阅读说明：本技术 导电性构件、电子照相用处理盒和电子照相图像形成设备 (Conductive member, process cartridge for electrophotography, and electrophotographic image forming apparatus ) 是由 仓地雅大 山内一浩 西冈悟 高岛健二 菊池裕一 于 2020-03-27 设计创作，主要内容包括：本发明涉及导电性构件、电子照相用处理盒和电子照相图像形成设备。导电性构件依次具有导电性支承体,和导电层,导电层包括基体和域,基体由包含第一橡胶的交联产物的第一橡胶组合物构成,域具有导电性,并且分散在基体中,域中的每一个由包含第二橡胶的交联产物和导电性颗粒的第二橡胶组合物构成,第一橡胶和第二橡胶为二烯系橡胶,第一橡胶具有至少一种单体单元,第二橡胶具有至少一种与第一橡胶具有的单体单元不同的单体单元；第一橡胶和第二橡胶之间的SP值的绝对值之差为0.2(J/cm<Sup>3</Sup>)<Sup>0.5</Sup>以上且4.0(J/cm<Sup>3</Sup>)<Sup>0.5</Sup>以下；并且tanδ1/tanδ2为0.45以上且2.00以下。(The invention relates to a conductive member, a process cartridge for electrophotography, and an electrophotographic image forming apparatus. The conductive member has a conductive support, and a conductive layer in this order, the conductive layer including a matrix composed of a first rubber composition containing a crosslinked product of a first rubber and domains having conductivity and dispersed in the matrix, each of the domains being composed of a second rubber composition containing a crosslinked product of a second rubber and conductive particles, the first rubber and the second rubber being diene-based rubbers, the first rubber having at least one monomer unit, the second rubber having at least one monomer unit different from the monomer unit of the first rubber; first rubberThe difference in the absolute value of SP value between the rubber and the secondary rubber was 0.2 (J/cm) 3 ) 0.5 Above and 4.0 (J/cm) 3 ) 0.5 The following; and tan1/tan2 is 0.45 to 2.00.)

1. An electroconductive member for electrophotography comprising an electroconductive support and an electroconductive layer in this order,

characterized in that the conductive layer comprises a matrix and domains,

the matrix is composed of a first rubber composition containing a crosslinked product of a first rubber,

the domains are electrically conductive and dispersed in the matrix,

each of the domains is composed of a second rubber composition containing a crosslinked product of a second rubber and conductive particles,

the first rubber and the second rubber are diene rubbers,

the first rubber has at least one monomer unit, and the second rubber has at least one monomer unit different from the monomer unit of the first rubber;

the difference between the solubility parameters of the first rubber and the second rubber, that is, the absolute value of the SP value is 0.2 (J/cm)³)^0.5Above and 4.0 (J/cm)³)^0.5The following; and

a ratio of tan1 to tan2, tan1/tan2, is 0.45 or more and 2.00 or less, where tan1 is a loss coefficient of the first rubber composition measured at a temperature of 23 ℃, a relative humidity of 50%, and a frequency of 80Hz, and tan2 is a loss coefficient of the second rubber composition measured at a temperature of 23 ℃, a relative humidity of 50%, and a frequency of 80 Hz.

2. The electroconductive member for electrophotography according to claim 1, wherein the first rubber and the second rubber are each independently selected from the group consisting of isoprene rubber, acrylonitrile-butadiene rubber NBR, styrene-butadiene rubber SBR, and butadiene rubber.

3. The electroconductive member for electrophotography according to claim 1 or 2, wherein the first rubber is NBR and the second rubber is SBR or isoprene rubber.

4. The electroconductive member for electrophotography according to claim 1 or 2, wherein the first rubber is SBR and the second rubber is NBR or isoprene rubber.

5. The electroconductive member for electrophotography according to claim 2, wherein a content ratio of the styrene-derived monomer unit in the SBR is 18% by mass or more and 40% by mass or less.

6. The electroconductive member for electrophotography according to claim 2, wherein a content ratio of a monomer unit derived from acrylonitrile in the NBR is 18% by mass or more and 40% by mass or less.

7. The electroconductive member for electrophotography according to claim 1 or 2, wherein a volume fraction of the domains in the electroconductive layer is 10 vol% or more and 40 vol% or less.

8. The electroconductive member for electrophotography according to claim 1 or 2, wherein the electroconductive particles are carbon black.

9. The electroconductive member for electrophotography according to claim 1 or 2, wherein the electroconductive layer comprises a crosslinked body of a rubber mixture for electroconductive layer formation comprising the first rubber, the second rubber, the electroconductive particles, sulfur and a vulcanization accelerator, wherein the vulcanization accelerator comprises a thiazole-based compound.

10. The electroconductive member for electrophotography according to claim 9, wherein the thiazole-based compound is a sulfenamide-based compound.

11. A process cartridge for electrophotography detachably mountable to a main body of an electrophotographic image forming apparatus, characterized in that the process cartridge comprises an electrophotographic photosensitive member and the electroconductive member for electrophotography according to any one of claims 1 to 10.

12. A process cartridge for electrophotography according to claim 11, wherein the conductive member is a charging member that charges the electrophotographic photosensitive member.

13. An electrophotographic image forming apparatus characterized by comprising the electroconductive member for electrophotography according to any one of claims 1 to 10.

Technical Field

The present disclosure relates to a conductive member used in forming an electrophotographic image. The present disclosure also relates to a process cartridge for electrophotography using the conductive member, and an electrophotographic image forming apparatus.

Background

In an electrophotographic image forming apparatus, a conductive member is used as a charging member, a transfer member, and a developing member. The charging member and the transfer member each have a function of charging a member to be charged, such as an electrophotographic photosensitive member or paper, disposed facing the member, by discharging electricity thereto.

Japanese patent application laid-open No.2002-3651 discloses a rubber composition having a matrix-domain structure comprising a continuous phase of a polymer composed of a matrix-domain structure composed mainly of a polymer having a volume resistivity of 1 × 10 and a particle phase of the polymer¹²An ion conductive rubber material formed of a raw material rubber A having a thickness of not more than Ω · cm, and a particle phase of the polymer is formed of an electron conductive rubber material which is electrically conductive by blending conductive particles in a raw material rubber B; and a charging member having an elastomer layer formed of a rubber composition.

Disclosure of Invention

An aspect of the present disclosure is directed to providing a conductive member for electrophotography that can uniformly charge a charged member even if compression permanent deformation occurs therein. In addition, another aspect of the present disclosure is directed to providing a process cartridge for electrophotography that contributes to stably forming a high-quality electrophotographic image. Further, another aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that can stably form a high-quality electrophotographic image.

According to an aspect of the present disclosure, there is provided a conductive member for electrophotography having a conductive support and a conductive layer in this order, the conductive layer including a base composed of a first rubber composition containing a crosslinked product of a first rubber and domains having conductivity and dispersed in the base, each of the domains being composed of a second rubber composition containing a second rubberA crosslinked product of a first rubber and a second rubber composition of conductive particles, the first rubber and the second rubber being diene rubbers, the first rubber having at least one monomer unit, the second rubber having at least one monomer unit different from the monomer unit of the first rubber; the difference in the absolute value of the solubility parameter (SP value) between the first rubber and the second rubber was 0.2 (J/cm)³)^0.5Above and 4.0 (J/cm)³)^0.5The following; and a ratio of tan1 to tan2, that is, tan1/tan2 is 0.45 or more and 2.00 or less; wherein tan1 is the loss factor of the first rubber composition measured at a temperature of 23 ℃, a relative humidity of 50%, and a frequency of 80Hz, and tan2 is the loss factor of the second rubber composition measured at a temperature of 23 ℃, a relative humidity of 50%, and a frequency of 80 Hz.

According to another aspect of the present disclosure, there is provided a process cartridge for electrophotography that is detachably mountable to a main body of an electrophotographic image forming apparatus, and includes an electrophotographic photosensitive member and the above-described conductive member.

According to still another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above-described conductive member.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Drawings

Fig. 1 shows a cross-sectional view perpendicular to the length direction of an electrically conductive member according to the present disclosure.

Fig. 2 illustrates a cross-sectional view perpendicular to a length direction of a conductive layer of a conductive member according to the present disclosure.

Fig. 3 illustrates a three-dimensional perspective view of an electrically conductive member according to the present disclosure.

Fig. 4 shows a graph of a calibration curve obtained from the correlation between the mass% and SP value of acrylonitrile in the NBR according to the present disclosure.

Fig. 5 shows a graph of a calibration curve obtained from a correlation between mass% and SP value of styrene in SBR according to the present disclosure.

Fig. 6 shows a sectional view of a process cartridge according to the present disclosure.

Fig. 7 illustrates a cross-sectional view of an electrophotographic image forming apparatus according to the present disclosure.

Fig. 8 is a schematic diagram of an apparatus for measuring the resistance of an electrically conductive member according to the present disclosure.

