Electrophotographic belt and electrophotographic image forming apparatus using the same

Abstract

To provide a belt for electrophotography whose toner releasability and cleanability are less likely to change even after a long-term use.SOLUTION: A belt for electrophotography has an endless shape and is provided with a base layer in an endless shape, an elastic layer on an outer peripheral surface of the base layer, and a surface layer on an outer peripheral surface of the elastic layer. The surface layer includes a urethane resin as a binder, polytetrafluoroethylene particles, and a compound having a perfluoropolyether structure and an oxyalkylene structure.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an electrophotographic belt that can be used, for example, as an intermediate transfer belt in an electrophotographic image forming apparatus such as a copying machine or a printer, and to an electrophotographic image forming apparatus. [Background technology]

[0002] 2. Description of the Related Art In electrophotographic image forming apparatuses, a tandem system is widely adopted in which toner images of Y, M, C, and K colors are superimposed on an intermediate transfer belt, and then all of the toner images are transferred onto paper or the like at once to obtain a full-color image. In such an electrophotographic image forming apparatus, an electrophotographic belt having an elastic layer may be used as an intermediate transfer belt in order to further improve the image quality of an electrophotographic image. Such an electrophotographic belt can reduce the pressure acting on the toner in the secondary transfer section, and can suppress the occurrence of an image defect called a hollow phenomenon. In addition, since the electrophotographic belt has excellent adhesion between the electrophotographic belt and paper in the secondary transfer section, it is also effective in improving the secondary transferability of the toner to thick paper or paper having unevenness.

[0003] In order to further increase the efficiency of toner transfer to paper in the secondary transfer section, the toner carrying surface of the electrophotographic belt (hereinafter also referred to as the "outer surface") may be configured with a surface layer that has excellent toner release properties. Here, Patent Document 1 discloses a conductive elastic belt having a conductive rubber base material, a release layer as a protective layer provided on the rubber base material, and an intermediate layer provided between the rubber base material and the release layer and having a lower Martens hardness than the release layer. It also discloses that it is preferable to use a urethane resin as the resin in the release layer, since it is easy to follow the elongation of the belt base material that accompanies changes in the usage environment. It also discloses that it is preferable to use polytetrafluoroethylene (PTFE) as a lubricant in the release layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-114907 A [Non-patent literature]

[0005] [Non-Patent Document 1] LOPEZ, Gerald, et al. An amphiphilic PEG-b-PFPE-b-PEG triblock copolymer: synthesis by CuAAC click chemistry and self-assembly in water. Polymer Chemistry, 2016, 7.2: 402-409. Summary of the Invention [Problem to be solved by the invention]

[0006] According to the study by the present inventors, in an electrophotographic belt having an elastic layer and a surface layer, the surface layer containing PTFE particles and a urethane resin as a binder resin, the PTFE particles in the surface layer are unevenly distributed on the side of the surface layer close to the elastic layer.This is considered to be due to the fact that the specific gravity of the PTFE particles is heavier than that of the urethane resin.And, in an electrophotographic belt having such a surface layer, the content of the PTFE particles changes as the surface layer wears with use, and accordingly, the toner releasing property and cleaning property of the outer surface of the electrophotographic belt may change. One aspect of the present disclosure is to provide an electrophotographic belt having toner releasability and cleaning property that are unlikely to change even after long-term use. Another aspect of the present disclosure is to provide an electrophotographic image forming apparatus capable of stably forming high-quality electrophotographic images. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, there is provided an electrophotographic belt having an endless shape, comprising an endless base layer, an elastic layer on an outer peripheral surface of the base layer, and a surface layer on the outer peripheral surface of the elastic layer, the surface layer including a urethane resin as a binder, polytetrafluoroethylene particles, and a compound having a perfluoropolyether structure and an oxyalkylene structure. According to another 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 belt that carries and transports the toner image, which has been primarily transferred from the image carrier, to a transfer material for secondary transfer, wherein the intermediate transfer belt is the electrophotographic belt described above. Effect of the Invention

[0008] According to one aspect of the present disclosure, it is possible to obtain an electrophotographic belt having an outer surface layer in which the toner releasability and cleaning property are unlikely to change even with long-term use, and according to another aspect of the present disclosure, it is possible to obtain an electrophotographic image forming apparatus capable of forming high-quality electrophotographic images for a long period of time. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing an example of an electrophotographic image forming apparatus using an electrophotographic belt according to an embodiment of the present disclosure. [Diagram 2] 1 is a cross-sectional view of an electrophotographic belt according to one embodiment of the present disclosure. [Diagram 3] FIG. 13 is a diagram for explaining curling of a blade. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an electrophotographic belt having an endless belt shape according to one embodiment of the present disclosure will be described, although the technical scope of the present disclosure is not limited to the following description. The electrophotographic belt is used, for example, as an intermediate transfer belt 7 in an electrophotographic image forming apparatus shown in FIG. A cross section of the electrophotographic belt in a direction perpendicular to the circumferential direction is shown in Fig. 2. The electrophotographic belt has a structure in which a base layer 21, an elastic layer 22, and a surface layer 23 are laminated together. However, the structure is not limited to these three layers, and a primer layer for improving adhesion between the layers, a stress relaxation layer for suppressing cracking of the surface layer 23, and an intermediate layer for suppressing bleeding may be added.

