Charging rolls for electrophotographic equipment

Abstract

To provide a charging roll for an electro-photographic apparatus capable of suppressing a bleeding of an ion conductive agent and a rise in resistance at energization durability.SOLUTION: A charging roll 10 for an electro-photographic apparatus includes a shaft body 12 and an elastic body layer 14 formed on an outer peripheral surface of the shaft body 12. The elastic body layer 14 is a cross-linked body of a rubber composition containing following (a) to (e): (a) one or two kinds selected from hydrin rubber or nitrile rubber; (b) a cross-linking agent; (c) an ion conductive agent; (d) one or two kinds selected from a piperidinyloxy radical compound and a phenolic antioxidant; and (e) one or two kinds selected from a salt of an annular amidine compound and a thiophthalimide compound.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a charging roll for electrophotographic equipment, which is suitably used in electrophotographic equipment such as copying machines, printers, and facsimiles that employ an electrophotographic system. [Background technology]

[0002] The charging roll of an electrophotographic device may require an ion conductive mechanism for electrical uniformity, etc. For example, Patent Document 1 discloses that an ion conductive agent is blended into the base layer of the charging roll. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-132020 Summary of the Invention [Problem to be solved by the invention]

[0004] If the charge roll continues to be subjected to an electrical load due to the passage of current, the electrical resistance of the charge roll increases, and there is a risk of image defects due to a decrease in charging ability. This is because when an electrical load is applied to the charge roll, the ionic conductive agent in the base layer rubber of the charge roll polarizes, and if the polarization of the ionic conductive agent is too rapid, the polarized anions and cations become excessively biased toward the positive and negative electrodes, respectively, resulting in less ionic conductive agent in the center of the base layer rubber and creating areas with high electrical resistance. If the amount of ionic conductive agent is excessively increased in order to suppress excessive polarization in the base layer rubber, this can lead to bleeding of the ionic conductive agent, which could result in image defects.

[0005] The problem to be solved by the present invention is to provide a charging roll for an electrophotographic device that can suppress an increase in resistance during long-term energization and bleeding of an ionic conductive agent. [Means for solving the problem]

[0006] The charging roll for an electrophotographic device according to the present invention comprises a shaft and an elastic layer formed on the outer peripheral surface of the shaft, and the elastic layer is a crosslinked body of a rubber composition containing the following (a) to (e): (a) One or more rubbers selected from hydrin rubber and nitrile rubber (b) Crosslinking agent (c) Ion conductive agent (d) one or more selected from piperidinyloxy radical compounds and phenolic antioxidants (e) one or more compounds selected from salts of cyclic amidine compounds and thiophthalimide compounds

[0007] The (e) may be a naphthoic acid salt of a cyclic amidine compound. The (e) may be N-cyclohexylthiophthalimide. The (c) may be an ammonium-based, phosphonium-based, or imidazolium-based ionic conductive agent. The (c) may be an ionic conductive agent containing a sulfonate anion having a fluorine atom, a bis(sulfonyl)imide anion having a fluorine atom, or a perchlorate anion. The rubber composition may further comprise a rubber having a specific surface area of ​​40 m 2 / g or more 300m 2 It is preferable that the carbon black content be 0.1g or less.

[0008] (1) The charging roll for an electrophotographic device according to the present invention comprises a shaft and an elastic layer formed on the outer peripheral surface of the shaft, and the elastic layer is a crosslinked body of a rubber composition containing the following (a) to (e): (a) One or more rubbers selected from hydrin rubber and nitrile rubber (b) Crosslinking agent (c) Ion conductive agent (d) one or more selected from piperidinyloxy radical compounds and phenolic antioxidants (e) one or more compounds selected from salts of cyclic amidine compounds and thiophthalimide compounds

[0009] (2) In the above (1), (e) may be a naphthoate salt of a cyclic amidine compound.

[0010] (3) In the above (1), (e) may be N-cyclohexylthiophthalimide.

[0011] (4) In any one of the above (1) to (3), the (c) may be an ammonium-based, phosphonium-based, or imidazolium-based ion-conducting agent.

[0012] (5) In any one of the above (1) to (4), the (c) may be an ion conductive agent containing a sulfonate anion having a fluorine atom, a bis(sulfonyl)imide anion having a fluorine atom, or a perchlorate anion.

[0013] (6) In any one of the above (1) to (5), the rubber composition further has a specific surface area of ​​40 m 2 / g or more 300m 2 It is preferable that the carbon black content be 0.1g or less. [Effects of the Invention]

[0014] The charging roll for electrophotographic equipment according to the present invention comprises a shaft and an elastic layer formed on the outer peripheral surface of the shaft, and the elastic layer is a crosslinked product of a rubber composition containing the above-mentioned (a) to (e), so that an increase in resistance during energization and bleeding of the ionic conductive agent are suppressed.

[0015] When the (e) is a naphthoic acid salt of a cyclic amidine compound, the effect of suppressing an increase in resistance during the application of current is particularly excellent.

[0016] Furthermore, when the (e) is N-cyclohexylthiophthalimide, the effect of suppressing an increase in resistance during energization is particularly excellent.

