JP2022029238A - Grease composition and heating device - Google Patents

Abstract

To solve the problem in which: when most of a thickener, tetrafluoroethylene in fluorine-based grease becomes fibrillated, which is interposed between an inner peripheral surface of a pressure film and a slide member (nip part formation member), stick-slip occurs between the inner peripheral surface of the pressure film and the nip part formation member, and abnormal noise is generated.SOLUTION: A grease composition includes base oil, a thickener, and inorganic oxide particles. The base oil includes perfluoropolyether. In volume based particle size distribution, the grease composition has two particle number maximum values derived from the thickener and the inorganic oxide particles. The thickener has a particle size P1 at which the number of particles becomes maximum within a particle size range of 0.1 μm to 0.5 μm. The inorganic oxide particles have a particle size P2 at which the number of particles becomes maximum within a particle size range of 0.15 μm to 3.0 μm. The P1 and the P2 have the relationship of P1<P2.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a fluorinated lubricating grease composition and a heating device mounted on an image forming device such as an electrophotographic printer or a copying machine.

An external heating type fixing device is known as a heating device mounted on an electrophotographic printer, an electrophotographic copying machine, or the like. In an external heating type fixing device, a fixing roller composed of a fixing roller that contacts and heats an image on a recording material, a pressure film consisting of an endless belt, and a pressure film that contacts the inner peripheral surface of the pressure film to form the pressure film. Some have a fixing roller and a nip portion forming member for forming the fixing nip portion. The recording material carrying the unfixed toner image is heated while being sandwiched and conveyed by the fixing nip portion, whereby the unfixed toner image is fixed on the recording material.
Here, by interposing a lubricant (grease) between the inner peripheral surface of the pressure film and the nip portion forming member, the slidability between the film and the film support member is ensured. ..
Fluorine-based lubricating grease is known as a lubricating grease that exhibits extremely good stability under harsh conditions such as a high temperature environment such as a fixing heating device.
As the fluorine-based lubricating grease used for the inner peripheral surface of the pressure film, a grease having a basic composition of a base oil, a thickening agent, and an additive is used. Patent Document 1 discloses a fluorine-based lubricating grease using perfluoropolyether (PFPE) as a base oil and a tetrafluoroethylene homopolymer (PTFE) or a copolymer as a thickening agent.

Japanese Unexamined Patent Publication No. 2005-317519

In the above method, most of the tetrafluoroethylene particles of the fluorinated lubricating grease thickener interposed between the inner peripheral surface of the pressure film and the nip portion forming member may be fibrillated (fibrous). .. As a result, there is a problem that stick slip occurs between the inner peripheral surface of the pressure film and the nip portion forming member, and abnormal noise is generated.
As the heating and cooling are repeated, the base oil separates from the fibrillated thickener, which is a phenomenon called oil separation, and it is considered that the stick slip is caused by the decrease in the base oil.
In addition, the fibrillation of the thickener causes uneven distribution of grease, increases the wear force between the pressure film and the nip portion forming member, and causes uneven wear of the inner peripheral surface of the pressure film. rice field.
Further, there is a problem that the base oil flows out from the end of the pressure film due to oil removal during a long-term stop, and contaminates driving parts such as gears and shafts.

The present disclosure is a grease composition comprising a base oil, a thickener, and inorganic oxide particles.
The base oil contains perfluoropolyether and
The grease composition has a maximum number of two particles derived from each of the thickener and the inorganic oxide particles in a volume-based particle size distribution.
The thickening agent has a particle size P1 in which the number of particles is maximized in the range of a particle size of 0.1 μm to 0.5 μm.
The inorganic oxide particles have a particle diameter P2 that maximizes the number of particles in the range of a particle diameter of 0.15 μm to 3.0 μm.
A grease composition in which the P1 and the P2 have a relationship of P1 <P2.

Further, the heating device according to the present disclosure is a heating device that heats the toner image while conveying the recording material carrying the toner image in the nip portion.
A rotating body that comes into contact with the recording material carrying the toner image, and
An endless belt that rotates in accordance with the rotating body,
A support that rotatably supports the endless belt and
A nip portion forming member that is supported by the support, comes into contact with the inner peripheral surface of the endless belt, and forms the nip portion together with the rotating body via the endless belt.
Have,
A heating device having the grease composition between the endless belt and the nip portion forming member.

The grease composition according to the present disclosure suppresses the fibrillation of the thickener and exhibits stable lubricity over a long period of time. Further, it is possible to reduce the wear of the sliding member and suppress the deterioration of the slidability.
Further, the heating device using the grease composition according to the present disclosure can suppress the occurrence of stick slip for a long period of time.

