JP6071536B2 - Charging member and electrophotographic apparatus - Google Patents

Description

  The present invention relates to a charging member used in an electrophotographic apparatus and an electrophotographic apparatus.

  An electrophotographic apparatus adopting an electrophotographic system mainly includes an electrophotographic photosensitive member, a charging device, an exposure device, a developing device, a transfer device, and a fixing device. As a charging method in the charging device, an electrophotographic photosensitive member is applied by applying a voltage (a voltage of only a DC voltage or a voltage in which an AC voltage is superimposed on a DC voltage) to a charging member that is in contact with or close to the surface of the electrophotographic photosensitive member. A system that charges the surface of the body is adopted.

  From the viewpoint of stably charging and reducing the generation of ozone, a contact-type charging method is preferably used. In the case of the contact charging method, a roller-shaped charging member (hereinafter referred to as “charging roller”) is preferably used. In addition, the charging roller is disposed so as to be in contact with the rotating electrophotographic photosensitive member by a predetermined pressing force such as a spring and to be driven to rotate. Therefore, the charging roller is often used in a configuration in which pressure for contact is applied from both ends of the shaft. In the normal cylindrical shape, the pressure at the central portion is weak due to the structure, and a gap may be generated between the electrophotographic photosensitive member and the charging roller. For the above reasons, in order to bring the charging roller into contact with the electrophotographic photosensitive member with uniform pressure in the axial direction of the charging roller, the center of the charging roller in the axial direction is formed in a crown shape having an outer diameter larger than the end portion. A charging roller is disclosed (see Patent Document 1).

JP 2010-243797 A

  In recent image forming apparatuses employing an electrophotographic system represented by printers and copiers, there is a growing demand for higher speed and higher durability. The image forming speed (hereinafter referred to as “process speed”) is improved, and the target durable life value of the unit including the charging member and the electrophotographic photosensitive member (hereinafter referred to as “photosensitive member”) is increased.

  However, in the method described in Patent Document 1, since the crown shape is formed by changing the thickness of the coating layer in the longitudinal direction of the charging member, when the photosensitive member and the charging member are driven by the improvement of the process speed. The twist applied to the charging member may increase. As a result, stick slip that occurs when the twist applied to the charging member is released may easily occur.

  Furthermore, there is a concern that an image that has not been generated before the improvement becomes apparent along with improvements in the electrophotographic apparatus for high speed, high durability, and high image quality. Therefore, the inventors of the present application have recognized that improving rotational stability over the entire longitudinal direction of the charging member is a problem to be solved in order to obtain more stable charging performance and electrophotographic performance.

  An object of the present invention is to provide a charging member that can be suitably used for a high-speed, high-durability electrophotographic apparatus and the like by reducing stick slip in the charging member of the electrophotographic apparatus. Another object of the present invention is to provide an electrophotographic apparatus that contributes to the formation of high-quality electrophotographic images.

According to the present invention,
In a charging member having a conductive substrate and a conductive elastic layer,
The conductive elastic layer contains, as a binder, at least one rubber selected from acrylonitrile butadiene rubber, styrene butadiene rubber, ethylene propylene diene rubber, and epichlorohydrin rubber,
The conductive elastic layer holds the multi-hollow particles in a state where a part thereof is exposed from the conductive elastic layer,
The charging member has a concave portion derived from a hollow portion of the multi-hollow particle on the surface,
The multi-hollow particles are
Copolymer of styrene, divinylbenzene and methyl acrylate,
A copolymer of styrene and divinylbenzene,
Copolymer of styrene, divinylbenzene and acrylonitrile,
A copolymer of styrene, divinylbenzene and vinylidene chloride, and
Copolymer of styrene, divinylbenzene and vinyl chloride
Resin particles made of any copolymer selected from the group consisting of, and having a plurality of pores therein,
A charging member is provided.

  Further, according to the present invention, there is provided an electrophotographic apparatus comprising an electrophotographic photosensitive member and a charging member disposed in contact with the electrophotographic photosensitive member, wherein the charging member is the above-described charging member. .

  According to the present invention, sticking slip of the charging member is suppressed and rotational stability over the entire longitudinal direction of the charging member is improved in high-speed printing and long-term printing regardless of the environment in which the charging member is used. Furthermore, according to the present invention, it is possible to suppress the generation of a horizontal striped banding image due to abnormal discharge accompanying a decrease in rotational stability over the entire longitudinal direction of the charging member.

It is the schematic of the process of forming a conductive elastic layer on a conductive shaft core. It is a schematic diagram which shows the cross section orthogonal to the axial direction of the charging member (roller shape) which concerns on this invention. (A) is a schematic cross-sectional view of a charging roller having a conductive base 201 and a conductive elastic layer 202, and (b) is a schematic cross-sectional view of a charging roller further having a surface layer 205. It is a schematic diagram which shows the cross section of the charging member (flat plate shape) which concerns on this invention. (A) is a schematic cross-sectional view of a charging roller having a conductive base 201 and a conductive elastic layer 202, and (b) is a schematic cross-sectional view of a charging roller further having a surface layer 205. It is a typical fragmentary sectional view which shows the cross section (conductive electroconductive layer surface vicinity) of the electroconductive elastic layer of the charging member which concerns on this invention. It is a schematic diagram which shows an example of the grinding | polishing method of the charging member by a plunge cut type cylindrical grinder. It is the schematic of the electrical resistance value measuring device of a charging roller. 1 is a schematic cross-sectional view illustrating an example of an embodiment of an electrophotographic apparatus using a charging member according to the present invention.

  The charging member according to the present invention includes at least a conductive substrate and a conductive elastic layer. If necessary, a surface layer can be provided on the conductive elastic layer. The conductive elastic layer contains at least one rubber selected from acrylonitrile butadiene rubber, styrene butadiene rubber, ethylene propylene diene rubber, and epichlorohydrin rubber as a binder.

The charging member according to the present invention has a concave portion derived from the hollow portion of the multi-hollow particle on the surface by holding the multi-hollow particle in a state in which the conductive elastic layer is partially exposed from the conductive elastic layer. It has become a thing.
The multi-hollow particles are formed from a copolymer of styrene and divinylbenzene, or a copolymer obtained by combining styrene and divinylbenzene with methyl acrylate, acrylonitrile, vinylidene chloride or vinyl chloride.
The multi-hollow particle has a plurality of hollow portions therein, and at least a part of the plurality of hollow portions is opened to the outer wall surface of the multi-hollow particle to form a recess. That is, at least a part of the plurality of hollow portions provided in the interior of the multi-hollow particle has an opening that forms a recess in the outer surface of the multi-hollow particle. On the surface of the charging member according to the present invention, a concave portion derived from the concave portion formed by the opening of the hollow portion formed on the outer wall surface of the porous hollow particle is formed. The concave portion derived from the hollow portion of the multi-hollow particle may be the concave portion itself formed by the opening of the hollow portion formed on the outer wall surface of the multi-hollow particle exposed on the surface of the charging member, or the opening of the hollow portion. It may be obtained in a state where the concave portion made of is covered with the surface layer.

  Hereinafter, preferred embodiments of the charging member according to the present invention will be described in detail.

<Charging member>
The charging member according to the present invention is an electrophotographic charging member having a conductive elastic layer on a conductive substrate, and is used to charge an object to be charged. For example, it is used to charge an electrophotographic photoreceptor. This conductive elastic layer contains particles having a large number of hollow portions inside the particles (hereinafter referred to as “multi-hollow particles”). As described above, the multi-hollow particle of the present invention is a copolymer of styrene and divinylbenzene, or a copolymer obtained by combining styrene and divinylbenzene with methyl acrylate, acrylonitrile, vinylidene chloride or vinyl chloride. It is formed.

  At least some of the multi-hollow particles of the multi-hollow particles contained in the conductive elastic layer are exposed from the conductive elastic layer, and the conductive elastic layer has a recess derived from the hollow portion of the multi-hollow particle. Have. That is, the above-described state is a state in which a part of the multi-hollow particles contained in the conductive elastic layer has a cross-section of the multi-hollow particles exposed on the surface of the conductive elastic layer. Since the multi-hollow particle has a large number of hollow portions inside the particle, it has a large number of concave portions derived from the hollow portion in its cross section, and the concave portions are exposed on the surface of the conductive elastic layer. That is, the recessed part produced when at least one part of the hollow part of the multi-hollow particle is opening in the outer wall surface of the multi-hollow particle is in the state exposed to the surface of the electroconductive elastic layer. As described above, the conductive elastic layer includes the multi-hollow particles inside thereof, and has the multi-hollow particles having the concave portions formed by the openings of the hollow portions in a state of being exposed on the surface thereof.

  In the case of the contact-type charging system, the charging member is preferably a roller-shaped charging member having a conductive base and a conductive elastic layer. The generation and suppression mechanism of stick slip of the charging member will be described using an example of a charging roller.

  In general, the charging roller is placed in contact with a rotating photosensitive member by applying a predetermined pressing force such as a spring to both ends of the conductive substrate, and is driven to rotate. Since the charging roller is applied with pressure for contact from both ends of the conductive substrate, in a normal cylindrical shape, the pressure at the central portion is weak in the axial direction of the roller due to the structure, and the contact between the photosensitive member and the charging roller is weak. Distribution occurs in contact pressure. Therefore, depending on the setting of the charging roller, the hardness, the pressing force, etc., a gap may be generated between the photosensitive member and the charging roller, and the charging roller may float. For the above reason, the charging roller is often formed in a crown shape having a thick central outer diameter in the axial direction and gradually reducing the diameter toward both ends. As a result, the charging roller can be brought into contact with the photosensitive member with a uniform pressure in the axial direction.

  In many cases, the charging roller is used in contact with a rotating photosensitive member and driven to rotate. Many photoreceptors having a uniform cylindrical outer diameter in the axial direction are used. Accordingly, when the charging roller having a crown shape is brought into contact with the photoconductor having a uniform outer diameter, the charging roller is driven and rotated in accordance with the rotation of the photoconductor. Since the rotation speed of the charging roller is a driven rotation that depends on the rotation speed of the photosensitive member, assuming that there is no slip between the photosensitive member and the charging roller, the peripheral speed of the photosensitive member (the circumferential length of the photosensitive member) X Number of rotations per unit time).

