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

Abstract

To provide an electrophotographic conductive roller that can reliably reduce leakage of electric charges of toner to the roller even when the electrophotographic conductive roller using an elastic layer having ion conductivity is used in an electrophotographic image forming apparatus applying high voltage to a developing blade.SOLUTION: An electrophotographic conductive roller has, in this order, a substrate having conductivity, an elastic layer having ion conductivity, and a surface layer. The surface layer includes resin and carbon black. An arithmetic mean value Rc of an equivalent circle diameter of the carbon block is 60.0 nm or less, and when the standard deviation of the equivalent circle diameter is defined as σc(nm), σc / Rc is 0.000-0.650. An arithmetic mean value d of the distance between wall surfaces of the carbon black in the surface layer is 80.0-150.0 nm. When the standard deviation of the distance between the wall surfaces is defined as σd(nm), σd / d is 0.000-0.600.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] As the process speed of electrophotographic image forming apparatuses continues to increase, new properties not previously required are being demanded of various electrophotographic conductive rollers such as developing rollers and charging rollers. As an example, there is a drawback to applying a voltage to a developing blade in contact with a developing roller and using that potential to more quickly charge the toner: when a higher voltage is applied to the developing blade to charge the toner more quickly in line with increasing process speeds, charge leakage from the toner to the developing roller can occur.

[0003] Furthermore, in recent cleanerless systems, a difference in peripheral speed between the photosensitive drum and the charging roller has been established as a countermeasure against drum contamination. However, this countermeasure increases the amount of charge injected from the charging roller to the photosensitive drum, and this has the drawback of making the conventional surface layer prone to uneven charging. Various technologies have been developed to prevent charge leakage, and for example, Patent Document 1 discloses a technology for increasing the resistance of a developing roller by introducing a specific structure having a polycarbonate structure into the surface layer, which discloses that charge leakage from the toner to the developing roller can be suppressed as a result. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-191316 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, the present inventors considered creating a developing roller using the surface layer technology described in Patent Document 1 on an elastic layer having ion conductivity, and applying this to an electrophotographic image forming apparatus equipped with a developing blade to which a high voltage can be applied. However, the present inventors recognized that even when the surface layer technology disclosed in Patent Document 1 is used, in an electrophotographic device equipped with a developing blade capable of applying a high voltage, charge leakage occurs from the toner injected with charge by the developing blade to the developing roller. This charge leakage causes a decrease in the charge amount of the toner, resulting in a charge amount below the design value, resulting in a decrease in image density and toner transfer to solid white areas on paper, a degradation in image quality known as "fogging."

[0006] As mentioned above, when a high voltage is applied by the developing blade in order to cope with the increase in the process speed of the electrophotographic image forming apparatus, the deterioration of the image quality is noticeable. Furthermore, in order to charge the drum uniformly, a technique for suppressing charge injection is also required for the charging roller. We have discovered that this technique can be achieved by the same method as the technique for suppressing charge leakage that occurs in the developing roller.

[0007] The present disclosure is directed to providing an electrophotographic conductive roller that can more reliably reduce toner charge leakage to a developing blade, even when the electrophotographic conductive roller uses an elastic layer having ionic conductivity, in an electrophotographic image forming apparatus that applies a high voltage to a developing blade. The present disclosure also aims to provide a process cartridge and an electrophotographic image forming apparatus that include the electrophotographic conductive roller. [Means for solving the problem]

[0008] According to at least one aspect of the present disclosure, An electrophotographic conductive roller having, in this order, a conductive substrate, an ionically conductive elastic layer, and a surface layer, the surface layer contains a resin and carbon black; the arithmetic mean value Rc of the equivalent circle diameters of the carbon black in the surface layer is 60.0 nm or less, and further, when the standard deviation of the equivalent circle diameters is σc (nm), σc / Rc is 0.000 to 0.650; The electrophotographic conductive roller also has an arithmetic mean value d of the distance between wall surfaces of the carbon black in the surface layer of 80.0 to 150.0 nm, and further has a σd / d of 0.000 to 0.600, where σd (nm) is the standard deviation of the distance between wall surfaces.

[0009] According to at least one aspect of the present disclosure, there is provided a process cartridge configured to be detachably attachable to a main body of an electrophotographic image forming apparatus, the process cartridge including the electrophotographic conductive roller of the present disclosure. Furthermore, according to at least one aspect of the present disclosure, there is provided an electrophotographic image forming apparatus having a photoreceptor and a developing roller that supplies a developer to an electrostatic latent image formed on the photoreceptor, wherein the developing roller is the electrophotographic conductive roller of the present disclosure. [Effects of the Invention]

[0010] According to at least one aspect of the present disclosure, it is possible to provide an electrophotographic conductive roller that can more reliably reduce toner charge leakage to the roller, even when an electrophotographic conductive roller using an elastic layer with ionic conductivity is used in an electrophotographic image forming apparatus that applies a high voltage to a development blade. According to at least one aspect of the present disclosure, it is possible to provide a process cartridge and an electrophotographic image forming apparatus that include the electrophotographic conductive roller. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing an example of an electrophotographic conductive roller according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of a process cartridge. [Figure 3]FIG. 1 is a schematic diagram of an electrophotographic image forming apparatus. [Figure 4] FIG. 1 is a schematic diagram showing an example of an apparatus for measuring the surface potential of an electrophotographic conductive roller. [Figure 5] FIG. 1 is a schematic diagram of an electrophotographic image forming apparatus for image evaluation. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] The present inventors have applied the surface layer technology of Patent Document 1 to an elastic layer having ion conductivity. The reason why charge leakage from the toner cannot be sufficiently prevented when combined with a developing blade to which a high voltage is applied is presumed to be as follows. The developing roller disclosed in Patent Document 1 uses a silicone rubber elastic layer with carbon black dispersed therein, resulting in a so-called electronically conductive elastic layer. In this case, the conductive paths of the carbon black account for a large proportion of the portion of the elastic layer that contributes to its conductivity. Furthermore, the surface of such an elastic layer is thought to be a mixture of conductive carbon black and insulating rubber. Therefore, it is thought that the charge flowing from the surface layer does not leak throughout the entire surface of the elastic layer, but leaks from the carbon black on the surface of the elastic layer.

[0014] Conversely, if ionically conductive rubber is used for the elastic layer, the entire surface of the elastic layer becomes conductive, which lowers the threshold for leakage, and we speculate that the surface layer technology in Patent Document 1 alone is insufficient. Based on the above speculation, the present inventors recognized that when an ionically conductive elastic layer is used, it is necessary to further improve the surface layer, and they have conducted extensive research.

[0015] As a result of our investigation, we found that controlling the dispersion state of carbon black in the surface layer is important for suppressing charge leakage. As mentioned above, in a mixture of resin and carbon black, carbon black contributes greatly to conductivity. In other words, the state of carbon black contributes greatly. In other words, we found that controlling the dispersion state of carbon black in the surface layer can significantly suppress charge leakage when controlling conductivity.

[0016] Specifically, the electrophotographic conductive roller of the present disclosure comprises, in this order, a conductive substrate, an ionically conductive elastic layer, and a surface layer. The surface layer contains a resin and carbon black. The arithmetic mean value Rc of the equivalent circle diameters of the carbon black in the surface layer is 60.0 nm or less, and further, when the standard deviation of the equivalent circle diameters is σc (nm), σc / Rc is 0.000 to 0.650. The arithmetic mean value d of the distance between the wall surfaces of the carbon black in the surface layer is 80.0 to 150.0 nm, and further, when the standard deviation of the distance between the wall surfaces is σd (nm), σd / d is 0.000 to 0.600. In these cases, it has been found that an electrophotographic conductive roller capable of suppressing charge leakage can be obtained even when the elastic layer has ion conductivity.

[0017] The present disclosure will be described in detail below. <Electrophotographic conductive roller> The electrophotographic conductive roller according to this embodiment (hereinafter also simply referred to as a conductive roller) has, in this order, a conductive substrate, an ionically conductive elastic layer, and a surface layer. An example of a conductive roller is shown in Fig. 1. The electrophotographic conductive roller 10 shown in Fig. 1 has a columnar or hollow cylindrical substrate 11, an elastic layer 12, and a surface layer 13, in this order. Specifically, the elastic layer 12 is laminated on the outer surface, i.e., the peripheral surface, of the substrate 11. Then, the surface layer 13 is laminated on the outer surface, i.e., the peripheral surface of the elastic layer 12.

[0018] [Base] The substrate 11 is conductive and functions as a support member for the electrophotographic conductive roller, and in some cases as an electrode. Specific examples of the substrate preferably have a solid columnar or hollow cylindrical shape.

[0019] The material for the substrate can be appropriately selected from those known in the field of electrophotographic conductive rollers and materials usable for such electrophotographic conductive rollers, such as metals typified by aluminum and stainless steel, carbon steel alloys, and conductive synthetic resins. , iron, copper alloys and other metals or alloys.

[0020] Furthermore, the material constituting the substrate may be subjected to an oxidation treatment or a plating treatment with chromium, nickel, or the like. Either electroplating or electroless plating can be used as the type of plating. Electroless plating is preferred from the viewpoint of dimensional stability. 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 considering the balance between work efficiency and rust prevention ability, the plating thickness is preferably 0.1 to 30 μm.

[0021] A primer may be applied to the surface of the substrate to improve adhesion between the substrate and the elastic layer. A known primer can be selected and used depending on the rubber material for forming the elastic layer and the material of the support. Examples of primer materials include thermosetting resins and thermoplastic resins, and specific examples of materials that can be used include phenolic resins, polyurethanes, acrylic resins, polyester resins, polyether resins, and epoxy resins.

[0022] [Elastic layer] The elastic layer 12 has ion conductivity and may contain other additives to provide the properties required for an electrophotographic conductive roller, such as conductivity and strength. The material used for the elastic layer is preferably a crosslinked product of a rubber composition that is crosslinkable and ionic conductive. Specifically, a method can be used in which epichlorohydrin rubber, which itself exhibits ionic conductivity, is mixed with acrylonitrile butadiene rubber (NBR) or ethylene propylene diene rubber (EPDM). That is, the elastic layer preferably contains epichlorohydrin rubber. It is more preferable that the elastic layer further contains NBR.

[0023] In order to further impart electrical conductivity to the elastic layer, the elastic layer preferably contains an electrical conductivity imparting agent such as an electronically conductive substance or an ionically conductive substance. Examples of the electronically conductive substance include the following substances: Conductive carbon, for example, carbon black such as Ketjenblack EC and acetylene black; carbon for rubber such as SAF (Super Abrasion Furnace), ISAF (Intermediate SAF), HAF (High Abrasion Furnace), FEF (Fast Extruding Furnace), GPF (General Purpose Furnace), SRF (Semi-Reinforcing Furnace), FT (Fine Thermal), and MT (Medium Thermal); oxidation-treated carbon for color (ink); metals and their metal oxides such as copper, silver, and germanium. Among these, conductive carbon is preferred because it is easy to control conductivity with a small amount.