Configuration diagram of an image forming apparatus used to explain an embodiment The figure which shows the cross-sectional structure of the heating apparatus 50 in an Example. Electron micrograph of thickener (PTFE particles, particle size 200 nm) in an unused grease composition Electron micrograph of fibrillated thickener (PTFE particles) in the durable grease composition The figure which shows the example of the bimodality of the particle size distribution of a grease composition.

Hereinafter, embodiments for carrying out the present invention will be described in detail exemplary with reference to the drawings. However, the scope of the present invention is not limited to the following embodiments.

<Grease composition>
The grease composition according to the present disclosure is composed of at least a base oil, a thickener, and an inorganic oxide.

<Base oil>
Perfluoropolyether (PFPE) is used as the base oil.
Commercially available products of perfluoropolyether that can be used include the following. Solvay's product name "FomblinY series", "FomblinM series", Chemours' product name "Krytox", Daikin Industries' product name "DemnumS series", etc. The structural formula of each perfluoropolyether is shown below.

<Thickening agent>
As the thickener, a fluororesin-based fine powder is preferable, and in particular, a tetrafluoroethylene homopolymer (PTFE) or a copolymer fine powder can be used. As the polytetrafluoroethylene (PTFE) fine powder, those having an average particle diameter of primary particles in the range of 0.1 μm to 0.5 μm can be used.

The smaller the particle size of polytetrafluoroethylene, the larger the contact area of the base oil with the perfluoropolyalkyl ether and the larger the affinity, so that the effect of reducing oil separation is recognized. However, when polytetrafluoroethylene having an average particle size of less than 0.1 μm is used, the particles tend to aggregate strongly with each other, making handling and dispersion difficult. On the other hand, when those having an average particle diameter of more than 0.5 μm are used, oil separation tends to be larger even with the same blending amount than those having an average particle diameter of 0.5 μm or less.

As the thickener other than polytetrafluoroethylene, one having a high affinity with the perfluoropolyether of the base oil can be used, and examples thereof include the following. Polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, etc.
The mixing ratio of the thickener in the grease composition is preferably 10 to 40% by mass, more preferably 15 to 35% by mass, based on the entire grease composition. By blending within this range, the hardness (consistency) can be adjusted so that the base oil does not leak and the torque can be kept low for a long time.

<Inorganic oxide particles>
As the inorganic oxide particles, it is preferable to use at least one selected from the group consisting of spherical silica (silicon oxide particles), alumina (aluminum oxide particles), and magnesium oxide particles. Examples of commercially available products that can be used include the following. Spherical silica manufactured by Sakai Chemical Industry Co., Ltd. Product name "Sciqas", product name "High-purity synthetic spherical alumina" manufactured by Admatex, and product name "Vaic phase method high-purity ultrafine powder magnesia" manufactured by Ube Material Industries Ltd. ..
When the shape of the inorganic oxide is spherical, it is possible to suppress the fibrillation of tetrafluoroethylene of the thickening agent and to reduce the wear between the pressure film to be rubbed and the nip portion forming member.

Further, in order to enhance the affinity with the base oil, it is preferable to perform surface treatment on the inorganic oxide particles with a fluorine-based silane coupling agent, a fluorine-based oil, or the like.
Further, in order to suppress the fibrillation of the thickener, the inorganic oxide particles having an average particle diameter of the primary particles in the range of 0.15 μm to 2 μm can be used in the grease composition.

The grease composition has two maximum particle numbers derived from each of the thickener and the inorganic oxide particles in the volume-based particle size distribution.
The thickening agent has a particle size P1 in which the number of particles is maximized in the range of a particle size of 0.1 μm to 0.5 μm.
The inorganic oxide particles have a particle diameter P2 in which the number of particles is maximized in the range of a particle diameter of 0.15 μm to 3.0 μm.
The P1 and the P2 have a relationship of P1 <P2.

Since the thickener and the inorganic oxide particles are aggregated in the grease composition, respectively, the particle size P1 and the inorganic particles have a maximum number of particles of the thickener than the average particle size of the thickener and the inorganic oxide particles. The magnitude relationship with the particle size P2 at which the number of oxide particles becomes maximum is important. The magnitude relationship between the particle size P1 at which the number of particles of the thickener is maximum and the particle size P2 at which the number of particles of the inorganic oxide particles is maximum is specified from the particle size distributions of the Examples and Comparative Examples described later. can.
When the particle size P1 and the particle size P2 satisfy the above magnitude relationship, the inorganic oxide particles act as spacers, making it difficult for high shear force and high frictional force to be applied to the tetrafluoroethylene particles which are thickeners. , It is considered that the film formation is suppressed.

