Electrophotographic roller, process cartridge and electrophotographic image forming apparatus

Abstract

An electrophotographic roller that can suppress scratches caused by abrasion and cracks that develop inside the roller, even when used repeatedly over long periods in high- and low-temperature environments. [Solution] An electrophotographic roller having a conductive substrate and a resin layer on the outer peripheral surface of the substrate, wherein the resin layer has a thickness of 2.0 to 30.0 μm, the resin layer contains a binder resin and carbon black dispersed in the binder resin, the arithmetic mean value Rc of the equivalent-circle diameters of the carbon black in the resin layer is 80 nm or less, the arithmetic mean value d of the distance between wall surfaces of the carbon black in the resin layer is 60 to 170 nm, and when the elastic modulus E1 of the binder resin in a first region from the outer surface of the resin layer to a depth of 0.1 μm, measured on a cross section in the thickness direction of the resin layer, is taken as E1, E1 satisfies the following formula (1): E1 ≥ 200 MPa ···(1);

Description

[Technical Field]

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

[0002] In electrophotographic image forming apparatuses (such as electrophotographic copiers, facsimiles, and printers), an image carrier is charged by a charging roller, and an electrostatic latent image is formed by a laser. Next, toner in a developer container is applied to the developing roller by a toner supply roller and a toner regulating member, and development with the toner occurs when the image carrier and the developing roller come into contact with or are in close proximity to each other. Thereafter, the toner on the image carrier is transferred to recording paper by a transfer means and fixed by heat and pressure, and any toner remaining on the image carrier is removed by a cleaning blade. In recent years, with the demand for even longer life for electrophotographic image forming apparatuses, even greater durability has been required for electrophotographic rollers.

[0003] For example, if the durability life of an electrophotographic image forming apparatus becomes extremely long, the surface of a conventional developing roller may be worn down and scratched due to repeated rubbing, which may impair the functionality required for electrophotography.

[0004] For example, in the case of a developing roller, repeated rubbing can abrade the surface, causing scratches. It is difficult to form high-quality electrophotographic images using such a developing roller. Furthermore, in the case of a charging roller, scratches can reduce charging uniformity, causing the electrophotographic image to become rough over time. In order to continue to stably output high-quality electrophotographic images for a long period of time, an electrophotographic roller is required in which scratches caused by abrasion are suppressed to a higher level, that is, which has superior durability. In Patent Document 1, an interpenetrating polymer network structure (hereinafter referred to as an IPN structure) of cross-linked urethane resin and cross-linked acrylic resin is formed near the outer surface, which can suppress scratches due to abrasion even during long-term use such as printing many sheets in a high-temperature environment. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2020-008847 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the investigations of the present inventors, there is still room for improvement in the scratch resistance of the electrophotographic roller disclosed in Patent Document 1. Specifically, for example, repeated use over a long period of time in high and low temperature environments can cause scratches caused by abrasion to progress to the interior, resulting in cracks.

[0007] The present disclosure provides an electrophotographic roller that can suppress scratches caused by abrasion and cracks caused by scratches progressing to the interior even when used repeatedly over long periods in high-temperature and low-temperature environments.The present disclosure also provides a process cartridge that contributes to the stable formation of high-quality electrophotographic images.Furthermore, the present disclosure provides an electrophotographic image forming apparatus that can form high-quality electrophotographic images. [Means for solving the problem]

[0008] The present disclosure relates to an electrophotographic roller having a conductive substrate and a resin layer on the outer peripheral surface of the substrate. There was, The resin layer has a thickness of 2.0 to 30.0 μm, the resin layer contains a binder resin and carbon black dispersed in the binder resin, the arithmetic mean value Rc of the equivalent circle diameter of the carbon black in the resin layer is 80 nm or less; the arithmetic mean value d of the distance between wall surfaces of the carbon black in the resin layer is 60 to 170 nm; When the elastic modulus of the binder resin in a first region from the outer surface of the resin layer to a depth of 0.1 μm, measured in a cross section in the thickness direction of the resin layer, is defined as E1, E1 can be expressed by the following formula (1): E1 ≥ 200 MPa ···(1); The present invention relates to an electrophotographic roller that satisfies the above requirements. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide an electrophotographic roller that can suppress scratches caused by abrasion and cracks caused by scratches progressing to the interior even when used repeatedly over a long period of time in high-temperature and low-temperature environments. Also, according to the present disclosure, it is possible to provide a process cartridge that contributes to the stable formation of high-quality electrophotographic images. Furthermore, according to the present disclosure, it is possible to provide an electrophotographic image forming apparatus that can form high-quality electrophotographic images. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing an example of an electrophotographic roller according to the present disclosure. [Figure 2] FIG. 10 is a schematic cross-sectional view showing another example of an electrophotographic roller according to the present disclosure. [Figure 3] 1 is a schematic diagram of an electrophotographic image forming apparatus according to the present disclosure; [Figure 4] FIG. 2 is a schematic view of a process cartridge according to the present disclosure. [Figure 5] 1 is a cross-sectional view of an electrophotographic roller according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the present disclosure, expressions such as "XX or more and YY or less" or "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined arbitrarily. Furthermore, in the present disclosure, expressions such as "at least one selected from the group consisting of XX, YY, and ZZ" mean 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. Note that when XX is a group, multiple XXs may be selected, and the same applies to YY and ZZ.

[0012] According to the study by the present inventors, there is still room for improvement in the scratch resistance of the electrophotographic roller disclosed in Patent Document 1 when used in a low-temperature environment. Specifically, for example, repeated use in high-temperature and low-temperature environments over a long period of time can cause scratches caused by abrasion to progress to the interior, resulting in cracks.

[0013] The electrophotographic roller disclosed in Patent Document 1 exhibits strength and flexibility by forming an IPN structure of cross-linked urethane resin and cross-linked acrylic resin near the outer surface. An IPN structure is a structure in which two or more polymer network structures are intertwined and entangled without being linked by covalent bonds. In the embodiment disclosed in Patent Document 1, a cross-linked acrylic resin, which has a higher elastic modulus than the cross-linked urethane resin, is used as the second polymer to form the network. As a result, scratches due to abrasion can be suppressed during durable use in high-temperature environments where a large number of sheets are printed.

[0014] However, the IPN structure of cross-linked urethane resin and cross-linked acrylic resin can lose its toughness and become brittle in low temperature environments, and any scratches that occur can progress to the inside and cause cracks. There is a possibility that this will become a problem. As a result of extensive investigations, the inventors have come to the conclusion that in order to obtain an electrophotographic roller that can suppress the occurrence of scratches and cracks due to abrasion when used repeatedly over long periods in high and low temperature environments, it is necessary to simultaneously satisfy the following two requirements:

[0015] Requirement (1) When the elastic modulus of the binder resin in a first region from the outer surface of the resin layer to a depth of 0.1 μm measured in a cross section in the thickness direction of the resin layer of the electrophotographic roller is defined as E1, E1 satisfies the following formula (1). E1 ≥ 200 MPa ···(1);

[0016] Requirement (2) The resin layer of the electrophotographic roller contains a binder resin and carbon black dispersed in the binder resin, and the arithmetic mean value Rc of the equivalent circle diameter of the carbon black in the resin layer is 80 nm or less, and the arithmetic mean value d of the distance between the wall surfaces of the carbon black in the resin layer is 60 to 170 nm.

[0017] The following provides a detailed explanation of the above requirements (1) and (2). <Technical significance of requirement (1)> Requirement (1) specifies the modulus of elasticity in a region extending from the outer surface of the electrophotographic roller to a depth of 0.1 μm. A high modulus of elasticity in this region indicates a high hardness on the outermost surface of the electrophotographic roller. Resin materials generally soften in high-temperature environments, so frictional force is higher in high-temperature environments than in room-temperature environments. In such environments, if an electrophotographic roller with a resin layer having a low modulus of elasticity is used for a long period of time, scratches due to abrasion will occur.

[0018] The elastic modulus E1 is 200 MPa or more, preferably 250 MPa or more, and more preferably 400 MPa or more. There is no particular upper limit, but the elastic modulus E1 is, for example, 600 MPa or less, or 550 MPa or less. The elastic modulus E1 is preferably 200 to 600 MPa, more preferably 250 to 600 MPa, and even more preferably 400 to 600 MPa. By setting the elastic modulus E1 within this range, it is possible to suppress to an extremely high level the occurrence of scratches due to abrasion even when used over a long period of time in a high temperature environment.

[0019] <Technical significance of requirement (2)> Requirement (2) specifies the dispersibility of carbon black contained in the resin layer of an electrophotographic roller. In electrophotographic rollers, a method of dispersing carbon black in the resin layer is preferably used to obtain electrical conductivity. The aforementioned cracks are more likely to occur in low-temperature environments where the toughness of the resin layer is reduced, as they start from scratches and progress along the resin-carbon black interface. After extensive research, the inventors discovered that by highly dispersing carbon black in the resin layer, it is possible to prevent scratches from progressing along the resin-carbon black interface.

[0020] In requirement (1), by increasing the modulus of elasticity in the region from the outer surface to a depth of 0.1 μm to 200 MPa or more, it was possible to suppress the occurrence of scratches due to abrasion to an extremely high level. However, in a low-temperature environment, the toughness in the region from the outer surface to a depth of 0.1 μm tends to decrease, so scratches that do occur will progress deeper and cause cracks.

[0021] In the present disclosure, the arithmetic mean value Rc of the equivalent circle diameter of the carbon black in the resin layer is 80 nm or less, and the arithmetic mean value d of the distance between the wall surfaces of the carbon black in the resin layer is 60 By setting Rc and d within the above ranges, scratches are less likely to progress to the inside even in a resin layer with reduced toughness, and the occurrence of cracks can be suppressed.

[0022] Scratches progress along the carbon black-resin layer interface. Therefore, if Rc is outside the above range, the carbon black-resin layer interface tends to be continuous, and scratches tend to progress. Also, if d is less than 60 nm, adjacent carbon black particles come close to each other, and scratches tend to progress in a similar manner. If d exceeds 170 nm, the distance between adjacent carbon black particles is too great, making it difficult to obtain good electrical conductivity in the resin layer.

[0023] The arithmetic mean value Rc of the equivalent circle diameter is preferably 60 nm or less, for example, 30 to 80 nm, preferably 40 to 65 nm, more preferably 40 to 60 nm, and even more preferably 50 to 60 nm. The arithmetic mean value d of the distance between the wall surfaces is preferably 80 to 150 nm, more preferably 100 to 130 nm. By keeping it within the above range, the occurrence of scratches and cracks can be more easily suppressed.

[0024] In order to obtain the effects of the present disclosure, it is important to simultaneously satisfy the above requirements. By simultaneously satisfying requirements (1) and (2), scratches due to abrasion and cracks caused by scratches progressing to the interior can be suppressed even when used repeatedly over long periods in high- and low-temperature environments. If requirement (1) is not satisfied, scratches due to abrasion cannot be suppressed, and if requirement (2) is not satisfied, cracks caused by scratches progressing to the interior cannot be suppressed. The selection of suitable materials and manufacturing conditions for satisfying requirements (1) and (2) will be described later.