Fig. 9 shows a diagram illustrating an example of resistance measurement of a conductive member according to the present disclosure.

Detailed Description

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

According to the studies of the present inventors, it has been recognized that the charging roller according to japanese patent application laid-open No. 2002-.

However, in the charging roller according to japanese patent application laid-open No.2002-3651, there is a case where deformation (hereinafter, also referred to as "compression set") that is not easily recovered occurs at a position where the elastic body layer abuts against other members when the charging roller is placed in a state of abutting against the other members. When a charging roller in which compression set has occurred in an elastomer layer is used to form an electrophotographic image, there is a case where a streak (hereinafter, also referred to as "settled set streak") due to compression set is generated in the electrophotographic image.

In other words, in the charging roller according to Japanese patent application laid-open No.2002-3651, the particle phase of the polymer contains conductive particles such as carbon black, and thus the elasticity of the rubber is reduced. As a result, when the domain is deformed by receiving an external force, the restorability of the domain is low. Therefore, it is considered that the charging roller tends to easily cause compression set.

In addition, it is considered that the positional relationship between the particle phases of the polymer in the elastic layer plays an important role in stabilizing discharge due to the charging roller, but the positional relationship between the particle phases of the polymer changes between a portion where compression set occurs in the elastic layer and a portion where compression set does not occur in the elastic layer, and it is considered that the discharge state is different between a portion where compression set occurs and a portion where compression set does not occur.

For this reason, the present inventors have repeated studies on a conductive member for electrophotography having a conductive layer in which domains containing conductive particles are dispersed in a matrix, so as to obtain a new configuration capable of preventing occurrence of discharge unevenness caused by compression set.

As a result, the present inventors have found that an electrophotographic conductive member satisfying the requirements described in the following (1) to (4) is effective for preventing the occurrence of discharge unevenness due to compression set.

The element (1) is a conductive support and a conductive layer in this order, wherein the conductive layer includes a matrix composed of a first rubber composition containing a crosslinked product of a first rubber, and a plurality of domains having conductivity dispersed in the matrix, wherein each of the domains is composed of a second rubber composition containing a crosslinked product of a second rubber and conductive particles.

The requirement (2) is that the first rubber and the second rubber are diene rubbers, wherein the first rubber has at least one monomer unit, and the second rubber has at least one monomer unit different from the monomer unit of the first rubber.

The requirement (3) is that the difference between the absolute values of the solubility parameters (SP values) of the first rubber and the second rubber is 0.2 (J/cm)³)^0.5Above and 4.0 (J/cm)³)^0.5The following.

The requirement (4) is the ratio of tan1 to tan2, i.e., tan1/tan2 is 0.45 to 2.00. Here, tan1 is the loss factor of the first rubber composition measured at a temperature of 23 ℃, a relative humidity of 50%, and a frequency of 80Hz, and tan2 is the loss factor of the second rubber composition measured at a temperature of 23 ℃, a relative humidity of 50%, and a frequency of 80 Hz.

In general, control for suppressing deformation occurring between the conductive member and the abutment member is mainly performed by optimizing the crosslinked form of the rubber constituting the conductive member, and by blending a filler or the like contained in the rubber. In addition, it is necessary for the conductive member to always contain a conductive substance in the rubber in order to achieve uniform discharge to an abutting object such as a photosensitive drum, an intermediate transfer body, and a printing medium. For example, when conductive particles are used as the conductive substance and contained in rubber, the elasticity of the rubber is reduced, and thus the recovery property against deformation is deteriorated. As a result, there are cases where adverse effects on the image, such as permanent deformation stripes, become noticeable.

On the other hand, particularly as the printing speed increases, a large amount of charge transfer is required per unit time, and therefore it is necessary to make the rubber contain a relatively large amount of conductive particles. There are cases where the large amount of conductive particles contained in the rubber causes a decrease in the elasticity of the rubber, and eventually, a decrease in the deformation recovery property.

In addition, when an external force such as a shearing force applied to the conductive member increases, the recovery of the deformation cannot simultaneously follow the deformation caused by the external force, and the mechanical deformation continues to accumulate; the conductive member potentially tends to be susceptible to deformation.

Therefore, it can be said that, particularly in a high-speed process, there is a trade-off relationship between sufficient deformation recovery properties of the elastomer layer and securing of a stable discharge amount.

The present inventors have repeatedly conducted studies in order to obtain a charging member capable of achieving a high level of deformation recovery and a stable amount of discharge. As a result, the present inventors have found that an electrophotographic conductive member having a conductive layer satisfying the above requirements (1) to (4) contributes to solving the above problems.

The matrix is composed of a first rubber composition containing a crosslinked product of a first rubber, and the domains are each composed of a second rubber composition containing a crosslinked product of a second rubber and conductive particles.

In the matrix-domain structure thus formed, not only are crosslinks formed that link between the second rubbers constituting the domains and between the first rubbers constituting the matrix, but crosslinks are also formed at the interface between the domains and the matrix. In the crosslinked form of these three types of combinations, a network is three-dimensionally formed in the rubber constituting the conductive layer, and in particular, the domains function as macroscopic crosslinking points. As a result, the conductive layer can exhibit an excellent effect of suppressing mechanical deformation against an external force.

In the conductive layer, the domains are responsible for the conductivity. That is, at the interface between the matrix and the domains, charge is exchanged between the domains by tunneling current. Thus, the domains contain a large number of conductive particles, while the matrix contains substantially no conductive particles. When an external force is applied to the conductive layer having a matrix-domain structure, it is considered that the mechanical deformation is mainly moderated in the matrix. In addition, since the domains each contain a large number of conductive particles, the domains have a relatively higher hardness than the matrix, and thus the domains are responsible for resisting deformation of the conductive layer. Further, according to the conductive member of the present disclosure, the content of the conductive particles for imparting conductivity required for uniform discharge to the conductive layer can be greatly reduced as compared with a conductive member including a conductive layer not having a matrix-domain structure.

In addition, a crosslinking reaction is performed between the matrix and the domains, thereby causing the domains to function as macroscopic crosslinking points; and the conductive member can exhibit excellent characteristics of mitigating mechanical deformation against external force.

The present inventors have focused on the chemical structure of the rubber constituting the domains and the matrix in the phase separation structure in order to perform a crosslinking reaction between the matrix and the domains and to effectively alleviate the mechanical deformation. As a result, the present inventors have found that the rubber constituting the matrix and the domains is a diene rubber; further, the rubber constituting the matrix has at least one monomer unit, and the rubber constituting the domain needs to have at least one monomer unit different from the monomer unit contained in the matrix.

In other words, the matrix and the domains are composed of rubbers different from each other. This is because the rubber constituting the domain has at least one monomer unit different from the monomer unit contained in the matrix, enabling formation of a matrix-domain structure required to exhibit the effects according to the present disclosure.

In addition, since both the rubbers constituting the matrix and the domain have a diene skeleton in the structure, they are thereby compatible with each other in a part of the interface, and contribute to improvement of the affinity of the interface between the matrix and the domain. In addition, diene rubbers have high chemical reactivity because they have double bonds in the main chain of the polymer. As a result, a crosslinking reaction between the matrix and the domains proceeds, the stability of the interface is improved, and the conductive member can exhibit excellent deformation responsiveness.

In addition, the mechanical properties of rubber, commonly referred to as viscoelastic frequency characteristics, show behavior that greatly changes depending on the frequency of an external force applied to the rubber.

For example, the behavior of mitigating mechanical deformation may be greatly different between a low-frequency region such as a stationary state and a high-frequency region such as during rotational driving.

In order for the matrix-domain structure to exhibit the effects according to the present disclosure, it is also important to approximate the viscoelastic frequency characteristics.

In the image output step, mechanical deformations of a plurality of frequency regions are applied to the conductive member.

Therefore, for example, if the viscoelastic frequency characteristics of the domain and the matrix are greatly different from each other, the relaxation behavior of the mechanical deformation between the domain and the matrix at the time of rotation and at the time of stop is greatly different, and there is a case where the discharge characteristic varies with the variation of the matrix-domain structure.

As a result, permanent deformation streaks may become noticeable. It has been found that this problem also occurs in the configuration of the present disclosure, for example, in which a large number of conductive particles are contained and a domain that is a starting point of discharge resists deformation caused by an external force.

These viscoelastic frequency characteristics are generally known to be due to molecular mobility and therefore depend greatly on the molecular structure of the material.

Therefore, in order for the conductive member to exhibit the effects according to the present disclosure, it is important to design a chemical structure at a molecular level and select materials constituting the domain and the matrix.

Here, the first rubber of the first rubber composition constituting the matrix has at least one monomer unit containing a diene skeleton. On the other hand, the second rubber of the second rubber composition constituting the domain has at least one monomer unit containing a diene skeleton, and at least one monomer unit different from the monomer unit of the first rubber. The monomer unit containing a diene skeleton in the second rubber may be the same monomer unit as the monomer unit of the first rubber. In this case, it means that the monomer units containing a diene skeleton in the first rubber and the diene skeleton in the second rubber, respectively, are different monomer units.

