JP2022056021A - Conductive member, process cartridge, and electrophotographic image forming apparatus - Google Patents

Abstract

To provide a conductive member CM that can prevent fogging.SOLUTION: A CM comprises: a conductive support; and a conductive layer CL that has a matrix Mt including a cross-linked product of first rubber and a plurality of domains Dm in the Mt. The Dm includes a cross-linked product of second rubber and conductive particles, and some of the Dm are exposed to an outer surface of the CM to cause first convex parts. The outer surface of the CM is composed of the Mt and the exposed Dm. The CL further includes insulating resin particles IP, and some of the IP causes second convex parts on the outer surface of the CM. When the length of the longitudinal direction of the CL is L and the thickness of the CL is T, and for cross-sections in the thickness direction at three points including the center in the longitudinal direction of the CL and L/4 directed from both ends to the center, when nine observation areas with 20-μm sides are placed at arbitrary three points in the thickness direction at a depth of 0.1-0.9 T, 80% by number or more of the Dm in the observation areas satisfy the following requirements. 1: the cross-sectional ratio of the conductive particles included in the Dm to the cross-section of the Dm is 20% or more. 2: when the peripheral length of the Dm is A and the envelope peripheral length of the Dm is B, A/B is 1.00-1.10.SELECTED DRAWING: Figure 2

Description

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

In an image forming apparatus adopting an electrophotographic method (hereinafter referred to as 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. Further, 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 more uniformly charged to abutting objects such as a photoconductor, an intermediate transfer body, and a printing medium. In addition, it is equipped with an energy-saving system that brings cleaning members such as cleaning blades into contact with light pressure, and a resource-saving simultaneous development cleaning system that does not have a waste toner box, and can output high-quality images for a long period of time. There is a demand for an electrophotographic image forming apparatus. These systems require a charging member that can maintain uniform charging without deteriorating uniform charging even after long-term use of more than several hundred thousand sheets, in addition to being a system in which more transfer residual toner rushes into the charging member than before. be.

Patent Document 1 describes a rubber composition having a sea-island structure including a polymer continuous phase made of an ionic conductive rubber material and a polymer particle phase made of an electronically conductive rubber material. The electronically conductive rubber material is mainly composed of a raw material rubber A having a volume specific resistance 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.

JP-A-2002-3651 WO2019 / 203225

One aspect of the present disclosure is to provide a conductive member for an electrophotographic that can stably suppress the occurrence of "fog" on an electrophotographic image for a longer period of time.
Another aspect of the present disclosure is to provide a process cartridge that contributes to the stable formation of high-quality and long-life 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 for a long period of time.

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 first 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.
The conductive layer further contains insulating resin particles, and at least a part of the resin particles causes a second convex portion on the outer surface of the conductive member.
When the conductive member is pressed against the transparent flat plate with a load applied to the transparent flat plate of 500 g, the second convex portion and the transparent flat plate come into contact with each other in the nip of the conductive member and the transparent flat plate. The distance of the space formed by the above is 3 μm or more and 30 μm or less, and there is no contact point between the first convex portion and the transparent flat plate in the nip.
A platinum electrode is directly provided 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 20 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 in the thickness direction of the conductive layer. In addition, 80% or more of the domains observed in each of the nine observation regions satisfy the following requirements (B1) and (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.

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 provided with 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 capable of suppressing fog even when used for a long period of time by increasing the charging bias.
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 and long-life 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 for a long period of time.

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, (a) shows the matrix-domain structure and the first convex part, (b) is the first. The convex portion of 2 is shown. 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. It is the schematic (a) and the enlarged view (b) of the device which measures the distance in the nip part of a conductive member and a photoconductor in an alternative manner.

The present inventors have attempted to obtain an electrophotographic image having a higher contrast in 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 an electrophotographic image when the charging bias is increased. In the process, attention was paid to the role of the polymer particle phase made of an 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 generation 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 charged 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 fog would occur in the electrophotographic image.
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, as a result of repeated studies based on such recognition, the support having a conductive outer surface and the conductive layer provided on the outer surface of the support are provided, and the following requirements (A) and the following requirements (A) and It has been found that, according to the conductive member satisfying the requirement (B), fog on the electrophotographic image can be effectively suppressed even when a high charging bias is applied (Patent Document 2).

Requirement (A):
The conductive layer has a matrix containing the crosslinked product of the first rubber and a plurality of domains (sea-island structures) dispersed in the matrix, and the domains are the crosslinked product of the second rubber and the conductivity. Contains particles. Further, a platinum electrode is directly provided 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 points L / 4 from both ends of the conductive layer toward the center. 20 μm square observation regions are placed 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 (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.

Each requirement will be described below.
Regarding requirement (A):
The requirement (A) represents the degree of conductivity of the conductive layer. The conductivity of the conductive member is such that the impedance at ¹ Hz is in the range of 103 Ω or more and ¹⁰⁸ Ω or less. By setting the impedance to ¹⁰³ Ω or more, it is possible to suppress an excessive increase in the amount of discharge current, and as a result, it is possible to prevent the occurrence of potential unevenness due to abnormal discharge. Further, by setting the impedance to ¹⁰⁸ Ω or less, it is possible to suppress a charge shortage due to a shortage of the total amount of discharge charge.

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, impedance measurement can be performed without being affected by fluctuations in the outer diameter of the charged 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 charged 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, impedance measurement is performed by connecting the aluminum sheet 34 to the measurement electrode 33 and the conductive support 31 in an impedance measuring device (Solartron 126609W type dielectric impedance measuring system manufactured by Toyo Technica Co., Ltd., not shown).
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 the absolute value of the impedance is obtained.
The conductive member is divided into 5 equal parts in the longitudinal direction, and the above measurement is performed 5 times in total, once from each region. The average value is taken as the impedance of the conductive member.

Requirements (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 outer peripheral surface of the domain had irregularities and that the domain had a shape with a high aspect ratio. As a result of diligent studies, the high voltage of the above-mentioned problem can be obtained by making the shape of the domain closer to a perfect circular shape with less unevenness, that is, by making the domain closer to a spherical shape. It was found that the fog at the time of application can be dramatically suppressed.
As described above, in the conductive domain / non-conductive matrix configuration in which only the domain has conductivity, a plurality of domains carry the conductivity inside the conductive member, and charge is transferred between the domains. .. When a convex portion is present in a domain, an electric field is concentrated on the convex portion, and charge transfer between the convex portion and an adjacent domain is likely to occur in the convex portion, and an excessive current flows in the convex portion. That is, the electric charge easily flows from the convex portion of the domain to the domain close to the convex portion. Due to this phenomenon, a strong electric discharge is locally generated from the surface of the conductive member, which causes potential unevenness of the photoconductor when the conductive member is used as a charging member.

That is, it is effective to make the cross-sectional shape of the domain appearing in the cross-sectional shape of the conductive layer in the thickness direction as close as possible to a perfect circular shape.
Regarding the requirement (B1), the present inventors have found that when focusing on one domain, 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. As the number of domains closer to the sphere increases, the concentration point of electron transfer between domains can be reduced. 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 area of the cross section 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, which can be a concentration point for sending and receiving electrons.
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. As 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 in 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. The envelope circumference is defined as the circumference of the convex hull of the domain. Specifically, for example, as shown in FIG. 5, it is the peripheral length (broken line 52) when the convex portions of the domain 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 found that 80% or more of the domains of the conductive layer cross section observed in each of the nine observation regions are conductive when the requirements (A) and (B) are satisfied 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 0.1T to 0.9T 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 domain existing in the range. ..