[0017] When the (c) ionic conductive agent is an ammonium-, phosphonium-, or imidazolium-based ionic conductive agent, the polar groups of the rubber component (a) tend to coordinate with the cations of the ionic conductive agent, which helps to suppress excessive polarization of the ionic conductive agent even during energization and durability testing, resulting in a particularly excellent effect of suppressing resistance increases during energization and durability testing. Furthermore, the salts of cyclic amidine compounds and thiophthalimide compounds of (e) tend to coordinate with the cations of the ionic conductive agent, which helps to suppress excessive polarization of the ionic conductive agent even during energization and durability testing, resulting in a particularly excellent effect of suppressing resistance increases during energization and durability testing. Furthermore, low resistance is easily achieved.

[0018] Ionic conductive agents containing sulfonate anions or bis(sulfonyl)imide anions containing fluorine atoms contain many fluorine groups in their structure, so the anions themselves have low basicity and form relatively weak ionic bonds with cations. Therefore, these ionic conductive agents are easily dissociated into ions in the rubber (a), making them more likely to achieve low resistance. Furthermore, these anions are all hydrophobic and have low moisture absorption, even in high-humidity environments. Therefore, they are highly effective in suppressing fluctuations in electrical resistance due to environmental changes. Ionic conductive agents containing perchlorate anions are more likely to achieve low resistance.

[0019] The rubber composition further has a specific surface area of ​​40 m 2 / g or more 300m 2 When the carbon black is contained in an amount of 1 / 2 g or less, the effect of suppressing bleeding of the ionic conductive agent is improved. [Brief explanation of the drawings]

[0020] [Figure 1] 1A is a schematic view of the appearance of a charging roll for an electrophotographic apparatus according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA thereof. DETAILED DESCRIPTION OF THE INVENTION

[0021] The charging roll for electrophotographic equipment (hereinafter, sometimes simply referred to as the charging roll) according to the present invention will be described in detail. Fig. 1 shows a schematic external view (a) of the charging roll for electrophotographic equipment according to one embodiment of the present invention, and a cross-sectional view (b) of the same taken along line AA.

[0022] The charge roll 10 comprises a shaft 12, an elastic layer 14 formed on the outer peripheral surface of the shaft 12, and a surface layer 16 formed on the outer peripheral surface of the elastic layer 14. The elastic layer 14 is a layer (base layer) that forms the base of the charge roll 10. The surface layer 16 is a layer that appears on the surface of the charge roll 10. Note that the charge roll of the present invention may not have a surface layer. In other words, the charge roll may comprise a shaft 12 and an elastic layer 14 formed on the outer peripheral surface of the shaft 12, but may not have a surface layer 16 on the outer peripheral surface of the elastic layer 14.

[0023] The shaft 12 is not particularly limited as long as it is electrically conductive. Specific examples include a solid or hollow core made of metal such as iron, stainless steel, or aluminum. The surface of the shaft 12 may be coated with an adhesive, a primer, or the like, as needed. That is, the elastic layer 14 may be bonded to the shaft 12 via an adhesive layer (primer layer). The adhesive, primer, or the like may be made electrically conductive as needed.

[0024] The elastic layer 14 is composed of a crosslinked rubber composition containing the following components (a) to (e): (a) One or more rubbers selected from hydrin rubber and nitrile rubber (b) Crosslinking agent (c) Ion conductive agent (d) one or more selected from piperidinyloxy radical compounds and phenolic antioxidants (e) one or more compounds selected from salts of cyclic amidine compounds and thiophthalimide compounds

[0025] Examples of hydrin rubbers include epichlorohydrin homopolymers (CO), epichlorohydrin-ethylene oxide copolymers (ECO), epichlorohydrin-allyl glycidyl ether copolymers (GCO), and epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymers (GECO). Among these, ECO and GECO, which contain ethylene oxide as a copolymerization component, are more preferred because they are more likely to produce low-resistance materials than those that do not contain ethylene oxide as a copolymerization component. Furthermore, GCO and GECO, which contain allyl glycidyl ether as a copolymerization component, are more preferred because they have double bonds and are less likely to settling than those that do not contain allyl glycidyl ether as a copolymerization component.

[0026] Nitrile rubber is acrylonitrile-butadiene rubber (NBR). Nitrile rubber is softer than hydrin rubber, which allows the ionic conductive agent to move more easily within the rubber. Even in this case, the configuration of the present invention suppresses the increase in resistance during energization and the bleeding of the ionic conductive agent. Furthermore, when nitrile rubber is included as (a), the hardness of the elastic layer 14 can be easily adjusted.

[0027] The crosslinking agent is not particularly limited. Examples of the crosslinking agent include a sulfur crosslinking agent, a peroxide crosslinking agent, and a dechlorination crosslinking agent. These crosslinking agents may be used alone or in combination of two or more.

[0028] Examples of sulfur crosslinking agents include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, sulfur chloride, thiuram vulcanization accelerators, and polymeric polysulfides.

[0029] Examples of peroxide crosslinking agents include peroxyketals, dialkyl peroxides, peroxyesters, ketone peroxides, peroxydicarbonates, diacyl peroxides, and hydroperoxides.

[0030] The peroxide crosslinking agent preferably has a decomposition temperature of 60°C or higher in a thermal storage test (BAM method: SADT) and a one-minute half-life temperature of 150°C or higher, from the viewpoint of having a relatively high decomposition temperature and being easy to mold at higher temperatures. A one-minute half-life temperature of 160°C or higher is more preferable, and a one-minute half-life temperature of 170°C or higher is even more preferable. On the other hand, from the viewpoint of excellent crosslinking speed, a one-minute half-life temperature of 200°C or lower is preferable. A one-minute half-life temperature of 190°C or lower is even more preferable, and a one-minute half-life temperature of 180°C or lower is even more preferable.

