JP2023143791A - Grease composition, heating device, and electrophotographic image forming apparatus - Google Patents

Abstract

To provide a heating device that can prevent the generation of ultrafine particles itself which is resulting from grease.SOLUTION: A heating device has: a rotating body for heating; an opposing member that is arranged opposite to the rotating body and forms a nip part with the rotating body; and an urging member that is arranged inside the rotating body, has an opposing surface to an inner peripheral surface of the rotating body, and urges the rotating body against the opposing member. The inner peripheral surface and the opposing surface are in contact with each other with a grease composition therebetween to form a slide part. The grease composition includes base oil. The base oil includes a fluoropolymer having a specific structure, and perfluoropolyether having a specific kinematic viscosity and a specific evaporation loss and having a specific structure.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to grease compositions, heating devices, and electrophotographic imaging devices.

In an electrophotographic image forming apparatus (hereinafter also referred to as an "image forming apparatus") that uses an electrophotographic process, a toner image formed on a photoreceptor with toner is transferred onto a recording medium and then passed through a heating device. By doing so, it is fixed (fixed) on the recording medium. As a heating device, a contact-type heating device is widely used, which is a fixing member heated to a predetermined fixing temperature by a heating member, and fixes an unfixed toner image formed on a recording medium as a fixed image by contact heating. It is used. Typical heating devices include film heating type heating devices described in Patent Document 1 and Patent Document 2.
When a film heating type heating device is driven, the film rubs against the heating member while receiving heat from the heating member. In order to reduce friction, a heat-resistant lubricant is used between the film and the heating member. Note that as the lubricant, fluorine-based oil or fluorine-based grease, which generally has high heat resistance, is used. Specifically, as the lubricant, fluorine-based grease or silicone oil is used in Patent Document 1, and fluorine-based grease or the like is used in Patent Document 2.

By the way, in an electrophotographic image forming apparatus equipped with a heat fixing device that heats a recording material carrying a toner image, the toner and grease are Ultrafine particles may be generated. Patent Document 3 discloses an electrophotographic image forming apparatus that can prevent such ultrafine particles from being released outside the electrophotographic image forming apparatus. Specifically, it includes a detection unit for ultrafine particles having a first particle size and a detection unit for ultrafine particles having a second particle size larger than the first particle size, and the detection result of the detection unit indicates An electrophotographic image forming apparatus is disclosed that executes control to suppress release of ultrafine particles to the outside of the apparatus based on information on the amount of ultrafine particles.

Japanese Patent Application Publication No. 05-027619 Japanese Patent Application Publication No. 08-076636 JP2020-020965A Japanese Patent Application Publication No. 02-123385 Japanese Patent Application Publication No. 04-044075

According to the electrophotographic image forming apparatus according to Patent Document 3, it is possible to certainly prevent ultrafine particles from being released outside the apparatus. However, installing a detection section for ultrafine particles and implementing a control section for reducing the amount of ultrafine particles may lead to an increase in size and cost of the electrophotographic image forming apparatus.

At least one aspect of the present disclosure is directed to providing a heating device and an electrophotographic image forming apparatus that can prevent the generation of ultrafine particles caused by grease. Furthermore, at least one aspect of the present disclosure is directed to providing a grease composition that can prevent the generation of ultrafine particles even when heated.

According to at least one aspect of the present disclosure,
A rotating body for heating,
a facing member disposed opposite to the rotating body and forming a nip portion together with the rotating body;
A heating device comprising: a biasing member disposed inside the rotary body, having a surface facing an inner circumferential surface of the rotary body, and biasing the rotary body toward the opposing member,
The inner circumferential surface and the opposing surface are in contact with each other via a grease composition to constitute a sliding part,
The grease composition includes a base oil;
The base oil includes a fluoropolymer and a perfluoropolyether,
The fluoropolymer has a structure represented by the following structural formula (1),
The perfluoropolyether is
The evaporation loss at 260°C in the thermogravimetric reduction curve obtained when the temperature is raised from 25°C at a rate of 10°C/min in a nitrogen atmosphere is 0.05% by mass or more and 2.0% by mass or less,
The kinematic viscosity at a temperature of 40° C. is 50 to 1500 cSt (0.5 to 15 cm ² /s), and
A perfluoropolyether having a structure represented by the following Structural Formula (2), a perfluoropolyether having a structure represented by the following Structural Formula (3), and a perfluoropolyether having a structure represented by the following Structural Formula (4). A heating device is provided comprising at least one perfluoropolyether selected from the group consisting of ethers:

(In Structural Formula (1), R represents an alkylene group, p and q each independently represent a positive number, and p+q represents that the kinematic viscosity of the fluoropolymer at a temperature of 40° C. is 1.0×10 ⁵ ~1.0×10 ⁷ cSt (1.0×10 ³ to 1.0×10 ⁵ cm ² /s).)

(In structural formula (2), k represents a positive number, and k is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). .)

(In structural formula (3), m1 and n1 each independently represent a positive ^number ; ).

(In structural formula (4), n2 represents a positive number, and n2 is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). ).

Further, according to at least one aspect of the present disclosure, there is provided an electrophotographic image forming apparatus having the above heating device.

Further, according to at least one aspect of the present disclosure,
Contains base oil,
The base oil includes a fluoropolymer and a perfluoropolyether,
The fluoropolymer has a structure represented by the following structural formula (1),
The perfluoropolyether is
The evaporation loss at 260°C in the thermogravimetric reduction curve obtained when the temperature is raised from 25°C at a rate of 10°C/min in a nitrogen atmosphere is 0.05% by mass or more and 2.0% by mass or less,
The kinematic viscosity at a temperature of 40° C. is 50 to 1500 cSt (0.5 to 15 cm ² /s), and
A perfluoropolyether having a structure represented by the following Structural Formula (2), a perfluoropolyether having a structure represented by the following Structural Formula (3), and a perfluoropolyether having a structure represented by the following Structural Formula (4). A grease composition is provided comprising at least one perfluoropolyether selected from the group consisting of ethers:

(In Structural Formula (1), R represents an alkylene group, p and q each independently represent a positive number, and p+q represents that the kinematic viscosity of the fluoropolymer at a temperature of 40° C. is 1.0×10 ⁵ ~1.0×10 ⁷ cSt (1.0×10 ³ to 1.0×10 ⁵ cm ² /s).)

(In structural formula (2), k represents a positive number, and k is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). .)

(In structural formula (3), m1 and n1 each independently represent a positive ^number ; ).

(In structural formula (4), n2 represents a positive number, and n2 is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). ).

According to at least one aspect of the present disclosure, it is possible to obtain a heating device and an electrophotographic image forming apparatus that can prevent the generation of ultrafine particles caused by grease. Furthermore, according to at least one aspect of the present disclosure, it is possible to obtain a grease composition that can prevent the generation of ultrafine particles even when heated.

FIG. 1 is a schematic cross-sectional view of a heating device having a heating sliding portion according to one aspect of the present disclosure. FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to one aspect of the present disclosure. FIG. 2 is a front view of a heating body and a schematic diagram showing an energization control circuit according to one embodiment of the present disclosure. FIG. 2 is a schematic diagram showing how a fluoropolymer according to one embodiment of the present disclosure is adsorbed onto the surface of a heating body or the inner peripheral surface of a heating film. FIG. 1 is a schematic cross-sectional view of a heating device having a pressure pad according to one aspect of the present disclosure. FIG. 2 is a schematic cross-sectional view of a heating device having a pressurized sliding portion according to one aspect of the present disclosure. FIG. 1 is a schematic cross-sectional view of a heating device having an intermediate rotating body according to one embodiment of the present disclosure.

Preferred embodiments of the present disclosure will be described below.