Here, the present inventors further examined the sticking of toner that can change the charging performance of the electrophotographic member according to Patent Document 2 over time. That is, the toner remaining on the photoconductor even after the transfer process (hereinafter, also referred to as “transfer residual toner”) is charged with the same polarity (positive electrode property) as the voltage polarity of the transfer process. many. Therefore, the transfer residual toner that reaches 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 a “first convex portion”) (hereinafter, also referred to as a requirement (C)) is 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 first convex portion, the transfer residual toner that reaches the nip portion between the charging member and the photosensitive drum is physically the first convex portion. Easy to contact. In addition, the positively charged transfer residue toner is electrostatically attracted to the first convex portion accumulating the negative charge. Due to these actions, the contact probability between the transfer residual toner and the first convex portion is increased. Then, a negative charge is injected into the transfer residual toner that comes into contact with the first convex portion, and the toner is negatively charged. Further, the domain that has transferred the charge to the transfer residual toner by contact with the transfer residual toner can be stably and continuously supplied with 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 made negative.

Specifically, the height of the first 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 first convex portion to 50 nm or more, the contact opportunity between the conductive first convex portion and the reversing toner can be increased. Further, by setting the height of the first convex portion 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 caused by the first convex portion is formed in the discharge region, the height of the first convex portion is preferably 200 nm or less.

Further, the arithmetic mean value Dm (hereinafter, also simply referred to as “inter-domain distance Dm”) of the distance between the wall surfaces of the domains on the outer surface of the conductive member 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 first convex portion and the reversing toner can be increased.

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

Furthermore, the present inventors have studied a configuration for stabilizing the performance of the electrophotographic member according to Patent Document 2 as a charging member for a longer period of time. As a result, in addition to the above requirements (A), (B) and (C), the physics of the transfer residual toner to the convex portion (first convex portion) formed by the domain exposed on the outer surface of the conductive member. It was found that it is effective to suppress the sticking.
For example, the energy-saving electrophotographic image forming apparatus in which a cleaning member such as a cleaning blade is brought into contact with the photosensitive drum with less pressure and the waste toner box are eliminated, and the photosensitive drum is cleaned at the same time as development. In the electrophotographic image forming apparatus, more transfer residual toner can reach the charged member. In the use of an electrophotographic image forming apparatus for a long period of time in which the number of printed sheets exceeds several hundred thousand, the number of times of contact between the charging member and the photosensitive drum increases, so that the transfer residual toner is used between the charging member and the photosensitive drum. It is crushed at the contact portion and strongly adheres to the surface of the charged member. Even with the electrophotographic member according to Patent Document 2, it has been difficult to completely prevent the adhesion of the transfer residual toner as a result of long-term use as described above. When the transfer residual toner adheres to the first convex portion exposed on the outer surface of the conductive member, which has the function of uniform discharge, the discharge from the first convex portion is hindered and is uniform. The flow of electric charge in the supposed conductive layer may be stagnant and concentrated on the first convex portion to which the transfer residual toner is not fixed. As a result, a portion where the discharge is locally strong may occur, and fog may occur in the electrophotographic image.

Therefore, in the conductive member according to the present disclosure, the present inventors have described a convex portion derived from an insulating resin particle (hereinafter, hereinafter) on the outer surface of the conductive member, in addition to the first convex portion derived from the domain. , Also referred to as a "second convex portion"), and has a configuration capable of preventing the transfer residual toner from sticking to the first convex portion.

A space is formed by the second convex portion in the nip portion between the surface of the conductive member and the photosensitive drum, and a value obtained by the following method can be adopted for the distance. That is, when the transparent flat plate is brought into contact with the conductive member and the load on the transparent flat plate is pressed with 500 g (the upper limit of the load on the charged member), the second is in the nip of the conductive member and the flat plate. The height of the space formed by the contact between the convex portion and the transparent flat plate is obtained. In the present disclosure, this distance is 3 μm or more and 30 μm or less. Further, there is no contact point between the first convex portion and the transparent flat plate in the nip, and the contact is made only at the second convex portion. As a result, it is possible to prevent the toner from sticking to the first convex portion.
As the transparent flat plate, any material can be used as long as it is a transparent flat plate that allows the second convex portion to be observed through the material and is not deformed by the above-mentioned pressing. Further, the thickness is such that the above-mentioned pressing can be stably applied, and can be used as long as the transparency is not affected. Typically, it is an inorganic transparent material, and for example, an optical glass plate such as BK7 or synthetic quartz can be used. Optical glass has high smoothness and is suitable for such measurements.

The details of measuring the distance between the surface of the conductive member and the nip portion of the photosensitive drum by the second convex portion will be described later, but as a transparent flat plate with respect to the conductive member as shown in FIG. 9A. This is done using a transparent glass plate 92. Further, a predetermined load can be applied using a jig having a structure capable of measuring the load, and the measurement can be performed from the glass plate 92 side by a device capable of scanning a height profile such as a laser microscope.

When the distance between the nip portion between the conductive member and the photosensitive drum is 3 μm or more, the destruction of the transfer residual toner can be suppressed at the contact portion. Further, a height of 5 μm or more is preferable because it is possible to form a gap in which the transfer residual toner is not deformed. On the other hand, since unevenness of discharge derived from the first convex portion is formed in the discharge region, the space distance needs to be 30 μm or less.

Further, the second convex portion is insulating so as not to interfere with the uniformity of the electric field due to the domain in the conductive phase and to prevent charge from being injected from the second convex portion into the photosensitive drum. Here, the insulating property of the second convex portion indicates that the volume resistivity ρp is 1.0 × 10 ¹⁰ Ωcm or more. The upper limit is not particularly limited, but is preferably 1.0 × 10 ¹⁷ Ωcm or less.

In the second convex portion on the order of micrometer, since the distance from the photosensitive drum is short, the amount of discharge is larger than that in the place other than the second convex portion, and the surface potential of the photosensitive drum is locally increased. It becomes high and can cause fog. Therefore, the initial conductive member that has not been subjected to the durability test tends to have more fog than the conductive member that does not have the second convex portion. However, for the deterioration of fog caused by toner sticking due to long-term use, a means for suppressing sticking of transfer residual toner by a second convex portion is extremely effective.

Further, in order to avoid promoting toner adhesion by scraping off the transfer residual toner when the conductive member and the photosensitive drum slip and have a relative speed at the time of starting rotation or the like, the second convex portion is provided. It is preferably present on the outer surface of the conductive member in the form of dots.

<Transparent flat plate>
In the present disclosure, as the transparent flat plate, for example, a glass plate having a material: BK7, a surface accuracy: a double-sided optically polished surface, a parallelism of 1 minute or less, and a thickness of 2 mm is used.

