Electrophotographic member and electrophotographic image forming device

Abstract

Provided is an electrophotographic member which is excellent in terms of consideration for the environment and contributes to the formation of a high-quality electrophotographic image over a long period of time. This electrophotographic member has at least a base layer and a surface layer and is characterized in that the surface layer contain the flowing A, B, and C.　A: a compound 1 having a structure represented by formula (I) and a structure represented by formula (II), B: perfluoropolyether, and C: a binder resin. In formula (I), R11 represents a hydrogen atom or a methyl group, R12 represents a single bond or an alkylene group having 1 to 3 carbon atoms, and Rf1 represents a perfluoroalkyl group having 1 to 4 carbon atoms. In formula (II), R21 represents a hydrogen atom or a methyl group, R22 represents a single bond or an alkylene group having 1 to 3 carbon atoms, and Rt1 represents a structure having a bicyclic monoterpene.

Description

Electrophotographic member and electrophotographic image forming apparatus

[0001] The present invention relates to an electrophotographic member used as an intermediate transfer member in an electrophotographic image forming apparatus such as a copying machine or a printer, and to an electrophotographic image forming apparatus equipped with the electrophotographic member.

[0002] In electrophotographic image forming apparatuses, a tandem system is widely adopted in which toner images of yellow (Y), magenta (M), cyan (C), and black (K) are superimposed on an intermediate transfer belt as an intermediate transfer member, and then transferred all at once onto paper to obtain a full-color image.

[0003] The intermediate transfer belt used here is generally a semiconductive belt, and a typical example is a belt formed by dispersing carbon black in a resin such as polyimide or polyamideimide. In this context, electrophotographic devices that require high speed and high durability are required to further improve the transfer characteristics of the intermediate transfer belt. One proposal has been made to reduce the adhesion of toner to the surface of the surface layer by incorporating an oil-like perfluoropolyether (hereinafter also referred to as "PFPE"), which has a very low surface free energy, into the surface layer of the intermediate transfer belt.

[0004] Paragraph 0071 of Patent Document 1 discloses the use of a compound having a perfluoroalkyl chain and a moiety with affinity for hydrocarbons as a dispersant to effectively disperse PFPE in the matrix resin in the surface layer. The longer the carbon number of the perfluoroalkyl group, the higher the affinity for PFPE. Therefore, from the perspective of PFPE dispersibility, compounds having a perfluoroalkyl chain with a long carbon number are advantageous. However, compounds having a perfluoroalkyl chain with a long carbon number are persistent and tend to remain in the environment. In recent years, restrictions on the use of compounds with six consecutive fluorine-bonded carbon atoms, such as perfluorohexanoic acid (PFHxA), have been considered. Therefore, it has been proposed to use compounds with a structure in which the number of consecutive fluorine-bonded carbon atoms is four or less as a dispersant for PFPE, as a compound with a relatively high degradability in the perfluoroalkyl chain moiety. Patent Document 2 discloses the use of an acrylic resin having a side chain with an ether structure introduced so that the number of consecutive fluorine-bonded carbon atoms is three or less as a dispersant for PFPE.

[0005] JP 2013-231964 A JP 2022-167788 A

[0006] According to the studies of the present inventors, the fluorine-containing copolymer disclosed in Patent Document 2 ensures high adsorption to PFPE by having many fluorine atoms in the side chain portion while limiting the number of consecutive carbon atoms to which fluorine atoms are bonded to three or less. However, copolymers having such a structure have a complex structure in which perfluoroalkyl chains are separated by ether structures, and therefore are expensive.

[0007] At least one aspect of the present disclosure is directed to an electrophotographic member that is environmentally friendly and contributes to the formation of high-quality electrophotographic images over a long period of time. Also, at least one aspect of the present disclosure is directed to an electrophotographic image forming apparatus that can stably form high-quality electrophotographic images.

[0008] According to at least one embodiment of the present disclosure, there is provided an electrophotographic member having at least a base layer and a surface layer, wherein the surface layer contains the following A, B, and C: A: Compound 1 having a structure represented by the following formula (I) and a structure represented by the following formula (II), B: Perfluoropolyether, C: Binder resin In formula (I), R １１ represents a hydrogen atom or a methyl group, and R １２ represents a single bond or an alkylene group having 1 to 3 carbon atoms, and Rf １ represents a perfluoroalkyl group having 1 to 4 carbon atoms, and in formula (II), R ２１ represents a hydrogen atom or a methyl group, and R ２２ represents a single bond or an alkylene group having 1 to 3 carbon atoms; Rt １ indicates a structure having a polycyclic monoterpene.

[0009] Furthermore, according to at least one aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including an image carrier that carries a toner image, and an intermediate transfer member that secondarily transfers the toner image that has been primarily transferred from the image carrier to a recording material, wherein the intermediate transfer member is the electrophotographic member described above.

[0010] According to at least one aspect of the present disclosure, it is possible to provide an electrophotographic member that is environmentally friendly and contributes to the formation of high-quality electrophotographic images over a long period of time.Furthermore, according to at least one aspect of the present disclosure, it is possible to provide an electrophotographic image forming apparatus that can stably form high-quality electrophotographic images.

[0011] Fig. 1 is a cross-sectional view showing an example of an image forming apparatus using an electrophotographic belt. Fig. 2 is a diagram schematically showing a cross section of an electrophotographic belt. Fig. 3 is an explanatory diagram of an estimated mechanism of dispersion of PFPE by a compound according to the present disclosure. Fig. 4 is an explanatory diagram of the dispersion state of PFPE by a dispersant not having the structure of formula (II). Fig. 5 is a schematic diagram of an electrophotographic member according to a second aspect of the present disclosure.

[0012] In the present disclosure, expressions such as "XX or more and YY or less" or "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. Furthermore, when a numerical range is described in stages, the upper and lower limits of each numerical range can be combined arbitrarily. Furthermore, in the present disclosure, expressions such as "at least one selected from the group consisting of XX, YY, and ZZ" mean any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ. Furthermore, in the present disclosure, "Ω / □" is a unit of surface resistivity and means "Ω / square."

[0013] The present inventors have conducted extensive research to obtain a compound that is exempt from the regulations on perfluorohexanoic acid (PFHxA), has four or fewer consecutive carbon atoms to which fluorine atoms are bonded, has a simpler structure than the compound proposed in Patent Document 2, and is capable of dispersing PFPE well in a (meth)acrylic resin. As a result, they have found that compounds having the structure represented by the following formula (I) and the structure represented by the following formula (II) are effective in achieving the above object.

[0014] In formula (I), R １１ represents a hydrogen atom or a methyl group, and R １２ represents a single bond or an alkylene group having 1 to 3 carbon atoms, and Rf １ represents a perfluoroalkyl group having 1 to 4 carbon atoms. ２１ represents a hydrogen atom or a methyl group, and R ２２ represents a single bond or an alkylene group having 1 to 3 carbon atoms; Rt １ indicates a structure having a polycyclic monoterpene.

[0015] The compounds having the structure represented by formula (I) and the structure represented by formula (II) described above have four or fewer consecutive carbon atoms bonded to fluorine atoms, and are therefore exempt from the regulations related to PFHxA, making them environmentally friendly. Here, because Rf1 is a perfluoroalkyl group having 1 to 4 carbon atoms, the adsorptivity to PFPE is reduced compared to the dispersant disclosed in Patent Document 2. However, as shown schematically in FIG. 3, Rt1 in the structure of formula (II) in the molecular chain 301 of compound 1 has a bulky structure, which is thought to cause steric hindrance, causing compound 1 to adsorb at a certain distance from PFPE. As a result, the proximity of PFPE domain 303 and PFPE domain 305 is also prevented. As a result, the dispersibility of PFPE in the surface layer is improved. For these reasons, it is believed that the compounds disclosed herein can effectively disperse PFPE in binder resins.