[0024] Examples of ion-conductive substances include the following substances: Inorganic ion-conductive substances such as sodium perchlorate, lithium perchlorate, calcium perchlorate, and lithium chloride; and organic ion-conductive substances such as modified aliphatic dimethylammonium ethosulfate and stearylammonium acetate.

[0025] The elastic layer may further contain various additives, as required, such as particles, plasticizers, fillers, extenders, crosslinking agents, crosslinking accelerators, vulcanization aids, crosslinking assistants, acid acceptors, curing inhibitors, antioxidants, and antioxidants. These optional components may be blended in amounts within a range that does not impair the properties required for the electrophotographic conductive roller.

[0026] Examples of sulfur-based crosslinking agents include powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersed sulfur, as well as tetramethylthiuram disulfide, tetrabenzyl sulfur, and the like. Examples include organic sulfur-containing compounds such as dithiuram disulfide and N,N-dithiobismorpholine. Examples of crosslinking accelerators for accelerating crosslinking include thiuram accelerators, thiazole accelerators, thiourea accelerators, guanidine accelerators, sulfenamide accelerators, and dithiocarbamate accelerators. Examples of the crosslinking aid include metal compounds such as zinc oxide, and conventionally known crosslinking aids such as stearic acid, oleic acid, and fatty acids.

[0027] The acid acceptor is used to prevent chlorine-based gas generated from epichlorohydrin rubber during crosslinking from remaining inside the finished electrophotographic member, which may result in crosslinking inhibition or contamination of other members. As the acid acceptor, various substances that act as acid acceptors can be used, but among them, hydrotalcites and the like that have excellent dispersibility are preferably used.

[0028] Examples of the filler that can be used include zinc oxide, silica, carbon black, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, etc. Among these, at least one selected from the group consisting of calcium carbonate and zinc oxide is preferred. By blending these fillers, it is expected that the mechanical strength of the resin will be improved. In order to provide flexibility, a foaming agent may be blended into the elastic layer, and foamed during molding.

[0029] [Surface layer] (resin) The surface layer contains a resin that acts as a binder resin. The binder resin for the surface layer 13 may be any resin that is generally used for electrophotographic conductive rollers, but it is preferable that the surface layer contains polyurethane from the viewpoint of improving abrasion resistance, which is a characteristic required for a roller. Furthermore, from the viewpoint of easily suppressing charge leakage from the toner to the electrophotographic conductive roller, it is preferable that the resin contained in the surface layer contains polyurethane having a polycarbonate structure. Furthermore, in order to easily maintain a light load on the toner and sufficient wear resistance of the surface layer while suppressing charge leakage from the toner to the electrophotographic conductive roller, it is more preferable to use polyurethane having the structure described below as the resin contained in the surface layer.

[0030] The polyurethane preferably satisfies at least one selected from the group consisting of the following (A), (B), and (C): Among these, from the viewpoints of maintaining a higher volume resistivity of the surface layer, retaining flexibility, suppressing abrasion, further suppressing fogging, and achieving better image density stability, it is more preferable that the polyurethane satisfy at least two selected from the group consisting of the following (A), (B), and (C): (A) having a structure represented by the following formula (1) in the molecule; (B) having one or both of the structures represented by the following formula (2) and the structure represented by the following formula (3) in the molecule; (C) The molecule has a structure represented by the following formula (4):

[0031] That is, it is preferable that the polyurethane satisfies at least one of the following requirements. Having at least the structure represented by formula (1) and the structure represented by formula (2) Having at least the structure represented by formula (1) and the structure represented by formula (3) Having at least the structure represented by formula (1) and the structure represented by formula (4) Having at least the structure represented by formula (2) and the structure represented by formula (4) Having at least the structure represented by formula (3) and the structure represented by formula (4) [ka]

[0032] In formula (1), R11, R12, and R13 each independently represent a divalent hydrocarbon group having 3 to 9 carbon atoms (preferably 4 to 6), R11 and R12 are different hydrocarbon groups, R13 is the same hydrocarbon group as R11 or R12, and m and n are the average number of moles added, each independently representing a number of 1.0 or more (preferably 1.0 to 20.0, more preferably 2.0 to 12.0, even more preferably 4.0 to 10.0, and particularly preferably 5.0 to 9.0). In formula (2), o and p are the average number of moles added, and each independently represents a number of 1.0 or more (preferably 1.0 to 15.0, more preferably 2.0 to 10.0, and even more preferably 4.0 to 10.0). In formula (3), R31 and R32 each independently represent a divalent hydrocarbon group having 3 to 8 carbon atoms. q and r each independently represent the average number of moles added and are a number of 1.0 or more (preferably 1.0 to 20.0, more preferably 2.0 to 14.0). In formula (4), R41 represents a divalent hydrocarbon group having 6 to 9 carbon atoms (preferably 5 to 8), and s represents the average number of moles added and is a number of 1.0 or more (preferably 1.0 to 22.0, more preferably 5.0 to 20.0, and even more preferably 4.0 to 18.0).

[0033] The structure shown in formula (1) is a structure in which a copolymer polycarbonate polyol, which has reduced crystallinity due to the presence of two different hydrocarbon groups, is reacted with an isocyanate. Because the crystallinity is reduced, the cohesive energy in the soft segments is small, which gives the surface layer flexibility and high volume resistivity. This makes it possible to suppress charge leakage that occurs in the resin portion of the surface layer to a higher degree. At the same time, it also becomes easier to ensure flexibility to suppress toner degradation. Furthermore, by using the structure represented by formula (1) in combination with the structure represented by formula (2), the structure represented by formula (3), or the structure represented by formula (4) in the surface layer, the adhesiveness of the surface layer can be reduced. That is, it is preferable that the polyurethane has, in its molecule, the structure represented by formula (1) and at least one structure selected from the group consisting of the structure represented by formula (2), the structure represented by formula (3), and the structure represented by formula (4). By reducing the adhesiveness of the surface layer, it is possible to prevent powders such as toner and paper dust from adhering to the surface layer. As a result, it is possible to suppress changes in surface properties due to contamination, and to maintain the performance originally intended for the roller for a long period of time.

[0034] In formula (1), when the carbon numbers of R11 and R12 are 3 or more, the amount of carbonate groups, which are polar functional groups with strong cohesive energy, in the polyurethane having a polycarbonate structure is not too large, making it easier to maintain the surface layer flexible and electrically high resistance. Also, when the carbon numbers of R11 and R12 are 9 or less, the amount of carbonate groups in the polyurethane is not too small, making it easier to maintain the strength of the polymer. The hydrocarbon groups represented by R11, R12 and R13 may have a branched structure or a cyclic structure.

[0035] The structures represented by formula (2) and formula (3) are structures obtained by reacting a copolymer polyol, in which a polycarbonate structure and a polyester structure are copolymerized, with an isocyanate. By copolymerizing a polycarbonate structure and a polyester structure, the crystallinity of the polymer can be suppressed. Furthermore, by introducing an ester group, which has a stronger cohesive energy than a carbonate group, the soft segment is appropriately reinforced, making it easier to impart abrasion resistance to the surface layer. When a surface layer is formed using a polyurethane having either or both of the structure represented by formula (2) and the structure represented by formula (3) and the structure represented by formula (1) or the structure represented by formula (4), the surface layer can be imparted with sufficient volume resistivity while having polar ester groups, and charge leakage can be further suppressed. That is, it is preferable that the polyurethane has, in its molecule, either or both of the structure represented by formula (2) and the structure represented by formula (3) and either or both of the structure represented by formula (1) and the structure represented by formula (4).

[0036] In formula (3), when R31 and R32 each have 3 or more carbon atoms, the amount of carbonate and ester groups in the polyurethane, which are polar functional groups with strong cohesive energy, is not too large, making it easier to maintain the flexibility of the surface layer. Furthermore, when R31 and R32 each have 8 or less carbon atoms, the amount of carbonate and ester groups in the polyurethane is not too small, making it easier to impart abrasion resistance to the surface layer.

[0037] The structure represented by formula (4) is a structure obtained by reacting a highly crystalline polycarbonate polyol having a type of hydrocarbon group with an isocyanate. This structure is highly crystalline and easily oriented in the soft segment, making it easy to impart abrasion resistance and high volume resistivity to the surface layer. By combining the structure represented by formula (4) with the structure represented by formula (1), the structure represented by formula (2), or the structure represented by formula (3) in the surface layer, the flexibility of the surface layer is easily maintained, making it easier to suppress damage to toner, etc. In other words, it is preferable that the polyurethane has, in its molecule, the structure represented by formula (4) and at least one structure selected from the group consisting of the structure represented by formula (1), the structure represented by formula (2), and the structure represented by formula (3).

[0038] In formula (4), when R41 has 6 or more carbon atoms, crystallinity is easily exhibited, making it easier to impart abrasion resistance and high volume resistivity to the surface layer. When R41 has 9 or less carbon atoms, excessive crystallinity can be suppressed. In this case, when the polyurethane has at least one structure selected from the group consisting of the structure represented by formula (1), the structure represented by formula (2), and the structure represented by formula (3) in its molecule, it is easier to suppress an increase in the hardness of the surface layer.

[0039] The structure of the resin contained in the surface layer of the electrophotographic conductive roller can be confirmed by, for example, pyrolysis GC / MS, FT-IR, or NMR analysis.

[0040] Polyurethane having a polycarbonate structure can be produced using a polyol compound and a polyisocyanate compound. The polyurethane can be synthesized by the following methods (I) and (II). (I) One-shot method in which a polyol compound and a polyisocyanate compound are mixed and reacted (II) A method in which an isocyanate-terminated prepolymer obtained by reacting a part of a polyol compound with an isocyanate compound is reacted with a chain extender such as a low molecular weight diol or low molecular weight triol.

[0041] In the present disclosure, polyurethane may be synthesized by any of the above methods, but a more preferred method is to subject an isocyanate-terminated prepolymer obtained by reacting a polyol compound with an isocyanate compound in a state where the isocyanate is in excess relative to the hydroxyl groups, to a thermosetting reaction with a hydroxyl-terminated prepolymer as a chain extender obtained by reacting a polyol compound with an isocyanate compound in a state where the hydroxyl groups are in excess relative to the isocyanate.

[0042] The polyurethane having a polycarbonate structure is preferably a reaction product of a mixture containing a hydroxyl-terminated prepolymer and an isocyanate-terminated prepolymer. The mixture can be used as a coating liquid for forming a surface layer. The polyurethane having a polycarbonate structure is more preferably a reaction product of a mixture containing a hydroxyl-terminated prepolymer, an isocyanate-terminated prepolymer, and an additive.

[0043] When the polyurethane contains a large amount of hydroxyl groups, isocyanate groups, urea bonds, allophanate bonds, isocyanurate bonds, etc., the polyurethane contains a large amount of polar functional groups. This increases the water absorption of the polymer, lowering the volume resistivity of the surface layer and potentially causing charge leakage in electrophotographic conductive rollers. On the other hand, by thermally curing the hydroxyl-terminated prepolymer and the isocyanate-terminated prepolymer, it is possible to obtain a polyurethane with little unreacted polyol or polar functional groups without using an excessive amount of isocyanate.