<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, an outer circumference of the support 2, that is, a conductive layer formed on the outer surface of the support.
FIG. 2 shows an enlarged 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. Further, 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 the first convex portion 3-1 on the outer surface of the conductive member.
Further, FIG. 2B shows a cross-sectional view at a lower magnification (for example, a magnification of 1/30) than that of FIG. 2A. As shown in FIG. 2B, the conductive layer 3 has the resin particles 3c added to the conductive layer 3, and the second convex portion 3 derived from the resin particles for forming a gap with the photosensitive drum. -2 is formed. The second convex portion 3-2 shows a case where the surface is polished and flattened for exposure as described later, but the second convex portion 3-2 is completely flattened. It is not always the case, and it may remain a spherical surface. Further, the area of the flat surface also differs due to the difference in the protrusion method, but the maximum height is controlled by this polishing. In FIG. 2B, the first convex portion 3-1 due to the domain 3b is omitted because the height is lower than that of the second convex portion 3-2. The first convex portion 3-1 is preferably formed on the outer surface of the conductive layer other than the second convex portion 3-2 so as not to form a contact point at the nip portion with the transparent flat plate. The first convex portion 3-1 may be formed on a part of the surface of the second convex portion 3-2 (such as a peripheral portion that does not come into contact with the transparent flat plate) as long as the effect of the present disclosure is not impaired.

<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 to obtain a suitable contrast between the conductive phase and the insulating phase. The fractured surface is formed and the pretreated flakes can be observed with a laser microscope, a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

The conductivity of the conductive member may be evaluated by measuring the impedance at 1 Hz, and specifically, the impedance at ¹ Hz is preferably in the range of 103 Ω or more and ¹⁰⁸ Ω or less. By setting it to 103 Ω or more ^, the amount of discharge current becomes excessive, and as a result, it is possible to prevent the occurrence of potential unevenness due to abnormal discharge. By setting it to ¹⁰⁸ Ω or less, it is possible to suppress a charge shortage due to a shortage of the total amount of discharge charge.

<Conductive support>
As the material constituting the support, a material known in the field of the conductive member for electrophotographic and a material that can be used as the conductive member 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 electric plating 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 the 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 1.0 × ¹⁰⁸ Ωcm or more, the influence of the conductivity of the matrix on the transfer of charges between the conductive domains can be suppressed. In particular, when the matrix is highly conductive (low volume resistivity) and exhibits ionic conductivity, the matrix excessively facilitates the transfer of charge between the 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 1.0 × ¹⁰⁸ Ωcm or more.
When the volume resistivity ρm is 1.0 × 10 ¹⁷ Ωcm or less, the required conductivity can be obtained for 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 resistance ρm of the matrix, for example, a slice 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 in the matrix in the slice. 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. 6B, the flakes are cut out to include at least a portion of a YZ plane (eg, 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 opposite to the ground surface of the thin piece, 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 and 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 piece 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, after cross-linking, the first rubber 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 includes, if necessary, a filler, a processing aid, a vulcanization aid, a vulcanization accelerator, and a vulcanization accelerator commonly used as a compounding agent for rubber. , Vulcanization retarder, anti-aging agent, softener, dispersant, colorant and the like may be added.

<Domain>
The domain is conductive and contains a second rubber crosslink and conductive particles. Here, conductivity means that the volume resistivity is less than 1.0 × ¹⁰⁸ Ωcm.

<Second rubber>
Specific examples of the second rubber include, for example, 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), kluruprene 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 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 electron conductive agent such as graphite. Further, if necessary, two or more kinds of these conductive particles may be appropriately mixed and used.
As for the conductive particles blended in the domain, the ratio of the cross-sectional area of the conductive particles to the cross-sectional area of the domain is at least 20% or more, preferably 25% or more and 30% or less, as specified in the requirement (B1). The addition amount 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 will be described later, carbon black having a DBP absorption amount of 40 cm ^3/100 g or more and 80 cm ^3/100 g or less can be particularly preferably used.

<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 toward 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 three cross sections in the thickness direction of the conductive layer as shown in FIG. 6 (b), 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 20 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 20 μm square region of the cross section in the thickness direction of the conductive layer need to satisfy the following requirements (B1) and (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 minimum ratio of the domain circumference of the requirement (B2) to the envelope circumference of the domain is 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 is present 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 vertical 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 representing 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. This is also because the miniaturization of the conductive domain makes it possible to miniaturize the discharge and improve the image quality.

<Measurement method of domain maximum ferret diameter, area, circumference length, envelope circumference length, and number of domains> The measurement method of domain maximum ferret diameter, area, circumference length, envelope circumference length, and number of domains is as follows. It should be carried out. 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 to obtain a suitable 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 by SEM at a magnification of 1,000 to 100,000.
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, an 8-bit grayscale image is obtained by using image processing software (trade name: ImageProPlus, manufactured by Media Cybernetics) or the like on the fracture surface image obtained by observation with SEM, and a 256-tone monochrome image is obtained. 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 domain groups in the image. For the above measurement, the sample is L / 4 toward the center of the conductive layer in the longitudinal direction and from both ends of the conductive layer to the center, where L is the length of the conductive layer in the longitudinal direction of the conductive member. 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 indicates a direction parallel to the longitudinal direction (axial direction) of the conductive member, and the Y-axis and the Z-axis indicate a direction perpendicular to the axial direction of the conductive member.

FIG. 6A shows an image diagram in which the conductive member is cut out 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 is in contact with the photoconductor drum and rotates and is discharged when passing through the gap with the photoconductor drum, the cross section 62a parallel to the XZ plane 62 is simultaneously discharged at a certain timing. 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 is locally increased and becomes a fog. An evaluation that correlates with the surface potential of the photosensitive drum that forms 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 in which the discharge occurs at the same time in a certain moment such as the cross section 62a. Evaluation in (63a to 63c) is necessary. 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 0.9T. Measurements may be performed at a total of 9 locations when 20 μm square observation areas are placed at any of the 3 locations.

<Control of domain shape>
The formation of a domain 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 the deformation of the domain, so that the resistance fluctuation is reduced.
The present inventors have investigated a method for making the cross-sectional shape of a domain circular, that is, making the domain shape closer 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 the number of different molecules surrounding them is greater than inside the matrix. In order to reduce this interfacial free energy, it is considered that the interfacial tension that tries to make the interface smaller works, and the domain approaches a spherical shape (a 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 domain

1. 1. Difference in interfacial tension between domain and matrix Generally, when two kinds of polymers are mixed, phase separation occurs. This phenomenon occurs because the interaction between the same polymers is stronger than the interaction between different macromolecules, 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, 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 difference in interfacial tension between the domain and the matrix is considered to correlate with the difference in SP value between the domain and the rubber material constituting the matrix, it can be controlled by selecting the raw material rubber of the matrix 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 separation structure can be formed, and the maximum ferret diameter of the domain can be reduced.

2. 2. Viscosity ratio of domain and matrix The closer the viscosity ratio of domain and matrix (ηd / ηm) is to 1, 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 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 viscosity 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 rubber may be used instead.

