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

Abstract

The invention relates to an electrophotographic roller, a developing apparatus, an electrophotographic image forming apparatus, and a process cartridge. The electrophotographic roller includes a substrate having an electrically conductive surface and an electrically conductive layer on the surface of the substrate, in which the electrically conductive layer is a surface layer of the electrophotographic roller and has a skeleton including a polyurethane and an electronically conductive filler in the polyurethane, the electrically conductive layer includes at least one void, at least a portion of an inner wall of the void is constituted by the skeleton, and the electrically conductive layer is formed on the surface of the substrate. And when the electrode is in contact with the outer surface of the conductive layer and an alternating current voltage having a peak-to-peak voltage of 50 V is applied between the electrode and the surface of the base body in a frequency range of 0.1 to 10 Hz, the absolute value of the phase delay theta of the alternating current impedance with respect to the alternating current voltage is 10 degrees or less.

Description

Technical Field

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

[0002] In an electrophotographic image forming apparatus (a copy machine, a fax machine, or a printer, etc. using an electrophotographic scheme; hereinafter, also referred to as an "image forming apparatus"), a toner is stably charged using an electrophotographic roller that performs toner supply (hereinafter, also referred to as a "toner supply roller"), the toner is supplied to a developing roller, and then developed, thereby obtaining an image on an electrophotographic photosensitive member. In order to stably charge the toner, an elastic roller having voids on the surface and having conductivity is used as the electrophotographic roller. Japanese Patent Application Laid-Open No. 2004-101958 discloses a conductive member having an elastic layer made of foam rubber into which carbon nanotubes are introduced.

[0003] In addition, Japanese Patent Application Laid-Open No. 2009-139866 discloses a conductive roller comprising a substrate made of soft polyurethane foam and a conductive coating, wherein the substrate is formed of a skeleton and a cell film, the conductive coating is provided on at least a portion of each surface of the skeleton and the cell film, and the conductive coating comprises a conductive polyurethane foam containing carbon nanotubes and a conductive foamed layer made of conductive polyurethane foam on a peripheral surface of a core metal.

[0004] An image forming apparatus capable of forming an excellent electrophotographic image that is stable even under a severe environment is required. Meanwhile, a conductive electrophotographic roller used in an image forming apparatus is required to have a resistance that is unlikely to change even if power is applied for a long time.

[0005] According to the research of the present inventors, when used as a toner supply roller, the conductive member according to Japanese Patent Application Laid-Open No. 2004-101958 tends to increase the resistance of the electrophotographic roller by long-term energization. In addition, the conductive roller according to Japanese Patent Application Laid-Open No. 2009-139866 is disadvantageous in terms of cost because the conductive coating is formed on the surface of the skeleton and the cell membrane by dip coating and the manufacturing steps are many. Summary of the invention

[0006] At least one aspect of the present disclosure is directed to providing an electrophotographic roller that exhibits little change in resistance even when powered on for a long time and that can be manufactured at low cost. In addition, at least one aspect of the present disclosure is directed to providing a developing device that can help develop an electrophotographic image stably with high quality. In addition, at least one aspect of the present disclosure is directed to providing an electrophotographic image forming device that can stably output an electrophotographic image with high quality. In addition, at least one aspect of the present disclosure is directed to providing a processing box that can help stabilize the output of an electrophotographic image with high quality.

[0007] At least one aspect of the present disclosure is directed to an electrophotographic roller comprising:

[0008] a substrate having a conductive surface; and

[0009] A conductive layer on the surface of the substrate, wherein

[0010] The conductive layer is the surface layer of the electrophotographic roller, and

[0011] The conductive layer has a skeleton comprising polyurethane as a binder and an electronically conductive filler in the polyurethane,

[0012] The conductive layer includes at least one void,

[0013] At least a portion of the inner wall of the void is formed of a skeleton, and

[0014] When an electrode is brought into contact with the outer surface of the conductive layer and an AC voltage of 50 V is applied between the electrode and the surface of the substrate in a frequency range of 0.1 Hz to 10 Hz, the absolute value of the phase delay θ of the AC impedance with respect to the AC voltage is less than 10 degrees.

[0015] At least one aspect of the present disclosure is to provide a developing device, which at least includes:

[0016] a developer roller; and

[0017] a developer supplying roller for supplying developer to the developing roller, wherein

[0018] The developing device is configured so that a voltage can be applied between the developing roller and the developer supplying roller, and

[0019] The developer supply roller is the above-mentioned electrophotographic roller.

[0020] At least one aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus including the above-mentioned developing apparatus.

[0021] At least one aspect of the present disclosure is directed to providing a process cartridge that is detachably mounted from a main body of an electrophotographic image forming apparatus,

[0022] Processing box includes:

[0023] a contact member electrically connected to an electrical contact of the main body when the process cartridge is mounted to the main body;

[0024] a developer roller; and

[0025] a developer supplying roller for supplying developer to the developing roller,

[0026] The process cartridge is configured so that a voltage can be applied between the developing roller and the developer supplying roller through an electrical connection with the main body, and

[0027] The developer supply roller is the above-mentioned electrophotographic roller.

[0028] According to at least one aspect of the present disclosure, an electronic photographic roller can be obtained that has a small change in on-resistance even for a long time and can be manufactured at low cost. In addition, according to at least one aspect of the present disclosure, a developing device that can help to stably develop an electronic photographic image with high quality can be obtained. In addition, according to at least one aspect of the present disclosure, an electronic photographic image forming device that can stably output an electronic photographic image with high quality can be obtained. In addition, according to at least one aspect of the present disclosure, a processing box that can help to stably output an electronic photographic image with high quality can be obtained.

[0029] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1A and Figure 1B are a schematic cross-sectional view and a schematic perspective view of an electrophotographic roller;

[0031] Figure 2A and Figure 2B is a schematic cross-sectional view of a developing device and a process cartridge;

[0032] Figure 3 is a schematic configuration diagram showing an electrophotographic image forming apparatus;

[0033] Figure 4 is a schematic diagram showing an RC parallel circuit;

[0034] Figure 5 is a schematic diagram showing the relationship between an applied voltage V, a current I flowing through an RC parallel circuit, and a phase delay θ;

[0035] Figure 6 is a schematic diagram showing a polar coordinate display of θ;

[0036] Figure 7 is a schematic diagram showing the frequency dependence of θ;

[0037] Fig. 8A and Figure 8B is a schematic diagram showing a method of measuring θ using an impedance analyzer;

[0038] Fig.9A and Fig. 9B is a schematic diagram showing a method of measuring power-on degradation; and

[0039] FIG. 10A to FIG. 10C is a schematic cross-sectional view illustrating a method of forming a conductive layer of an electrophotographic roller. DETAILED DESCRIPTION

[0040] In the present disclosure, unless otherwise specified, the expression "from XX to YY" or "XX to YY (XX~YY)" indicating a numerical range refers to a numerical range including a lower limit and an upper limit as endpoints. In addition, when a numerical range is described in a segmented manner, the upper limit and the lower limit of each numerical range can be arbitrarily combined. In addition, in the present disclosure, for example, an expression such as "at least one selected from the group consisting of XX, YY and ZZ" refers to any one of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, and a combination of XX, YY and ZZ.

[0041] As described above, in the conductive roller according to Japanese Patent Application Laid-Open No. 2004-101958, when it is used for image formation for a long time as a toner supply roller, the resistance may change. The inventors infer the reason as follows. In other words, in the conductive roller according to Japanese Patent Application Laid-Open No. 2004-101958, the foam rubber as the elastic layer is formed by mixing bubbles into a composition mixed with 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 above composition, the carbon nanotubes are dispersed in the rubber latex as emulsion particles surrounded by a surfactant. Therefore, the carbon nanotubes are present in each emulsion particle in the foam rubber after vulcanization, and it is believed that the ionic components responsible for transporting the charges present in the rubber and the surfactant are sandwiched between the carbon nanotubes.

[0042] Furthermore, it is considered that once a voltage is applied to the electrophotographic roller for a long period of time, the resistance will change due to the deterioration of the rubber sandwiched between the carbon nanotubes and the polarization of the ion components.

[0043] The present inventors have conducted research to obtain an electrophotographic roller having a simpler structure and a small change in resistance even when used for a long time. As a result, the present inventors have found that an electrophotographic roller having the following structure can contribute to the achievement of the above-mentioned object.