[0011] (base layer) The base layer 21 has the shape of an endless belt. Examples of materials suitable for the base layer 21 include: polyether ether ketone, polyethylene terephthalate, polybutylene naphthalate, polyester, polyimide, polyamide, polyamideimide, polyacetal, polyphenylene sulfide, polyvinylidene fluoride, and the like.

[0012] The resin for the base layer 21 may be made conductive by adding a conductive compound such as metal powder, conductive oxide powder, conductive carbon, lithium salt, ionic liquid, etc. In the following examples, polyvinylidene fluoride to which polyalkylene glycol and lithium salt have been added was used from the viewpoint of obtaining excellent productivity and conductivity, but a combination of other resins and conductive agents exemplified above may also be used. The thickness of the base layer 21 is preferably 10 μm to 500 μm. When the thickness is in this range, the electrophotographic belt having an endless shape can be given sufficient mechanical strength while maintaining its flexibility.

[0013] (Elastic layer) The elastic layer 22 needs to have a suitable degree of flexibility in order to conform to the surface shape of the recording medium. Materials suitable for such an elastic layer include the following: rubber materials and elastomer materials, such as silicone rubber, urethane rubber, chloroprene rubber, acrylic rubber, olefin elastomer, styrene elastomer, polyamide elastomer, polyester elastomer, and polyurethane elastomer.

[0014] Note that the elastic layer 22 may be made conductive by adding a conductive compound such as metal powder, conductive oxide powder, conductive carbon, lithium salt, ionic liquid, etc. In the following examples, a polyurethane elastomer to which polyalkylene glycol, which is a thermoplastic elastomer, and lithium salt have been added was used from the viewpoint of obtaining excellent productivity, but a combination of other resins and conductive agents exemplified above may also be used.

[0015] The thickness of the elastic layer 22 is preferably 100 μm to 1000 μm, and more preferably 200 μm to 500 μm. The JIS-A hardness of the elastic layer 22 is preferably 80 degrees or less. The amount of the conductive agent blended in the elastic layer 22 is preferably 10 parts by weight or less, and more preferably 5 parts by weight or less, per 100 parts by weight of the urethane resin, which gives the elastic layer 22 a stable conductivity suitable for an electrophotographic belt.

[0016] In addition, the elastic layer 22 may contain other additives such as fillers, crosslinking accelerators, crosslinking retarders, crosslinking assistants, scorch inhibitors, anti-aging agents, softeners, heat stabilizers, flame retardants, flame retardant assistants, ultraviolet absorbers, and rust inhibitors. Electrophotographic belts are required to be flame retardant because they pass electricity through the transfer area. It is difficult to ensure the necessary flame retardancy with various elastomers and rubbers without adding flame retardants. Flame retardants include metal hydroxides such as magnesium hydroxide and aluminum hydroxide that utilize endothermic properties, platinum compounds and phenolic compounds that suppress thermal decomposition, intumescent compounds that have an oxygen blocking effect, and phosphate ester condensation compounds.

[0017] Examples of the filler include reinforcing fillers such as fumed silica, crystalline silica, wet silica, fumed titanium oxide, and cellulose nanofibers. Furthermore, in order to improve adhesion, a primer layer (not shown) may be provided as necessary between the base layer 21 and the elastic layer 22. The thickness of the primer layer is preferably 0.1 μm or more and 2 μm or less from the viewpoint of reducing cohesive failure in the primer layer.

[0018] (Surface layer) The surface layer 23 contains a urethane resin 23-1 as a binder resin, PTFE particles 23-2, and a compound having a perfluoropolyether structure and an oxyalkylene structure (not shown). The PTFE particles 23-2 impart excellent toner releasability and excellent cleanability to a surface 23-5 of the surface layer 23 opposite to the side facing the elastic layer 21 (hereinafter also referred to as the "outer surface") 23-5. The outer surface 23-5 of the surface layer constitutes the toner carrying surface of the electrophotographic belt 7. The thickness of the surface layer 23 is preferably 0.5 μm to 20.0 μm, because the surface layer can well follow the deformation of the elastic layer when the electrophotographic belt is used for forming an electrophotographic image, and the surface layer can be prevented from peeling off from the elastic layer.

