Resin composition, method for producing same, and electrophotographic image forming apparatus

Abstract

To provide a resin composition which has high voltage resistance, excellent mechanical strength and high conductivity, and a method for producing the same.SOLUTION: A resin composition contains a thermoplastic resin (A), and a deformed filler (B) dispersed in the thermoplastic resin (A), wherein the deformed filler (B) holds a polyether ester amide resin (C) and a fluorine salt (D) thereon, and the resin composition has an impedance Z of an alternating current (200 Vp-p and frequency of 50 Hz) of 1×107 Ω or less, has bending fracture stress at a temperature of 150°C measured according to JIS K 7171 of 1.5 MPa or more, and is not dielectrically broken down even when an alternating current (peak-to-peak voltage of 5 kV, frequency of 50 Hz and current of 10 mA) is applied for 0.3 seconds.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present disclosure is directed to a resin composition, a method for producing the resin composition, and an electrophotographic image forming apparatus.

Background Art

[0002] As a method for imparting conductivity to a resin composition, there is a method in which an ionic conductive agent such as a fluorine-based salt (hereinafter, may also be referred to as "fluorine salt") is contained in the resin composition, and conductivity is exhibited by ions. The method of exhibiting conductivity using ions has high stability of the electrical resistance value (Patent Document 1), is less likely to cause dielectric breakdown even when excessive electricity flows, and can achieve a high withstand voltage. However, when ions are used, it is difficult to lower the electrical resistance. Generally, the lower limit of the electrical resistance of a resin composition using ionic conduction is about 10 to the 8th power Ω. Further, when a large amount of an ionic conductive agent is mixed in the resin composition, the mechanical properties of the resin composition itself may be significantly reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] One aspect of the present disclosure is directed to providing a resin composition having high withstand voltage properties, excellent mechanical strength, and high conductivity. Another aspect of the present disclosure is directed to providing a method for producing a resin composition having high withstand voltage properties, excellent mechanical strength, and high conductivity. Further, another aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus capable of forming a high-quality electrophotographic image.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, there is provided a resin composition containing a thermoplastic resin (A) and a deformed filler (B) dispersed in the thermoplastic resin (A), wherein the deformed filler (B) holds a polyether ester amide resin (C) and a fluoride salt (D) on its surface, and the resin composition has an impedance Z of alternating current (200 Vp-p, frequency 50 Hz) of 1×10 7 Ω or less, a flexural fracture stress at a temperature of 150°C measured in accordance with JIS K7171 of 1.5 MPa or more, and does not break down even when an alternating current (peak-to-peak voltage 5 kV, frequency 50 Hz, current 10 mA) is applied for 0.3 seconds. Further, according to another aspect of the present disclosure, there is provided a method for producing a resin composition, comprising: (i) kneading a deformed filler (B) and a resin mixture containing a polyether ester amide resin (C) and a fluoride salt (D) to obtain a masterbatch; and (ii) mixing the masterbatch with a thermoplastic resin (A). Furthermore, according to another aspect of the present disclosure, there is provided an image forming apparatus including the method for producing the resin composition and a pressure heater holder molded using the resin composition.

Advantages of the Invention

[0006] According to one aspect of the present disclosure, a resin composition having high breakdown voltage resistance, excellent mechanical strength, and high conductivity can be obtained. According to another aspect of the present disclosure, a method for producing a resin composition having high breakdown voltage resistance, excellent mechanical strength, and high conductivity can be obtained. Furthermore, according to another aspect of the present disclosure, an electrophotographic image forming apparatus capable of forming a high-quality electrophotographic image can be obtained.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] Hereinafter, with reference to the drawings, embodiments for carrying out the present disclosure will be exemplarily and specifically described. However, the scope of the present invention is not limited to the following embodiments. (Resin Composition) The resin composition of the present disclosure is a resin composition containing a thermoplastic resin (A) and a deformed filler (B) dispersed in the thermoplastic resin (A), The deformed filler (B) holds a polyether ester amide resin (C) and a fluorine salt (D) on its surface. Further, the resin composition The impedance Z of the alternating current (200 Vp-p, frequency 50 Hz) is 1×10 7 Ω or less, the flexural fracture stress at a temperature of 150 °C measured in accordance with JIS K7171 is 1.5 MPa or more, and it does not break down even when an alternating current (peak-to-peak voltage 5 kV, frequency 50 Hz, current 10 mA) is applied for 0.3 seconds.

[0009] The resin composition includes so-called resin molded articles such as resins obtained by molding the resin composition with a mold or the like, and sheet-like and flat plate-like resins obtained by extrusion molding, injection molding, or the like. The impedance Z of the alternating current (200 Vp-p, frequency 50 Hz) is 1×10 7 Ω or less, the flexural fracture stress at a temperature of 150 °C measured in accordance with JIS K7171 is 1.5 MPa or more, and The mechanism of the resin composition that does not break down even when an alternating current (peak-to-peak voltage 5 kV, frequency 50 Hz, current 10 mA) is applied for 0.3 seconds will be described below.

[0010] Conventionally, as one method for reducing the resistance of a resin composition, the method of using an ionic conductive agent is advantageous compared to the method of using an electronic conductive agent, which is another method for reducing the resistance, in that it is less likely to cause breakdown. On the other hand, it has been difficult to reduce the resistance by using an ionic conductive agent without impairing the mechanical strength.

[0011] The reason why the resistance cannot be reduced by ionic conduction is that, as shown in Fig. 7, a large amount of a polyether ester amide resin (hereinafter referred to as PEEA resin) 102 having a low glass transition temperature and being soft must be mixed into the resin 101 which is an insulator. For this reason, it could not be used for resin compositions that require high rigidity. Here, in order to have high rigidity and lower electrical resistance, it is sufficient that the PEEA resin with low electrical resistance is continuously connected throughout the resin. However, in the conventional method of mixing the PEEA resin 102 into the thermoplastic resin 101, it is not easy to realize a state where the PEEA resin 102 is continuously connected throughout the thermoplastic resin 101.

