Charging member

Abstract

An example charging member has a conductive support; a conductive elastomer layer on the conductive support; and a surface layer on the conductive elastomer layer, where the surface layer comprises a binder resin and particles, where the surface layer comprises the binder resin having a first portion of the particles and a second portion of the binder resin absent of the particles, and where the second portion has a peak height (Spk) / core roughness depth (Sk) of less than 0.2.

Description

Background Art

[0001] The electrophotographic image forming apparatus includes a photoconductor and a charging member, such as a charging roller, a developing roller, or a transfer roller, which are disposed around the photoconductor. The charging member charges the surface of the photoconductor to a predetermined voltage.

[0002] An electrostatic latent image corresponding to the print data is formed on the charged surface of the photoconductor by light emitted from the exposure unit. A developing roller supplies a developer to the photoconductor to develop the electrostatic latent image into a developer image. The developer image is transferred to an image receiving member passing between the photoconductor and the transfer roller by a transfer roller. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Various examples will be described below with reference to the following drawings.

[0004] Figure 1 is a cross-sectional view schematically illustrating an example of a charging member according to an example.

[0005] Figure 2 is a cross-sectional view schematically illustrating an enlarged surface layer of an example of a charging member according to an example.

[0006] Figure 3 is a cross-sectional view schematically illustrating an electrophotographic image forming apparatus and an electrophotographic cartridge including an example of a charging member according to an example. DETAILED DESCRIPTION

[0007] In the case of forming an electrostatic latent image, a contact charging method can be used, in which a charging roller contacts a photoconductor to charge the surface of the photoconductor as an image carrier. In the example, a conductive roller can be used as a charging roller. In this example method, the surface of the photoconductor is charged by applying a voltage to a conductive support (e.g., a shaft) using a charging roller to perform micro-discharge near the contact nip between the charging roller and the photoconductor. The charging roller may have a structure in which a conductive elastomer layer is formed on a conductive support (e.g., a shaft) and a surface layer or a resistive layer is formed on the conductive elastomer layer. In some examples, the charging member includes a conductive support, a conductive elastomer layer directly on the conductive support, and a surface layer directly on the conductive elastomer layer, as described in detail herein.

[0008] By using a contact charging method, a charging member (e.g., a charging roller) may be electrically degraded due to surface wear over time. In this case, the charging performance may also degrade over time. In the case of degraded charging performance, the charging ability of the charging member may be reduced, and image defects such as background (BG) defects and micro-jitter (fine horizontal stripes) defects may occur. In particular, micro-jitter and 2D noise may have inversely proportional characteristics, and therefore it may be challenging to meet both at the same time. For example, if larger particles (beads) are used, it has been determined that the amount of micro-jitter can be met, but 2D noise occurs. On the contrary, if smaller particles are used, the amount of 2D noise is met, but micro-jitter occurs.

[0009] Hereinafter, an example charging member and an electrophotographic imaging device and an electrophotographic cartridge including the charging member will be described. It is noteworthy that the charging member herein can satisfy both micro-jitter and 2D noise, and is also durable to provide a long operating life, and is electrically suitable for an electrophotographic imaging device. The description will be based on a charging roller as an example. However, the following description can be equally applied to a charging member having a shape other than a roller, such as a corona charger or a charging brush.

[0010] The charging member according to the example includes a conductive support, a conductive elastic body layer, and a surface layer as an outermost layer.

[0011] Figure 1 is a schematic cross-sectional view of an example of a charging member according to an example. Figure 1 In the charging roller 100, a conductive elastomer layer 102 and a surface layer 103 are provided on the outer peripheral surface of a conductive support member 101 having a shaft shape. The conductive elastomer layer 102 and the surface layer 103 may be provided in such an order: from the inner side in the diameter direction of the charging roller 100 toward the outer side in the diameter direction of the charging roller 100. In an example, the conductive elastomer layer 102 and the surface layer 103 may be integrally laminated on the outer peripheral surface of the conductive support member 101. An intermediate layer (not shown) such as a resistance adjustment layer for increasing voltage resistance (i.e., leakage resistance) may be formed between the conductive elastomer layer 102 and the surface layer 103.

[0012] In an example imaging device, Figure 1 The charging roller 100 shown in FIG. 1 is provided as a charging device for charging a body to be charged, and can be used as a charging device for charging the surface of a photoconductor as an image carrier.

[0013] Conductive support

[0014] In the example, the conductive support 101 comprises a metal having conductivity. For example, a metal hollow body (tubular) or a metal solid body (rod-shaped) including iron, copper, aluminum, nickel, or stainless steel can be used. The peripheral surface of the conductive support 101 can be electroplated to reduce or prevent rust or provide scratch resistance. The peripheral surface of the conductive support 101 can be electroplated to an extent that does not impair conductivity. In addition, the peripheral surface of the conductive support 101 can be coated with an adhesive, a primer, etc. to increase adhesion to the conductive elastomer layer 102. In this case, in order to provide conductivity, the adhesive, the primer, etc. can be made conductive themselves.

[0015] The conductive support member 101 may have a cylindrical shape with a diameter of about 4 mm to about 20 mm, for example, about 5 mm to about 10 mm, and a length of about 200 mm to about 400 mm, for example, about 250 mm to about 360 mm.

[0016] Conductive elastomer layer

[0017] In the example, the conductive elastomer layer 102 may have an elasticity suitable for ensuring uniform adhesion to the photoconductor. For example, the conductive elastomer layer 102 may be formed using a binder resin selected from the following: natural rubber; synthetic rubbers such as ethylene-propylene-diene monomer rubber (EPDM), styrene-butadiene rubber (SBR), silicone rubber, polyurethane-based elastomers, epichlorohydrin (ECO) rubber, isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), hydrogenated NBR (H-NBR) and chloroprene rubber (CR); and synthetic resins such as amide resins, urethane resins and silicone resins. These may be used alone or in combination of two or more. In the example, epichlorohydrin (ECO) rubber containing ethylene oxide (EO) residues in the molecule has ionic conductivity and is relatively low and stable in terms of resistance, so epichlorohydrin (ECO) rubber can be used as a binder resin. The conductive elastomer layer 102 may contain epichlorohydrin rubber, and may contain epichlorohydrin rubber as a main component. In an example, the conductive elastomer layer 102 may contain epichlorohydrin rubber in an amount of about 50.0 wt % or more, or about 90.0 wt % or more.

[0018] The charging roller 100 may be connected to a photoconductor (eg, Figure 3 The electrophotographic photoconductor drum 311 is in contact with the electrophotographic photoconductor drum 311, and can be spaced apart from the photoconductor when used in a non-contact developing method.

