JP7225005B2 - Conductive member and manufacturing method thereof, process cartridge and electrophotographic image forming apparatus - Google Patents

Description

The present disclosure relates to an electrophotographic conductive member and its manufacturing method, a process cartridge, and an electrophotographic image forming apparatus.

In an electrophotographic image forming apparatus, which is an image forming apparatus employing an electrophotographic method, conductive members are used for various purposes, for example, as conductive rollers and blades such as charging rollers, transfer rollers, developing rollers, and developing blades. ing. These conductive members have a conductive layer to which conductive particles such as carbon black (CB) are added in order to adjust the conductivity.

Patent document 1 has a sea-island structure comprising a polymer continuous phase made of an ion-conductive rubber material and a polymer particle phase made of an electronically-conductive rubber material, and the ion-conductive rubber material is mainly volume-specific A semi-conductive rubber made of a raw material rubber having a resistivity of 1×10 ¹² Ω·cm or less, wherein the electronic conductive rubber material is made conductive by blending an electronic conductive agent (conductive particles) into the raw rubber B. composition and a charging member having an elastic layer formed from the semiconductive rubber composition. Patent Literature 1 discloses that such a semiconductive rubber composition exhibits effects such as small voltage dependency and variation in electrical resistance and small environmental dependency of electrical resistance. .

Japanese Patent Application Laid-Open No. 2002-003651

In forming an electrophotographic image using the charging member disclosed in Patent Document 1, the present inventors have found that the charging bias to be applied between the charging member and the electrophotographic photosensitive member, which is the member to be charged, is generally A voltage (-800 to -1000 V) lower than the charging bias (for example, about -1100 V) was considered. In recent years, in response to the demand for further miniaturization and cost reduction of electrophotographic image forming apparatuses, the power supply can be made smaller if high-quality electrophotographic images can be obtained even if the charging voltage is lowered. It's for.

As a result, graininess in a halftone image caused by uneven surface potential of the electrophotographic photosensitive member may appear in the electrophotographic image.
It is desired to provide a conductive member for electrophotography which can be used as a charging member capable of uniformly charging a member to be charged even when the charging bias is lowered.

Therefore, one aspect of the present invention is that in a conductive member used with low voltage application, the movement of charges in the conductive path becomes extremely efficient, the electrical resistivity is less likely to change even under high-speed processes, and the conductive path The present invention aims at providing a conductive member for electrophotography in which discharge unevenness can be suppressed by homogenization of .
Another aspect of the present invention is directed to providing a process cartridge that contributes to the formation of high-quality electrophotographic images. Yet another aspect of the present invention is directed to providing an electrophotographic image forming apparatus capable of forming high-quality electrophotographic images.

According to one aspect of the invention,
An electrophotographic conductive member having a conductive layer having a matrix comprising a crosslinked product of a first rubber and a plurality of domains dispersed in the matrix, each domain comprising a second and conductive particles, and the first rubber differs from the second rubber in that the cross-sectional area of each of the domains appearing in the cross-section in the thickness direction of the conductive layer is Let μ be the average ratio of the cross-sectional area of the conductive particles included in each domain, and let σ be the standard deviation of the ratio. , 20% or more and 40% or less, and at least 8 of the first cubic samples with a side of 9 μm sampled from any 9 locations of the conductive layer, at least 8 samples under the following conditions ( Provided is a conductive member for electrophotography that satisfies 1).

Note that condition (1) is defined as follows: "When one sample is divided into 27 unit cubes each having a side of 3 μm, and the volume Vd of the domain contained in each of the unit cubes is obtained, Vd is 2. .The number of unit cubes of 7 to 10.8 μm ³ is at least 20.”

According to another aspect of the present invention, there is provided the electrophotographic conductive member manufacturing method described above, wherein the electrophotographic conductive member comprises a columnar or cylindrical conductive substrate; A charging roller, a transfer roller, or a developing roller having the conductive layer on the outer peripheral surface of the substrate,
The manufacturing method is
An unvulcanized rubber mixture containing a first unvulcanized rubber as a raw material of the first rubber, a second unvulcanized rubber as a raw material of the second rubber, and the conductive particles , a step of kneading using a kneader equipped with an extensional shear screw to obtain an unvulcanized rubber kneaded material that will be the material of the conductive layer ;
forming a layer of the unvulcanized rubber mixture on the outer peripheral surface of the conductive substrate;
and vulcanizing the first unvulcanized rubber and the second unvulcanized rubber in the layer of the unvulcanized rubber mixture to obtain the conductive layer. A method of manufacturing a component is provided.

According to another aspect of the present invention, there is provided a process cartridge detachably attached to a main body of an electrophotographic image forming apparatus, the process cartridge comprising the conductive member described above.
According to still another aspect of the present invention, there is provided an electrophotographic image forming apparatus comprising the conductive member described above.

According to one aspect of the present invention, in a conductive member used at low voltage application, the movement of charges in the conductive path becomes extremely efficient, the electrical resistivity is less likely to change even under high-speed processes, and the conductive member It is possible to obtain a conductive member for electrophotography in which discharge unevenness is suppressed by homogenization of paths.
Further, according to another aspect of the present invention, it is possible to obtain a process cartridge that contributes to the formation of high-quality electrophotographic images. Further, according to another aspect of the present invention, it is possible to obtain an electrophotographic image forming apparatus capable of forming high quality electrophotographic images.

1A shows an example of an electrophotographic conductive member according to one embodiment of the present invention; FIG. (b) A schematic diagram for explaining a first cube and a unit cube according to one aspect of the present invention. FIG. 2 is a schematic diagram for explaining the structure of a conductive layer having a matrix containing a crosslinked product of a first rubber and a plurality of domains dispersed in the matrix; BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram for explaining an example of an elongational shearing screw used for producing a conductive elastic layer according to this embodiment: (a) a screw provided with an elongational shear imparting mechanism inside the screw; A screw with an elongation shear imparting mechanism. 1 is a configuration diagram showing an electrophotographic image forming apparatus according to one aspect of the present invention; FIG. FIG. 3 is a diagram showing a process cartridge according to one aspect of the present invention; 1 is a configuration diagram showing an example of an electrical resistance measuring device that measures a current value flowing through a conductive member; FIG.

The inventors of the present invention have investigated the reason why it is difficult for the charging member according to Patent Document 1 to uniformly charge the surface of the electrophotographic photosensitive member when the charging bias is lowered. In the process, in the charging member according to Patent Document 1, attention was paid to the role of the polymer particle phase made of an electron conductive rubber material. That is, in the elastic layer (conductive layer), it is considered that electron conductivity is imparted to the conductive layer by transfer of electrons between polymer particle phases. Based on these considerations, it was presumed that the above-mentioned problem in the case of lower charging bias is caused by non-uniform dispersion of the polymer particle phase in the conductive layer. That is, by lowering the charging bias, it becomes difficult for electrons to be transferred between polymer particle phases. Here, when focusing on one polymer particle phase, when the charging bias is high, electrons from the polymer particle phase travel to a plurality of other polymer particle phases existing around the polymer particle phase. Even if there is variation in the distance, it is considered that the other polymer particle phase is delivered almost evenly. However, when the charging bias is low, the electrons from the polymer particle phase are preferentially transferred to other polymer particle phases existing closest among the polymer particle phases existing around the polymer particle phase. Conceivable. As a result, the flow of electrons becomes uneven in the conductive layer, and the discharge from the outer surface of the charging member to the electrophotographic photosensitive member becomes uneven. It is believed that this causes the surface potential of the electrophotographic photosensitive member to become non-uniform.
Therefore, the present inventors have considered that suppressing the variation in the distance between the polymer particle phases in the conductive layer can solve the above-mentioned problems when the charging bias is low. As a result of further studies based on such considerations, it was found that a conductive member that satisfies the following requirements (A) and (B) is effective in solving the problem.
A grainy image in a halftone image caused by uneven surface potential of an electrophotographic photosensitive member has uneven conductivity uniformity in the conductive member (conductive points are not uniformly dispersed). Therefore, it is presumed that unevenness in discharge uniformity occurs, and as a result, it occurs. Further, the graininess of the halftone image in the durability evaluation is lowered by the increase in the electric resistance value of the charging roller.

Requirement (A):
a conductive layer having a matrix containing a crosslinked product of a first rubber and a plurality of domains dispersed in the matrix;
each of said domains comprising a cross-linked product of a second rubber different from said first rubber and conductive particles;

Requirement (B)
When μ is the average ratio of the cross-sectional area ratio of the conductive particles contained in each domain to the cross-sectional area of each domain appearing in the cross section in the thickness direction of the conductive layer, and σ is the standard deviation of the ratio , σ/μ is 0 or more and 0.4 or less,
The μ is 20% or more and 40% or less, and
Of the first cubic samples with a side of 9 μm sampled from any 9 locations of the conductive layer, at least 8 samples satisfy the following condition (1):

Condition (1)
One sample is divided into 27 unit cubes each having a side of 3 μm, and the volume Vd of the domains contained in each of the unit cubes is found to be 2.7 to 10.8 μm ³ . The number of unit cubes should be at least 20.

In other words, when the relationship between μ and σ is “σ/μ is 0 or more and 0.4 or less”, the number and amount of conductive particles contained in each domain are less varied, so the result , becomes a domain with uniform electrical resistance. In particular, when the relationship between μ and σ is "σ/μ is 0 or more and 0.25 or less", the domain becomes more uniform in electric resistance, and the effect of the present invention tends to be enhanced, which is particularly preferable. .
In order to reduce the value of σ/μ, it is preferable to increase the number and amount of conductive particles contained in each domain, and it is also preferable to uniform the size of the domains.
Here, μ is 20% or more and 40% or less. When μ is 20% or more, the electrical connection of the conductive particles within the domain is stabilized. Further, when μ is 40% or less, it is possible to suppress deformation of the domain caused by the conductive particles due to an excessive amount of the conductive particles in the domain. The μ is more preferably 23% or more and 40% or less, and particularly preferably 28% or more and 40% or less.

10 to 40% by volume of domains are contained in the unit cube having a side of 3 μm, and the cubes are homogeneously present in the entire conductive layer. As a result, the conductive domains are three-dimensionally uniform and It becomes the structure densely arranged in the conductive layer. As will be described later, even when the total volume of the domains is increased, there is a tendency that the proportion of domains uniformly present in the entire conductive layer increases. Further, even if the total volume of the domains is the same, by decreasing the domain size and increasing the number of domains, there is a tendency that the proportion of domains homogeneously existing in the entire conductive layer increases dramatically.
That is, as the number of unit cubes having a side of 3 μm that satisfies the Vd value of the above condition (1) increases, the effect of this aspect can be enhanced. Therefore, the number of unit cubes is 20 or more, preferably 22 or more, and more preferably 25 or more.

In addition, since a conductive path is formed by connecting the conductive support to the surface of the conductive layer, the domains are arranged three-dimensionally. Here, "a conductive path is connected" refers to a state in which charges are exchanged between domains in accordance with a desired applied voltage. Although it depends on the applied voltage used, the thickness of the conductive layer, and the electrical resistance of the domains and the matrix, in a three-dimensional evaluation, for example, the distance between adjacent wall surfaces of domains is preferably 100 nm or less, and preferably 50 nm or less. , is particularly favorable for charge transport.

That is, by forming a conductive layer structure that satisfies the above relationship, even when the charging bias is lowered, it is possible to move charges in the conductive path extremely efficiently. As a result, the electrical resistivity does not easily change even under high-speed processing, and the homogenization of the conductive paths suppresses uneven charging and discharging, so that high-quality electrophotographic images can be stably formed. became feasible.

The present invention will be described in detail below. Although the electrophotographic conductive member is described using a charging roller as a representative example, the application of the conductive member of the present invention is not limited. The charging roller, the transfer roller, the developing roller, and the developing blade, which are embodiments of the present invention, can be manufactured by appropriately adjusting the shape of the conductive member of the present invention and using a conventionally known manufacturing method for each member. That is, in the same manner as when the charging bias is lowered, in the conductive member used at low voltage application, the movement of charges in the conductive path becomes extremely efficient, and the electrical resistivity does not easily change even under high-speed processes. In addition, the homogenization of the conductive path also achieves suppression of discharge unevenness.

<Conductive member>
The electrophotographic conductive member 1 according to this embodiment includes a crosslinked product of a first rubber on a conductive substrate (conductive mandrel) 11, as shown in cross section in FIG. 1(a). It has a conductive layer 12 having a matrix and a plurality of domains dispersed in the matrix. Note that another layer can be provided on the conductive layer, if necessary.
Regarding the electrical resistance of the conductive member, it is preferable to control the volume resistivity to 10 ⁴ to 10 ⁸ Ωcm. If it is 10 ⁴ Ωcm or more, the current damping property is good, and the occurrence of image defects can be suppressed. On the other hand, if it is 10 ⁸ Ωcm or less, a current sufficient to function as a conductive member can flow.

<Conductive substrate>
The conductive substrate can be appropriately selected and used from those known in the field of conductive members for electrophotography. For example, in the case of a conductive mandrel, the mandrel has a columnar shape formed by plating the surface of a carbon steel alloy with nickel to a thickness of about 5 μm. Alternatively, the substrate may be hollow and cylindrical. Also, a conductive adhesive (adhesive) may be applied to the substrate.

<Conductive layer>
The conductive layer has a matrix including a first rubber crosslinked product and a plurality of domains dispersed in the matrix. When μ is the average ratio of the cross-sectional area ratio of the conductive particles contained in each domain to the cross-sectional area of each domain appearing in the cross section in the thickness direction of the conductive layer, and σ is the standard deviation of the ratio , ``σ/μ is 0 or more and 0.4 or less, and the μ is 20% or more and 40% or less''. At the same time, at least eight of the first cubic samples (13) each having a side of 9 μm sampled from any nine locations of the conductive layer satisfy the following condition (1).
“Condition (1): One sample is divided into 27 unit cubes 14 each having a side of 3 μm, and when the volume Vd of the domain contained in each of the unit cubes is obtained, Vd is 2.7. The number of unit cubes that are ~10.8 μm ³ is at least 20'.