[0012] Therefore, in order to achieve a state where the PEEA resin 102 is evenly connected in the resin 101, as shown in FIG. 8, the inventor considered that it would be sufficient if the deformed filler 103 coated with the resin containing the PEEA resin 102 on its surface was dispersed as uniformly as possible in the resin 101. Therefore, the inventors have found that the above configuration can be achieved by dispersing a deformed filler having a resin mixture containing a PEEA resin and a fluoride salt on its surface in a thermoplastic resin. Here, simply mixing the deformed filler (B) and the polyether ester amide resin (C) with the thermoplastic resin (A) makes it difficult to hold the PEEA resin (C) 102 on the surface of the deformed filler (B) 103, as shown in FIG. 9. The resin composition according to the present disclosure (i) A step of kneading a deformed filler (B) and a resin mixture containing a polyether ester amide resin (C) and a fluoride salt (D) to obtain a masterbatch; (ii) A step of mixing the masterbatch with a thermoplastic resin (A), and can be obtained through these steps. In addition, the deformed filler (B) used in the above step (i) is preferably treated with a coupling agent (F) in advance. This can effectively prevent the resin mixture held on the surface of the deformed filler (B) from peeling off due to the shearing force in the step (ii) of mixing the masterbatch with the thermoplastic resin. Then, in the above step (ii), by mixing the masterbatch with the thermoplastic resin (A), the deformed filler (B) having a resin mixture containing the PEEA resin (C) and the fluoride salt held on its surface can be uniformly dispersed in the thermoplastic resin (A).

[0013] Also, with only the PEEA resin, the impedance Z of alternating current (200 Vp-p, frequency 50 Hz) is 1×10 7Since it cannot be less than Ω, mixing the fluorinated salt (D) with the PEEA resin can lower the resistance of the PEEA resin. Although the fluorinated salt (D) itself cannot conduct electricity in a salt state, in the PEEA resin, the fluorinated salt (D) dissociates into ions, enabling high ionic conductivity. Examples of the fluorinated salt that can be used in the present disclosure include potassium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, potassium nonafluorobutanesulfonate, and the like.

[0014] By mixing the PEEA resin (C) in which the fluorinated salt (D) is dissolved (ion-dissociated) and held on the surface of the shaped filler (B) with the thermoplastic resin (A), an ion-conductive network can be formed even with a small amount of the PEEA resin (C). Therefore, a resin composition with high conductivity (low resistance) can be achieved, and even when the PEEA resin (C) with low rigidity and a low glass transition temperature is mixed, the heat resistance will not be significantly reduced.

[0015] As a method for confirming the presence of the PEEA resin (C) on the surface of the shaped filler (B), there is a mapping method using SEM-EDS. This mapping method can confirm the ratio of the PEEA resin (C) present on the surface of the thermoplastic resin (A) part and the shaped filler (B). When the nitrogen atom (N) present in the PEEA resin (C) is not present in the main thermoplastic resin (A), EDS analysis (energy-dispersive X-ray spectroscopy, <X-MAXN 80> / manufactured by Oxford Instruments) is performed to calculate the abundance ratio of the nitrogen atom (N). By performing such atomic mapping, it is possible to compare the concentrations (abundance ratios) between the resin part serving as the main material and the vicinity of the surface of the shaped filler. The distance for determining the vicinity of the surface is set to up to 500 nm from the surface of the shaped filler. Although the effect is manifested if the nitrogen atom concentration in the vicinity of the surface of the shaped filler (hereinafter also referred to as the N concentration) is higher than the N concentration in the thermoplastic resin (A), it is preferably 1.3 or more as calculated by the following formula. (N concentration near the surface of the irregular filler) / (N concentration at a position 5 μm away from the surface of the irregular filler)

[0016] When the resin composition according to the present disclosure is used, for example, as a material for a member around a fixing device of an electrophotographic image forming apparatus, such as a pressure heater holder, it is preferable to make the resin composition flame retardant. Therefore, it is preferable to contain a flame retardant in the resin mixture held on the surface of the irregular filler. Usually, when trying to give a high flame retardancy to a resin composition, it is necessary to mix a large amount of a flame retardant. However, mixing a large amount of a flame retardant may cause embrittlement of the resin composition.

[0017] However, by containing a flame retardant in the vicinity of a PEEA resin having relatively low flame retardancy, the resin composition can be made flame retardant without containing a large amount of a flame retardant. That is, as shown in FIG. 10, by previously mixing a flame retardant 104 with a dissolved (ion-dissociated) PEEA resin 102, it is possible to prevent the resin composition from becoming brittle. If mixed in advance, the amount of the flame retardant 104 transferred to the thermoplastic resin 101 is very small, and the deterioration of physical properties can be minimized.

[0018] As a method for confirming that the flame retardant (E) is present on the surface of the irregular filler (B), there is a mapping method by SEM-EDS. By this mapping method, it is possible to confirm in what ratio the flame retardant (E) exists on the surface of the thermoplastic resin (A) portion and the irregular filler (B), respectively. When the bromine atom (Br) or phosphorus atom (P) present in the flame retardant (E) does not exist in the main thermoplastic resin (A), EDS analysis (energy dispersive X-ray spectroscopy, <X-MAXN 80> / manufactured by Oxford Instruments) is performed to calculate the abundance ratio of the bromine atom (Br) or phosphorus atom (P). By performing such atomic mapping, it is possible to compare the concentration (abundance ratio) between the resin portion serving as the main material and the vicinity of the surface of the irregular filler. The distance determined as the vicinity of the surface is 500 nm from the surface of the irregular filler.

[0019] It is preferable that the concentration of the flame retardant 104 near the surface of the irregular filler 103 is 1.3 times or more the concentration of the flame retardant 104 in the thermoplastic resin 101. Specifically, it is preferable that the value calculated by the following formula is 1.3 or more. (Concentration of bromine atoms (Br) near the surface of the irregular filler / (Concentration of bromine atoms (Br) at a position 5 μm away from the surface of the irregular filler) Or (Concentration of phosphorus atoms (P) near the surface of the irregular filler) / (Concentration of phosphorus atoms (P) at a position 5 μm away from the surface of the irregular filler)

[0020] Examples of the flame retardant that can be used in the present disclosure include brominated polystyrene, brominated bisphenol A type epoxy resin, red phosphorus, and the like. For the purpose of improving the flame retardant performance, flame retardant aids such as low-density polyethylene containing antimony trioxide, sodium antimonate, and zinc borate can also be used in combination as flame retardant aids.