[0019] In the case of a one-component contact developing method, the conductive elastomer layer 102 may be adjusted to have a hardness of about 25 to about 45 as measured by an Asker-A TYPE hardness meter, and in the case of a one-component non-contact developing method, the conductive elastomer layer 102 may be adjusted to have a hardness of about 25 to about 45 as measured by an Asker-A TYPE hardness meter. The hardness measured by the durometer is about 40 to about 65. In other examples, the hardness may be determined according to printer speed, life, cost, etc., and the hardness may vary according to the development method.

[0020] The conductive elastomer layer 102 may have a thickness of about 0.5 mm to about 8.0 mm, for example, about 1.25 mm to about 3.00 mm. Within this thickness range, the charging roller 100 exhibits elasticity and recovery against deformation, and stress applied to the toner may be reduced. In the case of a single-component non-contact developing method, the thickness of the conductive elastomer layer 102 may be about 0.5 mm to about 2.0 mm, and in the case of a single-component contact developing method, the thickness of the conductive elastomer layer 102 may be about 1.5 mm to about 8.0 mm.

[0021] The conductive elastomer layer 102 may include a conductive agent. The conductive agent may include an ionic conductive agent and an electronic conductive agent. In consideration of resistance stability, the conductive elastomer layer 102 may include an ionic conductive agent. Since the ionic conductive agent may be uniformly dispersed in the polymer elastomer to make the resistance of the conductive elastomer layer 102 uniform, uniform charging may be obtained even when the charging roller 100 is charged using a DC voltage.

[0022] The ion conductive agent may be selected according to the purpose. Examples of the ion conductive agent may include alkali metal salts, alkaline earth metal salts, perchlorates, chlorates, hydrochlorides, bromates, iodates, hydroborates, sulfates, trifluoromethylsulfate, sulfonates, and trifluoromethanesulfonates of quaternary ammonium. These may be used alone or in combination of two or more. The alkali metal salt may be selected according to the purpose. Examples of the alkali metal salt may include lithium salts, sodium salts, and potassium salts. These may be used alone or in combination of two or more. Examples of lithium salts may include Li[B(C 14 H 10 O3)2], Li(CF3SO2)2N, Li(C2F5SO2)2N, LiClO4, LiBF4, LiPF6, LiCF3SO3, LiAsF6 and LiC4F9SO3.

[0023] Examples of quaternary ammonium salts may include cationic surfactants (such as lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride, didecyl dimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, trioctylpropyl ammonium bromide, tetrabutyl ammonium chloride, and behenyl trimethyl ammonium chloride), amphoteric surfactants (such as lauryl betaine, stearyl betaine, dimethyl lauryl betaine), and tetraethyl ammonium perchlorate, tetrabutyl ammonium perchlorate, and trimethyloctadecyl ammonium perchlorate, etc.

[0024] The amount of the ion conductive agent used may be in the range of about 0.01 to about 10 parts by weight, or in the range of about 0.5 to about 5 parts by weight, based on 100 parts by weight of the binder resin. These ion conductive agents may be used alone or in combination of two or more.

[0025] The electronic conductive agent can be used in combination with the ionic conductive agent. As the electronic conductive agent, for example, carbon black can be used. Examples of carbon black can include conductive carbon black (such as oxidized carbon black, Ketjen black and acetylene black used in ink to improve dispersibility), carbon black for rubber (such as SAF, ISAF, HAF, FEF, GPF, SRF, FT and MT grades), and pyrolytic carbon black, natural graphite and artificial graphite. As the electronic conductive agent, for example, metal oxides (such as antimony-doped tin oxide, indium tin oxide (ITO), tin oxide, titanium oxide, zinc oxide), metals (such as nickel, copper, silver and germanium), conductive polymers (such as polyaniline, polypyrrole and polyacetylene), and conductive whiskers (such as carbon whiskers, graphite whiskers, titanium carbide whiskers, conductive potassium titanate whiskers, conductive barium titanate whiskers, conductive titanium oxide whiskers and conductive zinc oxide whiskers) can be used. In order to reduce the difference in resistance and reduce hardness, a small amount of electronic conductive agent can be used. The amount of the electron conductive agent used may be in the range of about 50 parts by weight or less, for example, in the range of about 15 parts by weight or less, based on 100 parts by weight of the binder resin.

[0026] The resistance value of the conductive elastomer layer 102 can be adjusted to about 10 3 Ω to about 10 11 Ω, and can be adjusted to about 10 4 Ω to about 10 9 Ω. The resistance value of the conductive elastic layer 102 is less than 10 3 Ω, the charge on the photoconductor may leak, and thus resistance imbalance may occur, resulting in spots on the image, or the hardness may increase, making it difficult to uniformly contact the photoconductor, and image stains may occur. When the resistance value of the conductive elastomer layer 102 is greater than 10 11 Ω, background (B / G) image defects may appear.

[0027] The hardness (ASKER-C) of the conductive elastomer layer 102 may be in the range of about 30° to about 99°. For example, the thickness of the conductive elastomer layer 102 may be in the range of about 0.5 mm to about 20 mm. When the thickness of the conductive elastomer layer 102 is within this range, the charging roller may have excellent elasticity, and deformation recovery of the roller base material may be ensured.

[0028] The conductive elastomer layer 102 may contain additives such as fillers, foaming agents, crosslinking agents, crosslinking accelerators, lubricants, and / or auxiliary agents. The crosslinking agent may include sulfur. The crosslinking accelerator may include tetramethylthiuram disulfide (CZ). The lubricant may include stearic acid. The auxiliary agent may include zinc oxide (ZnO).

[0029] Surface layer

[0030] The surface layer 103 may include a binder resin and particles as described herein dispersed in the binder resin.

[0031] Surface layer 103 may additionally include an ionically conductive agent and / or an electronically conductive agent, such as those described herein.

[0032] For example, the surface layer 103 may include an electronically conductive agent in the form of conductive particles, including carbon black, such as KETJEN EC and acetylene black; carbon black for rubber, such as super abrasion resistant furnace black (SAF), medium super abrasion resistant furnace black (ISAF), high abrasion resistant furnace black (HAF), superconducting furnace black (XCF), fast extrusion furnace black (FEF), general furnace black (GPF), semi-reinforced furnace black (SRF), fine thermal black (FT) and medium thermal black (MT); carbon black for oxidation treatment of color ink; metal particles and / or metal oxide particles of copper, silver or germanium. For example, carbon black can be used to control the conductivity of the surface layer 103. For example, based on 100 parts by weight of the binder resin, the amount of the conductive particles can be in the range of about 1 part to about 50 parts by weight.

