Electrophotographic roller, developing apparatus, electrophotographic image forming apparatus, and process cartridge

Abstract

To provide an electrophotographic roller that has little electric conduction deterioration even when it is used with electric conduction over a long period of time and a small change in electrical resistance regardless of electric conduction over a long period of time, and can be manufactured at low cost.SOLUTION: An electrophotographic roller has: a substrate having a conductive surface; and a conductive layer on the surface of the substrate. The conductive layer is a surface layer of the electrophotographic roller, and has a skeleton including polyurethane and an electron conductive filler in the polyurethane, the conductive layer has at least one void, and at least a part of an inner wall of the void is configured of the skeleton, and when an electrode is brought into contact with an outer surface of the conductive layer and an AC voltage with an inter-peak voltage of 50 V is applied between the electrode and the surface of the substrate in a frequency range of 0.1 to 10 Hz, an absolute value of a phase delay θ of an AC impedance with respect to the AC voltage is 10 degrees or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrophotographic roller, a developing device, an electrophotographic image forming apparatus, and a process cartridge used in an electrophotographic image forming apparatus.The present disclosure also relates to an electrophotographic image forming apparatus. [Background technology]

[0002] In an electrophotographic image forming apparatus (such as a copying machine, facsimile, or printer using an electrophotographic method, hereinafter also referred to as an "image forming apparatus"), a toner is stably charged using an electrophotographic roller (hereinafter also referred to as a "toner supply roller") that supplies toner, and the toner is then supplied to a developing roller, and developed to obtain an image on an electrophotographic photoreceptor. In order to stably charge the toner, an elastic roller having voids on its surface and having electrical conductivity is used as the electrophotographic roller. Patent Document 1 discloses a conductive member having an elastic layer made of foam rubber containing carbon nanotubes. Patent Document 2 discloses a conductive roller comprising a base made of soft polyurethane foam and a conductive coating layer, the base being formed of a skeleton and a cell membrane, the conductive coating layer being provided on at least a part of the surface of each of the skeleton and the cell membrane, the conductive coating layer being a conductive polyurethane foam containing carbon nanotubes, and a conductive foam layer made of the conductive polyurethane foam on the circumferential surface of a core metal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-101958 A [Patent Document 2] JP 2009-139866 A Summary of the Invention [Problem to be solved by the invention]

[0004] Image forming apparatuses are required to be able to stably form excellent electrophotographic images even under harsh environments, and accordingly, conductive electrophotographic rollers used in image forming apparatuses are required to have electrical resistance that is unlikely to change even when current is passed over them for a long period of time. According to the study by the present inventors, when the conductive member according to Patent Document 1 is used as a toner supply roller, it has been found that the electrical resistance of the electrophotographic roller is likely to increase due to long-term current application. Also, the conductive roller according to Patent Document 2 has a conductive coating layer formed on the surface of the skeleton and cell membrane by dip coating, and the manufacturing process is complicated, which is disadvantageous in terms of cost.

[0005] At least one aspect of the present disclosure is directed to providing an electrophotographic roller that exhibits small changes in electrical resistance even when energized for a long period of time and that can be manufactured at low cost. At least one aspect of the present disclosure is directed to providing a developing device that contributes to stable development of high-quality electrophotographic images. At least one aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that can stably output high-quality electrophotographic images. At least one aspect of the present disclosure is directed to providing a process cartridge that contributes to stable output of high-quality electrophotographic images. [Means for solving the problem]

[0006] According to at least one aspect of the present disclosure, A substrate having a conductive surface; a conductive layer on said surface of said substrate, The conductive layer is a surface layer of the electrophotographic roller, A backbone including a polyurethane as a binder and an electronically conductive filler in the polyurethane, The conductive layer has at least one void, and At least a part of the inner wall of the void is composed of the skeleton, When an electrode is brought into contact with the outer surface of the conductive layer and an AC voltage having a peak-to-peak voltage of 50 V in a frequency range of 0.1 to 10 Hz is applied between the electrode and the surface of the substrate, the absolute value of the phase lag θ of AC impedance with respect to the AC voltage is 10 degrees or less, thereby providing an electrophotographic roller. According to at least one aspect of the present disclosure, there is provided a developing device comprising at least a developing roller and a developer supply roller that supplies developer to the developing roller, configured so that a voltage can be applied between the developing roller and the developer supply roller, and the developer supply roller being the electrophotographic roller described above.

[0007] According to at least one aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above-described developing device. According to at least one aspect of the present disclosure, there is provided a process cartridge that is detachable from the main body of an electrophotographic image forming apparatus, the process cartridge having a contact member that is electrically connected to an electrical contact of the main body when attached to the main body, the process cartridge including a developing roller and a developer supply roller that supplies developer to the developing roller, and configured so that a voltage can be applied between the developing roller and the developer supply roller by electrical connection with the main body, and the developer supply roller being the electrophotographic roller described above. Effect of the Invention

[0008] According to at least one aspect of the present disclosure, it is possible to obtain an electrophotographic roller that exhibits little change in electrical resistance even when energized for a long period of time and that can be manufactured at low cost. Also, according to at least one aspect of the present disclosure, it is possible to obtain a developing device that contributes to stable development of high-quality electrophotographic images. Furthermore, according to at least one aspect of the present disclosure, it is possible to obtain an electrophotographic image forming apparatus that can stably output high-quality electrophotographic images. Also, according to at least one aspect of the present disclosure, it is possible to obtain a process cartridge that contributes to stable output of high-quality electrophotographic images. [Brief description of the drawings]

[0009] [Figure 1] 1A and 1B are a schematic cross-sectional view and a schematic perspective view of an electrophotographic roller; [Diagram 2] 2 is a schematic cross-sectional view of a developing device and a process cartridge. [Diagram 3] FIG. 1 is a schematic diagram illustrating an electrophotographic image forming apparatus. [Figure 4] FIG. 1 is a schematic diagram showing an RC parallel circuit. [Diagram 5] 1 is a schematic diagram showing the relationship between the applied voltage V, the current I flowing through an RC parallel circuit, and the phase lag θ. [Figure 6] FIG. 13 is a schematic diagram showing a polar coordinate representation of θ. [Figure 7] FIG. 13 is a schematic diagram showing the frequency dependence of θ. [Figure 8] FIG. 1 is a schematic diagram showing a method for measuring θ using an impedance analyzer. [Figure 9] FIG. 1 is a schematic diagram showing a method for measuring electrical deterioration. [Figure 10] 5A to 5C are schematic cross-sectional views showing a method for forming a conductive layer of an electrophotographic roller. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the present disclosure, the expressions "XX or more and YY or less" and "XX to YY" expressing a numerical range mean a numerical range including a lower limit and an upper limit which are endpoints, unless otherwise specified. When the range is described stepwise, any combination of the upper and lower limits of each numerical range is also disclosed. In addition, in the present disclosure, for example, a description such as "at least one selected from the group consisting of XX, YY, and ZZ" means any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ.

[0011] As described above, the conductive roller according to Patent Document 1 may have a change in electrical resistance when used as a toner supply roller for image formation over a long period of time. The present inventors speculate that the reason is as follows. That is, in the conductive roller according to Patent Document 1, the foam rubber as the elastic layer is formed by mixing air bubbles into a composition obtained by mixing rubber latex and an aqueous dispersion in which carbon nanotubes are dispersed using a surfactant, foaming the composition, and then vulcanizing the composition. In the composition, the carbon nanotubes are dispersed in the rubber latex as emulsion particles wrapped with a surfactant. Therefore, in the foam rubber after vulcanization, the carbon nanotubes are present in a dispersed state in each emulsion particle, and it is considered that an ionic component that is responsible for transporting electric charges and is present in the rubber or surfactant is present between the carbon nanotubes. It is believed that when a voltage is applied to the electrophotographic roller for a long period of time, the electrical resistance changes due to deterioration of the rubber interposed between the carbon nanotubes and polarization of the ionic components.

[0012] The present inventors have conducted research to obtain an electrophotographic roller that has a simpler configuration and exhibits little change in electrical resistance even after long-term use, and have found that an electrophotographic roller having the following configuration contributes to achieving the above-mentioned object.

[0013] An electrophotographic roller having a substrate having a conductive surface and a conductive layer on the surface of the substrate, the conductive layer being a surface layer of the electrophotographic roller and having a skeleton including polyurethane as a binder and an electronically conductive filler in the polyurethane. The conductive layer has at least one void, and at least a part of the inner wall of the void is composed of the skeleton. When an electrode is brought into contact with the outer surface of the conductive layer of the electrophotographic roller and an AC voltage of 50 V peak-to-peak and in a frequency range of 0.1 to 10 Hz is applied between the electrode and the surface of the substrate, the absolute value of the phase lag θ of the AC impedance with respect to the AC voltage is 10 degrees or less.