[0021] The content of the thermoplastic resin (A) is preferably 47 to 95% by mass with respect to 100% by mass of the resin composition. If it is less than 47% by mass, the strength of the resin composition decreases, which is not preferable. If it exceeds 95% by mass, the polyether ester amide resin for realizing conductivity is insufficient and electrification cannot be achieved, which is not preferable.

[0022] The content of the irregular filler (B) is preferably 5 to 30% by mass with respect to 100% by mass of the resin composition. If it is less than 5% by mass, the contact effect of conduction decreases, which is not preferable. If it exceeds 30% by mass, the resin composition becomes brittle, which is not preferable.

[0023] The content of the polyether ester amide resin (C) is preferably 5 to 30% by mass with respect to 100% by mass of the resin composition. If it is less than 5% by mass, the connection of conduction decreases and the conductivity deteriorates, which is not preferable. If it exceeds 30% by mass, the polyether ester amide resin is soft and the resin strength decreases, which is not preferable.

[0024] The content of the fluorinated salt (D) is preferably 0.5 to 3% by mass based on 100% by mass of the resin composition. If it is less than 0.5% by mass, the effect of conductivity decreases and the conductivity deteriorates, which is not preferable. If it exceeds 3% by mass, the ionized fluorinated salt bleeds out to the surface and stickiness occurs, which is not preferable.

[0026] As a method capable of treating more of the PEEA resin 102 and the flame retardant 104 on the surface of the shaped filler 103, there is a masterbatch method. The masterbatch method is preferably used because it can mix materials other than the main thermoplastic resin in advance with a twin-screw extruder or the like before molding, and the PEEA resin can be reactively contacted and retained on the surface of the shaped filler treated with a coupling agent. The masterbatch is mixed immediately before molding (for example, injection molding). Examples of the coupling agent that can be used in the present disclosure include silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, and titanate coupling agents such as isopropyl titanate triisostearate.

[0027] When heat resistance is required for the thermoplastic resin (A) used in the present disclosure, it is preferable to use a crystalline thermoplastic resin. The crystalline thermoplastic resin used in the present disclosure is not particularly limited, and for example, polyester resins such as polyphenylene sulfide (PPS) resin and polyethylene terephthalate (PET) resin can be used. In order to achieve a high elastic modulus, PPS resin is preferable. Further, in order to improve heat resistance, it is preferable to mix these resins with glass fibers.

[0028] Since these resins with high heat resistance have a high molding temperature of 280°C or higher, when mixing the masterbatch and the thermoplastic resin, it is preferable to carry out the mixing at a temperature at which PEEA does not decompose (for example, 250°C) in order to suppress the decomposition of the PEEA resin. Furthermore, when molding the main resin at a temperature of 280°C or higher, it is preferable to introduce nitrogen gas into the hopper (resin inlet) of the molding machine to remove oxygen inside the molding machine. Since the decomposition (deterioration) of the PEEA resin is greatly affected by oxygen, molding in a nitrogen atmosphere can significantly suppress the decomposition. The inflow rate of nitrogen depends on the molding amount, but is preferably 10 liters per minute or more.

[0029] The "anisotropic filler" in the present disclosure means a filler having a shape such as a shape that is not a cubic shape, a true spherical shape, etc., but a shape composed of a needle shape and four needle-shaped crystal parts radially extending from the core part to the outside (so-called "tetrapod" (registered trademark) shape). Examples of the filler material include zinc oxide, wollastonite, etc. The anisotropic filler (B) used in the present disclosure is not particularly limited, but specifically includes the following. "Panatetra" (trade name; manufactured by Amtech Co., Ltd., zinc oxide having a tetrapod (registered trademark) shape), wollastonite (needle-shaped wollastonite), "Moshighi" (fibrous basic magnesium sulfate), sepiolite, aluminum borate zonoite, etc. Among them, "Panatetra" is preferable because it has anisotropy as a single filler. Although other needle-shaped fillers do not have anisotropy as a single filler, if the single fillers are intertwined anisotropically in the resin, the effects of the present disclosure can be obtained.

[0030] In the present disclosure, the PEEA resin (C) is used as the conductive resin. The PEEA resin has a certain degree of conductivity, can be used as a solvent for ion-dissociating the fluorine salt (D), and has high miscibility with the main resin, so the conductivity uniformity is high. In addition, various additives can be added to the resin composition of the present disclosure in addition to the above materials. Examples of the various additives include various additives such as fillers, dispersants, antioxidants, weathering agents, and decomposition inhibitors.

[0031] The filler to be added is not particularly limited as long as it can be added in an amount that does not inhibit the effect of the irregularly shaped filler. For example, inorganic fillers include, but are not limited to, the following: glass fiber, mica, zinc oxide, titanium oxide, calcium carbonate, clays, silica, zeolite, diatomaceous earth, silica sand, pumice powder, slate powder, alumina, alumina white, aluminum sulfate, barium sulfate, fly ash, calcium sulfate, molybdenum disulfide, etc.

[0032] Also, as organic fillers, one or more of the following can be appropriately selected, but are not limited thereto: tetrafluoroethylene resin particles, chlorotrifluoroethylene resin particles, tetrafluoroethylene hexafluoropropylene resin particles, vinyl fluoride resin particles, vinylidene fluoride resin particles, dichlorodifluoroethylene resin particles, and copolymers thereof. Fluorocarbons, silicone resin particles, silicone-based compound rubber powders such as silicone rubber particles, ebonite powder, etc.

[0033] (Method for manufacturing resin composition) The method for manufacturing the resin composition according to the present disclosure is not particularly limited. For example, it can be manufactured by mixing a resin, carbon fiber, and a filler, and there are methods such as kneading and molding using various extruders such as a twin-screw extrusion method, a single-screw extrusion method, and a wire coating method. Also, there are methods using various mixers such as a kneader and a Banbury mixer, and methods of kneading and molding using various roll mills such as a two-roll and a three-roll mill.

