CN112020679A

CN112020679A - Conductive member, process for producing the same, process cartridge, and electrophotographic image forming apparatus

Info

Publication number: CN112020679A
Application number: CN201980026610.XA
Authority: CN
Inventors: 日野哲男; 伏本康宏; 村中则文; 教学正文; 山田真树; 井上宏; 古川匠; 渡边宏晓; 寺田健哉; 友水雄也; 中泽俊光
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2018-04-18
Filing date: 2019-04-16
Publication date: 2020-12-01
Anticipated expiration: 2039-04-16
Also published as: CN112020679B

Abstract

The conductive layer of the conductive member for electrophotography has a matrix-domain structure, the matrix having a first rubber, the domain having a second rubber and conductive particles, a ratio σ/μ of a standard deviation σ of a ratio of a sectional area of the conductive particles in each domain appearing in a section in a thickness direction of the conductive layer to an average μ of the ratios is 0 to 0.4 (inclusive), and in samples of a first cubic shape in which μ is 20 to 40% and one side is 9 μm sampled from nine arbitrary positions of the conductive layer, at least eight samples satisfy the following condition: wherein 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 unit cube is 2.7 to 10.8 μm³And the number of unit cubes is at least 20.

Description

Conductive member, process for producing the same, process cartridge, and electrophotographic image forming apparatus

Technical Field

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

Background

In an electrophotographic image forming apparatus as an image forming apparatus in which an electrophotographic system is employed, an electroconductive member is used for various purposes: as the conductive roller and the blade, there are, for example, a charging roller, a transfer roller, a developing roller and a developing blade. These conductive members include a conductive layer containing conductive particles of Carbon Black (CB) or the like for adjusting conductivity.

PTL 1 discloses a semiconductive rubber composition having a sea-island structure including a polymer continuous phase formed of an ion-conductive rubber material composed mainly of a polymer particle phase formed of an electron-conductive rubber material having a volume resistivity of 1 × 10¹²The material rubber is formed of a raw material rubber of Ω · cm or less, and the electron conductive rubber material is made conductive by adding an electron conductive agent (conductive particles) to the raw material rubber B. PTL 1 also discloses a charging member including an elastic layer formed of a semiconductive rubber composition. PTL 1 discloses that such a semiconductive rubber composition advantageously has small voltage dependence of resistance, small change in resistance, and small environmental dependence of resistance.

Reference list

Patent document

PTL 1: japanese patent application laid-open No.2002-003651

Disclosure of Invention

Problems to be solved by the invention

The present inventors have considered that, when an electrophotographic image is formed using a charging member, a charging bias applied between the charging member of PTL 1 and an electrophotographic photosensitive body as a body to be charged is set to a voltage (-800V to-1000V) lower than an ordinary charging bias (for example, about-1100V). This is because, in response to a demand for further reduction in size and cost of an electrophotographic image forming apparatus in recent years, if a high-quality electrophotographic image can be obtained even when the charging voltage is lowered, the size of the power supply can be made smaller.

As a result, graininess of a halftone image may occur in an electrophotographic image because the electrophotographic photoreceptor has a non-uniform surface potential.

Even when the charging bias is lowered, it is desirable to provide a conductive member for electrophotography usable as a charging member capable of uniformly charging an object to be charged.

An aspect of the present invention is directed to providing a conductive member for electrophotography for applying a low voltage, whereby transfer of charges in a conductive path is made very effective, resistivity is not easily changed even in high-speed processing, and the conductive path is uniformized to achieve suppression of discharge unevenness.

Another aspect of the present invention is directed to providing a process cartridge that facilitates formation of high-quality electrophotographic images. Still another aspect of the present invention is directed to provide an electrophotographic image forming apparatus capable of forming an electrophotographic image of high quality.

Means for solving the problems

According to an aspect of the present invention, there is provided an electrophotographic conductive member including a conductive layer having: a matrix comprising a crosslinked product of a first rubber; and a plurality of domains dispersed in the matrix, wherein each of the domains comprises a crosslinked product of a second rubber and conductive particles; the first rubber is different from the second rubber; σ/μ is 0 or more and 0.4 or less, where μ represents an average of ratios of sectional areas of the conductive particles contained in each of the domains to respective sectional areas of the domains appearing in a cross section in a thickness direction of the conductive layer, and σ represents a standard deviation of the ratios; mu is more than 20% and less than 40%; and among the samples of the first cubic shape having one side of 9 μm sampled from any nine portions of the conductive layer, at least eight samples satisfy the following condition (1).

Condition (A)1) To "divide one sample into 27 unit cubes each having a side of 3 μm, and calculate the volume Vd of the domain contained in each of the unit cubes, Vd is 2.7 to 10.8 μm³Is at least 20 ".

According to another aspect of the present invention, there is provided a method for manufacturing a conductive member for electrophotography, including the steps of: the conductive layer is formed from a rubber mixture comprising a first rubber composition comprising the first rubber and a second rubber composition comprising the second rubber using a mixer with an elongated shear screw.

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

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

ADVANTAGEOUS EFFECTS OF INVENTION

According to an aspect of the present invention, it is possible to obtain a conductive member for electrophotography for applying a low voltage, whereby the transfer of charges in a conductive path is made very effective, the resistivity is not easily changed even in high-speed processing, and the conductive path is uniformized to achieve the suppression of discharge unevenness.

According to another aspect of the present invention, a process cartridge which contributes to formation of a high-quality electrophotographic image can be obtained. According to still another aspect of the present invention, an electrophotographic image forming apparatus capable of forming an electrophotographic image of high quality can be obtained.

Drawings

[ FIG. 1A ]

Fig. 1A illustrates an example of an electrophotographic conductive member according to an aspect of the present invention.

[ FIG. 1B ]

FIG. 1B is a schematic diagram illustrating a first cube and a unit cube in accordance with an aspect of the present invention.

[ FIG. 2]

Fig. 2 is a schematic view illustrating a structure of a conductive layer having a matrix including a cross-linked product of a first rubber, and a plurality of domains dispersed in the matrix.

[ FIG. 3A ]

Fig. 3A is a schematic view illustrating one example of an elongation shear screw used in the production of the conductive elastic layer according to this aspect, wherein the screw has an elongation shear applying mechanism inside the screw.

[ FIG. 3B ]

Fig. 3B is a schematic view illustrating one example of an elongation shear screw used in the production of the conductive elastic layer according to this aspect, wherein the screw has an elongation shear applying mechanism outside the screw.

[ FIG. 4]

Fig. 4 is a schematic view illustrating an electrophotographic image forming apparatus according to an aspect of the present invention.

[ FIG. 5]

Fig. 5 shows a process cartridge according to an aspect of the present invention.

[ FIG. 6]

Fig. 6 is a schematic diagram showing an example of a resistance measuring device for measuring a value of current passing through a conductive member.

Detailed Description

The present inventors have examined the reason why the charging member of PTL 1 is difficult to uniformly charge the surface of the electrophotographic photoreceptor when the charging bias is lowered. In this inspection process, the role of the polymer particle phase formed of the electron conductive rubber material in the charging member of PTL 1 has been noted. That is, it is considered that in the elastic layer (conductive layer), electron conductivity is imparted to the conductive layer by electron transfer between the polymer particle phases. Based on the above-described consideration, it is presumed that the above-described problems relating to the decrease in the charging bias are attributed to the nonuniformity of the dispersed state of the polymer particle phase in the conductive layer. That is, the decrease in the charging bias makes it difficult to cause electron transfer between the polymer particle phases. Here, one polymer particle phase is noted. When the charging bias is high, electrons from the polymer particle phase can be almost equally transferred to the plurality of other polymer particle phases existing around the polymer particle phase even if there is a change in distance from the other polymer particle phases. However, when the charge bias is low, electrons from the polymer particle phase can be preferentially transferred to the polymer particle phase closest to the polymer particle phase in other polymer particle phases existing around the polymer particle phase. As a result, unevenness occurs in the flow of electrons in the conductive layer, so that the discharge from the outer surface of the charging member to the electrophotographic photoreceptor becomes uneven. This may result in the photoelectric photoreceptor having a non-uniform surface potential.

Therefore, the present inventors considered that the suppression of the variation in the distance between the polymer particle phases in the conductive layer can solve the above-described problems associated with the decrease in the charging bias. Based on such a consideration, the present inventors have further conducted studies and, as a result, found that an electrically conductive member satisfying the following requirements (a) and (B) is effective for solving the problem.

A graininess image in a halftone image caused by the unevenness of the surface potential of the electrophotographic photoreceptor may be generated as a result of the occurrence of the unevenness of discharge uniformity due to the unevenness of the conductive uniformity (uneven dispersion of conductive dots) in the conductive member. The graininess of the halftone image in the durability evaluation decreased with an increase in the resistance value of the charging roller.

Requirement (A)

Having a conductive layer having: a matrix comprising a crosslinked product of a first rubber; and a plurality of domains dispersed in the matrix, and

the domains each comprise a cross-linked product of a second rubber different from the first rubber, and conductive particles.

Requirement (B)

σ/μ is 0 or more and 0.4 or less, where μ represents an average of ratios of sectional areas of the conductive particles contained in the respective domains to sectional areas of the respective domains appearing on a cross section in a thickness direction of the conductive layer, and σ represents a standard deviation of the ratios,

mu is 20% or more and 40% or less, and

at least eight first cube-shaped samples, one side of which is 9 μm, sampled from any nine portions of the conductive layer satisfy the following condition (1):

condition (1)

Suppose that a sample is divided into 27 unit cubes each having a side of 3 μm, and the volume Vd of a domain contained in each unit cube is calculated, Vd being 2.7 to 10.8 μm³The number of unit cubes of (2) is at least 20.

That is, when the relationship between μ and σ satisfies the requirement "σ/μ is 0 or more and 0.4 or less", the change in the number/amount of conductive particles contained in the domain is small, and as a result, the resistance of the domain is uniform. In particular, it is particularly preferable that the relationship between μ and σ satisfies the requirement "σ/μ is 0 or more and 0.25 or less" because the resistance of the domain is more uniform, so that the effect of the present invention tends to be further improved.

In order to make the σ/μ value low, it is preferable to increase the number/amount of conductive particles contained in the domains, and it is also preferable to make the sizes of the domains equal.

Here, μ is 20% or more and 40% or less. When μ is 20% or more, the electrical connection between the conductive particles in the domains is stabilized. When μ is 40% or less, the shape of the domain can be suppressed from being changed by the conductive particles due to an excessive increase in the amount of the conductive particles in the domain. μ is more preferably 23% to 40%, and particularly preferably 28% to 40%.

The unit cubes of 3 μm on one side each contain domains in an amount of 10 to 40 vol%, and the cubes are uniformly present in the entire conductive layer. As a result, the conductive domains are three-dimensionally uniformly and densely arranged in the conductive layer. As described later, even when the total volume of the domains is increased, the proportion of the domains uniformly present in the entire conductive layer tends to increase. When the domain size is reduced to increase the number of domains without changing the total volume of the domains, the proportion of domains uniformly present in the entire conductive layer tends to increase significantly.

That is, the effect of this aspect can be improved as the number of unit cubes having a Vd value of 3 μm on one side satisfying the condition (1) increases. Therefore, the number of unit cubes is 20 or more, preferably 22 or more, and more preferably 25 or more.

Since the conductive path is formed so as to extend from the conductive support to the surface of the conductive layer, the domains are arranged three-dimensionally. The term "conduction path continuation" refers to a state in which charge is transferred between domains when a desired voltage is applied. Depending on the applied voltage, the thickness of the conductive layer, and the resistance of the domains and the matrix, for example, when three-dimensionally evaluated, the distance between the adjacent wall surfaces of each domain is preferably 100nm or less, and particularly preferably 50nm or less from the viewpoint of charge transfer.

That is, as a result of forming the conductive layer structure satisfying the above-described relationship, even when the charging bias is lowered, the transfer of the electric charge in the conductive path can be extremely efficiently performed. As a result, even in high-speed processing, the resistivity is not easily changed, and the conductive paths are uniformized to achieve suppression of charging unevenness and discharging unevenness, so that a high-quality electrophotographic image can be stably formed.

The present invention will be described in detail below. The electroconductive member for electrophotography is described as a charging roller, which is a typical example of the electroconductive member, but the use of the electroconductive member of the present invention is not limited. The charging roller, the transfer roller, the developing roller and the developing blade as embodiments of the present invention can be prepared by appropriately adjusting the shape of the conductive member of the present invention and carrying out a known conventional method for preparing each member. That is, with the conductive member used in applying a low voltage, charge transfer in the conductive path is made very effective, the resistivity is made not to easily change even in high-speed processing, and the conductive path is uniformized to achieve suppression of discharge unevenness, as in the case of reducing the charging bias.

< conductive Member >

Fig. 1A shows one example of an electroconductive member for electrophotography according to an aspect of the present invention, and fig. 1B is a schematic view illustrating a first cube and a unit cube according to an aspect of the present invention. As is apparent from the cross section shown in fig. 1A, the conductive member 1 for electrophotography according to this aspect includes a conductive layer 12 on a conductive base (conductive shaft core) 11, the conductive layer 12 having a matrix containing a crosslinked product of a first rubber and a plurality of domains dispersed in the matrix. Other layers may be further provided on the conductive layer, if desired.

Preferably, the resistance of the conductive member is controlled to 10 in terms of volume resistivity⁴～10⁸Omega cm. When the volume resistivity is 10⁴At Ω cm or more, a good current breaking property is exhibited, and adverse effects on the image can be suppressed. On the other hand, when the volume resistivity is 10⁸When Ω cm or less, a current sufficient to operate the conductive member can be supplied.

< conductive substrate >

From among conductive substrates known in the field of conductive members for electrophotography, an appropriate conductive substrate can be selected and used. For example, the conductive shaft core is a cylindrical carbon steel alloy plated with nickel having a thickness of about 5 μm on the surface. The base body may have a hollow cylindrical shape. The substrate may be coated with a conductive adhesive (pressure sensitive adhesive).

