Grease composition, heating device, and electrophotographic image forming apparatus

Abstract

This invention relates to a grease composition, a heating device, and an electrophotographic image forming apparatus. A heating device includes: a rotating member for heating; a opposing member configured to face the rotating member and forming a roll gap together with the rotating member; and a force-applying member disposed inside the rotating member, having opposing surfaces opposite to the inner circumferential surface of the rotating member, and applying force from the rotating member to the opposing member. The inner circumferential surface and the opposing surface are in contact with each other by a grease composition to form a sliding portion. The grease composition comprises a base oil. The base oil contains a fluoropolymer having a specific structure and a perfluoropolyether having a specific kinematic viscosity and specific evaporation loss and having a specific structure.

Description

Technical Field

[0001] This disclosure relates to grease compositions, heating devices, and electrophotographic image forming apparatus. Background Technology

[0002] In electrophotographic image forming apparatus (hereinafter sometimes referred to as "image forming apparatus") utilizing electrophotography, a toner image formed by toner on a photosensitive element is transferred to a recording medium, and then fixed (adheded) to the recording medium by passing through a heating device. As a heating device, a contact-type heating device is widely used. This contact-type heating device heats a fixing element to a predetermined fixing temperature by a heating element, and fixes the unfixed toner image formed on the recording medium into a fixed image by contact heating. As typical heating devices, film-heating type heating devices described in Japanese Patent Application Publication No. H05-027619 and Japanese Patent Application Publication No. H08-076636 are given respectively.

[0003] In a membrane heating device, the membrane slides together with the heating element while simultaneously receiving heat from the heating element. Furthermore, to reduce friction, a heat-resistant lubricant is used between the membrane and the heating element. Fluorinated oils or fluorinated greases with high heat resistance are typically used as lubricants. Specifically, Japanese Patent Application Publication No. H05-027619 uses fluorinated greases or silicone oils as lubricants, and Japanese Patent Application Publication No. H08-076636 uses fluorinated greases, etc., as lubricants.

[0004] Furthermore, in electrophotographic image forming apparatuses that include a thermal fixing device for heating a recording material carrying a toner image, ultrafine particles may be generated from the toner and grease due to the heat when the thermal fixing device heats the recording material carrying the toner image. Japanese Patent Application Publication No. 2020-020965 discloses an electrophotographic image forming apparatus capable of preventing such ultrafine particles from being discharged outside the apparatus. Specifically, an electrophotographic image forming apparatus is disclosed, comprising a detection unit for ultrafine particles each having a first particle size and a detection unit for ultrafine particles each having a second particle size larger than the first particle size, and performing control to suppress the discharge of ultrafine particles outside the apparatus based on information about the amount of ultrafine particles indicated by the detection results of the detection units.

[0005] In the electrophotographic image forming apparatus disclosed in Japanese Patent Application Publication No. 2020-020965, the discharge of ultrafine particles to the outside of the apparatus can be reliably prevented. However, the inclusion of a detection unit for ultrafine particles and the installation of a control unit for reducing the amount of ultrafine particles may increase the size and cost of the electrophotographic image forming apparatus. Summary of the Invention

[0006] At least one aspect of this disclosure aims to provide a heating device and an electrophotographic image forming apparatus that can prevent the generation of ultrafine particles themselves caused by grease. Furthermore, at least one aspect of this disclosure aims to provide a grease composition that prevents the generation of ultrafine particles even when heated.

[0007] According to at least one aspect of this disclosure, a heating device is provided, comprising: a rotating member for heating; a opposing member configured to be opposite to the rotating member and forming a roll gap together with the rotating member; and a force-applying member disposed inside the rotating member, having opposing surfaces opposite to the inner circumferential surface of the rotating member, and configured to apply force from the rotating member to the opposing member, wherein the inner circumferential surface and the opposing surface are in contact with each other by a grease composition to form a sliding portion, wherein the grease composition comprises a base oil, wherein the base oil contains a fluoropolymer and a perfluoropolyether, wherein the fluoropolymer has the structure shown in formula (1), wherein in the thermogravimetric reduction curve obtained when the perfluoropolyether is heated from 25°C at a rate of 10°C / min under a nitrogen atmosphere, the evaporation loss of the perfluoropolyether at 260°C is 0.05–2.0% by mass, and wherein the kinematic viscosity of the perfluoropolyether at 40°C is 0.5 cm⁻¹. 2 / s~15cm 2 / s, and wherein the perfluoropolyether comprises a perfluoropolyether having any one of the structures selected from the group consisting of the structures shown in formulas (2) to (4):

[0008] Equation (1)

[0009]

[0010] In equation (1), R represents an alkylene group, p and q are each independently positive numbers, and p+q is the kinematic viscosity of the fluoropolymer at 40°C that satisfies 1.0×10⁻⁶. 3 cm 2 / s~1.0×10 5 cm 2 The value of / s; Equation (2)

[0011]

[0012] In equation (2), k represents a positive number, and k is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s;

[0013] Equation (3)

[0014] CF3-(OCF2CF2) m1 -(OCF2) n1 -CF3

[0015] In equation (3), m1 and n1 each represent positive numbers independently, and m1+n1 is the value that makes the kinematic viscosity of the perfluoropolyether at 40°C satisfy 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s;

[0016] Equation (4)

[0017] F-(CF2CF2CF2O) n2 -CF2CF3

[0018] In equation (4), n2 represents a positive number, and n2 is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s.

[0019] In addition, according to at least one aspect of this disclosure, an electrophotographic image forming apparatus including the above-described heating device is provided.

[0020] Furthermore, according to at least one aspect of this disclosure, a lubricating grease composition is provided, comprising a base oil containing a fluoropolymer and a perfluoropolyether, wherein the fluoropolymer has the structure shown in formula (1), wherein in the thermogravimetric reduction curve obtained when the perfluoropolyether is heated from 25°C at a rate of 10°C / min under a nitrogen atmosphere, the evaporation loss of the perfluoropolyether at 260°C is 0.05–2.0% by mass, and wherein the kinematic viscosity of the perfluoropolyether at 40°C is 0.5 cm⁻¹. 2 / s~15cm 2 / s, and wherein the perfluoropolyether includes any one of the structures selected from the group consisting of the structures shown in formulas (2) to (4): Formula (1)

[0021]

[0022] In equation (1), R represents an alkylene group, p and q are each independently positive numbers, and p+q is the kinematic viscosity of the fluoropolymer at 40°C that satisfies 1.0×10⁻⁶. 3 cm 2 / s~1.0×10 5 cm 2 The value of / s;

[0023] Equation (2)

[0024]

[0025] In equation (2), k represents a positive number, and k is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s;

[0026] Equation (3)

[0027] CF3-(OCF2CF2) m1 -(OCF2) n1 -CF3

[0028] In equation (3), m1 and n1 each represent positive numbers independently, and m1+n1 is the value that makes the kinematic viscosity of the perfluoropolyether at 40°C satisfy 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s;

[0029] Equation (4)

[0030] F-(CF2CF2CF2O) n2 -CF2CF3

[0031] In equation (4), n2 represents a positive number, and n2 is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s.

[0032] Further features of this disclosure will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawings. Attached Figure Description

[0033] Figure 1 This is a schematic cross-sectional view of a heating device including a heating sliding part according to one aspect of this disclosure.

[0034] Figure 2 This is a schematic cross-sectional view of an image forming apparatus according to one aspect of this disclosure.

[0035] Figure 3 This is a front view of a heating element according to one aspect of this disclosure and a schematic diagram illustrating its energization control circuit.

[0036] Figure 4 This is a schematic diagram illustrating the adsorption state between the fluoropolymer of this disclosure and the front surface of the heating element or the inner circumferential surface of the heating film.