FIG. 4 shows an example of the bimodal nature of the particle size distribution of the grease composition. The vertical axis indicates the number of particles, the unit is cps (count per second), the horizontal axis indicates the particle diameter, and the unit is nm. FIG. 4 shows an example in which the particle size P1 at which the number of particles of the thickener is maximum is smaller than the particle size P2 at which the number of particles of the inorganic oxide particles is maximum.
If the particle size P2 at which the number of particles of the inorganic oxide particles is maximum is smaller than the particle size P1 at which the number of particles of tetrafluoroethylene as a thickener is maximum, the fibrillation of tetrafluoroethylene is suppressed. I can't.
Further, when the inorganic oxide particles having a particle diameter P2 of more than 3.0 μm are used, even if the blending amount is the same as that when the inorganic oxide particles having a particle diameter P2 of 3.0 μm or less are used, the base is used. Oil separation tends to increase. Further, when inorganic oxide particles having a particle diameter P2 of more than 3.0 μm are used, the wear of the inner peripheral surface of the pressure film tends to increase.

The content of the inorganic oxide particles is preferably in the range of 10 parts by mass to 50 parts by mass with respect to 100 parts by mass of the thickener. If the content is less than 10 parts by mass, it is difficult to suppress the fibrillation of the thickener. Further, if the content is more than 50 parts by mass, scratches and wear of the pressure film and the sliding member are promoted.

Further, in the grease composition, in addition to the above-mentioned essential components, if necessary, known additives used in conventional lubricants such as antioxidants, rust inhibitors, corrosion inhibitors, and extreme pressure agents are used depending on the application. Can be blended.
In general, the pressure film of the heating device and the nip portion forming member reach about 60 ° C. to 150 ° C. in the heated state of the heating unit. It must be taken into consideration that the conditions of. Various conditions that change include the film transport means, the coefficient of friction on the surface of the heated body, the thermal expansion of the parts themselves such as the film suspension transport roller, and the viscosity of the lubricating grease interposed between the film and the film support member. And so on.

<Manufacturing method of grease composition>
First, the base oil perfluoropolyether (PFPE) is uniformly dissolved at room temperature or by heating, and then a predetermined amount of polytetrafluoroethylene powder, inorganic oxide powder, and additives as thickeners are added to the mixer. Pre-knead using at room temperature or warming as needed. Examples of the mixer include a blade type mixer, a planetary mixer, a twin mix mixer and the like.
This pre-kneaded mixture is further kneaded with three rolls in which the rolls are temperature-controlled to a constant temperature.

<Manufacturing Examples 1 to 5>
The grease compositions of Production Examples 1 to 5 were prepared with the formulations shown in Table 1 and used in Examples 1 to 5.

<Manufacturing Examples 6 to 12>
The grease compositions of Production Examples 6 to 12 were prepared with the formulations shown in Table 2 and used in Comparative Examples 1 to 7.

<Measurement of apparent viscosity of grease>
The apparent viscosity of the obtained grease composition was measured with a rotary rheometer RS75 manufactured by Haake using a cone plate having a diameter of 25 mm. Specifically, test grease is filled between cone plates with a gap of 0.025 mm, and the apparent viscosity is continuously measured in the range of shear rate 100s ^-1 to 5000s ^-1 at 25 ° C., and then the shear rate 3000s ^-1 . The apparent viscosity (representative value) was determined.

<Measurement of particle size distribution of grease composition>
The fluorinated grease composition was diluted with a fluorinated solvent (manufactured by 3M, trade name: Novec7100) to a concentration of 0.5% by mass, and then treated with an ultrasonic homogenizer for 3 minutes. Using this treatment liquid, the distribution of the volume particle size of the thickener and the inorganic oxide particles in the fluorine-based grease composition is measured as follows using a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.). Measured under conditions.
[Measurement condition]
Measurement principle: Dynamic light scattering frequency analysis (FFT)
Light source: 3mW semiconductor laser 780nm
Measurement particle size distribution range: 0.8 nm to 6.5 μm
Measurement temperature (liquid temperature): 25 ° C
Hereinafter, the heating device according to the present disclosure will be described in detail with reference to the drawings.

