JP2007163849A - Conductive member for electrophotography, electrophotographic apparatus using this and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a conductive member for electrophotography provided with; low hardness appropriate for the conductive member for electrophotography, little variation in electrical resistance even when electrical resistance is obtained in a semi-conductive region by dispersing conductive particles, and little contamination in a body to be charged regardless of a surface layer. <P>SOLUTION: The conductive member for electrophotography is provided with a conductive elastic body with at least a phase (A) and a phase (B) on a conductive supporting body. Phase (A): A matrix phase containing acrylonitrile butadiene rubber and conductive particles. Phase (B): a domain phase containing at least one kind from acrylonitrile butadiene rubber and styrene butadiene rubber. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic conductive member such as a developing member, a charging member, or a transfer member used in an electrophotographic apparatus.

  Conventionally, many methods are known as electrophotographic methods. General examples include the following methods. First, an electric potential is applied to a charged object using a photosensitive (photoconductive) substance (charging process), and an electric latent image is formed by partially exposing the charged object (exposure process). . Next, the electric latent image is made visible with toner (development process), and the toner image is transferred to a transfer material such as paper (transfer process). Thereafter, there is a method in which a toner image is fixed on a transfer material by heat, pressure or the like (fixing step) to obtain an image. In addition, an additional process such as removing toner particles remaining on the charged body without being transferred onto the transfer material from the charged body by various means (cleaning process) may be added.

  In such electrophotography, various electrophotographic conductive members are used in various shapes such as rollers, blades, brushes, belts, films, sheets, and chips in processes such as charging, development, and transfer. Yes.

  Among these, in the case of a roller or belt-shaped conductive member for electrophotography, since it can be freely rotated, dirt such as toner, external additives, and paper dust that have an adverse effect on the image is hard to accumulate, and it continues to a specific location. Therefore, there is an advantage that the deterioration of energization of the member is suppressed. Among these, in the case of a roller shape, the function as an electrophotographic member can be satisfied with a simple member configuration.

In particular, when the electrophotographic conductive member is used in contact with a member to be charged, the electrophotographic conductive member desirably has a conductive elastic body that satisfies an appropriate low hardness. When the electrophotographic conductive member has a high hardness, the following adverse effects occur, resulting in image defects.
1) The object to be charged is scraped.
2) The electrophotographic conductive member becomes dirty because the toner and the external additive are pressure-bonded.
3) The object to be charged and the electrophotographic conductive member do not follow and stick-slip.
4) An appropriate nip between the member to be charged and the electrophotographic conductive member necessary for discharge cannot be obtained.

Moreover, in order to use suitably as a conductive member for electrophotography, since the electrical resistance of a semiconductive area | region of about 10 < ⁴ > -10 < ¹¹ > (omega | ohm) cm is needed, generally conductive rubber is used. The conductive development mechanism of the conductive rubber is roughly divided into an ion conductive mechanism and an electronic conductive mechanism. Among them, conductive rubber by electronic conduction mechanism is made by dispersing conductive particles such as carbon black, carbon fiber, graphite, metal fine powder, metal oxide, etc. as a conductivity imparting agent in rubber, and compounding with rubber. can get. Conductive rubber using an electronic conductive mechanism has advantages such as less resistance to temperature and humidity, low cost, and less bleeding and bloom than conductive rubber using an ionic conductive mechanism. For this reason, electrophotographic conductive members using conductive rubber using conductive particles are less susceptible to changes in usage environment such as temperature and humidity, have low contamination to the photoreceptor, and are intended to reduce costs. Is more preferable. However, since it is a dispersed composite material, physical properties such as conductivity greatly vary depending not only on the filling amount but also on the dispersed state. For this reason, there is a problem that electrical resistance varies greatly within the member and from production to production, and is difficult to control. In addition, conductive particles such as carbon black and fine metal powder have reinforcing properties, and when a certain amount is filled in order to obtain appropriate conductivity, the conductive elastic body tends to be too hard.

  Various devices have been devised in order to obtain conductive rubber using conductive particles that have semi-conductive electric resistance with small variations and moderate hardness. One method is to blend several unvulcanized rubbers with different affinity with conductive particles to form a domain structure (sea-island structure). The conductive particles are a rubber phase with high affinity with conductive particles. It is made to be unevenly distributed. Here, in this specification, the domain structure (sea-island structure) means “a single type having an average domain diameter of 50 nm or more without being completely compatible when two or more types of polymers are blended. The structure having a polymer phase of However, the average domain diameter is defined as an average value of domain diameters obtained by measuring the diameter passing through the center of gravity of each domain in increments of 2 ° and averaging them. In addition, as shown in the schematic diagram of the domain structure in FIG. 1, the continuous network phase is the matrix phase (sea phase) 11, and the discontinuous particulate phase is the domain phase (island phase) 12. . In this method, the electric resistance of the semiconductive region can be obtained even if the amount of the filled conductive particles is small, by being unevenly distributed in one rubber phase among the plurality of types of rubber phases in which the conductive particles are blended. Since the filling amount is small, a conductive elastic body having a low hardness can be obtained (see Patent Document 1).

However, this method also has many problems. The following are listed as examples.
1) As for conductive particles, the state of what percentage of conductive particles are unevenly distributed with respect to the amount of filler in the blended polymer changes depending on the kneading conditions and the combination of polymer blends used. Difficult to do.
2) Even if it is unevenly distributed, the structure of the polymer blend, such as the average domain diameter, domain diameter distribution, and domain phase anisotropy, varies depending on the kneading conditions and molding conditions, and these variations vary in the stability and uniformity of electrical resistance. Affects the controllability.
3) When the conductive particles are unevenly distributed on the domain phase side, variation in electric resistance is not so suppressed.
4) It is substantially impossible to unevenly distribute all the conductive particles added to one rubber phase among the plurality of blended rubber phases.

  Further, when this conductive elastic body is used while being in contact with a charged body, the low molecular weight component in the elastic body oozes out (bleeds or blooms) on the surface of the electrophotographic conductive member, and is covered. An image defect due to adhesion to the surface of the charged body may occur. This is called charged object contamination. In order to improve this, various devices have been made so far.

  The most common contrivance is to have a multi-layer structure of two or more layers with a surface layer on the outer periphery of the conductive elastic body, and to prevent exudation from the elastic body by the surface layer. There is. By optimizing the composition, thickness, and surface shape of the surface layer, contamination of the object to be charged by a substance that exudes from the elastic body is prevented. At the same time, the electrophotographic device having an elastic body can be incorporated into the electrophotographic apparatus because it can perform functions such as controlling electrical characteristics on the surface layer and preventing the toner and external additives from sticking. At that time, a good image can be obtained (see Patent Document 2). However, the surface layer has 1) a composition and thickness required for improving image characteristics, 2) a productive composition and thickness, and 3) a composition capable of preventing bleeding. Since the thickness was taken into consideration, the degree of freedom in designing the surface layer material was very low.

  Therefore, as a fundamental solution for preventing contamination of the charged body, it is preferable to reduce the low molecular weight component in the elastic body or suppress the migration of the low molecular weight component in the elastic body. In this case, 1) Do not add a material having high migratory properties such as a plasticizer or a softener, 2) Use a polymer having low migratory properties of low molecular weight components, 3) Use low molecular weight components themselves or other materials. Possible countermeasures include chemical reaction to increase molecular weight and lower transferability.

As an example using the polymer having a small migration of the low molecular weight component of 2) above, a semiconductive rubber roller having the following composition has been proposed (see Patent Document 3).
(A) Acrylonitrile butadiene rubber (NBR) 40 to 90 parts by mass (B) Liquid NBR 10 to 60 parts by mass (C) Other solid rubber 0 to 50 parts by mass (however, (A), (B) and (C) Is 100 copies)
As described above, it is known that the elastic body mainly composed of NBR suppresses the charged body contamination. However, even if conductive particles are used in the invention of Patent Document 3, the domain structure is not formed, and the electric resistance of the semiconductive region of 10 ⁹ Ωcm or less with little variation cannot be obtained.