[0037] Figure 5 This is a schematic cross-sectional view of a heating device including a pressure pad according to one aspect of this disclosure.

[0038] Figure 6 This is a schematic cross-sectional view of a heating device including a pressurized sliding part according to one aspect of this disclosure.

[0039] Figure 7This is a schematic cross-sectional view of a heating device including an intermediate rotating member according to one aspect of this disclosure. Detailed Implementation

[0040] Exemplary implementations of this disclosure are described below.

[0041] Electrophotographic image forming equipment

[0042] Figure 2 This is a schematic cross-sectional view of an image forming apparatus having a heating device mounted thereon, according to one aspect of this disclosure. The image forming apparatus is a laser beam printer that forms images on a recording medium P using a transfer-type electrophotographic method.

[0043] The electrophotographic drum 1 (hereinafter referred to as "drum"), which serves as the image carrier in the image forming unit, rotates clockwise (arrow direction) at a predetermined circumferential speed (processing speed). The surface of the drum 1 is uniformly charged (single charge) with predetermined polarity and potential by a charging unit 2, such as a contact charging roller. The laser beam scanner 3, which serves as the image exposure unit, outputs a laser light L that has been switched on / off modulated according to the time-series electro-digital pixel signal of the expected image information input from an external device such as an image scanner and a computer (not shown), and scans and exposes (irradiates) the charged surface of the drum 1. As a result of the scan exposure, the charge in the exposed bright areas of the drum 1 surface is removed, and an electrostatic latent image corresponding to the expected image information is formed on the surface of the drum 1. The developing apparatus 4 supplies recording material (toner) from the developing sleeve 4a to the surface of the drum 1, and sequentially develops the electrostatic latent image formed on the surface of the drum 1 into a toner image (a transferable image). In the case of laser beam printers, a reversal developing system is typically used to develop the electrostatic latent image by having toner adhere to the exposed bright areas of the image.

[0044] Recording medium P (e.g., paper) is loaded and stored in the paper feed cassette 5. The paper feed roller 6 is driven based on a paper feed start signal, and the recording media P in the paper feed cassette 5 are separated and fed one after another. Then, the recording media P passes between the positioning rollers 7 and through the sheet path 8a, and is introduced into the transfer section T at a predetermined time. This transfer section T is the abutment roller gap between the transfer roller 9, which serves as a contact / rotational transfer member, and the drum 1. That is, the transport of the recording medium P is controlled by the positioning roller 7 so that when the leading edge of the toner image on the drum 1 reaches the transfer section T, the leading edge of the recording medium P also reaches the transfer section T in a timely manner.

[0045] The recording medium P, introduced into the transfer section T, is held and conveyed through the transfer section T. During this time, a transfer voltage (transfer bias voltage) controlled in a predetermined manner is applied to the transfer roller 9 from a transfer bias voltage application power source (not shown). The transfer roller 9 and the control of the applied transfer voltage will be described later. When a transfer bias voltage with a polarity opposite to that of the toner is applied to the transfer roller 9, the toner image formed on the surface of the drum 1 is electrostatically transferred to the surface of the recording medium P at the transfer section T. The recording medium P with the toner image transferred thereon is then separated from the drum 1. Afterward, the recording medium P is conveyed through the paper path 8b and introduced into the heating device 11, where it undergoes heating and pressure fixing of the toner image. Meanwhile, after the toner, paper dust, etc., remaining from the transfer are removed by the cleaning device 10, the surface of the drum 1 repeatedly undergoes image formation after the recording medium is separated (after the toner image is transferred onto the recording medium P). The recording medium P, after passing through the heating device 11, is guided into the path on the paper path 8c side and output from the output port 13 to the output tray 14.

[0046] For example, an elastic roller comprising a conductive metal mandrel 9b formed of, for example, stainless steel (SUS) or Fe and a semi-conductive elastic layer 9a covering the outer peripheral surface of the metal mandrel can be used as a transfer roller 9. Preferably, the semi-conductive elastic layer 9a is adjusted to a resistance value of approximately 1.0 × 10⁻⁶ using, for example, an electronically or ionicly conductive agent such as carbon black. 6 Ω ~ Approximately 1.0 × 10 10 Ω. A non-limiting specific example of such a transfer roller is an ionically conductive elastic layer comprising a metal core 9b and a conductive elastic layer 9a covering the outer peripheral surface of the metal core, obtained by reacting NBR rubber with a surfactant, etc. Furthermore, the preferred resistance value of the transfer roller is 1 × 10⁻⁶. 8 Ω~5×10 8 Ω range. This value is the resistance value when a voltage of 2kV is applied between the metal mandrel of the transfer roller and the metal drum under the condition that the transfer roller is pressed against the metal drum with a load of 500gf.

[0047] The resistance value of the transfer roller 9 is prone to fluctuation depending on the ambient temperature and humidity, and this resistance fluctuation can lead to poor transfer and paper marks. Therefore, it is preferable to measure the resistance value of the transfer roller 9 and appropriately control the transfer voltage applied to the transfer roller 9 based on the measurement results (applied transfer voltage control) to prevent poor transfer and paper marks caused by resistance fluctuations in the transfer roller 9.

[0048] An example of applied transfer voltage control is the Active Transfer Voltage Control (ATVC) disclosed in Japanese Patent Application Publication No. H02-123385. ATVC is a method for optimizing the transfer bias applied to the transfer roller during transfer, preventing poor transfer and ink residue on the paper. Using this transfer bias, a constant current bias is applied from the transfer roller 9 to the drum 1 during the pre-rotation of the image forming apparatus, and the resistance value of the transfer roller 9 is detected from its bias value. Then, during the transfer process in the printing process, a transfer bias corresponding to the resistance value is applied to the transfer roller 9. Preferably, the above-described ATVC is also used in this embodiment.

[0049] <Heating device>

[0050] Next, the heating device according to this embodiment will be described. The heating device according to this embodiment includes a rotating member for heating; a opposing member configured to face the rotating member and together with the rotating member to form a roll gap; and a force-applying member disposed inside the rotating member, having an opposing surface relative to the inner circumferential surface of the rotating member, and causing the rotating member to apply force to the opposing member. First, as an example, a membrane heating type heating device will be described, which includes a sliding portion inside a rotating member for heating that is directly heated by a heat source. Figure 1 This is a schematic cross-sectional view of a film-heating type heating device 11 according to this embodiment. The heating device is, for example, a so-called tensionless heating device disclosed in Japanese Patent Application Publication No. H04-044075. The heating device 11 includes a heating film unit 15 containing a rotating member for heating, and a pressure roller 24 serving as a pressure member.

[0051] [Heating film unit]

[0052] According to one aspect of this disclosure, the heating device 11 uses a heating film (heat-resistant fixing film) 22 with an annular shape as a rotating member for heating, which is directly heated by a heat source (hereinafter sometimes referred to as a "heating body"). In this configuration, the heat capacity can be reduced, and the rapid start-up performance can be improved. The heating device 11 of this embodiment has a configuration in which at least a portion of the circumference of the heating film 22 is always in a tension-free state (a state without applied tension), and the heating film 22 is driven to rotate by the rotational driving force of the pressure roller 24. Figure 1 As shown, the heating film unit 15 includes a heating film 22, a support member 21, a U-shaped metal plate 20, and a heating element (heater) 23.

[0053] (Heating film)

[0054] The heating film 22 is embedded in the heating body 23 and the support member 21, which serves as a guide for the heating film 22. The inner circumference of the heating film 22 is, for example, about 3 mm longer than the outer circumference of the support member 21, which includes the heating body 23. Therefore, the heating film 22 is embedded in the support member 21 with a circumference allowance.