[0019] <Polytetrafluoroethylene (PTFE) particles> The number-average particle diameter of the polytetrafluoroethylene particles is appropriately selected to be less than 2.00 μm, on the premise that no protrusions due to the PTFE particles are formed on the outer surface of the surface layer 23, i.e., the outer surface of the electrophotographic belt. In particular, it is preferable to appropriately select and use particles having a number-average particle diameter within the range of 0.05 μm to 1.80 μm (50 nm to 1800 nm). Specific examples of PTFE particles include "Fluon (registered trademark) PTFE Lub series" (product name, manufactured by AGC Corporation) and "TLP 10F-1" (product name, manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.).

[0020] <Urethane resin> Urethane resin is a resin that contains a urethane bond (-NH-(C=O)-O-). The surface layer containing a urethane resin as a binder resin has excellent adhesion to the elastic layer, and can be made to conform well to the elastic deformation of the elastic layer. The raw material of the urethane resin is not particularly limited, and a known polyurethane resin liquid can be used. Examples of commercially available polyurethane resin liquids include "HYDRAN WLS-201" (trade name, manufactured by DIC Corporation) and "UCECOAT 7850" (trade name, manufactured by Daicel-Allnex Corporation).

[0021] <Compound Having Perfluoropolyether Structure and Oxyalkylene Structure> The surface layer 23 further contains a compound having a perfluoropolyether structure (hereinafter also referred to as a "PFPE structure") and an oxyalkylene structure (hereinafter also referred to as an "OR structure") (hereinafter sometimes referred to as a "PFPE / OR compound"). The oxyalkylene structure includes an oxyethylene structure or an oxypropylene structure. The PFPE / OR compound functions as a dispersant for dispersing the PTFE particles in the urethane resin. The PFPE / OR compound allows the PTFE particles to be uniformly present in the thickness direction of the surface layer 23. Therefore, at least a part of the PTFE particles is exposed on the outer surface of the electrophotographic belt even when it is new, or at least a part of the PTFE particles is exposed at a very early stage of image formation. Therefore, even if the electrophotographic belt has just been used, the sliding property between the outer surface and a contact member such as a cleaning blade is high, and stable electrophotographic images can be formed from the beginning. In addition, since the PTFE particles are uniformly present in the thickness direction of the surface layer, even if the outer surface of the electrophotographic belt is worn down by rubbing against a contact member, at least a part of the PTFE particles can always be exposed on the outer surface, and therefore, excellent sliding properties between the outer surface of the electrophotographic belt and the contact member can be maintained for a long period of time.

[0022] In the PFPE / OR compound, the number average molecular weight of the PFPE structure is preferably 500 to 10,000, and more preferably 1,200 to 4,000. The PFPE structure may be a linear structure or may partially have a branched structure. Specific examples of the PFPE structure include at least one selected from the group consisting of structures represented by the following structural formulas (i) to (iv). -CF 2 O-(i) -CF 2 CF 2 O-(ii) -CF 2 CF 2 CF 2 O-(iii) -CF(CF 3 )CF 2 O-(iv)

[0023] The OR structure includes, for example, a structure represented by the following structural formula (v). -[(CH 2 )nO]m- (v) In formula (v), n represents, for example, an integer of 1 to 5, and m represents an integer of 1 or more. The preferred number for n is 2 to 3. When the number average molecular weight of the oxyalkylene structure is Mn1 and the number average molecular weight of the perfluoropolyether structure is Mn2, the value of (Mn1 / Mn2) is preferably 0.3 to 2.0, and more preferably 0.5 to 1.0, which allows the PTFE particles to be more uniformly dispersed in the urethane resin.

[0024] As the PFPE / OR compound, for example, a ternary copolymer synthesized by a reaction (azide-alkyne cycloaddition reaction) between an azide compound of polyalkylene oxide and a diyne of perfluoropolyether in the presence of a copper catalyst can be used. The synthesis method of such a ternary copolymer is described, for example, in Non-Patent Document 1.

[0025] <Method of forming surface layer> A method for manufacturing the surface layer 23 includes, for example, applying a surface layer paint containing raw materials for urethane resin 23-1, PTFE particles 23-2, and a compound having a PFPE structure and an oxyalkylene structure to the elastic layer 22 to form a coating film of the surface layer paint. The coating method may be a known method such as a spray method or a dipping method. The coating film can then be cured by heating or by exposure to radiation such as electron beams or ultraviolet rays.