As described above, the electroconductive elastic body of the electrophotographic conductive member is required to have low hardness, low electrical resistance in the semiconductive region, and no contamination of the charged object.
JP-A-11-45013 JP-A-8-160716 JP-A-9-309975

  The object of the invention according to the present application is to have a low hardness suitable as a conductive member for electrophotography, and even when conductive particles are dispersed to obtain the electrical resistance of the semiconductive region, there is little variation in electrical resistance, and the surface layer It is to obtain an electrophotographic conductive member with little contamination of a charged body regardless of the presence or absence of the toner.

According to a first aspect of the present invention for solving the above-described problem, an electronic device comprising a conductive elastic body having at least a (A) phase and a (B) phase on a conductive support. This is a photographic conductive member.
(A) Phase: A matrix phase containing acrylonitrile butadiene rubber and conductive particles.
(B) Phase: A domain phase containing at least one of acrylonitrile butadiene rubber and styrene butadiene rubber.
According to the first invention, there can be obtained an electrophotographic conductive member comprising a conductive elastic body having a low hardness, a small variation in electric resistance, and a small amount of low molecular weight component exuded.

  A second invention is the electrophotographic conductive member according to the first invention, wherein the sphericity of the phase (B) is 2 or more and 10 or less. By so doing, variations in electrical resistance are reduced. The reason for this is not clarified in detail, but when the sphericity is too small, it is presumed that the conductivity is governed only by the carbon dispersion state as in the case where there is no domain phase. In addition, when the sphericity is too large, the conductive path is divided by the domain phase, so that it is presumed that the variation in electrical resistance increases because the difference in conductivity increases.

  A third invention is the first or second invention, wherein the dynamic friction coefficient between the polyester film (having a dynamic friction coefficient measured by ASTM D-1894 of 0.4 and a thickness of 100 μm) on the surface Is an electrophotographic conductive member having a value of 0.05 to 0.5. By doing so, the surface frictional property becomes appropriate as a conductive member for electrophotography.

  A fourth invention is an electrophotographic apparatus provided with the electrophotographic conductive member according to any one of the first to third inventions.

  A seventh invention is a process cartridge including the electrophotographic conductive member according to any one of the first to third inventions.

  In the fifth and eighth inventions, respectively, in the fourth and seventh inventions, the electrophotographic conductive member is in contact with or in proximity to a charged body having a charge transport layer containing a polycarbonate-based resin as an outermost layer. The electrophotographic apparatus and the process cartridge are arranged as described above. That is, the charge transport layer is formed of a resin such as a polycarbonate-based resin that has a characteristic that it is difficult for remaining charges to remain.

  In the sixth and ninth inventions, respectively, in the fourth and seventh inventions, the electrophotographic conductive member is in contact with a member to be charged whose outermost layer is a charge transport layer containing a polyarylate resin. An electrophotographic apparatus and a process cartridge which are arranged in close proximity. That is, the charge transport layer is formed of a resin that is not easily scraped by rubbing, such as a polyarylate-based resin, and hardly causes solvent cracks.

  According to the invention of the present application, the surface layer has a low hardness suitable as an electrophotographic conductive member, and there is little variation in electric resistance even when conductive particles are dispersed to obtain electric resistance of a semiconductive region. It is possible to obtain an electrophotographic conductive member with little contamination of the charged body regardless of the presence or absence of the toner.

More specifically, the following effects can be obtained by using the electrophotographic conductive member of the present invention in an electrophotographic apparatus.
1) Since the hardness of the conductive elastic body is low, image defects are less likely to occur due to the pressure bonding between the electrophotographic conductive member and the other member with the toner or external additive.
2) The conductive particles exist substantially only in the matrix phase regardless of the kneading conditions and molding conditions, the reproducibility of the formation state of the domain structure is good, and the conductive path is stably formed. Therefore, the variation in the electric resistance can be reduced while the electric resistance is in the semiconductive region, and the density unevenness of the image is less likely to occur.
3) Since both the domain phase and the matrix phase are mainly composed of acrylonitrile butadiene rubber (NBR) or styrene butadiene (SBR), which has a low migration rate of low molecular weight components, image defects due to bleeding are less likely to occur.

  In addition, by using the electrophotographic apparatus having the configuration of the present invention, a high-quality image can be output.

  In addition, by using the process cartridge having the configuration of the present invention, it is possible to easily exchange parts for maintaining image quality.

  The electrophotographic conductive member of the present invention comprises a predetermined conductive elastic body on a conductive support. As shown in FIG. 2, a conductive elastic body 22 is formed on the outer periphery of a conductive support (shaft) 21 and a high release layer 23 whose outermost surface is made high is formed. The electrophotographic conductive member can be exemplified.

  As a result of the examination, it has been clarified that acrylonitrile butadiene rubber (NBR) is an elastomer that is very unlikely to cause contamination of an object to be charged as compared with other general-purpose elastomers used for electrophotographic conductive members. Therefore, it has been found that the conductive elastic body is preferably composed of a composition mainly composed of NBR.

In particular, in the present invention, the conductive elastic body has at least the following (A) phase and (B) phase.
(A) Phase: A matrix phase containing acrylonitrile butadiene rubber and conductive particles.
(B) Phase: A domain phase containing at least one of acrylonitrile butadiene rubber and styrene butadiene rubber.

  The type of NBR used for the (A) phase is not particularly limited as long as it is a copolymer of at least an acrylonitrile monomer and a butadiene monomer. Other monomers capable of copolymerization with an acrylonitrile monomer and a butadiene monomer may be included. Any kind of NBR can be used for the amount of acrylonitrile, Mooney viscosity, and the like. Also, NBR with any modification such as carboxylated XNBR, NBIR in which a part of butadiene is replaced with isoprene, HNBR in which part of a double bond of butadiene is hydrogenated, or partially crosslinked NBR can be selected. . However, it is not preferable to use a stabilizer having a contamination or a plasticizer such as dioctyl phthalate because there is a risk of contamination of the charged body. Moreover, you may blend NBR which forms (A) phase, and another polymer in the range which does not impair to-be-charged body contamination. When blended, the other polymer is preferably in an amount not exceeding 30% by mass of the whole. Specifically, a thermoplastic elastomer used for a general electrophotographic conductive member and NBR can be blended and used. Thermoplastic elastomers include polyurethane rubber, silicone rubber, butadiene rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber, ethylene propylene rubber, polynorbornene rubber, epichlorohydrin rubber, ethylene oxide-propylene oxide-allyl glycidyl ether terpolymer. Examples thereof include rubbers containing at least one selected from coalescence, etc., and those containing at least one selected from general-purpose styrene elastomers, olefin elastomers, and the like.

  Among these, from the viewpoint of stabilizing the conductivity, it is better to select NBR having a high Mooney viscosity and a high amount of acrylonitrile. For example, NBR with Mooney viscosity of 50 to 90 ML (1 + 4) 100 ° C. can be selected, and NBR with acrylonitrile units of 30 to 50 mol% can be selected. The Mooney viscosity can be measured according to JIS K6300-1. By selecting such NBR, the conductive particles are likely to be sheared at the time of kneading, and a conductive rubber having a small variation in electric resistance can be obtained because the higher the polarity of the polymer, the easier the dispersion of the conductive particles. .

The (A) phase includes conductive particles. It is preferable to adjust the conductivity to about 10 ⁴ to 10 ¹¹ Ωcm by adding conductive particles. Furthermore, it is more preferable to adjust the conductivity to about 10 ⁴ to 10 ⁶ Ωcm.

