Electrophotographic belt and electrophotographic image forming apparatus

Abstract

To provide a high-quality electrophotographic belt.SOLUTION: The electrophotographic belt includes at least a base layer and a surface layer, and the surface layer includes A, B, and C as described below: A denotes a compound 1 having a structure shown by the following structural formula (I) and the structural formula (II); B denotes perfluoropolyether; and C denotes a binding resin.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This disclosure relates to an electrophotographic belt used in electrophotographic image forming apparatus such as a copier or printer, and to an electrophotographic image forming apparatus equipped with an electrophotographic belt. [Background technology]

[0002] In electrophotographic image forming apparatuses capable of forming full-color images, a tandem method is widely employed, in which toner images of each color (Y, M, C, and K) are superimposed on an intermediate transfer belt and then transferred to paper in a single transfer to obtain a full-color image. Y stands for yellow, M for magenta, C for cyan, and K for black. As an intermediate transfer belt used here, for example, an electrophotographic belt having a base layer in which carbon black is dispersed in a binder resin such as polyimide or polyetheretherketone is known.

[0003] With the increasing demand for higher image quality in electrophotographic images, there is a growing need for further improvements in the secondary transfer characteristics of toner in intermediate transfer belts. To improve the secondary transfer properties of intermediate transfer belts, it has been proposed to incorporate perfluoropolyether into the surface layer constituting the toner-carrying surface of the intermediate transfer belt (hereinafter simply referred to as the "surface") to enhance the toner release properties of the said surface. And, Patent Document 1 discloses an electrophotographic belt having a surface layer in which perfluoropolyether is dispersed in a binder resin using a comb-type graft copolymer. This comb-type graft copolymer is a copolymer of a (meth)acrylate having a specific molecular weight and a fluoroalkyl group, and a methacrylate macromonomer having polymethyl methacrylate as a side chain. It is disclosed that by using such a comb-type graft copolymer, the perfluoropolyether can be better dispersed in the binder resin. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-12265 [Overview of the project] [Problems that the invention aims to solve]

[0005] According to the inventors' research, the comb-type graft copolymer described in Patent Document 1 exhibited excellent dispersibility of perfluoropolyether. The inventors then investigated the possibility of limiting the number of consecutive carbon atoms to which fluorine atoms are bonded in the comb-type graft copolymer to three or fewer. Specifically, they investigated introducing oxygen atoms into the carbon chain constituting the main chain of the perfluoroalkyl group, thereby limiting the number of consecutive carbon atoms to which fluorine atoms are bonded to three or fewer. Organofluorine compounds with three or fewer consecutive carbon atoms to which fluorine atoms are bonded are considered to exhibit excellent decomposition in the natural environment and are less likely to remain in the environment. Therefore, the inventors investigated an electrophotographic belt having a surface layer in which perfluoropolyether is dispersed in a binder resin using the above-mentioned environmentally friendly comb-type graft copolymer. As a result, the cleanability of the surface of the electrophotographic belt sometimes decreased over time. One aspect of this disclosure aims to provide an electrophotographic belt that is environmentally friendly and can maintain good surface cleanability over a long period of time. Another aspect of this disclosure aims to provide an electrophotographic image forming apparatus that can stably form high-quality electrophotographic images. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, an electrophotographic belt is provided 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 the structure shown in the following chemical structural formula (I) and the structure shown in the following chemical structural formula (II) B: Perfluoropolyether C: Binding resin [ka] [ka]

[0007] Furthermore, according to another aspect of the present disclosure, an electrophotographic image forming apparatus is provided, comprising an image carrier for carrying a toner image, and an intermediate transfer belt for carrying and transporting the toner image, which has been primary transferred from the image carrier, to a transfer material for secondary transfer, wherein the intermediate transfer belt is the electrophotographic belt described above. [Effects of the Invention]

[0008] According to one aspect of this disclosure, an electrophotographic belt can be obtained that is highly adaptable to the environment and can form good electrophotographic images over a long period of time. Furthermore, according to one aspect of this disclosure, an electrophotographic image forming apparatus can be obtained that can stably form high-quality electrophotographic images. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] This is a cross-sectional view showing the configuration of an intermediate transfer belt according to an embodiment of the present disclosure. [Modes for carrying out the invention]