[0025] The present disclosure will be described in detail below. <Electrophotographic roller> The electrophotographic roller has a conductive substrate and a resin layer on the outer peripheral surface of the substrate. The resin layer is at least one layer, and may be a single layer. The resin layer preferably forms the outer surface of the electrophotographic roller. The substrate and the resin layer may be in direct contact with each other, or another layer may be present between the substrate and the resin layer.

[0026] An example of an electrophotographic roller is shown in Fig. 1. The electrophotographic roller 11 shown in Fig. 1 has a resin layer 13 laminated on the outer peripheral surface of a columnar or hollow cylindrical substrate 12. The layer configuration of the electrophotographic roller is not limited to the form shown in Fig. 1. Another form of electrophotographic roller is an electrophotographic roller having an intermediate layer 14 between the substrate 12 and the resin layer 13 provided on the outer peripheral surface thereof, as shown in Fig. 2.

[0027] [Base] The substrate is electrically conductive and functions as a support member for the electrophotographic roller, and in some cases as an electrode. Specific examples of the substrate preferably have a solid columnar or hollow cylindrical shape.

[0028] The material for the substrate can be appropriately selected from those known in the field of electrophotographic conductive members and materials usable for electrophotographic rollers, such as metals typified by aluminum and stainless steel, carbon steel alloys, conductive synthetic resins, iron, copper alloys, and other metals or alloys.

[0029] Furthermore, the material constituting the substrate may be subjected to an oxidation treatment or a plating treatment with chromium, nickel, etc. As the type of plating, either electroplating or electroless plating can be used. From the viewpoint of dimensional stability, electroless plating is preferred. Examples of the types of electroless plating used here include nickel plating, copper plating, gold plating, and various other alloy plating. The plating thickness is preferably 0.05 μm or more, and in consideration of the balance between work efficiency and rust prevention ability, the plating thickness is preferably 0.1 to 30 μm.

[0030] A primer may be applied to the surface of the substrate to improve adhesion between the substrate and the resin layer. A known primer can be selected and used depending on the rubber material for forming the conductive layer and the material of the support. Examples of primer materials include thermosetting resins and thermoplastic resins. Specific examples of materials that can be used include phenolic resins, polyurethanes, acrylic resins, polyester resins, polyether resins, and epoxy resins.

[0031] In a non-magnetic one-component contact development process, an electrophotographic roller is preferably used in which an intermediate layer 14 is laminated between a substrate 12 and a resin layer 13. The intermediate layer is preferably formed of a molded body of a normal rubber material. Examples of rubber materials include ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), fluororubber, silicone rubber, epichlorohydrin rubber, hydrogenated NBR, and urethane rubber. These can be used alone or in combination of two or more types.

[0032] [Resin layer]

[0033] (binder resin) The resin layer contains a binder resin. Known binder resins can be used as the binder resin. From the viewpoints of excellent flexibility and strength and facilitating the formation of an IPN structure described below, the binder resin preferably contains a cross-linked urethane resin.

[0034] The urethane resin can be obtained from a urethane raw material containing a polyol, an isocyanate, and optionally a chain extender. The urethane resin may be a cured product of the urethane raw material, or a cured product of a urethane raw material mixture containing the urethane raw material and additives such as a surface modifier and roughness-forming particles. Examples of polyols used as raw materials for the urethane resin include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, acrylic polyols, and mixtures thereof. Among these, polycarbonate polyols are preferred.

[0035] Examples of isocyanates that are raw materials for urethane resins include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), phenylene diisocyanate (PPDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), cyclohexane diisocyanate, polymeric MDI, and mixtures thereof.

[0036] Among the above, polymeric MDI is preferred. Polymeric MDI is a mixture of monomeric MDI and high molecular weight polyisocyanate, and is represented by the following formula (A): n in formula (A) is preferably 0 or more and 4 or less. Commercially available polymeric MDI may be used, and examples thereof include Millionate MR series (manufactured by Tosoh Corporation) such as Millionate MR400 (trade name). [ka]

[0037] Examples of chain extenders, which are raw materials for urethane resins, include bifunctional low-molecular-weight diols such as ethylene glycol, 1,4-butanediol, and 3-methylpentanediol, trifunctional low-molecular-weight triols such as trimethylolpropane, and mixtures thereof. Prepolymer-type isocyanate compounds having terminal isocyanate groups, obtained by preliminarily reacting the above-mentioned isocyanate compounds with various polyols in an excess state of isocyanate groups, may also be used. These isocyanate compounds may also be materials in which the isocyanate groups are blocked with various blocking agents such as MEK oxime.

[0038] Regardless of which material is used, a urethane resin can be obtained by reacting a polyol with an isocyanate under heat. If either the polyol or the isocyanate, or both, have a branched structure and three or more functional groups, the resulting urethane resin will be a crosslinked urethane resin.

[0039] Furthermore, from the viewpoint of the elastic modulus of the resin layer, the binder resin preferably contains a cross-linked urethane resin having a polycarbonate structure, which makes it easy to control E1 and E2 within suitable ranges.

[0040] It can be confirmed by, for example, pyrolysis GC / MS, FT-IR, or NMR analysis that the polymer contained in the resin layer of the electrophotographic roller is a crosslinked urethane resin having a polycarbonate structure.

[0041] (Crosslinked (meth)acrylic resin) Crosslinked (meth)acrylic resins (hereinafter simply referred to as "crosslinked acrylic resins") are harder than crosslinked urethane resins, and therefore can increase the hardness of the outermost surface. However, crosslinked acrylic resins are brittle when used alone, and are prone to scratches due to abrasion caused by friction. On the other hand, when an IPN structure, as described below, is introduced into the outer surface or near the outer surface of the resin layer, brittleness is less likely to occur, and high strength can be imparted while maintaining flexibility.

[0042] The resin layer preferably contains a cross-linked urethane resin and a cross-linked acrylic resin. The resin layer preferably contains a cross-linked urethane resin as a binder resin. In the resin layer, the cross-linked urethane resin and the cross-linked acrylic resin preferably form an interpenetrating polymer network structure (IPN structure).

[0043] The IPN structure is defined as a structure in which the network structures of two or more polymer compounds are intertwined and entangled without being linked by covalent bonds. The IPN structure in the resin layer is preferably formed by the incorporation of a cross-linked acrylic resin into the network of a three-dimensional cross-linked structure of a cross-linked urethane resin.

[0044] Crosslinked acrylic resins are formed by polymerization of (meth)acrylic monomers. Here, (meth)acrylic monomers refer to acrylic monomers and methacrylic monomers. That is, crosslinked acrylic resins are formed by polymerization of either or both of acrylic monomers and methacrylic monomers.

[0045] In order for the cross-linked acrylic resin to form an IPN structure with the cross-linked urethane resin on the outer surface of the resin layer or in the vicinity of the outer surface, it is preferable to impregnate the resin layer containing the cross-linked urethane with a liquid (meth)acrylic monomer and then cure it.

[0046] The types of (meth)acrylic monomers used here include polyfunctional monomers having multiple acryloyl or methacryloyl groups as functional groups to form a crosslinked structure. On the other hand, if the functional groups are four or more, the viscosity of the (meth)acrylic monomer increases, making it difficult for the (meth)acrylic monomer to penetrate into the surface of the resin layer made of crosslinked urethane resin, and as a result, it is difficult to form an IPN structure. Therefore, the (meth)acrylic monomer is preferably a monomer having two or three acryloyl and methacryloyl groups in one molecule, and more preferably a bifunctional (meth)acrylic monomer having two acryloyl and methacryloyl groups in one molecule. Furthermore, monofunctional monomers may be combined as needed.

[0047] The bifunctional (meth)acrylic monomer is preferably at least one selected from the group consisting of alkylene glycol di(meth)acrylates and alkylene oxide (ethylene oxide, propylene oxide) modified alkylene glycol di(meth)acrylates, such as propylene oxide modified neopentyl glycol diacrylate. Examples of trifunctional (meth)acrylic monomers include trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate.

[0048] The molecular weight of the (meth)acrylic monomer is preferably in the range of 200 to 750. By using a molecular weight in this range, an IPN structure can be easily formed relative to the network structure of the cross-linked urethane resin, and the strength of the resin layer can be effectively improved. The content of the cross-linked acrylic resin in the resin layer is preferably 3 to 20 parts by mass, more preferably 5 to 15 parts by mass, per 100 parts by mass of the cross-linked urethane resin.

[0049] As mentioned above, the (meth)acrylic monomer is impregnated into the resin layer containing the cross-linked urethane resin. To achieve this, the (meth)acrylic monomer must have an appropriate viscosity. That is, if the viscosity is high, impregnation is difficult, and if the viscosity is low, it is difficult to control the impregnation state. Therefore, the viscosity of the (meth)acrylic monomer is preferably 5.0 mPa·s or more and 140 mPa·s or less at 25°C. That is, by selecting one or more (meth)acrylic monomers that satisfy the above-mentioned molecular weight and viscosity ranges, impregnating the resin layer, and polymerizing them, an IPN structure of the cross-linked urethane resin and the cross-linked acrylic resin can be formed.

[0050] The polymerization method for the (meth)acrylic monomer is not particularly limited, and known methods can be used. Specific examples include methods such as heating and ultraviolet irradiation. Known radical polymerization initiators and ionic polymerization initiators can be used for each polymerization method. These polymerization initiators may be used alone or in combination of two or more.

[0051] Known heating devices and ultraviolet irradiation devices can be used as appropriate. Examples of light sources that can be used to irradiate ultraviolet light include LED lamps, high-pressure mercury lamps, metal halide lamps, xenon lamps, and low-pressure mercury lamps. The cumulative light intensity required for polymerization can be adjusted as appropriate depending on the types and amounts of compounds and polymerization initiators used.

[0052] (surface modifier) The resin layer may contain a surfactant such as a modified silicone compound or a modified fluorine compound in addition to the crosslinked urethane resin. The surfactant may have both a low-polarity group such as a silicone-containing group or a fluorine-containing group and a high-polarity group at the modified site. The surface modifier is preferably contained in the urethane raw material mixture that forms the crosslinked urethane resin.

[0053] Due to the large difference in polarity between the urethane groups or other highly polar groups of the cross-linked urethane resin and the low-polarity groups, such as silicone-containing or fluorine-containing groups, in the surfactant molecules, the surfactant migrates to and remains near the outer surface of the resin layer. Furthermore, when a (meth)acrylic monomer and a polymerization initiator are swollen from the outer surface of a cross-linked urethane resin containing a surfactant, using a (meth)acrylic monomer with a small difference in polarity from the highly polar groups in the surfactant molecule allows the (meth)acrylic monomer to remain near the surfactant. In other words, because the (meth)acrylic monomer remains near the outer surface and hardens, it becomes easier to form an IPN structure locally on the outer surface of the resin layer and near the outer surface.

[0054] (carbon black) The resin layer contains a binder resin and carbon black dispersed in the binder resin. The carbon black is dispersed in the resin layer to obtain electrical conductivity. Furthermore, to facilitate high dispersion in the resin layer, carbon black having a number-average diameter of primary particles of 30 nm or less, DBP absorption of 90 ml / 100 g or less, and a pH of 4.0 or less is preferred.

[0055] When the number-average diameter of primary particles of carbon black is 30 nm or less and the DBP absorption is 90 ml / 100 g or less, the aggregates (primary agglomerates), which are the smallest dispersible units of carbon black, become smaller, and the structure (the size of the connections between particles) also becomes smaller, making it easier to reduce the equivalent circle diameter Rc, which will be described later.