[0034] Also, the method for manufacturing the resin molded article according to the present disclosure is not particularly limited. For example, there are injection molding, extrusion molding, press molding, transfer molding, etc. Among these, injection molding is preferred. This is because injection molding can manufacture efficiently with a short molding cycle time. In order to apply the resin composition to this injection molding, the shape of the resin composition is preferably in the form of pellets. For example, after forming a linear molded article by a twin-screw extrusion method or the like, it can be formed into pellets by a strand cutter or the like. As the surface treatment method used in the present disclosure, coupling treatment using a mixer is preferable. The coupling treatment can be dry or wet, but the dry method is preferable because post-treatment of liquid is unnecessary.

[0035] (Image forming apparatus) The resin composition according to the present disclosure can be used, for example, as a material for a holder of a heater (hereinafter referred to as "pressure heater holder") that heats a fixing film in a heat fixing device of an electrophotographic image forming apparatus and presses the fixing film against a pressure member. An electrophotographic image forming apparatus equipped with such a heat fixing device using a pressure heater holder can form a high-quality electrophotographic image. That is, in an electrophotographic image, image defects called AC banding may occur due to an alternating current (AC) required for heating the heater of the fixing device. That is, paper placed in a high-temperature and high-humidity environment for a long time has a reduced electrical resistance due to moisture absorption. In the process of fixing an unfixed toner image on such paper, when the paper is sandwiched between a fixing member and a pressure member at the fixing nip portion, the alternating voltage applied at the fixing nip portion may be superimposed on the transfer voltage at the transfer nip portion via the paper. And the transfer voltage at the transfer nip portion may be fluctuated. As a result, the current flowing from the paper toward the electrophotographic photosensitive member fluctuates, unevenness occurs in transferability, and density unevenness may occur in the sub-scanning direction of the electrophotographic image. This is the image defect called AC banding.

[0036] In order to prevent such image defects, Patent Document 2 discloses that in a heating device for fixing composed of a heater and a film that slides on the heater, the film is grounded via a resistance element (resistance value is about 10 to the 6th power Ω). According to the configuration disclosed in Patent Document 2, the alternating voltage is removed via the resistance element before being transmitted to the transfer nip portion via the paper. Thereby, the occurrence of AC banding in the electrophotographic image can be prevented. However, the configuration described in Patent Document 2 increases the number of parts, which may cause a cost increase.

[0037] On the one hand, since the pressure heater holder formed using the resin composition according to the present disclosure has low resistance, the fixing film can be grounded without using a resistance element. As a result, it is possible to prevent the alternating voltage for fixing from being transmitted to the transfer nip portion. Further, the resin composition according to the present disclosure has high conductivity, excellent mechanical strength, and high withstand voltage characteristics peculiar to ionic conduction. Therefore, the pressure heater holder is excellent in both mechanical durability and electrical durability. As a result, the electrophotographic image forming apparatus according to the present disclosure can stably form high-quality electrophotographic images.

[0038] The overall configuration of the image forming apparatus of the present disclosure will be described with reference to FIG. 1. The image forming apparatus 1 used in the present disclosure is a laser beam printer. The image forming apparatus 1 includes a transfer material feeding unit and an image forming unit. In the transfer material feeding unit, the transfer material P loaded in the cassette 2 is picked up one by one from the uppermost transfer material P by the paper feeding roller 3 and sent to the registration unit. The transfer material P is aligned in the transport direction in the registration unit composed of the registration roller 4 and the registration roller 5, and then fed to the image forming unit.

[0039] The image forming unit includes a photosensitive drum 6 as an image carrier, a charger 7 for charging the photosensitive drum 6, a developing device 8 for developing the latent image on the photosensitive drum 6 with toner, and a cleaner 9 for removing the residual toner on the photosensitive drum 6. The photosensitive drum 6 is rotationally driven in the direction of the arrow (clockwise direction). The charger 7 uniformly charges the circumferential surface of the photosensitive drum 6. Above the image forming unit, a laser scanner 10 is arranged as an exposure means to irradiate the charged photosensitive drum 6 with a laser beam based on image information to form an electrostatic latent image on the photosensitive drum 6. The electrostatic latent image is formed as a toner image by the developing device 8. Then, the toner image formed on the photosensitive drum 6 is transferred to the transfer material P at the transfer nip portion 12 by applying a voltage of the opposite polarity to the charging polarity of the toner to the transfer roller 11 which is a transfer member from a transfer power source 25 (see FIG. 3) which is a DC power source.

[0040] The transfer material P onto which the toner image has been transferred is conveyed to a heat fixing device 13 disposed downstream of the transfer means, and the toner image on the transfer material P is heat-fixed at the fixing nip portion 23 of the heat fixing device 13. The transfer material P that has passed through the heat fixing device 13 is discharged onto a transfer material stacking portion 15 above the image forming apparatus 1 by a pair of paper discharge rollers 14.

[0041] (Heat fixing device) The heat fixing device 13 will be described. In the following description, regarding the heat fixing device 13 of the electrophotographic image forming apparatus and the members constituting the heat fixing device 13, the longitudinal direction is the direction orthogonal to the paper conveyance direction. FIG. 2 is a cross-sectional view of the heat fixing device 13 in the paper conveyance direction, and the heat fixing device 13 will be described with reference to FIG. 2. This heat fixing device 13 has a pressure roller 16 which is a pressure member (hereinafter also simply referred to as "pressure roller 16"), and a heating film 17 which is a heating member (hereinafter also simply referred to as "heating film 17"). The heat fixing device 13 is a device of a pressure roller drive method and film heating method that rotationally drives the pressure roller 16 and rotates the heating film 17 by the conveyance force of the pressure roller 16.