3. 3. The larger the shear rate during mixing / the amount of energy during shearing, and the larger the shear rate during mixing / the amount of energy during shearing, the smaller the maximum ferret diameter of the domain can be. 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, increasing the energy during shearing can be achieved 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 coalescence between the domain and the 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 content ratio of acrylonitrile or styrene is analyzed for the rubber constituting the matrix and the domain 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, as with SBR and NBR, the isomer content ratio can be analyzed by Py-GC, solid-state NMR, or the like, 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 the 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 chemisorption of rubber molecules 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 it is sufficient to increase the amount of carbon black that functions as an adsorbent.
We focused on the amount of DBP absorbed as an index for blending a large amount of carbon black in the domain. The amount of DBP absorbed (cm ^3/100 g) is the volume of dibutyl phthalate (DBP) that 100 g of carbon black can adsorb, and is measured according to JIS K 6217.
Generally, carbon black has a tufted high-order structure in which primary particles having an average particle size of 10 nm or more and 50 nm or less are aggregated. This tufted higher-order structure is called a structure, and its degree is quantified by the amount of DBP absorbed (cm ^3/100 g).
In general, carbon black with a well-developed structure has high reinforcing properties against rubber, the uptake of carbon black into rubber is poor, and the share torque during kneading is very high, so it is difficult to fill it with high filling. ..
As the conductive carbon black used in the present disclosure, it is preferable to use carbon black having a DBP absorption amount of 40 cm ^3/100 g or more and 80 cm ^3/100 g or less. By setting the amount of DBP absorbed to the above range, the amount of carbon gel can be increased by blending a large amount of carbon black with the 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, so that the carbon black is less agglomerated and the carbon book itself has an uneven shape. Less is. Therefore, it is easy to round the domain shape. That is, it is easy to make a spherical 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 aggregated state. Originally, carbon black has a concavo-convex shape because it has a tufted high-order structure as described above, but when they aggregate, it tends to become a mass having a larger uneven structure. When this carbon black aggregate 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 (hereinafter, also referred to as "arithmetic mean wall distance C"), which is the arithmetic mean of the distance between adjacent carbons, 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 arithmetic mean wall distance 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 repeated image output is suppressed. Furthermore, the amount of carbon gel exhibiting cross-linked 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 in a spherical shape during molding. As a result, changes in the distance between domains due to electric field concentration and deformation of the domain protrusions are suppressed, and it becomes easier 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 walls of the conductive carbon black 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 wall surfaces of the conductive carbon black, and is 0.0 when the distances between the wall surfaces 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 exchanged between the carbon blacks in the domain by the tunnel effect, and the volume resistance. 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 suitable 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 the first convex portion (convex derived from the domain)>
The domain-derived convex portion (first convex portion) 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. It is preferable that the convex portion derived from the domain is formed by a method of grinding with a polishing grindstone with a plunge type grinding machine.
The guessing mechanism that the convex part derived from the domain can be formed by grindstone polishing is shown. 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, it is possible to form a convex portion derived from the domain. In particular, since the conductive member according to the present embodiment has a structure in which a 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 grindstone, particle size, degree of bonding, binder, structure (abrasive grain ratio) and the like.
The above-mentioned "particle size of abrasive grains" indicates the size of the 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 to A, the softer the degree of coupling, and the closer to Z, the harder it is. The more the binder is contained in the grindstone, the harder the grindstone is. 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) and the like are appropriately used depending on the intended use. , Can be used.
Here, as the outer diameter shape of the polishing wheel in the longitudinal direction, it is preferable to have an inverted crown shape in which the outer diameter gradually decreases from the end to the center so that the conductive roller can be polished into a crown shape. .. The outer diameter shape of the polishing wheel is preferably an arc curve or a high-order curve having 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 quadratic curve or a sine function. The outer shape of the polishing grindstone is preferably one in which the change in the outer diameter changes smoothly, but an arc curve or the like may be a shape approximated to a polygonal shape 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 factors listed above and carrying out the grinding process 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.
As the treated grindstone, for example, a grindstone treated with a rubber member, specifically, a grindstone dressed with a rubber member containing the grindstone was subjected to a treatment such as abrading the grindstone by polishing the surface of the grindstone. A grindstone can be mentioned.

<Method of measuring the height of the first convex part (convex part derived from the 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 a 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 the first 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, the razor is razored from three places, the center in the longitudinal direction of the conductive layer 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. 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 divided into 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 binarization procedure is performed 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 wall surfaces 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 closest domains, and can be obtained by setting the measurement parameter as the distance between adjacent walls in the image processing software.

<Method of forming the second convex portion (convex portion derived from resin particles)>
As a method for forming the second convex portion derived from the resin particles, for example, when polishing the surface of the conductive member in the above-mentioned polishing step, a method of exposing the particles previously kneaded by the polishing step can be mentioned. The material of the particles is not particularly limited as long as the particles to be kneaded can be exposed on the outer surface, but a gap with the photosensitive drum can be secured and the hardness is higher than that of the rubber material constituting the conductive layer. High is preferable. If the hardness of the conductive layer is too low, the second convex portion will sink due to contact with the photosensitive drum, and a gap cannot be formed.
Further, the second convex portion needs to be insulating in order not to interfere with the uniformity of the electric field of the domain and to prevent the charge from being injected from the second convex portion into the photosensitive drum. Here, the insulating property means that the volume resistivity ρp of the convex portion is 1.0 × 10 ¹⁰ Ωcm or more. The method for measuring the volume resistivity will be described later. As the material of the resin particles which is a material having a high volume resistivity and can secure the above-mentioned hardness, organic resin particles containing a polymer material are preferable. Here, the polymer material means a material having a large molecular weight, and represents a polymer obtained by polymerizing a monomer such as a semi-synthetic polymer or a synthetic polymer, or a compound having a large molecular weight such as a natural polymer.

Examples of organic resin particles include polyamide resin, silicone resin, fluororesin, (meth) acrylic resin, styrene resin, polyethylene resin, phenol resin, polyester resin, melamine resin, urethane resin, olefin resin, epoxy resin, naphthalene resin, etc. Fran resin, xylene resin, divinylbenzene polymer, styrene-divinylbenzene copolymer, thermoplastic nitrile resin, resins such as these copolymers, modified products, derivatives, ethylene-propylene-diene copolymer (EPDM), styrene -Butadiene copolymer rubber (SBR), silicone rubber, urethane rubber, isoprene rubber (IR), butyl rubber, acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), epichlorohydrin rubber and other rubbers, polyolefin-based thermoplastic elastomers , Urethane-based thermoplastic elastomer, Polystyrene-based thermoplastic elastomer, Fluoro rubber-based thermoplastic elastomer, Polyester-based thermoplastic elastomer, Polyamide-based thermoplastic elastomer, Polybutadiene-based thermoplastic elastomer, Ethylene vinyl acetate-based thermoplastic elastomer, Polyvinyl chloride-based Examples thereof include thermoplastic elastomers such as thermoplastic elastomers and chlorinated polyethylene-based thermoplastic elastomers.
The distance between the photosensitive drum and the outer surface of the conductive member can be controlled by the number of additional portions of the organic resin particles forming the second convex portion and the particle size distribution. That is, the number of columns supporting the gap between the photosensitive drum and the outer surface of the conductive member is large, and the resin particles that can be increased can suitably form the gap.
Therefore, the average particle size Dp of the resin particles forming the second convex portion is preferably 4 μm or more and 50 μm or less.