[0056] The lower the number-average particle diameter, the better, and there is no particular lower limit. For example, the number-average particle diameter of primary particles of carbon black is preferably 5 to 30 nm, more preferably 20 to 30 nm. The primary particle diameter of carbon black can be calculated using a transmission electron microscope (TEM).

[0057] The lower the DBP absorption, the better, and there is no particular lower limit. For example, the DBP absorption of carbon black is preferably 30 to 90 ml / 100 g, more preferably 40 to 80 ml / 100 g.

[0058] When the pH of carbon black is 4.0 or less, the repulsion of the surface functional groups of the carbon black makes it difficult for the carbon black to aggregate, thereby achieving dispersion stability. The lower the pH of carbon black, the more preferable it is, and there is no particular lower limit. For example, the pH of carbon black is preferably 2.0 to 4.0, and more preferably 2.2 to 3.6.

[0059] However, even if the number-average diameter of the primary particles of carbon black, DBP absorption, and pH are within the above ranges, when polycarbonate urethane is used as the binder resin, the carbon black may not be sufficiently dispersed, and the desired dispersion state may not be obtained. The reason why carbon black, which has the desired raw material properties, cannot be dispersed when polycarbonate urethane is used as the binder resin is not clearly understood, but is speculated as follows.

[0060] The hydroxyl groups, which are the surface functional groups of carbon black, tend to interact with the terminal hydroxyl groups of polycarbonate diol. On the other hand, the structure of the carbonate bond and hydrocarbon group bonded between the two hydroxyl groups of polycarbonate diol is hydrophobic due to the presence of the hydrocarbon group, making it less likely to interact with carbon black. Since the structure is more stable when hydrophilic carbon black exists nearby, carbon black with the same hydrophilic property will exist near other hydrophilic carbon black. As a result, the carbon black tends to aggregate and become difficult to disperse.

[0061] In order to sufficiently disperse carbon black having the number average diameter of primary particles, DBP absorption amount, and pH within the above-mentioned ranges when using polycarbonate urethane as a binder resin, it is more preferable to add the additives described below.

[0062] Considering the reinforcing properties and conductivity of the resin layer, the carbon black content is preferably 5 to 45 parts by mass, more preferably 20 to 40 parts by mass, per 100 parts by mass of the binder resin that forms the resin layer. If the carbon black content exceeds 45 parts by mass, the distance between carbon black particles in the coating solution is maintained at an appropriate level, reducing the probability of collisions due to Brownian motion of carbon black particles and making carbon black less likely to aggregate. This facilitates dispersion of carbon black, and improves dispersion stability. As a result, carbon black dispersion is improved in the resin layer formed by coating the coating solution.

[0063] The arithmetic mean value Rc of the equivalent circle diameter of the carbon black in the resin layer must be 80 nm or less, and the arithmetic mean value d of the distance between the wall surfaces of the carbon black in the resin layer must be 60 to 170 nm. Furthermore, the arithmetic mean value Rc of the equivalent circle diameter is preferably 60 nm or less. Furthermore, the arithmetic mean value d of the distance between the wall surfaces is preferably 80 to 150 nm.

[0064] When the equivalent circle diameter and wall-to-wall distance are within the above ranges, scratches are less likely to penetrate deep into the resin layer that forms an IPN structure in a low-temperature environment, and cracking can be suppressed. If the arithmetic mean value Rc of the equivalent circle diameter exceeds 80 nm, scratches tend to progress along the resin-carbon black interface. If the arithmetic mean value d of the wall-to-wall distance is less than 60 nm, adjacent carbon black particles are likely to come into close proximity, causing scratches to progress. Furthermore, if d exceeds 170 nm, it is difficult to obtain adequate conductivity.

[0065] Furthermore, when the standard deviation of the circle-equivalent diameter is σc, σc / Rc is, for example, 0.000 to 0.730, preferably 0.000 to 0.650, and more preferably 0.500 to 0.650.

[0066] The arithmetic mean value Rc and standard deviation σc of the equivalent circle diameter can be changed, for example, by the dispersion state in a mill when preparing the resin layer coating. Weaker dispersion tends to increase Rc and σc, while stronger dispersion tends to decrease Rc and σc. Normally, Rc converges, so once a certain dispersion state is exceeded, σc can be reduced while Rc remains almost constant, and σc / Rc can be reduced.

[0067] Furthermore, when the standard deviation of the distance between the wall surfaces is σd, σd / d is, for example, 0.000 to 0.680, preferably 0.000 to 0.600, and more preferably 0.500 to 0.600. When σc / Rc and σd / d are within the above ranges, scratches and cracks can be more easily suppressed.

[0068] The arithmetic mean value d and standard deviation σd of the wall-to-wall distance can be changed, for example, by the dispersion state in a mill or the like when preparing the paint for the resin layer. Weaker dispersion tends to make d smaller and σd larger, while stronger dispersion tends to make d larger and σd smaller. Therefore, weaker dispersion tends to make σd / d larger, and stronger dispersion tends to make σd / d smaller.

[0069] If the dispersion state of the carbon black satisfies the above-mentioned requirements, Multiple types of blocks may be used in combination.

[0070] (resin particles) Resin particles may be added to the resin layer to form convex portions on the surface of the electrophotographic roller. To provide the resin layer with surface roughness, fine particles for imparting roughness to the resin layer may be added. Specifically, fine particles of polyurethane resin, polyester resin, polyether resin, polyamide resin, acrylic resin, or polycarbonate resin may be used. These may also preferably be crosslinked resin particles.

[0071] When an IPN structure is formed on the outer surface of the resin layer, an IPN structure may also be formed inside the crosslinked resin particles. The volume average particle diameter of the fine particles is preferably 1.0 μm or more and 30 μm or less. The surface roughness (ten-point average roughness) Rzjis formed by the fine particles is preferably 0.1 μm or more and 20 μm or less. Rzjis is a value measured based on JIS B0601 (1994).

[0072] (additives) Additives are preferably used to further improve the dispersibility of carbon black in a binder resin using polycarbonate urethane. The additives make it easier to achieve the above-mentioned ranges for Rc, d, σc / Rc, and σd / d. Here, the resin layer preferably contains, as an additive, at least one compound selected from the group consisting of a compound having a structure represented by the following structural formula (2), a compound having a structure represented by the following structural formula (3), and a compound having a structure represented by the following structural formula (4). One method for incorporating the additive into the resin layer is to incorporate a dispersant into the resin layer coating material. In a resin layer formed using a resin layer coating material containing at least one compound selected from the group consisting of a compound having a structure represented by structural formula (2) and a compound having a structure represented by structural formula (3), the compound may be incorporated at the end of the polyurethane polymer chain. Even in such cases, the effect of improving the dispersibility of carbon black can be expected. However, it is preferable for the additive to be present in the resin layer independently of the polyurethane.

[0073] Among these, structural formula (2) is more preferred because it has particularly excellent carbon black dispersibility and affinity with polycarbonate urethane. By satisfying the above, it becomes easier to achieve the above-mentioned carbon black dispersion state, and it becomes easier to keep Rc, d, σc / Rc, and σd / d within the above ranges. [ka]

[0074] In structural formula (2), R21 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms (preferably 3 to 12). t and u represent the average number of moles added, and each independently represents a number of 1 or more (preferably 5 to 30, more preferably 10 to 25). In structural formula (3), R31 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms (preferably 1 to 4). v and w represent the average number of moles added, and each independently represents a number of 1 or more (preferably 1 to 30, more preferably 5 to 30). In structural formula (4), R41 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms. x represents the average number of moles added and represents a number of 1 or more (preferably 1 to 30, more preferably 4 to 15).

[0075] Structural formula (2) is polyoxyethylene polyoxypropylene alkyl ether, a polyether monool with a block-type addition polymerization structure of ethylene oxide and propylene oxide. The terminal hydroxyl groups of this polyether monool interact with the surface functional groups of the conductive filler carbon black through hydrogen bonding, acting as a dispersant for the carbon black. In addition, the structure is compatible with polycarbonate urethane, enhancing its effectiveness as a dispersant for carbon black.

[0076] Ethylene oxide is introduced into the structure to ensure uniform distribution of additives throughout the polycarbonate urethane. This is believed to be because the ethylene group in ethylene oxide is compatible with the hydrophobic hydrocarbon group in the polycarbonate urethane. Propylene oxide is introduced into the structure to improve the dispersibility of carbon black dispersed in the resin layer. This is believed to be due to the interaction of the side chain methyl group of propylene oxide with the carbon black, improving the dispersibility of the carbon black.

[0077] R21, a monovalent hydrocarbon group having 1 to 12 carbon atoms, is introduced into the structure to allow the additive to be distributed uniformly throughout the polycarbonate urethane. Being a monovalent hydrocarbon group improves compatibility with the hydrophobic hydrocarbon groups in the polycarbonate urethane, allowing the additive to be distributed uniformly throughout the polycarbonate urethane. Having 12 or fewer carbon atoms reduces steric hindrance with the polycarbonate urethane, making it easier for the additive to be distributed uniformly. Furthermore, since the compound of formula (5) has a monool structure, it has poorer reactivity than a diol, and is less likely to be incorporated into the urethane reaction caused by the reaction of an isocyanate with a polyol.

[0078] The polyoxyethylene polyoxypropylene alkyl ether can be a commercially available product or can be obtained by synthesis. The synthesis of polyoxyethylene polyoxypropylene alkyl ether can be carried out by carrying out the following step (A) followed by step (B). Note that step (B) may also be carried out on a commercially available product whose structure has already been completed up to step (A).

[0079] Step (A): Reaction of alcohol with ethylene oxide Step (B): Reaction of the product obtained in step (A) with propylene oxide In step (A), the reaction can be carried out by adding ethylene oxide to an alcohol in the presence of a catalyst at 50 to 200°C, more preferably 100 to 160°C. Since ethylene oxide has a boiling point of 10.7°C and is in a gaseous state at this temperature, the reaction is preferably carried out in a pressurized environment in a sealed container. The pressure is preferably 0.1 MPa to 1.0 MPa. The reaction time is not particularly limited, but is preferably about 1 to 3 hours in order to reduce the amount of unreacted ethylene oxide.

[0080] The catalyst may be an acid catalyst or an alkali catalyst, but an alkali catalyst is preferred to facilitate purification after the reaction. Examples of alkali catalysts include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and barium hydroxide, ammonium hydroxide, and tertiary amines. In view of the ease and efficiency of the reaction, sodium hydroxide and potassium hydroxide are particularly preferred. Examples of acid catalysts include Bronsted acids such as sulfuric acid and phosphoric acid, and Lewis acids such as stannic chloride and boron trifluoride.

[0081] The amount of catalyst used is preferably 0.1 to 5 mol % per 1 mol of alcohol in the case of sodium hydroxide or potassium hydroxide. Since ethylene oxide reacts with water to produce ethylene glycol, it is important to prevent water from entering the reaction system as much as possible, and a dehydration treatment may be carried out before the reaction in step (A) as necessary.