Regarding the requirement (3), the solubility parameters of the rubbers constituting the matrix and the domain are each the square root of the cohesive energy density of the molecules, and represent the magnitude of the cohesive force between the molecules (intermolecular force).

Since the difference between SP values was set to 0.2 (J/cm)³)^0.5In the above, it is possible to form the two types of rubber materials into a matrix-domain phase separation structure and stabilize the interface between the domain and the matrix. As a result, migration of the conductive particles from the domains to the matrix can be suppressed.

Since the difference between SP values was set to 4.0 (J/cm)³)^0.5Hereinafter, the domains can be uniformly dispersed in the matrix; as a result, the matrix-domain structure effectively disperses the external force to which the conductive member is subjected when repeatedly sliding, and can exhibit sufficient responsiveness to deformation. Further, the conductive member can stably enclose the conductive particles within the domains, and can suppress a change in conductivity caused by aggregation (aggregation) of the domains with each other. As a result, the conductive member can suppress variations in conductivity of the abutting portion and the non-abutting portion between the abutting member and the conductive member.

Further, as for the requirement (4), when a viscoelastic body such as rubber or resin receives stress and deforms, the received stress is stored as energy of internal deformation, and becomes a driving force of recovery when the stress is removed. However, a part of the stress received is consumed by friction in the molecular structure resulting from deformation when the stress is applied, and is converted into thermal energy. Loss tangent (hereinafter, defined as tan) is used as a value of an index representing the magnitude of internal friction.

In order to stabilize the interface between the matrix and the domain in the matrix-domain structure, the relationship between the tan of the domain and the tan of the matrix becomes important. For example, when the tan of the domain is significantly different from that of the matrix, excessive external force is selectively concentrated on only one of the domain and the matrix, and mechanical deformation is excessively accumulated in the domain or the matrix. As a result, there are cases where domains are aggregated with each other, and the aggregation of domains destabilizes the exchange of charges between domains.

In fact, when the tan of the domains is greatly different from that of the matrix, the domains are concentrated on each other only at the abutting portions, and cause a difference in the amount of discharge between the abutting portions and the non-abutting portions: and there are cases where permanent deformation streaks occur.

Further, when the application and removal of the external force to the matrix and the domain are performed at high frequency, the tan of the matrix and the tan of the domain tend to be different from each other. Therefore, the requirement (4) specifies the ratio of the responsivity of the domain and the matrix to deformation at a frequency of 80Hz corresponding to the case where the application and removal of the external force to the domain and the matrix are performed at a high frequency. When tan1/tan2 is in the range of 0.45 to 2.00, even when an external force is applied and removed to the conductive member at a high frequency, it is difficult to cause deformation to accumulate only in the domain or the matrix, and thus the interface between the domain and the matrix is more stabilized.

The tan is controlled by the material of the rubber, the kind and amount of filler contained in the rubber, and the crosslinking form. The responsiveness to deformation represented by tan is characterized in that the responsiveness greatly varies depending on the frequency of repetition of applying and removing stress, in other words, the frequency of deformation and recovery. In a process cartridge and an electrophotographic image forming apparatus equipped with a conductive member, it is necessary to consider deformation and recovery in various frequency regions such as the frequency of vibration generated during sliding and the frequency peculiar to a driving system such as a gear and a motor. Further, in the image output step, mechanical deformations of various frequency regions are applied to the conductive member. Therefore, for example, if the viscoelastic frequency characteristics of the domain and the matrix are greatly different from each other, the relaxation behavior of the mechanical deformation between the domain and the matrix is greatly different at the time of rotation (high frequency region) and at the time of stop (low frequency region), and there is a case where the change of the discharge characteristic is caused with the change of the matrix-domain structure.

In the present disclosure, the material of the domains and the matrix is each selected from diene rubbers having a diene skeleton in the chemical structure. Due to the presence of the diene skeleton, the matrix-domain structure can not only facilitate approximation of tan values, but also reduce the difference between the frequency dependencies of tan.

For the above reasons, the matrix-domain structure effectively disperses stress even if sliding is repeated under a high-speed process, and contributes to stabilization of the interface between the domain and the matrix. As a result, the matrix-domain structure shows the effect according to the present disclosure.

A conductive member having a roller shape (hereinafter, also referred to as a "conductive roller") is taken as an example of an embodiment of the conductive member for electrophotography according to the present disclosure, and will be described in detail below.

Fig. 1 shows a cross-sectional view perpendicular to the longitudinal direction of the conductive roller 1. The conductive roller 1 includes a conductive support 2 having a cylindrical or hollow cylindrical shape having conductivity, and a conductive layer 3 formed on the outer periphery of the conductive support.

Fig. 2 shows a cross-sectional view perpendicular to the longitudinal direction of the conductive layer of the conductive roller. The conductive layer 3 has a matrix-domain structure including a matrix 3a serving as a sea region and domains 3b serving as island regions. In addition, the conductive particles 3c are unevenly distributed in the above-described domain 3 b.

< method for confirming matrix-Domain Structure >

The matrix-domain structure can be confirmed in the following manner.

Specifically, a slice may be made from the conductive layer of the conductive member, and observed in detail. Examples of devices used to make slices include sharp razors, microtomes, and FIBs. In addition, in order to appropriately observe the matrix-domain structure, the section may be subjected to pretreatment such as dyeing treatment or vapor deposition treatment that can appropriately obtain the contrast between the conductive phase and the insulating phase. The section on which the fracture surface has been formed and which has been subjected to the pretreatment can be observed with a laser microscope, a Scanning Electron Microscope (SEM), or a Transmission Electron Microscope (TEM).

< conductive support >

The material constituting the conductive support may be appropriately selected from materials known in the field of conductive members for electrophotography. Examples of materials include: metals such as aluminum and iron; alloys such as copper alloy and stainless steel; and a resin material having electrical conductivity. These materials may be subjected to oxidation treatment or plating treatment with chromium, nickel, or the like. Either of electroplating or electroless plating may be used as the plating method, but electroless plating is preferable from the viewpoint of dimensional stability. Examples of the kind of electroless plating used herein include nickel plating, copper plating, gold plating, and plating with other various alloys. The plating thickness is preferably 0.05 μm or more, and in view of the balance between the working efficiency and the rust inhibitive ability, the plating thickness is preferably 0.1 to 30 μm. Examples of the shape of the conductive support include a cylindrical shape and a hollow cylindrical shape. The outer diameter of the conductive support is preferably in the range of phi 3mm to phi 10 mm.

< conductive layer >

< matrix >

The matrix includes a first rubber having at least one monomer unit. In addition, the matrix has a relatively high volume resistivity compared to the domains. In other words, the content of the conductive particles in the matrix is relatively low compared to that in the domains, and thus the matrix may exhibit excellent elasticity of rubber compared to the domains.

[ first rubber composition ]

The first rubber composition is not particularly limited as long as the composition is a diene-based rubber, contains a crosslinked product of a first rubber different from a second rubber, satisfies the difference between the above SP values, and can form a matrix of a matrix-domain structure. Here, the diene rubber is defined as a rubber having a double bond in the main chain of the polymer.

On the other hand, when the main chain of the polymer does not have a double bond, or even if the main chain has a double bond, the equivalent is very small, the rubber is defined as a non-diene rubber. For example, an ethylene-propylene-diene terpolymer (EPDM) whose raw material monomer contains a diene is not contained in the diene-based rubber because the diene is consumed by the addition reaction and does not remain.

In addition, butyl rubber (IIR), which is a rubber obtained by polymerizing isobutylene and a small amount of isoprene at a low temperature, is classified as a non-diene rubber because double bonds derived from isoprene are very few.

Reinforcing carbon black as a reinforcing agent may also be blended to the base body to such an extent that the deformation recovery property of the first rubber is not affected. Examples of the reinforcing carbon black used herein include FEF, GPF, SRF, and MT carbon, which have low conductivity and small surface area.

In addition, in the first rubber forming the matrix, blending agents of commonly used rubbers including fillers, processing aids, vulcanization accelerating aids, vulcanization retarders, antioxidants, softeners, dispersants, and colorants may be added as necessary to such an extent that deformation recovery properties are not impaired.

< Domain >

The domains are composed of a second rubber composition containing a crosslinked product of a second rubber and conductive particles, the domains contain the conductive particles, thereby exhibiting conductivity, here, the conductivity means a volume resistivity of less than 1.0 × 10⁸Ω·cm。

< second rubber >

The second rubber has a different monomer unit than the first rubber. In addition, the second rubber is not particularly limited as long as the difference in the absolute value of the SP values of the second rubber and the first rubber is 0.2 (J/cm)³)^0.5Above and 4.0 (J/cm)³)^0.5Within the following range, and a phase separation structure may be formed. The second rubber used is selected from diene rubbers, similar to the first rubber.

