Electrophotographic member and electrophotographic image forming apparatus

Abstract

To provide a member for electrophotography that can achieve a further reduction in volume resistance value at low cost.SOLUTION: A member for electrophotography has a base layer and an elastic layer on the base layer. The elastic layer includes silicone rubber, at least one first cation selected from the group consisting of cations represented by the structural formulas (1-1)-(1-2), at least one second cation, and an anion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an electrophotographic member and an electrophotographic image forming apparatus equipped with the electrophotographic member. [Background technology]

[0002] For electrophotographic imaging devices, paper with a basis weight of 300 g / m 2 There is a demand for the ability to form high-quality electrophotographic images even on recording media with uneven surfaces, such as thick paper or embossed paper, exceeding 1000 kJ / cm. However, when forming an electrophotographic image on the surface of a recording medium with an uneven surface, there are cases in which toner is not sufficiently transferred to the recesses on the surface. To address this issue, it is effective to use an intermediate transfer belt having a conductive elastic layer containing rubber, such as silicone rubber, which has excellent conformability to the surface shape of the recording medium. In addition, ionic conductive agents having alkylammonium cations (Patent Document 1) and ionic conductive agents having alkylphosphonium cations (Patent Document 2) have been disclosed as materials that impart conductivity to resins and rubbers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-185140 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-48198 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the inventors' investigations, even when ionic conductive agents having alkylammonium cations or alkylphosphonium cations (hereinafter collectively referred to as "ammonium-based conductive agents") according to Patent Documents 1 and 2 are added to silicone rubber, it is sometimes impossible to sufficiently reduce the volume resistivity (hereinafter also referred to as "ρv") of the elastic layer. On the other hand, although there are ionic conductive agents that can reduce the ρv of the elastic layer more than ammonium-based conductive agents, they are more expensive than ammonium-based conductive agents. Therefore, the inventors recognized the need for the development of new technology that can further reduce the ρv of the elastic layer at lower cost.

[0005] One aspect of the present disclosure is to provide an electrophotographic member that can achieve a further reduction in volume resistivity at low cost. Another aspect of the present disclosure is to provide an electrophotographic image forming apparatus that can form high-quality electrophotographic images. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided an electrophotographic member having a base layer and an elastic layer on the base layer, the elastic layer including a silicone rubber, at least one first cation selected from the group consisting of cations represented by the following structural formulas (1-1) and (1-2), at least one second cation selected from the group consisting of cations represented by the following structural formulas (2-1) and (2-2), and an anion:

[0007] [ka]

[0008] (In structural formulas (1-1) to (1-2), R1 to R8 each independently represent an alkyl group having 1 to 14 carbon atoms. However, at least three of the alkyl groups represented by R1 to R4 and at least three of the alkyl groups represented by R5 to R8 have a linear portion having 6 or more carbon atoms.)

[0009] [ka]

[0010] (In structural formulas (2-1) to (2-2), R9 to R 16 each independently represents an alkyl group having 1 to 4 carbon atoms.

[0011] According to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus comprising the electrophotographic member described above as an intermediate transfer member. [Effects of the Invention]

[0012] According to one aspect of the present disclosure, an electrophotographic member capable of achieving a further reduction in volume resistivity at low cost can be obtained. Also, according to another aspect of the present disclosure, an electrophotographic image forming apparatus capable of forming high-quality electrophotographic images can be obtained. [Brief explanation of the drawings]

[0013] [Figure 1] 1A and 1B are schematic diagrams showing (first) cation-anion aggregates and (b) dissociation of (first) cation-anion aggregates upon addition of a second cation. [Figure 2] 1 is a schematic cross-sectional view showing an example of a full-color electrophotographic image forming apparatus. [Figure 3] 1 is a schematic diagram of an electrophotographic member having an endless belt shape according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present inventors speculate as follows about the reason why it is difficult to sufficiently reduce ρv even when the ammonium-based conductive agents disclosed in Patent Documents 1 and 2 are added to the silicone rubber elastic layer. Normally, when an ionic conductive agent is added to resin or rubber, the conductivity is proportional to the product of the number of carrier ions that provide conductivity and the ease of movement of the ions (ion mobility). Electrical resistance is inversely proportional to the product of the number of ions and ion mobility. Non-polar silicone rubber and polar ammonium-based conductive agents have low compatibility. Therefore, even if an ammonium-based conductive agent is incorporated into silicone rubber, the ammonium-based conductive agent is difficult to dissociate into cations and anions in the silicone rubber, forming aggregates due to the ordered arrangement of cations and anions (hereinafter also referred to as "cation-anion aggregates"). As a result, the amount of carrier ions generated is insufficient relative to the amount of ammonium-based conductive agent added, making it difficult to further reduce the ρv of the elastic layer.