  The driven rotation of the charging roller is a rotational motion by transmission of rolling friction drive due to contact between the photosensitive member and the charging roller. Therefore, the circumferential speed of the charging roller is the circumferential length of the charging roller × the number of rotations per unit time as in the case of the photoconductor.

  In addition, the charging roller having a crown shape has an outer diameter difference in the axial direction unlike the photosensitive member, and therefore the radius of the charging roller has a distribution in the axial direction. Since the photosensitive member has a uniform peripheral speed in the axial direction, when it is assumed that there is no slip between the photosensitive member and the charging roller, the peripheral speed transmitted to the charging roller is uniform in the axial direction. Since the radius of the charging roller has a distribution in the axial direction, when a uniform peripheral speed is transmitted from the photosensitive member in the axial direction, the rotation speed must be different in the axial direction. In other words, when comparing the central part where the outer diameter of the charging roller is thick and the end part where the outer diameter is thin, the peripheral speed of the charging roller has a uniform distribution unless the rotational speed of the end part is faster than the central part. Not.

  However, in reality, the charging roller has a conductive base and a conductive elastic layer that are continuous in the axial direction, and cannot have a different rotational speed in the axial direction. That is, the rotation speed of the charging roller is uniform in the axial direction. Therefore, the peripheral speed of the charging roller having a crown shape is such that the central portion where the outer diameter of the charging roller is thick is faster and the end portion where the outer diameter is thin is The peripheral speed is slower than the central part. That is, the circumferential speed of the charging roller having a crown shape does not have a uniform distribution in the axial direction.

  Due to the above reasons, a charging roller having a crown shape brought into contact with a photoconductor having a uniform outer diameter inevitably generates a difference in peripheral speed in the axial direction due to its structure.

  In the charging roller having a crown shape, a twisting force is generated in the conductive elastic layer in the direction opposite to the rotation direction of the charging roller due to the difference in peripheral speed. The distribution of the torsional force gradually increases in accordance with the peripheral speed difference from the central portion as it goes from the central portion of the charging roller to both end portions where the peripheral speed is low. This twisting force causes deformation, distortion, and twist in the conductive elastic layer, but the rebound resilience of the conductive elastic layer releases the twist, and the direction of rotation of the charging roller, that is, the direction in which the peripheral speed difference is eliminated. The conductive elastic layer is deformed. By repeating the twist and release of the conductive elastic layer such as stick-slip, the charging roller can rotate without the conductive elastic layer being twisted.

  However, stick slip generated between the conductive elastic layer and the photoconductor due to repeated twisting of the conductive elastic layer and release of twist by the restoring force of the conductive elastic layer causes abnormal discharge. As a result, a horizontal striped banding image may occur.

  In the charging member according to the present invention, a concave portion formed of a hollow portion in which a multi-hollow particle is contained in the conductive elastic layer, the multi-hollow particle is exposed on the surface of the conductive elastic layer, and the exposed multi-hollow particle is opened. The stick-slip is reduced by the structure that is exposed.

  Since the multi-hollow particles have higher hardness and higher elasticity than the conductive elastic layer, they exhibit high resilience when deformed. Therefore, even when a torsional force is generated in the conductive elastic layer, the multi-hollow particles are less likely to be twisted, the twist can be suppressed to a very small level, and the twist is released from a minute deformation state by repelling the twisting force. can do.

  Further, on the contact surface between the photosensitive member and the charging member, a portion where the cross section of a part of the multi-hollow particles contained in the conductive elastic layer is exposed on the surface of the conductive elastic layer, and the conductive elastic layer There is only a part. The cross section of the multi-hollow particle has a recess derived from the hollow portion of the multi-hollow particle. Therefore, compared with the case where only the conductive elastic layer is in contact with the photoconductor, the contact area between the photoconductor and the charging member is reduced due to the effect of the concave portion derived from the hollow portion of the multi-hollow particles. The contact surface has low friction.

  Therefore, when a torsional force is generated in the conductive elastic layer due to the peripheral speed difference of the charging member, the repulsive force of the multi-hollow particles in the conductive elastic layer and the low friction property of the cross-section of the multi-hollow particles exposed on the surface of the conductive elastic layer. Due to the effect, a slight slip occurs between the photosensitive member and the charging member in a direction to eliminate the peripheral speed difference of the charging member. That is, the twist of the conductive elastic layer is partially released on the surface of the multi-hollow particle with an effective speed.

  In the case of only the conductive elastic layer, a large twist and release of the conductive elastic layer are repeatedly generated, thereby causing a stick slip, which may result in vibration of the conductive elastic layer. In the charging member of the present invention, the hollow surface is exposed on the surface of the conductive elastic layer, and the exposed surface is formed with a recess due to the opening of the hollow portion on the outer wall surface of the hollow particle. Generation of such vibration can be reduced. As a result, the occurrence of banding images is reduced / suppressed by the mechanism described above.

  An example of the charging member according to the present invention is shown in FIG. 2 (roller shape) and FIG. 3 (flat plate shape). These drawings show schematic sectional views (cross sections orthogonal to the axial direction) of the charging member according to the present invention.

  FIG. 2A shows a charging roller having a conductive substrate 201 and a conductive elastic layer 202. FIG. 4 is a schematic partial cross-sectional view showing a cross section (near the surface of the conductive elastic layer) of the conductive elastic layer of the charging member according to the present invention. The conductive elastic layer 202 contains multi-hollow particles 203, and at least some of the multi-hollow particles are exposed on the surface of the conductive elastic layer. At least a part of the multi-hollow particles 204 exposed on the surface of the conductive elastic layer has a recess derived from the hollow portion of the multi-hollow particles. Furthermore, you may have the surface layer 205 on the electroconductive elastic layer 202 like FIG.2 (b) and FIG.3 (b).

  The conductive substrate 201 and the conductive elastic layer 202, or the layers sequentially stacked (for example, the conductive elastic layer and the surface layer shown in FIG. 2B) may be bonded via an adhesive layer. As the adhesive layer, known adhesives, adhesive films, and the like can be used as appropriate. In this case, the adhesive layer is preferably conductive. In order to make it electrically conductive, the adhesive layer can contain a known conductive agent.

  For example, examples of the binder of the adhesive include thermosetting resins and thermoplastic resins, and known ones such as urethane, acrylic, polyester, polyether, and epoxy can be used.

  As a conductive agent for imparting conductivity to the adhesive, it can be appropriately selected from conductive agents described in detail later, and can be used alone or in combination of two or more.

[Electrical resistance of charging member]
The electric resistance value of the charging member according to the present invention is not particularly limited and is appropriately set according to desired characteristics. For example, in order to improve the charging of the photoreceptor for use as a charging roller, the electrical resistance value is usually 1 × 10 ² Ω or more and 1 × 10 ¹⁰ Ω or less in an environment of 23 ° C. and 50% RH. Preferably, it is 1 × 10 ³ Ω or more and 1 × 10 ⁸ Ω or less. The electrical resistance value in the circumferential direction of the charging roller is preferably set so that the ratio between the maximum value and the minimum value is 1.0 to 5.0 times. More preferably, it is about 1.0 to 3.0 times.

  As an example, FIG. 6 shows a method of measuring the electrical resistance value of the charging roller. Both ends of the conductive substrate 201 are brought into contact with a metal cylinder 601 having the same curvature as that of the photosensitive member by a bearing 602 under load so that these axes are parallel to each other. In this state, the metal cylinder 601 is rotated by a motor, and a DC voltage of −200 V is applied from the stabilized power source 603 while the charging roller in contact is driven to rotate. At this time, the current flowing through the conductive elastic layer 202 is measured by an ammeter 604, and the electric resistance value of the charging roller is calculated. In the present invention, the load is 4.9 N, the metal cylinder has a diameter of 30 mm, and the rotation of the metal cylinder has a peripheral speed of 45 mm / sec.

[Conductive substrate]
The conductive substrate used in the charging member of the present invention is conductive and has a function of supporting a conductive elastic layer and the like provided thereon. Examples of the material include metals such as iron, copper, stainless steel, aluminum, nickel, and alloys thereof. In addition, for the purpose of imparting scratch resistance to these surfaces, plating treatment or the like may be performed as long as the conductivity is not impaired. Furthermore, as the conductive substrate, a resin substrate whose surface is made conductive by coating the surface with a metal or the like, or a substrate manufactured from a conductive resin composition can be used.

[Conductive elastic layer]
(Material of conductive elastic layer)
As a material used for the conductive elastic layer of the charging member of the present invention, acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), ethylene propylene are used from the viewpoint of easy resistance adjustment and low compression set. At least one rubber selected from diene rubber (EPDM) and epichlorohydrin rubber can be suitably used. Among these, it is more preferable to use polar rubber because it is easy to adjust the electric resistance value. Among these, epichlorohydrin rubber and NBR can be mentioned. These have an advantage that resistance value control and hardness control of the conductive elastic layer can be performed more easily. These rubber materials used for the conductive elastic layer may be used singly or as a mixture of two or more. However, these rubbers are used as a main component, and other general known rubber or A thermoplastic elastomer or resin may be contained. When other general known rubbers, thermoplastic elastomers, resins, and the like are contained, the content is more preferably in the range of 1 to 50 parts by mass with respect to 100 parts by mass of the rubber material.

  In the epichlorohydrin rubber, the polymer itself has conductivity in a medium resistance value region, and can exhibit good conductivity even if the amount of the conductive agent added is small. Moreover, since the variation in the electric resistance value depending on the position can be reduced, it is suitably used as a polymer elastic material.

Examples of the epichlorohydrin rubber include the following.
Epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide copolymer, epichlorohydrin-allyl glycidyl ether copolymer and epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer.

  Among these, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer is particularly preferably used since it exhibits stable conductivity in a medium resistance value region. The epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer can control conductivity and workability by appropriately adjusting the degree of polymerization and the composition ratio.