When used as a charging roller, the conductive layer of the conductive member should have uniform semi-conductivity in order to uniformly charge the member to be charged, and in addition, to uniformly charge the photosensitive member, which is the member to be charged. In order to ensure contact, the hardness is preferably low (for example, the modulus of elasticity of the conductive layer is 1 MPa or more and 100 MPa or less).

It is preferred that substantially only the domains are made conductive by the conductive particles, and the conductive particles are unevenly distributed in the domains.

〔matrix〕
(Material of the first rubber)
The conductive layer has a matrix containing a crosslinked product of the first rubber. The first rubber is not particularly limited as long as it can form a matrix containing the first rubber by blending with the second rubber described later in a predetermined ratio, and the desired physical properties can be obtained. A rubber composition known in the field of conductive members for electrophotography can be suitably used. Examples thereof include natural rubber, vulcanized rubber, and synthetic rubber. Synthetic rubbers include styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butadiene rubber (BR), epichlorohydrin rubber, silicone rubber, fluororubber, isoprene rubber, chloroprene rubber, ethylene-propylene rubber, and the like. . Modified rubbers and copolymers thereof, hydrogenated products thereof, and the like may also be used, and of course they may be combined as appropriate.
These rubbers may contain fillers, softeners, processing aids, tackifiers, antitackifiers, dispersants, which are generally used as compounding agents for rubbers, as long as they do not impair the effects of the present invention. Foaming agents, conductive aids, roughening particles and the like can be added. Needless to say, vulcanizing agents, vulcanizing auxiliaries and vulcanizing accelerators can also be added.
Although it depends on the raw material rubber to be selected, the rubber compounding agent to be mixed in the matrix is preferably 0.1 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the first rubber.

It has been experimentally confirmed that the diene rubber itself, which contains double bonds in its main chain, is good against electric current, that is, has resistance to deterioration in a rubber deterioration test due to electric current.
Therefore, as the synthetic rubber to be used, SBR, NBR, BR, which are diene rubbers, and their modified rubbers are preferable. In addition, NBR and SBR are particularly preferable as the rubber to be used because it has already been confirmed that NBR and SBR have little thermal deterioration during kneading. In addition, SBR tends to improve workability and polishability, and may be extremely preferable depending on the desired physical properties.

(matrix electrical resistance)
The matrix contains few conductive particles such as carbon black and has a higher electrical resistance than the domains.
When the matrix containing the crosslinked product of the first rubber is mainly formed from an ion-conductive raw material rubber having a specific volume resistivity of 1×10 ¹² Ω·cm or less, conduction between domains having conductive particles tends to be good, and it is easy to form a three-dimensionally good conductive path. On the other hand, when it is mainly formed from an insulating raw material rubber having a specific volume resistivity of 1×10 ¹² Ω·cm or more, the conductive particles necessary for satisfying the desired electrical resistance as the conductive member As a result, it becomes difficult to form a three-dimensionally good conductive path.

(Method for measuring electrical resistance of matrix)
The electrical resistance of the matrix can be measured by thinning the conductive layer of the conductive member and using micro terminals. Examples of thinning means include a sharp razor, a microtome, and an FIB (focused ion beam). Regarding the preparation of flakes, in order to eliminate the influence of domains and measure the electrical resistance of only the matrix, the film thickness is smaller than the inter-domain distance measured in advance by a transmission electron microscope (TEM) or a scanning electron microscope (SEM). to make a thin section of Therefore, as a means for thinning, a means capable of producing a very thin sample, such as a microtome, is preferable.

The electrical resistance value is measured by first grounding one side of the flake, and then using an atomic force microscope (AFM), scanning probe microscope (SPM), or the like to measure the electric resistance of the matrix and domains. Identify the location of the matrix and domains of SPM and AFM can also measure hardness distribution. Next, the probes of the matrix are brought into contact with each other, the ground current is measured when a DC voltage of 50 V is applied, and the electric resistance is calculated. At this time, a means such as SPM or AFM that can also measure the shape of the thin piece is suitable because it can measure the film thickness of the thin piece and measure the electrical resistivity.
The measurement of the electrical resistance as described above is performed by cutting out one thin piece sample from each of the regions obtained by dividing the conductive member into four in the circumferential direction and five in the longitudinal direction, and obtaining the above measured values. Calculated by arithmetic mean of 20 sample results.

(Regarding the comparison of matrix and domain electrical resistance)
As noted above, the matrix contains few conductive particles such as carbon black and has a higher electrical resistance than the domains. From the viewpoint of formation of conductive paths in the domains, it is effective that the ratio of volume resistivity between the matrix portion and the domain portion is preferably 5 times or more, more preferably 10 times or more.

The volume resistivity ratio between the matrix portion and the domain portion was measured as follows. A thin piece of the conductive layer was prepared in the same manner as the electrical resistance measurement of the matrix, and current measurement was performed in a minute region using an SPM having a current measurement function. Here, an SPM scan area containing at least one domain was set. For example, if the domain size is submicron, preferably a scanning area of several μm square is set so as to include a plurality of domains. One or more sub-areas corresponding to the matrix are set from the current mapping data (data in which the current value is stored in each pixel) obtained by scanning while applying a constant voltage, and the current in the plurality of sub-areas Calculate the average value of the data and let the average current value of the matrix part be Jd. A similar analysis is also performed for the domain portion, and the average current value of the domain portion is defined as Jm. From the above data, Jm/Jd was evaluated as the resistance ratio (reciprocal of current ratio) between the domain portion and the matrix portion.
The above current measurement is performed by cutting out one thin piece sample of the conductive layer from each of the regions obtained by dividing the conductive member into four in the circumferential direction and five in the longitudinal direction, and obtaining the above measured values. Calculated by arithmetic mean of sample results.

〔domain〕
(Material for second rubber)
The domains that make up the conductive layer have a second rubber. The material of the second rubber is not particularly limited as long as it can form a domain containing the second rubber by blending with the first rubber at a predetermined ratio. As the material for the second rubber, a rubber composition known in the field of electrophotographic conductive members can be suitably used depending on desired physical properties. That is, as long as it is incompatible with the material of the first rubber, for example, the rubber material shown in the above section "[Matrix] (first rubber material)" can be appropriately used.
In addition, in diene rubbers containing double bonds in the main chain, it is preferable to use carbon black as the conductive particles because the compatibility is enhanced depending on the combination. Diene-based rubbers having a styrene skeleton also tend to increase compatibility with carbon black depending on the combination, and are therefore preferable. In addition, in the case of a rubber material having a functional group such as carbon black that can be expected to interact with conductive particles in the main chain, side chain, or terminal portion of the second rubber, it is preferable from the viewpoint of immobilizing the conductive particles. . The viscosity of the material can be easily adjusted by appropriately blending a liquid rubber as the material of the second rubber.
As in the case of the first rubber material, the second rubber material forming the domains contains fillers generally used as compounding agents for the above-described rubbers, as long as the effects of the present invention are not impaired. Agents, softeners, processing aids, tackifiers, antiblocking agents, dispersants, foaming agents, conductive aids, etc. may also be added. Needless to say, vulcanizing agents, vulcanizing auxiliaries and vulcanizing accelerators can also be added.
The amount of the compounding agent for the rubber compounded in the domain is preferably 0.1 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the second rubber, depending on the selected raw material rubber.

(Electrical resistance of domain)
Domains are conductive phases that effectively transport charge along conductive paths in high speed processes. Therefore, it is preferable that the electrical resistivity is low, and specifically, it is preferably 10 ⁻¹ Ωcm to 10 ³ Ωcm. The electrical resistivity of the domain can be set to a desired value by appropriately adjusting the type and amount of conductive particles used.

(Conductive particles)
The conductive domains include crosslinks of the second rubber and conductive particles. Examples of conductive particles include the following conductive particles. Metal fine particles and fibers such as aluminum, palladium, iron, copper and silver; Metal oxide fine particles such as titanium oxide, tin oxide and zinc oxide; , electrolytic treatment, spray coating, composite particles surface-treated by mixing and shaking; conductive carbon black such as furnace black, thermal black, acetylene black, ketjen black; PAN (polyacrylonitrile)-based carbon, pitch-based carbon, etc. carbon powder. Moreover, if necessary, a plurality of these conductive particles can be used in combination.
Furnace blacks include the following. SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, I-ISAF-HS, HAF-HS, HAF, HAF-LS, T-HS, T-NS, MAF, FEF, GPF, SRF-HS- HM, SRF-LM, ECF, and FEF-HS. Thermal blacks include FT and MT. Also, these conductive particles (conductive carbon black) can be used alone or in combination of two or more.

The carbon black used is preferably conductive carbon black having a DBP absorption of 40 ml/100 g or more and 150 ml/100 g or less. The absorption of DBP (dibutyl phthalate) is a value obtained by indirectly quantifying the structure of primary particles of carbon black. In other words, by using carbon black with a well-developed structure having a DBP absorption within the above range, there is a tendency for the interaction with the rubber material to increase even when a second rubber material with low polarity is used. The DBP absorption of carbon black can be measured by the method described in JISK6217-4 (2001). Since conductive carbon black has a highly developed structure, it can be distinguished from other fillers such as reinforcing carbon black by microscopic observation or the like.

The amount of the conductive particles blended in the domains is 5 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the second rubber. More preferably, it is 20 parts by mass or more and 120 parts by mass or less. In particular, the percolation in the domain becomes good, so that the conductive particles are well connected to each other, and as a result, the conductive path in the domain is “electrically densely connected” and stably formed. more preferably 120 parts by mass or less. In addition, 60 parts by mass or more and 120 parts by mass or less is particularly preferable because the dispersion of the conductive particles contained between domains described later is extremely small.

When the amount of the conductive particles to be blended is 5 parts by mass or more with respect to 100 parts by mass of the second rubber, it becomes possible to act as a conductive domain. However, when the volume of the conductive particles is small, the particles may not be transferred to the domains during the blending process using a general mixing device such as a kneader or rolls, or depending on the conditions during processing as a conductive member. Domains may easily migrate and reaggregate due to heat or mechanical application. Therefore, the blending amount of the conductive particles is more preferably 20 parts by mass or more. Further, when the amount is more than 50 parts by mass, the effect tends to be enhanced, and the amount is preferably 60 parts by mass or more, particularly preferably 80 parts by mass or more. In other words, when the content of the conductive particles in the domain is large, the domain becomes hard and migration can be suppressed.

In addition, when the blending amount of the conductive particles is more than 50 parts by mass, a relatively large amount is blended as a general conductive member for electrophotography. The conductivity of the domain itself is developed by electrically connecting the conductive particles in the domain to form a good conductive path. The formation of the conductive path is correlated with the amount of conductive particles in the domain and the volume occupation ratio, and the higher the ratio, the more stable the percolation, so the efficiency of charge transfer in the conductive path can be increased. Therefore, by increasing the blending amount, the conductive properties are enhanced, and the preferable effects of the present invention are likely to be exhibited.

Most preferably, the conductive particles are present only in the domains. However, a method of preparing a masterbatch by adding conductive particles to only the second rubber contained in the domain in advance and then blending the obtained masterbatch with the first rubber to form the matrix was adopted. Even in this case, a phenomenon in which some of the conductive particles migrate to the matrix may be observed. In the present invention, the conductive particles may be present in the matrix as long as they do not contribute to conductivity. The amount of conductive particles that do not contribute to the conductivity of the matrix is preferably lower than the amount of conductive particles per unit volume of the matrix. , 1/5 or less, more preferably 1/10 or less, and still more preferably 1/100 or less.

(Method for measuring electrical resistance of domain)
The domain according to the present invention is a conductive phase, and the electrical resistance of the domain can be measured by the same measuring method as the electrical resistance of the matrix described above.
In addition, the measurement of the electrical resistance as described above is performed by cutting out one thin sample from each of the regions obtained by dividing the conductive member into four in the circumferential direction and five in the longitudinal direction, and obtaining the above measured values. , calculated by the arithmetic mean of the results of a total of 20 samples.

(Regarding domain formation (sea-island structure))
The knowledge known for polymer blends can also be applied to rubber blends in the conductive layer of the present invention.
In the case of immiscible polymer blends, the sea-island structure tends to be domains of polymers with a small composition ratio, although this depends on the viscosity of each polymer and blending conditions.

(means for uniformly dispersing the domains in the matrix)
One means of uniformly dispersing the domains in the matrix is to increase the total volume of the domains. That is, even if the number of domains in the matrix remains the same, the volume occupied by the domains increases. However, as will be described later, if the size of the domain becomes too large, the above condition (1) will not be satisfied. In that case, the distribution uniformity of the domains naturally deteriorates, and the effects of the present invention cannot be obtained.

Further, one of the more effective means for uniformly dispersing the domains throughout the matrix is to finely disperse the domains to a small size. In other words, even if the total volume of domains in the matrix is the same, the number of domains greatly increases due to miniaturization. According to a simple calculation, for example, if there are 100 perfectly spherical domains with a given radius, if the radii are all reduced to 1/2, the number of domains will be about 800 for the same total volume. For this reason, even if the total volume of the main is the same, by decreasing the domain size and increasing the number of domains, the proportion of the domains homogeneously existing in the entire conductive layer increases. As a result, the number of unit cubes that satisfy the condition (1) increases, and the effects of this aspect can be enhanced.