[0031] Preferred peroxide crosslinking agents include peroxyketals, dialkyl peroxides, and peroxyesters. Examples of peroxyketals include 1,1-di(tert-hexylperoxy)cyclohexane, 1,1-di(tert-butylperoxy)cyclohexane, and n-butyl 4,4-di(tert-butylperoxy)valerate. Examples of dialkyl peroxides include di(2-tert-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3. Examples of peroxyesters include tert-butyl peroxybenzoate, tert-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butylperoxy-2-ethylhexyl monocarbonate, tert-butyl peroxylaurate, tert-butylperoxy-3,5,5-trimethylhexanoate, tert-hexylperoxyisopropyl monocarbonate, etc. Among these, di(2-tert-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,1-di(tert-butylperoxy)cyclohexane, etc. are preferred from the viewpoints that unreacted components are less likely to remain and the decomposition products have relatively low boiling points, making them easy to remove.

[0032] Examples of the dechlorinating crosslinking agent include dithiocarbonate compounds, more specifically, quinoxaline-2,3-dithiocarbonate, 6-methylquinoxaline-2,3-dithiocarbonate, 6-isopropylquinoxaline-2,3-dithiocarbonate, and 5,8-dimethylquinoxaline-2,3-dithiocarbonate.

[0033] The amount of crosslinking agent to be added is preferably within a range of 0.1 to 2 parts by mass, more preferably within a range of 0.3 to 1.8 parts by mass, and even more preferably within a range of 0.5 to 1.5 parts by mass, per 100 parts by mass of the (a) specific polar rubber, from the viewpoint of preventing bleeding.

[0034] The content of the peroxide crosslinking agent, calculated as the amount of peroxide, is preferably 6 parts by mass or less per 100 parts by mass of component (a), from the viewpoint of easily achieving a low hardness of the elastic layer 14. It is more preferably 5 parts by mass or less, and even more preferably 4 parts by mass or less. Furthermore, from the viewpoint of achieving an excellent degree of crosslinking of the rubber and reducing settling resistance, it is preferably 0.2 parts by mass or more per 100 parts by mass of component (a), from the viewpoint of achieving an excellent degree of crosslinking of the rubber and reducing settling resistance. It is more preferably 0.4 parts by mass or more, and even more preferably 0.6 parts by mass or more.

[0035] The ionic conductive agent is not particularly limited. Any agent used in the field of electrophotographic equipment may be used. Examples of the ionic conductive agent include quaternary ammonium salts, quaternary phosphonium salts, imidazolium salts, borates, surfactants, etc. Among these, quaternary ammonium salts, quaternary phosphonium salts, and imidazolium salts are particularly preferred.

[0036] Examples of the cation of the quaternary ammonium salt include those having one or more alkyl or aryl groups having about 1 to 18 carbon atoms (e.g., methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, phenyl, xylyl, etc.). The alkyl or aryl group of the cation of the quaternary ammonium salt preferably has 1 to 10 carbon atoms. Examples of the anion of the quaternary ammonium salt include F- ,Cl - ,Br - ,I - Halogen ions such as ClO4 - , BF4 - , PF6 - , SO4 2- , HSO4 - , C2H5SO4 - , CF3COO - , CF3SO3 - , (CF3SO2)2N - , (CF3CF2SO2)2N - , CF3(CF2)3SO3 - , (CF3SO2)3C - , CF3(CF2)2COO - Examples of anions of quaternary ammonium salts include ClO4 - , (CF3SO2)2N - , CF3SO3 - etc. are more preferable.

[0037] Examples of the cation of the quaternary phosphonium salt include those having one or more alkyl or aryl groups having about 1 to 18 carbon atoms (e.g., methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, phenyl, xylyl, etc.). The alkyl or aryl group of the cation of the quaternary phosphonium salt preferably has 1 to 10 carbon atoms. Examples of the anion of the quaternary phosphonium salt include F - ,Cl - ,Br - ,I - Halogen ions such as ClO4 - , BF4 - , PF6 - , SO4 2- , HSO4 - , C2H5SO4 - , CF3COO - , CF3SO3 - , (CF3SO2)2N - , (CF3CF2SO2)2N - , CF3(CF2)3SO3 - , (CF3SO2)3C -, CF3(CF2)2COO - Examples of the anion of the quaternary phosphonium salt include ClO4 - , (CF3SO2)2N - , CF3SO3 - etc. are more preferable.

