JP2021067924A - Conductive member, process cartridge, and electrophotographic image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive member capable of suppressing fog even when a high bias is applied in order to cope with a high-speed process and high image quality. A conductive layer 3 provided on an outer surface of a support has a matrix 3a containing a crosslinked product of a first rubber and a plurality of domains 3b dispersed in the matrix. A second rubber cross-linked product and conductive particles are contained, and at least a part of the domain is exposed on the outer surface of the conductive member, and a convex portion is formed on the outer surface of the conductive member. 80% or more satisfy the following formulas (1) and (2): (1) The ratio of the cross-sectional area of the conductive particles to the cross-sectional area of the domain is 20% or more; (2) Around the domain. When the length is A and the circumference of the domain is B, the A / B is 1.00 or more and 1.10 or less. [Selection diagram] Fig. 2

Description

The present disclosure is for electrophotographic conductive members, process cartridges and electrophotographic image forming apparatus.

In an image forming apparatus adopting an electrophotographic method (hereinafter, an electrophotographic image forming apparatus), conductive members such as a charging member, a transfer member, and a developing member are used. The conductive member is composed of a conductive layer coated on the outer peripheral surface of the conductive support, transports electric charges from the conductive support to the surface of the conductive member, and charges the abutting object by electric discharge or the like. Takes the role of giving.
For example, the charging member is a member that generates an electric discharge with the photoconductor to charge the surface of the photoconductor. The transfer member is a member that transfers a developer from a photoconductor to a printing medium or an intermediate transfer body, and at the same time generates a discharge to stabilize the developer after transfer.
In response to the recent demand for higher image quality of electrophotographic image forming apparatus, it is considered to increase the voltage applied to the conductive member in order to achieve high contrast. Under such high voltage application conditions, these conductive members are required to be even more uniformly charged to a contact object such as a photoconductor, an intermediate transfer body, or a printing medium.

Patent Document 1 describes a rubber composition having a sea-island structure including a polymer continuous phase made of an ion conductive rubber material and a polymer particle phase made of an electron conductive rubber material. The electronically conductive rubber material is mainly composed of a raw material rubber A having a volume resistivity of 1 × 10 ¹² Ω · cm or less, and the electronically conductive rubber material is disclosed as a charged member that is made conductive by blending conductive particles with the raw material rubber B. Has been done.

Japanese Unexamined Patent Publication No. 2002-3651

One aspect of the present disclosure is to provide a conductive member for electrophotographic that can stably suppress the occurrence of "fog" on an electrophotographic image even when the charging bias is increased.
Another aspect of the present disclosure is to provide a process cartridge that contributes to the stable formation of high-quality electrophotographic images. Further, another aspect of the present disclosure is aimed at providing an electrophotographic image forming apparatus capable of stably forming a high-quality electrophotographic image.

According to one aspect of the present disclosure
A support with a conductive outer surface and
An electrophotographic conductive member having a conductive layer provided on the outer surface of the support.
The conductive layer has a matrix containing a crosslinked product of the first rubber and a plurality of domains dispersed in the matrix.
The domain contains a second rubber crosslink and conductive particles.
At least a part of the domain is exposed on the outer surface of the conductive member, and a convex portion is formed on the outer surface of the conductive member.
The outer surface of the conductive member is composed of the matrix and the domain exposed on the outer surface of the conductive member.
A platinum electrode is provided directly on the outer surface of the conductive member, and the amplitude is 1 V and the frequency is 1.0 Hz between the outer surface of the support and the platinum electrode in an environment of a temperature of 23 ° C. and a relative humidity of 50%. The impedance when the AC voltage is applied is 1.0 × 10 ³ Ω or more and 1.0 × 10 ⁸ Ω or less, and
When the length of the conductive layer in the longitudinal direction is L and the thickness of the conductive layer is T, the center of the conductive layer in the longitudinal direction and L / 4 from both ends of the conductive layer toward the center are three. For each of the cross sections of the conductive layer in the thickness direction, 15 μm square observation regions are placed at any three locations in the thickness region from the outer surface of the elastic layer to a depth of 0.1 T to 0.9 T. At that time, a conductive member is provided in which 80% or more of the domains observed in each of the nine observation regions satisfy the following requirements (1) and (2):
(1) The ratio of the cross-sectional area of the conductive particles contained in the domain to the cross-sectional area of the domain is 20% or more;
(2) When the perimeter of the domain is A and the perimeter of the domain is B, the A / B is 1.00 or more and 1.10 or less.

Further, according to another aspect of the present disclosure, there is provided a process cartridge that is detachably configured on the main body of the electrophotographic image forming apparatus and includes the above-mentioned conductive member.
Further, according to another aspect of the present disclosure, an electrophotographic image forming apparatus including the above-mentioned conductive member is provided.

According to one aspect of the present disclosure, it is possible to obtain a conductive member for electrophotographic that can be used as a charging member that can suppress fog even when the charging bias is increased.
Further, according to another aspect of the present disclosure, it is possible to obtain a process cartridge that contributes to the formation of a high-quality electrophotographic image.
Further, according to another aspect of the present disclosure, it is possible to obtain an electrophotographic image forming apparatus capable of forming a high-quality electrophotographic image.

It is sectional drawing in the direction perpendicular to the longitudinal direction of the conductive member which concerns on one aspect of this disclosure. It is sectional drawing in the direction perpendicular to the longitudinal direction of the conductive layer of the conductive member which concerns on one aspect of this disclosure. It is explanatory drawing of the impedance measurement of the conductive layer of a conductive member. It is a conceptual diagram explaining the maximum ferret diameter of the domain which concerns on this disclosure. It is a conceptual diagram explaining the envelope circumference length of the domain which concerns on this disclosure. It is a conceptual diagram of the section which measures the domain shape which concerns on this disclosure. It is sectional drawing of the process cartridge which concerns on one aspect of this disclosure. It is sectional drawing of the electrophotographic image forming apparatus which concerns on one aspect of this disclosure.

The present inventors have attempted to obtain an electrophotographic image having a higher contrast when forming an electrophotographic image using the charging member according to Patent Document 1. Specifically, the charging bias between the charging member and the electrophotographic photosensitive member was increased to a voltage higher than a general charging bias (for example, −1000V) (for example, -1500V or more). As a result, for example, the inverted toner may be developed on the solid white portion on the photosensitive drum where the toner is not originally developed, and an image in which so-called "fog" is generated may be formed. In addition, the so-called transfer residual toner may adhere to the surface of the charging member, and the charging performance may change over time.
The present inventors have investigated the reason why the charging member according to Patent Document 1 causes fog in the electrophotographic image when the charging bias is increased. In the process, attention was paid to the role of the polymer particle phase made of the electronically conductive rubber material in the charged member according to Patent Document 1. That is, it is considered that the polymer particle phase imparts electron conductivity to the elastic body layer by transferring electrons between the polymer continuous phases existing in the vicinity in the elastic body layer. Then, it was speculated that the occurrence of fog when the charging bias was increased was caused by the electric field concentration. Electric field concentration is a phenomenon in which the current when energized is concentrated at a specific location.

That is, according to the observation by the present inventors, the polymer particle phase according to Patent Document 1 had an irregular shape and had irregularities on the outer surface. Between such polymer particle phases, the transfer of electrons is concentrated on the convex portion of the polymer particle phase, and the current flows from the vicinity of the conductive support to which the charging bias of the charging member is applied to the outer surface of the charging member. Becomes non-uniform. Therefore, the discharge from the outer surface of the charging member to the electrophotographic photosensitive member, which is the charged body, becomes non-uniform, and the surface potential of the electrophotographic photosensitive member also becomes non-uniform. As a result, it was speculated that the electrophotographic image would be fogged.
Therefore, the present inventors have recognized that eliminating the concentration point of electron transfer between the polymer particle phases when the charge bias is increased is effective in improving the fog of the electrophotographic image.
Then, based on this recognition, as a result of repeated studies, a support having a conductive outer surface and a support
According to a conductive member having a conductive layer provided on the outer surface of the support and satisfying the following requirements (A) and (B), even when a high charging bias is applied, electrons are received. We have found that fog on photographic images can be effectively suppressed.
Requirement (A):
The conductive layer has a matrix containing a crosslinked product of the first rubber and a plurality of domains (sea-island structures) dispersed in the matrix, and the domain is a crosslinked product of the second rubber and conductive. Including particles. Further, a platinum electrode is provided directly on the outer surface of the conductive member, and an alternating current having an amplitude of 1 V and a frequency of 1.0 Hz is provided between the outer surface of the support and the platinum electrode in an environment of a temperature of 23 ° C. and a relative humidity of 50%. The impedance when a voltage is applied shall be in the following range.
1.0 x 10 ³ Ω or more and 1.0 x 10 ⁸ Ω or less.

Requirement (B):
Let L be the length of the conductive layer in the longitudinal direction, and T be the thickness of the conductive layer. The depth from the outer surface of the elastic layer for each of the three cross sections in the thickness direction of the conductive layer at the center in the longitudinal direction of the conductive layer and at three locations L / 4 from both ends of the conductive layer toward the center Place a 15 μm square observation region at any three locations in the thickness region from 0.1 T to 0.9 T. At that time, 80% or more of the domains observed in each of the nine observation regions satisfy the following requirements (B1) and requirements (B2):
Requirement (B1) The ratio of the cross-sectional area of the conductive particles contained in the domain to the cross-sectional area of the domain is 20% or more;
Requirement (B2) When the perimeter of the domain is A and the perimeter of the domain is B, the A / B must be 1.00 or more and 1.10 or less.

Hereinafter, each requirement will be described in detail.
Regarding requirement (A):
Requirement (A) represents the degree of conductivity of the conductive layer. The conductivity of the conductive member, the impedance of 1Hz is in the range of less than 10 ³ Omega least 10 ⁸ Omega. By the impedance over 10 ³ Omega, to prevent the excessive amount of discharge current increases, so that the potential non-uniformity of abnormal discharge caused can be prevented from occurring. Also by the impedance below 10 ⁸ Omega, the total amount of the discharge charge quantity can inhibit the charging shortage due to lack.

The impedance according to the requirement (A) can be measured by the following method.
In measuring impedance, in order to eliminate the influence of contact resistance between the charging member and the measuring electrode, a platinum thin film is formed on the outer surface of the charging member, and the thin film is used as an electrode, while being conductive. It is preferable to measure the impedance with two terminals using the support as a ground electrode.
Examples of the method for forming the thin film include a method for forming a metal film such as metal vapor deposition, sputtering, application of a metal paste, and application of a metal tape. Among these, a method of forming a platinum thin film by thin film deposition is preferable from the viewpoint of reducing the contact resistance with the charged member.
When forming a platinum thin film on the surface of a charged member, considering its simplicity and uniformity of the thin film, a mechanism capable of gripping the charged member is provided to the vacuum vapor deposition apparatus, and the charged member having a columnar cross section is provided with a mechanism. It is preferable to use a vacuum vapor deposition apparatus further provided with a rotation mechanism.
For a charged member having a columnar cross section, a platinum electrode having a width of about 10 mm in the longitudinal direction as the axial direction of the columnar shape is formed, and a metal sheet wound around the platinum electrode so as to be in contact with the platinum electrode is measured. It is preferable to perform the measurement by connecting to the measuring electrode coming out of. As a result, the impedance measurement can be performed without being affected by the fluctuation of the outer diameter of the charging member and the surface shape. As the metal sheet, aluminum foil, metal tape, or the like can be used.
The impedance measuring device may be any device that can measure impedance, such as an impedance analyzer, a network analyzer, and a spectrum analyzer. Among these, it is preferable to measure from the electric resistance range of the charging member with an impedance analyzer.
FIG. 3 shows a schematic view of a state in which a measurement electrode is formed on a conductive member. In FIG. 3, 31 is a conductive support, 32 is a conductive layer, 33 is a platinum-deposited layer which is a measurement electrode, and 34 is an aluminum sheet. FIG. 3A shows a perspective view, and FIG. 3B shows a cross-sectional view. As shown in the figure, it is important that the conductive layer 32 is sandwiched between the conductive support 31 and the conductor layer 33 of the measurement electrode.