The following formula is known as a theoretical formula for reducing the domain size in a polymer blend.
D = [Cσ/η0γ・]・f(η0/η)
D: Dispersed particle size (domain particle size) σ: Interfacial tension η0: Matrix viscosity η: Dispersed phase viscosity (domain viscosity) C: Constant γ・: Shear rate

In other words, in the present invention, the following three methods are generally conceivable for reducing the grain size of the domain (island size):
(Method A) Reduce the interfacial tension between the first rubber and the second rubber.
(Method B) Bringing the viscosity of the first rubber close to the viscosity of the second rubber.
(Method C) Increase the shear rate during blending.

-Method A: Specifically, the combination of the first rubber and the second rubber in which the difference between the solubility constants (Solubility Parameter: SP value) is small is selected in order to uniformly disperse the conductive domains. preferred for Moreover, as a method for reducing the interfacial tension, a method of adding a compatibilizer is also suitable. If the SP value difference is too small, it may become difficult to unevenly distribute the conductive particles in the domain only in the domain, or the compatibility may become too strong to stably form a sea-island structure.

・Method B: Specifically, the conductive domains are uniformly dispersed by selecting the first rubber and the second rubber from a combination of materials having similar viscosities at the kneading temperature. preferred for Here, it is also effective to use liquid rubber or the like for part of the second rubber of the domain.

Method C: It is effective to simply increase the shear rate during blending or lengthen the shear time. Although the details will be described later, it is particularly effective for the inventors to use "extensional shear" rather than "simple shear" as the shearing mechanism to be applied in addition to increasing the shear rate.

(domain size)
As described above, the smaller the domain size in the present invention, the better.
Specifically, in order to satisfy the above condition (1), the domain size in the cross section is preferably 0.1 to 2 μm or less, more preferably 1 μm or less, and even more preferably It is 0.5 μm or less. In particular, when the thickness is 0.4 μm or less, an extremely high effect in the present invention can be expected. If the domain size is less than 0.1 μm, a large amount of conductive particles may not be blended in the domain. Note that the domain size refers to the diameter of the equivalent circle diameter. Also, the average domain size indicates an area-weighted average domain size.

(Method of measuring domain size)
In the method for measuring the domain size according to the present invention, first, a clean fracture surface is formed at the measurement location of the sample by the following means. Here, the preparation of the fractured surface may be performed on the thin piece using a freeze fracture method, a cross polisher method, a focused ion beam method (FIB), or the like. Considering the smoothness of the fracture surface and the pretreatment for observation, the FIB method is preferable.
Next, in order to suitably observe the domain structure, a pretreatment such as dyeing treatment, vapor deposition treatment, or the like, which can suitably obtain a contrast between the domain and the matrix, may be performed.
A thin piece on which fracture surfaces have been formed and pretreated can be observed with a laser microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM). Among these, it is preferable to observe with a SEM at a magnification of 10,000 to 100,000 in order to accurately quantify the area of the domain, which is the conductive phase.

The case of the conductive roller will be specifically described below.
First, a round slice sample is produced from a conductive roller using a sharp razor. Here, when the length in the longitudinal direction is l, the conductive layer is arranged so that it can be measured at three positions of (1/4)l, (2/4)l, and (3/4)l from the end. Create a round slice sample. The cross-section of the conductive layer of the sliced sample is subjected to cryo-ion milling treatment at intervals of 90 degrees in the circumferential direction of the roller, near the center of the metal core and the surface. The surface is exposed by cryo-ion milling. Then, the conductive layer cross section in each cross section at (1/4)l, (2/4)l, and (3/4)l is SEMed at every 90 degrees in the circumferential direction of the roller, and the central part of the surface from the core bar position (product name: Ultraplus, manufactured by Carl Zeiss Co.), and the number of pixels is 4096×3072 at a magnification of 5000 (a total of 12 images, for example, 20 μm square SEM images can be obtained).
After that, the images obtained by the above observations are each subjected to binarization and image analysis using an image analysis device (product name: LUZEX-AP, manufactured by Nireco), and the obtained domain area S is calculated. Calculate the equivalent circle diameter by applying the calculation formula of √S/√π. In the present disclosure, the equivalent circle diameter is defined as the domain size.

(Method for measuring domain volume)
The volume of the domain can be determined by measuring the conductive layer in three dimensions using FIB-SEM.
FIB-SEM is a method of observing a cross-section of a sample processed and exposed with an FIB (Focused Ion Beam) apparatus with a scanning electron microscope (SEM). In order to investigate the three-dimensional structure, after acquiring many photographs by repeating continuous processing and observation, the SEM images are subjected to 3D reconstruction processing with computer software to create a three-dimensional image of the sample structure. It is possible to do it by constructing as

As a specific method for measuring the domain volume, a three-dimensional stereoscopic image represented by FIG. It was confirmed.
In other words, the conductive layer is sampled from any 9 locations, but in the case of a roller shape, when the length in the longitudinal direction is l, (1/4)l, (2/4) from the end. One sample is cut out from each of three locations near l and (3/4)l at intervals of 120 degrees in the circumferential direction of the roller.
After that, three-dimensional measurement is performed using FIB-SEM, and a cubic image having a side of 9 μm is measured at intervals of 60 nm. Here, the cross section of the conductive layer in each cross section of (1/4) l, (2/4) l, and (3/4) l is measured every 120 degrees in the circumferential direction of the roller, from the core metal position to the center of the surface. measurement.

In addition, in order to suitably observe the domain structure, it is also preferable to perform a pretreatment that suitably obtains a contrast between the domain and the matrix. Dyeing treatment can be preferably used here.
Using the 3D visualization and analysis software Avizo (registered trademark, manufactured by FEI Co., Ltd.), the images obtained after that are 27 pieces contained in one cubic sample with a side of 9 μm, one side Calculate the volume of the domain in the unit cube of 3 μm.
The distance between the adjacent wall surfaces of the domain can be similarly measured using the above 3D visualization and analysis software, and after obtaining the above measurement value, the arithmetic average of the total 27 samples can be calculated. can.

(regarding the conductive particles in the domain)
As described above, when "σ/μ is 0 or more and 0.4 or less, and the μ is 20% or more and 40% or less", the number of conductive particles contained in each domain・Because there is little variation in the amount, the domains have uniform electrical resistance. In particular, when the relationship between μ and σ is "σ/μ is 0 or more and 0.25 or less", the domain becomes more uniform in electric resistance, so that the variation of the conductive particles becomes extremely small, It is more preferable because it tends to enhance the effect of the present invention.
As one of the methods for realizing "σ/μ is 0 or more and 0.25 or less", as described above, it is effective to increase the filling amount of the conductive particles blended in the domain. In particular, as a result of extensive studies, the inventors have found that the ratio of the cross-sectional area of the conductive particles contained in each domain to the cross-sectional area of each domain appearing in the conductive layer is 23% or more, more preferably It has been found that there is a tendency to be achievable when it is 28% or more. As will be described later, mixing treatment using an extensional shearing device is also preferred, and mixing treatment using a continuous extensional shearing device is more preferred.

When the conductive particles are carbon black, fine particles preferably have an average primary particle size of 5 nm or more and 60 nm or less, particularly 10 nm or more and 50 nm or less. Here, the average primary particle size of the conductive particles is the arithmetic mean particle size. The definition of the average primary particle size is a single crystal or a collection of crystallites close to it microscopically, each having a size of 5 nm or more and 60 nm or less. In addition, as a measurement method, (1) a transmission electron microscope (TEM) in which an object irradiated with an electron beam is observed through transmission, and (2) a scanning electron microscope (TEM) in which the surface of an object irradiated with an electron beam is observed. There is a method using a microscope (SEM). As a method of calculating the average primary particle size, a method of directly obtaining the above-described measured image is suitable.

(A method for measuring the area of conductive particles in the domain and a method for calculating the variation (σ/μ) of the conductive particles)
It can be calculated using the SEM image observed in the above "Measuring method of domain size".
A central 3 μm square is extracted from the above SEM images (total of 12 images), and each is analyzed with an image analyzer (product name: LUZEX-AP, manufactured by Nireco), using the contrast difference inside each domain. The area of the conductive particles represented by carbon black and the area of the domains are analyzed, and the cross section of the conductive particles included in each of the domains with respect to the cross section of each of the domains appearing in the cross section in the thickness direction of the conductive layer. “σ/μ” is calculated, where μ is the average value of the area ratios and σ is the standard deviation of the ratios. In addition, when there is no domain at all in the center 3 μm square, another place is randomly observed with SEM.

(domain shape)
The cross-sectional shape of the domain according to the present invention is preferably close to circular. Specifically, it is preferable that the circularity value shown below is 1 or more and less than 2. A roundness of 1 indicates a perfect circle.
In order to obtain the effects of the present invention, it is preferable that the number ratio of domains having a circularity of 1 or more and less than 2 among the domains appearing in the cross section of the conductive layer is 70% or more. In addition, since the effect of the present invention increases when this ratio is high, it is more preferably 80% or more.
Generally, it is known that the shape and anisotropy of the conductive particles greatly change the conductive properties (Matsutani et al., Int. J. Mod. Phys. C 21 (2010) 709). In other words, in a domain with a high aspect ratio and poor circularity, the electric field distribution of the domain has an aspect ratio, that is, electric field anisotropy occurs. As a result, an electric field concentration point is formed, which tends to make it difficult to obtain a homogeneous conductive path.

In addition, when the circularity value of the domain is less than 2 and 1.1 or more, preferably 1.5 or more, the interfacial area with the matrix increases, and the following effects can be expected, which is preferable in some cases. be. That is, when the conductive member is placed in contact with the photoreceptor, the conductive member is repeatedly mechanically compressed in the vicinity of the nip formed between the photoreceptor and the conductive member. At that time, in the case of a perfect circle with an extremely high roundness, migration of domains based on the application of mechanical energy is likely to be induced, and as a result, the network structure of the conductive path changes, and the electrical resistance value of the conductive layer fluctuates. It is assumed that On the other hand, when the circularity value of the domain is 1.1 or more, preferably 1.5 or more, it is assumed that this fluctuation is suppressed because the interfacial area with the matrix increases.

(Domain shape control method)
In the present invention, as a technique for controlling the shape of the domains, particularly for obtaining domains with good roundness, it is effective to increase the filling amount of the conductive particles in the domains, as described above. In other words, when the amount of conductive particles is small, domains may be affected by heat or mechanical application during a blending process using a general mixing device such as a kneader or rolls, or depending on the conditions during processing as a conductive member. It may easily migrate and reaggregate. However, when the filling amount of the conductive particles in the domain is high, the domain becomes hard, and as a result, the migration can be suppressed, and deterioration of circularity due to reaggregation can be suppressed.
It should be noted that by increasing the filling amount, the second rubber mixed with the conductive particles is likely to be sheared during kneading, and it can be expected that the roundness of the domain will be improved.

In addition, the above-described methods of reducing the size of the domain (island size) (methods A to C above) are also effective. That is, the smaller the domain size, the smaller the aspect ratio. In addition to increasing the shear rate, the inventors found that it is effective to use "extensional shear" rather than "simple shear" as the shearing mechanism to be imparted, although the details will be described later. In particular, mixed processing using a continuous extensional shear device tends to give more favorable results.

(Measurement method of domain shape - Calculation method of roundness)
The shape of the domain according to the present invention can be quantified using an SEM image obtained by fabricating and observing a fractured surface in the same manner as the "method for measuring domain size" above.
That is, each domain in the SEM image obtained above is subjected to binarization and image analysis by an image analysis device (LUZEX-AP, manufactured by Nireco), and the roundness is calculated from the average value. Here, the circularity is ``JIS B 0621; when a circular body is sandwiched between two concentric geometric circles, the difference between the radii of the two concentric circles is expressed as the minimum distance between the two concentric circles.'' is parsed according to the definition of
In addition, when inorganic fillers and roughening particles affect image processing in SEM observation of domains, etc., contrast difference, EDX measurement (SEM / EDX (scanning electron microscope / energy dispersive X-ray spectroscopy), , can be calculated by appropriately excluding by using hardness measurement using SPM measurement separately.
Here, domains with equivalent circle radii of 100 nm or more are used for the calculation.

(domain size distribution)
In the conductive layer according to this aspect, conductive domains with uniform electrical resistance are arranged three-dimensionally evenly and densely. Therefore, as for the size distribution of the domains, it is preferable that the domain sizes are uniform and the domains are fine. Specifically, it was confirmed that the effects of the present invention are exhibited when the relationship between the domain size and the number of domains in the cross section of the conductive layer satisfies the following relational expressions (1) and (2).
Relational expression (1)
80≦100×L2/L1≦100;
Relational expression (2)
0≦100×L3/L1≦20.
In the formula, L1 is the total number of the domains appearing in the cross section of the conductive layer in the thickness direction, L2 is the area of the domains measured in the cross section of 3.0×10 ⁴ nm ² or more, 1. L3 indicates the number of domains with an area of less than 2×10 ⁵ nm ² and the number of domains with an area of 1.2×10 ⁵ nm ² or more.
Furthermore, when the "100×L2/L1" is 95 or more and the "100×L3/L1" is 5 or less, the uniformity of the domain size distribution can be made extremely high.

(Method for measuring domain size distribution - "100 x L2/L1" and "100 x L3/L1")
It can be calculated from the area and the number of domains in each domain obtained by analysis in the above section "Method for measuring domain size".
That is, here, the total number of the domains is L1, the number of the domains having an area of 3.0×10 ⁴ nm ² or more and less than 1.2×10 ⁵ nm ² is L2, and the area is 1.2×10 The number of domains having a size of ⁵ nm ² or more is defined as L3, and "100×L2/L1" and "100×L3/L1" are calculated.

(Method for controlling domain size distribution)
The key here is to refine domains and suppress reaggregation between domains. In other words, the technique described in the above-mentioned "means for uniformly dispersing domains in a matrix" and the technique for suppressing reaggregation of domains described in the above-mentioned "method for controlling the shape of domains" are preferably used.