[0055] From the viewpoint of heat capacity and rapid start-up performance, the thickness of the heating film 22 is preferably 100 μm or less, more preferably 20 μm or more and 50 μm or less. For example, a single-layer film of heat-resistant polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroether copolymer (PFA), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) can be used as the heating film 22. Alternatively, a multilayer film obtained by coating the outer peripheral surface of a film such as polyimide, polyamide-imide, polyether ether ketone (PEEK), polyether sulfone (PES), or polyphenylene sulfide (PPS) with PTFE, PFA, FEP, etc., can also be used as the heating film 22.

[0056] (Guide member and backup member)

[0057] The support member 21 is a membrane guide that serves as a guiding member and is formed of a component that combines heat resistance and rigidity to maintain both the heating element 23 and the guiding heating membrane 22. Specifically, the support member 21 is made of a highly heat-resistant resin, such as polyimide, polyamide-imide, PEEK, PPS, or liquid crystal polymer, or a composite material of these resins with ceramics, metals, and glass, etc. Figure 1 In the heating device shown, the support member 21 also functions as a force-applying member that forces the heating film 22 onto the pressure roller 24. Furthermore, the U-shaped metal plate 20 is a supporting member that reinforces the support member 21 and is formed of a rigid member made of a metal such as stainless steel (SUS) or iron. The heating element 23 is disposed on the lower surface of the support member 21 along the length direction of the support member (the direction intersecting the transport direction of the recording medium).

[0058] (Heating element)

[0059] The heating element 23 is typically a heater, such as a ceramic heater. Figure 1 In the heating device shown, the heating element 23 also functions as a force-applying component that causes the heating film 22 to exert force on the pressure roller 24. Figure 3This is a front view of the heating element 23 of this embodiment and a schematic diagram illustrating its energization control circuit. The heating element 23 is disposed on a substrate 27, which is the material to be heated and has heat resistance, insulation, and satisfactory thermal conductivity. The substrate 27 is an elongated member having a length direction perpendicular to the transport direction "a" of the recording medium. That is, a resistance heating element 26 is formed and disposed along the length direction of the substrate on the front surface (film sliding surface) side of the substrate 27. In addition, the heating element 23 includes a heat-resistant outer coating 28 on which the resistance heating element 26 is formed and which protects the front surface of the heating element, and electrodes 29 and 30 for energizing at the ends of the resistance heating element 26 in the length direction. Therefore, a heating element with a low overall heat capacity is formed.

[0060] The resistance heating element 26 of this embodiment can be obtained, for example, by forming a strip on a substrate 27 from a paste prepared by kneading silver, palladium, glass powder (inorganic binder) and organic binder using screen printing. In addition to silver and palladium (Ag / Pd), resistive materials such as RuO2 or Ta2N can be used as the resistance heating element 26.

[0061] The substrate 27 is made of a heat-resistant and insulating material, such as a ceramic material like alumina or aluminum nitride. The outer coating 28 ensures electrical insulation between the resistance heating element 26 and the front surface of the heating body 23, as well as the sliding properties of the heating film 22.

[0062] Figure 3 A plan view of the heating element 23 as seen from its back side (non-film sliding surface) is shown. For example, an externally contactable thermistor separate from the heating element 23 can be used as a temperature sensing element 25 to detect the temperature of the heating element 23. The temperature sensing element 25 has the following configuration: an insulating layer is formed, for example, on a support, an element of the chip thermistor is fixed to the insulating layer, and this element faces downward (towards the back side of the heating element) to abut against the back side of the heating element using a predetermined pressure. The temperature sensing element 25 is disposed in the minimum paper passage area and communicates with the CPU 31. The surface of the outer coating 28 covering the heating element 23 is exposed downwards and held and fixed to the lower surface side of the support 21. By employing the above configuration, a lower heat capacity is allowed for the entire heating element compared to a heating roller system, and rapid start-up can be performed.

[0063] Here, when the resistance heating element 26 generates heat over its entire length by supplying power to the electrodes 29 and 30 at its ends along the longitudinal direction, the temperature of the heating element 23 rises. This temperature rise is detected by the temperature sensing element 25, and its output is converted by an A / D converter and received by the CPU 31. Based on this information, the power supplied to the resistance heating element 26 by the triac 32 is controlled via phase control, wavenumber control, etc., and the temperature of the heating element 23 is controlled. Specifically, the power supply is controlled such that the temperature of the heating element 23 increases when the detected temperature by the temperature sensing element 25 is lower than a predetermined set temperature, and decreases when the detected temperature is higher than the set temperature. Therefore, the heating element 23 maintains a constant temperature during fixing.

[0064] With the heating element 23 heated to a predetermined temperature and the rotational speed of the heating film 22 caused by the rotation of the pressure roller 24 stabilizing, the recording medium is introduced from the transfer section into the roll gap N between the heating film 22 formed by the heating element 23 and the pressure roller 24. Then, as the recording medium and the heating film 22 are held together and conveyed through the roll gap N, the heat from the heating element 23 is applied to the recording medium via the heating film 22. As a result, the unfixed toner image on the recording medium is heated to fix it onto the recording medium. The recording medium, having passed through the roll gap N, is then separated from the heating film 22 and conveyed.

[0065] [Pressure component]

[0066] The pressure roller 24, serving as a pressure member, is a film outer surface contact drive unit configured to face the heating film 22, forming a roll gap N together with the heating film 22, and driving the heating film 22 to rotate. That is, the pressure roller 24 corresponds to the opposing member for the heating film 22. The pressure roller 24 includes a metal mandrel, an elastic layer, and a release layer serving as the outermost layer, and is configured to press against the front surface of the heating body 23 to clamp the heating film 22 between the pressure roller 24 and the heating body 23 under a predetermined pressing pressure by a bearing unit and a force-applying unit (not shown).

[0067] The pressure roller 24 is also opposite to the support member 21 and is driven by a drive system (not shown) along... Figure 1Arrow A indicates rotation at a predetermined circumferential speed. Driven by the rotation of the pressure roller 24, friction is generated between the pressure roller 24 and the outer surface of the heating film 22 in the roll gap N, and rotational force acts on the heating film 22. Thus, the inner circumferential surface of the heating film 22 is in close contact with the front surface (opposite surface) of the heating body 23 in the roll gap N, and the film rotates around the outer periphery of the support member 21 in the direction of arrow B while sliding together with the heating body 23. Therefore, in the heating device 11, a sliding portion is formed on the inner circumferential surface of the heating film 22 and on the opposing surfaces of the support member 21 and the heating body 23, which respectively serve as force-applying members. A grease composition according to one aspect of this disclosure is applied as a lubricant to the sliding portion. Therefore, friction generated mainly in the portion of the heating body 23 that is in contact with the heating film 22 while being pressurized in the roll gap N and in the portion of the support member 21 that is in contact with the heating film 22, which serves as the sliding portion inside the heating film, is reduced, and lubricity is maintained. As a result, the heating film 22 rotates along with the pressure roller 24 at approximately the same circumferential speed as the pressure roller 24. Figure 1 An example is shown where the sliding portion is formed by the inner circumferential surface of the heating film 22, a portion of the support member 21 that serves as a force-applying member opposite to the inner circumferential surface, and the surface of the heating body 23 that faces the inner circumferential surface. However, the heating device according to one aspect of this disclosure is not limited to this configuration.