Then, the impedance measuring device (Solartron 126609W type dielectric impedance measuring system manufactured by Toyo Technica Co., Ltd., not shown) is connected to the measuring electrode 33 and the conductive support 31 from the aluminum sheet 34 to measure the impedance.
The impedance is measured at a vibration voltage of 1 Vpp and a frequency of 1.0 Hz in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and an absolute value of impedance is obtained.
The conductive member is divided into five regions in the longitudinal direction into five equal parts, and the above measurement is performed a total of five times, arbitrarily once from each region. The average value is taken as the impedance of the conductive member.

Requirement (B)
In the requirement (B), the requirement (B1) defines the amount of conductive particles contained in each of the domains contained in the conductive layer. Further, the requirement (B2) stipulates that the outer peripheral surface of the domain has little or no unevenness.
When the conductive member described in Patent Document 1 was analyzed, it was confirmed that the domain had irregularities and had a shape with a high aspect ratio. As a result of diligent studies, it was found that the fog at the time of applying a high voltage of the above-mentioned problem can be dramatically suppressed by making the shape of the domain close to a perfect circular shape with less unevenness.
As described above, in the conductive domain / non-conductive matrix configuration in which only the domains are conductive, a plurality of domains are responsible for conductivity inside the conductive member, and charges are transferred between the domains. .. When the convex portion exists in the domain, the electric field is concentrated on the convex portion, and the transfer of electric charge between the convex portion and the adjacent domain is likely to occur in the convex portion, and an excessive current flows through the convex portion. That is, the electric charge easily flows from the convex portion of the domain to the domain adjacent to the convex portion. Due to this phenomenon, a strong electric discharge is locally generated from the surface of the conductive member, and when the conductive member is used as the charging member, the potential unevenness of the photoconductor is caused.

That is, it is effective to make the domain as close to a perfect circle as possible.
Regarding the requirement (B1), when focusing on one domain, the present inventors have found that the amount of conductive particles contained in the domain affects the outer shape of the domain. .. That is, it was found that as the filling amount of the conductive particles of one domain increases, the outer shape of the domain becomes closer to a sphere. The greater the number of domains that are closer to the sphere, the less the concentration point of electron transfer between domains. As a result, it is possible to reduce the fog on the electrophotographic image observed in the charged member according to Patent Document 1.
According to the study by the present inventors, the domains in which the ratio of the total cross-sectional area of the conductive particles observed in the cross section is 20% or more based on the cross-sectional area of one domain are between domains. It is possible to take an outer shape that can significantly alleviate the concentration of electron transfer in. Specifically, it can take a shape closer to a sphere.
Requirement (B2) defines the degree of unevenness on the outer peripheral surface of the domain that can be a concentration point for electron transfer.
That is, when the perimeter of the domain is A and the perimeter of the envelope of the domain is B, and the value (A / B) of the requirement (B2) indicating the degree of unevenness is 1.00, there is no unevenness. Shown, the concentration of the electric field can be suppressed more reliably. Further, the larger the value of the requirement (B2) is, the more uneven the shape is. The larger this value is, the more the domain has an uneven shape, so that the electric field is more likely to be concentrated on the convex portion. It has been found that the electric field concentration caused by the convex portion of the domain shape can be suppressed by setting the value of the requirement (B2) to 1.10 or less. As shown in FIG. 5, the envelope peripheral length is the peripheral length (broken line 52) when the convex portions of the domains 51 observed in the observation region are connected to each other and the peripheral length of the concave portion is ignored.

From the above results, the present inventors have conducted when 80% or more of the domains of the conductive layer cross section observed in each of the nine observation regions satisfy the requirements (A) and (B) at the same time. It was found that uniform discharge can be achieved by suppressing the electric field concentration inside the member. As a result, fog on the photoconductor can be suppressed when a high voltage is applied as a charging member. In the requirement (B), the observation target of the domain is within the range of 0.1 T to 0.9 T in depth from the outer surface of the conductive layer in the cross section in the thickness direction of the conductive layer. This is because it is considered that the movement of electrons in the conductive layer from the conductive support side to the outer surface side of the conductive layer is mainly controlled by the domains existing in the range. ..

The present inventors further investigated the adhesion of the toner to the surface, which changes the charging performance of the charging member according to Patent Document 1 with time. The toner remaining on the photoconductor even after the transfer process (hereinafter, also referred to as “transfer residual toner”) is often charged with the same polarity (positive electrode property) as the voltage polarity of the transfer process. Therefore, the transfer residual toner that has reached the nip portion between the photoconductor and the charging member electrostatically adheres to the surface of the charging member. As a result, the surface of the charged member is gradually contaminated with the transfer residual toner, which may hinder stable discharge from the surface of the charged member. Then, in order to suppress the electrostatic adhesion of the transfer residual toner to the outer surface of the charging member, it is effective to invert the charge of the transfer residual toner.

Here, the present inventors use a conductive member having the above requirements (A) and (B), which can effectively suppress fog on an electrophotographic image even when a high charge bias is applied. Therefore, it was examined to invert the charge of the transfer residual toner. As a result, in addition to the requirements (A) and (B), at least a part of the domain is exposed to the outer surface of the conductive member, and the domain is derived from the outer surface of the conductive member. It has been found that creating a convex portion (hereinafter, also referred to as requirement (C)) is extremely effective in reversing the charge of the transfer residual toner.

By exposing the domain on the outer surface of the conductive member and forming the convex portion, the transfer residual toner that has reached the nip portion between the charging member and the photosensitive drum easily comes into physical contact with the convex portion. In addition, the positively charged transfer residual toner is electrostatically attracted to the convex portion accumulating the negative charge. Due to these actions, the contact probability between the transfer residual toner and the convex portion derived from the domain is increased. Then, a negative charge is injected into the transfer residual toner that comes into contact with the convex portion to make it negative.
Further, the domain that has transferred the charge to the transfer residual toner by contact with the transfer residual toner can stably and continuously receive the charge from other domains existing in the conductive layer. Therefore, it is considered that the transfer residual toner that reaches the nip portion can be more reliably negativeized.

Specifically, the height of the domain-derived convex portion on the outer surface of the conductive member is preferably 50 nm or more and 200 nm or less. By setting the height of the convex portion to 50 nm or more, the chance of contact between the conductive convex portion and the reversing toner can be increased. Further, by setting the height to 100 nm or more, the contact opportunity can be further increased and the inverted toner fog can be reduced. On the other hand, since unevenness of discharge derived from the convex portion is formed in the discharge region, the height of the convex portion is preferably 200 nm or less.

Further, the arithmetic mean value Dm of the distance between the walls of the domains on the outer surface of the conductive member (hereinafter, also simply referred to as “distance between domains Dm”) is preferably 2.00 μm or less. By setting the inter-domain distance Dm to 2.00 μm or less, the chance of contact between the convex portion derived from the conductive domain and the reversing toner can be increased.

Therefore, according to the requirements (A) and (B), the conductive member brings the domain closer to a perfect circle shape to suppress the concentration of the electric field in the conductive layer, and further, according to the requirement (C), the convexity derived from the domain. Inverted toner adhesion is suppressed by injection charging by the part. As a result, fog can be significantly reduced even if the charging bias is high.

<Conductive member>
As one aspect of the conductive member for electrophotographic according to the present disclosure, a conductive member having a roller shape (hereinafter, also referred to as “conductive roller”) will be described with reference to the drawings.
FIG. 1 is a cross-sectional view perpendicular to the direction along the axis of the conductive roller (hereinafter, also referred to as “longitudinal direction”). The conductive roller 1 has a columnar conductive support 2 and a conductive layer formed on the outer periphery of the support 2, that is, on the outer surface of the support.
FIG. 2 shows a cross-sectional view of the conductive layer 3 in a direction perpendicular to the longitudinal direction of the conductive roller. The conductive layer 3 has a matrix-domain structure having a matrix 3a and a domain 3b. In addition, the domain 3b contains conductive particles (not shown). Further, a part of the domain 3b is exposed on the outer surface of the conductive member, that is, the surface facing the charged body such as a photoconductor. The domain 3b exposed on the outer surface causes a convex portion on the outer surface of the conductive member.

<Matrix-How to check the domain structure>
The existence of the matrix-domain structure can be confirmed, for example, as follows. Specifically, a thin piece of the conductive layer may be produced from the conductive member and detailed observation may be performed. Examples of the means for thinning include a sharp razor, a microtome, and a FIB. Further, in order to preferably observe the matrix-domain structure, a pretreatment such as a dyeing treatment or a vapor deposition treatment may be performed so as to preferably obtain a contrast between the conductive phase and the insulating phase. The flakes that have been formed and pretreated can be observed with a laser microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM).

Conductivity of the conductive member may be assessed by impedance measurement 1Hz, specifically, the impedance of 1Hz is preferably in the range of 10 ³ Omega least 10 ⁸ Omega. By the above 10 ³ Omega, the amount of discharge current becomes excessive, As a result, the potential non-uniformity of abnormal discharge caused can be prevented from occurring. By the 10 ⁸ Omega less, the total amount of the discharge charge quantity can be prevented insufficiently charged due to lack.

<Conductive support>
As the material constituting the support, materials known in the field of conductive members for electrophotographic and materials that can be used as conductive members can be appropriately selected and used. Examples include metals or alloys such as aluminum, stainless steel, conductive synthetic resins, iron and copper alloys.
Further, these may be subjected to an oxidation treatment or a plating treatment with chromium, nickel or the like. As the type of plating, either electroplating or electroless plating can be used. Electroless plating is preferable from the viewpoint of dimensional stability. Examples of the type of electroless plating used here include nickel plating, copper plating, gold plating, and various other alloy platings. The plating thickness is preferably 0.05 μm or more, and the plating thickness is preferably 0.10 μm or more and 30.00 μm or less in consideration of the balance between work efficiency and rust prevention ability. The cylindrical shape of the support may be a solid cylindrical shape or a hollow cylindrical shape (cylindrical shape). The outer diameter of the support is preferably in the range of 3 mm or more and 10 mm or less.

<Conductive layer>
<Matrix>
The matrix contains a first rubber crosslinked product. The volume resistivity ρm of the matrix is preferably 1.0 × 10 ⁸ Ωcm or more and 1.0 × 10 ¹⁷ Ωcm or less.
When the volume resistivity of the matrix is not less than 1.0 × 10 ⁸ Ωcm, it can suppress the effect of conductivity of the matrix given to transfer of charge between the conductive domains. In particular, when the matrix is highly conductive (low volume resistivity) and exhibits ionic conductivity, the matrix excessively promotes charge transfer between conductive domains, and a slight change in domain shape causes an electric field. When concentration occurs, excessive current tends to flow. Therefore, in order to suppress the ionic conductivity of the matrix, the volume resistivity ρm is preferably at 1.0 × 10 ⁸ Ωcm or more.
When the volume resistivity ρm is 1.0 × 10 ¹⁷ Ωcm or less, the required conductivity can be obtained as the entire conductive layer without hindering the transfer of electric charge between the conductive domains. Can be prevented.
The volume resistivity ρm is more preferably 1.0 × 10 ¹⁰ Ωcm or more and 1.0 × 10 ¹⁷ Ωcm or less. Within this range, the influence of the ionic conductivity of the matrix can be suppressed, and the volume resistivity required for the conductive member can be obtained. The most preferable range of the volume resistivity ρm is 1.0 × 10 ¹² Ωcm or more and 1.0 × 10 ¹⁷ Ωcm or less. Within this range, electric field concentration can be strongly suppressed even when a high voltage is applied, and the volume resistivity required for the conductive member can be obtained.