< conductive layer >

The conductive layer has a matrix including a crosslinked product of the first rubber and a plurality of domains dispersed in the matrix. When μ represents an average value of a ratio of a cross-sectional area of the conductive particle contained in each domain appearing on a cross-section of the conductive layer in a thickness direction to a cross-sectional area of each domain, and σ represents a standard deviation of the ratio, the following relationship is satisfied: "σ/μ is 0 to 0.4 inclusive, and μ is 20 to 40% inclusive. Meanwhile, at least eight first cube-shaped samples (13) having a side of 9 μm sampled from any nine portions of the conductive layer satisfy the following condition (1):

"condition (1): suppose that a sample is divided into 27 unit cubes each having a side of 3 μm, and the volume Vd of a domain contained in each unit cube is calculated, Vd being 2.7 to 10.8 μm³Is at least 20 ".

When the conductive member is used as a charging roller, it is preferable that the conductive layer of the conductive member has uniform semiconductivity to uniformly charge the body to be charged, and has low hardness (for example, elastic modulus of the conductive layer is 1MPa or more and 100MPa or less) to ensure uniform contact with the photoreceptor as the body to be charged.

Preferably, substantially only the domains are electrically conductive through the conductive particles, and the conductive particles are non-uniformly distributed in the domains.

[ substrate ]

(Material of first rubber)

The conductive layer has a matrix including 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 when blended with the second rubber in a predetermined ratio as described later, and a rubber composition known in the field of conductive members for electrophotography can be appropriately used according to desired physical properties. Examples thereof include natural rubber, vulcanizates thereof, and synthetic rubbers. Examples of the synthetic rubber include styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), Butadiene Rubber (BR), epichlorohydrin rubber, silicone rubber, fluororubber, isoprene rubber, chloroprene rubber, and ethylene-propylene rubber. Modified rubbers and copolymers thereof, and hydrogenated products thereof may be used, and of course, these rubbers may be appropriately combined and used.

Fillers, softeners, processing aids, tackifiers, anti-blocking agents, dispersants, foaming agents, conductive aids, and roughening particles, etc., which are generally used as rubber compounding agents, may be added to the rubber as long as the effects of the present invention are not impaired. Needless to say, a vulcanizing agent, a vulcanization aid, and a vulcanization accelerator may be added.

The content of the rubber compounding agent blended in the matrix depends on the selected raw material rubber, and is preferably 0.1 part 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 containing a double bond in the main chain has good resistance to passage of electric current, i.e., resistance to deterioration in a rubber deterioration test caused by passage of electric current.

Therefore, the synthetic rubber used is preferably SBR, NBR or BR, which is a diene rubber, or a modified rubber thereof. The rubber used is particularly preferably NBR or SBR, since it has been confirmed that NBR and SBR undergo less thermal deterioration during compounding. SBR tends to improve processability and abrasiveness, and may be very preferable according to desired physical properties.

(resistance of substrate)

The matrix is almost free of conductive particles of carbon black or the like, and has a higher resistance than the domains.

When the matrix comprising the crosslinked product of the first rubber is composed mainly of a matrix having a volume resistivity of 1X 10¹²When the ion conductive raw material rubber of Ω · cm or less is formed, conduction between domains having conductive particles tends to be improved, so that a three-dimensionally good conductive path is easily formed. On the other hand, when the matrix is composed mainly of a material having a volume resistivity of more than 1X 10¹²When the insulating raw material rubber of Ω · cm is formed, the amount/number of domains having conductive particles necessary to satisfy a desired resistance as a conductive member tends to increase, and as a result, it is difficult to form a three-dimensionally good conductive path.

(method of measuring the resistance of substrate)

The resistance of the substrate can be measured with a minute terminal using a sheet obtained by slicing the conductive layer of the conductive member. Examples of means for obtaining the thin slice include a sharp razor, a microtome, and FIBS (focused ion beam). Regarding the preparation of the flakes, the flakes having a thickness smaller than the inter-domain distance previously measured with a Transmission Electron Microscope (TEM) or a Scanning Electron Microscope (SEM) were prepared to eliminate the influence of the domains, thereby measuring only the resistance of the matrix. Therefore, the means for slicing the conductive layer is preferably a means capable of preparing a very thin sample, such as a microtome.

For the measurement of the resistance value, first, one surface of the sheet is grounded, and the position of the matrix and domain in the sheet is identified with a means capable of measuring the resistance value of the matrix and domain, such as an Atomic Force Microscope (AFM), a Scanning Probe Microscope (SPM), or the like. SPM and AFM are also capable of measuring hardness distributions. Subsequently, the probe was brought into contact with the substrate, and the ground current at the time of applying a DC voltage of 50V was measured and calculated as the resistance. Here, a means (such as SPM or AFM) capable of measuring the shape of the flake is preferable because the thickness of the flake can be measured and thus the resistivity can be measured.

In the measurement of the above-described resistance, one sheet sample was cut out from each region obtained by dividing the conductive member into four in the circumferential direction and five in the longitudinal direction, and the above-described measurement values were obtained, and then the arithmetic average of the results of a total of 20 samples was calculated.

(comparison between the resistances of the substrate and the domain)

As described above, the matrix is almost free of conductive particles of carbon black or the like, and has a higher resistance than the domains. From the viewpoint of forming the conductive path of the domain, the ratio of the volume resistivity of the matrix portion to the volume resistivity of the domain portion is preferably 5 or more, and more preferably 10 or more.

The ratio of the volume resistivity of the matrix portion to the volume resistivity of the domain portion is measured in the following manner. As in the measurement of the resistance of the substrate, a sheet of the conductive layer is prepared, and the current is measured in a minute area using an SPM having a current measuring function. Here, an SPM scanning area including at least one domain is selected. For example, when the size of the domain is in the submicron order, it is preferable to select a scanning area of several μm square containing a plurality of domains. One or more sub-regions corresponding to the substrate are selected from current map data (data of pixels having respective stored current values) obtained by scanning while applying a fixed voltage, the average value of the current data in the plurality of sub-regions is calculated, and the average current value of the substrate portion is defined as Jd. For the domain portion, similar analysis is performed, and the average current value of the domain portion is defined as Jm. From the above data, Jm/Jd was determined as the resistance ratio (reciprocal of current ratio) between the domain portion and the matrix portion, and evaluated.

In the measurement of the above current, a sheet sample of one conductive layer was cut out from each region obtained by dividing the conductive member into four in the circumferential direction and five in the longitudinal direction, and the above measured values were obtained, and then the arithmetic average of the results of a total of 20 samples was calculated.

[ Domain ]

(Material of second rubber)

The domains forming the conductive layer comprise a second rubber. The material of the second rubber is not particularly limited as long as it can form a domain including the second rubber when blended with the first rubber in a predetermined ratio. As the material of the second rubber, a rubber composition known in the field of conductive members for electrophotography can be suitably used in accordance with desired physical properties. That is, for example, the rubber materials shown in the above-mentioned "[ material of matrix ] (material of first rubber)" portion may be suitably used as long as these materials are incompatible with the material of the first rubber.

Diene rubbers containing a double bond in the main chain are preferable because compatibility improves according to the combination when carbon black is used for the conductive particles. Diene rubbers having a styrene skeleton are preferable because compatibility with carbon black tends to be improved depending on the combination. From the viewpoint of fixing the conductive particles, a rubber material having a functional group that can be expected to interact with the conductive particles of carbon black or the like in the main chain or side chain or terminal portion of the second rubber is preferable. The material viscosity can be easily adjusted by appropriately blending a liquid rubber as a material of the second rubber.

As in the case of the material of the first rubber, a filler, a softener, a processing aid, a tackifier, a releasing agent, a dispersant, a foaming agent, a conductive aid, and the like, which are generally used as a rubber compounding agent, may be added to the material of the second rubber forming the domains, as long as the effects of the present invention are not impaired. Needless to say, a vulcanizing agent, a vulcanization aid, and a vulcanization accelerator may be added.

The content of the rubber compounding agent blended in the domains depends on the selected raw material rubber, and is preferably 0.1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the second rubber.

(resistance of field)

The domains are conductive phases and efficiently transport charge in the conductive paths in high speed processing. Therefore, the resistivity is preferably low, and specifically, the resistivity is preferably 10^-1Ωcm～10³Omega cm. By appropriately adjusting the kind and amount of the conductive particles, the resistance of the domain can be adjustedThe rate is set to a desired value.

(conductive particles)

The conductive domain includes a crosslinked product of the second rubber and conductive particles. Examples of the conductive particles include the following conductive particles: fine particles and fibers of metal systems such as aluminum, palladium, iron, copper, and silver; fine particles of metal oxides such as titanium oxide, tin oxide, and zinc oxide; composite particles obtained by treating the surfaces of the above-mentioned metal-based fine particles, fibers and metal oxides by electrolysis, spraying or mixing and shaking; conductive carbon black such as furnace black, thermal black, acetylene black and ketjen black; and carbon powders such as PAN (polyacrylonitrile) -based carbon and pitch-based carbon. Two or more of these kinds of conductive particles may be used in combination, if necessary.

Here, examples of furnace black include the following: SAF-HS, SAF, ISAF-HS, ISAF-LS, I-ISAF-HS, HAF-LS, T-HS, T-NS, MAF, FEF, GPF, SRF-HS-HM, SRF-LM, ECF, and FEF-HS. Examples of thermal carbon blacks include FT and MT. One of these kinds of conductive particles (conductive carbon black) may be used alone, or two or more thereof may be used in combination.

The carbon black used is preferably a conductive carbon black having a DBP absorption of 40ml/100g or more and 150ml/100g or less. The DBP (dibutyl phthalate) absorption amount is a value obtained by indirectly quantifying the structure of the primary particles of the carbon black. That is, it has been found that, even when a material of the second rubber of low polarity is used, the use of developed carbon black in which the structure has a DBP absorption amount within the above-described range tends to improve the interaction with the rubber material. The DBP absorption of carbon black can be measured by the method described in JIS K6217-4 (2001). The conductive carbon black can be distinguished from other fillers such as reinforcing carbon black by microscopic observation or the like because the structure is highly developed.

The content of the conductive particles blended in the domains is 5 parts by mass or more and 150 parts by mass or less, more preferably 20 parts by mass or more and 120 parts by mass or less, with respect to 100 parts by mass of the second rubber. In particular, the content of the conductive particles is still more preferably 50 parts by mass or more and 120 parts by mass or less because percolation in the domains is improved to sufficiently connect the conductive particles, and as a result, the conductive paths in the domains are "densely electrically connected" and are stably formed. In addition, the content of the conductive particles is particularly preferably 60 parts by mass or more and 120 parts by mass or less because the variation of the contained conductive particles between the domains becomes extremely small as described later.

When blended in an amount of 5 parts by mass or more with respect to 100 parts by mass of the second rubber, the conductive particles may function as a conductive domain. However, when the volume amount of the conductive particles is small, the domains can be easily migrated and re-aggregated by applying heat and kinetics to the domains, depending on the conditions during the blending process using a general mixing device such as a mixer or a roller, or during the process of the conductive member. Therefore, the content of the conductive particles is more preferably 20 parts by mass or more. Further, when the content of the conductive particles is more than 50 parts by mass, the effect tends to be improved. The content of the conductive particles is preferably 60 parts by mass or more, and particularly preferably 80 parts by mass or more. That is, when the content of the conductive particles in the domain is high, the domain becomes hard, so that migration can be suppressed.

In addition, when the content of the conductive particles is more than 50 parts by mass, the conductive member contains a larger amount of the conductive particles than a general conductive member for electrophotography. When the conductive particles in the domains are electrically connected to form a good conductive path, the conductivity of the domains themselves is exhibited. The formation of the conductive path is related to the content and volume occupancy of the conductive particles in the domain, and as the ratio of the conductive particles becomes higher, since the conductive path is stable in percolation, the charge transfer efficiency in the conductive path can be improved. Therefore, an increase in the content of the conductive particles improves the conductive characteristics, so that the preferable effects of the present invention are easily exhibited.

Most preferably, the conductive particles are present only in the domains. However, even when a method is employed in which a master batch having conductive particles added only to the second rubber contained in the domain is prepared in advance, and then the resulting master batch is blended with the first rubber for forming the matrix, a phenomenon may occur in which a small amount of conductive particles are transferred to the matrix. In the present invention, the conductive particles may be present in the matrix in a small amount sufficient to avoid contributing to the conductivity. The amount of conductive particles present in the matrix, which is small enough to avoid contributing to the conductivity, is such that the amount of conductive particles present in the matrix per unit volume is preferably lower than the amount of conductive particles present in the domains per unit volume, and is preferably equal to or less than 1/5, more preferably equal to or less than 1/10, still more preferably equal to or less than 1/100 of the amount of conductive particles present in the domains per unit volume.

(method of measuring electric resistance of field)

The domains according to the invention are electrically conductive phases and the resistance of the domains can be measured in the same way as in the measurement of the resistance of the matrix.

In the measurement of the above-described resistance, one sheet sample was cut out from each region obtained by dividing the conductive member into four in the circumferential direction and five in the longitudinal direction, and the above-described measurement values were obtained, and then the arithmetic average of the results of a total of 20 samples was determined.

(Domain formation (sea-island Structure))

The findings known for polymer blends can be applied to the rubber blends in the conductive layer according to the invention.

In the case of a non-compatible polymer blend, its sea-island structure depends on the viscosity of each polymer and blending conditions, and polymers having a small composition ratio tend to form domains.

(means for uniformly dispersing domains in the matrix)

As a means of uniformly dispersing the domains in the matrix, the total volume of the domains is increased. That is, even if the number of domains in the matrix is not changed, the volume occupied by the domains increases. However, when the size of the domain becomes unnecessarily large as described later, the above-described condition (1) is not satisfied. In this case, naturally, the dispersion uniformity of the domains deteriorates, and the effects of the present invention cannot be obtained.

