Electrophotographic belt and electrophotographic image forming apparatus

Abstract

To provide a belt for electrophotography that has stabilized the amount of reflected light from an outer peripheral surface, while having a plurality of grooves in the outer peripheral surface.SOLUTION: A belt for electrophotography has a substrate having an endless shape and a surface layer on an outer peripheral surface of the substrate. An outside surface of the surface layer is provided with a plurality of grooves extending in a circumferential direction. The substrate includes thermoplastic polyester resin and filler. The surface layer includes acrylic resin. The thickness T of the substrate is 30 μm or more, and the content of the filler in the substrate is 0.1 volume% or more and 10.0 volume% or less based on the total volume of the substrate. The average value A of an element ratio derived from the filler in an area of the surface layer with a thickness of 0.25 times the average particle diameter of the filler from a first surface facing the substrate toward a second surface on the opposite side of the first surface is 0.0 atom% or more and 1.0 atom% or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an electrophotographic belt and an electrophotographic image forming apparatus. [Background technology]

[0002] Among electrophotographic image forming apparatuses (hereinafter also referred to as "electrophotographic apparatuses"), there are electrophotographic apparatuses having a cleaning blade disposed in contact with the outer peripheral surface, which is the toner carrying surface, of an endless intermediate transfer belt. An electrophotographic belt having an endless shape and having grooves extending in the circumferential direction on its outer peripheral surface may be used as the intermediate transfer belt whose outer peripheral surface is cleaned by the cleaning blade. This reduces the frictional force between the cleaning blade and the outer peripheral surface, thereby improving the cleaning performance of the outer peripheral surface. Patent Document 1 discloses an electrophotographic belt having a plurality of grooves extending in the circumferential direction on its outer surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-191568 Summary of the Invention [Problem to be solved by the invention]

[0004] Some recent electrophotographic devices have achieved high color reproducibility. These electrophotographic devices form a correction toner image on a portion of the outer peripheral surface of an intermediate transfer belt, detect the correction toner image by detecting reflected light of incident light from an optical sensor, and perform image control based on the detection results. The optical sensor detects the correction toner image using the contrast between light reflected from the correction toner image and light reflected from the portion of the outer peripheral surface where the correction toner image is not formed. Therefore, to accurately detect the correction toner image, it is effective to stabilize the amount of light reflected from the portion of the outer peripheral surface of the electrophotographic belt other than the correction toner image. However, according to the inventors' investigations, in electrophotographic belts with grooves on the outer peripheral surface, incident light from the sensor is diffused by the grooves, and the amount of light reflected from the outer peripheral surface can vary significantly depending on the position. One aspect of the present disclosure is to provide an electrophotographic belt having a plurality of grooves on its outer peripheral surface and a stable amount of reflected light from the outer peripheral surface. 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]

[0005] According to one aspect of the present disclosure, there is provided an electrophotographic belt having an endless shape, the belt comprising: a substrate having an endless shape; and a surface layer on an outer peripheral surface of the substrate, A plurality of grooves extending in the circumferential direction are provided on the outer surface of the surface layer, the substrate comprises a thermoplastic polyester resin and a filler; the surface layer contains an acrylic resin, the thickness T of the substrate is 30 μm or more, and the content of the filler in the substrate is 0.1 vol % or more and 10.0 vol % or less, based on the total volume of the substrate; The electrophotographic belt has an average value A of the ratio of elements derived from the filler in a region of the surface layer having a thickness of 0.25 times the average particle diameter of the filler from a first surface on the side facing the substrate toward a second surface on the opposite side to the first surface, of 0.0 atomic % or more and 1.0 atomic % or less. According to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above-described electrophotographic belt as an intermediate transfer belt. [Effects of the Invention]

[0006] According to one aspect of the present disclosure, it is possible to obtain an electrophotographic belt having a plurality of grooves on its outer peripheral surface and a stable amount of reflected light from the outer peripheral surface, and according to another aspect of the present disclosure, it is possible to obtain an electrophotographic image forming apparatus capable of stably forming high-quality electrophotographic images. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a graph showing an example of output from a sensor that receives specularly reflected light of light irradiated onto the outer surface of an electrophotographic belt having grooves on its outer peripheral surface and an electrophotographic belt having no grooves on its outer peripheral surface. [Figure 2] 1 is a schematic cross-sectional view illustrating a configuration of an electrophotographic belt according to one embodiment of the present disclosure. [Figure 3] 1 is a schematic diagram illustrating a configuration of a surface of an electrophotographic belt according to an embodiment of the present disclosure. [Figure 4] 4 is a schematic enlarged view of a groove portion in a cross section of the electrophotographic belt shown in FIG. 3 in a direction perpendicular to the circumferential direction. FIG. [Figure 5] FIG. 1 is a schematic diagram illustrating an example of the configuration of an intermediate transfer type image forming apparatus. [Figure 6] FIG. 2 is a schematic diagram illustrating an example of the configuration of a concentration detection sensor. [Figure 7] 1 is a graph showing an example of an output from a sensor that receives specularly reflected light from the surface of an electrophotographic belt according to one embodiment of the present disclosure and an electrophotographic belt that does not have grooves. [Figure 8] 1 is a schematic cross-sectional view of a substrate of an electrophotographic belt according to one embodiment of the present disclosure. [Figure 9] FIG. 2 is a schematic cross-sectional view showing the interface (first surface B1) between the substrate and the surface layer. [Figure 10] FIG. 2 is a schematic cross-sectional view illustrating a position 0.25P from the first surface B1. [Figure 11] FIG. 1 is a schematic diagram of a biaxial stretching apparatus used in the examples. [Figure 12] FIG. 2 is a schematic diagram of a device for removing foreign matter from a substrate surface used in the examples. [Figure 13] FIG. 1 is a schematic diagram of an imprint processing apparatus used in the examples. [Figure 14] FIG. 2 is a schematic cross-sectional view of a cylindrical mold used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0008] Light from a sensor is irradiated onto the outer peripheral surface of an electrophotographic belt, and the output from the sensor that receives the specularly reflected light is designated as output 304. Furthermore, light from a sensor is irradiated onto the outer peripheral surface of an electrophotographic belt having a plurality of grooves extending in the circumferential direction on the outer peripheral surface, and the output from the sensor that receives the specularly reflected light is designated as output 305. These outputs are shown in FIG. The output from the sensor that detects the specularly reflected light from the outer peripheral surface of an electrophotographic belt that does not have grooves on the outer peripheral surface is almost constant. On the other hand, the output from the sensor that detects the specularly reflected light from the outer peripheral surface of an electrophotographic belt that has grooves on the outer peripheral surface fluctuates greatly. Therefore, when a corrective toner image is formed on the outer peripheral surface of such an electrophotographic belt, the output from the sensor becomes small even in areas where the corrective toner image does not exist, and it may be determined as if the corrective toner image exists. The reflected light received by the sensor includes a component reflected from the outermost surface and a component reflected from the substrate. That is, a portion of the incident light irradiated from the optical sensor passes through the surface layer, reaches the substrate, is reflected by the substrate, and is received by the sensor. Therefore, the inventors investigated ways to suppress fluctuations in the amount of reflected light due to the presence of grooves by increasing the proportion of the component of light reflected from the base, relative to the component of light reflected from the outermost surface of the outer circumferential surface, which is more susceptible to the influence of grooves, among the reflected light received by the sensor.As a result, the inventors found that by incorporating a predetermined amount of filler into the base and controlling the state of presence of the filler in the interface region between the base and the surface layer, it is possible to stabilize the amount of reflected light received by the sensor, even when grooves are present on the outer circumferential surface.