[0038] Examples of the imidazolium salt include unsubstituted imidazolium salts, 1-alkylimidazolium salts, 3-alkylimidazolium salts, 1,3-dialkylimidazolium salts, and 1,2,3-trialkylimidazolium salts. More specifically, examples of the imidazolium salt include 1-methylimidazolium salt, 1,3-dimethylimidazolium salt, 1,3-diethylimidazolium salt, 1,3-dipropylimidazolium salt, 1,3-dibutylimidazolium salt, 1,3-dicyclohexylimidazolium salt, 1-ethyl-3-methylimidazolium salt, 1-propyl-3-methylimidazolium salt, 1-butyl-3-methylimidazolium salt, 1-hexyl-3-methylimidazolium salt, 1-ethyl-2,3-dimethylimidazolium salt, 1-propyl-2,3-dimethylimidazolium salt, and 1-butyl-2,3-dimethylimidazolium salt. The anion of the imidazolium salt may be F. - ,Cl - ,Br - ,I - Halogen ions such as ClO4 - , BF4 - , PF6 - , SO4 2- , HSO4 - , C2H5SO4 - , CF3COO - , CF3SO3 - , (CF3SO2)2N - , (CF3CF2SO2)2N - , CF3(CF2)3SO3 - , (CF3SO2)3C - , CF3(CF2)2COO - Examples of the anion of imidazolium salts include ClO4 - , (CF3SO2)2N - , CF3SO3- etc. are more preferable.

[0039] Examples of borates include those having one or more alkyl or aryl groups having about 1 to 18 carbon atoms (e.g., methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, phenyl, xylyl, etc.), and containing alkali metal ions or alkaline earth metal ions such as lithium ions, sodium ions, potassium ions, and calcium ions.

[0040] From the viewpoint of low resistance, the content of the ionic conductive agent is preferably 0.1 parts by mass or more per 100 parts by mass of component (a). It is more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more. Furthermore, from the viewpoint of easily suppressing bleeding of the ionic conductive agent, it is preferably 5.0 parts by mass or less per 100 parts by mass of component (a). It is more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less.

[0041] The piperidinyloxy radical compound functions as a retarder during crosslinking. The piperidinyloxy radical compound maintains equilibrium with the radicals generated by the thermal decomposition of the crosslinking agent. In the early stages of crosslinking, when the amount of radicals generated is relatively small, the piperidinyloxy radical compound maintains equilibrium with the generated radicals and suppresses the crosslinking reaction (delaying the crosslinking initiation time (T10)). On the other hand, increasing the crosslinking temperature can accelerate the crosslinking rate. This delays only the crosslinking initiation time (T10) without delaying the overall crosslinking rate (T90). Adjusting the crosslinking rate in this way controls the molecular arrangement of the polymer. This creates adequate gaps within the polymer for the ions of the ionic conductive agent to enter, allowing the polar groups of the polymer to appropriately coordinate with the ions of the ionic conductive agent. This prevents excessive polarization of the ionic conductive agent even when an electrical load is applied by passing current through the polymer. Furthermore, delaying T10 allows salts of cyclic amidine compounds and other compounds to diffuse uniformly into the rubber by thermal diffusion before the rubber begins to harden. This allows the ionic conductive agent to be dispersed uniformly throughout the rubber, preventing excessive polarization of the ionic conductive agent even when an electrical load is applied by passing a current through it. Note that T10 is the time (s) required to reach 10% of the maximum torque at the molding temperature (crosslinking temperature), and T90 is the time (s) required to reach 90% of the maximum torque at the molding temperature (crosslinking temperature).

[0042] The piperidinyloxy radical compound is a compound represented by the following general formula (1). [ka]

[0043] Examples of R1 to R4 include hydrogen and alkyl groups having 1 to 4 carbon atoms. Examples of R5 include hydrogen, alkyl groups having 1 to 4 carbon atoms, aryl groups, acetoxy groups, benzyloxy groups, carboxylic acid groups, acetamide groups, and aldehyde groups.

[0044] Preferred examples of the piperidinyloxy radical compound include 2,2,6,6-tetramethylpiperidinyloxy radical, 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy radical, 4-benzoyloxy-2,2,6,6-tetramethylpiperidinyloxy radical, 4-acetamido-2,2,6,6-tetramethylpiperidinyloxy radical, etc. Among these, 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy radical, 4-benzoyloxy-2,2,6,6-tetramethylpiperidinyloxy radical, 4-acetamido-2,2,6,6-tetramethylpiperidinyloxy radical, etc. are more preferred from the viewpoints of a melting point within an optimum range relative to the molding temperature of rubber, radical scavenging ability, storage stability, cost, etc.

[0045] The phenolic antioxidant exhibits the same effect as the piperidinyloxy radical compound in the reaction system of the present invention. That is, it delays only the crosslinking initiation time (T10) without delaying the overall crosslinking rate (T90). As the phenolic antioxidant, a hindered phenolic antioxidant can be used. In addition, monophenolic, diphenolic, triphenolic, and polyphenolic antioxidants can be used.

[0046] Hindered phenol antioxidants include 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5 -triazine-2,4,6(1H,3H,5H)-trione, 2,6-di-tert-butyl-4-methylphenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4',4''-[(2,4,6-tri)methylbenzene-1,3,5-triyl]tris(methylene)]tris(2,6-di-tert-butylphenol), and the like.

[0047] From the viewpoint of suitability for adjusting the crosslinking rate, the content of (d) is preferably 0.05 parts by mass or more per 100 parts by mass of component (a). It is more preferably 0.1 parts by mass or more, and even more preferably 0.2 parts by mass or more. Furthermore, it is preferably 3.0 parts by mass or less per 100 parts by mass of component (a). It is more preferably 2.0 parts by mass or less, and even more preferably 1.0 part by mass or less.