[0026] (Electrophotographic image forming apparatus) An example of an electrophotographic image forming apparatus using the electrophotographic belt according to the present embodiment as an intermediate transfer belt will be described with reference to FIG. 1. The electrophotographic image forming apparatus 100 shown in FIG. 1 is a color electrophotographic image forming apparatus (color laser printer). In this electrophotographic image forming apparatus, image forming units (Py, Pm, Pc, Pk) of each color, yellow (Y), magenta (M), cyan (C), and black (K), are arranged in order along the flat portion of the intermediate transfer belt 7, which is an intermediate transfer body, in the moving direction of the intermediate transfer belt. Each image forming unit of each color includes an electrophotographic photosensitive member (1Y, 1M, 1C, 1K), a charging roller (2Y, 2M, 2C, 2K), a laser exposure device (3Y, 3M, 3C, 3K), and a developing device (4Y, 4M, 4C, 4K). The electrophotographic image forming apparatus 100 also includes primary transfer rollers (5Y, 5M, 5C, 5K) at positions facing the respective photoconductors with the intermediate transfer belt 7 in between. Since the basic configuration of each image forming unit is the same, the yellow image forming unit Py will be described in detail below.

[0027] The yellow image forming unit Py has a drum-shaped electrophotographic photosensitive member (hereinafter also referred to as a "photosensitive drum" or a "first image bearing member") 1Y as an image bearing member. The photosensitive drum 1Y is formed by laminating a charge generating layer, a charge transport layer, and a surface protective layer in this order on an aluminum cylinder as a base. Further, the yellow image forming unit Py includes a charging roller 2Y as a charging means. By applying a charging bias to the charging roller 2Y, the surface of the photosensitive drum 1Y is uniformly charged.

[0028] A laser exposure device 3Y is disposed above the photosensitive drum 1Y as an image exposure means. The laser exposure device 3Y scans and exposes the uniformly charged surface of the photosensitive drum 1Y in accordance with image information, forming an electrostatic latent image of a yellow color component on the surface of the photosensitive drum 1Y. The electrostatic latent image formed on the photosensitive drum 1Y is developed with toner, which is a developer, by 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, which is a developer. The developing roller 4Ya, to which the yellow toner is supplied, is lightly pressed against the photosensitive drum 1Y in the developing section, and is rotated in the forward direction with a speed difference from 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 developing bias to the developing roller 4Ya. As a result, a visible image (yellow toner image) is formed on the photosensitive drum 1Y.

[0029] The intermediate transfer belt 7 is stretched around a drive roller 71, a tension roller 72, and a driven roller 73, and is moved (rotationally driven) in the direction of the arrow in the figure while in contact with the photosensitive drum 1Y. The yellow toner image on the photosensitive drum (on the first image carrier) that has reached the primary transfer portion Ty is primarily transferred onto the intermediate transfer belt 7 by a primary transfer body (primary transfer roller 5Y) that is arranged opposite the photosensitive drum 1Y via the intermediate transfer belt 7.

[0030] Similar to the yellow toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (K) toner image are transferred onto the intermediate transfer belt 7 at the primary transfer portion (Tm, Tc, Tk) as the intermediate transfer belt 7 moves. The four color toner images thus transferred onto the intermediate transfer belt 7 are transported as the intermediate transfer belt 7 moves. Then, at the secondary transfer portion T', the toner images are transferred collectively onto a transfer material S (hereinafter also referred to as "second image carrier") transported at a predetermined timing by a secondary transfer outer roller 8 and a secondary transfer inner roller 73 as secondary transfer means. In such secondary transfer, a transfer voltage of several kV is usually applied to ensure a sufficient transfer rate.

[0031] The transfer material S is supplied to a conveying path from a cassette 12 in which the transfer material S is stored by a pickup roller 13. The transfer material S supplied to the conveying path is conveyed to a secondary transfer portion T' in synchronization with the four-color toner image transferred to the intermediate transfer belt 7 by a conveying roller pair 14 and a registration roller pair 15. The toner image transferred to the transfer material S is fixed by a fixing device 9 to become, for example, a full-color image. The fixing device 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 applying heat and pressure. Thereafter, the transfer material S is discharged outside the machine by a pair of conveying rollers 16, a pair of discharge rollers 17, etc.

[0032] A cleaning unit 11 for the intermediate transfer belt 7 is disposed downstream of the secondary transfer portion T' in the driving direction of the intermediate transfer belt 7, and removes residual toner that has not been transferred to the transfer material S at the secondary transfer portion T' and remains on the intermediate transfer belt 7. The example of the cleaning unit 11 shown in FIG. 1 includes a cleaning roller arranged in contact with the outer circumferential surface of the intermediate transfer belt 7 as a cleaning member. However, the cleaning member in the electrophotographic image forming apparatus according to the present disclosure is not limited to this form. For example, as shown in FIG. 3, a cleaning blade 32 arranged so that at least a part of it is in contact with the outer circumferential surface of the intermediate transfer belt 7 may be included as a cleaning member. As described above, the electrical transfer process of the toner image is repeated from the photoconductor to the intermediate transfer belt and from the intermediate transfer belt to the transfer material. Furthermore, by repeating recording on a large number of transfer materials, the electrical transfer process is further repeated. EXAMPLES

[0033] (Preparation of resin pellets for forming base layer) The materials shown in Table 1 below were kneaded using a twin-screw kneader (product name: PCM30, manufactured by Ikegai Corp.) to obtain resin pellets.