[0009] An electrophotographic belt according to one embodiment of the present disclosure includes a substrate having an endless shape and a surface layer on the outer peripheral surface of the substrate, and the outer surface of the surface layer is provided with a plurality of grooves extending in the circumferential direction. The substrate is formed from a thermoplastic resin composition containing a thermoplastic polyester resin, a filler, and preferably a conductive agent, and the surface layer is formed from an acrylic resin composition. The substrate has a thickness T of 30 μm or more, and the content of the filler in the substrate is 0.1% by volume or more and 10% by volume or less, based on the total volume of the substrate. Furthermore, a region of the surface layer extending from a first surface B1 facing the substrate toward a second surface B2 opposite the first surface B1 and having a thickness of 0.25 times the average particle diameter of the filler is designated "region Y." In region Y, the average value A of the ratio of elements derived from the filler is 0.0 atomic % or more and 1.0 atomic % or less.

[0010] That is, by making the thickness of the substrate 30 μm or more and incorporating a filler in the substrate in an amount of 0.1 to 10.0 volume % based on the total volume of the substrate, it is possible to more reliably reflect light from the sensor that has passed through the surface layer. Furthermore, by setting the average value A of the element ratio derived from the filler in the interface region between the surface layer and the substrate, specifically in the region Y, to 0.0 to 1.0 atomic %, it is possible to prevent diffuse reflection by the filler in the interface region. Therefore, it is possible to more reliably return light from the sensor that has passed through the surface layer to the light-receiving sensor. As a result, even in an electrophotographic belt with grooves formed on the outer surface, it is possible to more reliably stabilize the specular reflection of light from the sensor that is irradiated onto the outer peripheral surface and received by the light-receiving sensor. Hereinafter, an electrophotographic endless belt according to one embodiment of the present disclosure will be described in detail with reference to the drawings, although the present disclosure is not limited to the following embodiment.

[0011] <Electrophotographic belt> Fig. 2 is a schematic cross-sectional view showing an embodiment of an electrophotographic belt according to the present disclosure, and Fig. 3 is a schematic view showing the surface configuration of the electrophotographic belt. As shown in FIG. 2, the electrophotographic belt 5 according to the present disclosure has a substrate 312 and a surface layer 311 on the outer peripheral surface of the substrate 312 . As shown in FIG. 3, a plurality of grooves 199 are provided in the surface of the surface layer of the electrophotographic belt 5 opposite the substrate side in a direction perpendicular to the circumferential direction (also referred to as the width direction). The grooves are provided substantially in the circumferential direction 200 of the electrophotographic endless belt. It is preferable that the grooves 199 are connected in the circumferential direction. The groove may be a single groove continuing in a spiral shape, and in this case, multiple grooves are present in the width direction. Alternatively, multiple spiral grooves may be used. FIG. 4 is an enlarged cross-sectional view of the belt 5 in a direction perpendicular to the circumferential direction, showing the surface portion where the grooves are provided. In FIG. 4, W1 denotes the groove width, H1 denotes the groove depth, and P1 denotes the groove spacing.

[0012] The number n of grooves is 1 or 2 or more, and is not particularly limited as long as toner cleaning can be performed stably, but for an electrophotographic endless belt having a width of 250 mm, it is preferable that the number n be 2,000 to 120,000 in the width direction. If the number is 2,000 or more, the area of ​​the cleaning blade contacting the non-grooved portion is reduced, thereby reducing the friction force generated between the cleaning blade and the electrophotographic endless belt. If the number is 120,000 or less, toner on the grooves can be transferred more efficiently.

[0013] The spacing P1 between adjacent grooves is not particularly limited as long as it is within the above-mentioned range of the number of grooves, but from the perspective of toner cleaning, it is preferable that the spacing be approximately uniform, and more preferably 2.0 μm or more and 125 μm or less. If the spacing P1 is 125 μm or less, 2,000 or more grooves are provided on the surface of an electrophotographic endless belt having a width of 250 mm. This reduces the likelihood of localized blade wear, allowing the cleaning blade to maintain stable contact with the electrophotographic belt over a long period of time. Furthermore, if the spacing is 2.0 μm or more, the number of grooves provided is 120,000 or less, allowing the transferability of toner on the grooves to be maintained.

[0014] The width W1 of the groove is preferably 0.10 μm or more and less than 3.0 μm, and more preferably 0.20 μm or more and less than 2.0 μm. When it is 0.10 μm or more, the disappearance of the groove due to wear of the electrophotographic belt surface is suppressed. When it is 3.0 μm or less, the transferability of the toner on the groove can be maintained, and the image quality of the electrophotographic belt can be maintained.