[0016] On the other hand, in the case of a dispersant not having the structure of formula (II), the steric hindrance caused by Rt1 does not act, and therefore, as shown in Figure 4, molecular chains 401 of the dispersant may be non-uniformly adsorbed to PFPE, and may not be able to prevent PFPE domain 403 from coming close to PFPE domain 405. As a result, it is thought that the PFPE domains coalesce to form a larger domain.

[0017] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the following embodiments may be changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions, and are not intended to limit the scope of the present invention to these alone.

[0018] [Electrophotographic Member] The electrophotographic member has at least a base layer and a surface layer. One embodiment of the electrophotographic member 7 according to the present disclosure is, for example, an endless electrophotographic belt having a two-layer structure of a base layer 31 and a surface layer 32 provided on the outer peripheral surface of the base layer 31, as shown in Figure 2. The surface layer 32 contains a binder resin 33 and a domain 34 containing PFPE.

[0019] The configuration of the electrophotographic member is not limited to the two-layer laminate described above, and may include, for example, a primer layer (not shown) between the base layer 31 and the surface layer 32 to improve adhesion, a stress relaxation layer to prevent cracking of the surface layer 32, or an intermediate layer to prevent bleeding (none of which are shown).

[0020] <Base Layer> The material constituting the base layer 31 is preferably a resin having the mechanical strength and flex resistance required for an intermediate transfer belt for an electrophotographic device. Specific examples include the following: polyamide, polyacetal, polyarylate, polycarbonate, polyphenylene ether, polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polysulfone, polyether sulfone, polyphenyl sulfide, polybutylene terephthalate, polyether ether ketone, polyvinylidene fluoride, polyvinyl fluoride, polyether amide copolymer, polyurethane copolymer, polyimide, polyamide imide, etc. The base layer 31 is formed from one of these resins or a mixture of these resins, and typically, a conductive substance can be added to impart conductivity. The base layer preferably contains polyimide, which imparts excellent strength to the base layer.

[0021] As the conductive material, inorganic conductive particles such as carbon black, carbon fiber, and carbon nanotubes, and conductive particles such as metal oxide particles such as zinc antimonate particles, zinc oxide particles, tin oxide particles, and titanium oxide particles are used. By blending such conductive materials, the volume resistivity can be increased to 1×10 ８ ~1 x 10 １２ It is preferable that the surface resistivity is adjusted to the range of 1×10 ８ ~1 x 10 １４ It is preferable that the resistance is adjusted to within the range of [Ω / □].

[0022] Volume resistivity is 10 １２ When the volume resistivity is 10 [Ω·cm] or less, the primary transferability or secondary transferability by applying a predetermined transfer bias is good. ８When the surface resistivity of the base layer is [Ω·cm] or more, uneven resistance is small, and image defects such as uneven transfer are unlikely to occur. Furthermore, by setting the surface resistivity of the base layer within the above range, it is possible to reduce image defects caused by separation discharge when the recording material separates from the intermediate transfer belt and toner scattering. The thickness of the base layer 31 is preferably 40 μm to 200 μm in order to obtain excellent mechanical strength and flex resistance.

[0023] It is also preferable that the electrical resistance of the electrophotographic member for electrophotography after forming the surface layer on the base layer exhibits a similar value. For this reason, it is preferable that the surface layer of the electrophotographic member is also semiconductive. That is, the volume resistivity of the surface layer of the electrophotographic member is 10 ８ ~10 １２ It is preferable that the surface resistivity is adjusted to the range of 10 [Ω cm]. ８ ~10 １４ It is preferable that the surface layer contains a conductive agent to adjust the volume resistivity and surface resistivity of the electrophotographic member. The conductive agent contained in the surface layer may be the same as the conductive agent (conductive substance) that can be used in the base layer.

[0024] <Surface Layer> The surface layer 32 is formed on the outer peripheral surface side of the base layer 31 and is the outermost layer of the electrophotographic member. The surface layer contains the following A, B, and C: A: Compound 1 having a structure represented by formula (I) and a structure represented by formula (II), B: Perfluoropolyether, C: Binder resin

[0025] In addition to the above-described A, B, and C, the surface layer 32 may contain other materials such as a photopolymerization initiator and a conductive substance, provided that the effects of the present disclosure are not impaired. Whether the domains contain PFPE (preferably as a main component) can be confirmed by observing fragments of fluorocarbon ether structures derived from PFPE from the domains using energy dispersive X-ray analysis (EDX) or TOF-SIMS.

[0026] Preferably, the domain containing PFPE and the binder resin are phase-separated in the surface layer 32. For example, the surface layer is phase-separated into the domain containing PFPE and the matrix containing the binder resin.

[0027] In the surface layer of the electrophotographic member according to the first aspect of the present disclosure, by using Compound 1 according to A above, domains containing PFPE can be finely dispersed in a matrix containing a binder resin throughout the thickness direction of the surface layer. This allows PFPE to be continuously present on the surface of the electrophotographic member. That is, an intermediate transfer belt having PFPE on its outer surface, which is the toner image bearing surface, exhibits excellent secondary transfer performance, but the PFPE on the outer surface disappears after being used for forming electrophotographic images over a long period of time. Therefore, in order to continuously maintain high secondary transfer performance, it is preferable to supply PFPE from the inside. To this end, it is effective to have PFPE present in the form of domains in the thickness direction of the surface layer. Furthermore, by using Compound 1 according to A above, fine domains of PFPE can be present in the thickness direction of the surface layer.

[0028] Use of Compound 1 according to the present disclosure can effectively suppress the aggregation of PFPE molecules in a coating material for forming a surface layer. As a result, when a cross-section of the surface layer is observed using a scanning electron microscope, the average major axis of PFPE-containing domains can be small, such as 1 to 70 nm, and particularly 25 to 70 nm, in the surface layer. By allowing PFPE-containing domains of such sizes to be present in the surface layer, the surface gloss of the surface layer can be high, for example, 70 to 90 GU (Gloss Unit), particularly 75 to 85 GU, as measured at an incident angle of 20°. Increasing the surface gloss of an electrophotographic member is advantageous, for example, in detecting toner images (patch images) with high accuracy for controlling image formation conditions when the electrophotographic member is used as an intermediate transfer member.

[0029] Although it is preferable that the domains are substantially composed of PFPE, chemical species other than PFPE may be present in addition to PFPE in the domains, and additives compatible with PFPE may be added to adjust other properties, as long as the effects of the present disclosure are exhibited. Furthermore, even if the domains are not completely filled with PFPE and voids exist, the effects of the present disclosure can be exhibited.

[0030] Generally, even when phase separation occurs, the component compositions of the two phases are not strictly defined. Even when phase separation occurs with a clear interface, each phase may contain a trace amount of the component of the other phase. It is also academically said that an intermediate composition exists at the interface with a very narrow width of around 10 nm.

[0031] In the electrophotographic member according to the second aspect of the present disclosure, as shown in FIG. 5 , in the surface layer 32, some of the domains 501 containing PFPE are interconnected (interconnected), forming PFPE flow paths indicated by arrows 505 in a matrix 503 containing a binder resin. In a surface layer having such a configuration, the PFPE in the surface layer can be more stably transferred to the surface 507 of the surface layer. Therefore, when the electrophotographic member is used as an intermediate transfer belt, the PFPE on the surface of the surface layer is less likely to be depleted, even when multiple electrophotographic images are formed. The interconnected structure of the domains can be confirmed by cutting a sample from the surface layer, exposing the cross section of the surface layer in the entire thickness direction, removing the PFPE, and then observing the surface of the sample corresponding to the cross section of the surface layer in the thickness direction and the surface corresponding to the outer surface of the surface layer using a scanning electron microscope (SEM). The method of removing the PFPE will be described later.