[0044] The electrophotographic roller includes a substrate having a conductive surface and a conductive layer on the substrate surface. The conductive layer is a surface layer of the electrophotographic roller and has a skeleton containing polyurethane as a binder and an electronically conductive filler in the polyurethane. The conductive layer includes at least one void, and at least a portion 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 with a peak-to-peak voltage of 50 V is applied between the electrode and the surface of the substrate in a frequency range of 0.1 Hz to 10 Hz, the absolute value of the phase delay θ of the AC impedance relative to the AC voltage is 10 degrees or less.

[0045] The electrophotographic roller includes a substrate having a conductive surface and a conductive layer on the outer peripheral surface of the substrate. The conductive layer is the surface layer of the electrophotographic roller.

[0046] When an electrode is brought into contact with the outer surface of the conductive layer and an AC voltage of 50 V is applied between the electrode and the conductive outer surface of the substrate in a frequency range of 0.1 Hz to 10 Hz, the absolute value of the phase delay θ of the AC impedance with respect to the AC voltage is 10.0 degrees or less.

[0047] The reason why the peak-to-peak voltage is set to 50 V is to be compatible with a voltage to be applied when the electrophotographic roller is actually used in an electrophotographic apparatus.

[0048] In addition, the frequency range of the applied AC voltage is set to 0.1 Hz to 10 Hz because the measurement accuracy of θ is high, the influence of the capacitance component caused by the interface between the surface of the electronic conductive filler and the polyurethane can be reduced to a negligible level, and the absolute value of θ is well correlated with the change trend of the resistance by power supply. In other words, by applying an AC voltage with a peak-to-peak voltage of 50 V in the frequency range of 0.1 Hz to 10 Hz, the absolute value of θ can be accurately measured under conditions corresponding to the state of actual use of the electrophotographic roller.

[0049] The absolute value of θ is preferably 5.0 degrees or less, and more preferably 3.0 degrees or less. In other words, θ is -10.0 degrees to 10.0 degrees, preferably -5.0 degrees to 5.0 degrees, and more preferably -3.0 degrees to 3.0 degrees.

[0050] The impedance of the electrophotographic roller according to the present disclosure can be given by Figure 4 The current flowing through the electronic photographic roller is I flowing through the resistance component R relative to the applied AC voltage. R and I flowing through the capacitive component C C The sum of I R+C I R It is in I R+C The component in phase with the applied voltage, I CIt is the component that is 90° phase delayed relative to the applied voltage.

[0051] If the graph shows the applied voltage or current (relative value) on the vertical axis and the phase on the horizontal axis, the steady-state I R+C and applied voltage V, then Figure 5 That means. R+C The phase of is delayed by an angle θ relative to the applied voltage V. In addition, when expressed in polar coordinates, it can be expressed as Figure 6 When the applied voltage V is represented by the horizontal axis, the current component I R and the capacitive component current I whose phase is delayed by 90° relative to the applied voltage V C The resultant vector is I R+C , and I R+C The angle formed with the horizontal axis is the phase delay θ of the AC impedance.

[0052] Figure 7 A graph comparing the relationship between θ and frequency of an electrophotographic roller according to the present disclosure and an electrophotographic roller of the prior art is shown. In the electrophotographic roller according to the present disclosure, θ satisfies -10≤θ≤10 in the frequency range of 0.1 Hz to 10 Hz (1.0E-01 Hz to 1.0E+01 Hz). In other words, the absolute value of the phase delay 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 region of 0.1 Hz to 10 Hz.

[0053] The fact that the absolute value of θ is small indicates that I R+C The component in phase with the applied voltage (I R ) is large, and the phase is delayed by 90° relative to the applied voltage (I C In other words, the amount of the electronic conductivity current component attributable to the current proportional to the applied voltage is large, while the amount of the ionic conductivity current component is small.

[0054] In the case of considering the deterioration caused by power-on, the change of the electronic conductivity current component is small even after long-term power-on, while the ionic conductivity current component gradually decreases due to the movement and polarization of ions during the long-term power-on. Therefore, as a characteristic of the electrophotographic roller capable of suppressing the deterioration caused by power-on, the amount of the ionic conductivity current component is preferably small. In other words, by controlling in such a way that θ becomes small, an electrophotographic roller having a small ionic conductivity current component and not easily causing power-on deterioration can be obtained.

[0055] In addition, since the potential difference between the electrodes is constant, the current change when the DC voltage is continuously applied will not be repeated cyclically, and the change can be regarded as the current change when the limit is taken in the direction of frequency zero. Therefore, if the absolute value of θ is small in the low frequency region (frequency region of 0.1 Hz to 10 Hz), the amount of the ionic conductivity current component is small, and the power-on degradation can be reduced.

[0056] The inventors of the present application discovered, based on the above-mentioned reasons, that when a developing member is brought into contact with the outer surface of the conductive layer of an electronic photographic roller and an AC voltage with a peak-to-peak voltage of 50 V is applied between the developing member and the conductive layer in a frequency range of 0.1 Hz to 10 Hz, by setting the absolute value of the phase delay θ of the AC impedance relative to the AC voltage to less than 10 degrees, an electronic photographic roller with little power-on degradation can be obtained even when it is used for a long period of time, and the present invention was designed accordingly.

[0057] As a specific method for reducing the absolute value of θ in the frequency range of 0.1 Hz to 10 Hz, it is preferable to increase the proportion of the electron conductive current component in the conductive layer and reduce the proportion of the ion conductive current component.

[0058] For example, the absolute value of θ in the frequency range of 0.1 Hz to 10 Hz can be reduced by changing the type of the electronically conductive filler, increasing the content of the electronically conductive filler in the conductive layer, or forming the conductive layer while foaming with an increased porosity of the conductive layer.

[0059] In other words, by adopting a structure in which conductive material sheets are arranged in contact with each other inside the skeleton as described below, the capacitance component caused by interface polarization between electron conductive filler particles is reduced, thereby forming a conductive path and reducing the absolute value of θ in the frequency region of 0.1 Hz to 10 Hz.

[0060] In order to increase the medium resistance area (10 5 ~10 9 The ratio of the electronic conductive current component in θ (Ω·cm) requires a conductive path connected to the electronic conductive filler. Although if a large amount of electronic conductive filler is added, the conductive path is connected and works in the direction of decreasing the absolute value of θ, on the other hand, since the addition of the electronic conductive filler makes the conductive layer hard, it is not suitable as an electrophotographic roller that requires flexibility.

[0061] In other words, there is a problem of obtaining an electrophotographic roller having appropriate hardness and flexibility as the electrophotographic roller while increasing the proportion of the electron conductive current component by increasing the amount of the electron conductive filler added.

[0062] The present inventors have found through intensive research that, by including a conductive layer of carbon nanotubes, the absolute value of θ in the frequency region of 0.1 Hz to 10 Hz can be reduced, and the deterioration caused by power-on can be suppressed, while the appropriate flexibility for the electrophotographic roller can be exhibited. More specifically, by using a nonionic surfactant to improve the dispersibility of carbon nanotubes in polyurethane, an electrophotographic roller that can further reduce θ and thus further reduce the deterioration caused by power-on and exhibits appropriate hardness can be obtained as an electrophotographic roller.

[0063] Electrophotographic roller

[0064] Figure 1A A schematic cross-sectional view showing an electrophotographic roller, and Figure 1B A schematic perspective view of an electrophotographic roller is shown. 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 supplying roller of an electrophotographic image forming apparatus.

[0065] The conductive layer is a surface layer of the electrophotographic roller and has a skeleton comprising polyurethane and an electronically conductive filler in the polyurethane. The polyurethane is used as a binder resin for the conductive layer. The conductive layer includes at least one void. The polyurethane may be a foamed polyurethane. In other words, the conductive layer may be a foamed layer.

[0066] Note that the layer configuration of the electrophotographic roller 1 is not limited to the configuration including only the substrate 2 and the conductive layer 3 , and may also include other layers such as a conductive elastic layer between the substrate 2 and the conductive layer 3 .

[0067] Hereinafter, the configuration of the electrophotographic roller will be described in detail.

[0068] Matrix

[0069] The substrate 2 has a conductive surface, and serves as a supporting member and an electrode of the electrophotographic roller.

[0070] The substrate is composed of, for example, a metal or alloy such as aluminum, copper alloy, or stainless steel; iron plated with chromium or nickel; and a conductive material such as a synthetic resin having conductivity. For example, the substrate may be a core metal. The substrate has, for example, a solid columnar shape or a hollow cylindrical shape.

[0071] Conductive layer

[0072] The conductive layer is formed on the outer peripheral surface of the substrate. The conductive layer is the surface layer of the electrophotographic roller.