[0068] <Lubricating Grease Composition>

[0069] Next, a grease composition according to one aspect of the present disclosure will be described. The grease composition according to one aspect of the present disclosure is a fluorinated grease containing a fluorinated base oil. The grease composition functions as a lubricant for reducing friction in sliding portions between the heating film 22 and the guide member (support) 21, and between the heating film 22 and the heating element (heater) 23. That is, the inner circumferential surface of the heating film (rotating member) and the opposing surfaces of the support member and the heating element, which respectively serve as force-applying members, come into contact with each other by the grease composition. The grease composition may be made solely of base oil, but from the viewpoint that the base oil remains on the inner circumferential surface of the film for a long time, it is preferable that the grease composition is made of a mixture of base oil and a fluorinated thickener. In the grease composition according to one aspect of the present disclosure, the evaporation of the base oil at high temperatures during heating device operation can be more reliably suppressed by the composition of the base oil described below.

[0070] <Base Oil>

[0071] The base oil contained in the grease composition according to one aspect of this disclosure comprises a perfluoropolyether and a fluoropolymer. Each component is described below.

[0072] (Perfluoropolyether)

[0073] Perfluoropolyethers are components used as base materials in lubricants. Regarding the viscosity of perfluoropolyethers, the kinematic viscosity at 40°C is 50 cSt to 1,500 cSt (0.5 cm⁻¹). 2 / s~15cm 2 Perfluoropolyethers with kinematic viscosities within the aforementioned range are used. When perfluoropolyethers with kinematic viscosities within the above range are introduced into base oils, the viscosity of the grease composition can be more easily adjusted to a range that maintains smoother sliding while inhibiting flow of the grease composition from the sliding parts. In this disclosure, kinematic viscosity is a value measured in accordance with ASTM D445: Standard Test Method (and Calculation of Dynamic Viscosity) for Kinematic Viscosities of Transparent and Opaque Liquids. This also applies to the fluoropolymers described later.

[0074] From the viewpoint of high heat resistance, perfluoropolyethers include at least one perfluoropolyether selected from the group consisting of: perfluoropolyethers having the structure shown in structural formula (2); perfluoropolyethers having the structure shown in structural formula (3); and perfluoropolyethers having the structure shown in structural formula (4). Among them, perfluoropolyethers having the structure shown in structural formula (3) are particularly suitable for use.

[0075] Structural formula (2)

[0076]

[0077] In structural formula (2), "k" represents a positive number, and "k" is the value that makes the kinematic viscosity of the perfluoropolyether at 40°C satisfy 50 cSt~1,500 cSt (0.5 cm⁻¹). 2 / s~15cm 2 The value of / s).

[0078] Structural formula (3)

[0079] CF3-(OCF2CF2) m1 -(OCF2) n1 -CF3

[0080] In structural formula (3), m1 and n1 each independently represent positive numbers, and m1+n1 is the value that makes the kinematic viscosity of the perfluoropolyether at 40°C satisfy 50 cSt~1,500 cSt (0.5 cm⁻¹). 2 / s~15cm 2 The value of m1 / n1 is preferably 0.5 to 2.0, more preferably 0.5 to 1.5, still more preferably 0.5 to 1.0, and particularly preferably 1.0, to prevent extreme increase in viscosity at low temperatures and extreme decrease in viscosity at high temperatures.

[0081] Structural formula (4)

[0082] F-(CF2CF2CF2O)n2 -CF2CF3

[0083] In structural formula (4), n2 represents a positive number, and n2 is the value that makes the kinematic viscosity of the perfluoropolyether at 40°C satisfy 50 cSt~1,500 cSt (0.5 cm⁻¹). 2 / s~15cm 2 The value of / s).

[0084] Typically, perfluoropolyethers are oils with high heat resistance. Therefore, even when exposed to a high temperature of approximately 200°C during heating in heating device 11, the perfluoropolyether will not decompose and can maintain lubrication between heating film 22 and heating element 23. However, when commercially available perfluoropolyethers with a kinematic viscosity within the aforementioned range are used in heating devices reaching a high temperature of approximately 200°C, some perfluoropolyethers may easily become ultrafine particles. That is, the perfluoropolyether has a molecular weight distribution in which molecules with low molecular weights (hereinafter sometimes referred to as "low molecular weight components") easily become ultrafine particles. Therefore, by specifying the kinematic viscosity, which is proportional to the average molecular weight, within the aforementioned range, the proportion of high molecular weight molecules that are less likely to become ultrafine particles can be increased. However, when the proportion of low molecular weight components as a molecular weight distribution is large, the amount of perfluoropolyether that easily becomes ultrafine particles also increases.

[0085] In view of the above, the inventors investigated the amount of low molecular weight components that easily turn into ultrafine particles contained in commercially available perfluoropolyethers using thermogravimetric analysis (TGA). Specifically, the inventors studied the evaporation loss at 260°C in the thermogravimetric reduction curve obtained by increasing the temperature from 25°C at a rate of 10°C / min under a nitrogen atmosphere. The results showed that the evaporation loss, including batch-to-batch variations, fell within the range of 0.05–2.0% by mass.

[0086] By using perfluoropolyethers with low molecular weight components, i.e., perfluoropolyethers with an evaporation loss of less than 0.05% by mass as determined by the thermogravimetric analysis, the generation of ultrafine particles can be suppressed. However, to reduce the content of low molecular weight components in the perfluoropolyether, repeated distillation of the perfluoropolyether is required, leading to an increase in the cost of the perfluoropolyether.

[0087] (Fluoropolymers)

[0088] In view of the above, the inventors conducted in-depth research to obtain a grease composition that can prevent the generation of ultrafine particles even when using perfluoropolyethers with a high content of low molecular weight components. As a result, it has been found that using a fluoropolymer having the structure shown in the following structural formula (1) together with the aforementioned perfluoropolyether as a base oil in a grease composition is extremely effective in preventing the generation of ultrafine particles caused by the low molecular weight components of the perfluoropolyether. That is, a grease composition according to one aspect of this disclosure comprises a modified perfluoropolyether as shown in the following structural formula (1) as a base oil.

[0089] Structural formula (1)

[0090]

[0091] In structural formula (1), R represents an alkylene group. The alkylene group is not specifically defined, but for example, it is an alkylene group having 6 carbon atoms. Furthermore, "p" and "q" each independently represent positive numbers, and p+q is the kinematic viscosity of the fluoropolymer at 40°C that satisfies 1.0 × 10⁻⁶. 5 cSt ~ 1.0 × 10 7 cSt(1.0×10 3 cm 2 / s~1.0×10 5 cm 2 The value of p / q is ( / s). Furthermore, from the viewpoint of preventing extreme increases in viscosity at low temperatures and extreme decreases in viscosity at high temperatures, the value of p / q is preferably 0.5 to 2.0, particularly preferably 0.5 to 1.0, and even more preferably 1.0.

[0092] Furthermore, when the kinematic viscosity of the fluoropolymer is too low, it evaporates easily, making it difficult to achieve the desired capture effect of perfluoropolyethers in the base oil described later. Conversely, when the kinematic viscosity is too high, the fluoropolymer becomes extremely difficult to handle; therefore, the kinematic viscosity of the fluoropolymer at 40°C is required to be 1.0 × 10⁻⁶. 5 cSt ~ 1.0 × 10 7 cSt. Fluoropolymers that meet these conditions can be, for example, commercially available fluoropolymers as “Fluorolink PA100E” (product name, manufactured by Solvay Specialty Polymers), wherein R in structural formula (1) represents hexamethylene (-(CH2)6-).

[0093] The inventors envision that a grease composition comprising a base oil containing a fluoropolymer having the structure shown in formula (1) and a perfluoropolyether can reduce the generation of ultrafine particles caused by perfluoropolyether, as described below.