[0082] Step (B) can be carried out under the same conditions as step (A). Propylene oxide has a boiling point of 34.2°C and is in a gaseous state at reaction temperatures of 50 to 200°C, so the reaction is preferably carried out in a pressurized environment in a sealed container. The catalyst used in step (A) may be used as is, or a new catalyst may be added. When a new catalyst is added, the catalyst used in step (A) is preferred.

[0083] Structural formula (3) is a polyetheramine (monoamine) with a block-type addition polymerization structure of ethylene oxide and propylene oxide. The amino groups at the terminals of this polyetheramine interact with the surface functional groups of the conductive filler carbon black through hydrogen bonding, acting as a dispersant for the carbon black. Furthermore, to enhance its effectiveness as a dispersant, R31, a monovalent hydrocarbon group with 1 to 8 carbon atoms, is introduced, resulting in a structure that is easily compatible with the hydrophobic functional groups of polycarbonate urethane, resulting in a structure that is also highly compatible with polycarbonate urethane.

[0084] The polyether monoamine can be a commercially available product or can be obtained by synthesis. The synthesis of the polyether monoamine can be carried out by carrying out the following step (C) followed by step (D).

[0085] Step (C): Oxidation reaction of the compound of structural formula (5), which is a secondary alcohol Step (D): Reductive amination of the product obtained in step (C) Step (C) is a reaction to produce a ketone by oxidation of a secondary alcohol. The synthesis of a ketone by oxidation of a secondary alcohol is carried out using heavy metal salts such as chromic acid and manganese dioxide and their There are two types of oxidation reactions: oxidation reactions using derivatives and oxidation reactions using non-heavy metal salts using dimethyl sulfoxide (DMSO) or hypohalous acids such as hypochlorous acid.

[0086] Although either method can be used for synthesis, oxidation reactions using hypohalous acids such as dimethyl sulfoxide (DMSO) or hypochlorous acid are preferred due to the environmental impact of heavy metals. Furthermore, dimethyl sulfoxide (DMSO) can undergo explosive reactions at room temperature depending on the electrophilic activating reagent used, requiring temperatures as low as -60°C, making the method using hypohalous acids more preferable. Examples of hypohalous acids include hypochlorites such as sodium hypochlorite and calcium hypochlorite (bleaching powder). Ketones can be obtained by reacting these hypochlorites with secondary alcohols in acetic acid.

[0087] When using dimethyl sulfoxide (DMSO), an electrophilic activating reagent is required. The electrophilic activating reagent increases the electrophilicity of the sulfur in DMSO, allowing it to undergo nucleophilic attack by the alcohol's hydroxyl group. This nucleophilic attack generates a dimethylalkoxysulfonium salt, which decomposes to yield a ketone and dimethyl sulfide. Examples of electrophilic activating reagents include dicyclohexylcarbodiimide (DCC), acetic anhydride, phosphorus pentoxide, sulfur trisulfide-pyridine complex, trifluoroacetic anhydride, oxalyl chloride, and halogens.

[0088] Step (D) is a reductive amination reaction that converts a ketone to an amine. The reaction is divided into two steps. First, a carbonyl group reacts with an amine to generate an iminium cation. Next, a hydride reducing agent nucleophilically attacks the iminium cation to generate an amine. A borohydride reagent is preferably used as the reducing agent. Examples of borohydride reagents include sodium cyanoborohydride, sodium triacetoxyborohydride, and 2-picoline borane. Among these, sodium triacetoxyborohydride and 2-picoline borane are preferred due to their low toxicity. In the reductive amination reaction using a borohydride reagent, if the reagent has a bulky structure, steric hindrance makes it difficult to generate an iminium cation. Therefore, 31 in structural formula (3) is preferably a monovalent hydrocarbon group having 1 to 8 carbon atoms.

[0089] Structural formula (4) is polyoxyethylene alkyl ether acetic acid. The terminal carboxylic acid in structural formula (4) interacts with the surface functional groups of the conductive filler carbon black through hydrogen bonding, acting as a dispersant for the carbon black. In addition, to enhance its effectiveness as a dispersant, R41, a monovalent hydrocarbon group with 1 to 12 carbon atoms, is introduced, resulting in a structure that is easily compatible with the hydrophobic functional groups of polycarbonate urethane, resulting in a structure that is also compatible with polycarbonate urethane.

[0090] Polyoxyethylene alkyl ether acetic acid can be obtained by synthesis or commercially available products. Polyoxyethylene alkyl ether acetic acid can be synthesized by carrying out the following step (E) followed by step (F). Note that step (F) may also be carried out on a commercially available product whose structure has been completed up to step (E). Step (E): Reaction of alcohol with ethylene oxide Step (F): Oxidation reaction of the primary alcohol, which is the product of step (E) Step (E) is the same as step (A) and can be prepared by the same method as step (A).

[0091] Step (F) is a step in which a primary alcohol is oxidized to produce a carboxylic acid. In the oxidation of a primary alcohol, an aldehyde is produced, and then a carboxylic acid is produced by further oxidation. Therefore, it is necessary to select a reaction method and conditions that do not stop at the aldehyde. Methods for obtaining a carboxylic acid by oxidation of a primary alcohol include oxidation with an oxidizing agent and oxidation with a catalyst. Catalytic dehydrogenation is one example. Oxidizing agents include permanganate, chromic acid, ruthenium tetroxide, and hypochlorite. Dehydrogenation catalysts include palladium, platinum, iridium, rhodium, and manganese.

[0092] The compounds represented by structural formulas (2) to (4) function as dispersants for carbon black and have high affinity with polycarbonate urethane. Surfactants are typically used to improve the dispersibility and dispersion stability of carbon black. However, the compounds represented by structural formulas (2) to (4) have a low number of functional groups that interact with the surface functional groups of carbon black, resulting in weak surfactant properties and making them uncommonly used. Coupling agents and nonionic surfactants are commonly used as dispersants for carbon black.

[0093] Silane coupling agents, titanate coupling agents, and aluminum coupling agents are used as coupling agents, while polyester and polyether-based nonionic surfactants are used. However, adding these dispersants to polycarbonate urethane to a level that sufficiently enhances the dispersibility of carbon black (50 to 100% by mass relative to the carbon black) inhibits the conductivity of the carbon black and binder resin. Conversely, adding them in an amount that does not inhibit the conductivity of the carbon black and binder resin (10 to 40% by mass relative to the carbon black) does not result in sufficient dispersibility of the carbon black.

[0094] The amount of the compound represented by structural formulas (2) to (4) added is preferably within the following range: the content of the compound represented by structural formulas (2) to (4) in the resin layer is preferably 3.0 to 7.0 mass %, and is preferably 18.9 to 46.0 mass parts per 100 mass parts of carbon black.

[0095] When the content is equal to or greater than the lower limit, the dispersibility of the carbon black is further improved, and the desired dispersibility is more easily achieved.When the content is equal to or less than the upper limit, the urethane polymerization reaction is less likely to be inhibited, and the desired hardness and resistance are more easily achieved.

[0096] The presence of additives in the resin layer can be confirmed and quantitatively evaluated by the following method: The resin layer of the electrophotographic roller is cut out, and the cut piece is subjected to, for example, 1 H-NMR, 13 Analysis is performed using C-NMR, XPS, and FT-IR. This allows the detection of the carbonate structure of the binder resin, and the ether structure, amine structure, and carboxylic acid structure of the additive in the resin layer, and the ratio can be calculated from the peak ratios, etc. Alternatively, sections can be extracted by soaking them overnight in an organic solvent such as methyl ethyl ketone, and the extract and the extracted sections can be analyzed. 1 H-NMR, 13 Analysis using C-NMR, XPS, and FT-IR allows calculation of the proportion of additives incorporated into the resin during the polymerization reaction and those that are not.

[0097] The resin layer may have a structure in which at least one of the compounds having the structures represented by structural formulas (2) and (3) is bonded to polyurethane (a structure resulting from a reaction during polyurethane polymerization). Examples of the structure resulting from a reaction during polyurethane polymerization include the following: In the case of the structure represented by structural formula (2), in polyurethane, the compound having the structure represented by structural formula (2) is a urethane structure. In the case of the structure represented by structural formula (3), in polyurethane, the compound having the structure represented by structural formula (3) is a urea-modified structure.

[0098] (Other additives) In addition to the above-described components, the resin layer may contain a crosslinking agent, Various additives such as crosslinking aids, plasticizers, fillers, extenders, vulcanizing agents, vulcanization aids, antioxidants, antiaging agents, processing aids, dispersants, and leveling agents can be added.

[0099] (Manufacturing method) (Resin layer manufacturing method) The method for manufacturing an electrophotographic roller preferably includes a step of preparing a conductive substrate and a step of forming a resin layer on the outer peripheral surface of the substrate. The step of forming the resin layer preferably includes a step of applying and curing a urethane raw material mixture (resin layer coating material) containing a urethane raw material for forming a crosslinked urethane resin and a surface modifier to obtain a crosslinked urethane resin. Furthermore, it is preferable to impregnate the crosslinked urethane resin with a (meth)acrylic monomer for forming a crosslinked acrylic resin, polymerize the (meth)acrylic monomer, and form a crosslinked acrylic resin to obtain the resin layer.

[0100] Before the step of forming the resin layer, a step of forming an elastic layer on the outer surface of the substrate may be carried out. The elastic layer can be obtained, for example, by applying a silicone rubber mixture to the outer surface of the substrate and curing it.

[0101] The method for forming the resin layer containing the crosslinked urethane resin is not particularly limited, but a coating molding method using a liquid paint is preferred. For example, it is preferable to disperse and mix the materials for the resin layer in a solvent to form a urethane raw material mixture, and then coat the resulting paint on a conductive substrate and dry or heat cure it.

[0102] As the solvent, a polar solvent is preferred from the viewpoint of compatibility with polyols and isocyanate compounds, which are raw materials for the crosslinked urethane resin. Examples of polar solvents include alcohols such as methanol, ethanol, and n-propanol, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and esters such as methyl acetate and ethyl acetate. Of these, solvents that are compatible with other materials can be used alone or in combination of two or more.

[0103] The solid content of the paint can be freely adjusted by the amount of solvent mixed, but is preferably 20% by mass or more and 40% by mass or less from the viewpoint of uniformly dispersing the electronically conductive material such as carbon black (described later). For dispersion and mixing, known dispersion devices using beads, such as a sand mill, paint shaker, dyno mill, or pearl mill, can be used. The coating method can be dip coating, ring coating, spray coating, or roll coating.

[0104] For example, a liquid coating is prepared by mixing raw materials for the binder resin, such as polyol, an isocyanate compound, carbon black, a surface modifier, and additives. The resin layer coating is then applied to the substrate. The resulting coating is then dried and solidified, or heated and cured, to form a crosslinked urethane resin.

[0105] Next, the resin layer formed as described above is impregnated with a liquid (meth)acrylic monomer. The liquid (meth)acrylic monomer can be used as is or as an impregnation treatment liquid diluted appropriately with various solvents. By appropriately diluting the liquid (meth)acrylic monomer with various solvents, a resin layer with a more uniform surface composition can be obtained.

[0106] The solvent can be freely selected as long as it has both affinity with the resin layer and solubility for the (meth)acrylic monomer, for example, alcohols such as methanol, ethanol, and n-propanol, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and esters such as methyl acetate and ethyl acetate.