< selection of first rubber and second rubber >

The materials constituting the domains and the matrix of the conductive layer will be described in detail below. The dominant factor determining the properties of matrix-domain structure and moderation of mechanical deformation is the combination of matrix and rubber contained in the domains.

The rubber material contained in the domains and the matrix refers to a first rubber contained in a first rubber composition constituting the matrix, and a second rubber contained in a second rubber composition constituting the domains.

The first rubber and the second rubber are selected from diene-based rubbers so that the first rubber and the second rubber satisfy the difference between the SP values in the above requirement (3). Useful examples of such diene-based rubbers include Isoprene Rubber (IR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), Butadiene Rubber (BR), and Chloroprene Rubber (CR). The SP values of the first rubber and the second rubber can be controlled by adjusting the selection of materials, and/or the selection of the copolymerization ratio of segments containing monomer units derived from styrene in the case of SBR and monomer units derived from acrylonitrile in the case of NBR, and the like.

SBR is a copolymer of styrene and butadiene. The content ratio of the styrene-derived monomer units in the SBR (styrene content) is preferably 18 mass% or more and 40 mass% or less. SBR can easily control its SP value by the polymerization ratio of styrene units. When the content of the styrene unit is controlled to 18% by mass or more, the SBR may have an SP value which is appropriately poor from that of the NBR having a relatively high polarity. When the content of the styrene unit is controlled to 40% by mass or less, an excessive increase in the SP value of SBR can be suppressed. In addition, the monomer unit having a diene skeleton is sufficiently present in the matrix, and therefore, the approximation of the viscoelastic properties of the domain and the matrix is promoted. Furthermore, the affinity between the matrix and the domain is sufficiently obtained at the interface, which can increase the amount of chemical bond between the matrix and the domain.

The styrene content in SBR can be quantified using a known analytical method such as pyrolysis gas chromatography (Py-GC) or solid-state NMR.

NBR is a copolymer of acrylonitrile and butadiene. The content ratio of the monomer unit derived from acrylonitrile (nitrile content) is preferably 18% by mass or more and 40% by mass or less. When the content of nitrile is 18% by mass or more, the NBR can form an appropriate difference between the SP value of NBR and the SP values of polyisoprene and SBR, which are relatively low in polarity. On the other hand, when the content is 40 mass% or less, the NBR has effects on the stabilization of the interface between the matrix and the domain, the homogenization of the domain, and the approximation of the viscoelastic frequency characteristics for the same reasons as the above SBR. Furthermore, the affinity between the matrix and the domain is sufficiently obtained at the interface.

Similarly to the quantification of the styrene content in SBR, the nitrile content can be quantified using a known analytical method such as Py-GC or solid-state NMR.

Further, Isoprene Rubber (IR) is a diene rubber derived from hydrocarbon and having two double bonds in the structure. As the isoprene rubber, 1, 2-polyisoprene, 1, 3-polyisoprene, 3, 4-polyisoprene, cis-1, 4-polyisoprene, trans-1, 4-polyisoprene, a copolymer thereof, and the like can be selected. These chemical structures and copolymerization ratios can be determined by NMR which is a well-known analytical method. The isoprene rubber can be used with an appropriate difference between the SP value of the isoprene rubber and the SP values of BR, CR, NBR and SBR which are relatively high in polarity. In addition, the monomer unit having a diene skeleton is sufficiently present in the structure, and therefore, the approximation of the viscoelastic frequency characteristics of the domain and the matrix is promoted. Furthermore, the affinity between the matrix and the domain is sufficiently obtained at the interface, which can increase the amount of chemical bond between the matrix and the domain.

The Chloroprene Rubber (CR) can be controlled by the selection of thiol modification or sulfur modification, and the content of monomer units derived from 2, 3-dichloro-1, 3-butadiene, and the like. The chemical structures and copolymerization ratios of IR and CR can be determined using NMR, which is a well-known analytical method.

In the above diene-based rubber, it is preferable that the first rubber and the second rubber are each independently selected from the group consisting of isoprene rubber, NBR, SBR and butadiene rubber. In addition, when the first rubber is NBR, it is preferable that the second rubber is selected from any one of SBR and isoprene rubber. Further, when the first rubber is SBR, it is preferable that the second rubber is any one selected from NBR and isoprene rubber. An important point showing the effect according to the present disclosure is to achieve both the formation of the interface between the matrix and the domain and the improvement of the reactivity at the interface. As described above, the combination of NBR and SBR can easily control the SP value by the nitrile content and the styrene content, respectively. As a result, the combination can achieve suppression of migration of the conductive particles in the domains, and uniform formation of the domains due to control of the difference between the SP values. In addition, since a diene skeleton is present in both the first rubber and the second rubber, the interfaces between the first rubber and the second rubber tend to be compatible with each other when the matrix-domain structure is formed. As a result, the domain and the matrix are chemically bonded at the interface therebetween, and therefore, even when a large external force is applied to the conductive layer, peeling of the interface of the matrix-domain structure can be effectively suppressed. Further, a part of the chemical structures of the main components of the rubber constituting the domains and the matrix are equal at a molecular level, and an approximation of the viscoelastic frequency characteristics can be achieved at a high dimensional level.

< method for measuring SP value >

By making a calibration curve using a material whose SP value is known, the SP values of the first rubber and the second rubber can be accurately calculated. As the known SP value, a value in a catalog of a material manufacturer can be used. For example, the SP values of NBR and SBR do not depend on the molecular weight, and are determined by the content ratio of the monomer unit derived from acrylonitrile and the monomer unit derived from styrene, respectively. Therefore, based on the analysis of the nitrile content and the styrene content in the rubber constituting the matrix and the domain using an analysis method such as Py-GC and solid-state NMR, the SP value can be calculated from calibration curves obtained from materials whose SP values are known, respectively. The SP value of isoprene is determined by the structures of 1, 2-polyisoprene, 1, 3-polyisoprene, 3, 4-polyisoprene, cis-1, 4-polyisoprene, trans-1, 4-polyisoprene and the like. Therefore, in the same manner as SBR and NBR, the SP value can be calculated from a material whose SP value is known, based on analysis of the content ratio of the isoprene isomer structure by Py-GC, solid state NMR or the like.

< method of measuring tan >

The tan1 of the first rubber composition containing the crosslinked product of the first rubber constituting the matrix and the tan2 of the second rubber composition containing the crosslinked product of the second rubber and the conductive particles constituting the domain can be measured using a publicly known dynamic viscoelasticity measuring apparatus. A measurement sample was prepared by: weighing each of raw rubber, conductive particles, fillers, and the like constituting the matrix and the domains, respectively; respectively carrying out rubber mixing treatment on the materials; adding a vulcanizing agent/a vulcanization accelerator at the same ratio as the rubber composition for molding the conductive member; and the resulting rubber is vulcanized. Specifically, an unvulcanized domain rubber composition to which a vulcanizing agent was added and an unvulcanized matrix rubber composition were placed in a mold having a thickness of 2mm, respectively; and the composition was crosslinked at 10MPa and 170P for 60 minutes, a rubber sheet having a thickness of 2mm was obtained. The sample was measured in a tensile test mode or a compression test mode, respectively, and tan1 and tan2 can be measured.

< viscoelastic frequency characteristics >

As described above, in order to prevent domains from aggregating in the conductive layer, tan1/tan2 needs to be in the range of 0.45 to 2.00, where tan1 and tan2 are measured at 80Hz in an environment of a temperature of 23 ℃ and a relative humidity of 50%.

< conductive particles >

Examples of the conductive particles include carbon materials such as carbon black and graphite; oxides such as titanium oxide and tin oxide; metals such as Cu and Ag; particles whose surfaces are coated with an oxide or a metal and made conductive.

In addition, two or more of these conductive particles may be appropriately combined and blended as necessary.

Among the materials, conductive carbon black is preferred for the following reasons: high efficiency in suppressing a large decrease in elasticity of rubber and imparting conductivity to the conductive layer; has high affinity with rubber; and facilitating control of the distance between the conductive particles, and the like.

The kind of the conductive carbon black is not particularly limited. Specific examples thereof include gas furnace black, oil furnace black, thermal black, lamp black, and acetylene black.

In addition, the amount of the conductive particles in the domains is preferably 30 to 200 parts by mass, more preferably 50 to 150 parts by mass, relative to 100 parts by mass of the second rubber. The domain containing the conductive particles in the amount as described above is relatively harder than the matrix, and thus the domain can resist deformation when an external force is applied. As a result, domain accumulation mechanical deformation can be suppressed. In addition, excessive reduction in the elasticity of the domain can be suppressed, and therefore, sufficient followability to deformation can be maintained for the domain. As a result, even when an external force is repeatedly applied to the conductive layer, aggregation of domains can be suppressed. Further, since the conductive particles can be stably present in the domains, the domains suppress migration of the conductive particles (conductive carbon black) to the matrix, and make it easy to exhibit the effects according to the present disclosure. In addition, when the amount of the conductive particles to be blended is within the above range, the domains have sufficient conductivity.