As a more effective means of uniformly dispersing the domains throughout the matrix, the domains are reduced in size and finely dispersed. That is, even if the total volume of domains in the matrix is not changed, the number of domains is significantly increased due to the reduction in size. For example, if there are 100 domains in a regular sphere shape having a certain radius, and the radius of all the domains is reduced to 1/2, a simple calculation shows that the number of domains becomes about 800 while the total volume of the domains is constant. Therefore, even if the total volume of the domains is not changed, the proportion of the domains uniformly existing in the entire conductive layer is increased by decreasing the domain size to increase the number of the domains. As a result, the number of unit cubes satisfying the condition (1) increases, so that the effect according to this aspect can be improved.

As a theoretical equation in which the domain size is reduced in a polymer blend, the following equation is known.

D＝[Cσ/η0γ·]·f(η0/η)

D: dispersed particle diameter (particle diameter of domain) σ: interfacial tension η 0: viscosity η of the matrix: viscosity of dispersed phase (viscosity of domain) C: constant γ ·: shear rate

That is, in the present invention, the following three methods are roughly envisaged to reduce the diameter of the domain (island size):

(method a) reducing the interfacial tension between the first rubber and the second rubber;

(method B) bringing the viscosity of the first rubber and the viscosity of the second rubber close to each other; and

(method C) increase shear rate during blending.

Method A: specifically, in order to uniformly disperse the conductive domains, it is preferable to select a combination that ensures that the difference in solubility parameter (SP value) between the first rubber and the second rubber is small. As a method of reducing the interfacial tension, addition of a compatibilizing agent is preferable. When the SP value difference is too small, it may be difficult to ensure that the conductive particles in the domain are unevenly present only in the domain, or the compatibility may become too high to stably form the sea-island structure.

Method B: specifically, in order to uniformly disperse the conductive domains, it is preferable to select a combination of materials of the first rubber and the second rubber such that the viscosities of the rubbers are close to each other at the temperature during kneading. Here, it is effective to use a liquid rubber or the like as a part of the second rubber of the domains.

Method C: it is effective to simply increase the shear rate during blending or increase the shear time. As described in detail later, the present inventors have found that, in addition to increasing the shear rate, the use of "extensional shear" as the shearing mechanism to be applied, rather than "simple shear," is also particularly effective.

(size of the Domain)

The size of the domains in the present invention is preferably small as described above.

Specifically, in order to satisfy the condition (1), the size of the domains in the cross section is preferably 0.1 to 2 μm or less, more preferably 1 μm or less, and still more preferably 0.5 μm or less. Particularly, when the size of the domain is 0.4 μm or less, the extremely high effect of the present invention can be expected. When the size of the domains is less than 0.1 μm, it is impossible to blend a large amount of conductive particles in the domains. The size of the domains refers to the equivalent circular diameter. Average domain size refers to area weighted average domain size.

(method of measuring the size of the Domain)

In the method of measuring the size of a domain according to the present invention, first, a fracture surface is neatly formed at a measurement point on a sample by the following means. Here, the fracture surface may be formed by applying a freeze fracture method, a cross polisher method (cross polish method), a Focused Ion Beam (FIB) method, or the like to an appropriate sheet. The FIB method is preferable in view of smoothness of the fracture surface and pretreatment for observation.

Next, in order to sufficiently observe the domain structure, a pretreatment such as a dyeing treatment or a vapor deposition treatment for obtaining sufficient contrast between the domain and the substrate may be performed.

The fracture surface formed and pretreated flakes can be observed with a laser microscope, a Scanning Electron Microscope (SEM), or a Transmission Electron Microscope (TEM). In particular, from the viewpoint of accuracy in quantifying the area of the domain (which is a conductive phase), it is preferable to observe the sheet under a magnification of 10,000 to 100,000 times with an SEM.

The following will be described in detail in the case of the conductive roller.

First, a conductive roller was cut into circular cut piece samples using a sharp razor blade. Here, circular slice samples of the conductive layer were prepared so that measurements can be made at three positions of (1/4) l, (2/4) l, and (3/4) l from the end, where l is the length in the longitudinal direction. The cross-sectional portion of the conductive layer of the circular cut sample was subjected to the frozen ion milling treatment at 90-degree intervals in the circumferential direction of the roller in the vicinity of the centers of the core and the surface. The surface is exposed by a freeze ion milling process. Subsequently, the sections of the conductive layer in each of the sections at (1/4) l, (2/4) l and (3/4) l were observed at 90-degree intervals from the core position to the central portion of the surface in the circumferential direction of the roller, wherein observation was performed at a magnification of 5,000 times and a number of pixels of 4,096 × 3,072 using an SEM (trade name: Ultraplus, manufactured by Carl Zeiss Company) (a total of 12 images, for example, SEM images of 20 μm square can be obtained).

Thereafter, by observing the obtained images, each binarization and image analysis was performed with an image analysis apparatus (trade name: LUZEX-AP, manufactured by NICECO CORPORATION), the obtained domain area S was calculated and then substituted into the calculation formula of √ S/√ π to determine the circle-equivalent diameter. In the present disclosure, the circle-equivalent diameter is defined as the size of the domain.

(method of measuring volume of field)

The volume of the domains can be determined by three-dimensional measurement of the conductive layer using FIB-SEM.

FIB-SEM refers to a method in which a sample is processed with a FIB (focused ion beam) apparatus, and the exposed cross section is observed with an SEM (scanning electron microscope). The three-dimensional structure can be examined by repeating the sequential processing and observation to obtain a large number of photographs, and then subjecting the SEM image to a 3D reconstruction process using computer software to construct a sample structure as a three-dimensional image.

Fig. 2 is a schematic view illustrating a structure of a conductive layer having a matrix including a cross-linked product of a first rubber, and a plurality of domains dispersed in the matrix. As a specific measurement method of the volume of the domain, a three-dimensional stereoscopic image represented by fig. 2 was obtained using FIB-SEM (manufactured by FEI Company) (as described in detail above), and the above-described configuration was confirmed in the obtained image.

That is, sampling from the conductive layer was performed at arbitrary nine positions, and when the conductive member had a roll shape, one sample was cut out at intervals of 120 degrees each in the circumferential direction of the roll at three points in the vicinity of the distance ends (1/4) l, (2/4) l, and (3/4)1, with the length in the longitudinal direction being l.

Thereafter, images of a cubic shape with a side of 9 μm were measured at 60nm intervals by three-dimensional measurement using FIB-SEM. Here, the sections of the conductive layer on the respective sections at (1/4) l, (2/4) l, and (3/4) l are measured at intervals of 120 degrees in the circumferential direction of the roller, where the measurement is made from the core position to the central portion of the surface.

In order to properly observe the domain structure, a pretreatment for obtaining a proper contrast between the domain and the matrix is preferably performed. Here, the dyeing treatment can be preferably performed.

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

The distance between adjacent walls of each domain can be similarly measured using the above-described 3D visualization/analysis software, and can be calculated from the arithmetic mean of a total of 27 samples after obtaining the above-described measurement values.

(conductive particles in domains)

As described above, when "σ/μ is 0 or more and 0.4 or less, and μ is 20% or more and 40% or less", the change in the number/amount of the conductive particles in each domain is small, and therefore, the resistance of the domain is uniform. In particular, it is more preferable that the relationship between μ and σ satisfies the requirement "σ/μ is 0 or more and 0.25 or less" because the resistance of the domain is more uniform, and therefore the variation of the conductive particles becomes extremely small, so that the effect of the present invention tends to be improved.

As one method of satisfying the requirement "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, the present inventors have conducted intensive studies and as a result, found that when the ratio of the sectional area of the conductive particles contained in each domain appearing on the conductive layer to the sectional area of each domain is 23% or more, more preferably 28% or more, this requirement tends to be satisfied. As described later, the mixing processing using an elongation shearing apparatus is preferable, and particularly, the mixing processing using a continuous elongation shearing apparatus is more preferable.

When the conductive particles are carbon black, the average primary particle diameter is 5nm or more and 60nm or less, and particularly, 10nm or more and 50nm or less is preferable. Here, the average primary particle diameter of the conductive particles is an arithmetic average particle diameter. The average primary particle diameter is defined as the average primary particle diameter of a single crystal or a crystallite similar to a single crystal on a microscope having a size of 5nm or more and 60nm or less. Examples of the method of measuring the average primary particle diameter include (1) a method using a Transmission Electron Microscope (TEM) in which an object irradiated with an electron beam is observed transparently; (2) a method using a Scanning Electron Microscope (SEM), in which the surface of an object irradiated with an electron beam is observed. The method of calculating the average primary particle diameter is preferably a method in which the average primary particle diameter is directly determined from a measurement image.

(method of measuring area of conductive particle in domain-method of calculating variation in conductive particle (. sigma./μ))

The change can be calculated using the SEM image observed in the "measurement method of the size of the domain" section.

A central portion of a 3 μm square was extracted from SEM images (12 images in total), and the area of the conductive particles represented by carbon black in each domain and the domain area were each subjected to analysis processing by means of contrast difference within the domain using an image analysis apparatus (trade name: LUZEX-AP, manufactured by NIRECO CORPORATION), and "σ/μ" was calculated, where μ represents an 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 on a cross-section in the thickness direction of the conductive layer, and σ represents a standard deviation of the ratio. If no domain is present in the center part of the 3 μm square, other domains are randomly selected and observed with SEM.

(shape of field)

The cross-sectional shape of the domains according to the invention is preferably close to circular. Specifically, the value of circularity shown below is preferably 1 or more and less than 2. A circularity of 1 indicates a true circle.

In order to obtain the effect of the present invention, the proportion of the number of domains having a circularity of 1 or more and less than 2 among the domains appearing on the cross section of the conductive layer is preferably 70% or more. The ratio is more preferably 80% or more because the effect of the present invention increases as the ratio increases. It is known that, in general, the conductive characteristics significantly vary depending on the shape and anisotropic properties of the conductive particles (Matsutani et al, int.j.mod.phys.c 21(2010) 709). That is, in a domain having poor circularity, high aspect ratio, and the like, the electric field distribution of the domain has an aspect ratio, that is, exhibits anisotropic properties. Therefore, electric field concentration points are formed, whereby it tends to be difficult to obtain a uniform conductive path.

When the value of the circularity of the domain is 1.1 or more, preferably 1.5 or more and less than 2, the interface area with the matrix increases, so that the following effects can be expected, which may be preferable. That is, when the conductive member is disposed while being in contact with the photoreceptor, the conductive member is mechanically compressed in a repeated manner in the vicinity of the joint formed between the photoreceptor and the conductive member. Here, in the case of a true circle having an extremely high circularity, it is presumed that migration of a domain based on application of mechanical energy is easily induced, and as a result, the network structure of the conductive path changes, so that the resistance value of the conductive layer changes. On the other hand, when the value of the circularity of the domain is 1.1 or more, preferably 1.5 or more, the variation can be suppressed because the interface area with the matrix increases.

(method of controlling shape of field)

As a method of controlling the shape of the domain, particularly a method for obtaining a domain having a good circularity, in the present invention, as described above, it is effective to increase the filling amount of the conductive particles in the domain. That is, when the amount of the conductive particles is small, the domains can be easily migrated and reaggregated by applying heat and kinetics according to conditions during blending processing using a general mixing device such as a mixer or a roll, or during processing of the conductive member. However, when the filling amount of the conductive particles in the domain is high, the domain becomes hard, and as a result, migration can be suppressed, thereby suppressing deterioration of circularity due to reaggregation.

By increasing the loading, shear can be easily applied when the second rubber blended with the conductive particles is kneaded, resulting in improvement in circularity of the domains.

The above-described method of reducing the domain size (island size) (methods a to C) is also effective. That is, as the domain size decreases, the aspect ratio becomes lower. As described in detail later, the present inventors have found that, in addition to increasing the shearing speed, it is also effective to use "elongation shearing" instead of "simple shearing" as the shearing mechanism to be applied. In particular, a mixing process using a continuous elongation shearing apparatus tends to give further preferable results.

(method of measuring shape of field and method of calculating circularity)

The shape of the domain according to the present invention can be quantified using an SEM image obtained by performing formation and observation of a fracture surface by a method similar to that described in "method of measuring the size of the domain".

That is, for the domains in the SEM image obtained as described above, binarization and image analysis were performed with an image analysis device (LUZEX-AP, manufactured by nireo CORPORATION), and circularity was calculated from the average value thereof. Here, based on the definition "JIS B0621: the circularity of a circular body is represented by the difference between the radii of two concentric geometric circles, by which the circularity is analyzed by clamping the circular body to give the minimum distance between the two concentric circles.

When the inorganic filler or the roughening particles affect the image processing in the observation domain with SEM, the circularity can be calculated by also applying contrast difference, EDX measurement (SEM/EDX (scanning electron microscope/energy dispersive X-ray spectroscopy)), hardness measurement using SPM measurement alone, or the like with the filler or particles appropriately excluded.

Here, a domain having a circle equivalent radius of 100nm or more is used for calculation.

(domain size distribution)

In the conductive layer according to this aspect, conductive domains having uniform resistance are arranged three-dimensionally and uniformly and densely. Thus, the domain size distribution is preferably such that the domain size is uniform and the domain size is small. Specifically, it has been confirmed that the effect of the present invention is exhibited when the relationship between the domain size and the number of domains satisfies the following relational expressions (1) and (2) on the cross section of the conductive layer.

Relational expression (1)

80 is less than or equal to 100 multiplied by L2/L1 is less than or equal to 100; and

relational expression (2)

0 is less than or equal to 100 multiplied by L3/L1 is less than or equal to 20

Where L1 denotes the total number of domains present in a cross section in the thickness direction of the conductive layer, and L2 denotes an area of 3.0 × 10 measured in the cross section⁴nm²Above and less than 1.2 x 10⁵nm²The area of L3 measured in cross section is 1.2X 10⁵nm²The number of the above fields.

When "100 × L2/L1" is 95 or more and "100 × L3/L1" is 5 or less, the uniformity of the domain size distribution can be extremely high.

(measurement method of Domain size distribution- "100 XL 2/L1" and "100 XL 3/L1")

"100 × L2/L1" and "100 × L3/L1" can be calculated from the area and the number of domains in each domain obtained by analysis in the "measurement method of domain size" section.