The conductive development mechanism of the conductive rubber is roughly divided into an ion conductive mechanism and an electronic conductive mechanism. An ionic conductive agent that exhibits electrical conductivity by an ionic conductive mechanism exhibits a great effect of reducing resistance when used together with a polar rubber typified by epichlorohydrin rubber, chloroprene rubber, and acrylonitrile-butadiene rubber. However, the rubber material of the ionic conduction mechanism is highly dependent on the environment of the electrical resistance, and it is difficult to reduce the resistance to 10 ⁶ Ωcm or less. Prone to bloom.

On the other hand, conductive rubber by an electronic conductive mechanism is obtained by dispersing and compounding carbon black, carbon fiber, graphite, metal fine powder, metal oxide, etc. as conductive particles in the rubber. Compared to ion conductive rubber, electronic conductive rubber is less dependent on temperature and humidity of electric resistance, easy to reduce the resistance of 10 ⁶ Ωcm or less, less bleed and bloom, inexpensive There is. The electrophotographic conductive member is required to have a lower resistance with the recent increase in the output speed of the electrophotographic apparatus, and is required to further reduce the amount of bleeding as compared with the previous one as the image quality is improved. . Therefore, in the electrophotographic technology where the speed is increased and the image quality is improved, conductive rubber using an electronic conductive mechanism is preferable.

  (A) The conductive particles used in the phase include conductive carbon such as ketjen black EC and acetylene black; carbon for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT and MT; Examples thereof include carbon for color (ink), pyrolytic carbon, natural graphite, artificial graphite; metals such as tin oxide, titanium oxide, zinc oxide, copper, silver, and metal oxides.

  The filling amount of these conductive particles is appropriately determined so that the conductive elastic member has a desired electrical resistance depending on the type of conductive elastic member, NBR, and conductive particles of the electrophotographic apparatus. You can choose. For example, with respect to 100 parts by mass of the polymer component containing NBR, the amount can be 0.5 parts by mass to 100 parts by mass, preferably 2 parts by mass to 50 parts by mass.

  However, since the conductive rubber by the electronic conductive mechanism is a dispersed composite material, the physical properties greatly change depending not only on the filling amount but also on the dispersed state. For this reason, there is a problem that electrical resistance varies greatly within the member and from production to production, and is difficult to control. Further, when conductive particles are added in order to obtain desired conductivity, the hardness tends to be too high for use as an electrophotographic conductive member.

  Therefore, in this invention, it is set as the structure which has a domain phase containing at least 1 sort (s) of acrylonitrile butadiene rubber and styrene butadiene rubber as (B) phase. The phase (B) preferably does not contain conductive particles. When the conductive particles are included, for example, the amount is preferably not more than 1 part by mass with respect to 100 parts by mass of the polymer component in the (B) phase. By doing so, the hardness of the conductive elastic body can be reduced, and the conductive particles are unevenly distributed in the matrix phase, so that the conductive path of the conductive particles is stabilized and the variation in electric resistance is reduced.

  As a method for forming such a phase (B), after previously forming crosslinked rubber particles obtained by crosslinking the uncrosslinked rubber forming the (B) phase, and kneading together with the uncrosslinked rubber forming the (A) phase. (A) A method of crosslinking and molding uncrosslinked rubber forming the phase is preferable. With this method, it is possible to form a domain phase that does not contain conductive particles, and it is easy to control the domain structure such as average domain diameter, domain diameter distribution, and domain phase isotropicity.

  The type of NBR that can be used for the (B) phase is not particularly limited, and may be a copolymer of at least an acrylonitrile monomer and a butadiene monomer. Other monomers capable of copolymerization with an acrylonitrile monomer and a butadiene monomer may be included. Any kind of NBR can be used for the amount of acrylonitrile, Mooney viscosity, and the like. For example, NBR with Mooney viscosity of 20 to 90 ML (1 + 4) 100 ° C. can be selected, and NBR with acrylonitrile units of 10 to 50 mol% can be selected. Also, NBR with any modification such as carboxylated XNBR, NBIR in which a part of butadiene is replaced with isoprene, HNBR in which part of a double bond of butadiene is hydrogenated, or partially crosslinked NBR can be selected. . However, it is not preferable to use a stabilizer having a contamination or a plasticizer such as dioctyl phthalate because there is a risk of contamination of the charged body.

  Moreover, the kind of SBR that can be used for the (B) phase is not particularly limited as long as it is a copolymer of at least a styrene monomer and a butadiene monomer. Other monomers capable of copolymerization with a styrene monomer and a butadiene monomer may be included. Any kind of SBR can be used for the amount of styrene, Mooney viscosity, and the like. For example, NBR with Mooney viscosity of 20 to 90 ML (1 + 4) 100 ° C. can be selected, and NBR with acrylonitrile units of 10 to 50 mol% can be selected. The synthesis method may be emulsion polymerization or solution polymerization. However, it is not preferable to use a stabilizer having a contamination or a plasticizer such as dioctyl phthalate because there is a risk of contamination of the charged body.

For the phase (B), either NBR or SBR can be used, but NBR is more preferable. This is because if both the domain phase and the matrix phase are NBR, there are the following advantages.
-Since the electrical resistance difference is small, it is easy to control the electrical resistance depending on the volume ratio of the domain phase and the matrix phase.
-Adhesion between the domain phase and the matrix phase is increased, and mechanical strength such as compression set is increased.
・ Recyclability is improved.
NBR and SBR can be used in combination. When used together, it is preferable that NBR is contained in an amount of 50% by mass or more in the total amount of NBR and SBR. It is also preferred to use NBR alone.

  Moreover, you may blend NBR and / or SBR which form (B) phase, and another polymer in the range which does not impair to-be-charged body contamination. When blended, the other polymer is preferably in an amount not exceeding 30% by mass of the whole.

  (B) As a manufacturing method of the crosslinked rubber particle which bridge | crosslinked the uncrosslinked rubber which forms a phase, the method of grind | pulverizing vulcanized rubber and the method of superposing | polymerizing from latex are mentioned.

  In the case of a method of pulverizing vulcanized rubber, at least NBR and / or SBR and a crosslinking agent are mixed and vulcanized. At that time, in order to improve the grindability, it is preferable to select a composition that provides a vulcanized rubber having a small elongation at break and stress at break. In particular, the elongation at break in JIS K6251 is preferably 1000% or less, and the stress at break is preferably 20 MPa or less. In order to reduce the breaking elongation and breaking stress, it is preferable to select a filler or a crosslinking agent. In addition, pulverization can be improved by freeze pulverization.

  In particular, the method of polymerizing from latex is preferable because fine particles having a nearly spherical shape and a relatively uniform particle diameter can be obtained. As a production method for polymerizing from latex, a method of crosslinking latex with high-energy radiation such as γ-rays or electron beams is preferably used. Examples of the latex include styrene butadiene rubber (SBR), acrylic rubber, acrylonitrile-butadiene rubber (NBR), carboxylic acid-modified acrylonitrile-butadiene rubber (XNBR), and the like. Examples of the irradiation dose include 10 kGy to 10000 kGy. At this time, it is also possible to improve the efficiency of crosslinking by using a crosslinking agent in combination. Examples of the crosslinking agent include polyfunctional acrylates such as Trimethylol propylene triacrylate (TMPTA) and Iso-octyl acrylate (OMA), polyhalides such as polythiol and hexachloroethane. The crosslinked rubber particles produced by this method have a particle size equivalent to the particle size of the rubber present in the latex, resulting in crosslinked rubber particles having an average particle size as small as 50 to 500 nm and a narrow particle size distribution. Therefore, it is suitable for the present invention.

If the domain phase is too small, the effect of stably forming the conductive path of the conductive particles is lost. In the case of a domain phase that is too coarse, a black image defect occurs. Accordingly, the projected area of the domain phase is preferably 0.01 [mu] m ² or more 100 [mu] m ² or less, further more preferably 0.1 [mu] m ² or more 25 [mu] m ² or less. The projected area of the domain phase refers to the area of the domain phase in an image obtained by a method for measuring the sphericity of the domain phase described later.