<Measuring method of the distance between the conductive member and the photosensitive drum>
The distance between the conductive member formed by the second convex portion and the photosensitive drum is measured by using the jig shown in FIG. 9 (a), and the second convex portion is measured as shown in FIG. 9 (b). It is possible to simulate a state in which a space is formed between the conductive layer 96 and the glass plate 92 by 95.
The measurement of the space distance d between the glass plate 92 and the conductive layer 96 shown in FIG. 9B is a method capable of measuring the distance d via the glass plate 92 such as an optical microscope, a laser microscope, and an electron scanning microscope. There is no particular limitation as long as it is limited, but it may be measured with a laser microscope at a point where the second convex portion on the order of micrometer can be measured accurately. The specific procedure will be described later.

<Manufacturing method of conductive member>
An example of a method for manufacturing a 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 composition prepared in the steps (A) to (C). ..
The conductive layer may be adhered to the conductive support via an adhesive, if necessary. 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.
Further, in the step (B) or (C), the resin particles to be the second convex portion can be added. In particular, it is preferable to add resin particles in the step (C).

<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 a developing roller 103, a toner container 106, and a 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 a conductive member according to an 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 toner 209 is uniformly coated on the surface of the developing roller 203 by the developing blade 208 which is arranged in contact with 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 contact-arranged with respect to 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 to form a color image on the intermediate transfer belt.
The transfer material 219 is fed into the apparatus by the paper feed roller and is conveyed between the intermediate transfer belt 215 and the secondary transfer roller 216. A voltage is applied from the secondary transfer bias power supply to the secondary transfer roller 216, and the color image on the intermediate transfer belt 215 is transferred 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 scrapped 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 a monochrome electrophotographic apparatus (not shown), the process cartridge is only a product using black toner. A monochrome image is formed directly on the transfer material by the process cartridge and the primary transfer roller (without the secondary transfer roller) without going through 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) (trade 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) (trade 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 Kosan Co., 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 Kosan Co., 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: Esprene 505A, 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) (Product name: TOKABLACK # 5500, DBP absorption amount: 155 cm ^3/100 g, manufactured by Tokai Carbon Co., Ltd., abbreviation: # 5500)
-Carbon black (2) (Product name: TOKABLACK # 7360SB, DBP absorption amount: 87 cm ^3/100 g, manufactured by Tokai Carbon Co., Ltd., abbreviation: # 7360)
-Carbon black (3) (Product name: TOKABLACK # 7270SB, DBP absorption amount: 62 cm ^3/100 g, manufactured by Tokai Carbon Co., Ltd., abbreviation: # 7270)
-Carbon black (4) (Product name: # 44, DBP absorption amount: 78 cm ^3/100 g, manufactured by Mitsubishi Chemical Corporation, abbreviation: # 44)
-Carbon black (5) (Product name: Asahi # 35, DBP absorption amount: 50 cm ^3/100 g, manufactured by 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-based 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: Sunseller 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)
<Resin particles>
-Polyethylene particle 1 (trade name: Miperon XM-221U, polyethylene resin, average particle size 25 μm, manufactured by Mitsui Chemicals, Inc.)
-Polyethylene particles 2 (trade name: Miperon PM-200, polyethylene resin, average particle size 25 μm, manufactured by Mitsui Chemicals, Inc.)
-Acrylic particles (trade name: Ganzpearl GM-2801, polymethacrylic methacrylate resin, average particle size 28 μm, manufactured by Aica Kogyo Co., Ltd.)
-Acrylic particles 2 (trade name: Ganzpearl GM-0401S, polymethacrylic methacrylate resin, average particle size 28 μm, manufactured by Aica Kogyo Co., Ltd.)
-Urethane particles (trade name: Art Pearl C-300T, polyurethane resin, average particle size 22 μm, manufactured by Negami Kogyo Co., Ltd.)
-Graphitized carbon particles (trade name: Nika beads PC-1020, graphitized carbon resin, average particle size 10 μm, manufactured by Nippon Carbon Co., Ltd.)

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 exemplified 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 pressurized 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: Metalloc 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 supply mechanism for a conductive support and a discharge mechanism for 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 crosshead, 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 peripheral portion 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 the 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 having a diameter of .44 mm was obtained.
(Polishing condition 1)
As a grindstone, a cylindrical grindstone (manufactured by Taken 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 texture (abrasive grain ratio) abrasive grains are as follows.
Abrasive grain material: GC (green silicon carbide), (JIS R6111-2002)
-Abrasion grain size: # 80 (average particle size 177 μm JIS B4130)
・ Coupling degree of abrasive grains: HH (JIS R6210)
-Binder: V4PO (Vitrify)
・ 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. It was invaded by 24 mm.
As a precision polishing step, the penetration speed was changed to 0.5 mm / sec, and after 0.01 mm penetration, the grindstone was separated from the conductive member to complete the polishing. As the polishing method, an uppercut method was adopted in which the rotation direction of the grindstone and the conductive member were the same.

The conductive members 2 to 51 were manufactured by the same method as the conductive member 1 except that the starting materials shown in Tables 4-1 to 4-5 and the polishing conditions shown below were changed. Tables 4-1 to 4-5 show the mass parts and physical properties of the starting raw materials used for producing each conductive member.

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)
It is the same as the polishing condition 1 except that the penetration speed in the precision polishing step is changed to 0.1 mm / sec, the penetration is 0.01 mm, and then the polishing is continued for 4 seconds.
The obtained results are shown in Tables 5-1 to 5-5.

<3. Characteristic evaluation>
Subsequently, the characteristic evaluations for the following items in the examples and comparative examples of the present disclosure will be described below.
<3-1. Matrix-Confirm domain structure>
The presence of the matrix-domain structure in the conductive layer was confirmed by the following method.
A section (thickness 500 μm) was cut out using a razor so that a cross section perpendicular to the longitudinal direction of the conductive layer of the conductive member could be observed. Next, platinum was deposited on the surface of the section corresponding to the cross section of the conductive layer. The platinum-deposited surface of the section was photographed at 1000 times using a scanning electron microscope (SEM) (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image. In the SEM image, when a plurality of domains were dispersed in the matrix and a structure in which the matrices were communicated was confirmed, the matrix-domain structure was determined to be "presence".

<3-2. How to measure domain maximum ferret diameter, perimeter, and envelope perimeter>
The maximum ferret diameter, perimeter, and envelope perimeter of the domain according to the present disclosure were measured as follows.
First, from the conductive layer of the conductive member, a microtome (trade name: Leica EM FCS, manufactured by Leica Microsystems) was used so that the cross section perpendicular to the longitudinal direction of the conductive layer of the conductive member could be observed. A thin piece (thickness 1 μm) including a cross section for the entire thickness was cut out. When the length of the conductive layer in the longitudinal direction is L and the thickness of the conductive layer is T, the cutting position from the conductive layer is the center in the longitudinal direction and L / 4 from both ends of the conductive layer toward the center. I made it a place.
For each of the obtained flakes, platinum was vapor-deposited on the surface corresponding to the cross section of the elastic layer. Next, the platinum-deposited surface of the flakes was photographed at a magnification of 5,000 using a scanning electron microscope (SEM) (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain an SEM image. The obtained SEM image was converted into an 8-bit gray scale using image processing software (trade name: ImageProPlus, manufactured by Media Cybernetics) to obtain a 256-gradation monochrome image. Next, the black and white of the image is inverted so that the domain in the monochrome image becomes white, and the binarization threshold is set for the luminance distribution of the image based on the algorithm of Otsu's discriminant analysis method. A binarized image was obtained. The obtained binarized image has a depth of 0.1 T to 0.9 T from the outer surface of the conductive layer (the surface opposite to the surface facing the support) when the thickness of the conductive layer is T. A square observation region with a side of 20 μm is placed at any three locations in the thickness region of the above, and for each of the domains existing in each observation region, the maximum ferret diameter and the peripheral length are used by using the counting function of the above image processing software. A, the envelope perimeter B was calculated.
A / B values were calculated using the perimeter and envelope perimeter measured for each of the domains observed in each observation area. Then, out of all the observation domains, the number% of the domains satisfying the requirement (B2) was obtained.