[0032] Here, the interconnected structure will be described. By having a large number of domains containing PFPE present in the thickness direction of the surface layer, as in the surface layer according to the first embodiment, the PFPE can be gradually exuded to the surface of the surface layer, thereby continuously maintaining high toner releasability on the surface of the surface layer. However, when individual domains exist independently, the migration rate of PFPE to the surface may be slow. That is, if the PFPE on the surface of the surface layer disappears after forming a large number of electrophotographic images, it is expected that it will take time for the high toner releasability of the surface of the surface layer to be restored. Therefore, by interconnecting the domains containing PFPE in the surface layer, the PFPE present inside the surface layer can be more efficiently migrated to the outer surface of the surface layer. As a result, high secondary transfer performance can be maintained more stably.

[0033] Although it is preferable that the domains are substantially composed of PFPE, chemical species other than PFPE may be present in addition to PFPE in the domains, and additives compatible with PFPE may be added to adjust other properties, as long as the effects of the present disclosure are exhibited. Furthermore, even if the domains are not completely filled with PFPE and voids exist, the effects of the present disclosure can be exhibited.

[0034] A preferred embodiment of the interconnected structure will now be described. In an electrophotographic member, perfluoropolyether is removed from a surface layer to produce a perfluoropolyether-removed surface layer. The surface layer from which the perfluoropolyether has been removed preferably has voids with openings on its outer surface. The ratio of the total volume of the voids to the volume of the surface layer from which the perfluoropolyether has been removed, assuming that it is solid (void volume ratio), is preferably 8.0 to 25.0%, more preferably 10.0 to 20.0%, and even more preferably 13.0 to 20.0%.

[0035] When the void volume ratio is within the above range, the domains are easily connected to each other, and PFPE is easily supplied to the outermost surface for a longer period of time.The void volume ratio can be increased by the domains containing PFPE being connected to each other in the process of forming the surface layer.Therefore, in order to increase the void volume ratio, it is effective to use a low-viscosity PFPE as the PFPE used for forming the surface layer, and / or to increase the temperature of the coating film of the surface layer forming paint when curing by UV irradiation in the process of forming the surface layer, thereby increasing the fluidity of PFPE.

[0036] In addition, even when the surface layer has a structure in which PFPE-containing domains are interconnected, compound 1 according to the present disclosure plays an important role. That is, as described above, the interconnected structure of PFPE-containing domains is formed by the interconnection of isolated PFPE-containing domains in the coating film of the surface layer-forming paint during the curing process of the coating film. In this case, if the size of the isolated PFPE-containing domains before interconnection is large, the size of the PFPE domains after interconnection will also be large. As a result, the gloss of the surface layer may increase. In addition, PFPE may migrate excessively to the surface of the surface layer, resulting in early depletion of PFPE. Therefore, it is preferable to reduce the size of the isolated PFPE-containing domains in the coating film of the surface layer-forming paint formed during the surface layer formation process. For this purpose, it is effective to use compound 1 according to the present disclosure.

[0037] The unit area (1 μm ) of the outer surface of the surface layer from which the perfluoropolyether has been removed ２ The ratio of the total area of ​​the openings per unit area (opening area ratio) is preferably 10.0 to 35.0%, more preferably 17.0 to 30.0%, and even more preferably 19.0 to 25.0%.

[0038] When the opening area ratio is within the above range, the rate at which PFPE migrates to the outer surface of the surface layer can be more favorably controlled.When the opening area ratio is 10.0% or more, the amount of PFPE exposed per unit time is appropriate, and the releasability is more likely to be improved.When the opening area ratio is less than 35.0%, PFPE is less likely to be depleted, and the releasability is more likely to be maintained for a longer period of time.The opening area ratio can be increased by lowering the viscosity of PFPE and increasing the temperature during UV treatment.Conversely, the opening area ratio can be decreased by increasing the viscosity of PFPE and decreasing the temperature during UV treatment.

[0039] In addition, the unit area (1 μm ) of the outer surface of the surface layer from which the perfluoropolyether has been removed ２The number of openings per 1 μm is preferably 10 to 500, more preferably 135 to 300, and even more preferably 140 to 250. ２ When the number of openings (number of openings / 1 μm) is within the above range, PFPE can be easily transferred uniformly to the outer surface of the surface layer. ２ Since the number of openings increases by improving the dispersibility of the PFPE domains (reducing the particle size), the number of openings can be increased by increasing the amount of dispersant added. Conversely, the number of openings can be reduced by reducing the amount of dispersant added and decreasing the dispersibility of the PFPE domains.

[0040] <Binder Resin> The surface layer contains a binder resin. Any binder resin known for use in electrophotographic members such as intermediate transfer belts can be used. The binder resin preferably contains at least one resin selected from the group consisting of (meth)acrylic resins and epoxy resins. The binder resin more preferably contains a (meth)acrylic resin. (Meth)acrylic resins are preferred from the viewpoints of dispersing PFPE, ensuring adhesion to the base layer 31, and ensuring mechanical strength properties. As the (meth)acrylic resin, methacrylic resins or acrylic resins are preferably used. Hereinafter, methacrylic resins and acrylic resins will be collectively referred to as (meth)acrylic resins.

[0041] Examples of polymerizable monomers for forming the (meth)acrylic resin include at least one selected from the group consisting of the following (i) and (ii). Preferably, at least one selected from the group consisting of the following (i). As the polymerizable monomer, those commercially available as paints can also be used.

[0042] (i) at least one acrylate selected from the group consisting of pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate, alkyl acrylate, benzyl acrylate, phenyl acrylate, ethylene glycol diacrylate, and bisphenol A diacrylate;

[0043] (ii) at least one methacrylate selected from the group consisting of pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, ditrimethylolpropane tetramethacrylate, dipentaerythritol hexamethacrylate, alkyl methacrylate, benzyl methacrylate, phenyl methacrylate, ethylene glycol dimethacrylate, and bisphenol A dimethacrylate;

[0044] Among these, high hardness is preferable in consideration of rubbing with other members such as a photoreceptor and a cleaning blade. Therefore, it is preferable to use a large amount of bifunctional or higher crosslinkable monomers in the (meth)acrylic resin to achieve higher hardness. In addition, to form a (meth)acrylic resin from such polymerizable monomers, there is a method in which a photopolymerization initiator is added and polymerization is carried out by electron beam or ultraviolet light.

[0045] Examples of the photopolymerization initiator include radical-generating photopolymerization initiators such as benzophenone, thioxanthone, benzyl dimethyl ketal, α-hydroxyketone, α-hydroxyalkylphenone, α-aminoketone, α-aminoalkylphenone, monoacylphosphine oxide, bisacylphosphine oxide, hydroxybenzophenone, aminobenzophenone, titanocene, oxime ester, and oxyphenylacetic acid ester. The content of the binder resin in the surface layer is preferably 20 to 90% by mass, and more preferably 40 to 70% by mass, based on the mass of the surface layer.

[0046] <Perfluoropolyether> Perfluoropolyether (PFPE) is an oligomer or polymer having perfluoroalkylene ether as a repeating unit. There are no particular limitations on the PFPE, and known PFPEs can be used. Preferable PFPEs include those having a structure represented by the following formula (III) in the molecule:

[0047] In formula (III), a, b, c, d, e, and f each independently represent 0 or a positive integer, satisfying 1≦a+b+c+d+e+f≦600, and at least one of a, b, c, and d being a positive integer. Furthermore, in formula (III), a plurality of repeating units may be present at a plurality of positions in the PFPE. That is, the PFPE represented by formula (1) may be a block copolymer or a random copolymer.

[0048] The perfluoropolyether preferably has at least one structure selected from the group consisting of the following formulae (IV) to (VII) in the molecule.

[0049] In formula (IV), n is a positive number.

[0050] In formula (V), n' is a positive number.

[0051] In formula (VI), n'' is a positive number.

[0052] In formula (VII), n''' and m' are each independently a positive number.