  The crosslinked rubber particles obtained in this manner are mixed with uncrosslinked rubber forming a matrix phase (A) to make the domain phase (B). When this crosslinked rubber particle is mixed with uncrosslinked rubber containing NBR that forms the (A) phase, the molecular chains of the two tend to entangle and the viscosity tends to increase. Therefore, molding processability such as extrusion deteriorates. In order to suppress the increase in viscosity, it is preferable to use crosslinked rubber particles having inorganic fine particles such as calcium carbonate, titanium oxide, silica, clay and talc in the vicinity of the surface. The particle diameter of these inorganic fine particles is preferably smaller than the diameter of the crosslinked rubber particle, and examples thereof include 10 nm to 1000 nm. The inorganic fine particles function as an anti-sticking agent and are preferably attached to the crosslinked rubber particles at a ratio of 1 to 20% by mass with respect to the mass of the crosslinked rubber particles. As a method of mixing the inorganic fine particles and the crosslinked rubber particles, a method in which inorganic fine particles are mixed in an uncrosslinked latex and then dispersed by a wet disperser is cured, and fixed to the crosslinked rubber particles by a dry disperser. And the like. When the crosslinked rubber particles containing the anti-sticking agent are used, an increase in the viscosity of the rubber composition in the unvulcanized state, which is characteristic when fine crosslinked rubber particles are mixed, can be suppressed.

  The crosslinked rubber particles forming the (B) phase can be 10 parts by mass to 200 parts by mass, preferably 30 parts by mass to 100 parts by mass with respect to 100 parts by mass of the NBR forming the phase (A). .

  Moreover, the sphericity of the crosslinked rubber particles forming the (B) phase can be set to 2 to 10 or the like in the measurement method described later. By setting such a sphericity range, the variation in electrical resistance becomes smaller and the density unevenness of the image becomes smaller.

  In addition, the (A) phase and the (B) phase are generally used as an elastomer compounding agent as long as the characteristics of the electrophotographic conductive member of the present invention, such as low hardness and low charged object contamination, are not lost. An agent can be added. For example, processing aids, crosslinking agents, crosslinking accelerators, crosslinking acceleration aids, crosslinking retarders, fillers, dispersants, foaming agents, lubricants, anti-aging agents, ozone degradation inhibitors, antioxidants, conductive agents, etc. Can be added.

  Examples of the crosslinking agent include sulfur, organic sulfur-containing compounds, and organic peroxides. Examples of the crosslinking accelerator include aldehyde ammonias, aldehyde amines, guanidines, thiazoles, sulfenamides, thiurams, dithiocarbamates, xanthates, and the like. Examples of the crosslinking accelerating aid include metal oxides and fatty acids. Examples of the crosslinking retarder include organic acids, nitroso compounds, N-cyclohexylthiophthalimide and the like. Examples of lubricants include metal stearates. Examples of the antioxidant include amine ketones, aromatic secondary amines, monophenols, bisphenols, benzimidazoles, thiocarbamic acids, and thiourea antioxidants. Examples of the antioxidant include phenolic, phosphite and thioether antioxidants.

  As a method for mixing these components forming the phase (A) and the phase (B), a method using a closed mixer such as a Banbury mixer, an intermix or a pressure kneader, or an open type mixing such as an open roll is used. A method using a machine can be exemplified. Examples of the curing method of the mixture include mold vulcanization, can vulcanization, and continuous vulcanization.

  Here, examples of the roller molding method of the mixture include the following, but are not limited thereto. First, the composition extruded into a tube shape with an extruder is steam vulcanized with a vulcanizer. This tube is press-fitted into a cylindrical shaft made of SUS or aluminum, the surface of which is coated with a hot melt adhesive. Then, the shaft and the tube are bonded by heating in a hot air furnace. And a rubber roller is obtained by cut | disconnecting the both ends of a tube to desired length, and grind | polishing the tube surface.

  In the electrophotographic conductive member of the present invention, the surface of the conductive elastic body is highly releasable in order to control the adhesion and electrical characteristics of the toner and external additives and the contamination of the charged body. It is preferable to have a release layer. As a method for increasing the mold release, conventionally, a material having a composition different from that of a conductive elastic body is generally coated on the surface, such as coating. In this case, the functions such as low adhesion, non-contamination, conductivity, and setability can be separated between the coating layer and the conductive elastic body. A sex member is made.

  In addition, as a method of increasing the mold release that is simpler than coating, there is a method of highly crosslinking the surface of an elastic body by irradiating energy rays represented by electron beams, ultraviolet rays, X-rays, infrared rays, plasma, and the like. Energy beam irradiation has advantages such as no material costs and short processing steps.

  Among these highly crosslinking treatments, irradiation with ultraviolet rays is most preferable. By irradiating with ultraviolet rays, the desired electrical characteristics can be controlled, and the adhesiveness and friction coefficient are reduced, so that the toner and the external additive are prevented from sticking to the conductive elastic body, and a good image can be obtained. Irradiation conditions are not particularly limited as long as light having a wavelength of 200 nm to 450 nm is uniformly irradiated on the surface of the conductive elastic body, and the light source can irradiate ultraviolet rays in the wavelength range. For example, a known light source such as a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, or an excimer lamp can be used. It is preferable to use a lamp with a lamp output of 80 W / cm and a rated power of 4000 W. The closer the conductive elastic body is to the lamp, the better the irradiation efficiency, and the surface can be uniformly treated when irradiated while rotating. The optimal range of irradiation time varies depending on the type of lamp, irradiation distance, etc., but it is preferable that the adhesiveness and friction coefficient of the surface are sufficiently lowered and satisfy the required electrical characteristics within several seconds to several tens of minutes.

  The value of the dynamic friction coefficient with the polyester film on the surface of the electrophotographic conductive member obtained in this manner is a value measured by the method described below, and is preferably 0.05 or more and 0.5 or less, Is more preferably 0.1 or more and 0.3 or less. Here, as a polyester film, a dynamic friction coefficient measured by ASTM D-1894 is 0.4 and a thickness is 100 μm. As an example, a trade name “Lumirror S10 # 100” manufactured by Toray Industries, Inc. can be mentioned. When the dynamic friction coefficient is 0.05 or more, there is an appropriate frictional force, and the driven object can be driven. Therefore, image defects due to slip are less likely to occur without providing a drive mechanism for the electrophotographic conductive member. On the other hand, if the coefficient of dynamic friction is 0.5 or less, the adhesiveness is low and the toner and external additives are difficult to adhere.

  It is preferable that the micro rubber hardness of the obtained electrophotographic conductive member is 40 to 70. A method for measuring the micro rubber hardness will be described later.

The electric resistance of the obtained electrophotographic conductive member is preferably 2.0 × 10 ^{4 to} 5.0 × 10 ⁷ Ω. A method for measuring the electrical resistance will be described later.

  The electrophotographic apparatus of the present invention includes the above electrophotographic conductive member. Such an electrophotographic apparatus can output a high-quality image.

  FIG. 3 shows an example in which the electrophotographic conductive member of the present invention is applied to an electrophotographic apparatus. Reference numeral 31 denotes a rotating drum type electrophotographic photosensitive member (charged member) as an image carrier. The charged body 31 is rotationally driven at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow in the drawing. For example, a known charged body having at least a roll-shaped conductive support and a photosensitive layer containing an inorganic photosensitive material or an organic photosensitive material on the support may be adopted as the charged body 31.

  Reference numeral 32 denotes a charging roller. As the charging device, known means other than the charging roller can be used. In this example, a charging unit is configured by the charging roller 32 and a charging bias application power source S1 that applies a charging bias to the charging roller 32. The charging roller 32 is brought into contact with the body to be charged 31 with a predetermined pressing force, and is driven to rotate in the forward direction with respect to the rotation of the body to be charged 31 in this example. By applying a predetermined DC voltage (for example, −1200 V) from the charging bias application power source S1 to the charging roller 32, the surface of the charged body 31 has a predetermined polarity potential (for example, a dark portion potential of −600 V). Are uniformly charged (DC charging). In addition to this DC charging, known charging methods such as AC / DC superimposed charging and injection charging can be used. The electrophotographic conductive member of the present invention can be suitably used for this charging roller.