[0048] A cyclic amidine compound is a cyclic compound containing an amidine structure in its structure. A salt of a cyclic amidine compound has an appropriate polarity that allows it to coordinate with the ions (cations) of an ionic conductive agent. By coordinating the salt of a cyclic amidine compound with the ions of an ionic conductive agent, excessive polarization of the ionic conductive agent is suppressed even when an electrical load is applied by passing current through the cyclic amidine compound. The cyclic amidine compound effectively exhibits the above effects in the form of a salt.

[0049] As the cyclic amidine compound, a bicyclic amidine compound is preferred from the viewpoint of availability, etc. Examples of the cyclic amidine compound include diazabicycloundecene (1,8-diazabicyclo(5.4.0)undecene-7) and diazabicyclononene (1,5-diazabicyclo(4.3.0)nonene-5). As the cyclic amidine compound, diazabicycloundecene is more preferred from the viewpoint of cation coordination ability, storage stability, etc.

[0050] Examples of the salt of the cyclic amidine compound include naphthoic acid salts of the cyclic amidine compound, phenolic resin salts of the cyclic amidine compound, aliphatic carboxylate salts, phenol salts, borate salts, etc. As the salt of the cyclic amidine compound, naphthoic acid salts of the cyclic amidine compound are more preferred because they cause a small increase in resistance due to polarization of the ion conductive agent during energization durability.

[0051] A thiophthalimide compound is a compound containing a thiophthalimide structure in its structure. In the reaction system of the present invention, the thiophthalimide compound exhibits the same effects as a salt of a cyclic amidine compound. That is, the thiophthalimide compound has an appropriate polarity that allows it to coordinate with the ions of an ionic conductive agent, and by coordinating with the ions of the ionic conductive agent, excessive polarization of the ionic conductive agent is suppressed even when an electrical load is applied by passing a current through the ion conductive agent. Examples of thiophthalimide compounds include N-cyclohexylthiophthalimide, N-trifluoromethylthiophthalimide, N-phenylthiophthalimide, and N,N'-thiodiphthalimide.

[0052] The content of (e) is preferably 0.1 parts by mass or more per 100 parts by mass of component (a), from the viewpoint of being effective in suppressing excessive polarization of the ionic conductive agent even when an electrical load is applied due to current flow. It is more preferably 0.5 parts by mass or more, and even more preferably 1.0 part by mass or more. Furthermore, from the viewpoint of suppressing bleeding of (e), it is preferably 5.0 parts by mass or less per 100 parts by mass of component (a), more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0053] The rubber composition may contain other additives as needed, such as an electronic conductor, a lubricant, an antioxidant, a light stabilizer, a viscosity modifier, a processing aid, a flame retardant, a plasticizer, a filler, a dispersant, a pigment, and a mold release agent.

[0054] Examples of the electronic conductive agent include carbon black, graphite, conductive titanium oxide, conductive zinc oxide, and conductive tin oxide.

[0055] The rubber composition may further contain carbon black. Carbon black can suppress bleeding of the ionic conductive agent by adsorbing cations of the ionic conductive agent. Carbon black having a specific surface area within a specific range can be preferably used. The larger the specific surface area of ​​carbon black, the easier it is to adsorb cations of the ionic conductive agent. On the other hand, the larger the specific surface area, the more likely carbon black aggregation occurs and the more likely electrical conductivity decreases. Therefore, in order to balance the effect of suppressing bleeding of the ionic conductive agent and the effect of suppressing a decrease in electrical conductivity, the specific surface area of ​​carbon black is set to 40 m 2 / g or more 300m 2 / g or less, more preferably 42m 2 / g or more 240m 2 The specific surface area of ​​carbon black can be measured by a nitrogen adsorption method.

[0056] The content of carbon black is preferably 5 to 40 parts by mass, more preferably 10 to 30 parts by mass, per 100 parts by mass of component (a), taking into consideration the hardness and conductivity of the elastic layer 14.

[0057] The thickness of the elastic layer 14 is not particularly limited, but is preferably in the range of 0.1 to 10 mm, more preferably in the range of 0.5 to 5 mm, and even more preferably in the range of 1 to 3 mm.

[0058] The volume resistivity of the elastic layer 14 is not particularly limited, but is preferably 102 ~10 10 Ω·cm, more preferably 10 3 ~10 9 Ω·cm, more preferably 10 4 ~10 8 It is in the range of Ω·cm.

[0059] The surface layer 16 can function as a protective layer for the roll surface. The surface layer 16 preferably contains, as a main material, a polymer component such as polyamide, polyurethane, acrylic resin, alkyd resin, phenolic resin, fluororesin, silicone resin, or modified versions of these. Examples of the modified groups in the modified versions include N-methoxymethyl groups, silicone groups, and fluorine groups. These polymer components may be contained alone or in combination as the surface layer material. The polymer component of the surface layer 16 may be crosslinked.

[0060] To impart conductivity to the surface layer 16, conductive agents such as carbon black, graphite, conductive titanium oxide, conductive zinc oxide, conductive tin oxide, and ionic conductive agents (quaternary ammonium salts, borates, surfactants, etc.) can be added as appropriate. Various additives may also be added as appropriate, as needed. Roughness-imparting particles may also be added to ensure surface roughness.

[0061] The roughness-forming particles form surface irregularities on the surface layer 16. Examples of the roughness-forming particles include resin particles and silica particles. Examples of the resin particles include urethane particles, silicone particles, and acrylic particles. The average particle diameter of the roughness-forming particles is preferably within the range of 3 to 50 μm. The average particle diameter of the roughness-forming particles can be calculated from the median diameter using a laser diffraction particle size distribution analyzer.