[0053] The viscosity of PFPE at a temperature of 20°C is preferably 100 mPa·s to 2500 mPa·s, more preferably 100 mPa·s to 1000 mPa·s. PFPE in this viscosity range contributes to stable migration of the surface layer to the surface. The viscosity of the PFPE can be measured, for example, using a Brookfield rotational viscometer, Type B, in accordance with Japanese Industrial Standards (JIS) K7117-1:1999.

[0054] Examples of commercially available PFPEs within the above viscosity range include "Fluorolink MD700" (viscosity 850 mPa / s) and "Fomblin D2" (viscosity 150 mPa s). Note that all of these PFPEs have the structure of formula (VI) in the molecule.

[0055] Here, when the surface layer is the surface layer according to the first embodiment, it is preferable to use a PFPE having a high viscosity within the above-mentioned viscosity range. Specifically, it is preferable to use a PFPE having a viscosity within the range of, for example, 350 to 2000 mPa·s, particularly 500 to 1000 mPa·s. By using a PFPE within this range, domains containing PFPE can be finely dispersed in the surface layer while being independent of each other. This makes it easier to supply PFPE to the surface for a longer period of time, and to maintain releasability for a long period of time. Furthermore, even if the domains containing PFPE exist independently of each other, they can stably migrate to the surface of the surface layer.

[0056] On the other hand, when the surface layer is the surface layer according to the second embodiment, it is preferable to use a PFPE having a low viscosity within the above range. Specifically, for example, a PFPE having a viscosity within the range of 30 to 550 mPa·s, particularly 50 to 200 mPa·s, and even more preferably 50 to 150 mPa·s is preferably used. By using a PFPE within this range, it is possible to more easily form a surface layer having a structure in which domains containing PFPE are connected to each other. That is, as described above, the viscosity of the PFPE in the domains can be reduced when the coating film of the coating material for forming the surface layer is heated. As a result, the domains can be more easily connected to each other during the curing process of the coating film. Furthermore, by incorporating a PFPE having a viscosity within the above range into the interconnected domains, the PFPE can be stably transferred to the surface of the surface layer.

[0057] The weight-average molecular weight Mw of PFPE is preferably 100 or more and 20,000 or less, from the viewpoint of migration of PFPE to the surface of an electrophotographic member. The weight-average molecular weight referred to here is a value obtained by dissolving PFPE in Zeorora H (manufactured by Zeon Corporation) and measuring the resulting liquid with a liquid chromatography analyzer (manufactured by Shimadzu Corporation). The chemical name of Zeorora H is 1,1,2,2,3,3,4-heptafluorocyclopentane.

[0058] The content of PFPE in the surface layer is preferably 20 to 40% by mass, and more preferably 25 to 35% by mass, based on the mass of the surface layer (including the mass of PFPE). When the content is 20% by mass or more, the low adhesion of the surface layer is more easily maintained. When the content is 40% by mass or less, the film strength is more easily increased. By adjusting the PFPE content within the above range, even when repeated transfers are performed, PFPE is supplied from the surface layer of the intermediate transfer belt to the surface of the intermediate transfer belt, making it easier to suppress a decrease in the releasability of the intermediate transfer belt surface.

[0059] <Dispersant> The surface layer contains compound 1 having a structure represented by the following formula (I) and a structure represented by formula (II) as a dispersant for dispersing perfluoropolyether. The structure represented by formula (I) has few fluorine-bonded carbon atoms and is an environmentally friendly structure. Furthermore, as described above, it is thought that compound 1 having the structure represented by formula (II) suppresses the adsorption and proximity of dispersants to each other, adsorbs to perfluoropolyether at a constant distance, and is evenly arranged on the surface of perfluoropolyether. This is thought to be due to the fact that the structure represented by formula (II) has a three-dimensional steric structure, so that dispersants do not become entangled with each other and are likely to have a structural repulsive force.

[0060] In formula (I), R １１ represents a hydrogen atom or a methyl group, and R １２ represents a single bond or an alkylene group having 1 to 3 carbon atoms, and Rf １ represents a perfluoroalkyl group having 1 to 4 carbon atoms. ２１ represents a hydrogen atom or a methyl group, and R ２２ represents a single bond or an alkylene group having 1 to 3 carbon atoms; Rt １ The structure represented by formula (I) can be obtained by using, for example, 1H,1H,2H,2H-nonafluorohexyl (meth)acrylate, 2,2,3,3,4,4,4-heptafluorobutyl (meth)acrylate, or the like as a monomer.

[0061] R in formula (I)１２ represents a single bond or an alkylene group having 1 to 3 carbon atoms, preferably an alkylene group having 1 or 2 carbon atoms. １ represents a perfluoroalkyl group having 1 to 4 carbon atoms (preferably 2 to 4 carbon atoms, more preferably 3 or 4 carbon atoms).

[0062] Rf １ Examples of such a compound include the structures shown in (Rf1-1) to (Rf1-8) below, with (Rf1-3) and (Rf1-5) being preferred.

[0063] R in the formula (II) ２２ represents a single bond or an alkylene group having 1 to 3 carbon atoms, preferably a single bond or an alkylene group having 1 carbon atom. １ represents a structure having a polycyclic monoterpene. １ Examples of the structure having a polycyclic monoterpene include the structures (Rt1-1) to (Rt1-8) shown below. (Rt1-1) and (Rt1-8) are preferred. As the structure having a polycyclic monoterpene, (Rt1-1) is more preferred.

[0064] The structure of formula (II) can be formed, for example, by using (meth)acrylic monomers having the structures (Rt1-1) to (Rt1-8). Specific examples include isobornyl (meth)acrylate and adamantan-1-yl (meth)acrylate.

[0065] The content of the structure represented by formula (I) in Compound 1 is preferably 10 to 75 mass%, more preferably 12 to 65 mass%. The content of the structure represented by formula (II) in Compound 1 is preferably 25 to 90 mass%, more preferably 35 to 88 mass%. Within the above range, the above-mentioned dispersing effect due to the structure represented by formula (II) is easily obtained.

[0066] Compound 1 is a copolymer having a structure represented by formula (I) and a structure represented by formula (II). Compound 1 is, for example, a (meth)acrylic resin. Compound 1 may also have a structure corresponding to at least one other (meth)acrylate selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate, to the extent that the effects of the present disclosure are not impaired. In other words, Compound 1 may be a copolymer of three or more types of monomers including other (meth)acrylates.

[0067] For example, Compound 1 may further have a structure represented by formula (III). For example, Compound 1 may contain the structure represented by formula (III) in an amount of preferably 0 to 30% by mass, more preferably 0 to 25% by mass. In formula (III), R ３１ represents a hydrogen atom or a methyl group, and R ３２ represents an alkyl group having 1 to 4 carbon atoms (preferably 1 or 2, more preferably 1).

[0068] Furthermore, from the viewpoint of the dispersing effect on the perfluoropolyether and the connectivity of the domains, Compound 1 preferably has a weight average molecular weight of 15,000 to 80,000, more preferably 20,000 to 40,000.

[0069] When the weight-average molecular weight is 15,000 or more, the steric hindrance effect is further improved, and the effect of suppressing aggregation of perfluoropolyethers is more likely to be obtained. Therefore, the domain size tends to be small. Furthermore, when the molecular weight is 80,000 or less, the perfluoropolyether tends to dissolve in solvents and the like.

[0070] The weight-average molecular weight referred to here is measured by gel permeation chromatography (GPC). The measurement method will be described later. The content of Compound 1 is preferably 5% by mass or more and 30% by mass or less, and more preferably 15% by mass or more and 25% by mass or less, based on the mass of the total solid content in the surface layer.

[0071] <Conductive Agent> The surface layer may contain a conductive agent to impart conductivity to the surface layer. Examples of the conductive agent include inorganic carbon-based conductive particles such as carbon black, carbon fiber, and carbon nanotubes, and metal oxides such as zinc antimonate, zinc oxide, tin oxide, and titanium oxide.