<Volume resistivity of matrix ρm>
For the volume resistivity ρm of the matrix, for example, a thin piece having a predetermined thickness (for example, 1 μm) containing the matrix domain structure is cut out from the conductive layer, and a scanning probe microscope (SPM) or a scanning probe microscope (SPM) is used for the matrix in the thin piece. It can be measured by contacting a micro probe of an atomic force microscope (AFM).
For example, as shown in FIG. 6A, the thin section is cut out from the elastic layer when the longitudinal direction of the conductive member is the X-axis, the thickness direction of the conductive layer is the Z-axis, and the circumferential direction is the Y-axis. The flakes are cut out to include at least a portion of the XZ plane and the flat lake cross section 62a. Alternatively, as shown in FIG. 6 (b), the flakes are cut out so as to include at least a part of the YZ plane (for example, 63a, 63b, 63c) perpendicular to the axial direction of the conductive member. For example, a sharp razor, a microtome, a focused ion beam method (FIB), and the like can be mentioned.
For the measurement of volume resistivity, one side of the thin section cut out from the conductive layer is grounded. Next, a small beauty probe of a scanning probe microscope (SPM) or an atomic force microscope (AFM) is brought into contact with the matrix portion of the surface of the thin section opposite to the ground surface, and a DC voltage of 50 V is applied to 5. The electric resistance value is calculated by applying the voltage for 2 seconds, calculating the arithmetic average value from the value measured for 5 seconds of the ground current value, and dividing the applied voltage by the calculated value. Finally, the film thickness of the flakes is used to convert the resistance value into volume resistivity. At this time, the SPM or AFM can measure the film thickness of the thin section at the same time as the resistance value.
For the value of the volume resistivity of the matrix in the columnar charging member, for example, one slice sample is cut out from each of the regions in which the conductive layer is divided into four in the circumferential direction and five in the longitudinal direction, and the above measured values are used. After obtaining, it is obtained by calculating the arithmetic mean value of the volume resistivity of a total of 20 samples.

<First rubber>
The first rubber is a component having the largest blending ratio in the rubber mixture for forming the conductive layer, and the crosslinked product of the first rubber controls the mechanical strength of the conductive layer. Therefore, the first rubber, after cross-linking, exhibits the strength required for the conductive member for electrophotographic in the conductive layer, is phase-separated from the second rubber described later, and has a matrix-domain structure. Those that can form are used.

Preferred examples of the first rubber are listed below.
Natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene-propylene-diene ternary copolymer rubber ( EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), NBR hydrogenated additive (H-NBR), silicone rubber and the like.
<Reinforcing material>
Further, it is also possible to add reinforcing carbon black as a reinforcing agent to the matrix to the extent that the conductivity of the matrix is not affected. Examples of the reinforcing carbon black used here include FEF, GPF, SRF, and MT carbon having low conductivity.
Further, the first rubber forming the matrix may contain, if necessary, a filler, a processing aid, a vulcanization aid, a vulcanization accelerator, and a vulcanization accelerator commonly used as a rubber compounding agent. , Vulcanization retarder, anti-aging agent, softener, dispersant, colorant and the like may be added.

<Domain>
The domain is conductive and contains a second rubber crosslinked product and conductive particles. In this case, the conductive and the volume resistivity refers to less than 1.0 × 10 ⁸ Ωcm.

<Second rubber>
Specific examples of the second rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butyl rubber (IIR), and ethylene. From the group consisting of propylene rubber (EPM), ethylene propylene diene rubber (EPDM), kururuprene rubber (CR), nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), silicone rubber, and urethane rubber (U). At least one selected is preferred.

<Conductive particles>
The conductive particles to be blended in the domain include carbon materials such as conductive carbon black and graphite; oxides such as titanium oxide and tin oxide; metals such as Cu and Ag; oxides or metals are coated on the surface to make them conductive. An example is an electronically conductive agent such as graphite. Further, if necessary, two or more kinds of these conductive particles may be blended in an appropriate amount and used.
Then, as specified in the requirement (B1), the ratio of the cross-sectional area of the conductive particles to the cross-sectional area of the domain of the conductive particles blended in the domain is at least 20% or more, preferably 25% or more and 30% or less. The amount of addition is preferable. Within the above range, the domain can be filled with conductive particles at high density. Then, the outer shape of the domain can be made closer to a sphere, and the unevenness can be made small as defined in the above requirement (B2). Furthermore, a sufficient amount of charge can be supplied even under a high-speed process.
Among the above-mentioned conductive particles, conductive carbon black is contained as a main component for reasons such as high conductivity efficiency, high affinity with rubber, and easy control of the distance between the conductive particles. Conductive particles are preferred. The type of conductive carbon black blended in the domain is not particularly limited. Specific examples thereof include gas furnace black, oil furnace black, thermal black, lamp black, acetylene black, and Ketjen black. Among them, as described below, may be used carbon black DBP absorption is less than 40 cm ^3/100 g or more 80 cm ^3/100 g, especially preferably.

<Shape of conductive domain>
The present inventors suppress excessive charge transfer even when a high voltage is applied by minimizing the electric field concentration caused by the convex shape of the conductive domain by making the conductive domain closer to a circular shape. It has been found that the photoconductor can be uniformly charged, and as a result, fog can be suppressed.
The shape of the domain is 2 of L / 4 from the center in the longitudinal direction of the conductive layer and the center from both ends thereof, where L is the length in the longitudinal direction of the conductive layer and T is the thickness of the conductive layer. Decide a total of 3 locations. For each of the cross sections in the thickness direction of the conductive layer as shown in FIG. 6 (b) at the three locations, the thickness region from the outer surface of the conductive layer to a depth of 0.1 T or more and 0.9 T or less. Place a 15 μm square observation area at any three locations. At that time, it is defined by the shape of the domain observed in each of the nine observation regions.
The shape of the domain is preferably close to a circle as described above. Specifically, 80% or more of the domains in the 15 μm square region of the cross section in the thickness direction of the conductive layer need to satisfy the following requirements (B1) and requirements (B2).
Requirement (B1): The ratio of the cross-sectional area of the conductive particles contained in the domain to the cross-sectional area of the domain is 20% or more;
Requirement (B2): When the perimeter of the domain is A and the perimeter of the domain is B, the A / B is 1.00 or more and 1.10 or less.

The ratio of the domain circumference of the requirement (B2) to the envelope circumference of the domain has a minimum value of 1.00, and a state of 1.00 indicates that the domain is a perfect circle or an ellipse. When the ratio exceeds 1.10, a large uneven shape exists in the domain, that is, electric field concentration is likely to occur. When the above requirement (B2) is satisfied, the electric field concentration is suppressed, so that fog can be suppressed.
As shown in FIG. 4, the maximum ferret diameter Df is the longest perpendicular line length when the outer circumference of the observed domain 41 is sandwiched between two parallel lines and the two parallel lines are connected by a perpendicular line. The value of the hour.
The domain size is preferably within a certain range, and the maximum ferret diameter, which is an index indicating the domain size, is preferably 0.1 μm or more and 5.0 μm or less. If the maximum ferret diameter is in this range, the domain tends to have a circular shape.
As a result, fog is reduced. Further, by miniaturizing the conductive domain, the discharge is also miniaturized, and high image quality is possible.

<Measurement method of domain maximum ferret diameter, area, perimeter, envelope perimeter, and number of domains>
The method for measuring the maximum ferret diameter, area, perimeter, envelope perimeter, and number of domains of a domain may be carried out as follows. First, a section is prepared by the same method as the method for measuring the volume resistivity of the matrix described above. Next, flakes having a fracture surface can be formed by means such as a lower freeze fracture method, a cross polisher method, and a focused ion beam method (FIB). The FIB method is preferable in consideration of the smoothness of the fracture surface and the pretreatment for observation. Further, in order to preferably observe the matrix-domain structure, a pretreatment such as a dyeing treatment or a vapor deposition treatment may be performed so as to preferably obtain a contrast between the conductive phase and the insulating phase.
The flakes that have been formed and pretreated can be observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Among these, from the viewpoint of the accuracy of quantification of the domain area, it is preferable to perform observation at 1,000 to 100,000 times by SEM.
Measurements of domain maximum ferret diameter, area, perimeter, enveloping perimeter, and number of domains can be obtained by quantifying the captured image above. That is, the fracture surface image obtained by the observation with SEM is grayscaled to 8 bits by using image processing software (trade name: ImageProPlus, manufactured by Media Cybernetics) or the like, and a 256-tone monochrome image To get. Next, the black and white of the image is inverted and binarized so that the domain in the fracture surface becomes white. Next, the maximum ferret diameter, area, perimeter, envelope perimeter, and number of domains may be calculated from each of the domains in the image.
For the above measurement, when the length of the conductive member in the longitudinal direction of the conductive member is L, the sample is L / 4 toward the center of the conductive layer in the longitudinal direction and from both ends of the conductive layer toward the center. Cut out sections from a total of 3 locations in 2 locations. The direction in which the section is cut out is a direction in which the cross section is perpendicular to the longitudinal direction of the conductive layer.
The reason for evaluating the shape of the domain in the cross section perpendicular to the longitudinal direction of the conductive layer as described above will be described with reference to FIG.
FIG. 6 shows a diagram showing the shape of the conductive member 61 as three dimensions, specifically, three dimensions of the X, Y, and Z axes. In FIG. 6, the X-axis shows a direction parallel to the longitudinal direction (axial direction) of the conductive member, and the Y-axis and the Z-axis show a direction perpendicular to the axial direction of the conductive member.

FIG. 6A shows an image diagram of cutting out the conductive member with a cross section 62a parallel to the XZ plane 62 with respect to the conductive member. The XZ plane can rotate 360 ° about the axis of the conductive member. Considering that the conductive member comes into contact with the photoconductor drum, rotates, and discharges when passing through the gap with the photosensitive drum, the cross section 62a parallel to the XZ plane 62 is discharged at a certain timing at the same time. Will show the side where. Therefore, the surface potential of the photosensitive drum is formed by passing a certain amount of the surface corresponding to the cross section 62a. Due to a large local discharge due to the concentration of the electric field in the conductive member, the surface of the photosensitive drum locally increases and becomes a fog, so that a fixed amount of cross sections 62a passes through instead of one sheet. An evaluation that correlates with the surface potential of the photosensitive drum to be formed is required. Therefore, a cross section parallel to the YZ plane 63 perpendicular to the axial direction of the conductive member, which can evaluate the domain shape including a certain amount of the cross section 62a, instead of analyzing the cross section such as the cross section 62a in which discharges occur at the same time in a certain moment. Evaluation in (63a to 63c) is required. The cross sections 63a to 63c are the cross section 63b at the center of the conductive layer in the longitudinal direction and L / 4-2 from both ends of the conductive layer toward the center, where L is the length in the longitudinal direction of the conductive layer. Select a total of three cross sections (63a and 63c).
The observation positions of the cross sections of the cross sections 63a to 63c are as follows, that is, when the thickness of the conductive layer is T, the depth of each section is 0.1 T or more from the outer surface. Specify any three locations in the thickness region up to 0.9 T or less. Measurements may be performed at a total of 9 locations when 15 μm square observation areas are placed at any of the 3 locations.

<Control of domain shape>
The formation of a domain that is close to a circle in the matrix-domain structure is an important point in exerting the effects of the present disclosure. The formation of a domain close to a circular shape and the reduction of size unevenness of the maximum ferret diameter suppress the electric field concentration and domain deformation, so that the resistance fluctuation is reduced.
The present inventors have investigated a method of making the cross-sectional shape of the domain a circular shape, that is, a method of making the domain shape close to a spherical shape. As a result, it was found that it can be achieved by using the following two methods.
-Reduce the domain size (maximum ferret diameter).
-Increase the amount of carbon gel in the domain.
By reducing the domain size (maximum ferret diameter), the reason why the domain approaches the spherical shape is estimated as follows. If the domain size is small even at the same domain volume fraction, the surface area of the domain increases, and as a result, the interface with the matrix increases. Molecules near the interface will have more free energy than the molecules inside the domain because there are more different molecules surrounding them than inside the matrix. In order to reduce the interfacial free energy, it is considered that the interfacial tension for reducing the interface acts and the domain approaches a spherical shape (circular shape in the cross section in the thickness direction of the conductive layer). As a result, electric field concentration can be suppressed.