[0062] The thickness of the surface layer 16 is not particularly limited, but is preferably in the range of 0.01 to 100 μm, more preferably in the range of 0.1 to 20 μm, and even more preferably in the range of 0.3 to 10 μm. The volume resistivity of the surface layer 16 is preferably 107 ~10 12 Ω·cm, more preferably 10 8 ~10 11 Ω·cm, more preferably 10 9 ~10 10 It is in the range of Ω·cm.

[0063] The charge roll 10 can be manufactured, for example, as follows. First, the shaft 12 is coaxially placed in the hollow portion of a roll-molding die, and a rubber composition is injected and heated / cured. After that, the elastic layer 14 is formed on the outer periphery of the shaft 12 by, for example, demolding or extrusion molding the rubber composition onto the surface of the shaft 12. Next, a surface layer-forming composition is applied to the outer periphery of the formed elastic layer 14, and the surface layer 16 is formed by ultraviolet irradiation or heat treatment as necessary. In this manner, the charge roll 10 can be manufactured.

[0064] The surface layer-forming composition contains the above-mentioned main material, a conductive agent, and other additives as needed. Examples of other additives include a crosslinking agent for the polymer component, a leveling agent, and a surface modifier. To adjust viscosity, the surface layer-forming composition may contain an appropriate solvent, such as an organic solvent (e.g., methyl ethyl ketone, toluene, acetone, ethyl acetate, butyl acetate, methyl isobutyl ketone (MIBK), THF, or DMF), or a water-soluble solvent (e.g., methanol or ethanol). Various coating methods, such as roll coating, dipping, and spray coating, can be used for application.

[0065] In the charging roll 10 configured as described above, the elastic layer 14 is composed of a crosslinked rubber composition containing the above-mentioned (a) to (e), thereby suppressing resistance increases and bleed-out of the ionic conductive agent during long-term application of electricity. This is believed to be due to the following mechanism: The salt of a cyclic amidine compound or a thiophthalimide compound coordinates with the ions of the ionic conductive agent, thereby suppressing excessive polarization of the ionic conductive agent even when an electrical load is applied due to application of electricity. Furthermore, the use of a piperidinyloxy radical compound or a phenolic antioxidant slows only the crosslinking initiation time (T10) during crosslinking of hydrin rubber or nitrile rubber, without slowing the overall crosslinking rate (T90). Adjusting the crosslinking rate in this way controls the molecular arrangement of the polymer. Because adequate gaps are created within the polymer that allow the ions of the ionic conductive agent to enter, the polar groups of the polymer can appropriately coordinate with the ions of the ionic conductive agent. This suppresses excessive polarization of the ionic conductive agent even when an electrical load is applied due to application of electricity. In addition, the delay in T10 allows the salt of the cyclic amidine compound and other compounds to diffuse uniformly throughout the rubber through thermal diffusion before the rubber hardens. This allows the ionic conductive agent to be uniformly dispersed throughout the rubber, suppressing excessive polarization of the ionic conductive agent even when an electrical load is applied due to current flow. This suppresses resistance increases during endurance testing. Furthermore, since excessive polarization of the ionic conductive agent is not suppressed by increasing the amount of ionic conductive agent, bleeding of the ionic conductive agent is also suppressed. Furthermore, by slowing the crosslinking initiation time (T10) without delaying the overall crosslinking rate (T90), adequate gaps are created within the polymer for the ions of the ionic conductive agent to enter. This allows the polar groups of the polymer to appropriately coordinate with the ions of the ionic conductive agent, making bleeding of the ionic conductive agent more difficult. Therefore, bleeding of the ionic conductive agent is suppressed even when the amount of ionic conductive agent is increased.

[0066] Furthermore, when the ionic conductive agent is an ammonium-based, phosphonium-based, or imidazolium-based agent, the polar groups of the rubber component (a) tend to coordinate with the cations of the ionic conductive agent, which helps to suppress excessive polarization of the ionic conductive agent even during electrical durability testing, resulting in a particularly excellent effect of suppressing resistance increases during electrical durability testing. Furthermore, the salts of cyclic amidine compounds and thiophthalimide compounds (e) tend to coordinate with the cations of the ionic conductive agent, which helps to suppress excessive polarization of the ionic conductive agent even during electrical durability testing, resulting in a particularly excellent effect of suppressing resistance increases during electrical durability testing. Furthermore, low resistance is easily achieved.

[0067] Furthermore, when the ionic conductive agent contains a sulfonate anion having a fluorine atom or a bis(sulfonyl)imide anion having a fluorine atom, the anion itself has low basicity due to the large number of fluorine groups in its structure, and forms a relatively weak ionic bond with the cation. Therefore, these ionic conductive agents are easily dissociated into ions in the rubber (a), making it easy to achieve low resistance. In addition, all of these anions are hydrophobic and have low hygroscopicity even in high-humidity environments. Therefore, they are excellent at suppressing fluctuations in electrical resistance due to environmental changes. Furthermore, ionic conductive agents containing perchlorate anions are easy to achieve low resistance. [Example]

[0068] The present invention will be described in detail below using examples and comparative examples.