[0010] The reason why the surface cleaning performance of an electrophotographic belt equipped with a surface layer made by dispersing perfluoropolyether in a binder resin using the aforementioned comb-type graft copolymer, which is considered environmentally friendly, deteriorates over time is thought to be as follows: In other words, it is thought that comb-type graft copolymers in which the number of consecutive carbon atoms bonded to fluorine atoms is 3 or less have low perfluoropolyether dispersion ability. Therefore, it becomes difficult to finely disperse perfluoropolyether in the binder resin. As a result, large domains of perfluoropolyether exist in the surface layer. Such a surface layer has low hardness and is worn away by repeated cleaning with a cleaning blade. Along with this, it is thought that perfluoropolyether is also lost from the surface layer, and the toner release properties of the surface decrease. Based on these considerations, further investigations were conducted. As a result, it was found that compounds having the structure shown in chemical structural formula (I) above and the structure shown in chemical structural formula (II) below are environmentally friendly structures and also exhibit excellent dispersibility in perfluoropolyether binder resins. Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, the specific aspects described in the following embodiments, such as the dimensions, materials, shapes, and relative arrangements of components, may be modified as appropriate depending on the configuration and various conditions of the apparatus to which the present disclosure applies, and the scope of the present disclosure is not limited to these specific aspects.

[0011] [Image forming apparatus] Figure 1 shows a schematic cross-sectional view of an electrophotographic image forming apparatus 100 equipped with an electrophotographic belt according to one embodiment of this invention. In this electrophotographic image forming apparatus, image forming units Py, Pm, Pc, and Pk for yellow (Y), magenta (M), cyan (C), and black (K) are arranged in order along the moving direction on the flat portion of an intermediate transfer belt 7, which is an intermediate transfer member. Here, 1Y, 1M, 1C, and 1K each indicate an electrophotographic photosensitive member, and 2Y, 2M, 2C, and 2K each indicate a charging roller. Also, 3Y, 3M, 3C, and 3K each indicate a laser exposure device, 4Y, 4M, 4C, and 4K each indicate a developing device, and 5Y, 5M, 5C, and 5K each indicate a primary transfer roller. Since the basic configuration of each image forming unit is the same, only the yellow image forming unit Py will be described in detail regarding the details of the image forming unit.

[0012] The yellow image forming unit Py has a drum-type electrophotographic photosensitive member (hereinafter also referred to as "photosensitive drum" or "first image carrier") 1Y as an image carrier. The photosensitive drum 1Y is formed by sequentially laminating a charge generation layer, a charge transport layer, and a surface protection layer on an aluminum cylinder as a substrate. Also, the yellow image forming unit Py includes a charging roller 2Y as charging means. By applying a charging bias to the charging roller 2Y, the surface of the photosensitive drum 1Y is uniformly charged. Above the photosensitive drum 1Y, a laser exposure device 3Y as image exposure means is arranged. The laser exposure device 3Y scans and exposes the uniformly charged surface of the photosensitive drum 1Y according to image information to form an electrostatic latent image of the yellow color component on the surface of the photosensitive drum 1Y.

[0013] The electrostatic latent image formed on the photosensitive drum 1Y is developed by toner, which is a developer, using a developing device 4Y as a developing means. The developing device 4Y includes a developing roller 4Ya, which is a developer carrier, and a regulating blade 4Yb, which is a developer amount regulating member, and also contains yellow toner as a developer. The developing roller 4Ya supplied with yellow toner is lightly pressed against the photosensitive drum 1Y in the developing section and rotated with a speed difference in the forward direction with respect to the photosensitive drum 1Y. The yellow toner conveyed to the developing section by the developing roller 4Ya adheres to the electrostatic latent image formed on the photosensitive drum 1Y by applying a development bias to the developing roller 4Ya. As a result, a visible image (yellow toner image) is formed on the photosensitive drum 1Y.

[0014] The intermediate transfer belt 7 is stretched over a driving roller 71, a tension roller 72, and a driven roller 73, and contacts the photosensitive drum 1Y and is moved (rotationally driven) in the direction of the arrow in the figure. The yellow toner image formed on the photosensitive drum (on the first image carrier) that has reached the primary transfer section Ty is primarily transferred onto the intermediate transfer belt 7 by a primary transfer member (primary transfer roller 5Y) disposed opposite the photosensitive drum 1Y via the intermediate transfer belt 7.

[0015] Similarly, the above image forming operation is performed in each of the magenta (M), cyan (C), and black (K) units Pm, Pc, and Pk as the intermediate transfer belt 7 moves, and yellow, magenta, cyan, and black four-color toner images are laminated on the intermediate transfer belt 7. The laminated four-color toner images are conveyed as the intermediate transfer belt 7 moves, and at the secondary transfer section T’, they are collectively transferred onto a transfer material S (hereinafter also referred to as the “second image carrier”) that is conveyed at a predetermined timing by a secondary transfer roller 8 as secondary transfer means. In such secondary transfer, usually, a transfer voltage of several kV is applied to ensure a sufficient transfer rate.