  Moreover, the electroconductivity of an elastic layer can be made into a predetermined value by using a conductive agent suitably. The electrical resistance value of the charging member can be adjusted by appropriately selecting the type and amount of the electronic conductive filler used as the conductive agent.

  The electroconductive filler is not particularly limited as long as it is conductive particles exhibiting electronic conductivity, and various known ones can be used. For example, carbon black such as furnace black, thermal black, acetylene black, and ketjen black can be used. Specifically, Super Abrasion Furnace (SAF: Super Abrasion Resistance), Intermediate Super Abrasion Furnace (ISAF: Quasi Super Abrasion Resistance), High Abrasion Furnace (HAF: High Wear Resistance) Each rubber such as extrudability), General Purpose Furnace (GPF: versatility), Semi Rein Forcing Furnace (SRF: medium reinforcement), Fine Thermal (FT: fine particle thermal decomposition) and Medium Thermal (MT: medium particle thermal decomposition) For carbon.

  In addition, graphite such as natural graphite and artificial graphite, metal oxide conductive particles such as titanium oxide, tin oxide, and zinc oxide, and metal conductive particles such as aluminum, iron, copper, and silver can be given. These electronic conductive fillers can be used alone or in combination of two or more.

  Further, a conductive polymer, an ionic conductive agent or the like may be used in combination with the electronic conductive filler to impart conductivity to the elastic layer. The ionic conductive agent is not particularly limited as long as it is an ionic conductive agent exhibiting ionic conductivity. Examples of the ionic conductive agent include the following. Examples include inorganic ionic substances such as lithium perchlorate, sodium perchlorate, and calcium perchlorate. Examples thereof include quaternary ammonium salts such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, and tetrabutylammonium perchlorate. Examples thereof include organic acid inorganic salts such as lithium trifluoromethanesulfonate and potassium perfluorobutanesulfonate. These can be used alone or in combination of two or more. Among ionic conductive agents, quaternary ammonium perchlorate is particularly preferably used because of its resistance to environmental changes.

  In addition, an inorganic or organic filler or a crosslinking agent may be added to the rubber mixture for forming the conductive elastic layer.

Examples of the additive for crosslinking the rubber mixture include a vulcanizing agent and a vulcanization accelerator. Examples of the filler include at least one selected from silica (white carbon), calcium carbonate, magnesium carbonate, clay, talc, zeolite, alumina, barium sulfate, aluminum sulfate, and the like. As the vulcanizing agent, known vulcanizing agents can be used as appropriate, and examples thereof include powdered sulfur and organic peroxides. When powdered sulfur is used as a vulcanizing agent, a known vulcanizing accelerator can be appropriately used as the vulcanizing accelerator, and examples thereof include thiazole, dithiocarbamate, sulfenamide, and thiuram. It is done.

Moreover, in order to adjust hardness etc., you may add additives, such as a softening oil and a plasticizer, to a conductive elastic layer. The amount of the plasticizer or the like is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass with respect to 100 parts by mass of the elastic layer material. It is more preferable to use a polymer type plasticizer. The molecular weight of the polymer plasticizer is preferably 2000 or more, more preferably 4000 or more. Furthermore, the elastic layer may appropriately contain materials that impart various functions.
Furthermore, anti-aging agents, antistatic agents, ultraviolet absorbers, reinforcing agents, fillers, lubricants, mold release agents, pigments, dyes, flame retardants, and the like can be appropriately added as necessary.

(Multi hollow particles)
The elastic layer of the elastic roller used in the present invention contains multi-hollow particles. The multi-hollow particle in the present invention refers to a particle having a plurality of pores (hollow) inside the particle.
As the material of the multi-hollow particles, at least one resin selected from acrylic resin, styrene resin, acrylonitrile resin, vinylidene chloride resin, and vinyl chloride resin can be used. These resins can be used alone or in combination of two or more. Further, monomers of these resins may be copolymerized and used as a copolymer. Among these, it is preferable to use at least one resin selected from an acrylic resin, acrylonitrile resin, and vinylidene chloride resin exhibiting high impact resilience. You may contain other general well-known resin etc. as needed by using these resins as a main component.
Based on the above, in the present invention, one of the following copolymers is used as the material of the multi-hollow particles.
・ Copolymer of styrene, divinylbenzene and methyl acrylate
・ Styrene and divinylbenzene copolymer
・ Styrene, divinylbenzene and acrylonitrile copolymer
・ Copolymers of styrene, divinylbenzene and vinylidene chloride
・ Copolymer of styrene, divinylbenzene and vinyl chloride

  These multi-hollow particles can be produced by a known production method such as a suspension polymerization method, an interfacial polymerization method, an interfacial precipitation method, or a submerged drying method. Moreover, the well-known multi-hollow particle | grains which are marketed can also be used.

An example of producing multi-hollow particles is shown below.
(1-1) First, a solution in which a cellulose resin is dissolved in a monomer mixture composed of a styrene monomer and a polyfunctional polymerizable monomer is obtained.

[Polyfunctional polymerizable monomer]
Examples of the polyfunctional polymerizable monomer include aromatic divinyl compounds, polyhydric alcohol acrylic esters, polyhydric alcohol methacrylates, and the like. These can be used alone or in combination of two or more.

  Specifically, examples of the aromatic divinyl compound include divinylbenzene and divinylnaphthalene. Examples of the (meth) acrylic acid ester of polyhydric alcohol include ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and trimethylolpropane trimethacrylate. In addition, (meth) acrylate means an acrylate or a methacrylate. Of these, divinylbenzene and ethylene glycol dimethacrylate are preferably used to form good pores. Here, the term “good vacancies” means that the particles have more vacancies. That is, the larger the proportion of holes in the particles and the greater the number of holes, the greater the number of recesses derived from the hollow portions of the multi-hollow particles, and the contact area between the photoreceptor and the charging member decreases, and The contact surface between the body and the charging member can obtain an effect of low friction. Therefore, adding a small amount of multi-hollow particles as an elastic layer means that a good effect can be obtained.

  The polyfunctional polymerizable monomer is used in an amount of 5 to 100 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the styrene monomer. When an amount less than 5 parts by weight or more than 100 parts by weight is used, it is difficult to obtain the intended multi-hollow particles.

Moreover, you may add the other monomer copolymerizable with the said polyfunctional monomer and a styrene monomer in the range which does not impair the characteristic of a multi-hollow particle. Examples of other copolymerizable monomers include the following.
Acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, ethylene, propylene, Examples include ethylene unsaturated monoolefins such as butylene and isobutylene, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride, vinyl esters such as vinyl acetate, vinyl propionate and vinyl butyrate. .

[Cellulose resin]
Examples of the cellulose resin include cellulose acetate, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl ethyl cellulose and the like. Of these, ethyl cellulose is preferable for forming good pores.

  Ethyl cellulose is generally an ethyl cellulose ether obtained by reacting ethyl chloride with alkali cellulose. Commercially available ethyl cellulose usually has an ethoxyl group content of 44 to 50% by weight. Among ethyl celluloses, those having a viscosity (viscosity when 5% by weight of ethyl cellulose is dissolved in a mixed solution of toluene: ethanol = 80: 20 by weight) of 10 to 200 cP can be suitably used. More preferably, 20 to 100 cP is used. When the viscosity exceeds 200 cP, the viscosity of the solution becomes high, which is not preferable because the stability of the polymerization system during suspension polymerization and the control of the particle diameter of the multi-hollow particles become difficult. When the viscosity is less than 10 cP, it is difficult to obtain multi-hollow particles, which is not preferable.

  The viscosity is a value measured at a temperature of 25 ° C. ± 0.5 ° C. with an Ubbelohde viscometer (capillary viscometer) according to JIS Z8803.

  The cellulose resin is used in a proportion of 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight, based on 100 parts by weight of the monomer mixture obtained by adding the styrene monomer and the polyfunctional polymerizable monomer. When an amount exceeding 5 parts by weight is used, it may be substantially difficult to dissolve the cellulose resin in the monomer mixture due to an increase in viscosity, and the viscosity of the solution becomes high and the suspension is suspended. This is not preferable because the stability of the polymerization system during polymerization and the control of the particle diameter of the multi-hollow particles become difficult. When it is less than 0.5% by weight, it is not preferable because multi-hollow particles cannot be obtained.

[Polymerization initiator]
The solution may contain a polymerization initiator. As the polymerization initiator, an oil-soluble peroxide-based or azo-based initiator usually used for suspension polymerization can be used.

  For example, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, cumene hydroperoxide, cyclohexanone peroxide, t-butyl hydroperoxide , Peroxide initiators such as diisopropylbenzene hydroperoxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis ( 2,3-dimethylbutyronitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,3,3-trimethylbutyronitrile), 2,2′-azobis (2-Isopropylbutyronitrile ), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2- (carbamoylazo) isobutyronitrile, 4, Examples thereof include azo initiators such as 4′-azobis (4-cyanovaleric acid) and dimethyl-2,2′-azobisisobutyrate.

  Among these, 2,2'-azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile) are preferable from the viewpoint that multi-hollow particles can be easily obtained.

  The use ratio of the polymerization initiator is preferably 0.01 to 10% by weight, particularly preferably 0.1 to 5.0% by weight, based on the monomer mixture.

(1-2) Next, the solution is dispersed in an aqueous dispersion medium.
[Aqueous dispersion medium]
Examples of the aqueous dispersion medium include water and a mixed medium of water and a water-soluble organic solvent (such as a lower alcohol). Further, the aqueous dispersion medium preferably contains about 100 to 1000 parts by weight of water with respect to 100 parts by weight of the solution. By containing water in this range, the suspension particles can be stabilized during the aqueous suspension polymerization.

[Dispersion stabilizer]
Furthermore, a dispersion stabilizer may be added to the aqueous dispersion medium. Dispersion stabilizers include phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate, pyrophosphates such as calcium pyrophosphate, magnesium pyrophosphate, aluminum pyrophosphate and zinc pyrophosphate, calcium carbonate, magnesium carbonate , Calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, colloidal silica and other poorly water-soluble inorganic compounds, polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone and other water-soluble polymers . Among these, tricalcium phosphate and colloidal silica are particularly preferable in that multi-hollow particles can be stably obtained.

