JP5836734B2 - Conductive member and manufacturing method thereof - Google Patents

Description

  The present invention relates to a conductive member and a manufacturing method thereof, and more particularly to a conductive member used in an electrophotographic apparatus such as a copying machine or a printer and a manufacturing method thereof.

  In electrophotographic apparatuses, various types of conductive members such as a charging member, a developing roller, a transfer roller, and a cleaning roller are used. These conductive members are often used in contact with a photoreceptor. During use, it is repeatedly subjected to stress strain due to relative rotational motion and vibration with the photosensitive member and other members. Further, these conductive members are often used while applying a high voltage used in an electrophotographic apparatus. That is, the electrophotographic conductive member has a problem in that the electrical characteristics gradually change during use due to the repeated stress strain and energization in a high voltage application state. Many proposals have been made for electrophotographic conductive members that suppress changes in electrical characteristics due to the use of conductive members.

  Of the electrophotographic conductive members, the electroconductive conductive members are often formed of a composite material in which electroconductive fine particles are dispersed in a polymer binder. In such a composite material in which electronic conductive fine particles are dispersed in such a polymer binder, the dispersion state of the conductive fine particles gradually changes due to the above-described repeated stress strain and energization in a high voltage applied state. Characteristics may change. In order to suppress such a change in the dispersion state of the conductive fine particles, many attempts have been made to fix the conductive fine particles to the polymer binder. In addition, when the conductive member made of the composite material is viewed from the manufacturing side, it is necessary to suppress the variation in the position of the electric resistance value due to the dispersion of the conductive fine particles. It is said that fixing fine particles is useful (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 07-020679

  However, in the above conventional example, the purpose of uniform dispersion of the conductive fine particles is achieved by fixing the carbon as the conductive fine particles to the polymer binder. On the other hand, the electrical characteristics in the usage state of the member are achieved. There is still room for improvement in terms of restraining change. That is, the fixing of the conductive agent by the method of the conventional example cannot be achieved until the change in the dispersion state of the conductive fine particles due to the repeated stress strain and the energization in a high voltage applied state is sufficiently suppressed.

  It is an object of the present invention to provide a conductive member having a small change in electrical characteristics when used in a harsh environment that is subjected to repeated stress strain and energization under a high voltage applied state.

According to the present application, a conductive member having at least a conductive layer on a conductive support, wherein the conductive layer includes at least conductive fine particles A and a polymer binder, and the conductive fine particles A include at least An acrylic polyol which is bonded to the polymer binder via at least one group selected from the groups represented by formulas (1) and (2), and the polymer binder is soluble or dispersible in water. Alternatively, a conductive member that is a reaction product of a methacrylic polyol that is soluble or dispersible in water and an isocyanate compound that is soluble or dispersible in water is provided.

  According to the present application, at least an acrylic polyol having a hydroxyl group and a carboxyl group in the side chain, an isocyanate compound having at least one of a plurality of isocyanate groups or blocked isocyanate groups and a carboxyl group, and a formula (3 ) And conductive fine particles B having at least one group selected from the groups represented by formula (4) on the surface thereof to mix to create a coating, and coating the coating on the conductive support The manufacturing method of the electroconductive member which has the process 2 to perform and the process 3 to harden the coated coating material is provided.

  According to the present invention, the conductive fine particles are firmly fixed to the polymer binder, whereby the conductivity in the polymer binder due to repetitive stress strain during use of the conductive member and energization in a high voltage applied state. The movement of fine particles can be suppressed.

  In addition, since the group fixing the conductive fine particles and the polymer binder is a group having both a benzene ring containing π electrons and an unpaired electron of oxygen, current flows smoothly from the conductive fine particles to the polymer binder. There is an effect that flows. In general, as a polymer binder constituting the conductive layer, a polymer binder having a high resistance value close to that of an insulating material is selected in order to suppress environmental fluctuation of the electric resistance value. The group represented by the formula (1) and / or the formula (2) is present between the conductive fine particles having a small electric resistance value and the polymer binder having a large electric resistance value. The electric potential gradient at the boundary with the binder is relaxed. When the group does not exist, radicals are generated at the boundary between the conductive particles and the polymer binder due to a steep gradient of the electric potential, which may break the chemical bond between the polymer binder and the conductive fine particles. Then, the electric resistance value of the polymer binder or the conductive fine particles is changed, and there is an adverse effect that the electric resistance value of the conductive member varies. Alternatively, when the molecular weight of the polymer binder is reduced or the bond between the polymer binder and the conductive fine particles is cut, the conductive fine particles move or aggregate, and the electrical resistance of the conductive member is also reduced. The value may fluctuate.

  On the other hand, according to the configuration of the present invention, the bonding between the conductive fine particles and the polymer binder is strong, and the position change of the electric potential inside the member is mitigated. Generation can be suppressed. Therefore, it is possible to suppress fluctuations in the electric resistance of the conductive member, and there is an effect of dramatically increasing the possibility of repeated use when used in an electrophotographic apparatus.

  Further, according to the production method of the present invention, it is possible to produce a conductive member in which the conductive fine particles and the polymer binder are firmly bonded by a simple method, and therefore a method for producing a conductive member for electrophotography. As industrially useful.

It is the schematic showing the cross section of one Embodiment of the electroconductive member which concerns on this invention. (A) is a cross-sectional view of an electroconductive member, (b) is a longitudinal cross-sectional view of an electroconductive member. 1 is a schematic view of an image forming apparatus using a conductive member according to the present invention. 1 is a schematic view of a color image forming apparatus using a conductive member according to the present invention. It is a schematic explanatory drawing of the measuring method of the electrical resistance value of an electroconductive member.

  Hereinafter, embodiments of the present invention will be described in detail. Fig.1 (a) is a schematic sectional drawing of the direction orthogonal to the axial direction of the electroconductive support body which is a shaft body of the electroconductive member which concerns on this invention. FIG. 1B is a schematic sectional view in the axial direction. This figure shows a conductive member comprising a conductive support 1, a conductive base layer 2 covering the periphery of the conductive support, and a conductive layer 3 covering the periphery of the conductive base layer. The form is shown. As shown in this figure, the conductive layer may have a multilayer structure of two or more layers.