When the average value of the ratio of the cross-sectional area of the conductive carbon black contained in each domain appearing in the cross section in the thickness direction of the conductive layer to each cross-sectional area of the domain is defined as μ, it is preferable that μ be 20% or more and 40% or less.

As for the amount and area occupancy of the conductive carbon black to be blended, the conventional conductive member for electrophotography is characterized in that the conductive carbon black is blended in a large amount. The conductivity of carbon black is developed by tunnel current flowing between carbons. This deviation in the amount of tunnel current is correlated with the distribution of the distance between the carbon particles. Therefore, as the addition amount and the area occupancy of the conductive carbon black contained in the domains increase, the distribution of the distance between carbons becomes more uniform, which can suppress the deviation. Therefore, when the average value of the ratio of the cross-sectional areas is within the above range, uniform discharge can be promoted.

When μ is 20% or more, the amount of the conductive carbon black is sufficient, and the electrical connection between the carbon blacks in the domains becomes stable as if percolation. Because of this, it becomes difficult to cause a difference in discharge amount between the abutting portion and the non-abutting portion, and the permanent deformation stripes left alone become less likely to occur. In addition, when μ is 40% or less, the conductive carbon black exists in the domain in a more stable state, and migration of the conductive carbon black to the matrix can be more reliably prevented.

As the conductive carbon black to be blended in the domain, carbon black having a neutral surface with a pH value of 6.0 or more is particularly preferable. Further, it is particularly preferable that the DBP absorption amount of the conductive carbon black to be blended in the domains is 85cm³A density of 160cm and above 100g³The volume is less than 100 g. For reference, the DBP absorption of carbon black can be measured according to JIS K6217. Alternatively, values in the manufacturer's catalog may be used. When pH is 6.0 or more and DBP absorption is 85cm³A density of 160cm and above 100g³A guide wire of less than 100gIn the case of electrical black, the conductive layer can maintain the resistance value within a suitable range even if it has a domain structure. Further, the conductive carbon black can exhibit excellent affinity with diene rubbers. Therefore, the conductive carbon black interacts with the second rubber, whereby aggregation between the domains can be suppressed even when the deformation behavior of the conductive member after repeatedly receiving an external force is relaxed. As a result, the conductive member suppresses a change in the amount of discharge at the abutting portion of the abutting member, which is particularly susceptible to mechanical deformation, and can easily suppress permanent deformation streaks left alone.

< vulcanizing agent/vulcanization accelerator >

In order to obtain a crosslinked product of the first rubber and a crosslinked product of the second rubber, a vulcanizing agent and a vulcanization accelerator may be used for the conductive layer. The vulcanizing agent is not particularly limited, and sulfur, metal oxide, peroxide, and the like can be used. Among these vulcanizing agents, sulfur is more preferable from the viewpoint that sulfur molecules bond molecular chains with the molecular chains to form a network molecular structure, and thereby the amount of chemical bonds at the matrix-domain interface can be increased. Since the conductive layer is crosslinked by using sulfur, three-dimensional network-like crosslinks are also formed in the matrix-domain structure due to sulfur molecules that bond molecular chains to the molecular chains, which promotes an increase in the amount of chemical bonds at the interface between the matrix and the domains.

In addition, a masterbatch type vulcanizing agent in which a vulcanizing agent is compounded into a small amount of the first rubber and/or the second rubber may be preferably used. The use of the masterbatch type vulcanizing agent promotes uniform dispersion of the vulcanizing agent into the rubber raw material. Further, a masterbatch type sulfur in which sulfur is kneaded into a small amount of the first rubber and/or the second rubber may be suitably used. The use of the masterbatch-type sulfur promotes uniform dispersion of sulfur into the rubber raw material. As a result, the masterbatch-type sulfur suppresses uneven distribution of sulfur, increases the amount of chemical bonds at the interface of the matrix-domain structure, and thus makes it easier to stabilize the interface. Two or more kinds of master batch type sulfur may be mixed in an arbitrary ratio so as to be suitable for the materials constituting the domains and the matrix structure and the blending ratio. For example, when the crosslinked product of the first rubber and the crosslinked product of the second rubber are blended in proportions of 70 mass% and 30 mass%, respectively, the masterbatch-type sulfur of the first rubber and the second rubber is added in proportions of 70 mass% and 30 mass%, respectively, whereby more uniform crosslinking can be formed. From the viewpoint of uniformly performing crosslinking and suppressing blooming, it is preferable that the amount of sulfur to be blended is in the range of 0.5 to 7 parts by mass with respect to 100 parts by mass of the unvulcanized rubber component (100 parts by mass in total of the first rubber and the second rubber) in the conductive layer. The amount of sulfur is more preferably 1 to 4 parts by mass.

In addition, it is important to greatly reduce the vulcanization time by using a vulcanization accelerator in combination with a vulcanizing agent so that crosslinking is formed at the interface. In particular, in a system in which two rubbers are blended as in the present disclosure, there are cases where the time required for vulcanization differs between the two rubbers.

At this time, a difference in mobility is caused between the filler or the vulcanizing agent such as sulfur present in the rubber due to the difference between the melt viscosities of the rubbers. Specifically, the filler and the vulcanizing agent are made to be easily unevenly distributed from the rubber in which vulcanization is easily performed to the rubber in which vulcanization is difficult to perform. As a result, the amount of chemical bonds at the interface of the matrix-domain structure decreases because of uneven distribution of the vulcanizing agent, and the interface becomes unstable. Thus, the combined use of the vulcanization accelerator reduces the vulcanization time, thereby suppressing uneven distribution of the vulcanizing agent and can promote crosslinking at the interface between the matrix and the domains.

The vulcanization accelerator is not particularly limited, and usable examples include the vulcanization accelerators shown below: aldehyde-ammonia series, aldehyde-amine series, thiourea series, guanidine series, thiazole series, sulfenamide series, thiuram series, dithiocarbamate series, xanthate series, and mixed accelerators thereof. In these examples, in particular, it is preferable that the rubber contains a thiazole-based compound. More preferably, the rubber contains a sulfenamide compound. Examples include N-tert-butyl-2-benzothiazylsulfenamide, and N-cyclohexyl-2-benzothiazylsulfenamide.

The solubility ratio of the vulcanization accelerator, which is an index of affinity with rubber, varies depending on the chemical structure. In general, this solubility ratio is correlated with the difference between the SP values of the vulcanization accelerator and the rubber to be mixed, and thus varies depending on the kind of rubber, in other words, depending on the SP value of the rubber. In particular, the optimum blend of vulcanization accelerators varies depending on the chemical structure of the rubber. The thiazole-based compound has almost the same solubility ratio as butadiene rubber, chloroprene rubber, isoprene rubber, SBR and NBR, which are preferable materials constituting the domain and the matrix of the present disclosure, and makes it easy to uniformly disperse the vulcanization accelerator in the rubber raw material. As a result, in combination with the effect of suppressing uneven distribution of the vulcanizing agent due to shortening of the vulcanization time, the vulcanizing agent and the vulcanization accelerator can be uniformly dispersed in the conductive layer. With the uniform dispersion described above, crosslinking proceeds uniformly in the respective interiors of the domains and the matrix, and at the same time, the amount of chemical bonds at the interface increases. As a result, in combination with the effects of the requirements (1), (2), and (3), when an external force is applied, the thiazole-based compound can form three-dimensional network-like crosslinks that can exhibit an effect of suppressing mechanical deformation at a high dimensional level.

Further, other vulcanization accelerators shown above may be used together with the vulcanization accelerator for thiazole-based compounds. As the vulcanization accelerator used together, a vulcanization accelerator selected from the thiuram type and the thiourea type is particularly preferable. When these vulcanization accelerators are used together, the vulcanization time can be easily adjusted. As a result, the combined use suppresses uneven distribution of the vulcanizing agent, and can promote crosslinking at the interface between the matrix and the domain.

< method for analyzing crosslinked rubber >

The conductive layer can be analyzed for the presence or absence of the crosslinked rubber of the first rubber and the second rubber by a known analysis method such as pyrolysis gas chromatography (Py-GC), solid nuclear magnetic resonance spectroscopy (NMR method), raman spectroscopy, or the like. In raman spectroscopy, the presence or absence of sulfur crosslinking in SBR can be determined. In the Raman spectrum, at 438cm^-1、475cm^-1And 509cm^-1The peak of sulfur crosslinking derived from SBR is detected at the position of (2), and therefore the sulfur crosslinking structure can be directly detected by the presence or absence of the peak. In addition, Py may be usedGC determines the presence or absence of sulfur crosslinking in NBR and isoprene rubber. The sample is pyrolyzed in a temperature range of 550 to 600 ℃, and the formed pyrolysis product is separated by a separation column, and the resulting product is detected by a hydrogen flame ionization detector, and a pyrogram is obtained. Further, by measuring the sample under the same conditions and detecting carbon and sulfur by an atomic luminescence detector, a pyrogram of carbon and sulfur is obtained; identifying peaks using mass spectrometry; from this, the presence or absence of sulfur crosslinking can be determined.