<Electrophotographic image forming apparatus>
FIG. 2 is a schematic cross-sectional view of an image forming apparatus equipped with a heating device according to one embodiment of the present disclosure. This image forming apparatus is a laser beam printer that forms an image on a recording medium P using a transfer electrophotographic process.
Reference numeral 1 denotes an electrophotographic photosensitive drum (hereinafter referred to as "drum") as an image carrier in the image forming section, which is rotated clockwise (in the direction of the arrow) at a predetermined circumferential speed (process speed). Reference numeral 2 denotes a charging means such as a contact charging roller, which uniformly charges the surface of the drum 1 to a predetermined polarity and potential (primary charging). 3 is a laser beam scanner as an image exposure means. A laser beam L that is on/off modulated is output to scan the charged surface of the drum 1 in response to a time-series electric digital pixel signal of target image information input from an external device such as an image scanner or computer (not shown). Expose (irradiate). This scanning exposure removes the electric charges on the exposed bright areas on the surface of the drum 1, and an electrostatic latent image corresponding to the target image information is formed on the surface of the drum 1. A developing device 4 supplies recording material (toner) from a 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 as a transferable toner image. do. In the case of laser beam printers, a reversal development method is generally used in which toner is attached to the brightly exposed areas of an electrostatic latent image for development.

Recording media P such as paper are stacked and stored in a paper feed cassette 5. The paper feed roller 6 is driven based on the paper feed start signal, and the recording media P in the paper feed cassette 5 are separated and fed one by one. Then, the recording medium P passes through the registration rollers 7 and the sheet path 8a, and is delivered at a predetermined timing to the transfer site T, which is the abutting nip between the drum 1 and the transfer roller 9, which is a contact-type rotary transfer member. will be introduced in That is, when the leading edge of the toner image on the drum 1 reaches the transfer site T, the recording medium P is conveyed by the registration rollers 7 so that the leading edge of the recording medium P also reaches the transfer site T. controlled.
The recording medium P introduced into the transfer site T is conveyed while being held therebetween. During this time, a predetermined controlled transfer voltage (transfer bias) is applied to the transfer roller 9 from a transfer bias application power source (not shown). Note that the transfer roller 9 and applied transfer voltage control will be described later. By applying a transfer bias having a polarity opposite to that of the toner to the transfer roller 9, the toner image formed on the surface of the drum 1 at the transfer portion T is electrostatically transferred onto the surface of the recording medium P. After the recording medium P to which the toner image has been transferred is separated from the drum 1, it is conveyed and introduced into the heating device 11 through the sheet path 8b, where the toner image is subjected to heating and pressure fixing processing. On the other hand, after the recording medium has been separated (after the toner image has been transferred to the recording medium P), the cleaning device 10 removes residual toner, paper dust, etc. from the surface of the drum 1, and the surface is repeatedly used for image formation. The recording medium P that has passed through the heating device 11 is guided toward the sheet path 8c and is discharged from the paper discharge port 13 onto the paper discharge tray 14.

As the transfer roller 9, for example, an elastic roller including a conductive core metal 9b made of stainless steel (SUS) or Fe, and a semiconductive elastic layer 9a covering the outer peripheral surface of the core metal is used. Can be used. The semiconductive elastic layer 9a is preferably adjusted to have a resistance value of about 1.0×10 ⁶ to 1.0×10 ¹⁰ Ω using an electronically conductive agent or an ionically conductive agent such as carbon black, for example. As a non-limiting specific example of the structure of such a transfer roller, for example, conductivity obtained by reacting the core bar 9b with NBR rubber and a surfactant, etc., which coat the outer circumferential surface of the core bar 9b. For example, an ion conductive elastic roller having an elastic layer 9a having the above-mentioned elastic layer 9a may be mentioned. Further, a preferable resistance value of the transfer roller is in the range of 1×10 ⁸ to 5×10 ⁸ Ω. This value is calculated when a voltage of 2 kV is applied between the core metal of the transfer roller and the metal drum while the transfer roller is pressed against the metal drum with a load of 500gf (4.90N). It is the resistance value.

The resistance value of the transfer roller 9 tends to fluctuate depending on the temperature and humidity of the atmospheric environment, and the fluctuation in the resistance of the transfer roller 9 causes transfer defects, paper marks, and the like. Therefore, in order to prevent transfer defects and paper marks caused by resistance fluctuations of the transfer roller 9, the resistance value of the transfer roller 9 is measured, and the transfer voltage applied to the transfer roller 9 is adjusted according to the measurement result. Appropriate control (applied transfer voltage control) is preferable.
An example of applied transfer voltage control is ATVC control (Active Transfer Voltage Control) disclosed in Patent Document 4. ATVC control is a means of optimizing the transfer bias applied to the transfer roller during transfer, and is intended to prevent transfer defects and paper marks from occurring. For such a transfer bias, a constant current bias is applied from the transfer roller 9 to the drum 1 during the pre-rotation process of the image forming apparatus, and the resistance value of the transfer roller 9 is detected from the bias value. Then, during transfer in the printing process, a transfer bias corresponding to the resistance value is applied to the transfer roller 9. Also in this embodiment, it is preferable to use the ATVC control described above.

<Heating device>
Next, a heating device according to one aspect of the present disclosure will be described. The heating device according to this embodiment includes: a heating rotating body; a facing member disposed opposite to the rotating body and forming a nip portion together with the rotating body; It has a biasing member that has a surface facing the inner circumferential surface and biases the rotating body toward the opposing member. First, a description will be given by taking as an example a film heating type heating device that has a sliding part inside a heating rotating body that is directly heated from a heating source. FIG. 1 is a schematic cross-sectional view of a film heating type heating device 11 according to one embodiment of the present disclosure. This heating device is, for example, a so-called tensionless type heating device disclosed in Patent Document 5. The heating device 11 includes a heating film unit 15 including a rotating body for heating, and a pressure roller 24 as a pressure member.

[Heating film unit]
The heating device 11 according to one aspect of the present disclosure uses an endless heating film (heat-resistant fixing film) 22 as a heating rotating body that is directly heated from a heat source (hereinafter also referred to as a “heating body”). ing. Thereby, the heat capacity can be reduced and quick start performance can be improved. In the heating device 11 in this embodiment, at least a part of the circumference of the heating film 22 is always in a tension-free state (no tension is applied), and the heating film 22 is driven by rotation of the pressure roller 24. It is configured to be rotationally driven by force. As shown in FIG. 1, the heating film unit 15 includes a heating film 22, a stay 21, a U-shaped metal plate 20, and a heating body (heater) 23.

(heating film)
The heating film 22 is fitted onto a stay 21 that is a guide member that guides the heating body 23 and the heating film 22 . The inner circumferential length of the heating film 22 is greater than the outer circumferential length of the stay 21 including the heating body 23 by, for example, about 3 mm. Therefore, the heating film 22 is fitted onto the stay 21 with a margin in circumference.
The thickness of the heating film 22 is preferably 100 μm or less, more preferably 20 μm or more and 50 μm or less, from the viewpoint of heat capacity and quick start performance. As the heating film 22, a single layer film of heat resistant PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), etc. can be used. Alternatively, the heating film 22 may be a composite layer made of polyimide, polyamideimide, PEEK (polyetheretherketone), PES (polyethersulfone), PPS (polyphenylene sulfide), etc., coated on the outer peripheral surface with PTFE, PFA, FEP, etc. Film can also be used.

(Guide member, backup member)
The stay 21 is a film guide serving as a guide member, and is made of a heat-resistant and rigid member that also serves to hold the heating body 23 and guide the heating film 22. Specifically, the stay 21 is made of a highly heat-resistant resin such as polyimide, polyamideimide, PEEK, PPS, or liquid crystal polymer, or a composite material of these resins and ceramics, metal, glass, or the like. In the heating device shown in FIG. 1, the stay 21 also serves as a biasing member that biases the heating film 22 against the pressure roller 24. Further, the U-shaped metal sheet 20 is a backup member that reinforces the stay 21, and is made of a rigid member made of metal such as stainless steel (SUS) or iron. The heating body 23 is disposed on the lower surface of the stay 21 along the longitudinal direction of the stay (the direction that intersects the conveyance direction of the recording medium).