That is, here, "100 XL 2/L1" and "100 XL 3/L1" are calculated, where L1 is the total number of domains and L2 is an area of 3.0X 10⁴nm²Above and less than 1.2 x 10⁵nm²L3 is an area of 1.2X 10⁵nm²The number of the above fields.

(method of controlling Domain size distribution)

Here, miniaturization of domains and suppression of inter-domain re-aggregation are crucial. That is, the method of inhibiting reaggregation of domains described in the "means for uniformly dispersing domains in a matrix" and the "method for controlling the shape of domains" are suitably used.

[ method for producing electroconductive Member for electrophotography ]

The method for producing the conductive member for electrophotography in the present invention is not particularly limited as long as it can form a conductive layer having the structure of the present invention as described above, and the conductive member can be formed by appropriately adjusting the following requirements:

(1) selecting raw materials at the time of kneading a conductive rubber mixture comprising a raw material of a first rubber and a raw material of a second rubber containing conductive particles;

(2) composition in mixing the rubber mixture; and

(3) the kind of mixer, the shear rate, the shear force and the mixing time when mixing the rubber mixture.

For example, an unvulcanized first rubber is mixed with a separately prepared unvulcanized second rubber containing conductive particles, and the mixture is vulcanized and cured by a suitable processing process to obtain a conductive member including a conductive layer having a matrix containing a crosslinked product of the first rubber and a plurality of domains dispersed in the matrix and containing a crosslinked product of the second rubber.

< kneading Process >

In addition to a simple shear type dispersing apparatus generally used for mixing and kneading a rubber, an elongation shear type dispersing apparatus is suitably used.

Generally, as described above, as the shear force increases or the shear time (frequency) increases, dispersion of the incompatible rubber tends to be promoted. On the other hand, it is known that as the shearing force or shearing time increases, the shearing heat generation amount increases, thereby promoting cleavage of rubber molecular chains, resulting in deterioration of the material, and domain re-aggregation. That is, it is important to control the temperature during the processing while applying the shearing force.

< investigation of kneading Mixer >

(comparison of simple shear type dispersing device with elongation shear type dispersing device)

As a simple shear type dispersing device, conventional rubber mixing devices such as a pressure type kneader and open rolls, and a twin-screw kneading extruder capable of applying a larger shearing force than the above devices have hitherto been known. However, in the present invention, the filling amount of the conductive particles in the domain tends to increase. In the studies of the present inventors, there are cases where: in which with a simple shear type dispersing apparatus, it is impossible to uniformly apply shear sufficient to disperse the second rubber containing conductive particles, local heat generation occurs during processing, etc., and as a result, domains cannot be sufficiently uniformly dispersed.

The present inventors have conducted intensive studies and, as a result, found that a mixing mill comprising an elongated shear screw is suitable for dispersing domains according to the present invention sufficiently uniformly throughout a matrix.

Unlike a simple shearing mechanism in a pressure type mixer, an open roll or a twin-screw mixing extruder, in which a material is gradually crushed and dispersed, elongation shearing finely stretches and divides the material, it is easy to obtain domains that are fine and uniform in size. The fact that the rubber exhibits entropic elasticity and therefore has endothermic properties when stretched is advantageous for this system, and this may be the reason why local heating in an elongation shear system can be suppressed.

In this system, even when the filling amount of the conductive particles in the domains is increased, uniform and fine dispersion can be performed because higher shear is uniformly applied as compared with a simple shearing system. Here, it has been confirmed that the uniform dispersion treatment can be completed in an extremely short time (several seconds).

The present inventors have confirmed that there are cases in which domains cannot be uniformly and finely dispersed in a matrix by merely increasing the shearing force in a simple shearing process. Specifically, studies have been made using a twin-screw kneading extruder (trade name: KZW15TW-4MG-NH (-6000), manufactured by TECHNOLOGEL CORPORATION) capable of rotating at high speed and achieving a shear rate that cannot be achieved with a conventional pressure type kneading machine, roll mill, or extruder for rubber. Therefore, there are cases in which gelation and reaggregation of the material, etc. occur and the domains cannot be uniformly and finely dispersed in the matrix by merely increasing the shear rate in simple shear processing.

As described above, the mechanism of elongation shearing is significantly different from the mechanism of simple shearing. That is, shear flow in simple shear is a flow in which the material is torn by a velocity gradient, while elongation flow in elongation shear is a flow in which the material is stretched in the direction of principal stress. In addition to the dispersion of the rubber material (viscoelastic body) in the present invention, Kaziwara et al have reported that in a newtonian fluid/newtonian fluid dispersion system, the viscosity ratio in a simple shear flow field is preferably about 1, while in an elongation flow, droplet stretching and division are independent of the viscosity ratio, and fine dispersion can be performed even in a system of a large viscosity ratio of about 5 or more [ Molding, vol.23, No.2, pp.72-77(2011) ]. It is considered that, in the present invention, the effect of "easily dispersing in elongation shear even when the viscosity ratio of the material is large" is exerted in the blend system of the rubber material as the viscoelastic body. This is probably the reason why uniform fine dispersion can be performed between the matrix material and the domain material containing a large number of conductive particles.

That is, it is preferable that the conductive member for electrophotography including the conductive layer is manufactured by the steps of: (1) an unvulcanized rubber kneaded product is prepared by kneading an unvulcanized rubber mixture containing a first unvulcanized rubber as a raw material of a first rubber, a second unvulcanized rubber as a raw material of a second rubber and conductive particles using a kneader including an elongated shear screw, (2) a layer of the unvulcanized rubber kneaded product is formed on an outer surface of a conductive substrate, and (3) the first unvulcanized rubber and the second unvulcanized rubber in the layer of the unvulcanized rubber kneaded product are vulcanized to prepare a conductive layer.

Fig. 3A and 3B are schematic diagrams illustrating one example of an elongation shear screw used in the production of the conductive elastic layer according to this aspect. Fig. 3A shows a screw having an elongation shear applying mechanism inside the screw, and fig. 3B shows a screw having an elongation shear applying mechanism outside the screw. Preferably, an elongation shearing apparatus comprising an elongation shearing screw 31 as shown in fig. 3A and 3B is used to apply elongation shear. The elongation screws were classified into "a batch circulation type" of the screw 3A having the elongation shear applying mechanism (narrow tube) inside the screw 31 as shown in fig. 3A, and "a continuous type" of the screw 3B having the elongation shear applying mechanism (narrow tube) outside the screw 31 as shown in fig. 3B.

In the elongation shear processing apparatus having the screw 3a of the intermittent circulation type, the hole 32 of the narrow tube is provided inside the screw. The device has the following mechanisms: during kneading, the rubber composition reaches the front end portion of the screw 31, and then returns to the rear end portion of the screw 31 through the hole 32 of the tubule at the front end of the screw 31. Thus, the rubber composition repeatedly passes through the pores of the tubule, and a shear force associated with the elongation motion is applied at the pores of the tubule. The rubber composition can be continuously maintained in an elongation shear field, and thus a large shear force can be applied in a short time. However, the reaggregation may occur in some portions depending on the residence time, and therefore a continuous type elongation shear processing apparatus may be preferable.

Here, in order to apply elongation shear, the pore diameter of the tubule is preferably more than 0.5mm and not more than 5.0 mm. It has been confirmed that when the pore diameter of the thin tube is 5.0mm or less, the shearing in the elongation shearing is sufficient, and when the pore diameter of the thin tube is more than 0.5mm, there is no case where it is difficult to process because the rubber cannot sufficiently pass through the pores of the thin tube. The pore diameter of the thin tube is preferably 1.0-3.0 mm. The kneading is particularly preferably carried out in a short time for the treatment time. The shear energy applied to the rubber composition varies depending on the size of the pore diameter of the tubule. Therefore, from the viewpoint of suppressing heat generation during the shearing process, determination of the pore diameter of the narrow tube, control of the material feeding speed and the material temperature during the mixing, and the like are one of important factors of the processing conditions. The number of pores of the tubule is not particularly limited as long as the desired domains can be uniformly dispersed, and a structure capable of obtaining a similar elongation shear effect (for example, a double cylindrical structure) may be used instead of the tubule.

The present inventors have conducted intensive studies and, as a result, found that, in terms of processing conditions, the continuous type is particularly preferable because only elongation shear is effectively applied.

As the intermittent circulation type apparatus, for example, an elongated shearing apparatus (a microshear apparatus manufactured by Imoto Machinery co., ltd., or a high speed shearing apparatus manufactured by NIIGATA MACHINE techon co., ltd.) is preferably used. As the continuous type apparatus, it is preferable to use an apparatus obtained by modifying the screw section of the intermittent circulation type apparatus so that the elongation shear applying mechanism is disposed not inside but outside the screw as shown in fig. 3B. The apparatus described in Bando TECHNICAL REPORT No.18/20147, P2, etc. can also be suitably used.

The present inventors have made intensive studies and, in the dispersion treatment step, as a result, confirmed that setting the material temperature during dispersion to 170 ℃ or less, which is measured using an infrared thermometer capable of direct measurement, gives good results of uniform dispersion. When the temperature at the time of kneading the materials is measured with a thermocouple, it is likely that the measured value tends to be lower than that measured with an infrared thermometer, and therefore good results may not be obtained even when the processing treatment is performed at a temperature of 170 ℃ or lower. That is, it is effective to precisely control the processing temperature using a mixing device including an elongated shearing mechanism having a function (IR sensor) of precisely measuring the temperature of the material.

It is also preferable to additionally provide a refrigerator that can control the temperature in the range of-20 ℃ to room temperature in order to prevent deterioration of the rubber composition caused by shear heat generation in the shear processing of the rubber composition. That is, when the screw portion is provided with the infrared temperature sensor that accurately monitors the temperature of the material during mixing as described above, the mixing conditions can be accurately controlled, and in particular, when the temperature during mixing is set to 170 ℃ or less, good results are obtained.

< electrophotographic image Forming apparatus >

An electrophotographic image forming apparatus according to an aspect of the present invention includes the conductive member for electrophotography according to an aspect of the present invention. Fig. 4 is a schematic outline view showing one example of an electrophotographic image forming apparatus. The photoreceptor 41 as a body to be charged has a drum shape including a conductive support 41b of aluminum or the like having conductivity and a photosensitive layer 41a stacked thereon, and is rotationally driven around a support shaft 41c in a clockwise direction in the figure at a predetermined peripheral speed.

The conductive shaft core 11 of the charging roller 1, which is a conductive member for electrophotography according to an aspect of the present invention, is pressed at both ends with pressing means (not shown) so that the conductive layer 12 to which a Direct Current (DC) bias is applied via the conductive shaft core by the power source 42 and the sliding electrode 43a is brought into contact with the photoconductor 41. Since the charging roller 1 rotates according to the rotation of the photoconductor 41, the photoconductor 41 is uniformly charged to a predetermined polarity and potential (primary charging).

Subsequently, an electrostatic latent image corresponding to the target image information is formed on the circumferential surface of the photoreceptor on which exposure (laser beam scanning exposure, slit exposure of an original image, or the like) to the target image information is performed from the exposure device 44. The toner supplied by the developing member 45 adheres to the electrostatic latent image on the photoconductor to form the electrostatic latent image into a toner image. Subsequently, the transfer material 47 is conveyed from a paper feeding section (not shown) to a transfer section between the photosensitive body 41 and the transfer member 46 in synchronization with the rotation of the photosensitive body 41, and the transfer member having a polarity opposite to that of the toner image is pressed from the back side of the transfer material to sequentially transfer the toner images onto the transfer material 47.

The transfer material 47 to which the toner image has been transferred is separated from the photosensitive body 41, and conveyed to a fixing means (not shown) to fix the toner image onto the transfer material, and the transfer material is output as an image forming material. In an electrophotographic image forming apparatus in which an image is also formed on the back surface, the transfer material 47 is re-conveyed between the photosensitive body 41 and the transfer member 46 by re-conveying means in order to perform image formation again.

The peripheral surface of the photoreceptor 41 after the image transfer is subjected to pre-exposure by the pre-exposure device 48 to remove residual charges on the photoreceptor (neutralization is performed). For the pre-exposure device 48, known means can be used, and preferable examples thereof include an LED chip array, a fuse lamp, a halogen lamp, and a fluorescent lamp. The neutralized peripheral surface of the photoreceptor 41 is cleaned while removing adhering contaminants such as untransferred toner by the cleaning member 49, and is supplied for image formation in a repeated manner.

In the electrophotographic image forming apparatus, the charging roller 1 may be driven in accordance with the photoconductor 41, may not be rotated, or may be positively rotationally driven at a predetermined peripheral speed in a forward or reverse direction with respect to a surface moving direction of the photoconductor 41. In the case where the electrophotographic image forming apparatus is used as a copying machine, exposure may be performed in the following manner: reflected light or transmitted light from an original is applied, the original is read and converted into a signal, and based on the signal, a laser beam is scanned, or an LED array is driven, or a liquid crystal shutter array is driven.

Examples of the electrophotographic image forming apparatus of the present invention include a copying machine, a laser beam printer, an LED printer, and an electrophotographic application apparatus such as an electrophotographic plate making system.

< Process Cartridge >

A process cartridge according to an aspect of the present invention includes a conductive member, and is detachably attached to a main body of an electrophotographic image forming apparatus. Fig. 5 is a schematic view showing one example of the process cartridge. The process cartridge includes a roller-shaped conductive member according to an aspect of the present invention as the charging roller 51. An electrophotographic photosensitive body (hereinafter, also referred to as "electrophotographic photosensitive drum") 53 in a drum shape is provided so that the electrophotographic photosensitive body 53 can be charged by the charging roller 51. Here, specifically, the charging roller 51 is pressed to contact the electrophotographic photosensitive drum 53. Further, a developing roller 55 for supplying a developer to develop an electrostatic latent image formed on the surface of the electrophotographic photosensitive drum 53 and a cleaning blade 57 for removing the developer remaining on the circumferential surface of the electrophotographic photosensitive drum 53 are provided. The developing blade 59 is in contact with the developing roller 55. For the developing blade 59, a blade-shaped conductive member according to an aspect of the present invention may be used.