[0016] The transfer material S is supplied to the transport path from the cassette 12 in which the transfer material S is stored by the pickup roller 13. The transfer material S supplied to the transport path is transported to the secondary transfer section T' in synchronization with the four-color toner image transferred to the intermediate transfer belt 7 by the transport roller pair 14 and the registration roller pair 15. The toner image transferred to the transfer material S is fixed by the fuser 9 to become, for example, a full-color image. The fuser 9 has a fixing roller 91 equipped with a heating means and a pressure roller 92, and fixes the unfixed toner image on the transfer material S by heating and pressurizing it. After that, the transfer material S is discharged from the machine by a transport roller pair 16, a discharge roller pair 17, etc.

[0017] The cleaning unit 11 for the intermediate transfer belt 7 is located downstream of the secondary transfer section T' in the driving direction of the intermediate transfer belt 7, and removes any remaining transfer toner that was not transferred to the transfer material S in the secondary transfer section T' and remains on the intermediate transfer belt 7. As explained above, the electrical transfer process of the toner image is repeatedly performed from the photoreceptor to the intermediate transfer belt, and from the intermediate transfer belt to the transfer material. Furthermore, the electrical transfer process is repeated even more by repeatedly recording onto multiple transfer materials.

[0018] [Electrophotographic belt] As illustrated in Figure 2, the electrophotographic belt 200 of this embodiment is a laminate composed of at least two layers: a base layer 21 and a surface layer 22. The surface layer 22 constitutes the toner-carrying surface of the electrophotographic belt 200, i.e., surface 200-1. Furthermore, the configuration of the electrophotographic belt relating to this disclosure is not limited to the two-layer laminate described above. For example, a primer layer (not shown) for improving adhesion, a stress relaxation layer to suppress cracking of the surface layer 22, and an intermediate layer (neither shown) to suppress bleeding can also be provided between the base layer 21 and the surface layer 22.

[0019] (base layer) The base layer 21 has a cylindrical shape that is either roll-shaped or belt-shaped, forming an endless loop. Examples of materials suitable for the base layer 21 include the following: polyetheretherketone, polyethylene terephthalate, polybutylene naphthalate, polyester, polyimide, polyamide, polyamideimide, polyacetal, polyphenylene sulfide, polyvinylidene fluoride, etc.

[0020] In addition, conductive compounds such as metal powder, conductive oxide powder, conductive carbon, lithium salt, and ionic liquid may be added to the resin for the base layer 21 to impart conductivity. In the following examples, polyimide with carbon black added was used from the viewpoint of obtaining excellent conductivity and environmental stability, but combinations of other exemplified resins and conductivity-imparting agents may also be used. The film thickness of the base layer 21 is preferably 10 μm or more and 500 μm or less. If it is less than 10 μm, the mechanical strength may be significantly reduced, and if it is greater than 500 μm, the rigidity may become too strong, which may make it difficult to use as an intermediate transfer belt.

[0021] (Surface layer) The surface layer 22 is formed on the base layer 21 and becomes the outermost layer of the intermediate transfer belt according to this embodiment, and contains all of the following A, B, and C. A: Compound 1 having the structure represented by the above chemical structural formula (I) and the structure represented by the above chemical structural formula (II) (hereinafter also referred to as a graft copolymer). B: Perfluoropolyether (hereinafter also referred to as PFPE). C: Binder resin The surface layer 22 may contain a photoinitiator, a conductive substance, etc. in addition to the above binder resin, PFPE, and graft copolymer.

[0022] <C: Binder resin> As the binder resin, one or more resins selected from the group consisting of acrylic resin, methacrylic resin, and epoxy resin can be used. "One or more resins" includes a mixed resin of resins selected from the above group. The binder resin functions as a dispersion medium for PFPE. It also serves to ensure adhesion of the surface layer to the base layer 21 and to ensure the mechanical strength of the surface layer itself.

[0023] Among the above-mentioned binder resins, methacrylic resin or acrylic resin is preferred because it can effectively disperse the PFPE constituting the surface layer 22 of the electrophotographic belt. Hereinafter, methacrylic resin and acrylic resin will be collectively referred to as acrylic resins. Examples of polymerizable monomers for forming acrylic resins include (i) or (ii) below. It is also possible to use polymerizable monomers that are commercially available as paints.

[0024] (i) At least one acrylate selected from the group consisting of the following: pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate, alkyl acrylate, benzyl acrylate, phenyl acrylate, ethylene glycol diacrylate, and bisphenol A diacrylate.

[0025] (ii) At least one methacrylate selected from the group consisting of the following: pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, ditrimethylolpropane tetramethacrylate, dipentaerythritol hexamethacrylate, alkyl methacrylate, benzyl methacrylate, phenyl methacrylate, ethylene glycol dimethacrylate, and bisphenol A dimethacrylate.

