Resin component and image forming apparatus

Abstract

To provide a resin member that can achieve both prevention of a reduction in electric resistance and prevention of molding failure.SOLUTION: A resin member is used for an electrophotographic image forming apparatus. The resin member contains thermoplastic resin and carbon black. The thermoplastic resin contains polyether ether ketone resin and second resin different from the polyether ether ketone resin. A value of the structure volume of the carbon black is 50-250 nm2 ml / 100 g. The content ratio of the carbon black in the resin member is 19.0-30.0 mass%. The content ratio of the second resin in the thermoplastic resin is 16.0 mass% or more. A temperature-falling crystallization temperature of the resin member measured in differential scanning calorimetry is 299.0°C or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a resin component used in image forming apparatuses such as photocopiers, printers, and facsimile machines that use electrophotographic or electrostatic recording methods, and to an image forming apparatus that includes the resin component as an intermediate transfer belt. [Background technology]

[0002] As an electrophotographic image forming apparatus, one method of transferring a toner image to a transfer material involves first transferring the toner image formed on a photoreceptor onto a belt-shaped intermediate transfer belt, and then secondarily transferring the toner image onto the transfer material.

[0003] The electrophotographic belt used in the above-mentioned intermediate transfer belt preferably has a volume resistivity in the semiconducting region, and also preferably has small variation in volume resistivity depending on the location of the member, in order to accurately electrostatically transfer the toner image from the surface of the photoreceptor onto the transfer material. Therefore, it is required that the in-plane surface involved in image formation be substantially uniform. As an example of the electrical resistance value of the intermediate transfer belt, a volume resistivity of 1 × 10⁻⁶ is desirable. 8 ~1 × 10 13 Ω cm, surface resistivity 1×10 9 ~1 × 10 15 Many are adjusted to within the range of Ω / □. The target range of electrical resistance is selected to be optimal according to the transfer section configuration of the image forming apparatus in which the intermediate transfer belt is used and the charging characteristics of the toner particles.

[0004] Patent Document 1 discloses a belt obtained by extruding polyether ether ketone (PEEK) containing a conductive filler into a tubular film and then cutting it perpendicular to the axial direction. Furthermore, the volume electrical resistance of each part of the belt is 10 8 ~10 17 It has been disclosed that it is Ω·cm. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 06-254941 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, electrophotographic belts that use conductive fillers to achieve conductivity may experience a decrease in electrical resistance after being subjected to electrophotographic image formation over a long period of time. Furthermore, it has become clear that in intermediate transfer belts containing conductive fillers, the thickness of the belt can become unstable during cylindrical belt molding, sometimes leading to molding defects. One aspect of this disclosure relates to a resin component that can suppress both the reduction of electrical resistance and the suppression of molding defects. Furthermore, this disclosure relates to an image forming apparatus equipped with the resin component as an intermediate transfer belt. [Means for solving the problem]

[0007] According to one aspect of this disclosure, A resin component used in an electrophotographic image forming apparatus, The resin component contains thermoplastic resin and carbon black, The thermoplastic resin comprises a first resin and a second resin different from the first resin. The first resin is a polyether ether ketone, The second resin is a polyether ketone, When the structural volume of the carbon black is a, a is calculated by the following formula (4): a = (1 / 3) × π × (d 2 / 2)×(0.0046×D+0.1435) ···(4) In formula (4), d is the number-average particle size (nm) of the primary particles of carbon black. D is the DBP oil absorption capacity of carbon black (mL / 100g), The structural volume of the carbon black a The value is 50-250nm 2 ·m L It is / 100g, A content ratio of the carbon black in the resin member is 19.0 to 30.0% by mass, a content ratio of the second resin in the thermoplastic resin is 16.0% by mass or more, and a cooling crystallization temperature of the resin member measured by differential scanning calorimetry is 299.0° C. or higher.

[0008] According to another aspect of the present disclosure, there is provided an image forming apparatus comprising: a first image carrier that carries an unfixed toner image; an intermediate transfer belt onto which the toner image formed on the first image carrier is primarily transferred; and a secondary transfer unit that secondarily transfers the toner image, which has been primarily transferred onto the intermediate transfer belt, onto a second image carrier, wherein the intermediate transfer belt is the resin member described above. Effects of the Invention

[0009] According to the present disclosure, a resin member that can achieve both suppression of a decrease in electrical resistance and suppression of molding defects can be provided. Brief Description of the Drawings

[0010] [Figure 1] Schematic cross-sectional view of an image forming apparatus using an electrophotographic belt as an intermediate transfer belt [Figure 2] Schematic diagram of thickness measurement locations on an electrophotographic belt Mode for Carrying Out the Invention

[0011] In the present disclosure, unless otherwise specified, the descriptions "from XX to YY" and "XX~YY" representing numerical ranges mean numerical ranges that include the lower limit and upper limit, which are the endpoints. When numerical ranges are described stepwise, the upper limit and lower limit of each numerical range can be combined arbitrarily.

[0012] Hereinafter, an electrophotographic belt, a method for manufacturing an electrophotographic belt, and an electrophotographic image forming apparatus (hereinafter also simply referred to as "image forming apparatus") as examples of resin components relating to this disclosure will be described with reference to the drawings.

[0013] 1. Image forming apparatus First, an embodiment of an image forming apparatus using an endless electrophotographic belt as an intermediate transfer belt, according to one aspect of the present disclosure, will be described. Figure 1 is a schematic cross-sectional view of the image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment is a tandem-type color laser printer employing an intermediate transfer method that is capable of forming full-color images using an electrophotographic method.