[ examples ]

The present invention will be described in more detail below by way of examples, which should not be construed as limiting the invention. Hereinafter, "parts" means "parts by mass" unless otherwise specified, and commercially available high purity products are used as reagents and the like unless otherwise specified.

In the examples, the a-compounded rubber composition (mixture) refers to an unvulcanized rubber composition (mixture) containing no crosslinking agent and vulcanization accelerator, and the B-compounded rubber composition (mixture) refers to an unvulcanized rubber composition (mixture) containing a crosslinking agent and vulcanization accelerator.

< example 1>

(preparation of rubber mixture)

100 parts of an ethylene-propylene-diene terpolymer (trade name: EPT4045, manufactured by Mitsui Chemical, Incorporated) as a raw material of the domains, 3 parts of CARBON Black (trade name: Ketjen Black EC600JD, manufactured by Ketjen Black International Company) as a conductive particle, 40 parts of CARBON Black (trade name: TOKABLACK #7360, manufactured by TOKAI CARBON CO., LTD.), 10 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 master batch 1.

Next, 180 parts of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (trade name: EPICHLOMER CG, manufactured by OSAKA SODA CO., LTD.), 1 part of stearic acid as a processing aid, 145 parts of a master batch, 2.5 parts of 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexyne (trade name: PERHEXA 25B-40, manufactured by NOF CORPORATION) as a vulcanizing agent, and 1.5 parts of triallyl isocyanurate (trade name: TAIC-M60, manufactured by Nippon Kasei Chemical Company Limited) as a crosslinking aid were mixed by open rolls to obtain an unvulcanized rubber mixture (B compounded rubber composition 1). The masterbatch 1 was divided into five parts and mixed stepwise.

Preparation of conductive roller

A round bar having a total length of 252mm and an outer diameter of 6mm was prepared from free-cutting steel having been subjected to electroless nickel plating. Next, the round bar was coated with an adhesive over the entire circumference of a length of 230mm (excluding a length of 11mm from both ends). As the adhesive, a conductive hot-melt type adhesive is used. For coating, a roll coater was used. A round bar coated with an adhesive was used as the conductive shaft core body (core metal).

Next, a cross-head extruder having a conductive shaft core supply mechanism and an unvulcanized rubber roll discharge mechanism was prepared. A die having an inner diameter of 12.5mm was mounted to the crosshead, the extruder and the crosshead were adjusted to 80 ℃, and the conveying speed of the conductive shaft core body was adjusted to 60 mm/sec. Under these conditions, the B kneaded rubber composition 1 was supplied from the kneading extruder, and a rubber layer of the B kneaded rubber composition 1 was formed on the outer peripheral surface of the conductive shaft core in the crosshead to obtain an unvulcanized rubber roll. Next, the unvulcanized rubber roller was put into a hot air vulcanizing furnace at 170 ℃ and heated for 60 minutes to obtain a vulcanized rubber roller. Thereafter, the end of the vulcanized rubber layer was removed by cutting to set the length of the rubber layer to 230 nm. Finally, the surface of the elastic layer is ground with a rotating grinding wheel. In this way, a crown-shaped conductive roller having a diameter of 8.4mm at a position of 90mm from the central portion toward each of the both end portions and a diameter of 8.5mm at the central portion was prepared.

The resistivity of the roll was 5.0X 10⁵Omega cm. As the measuring method of the electric resistance, a method as described in "measurement of the electric resistance value of the portion of the conductive roller" later is used.

Evaluation of conductive roller

The conductive roller was evaluated as follows. Table 1 shows the evaluation results.

Evaluation of conductive layer

Details were evaluated by the above measurement method.

The conductive elastic layer of the conductive roller of each example was confirmed to have a plurality of domains in the matrix of the first rubber by the method described in the domain measurement method and the like; obtaining a configuration in which each domain comprises conductive particles; an average value [ mu ] 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% to 40%; and so on. Unless otherwise noted, Leica EM UC7 (trade name) manufactured by Leica was used as a microtome, Leica EMITIC3X (trade name) manufactured by Leica Company was used as an ion milling apparatus, and Ultraplus (trade name) manufactured by Carl Zeiss Company was used as an SEM. Specifically, as a three-dimensional stereo image measuring apparatus (FIB-SEM) represented by fig. 2, the structures of the conductive layers in all the examples were examined using a CRYO FIB/SEM, Helios G4 UC (trade name) manufactured by FEI Company.

Evaluation of the Uniform dispersibility of domains in the conductive layer

By the method described in "the method of measuring the volume of the domain", it was confirmed that the conductive domains are equally and densely arranged in the conductive layer in three dimensions. Here, as described above, three-dimensional measurement was performed with FIB-SEM to check whether or not at least eight samples of the first cubic shape with 9 μm on one side satisfied the condition (1): "in 27 unit cubes having 3 μm on one side contained in one sample, the total volume of domains is 2.7 to 10.8 μm³Is at least 20 ".

By increasing the number of unit cubes satisfying the above condition (1), the effect according to this aspect can be improved. From the above measurement results, the level of uniform dispersibility of the domains was evaluated based on the following criteria. The level of uniformity and stability in the electrical characteristics of the conductive layer is indicated by grades I, II, III, IV and V in descending order.

Grade I: the uniform dispersibility was extremely good (the number of unit cubes satisfying the condition (1) was 25 or more in each of at least 8 samples).

Grade II: the uniform dispersibility was rather good (the number of unit cubes satisfying the condition (1) was less than 25 in each of at least 2 samples, and 22 or more in each of at least 8 samples).

Grade III: the uniform dispersibility was good (the number of unit cubes satisfying the condition (1) was less than 22 in each of at least 2 samples, and 20 or more in each of at least 8 samples).

Grade IV: no uniform dispersibility (the number of unit cubes satisfying the condition (1) is less than 20 in each of at least 2 samples, and 12 or more in each of at least 8 samples).

Grade V: the uniform dispersibility was extremely poor (the number of unit cubes satisfying the condition (1) was less than 12 in each of at least 2 samples).

Evaluation of change of conductive particles in domains in conductive layer

By the above measurement method, it was confirmed that the resistance of the conductive domain was uniform.

The effect according to this aspect is improved as "σ/μ" becomes smaller, where μ denotes an average of ratios of sectional areas of the conductive particles contained in the respective domains to the sectional areas of the respective domains appearing on a cross section in the thickness direction of the conductive layer, and σ denotes a standard deviation of the ratios. From the above measurement results, the level of change of the conductive particles in the domain was evaluated based on the following criteria. The level of uniformity of the resistance is indicated by the grades i, ii and iii in descending order.

Grade i: the variation of the conductive particles is very small (0. ltoreq. sigma./μ. ltoreq.0.25).

Grade ii: the change of the conductive particles is small (0.25< sigma/. mu.ltoreq.0.4)

Grade iii: the variation of the conductive particles is large (sigma/. mu. <0.4)

Evaluation of Domain shape in conductive layer of conductive roller-circularity)

The shape of the domain is preferably close to a circle and is evaluated by circularity based on the above-described measurement method.

The level of circularity was evaluated based on the following criteria. The level of circularity is indicated by the grades a, b, c and d in descending order.

Grade a: the circularity is extremely good (the average value of the circularity is 1 or more and less than 1.90).

Grade b: the circularity is good (the average value of the circularity is 1.90 or more and less than 2.0).

Grade c: the circularity was poor (the average value of circularity was 2.10 or more and less than 22.60).

Grade d: the circularity is extremely poor (the average value of circularity is 2.60 or more).

Evaluation of Domain size distribution in conductive layer

For the domain size distribution, it is preferable that the domains be uniform in size and small in size. Based on the above measurement method, evaluation was made by the uniformity of particle size distribution according to the ratio of large domains to small domains.

Here, the uniformity of particle size distribution was calculated from the evaluation of 12 or more SEM images.

The level of uniformity of the particle size distribution was evaluated based on the following criteria. The level of uniformity of the particle size distribution is indicated by grades 1,2, 3 and 4 in descending order.

Grade 1: the uniformity of the particle size distribution is extremely high (95 is not more than 100 XL 2/L1 is not more than 100 and 0 is not more than 100 XL 3/L1 is not more than 5).

Grade 2: the uniformity of the particle size distribution is high (80 is less than or equal to 100 xL 2/L1 is less than 95 and/or 15 is less than 100 xL 3/L1 is less than or equal to 20).

Grade 3: the uniformity of the particle size distribution was poor (100 XL 2/L1<80 and/or 20<100 XL 3/L1).

Grade 4: the uniformity of the particle size distribution is extremely poor (100 XL 2/L1 is less than or equal to 65 and/or 35 is less than or equal to 100 XL 3/L1).

Measuring the resistance of the conductive roller

The resistance of the conductive roller is appropriately measured according to the following two types of "measurement of the resistance value of the portion of the conductive roller".

Measurement of resistance value of conductive roller part (method using fixed electrode)

The current value passing through any local region of the conductive roller is measured using a current resistance measuring device as described in detail below. First, both end portions of the conductive shaft core of the conductive roller are pressed to contact the metal electrodes. The metal electrode is cut so that the surface contacting the conductive roller has almost the same curvature as the curvature of the outer periphery of the conductive roller, and the length of the circular arc is equal to or less than 1/4 of the length of the outer periphery of the conductive roller. Therefore, the metal electrode can be brought into close contact with the conductive roller. The length of the metal electrode was set so that the area of the contact portion with the conductive roller was about 0.5cm²。

The resistance of a local area of the conductive roller is measured while applying a direct-current voltage to the conductive shaft core of the conductive roller as the metal electrode is pressed into contact with the conductive roller using an external power supply. The voltage across both ends of a reference resistor connected in series to the metal electrode is measured, and the current value passing through the local area is calculated based on the voltage and the resistance value of the reference resistor.

Alternatively, the resistance value of the conductive roller may be measured in the following manner: the current value is measured using an electrometer capable of measuring a very small current while applying a constant direct-current voltage between the conductive shaft core of the conductive roller and the metal electrode. The current value of the conductive roller was measured after 10 seconds elapsed while applying a fixed direct-current voltage of 20V between the conductive shaft core and the metal electrode in an environment of a temperature of 23 ℃ and a relative humidity of 50%.

The volume resistivity (Ω · cm) of the local region was calculated from the measured current value, the area of the contact portion 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 resistance value of conductive roller part (method using rotating electrode)

The current value passing through the local region of the conductive roller was measured using a current resistance measuring device as described in detail below. In this device, a cylindrical metallic rotary electrode having a diameter of 30mm and a width of 20mm is pressed under a fixed pressure to contact a conductive roller at an arbitrary position, and the conductive roller is rotated so that the rotary electrode is rotated in accordance with the rotational movement of the conductive roller. Further, while a direct-current voltage is applied to the conductive shaft core of the conductive roller using an external power supply, the voltage of both ends of a reference resistor connected in series to the rotary electrode is measured. Thus, a current value is obtained through the area of the conductive layer of the conductive roller, which current value is defined by the contact surface between the rotating electrode and the conductive roller. The area of the contact surface depends on the hardness of the conductive layer and is about 0.05-0.2 cm²。

The rotation speed of the conductive roller was set to 30rpm, the data sampling frequency was set to 20Hz, and the resistance value of the reference resistor was set to 1k Ω. The applied voltage depends on the resistivity of the conductive layer, and the fixed voltage is set between 10V and 200V so that the current value is about 0.1 mA. The above conditions enable measurements to be made on the roll surface at intervals of about 0.6mm in the circumferential direction, so that about 12 zones can be measured every one revolution. The rotating electrode was sequentially moved in the longitudinal direction of the roller, and current measurements were similarly performed in about 140 areas while the conductive roller was rotated.

From the measured current value, the surface of the contact part between the conductive roller and the rotating electrodeVolume resistivity (Ω · cm) of a local region was calculated from the product, the thickness of the conductive layer of the conductive roller, and the voltage applied to the conductive layer. Through sigma_R/μ_RTo evaluate the change in volume resistivity in the conductive roller, where_RAs an average of the volume resistivities of the local regions under measurement, σ_RIs dispersion.

From the above results, σ in resistance was evaluated based on the following criteria_R/μ_RThe level of (c). The level of uniformity and stability in the electrical characteristics of the conductive layer is indicated in descending order by grades A, B, C and D.

Grade A: sigma_R/μ_RMinimum (σ)_R/μ_R<0.3)

Grade B: sigma_R/μ_RIs quite small (0.3)<σ_R/μ_R≤0.4)

Grade C: sigma_R/μ_RSmall (0.4)<σ_R/μ_R<0.5)

Grade D: sigma_R/μ_RLarge (0.5 ≤ sigma)_R/μ_R)

Deterioration test of energization in conductive roller-measurement of Current maintenance Rate

The value of the current passing through the conductive roller was measured using a resistance measuring device schematically shown in fig. 6. In this apparatus, both end portions of the conductive shaft core 11 of the conductive roller are pressed using pressing means (not shown) to contact a cylindrical metal drum having a diameter of 30mm, so that the conductive roller is rotated in accordance with the rotational drive of the metal drum. Further, while a direct-current voltage is applied to the conductive shaft core of the conductive roller using an external power supply, the voltage across the reference resistor connected in series to the metal drum is measured. The value of the current passing through the conductive roller is calculated based on the resistance value of the reference resistor 63 and the voltage at both ends of the reference resistor.

Using the resistance measuring apparatus of fig. 6, an energization deterioration test in the conductive roller was performed under an environment of a temperature of 23 ℃ and a relative humidity of 50%. Here, a fixed dc voltage set at 50V was applied between the conductive shaft core and the metal drum for 10 minutes. The rotation speed of the metal drum was set to 30rpm, and the resistance value of the reference resistor was set between 100 Ω to 1k Ω. The data sampling frequency was set to 20Hz, and the average of the measurement values for 10 minutes was defined as the current value passing through the conductive roller. The flow maintenance rate (%) was calculated from the ratio of I1 to I0, where I0 is the initial current value and I1 is the current value at the end of the energization test.