  The dispersion stabilizer is used by appropriately adjusting the selection, combination, addition amount, etc. in consideration of the particle diameter of the obtained multi-hollow particles and the dispersion stability of the solution during polymerization. For example, the amount of the dispersion stabilizer added to the monomer mixture is about 0.5 to 20% by weight.

[Surfactant]
In addition to the above dispersion stabilizer, the aqueous dispersion medium uses a surfactant such as an anionic surfactant, a cationic surfactant, a zwitterionic surfactant, and a nonionic surfactant. Also good.

  Examples of anionic surfactants include fatty acid oils such as sodium oleate and castor oil potassium, alkyl sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and alkylnaphthalene sulfonates. , Alkane sulfonate, dialkyl sulfosuccinate, alkyl phosphate ester salt, naphthalene sulfonate formalin condensate, polyoxyethylene alkylphenyl ether sulfate, polyoxyethylene alkyl sulfate, and the like.

  Nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, oxyethylene- Examples include oxypropylene block polymers.

  Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride.

  Examples of the zwitterionic surfactant include lauryl dimethylamine oxide.

  The surfactant is used by appropriately adjusting the selection, combination, addition amount, etc. in consideration of the particle diameter of the obtained multi-hollow particles and the dispersion stability of the solution during polymerization. For example, the addition amount of the surfactant is about 0.001 to 0.1% by weight with respect to the aqueous dispersion medium.

[Water-soluble polymerization inhibitor]
In order to suppress the polymerization of the monomer in the aqueous dispersion medium, about 0.01 to 1% by weight of a water-soluble polymerization inhibitor may be added to the aqueous dispersion medium. The water-soluble polymerization inhibitor is not particularly limited, and a known inhibitor can be used, and examples thereof include nitrites and hydroquinone.

[Dispersion method of solution]
Examples of a method for dispersing a solution in an aqueous dispersion medium include a method of dispersing by a stirring force such as a propeller blade, a homomixer that is a disperser that includes a rotor and a stator and uses a high shear force, and an ultrasonic disperser. And the like, and the like. The dispersed solution is present as droplets in the aqueous dispersion medium. In order to make the particle size distribution of the obtained multi-hollow particles uniform, a high-pressure disperser using a collision between droplets such as a microfluidizer or a nanomizer or a collision force against the machine wall may be used. Further, the solution may contain a surfactant as required, but it is preferable that the solution is not contained as much as possible.

  (1-3) Furthermore, the monomer mixture contained in the solution dispersed in the aqueous dispersion medium is polymerized in the aqueous dispersion medium.

  The polymerization is performed by heating an aqueous dispersion medium in which droplets made of a monomer mixture are dispersed. The polymerization temperature is usually 30 to 100 ° C, preferably 40 to 80 ° C. The time for maintaining this polymerization temperature is generally about 0.1 to 10 hours. During the polymerization, it is preferable to perform gentle stirring to such an extent that droplets can be prevented from floating and sedimentation of the multi-hollow particles after the polymerization can be prevented.

After the completion of the polymerization, if desired, the dispersion stabilizer may be dissolved with hydrochloric acid or the like, and the resin particles may be separated from the dispersion medium by operations such as suction filtration, centrifugation, and centrifugal filtration, and further washed with ion exchange water or the like. . Furthermore, after that, multi-hollow particles having a desired particle diameter may be obtained by drying, crushing, and classification.
In the present invention, divinylbenzene is used as the polyfunctional polymerizable monomer used in combination with styrene, and the specific monomers listed above using methyl acrylate, acrylonitrile, vinylidene chloride or vinyl chloride as the monomer polymerizable with styrene. Multi-hollow particles made of a monomer-structured copolymer are produced.

  In the present invention, the average particle size of the multi-hollow particles is preferably 5 μm or more and 100 μm or less. More preferably, they are 15 micrometers or more and 50 micrometers or less. By setting the size of the multi-hollow particles in the elastic layer within this range, the effect of the multi-hollow particles can be effectively realized by minimizing the twist applied to the charging member and releasing the twist from the micro state. In addition, it is possible to suppress the occurrence of abnormal discharge due to adhesion of toner or external additives to the surface of the multi-hollow particles having a relatively large particle diameter exposed from the elastic layer.

  The content of the multi-hollow particles contained in the elastic layer is preferably 5 parts by mass or more and 80 parts by mass or less, and more preferably 10 parts by mass or more and 50 parts by mass with respect to 100 parts by mass of the rubber constituting the elastic layer. The following is more preferable. By setting this range, the twist of each of the multi-hollow particles is suppressed to a small level, and the characteristics of the multi-hollow particles such as release from a small state of twist due to high resilience are more effectively realized.

  The pore diameter in the multi-hollow particles is preferably 1 μm or more and 15 μm or less as an average pore diameter. By setting the pore diameter of the multi-hollow particles within this range, it is possible to more effectively impart the characteristics of low hardness and high resilience to the multi-hollow particles.

  The specific gravity of the multi-hollow particles is preferably 50% or more and 80% or less with respect to the specific gravity of the solid particles having no pores inside. Since the multi-hollow particles have a plurality of pores inside, the specific gravity is lighter than that of solid particles. The specific gravity of multi-hollow particles becomes light when the number of pores contained in the particle is large or the pore diameter is large, and becomes heavy when the number of pores is small or the pore diameter is small, and the specific gravity of solid particles Get closer to.

  The diameter of the pores contained in the multi-hollow particles is preferably 10% to 25% with respect to the particle size of the multi-hollow particles. When the hole diameter is large or the number of holes is too large, the resilience of the particles is lowered, and the twist of the elastic layer cannot be released, and the effect of the present invention is reduced. If the hole diameter is small or the hole diameter is too small, the number of recesses in the cross section of the multi-hollow particles on the elastic layer surface decreases, and the contact surface between the photoconductor and the charging member increases. The effect of the invention is reduced. By making this range, the twist of each multi-hollow particle contained in the elastic layer is suppressed to a small level, and the characteristics of the multi-hollow particle, which is the release from a minute state of twist due to high resilience, is more effective. Realized.

In addition, the various measuring methods used for evaluation are as follows.
<Measurement of average particle diameter>
The electrolyte solution is filled in pores having a pore diameter of 50 to 280 μm, the volume is determined from the change in conductivity of the electrolyte solution when the hollow particles pass through the electrolyte solution, and the volume average particle diameter is calculated. Specifically, it is a volume average particle diameter measured by a Coulter Multisizer 2 manufactured by Beckman Coulter. In the measurement, calibration is performed using an aperture suitable for the particle diameter of the multi-hollow particles to be measured according to REFERENCE MANUAL FOR THE COULTER MULTISIZER (1987) issued by Coulter Electronics Limited.

  Specifically, 0.1 g of multi-hollow particles and 10 ml of a 0.1% nonionic surfactant solution are put into a commercially available glass test tube, and mixed for 2 seconds with a touch mixer TOUCHMIXERMT-31 manufactured by Yamato Kagaku. Thereafter, the test tube is predispersed for 10 seconds using a ULTRASONIC CLEANER VS-150 manufactured by Vervocrea, a commercially available ultrasonic cleaner. In a beaker filled with ISOTON2 (manufactured by Beckman Coulter, Inc .: electrolyte for measurement) equipped with a main body, this is dropped with a dropper while gently stirring, and the concentration meter reading on the main body screen is adjusted to about 10%. Next, the aperture size, Current, Gain, and Polarity are input to the Multisizer 2 main body according to REFERENCE MANUAL FOR THE MULTILIZER (1987) issued by Coulter Electronics Limited, and measured manually. During the measurement, the beaker is stirred gently to the extent that bubbles do not enter, and the measurement is terminated when 10,000 multi-hollow particles are measured.

<Measurement of average pore diameter>
The average pore diameter of the multi-hollow particles can be measured by the following method.
The appearance and cross section of the multi-hollow particles are observed with a scanning electron microscope. Specifically, the cross-section of the multi-hollow particle is exposed by solidifying the multi-hollow particle using a two-pack type epoxy adhesive and slicing with a razor blade after curing. Then, it observes with a scanning electron microscope and the hole diameter which exists in the cross section of many hollow particles is measured. The scanning electron microscope used was FE-SEM (S-4700, manufactured by Hitachi, Ltd.). This measurement is performed on 100 multi-hollow particles. The average value of the pore diameters present in the cross section of the total of 100 obtained multi-hollow particles is calculated and set as the average pore diameter of the multi-hollow particles.

<Measurement of average specific gravity>
Multi-hollow particles are packed into a known cylindrical container of mass M ₀ (g) and volume V (cm ³ ). Scrape off excess amount of multi-hollow particles deposited on top of container. After removing the multi-hollow particles adhering to the side surface or the like of the container using a brush or the like, the entire mass M _t (g) is measured. The specific gravity ρ _t (g / cm ³ ) of the multi-hollow particles is calculated by the following formula.
ρ _t = (M _t −M ₀ ) / V
The measurement is repeated 10 times, and the average value is defined as the specific gravity of the multi-hollow particles. Similarly, by measuring the specific gravity of the solid particles ρ ₀ and calculating ρ _t / ρ ₀ , the ratio of the specific gravity of the multi-hollow particles to the solid particles is calculated.

(Formation of conductive elastic layer)
There is no restriction | limiting in particular as a formation method of a conductive elastic layer, What is necessary is just to use a well-known method suitably. For example, the conductive elastic layer is formed by using a known method such as mixing the above-mentioned various rubber components and other components with a ribbon blender, nauter mixer, Henschel mixer, super mixer, Banbury mixer, pressure kneader, etc. An unvulcanized rubber composition is obtained. Furthermore, the above-mentioned multi-hollow particles are mixed into the obtained unvulcanized rubber composition using a two-roll machine or the like.

  The unvulcanized rubber composition containing the obtained multi-hollow particles is integrally extruded with the conductive substrate and the unvulcanized rubber composition using an extruder equipped with a crosshead to produce a preform. be able to. A crosshead is an extrusion die that is used at the tip of a cylinder of an extruder, which is used to form a coating layer for electric wires and wires. Furthermore, the obtained preform is heated and crosslinked in a high temperature atmosphere such as a hot stove to obtain a charging member.