[0014] The electrophotographic roller has a substrate having a conductive surface and a conductive layer on the outer peripheral surface of the substrate, the conductive layer being a surface layer of the electrophotographic roller. When an electrode is placed in contact with the outer surface of the conductive layer and an AC voltage of 50 V peak-to-peak in a frequency range of 0.1 to 10 Hz is applied between the electrode and the conductive outer surface of the base, the absolute value of the phase lag θ of the AC impedance relative to the AC voltage is 10.0 degrees or less.

[0015] The peak-to-peak voltage is set to 50 V because this corresponds to the voltage applied when the electrophotographic roller is actually used in an electrophotographic apparatus. The reason for setting the frequency range of the applied AC voltage to 0.1 to 10 Hz is that the measurement accuracy of θ is high, the effect of the capacitive component caused by the interface between the surface of the electronically conductive filler and the polyurethane can be made negligibly small, and the absolute value of θ correlates well with the tendency of fluctuation in electrical resistance due to current flow. That is, by applying an AC voltage with a peak-to-peak voltage of 50 V in the frequency range of 0.1 to 10 Hz, the absolute value of θ can be accurately measured under conditions corresponding to the conditions in which the electrophotographic roller is actually used. The absolute value of θ is preferably 5.0 degrees or less, and more preferably 3.0 degrees or less. That is, θ is −10.0 degrees or more and 10.0 degrees or less, preferably −5.0 degrees or more and 5.0 degrees or less, and more preferably −3.0 degrees or more and 3.0 degrees or less.

[0016] The impedance of the electrophotographic roller of the present disclosure can be expressed by the impedance of an RC parallel circuit shown in Fig. 4. The current flowing through the electrophotographic roller in response to an applied AC voltage is expressed as I R and I flowing through the capacitance component C C Combined with I R+C It is. R I R+C is the component in phase with the applied voltage, and I C is a component that lags behind the applied voltage by 90°.

[0017] Steady-state I R+CWhen I and the applied voltage V are plotted on a graph with the applied voltage or current (relative value) on the vertical axis and the phase on the horizontal axis, it can be shown as in Figure 5. R+C The angle of phase delay of is θ. This θ can be expressed in polar coordinates as shown in Figure 6. When the horizontal axis is the applied voltage V, the current component I R and the current I of the capacitive component that lags behind the applied voltage V by 90° C The composite vector with I R+C And this I R+C The angle between this and the horizontal axis is the phase lag θ of the AC impedance.

[0018] 7 shows a comparison of the relationship between θ and frequency for the electrophotographic roller of the present disclosure and that of the electrophotographic roller of the prior art. The θ of the electrophotographic roller of the present disclosure satisfies -10≦θ≦10 in the frequency range of 0.1 to 10 Hz (1.0E-01 to 1.0E+01 Hz). In other words, the absolute value of the phase lag θ is 10 degrees or less. On the other hand, the absolute value of θ of the electrophotographic roller of the prior art is greater than 10 in the frequency range of 0.1 to 10 Hz.

[0019] The smaller the absolute value of θ, the smaller the I R+C The component in phase with the applied voltage (I R ) is large, and the component (I C ) is small. In other words, it indicates that the electronic conductive current component resulting from the current proportional to the applied voltage is large, and the ionic conductive current component is small.

[0020] When considering deterioration due to electrical conduction, the electronic conductive current component changes little even after electrical conduction for a long time, but the ionic conductive current component gradually decreases during electrical conduction for a long time due to ion migration and polarization. Therefore, as a property of an electrophotographic roller that can suppress electrical conduction deterioration, it is preferable that the ionic conductive current component is small. In other words, by controlling θ to be small, an electrophotographic roller with a small ionic conductive current component and less prone to electrical conduction deterioration can be obtained.

[0021] In addition, the change in current when a DC voltage is continuously applied does not repeat periodically because the potential difference between the electrodes is constant, and can be considered as the change in current when the limit is taken in the direction of zero frequency. Therefore, if the absolute value of θ is small in the low frequency region (frequency region of 0.1 to 10 Hz), the ionic conductive current component is small, and deterioration due to electrical current can be reduced.

[0022] For the above reasons, the inventors of the present application have discovered that when a developing member is brought into contact with the outer surface of the conductive layer of an electrophotographic roller and an AC voltage of 50 V peak-to-peak and in a frequency range of 0.1 to 10 Hz is applied between the developing member and the conductive layer, by setting the absolute value of the phase lag θ of the AC impedance with respect to the AC voltage to 10 degrees or less, it is possible to obtain an electrophotographic roller that is less susceptible to deterioration due to current flow even when used for long periods of time with current flowing through it, and have arrived at the present invention.

[0023] As a specific method for reducing the absolute value of θ in the frequency range of 0.1 to 10 Hz, it is preferable to increase the proportion of the electronically conductive current component of the conductive layer and decrease the proportion of the ionic conductive current component. For example, the absolute value of θ in the frequency range of 0.1 to 10 Hz can be reduced by changing the type of electronically conductive filler, increasing the content of electronically conductive filler in the conductive layer, or increasing the porosity of the conductive layer and foaming the conductive layer while molding it. In other words, by configuring the conductive materials in the skeleton described below to come into contact with each other and be oriented to form a conductive path, the capacitance component due to interfacial polarization between electronically conductive fillers is reduced, and the absolute value of θ in the frequency range of 0.1 to 10 Hz can be reduced.

[0024] The medium resistance region (10 5 ~10 9In order to increase the proportion of the electronically conductive current component in Ω·cm, it is necessary to connect the conductive paths of the electronically conductive filler. Adding a large amount of electronically conductive filler connects the conductive paths and acts to reduce the absolute value of θ, but on the other hand, adding electronically conductive filler makes the conductive layer harder, making it unsuitable for use as an electrophotographic roller, which requires flexibility. That is, there is a problem in obtaining an electrophotographic roller having appropriate hardness and flexibility as an electrophotographic roller while increasing the proportion of the electronically conductive current component by increasing the amount of electronically conductive filler added.

[0025] After extensive research, the present inventors have found that by including carbon nanotubes in the conductive layer, it is possible to reduce the absolute value of θ in the frequency range of 0.1 to 10 Hz and suppress electrical deterioration while maintaining appropriate flexibility as an electrophotographic roller. More preferably, by using a nonionic surfactant to improve the dispersion of carbon nanotubes in polyurethane, it is possible to obtain an electrophotographic roller that has appropriate hardness as an electrophotographic roller and can reduce θ to further reduce electrical deterioration.

[0026] <Electrophotographic roller> Fig. 1A shows a schematic cross-sectional view of an electrophotographic roller, and Fig. 1B shows a schematic perspective view of the electrophotographic roller. The electrophotographic roller 1 has a conductive substrate 2 and a conductive layer 3 on the outer peripheral surface of the substrate. The electrophotographic roller can be used as a developer supply roller of an electrophotographic image forming apparatus. The conductive layer is a surface layer of the electrophotographic roller, and has a skeleton including polyurethane and an electronically conductive filler in the polyurethane. The polyurethane acts as a binder resin of the conductive layer. The conductive layer has at least one void. The polyurethane may be a foamed polyurethane. That is, the conductive layer may be a foamed layer. The layer structure of the electrophotographic roller 1 is not limited to one consisting of only the substrate 2 and the conductive layer 3, and other layers such as a conductive elastic layer may be further provided between the substrate 2 and the conductive layer 3. The configuration of the electrophotographic roller will be described in detail below.

[0027] <<Base>> The substrate 2 has a conductive surface and functions as a support member and an electrode for the electrophotographic roller. The substrate may be made of a conductive material such as a metal or alloy, such as aluminum, copper alloy, or stainless steel; iron plated with chromium or nickel; or a conductive synthetic resin. For example, the substrate may be a cored bar. The substrate may be, for example, in the shape of a solid cylinder or a hollow cylinder.

[0028] <<Conductive layer>> The conductive layer is formed on the outer peripheral surface of the substrate, the conductive layer being the surface layer of the electrophotographic roller. The conductive layer 3 has a skeleton containing polyurethane as a binder and an electronically conductive filler in the polyurethane. The conductive layer has at least one void. The void in the conductive layer stores the toner in the conductive layer, and uniformly supplies the toner to the surface of the developing roller (developing member) as a developer supply roller. In other words, the electrophotographic roller can be used as a developer supply roller.

[0029] <<<Void>>> The conductive layer has at least one void. The shape of the void is not particularly limited, but for example, The voids may be through holes or blind holes that open to the outer surface of the conductive layer and extend in the thickness direction of the conductive layer. The void may be formed as a single void, or as another example, a plurality of voids may be formed in a bubble state (open cell state) in which the voids are interconnected with each other. That is, the conductive layer may be porous having a large number of voids. The conductive layer preferably has a plurality of voids, and the voids are preferably formed in an open cell state.

[0030] At least a portion of the inner wall of the void is preferably made of a skeleton including polyurethane and an electronically conductive filler in the polyurethane. Preferably, the inner wall of the void is made of a skeleton. More preferably, the inner wall of the void is made of polyurethane and an electronically conductive filler in the polyurethane.