[0107] In addition, a polymerization initiator is appropriately mixed into the impregnation treatment solution. The method for impregnating the impregnation treatment solution is not particularly limited, but dip coating, ring coating, spray coating, or roll coating can be used. After that, the material is dried, for example, at 80 to 120°C for 0.5 to 3 hours to volatilize the solvent.

[0108] By this process, the crosslinked (meth)acrylic resin is introduced into the network structure of the crosslinked urethane resin in the resin layer in a mutually entangled manner, thereby forming an IPN structure. In particular, it is preferable to form an IPN structure using a crosslinked polymer with a higher elastic modulus than the crosslinked urethane resin, particularly a crosslinked (meth)acrylic resin.

[0109] This IPN structure is formed by impregnating a cross-linked urethane resin (first component) with a (meth)acrylic monomer and a polymerization initiator from the outer surface, and then forming a cross-linked acrylic resin (second component) polymer. In this case, the (meth)acrylic monomer penetrates into the three-dimensional network structure of the cross-linked urethane resin and polymerizes to form a network structure of the cross-linked acrylic resin.

[0110] The thickness of the resin layer is 2.0 to 30.0 μm, preferably 5.0 to 30.0 μm, and more preferably 10.0 to 20.0 μm.

[0111] <Process cartridge and electrophotographic image forming apparatus> The electrophotographic image forming apparatus includes an electrophotographic roller. The electrophotographic image forming apparatus of the present disclosure includes an image carrier for carrying an electrostatic latent image, a charging roller for primarily charging the image carrier, and a developing roller for developing the electrostatic latent image with toner to form a toner image. The electrophotographic image forming apparatus may have an image carrier for carrying an electrostatic latent image, a charging roller for primarily charging the image carrier, an exposure device for forming an electrostatic latent image on the primarily charged image carrier, a developing roller for developing the electrostatic latent image with toner to form a toner image, and a transfer device for transferring the toner image to a transfer material. Preferably, either or both of the charging roller and the developing roller are electrophotographic rollers of the present disclosure.

[0112] FIG. 3 is a cross-sectional view showing a schematic configuration of an electrophotographic image forming apparatus according to one embodiment of the present disclosure. FIG. 4 is an enlarged cross-sectional view of a process cartridge 22 to be mounted in the electrophotographic image forming apparatus of FIG. 3. The process cartridge 22 includes an image carrier 19, a charging device including a charging roller 20, and a developing device including a developing roller 15. The process cartridge may also include a cleaning device including a cleaning member 21. The process cartridge includes an electrophotographic roller. It is preferable that either or both of the charging roller and the developing roller be the electrophotographic roller of the present disclosure. The process cartridge is configured to be detachably mountable to the main body of the electrophotographic image forming apparatus of FIG. 3.

[0113] The image carrier 19 is uniformly charged (primary charging) by a charging roller 20 connected to a bias power supply (not shown). At this time, the charged potential of the image carrier 19 is between -800V and -400V. Next, the image carrier 19 is irradiated with exposure light 23 for writing an electrostatic latent image by an exposure device (not shown), and an electrostatic latent image is formed on its surface. Either LED light or laser light can be used as the exposure light 23. The surface potential of the exposed portion of the image carrier 19 is between -200V and -100V.

[0114] Next, negatively charged toner 31 is applied (developed) to the electrostatic latent image by the developing roller 15, forming a toner image on the image carrier 19 and converting the electrostatic latent image into a visible image. At this time, a voltage of -500 V or more and -300 V or less is applied to the developing roller 15 by a bias power supply (not shown). The developing roller 15 is in contact with the image carrier 19 with a nip width of 0.5 mm or more and 3 mm or less.

[0115] In a process cartridge according to one embodiment of the present disclosure, a toner supply roller 17 is rotatably brought into contact with the developing roller 15, upstream of the contact portion between the developing blade 16, which is a toner regulating member, and the developing roller 15 in the rotational direction of the developing roller 15. A toner image developed on the image carrier 19 is primarily transferred to the intermediate transfer belt 24. A primary transfer member 25 is in contact with the rear surface of the intermediate transfer belt 24, and a voltage of +100 V or more and +1500 V or less is applied to the primary transfer member 25 to primarily transfer the negative polarity toner image from the image carrier 19 to the intermediate transfer belt 24. The primary transfer member 25 may be in the form of a roller or a blade.

[0116] When the electrophotographic image forming apparatus is a full-color image forming apparatus, the above-mentioned charging, exposure, development, and primary transfer processes are performed for each of the colors yellow, cyan, magenta, and black. To this end, the electrophotographic image forming apparatus shown in FIG. 3 has four process cartridges, one for each color, each containing a toner of the above color, detachably mounted in the main body of the electrophotographic image forming apparatus. The above-mentioned charging, exposure, development, and primary transfer processes are performed sequentially with a predetermined time difference, and a state in which four color toner images are superimposed on the intermediate transfer belt 24 to represent a full-color image is created.

[0117] The toner image on the intermediate transfer belt 24 is conveyed to a position facing the secondary transfer member 26 as the intermediate transfer belt 24 rotates. A recording sheet is conveyed along the conveyance route 27 of the recording sheet between the intermediate transfer belt 24 and the secondary transfer member 26 at a predetermined timing. By applying a secondary transfer bias to the secondary transfer member 26, the toner image on the intermediate transfer belt 24 is transferred to the recording sheet. At this time, the bias voltage applied to the secondary transfer member 26 is +1000 V or more and +4000 V or less.

[0118] The recording sheet onto which the toner image has been transferred by the secondary transfer member 26 is conveyed to the fixing device 28. After melting the toner image on the recording sheet and fixing it on the recording sheet, the recording sheet is discharged outside the electrophotographic image forming apparatus, thereby completing the printing operation. Note that the toner remaining on the image carrier 19 without being transferred from the image carrier 19 to the intermediate transfer belt 24 is scraped off by the cleaning member 21 for cleaning the surface of the image carrier 19, and the surface of the image carrier 19 is cleaned.

[0119] <Method for Measuring SPM Elastic Modulus> First, a region including a cross-section in the thickness direction of the resin layer of the electrophotographic roller is cut out into a thin slice using a diamond knife while being held at -110°C with a cryomicrotome (trade name: EMFC6, manufactured by Leica Microsystems). Further, a sample with a size of 100 μm square and a depth direction width of 100 μm is produced from the thin slice. Here, FIG. 5 shows a schematic cross-sectional view of the resin layer 54 formed on the conductive substrate 53. In the present disclosure, as shown in FIG. 5, a region from the outer surface of the resin layer 54 to a depth of 0.1 μm is defined as the first region 51, and a region from the outer surface to a depth of 1.0 μm to 1.1 μm is defined as the second region 52. The elastic modulus of the binder resin, which contains a cross-linked urethane resin as a binder, was measured in each region of the cross-section of the prepared sample. Measurements were performed using an SPM device (product name: MFP-3D-Origin, Oxford Instruments) and a probe (product name: AC160, Olympus). After first acquiring a 5 μm square topography image, the force curve was measured 10 times at positions in the binder resin other than the roughness-forming particles and carbon black. The arithmetic mean of the eight points excluding the highest and lowest values ​​was calculated, and the elastic modulus was calculated using Hertz's law. The elastic moduli of the binder resin in the first region 51 and the second region 52 were designated E1 and E2, respectively.

[0120] The meaning of E1 in the first area is as explained in the above section <Technical significance of requirement (1)>. E2 in the second region is the elastic modulus in a region from the outer surface to a depth of 1.0 μm to 1.1 μm. That is, E2 is the elastic modulus of the binder resin in the second region from the outer surface of the resin layer to a depth of 1.0 to 1.1 μm, measured on a cross section in the thickness direction of the resin layer. In this case, the elastic modulus E2 is, for example, 120 to 250 MPa, preferably 120 to 200 MPa, and more preferably 140 to 190 MPa.

[0121] When E2 in the second region is within the above-mentioned range, the load when the electrophotographic roller comes into contact with the toner is reduced, and filming caused by the toner being physically crushed can be suppressed. In the present invention, it is more preferable to simultaneously satisfy E1, E2, and high dispersion of carbon black. By simultaneously satisfying the ranges of E1, E2, the arithmetic mean value Rc of the carbon black's equivalent circle diameter, and the arithmetic mean value d of the wall-to-wall distance, filming, scratches due to abrasion, and cracks due to the progression of scratches can be simultaneously suppressed, thereby significantly improving the durability of the electrophotographic roller. The use of an IPN structure is preferred as a method for increasing the elastic modulus E1, as it allows selective increase of E1 without increasing E2. Therefore, the second region does not need to have an IPN structure.

[0122] One way to increase E1 is to significantly increase the crosslink density of the rubber that constitutes the surface of the electrophotographic roller, but this approach tends to increase hardness even to the inside of the resin layer. By keeping the elastic modulus E2 within the above range, scratches and filming can be more easily suppressed.

[0123] <How to check the interpenetrating polymer network (IPN) structure> The IPN structure is verified by microsampling mass spectrometry, which uses an ion trap mass spectrometer. The sample is fixed to a filament at the tip of the probe and inserted directly into the ionization chamber. It is then rapidly heated from room temperature to 1000°C at a constant heating rate. The sample is decomposed by heating, and the evaporated sample is ionized by irradiation with an electron beam and detected by a mass spectrometer.

[0124] Under conditions of a constant heating rate, a thermal chromatogram similar to that of TG-MS (simultaneous thermogravimetry-mass analysis) is obtained, with a mass spectrum called a total ion chromatogram (TIC). Furthermore, a thermal chromatogram for a given mass fragment can be obtained, allowing the peak temperature of the thermal chromatogram to be determined, corresponding to the decomposition temperature of the desired molecular structure. The peak temperature of the thermal chromatogram correlates with the cross-linking structure in the resin structure; the denser the cross-linking, the higher the peak temperature. In other words, the peak temperature of the thermal chromatogram where the cross-linked urethane resin and cross-linked (meth)acrylic resin form an IPN structure is higher than that of the cross-linked (meth)acrylic resin alone.

[0125] A peak top temperature A1 of a thermal chromatogram derived from a cross-linked acrylic resin is obtained from a first sample obtained from a first region, which is a region extending from the outer surface of the resin layer to a depth of 0.1 μm. Furthermore, a peak top temperature A2 of a thermal chromatogram derived from the cross-linked acrylic resin is measured from a second sample obtained by decomposing the cross-linked urethane resin contained in the first sample. When an IPN structure is formed, A1 will be higher than A2 in terms of the peak temperature of the thermal chromatogram. A2 is a value obtained by performing microsampling mass spectrometry on a second sample obtained after decomposing the crosslinked urethane by the pyridine decomposition method described below.

[0126] <Pyridine decomposition method> The pyridine decomposition method is a method for selectively decomposing urethane bonds. By performing the pyridine decomposition method on a sample with an IPN structure of cross-linked acrylic resin and cross-linked urethane resin, After removing the structure derived from the crosslinked urethane, a crosslinked acrylic resin can be obtained. The presence or absence of an IPN structure can be confirmed by monitoring the change in peak temperature in the thermal chromatogram of this crosslinked acrylic resin. The pyridine decomposition method is specifically performed as follows.