[0014] The image forming apparatus 100 has a plurality of image forming sections, namely the first, second, third, and fourth image forming sections PY, PM, PC, and PK. These first, second, third, and fourth image forming sections PY, PM, PC, and PK are arranged in this order along the direction of movement of the flat portion (image transfer surface) of the intermediate transfer belt 7, which will be described later. Elements in the first, second, third, and fourth image forming sections PY, PM, PC, and PK that have the same or corresponding function or configuration may be described collectively by omitting the Y, M, C, and K at the end of the symbols indicating that they are elements for any of the colors. In this embodiment, the image forming section P is composed of a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, and a primary transfer roller 5, which will be described later.

[0015] The image forming unit P has a photosensitive drum 1, which is a drum-shaped (cylindrical) photoreceptor (electrophotographic photoreceptor) that serves as an image carrier (first image carrier) for holding the unfixed toner image. For example, the first example is formed by sequentially laminating a charge generation layer, a charge transport layer, and a surface protection layer on an aluminum cylinder serving as a base. The photosensitive drum 1 is driven to rotate in the direction of arrow R1 (counterclockwise) in the figure. The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential with a predetermined polarity (negative polarity in this embodiment) by a charging roller 2, which is a roller-shaped charging member acting as a charging means. During the charging process, a predetermined charging bias (charging voltage) including a negative DC component is applied to the charging roller 2. The charged surface of the photosensitive drum 1 is scanned and exposed according to image information by an exposure device (laser scanner) 3 acting as an exposure means, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 1.

[0016] The electrostatic image formed on the photosensitive drum 1 is developed (visualized) by a developing device 4, which supplies toner as a developer, and an unfixed toner image (developer image) is formed on the photosensitive drum 1. During the development process, a predetermined development bias (development voltage) containing a negative DC component is applied to the developing roller 4a, which serves as a developer carrier in the developing device 4. In this embodiment, toner charged with the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this embodiment) adheres to the exposed area (image area) on the photosensitive drum 1, where the absolute value of the potential has decreased after uniform charging treatment and exposure.

[0017] An intermediate transfer belt 7, composed of an endless belt, is positioned opposite the four photosensitive drums 1. The intermediate transfer belt 7 is stretched over a plurality of tension rollers, including drive rollers 71, tension rollers 72, and secondary transfer opposing rollers 73, and is taut with a predetermined tension. The intermediate transfer belt 7 rotates (circumvents) in the direction of arrow R2 (clockwise) in the figure when the drive rollers 71 are rotated, and comes into contact with the photosensitive drums 1. On the inner circumferential surface of the intermediate transfer belt 7, a primary transfer roller 5, which is a roller-shaped primary transfer member serving as a primary transfer means, is arranged corresponding to each photosensitive drum 1. The primary transfer roller 5 is pressed toward the photosensitive drum 1 via the intermediate transfer belt 7, forming a primary transfer section (primary transfer nip) T where the photosensitive drum 1 and the intermediate transfer belt 7 come into contact. As described above, the unfixed toner image formed on the photosensitive drum 1 is primary transferred onto the rotating intermediate transfer belt 7 in the primary transfer section T by the action of the primary transfer roller 5. During the primary transfer process, a primary transfer bias (primary transfer voltage), which is a DC voltage with the opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner (charging polarity during the developing process), is applied to the primary transfer roller 5. The primary transfer roller 5 is often composed of a metal rotating shaft and an elastic layer formed on the outer surface of the rotating shaft, and is adjusted to a desired resistance value. However, it may also be composed of a metal roller made of SUM (sulfur and sulfur composite free-cutting steel) or SUS (stainless steel) and having a straight shape in the thrust direction.

[0018] On the outer circumferential surface of the intermediate transfer belt 7, a secondary transfer roller 8, which is a roller-shaped secondary transfer member serving as a secondary transfer means, is positioned opposite the secondary transfer opposing roller 73. The secondary transfer roller 8 is pressed toward the secondary transfer opposing roller 73 via the intermediate transfer belt 7, forming a secondary transfer portion (secondary transfer nip) T' where the intermediate transfer belt 7 and the secondary transfer roller 8 come into contact. As described above, the toner image formed on the intermediate transfer belt 7 is secondarily transferred in the secondary transfer section T' to a second image carrier that is held and transported between the intermediate transfer belt 7 and the secondary transfer roller 8 by the action of the secondary transfer roller 8. The second image carrier is a recording material (sheet, transfer material) S such as paper. During the secondary transfer process, a secondary transfer bias (secondary transfer voltage), which is a DC voltage with the opposite polarity to the normal charge polarity of the toner, is applied to the secondary transfer roller 8. In secondary transfer, a transfer voltage of several kV is usually applied to ensure sufficient transfer efficiency. The recording material S is moved from the cassette 12 in which the recording material S is stored to the pickup roller 13. Therefore, it is supplied to the transport path. The recording material S supplied to the transport path is transported to the secondary transfer section T' by the transport roller pair 14 and the resist roller pair 15, in time with the toner image on the intermediate transfer belt 7.

[0019] The recording material S onto which the toner image has been transferred is transported to a fixing device 9, which serves as a fixing means. The fixing device 9 is equipped with a pressure roller 91 and a heating roller 92. The fixing device 9 heats and pressurizes the recording material S carrying the unfixed toner image, thereby fixing (melting and solidifying) the toner image onto the recording material S. The recording material S with the fixed toner image is discharged (output) to the outside of the main body of the image forming apparatus 100 by a transport roller pair 16, an discharge roller pair 17, etc.