[0044] [Polyol compounds] The polyol compound is selected from known polycarbonate polyols and polyester-polycarbonate copolymer polyols. Examples of polycarbonate polyols include polynonamethylene carbonate diol, poly(2-methyl-octamethylene) carbonate diol, polyhexamethylene carbonate diol, polypentamethylene carbonate diol, poly(3-methylpentamethylene) carbonate diol, polytetramethylene carbonate diol, polytrimethylene carbonate diol, poly(1,4-cyclohexanedimethylene carbonate) diol, poly(2-ethyl-2-butyl-trimethylene) carbonate diol, and random / block copolymers thereof.

[0045] Examples of polyester polycarbonate copolymer polyols include the following: copolymers obtained by polycondensing the above-mentioned polycarbonate polyols with lactones such as ε-caprolactone, and copolymers obtained by polycondensing diols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methylpentanediol, and neopentyl glycol with dicarboxylic acids such as adipic acid and sebacic acid, and alkylene carbonates such as ethylene carbonate.

[0046] [Polyisocyanate compounds] The polyisocyanate compound is selected from commonly used known compounds, such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric diphenylmethane polyisocyanate, hydrogenated MDI, and chiral diisocyanate. Silylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), polymethylene polyphenyl polyisocyanate (polymeric MDI), derivatives thereof, and isocyanurates thereof. Among these, aromatic isocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric diphenylmethane polyisocyanate, and polymeric MDI are more preferably used.

[0047] 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]

[0048] Other polyisocyanates may also be used as appropriate, provided that they do not affect the surface potential of the electrophotographic conductive roller.

[0049] The ratio of the number of isocyanate groups to the number of hydroxyl groups (hereinafter also referred to as "NCO / OH ratio") is preferably 1.0 to 2.0. If this NCO / OH ratio is 1.0 to 2.0, the crosslinking reaction proceeds, and the bleeding of unreacted components and low-molecular-weight polyurethane, known as "bleeding," is easily suppressed. The NCO / OH ratio is more preferably 1.0 to 1.6. If this NCO / OH ratio is 1.0 to 1.6, bleeding is suppressed and the hardness of the polymer is easily reduced. The content of polyurethane in the surface layer is not particularly limited, but is preferably 50 to 95% by mass, more preferably 60 to 80% by mass, and even more preferably 65 to 75% by mass.

[0050] (carbon black) The surface layer contains carbon black. The carbon black makes the surface layer conductive. Although there are no particular limitations on the carbon black, it is preferable that the carbon black has a surface functional group capable of interacting with a functional group present in the additive described below. Examples of carbon black that exhibits these properties include furnace black, thermal black, acetylene black, and ketjen black.

[0051] As mentioned above, charge leakage can be suppressed by controlling the dispersion of carbon black in the surface layer relative to the ion-conductive elastic layer. Specifically, the arithmetic mean value Rc of the equivalent circle diameters of the carbon black in the surface layer is 60.0 nm or less. When the standard deviation of the equivalent circle diameters is σc [nm], σc / Rc is 0.000 to 0.650. Rc indicates the dispersed particle size of the carbon black. In addition, the distance between the carbon black particles is determined such that the arithmetic mean value d of the distance between the wall surfaces of the carbon black particles in the surface layer is 80.0 to 150.0 nm, and the standard deviation of the distance between the wall surfaces is When σd [nm], σd / d is 0.000 to 0.600.

[0052] The reason why charge leakage can be suppressed even in an ionic conductive elastic layer when the dispersion state of carbon black in the surface layer is within the above-mentioned ranges of the equivalent circle diameter and wall-to-wall distance is presumed to be as follows. If the dispersed particle size of the carbon black is large, the distance between the walls of the entire surface layer is likely to vary. As a result, there are localized areas where the distance between the walls is close, and a conductive path of the carbon black is formed. As mentioned above, it is thought that in an ionically conductive elastic layer, the entire surface area of ​​the elastic layer contributes to charge leakage. Therefore, the formation of a conductive path inside the surface layer is almost equivalent to the formation of a conductive path that directly connects the surface of the surface layer and the surface of the elastic layer. Therefore, it is thought that if the dispersed particle size of the carbon black is large, charge leakage is more likely to occur.

[0053] On the other hand, when the dispersed particle size becomes smaller, the distance between the walls becomes uniform across the entire surface layer, making it less likely for variations to occur. As a result, there are fewer areas where the distance between the walls is locally close, making it difficult for the carbon black to form a conductive path, and increasing resistance. Furthermore, the capacitance also decreases, resulting in higher impedance. In other words, the carbon black has high resistance, which increases the influence of the capacitance component and makes it act as a pseudo-capacitor component. As a result, charge leakage is suppressed. In addition, multiple types of carbon black may be used in combination as long as the above-mentioned dispersed state can be maintained.

[0054] The arithmetic mean value Rc of the equivalent circle diameter of the carbon black in the surface layer is preferably 55.0 nm or less. Although there is no particular lower limit, it is preferably 40.0 to 60.0 nm, and more preferably 45.0 to 55.0 nm. σc / Rc is preferably 0.600 or less. There is no particular lower limit to the σc / Rc ratio, but it is preferably 0.500 to 0.650, more preferably 0.550 to 0.650, and even more preferably 0.550 to 0.600. The standard deviation σc of the equivalent circle diameter is not particularly limited, but may be 0.0 to 40.0 nm, preferably 25.0 to 40.0 nm, and more preferably 25.0 to 35.0 nm. Rc and σc are measured using an SEM. The specific measurement method will be described later.

[0055] 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 or the like when preparing the coating liquid for forming the surface layer. Specifically, weakening the dispersion increases Rc and σc, while strengthening the dispersion decreases Rc and σc. Normally, Rc converges when the particles are sufficiently dispersed. Therefore, once a certain dispersion state is exceeded, σc can be reduced while Rc remains almost constant. As a result, σc / Rc can be reduced. Additionally, σc and Rc can be reduced by using carbon black with a small primary particle size or DBP absorption. σc and Rc can also be reduced by using the additives described below. σc and Rc can also be increased by using carbon black with a large primary particle size or DBP absorption.

[0056] The arithmetic mean value d of the distance between the wall surfaces of the carbon black in the surface layer is preferably 90.0 to 120.0 nm, more preferably 92.0 to 115.0 nm. σd / d is more preferably 0.500 to 0.600, and further preferably 0.550 to 0.600. The standard deviation σd of the distance between the wall surfaces is not particularly limited, but may be 0.0 to 95.0 nm, preferably 50.0 to 95.0 nm, and more preferably 60.0 to 85.0 nm. d and σd are measured using an SEM. Specific measurement methods will be described later.

[0057] The arithmetic mean value d and standard deviation σd of the wall-to-wall distance can be changed, for example, by the dispersion state of the mill when preparing the resin layer-forming coating liquid. Specifically, weakening the dispersion tends to decrease d and increase σd, while strengthening the dispersion tends to increase d and decrease σd. Therefore, weak dispersion tends to increase σd / d, and strong dispersion tends to decrease σd / d. In addition, d can be reduced by using carbon black with a small primary particle size or DBP absorption. d can also be reduced by using the additives described below. d can also be increased by using carbon black with a large primary particle size or DBP absorption.

[0058] The number-average diameter of the primary particles of the carbon black is not particularly limited, but from the viewpoint of making it easier to obtain a desired dispersion state and a surface potential required for the completed electrophotographic conductive roller, the number-average diameter of the primary particles of the carbon black is preferably 30 nm or less. When the number-average diameter of the primary particles of carbon black is 30 nm or less, the aggregates (primary agglomerates), which are the smallest dispersible units of carbon black, become small. Furthermore, the structure (the size of the connections between primary particles) also becomes small. As a result, it becomes difficult to form conductive paths. Therefore, it becomes easier to form the intended dispersion state. The lower the number-average diameter, the better, and there is no particular lower limit, but 5 to 30 nm is preferred. The number average diameter of primary particles of carbon black is calculated using a transmission electron microscope (TEM).

[0059] The DBP absorption of carbon black is not particularly limited, but is preferably 90 mL / 100 g or less. When the DBP absorption of carbon black is 90 mL / 100 g or less, the carbon black structure becomes small, making it difficult to form conductive paths, making it easier to obtain a sufficiently high impedance. For example, the DBP absorption of carbon black is preferably 30 to 90 mL / 100 g, and more preferably 30 to 70 mL / 100 g.

[0060] The pH of carbon black is not particularly limited, but is preferably 4.0 or less. When the pH of carbon black is 4.0 or less, the repulsion of the surface functional groups of the carbon black when dispersed in a resin provides dispersion stability, making the carbon black less likely to aggregate. As a result, a sufficiently high impedance is easily obtained. 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.

[0061] Even if the number-average diameter of primary particles of carbon black, DBP absorption, and pH are within the above ranges, when polyurethane having a polycarbonate structure (hereinafter also referred to as 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 for this is not clearly understood, but is speculated as follows.

[0062] The hydroxyl groups, which are 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, and is less likely to interact with carbon black. When hydrophobic moieties exist close to each other or when hydrophilic moieties exist close to each other, the structure is more stable, so hydrophilic carbon black will exist near other hydrophilic carbon black. As a result, carbon black particles tend to aggregate together, which is thought to be a factor that can hinder dispersion. In such cases, the additives described below may be used to obtain a desired dispersion state of the carbon black.

[0063] The amount of carbon black is not particularly limited, but it is desirable to add it so as to achieve the desired volume resistivity and surface potential. For example, the amount of carbon black is preferably 30 parts by mass or less per 100 parts by mass of the resin forming the surface layer. It is more preferably 10 to 30 parts by mass, and even more preferably 15 to 25 parts by mass. When the carbon black content is 30 parts by mass or less, the distance between carbon black particles in the coating liquid is maintained at an appropriate level. As a result, the probability of collisions due to Brownian motion of carbon black particles is reduced, making carbon black particles less likely to aggregate. This makes carbon black more easily dispersed and improves dispersion stability. As a result, it is easier to achieve a desired carbon black dispersion state in the surface layer formed by coating the coating liquid.

[0064] (additives) One preferred embodiment is to use an additive to further improve the dispersibility of carbon black in the resin. That is, the surface layer preferably contains an additive. Here, for example, at least one compound selected from the group consisting of a compound represented by the following formula (5), a compound represented by the following formula (6), and a compound represented by the following formula (7) can be suitably used as the additive. That is, the surface layer preferably further contains at least one compound selected from the group consisting of a compound represented by the following formula (5), a compound represented by the following formula (6), and a compound represented by the following formula (7).