[0026] Among these, high hardness is preferable when considering friction with other components such as photoreceptors and cleaning blades. For this reason, it is preferable to use a large amount of bifunctional or crosslinkable monomers in the acrylic resin to achieve even higher hardness. Furthermore, to form acrylic resins from such polymerizable monomers, one method involves adding a photopolymerization initiator and polymerizing it using electron beams or ultraviolet light.

[0027] Examples of photopolymerization initiators include: radical-generating photopolymerization initiators such as benzophenone, thioxanthone derivatives, benzyldimethyl ketal, α-hydroxyketone, α-hydroxyalkylphenone, α-aminoketone, α-aminoalkylphenone, monoacylphosphine oxide, bisacylphosphine oxide, hydroxybenzophenone, aminobenzophenone, titanocene derivatives, oxime esters, and oxyphenyl acetate. The content of the binder resin in the surface layer is preferably 20% by mass or more and 70% by mass or less, relative to the total mass of the surface layer 22, in order to provide the surface layer with excellent strength and to support excellent toner release properties on the outer surface of the surface layer.

[0028] <B:パーフルオロポリエーテル> Perfluoropolyether (hereinafter also referred to as PFPE) is an oligomer or polymer having perfluoroalkylene ether as a repeating unit. Examples of repeating units for perfluoroalkylene ethers include perfluoromethylene ether, perfluoroethylene ether, and perfluoropropylene ether. Commercially available PFPEs can be used. Examples of such commercial products include, but are not limited to, PFPEs represented by structural formula (1) (e.g., Demnum S-200, Demnum S-65 (both trade names), manufactured by Daikin Industries, Ltd.), PFPEs represented by structural formula (2) (e.g., Krytox GPL-107, Krytox GPL-106, Krytox GPL-105 (all trade names), manufactured by Chemours), PFPEs represented by structural formula (3) (e.g., Fomblin M60, Fomblin Z25 (both trade names), manufactured by Solvay Specialty Polymers), and PFPEs represented by structural formula (4) (e.g., Fomblin Y45, Fomblin Y25 (both trade names), manufactured by Solvay Specialty Polymers).

[0029] [ka] (In equation (1), n ​​is a positive number, and n is the kinematic viscosity at 40°C between 10 and 300 mm².) 2 This is the number of values ​​within the range that satisfies the range of / s.

[0030] [ka] (In equation (2), n' is a positive number, and n' is the kinematic viscosity at 40°C between 5 and 1200 mm².) 2 This is the number of values ​​within the range that satisfies the range of / s.

[0031] [ka] (In equation (3), n'' and m are each positive numbers, m / n'' is a number between 0.5 and 2, and n''+m is the kinematic viscosity at 40°C between 10 and 900 mm².) 2 It is a number that satisfies the range / s.

[0032]

Chem.

[0033] In addition, PFPE may have a reactive functional group capable of forming a bond or a state close to a bond with the above binder resin, and a non-reactive functional group incapable of forming a bond or a state close to a bond with the above binder resin. Examples of the reactive functional group include, for example, an acrylic group, a methacrylic group, and an oxy-silyl group. Examples of the non-reactive functional group include, for example, a hydroxyl group, a trifluoromethyl group, and a methyl group. Examples of commercially available PFPE having the reactive functional group as described above include, for example, the following. "Fluorolink MD700", "Fluorolink AD1700", "Fluorolink S10" (all are trade names; manufactured by Solvay), "Optool DAC" (trade name; manufactured by Daikin). Note that "MD-500" is a PFPE having a methacrylic group as a functional group, and "Fluorolink AD1700" is a PFPE having an acrylic group as a functional group.

[0034] Examples of commercially available PFPE having the non-reactive functional group as described above include "Fluororing D10H", "Fluorolink D4000", "Fomblin Z15" (all are trade names, manufactured by Solvay), "Demnum S-20", "Demnum S-65", "Demnum S200" (all are trade names, manufactured by Daikin).

[0035] <A: Compound 1> Compound 1, which relates to component A, has the structure shown in chemical structural formula (I) and the structure shown in chemical structural formula (II). Compound 1 functions as a dispersant for dispersing PFPE in a binder resin. The graft copolymer relating to compound 1 has both the first unit shown in the following chemical structural formula (I) and the second unit shown in the following chemical structural formula (II). The first unit is a site with excellent affinity for PFPE, while the second unit has excellent affinity for the binder resin. Furthermore, the first unit has a perfluoromethyl group as a side chain. This is thought to compensate for the decrease in the dispersibility of PFPE in the binder resin caused by introducing an oxygen atom and reducing the number of consecutive carbon atoms in the perfluoroalkyl group to three or less. As a result, compound 1 according to this disclosure can better disperse PFPE with low surface free energy in the binder resin.