[0072] The thickness of the surface layer is preferably 2 to 20 μm, and more preferably 3 to 10 μm. When the thickness of the surface layer is 2 μm or more, durability is likely to be improved. On the other hand, when the thickness is 20 μm or less, folding endurance is likely to be good.

[0073] <Method for Manufacturing Electrophotographic Member> A specific method for manufacturing an electrophotographic member will be described below. However, the method for manufacturing an electrophotographic member is not limited to the following manufacturing method. The base layer of an electrophotographic member can be manufactured by the following method. For example, in the case of a thermosetting resin such as polyimide, carbon black, which is a conductive agent, is dispersed in a varnish together with a precursor of the thermosetting resin or a soluble thermosetting resin and a solvent, and this varnish is coated onto a molding die of a centrifugal molding machine. The coated film is then baked to form a semiconductive film.

[0074] When a thermoplastic resin is used, the conductive agent carbon black is mixed with the thermoplastic resin, and if necessary, additional additives are added, followed by melt-kneading using a twin-screw kneader or similar to produce a semiconductive resin composition. This resin composition is then melt-extruded into a sheet, film, or seamless belt to produce a semiconductive film. The seamless belt may be extruded from a cylindrical die to produce a belt, or may be seamlessly formed by joining extruded sheets. In addition to these molding methods, molding may also be performed using a heat press or injection molding. The thickness of the semiconductive film serving as the base layer is preferably 30 μm or more and 150 μm or less.

[0075] Furthermore, in order to enhance the mechanical strength and durability of the electrophotographic member, it is preferable to carry out a crystallization treatment. The crystallization treatment is, for example, an annealing treatment at a temperature equal to or higher than the glass transition temperature of the resin used, which can promote the crystallization of the resin used. The electrophotographic member obtained in this manner can be produced not only with excellent mechanical strength and durability, but also with excellent abrasion resistance, chemical resistance, sliding properties, toughness, and flame retardancy.

[0076] <Method for Forming Surface Layer> Examples of methods for forming the surface layer according to the first embodiment, in which independent domains containing PFPE are dispersed in the thickness direction, include the following. First, the above-described constituent components of the surface layer, i.e., the binder resin or binder resin raw materials (monomer, oligomer, etc.), PFPE, and Compound 1, are dissolved, dispersed, or both dissolved and dispersed in an organic solvent to obtain a surface layer coating liquid. Next, the surface layer coating liquid is applied to the outer periphery of the base layer by a method such as ring coating, dip coating, or spray coating to form a coating film of the surface layer coating liquid. Next, if necessary, the coating film is dried, for example, at a temperature of 60 to 90°C to evaporate at least a portion of the organic solvent in the coating film. If the coating film contains raw materials for the binder resin, the coating film can be cured by an appropriate method to form the surface layer.

[0077] When forming the surface layer according to the second embodiment, it is preferable to heat the belt at a temperature of 40 to 90°C during the binder resin curing process while irradiating the coating with ultraviolet light to cure the coating, thereby forming the surface layer. As described above, heating the coating during the curing process facilitates the flow of PFPE in isolated domains in the coating. Furthermore, as the polymerization of the binder resin raw materials (monomers, oligomers) in the coating progresses, phase separation between the polymer and PFPE progresses, and the isolated domains bond together. Finally, when the polymerization of the binder resin raw materials is completed to form the binder resin, the interconnected structure of the PFPE-containing domains is fixed, thereby forming the surface layer according to the second embodiment. When obtaining a surface layer having an interconnected structure of PFPE-containing domains, it is preferable to select a PFPE with low viscosity. This is because the isolated PFPE-containing domains are more likely to bond together during the coating film curing process. Therefore, in order to form a surface layer in which domains containing PFPE have an interconnected structure, it is preferable to adopt at least one method selected from the group consisting of selecting a PFPE with low viscosity and heating the coating film when hardening the coating film of the paint for forming the surface layer.

[0078] [Outline and Operation of Electrophotographic Image Forming Apparatus] FIG. 1 is a schematic cross-sectional view of an electrophotographic image forming apparatus (hereinafter also simply referred to as "image forming apparatus") showing the present embodiment. The image forming apparatus includes at least an image carrier that carries a toner image, and an intermediate transfer member that secondarily transfers the toner image, which has been primarily transferred from the image carrier, to a recording material. The electrophotographic member according to the present disclosure can be used as the intermediate transfer member. The electrophotographic member may be an electrophotographic belt. For example, the electrophotographic member is an intermediate transfer belt. The electrophotographic belt or intermediate transfer belt may have an endless shape. Below, an image forming apparatus using an intermediate transfer belt will be described as an example of an electrophotographic member.

[0079] As shown in Figure 1, the image forming apparatus has four process units serving as image forming means, each including a charging means, an exposure means, a developing means, a cleaner, etc., arranged around a photosensitive drum serving as an image carrier. Images formed on the photosensitive drums in each process unit are sequentially transferred in multiple layers at multiple primary transfer stations onto an intermediate transfer belt 7 serving as an intermediate transfer member that moves adjacent to the photosensitive drums, forming full-color toner images. Thereafter, the toner images formed on the intermediate transfer belt 7 are transferred collectively onto a recording material (transfer material) such as paper at a secondary transfer station. The toner image on the recording material is then fused and fixed to the recording material by heat and pressure at a fixing station.

[0080] The image forming apparatus according to this embodiment will now be described in detail. This image forming apparatus has four image forming units, designated first through fourth, Y, M, C, and K, arranged in parallel from left to right in the drawing. Each of the image forming units Y, M, C, and K is a laser scanning exposure type electrophotographic process mechanism having the same configuration, and includes a drum-type electrophotographic photosensitive member (hereinafter referred to as "drum") 1 as an image carrier. The electrophotographic process means acting on the drum 1 include a charging roller 2 as charging means, an exposure device 3 as exposure means, a developing device 4 as developing means, a primary transfer roller 5 as primary transfer means, and a drum cleaner 6.

[0081] The intermediate transfer belt 7 is stretched over three parallel rollers: a drive and secondary transfer opposing roller 8, a tension and deviation correction roller 9, and a driven roller 10. The tension and deviation correction roller 9 is located on the first image forming unit Y side, the drive and secondary transfer opposing roller 8 is located on the fourth image forming unit K side, and the driven roller 10 is located below the drive and secondary transfer roller 8. The lower surface of the intermediate transfer belt between the tension and deviation correction roller 9 and the driven roller 10 is in contact with the upper surfaces of the drums 1 of the image forming units Y, M, C, and K. The tension and deviation correction roller 9 can be aligned to control the deviation of the intermediate transfer belt.

[0082] The primary transfer roller 5 of each image forming unit Y, M, C, and K is disposed inside the intermediate transfer belt between the tension / shift correction roller 9 and the driven roller 10, and is pressed against the upper surface of the drum 1 with the intermediate transfer belt 7 sandwiched therebetween. The contact area between the drum 1 of each image forming unit Y, M, C, and K and the intermediate transfer belt 7 is the primary transfer nip T1. The contact area between the intermediate transfer belt 7 and the secondary transfer roller 12 is the secondary transfer nip T2. A registration roller pair 13 is disposed upstream of the secondary transfer nip T2 in the recording material conveyance direction. Furthermore, a recording material conveyance belt device and a fixing device (not shown) are disposed downstream of the secondary transfer nip T2 in the recording material conveyance direction.

[0083] The operation for forming a full-color image is as follows. The first to fourth image forming units Y, M, C, and K are driven at predetermined control timings in the image forming sequence. As a result, each drum 1 is driven to rotate in the clockwise direction indicated by the arrow at the same predetermined speed. The intermediate transfer belt 7 is also rotated in the counterclockwise direction indicated by the arrow by the driving and secondary transfer opposing roller 8 at the same speed as the drums 1.