[0065] One method for incorporating the additives into the surface layer is to incorporate the additives into a coating liquid for forming the surface layer. The compound represented by the following formula (5) has a terminal hydroxyl group, and the compound represented by the following formula (6) has a terminal amino group. Therefore, in a surface layer formed using a coating liquid for forming a surface layer containing at least one compound selected from the group consisting of the compound represented by the following formula (5) and the compound represented by the following formula (6), the compound may be incorporated at the end of the polyurethane polymer chain. Even in such a case, the effect of improving the dispersibility of carbon black can be expected. This is thought to be due to the interaction between the side chain methyl group of propylene oxide and carbon black. That is, the polyurethane may be a reaction product of a polyol compound, a polyisocyanate compound, and at least one compound selected from the group consisting of the compound represented by the following formula (5) and the compound represented by the following formula (6). The additive is preferably present in the surface layer independently of the polyurethane.

[0066] Among the compounds represented by the following formula (5), the compounds represented by the following formula (6), and the compounds represented by the following formula (7), the compound represented by formula (5) is preferred because it has particularly excellent dispersibility of carbon black and affinity with polycarbonate urethane. [ka] In formula (5), R51 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms (preferably 3 to 12, more preferably 3 to 8, and even more preferably 3 to 5), and t and u represent the average number of moles added and each independently represents a number of 1.0 or more (preferably 5.0 to 30.0, and more preferably 10.0 to 25.0). In formula (6), R61 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms (preferably 1 to 4), and v and w represent the average number of moles added, each independently representing a number of 1.0 or more (preferably 1.0 to 30.0, more preferably 5.0 to 30.0). In formula (7), R71 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms (preferably 1 to 8, more preferably 1 to 4), and x represents the average number of moles added and is a number of 1.0 or more (preferably 1.0 to 30.0, more preferably 4.0 to 15.0).

[0067] The compound represented by formula (5) is a 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 carbon black through hydrogen bonding, acting as a dispersant for carbon black. In addition, the compound represented by formula (5) has a structure that is compatible with polycarbonate urethane, making it easy to disperse carbon black in polycarbonate urethane. Ethylene oxide is incorporated into the structure to ensure uniform distribution of the additive in the polycarbonate urethane. It is believed that this effect is achieved because the ethylene group in ethylene oxide is compatible with the hydrophobic hydrocarbon group in the polycarbonate urethane. Propylene oxide is incorporated into the structure to improve the dispersibility of the carbon black dispersed in the surface layer. It is believed that the side-chain methyl group of propylene oxide interacts with the carbon black, improving the dispersibility of the carbon black.

[0068] R51, 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. This effect is thought to be achieved because the monovalent hydrocarbon group has good compatibility with the hydrophobic hydrocarbon group in the polycarbonate urethane. By having 12 or fewer carbon atoms, steric hindrance with the polycarbonate urethane is less likely to occur, making it easier for the additive to be distributed uniformly. Furthermore, since the compound represented by formula (5) has a mono-ol structure, it is less reactive than a diol, and as a result, it is less likely to be incorporated into polyurethane during the urethanization reaction between isocyanate and polyol, and the introduction of an ether structure into polycarbonate urethane is less likely to result in a decrease in polyurethane resistance.

[0069] 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). Step (b) may also be carried out on a commercially available compound obtained in step (a). Step (a): Reacting alcohol with ethylene oxide Step (b): reacting the product obtained in step (a) with propylene oxide.

[0070] Step (a) can be carried out, for example, by adding ethylene oxide to an alcohol in the presence of a catalyst at 50 to 200°C, more preferably 100 to 160°C, and allowing the reaction to occur. The boiling point of ethylene oxide is 10.7°C, and it is in a gaseous state at this temperature. Therefore, it is preferable to carry out the reaction in a pressurized environment in a sealed container. The pressure is preferably 0.1 to 1.0 MPa. The reaction time is not particularly limited, but is preferably 1 to 5 hours, more preferably 1 to 3 hours, in order to reduce the amount of unreacted ethylene oxide.

[0071] The catalyst can be an acid catalyst or an alkali catalyst. Alkaline catalysts are 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 preferred, with potassium hydroxide being particularly preferred. Examples of the acid catalyst include Bronsted acids such as sulfuric acid and phosphoric acid, and Lewis acids such as stannic chloride and boron trifluoride.

[0072] The amount of catalyst used is preferably 0.1 to 5 mol% per 1 mol of alcohol. Since ethylene oxide reacts with water to produce ethylene glycol, it is important to minimize the inclusion of moisture, and a dehydration treatment may be carried out before the reaction in step (a) as needed.

[0073] Step (b) can be carried out under the conditions described in the description of 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. If a new catalyst is added, it is preferable that the catalyst be the same as that used in step (a).

[0074] The compound represented by formula (6) 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 carbon black through hydrogen bonding, acting as a dispersant for carbon black. Ethylene oxide and propylene oxide have the same effect as the compound represented by formula (5) above. R61, which is a monovalent hydrocarbon group having 1 to 8 carbon atoms, has good compatibility with the hydrophobic hydrocarbon groups in the polycarbonate urethane, making it easier for the additive to be uniformly present in the polycarbonate urethane.

[0075] The polyetheramine can be a commercially available product or can be obtained by synthesis. The synthesis of the polyetheramine can be carried out by carrying out the following step (c) followed by step (d). Step (c): An oxidation step of subjecting the compound represented by formula (5), which is a secondary alcohol, to an oxidation reaction. Step (d): An amination step in which the product obtained in step (c) is subjected to a reductive amination reaction.

[0076] Step (c) is a step of carrying out a reaction to produce a ketone by oxidation of a secondary alcohol. Examples of oxidation reactions used in synthesizing a ketone by oxidation of a secondary alcohol include oxidation reactions using heavy metal salts such as chromic acid or manganese dioxide or their derivatives, and oxidation reactions using hypohalous acids such as hypochlorous acid or dimethyl sulfoxide (DMSO) without using heavy metal salts.

[0077] Either method may be used, but in consideration of the environmental impact of heavy metals, oxidation reactions that do not use hypohalous acids such as hypochlorous acid or heavy metal salts such as dimethyl sulfoxide (DMSO) are preferred. Furthermore, dimethyl sulfoxide (DMSO) can react explosively at room temperature depending on the electrophilic activating reagent used, so a low temperature such as -60°C may be required, making methods that use hypohalous acids more preferable. Examples of hypohalous acids include hypochlorites such as sodium hypochlorite and calcium hypochlorite (bleaching powder), and hypobromites such as sodium hypobromite and calcium hypobromite, with hypochlorite being preferred. These hypohalites are reacted with the compound represented by formula (5), which is a secondary alcohol, in acetic acid to produce a ketone.

[0078] When using dimethyl sulfoxide (DMSO), an electrophilic activating reagent is also used. The electrophilic activating reagent increases the electrophilicity of the sulfur atom in DMSO, allowing the sulfur atom to be subjected to nucleophilic attack by the alcohol hydroxyl group. This nucleophilic attack produces a dimethylalkoxysulfonium salt, which then decomposes to produce 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.

[0079] 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 the borohydride reagent include at least one selected from the group consisting of sodium cyanoborohydride, sodium triacetoxyborohydride, and 2-picoline borane. Among these, at least one selected from the group consisting of sodium triacetoxyborohydride and 2-picoline borane is preferred, as it is less toxic, and 2-picoline borane is even more preferred. In the reductive amination reaction using a borohydride reagent, if the substrate has a bulky structure, steric hindrance makes it difficult to generate an iminium cation, so R61 in the compound represented by formula (6) is preferably a monovalent hydrocarbon group having 1 to 8 carbon atoms.

[0080] The compound represented by formula (7) is polyoxyethylene alkyl ether acetic acid. The terminal carboxylic acid in formula (7) interacts with the surface functional groups of carbon black through hydrogen bonding, acting as a dispersant for carbon black. Furthermore, R71, a monovalent hydrocarbon group having 1 to 12 carbon atoms, is compatible with the hydrophobic hydrocarbon groups in polycarbonate urethane, making it easier for additives to be uniformly distributed in the polycarbonate urethane.

[0081] Polyoxyethylene alkyl ether acetic acid can be a commercially available product or can be obtained by synthesis. Polyoxyethylene alkyl ether acetic acid can be synthesized by carrying out the following step (e) followed by step (f). Step (f) may also be carried out on a commercially available compound obtained in step (e). Step (e): Reacting alcohol with ethylene oxide Step (f): An oxidation step of subjecting the product obtained in step (e) to an oxidation reaction.

[0082] Step (e) is the same as step (a). Specifically, the method described in the description of step (a) can be used. Step (f) is the step of oxidizing a primary alcohol to produce a carboxylic acid. When a primary alcohol is oxidized, an aldehyde is first produced, and then the aldehyde is further oxidized to produce a carboxylic acid. Therefore, it is necessary to select a reaction method and conditions that will allow oxidation to the carboxylic acid. Methods for obtaining carboxylic acids by oxidation of primary alcohols include oxidation with an oxidizing agent and catalytic dehydrogenation using a catalyst. Examples of oxidizing agents include permanganates such as potassium permanganate, chromic acid, ruthenium tetroxide, and hypochlorite, with permanganates being preferred. Examples of catalysts for dehydrogenation include palladium, platinum, iridium, rhodium, and manganese.

[0083] The compounds represented by the above formulas (5), (6), and (7) 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 the above formulas (5), (6), and (7) have a small number of functional groups that interact with the surface functional groups of carbon black, resulting in weak surfactant activity and not being commonly used. However, the present inventors have discovered that these compounds function as dispersants for carbon black in polycarbonate urethane due to the above-mentioned mechanism.

[0084] Coupling agents and nonionic surfactants are commonly used as dispersants for carbon black. Silane coupling agents, titanate coupling agents, and aluminum coupling agents are used as coupling agents, and polyester and polyether coupling agents are used as nonionic surfactants. However, if these dispersants are added in an amount sufficient to sufficiently increase the dispersibility of carbon black in polycarbonate urethane, for example, at a mass ratio of 50% or more to the carbon black, it is thought that the conductivity of the carbon black and binder resin will be impaired. Conversely, if the amount added does not impair the conductivity of the carbon black and binder resin, it is thought that the desired dispersibility of carbon black cannot be achieved. If the surface of carbon black is coated with an insulating material such as a silane coupling agent, it will no longer be able to function as a pseudo-capacitor, resulting in high impedance and surface potential.

[0085] The content of at least one compound selected from the group consisting of the compound represented by the formula (5), the compound represented by the formula (6), and the compound represented by the formula (7) in the coating liquid for forming a surface layer is preferably 3.0 to 7.0 mass% based on the solid content in the coating liquid for forming a surface layer. When multiple compounds are contained, this content indicates the total content. The total content is preferably 18.9 to 46.0 parts by mass relative to 100 parts by mass of carbon black in the coating liquid for forming the surface layer. By keeping the content of the additive in the surface layer-forming coating liquid within the above range, the dispersibility of carbon black in polyurethane is further improved, and the desired dispersion state can be easily achieved.