[0020] Toner that remains on the surface of the photosensitive drum 1 without being transferred to the intermediate transfer belt 7 during the primary transfer process (primary transfer residue toner) is developed and recovered simultaneously by the developing device 4, which also serves as a photoreceptor cleaning means 4b. Furthermore, toner that remains on the surface of the intermediate transfer belt 7 without being transferred to the recording material S during the secondary transfer process (secondary transfer residue toner) is removed from the surface of the intermediate transfer belt 7 and recovered by the belt cleaning device 11, which serves as an intermediate transfer belt cleaning means. The belt cleaning device 11 is positioned downstream of the secondary transfer section T' and upstream of the primary transfer section Ty, which is the uppermost section, in the rotational direction of the intermediate transfer belt 7 (in this embodiment, at a position opposite the drive roller 71). The belt cleaning device 11 uses a cleaning blade, which is positioned to contact the surface of the intermediate transfer belt 7, to scrape off the residual secondary transfer toner from the surface of the rotating intermediate transfer belt 7 and collect it in the collection container 11b.

[0021] Thus, in the image forming operation, the electrical transfer process of the toner image from the photosensitive drum 1 to the intermediate transfer belt 7, and from the intermediate transfer belt 7 to the recording material S, is repeatedly performed. Furthermore, by repeatedly forming images on multiple recording materials S, the electrical transfer process is repeated even more times.

[0022] 2. Intermediate transfer belt The intermediate transfer belt 7 includes at least a base layer (base material), and may be a laminate composed of a plurality of layers further including a surface layer or the like. As described below, the base layer is a semiconductive film obtained by containing a conductive filler in a resin.

[0023] 2-1. Configuration and characteristics of the intermediate transfer belt The inventors of the present invention found that, for stabilizing the conductivity of a conductive electrophotographic belt, when the structure volume is 50 to 250 nm 2 It has been found that use of carbon black falling within the range of ·ml / 100g is effective. Accordingly, an endless-shaped resin member was produced by melt-extruding, from a cylindrical die, a resin composition obtained by dispersing carbon black having a structure volume falling within the above numerical range in a thermoplastic resin. However, the obtained resin member had variation in film thickness. Accordingly, the inventors of the present invention recognized that, in order to obtain an electrophotographic belt whose conductivity hardly changes even after long-term use by using carbon black having a structure volume falling within the above numerical range, it is necessary to improve thickness unevenness.

[0024] Here, the inventors of the present invention presume the reason why thickness unevenness occurs in a cylindrical extrusion molded article of a resin composition containing carbon black having a structure volume falling within the above numerical range as follows. That is, the thickness of a cylindrical resin member molded by a cylindrical extrusion molding method is adjusted when the resin composition is extruded from a cylindrical die in a molten state and taken downward. The inventors of the present invention found that the cooling crystallization temperature of the resin composition containing said carbon black, compared with a resin composition containing carbon black having a structure volume larger than the above numerical range, is decreased. When the crystallization temperature is low, the resin material extruded from the cylindrical die is taken off without being sufficiently crystallized, so that force is not transmitted in the take-off direction, resulting in a reduced thickness. As the thickness decreases, material accumulates at the exit of the cylindrical die, but it is pushed out from behind, causing the material to be suddenly pushed out at a certain point, resulting in increased thickness. It is believed that this repeated process caused the uneven thickness.

[0025] Furthermore, our investigations revealed that thickness variations are particularly likely to occur when the cooling crystallization temperature is lower than 299.0°C. Therefore, in order to obtain an electrophotographic belt that achieves both stable conductivity and uniform film thickness at a high level, it is important to set the cooling crystallization temperature of the resin composition containing carbon black with a structure volume within the above numerical range to 299.0°C or higher.

[0026] The cooling crystallization temperature of the resin component must be 299.0°C or higher, but is preferably 299.0 to 380°C, more preferably 299.5 to 360.0°C, and even more preferably 300.0 to 340.0°C. The cooling crystallization temperature of the resin component can be controlled by the type and content of the second resin.

[0027] <Method for measuring the cooling crystallization temperature> In a scanning calorimetry (DSC) system, the peak temperature detected during the cooling process from the molten state is defined as the cooling crystallization temperature. The cooling crystallization temperature is determined by cutting a resin component into pieces of approximately 2-3 mg, setting the sample in a DSC (Q2000, manufactured by T.A. Instruments Japan Co., Ltd.), heating it to 400°C at 10°C / min, and then measuring the peak temperature that appears when it is cooled to room temperature at 10°C / min.

[0028] <Resin materials> For resin components such as intermediate transfer belts composed of a single layer, a thermoplastic resin is used as the resin material. The thermoplastic resin includes a first resin and a second resin different from the first resin. The first resin is polyetheretherketone (PEEK). Intermediate transfer belts using PEEK resin are less prone to stretching even under long-term tensile loads and are less susceptible to surface wear from friction by cleaning blades. The content of thermoplastic resin in the resin component is preferably 70.0 to 81.0% by mass, and more preferably 75.0 to 80.0% by mass. The PEEK content in the thermoplastic resin is preferably 84.0% by mass or less, and more preferably, for example, 35.0-84.0% by mass, 50.0-8.0% by mass, 60.0-8.0% by mass, or 70.0-8.0% by mass.