[0015] Therefore, the present inventors have conducted extensive research to improve the degree of dissociation between the anions and cations that constitute the ammonium-based conductive agent in the silicone rubber, and have found that allowing two types of ammonium-based cations with different molecular structures to coexist in the silicone rubber is effective in improving the degree of ionic dissociation of the ammonium-based conductive agent in the silicone rubber. That is, as described above, it is considered that the ammonium-based conductive agent forms aggregates 100 of first cations 101 and anions 102 in the silicone rubber, as shown in Fig. 1(a). Therefore, the number of carrier ions is reduced, and the effect of improving the conductivity of the elastic layer containing the silicone rubber is limited. On the other hand, as shown in Figure 1(b), the presence of second cations 103, which have a molecular structure different from that of first cations 101, in silicone rubber is believed to inhibit the formation of aggregates 100 resulting from the regular arrangement of the first cations and anions. Specifically, the presence of first cations 101 having three or more alkyl groups (hereinafter also referred to as "long-chain alkyl groups") with a structure in which six or more carbon atoms are arranged in a linear chain and second cations 103 having only alkyl groups with four or fewer carbon atoms (hereinafter also referred to as "short-chain alkyl groups") in silicone rubber is considered to be effective. Here, the first cations having three or more long-chain alkyl groups have a bulky structure that extends in three or more directions from the nitrogen or phosphorus atom in the cation, while the second cations having only short-chain alkyl groups are not bulky. In other words, these two types of cations have significantly different shapes. As a result, as shown in Figure 1(b), the formation of aggregates 100 by the first cations 101 and anions 102 is inhibited, and the number of carrier ions can be increased. As a result, it is believed that even when an ammonium-based conductive agent is used, the resistance of the elastic layer can be more reliably reduced. Hereinafter, embodiments of the electrophotographic member according to the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0016] <Electrophotographic materials> An electrophotographic member according to one embodiment of the present disclosure has a base layer and an elastic layer on the base layer. The shape of the electrophotographic member is not particularly limited and may be, for example, a cylindrical, columnar, or endless belt shape. FIG. 3 is a schematic diagram of an electrophotographic member (hereinafter also referred to as an "electrophotographic belt") 300 having an endless belt shape according to one embodiment of the present disclosure. The electrophotographic belt 300 is composed of an endless belt-shaped base layer 302 and an elastic layer 301 formed on the outer peripheral surface thereof. Note that, if necessary, a surface layer (not shown) may be further provided on the outer peripheral surface of the elastic layer 301. The volume resistivity of the electrophotographic member is 1.0×10 8 Ω cm or more 2.0×10 11It is preferable that the volume resistivity is Ω·cm or less. Note that the volume resistivity of an electrophotographic member that has been given conductivity by an ion conductive agent may increase with long-term use. Therefore, the volume resistivity before use in an electrophotographic image forming apparatus (immediately after the electrophotographic member is produced) is set to 1.0×10 8 Ω cm or more 8.0×10 10 It is more preferable that the volume resistivity is 1.0×10 Ω·cm or less. 8 Ω cm or more 5.0×10 10 It is particularly preferable that the resistivity is Ω·cm or less.

[0017] [Base layer] The base layer may be cylindrical, columnar, or endless belt-shaped, depending on the shape of the electrophotographic member.The material of the base layer is not particularly limited as long as it has excellent heat resistance and mechanical strength.For example, metals such as aluminum, iron, copper, and nickel; alloys such as stainless steel and brass; ceramics such as alumina and silicon carbide; and resins such as polyether ether ketone, polyethylene terephthalate, polybutylene naphthalate, polyester, polyimide, polyamide, polyamideimide, polyacetal, and polyphenylene sulfide can be mentioned. When a thermosetting resin or a thermoplastic resin is used as the material of the base layer, conductive powder such as metal powder, conductive oxide powder, or conductive carbon may be added to impart conductivity. The preferred volume resistivity of the base layer is, for example, 1.0×10 8 Ω cm or more, 1.0×10 11 The surface resistivity of the base layer is preferably 3.0×10 9 Ω / □ or more, 3.0×10 12 It is Ω / □ or less. The base layer is preferably made of a resin having excellent flexibility and mechanical strength, and more preferably made of polyether ether ketone containing carbon black as a conductive powder or polyimide containing carbon black as a conductive powder. The thickness of the endless belt-shaped base layer is, for example, 10 μm to 500 μm, particularly 30 μm to 150 μm.

[0018] [Elastic layer] The elastic layer contains silicone rubber as a matrix material and first cations, second cations, and anions dispersed in the silicone rubber. More specifically, the elastic layer is composed of a cured product obtained by curing a silicone rubber mixture containing at least the raw materials of the silicone rubber (base polymer, crosslinking agent, etc.) and the first cations, second cations, and anions. Because silicone rubber mixtures are often liquid, the elasticity of the elastic layer can be easily adjusted by adjusting the degree of crosslinking depending on the type and amount of added materials. The silicone rubber contained in the elastic layer will be described below.

[0019] (silicone rubber) Silicone rubber is a cured product obtained by curing addition-curing liquid silicone rubber. Generally, addition-curing liquid silicone rubber contains the following components (a), (b), and (c): (a) an organopolysiloxane having an unsaturated aliphatic group; (b) an organopolysiloxane having active hydrogen atoms bonded to silicon atoms; (c) Platinum compounds as cross-linking catalysts.

[0020] Examples of the organopolysiloxane having an unsaturated aliphatic group, component (a), include the following: Both ends of the molecule are (R 21 )2R 22 SiO 1 / 2 The intermediate unit is (R 21 )2SiO and R 21 R 22 Linear organopolysiloxanes represented by SiO; Both ends of the molecule are (R 21 )2R 22 SiO 1 / 2 It is expressed as R 21 SiO 3 / 2 or SiO 4 / 2 A branched organopolysiloxane comprising:

[0021] where R21 represents an unsubstituted or substituted monovalent hydrocarbon group that is bonded to the silicon atom in the above formula and does not contain an unsaturated aliphatic group. Specific examples of such hydrocarbon groups include the following: alkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, etc.); Aryl groups (phenyl, naphthyl, etc.). Examples of the substituent that the hydrocarbon group may have include halogen atoms such as fluorine atoms and chlorine atoms; alkoxy groups such as methoxy groups and ethoxy groups; and cyano groups. Specific examples of the substituted hydrocarbon group include chloromethyl groups, 3-chloropropyl groups, 3,3,3-trifluoropropyl groups, 3-cyanopropyl groups, and 3-methoxypropyl groups. Among these, R 21 It is preferable that 50% or more of R are methyl groups, and all of R 21 is more preferably a methyl group.

[0022] Also, R 22 represents an unsaturated aliphatic group bonded to the silicon atom in the above formula. Examples of unsaturated aliphatic groups include vinyl groups, allyl groups, 3-butenyl groups, 4-pentenyl groups, and 5-hexenyl groups. Among these, vinyl groups are preferred because they are easy to synthesize and handle and facilitate the crosslinking reaction of silicone rubber.

[0023] The organopolysiloxane having active hydrogen atoms bonded to silicon atoms (component (b)) is a crosslinking agent that reacts with the unsaturated aliphatic groups in component (a) under the catalytic action of the platinum compound (component (c)) to form a crosslinked structure. The number of active hydrogen atoms bonded to silicon atoms in component (b) is preferably more than 3 on average per molecule. The organic group bonded to the silicon atom in the organopolysiloxane having active hydrogen bonded to the silicon atom, which is component (b), is R 21Examples of the organic group include unsubstituted or substituted monovalent hydrocarbon groups that do not contain unsaturated aliphatic groups, such as those shown in the formula (1). In particular, a methyl group is preferred as the organic group because of its ease of synthesis and handling.