From the above results, the level of the current maintenance rate was evaluated based on the following criteria.

The level of uniformity and stability in the electrical characteristics of the conductive layer is indicated in descending order by grades A, B, C and D.

Grade A: the current maintenance rate is extremely high (the maintenance rate is more than 85%).

Grade B: the current maintenance rate is slightly lower (the maintenance rate is 70% or more and less than 85%).

Grade C: the current maintenance rate is moderate (the maintenance rate is 60% or more and less than 70%).

Grade D: the current maintenance rate was poor (maintenance rate was less than 60%).

Image evaluation of conductive roller

The image evaluation was performed on the conductive member in a high-speed process.

First, an electrophotographic laser printer (trade name: Laserjet M608dn, manufactured by Hewlett Packard Company) was prepared as an electrophotographic apparatus. Next, the conductive member, the electrophotographic apparatus, and the process cartridge were left in an environment of 23 ℃ and 50% RH for 48 hours to accommodate the measurement environment.

For evaluation in high-speed processing, the laser printer was modified so that the number of sheets output per unit time was larger than the original number of sheets output, that is, 75 sheets of a4 size paper were output per minute. Here, the output speed of the recording medium was 370 mm/sec, and the image resolution was 1,200 dpi.

The prepared conductive roller was mounted as a charging roller to an electrophotographic process cartridge. In the same environment as above, a voltage of-900V was applied to the conductive member by an external power supply (TREK 615 manufactured by TREK JAPAN) to output a halftone image. That is, one sheet of an electrophotographic image in which a halftone image (an image having lines of 1 dot width drawn at 2 dot intervals in a direction perpendicular to the rotational direction of the electrophotographic photoreceptor) is formed on a sheet of a 4-sized paper is output. This image is referred to as the "first image". Subsequently, 2,500 sheets of electrophotographic images in which the 14-dot-sized letter symbol "E" was drawn on a 4-sized paper at a print density of 1% were output. Subsequently, one sheet of the electrophotographic image in which a halftone image was formed on a 4-sized paper was output. This image is referred to as "2,501 th image". All electrophotographic images were output in an environment of 15 ℃ temperature and 10% relative humidity. The first image and the 2,501 th image were visually observed, and the graininess in the initial halftone image (first image), the occurrence of graininess deterioration in the halftone image after the endurance (2,501 th image) that may be caused by an increase in the resistance value of the charging roller, and the degree thereof were evaluated based on the following criteria.

Grade A: the image had no graininess from the initial stage and was uniform, and the graininess did not deteriorate even after the durability.

Grade B: the image had no graininess at the initial stage and was uniform, and the graininess was slightly deteriorated after the durability.

Grade C: there is an image having graininess from the beginning (graininess deterioration).

Grade D: there is an image with graininess (graininess deterioration) evident from the beginning.

< example 2>

100 parts of SBR (trade name: TUFDENE 2003, manufactured by ASAHI KASEI CORPORATION) as a raw material of the domains, 3 parts of CARBON Black (trade name: Ketjen Black EC600JD, manufactured by Ketjen Black International Company) as conductive particles, 40 parts of CARBON Black (trade name: TOKABLACK #5500, manufactured by TOKAI CARBON CO., LTD) as a processing aid, and 1 part of stearic acid as a processing aid were kneaded by a pressure kneader to obtain a masterbatch 2.

Next, to 100 parts by mass of NBR (trade name: N230SV, manufactured by JSR Corporation), 8 parts of zinc oxide (class 2 zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd.), 1 part of zinc stearate (trade name: SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.), and 10 parts of Calcium carbonate (trade name: NANOX #30, manufactured by Maruo Calcium Co., Ltd.) were added. The mixture was stirred using a pressure mixer (trade name: TD6-15 MDX: manufactured by Toshin Co., Ltd.) adjusted to 50 ℃ under conditions of a filling rate of 70%, a blade rotation speed of 30rpm, and a mixing time of 16 minutes to obtain a matrix rubber composition 2.

Next, using a pressure mixer, 20 parts of the master batch 2 prepared as described above and 70 parts of the rubber composition for matrix 2 were mixed for 12 minutes to obtain an unvulcanized rubber mixture 2.

To 2100 parts by mass of the unvulcanized rubber mixture were added 1.8 parts of a vulcanizing agent/sulfur (trade name: SULFAX PMC, manufactured by Tsurumi Chemical Industry co., ltd.), and a vulcanization accelerator (trade name: perforcit TBzTD, manufactured by Performance Additives Company). The mixture was kneaded for 10 minutes using a two-roll mill cooled to a temperature of 25 ℃ to obtain the corresponding B kneaded rubber composition 2. The same procedure as in example 1 was carried out except for the above to prepare a conductive roller, and various characteristics were evaluated.

The resistance value of the roller was 6.5X 10⁵Ω·cm。

< example 3>

90 parts of SBR (product name: TUFDENE 2003, manufactured by ASAHI KASEI CORPORATION) and 10 parts of liquid SBR (product name: LIR-310, manufactured by KURARARAY CO., LTD.) as raw materials of the domains, 60 parts of CARBON black (product name: TOKABLACK #5500, manufactured by TOKAI CARBON CO., LTD) as conductive particles, and 1 part of stearic acid as a processing aid were kneaded by a pressure kneader to obtain a master batch 3. Next, using a pressure mixer, 20 parts of the master batch 3 prepared as described above and 72 parts of the rubber composition for a matrix 2 prepared in example 2 were mixed for 13 minutes to obtain an unvulcanized rubber mixture 3. Here, the masterbatch was divided into five equal parts and mixed stepwise.

The same procedure as in example 2 was carried out except for the above to prepare a conductive roller, and various characteristics were evaluated.

The resistance of the roller was 8.5X 10⁵Ω·cm。

< example 4>

Corresponding rubber mixtures were prepared in the same manner as in example 1.

That is, 120 parts of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (trade name: EPICHLOMER CG, manufactured by OSAKA SODA CO., LTD.), 1 part of stearic acid as a processing aid, and 140 parts of the master batch prepared in example 1 were mixed by roll mill to obtain an unvulcanized rubber mixture 4. Here, the masterbatch was divided into five equal parts and mixed stepwise.

Next, a processing machine (trade name: NHSS8-28, manufactured by NIIGATA MACHINE TECHNO CO., LTD.) including a screw having an elongation shear applying mechanism inside the screw as shown in FIG. 3A was used as an elongation shear molding processing machine to knead the unvulcanized rubber (A compounding rubber composition). First, the hole size of a narrow tube of a screw provided in a processing machine was set to 2.0mm, the temperature of a plasticizing part was set to 100 ℃, the temperature of a kneading part was set to 150 ℃, the screw rotation speed was set to 750rpm, and the a-kneaded rubber composition was kneaded for 5 seconds. Thereafter, the kneaded rubber composition a was discharged from the kneading section to obtain a rubber composition subjected to elongation shear processing. This procedure was repeated to prepare a sufficient amount of the rubber composition for the preparation of the conductive roller. Here, in order to reduce the heat generation by shearing, the temperature was controlled using a cooling mechanism so that the temperature of the kneading section did not exceed 170 ℃.

To 100 parts by mass of the a-compounded rubber composition compounded in the above-mentioned step, 1.8 parts of a vulcanizing agent/sulfur (trade name: SULFAX PMC, manufactured by Tsurumi Chemical Industry co., ltd.) and 6.8 parts of a vulcanization accelerator (trade name: perfacit TBzTD, manufactured by Performance Additives Company) were added. Subsequently, the mixture was kneaded for 10 minutes using a two-roll mill cooled to a temperature of 25 ℃ to obtain a B-kneaded rubber composition 4. The same procedure as in example 1 was carried out except for the above to prepare a conductive roller, and various characteristics were evaluated.

The resistance of the roller was 1.0X 10⁶Ω·cm。

< example 5>

100 parts of SBR (trade name: TUFDENE 2003, manufactured by ASAHI KASEI CORPORATION) as a raw material of the domains, 70 parts of CARBON black (trade name: TOKABLACK #5500, manufactured by TOKAI CARBON CO., LTD) as conductive particles, and 1 part of stearic acid as a processing aid were kneaded by a pressure kneader to obtain a master batch 5. Next, using a pressure mixer, 22 parts of the master batch 5 and 68 parts of the rubber composition for a matrix 2 prepared in example 2 were mixed for 20 minutes to obtain an unvulcanized rubber composition 5.

The resistance of the roller was 4.0X 10⁵Ω·cm。

< example 6>

100 parts of terminal-modified SBR (trade name: TUFDENE E581, manufactured by ASAHI KASEI CORPORATION) as a raw material of the domains, 80 parts of CARBON black (trade name: TOKABLACK #5500, manufactured by TOKAI CARBON CO., LTD) as conductive particles, and 1 part of stearic acid as a processing aid were kneaded by a pressure kneader to obtain a masterbatch 6.

Next, using a pressure mixer, 25 parts of the master batch 6 prepared as described above and 70 parts of the rubber composition for a matrix 2 prepared in example 2 were mixed for 16 minutes to obtain an unvulcanized rubber composition 6. Here, the master batch was divided into five equal parts and gradually mixed with the rubber composition for matrix 2.

The resistance of the roller was 3.5X 10⁵Ω·cm。

< example 7>

100 parts of SBR (trade name: TUFDENE 2003, manufactured by ASAHI KASEI CORPORATION) as a raw material of the domains, 85 parts of CARBON black (trade name: TOKABLACK #7360, manufactured by TOKAI CARBON co., ltd.) as conductive particles, and 1 part of stearic acid as a processing aid were kneaded by a pressure kneader to obtain a master batch 7. Next, 30 parts of the master batch 7 and 65 parts of the rubber composition for matrix 2 which had been prepared in example 2 were mixed by open rolls to obtain a corresponding unvulcanized rubber mixture 7. Next, in the same manner as in example 4, an unvulcanized rubber (a kneaded rubber composition) was kneaded using an elongation shear molding machine including a screw having an elongation shear applying mechanism inside the screw. Here, the processing was carried out under the same conditions except that the screw rotation speed was 800 rpm. The same procedure as in example 4 was carried out except for the above to prepare a conductive roller, and various characteristics were evaluated.

The resistance of the roller was 8.0X 10⁵Ω·cm。

< example 8>

Emulsion-polymerized styrene-butadiene rubber, E-SBR (product name: JSR0202, manufactured by JSR Corporation) 100 parts, liquid SBR (product name: LIR-310, KURARAY co., LTD.)10 parts, CARBON black (product name: TOKABLACK #5500, manufactured by TOKAI CARBON co., LTD) 100 parts, which is a conductive particle, and stearic acid 1 part, which is a processing aid, were kneaded with a pressure kneader to obtain a master batch 8. Next, 34 parts of the master batch 8 and 70 parts of the rubber composition for matrix 2 which had been prepared in example 2 were mixed by an open roll to obtain an unvulcanized rubber mixture 8.

As the elongation shear forming processor, an elongation shear forming processor (trade name: NHSS8-28, manufactured by NIIGATA MACHINE techo co., ltd.) including a screw having an elongation shear applying mechanism inside the screw, which had been used in example 7, was modified and used as a continuous processor including a screw having an elongation shear applying mechanism outside the screw. That is, using a device modified at the tip end portion of the screw such that the hole 32 of the narrow tube is provided not inside the screw but outside the screw as shown in fig. 3B enables continuous stretch-shear forming.

Next, in the same manner as in example 4, the unvulcanized rubber (a kneaded rubber composition) was kneaded using the continuous elongation shear molding machine including the screw having the elongation shear applying mechanism. Here, the processing was carried out under the same conditions except that the screw rotation speed was 600 rpm. The same procedure as in example 4 was carried out except for the above to prepare a conductive roller, and various characteristics were evaluated.

The resistance of the roller was 8.0X 10⁵Ωcm。

< example 9>

100 parts of NBR (trade name: N230SV, manufactured by JSR Corporation) as a raw material of the domains, 60 parts of CARBON Black (trade name: TOKABLACK #7360, manufactured by TOKAI CARBON co., ltd.) as a conductive particle, 10 parts of CARBON Black (trade name: Ketjen Black EC600JD, manufactured by Ketjen Black International Company) and 1 part of stearic acid as a processing aid were kneaded with a pressure kneader to obtain a masterbatch 9.

Next, to 100 parts by mass of SBR (trade name: ASAPRENE Y031, manufactured by ASAHI KASEI CORPORATION) were added 8 parts by mass of zinc oxide (class 2 zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd.), 1 part by mass of zinc stearate (trade name: SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.) and 10 parts by mass of Calcium carbonate (trade name: NANOX #30, manufactured by Maruo Calcium Co., Ltd.). The mixture was stirred using a pressure mixer (trade name: TD6-15 MDX: manufactured by Toshin Co., Ltd.) adjusted to 50 ℃ under conditions of a filling rate of 70%, a blade rotation speed of 30rpm, and a mixing time of 16 minutes to obtain a matrix rubber composition 9.

Next, 35 parts of the master batch 9 and 70 parts of the rubber composition for matrix 9 were mixed by an open roll to obtain a corresponding unvulcanized rubber mixture.

Next, the unvulcanized rubber was kneaded (a kneaded rubber composition) using a continuous elongation shear forming machine including a screw having an elongation shear applying mechanism outside the screw, which had been used in example 8. Here, the processing was carried out under the same conditions except that the screw rotation speed was 650 rpm. The same procedure as in example 4 was carried out except for the above to prepare a conductive roller, and various characteristics were evaluated.

The resistance of the roller was 8.3X 10⁵Ωcm。

Comparative example 1

A rubber mixture was prepared according to PTL 1.