  The conductive member according to the present invention is used as a conveying member such as a charging member (charging roller), a developing member (developing roller), a transfer member (transfer roller), a charge eliminating member, and a sheet feeding roller in an electrophotographic image forming apparatus. It can be used. Further, it is suitable for a conductive member that constantly energizes, such as a charging blade or a transfer pad. Hereinafter, the present invention will be described using a charging roller, a developing roller, and the like, which are representative examples of conductive members.

[Conductive layer]
In the conductive member according to the present invention, the conductive layer includes at least conductive fine particles as a conductive material and a polymer binder. The conductive fine particles and the polymer binder are bonded via at least one group selected from the groups represented by the formulas (1) and (2).

<Conductive fine particles A>
The conductive fine particles A are evenly or almost uniformly dispersed in the conductive layer, and are bonded to the polymer binder via at least one group selected from the groups represented by the formulas (1) and (2), so that the conductivity of the conductive layer Is responsible.

  Examples of the material or form of the conductive fine particles A include the following (a) to (h). (A) Metal powder or fiber such as aluminum, palladium, iron, copper, silver, etc. (b) Carbon powder, carbon powder such as graphite; (c) Metal powder; (d) Titanium oxide, tin oxide, oxidation Metal oxides such as zinc; (e) Metal compound powders such as copper sulfide and zinc sulfide; (f) Tin oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, chromium on the surface of suitable particles , Cobalt, iron, platinum, rhodium, carbon powder deposited by electrolytic treatment, spray coating, mixed shaking; (g) acetylene black, ketjen black, PAN (polyacrylonitrile) carbon, pitch carbon, etc. (H) A combination of two or more selected from the group (a) to (g) above.

The material of the conductive fine particles is particularly preferably carbon black and / or graphite. The surface area of carbon black and graphite is preferably 25 m ² / g to 600 m ² / g.

  Examples of the raw material of the conductive fine particles A that form a chemical bond with the polymer binder include conductive fine particles B having at least one group selected from the groups represented by the formulas (3) and (4) on the surface. It is done. Such conductive fine particles B can be obtained by reacting the conductive fine particles C with at least one compound selected from the compounds represented by the formulas (5) and (6).

  That is, carbon black or graphite is used as the conductive fine particles C, and the carbon black or graphite is reacted with at least one compound selected from the compounds represented by formula (5) and formula (6) to obtain a formula ( 3) Carbon black or graphite having at least one group selected from the groups represented by formula (4) on the surface is produced.

The density of the group represented by the formula (3) and / or the formula (4) on the surface of the conductive fine particle B is preferably 0.02 × 10 ⁻³ mol / g or more, more preferably 0.04 × 10 ^{−. 3} mol / g or more. If the density is small, the conductive particles A and the polymer binder are not sufficiently fixed, and deterioration of the conductive member is not suppressed. The group represented by the formula (3) and / or the formula (4) on the surface of the conductive fine particle B is acidic. The density of these groups can be determined by neutralization titration with potassium hydroxide or the like. Hereinafter, the group represented by the formula (3) and / or the formula (4) obtained by neutralization titration is referred to as “acidic functional group”.

<Polymer binder>
As the polymer binder that forms the conductive layer together with the conductive fine particles, a resin such as a thermosetting resin or a thermoplastic resin is used. Specific examples include: Manufactured from various polyamides, fluororesins, hydrogenated styrene-butylene resins, urethane resins, silicone resins, polyester resins, phenol resins, imide resins, urea resins, olefin resins, and two or more monomer raw materials for these resins. Copolymer. In the present invention, a urethane resin is particularly preferably used.

  As the polymer binder, thermosetting urethane is particularly preferable. When the unreacted polymer binder solution dispersed together with the conductive fine particles is applied and then the coating film is cured, it is most preferable to bond the polymer binder and the conductive fine particles simultaneously with the curing of the polymer binder. Examples of the raw material for the thermosetting urethane polymer binder include a polyol and an isocyanate compound. The polymer binder is preferably a binder obtained by reacting an isocyanate compound.

  Examples of the polyol include polyester polyol, polyether polyol, polyvinyl alcohol, acrylic polyol, and fluorine-based polyol. The polyol is more preferably water-soluble or water-dispersible, and particularly preferably an acrylic polyol that is soluble or dispersible in water. The water dispersibility is preferable because the potential of the surface of the conductive fine particles is stable when mixed with the above-mentioned conductive fine particles having a large polarity, and the property change of the paint is small even when left for a long period of time.

  The following are mentioned as an isocyanate compound. Hexamethylene diisocyanate isocyanate compound, diphenylmethane diisocyanate isocyanate compound, toluene diisocyanate isocyanate compound, isophorone diisocyanate isocyanate compound, and the like. The isocyanate compound preferably has a functional group of 2 or more functional groups, more preferably 3 or more functional groups. Furthermore, the isocyanate group is preferably blocked with a blocking agent. Blocking with a blocking agent is preferable because it can suppress changes in the properties of the paint due to the influence of water. Furthermore, it is more preferable that the isocyanate compound is soluble or dispersible in water. The water dispersibility is preferable because the surface potential is stable when mixed with the above conductive fine particles having a large polarity, and the property change of the paint is small even when left for a long period of time.

  A particularly preferred polymer binder is a polymer binder obtained by reacting an acrylic polyol that can be dissolved or dispersed in water with an isocyanate compound that can be dissolved or dispersed in water.

  Examples of acrylic polyols that can be dissolved or dispersed in water include the following. Bihydrol A145, Bihydrol VPLS2058, Bihydrol XP2427, Bihydrol XP2470, Bihydrol VPLS2139 / 2 (all are trade names, manufactured by Sumika Bayer Urethane Co., Ltd.).

  Examples of isocyanate compounds that can be dissolved or dispersed in water include the following. Bihydur BL5140, Bihydre VPLS2240, Bihydrol VPLS2310, Bihydrol 110, Bihydrol 124, Bihydrol PR135, Bihydrol PR240, Bihydrol PR340 / 1, Bihydrol PR650, Bihydrol VPLS2342, Bihydrol VPLS2952 / 1, Bihydrol XP2621 (Made by Co., Ltd.).