(heating body)
The heating body 23 is generally a heater such as a ceramic heater. In the heating device shown in FIG. 1, the heating body 23 also serves as a biasing member that biases the heating film 22 against the pressure roller 24. FIG. 3 is a front view of the heating body 23 and a schematic diagram showing a circuit that performs energization control according to one aspect of the present disclosure. The heating body 23 is provided on a substrate 27 that is a material to be heated and has heat resistance, insulation properties, and good thermal conductivity. The substrate 27 is an elongated member whose longitudinal direction is perpendicular to the conveyance direction a of the recording medium. That is, a resistance heating element 26 is provided on the surface (film sliding surface) side of the substrate 27 along the longitudinal direction of the substrate. The heating element 23 includes a heat-resistant overcoat layer 28 that protects the surface of the heating element on which the resistance heating element 26 is formed, and power feeding electrodes 29 and 30 at the longitudinal ends of the resistance heating element 26. As a whole, it constitutes a heating element with a low heat capacity.

The resistance heating element 26 of this embodiment is formed by screen printing a paste prepared by kneading silver, palladium, glass powder (inorganic binder), and an organic binder in the form of a strip on a substrate 27. You can get it. As the resistance heating element 26, an electrical resistance material such as RuO ₂ or Ta ₂ N may be used in addition to silver palladium (Ag/Pd).

The substrate 27 is made of a heat-resistant and insulating material, for example, a ceramic material such as alumina or aluminum nitride. The overcoat layer 28 ensures electrical insulation between the resistance heating element 26 and the surface of the heating element 23 and slidability of the heating film 22.

FIG. 3 shows a plan view of the heating body 23 viewed from the back surface (non-film sliding surface). As the temperature measuring element 25 that detects the temperature of the heating body 23, for example, an external contact type thermistor that is separated from the heating body 23 can be used. The temperature measuring element 25 is constructed by, for example, providing a heat insulating layer on a support, fixing a chip thermistor element on the heat insulating layer, and applying a predetermined pressure to the back surface of the heating element with the element facing downward (back side of the heating element). The structure is such that it comes into contact with the Note that the temperature measuring element 25 is provided within the minimum paper passing area and communicates with the CPU 31. The surface of the overcoat layer 28 covering the heating body 23 is exposed downward and is held and fixed on the lower surface side of the stay 21. By employing the above configuration, the entire heating body can be made to have a lower heat capacity than the heat roller type, and a quick start is possible.

Here, the temperature of the heating element 23 is raised by the resistance heating element 26 generating heat over its entire length in the longitudinal direction by power feeding to the power feeding electrodes 29 and 30 at the longitudinal ends of the resistance heating element 26.
The temperature rise is detected by the temperature measuring element 25, and the output of the temperature measuring element 25 is A/D converted and taken into the CPU 31. Based on this information, the triac 32 controls the power supplied to the resistance heating element 26 by phase control, wave number control, etc., thereby controlling the temperature of the heating element 23. That is, by controlling the energization so that the temperature of the heating element 23 increases when the temperature detected by the temperature detection element 25 is lower than a predetermined set temperature, and decreases when the temperature is higher than the predetermined set temperature, the heating element 23 is heated. , maintained at a constant temperature during fusing.

In a state where the heating body 23 has risen to a predetermined temperature and the peripheral speed of rotation of the heating film 22 due to the rotation of the pressure roller 24 has stabilized, the heating body 23 and the pressure roller 24 are formed with the heating film 22 in between. A recording medium is introduced into the nip portion N from the transfer portion. Then, as the recording medium is sandwiched and conveyed through the nip portion N together with the heating film 22, the heat of the heating body 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 and fixed onto the recording medium. Then, the recording medium that has passed through the nip portion N is separated from the heating film 22 and conveyed.

[Pressure member]
The pressure roller 24, which is a pressure member, is disposed to face the heating film 22, forms a nip portion N together with the heating film 22, and is a film outer surface contact drive means for rotationally driving the heating film 22. That is, the pressure roller 24 corresponds to an opposing member for the heating film 22. The pressure roller 24 is made up of a core metal, an elastic layer, and an outermost release layer, and holds the heating film 22 between them with a predetermined pressing force by bearing means and urging means (not shown), and presses the heating film 22 against the heating body 23. is placed in pressure contact with the surface of the

The pressure roller 24 also faces the stay 21 and is rotationally driven in the direction of arrow A shown in FIG. 1 at a predetermined circumferential speed by a drive system (not shown). This rotational drive of the pressure roller 24 generates a frictional force between the pressure roller 24 and the outer surface of the heating film 22 at the nip portion N, and a rotational force acts on the heating film 22. Then, the heating film 22 rotates around the outside of the stay 21 in the direction of the arrow B while sliding, with its inner circumferential surface side in close contact with the surface (opposing surface) of the heating body 23 at the nip portion N. In this manner, in the heating device 11, the inner circumferential surface of the heating film 22 and the facing surfaces of the stay 21 and the heating body 23, which serve as biasing members, constitute a sliding portion.
A grease composition according to one embodiment of the present disclosure is applied as a lubricant to this sliding portion. As a result, as sliding parts inside the heating film, mainly a part of the heating body 23 that contacts the heating film 22 while being pressurized at the nip part N, and a part of the stay 21 that contacts the heating film 22 The resulting friction is reduced and lubricity is maintained. As a result, the heating film 22 is driven to rotate at approximately the same circumferential speed as the rotational circumferential speed of the pressure roller 24 . In addition, in FIG. 1, the sliding portion includes the inner circumferential surface of the heating film 22, a portion of the stay 21 as a biasing member that faces the inner circumferential surface, and the inner circumferential surface of the heating body 23. Although an example is shown in which the heating device is configured with two opposing surfaces, the heating device according to one embodiment of the present disclosure is not limited to this configuration.

<Grease composition>
Next, a grease composition according to one embodiment of the present disclosure will be described. A grease composition according to one embodiment of the present disclosure is a fluorine-based grease containing a fluorine-based base oil. The grease composition functions as a lubricant that reduces friction in the sliding parts between the heating film 22 and the guide member (stay) 21 and between the heating film 22 and the heating body (heater) 23. take charge That is, the inner circumferential surface of the heating film (rotating body) and the facing surfaces of the stay and the heating body, which are biasing members, are in contact with each other via the grease composition. The grease composition may be composed only of base oil, but it is preferable that it is a mixture of base oil and a fluorine-based thickener so that the base oil can be retained on the inner peripheral surface of the film for a long period of time. preferred. The grease composition according to one aspect of the present disclosure can more reliably suppress evaporation of the base oil at high temperatures when the heating device is driven by the structure of the base oil described below.

<Base oil>
The base oil contained in the grease composition according to one aspect of the present disclosure includes a perfluoropolyether and a fluoropolymer. Each component will be explained below.

(perfluoropolyether)
Perfluoropolyether is a base component of lubricants. The perfluoropolyether used has a kinematic viscosity of 50 to 1500 cSt (0.5 to 15 cm ² /s) at a temperature of 40°C. By containing perfluoropolyether having a kinematic viscosity within this range in the base oil, the viscosity of the grease composition can be reduced to suppress the grease composition from flowing out from the sliding parts and to improve smoother sliding. It can be more easily adjusted to a maintainable range. Note that in the present disclosure, kinematic viscosity is a value measured in accordance with ASTM D445: Standard test method for kinematic viscosity of transparent and opaque liquids (and calculation of dynamic viscosity). The same applies to the fluoropolymer described below.

From the viewpoint of having high heat resistance, perfluoropolyethers include perfluoropolyethers having a structure represented by the following structural formula (2), perfluoropolyethers having a structure represented by the following structural formula (3), and It contains at least one perfluoropolyether selected from the group consisting of perfluoropolyethers having a structure represented by the following structural formula (4). Among these, perfluoropolyether having a structure represented by structural formula (3) is particularly preferably used.

In structural formula (2), k represents a positive number, and k is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s).