[0015] The groove depth H1 is preferably set to 15% or more and less than 35% of the surface layer thickness T1, and is usually set in the range of 0.10 μm or more and less than 2.0 μm. When the depth H1 is 15% or more of the surface layer thickness T1, the disappearance of the grooves due to wear of the electrophotographic belt surface is suppressed. When the depth H1 is 35% or less of the surface layer thickness T1, the possibility of the surface layer being damaged is reduced.

[0016] The grooves can be formed by known methods such as cutting, etching, and imprinting, but imprinting is preferred from the viewpoints of the reproducibility of the grooves and the processing costs. In imprinting, a coating film of the surface layer is formed on a substrate and cured, and then a mold having convex portions corresponding to the grooves is pressed against the coating film to transfer and form the grooves on the surface layer.

[0017] <Base> The substrate contains a thermoplastic polyester resin and a filler. The thickness T of the substrate is 30 μm or more, preferably 50 μm or more, in order to reduce the transmission of incident light irradiated from the optical sensor. There is no particular upper limit to the thickness T, but it is usually 500 μm or less, preferably 100 μm or less. The substrate is preferably stretched in the circumferential direction and in the direction perpendicular to the circumferential direction in order to increase the strength. In addition, the belt preferably has a tensile modulus of elasticity in the circumferential direction (Ep) and a tensile modulus of elasticity in the direction perpendicular to the circumferential direction (Ea) of 1200 MPa or more in terms of flexibility.

[0018] <Thermoplastic polyester resin> Thermoplastic polyester resins can be obtained by polycondensation of dicarboxylic acids and diols, polycondensation of hydroxycarboxylic acids or lactones, or polycondensation of a combination of these components. A polyfunctional monomer may also be used. Thermoplastic polyester resins may be homopolyesters containing one type of ester bond, or copolyesters (copolymers) containing multiple ester bonds. Suitable examples of the thermoplastic polyester resin include at least one selected from the group consisting of polyalkylene terephthalates and polyalkylene naphthalates, which have high crystallinity and excellent heat resistance. Copolymers of polyalkylene naphthalates and polyalkylene isophthalates are also suitable. The copolymer may be in the form of a block copolymer or a random copolymer. From the viewpoint of high crystallinity and heat resistance, the number of carbon atoms in the alkylene in polyalkylene terephthalate, polyalkylene naphthalate, and polyalkylene isophthalate is preferably 2 or more and 16 or less. More specifically, the thermoplastic polyester resin is preferably polyethylene terephthalate, polyethylene naphthalate, or a copolymer of polyethylene terephthalate and polyethylene isophthalate. The content of the thermoplastic polyester resin in the thermoplastic resin composition is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total mass of the thermoplastic resin composition. By making the content of the thermoplastic polyester resin 50% by mass or more based on the total mass of the thermoplastic resin composition, it is easy to increase the mechanical strength of the thermoplastic resin composition.

[0019] <Filler> The filler is contained in the substrate to reliably specularly reflect light that has entered from the outer peripheral surface of the electrophotographic belt according to an embodiment of the present disclosure and passed through the surface layer, and to detect the reflected light with a light-receiving sensor. Therefore, the content of the filler in the substrate is 0.1% by volume or more and 10.0% by volume or less, and preferably 0.5% by volume or more and 5.0% by volume or less, based on the total volume of the substrate. Examples of such fillers include calcium carbonate, talc, clay, wollastonite, potassium titanate, barium titanate, lead zirconate titanate, aramid particles, mica, glass beads, glass balloons, zeolite, alumina, ferrite, barium sulfate, molybdenum sulfide, magnesium oxide, calcium oxide, hydrotalcite, zinc oxide, iron oxide, carbon black, carbon fiber, carbon nanotubes, carbon nanofibers, conductive titanium oxide, conductive tin oxide, conductive mica, calcium sulfate, strontium titanate, titanium oxide, magnesium hydroxide, aluminum hydroxide, kaolin, silica, silicone particles, PTFE particles, PFPE particles, PFA particles, calcium carbonate, barium carbonate, nickel carbonate, quartz powder, and thermosetting resin fine particles. These may be used alone or in combination of two or more. The filler is not particularly limited in shape or size, but is preferably spherical. This is because a spherical filler can more easily obtain isotropy in dispersion and orientation, compared with amorphous particles or fibrous materials, regardless of the manufacturing method for the electrophotographic belt. If isotropy is obtained, stable reflected light can be obtained in response to incident light from an image control optical sensor, regardless of the dispersion and orientation. Among the above fillers, silica and silicone resin particles, particularly spherical silica and spherical silicone particles, are preferred because they can increase the amount of light reflected from the substrate.

[0020] <Conductive agent> The substrate may also contain a conductive agent. Examples of conductive agents include low-molecular-weight ionic conductive agents such as surfactants and ionic liquids, and conductive polymers such as polyether ester amides. If necessary, two or more of these conductive agents may be blended in appropriate amounts.

[0021] <Additives> Other components may be added to the substrate as long as they do not impair the effects of the electrophotographic belt according to the present disclosure. Examples of other components include conductive polymer compounds, antioxidants, UV absorbers, organic pigments, inorganic pigments, pH adjusters, crosslinking agents, compatibilizers, release agents, coupling agents, lubricants, etc. These additives may be used alone or in combination of two or more. The amount of additive used can be set appropriately and is not particularly limited.

[0022] The thermoplastic resin composition according to the present disclosure can be obtained by hot melt kneading a thermoplastic polyester resin and a filler. Hot melt kneading refers to heating the thermoplastic polyester resin to be contained in the thermoplastic resin composition and kneading it in a molten state. During hot melt kneading, it is preferable to knead at a temperature equal to or higher than the highest melting point of the thermoplastic polyester resins to be contained in the thermoplastic resin composition so that the thermoplastic polyester resin having the highest melting point is well kneaded. The kneading method is not particularly limited, and a single-screw extruder, a twin-screw kneading extruder, a Banbury mixer, a roll, a Brabender, a Plastograph, a kneader, or the like can be used.