[Method for producing conductive member for electrophotography]
The method for manufacturing the electrophotographic conductive member of the present invention is not particularly limited as long as the conductive layer having the structure of the present invention described above can be formed, and can be formed by appropriately adjusting the following requirements. .
(1) Selection of raw materials for kneading a conductive rubber mixture containing a first rubber raw material and a second rubber raw material blended with conductive particles.
(2) Compounding during kneading of the rubber mixture.
(3) Type of kneader, shear rate, shear force and kneading time when kneading the rubber mixture.

For example, by mixing an unvulcanized first rubber and a second unvulcanized rubber mixed with electrically conductive particles prepared separately, and vulcanizing and curing in accordance with an appropriate processing process, A conductive member having a conductive layer having a matrix containing a crosslinked product of the first rubber and domains containing a plurality of crosslinked products of the second rubber dispersed in the matrix is obtained.

<Regarding the kneading process>
In addition to a simple shear dispersing device generally used for rubber mixing and kneading, a stretching shear dispersing device is also suitable for use.
As described above, the greater the shearing force and the greater the time (number of times) of shearing, generally the more the immiscible rubber tends to disperse. On the other hand, it is also known that shear heat generation increases at the same time, promoting scission of rubber molecular chains, degrading the material, and causing reaggregation of domains. In other words, it is important to control the temperature during the working process as well as applying the shear force.

<Examination of mixer for kneading>
(Comparison of dispersing device by simple shear and dispersing device by elongational shear)
Conventional rubber mixing devices such as pressurized kneaders and open rolls, as well as twin-screw kneading extruders capable of applying a larger shearing force than these, have been well known as dispersing devices by simple shearing. there is However, in the present invention, as described above, the filling amount of conductive particles in the domains tends to be high. According to the study by the inventors, a dispersing device that uses simple shearing cannot uniformly impart sufficient shear to disperse the second rubber compounded with conductive particles, and local heat generation occurs during processing. As a result, in some cases, the domains could not be well and uniformly dispersed.
As a result of extensive studies, the inventors also found that a kneader equipped with an elongating shear screw is suitable for uniformly dispersing the domains of the present invention throughout the matrix.
Elongational shearing is a simple shearing mechanism in pressurized kneaders, open rolls, and twin-screw kneading extruders. domain size is easy to obtain. Since rubber exhibits entropy elasticity, it is also suitable for this system because it absorbs heat when stretched. are doing.
In addition, even if the amount of conductive particles in the domain is high, this method can uniformly impart a higher shear than the simple shear method, so uniform fine dispersion can be achieved. Here, it is also confirmed that uniform dispersion processing can be completed in an extremely short dispersion time (several seconds).

The inventors have also confirmed that simply increasing the shearing force in simple shearing may not be able to uniformly finely disperse the domains in the matrix. Specifically, a twin-screw kneading extruder (product name: KZW15TW-4MG-NH (-6000), manufactured by Technobell) was used for the examination. In such a simple shearing process, simply increasing the shearing speed causes gelation and reaggregation of the material, and sometimes the domains cannot be uniformly finely dispersed in the matrix.

As mentioned above, the mechanisms of extensional shear and simple shear are very different. Shear flow in simple shear is a flow in which a material is torn off by a velocity gradient, while elongational flow in elongational shear is a flow in which a material is stretched in the principal stress direction. Although different from the dispersion of a rubber material (viscoelastic body) like the present invention, Kajiwara et al. It has been reported that the droplets are stretched and split regardless of the viscosity ratio, and that fine dispersion can be achieved even in a system with a viscosity ratio separated by about 5 or more [Molding Process, Vol. 23, No. 2, pp. 72-77 (2011)]. Probably, it can be inferred that the above-mentioned "effect of easy dispersion by elongation shear even if the viscosity ratio of the materials is different" acts similarly in the blend material system of the rubber material that is the viscoelastic body in the present invention. As a result, it is assumed that uniform fine dispersion of the matrix material and the domain material containing a large amount of conductive particles could be achieved.

That is, the conductive member for electrophotography provided with the conductive layer described above comprises (1) a first unvulcanized rubber as a raw material of the first rubber and a second rubber as a raw material of the second rubber; (2) kneading the unvulcanized rubber mixture containing the unvulcanized rubber and the conductive particles using a kneader equipped with an extensional shear screw to obtain an unvulcanized rubber kneaded product; forming a layer of said unvulcanized rubber mixture on the outer surface of said conductive substrate; 2, vulcanizing the unvulcanized rubber to obtain the conductive layer.

It is preferable to use an extensional shearing device equipped with an extensional shearing screw 31 as shown in FIG. 3 to apply the extensional shear. 3 (a), "a "batch circulation system" with a screw 3a having an elongating shear applying mechanism (capillary) inside the screw 31", and "a screw 31 outside the screw 31" shown in FIG. 3 (b) There is a "continuous method" equipped with a screw 3b having an elongating shear imparting mechanism (capillary).
In the elongation shearing device equipped with the screw 3a of the batch circulation method, the hole 32 of the thin tube is opened inside the screw, and the rubber composition reaches the tip of the screw 31 during kneading, and then passes through the hole of the thin tube at the tip of the screw 31. It has a mechanism that returns to the rear end of the screw 31 through 32 . Therefore, the rubber composition repeatedly passes through the pores of the capillaries, and shear force is applied to the pores of the capillaries due to the elongation motion. In addition, since the rubber composition can be continuously retained in the elongation shear field, it is possible to apply a large shear force in a short time. However, depending on the residence time, some reaggregation may occur, so a continuous elongational shearing device may be preferable.

Here, it is preferable that the hole diameter of the thin tube to which the elongational shear is applied is larger than 0.5 mm and 5.0 mm or less. If it is 5.0 mm or less, the share in elongational shear is sufficient, and if the hole diameter of the capillary tube is larger than 0.5 mm, the rubber does not sufficiently pass through the hole of the capillary tube and processing becomes difficult. is confirmed. The hole diameter of the capillary is preferably 1.0 to 3.0 mm. In addition, it is particularly preferable to perform the kneading in a short treatment time. Note that the shear energy applied to the rubber composition changes depending on the size of the hole diameter of the fine tube. Therefore, from the viewpoint of suppressing heat generation during shearing, the selection of the hole diameter of the thin tube is one of the important factors in the processing conditions, along with the feed rate of the material and the control of the temperature of the material during mixing. The number of holes in the capillaries is not particularly limited as long as the desired uniform dispersion of the domains can be achieved. good too.
As a result of intensive studies, the inventors also found that the continuous type is particularly suitable as processing conditions because it has a structure in which only elongational shear is efficiently imparted.

As a batch circulation type apparatus, for example, an elongational shearing apparatus (a micro shearing apparatus: manufactured by Imoto Seisakusho and a high speed shearing apparatus: manufactured by Niigata Machine Techno Co., Ltd.) is also preferably used. Further, as a continuous system apparatus, as shown in FIG. 3(b), the screw part of the batch circulation system apparatus can be preferably used by modifying the apparatus so that the elongation shear imparting mechanism inside the screw is provided outside. can be done. Also, BANDO TECHNICAL REPORT No. 18/20147 P2, etc. can also be used as appropriate.

As a result of intensive study, it was confirmed that in the dispersion treatment process, the temperature of the material during dispersion is measured using an infrared thermometer that can be directly measured, and that setting the temperature to 170°C or less gives good results for uniform dispersion. are doing. In addition, when the temperature at the time of kneading the material is measured with a thermocouple, it probably tends to be measured lower than the infrared temperature sensor, and good results can be obtained even with the same processing at 170 ° C. or less. may not be available. In other words, it is effective to precisely control the working process temperature using a mixing device having an extensional shearing mechanism equipped with a precise material temperature measurement function (IR sensor).

In addition, when shearing the rubber composition, it is also preferable to provide a chiller capable of temperature control to −20° C. below room temperature in order to prevent deterioration of the rubber composition due to shear heat generation. In other words, if the screw portion is equipped with an infrared temperature sensor that accurately monitors the temperature of the material during mixing as described above, it is possible to precisely control the mixing conditions. It is suitable for the following settings.

<Electrophotographic image forming apparatus>
An electrophotographic image forming apparatus according to an aspect of the present invention comprises an electrophotographic conductive member according to an aspect of the present invention. An example of the electrophotographic image forming apparatus is shown in the schematic diagram of FIG. The photoreceptor 41, which is a member to be charged, has a drum shape with a conductive support 41b made of aluminum or the like and a photosensitive layer 41a laminated thereon. It is rotationally driven in the direction with a predetermined peripheral speed.

Both ends of the conductive mandrel 11 of the charging roller 1, which is a conductive member for electrophotography according to one aspect of the present invention, are pressed against the photoreceptor 41 by pressing means (not shown), thereby pressing the conductive mandrel. The conductive layer 12 to which a direct current (DC) bias is applied by the power source 42 and the rubbing electrode 43a is placed in contact therewith. As the charging roller 1 rotates following the rotation of the photoreceptor 41, the photoreceptor 41 is uniformly charged (primary charging) to a predetermined polarity and potential.

Next, an electrostatic latent image corresponding to the target image information is formed on the peripheral surface of the photosensitive member exposed to the target image information from the exposing device 44 (laser beam scanning exposure, document image slit exposure, etc.). The electrostatic latent image on the photoreceptor is formed into a toner image by adhering toner supplied by the developing member 45 . Next, a transfer material 47 is conveyed from a paper supply unit (not shown) to a transfer unit between the photoreceptor 41 and the transfer member 46 in synchronism with the rotation of the photoreceptor 41. The polarized transfer member is pressed and the toner images are sequentially transferred onto the transfer material 47 .

The transfer material 47 to which the toner image has been transferred is separated from the photoreceptor 41 and conveyed to fixing means (not shown) where the toner image is fixed and output as an image formed product. In an electrophotographic image forming apparatus that also forms an image on the rear surface, the transfer material 47 is re-conveyed between the photoreceptor 41 and the transfer member 46 in order to perform image formation again by the re-conveying means.

After the image transfer, the peripheral surface of the photoreceptor 41 is subjected to pre-exposure by a pre-exposure device 48 to remove (discharge) residual charges on the photoreceptor. Known means can be used for the pre-exposure unit 48, and suitable examples include LED chip arrays, fuse lamps, halogen lamps and fluorescent lamps. The peripheral surface of the photoreceptor 41 from which the charges have been removed is washed by a cleaning member 49 to remove adhering contaminants such as transfer residual toner, and is repeatedly used for image formation.

In the electrophotographic image forming apparatus, the charging roller 1 may be driven by the photoreceptor 41 or may be non-rotating. may be rotationally driven. When the electrophotographic image forming apparatus is used as a copier, exposure is performed by using reflected light or transmitted light from the original, reading the original into a signal, and based on this signal, scanning a laser beam or driving an LED array. Alternatively, it may drive a liquid crystal shutter array.

Examples of the electrophotographic image forming apparatus of the present invention include copiers, laser beam printers, LED printers, and electrophotographic applied apparatuses such as electrophotographic plate making systems.

<Process cartridge>
A process cartridge according to an aspect of the present invention includes the conductive member, and is detachably attached to a main body of an electrophotographic image forming apparatus. An example of the process cartridge is shown in the block diagram of FIG. This process cartridge includes a roller-shaped conductive member according to one aspect of the present invention as a charging roller 51 . A drum-shaped electrophotographic photosensitive member (hereinafter also referred to as an “electrophotographic photosensitive drum”) 53 is arranged so as to be charged by a charging roller 51 . Here, specifically, the charging roller 51 is pressed against and contacts the electrophotographic photosensitive drum 53 . Further, a developing roller 55 for supplying developer for developing an electrostatic latent image formed on the surface of the electrophotographic photosensitive drum 53 and a developer remaining on the circumferential surface of the electrophotographic photosensitive drum 53 are removed. A cleaning blade 57 is provided for removal. A developing blade 59 is in contact with the developing roller 55 . A blade-shaped conductive member according to one aspect of the present invention can also be used for the developing blade 59 .

EXAMPLES The present invention will be described in more detail below with reference to examples, but these are not intended to limit the present invention in any way. Unless otherwise specified, "parts" means "parts by mass", and unless otherwise specified, reagents and the like were commercially available high-purity products.
In the examples, A kneaded rubber composition (mixture) refers to an unvulcanized rubber composition (mixture) to which no crosslinking agent or vulcanization accelerator is added, and B kneaded rubber composition (mixture) refers to a crosslinking agent or Refers to an unvulcanized rubber composition (mixture) to which a vulcanization accelerator is added.

<Example 1>
(Production of rubber mixture)
100 parts of an ethylene-propylene-diene terpolymer (trade name: EPT4045, manufactured by Mitsui Chemicals, Inc.) as a raw material for the domain, and carbon black (trade name: Ketjenblack EC600JD, manufactured by Ketjenblack International Co., Ltd.) as conductive particles. ) 3 parts and carbon black (trade name: Toka Black #7360, manufactured by Tokai Carbon Co., Ltd.) 40 parts, paraffin oil as a softening agent (trade name: PW-380, manufactured by Idemitsu Kosan Co., Ltd.) 10 parts, stearic acid as a processing aid One part was kneaded with a pressure kneader to obtain a masterbatch 1.
Next, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (trade name: Epichromer CG, manufactured by Osaka Soda Co., Ltd.) 180 parts, stearic acid 1 part as a processing aid, masterbatch 1 45 parts, vulcanizing agent 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne (trade name: Perhexa 25B-40, manufactured by NOF Corporation) as 2.5 parts, and triallyl isocyanurate (trade name: TAIC-M60, manufactured by Nippon Kasei Co., Ltd.) was mixed in an open roll to obtain an unvulcanized rubber mixture (B kneaded rubber composition 1). The masterbatch 1 was divided into 5 parts and mixed step by step.