(Amount of conductive fine particles)
The compounding amount of the conductive fine particles A in the conductive layer is preferably such that the volume resistivity of the conductive layer is 1 × 10 ⁶ to 1 × 10 ¹⁵ Ω · cm in the following three environments.
Low temperature and low humidity (L / L) environment (temperature 15 ° C., relative humidity 10%).
Normal temperature and humidity (N / N) environment (temperature 23 ° C., relative humidity 55%).
High temperature and high humidity (H / H) environment (temperature 30 ° C., relative humidity 80%).

  By setting the volume resistivity of the conductive layer within the above range, the photosensitive member can be uniformly charged when the conductive member is used as a charging roller. In addition, even if there is a pinhole in the photoconductor, it is difficult for an excessive current to flow through the pinhole.

(Thickness of conductive layer)
The thickness of the conductive layer is preferably 0.3 to 100 μm, particularly 2 to 50 μm, and more preferably 5 to 30 μm. This is because streaky image unevenness caused by uneven charging on an electrophotographic image formed in a low temperature and low humidity environment can be suppressed. In addition, the film thickness of a conductive layer can be measured by cutting out the surface of a conductive member with a sharp blade and observing with an optical microscope or an electron microscope.

(Method for forming conductive layer)
Examples of the method for forming the conductive layer include the following [Method 1] and [Method 2].
[Method 1]: A method in which a polymer binder in which conductive fine particles are dispersed is extruded into a tube shape and coated around the conductive support. In this case, the conductive fine particles and the polymer binder may be bonded via a group represented by the formula (1) and / or the formula (2) before forming the tube, or may be bonded after forming the tube. good.
[Method 2]: A method in which a binder and conductive fine particles are dispersed together with a solvent to form a paint, and the paint is applied to a conductive support. Also in this case, the conductive fine particles and the polymer binder may be bonded via a group represented by the formula (1) and / or the formula (2) before coating, or may be bonded after coating. good.

  In particular, the conductive fine particles and the raw material of the polymer binder are dispersed to form a paint, and the paint is applied to the conductive support. After the coating, the polymer binder is formed by heat or electromagnetic waves, and the conductive fine particles The polymer binder is preferably bonded via a group represented by the formula (1) and / or the formula (2).

In the above [Method 2], a coating material for forming a conductive layer can be prepared by dispersing a polymer binder and conductive fine particles by a known method. Examples of known dispersing methods include methods using the following dispersing devices (i) to (iii).
(I) Rotating blades rotated by a motor or a stirring and dispersing device such as a homogenizer.
(Ii) A fine orifice dispersing device that disperses the pigment by colliding with the accelerated paint.
(Iii) A conventionally known dispersion apparatus using beads such as a sand mill, a paint shaker, a dyno mill, and a pearl mill.

  Moreover, as a specific method of coating in the above [Method 2], a dip coating method that can make the thickness of the conductive layer more uniform is preferable. Furthermore, in the above [Method 2], various conductive agents and leveling agents may be mixed in the paint. Examples of the leveling agent include silicone oil. Furthermore, in the above [Method 2], the film thickness of the conductive layer can be adjusted by adjusting the binder solid content in the paint and the pulling rate during dip coating. When the solid content of the resin in the paint is increased, the film thickness of the conductive layer can be increased. If the solid content is reduced, the film thickness can be reduced. The solid content of the binder in the paint can be adjusted within the range of 10 to 40% by mass, and when dip coating is employed, the coating pull-up speed can be adjusted within the range of 0.2 to 300 mm / s. preferable. This is because manufacturing management is easy.

[Method for producing conductive member]
The following method is mentioned as a preferable manufacturing method of the electroconductive member of this invention.

  At least an acrylic polyol having a hydroxyl group and a carboxyl group in the side chain; an isocyanate compound having at least one of a plurality of isocyanate groups or blocked isocyanate groups and a carboxyl group; and formula (3) and / or formula (4) Step 1 for preparing a paint by mixing conductive fine particles B having a group represented by the following: Step 2 for applying the paint on the conductive support; and curing the applied paint The manufacturing method of the electroconductive member characterized by having the process 3 to make.

  The following are mentioned as an acrylic polyol which has a hydroxyl group and a carboxyl group in a side chain. Bayhydrol A145 (trade name, Sumika Bayer Urethane Co., Ltd.), Bayhydrol VPLS2058 (trade name, Sumika Bayer Urethane Co., Ltd.), Bayhydrol XP2427 (trade name, Sumika Bayer Urethane Co., Ltd.), Bayhydrol XP2470 (trade name) Sumika Bayer Urethane Co., Ltd.).

  Examples of the isocyanate compound having at least one of a plurality of isocyanate groups or blocked isocyanate groups and a carboxyl group include the following. Bayhijoule BL5140 (trade name, Sumika Bayer Urethane Co., Ltd.), Bayhijoule VPLS 2240 (trade name, Sumika Bayer Urethane Co., Ltd.), Bayhydrol VPLS2310 (trade name, Sumika Bayer Urethane Co., Ltd.) and the like.

  For the preparation and curing of the paint, a method similar to the method described in the column “Method for forming conductive layer” can be employed.

  In the production method, the conductive fine particles B are preferably conductive fine particles obtained by reacting the conductive fine particles C with the compound represented by the formula (5) and / or the formula (6).

  Examples of the conductive fine particles C include carbon black or graphite. The reaction between the conductive fine particles C and the compound represented by the formula (5) and / or the formula (6) is performed by reacting in a liquid reaction medium.

Examples of the reaction step include the following methods.
(1): A method in which conductive fine particles C are placed in a reaction medium prepared by preparing a diazonium salt of a compound represented by formula (5) and / or formula (6), and stirred to react as a slurry.
(2): Conductive fine particles C are put in a reaction medium and stirred to obtain a slurry. 4-Aminobenzoic acid and / or sulfanilic acid is added, and an alkali metal salt of nitrous acid is further added and stirred. How to react.

  By refine | purifying after reaction, the electroconductive fine particle B which has the group shown by Formula (3) and / or Formula (4) on the surface can be obtained.

  Examples of the reaction medium include water, an arbitrary medium containing water, and an arbitrary medium containing alcohol, and water is most preferable.

[Conductive support]
As a material constituting the conductive support, a known material that is rigid and exhibits conductivity can be used. Specific examples include the following.
-Metals such as iron, aluminum, titanium, copper and nickel.
-Alloys such as stainless steel, duralumin, brass and bronze containing these metals.
・ Composite materials such as carbon black and carbon fiber hardened with plastic.
Moreover, as a shape, it can also be set as the cylindrical shape which made the center part the cavity other than column shape. A preferable conductive support is a cylinder having a surface of a carbon steel alloy plated with nickel having a thickness of 5 μm.