[0023] As described above, the thermoplastic resin composition obtained by hot melt kneading is pelletized, and the pellets are molded by a known molding method to obtain an endless belt-shaped substrate. Known molding methods include continuous melt extrusion, injection molding, stretch blow molding, inflation molding, etc. Among these, stretch blow molding is more preferred because it stretches the substrate in biaxial directions and can increase strength.

[0024] <Surface layer> The surface layer 13 contains an acrylic resin. The thickness T1 of the surface layer is not particularly limited, but is preferably 0.1 μm or more and 50 μm or less. Within this range, the groove shape formed can be maintained even with repeated use, and cracking due to repeated bending can be easily suppressed. The acrylic resin used in the acrylic resin composition is preferably a polyfunctional acrylate monomer. Examples of polyfunctional acrylate monomers that can be used include dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, trimethylolpropane PO-modified triacrylate, trimethylolpropane EO-modified triacrylate, isocyanuric acid EO-modified triacrylate, ditrimethylolpropane tetraacrylate, diglycerin EO-modified acrylate, and bisphenol EO-modified diacrylate. Here, "EO" means "ethylene oxide" and "PO" means "propylene oxide." These acrylic resins may be either homopolymers or copolymers, or may be mixtures of a plurality of types of acrylic resins. The acrylic resin composition may contain a fluororesin. Examples of the fluororesin include polytetrafluoroethylene, perfluoropolyether, perfluoroalkoxy fluororesin, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and ethylene-tetrafluoroethylene copolymer, with polytetrafluoroethylene (PTFE) being preferred. The fluororesin may be a homopolymer or copolymer, or may be a mixture of multiple types of fluororesins. In addition to the acrylic resin and fluororesin, conductive agents, antioxidants, dispersants, and the like may be added to the acrylic resin composition as needed.

[0025] The surface layer can be formed on the endless belt-shaped substrate by using a known forming method such as dip coating, spray coating, flow coating, shower coating, roll coating, spin coating, or ring coating.

[0026] As described below, depending on the manufacturing method, a substrate formed from a thermoplastic resin composition containing a thermoplastic polyester resin and a filler may have the filler exposed on its outer peripheral surface, forming convex portions on the outer peripheral surface. When a surface layer is formed on a substrate with partially exposed filler and convex portions, as shown in FIG. 9(a), a portion of the filler 310 penetrates into the surface layer 311 at the interface between the substrate 312 and the surface layer 311, as shown in FIG. 9(a). Such filler may cause diffuse reflection of light reflected from the substrate. Therefore, in the present disclosure, as shown in FIG. 9(b), the region extending from the interface B1 between the substrate and the surface layer (referred to as the first surface of the surface layer) toward the second surface B2 of the surface layer, with a thickness 0.25 times the average particle diameter P of the filler, is defined as the "interface region Y." The average value A of the ratio of elements derived from the filler in the interface region Y is set to be 0.0 atomic % or more and 1.0 atomic % or less. The term "elements derived from the filler" refers to elements characteristic of the filler added to the substrate, as exemplified above, and is preferably an element not contained in the acrylic resin composition constituting the surface layer. For example, in the case of silicone particles or silica, which are the preferred fillers mentioned above, it refers to the Si element. Furthermore, carbon elements in carbon-based fillers, fluororesin particles such as PTFE, and thermosetting resin microparticles, etc., which can be distinguished from the same elements in the acrylic resin composition based on their bonding state, are also included.

[0027] The average value A of the element ratio derived from the filler can be confirmed by using an energy dispersive X-ray analyzer (EDS) equipped on a scanning electron microscope (SEM) to determine the distribution of the element ratio derived from the filler in the interface region Y using the following calculation method.

[0028] (Measurement of the average particle size of the filler) (i) A plurality of measurement samples are taken from a plurality of arbitrary locations on the belt. (ii) A portion of the cross section of each sample is cut out using a microtome or the like, and observed under a scanning electron microscope (SEM) at a specific magnification to obtain a photograph. From the photograph obtained, the diameters of the filler in the belt thickness direction and in the direction perpendicular to the belt thickness direction are measured, and the average value thereof is calculated as the particle diameter P of the filler. (Method for calculating the average value A of the element ratio derived from the filler) (i) A plurality of measurement samples are taken from a plurality of arbitrary locations on the belt. (ii) The cross section of the collected measurement sample in the circumferential direction of the belt, that is, the cross section including the thickness-circumferential cross section of the belt, is polished using an ion beam to prepare a cross section for observation. (iii) In the observation cross section, elements derived from the filler at any position in region Y are subjected to line analysis using an energy dispersive X-ray analyzer (EDS), and the ratio of elements derived from the filler for each measurement sample is determined. (iv) The element ratios in the measurement sample determined in (iii) above are arithmetically averaged at all measurement positions to obtain the average value of the element ratios derived from the filler. (v) The above operations (i) to (iv) are carried out and analyzed for a plurality of measurement samples to calculate the average value of the ratio of elements derived from the filler. (vi) The average value of the ratio of elements derived from the filler of each sample obtained is arithmetically averaged to determine the average value of the ratio of elements derived from the filler in region Y. A more detailed calculation method is described in the Examples.