[0036] [ka]

[0037] [ka]

[0038] Examples of the linking group R1 in chemical structural formula (I) include alkylene groups having 1 to 6 carbon atoms, and groups composed of carbon atoms, hydrogen atoms, nitrogen atoms, and oxygen atoms, with a main chain of 6 or fewer atoms. Specifically, examples include alkylene groups having 1 to 6 carbon atoms (e.g., -CH2-, -CH2CH2-), and groups like the one shown in structural formula (i) below, in which a methylene group (CH2) and an ethylene group (CH2CH2) are linked by a urethane bond (-OC(=O)NH-). In structural formula (1), the main chain refers to -COCNCC-. (i) -CH2OC(=O)NHCH2CH2-

[0039] Examples of the linking group R4 in chemical structural formula (II) include groups with nine or fewer atoms constituting the main chain. For example, a group composed of a carbon atom, a hydrogen atom, an oxygen atom, and a sulfur atom, with nine or fewer atoms constituting the main chain, and a group composed of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, and a sulfur atom, with nine or fewer atoms constituting the main chain. Specific examples of such groups are shown in structural formulas (ii) to (iv) below. In structural formula (ii), the main chain is -SCCOCCCOC-. In structural formula (iii), the main chain is -SCCCNCCOC-. In structural formula (iv), the main chain is -SCCNCCOC-. (ii) -SCH2C(=O)OCH2CH(OH)CH2OC(=O)- (iii) -SCH2CH2C(=O)NHCH2CH2OC(=O)- (iv) -SCH2C(=O)NHCH2CH2OC(=O)-

[0040] The peak top molecular weight of compound 1 is preferably between 20,000 and 40,000. By having the above-mentioned numerical range for peak top molecular weight, it exhibits a high steric hindrance effect and can effectively suppress aggregation of PFPEs. Compound 1 can also be defined as an acrylic resin or methacrylic resin in which a group having a perfluoroalkyl group with three carbon atoms is grafted. Such a compound can be obtained by copolymerizing a macromonomer with a monofunctional monomer. Here, the macromonomer is a compound that has a higher molecular weight and a reactive group compared to a general monomer. Among such macromonomers, a graft copolymer can be obtained by polymerizing a macromonomer having one polymerizable functional group per molecule with a monomer having one polymerizable functional group per molecule. [Examples]

[0041] The following provides a more detailed explanation of the electrophotographic belt related to this disclosure, including some non-limiting specific examples.

[0042] <Preparation of macromonomers> <<Macromonomer No. 1>> A macromonomer having a methyl methacrylate segment (product name: AA-6; manufactured by Toagosei Co., Ltd., R3 and R5: -CH3, number average molecular weight: 6000) was prepared as macromonomer No. 1. <<Macromonomer No. 2>> The materials listed in Table 1 below were added to a glass flask equipped with a reflux condenser, and then purged with nitrogen while maintaining the temperature at 15°C in a water bath.

[0043] [Table 1]

[0044] Subsequently, the polymerization reaction was carried out for 5 hours under a nitrogen atmosphere by adjusting the temperature of the water bath to 85°C in the reaction solution. The polymerization reaction was stopped by ice cooling, and a solution containing the compound shown in chemical formula (III) was obtained.

[0045] [ka]

[0046] Next, 60 parts by mass of toluene were added to bring the triethylamine concentration to 0.5 wt% relative to the amount of Tert-butyl methacrylate monomer added, and the hydroquinone monomethyl ether concentration to 200 ppm relative to the amount of Tert-butyl methacrylate monomer added. Ten times the molar amount of glycidyl methacrylate relative to the acid value of the obtained chemical formula (III) was added, and the reaction was carried out at 110°C for 11 hours. The reaction was stopped by water cooling, n-hexane was added, and the precipitate was obtained by centrifugation. Subsequently, macromonomer No. 2 shown in formula (IV) was obtained by vacuum drying at 80°C and below 1325 Pa for 3 hours.

[0047] [ka]

[0048] <<Macromonomer No. 3>> Macromonomer No. 3 was prepared in the same manner as macromonomer No. 2, except that glycidyl methacrylate used in the preparation of macromonomer No. 2 was replaced with glycidyl acrylate, and macromonomer No. 3, shown by chemical formula (V), was obtained.