[0073] The conductive layer 3 has a skeleton containing polyurethane as a binder and an electronically conductive filler in the polyurethane. The conductive layer includes at least one void. The void in the conductive layer accommodates the toner inside the conductive layer, and the toner is uniformly supplied to the surface of the developer roller (developing member) in the developer supply roller. In other words, the electrophotographic roller can be used as a developer supply roller.

[0074] Gap

[0075] The conductive layer includes at least one void. Although the shape of the void is not particularly limited, for example, a void that opens from the outer surface of the conductive layer and extends along the thickness direction of the conductive layer is exemplified. The void may be a through hole or a non-through hole.

[0076] In addition, the voids may be formed individually, or in other examples, a plurality of voids may be formed in a foamed (continuous foamed) state that is combined with each other. In other words, the conductive layer may be a porous form including a large number of voids. The conductive layer preferably includes a plurality of voids, and the voids are preferably formed in a continuous foamed state.

[0077] At least a portion of the inner wall of each void is preferably formed of a skeleton comprising polyurethane and an electronically conductive filler in the polyurethane. The inner wall of the void is preferably formed of a skeleton. The inner wall of the void is preferably formed of polyurethane and an electronically conductive filler in the polyurethane.

[0078] The porosity as the volume fraction of the voids in the conductive layer is preferably 50 volume % to 97 volume %. If the porosity is within the above range, the electrophotographic roller can store the toner appropriately, which is preferred. In addition, by increasing the porosity, the conductive paths between the electron conductive filler particles forming the inner wall of the void are more easily connected, and the proportion of the electron conductive current component can be increased. As a result, θ can be reduced and deterioration due to power-on can be suppressed, which is preferred. The porosity can be measured by the method described later.

[0079] The porosity of the conductive layer is more preferably 60% to 95% by volume, and further preferably 70% to 90% by volume. By foaming the material during the manufacturing process of the conductive layer, voids are formed in the conductive layer. The porosity can be controlled by the type and amount of the foaming agent. Specifically, the porosity can be increased by increasing the amount of the foaming agent added, and the porosity can be reduced by reducing the amount of the foaming agent added.

[0080] For the conductive layer having such voids, the average cell diameter on the surface of the conductive layer, the number of cells, the air permeability, the density of the entire layer, etc. can be arbitrarily set. Although the physical property values ​​of the conductive layer (foamed layer) are not particularly limited, for example, the conductive layer preferably has a value within the following numerical range.

[0081] The average cell diameter of the surface is a value representing the equivalent circular diameter of the opening of the voids appearing in the surface of the conductive layer. The average cell diameter of the surface is preferably, for example, 100 μm to 500 μm. The number of cells is a value representing the number of openings of the voids appearing in the surface of the conductive layer per unit length (per 1 inch) in the surface of the conductive layer. The number of cells is preferably, for example, 50 cells / inch to 300 cells / inch. The cell diameter and the number of cells can be obtained by processing an image obtained by photographing the surface of the electrophotographic roller, for example, using a video microscope.

[0082] The air permeability is a value indicating how easily air passes through the conductive layer. The air permeability is obtained by clamping the electrophotographic roller with a clamp having a cylindrical shape with a diameter 1 mm smaller than the diameter of the electrophotographic roller and provided with a hole with a diameter of 10 mm at a position facing the electrophotographic roller in the circumferential direction, and measuring the amount of air flow per minute when the pressure difference of the hole 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 overall layer is a value indicating the density of the overall conductive layer having the skeleton and voids described later. The density of the overall layer is preferably, for example, 0.05 g / cm 3 ~0.20g / cm 3 The volume of the conductive layer having the skeleton and the voids is obtained from the outer diameter of the electrophotographic roller, the diameter of the substrate, the length of the conductive layer, etc., and thus the density of the entire conductive layer can be obtained from the volume and mass of the conductive layer.

[0083] skeleton

[0084] The conductive layer has a skeleton including polyurethane and an electronically conductive filler in the polyurethane. The polyurethane serves as a binder resin in the conductive layer. As the electronically conductive filler, the electronically conductive fillers listed below can be used.

[0085] The polyurethane is preferably a cross-linked polyurethane resin that has been cross-linked. The cross-linked polyurethane resin is a reaction product of a polyol and a compound having an isocyanate group. For example, if a compound having an isocyanate group is added to a mixture of an electronically conductive filler and a polyol and mixed with the mixture of the electronically conductive filler and the polyol, and the mixture is reacted, the mixture foams and hardens, generating a skeleton constituting the conductive layer and a void as a gap in the skeleton. As a result, a conductive layer having a skeleton comprising polyurethane and an electronically conductive filler and having a void can be obtained.

[0086] Electronically conductive fillers

[0087] As the conductive agent of the electrophotographic roller, an electron conductive filler can be used. Although the electron conductive filler is not particularly limited, for example, the following (1) to (7) can be listed.

[0088] (1) Carbon nanotubes

[0089] (2) Carbon powders such as acetylene black, Ketjen black, polyacrylonitrile (PAN) carbon or pitch carbon

[0090] (3) Graphite

[0091] (4) Fine metal particles or fibers such as aluminum, palladium, nickel, iron, copper or silver

[0092] (5) Fine particles of metal oxides such as conductive titanium oxide, conductive tin oxide or conductive zinc oxide

[0093] (6) Metal compound powders such as copper sulfide or zinc sulfide

[0094] (7) A powder obtained by attaching tin oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, titanium, chromium, tungsten, iron, cobalt, nickel, palladium, rhodium, osmium, iridium or platinum to the surface of appropriate particles by electrolysis, spraying or vibration mixing.

[0095] The electronically conductive filler may be used alone, or two or more thereof may be used in combination. In other words, 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 comprises carbon nanotubes. Since carbon nanotubes have high conductivity, and conductivity can be applied to the skeleton by adding a small amount of carbon nanotubes, carbon nanotubes are preferred from the viewpoint of obtaining appropriate flexibility of the developer supply roller.

[0096] Carbon nanotubes include metal conductive carbon nanotubes and semiconductor conductive carbon nanotubes. The carbon nanotubes in the electron conductive filler preferably include metal conductive carbon nanotubes.

[0097] In addition, as carbon nanotubes, there are single-walled carbon nanotubes and multi-walled carbon nanotubes. As the carbon nanotubes in the electron conductive filler, single-walled carbon nanotubes are preferably included. Single-walled carbon nanotubes have conductivity and are flexible and therefore exhibit sufficient conductivity for the conductive layer of the electrophotographic roller and can have appropriate hardness and flexibility, and are therefore more preferred.

[0098] The electron conductive filler may further include a second electron conductive filler different from the above-mentioned first electron conductive filler. The second electron conductive filler preferably contains at least one selected from the group consisting of carbon black, graphite, metal fine particles and tin oxide.

[0099] The content of the electron conductive filler in the conductive layer is preferably 0.001 to 15 mass %, and more preferably 0.001 to 5 mass %. When a plurality of electron conductive fillers are included, the sum of the contents of the respective electron conductive fillers (total content) is preferably within the above range.

[0100] The content of the first electronic conductive filler in the conductive layer is preferably 0.001% to 0.8% by mass, and more preferably 0.001% to 0.05% by mass. In the case where the conductive layer contains carbon nanotubes as the first electronic conductive filler, the content of the carbon nanotubes in the conductive layer is preferably 0.001% to 1% by mass, and more preferably 0.001% to 0.8% by mass.

[0101] The content of the second electronically conductive filler in the conductive layer is preferably 0.001% to 1.0% by mass, and more preferably 0.5% to 4.95% by mass. When two or more conductive fillers are included as the second electronically conductive filler, the sum of the contents of the conductive fillers used as the second electronically conductive filler (total content) is preferably within the above range.

[0102] By setting the content of the electron conductive filler in the conductive layer within the above range, the absolute value of θ can be further reduced, and current-carrying degradation can be further suppressed.

[0103] The electronically conductive filler is preferably added as a dispersion obtained by dispersing the electronically conductive filler in a solution. Examples of the solution include polyethylene glycol alkyl ethers and aliphatic carboxylic acid derivatives. For example, a polyethylene glycol alkyl ether dispersion of carbon nanotubes or an aliphatic carboxylic acid derivative dispersion of carbon nanotubes can be used. The above dispersion preferably contains 5% to 15% by mass of the electronically conductive filler.

[0104] The conductive path of the electronic conductive filler is easily connected, and by adding the electronic conductive filler as a dispersion, the absolute value of θ can be reduced. As a result, it is easier to suppress the deterioration of the current, which is preferred. In addition, the electronic conductive filler and the dispersion of the electronic conductive filler can be used together.