[0033] The surface layer 103 may contain an ion conductive agent in the form of an ion conductive material in a binder resin. Examples of the ion conductive material include inorganic ion conductive materials such as sodium perchlorate, lithium perchlorate, calcium perchlorate, or lithium chloride; organic ion conductive materials such as modified aliphatic dimethyl aluminum isosulfate or stearyl ammonium acetate; or mixtures thereof. The amount of the ion conductive material may be in the range of about 1 part to about 50 parts by weight based on 100 parts by weight of the resin.

[0034] Figure 2 is a schematic cross-sectional view illustrating an enlarged surface layer of a charging member according to an example.

[0035] refer to Figure 2, the surface layer 203 may contain a urethane resin forming a matrix material as a binder resin 203a, and may contain particles 203b having an average particle size of about 1 μm to about 35 μm, for example, an average particle size of about 18 μm to about 27 μm. As used herein, the average particle size refers to the diameter of spherical particles, or the average diameter of non-spherical particles (for example, the average value of multiple diameters of non-spherical particles).

[0036] Urethane resin is a polymer having urethane bonds. For example, urethane resin may include an isocyanate portion containing an isocyanate group and a polyol portion containing a hydroxyl group. Examples of the isocyanate portion may include toluene diisocyanate (TDI), 4,4'-methylene diphenyl diisocyanate (MDI), polymeric MDI, modified MDI, 1,5-naphthalene diisocyanate, triazine diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, p-phenylene diisocyanate, trans-1,4-cyclohexane diisocyanate, xylene diisocyanate (XDI), hydrogenated XDI, hydrogenated MDI, lysine diisocyanate , triphenylmethane triisocyanate, thiophosphorothioate tris (phenyl isocyanate), tetramethylxylene diisocyanate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, 1,3,6-hexamethylene triisocyanate, dicycloheptane triisocyanate, trimethylhexamethylene diisocyanate, blocked isocyanate (having a structure in which isocyanate is masked by a blocking agent), or a combination thereof. Blocked isocyanate does not react at room temperature, but when heated to a temperature at which the blocking agent dissociates, isocyanate groups can be reproduced in the blocked isocyanate. These can be used as a single material or as a combination of at least two selected therefrom. Examples of the polyol portion may include polyoxypropylene glycol, polytetramethylene ether glycol, THF-alkylene oxide copolymer polyol, polyester polyol, acrylic polyol, polyolefin polyol, partial hydrolyzate of ethylene-vinyl acetate copolymer, phosphate ester-based polyol, halogen-containing polyol, adipate-based polyol, polycarbonate polyol, polycaprolactone-based polyol, polybutadiene polyol, or a combination of at least two selected therefrom.

[0037] If necessary, the urethane resin material may further include a catalyst. Examples of catalysts may include triethylamine, N,N,N',N'-tetramethyl-ethylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, triethylenediamine, dimethylethanolamine, bis(2-methylaminoethyl)ether, or a combination of at least two selected therefrom. The amount of the catalyst may be, for example, in the range of about 0.05 parts to about 5 parts by weight, based on 100 parts by weight of the sum of the polyol component and the isocyanate component. The urethane resin material may further include additional resins and functional additives.

[0038] Examples of other resins may include styrene resins, acrylic resins, vinyl chloride resins, styrene-vinyl acetate copolymers, modified maleic acid resins, phenolic resins, epoxy resins, polyester resins, fluororesins, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resins, polyurethane resins, nylon resins, silicone resins, ketone resins, ethylene-ethyl acrylate copolymers, xylene resins, polyvinyl butyral resins, or a combination of at least two selected therefrom. In particular, urethane resins, nylon resins, acrylic resins, or fluororesins may be used because they have excellent wear resistance, toner charging characteristics, and toner transport characteristics. Functional additives may be, for example, conductive agents such as carbon black or metal oxides; stabilizers; or combinations thereof.

[0039] The binder resin 203a can be selected to avoid contaminating the photoconductor (as the body to be charged). Examples of binder resins may include fluororesins, polyamide resins, acrylic resins, nylon resins, urethane resins, silicone resins, butyral resins, styrene-ethylene / butene-olefin copolymers (SEBC) and olefin-ethylene / butene-olefin copolymers (OEBC). These can be used alone or in a combination of two or more. In the example, the binder resin can be selected from fluororesins, acrylic resins, nylon resins, urethane resins and silicone resins. The binder resin can be selected from nylon resins and urethane resins. The binder resin may contain urethane resin.

[0040] In the case where the binder resin contains a urethane resin, the urethane resin can be formed by a chain extension reaction of a polyol mixture of a polyester polyol and a polyether polyol with a polyisocyanate.

[0041] The urethane resin formed by the chain extension reaction of polyester polyol and polyisocyanate has excellent wear resistance at a relatively low hardness. However, since the urethane resin obtained by using polyester polyol may deteriorate at low temperatures, when the urethane resin is used for a long period of time under a low temperature environment, the resistance may change and a background (B / G) image may appear. In addition, since ester-based urethane may be easily hydrolyzed, when ester-based urethane is used under a high temperature and high humidity environment, its characteristics may change.

[0042] The urethane resin formed by the chain extension reaction of polyether polyol and polyisocyanate has low temperature flexibility, relatively low resistance, and therefore has stability. However, polyester polyol has poor compatibility with polyether polyol and may therefore cause separation or curing difficulties. In the case of using a polyether polyol having an ethylene oxide (EO) content of about 60wt% to about 90wt%, compatibility with polyester polyol can be solved. The polyether polyol having an ethylene oxide (EO) content of about 60wt% to about 90wt% can have good compatibility with polyester polyol. In addition, the surface layer 203 produced using the urethane resin can have low temperature flexibility, relatively low resistance, physical stability and resistance stability at low hardness.

[0043] The surface layer 203 may include a urethane resin formed by a chain extension reaction of a polyol mixture of a polyester polyol and a polyether polyol having an ethylene oxide (EO) content of about 60 wt % to about 90 wt % with a polyisocyanate. The content ratio of the polyester polyol and the polyether polyol may be adjusted within a range of 8:2 to 2:8. In the case where the content ratio of any one of the polyester polyol and the polyether polyol is too low, the improvement effect may be reduced.

[0044] As polyester polyols, polyols based on polycaprolactam, polyols based on adipic acid, etc. can be used. Polyester polyols can be obtained by esterification reaction between a compound having two or more hydroxyl groups and a polyacid, or can be obtained by ring-opening addition reaction of cyclic esters (such as ε-caprolactone, β-butyrolactone, γ-butyrolactone, γ-valerolactone and δ-valerolactone) using a compound having two or more hydroxyl groups as an initiator. Although polyols based on polylactone may be different from polyester polyols, they are considered as a kind of polyester polyols here.