[0024] The molecular weight of component (b) is not particularly limited. The viscosity of component (b) at 25°C is 10 mm 2 / s or more 100,000mm 2 / s or less is preferable, 15 mm 2 / s or more 1,000mm 2 If the viscosity of component (b) at 25°C is within the above range, it will not volatilize during storage, preventing the desired degree of crosslinking and physical properties of the molded product from being obtained, and it will be easier to synthesize and handle, and it will be easier to disperse uniformly in the system.

[0025] The siloxane skeleton of component (b) may be linear, branched, or cyclic, or a mixture of these may be used. From the viewpoint of ease of synthesis, the siloxane skeleton of component (b) is preferably linear. In addition, in component (b), Si-H bonds may be present in any siloxane unit in the molecule, but at least a portion of them should be (R 21 )2HSiO 1 / 2 It is preferred that the siloxane units are present at the terminals of the molecules, such as the units.

[0026] The addition-curable liquid silicone rubber preferably has an unsaturated aliphatic group content of 0.1 mol % to 2.0 mol %, more preferably 0.2 mol % to 1.0 mol %, per mole of silicon atom.

[0027] As the component (c), known platinum compounds can be used.

[0028] (first cation) The first cation is at least one selected from the group consisting of cations represented by the following structural formulas (1-1) to (1-2).

[0029] [ka]

[0030] In structural formulas (1-1) to (1-2), R1 to R8 each independently represent an alkyl group having 1 to 14 carbon atoms. However, at least three of the alkyl groups represented by R1 to R4 and at least three of the alkyl groups represented by R5 to R8 have a straight-chain portion having 6 or more carbon atoms. Here, "a straight-chain portion having 6 or more carbon atoms" refers to a structure in which six carbon atoms are arranged in a straight chain. Furthermore, an alkyl group "having a straight-chain portion having 6 or more carbon atoms" refers to an alkyl group having 6 to 14 carbon atoms, including the straight-chain portion.

[0031] The alkyl groups represented by R1 to R4 in the structural formula (1-1) and R5 to R8 in the structural formula (1-2) may have a linear or branched structure. Furthermore, R1 to R4 may be all the same or all different from one another. However, it is preferable that R1 to R4 are not all the same alkyl group. That is, it is preferable that at least one substituent selected from R1 to R4 is an alkyl group different from the other substituents. Specifically, for example, it is preferable that R1 to R3 are the same alkyl group and R4 is an alkyl group different from R1 to R3. When R1 to R4 are not all the same alkyl group, the structural symmetry of the cation is reduced, thereby further enhancing the dissociation between the first cation and the anion. As a result, the effect of preventing the formation of first cation-anion aggregates by the second cation is further improved. As described above, R5 to R8 may also be all the same or all different from one another, but it is preferable that they are not all the same alkyl group. That is, it is preferable that at least one substituent selected from R5 to R8 is an alkyl group different from the other substituents.

[0032] Furthermore, R1 to R4 may all be long-chain alkyl groups having a linear portion with 6 or more carbon atoms. However, if all four are long-chain alkyl groups, adjacent alkyl chains will be oriented and stabilized, which may hinder the promotion of ionic dissociation when a second cation is added. Therefore, it is preferable that three of R1 to R4 have a linear portion with 6 or more carbon atoms, and the remaining one does not have a linear portion with 6 or more carbon atoms. Similarly, R5 to R8 may all be long-chain alkyl groups having a linear portion with 6 or more carbon atoms. However, it is preferable that three of R5 to R8 have a linear portion with 6 or more carbon atoms, and the remaining one does not have a linear portion with 6 or more carbon atoms. Note that an alkyl group "not having a linear portion with 6 or more carbon atoms" refers to an alkyl group having 5 or less carbon atoms, or, in the case of an alkyl group having 6 to 14 carbon atoms, the linear portion of the alkyl group has 5 or less carbon atoms.

[0033] Specific examples of the first cation represented by the structural formula (1-1) are listed below. Methyltri-n-hexylammonium ion, methyltri-n-octylammonium ion, methyltridecylammonium ion, methyltritetradecylammonium ion, tri-n-hexyl-n-butylammonium ion, tri-n-hexyl-n-octylammonium ion, tri-n-hexyltetradecylammonium ion, and tetra-n-octylammonium ion. Among these, the methyltri-n-hexylammonium ion, methyltri-n-octylammonium ion, methyltridecylammonium ion, methyltritetradecylammonium ion, and tri-n-hexyl-n-butylammonium ion are particularly preferred, since three of R1 to R4 have a linear chain portion having 6 or more carbon atoms and the remaining one does not have a linear chain portion having 6 or more carbon atoms.

[0034] Specific examples of the first cation represented by the structural formula (1-2) are listed below. Methyl tri-n-hexyl phosphonium ion, methyl tri-n-octyl phosphonium ion, methyl tridecyl phosphonium ion, methyl tritetradecyl phosphonium ion, tri-n-hexyl-n-butyl phosphonium ion, tri-n-hexyl-n-octyl phosphonium ion, tri-n-hexyltetradecyl phosphonium ion, tetra-n-octyl phosphonium ion.

[0035] (second cation) The second cation is at least one selected from the group consisting of cations represented by the following structural formulas (2-1) to (2-2).

[0036] [ka]

[0037] In structural formula (2-1), R9~R 12 are each independently an alkyl group having 1 to 4 carbon atoms. 13 ~R 16 are each independently an alkyl group having 1 to 4 carbon atoms. 16 may have a linear or branched structure.

[0038] Specific examples of the cation represented by the above structural formula (2-1) are listed below. Ethyltrimethylammonium ion, triethylmethylammonium ion, trimethyl-n-propylammonium ion, trimethyl-n-butylammonium ion, tri-n-butylmethylammonium ion, tert-butyltrimethylammonium ion, tetraethylammonium ion, tetra-n-propylammonium ion, and tetra-n-butylammonium ion. Among these, R9 to R 12In particular, ethyltrimethylammonium ion, triethylmethylammonium ion, trimethyl-n-propylammonium ion, trimethyl-n-butylammonium ion, tri-n-butylmethylammonium ion, and tert-butyltrimethylammonium ion are preferred, in which not all of the alkyl groups are the same.