[0086] The presence of additives in the surface layer can be confirmed and quantitatively evaluated by the following analytical method. First, the surface layer of the electrophotographic conductive roller is cut out to obtain a slice. Then, for example, 1 H-NMR, 13 By using C-NMR, XPS, and FT-IR, The carbonate structure of the binder resin, and the ether structure, amine structure, and carboxylic acid structure of the additives can be detected in the layer. The presence of additives can be confirmed from the ratio of peaks in each measurement, and the ratio can be calculated for quantitative evaluation. Alternatively, the above sections can be extracted by immersing them overnight in an organic solvent such as 2-butanone (methyl ethyl ketone; MEK), and the extract and the extracted sections can be analyzed. 1 H-NMR, 13 By using C-NMR, XPS, and FT-IR, it is possible to calculate the ratio of additives that are incorporated into the resin during the polymerization reaction and those that are not.

[0087] Examples of the structure in which at least one selected from the group consisting of the compound represented by formula (5) and the compound represented by formula (6) is bonded to polyurethane (the structure resulting from the reaction during polymerization of polyurethane) include the following: In the case of the compound represented by formula (5), the compound represented by formula (5) is urethane-modified and incorporated into the polyurethane structure. In the case of the compound represented by formula (6), in polyurethane, the compound represented by formula (6) is ureated and incorporated into the polyurethane structure.

[0088] [Roughness forming particles] The surface layer may contain roughness-imparting particles to impart roughness to the surface of the surface layer. The roughness-imparting particles are not particularly limited, but are preferably resin particles, and more preferably spherical particles. The particle size of the roughness-imparting particles is not particularly limited, but is preferably in the range of 1 to 150 μm, and more preferably in the range of 5 to 30 μm. The resin particles are not particularly limited, but examples thereof include urethane resin particles, acrylic resin particles, phenolic resin particles, silicone resin particles, polyacrylonitrile resin particles, polystyrene resin particles, polyurethane resin particles, nylon resin particles, polyethylene resin particles, and polypropylene resin particles. Urethane resin particles are preferred. The content of the roughness-imparting particles is not particularly limited, and is preferably, for example, 10 to 20 parts by mass per 100 parts by mass of the resin component that forms the surface layer.

[0089] (Manufacturing method) The method for forming the surface layer is not particularly limited, and examples thereof include spraying, dip coating, and roll coating. For example, the surface layer can be formed by applying a coating liquid for forming the surface layer onto the elastic layer by a known method and then drying by heating. The conditions for heat drying are not particularly limited, and examples thereof include a method of drying under conditions of 120 to 200° C. The drying time is not particularly limited, and examples thereof include 0.5 to 2.0 hours. The thickness of the surface layer is not particularly limited, but is preferably 1 to 50 μm, and more preferably 5 to 20 μm.

[0090] <Process cartridge and electrophotographic image forming apparatus> The electrophotographic conductive roller according to the present disclosure can be suitably used as a developing roller, a toner supply roller, and a developing sleeve in a process cartridge. FIG. 2 is a schematic cross-sectional view of an example of a process cartridge according to one embodiment of the present disclosure. In FIG. 2, the electrophotographic conductive roller is mounted as a developing roller 21. A process cartridge 22 is configured to be detachably attached to the main body of an electrophotographic image forming apparatus. The process cartridge 22 integrates a developing device 24 including the developing roller 21 and a developing blade 23, a photoreceptor 25, a charging roller 26, and a cleaning blade 27. The developing device 24 is further filled with toner 28. The toner 28 is supplied to the surface of the developing roller 21 by a toner supply roller 29, and a layer of toner 28 of a predetermined thickness is formed on the surface of the developing roller 21 by the developing blade 23.

[0091] The developing roller 21 is in contact with the photosensitive member 25 and is driven to rotate at a predetermined peripheral speed ratio relative to the photosensitive member 25. A predetermined bias is applied to the developing roller 21, and the electrostatic latent image on the photosensitive member 25 is developed with toner 28 to be visualized.

[0092] The toner supply roller 29 comes into contact with the developing roller 21, penetrates to a predetermined depth, and rotates in the same direction as or opposite to the rotation of the developing roller 21. The toner supply roller 29 is also designed so that it can be given a potential difference with respect to the developing roller 21 depending on the purpose.

[0093] One end of the developing blade 27 is fixed to the developing device 24, and the other free end is arranged in contact with the developing roller 21 in the counter direction to the rotation direction. By arranging the developing blade 27 in contact with the developing roller 21, the amount of toner on the developing roller 21 is regulated, making the layer thinner and forming a toner layer of uniform thickness. In addition, a predetermined bias is applied to the developing blade 23, imparting an electric charge to the toner 28.

[0094] The electrophotographic image forming apparatus has a photoreceptor and a developing roller that supplies a developer to an electrostatic latent image formed on the photoreceptor, and the developing roller is the electrophotographic conductive roller of the present disclosure.

[0095] 3 is a schematic cross-sectional view showing an example of an electrophotographic image forming apparatus equipped with an electrophotographic conductive roller according to the present disclosure as a developing roller of a contact-type developing device using one-component toner. The developing device 24 includes toner 28 as one-component toner, a developing roller 21, a toner supply roller 29 that supplies toner to the developing roller 21, and a developing blade 23 that regulates the thickness of the toner layer on the developing roller 21. The developing roller 21 is located in an opening extending in the longitudinal direction of the developing device 24 and is installed in contact with a photoreceptor 25. The photoreceptor 25, charging roller 26, and cleaning blade 27 may be provided in the main body of the electrophotographic image forming apparatus. The developing device 21 is equipped with black, cyan, magenta, and yellow toners, enabling color printing.

[0096] The printing operation of the electrophotographic image forming apparatus will be described below. The photoconductor 25 rotates in the direction of the arrow and is uniformly charged by a charging roller 26 that charges the photoconductor 25. Next, an electrostatic latent image is formed on the surface of the photoconductor 25 by a laser beam 31, which serves as an exposure means. The electrostatic latent image is visualized as a toner image (developed) by the developing device 24, which applies toner 28 from a developing roller 21 that is placed in contact with the photoconductor 25. The development is what is known as reversal development, in which a toner image is formed in the exposed area.

[0097] The toner image formed on the photosensitive member 25 is transferred onto an intermediate transfer member 33 in the form of an endless belt by a transfer roller 32 which is a transfer member. Paper 34, which is a recording medium, is fed into the device by paper feed roller 35 and secondary transfer roller 36, and is transported together with intermediate transfer body 33 bearing a toner image to the nip between secondary transfer roller 36 and driven roller 37, where the toner image is transferred to paper 34. Intermediate transfer body 33 is operated by driven roller 37, drive roller 38, and tension roller 39. Toner remaining on the intermediate transfer body is cleaned by cleaning device 310.

[0098] A voltage is applied to the developing roller 21, developing blade 23, transfer roller 32, and secondary transfer roller 36 from a bias power supply 311. The paper 34 onto which the toner image has been transferred is fixed by a fixing device 312 and then ejected outside the device, completing the printing operation. Meanwhile, residual toner remaining on the photoreceptor 25 without being transferred is scraped off by a cleaning blade 27, which is a cleaning member for cleaning the surface of the photoreceptor. The cleaned photoreceptor 25 repeats the above printing operation.

[0099] <Surface potential> The method for measuring the surface potential will be described. The surface potential is measured using a charge amount measuring device (product name: DRA-2000L, manufactured by QEA). Specifically, in an environment of 23°C temperature and 50% relative humidity, a corona discharger having a 3.0 mm wide grid is placed so that the distance between the grid and the outer surface of the electrophotographic conductive roller is 1.0 mm and the direction of the grid width coincides with the axial direction of the electrophotographic conductive roller. Next, a voltage of 8 kV is applied to the grid, and the corona discharger is moved relatively along the axial direction of the electrophotographic conductive roller at a speed of 400 mm / sec to charge the outer surface of the electrophotographic conductive roller. At this time, the potential of the outer surface is measured 0.06 seconds after the grid passes. The obtained potential is the surface potential of the electrophotographic conductive roller. This allows the degree of charge-up on the outer surface of the electrophotographic conductive roller to be evaluated.

[0100] The surface potential of the electrophotographic conductive roller can be measured, for example, using the device shown in Fig. 4. Both ends of the substrate 11 of the electrophotographic conductive roller 10 are held by chucks 41, and a measuring unit 44, which has a corona discharger 42 and a surface potentiometer 43 arranged in parallel with an interval of 25 mm, is placed facing the surface of the electrophotographic conductive roller at a distance of 1.0 mm. With the electrophotographic conductive roller 10 stationary, a voltage of 8 kV is applied to the grid portion of the corona discharger 42, and the measuring unit 44 is moved in the axial direction of the electrophotographic conductive roller 10 at a speed of 400 mm / sec. At this time, the surface potential is measured by the surface potentiometer 43 0.06 seconds after passing the corona charger 42. Furthermore, the chuck 41 is rotatable, and it is possible to perform measurements while changing the phase of the electrophotographic conductive roller.

[0101] The surface potential of an electrophotographic conductive roller indicates the tendency for charge to remain on the surface of the electrophotographic conductive roller, and is a physical property that indicates the degree of excessive charging of toner. Charge-bearing toner is electrically attracted to the surface of the electrophotographic conductive roller. If residual charge exists on the outer surface of the electrophotographic conductive roller, this electrical adhesion force becomes even stronger, causing the charged toner to continue to adhere to the electrophotographic conductive roller. As this adhered toner continues to remain on the roller, it increases the opportunity for friction with surrounding components, further increasing the amount of triboelectric charge. As a result, excessive charging of the toner can occur. The maximum value of the surface potential is preferably less than 20.0 V. By satisfying this range, the electrical adhesion between the toner and the electrophotographic conductive roller is suppressed. Therefore, the contact opportunity between the toner and the electrophotographic conductive roller is reduced, which reduces the amount of triboelectric charge and makes it easier to suppress excessive charging of the toner.

[0102] In addition, 0.06 seconds after passing the grid part of the corona discharger, this simulates a model with a high process speed. The surface potential is measured by applying a voltage of 8 kV to the grid portion and moving the corona discharger relatively along the axial direction of the electrophotographic roller at a speed of 400 mm / sec. The maximum value 0.06 sec after the grid portion of the corona discharger has passed is taken as the surface potential of the electrophotographic conductive roller.

[0103] The surface potential of the electrophotographic conductive roller is more preferably 10.0 V or less, and even more preferably 7.0 V or less. The lower the maximum value of the potential of the outer surface, the better, and there is no particular lower limit. The surface potential of the electrophotographic conductive roller is, for example, preferably 0.0 to 20.0 V, more preferably 0.0 to 10.0 V, and even more preferably 0.0 to 7.0 V. The surface potential of the electrophotographic conductive roller can be controlled by adjusting the particle size of the dispersed carbon black. For example, if the particle size of the dispersed carbon black is reduced, the surface potential of the entire surface layer When viewed from above, the distance between the walls becomes more uniform, making it difficult to form a conductive path, increasing resistance and decreasing capacitance, resulting in higher impedance. In terms of surface potential, resistance becomes high, the effect of the capacitance component becomes greater, and the surface potential can be reduced by the amount of charge that can be stored in the pseudo-capacitor component. [Example]

[0104] 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.