[0045] Examples of the above-mentioned compounds having two or more hydroxyl groups may include diol compounds (such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-cyclohexanedimethanol), diol compounds having a branched structure (such as 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-butanediol, 1,3-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-propylene glycol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-isopropyl-1,4-butanediol, 2,4-dimethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-ethyl-1,6-hexanediol, 3,5-pentanediol and 2-methyl-1,8-octanediol), as well as trimethylolpropane, trimethylolethane, pentaerythritol and sorbitol. These compounds can be used alone or in combination of two or more.

[0046] Among ester-based polyols, ester-based polyols having a liquid phase at room temperature may be easy to handle, may be difficult to aggregate in a coating composition, may not generate spots on an image, and may be frequently used. In addition, ester-based polyols having three or more hydroxyl groups may have a smaller amount of permanent deformation and good stability.

[0047] Examples of the polyacid may include adipic acid, succinic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and anhydrides thereof. These polyacids may be used alone or in combination of two or more.

[0048] As polyether polyols with an ethylene oxide (EO) content of about 60wt% to about 90wt%, difunctional diols or trifunctional or more functional polyether polyols, such as ethylene oxide-polypropylene oxide copolymers, can be used. In the example, ethylene oxide-polypropylene oxide copolymers can be random copolymers because the hardness of urethane resins may be reduced due to low crystallinity. Polyether polyols with an ethylene oxide (EO) content of about 60wt% to about 90wt% can be polyether polyols produced by random addition and / or block addition of alkylene oxides of 2 to 6 carbon atoms to the above-mentioned compounds with two or more hydroxyl groups. Examples of polyether polyols can include polyoxyethylene polyoxypropylene polyols and polyoxyethylene polyoxytetramethylene polyols. For example, trifunctional or more functional polyoxyethylene polyoxypropylene polyols with ethylene oxide residues at molecular ends obtained by random addition polymerization of ethylene oxide and propylene oxide can be used. Compared with difunctional or less-functional polyoxyethylene polyoxypropylene polyol, trifunctional or more-functional polyoxyethylene polyoxypropylene polyol may be used to suppress the occurrence of image defects in a low-temperature and low-humidity environment.

[0049] As a polyisocyanate chain-extended with a polyol mixture comprising a polyester polyol and a polyether polyol having an ethylene oxide (EO) content of about 60 wt % to about 90 wt %, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated toluene diisocyanate, or hexamethylene diisocyanate (HDI) can be used. In addition, the blocked polyisocyanate obtained by reacting HDI with a blocking agent has storage stability because the reactive isocyanate group is blocked to inhibit the reaction at room temperature. As a blocking agent, for example, methyl ethyl ketoxime can be used, which has good storage stability and productivity and can adjust the dissociation temperature in the range of about 120° C. to about 160° C. When the blocking agent is dissociated by heating, the isocyanate group is regenerated, and thus the blocked polyisocyanate can react with the polyol.

[0050] The amount of the polyisocyanate added may be adjusted so that the molar ratio ([NCO] / [OH]) of the isocyanate (NCO) group of the polyisocyanate to the total hydroxyl (OH) group of the polyol mixture is in the range of about 12 to about 25. The polyether polyol may have lower reactivity than the polyester polyol, and an unreacted product may remain if the molar ratio is less than 12, and low-temperature flexibility may deteriorate if the molar ratio is greater than 25.

[0051] In the case of using urethane resin as the binder resin of the surface layer 203, the surface layer 203 may contain a small amount of other resin components for the purpose of modifying the surface layer 203. As other resin components, silicone graft polymers, silicone oils, acrylic resins, or fluororesins can be used to improve the contamination resistance of the surface.

[0052] The surface layer 203 may contain other additives such as a conductive agent, a leveling agent, a filler, a defoaming agent, a surface modifier, a dispersant, and a charge control agent. In this case, an ion conductive agent and / or an electronic conductive agent may be used as the conductive agent.

[0053] As the ion conductive agent that can be used for the surface layer, there are alkali metal salts, alkaline earth metal salts, and quaternary ammonium salts that can be used for the above-mentioned conductive elastic body layer 202. For example, a cation having a chemical structure of (n-Bu)3MeN +- Ionic liquid (3M TM Ionic liquid antistatic agent FC-5000) is used as an ionic conductive agent because it has thermal stability and can therefore be easily dispersed in urethane resin. Based on 100 parts by weight of urethane resin, the amount of the combined ionic conductive agent can be in the range of about 0.01 parts by weight to about 10 parts by weight or in the range of about 0.5 parts by weight to about 5 parts by weight. As an electronic conductive agent that can be used for surface layer 203, the above-mentioned electronic conductive agent that can be used for conductive elastomer layer 202 can be used. For example, oxidized carbon black with good dispersibility in surface layer 203 can be used. Because the electronic conductive agent can have a small resistance change, the amount of the combined electronic conductive agent can be in the range of about 0.5 parts by weight to about 10 parts by weight based on 100 parts by weight of urethane resin.

[0054] In order to stably charge the photoconductor, the surface layer 203 may contain particles that form unevenness on its surface (i.e., particles for forming roughness). The particles for forming roughness may include resin particles or inorganic particles. Examples of resin particles may include acrylic resin particles, styrene resin particles, polyamide resin particles, silicone resin particles, vinyl chloride resin particles, vinylidene chloride resin particles, acrylonitrile resin particles, fluororesin particles, phenol resin particles, polyester resin particles, melamine resin particles, urethane resin particles, olefin resin particles, and epoxy resin particles. Inorganic particles may include silica particles, aluminum oxide particles, etc.

[0055] In the example, when the surface layer 203 contains particles 203b (such as acrylic resin particles with an average particle size of about 1 μm to about 50 μm) as the first particles, the wear resistance and electrical degradation resistance of the charging roller of the present invention can be increased, and the charging non-uniformity can be effectively suppressed, so that the charging performance of the charging roller can be fully maintained even when the charging roller is used for a longer period of time. The average particle size of the first particles can be in the range of about 1 μm to about 50 μm, for example, in the range of about 18 μm to about 27 μm. Therefore, even when the example charging roller of the present invention is used in a contact charging manner, the ability to uniformly charge the photoconductor can be maintained for a longer period of time. Therefore, since the charging roller of the present invention can maintain the charging performance and charging uniformity even when the charging roller is used for a longer time in the electrophotographic imaging device, high-quality images can be stably obtained, wherein image defects (such as background (BG) and micro-jitter) are suppressed. In addition, even when a DC voltage is applied, the charging roller can maintain a stable charging characteristic for a longer time, so that a high-quality output image can be obtained, and any BG problem in a low temperature and low humidity environment can be reduced or prevented. The average particle size of the particles can be measured by a particle size distribution measuring device (manufacturer: Beckman Coulter ), trade name: Multisizer3) for measurement.