In structural formula (3), m1 and n1 each independently represent a positive number, and m1+n1 represents the perfluoropolyether having a kinematic viscosity of 50 to 1500 cSt (0.5 to 15 cm ² /s) at a temperature of 40°C. This value satisfies the following. The value of m1/n1 is preferably 0.5 to 2.0, more preferably 0.5 to 1.5, in order to prevent an excessive increase in viscosity at low temperatures and an excessive decrease in viscosity at high temperatures. It is more preferably 0.5 to 1.0, and particularly preferably 1.0.

In structural formula (4), n2 represents a positive number, and n2 is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s).

Generally, perfluoropolyethers are highly heat resistant oils. Therefore, even if it is exposed to a high temperature of around 200° C. during heating by the heating device 11, it does not decompose, and the lubricity between the heating film 22 and the heating body 23 can be maintained. However, when a commercially available perfluoropolyether having a kinematic viscosity within the above range is used in a heating device that heats up to a high temperature of around 200°C, there may be some perfluoropolyether that tends to become ultrafine particles. That is, perfluoropolyether has a molecular weight distribution, and low molecular weight molecules in the distribution (hereinafter also referred to as "low molecular weight components") tend to become ultrafine particles. Therefore, by specifying the kinematic viscosity, which is proportional to the average molecular weight, within the above range, it is possible to increase the proportion of high molecular weight molecules that are less likely to form ultrafine particles. However, when the proportion of low molecular weight components in the molecular weight distribution is high, the amount of perfluoropolyether that tends to form ultrafine particles also increases.

Therefore, the present inventors investigated the amount of low molecular weight components that tend to form ultrafine particles contained in commercially available perfluoropolyethers by thermogravimetric analysis (TGA). That is, in TGA, the evaporation loss at 260° C. in the thermogravimetric reduction curve obtained when the temperature was raised from 25° C. at a rate of 10° C./min in a nitrogen atmosphere was investigated. As a result, the evaporation loss was in the range of 0.05% by mass or more and 2.0% by mass or less, including variations between lots.

By using a grade of perfluoropolyether with a low content of low molecular weight components, that is, a perfluoropolyether with an evaporation loss of less than 0.05% by mass according to the thermogravimetric analysis described above, ultrafine particles can be formed. The amount generated can be suppressed. However, in order to reduce the content of low molecular weight components in the perfluoropolyether, it is necessary to repeat the distillation of the perfluoropolyether, which increases the cost of the perfluoropolyether.

(fluoropolymer)
Therefore, the present inventors conducted repeated studies in order to obtain a grease composition that can prevent the generation of ultrafine particles even when perfluoropolyether with a high content of low molecular weight components is used. As a result, it has been found that using a fluoropolymer having a structure represented by the following structural formula (1) together with the above-mentioned perfluoropolyether as a base oil in a grease composition is effective because ultrafine particles caused by the low molecular weight components of the perfluoropolyether are We have found that this method is extremely effective in preventing the occurrence of. That is, the grease composition according to one embodiment of the present disclosure includes a modified perfluoropolyether represented by the following structural formula (1) as a base oil.

In the above structural formula (1), R represents an alkylene group. The alkylene group is not particularly limited, but includes, for example, an alkylene group having 6 carbon atoms. In addition, p and q each independently represent a positive number, and p+q means that the kinematic viscosity of the fluoropolymer at a temperature of 40° C. is 1.0×10 ⁵ to 1.0×10 ⁷ cSt (1.0×10 ³ to 1.0×10 ⁵ cm ² /s). In addition, the value of p/q is preferably 0.5 to 2.0 from the viewpoint of preventing an excessive increase in viscosity at low temperatures and an excessive decrease in viscosity at high temperatures, and in particular, It is preferably 0.5 to 1.0, more preferably 1.0.

Furthermore, if the kinematic viscosity of the fluoropolymer is too low, it will easily evaporate, making it difficult to obtain the effect of entangling perfluoropolyether in the base oil, which will be described later. On the other hand, if the kinematic viscosity is too high, handling becomes extremely difficult, so the kinematic viscosity of the fluoropolymer at a temperature of 40° C. needs to satisfy 1.0×10 ⁵ to 1.0×10 ⁷ cSt. An example of a fluoropolymer that satisfies these conditions is "Fluorolink PA100E" (trade name, Solvay Specialty Polymers, Inc.), in which R in structural formula (1) is a hexamethylene group (-(CH ₂ ) ₆ -). Examples include those commercially available as (manufactured by).

Regarding the reason why a grease composition containing a base oil containing a fluoropolymer having the structure represented by the above structural formula (1) together with perfluoropolyether can reduce the generation of ultrafine particles caused by perfluoropolyether. , the present inventors speculate as follows.
In the structure represented by the above structural formula (1) that the fluoropolymer has, the amide group has strong polarity. On the other hand, functional groups such as hydroxyl groups are exposed on the outermost surfaces of the surface (opposing surface) of the substrate 27 (heating body 23) and the inner peripheral surface of the heating film 22, and these functional groups also have polarity. Therefore, these functional groups interact with the amide group in the above structural formula (1). As a result, the fluoropolyether structure in the molecular chain of the fluoropolymer is located on the opposite side of the heating body 23 and the heating film 22, as shown in FIG. It will be attracted towards you. Note that FIG. 4 is a schematic diagram showing how the fluoropolymer according to one embodiment of the present disclosure is adsorbed to the surface of the heating body (substrate) or the inner peripheral surface of the heating film.

This adsorption is maintained even at high temperatures during operation of the heating device. Furthermore, the fluoropolyether structure facing outward with respect to the adsorption surface has the same structure as the perfluoropolyether represented by structural formulas (2) to (4) in the base oil, and High affinity with polyether. Therefore, the fluoropolyether structure can entangle perfluoropolyethers represented by structural formulas (2) to (4) in the base oil. As a result, the perfluoropolyethers represented by structural formulas (2) to (4) are trapped on the surfaces of the heating body 23 and the heating film 22 via the fluoropolyether structure of the fluoropolymer. As a result, the perfluoropolyether becomes difficult to evaporate, and the generation of ultrafine particles is suppressed.

In the grease composition according to one aspect of the present disclosure, the content of the fluoropolymer having the structure represented by structural formula (1) with respect to the total mass of the grease composition is 0.1% by mass or more and 10.0% by mass or less. It is preferable that it is in the range of . With such a content ratio, generation of ultrafine particles from perfluoropolyether can be effectively suppressed at low cost.

(Thickener)
Furthermore, the grease composition according to one aspect of the present disclosure may include a fluorine-based thickener. Specifically, fine particles of fluororesin such as PTFE, PFA, and FEP can be used as the fluorine-based thickener. Since these fine particles of fluororesin can be surrounded by the fluorine-based base oil, the base oil can be made difficult to flow out even under the high temperature of the heating device. In particular, from the viewpoint of durability, the thickener preferably contains PTFE fine particles (polytetrafluoroethylene fine particles). Note that the particle size of the fluororesin fine particles is preferably 50 nm to 1 μm from the viewpoint of enveloping the fluorine base oil. Here, the particle size of the fine particles of the fluororesin means the average primary particle size of the thickener observed with a SEM (scanning electron microscope).

Further, it is preferable that the mixing ratio of the fluorine-based thickener and the perfluoropolyether, which is a fluorine-based oil, be such that the amount of the fluorine-based oil is relatively large. Specifically, it is preferable to contain 10 to 100 parts by mass of a thickener per 100 parts by mass of the base oil. With such a mixing ratio, the effect of suppressing friction that occurs between the heating film, the heating body, and a portion of the stay can be more effectively exerted. Furthermore, even under the high temperature of the heating device, the grease composition is more easily retained on the inner circumferential surface of the heating film, so that the friction suppressing effect can be stably exhibited over a long period of time.