[0031] The porosity, which is the volume fraction of the voids in the conductive layer, is preferably 50 to 97% by volume. When the porosity is in the above range, the electrophotographic roller can appropriately store the toner, which is preferable. In addition, by increasing the porosity, the conductive paths between the electronically conductive fillers forming the inner walls of the voids are easily connected, and the proportion of the electronically conductive current component can be increased. As a result, θ can be reduced, which is preferable because electrical deterioration can be suppressed. The porosity can be measured by the method described below.

[0032] The porosity of the conductive layer is more preferably 60 to 95% by volume, and even more preferably 70 to 90% by volume. In the manufacturing process of the conductive layer, the material is foamed, thereby forming voids in the conductive layer. The porosity can be controlled by the type and amount of foaming agent added. Specifically, the porosity can be increased by increasing the amount of foaming agent added, and the porosity can be decreased by decreasing the amount of foaming agent added.

[0033] In such a conductive layer having voids, the average cell size on the surface of the conductive layer, the number of cells, the amount of air permeability, the density of the entire layer, etc. can be set as desired. The physical properties of the conductive layer (foam layer) are not particularly limited, but it is preferable that the values ​​are within the following numerical ranges, for example. The average cell diameter of the surface is a value indicating the circle-equivalent average diameter of the openings of the voids appearing on the surface of the conductive layer. The average cell diameter of the surface is preferably, for example, 100 μm or more and 500 μm or less. The number of cells is a value indicating the number of openings of the voids appearing on the surface of the conductive layer that exist per unit length (per inch) of the conductive layer surface. The number of cells is preferably, for example, 50 cells / inch or more and 300 cells / inch or less. The cell diameter and number of cells can be determined, for example, by processing an image obtained by photographing the surface of the electrophotographic roller with a video microscope.

[0034] The air permeability is a value indicating the ease with which air passes through the conductive layer. The electrophotographic roller is sandwiched between cylindrical jigs having a diameter 1 mm smaller than the diameter of the electrophotographic roller and having holes with a diameter of 10 mm at opposing positions in the circumferential direction, and the air flow rate per minute is measured when the pressure difference between the holes is set to 125 Pa. The air permeability is preferably, for example, 0.5 L / min to 3.0 L / min. The density of the entire layer is a value indicating the density of the entire conductive layer including the skeleton and voids described below. The density of the entire layer is, for example, 0.05 g / cm 3 More than 0.20g / cm 3 The volume of the conductive layer consisting of the skeleton and voids can be calculated from the outer diameter of the electrophotographic roller, the diameter of the substrate, the length of the conductive layer, etc., and the density of the entire conductive layer can be calculated from the volume and the mass of the conductive layer.

[0035] <<<Skeleton>>> The conductive layer has a skeleton including polyurethane and an electronically conductive filler in the polyurethane. The polyurethane acts as a binder resin for the conductive layer. The electronically conductive filler may be any of those described below.

[0036] The polyurethane is preferably a crosslinked urethane resin. The crosslinked urethane resin is a reaction product of a polyol and a compound having an isocyanate group. For example, when a compound having an isocyanate group is added to a mixture of an electronically conductive filler and a polyol, the mixture is mixed and reacted, and foaming and curing occur, resulting in the formation of a skeleton constituting a conductive layer and voids between the skeletons. As a result, a conductive layer having a skeleton containing polyurethane and an electronically conductive filler and having voids can be obtained.

[0037] <<<Electronically conductive filler>>> As the conductive agent for the electrophotographic roller, an electronically conductive filler can be used. The electronically conductive filler is not particularly limited, but examples thereof include the following (1) to (7). (1) Carbon nanotubes (2) Carbon powders such as acetylene black, ketjen black, PAN (polyacrylonitrile) carbon, and pitch carbon. (3) Graphite. (4) Metallic particles and fibers, such as aluminum, palladium, nickel, iron, copper, and silver. (5) Metal oxide particles such as conductive titanium oxide, conductive tin oxide, and conductive zinc oxide. (6) Powder of metal compounds such as copper sulfide and zinc sulfide. (7) Powders in which tin oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, titanium, chromium, tungsten, iron, cobalt, nickel, palladium, rhodium, osmium, iridium, platinum, etc. are attached to the surface of suitable particles by electrolytic treatment, spray coating, mixing and shaking, etc.

[0038] The electronically conductive filler may be used alone or in combination of two or more kinds. That is, the electronically conductive filler may include a first electronically conductive filler and a second electronically conductive filler different from the first electronically conductive filler. The first electronically conductive filler preferably includes carbon nanotubes. Carbon nanotubes have high conductivity and can impart conductivity to the skeleton by adding a small amount, so that it is preferable from the viewpoint of obtaining suitable flexibility as a developer supply roller.

[0039] Carbon nanotubes include metallic conductive carbon nanotubes and semiconducting conductive carbon nanotubes. The carbon nanotubes in the electronically conductive filler more preferably contain metallic conductive carbon nanotubes. Carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes. The carbon nanotubes in the electronically conductive filler preferably contain single-walled carbon nanotubes. Single-walled carbon nanotubes are conductive and flexible, so they are more preferable because they can exhibit sufficient conductivity as the conductive layer of the electrophotographic roller while having appropriate hardness and flexibility.

[0040] The electronically conductive filler may further include a second electronically conductive filler different from the first electronically conductive filler. The second electronically conductive filler preferably includes at least one selected from the group consisting of carbon black, graphite, metal particles, and tin oxide.

[0041] The content of the electronically conductive filler in the conductive layer is preferably 0.001 to 15 mass%, more preferably 0.001 to 5 mass%. When a plurality of electronically conductive fillers are contained, the sum of the contents of the respective electronically conductive fillers (total content) is preferably within the above range. The content of the first electronically conductive filler in the conductive layer is preferably 0.01 to 0.8% by mass, and more preferably 0.001 to 0.05% by mass. When carbon nanotubes are contained as the secondary conductive filler, the content of the carbon nanotubes in the conductive layer is preferably 0.001 to 1 mass %, and more preferably 0.001 to 0.8 mass %. The content of the second electronically conductive filler in the conductive layer is preferably 0.001 to 1.0 mass%, more preferably 0.5 to 4.95 mass%. When the second electronically conductive filler contains two or more kinds of conductive fillers, the total content (total content) of the conductive fillers used as the second electronically conductive filler is preferably within the above range. By setting the content of the electronically conductive filler in the conductive layer within the above range, the absolute value of θ can be made smaller, and deterioration due to electrical conduction can be further suppressed.

[0042] The electronically conductive filler is preferably added as a dispersion in which the electronically conductive filler is dispersed in a solution. Examples of the solution include polyethylene glycol alkyl ether and aliphatic carboxylic acid derivatives. For example, a polyethylene glycol alkyl ether dispersion of carbon nanotubes and aliphatic carboxylic acid derivative dispersion of carbon nanotubes can be used. The dispersion preferably contains 5 to 15 mass % of the electronically conductive filler. By adding the electronically conductive filler as a dispersion, the conductive path of the electronically conductive filler is easily connected, and the absolute value of θ can be reduced. As a result, it is preferable because it is easier to suppress electrical deterioration. In addition, the electronically conductive filler and a dispersion of the electronically conductive filler may be used in combination.

[0043] <<<Polyurethane>>> Polyurethane is a reaction product of a polyol and a compound having an isocyanate group (isocyanate compound). The polyurethane is obtained by reacting a polyol with an isocyanate compound.

[0044] <<<<Polyol>>>> Examples of polyols that form polyurethane include polyester polyols, polyether polyols, acrylic polyols, polycarbonate polyols, polycaprolactone polyols, etc. Among these, it is preferable to use polyether polyols because the crosslinked urethane resin that is formed has sufficient flexibility.

[0045] Examples of polyether polyols include the following. Polyethylene glycol, polypropylene glycol, poly 1,4-butanediol, poly 1,5-pentanediol, polyneopentyl glycol, poly 3-methyl-1,5-pentanediol, poly 1,6-hexanediol, poly 1,8-octanediol, poly 1,9-nonanediol, etc. Among these, polypropylene glycol, poly 1,4-butanediol, poly 1,5-pentanediol, polyneopentyl glycol, poly 3-methyl-1,5-pentanediol, and poly 1,6-hexanediol are preferred from the viewpoint of suppressing the increase in hardness of the crosslinked urethane resin. The polyol preferably contains, for example, polyethylene propylene ether triol. For example, polyethylene propylene ether triol having a molecular weight of about 2000 to 6000 can be used. Examples of commercially available products that can be used include Actocol EP-550N (product name, manufactured by Mitsui Chemicals), Actocol EP-950P (product name, manufactured by Mitsui Chemicals), and Actocol EP-505S (product name, manufactured by Mitsui Chemicals).