< method for identifying vulcanization accelerators >

Since the vulcanization accelerator has been decomposed or the structure has been changed during vulcanization, the vulcanization accelerator contained in the crosslinked product of the first rubber and the second rubber in the conductive layer is present in a low molecular weight state and can therefore be identified by analysis with head-space gas-chromatographic method. Specifically, 100mg of the conductive layer was taken out in portions and placed in a headspace sampler; the volatile components are removed and trapped in the adsorbent. Then, the volatile component is thermally desorbed by Curie point heating, and the resultant volatile component is analyzed by GC/MS, whereby the chemical structure of the vulcanization accelerator can be analyzed. The amount of the vulcanization accelerator to be blended may be analyzed by subjecting the vulcanization accelerator to a known quantitative analysis such as a sodium sulfide method, a cyanamide method, a hydrogen iodide reduction method, a sodium sulfite method, and an amine method.

< volume fraction of domain >

The volume fraction of the domains in the conductive layer is preferably 10 vol% or more and 40 vol% or less. By controlling the volume fraction to 10 vol% or more, a sufficient amount of matrix-domain interface can be formed, and the function of the domain showing macroscopic crosslinking points becomes easy. As a result, the conductive layer can exhibit an excellent effect of suppressing mechanical deformation against an external force. In addition, the volume fraction can suppress excessive addition of the conductive particles in the domains. As a result, the conductive layer can suppress excessive reduction in elasticity of the rubber in the domain, and can exhibit sufficient followability to deformation of the domain and the base; therefore, even when an external force is repeatedly applied thereto, aggregation of the domains with each other can be suppressed.

On the other hand, by controlling the volume fraction to 40 vol% or less, the conductive layer can suppress aggregation of domains with each other when an external force is applied and mechanical deformation is relaxed, and makes it easy to suppress variation in discharge characteristics. In addition, the conductive layer may have a structure in which the matrix is relatively large in number with respect to the domains, and thus the matrix excellent in elasticity of rubber may be made to exhibit deformation recovery properties. In addition, the volume fraction suppresses an excessive increase in the number of interfaces between the domain and the matrix; thus, when the sliding is repeated, the conductive layer can effectively disperse the stress, and thus makes it easy to display the effect according to the present disclosure.

< method for measuring volume fraction of domain >

The volume of the domain may be determined from a three-dimensional (3D) image of the domain by using a FIB-SEM.

FIB-SEM is a technique of processing a sample with an FIB (Focused Ion Beam) apparatus and observing the exposed cross section with an SEM (scanning electron microscope). A 3D image of the field may be generated by obtaining a large number of cross-sectional images of the conductive layer and reconstructing a 3D image of the conductive layer from the cross-sectional images using computer software.

As for a specific method of measuring the volume of the domain, a three-dimensional stereoscopic image represented by fig. 3 was obtained using FIB-SEM (manufactured by FEI company ltd.) (described in detail above), and the above-described configuration was confirmed from the image. In fig. 3, domains 23 are dispersed in a matrix 22 in a cubic shape 21 with a side of 9 μm. The domains 23 contain conductive particles 24 in dispersed form. Note that the size and configuration of the domains 23 are not limited to those shown in the schematic perspective view of fig. 3.

Taking out samples from any nine parts of the conductive layer; in the case of the roll shape, when the length in the longitudinal direction is determined to be 1, samples are cut every 120 degrees in the circumferential direction of the roll from the vicinities of three portions distant from the ends of (1/4) l, (2/4) l, and (3/4)1, respectively.

Thereafter, the sample was three-dimensionally measured using FIB-SEM, and images of a cubic shape with one side of 9 μm were measured at intervals of 60 nm. Here, the cross section of the conductive layer in each of the (1/4) l, (2/4) l, and (3/4)1 sections is measured at the center portion between the core metal position and the surface every 90 degrees in the circumferential direction of the roller, respectively.

In addition, it is also preferable to subject the sample to a pretreatment that can appropriately obtain the contrast between the domain and the substrate in order to appropriately observe the domain structure. Here, a dyeing process may be preferably used.

Thereafter, the obtained image was analyzed using 3D visualization/analysis software Avizo (registered trademark, manufactured by FEI Company, ltd.), and the volume of the domain in 27 unit cubes of 3 μm on one side contained in one sample of a cube shape of 9 μm on one side was calculated.

In addition, using the above-described 3D visualization/analysis software, the distance between the adjacent wall surfaces of the domain is measured in the same manner, and after obtaining the above-described measurement values, the distance can be calculated from the arithmetic mean of 27 samples in total.

< Domain size >

It is preferred that the size of the domains is in the range of 0.1 μm to 4 μm. More preferably in the range of 0.2 μm to 2 μm in size. By controlling the size to 0.1 μm or more, the domain suppresses the movement of the conductive particles from the domain to the matrix, and can suppress the decrease in the elasticity of the rubber in the matrix. In addition, the size facilitates the function of the domain to display macroscopic cross-linking points. As a result, the conductive layer can exhibit an excellent effect of suppressing mechanical deformation against an external force. Further, the conductive layer can suppress variation in conductivity caused by aggregation of domains with each other. As a result, the conductive member makes it easy to suppress variations in the conductivity of the abutting portion and the non-abutting portion between the abutting member and the conductive member. On the other hand, by controlling the size to 4 μm or less, the domain exhibits a charge transport effect due to the tunnel current even in a high-speed process, and charging failure can be suppressed. In addition, the conductive layer can suppress variation in the amount of discharge caused by aggregation of domains with each other. Further, by controlling the size to 2 μm or less, the domain suppresses a reduction in the area of the interface between the domain and the matrix, and it becomes easy for the domain to exhibit a sufficient function as a macroscopic crosslinking point. As a result, the conductive layer can exhibit an excellent effect of suppressing mechanical deformation against an external force.

< method for measuring Domain size >

The measurement of the domain size can be carried out in the following manner. First, a section was prepared by the same method as the method for confirming the matrix-domain structure described above. Next, the fracture surface can be formed by a means such as a freeze fracture method, a cross polishing method, or a focused ion beam method (FIB). The FIB method is preferable in view of smoothness of the fracture surface and pretreatment for observation. In addition, in order to appropriately observe the matrix-domain structure, the section may be subjected to pretreatment such as dyeing treatment or vapor deposition treatment that can appropriately obtain the contrast between the conductive phase and the insulating phase.

The section on which the fracture surface has been formed and which has been subjected to the pretreatment can be observed with a laser microscope, a Scanning Electron Microscope (SEM), or a Transmission Electron Microscope (TEM). In these microscopes, considering the accuracy of the quantification of the area of the conductive phase, it is preferable to observe the section with an SEM at a magnification of 1000 to 100000.

The domain size can be obtained by quantifying the captured images. An Image of a fracture surface obtained by observation with an SEM is converted into 8-bit gradation using Image processing software such as Image Pro Plus (registered trademark, manufactured by Media Cybernetics, inc.), and a 256-gradation monochrome Image is obtained. Next, the black and white portions of the image are inverted so that the domain in the fracture surface is whitened, and binarization is performed. Next, an arithmetic average value can be obtained by calculating the diameters of the circle-equivalent diameters from the area values of the domain size groups in the image, respectively.

The above-mentioned domain size can be measured by the following steps: the conductive member was divided into four in the circumferential direction and five in the longitudinal direction, one cut sample was cut out at an arbitrary position of each divided region, the above measurement was performed to obtain measurement values of 20 points in total, and the domain size was calculated from the arithmetic average of the measurement values.

< distance between domains >

The distance between the domains is defined by the distance between the insulating phases (matrix) sandwiched between the conductive phases (domains). The distance between the domains is in the range of 0.2 μm to 2 μm. Controlling the distance between the domains to be 0.2 μm or more can make it easy to suppress aggregation of the domains with each other. By controlling the distance to 2 μm or less, an area in which a crosslink is formed between the domain and the matrix can be sufficiently obtained. As a result, the effect of the three-dimensional network in which the domains function as macroscopic crosslinking points can be sufficiently obtained, and therefore, the excellent effect of suppressing mechanical deformation against an external force is made to be easily exhibited.

< method for measuring distance between fields >

The distance between the domains can be measured by observing the cross section of the conductive layer in the same manner as the measurement method of the domain size.

After binarizing the image of the fracture surface in the same manner as the above-described method of measuring the domain size, the distance between the wall surfaces of the domain group in the image is calculated using image processing software. The distance between the wall surfaces at this time is the shortest distance between the wall surfaces of the domains located closest to each other in the adjacent domains.