[Other embodiments of heating device]
(Embodiment using a pressure pad as a pressure member)
In the above embodiment, the explanation was given using a film heating type heating device 11 that has a sliding part on the heating side and has a pressure roller 24 as an opposing member, but a heating device according to an aspect of the present disclosure may include a pressure pad instead of a pressure roller as the opposing member. An example is a film heating type heating device 111 having a pressure pad 124 as shown in FIG. The film heating type heating device 111 having a pressure pad is the same as the film heating type heating device 11 described above except for the pressure pad 124, the film drive roller 125, and the heating film 122. That is, since the pressure pad 124 is used instead of the pressure roller 24, the heating film 122 cannot be driven. Therefore, the heating device 111 includes a film drive roller 125 to drive the heating film 122. The film drive roller 125 is driven by rotation from a motor (not shown), and can drive the heating film 122.

Here, the pressure pad 124 is composed of a pressure pad base 124a made of a rigid member such as metal such as stainless steel (SUS) or aluminum, and a pressure pad surface layer 124b formed on the pressure pad base 124a. ing. The pressure pad surface layer 124b is made of a low-friction, heat-resistant, and elastic material, and is made of heat-resistant resins such as PTFE, PFE, polyimide, polyamide-imide, and aramid, and woven fabrics made of fibers thereof. Non-woven fabric etc. can be used. Further, the pressure pad 124 is pressed against the heating film 122 by springs (not shown) at the lower portions of both longitudinal ends of the pressure pad base 124a, and forms a nip portion Nk together with the heating film 122.
Further, the film drive roller 125 is a metal core with a roughened surface in order to drive the heating film 122, and stainless steel (SUS), aluminum, or the like can be used as the metal. Further, the heating film 122 is the same as the heating film 22 except that it has a larger inner diameter than the heating film 22 because it includes the film driving roller 125 .

Similarly to the heating device 11, the heating device 111 of the film heating type having the pressure pad as described above also has the inner circumferential surface of the heating film 122 as a sliding part on the heating side and the stay 21 as a biasing member. It has a sliding portion that is constituted by a part of the portion facing the inner peripheral surface and a surface of the heating body 23 facing the inner peripheral surface. Therefore, by using the grease composition according to one embodiment of the present disclosure as a lubricant in the sliding portion, the effect of suppressing the generation of ultrafine particles can be obtained, similar to the heating device 11.

(Embodiment with pressure side sliding part)
In the above embodiments, a rotating body that is directly heated from a heat source, that is, a film heating type heating device having a sliding portion on the heating side has been described. However, the grease composition according to one embodiment of the present disclosure can be similarly applied to a rotating body that is indirectly heated from a heat source, that is, a heating device that has a sliding part that slides on the rotating body on the pressurizing side by rotation. It has the effect of As an example, a heating device 50 having a pressurized film unit shown in FIG. 6 can be mentioned.

The heating device 50 includes a pressure film unit 56 and a fixing roller 51 that is an opposing member that faces and presses against the pressure film unit 56 to form a nip portion Np. The fixing roller 51 has a heat source (heating body) 57 inside, and when the fixing roller 51 reaches a high temperature, the pressure film unit 56 is heated. That is, the pressure film unit 56 is configured to be heated indirectly from a heat source via the fixing roller 51, and the recording medium carrying the recording material is heat-treated by passing through the nip portion Np.

The fixing roller 51 has a cylindrical core metal 51a made of a metal material such as iron, stainless steel (SUS), or aluminum. A highly thermally conductive elastic layer 51b containing a thermally conductive filler such as alumina, silicon metal, silicone carbide, or silica is formed on the outer circumferential surface of the cylindrical core metal 51a using silicone rubber as a base. Further, a release layer (outermost layer) 51c mainly composed of PTFE, PFA, FEP, etc. is formed on the outer peripheral surface of the elastic layer 51b. Bearings (not shown) are fitted onto both ends of the fixing roller 51, and by fixing the bearings to the device frame, the fixing roller 51 is rotatably fixed to the device frame.

The fixing roller 51 has a built-in halogen heater 57 as a heating body. 58 is a temperature detection element that detects the surface temperature of the fixing roller 51, and a thermopile, a radiation thermometer, or the like can be used. The temperature detected by the temperature detection element 58 is fed back to the CPU (not shown), and the halogen heater 57 controls the CPU (not shown) so that the surface temperature of the fixing roller 51 detected by the temperature detection element 58 reaches a predetermined temperature. The energization is controlled by.

The pressure film unit 56 includes an endless pressure film (pressure belt) 52, a stay 53 as a guide member for the pressure film, and a metal U-shaped U-shaped back-up member for reinforcing the stay 53. It has a sheet metal 54 and a nip forming member 55. Furthermore, both ends of the stay 53 are provided with pressure film unit flanges (not shown) that regulate the longitudinal position of the pressure film.
The nip forming member 55 is formed to have a rectangular cross section, and its surface is adjusted to have a predetermined roughness. The stay 53 is molded using a heat-resistant resin material so that its cross section has a substantially inverted gutter shape, and a recess 53a formed along the longitudinal direction is formed using a heat-resistant resin material. It supports the nip forming member 55. The pressure film 52 is loosely fitted around the outer periphery of the stay 53.
The pressure film 52 has a base layer formed mainly of heat-resistant resin such as polyimide resin, PEEK, PEI (polyetherimide), stainless steel (SUS), metal such as nickel, and PFA, PTFE on the outer peripheral surface of the base layer. , and a release layer formed mainly of a fluororesin such as FEP.

The pressure film unit 56 is supported by the device frame by supporting pressure film unit flanges (not shown) at both ends of the stay 53 in the longitudinal direction. Furthermore, a pressure spring (not shown) presses the pressure film unit 56 in the direction of the fixing roller 51 via a pressure film unit flange (not shown). As a result, the nip forming member 55 and the stay 53 are pressed against the fixing roller 51 via the pressure film 52, and a nip portion Np of the heating device having the pressure film unit 56 is formed.
Further, the inner peripheral surface of the pressure film 52 slides on the nip forming member 55 and the stay 53. That is, in the heating device shown in FIG. 6, the sliding portion faces the inner circumferential surface of the pressure film 52, the surface facing the inner circumferential surface of the nip forming member 55, and the inner circumferential surface of the stay 53. It consists of a part of the Then, in order to reduce friction in the sliding portion, a grease composition according to one embodiment of the present disclosure is applied as a lubricant to the inner circumferential surface of the pressure film 52.

In the heating device 50, a motor (not shown) is rotationally driven in response to a print command, and the rotation of the output shaft of the drive motor is transmitted to the cylindrical core metal 51a of the fixing roller 51 via a predetermined gear mechanism (not shown). communicated. As a result, the fixing roller 51 is rotated in the direction of the arrow, and the pressure film 52 is also driven to rotate. Further, along with the print command, the CPU (not shown) starts energizing the halogen heater 57, and controls the energization so that the temperature detection element 58 reaches a predetermined temperature. Then, by passing the recording medium through the nip portion Np, the recording medium is subjected to heat fixing processing, similar to a film heating type heating device.

In the heating device 50 having the pressure film unit 56 as described above, the pressure film unit 56 receives heat from the fixing roller 51 heated by the heating body 57 and reaches a high temperature. Therefore, the lubricant applied to the inner circumferential surface of the pressure film 52 is also exposed to high temperatures. By using the grease composition according to one embodiment of the present disclosure as a lubricant, the generation of ultrafine particles due to evaporation of the lubricant and the adhesion of ultrafine particles inside the image forming apparatus can be suppressed, similar to a film heating type heating device. You can get the desired effect.

(Embodiment with intermediate rotating body)
Further, as an example of another heating device, a heating device 211 having an intermediate rotating body 224 as shown in FIG. 7 can be mentioned. That is, it has an intermediate rotary body 224 as an opposing member that is pressed and heated by the heating film unit 15, and the intermediate rotary body 224 is in pressure contact with the pressure film unit 56, thereby forming a nip portion Np. be.
Here, the intermediate rotating body 224 has the same configuration as the pressure roller 24 except that it has a heat storage layer having a heat conductive filler between the release layer and the elastic layer on the outermost surface. The heat storage layer is made of silicone rubber containing a filler with high thermal conductivity and high heat capacity (for example, alumina, silicon carbide, silica), and can store heat from the heating film unit 15. As a result, by passing the recording medium through the nip portion Np formed by the intermediate rotary body 224 and the pressure film unit 56, the recording medium is subjected to heat fixing processing, similar to a film heating type heating device.
Even in the heating device having such a configuration, the grease composition according to one embodiment of the present disclosure can be applied as a lubricant to at least one of the heating film unit 15 and the pressure film unit 56. As a result, similar to a heating device using a film heating method or a heating device using a pressurized film unit, it is possible to suppress the generation of ultrafine particles due to evaporation of lubricant and the adhesion of ultrafine particles inside the image forming device. .