[0127] Using a microtome, a 0.1 μm thick sample was cut from the outer surface of the resin layer of the electrophotographic roller, and 500 mg of the sample was collected. 0.5 mL of a 3:1 mixture of pyridine (Wako Pure Chemical Industries, Ltd.) and water was added to the resulting sample, which was then decomposed by heating at 130°C for 15 hours in a sealed container made of fluororesin (Teflon®) with a stainless steel jacket. The resulting decomposition product was then subjected to reduced pressure to remove the pyridine. The sample thus obtained was subjected to the microsampling mass spectrometry described above to obtain the A2 value.

[0128] <Calculation of various physical properties such as the equivalent circle diameter and wall distance of carbon black dispersed in a resin layer> The circle-equivalent diameter and wall-to-wall distance of the carbon black dispersed in the resin layer were measured by the following method. First, a slice (0.5 to 1.0 mm thick) is cut out using a razor so that a cross section perpendicular to the longitudinal direction of the electrophotographic roller can be observed. If the adhesion between the substrate and the resin layer is high and cutting out with a razor is difficult, the substrate can be cut out with a hacksaw or similar tool, and then the cross section can be processed using a FIB (Focused Ion Beam) device.

[0129] Next, the slice is platinum-deposited, and the resin layer is photographed at 15,000x magnification using a scanning electron microscope (SEM) (trade name: JSM-7800F, manufactured by JEOL Ltd.) to obtain a cross-sectional image. Furthermore, to quantify the cross-sectional images obtained by SEM observation, the cross-sectional images were converted to 8-bit grayscale using image processing software (trade name: Luzex AP, manufactured by Nireco Corporation) to obtain a monochrome image with 256 gradations. Next, the black and white of the image were inverted so that the carbon black in the cross-sectional image appeared white, and then a binarization threshold was set for the brightness distribution of the image based on the algorithm of Otsu's discriminant analysis method, obtaining a binarized image in which the carbon black appeared white and the binder resin appeared black.

[0130] Then, using image processing software (trade name: Luzex AP, manufactured by Nireco Corporation) on the obtained binarized image, the equivalent circle diameter Rc and the distance between adjacent wall surfaces d of the whitened carbon black portions are calculated. The image region for calculating the equivalent circle diameter and the distance between adjacent wall surfaces is set to an area 0.075 μm inside in actual image dimensions (if there is a text section describing the SEM measurement conditions, etc., then 0.075 μm inside from where the actual image begins) to eliminate uncertainty in the calculated values ​​for the carbon black that is divided at the top, bottom, left, and right edges of the image, and the equivalent circle diameter and the distance between adjacent wall surfaces are calculated for all carbon black within the specified image region.

[0131] The arithmetic mean and standard deviation of the obtained distribution of the equivalent circle diameter and the distance between adjacent wall surfaces are then calculated. The number of images used for image analysis is 12, divided into four equal parts in the longitudinal direction of the roller, and taken at positions 1 / 4, 1 / 2, and 3 / 4 of the way from the end, at 0°, 90°, 180°, and 270° in the circumferential direction.

[0132] The number-average diameter of the primary particles of the carbon black dispersed in the resin was measured using a transmission electron microscope (TEM). First, a thin sectioned sample was prepared. A known method can be used for thinning. For example, a sample can be thinned using an ion beam or a diamond knife. In this disclosure, a 40-nm-thick thin sectioned sample for observation was prepared using an ultramicrotome (product name: ULTRACUT-S, manufactured by Leica Microsystems). Then, a TEM image was obtained using a transmission electron microscope (product name: H-7100FA, manufactured by Hitachi High-Technologies Corporation) under measurement conditions of TE mode and an accelerating voltage of 100 kV. Then, using image analysis software (trade name: WinROOF, manufactured by Mitani Shoji Co., Ltd.) for the obtained TEM image, the circle-equivalent diameters of 50 primary particles of carbon black in the TEM image were measured, and the number-average value of the 50 particles was defined as the number-average diameter of the primary particles.

[0133] (Measurement of DBP absorption amount of carbon black) The DBP absorption amount of carbon black was measured for carbon black powder in accordance with Japanese Industrial Standards (JIS) K6217-4.

[0134] (Measurement of pH of carbon black) The pH of the carbon black was measured on the carbon black powder according to ASTM D1512.

[0135] (Measurement of resin layer thickness on developing roller) The thickness of the resin layer is measured by using an optical microscope or electron microscope to measure the thickness of the resin part that does not contain fine particles on a cross section of the resin layer in the thickness direction. Measurements are made at nine locations in total: three locations in the circumferential direction of the developing roller and three locations in the direction perpendicular to the circumferential direction (axial direction). The arithmetic mean value of the film thickness at each measurement location is then taken as the thickness of the resin layer. [Example]

[0136] The present disclosure will be described in more detail below with reference to examples, but these examples are not intended to limit the present disclosure in any way.

[0137] Example 1 [1. Preparation of conductive substrate] A primer (product name: DY35-051, manufactured by Dow Corning Toray Co., Ltd.) was applied to a SUS304 core bar with an outer diameter of 6 mm and a length of 270 mm, and the core bar was heated at a temperature of 150°C for 20 minutes. This core bar was then placed concentrically within a cylindrical mold with an inner diameter of 12.0 mm to serve as a substrate.

[0138] To prepare the intermediate elastic layer, the materials shown in Table 1 below were mixed in a kneader (product name: Trimix TX-15, manufactured by Inoue Seisakusho Co., Ltd.) to form an addition-curing liquid silicone rubber mixture, which was then poured into a mold heated to 115°C. After the material was poured, the mixture was heated and molded at 120°C for 10 minutes, cooled to room temperature, and then demolded from the mold, yielding a conductive substrate (elastic roller 1) with a 3.0 mm-thick elastic layer formed on the outer periphery of the substrate.

[0139] [Table 1]

[0140] [2. Formation of resin layer] The resin layer materials, listed in Table 2 below, were prepared by stirring and mixing the polyol, isocyanate, and additives (materials other than carbon black and roughness-forming particles) in a disperser. Next, the carbon black in Table 2 below was added in small amounts while stirring and mixing in a disperser. After the addition was complete, the mixture was stirred and mixed for 30 minutes. The mixture was then dissolved in methyl ethyl ketone to a solids concentration of 30% by mass, premixed for an additional hour, and then dispersed for 4 hours in a sand mill using glass beads with a particle size of 1.5 mm. Roughness-forming particles were then added and dispersed for an additional 10 minutes in a sand mill to obtain resin layer coating material 1. The elastic roller 1 was immersed in the coating material to coat it so that the resin layer had a thickness of 15 μm, and then heated at a temperature of 135° C. for 60 minutes to dry and harden the coating film, thereby forming a cross-linked urethane resin in the resin layer.

[0141]

Table 2

[0142] Subsequently, the impregnation and curing treatment of the (meth)acrylic monomer capable of forming a crosslinked acrylic resin were carried out by the following method. As the material of the impregnation treatment liquid for the impregnation treatment, the materials shown in Table 3 below were dissolved and mixed. The elastic roller formed with the crosslinked urethane resin was immersed in this impregnation treatment liquid for 2 seconds for the impregnation treatment to impregnate the (meth)acrylic monomer component. Then, it was immediately dried at 90°C for 1 hour to volatilize the solvent. While rotating the dried elastic roller, ultraviolet rays were irradiated so that the integrated light quantity became 15000 mJ / cm 2 to cure the (meth)acrylic monomer to form an IPN structure and obtain a resin layer. As the ultraviolet irradiation device, a high-pressure mercury lamp (product name: Handy Type UV Curing Device, manufactured by Marionetwork Co., Ltd.) was used.

[0143]

Table 3

[0144] The following evaluations were performed on the obtained electrophotographic roller. [Evaluation Method] <Calculation of the equivalent circle diameter and wall surface distance of carbon black dispersed in the resin layer> By the method for calculating the equivalent circle diameter and wall surface distance of carbon black dispersed in the resin layer described above, when the equivalent circle diameter Rc, wall surface distance d, the standard deviation of the equivalent circle diameter was σc [nm], and the standard deviation of the wall surface distance was σc [nm], σc / Rc and σc / d were determined. The results are shown in Table 9.

[0145] <Measurement of SPM elastic modulus> By the measurement method of the SPM elastic modulus described above, the elastic moduli E1 and E2 in the first region and the second region were determined. The results are shown in Table 9.

[0146] <Durability evaluation> The electrophotographic roller was mounted in a process cartridge as a developing roller for a color laser printer (product name: HP Color LaserJet Enterprise M652dn, manufactured by HP), and the process cartridge was mounted in the color laser printer to evaluate the state of scratches caused by scraping on the surface of the electrophotographic roller. The evaluation procedure was as follows:

[0147] After leaving the process cartridge in a high-temperature, high-humidity environment of 30°C and 95% relative humidity for 16 hours, a low-print image with a print rate of 0.2% was continuously output onto recording paper in order to evaluate the performance of printing a large number of sheets under the same environment. However, since toner is consumed during printing, toner was replenished so that the toner weight in the process cartridge became 100g every time 50,000 sheets were output. After printing 200,000 sheets, the developing roller was removed from the process cartridge, and the roller surface was cleaned with air to remove the toner from the surface. The roller surface condition was then visually observed and evaluated according to the following criteria. The evaluation results are shown in Table 9. Evaluation criteria Rank "A": No scratches due to abrasion can be seen on the surface. Rank "B": Scratches are visible, but the largest scratch is less than 1mm in length. Rank "C": Scratches of 1mm or more can be seen.

[0148] <Crack resistance evaluation> The electrophotographic roller after the durability printing was aged for 24 hours or more in a low temperature environment of 10°C and 15% relative humidity, and the surface roughness Ra was measured by the method described later. Under the same conditions, a SUS304 brush (product name: SUS304 stainless steel brush, manufactured by Taiyo Shokai) was placed perpendicularly against the surface of the test piece, rubbed 10 times with a load of 10 N, and then left for 1 hour. The surface roughness Ra was then measured again under the same conditions, and the difference ΔRa between the surface roughness Ra before and after evaluation was evaluated according to the following criteria. The evaluation results are shown in Table 9. Evaluation criteria Rank "A": ΔRa before and after evaluation is 0.20 μm or less. Rank "B": ΔRa before and after evaluation is more than 0.20 μm and 0.40 μm or less. Rank "C": ΔRa before and after evaluation exceeds 0.40 μm.

[0149] <Method for measuring surface roughness (Ra)> The surface roughness Ra (JIS B0601) of the electrophotographic roller was measured using a surface roughness meter (product name: Surfcom 480A, manufactured by Tokyo Seimitsu Co., Ltd.), and the Ra value was recorded. The measurement conditions were a stylus with a radius of 2 μm, a pressing pressure of 0.7 mN, a measurement speed of 0.3 mm / sec, a measurement magnification of 5000x, a cutoff wavelength of 0.8 mm, and a measurement length of 2.5 mm. The measurement was performed at 1 / 4, 1 / 2, and 3 / 4 of the way from the end, and the arithmetic average value of nine points at 0°, 120°, and 240° in the circumferential direction was used.

[0150] (Examples 2, 4 to 11, 13 to 15, Comparative Examples 1, 4, and 6) Using the same method as in Example 1, each resin layer coating material was prepared using the materials shown in Table 7, each impregnation treatment liquid was prepared using the materials shown in Table 8, and each electrophotographic roller was manufactured using the combinations shown in Table 9. The obtained electrophotographic rollers were evaluated using the same method as in Example 1. The evaluation results are shown in Table 9.