  Alternatively, after forming an unvulcanized rubber composition containing multi-hollow particles into a sheet shape or tube shape formed in advance to a predetermined film thickness, it is bonded to or coated on a conductive substrate to produce a charging member preform. To do. Next, there is a method in which the preform is placed in a cylindrical mold or split mold having a cylindrical cavity and heated to obtain a charging member having a predetermined dimension. Further, a method in which an unvulcanized rubber composition and a conductive substrate are placed in the cylindrical mold and then heat-crosslinked is also used.

[Polishing the conductive elastic layer]
Next, the outer peripheral surface of the conductive elastic layer is polished in order to expose the end surface where the hollow portions of the multi-hollow particles contained in the conductive elastic layer are open to the surface of the conductive elastic layer. For example, in general, the charging roller uniformly contacts the other end of the conductive shaft core with a spring. Therefore, considering the bending due to the contact of the charging roller, the outer diameter of the central portion called a crown shape is the end. Finish in a shape that is thicker than the outer diameter of the part. Since it is difficult to remove such a shape with a cylindrical mold, it is preferable to finish with a polishing machine. An example of a polishing machine that performs polishing is a cylindrical polishing machine. Examples include a traverse type NC cylindrical polishing machine and a plunge cut type NC cylindrical polishing machine. The plunge cut type NC polishing machine uses a grinding wheel that is wider than that of the traverse type, and can preferably polish the entire length of the conductive elastic layer at the same time, so that the processing time can be shortened.

  FIG. 5 is a schematic view showing an example of a charging roller polishing method using a plunge cut type cylindrical polishing machine. The charging roller held at both ends by the gripping jig such as the collet chuck 501 via the conductive substrate 201 is rotated by the drive motor 502 together with the collet chuck 501. The rotation center of the grinding wheel 503 is arranged in parallel with the rotation center of the charging roller, and is driven to rotate separately from the charging roller by the grinding wheel drive motor 504. The polishing grindstone 503 is configured to be movable in a direction orthogonal to the rotation center of the charging roller and the rotation center of the polishing grindstone. The surface of the elastic layer 202 of the charging roller is polished by appropriately selecting the moving amount and moving speed of the polishing wheel, the number of rotations of the polishing wheel and the number of rotations of the charging roller, and the shape is finished to a desired shape. Both ends may be held by a known diaphragm chuck or the like instead of the collet chuck. As the shape of the grinding wheel 503, a crown shape is formed on the elastic layer of the charged roller after polishing, so that the outer diameter gradually decreases from the end portion toward the center portion (hereinafter referred to as an inverted crown shape). ) Is preferred.

[Surface layer]
The charging member of the present invention may be hollow portion of the multi-hollow particles contained in the multi-hollow particles and a conductive elastic layer exposed to the conductive elastic layer and a conductive elastic layer surface to form a surface layer on the end face of the opening it can. The surface layer is formed for the purpose of further enhancing the function and durability of the charging member. For example, by making the surface layer function as a resistance adjusting layer, charging uniformity and leakage resistance can be improved when used as a charging roller.

  For the step of forming the surface layer on the conductive elastic layer, a coating method such as electrostatic spray coating or dipping coating can be used. Alternatively, the surface layer can be formed by adhering or covering a sheet-shaped or tube-shaped layer that has been previously formed to a predetermined film thickness. Alternatively, a method of curing and molding the material into a predetermined shape in the mold can also be used. Among these, it is preferable to apply a paint by a coating method to form a coating film.

  When a layer is formed by a coating method, the solvent used in the coating solution may be any solvent that can dissolve the binder resin. Specifically, alcohols such as methanol, ethanol, isopropanol, ketones such as acetone, methyl ethyl ketone, cyclohexanone, amides such as N, N-dimethylformamide, N, N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, Examples thereof include ethers such as tetrahydrofuran, dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, and aromatic compounds such as xylene, ligroin, chlorobenzene and dichlorobenzene. These solvents are appropriately selected according to the binder resin used.

  As a method for dispersing the binder, particles and the like in the coating solution, known solution dispersing means such as a ball mill, a sand mill, a paint shaker, a dyno mill, and a pearl mill can be used.

  The surface layer can contain other particles as long as the effects of the present invention are not impaired. Examples of the other particles include insulating particles or conductive particles. Insulating particles or conductive particles may be used singly or in combination of two or more types, or may be subjected to surface treatment, modification, introduction of functional groups or molecular chains, coating, etc. . In order to improve the dispersibility of the particles, the particles are more preferably subjected to a surface treatment.

  The surface layer may further contain a release agent in order to improve the releasability. By including a release agent in the surface layer, it is possible to prevent dirt from adhering to the surface of the charging member and improve the durability of the charging member. When the release agent is a liquid, it also acts as a leveling agent when forming the surface layer. Various known paints can also be applied as a surface layer.

  The surface layer preferably has a thickness of 0.01 μm or more and 10 μm or less. More preferably, it is 0.1 μm or more and 5 μm or less. The film thickness of the surface layer is such that the hollow portion exposed on the surface of the conductive elastic layer does not fill the concave portion derived from the end face where the hollow portion opens in order to maintain the low friction of the cross section of the hollow particle. Thickness is preferred. When the surface layer is formed as described above, the repulsive force of the multi-hollow particles in the conductive elastic layer and the low friction effect of the cross-section of the multi-hollow particles exposed on the surface of the conductive elastic layer are maintained. Stick-slip is reduced and the generation of banding images is reduced / suppressed. The film thickness of the surface layer can be measured by cutting the charging member cross section with a sharp blade and observing with an optical microscope or an electron microscope. In the measurement of the film thickness of the outermost layer in the present invention, several points are measured at a magnification of 10,000 times using a scanning electron microscope (SEM), and the average value is defined as the average film thickness.

  Examples of the step of forming the surface layer on the conductive elastic layer include a method of modifying the surface of the conductive elastic layer by irradiation with a known energy beam such as an ultraviolet ray or an electron beam. For example, a high-pressure mercury lamp, a metal halide lamp, a low-pressure mercury lamp, an excimer UV lamp, or the like can be used for ultraviolet irradiation. Among these, an ultraviolet ray source rich in light having an ultraviolet wavelength of 150 nm to 480 nm is preferable. Used for.

The integrated light quantity of ultraviolet rays is defined as follows.
UV integrated light quantity [mJ / cm ² ] = UV intensity [mW / cm ² ] × irradiation time [s]
The adjustment of the integrated amount of ultraviolet light can be performed by the irradiation time, lamp output, distance between the lamp and the irradiated object, and the like. Moreover, you may give a gradient to integrated light quantity within irradiation time.

  In the case of using a low-pressure mercury lamp, the integrated light amount of ultraviolet rays can be measured using an ultraviolet integrated light amount meter UIT-150-A or UVD-S254 manufactured by USHIO INC. When an excimer UV lamp is used, the integrated light quantity of ultraviolet rays can be measured using an ultraviolet integrated light quantity meter UIT-150-A or VUV-S172 manufactured by USHIO INC.

For example, the electron beam irradiation apparatus irradiates the surface of the conductive elastic layer while rotating an elastic roller, and includes an electron beam generation unit, an irradiation chamber, and an irradiation port.
The electron beam generator includes a terminal that generates an electron beam and an acceleration tube that accelerates the electron beam generated at the terminal in a vacuum space (acceleration space). The inside of the electron beam generator is kept at a vacuum of about 10 ⁻³ to 10 ⁻⁴ [Pa] by a vacuum pump or the like in order to prevent electrons from colliding with gas molecules and losing energy.

  When a filament is heated by a power source through a current, the filament emits thermoelectrons, and only those thermoelectrons that have passed through the terminal are effectively extracted as electron beams. And after accelerating in the acceleration space in an acceleration tube with the acceleration voltage of an electron beam, it penetrates through an irradiation opening foil, and is irradiated to the roller conveyed in the irradiation chamber under the irradiation opening.

  When the elastic roller is irradiated with an electron beam, the inside of the irradiation chamber is a nitrogen atmosphere or an air atmosphere. Further, the roller is rotated by a roller rotating member, and can move and pass through the irradiation chamber by the conveying means. In addition, the surroundings of the electron beam generator and the irradiation chamber are shielded from lead so that X-rays that are secondarily generated during electron beam irradiation do not leak to the outside.

  The irradiation port foil is made of a metal foil, and partitions the vacuum atmosphere in the electron beam generator and the air atmosphere in the irradiation chamber, and takes out the electron beam into the irradiation chamber through the irradiation port foil. When an electron beam is applied to the irradiation of the roller, the inside of the irradiation chamber in which the roller is irradiated with the electron beam is a nitrogen atmosphere or an air atmosphere. Therefore, the irradiation mouth foil provided at the boundary between the electron beam generating part and the irradiation chamber has no pinhole, has a mechanical strength that can sufficiently maintain the vacuum atmosphere in the electron beam generating part, and is easy to transmit the electron beam. A metal having a small specific gravity and a small thickness is desirable. For example, Ti having a thickness of about 5 to 15 μm is often used as a metal used for the irradiation port foil. For example, an electron beam irradiation apparatus (manufactured by Iwasaki Electric Co., Ltd.) having a maximum acceleration voltage of 150 kV and a maximum electron current of 40 mA is used. In addition, although irradiation is performed in a nitrogen atmosphere or an air atmosphere, irradiation in a nitrogen atmosphere is preferable, and an environment having an oxygen concentration of 500 ppm or less is preferable.

The electron beam dose is defined below.
Dose (kGy) = [equipment constant K × electron current (mA)] / processing speed (m / min)
Here, the device constant K is a constant representing the efficiency of each device, and serves as an index of device performance. For example, in an electron beam irradiation apparatus, it is originally necessary to set K = 18 or more. Therefore, for a certain electron current and processing speed, the acceleration voltage is changed, the dose is measured, and the acceleration voltage is determined by obtaining the acceleration voltage so that the device constant K obtained from this is a predetermined value or more. Is obtained.