[0046] Examples of polyester polyols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, and 1,6-hexane. polyester polyols obtained by condensation reaction of a diol component such as diol, 1,8-octanediol, 1,9-nonanediol, or a triol component such as trimethylolpropane with a dicarboxylic acid such as adipic acid, suberic acid, sebacic acid, phthalic anhydride, terephthalic acid, hexahydroxyphthalic acid, etc. Among these, polyester polyols obtained by condensation reaction of a diol component such as propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol with a dicarboxylic acid such as adipic acid, suberic acid, sebacic acid, etc. are preferred from the viewpoint of suppressing an increase in hardness of the crosslinked urethane resin.

[0047] Examples of polycaprolactone polyols include poly-ε-caprolactone and poly-γ-caprolactone. Examples of polycarbonate polyols include the following: polycarbonate polyols obtained by a condensation reaction with a diol component such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, or 1,9-nonanediol, a dialkyl carbonate such as phosgene or dimethyl carbonate, or a cyclic carbonate such as ethylene carbonate. Among these, from the viewpoint of suppressing an increase in hardness of the crosslinked urethane resin, polycarbonate polyols obtained by a condensation reaction with a diol component such as neopentyl glycol, 3-methyl-1,5-pentanediol, 1,5-pentanediol, 1,6-hexanediol, or 1,8-octanediol, or a dialkyl carbonate such as dimethyl carbonate are preferred.

[0048] These polyol components may be prepolymerized by chain extension with an isocyanate compound such as 2,4-tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), or isophorone diisocyanate (IPDI) as required. These polyols may be used alone or in combination of two or more. The polyol may be mixed with an electronically conductive filler and a foaming agent, foam stabilizer, and catalyst as described below as required, and added as a polyol mixture.

[0049] <<<<Isocyanate compounds>>>> The isocyanate compound has an isocyanate group. Although not particularly limited, examples thereof include the following: Aliphatic polyisocyanates such as ethylene diisocyanate and 1,6-hexamethylene diisocyanate (HDI); alicyclic polyisocyanates such as isophorone diisocyanate (IPDI), cyclohexane-1,3-diisocyanate and cyclohexane-1,4-diisocyanate; aromatic isocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), polymeric diphenylmethane diisocyanate, xylylene diisocyanate and naphthalene diisocyanate; and copolymers thereof, isocyanurates, TMP adducts, biuret bodies, block bodies thereof, etc. Among these, aromatic isocyanates such as tolylene diisocyanate and diphenylmethane diisocyanate are preferred.

[0050] The isocyanate compound may be used alone or in combination of two or more kinds. For example, the isocyanate compound is preferably a mixture containing tolylene diisocyanate and diphenylmethane diisocyanate. Examples of such an isocyanate compound include Cosmonate TM20 (trade name, manufactured by Mitsui Chemicals), Cosmonate TM50 (trade name, manufactured by Mitsui Chemicals), and the like. , manufactured by Mitsui Chemicals, Inc.) can be used. The polyol and the isocyanate compound are preferably mixed so that the ratio (molar ratio) of the isocyanate group contained in the isocyanate compound to 1.0 mole of the hydroxyl group contained in the polyol is in the range of 0.9 to 2.0. It is more preferable to mix so that the molar ratio is in the range of 0.95 to 1.05. If the mixing ratio is within the above range, it is possible to suppress the remaining of unreacted components after the reaction between the polyol and the isocyanate compound.

[0051] <<<<Dispersant>>>> The conductive layer may contain a dispersant. The dispersant is preferably a nonionic surfactant. By containing a dispersant in the conductive layer, the electronic conductive filler can be easily dispersed in the skeleton, and the conductive path between the electronic conductive fillers can be easily connected, which is preferable. In particular, when carbon nanotubes are used as the electronically conductive filler, it is preferable that the conductive layer contains a nonionic surfactant as a dispersant for dispersing the carbon nanotubes. By using a nonionic surfactant, the dispersibility of the carbon nanotubes in the polyurethane can be improved. A dispersant such as a nonionic surfactant contained in the conductive layer can be extracted from the conductive layer using a solvent such as acetone, methyl ethyl ketone, or tetrahydrofuran. The extracted nonionic surfactant is dissolved in a solvent such as deuterated chloroform or deuterated acetone, and analyzed by NMR (nuclear magnetic resonance) or GPC (gel permeation chromatography) to identify the type of dispersant contained in the conductive layer.

[0052] Cationic surfactants (ionic surfactants) are not preferred because they disrupt the conductive paths of the carbon nanotubes, resulting in a skeleton that is prone to electrical degradation, whereas nonionic surfactants disperse the carbon nanotubes in the skeleton and connect the conductive paths of the carbon nanotubes, making them less prone to electrical degradation and more preferred as dispersants.

[0053] The nonionic surfactant is not particularly limited, but examples thereof include the following: Block polymers of higher alcohols and polyethers, including polyalkylene glycol alkyl ethers; polyether adducts of nonylphenol; polymers of polyethers added to polyhydric alcohols; polymers of polyethers added to alkylamines, etc. The nonionic surfactant preferably contains a polyalkylene glycol alkyl ether. The polyethylene glycol alkyl ether may be, for example, polyethylene glycol monolauryl ether. The content of these nonionic surfactants in the skeleton is preferably equal to or greater than the content of carbon nanotubes in the skeleton. The content of the nonionic surfactant in the skeleton is preferably 1 to 10 times, more preferably 3 to 10 times, the content of carbon nanotubes in the skeleton.

[0054] <<<<Other additives>>>> The backbone may optionally contain a catalyst, a blowing agent, a foam stabilizer, and other additives, which may be premixed with the polyol and the electronically conductive filler and added as a polyol mixture. The catalyst is not particularly limited, and can be appropriately selected from various conventionally known catalysts. For example, amine catalysts (triethylenediamine, bis(dimethylaminoethyl)ether, N,N,N',N'-tetramethylhexanediamine, 1,8-diazabicyclo(5.4.0)undecene-7, 1,5-diazabicyclo(4.3.0)-5-nonene, 1,2-dimethylimidazole, N-ethylmorpholine, N-methylmorpholine, etc.), Organometallic catalysts (such as tin octylate, tin oleate, dibutyltin dilaurate, dibutyltin diacetate, tetra-i-propoxytitanium, tetra-n-butoxytitanium, tetrakis(2-ethylhexyloxy)titanium, etc.), and acid salt catalysts (such as carboxylates, formates, octylates, borates, etc.) in which the initial activity of the amine catalysts and organometallic catalysts is reduced are used. The catalysts may be used alone or in combination of two or more.

[0055] The foaming agent is not particularly limited, and can be appropriately selected from various foaming agents known in the art. In particular, water is preferably used as a foaming agent because it reacts with polyisocyanate to generate carbon dioxide gas. In addition, other foaming agents and water may be used in combination. For example, ion-exchanged water can be used as the foaming agent. The amount of the foaming agent added in the material for forming the conductive layer is preferably 0.5 to 3.0 parts by mass, more preferably 1.0 to 2.0 parts by mass. By setting the amount of the foaming agent added in the above range, the porosity of the conductive layer can be set in an appropriate range.

[0056] The foam stabilizer is not particularly limited, and may be appropriately selected from various conventionally known foam stabilizers. For example, a silicone foaming agent may be used. Other additives, such as crosslinking assistants, flame retardants, colorants, ultraviolet absorbers, and antioxidants, may be used as necessary within the scope that does not impair the effects of the present disclosure.

[0057] <Average elastic modulus of conductive layer> If the hardness of the conductive layer of the electrophotographic roller is too high, when the electrophotographic roller is used as a toner supply roller, the toner carrier roller in contact therewith may be scraped, causing scratches on the surface of the toner carrier roller. The conductive layer of the electrophotographic roller preferably has an average elastic modulus of 2000 MPa or less as measured using SPM. By setting the average elastic modulus of the conductive layer to 2000 MPa or less, the flexibility of the conductive layer, which is the outer surface of the electrophotographic roller, becomes appropriate, which is preferable because it makes it difficult to scrape the toner carrier roller.

[0058] The average elastic modulus of the conductive layer is preferably 1000 to 2000 MPa, and more preferably 1300 to 1800 MPa. The average elastic modulus of the conductive layer can be controlled, for example, by the type and amount of electronically conductive filler. For example, the average elastic modulus of the conductive layer can be reduced by including carbon nanotubes in the electronically conductive filler. In addition, the average elastic modulus of the conductive layer can be increased by increasing the amount of electronically conductive filler in the material forming the conductive layer.

[0059] <Method of forming conductive layer> The method for forming the conductive layer is not particularly limited. Methods that use a foaming agent, methods that incorporate air bubbles by mechanical stirring, etc. can be used. The foaming ratio may be appropriately determined and is not particularly limited.

[0060] For example, by adding a compound having an isocyanate group to a mixture of an electronically conductive filler and a polyol and mixing the mixture, the mixed composition is foamed and cured to form a conductive layer. That is, the method for producing an electrophotographic roller preferably includes a step of foaming and curing a composition containing the following materials to obtain a conductive layer. (1) Electronically conductive filler (2) Polyol (3) Isocyanate compounds (4) Foaming agent (5) Foaming agents (6) Catalyst

[0061] As described above, the polyol and the isocyanate compound are materials that form polyurethane. The electronically conductive filler and the polyol may be mixed in advance to form a polyol mixture. The polyol mixture may contain a foaming agent, a foaming agent, and a catalyst. That is, a polyol mixture containing the electronically conductive filler, the polyol, the foaming agent, the foaming agent, and the catalyst is mixed with an isocyanate compound, and the resulting composition is foamed and cured to obtain a conductive layer. The electrophotographic roller of the present disclosure can be easily produced since the conductive layer can be formed by the above reaction alone.