- Fabrication of Conductive Roller A round bar having a total length of 252 mm and an outer diameter of 6 mm was prepared by applying electroless nickel plating to the surface of free-cutting steel. Next, an adhesive was applied over the entire circumference of the round bar with a length of 230 mm excluding 11 mm at each end of the bar. A conductive hot-melt type adhesive was used. A roll coater was used for coating. A round bar coated with this adhesive was used as a conductive mandrel (core bar).

Next, a crosshead extruder having a supply mechanism for the conductive mandrel and a discharge mechanism for the unvulcanized rubber roller was prepared. A die with an inner diameter of 12.5 mm was attached to the crosshead, the extruder and crosshead were adjusted to 80° C., and the conveying speed of the conductive mandrel was adjusted to 60 mm/sec. Under these conditions, the B kneaded rubber composition 1 is supplied from a kneading extruder to form a rubber layer of the B kneaded rubber composition 1 on the outer peripheral surface of the conductive mandrel in the crosshead, and the A sulfur rubber roller was obtained. Next, the unvulcanized rubber roller was placed in a hot air vulcanizing furnace at 170° C. and heated for 60 minutes to obtain a vulcanized rubber roller. After that, the ends of the vulcanized rubber layer were cut off to make the length of the rubber layer 230 mm. Finally, the surface of the elastic layer was polished with a rotary grindstone. As a result, a crown-shaped conductive roller having a diameter of 8.4 mm at each position of 90 mm from the center to both ends and a diameter of 8.5 mm at the center was obtained.
The electric resistance value of the roller was 5.0×10 ⁵ Ω·cm. As for the measurement method, the "measurement of partial resistance value of the conductive roller", which will be described later, was used.

-Evaluation of conductive roller The following evaluations were performed on the conductive roller. Table 1 shows the evaluation results.

-Evaluation of conductive layer The details were evaluated by the measurement method shown above.
It should be noted that the conductive elastic layer of the conductive roller according to each example has a plurality of domains in the matrix of the first rubber, and each domain satisfies the configuration containing conductive particles. The average value μ of the ratio of the cross-sectional area of the conductive particles contained in each domain to the cross-sectional area of each domain is 20% or more and 40% or less, etc., as shown in the above-described domain measurement method. confirmed by the method. Unless otherwise specified, the microtome is Leica EM UC7 manufactured by Leica, the ion milling is Leica EMTIC3X manufactured by Leica, and the SEM is Ultraplus manufactured by Carl Zeiss. board. In addition, as a three-dimensional stereoscopic image measurement device (FIB-SEM), which is particularly represented in FIG. Structures were confirmed in all examples.

・(Evaluation of uniform distribution of domains in conductive layer)
It was verified by the method described in (Method for Measuring Domain Volume) that the conductive domains were three-dimensionally evenly and densely arranged in the conductive layer. Here, as described above, three-dimensional measurement using FIB-SEM is performed, and at least eight of the first cubic samples with one side of 9 μm meet the condition (1); At least 20 of the 27 unit cubes of 3 μm on a side contained in the sample are evaluated whether the total volume of the domains satisfies 2.7-10.8 μm ³ ″.

As described above, the effect of this aspect can be enhanced by increasing the number of unit cubes that satisfy the condition (1). The uniform dispersion level of domains was evaluated based on the following criteria based on the above measurement results. The order of rank I>II>III>IV>V indicates that the conductive layer exhibits uniform and stable electrical characteristics.

Rank I: Very good uniform dispersibility is observed.
(The number of unit cubes satisfying condition (1) is 25 or more in at least 8 samples)
Rank II: Fairly good uniform dispersibility is observed.
(The number of unit cubes satisfying condition (1) is less than 25 in at least 2 samples and 22 or more in at least 8 samples)
Rank III: Good uniform dispersibility is observed.
(The number of unit cubes satisfying condition (1) is less than 22 in at least 2 samples and 20 or more in at least 8 samples)
Rank IV: Homogeneous dispersion is not observed.
(The number of unit cubes satisfying condition (1) is less than 20 in at least 2 samples and 12 or more in at least 8 samples)
Rank V: Extremely poor uniform dispersibility.
(The number of unit cubes satisfying condition (1) is less than 12 in at least two samples)

・(Evaluation of conductive particle variation in each domain in the conductive layer)
Using the measurement method described above, it was verified that the conductive domains were domains with uniform electrical resistance.
"The average value of the ratio of the cross-sectional area of the conductive particles contained in each domain to the cross-sectional area of each domain appearing in the cross section in the thickness direction of the conductive layer is μ, and the standard deviation of the ratio is σ. When "σ/μ" is smaller, the effect of this embodiment is enhanced.The level of dispersion of the conductive particles in each domain was evaluated according to the following criteria based on the above measurement results. The order of rank i > ii > iii indicates domains with uniform electrical resistance.
Rank i: Variation in conductive particles is extremely small. (0≦σ/μ≦0.25)
Rank ii: Variation in conductive particles is small. (0.25<σ/μ≦0.4)
Rank iii: Large variation in conductive particles. (σ/μ<0.4)

・(Evaluation of the shape of the domain in the conductive layer of the conductive roller-circularity)
A domain shape close to a circle is preferable, and the roundness was evaluated based on the measurement method described above.
The level of roundness was evaluated based on the following criteria. It should be noted that the order of rank a>b>c>d indicates that the shape is closer to a circle.

Rank a: Very good roundness is observed. (The average value of roundness is 1 or more and less than 1.90)
Rank b: Good roundness is observed. (The average value of roundness is 1.90 or more and less than 2.0)
Rank c: Poor roundness. (The average value of roundness is 2.10 or more and less than 22.60)
Rank d: Roundness is extremely poor. (The average value of roundness is 2.60 or more)

(Evaluation of domain size distribution in conductive layer)
As for the size distribution of the domains, it is preferable that the domain sizes are uniform and the domains are fine. Based on the measurement method described above, the particle size distribution uniformity was evaluated based on the ratio of large domains and small domains. .
Here, the SEM image is calculated from the evaluation of 12 or more sheets.

The level of particle size distribution uniformity was evaluated based on the following criteria. The order of rank 1>2>3>4 indicates that the particle size distribution uniformity is high.
Rank 1: Extremely high uniformity of particle size distribution.
(95≦100×L2/L1≦100 and 0≦100×L3/L1≦5)
Rank 2: High uniformity of particle size distribution.
(80≦100×L2/L1<95 and/or 15<100×L3/L1≦20)
Rank 3: Poor uniformity of particle size distribution.
(100 x L2/L1 < 80 and/or 20 < 100 x L3/L1)
Rank 4: Extremely poor uniformity of particle size distribution.
(100 x L2/L1 ≤ 65 and/or 35 ≤ 100 x L3/L1)

・(Resistance measurement of conductive roller)
The resistance measurement of the conductive roller was appropriately performed by the following two "measurement of partial resistance value of the conductive roller".

・Measurement of partial resistance value of conductive roller (method using fixed type electrode)
A current resistance measuring device, which will be described in detail below, was used to measure the current value flowing through an arbitrary partial region of the conductive roller. First, both ends of the conductive mandrel of the conductive roller are pressed against the metal electrodes. The surface of the metal electrode in contact with the conductive roller has approximately the same curvature as the outer circumference of the conductive roller, and is cut so that the length of the arc is 1/4 or less of the outer circumference of the conductive roller. Thereby, the metal electrode can be brought into close contact with the conductive roller. The length of the metal electrode was set so that the contact area with the conductive roller was about 0.5 cm ² .
The electrical resistance of the conductive roller in the partial region was measured in a state in which a metal electrode was pressed against the conductive roller and a DC voltage was applied to the conductive mandrel of the conductive roller using an external power supply. The value of the current flowing through the partial region was calculated by measuring the voltage across a reference resistor connected in series with the metal electrode and based on this voltage and the electrical resistance value of the reference resistor.
Alternatively, the resistance value of the conductive roller is measured using an electrometer or the like capable of measuring a minute current, and a constant DC voltage is applied between the conductive mandrel of the conductive roller and the metal electrode. You can measure the current value with The current value of the conductive roller was measured after 10 seconds while a fixed DC voltage of 20 V was applied between the conductive mandrel and the metal electrode in an environment of 23°C temperature and 50% relative humidity. went later.
The volume resistivity (Ω cm) of the partial region was calculated from the measured current value, the area of contact between the conductive roller and the metal electrode, the thickness of the conductive layer of the conductive roller, and the voltage applied to the conductive layer. .

・Measurement of partial resistance value of conductive roller (method using rotating electrode)
A current value flowing through a partial area of the conductive roller was measured using an electrical resistance measuring device described in detail below. In this device, a cylindrical metal rotating electrode with a diameter of 30 mm and a width of 20 mm is pressed against an arbitrary position of the conductive roller at a constant pressure, and the conductive roller is rotated. The electrode is driven to rotate. Furthermore, the voltage across the reference resistor connected in series with the rotating electrode is measured while a DC voltage is applied to the conductive mandrel of the conductive roller using an external power source. As a result, the value of current flowing through the area defined by the contact surface between the rotating electrode and the conductive roller in the conductive layer of the conductive roller is obtained. The area of the contact surface is about 0.05 to 0.2 cm ² depending on the hardness of the conductive layer.
The rotational speed of the conductive roller was set to 30 rpm, the data sampling frequency was set to 20 Hz, and the electrical resistance value of the reference resistance was set to 1 kΩ. Although the applied voltage depends on the electrical resistivity of the conductive layer, a fixed voltage of 10 to 200 V was set so that the current value was approximately 0.1 mA. Under the above conditions, the roller surface can be measured in about 12 regions per one rotation at intervals of about 0.6 mm in the circumferential direction. The rotating electrode was sequentially moved in the longitudinal direction of the roller, and the electric current was measured in a total of about 140 regions while rotating the conductive roller in the same manner.
Further, the volume resistivity (Ω cm) of the partial region is calculated from the measured current value, the contact area between the conductive roller and the rotating electrode, the thickness of the conductive layer of the conductive roller, and the voltage applied to the conductive layer. bottom. Variation _in volume resistivity within the conductive roller was evaluated by σ R /μ _R , where µ _R is the average of the volume resistivity of the partial regions measured above, and σ _R is the variance.

Based on the above results, the electrical resistance σ _R /μ _R level was evaluated based on the following criteria. The order of rank A>B>C>D indicates that the conductive layer exhibits uniform and stable electrical characteristics.
Rank A: σ _R /μ _R is extremely small. ( _σR / _μR < 0.3)
Rank B: σ _R /μ _R is considerably small. (0.3< _σR / _μR ≦0.4)
Rank C: σ _R /μ _R is small. (0.4< _σR / _μR <0.5)
Rank D: σ _R /μ _R is large. (0.5≦ _σR / _μR )

Conductive Degradation Test of Conductive Roller—Measurement of Current Maintenance Ratio Using an electrical resistance measuring device schematically shown in FIG. 6, the value of the current flowing through the conductive roller was measured. In this device, both ends of the conductive shaft body 11 of the conductive roller are pressed against a cylindrical metal drum having a diameter of 30 mm by pressing means (not shown), and the conductive roller is driven to rotate as the metal drum is driven to rotate. Let Furthermore, the voltage across the reference resistor connected in series to the metal drum is measured while a DC voltage is applied to the conductive mandrel of the conductive roller using an external power supply. The current value flowing through the conductive roller is calculated based on the electrical resistance value of the reference resistor 63 and the voltage across the reference resistor.

Using the electrical resistance measuring apparatus of FIG. 6, an electrical deterioration test of the conductive roller was conducted under an environment of a temperature of 23° C. and a relative humidity of 50%. At this time, a constant voltage of 50 V direct current was applied between the conductive mandrel and the metal drum for 10 minutes. The rotational speed of the metal drum was set at 30 rpm, and the electric resistance value of the reference resistance was set between 100Ω and 1 kΩ. The data sampling frequency was set to 20 Hz, and the average value of the measured values for 10 seconds was taken as the current value flowing through the conductive roller. Assuming the initial current value I0 and the current value I1 at the end of the current application test, the current maintenance rate (%) was calculated as the ratio of I1 to I0.

Based on the above results, the level of the current maintenance rate was evaluated based on the following criteria.
Of course, the order of rank A>B>C>D indicates that the conductive layer exhibits uniform and stable electrical characteristics.
Rank A: The current maintenance rate is extremely high. (Maintenance rate is 85% or more)
Rank B: Current maintenance rate is slightly observed. (Maintenance rate is 70% or more and less than 85%)
Rank C: A current maintenance rate is recognized. (Maintenance rate is 60% or more and less than 70%)
Rank D: No current maintenance rate is observed. (Retention rate less than 60%)

Image Evaluation of Conductive Roller Image evaluation was carried out in a high-speed process of a conductive member.
First, an electrophotographic laser printer (trade name: Laserjet M608dn, manufactured by HP) was prepared as an electrophotographic apparatus. Next, the conductive member, the electrophotographic apparatus, and the process cartridge were left in an environment of 23° C. and 50% RH for 48 hours for the purpose of adjusting to the measurement environment.
In addition, in order to evaluate the high-speed process, the laser printer was modified so that the number of output sheets per unit time was 75 sheets/minute on A4 size paper, which is larger than the number of original output sheets. At that time, the output speed of the recording medium was 370 mm/sec, and the image resolution was 1,200 dpi.
The produced conductive roller was used as a charging roller and mounted in an electrophotographic process cartridge. A voltage of -900 V was applied to the conductive member by an external power source (Trek 615, manufactured by Trek Japan) under the same environment as above to output a halftone image. That is, one sheet of electrophotographic image in which a halftone image (an image in which lines each having a width of 1 dot are drawn at an interval of 2 dots in a direction perpendicular to the rotation direction of the electrophotographic photosensitive member) was output on A4 size paper. This image is referred to as the "first image". Next, 2,500 sheets of electrophotographic images were output on A4 size paper, in which the letter "E" of 14 point size was formed so as to have a print density of 1%. Subsequently, one sheet of electrophotographic image in which a halftone image was formed was output on A4 size paper. This image is called the "2501st image". All electrophotographic images were output under an environment of a temperature of 15° C. and a relative humidity of 10%. Visually observe the 1st image and the 2501st image, the halftone image that may occur due to the initial (first) graininess in the halftone image and the increase in the electrical resistance value of the charging roller. The presence or absence of deterioration of graininess after the endurance (2501st sheet) and the degree thereof were evaluated according to the following criteria.
Rank A: The image is uniform without graininess from the initial stage, and no deterioration in graininess is observed even after running.
Rank B: A uniform image without graininess at the initial stage, and a slight deterioration in graininess is recognized after the endurance test.
Rank C: An image with graininess (deterioration of graininess) is observed from the initial stage.
Rank D: An image with graininess (deterioration of graininess) is remarkably observed from the initial stage.