<3-3. How to measure the volume resistivity of the matrix>
The volume resistivity of the matrix was measured as follows using a scanning probe microscope (SPM) (trade name: Q-Scope250, manufactured by Questant Instrument Corporation) in contact mode. The measurement environment was a temperature of 23 ° C. and a humidity of 50% RH.
First, flakes were cut out from the conductive layer in the same manner as in 3-2 above. Next, the flakes were placed on the surface of the metal plate so that one side of the section corresponding to the cross section of the elastic layer was in contact with the surface of the metal plate. Then, the cantilever of SPM was brought into contact with the portion of the section corresponding to the matrix among the surfaces on the side opposite to the surface in contact with the metal plate. Next, a voltage of 50 V was applied to the cantilever, and the current value was measured. Further, the surface shape of the measurement section was measured by the SPM, and the thickness of the measurement point was calculated from the obtained height profile. The volume resistivity of the measurement point was calculated from the thickness of the measurement point and the current value.
The measurement was performed at a depth of 0.1 T to 0.9 T from the outer surface of the conductive layer (the surface opposite to the surface facing the support) when the thickness of the conductive layer was T among the flakes. This was done at any three points in the matrix portion of the region corresponding to the thickness region of. The arithmetic mean value of the volume resistivity calculated from the measurement results at a total of 9 points obtained from each piece was used as the volume resistivity of the matrix of the conductive member to be measured. The evaluation results are shown in Table 5-1 and Table 5-2.

<3-4. Measurement method of DBP absorption amount of carbon black>
The amount of DBP absorbed by carbon black was measured according to Japanese Industrial Standards (JIS) K 6217.
<3-5. Arithmetic mean C of distance between conductive carbon black walls in a domain, standard deviation σm, coefficient of variation σm / C, and method of measuring the ratio of the cross-sectional area of carbon black contained in the domain to the domain area>
The arithmetic mean C, standard deviation σm, coefficient of variation σm / C of the distance between the walls of the conductive carbon black in the domain and the ratio of the cross-sectional area of the carbon black contained in the domain to the domain area were measured as follows.
First, the above 3-2. The platinum-deposited surface of the sample prepared in 3-2. Magnification 20 using a scanning electron microscope (SEM) (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) at a location corresponding to an observation area with a side of 20 μm placed on the binarized image in the evaluation of The image was taken at 000 times and an SEM image was obtained.
The arithmetic mean distance between walls of carbon black and the area of carbon black in the domain were obtained by quantifying the above SEM images. That is, the SEM image was grayscaled in 8-bit using an image analysis device (product name: LUZEX-AP, manufactured by Nireco Corporation) to obtain a 256-tone monochrome image. Next, the black and white of the image is inverted so that the domain in the fracture surface becomes white, and the binarization threshold is set for the luminance distribution of the image based on the algorithm of Otsu's discriminant analysis method. The image was obtained. Next, an observation region having a size that accommodates at least one domain was extracted from the above binarized image. Then, the distance Ci between the wall surfaces of the carbon black in the domain was calculated. Then, the arithmetic mean wall distance C was calculated by obtaining the arithmetic mean of the wall distance. The cross section of the domain and the cross section of carbon black in the domain were also calculated. Then, from these results, the ratio (number%) of the number of domains satisfying the requirement (B1) to the number of all observed domains was calculated. In addition, the above 3-2. Based on the results of, the ratio (number%) of the number of domains satisfying the requirements (B1) and (B2) was calculated.
Further, the standard deviation σm was obtained from the distance between the wall surfaces of the conductive carbon black in the obtained domain and its arithmetic mean C. Then, the coefficient of variation σm / C was calculated by dividing the standard deviation σm by the arithmetic mean C.
Further, for the domains satisfying the requirements (B1) and (B2), the arithmetic average value of the carbon black wall surface distance C, the coefficient of variation σm / C, and the ratio of the carbon black cross-sectional area to the domain cross-sectional area was calculated. Further, for the domains satisfying the requirement (B1) and the requirement (B2), the arithmetic mean value of A / B and the arithmetic mean value of the maximum ferret diameter were calculated. The results are shown in Tables 5-3 to 5-5.

<3-6. SP value of rubber constituting matrix and domain>
The SP value was measured using a conventional swelling method. That is, the rubber 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 was calculated by analysis using the value of the degree of swelling for each solvent. It should be noted that the calculation can be performed accurately by creating a calibration curve using a material having a known SP value. 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 and Table 5-2.

<3-7. How to measure impedance of conductive member>
The impedance of the conductive member was measured by the following measuring method.
First, while rotating the conductive member, platinum was vapor-deposited on the outer surface of the conductive member to prepare an electrode. At this time, using masking tape, an electrode having a width of 1.5 cm and uniform in the entire circumferential direction was produced. By forming such an 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 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 the impedance was obtained. The conductive member (length in the longitudinal direction: 232 mm) is divided into 5 equal parts in the longitudinal direction, and measurement electrodes are formed at 5 points in total, one point arbitrarily from each region, and the above measurement is performed. gone. The average value was taken as the impedance of the conductive member. The evaluation results are shown in Table 5-1 and Table 5-2.

<3-8. Measurement of the height of the first convex part (convex part derived from the domain)>
A slice 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 were made to be a plane perpendicular to the axis of the conductive support. The cutting positions from the conductive layer were set to three locations, L 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.
Next, with respect to the section including the surface of the conductive member obtained as described above, the surface of the conductive member was subjected to the following conditions using SPM (MFP-3D-Origin Oxford Instruments Co., Ltd.). Was measured. 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 ・ Probe: Olympus OMCL-AC160TS
-Resonance frequency: 251.825 to 261.08 kHz
-Spring constant: 23.59 to 25.18 N / m
・ Scan speed: 0.8-1.5Hz
-Scan size: 10 μm, 5 μm, 3 μm
-Target April: 3V and 4V
・ Set Point: All 2V
Next, it was confirmed that the convex portion in the surface shape profile obtained by the above measurement was derived from the domain having higher conductivity than the surroundings in the electrical resistance value profile.
Further, the height of the first convex portion was calculated from the profile.
The calculation method was obtained by taking the difference between the arithmetic mean value of the shape profile derived from the domain and the arithmetic mean value of the shape profile of the adjacent matrix. The arithmetic mean value was 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 Tables 5-3 to 5-5.