[0069] (Experimental Example 1) <Preparation of Rubber Composition> A rubber composition was prepared by mixing and stirring 100 parts by mass of hydrin rubber (ECO), 3 parts by mass (1.2 parts by weight in terms of the amount of raw materials) of a peroxide crosslinking agent (Peroximone F40), 0.2 parts by mass of a piperidinyloxy radical compound (4-hydroxy TEMPO radical), 5 parts by mass of an acid acceptor, 1 part by mass of an ion conductive agent, and 0.1 part by mass of a salt of a cyclic amidine compound (naphthoic acid salt of diazabicycloundecene) using a stirrer.

[0070] <Formation of elastic layer> A core metal (diameter 6 mm) was set in a molding die, and the rubber composition was poured into the die at 120°C and heated at 175°C for 30 minutes to crosslink the rubber composition. After that, the die was cooled and demolded, and a 2 mm thick elastic layer was formed on the outer periphery of the core metal.

[0071] <Surface formation> A surface layer-forming composition was prepared by mixing 100 parts by mass of N-methoxymethylated nylon ("EF30T" manufactured by Nagase ChemteX), 60 parts by mass of conductive tin oxide ("S-2000" manufactured by Mitsubishi Materials), 1 part by mass of citric acid, and 300 parts by mass of methanol. The surface of the elastic layer was then roll-coated with the surface layer-forming composition and heated at 120°C for 50 minutes to form a 10 μm-thick surface layer on the outer periphery of the elastic layer. This produced the charging roll of Example 1.

[0072] (Experimental Example 2) A charging roll was produced in the same manner as in Experimental Example 1, except that the amount of the salt of the cyclic amidine compound compounded was changed in the preparation of the rubber composition.

[0073] (Experimental Examples 3-4) A charging roll was produced in the same manner as in Experimental Example 1, except that in the preparation of the rubber composition, the compounded amounts of the salt of the cyclic amidine compound and the piperidinyloxy radical compound were changed.

[0074] (Experimental Examples 5-6) A charging roll was produced in the same manner as in Experimental Example 1, except that in the preparation of the rubber composition, the type and amount of the salt of the cyclic amidine compound were changed.

[0075] (Experimental Example 7) A charging roll was produced in the same manner as in Experimental Example 1, except that in the preparation of the rubber composition, a thiophthalimide compound was used instead of the salt of the cyclic amidine compound and the compounding amount was changed.

[0076] (Experimental Example 8) A charging roll was produced in the same manner as in Experimental Example 1, except that in preparing the rubber composition, nitrile rubber (NBR) was used instead of hydrin rubber (ECO) and the compounded amount of the cyclic amidine compound was changed.

[0077] (Experimental Example 9) A charging roll was produced in the same manner as in Experimental Example 1, except that in the preparation of the rubber composition, a phenolic antioxidant was used instead of the piperidinyloxy radical compound, the blending amount of the phenolic antioxidant was changed, and further, the blending amount of the cyclic amidine compound was changed.

[0078] (Experimental Example 10) A charging roll was produced in the same manner as in Experimental Example 1, except that in preparing the rubber composition, the compounded amount of the salt of the cyclic amidine compound was changed, and further, the compounded amount of the ionic conductive agent was changed.

[0079] (Experimental Examples 11-12) A charging roll was produced in the same manner as in Experimental Example 10, except that the type of ionic conductive agent used in preparing the rubber composition was changed.

[0080] (Experimental Example 13) A charging roll was produced in the same manner as in Experimental Example 1, except that in the preparation of the rubber composition, the amount of the salt of the cyclic amidine compound was changed and carbon black was further added.

[0081] (Experimental Example 21) A charging roll was produced in the same manner as in Experimental Example 1, except that the salt of the cyclic amidine compound and the piperidinyloxy radical compound were not blended in the preparation of the rubber composition.

[0082] (Experimental Example 22) A charging roll was produced in the same manner as in Experimental Example 21, except that the amount of the ionic conductive agent was increased in the preparation of the rubber composition.

[0083] (Experimental Examples 23-26) A charging roll was produced in the same manner as in Experimental Examples 4 to 7, except that the piperidinyloxy radical compound was not blended in the preparation of the rubber composition.

[0084] (Experimental Example 27) A charging roll was produced in the same manner as in Experimental Example 4, except that the salt of the cyclic amidine compound was not blended in the preparation of the rubber composition.

[0085] (Experimental Example 28) A charging roll was produced in the same manner as in Experimental Example 9, except that in preparing the rubber composition, the salt of the cyclic amidine compound was not compounded and further the amount of the phenolic antioxidant compounded was changed.

[0086] The following materials were prepared as materials for the elastic layer-forming composition. Hydrin rubber (ECO): Osaka Soda's "Epichromer CG102" Nitrile rubber (NBR): Zeon Corporation "Nipol DN3335" Crosslinking agent: NOF's "Peroximon F40" Diazabicycloundecene salts <1> : 3-hydroxy-2-naphthoic acid salt of 1,8-diazabicyclo(5.4.0)undecene-7 Diazabicycloundecene salts <2> : Phenolic resin salt of 1,8-diazabicyclo(5.4.0)undecene-7 Diazabicyclononene salts: phenolic resin salts of 1,5-diazabicyclo(4.3.0)nonene-5 Thiophthalimide compounds: N-cyclohexylthiophthalimide ·Piperidinyloxy radical compound: 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy radical Phenolic antioxidant: 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate Acid acceptor: Kyowa Chemical Industry's "DHT-4A" Ionic conductive agent <1> : "Tetrabutylammonium triflate" manufactured by Tokyo Chemical Industry Co., Ltd. Ionic conductive agent <2> : The following phosphonium salts (synthetic products) Ionic conductive agent <3> : 1-Ethyl-3-methylimidazolium bromide manufactured by Shikoku Chemical Industry Co., Ltd. Carbon black: Tokai Carbon "Seast 9" (specific surface area 142 m 2 / g)