  Reference numeral 33 denotes exposure means. A known means can be used for the exposure means 33. For example, a laser beam scanner or the like can be preferably exemplified. In this case, exposure is performed with laser light L.

  When the exposure unit 33 performs image exposure corresponding to target image information on the surface to be charged 31 of the object 31 to be charged, the potential of the exposed bright portion of the charged surface (in this example, the bright portion potential is −350 V). The electrostatic latent image is formed on the charged body 31 by being selectively lowered (attenuated).

  Reference numeral 34 denotes developing means. As the developing unit 34, a known unit can be used. In this example, a toner carrier 34a that is disposed in an opening of a developing container that contains toner and carries and transports the toner, an agitating member 34b that stirs the contained toner, and a toner carrier of the toner carrier 34a. And a toner regulating member 34c that regulates the amount (toner layer thickness). The developing means 34 is a toner (negative toner, in this example, charged with a developing bias of −350 V) charged in the exposed bright portion of the electrostatic latent image on the surface of the charged body 31 with the same polarity as the charged polarity of the charged body 31. ) Is selectively attached to visualize the electrostatic latent image as a toner image. There is no particular limitation on the development method, and all existing methods can be used. As existing methods, for example, there are a jumping development method, a contact development method, a magnetic brush method, and the like. Especially in an image forming apparatus that outputs a color image, a contact development method is used for the purpose of improving toner scattering properties. The developing roller is preferable. The electrophotographic conductive member of the present invention can be suitably used for this developing roller.

  Reference numeral 35 denotes a transfer roller. The transfer roller 35 is brought into contact with the member to be charged 31 with a predetermined pressing force to form a transfer nip portion. The peripheral speed of the transfer roller 35 is substantially the same as the rotation peripheral speed of the member to be charged 31 in the forward direction. Rotate with. Further, a transfer voltage having a polarity opposite to the charging characteristics of the toner is applied from the transfer bias application power source S2. The transfer material P is fed to the transfer nip from a paper feeding mechanism (not shown) at a predetermined timing, and the back surface of the transfer material P is opposite to the charging polarity of the toner by the transfer roller 35 to which a transfer voltage is applied. Charged to polarity. Then, the toner image on the charged object 31 surface side is electrostatically transferred to the surface side of the transfer material P in the transfer nip portion. The electrophotographic conductive member of the present invention can be suitably used for this transfer roller.

  The transfer material P that has received the transfer of the toner image at the transfer nip part is separated from the surface of the charged body, introduced into a toner image fixing unit (not shown), and fixed as a toner image and output as an image formed product. In the case of the double-sided image forming mode or the multiple image forming mode, the image formed product is introduced into a recirculation conveyance mechanism (not shown) and reintroduced into the transfer nip portion.

  Residues on the member 31 such as transfer residual toner are collected from the member to be charged by a cleaning means 36 such as a blade type.

  Further, from the viewpoint of image defects and the like, pre-exposure means 37 may be provided if necessary. In the case where the staying charge remains on the body 31 to be charged, it is better to remove the staying charge on the body 31 to be charged by the pre-exposure device 37 before the primary charging by the charging member 32.

  In addition, a plurality of members to be charged, the charging member, the developing member, the cleaning member, the toner, the toner container, the waste toner container, and the like are integrally coupled, and the electrophotographic conductive material is used as at least one member. A process cartridge provided with members can also be used. The process cartridge may be configured to be detachable from an electrophotographic apparatus such as a copying machine or a laser beam printer. By using a process cartridge, it is easy to replace parts to maintain image quality, etc., parts that are severely deteriorated can be replaced at once, and toner can be replenished and discarded without toner scattering. There is an advantage that toner can be collected.

  As the member to be charged used in the electrophotographic apparatus using the electrophotographic conductive member of the present invention, a conventionally known one can be used without particular limitation, but an organic photosensitive layer is provided on the conductive support. An organic photoreceptor is preferably used.

  As an example of the structure of the organic photoreceptor, there is one in which an undercoat layer having a barrier function and an adhesive function, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive support. In the case of this function-separated layered structure, a good image can be obtained because the efficiency of charge generation and extraction is high.

  As the conductive support, for example, a support having a conductive property such as metal (aluminum, aluminum alloy, stainless steel, chromium, titanium, etc.), a conductive polymer, or the like can be used. Alternatively, a metal, resin, fiber, paper, or the like having a layer in which aluminum, an aluminum alloy, an indium oxide-tin oxide alloy, or the like is formed by vacuum deposition on the surface can be used. Furthermore, what disperse | distributed electroconductive particle (For example, carbon black, a tin oxide, a metal powder, etc.) to the high molecular compound can be used. Examples of the shape include a drum shape, a sheet shape, and a belt shape.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer. The undercoat layer can be formed of, for example, casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane, gelatin, aluminum oxide, or the like. The thickness of the undercoat layer is preferably 5 μm or less, more preferably 0.5 to 3 μm. The undercoat layer is desirably 1 × 10 ⁷ Ωcm or more in order to exhibit its function.

  The charge generation layer can be obtained by coating a solution in which the charge generation material is dispersed in a binder resin using an appropriate solvent.

  Examples of the charge generation material include phthalocyanine pigments, indigo pigments, polycyclic quinone pigments, perylene pigments, squarylium pigments, pyrylium and thiapyrylium salts, and triphenylmethane pigments.

  The binder resin used for the charge generation layer is selected from various insulating resins or organic photoconductive polymers. For example, polyvinyl butyral, polyvinyl benzal, polyarylate, polycarbonate, polyester, phenoxy, cellulose, acrylic and polyurethane resins are preferred.

  The charge transport layer is stacked on the charge generation layer and has a function of receiving charge carriers from the charge generation layer and transporting them in the presence of an electric field. The charge transport layer can be obtained by coating a solution in which the charge transport material is dispersed in a binder resin using an appropriate solvent.

  Charge transport materials are roughly classified into electron transport materials and hole transport materials. Examples of the electron transporting material include an electron withdrawing material and a hole transporting material. Examples of the electron withdrawing material include 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, crawlanyl, and tetracyanoquinodimethane. Examples of the hole transporting material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, benzidine compounds, triarylmethane compounds, triphenylamine compounds, and the like. In addition, a polymer having a multimer of these charge transport materials or a group derived from these charge transport materials in the main chain or side chain may be used. These charge transport materials may be used alone or in combination of two or more.

  The binder resin used for the charge transport layer may be an acrylic, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, polyacrylamide, polyamide, chlorinated rubber or other insulating resin, or poly And organic photoconductive polymers such as -N-vinylcarbazole and polyvinylanthracene.

  Since the charge transport layer is in contact with another electrophotographic member, it is preferable that the charge transport layer has a strong resistance to solvent cracks caused by exudates from the other member. In particular, polyarylate-based resins are preferable because they do not easily cause solvent cracks due to exudates from other members and are not easily scraped off by rubbing against other members, so that high-quality images can be obtained over a long period of use.

  Further, from the viewpoint of improving the image quality of the electrophotographic apparatus, the charge transport layer is preferably one in which the staying charge hardly remains. If the staying charge tends to remain, the charging history of the charged object remains at the next charging, and an error (ghost) from the intended image density occurs. This is hereinafter referred to as “ghost phenomenon”. Polycarbonate resins are preferred because this stagnant charge is unlikely to remain and ghosting is unlikely to occur due to good charging ability. However, the polycarbonate resin has a property that solvent cracks easily occur. However, if the electrophotographic conductive member of the present invention is used, no solvent cracks occur.