[0039] Specific examples of the cation represented by the above structural formula (2-2) are listed below. Ethyltrimethylphosphonium ion, triethylmethylphosphonium ion, trimethyl-n-propylphosphonium ion, trimethyl-n-butylphosphonium ion, tri-n-butylmethylphosphonium ion, tert-butyltrimethylphosphonium ion, tetraethylphosphonium ion, tetra-n-propylphosphonium ion, and tetra-n-butylphosphonium ion. Among these, R 13 ~R 16 In particular, the alkyl groups are not all the same, and examples thereof include an ethyltrimethylphosphonium ion, a triethylmethylphosphonium ion, a trimethyl-n-propylphosphonium ion, a trimethyl-n-butylphosphonium ion, a tri-n-butylmethylphosphonium ion, and a tert-butyltrimethylphosphonium ion.

[0040] The ratio of the amount of the first cation to the amount of the second cation is preferably X / (X+Y) in the range of 0.2 to 0.7, where X is the number of moles of the first cation and Y is the number of moles of the second cation. By setting the ratio of the amount of the first cation to the amount of the second cation within the above range, the formation of first cation-anion aggregates can be more reliably prevented.

[0041] When two or more types of the first cations and two or more types of the second cations are used in combination, the number of moles X of the first cations and the number of moles Y of the second cations respectively mean the total number of moles of the multiple first cations and the multiple second cations.

[0042] The elastic layer may also contain cations other than the first and second cations. For example, cations modified with dimethylsiloxane chains have a similar chemical structure to curable silicone rubber and have a high affinity with curable silicone rubber. Therefore, when the elastic layer contains cations modified with dimethylsiloxane chains, the electrophotographic member exhibits a more uniform volume resistivity.

[0043] (anion) The anion is not particularly limited, and specific examples of the anion are listed below. F - , Cl - , Br - , I - , AlCl4 - , NO3 - , BF4 - , PF6 - , AsF6 - , SbF6 - , CH3COO - , CF3COO - , (C2F5)3PF3 - , C n F 2n+1 SO3 - , (C m F 2m+1 SO2)(C n F 2n+1 SO2)N - Here, m and n each independently represent an integer of 0 or greater. There are no particular limitations on the upper limits of m and n, but from the viewpoint of ensuring good anion mobility, it is preferable that each be 4 or less. That is, it is preferable that m and n each independently be an integer of 0 or greater and 4 or less. The anions listed above may be used alone or in combination of two or more. m F 2m+1 SO2)(C n F 2n+1 SO2)N -Among the anions represented by the formula (1), anions in which both m and n are 1 or more are preferred because they are highly hydrophobic and less susceptible to the influence of humidity on mobility. Furthermore, among these, anions represented by the following structural formula (3) are more preferred. This is because a small anion size leads to high ion mobility, which is advantageous for reducing the resistance of the elastic layer.

[0044] [ka]

[0045] The presence of the first cation, second cation, and anion in the elastic layer can be confirmed by immersing the elastic layer in a solvent such as methanol or methyl ethyl ketone (MEK), extracting the components dissolved in the solvent, and analyzing them. Examples of analytical methods include liquid chromatography mass spectrometry and nuclear magnetic resonance spectroscopy.

[0046] The total amount of the first cations and the second cations per 100 g of silicone rubber in the elastic layer is preferably 0.3 mmol to 18 mmol. By keeping the total amount of the first cations and the second cations relative to the silicone rubber in the elastic layer within this range, it becomes easy to adjust the volume resistivity of the elastic layer within the semiconductive region. Here, the volume resistivity of the elastic layer can be adjusted by adjusting the amount of the first and second cations and anions added, the ratio of the first cations to the second cations, the amount of filler added (described below), and the like. When the base layer is conductive as described above, the ratio of the volume resistivity of the elastic layer to the volume resistivity of the base layer (volume resistivity of the elastic layer / volume resistivity of the base layer) is preferably 0.01 to 100. Regarding volume resistivity, the semiconductive region is 1.0 × 10 8 Ω cm or more 2.0×10 11 The range is Ω·cm or less.

[0047] (additives) The elastic layer according to the present disclosure may contain additives such as fillers, colorants, crosslinking accelerators, crosslinking retarders, crosslinking aids, scorch inhibitors, antiaging agents, softeners, heat stabilizers, scavengers, flame retardants, flame retardant aids, ultraviolet absorbers, rust inhibitors, and electronic conductive agents, within the scope that does not impair the effects according to the present embodiment.

[0048] Examples of the filler include reinforcing fillers such as fumed silica, crystalline silica, wet silica, fumed titanium oxide, cellulose nanofiber, etc. Since the reinforcing filler is easily dispersed in the silicone rubber, it may be surface-modified with an organosilicon compound such as an organoalkoxysilane, an organohalosilane, an organosilazane, a diorganosiloxane oligomer in which both molecular chain terminals are blocked with silanol groups, or a cyclic organosiloxane. Among these, hydrophilic silica is preferred because it can significantly adjust the viscosity of the addition-curing liquid silicone rubber mixture used to form the elastic layer. Here, hydrophilic silica specifically refers to silica with a pH value of 7.0 or less, particularly 3.5 to 5.0. Examples of such hydrophilic silica include "AEROSIL 90" (pH: 3.7-4.7), "AEROSIL 130" (pH: 3.7-4.5), "AEROSIL 150" (pH: 3.7-4.5), "AEROSIL 200" (pH: 3.7-4.5), "AEROSIL 255" (pH: 3.7-4.5), "AEROSIL 300" (pH: 3.7-4.5), and "AEROSIL 380" (pH: 3.7-4.5), all of which are product names manufactured by Nippon Aerosil Co., Ltd.

[0049] Examples of electronic conductive agents include conductive carbon black such as acetylene black and ketjen black, graphite, graphene, carbon fiber, carbon nanotubes, metal powder such as silver, copper, and nickel, conductive zinc oxide, conductive calcium carbonate, conductive titanium oxide, conductive tin oxide, and conductive mica. However, when an electronic conductive agent is contained in the elastic layer according to this embodiment, the voltage dependence of the elastic layer tends to increase, and therefore it is preferable that the electronic conductive agent is not contained, or if it is contained, it is contained in an amount that hardly exhibits electronic conductivity.