[0049] [ka]

[0050] <<Macromonomer No. 4>> Tert-butyl methacrylate monomer is converted to methyl methacrylate monomer. Thioglycolic acid to 3-mercaptopropionic acid, Glycidyl methacrylate is converted to 2-isocyanatoethyl methacrylate. Triethylamine is converted to zirconium(IV) acetylacetonate. Change 10 times the molar amount to 2 times the molar amount. The reaction time was changed from 110°C for 11 hours to 50°C for 24 hours. Macromonomer No. 4 was prepared in the same manner as macromonomer No. 2, with the exception of some modifications. Macromonomer No. 4, represented by chemical formula (VI), was obtained.

[0051] [ka]

[0052] <<Macromonomer No. 5>> We prepared Polymer Source's POLY (METHYL METHACRYLATE) MACROMONOMER, ΩVINYL-TERMINATED, with a number-average molecular weight of 2800, as Macromonomer No. 5.

[0053] <<Macromonomer No. 6>> Polymer Source's POLY (METHYL METHACRYLATE) MACROMONOMER, ΩVINYL-TERMINATED, with a number-average molecular weight of 9900, was prepared as Macromonomer No. 6. The structures of macromonomers No. 2-6 are shown in Table 2. The value of m was determined by the peak area ratio of the 1H NMR spectrum in CDCl3 solvent.

[0054] [Table 2]

[0055] <Preparation of monomers having a perfluoro structure> <<Perfluorostructure-containing monomer No. 1>> 1H,1H-Perfluoro(2,5-dimethyl-3,6-dioxanonanoyl)acrylate having the structure shown in the following chemical formula (VIII) was designated as perfluoro structure-containing monomer No. 1. Perfluoro structure-containing monomer No. 1 is a material that yields the structure shown in chemical structural formula (I). In the structure shown in chemical structural formula (I) formed by this perfluoro structure-containing monomer No. 1, R1 is a methylene group (CH2) and R2 is a hydrogen atom (H).

[0056] [ka]

[0057] <<Perfluorostructure-containing monomer No. 2>> The materials listed in Table 3 were mixed in a glass flask equipped with a stirrer, reflux condenser, nitrogen gas inlet tube, constant temperature bath, and thermometer at 20°C under a nitrogen atmosphere for 30 minutes, and then the mixture was heated to 50°C and reacted for 24 hours. As a result, perfluorostructure-containing monomer No. 2, represented by chemical formula (VII), was obtained.

[0058] [Table 3]

[0059] [ka]

[0060] <Preparation of graft copolymers> <<Graft Copolymer No. 11>> The materials shown in Table 4 below were mixed in a glass flask equipped with a stirrer, reflux condenser, nitrogen gas inlet tube, constant temperature bath, and thermometer at 20°C under a nitrogen atmosphere for 30 minutes. The reaction solution was then heated to 85-90°C and allowed to react for 5 hours. The reaction was stopped by ice cooling, and 1500 parts by mass of 2-propanol was added to obtain a precipitate. This precipitate was washed with a mixed solvent of n-butyl acetate and 2-propanol in a ratio of 1:5, and dried at 80°C under reduced pressure of 1325 Pa or less for 3 hours to obtain graft copolymer No. 11, which is a copolymer of macromonomer No. 1 and perfluorostructure-containing monomer No. 1.

[0061] [Table 4]

[0062] <<Graft copolymers No. 21, 22, 31, 32, 41, 51, 52, 61, 62>> Graft copolymers No. 21, 22, 31, 32, 41, 51, 52, 61, and 62 were prepared in the same manner as graft copolymer 11, except that the amounts of macromonomer species, perfluorostructure-containing monomer species, and 1,1'-azobis(1-acetoxy-1-phenylethane) were as shown in Table 5.

[0063] [Table 5]

[0064] <<Graft Copolymer No. 90>> Graft copolymer No. 90 was obtained by the same method as graft copolymer 11, except that perfluoro structure-containing monomer No. 1 was changed to 2,2,3,3,4,4,4-heptafluorobutyl acrylate having the structure shown in the following chemical formula (IX). [ka]

[0065] <Measurement of peak top molecular weight> Table 6 shows the peak-top molecular weights of the obtained graft copolymers. The peak-top molecular weight was measured using a GPC-104 gel permeation chromatograph (GPC) (Showdex Corporation) after preparing a 0.2% by mass solution by dissolving the sample in tetrahydrofuran (hereinafter also referred to as THF). For molecular weight measurement, a column consisting of one Showdex Corporation "GPC KF-603" and one "GPC KF-604" linked together was used, 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 (Showdex Corporation SM-105) with a known molecular weight.

[0066] [Table 6]

[0067] [Example 1] The materials shown in Table 7 below were mixed in a homogenizer to obtain paint A.