[0151] Example 3 <Synthesis of Polyoxyethylene Methyl Ether Acetate: Additive A> 169.3 g of 1-octanol (Tokyo Chemical Industry Co., Ltd.) and 3.0 g of potassium hydroxide were placed in an autoclave equipped with a stirrer, temperature controller, and automatic feeder, and dehydration was carried out at 110°C and 1.2 kPa for 30 minutes. After completion of dehydration, the atmosphere was purged with nitrogen, and the temperature was raised to 150°C, after which 858.0 g of ethylene oxide (15 mol relative to alcohol) was added. The reaction was carried out at 150°C for 1 hour, yielding an ethylene oxide adduct with an average added mole number of 15 mol.

[0152] 77.4 g of the resulting ethylene oxide adduct was mixed with 510 ml of 1 mol / L aqueous sodium hydroxide, and 71.1 g of potassium permanganate was added and stirred at room temperature for 6 hours. Then, 760 ml of 2-propanol was added and stirred for 1 hour to quench the excess potassium permanganate. The by-product manganese oxide was then filtered. The aqueous layer was extracted and purified with dichloromethane to obtain Additive A, which is polyoxyethylene methyl ether acetic acid. The structure of R41 and the value of x for Additive A are shown in Table 5.

[0153] Except for using additive A in the resin layer coating, a resin layer coating was prepared with the materials shown in Table 7, an impregnation treatment liquid was prepared with the materials shown in Table 8, and an electrophotographic roller of Example 3 was produced using the combinations shown in Table 9 in the same manner as in Example 1. The obtained electrophotographic roller was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 9.

[0154] Example 12 <Synthesis of Polyetheramine: Additive B> A three-necked flask was equipped with a stirrer, and 1658 g of polyoxyethylene polyoxypropylene octyl ether and 460 ml of acetic acid were added. 600 ml of a 2 mol / l aqueous solution of sodium hypochlorite was added dropwise over 1 hour. The reaction vessel was placed in an ice bath and cooled to a temperature within the range of 15 to 25°C. After the dropwise addition was completed, stirring was continued for 1 hour. Dichloromethane was added to the resulting solution, and the aqueous layer was extracted, post-treated, and purified using a column to obtain a compound in which the secondary alcohol was ketone. The mixture was cooled to 0°C in an ice bath, and 41.4 g of the resulting compound, which was ketone from a secondary alcohol, was added to 250 ml of a methanol-acetic acid mixed solution (volume ratio 10:1), followed by 2.7 g of 2-picoline borane. The ice bath was removed, and the mixture was stirred overnight in an open system at room temperature. After concentration, the mixture was cooled to 0°C, and 360 ml of 35% aqueous hydrochloric acid was added, followed by stirring at room temperature for 2 hours. Aqueous sodium hydroxide was added to make the mixture basic, and the aqueous layer was extracted with dichloromethane, post-treated, and purified using a column to obtain Additive B, a polyetheramine. The structure of R31 and the values ​​of v and w for Additive B are shown in Table 5.

[0155] A resin layer coating material was prepared using the materials shown in Table 7 in the same manner as in Example 1, except that additive B was used in the resin layer coating material, and the electrophotographic roller of Example 12 was produced using the combinations shown in Table 9. The obtained electrophotographic roller was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 9.

[0156] (Example 16: Charging Roller) [Preparation of conductive substrate] A primer (product name: Metalock N-33, manufactured by Toyo Kagaku Kenkyusho Co., Ltd.) was applied to a SUS304 core bar having an outer diameter of 6 mm and a length of 252 mm, and the core bar was heated at a temperature of 80°C for 30 minutes, and then further heated at 120°C for 1 hour. As the material for the intermediate layer, the materials shown in component 1 in Table 4 below were mixed in a pressure kneader to obtain kneaded rubber composition A. Furthermore, the materials shown in the component 2 column in Table 4 were mixed with this kneaded rubber composition A in an open roll to prepare an unvulcanized rubber composition. Next, a die with an inner diameter of 16.5 mm was attached to a crosshead extruder equipped with a substrate supply mechanism and an unvulcanized rubber roller discharge mechanism. The extruder and die (crosshead) were heated to 80°C, and the conductive substrate conveyance speed was adjusted to 60 mm / sec. Under these conditions, an unvulcanized rubber composition was fed from the extruder, and the unvulcanized rubber composition was coated as an elastic layer on the outer periphery of the conductive substrate in the crosshead. This was then placed in a hot-air vulcanization furnace at 170°C and heated for 60 minutes. After cooling, the edges of the elastic layer were cut and removed, and the surface of the elastic layer was ground with a grindstone to produce a conductive substrate (elastic roller 2) with a diameter of 8.4 mm at each end 90 mm from the center in the axial direction and a central diameter of 8.5 mm.

[0157] [Table 4]

[0158] Except for using the elastic roller 2 as the substrate, a coating material for a resin layer was prepared using the materials shown in Table 7, an impregnation treatment liquid was prepared using the materials shown in Table 8, and the electrophotographic roller of Example 16 was produced using the combinations shown in Table 9 in the same manner as in Example 1.

[0159] The obtained electrophotographic roller was mounted in a process cartridge as a charging roller for a color laser printer (product name: HP Color LaserJet Enterprise M652dn, manufactured by HP), and the process cartridge was mounted in the color laser printer to evaluate the state of scratches caused by scraping on the surface of the electrophotographic roller. Note that a process cartridge for the color laser printer (cyan, product name: HP 656X High Yield Cyan Original LaserJet Toner Cartridge, manufactured by HP) was used for the evaluation. The evaluation procedure was as follows.

[0160] The process cartridge was left in a high-temperature, high-humidity environment (temperature 30°C, relative humidity 95%) for 16 hours, and then, to evaluate the performance of printing a large number of sheets under the same environment, low-print images with a print rate of 0.2% were continuously output onto recording paper. However, because toner is consumed during printing, toner was replenished so that the toner weight in the process cartridge was 100 g every time 50,000 sheets were output. After printing 200,000 sheets, the charging roller was removed from the process cartridge, and the roller surface was air-blown to remove the toner from the surface. Evaluation was then performed in the same manner as in Example 1. The evaluation results are shown in Table 9.

[0161] (Comparative Example 2) <Synthesis of Polyetheramine: Additive C> Additive C, a polyetheramine, is obtained by synthesizing polyoxyethylene polyoxypropylene decyl ether, then ketonizing it by oxidation of a secondary alcohol, followed by reductive amination.

[0162] (Synthesis of polyoxyethylene polyoxypropylene decyl ether) 205.8 g of 1-decanol (Tokyo Chemical Industry Co., Ltd.) and 3.0 g of potassium hydroxide were placed in an autoclave equipped with a stirrer, temperature controller, and automatic feeder, and dehydration was carried out at 110°C and 1.2 kPa for 30 minutes. After completion of dehydration, the atmosphere was purged with nitrogen, and the temperature was raised to 150°C, after which 858.0 g of ethylene oxide (15 mol relative to alcohol) was added. The reaction was carried out at 150°C for 1 hour, yielding an ethylene oxide adduct with an average added mole number of 15 mol. The resulting ethylene oxide adduct was cooled to 130°C, and then 1132.6 g of propylene oxide (relative to the alcohol: 15 mol) was added. After the addition was completed, the reaction was carried out at 130°C for 5 hours to obtain a polyoxyethylene polyoxypropylene decyl ether adduct, which was a block polymer having an average added mole number of 15 mol of ethylene oxide and 15 mol of propylene oxide. The obtained polyoxyethylene polyoxypropylene octyldecyl adduct was cooled to 80°C and the unreacted ethylene oxide and propylene oxide were removed at 2.5 kPa for 30 minutes. Next, 6.0 g of 90% lactic acid was added to the autoclave and stirred at 80°C for 30 minutes, followed by extraction to obtain polyoxyethylene polyoxypropylene decyl ether.

[0163] (Synthesis of Polyetheramine: Additive C) A three-necked flask was equipped with a stirrer and charged with 1688 g of polyoxyethylene polyoxypropylene decyl ether and 460 ml of acetic acid. 600 ml of a 2 mol / L aqueous solution of sodium hypochlorite was added dropwise over one hour. The reaction vessel was placed in an ice bath and cooled to a temperature between 15 and 25°C. After the addition was complete, stirring was continued for one hour. Dichloromethane was added to the resulting solution, and the aqueous layer was extracted. After post-treatment and purification using a column, a compound in which the secondary alcohol was ketone was obtained. The mixture was cooled to 0°C in an ice bath, and 41.4 g of the resulting compound, obtained by ketone conversion of a secondary alcohol, was added to 250 ml of a methanol-acetic acid mixed solution (volume ratio 10:1), followed by 2.7 g of 2-picoline borane. The ice bath was removed, and the mixture was stirred overnight in an open system at room temperature. After concentration, the mixture was cooled to 0°C, and 360 ml of 35% aqueous hydrochloric acid was added, followed by stirring at room temperature for 2 hours. Aqueous sodium hydroxide was added to make the mixture basic, and the aqueous layer was extracted with dichloromethane, post-treated, and purified using a column to obtain Additive C, a polyetheramine. The structure of R31 and the values ​​of v and w for Additive C are shown in Table 5.

[0164] Except for using additive C in the resin layer coating, a resin layer coating was prepared using the materials shown in Table 7, an impregnation treatment liquid was prepared using the materials shown in Table 8, and an electrophotographic roller of Comparative Example 2 was produced using the combinations shown in Table 9 in the same manner as in Example 1. The obtained electrophotographic rollers were each evaluated using the same methods as in Example 1. The evaluation results are shown in Table 9.

[0165] (Comparative Example 3) <Synthesis of Polyoxyethylene Methyl Ether Acetic Acid: Additive D> 315.2 g of 1-hexadecanol (Tokyo Chemical Industry Co., Ltd.) and 3.0 g of potassium hydroxide were placed in an autoclave equipped with a stirrer, temperature controller, and automatic feeder, and dehydration was carried out at 110°C and 1.2 kPa for 30 minutes. After completion of dehydration, the atmosphere was purged with nitrogen, and the temperature was raised to 150°C, after which 858.0 g of ethylene oxide (15 mol relative to alcohol) was added. The reaction was carried out at 150°C for 1 hour, yielding an ethylene oxide adduct with an average added mole number of 15 mol. 90.2 g of the resulting ethylene oxide adduct was mixed with 510 ml of 1 mol / L aqueous sodium hydroxide, and 71.1 g of potassium permanganate was added and stirred at room temperature for 6 hours. Then, 760 ml of 2-propanol was added and stirred for 1 hour to quench the excess potassium permanganate. The by-product manganese oxide was then filtered. The aqueous layer was extracted and purified with dichloromethane to obtain Additive D, which is polyoxyethylene methyl ether acetic acid. The structure of R41 and the value of x for Additive D are shown in Table 5.

[0166] Except for using additive D in the resin layer coating, a resin layer coating was prepared with the materials shown in Table 7, an impregnation treatment liquid was prepared with the materials shown in Table 8, and an electrophotographic roller of Comparative Example 3 was produced using the combination shown in Table 9 in the same manner as in Example 1. The obtained electrophotographic roller was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 9.