[0050] As the other additives, known additives can be appropriately selected and used.

[0051] The hardness of the elastic layer is preferably 20 to 80 degrees, and more preferably 45 to 80 degrees, in Type A hardness. In addition, the thickness of the elastic layer is preferably 50 to 500 μm, and more preferably 100 to 400 μm, taking into consideration mechanical strength and flexibility.

[0052] To further strengthen the adhesion between the base layer and the elastic layer, a primer may be applied to the outer surface of the base layer. The primer used here is a coating material in which a silane coupling agent, silicone polymer, hydrogenated methylsiloxane, alkoxysilane, reaction-accelerating catalyst, and colorant such as red iron oxide are appropriately blended and dispersed in an organic solvent. Commercially available primers can be used. Primer treatment is performed by applying the primer to the outer surface of the base layer and drying or baking it. The primer can be selected appropriately depending on the material of the base layer, the type of elastic layer, and the form of crosslinking reaction. In particular, when the elastic layer contains a large amount of unsaturated aliphatic groups, a primer containing hydrosilyl groups is preferably used to impart adhesion through reaction with the unsaturated aliphatic groups. An example of a commercially available primer with these characteristics is DY39-051A / B (trade name, manufactured by Dow Corning Toray Co., Ltd.). Furthermore, when the elastic layer contains a large amount of hydrosilyl groups, a primer containing an unsaturated aliphatic group is preferably used. A commercially available primer with such characteristics is DY39-067 (trade name, manufactured by Dow Corning Toray Co., Ltd.). Primers containing alkoxy groups are also suitable. Furthermore, by subjecting the surface of the base layer to a surface treatment such as ultraviolet irradiation, the crosslinking reaction between the base layer and the elastic layer can be promoted, further strengthening the adhesive strength. Other examples of primers include X-33-156-20, X-33-173A / B, and X-33-183A / B (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), and DY39-90A / B, DY39-110A / B, DY39-125A / B, and DY39-200A / B (all trade names, manufactured by Dow Corning Toray Co., Ltd.).

[0053] [Surface layer] The surface layer of an electrophotographic member is required to be resistant to abrasion caused by rubbing against a recording medium such as paper or various contact members such as a drum, and to have low adhesion so that toner and the like do not adhere. There are no particular restrictions on the resin used for the surface layer as long as it has low adhesion, and examples include fluororesins, fluorine-containing urethane resins, fluorine rubber, and siloxane-modified polyimides. Among these, the surface layer for an intermediate transfer belt is preferably made of a fluorine-containing urethane resin from the viewpoint of not impairing the elastic function of the elastic layer.

[0054] The thickness of the surface layer is preferably 0.5 μm to 20 μm, more preferably 1 μm to 10 μm. If the thickness of the surface layer is 0.5 μm or more, it is easy to suppress the loss of toner due to wear of the surface layer during use. Furthermore, if the thickness of the surface layer is 20 μm or less, the elastic function of the elastic layer is not impaired. The surface layer may contain the above-mentioned electronic conductive agent as needed. From the viewpoints of adhesion and mechanical strength, the content of the electronic conductive agent in the surface layer is preferably 30 parts by mass or less per 100 parts by mass of the surface layer. If necessary, a primer layer may be provided between the elastic layer and the surface layer. The thickness of the primer layer is preferably 0.1 μm or more and 15 μm or less, more preferably 0.5 μm or more and 10 μm or less, from the viewpoint of not impairing the elastic function.

[0055] <Electrophotographic image forming apparatus> An electrophotographic image forming apparatus according to one aspect of the present disclosure includes the electrophotographic member according to the present disclosure as an intermediate transfer member (intermediate transfer belt). An example of an embodiment of the electrophotographic image forming apparatus will be described with reference to FIG. The electrophotographic image forming apparatus of this embodiment has a so-called tandem configuration in which image forming stations of multiple colors are arranged side by side in the rotation direction of an electrophotographic endless belt (hereinafter referred to as an "intermediate transfer belt"). In the following description, the symbols for the components of each color, yellow, magenta, cyan, and black, are given suffixes Y, M, C, and k, respectively, but the suffixes may be omitted for similar components.

[0056] In FIG. 2, reference symbols 1Y, 1M, 1C, and 1k denote photosensitive drums (photoconductors, image carriers). Around the photosensitive drum 1, charging devices 2Y, 2M, 2C, and 2k, exposure devices 3Y, 3M, 3C, and 3k, developing devices 4Y, 4M, 4C, and 4k, and an intermediate transfer belt (intermediate transfer member) 6 are arranged. The photosensitive drum 1 is rotated in the direction of arrow F at a predetermined peripheral speed (process speed). The charging device 2 charges the peripheral surface of the photosensitive drum 1 to a predetermined polarity and potential (primary charging). The exposure device 3, a laser beam scanner, outputs on / off-modulated laser light in response to image information input from an external device such as an image scanner or computer (not shown), scanning and exposing the charged surface of the photosensitive drum 1. This scanning and exposure forms an electrostatic latent image on the surface of the photosensitive drum 1 according to the desired image information.

[0057] The developing devices 4Y, 4M, 4C, and 4k contain toner of each color component: yellow (Y), magenta (M), cyan (C), and black (k), respectively. The developing device 4 to be used is selected based on image information, and developer (toner) is developed on the photosensitive drum 1, visualizing the electrostatic latent image as a toner image. In this embodiment, a reversal development method is used in which toner is deposited on the exposed portion of the electrostatic latent image to develop it. The charging device, exposure device, and developing device constitute an image forming means.