[0094] In the structure shown in formula (1) of the fluoropolymer, the amide group is highly polar. Meanwhile, the front surface (opposite surface) of the substrate 27 (heater 23) and the inner peripheral surface of the heating film 22 each have functional groups such as hydroxyl groups exposed on their outermost surfaces, and these functional groups are also polar. Therefore, these functional groups interact with the amide group in formula (1). Thus, as... Figure 4 As shown, the fluoropolymer is adsorbed onto the front surface of the heating element 23 and the inner peripheral surface of the heating film 22, such that the fluoropolyether structure in the molecular chain faces the opposite sides of the heating element 23 and the heating film 22. Figure 4 This is a schematic diagram illustrating the state in which the fluoropolymer of this disclosure is adsorbed onto the front surface of the heating element (substrate) or the inner circumferential surface of the heating film.

[0095] During operation of the heating device, adsorption is maintained even at high temperatures. Furthermore, the fluorinated polyether structural portion facing outwards has the same structure as the perfluoropolyethers shown in structural formulas (2) to (4) in the base oil, and exhibits high affinity. Therefore, the fluorinated polyether structural portion can capture the perfluoropolyethers shown in structural formulas (2) to (4) in the base oil. As a result, the perfluoropolyethers shown in structural formulas (2) to (4) are captured onto the surfaces of the heating element 23 and the heating film 22 through the fluorinated polyether structural portion of the fluoropolymer. Consequently, the perfluoropolyether is less prone to evaporation, and the generation of ultrafine particles is suppressed.

[0096] In a grease composition according to one aspect of the present disclosure, the content ratio of the fluoropolymer having the structure shown in formula (1) to the total mass of the grease composition is preferably in the range of 0.1 to 10.0% by mass. When such a content ratio is set, the generation of ultrafine particles from perfluoropolyethers can be effectively suppressed at low cost.

[0097] (Thickener)

[0098] Furthermore, the grease composition disclosed herein may also contain a fluorinated thickener. Specifically, fine particles of fluoropolymers such as PTFE, PFA, or FEP can be used as a fluorinated thickener. These fine fluoropolymer particles can encircle the fluorinated base oil, thus making it difficult for the base oil to flow out even at the high temperatures of the heating device. In particular, from the viewpoint of durability, the thickener preferably contains fine polytetrafluoroethylene (PTFE) particles. From the viewpoint of encircling the fluorinated base oil, the particle size of each fine fluoropolymer particle is preferably 50 nm to 1 μm. Here, the particle size of each fine fluoropolymer particle refers to the average primary particle size of the thickener observed using a scanning electron microscope (SEM).

[0099] Furthermore, preferably, the mixing ratio between the fluorinated thickener and the perfluoropolyether, which is a fluorinated oil, is set to include the fluorinated oil in a relatively large amount. Specifically, preferably, the thickener is included in an amount of 10 to 100 parts by weight relative to 100 parts by weight of the base oil. When the mixing ratio is set as described above, a friction-suppressing effect can be further exhibited between the heating film and a portion of the heating element and support. In addition, even at the high temperature of the heating device, the grease composition is more easily retained on the inner circumferential surface of the heating film, thus exhibiting a stable friction-suppressing effect for a long time.

[0100] [Other implementation schemes for the heating device]

[0101] (Implementation scheme using a pressure pad as a pressure component)

[0102] In the above embodiments, a membrane heating type heating device 11 has been described, which specifically includes a sliding portion on the heating side and a pressure roller 24 serving as a counter member. However, a heating device according to one aspect of this disclosure may have a configuration that includes a pressure pad instead of a pressure roller as the counter member. As an example, as shown... Figure 5 The illustrated heating device 111 includes a pressure pad 124. The heating device 111 including the pressure pad is identical to the heating device 11 in that it includes the pressure pad 124, the film drive roller 125, and the heating film 122. That is, the pressure pad 124 is used instead of the pressure roller 24, therefore the heating film 122 cannot be driven. For this reason, the heating device 111 includes the film drive roller 125 to drive the heating film 122.

[0103] The membrane drive roller 125 is driven by receiving a rotational drive from a motor (not shown) and can drive the heated membrane 122.

[0104] Here, the pressure pad 124 includes a pressure pad base 124a formed of a rigid member, such as a metal (e.g., stainless steel (SUS) or aluminum), and a pressure pad surface layer 124b formed on the pressure pad base 124a. The pressure pad surface layer 124b is formed of a member having low friction, heat resistance, and elasticity, and can use heat-resistant resins, such as PTFE, PFE, polyimide, polyamide-imide, and aromatic polyamide, as well as fabrics and nonwovens formed from their fibers. Furthermore, the pressure pad 124 is pressed against the heating film 122 at the lower part of both longitudinal ends of the pressure pad base 124a by springs (not shown), thereby forming a roll gap Nk together with the heating film 122.

[0105] Furthermore, the film drive roller 125 is a metal mandrel with a rough surface to drive the heating film 122, and stainless steel (SUS) or aluminum can be used as the metal. In addition, the heating film 122 is the same as the heating film 22, except that the heating film 122 has a larger inner diameter than the heating film 22 to enclose the film drive roller 125.

[0106] Similar to heating device 11, as described above, the film heating type heating device 111 including the pressure pad also includes a sliding portion formed by the inner peripheral surface of the heating film 122, a portion of the support member 21 serving as a force-applying member opposite to the inner peripheral surface, and a sliding portion on the surface of the heating body 23 opposite to the inner peripheral surface as the heating side. Therefore, by using a grease composition according to one aspect of the present disclosure as a lubricant in the sliding portion, the suppression effect on the generation of ultrafine particles can be obtained in the same manner as in heating device 11.

[0107] (An embodiment including a sliding part on the pressurized side)

[0108] In each of the above embodiments, a film heating type heating device has been described, particularly including a rotating member directly heated by a heat source, i.e., a sliding portion on the heating side. However, a grease composition according to one aspect of this disclosure also exhibits the same effect in a heating device including a rotating member indirectly heated by a heat source (i.e., including a sliding portion on the pressure side that slides as the rotating member rotates). As an example, a grease composition including... Figure 6 The heating device 50 of the pressure membrane unit shown.

[0109] The heating device 50 includes a pressure film unit 56 and a fixing roller 51, which serves as a counter member opposite to the pressure film unit 56 in forming a roll gap Np. The fixing roller 51 includes an internal heat source (heating element) 57, and heats the pressure film unit 56 when the fixing roller 51 reaches a high temperature. That is, the pressure film unit 56 has a structure in which it is indirectly heated by the heat source through the fixing roller 51, and the recording medium carrying the recording material undergoes heating treatment by passing through the roll gap Np.

[0110] The fixing roller 51 includes a cylindrical metal mandrel 51a formed of a metallic material such as iron, stainless steel (SUS), or aluminum. Furthermore, a highly thermally conductive elastic layer 51b is formed on the outer peripheral surface of the cylindrical metal mandrel 51a, containing silicone rubber serving as a base and thermally conductive fillers such as alumina, metallic silicon, silicon carbide, or silica. Additionally, a release layer (outermost layer) 51c containing PTFE, PFA, or FEP as main components is formed on the outer peripheral surface of the elastic layer 51b. Bearings (not shown) are externally fitted to both ends of the fixing roller 51. When the bearings are fixed to the device frame, the fixing roller 51 is rotatably fixed to the device frame.

[0111] A halogen heater 57, serving as the heating element, is built into the fixing roller 51. A temperature sensing element 58 detects the surface temperature of the fixing roller 51, and a thermopile or a radiation thermometer, etc., can be used as the temperature sensing element 58. The temperature detected by the temperature sensing element 58 is fed back to the CPU (not shown), and the halogen heater 57 is energized by the CPU (not shown) so that the surface temperature of the fixing roller 51 detected by the temperature sensing element 58 reaches a predetermined temperature.