<3-9. Measurement of distance Dm between domains on the outer surface of the conductive member>
The distance Dm between domains on the outer surface of the conductive member was 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 was cut out at a depth of about 500 μm including the surface of the conductive member in the length and depth direction of the above. The cutting positions from the conductive layer were set to three locations, L 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 was vapor-deposited on the surface of the obtained section corresponding to the outer surface of the conductive member. Next, a 5000 times SEM image of the platinum-deposited surface of the section was obtained by a scanning electron microscope (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation). An image processing software (trade name: LUZEX, manufactured by Nireco Corporation) was used for the obtained SEM image to obtain a binarized image. The binarization procedure was performed as follows. The observed image was grayscaled by 8 bits to obtain a 256-tone monochrome image. Then, the black and white of the image is inverted so that the domain in the fracture surface becomes white, and the binarization threshold is set for the luminance distribution of the image based on the algorithm of Otsu's discriminant analysis method. I got the image. Next, the distribution of the distance between the wall surfaces of the domain was calculated for the binarized image, and then the arithmetic mean value Dm of the distribution was calculated. The distance between the walls is the shortest distance between the walls of adjacent domains. Specifically, in the image processing software, the measurement parameter was set as the distance between adjacent wall surfaces. note that. Here, Tables 5-3 to 5-5 show the arithmetic mean values of 10 observation images in which the outer surface of the conductive member is randomly selected as the distance between adjacent wall surfaces of the conductive member.

<3-10. Measurement of the distance of the space formed between the conductive member and the glass plate>
A jig and a glass plate having the mechanism of FIG. 9A were used.
A jig having a lower stage 91, an upper stage 93, and a load meter 94 shown in FIG. 9A was used. The lower stage has a structure in which a charging member can be placed and is movable in the vertical vertical direction. Further, the load applied when the conductive member is pressed against the glass plate is configured to be detectable by the load meter 94.
A 20 mm square, 2 mm thick glass plate set on the upper stage by moving the lower stage on which the conductive member is placed vertically upward (material: BK7, surface accuracy: double-sided optical polishing surface, parallelism: within 1 minute ) 92 was pressed so that the load was 500 g. Then, the contact surface between the conductive member and the glass plate is viewed from the glass plate side, and the glass plate is used with a laser microscope (trade name: VK-8700, manufactured by KEYENCE CORPORATION) in which the stage is modified so that the jig can be installed. The surface shape of the conductive member pressed against the glass was measured. The observation magnification was 160 times. In the surface profile obtained in the shape measurement, the distance of the flat portion was measured by pressing the glass of the cross-sectional profile with the nip width (nip length in the circumferential direction) L μm. Next, a scan measurement in the height direction was performed on the abutting nip portion, and it was formed between the conductive member and the glass surface in the region of [nip width L μm] × [longitudinal direction A μm in the measurement range]. The space volume V1 (μm ³ ) of the space was calculated. Furthermore, the formula:
d = V1 / (L × A)
The distance d in the space was obtained and the average value thereof was calculated. It should be noted that the above measurement was performed at three locations in the circumferential direction (at intervals of 120 degrees) at three locations of 90 mm each from the central portion in the longitudinal direction and the central portion to both ends of the conductive member, for a total of nine locations. rice field. The arithmetic mean value of the measured values at these nine points was calculated as the gap distance (μm) in the nip between the conductive member and the photosensitive drum. The evaluation results are shown in Tables 5-3 to 5-5.

<3-11. Measurement of volume resistivity ρp of the second convex portion (convex portion derived from resin particles)>
The volume resistivity ρp of the second convex portion was measured as follows.
When observing the outer surface of the conductive member and measuring ρp, 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 was cut out at a depth of about 500 μm including the surface of the conductive member in the length and depth direction of the above.
The electrical resistivity profile of the section is obtained by the same method as in the above <Measurement of height of the first convex portion (convex portion derived from the domain)> with respect to the surface corresponding to the outer surface of the conductive member. The measurement was performed, and the volume resistivity ρp derived from the resin particles, which is the second convex portion, was measured. It should be noted that the above measurement was performed at three locations in the circumferential direction (at intervals of 120 degrees) at three locations of 90 mm each from the central portion in the longitudinal direction and the central portion to both ends of the conductive member, for a total of nine locations. rice field. The arithmetic mean value of the measured values at these nine points in total was calculated as the volume resistivity ρp derived from the resin particles which are the second convex portions. The evaluation results are shown in Table 5.

<4. Image evaluation>
[4-1] Fog evaluation In order to confirm the uniformity of discharge when the produced conductive member was used as a charging member, the following evaluation was performed.
First, as an electrophotographic apparatus, a laser printer (trade name: Laserjet M608dn, manufactured by HP) was prepared. Then, the charging member, the developing member, and the intermediate transfer belt of this laser printer were modified so that an arbitrary voltage could be applied from an external power source (trade name: Model615; manufactured by Trek Japan Co., Ltd.). In addition, the amount of the cleaning blade penetrating into the photosensitive drum was reduced.
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, as the charging member, the process cartridge incorporating the produced conductive member was loaded into the laser printer. Then, a DC voltage of -1700V is applied to the conductive support of the conductive member, and a voltage is applied to the developing member so that Vback (voltage of the difference between the surface potential of the photoconductor and the voltage applied to the developing member) becomes -350V. Was applied, and image formation conditions were constructed so that the applied voltage of the intermediate transfer belt was 2000 V. Then, a solid white image was output in an environment of a temperature of 30 ° C. and a relative humidity of 80%, and the fog on the solid white image was observed and evaluated by the following method. The evaluation result at this time is also referred to as "initial number of fog".
Next, under the same environment, using the above laser printer, the letter "E" in the alphabet with a size of 4 points has a coverage of 1 with respect to the area of A4 size paper while maintaining the image formation conditions. An image printed so as to be% (hereinafter, also referred to as “E character image”) was formed in 500,000 sheets, and subsequently, one solid white image was output. Fog on the obtained solid white image was observed and evaluated by the following method. The evaluation result at this time is also referred to as "the number of fog after durability".
Here, the developer mounted on the laser printer is negatively charged. Therefore, when a solid white image is output, the developer does not originally move to the photoconductor and the paper. However, as described above, when the charging bias is increased, an excessively charged portion may be generated on the surface of the photoconductor due to a locally strong discharge from the charging member. A small amount of positively charged developer present in the developer migrates to the overcharged portion of the photoconductor, and as a result, black spots derived from the developer are observed even when a solid white image is formed, and white is observed. So-called "fog" will occur in the solid image. Such a phenomenon is remarkably likely to occur when the Vback is large, such as -350V.

(Evaluation method of fog)
Arbitrary 9 points of a solid white image were observed with an optical microscope at a magnification of 500, and the number of black spots caused by toner particles existing in an observation area of 400 μm square was counted, and the number was taken as the number of fog on paper.
In the present disclosure, the initial number of fogs is preferably 200 or less, and more preferably 150 or less. Further, it is preferable that the ratio of the number of fog after durability to the initial number of fog is 130% or less, particularly 115% or less. The evaluation results are shown in Table 5-1 and Table 5-3.

<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 5-3.

<Examples 6 to 57>
Similar to the conductive member 1 of Example 1, the conductive members 6 to 57 were used as charging rollers, and the same evaluation as in Example 1 was performed. The results of each evaluation in Examples 6 to 57 are shown in Tables 5-1 to 5-5.