[0029] <Method for manufacturing an electrophotographic belt> An embodiment of a method for producing an electrophotographic belt according to an embodiment of the present disclosure will be described below. First, a substrate having an endless shape is prepared. For example, a test-tube-shaped preform is prepared using a thermoplastic resin composition containing a thermoplastic polyester resin and a predetermined amount of filler. The preform can be prepared, for example, by injection molding pellets of the thermoplastic resin composition. The preform is then biaxially stretched using a biaxial stretching apparatus (stretch blow molding machine) as shown in FIG. 11. Prior to biaxial stretching, the preform 104 is placed in a heating device 107 equipped with a non-contact heater (not shown) for heating the outer and inner walls of the preform 104. The heater heats the preform's outer surface to, for example, 150°C. The heated preform 104 is then placed in a blow mold 108, the mold temperature of which is maintained at, for example, 30°C, and stretched in the axial direction using a stretching rod 109. Simultaneously, air adjusted to, for example, 23°C is introduced into the preform 104 through a blow air injection section 110 to stretch the preform 104 in the radial direction. This produces a biaxially stretched bottle-shaped molded product 112. The body of the resulting bottle-shaped molded product 112 is then cut to produce the base of an endless belt. The substrate thus obtained is stretched in both the circumferential direction and the direction perpendicular to the circumferential direction (biaxial stretching), and has excellent strength. However, the filler is exposed on the outer peripheral surface of the substrate formed by such a method, and protrusions due to the filler are likely to form. Therefore, if a surface layer is formed on the outer peripheral surface of a biaxially stretched substrate without performing the surface treatment described below, a large amount of filler may be present in the interface region between the surface layer and the substrate. As a result, light from the sensor incident on the outer peripheral surface may be diffused, and the amount of specularly reflected light incident on the light-receiving sensor may decrease. Therefore, it is preferable to surface-treat the outer peripheral surface of the substrate obtained by the above method. Specifically, for example, while rotating the substrate, it is preferable to bring a member such as a nonwoven fabric, a rubber blade, or a brush into contact with the outer peripheral surface and remove the filler that has caused the convex portions on the outer peripheral surface. Specifically, for example, as shown in Figure 12, nonwoven fabric 72 is pressed against the outer peripheral surface of substrate 312 with a predetermined pressure, and the outer peripheral surface is rubbed with the nonwoven fabric to remove the filler that has caused the convex portions on the outer peripheral surface. Thereafter, a coating film of a coating material for forming a surface layer is formed on the surface-treated outer peripheral surface of the substrate by a known coating method such as dip coating, spray coating, spin coating, ring coating, or roll coating, and the coating film is then cured to form a cured film. Next, as shown in Figure 13, a cylindrical mold 81 is placed relative to a holding mold 90 holding a substrate 5 with a cured film formed on its outer surface so that the rotation axes of the holding mold 90 and the cylindrical mold 81 are parallel and the outer surface of the cylindrical mold is in contact with the outer surface of the cured film. The outer surface of the cylindrical mold is formed with protrusions having a shape corresponding to the shape of the grooves to be formed in the outer surface of the surface layer. Then, while rotating the holding mold and the cylindrical mold at a predetermined speed, the protrusions are pressed against the cured film, thereby transferring grooves extending in the circumferential direction of the substrate to the surface of the cured film.

[0030] <Electrophotographic image forming apparatus> FIG. 5 shows an example of an electrophotographic device equipped with an electrophotographic belt according to one embodiment of the present disclosure as an intermediate transfer belt. This electrophotographic device forms color images on a recording medium S, such as paper, supplied from a paper feed cassette 20 using four colors of toner: yellow (Y), magenta (M), cyan (C), and black (K). Image forming stations for each color are arranged side by side in a substantially horizontal direction. These image forming stations are equipped with photosensitive drums 1y, 1m, 1c, and 1k, respectively. The subscripts "y," "m," "c," and "k" are added to reference numerals to indicate which color image forming station the corresponding component belongs to. The image forming device is equipped with a laser scanner 3, which is a laser optical unit. Laser beams 3y, 3m, 3c, and 3k corresponding to image signals for each color are emitted from the laser scanner 3 toward the photosensitive drums 1y, 1m, 1c, and 1k, respectively. Since all image forming stations have the same structure, only the K image forming station will be described here. Surrounding the photosensitive drum 1k are arranged a conductive roller 2k which is a contact charging device, a developing unit 4k, a conductive roller 8k which is a primary transfer roller, and a toner recovery blade 14k which is used to clean the photosensitive drum 1k. The developing unit 4k is provided with a developing roller 41k which is a developer carrier that develops the latent image on the photosensitive drum 1k, a developing container 42k which holds toner supplied to the developing roller 41k, and a developing blade 43k which regulates the amount of toner on the developing roller 41k and applies an electric charge to the toner.

[0031] The electrophotographic belt (intermediate transfer belt) 5 is an endless belt commonly provided to the image forming stations for each color. The intermediate transfer belt 5 is stretched over a secondary transfer opposing roller 92, a tension roller 6, and a drive roller 7, and rotated in the direction of the arrow by the drive roller 7. The intermediate transfer belt 5 contacts the surfaces of the photosensitive drums 1y, 1m, 1c, and 1k in sequence between the tension roller 6 and the drive roller 7, and is pressed toward the photosensitive drums 1y, 1m, 1c, and 1k by primary transfer rollers 8y, 8m, 8c, and 8k, respectively. This causes the toner images formed on the surfaces of the photosensitive drums 1y, 1m, 1c, and 1k to be transferred to the surface of the intermediate transfer belt 5. A secondary transfer roller 9 is provided opposite the secondary transfer opposing roller 92, and the intermediate transfer belt 5 is pressed toward the opposing roller 92 by the secondary transfer roller 9. A secondary transfer voltage is applied to the secondary transfer roller 9 from a power source via a current detection circuit 10. The secondary transfer roller 9 and the opposing roller 92 constitute a secondary transfer unit. The recording medium S passes through the nip between the intermediate transfer belt 5 and the secondary transfer roller 9 at the position of the opposing roller 92 via the feed roller 12 and the transport roller 13, whereby the toner image held on the outer surface of the intermediate transfer belt 5 is transferred to the recording medium S. This forms an image on the surface of the recording medium S. The recording medium S with the transferred toner image passes through a fixing device 15 consisting of a pair of rollers, a heating roller 151 and a pressure roller 152, whereby the image is fixed and the recording medium S is discharged to a paper output tray 21. A cleaning blade 11 is provided at the position of the tension roller 6 and abuts against the outer surface of the intermediate transfer belt 5. Toner remaining on the outer surface of the intermediate transfer belt 5 without being transferred to the recording medium S is scraped off and removed by the cleaning blade 11. The cleaning blade 11 is a member extending in a direction substantially perpendicular to the direction of movement of the intermediate transfer belt 5. The cleaning blade 11 is not particularly limited as long as it is suitable for toner cleaning. Examples include urethane rubber, acrylic rubber, nitrile rubber, and EPDM rubber, and from the viewpoint of toner cleaning, urethane rubber is preferred.