[0084] The surface of the rotating drum 1 is uniformly charged to a predetermined polarity and potential by a charging roller 2. The charged surface of the drum 1 is image-exposed by an exposure device 3. In this embodiment, the exposure device 3 is a laser scanner that outputs laser light modulated in accordance with an image information signal to scan and expose the charged surface of the drum 1. As a result, an electrostatic image (electrostatic latent image) corresponding to the scanning and exposure pattern is formed on the drum surface. The formed electrostatic image is developed into a toner image by a developing device 4.

[0085] By the electrophotographic process described above, the first image forming unit Y forms a yellow toner image corresponding to the yellow component image of the color separation component images of the full-color original image on the surface of the drum 1. The second image forming unit M forms a magenta toner image corresponding to the magenta component image, and the third image forming unit C forms a cyan toner image corresponding to the cyan component image, each at a predetermined control timing. Furthermore, the fourth image forming unit K forms a black toner image corresponding to the black component image at a predetermined control timing.

[0086] Then, at the primary transfer nip T1 of the first image forming unit Y, the yellow toner image formed on the drum 1 is primarily transferred onto the rotating intermediate transfer belt 7. Next, at the primary transfer nip T1 of the second image forming unit M, the magenta toner image formed on the drum 1 is primarily transferred and superimposed on the yellow toner image on the intermediate transfer belt 7. Similarly, at the primary transfer nip T1 of the third image forming unit C and the fourth image forming unit K, a cyan toner image and a black toner image are sequentially primarily transferred onto the intermediate transfer belt 7.

[0087] That is, toner images of four colors, yellow, magenta, cyan, and black, are sequentially superimposed (multiple) onto the intermediate transfer belt 7 in a predetermined manner, thereby forming a composite full-color unfixed toner image. At each primary transfer nip T1, the primary transfer of the toner image from the drum 1 to the intermediate transfer belt 7 is performed by applying a predetermined primary transfer bias to the primary transfer roller 5 from a primary transfer power supply unit (not shown), and electrostatically transferring the toner image from the drum 1 to the intermediate transfer belt 7.

[0088] The primary transfer bias is a DC voltage of a predetermined potential and has a polarity opposite to the charge polarity of the toner. In each of the image forming units Y, M, C, and K, the surface of the drum 1 after passing through the primary transfer nip is cleaned by a drum cleaner 6 to remove residual toner from the drum 1, and the drum is then repeatedly used for image formation.

[0089] The unfixed full-color toner image compositely formed on the intermediate transfer belt 7 as described above is transported by the continued rotation of the intermediate transfer belt 7 to a secondary transfer nip T2, which is the contact point between the secondary transfer roller 12 and the intermediate transfer belt 7. When the leading edge of the unfixed full-color toner image formed on the intermediate transfer belt 7 reaches the secondary transfer nip T2, the start of rotation of the registration roller pair 13 is controlled so that the print start position of the recording material P coincides with the secondary transfer nip T2. As the recording material P is nipped and transported through the secondary transfer nip T2, a secondary transfer bias of a predetermined potential and of a polarity opposite to the charge polarity of the toner is applied from a secondary transfer power supply to the secondary transfer roller 12. The secondary transfer bias is a DC voltage of a predetermined potential and of a polarity opposite to the charge polarity of the toner.

[0090] As a result, the full-color unfixed toner images on the intermediate transfer belt 7 are secondarily transferred all at once onto the recording material P. The recording material P that has left the secondary transfer nip portion T2 is separated from the intermediate transfer belt 7 and introduced into a fixing device by a recording material conveying belt device, where the toners of the respective color toner images are melted and mixed and fixed (fixed imaged) onto the surface of the recording material P as a full-color print image, and the full-color print is then discharged outside the apparatus.

[0091] After the recording material is separated, the surface of the intermediate transfer belt 7 is cleaned by the intermediate transfer belt cleaner 11 to remove residual toner from the secondary transfer during the subsequent rotation of the intermediate transfer belt 7, and is prepared for the next image formation process. In the intermediate transfer belt cleaner 11, a cleaning blade is brought into contact with the surface of the belt 7 to scrape off residual toner from the belt surface, and the scraped toner is collected as recovered toner in a recovered toner box in the intermediate transfer belt cleaner 11.

[0092] A patch detection sensor 20 (toner image detection means) capable of detecting image density is positioned opposite the intermediate transfer belt stretched by the tension roller 10. This sensor optically detects reflected and scattered light from an adjustment toner image (patch image) formed on the intermediate transfer belt. The adjustment toner image (patch image) is formed on the intermediate transfer belt during a period other than the period during which the toner image to be secondarily transferred to the recording material is primarily transferred. Image formation conditions are adjusted based on the results. To more stably and accurately measure the density for controlling the image formation conditions, it is preferable that the intensity of reflected light from the surface of the intermediate transfer belt be above a certain level. This allows for accurate density detection and facilitates suppression of density unevenness between images.

[0093] The present disclosure will be described in more detail below with specific examples, but the present disclosure is not limited to the following examples.

[0094] First, the preparation of the copolymer, Compound 1, will be described. <Preparation of Copolymer> (Copolymer 1) The materials shown in Table 1 below were mixed in a glass flask equipped with a stirrer, reflux condenser, nitrogen gas inlet tube, thermostatic bath, and thermometer at 20°C under a nitrogen atmosphere for 30 minutes, and then the reaction solution was heated to a temperature of 85 to 90°C and reacted for 5 hours. The reaction was stopped by ice cooling, and 1,500 parts by mass of 2-propanol was added to obtain a precipitate. This precipitate was washed with a mixed solvent of n-butyl acetate:2-propanol = 1:5 and dried at 80°C and under a reduced pressure of 1,325 Pa or less for 3 hours, thereby obtaining Copolymer 1.

[0095]

[0096] (Copolymers 2 to 12) Copolymers 2 to 12 were obtained in the same manner as Copolymer 1, except that the materials and parts by mass used were changed as shown in Table 2. The materials used are as follows: Isobornyl acrylate (Tokyo Chemical Industry Co., Ltd.) 1H,1H,2H,2H-nonafluorohexyl acrylate (Tokyo Chemical Industry Co., Ltd.) Methyl methacrylate (Tokyo Chemical Industry Co., Ltd.) 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (Tokyo Chemical Industry Co., Ltd.) Adamantan-1-yl acrylate (Tokyo Chemical Industry Co., Ltd.) Butyl methacrylate (Tokyo Chemical Industry Co., Ltd.)

[0097] <Measurement of Weight-Average Molecular Weight> The weight-average molecular weight of the obtained copolymer was measured. The weight-average molecular weight was measured by dissolving the measurement sample in tetrahydrofuran (hereinafter also referred to as THF) to prepare a solution with a concentration of 0.2% by mass, and then using a gel permeation chromatograph (hereinafter also referred to as GPC) apparatus GPC-104 (manufactured by Showdex). The molecular weight was measured using a column consisting of one connected "GPC KF-603" and one connected connected "GPC KF-604" manufactured by Showdex, with a column temperature of 40°C and a THF flow rate of 1.0 mL / min. The weight-average molecular weight (Mw) of the sample was calculated from a calibration curve prepared in advance using a polystyrene standard substance (SM-105 manufactured by Showdex) with a known molecular weight.

[0098] The types and amounts of monomers used in the prepared copolymers are listed in Table 2. Copolymers No. 11 and 12 are comparative copolymers that do not have the structure shown in formula (II). The weight-average molecular weights of the prepared copolymers, measured by the above method, are listed in Table 3.

[0099]

[0100] (PFPE) Table 4 shows the PFPEs used in the examples and comparative examples.

[0101] [Example 1] An intermediate transfer belt made of polyimide, which was installed in a color multifunction printer (product name: iRC2620) manufactured by Canon Inc., was used as a base layer, and a surface layer was formed on this base layer by the method described below, to produce an electrophotographic belt according to this example.