[0105] [1. Preparation and manufacturing of raw materials for forming surface layer] <1-1. Preparation of raw polyol and manufacturing example> The raw material polyols used in the surface layer of the present disclosure are shown below.

[0106] [Measurement of number average molecular weight of raw material polyol] The apparatus and conditions used for measuring the number average molecular weight (Mn) in this production example are as follows. Measuring device: HLC-8120GPC (Tosoh Corporation) Column: TSKgel Super HZMM (Tosoh Corporation) x 2 Solvent: tetrahydrofuran (THF) (20 mmol / l triethylamine added) Temperature: 40℃ THF flow rate: 0.6 ml / min The measurement sample was a 0.1% by mass THF solution. Furthermore, the measurement was carried out using an RI (refractive index) detector as the detector. A calibration curve was created using TSK standard polystyrenes A-1000, A-2500, A-5000, F-1, F-2, F-4, F-10, F-20, F-40, F-80, and F-128 manufactured by Tosoh Corporation as standard samples. Based on this calibration curve, the number average molecular weight was calculated from the retention time of the obtained measurement sample.

[0107] [Preparing raw polyol] The 16 raw material polyols A-1 to A-16 shown in Table 1 below were purchased commercially. Raw material polyols A-17 and A-18 were synthesized according to the following procedure. [Table 1]

[0108] [Synthesis of raw material polyol A-17] Under a nitrogen atmosphere, 100.0 g of 1,3-propanediol, 49.4 g of adipic acid, and 69.5 g of ethylene carbonate were mixed and heated, and the temperature was raised to 200°C while distilling off the ethylene glycol and water produced from the reaction system. After the ethylene glycol and water were distilled off, 15 ppm of titanium tetraisopropoxide was added, and the polycondensation reaction was further carried out under a reduced pressure of 266.7 Pa. The reaction solution was cooled to room temperature to obtain raw material polyol A-17. The number average molecular weight of the resulting raw material polyol A-17 was 2030.

[0109] [Synthesis of raw material polyol A-18] Raw material polyol A-18 was synthesized in the same manner as raw material polyol A-17, except that the diols and dicarboxylic acids shown in Table 2 below were used. The number average molecular weight of raw material polyol A-18 was 2,040. [Table 2]

[0110] <1-2. Preparation of raw material isocyanates B-1 to B-6> The raw material isocyanates shown in Table 3 below were prepared. [Table 3]

[0111] <1-3. Production Examples of Hydroxyl-Terminated Prepolymers C-1 to C-14> [Synthesis of hydroxyl-terminated prepolymer C-1] Under a nitrogen atmosphere, the materials listed in Table 4 below were reacted by heating and stirring at a temperature of 90°C for 3 hours. Then, 2-butanone (MEK) was added to the resulting reaction product to prepare a solution with a solid content of 50% by mass, thereby producing hydroxyl-terminated prepolymer C-1. [Table 4]

[0112] [Synthesis of hydroxyl-terminated prepolymers C-2 to C-14] Hydroxyl-terminated prepolymers C-2 to C-14 were synthesized in the same manner as in the synthesis of hydroxyl-terminated prepolymer C-1, except that the raw polyols and raw isocyanates shown in Table 5 below were used. The chemical structures of these hydroxyl-terminated prepolymers C-1 to C-14 are as follows: 1 H-NMR and 13 The m, n, o, p, q, r, and s in the formulas (1), (2), (3), and (4) in Table 5 represent the average number of moles added. [Table 5] In the table, Me represents a methyl group.

[0113] [Production Example of Hydroxyl-Terminated Prepolymer C-15] A mixture of 144.2 g of dry tetrahydrofuran and 172.2 g of dry 3-methyltetrahydrofuran (molar ratio 50:50) was maintained at 10°C in a reaction vessel. Next, 13.1 g of 70% aqueous perchloric acid solution and 120 g of acetic anhydride were added, and the reaction was carried out for 1.5 hours. The reaction mixture was then poured into 600 g of 20% aqueous sodium hydroxide solution for purification. Furthermore, the remaining water and solvent components were removed under reduced pressure, yielding liquid polyether diol C-15. The number-average molecular weight of the resulting polyether diol was 1,000.

[0114] <1-4. Production Examples of Isocyanate-Terminated Prepolymers D-1 to D-9> [Synthesis of isocyanate-terminated prepolymer D-1] The materials listed in Table 6 below were reacted under a nitrogen atmosphere by heating and stirring at 90°C for 3 hours. 2-Butanone (MEK) was then added to the resulting reaction product to prepare a solution with a solids content of 50% by mass, synthesizing isocyanate-terminated prepolymer D-1. [Table 6]

[0115] [Synthesis of Isocyanate-Terminated Prepolymers D-2 to D-9] Isocyanate group-terminated prepolymers D-2 to D-9 were produced in the same manner as in the synthesis of isocyanate group-terminated prepolymer D-1, except that the types and amounts of starting materials shown in Table 7 below were used. The chemical structures of these isocyanate group-terminated prepolymers D-1 to D-9 are as follows: 1 H-NMR and 13 The molecular weights of the compounds were determined using C-NMR. In Table 7, m, n, o, p, q, r, and s in the structural formulae (1), (2), (3), and (4) represent the average number of moles added. [Table 7] In the table, Et represents an ethyl group, and Bu represents an n-butyl group.

[0116] [Synthesis of isocyanate-terminated prepolymer D-10] Under a nitrogen atmosphere, 200.0 g of polyether diol C-15 was slowly added dropwise to 76.5 g of polymeric MDI (trade name: Millionate MR200, manufactured by Tosoh Corporation) in a reaction vessel while maintaining the temperature inside the reaction vessel at 65°C. After completion of the addition, the mixture was allowed to react at 65°C for 2 hours. The resulting reaction mixture was cooled to room temperature to obtain isocyanate-terminated prepolymer D-10.

[0117] [2. Preparation and manufacturing of additive raw materials used in the surface layer] <2-1. Preparation of polyoxyethylene polyoxypropylene alkyl ether, manufacturing example> [Preparation of polyoxyethylene polyoxypropylene alkyl ether] Polyoxyethylene polyoxypropylene alkyl ethers E-1 to E-5 shown in Table 8 below were purchased commercially. Polyoxyethylene polyoxypropylene alkyl ethers E-6 and E-7 were synthesized according to the following procedure.

[0118] [Synthesis of polyoxyethylene polyoxypropylene alkyl ether E-6] 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 number of moles added of 15.

[0119] The resulting ethylene oxide adduct was cooled to 130°C, and then 1132.6 g of propylene oxide (15 mol relative to the alcohol) was added. After the addition was completed, the reaction was carried out at 130°C for 5 hours to obtain polyoxyethylene polyoxypropylene octyl ethylene carbonate, which is a block polymer having an average number of ethylene oxide added of 15 and an average number of propylene oxide added of 15. The ether adduct was obtained. The resulting polyoxyethylene polyoxypropylene octyl ether adduct was cooled to 80°C and stirred at 2.5 kPa for 30 minutes to remove unreacted ethylene oxide and propylene oxide. 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 alkyl ether E-6. The structure of R51 and the values ​​of t and u of E-6 are shown in Table 8.

[0120] [Synthesis of polyoxyethylene polyoxypropylene alkyl ether E-7] 550.0 g of polyoxyethylene methyl ether (trade name: BRAWNON MP-550, manufactured by Aoki Oil & Fat Chemicals Co., Ltd., average number of moles of ethylene oxide added relative to alcohol: 12 mol) and 3.0 g of potassium hydroxide were charged into an autoclave equipped with a stirrer, temperature controller, and automatic charger, and dehydration was carried out at 110°C and 1.2 kPa for 30 minutes. After completion of dehydration, nitrogen substitution was carried out, and the temperature was raised to 130°C, after which 871.2 g of propylene oxide (12 mol relative to alcohol) was charged. After completion of charging, a reaction was carried out at 130°C for 4 hours, yielding a polyoxyethylene polyoxypropylene methyl ether adduct, which is a block polymer with an average number of moles of ethylene oxide added of 12 and an average number of moles of propylene oxide added of 12.

[0121] The resulting polyoxyethylene polyoxypropylene methyl ether adduct was cooled to 80°C and stirred at 2.5 kPa for 30 minutes to remove unreacted propylene oxide. 6.0 g of 90% lactic acid was then added to the autoclave and stirred at 80°C for 30 minutes, followed by extraction to obtain polyoxyethylene polyoxypropylene alkyl ether E-7. The structure of R51 and the values ​​of t and u for E-7 are shown in Table 8. [Table 8]

[0122] <2-2. Preparation of polyetheramine, manufacturing example> [Preparation of polyetheramine] Polyetheramines E-8 and E-9 shown in Table 9 below were purchased commercially. Polyetheramine E-10 was synthesized according to the following procedure.

[0123] [Synthesis of Polyetheramine E-10] 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 an aqueous solution of sodium carbonate was added dropwise over 1 hour. During this time, the flask was placed in an ice bath to cool the temperature to 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. Next, while cooling to 0°C in an ice bath, 250 mL of a methanol-acetic acid mixed solution (volume ratio 10:1) was added to 41.4 g of the resulting compound obtained by ketonizing the secondary alcohol, and 2.7 g of 2-picoline borane was added. 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 solution basic, and the aqueous layer was extracted with dichloromethane, post-treated, and purified using a column to obtain polyetheramine E-10. The structure of R61 of E-10 and the values ​​of v and w are shown in Table 9. [Table 9]

[0124] <2-3. Preparation of polyoxyethylene alkyl ether acetic acid, manufacturing example> [Preparation of polyoxyethylene alkyl ether acetic acid] Polyoxyethylene alkyl ether acetic acid E-11 shown in Table 10 below was purchased commercially. Polyoxyethylene alkyl ether acetic acids E-12 and E-13 were synthesized according to the following procedure.

[0125] [Synthesis of Polyoxyethylene Alkyl Ether Acetate E-12] 55.0 g of polyoxyethylene methyl ether (trade name: Brownon MP-550, manufactured by Aoki Oil & Fat Chemicals Co., Ltd., average number of moles of ethylene oxide added relative to alcohol: 12) was mixed with 510 mL of 1 mol / L aqueous sodium hydroxide solution, 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 filtered. The aqueous layer was extracted and purified with dichloromethane to obtain polyoxyethylene methyl ether acetic acid E-12. The structure of R71 and the value of x for E-12 are shown in Table 10.