  What is necessary is just to select suitably about the dose of an electron beam according to the effect of surface treatment. The adjustment can be performed using either an electronic current or a processing speed, and it is sufficient to determine that a desired dose can be obtained.

[Electrophotographic equipment]
FIG. 7 shows a schematic configuration of an example of an electrophotographic apparatus provided with a charging member manufactured according to the present invention as a charging roller.

  The electrophotographic apparatus includes a photosensitive member, a charging device that charges the photosensitive member, a latent image forming device that performs exposure, a developing device that develops the toner image, a transfer device that transfers to a transfer material, and a cleaning that collects the transfer toner on the photosensitive member. And a fixing device for fixing the toner image.

  The photoreceptor 701 is a rotating drum type having a photosensitive layer on a conductive shaft core. The photoreceptor is driven to rotate in the direction of the arrow at a predetermined peripheral speed (process speed). The charging device includes a contact-type charging roller 702 that is placed in contact with the photosensitive member 701 by contacting the photosensitive member 701 with a predetermined pressing force. The charging roller 702 is driven rotation that rotates in accordance with the rotation of the photoconductor, and charges the photoconductor to a predetermined potential by applying a predetermined voltage from the charging power source 712. For example, an exposure apparatus such as a laser beam scanner is used as the latent image forming apparatus 708 that forms an electrostatic latent image on the photoreceptor 701. An electrostatic latent image is formed by performing exposure corresponding to image information on a uniformly charged photoconductor.

  The developing device has a developing roller 703 disposed close to or in contact with the photoreceptor 701. The developing roller 703 is in contact with the toner supply roller 710, and toner is supplied to the surface of the developing roller. The developing roller 703 is in contact with the elasticity regulating blade 709 and regulates the amount of toner carried on the developing roller surface. By applying a predetermined voltage from the developing power supply 711 to the developing roller 703, the toner supply roller 710, and the elasticity regulating blade 709, the toner electrostatically processed to the same polarity as the photosensitive member charging polarity is reversely developed. Thus, the electrostatic latent image is visualized and developed into a toner image.

  The transfer device includes a contact-type transfer roller 705, and a predetermined voltage is applied from a transfer power supply 713. The toner image is transferred from the photoreceptor to a print medium 704 such as plain paper (the print medium is conveyed by a paper feed system having a conveyance member).

  The cleaning device has a blade-type cleaning blade 707 and a recovery container, and after transferring, mechanically scrapes and recovers transfer residual toner remaining on the photosensitive member. Here, it is possible to omit the cleaning device by adopting a development simultaneous cleaning system in which the transfer device collects the transfer residual toner. The fixing device 706 includes a heated roller or the like, fixes the transferred toner image on the print medium 704, and discharges the image to the outside.

  Hereinafter, the charging member of the present invention described above will be described in more detail by way of specific examples and comparative examples, but the technical scope of the present invention is not limited to these.

Production Examples 1 to 13 are production examples of the multi-hollow particles A1 to A13. In addition, Production Examples 14 to 18 are production examples of solid particles A1 to A5. In addition, Production Examples 19 to 22 are production examples of unvulcanized rubber compositions A1 to A4 used for the conductive elastic layer. In the following, “part” and “%” are based on weight unless otherwise specified.
[Production Example 1] Preparation of multi-hollow particles A1 300 g of water and 300 g of a commercially available tricalcium phosphate slurry (solid content 10%, trade name: Supertite Nippon Kasei Co., Ltd.) as a dispersion stabilizer were placed in a 1000 ml beaker, Then, 0.12 g of sodium lauryl sulfate as a surfactant was dissolved in water to prepare an aqueous dispersion medium.

  Separately, 200 g of styrene, 50 g of divinylbenzene, and 40 g of methyl acrylate were mixed to prepare a monomer mixture. 200 g of the monomer mixture was weighed into a beaker, 5 g of ethyl cellulose resin (45 cP manufactured by Kanto Chemical Co., Inc.) was added and mixed and dissolved uniformly, and then 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator 2.0 g was mixed and dissolved uniformly to obtain a solution.

  The obtained solution was mixed with the aqueous dispersion medium, and the mixture was dispersed at 6000 rpm for 30 seconds with a homomixer (ULTRATRARAX T-25 manufactured by IKA). The obtained dispersion was put into a 1000 ml separable flask, a stirring blade, a thermometer and a reflux condenser were attached, and the flask was purged with nitrogen and then bathed in water at 60 ° C. Polymerization was carried out by continuing heating at a stirring speed of 200 rpm for 10 hours.

  After confirming that the polymerization was completed, the dispersion was cooled, and hydrochloric acid was added until the pH of the slurry was about 2, whereby the dispersion stabilizer was decomposed. The polymer was suction filtered through a Buchner funnel using filter paper, washed with 5 liters of ion exchange water to remove the dispersion stabilizer, and dried in an oven at 60 ° C. for 24 hours to obtain resin particles.

The obtained resin particles have an average particle diameter of 5.1 μm, and when observed with a scanning electron microscope, they were spherical resin particles and confirmed to be multi-hollow particles having a plurality of pores inside. . Furthermore, multi-hollow particles A1 were obtained by classifying the resin particles. Further, solid particles were prepared in the same manner as in Production Example 1 except that divinylbenzene was not added, and the ratio ρ _t / ρ ₀ of the specific gravity between the multi-hollow particles and the solid particles was measured. Table 2 shows the measurement results of the average particle diameter, average pore diameter, and specific gravity ratio of the multi-hollow particles A1.
[Production Examples 2 to 9] Production of multi-hollow particles A2 to A9 Multi-hollow particles A2 to A9 were produced in the same manner as in Production Example 1 except that the amount of divinylbenzene and the stirring speed were adjusted. Table 1 shows the composition, dispersion conditions, and polymerization conditions of the monomer mixture, and Table 2 shows the measurement results of the particles.
[Production Example 10] Production of multi-hollow particles A10 Multi-hollow particles A10 were produced in the same manner as in Production Example 4 except that methyl acrylate was not used in Production Example 4. Table 1 shows the composition, dispersion conditions, and polymerization conditions of the monomer mixture, and Table 2 shows the measurement results of the particles.
[Production Example 11] Production of multi-hollow particles A11 Multi-hollow particles A11 were produced in the same manner as in Production Example 4 except that methyl acrylate was changed to acrylonitrile in Production Example 4. Table 1 shows the composition, dispersion conditions, and polymerization conditions of the monomer mixture, and Table 2 shows the measurement results of the particles.
[Production Example 12] Production of multi-hollow particles A12 Multi-hollow particles A12 were produced in the same manner as in Production Example 4, except that methyl acrylate was changed to vinylidene chloride. Table 1 shows the composition, dispersion conditions, and polymerization conditions of the monomer mixture, and Table 2 shows the measurement results of the particles.
[Production Example 13] Production of multi-hollow particles A13 Multi-hollow particles A13 were produced in the same manner as in Production Example 4 except that methyl acrylate was changed to vinyl chloride in Production Example 4. Table 1 shows the composition, dispersion conditions, and polymerization conditions of the monomer mixture, and Table 2 shows the measurement results of the particles.
[Production Examples 14 to 18] Production of solid particles A1 to A5 Solid particles A1 to A5 were produced in the same manner as in Production Examples 4 and 10 to 13 except that divinylbenzene was not added. Table 1 shows the composition, dispersion conditions, and polymerization conditions of the monomer mixture, and Table 2 shows the measurement results of the particles.

[Production Example 19] Preparation of unvulcanized rubber composition A1 using NBR Acrylonitrile butadiene rubber (NBR) (trade name: N230SV, manufactured by JSR) 100 parts by mass, the following 4 components were added to 50 ° C The mixture was kneaded for 15 minutes with a controlled closed mixer.
Carbon black (trade name: Toka Black # 7360SB, manufactured by Tokai Carbon Co., Ltd.): 48 parts by mass
-Zinc stearate (trade name: SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.): 1 part by mass,
-Zinc oxide (trade name: Zinc Hana 2 types, manufactured by Sakai Chemical Industry Co., Ltd.): 5 parts by mass
Calcium carbonate (trade name: Silver W, manufactured by Shiroishi Kogyo Co.): 20 parts by mass.

To this, 13 parts by mass of the multi-hollow particles A1, 1.2 parts by mass of sulfur as a vulcanizing agent, and tetrabenzylthiuram disulfide (TBzTD) (trade name: Parkasit TBzTD, manufactured by Flexis) as a vulcanization accelerator 4.5 mass Then, the mixture was kneaded for 10 minutes with a two-roll mill cooled to 25 ° C. to obtain an unvulcanized rubber composition A1.
[Production Example 20] Preparation of unvulcanized rubber composition A2 using epichlorohydrin rubber Epichlorohydrin rubber (EO-EP-AGE ternary co-compound) (trade name: Epion ON301, manufactured by Daiso Corporation) Seven components were added and kneaded for 10 minutes in a closed mixer adjusted to 50 ° C.
Calcium carbonate (trade name: Nanox # 30, manufactured by Maruo Calcium Co.): 60 parts by mass
Aliphatic polyester plasticizer (trade name: Polycizer P-202, manufactured by Dainippon Ink & Chemicals, Inc.): 10 parts by mass
-Zinc stearate (trade name: SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.): 1 part by mass,
2-mercaptobenzimidazole (trade name: NOCRACK NS-5, manufactured by Ouchi Shinsei Chemical Co., Ltd.): 0.5 parts by mass,
・ Zinc oxide (trade name: Zinc Hana 2 types, manufactured by Sakai Chemical Industry Co., Ltd.): 2 parts by mass
-Quaternary ammonium salt (trade name: Adeka Sizer LV70, manufactured by Asahi Denka Kogyo Co., Ltd.): 2 parts by mass,
Carbon black (trade name: Seast GSO, manufactured by Tokai Carbon Co., Ltd.): 5 parts by mass.