[0034] [Table 1]

[0035] (Preparation of resin pellets for forming elastic layer) The materials shown in Table 2 below were kneaded using a twin-screw kneader (product name: PCM30, manufactured by Ikegai Corp.) to obtain resin pellets.

[0036] [Table 2]

[0037] "Pluronic F-127" is a nonionic surfactant represented by the following structural formula: In the structural formula, a, b, and c are each an integer of 1 or more. HO-(CH 2 CH 2 O)a-(CH 2 (CH(CH 3 )O)b-(CH 2 CH 2 O)cH

[0038] (Preparation of a two-layer belt consisting of a base layer and an elastic layer) The resin pellets for forming the base layer and the resin pellets for forming the elastic layer prepared above were used to produce a two-layer laminated belt by co-extrusion. Specifically, two single-screw extruders (product name: GT40, manufactured by Plastics Engineering Research Institute Co., Ltd.) were prepared. These single-screw extruders were connected to a cylindrical die for co-extrusion. Then, the resin pellets for forming the base layer and the resin pellets for forming the elastic layer were placed in each single-screw extruder, and the resin for forming the base layer and the resin for forming the elastic layer were co-extruded from the cylindrical die. In this way, an endless laminated belt was obtained, the inner layer of which was polyvinylidene fluoride, the outer layer of which was thermoplastic polyurethane, and the width of which was 460 mm.

[0039] (Surface modification of elastic layer) In order to improve the adhesion between the elastic layer and the surface layer, the outer peripheral surface of the elastic layer was irradiated with ultraviolet light using an excimer lamp (manufactured by M.D.COM Co., Ltd.) that emits a single wavelength of 172 nm as an excimer UV irradiation unit, thereby performing surface modification. Specifically, the laminated belt was fitted into a cylindrical core, and irradiation was performed for 30 minutes in a space where nitrogen gas was flowing in while the core, which was located 1 mm away from the surface of the excimer lamp, was rotated at a rotation speed of 5 rpm.

[0040] (Preparation of PFPE Copolymer) Preparation of PFPE copolymer A Linear perfluoropolyether with -CH at both ends 2 16.7 mmol of raw material perfluoropolyether having -OH (product name: Fluorolink D10H, manufactured by Solvay Specialty Polymers, number average molecular weight 1200) was dropped into a mixed solvent of 80 ml of acetonitrile and 80 ml of tetrahydrofuran in which 3.2 g of sodium hydroxide was dissolved. Then, the mixture was heated to a temperature of 55°C under a nitrogen atmosphere. 10 ml of an 80% toluene solution of 3-bromo-1-propyne was added while stirring while maintaining the nitrogen atmosphere. Then, the mixture was reacted at a temperature of 55°C for 3 days. Next, the obtained reaction liquid was cooled to room temperature (temperature 25°C) and solid matter was removed using a filter paper with a pore size of 7 μm. The solvent was removed from the obtained solution, and the mixture was dried at a temperature of 100°C and a pressure of 1 Pa for 6 hours using a reduced pressure oven. Next, the mixture was filtered using a polytetrafluoroethylene filter with a particle retention capacity of 0.22 μm to obtain a compound S1 represented by the following structural formula.

[0041] [ka]

[0042] 1 mmol of polyethylene glycol monomethyl ether (molecular weight 2000) was added to a mixed solution of 25 ml of dichloromethane (super dehydrated) and 1.5 mo of triethylamine. 1.91 g of p-toluenesulfonyl chloride was further added to this solution, and the solution was substituted with nitrogen and stirred at a temperature of 25°C for 2 days. The resulting solution was washed twice with ion-exchanged water, the organic layer was taken out, and magnesium sulfate was added to dehydrate it. Next, the solid matter was removed using a filter paper with a pore size of 7 μm, and the solvent was removed from the resulting solution. The resulting solid matter was dissolved in dichloromethane, and the process of reprecipitation by adding diethyl ether was repeated twice to obtain compound T1 represented by the following structural formula.