[0042] The heat fixing device 13 has a heater 18 as a heating element supported by a pressure heater holder (hereinafter also simply referred to as "heater holder") 19 as a support member. The heater 18 has a heating resistor (not shown) formed on a ceramic substrate such as alumina by screen printing. Further, the heater 18 is configured to generate heat when an AC voltage is applied from a commercial power supply 24 (see FIG. 3), which is an AC power source, to the heating resistor (not shown). Further, a pressure stay 20 is disposed on the opposite side of the heater 18 with the heater holder 19 interposed therebetween. The pressure stay 20 abuts on the heater holder 19 and transmits a pressure force to a pressure roller 16 composed of a mandrel portion 21 and a heat-resistant elastic layer 22. A heating film 17 as a cylindrical flexible member is externally fitted over the heater holder 19, the heater 18, and the pressure stay 20. Further, since the heater holder 19 is biased toward the axis of the pressure roller 16 via the pressure stay 20, a fixing nip portion 23 having a predetermined width is formed between the heating film 17 and the pressure roller 16. Note that the heating film 17 is composed of a base layer (not shown), an elastic layer (not shown) formed on the outer peripheral surface side of the base layer, and a release layer (not shown) formed on the outer peripheral surface side of the elastic layer. The base layer of the heating film 17 requires heat resistance for receiving the heat of the heater 18 and durability for rubbing against the heater 18, and it is preferable to use a metal such as stainless steel or nickel or a heat-resistant resin such as polyimide. Further, for the release layer of the heating film 17, it is preferable to use a fluororesin such as perfluoroalkoxy resin (PFA) or polytetrafluoroethylene resin (PTFE).

[0043] (Mechanism of generation of AC banding) The mechanism of generation of AC banding will be described with reference to FIG. 3 based on the configuration disclosed in Patent Document 2. The heating film 17 is grounded via a resistance element 26. Note that, in the heat fixing device 13, the following conditions are satisfied for the transfer material P necessary for transferring a toner image from the photoreceptor drum 6 to the same transfer material P at the transfer nip portion 12 while fixing the toner image to the transfer material P at the same time. Condition: The length of the transfer material P in the conveyance direction is longer than the distance from the transfer nip portion to the fixing nip portion.

[0044] When performing image formation on a transfer material P with a low resistance value such as the moisture-absorbed transfer material P, the image defect generated by the AC voltage of the commercial power supply 24 being superimposed on the transfer voltage at the transfer nip portion 12 through the transfer material P will be described with reference to FIG. 3. FIG. 3 is a schematic diagram for explaining the mechanism in which the AC voltage of the commercial power supply 24 is superimposed on the transfer voltage at the transfer nip portion 12 to cause an image defect. Note that the transfer material P in the following description is the transfer material P that has been left in a high-temperature and high-humidity environment for a long time and has absorbed moisture, and is, for example, A4-sized paper whose length in the conveyance direction of the transfer material P is longer than the distance from the transfer nip portion 12 to the fixing nip portion 23.

[0045] When the transfer material P that has absorbed moisture by being left in a high-temperature and high-humidity environment or the like is sandwiched between the fixing nip portions 23 in a state where the toner image has been transferred from the photosensitive drum 6 at the transfer nip portion 12, an AC voltage is applied from the commercial power supply 24 to the heater 18. The transfer material P sandwiched between the fixing nip portions 23 is in contact with the heating film 17, and at the fixing nip portion 23, the heating film 17 is in contact with the heater 18.

[0046] As shown in FIG. 3, when the resistance value of the transfer material P is low, the AC voltage applied to the heater 18 fluctuates the transfer voltage at the transfer nip portion 12 through the heating film 17 and the transfer material P. As a result, AC banding occurs in which the current flowing from the transfer roller 11 toward the photosensitive drum 6 fluctuates. At this time, since the current flowing from the transfer roller 11 to the photosensitive drum 6 fluctuates at the power supply frequency period of the commercial power supply 24, the trough portion of the AC waveform falls below the appropriate range of the current from the transfer power supply 25 when transferring the toner image to the moisture-absorbed transfer material P. As a result, the current is insufficient at the power supply frequency period of the commercial power supply 24, and uneven density occurs in the image transferred from the photosensitive drum 6 to the transfer material P after the transfer material P enters the fixing nip portion 23 at the power supply frequency period of the commercial power supply 24. Here, by setting the resistance value of the resistance element 26 low enough so that the AC current of the commercial power supply 24 does not fluctuate the transfer voltage, AC banding can be prevented.

[0047] (Mechanism of transfer omission) The mechanism of transfer omission will be described. Similar to the mechanism of AC banding described above, the description will be based on the configuration of Patent Document 1. Regarding image defects that occur when an image is formed on a transfer material P with a low resistance value such as a moisture-absorbed transfer material P, the current of the transfer power supply 25 flows through the transfer material P into the resistance element 26, and this will be described with reference to FIG. 4. FIG. 4 is a schematic diagram for explaining the mechanism in which image defects occur due to the current of the transfer power supply 25 leaking through the transfer material P.

[0048] The transfer material P that has absorbed moisture due to being left in a high-temperature and high-humidity environment or the like is sandwiched between the fixing nip portion 23 while the toner image is being transferred from the photosensitive drum 6 at the transfer nip portion 12. As shown in FIG. 4, when the resistance value of the transfer material P is low, the current for transferring the toner image to the transfer material P flows through the transfer material P into the resistance element 26, and transfer omission occurs because the current required for transferring the toner image is insufficient. As a result, it becomes difficult for the toner image to be transferred from the photosensitive drum 6 to the transfer material P, so a faint image is generated on the transfer material P. Here, by setting the resistance value of the resistance element 26 high enough so that the current of the transfer power supply 25 does not flow through the transfer material P, transfer omission can be prevented.

[0049] (Relationship between miniaturization of the image forming apparatus, AC banding, and occurrence of image defects due to transfer omission) As the image forming apparatus is miniaturized, the distance from the transfer nip portion 12 to the fixing nip portion 23 becomes shorter. As this distance becomes shorter, the resistance value of the transfer material P from the portion sandwiched between the transfer nip portion 12 to the portion sandwiched between the fixing nip portion 23 becomes lower. As a result, the possibility of occurrence of image defects due to AC banding and transfer omission increases. Specifically, since the resistance value of the transfer material P from the portion sandwiched by the transfer nip portion 12 to the portion sandwiched by the fixing nip portion 23 becomes low, from the viewpoint of AC banding, the resistance element 26 needs to have a lower resistance value. On the other hand, from the viewpoint of transfer omission, the resistance element 26 needs to have a higher resistance value. That is, the setting of the resistance value to prevent image defects caused by these two phenomena is in a trade-off relationship, and it becomes more difficult to achieve both as the image forming apparatus is miniaturized. In addition, components from the heating film 17 to the ground via the resistance element 26 also require space saving.