[0062] There is no particular restriction on the method of bonding the substrate and the conductive layer. A method of disposing the substrate in a mold in advance and casting and hardening the raw material composition as described above, or a method of forming the raw material composition into a predetermined shape to be the conductive layer in advance and then bonding it to the substrate can be used. In either method, other layers such as a conductive adhesive layer or an elastic layer may be provided between the substrate and the conductive layer as necessary.

[0063] In the case of the casting curing method, a release agent may be applied to the inner wall of the mold in advance. As the release agent, a known release agent can be used. For example, a water-based release agent containing an olefin component and a silicone component, or a release agent in which a fluorine component is dissolved in a fluorine-based solvent can be used. In order to easily form an opening on the outer surface of the conductive layer, it is preferable to use a water-based release agent containing an olefin component and a silicone component.

[0064] The method for forming the conductive layer is not particularly limited. For example, in addition to the above-mentioned method of casting into a mold of a predetermined shape, a method of cutting a block-state foam (so-called slab foam) to a predetermined size by cutting and then polishing it into a cylindrical shape, or a method of molding to a predetermined size by an extruder can be used.

[0065] <Developing device> FIG. 2A shows an example of a schematic cross-sectional view of the developing device 4. The developing device 4 includes at least a developing roller 5 and a developer supply roller 1 that supplies developer to the developing roller 5. Also, a voltage can be applied between the developing roller 5 and the developer supply roller 1. The developing device 4 has toner 8 as a developer, and has an electrophotographic roller used as the developer supply roller 1. That is, the developer supply roller is an electrophotographic roller. In addition, it is preferable that the developer supply roller is the above-mentioned specific electrophotographic roller. The developing device 4 includes a developing roller 5, which is a developing means, and a developing blade 6. The developing device 4 further includes a toner container 7, which is filled with toner 8. The toner 8 in the toner container 7 is supplied to the surface of the developing roller 5 by the developer supply roller 1, and a layer of toner 8 of a predetermined thickness is formed on the surface of the developing roller 5 by the developing blade 6.

[0066] <<Other components of the developing device>> The developing device is not particularly limited as long as it includes a developing roller and the above-mentioned specific developer supply roller 1. The developing device may include other components in addition to those described above. For example, the developing device may include a developing blade 6, a toner container 7, and a toner 8 as shown in FIG. 2A, and these may be conventionally known components.

[0067] <Process cartridge> Another aspect of the present disclosure provides a process cartridge that is detachably attached to the main body of an electrophotographic image forming apparatus and includes the electrophotographic roller. The process cartridge has a contact member that is electrically connected to an electrical contact of the main body of the electrophotographic image forming apparatus when the process cartridge is attached to the main body of the electrophotographic image forming apparatus. By connecting the developing roller and the developer supply roller, a voltage can be applied between them. The process cartridge preferably includes a developing device 4 having at least a photosensitive member, a developing roller for conveying toner to the surface of the photosensitive member, and a developer supply roller 1 for supplying developer to the developing roller.

[0068] Fig. 2B is a schematic cross-sectional view showing an example of a process cartridge. The process cartridge 9 is configured to be detachably attached to the main body (not shown) of an electrophotographic image forming apparatus. The process cartridge 9 also has a developing device 4, an electrophotographic photosensitive member 10, a cleaning blade 11 as cleaning means, a waste toner storage container 12, and a charging roller 13 as charging means. Here, the developing device 4 is the one shown in Fig. 2A, and has a developing roller and a developer supply roller. The developer supply roller is preferably the specific electrophotographic roller described above.

[0069] <Electrophotographic image forming apparatus> An electrophotographic image forming apparatus according to another embodiment of the present disclosure is an electrophotographic image forming apparatus including the above-mentioned electrophotographic roller. The electrophotographic image forming apparatus may be an electrophotographic image forming apparatus including the above-mentioned developing device 4. Fig. 3 is a schematic cross-sectional view showing an example of an electrophotographic image forming apparatus equipped with a contact type developing device using a one-component developer (toner). In Fig. 3, process cartridges 9 shown in Fig. 2B are prepared for each color of black (Bk), cyan (C), magenta (M), and yellow (Y), and each developing device 4 is filled with toner 8 of each color to enable color printing. The printing operation of the electrophotographic image forming apparatus will now be described.

[0070] The electrophotographic photoreceptor 10 rotates in the direction of the arrow shown in Fig. 3, and is uniformly charged by a charging roller 13 for charging the electrophotographic photoreceptor 10. Then, an electrostatic latent image is formed on the surface of the electrophotographic photoreceptor 10 by a laser beam 14, which is an exposure means. A developer supply roller 1 in a developing device 4 supplies toner 8 to a developing roller 5 arranged so as to contact the surface of the electrophotographic photoreceptor 10. As a result, the toner 8 is transferred to the surface of the electrophotographic photoreceptor 10, and the electrostatic latent image is visualized as a toner image (developed). The development is a so-called reversal development in which a toner image is formed on the exposed portion of the electrophotographic photoreceptor 10. The toner image formed on the electrophotographic photoreceptor 10 is transferred to paper 16, which is a recording medium, by a transfer roller 15, which is a transfer member. The paper 16 is fed into the device via a paper feed roller 17 and an adsorption roller 18, and is transported between the electrophotographic photoreceptor 10 and the transfer roller 15 by an endless belt-like transfer conveyor belt 19. The transfer conveyor belt 19 is driven by a driven roller 20, a driving roller 21, and a tension roller 22. A voltage is applied from a bias power source 23 to the developing roller 5, the developing blade 6, the developer supply roller 1, and the adsorption roller 18. The paper 16 to which the toner image has been transferred is fixed by a fixing device 24, and then discharged outside the device, and the printing operation is completed. On the other hand, the transfer residual toner remaining on the electrophotographic photoreceptor 10 without being transferred is scraped off by a cleaning blade 11, which is a cleaning member for cleaning the photoreceptor surface, and stored in a waste toner storage container 12. The cleaned electrophotographic photoreceptor 10 repeats the above printing operation.

[0071] The electrophotographic image forming apparatus may include, for example, a photoconductor, a developing roller for conveying toner to the surface of the photoconductor, a developer supply roller for supplying developer to the surface of the developing roller, and a cleaning roller for cleaning the photoconductor. It is preferable that the electrophotographic roller is the developer supply roller. EXAMPLES

[0072] The present disclosure will be described below with reference to examples and comparative examples, but the present disclosure is not limited to these examples. In the examples and comparative examples, "parts" refers to parts unless otherwise specified. In all cases, all data are by weight.

[0073] <<Evaluation method for electrophotographic rollers>> <<<Measuring method for phase delay θ>>> The value of θ was measured in an environment with a temperature of 23° C. and a relative humidity of 52%. As shown in FIG 8A, rollers 25 were attached to both ends of electrophotographic roller 1, and metal bearings 26 were used to press rollers 25 against each other to fix the electrophotographic roller in place. The electrophotographic roller 1 was brought into contact with a metal drum 27 that had been hard chrome plated with a surface roughness Ra of 1 μm or less, with a load of 4.9 N applied to one side. As shown in FIG. 8B, electrodes of an impedance analyzer 28 (SOLARTRON1260A / 1296: manufactured by Hokuto Denko Corporation) were connected to the shaft (end of the substrate) of the electrophotographic roller and the metal drum 27. A DC voltage of 50 V was applied to the impedance analyzer, and an AC voltage with an amplitude of 50 V and a frequency of 1.0 × 10 -1 ~1.0×10 5 The impedance phase delay θ was measured while changing the frequency between 1.0×10 -1 ~1.0×10 5 Five points were measured in each digit so that the measurement frequency interval was 1.58489 times the frequency of 1.0×10 -1 ~1.0×10 1 Among the values ​​of θ obtained within the Hz range, the maximum absolute value of θ (ie, the absolute value of θ when the phase lag is maximum) was defined as max|θ|, and was taken as the absolute value of the phase lag θ.

[0074] <<<Method for measuring the initial resistance of an electrophotographic roller>>> The initial resistance value of the electrophotographic roller was measured in an environment with a temperature of 23° C. and a relative humidity of 52%. As shown in FIG. 9A, the electrophotographic roller 1 was brought into contact with a metal drum 27. Rollers 25 were fitted to the ends of the substrate of the electrophotographic roller 1, both ends of the substrate were pressed with metal bearings 26, and a load of 4.9 N was applied to the metal drum on one side to bring the electrophotographic roller into contact. A power source 29, a resistor 30, and a voltmeter 31 were connected to the shaft (substrate end) of the electrophotographic roller and the metal drum 27 as shown in FIG. 9B. A voltage of 200 V was applied while rotating the metal drum at 30 rpm in the direction of the arrow in FIG. 9B, and the voltage from 2 seconds to 5 seconds after the start of voltage application was recorded at 100 Hz using a data logger (not shown) connected to the voltmeter 31, and the initial resistance value (Ω) of the electrophotographic roller was obtained from the average voltage.