[0032] The color of printed matter changes depending on the conditions of the image forming device, such as the operating environment. Therefore, it is necessary to measure the density as needed and provide feedback to the control mechanism inside the device. The toner image for density correction is transferred to the surface of the intermediate transfer belt 5, and then transported to the position of the drive roller 7 as the intermediate transfer belt 5 rotates. The toner density is detected by the density detection sensor 160, which is located on the opposite side of the intermediate transfer belt 5 from the drive roller 7.

[0033] 6 is a schematic diagram of the density detection sensor 160, which is an optical sensor. The density detection sensor 160 is composed of a light-emitting element 161 and a specular reflection light-receiving element 163. The light-emitting element 161 emits infrared light, which is reflected by the surface of a correction toner image (hereinafter simply referred to as a "toner image") X. The specular reflection light-receiving element 163 is disposed in the specular reflection direction relative to the position of the toner image X, and detects the specular reflection light at the position of the toner image X.

[0034] FIG. 7 is a graph showing the base output 307 at multiple locations on the endless belt according to the present disclosure measured by a density detection sensor, and the output 306 of the sensor receiving light reflected from the toner image at those locations. For comparison, FIG. 7 also shows the output 304 of the sensor receiving light reflected from non-toner image portions at multiple locations on a smooth-surface belt. As shown in FIG. 7, the output 307 from the non-toner image portions of the endless belt according to the present disclosure is lower than the base output 304 of the smooth-surface belt. However, the output 307 exhibits little variation with position and is significantly different from the output 306, allowing accurate detection of the toner image density. [Example]

[0035] Hereinafter, examples and comparative examples will be shown to specifically explain the electrophotographic belt according to the present disclosure, but the electrophotographic belt according to the present disclosure is not limited to the configurations embodied in these examples.

[0036] As materials used in manufacturing electrophotographic belts according to Examples and Comparative Examples, thermoplastic resin compositions shown in Table 1 below and acrylic resin compositions shown in Table 2 below were prepared.

[0037] [Table 1]

[0038] [Table 2]

[0039] (Methods for measuring and evaluating characteristic values) The methods for measuring and evaluating the characteristic values ​​of the electrophotographic belts according to the examples and comparative examples are as follows (1) to (5). (1) Evaluation of the average particle size P of the filler The average particle diameter P of the filler was evaluated by the following method: First, measurement samples 5 mm long, 5 mm wide, and the same thickness as the entire thickness of the transfer belt were cut out from 20 random locations on the obtained electrophotographic belt. A portion of the cross section of each of the obtained measurement samples was further cut out using a microtome or the like, and observed at 5000x magnification using an FE-SEM (product name: Sigma500VP, manufactured by Carl Zeiss Microscopy) to obtain an image (photograph). Furthermore, elemental analysis was performed on each measurement sample using EDX (Energy Dispersive X-ray Spectroscopy) to identify the elements contained in the filler. Furthermore, from the obtained images, the diameters of the filler in the belt thickness direction and in the direction perpendicular to the belt thickness direction were measured, and the arithmetic average value was taken as the particle diameter of the filler. The particle diameters of at least 200 or more fillers were measured in the same manner, and the average value of the top 50 particle diameters among the measured particle diameters was taken as the average particle diameter P of the filler.

[0040] (2) Measurement of filler content in the substrate A total of 100 measurement samples, each 5 mm long and 5 mm wide, and corresponding to the entire thickness of the transfer belt, were cut out from 20 random locations along the circumferential direction of the resulting endless belt. For each of the 100 measurement samples, the circumferential cross section of the transfer belt, i.e., a cross section including the first cross section along the thickness direction of the substrate, was polished. A cross-section polisher (product name: SM09010, manufactured by JEOL Ltd.) was used for polishing. The polishing was performed under the conditions of irradiating an ion beam for 11 hours at an applied voltage of 4.5 V in an argon gas atmosphere. A gold-palladium film was then formed on the polished cross section to make it conductive, and a cross section for observation was prepared. The gold-palladium film was formed by sputter coating at 30 mA for 20 seconds using a sputter coater (product name: 108 Auto Sputter Coater, manufactured by Cressington). The cross section for observation was subjected to secondary electron image observation using an FE-SEM (product name: Sigma500VP, manufactured by Carl Zeiss Microscopy) under conditions of an acceleration voltage of 10 kV, a spot size of 60 μm, an observation magnification of 1000 times, and a WD of 8.5 mm. As shown in Fig. 8, the observation area was adjusted so that only the substrate portion of the endless belt was included in the field of view. The SEM image to be used for EDS analysis was determined, and the ratio of elements derived from the filler (silica particles in Example 1) within the field of view was measured, and this was taken as the filler content (volume %) in the substrate. An energy dispersive X-ray analyzer (EDS) (trade name: X-MAXN80, manufactured by Oxford) was used to measure the element ratio.

[0041] (3) Measurement of the ratio of elements derived from the filler in the interface region between the substrate and the surface layer Using the measurement sample cut out in (2) above, an observation point was adjusted so that the interface (first surface B1) between the substrate and the surface layer of the electrophotographic belt was included in the field of view at the top of the screen, as shown in FIG. 9, and an SEM image to be used for EDS analysis was determined. Next, the ratio of elements derived from the filler (Si in silica particles in Example 1) in region Y was measured as shown in Fig. 10. An energy dispersive X-ray analyzer (EDS) (product name: X-MAXN80, manufactured by Oxford Corporation) was used to measure the element ratio. Here, 300 measurement points were arbitrarily selected from the manufactured electrophotographic belt. First, the obtained SEM image was captured as the EDS analysis area. As shown in Figure 10, within the field of view of the obtained SEM image, the element ratio derived from the filler was measured by line analysis in a direction parallel to the first surface B1 at least in region Y, corresponding to 300 arbitrarily selected locations L1 to L300. The analysis was performed in line analysis mode, with EDS line data collection settings of 4 scans and a pixel dwell time of 5 ms, and the element ratios derived from the filler were obtained at 300 selected locations. The measurement results obtained at each location were then averaged over all measurement positions (300 locations) to obtain an average value of the element ratio in region Y. Gold and palladium elements are elements derived from the conductive treatment, not elements derived from the electrophotographic belt, and were therefore excluded from the analysis. The element ratio of the filler in region Y was generally 0 atomic % or more and 1.0 atomic % or less.