-Method for reducing the domain size (maximum ferret diameter) Regarding the dispersed particle size (domain size) D when two incompatible polymers are melt-kneaded, the Taylor formulas shown in the following formulas (4) to (7) are used. , Wu's empirical formula and Tokita's formula have been proposed (see Sumitomo Chemical Technical Journal 2003-II, 42).
・ Taylor's formula (4)
D = [C ・ σ / ηm ・ γ] ・ f (ηm / ηd)
・ Wu's empirical formula (5)
γ ・ D ・ ηm / σ = 4 (ηd / ηm) ^0.84・ ηd / ηm> 1
Equation (6)
γ ・ D ・ ηm / σ = 4 (ηd / ηm) ^−0.84・ ηd / ηm <1

In equations (4) to (7)
D: domain size, C: constant, σ: interfacial tension,
ηm: matrix viscosity, ηd: domain viscosity,
γ: Shear velocity, η: Viscosity of mixed system, P: Collision coalescence probability, φ: Domain phase volume, EDK: Domain phase cutting energy :.

As shown in the above equation, the formation of a domain close to a spherical shape can be controlled mainly by the following four points.
1. 1. Interfacial tension difference between domain and matrix 2. Domain to matrix viscosity ratio 3. Shear velocity during mixing / energy amount during shearing 4. Volume fraction of the domain

1. 1. Difference in interfacial tension between domain and matrix Generally, when two types of polymers are mixed, phase separation occurs. This phenomenon occurs because the interaction between the same polymers is stronger than the interaction between different polymers, so that the same polymers aggregate to reduce the free energy and try to stabilize it. Since the interface of the phase-separated structure comes into contact with different macromolecules, the free energy is higher than that of the inside stabilized by the interaction between the same molecules. As a result, in order to reduce the free energy of the interface, an interfacial tension is generated to reduce the area of contact with the dissimilar polymer. When this interfacial tension is small, even dissimilar polymers tend to be mixed more uniformly in order to increase entropy. The uniformly mixed state is dissolution, and the SP value, which is a measure of solubility, and the interfacial tension tend to correlate with each other. That is, since the interfacial tension difference between the domain and the matrix is considered to correlate with the SP value difference between the domain and the rubber material constituting the matrix, it can be controlled by selecting the raw material rubber of the domain and the domain. The difference between the absolute values of the solubility parameters of the first rubber and the second rubber was stable if it ^{was 0.4 (J / cm 3} ) ^0.5 or more and 4.0 (J / cm ³ ) ^{0.5 or less.} A phase-separated structure can be formed. More preferably, it is 0.4 (J / cm ³ ) ^0.5 or more and 2.2 (J / cm ³ ) ^0.5 or less. Within this range, a stable phase-separated structure can be formed, and the maximum ferret diameter of the domain can be reduced.

2. Domain-matrix viscosity ratio The closer the domain-matrix viscosity ratio (ηd / ηm) is, the smaller the maximum ferret diameter of the domain can be. The viscosity ratio between the domain and the matrix can be adjusted by selecting the Mooney viscosity of the rubber raw material and by blending the type and amount of the filler. It is also possible to add a plasticizer such as paraffin oil to the extent that it does not interfere with the formation of the phase-separated structure. Further, the viscosity ratio can be adjusted by adjusting the temperature at the time of kneading. The viscosities of the domain and the matrix can be obtained by measuring the Mooney viscosity ML (1 + 4) at the rubber temperature at the time of kneading based on JIS K6300-1: 2013. Further, the catalog value of the raw material rubber may be used instead.

3. 3. Shear velocity during mixing / energy amount during shearing As for the shear rate during mixing / energy amount during shearing, the maximum ferret diameter of the domain can be reduced as the amount increases. The shear rate can be increased by increasing the inner diameter of the stirring member such as the blade or screw of the kneader, reducing the gap from the end face of the stirring member to the inner wall of the kneader, or increasing the rotation speed. Further, the energy at the time of shearing can be increased by increasing the rotation speed of the stirring member or increasing the viscosities of the domain raw material rubber and the matrix raw material rubber.

4. Volume fraction of the domain The volume fraction of the domain in the conductive layer correlates with the collision coalescence probability of the domain and the matrix. Specifically, reducing the volume fraction in the conductive layer reduces the probability of collision and coalescence of the domain and matrix. That is, the domain size can be reduced by reducing the volume fraction of the domain within the range where the required conductivity can be obtained.

<Measurement method of SP value>
The SP value of the rubber constituting the matrix and the domain can be calculated accurately by creating a calibration curve using a material having a known SP value. As this known SP value, the catalog value of the material manufacturer can also be used. For example, the NBR and SBR that can be used in the present disclosure do not depend on the molecular weight, and the SP value is almost determined by the content ratio of acrylonitrile and styrene. Therefore, the rubber constituting the matrix and the domain is analyzed for the content ratio of acrylonitrile or styrene by using an analysis method such as pyrolysis gas chromatography (Py-GC) and solid-state NMR. Thereby, the SP value can be calculated from the calibration curve obtained from the material whose SP value is known.
The isoprene rubber is an isomer such as 1,2-polyisoprene, 1,3-polyisoprene, 3,4-polyisoprene, and cis-1,4-polyisoprene, trans-1,4-polyisoprene. The structure determines the SP value. Therefore, the isomer content ratio can be analyzed by Py-GC, solid-state NMR, or the like in the same manner as SBR and NBR, and the SP value can be calculated from a material having a known SP value.
The SP value of the material whose SP value is known is obtained by the Hansen sphere method.

Next, the reason why the domain approaches a spherical shape by increasing the amount of carbon gel in the domain will be described. The carbon gel is a particulate matter in a pseudo-crosslinked state due to the adsorption of rubber molecules on carbon black. The carbon gel does not dissolve even in an organic solvent that dissolves the raw rubber. That is, it is considered that the rubber molecules are three-dimensionally crosslinked by physical adsorption or chemical adsorption on the surface of carbon black and behave as rubber particles. As a result, it is speculated that the rubber particles formed by the carbon gel become nuclei and form domains. By increasing the amount of carbon gel, the uneven shape of the domain, which is applied to the requirement (B2), can be suppressed, and the electric field concentration can be suppressed.

In order to increase the amount of carbon gel, it is preferable to add a large amount of carbon black to the rubber, and the amount of carbon black that functions as an adsorbent may be increased.
We focused on the amount of DBP absorbed as an index for blending a large amount of carbon black in the domain. DBP absorption and ^(cm 3 / 100g) is the volume of dibutyl phthalate carbon black 100g can adsorb (DBP), it is measured according to JIS K 6217.
In general, carbon black has a tufted higher-order structure in which primary particles having an average particle size of 10 nm or more and 50 nm or less are aggregated. The tufted conformation called structure, the degree is quantified by DBP absorption ^(cm 3 / 100g).
In general, carbon black with a well-developed structure has high reinforcing properties against rubber, which makes it difficult to take in carbon black into rubber and also has a very high share torque during kneading, so it is difficult to fill it with high filling. ..
The conductive carbon black used in the present disclosure, DBP absorption ^amount, it is preferred to use carbon black is less than 40 cm 3/100 g or more 80 cm ^3/100 g. By setting the amount of DBP absorbed within the above range, the amount of carbon gel can be increased by blending a large amount of carbon black with rubber.
Further, when the amount of DBP absorbed is within the above range, the structure of the conductive carbon black is small and the dispersibility of the carbon black in the rubber is good. Less is. Therefore, it is easy to round the domain shape. When carbon black with a well-developed structure is used, it is difficult to disperse it uniformly with rubber, and the carbon black tends to disperse in an agglomerated state. Originally, carbon black has a concavo-convex shape because it has a tufted higher-order structure as described above, but when they aggregate, it tends to become a mass having a larger uneven structure. When this carbon black agglomerate is present at the outer edge of the domain, it may affect the domain shape and form an uneven structure.

The amount of conductive carbon black added to the domain is such that C, which is the arithmetic mean of the distance between adjacent carbons (hereinafter, also referred to as "arithmetic mean wall distance C"), is 110 nm or more and 130 nm or less. The amount of addition is preferable. When the arithmetic mean wall distance C is 110 nm or more and 130 nm or less, electrons can be transferred between carbon black particles by the tunnel effect between almost all carbon blacks in the domain. That is, if the above arithmetic mean distance between the wall surfaces is satisfied, the volume resistivity of the domain becomes almost constant and the electric field concentration is suppressed. This is also because the resistance fluctuation due to the change in the distance between the carbon black wall surfaces due to the repeated image output is suppressed. Furthermore, the amount of carbon gel exhibiting crosslinked rubber-like properties increases in the rubber in which carbon black is dispersed, which makes it easier to maintain the shape and makes it easier to maintain the domain at the time of molding into a circular shape. As a result, changes in the distance between domains due to electric field concentration and deformation of the convex portion of the domain are suppressed, and it becomes easy to achieve uniform discharge.
Further, the arithmetic mean distance between the wall surfaces of the conductive carbon black C is 110 nm or more and 130 nm or less, and the standard deviation of the distribution of the distance between the wall surfaces of the conductive carbon black is σm. At that time, it is more preferable that the coefficient of variation σm / C of the distance between the conductive carbon black walls is 0.0 or more and 0.3 or less. The coefficient of variation is a value indicating the variation in the distance between the walls of the conductive carbon black, and is 0.0 when the distances between the walls of the conductive carbon black are all the same.
When the coefficient of variation σm / C satisfies 0.0 or more and 0.3 or less, the variation in the distance between the wall surfaces between the carbon blacks is small, so that electrons can be transferred between the carbon blacks in the domain by the tunnel effect, and the volume resistivity. The rate tends to be almost constant. Further, since the carbon black is uniformly dispersed, the uneven distribution of the conductive paths in the domain can be suppressed, so that the electric field concentration in the domain can be suppressed. As a result, in addition to the domain shape, the electric field concentration in the domain can be suppressed, so that more uniform discharge can be easily achieved.

The arithmetic mean value C of the distance between the walls of the conductive carbon black in the domain and the ratio of the carbon black cross section to the domain cross section may be measured as follows. First, a thin piece of the conductive layer is produced. In order to favorably observe the matrix-domain structure, pretreatments such as dyeing and vapor deposition may be performed to obtain a favorable contrast between the conductive phase and the insulating phase.
The flakes that have been formed and pretreated can be observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Among these, from the viewpoint of the accuracy of quantification of the area of the domain which is the conductive phase, it is preferable to perform the observation by SEM at a magnification of 1,000 to 100,000. The arithmetic mean wall-to-wall distance and the ratio can be obtained by binarizing and analyzing the obtained observation image using an image analysis device or the like.

<Method of forming convex parts derived from domain>
The domain-derived protrusions can be formed by grinding the surface of the conductive member. Further, the inventors believe that the domain-derived convex portion can be suitably formed by the grinding process using a grindstone because the conductive layer has a matrix-domain structure. The domain-derived convex portion is preferably formed by a method of grinding with a polishing grindstone with a plunge type polishing machine.
We show the speculation mechanism that domain-derived protrusions can be formed by grinding wheel polishing. First, the domains dispersed in the matrix are filled with conductive particles such as carbon black, and have higher reinforcing properties than the matrix not filled with the conductive particles. That is, when grinding with the same grindstone is performed, the domain is more difficult to grind than the matrix because of its high reinforcing property, and convex portions are likely to be formed. By utilizing the difference in grindability caused by this difference in reinforcing property, a convex portion derived from the domain can be formed. In particular, since the conductive member according to the present embodiment has a structure in which the domain is filled with a large number of conductive particles, it is possible to suitably form the convex portion.

Here, a polishing grindstone for a plunge type polishing machine used for polishing will be described. The surface roughness of the polishing grindstone can be appropriately selected according to the polishing efficiency and the type of the constituent material of the conductive layer. The roughness of the surface of the grindstone can be adjusted by the type of abrasive grains, the particle size, the degree of bonding, the binder, the structure (abrasive grain ratio), and the like.
The above-mentioned "particle size of abrasive grains" indicates the size of abrasive grains, and is expressed as, for example, # 80. The number in this case means how many stitches per inch (25.4 mm) of the mesh for selecting the abrasive grains, and the larger the number, the finer the abrasive grains. The above-mentioned "coupling degree of abrasive grains" indicates hardness, and is represented by alphabets A to Z. The closer it is to A, the softer it is, and the closer it is to Z, the harder it is. The larger the amount of the binder contained in the abrasive grains, the harder the grindstone becomes. The above-mentioned "abrasive grain structure (abrasive grain ratio)" represents the volume ratio of the abrasive grains to the total volume of the grindstone, and the size of the structure represents the coarseness and density of the structure. The larger the number indicating the tissue, the coarser it is. A grindstone having a large number of structures and large pores is called a porous grindstone, and has advantages such as preventing clogging and burning of the grindstone.