[0056] Based on 100 parts by weight of the binder resin, the content of the particles is in the range of about 1 part by weight to about 50 parts by weight, for example, about 5 parts by weight to about 20 parts by weight, about 5 parts by weight to about 15 parts by weight, or about 10 parts by weight to about 15 parts by weight. In other words, the content of the particles is in the range of about 1 to about 50 phr, for example, about 5 to about 20 phr, about 5 to about 15 phr, or about 10 to about 15 phr per hundred parts of the binder resin / rubber in the surface layer.

[0057] The particles 203b may be acrylic-based resins, such as polyacrylate or polymethacrylate; polyamide-based resins, such as nylon; polyolefin-based resins, such as polyethylene or polypropylene; silicon-based resins; phenol-based resins; polyurethane-based resins; styrene-based resins; benzoguanamine resins; polyvinylidene fluoride-based resins; metal oxide powders, such as silicon dioxide, aluminum oxide, titanium oxide, and iron oxide; boron nitride; silicon carbide; or a combination of at least two selected therefrom. The particles 203b may be spherical, flake-like, or irregularly shaped. For example, in some examples, the particles 203b are spherical.

[0058] In some examples, the particles 203b may be acrylic resin particles. Examples of acrylic resin particles include polymethyl methacrylate (PMMA) particles and / or polymethyl acrylate (PMAA) particles. In the case of monodisperse acrylic particles, for example, monodisperse PMMA particles in which the average particle size of the particles is within the above range and 95% or more of the particles include particles within the range of ±2 μm of the average particle size of the particles, unevenness may be formed on the surface of the surface layer 203, and discharge points may be ensured, so that the charging characteristics are good. The reason for this may be that an appropriate gap is formed in the roller gap of the contact portion of the photoconductor and the charging roller in this article, thereby improving the charging performance.

[0059] In some examples, in addition to the acrylic-based resin particles, the particles 203b may also include silica particles. The spherical silica particles may be unaggregated silica particles, and may include spherical silica particles, roughly spherical silica particles, and elliptical silica particles. The silica particles may exist as aggregate particles in which small particles are aggregated, and such aggregate particles are irregularly shaped particles rather than spherical silica particles. Since aggregated silica particles are difficult to stably provide an uneven shape to the surface layer 203, and their aggregation is partially destroyed due to dispersion by a bead mill or the like, aggregated silica particles are not suitable as particles for imparting a uniform uneven surface shape to the surface layer 203. In order for the charging roller of the present invention to exhibit the various technical aspects described above, the specific surface area of ​​the spherical silica particles may be about 3 m 2 / g to about 50m 2 / g, for example, about 10m 2 / g to about 50m 2 / g, about 20m 2 / g to about 50m 2 / g, or about 30m 2 / g to 50m 2 / g range to improve charging capacity and charging uniformity. The specific surface area of ​​particles (such as silica particles) can be measured by a specific surface area / pore size distribution measuring instrument (manufacturer: Microtrac BEL, trade name: BELSORP-miniX). In the case where silica particles have the same particle size, as the specific surface area of ​​the silica particles increases, the silica particles are closer to porous particles.

[0060] like Figure 2As shown in , the particles 203b can be completely disposed in the binder resin 203a, and thus can form a binder resin portion that protrudes above other portions of the binder resin that do not include the particles 203b. Having the particles 203b completely disposed in the binder resin 203a can promote aspects of the present invention, such as having a given Spk value.

[0061] As mentioned, the particles may be present in a first portion or first region of the binder resin of the surface layer 203. For example, the particles 203b may be present in the first portion 205 of the binder resin 203a, such as Figure 2 In other words, the particle 203b is along a plane extending in the A direction (in Figure 2 203a). In contrast, particles are not present in the second portion or second region of the binder resin of the surface layer 203. For example, particles 203b are not present in the second portion 207 of the binder resin 203a. In other words, particles 203b are not present in the second portion 207 of the binder resin 203a along a plane extending in the A direction of the binder resin 203a.

[0062] When using the charging roller having the surface layer 203 satisfying the above conditions in the present invention, the stable charging characteristics can be maintained for a longer period of time even when a DC voltage is applied, and a high-quality output image can be obtained. The mechanism showing this effect can be inferred as follows. In order to maintain good charging characteristics over a long period of time, particles are added to the surface layer 203, which is the outermost layer of the charging member. However, when a voltage is applied to such a charging member, the electric field is concentrated on the convex portion formed by the particles. Therefore, the convex portion tends to produce discharge, and the quality of the output image tends to deteriorate. In the example, since the discharge from the convex portion can be weakened by making the surface layer 203 satisfy the above conditions, it is inferred that the unevenness of the electric field on the surface of the conductive resin layer (i.e., the surface layer 203) is weakened. Therefore, it is inferred that uniform discharge can occur from the entire surface of the conductive resin layer, and the quality of the output image can be improved.

[0063] Therefore, even when the charging roller of the present invention is used in a contact charging mode, the charging roller can maintain the ability to uniformly charge the photoconductor for a longer period of time. Therefore, since the charging roller of the present invention can maintain the charging performance and charging uniformity even when the charging roller is used for a longer time in the electrophotographic imaging device, high-quality images can be stably obtained, wherein image defects suppress both background (BG) and micro-jitter. In addition, even when a DC voltage is applied, the charging roller of the present invention can maintain stable charging characteristics for a longer period of time, high-quality output images can be obtained, and the occurrence of BG in a low temperature and low moisture environment can be reduced or prevented.

[0064] In some examples, the second portion has a second portion peak height (Spk) / core roughness depth (Sk) in the range of about 0.04 to about 0.2. For example, the second portion Spk / Sk can be less than about 0.2, less than about 0.19, less than about 0.18, less than about 0.16, less than about 0.14, less than about 0.12, or less than about 0.10. For example, the second portion can have a Spk / (Sk) of less than 0.2.

[0065] In some examples, Spk / Sk of the first portion / Spk / Sk of the second portion is in a range of about 8 to about 76, or about 10 to about 76. In some examples, Spk / Sk of the first portion / Spk / Sk of the second portion is greater than about 10, greater than about 8, greater than about 12, or greater than about 14. For example, Spk / Sk of the first portion / Spk / Sk of the second portion may be greater than 8 or greater than 10.