Although the image forming apparatus of this embodiment has been described using an electrophotographic process using toner as a recording material, it is also possible to use an image forming apparatus using a recording material other than toner. Good too. For example, it goes without saying that similar effects can be achieved even in an inkjet type image forming apparatus using ink as a recording material, as long as it has a heating device that heats a recording medium on which a recording material is placed.

As explained above, according to the heating device using the grease composition of the present disclosure, evaporation of perfluoropolyether in the grease composition during operation of the heating device can be achieved while suppressing cost increase and device enlargement. can be suppressed. As a result, generation of ultrafine particles can be suppressed.

Hereinafter, the specific structure of the fluorine-based grease composition of the present disclosure and the effects when used in a heating device will be explained. In the following description, "parts" means "parts by mass" unless otherwise specified. The kinematic viscosity of the fluoropolymer and perfluoropolyether is a value measured in accordance with ASTM D445 at a temperature of 40°C. In addition, the evaporation loss of perfluoropolyether is obtained when the temperature is raised from 25°C at a rate of 10°C/min in a nitrogen atmosphere using a TGA device (product name: TGA/SDTA851e, manufactured by METTLER TOLEDO). This is the evaporation loss at 260°C in the thermogravimetric loss curve.

[Example 1]
"Fomblin M60" (trade name, manufactured by Solvay Specialty Chemicals) having the structure represented by the structural formula (3) was distilled at a temperature of 240° C. until the evaporation loss was 2.00% by mass. Perfluoropolyether No. 3 has a kinematic viscosity of 310 cSt at a temperature of 40°C. 1 was prepared. Note that "Fomblin M60" had m1/n1 in structural formula (3) of 0.8 to 0.9.
Furthermore, "Fluorolink PA100E" (trade name, manufactured by Solvay Specialty Polymers) was prepared as a fluoropolymer according to one aspect of the present disclosure. Note that "Fluorolink PA100E" has a structure represented by the above structural formula (1), R is a hexamethylene group, p/q = 1, and a kinematic viscosity at a temperature of 40 ° C. is 8.75. ×10 ⁵ cSt. Next, 5.0 parts of the fluoropolymer was diluted five times with a fluorinated solvent (trade name: Novec 7100, manufactured by 3M) to prepare a diluted solution.
Further, as a thickener, PTFE particles (trade name: Polyflon PTFE L-5F, manufactured by Daikin Industries, Ltd.) having an average primary particle diameter of 130 nm were prepared.
Next, perfluoropolyether No. prepared above was used. 70.0 parts of base grease No. 1 and 30.0 parts of the above thickener were mixed using a kneader to prepare base grease No. 1. 1 was prepared. This base grease No. The diluted solution of the above fluoropolymer was added to 95.0 parts of 1 and kneaded so that the amount of the fluoropolymer added was 5.0 parts. Thereafter, the kneaded product was left standing in a constant temperature bath maintained at a temperature of 25° C. for 48 hours, and grease No. 1 consisting of perfluoropolyether, a thickener, and a fluoropolymer was prepared. 1 was prepared.

[Example 2]
"Fomblin M60" was distilled at a temperature of 240°C until the evaporation loss was 0.70% by mass, and perfluoropolyether No. 1 with a kinematic viscosity of 320 cSt at a temperature of 40°C was obtained. 2 was prepared. The obtained perfluoropolyether No. Base grease No. 2 was used in the same manner as in Example 1, except that base grease No. 2 was used. Preparation of Grease No. 2 and Grease No. 2 was prepared.

[Example 3]
"Fomblin M60" was distilled at a temperature of 240°C until the evaporation loss was 0.05% by mass, and perfluoropolyether No. 1 with a kinematic viscosity of 350 cSt at a temperature of 40°C was obtained. 3 was prepared. The obtained perfluoropolyether No. Base grease No. 3 was used in the same manner as in Example 1 except that base grease No. 3 was used. Preparation of Grease No. 3 and Grease No. 3 was prepared.

[Example 4]
Base grease No. The diluted solution of the fluoropolymer prepared in Example 1 was added to 99.9 parts of fluoropolymer No. 2 so that the amount of the fluoropolymer added was 0.1 part. Other than that, grease No. Grease No. 2 in the same manner as above. 4 was prepared.

[Example 5]
Base grease No. The diluted solution of the fluoropolymer prepared in Example 1 was added to 90.0 parts of No. 2 so that the amount of the fluoropolymer added was 10.0 parts. Other than that, grease No. Grease No. 2 in the same manner as above. 5 was prepared.

[Example 6]
Perfluoropolyether (trade name: Krytox GPL107, manufactured by Chemours) having a structure represented by structural formula (2) was distilled at a temperature of 240° C. until the evaporation loss was 0.70% by mass. Perfluoropolyether No. 1 having a kinematic viscosity of 500 cSt at a temperature of 40°C. 4 was prepared.
Perfluoropolyether No. obtained here. Base grease No. 4 of Example 1 was used except that base grease No. 4 was used. Apply base grease No. 1 in the same manner as in step 1. 4 was prepared. Next, base grease No. The diluted solution of the fluoropolymer prepared in Example 1 was added to 95.0 parts of fluoropolymer No. 4 so that the amount of the fluoropolymer added was 5.0 parts. Other than that, grease No. Grease No. 1 in the same manner as above. 6 was prepared.

[Example 7]
Perfluoropolyether (trade name: Demnum S-200, manufactured by Daikin Corporation) having the structure represented by the structural formula (4) was distilled at a temperature of 240° C. until the evaporation loss was 0.70% by mass. Perfluoropolyether No. 2 has a kinematic viscosity of 220 cSt at a temperature of 40°C. 5 was prepared.
Perfluoropolyether No. obtained here. Base grease No. 5 of Example 1 was used except that base grease No. 5 was used. Apply base grease No. 1 in the same manner as in step 1. 5 was prepared. Next, base grease No. The diluted solution of the fluoropolymer prepared in Example 1 was added to 95.0 parts of fluoropolymer No. 5 so that the amount of the fluoropolymer added was 5.0 parts. Other than that, grease No. Grease No. 1 in the same manner as above. 7 was prepared.

[Comparative example 1]
Base grease No. Grease No. 1 according to this comparative example. It was set as C1. That is, grease No. C1 does not contain a fluoropolymer having the structure represented by Structural Formula (1).

[Comparative example 2]
Base grease No. Grease No. 2 according to this comparative example. It was set as C2. That is, grease No. C2 does not contain a fluoropolymer having the structure represented by Structural Formula (1).

[Comparative example 3]
Base grease No. Grease No. 3 according to this comparative example. It was set as C3. That is, grease No. C3 does not contain a fluoropolymer having the structure represented by Structural Formula (1).

[Comparative example 4]
Perfluoropolyether No. prepared in Example 3 3 was further distilled at a temperature of 240° C. for 60 minutes to obtain perfluoropolyether No. 3 with an evaporation loss of 0.01% by mass. C1 was prepared. Perfluoropolyether No. The kinematic viscosity of C1 at a temperature of 40° C. was 370 cSt. The obtained perfluoropolyether No. Except for using C1, base grease No. Apply base grease No. 1 in the same manner as in step 1. C1 was prepared. Then, the obtained base grease No. Grease No. C1 according to this comparative example was used as it was. It was set as C4. Therefore, grease No. C4 does not contain a fluoropolymer having the structure represented by Structural Formula (1).