Generally, this polishing grindstone can be manufactured by mixing raw materials (abrasive material, binder, pore agent, etc.), press molding, drying, firing, and finishing. As the abrasive grains, green silicon carbide (GC), black silicon carbide (C), white alumina (WA), brown alumina (A), zirconia alumina (Z) and the like can be used. These materials can be used alone or in combination of two or more. Further, as the above-mentioned binder, vitrify (V), resinoid (B), resinoid reinforcement (BF), rubber (R), silicate (S), magnesia (Mg), shellac (E), etc. , Can be used.
Here, as the outer diameter shape of the polishing grindstone in the longitudinal direction, it is preferable to have an inverted crown shape in which the outer diameter gradually decreases from the end portion to the center portion so that the conductive roller can be polished into a crown shape. .. The outer diameter shape of the grinding wheel is preferably an arc curve or a higher-order curve of a second order or higher with respect to the longitudinal direction. In addition to this, the outer diameter shape of the polishing wheel may be a shape expressed by various mathematical formulas such as a quartic curve and a sine function. The outer shape of the grinding wheel is preferably one in which the change in outer diameter changes smoothly, but an arc curve or the like may be a shape similar to a polygonal shape formed by a straight line. The width in the direction corresponding to the axial direction of the polishing grindstone is preferably equal to or larger than the axial width of the conductive roller.
By appropriately selecting the grindstone in consideration of the above-mentioned factors and carrying out the grinding step under the conditions that promote the difference in grindability between the domain and the matrix, the convex portion derived from the domain can be formed.

Specifically, conditions in which polishing is suppressed and conditions in which abrasive grains with poor sharpness are used are preferable. For example, the time required for the precision polishing process after rough cutting is shortened, and polishing is performed using a treated grindstone. By taking measures, the convex portion derived from the domain can be preferably formed.
The treated grindstone includes, for example, a grindstone treated with a rubber member, specifically, a grindstone dressed with a rubber member containing abrasive grains to grind the surface of the grindstone to wear the abrasive grains. A grindstone can be mentioned.

<Measurement method of convex part derived from domain>
A thin piece including a surface can be taken out from the conductive layer, and the convex shape can be confirmed and the convex shape can be measured by the domain by a micro probe. The surface profile and electrical resistance profile of the flakes sampled from the conductive member are measured by SPM. From this, it can be confirmed that the convex portion is a convex portion derived from the domain. At the same time, it is possible to quantify and evaluate the height of the convex portion from the shape profile. The specific procedure will be described later.

<Measuring method of distance Dm between domains on the outer surface of the conductive member>
When the length of the conductive layer in the longitudinal direction is L and the thickness of the conductive layer is T, razors are sewn from three places, the center of the conductive layer in the longitudinal direction and L / 4 from both ends of the conductive layer toward the center. The sample is cut out so as to include the outer surface of the charging member using. The size of the sample was 2 mm in each of the circumferential direction and the longitudinal direction of the charging member, and the thickness was the thickness T of the conductive layer. For each of the three obtained samples, 50 μm square analysis regions were placed at arbitrary three locations on the surface corresponding to the outer surface of the charging member, and the three analysis regions were used as scanning electron microscopes (trade name: S-). 4800, manufactured by Hitachi High-Technologies Corporation) is used to shoot at a magnification of 5000 times. Each of the obtained nine captured images is binarized using image processing software (trade name: LUZEX; manufactured by NIRECO CORPORATION).
The procedure for binarization is as follows. The captured image is grayscaled with 8 bits to obtain a monochrome image with 256 gradations. Then, the domain in the captured image is binarized so as to be black, and a binarized image of the captured image is obtained. Next, for each of the nine binarized images, the distance between the walls of the domain is calculated, and the arithmetic mean value thereof is calculated. Let this value be Dm. The distance between walls is the distance between the walls of the domains closest to each other, and can be obtained by setting the measurement parameter as the distance between adjacent walls in the above image processing software.

<Manufacturing method of conductive member>
An example of the method for manufacturing the conductive member according to the present disclosure is shown below. In this example, the manufacturing method is characterized by including the following steps (A) to (C), but is not particularly limited as long as the configuration of the present disclosure can be achieved.

Step (A): A step of preparing a carbon masterbatch (hereinafter, also referred to as “CMB”) for domain formation, which comprises carbon black and rubber;
Step (B): A step of preparing a rubber composition for forming a matrix (hereinafter, also referred to as "MRC");
Step (C): A step of kneading the CMB and the MRC to prepare a rubber composition having a matrix-domain structure.
Step (D): A step of forming a conductive layer on a conductive support by a known method such as extrusion molding, injection molding, compression molding, etc., using the rubber compositions prepared in the steps (A) to (C). ..
If necessary, the conductive layer may be adhered onto the conductive support via an adhesive. If necessary, the conductive layer formed on the conductive support is vulcanized, and after the polishing treatment, the surface treatment of the ultraviolet treatment can be performed.

<Process cartridge>
FIG. 7 is a schematic cross-sectional view of a process cartridge 100 for electrophotographic, which includes a conductive member according to an embodiment of the present disclosure as a charging member (charging roller). This process cartridge integrates a developing device and a charging device, and is configured to be removable from the main body of the electrophotographic device. The developing apparatus integrates at least the developing roller 103, the toner container 106, and the toner 109, and may include a toner supply roller 104, a developing blade 108, and a stirring blade 110, if necessary. The charging device is at least integrated with the photosensitive drum 1-1 and the charging roller 102, and may include a cleaning blade 105 and a waste toner container 107. A voltage is applied to each of the charging roller 102, the developing roller 103, the toner supply roller 104, and the developing blade 108.

<Electrophotograph image forming apparatus>
FIG. 8 is a schematic configuration diagram of an electrophotographic image forming apparatus 200 using the conductive member according to the embodiment of the present disclosure as a charging member (charging roller). This device is a color electrophotographic device to which the four process cartridges 100 are detachably attached. Black, magenta, yellow, and cyan toners are used in each process cartridge. The photosensitive drum 201 rotates in the direction of the arrow and is uniformly charged by the charging roller 202 to which a voltage is applied from the charging bias power supply, and an electrostatic latent image is formed on the surface by the exposure light 211. On the other hand, the toner 209 stored in the toner container 206 is supplied to the toner supply roller 204 by the stirring blade 210 and conveyed onto the developing roller 203. Then, the developing blade 208 arranged in contact with the developing roller 203 uniformly coats the toner 209 on the surface of the developing roller 203, and the toner 209 is charged by triboelectric charging. The electrostatic latent image is developed by applying toner 209 conveyed by a developing roller 203 contacted with the photosensitive drum 101, and is visualized as a toner image.

The visualized toner image on the photosensitive drum is transferred to the intermediate transfer belt 215 supported and driven by the tension roller 213 and the intermediate transfer belt drive roller 214 by the primary transfer roller 212 to which a voltage is applied by the primary transfer bias power supply. Toner. Toner images of each color are sequentially superimposed, and a color image is formed on the intermediate transfer belt.
The transfer material 219 is fed into the apparatus by the paper feed roller and conveyed between the intermediate transfer belt 215 and the secondary transfer roller 216. A voltage is applied to the secondary transfer roller 216 from the secondary transfer bias power supply to transfer the color image on the intermediate transfer belt 215 to the transfer material 219. The transfer material 219 on which the color image is transferred is fixed by the fixing device 218, and is discarded outside the apparatus to complete the printing operation.
On the other hand, the toner remaining on the photosensitive drum without being transferred is scraped off by the cleaning blade 205 and stored in the waste toner storage container 207, and the cleaned photosensitive drum 201 repeats the above steps. Further, the toner remaining on the primary transfer belt without being transferred is also scraped off by the cleaning device 217.
Although a color electrophotographic apparatus is shown as an example, in the monochrome electrophotographic apparatus (not shown), the process cartridge is only a product using black toner. A monochrome image is directly formed on the transfer material by the process cartridge and the primary transfer roller (without the secondary transfer roller) without using the intermediate transfer belt. After that, the paper is fixed by the fixing device and the paper is discharged to the outside of the device, so that the printing operation is completed.

Subsequently, the conductive members in the examples and comparative examples of the present disclosure were subsequently produced using the materials shown below.

<NBR>
-NBR (1) (Product name: JSR NBR N230SV, Acrylonitrile content: 35%, Mooney viscosity ML (1 + 4) 100 ° C: 32, SP value: 20.0 (J / cm ³ ) ^0.5 , JSR Corporation Made, abbreviation: N230SV)
-NBR (2) (Product name: JSR NBR N215SL, Acrylonitrile content: 48%, Mooney viscosity ML (1 + 4) 100 ° C: 45, SP value: 21.7 (J / cm ³ ) ^0.5 , JSR Corporation Made, abbreviation: N215SL)
NBR (3) (trade name: Nipol DN401LL, acrylonitrile content: 18.0%, Mooney viscosity ML (1 + 4) 100 ° C.: 32, SP value: 17.4 (J / cm ³ ) ^0.5 , ZEON Made by Co., Ltd., abbreviation: DN401LL)
<Isoprene rubber IR>
-Isoprene rubber (trade name: Nipol IR2200L, Mooney viscosity ML (1 + 4) 100 ° C: 70, SP value: 16.5 (J / cm ³ ) ^0.5 , manufactured by Nippon Zeon Corporation, abbreviation: IR2200L)
<butadiene rubber BR>
-Butadiene rubber (1) (trade name: UBEPOL BR130B, Mooney viscosity ML (1 + 4) 100 ° C.: 29, SP value: 16.8 (J / cm ³ ) ^0.5 , manufactured by Ube Industries, Ltd., abbreviation: BR130B)
-Butadiene rubber (2) (trade name: UBEPOL BR150B, Mooney viscosity ML (1 + 4) 100 ° C.:40, SP value: 16.8 (J / cm ³ ) ^0.5 , manufactured by Ube Industries, Ltd., abbreviation: BR150B)
<SBR>
-SBR (1) (Product name: Asaprene 303, Styrene content: 46%, Mooney viscosity ML (1 + 4) 100 ° C: 45, SP value: 17.4 (J / cm ³ ) ^0.5 , manufactured by Asahi Kasei Corporation , Abbreviation: A303)
-SBR (2) (Product name: Toughden 2003, Styrene content: 25%, Mooney viscosity ML (1 + 4) 100 ° C: 33, SP value: 17.0 (J / cm ³ ) ^0.5 , manufactured by Asahi Kasei Corporation , Abbreviation: T2003)
-SBR (3) (Product name: Toughden 2100R, Styrene content: 25%, Mooney viscosity ML (1 + 4) 100 ° C: 78, SP value: 17.0 (J / cm ³ ) ^0.5 , manufactured by Asahi Kasei Corporation , Abbreviation: T2100R)
-SBR (4) (Product name: Toughden 2000R, Styrene content: 25%, Mooney viscosity ML (1 + 4) 100 ° C: 45, SP value: 17.0 (J / cm ³ ) ^0.5 , manufactured by Asahi Kasei Corporation , Abbreviation: T2000R)
-SBR (5) (Product name: Toughden 1000, Styrene content: 18%, Mooney viscosity ML (1 + 4) 100 ° C: 45, SP value: 16.8 (J / cm ³ ) ^0.5 , manufactured by Asahi Kasei Corporation , Abbreviation: T1000)
<Chloroprene rubber (CR)>
-Chloroprene rubber (trade name: SKYPRENE B31, Mooney viscosity ML (1 + 4) 100 ° C.:40, SP value: 17.4 (J / cm ³ ) ^0.5 , manufactured by Tosoh Corporation, abbreviation: B31)
<EPDM>
EPDM (trade name: Esprene505A, Mooney viscosity ML (1 + 4) 100 ° C.: 47, SP value: 16.0 (J / cm ³ ) ^0.5 , manufactured by Sumitomo Chemical Co., Ltd., abbreviation: E505A)