[0102] Dipentaerythritol hexaacrylate (DPEH) 7.0 parts by mass Pentaerythritol tetraacrylate (PETA) 15.0 parts by mass Pentaerythritol triacrylate (PETRA) 4.4 parts by mass Methyl ethyl ketone 26.4 parts by mass Celnax CX-Z210IP (Nissan Chemical Industries, Ltd.) 4.5 parts by mass Photopolymerization initiator (BASF Irgacure (registered trademark) 184) 2.0 parts by mass PFPE2 14.8 parts by mass (Solvay Specialty Polymers Fluorolink (registered trademark) MD700) Copolymer 1 25.9 parts by mass These materials were mixed and dispersed using a stirring homogenizer (As One Corporation), and then dispersed using a dispersion device Nanomizer (Yoshida Kikai Kogyo Co., Ltd.) to prepare a coating material for forming a surface layer. This paint was applied to the outer peripheral surface of the base layer and dried at a temperature of 70°C for 3 minutes to form a coating film of the paint. Next, the coating film was irradiated with 500 mJ / cm2 of UV light using a UV treatment device (manufactured by Eye Graphics Co., Ltd.) in an environment at a temperature of 25°C. ２ The coating film was cured by irradiating it with ultraviolet light of 1000 kJ / cm, thereby forming a surface layer with a film thickness of 4 μm. In this way, electrophotographic belt No. 1 was obtained. The obtained electrophotographic belt No. 1 was subjected to the following evaluations.

[0103] <Gloss Measurement> When the domains of PFPE in the surface layer are large, specifically, when the average major axis exceeds 60 nm, the surface gloss of the surface layer decreases. Therefore, as a measure of whether the domains of PFPE in the surface layer are small, the surface gloss of the surface layer was measured by the following method. That is, the gloss of the central part in the width direction of the electrophotographic belt was measured at 20 points equidistantly in the circumferential direction of the electrophotographic belt. For the gloss measurement, a handy gloss meter (product name: PG-IIM; manufactured by Nippon Denshoku Industries Co., Ltd.) was used, the incident angle was set to 20°, and the arithmetic mean value of the measured values ​​at any 20 points was taken as the gloss of the electrophotographic belt to be measured.

[0104] <Average major axis of domains> The average major axis of the domains was determined by observing the cross section of the surface layer of the electrophotographic belt using a scanning electron microscope (S-4800 manufactured by Hitachi High-Technologies Corporation). First, a microtome (product name: EMUC7 manufactured by Leica Microsystems) was used to expose the cross section of the surface layer in the entire thickness direction. Then, the cross section in the thickness direction of the surface layer was divided into three equal parts. Then, ten randomly selected points of each of the three parts were observed at a magnification of 20,000 times using the above scanning electron microscope, and SEM images in which at least one PFPE domain was observed in a 15 μm square area were obtained. That is, ten SEM images (30 in total) were prepared for each part. For each of the obtained SEM images, if there were 10 or fewer PFPE domains, the major axes of all domains in the SEM image were measured. Furthermore, if there were more than 10 PFPE domains in the SEM image, ten randomly selected domains were selected and their major axes were measured. The above observation and calculation were carried out on 10 SEM images of each portion, and the average value of the major axis of the PFPE domains obtained was calculated.

[0105] <Image Evaluation - Evaluation of Transferability> The electrophotographic belt of the Example or Comparative Example was installed in place of the polyimide intermediate transfer belt installed in a color multifunction printer (product name: iRC2620; manufactured by Canon Inc.), and printing was performed. At this time, the images printed immediately after the start of printing and after 200,000 sheets had been printed (after 200,000 repeated transfers) were evaluated. The image evaluation criteria are as follows: Rank A: No degradation in image quality due to defective secondary transfer was observed. Rank B: Degradation in image quality due to defective secondary transfer was observed. However, the area where degradation in image quality due to defective transfer occurred was 20% or less of the printed area. Rank C: The area where degradation in image quality due to defective secondary transfer occurred was more than 20% but not more than 50% of the printed area. Rank D: The area where degradation in image quality due to defective secondary transfer occurred was more than 50% of the printed area.

[0106] [Examples 2 to 10, Comparative Examples 1 to 4] Electrophotographic belts 102 to 110 according to Examples 2 to 10 and electrophotographic belts C101 to C102 according to Comparative Examples 1 and 2 were produced in the same manner as in Example 1, except that the copolymers shown in Table 5 were used instead of Copolymer 1 in Example 1. Then, electrophotographic belts 102 to 110 and C101 to C102 were evaluated by the method described in Example 1. The evaluation results are shown in Table 6.

[0107]

[0108]

[0109] The electrophotographic belts of Examples 1 to 10 had a matrix-domain structure in the surface layer in the thickness direction, and the average major axis of the domains was 30 nm or more and 70 nm or less. The belt surface also had high gloss. Furthermore, the electrophotographic belts of Examples 1 to 10 hardly showed any deterioration in image quality due to transfer failure. Moreover, these performances were maintained over a long period of time.

[0110] In contrast, the electrophotographic belts according to Comparative Examples 1 and 2 have a matrix-domain structure in the surface layer in the thickness direction. In Comparative Examples 1 and 2, copolymers 11 and 12 were used, and these copolymers are dispersants that do not have the structure represented by formula (II). It is believed that this is why the average major axis of the domains was larger than that of Examples 1 to 10. It is also believed that the gloss level was reduced due to the larger average major axis of the domains containing PFPE. Furthermore, it is believed that the size of the domains containing PFPE was larger than that of the Examples, and as a result, the PFPE that migrated to the surface of the surface layer was depleted relatively quickly. As a result, the electrophotographic belts according to Comparative Examples 1 and 2 received a rank C in the evaluation of images after printing 200,000 sheets.

[0111] Example 11 An intermediate transfer belt made of polyimide, which was provided in a full-color multifunction printer (product name: imageRUNNER ADVANCE C5051; manufactured by Canon Inc.), was used as a base layer, and a surface layer was formed on this base layer by the method described below, to produce an electrophotographic belt 201 according to this example.

[0112] Dipentaerythritol hexaacrylate 5.0 parts by mass Pentaerythritol tetraacrylate 8.0 parts by mass Pentaerythritol triacrylate 4.0 parts by mass 2-2-2 trifluoroethanol 26.0 parts by mass Celnax CX-Z210IP (Nissan Chemical Industries, Ltd.) 8.0 parts by mass Irgacure 184 (IGM-Resins Co., Ltd.) 1.0 part by mass PFPE1 (Fomblin D2, Solvay Specialty Polymers) 14.8 parts by mass Dispersant (copolymer 1 after volatilizing the solvent and redissolving in 2-2-2 trifluoroethanol at a solids concentration of 20%) 14.8 parts by mass

[0113] These materials were mixed and dispersed using a stirring homogenizer (manufactured by AS ONE Corporation), and then dispersed using a dispersing device, Nanomizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.) to obtain a mixed dispersion. This was coated on the outer peripheral surface of the above-mentioned base layer, dried at 70°C for 3 minutes, and then heated to 50°C. At the same time, the intermediate transfer body was irradiated with 500 mJ / cm using a UV treatment device (manufactured by iGraphics Co., Ltd.).２ The electrophotographic belt 201 thus obtained was subjected to the following evaluations.

[0114] <Removal of PFPE> A sample (length: 50 mm, width: 50 mm, thickness: total thickness of the surface layer) cut out from the surface layer of the electrophotographic belt was immersed in 200 mL of a fluorine-based solvent containing 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (trade name: Asahiklin AE-3000; manufactured by AGC Corporation) in which PFPE can be dissolved, and ultrasonic waves were applied for 10 minutes using an ultrasonic cleaning device. Thereafter, the sample was removed from the fluorine-based solvent and left to dry in an environment at a temperature of 25°C for 24 hours.