[Conductive base layer]
In the conductive member of the present invention, a conductive base layer can be disposed under the conductive layer. As shown in FIG. 1, a conductive base layer is formed on the outer periphery of the conductive support, and a conductive layer is formed on the outer periphery thereof. A material constituting such a conductive base layer is, for example, a conductive elastic body. For example, the conductive elastic body is formed by mixing a conductive agent and a polymer elastic body.

<Polymer elastic body>
Specific examples of the polymer elastic body include the following. Epichlorohydrin rubber; EPM (ethylene propylene rubber); EPDM (ethylene propylene rubber); norbornene rubber; NBR (nitrile rubber); chloroprene rubber; natural rubber; isoprene rubber; butadiene rubber; Urethane rubber; Styrenic block copolymer (SBS (styrene / butadiene / styrene / block copolymer), SEBS (styrene / ethylene butylene / styrene / block copolymer), etc.); Silicone rubber and the like.

<Conductive agent>
Examples of the conductive agent include an ionic conductive agent and an electronic conductive conductive agent. A combination of several types of ionic conductive agents and several types of electronic conductive agents may be used.

(1) Ionic conductive agent Examples of the ionic conductive agent include perchlorates such as LiClO ₄ and NaClO ₄ and quaternary ammonium salts. These can be used alone or in combination of two or more.

(2) Electroconductive conductive agent Specific examples of the electronic conductive conductive material include the same materials as (a) to (h) exemplified as the material or form of the conductive fine particles A.

<Amount of conductive agent>
The amount of these conductive agents is such that the volume resistivity of the conductive elastic body is in the middle resistance region (volume resistivity is 1 × 10 ⁴ to 1 × 10 ⁷ Ω · cm) in each of the following three environments. A small amount is preferred.
Low temperature and low humidity (L / L) environment (temperature 15 ° C., relative humidity 10%).
Normal temperature and humidity (N / N) environment (temperature 23 ° C., relative humidity 55%).
High temperature and high humidity (H / H) environment (temperature 30 ° C., relative humidity 80%).

<Method for measuring volume resistivity of conductive elastic body>
The volume resistivity of the conductive elastic body is determined by the following method.
After forming into a sheet with a thickness of 1 mm, platinum is vapor-deposited on both sides to produce an electrode and a guard electrode. And the voltage of 200V is applied between both electrodes using the microammeter (ADVANTEST R8340A ULTRA HIGH RESISTANCE METER Co., Ltd. product), and the electric current 30 seconds after is measured. The volume resistivity is calculated from the measured value, the film thickness, and the electrode area.

  By setting the volume resistivity of the conductive elastic body within the above numerical range, when it is used as a charging roller, even if there is a pinhole in the photoconductor that is the image carrier, a large current flows into the pinhole at once. It can avoid concentrating and making the hole larger. In addition, it is possible to effectively suppress a portion where the current does not flow in a place other than the hole and a black band is formed on the high-definition halftone image and the charged potential is insufficient, which can be visually recognized. Furthermore, it can be avoided that the applied voltage drops due to the conductive elastic body and the required discharge current cannot be obtained and the photosensitive member cannot be uniformly charged to a desired potential.

<Other additives>
Other additives such as plasticizers, fillers, vulcanizing agents, vulcanization accelerators, anti-aging agents, scorch preventing agents, dispersants and mold release agents are added to the conductive elastic body as necessary. It is also preferable.

<Method for forming conductive base layer>
Examples of a method for forming the conductive base layer include known methods such as extrusion molding, injection molding, and compression molding by mixing the raw materials for the conductive elastic body. The conductive base layer may be produced by directly forming a conductive elastic body on the conductive support, or the conductive elastic body formed into a tube shape may be coated on the conductive support. . Note that the surface may be polished and the shape may be adjusted after the production of the conductive base layer.

  The shape of the conductive base layer is such that the contact nip width between the completed conductive member and the photosensitive member is as uniform as possible in the longitudinal distribution of the conductive member, so that the central portion of the conductive base layer on the photosensitive member side is as uniform as possible. It is preferable that the protrusion protrudes from the end toward the photoreceptor. When the shape of the conductive member is a roller shape, it is preferable that the diameter of the central portion of the roller is a crown shape larger than the diameter of the end portion. Further, since the contact nip width of the completed roller becomes uniform, it is preferable that the deflection of the base layer roller having the conductive base layer is small.

<Asker C hardness of conductive base layer>
The Asker C hardness of the conductive base layer is preferably 85 ° or less. Under these conditions, a nip between the conductive member and the photosensitive member can be secured, so that charging is stabilized. The Asker C hardness is a hardness measured using an Asker C spring rubber hardness tester (manufactured by Kobunshi Keiki Co., Ltd.) in accordance with the Japan Rubber Association standard SRIS0101. In the present invention, a value measured 30 seconds after the hardness meter is brought into contact with a conductive member left in an N / N environment for 12 hours or more with a force of 10 N is employed.

  In order to adjust Asker C hardness, a plasticizer may be blended in the conductive base layer. The blending amount is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the polymer elastic body to be blended with the conductive elastic body. As the plasticizer, for example, an ester-based polymer plasticizer such as a copolymer of sebacic acid and propylene glycol can be used. The conductive base layer is bonded to the conductive support through an adhesive as necessary. In this case, the adhesive is preferably conductive. In order to make it conductive, the adhesive may have the above-described conductive agent. Examples of the binder of the adhesive include resins such as a thermosetting resin and a thermoplastic resin, and known adhesives such as urethane, acrylic, polyester, polyether, and epoxy can be used.

<Electrical resistance value of conductive member>
The electric resistance value of the conductive member is preferably 1 × 10 ⁴ Ω or more in the H / H environment and 1 × 10 ⁸ Ω or less in the L / L environment. In an N / N environment, it is preferably 2 × 10 ⁴ Ω or more and 6 × 10 ⁷ Ω or less. It is preferable to make the electric resistance value in the L / L environment equal to or less than the above-mentioned value because it is difficult to cause charging potential unevenness due to variation in the position of the electric resistance value of the conductive member. In addition, by setting the electric resistance value in a high temperature and high humidity environment to the above value or more, even if there is a pinhole in the photoconductor, the applied current does not leak, and uneven density of the charge appears on the halftone image. This is preferable because there is not.