  That is, in the electrophotographic apparatus and the process cartridge of the present invention, the electrophotographic conductive member is disposed in contact with or in close proximity to a member to be charged whose outermost layer is a charge transport layer mainly including a polycarbonate-based resin. It is preferable. With such a configuration, it is possible to provide an electrophotographic apparatus and a process cartridge in which image defects (ghost) due to staying charges are small.

  Further, in the electrophotographic apparatus and the process cartridge of the present invention, the electrophotographic conductive member is disposed in contact with or in proximity to a charged body having a charge transport layer mainly comprising a polyarylate resin as an outermost layer. Preferably it is. The charge transport layer mainly composed of polyarylate resin is hard to be scraped off by rubbing, and the charge transport layer is less likely to cause solvent cracks (cracks caused by the penetration of substances that contaminate the charged body). To be charged. An electrophotographic apparatus and a process cartridge that are low in hardness and hardly cause solvent cracks, and that are less likely to cause image defects when used in a long-term and high-temperature and high-humidity environment. Can be provided.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to the following. In the following, unless otherwise specified, commercially available high-purity products were used unless otherwise specified.

[Example 1]
The following components were kneaded with a pressure kneader for 15 minutes.
[Components forming (A) phase (matrix phase containing acrylonitrile butadiene rubber and conductive particles)]
・ NBR 100 parts by mass (trade name “Nipol DN219”: manufactured by Nippon Zeon Co., Ltd.)
Carbon black 1 (conductive particles) 14 parts by mass (trade name “Asahi HS-500”: manufactured by Asahi Carbon)
・ Carbon black 2 (conductive particles) 6 parts by mass (trade name “Ketjen Black EC600JD”: manufactured by Lion)
・ Zinc stearate 1 part by mass ・ Zinc oxide 5 parts by mass ・ Liquid epoxidized polybutadiene 10 parts by mass (trade name “Adekaizer BF-1000” manufactured by Asahi Denka Kogyo Co., Ltd.)
・ Calcium carbonate 30 parts by mass (trade name “Nanox # 30” manufactured by Maruo Calcium Co., Ltd.)
[Components forming (B) phase (domain phase including at least one of acrylonitrile butadiene rubber and styrene butadiene rubber)]
・ 50 mass parts of crosslinked NBR particles containing 5% by mass of calcium carbonate (trade name “Baymod N PV KA 8641” manufactured by Bayer Co., Ltd.)
Furthermore, the following components were added and kneaded with an open roll for 15 minutes.

-1 part by weight of dibenzothiazolyl disulfide (trade name “Noxeller DM-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Tetrabenzylthiuram disulfide 3 parts by mass (trade name “Parkasit TBzTD”: manufactured by Flexis Co., Ltd.)
・ Sulfur (vulcanizing agent) 1.2 parts by mass Carbon black has a higher conductivity, the percolation threshold (additional part on the horizontal axis and electrical resistance change on the vertical axis, which causes a sudden change in electrical resistance) The electrical resistance change in the vicinity of the number of copies) is abrupt. However, since the change in electrical resistance can be slowed by blending with carbon black having slightly low conductivity, two types of carbon black are blended and used.

  Liquid epoxidized polybutadiene has a low viscosity at room temperature and has an effect of plasticizing a rubber mixture because it has a polar group and a nonpolar group. Furthermore, it is crosslinked and cured by heating. Therefore, after vulcanizing NBR, it does not ooze out on the surface of the elastic body, and is applied to general liquid plasticizers and softeners for rubber, and other liquid rubbers such as liquid isoprene, liquid butyl rubber, and liquid NBR. It is used because it has less transferability.

  Tetrabenzyl thiuram disulfide is used because it has a higher molecular weight than other thiuram vulcanization accelerators and does not ooze out to the elastic surface.

  This kneaded composition was extruded into a cylindrical shape having an outer diameter of 15 mm and an inner diameter of 5.5 mm with a rubber extruder, cut into a length of 250 mm, and primary vulcanized with steam at 160 ° C. for 40 minutes in a vulcanizing can. A conductive elastic body primary vulcanization tube was obtained. Next, a hot-melt adhesive was applied to the central portion 231 mm in the axial direction of the cylindrical surface of a cylindrical conductive support (steel, nickel-plated surface product) having a diameter of 6 mm and a length of 256 mm, and dried. This conductive support is inserted into the conductive elastic body primary vulcanization tube, then placed in an electric oven, subjected to secondary vulcanization and adhesive curing at 160 ° C. for 1 hour, and an unpolished conductive member is removed. Obtained. After cutting both ends of the rubber part of this unpolished product to make the length of the rubber part 231 mm, the rubber part is polished with a rotating grindstone, and the crown shape with an end diameter of 8.3 mm and a central part of 8.5 mm is used. An electrophotographic conductive member having a ten-point average roughness Rz of 4 μm and a deflection of 40 μm was obtained.

  This electrophotographic conductive member was used as a charging member for an electrophotographic apparatus having the structure shown in FIG. 3 to produce an electrophotographic apparatus in contact with an object to be charged having a charge transport layer made of a polyarylate resin.

[Example 2]
Using a low-pressure mercury lamp as the electrophotographic conductive member of Example 1, uniformly irradiating the electrophotographic conductive member while rotating the electrophotographic conductive member so that the amount of ultraviolet light is 8000 mJ / cm ² with a sensitivity of 254 nm sensor. The same operation as in Example 1 was performed except that.

[Example 3]
It implemented similarly to Example 2 except having used the bridge | crosslinking NBR particle | grains (brand name "Baymod NXL3820": Bayer Co., Ltd. product) which contains 5 mass% of talc instead of the bridge | crosslinking NBR particle | grains containing 5 mass% of calcium carbonate.

[Example 4]
Except for the addition of the crosslinked NBR particles containing 5% by mass of calcium carbonate, the crosslinked SBR particles containing 13% by mass of calcium carbonate (trade name “Narpow VP-121”: manufactured by Beijing Chemical Research Laboratory) were added in the same manner as in Example 2. Carried out.

[Example 5]
The electrophotographic conductive member of Example 2 was used as a charging member of an electrophotographic apparatus having the configuration shown in FIG. 3, and an electrophotographic apparatus was produced in contact with a member to be charged having a charge transport layer made of a polycarbonate resin. .

[Comparative Example 1]
The same procedure as in Example 2 was performed except that the crosslinked NBR particles containing 5% by mass of calcium carbonate were not used, and the amount of carbon black 2 used was 3 parts by mass.

[Comparative Example 2]
The same procedure as in Comparative Example 1 was performed except that the amount of NBR used was 50 parts by mass, and 50 parts by mass of liquid NBR (trade name “Nipol 1312” manufactured by Nippon Zeon Co., Ltd.) was added.

[Comparative Example 3]
Except for using NBR and liquid epoxidized polybutadiene, adding 100 parts by mass of epichlorohydrin rubber (trade name “Epichromer CG105” manufactured by Daiso Corporation) and reducing the amount of carbon black 2 used to 4 parts by mass. The same operation as in Example 2 was performed.

[Comparative Example 4]
The same operation as in Example 2 was performed except for the following points.
-NBR, liquid epoxidized polybutadiene and calcium carbonate are not used.
Add 100 parts by mass of ethylene propylene rubber (EPDM) (trade name “EPT4045” manufactured by Mitsui Chemicals, Inc.) and 50 parts by mass of process oil (trade name “PW380” manufactured by Idemitsu Kosan Co., Ltd.).
-Change the usage amount of carbon black 1 to 20 parts by mass and the usage amount of carbon black 2 to 5.6 parts.

[Comparative Example 5]
The same operation as in Comparative Example 1 was performed except for the following points.
・ Change the amount of NBR used to 50 parts by mass.
・ Do not use liquid epoxidized polybutadiene.
Add 50 parts by mass of epichlorohydrin rubber (trade name “Epichromer CG105” manufactured by Daiso Corporation).

  The measurement conditions for each evaluation item are described below.