The distance between the domains may be measured by: the conductive member was divided into four in the circumferential direction and five in the longitudinal direction, one cut sample was cut out at an arbitrary position of each divided region, the above measurement was performed to obtain measurement values of 20 points in total, and the distance between the domains was calculated from the arithmetic average of the measurement values.

< uniformity of arrangement of domains >

It is preferable that the domains in the matrix-domain structure are uniformly arranged. Specifically, the distribution of the inter-gravity center distances of the domains is 0 or more and 0.4 or less. By controlling the distribution to 0.4 or less, the deviation of the distance between the domains can be reduced. This can suppress variation in mechanical deformation with respect to the domains and the base, thereby facilitating effective relaxation of mechanical deformation. In addition, aggregation of domains occurs from a site where the distances between the domains are closest to each other; therefore, due to the suppression of the deviation of the distance between the domains, it becomes easy to suppress the aggregation between the domains, and it also becomes easy to display the uniform discharge characteristic.

The uniformity of the configuration of the domains can be measured in the following manner. First, three square observation regions were set in a region having a thickness of 0.1T to 0.9T from the outer surface of the conductive layer of each cross section of (1/4) l, (2/4) l, and (3/4)1 obtained in the measurement of the shape of the domain described above. Here, T defines the thickness of the conductive layer.

Next, scanning electron microscope images of the square observation regions were obtained, and then binarized images thereof were obtained.

Then, the obtained binarized image is processed with image processing software such as LUZEX (registered trademark: Special image processing analysis System, trade name: Luzex SE, manufactured by Nireco Corporation), and the distribution of the inter-gravity center distance of the domain is calculated.

Finally, the standard deviation E, the mean F, are obtained from the distribution, and E/F is calculated.

In the present disclosure, the average value of each E/F from the nine square observation regions is used as a parameter of the uniformity of the arrangement of the domains.

< method for controlling uniformity of domain size, distance between domains, and arrangement of domains >

It is preferable to form uniform domains in the matrix-domain structure in order to achieve both deformation recovery and the securing of a stable discharge amount at a higher level.

Here, "uniform" is defined as (1) the domains have the same size, and (2) there is no deviation in the arrangement of the domains in the matrix.

The uniformly formed domains suppress concentration of stress with respect to the deformed portion occurring at the time of sliding, and effective relaxation of mechanical deformation can be achieved. Further, in combination with the effect of approximating the viscoelastic frequency characteristics of the domains and the matrix, uniformly formed domains make it easy to display the effect according to the present disclosure.

As for the particle diameter (domain size) D of the dispersed particles in the case of melt-kneading two types of incompatible polymers, the following formulas of Taylor, Wu (Wu), and Tokita are proposed.

Taylor's formula

D＝[C×σ/ηm×γ]×f(ηm/ηd)

Empirical formula of Wu

γ×D×ηm/σ＝4(ηd/ηm)0.84×ηd/ηm>1

γ×D×ηm/σ＝4(ηd/ηm)-0.84×ηd/ηm<1

Tokita's formula

D＝f((1/η)*(1/γ)*(ηd/ηm)*P*φ*σ*(1/EDK)*(1/τ)*χ12)

D: domain size, C: constant, σ: interfacial tension,

η m: viscosity of matrix,. eta.d: viscosity of the domains,

γ: shear rate, η: viscosity of the mixed system, P: probability of collision and coalescence,

Phi: volume of domain phase, EDK; energy of domain phase cutting

τ: critical intercalary distance, χ 12: dimensionless parameter representing the interaction between the two

As shown in the above equation, the domain size and the distance between the domains can be controlled mainly by the following four points.

(1) Difference in interfacial tension between domain and substrate

(2) Viscosity ratio between domains and matrix

(3) Shear rate at kneading/energy at shearing

(4) Volume fraction of domains in the conductive layer

(1) Is related to the difference between the SP values of the first rubber constituting the matrix and the second rubber constituting the domains, so that the interfacial tension can be controlled by the selection of the materials of the first rubber and the second rubber. Specifically, the interfacial tension can be reduced by reducing the difference between the SP values. Therefore, the difference between the SP values and the interfacial tension can be simultaneously controlled by selecting the chemical structures of the first rubber and the second rubber selected from the diene-based rubbers (in particular, selected from the isoprene rubber, NBR, and SBR).

The viscosity ratio between the domains and the matrix in (2) can be adjusted by selection of the mooney viscosity of the rubber raw material and compounding of the kind and amount of the filler. The viscosity ratio may be adjusted by adding a plasticizer such as paraffin oil to the extent that the plasticizer does not inhibit the formation of a phase separation structure. The viscosity ratio can be adjusted by adjusting the temperature at the time of kneading the polymer. For reference, the viscosities of domains and matrices can be obtained by measuring the mooney viscosity ML (1+4) at the rubber temperature at the time of polymer kneading based on JIS K6300-1: 2013. In addition, the viscosity may be replaced with the index value of the raw rubber.

The shear rate at the time of kneading/the energy at the time of shearing in (3) can be controlled by the rotation speed at the time of kneading the rubber and the feed rate at the time of extruding the rubber. Specifically, by increasing the rotation speed and the kneading time at the time of kneading the rubber and the feed rate at the time of extruding the rubber, the shear rate at the time of kneading/the energy at the time of shearing can be increased.

(4) The volume fraction of domains in the conductive layer is related to the probability of collisional coalescence between the domains and the matrix. In particular, by increasing the volume fraction of domains in the conductive layer, the probability of collisional coalescence between domains and matrix can be increased.

Specifically, the reduction in domain size can be controlled by the following technique.

Reduction of the interfacial tension between the rubber compositions forming domains and matrices, respectively

Reduction of the difference between the viscosities of the rubber compositions which form domains and matrix respectively

Increase of shear rate in kneading

In addition, in order to reduce the distance between the domains, the distance may be controlled by the following technique together with a technique of reducing the domain size.

Increase energy at shear

Increasing the volume fraction of the domain

Increase probability of collisional coalescence

< volume resistivity of domain >

The volume resistivity of the domains is preferably low relative to the volume resistivity of the matrix, specifically, the volume resistivity is 1.0 × 10¹To 1.0 × 10⁴Omega cm. further, from the viewpoint of coping with the easy movement of charges and the reduction of volume resistivity in a high-speed process, electron conduction is more preferable than ion conduction because the volume resistivity of the domain is controlled to 1.0 × 10¹Omega cm or moreIn addition, since the conductive particles may exist in a stable state in the domain, the domain suppresses migration of the conductive particles to the base, and makes it easy to exhibit the effect according to the present disclosure, in addition, since the volume resistivity of the domain is controlled to 1.0 × 10⁴The domains themselves may contain a sufficient amount of conductive particles, and therefore, the domains may become relatively hard with respect to the matrix, resist deformation caused by external forces, and make it easy to suppress accumulation of mechanical deformation⁴The conductive layer can secure a sufficient amount of discharge charge particularly in a high-speed process even when the discharge voltage is not more than Ω · cm. Further, since the volume resistivity is controlled within the above range, the domain exhibits ohmic behavior even when the conductive particles are used, thereby reducing voltage dependence and making it easy to achieve uniform discharge. As a result, the conductive layer makes it easy to display the effect according to the present disclosure.

< method for measuring volume resistivity of domain >

The volume resistivity of the domains can be measured by making slices of the conductive member and using a microprobe. Examples of devices used to make slices include sharp razors, microtomes, and FIBs.

Since it is necessary to measure the volume resistivity only on the domain, when making the slice, it is necessary to make a slice having a film thickness smaller than the distance between the domains measured in advance by SEM, TEM, or the like. Therefore, as a device for making a slice, a device that can make a very thin sample such as a microtome is preferable.

Regarding the measurement of the volume resistivity, first, one surface of the slice is grounded, and then the positions of the matrix and domain in the slice are determined by a device that can measure the volume resistivity or hardness distribution of the matrix and domain, such as SPM and AFM. Subsequently, the probe may be brought into contact with the domain to measure the ground current when a DC voltage of 1V is applied, and the resistance is calculated from the current. At this time, a device such as SPM or AFM, which can also measure the slice shape, is preferable because the device can determine the film thickness of the slice and measure the volume resistivity.

The above volume resistivity can be measured by the following steps: the conductive member was divided into four in the circumferential direction and five in the longitudinal direction, sliced samples were cut out from each divided region, and the above-described measurement values were obtained, whereby the volume resistivity was calculated from the arithmetic average of the volume resistivities of 20 samples in total.