[0029] <Second resin material> The thermoplastic resin contains a second resin different from polyether ether ketone. Preferably, the second resin is a resin that maintains physical properties equivalent to those of the PEEK resin, but exhibits a cooling crystallization temperature higher than that of the PEEK resin. The cooling crystallization temperature of the second resin is preferably, for example, 299.0 to 350.0°C, and more preferably 300.0 to 330.0°C. Examples of thermoplastic resins, in addition to PEEK resin, include polyaryletherketone (PAEK), polyetherketoneketone (PEKK), and polyetherketone (PEK). The second resin is preferably polyetherketone (PEK). Furthermore, two or more of these resins may be selected and mixed as needed. That is, the thermoplastic resin may further consist of a third resin, a fourth resin, and so on, different from PEEK resin and the second resin. It may contain the nth resin.

[0030] <Content ratio of the second resin> The content of the second resin in the thermoplastic resin is 16.0% by mass or more, from the viewpoint of increasing the cooling crystallization temperature. More preferably, the content of the second resin in the thermoplastic resin is, for example, 16.0 to 65.0% by mass, 16.0 to 50.0% by mass, 16.0 to 40.0% by mass, or 16.0 to 30.0% by mass.

[0031] <Measurement of the content ratio of each resin in thermoplastic resins in resin components> The content ratio of each resin in a thermoplastic resin can be measured using known methods. For example, if the thermoplastic resin is PEEK and PEK, the cooling crystallization temperature changes depending on the proportion of PEEK and PEK contained. Therefore, by obtaining a calibration curve from the relationship between the proportion of PEEK and PEK contained and the cooling crystallization temperature, the proportion of each resin can be calculated based on the cooling crystallization temperature. In this way, after understanding the resin components contained in the thermoplastic resin by known means, the proportion of each resin can be calculated from the cooling crystallization temperature.

[0032] <Conductive filler> For purposes such as imparting conductivity to the intermediate transfer belt, at least one conductive filler, such as carbon black or metal nanoparticles, is blended into the resin material. In this disclosure, carbon black is used from the standpoint of mechanical properties. That is, the resin component contains carbon black. Carbon black has various names depending on its manufacturing method and raw materials. Specifically, these include Ketjenblack, furnace black, acetylene black, thermal black, and gas black.

[0033] Various known carbon blacks can be used. Specifically, these include Ketjen black, furnace black, acetylene black, thermal black, and gas black. Among these, acetylene black and furnace black are preferred because they contain fewer impurities, result in fewer foreign matter defects when molded into a film with the thermoplastic resin mentioned above, and make it easier to obtain the desired conductivity. Furnace black is more preferred.

[0034] Examples of acetylene black include the following (all are brand names): "Denka Black" series (manufactured by Denka Co., Ltd.), "Mitsubishi Conductive Filler" series (manufactured by Mitsubishi Chemical Corporation), "Vulcan" series (manufactured by Cabot Corporation), "Brintex" series (manufactured by Degussa Corporation), and "SRF" (manufactured by Asahi Carbon Co., Ltd.). Examples of furnace black include the "Mitsubishi Carbon Black" series (manufactured by Mitsubishi Chemical Corporation), the "Tokai Black" series (manufactured by Tokai Carbon Co., Ltd.), the "Asahi Carbon Black" series (manufactured by Asahi Carbon Co., Ltd.), and the "Nitelon" series (manufactured by Nippon Steel Carbon Co., Ltd.).

[0035] <Carbon black content> The carbon black content is selected considering the ability to impart the necessary conductivity to the belt material, the mechanical strength such as the bending resistance and elastic modulus of the belt material, and the thermal conductivity. The carbon black content in the resin component is 19.0 to 30.0% by mass. By keeping the carbon black content within this range, it is possible to ensure suitable conductivity for resin components such as intermediate transfer belts, as well as sufficient mechanical strength. If the carbon black content in the resin component falls below 19.0% by mass, whitening is more likely to occur. The carbon black content in the resin component is preferably 20.0 to 28.0% by mass, more preferably 20.0 to 25.0% by mass, and even more preferably 21.0 to 24.0% by mass.

[0036] <Method for measuring the carbon black content> Cut pieces of the resin component are dissolved in 20 ml of concentrated sulfuric acid to obtain a cut piece solution. The cut piece solution is neutralized with an appropriate alkaline solution (e.g., 1 mol / L sodium hydroxide aqueous solution) to obtain a neutralized cut piece solution. After diluting the neutralized cut piece solution twice with water, the mass of the residue obtained by drying the diluted solution can be used to estimate the carbon black content to be included in the resin component.

[0037] 2-2. Method for manufacturing an intermediate transfer belt The method for manufacturing resin components such as intermediate transfer belts is not particularly limited and any known method may be used. The base layer of an intermediate transfer belt, which consists of a single layer or at least two layers, is manufactured through the following steps (1) and (2). (1) Mixing process to obtain a resin composition by mixing a resin material (thermoplastic resin) and a conductive filler in a temperature environment where the temperature of the resin material is above the glass transition temperature of the resin material. (2) Molding process: The resin composition obtained in the mixing step is melted at a temperature above the melting temperature of the resin material and formed into a cylindrical tube shape. The following describes each of the steps in (1) and (2).

[0038] <Mixing process> In the mixing process, a thermoplastic resin and a conductive filler are mixed in a temperature environment above the glass transition point of the thermoplastic resin to obtain a resin composition. As a mixer used in the mixing process, for example, a twin-screw kneader equipped with two screws in a barrel or cylinder can be used.

[0039] The mixture of materials supplied from the supply hole in the supply unit advances toward the die as the screw rotates, and is melted and mixed due to shear heat generated by friction between the barrel or cylinder, the screw, and the raw material. It is preferable to control the temperature of the raw material so that it does not become too high by cooling or adjusting the temperature from outside the barrel or cylinder, or by adjusting the rotation speed of the screw.