<Conductive particles>
Carbon black (1) (trade name: TOKABLACK♯5500, DBP absorption ^amount: 155cm 3 / 100g, Tokai Carbon Co., Ltd., abbreviation: ♯5500)
Carbon black (2) (trade name: TOKABLACK♯7360SB, DBP absorption ^amount: 87cm 3 / 100g, Tokai Carbon Co., Ltd., abbreviation: ♯7360)
Carbon black (3) (trade name: TOKABLACK♯7270SB, DBP absorption ^amount: 62cm 3 / 100g, Tokai Carbon Co., Ltd., abbreviation: ♯7270)
Carbon black (4) (trade name: # 44, DBP absorption ^amount: 78cm 3 / 100g, Mitsubishi Chemical Co., Ltd., abbreviation: # 44)
Carbon black (5) (trade name: Asahi # 35, DBP absorption ^amount: 50cm 3 / 100g, Asahi Carbon Co., Ltd., abbreviation: # 35)
-Carbon black (6) (Product name: # 45L, DBP absorption amount: 45cm ³ / 100g, manufactured by Mitsubishi Chemical Corporation, abbreviation: # 45L)
-Tin oxide (trade name: S-2000, manufactured by Mitsubishi Materials Electronics Chemical Co., Ltd., abbreviation: tin oxide)
<Vulcanizing agent>
-Vulcanizing agent (1) (Product name: SULFAX PMC, sulfur content 97.5%, manufactured by Tsurumi Chemical Industry Co., Ltd., abbreviation: sulfur)
<Vulcanization accelerator>
-Vulcanization accelerator (1) (trade name: Suncella TBZTD, tetrabenzyl thiuram disulfide, manufactured by Sanshin Chemical Industry Co., Ltd., abbreviation: TBZTD)
-Vulcanization accelerator (2) (Product name: Noxeller TBT, Tetrabutyl thiuram disulfide, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., abbreviation: TBT)
-Vulcanization accelerator (3) (trade name: Noxeller EP-60, vulcanization accelerator mixture, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., abbreviation: EP-60)
-Vulcanization accelerator (4) (trade name: SANTOCURE-TBSI, Nt-butyl-2-benzothiazolesulfenimide, manufactured by FLEXSYS, abbreviation: TBSI)
<Filler>
-Filler (1) (Product name: Nanox # 30, calcium carbonate, manufactured by Maruo Calcium Co., Ltd., abbreviation: # 30)
-Filler (2) (Product name: Nipsil AQ, silica, manufactured by Tosoh Corporation, abbreviation: AQ)

Hereinafter, the conductive member, the process cartridge, and the electrophotographic image forming apparatus of the present disclosure will be described in detail, but the technical scope of the present disclosure is not limited thereto. First, a method for producing a conductive member in the examples and comparative examples of the present disclosure will be specifically illustrated and described.
<Example 1>
[1-1. Preparation of carbon masterbatch (CMB) for domain formation]
Each material of the type and the blending amount shown in Table 1 was mixed with a 6 L pressure type kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.) to obtain a CMB for domain formation. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and 16 minutes.

[1-2. Preparation of rubber composition for matrix formation]
Each material of the type and the blending amount shown in Table 2 was mixed with a 6 L pressure type kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.) to obtain a rubber composition for matrix formation. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and 18 minutes.

Each material of the type and the blending amount shown in Table 3 was mixed with an open roll to prepare a rubber composition for forming a conductive resin layer. As the mixer, an open roll having a roll diameter of 12 inches was used. The mixing conditions were a front roll rotation speed of 10 rpm and a rear roll rotation speed of 8 rpm, and after turning left and right 20 times in total with a roll gap of 2 mm, thinning was performed 10 times with a roll gap of 1.0 mm.

<2. Molding of conductive members ＞
A round bar having a total length of 252 mm and an outer diameter of 6 mm was prepared by subjecting the surface of the free-cutting steel to electroless nickel plating. Next, using a roll coater, an adhesive (trade name: Metallock U-20, manufactured by Toyo Kagaku Kenkyusho Co., Ltd.) was applied over the entire circumference of a range of 230 mm excluding 11 mm at both ends of the round bar. In this example, the round bar coated with the adhesive was used as the conductive support.
Next, a die with an inner diameter of 10.0 mm is attached to the tip of a crosshead extruder having a mechanism for supplying a conductive support and a mechanism for discharging unvulcanized rubber rollers, and the temperature of the extruder and the crosshead is set to 100 ° C. The transport speed of the sex support was adjusted to 60 mm / sec. Under these conditions, the rubber composition for forming the conductive resin layer is supplied from the extruder, the outer peripheral portion of the conductive support is covered with the rubber composition for forming the conductive resin layer in the cross head, and the rubber composition is not vulcanized. Obtained a rubber roller.
Next, the unvulcanized rubber roller is put into a hot air vulcanizer at 170 ° C. and heated for 60 minutes to vulcanize the unvulcanized rubber composition, and a conductive resin layer is formed on the outer periphery of the conductive support. Was formed to obtain a conductive roller. Then, both ends of the conductive resin layer were cut off by 10 mm each to set the length of the conductive resin layer in the longitudinal direction to 232 mm.

[2-1. Polishing of conductive layer]
Next, by polishing the surface of the conductive layer under the polishing conditions described in the following polishing condition 1, the diameter of the central portion is 8.5 mm, and each diameter at a position of 90 mm from the central portion to both ends is 8 A conductive member 1 having a crown shape and having a diameter of .44 mm was obtained.
(Polishing condition 1)
As a grindstone, a cylindrical grindstone (manufactured by Teiken Co., Ltd.) having a diameter of 305 mm and a length of 235 mm was prepared. The types of abrasive grains, particle size, degree of coupling, binder, and structure (abrasive grain ratio) abrasive grains are as follows.
-Abrasive grain material: GC (green silicon carbide), (JIS R6111-2002)
-Abrasive grain size: # 80 (average particle size 177 μm JIS B4130)
・ Abrasive grain coupling: HH (JIS R6210)
-Binder: V4PO (Vitrified)
-Abrasive grain structure (abrasive grain ratio): 23 (abrasive grain content 16% JIS R6242)
The polishing conditions are as follows: the rotation speed of the grindstone is 2100 rpm, the rotation speed of the conductive member is 250 rpm, and as a rough cutting process, the grindstone enters the conductive member at a speed of 20 mm / sec and comes into contact with the outer peripheral surface of the conductive member. Invade 24 mm.
As a precision polishing step, the penetration speed is changed to 0.5 mm / sec, and after 0.01 mm penetration, the grindstone is separated from the conductive member to complete the polishing.
As the polishing method, an upper cut method is adopted in which the rotation directions of the grindstone and the conductive member are the same.

The conductive members 2 to 45 were produced in the same manner as the conductive member 1 except that the starting materials shown in Tables 4-1 and 4-2 and 4-3 were changed to the polishing conditions shown below. The mass parts and physical properties of the starting raw material used for producing each conductive member are shown in Table 4-1, Table 4-2 and Table 4-3.

Details of polishing conditions 2 to 5 are shown below.
(Polishing condition 2)
It is the same as the polishing condition 1 except that the penetration speed in the precision polishing step is set to 2.0 mm / sec.
(Polishing condition 3)
It is the same as the polishing condition 1 except that the penetration speed in the precision polishing step is 1.0 mm / sec.
(Polishing condition 4)
It is the same as the polishing condition 1 except that the penetration speed in the precision polishing step is set to 0.2 mm / sec.
(Polishing condition 5)
The same as the polishing condition 1 except that the penetration speed in the precision polishing step was changed to 0.1 mm / sec, the penetration was 0.01 mm, and then polishing was continued for 4 seconds.
The results obtained are shown in Table 5-1 and Table 5-2.

<3. Characteristic evaluation>
Subsequently, the characteristic evaluation for the following items in the examples and comparative examples of the present disclosure will be described below.
<Confirmation of matrix-domain structure>
The presence or absence of the formation of the matrix-domain structure in the conductive layer is confirmed by the following method.
A section (thickness 500 μm) is cut out using a razor so that a cross section perpendicular to the longitudinal direction of the conductive layer of the conductive member can be observed. Next, platinum vapor deposition is performed, and a scanning electron microscope (SEM) (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) is used to take an image at 1000 times to obtain a cross-sectional image.
Further, in order to quantify the obtained captured image, an 8-bit image processing software (trade name: ImageProPlus, manufactured by Media Cybernetics) was used on the fracture surface image obtained by observation with SEM. Grayscale is performed to obtain a monochrome image with 256 gradations. Next, after inverting the black and white of the image so that the domain in the fracture surface becomes white, the binarization threshold is set for the brightness distribution of the image based on the algorithm of Otsu's discriminant analysis method. Obtain a valued image.
With the counting function for the binarized image, the domains are different from each other as described above with respect to the total number of domains existing in the area of 50 μm square and having no contact with the border of the binarized image. Calculate the number percent K of domains that are isolated without connection.
Specifically, the counting function of the image processing software is set so that domains having contacts at the borders at the ends of the binarized images in the four directions are not counted.
The conductive layer of the conductive member is evenly divided into five equal parts in the longitudinal direction, and the section is prepared from a total of 20 points, one point at an arbitrary point from each of the regions obtained by evenly dividing into four equal parts in the circumferential direction. The arithmetic mean value (number%) of K when the above measurement is performed is calculated.
When the arithmetic mean value (number%) of K is 80 or more, the matrix domain structure is evaluated as "yes", and when the arithmetic mean value (number%) of K is less than 80, it is evaluated as "none".

<Measurement method of domain maximum ferret diameter, circumference, and envelope circumference>
The method for measuring the maximum ferret diameter, the peripheral length, and the envelope peripheral length of the domain according to the present disclosure may be carried out as follows.
First, a thin section having a thickness of 1 μm is cut out from the conductive layer of the conductive member using a microtome (trade name: Leica EM FCS, manufactured by Leica Microsystems, Inc.) at a cutting temperature of -100 ° C.
When the length of the conductive layer in the longitudinal direction is L and the thickness of the conductive layer is T, the cutting positions from the conductive layer are the center in the longitudinal direction and L / 4 3 from both ends of the conductive layer toward the center. Place.
Platinum was vapor-deposited on the sections obtained by the above method to obtain thin-film deposition sections. Next, the surface of the vapor-deposited section was photographed with a scanning electron microscope (SEM) (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) at a magnification of 5,000 to obtain a surface image.
The maximum ferret diameter, perimeter, and enveloping perimeter of the domain according to the present disclosure can be obtained by quantifying the image taken above. The obtained fracture surface image is grayscaled in 8-bit using image software (trade name: ImageProPlus, manufactured by Media Cybernetics) to obtain a 256-tone monochrome image. Next, the black and white of the image is inverted and binarized so that the domain in the fracture surface becomes white. Next, the maximum ferret diameter, the peripheral length A, and the envelope peripheral length B were calculated from each of the domains in the image.
In the above measurement, when the thickness of the conductive layer is T, each of the three sections is 15 μm at any three locations in the thickness region from the outer surface to a depth of 0.1 T to 0.9 T, for a total of nine locations. We performed on all four observation areas.
The value of A / B is calculated using the perimeter and the perimeter of the envelope measured for each of the domains observed in each observation region. Of all the observation domains, the number% of the domains satisfying the requirement (B2) was calculated.
Further, for the domain satisfying the requirement (B1) and the requirement (B2), the arithmetic mean value of A / B, which is an index of the uneven shape of the domain, and the arithmetic mean value of the maximum ferret diameter were calculated. The evaluation results are shown in Table 5-2.

<Measurement method of matrix volume resistivity>
The volume resistivity of the matrix is operated in a contact mode using a scanning probe microscope (SPM) (trade name: Q-Scope250, manufactured by Quest Instrument Corporation).
First, a section was cut out at the same position and method as the method for measuring the maximum ferret diameter, the peripheral length, the envelope peripheral length, and the number of domains of the domain. Next, in an environment of temperature 23 ° C. and humidity 50% RH, the section is placed on a metal plate, selected from the parts that are in direct contact with the metal plate, and the parts corresponding to the matrix are brought into contact with the SPM cantilever. Then, a voltage of 50 V was applied to the cantilever, and the current value was measured.
The surface shape of the measurement section was observed with the SPM, and the thickness of the measurement point was calculated from the obtained height profile. The volume resistivity was calculated from the thickness and the current value, and used as the volume resistivity of the matrix.
When the thickness of the conductive layer is T, the measurement positions are 9 at any 3 points in the matrix portion of the thickness region from the outer surface to the depth of 0.1 T to 0.9 T of each section. Measurements were made at the site. The average value was taken as the volume resistivity of the matrix. The evaluation results are shown in Table 5-1.