<Example 58>
The conductive member 1 of Example 1 was subjected to an ultraviolet treatment as a surface treatment to prepare a conductive member 58. Other than that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 5-2 and Table 5-5.
(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 a round bar similar to that in Example 1 as a 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 Tables 6-1 and 6-2 above are as follows.
CG102: Epichlorohydrin rubber (EO-EP-AGE ternary co-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-based 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) (trade 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) hexin (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 (100 parts by mass of solid content) of this acrylic polyol solution. 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 obtain a paint for forming a surface layer. Obtained.
The conductive roller obtained above was dipped in the paint for forming the surface layer with its longitudinal direction in the vertical direction, and coated by a dipping method. The dipping time was 9 seconds, and the pulling speed was 20 mm / sec for the initial speed and 2 mm / sec for 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 of an ion conductive 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. Further, this comparative example has a configuration having a second convex portion. Therefore, the initial number of paper fog was 380, the number of endurance paper fog was 409, and the rate of change of paper fog was 108%.

<Comparative Example 2>
The domain forming CMB was changed to that shown in Table 6-1 and the conductive member C2 was manufactured and evaluated in the same manner as in Example 1 except that 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 only of a domain material, electric field concentration occurs in the conductive layer and excessive charges tend to flow in the conductive path. It is composed. Further, this comparative example has a configuration having a second convex portion. Therefore, the initial number of paper fog was 484, the number of endurance paper fog was 522, and the rate of change of paper fog was 108%.

<Comparative Example 3>
The conductive member C3 was manufactured 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 6-1. 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. Further, this comparative example has a configuration having a second convex portion. Therefore, the initial number of paper fog was 412, the number of endurance paper fog was 440, and the rate of change of paper fog was 107%.

<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 6-1. 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. Further, this comparative example has a configuration having a second convex portion. Therefore, the initial number of paper fog was 440, the number of endurance paper fog was 476, and the rate of change of paper fog was 108%.

<Comparative Example 5>
The 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 6-1. 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 to the matrix. 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 in the conductive path. Further, this comparative example has a configuration having a second convex portion. Therefore, the initial number of paper fog was 420, the number of post-durability paper fog was 448, and the rate of change of paper fog was 107%.

<Comparative Example 6>
The 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 6-1. 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 in the conductive path. Further, this comparative example has a configuration having a second convex portion. Therefore, the initial number of paper fog was 428, the number of endurance paper fog was 457, and the rate of change of paper fog was 107%.

<Comparative Example 7>
The 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 6-2. 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 spherical 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. Further, this comparative example has a configuration having a second convex portion. Therefore, the initial number of paper fog was 388, the number of endurance paper fog was 395, and the rate of change of paper fog was 102%.

<Comparative Example 8>
The conductive member C8 was manufactured 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 6-2. 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 a reinforcing property 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 did not become spherical, and the unevenness and the 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. Further, this comparative example has a configuration having a second convex portion. Therefore, the initial number of paper fog was 528, the number of endurance paper fog was 541, and the rate of change of paper fog was 102%.

<Comparative Example 9>
The CMB for domain formation was changed to rubber particles that were freeze-ground after the rubber for forming the conductive layer of Comparative Example 2 was vulcanized by heating alone, and the MRC for matrix formation was changed to the one shown in Table 6-2. The conductive member C9 was manufactured and evaluated in the same manner as in Example 1. 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. Further, this comparative example has a configuration having a second convex portion. Therefore, the initial number of paper fog was 504, the number of endurance paper fog was 548, and the rate of change of paper fog was 109%.

<Comparative Example 10>
The conductive member C10 was manufactured and evaluated in the same manner as in Comparative Example 3 except that the configuration was changed so that no resin particles were added. The evaluation results are shown in Table 8.
In this comparative example, the roundness of the domain shape is low, and the volume resistivity of the matrix is low, so that the uniformity of the electric field in the conductive layer is low. Further, due to the durability, toner sticking was remarkably observed because it did not have the second convex portion. Therefore, the initial number of paper fog was 103, the number of endurance paper fog was 253, and the rate of change of paper fog was 246%.

<Comparative Example 11>
The conductive member C11 was manufactured and evaluated in the same manner as in Example 1 except that the configuration was changed so that no resin particles were added. The evaluation results are shown in Table 8.
In this comparative example, the uniformity of the electric field in the conductive layer is high, but since the second convex portion is not provided, toner sticking is remarkably observed due to durability. Therefore, the initial number of paper fog was 29, the number of post-durability paper fog was 201, and the rate of change of paper fog was 693%.

<Comparative Example 12>
The conductive member C12 was provided in the same manner as in Example 1 except that the resin particles were changed to graphitized carbon particles (trade name: Nika beads PC-1020, graphitized carbon resin, average particle size 10 μm, manufactured by Nippon Carbon Co., Ltd.). Manufactured and evaluated. The evaluation results are shown in Table 8.
In this comparative example, since conductive resin particles that are not insulating are used, the uniformity of the electric field in the conductive layer is low, while the distance from the photosensitive drum is large, so that the initial stage is achieved. The result was that the number of fog was remarkably large. Therefore, the initial number of paper fog was 350, the number of endurance paper fog was 424, and the rate of change of paper fog was 108%.

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

Claims (18)

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 first 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.
The conductive layer further contains insulating resin particles, and at least a part of the resin particles causes a second convex portion on the outer surface of the conductive member.
When the conductive member is pressed against the transparent flat plate with a load applied to the transparent flat plate of 500 g, the second convex portion and the glass plate come into contact with each other in the nip of the conductive member and the transparent flat plate. The distance of the space formed by the above is 3 μm or more and 30 μm or less, and there is no contact point between the first convex portion and the transparent flat plate in the nip.
A platinum electrode is directly provided 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 20 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 in the thickness direction of the conductive layer. In addition, 80% or more of the domains observed in each of the nine observation regions satisfy the following requirements (B1) and (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. 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 requirement (B1) and the requirement (B2) 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 (B1) 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 conductive member according to claim 5, wherein the amount of DBP absorbed by the conductive carbon black is 40 cm ^3/100 g or more and 80 cm ^3/100 g or less. The arithmetic mean wall-to-wall distance C of the conductive carbon black contained in each of the domains satisfying the requirement (B1) and the requirement (B2) is 110 nm or more and 130 nm or less, and the distance between the conductive carbon black wall surfaces. 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. The 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 first 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. The conductivity according to any one of claims 1 to 12, wherein the volume resistivity ρp of the resin particles that cause the second convex portion is 1.0 × 10 ¹⁰ Ωcm or more and 1.0 × 10 ¹⁷ Ωcm or less. Element. The conductive member according to any one of claims 1 to 13, wherein the average particle size Dp of the resin particles that cause the second convex portion is 4 μm or more and 50 μm or less. A process cartridge that is removable from the main body of the electrophotographic image forming apparatus and includes the conductive member according to any one of claims 1 to 14. The process cartridge according to claim 16, wherein the conductive member is provided as a charging member. An electrophotographic image forming apparatus comprising the conductive member according to any one of claims 1 to 14. The electrophotographic image forming apparatus according to claim 17, wherein the conductive member is provided as a charging member.

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