[0042] (4) Evaluation of tensile modulus The tensile modulus was measured using a low-load universal testing machine (product name: 34TM-5, manufactured by Instron) equipped with a 5 kN load cell in an environment of 23°C and 50% humidity. Sample pieces measuring 100 mm in the circumferential direction and 20 mm in the longitudinal direction and 20 mm in the circumferential direction and 100 mm in the longitudinal direction were cut from the produced electrophotographic belt, and the sample pieces were gripped with pneumatic grips with a chuck distance of 50 mm. The gripped sample pieces were pulled at a constant speed of 5 mm / min, and the modulus of elasticity was calculated from the stress value at 0.25% strain based on the obtained stress-strain curve and the thickness of the electrophotographic belt. The measurement results of five sample pieces cut from the same electrophotographic belt were averaged to determine the tensile modulus of elasticity Ep in the circumferential direction and the tensile modulus of elasticity Ea in the direction perpendicular to the circumferential direction of the electrophotographic belt.

[0043] (5) Evaluation of reflected light amount An electrophotographic image forming apparatus having the configuration shown in FIG. 5 was used, and an endless belt manufactured in the Examples or Comparative Examples described below was installed as an intermediate transfer belt. The specular reflection output per revolution of the endless belt was measured in 1 mm increments, and the average value of the measured outputs, V ave , maximum value V max , minimum value V min The runout rate was calculated using the following formula (1). The density detection sensor is positioned at a distance of ±100 mm from the center of the electrophotographic belt in the width direction. Since the specular reflection output varies depending on the conditions of the grooves provided on the surface of the electrophotographic belt, this evaluation was performed by adjusting the light intensity output so that the specular reflection output would be 3.0 V. Swing rate=(V max -V min ) / V ave Formula (1)

[0044] [Examples 1 to 10] (Manufacture of the substrate) The materials were preblended in advance according to the composition shown in Table 3, and then hot-melt kneaded using a twin-screw extruder (product name: TEX30α, manufactured by The Japan Steel Works, Ltd.) to prepare a thermoplastic resin composition. The hot-melt kneading temperature was adjusted to a range of 270°C or higher and 300°C or lower, and the hot-melt kneading time was approximately 3 to 5 minutes. The obtained thermoplastic resin composition was pelletized and dried at a temperature of 140°C for 6 hours. The dried pelletized thermoplastic resin composition was then loaded into an injection molding machine (product name: SE180D, manufactured by Sumitomo Heavy Industries, Ltd.). The cylinder temperature was set to 300°C, and the thermoplastic resin composition was injection-molded into a mold temperature-controlled at 30°C to produce a preform. The obtained preform had a test tube shape with an outer diameter of 50 mm, an inner diameter of 46 mm, and a length of 100 mm.

[0045] Next, the above preform is biaxially stretched using a biaxial stretching apparatus (stretch blow molding machine) shown in Fig. 11. Before biaxial stretching, the preform 104 is placed in a heating device 107 equipped with a non-contact heater (not shown) for heating the outer and inner walls of the preform 104, and heated with the heater so that the outer surface temperature of the preform becomes 150°C. Next, the heated preform 104 was placed in a blow mold 108 with the mold temperature maintained at 30°C, and stretched in the axial direction using a stretching rod 109. At the same time, air adjusted to a temperature of 23°C was introduced into the preform 104 from a blow air injection section 110 to stretch the preform 104 in the radial direction. In this way, a bottle-shaped molded product 112 was obtained. Next, the body of the bottle-shaped molded product 112 was cut to obtain a substrate for an electrophotographic belt, which had a circumferential length of 680 mm and a width of 250 mm.

[0046] (Surface treatment of the outer surface of the base) The substrate of the obtained electrophotographic belt was subjected to surface treatment by pressing a cleaning cloth (product name: Toraysee MK (industrial use); manufactured by Toray Industries, Inc.) against the substrate to remove the filler that was exposed on the outer peripheral surface of the substrate and causing protrusions on the outer peripheral surface. Specifically, as shown in FIG. 12 , the substrate 312 of the electrophotographic belt was held against the outer peripheral surface of a cylindrical holding mold 70, and a cleaning cloth 72 stretched over a sheet driving roller 71 was pressed against the substrate at a pressure of 0.5 MPa. In this state, the cylindrical holding mold 70 was rotated at 1 rpm. The cleaning cloth was also rotated at 0.1 rpm. In this way, the outer peripheral surface of the substrate was surface-treated to remove the filler that had caused protrusions on the outer peripheral surface. The surface of the cleaning cloth after the treatment was observed using a field emission scanning electron microscope (FE-SEM) and subjected to elemental analysis using an energy dispersive X-ray analyzer (EDS), detecting elements (silicon atoms) derived from the filler.

[0047] (Preparation of coating liquid) The materials listed in Table 2 were weighed out in a ratio of AN / PTFE / GF / SL / IRG = 66 / 20 / 1.0 / 12 / 1.0 (weight ratio converted to solid content) and subjected to a coarse dispersion treatment. The solution after the coarse dispersion treatment was subjected to a main dispersion treatment using a high-pressure emulsifying disperser (product name: Nanovaita, manufactured by Yoshida Kikai Kogyo Co., Ltd.) to obtain a coating solution consisting of an acrylic resin composition. The main dispersion treatment was continued until the 50% average particle size of the contained PTFE reached 200 nm.