<Example 2>
100 parts of SBR (trade name: Tufden 2003, manufactured by Asahi Kasei Corporation) as the raw material for the domain, 3 parts of carbon black (trade name: Ketjen Black EC600JD, manufactured by Ketjen Black International Co., Ltd.) and carbon black (trade name) as conductive particles. : Toka Black #5500, manufactured by Tokai Carbon Co., Ltd.) and 1 part of stearic acid as a processing aid were kneaded with a pressure kneader to obtain a masterbatch 2.
Next, to 100 parts by mass of NBR (trade name: N230SV, manufactured by JSR), 8 parts of zinc oxide (zinc white, manufactured by Sakai Chemical Industry Co., Ltd.), zinc stearate (trade name: SZ-2000, manufactured by Sakai Chemical) Kogyo Co., Ltd.) and 10 parts of calcium carbonate (trade name: Nanox #30, Maruo Calcium Co., Ltd.) were added, and a pressure kneader (trade name: TD6-15MDX: manufactured by Toshin Co., Ltd.) adjusted to 50 ° C. was used. , a filling rate of 70%, a blade rotation speed of 30 rpm, and a mixing time of 16 minutes to obtain a rubber composition 2 for a matrix.
Next, 20 parts of the masterbatch 2 prepared above and 70 parts of the matrix rubber composition 2 were mixed for 12 minutes using a pressure kneader to obtain an unvulcanized rubber mixture 2 .
To 100 parts by mass of the unvulcanized rubber mixture 2, 1.8 parts of a vulcanizing agent/sulfur (trade name: SULFAX PMC, manufactured by Tsurumi Chemical Industry Co., Ltd.), a vulcanization accelerator (trade name: Perkacit TBzTD, Performance・Adidiv Co.) was added and kneaded for 10 minutes with a two-roll machine cooled to 25° C. to obtain a corresponding B kneaded rubber composition 2. Except for these, a conductive roller was produced in the same manner as in Example 1, and each evaluation was performed.
The electric resistance value of the roller was 6.5×10 ⁵ Ω·cm.

<Example 3>
90 parts of SBR (trade name: Tufden 2003, manufactured by Asahi Kasei Corporation) and 10 parts of liquid SBR (trade name: LIR-310, manufactured by Kuraray Co., Ltd.) were used as raw materials for the domain, and carbon black (trade name: Toka Black) was used as the conductive particles. #5500, manufactured by Tokai Carbon Co., Ltd.) and 1 part of stearic acid as a processing aid were kneaded with a pressure kneader to obtain a masterbatch 3. Next, 20 parts of the masterbatch 3 prepared above and 72 parts of the matrix rubber composition 2 prepared in Example 2 were mixed for 13 minutes using a pressure kneader to obtain an unvulcanized rubber mixture 3. got Here, the masterbatch was divided into 5 equal parts and mixed stepwise.
Except for these, a conductive roller was produced in the same manner as in Example 2, and each evaluation was performed.
The electric resistance of the roller was 8.5×10 ⁵ Ω·cm.

<Example 4>
A corresponding rubber mixture was prepared analogously to Example 1.
That is, 120 parts of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (trade name: Epichromer CG, manufactured by Osaka Soda Co., Ltd.), 1 part of stearic acid as a processing aid, and 40 parts of masterbatch 1 prepared in Example 1. , were mixed in an open roll to obtain an unvulcanized rubber mixture 4. Here, the masterbatch was divided into 5 equal parts and mixed stepwise.
Next, using a processing machine (product name: NHSS8-28, manufactured by Niigata Machine Techno) having a screw equipped with an extensional shearing mechanism inside the screw as an extensional shear forming processing machine shown in FIG. 3(a), The unvulcanized rubber (A kneaded rubber composition) was kneaded. First, setting the hole of the thin tube of the screw equipped in the processing machine to 2.0 mm, the temperature of the plasticizing section to 100°C, the temperature of the kneading section to 150°C, and the screw rotation speed to 750 rpm, the A kneaded rubber composition was mixed for 5 seconds. Kneaded. Thereafter, a rubber composition subjected to elongation shear processing was obtained by discharging from the kneading section. By repeating this, a sufficient amount for manufacturing a conductive roller was produced. At that time, in order to reduce shear heat generation, a cooling mechanism was used to control the temperature of the kneading section so as not to exceed 170°C.
To 100 parts by mass of the A kneaded rubber composition kneaded in the above step, 1.8 parts of a vulcanizing agent/sulfur (trade name: SULFAX PMC, manufactured by Tsurumi Chemical Industry Co., Ltd.), a vulcanization accelerator (trade name: Perkacit TBzTD, (manufactured by Performance Additive) was added. Then, the mixture was kneaded for 10 minutes with a two-roll machine cooled to 25° C. to obtain a B kneaded rubber composition 4. Except for these, a conductive roller was produced in the same manner as in Example 1, and each evaluation was performed.
The electric resistance of the roller was 1.0×10 ⁶ Ω·cm.

<Example 5>
100 parts of SBR (trade name: Tufden 2003, manufactured by Asahi Kasei Corporation) as a raw material for the domain, 70 parts of carbon black (trade name: Toka Black #5500, manufactured by Tokai Carbon Co., Ltd.) as conductive particles, and 1 part of stearic acid as a processing aid The parts were kneaded with a pressure kneader to obtain a masterbatch 5. Next, 22 parts of the masterbatch 5 and 68 parts of the matrix rubber composition 2 prepared in Example 2 were mixed for 20 minutes using a pressure kneader to obtain an unvulcanized rubber composition 5. .
Except for these, a conductive roller was produced in the same manner as in Example 2, and each evaluation was performed.
The electric resistance of the roller was 4.0×10 ⁵ Ω·cm.

<Example 6>
100 parts of terminal-modified SBR (trade name: Tuffdene E581, manufactured by Asahi Kasei Corporation) as a raw material for the domain, 80 parts of carbon black (trade name: Toka Black #5500, manufactured by Tokai Carbon Co., Ltd.) as conductive particles, and stearin as a processing aid One part of the acid was kneaded with a pressure kneader to obtain a masterbatch 6.
Next, 25 parts of the masterbatch 6 prepared above and 70 parts of the matrix rubber composition 2 prepared in Example 2 were mixed for 16 minutes using a pressure kneader to obtain an unvulcanized rubber composition. got 6. Here, the masterbatch was divided into 5 equal parts and mixed stepwise with the rubber composition 2 for the matrix.
The electric resistance of the roller was 3.5×10 ⁵ Ω·cm.

<Example 7>
100 parts of SBR (trade name: Tufden 2003, manufactured by Asahi Kasei Corporation) as a raw material for the domain, 85 parts of carbon black (trade name: Toka Black #7360, manufactured by Tokai Carbon Co., Ltd.) as conductive particles, and 1 part of stearic acid as a processing aid The parts were kneaded with a pressure kneader to obtain a masterbatch 7. Next, 30 parts of the masterbatch 7 and 65 parts of the matrix rubber composition 2 prepared in Example 2 were mixed with an open roll to obtain a corresponding unvulcanized rubber mixture 7 . Next, in the same manner as in Example 4, the unvulcanized rubber (A kneaded rubber composition) was kneaded using an elongational shear molding machine having a screw with an elongational shear applying mechanism inside the screw. In addition, processing was performed under the same conditions except that the number of rotations of the screw was changed to 800 rpm.
Except for these, a conductive roller was produced in the same manner as in Example 4, and each evaluation was performed.
The electric resistance of the roller was 8.0×10 ⁵ Ω·cm.

<Example 8>
Emulsion-polymerized styrene-butadiene rubber, 100 parts of E-SBR (trade name: JSR0202, manufactured by JSR) and 10 parts of liquid SBR (trade name: LIR-310, manufactured by Kuraray Co., Ltd.) were used as raw materials for the domains, and carbon was used as the conductive particles. 100 parts of black (trade name: Toka Black #5500, manufactured by Tokai Carbon Co., Ltd.) and 1 part of stearic acid as a processing aid were kneaded with a pressure kneader to obtain a masterbatch 8. Next, 34 parts of the masterbatch 8 and 70 parts of the matrix rubber composition 2 prepared in Example 2 were mixed with an open roll to obtain an unvulcanized rubber mixture 8 .
As an extensional shear forming processing machine, as a continuous type processing machine having a screw equipped with an extensional shear imparting mechanism on the outside of the screw, an extensional shearing molding having a screw with an extensional shear imparting mechanism inside the screw used in Example 7 A processing machine (product name: NHSS8-28, manufactured by Niigata Machine Techno) was modified and used. In other words, continuous elongation shear forming processing is possible by adopting the device configuration shown in FIG. rice field.
Next, in the same manner as in Example 4, the unvulcanized rubber (A kneaded rubber composition) was kneaded using a continuous extensional shear molding machine having a screw equipped with the extensional shear applying mechanism. In addition, here, processing was performed under the same conditions except that the screw rotation speed was changed to 600 rpm.
Except for these, a conductive roller was produced in the same manner as in Example 4, and each evaluation was performed.
The electric resistance of the roller was 8.0×10 ⁵ Ωcm.

<Example 9>
100 parts of NBR (trade name: N230SV, manufactured by JSR Corporation) as a raw material for the domain, 60 parts of carbon black (trade name: Toka Black #7360, manufactured by Tokai Carbon Co., Ltd.) as conductive particles, and carbon black (trade name: Ketjen) 10 parts of Black EC600JD (manufactured by Ketjen Black International Co., Ltd.) and 1 part of stearic acid as a processing aid were kneaded with a pressure kneader to obtain Masterbatch 9.
Next, for 100 parts by mass of SBR (trade name: Asaprene Y031, manufactured by Asahi Kasei Co., Ltd.), 8 parts of zinc oxide (zinc white, manufactured by Sakai Chemical Industry Co., Ltd.), zinc stearate (trade name: SZ-2000, manufactured by Sakai Kagaku Kogyo Co., Ltd.) and 10 parts of calcium carbonate (trade name: Nanox #30, Maruo Calcium Co., Ltd.) were added, and a pressure kneader (trade name: TD6-15MDX, Toshin Co., Ltd.) adjusted to 50 ° C. A rubber composition 9 for a matrix was obtained by mixing under conditions of a filling rate of 70%, a blade rotation speed of 30 rpm, and a mixing time of 16 minutes.
Next, 35 parts of the masterbatch 9 and 70 parts of the matrix rubber composition 9 were mixed with an open roll to obtain a corresponding unvulcanized rubber mixture.
Next, the unvulcanized rubber (A kneaded rubber composition) was kneaded using the continuous extensional shear molding machine used in Example 8, which has a screw provided with an extensional shear imparting mechanism on the outside of the screw. In addition, processing was performed under the same conditions except that the screw rotation speed was changed to 650 rpm.
Except for these, a conductive roller was produced in the same manner as in Example 4, and each evaluation was performed.
The electric resistance of the roller was 8.3×10 ⁵ Ωcm.

[Comparative Example 1]
A rubber mixture was prepared based on Patent Document 1.
That is, 100 parts of ethylene-propylene-diene terpolymer (trade name: EPT4045, manufactured by Mitsui Chemicals, Inc.) as the domain material, and carbon black (trade name: Ketjenblack EC600JD, manufactured by Ketjenblack International Co., Ltd.) as the conductive particles. ), 30 parts of paraffin oil (trade name: PW-380, manufactured by Idemitsu Kosan Co., Ltd.) as a softening agent, and 1 part of stearic acid as a processing aid were kneaded with a pressure kneader to obtain a masterbatch. Next, 75 parts of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (trade name: Epichroma CG, manufactured by Osaka Soda Co., Ltd.) as a matrix material, 1 part of stearic acid as a processing aid, and 35.25 parts of masterbatch 10. part, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne (trade name: Perhexa 25B-40, manufactured by NOF Corporation) as a vulcanizing agent, 2.5 parts, triallyl isocyanate as a cross-linking aid 1.5 parts of nurate (trade name: TAIC-M60, manufactured by Nippon Kasei Co., Ltd.) was mixed with an open roll to obtain an unvulcanized rubber mixture 1A. Except for these, a conductive roller was produced in the same manner as in Example 1, and each evaluation was performed.
The electric resistance of the roller was 7.3×10 ⁵ Ωcm.

[Comparative Example 2]
In Example 2, the amount of ketjen black in masterbatch 2 was changed to 3.5 parts and the amount of carbon black was changed to 35 parts to prepare corresponding unvulcanized rubber composition 2A, and unvulcanized A conductive roller was produced in the same manner as in Example 1 except that the kneading time of the pressure kneader was changed to 5 minutes when producing the rubber composition 2A, and each evaluation was performed.
The electric resistance of the roller was 4.1×10 ⁶ Ωcm.