[0068] [Table 7]

[0069] A coating of paint A was applied to the outer surface of an endless electrophotographic belt made of polyimide resin with dispersed carbon black, which is installed as an intermediate transfer belt in a full-color multifunction printer (product name: imageRUNNER ADVANCE C5051; manufactured by Canon Corporation), to a dry film thickness of 6 μm. It was then dried at 70°C for 3 minutes. Afterward, a high-pressure mercury lamp was used to achieve a peak illuminance of 200 mW / cm² at a wavelength of 365 nm. 2 , cumulative light intensity 2 J / cm 2 The coating was cured by irradiating it with ultraviolet light under the specified conditions to form a surface layer, and electrophotographic belt No. 1 was obtained. The obtained electrophotographic belt was subjected to the following evaluations 1 and 2.

[0070] <Evaluation 1: Measurement of the hardness of the electrophotographic belt> The hardness of electrophotographic belts was measured using the nanoindentation method. Specifically, a microhardness tester (product name: PICODENTOR HM500; manufactured by Fischer Instruments) was used, and a Vickers indenter was used as the indenter. Nanoindentation tests were performed under conditions where the indentation depth was 100-200 nm, and the indentation hardness was determined.

[0071] <Evaluation 2: Electrophotographic characteristics evaluation> Electrophotographic images were formed using the electrophotographic belts obtained in Examples 1 to 11 and Comparative Example 1, and the resulting electrophotographic images were evaluated. Specifically, an electrophotographic belt was mounted as an intermediate transfer belt in a full-color multifunction printer (product name: imageRUNNER ADVANCE C5760F; manufactured by Canon), and 30,000 electrophotographic images were formed consecutively under the following conditions. The electrophotographic images were formed by creating 97 solid images, followed by 3 solid white images, and repeating this cycle 300 times to form 30,000 images. 97 solid images to be formed: The amount of cyan (C), magenta (M), yellow (Y), and black (K) toner applied to the surface of the electrophotographic belt is 0.4 mg / cm². 2 Furthermore, a solid image with a 100% aspect ratio. Three solid white images formed: The amount of each toner of CMYK loaded on the surface of the electrophotographic belt is 0 mg / cm 2 , a solid white image with an image ratio of 100% The formation of the electrophotographic image was carried out in an environment of temperature: 30 °C and relative humidity: 80%. Also, the paper used was "GF-C081" (A3 size, basis weight 81.4 g / m 2 , thickness 97 μm, whiteness of about 100%, manufactured by Canon Inc.).

[0072] Then, the solid white image with a loading amount of 0 mg / cm 2 was visually observed, and it was confirmed whether streak-like images caused by poor cleaning of the surface of the electrophotographic belt were formed on the solid white image where no toner should have been transferred at all. And when streak-like images were observed, the cleaning blade in contact with the surface of the electrophotographic belt was visually observed. And it was confirmed whether the toner that was not secondarily transferred (remaining transferred toner) on the surface of the electrophotographic belt was being cleaned by the cleaning blade. And when it was confirmed that the remaining transferred toner was not being cleaned by the cleaning blade, it was determined that the streak-like images were caused by poor cleaning of the surface of the electrophotographic belt. This evaluation was carried out based on the above observation results according to the following criteria. Rank A: No streak-like images caused by poor cleaning of the surface of the electrophotographic belt were observed on the solid white image. Rank B: Streak-like images caused by poor cleaning of the surface of the electrophotographic belt were observed on the solid white image.

[0073] [Examples 2 to 10] As shown in Table 8, paints were prepared in the same manner as in Example 1 except that the graft copolymer 11 was changed, and electrophotographic belts No. 2 to 10 were obtained. The obtained electrophotographic belts were subjected to the above Evaluation 1 and Evaluation 2.

[0074]

Table 8

[0075] [Example 11] 95 parts by mass of pentaerythritol triacrylate was replaced with 40 parts by mass of bisphenol A type epoxy acrylate (EBECRYL 600, manufactured by Daicel Ornex) and 55 parts by mass of pentaerythritol triacrylate. Except for this change, the paint was prepared in the same manner as in Example 2 to obtain electrophotographic belt No. 11. The obtained electrophotographic belt was subjected to evaluations 1 and 2 described above.

[0076] [Comparative Example 1] A coating was prepared in the same manner as in Example 1, except that graft copolymer No. 11 was replaced with graft copolymer No. 90, to obtain electrophotographic belt No. 90. The obtained electrophotographic belt No. 90 was subjected to the above evaluations 1 and 2. In evaluation 2, streaks caused by poor cleaning appeared in the solid white image formed at the 100th cycle, so image formation was stopped at the end of the 200th cycle. The evaluation results for Examples 1-11 and Comparative Example 1 are shown in Table 9.