< volume resistivity of matrix >

It is preferable that the volume resistivity of the matrix is high relative to the volume resistivity of the domains in order to achieve more stable and sustained discharge of the conductive member according to the present disclosure, specifically, the volume resistivity is 1.0 × 10⁸Omega cm or more, and more preferably 1.0 × 10¹²Omega cm or more, when the volume resistivity is 1.0 × 10⁸Above Ω · cm, the domains are caused to separate from each other by the high-resistance matrix, the interface becomes able to accumulate more electric charges therein, and the structure becomes more suitable for achieving stable and sustained discharge. In addition, to achieve such high volume resistivity, the matrix should not substantially contain conductive particles. As a result, the matrix exhibits excellent elasticity of the rubber, and a structure advantageous for exhibiting more excellent deformation recovery properties is formed.

< method for measuring volume resistivity of substrate >

The volume resistivity of the matrix can be measured by the same method as in the measurement of the volume resistivity of the domain described above, except that the ground current is measured when the DC voltage of 50V is applied. The above volume resistivity can be measured by the following steps: the conductive member was divided into four in the circumferential direction and five in the longitudinal direction, sliced samples were cut out from each divided region, and the above-described measurement values were obtained, whereby the volume resistivity was calculated from the arithmetic average of the volume resistivities of 20 samples in total.

< shape of conductive Member >

A conductive member having a roller shape is used in a contact state as a charging member for charging an electrophotographic photosensitive member (photosensitive drum). In this case, it is preferable that the conductive member has a shape in which the outer diameter of the central portion is thickest in the longitudinal direction and the outer diameter is reduced in the longitudinal direction in the direction toward both end portions, that is, a so-called crown shape, in order to make the width of the nip between the charging member and the photosensitive drum extending in the longitudinal direction more uniform. Regarding the amount of protrusion, it is preferable that the difference between the outer diameter of the central portion in the longitudinal direction and the average of the outer diameters of two points located at positions on the left and right of 90mm from the central portion be 30 μm or more and 160 μm or less. Since the amount of projection is set within this range, the conductive member can make the contact state between itself and the photosensitive drum more stable. As a result, the external force tends to be easily applied uniformly to the entire region of the abutting portion between the conductive member and the photosensitive drum, whereby partial accumulation of mechanical deformation and unevenness of relaxation of deformation can be suppressed.

< hardness of conductive layer >

The hardness of the conductive layer of the conductive member is preferably 90 ° or less in terms of microhardness (MD-1 type), and more preferably 50 ° or more and 85 ° or less. Because the micro-hardness is controlled to be more than 50 degrees, the rubber can obtain sufficient elasticity; and the conductive layer hardly causes deformation even when it is abutted on the photosensitive drum for a long time, and makes it easy to suppress permanent deformation stripes left standing. Since the micro-hardness is controlled to 85 ° or less, the conductive layer can suppress an excessive decrease in the nip width in abutment on the photosensitive drum, thereby suppressing a change in the member due to excessive concentration of stress in the abutment portion, and movement of the conductive particles. As a result, the conductive layer suppresses the difference between the electrical characteristics of the abutting portion and the non-abutting portion, in other words, the discharge amount. Further, since the micro-hardness is controlled within the above range, the conductive layer becomes easy to stabilize the abutment on the photosensitive drum, and the conductive member can charge the photosensitive drum more uniformly. For reference, micro hardness (MD-1 type) is hardness measured by pressing a stylus against the outer surface of the conductive layer using a micro rubber durometer. The hardness of the conductive layer can be adjusted by the amount of sulfur contained in the material mixture for forming the conductive layer, the kind and amount of the vulcanization accelerator, the vulcanization temperature, the vulcanization time, and the contents of the conductive particles and the filler.

< method for producing conductive Member >

A method of manufacturing an electrically conductive member according to an aspect of the present disclosure will be described below.

(A) A step of preparing a Carbon Master Batch (CMB) for domain formation containing a conductive carbon black and a second rubber;

(B) a step of preparing a first rubber composition to be a base; and

(C) a step of mixing the carbon master batch and the first rubber composition to prepare a rubber composition having a matrix-domain structure.

In the domains, conductive particles such as conductive carbon black are unevenly distributed. In order to obtain such a constitution, a method of producing a semiconductive rubber composition by the following steps is effective: a master batch in which only the conductive particles are previously added to the domains is produced as in the above step (a), and then the obtained master batch is blended with the first rubber composition which becomes the matrix. In other words, a rubber composition (rubber compound) in which conductive particles are unevenly distributed in domains can be produced by the steps of: CMB is prepared by blending conductive particles with a second rubber raw material, and the obtained CMB is blended with a first rubber composition which becomes a matrix.

In the above step (C), as to a method of kneading the CMB becoming a domain and the unvulcanized rubber composition becoming a matrix to obtain an unvulcanized rubber composition having a matrix-domain structure, examples thereof include the following methods.

Each of the CMB in the form of domains and the unvulcanized rubber composition as a base is mixed using a closed mixer such as a banbury mixer or a pressure type kneader; then, the CMB in the form of domains, the unvulcanized rubber composition serving as a matrix, and raw materials such as a vulcanizing agent and a vulcanization accelerator are kneaded using an open mixer such as an open roll to integrate the materials.

Mixing the CMB in the form of domains with a closed mixer such as a banbury mixer or a pressure kneader, and then mixing the CMB in the form of domains with a raw material of an unvulcanized rubber composition to be a base body with the closed mixer; then, the materials are kneaded using an open mixer such as an open roll to integrate the materials, for example, a vulcanizing agent and a vulcanization accelerator.

The conductive layer is formed by molding a rubber composition having a matrix-domain structure on the conductive support by a known method such as extrusion molding, injection molding, and compression molding. Further, the conductive layer is bonded to the conductive support via an adhesive as needed, and thereafter, the conductive layer formed on the conductive support is vulcanized to become a crosslinked body of the rubber compound.

The matrix-domain structure of the conductive layer can be controlled by the mixing time in the above closed mixer and open mixer such as open rolls, the gap between the rolls of the mixer, and the forming speed in extrusion molding, injection molding, compression molding, or the like.

< Process Cartridge for electrophotography >

Fig. 6 shows a schematic sectional view of a process cartridge for electrophotography including the conductive member according to the present disclosure as a charging roller. The process cartridge is an apparatus that integrates a developing apparatus with a charging apparatus, and is configured to be detachably mounted to a main body of an electrophotographic image forming apparatus. The developing device is a device that integrates at least the developing roller 43 and the toner container 46, and may include a toner supply roller 44, a toner 49, a developing blade 48, and an agitating blade 410 as necessary. The charging apparatus is an apparatus that integrates at least the electrophotographic photosensitive member (photosensitive drum) 41, the cleaning blade 45, and the charging roller 42, and may include a waste toner container 47. The charging roller 42, the developing roller 43, the toner supply roller 44, and the developing blade 48 are configured such that a voltage is applied to each thereof.

< electrophotographic image forming apparatus >

Fig. 7 shows a schematic configuration diagram of an electrophotographic image forming apparatus using the conductive member according to the present disclosure as a charging roller. An electrophotographic image forming apparatus is a color electrophotographic image forming apparatus on which four electrophotographic process cartridges are detachably mounted. In each process cartridge, toner of each color of Black (BK), magenta (M), yellow (Y), and cyan (C) is used. The photosensitive drum 51 rotates in the direction of the arrow, and is uniformly charged by the charging roller 52 to which a voltage from a charging bias power supply is applied; and an electrostatic latent image is formed on the surface thereof by the exposure light 511. On the other hand, the toner 59 stored in the toner container 56 is supplied to the toner supply roller 54 by the stirring blade 510, and is conveyed onto the developing roller 53. Then, the surface of the developing roller 53 is uniformly coated with the toner 59 by the developing blade 58 disposed in contact with the developing roller 53, and at the same time, the toner 59 is provided with electric charge by triboelectric charging. The toner 59 is conveyed by the developing roller 53 disposed in contact with the photosensitive drum 51, and is imparted to the photosensitive drum 51; the above electrostatic latent image is developed by the toner 59, and is visualized as a toner image.

The visualized toner image on the photosensitive drum is transferred to an intermediate transfer belt 515 supported and driven by a tension roller 513 and an intermediate transfer belt driving roller 514 by a primary transfer roller 512 to which a voltage is applied by a primary transfer bias power source. The toner images of the respective colors are sequentially superimposed, and a color image is formed on the intermediate transfer belt.

The transfer material 519 is fed into the apparatus by a feed roller, and conveyed to a space between the intermediate transfer belt 515 and the secondary transfer roller 516. A voltage is applied from the secondary transfer bias power source to the secondary transfer roller 516, and the color image on the intermediate transfer belt 515 is transferred to the transfer material 519. The transfer material 519 to which the color image is transferred is subjected to fixing processing by a fixing device 518 and is discharged to the outside of the apparatus; and the printing operation ends.

On the other hand, the toner remaining on the photosensitive drum without being transferred is wiped off by the cleaning blade 55 and stored in the waste toner containing container 57; and the cleaned photosensitive drum 51 repeats the above steps. Further, the toner remaining on the primary transfer belt without being transferred is also erased by the cleaning device 517.