[0105] Polyurethane

[0106] Polyurethane is a reaction product of a polyol and a compound having an isocyanate group (isocyanate compound).

[0107] Polyurethane can be obtained by reacting a polyol with an isocyanate compound.

[0108] Polyols

[0109] Examples of polyols forming polyurethane include polyether polyols, polyester polyols, acrylic polyols, polycarbonate polyols, and polycaprolactone polyols. Among them, polyether polyols are preferably used because a cross-linked polyurethane resin formed from the polyether polyols has sufficient flexibility.

[0110] As polyether polyols, the following polyether polyols can be listed, for example: polyethylene glycol, polypropylene glycol, poly 1,4-butylene glycol, poly 1,5-pentanediol, polyneopentyl glycol, poly 3-methyl-1,5-pentanediol, poly 1,6-hexanediol, poly 1,8-octanediol, and poly 1,9-nonanediol. Among them, from the viewpoint of suppressing the increase in hardness of the cross-linked polyurethane resin, polypropylene glycol, poly 1,4-butylene glycol, poly 1,5-pentanediol, polyneopentyl glycol, poly 3-methyl-1,5-pentanediol, and poly 1,6-hexanediol are preferably used. Polyols preferably include, 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 (trade name, manufactured by Mitsui Chemicals, Inc.), ACTOCOL EP-950P (trade name, manufactured by Mitsui Chemicals, Inc.), ACTOCOL EP-505S (trade name, manufactured by Mitsui Chemicals, Inc.), and the like.

[0111] As the polyester polyol, there can be listed polyester polyols such as those obtained by condensation reaction of 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 or a triol component such as trimethylolpropane with a dicarboxylic acid ester bond such as adipic acid, suberic acid, sebacic acid, phthalic anhydride, terephthalic acid or hexahydroxyphthalic acid. Among them, from the viewpoint of suppressing an increase in the hardness of the cross-linked polyurethane resin, it is preferred to use a polyester polyol obtained by condensation reaction between a diol component such as propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol or 1,6-hexanediol and a dicarboxylic acid such as adipic acid, suberic acid or sebacic acid.

[0112] As the polycaprolactone polyol, the following polycaprolactone polyols can be listed, for example: poly ε-caprolactone and poly γ-caprolactone.

[0113] As the polycarbonate polyol, there can be listed 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.

[0114] Among them, from the viewpoint of suppressing an increase in the hardness of the cross-linked polyurethane resin, it is preferable to use a polycarbonate polyol 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 and a dialkyl carbonate such as dimethyl carbonate.

[0115] Such a polyol component can be preformed into a prepolymer having a chain extended by an isocyanate compound such as 2,4-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI) or isophorone diisocyanate (IPDI) as required. In addition, the polyol can be used alone, or two or more thereof can be used in combination. The polyol can be mixed with an electronically conductive filler and a foaming agent, a foam stabilizer and a catalyst described later, and can be added as a polyol mixture as required.

[0116] Isocyanate compounds

[0117] Isocyanate compounds have isocyanate groups. Although not particularly limited, the following examples can be listed: aliphatic polyisocyanates, such as ethylene diisocyanate and 1,6-hexamethylene diisocyanate (HDI), etc.; alicyclic polyisocyanates, such as isophorone diisocyanate (IPDI), cyclohexane-1,3-diisocyanate, and cyclohexane-1,4-diisocyanate; aromatic isocyanates, such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), polymerized diphenylmethane diisocyanate, xylene diisocyanate and naphthalene diisocyanate; and copolymers thereof, isocyanurates, TMP adducts, biuret, and blocks, etc. Among them, aromatic isocyanates such as toluene diisocyanate or diphenylmethane diisocyanate are preferably included.

[0118] The isocyanate compound may be used alone or in combination of two or more thereof. For example, the isocyanate compound is preferably a mixture comprising toluene diisocyanate and diphenylmethane diisocyanate. As such an isocyanate compound, for example, COSMONATE TM20 (trade name: manufactured by Mitsui Chemicals, Inc.) or COSMONATE TM50 (trade name: manufactured by Mitsui Chemicals, Inc.) may be used.

[0119] The polyol and the isocyanate compound are preferably mixed so that the ratio (molar ratio) of the isocyanate group contained in the isocyanate compound falls within the range of 0.9 to 2.0 relative to 1.0 mole of hydroxyl groups contained in the polyol. In addition, the polyol and the isocyanate compound are more preferably mixed in a manner such that the above-mentioned molar ratio falls within the range of 0.95 to 1.05. If the mixing ratio is within the above-mentioned range, the unreacted components remaining after the reaction between the polyol and the isocyanate compound can be reduced.

[0120] Dispersants

[0121] The conductive layer may contain a dispersant. As the dispersant, a nonionic surfactant (nonionic surfactant) is preferably contained. By containing a dispersant in the conductive layer, the electronic conductive filler is easily dispersed in the skeleton, and the conductive paths between the electronic conductive filler particles are easily connected, which is preferred.

[0122] In particular, when carbon nanotubes are used as the electron conductive filler, the conductive layer preferably 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.

[0123] The dispersant such as the nonionic surfactant contained in the conductive layer may be extracted from the conductive layer using a solvent such as acetone, methyl ethyl ketone, or tetrahydrofuran.

[0124] The kind of the dispersant contained in the conductive layer can be identified by dissolving the extracted nonionic surfactant in a solvent such as deuterated chloroform or deuterated acetone and analyzing by nuclear magnetic resonance (NMR) or gel permeation chromatography (GPC).

[0125] Cationic surfactants (ionic surfactants) are not preferred because they disconnect the conductive path of carbon nanotubes and form a skeleton that is prone to electrical degradation. On the other hand, nonionic surfactants (nonionic surfactants) have the function of dispersing carbon nanotubes in the skeleton and connecting the conductive path of carbon nanotubes, and are not prone to electrical degradation, so they are more preferred as dispersants.

[0126] Although the nonionic surfactant is not particularly limited, the following examples can be listed: a block polymer of a higher alcohol containing a polyalkylene glycol alkyl ether and a polyether; a polymer obtained by adding a polyether to a polyol; and a polymer obtained by adding a polyether to an alkylamine.

[0127] The nonionic surfactant preferably comprises a polyalkylene glycol alkyl ether. As the polyethylene glycol alkyl ether, for example, polyethylene glycol monolauryl ether or the like can be used. The content of such a nonionic surfactant in the skeleton is preferably equal to the content of the carbon nanotubes in the skeleton or preferably greater than the content of the carbon nanotubes in the skeleton. The content of the nonionic surfactant in the skeleton is preferably 1 to 10 times the content of the carbon nanotubes in the skeleton, and more preferably 3 to 10 times the content of the carbon nanotubes in the skeleton.

[0128] Other additives

[0129] The framework may contain catalysts, blowing agents, foam stabilizers and other additives as required. Such additives may be pre-mixed with the polyol and the electronically conductive filler and may be added as a polyol mixture.

[0130] The catalyst is not particularly limited, and a suitable catalyst can be selected from various catalysts known in the prior art and used. For example, an amine catalyst (e.g., triethylenediamine, bis(dimethylaminoethyl)ether, N,N,N',N'-tetramethylhexanediamine, 1,8-diazabicyclo(5.4.0)undecane-7,1,5-diazabicyclo(4.3.0)-5-nonene, 1,2-dimethylimidazole, N-ethylmorpholine or N-methylmorpholine), an organometallic catalyst (e.g., tin octoate, tin oleate, dibutyltin dilaurate, dibutyltin diacetate, tetraisopropoxytitanium, tetra-n-butoxytitanium or tetra(2-ethylhexyloxy)titanium) or an acid salt catalyst (e.g., carboxylate, formate, octoate or borate) obtained by reducing the initial activity of an amine catalyst and an organometallic catalyst. The catalyst can be used alone or in combination of two or more thereof.

[0131] The blowing agent is not particularly limited, and a suitable blowing agent can be selected from various blowing agents known in the prior art. In particular, water is suitable for use as a blowing agent because water reacts with polyisocyanate and generates carbon dioxide gas. In addition, other blowing agents and water can be used together. For example, ion exchange water can be used as a blowing agent.

[0132] The amount of the foaming agent added to the material 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 within the above range, the porosity of the conductive layer can be within an appropriate range.

[0133] The foam stabilizer is not particularly limited, and an appropriate foam stabilizer can be selected from various foam stabilizers known in the art and used. For example, a polysiloxane foam stabilizer or the like can be used.

[0134] As other additives, a cross-linking auxiliary agent, a flame retardant, a colorant, an ultraviolet absorber, an antioxidant, or the like may be used as needed within a range not impairing the effects of the present disclosure.