[0167] [Table 5]

[0168] (Comparative Example 5) With reference to the examples in JP-A No. 2003-113347, the materials shown in Table 6 were used and stirred with zirconia beads in a paint shaker for 1 hour to obtain a resin layer coating material 20. An electrophotographic roller of Comparative Example 5 was produced in the same manner as in Example 1, except that the resin layer was formed using the resin layer coating material 20. The evaluation results are shown in Table 9.

[0169] [Table 6]

[0170] *The materials listed in the table are as follows: ME823LP: (Manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) A-187: (Momentive) Disperbyk-185: (BYK) MA77: (Mitsubishi Chemical Corporation) FF-101(D): (Manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) GS-30: (Manufactured by Toagosei Co., Ltd.) C400T: Art Pearl C400T cross-linked urethane resin particles (Negami Chemical Industrial Co., Ltd., average particle size 15 μm)

[0171] [Table 7]

[0172] *The numbers in the table represent the amount of each material mixed in parts by mass. *The materials listed in the table are as follows: polyol Kuraray Polyol C2090: Polycarbonate polyol (Kuraray Co., Ltd., molecular weight 2000) Kuraray Polyol C3090: Polycarbonate polyol (Kuraray Co., Ltd., molecular weight 3000) PTMG1000: Polytetramethylene glycol (Hodogaya Chemical Co., Ltd., molecular weight 1000) PTMG650: Polytetramethylene glycol (Hodogaya Chemical Co., Ltd., molecular weight 650) PTGL1000: Polyether polyol (manufactured by Hodogaya Chemical Co., Ltd.)

[0173] Isocyanate Millionate MR-400: Isocyanate compound, polymeric MDI (manufactured by Tosoh Corporation)

[0174] additives Unilube 50MB-26: Polyoxyethylene polyoxypropylene butyl ether (NOF Corporation) JEFFAMINE M-2005: Polyetheramine (Huntsman) Nonion A-13PR: Polyoxyethylene polyoxypropylene lauryl ether (NOF Corporation) Taipol Soft ECA-490: Polyoxyethylene lauryl ether acetate (manufactured by Taiko Yushi Kagaku Kogyo Co., Ltd.) Unisafe 20P-8: Polyoxyethylene polyoxypropylene cetyl ether (NOF Corporation) Newpol 50HB-100: (Poly(oxyethyleneoxypropylene) glycol monobutyl ether (manufactured by Sanyo Chemical Industries, Ltd.))

[0175] Modified silicone oil TSF4445: Modified silicone compound (manufactured by Momentive Performance Materials Japan)

[0176] carbon black MA8: Carbon black (manufactured by Mitsubishi Chemical Corporation, primary particle number average diameter: 24 nm, DBP oil absorption: 51 mL / 100 g, pH: 3.0) SUNBLACK X55 (manufactured by Asahi Carbon Co., Ltd., primary particle number average diameter: 25 nm, DBP oil absorption: 77 mL / 100 g, pH: 3.0) MA11: Carbon black (manufactured by Mitsubishi Chemical Corporation, primary particle number average diameter: 29 nm, DBP oil absorption: 64 mL / 100 g, pH: 3.5) SUNBLACK X15: (Asahi Carbon Co., Ltd., primary particle number average diameter: 20 nm, DBP oil absorption: 96 mL / 100 g, pH: 3.5)

[0177] Roughness forming particles Art Pearl C400T: Cross-linked urethane resin particles (Negami Chemical Industrial Co., Ltd., average particle size 15 μm) Daimic Beads UCN-5090: Cross-linked urethane resin particles (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., average particle size 9 μm)

[0178] [Table 8]

[0179] *The numbers in the table represent the amount of each material mixed in parts by mass. *The materials listed in the table are as follows: EBECRYL145: Difunctional acrylic monomer (manufactured by Daicel-Allnex Co., Ltd.) TMPTA: Trifunctional acrylic monomer (manufactured by Daicel-Allnex Co., Ltd.) Omnirad184: Photopolymerization initiator (manufactured by IGM Resins)

[0180] [Table 9]

[0181] In Examples 1 to 9 and 16, Comparative Examples 1 to 4 and 6, the first region was made of crosslinked urethane. It was confirmed that the acrylic resin and the cross-linked acrylic resin formed an interpenetrating polymer network (IPN).

[0182] The present disclosure relates to the following configurations. (Configuration 1) An electrophotographic roller having a conductive substrate and a resin layer on an outer peripheral surface of the substrate, The resin layer has a thickness of 2.0 to 30.0 μm, the resin layer contains a binder resin and carbon black dispersed in the binder resin, the arithmetic mean value Rc of the equivalent circle diameter of the carbon black in the resin layer is 80 nm or less; the arithmetic mean value d of the distance between wall surfaces of the carbon black in the resin layer is 60 to 170 nm; When the elastic modulus of the binder resin in a first region from the outer surface of the resin layer to a depth of 0.1 μm, measured in a cross section in the thickness direction of the resin layer, is defined as E1, E1 can be expressed by the following formula (1): E1 ≥ 200 MPa ···(1); Electrophotographic roller characterized by satisfying the above. (Configuration 2) 2. The electrophotographic roller according to claim 1, wherein the binder resin comprises a cross-linked urethane resin. (Configuration 3) The electrophotographic roller according to Structure 1 or 2, wherein the resin layer contains at least one compound selected from the group consisting of a compound having a structure represented by the following structural formula (2), a compound having a structure represented by the following structural formula (3), and a compound having a structure represented by the following structural formula (4): TIFF2026036392000013.tif88153 In structural formula (2), R21 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms, and t and u represent the average number of moles added, each independently representing a number of 1 or more. In structural formula (3), R31 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms, v and w represent the average number of moles added, and each independently represents a number of 1 or more. In structural formula (4), R41 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms, and x represents the average number of moles added and is a number of 1 or more. (Configuration 4) The E1 is 250 MPa or more, The binding in the second region from the outer surface of the resin layer to a depth of 1.0 to 1.1 μm When the elastic modulus of the resin is E2, 4. The electrophotographic roller according to any one of Configurations 1 to 3, wherein E2 is 120 to 200 MPa. (Configuration 5) the resin layer contains a cross-linked urethane resin and a cross-linked (meth)acrylic resin, 5. The electrophotographic roller according to any one of Configurations 1 to 4, wherein in the first region, the cross-linked urethane resin and the cross-linked (meth)acrylic resin form an interpenetrating polymer network structure. (Configuration 6) the binder resin contains a cross-linked urethane resin, 6. The electrophotographic roller according to any one of Configurations 1 to 5, wherein the crosslinked urethane resin has a polycarbonate structure. (Configuration 7) the arithmetic mean value Rc of the equivalent circle diameter is 60 nm or less, When the standard deviation of the equivalent circle diameter is σc, σc / Rc is 0.000 to 0.650, the arithmetic mean value d of the distance between the wall surfaces is 80 to 150 nm; 7. The electrophotographic roller according to any one of Configurations 1 to 6, wherein σd / d is 0.000 to 0.600, where σd is the standard deviation of the distance between the wall surfaces. (Configuration 8) the number average diameter of the primary particles of the carbon black is 30 nm or less; The carbon black has a DBP absorption of 90 ml / 100 g or less; and 8. The electrophotographic roller according to any one of Configurations 1 to 7, wherein the carbon black has a pH of 4.0 or less. (Configuration 9) A process cartridge configured to be detachably mounted in a main body of an electrophotographic image forming apparatus, A process cartridge comprising the electrophotographic roller according to any one of Configurations 1 to 8. (Configuration 10) An electrophotographic image forming apparatus, The electrophotographic image forming apparatus includes an image carrier for carrying an electrostatic latent image, a charging roller for primarily charging the image carrier, and a developing roller for developing the electrostatic latent image with toner to form a toner image, 9. An electrophotographic image forming apparatus, wherein either or both of the charging roller and the developing roller are the electrophotographic roller according to any one of Configurations 1 to 8.

Claims

1. An electrophotographic roller having a conductive substrate and a resin layer on an outer peripheral surface of the substrate, The thickness of the resin layer is 2.0 to 30.0 μm, the resin layer contains a binder resin and carbon black dispersed in the binder resin, the arithmetic mean value Rc of the equivalent circle diameter of the carbon black in the resin layer is 80 nm or less; the arithmetic mean value d of the distance between wall surfaces of the carbon black in the resin layer is 60 to 170 nm; When the elastic modulus of the binder resin in a first region from the outer surface of the resin layer to a depth of 0.1 μm, which is measured in a cross section in the thickness direction of the resin layer, is defined as E1, E1 can be expressed by the following formula (1): E1 ≥ 200 MPa (1); Electrophotographic roller characterized by satisfying the above.

2. 2. The electrophotographic roller according to claim 1, wherein the binder resin comprises a cross-linked urethane resin.

3. 2. The electrophotographic roller according to claim 1, wherein the resin layer contains at least one compound selected from the group consisting of a compound having a structure represented by the following structural formula (2), a compound having a structure represented by the following structural formula (3), and a compound having a structure represented by the following structural formula (4): In structural formula (2), R21 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms, and t and u represent the average number of moles added, each independently representing a number of 1 or more. In structural formula (3), R31 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms, v and w represent the average number of moles added, and each independently represents a number of 1 or more. In structural formula (4), R41 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms, and x represents the average number of moles added and is a number of 1 or more.

4. The E1 is 250 MPa or more, When the elastic modulus of the binder resin in the second region from the outer surface of the resin layer to a depth of 1.0 to 1.1 μm is E2, 2. The electrophotographic roller according to claim 1, wherein E2 is 120 to 200 MPa.

5. the resin layer contains a cross-linked urethane resin and a cross-linked (meth)acrylic resin, 2. The electrophotographic roller according to claim 1, wherein in said first region, said cross-linked urethane resin and said cross-linked (meth)acrylic resin form an interpenetrating polymer network structure.

6. the binder resin contains a cross-linked urethane resin, 2. The electrophotographic roller of claim 1, wherein the cross-linked urethane resin has a polycarbonate structure.

7. the arithmetic mean value Rc of the equivalent circle diameter is 60 nm or less; When the standard deviation of the equivalent circle diameter is σc, σc / Rc is 0.000 to 0.650, the arithmetic mean value d of the distance between the wall surfaces is 80 to 150 nm; 2. The electrophotographic roller according to claim 1, wherein σd / d is 0.000 to 0.600, where σd is the standard deviation of the distance between the wall surfaces.

8. the number average diameter of primary particles of the carbon black is 30 nm or less; The carbon black has a DBP absorption of 90 ml / 100 g or less; and 2. The electrophotographic roller of claim 1, wherein the carbon black has a pH of 4.0 or less.

9. A process cartridge configured to be detachably mounted in a main body of an electrophotographic image forming apparatus, 9. A process cartridge comprising the electrophotographic roller according to claim 1.

10. An electrophotographic image forming apparatus, The electrophotographic image forming apparatus includes an image carrier for carrying an electrostatic latent image, a charging roller for primarily charging the image carrier, and a developing roller for developing the electrostatic latent image with toner to form a toner image, 9. An electrophotographic image forming apparatus, wherein either or both of said charging roller and said developing roller are the electrophotographic roller according to any one of claims 1 to 8.

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