[Comparative example 5]
Base grease No. Grease No. 4 according to this comparative example. It was set as C5. That is, grease No. C5 does not contain a fluoropolymer having the structure represented by Structural Formula (1).

[Comparative example 6]
Base grease No. Grease No. 5 according to this comparative example. It was set as C6. That is, grease No. C6 does not contain a fluoropolymer having the structure represented by Structural Formula (1).

Base grease No. 1 to 5 and C1, and Grease No. 1 to 7 and grease No. The formulations and physical properties of C1 to C6 are summarized in Tables 1 and 2.

Grease No. according to the example. Grease Nos. 1 to 7 and comparative examples. Regarding C1 to C6, the degree of generation of ultrafine particles was evaluated by a method of measuring the concentration of ultrafine particles directly generated from the heating device.
Note that when the heating device is inside the electrophotographic image forming apparatus, the concentration of ultrafine particles leaked outside the electrophotographic image forming apparatus is measured, not 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. Therefore, in this embodiment, in the heating device 11 shown in FIG. A rotating device (motor) (not shown) that can be rotated was installed.

Here, the temperature controller is only a circuit section for controlling energization to the heating body 23 in the electrophotographic image forming apparatus shown in FIG. 3, and can control the heating body 23 to a desired temperature. Further, the rotating device can rotate the pressure roller 24 to a predetermined circumferential speed (rotation speed).

Here, the specific configuration of the heating device 11 is as follows.
As the heating film 22, a polyimide film having a thickness of 50 μm and coated with PTFE on the outer peripheral surface was used. The outer diameter of the heating film 22 was 18 mm.
As the pressure roller 24, one constructed of a metal core made of aluminum, an elastic layer made of silicone rubber, and a release layer made of a PFA tube was used. The outer diameter of the pressure roller 24 was 20 mm, the thickness of the elastic layer was 3 mm, and the thickness of the release layer was 30 μm.
The substrate 27 was an alumina substrate with a width of 7 mm, a length of 270 mm, and a thickness of 1 mm. Then, a paste prepared by kneading silver, palladium, glass powder, and an organic binder was formed into a linear strip shape on the substrate 27 by screen printing, thereby producing a resistance heating element 26. The resistance value of the resistance heating element 26 was set to 20Ω at room temperature. Furthermore, a heat-resistant glass layer with a thickness of about 50 μm was formed as an overcoat layer 28, and power supply electrodes 29 and 30 were attached using a silver-palladium screen printing pattern to produce a ceramic heater 23. As the temperature measuring element 25, an external contact type thermistor was used, which was constructed by laminating a highly heat-resistant liquid crystal polymer as a support and ceramic paper as a heat insulating layer.
The power supplied to the resistance heating element 26 by the triac 32 was controlled by phase control, and the voltage output from the AC power source 33 was varied in 21 steps in 5% increments from 0 to 100%. Here, 100% output means the output when the heating body 23 is fully energized.

The greases prepared in each of the above Examples and Comparative Examples were evaluated as follows.
That is, a heating device in which 250 mg of the grease to be evaluated was coated on the surface of the ceramic heater 23 was placed in a chamber with an internal volume of 4.5 m ³ in a room temperature (23° C.) environment. Then, the ceramic heater was heated by applying electricity using a temperature controller so that the temperature detected by the temperature measuring element 25 on the ceramic heater 23 was 200°C. Further, the pressure roller 24 was rotated using a rotating device so that the process speed (peripheral speed of the pressure roller) was 200 mm/sec. Then, the concentration of ultrafine particles in the chamber 10 minutes after the start of electricity supply to the ceramic heater was measured using a Fast Mobility Particle Sizer (FMPS) "Model 3091" (trade name, manufactured by TSI). The number of ultrafine particles per unit volume (1 m ³ ) was calculated. The results are shown in Table 3.

As can be seen from Table 3, grease No. 1 according to Comparative Examples 1 to 3. Grease No. 1 according to Examples 1 to 3, in which 5.0% by mass of a fluoropolymer having a structure represented by structural formula (1) was mixed in each of C1 to C3. In all samples 1 to 3, a significant decrease in the concentration of ultrafine particles was observed.
Further, from a comparison of the results of Examples 1 to 3, it can be seen that the smaller the evaporation loss of perfluoropolyether, the lower the ultrafine particle concentration.
Furthermore, from the results of Example 4, even when the content of the fluoropolymer having the structure represented by structural formula (1) in the grease was 0.1% by mass, the effect of suppressing the generation of ultrafine particles was observed. .
Furthermore, from the results of Examples 2, 6 and 7, the effect of suppressing the generation of ultrafine particles by the fluoropolymer having the structure represented by Structural Formula (1) is lower than that of the perfluoropolymer having the structure represented by Structural Formulas (2) to (4). It was found to be effective for all polyethers.
On the other hand, grease No. 4 according to Comparative Example 4. Although C4 does not contain a fluoropolymer having the structure represented by structural formula (1), the generation of ultrafine particles was suppressed to the same extent as in Examples. However, it is necessary to purify the perfluoropolyether until the evaporation loss is 0.01% by mass, and such purification results in an increase in cost.

The present invention includes the following configurations.
[Configuration 1]
A rotating body for heating,
a facing member disposed opposite to the rotating body and forming a nip portion together with the rotating body;
A heating device comprising: a biasing member disposed inside the rotary body, having a surface facing an inner circumferential surface of the rotary body, and biasing the rotary body toward the opposing member,
The inner circumferential surface and the opposing surface are in contact with each other via a grease composition to constitute a sliding part,
The grease composition includes a base oil;
The base oil includes a fluoropolymer and a perfluoropolyether,
The fluoropolymer has a structure represented by the following structural formula (1),
The perfluoropolyether is
The evaporation loss at 260°C in the thermogravimetric reduction curve obtained when the temperature is raised from 25°C at a rate of 10°C/min in a nitrogen atmosphere is 0.05% by mass or more and 2.0% by mass or less,
The kinematic viscosity at a temperature of 40° C. is 50 to 1500 cSt (0.5 to 15 cm ² /s), and
A perfluoropolyether having a structure represented by the following Structural Formula (2), a perfluoropolyether having a structure represented by the following Structural Formula (3), and a perfluoropolyether having a structure represented by the following Structural Formula (4). A heating device comprising at least one perfluoropolyether selected from the group consisting of ethers:

(In Structural Formula (1), R represents an alkylene group, p and q each independently represent a positive number, and p+q represents that the kinematic viscosity of the fluoropolymer at a temperature of 40° C. is 1.0×10 ⁵ ~1.0×10 ⁷ cSt (1.0×10 ³ to 1.0×10 ⁵ cm ² /s).)

(In structural formula (2), k represents a positive number, and k is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). .)

(In structural formula (3), m1 and n1 each independently represent a positive ^number ; ).

(In structural formula (4), n2 represents a positive number, and n2 is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). ).

[Configuration 2]
The rotating body is an endless heating film,
The opposing member is a pressure roller,
The biasing member includes a guide member disposed inside the heating film that guides the heating film, and a heating body that heats the heating film,
The heating device according to configuration 1, wherein the sliding portion is comprised of at least an inner circumferential surface of the heating film and a surface facing the inner circumferential surface of the heating body.
[Configuration 3]
The heating device according to configuration 1 or 2, wherein a content ratio of the fluoropolymer to the total mass of the grease composition is 0.1% by mass or more and 10.0% by mass or less.
[Configuration 4]
The heating device according to any one of configurations 1 to 3, wherein p/q in structural formula (1) is 0.5 to 2.0.
[Configuration 5]
Any of configurations 1 to 4, wherein the perfluoropolyether has a structure represented by the structural formula (3) and m1/n1 is 0.5 to 2.0. The heating device described in Crab.
[Configuration 6]
The heating device according to any one of configurations 1 to 5, wherein the grease composition further contains polytetrafluoroethylene fine particles.
[Configuration 7]
The heating device according to configuration 6, wherein the grease composition contains 10 to 100 parts by mass of the polytetrafluoroethylene fine particles based on 100 parts by mass of the base oil.
[Configuration 8]
An electrophotographic image forming apparatus comprising the heating device according to any one of Structures 1 to 7.