[0075] <<<Evaluation method for electrical deterioration>> The electrophotographic roller whose initial resistance value was measured by the above-mentioned method was used, and the resistance value after rotating with current for 12 hours was measured using the same device as in the measurement of the initial resistance value, to evaluate the current degradation. In an environment with a temperature of 23°C and a relative humidity of 52%, the electrophotographic roller whose initial resistance value had been measured was brought into contact with a metal drum as shown in Fig. 9A. Rollers were fitted to the ends of the substrate, both ends of the substrate were pressed with metal bearings, and a load of 4.9 N was applied to one side of the metal drum to bring the electrophotographic roller into contact. A power source, resistor, and voltmeter were connected to the shaft of the electrophotographic roller (ends of the substrate) and the metal drum as shown in Fig. 9B. The metal drum was rotated at 30 rpm in the direction of the arrow in Fig. 9B, and was rotated with electricity for 12 hours while a voltage of 200 V was applied. The voltage was recorded at 100Hz from 2 to 5 seconds after the end of the energized rotation, and the resistance value (Ω) of the electrophotographic roller after energization was calculated from the average voltage. The ratio of the initial resistance value to the obtained resistance value after energization (resistance value after energization / initial resistance value) was taken as the resistance change rate and was evaluated as an index of degradation due to energization. The higher the resistance change rate, the larger the resistance value after energization for a long time, indicating that degradation due to energization has occurred.

[0076] <<<Porosity measurement method>>> The porosity of the conductive layer of the electrophotographic roller was measured using a three-dimensional measurement X-ray CT device (TDM1001-DD, manufactured by Yamato Scientific Co., Ltd.). The electrophotographic roller was cut into a cylindrical shape with a length of 10 mm together with the substrate, and a three-dimensional image was obtained using the above three-dimensional measurement X-ray CT device. The porosity was determined from the obtained three-dimensional image using the following formula (1). The measurement conditions are as follows. Target material: tungsten, filament material: tungsten, X-ray intensity: 100 kV. Porosity (volume %) = Volume of voids / (Volume of cylinder - Volume of substrate) (1)

[0077] <<<Measurement method of average elastic modulus using SPM>>> The cross-section of the conductive layer of the electrophotographic roller was cut into thin slices using a cryomicrotome (trade name: EMFC6, manufactured by Leica Microsystems) at -110°C using a diamond knife. Further, a measurement region with a size of 100 μm square and a depth of 100 μm from the surface of the thin slice was cut out to prepare a sample. The elastic modulus of the surface of the inner wall of the skeleton containing polyurethane as a binder was measured. For the measurement, an SPM device (trade name: MFP-3D-Origin, manufactured by Oxford Instruments) and a probe (trade name: AC160, manufactured by Olympus) were used. At this time, the force curve was measured 25 times in total at 5 points in the vertical direction × 5 points in the horizontal direction, and the arithmetic mean of 23 points excluding the maximum value and the minimum value was obtained, and the average elastic modulus was calculated using Hertz theory.

[0078] <<<Method for identifying each constituent component in the conductive layer>>> Dispersants such as nonionic surfactants contained in the conductive layer can be extracted from the conductive layer using a solvent such as acetone, methyl ethyl ketone, or tetrahydrofuran. The extracted nonionic surfactant is dissolved in a solvent such as deuterated chloroform or deuterated acetone, and the type of the dispersant contained in the conductive layer can be identified using NMR (nuclear magnetic resonance) or GPC (gel permeation chromatography). The electronically conductive filler contained in the conductive layer can be separated from the conductive layer by heating the conductive layer to 500°C in a nitrogen atmosphere to pyrolyze the binder resin. The residue after the pyrolysis is the electronically conductive filler contained in the conductive layer. The components of the electronically conductive filler separated from the conductive layer can be identified by various chemical analyses such as NMR (nuclear magnetic resonance).

[0079] <<<Method for measuring the content of electronic conductive filler in conductive layer>>> When determining the content of the electronically conductive filler in the conductive layer of the electrophotographic roller, the following method can be used. The conductive layer is cut out from the substrate, removed, and its mass is measured. It is then heated at 500°C in a nitrogen atmosphere to thermally decompose the binder resin. The conductive particle residue is then collected and its mass is measured. The content of the electronic conductive filler in the conductive layer is calculated as (mass of conductive particle residue / mass of conductive layer) x 100.

[0080] <<Electrophotographic roller materials>> The materials of the electrophotographic roller used are shown in Tables 1 and 2. [Table 1]

[0081] [Table 2]

[0082] Example 1 As shown in FIGS. 10A to 10C, a cylindrical member (pipe mold 35) with a release agent applied to the inner surface, a molding die 36 consisting of an upper bridge member 37 and a lower bridge member 34, and a base body 33 were prepared. The base 33 was made of iron (material name: SUM24) with an outer diameter of 5 mm and a length of 272 mm, which was electroless nickel plated. The molding die 36 was a cylindrical mold with a cavity inner diameter of 11.00 mm and a cavity length of 220 mm. The molding die 36, lower bridge member 34, and upper bridge member 37 were released using a release agent (product name: Frelease 690, manufactured by Neos Corporation). The release process was carried out after the molding die 36, lower bridge member 34, and upper bridge member 37 were preheated to 75°C.

[0083] The following materials (1), (2), and (3) were weighed into a container and mixed at 3,000 rpm for 20 minutes using a Homo Disper 2.5 model (manufactured by Primix Corporation). (1): First electronic conductive filler E-1: 0.5 parts by mass (2): Polyol P-1: 90.0 parts by mass (3): Polyol P-3: 10.0 parts by mass Furthermore, the following materials (4), (5), (6) and (7) were added to the container and mixed by stirring at 1500 rpm for 5 minutes using a Homo Disper 2.5 to obtain a polyol mixture. (4): Foaming agent W: 1.5 parts by mass (5): Foam stabilizer S-1: 0.4 parts by mass (6):Catalyst C-1: 1.0 parts by mass (7): Catalyst C-2: 0.5 parts by mass

[0084] 24.7 parts by mass of the isocyanate compound (N-1) was added to the polyol mixture, the liquid temperature was adjusted to 26°C, and the liquid was mixed and stirred in a casting machine to prepare a conductive layer forming material. The polyol mixture and the isocyanate compound were mixed immediately before being poured into the mold. 10A, 2.3 g of conductive layer forming material 32 was poured into a molding die 36 made of a lower bridge member 34 having a base 33 placed thereon and a pipe mold 35. The base and the lower bridge member had been preheated to 70°C.

[0085] The conductive layer-forming material was injected with the base in mold 36 at the top end position, tilted diagonally and shifted 3 mm from the center of the mold to the opposite side to the injection side (Fig. 10A). As shown in Fig. 10B, after the conductive layer-forming material was injected, upper bridge member 37, which had been preheated to 75°C, was fitted into mold 36, and heating was continued by bringing them into close contact with hot plate 38 incorporating heater 40, and heat curing was performed at 75°C for 8 minutes. During this heat curing, the foamed conductive layer forming material 39 expands in the mold, and when heating is completed, it spreads throughout the entire space in the mold as shown in Fig. 10C. The resin then hardens to form the conductive layer of the electrophotographic roller. After heat curing is completed, the upper and lower bridge members are removed, the mold is demolded, and the electrophotographic roller having the base and conductive layer is taken out. By the above method, the electrophotographic roller A-1 of Example 1 was formed.

[0086] (Examples 2 to 19, 38, 40 to 43, and 50 to 52) Except for changing the amount of the first electronically conductive filler, the type of polyol, the type and amount of isocyanate, and the amount of foaming agent as shown in Tables 3, 6, and 7, the electrophotographic rollers A-2 to A-19, 38, 40 to 43, and 50 to 52 of Examples 2 to 19, 38, 40 to 43, and 50 to 52 were obtained in the same manner as in the manufacturing method of the electrophotographic roller A-1. Table 3 shows the composition of the conductive layer forming materials used in the electrophotographic rollers A-1 to A-19. Table 6 shows the composition of the conductive layer forming materials used in the electrophotographic roller A-38. Table 7 shows the composition of the conductive layer forming materials used in the electrophotographic rollers A-40 to A-43 and A-50 to A-52. [Table 3]

[0087] Table 4 shows the physical properties and evaluation results of the electrophotographic rollers A-1 to A-19. [Table 4] In the table, max|θ| indicates the absolute value of the phase lag θ. The SPM hardness indicates the average elastic modulus measured using an SPM. For example, 8.01E+08 in the table indicates 8.01×10 8 This indicates that.