[0048] (Formation of surface layer) The biaxially stretched substrate was fitted onto the outer periphery of a cylindrical mold (circumference 680 mm), the edges were sealed, and the mold was then immersed in a container filled with the coating liquid. A coating film composed of the coating liquid was formed on the substrate surface by lifting the substrate so that the relative speed between the coating liquid surface and the substrate was constant. The lifting speed (relative speed between the coating liquid surface and the substrate) and the solvent ratio of the coating liquid can be adjusted depending on the desired film thickness. In this example, the lifting speed was set to 10 to 50 mm / sec, and was adjusted so that the coating film thickness achieved the desired surface layer thickness after curing. In this example, the coating direction refers to the direction opposite to the direction in which the substrate was lifted. In other words, the point where the substrate was first lifted from the coating liquid is the most upstream. The coated substrate was then removed from the cylindrical mold and dried for 1 minute in an exhausted environment at 23°C. The drying temperature and drying time were adjusted appropriately depending on the solvent type, solvent ratio, and film thickness. After that, the coating was irradiated with a UV irradiator (product name: UE06 / 81-3, manufactured by Eye Graphics Co., Ltd.) with an accumulated light dose of 600 mJ / cm 2 The coating was cured by irradiating it with ultraviolet light until the thickness reached 1.0 μm. The thickness of the surface layer was measured by destructive testing in which an electrophotographic belt separately prepared under the same conditions was cut and the cross section was observed with an electron microscope (product name: XL30-SFEG, manufactured by FEI). The destructive testing results showed that the thickness of the surface layer was 3.0 μm.

[0049] (groove formation) Using the imprint processing device shown in FIG. 13, grooves were formed in the endless belt 5 that held the cured surface layer. The imprint processing device is composed of a cylindrical mold 81 and a cylindrical belt-supported mold 90. The cylindrical mold 81 can be pressed against the cylindrical belt-supported mold 90 while maintaining its axis parallel to the cylindrical mold. At this time, the cylindrical mold 81 and the cylindrical belt-supported mold 90 rotate synchronously without slippage. The cylindrical mold 81 is made of carbon steel with electroless nickel plating and has a diameter of 50 mm and a length of 250 mm. A fine convex shape is formed on the surface of the cylindrical mold 81. The convex pattern is formed in a spiral shape with an angle of 0.1° relative to the circumferential direction of the cylindrical mold. The convex pattern of the cylindrical mold 81 used in this example has the shape shown in FIG. 14, with the dimensions of H = 3.5 μm, Wb = 2.0 μm, Wt = 0.2 μm, and P = 20 μm. A cartridge heater (not shown) is embedded in the cylindrical mold 81 to enable heating. Next, a substrate with a coating film formed thereon was fitted onto the outer periphery of a cylindrical belt holding mold 90 (circumferential length 680 mm). The cylindrical belt holding mold 90 and the cylindrical mold 81 were rotated at a peripheral speed of 1 mm / sec (the rotation directions were opposite to each other), and while maintaining their axial centerlines parallel to each other, the cylindrical mold 81 heated to 130°C was brought into contact with them and a pressure of 8.0 kN was applied at a rate of 1.0 kN / s. Then, while maintaining the pressure at 8.0 kN, the cylindrical belt holding mold 90 and the cylindrical mold 81 were rotated, and the groove-imparting cylindrical mold 81 was released upon completion of imprint processing for one revolution of the belt. This transferred the convex shape of the groove-imparting cylindrical mold 81 to the surface of the surface layer of the electrophotographic belt. The groove pattern of the electrophotographic belt obtained through the above steps had 12,200 grooves, with groove width and depth W1=0.6 μm, H1=0.6 μm, and P1=20 μm, respectively. The electrophotographic belt was mounted in an electrophotographic image forming apparatus shown in FIG. 5, and the regular reflection output was evaluated. It was confirmed that the deviation rates were all 25% or less, which was very small.

[0050] [Table 3]

[0051] [Comparative Examples 1 to 5] An electrophotographic belt was produced in the same manner as in Example 1, except that the types and amounts of materials, and whether or not the substrate was cleaned, were as shown in Table 4 below. The evaluation results are shown in Table 4. In Comparative Example 1, the filler content was low, and sufficient specular reflection output was not obtained, resulting in a large deviation rate relative to the average specular reflection output.In Comparative Example 2, the filler content was high, and therefore the average specular reflection output was large, but the amount of filler in the 0.25P region was also large, and the amount of diffused reflection light increased, resulting in a large deviation rate relative to the average specular reflection output.In Comparative Examples 3 to 5, the substrate was not cleaned, and therefore the amount of filler in the 0.25P region was also large, and the amount of diffused reflection light increased, resulting in a large deviation rate relative to the average specular reflection output.

[0052] [Table 4]

[0053] 5 Endless belt for electrophotography 199 Groove 200 Belt circumferential direction 310 Filler 311 Surface layer 312 Base

Claims

1. An electrophotographic belt having an endless shape, comprising: a substrate having an endless shape; a surface layer on the outer peripheral surface of the substrate; A plurality of grooves extending in the circumferential direction are provided on the outer surface of the surface layer, the substrate comprises a thermoplastic polyester resin and a filler; the surface layer contains an acrylic resin, the thickness T of the substrate is 30 μm or more, and the content of the filler in the substrate is 0.1 vol % or more and 10.0 vol % or less, based on the total volume of the substrate; an average value A of the ratio of elements derived from the filler in a region of the surface layer having a thickness of 0.25 times the average particle diameter of the filler from a first surface on the side facing the substrate toward a second surface on the opposite side to the first surface is 0.0 atomic % or more and 1.0 atomic % or less.

2. 2. The electrophotographic belt according to claim 1, wherein said substrate is stretched in a circumferential direction and in a direction perpendicular to the circumferential direction.

3. 3. The electrophotographic belt according to claim 1, wherein the electrophotographic belt has a tensile modulus of elasticity Ep in the circumferential direction and a tensile modulus of elasticity Ea in the direction perpendicular to the circumferential direction, both of which are 1200 MPa or more.

4. 3. The electrophotographic belt according to claim 1, wherein the thermoplastic polyester resin contains at least one selected from the group consisting of polyalkylene terephthalate and polyalkylene naphthalate.

5. 3. The electrophotographic belt according to claim 1, wherein the filler comprises at least one selected from the group consisting of spherical silica and spherical silicone particles.

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

Images