[0135] Average elastic modulus of the conductive layer

[0136] If the hardness of the conductive layer in the electrophotographic roller is too high, when the electrophotographic roller is used as a toner supply roller, the conductive layer may scrape the toner carrying roller abutting against the conductive layer, and the surface of the toner carrying roller may be scratched. The average elastic modulus of the conductive layer of the electrophotographic roller measured using SPM is preferably 2000 MPa or less. By setting the average elastic modulus of the conductive layer to 2000 MPa or less, appropriate softness of the conductive layer as the outer surface of the electrophotographic roller is achieved, and the toner carrying roller is not easily scratched, which is preferred.

[0137] The above average elastic modulus of the conductive layer is preferably 1000MPa to 2000MPa, more preferably 1300MPa to 1800MPa. The average elastic modulus of the conductive layer can be controlled, for example, by the type and amount of the electronically conductive filler. For example, the average elastic modulus of the conductive layer can be reduced by an electronically conductive filler containing carbon nanotubes. In addition, the average elastic modulus of the conductive layer can be increased by increasing the amount of the electronically conductive filler introduced into the material forming the conductive layer.

[0138] Method for forming conductive layer

[0139] The method for forming the conductive layer is not particularly limited. A method using a foaming agent or a method of mixing bubbles by mechanical stirring, etc. can be used. Note that the foaming rate can be appropriately set and is not particularly limited.

[0140] For example, a compound having an isocyanate group is added to a mixture of an electronically conductive filler and a polyol and mixed with the mixture, thereby foaming and hardening the mixed composition, thereby forming a conductive layer. In other words, the method for manufacturing an electrophotographic roller preferably includes a process of foaming and hardening a composition containing the following materials to obtain a conductive layer.

[0141] (1) Electronically conductive fillers

[0142] (2) Polyols

[0143] (3) Isocyanate compounds

[0144] (4) Foaming agent

[0145] (5) Foam stabilizer

[0146] (6) Catalyst

[0147] As mentioned above, polyol and isocyanate compound are materials for forming polyurethane.Electronic conductive filler and polyol can be premixed to obtain polyol mixture.Polyol mixture can include blowing agent, foam stabilizer and catalyst.In other words, by the composition obtained by mixing the polyol mixture including electronic conductive filler, polyol, blowing agent, foam stabilizer and catalyst with isocyanate compound, foaming and hardening, conductive layer can be obtained.

[0148] Since the conductive layer can be formed only by the above-mentioned reaction, the electrophotographic roller according to the present disclosure can be easily produced.

[0149] There is no particular limitation on the method for joining the substrate and the conductive layer. A method in which the substrate is pre-arranged in a mold (forming mold) as described above and the raw material composition is poured and hardened, or a method in which the raw material composition is pre-formed into a predetermined shape of the conductive layer and bonded to the substrate, etc., can be used. In any method, other layers such as a conductive adhesive layer or an elastic layer may be included between the substrate and the conductive layer as required.

[0150] In the case of a method for casting and hardening the raw material composition, a release agent can also be applied to the inner wall of the mold in advance. As a release agent, a known release agent can be used. Examples of release agents include aqueous release agents comprising an olefin component and a polysiloxane component, a release agent obtained by dissolving a fluorine component in a fluorine-based solvent, etc. In order to easily form an opening on the outer surface of the conductive layer, it is preferred to use an aqueous release agent comprising an olefin component and a polysiloxane component.

[0151] The method for forming the shape of the conductive layer is not particularly limited. In addition to the above-mentioned method of pouring the raw material composition into a mold having a predetermined shape, examples thereof include a method of cutting a foaming member in a block state (so-called slabstock foam) into a predetermined size by cutting processing and then grinding it into a cylindrical shape, and a method of forming the raw material composition into a predetermined size using an extruder, etc.

[0152] Development equipment

[0153] Figure 2A An example of a schematic cross-sectional view of the developing device 4 is shown.

[0154] The developing device 4 includes at least a developing roller 5 and a developer supplying roller 1 that supplies developer to the developing roller. Further, the developing device 4 is configured so that a voltage can be applied between the developing roller 5 and the developer supplying roller 1.

[0155] The developing device 4 has a toner 8 as a developer, and includes an electrophotographic roller serving as a developer supplying roller 1. In other words, the developer supplying roller is an electrophotographic roller. In addition, the developer supplying roller is preferably the above-mentioned specific electrophotographic roller.

[0156] The developing device 4 includes a developing roller 5 as a developing mechanism and a developing blade 6. The developing device 4 also includes a toner container 7, and the interior of the toner container 7 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 the toner 8 having a predetermined thickness is formed on the surface of the developing roller 5 by the developing blade 6.

[0157] Other parts of the developing equipment

[0158] There is no particular limitation on the developing device as long as the developing device has a configuration including a developing roller and the above-mentioned specific developer supply roller 1. The developing device may include components other than the above-mentioned components. For example, it may include Figure 2A The developing blade 6, toner container 7, and toner 8 etc. are shown, and the developing blade, toner container and toner known in the related art can be used.

[0159] Processing box

[0160] In another aspect of the present disclosure, a process cartridge is provided, which is configured to be detachably mounted from a main body of an electrophotographic image forming apparatus and includes the above-mentioned electrophotographic roller. The process cartridge includes a contact member, which is electrically connected to an electrical contact in the main body of the electrophotographic image forming apparatus when the process cartridge is mounted to the main body of the electrophotographic image forming apparatus. The process cartridge is configured so that a voltage can be applied between the developer roller and the developer supply roller through the electrical connection.

[0161] The process cartridge preferably includes a developing device 4 including at least a photosensitive member, a developing roller that conveys toner to the surface of the photosensitive member, and a developer supplying roller 1 that supplies the developer to the developing roller.

[0162] Figure 2B 1 is a schematic cross-sectional view showing an example of a process cartridge. The process cartridge 9 is configured to be detachably mounted from a main body (not shown) of an electrophotographic image forming apparatus. In addition, the process cartridge 9 includes a developing device 4, an electrophotographic photosensitive member 10, a cleaning blade 11 as a cleaning mechanism, a waste toner storage container 12, and a charging roller 13 as a charging mechanism. Here, the developing device 4 is as shown in FIG. Figure 2A As shown, and includes a developing roller and a developer supplying roller. The developer supplying roller is preferably the above-mentioned specific electrophotographic roller.

[0163] Electrophotographic image forming apparatus

[0164] An electrophotographic image forming apparatus according to another aspect of the present disclosure is an electrophotographic image forming apparatus including the above-described electrophotographic roller. The electrophotographic image forming apparatus may be an electrophotographic image forming apparatus including the above-described developing device 4.

[0165] Figure 3 : is a schematic cross-sectional view showing an example of an electrophotographic image forming apparatus equipped with a contact developing apparatus using a one-component system developer (toner). Figure 3 In the example, a plurality of color chromatic aberrations are prepared for each color, namely, black (Bk), cyan (C), magenta (M), and yellow (Y). Figure 2B The process cartridge 9 is shown, and each developing device 4 is filled with toner 8 of each color, so that color printing can be performed.

[0166] Hereinafter, a printing operation of the electrophotographic image forming apparatus will be described.

[0167] The electrophotographic photosensitive member 10 is Figure 3 The electrophotographic photosensitive member 10 is rotated in the direction of the arrow shown, and is uniformly charged by a charging roller 13 for performing a charging process on the electrophotographic photosensitive member 10. Then, an electrostatic latent image is formed on the surface of the electrophotographic photosensitive member 10 by a laser 14 as an exposure mechanism. The developer supply roller 1 in the developing device 4 supplies the toner 8 to the developing roller 5 arranged in contact with the surface of the electrophotographic photosensitive member 10. Thus, the toner 8 is transferred to the surface of the electrophotographic photosensitive member 10, whereby the electrostatic latent image is visualized (developed) as a toner image.

[0168] The development is a so-called reverse development in which a toner image is formed on the exposed portion of the electrophotographic photosensitive member 10. The toner image formed on the electrophotographic photosensitive member 10 is transferred to the paper 16 as a recording medium by the transfer roller 15 as a transfer member. The paper 16 is fed to the inside of the apparatus by the paper supply roller 17 and the adsorption roller 18, and is transferred to the portion between the electrophotographic photosensitive member 10 and the transfer roller 15 by the transfer conveyor belt 19 in the shape of an endless belt. The transfer conveyor belt 19 is operated 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 is transferred is subjected to a fixing process by the fixing device 24, and is discharged to the outside of the apparatus, and the printing operation is ended. On the other hand, the transfer residual toner remaining on the electrophotographic photosensitive member 10 without being transferred is scraped off by a cleaning blade 11 as a cleaning member for cleaning the surface of the photosensitive member and then stored in a waste toner storage container 12. The electrophotographic photosensitive member 10 after cleaning can repeatedly perform the above-mentioned printing operation.