<Measurement method of DBP absorption amount of carbon black>
The amount of DBP absorbed by carbon black was measured according to JIS K 6217. Further, the manufacturer catalog value may be used.
<Measurement method of arithmetic mean C of distance between conductive carbon black walls in domain, standard deviation σm, coefficient of variation σm / C, and ratio of cross-sectional area of carbon black in domain to domain area>
The arithmetic mean C, standard deviation σm, coefficient of variation σm / C, and the ratio of the cross-sectional area of carbon black contained in the domain to the domain area may be measured as follows.
First, a section is prepared by the same method as in the method for measuring the maximum ferret diameter, area, perimeter, and envelope perimeter of the domain described above.
Platinum was vapor-deposited on the sections obtained by the above method to obtain thin-film deposition sections. Next, the surface of the vapor-deposited section was photographed at a magnification of 20,000 using a scanning electron microscope (SEM) (product name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain a surface image.
The arithmetic mean distance between walls of carbon black and the area of carbon black within the domain can be obtained by quantifying the captured image above. An image analyzer (product name: LUZEX-AP, manufactured by Nireco) is used to grayscale the fracture surface image obtained by observation with SEM to 8-bit grayscale to obtain a 256-tone monochrome image. .. Next, the black and white of the image is inverted and binarized so that the domain in the fracture surface becomes white.
Next, an observation region having a size that can accommodate at least one domain is extracted from the above SEM image. Then, the distance Ci between the wall surfaces of the carbon black in the domain is calculated. Then, the arithmetic mean wall-to-wall distance C is calculated by obtaining the arithmetic mean of the wall-to-wall distance.
The cross-sectional area of the domain and the cross-sectional area of carbon black in the domain are also calculated from the above SEM image.
The domain cross-sectional area and the arithmetic mean wall-to-wall distance and cross-sectional area of carbon black in the domain are obtained as follows. That is, when the thickness of the conductive layer is T, measurement is performed at three locations in an arbitrary domain portion in a thickness region from the outer surface to a depth of 0.1 T to 0.9 T of each of the three sections, for a total of nine locations. Then, it may be calculated from the arithmetic mean of the measured values.
The standard deviation is σm from the distance between the walls of the conductive carbon black in the obtained domain and its arithmetic mean C. Then, the coefficient of variation σm / C is obtained by dividing the standard deviation σm by the arithmetic mean C. Of all the observation domains, the number% of the domains satisfying the requirement (B1) was calculated.
For domains that meet requirements (1) and (2), the arithmetic mean distance C of carbon black, the coefficient of variation σm / C, and the arithmetic mean value of the ratio of the cross-sectional area of carbon black to the cross-sectional area of the domain are calculated. did.
The results are shown in Table 5-2.

<SP value of rubber constituting matrix and domain>
The SP value can be measured using a conventional swelling method. Each of the rubbers constituting the matrix and the domain is separated by using a manipulator or the like, immersed in a solvent having a different SP value, and the degree of swelling is measured from the change in the mass of the rubber. The solubility parameter (HSP) of Hansen can be calculated by analyzing using the value of the degree of swelling for each solvent. Further, by creating a calibration curve using a material having a known SP value, it is possible to calculate with high accuracy. As the value of this known SP value, the catalog value of the material manufacturer can also be used. The evaluation results are shown in Table 5-1.

<Analysis of the chemical composition of the first rubber and the second rubber>
Material identification, first and second rubbers, styrene content in SBR and acrylonitrile content in NBR can be performed using conventional analyzers such as FT-IR and 1H-NMR. .. The evaluation results are shown in Table 5-1.
<Measurement method of impedance of conductive member>
The impedance of the conductive member was measured by the following measuring method.
First, as a pretreatment, a measurement electrode was produced by vacuum-platinum vapor deposition on the conductive member while rotating. At this time, using masking tape, an electrode having a width of 1.5 cm and uniform in the circumferential direction was produced. By forming the electrode, the contribution of the contact area between the measurement electrode and the conductive member can be reduced as much as possible due to the surface roughness of the conductive member. Next, the aluminum sheet was wound around the electrode so as to be in contact with the platinum-deposited film to form the measurement sample shown in FIG.
Then, an impedance measuring device (Solartron 126096W manufactured by Toyo Corporation) was connected from the aluminum sheet to the measuring electrode and to the conductive support.
The impedance was measured at a temperature of 23 ° C. and a relative humidity of 50% at a vibration voltage of 1 Vpp and a frequency of 1.0 Hz to obtain an absolute value of impedance.
The conductive member (length in the longitudinal direction: 232 mm) is divided into five regions in the longitudinal direction into five equal parts, and measurement electrodes are formed at an arbitrary one point from each region, for a total of five points, and the above measurement is performed. went. The average value was taken as the impedance of the conductive member. The evaluation results are shown in Table 5-1.

<Measurement of convex parts derived from domain>
A thin section having a thickness of 1 μm is cut out from the conductive layer of the conductive member using a microtome (trade name: Leica EM FCS, manufactured by Leica Microsystems, Inc.) at a cutting temperature of -100 ° C. At this time, the flakes are made to be a plane perpendicular to the axis of the conductive support.
The cutout position from the conductive layer is L at the length in the longitudinal direction of the conductive layer, and L / 4 from both ends of the conductive layer toward the center in the longitudinal direction.
At this time, in order to confirm the convex shape derived from the domain, care should be taken not to apply any processing to the surface of the conductive member. Next, with respect to the section containing the surface of the conductive member obtained as described above, the surface of the conductive member was subjected to the following conditions using SPM (manufactured by MFP-3D-Origin Oxford Instruments Co., Ltd.). I measured it. By this measurement, the profile of the electric resistance value and the shape profile were measured.
-MFP-3D-Origin manufactured by Oxford Instruments Co., Ltd.
-Measurement mode: AM-FM mode-Explorer: Olympus OMCL-AC160TS
-Resonance frequency: 251.825-261.08 kHz
-Spring constant: 23.59 to 25.18 N / m
・ Scan speed: 0.8 to 1.5Hz
-Scan size: 10 μm, 5 μm, 3 μm
-Target April: 3V and 4V
・ Set Point: All 2V
Next, it is confirmed that the convex portion in the surface shape profile obtained by the above measurement is derived from the domain having higher conductivity than the surroundings in the electrical resistance value profile.
Further, the height of the convex shape is calculated from the profile.
The calculation method is obtained by taking the difference between the arithmetic mean value of the profile of the shape derived from the domain and the arithmetic mean value of the shape profile of the adjacent matrix. The arithmetic mean value is calculated from the measured values of 20 randomly selected convex portions in each of the sections cut out from the above three locations.
The values are shown in Table 5-2.

<Measurement of inter-domain distance Dm on the outer surface of the conductive member>
The inter-domain distance Dm on the outer surface of the conductive member is measured as follows.
When observing the outer surface of the conductive member and measuring Dm, the measurement sample uses a razor with respect to the surface of the conductive member, and is about 2 mm in the circumferential direction and the longitudinal direction of the conductive layer of the conductive member, respectively. A section is cut out at a depth of about 500 μm including the surface of the conductive member in the length and depth directions of the above. The cutout position from the conductive layer is L at the length in the longitudinal direction of the conductive layer, and L / 4 from both ends of the conductive layer toward the center in the longitudinal direction.
Platinum is vapor-deposited on the surface of the obtained section corresponding to the outer surface of the conductive member to obtain a vapor-deposited section. Next, a 5000 times observation image of the surface of the vapor-deposited section is obtained with a scanning electron microscope (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation). For the obtained observation image, a binarized image is obtained by using the image processing software LUZEX (manufactured by Nireco Corporation).
The procedure for binarization is as follows. The observed image is grayscaled with 8 bits to obtain a 256-tone monochrome image. Then, the black and white of the image is inverted and binarized so that the domain in the fracture surface becomes white. Next, the distribution of the distance between the walls of the domain is calculated for the binarized image, and then the arithmetic mean value Dm of the distribution is calculated. The wall-to-wall distance is the shortest distance between adjacent domains.
Specifically, in the image processing software, the measurement parameter is set as the distance between adjacent wall surfaces.
The arithmetic mean value of 10 observation images in which the outer surface of the conductive member is randomly selected is adopted.
The values are shown in Table 5-2.

<4. Image evaluation>
[4-1] Fog Evaluation Using the obtained conductive member, an image was formed as follows, and a fog evaluation was performed to confirm the discharge unevenness of the conductive member. As the electrophotographic image forming apparatus, a Laserjet M608dn (trade name) manufactured by HP, which was modified so that a high voltage could be applied to each of the charging member and the developing member from an external power source (trade name: Model615; manufactured by Trek Japan), was prepared. ..
Next, the conductive member, the modified electrophotographic image forming apparatus, and the process cartridge were left in an environment of 30 ° C. and 80% RH for 48 hours. Then, a conductive member was incorporated as a charging member of the process cartridge. Then, a DC voltage of -1700 V is applied to the conductive support of the conductive member, and a voltage is applied to the developing member so that Vback (voltage obtained by subtracting the voltage applied to the developing member from the surface potential of the photoconductor) becomes -350V. Was applied to output a completely white image.
Since the developer of this electrophotographic image forming apparatus is negatively charged, normally, when a completely white image is output, the developer does not normally transfer to the photoconductor and paper. However, when a positively charged developer is present in the developer, so-called inversion fog occurs in which the positively charged developer is transferred to the overcharged portion on the surface of the photoconductor due to a locally strong discharge from the charged member. To do. As a result, it becomes apparent as fog on paper. This phenomenon is remarkably likely to occur when the Vback is large, such as -350V.
With the electrophotographic image forming apparatus set in this way, a white image was output on the entire surface in an environment of 30 ° C./80% RH, and the amount of fog on the paper was measured. The amount of fog was measured by the following method. (Measurement of fog on paper)
A white image was printed on the entire surface, and any nine points on the paper after the image was formed were observed with an optical microscope at a magnification of 500, and the developing agents present in the observation area of 400 μm square were counted, and the number was taken as the amount of fog on the paper. When the amount of fog on the paper is 60 or less, a good image with less fog can be obtained. More preferably, the number is 50 or less. The evaluation results are shown in Table 5.

<Examples 2 to 5>
Conductive members 2 to 5 were produced in the same manner as in Example 1 except that the polishing conditions of Example 1 were changed to polishing conditions 2 to 5, and the same evaluation as in Example 1 was performed. The results of each evaluation in Examples 2 to 5 are shown in Table 5-1 and Table 5-2.

<Examples 6 to 45>
Similar to the conductive member 1 of Example 1, the conductive members 6 to 45 were used as charging rollers, and the same evaluation as in Example 1 was performed. The results of each evaluation in Examples 6 to 45 are shown in Tables 5-1 and 5-2.

<Example 46>
The conductive member 1 of Example 1 was subjected to an ultraviolet treatment as a surface treatment to prepare a conductive member 46. Other than that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 5-1 and Table 5-2.
(Surface UV treatment)
While rotating the conductive member, the surface of the conductive member was irradiated with ultraviolet rays by a low-pressure mercury lamp (manufactured by Harison Toshiba Lighting) for 5 minutes. The low-pressure mercury lamp was mainly ultraviolet rays having a wavelength of 254 nm, and the integrated ultraviolet light amount at this time was about 10,000 mJ / cm ² (ultraviolet intensity was 35 mW / cm ² ).

<Comparative example 1>
Table 6 shows a carbon masterbatch for domain formation (CMB), a rubber composition for matrix formation (MRC), and a rubber composition for forming a conductive layer using the same round bar as in Example 1 as the conductive support. A conductive layer was produced in the same manner as in Example 1 except that the matrix-forming MRC was not used, and a surface layer was formed on the conductive layer as described below to produce a conductive roller.