[0066] In some examples, the sum of Spk of the first portion plus the Sk of the first portion is in a range of about 8 to about 30, in a range of about 8 to about 20, or in a range of about 15 to about 20. In some examples, the sum of Spk / Sk of the first portion and Spk / Sk of the first portion is greater than about 8, greater than about 10, greater than about 12, or greater than about 15. For example, the sum of Spk / Sk of the first portion and Spk / Sk of the second portion can be greater than 8.

[0067] The thickness of the surface layer 532 may be in the range of about 0.1 μm to about 100 μm, or, for example, about 3 μm to about 30 μm. The thickness of the surface layer 203 may be the layer thickness of the portion formed only by the binder resin (eg, Figure 2 The thickness of the surface layer 203 is obtained in the 'A' direction of the portion of the conductive resin layer. For example, the thickness of the conductive resin layer is the thickness of the binder resin at a point such as a midpoint between adjacent particles. The thickness of the surface layer 203 can be measured by cutting out a cross section of the charging roller with a sharp blade and observing the piece with an optical microscope or an electron microscope.

[0068] In an example, a charging roller (e.g., Figure 1 In the embodiment of the present invention, a DC voltage is applied to the charging roller 100 (shown in FIG. 1 ). For example, the bias voltage applied during image output may be about -1500V to about -1000V. This may help control image density and various conditions while maintaining charging performance under various environments. In the case where the bias voltage is higher than -1000V, it becomes difficult to optimize the developing conditions for image formation. In contrast, in the case where the bias voltage is lower than -1500V, overdischarge tends to occur in the particle portion of the conductive resin layer, and white spot-like image defects tend to occur after image formation.

[0069] Method for manufacturing charging member

[0070] Figure 1 The charging member of the example shown in can be manufactured as follows. In the example method, the material components for the conductive elastomer layer 102 are kneaded using a kneading machine to prepare the material for the conductive elastomer layer 102. The material for the surface layer 103 is kneaded using a kneading machine (such as a roller) to obtain a mixture, and an organic solvent is added to the mixture, mixed and stirred to prepare a coating liquid for the surface layer 103. The mold for injection molding in which the core (usually the shaft) as the conductive support 101 is provided is filled with the material for the conductive elastomer layer 102 by injecting the material, and then heated and cross-linked under predetermined conditions. The base roll (baseroll) in which the conductive elastomer layer 102 is formed along the outer peripheral surface of the conductive support 101 is demoulded. The coating liquid for the surface layer 103 is applied to the outer peripheral surface of the base roll to form the surface layer 103. In this way, the charging roller 10 in which the conductive elastomer layer 102 is formed on the outer peripheral surface of the conductive support 101 and the surface layer 103 is formed on the outer periphery of the conductive elastomer layer 102 can be manufactured.

[0071] However, the method of forming the conductive elastic body layer 102 is not limited to injection molding, and casting, press molding, polishing or a combination thereof may be employed. The method of applying the coating liquid for the surface layer 103 is not particularly limited, and dipping, spraying and roller coating may be employed.

[0072] Electrophotographic imaging equipment

[0073] The charging roller according to an example may be integrated into an electrophotographic cartridge or an electrophotographic image forming apparatus such as a printer, a copier, a scanner, a fax machine, or a multifunction peripheral incorporating two or more of these.

[0074] Figure 3 is a cross-sectional view schematically illustrating an electrophotographic image forming apparatus including a charging roller and an electrophotographic cartridge according to an example.

[0075] refer to Figure 3, the electrophotographic imaging device 331 may include an electrophotographic box 330. The electrophotographic box may include an electrophotographic photoconductor drum 311 charged by a charging roller 300 according to the example, which is a charging device arranged to contact the electrophotographic photoconductor drum 311. The electrophotographic photoconductor drum 311 can be driven to rotate around an axis at a predetermined circumferential speed. During the rotation, the electrophotographic photoconductor drum 311 can be uniformly charged with a positive or negative predetermined potential on its surface by the charging roller 310. The voltage applied to the charging roller 310 can be, for example, a DC voltage. However, the voltage applied to the charging roller 310 can be, for example, a combination of an AC voltage and a DC voltage. In the electrophotographic imaging device 331 according to the example, even when a DC voltage is applied to the charging roller 310, a stable charging characteristic can be maintained for a longer period of time, and a high-quality output image can be obtained.

[0076] The charging roller 310 can charge the surface of the electrophotographic photoconductor drum 311 to a uniform potential value while rotating in contact with the electrophotographic photoconductor drum 311. An image portion is exposed by laser to form an electrostatic latent image on the electrophotographic photoconductor drum 311. After the electrostatic latent image is converted into a visible image (e.g., a toner image) by the developing unit 315, the toner image is transferred to an image receiving member 319 (e.g., paper) by a transfer unit (e.g., a transfer roller 317) to which a voltage is applied. After the image is transferred, the toner remaining on the surface of the electrophotographic photoconductor drum 311 is cleaned by a cleaning unit (e.g., a cleaning blade 321). The electrophotographic photoconductor drum 311 can be used for image formation again. The developing unit 315 includes an adjusting blade 323, a developing roller 325, and a supply roller 327.

[0077] The electrophotographic cartridge 330 according to the example may integrally support the electrophotographic photoconductor drum 311, the charging roller 300, and the cleaning blade 321, and may be attached to and detached from the electrophotographic image forming apparatus 331. Another cartridge 329 may integrally support the developing unit 315 including the regulating blade 323, the developing roller 325, and the supplying roller 327, and may be attached to and detached from the electrophotographic image forming apparatus 331. Toner (not shown) may be located inside the developing unit 315.

[0078] Example

[0079] Hereinafter, various examples will be described. However, the scope of the present disclosure is not limited thereto.

[0080] Formation of conductive elastomer layer

[0081] Adhesive is applied to the cylindrical stainless steel shaft (its surface is electrolessly plated with nickel) that diameter is 8mm and total length is 324mm and is dried.The shaft is used as support.The epichlorohydrin rubber (manufacturer: Daso Chemical Co., Ltd., product name: EPICHLOMER DG) of 100 weight parts, the calcium carbonate of 20 weight parts, the carbon black (manufacturer: Mitsubishi Chemical Corporation, product name: MA100) of 2 weight parts (as filler), the zinc oxide of 5 weight parts and the tetrabutylammonium chloride of 2 weight parts (as ion conductive agent) are put into closed mixer and kneaded 20 minutes, and then further add 1.5 weight parts of dibenzothiazole disulfide (as vulcanization accelerator), 1.2 weight parts of tetrapentamethylenethiuram and 1.0 weight parts of sulphur (as crosslinking agent) thereto, and in open mill, knead about 15 minutes to obtain rubber composition. The rubber composition is extruded together with the shaft using a crosshead rubber extruder to form a roller shape having an outer diameter of about 13 mm. Next, after a vulcanization process of about 1.5 hours at about 160° C. in a vulcanizing tube, both ends of the rubber are cut, the rubber surface is polished so that the outer diameter of the central part of the roller becomes about 12 mm, and then the surface is washed, dried, and then irradiated with ultraviolet light to form a conductive elastomer layer (e.g., conductive elastomer layer 102). Thus, a conductive elastomer layer having a thickness of about 4 mm and formed along the outer peripheral surface of the shaft is obtained.