[0058] The intermediate transfer belt 6 is an electrophotographic endless belt according to the present disclosure, arranged to contact the surface of the photosensitive drum 1 and stretched around multiple tension rollers 20, 21, and 22. It rotates in the direction of arrow G. In this embodiment, the tension roller 20 is a tension roller that maintains a constant tension on the intermediate transfer belt 6, the tension roller 22 is a drive roller for the intermediate transfer belt 6, and the tension roller 21 is an opposing roller for secondary transfer. Primary transfer rollers 5Y, 5M, 5C, and 5k are disposed at primary transfer positions facing the photosensitive drum 1 across the intermediate transfer belt 6. The unfixed toner images of each color formed on the photosensitive drum 1 are electrostatically and primarily transferred onto the intermediate transfer belt 6 by applying a primary transfer bias of a polarity opposite to the toner charge polarity (e.g., positive polarity) to the primary transfer roller 5 from a constant voltage or constant current source. A full-color image is then obtained on the intermediate transfer belt 6, with the unfixed toner images of four colors superimposed on top of each other. The intermediate transfer belt 6 rotates while carrying the toner image thus transferred from the photosensitive drum 1. After the primary transfer, the surface of the photosensitive drum 1 is cleaned of residual toner by cleaning devices 11Y, 11M, 11C, and 11k, and the image formation process is repeated.

[0059] At the secondary transfer position of the intermediate transfer belt 6 facing the conveyance path of the recording material 7, a secondary transfer roller (transfer unit) 9 is disposed in pressure contact with the toner image bearing surface of the intermediate transfer belt 6. At the secondary transfer position, on the back side of the intermediate transfer belt 6, a counter roller 21 is disposed, which serves as an opposing electrode to the secondary transfer roller 9 and to which a bias is applied. When the toner image on the intermediate transfer belt 6 is transferred to the recording material 7, a bias of the same polarity as the toner is applied to the counter roller 21 by a secondary transfer bias application unit 28. A voltage of, for example, −1000 to −3000 V is applied to the counter roller 21, causing a current of −10 to −50 μA to flow. The transfer voltage at this time is detected by a transfer voltage detection unit 29. A cleaning device (belt cleaner) 12 is disposed downstream of the secondary transfer position to remove toner remaining on the intermediate transfer belt 6 after the secondary transfer. The recording material 7 introduced from the registration roller pair 8 to the secondary transfer position is sandwiched and transported at the secondary transfer position, and at this time, a predetermined controlled constant voltage bias (transfer bias) is applied from secondary transfer bias application means 28 to the opposing roller 21 of the secondary transfer roller 9. By applying a transfer bias of the same polarity as the toner to the opposing roller 21, the four-color full-color image (toner image) superimposed on the intermediate transfer belt 6 at the transfer position is transferred all at once to the recording material 7, and an unfixed full-color toner image is formed on the recording material. The recording material 7 to which the toner image has been transferred is transported from the secondary transfer position in the direction of arrow H and introduced into a fixing unit (not shown) where it is heated and fixed. [Example]

[0060] The ionic conductive agents used in each of the examples and comparative examples are shown in Table 1 below.

[0061] [Table 1]

[0062] <Production of electrophotographic belt> [Example 1-1] (Formation of the base layer) The following materials were each fed into a twin-screw kneader (trade name: PCM30, manufactured by Ikegai Corporation) using a gravimetric feeder and kneaded. The cylinder temperature of the twin-screw kneader was set to 320°C at the material feeding point and 360°C downstream of the cylinder and the die. The screw rotation speed of the twin-screw kneader was 300 rpm, and the material feed rate was 8 kg / h. The resulting kneaded product was cut to prepare resin pellets. Polyether ether ketone (product name: VICTREXPEEK450G, manufactured by Victrex): 75 parts by weight Acetylene black (product name: Denka Black Granules, manufactured by Denka Co., Ltd.): 25 parts by mass The resin pellets were then extruded cylindrically to produce an endless belt-shaped base layer. The extrusion was performed using a single-screw extruder (product name: GT40, manufactured by Plastics Engineering Research Institute Co., Ltd.) equipped with a cylindrical die having a ring-shaped opening with a diameter of 300 mm and a gap of 1 mm at the tip. Specifically, resin pellets were fed into a single-screw extruder at a rate of 4 kg / h using a gravimetric feeder. The cylinder temperature setting of the single-screw extruder was 320°C at the material inlet, and 380°C downstream of the cylinder and the cylindrical die. The resin tube extruded from the cylindrical die was taken up by a cylindrical take-up machine so as to have a thickness of 60 μm. During the take-up process, the resin tube was brought into contact with a cooling mandrel installed between the cylindrical die and the cylindrical take-up machine, whereby it was cooled and solidified. The solidified resin tube was cut by a cylindrical cutter installed below the cylindrical take-up machine so that the length (width) in the direction perpendicular to its circumferential direction was 400 mm. In this way, an endless belt-shaped base layer according to this example was produced. The volume resistivity of the base layer thus obtained was 1.0 × 10 9 The volume resistivity of the base layer was measured in the same manner as in the measurement of the volume resistivity of the electrophotographic belt, which will be described later.

[0063] (Formation of elastic layer) To 100 parts by mass of addition-curing liquid silicone rubber (trade name: TSE3450 A / B, manufactured by Momentive Performance Materials, Inc.), 5.2 parts by mass of ammonium 1 (8.0 mmol per 100 g of silicone rubber) and 0.76 parts by mass of ammonium 3 (2.0 mmol per 100 g of silicone rubber) were added as ionic conductive agents and mixed. Next, 3.0 parts by mass of hydrophilic silica (trade name: AEROSIL380, manufactured by Nippon Aerosil Co., Ltd.) and 1.0 part by mass of black colorant (trade name: LIMS Color 02, manufactured by Shin-Etsu Chemical Co., Ltd.) were added. The mixture was then stirred and degassed using a planetary stirring and degassing device (trade name: HM-500, manufactured by Keyence Corporation) to obtain an addition-curing liquid silicone rubber mixture. Next, the outer surface of the base layer was subjected to ultraviolet irradiation, after which a primer (product name: DY39-051, manufactured by Dow Corning Toray Co., Ltd.) was applied and dried by heating. The base layer with the primer layer formed on its outer surface was attached to a cylindrical core, and a ring nozzle for discharging rubber was attached coaxially with the core. The addition-curing liquid silicone rubber mixture was supplied to the ring nozzle using a liquid feed pump and discharged through a slit, forming a layer of the addition-curing liquid silicone rubber mixture on the base layer. The relative movement speed and the discharge rate of the liquid feed pump were adjusted so that the cured elastic layer would be 280 μm thick. The core-attached base layer was placed in a heating furnace and heated at 130°C for 15 minutes, then at 180°C for 60 minutes, curing the layer of the addition-curing liquid silicone rubber mixture to form an elastic layer.