[0112] The pressure membrane unit 56 includes a pressure membrane (pressure belt) 52 with an annular shape, a support member 53 serving as a guide member for the pressure membrane, a U-shaped metal plate 54 made of metal serving as a support member for reinforcing the support member 53, and a roll gap forming member 55. Furthermore, pressure membrane unit flanges (not shown) for adjusting the longitudinal position of the pressure membrane are disposed at both ends of the support member 53.

[0113] The roll gap forming member 55 is formed with a rectangular cross-section, and its surface is adjusted to a predetermined roughness. The support member 53 is formed using a heat-resistant resin material, such that its cross-section has an approximately inverted groove shape, and supports the roll gap forming member 55, also formed of a heat-resistant resin material, in a recess 53a formed along the length direction. The pressure diaphragm 52 is loosely fitted to the outer periphery of the support member 53.

[0114] The pressure membrane 52 includes a base layer formed by using a heat-resistant resin such as polyimide resin, PEEK or polyetherimide (PEI) or a metal such as stainless steel (SUS) or nickel as the main component, and a release layer formed on the outer peripheral surface of the base layer by using a fluoropolymer such as PFA, PTFE or FEP as the main component.

[0115] When the pressure film unit flanges (not shown) at both ends of the support member 53 in the longitudinal direction are supported by the device frame, the pressure film unit 56 is also supported by the device frame. Furthermore, a pressure spring (not shown) presses the pressure film unit 56 along the direction of the fixing roller 51 via the pressure film unit flanges (not shown). With this configuration, the gap forming member 55 and the support member 53 press against the fixing roller 51 via the pressure film 52 to form the gap portion Np of the heating device including the pressure film unit 56.

[0116] Furthermore, the inner circumferential surface of the pressure diaphragm 52 slides together with the gap forming member 55 and the support member 53. That is, in Figure 6 In the heating device shown, the sliding portion is formed by the inner peripheral surface of the pressure film 52, the surface of the roller gap forming member 55 opposite to the inner peripheral surface, and a portion of the support member 53 opposite to the inner peripheral surface. To reduce friction in the sliding portion, a grease composition according to one aspect of the present disclosure is applied to the inner peripheral surface of the pressure film 52 as a lubricant.

[0117] In the heating device 50, a motor (not shown) is driven to rotate in response to a printing command, and the rotation of the output shaft of the drive motor is transmitted to the cylindrical metal mandrel 51a of the fixing roller 51 via a predetermined gear mechanism (not shown). As a result, the fixing roller 51 rotates in the direction of the arrow, and the pressure film 52 also rotates accordingly. In addition, the halogen heater 57 is energized by the CPU (not shown) along with the printing command, and energization control is performed so that the temperature detection element 58 reaches a predetermined temperature. Then, when the recording medium passes through the roller gap Np, the recording medium is subjected to thermal fixing in the same manner as in a film-heated heating device.

[0118] In the heating apparatus 50 including the pressure film unit 56 as described above, the pressure film unit 56 reaches a high temperature by receiving heat from the fixing roller 51 heated by the heating element 57. As a result, the lubricant applied to the inner circumferential surface of the pressure film 52 is also exposed to the high temperature. By using a grease composition according to one aspect of this disclosure as the lubricant, the effect of suppressing the generation of ultrafine particles associated with lubricant evaporation and the adhesion of ultrafine particles to the interior of the image forming apparatus is obtained in the same manner as in film heating type heating apparatuses.

[0119] (Including the implementation scheme for the intermediate rotating component)

[0120] As another example of a heating device, the following can be given: Figure 7 The heating device 211 shown includes an intermediate rotating member 224. That is, the heating device 211 has the following structure: wherein the heating device 211 includes an intermediate rotating member 224 which serves as an opposing member to which the heating film unit 15 is pressed and heated, and the intermediate rotating member 224 is pressed with the pressure film unit 56 to form a roll gap Np.

[0121] Here, except that the intermediate rotating member 224 has a heat storage layer containing thermally conductive filler between the release layer and the elastic layer on its outermost surface, the intermediate rotating member 224 has the same structure as the pressure roller 24. The heat storage layer is made of silicone rubber containing fillers with high thermal conductivity and high heat capacity (e.g., alumina, silicon carbide, silicon dioxide), and can store heat from the heating film unit 15. With this structure, when the recording medium passes through the roll gap Np formed by the intermediate rotating member 224 and the pressure film unit 56, the recording medium is thermally fixed in the same manner as in a film-heated heating device.

[0122] Similarly, in a heating device having this configuration, a grease composition according to one aspect of this disclosure can be applied as a lubricant to at least one of the heating film unit 15 or the pressurized film unit 56. As a result, the effect of suppressing the generation of ultrafine particles associated with lubricant evaporation and the adhesion of ultrafine particles to the interior of the image forming apparatus is obtained in the same manner as in film heating type heating devices and heating devices using pressurized film units.

[0123] As an example of the image forming apparatus of this embodiment, an image forming apparatus using electrophotography with toner as the recording material has been described. However, an image forming apparatus using recording materials other than toner can be used. For example, in an image forming apparatus, such as an inkjet system using ink as the recording material, needless to say, as long as the structure has a heating device for performing heat treatment on the recording medium on which the recording material is loaded, the same effect will be exhibited.

[0124] As described above, in heating devices using the grease composition of this disclosure, the evaporation of perfluoropolyether in the grease composition can be suppressed when the heating device is driven, while also suppressing increases in device cost and size. As a result, the generation of ultrafine particles can be suppressed.

[0125] According to one aspect of this disclosure, a heating device and an electrophotographic image forming apparatus that can prevent the generation of ultrafine particles caused by grease can be obtained. Furthermore, according to another aspect of this disclosure, a grease composition that prevents the generation of ultrafine particles even when heated can be obtained.

[0126] Example

[0127] The specific composition of the fluorinated grease composition disclosed herein and its effects when used in heating devices are described below. In the following description, the term "parts" means "parts by weight" unless otherwise stated. The kinematic viscosity of each of the fluoropolymer and the perfluoropolyether is the value measured in accordance with ASTM D445 at 40°C. Furthermore, the evaporation loss of the perfluoropolyether is the evaporation loss at 260°C in the thermogravimetric analysis curve obtained by using a TGA apparatus (product name: TGA / SDTA 851e, manufactured by Mettler Toledo) when heated from 25°C at a rate of 10°C / min under a nitrogen atmosphere.

[0128] [Example 1]

[0129] Fomblin M60 (product name, manufactured by Solvay Specialty Chemicals) with the structure shown in formula (3) was distilled at 240°C until the evaporation loss reached 2.00% by mass. Then, perfluoropolyether No.1 with a kinematic viscosity of 310 cSt at 40°C was prepared. For Fomblin M60, m1 / n1 in formula (3) is 0.8 to 0.9.

[0130] Furthermore, “Fluorolink PA100E” (product name, manufactured by Solvay Specialty Polymers) is prepared as a fluoropolymer according to one aspect of this disclosure. “Fluorolink PA100E” has the structure shown in formula (1), where R represents hexamethylene and satisfies p / q = 1, and its kinematic viscosity at 40°C is 8.75 × 10⁻⁶. 5 cSt. Then, 5.0 parts of the fluoropolymer were diluted 5 times with a fluorinated solvent (product name, Novec 7100, manufactured by 3M Company) to prepare a diluted solution.

[0131] In addition, PTFE particles with an average primary particle size of 130 nm (product name, Polyflon PTFE L-5F, manufactured by Daikin Industries, Ltd.) were prepared as a thickener.