[0088] (Example 20) The following materials (1), (2), (3), and (4) were weighed into a container and mixed at 3,000 rpm for 20 minutes using a Homo Disper 2.5 model (manufactured by Primix Corporation). (1): First electronic conductive filler E-1: 0.01 part by mass (2): Second electronic conductive filler E-5: 0.5 parts by mass (3): Polyol P-1: 90.0 parts by mass (4): Polyol P-3: 10.0 parts by mass Furthermore, the following materials (5), (6), (7) and (8) were added to the container and mixed by stirring at 1500 rpm for 5 minutes using a Homo Disper 2.5 to obtain a polyol mixture. (5): Foaming agent W: 1.5 parts by mass (6): Foam stabilizer S-1: 0.4 parts by mass (7):Catalyst C-1: 1.0 parts by mass (8): Catalyst C-2: 0.5 parts by mass 24.7 parts by mass of an isocyanate compound (N-1) was added to the polyol mixture to obtain a conductive layer-forming material. The obtained conductive layer-forming material was molded in the same manner as the electrophotographic roller A-1 of Example 1 to obtain the electrophotographic roller A-20 of Example 20.

[0089] (Examples 21 to 31, 39, 44 to 49, 53 and 54) Except for changing the type and blending amount of the first electronically conductive filler and the type and blending amount of the second electronically conductive filler as shown in Tables 5 and 7, electrophotographic rollers A-21 to A-31, A-39, A-44 to A-49, A-53 and A-54 of Examples 21 to 31, 39, 44 to 49, 53 and 54 were formed in the same manner as in the manufacturing method of electrophotographic roller A-20.

[0090] Example 32 The following materials (1), (2), (3), and (4) were weighed into a container and mixed at 3,000 rpm for 20 minutes using a Homo Disper 2.5 model (manufactured by Primix Corporation). (1): First electronic conductive filler E-4: 0.005 parts by mass (2): Polyol P-1: 90.0 parts by mass (3): Polyol P-3: 10.0 parts by mass (4): Dispersant D-2: 0.045 parts by mass Furthermore, the following materials (5), (6), (7) and (8) were added to the container and mixed by stirring at 1500 rpm for 5 minutes using a Homo Disper 2.5 to obtain a polyol mixture. (5): Foaming agent W: 1.5 parts by mass (6): Foam stabilizer S-1: 0.4 parts by mass (7):Catalyst C-1: 1.0 parts by mass (8): Catalyst C-2: 0.5 parts by mass 24.7 parts by mass of an isocyanate compound (N-1) was added to the polyol mixture to obtain a conductive layer-forming material. The obtained conductive layer-forming material was molded in the same manner as the electrophotographic roller A-1 of Example 1 to obtain the electrophotographic roller A-32 of Example 32.

[0091] (Examples 33 and 34) Electrophotographic rollers A-33 and A-34 of Examples 33 and 34 were formed by changing the blending amount of the first electronically conductive filler and the blending amount of the dispersant from the electrophotographic roller A-32 of Example 32.

[0092] (Example 35) The following materials (1), (2), (3), (4), and (5) were weighed into a container and mixed at 3000 rpm for 20 minutes using a Homo Disper 2.5 model (manufactured by Primix Corporation). (1): First electronic conductive filler E-4: 0.05 parts by mass (2): Second electronic conductive filler E-5: 1.0 part by mass (3): Polyol P-1: 90.0 parts by mass (4): Polyol P-3: 10.0 parts by mass (5): Dispersant D-2: 0.45 parts by mass Furthermore, the following materials (6), (7), (8) and (9) were added to the container and mixed by stirring at 1500 rpm for 5 minutes using a Homo Disper 2.5 to obtain a polyol mixture. (6): Foaming agent W: 1.5 parts by mass (7): Foam stabilizer S-1: 0.4 parts by mass (8):Catalyst C-1: 1.0 parts by mass (9): Catalyst C-2: 0.5 parts by mass 24.7 parts by mass of an isocyanate compound (N-1) was added to the polyol mixture to obtain a conductive layer-forming material. The obtained conductive layer-forming material was molded in the same manner as the electrophotographic roller A-1 of Example 1 to obtain the electrophotographic roller A-35 of Example 35.

[0093] (Examples 36 and 37) Except for changing the type and blending amount of the first electronically conductive filler, the type and blending amount of the second electronically conductive filler, and the blending amount of the dispersant as shown in Table 5, the same manufacturing method as that of the electrophotographic roller A-35 was used to obtain electrophotographic rollers A-36 and A-37 of Examples 36 and 37. Table 5 shows the compositions of the conductive layer-forming materials used in the electrophotographic rollers A-20 to A-39. [Table 5]

[0094] Table 6 shows the physical properties and evaluation results of the electrophotographic rollers A20 to A-39. [Table 6]

[0095] (Comparative Examples 1 and 2) The following materials (1), (2), and (3) were weighed into a container and mixed at 3,000 rpm for 20 minutes using a Homo Disper 2.5 model (manufactured by Primix Corporation). (1): First electronic conductive filler I-1: 2.0 parts by mass (2): Polyol P-1: 90.0 parts by mass (3): Polyol P-3: 10.0 parts by mass Furthermore, the following materials (4), (5), (6) and (7) were added to the container and mixed by stirring at 1500 rpm for 5 minutes using a Homo Disper 2.5 to obtain a polyol mixture. (4): Foaming agent W: 1.5 parts by mass (5): Foam stabilizer S-1: 0.4 parts by mass (6):Catalyst C-1: 1.0 parts by mass (7): Catalyst C-2: 0.5 parts by mass 24.7 parts by mass of an isocyanate compound (N-1) was added to the polyol mixture to obtain a conductive layer-forming material. The obtained conductive layer-forming material was molded in the same manner as the electrophotographic roller A-1 of Example 1 to obtain the electrophotographic roller B-1 of Comparative Example 1. In addition, the type and amount of the first electroconductive filler were changed from those of the electrophotographic roller B-1 of Comparative Example 1 to obtain the electrophotographic roller B-2 of Comparative Example 2.

[0096] (Comparative Examples 3 and 4) The following materials (1), (2), (3), and (4) were weighed into a container and mixed at 3,000 rpm for 20 minutes using a Homo Disper 2.5 model (manufactured by Primix Corporation). (1): First electronic conductive filler E-9: 1.0 part by mass (2): Polyol P-1: 90.0 parts by mass (3): Polyol P-3: 10.0 parts by mass (4): Dispersant D-1: 6.0 parts by mass Furthermore, the following materials (5), (6), (7) and (8) were added to the container and mixed by stirring at 1500 rpm for 5 minutes using a Homo Disper 2.5 to obtain a polyol mixture. (5): Foaming agent W: 1.5 parts by mass (6): Foam stabilizer S-1: 0.4 parts by mass (7):Catalyst C-1: 1.0 parts by mass (8): Catalyst C-2: 0.5 parts by mass 24.7 parts by mass of an isocyanate compound (N-1) was added to the polyol mixture to obtain a conductive layer-forming material. The obtained conductive layer-forming material was molded in the same manner as the electrophotographic roller A-1 of Example 1 to obtain the electrophotographic roller B-3 of Comparative Example 3. Moreover, the electrophotographic roller B-4 of Comparative Example 4 was obtained by changing the blending amount of the first electronically conductive filler from that of the electrophotographic roller B-3 of Comparative Example 3.

[0097] Table 7 shows the compositions of the conductive layer-forming materials used in the electrophotographic rollers A-40 to A-54 and B-1 to B-4. [Table 7]

[0098] Table 8 shows the physical properties and evaluation results of the electrophotographic rollers A-40 to A-54 and B-1 to B-4. [Table 8]

[0099] From the evaluation results of the examples, it was confirmed that the absolute value of the phase lag θ of the electrophotographic roller of the present disclosure when an AC voltage of 50 V peak-to-peak voltage in the frequency range of 0.1 to 10 Hz is applied is 10 degrees or less, and therefore the rate of resistance change is small and electrical deterioration is unlikely to occur even when a high voltage is applied for a very long period of time to perform electrical idle rotation. It was also confirmed that if the absolute value of the phase lag θ is 5 degrees or less, the rate of resistance change when a high voltage is applied for a very long period of time and idle rotation is performed with current flowing, can be further reduced.

[0100] The electrophotographic rollers of Examples 1 to 19 contain carbon nanotubes as a conductive filler, and are produced by changing the blending amount of carbon nanotubes, the types and blending amounts of polyol and isocyanate (ratio of hydroxyl groups to isocyanate groups in the polyol), and the added amount of foaming agent. The absolute value of the phase lag θ of all the electrophotographic rollers of Examples 1 to 19 was 10 degrees or less, and degradation due to electrical current was suppressed.

[0101] The electrophotographic rollers of Examples 20 to 31, 38 and 39 were produced by changing the type, blending amount and combination of the electroconductive filler. The electrophotographic rollers of Examples 20 to 31, 38 and 39 all had an absolute value of phase lag θ of 10 degrees or less, and electrical deterioration was suppressed. In particular, it was confirmed that increasing the blending amount of carbon nanotubes reduces the absolute value of phase lag θ, and electrical deterioration can be further suppressed.