When the conductive member is not in the shape of a roller, the electric resistance value expressed by the electric resistance value per 1 cm ² can be adjusted within the above range by satisfying the following conditions (1) to (3). Good.
(1) The volume resistivity of the conductive base layer of the conductive member is set to 1 × 10 ⁴ Ω · cm or more and 1 × 10 ⁷ Ω · cm or less.
(2) The volume resistivity of the conductive layer is set to 1 × 10 ⁸ Ω · cm or more and 1 × 10 ¹⁵ Ω · cm or less.
(3) The film thickness of the conductive layer is 10 μm or more and 50 μm or less.

Specifically, the electrical resistance value of the conductive member is measured as follows.
That is, as shown in FIG. 4, the resistance is measured when energized while contacting a cylindrical metal 32 having the same curvature as that of the photosensitive member under the same stress as that in the usage state when used in an image forming apparatus. In FIG. 4A, 33 a and 33 b are bearings fixed to weights, and apply a stress that pushes the shaft 1 of the charging roller 6 downward in the vertical direction. A cylindrical metal 32 is positioned in the vertical downward direction of the charging roller 6 in parallel with the charging roller 6. Then, while rotating the columnar metal 32 by a driving device (not shown), the charging roller is pressed against the bearings 33a and 33b as shown in FIG. 4B. The cylindrical metal 32 is rotated at the same rotational speed as that of the photosensitive drum in use, and a DC voltage of −200 V is applied from the power supply 34 while the charging roller 6 is driven to rotate. Measure with total A. The electric resistance value of the charging member is calculated from the applied voltage and the measured current at this time. In the present invention, a force of 5 N is applied to both ends of the shaft to contact a metal cylinder having a diameter of 30 mm, and the metal cylinder is rotated at a peripheral speed of 150 mm / s.

[Image forming apparatus]
FIG. 2 shows an electrophotographic image forming apparatus using a conductive member 6 as an embodiment of the conductive member according to the present invention as a charging roller. The photosensitive drum 5 as an image carrier is primarily charged by the charging roller 6 while rotating in the direction of the arrow, and then an electrostatic latent image is formed by the exposure light 11 from an exposure unit (not shown). The developer in the developer container 31 is carried on the surface of the developing roller 4 while being rubbed and charged between the developing roller 4 and the developing blade 30 and conveyed to the surface of the photosensitive drum 5. As a result, the electrostatic latent image is developed and a toner image is formed.

  The toner image is transferred to the recording medium 7 between the transfer roller 8 and the photosensitive drum 5, and then fixed by the fixing unit 9. The toner remaining on the surface of the photoreceptor 5 without being transferred is collected by the cleaning blade 10.

  Voltages are applied to the developing roller 4, the charging roller 6, the transfer roller 8, and the like from power sources 18, 20, and 22 of the image forming apparatus, respectively.

  Here, a DC voltage is applied to the charging roller 6 from the power supply 20. By using a DC voltage as the applied voltage, there is an advantage that the cost of the power supply can be kept low. There is also an advantage that no charging noise is generated.

  The absolute value of the DC voltage to be applied is preferably the sum of the discharge start voltage of air and the primary charging potential of the surface of the member to be charged (photosensitive member surface). Usually, the discharge start voltage of air is about 600 to 700 V, and the primary charging potential of the photoreceptor surface is about 300 to 800 V. Therefore, the specific primary charging voltage is preferably 900 to 1500 V.

  Further, the electrophotographic image forming apparatus may be a color electrophotographic image forming apparatus provided with four colors of members necessary for image formation as shown in FIG. While the recording medium 7 moves in the direction of the arrow, the toner image is exposed between the photosensitive drum 5d and the transfer roller 8d, between the photosensitive drum 5c and the transfer roller 8c, between the photosensitive drum 5b and the transfer roller 8b, and between the photosensitive drum 5b and the transfer roller 8b. Transfer is performed sequentially between the body drum 5a and the transfer roller 8a. The toner image transferred to the recording medium 7 is fixed in the fixing unit 9. The charging rollers 6a, 6b, 6c, and 6d charge the photosensitive drums 5a, 5b, 5c, and 5d, respectively. In order to form a color electrophotographic image, toners of four colors of cyan, yellow, magenta and black are usually used. The four color toners may be transferred to the recording medium 7 in any order.

  Hereinafter, the present invention will be described more specifically with reference to production examples and examples. Production Examples 1 to 20 are production examples of conductive fine particles 1 to 20. Untreated particles used in Production Examples 1 to 20 are shown in Table 1. Graphite 1 and graphite 2 are particles obtained by pulverizing and classifying a lump of graphite obtained by firing carbon black in an oxygen-free atmosphere at 2800 ° C. Graphite 1 has a smaller surface area per unit mass and larger particle size than graphite 2. In addition, Table 2 shows isocyanate compounds and polyol compounds used in the examples.

[Production Example 1]
90 g of 4-aminobenzoic acid was added to 950 ml of ion exchange water. The mixture was cooled in an ice bath and 163 ml concentrated hydrochloric acid was added. An additional 50 ml of acetone was added to completely dissolve 4-aminobenzoic acid. To this cooled mixture was added 45 g of sodium nitrite solution dissolved in 100 ml of ion exchange water. The mixture became dark and some gas was released. The concentration of 4-aminobenzoic acid diazonium salt in this solution is 6% by mass. This was designated as diazonium salt solution 1.

200 g of carbon black 1 was added to 2 liters of ion-exchanged water cooled in an ice bath and stirred well to obtain a slurry. To this slurry, 800 g of diazonium salt solution 1 was added and stirred. Stirring was continued until no gas evolution was observed. The slurry from which gas generation ceased was vacuum filtered, then washed with ion-exchanged water, and finally dried in an oven at 75 ° C. When the obtained surface-treated carbon black (conductive fine particles 1) was subjected to neutralization titration, 0.8 × 10 ⁻³ mol / g acidic functional group was confirmed on the surface.