[0132] Then, using a kneader, 30.0 parts of thickener were mixed with more than 70.0 parts of the prepared perfluoropolyether No.1 to prepare base grease No.1. A diluted solution of the fluoropolymer was added to 95.0 parts of base grease No.1, so that the amount of fluoropolymer added was 5.0 parts, and then kneaded. Afterwards, the kneaded product was left to stand in a constant temperature bath at 25°C for 48 hours to prepare grease No.1 formed from perfluoropolyether, thickener, and fluoropolymer.

[0133] [Example 2]

[0134] Fomblin M60 was distilled at 240°C until the evaporation loss reached 0.70% by mass to prepare perfluoropolyether No.2 with a kinematic viscosity of 320 cSt at 40°C. Except for using the obtained perfluoropolyether No.2, the preparation of base grease No.2 and grease No.2 was carried out in the same manner as in Example 1.

[0135] [Example 3]

[0136] Fomblin M60 was distilled at 240°C until the evaporation loss reached 0.05% by mass to prepare perfluoropolyether No.3 with a kinematic viscosity of 350 cSt at 40°C. The preparation of base grease No.3 and grease No.3 was carried out in the same manner as in Example 1, except that the obtained perfluoropolyether No.3 was used.

[0137] [Example 4]

[0138] A diluted solution of the fluoropolymer prepared in Example 1 was added to 99.9 parts of base grease No. 2, reducing the amount of fluoropolymer added to 0.1 parts. Grease No. 4 was prepared in the same manner as grease No. 2, except as described above.

[0139] [Example 5]

[0140] A diluted solution of the fluoropolymer prepared in Example 1 was added to 90.0 parts of base grease No. 2, so that the amount of fluoropolymer added was 10.0 parts. Grease No. 5 was prepared in the same manner as grease No. 2, except as described above.

[0141] [Example 6]

[0142] A perfluoropolyether (product name: KrytoxGPL107, manufactured by Chemours Company) having the structure shown in formula (2) was distilled at 240°C until the evaporation loss reached 0.70% by mass. Then, perfluoropolyether No.4 with a kinematic viscosity of 500 cSt at 40°C was prepared.

[0143] Except for using the perfluoropolyether No. 4 thus obtained, base grease No. 4 was prepared in the same manner as base grease No. 1 in Example 1. Then, a diluted solution of the fluoropolymer prepared in Example 1 was added to 95.0 parts of base grease No. 4, so that the amount of fluoropolymer added was 5.0 parts. Except as described above, grease No. 6 was prepared in the same manner as grease No. 1.

[0144] [Example 7]

[0145] A perfluoropolyether (product name: Demnum S-200, manufactured by Daikin Industries, Ltd.) having the structure shown in formula (4) was distilled at 240°C until the evaporation loss reached 0.70% by mass. Then, perfluoropolyether No. 5 with a kinematic viscosity of 220 cSt at 40°C was prepared. Base grease No. 5 was prepared in the same manner as base grease No. 1 of Example 1, except that the perfluoropolyether No. 5 thus obtained was used. Then, a diluted solution of the fluoropolymer prepared in Example 1 was added to 95.0 parts of base grease No. 5, so that the amount of fluoropolymer added was 5.0 parts. Grease No. 7 was prepared in the same manner as grease No. 1, except as described above.

[0146] [Comparative Example 1]

[0147] The base grease No.1 was used as the grease No.C1 according to this comparative example. That is, grease No.C1 does not contain fluoropolymers having the structure shown in formula (1).

[0148] [Comparative Example 2]

[0149] Base grease No. 2 was used as grease No. C2 according to this comparative example. That is, grease No. C2 does not contain fluoropolymers having the structure shown in formula (1).

[0150] [Comparative Example 3]

[0151] Base grease No. 3 was used as grease No. C3 according to this comparative example. That is, grease No. C3 does not contain fluoropolymers having the structure shown in structural formula (1).

[0152] [Comparative Example 4]

[0153] The perfluoropolyether No. 3 prepared in Example 3 was further distilled at 240°C for 60 minutes to prepare perfluoropolyether No. C1 with an evaporation loss of 0.01% by mass. The kinematic viscosity of perfluoropolyether No. C1 at 40°C was 370 cSt. Base grease No. C1 was prepared in the same manner as base grease No. 1, except that the obtained perfluoropolyether No. C1 was used. The obtained base grease No. C1 was then used directly as grease No. C4 according to this comparative example. Therefore, grease No. C4 does not contain fluoropolymers having the structure shown in formula (1).

[0154] [Comparative Example 5]

[0155] Base grease No. 4 was used as grease No. C5 according to this comparative example. That is, grease No. C5 does not contain fluoropolymers having the structure shown in formula (1).

[0156] [Comparative Example 6]

[0157] Base grease No. 5 was used as grease No. C6 according to this comparative example. That is, grease No. C6 does not contain fluoropolymers having the structure shown in formula (1).

[0158] The formulations and physical properties of base greases No.1 to No.5 and No.C1, greases No.1 to No.7, and greases No.C1 to No.C6 are shown together in Tables 1 and 2.

[0159] Table 1

[0160]

[0161] Table 2

[0162]

[0163] Regarding the greases No.1 to No.7 according to the embodiments and the greases No.C1 to No.C6 according to the comparative examples, the degree of generation of ultrafine particles is evaluated by a method involving measuring the concentration of ultrafine particles generated directly from the heating device.

[0164] When the heating device is located within the electrophotographic image forming apparatus, the concentration of ultrafine particles that have leaked out of the electrophotographic image forming apparatus is measured, rather than the concentration of ultrafine particles generated within the electrophotographic image forming apparatus. Therefore, the amount of ultrafine particles generated from the heating device itself cannot be measured. In view of the above, in this embodiment, in... Figure 1 The heating device 11 shown is equipped with a temperature controller (not shown) that can directly energize the heating element 23 to heat the heating element, and a rotating device (motor) (not shown) that can rotate the pressure roller 24.

[0165] Here, the temperature controller only takes out Figure 3 The heating element 23 in the electrophotographic image forming apparatus shown is obtained through an energization control circuit, and the heating element 23 can be controlled to a desired temperature. Furthermore, the rotating device can rotate the pressure roller 24 at a predetermined circumferential speed (number of revolutions). The specific structure of the heating device 11 is described below.

[0166] A 50 μm thick polyimide film coated with PTFE on its outer surface is used as the heating film 22. The outer diameter of the heating film 22 is set to 18 mm.

[0167] The pressure roller 24 comprises a metal mandrel made of aluminum, an elastic layer made of silicone rubber, and a release layer formed of PFA tubing. The outer diameter of the pressure roller 24 is set to 20 mm, the thickness of the elastic layer is set to 3 mm, and the thickness of the release layer is set to 30 μm.

[0168] As substrate 27, an alumina substrate with a width of 7 mm, a length of 270 mm, and a thickness of 1 mm is used. Then, a strip is formed on substrate 27 by screen printing of a paste prepared by kneading silver, palladium, glass powder, and an organic binder to produce a resistance heating element 26. The resistance value of the resistance heating element 26 is set to 20 Ω at room temperature. Furthermore, a heat-resistant glass layer with a thickness of approximately 50 μm is formed as an outer coating 28, and electrodes 29 and 30 for electrical supply are attached using a screen-printed pattern of silver and palladium to produce a ceramic heater 23. As temperature sensing element 25, an external contact type thermistor is used, formed by laminating a high heat-resistant liquid crystal polymer as a support and ceramic paper as an insulating layer.

[0169] The power supplied to the resistance heating element 26 by the triac 32 is controlled by phase control, and the voltage output from the AC power supply 33 varies in 21 levels from 0% to 100% in 5% increments. Here, 100% output refers to the output when the heating element 23 is fully energized.