[0102] The electrophotographic rollers of Examples 32 to 37 were produced by changing the blending amount of nonionic surfactant (dispersant). The electrophotographic rollers of Examples 32 to 37 all had an absolute value of phase lag θ of 10 degrees or less, and deterioration due to electrical current was suppressed. When a dispersant was used, the absolute value of the phase lag θ became smaller than 5 degrees, and an electrophotographic roller in which electrical deterioration was further suppressed was obtained. Furthermore, it was confirmed that when the blending amount of the nonionic surfactant was three times or more the blending amount of the carbon nanotubes, the absolute value of the phase lag θ became smaller, and electrical deterioration was further suppressed.

[0103] On the other hand, the electrophotographic rollers of Comparative Examples 1 and 2 use an ionically conductive filler. Therefore, the absolute value of the phase lag θ exceeds 10 degrees, and the resistance change rate is very high. In other words, it was confirmed that degradation due to electrical current had occurred. In the electrophotographic rollers of Comparative Examples 3 and 4, an ionic surfactant is used to disperse the electronically conductive filler (carbon nanotubes). Therefore, it was confirmed that the absolute value of the phase lag θ exceeds 10 degrees and the electrical deterioration is also large.

[0104] The present disclosure includes the following configurations. (Configuration 1) A substrate having a conductive surface; a conductive layer on said surface of said substrate, The conductive layer is a surface layer of the electrophotographic roller, A backbone including a polyurethane as a binder and an electronically conductive filler in the polyurethane, The conductive layer has at least one void, and At least a part of the inner wall of the void is composed of the skeleton, an electrophotographic roller characterized in that when an electrode is brought into contact with an outer surface of the conductive layer and an AC voltage of 50 V peak-to-peak and in a frequency range of 0.1 to 10 Hz is applied between the electrode and the surface of the substrate, the absolute value of a phase lag θ of AC impedance with respect to the AC voltage is 10 degrees or less. (Configuration 2) 2. The electrophotographic roller according to configuration 1, wherein the absolute value of θ is 5 degrees or less. (Configuration 3) 3. The electrophotographic roller according to Configuration 1 or 2, wherein the content of the electronically conductive filler in the conductive layer is 0.001 to 5% by mass. (Configuration 4) 4. The electrophotographic roller according to any one of configurations 1 to 3, wherein the electronically conductive filler comprises carbon nanotubes as a first electronically conductive filler. (Configuration 5) 5. The electrophotographic roller according to configuration 4, wherein the conductive layer has a content of the carbon nanotubes of 0.001 to 0.8% by mass. (Configuration 6) the electronically conductive filler comprises a second electronically conductive filler different from the first electronically conductive filler; 5. The electrophotographic roller according to claim 4, wherein the second electronically conductive filler comprises at least one selected from the group consisting of carbon black, graphite, metal particles, and tin oxide. (Configuration 7) the content of the first electronically conductive filler in the conductive layer is 0.01 to 0.8% by mass; 7. The electrophotographic roller according to Configuration 6, wherein the content of the second electronically conductive filler in the conductive layer is 0.001 to 1.0% by mass. (Configuration 8) the content of the first electronically conductive filler in the conductive layer is 0.001 to 0.05% by mass, 7. The electrophotographic roller according to Configuration 6, wherein the content of the second electronically conductive filler in the conductive layer is 0.5 to 4.95% by mass. (Configuration 9) 9. The electrophotographic roller according to any one of Configurations 1 to 8, wherein the conductive layer further contains a nonionic surfactant. (Configuration 10) The nonionic surfactant comprises a polyalkylene glycol alkyl ether. 10. The electrophotographic roller according to claim 9. (Configuration 11) 11. The electrophotographic roller according to any one of configurations 1 to 10, wherein the average elastic modulus of the surface of the inner wall measured with an SPM is 2000 MPa or less. (Configuration 12) 12. The electrophotographic roller according to any one of claims 1 to 11, wherein the conductive layer has a porosity of 50 to 97% by volume. (Configuration 13) 12. The electrophotographic roller according to any one of configurations 1 to 11, wherein the conductive layer has a porosity of 70 to 90% by volume. (Configuration 14) 14. The electrophotographic roller according to any one of claims 1 to 13, wherein the conductive layer is a foam layer. (Configuration 15) A developing device including at least a developing roller and a developer supply roller that supplies a developer to the developing roller, A voltage can be applied between the developing roller and the developer supply roller, 15. A developing device, wherein the developer supply roller is the electrophotographic roller according to any one of Configurations 1 to 14. (Configuration 16) 16. An electrophotographic image forming apparatus comprising the developing device according to configuration 15. (Configuration 17) A process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, the process cartridge has a contact member which is electrically connected to an electrical contact of the main body when the process cartridge is mounted in the main body; The process cartridge includes a developing roller and a developer supply roller for supplying developer to the developing roller. a voltage can be applied between the developing roller and the developer supply roller by electrical connection with the main body; 15. A process cartridge, wherein the developer supply roller is an electrophotographic roller according to any one of Configurations 1 to 14. [Explanation of symbols]

[0105] 1 electrophotographic roller, 2 core metal, 3 conductive layer, 4 developing device, 5 developing roller, 9 process cartridge, 13 charging roller

Claims

1. A substrate having a conductive surface, An electrophotographic roller having a conductive layer on the surface of the substrate, The conductive layer is This is the surface layer of the electrophotographic roller, It has a framework comprising polyurethane as a binder and an electronically conductive filler in the polyurethane, The conductive layer has at least one void, At least a portion of the inner wall of the void is composed of the framework, An electrophotographic roller characterized in that, when an electrode is brought into contact with the outer surface of the conductive layer, and an AC voltage with a peak-to-peak voltage of 50 V in the frequency range of 0.1 to 10 Hz is applied between the electrode and the surface of the substrate, the absolute value of the phase lag θ of the AC impedance with respect to the AC voltage is 10 degrees or less.

2. The electrophotographic roller according to claim 1, wherein the absolute value of θ is 5 degrees or less.

3. The electrophotographic roller according to claim 1, wherein the content of the electronically conductive filler in the conductive layer is 0.001 to 5% by mass.

4. The electrophotographic roller according to claim 1, wherein the electronically conductive filler includes a carbon nanotube as a first electronically conductive filler.

5. The electrophotographic roller according to claim 4, wherein the content of carbon nanotubes in the conductive layer is 0.001 to 0.8% by mass.

6. The electronically conductive filler includes a second electronically conductive filler that is different from the first electronically conductive filler. The electrophotographic roller according to claim 4, wherein the second electronically conductive filler comprises at least one selected from the group consisting of carbon black, graphite, metal fine particles, and tin oxide.

7. The content of the first electronically conductive filler in the conductive layer is 0.01 to 0.8% by mass. The electrophotographic roller according to claim 6, wherein the content of the second electronically conductive filler in the conductive layer is 0.001 to 1.0% by mass.

8. The content of the first electronically conductive filler in the conductive layer is 0.001 to 0.05% by mass. The electrophotographic roller according to claim 6, wherein the content of the second electronically conductive filler in the conductive layer is 0.5 to 4.95% by mass.

9. The electrophotographic roller according to claim 1, wherein the conductive layer further comprises a nonionic surfactant.

10. The electrophotographic roller according to claim 9, wherein the nonionic surfactant comprises a polyalkylene glycol alkyl ether.

11. The electrophotographic roller according to claim 1, wherein the average modulus of elasticity measured using SPM on the surface of the inner wall is 2000 MPa or less.

12. The electrophotographic roller according to claim 1, wherein the porosity of the conductive layer is 50 to 97 volume percent.

13. The electrophotographic roller according to claim 1, wherein the porosity of the conductive layer is 70 to 90 volume percent.

14. The electrophotographic roller according to claim 1, wherein the conductive layer is a foamed layer.

15. The electrophotographic roller according to claim 1, which is a developer supply roller.

16. The electrophotographic roller according to claim 1, wherein the polyurethane is foamed polyurethane.

17. A developing apparatus comprising at least a developing roller and a developing agent supply roller for supplying a developing agent to the developing roller, The developing roller and the developer supply roller are configured to allow voltage to be applied between them. The developing apparatus is characterized in that the developer supply roller is an electrophotographic roller according to any one of claims 1 to 16.

18. An electrophotographic image forming apparatus characterized by comprising the developing apparatus described in claim 17.

19. A process cartridge that can be attached to and detached from the main body of an electrophotographic image forming apparatus, The process cartridge has a contact member that, when installed in the main body, is electrically connected to the electrical contacts of the main body. The process cartridge comprises a developing roller and a developing roller that supplies developing agent to the developing roller. The developing roller and the developer supply roller are configured to allow voltage to be applied through an electrical connection to the main body. A process cartridge characterized in that the developer supply roller is an electrophotographic roller according to any one of claims 1 to 16.

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