[Comparative Example 3]
Based on Comparative Example 1, a conductive roller was produced and each evaluation was performed.
Here, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (trade name: Epichroma CG, manufactured by Osaka Soda Co., Ltd.) 120 parts, stearic acid 1 part as a processing aid, masterbatch 1, 40.5 parts They were mixed in an open roll to obtain an unvulcanized rubber mixture.
Next, the A kneaded rubber composition is sheared using a twin-screw kneading device (product name “KZW15TW-4MG-NH (-6000)” manufactured by Technobell) at a rotational speed of 1000 rpm. The mixture (A kneaded rubber composition) was kneaded.
To 100 parts by mass of the unvulcanized rubber composition kneaded in the above step, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne (trade name: Perhexa 25B-40, NOF) was added as a vulcanizing agent. Co.) 2.5 parts and 1.5 parts of triallyl isocyanurate (trade name: TAIC-M60, manufactured by Nippon Kasei Co., Ltd.) as a crosslinking aid are mixed in an open roll to form an unvulcanized rubber mixture (B kneaded rubber A conductive roller was produced in the same manner as in Comparative Example 1, except for those in which composition 3A) was obtained, and each evaluation was performed.
The electric resistance of the roller was 1.2×10 ⁷ Ωcm.

[Comparative Example 4]
In Example 2, the amount of ketjen black in masterbatch 2 was changed to 3.5 parts and the amount of carbon black was changed to 35 parts to prepare corresponding unvulcanized rubber composition 4A, and unvulcanized Except for changing the kneading time of the pressure kneader to 40 minutes when producing rubber composition 4A of No. (here, the material temperature during kneading (measured using an infrared thermometer) had risen to 183 degrees) A conductive roller was produced in the same manner as in Example 2, and each evaluation was performed.
The electric resistance of the roller was 2.2×10 ⁶ Ωcm.

[Comparative Example 5]
25 parts of the masterbatch 3 prepared above in Example 3 and 70 parts of the matrix rubber composition 2 prepared in Example 2 were mixed using a double roll. Then, using the twin-screw kneading device shown in Comparative Example 3, the same procedure as in Example 3 was carried out, except that the corresponding unvulcanized rubber mixture 5A (A kneaded rubber composition) was kneaded at a rotational speed of 1000 rpm. , a conductive roller was produced, and each evaluation was performed.
The electric resistance of the roller was 9.6×10 ⁶ Ωcm.

[Comparative Example 6]
In addition to mixing for 10 minutes using a pressure kneader instead of the extensional shear molding machine in Example 8, 20 parts of masterbatch 8 and rubber composition 2 for the matrix prepared in Example 2 were added. A conductive roller was produced in the same manner as in Example 8 except that 70 parts were used, and each evaluation was performed.
The electric resistance of the roller was 9.0×10 ⁵ Ωcm.

[Comparative Example 7]
In addition to mixing in Example 8 using a twin roll instead of an extensional shear forming machine (here, the masterbatch was divided into 10 equal parts and mixed in stages), masterbatch 8 was mixed in 14. A conductive roller was produced in the same manner as in Example 8 except that 6 parts and 70 parts of the matrix rubber composition 2 produced in Example 2 were used, and each evaluation was performed.
The electric resistance of the roller was 4.9×10 ⁶ Ωcm.

Table 1 below shows the evaluation of uniform dispersion of the domains, the evaluation of the dispersion of the conductive particles in each domain, the evaluation of the shape of the domains, and the evaluation of the particle size distribution of the domains in Examples 1-9 and Comparative Examples 1-7. , the mixing device used, the average domain size in the cross section, the evaluation of the conductive roller: electric resistance σ/μ, and the evaluation of the conductive roller: the current maintenance rate, and the evaluation results of the image quality rank.

The following shows the results of examination of application to a transfer roller as a conductive roller.
<Example 10>
- Fabrication of Conductive Roller A round bar with a total length of 240 mm and an outer diameter of 5 mm was prepared by subjecting the surface of free-cutting steel to electroless nickel plating treatment. Next, an adhesive was applied over the entire circumference of the round bar with a length of 210 mm excluding 15 mm at each end of the bar. A conductive hot-melt type adhesive was used. A roll coater was used for coating. A round bar coated with this adhesive was used as a conductive mandrel (core bar).

Next, a crosshead extruder having a supply mechanism for the conductive mandrel and a discharge mechanism for the unvulcanized rubber roller was prepared. Second, the conveying speed of the conductive mandrel was adjusted to 60 mm/sec. Under these conditions, the unvulcanized rubber mixture 2 obtained in Example 2 was supplied from a kneading extruder to form a rubber layer of the unvulcanized rubber mixture on the outer peripheral surface of the conductive mandrel in the crosshead. to obtain an unvulcanized rubber roller. Next, the unvulcanized rubber roller was placed in a hot air vulcanizing furnace at 170° C. and heated for 60 minutes to obtain a vulcanized rubber roller. After that, the ends of the vulcanized rubber layer were cut off, and the length of the rubber layer was set to 215 mm. Finally, the surface of the elastic layer was polished with a rotary grindstone. As a result, a conductive roller having a diameter of 11.3 mm at each position of 90 mm from the center to both ends and a diameter of 11.5 mm at the center was obtained.
The electric resistance of the roller was 2.0×10 ⁶ Ω·cm.

The obtained conductive roller was evaluated in the same manner as in Example 1, except for image quality evaluation. Here, the image quality evaluation 1 of the conductive roller and the image quality evaluation 2 of the conductive roller below are added instead.

・Image evaluation 1 of conductive roller
An electrophotographic process cartridge (trade name: HP 30A Black Original LaserJet Toner, manufactured by HP) was equipped with the conductive roller as a transfer roller. This process cartridge was mounted in an electrophotographic image forming apparatus capable of outputting A4 size paper (trade name: HP LaserJet Pro M203dw, manufactured by HP) to form an electrophotographic image. One sheet of electrophotographic image in which a vertical line image (an image in which lines with a width of 4 dots are drawn at intervals of 4 dots in the rotation direction of the electrophotographic photosensitive member) was output on A4 size paper. The output of the electrophotographic image was performed under an environment of a temperature of 15° C. and a relative humidity of 10%. The image was visually observed, and the presence or absence of crushing of the spot-like image and vertical lines, which may occur due to abnormal discharge of the transfer roller, and the degree thereof were evaluated according to the following criteria.
Rank A: No crushing of vertical lines or generation of spot-like images is observed.
Rank B: Collapse of vertical lines and occurrence of spot-like images are slightly observed.
Rank C: Collapse of vertical lines and generation of spot-like images are observed.
Rank D: Collapse of vertical lines and generation of spot-like images are remarkably observed.

・Image evaluation 2 of conductive roller
The electrophotographic process cartridge (trade name: HP 30A Black Original LaserJet Toner, manufactured by HP) was mounted as a transfer roller after the conductive deterioration test was performed. This process cartridge was mounted in an electrophotographic image forming apparatus capable of outputting A4 size paper (trade name: HP LaserJet Pro M203dw, manufactured by HP) to form an electrophotographic image. An electrophotographic image in which a halftone image (an image in which a line with a width of 1 dot is drawn at an interval of 2 dots in the direction perpendicular to the rotation direction of the electrophotographic photosensitive member) was formed on a sheet of A4 size paper. The output of the electrophotographic image was performed under an environment of a temperature of 15° C. and a relative humidity of 10%. The image was visually observed, and the presence or absence of a spot-like image, which may occur due to an increase in the electrical resistance of the transfer roller, and the degree thereof were evaluated according to the following criteria.
Rank A: No generation of spot-like images is observed.
Rank B: Occurrence of spot-like images is slightly observed.
Rank C: Occurrence of spot-like images is recognized.
Rank D: Remarkable generation of spot-like images is observed.

<Example 11>
In Example 11, the unvulcanized rubber mixture 4 obtained in Example 4 was used as the unvulcanized rubber mixture.
Otherwise, a conductive roller was produced in the same manner as in Example 10, and each evaluation was performed.
The electric resistance of the roller was 3.2×10 ⁶ Ωcm.

<Example 12>
In Example 12, the unvulcanized rubber mixture 8 obtained in Example 8 was used as the unvulcanized rubber mixture.
Otherwise, a conductive roller was produced in the same manner as in Example 10, and each evaluation was performed.
The electric resistance of the roller was 2.4×10 ⁶ Ωcm.

[Comparative Example 8]
In Example 10, the unvulcanized rubber mixture 1A obtained in Comparative Example 1 was used as the unvulcanized rubber mixture.
Otherwise, a conductive roller was produced in the same manner as in Example 10, and each evaluation was performed.
The electric resistance of the roller was 2.1×10 ⁶ Ωcm.

Table 2 below shows evaluation of uniform dispersion of domains, evaluation of dispersion of conductive particles in each domain, evaluation of domain shape, evaluation of domain particle size distribution, and use in Examples 10 to 12 and Comparative Example 8. The evaluation results of the mixing device used, the average domain size in the cross section, and the evaluation of the conductive roller are shown.

Below, the results of a study of applying a conductive blade as a conductive roller are shown.
<Example 13>
- Production of conductive blade The B kneaded rubber mixture 2 (unvulcanized rubber mixture) obtained in Example 2 was used. Here, the B kneaded rubber mixture 2 was pressurized in a mold having a width of 250 mm, a length of 150 mm, and a thickness of 0.7 mm by a pressure press machine at 160° C. for 10 minutes to obtain a corresponding thickness of 0.7 mm. A rubber sheet 1 of 7 mm was obtained.
The rubber sheet 1 is cut into a width of 216 mm and a length of 12 mm, and is adhered to a sheet metal processed in advance so as to be attached to a predetermined cartridge (almost the same shape as the sheet metal used for the developing blade of the electrophotographic process cartridge described later). A conductive rubber blade 1 was obtained by bonding using an agent. At this time, of the 12 mm length of the conductive blade, the portion overlapping the sheet metal was set to 4.5 mm, and the remaining 7.5 mm was adhered so as to protrude from the sheet metal. A conductive hot-melt type adhesive was used.
The electric resistance of the conductive blade was 4.2×10 ⁵ Ωcm.

-Evaluation of conductive blade The following evaluation was performed on the conductive blade. Table 1 shows the evaluation results.

(Evaluation of conductive layer)
The following four items regarding the evaluation of the conductive layer were performed in the same manner as in Example 1.
The measurement points were changed as follows.

-Evaluation of Uniform Dispersion of Domains in Conductive Layer Measurement points: 9 points near the center of each of 9 sections of width 24 mm length 12 mm thickness 0.7 mm obtained by dividing the width of the rubber sheet.
-Evaluation of the variation of the conductive particles in each domain in the conductive layer Measurement points: 12 points near the center of each section of 18 mm width, 12 mm length, and 0.7 mm thickness obtained by dividing the width of the rubber sheet into 12 parts.
・Evaluation of the shape of the domain in the conductive layer of the conductive blade-Circularity measurement points: 12 points near the center of each section of width 18 mm length 12 mm thickness 0.7 mm, which is obtained by dividing the width of the rubber sheet into 12 measurement.
-Evaluation of particle size distribution of domains in the conductive layer Measurement points: The width of the rubber sheet was divided into 12 sections, and measurements were taken at 12 points near the center of each section of 18 mm width, 12 mm length, and 0.7 mm thickness.

(Current value measurement of conductive blade)
Measurement of Partial Resistance Value of Conductive Blade A current resistance measuring device outlined below was used to measure the value of current flowing in an arbitrary partial region of the conductive blade. In this device, a metal electrode is brought into pressure contact with a load of 200 gw to an arbitrary position of the rubber portion of the conductive blade. The metal electrode used had a circular shape with a diameter of 10 mm in contact with the conductive blade. Furthermore, the voltage across the reference resistor connected in series with the metal electrode is measured while a DC voltage is applied to the sheet metal of the conductive blade using an external power source. This gives the value of the current flowing through any partial area of the conductive blade. The electrical resistance value of the reference resistor was set to 1 kΩ. In addition, the length of the conductive blade was divided into 20 parts, and a total of 20 points in between were measured.
The volume resistivity of the conductive blade was calculated by calculating the volume resistivity (Ω cm) of the partial region from the area of the conductive blade rubber portion and the metal electrode, the thickness of the rubber portion of the conductive blade, and the applied voltage. . Variation _in volume resistivity within the conductive blade was evaluated by σ R /μ _R , where μ _R is the average of the volume resistivity of the partial regions measured above, and σ _R is the variance.

Based on the above results, the electrical resistance σ _R /μ _R level was evaluated based on the following criteria. The order of rank A>B>C>D indicates that the conductive layer exhibits uniform and stable electrical characteristics.
Rank A: σ _R /μ _R is extremely small. ( _σR / _μR < 0.25)
Rank B: σ _R /μ _R is considerably small. (0.25< _σR / _μR ≦0.32)
Rank C: σ _R /μ _R is small. (0.32< _σR / _μR <0.4)
Rank D: σ _R /μ _R is large. (0.4≦ _σR / _μR )

· Conductive degradation test of conductive blade-measurement of current maintenance rate Using the above-mentioned electrical resistance measuring device, the conductive blade was subjected to an electrical degradation test in an environment with a temperature of 23 ° C. and a relative humidity of 50%. At this time, a constant voltage set between 20 and 200 V direct current was applied to the sheet metal of the conductive blade for 10 minutes. The data sampling frequency was set to 20 Hz, and the average value of the measured values for 10 seconds was taken as the current value flowing through the conductive blade. Assuming the initial current value I0 and the current value I1 at the end of the current application test, the current maintenance rate (%) was calculated as the ratio of I1 to I0.