[0050] (Pressing block using the conductive resin composition of the present disclosure) Therefore, in the present disclosure, a configuration will be described in which image defects due to AC banding and image defects due to transfer omission can be suppressed even when the image forming apparatus is miniaturized without using the resistance element 26. FIG. 5 shows a cross-sectional view of the heat fixing device 13 in the paper conveyance direction. FIG. 6 shows the configuration of the present disclosure. In the heat fixing device 13, the pressing blocks 27 and 28 are in contact with the pressing stage 20, and the pressing blocks 27 and 28 are pressed by a pressing spring 31 having a compression spring structure via pressing plates 29 and 30 with a constant pressing force. Thereby, the fixing nip portion 23 is formed. Further, the fulcrum portions 32 of the pressure roller 16, the pressing blocks 27 and 28, the pressing plate 29, the fulcrum portion 33 of the pressing plate 30, and the end portion 34 of the pressing spring 31 are positioned by a frame (not shown). Specifically, the pressing blocks 27 and 28 are positioned so as to be movable in the pressing direction so that the fixing nip portion 23 can be formed by the pressing force of the pressing spring 31. Also, the fulcrum portion 32 of the pressing plate 29 and the fulcrum portion 33 of the pressing plate 30 are positioned so as to be rotatable freely in the pressing direction, and the end portion 34 of the pressing spring 31 is configured to receive the reaction force in the pressing direction by a frame (not shown).

[0051] Next, the conduction path in the heat fixing device in the present disclosure will be described. FIG. 5 is a cross-sectional view with a different longitudinal position from the cross-sectional view shown in FIG. 2. A conductive sheet-like conduction sheet 35 is disposed so as to contact the inside of the heating film 17. The conduction sheet 35 has holes (not shown), and a protrusion 36 of the heater holder 19 is inserted into the holes (not shown). Then, the conduction sheet 35 in contact with the inner peripheral surface of the heating film 17 is prevented from being carried by the rotating heating film 17. Further, the conduction sheet 35 also contacts the pressure stay 20 to ensure conduction between the heating film 17 and the pressure stay 20.

[0052] As shown in FIG. 5, the pressure stay 20 is in contact with the pressure block 28, and similarly, the pressure stay 20 is also in contact with the pressure block 27. Further, the pressure block 27 is electrically connected from the fulcrum portion 32 of the pressure plate 29, and the pressure block 28 is electrically connected from the fulcrum portion 33 of the pressure plate 30 to a frame (not shown) grounded (hereinafter, this grounding is also referred to as "frame ground"). Here, at least one of the pressure blocks 27 and 28 is a resin member having a matrix domain structure composed of a matrix containing a non-conductive resin, a conductive resin capable of ionic dissociation, and a domain containing a salt capable of dissociating into cations and anions. The characteristic configuration of the image forming apparatus according to the present disclosure is this resin member, i.e., the pressure block portion. With such a configuration, in addition to the role of positioning the pressure block on a conventional frame (not shown) and receiving a pressing force, the pressure block can also serve as a resistor that can maintain a lower resistance value for alternating current than for direct current.

Examples

[0053] Hereinafter, the present disclosure will be described in detail using examples and comparative examples. However, the present disclosure is not limited by these examples. In the examples and comparative examples, measurement and evaluation were performed on the following items.

[0054] <Impedance Z> Using an injection molding device, a Charpy measurement sample 401 was created. As shown in Fig. 13, copper foils 402 and 403 were clamped by a vise with insulating materials 404 and 405, and a circuit as shown in Fig. 14 was created. A 100 kΩ resistor 407 was connected, and in an environment with a temperature of 23°C and a relative humidity of 55%, an alternating current (200 Vp-p, frequency 50 Hz) was applied from a stabilized power supply 406, and the impedance Z was measured by measuring the voltage with an alternating current voltmeter 408.

[0055] <Dielectric breakdown test> Using an injection molding device, a Charpy measurement sample 401 was created. As shown in Fig. 13, copper foils 402 and 403 were clamped by a vise with insulating materials 404 and 405, and an alternating current (5000 Vp-p, frequency 50 Hz, current 10 mA) was applied for 0.3 seconds. Then, in an environment with a temperature of 23°C and a relative humidity of 55%, an alternating current (200 Vp-p, frequency 50 Hz) was applied before and after the application, and the impedance Z was measured. If the change in the impedance Z before and after applying the alternating current (5000 Vp-p, frequency 50 Hz, current 10 mA) was less than one digit, it was considered qualified; if it was one digit or more, it was considered unqualified.

[0056] <Flexural breaking stress> After the resin composition was injection molded as a Charpy piece, a jig for a three-point bending test with a support base and a central indenter having a diameter of 10 mm was attached to a tensile testing machine manufactured by Instron Corporation, the molded product was placed, and the measurement was performed at a distance between supports of 64 mm and a speed of 2 mm / min. The measurement was started without applying a preload. The measurement environment was set to a temperature of 150°C ± 1°C. The flexural breaking stress was the value calculated by the software of Instron Corporation according to the tangent method of JIS (JIS K7171).

[0057] <Thermoplastic resin> Polyphenylene sulfide (PPS) Trellina A310MX04 (manufactured by Toray Industries, Inc.), glass fiber mixture Polyethylene terephthalate (PET) RE19045 (manufactured by DuPont Kabushiki Kaisha), glass fiber mixture

[0058] <Irregular filler> Panatetra (registered trademark) WZ-0501, tetrahedral zinc oxide (manufactured by Amtech Co., Ltd.) <Polyether ester amide resin (PEEA)> TPAE-H151 (manufactured by T&K TOKA Co., Ltd.)