[Production Example 2]
14.5 g of sulfanilic acid was added to 950 ml of ion exchange water. The mixture was then heated to 70-90 ° C. Carbon black 1 was added to this solution and stirred well to form a slurry. To this slurry was added 1.2 g of an aqueous sodium nitrite solution dissolved in 1 ml of ion exchange water. Gas evolved in a few minutes. After gas generation stopped, the slurry was cooled to room temperature. The slurry cooled to room temperature was vacuum filtered, then washed with ion-exchanged water, and finally dried while evacuating in an oven at 80 ° C. When the obtained surface-treated carbon black (conductive fine particles 2) was subjected to neutralization titration, 0.8 × 10 ⁻³ mol / g acidic functional group was confirmed on the surface.

[Production Examples 3 to 18]
Conductive fine particles 3 to 18 were obtained in the same manner as in Production Example 1 or Production Example 2, except that the type of untreated particles and the type and amount of surface treatment agent were changed to the conditions shown in Table 3. In addition, when the diazonium salt solution 1 was used as the surface treatment agent, the conditions of Production Example 1 were adopted, and when sulfanilic acid was used as the surface treatment agent, the conditions of Production Example 2 were adopted. Table 3 shows the amount of acidic functional groups on the surface of each conductive fine particle.

[Production Example 19]
7.1 g of sulfanilic acid was added to 950 ml of ion exchange water. The mixture was then heated to 70-90 ° C. Carbon black 1 was added to this solution and stirred well to form a slurry. To this slurry was added 1.2 g of an aqueous sodium nitrite solution dissolved in 1 ml of ion exchange water. Gas evolved in a few minutes. The slurry was cooled in an ice bath after gas evolution ceased.

Next, 1 liter of ion-exchanged water was added to the slurry cooled in the ice bath, stirred and continuously cooled. 400 g of the diazonium salt solution 1 was added to the slurry and stirred. Stirring was continued until no gas evolution was observed. The slurry from which gas generation ceased was vacuum filtered, then washed with ion-exchanged water, and finally dried while evacuating in an oven at 80 ° C. When the obtained surface-treated carbon black (conductive fine particles 19) was subjected to neutralization titration, 0.8 × 10 ⁻³ mol / g acidic functional group was confirmed on the surface.

[Production Example 20]
Conductive fine particles 20 were obtained in the same manner as in Production Example 19 except that the type of untreated particles and the type and amount of surface treatment agent were changed to the conditions shown in Table 3. Table 3 shows the amount of acidic functional groups on the surface of the conductive fine particles.

[Example 1]
<1. Manufacture of conductive layer paint>
The materials shown in Table 4 below were weighed into 450 ml mayonnaise bottles. These were dispersed with a paint shaker for 10 minutes, and then a conductive layer paint 1 for a conductive member was obtained through a 200 mesh nylon mesh.

<2. Preparation of conductive base layer>
The materials of component (1) shown in Table 5 below were mixed and kneaded for 20 minutes with an open roll. Subsequently, each material of the component (2) shown in Table 5 was further added and kneaded with an open roll for 15 minutes.

  The obtained mixture was extruded into a cylindrical shape having an outer diameter of 13 mm and an inner diameter of 5.5 mm using a rubber extruder, and an unvulcanized rubber tube cut to a length of 250 mm was formed. This unvulcanized rubber tube was put into a vulcanizing can and subjected to primary vulcanization for 40 minutes using steam at a temperature of 160 ° C. to obtain a primary vulcanized rubber tube. On the other hand, thermosetting property of metal and rubber is 231 mm in the axial central portion of the cylindrical surface of a cylindrical conductive support (made of steel and having a surface plated with nickel) having a diameter of 6 mm and a length of 256 mm. An adhesive (trade name: METALOC U-20: manufactured by Toyo Chemical Laboratory Co., Ltd.) was applied. The conductive support coated with the adhesive was dried at a temperature of 80 ° C. for 30 minutes, and further dried at a temperature of 120 ° C. for 1 hour. The conductive support is inserted into the primary vulcanized rubber tube, and then heated in an electric oven at a temperature of 160 ° C. for 2 hours to perform secondary vulcanization of the rubber tube and a thermosetting adhesive. Curing was performed. Both ends of the secondary vulcanized rubber tube were cut off to a length of 231 mm. Next, it was polished so as to be a base layer roller having a conductive base layer having a crown shape with an end diameter of 8.40 mm, a center diameter of 8.50 mm, a 10-point average roughness Rz of 10 μm, and a runout of 25 μm. . The average roughness Rz was measured with a surf coder SE3400 manufactured by Kosaka Laboratory, based on JIS B0601: 1982. For each roller, the roughness curve is measured for a total of 6 points: 3 points in the axial direction (90 mm each in the center and both ends from the center) and 2 points in the circumferential direction (180 degree intervals) to calculate the Rz value. The average value of Rz of these 6 points was defined as the Rz value of the roller. As a measurement condition, a diamond contact needle having a tip radius of 2 μm was used. The measurement speed was 0.5 mm / s, the cut-off frequency λc was 0.8 mm, the reference length was 0.8 mm, and the evaluation length was 8.0 mm.

In addition, after the base layer roller having the conductive base layer is left in an N / N (temperature 23 ° C., relative humidity 55%) environment for 24 hours or more, it is electrically conductive by a method similar to the method for measuring the electrical resistance value of the conductive member. The electrical resistance value of the base layer roller having the conductive base layer was measured. The electric resistance value was 3.0 × 10 ⁵ Ω. The Asker C hardness of the conductive base layer was 74 °.

<3. Coating of conductive layer>
The conductive layer coating 1 was placed in a coating tank, and after the bubbles were removed and stabilized, the coating was applied to the surface of the base layer roller having the conductive base layer. In this case, the descending speed is 30 mm / s, and after stopping for 4 seconds at the lowest point, it becomes a linear function so that the initial speed is 25 mm / s and the final speed (speed at which the lower end is applied) is 2 mm / s. The base roller was moved up and down with a speed gradient. Thus, the coating was performed so that the film thickness of the conductive layer was substantially uniform at the vertical position in the coating state of the base layer roller. Thereafter, it was air-dried at 23 ° C. for 30 minutes, dried in a clean oven at 90 ° C. for 60 minutes, and then dried in an oven at 160 ° C. for 60 minutes. In the conductive member 1 thus obtained, a conductive layer having a uniform film thickness of 16 μm was formed over the entire region of the conductive base layer.

