.)
[Softener]
Sebacic acid-based polyester (trade name “Polysizer P-202” manufactured by Dainippon Ink and Chemicals, Inc.)
[Conductive agent]
Quaternary ammonium salt (trade name “Adekasizer LV70” manufactured by Asahi Denka Kogyo Co., Ltd.)
[Vulcanizing agent]
Sulfur (trade name "Salfax PMC": manufactured by Tsurumi Chemical Co., Ltd.)
[Vulcanization accelerator]
Dibenzothiazyl disulfide (DM) (trade name “Noxeller DM”: Ouchi Shinsei Chemical Co., Ltd.)
Tetrakis 2-ethylhexyl thiuram disulfide (TOT) (trade name “Noxeller TOT” manufactured by Ouchi Shinsei Chemical Co., Ltd.)
[Vulcanization acceleration aid]
Zinc oxide (trade name “Zinc Hana 2”: manufactured by Hakusui Tech Co., Ltd.)
Stearic acid (trade name “Lunac S” manufactured by Kao Corporation)

  Using these components, the content (parts by mass) of each component was set to the values shown in Tables 1 and 2. An open roll was used for kneading to obtain a uniform composition.

  For extruding the unvulcanized unfoamed raw material composition for the foam rubber layer, an extruder with a screw diameter of Φ40 mm is used. For extruding the unvulcanized nonfoamed raw material composition for the non-foamed rubber layer, an extruder with a screw diameter of Φ30 mm is used. The rubber composition was extruded into a tube shape simultaneously and integrally with each other. Regarding the thickness of the foamed rubber layer and the non-foamed rubber layer, the thickness of the unvulcanized unfoamed raw material composition for the foamed rubber layer and the thickness of the unvulcanized unfoamed raw material composition for the non-foamed rubber layer are extruded. It was controlled by adjusting the screw rotation speed of the machine so as to obtain a predetermined wall thickness.

  Next, after extruding the rubber composition into a tube shape having an outer diameter of 14 mm and an inner diameter of 6.0 mm, the rubber composition was cut to a length of 400 mm and subjected to primary vulcanization in steam at 160 ° C. for 40 minutes using a vulcanizer. A conductive elastic layer rubber primary vulcanized tube was obtained. Next, a thermosetting adhesive (product for bonding metal and rubber to the axial center portion 317 mm of the cylindrical surface of a cylindrical conductive support member (steel, surface industrial nickel plating) having a diameter of 9 mm and a length of 354 mm Name: METALOC U-20) was applied, 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-mentioned 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. After cutting off both ends of the rubber part of this unpolished layer and setting the length of the rubber part to 319 mm, the rubber part is polished with a rotating grindstone to form a crown shape having an end diameter of 13.95 mm and a central part diameter of 14.00 mm. A rubber roller having a conductive elastic body layer having a two-layer structure of a foam layer and a non-foam layer was obtained.

-Creation of surface layer The surface layer as shown below was applied and formed on the said rubber roller.

  The coating material for forming the surface layer was prepared as follows. First, 100 parts of lactone-modified acrylic polyol (solid content: 70%, trade name “Placcel DC2016” manufactured by Daicel Chemical Industries, Ltd.) was dissolved in 98 parts of methyl isobutyl ketone. The following each component was mix | blended with this.

107 parts of blocked isocyanate (IPDI) (solid content 60%, trade name “Duranate MF-K60X” manufactured by Asahi Kasei Chemicals Corporation)
Acrylic fluorinated polymer 24 parts (30% solids, trade name "Modiper F200": manufactured by NOF Corporation)
11 parts of carbon black (trade name “MA100” manufactured by Mitsubishi Chemical Corporation)
0.2 parts of modified dimethyl silicone oil (trade name “SH-28PA” manufactured by Toray Dow Corning Silicone)

  This was dispersed for 6 hours using a paint shaker to prepare a paint. The solid content of this paint was 45%. This surface layer forming coating was applied to the surface of the rubber roller obtained as described above by the ring coating method described above. The film thickness of the surface layer was controlled by adjusting the amount of paint discharged. After air drying for 30 minutes, it was sintered and dried at 110 ° C. for 60 minutes. Thus, a roller-shaped charging member was obtained.