[0040] From the viewpoint of improving the dispersion state of conductive fillers and obtaining a resin composition with excellent mechanical, electrical, and optical properties, the temperature during kneading is preferably 300 to 400°C, and more preferably 340 to 380°C. A strand die is usually installed at the tip of a twin-screw kneader, and the resin composition is extruded into a rod shape, air-cooled, and then cut to produce pellet-shaped resin composition. The extrusion amount and rotation speed of the device during kneading can be set appropriately from the viewpoint of uniformly mixing the resin composition.

[0041] Furthermore, a pre-mixing step may be provided before the mixing process in which the thermoplastic resin and conductive filler are mixed using a fluidized bed mixer in a temperature environment below the glass transition point of the thermoplastic resin. Various known fluidized bed mixers that utilize the fluid motion of solids for mixing can be used, but specifically, mixers such as Henschel mixers, ribbon mixers, and planetary mixers can be used. Among these, a Henschel mixer is preferable from the viewpoint of mixing efficiency. Furthermore, the rotation speed, processing time, and processing volume of the fluidized bed mixer should be appropriately selected according to the materials.

[0042] <Forming process> In the molding process, the resin composition obtained in the mixing process is molded into a resin component. For example, it is molded into an endless belt-shaped resin component such as a cylindrical tube. Depending on the resin used, methods such as extrusion molding and inflation molding can be selected for molding, but from the viewpoint of productivity, cylindrical extrusion molding is preferred. The resin component is an extruded product. It is preferable to have one. In the extrusion molding method, either a single-screw extruder with one screw in a barrel or cylinder, or a multi-screw extruder with two or more screws, can be used. The pelletized resin composition supplied from the supply hole of the supply section moves forward toward the die due to the rotation of the screw, receiving thermal energy from the barrel or cylinder and mechanical energy from the screw, and is substantially completely melted and supplied in a fixed quantity to the tip of the extruder. A cylindrical die is installed at the tip of the extruder, and the resin composition is molded into a cylindrical tube shape by extruding it downward from the cylindrical die and taking it back from below. The temperature during extrusion molding (e.g., die temperature) is not particularly limited, but is preferably 300-400°C, and more preferably 340-380°C.

[0043] The thickness of the base layer (i.e., the thickness of the resin member) of an intermediate transfer belt consisting of a single layer or an intermediate transfer belt consisting of at least two layers is not particularly limited, but is preferably about 10 to 500 μm, and more preferably about 50 to 200 μm.

[0044] 2-3. Reduced resistance of the intermediate transfer belt When conductive filler carbon black (hereinafter referred to as CB) is added to a thermoplastic resin, kneaded, and the mixture is formed into a sheet to exhibit conductivity, multiple conductive paths formed by the linkage of numerous CBs exist within the resin, extending from the surface to the back of the sheet. In this case, the electrical resistance of the conductive path is the sum of the electrical resistance of the conductive part made up of CBs and the electrical resistance of the contact points where the CBs are linked together.

[0045] For example, in the case of an intermediate transfer belt that exhibits conductivity using conductive fillers, as mentioned above, its electrical resistance may decrease after being subjected to electrophotographic image formation over a long period of time. This is thought to be because discharge occurs between the secondary transfer roller and the intermediate transfer belt during printing. In such cases, the load due to the current flowing through the intermediate transfer belt becomes concentrated, causing the electrical resistance of the intermediate transfer belt to decrease over time, resulting in a decrease in image quality, such as the occurrence of white spots.

[0046] More specifically, in the primary transfer section, if a gap occurs between the inner surface of the intermediate transfer belt and the primary transfer roller, a discharge occurs between the intermediate transfer belt and the primary transfer roller, causing a localized decrease in the electrical resistance of the intermediate transfer belt. In this case, toner is not transferred to the areas where the electrical resistance has decreased, resulting in a white, untransferred image (whiteout). Furthermore, in the secondary transfer section, if a gap occurs between the outer surface of the intermediate transfer belt and the paper, a discharge occurs between the intermediate transfer belt and the paper. It is thought that the charge polarity of the toner on the intermediate transfer belt reverses due to the discharge, preventing it from being transferred to the paper and resulting in white spots. These phenomena are particularly noticeable when the dispersibility of the CB is low or in low-humidity environments.

[0047] This is because the electrical resistance of the conductive path formed by the connection of numerous CBs decreased. Looking at it in more detail, it can be inferred that this localized discharge occurs not because the electrical resistance of the CB sections (conductive parts) within the conductive path decreased, but rather because the electrical resistance of the contact points where the CBs are connected decreased. It is believed that the electric field concentrated at the contact point between the CBs due to the voltage applied during printing, and that the heat generated by the electric field concentration over a long period of time during printing caused the resin around the contact point to carbonize, leading to dielectric breakdown. Therefore, in order to prevent a decrease in the electrical resistance of the conductive path, it is important to suppress the heat generated by the electric field concentration and prevent the resin around the contact point from carbonizing.

[0048] The amount of heat generated Q at the contact point when two CBs in a conductive path are connected is given by equation (1), and in order to reduce the amount of heat generated, it is necessary to lower the voltage (V) or increase the resistance value (R). Q = V × V × t / R ... (1) Q: Heat output V: Voltage flowing through the path R: Resistance value of the contact area t: time The voltage (V) is determined by the printing conditions, so it cannot be lowered.