<Micro rubber hardness measurement>
The micro rubber hardness of the conductive elastic body of the electrophotographic conductive member was measured using MD-1 type (trade name) manufactured by Kobunshi Keiki Co., Ltd. And the average value of the six points was calculated.

<Sphericality of domain phase>
In order to evaluate the formation state of the domain phase, the sphericity was measured. The sphericity of the domain phase is defined as measured as follows. First, an ultrathin section having a thickness of about 50 nm is prepared from the conductive elastic body of the electrophotographic conductive member prepared by the above procedure using a cryomicrotome. The cut surface of the conductive elastic body was observed with a transmission electron microscope (TEM) 10,000 times, and the domain structure was photographed. When the brightness contrast between the domain phase and the matrix phase is small on the photographed image, staining may be performed. As an example, there is a method of staining a phase having a double bond with osmium tetroxide. The image obtained here is taken into image processing software (trade name “Image-Pro Plus”: manufactured by Planetron Co., Ltd.), and the roundness of the crosslinked rubber particles is determined according to the count / size (in the present invention, this value is a true sphere). Automatically extracted). At this time, the “sphericity” is given by the following equation.

Sphericality = (Projected circumference of domain phase) ² / (4π x Projected area of domain phase)
However, as measurement conditions, the domain phase with a projected area of the domain phase of less than 0.01 μm ^{2 and} the domain phase that partially touches the image contour are excluded, and the average value of the sphericity of each domain phase is excluded. The sphericity was assumed. The ultra-thin slice was cut out in the three axial directions of the X-axis, Y-axis, and Z-axis, and each was photographed to cancel the influence of orientation. The number of domain phase counts was an average value of 100 or more.

<Dynamic friction coefficient>
FIG. 4 shows an example (outline) of a method for measuring the dynamic friction coefficient between the electrophotographic conductive member surface and the polyester film. This measurement method is a method suitable for the case where the measurement object has a roller shape, and is a method based on the Euler belt type. According to this method, a belt (thickness: 100 μm, width: 30 mm, length: 180 mm) in contact with an electrophotographic conductive member as a measurement object at a predetermined angle (θ) has one end at the measurement portion (load meter). ) And the other end are connected to the weight W. In this state, when the conductive member is rotated at a predetermined direction and speed, when the force measured by the measurement unit is F (g) and the weight of the weight is W (g), the friction coefficient (μ) is Determined by the following formula;
μ = (1 / θ) ln (F / W)
An example of a chart obtained by this measurement method is shown in FIG. Here, it can be seen that the value immediately after rotating the electrophotographic conductive member is the force necessary to start the rotation, and the subsequent force is the force necessary to continue the rotation. Therefore, the force at the rotation start point (that is, at time t = 0 seconds) was defined as the static friction force, and the average value in the time between 8 <t (seconds) ≦ 10 was defined as the dynamic friction force.

  As other measurement conditions, a polyester film (trade name “Lumirror S10 # 100” manufactured by Toray Industries, Inc.) is used as the material of the belt, the load is 100 g, the rotation speed is 115 rpm, and the data accumulation interval is 100 times / second. went. The dynamic friction coefficient was calculated from the dynamic friction force obtained under these conditions.

<Electrical resistance and electrical resistance variation>
FIG. 6 shows a schematic diagram of an electrical resistance measuring device for an electrophotographic conductive member. Both ends of the cored bar (shaft) 21 of the electrophotographic conductive member 2 are pressed against the cylindrical stainless steel drum 61 by pressing means (not shown), and are driven to rotate as the stainless steel drum 61 is driven to rotate. In this state, a DC voltage is applied to the shaft 21 of the electrophotographic conductive member 2 using the external power source 62, and the electric resistance of the charging roller is determined from the voltage applied to the reference resistor 63 connected in series to the aluminum drum 61. Calculated.

  A small power source PL-650-0.1 (trade name, manufactured by Matsusada Precision Co., Ltd.) was used as the DC power source, and a digital multimeter Fluke 83 (trade name, manufactured by Fluke) was used as the voltmeter.

  The electric resistance of the charging roller is as follows: temperature 23 ° C./humidity 50% R.D. H. Under the environment, the apparatus of FIG. 6 was used, and a voltage of DC 50 V was applied between the metal core and the metal drum, and measurement was performed every 0.1 second for 5 seconds. The average value was calculated as the electric resistance, and the maximum value / the minimum value of the measured values was calculated as the electric resistance variation.

<Image evaluation>
《Bleed trace evaluation》
The electrophotographic conductive members obtained in the above Examples 1 to 5 and Comparative Examples 1 to 5 were brought into contact with the member to be charged by applying a load of 500 g to both ends of the conductive support, and the room temperature was 40 ° C. It was left in a constant temperature and humidity chamber with a humidity of 95% for 1 week. Note that the member to be charged used in Example 5 has a charge transport layer mainly composed of a polycarbonate resin. The member to be charged other than Example 5 has a charge transport layer mainly composed of polyarylate resin.

The electrophotographic conductive member and the member to be charged are taken out from the thermo-hygrostat, and the electrophotographic conductive member is charged to LBP5500 (trade name, manufactured by Canon Inc.) which is an electrophotographic apparatus having the configuration of FIG. As a roller, it was incorporated with the body to be charged. A halftone image was output in an environment of a temperature of 23 ° C. and a humidity of 50% RH. It was evaluated whether the halftone image was a white image defect (exudation trace) in the circumferential period of the electrophotographic conductive member and the charged object, that is, the contact portion. Specifically, the evaluation was made according to the following criteria. If it is more than B evaluation, it is a level which is satisfactory practically.
A: When the bleeding trace cannot be recognized on the image.
B: A slight bleeding trace appears on the first image, but it cannot be confirmed after several sheets are passed.
C: When a clear oozing trace can be recognized.
D: When the oozing trace can be clearly confirmed and a solvent crack is confirmed on the member to be charged.

<Evaluation of density unevenness>
The electrophotographic conductive members obtained in Examples 1 to 5 and Comparative Examples 1 to 5 described above are used as charging rollers in LBP5500 (trade name, manufactured by Canon Inc.), which is an electrophotographic apparatus having the configuration of FIG. Attached together with the object to be charged. Note that the member to be charged used in Example 5 has a charge transport layer mainly composed of a polycarbonate resin. The member to be charged other than Example 5 has a charge transport layer mainly composed of polyarylate resin. A halftone image was output in an environment of a temperature of 15 ° C. and a humidity of 10% RH. At this time, irregular “image density unevenness” due to uneven resistance of the charging roller was evaluated. Based on the density difference between the bright part and the dark part, the following criteria were used for evaluation. In practical use, there is no problem as long as it is B or higher.
A: No difference in density.
B: The density difference is slight.
C: There is a clear density difference.

This adverse effect of image density unevenness is greatly affected by the aforementioned electrical resistance and variations in electrical resistance. When the electrical resistance is less than 5.0 × 10 ⁵ Ω, the variation in electrical resistance is less than 3, and the evaluation is A, and when the electrical resistance is 3 or more and less than 10, there is almost no C evaluation. When the electrical resistance is 5.0 × 10 ⁵ Ω or more and less than 5.0 × 10 ⁷ Ω, the variation in electrical resistance is less than 1.3, so that the A evaluation is 1.3 or more and less than 2.5. In B evaluation, it becomes C evaluation by becoming 2.5 or more. When the electric resistance is 5.0 × 10 ⁷ Ω or more, A evaluation is not obtained, and B variation is obtained when variation in electric resistance is 1.5 or less. However, when the electric resistance is lowered, dielectric breakdown occurs in the undercoat layer, the charge generation layer, and the charge transport layer on the surface of the member to be charged, so that a large current flows between the member to be charged and the charging roller and tends to be a bad image.