[Configuration 9]
Contains base oil,
The base oil includes a fluoropolymer and a perfluoropolyether,
The fluoropolymer has a structure represented by the following structural formula (1),
The perfluoropolyether is
The evaporation loss at 260°C in the thermogravimetric reduction curve obtained when the temperature is raised from 25°C at a rate of 10°C/min in a nitrogen atmosphere is 0.05% by mass or more and 2.0% by mass or less,
The kinematic viscosity at a temperature of 40° C. is 50 to 1500 cSt (0.5 to 15 cm ² /s), and
A perfluoropolyether having a structure represented by the following Structural Formula (2), a perfluoropolyether having a structure represented by the following Structural Formula (3), and a perfluoropolyether having a structure represented by the following Structural Formula (4). A grease composition comprising at least one perfluoropolyether selected from the group consisting of ethers:

(In Structural Formula (1), R represents an alkylene group, p and q each independently represent a positive number, and p+q represents that the kinematic viscosity of the fluoropolymer at a temperature of 40° C. is 1.0×10 ⁵ ~1.0×10 ⁷ cSt (1.0×10 ³ to 1.0×10 ⁵ cm ² /s).)

(In structural formula (2), k represents a positive number, and k is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). .)

(In structural formula (3), m1 and n1 each independently represent a positive ^number ; ).

(In structural formula (4), n2 represents a positive number, and n2 is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). ).

[Configuration 10]
The grease composition according to configuration 9, wherein the content ratio of the fluoropolymer to the total mass of the grease composition is 0.1% by mass or more and 10.0% by mass or less.
[Configuration 11]
The grease composition according to configuration 9 or 10, wherein p/q in the structural formula (1) is 0.5 to 2.0.
[Configuration 12]
Any of Structures 9 to 11, wherein the perfluoropolyether has a structure represented by the structural formula (3) and m1/n1 is 0.5 to 2.0. A grease composition according to claim 1.
[Configuration 13]
The grease composition according to any one of structures 9 to 12, wherein the grease composition further contains polytetrafluoroethylene fine particles.
[Configuration 14]
The grease composition according to configuration 13, wherein the grease composition contains 10 to 100 parts by mass of the polytetrafluoroethylene fine particles based on 100 parts by mass of the base oil.

11... Film heating type heating device 21... Stay (film guide)
22... Heating film (heat-resistant fixing film)
23... Heating body (ceramic heater)
24... Pressure roller N... Nip portion 50... Heating device 51 having a pressure film unit... Fixing roller 52... Pressure film 57... Heating body (halogen heater)
Np...Nip part 111...Film heating type heating device 122 having a pressure pad...Fixing film 124...Pressure pad Nk...Nip part 221...Heating having an intermediate rotating body Device 224... intermediate rotating body

Claims (14)

A rotating body for heating,
a facing member disposed opposite to the rotating body and forming a nip portion together with the rotating body;
A heating device comprising: a biasing member disposed inside the rotary body, having a surface facing an inner circumferential surface of the rotary body, and biasing the rotary body toward the opposing member,
The inner circumferential surface and the opposing surface are in contact with each other via a grease composition to constitute a sliding part,
The grease composition includes a base oil;
The base oil includes a fluoropolymer and a perfluoropolyether,
The fluoropolymer has a structure represented by the following structural formula (1),
The perfluoropolyether is
The evaporation loss at 260°C in the thermogravimetric reduction curve obtained when the temperature is raised from 25°C at a rate of 10°C/min in a nitrogen atmosphere is 0.05% by mass or more and 2.0% by mass or less,
The kinematic viscosity at a temperature of 40° C. is 50 to 1500 cSt (0.5 to 15 cm ² /s), and
A perfluoropolyether having a structure represented by the following Structural Formula (2), a perfluoropolyether having a structure represented by the following Structural Formula (3), and a perfluoropolyether having a structure represented by the following Structural Formula (4). A heating device comprising at least one perfluoropolyether selected from the group consisting of ethers:
(In Structural Formula (1), R represents an alkylene group, p and q each independently represent a positive number, and p+q represents that the kinematic viscosity of the fluoropolymer at a temperature of 40° C. is 1.0×10 ⁵ ~1.0×10 ⁷ cSt (1.0×10 ³ to 1.0×10 ⁵ cm ² /s).)

(In structural formula (2), k represents a positive number, and k is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). .)

(In structural formula (3), m1 and n1 each independently represent a positive ^number ; ).

(In structural formula (4), n2 represents a positive number, and n2 is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). ). The rotating body is an endless heating film,
The opposing member is a pressure roller,
The biasing member includes a guide member disposed inside the heating film that guides the heating film, and a heating body that heats the heating film,
The heating device according to claim 1, wherein the sliding portion includes at least an inner circumferential surface of the heating film and a surface facing the inner circumferential surface of the heating body. The heating device according to claim 1, wherein a content ratio of the fluoropolymer to the total mass of the grease composition is 0.1% by mass or more and 10.0% by mass or less. The heating device according to claim 1, wherein p/q in the structural formula (1) is 0.5 to 2.0. The perfluoropolyether according to claim 1, wherein the perfluoropolyether has a structure represented by the structural formula (3) and has a m1/n1 of 0.5 to 2.0. heating device. The heating device according to claim 1, wherein the grease composition further contains polytetrafluoroethylene fine particles. The heating device according to claim 6, wherein the grease composition contains 10 to 100 parts by mass of the polytetrafluoroethylene fine particles based on 100 parts by mass of the base oil. An electrophotographic image forming apparatus comprising the heating device according to claim 1. Contains base oil,
The base oil includes a fluoropolymer and a perfluoropolyether,
The fluoropolymer has a structure represented by the following structural formula (1),
The perfluoropolyether is
The evaporation loss at 260°C in the thermogravimetric reduction curve obtained when the temperature is raised from 25°C at a rate of 10°C/min in a nitrogen atmosphere is 0.05% by mass or more and 2.0% by mass or less,
The kinematic viscosity at a temperature of 40° C. is 50 to 1500 cSt (0.5 to 15 cm ² /s), and
A perfluoropolyether having a structure represented by the following Structural Formula (2), a perfluoropolyether having a structure represented by the following Structural Formula (3), and a perfluoropolyether having a structure represented by the following Structural Formula (4). A grease composition comprising at least one perfluoropolyether selected from the group consisting of ethers:
(In Structural Formula (1), R represents an alkylene group, p and q each independently represent a positive number, and p+q represents that the kinematic viscosity of the fluoropolymer at a temperature of 40° C. is 1.0×10 ⁵ ~1.0×10 ⁷ cSt (1.0×10 ³ to 1.0×10 ⁵ cm ² /s).)

(In structural formula (2), k represents a positive number, and k is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). .)

(In structural formula (3), m1 and n1 each independently represent a positive ^number ; ).

(In structural formula (4), n2 represents a positive number, and n2 is a value that satisfies the kinematic viscosity of the perfluoropolyether at a temperature of 40°C of 50 to 1500 cSt (0.5 to 15 cm ² /s). ). The grease composition according to claim 9, wherein the content ratio of the fluoropolymer to the total mass of the grease composition is 0.1% by mass or more and 10.0% by mass or less. The grease composition according to claim 9 or 10, wherein in the structural formula (1), p/q is 0.5 to 2.0. 11. The perfluoropolyether according to claim 9 or 10, wherein the perfluoropolyether has a structure represented by the structural formula (3) and has a m1/n1 of 0.5 to 2.0. Grease composition as described. The grease composition according to claim 9 or 10, wherein the grease composition further contains polytetrafluoroethylene fine particles. The grease composition according to claim 13, wherein the grease composition contains 10 to 100 parts by mass of the polytetrafluoroethylene fine particles based on 100 parts by mass of the base oil.

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