<Measurement evaluation of charging member>
・ Ten point average surface roughness (Rz)
The surface roughness of the charging member obtained as described above was measured as follows. The measurement is performed using a surface roughness meter (model “SE-3300H”: manufactured by Kosaka Laboratory Co., Ltd.), and the measurement conditions are a cutoff of 0.8 mm, a measurement distance of 8 mm, and a feed rate of 0.5 mm / second. Rz average values at three central portions (in increments of 120 ° starting from an arbitrary location) of the charging member were determined. The results are shown in Tables 3 and 4.

-Continuous multiple image output durability test The charging member obtained as described above is mounted on an electrophotographic apparatus (product name "SateraLBP5900": manufactured by Canon Inc.), and in an atmosphere at a temperature of 23 ° C and a relative humidity of 55%. Then, an endurance test for continuous image printing was performed. Using this apparatus, halftone printing was performed on 50,000 sheets, and the obtained images were visually evaluated. The results are shown in Tables 3 and 4.

  “Good”, “possible”, and “bad” in the table are obtained by ranking the halftone image quality in three stages with respect to the level of occurrence of charging unevenness due to surface roughness factors. Note that “good” indicates that there is no occurrence of uneven charging, “good” indicates that the occurrence of charging unevenness is minor, but is minor and has no practical problem, and “bad” indicates that charging is not performed. Indicates that the level of unevenness is not practical.

Contamination of charged object The charging member obtained as described above is mounted on an electrophotographic apparatus (product name “SateraLBP5900” manufactured by Canon Inc.) (coaxially contacted with a φ30 mm photoconductor with 700 g load on both ends of the roller) And left in an environment of 40 ° C. and 95% relative humidity for 30 days. Thereafter, image evaluation was performed in an environment of a temperature of 23 ° C. and a relative humidity of 55%. The image at the contact portion of the member to be charged with the charging member was visually evaluated. The results are shown in Tables 3 and 4.

  In the table, “◯” indicates good, and “×” indicates that the defective image due to contamination of the charged body is confirmed and is not at a practical level.

<Roller hardness>
The hardness of the charging member obtained as described above was measured as follows. Using an Asker C-type hardness meter (manufactured by Kobunshi Keiki Co., Ltd.), the measurement load was 500 g. The difference between the hardness of the foamed rubber layer and the hardness of the non-foamed rubber layer was measured by the following procedure. As for the hardness of the non-foamed rubber layer, the non-foamed rubber layer of the rubber roller is peeled off, and the inner surface of the non-foamed rubber layer is covered on a conductive support member (round bar), and laminated to a thickness of 4 mm or more. C hardness was measured. Similarly, regarding the hardness of the foamed rubber layer, the rubber peeled off so as to have a thickness of 4 mm or more was laminated and the Asker C hardness was measured. The difference between the Asker C hardness of the foamed rubber layer and the Asker C hardness of the non-foamed rubber layer was calculated from each Asker C hardness thus measured. The results are shown in Tables 3 and 4.

<Compression set>
The charging member obtained as described above was mounted on an electrophotographic apparatus (product name “SateraLBP5900” manufactured by Canon Inc.) (coaxially contacted with a 30 mm diameter photosensitive member with a load of 700 g on both ends of the roller), and a temperature of 40 ° C. It was left for 30 days in an environment with a relative humidity of 95%. Thereafter, the charging member is removed from the electrophotographic apparatus and left for 4 hours in an environment of a temperature of 23 ° C. and a relative humidity of 55%. Then, the outer diameter value of the charging member is measured, and the outer diameter value of the contact portion with the photosensitive drum is measured. And the difference between the outer diameter values of the other non-contact portions and the compression set. The results are shown in Tables 3 and 4.

<Measurement of charged sound>
The charging member obtained as described above was mounted on an electrophotographic apparatus (product name “SateraLBP5900” manufactured by Canon Inc.) (coaxially contacted with a 30 mm diameter photosensitive member with a load of 700 g on both ends of the roller), and a temperature of 40 ° C. It was left for 30 days in an environment with a relative humidity of 95%. Thereafter, in an environment of a temperature of 23 ° C. and a relative humidity of 55%, the process cartridge was measured for charging sound by an AC charging method (applied voltage DC: −600 V, AC: 1398 Hz, 2.0 KVpp). The charged sound was measured using a sound level meter (manufactured by Lion Corporation: NL-05 INTERGRATING SOUND REVER METER) and the A characteristic of JIS C1502 at a distance from the cartridge of 30 cm. For the charging sound, values from 10 seconds to 30 seconds after voltage application were taken, the noise level was the average value in this section, and the swell was the difference between the maximum value and the minimum value in this section. The results are shown in Tables 3 and 4.