[0043] [ka]

[0044] Compound T1, 0.5 mmol of the above compound T1 was dissolved in 40 ml of N,N-dimethylformamide, 0.325 g of sodium azide was added, and the mixture was stirred at 25°C for 2 days. Dichloromethane and water were added to the reaction solution, and the organic layer was taken out and washed three times with ion-exchanged water. Magnesium sulfate was added to the washed organic layer to dehydrate it, and then the solid matter was removed with a filter paper having a pore size of 7 μm, and the solvent was removed from the obtained filtrate. The obtained solid matter was dissolved in dichloromethane, and diethyl ether was added to reprecipitate. This process was repeated twice to obtain compound U1 of the following structural formula.

[0045] [ka]

[0046] 0.42 mmol of compound S1 and 0.84 mmol of compound U1 were added to 20 ml of N,N-dimethylformamide, and the mixture was purged with nitrogen for 30 minutes while stirring. Furthermore, 6.0 mg of copper bromide (I) and 7.0 mg of N,N,N',N",N"-pentamethyldiethylenetriamine were added in a nitrogen-purged state, and the mixture was stirred at 25°C for 24 hours. Diethyl ether at 5°C was added dropwise to the obtained solution, and the solid matter was filtered off. The mixture was dried at 25°C and 1 Pa for 24 hours to prepare PEG-PFPE-PEG copolymer A represented by chemical structural formula (1). Note that PFPE is an abbreviation for perfluoropolyether, and PEG is an abbreviation for polyethylene glycol.

[0047] [ka] (p, m, and n are positive integers that indicate the number of repeating structural units. Parts without an element symbol are composed only of carbon and hydrogen atoms.)

[0048] Preparation of PFPE copolymer B PFPE Copolymer B was prepared in the same manner as PFPE Copolymer A, except that polyethylene glycol monomethyl ether (molecular weight 2000) was replaced with poly(propylene glycol) monobutyl ether (molecular weight 2000). Preparation of PFPE copolymer C Linear perfluoropolyether with -CH at both ends 2 PFPE copolymer C was prepared in the same manner as PFPE copolymer A, except that the raw material perfluoropolyether having --OH was changed to "Fomblin Z-DOL4000" (product name, manufactured by Solvay Specialty Polymers, number average molecular weight = 4000). Preparation of PFPE copolymer D PFPE copolymer D was prepared in the same manner as PFPE copolymer A, except that polyethylene glycol monomethyl ether (molecular weight 2000) was changed to polyethylene glycol monomethyl ether (molecular weight 1000). Preparation of PFPE copolymer E PFPE copolymer E was prepared in the same manner as PFPE copolymer C, except that polyethylene glycol monomethyl ether (molecular weight 2000) was changed to polyethylene glycol monomethyl ether (molecular weight 4000). A list of PFPE copolymers A to E is shown in Table 1.

[0049] [Table 3]

[0050] (Preparation of Surface Layer Paint) Preparation of PTFE dispersion IA As a preliminary step for preparing the surface layer coating material, PTFE dispersion IA was prepared. Specifically, the materials shown in Table 4 below were premixed with a homogenizer, and then dispersed with a high-pressure homogenizer to obtain PTFE dispersion IA.

[0051] [Table 4]

[0052] Preparation of PTFE dispersions IB~IE A dispersion was prepared in the same manner as for PTFE dispersion IA except that the PFPE copolymer shown in Table 5 was used as a dispersant, to obtain PTFE dispersions IB to IE.

[0053] [Table 5]

[0054] Preparation of surface layer paint 1-A The PTFE dispersion IA and polyurethane resin liquid (product name: Hydran WLS-201, manufactured by DIC Corporation, solid content ratio 35%, viscosity at 25°C 150 mPa·s) were mixed in the following ratio to obtain surface layer coating material 1-A. ·PTFE dispersion IA 30 parts by mass Polyurethane resin liquid 70 parts by weight

[0055] Preparation of surface layer paint 1-B Surface layer coating material 1-B was obtained in the same manner as surface layer coating material 1-A, except that PTFE dispersion IA was changed to PTFE dispersion IB. Preparation of surface layer paint 1-C Surface layer coating material 1-C was obtained in the same manner as surface layer coating material 1-A, except that PTFE dispersion IA was changed to PTFE dispersion IC. Preparation of 1-D surface layer paint Surface layer coating material 1-D was obtained in the same manner as surface layer coating material 1-A, except that PTFE dispersion IA was changed to PTFE dispersion ID. Preparation of surface layer paint 1-E Surface layer coating material 1-E was obtained in the same manner as surface layer coating material 1-A, except that PTFE dispersion IA was changed to PTFE dispersion IE.

[0056] Preparation of surface layer paint 2-A Surface layer paint 2-A was prepared in the same manner as surface layer paint 1-A, except that the polyurethane resin liquid was changed to "UCECOAT 7850" (trade name, manufactured by Daicel Allnex Corporation). "UCECOAT 7850" is a dispersion-type water-dispersible resin with the following physical properties: Solid content 35%, average particle size less than 100 nm, viscosity at 25°C 200 mPa·s, weight average molecular weight 10,000.