Specifically, 100 parts of an ethylene-propylene-diene terpolymer (trade name: EPT4045, manufactured by Mitsui Chemical, Incorporated) as a domain material, 10 parts of carbon Black (trade name: Ketjen Black EC600JD, manufactured by Ketjen Black International Company) as a conductive particle, 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 master batch. Next, 75 parts of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (trade name: EPICHLOMER CG, manufactured by OSAKA SODA CO., LTD.) as a matrix material, 1 part of stearic acid as a processing aid, 1035.25 parts of a master batch, 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexyne (trade name: PERHEXA 25B-40, manufactured by NOF CORPORATION) 2.5 parts as a vulcanizing agent, and 1.5 parts of triallyl isocyanurate (trade name: TAIC-M60, manufactured by Nippon Kasei Chemical Company Limited) as a crosslinking aid were mixed by open rolls to obtain an unvulcanized rubber mixture 1A. The same procedure as in example 1 was carried out except for the above to prepare a conductive roller, and various characteristics were evaluated.

The resistance of the roller was 7.3X 10⁵Ωcm。

Comparative example 2

The same procedure as in example 1 was carried out to prepare a conductive roller, and various characteristics were evaluated, except that the corresponding unvulcanized rubber composition 2A was prepared from a masterbatch different from the masterbatch 2 of example 2 (except that the amount of ketjen black was 3.5 parts and the amount of carbon black was 35 parts), and the kneading time in the pressure kneader during the preparation of the unvulcanized rubber composition 2A was 5 minutes.

The resistance of the roller was 4.1X 10⁶Ωcm。

Comparative example 3

A conductive roller was prepared based on comparative example 1, and various characteristics were evaluated.

Here, 120 parts of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (trade name: epichlome CG, manufactured by OSAKA SODA co., ltd.), 1 part of stearic acid as a processing aid, and 140.5 parts of a master batch were mixed by open rolls to obtain an unvulcanized rubber mixture.

Next, shearing processing of the A-kneaded rubber composition was performed so that the unvulcanized rubber composition (A-kneaded rubber composition) was kneaded at a rotation speed of 1,000rpm using a twin-screw kneading processing apparatus (trade name: KZW15TW-4MG-NH (-6000), manufactured by TECHNOLOGICAL CORPORATION).

100 parts by mass of the unvulcanized rubber composition prepared in the above-mentioned step was mixed with 2.5 parts by mass of 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexyne (trade name: PERHEXA 25B-40, manufactured by NOF CORPORATION) as a vulcanizing agent and 1.5 parts by mass of triallyl isocyanurate (trade name: TAIC-M60, manufactured by Nippon Kasei Chemical Company Limited) as a crosslinking aid by open rolls to obtain an unvulcanized rubber mixture (B compounded rubber composition 3A). The same procedure as in comparative example 1 was carried out except for the above to prepare a conductive roller, and various characteristics were evaluated.

The resistance of the roller was 1.2X 10⁷Ωcm。

Comparative example 4

The same procedure as in example 2 was conducted to prepare a conductive roller, except that the corresponding unvulcanized rubber composition 4A was prepared from a masterbatch different from the masterbatch 2 of example 2 except that the amount of ketjen black was 3.5 parts and the amount of carbon black was 35 parts, and the kneading time in the pressure kneader during the preparation of the unvulcanized rubber composition 4A was 40 minutes (here, the material temperature during kneading (measured with an infrared thermometer) was increased to 183 degrees), and various characteristics were evaluated.

The resistance of the roller was 2.2X 10⁶Ωcm。

Comparative example 5

25 parts of the master batch 3 prepared in example 3 and 70 parts of the rubber composition for matrix 2 already prepared in example 2 were mixed using a two-roll mill. Thereafter, 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 rotation speed of 1,000rpm using the twin-screw kneading processing apparatus shown in comparative example 3 to prepare a conductive roller, and various properties were evaluated.

The resistance of the roller being 9.610⁶Ωcm。

Comparative example 6

The same procedure as in example 8 was carried out to prepare a conductive roller, and various properties were evaluated, except that the mixing in example 8 was carried out for 10 minutes using a pressure kneader instead of the elongation shear molding machine, and 20 parts of the master batch 8 and 70 parts of the rubber composition for matrix 2 prepared in example 2 were used.

The resistance of the roller was 9.0X 10⁵Ωcm。

Comparative example 7

The same procedure as in example 8 was carried out to prepare a conductive roller, except that the mixing in example 8 was carried out using a two-roll mill instead of the elongation shear former (here, the master batch was divided into ten equal parts and mixed stepwise), 14.6 parts of the master batch 8 and 70 parts of the rubber composition for matrix 2 which had been prepared in example 2 were used, and various characteristics were evaluated.

The resistance of the roller was 4.9X 10⁶Ωcm。

The following table 1 shows the evaluation results of the uniformity of domains, the variation of conductive particles in domains, the domain shape, the particle size distribution of domains, the mixing device used, the average domain size in cross section, and the conductive roller in examples 1 to 9 and comparative examples 1 to 7: resistance σ/μ and current maintenance rate, and evaluation results of image quality grade.

[ Table 1]

The evaluation results of the conductive member applied to the transfer roller as the conductive roller will be described below.

< example 10>

Preparation of conductive roller

A round bar having a total length of 240mm and an outer diameter of 5mm was prepared from free-cutting steel having been subjected to electroless nickel plating. Next, the round bar was coated with an adhesive over the entire circumference of a length of 210mm (excluding a length of 15mm from both ends). As the adhesive, a conductive hot-melt type adhesive is used. For coating, a roll coater was used. A round bar coated with an adhesive was used as the conductive shaft core body (core metal).

Next, a cross-head extruder having a conductive shaft core supply mechanism and an unvulcanized rubber roll discharge mechanism was prepared. A die having an inner diameter of 13.5mm was mounted to the crosshead, the extruder and the crosshead were adjusted to 80 ℃, and the conveying speed of the conductive shaft core body was adjusted to 60 mm/sec. Under the conditions, the unvulcanized rubber mixture 2 obtained in example 2 was supplied from a kneading extruder, and a rubber layer of the unvulcanized rubber mixture was formed on the outer peripheral surface of the conductive shaft core in a crosshead to obtain an unvulcanized rubber roller. Next, the unvulcanized rubber roller was put into a hot air vulcanizing furnace at 170 ℃ and heated for 60 minutes to obtain a vulcanized rubber roller. Thereafter, the end of the vulcanized rubber layer was removed by cutting to set the length of the rubber layer to 215 mm. Finally, the surface of the elastic layer is ground with a rotating grinding wheel. In this way, a crown-shaped conductive roller having a diameter of 11.3mm at a position of 90mm from the central portion toward each of the both end portions and a diameter of 11.5mm at the central portion was prepared.

The resistivity of the roll was 2.0X 10⁶Ω·cm。

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

Image evaluation 1 of conductive roller

As the transfer roller, a conductive roller was mounted on an electrophotographic process cartridge (trade name: HP 30A Black organic laser jet Toner, manufactured by Hewlett Packard Company). The process cartridge was mounted on an electrophotographic image forming apparatus (trade name: HP laser jet Pro M203dw, manufactured by Hewlett Packard Company) capable of processing a 4-size paper, thereby forming an electrophotographic image. One sheet of an electrophotographic image in which a longitudinal line image (an image of lines having a width of 4 dots drawn at 4 dot intervals in the rotation direction of the electrophotographic photoreceptor) was formed on a paper of a4 size was output. The electrophotographic image was output in an environment of a temperature of 15 ℃ and a relative humidity of 10%. The image was visually observed, and the occurrence of a dotted image or a broken vertical line, which may be caused by abnormal discharge of the transfer roller, and the degree thereof were evaluated based on the following criteria.

Grade A: no broken longitudinal lines or dot-like images appear.

Grade B: a broken longitudinal line or dot pattern slightly appears.

Grade C: a broken longitudinal line or dot pattern appears.

Grade D: a broken longitudinal line or dot pattern appears clearly.

Image evaluation of conductive roller 2

As the transfer roller, the conductive roller after the electrification deterioration test was performed was mounted on an electrophotographic process cartridge (trade name: HP 30A, Black organic laser jet Toner, manufactured by Hewlett Packard Company). The process cartridge was mounted to an electrophotographic image forming apparatus (trade name: HP laser jet Pro M203dw, manufactured by Hewlett Packard Company) capable of processing a 4-size paper, thereby forming an electrophotographic image. One sheet of an electrophotographic image in which a halftone image (an image having lines of 1 dot width drawn at 2 dot intervals in a direction perpendicular to the rotational direction of the electrophotographic photoreceptor) was formed on a 4-size paper was output. The electrophotographic image was output in an environment of a temperature of 15 ℃ and a relative humidity of 10%. The image was visually observed, and the appearance of a dotted image which may be caused by an increase in the resistance value of the transfer roller and the degree thereof were evaluated based on the following criteria.

Grade A: no dot image appears.

Grade B: a punctiform image appears slightly.

Grade C: a dot-like image appears.

Grade D: a dot-like image appears clearly.

< example 11>

In example 11, the unvulcanized rubber mixture 4 obtained in example 4 was used as an unvulcanized rubber mixture.

The same procedure as in example 10 was carried out except for the above to prepare a conductive roller, and various characteristics were evaluated.

The resistivity of the roll was 3.2X 10⁶Ωcm。

< example 12>

In example 12, the unvulcanized rubber mixture 8 obtained in example 8 was used as an unvulcanized rubber mixture.

The resistivity of the roll was 2.4X 10⁶Ωcm。

Comparative example 8

The unvulcanized rubber mixture 1A obtained in comparative example 1 was used as an unvulcanized rubber mixture with respect to example 10.

The resistivity of the roll was 2.1X 10⁶Ωcm。

Table 2 below shows the evaluation results of the uniformity of the domains, the evaluation results of the change of the conductive particles in the domains, the evaluation results of the shapes of the domains, the evaluation results of the particle size distribution of the domains, the mixing device used, the average domain size on the cross section, and the evaluation results of the conductive roller in examples 10 to 12 and comparative example 8.

[ Table 2]

The evaluation results of the conductive member applied to the conductive blade as the conductive roller will be described below.

< example 13>

Preparation of conductive blade

The rubber mixture 2 (unvulcanized rubber mixture) obtained in example 2 was used. Here, the B-kneaded rubber mixture 2 was placed in a mold having a width of 250mm, a length of 150mm and a thickness of 0.7mm, and treated with pressure applied by a press at 160 ℃ for 10 minutes to obtain a corresponding rubber sheet 1 having a thickness of 0.7 mm.

The rubber sheet 1 was cut into a width of 216mm and a length of 12mm, and adhered with an adhesive to a metal plate (substantially the same shape as that of a metal plate used for a developing blade of an electrophotographic process cartridge described later) which had been previously processed in such a manner as to be mountable to a predetermined cartridge, to obtain a conductive rubber blade 1. Here, the bonding is performed in such a manner that a portion of the conductive blade having a length of 12mm overlapping the metal plate has a length of 4.5mm, and the other portion having a length of 7.5mm protrudes from the metal plate. As the adhesive, a conductive hot-melt type adhesive is used.

The resistance of the conductive blade was 4.2X 10⁵Ωcm。

Evaluation of conductive blade

The conductive blade was evaluated as follows. Table 1 shows the evaluation results.

(evaluation of conductive layer)

For the following four evaluation items of the conductive layer, evaluation was performed in the same manner as in example 1.

The measurement points were changed as follows.

Evaluation of Uniform dispersibility of domains in the conductive layer

Measurement points are as follows: nine points obtained by dividing the rubber sheet into nine parts in the width direction and in the vicinity of the center of each of the sections of 24mm in width, 12mm in length, and 0.7mm in thickness.

Evaluation of the variation of conductive particles in the domains in the conductive layer

Measurement points are as follows: twelve points obtained by dividing the rubber sheet into twelve in the width direction and in the vicinity of the center of each of sections having a width of 18mm, a length of 12mm, and a thickness of 0.7 mm.

Evaluation of domain shape in conductive layer of conductive blade-circularity

Evaluation of particle size distribution of domains in the conductive layer

(measurement of Current value of conductive blade)

Measurement of the resistance value of the conductive blade portion

The current value passing through an arbitrary local area of the conductive blade is measured using a current resistance measuring device schematically shown below. In this device, under a load of 200gw, a metal electrode is pressed to contact the conductive blade at an arbitrary position of the rubber portion of the conductive blade. The contact portion of the metal electrode and the conductive blade has a circular shape of 10mm, and further, the voltage across both ends of a reference resistor connected in series to the metal electrode is measured while applying a direct-current voltage to the metal plate of the conductive blade using an external power supply. In this way, a current value passing through an arbitrary local area of the conductive blade is obtained. The resistance value of the reference resistor is set to 1k Ω. The conductive blade was divided into 20 parts in the longitudinal direction, and the total of 20 regions thus obtained was measured.

The volume resistivity (Ω · cm) of a local region was calculated from the areas of the rubber portion of the conductive blade and the metal electrode, the thickness of the rubber portion of the conductive blade, and the applied voltage, and the volume resistivity of the conductive blade was determined. Through sigma_R/μ_RTo evaluate the change in the volume resistivity in the conductive blade, wherein_RIs the average of the volume resistivity of the local area under measurement, σ_RAre dispersed.

From the above results, σ of the resistance was evaluated based on the following criteria_R/μ_RThe level of (c). The level of uniformity and stability in the electrical characteristics of the conductive layer is indicated in descending order by grades A, B, C and D.

Grade A: sigma_R/μ_RMinimum (σ)_R/μ_R<0.25)

Grade B: sigma_R/μ_RIs quite small (0.25)<σ_R/μ_R≤0.32)

Grade C: sigma_R/μ_RSmall (0.32)<σ_R/μ_R<0.4)

Grade D: sigma_R/μ_RLarge (0.4 ≤ sigma)_R/μ_R)

Measurement of Current maintenance Rate for conductive blade

The conductive blade was subjected to an energization deterioration test in an environment of 23 ℃ temperature and 50% relative humidity using the above resistance value measuring apparatus. Here, a fixed dc voltage set between 20V and 200V was applied to the metal plate of the conductive blade for 10 minutes. The data sampling frequency was set to 20Hz, and the average of the 10-second measurement values was defined as the value of the current passing through the conductive blade. The current maintenance rate (%) was calculated from the ratio of I1 to I0, where I0 is the initial current value and I1 is the current value at the end of the energization test.