[0169] The electrophotographic image forming apparatus may include, for example, a photosensitive member, a developing roller that conveys toner to the surface of the photosensitive member, a developer supplying roller that supplies developer to the surface of the developing roller, and a cleaning roller that cleans the photosensitive member. In addition, the above-mentioned electrophotographic roller is preferably a developer supplying roller.

[0170] Example

[0171] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Parts used in Examples are based on mass unless otherwise specified.

[0172] Evaluation method of electrophotographic roller

[0173] Phase delay θ measurement method

[0174] The θ value was measured in an environment with a temperature of 23°C and a relative humidity of 52%. Fig. 8A As shown, rollers 25 are attached to both end portions of the electrophotographic roller 1, and bearings 26 made of metal abut against the rollers 25 so that the electrophotographic roller is fixed.

[0175] The electrophotographic roller 1 was brought into contact with a metal drum 27 on which hard chrome plating was performed so that the surface roughness Ra was 1 μm or less, by applying a load of 4.9 N to one side. Figure 8B As shown, electrodes of an impedance analyzer 28 (SOLARTRON 1260A / 1296; manufactured by Hokuto Denko Corporation) are connected to the shaft (substrate end) of the electrophotographic roller and the metal drum 27.

[0176] The impedance analyzer applied a 50V DC voltage at 1.0×10 -1 Hz~1.0×10 5 Hz, an AC voltage with an amplitude of 50 V was applied and the phase delay θ of the impedance was measured. -1 Hz~1.0×10 5 The frequency is measured at intervals of 1.58489 times of Hz, and each number is measured at 5 points. -1 Hz~1.0×10 1 The maximum value of the absolute value θ obtained within the frequency range of Hz (ie, the absolute value of θ when the phase delay is maximum) is defined as max|θ|, and is defined as the absolute value of the phase delay θ.

[0177] Method for measuring initial resistance value of electrophotographic roller

[0178] The initial resistance value of the electrophotographic roller was measured in an environment of a temperature of 23° C. and a relative humidity of 52%. Fig.9A As shown, the electrophotographic roller 1 is brought into contact with the metal drum 27. The roller 25 is fitted into the base end of the electrophotographic roller 1, and the two base ends are pressed through the bearing 26 made of metal to apply a load of 4.9N on one side to the metal drum, so that the electrophotographic roller is brought into contact with the metal drum. Fig. 9B As shown in FIG. 1 , a power source 29, a resistor 30 and a voltmeter 31 are connected to the shaft (end of the substrate) of the electrophotographic roller and the metal drum 27. Fig. 9B A voltage of 200 V is applied while rotating at 30 rpm in the direction of the arrow in the figure, and the voltage from 2 seconds to 5 seconds after the start of voltage application is recorded at 100 Hz using a data recorder (not shown) connected to the voltmeter 31, and the initial resistance value (Ω) of the electronic photographic roller is obtained from its average voltage.

[0179] Evaluation method of power-on degradation

[0180] The electrophotographic roller after the initial resistance value was measured by the above method was used, and the resistance value after energized rotation for 12 hours was measured using an apparatus similar to the apparatus used for measuring the initial resistance value, thereby evaluating energization degradation.

[0181] In an environment with a temperature of 23°C and a relative humidity of 52%, Fig.9A As shown in FIG. 1 , the electrophotographic roller after the initial resistance value is measured is brought into contact with the metal drum. The roller is engaged with the end of the substrate, and the two ends of the substrate are pressed with a bearing made of metal to apply a load of 4.9N on one side to the metal drum, thereby bringing the electrophotographic roller into contact with the metal drum. Fig. 9B As shown in FIG. 1 , a power source, a resistor, and a voltmeter are connected to the shaft (end of the substrate) and the metal drum of the electrophotographic roller. The metal drum is moved along Fig. 9B The machine was rotated at 30 rpm in the direction of the arrow in the figure, and a voltage of 200 V was applied while the machine was powered on and rotated for 12 hours.

[0182] The voltage from 2 seconds to 5 seconds after the timing of the end of the power-on rotation was recorded at 100 Hz, and the resistance value (Ω) of the electronic photographic roller after power-on was obtained from the average voltage. The ratio of the initial resistance value to the resistance value after power-on obtained in this way (resistance value after power-on / initial resistance value) was defined as the resistance change rate, and was evaluated as an index of power-on degradation. A higher resistance change rate indicates a higher resistance value after long-term power-on, and power-on degradation occurs.

[0183] Porosity measurement method

[0184] Regarding the porosity of the conductive layer of the electrophotographic roller, the porosity of the conductive layer of the electrophotographic roller was measured using a three-dimensional measurement X-ray CT apparatus (TDM1001-DD; manufactured by Yamato Scientific Co., Ltd.).

[0185] 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-mentioned three-dimensional measurement X-ray CT equipment. From the obtained three-dimensional image, the porosity was obtained using the following formula (1). Note that the measurement conditions are as follows.

[0186] Target material: tungsten, Filament material: tungsten, X-ray intensity: 100Kv

[0187] Porosity (volume %) = volume of voids / (volume of cylinder - volume of matrix) (Formula (1))

[0188] Method for measuring average elastic modulus using SPM

[0189] While the electrophotographic roller is kept at -110°C using a cryostat (product name: EMFC 6, manufactured by Leica Microsystems), a portion of the conductive layer of the electrophotographic roller is cut into and extracted as a thin slice using a diamond knife. In addition, a measurement area with a side length of 100 μm and 100 μm from the surface of the slice in the depth direction is extracted from the thin slice to prepare a sample. The elastic modulus of the inner wall surface of the skeleton containing polyurethane as a binder is measured. For the measurement, an SPM device (product name: MFP-3D-Origin, manufactured by Oxford Instruments) and a probe (product name: AC 160, manufactured by Olympus Corporation) are used. At this time, the force curve is measured at 5 positions in the vertical direction × 5 positions in the horizontal direction, that is, a total of 25 times, and the arithmetic mean of 23 points other than the highest and lowest values ​​is obtained, and the average elastic modulus is calculated based on the Hertz theory.

[0190] Method for identifying components in the conductive layer

[0191] The dispersant such as the 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.

[0192] The extracted nonionic surfactant is dissolved in a solvent such as deuterated chloroform or deuterated acetone, and the kind of the dispersant contained in the conductive layer can be identified using nuclear magnetic resonance (NMR) or gel permeation chromatography (GPC).

[0193] In addition, the electronic 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 and thermally decomposing the binder resin. The residue after the thermal decomposition is the electronic conductive filler contained in the conductive layer. The components of the electronic conductive filler separated from the conductive layer can be determined by various chemical analyses such as nuclear magnetic resonance (NMR).

[0194] Method for measuring the content of electronically conductive filler in conductive layer

[0195] When obtaining the content of the electron conductive filler in the conductive layer from the electrophotographic roller, the following method can be used.

[0196] The conductive layer was extracted from the substrate and taken out, the mass was measured, and then the conductive layer was heated at 500°C in a nitrogen atmosphere, thereby thermally decomposing the binder resin. After that, the residue of the conductive particles was collected and the mass was measured. (The mass of the residue of the conductive particles / the mass of the conductive layer)×100 was defined as the content of the electronic conductive filler in the conductive layer.

[0197] Materials for electrophotographic rollers

[0198] Table 1 and Table 2 describe the materials used for the electrophotographic roller.

[0199] [Table 1]

[0200]

[0201] [Table 2]

[0202]

[0203] (Example 1)

[0204] like Figures 10A to 10C As shown, a mold 36 including a cylindrical member (tube mold 35) whose inner surface is coated with a release agent, an upper member 37 and a lower member 34, and a base 33 are prepared.

[0205] As the substrate 33, a substrate obtained by chemically nickel plating iron (material name: SUM24) having an outer diameter of 5 mm and a length of 272 mm was used. As the mold 36, a cylindrical mold having a cavity inner diameter of 11.00 mm and a cavity length of 220 mm was used. For the demolding treatment for the mold 36, the lower member 34, and the upper member 37, a demolding agent (product name: FRELEASE 690, manufactured by Neos Company Limited) was used. The demolding treatment was performed by preheating the mold 36, the lower member 34, and the upper member 37 to 75°C in advance.