[0082] Formation of a conductive surface layer

[0083] Examples 1 to 11 and Comparative Examples 1 to 10

[0084] 69.26 parts by weight of polycaprolactone polyol (manufacturer: Daicel Chemical Industries, product name: PCL320, hydroxyl value: 84 KOH mg / g), 51.24 parts by weight of isocyanate-terminated HDI (manufacturer: Aekyung Chemical Co., Ltd., product name: D660, non-volatile matter 60%, NCO 6.5%, blocking agent: methyl ethyl ketone oxime), 1 part by weight of a polymer dispersant (manufacturer: Lubrizol Co., Ltd., product name: SOLSPERSE TM 20000), 3 parts by weight of carbon black (manufacturer: Mitsubishi Chemical Corporation, product name: MA100, specific surface area: 110 m 2 / g, pH 3.5), 2 parts by weight of hydrophobic fumed silica (manufacturer: Evonik Resource Efficiency GmbH, trade name: AEROSIL R 974, specific surface area: 110 m 2 / g) and 0.1 parts by weight of silicone oil (manufacturer: ShineEtsu Chemical Co., Ltd., product name: KF6002) were mixed with 200 parts by weight of methyl isobutyl ketone (MIBK) solvent.

[0085] Then, resin particles and / or inorganic particles were added as roughness forming particles in the amounts given in Tables 1, 2A, 2B, 3A and 3B according to the examples and comparative examples. The particles were then stirred sufficiently until the coating liquid became uniform to prepare a coating liquid for forming a surface layer.

[0086] A coating liquid for forming a surface layer is applied to the surface of a roller having a conductive elastomer layer by a roller coating method. In this case, in order to obtain a specific layer thickness, coating is performed while scraping off the extra coating liquid with a scraper. The coated roller is air-dried for about 10 minutes, and then dried for about 1 hour at 160° C. using an oven. Thus, a charging roller in which a surface layer having a thickness of about 1.0 μm is laminated on the conductive elastomer layer is obtained. Thus, a charging roller comprising a shaft as a conductive support, a conductive elastomer layer laminated along the outer peripheral surface of the shaft, and a surface layer laminated along the outer peripheral surface of the conductive elastomer layer is manufactured.

[0087] The types and characteristics of the resin particles or inorganic particles used in Examples 1 to 11 and Comparative Examples 1 to 10 are summarized in Table 1. The evaluation results of the charging rollers are summarized in Tables 2A, 2B, 3A, and 3B.

[0088] Table 1

[0089]

[0090] “N / A” refers to products for which no commercial product name is available.

[0091] Table 2A

[0092]

[0093] Example

[0094] Table 2A

[0095]

[0096] Table 3A

[0097]

[0098] *CE: Comparative example

[0099] Table 3B

[0100]

[0101] Surface layer assessment :

[0102] The reduced peak height (Spk) and the core roughness depth or core height (Sk) are determined using available methods. For example, an image of the charging roller surface is captured by a laser microscope VK-X100 manufactured by KEYENCE with an objective lens of 50 times magnification, thereby obtaining three-dimensional height data with an area of ​​280 μm (width) × 210 μm (length), and the curvature of the surface is automatically corrected. The initial image (after printing 20 sheets) and the subsequent image (after printing 350,000 sheets) are measured. The reduced peak height Spk and the core height Sk are obtained by using a multi-file analysis application manufactured by KEYENCE that complies with ISO 25178.

[0103] Image evaluation :

[0104] Image evaluation in the case of using the charging rollers obtained in Examples 1 to 11 and Comparative Examples 1 to 10 was performed as follows. After removing the charging roller from a commercially available laser printer (manufacturer: Hewlett-Packard Company (HP), model: HP 50PPM Color LaserJet A3), each of the charging rollers obtained in Examples 1 to 11 and Comparative Examples 1 to 11 was installed thereon to replace the above-mentioned charging roller. The printer was placed under N / N (temperature 23°C and relative humidity 55%) environmental conditions for 8 hours. With respect to the initial image obtained using the printer and the image after printing 350,000 sheets of paper, micro-jitter (M / J), background (B / G) and image uniformity were evaluated as follows. The results are summarized in Tables 2A, 2B, 3A and 3B. In this case, the printing conditions are as follows.

[0105] Printing speed: typical speed 500mm / sec;

[0106] Printing paper type: office paper EC;

[0107] Applied bias voltage: The DC voltage applied to the charging roller in contact with the photoconductor was appropriately adjusted so that the photoconductor surface potential was -600V.

[0108] Micro-jitter (M / J) evaluation

[0109] The electrophotographic image used for micro-jitter evaluation is a halftone image (a medium-density image having horizontal stripes with a width of 1 dot and an interval of 2 dots in a direction perpendicular to the rotation direction of the photoconductor). The image is observed, and the presence or absence and / or degree of fine horizontal stripes (micro-jitter (M / J)) are evaluated according to the following criteria.

[0110] ◎: There is no micro-jitter in the image;

[0111] ○: Slight micro-shake occurs on part of the image, but there is no actual problem.

[0112] △: Slight micro-shake appears at the front of the image, but this is within the usable range; and

[0113] x: Micro-jitter appears in the front of the image, causing practical problems.

[0114] Background (B / G) Assessment

[0115] The electrophotographic image used for background evaluation is a white image with a medium concentration (density). The whiteness of the output image is measured by a "Reflectometer" (manufacturer: Nippon Denshoku Ind., model name: Microscopic Area Color Meter / Reflectometer VSR 400).

[0116] Then, the background concentration (background density) (%) was calculated from the difference between the whiteness of the output image and the whiteness of the paper. The image background was evaluated according to the following criteria.

[0117] ◎: Background density is less than 0.8% (best available);

[0118] ○: Background density is 0.8% or more and less than 1.5% (usable);

[0119] △: Background density is 1.5% or more and less than 2.5% (in some cases, usable); and

[0120] x: Background density is 2.5% or more (unusable).