<4. Evaluation of conductive member>
4-1. Image Evaluation The electrophotographic laser printer was for A4 portrait output, and an electrophotographic laser printer with a recording medium output speed of 160 mm / s and an image resolution of 600 dpi was prepared. The photoreceptor is a reverse development type photoreceptor drum in which an aluminum cylinder is coated with an OPC layer having a film thickness of 16 μm, and the outermost layer is a charge transport layer using a modified polyarylate resin as a binder resin. The toner is made by polymerizing a random copolymer of styrene and butyl acrylate containing a charge control agent, a pigment and the like with a wax at the center, further polymerizing a polyester thin layer on the surface, and externally adding silica fine particles, a glass transition temperature of 63 ° C., It is a polymerized toner having a mass average particle diameter of 6.5 μm.

  First, the conductive member according to this example was placed in an N / N environment for 12 hours, and then the electric resistance value was measured in the N / N environment according to the method for measuring the electric resistance of the conductive member. Next, the conductive member according to this example was mounted as a charging roller on the electrophotographic laser printer. The electrophotographic laser printer was placed in an N / N environment for 12 hours, and then an image was output in the N / N environment. A primary charging voltage of −1150 V was applied to the charging roller. As an image pattern, a halftone pattern (an image in which a horizontal line having a width of 1 dot and an interval of 2 dots is drawn in the direction perpendicular to the rotation direction of the photosensitive member) is used.

  Next, in the N / N environment using the above-mentioned electrophotographic laser printer, after continuously outputting 3000 patterns for drawing horizontal lines with a width of 2 dots and a spacing of 98 dots, the half-printing is performed under the same environment. A tone image pattern was output. Thereafter, the charging roller was taken out from the laser printer, and the charging roller was washed by spraying high-pressure ion exchange water with a high-pressure water washer, and high-pressure dry air was blown to drain the water. The charged roller after washing was again left in the N / N environment for 12 hours, and the electric resistance value was measured in the N / N environment according to the method for measuring the electric resistance of the conductive member. After that, the initial image output, the 3000 sheet durable output, and the final halftone image output were performed again in the N / N environment.

As an evaluation criterion for the image of this example, it was observed how many times the above-mentioned durability was performed and when a final image was performed, a horizontal streak-like image defect was observed on the halftone image. This was defined as the horizontal streak rank of the image deterioration due to the deterioration of the energization resistance, and each horizontal streak rank was defined as follows. The larger the numerical value of the rank, the better the performance of the conductive member.
Rank 5: No horizontal streak-like image defect occurred even after durability was applied four times.
Rank 4: Horizontal streak-like image defects occurred after endurance four times.
Rank 3: A horizontal streak-like image defect occurred after endurance three times.
Rank 2: Horizontal streak-like image defects occurred after endurance twice.
Rank 1: Horizontal streak-like image defects occurred after endurance once.
The conductive member 1 of Example 1 was rank 5.

  Further, a value obtained by dividing the electrical resistance value of the conductive member after the first durability by the electrical resistance value of the conductive member before the durability was defined as the resistance increase rate of the conduction resistance deterioration. As the performance of the conductive member, a smaller resistance increase rate is preferable. The rate of increase in resistance of the conductive member 1 of Example 1 was 2.3 times.

4-2. Evaluation of Environmental Variation of Electrical Resistance Value of Conductive Member Each electrical resistance value in the H / H environment and the L / L environment is measured using a conductive member different from the evaluation of the horizontal stripe. It is preferable that the ratio of the electrical resistance value in the L / L environment to the electrical resistance value in the H / H environment is small because the environmental variation in charging characteristics is small. The evaluation rank of the present invention was as follows. The smaller the environmental change, the higher the rank number. The conductive member 1 of Example 1 had an environmental change of less than 2.5 times and an evaluation rank of 4.
Rank 4: The ratio of the electrical resistance value in the L / L environment to the electrical resistance value in the H / H environment was less than 2.5 times.
Rank 3: The ratio was 2.5 times or more and less than 3.5 times.
Rank 2: The ratio was 3.5 times or more and less than 5 times.
Rank 1: The ratio was 5 times or more.

4-3. Evaluation of the standing stability of the conductive layer coating The conductive layer coating 1 used for coating the conductive layer was left in an N / N environment for 2 weeks. Two weeks later, the coating solution that had been allowed to stand was stirred for 30 minutes on a rotating frame, and then the conductive member was coated again. The electrical resistance value in the N / N environment was also measured for the conductive member coated after 2 weeks. Then, the variation rate of the electrical resistance value of the conductive member applied after 2 weeks with respect to the electrical resistance value of the conductive member applied 2 weeks ago was calculated. The smaller the resistance fluctuation rate, the greater the manufacturing stability and the industrial advantage. Therefore, the rank of the standing stability evaluation was as follows. The standing stability evaluation of the conductive member 1 of Example 1 was rank 3.
Rank 4: The ratio of the electrical resistance value of the conductive member applied after 2 weeks to the electrical resistance value of the conductive member applied in the initial stage was less than 1.1 times.
Rank 3: The ratio was 1.1 times or more and less than 1.3 times.
Rank 2: The ratio was 1.3 times or more and less than 1.7 times.
Rank 1: The ratio was 1.7 times or more.
Rank 0: The ratio was 1.7 times or more, and aggregation of conductive fine particles was observed in the conductive layer of the conductive member applied after 2 weeks.

[Examples 2 to 8]
Conductive members 2 to 8 were obtained in the same manner as in Example 1 except that the conductive fine particles 1 were changed to the conductive fine particles 2 to 8 in Example 1. Table 8 shows the results of evaluating each of these conductive members in the same manner as in Example 1.

[Examples 9 to 11]
In the production of the conductive layer coating material of Example 1, the conductive members 9 to 11 were carried out in the same manner as in Example 1 except that the type and amount of conductive fine particles and the amount of ion-exchanged water were changed to the conditions shown in Table 8. Got. Results evaluated in the same manner as in Example 1 are shown in Table 8.

[Examples 12 to 16]
Conductive members 12 to 16 were obtained in the same manner as in Example 11 except that in the production of the conductive layer paint of Example 11, the type of conductive fine particles was changed to the conductive fine particles shown in Table 8. Results evaluated in the same manner as in Example 1 are shown in Table 8.