[0126] [Synthesis of Polyoxyethylene Alkyl Ether Acetic Acid E-13] 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 number of moles added of 15. 77.4 g of the resulting ethylene oxide adduct was mixed with 510 ml of a 1 mol / L aqueous sodium hydroxide solution, and 71.1 g of potassium permanganate was added and stirred at room temperature for 6 hours. 760 ml of 2-propanol was then added and stirred for 1 hour to quench the excess potassium permanganate, and the by-product manganese oxide was filtered. The aqueous layer was then washed with dichloromethane. After extraction and purification, polyoxyethylene octyl ether acetic acid E-13 was obtained. The structure of R71 and the value of x of E-13 are shown in Table 10. [Table 10]

[0127] [3. Manufacturing examples of surface layer forming coating solutions F-1 to F-44] <3-1. Preparation of coating solution F-1 for forming surface layer> The materials for surface layer-forming coating solution F-1, the types and amounts of which are listed in Table 11 below, were added to a reaction vessel and stirred. Next, 2-butanone (MEK) was added so that the total solids ratio was 30% by mass, and the mixture was mixed using a sand mill. Next, 2-butanone (MEK) was added to adjust the viscosity of the solution to within the range of 6 to 10 mPa·s, producing surface layer-forming coating solution F-1. [Table 11]

[0128] <3-2. Preparation of surface layer forming coating solutions F-2 to F-46> Surface layer forming coating solutions F-2 to F-46 were prepared in the same manner as in the preparation of surface layer forming coating solution F-1, except that the hydroxyl group-terminated prepolymer, isocyanate group-terminated prepolymer, additives, carbon black, and roughness-forming particles listed in Table 12 below were used. [Table 12]

[0129] Example 1 <1. Manufacture of electrophotographic conductive roller> In this example, an electrophotographic conductive roller is described in which a surface layer is coated on an elastic roller having an elastic layer provided on the outer surface of a substrate, but the present disclosure is not limited to this configuration.

[0130] [1-1. Preparation of the substrate] As the base, a conductive vulcanizing adhesive (product name: Metalock U-20, manufactured by Toyo Kagaku Kenkyusho Co., Ltd.) was applied to the circumferential surface of a stainless steel (SUS304) core bar with a diameter of 6.0 mm and a length of 260.0 mm, and then baked to prepare a mandrel that would serve as the base.

[0131] [1-2. Preparation of Elastic Layer] The materials shown in Table 13 below were mixed for 16 minutes using a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshin Co., Ltd.) at a filling rate of 70% by volume and a blade rotation speed of 30 rpm to obtain mixture 1. [Table 13]

[0132] Next, the materials shown in Table 14 below were subjected to a total of 20 left-right reversals using an open roll with a roll diameter of 12 inches (0.30 m), with the front roll rotating at 10 rpm, the rear roll rotating at 8 rpm, and a roll gap of 2 mm. Thereafter, the roll gap was set to 0.5 mm and thin-threading was performed 10 times to obtain Mixture 2. [Table 14]

[0133] Next, the above-mentioned mixture 2 was extruded simultaneously with the substrate by extrusion molding using a crosshead, while being molded into a cylindrical shape coaxially with the substrate at the center, to form a layer of mixture 2 on the outer peripheral surface of the substrate. An extruder with a cylinder diameter of 45 mm (Φ45) and L / D=20 was used, and the temperature during extrusion was controlled at 90°C for the head, cylinder, and screw. Both ends of the layer of mixture 2 in the longitudinal direction of the substrate were cut, and the length of the layer of mixture 2 in the longitudinal direction of the substrate was adjusted to 234.2 mm. Thereafter, the substrate provided with the layer of mixture 2 was heated in an electric furnace at a temperature of 160°C for 40 minutes, and the layer of mixture 2 was vulcanized to form a vulcanized member. Subsequently, the surface of the vulcanized member was polished with a plunge-cut cutting type polishing machine to obtain an elastic layer roller. The outer diameter of the elastic layer roller was measured using a laser length measuring device (product name: Control Component LS-7000, sensor head LS-7030R, manufactured by Keyence Corporation). The outer diameter was measured at 10 mm intervals in the longitudinal direction, and the difference between the outer diameter at 10 mm from the end of the elastic layer and the outer diameter at the center of the member was taken as the crown amount. The outer diameter of the end of the obtained elastic layer roller was 11.458 mm, and the outer diameter at the center of the elastic layer roller was The diameter was 11.508 mm and the crown amount was 50 μm.

[0134] [1-3. Preparation of surface layer] The surface of the elastic layer roller was previously modified using an excimer lamp in order to improve adhesion to the surface layer. Next, the elastic layer roller was oriented such that its longitudinal direction was vertical, and its upper end was gripped. The elastic layer roller was then immersed (dipped) in the surface layer-forming coating solution F-1 to coat the surface of the elastic layer roller with the coating solution. The resulting coating was air-dried at room temperature for 30 minutes, and then dried for 1 hour in a hot air circulating dryer set at 160°C. In this way, an electrophotographic conductive roller G-1 was obtained, in which a surface layer with a thickness of 12 μm was formed on the elastic layer.

[0135] <3. Measurement of surface potential> The surface potential of the electrophotographic conductive roller was measured using a charge amount measuring device (product name: DRA-2000L, manufactured by QEA). Specifically, in an environment of 23°C temperature and 50% relative humidity, the grid portion of the corona discharger of the charge amount measuring device was positioned so that the gap between it and the outer surface of the electrophotographic conductive roller was 1 mm. Next, a voltage of 8 kV was applied to the corona discharger, and the corona discharger was moved relatively along the axial direction of the electrophotographic conductive roller at a speed of 400 mm / sec, thereby charging the surface of the electrophotographic conductive roller. At this time, the potential of the outer surface was measured 0.06 seconds after the grid passed. This was measured at 0.1 mm intervals in the longitudinal direction and at 30 degree intervals in the rotation direction, and the potential of the outer surface of the conductive roller was mapped, and the arithmetic mean value was taken as the surface potential of the conductive roller.

[0136] 4. Calculation of the equivalent circle diameter and wall distance of carbon black dispersed in the surface layer The particle size of the carbon black dispersed in the surface layer and the wall-to-wall distance were measured by the following method. First, a section (0.5 to 1.0 mm thick) was cut using a razor so that a cross section perpendicular to the longitudinal direction of the electrophotographic conductive roller could be observed. When the adhesion between the substrate and the surface layer was high and cutting with a razor was difficult, the entire substrate was cut using a hacksaw or the like, and then the cross section was processed using a FIB (Focused Ion Beam) device.

[0137] Next, the slices were coated with platinum, and the surface layer was photographed at 15,000x magnification using a scanning electron microscope (SEM) (trade name: JSM-7800F, manufactured by JEOL Ltd.) to obtain cross-sectional images. 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. The image was then inverted to make the carbon black appear white. A binarization threshold was then set for the brightness distribution of the image based on the algorithm of Otsu's discriminant analysis, and a binarized image was obtained in which the carbon black appeared white and the binder resin appeared black.

[0138] The resulting binarized image was then processed using image processing software (product name: Luzex AP, manufactured by Nireco Corporation) to calculate the equivalent circle diameter and the distance between adjacent wall surfaces of the whitened carbon black areas. The image area for calculating the equivalent circle diameter and the distance between adjacent wall surfaces was determined to be within 0.075 μm of the actual image dimensions (0.075 μm inside the beginning of the actual image if there was a text section describing the SEM measurement conditions, etc.) to eliminate uncertainty in the calculated values ​​for the carbon black, which was divided at the top, bottom, left, and right edges of the image. The equivalent circle diameter and the distance between adjacent wall surfaces for all carbon black particles within the specified image area were then calculated. The arithmetic mean and standard deviation were then calculated for the distribution of the obtained equivalent circle diameter and the distance between adjacent wall surfaces. Regarding the number of images to be analyzed, in order to eliminate the influence of differences in the longitudinal direction of the carbon black dispersed in the surface layer of the electrophotographic conductive roller, the surface layer of the electrophotographic conductive roller was divided into five equal parts in the longitudinal direction, and one slice was cut out from each part. The surface layer was divided into five equal sections in the longitudinal direction, and each section was cut out from the longitudinal center. One image was taken for each section, for a total of five images, and the arithmetic mean value of the five images was used as the value of the conductive roller.

[0139] 5. Image Evaluation The image evaluation method will be explained below. The electrophotographic image forming apparatus used was a modified version of a commercially available laser printer, the LBP-7600C (manufactured by Canon Inc.). The configuration of the modified apparatus is shown in Figure 5. The modified parts included connecting it to an external high-voltage power supply so that an arbitrary potential difference could be set between the developing blade and the electrophotographic conductive roller, and the output rate per unit time was set to 50 sheets per minute for A4 size paper in order to evaluate a high-speed process. The process cartridge used was a commercially available toner cartridge 318 (black) (manufactured by Canon Inc.), and the developing roller was replaced with an electrophotographic conductive roller G-1. The toner loading amount was adjusted to 100 g. The yellow, cyan, and magenta stations were each evaluated by removing the product toner and inserting yellow, cyan, and magenta cartridges with their remaining toner amount detection mechanisms disabled.

[0140] [5-1.Fog evaluation] The prepared process cartridge was installed in the main body of an electrophotographic image forming apparatus and left in an environment of 30°C and 80% relative humidity for 24 hours. Thereafter, an external high-voltage power supply was used to set the potential difference between the developing blade and the electrophotographic conductive roller to -300V. In the same environment, an image of a 4-point "E" letter was continuously printed on an A4 evaluation sheet (GF-C081, manufactured by Canon Inc.) with a print coverage of 2% of the A4 paper area. A solid white image was printed every 1,000 sheets, and this process was repeated up to 20,000 sheets. The fogging value was measured using the following method.

[0141] Using a reflection densitometer (product name: TC-6DS / A, manufactured by Tokyo Denshoku Technology Center Co., Ltd.), the reflection density R1 of the recording material before image formation and the reflection density R2 of the recording material with a solid white image printed thereon were measured. The increase in reflection density (R2 - R1) was defined as the "fog value" of the electrophotographic conductive roller. The reflection density was measured across the entire image printing area of ​​the recording material. The arithmetic mean value was used for the recording material before image formation, and the maximum value was used for the recording material with a solid white image printed thereon. Next, the arithmetic mean value of the fog values ​​for each image up to 20,000 sheets was calculated. Note that a smaller fog value is better; typically, toner is not transferred onto the transfer paper on which a solid white image has been formed. If the toner charge is insufficient, toner will migrate onto the photoreceptor even during the formation of a solid white image, and then be transferred onto the transfer paper, increasing the fog value. The evaluation results are shown in Tables 16-1 and 16-2. Incidentally, since fogging tends to occur more easily in high temperature and humidity environments of 30°C and 80% relative humidity, the evaluation was carried out in the above environment.

[0142] [5-2. Evaluation of image density stability] The prepared process cartridge was installed in the main body of an electrophotographic image forming apparatus and left for 24 hours in an environment with a temperature of 23°C and a relative humidity of 50%. Then, using an external high-voltage power supply, the potential difference between the developing blade and the electrophotographic conductive roller was set to -300 V, and one solid black halftone image, 48 solid white images, and one solid black halftone image were continuously printed in this order. The densities of the obtained halftone images on the first and 50th sheets were measured using a spectrodensitometer (product name: 508, manufactured by Xrite Corporation), and the density difference between the first and 50th sheets was calculated. Note that a smaller density difference is better. The evaluation results are shown in Tables 16-1 and 16-2.