[0206] The following materials (1), (2), and (3) were weighed in a container and mixed with stirring at 3000 rpm for 20 minutes using a HOMODISPER Model 2.5 (manufactured by Primix Corporation).

[0207] (1): First electronically conductive filler E-1: 0.5 parts by mass

[0208] (2): Polyol P-1: 90.0 parts by mass

[0209] (3): Polyol P-3: 10.0 parts by mass

[0210] Furthermore, the following materials (4), (5), (6) and (7) were added to the container, and stirred and mixed at 1500 rpm for 5 minutes using a HOMODISPER 2.5 model to obtain a polyol mixture.

[0211] (4): Foaming agent W: 1.5 parts by mass

[0212] (5): Foam stabilizer S-1: 0.4 parts by mass

[0213] (6): Catalyst C-1: 1.0 parts by mass

[0214] (7): Catalyst C-2: 0.5 parts by mass

[0215] As the conductive layer forming material, a liquid obtained by adding 24.7 parts by mass of the isocyanate compound (N-1) to the above polyol mixture, adjusting the liquid temperature to 26° C., and mixing and stirring with a casting machine was used. Note that the polyol mixture and the isocyanate compound were mixed immediately before pouring into the mold.

[0216] like Fig. 10A As shown, 2.3 g of the conductive layer forming material 32 is poured into a mold 36 formed by combining a lower member 34 carrying a base 33 and a tube mold 35. Note that the base and the lower member are preheated to 70°C.

[0217] The conductive layer forming material is poured into the base body in the mold 36 in a state where the upper end position is tilted 3 mm away from the center position of the mold toward the side opposite to the injection side ( Fig. 10A ).like Fig. 10B As shown, after the conductive layer forming material is poured in, the upper member 37 preheated to 75°C is fitted into the mold 36, and heating is continued by closely fitting the hot plate 38 of the heater 40, and heat curing is performed at 75°C for 8 minutes.

[0218] During the heat curing, the conductive layer forming material 39 foamed in the mold is as follows at the end of the heating. Fig. 10C The resin expands and spreads to the entire space in the mold as shown. Then, the resin is cured to form the conductive layer of the electrophotographic roller. After the heat curing is completed, the upper member and the lower member are removed from the mold and the electrophotographic roller including the substrate and the conductive layer is taken out.

[0219] The electrophotographic roller A-1 in Example 1 was formed by the above-described method.

[0220] (Examples 2 to 19, 38, 40 to 43, and 50 to 52)

[0221] Except for changing the introduction amount of the first electron conductive filler, the type of polyol, the type and amount of the introduced isocyanate, and the amount of the foaming agent as shown in Tables 3, 6, and 7, the electronic photographic rollers A-2 to A-19, A-38, A-40 to A-43, and A-50 to A-52 in Examples 2 to 19, 38, 40 to 43, and 50 to 52 were obtained in the same manner as the manufacturing method of the electronic photographic roller A-1.

[0222] Table 3 shows the composition of the conductive layer forming material used for electrophotographic rollers A-1 to A-19. Table 6 shows the composition of the conductive layer forming material used for electrophotographic roller A-38. Table 7 shows the composition of the conductive layer forming material used for electrophotographic rollers A-40 to A-43 and A-50 to A-52.

[0223] [Table 3]

[0224]

[0225] Table 4 shows the physical properties and evaluation results of the electrophotographic rollers A-1 to A-19.

[0226] [Table 4]

[0227]

[0228] In the table, max|θ| represents the absolute value of the phase retardation θ. SPM hardness represents the average elastic modulus measured using SPM. In the table, for example, 8.01E+08 represents 8.01×10 8 .

[0229] (Example 20)

[0230] The following materials (1), (2), (3), and (4) were weighed in a container and stirred and mixed at 3000 rpm for 20 minutes using a HOMODISPER Model 2.5 (manufactured by Primix Corporation).

[0231] (1): First electronically conductive filler E-1: 0.01 parts by mass

[0232] (2): Second electronically conductive filler E-5: 0.5 parts by mass

[0233] (3): Polyol P-1: 90.0 parts by mass

[0234] (4): Polyol P-3: 10.0 parts by mass

[0235] Furthermore, the following materials (5), (6), (7) and (8) were added to the container, and stirred and mixed at 1500 rpm for 5 minutes using a HOMODISPER 2.5, thereby obtaining a polyol mixture.

[0236] (5): Foaming agent W: 1.5 parts by mass

[0237] (6): Foam stabilizer S-1: 0.4 parts by mass

[0238] (7): Catalyst C-1: 1.0 parts by mass

[0239] (8): Catalyst C-2: 0.5 parts by mass

[0240] 24.7 parts by mass of the isocyanate compound (N-1) was added to the polyol mixture to obtain a conductive layer forming material. The conductive layer forming material obtained was formed in the same manner as the electrophotographic roller A-1 in Example 1 to form an electrophotographic roller A-20 in Example 20.

[0241] (Examples 21 to 31, 39, 44 to 49, 53, and 54)

[0242] Except for changing the type and amount of the introduced first electron conductive filler and the type and amount of the introduced second electron conductive filler as shown in Tables 5 and 7, the electrophotographic rollers A-21 to A-31, A-39, A-44 to A-49, A-53, and A-54 in Examples 21 to 31, 39, 44 to 49, 53, and 54 were formed in the same manner as the manufacturing method of the electrophotographic roller A-20.

[0243] (Example 32)

[0244] The following materials (1), (2), (3), and (4) were weighed in a container and stirred and mixed at 3000 rpm for 20 minutes using a HOMODISPER 2.5 model (manufactured by Primix Corporation).

[0245] (1) First electronically conductive filler E-4: 0.005 parts by mass

[0246] (2): Polyol P-1: 90.0 parts by mass

[0247] (3): Polyol P-3: 10.0 parts by mass

[0248] (4): Dispersant D-2: 0.045 parts by mass

[0249] Furthermore, the following materials (5), (6), (7) and (8) were added to the container, and stirred and mixed at 1500 rpm for 5 minutes using a HOMODISPER 2.5, thereby obtaining a polyol mixture.

[0250] (5): Foaming agent W: 1.5 parts by mass

[0251] (6): Foam stabilizer S-1: 0.4 parts by mass

[0252] (7): Catalyst C-1: 1.0 parts by mass

[0253] (8): Catalyst C-2: 0.5 parts by mass

[0254] 24.7 parts by mass of the isocyanate compound (N-1) was added to the polyol mixture to obtain a conductive layer forming material. The conductive layer forming material obtained was molded in the same manner as the electrophotographic roller A-1 in Example 1 to form an electrophotographic roller A-32 in Example 32.

[0255] (Examples 33 and 34)

[0256] The electrophotographic rollers A-33 and A-34 in Examples 33 and 34 were formed by changing the introduced amount of the first electron conductive filler and the introduced amount of the dispersant of the electrophotographic roller A-32 in Example 32.

[0257] (Example 35)

[0258] The following materials (1), (2), (3), (4), and (5) were weighed in a container and mixed with stirring at 3000 rpm for 20 minutes using a HOMODISPER Model 2.5 (manufactured by Primix Corporation).

[0259] (1): First electronically conductive filler E-4: 0.05 parts by mass

[0260] (2): Second electron conductive filler E-5: 1.0 parts by mass

[0261] (3): Polyol P-1: 90.0 parts by mass

[0262] (4): Polyol P-3: 10.0 parts by mass

[0263] (5): Dispersant D-2: 0.45 parts by mass

[0264] Furthermore, the following materials (6), (7), (8), and (9) were added to the container, and stirred and mixed at 1500 rpm for 5 minutes using a HOMODISPER 2.5, thereby obtaining a polyol mixture.

[0265] (6): Foaming agent W: 1.5 parts by mass

[0266] (7): Foam stabilizer S-1: 0.4 parts by mass

[0267] (8): Catalyst C-1: 1.0 parts by mass

[0268] (9): Catalyst C-2: 0.5 parts by mass

[0269] 24.7 parts by mass of the isocyanate compound (N-1) was added to the polyol mixture to obtain a conductive layer forming material. The conductive layer forming material obtained was molded in the same manner as the electrophotographic roller A-1 in Example 1 to form an electrophotographic roller A-35 in Example 35.

[0270] (Examples 36 and 37)

[0271] Except for changing the type and amount of the introduced first electron conductive filler, the type and amount of the introduced second electron conductive filler, and the introduced amount of the dispersant as shown in Table 5, the electrophotographic rollers A-36 and A-37 in Examples 36 and 37 were obtained in the same manner as the manufacturing method of the electrophotographic roller A-35.