[0170] Then, the greases prepared in the above embodiments and comparative examples were evaluated as follows.

[0171] That is, in an environment of room temperature (23°C), a heating device in which 250 mg of the grease to be evaluated is applied to the surface of the ceramic heater 23 is placed in an internal volume of 4.5 m³. 3 In the chamber, the ceramic heater is then energized to heat the ceramic heater via a temperature controller, causing the temperature detected by the temperature sensing element 25 on the ceramic heater 23 to reach 200°C. Additionally, the pressure roller is rotated using a rotating device, causing the processing speed (circumferential speed of the pressure roller) to reach 200 mm / s. Then, the concentration of ultrafine particles in the chamber after 10 minutes from the start of energizing the ceramic heater is measured using a FastMobility Particle Sizer (FMPS) "Model 3091" (product name, manufactured by TSI) to calculate the concentration per unit volume (1 m³). 3 The number of ultrafine particles was determined. The results are shown in Table 3.

[0172] Table 3

[0173]

[0174] As can be understood from Table 3, in any one of the greases No.1 to No.3 according to Examples 1 to 3, in which 5.0% by mass of the fluoropolymer having the structure shown in formula (1) was mixed with greases No.C1 to No.C3 according to Comparative Examples 1 to 3, a significant reduction in the concentration of ultrafine particles was confirmed.

[0175] Furthermore, a comparison of the results from Examples 1 to 3 shows that the smaller the evaporation loss of the perfluoropolyether, the lower the concentration of ultrafine particles becomes.

[0176] Furthermore, the results of Example 4 show that even when the content of the fluorinated polymer having the structure shown in formula (1) in the grease is 0.1% by mass, the inhibition effect on the generation of ultrafine particles is confirmed.

[0177] Furthermore, it can be understood from the results of Examples 2, 6 and 7 that the inhibitory effect on the generation of ultrafine particles exhibited by fluoropolymers having the structure shown in formula (1) is effective for any of the perfluoropolyethers shown in formulas (2) to (4).

[0178] Meanwhile, the grease No. C4 according to Comparative Example 4 does not contain a fluoropolymer having the structure shown in formula (1), but it is able to suppress the generation of ultrafine particles to the same extent as in the examples. However, purification is required until the evaporation loss of the perfluoropolyether becomes 0.01% by mass, and this purification leads to increased costs.

[0179] Although this disclosure has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be accorded the broadest interpretation so as to cover all such modifications and equivalent structures and functions.

Claims

1. A heating device, characterized in that, It includes: Rotating components for heating; A relative member, configured to be opposite to the rotating member and together with the rotating member forming a roll gap; as well as A force-applying member is disposed inside the rotating member, has an opposing surface relative to the inner circumferential surface of the rotating member, and is configured to cause the rotating member to apply a force to the opposing member. The inner circumferential surface and the opposing surface come into contact with each other by a grease composition to form a sliding portion. The grease composition contains a base oil. The base oil contains fluoropolymers and perfluoropolyethers. The fluoropolymer has the structure shown in formula (1): Equation (1) In equation (1), R represents an alkylene group, p and q are each independently positive numbers, and p+q is the kinematic viscosity of the fluoropolymer at 40°C that satisfies 1.0 × 10⁻⁶. 3 cm 2 / s~1.0×10 5 cm 2 The value of / s; The perfluoropolyether: When the perfluoropolyether is heated from 25°C at a rate of 10°C / min under a nitrogen atmosphere, the evaporation loss at 260°C is 0.05–2.0% by mass in the thermogravimetric reduction curve. The kinematic viscosity at 40℃ is 0.5 cm⁻¹. 2 / s~15cm 2 / s, and Includes at least one perfluoropolyether selected from the group consisting of a perfluoropolyether having the structure shown in formula (2), a perfluoropolyether having the structure shown in formula (3), and a perfluoropolyether having the structure shown in formula (4): Equation (2) In equation (2), k represents a positive number, and k is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s; Equation (3) CF3-(OCF2CF2) m1 -(OCF2) n1 -CF3 In equation (3), m1 and n1 each represent positive numbers independently, and m1+n1 is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s; Equation (4) F-(CF2CF2CF2O) n2 -CF2CF3 In equation (4), n2 represents a positive number, and n2 is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s.

2. The heating device according to claim 1, The rotating component is a heating film with an annular shape. The opposing components mentioned above are pressure rollers. in, The force-applying component includes a guide member configured to guide the heating film and a heating element configured to heat the heating film, the guide member and the heating element being disposed inside the heating film. The sliding portion is formed by at least the inner circumferential surface of the heating film and the surface of the heating element opposite to the inner circumferential surface.

3. The heating device according to claim 1 or 2, wherein the content ratio of the fluoropolymer to the total mass of the grease composition is 0.1 to 10.0% by mass.

4. The heating device according to claim 1 or 2, wherein p / q in formula (1) is 0.5 to 2.

0.

5. The heating device according to claim 1 or 2, wherein the perfluoropolyether comprises a perfluoropolyether having the structure shown in formula (3) and wherein m1 / n1 is 0.5 to 2.

0.

6. The heating device according to claim 1 or 2, wherein the grease composition further comprises fine polytetrafluoroethylene particles.

7. The heating device according to claim 6, wherein, The grease composition contains the polytetrafluoroethylene fine particles in an amount of 10 to 100 parts by weight relative to 100 parts by weight of the base oil.

8. An electrophotographic image forming apparatus, characterized in that, Includes the heating device according to any one of claims 1 to 7.

9. A lubricating grease composition, characterized in that, It includes: Base oils containing fluoropolymers and perfluoropolyethers The fluoropolymer has the structure shown in formula (1): Equation (1) In equation (1), R represents an alkylene group, p and q are each independently positive numbers, and p+q is the kinematic viscosity of the fluoropolymer at 40°C that satisfies 1.0 × 10⁻⁶. 3 cm 2 / s~1.0×10 5 cm 2 The value of / s; The perfluoropolyether: When the perfluoropolyether is heated from 25°C at a rate of 10°C / min under a nitrogen atmosphere, the evaporation loss at 260°C is 0.05–2.0% by mass in the thermogravimetric reduction curve. The kinematic viscosity at 40℃ is 0.5 cm⁻¹. 2 / s~15cm 2 / s, and Includes at least one perfluoropolyether selected from the group consisting of a perfluoropolyether having the structure shown in formula (2), a perfluoropolyether having the structure shown in formula (3), and a perfluoropolyether having the structure shown in formula (4): Equation (2) In equation (2), k represents a positive number, and k is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s; Equation (3) CF3-(OCF2CF2) m1 -(OCF2) n1 -CF3 In equation (3), m1 and n1 each independently represent positive numbers, and m1+n1 is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s; Equation (4) F-(CF2CF2CF2O) n2 -CF2CF3 In equation (4), n2 represents a positive number, and n2 is the kinematic viscosity of the perfluoropolyether at 40°C that satisfies 0.5 cm⁻¹. 2 / s~15cm 2 The value of / s.

10. The grease composition according to claim 9, wherein the fluoropolymer content relative to the total mass of the grease composition is 0.1 to 10.0% by mass.

11. The grease composition according to claim 9 or 10, wherein p / q in formula (1) is 0.5 to 2.

0.

12. The grease composition according to claim 9 or 10, wherein the perfluoropolyether comprises a perfluoropolyether having the structure shown in formula (3) and wherein m1 / n1 is 0.5 to 2.

0.

13. The grease composition according to claim 9 or 10, further comprising fine polytetrafluoroethylene particles.

14. The grease composition according to claim 13, wherein the polytetrafluoroethylene fine particles are contained in an amount of 10 to 100 parts by weight relative to 100 parts by weight of the base oil.

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