[Examples 17 and 18]
Conductive members 17 and 18 were produced in the same manner as in Example 1 except that the type and amount of conductive fine particles and the amount of ion-exchanged water were changed to the conditions shown in Table 8 in the production of the conductive layer paint of Example 1. Got. Results evaluated in the same manner as in Example 1 are shown in Table 8.

Example 19
A conductive member 19 was obtained in the same manner as in Example 1 except that in the production of the conductive layer paint of Example 1, the type of conductive fine particles was changed to the conditions shown in Table 8. Results evaluated in the same manner as in Example 1 are shown in Table 8.

Example 20
A conductive member 20 was obtained in the same manner as in Example 11 except that the conductive fine particles 11 were changed to the conductive fine particles 20 in the production of the conductive layer coating material of Example 11. Results evaluated in the same manner as in Example 1 are shown in Table 8.

[Comparative Examples 1-4]
In the production of the conductive layer paint of Example 1, 9, 11 or 17, untreated particles shown in Table 6 were used in place of the conductive fine particles, and the composition of the materials was changed to the conditions shown in Table 6. Other than that was carried out similarly to Example 1, 9, 11 or 17, and obtained the conductive members 101-104. Results evaluated in the same manner as in Example 1 are shown in Table 8.

[Examples 21 to 41]
In Examples 21 to 33, the conductive fine particles were fixed to the conductive fine particles 1, and the types and blending ratios of the polyol and the isocyanate compound as raw materials of the thermosetting urethane as the polymer binder were set to the conditions shown in Table 9. changed. In Examples 34 to 41, the conductive fine particles are fixed to the conductive fine particles 2, and the types and blending ratios of the polyol and the isocyanate compound which are raw materials of the thermosetting urethane as the polymer binder are shown in Table 9. Changed to conditions. Conductive members 21 to 41 were obtained in the same manner as in Example 1 except for these conditions. Table 9 shows the results evaluated in the same manner as in Example 1.

[Comparative Examples 5 to 8]
Carbon black 1 that does not have a group represented by formula (3) or formula (4) on the surface as conductive fine particles, and each type of polyol and isocyanate compound that is a raw material of thermosetting urethane as a polymer binder The blending ratio was changed to the conditions shown in Table 9. Conductive members 105 to 108 were obtained in the same manner as in Example 1 except for these conditions. Table 9 shows the results evaluated in the same manner as in Example 1.

[Examples 42 to 47 and Comparative Examples 9 to 11]
In Examples 42 to 47, as compared with Example 1, the raw material of thermosetting urethane as a polymer binder was changed to an organic solvent-based isocyanate compound solution and an organic solvent-based polyol compound. Moreover, Comparative Examples 9-11 use the carbon black 1 which does not have group shown by Formula (3) or Formula (4) on the surface as electroconductive fine particles, The raw material of the thermosetting urethane as a polymer binder, It is changed to an organic solvent-based isocyanate compound solution and an organic solvent-based polyol compound.

  In Examples 42 to 47, in the production of the conductive layer coating material, the materials and glass beads shown in Table 7 below were weighed and blended in 450 ml of mayonnaise bottle. The mayonnaise bin was dispersed with a paint shaker for 4 hours. Thereafter, each conductive layer paint was obtained through a 200-mesh nylon mesh. The obtained paint was applied under the same conditions as in Example 1 to obtain conductive members 42 to 47 (Examples 42 to 47).

  Moreover, in Comparative Examples 9-11, in manufacture of a conductive layer coating material, the material shown in the following Table 7 was measured and mix | blended with the mayonnaise bin. Thereafter, conductive members 109 to 111 (Comparative Examples 9 to 11) were obtained in the same manner as in Example 42. Table 10 shows the results of evaluating the obtained conductive member in the same manner as in Example 1.

[Examples 48 to 75]
In Examples 48 to 70, two types of conductive fine particles were used in combination, and in Examples 71 to 75, three types of conductive fine particles were used in combination. Conductive members 48 to 75 were obtained in the same manner as in Example 1 except for these conditions. The results evaluated in the same manner as in Example 1 are shown in Table 11.

[Examples 76 to 80]
In Examples 76 to 78, 4 types of conductive fine particles were used in combination, in Example 79, 5 types of conductive fine particles were used in combination, and in Example 80, 6 types of conductive fine particles were used in combination. Conductive members 76-80 were obtained in the same manner as in Example 1 except for these conditions. The results evaluated in the same manner as in Example 1 are shown in Table 12.

DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Conductive base layer 3 Conductive layer 4 Developing roller 5 Photosensitive drum 6 Charging roller 7 Recording medium 8 Transfer roller 9 Fixing part 10 Cleaning blade 11 Exposure light 18 Developing power supply 20 Charging power supply 22 Transfer power supply 28 Toner supply roller 30 Developing Blade 32 Cylindrical Metal 33 Bearing 34 Power Supply

Claims (5)

A conductive member having at least a conductive layer on a conductive support, wherein the conductive layer includes at least conductive fine particles A and a polymer binder, and the conductive fine particles A are at least represented by the formula (1) and the formula It is bonded to the polymer binder via at least one group selected from the group represented by (2) ,
The polymer binder is a reaction product of an acrylic polyol that can be dissolved or dispersed in water or a methacrylic polyol that can be dissolved or dispersed in water and an isocyanate compound that can be dissolved or dispersed in water. Characteristic conductive member:

  The conductive member according to claim 1, wherein the conductive fine particles A are at least one selected from carbon black and graphite.   The conductive member according to claim 1, wherein the polymer binder is a binder obtained by reacting an isocyanate compound. At least an acrylic polyol having a hydroxyl group and a carboxyl group in the side chain; an isocyanate compound having at least one of a plurality of isocyanate groups or blocked isocyanate groups and a carboxyl group; and formula (3) and / or formula (4) Step 1 for preparing a paint by mixing conductive fine particles B having a group represented by the following: Step 2 for applying the paint on a conductive support; and curing the applied paint And a process for producing a conductive member comprising:

The conductive fine particles B are conductive fine particles C and the formula (5) and according to claim 4, wherein the conductive fine particles obtained by reacting at least one compound selected from the compound represented by (6) Manufacturing method of conductive member:

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