《Ghost evaluation》
The electrophotographic conductive members obtained in Examples 1 to 5 and Comparative Examples 1 to 5 described above are used as charging rollers in LBP5500 (trade name, manufactured by Canon Inc.), which is an electrophotographic apparatus having the configuration of FIG. Attached together with the object to be charged. Note that the member to be charged used in Example 5 has a charge transport layer mainly composed of a polycarbonate resin. The member to be charged other than Example 5 has a charge transport layer mainly composed of polyarylate resin. And the ghost evaluation image was output in the environment of temperature 30 degreeC and humidity 80% RH. At this time, the pre-exposure means was not used. The ghost evaluation image refers to a solid black portion (dark black portion) of 25 mm square arranged on one rotation portion of the charged body from the print image writing, and halftone (light black) after the second rotation of the electrophotographic photosensitive member. (Part) is a test chart. The fact that the afterimage of the solid black portion of the first rotation remains in this halftone portion is called ghost. Based on the difference in ghost density, the following criteria were used for evaluation. In actual use, there is no problem as long as it is above this B evaluation.
A: No difference in density.
B: The density difference is slight.
C: There is a clear density difference.

《Durable dirt evaluation》
The electrophotographic conductive members obtained in Examples 1 to 5 and Comparative Examples 1 to 5 described above are used as charging rollers in LBP5500 (trade name, manufactured by Canon Inc.), which is an electrophotographic apparatus having the configuration of FIG. Attached together with the object to be charged. Note that the member to be charged used in Example 5 has a charge transport layer mainly composed of a polycarbonate resin. The member to be charged other than Example 5 has a charge transport layer mainly composed of polyarylate resin. Then, an image output durability test was performed in an environment of a temperature of 30 ° C. and a humidity of 80% RH. As test conditions, 6,000 continuous sheets were passed by the method described above. At this time, the evaluation of dot-like or linear image defects (durable stains) due to the toner and external additives fixed to the charging roller was evaluated as follows based on the occurrence frequency.
A: Not at all.
B: Very rarely present.
C: A large amount exists.

This durable stain occurs when toner or an external additive is pressure-bonded between the charging roller and the member to be charged, and the elastic body of the charging roller is more easily fixed as the hardness is higher. Even if the hardness is moderately low, if the coefficient of dynamic friction is high and the adhesiveness is high, the toner and the external additive are easily fixed.
《Explanation of image evaluation results》
The evaluation of the bleeding trace was as follows. In Examples 2 to 5 and Comparative Example 1, a conductive elastic body mainly composed of NBR having low contamination of the charged body is used, and the surface is highly crosslinked by UV treatment. The molecular weight component is difficult to ooze out and is rated A. Example 1 was evaluated as B because there was a slight oozing deposit due to the absence of UV treatment compared to Example 2. Comparative Example 2 uses a conductive elastic body mainly composed of NBR, but the immobilization inside the elastic body due to the cross-linking of liquid NBR is incomplete, so that exudation occurs and the C evaluation. It was. In Comparative Examples 3 to 5, low molecular weight components derived from elimination of chlorine groups in epichlorohydrin and process oil added for improving the processability of EPDM exude, resulting in exudation traces and D evaluation. .

  The evaluation of uneven density was as follows. In Examples 1, 2 and 5, since NBR rubber particles to which a small amount of calcium carbonate is added are used as the crosslinked rubber particles, a domain phase with good dispersibility and uniform sphericity is formed. Therefore, the variation in electric resistance is small, and the density unevenness is evaluated as A. In Example 3, since NBR rubber particles to which a small amount of talc is added are used, there is a large variation in the domain phase compared to Example 2 to which calcium carbonate is added. Since Example 4 uses SBR rubber particles to which a small amount of calcium carbonate is added, the domain phase particles are too small compared to Example 2 and the like, which are NBR particles, and accordingly the sphericity is also small. Become. Therefore, since the control of the conductive path becomes difficult on the contrary, the variation in electric resistance is large, which is B evaluation. Comparative Examples 3 and 4 are rated B because the matrix phase mainly composed of epichlorohydrin or EPDM is inferior in dispersibility with carbon black compared to NBR and inferior in dispersibility with NBR particles. In Comparative Examples 1, 2, and 5, since the conductive elastic body did not form a domain structure and the conductive path was unstable, the electric resistance varied and the C evaluation was made.

  The evaluation of the ghost is the A evaluation only in Example 5 in which the charged object is less likely to remain and the charge-transporting layer is made of a highly chargeable polycarbonate resin. Examples 1 to 4 and Comparative Example 1 Since -5 was a polyarylate resin, it was evaluated as B.

  The evaluation of the durability stains was that Examples 2 to 5 and Comparative Examples 2 to 4 had a low coefficient of dynamic friction and a low hardness so that the charged object and the electrophotographic conductive member did not slip. It was evaluation. In Example 1, since the UV treatment was not performed, the coefficient of dynamic friction was high, and stains with partial vertical streaks were observed. In Comparative Examples 1 and 5, since the hardness is not reduced by the crosslinked rubber particles or the liquid rubber, the hardness is high, the toner and the external additive are pressure-bonded, and a large number of vertical lines are confirmed. It was C evaluation.

  Table 1 shows a summary of the material composition and evaluation results together with the above-described Examples and Comparative Examples.

It is a schematic diagram of the domain structure of the present invention. It is the schematic which shows an example of the electrophotographic conductive member of this invention. It is the schematic which shows an example of the electrophotographic apparatus using the electroconductive electroconductive member of this invention. It is the schematic which shows the example of a measurement of the dynamic friction coefficient of the electrophotographic conductive member in this invention. It is the schematic which shows the chart which measured the dynamic friction force of the electroconductive electroconductive member in this invention. It is the schematic which shows the example of a measurement of the electrical resistance of the electroconductive member in this invention.

Explanation of symbols

11 Matrix phase (sea phase)
12 Domain phase (island phase)
2 Electrophotographic conductive member 21 Conductive support (shaft)
22 conductive elastic body 23 high release layer 31 electrophotographic photosensitive member (charged body)
32 Charging member (charging roller)
33 Exposure means 34 Development means 34a Toner carrier 34b Stirring member 34c Toner regulating member 35 Transfer means (transfer roller)
36 Cleaning means 37 Pre-exposure means 61 Aluminum drum 62 External power supply 63 Reference resistance L Laser light S1, S2 Bias application power supply P Transfer material

Claims (9)

An electrophotographic conductive member comprising a conductive elastic body having at least a phase (A) and a phase (B) on a conductive support.
(A) Phase: A matrix phase containing acrylonitrile butadiene rubber and conductive particles.
(B) Phase: A domain phase containing at least one of acrylonitrile butadiene rubber and styrene butadiene rubber.   2. The electrophotographic conductive member according to claim 1, wherein the sphericity of the phase (B) is 2 or more and 10 or less.   The dynamic friction coefficient between the polyester film (having a dynamic friction coefficient measured by ASTM D-1894 of 0.4 and a thickness of 100 μm) on the surface is 0.05 or more and 0.5 or less. The electrophotographic conductive member according to claim 1 or 2.   An electrophotographic apparatus comprising the electrophotographic conductive member according to claim 1.   5. The electrophotographic apparatus according to claim 4, wherein the electrophotographic conductive member is disposed in contact with or close to a member to be charged whose outermost layer is a charge transport layer containing a polycarbonate-based resin.   5. The electrophotographic apparatus according to claim 4, wherein the electrophotographic conductive member is disposed in contact with or in proximity to a member to be charged whose outermost layer is a charge transport layer containing a polyarylate resin. .   A process cartridge comprising the electrophotographic conductive member according to any one of claims 1 to 3.   8. The process cartridge according to claim 7, wherein the electrophotographic conductive member is disposed in contact with or close to a member to be charged having a charge transport layer containing a polycarbonate-based resin as an outermost layer. 8. The process cartridge according to claim 7, wherein the electrophotographic conductive member is disposed in contact with or in proximity to a member to be charged whose outermost layer is a charge transport layer containing a polyarylate-based resin.

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