[0087] <Synthesis of phosphonium salts> Tri-n-butyldodecylphosphonium bromide and bis(trifluoromethanesulfonyl)imidic acid were added to a mixture of methylene chloride and ion-exchanged water (1:1), and the mixture was stirred at room temperature for 4 hours. After that, tri-n-butyldodecylphosphonium bis(trifluoromethanesulfonyl)imide was obtained from the organic layer.

[0088] The produced charging roll was evaluated for resistance change during energization and bleeding of the ionic conductive agent.

[0089] <Method for evaluating changes in electrical resistance> A 700g load was applied to each end of the charging roll on a 30mm diameter metal drum, and the metal drum was rotated at 90 rpm, resulting in an electrical current test of 20,000μA·h. The resistance values ​​were measured before and after the test, and the resistance change was calculated in digits. A resistance change of less than 0.7 digits was rated "A," a resistance change of 0.7 to 1.0 digits was rated "B," and a resistance change of 1.0 digit or more was rated "C."

[0090] <Bleeding evaluation method> The charging roll was left in a humid and hot environment at 40°C for 30 days, and then the surface of the charging roll was observed to see if there was any bleeding. If no bleeding was observed, it was rated "A", and if bleeding was observed, it was rated "B".

[0091] [Table 1]

[0092] [Table 2]

[0093] In Experimental Examples 1 to 13, the rubber compositions were prepared by blending one or more selected from hydrin rubber and nitrile rubber, a crosslinking agent, an ionic conductive agent, one or more selected from piperidinyloxy radical compounds and phenolic antioxidants, and one or more selected from salts of cyclic amidine compounds and thiophthalimide compounds, and the resistance increase due to polarization of the ionic conductive agent was small during electrical durability testing, and no bleeding of the ionic conductive agent was observed.

[0094] In Experimental Example 21, the rubber composition was prepared without the addition of a cyclic amidine compound salt, a thiophthalimide compound, a piperidinyloxy radical compound, or a phenolic antioxidant, and the resistance increase due to polarization of the ionic conductive agent was large during the energization and durability test. In Experimental Example 22, the resistance increase during the energization and durability test was suppressed by increasing the amount of ionic conductive agent, but bleeding of the ionic conductive agent was observed. In Experimental Examples 23 to 26, the rubber composition was prepared without the addition of a piperidinyloxy radical compound or a phenolic antioxidant, and the resistance increase due to polarization of the ionic conductive agent was somewhat large during the energization and durability test. In Experimental Examples 27 and 28, the rubber composition was prepared without the addition of a cyclic amidine compound salt or a thiophthalimide compound, and the resistance increase due to polarization of the ionic conductive agent was large during the energization and durability test.

[0095] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications are possible within the scope of the invention. [Explanation of symbols]

[0096] 10 Charging roll 12 shaft body 14 Elastic layer 16 Surface layer

Claims

1. a shaft body; and an elastic layer formed on an outer peripheral surface of the shaft body, The charging roll for an electrophotographic device, wherein the elastic layer is a crosslinked product of a rubber composition containing the following (a) to (e): (a) One or more rubbers selected from hydrin rubbers and nitrile rubbers (b) Crosslinking Agent (c) Ion Conductive Agent (d) one or more selected from piperidinyloxy radical compounds (e) one or more compounds selected from salts of cyclic amidine compounds and thiophthalimide compounds

2. 2. The charging roll for an electrophotographic apparatus according to claim 1, wherein said (e) is a naphthoic acid salt of a cyclic amidine compound.

3. 2. The charging roll for electrophotographic equipment according to claim 1, wherein said (e) is N-cyclohexylthiophthalimide.

4. 3. The charging roll for an electrophotographic apparatus according to claim 1, wherein the (c) is an ammonium-based, phosphonium-based, or imidazolium-based ionic conductive agent.

5. 3. The charging roll for an electrophotographic apparatus according to claim 1, wherein the (c) is an ionic conductive agent containing a sulfonate anion having a fluorine atom, a bis(sulfonyl)imide anion having a fluorine atom, or a perchlorate anion.

6. The rubber composition further has a specific surface area of ​​40 m ２ / g or more 300m ２ 3. The charging roll for an electrophotographic apparatus according to claim 1, wherein the carbon black has a surface roughness of 0.1 to 0.2g.

7. (e) is a naphthoate salt of a cyclic amidine compound or N-cyclohexylthiophthalimide; the (c) is an ammonium-based, phosphonium-based, or imidazolium-based ion-conducting agent containing a sulfonate anion having a fluorine atom, a bis(sulfonyl)imide anion having a fluorine atom, or a perchlorate anion; The rubber composition further has a specific surface area of ​​40 m ２ / g or more 300m ２ 2. The charging roll for an electrophotographic apparatus according to claim 1, comprising carbon black having a surface roughness of 0.1 to 0.2g.

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