In addition, 1 part by mass of the multi-hollow particles A3, 0.8 part by mass of sulfur as a vulcanizing agent, dibenzothiazyl sulfide (DM) as a vulcanization accelerator (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1 part by mass, 0.5 part by mass of tetramethylthiuram monosulfide (TS) (trade name: Noxeller TS, manufactured by Ouchi Shinsei Chemical Co., Ltd.) is added, and the mixture is kneaded for 10 minutes with a two-roll mill cooled to 25 ° C. Thus, an unvulcanized rubber composition A2 was obtained.
[Production Example 21] Preparation of unvulcanized rubber composition A3 using SBR Styrene butadiene rubber (SBR) (trade name: SBR1500, manufactured by JSR) 100 parts by mass, the following 6 components were added to 80 ° C The mixture was kneaded for 15 minutes with a controlled closed mixer.
-Zinc oxide (trade name: Zinc Hana 2 types, manufactured by Sakai Chemical Industry Co., Ltd.): 5 parts by mass
-Zinc stearate (trade name: SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.): 2 parts by mass
Carbon black (trade name: Ketjen Black EC600JD, manufactured by Lion): 8 parts by mass
Carbon black (trade name: Seast S, manufactured by Tokai Carbon Co.): 40 parts by mass
Calcium carbonate (trade name: Nanox # 30, manufactured by Maruo Calcium Co., Ltd.): 15 parts by mass
Paraffin oil (trade name: PW380, manufactured by Idemitsu Kosan Co., Ltd.): 20 parts by mass.

To this, 5 parts by mass of multi-hollow particles A3, 1 part by mass of sulfur as a vulcanizing agent, 1 part by mass of dibenzothiazyl sulfide (DM) as a vulcanization accelerator (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1 part by mass of tetramethylthiuram monosulfide (TS) (trade name: Noxeller TS, manufactured by Ouchi Shinsei Chemical Co., Ltd.), kneaded for 10 minutes with a two-roll mill cooled to 25 ° C. A vulcanized rubber composition A3 was obtained.
[Production Example 22] Production of unvulcanized rubber composition A4 using EPDM The following 6 components were added to 100 parts by mass of ethylene propylene diene rubber (EPDM) (trade name: Esprene EPDM505A, manufactured by Sumitomo Chemical Co., Ltd.). The mixture was kneaded for 15 minutes in a closed mixer adjusted to 80 ° C.
-Zinc oxide (trade name: 2 types of zinc white, manufactured by Sakai Chemical Industry Co., Ltd.): 5 parts by mass-Zinc stearate (trade name: SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.): 2 parts by mass,
Carbon black (trade name: Ketjen Black EC600JD, manufactured by Lion): 8 parts by mass
Carbon black (trade name: Seast S, manufactured by Tokai Carbon Co.): 30 parts by mass
Calcium carbonate (trade name: Nanox # 30, manufactured by Maruo Calcium Co., Ltd.): 15 parts by mass
Paraffin oil (trade name: PW380, manufactured by Idemitsu Kosan Co., Ltd.): 20 parts by mass.

  To this, 1 part by mass of multi-hollow particles A3, 1 part by mass of sulfur as a vulcanizing agent, and 1 part by mass of dibenzothiazyl sulfide (DM) (trade name: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd.) as a vulcanization accelerator 1 part by mass of tetramethylthiuram monosulfide (TS) (trade name: Noxeller TS, manufactured by Ouchi Shinsei Chemical Co., Ltd.), kneaded for 10 minutes with a two-roll mill cooled to 25 ° C. A vulcanized rubber composition A4 was obtained.

[Example 1]
(Production of elastic roller)
A thermosetting adhesive (trade name: “Metaloc U-20”, manufactured by Toyo Chemical Laboratories) was applied to a stainless steel rod having a diameter of 6 mm and a length of 258 mm in advance to the area excluding both ends 12 mm, and the temperature was adjusted to 180 ° C. It left still for 30 minutes in the adjusted hot stove, and obtained the electroconductive base | substrate.

  Subsequently, as an extrusion molding apparatus having the single-layer crosshead 102 shown in FIG. 1, a general-purpose rubber extruder 101 (trade name: “extruder with vent”, manufactured by Mitsuba Seisakusho; screw diameter: 45 mm, L / L D = 20 extruder, L is screw length, D is screw diameter). The flight shape of the screw was a full flight shape except for the vacuum vent zone. The temperature during extrusion was set at a head temperature of 80 ° C, a cylinder temperature of 80 ° C, and a screw temperature of 80 ° C. A base having an inner diameter of 9.8 mm was attached to the tip of the single-layer crosshead. The screw rotation speed of the extruder was set to 10.5 rpm so that the discharge speed (the amount of extrusion per unit time) of the unvulcanized rubber composition A1 by the extruder (FIG. 1) became the predetermined outer diameter of the elastic roller.

  Using the extruder and the single-layer crosshead, the conductive substrate 201 is inserted into the crosshead by the feed roll 103, and the unvulcanized rubber composition A1 is formed coaxially and cylindrically with the conductive substrate 201 as the central axis. To obtain a charging member preform 104 having an outer diameter of Φ9.4 mm.

  This charging member preform was heated in a hot air oven at 160 ° C. for 1 hour and vulcanized to form a conductive coating layer on the outer periphery of the conductive substrate. Both ends of this conductive coating layer were cut and removed to obtain a roller having a conductive coating layer having a length of 224.2 mm.

Next, the outer peripheral surface of the conductive coating layer is polished by using a plunge cut type cylindrical polishing machine (manufactured by Mizuguchi Seisakusho, grindstone: GC-120), and the outer diameter is Φ8.5 mm and the length is 224.2 mm. An elastic roller A1 having a conductive elastic layer was obtained. The crown amount was 100 μm.
(Crown amount measurement method)
As the outer diameter measuring device, (product names: “LS-7500 (controller)” and “LS-7030M (measurement unit)”, manufactured by Keyence Corporation) are used, and the central portion (112 0.1 mm) and three outer diameters of 90 mm portions (22.1 mm, 202.1 mm) in the both end directions from the center portion. The outer diameter of the central portion was D2, the outer diameter of each 90 mm portion in both end directions was D1 and D3, and the crown amount D was calculated as D = (D2− (D1 + D3) / 2).
(Create surface layer)
Surface layer A1:
An irradiation port of an electron beam irradiation apparatus (manufactured by Iwasaki Electric Co., Ltd.) having a maximum acceleration voltage of 150 kV and a maximum electron current of 40 mA is installed in parallel with the axial direction of the elastic roller A1, and the elastic roller A1 is set at 500 rpm in the circumferential direction. The electron beam treatment layer (surface layer A1) was formed on the surface by directly irradiating the conductive elastic layer with an electron beam while rotating at a rotational speed. In this way, a charging roller A1 was obtained. The electron beam irradiation conditions were set to an acceleration voltage of 150 KV, an electron current of 15 mA, and an irradiation time of 1 sec. The irradiation was performed in a nitrogen atmosphere (oxygen concentration of about 300 ppm). Regarding the charging roller A1, Table 4-1 shows the type of the conductive elastic layer, the type (number) and amount of the hollow particles, the crown amount of the charging roller A1, and the type of the surface layer.

[Evaluation of durability]
A color laser printer (trade name: HPolar LaserJet CP4525dn, manufactured by Hewlett-Packard Company), which is an electrophotographic apparatus having the configuration shown in FIG. 7, is modified and used so that a recording medium can be output at 60 ppm (A4 vertical output). did. The primary charging output is a DC voltage (Vdc) of −1100V. The resolution of the image is 600 dpi. As the photoreceptor 701, an organic photoreceptor drum having a total film thickness including the photosensitive layer of 40 μm was used. The charging roller was removed from the process cartridge of the electrophotographic apparatus, and the charging roller 1 was set. Further, as shown in FIG. 7, the charging roller 1 was brought into contact with the photosensitive member by a pressing force of a spring of 4.9 N at one end and a total of 9.8 N at both ends.

  The process cartridge on which the charging roller 1 was set was left in a 15 ° C., 10% RH environment (environment 1), 23 ° C., 50% RH environment (environment 2), and 30 ° C., 80% RH environment (environment 3) for 24 hours. Later, durability performance was evaluated in each environment.

Specifically, a two-sheet intermittent durability performance test (an evaluation of durability performance was performed by stopping the rotation of the printer for 3 seconds for every two sheets) was performed at an image density of 1% at a speed of 60 ppm. In the evaluation method, after passing 50,000 sheets, a halftone image (an image in which a horizontal line having a width of 1 dot and an interval of 2 dots is drawn in a direction perpendicular to the rotation direction of the photosensitive member) is output and evaluated. In the evaluation, the obtained halftone image is visually observed, and the banding image (horizontal striped image) of the charging member period generated due to the above-described contamination on the surface of the charging roller, and the rough image are displayed. ,evaluated.
Here, the evaluation criteria are as follows.
Rank A: No horizontal striped banding image is generated.
Rank B: A very slight horizontal stripe image is recognized at the end.
Rank C: A partially banded banding image can be confirmed by the pitch of the charging roller, but the image quality has no practical problem.
Rank D: A horizontal striped banding image is conspicuous, and deterioration in image quality is observed.

As a result of the image evaluation test, for the charging roller A1 of the present example, a horizontal striped banding image was not generated and a good image was obtained. The image rank was rank A. The evaluation results are shown in Table 4-1 .