[0049] On the other hand, the resistance R at the contact points between CB particles is expressed by equation (2). In order to increase the resistance R at the contact points, it is necessary to reduce the structural volume a of the CB. R = ρ / (2 × a × n) ... (2) R: Resistance value of the contact area ρ: Resistivity of carbon black a: Structural volume of carbon black n: Number of contact points

[0050] 2-7. Structural Volume CB has a structure in which multiple spherical primary particles are randomly fused together. This structure is called the structure as the minimum structure of CB, and it is one of the characteristics that describe the bonding state of CB particles. The volume index α, which correlates with the structural volume of CB, is expressed by equation (3). α=(d 2 ) × (D × c1 + c2) ... (3) d: Number-average particle size of primary particles (nm) D:DBP oil absorption (mL / 100g) c1, c2: constants

[0051] The smaller the volume index value α, the smaller the structural volume of the CB. This increases the resistance value R at the contact points between CB particles, suppresses the heat generation Q at the contact points, and thus suppresses the decrease in electrical resistance over time due to the concentration of load caused by current flowing through the intermediate transfer belt.

[0052] The structural volume of carbon black was evaluated by the method described below, and the range was 50-250 nm. 2 The concentration is ml / 100g. The structural volume is 250 nm. 2 • When the concentration exceeds ml / 100g, electric field concentration at the contact point between CBs is likely to cause a decrease in the resistance of the intermediate transfer belt. Also, when the structure volume is 50nm 2 If the concentration falls below ml / 100g, the cohesive force between the CBs becomes too strong, making it difficult to maintain a good dispersion state of the conductive filler within the intermediate transfer belt.

[0053] The structural volume of carbon black is 70-230 nm. 2 Preferably ml / 100g, and 100-220nm 2 It is more preferable that the concentration is ml / 100g. The structural volume of carbon black is an evaluation value calculated from the primary particle size and DBP oil absorption rate of the carbon black, and it varies depending on the type of carbon black. Therefore, to achieve the desired structural volume, you should select carbon black that meets the conditions.

[0054] There are degrees of freedom between the structural volume a and the volume index value α, with respect to the constants c1 and c2, as shown in equation (3). On the other hand, the structural volume a relating to this disclosure is calculated by equation (4). a = (1 / 3) × π × (d 2 / 2) × (0.0046 × D + 0.1435) ... (4) d: Number-average particle size (nm) of primary carbon black particles D: DBP oil absorption capacity of carbon black (mL / 100g)

[0055] 2-4. Number-average particle size of primary particles in carbon black The number-average particle size of the primary carbon black particles is preferably 10 to 30 nm. If the number-average particle size of the primary particles is 10 nm or larger, re-aggregation of the filler is less likely to occur. More preferably, it is 20 to 28 nm. On the other hand, if the number-average particle size of the primary particles is 30 nm or less, dispersibility is less likely to decrease even if agglomeration occurs, and the decrease in resistance of the intermediate transfer belt due to discharge is more easily suppressed. Therefore, by using carbon black with a number-average particle size of primary particles within the above range, better resistance maintenance can be obtained.

[0056] 2-5. Method for evaluating the number-average particle size of primary carbon black contained in resin components. The carbon black contained in the resin component will be observed using a scanning electron microscope (SEM). The thin section samples will be prepared before observation using the following method: The resin component will be cut using a Leica "ULTRACUT-S" and observation cutting samples with a thickness of 40 nm will be collected. Specifically, samples will be taken from the area of ​​the resin component that is in contact with the recording material and the above processing will be performed. A Hitachi S-4700 scanning electron microscope (SEM) was used to acquire SEM images under a measurement condition of an acceleration voltage of 3kV. The resulting SEM images were analyzed using the image analysis software "ImageJ" (free software). The diameters of 50 primary carbon black particles were measured, and the average number of these particles was used as the number-average particle size of the primary particles. The specific operation of "ImageJ" involves importing SEM images into ImageJ, removing noise, and then performing binarization (Otsu binarization method, IEEE TRANSACTIONS ON). The carbon black portion was extracted using the method described in SYSTEMS, MAN, AND CYBERNETICS, VOL. SMC-9, NO.1, JANUARY 1979, PP.62-66), and the particle size (maximum diameter) of each carbon black particle was calculated using the measurement function (Analyze Particles).

[0057] 2-6. Method for evaluating the DBP oil absorption amount of carbon black contained in resin components The amount of DBP (dibutyl phthalate) absorbed by the carbon black contained in the intermediate transfer belt being measured can be confirmed as follows. The carbon black contained in the intermediate transfer belt can be observed using a transmission electron microscope (TEM). The thin section samples for observation were prepared as follows: A resin component was cut using a Leica "ULTRACUT-S" and 40 nm thick observation pieces were collected. Specifically, samples were taken from the area of ​​the resin component in contact with the recording material. A Hitachi H-7100FA transmission electron microscope (TEM) was used. TEM images were acquired under measurement conditions of TE mode, acceleration voltage of 100kV, and magnification such that one side of the image was 3μm or less. Since the smallest structural unit of carbon black is a primary aggregate composed of linked primary particles, the distribution of the maximum Ferret diameter in the carbon black primary aggregate was analyzed from the obtained TEM images. The maximum Ferret diameter corresponds to the length of the longest side of the rectangle circumscribing the carbon black primary aggregate.