[0057] Preparation of surface layer paint 3-A "Fluon PTFE AD915E" (product name, manufactured by AGC) was used as the PTFE dispersion liquid, and polyurethane resin liquid (product name: Hydran WLS-201, manufactured by DIC Corporation, solid content ratio 30%) was mixed in the following ratio to prepare surface layer paint 3-A. The solid content ratio of "Fluon PTFE AD915E" was 61%, the average particle size of the PTFE particles was 0.25 μm, and the viscosity at a temperature of 23°C was 19 mPa·s. The dispersant for the PTFE particles contained in "Fluon PTFE AD915E" was polyoxyalkylene alkyl ether. In other words, it did not have a perfluoropolyether structure. ·PTFE dispersion liquid 20 parts by mass Polyurethane resin liquid 80 parts by weight

[0058] Example 1 The laminated belt with the outer peripheral surface of the elastic layer modified as described above was fitted into a core, and while rotating at 90 rpm, the outer peripheral surface of the elastic layer was coated with the surface layer coating material 1-A using a spray gun (product name: W-101, manufactured by Anest Iwata Corporation). The amount of coating material discharged during coating was set so that the dry thickness of the coating film of the surface layer coating material 1-A was 3 μm. The laminated belt on which the coating film of the surface layer coating material 1-A was formed was heated in a heating furnace at a temperature of 130° C. for 30 minutes. Thereafter, it was removed from the heating furnace to obtain an electrophotographic belt 1.

[0059] The obtained electrophotographic belt 1 was mounted as an intermediate transfer belt in an electrophotographic image forming apparatus (product name: imageRUNNER ADVANCE C7580; manufactured by Canon Inc.), and 30,000 electrophotographic images were formed continuously under the following conditions. Temperature: 23°C, Relative humidity: 50% -Paper used: GF-C081 A3 size (grammage 81.4g / m 2 , thickness 97μm, whiteness approx. 100%, manufactured by Canon Inc.) Printed image: The amount of CMYK toner on the intermediate transfer belt is 0.4mg / cm 2 , Image ratio 100% The evaluation was carried out on the following two points.

[0060] [(Evaluation 1) Abnormal noise and peeling of the cleaning unit] During the image formation process of 30,000 sheets, if a sound that does not occur during normal printing was heard from the cleaning unit of the transfer unit (hereinafter referred to as the CLN unit), it was deemed to be an abnormal noise. 3, the blade holding member 31 holds the upper surface 32a of the cleaning blade 32. Normally, the vicinity of the tip of the lower surface 32b of the cleaning blade 32 opposite to the upper surface 32a comes into contact with the outer circumferential surface of the intermediate transfer belt 7, and cleans the outer circumferential surface of the intermediate transfer belt 7 while the intermediate transfer belt 7 moves in the direction of the arrow 34. When the vicinity of the tip of the upper surface 32a of the cleaning blade 32 comes into contact with the outer circumferential surface of the intermediate transfer belt 7, it is determined that the "blade has turned over." The observation results were evaluated according to the following criteria. Rank A: No abnormal noise or blade curling was observed. Rank B: Either abnormal noise or blade curling was observed.

[0061] [(Evaluation 2) Outer surface of electrophotographic belt] After printing 30,000 sheets, the electrophotographic belt was removed from the electrophotographic image forming apparatus, and the entire outer surface was cleaned using a cleaning wiper (product name: Dusper μ; manufactured by Ozu Sangyo Co., Ltd.) Thereafter, the outer surface was observed under an optical microscope at magnifications of 50x, 200x, and 1000x, and evaluated according to the following criteria. Rank A: No toner agglomerates with a maximum Feret diameter of 20 μm or more were observed. Rank B: Toner agglomerates with a maximum Feret diameter of 20 μm or more were observed.

[0062] (Examples 2 to 5) Electrophotographic belts 2 to 5 were produced and evaluated in the same manner as in Example 1, except that the coating material for the surface layer shown in Table 6 was used.

[0063] Example 6 Except for using the surface layer coating material 2-A, a coating film of the surface layer coating material 2-A was formed on the outer circumferential surface of the laminated belt in the same manner as in Example 1. Next, ultraviolet light having a wavelength of 365 nm was irradiated onto the coating film of the surface layer coating material 2-A using a high-pressure mercury lamp at an integrated light quantity of 2 J / cm. 2 The coating was cured by irradiation so as to obtain the electrophotographic belt 6 according to this example. The electrophotographic belt 6 thus obtained was evaluated in the same manner as in Example 1.