The raw materials in Table 6 above are as follows.
-CG102: Epichlorohydrin rubber (EO-EP-AGE ternary compound) (Product name: Epichromer CG102, SP value: 18.5 (J / cm ³ ) 0.5, manufactured by Osaka Soda Co., Ltd.)
-LV: Quaternary ammonium salt (trade name: ADEKA Sizer LV70, manufactured by ADEKA CORPORATION)
-P202: Aliphatic polyester plasticizer (trade name: Polysizer P-202, manufactured by DIC Corporation)
・ MB: 2-Mercaptobenzimidazole (trade name: Nocrack MB, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
・ TS: Tetramethylthiuram monosulfide (trade name: Noxeller TS, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
-DM: Di-2-benzothiazolyl disulfide (DM) (Product name: Noxeller DM-P (DM), manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
-EC600JD: Ketjen Black (Product name: Ketjen Black EC600JD, manufactured by Lion Specialty Chemicals Co., Ltd.)
-PW380: Paraffin oil (trade name: PW-380, manufactured by Idemitsu Kosan Co., Ltd.)
25-B-40: 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne (trade name: Perhexa 25B-40, manufactured by Nippon Oil Co., Ltd.)
TAIC-M60: Triallyl isocyanurate (trade name: TAIC-M60 manufactured by Mitsubishi Chemical Corporation)
Then, according to the following method, a surface layer was further provided on the conductive layer of the conductive layer roller obtained above to manufacture a two-layer conductive member C1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 8.
First, methyl isobutyl ketone was added to a caprolactone-modified acrylic polyol solution to adjust the solid content to 10% by mass. A mixed solution was prepared using the materials shown in Table 7 below with respect to 1000 parts by mass of this acrylic polyol solution (100 parts by mass of solid content). At this time, the mixture of block HDI and block IPDI was "NCO / OH = 1.0".

Next, 210 g of the mixed solution and 200 g of glass beads having an average particle size of 0.8 mm were mixed in a 450 mL glass bottle and pre-dispersed for 24 hours using a paint shaker disperser to prepare a paint for forming a surface layer. Obtained.
The conductive roller obtained above was dipped in the coating material for forming a surface layer with its longitudinal direction in the vertical direction, and coated by a dipping method. The immersion time of the dipping coating was 9 seconds, and the pulling speed was 20 mm / sec at the initial speed and 2 mm / sec at the final speed, during which the speed was changed linearly with time. The obtained coated product was air-dried at room temperature for 30 minutes, then dried in a hot air circulation dryer set at 90 ° C. for 1 hour, and further dried in a hot air circulation dryer set at 160 ° C. for 1 hour.

In this comparative example, the conductive member C1 has a two-layer structure consisting of an ionic conductive layer and an electron conductive surface layer, but the surface layer does not have a matrix-domain structure. For this reason, the dispersion uniformity of the conductive particles is lowered, electric field concentration is generated, and an excessive charge easily flows in the conductive path. Therefore, the number of fog on paper was 95.
<Comparative example 2>
The conductive member C2 was produced and evaluated in the same manner as in Example 1 except that the domain forming CMB was changed to that shown in Table 6 and the matrix forming MRC was not used. The evaluation results are shown in Table 8.
In this comparative example, since the conductive layer of the conductive member C2 does not have a matrix-domain structure and is composed of only a domain material, electric field concentration occurs in the conductive layer and excessive charges easily flow in the conductive path. It is composed. Therefore, the fog on the paper was 121, and a remarkable fog image was confirmed.

<Comparative example 3>
The conductive member C3 was produced and evaluated in the same manner as in Example 1 except that the domain forming CMB and the matrix forming MRC were changed to those shown in Table 6. The evaluation results are shown in Table 8.
In this comparative example, the conductive member C3 has a domain and a matrix, but the number of domains satisfying the requirements (B1) and (B2) is small, and the domain shape is distorted, so that the electric field concentration derived from the domain shape is concentrated. Excessive transfer of charge occurs due to. Therefore, the number of fog on paper was 103.

<Comparative example 4>
The conductive member C4 was produced and evaluated in the same manner as in Example 1 except that the domain forming CMB and the matrix forming MRC were changed to those shown in Table 6. The evaluation results are shown in Table 8.
In this comparative example, since the conductive particles are added to the matrix of the conductive member C4, the volume resistivity is low, and the conductive member has a single conductive path. The structure is such that electric field concentration occurs and excessive charge easily flows in the conductive path. Therefore, the number of fog on paper was 110.

<Comparative example 5>
A conductive member C5 was produced and evaluated in the same manner as in Example 1 except that the domain forming CMB and the matrix forming MRC were changed to those shown in Table 6. The evaluation results are shown in Table 8.
In this comparative example, the conductive member C5 has a matrix-domain structure, but has a high volume resistivity because no conductive agent is added to the domain, and the matrix has a volume resistivity because conductive particles are added. The rate is low. That is, since the conductive member has a single conductive path, electric field concentration occurs in the conductive layer, and an excessive charge easily flows through the conductive path. Therefore, the number of fog on paper was 105.

<Comparative Example 6>
A conductive member C6 was produced and evaluated in the same manner as in Example 1 except that the domain forming CMB and the matrix forming MRC were changed to those shown in Table 6. The evaluation results are shown in Table 8.
In this comparative example, the conductive member C6 does not have a matrix-domain structure, but has a co-continuous structure of the conductive phase and the insulating phase. That is, since the conductive member has a single conductive path, electric field concentration occurs in the conductive layer, and an excessive charge easily flows through the conductive path. Therefore, the number of paper fog was 107.

<Comparative Example 7>
A conductive member C7 was produced and evaluated in the same manner as in Example 1 except that the domain forming CMB and the matrix forming MRC were changed to those shown in Table 6. The evaluation results are shown in Table 8.
In this comparative example, the conductive member C7 has a matrix-domain structure, but the number of domains satisfying the requirements (B1) and (B2) is 80% or less. It is considered that the reason for this is that the amount of carbon black added to the domain was small and the amount of carbon gel could not be sufficiently formed, so that the domain shape did not become circular and the unevenness and aspect ratio became large. As a result, electric field concentration occurs in the conductive layer, and an excessive charge easily flows in the conductive path. Therefore, the number of fog on paper was 97.

<Comparative Example 8>
A conductive member C8 was produced and evaluated in the same manner as in Example 1 except that the domain forming CMB and the matrix forming MRC were changed to those shown in Table 6. The evaluation results are shown in Table 8.
In this comparative example, the conductive member C8 has a matrix-domain structure, but the number of domains satisfying the requirements (B1) and (B2) is 0%. The reason for this is considered to be the following two points.
(1) Since silica having reinforcing properties is added, the viscosity of the carbon masterbatch forming the domain is large, and the viscosity difference from the rubber composition for matrix formation is large.
(2) The SP value difference between the first rubber and the second rubber is large.
Therefore, it is considered that the domain shape does not become a circular shape, and the unevenness and the aspect ratio become large. As a result, electric field concentration occurs in the conductive layer, and an excessive charge easily flows in the conductive path. Therefore, the number of fog on the paper was 132, and remarkable fog was confirmed.

<Comparative Example 9>
Example 1 except that the domain-forming CMB was changed to rubber particles obtained by heat-vulcanizing the conductive layer-forming rubber of Comparative Example 2 alone and then freeze-milled, and the matrix-forming MRC was changed to that shown in Table 6. The conductive member C9 was manufactured and evaluated in the same manner as in the above. The evaluation results are shown in Table 8.
In this comparative example, the conductive member C9 has a matrix-domain structure, but the number of domains satisfying the requirements (B1) and (B2) is 0%. The reason for this is that the large-sized and anisotropic conductive rubber particles formed by freeze-milling are dispersed. As a result, electric field concentration occurs in the conductive layer, and an excessive charge easily flows in the conductive path. Therefore, the number of fog on the paper was 126, and remarkable fog was confirmed.

1 Conductive member 2 Conductive support 3 Conductive layer 3a Matrix 3b Domain 3c Conductive particles

Claims (16)

A support with a conductive outer surface and
An electrophotographic conductive member having a conductive layer provided on the outer surface of the support.
The conductive layer has a matrix containing a crosslinked product of the first rubber and a plurality of domains dispersed in the matrix.
The domain contains a second rubber crosslink and conductive particles.
At least a part of the domain is exposed on the outer surface of the conductive member, and a convex portion is formed on the outer surface of the conductive member.
The outer surface of the conductive member is composed of the matrix and the domain exposed on the outer surface of the conductive member.
A platinum electrode is provided directly on the outer surface of the conductive member, and the amplitude is 1 V and the frequency is 1.0 Hz between the outer surface of the support and the platinum electrode in an environment of a temperature of 23 ° C. and a relative humidity of 50%. The impedance when the AC voltage is applied is 1.0 × 10 ³ Ω or more and 1.0 × 10 ⁸ Ω or less, and
The length of the conductive layer in the longitudinal direction is L, the thickness of the conductive layer is T, and the center of the conductive layer in the longitudinal direction and L / 4 from both ends of the conductive layer toward the center. When observation regions of 15 μm square are placed at any three locations in the thickness region from the outer surface of the conductive layer to a depth of 0.1 T to 0.9 T for each of the cross sections of the conductive layer in the thickness direction. In addition, 80% or more of the domains observed in each of the nine observation regions satisfy the following requirements (1) and (2):
Requirement (1) The ratio of the cross-sectional area of the conductive particles contained in the domain to the cross-sectional area of the domain is 20% or more;
Requirement (2) When the perimeter of the domain is A and the perimeter of the domain is B, the A / B must be 1.00 or more and 1.10 or less. The conductive member according to claim 1, wherein the volume resistivity ρm of the matrix is 1.0 × 10 ⁸ Ωcm or more and 1.0 × 10 ^{17 Ωcm or less.} The conductive member according to claim 1 or 2, wherein the average of the maximum ferret diameter Df of the domain satisfying the requirements (1) and the requirements (2) is in the range of 0.1 μm or more and 5.0 μm or less. The conductive member according to any one of claims 1 to 3, wherein the ratio of the cross-sectional area of the conductive particles to the cross-sectional area of the domain in the requirement (1) is 25% or more and 30% or less. The conductive member according to any one of claims 1 to 4, wherein the conductive particles are conductive carbon black. The DBP absorption of the conductive carbon ^black, conductive member according to claim 5 is 40 cm 3/100 g or more 80 cm ^3/100 g or less. The arithmetic mean distance C between the walls of the conductive carbon black contained in each of the domains satisfying the requirements (1) and (2) is 110 nm or more and 130 nm or less, and the distance between the walls of the conductive carbon black is 110 nm or more. The conductive member according to claim 5 or 6, wherein σm / C is 0.0 or more and 0.3 or less when the standard deviation of the distance is σm. Claim that the difference between the absolute values of the solubility parameters of the first rubber and the second rubber is 0.4 (J / cm ³ ) ^0.5 or more and 4.0 (J / cm ³ ) ^0.5 or less. The conductive member according to any one of 1 to 7. The conductive member according to any one of claims 1 to 8, wherein the height of the convex portion is 50 nm or more and 200 nm or less. The conductive member according to any one of claims 1 to 9, wherein the arithmetic mean value Dm of the distance between the wall surfaces of the domain causing the convex portion is 2.00 μm or less. The conductive member according to any one of claims 1 to 10, wherein the volume resistivity ρm of the matrix is 1.0 × 10 ¹⁰ Ωcm or more and 1.0 × 10 ^{17 Ωcm or less.} The conductive member according to any one of claims 1 to 11, wherein the volume resistivity ρm of the matrix is 1.0 × 10 ¹² Ωcm or more and 1.0 × 10 ^{17 Ωcm or less.} A process cartridge for electrophotograph, which is a process cartridge that can be attached to and detached from the main body of the electrophotographic image forming apparatus and includes the conductive member according to any one of claims 1 to 13. The process cartridge according to claim 13, further comprising the conductive member as a charging member. An electrophotographic image forming apparatus comprising the conductive member according to any one of claims 1 to 12. The electrophotographic image forming apparatus according to claim 15, further comprising the conductive member as a charging member.

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