[0058] To analyze the maximum Ferret diameter from the obtained TEM images, we used "ImageJ" (free software). By binarizing the images and extracting the carbon black, we were able to analyze the distribution of the maximum Ferret diameter of the primary carbon black aggregates scattered throughout the images. Specifically, after removing noise from the acquired TEM images, we performed binarization (Otsu's binarization method) to extract the primary carbon black aggregates, and then calculated the Ferret diameter using the particle analysis function. At this time, it is known that there is a correlation between the peak top position of the maximum ferret diameter and the DBP oil absorption amount, which is an indicator of the size of the primary aggregates of carbon black. By checking the number and position of the peak tops of the maximum ferret diameter, it is possible to identify carbon blacks with different DBP oil absorption amounts. The type of carbon black and the DBP oil absorption capacity of each carbon black can be checked. For example, the peak top position of the maximum ferret diameter distribution is 100-160 nm, and the DBP oil absorption rate is 93-127 ml / 100 g.

[0059] According to one aspect of this disclosure, a resin member for use in an electrophotographic image forming apparatus can be obtained that exhibits excellent moldability into intermediate transfer belts and other forms, while simultaneously suppressing both a decrease in electrical resistance and a decrease in molding defects. In other words, the resin member is preferably an intermediate transfer belt. Furthermore, according to other aspects of this disclosure, it is possible to provide an image forming apparatus using the resin member. The image forming apparatus is A first image carrier that holds an unfixed toner image, An intermediate transfer belt on which the toner image formed on the first image carrier is first transferred, The system includes a secondary transfer means for transferring the toner image, which has been primary transferred onto the intermediate transfer belt, onto a second image carrier, The intermediate transfer belt is the resin component described above in the image forming apparatus. [Examples]

[0060] The present disclosure will be described in detail below using examples. However, this disclosure is not limited to the configurations embodied in the examples. Furthermore, unless otherwise specified, the number of copies in the examples and comparative examples is by mass.

[0061] [Example 1] The materials listed below were melted and kneaded using a twin-screw compounding extruder (Ikegai Co., Ltd., PCM43) under the following conditions to produce a resin composition. Resin material: PEEK resin (product name: 450G; manufactured by Victrex) Cooling crystallization temperature: 298.0℃ Second resin: PEK resin (product name: HTP45PF; manufactured by Victrex) Cooling crystallization temperature: 320.0℃ Conductive filler: Carbon black (Product name: #44; manufactured by Mitsubishi Chemical Corporation) The proportions were as follows, with a total of 100 parts of belt material. • PEEK resin: 62.4 parts (80 parts when the total resin is 100 parts) • PEK resin: 15.6 parts (20 parts when the total resin is 100 parts) • Carbon black: 22.0 parts (22.0% by mass of the resin component) The conditions for the twin-screw compounding extruder were as follows: Extrusion rate: 6 kg / h Screw rotation speed: 225 rpm Barrel control temperature: 360℃

[0062] Next, the prepared resin composition was subjected to melt extrusion using a single-screw extruder (Plastics Engineering Research Institute Co., Ltd.) equipped with a spiral cylindrical die (inner diameter: 285 mm, slit width: 1.1 mm) at its tip, under the following conditions, to produce a tubular electrophotographic belt (φ280 mm, thickness 60 μm) according to this embodiment. The conditions for the single-screw extruder were as follows: Extrusion rate: 6 kg / h Die temperature: 360℃

[0063] [Comparative Examples 1-5] An electrophotographic intermediate transfer belt was prepared in the same manner as in Example 1, except that the type and amount of the second resin, and the type and amount of carbon black were as shown in Table 1 below. For the polyaryletherketone (PAEK), AV-651 (Solvay Specialty Polymers Japan Co., Ltd.) was used, with a cooling crystallization temperature of 285.0°C. [Table 1]

[0064] The electrophotographic intermediate transfer belts according to Example 1 and Comparative Examples 1-3 were subjected to the following evaluations 1 and 2. The results are shown in Table 2.

[0065] [Rating 1] The thickness of each electrophotographic intermediate transfer belt according to Example 1 and Comparative Examples 1-3 was measured using a thickness measuring instrument, the Digimatic Indicator ID-C125B (manufactured by Mitutoyo Corporation). The amount was measured. The thickness measurement point 200 is as shown in Figure 2, in direction a in Figure 2 (perpendicular to the circumferential direction and the belt) There were 5 locations along belt 7 and 8 locations evenly spaced in the circumferential direction of belt 7 (indicated by 'b' in the figure) (8 locations at 45-degree intervals when belt 7 is placed in a circle), for a total of 40 locations (Note that for convenience, only 15 of the 40 locations are shown in Figure 2). The standard deviation σ of the thickness at the 40 locations was calculated, and the value obtained by dividing σ by the average thickness was used as the thickness unevenness evaluation value. Since a thickness unevenness evaluation value of 0.1 or higher indicates a molding defect, a value of less than 0.08 was evaluated as moldability A, and a value of 0.08 or higher was evaluated as moldability B.

[0066] In other words, when the thickness of the resin component is measured at 40 locations using a thickness measuring instrument, it is preferable that the value obtained by dividing the standard deviation σ of the thickness by the average thickness is less than 0.08.

[0067] [Rating 2] Each of the electrophotographic intermediate transfer belts from Example 1 and Comparative Examples 1-3 was mounted as an intermediate transfer belt in the electrophotographic image forming apparatus (product name: imageRUNNER-ADVANCE-C5540; manufactured by Canon Corporation) shown in Figure 1. Using this electrophotographic image forming apparatus, 600,000 solid white images were printed on A3 size plain paper (product name: CS068; manufactured by Canon Corporation) in a low humidity environment (temperature 23°C / relative humidity 5%). During this process, for every 10,000 solid white images produced, five consecutive full-black halftone images were produced. The 60th set, i.e., the five full-black halftone images produced after the formation of 600,000 solid white images, were visually observed and evaluated based on the following criteria. Rank A: No white spots were observed in any of the five halftone images. (The intermediate transfer material does not easily lose electrical resistance, i.e., it has high resistance retention). Regarding Rank B, one or more of the five halftone images showed areas of whiteness. [Table 2] In the table, CB particle size represents the number-average particle size of carbon black particles.