[0059] <Fluoride salt> Eftop (registered trademark) EF-N112, potassium bis(trifluoromethanesulfonyl)imide (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) <Flame retardant> SAYTEX (registered trademark) HP-7010G, brominated polystyrene (manufactured by Albemarle Japan Co., Ltd.) <Flame retardant aid> Hiro Master C-380 (manufactured by Suzuhiro Chemical Co., Ltd.) (Base resin: low-density polyethylene, antimony trioxide concentration 80%)

[0060] <Coupling agent> Silane coupling agent 3-glycidoxypropyltrimethoxysilane KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) <Conductive carbon black> Denka Black (registered trademark) granular product (manufactured by Denka Co., Ltd.) <Talc masterbatch> HI-CON TALC MASTER (manufactured by Matsumura Sangyo Co., Ltd.)

[0061] (Example 1) <Surface treatment of Panatetra with a coupling agent> シ The silane coupling agent KBM-403 was dropped into an aqueous solution with an acetic acid concentration of 1.0% while stirring to prepare a 10% aqueous solution of the silane coupling agent. Next, while stirring Panatetra with a mixer, 5% of the above-mentioned 10% aqueous solution of the silane coupling agent was dropped into Panatetra. Since it is a 10% solution, the coupling agent is 0.5It becomes %. After dropping and attaching the coupling agent to the surface, it was dried at a temperature of 110 °C for 30 minutes to perform a coupling treatment on the surface of the panatetra.

[0062] <Manufacture of Conductive Masterbatch> As shown in Fig. 11, a twin-screw extruder 201 made by Japan Steel Works, Ltd., TEX44αII (L / D = 38.5, using 11 blocks) was used. The detailed conditions of the twin-screw extruder are as follows. Configuration of screw 203: Kneading screws were attached to the 4th, 7th, and 8th blocks from the tip, and the rest were full flights. Material feeding location: Hopper 202 Screw rotation speed: 200 rpm Extruder temperature: Set at 250 °C Die temperature: 250 °C Resin discharge amount: 50 kg / h

[0063] The materials were mixed in the following composition ratios. PEEA resin (C): 41.65% by mass Fluoride salt (D) Potassium bis(trifluoromethanesulfonyl)imide EF-N112: 8.09% by mass Shaped filler (B) Coupling-treated panatetra: 42.81% by mass Flame retardant (E) SAYTEX HP-7010G: 6.39% by mass Flame retardant aid Hiro-master C-380: 1.06% by mass This mixed material was extruded into a strand 205, and the obtained strand 205 was water-cooled in the cooling section 206 and cut by a strand cutter 207 into a diameter of 2.5 mm and a length of 3.5 mm to obtain pellet-shaped masterbatch 111.

[0064] <Manufacture of Samples for Physical Property Evaluation and Pressurized Blocks> As the molding machine, SE180EV-A manufactured by Sumitomo Heavy Industries, Ltd. was used. Mold Charpy piece (shape according to JIS K7111) The following materials were mixed before forming. Thermoplastic resin (A) PPS resin Trellina A310MX04: 76.3 mass% Conductive masterbatch: 23.7 mass%

[0065] The PPS resin was dried at a temperature of 130°C for 3 hours, and the conductive masterbatch was dried at a temperature of 80°C for 6 hours. Then, the pelletized resin composition A1 obtained was dried at 120°C for 6 hours. After that, it was mixed according to the above formulation and put into the hopper 311 of the injection molding apparatus 301 shown in Fig. 12. The temperature of the injection molding apparatus was set to 290°C, the temperatures of the molds 302 and 305 were set to 150°C, and the hopper was filled with nitrogen gas for injection molding to obtain a molded body 304 (Charpy piece B1). Size of the molded body 304 (Charpy piece): 80 mm × 10 mm × 4 mm Also, for image output, the resin composition was injection molded into a pressure block shape (resin temperature 290°C, mold temperature 150°C, nitrogen gas inflow) to obtain a pressure block component.

[0066] <Evaluation results> Physical property evaluation was carried out using a physical property evaluation mold (Charpy shape). The evaluation results are shown in Table 1. The impedance Z was 8 × 10^5 Ω. In the dielectric breakdown test, the difference in impedance before and after applying alternating current (5000 Vp-p, frequency 50 Hz, current 10 mA) for 0.3 seconds was within one digit. The flexural fracture stress at a temperature of 150°C was 140 N, and it was a resin composition with high heat resistance.

[0067] The flame retardancy according to the "Combustion Test Standard for Plastic Materials of Apparatus and Equipment" recognized by UL94 standard (Underwriters Laboratories Inc.: American Insurance Industry Safety Testing Institute) was equivalent to V-0. Image evaluation: Image output was performed in an environment of temperature 30°C and relative humidity 80%, and no transfer defect (banding) due to alternating current flowing from the fixing unit to the transfer unit was observed. The nitrogen concentration near the surface of the irregular filler was twice that of the resin part, and it was confirmed that the PEEA resin was localized near the surface of the irregular filler.

[0068] (Example 2) <Surface treatment with a coupling agent of Panasonic Tetra> Same as Example 1 <Manufacture of conductive masterbatch> Same as Example 1 <Manufacture of samples for physical property evaluation and pressure blocks> Thermoplastic resin (A) PET resin: 66.3% by mass Talc masterbatch HI-CON TALC MASTER: 10.0% by mass Conductive masterbatch: 23.7% by mass The temperature of the injection molding apparatus was set at 280°C. Other than the above was the same as in Example 1.

[0069] <Evaluation results> The physical property evaluation was performed using a mold for physical property evaluation (Charpy shape). The evaluation results are shown in Table 1. The impedance Z was 7×10^5 Ω. In the insulation breakdown test, the difference in impedance before and after applying alternating current (5000 Vp-p, frequency 50 Hz, current 10 mA) for 0.3 seconds was within one digit. The flame retardancy was equivalent to V-0. The flexural fracture stress at 150°C was 60 N, and it was a resin composition with high heat resistance. Image evaluation: Images were output in an environment of 30°C and 80% relative humidity, but no transfer defect (banding) due to alternating current flowing from the fixing unit to the transfer part was observed. The nitrogen concentration near the surface of the irregular filler was 1.5 times that of the resin part, and it was confirmed that the PEEA resin was localized near the surface of the irregular filler.