Grade D: the current maintenance rate is obvious (the maintenance rate is less than 60%).

[ evaluation of triboelectric Charge quantity distribution of toner ]

In order to evaluate the degree of triboelectric charge amount of the toner, triboelectric charge amount distribution was measured.

As the developing blade, a conductive blade was mounted on an electrophotographic process Cartridge (trade name: 37X Black Toner Cartridge, manufactured by Hewlett Packard Company). The process cartridge was mounted on an electrophotographic image forming apparatus (trade name: HP laser jet Enterprise M608dn, manufactured by Hewlett Packard Company) capable of processing a 4-size paper, placed in a high-temperature high-humidity environment of an atmospheric temperature of 32 ℃ and a relative humidity of 85% RH, and then left to stand for 6 hours or more. Subsequently, an image having the letter "E" of the alphabet of 14 dot size printed at a coverage of 1% for an area of a 4-sized paper sheet (hereinafter, also referred to as "letter E image") was continuously output to 100 copy sheets, and then a white solid image was output to a new copy sheet, and the printer was stopped during the output of the white solid image.

Here, the triboelectric charge amount distribution was measured for the toner carried on a portion having a narrow area among portions of the developing sleeve between the developing blade and the photoreceptor contact position.

The triboelectric charge amount distribution was measured using E-spark Analyzer Model EST-III (manufactured by Hosokawa Micron Corporation).

The number of particles measured was about 3,000, and the standard deviation σ of the measured values was defined as the triboelectric charge amount distribution of the toner.

The evaluation criteria of the triboelectric charge amount distribution of the toner are as follows.

Grade A: the triboelectric charge quantity distribution was extremely good (sigma <3.0)

Grade B: the triboelectric charge quantity distribution is quite good (3.0 ≦ sigma <4.0)

Grade C: the friction charge quantity is well distributed (4.0 ≤ sigma <5.0)

Grade D: poor distribution of frictional electrification amount (. sigma. >5.0)

Needless to say, the better the conductive path formed in the conductive layer, the better the triboelectric charge amount distribution of the toner.

Image evaluation of conductive blade

As the developing blade, a conductive blade was mounted on an electrophotographic process Cartridge (trade name: 37X Black Toner Cartridge, manufactured by Hewlett Packard Company). The process cartridge was mounted on an electrophotographic image forming apparatus (trade name: HP laser jet Enterprise M608dn, manufactured by Hewlett Packard Company) capable of processing a 4-size paper, thereby forming an electrophotographic image. Here, the metal portion of the developing sleeve is electrically connected to the metal plate of the developing blade. Three electrophotographic images having a solid black image formed on a paper of a4 size were output, and then one electrophotographic image having a halftone image (an image having lines of 1 dot width drawn at 2 dot intervals in a direction perpendicular to the rotational direction of the electrophotographic photosensitive body) formed on a paper of a4 size was output. The electrophotographic image was output at a temperature of 15 ℃ and a relative humidity of 10%. The center portion of the image was visually observed, and the occurrence of density unevenness that may be caused by unevenness of the conductive points of the conductive blade and the degree thereof were evaluated based on the following criteria.

Grade A: there is no concentration unevenness.

Grade B: there was slight concentration unevenness.

Grade C: there is a concentration unevenness.

< example 14>

The unvulcanized rubber mixture 4 obtained in example 4 was used as an unvulcanized rubber mixture with respect to example 13.

The same procedure as in example 10 was carried out except for the above to prepare a conductive blade, and various characteristics were evaluated.

The resistivity of the conductive blade was 6.3X 10⁵Ωcm。

< example 15>

The unvulcanized rubber mixture 8 obtained in example 8 was used as an unvulcanized rubber mixture with respect to example 13.

The resistivity of the conductive blade was 5.0X 10⁵Ωcm。

< comparative example 9>

The unvulcanized rubber mixture 9 obtained in comparative example 1 was used as an unvulcanized rubber mixture with respect to example 13.

The resistivity of the conductive blade was 4.6X 10⁵Ωcm。

Table 3 below shows the evaluation results of the uniformity of the domains, the evaluation results of the change of the conductive particles in the domains, the evaluation results of the shapes of the domains, the evaluation results of the particle size distribution of the domains, the mixing device used, the average domain size on the cross section, and the evaluation results of the conductive blade in examples 13 to 15 and comparative example 9.

[ Table 3]

The evaluation results of the conductive member applied to the developing roller as the conductive roller will be described below.

< production of developing roller >

[ example 16]

(1. production of masterbatch 16)

[1-1. preparation of masterbatch 16]

Materials of the kinds and amounts shown in table 4 were mixed by a pressure mixer to obtain a master batch 16.

[ Table 4]

TABLE 4 stock for masterbatch 16

[1-2. preparation of unvulcanized rubber composition ]

Materials of the kind and amount shown in table 5 were mixed by a pressure kneader to obtain an unvulcanized rubber composition.

[ Table 5]

TABLE 5 raw materials for unvulcanized rubber compositions

Materials of the kinds and amounts shown in table 6 were mixed by open rolls to prepare a rubber composition 16 for conductive member formation.

[ Table 6]

TABLE 6 rubber composition for Forming conductive Member

(2. formation of conductive Member)

[2-1. conductive shaft core ]

A core metal having an outer diameter of 6mm was prepared from a free-cutting steel having a surface subjected to electroless nickel plating. Next, using a roll coater, the core metal was coated with an adhesive over the entire circumference except for 15mm of both end portions: METALOC U-20 (manufactured by TOYOKAGAKU KENKYUSHO CO., LTD.). In this embodiment, a gold core coated with an adhesive is used as the conductive shaft core body.

Next, a die having an inner diameter of 16.0mm was mounted on the tip of a crosshead extruder having a conductive shaft core supply mechanism and an unvulcanized rubber roll discharge mechanism. The temperature of the extruder and the crosshead was adjusted to 80 ℃, and the conveying speed of the conductive shaft core body was adjusted to 60 mm/sec. Under these conditions, an unvulcanized rubber composition was supplied from an extruder, and the outer peripheral portion of the conductive shaft core was covered with the unvulcanized rubber composition in a crosshead to obtain an unvulcanized rubber roller.

Next, the unvulcanized rubber roller was put into a hot air vulcanizing oven at 170 ℃ and heated for 60 minutes to vulcanize the unvulcanized rubber composition, thereby obtaining a roller having a conductive resin layer formed on the outer peripheral portion of the conductive shaft core. Thereafter, the end portion of the conductive resin layer is removed by cutting, and the surface of the conductive resin layer is ground with a rotating grinding wheel. In this way, the developing roller 100 having a diameter of 12.0mm at a position of 90mm from the central portion toward each of the both end portions and a diameter of 12.2mm at the central portion was prepared.

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

[ evaluation of triboelectric Charge quantity distribution of toner ]

The developing roller of each of the examples and comparative examples was loaded into a magenta toner cartridge for a laser printer (trade name: HP Color laser jet Enterprise CP4515dn, manufactured by Hewlett Packard Company). Subsequently, the cartridge was loaded into a laser printer, placed in a high-temperature high-humidity environment (modified to a high-speed system) at an atmospheric temperature of 32 ℃ and a relative humidity of 85% RH, and then left to stand for 6 hours or more. Subsequently, an image having the letter "E" of the alphabet of 14 dot size printed at a coverage of 1% for an area of a 4-sized paper sheet (hereinafter, also referred to as "letter E image") was continuously output to a predetermined number of copies, and then a white solid image was output to a new copy, and the printer was stopped during the output of the white solid image.

Here, the triboelectric charge amount distribution was measured for the toner carried on a portion having a narrow area among portions of the developing roller between the toner regulating blade and the photoreceptor contact position.

The number of particles measured was about 3,000. The standard deviation was calculated from the obtained triboelectric charge amount distribution. The standard deviation of the values measured after outputting 100 sheets was defined as the initial triboelectric charge amount distribution of the toner, and the standard deviation of the values measured after outputting 30,000 sheets was defined as the durable post-triboelectric charge amount distribution of the toner.

Grade C: the friction charge quantity is well distributed (4.0 ≤ sigma <5.0)

Grade D: poor distribution of frictional electrification amount (. sigma. >5.0)

Evaluation of image of developing roller (L/L ghost)

The developing rollers obtained in each of the examples and comparative examples were loaded into a process cartridge for a laser printer (trade name: LBP7700C, manufactured by Canon inc.). The process cartridge is introduced into a laser printer, thereby forming an electrophotographic image. 7,000 electrophotographic images were output, in which the letter "E" of the alphabet of 4 dot size was drawn on A4-size paper at a print density of 1%.

Subsequently, ghost image evaluation was performed. That is, as an image pattern, a solid black image 15mm square is printed at the leading end portion, and then a halftone image is printed on the entire surface of each sheet using black toner. Next, the density unevenness (ghost) of the toner carrier cycle appearing on the halftone portion was visually observed.

Evaluation criteria for ghosting are as follows.

Grade A: no ghosting is present.

Grade B: there was a slight ghost.

Grade C: ghosting exists.

Grade D: there are significant ghosts.

[ example 17]

The same procedure as in example 7 was carried out, except that the screw rotation speed in the elongation shear processing during the kneading of the unvulcanized rubber mixture 7(a kneaded rubber composition) in example 7 was changed to 850rpm, to obtain a corresponding B kneaded rubber composition 17. Thereafter, a conductive roller for evaluation of a developing roller was prepared in the same manner as in example 16, and various characteristics were evaluated.

[ example 18]

The same procedure as in example 8 was conducted, except that the screw rotation speed in the elongation shear processing during the kneading of the unvulcanized rubber mixture 8(a kneaded rubber composition) in example 8 was changed to 630rpm, to obtain a corresponding B kneaded rubber composition 18. Thereafter, a conductive roller for evaluation of a developing roller was prepared in the same manner as in example 16, and various characteristics were evaluated.

Comparative example 10

The same procedure as in comparative example 1 was carried out to obtain a corresponding B kneaded rubber composition, and thereafter, a conductive roller for development roller evaluation was prepared in the same manner as in example 16, and various characteristics were evaluated.

Table 7 shows the evaluation results of the conductive member applied to the developing roller.

[ Table 7]

The present invention is not limited to the above-described embodiments, and various changes and modifications may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the appended claims disclose the scope of the invention.

The present application claims priority based on Japanese patent application No.2018-079952 filed on 18.4.2018, Japanese patent application No.2019-032936 filed on 26.2.2019 and Japanese patent application No.2019-069095 filed on 29.3.2019, the entire disclosures of which are incorporated herein by reference.

Description of the reference numerals

1 conductive member

11 conductive shaft body

12 conductive layer

13 first cube shape

14 unit cube

21 unit cube

22 matrix

23 field

24 conductive particles

Claims

1. An electroconductive member for electrophotography, comprising an electroconductive layer, characterized in that the electroconductive layer comprises:

a matrix comprising a crosslinked product of a first rubber; and

a plurality of domains dispersed in the matrix, wherein

The domains each comprise a crosslinked product of a second rubber and conductive particles,

the first rubber is different from the second rubber,

σ/μ is 0 or more and 0.4 or less, where μ represents an average of ratios of sectional areas of the conductive particles contained in each of the domains to respective sectional areas of the domains appearing in a cross section in a thickness direction of the conductive layer, and σ represents a standard deviation of the ratios,

mu is 20% or more and 40% or less, and

of the first cube-shaped samples having one side of 9 μm sampled from any nine portions of the conductive layer, at least eight samples satisfy the following condition (1):

condition (1)

Assuming that a 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 calculated, Vd being 2.7 to 10.8 μm³The number of unit cubes of (2) is at least 20.

2. The electroconductive member for electrophotography according to claim 1, wherein σ/μ is 0 or more and 0.25 or less.

3. The electroconductive member for electrophotography according to claim 1 or 2, wherein a proportion of domains having a circularity of 1 or more and less than 2 with respect to the number of domains appearing on a cross section in a thickness direction of the electroconductive layer is 70% or more.

4. The electroconductive member for electrophotography according to any one of claims 1 to 3, wherein

L1 represents the total number of domains present in a cross section in the thickness direction of the conductive layer,

l2 denotes an area of 3.0X 10 measured on the cross section⁴nm²Above and less than 1.2 x 10⁵nm²And L3 denotes an area of 1.2 × 10 measured on the cross section⁵nm²The number of the above-mentioned fields,

l1, L2 and L3 satisfy the following relationships (1) and (2):

relational expression (1)

80 is less than or equal to 100 multiplied by L2/L1 is less than or equal to 00; and is

Relational expression (2)

0 is less than or equal to 100 multiplied by L3/L1 is less than or equal to 20.

5. The electroconductive member for electrophotography according to any one of claims 1 to 4,

wherein the electroconductive member for electrophotography is a charging roller or a transfer roller, and includes a columnar or cylindrical electroconductive substrate, and the electroconductive layer on an outer peripheral surface of the substrate.

6. The electroconductive member for electrophotography according to any one of claims 1 to 4,

wherein the conductive member for electrophotography is a conductive blade, and includes a metal plate, and the conductive layer covering at least a part of a surface of the metal plate.

7. The electroconductive member for electrophotography according to any one of claims 1 to 4,

wherein the electroconductive member for electrophotography is a developing roller, and includes a columnar or cylindrical electroconductive substrate, and the electroconductive layer on an outer peripheral surface of the substrate.

8. A method of manufacturing the electroconductive member for electrophotography according to any one of claims 1 to 6, comprising the steps of:

(1) preparing an unvulcanized rubber kneaded product by kneading 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 using a kneader including an elongated shear screw;

(2) forming a layer of the unvulcanized rubber kneaded product on an outer surface of the conductive base; and is

(3) Vulcanizing the first unvulcanized rubber and the second unvulcanized rubber in the layer of the unvulcanized rubber kneaded product to prepare the conductive layer.