[0068] In Example 1, no white areas were observed, and good resistance retention was obtained. In addition, it also exhibited good moldability, resulting in an intermediate transfer belt that achieved both resistance retention and moldability.

[0069] In Comparative Examples 1 and 2, while resistance retention was good, moldability was poor, resulting in molding defects. This is thought to be because the cooling crystallization temperature for both formulations was lower than 299.0°C, causing uneven thickness.

[0070] In Comparative Example 3, although the moldability was good, it is thought that the large structure volume caused a decrease in the resistance of the intermediate transfer belt due to electric field concentration at the contact points between the carbons. In Comparative Example 4, the low carbon black content and the increased distance between the CBs led to greater concentration of the electric field during discharge, causing the resin to carbonize, which is thought to have resulted in a decrease in the resistance of the intermediate transfer belt. Furthermore, a low carbon black content prevents the belt material from achieving the necessary conductivity. In Comparative Example 5, the structure volume was small, the cohesive force of the carbon black increased, and the dispersibility decreased, which is thought to have caused a decrease in the resistance of the intermediate transfer belt.

[0071] This disclosure relates to the following configuration. (Composition 1) A resin component used in an electrophotographic image forming apparatus, The resin component contains thermoplastic resin and carbon black, The thermoplastic resin comprises a first resin and a second resin different from the first resin. The first resin is a polyether ether ketone, The structural volume of the carbon black is 50-250 nm 2 It is ml / 100g, The carbon black content in the resin component is 19.0 to 30.0% by mass. The content ratio of the second resin in the thermoplastic resin is 16.0% by mass or more. A resin component characterized in that its cooling crystallization temperature, as measured in scanning calorimetry, is 299.0°C or higher. (Configuration 2) The resin member according to configuration 1, wherein the cooling crystallization temperature of the second resin is higher than the cooling crystallization temperature of the polyetheretherketone. (Composition 3) The resin member according to configuration 1 or 2, wherein the second resin is polyetherketone. (Composition 4) The resin member according to any one of configurations 1 to 3, wherein the content ratio of the polyetheretherketone in the thermoplastic resin is 35.0 to 84.0% by mass. (Composition 5) The resin member according to any one of configurations 1 to 4, wherein the number-average particle size of the primary particles of the carbon black is 10 to 30 nm. (Composition 6) The resin member is a resin member according to any one of configurations 1 to 5 having an endless belt shape. (Composition 7) The resin member is an electrophotographic belt, as described in any of configurations 1 to 6. (Configuration 8) A first image carrier that holds an unfixed toner image, An intermediate transfer belt on which the toner image formed on the first image carrier is first transferred, A secondary transfer means for transferring the toner image, which has been primary transferred onto the intermediate transfer belt, onto a second image carrier, Equipped with, An image forming apparatus in which the intermediate transfer belt is a resin member according to any of the configurations 1 to 7. [Explanation of symbols]

[0072] 1 Photosensitive drum, 2 Primary charging device, 3 Exposure device, 4 Developing device, 5 Primary transfer roller, 7 Intermediate transfer belt, 8 Secondary transfer outer roller, 9 Fixing device, 12 Cassette, 13 Pickup roller, 15 Resist roller, 71 Intermediate transfer belt tensioning roller (drive roller), 72 Intermediate transfer belt tensioning roller (tension roller), 73 Intermediate transfer belt tensioning roller (secondary transfer inner roller), 10 Base layer, 11 Surface layer, 100 Image forming apparatus, 200 Thickness measurement point

Claims

1. A resin component used in an electrophotographic image forming apparatus, The resin component contains thermoplastic resin and carbon black, The thermoplastic resin comprises a first resin and a second resin different from the first resin. The first resin is a polyether ether ketone, The second resin is a polyether ketone, When the structural volume of the carbon black is denoted as a, a is calculated by the following formula (4): a=(1 / 3)×π×(d 2 / 2)×(0.0046×D+0.1435) ...(4) In formula (4), d is the number-average particle size (nm) of the primary particles of carbon black. D is the DBP oil absorption capacity of carbon black (mL / 100g), The structural volume a of the carbon black is 50 to 250 nm. ２ • mL / 100g, The carbon black content in the resin member is 19.0 to 30.0% by mass. The content ratio of the second resin in the thermoplastic resin is 16.0% by mass or more. A resin component characterized in that its cooling crystallization temperature, as measured in scanning calorimetry, is 299.0°C or higher.

2. The resin member according to claim 1, wherein the cooling crystallization temperature of the second resin is higher than the cooling crystallization temperature of the polyetheretherketone.

3. The resin member according to claim 1, wherein the content ratio of the polyetheretherketone in the thermoplastic resin is 35.0 to 84.0% by mass.

4. The resin member according to claim 1, wherein the number-average particle size of the primary particles of the carbon black is 10 to 30 nm.

5. The resin member according to claim 1, wherein the resin member has an endless belt shape.

6. The resin member according to claim 5, wherein the resin member is an electrophotographic belt.

7. A first image carrier that holds an unfixed toner image, An intermediate transfer belt on which the toner image formed on the first image carrier is first transferred, A secondary transfer means for transferring the toner image, which has been primary transferred onto the intermediate transfer belt, onto a second image carrier, Equipped with, An image forming apparatus in which the intermediate transfer belt is a resin member according to any one of claims 1 to 6.

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