[0272] Table 5 shows the incorporation of conductive layer-forming materials used in electrophotographic rollers A-20 to A-39.

[0273] [Table 5]

[0274]

[0275] Table 6 shows the physical properties and evaluation results of the electrophotographic rollers A-20 to A-39.

[0276] [Table 6]

[0277]

[0278] (Comparative Examples 1 and 2)

[0279] The following materials (1), (2), and (3) were weighed in a container and stirred and mixed at 3000 rpm for 20 minutes using a HOMODISPER Model 2.5 (manufactured by Primix Corporation).

[0280] (1): First electronically conductive filler I-1: 2.0 parts by mass

[0281] (2): Polyol P-1: 90.0 parts by mass

[0282] (3): Polyol P-3: 10.0 parts by mass

[0283] Furthermore, the following materials (4), (5), (6) and (7) were added to the container and stirred and mixed at 1500 rpm for 5 minutes using a HOMODISPER 2.5 model, thereby obtaining a polyol mixture.

[0284] (4) Foaming agent W: 1.5 parts by mass

[0285] (5) Foam stabilizer S-1: 0.4 parts by mass

[0286] (6) Catalyst C-1: 1.0 parts by mass

[0287] (7) Catalyst C-2: 0.5 parts by mass.

[0288] 24.7 parts by mass of the isocyanate compound (N-1) was added to the above polyol mixture, thereby obtaining a conductive layer forming material. The conductive layer forming material thus obtained was formed in the same manner as the electrophotographic roller A-1 in Example 1, thereby forming an electrophotographic roller B-1 in Comparative Example 1. In addition, the type and amount of the first electron conductive filler introduced were changed from those of the electrophotographic roller B-1 in Comparative Example 1, thereby obtaining an electrophotographic roller B-2 in Comparative Example 2.

[0289] (Comparative Examples 3 and 4)

[0290] The following materials (1), (2), (3), and (4) were weighed in a container and mixed with stirring at 3000 rpm for 20 minutes using a HOMODISPER Model 2.5 (manufactured by Primix Corporation).

[0291] (1): First electronically conductive filler E-9: 1.0 parts by mass

[0292] (2): Polyol P-1: 90.0 parts by mass

[0293] (3): Polyol P-3: 10.0 parts by mass

[0294] (4): Dispersant D-1: 6.0 parts by mass

[0295] Furthermore, the following materials (5), (6), (7), and (8) were added to the container, and the mixture was stirred and mixed at 1500 rpm for 5 minutes using a HOMODISPER 2.5 model, thereby obtaining a polyol mixture.

[0296] (5): Foaming agent W: 1.5 parts by mass

[0297] (6): Foam stabilizer S-1: 0.4 parts by mass

[0298] (7): Catalyst C-1: 1.0 parts by mass

[0299] (8): Catalyst C-2: 0.5 parts by mass

[0300] 24.7 parts by mass of the isocyanate compound (N-1) was added to the polyol mixture to obtain a conductive layer forming material. The conductive layer forming material thus obtained was formed in the same manner as the electrophotographic roller A-1 in Example 1 to form an electrophotographic roller B-3 in Comparative Example 3. In addition, the amount of the first electron conductive filler introduced was changed from the electrophotographic roller B-3 in Comparative Example 3 to obtain an electrophotographic roller B-4 in Comparative Example 4.

[0301] Table 7 shows the incorporated materials used to form the conductive layers used in the electrophotographic rollers A-40 to A-54 and B-1 to B-4.

[0302] [Table 7]

[0303]

[0304] Table 8 shows the physical properties and evaluation results of the electrophotographic rollers A-40 to A-54 and B-1 to B-4.

[0305] [Table 8]

[0306]

[0307] It is confirmed from the evaluation results of the embodiments that in the electronic photographic roller according to the present disclosure, since the absolute value of the phase delay θ when an AC voltage with a peak-to-peak voltage of 50 V is applied in the frequency range of 0.1 Hz to 10 Hz is less than 10 degrees, the resistance change rate is low, and even when a high voltage is applied for a very long time and idling with power on is performed, power-on degradation is not likely to occur.

[0308] Furthermore, it was confirmed that when the absolute value of the phase delay θ was 5 degrees or less, the resistance change rate in the case where a high voltage was applied for a very long time and idling with power on was performed could be further reduced.

[0309] The electrophotographic rollers in Examples 1 to 19 were produced by containing carbon nanotubes as a conductive filler and changing the amount of carbon nanotubes introduced, the types and amounts of polyol and isocyanate introduced (ratio between hydroxyl groups and isocyanate groups in the polyol), and the amount of foaming agent added. In all the electrophotographic rollers in Examples 1 to 19, the absolute value of the phase retardation θ was 10 degrees or less, and the energization degradation was suppressed.

[0310] The electrophotographic rollers in Examples 20 to 31, 38 and 39 were produced by changing the type and amount of the introduced electron conductive filler and the combination. In all the electrophotographic rollers in Examples 20 to 31, 38 and 39, the absolute value of the phase retardation θ was 10 degrees or less, and the energization degradation was suppressed. In particular, it was confirmed that when the amount of carbon nanotubes introduced was increased, the absolute value of the phase retardation θ decreased, and the energization degradation could be further suppressed.

[0311] The electrophotographic rollers in Examples 32 to 37 were produced by changing the amount of the nonionic surfactant (dispersant) introduced. In all of the electrophotographic rollers in Examples 32 to 37, the absolute value of the phase retardation θ was 10 degrees or less, and the energization degradation was suppressed.

[0312] When the dispersant is used, the absolute value of the phase retardation θ is less than 5 degrees, and an electrophotographic roller with further suppressed energization degradation is obtained. In addition, it is confirmed that when the amount of the nonionic surfactant introduced is 3 times or more of the amount of the carbon nanotube introduced, the absolute value of the phase retardation θ is smaller, and the energization degradation is further suppressed.

[0313] On the other hand, the electrophotographic rollers in Comparative Examples 1 and 2 used an ionically conductive electron conductive filler. Therefore, the absolute value of the phase retardation θ exceeded 10 degrees, and the resistance change rate was significantly high. In other words, it was confirmed that the current-carrying degradation occurred.

[0314] In the electrophotographic rollers of Comparative Examples 3 and 4, the electron conductive filler (carbon nanotube) was dispersed using an ionic surfactant. Therefore, the absolute value of the phase retardation θ exceeded 10 degrees, and significant deterioration due to conduction was also confirmed.

[0315] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An electrophotographic roller comprising: A substrate having a conductive surface; and a conductive layer on the surface of the substrate, wherein The conductive layer is a surface layer of the electrophotographic roller, and The conductive layer has a skeleton comprising polyurethane as a binder and an electronically conductive filler in the polyurethane, The conductive layer comprises at least one void, At least a portion of the inner wall of the void is formed by the skeleton, and 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 is applied between the electrode and the surface of the substrate within a frequency range of 0.1 Hz to 10 Hz, an absolute value of a phase delay θ of the AC impedance relative to the AC voltage is less than 10 degrees.

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

3. The electrophotographic roller according to claim 1 or 2, 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 or 2, wherein The electronically conductive filler includes carbon nanotubes as a first electronically conductive filler.

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

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

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

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

9. The electrophotographic roller according to claim 1 or 2, wherein The conductive layer further comprises a non-ionic 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 or 2, wherein The average elastic modulus of the surface of the inner wall measured by SPM is 2000 MPa or less.

12. The electrophotographic roller according to claim 1 or 2, wherein The porosity of the conductive layer is 50 to 97 volume %.

13. The electrophotographic roller according to claim 1 or 2, wherein The porosity of the conductive layer is 70 to 90 volume %.

14. The electrophotographic roller according to claim 1 or 2, wherein The conductive layer is a foamed layer.

15. A developing device, comprising at least: Developing roller; and a developer supplying roller for supplying developer to the developing roller, wherein The developing device is configured so that a voltage can be applied between the developing roller and the developer supplying roller, and The developer supply roller is the electrophotographic roller according to claim 1 or 2.

16. An electrophotographic image forming apparatus comprising the developing apparatus according to claim 15.

17. A process cartridge detachably mounted from a main body of an electrophotographic image forming apparatus, The processing box comprises: a contact member electrically connected to an electrical contact of the main body when the process cartridge is mounted to the main body; Developing roller; and a developer supplying roller for supplying developer to the developing roller, The process cartridge is configured so that a voltage can be applied between the developing roller and the developer supplying roller through an electrical connection with the main body, and The developer supply roller is the electrophotographic roller according to claim 1 or 2.

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