Based on the above results, the level of the current maintenance rate was evaluated based on the following criteria.
Of course, the order of rank A>B>C>D indicates that the conductive layer exhibits uniform and stable electrical characteristics.
Rank A: The current maintenance rate is extremely high. (Maintenance rate is 85% or more)
Rank B: Current maintenance rate is slightly observed. (Maintenance rate is 70% or more and less than 85%)
Rank C: A current maintenance rate is recognized. (Maintenance rate is 60% or more and less than 70%)
Rank D: Remarkable current maintenance rate. (Retention rate less than 60%)

[Evaluation of triboelectric charge distribution of toner]
In order to evaluate the spread of the triboelectric charge amount of the toner, the triboelectric charge amount distribution was measured.
The above conductive blade was used as a developing blade and attached to an electrophotographic process cartridge (trade name: 37X black toner cartridge, manufactured by HP). This process cartridge was mounted in an electrophotographic image forming apparatus capable of outputting A4 size paper (trade name: HP LaserJet Enterprise M608dn, manufactured by HP), and placed in a high-temperature and high-humidity environment with a temperature of 32°C and a relative humidity of 85% RH. After installation, it was left for more than 6 hours. Next, an image in which the letter "E" of the alphabet with a size of 14 points is printed so that the coverage rate is 1% with respect to the area of A4 size paper (hereinafter also referred to as "E character image") was continuously output on 100 sheets of copy paper, a white solid image was output on new copy paper, and the printer was stopped during the output of the white solid image.

At this time, the triboelectrification amount distribution was measured for the toner carried on the narrower portion of the developing sleeve sandwiched between the developing blade and the photosensitive member contact position.
The triboelectric charge distribution was measured using an E-spart Analyzer Model EST-III (manufactured by Hosokawa Micron Corporation).
About 3000 particles were measured, and the standard deviation σ of the measured values was defined as the triboelectric charge amount distribution of the toner.

Evaluation criteria for evaluation of the triboelectric charge amount distribution of the toner are as follows.
Rank A: Very good triboelectric charge distribution. (σ<3.0)
Rank B: The triboelectrification amount distribution is fairly good. (3.0≦σ<4.0)
Rank C: Good triboelectric charge distribution. (4.0≦σ<5.0)
Rank D: Poor triboelectric charge distribution. (σ>5.0)

Needless to say, the better the triboelectrification amount distribution of the toner, the better the conductive paths in the conductive layer are formed.

Image Evaluation of Conductive Blade The above conductive blade was attached as a developing blade to an electrophotographic process cartridge (trade name: 37X black toner cartridge, manufactured by HP). This process cartridge was mounted in an electrophotographic image forming apparatus capable of outputting A4 size paper (trade name: HP LaserJet Enterprise M608dn, manufactured by HP) to form an electrophotographic image. At that time, the metal portion of the developing sleeve and the sheet metal of the developing blade were electrically connected. After printing 3 sheets of electrophotographic images with a solid black image on A4 size paper, a halftone image (an image in which 1-dot wide lines are drawn at 2-dot intervals in the direction perpendicular to the rotating direction of the electrophotographic photosensitive member) is produced. One sheet of the formed electrophotographic image was output. The output of the electrophotographic image was performed under an environment of a temperature of 15° C. and a relative humidity of 10%. The central portion of the image was visually observed, and the presence or absence of unevenness in density, which may occur due to unevenness in the conductive points of the conductive blade, and the degree thereof were evaluated according to the following criteria.
Rank A: No density unevenness is observed.
Rank B: Density unevenness is slightly observed.
Rank C: Density unevenness is observed.

<Example 14>
In Example 13, the unvulcanized rubber mixture 4 obtained in Example 4 was used as the unvulcanized rubber mixture.
Other than that, a conductive blade was produced in the same manner as in Example 10, and each evaluation was performed.
The electric resistance of the conductive blade was 6.3×10 ⁵ Ωcm.

<Example 15>
In Example 13, the unvulcanized rubber mixture 8 obtained in Example 8 was used as the unvulcanized rubber mixture.
Other than that, a conductive blade was produced in the same manner as in Example 10, and each evaluation was performed.
The electric resistance of the conductive blade was 5.0×10 ⁵ Ωcm.

[Comparative Example 9]
In Example 13, the unvulcanized rubber mixture 9 obtained in Comparative Example 1 was used as the unvulcanized rubber mixture.
Other than that, a conductive blade was produced in the same manner as in Example 10, and each evaluation was performed.
The electric resistance of the conductive blade was 4.6×10 ⁵ Ωcm.

Table 3 below shows evaluation of uniform dispersion of domains, evaluation of dispersion of conductive particles in each domain, evaluation of domain shape, evaluation of domain particle size distribution, and use in Examples 13 to 15 and Comparative Example 9. The evaluation results of the mixed device, the average domain size in the cross section, and the evaluation of the conductive blade are shown.

Below, the results of a study of application to a developing roller as a conductive roller are shown.

<Production of developing roller>
[Example 16]
(1. Production of Masterbatch 16)
[1-1. Preparation of Masterbatch 16]
A masterbatch 16 was obtained by mixing the types and amounts of each material shown in Table 4 with a pressure kneader.

[1-2. Preparation of unvulcanized rubber composition]
The types and amounts of each material shown in Table 5 were mixed with a pressure kneader to obtain an unvulcanized rubber composition.

The types and amounts of materials shown in Table 6 were mixed in an open roll to prepare a rubber composition 16 for forming a conductive member.

(2. Molding of conductive member)
[2-1. Conductive mandrel]
A cored bar having an outer diameter of 6 mm was prepared by subjecting the surface of free-cutting steel to electroless nickel plating treatment. Next, using a roll coater, Metalloc U-20 (trade name, manufactured by Toyo Kagaku Kenkyusho Co., Ltd.) was applied as an adhesive over the entire circumference of the metal core except for 15 mm at each end. In this example, the core metal coated with the adhesive was used as the conductive mandrel.

Next, a die with an inner diameter of 16.0 mm was attached to the tip of a crosshead extruder having a mechanism for supplying a conductive mandrel and a mechanism for discharging unvulcanized rubber rollers, and the temperature of the extruder and the crosshead was raised to 80°C. , the conveying speed of the conductive mandrel was adjusted to 60 mm/sec. Under these conditions, an unvulcanized rubber composition was supplied from the extruder, and the outer periphery of the conductive mandrel was coated with the unvulcanized rubber composition in the crosshead to obtain an unvulcanized rubber roller. .

Next, the unvulcanized rubber roller is placed in a hot air vulcanizing furnace at 170° C. and heated for 60 minutes to vulcanize the unvulcanized rubber composition, and a conductive A roller having a resin layer formed thereon was obtained. After that, both ends of the conductive resin layer were cut off, and the surface of the conductive resin layer was polished with a rotary grindstone. As a result, a developing roller 100 having a diameter of 12.0 mm at each 90 mm position from the center to both ends and a diameter of 12.2 mm at the center was obtained.

The obtained conductive roller was evaluated in the same manner as in Example 1, except for image quality evaluation. Here, the following evaluation of triboelectric charge amount distribution of toner and image evaluation of developing roller (L/L ghost) are added instead.

[Evaluation of triboelectric charge distribution of toner]
In order to evaluate the spread of the triboelectric charge amount of the toner, the triboelectric charge amount distribution was measured.
A magenta toner cartridge for a laser printer (trade name: HP Color Laserjet Enterprise CP4515dn, manufactured by HP) was loaded with the developing roller according to each of Examples and Comparative Examples. Next, the cartridge was loaded into the laser printer (changed to a high-speed system), placed in a high-temperature and high-humidity environment with an air temperature of 32° C. and a relative humidity of 85% RH, and left for 6 hours or longer. Next, an image in which the letter "E" of the alphabet with a size of 14 points is printed so that the coverage rate is 1% with respect to the area of A4 size paper (hereinafter also referred to as "E character image") was continuously output on a predetermined number of copy sheets, a white solid image was output on new copy sheets, and the printer was stopped while the white solid image was being output.

At this time, the triboelectrification amount distribution was measured for the toner carried on the narrower portion of the developing roller sandwiched between the toner regulating blade and the photosensitive member contact position.
The triboelectric charge distribution was measured using an E-spart Analyzer Model EST-III (manufactured by Hosokawa Micron Corporation).
The number of particles to be measured was about 3000. The standard deviation of the triboelectrification amount distribution was calculated from the obtained triboelectrification amount distribution. The triboelectrification amount distribution was used.

Evaluation criteria for evaluation of the triboelectric charge amount distribution of the toner are as follows.
Rank A: Very good triboelectric charge distribution. (σ<3.0)
Rank B: The triboelectrification amount distribution is fairly good. (3.0≦σ<4.0)
Rank C: Good triboelectric charge distribution. (4.0≦σ<5.0)
Rank D: Poor triboelectric charge distribution. (σ>5.0)

Needless to say, the better the triboelectrification amount distribution of the toner, the better the conductive paths in the conductive layer are formed.

・Evaluation of developing roller image (L/L ghost)
A process cartridge for a laser printer (trade name: LBP7700C, manufactured by Canon Inc.) was loaded with the developing roller obtained in each example and comparative example as a developing roller. Then, the process cartridge was incorporated into the laser printer to form an electrophotographic image. 7,000 sheets of electrophotographic images were output on A4 size paper, in which the letter "E" of 4 point size was formed so as to have a print density of 1%.
Evaluation of ghost images was then carried out. That is, using a black toner, a 15 mm square solid black image was printed on the front end of one sheet as an image pattern, followed by a halftone image on the entire surface. Next, density unevenness (ghost) in the period of the toner carrier appearing in the halftone portion was visually confirmed.

The evaluation criteria for ghost evaluation are as follows.
Rank A: No ghost is observed.
Rank B: Generation of ghost is faintly recognized.
Rank C: Occurrence of ghost is observed.
Rank D: Remarkable generation of ghost is observed.

[Example 17]
A corresponding B kneaded rubber composition 17 was prepared in the same manner as in Example 7, except that the number of screw revolutions in the elongational shearing process during kneading of the unvulcanized rubber mixture 7 (A kneaded rubber composition) in Example 7 was changed to 850 rpm. Obtained. After that, a conductive roller for evaluation of the developing roller was produced in the same manner as in Example 16, and each evaluation was performed.

[Example 18]
A corresponding B kneaded rubber composition 18 was prepared in the same manner as in Example 8, except that the number of screw revolutions in the elongational shearing process during kneading of the unvulcanized rubber mixture 8 (A kneaded rubber composition) in Example 8 was changed to 630 rpm. Obtained. After that, a conductive roller for evaluation of the developing roller was produced in the same manner as in Example 16, and each evaluation was performed.

[Comparative Example 10]
A corresponding B kneaded rubber composition was obtained in the same manner as in Comparative Example 1. After that, a conductive roller for evaluation of the developing roller was produced in the same manner as in Example 16, and each evaluation was performed.

Table 7 shows the results of examination applied to the developing roller.

1 conductive member 11 conductive shaft 12 conductive layer 13 first cubic shape 14 unit cube 21 unit cube 22 matrix 23 domain 24 conductive particles

Claims (8)

a matrix comprising a crosslinked product of a first rubber;
An electrophotographic conductive member having a conductive layer comprising a plurality of domains dispersed in the matrix, the conductive member comprising:
each of the domains includes a second rubber crosslink and conductive particles;
The first rubber is different from the second rubber,
When μ is the average ratio of the cross-sectional area ratio of the conductive particles contained in each domain to the cross-sectional area of each domain appearing in the cross section in the thickness direction of the conductive layer, and σ is the standard deviation of the ratio. , σ/μ is 0 or more and 0.4 or less,
The μ is 20% or more and 40% or less, and
Of the first cubic samples with a side of 9 μm sampled from any 9 locations of the conductive layer, at least 8 samples satisfy the following condition (1) for electrophotography: Conductive member:
Condition (1)
One sample is divided into 27 unit cubes each having a side of 3 μm, and the volume Vd of the domains contained in each of the unit cubes is found to be 2.7 to 10.8 μm ³ . The number of unit cubes should be at least 20. 2. The conductive member for electrophotography according to claim 1, wherein σ/μ is 0 or more and 0.25 or less. 3. The conductive layer for electrophotography according to claim 1, wherein the number of domains having a circularity of 1 or more and less than 2 out of the domains appearing in the cross section in the thickness direction of the conductive layer is 70% or more. sex material. Let L1 be the total number of the domains appearing in the cross section of the conductive layer in the thickness direction,
Among the domains, L2 is the number of domains having an area of 3.0×10 ⁴ nm ² or more and less than 1.2×10 ⁵ nm ² as measured in the cross section, and the area is 1.2×10 ⁵ . When the number of domains with nm ² or more is L3,
The conductive member for electrophotography according to any one of claims 1 to 3, wherein L1, L2 and L3 satisfy the following relational expressions (1) and (2):
Relational expression (1)
80≦100×L2/L1≦100;
Relational expression (2)
0≦100×L3/L1≦20. wherein the conductive member for electrophotography is a charging roller or a transfer roller,
5. The conductive member for electrophotography according to claim 1, comprising a columnar or cylindrical conductive base and said conductive layer on the outer peripheral surface of said base. The conductive member for electrophotography is a conductive blade,
5. The conductive member for electrophotography according to claim 1, comprising a sheet metal and said conductive layer covering at least a part of the surface of said sheet metal. The conductive member for electrophotography is a developing roller,
5. The conductive member for electrophotography according to claim 1, comprising a columnar or cylindrical conductive base and said conductive layer on the outer peripheral surface of said base. 8. A method for manufacturing an electrophotographic conductive member according to claim 5 or 7 ,
(1) Unvulcanized rubber containing a first unvulcanized rubber as a raw material of the first rubber, a second unvulcanized rubber as a raw material of the second rubber, and the conductive particles (2) a step of kneading the mixture using a kneader equipped with an elongating shear screw to obtain an unvulcanized rubber kneaded material ; and (3) vulcanizing the first unvulcanized rubber and the second unvulcanized rubber in the layer of the unvulcanized rubber mixture to obtain the conductive layer. A method for manufacturing a conductive member, characterized by:

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