[0115] <Measurement of Domain Void Volume Fraction after PFPE Removal> After removing the PFPE using the above procedure, the mass of a sample measuring 50 mm in length and 50 mm in width was measured. The sample was then immersed in PFPE oil (Fomblin M03, Fomblin Y04 (manufactured by Solvay Specialty Polymers)) with a known specific gravity and left under vacuum (100 Pa or less) for approximately 1 hour so that the PFPE oil was impregnated into the voids. The sample was then removed from the PFPE oil, the PFPE oil on the surface was wiped off, and the mass was measured. The volume of the impregnated PFPE oil, i.e., the volume of the voids, was calculated from the difference in mass before and after impregnation with the PFPE oil, and the void volume fraction was calculated by dividing the volume of the voids by the volume of the surface layer of the intermediate transfer belt (50 mm in length × 50 mm in width × thickness of the surface layer).

[0116] <Measurement of the area ratio of void openings and the number of void openings on the outer surface of the surface layer after PFPE removal> The surface corresponding to the outer surface of the surface layer of the sample after PFPE removal obtained by the above operation was observed using a scanning electron microscope, and an SEM image (magnification 10,000x) of a rectangular observation area measuring 8 μm in length and 11 μm in width was obtained. The resolution was set to 717 pixels in length and 986 pixels in width so that the openings could be recognized. The obtained SEM image was converted to an 8-bit grayscale image using image processing software (product name: Image-J, manufactured by the National Institutes of Health (NIH)). A median filter was applied to the obtained grayscale image, and then binarization processing was performed using the image processing software to obtain a binary image. The binarization processing used the YEN method to distinguish between the portions corresponding to the openings and the portions corresponding to the PFA in the SEM image. The number of pixels corresponding to the openings in the obtained binary image was then counted. The ratio of the number of pixels corresponding to the openings to the number of pixels in the entire image was calculated. Here, the observation areas were set at 10 arbitrary locations on the surface of the surface layer having openings, and the average number of pixels corresponding to the openings counted from each observation area was taken as the number of openings, and this was divided by the area of ​​the observation area to obtain the number of openings per 1 μm. ２ The number of openings per observation area was calculated. The arithmetic mean value of the ratio calculated from each observation area was taken as the opening area ratio. Note that the observation areas were positioned so that they did not overlap each other.

[0117] <Image Evaluation - Evaluation of Transferability> The prepared electrophotographic belt was mounted as an intermediate transfer belt in an electrophotographic image forming apparatus (product name: imageRUNNER ADVANCE C5051; manufactured by Canon Inc.). Electrophotographic images were printed using this electrophotographic image forming apparatus. Image 1 printed immediately after the start of printing (initial stage), image 2 printed after 200,000 sheets were printed (after 200,000 repeated transfers (after 200,000 sheets were printed)), and image 3 printed after 600,000 sheets were printed (after 600,000 repeated transfers (after 600,000 sheets were printed)), were visually evaluated and evaluated according to the following criteria: Rank A: No degradation in image quality due to defective secondary transfer was observed. Rank B: Degradation in image quality due to defective secondary transfer was observed. However, the area where degradation in image quality occurred due to defective secondary transfer was 20% or less of the printed area. Rank C: The area where degradation in image quality occurred due to defective secondary transfer was more than 20% but not more than 50% of the printed area. Rank D: The area where image quality is degraded due to secondary transfer defects is more than 50% of the printed area.

[0118] [Examples 12 to 20, Comparative Examples 3 to 4] Electrophotographic belts 202 to 210 according to Examples 12 to 20 and electrophotographic belts C201 to C202 according to Comparative Examples 3 and 4 were produced in the same manner as in Example 11, except that the copolymers shown in Table 7 were used instead of Copolymer 1 in Example 11. Electrophotographic belts 202 to 210 and C201 to C202 were evaluated by the method described in Example 11. The evaluation results are shown in Table 8.

[0119]

[0120]

[0121] In the surface layers of electrophotographic belts C201 and C202 according to Comparative Examples 3 and 4, copolymers 11 and 12 were used, respectively, and these copolymers are dispersants that do not have the structure represented by formula (II). Therefore, it is believed that the function of dispersing PFPE was reduced, and the individual domain sizes became larger. This is believed to have resulted in the early appearance of PFPE, and therefore the secondary transfer efficiency decreased with repeated printing.

[0122] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the present disclosure. Therefore, the following claims are appended to clarify the scope of the present disclosure. This application claims priority based on Japanese Patent Application No. 2023-121642 filed on July 26, 2023, the entire contents of which are incorporated herein by reference.

[0123] REFERENCE SIGNS LIST 1 Photosensitive drum, 2 Charging roller, 3 Exposure device, 4 Developing device, 5 Primary transfer roller, 6 Drum cleaner, 7 Intermediate transfer belt, 8 Drive and secondary transfer opposing roller, 9 Tension and deviation correction roller, 10 Driven roller, 11 Intermediate transfer body cleaner, 12 Secondary transfer roller, 13 Registration roller pair, 20 Patch detection sensor, 31 Base layer, 32 Surface layer

Claims

1. An electrophotographic member having at least a base layer and a surface layer, characterized in that the surface layer contains the following A, B, and C: A: Compound 1 having a structure represented by the following formula (I) and a structure represented by the following formula (II), B: Perfluoropolyether, C: Binder resin. In formula (I), R １１ represents a hydrogen atom or a methyl group, R １２ represents a single bond or an alkylene group having 1 to 3 carbon atoms; Rf １ represents a perfluoroalkyl group having 1 to 4 carbon atoms, and in formula (II), R ２１ represents a hydrogen atom or a methyl group, R ２２ represents a single bond or an alkylene group having 1 to 3 carbon atoms; １ represents a structure having a polycyclic monoterpene.

2. The electrophotographic member according to claim 1, wherein the polycyclic monoterpene-containing structure is represented by the following formula (Rt1-1):

3. The above Rf １ 3. The electrophotographic member of claim 1, wherein R is a perfluoroalkyl group having 3 or 4 carbon atoms.

4. The electrophotographic member according to any one of claims 1 to 3, wherein the binder resin contains at least one resin selected from the group consisting of (meth)acrylic resins and epoxy resins.

5. The electrophotographic member according to any one of claims 1 to 4, wherein the weight average molecular weight of said compound 1 is 15,000 to 80,000.

6. The electrophotographic member according to any one of claims 1 to 5, wherein, when the perfluoropolyether is removed from the surface layer to produce a surface layer from which the perfluoropolyether has been removed, the surface layer from which the perfluoropolyether has been removed has voids having openings on its outer surface, and the ratio of the total volume of the voids to the volume of the surface layer from which the perfluoropolyether has been removed when it is assumed to be solid (void volume ratio) is 8.0 to 25.0%.

7. The unit area (1 μm 2 ) of the outer surface of the surface layer from which the perfluoropolyether has been removed ２ 7. The electrophotographic member of claim 6, wherein the percentage of the total area of ​​said openings per unit area is from 10.0 to 35.0%.

8. The unit area (1 μm 2 ) of the outer surface of the surface layer from which the perfluoropolyether has been removed ２ 8. The electrophotographic member of claim 7 wherein the number of said openings per layer is from 10 to 500.

9. The electrophotographic member according to any one of claims 1 to 8, wherein in the surface layer, a domain containing the perfluoropolyether and the binder resin are phase-separated.

10. The electrophotographic member of any one of claims 1 to 9, wherein said electrophotographic member is an electrophotographic belt having an endless configuration.

11. An electrophotographic image forming apparatus comprising: an image carrier that carries a toner image; and an intermediate transfer member that performs a second transfer of the toner image, which has been primarily transferred from the image carrier, onto a recording material; and wherein the intermediate transfer member is an electrophotographic member according to any one of claims 1 to 10.

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