[0064] (Formation of surface layer) A fluorine-containing polyurethane resin liquid (trade name: Emralon T-861, manufactured by Henkel Japan) in which polytetrafluoroethylene was dispersed in a polyurethane dispersion was prepared. The outer surface of the elastic layer was then hydrophilized by excimer UV irradiation. The base layer on which the elastic layer was formed was then fitted into a core, and while rotating at 200 rpm, the polyurethane resin liquid was applied using a spray gun (trade name: W-101, manufactured by Anest Iwata Corporation) to form a coating of the polyurethane resin liquid on the elastic layer. The base layer with the coating formed on its outer surface was then placed in a heating furnace at 130°C while still attached to the core, and heated for 30 minutes to harden the coating and form a surface layer. Thus, an electrophotographic belt was obtained, comprising a base layer, an elastic layer on the outer peripheral surface of the base layer, and a 3 μm-thick surface layer on the outer surface of the elastic layer.

[0065] (Identification of ammonium 1 and ammonium 3 in the elastic layer) The ammonium 1 and ammonium 3 contained in the elastic layer of the electrophotographic belt prepared above were identified by the following method. A 200 mg sample was taken from the elastic layer of the electrophotographic belt. The sample was immersed in 1 mL of methanol, and 40 kHz ultrasound was applied to the methanol containing the sample for 10 minutes. The methanol containing the sample was then centrifuged at 12,000 rpm for 10 minutes using a high-speed centrifuge (Model 7780, manufactured by Kubota Shoji Co., Ltd.). The supernatant was collected to prepare a cation and anion extract. Subsequently, mass spectrometry of the cation and anion extract was performed using a liquid chromatography mass spectrometer (Thermo Scientific LTQ Orbitrap XL, manufactured by Thermo Fisher Scientific) under the following conditions: [Mass spectrometry conditions] ·Direct introduction method ·Injection volume: 2μL Ionization method: Electrospray ionization (ESI)

[0066] Mass spectrometry confirmed that peaks were present at the positions corresponding to the molecular weights of two cations and one anion of the two ion conductive agents (ammonium 1 and ammonium 3) used in producing the elastic layer.

[0067] After removing the methanol solvent from the cation and anion extract, the solution was redissolved in deuterated methanol. 1 Measurement was performed using H-NMR (trade name: AL400 type FT-NMR, manufactured by JEOL Ltd.). [Measurement conditions] Frequency: 400MHz Number of times accumulated: 32 ·Measurement temperature: 25℃

[0068] The obtained spectral peaks were assigned to the protons of the cation structure of ammonium 1 and the cation structure of ammonium 3. From the above, ammonium 1 and ammonium 3 contained in the elastic layer were identified.

[0069] [Examples 1-2 to 1-8, Reference Examples 1-1 to 1-8-3] Electrophotographic belts according to Examples 1-2 to 1-8 and Reference Examples 1-1 to 1-8-3 were obtained in the same manner as in Example 1-1, except that the type and composition of the ionic conductive agent used were changed as shown in Tables 2-1 to 2-5 below. In the tables, the units of values ​​are mmol of each ionic conductive agent per 100 g of silicone rubber.

[0070] [Table 2-1]

[0071] [Table 2-2]

[0072] [Table 2-3]

[0073] [Table 2-4]

[0074] [Table 2-5]

[0075] [Comparative Example 1, Reference Examples 9-1 to 9-2] Electrophotographic belts according to Comparative Example 1 and Reference Examples 9-1 and 9-2 were obtained in the same manner as in Example 1-1, except that the type and composition of the ionic conductive agent used were changed as shown in Table 2-6 below. In the table, the units of values ​​are mmol of each ionic conductive agent per 100 g of silicone rubber.

[0076] [Table 2-6]

[0077] <Evaluation> [Volume resistivity measurement] The volume resistivity ρv of each of the electrophotographic belts according to the above-mentioned Examples, Reference Examples and Comparative Examples was measured as follows. That is, the volume resistivity value was defined as the average value of values ​​obtained by measuring 58 points at 20 mm intervals for each electrophotographic belt having a circumference of 1147 mm. The volume resistivity was measured in accordance with Japanese Industrial Standards (JIS) K6271-1:2015, "Vulcanized rubber and thermoplastic rubber - Determination of electrical resistivity - Part 1: Double ring electrode method," using a high resistivity meter (product name: Hiresta MCP-HT450, manufactured by Nitto Seiko Analytech Co., Ltd.). A "UR probe" was used as the electrode, and the value measured when a voltage of 100 V was applied for 10 seconds was used. The measurement was performed in an environment with a temperature of 25°C and a relative humidity of 55%.

[0078] [Evaluation of low resistance] The volume resistivity reduction effect of each Example was evaluated by comparing it with the measurement results of the corresponding Reference Example. Specifically, the value obtained by subtracting the common logarithm LOG(P) of the measured volume resistivity P in each Example from the common logarithm LOG(Q) of the smallest measured volume resistivity Q of the two or three Reference Examples corresponding to each Example was evaluated according to the following criteria. (Low resistance evaluation criteria) Rank A: (LOG(Q)-LOG(P)≧0.4) Rank B: (0.4>LOG(Q)-LOG(P)≧0.1) Rank C: (LOG(Q)-LOG(P)<0.1)

[0079] The evaluation results are shown in Tables 3-1 to 3-6. In Tables 3-1 to 3-6, X represents the number of moles of the first cation, and Y represents the number of moles of the second cation. However, in Comparative Example 1 and Reference Examples 9-1 and 9-2, the first cation was not used, so the number of moles of ammonium 2 was taken as X, and the number of moles of ammonium 3 was taken as Y. In Tables 3-1 to 3-6, the value of LOG(Q)-LOG(P) is shown in the column "Effect of reducing resistance."