[0077] [Table 9]

[0078] The results of Evaluation 1 and Evaluation 2 for the electrophotographic belt No. 90 in Comparative Example 1 are thought to be due to the difference in the surface free energy of the comb-shaped graft copolymer. Specifically, the surface free energy of comb-shaped graft copolymer No. 90 is different from that of the comb-shaped graft copolymer used in the example, which is thought to be the reason for the low dispersibility of PFPE in the binder resin. In electrophotographic belt No. 90, the PFPE in the surface layer is not finely dispersed, and as is clear from the results of Evaluation 1, the hardness of the surface layer decreased. As a result, it is thought that the surface layer was worn down by repeated cleaning of the electrophotographic belt surface, and the PFPE in the surface layer was lost along with the wear. Therefore, it is estimated that the cleanability of the electrophotographic belt surface decreased over time. On the other hand, in the electrophotographic belts according to each embodiment, the hardness of the surface layer is maintained at a high level because the PFPE in the surface layer is finely dispersed. Therefore, the surface layer is less likely to wear down even if the surface of the electrophotographic belt is repeatedly cleaned. In addition, because the PFPE is finely dispersed, even if the surface layer wears down, the PFPE domains are present almost uniformly in the thickness direction of the surface layer, which is thought to prevent the cleanability of the electrophotographic belt surface from deteriorating even with repeated use. Table 10 shows the n-hexadecane contact angles for thin films of graft copolymer No. 21 and graft copolymer No. 90 to illustrate the difference in surface free energy between the examples and comparative examples.

[0079] [Table 10]

[0080] Table 11 lists the CAS numbers and manufacturer names of the materials used in the examples, indicated by their common names.

[0081] [Table 11] [Explanation of symbols]

[0082] Py: Yellow image forming unit Pm: Magenta Image Forming Unit Pc: Cyan image forming unit Pk: Black image forming unit 1Y: Yellow Photosensitive Drum 1M: Magenta photosensitive drum 1C: Cyan photosensitive drum 1K: Black photosensitive drum 4Y: Yellow developing unit 4M: Magenta Developer 4C: Cyan Developer 4K: Black Developing Machine 5Y, 5M, 5C, 5K: Primary transfer rollers Ty, Tm, Tc, Tk: Primary transfer area 73: Secondary transfer inner roller 100: Image forming apparatus 2Y, 2M, 2C, 2K: Charger 3Y, 3M, 3C, 3K: Laser Scanners 11: Transfer belt cleaning unit 12: Paper feed cassette 15: Resistola vs. 7: Intermediate transfer belt 8:2nd secondary transfer outer roller 9: Fuser 91: Fixing film 92: Pressure roller S: Transfer material

Claims

1. An electrophotographic belt having at least a base layer and a surface layer, The surface layer contains the following A, B, and C: A: Compound 1 having the structure shown in the following chemical structural formula (I) and the structure shown in the following chemical structural formula (II) B: Perfluoropolyether C: Binding resin 【Chemistry 1】 【Chemistry 2】 An electrophotographic belt in which the linking group R1 is represented by the following structural formula (i): (i) -CH2OC(=O)NHCH2CH2-.

2. The aforementioned linking base R4 A group composed of carbon atoms, hydrogen atoms, oxygen atoms, and sulfur atoms, with a main chain having 9 or fewer atoms; or, The electrophotographic belt according to claim 1, wherein the group is composed of carbon atoms, hydrogen atoms, nitrogen atoms, oxygen atoms, and sulfur atoms, and the number of atoms constituting the main chain is nine or less.

3. The electrophotographic belt according to claim 1 or 2, wherein the linking group R4 is selected from the group consisting of the following structural formulas (ii) to (iv): (ii) -SCH ２ C(=O)OCH ２ CH(OH)CH ２ OC(=O)- (iii) -SCH ２ CH ２ C(=O)NHCH ２ CH ２ OC(=O)- (iv) -SCH ２ C(=O)NHCH ２ CH ２ OC(=O)- 。

4. The electrophotographic belt according to any one of claims 1 to 3, wherein the binding resin is one or more resins selected from the group consisting of acrylic resin, methacrylic resin, and epoxy resin.

5. The electrophotographic belt according to any one of claims 1 to 4, wherein the peak top molecular weight of compound 1 is 20,000 or more and 40,000 or less.

6. An electrophotographic image forming apparatus comprising an image carrier for carrying a toner image, and an intermediate transfer belt for carrying and transporting the toner image, which has been primary transferred from the image carrier, to a transfer material for secondary transfer, wherein the intermediate transfer belt is an electrophotographic belt according to any one of claims 1 to 5.

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