[0064] Comparative Example 1 An electrophotographic belt was produced and evaluated in the same manner as in Example 1, except that the surface layer coating material 1-A was changed to the surface layer coating material 3-A. The evaluation results are shown in Table 6.

[0065] [Table 6]

[0066] From the evaluation results shown in Table 6, it was found that the use of a compound having a perfluoropolyether structure and an oxyalkylene structure prevents problems in the cleaning unit and toner adhesion to the ITB surface. This is presumably due to the good dispersion state of polytetrafluoroethylene (PTFE) particles in the surface layer containing a compound having a perfluoropolyether structure and an oxyalkylene structure. If the dispersion state of the PTFE particles is good, even if the surface layer of the electrophotographic belt is slightly scraped off as a result of printing on a large amount of paper, and the part closer to the elastic layer becomes the outermost surface, it is presumed that the dispersion state of the PTFE particles does not change, and therefore the toner releasability and cleaning properties do not change. [Explanation of symbols]

[0067] Py: Yellow image forming section 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 developing device 4C: Cyan developing unit 4K: Black developing device 5Y, 5M, 5C, 5K: Primary transfer roller Ty, Tm, Tc, Tk: Primary transfer section 73: Secondary transfer inner roller 100: Image forming device 2Y, 2M, 2C, 2K: Charger 3Y, 3M, 3C, 3K: Laser scanner 11: Transfer belt cleaning unit 12: Paper feed cassette 15: Registration roller pair 7: Intermediate transfer belt 8: Secondary transfer outer roller 9: Fixing unit 91: Fixing film 92: Pressure roller S: Transfer material 21: Base layer 22: Elastic layer 23: Surface layer

Claims

1. An electrophotographic belt having an endless shape, Endless shape base layer, an elastic layer on an outer peripheral surface of the base layer; and A surface layer is provided on an outer peripheral surface of the elastic layer, The surface layer is Urethane resin as a binder; Polytetrafluoroethylene particles; A compound having a perfluoropolyether structure and an oxyalkylene structure, 1. An electrophotographic belt comprising:

2. 2. The electrophotographic belt according to claim 1, wherein the oxyalkylene structure is an oxyethylene structure or an oxypropylene structure.

3. 3. The electrophotographic belt according to claim 1, wherein the perfluoropolyether structure has a number average molecular weight of 500 to 10,000.

4. The electrophotographic belt according to any one of claims 1 to 3, wherein the perfluoropolyether structure is at least one selected from the group consisting of structures represented by the following structural formulas (i) to (iv): -CF ２ O- (i) -CF ２ CF ２ O- (ii) -CF ２ CF ２ CF ２ O- (iii) -CF(CF ３ )CF ２ O- (iv)。

5. 5. The electrophotographic belt according to claim 1, wherein a value of (Mn1 / Mn2) is 0.3 to 2.0, where Mn1 is a number average molecular weight of the oxyalkylene structure and Mn2 is a number average molecular weight of the perfluoropolyether structure.

6. 6. The electrophotographic belt according to claim 5, wherein the value of (Mn1 / Mn2) is 0.5 to 1.

0.

7. 7. The electrophotographic belt according to claim 1, wherein the thickness of the base layer is from 10 μm to 500 μm.

8. 8. The electrophotographic belt according to claim 1, wherein the elastic layer has a thickness of 100 μm to 1000 μm.

9. 9. The electrophotographic belt according to claim 1, wherein the surface layer has a thickness of 0.5 μm to 20.0 μm.

10. 10. The electrophotographic belt according to claim 1, wherein the polytetrafluoroethylene particles have a number average particle size in the range of 0.05 μm to 1.80 μm.

11. The toner image transfer apparatus includes an image carrier that carries a toner image, and an intermediate transfer belt that carries and transports the toner image that has been primarily transferred from the image carrier to a transfer material for secondary transfer, The intermediate transfer belt is Endless shape base layer, an elastic layer on an outer peripheral surface of the base layer; and A surface layer is provided on an outer peripheral surface of the elastic layer, The surface layer is Urethane resin as a binder; Polytetrafluoroethylene particles; A compound having a perfluoropolyether structure and an oxyalkylene structure, 13. An electrophotographic image forming apparatus comprising:

12. the electrophotographic image forming apparatus further comprises a cleaning member, 12. The electrophotographic image forming apparatus according to claim 11, wherein at least a portion of said cleaning member is disposed in contact with the outer surface of said surface layer of said electrophotographic belt.

13. 13. The electrophotographic image forming apparatus according to claim 12, wherein said cleaning member is a cleaning roller.

14. 13. The electrophotographic image forming apparatus according to claim 12, wherein the cleaning member is a cleaning blade.

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