[0080] [Table 3-1]

[0081] [Table 3-2]

[0082] [Table 3-3]

[0083] [Table 3-4]

[0084] [Table 3-5]

[0085] [Table 3-6]

[0086] The present disclosure includes the following configurations. [Configuration 1] An electrophotographic member having a base layer and an elastic layer on the base layer, The elastic layer is Silicone rubber, At least one first cation selected from the group consisting of cations represented by the following structural formulas (1-1) to (1-2): At least one second cation selected from the group consisting of cations represented by the following structural formulas (2-1) to (2-2), and anions An electrophotographic member comprising:

[0087] [ka]

[0088] (In structural formulas (1-1) to (1-2), R1 to R8 each independently represent an alkyl group having 1 to 14 carbon atoms. However, at least three of the alkyl groups represented by R1 to R4 and at least three of the alkyl groups represented by R5 to R8 have a linear portion having 6 or more carbon atoms.)

[0089] [ka]

[0090] (In structural formulas (2-1) to (2-2), R9 to R 16 each independently represents an alkyl group having 1 to 4 carbon atoms.

[0091] [Configuration 2] The anion is F - , Cl- , Br - , I - , AlCl4 - , NO3 - , BF4 - , PF6 - , AsF6 - , SbF6 - , CH3COO - , CF3COO - , (C2F5)3PF3 - , C n F 2n+1 SO3 - , and (C m F 2m+1 SO2)(C n F 2n+1 SO2)N - (wherein m and n each independently represent an integer of 0 to 4) is at least one selected from the group consisting of: [Configuration 3] The electrophotographic member according to Constitution 2, wherein the anion is an anion represented by the following structural formula (3):

[0092] [ka]

[0093] [Configuration 4] The electrophotographic member according to any one of configurations 1 to 3, wherein the alkyl groups represented by R1 to R4 are not all the same alkyl group, and the alkyl groups represented by R5 to R8 are not all the same alkyl group. [Configuration 5] The electrophotographic member according to Configuration 4, wherein, among the alkyl groups represented by R1 to R4, three have a linear portion having 6 or more carbon atoms, and the remaining one does not have a linear portion having 6 or more carbon atoms; and among the alkyl groups represented by R5 to R8, three have a linear portion having 6 or more carbon atoms, and the remaining one does not have a linear portion having 6 or more carbon atoms. [Configuration 6] 6. The electrophotographic member according to any one of Configurations 1 to 5, wherein X / (X+Y) is 0.2 or more and 0.7 or less, where X is the number of moles of the first cations contained in the elastic layer, and Y is the number of moles of the second cations. [Configuration 7] 7. The electrophotographic member according to any one of configurations 1 to 6, wherein the total amount of the first cation and the second cation relative to 100 g of the silicone rubber contained in the elastic layer is 0.3 mmol or more and 18 mmol or less. [Configuration 8] 8. The electrophotographic member according to any one of Configurations 1 to 7, wherein the elastic layer is a cured product of an addition-curing liquid silicone rubber mixture containing an addition-curing liquid silicone rubber, the first cation, the second cation, and the anion. [Configuration 9] 9. The electrophotographic member according to any one of configurations 1 to 8, wherein the electrophotographic member is an electrophotographic belt having an endless belt shape. [Configuration 10] An electrophotographic image forming apparatus comprising the electrophotographic member according to any one of the first to ninth aspects as an intermediate transfer member. [Explanation of symbols]

[0094] 101 First Cation 102 Anions 103 Second Cation 300 Electrophotographic Belt 301 Elastic layer 302 Base layer

Claims

1. An electrophotographic member having a base layer and an elastic layer on the base layer, The elastic layer is Silicone rubber, At least one first cation selected from the group consisting of cations represented by the following structural formulas (1-1) to (1-2): At least one second cation selected from the group consisting of cations represented by the following structural formulas (2-1) to (2-2), and anions an electrophotographic member comprising: 【Chemical 1】 (In structural formulas (1-1) to (1-2), R １ ~R ８ Each independently represents an alkyl group having 1 to 14 carbon atoms. １ ~R ４ and at least three of the alkyl groups represented by R ５ ~R ８ At least three of the alkyl groups represented by the formula (I) have a linear portion having 6 or more carbon atoms. 【Chemistry 2】 (In structural formulas (2-1) to (2-2), R ９ ~R １６ each independently represents an alkyl group having 1 to 4 carbon atoms.

2. The anion is F － , Cl － ,Br － , I － , AlCl ４ － , NO ３ － , B.F. ４ － , P.F. ６ － , AsF ６ － , SbF ６ － , C.H. ３ COO － , C.F. ３ COO － , (C ２ F ５ ) ３ PF ３ － , C ｎ F ２ｎ＋１ SO ３ － , and (C ｍ F ２ｍ＋１ SO ２ ) (C ｎ F ２ｎ＋１ SO ２ ) N － 2. The electrophotographic member according to claim 1, wherein m and n each independently represent an integer of 0 to 4.

3. 3. The electrophotographic member according to claim 2, wherein the anion is an anion represented by the following structural formula (3): 【Chemistry 3】

4. The R １ ~R ４ The alkyl groups represented by R ５ ~R ８ 2. The electrophotographic member of claim 1, wherein all of the alkyl groups represented by the formula: are not the same alkyl group.

5. The R １ ~R ４ Among the alkyl groups represented by the formula (I), three have a linear portion having 6 or more carbon atoms, and the remaining one does not have a linear portion having 6 or more carbon atoms, ５ ~R ８ 5. The electrophotographic member according to claim 4, wherein three of the alkyl groups represented by the following formula have a straight chain portion having 6 or more carbon atoms, and the remaining one does not have a straight chain portion having 6 or more carbon atoms.

6. 2. The electrophotographic member according to claim 1, wherein, when the number of moles of the first cations contained in the elastic layer is X and the number of moles of the second cations is Y, X / (X+Y) is 0.2 or more and 0.7 or less.

7. 2. The electrophotographic member according to claim 1, wherein the total amount of the first cations and the second cations relative to 100 g of the silicone rubber contained in the elastic layer is 0.3 mmol or more and 18 mmol or less.

8. 2. The electrophotographic member according to claim 1, wherein the elastic layer is a cured product of an addition-curing liquid silicone rubber mixture containing an addition-curing liquid silicone rubber, the first cation, the second cation, and the anion.

9. 2. The electrophotographic member according to claim 1, wherein the electrophotographic member is an electrophotographic belt having an endless belt shape.

10. 10. An electrophotographic image forming apparatus comprising the electrophotographic member according to claim 1 as an intermediate transfer member.

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