  In the table, “A” indicates excellent hearing, “B” indicates good, “C” indicates that practical use is possible, and “D” indicates that the level is not practical.

  As is clear from Table 3, it was confirmed that the charging member according to the present invention has a remarkable effect. In other words, this charging member does not cause image defects due to uneven smearing even when a plurality of images are continuously printed, and there is no contamination of the charged body due to the exudation of the plasticizer from the member to the charged body. The permanent distortion was small, the noise level of the charged sound was low when an alternating electric field was applied, and the undulation of the charged sound was also low. On the other hand, as is clear from Table 4, the charging member of Comparative Example 1 in which the difference in hardness between the foamed rubber layer and the non-foamed rubber layer is less than 20 degrees has a large compression set and the undulation of the charging sound is poor. . The charging member of Comparative Example 2 in which the difference in hardness between the foamed rubber layer and the non-foamed rubber layer was greater than 50 degrees had poor surface smoothness, and image defects occurred when a plurality of images were continuously printed. The charging member of Comparative Example 3 in which the thickness of the non-foamed rubber layer was less than 100 μm had a large compression set and a poor charging sound. In the charging member of Comparative Example 4 in which the thickness of the non-foamed rubber layer was larger than 2 mm, the charging member had a high hardness and a low noise level of the charging sound. In the charging member of Comparative Example 5 in which the thickness of the surface layer was less than 5 μm, the softening oil and the ionic conductive agent contained in the conductive elastic layer oozed out and contaminated the member to be charged. The charging member of Comparative Example 6 having a surface layer thickness greater than 50 μm had a high charging member hardness and a poor charging noise level.

FIG. 3 is a schematic cross-sectional view illustrating a configuration of a charging member according to the present invention. It is a schematic longitudinal cross-sectional view which shows the structure of the charging member by this invention. It is the schematic which shows an example of the apparatus used for the ring coat method. It is the schematic of the periphery of the ring coating head in the apparatus shown in FIG. 1 is a schematic configuration diagram of an example of an electrophotographic apparatus using a charging member according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Conductive support member 1b Foam rubber layer 1c Non-foam rubber layer 1d Surface layer 2a Rubber roller 2b Roller gripping shaft 2c Roller gripping shaft 2d Ring coating head 2e Syringe pump 2f Paint storage tank 2g Motor 2h Pulley and belt 2i Ball screw 2j Slide guide 2k LM guide 2l Bracket 3a Discharge port 3b Liquid supply port 3c Liquid distribution chamber 21 Photosensitive drum 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 L Exposure P Transfer material S1 Bias application power source S2 Bias application power source S3 Bias application power source

Claims (5)

A conductive support member; a foamed rubber layer provided on the conductive support member; a non-foamed rubber layer provided on the foamed rubber layer; and a surface layer formed on the non-foamed rubber layer. In the charging member,
The difference between the Asker C hardness of the foamed rubber layer and the Asker C hardness of the non-foamed rubber layer is 20 degrees or more and 50 degrees or less,
The non-foamed rubber layer has a thickness of 100 μm or more and 2 mm or less,
The charging member, wherein the surface layer is a crosslinked resin layer having a thickness of 5 μm or more and 50 μm or less.   The charging member according to claim 1, wherein the surface layer includes a resin mainly composed of a urethane resin obtained by crosslinking a polyol with an isocyanate.   The charging member according to claim 1, wherein the surface layer is made of a urethane resin containing fluorine.   The charging member according to claim 1, wherein the foamed rubber layer and the non-foamed rubber layer are formed by being extruded and vulcanized simultaneously and integrally in a tube shape by an extruder and then subjected to polishing.   5. An electrophotographic apparatus according to claim 1, wherein the charging means is the charging member according to any one of claims 1 to 4.