[0143] (Examples 2 to 46) In Examples 2 to 46, the coating liquid for forming the surface layer (F Electrophotographic conductive rollers G-2 to G-46 were produced in the same manner as in Example 1, except that the rollers were changed to F-2 to F-46, and then measurements and evaluations were carried out in the same manner as in Example 1. The evaluation results are shown in Tables 16-1 and 16-2. [Table 15-1] [Table 15-2] [Table 16-1] [Table 16-2]

[0144] (Comparative Examples 1 and 2) Surface layer-forming coating solutions F-47 and F-48 and electrophotographic conductive rollers G-47 and G-48 were prepared and evaluated in the same manner as in Example 1, except that the carbon black used in surface layer-forming coating solution F-1 was changed to the material shown in Table 17 below. The evaluation results are shown in Table 20. [Table 17]

[0145] (Comparative Examples 3 to 4) Surface layer-forming coating solutions F-49 and F-50 and electrophotographic conductive rollers G-49 and G-50 were prepared and evaluated in the same manner as in Example 1, except that the additives used in surface layer-forming coating solution F-1 were changed to the materials listed in Table 18 below. The evaluation results are shown in Table 20. [Table 18]

[0146] (Comparative Examples 5 to 6) Surface layer-forming coating solutions F-51 and F-52 and electrophotographic conductive rollers G-51 and G-52 were prepared and evaluated in the same manner as in Example 45, except that the additives used in surface layer-forming coating solution F-45 were changed to the materials listed in Table 19 below. The evaluation results are shown in Table 20. [Table 19] [Table 20]

[0147] Examples 1 to 46 show good or almost good results in the evaluation of fog and image density stability. In particular, when a polycarbonate structure is included as in Examples 1 to 44, the fog and density stability are superior compared to Examples 45 and 46, which do not have a polycarbonate structure. This is thought to be because the binder also contributes to a certain degree to the charge leakage. Furthermore, among Examples 1 to 44, good results were obtained when polyurethanes having a combination of the structure represented by formula (1) and the structure represented by formula (4) were used. The structure represented by formula (2) and the structure represented by formula (3) each contain an ester structure. Since the ester structure is more electrically conductive than the polycarbonate structure, it is believed that the combination of the structure represented by formula (1) and the structure represented by formula (4), which includes the polycarbonate structure, shows better results.

[0148] Furthermore, when R12 in formula (1) and R41 in formula (4) have hydrocarbon groups on the side chains, this shows favorable trends. Although the details are not known, it is speculated that the hydrocarbon groups on the side chains in the polyurethane structure interact with the hydrophobic carbon black, increasing the dispersibility of the carbon black and resulting in favorable results.

[0149] On the other hand, in Comparative Examples 1 to 9, the process speed was high and the configuration of the high blade bias resulted in poor evaluation of fogging and evaluation of image density stability. In Comparative Examples 1 and 2, the arithmetic mean value of the circle equivalent diameter was large and the arithmetic mean value of the wall-to-wall distance was also large, so these evaluations were poor. Comparative Examples 3 and 4 are examples in which the amounts and types of additives used in Example 1 were changed. The dispersion state of the carbon black was not as intended, and the evaluation of fogging and the evaluation of image density stability were poor. In addition, due to the uneven dispersion of the carbon black, the roller surface potential tended to be high, confirming the importance of achieving an appropriate dispersion state. Comparative Examples 5 and 6 are examples in which the amounts and types of additives were changed from those in Example 45. The dispersion state of the carbon black was poor, and therefore the evaluation of fogging and the evaluation of image density stability were not excellent.

[0150] The present disclosure includes the following configurations. (Configuration 1) An electrophotographic conductive roller having, in this order, a conductive substrate, an ionically conductive elastic layer, and a surface layer, the surface layer contains a resin and carbon black; the arithmetic mean value Rc of the equivalent circle diameters of the carbon black in the surface layer is 60.0 nm or less, and further, when the standard deviation of the equivalent circle diameters is σc (nm), σc / Rc is 0.000 to 0.650; and wherein the arithmetic mean value d of the distance between wall surfaces of the carbon black in the surface layer is 80.0 to 150.0 nm, and further, when the standard deviation of the distance between wall surfaces is σd (nm), σd / d is 0.000 to 0.600. (Configuration 2) 2. The electrophotographic conductive roller according to claim 1, wherein the resin comprises polyurethane having a polycarbonate structure. (Configuration 3) The electrophotographic conductive roller according to Configuration 2, wherein the polyurethane satisfies at least one selected from the group consisting of the following (A), (B), and (C): (A) Having a structure represented by the following formula (1) in the molecule: (B) having one or both of a structure represented by the following formula (2) and a structure represented by the following formula (3) in the molecule: (C) Having a structure represented by the following formula (4) in the molecule: TIFF2025176784000026.tif102170 In formula (1), R11, R12, and R13 each independently represent a divalent hydrocarbon group having 3 to 9 carbon atoms; R11 and R12 are different hydrocarbon groups, R13 is the same hydrocarbon group as R11 or R12, m and n are the average number of moles added, each independently representing a number of 1.0 or more; In formula (2), o and p are the average number of moles added, each independently representing a number of 1.0 or more; In formula (3), R31 and R32 each independently represent a divalent hydrocarbon group having 3 to 8 carbon atoms; q and r are the average number of moles added, each independently representing a number of 1.0 or more; In formula (4), R41 represents a divalent hydrocarbon group having 6 to 9 carbon atoms; s is the average number of moles added and is a number of 1.0 or more. (Configuration 4) 4. The electrophotographic conductive roller according to any one of Configurations 1 to 3, wherein the surface layer further contains at least one selected from the group consisting of a compound represented by the following formula (5), a compound represented by the following formula (6), and a compound represented by the following formula (7): TIFF2025176784000027.tif77170In formula (5), R51 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms, t and u represent the average number of moles added, and each independently represents a number of 1.0 or more; In formula (6), R61 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms, v and w represent the average number of moles added, each independently representing a number of 1.0 or more; In formula (7), R71 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 1.0 or more. (Configuration 5) 5. The electrophotographic conductive roller according to any one of Configurations 1 to 4, wherein a corona charger having a grid part with a width of 3.0 mm is arranged in an environment of a temperature of 23°C and a relative humidity of 50%, with the distance between the grid part and the outer surface of the electrophotographic conductive roller being 1.0 mm and the direction of the width of the grid coinciding with the axial direction of the electrophotographic conductive roller, a voltage of 8 kV is applied to the grid part, and the corona charger is moved relatively along the axial direction of the electrophotographic conductive roller at a speed of 400 mm / sec to charge the outer surface of the electrophotographic conductive roller, and the maximum value of the potential of the outer surface measured 0.06 seconds after the grid has passed is less than 20.0 V. (Configuration 6) A process cartridge configured to be detachably mounted on a main body of an electrophotographic image forming apparatus, A process cartridge comprising the electrophotographic conductive roller according to any one of Configurations 1 to 5. (Configuration 7) An electrophotographic image forming apparatus having a photosensitive member and a developing roller that supplies a developer to an electrostatic latent image formed on the photosensitive member, 6. An electrophotographic image forming apparatus, wherein the developing roller is the electrophotographic conductive roller according to any one of Configurations 1 to 5. [Explanation of symbols]

[0151] 10: electrophotographic conductive roller, 11: substrate, 12: elastic layer, 13: surface layer 21: developing roller, 22: process cartridge, 23: developing blade, 24: developing device, 25: photosensitive member, 26: charging roller, 27: cleaning blade, 28: toner, 29: toner supply roller

Claims

1. An electrophotographic conductive roller having, in this order, a conductive substrate, an ionically conductive elastic layer, and a surface layer, the surface layer contains a resin and carbon black; the arithmetic mean value Rc of the equivalent circle diameters of the carbon black in the surface layer is 60.0 nm or less, and further, when the standard deviation of the equivalent circle diameters is σc (nm), σc / Rc is 0.000 to 0.650; and the arithmetic mean value d of the distance between the wall surfaces of the carbon black in the surface layer is 80.0 to 150.0 nm, and further, when the standard deviation of the distance between the wall surfaces is σd (nm), σd / d is 0.000 to 0.

600.

2. 2. The electrophotographic conductive roller of claim 1, wherein the resin comprises a polyurethane having a polycarbonate structure.

3. 3. The electrophotographic conductive roller according to claim 2, wherein the polyurethane satisfies at least one selected from the group consisting of the following (A), (B), and (C): (A) Having a structure represented by the following formula (1) in the molecule: (B) having one or both of a structure represented by the following formula (2) and a structure represented by the following formula (3) in the molecule: (C) Having a structure represented by the following formula (4) in the molecule: In formula (1), R11, R12, and R13 each independently represent a divalent hydrocarbon group having 3 to 9 carbon atoms; R11 and R12 are different hydrocarbon groups, R13 is the same hydrocarbon group as R11 or R12, m and n are the average number of moles added, each independently representing a number of 1.0 or more; In formula (2), o and p are the average number of moles added, each independently representing a number of 1.0 or more; In formula (3), R31 and R32 each independently represent a divalent hydrocarbon group having 3 to 8 carbon atoms; q and r each independently represent an average number of moles added of 1.0 or more; In formula (4), R41 represents a divalent hydrocarbon group having 6 to 9 carbon atoms; s is the average number of moles added and is a number of 1.0 or more.

4. 2. The electrophotographic conductive roller according to claim 1, wherein the surface layer further contains at least one selected from the group consisting of a compound represented by the following formula (5), a compound represented by the following formula (6), and a compound represented by the following formula (7): In formula (5), R51 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms, t and u represent the average number of moles added, and each independently represents a number of 1.0 or more; In formula (6), R61 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 1.0 or more; In formula (7), R71 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 1.0 or more.

5. 2. The electrophotographic conductive roller according to claim 1, wherein a corona charger having a grid portion with a width of 3.0 mm is disposed in an environment of a temperature of 23° C. and a relative humidity of 50% such that the distance between the grid portion and the outer surface of the electrophotographic conductive roller is 1.0 mm and the direction of the width of the grid coincides with the axial direction of the electrophotographic conductive roller, a voltage of 8 kV is applied to the grid portion, and the corona charger is moved relatively along the axial direction of the electrophotographic conductive roller at a speed of 400 mm / sec to charge the outer surface of the electrophotographic conductive roller, and when the potential of the outer surface is measured 0.06 seconds after the grid has passed, the maximum value of the potential is less than 20.0 V.

6. A process cartridge configured to be detachably mounted on a main body of an electrophotographic image forming apparatus, A process cartridge comprising the electrophotographic conductive roller according to any one of claims 1 to 5.

7. An electrophotographic image forming apparatus having a photosensitive member and a developing roller that supplies a developer to an electrostatic latent image formed on the photosensitive member, 6. An electrophotographic image forming apparatus, wherein the developing roller is the electrophotographic conductive roller according to any one of claims 1 to 5.

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