[Examples 2 to 21]
Example 1 except that the type of the conductive elastic layer, the type (number) of the multi-hollow particles, the number of added parts of the multi-hollow particles, and the crown amount of the charging roller are the combinations shown in Tables 4-1 and 4-2. Similarly, charging rollers A2 to A21 were produced. The evaluation results are shown in Tables 4-1 and 4-2.
[Example 22]
A charging roller A22 was produced in the same manner as in Example 4 except that the surface layer A1 was changed to the following surface layer A2 in Example 4. The evaluation results are shown in Table 4-2 .
Surface layer A2:
An ultraviolet lamp having a wavelength of 250nm near installed parallel to the axial direction of the elastic roller A1, as ultraviolet integrated light amount of the wavelength of 254nm while rotating the roller A1 in the circumferential direction is 9000 mJ / cm ² 2 Irradiated for minutes to form an ultraviolet treatment layer on the surface. A low pressure mercury lamp (trade name: “QLC500”, manufactured by Harrison Toshiba Lighting Co., Ltd.) was used for ultraviolet irradiation.
Example 23
In Example 4, a charging roller A23 was produced in the same manner as in Example 4 except that the surface layer A1 was changed to the following surface layer A3. The evaluation results are shown in Table 4-2 .
Surface layer A3:
First, the following four components were mixed and then stirred at room temperature for 30 minutes.
3-glycidoxypropyltrimethoxysilane (hydrolyzable silane compound (A), Shin-Etsu Chemical Co., Ltd.): 10.62 g (0.045 mol),
Hexyltrimethoxysilane (hydrolyzable silane compound (B), Shin-Etsu Chemical Co., Ltd.): 26.82 g (0.13 mol),
-Ethanol: 40.50 g,
-Ion exchange water: 9.45g.

  Subsequently, a condensate A1 was obtained by heating and refluxing at 120 ° C. for 20 hours using an oil bath. The theoretical solid content of this condensate A1 (the mass ratio of the polysiloxane polymer to the total weight of the solution when it is assumed that all hydrolyzable silane compounds have been dehydrated and condensed) is 28.0% by mass. The value of (D) / {(A) + (B)} at this time was 3.0.

0.7 g of an aromatic sulfonium salt (trade name: Adekaoptomer SP-150, manufactured by Asahi Denka Kogyo Co., Ltd.) as a photocationic polymerization initiator diluted to 10% by mass with 25 g of the condensate A1 is added. Condensate 1-2 was obtained. The condensate 1-2 was diluted with a mixed solution of ethanol and 2-butanol (ethanol: 2-butanol = 1: 1) so that the solid content was 5.0% by mass to prepare a coating solution A1 for the surface layer. . Using the surface layer coating liquid A1, coating was performed once on the surface of the conductive elastic layer using a ring coating apparatus (not shown). After air-drying in the atmosphere at 25 ° C. for 30 seconds, ultraviolet rays were irradiated in the same manner as in Example 22 to treat the surface layer with ultraviolet rays. At this time, the film thickness of the surface layer was 0.05 μm.
Example 24
In Example 4, a conductive elastic layer was formed using the unvulcanized rubber composition A2, and the charging roller A24 was changed in the same manner as in Example 4 except that the surface layer A1 was changed to the following surface layer A4. Produced. The evaluation results are shown in Table 4-2 .
Surface layer A4:
Methyl isobutyl ketone (MIBK) was added to a caprolactone-modified acrylic polyol solution (trade name: Plaxel DC2016, manufactured by Daicel Chemical Industries) to adjust the solid content to 2% by mass. The following three components were added to 1000 parts by mass of this solution (100 parts by mass of acrylic polyol solid content) to prepare a mixed solution.
Carbon black (trade name: # 52, manufactured by Mitsubishi Chemical Corporation): 25 parts by mass
Modified dimethyl silicone oil (trade name: SH28PA, manufactured by Toray Dow Corning Silicone): 0.08 parts by mass,
Block isocyanate mixture (7: 3 mixture of each butanone oxime block body of HDI (trade name: Duranate TPA-B80E, manufactured by Asahi Kasei Kogyo) and IPDI (trade name: Bestanat B1370, manufactured by Degussa Huls)): 80. 14 parts by weight.
At this time, the blocked isocyanate mixture was such that the amount of isocyanate was “NCO / OH = 1.0”.

  200 g of the above mixed solution is put in a glass bottle with an internal volume of 450 mL together with 200 g of glass beads having an average particle diameter of 0.8 mm as a medium, and dispersed for 28 hours using a paint shaker disperser to remove the glass beads and apply for the surface layer. A liquid A2 was obtained.

Using the above surface layer coating solution A2, dip coating was performed once on the surface of the conductive elastic layer using a coating apparatus (not shown). Here, the dipping coating is as follows. The immersion time was 9 seconds, the dipping coating lifting speed was an initial speed of 20 mm / s and a final speed of 2 mm / s, and the speed was changed linearly with respect to the time. After coating, the film was air-dried at room temperature for 30 minutes or more, and then dried with a hot air circulating dryer at 80 ° C. for 1 hour and further at 160 ° C. for 1 hour to form a surface layer A4 on the conductive elastic layer. At this time, the film thickness of the surface layer was 1.5 μm.
Example 25
In Example 24, except that the conductive elastic layer was formed using the unvulcanized rubber composition A2 and the multi-hollow particles A5, and the surface layer A4 was changed to the following surface layer A5, the same as in Example 24. Thus, a charging roller A25 was produced. The evaluation results are shown in Table 4-2 .
Surface layer A5:
Methyl isobutyl ketone was added to the surface layer coating solution A2 of Example 24, and the surface layer A5 was formed using the surface layer coating solution A3 adjusted to have a solid content of 5% by mass. The film thickness of the surface layer was 4.1 μm.
[Examples 26 and 27]
In Example 4, charging rollers A26 and A27 were produced in the same manner as in Example 4 except that the crown amount of the charging roller was changed by changing the shape of the grindstone. The crown amount of the charging roller at that time was 73 μm and 96 μm, respectively. The evaluation results are shown in Table 4-2 .
[ Reference Example 1 ]
In Example 1, charging was carried out in the same manner as in Example 1 except that multi-hollow particles (manufactured by Sekisui Plastics Co., Ltd., acrylic resin, particle size 30 μm) were used as multi-hollow particles A14 instead of multi-hollow particles A1. Roller A28 was produced. The average pore diameter was 2.6 μm, the specific gravity ρt was 0.51 g / cm ³ , and ρt / ρ0 was 0.73. The evaluation results are shown in Table 4-2 .
[ Reference Example 2 ]
In Example 9, charging was performed in the same manner as in Example 9 except that multi-hollow particles (manufactured by Sekisui Plastics Co., Ltd., acrylic resin, particle size 20 μm) were used as multi-hollow particles A15 instead of multi-hollow particles A4. Roller A29 was produced. The average pore diameter was 2.1 μm, the specific gravity ρt was 0.52 g / cm ³ , and ρt / ρ0 was 0.75. The evaluation results are shown in Table 4-2 .

[Comparative Example 1]
In Example 4, a charging roller A30 was produced in the same manner as in Example 4 except that the multi-hollow particles A4 were changed to solid particles A1. The evaluation results are shown in Table 4-2 .
[Comparative Example 2]
In Example 4, a charging roller A31 was produced in the same manner as in Example 4 except that the multi-hollow particles A4 were changed to solid particles A2. The evaluation results are shown in Table 4-2 .
[Comparative Example 3]
In Example 10, a charging roller A32 was produced in the same manner as in Example 10 except that the multi-hollow particles A4 were changed to solid particles A3. The evaluation results are shown in Table 4-2 .
[Comparative Example 4]
In Example 20, a charging roller A33 was produced in the same manner as in Example 20 except that the multi-hollow particles A4 were changed to solid particles A4. The evaluation results are shown in Table 4-2 .
[Comparative Example 5]
In Example 21, a charging roller A34 was produced in the same manner as in Example 21, except that the multi-hollow particles A4 were changed to solid particles A5. The evaluation results are shown in Table 4-2 .

DESCRIPTION OF SYMBOLS 101 ... Extruder 102 ... Single layer crosshead 103 ... Feed roll 104 ... Charged member preform 201 ... Conductive base 202 ... Conductive elastic layer 203 ... Multi hollow particle 204 ... Conductive elasticity Multi-hollow particles 501 exposed on the surface of the layer Collet chuck 502 Drive motor 503 Polishing wheel 504 Polishing wheel drive motor 601 Metal cylinder 602 Bearing 603 Stabilizing power supply 604 Ammeter 701 ... Photoconductor 702 ... Charging roller 703 ... Development roller 704 ... Printing media 705 ... Transfer roller 706 ... Fixing device 707 ... Cleaning blade 708 ... Latent image forming device 709 ... Elasticity regulating blade 710 ... Toner supply roller 711 ... Development power supply 712 ... Charging power supply 713 ... Transfer power supply

Claims (7)

In a charging member having a conductive substrate and a conductive elastic layer,
The conductive elastic layer contains, as a binder, at least one rubber selected from acrylonitrile butadiene rubber, styrene butadiene rubber, ethylene propylene diene rubber, and epichlorohydrin rubber,
The conductive elastic layer holds the multi-hollow particles in a state where a part thereof is exposed from the conductive elastic layer,
The charging member has a concave portion derived from a hollow portion of the multi-hollow particle on the surface,
The multi-hollow particles are
Copolymer of styrene, divinylbenzene and methyl acrylate,
A copolymer of styrene and divinylbenzene,
Copolymer of styrene, divinylbenzene and acrylonitrile,
A copolymer of styrene, divinylbenzene and vinylidene chloride, and
Copolymer of styrene, divinylbenzene and vinyl chloride
Resin particles made of any copolymer selected from the group consisting of, and having a plurality of pores therein,
A charging member. A surface layer covering the surface of the conductive elastic layer and the multi-hollow particles exposed from the surface of the conductive elastic layer;
The charging member according to claim 1, wherein the surface layer has a concave portion derived from a hollow portion of the multi-hollow particle on the surface.   The content rate of the said hollow particle in the said electroconductive elastic layer is 5 mass parts or more and 80 mass parts or less with respect to 100 mass parts of said rubber | gum in the said electroconductive elastic layer. Charging member.   The charging member according to claim 1, wherein the multi-hollow particles have an average particle size of 5 μm to 100 μm.   5. The charging member according to claim 1, wherein a pore diameter in the multi-hollow particles is 1 μm or more and 15 μm or less as an average pore diameter.   The charging member according to any one of claims 1 to 5, wherein the specific gravity of the multi-hollow particles is 50% or more and 80% or less with respect to the specific gravity of the solid particles having no pores therein.   An electrophotographic photosensitive member and a charging member disposed in contact with the electrophotographic photosensitive member, wherein the charging member is the charging member according to any one of claims 1 to 6. An electrophotographic device.

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