[0121] Evaluation of image uniformity (2D noise)

[0122] Similar to the electrophotographic image for microjitter evaluation, the electrophotographic image for image uniformity evaluation was a halftone image (a medium-density image having horizontal stripes with a width of 2 dots and an interval of 2 dots in a direction perpendicular to the rotation direction of the photoconductor). This image was observed, and image uniformity was evaluated according to the following criteria.

[0123] ◎: There is no image density unevenness (so-called image stain);

[0124] ○: There is no image density unevenness, but the image has slight graininess;

[0125] △: Image density unevenness is slightly present to the extent that there is no practical problem; and

[0126] x: There is image density unevenness and image quality is impaired.

[0127] Referring to Tables 2A, 2B, 3A and 3B, it can be found that the example image forming apparatus provided with the charging member of Examples 1 to 11 can stably produce high-quality images without image defects such as background (B / G), micro-jitter (M / J) and image density non-uniformity, wherein the particles have a diameter within a given range (such as a diameter within a range of 1 micrometer (um) to about 35um (e.g., about 18um to about 27um)) and the ratio of the reduced peak height (Spk) / core roughness depth (Sk) of the first part to the Spk / Sk of the second part is >10 and / or the ratio of the Spk / Sk of the first part to the Spk / Sk of the second part is >10. The reason for this may be that particles of a given diameter (e.g., beads) produce improved wear resistance, and thus stable charging characteristics can be maintained over the operating life of the charging member. Conversely, if a larger particle size / range is used, M / J is satisfied, but 2D noise occurs, and if a smaller particle size / range is used, 2D noise is satisfied, but M / J occurs.

[0128] Although examples of the present disclosure have been shown and described above, the present disclosure is not limited thereto, and various modifications and changes may be made by those skilled in the art to which the present disclosure belongs without departing from the spirit and scope of the present disclosure claimed in the claims. These modifications and changes will fall within the scope of the present disclosure.

[0129] It will be understood that when an element is referred to as being "on another element," "connected to another element," "coupled to another element," or "coupled with another element," the element may be directly on, connected to, or coupled with another element, or there may be intermediate elements. In contrast, when an object is "directly coupled to another element" or "directly coupled with another element," it may be understood that there are no intermediate elements (adhesives, screws, other elements), etc. As used herein, the term "about" refers to one or more values ​​within 10%, within 5%, or within 1% of a given value modified by the term about. For example, the term about may refer to one or more values ​​within 10% of a given value.

[0130] The drawings herein follow a numbering convention in which the first digit corresponds to the drawing number, and the remaining digits identify an element or component in the drawing. For example, reference numeral 103 may refer to Figure 1 103 in the element, and Figure 2 , similar elements may be identified by reference numeral 203. Elements shown in the various figures herein may be added, exchanged, and / or eliminated to provide additional examples of the present disclosure. In addition, the proportions and relative scales of the elements provided in the drawings are intended to illustrate examples of the present disclosure and should not be considered to be limiting.

Claims

1. A charging member, comprising: A conductive support; a conductive elastomer layer on the conductive support; as well as A surface layer on the conductive elastomer layer, wherein the surface layer comprises a binder resin and particles, and wherein the surface layer comprises a first portion of the binder resin having the particles and a second portion of the binder resin without the particles, and wherein the second portion has a peak height (Spk) / core roughness depth (Sk) of less than 0.

2.

2. The charging member according to claim 1, wherein The particles have an average diameter in the range of about 1 micrometer (um) to about 35 um.

3. The charging member according to claim 1, wherein The particles may be present in an amount ranging from about 1 part by weight to about 50 parts by weight based on 100 parts by weight of the binder resin.

4. The charging member according to claim 1, wherein The binder resin is a urethane resin.

5. The charging member according to claim 1, wherein A ratio of Spk / Sk of the first portion to Spk / Sk of the second portion is >10.

6. The charging member according to claim 1, wherein The average diameter of the particles ranges from about 18 micrometers (um) to about 27 um.

7. The charging member according to claim 1, wherein The particles further include acrylic resin particles, and wherein the acrylic resin particles include polymethyl methacrylate (PMMA) particles or polymethyl acrylate (PMAA) particles.

8. The charging member according to claim 1, wherein The charging member is formed as a charging roller.

9. A cartridge for an electrophotographic imaging device, the cartridge comprising: A conductive support; a conductive elastomer layer on the conductive support; as well as A surface layer on the conductive elastomer layer, wherein the surface layer comprises a binder resin and particles, wherein the surface layer comprises a first portion of the binder resin having the particles arranged in the binder resin and a second portion of the binder resin in which the particles arranged in the binder resin are not present, and wherein a ratio of a peak height (Spk) / core roughness depth (Sk) of the first portion to Spk / Sk of the second portion is >10.

10. The cartridge of claim 9, wherein: The Spk / Sk of the second portion is less than 0.

2.

11. The cartridge of claim 9, wherein: The sum of the Spk of the first part and the Sk of the first part is greater than 8.

12. The cartridge of claim 9, wherein: The surface layer is formed of fluororesin, polyamide resin, acrylic resin, nylon resin, urethane resin, silicone resin, butyral resin, styrene-ethylene / butene-olefin copolymer (SEBC), olefin-ethylene / butene-olefin copolymer (OEBC), or any combination thereof; and Herein, the particles are present in an amount ranging from about 5 parts by weight to about 20 parts by weight based on 100 parts by weight of the binder resin.

13. An electrophotographic imaging device comprising: Electrophotographic photoconductors; as well as a charging member contacting the electrophotographic photoconductor to charge the electrophotographic photoconductor, the charging member comprising: A conductive support; a conductive elastomer layer on the conductive support; Particles with diameters ranging from 18 micrometers (um) to about 27 um; and a surface layer on the conductive elastomer layer, the surface layer having a first portion containing the particles and a second portion without the particles, and wherein: The ratio of the reduced peak height (Spk) / core roughness depth (Sk) of the first portion to the Spk / Sk of the second portion is > 10; and The second portion has a Spk / Sk of less than 0.

2.

14. The electrophotographic image forming apparatus of claim 13, further comprising: an exposure unit for forming an electrostatic latent image on the surface layer; a developing unit, used for developing the electrostatic latent image into a visible image; as well as A transfer unit is used for transferring the visible image to an image receiving member.

15. The electrophotographic image forming apparatus according to claim 14, wherein: The amount of micro-jitter of the visible image is reduced compared to the amount of micro-jitter of an image formed by a comparative charging member that does not have the following situations: the ratio of Spk / Sk of the first portion to Spk / Sk of the second portion is >10, the second portion has a Spk / Sk of less than 0.2, or both.

Images