[0070] (Comparative Example 1) <Material kneading> PPS resin: 87% by mass Denka Black: 13 mass% The above materials were mixed using a twin-screw kneader to obtain a resin composition. <Manufacture of Samples for Physical Property Evaluation and Pressure Blocks> SE180EV-A manufactured by Sumitomo Heavy Industries, Ltd. was used as the molding machine. Mold Charpy piece (shape according to JIS K7111) The temperature of the injection molding apparatus was set to 300 °C, and the temperature of the mold was set to 150 °C, followed by injection to obtain a molded body (Charpy piece B3). Similarly, the mold was changed to a mold for a pressure block and molded to obtain a pressure block.

[0071] <Evaluation Results> The physical property evaluation was performed using a mold for physical property evaluation (Charpy shape). The evaluation results are shown in Table 1. The impedance Z was 3×10^5 Ω. In the insulation breakdown test, alternating current (5000 Vp-p, frequency 50 Hz, current 10 mA) was applied for 0.3 seconds. The impedance decreased by two digits before and after the application, indicating that leakage occurred inside. The flame retardancy did not meet the UL94 V-0 standard because carbon was added. The flexural fracture stress at 150 °C was 180 N, indicating a resin composition with high heat resistance. Image evaluation: Images were output in an environment of 30 °C and 80% relative humidity. No transfer defect (banding) due to alternating current flowing from the fixing unit to the transfer section was observed.

[0072] (Comparative Example 2) <Material Kneading> Without performing the coupling treatment carried out in Example 1 and without preparing a masterbatch, a material without a coupling agent was charged into a twin-screw extruder to obtain a resin composition. <Manufacture of Samples for Physical Property Evaluation and Pressure Blocks> The resin composition was charged into an injection molding machine and molded at 280 °C. Nitrogen gas was not used. <Evaluation Results> The physical property evaluation was performed using a mold for physical property evaluation (Charpy shape). The evaluation results are shown in Table 1. The impedance Z was 7×10^7 Ω. In the dielectric breakdown test, the difference in impedance was within one digit before and after applying alternating current (5000 Vp-p, frequency 50 Hz, current 10 mA) for 0.3 seconds. The flame retardancy did not meet V-0 of the UL94 standard. The flexural fracture stress at 150 °C was 30 N, and it was a resin composition with low heat resistance. Image evaluation: Images were output in an environment of 30 °C and 80% relative humidity, but transfer defects due to alternating current flowing from the fixing unit to the transfer unit occurred. The nitrogen concentration near the surface of the irregular filler was 1.0 times that of the resin part, and no difference was observed, so the PEEA resin was not localized near the surface of the irregular filler.

[0073]

Table 1

Explanation of Symbols

[0074] 1 Image forming apparatus 2 Cassette 3 Feed roller 4 Resist roller 5 Resist roller 6 Photoconductor drum 7 Charger 8 Developing device 9 Cleaner 10 Laser scanner 11 Transfer roller 12 Transfer nip part 13 Heat fixing device 14 Pair of paper discharge rollers 15 Transfer material loading part 16 Pressing roller 17 Heating film 18 Heater 19 Heater holder 20 Pressing stage 21 Mandrel part 22 Heat-resistant elastic layer 23 Fixing nip part 24 Commercial power supply 25 Transfer power supply 26 Resistance element 27, 28 Pressing blocks 29, 30 Pressing plates 31 Pressing spring 32, 33 Fulcrum parts 34 End part of the pressing spring 31 35 Conductive sheet 101 Resin 102 PEEA resin 103 Anisotropic filler 104 Flame retardant 111 Masterbatch 201 Twin-screw extruder 202 Hopper 203 Screw 204 Die 205 Strand 206 Cooling part 207 Strand cutter 301 Twin-screw extruder 302 Mold 304 Formed body 305 Mold 401 Charpy measurement sample 402, 403 Copper foil 404, 405 Insulating material 406 Stabilized power supply 407 100 kΩ resistor 408 AC voltmeter

Claims

1. A resin composition comprising a thermoplastic resin (A) and an irregularly shaped filler (B) dispersed in the thermoplastic resin (A), The thermoplastic resin (A) is a polyphenylene sulfide (PPS) resin or a polyethylene terephthalate (PET) resin, The irregularly shaped filler (B) has a needle shape or a shape consisting of four needle-like crystal parts extending radially outward from a core part, and holds a polyether ester amide resin (C) and a fluorine salt (D) on its surface, the fluorine salt (D) is potassium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or potassium nonafluorobutanesulfonate; The resin composition was molded into a Charpy specimen (80 mm x 10 mm x 4 mm) by injection molding and measured. Impedance Z of AC (200 Vp-p, frequency 50 Hz) is 1 x 10 ７ Ω or less, The bending fracture stress at 150°C measured in accordance with JIS K7171 is 1.5 MPa or more, and A resin composition which does not suffer from dielectric breakdown even when an alternating current (peak-to-peak voltage 5 kV, frequency 50 Hz, current 10 mA) is applied thereto for 0.3 seconds.

2. The resin composition according to claim 1, wherein the irregularly shaped filler further carries a flame retardant (E) on the surface thereof.

3. The resin composition according to claim 1 or 2, wherein the nitrogen atom concentration in a region from the surface of the irregularly shaped filler (B) to 500 nm is 1.3 times or more the nitrogen atom concentration in the interior at a distance of 5 μm or more from the surface of the thermoplastic resin (A).

4. The resin composition according to any one of claims 1 to 3, wherein the flame retardancy of the resin composition is V-0 according to the UL94 standard.

5. A method for producing the resin composition according to any one of claims 1 to 4, (i) kneading an irregularly shaped filler (B) with a resin mixture containing a polyether ester amide resin (C) and a fluorine salt (D) to obtain a master batch; (ii) mixing the masterbatch with a thermoplastic resin (A).

6. The method for producing a resin composition according to claim 5, wherein the irregularly shaped filler used in the step (i) is treated with a coupling agent.

7. The method for producing a resin composition according to claim 5 or 6, wherein the resin mixture used in the step (i) further contains a flame retardant.

8. 5. An image forming apparatus comprising a pressure heater holder formed from a molded product of the resin composition according to claim 1.

Images