<Image forming device>
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a cross-sectional side surface of an image forming apparatus equipped with the heating apparatus according to the present embodiment. This image forming apparatus is an electrophotographic laser beam printer.
The operation of the image forming apparatus will be described with reference to FIG.
The image forming apparatus is
Paper feed unit 20,
Photoreceptors (hereinafter, also referred to as photosensitive drums) for each station juxtaposed for the developed colors 22Y, 22M, 22C, 22K,
Chargers 23Y, 23M, 23C, 23K, which constitute the charging means,
Toner cartridge 25Y, 25M, 25C, 25K,
Developers 26Y, 26M, 26C, 26K, constituting the developing means,
Intermediate transcript 30,
Primary transfer means 31Y, 31M, 31C, 31K,
It is composed of a secondary transfer roller 32, an intermediate transfer body cleaning means 33, a fixing portion 50, and the like.

An electrostatic latent image is formed by the exposure light controlled by the control unit 40 based on the image signal, the electrostatic latent image is developed to form a monochromatic toner image, and the monochromatic toner images are superimposed to form a multicolor toner image. It is formed and the multicolor toner image is transferred to the recording medium 11. Then, the multicolor toner image on the recording medium 11 is fixed to the recording medium 11 by the fixing unit 50.

The photosensitive drums 22Y, 22M, 22C, and 22K are configured by applying an organic optical transmission layer to the outer periphery of an aluminum cylinder, and the driving force of a drive motor (not shown) is transmitted to rotate the photosensitive drums in the counterclockwise direction.
As charging means, each station is equipped with four chargers 23Y, 23M, 23C, 23K for charging yellow (Y), magenta (M), cyan (C), and black (K) photosensitive drums. ..

The exposure light to the photosensitive drums 22Y, 22M, 22C, 22K is sent from the scanner units 24Y, 24M, 24C, 24K, and the surface of the photosensitive drums 22Y, 22M, 22C, 22K is selectively exposed to electrostatically latent. It is configured to form an image.
As a developing means, four developing machines 26Y, 26M, which develop yellow (Y), magenta (M), cyan (C), and black (K) for each station in order to visualize the electrostatic latent image. It is equipped with 26C and 26K.

The intermediate transfer body 30 is composed of a resin-made endless belt and is in contact with the photosensitive drums 22Y, 22M, 22C, 22K, and a drive motor (not shown) rotates the intermediate transfer body 30 in the clockwise direction. The photosensitive drums 22Y, 22M, 22C, and 22K rotate according to the image forming operation, and by applying a voltage to the primary transfer means 31Y, 31M, 31C, and 31K, the monochromatic toner image is sequentially transferred to the intermediate transfer body 30. Is transferred to (primary transfer). The transfer residual toner remaining on the photoconductor is recovered by the cleaning means 27Y, 27M, 27C, 27K of the photosensitive drum provided on each photoconductor.

The recording medium 11 prepared in advance in the paper feed unit 20 is fed by the paper feed roller 21 and the retard roller 28, and is sandwiched and conveyed by the resist roller 29. After that, the secondary transfer means 32 provided so as to come into contact with the intermediate transfer body 30 and the intermediate transfer body 30 narrowly conveys the recording medium 11 and applies a voltage to the secondary transfer means 32 to apply the recording medium 11. The multicolor toner image on the intermediate transfer member 30 is transferred to (secondary transfer). The residual toner charging means 33 charges the toner remaining on the intermediate transfer member 30. The toner remaining on the intermediate transfer body 30 after transferring the multicolor toner image to the recording medium 11 is charged with a polarity opposite to the original polarity by the charging means 33 of the residual toner, and the photosensitive drum 22 is charged by the primary transfer means 31. Electrostatically recovered on top. The residual toner electrostatically recovered on the photosensitive drum 22 is recovered by the cleaning means 27 of the photosensitive drum 22.

The fixing unit 50 melts and fixes the transferred multicolor toner image while holding and transporting the recording medium 11, and the detailed configuration will be described later.
The recording medium 11 after the toner image is fixed is then discharged to the discharge tray 56 by the paper discharge rollers 54 and 55, and the image forming operation is completed.

<Heating device>
Next, the configuration of the heating device 50 mounted on the image forming device will be described with reference to FIG.
FIG. 2 is a cross-sectional view of the heating device 50.
The heating device 50 includes a fixing roller 51 (rotating body), a heating unit 52, and a pressurizing unit 53.
The fixing roller 51 has a round shaft-shaped core metal 60 made of a metal material such as iron, SUS, and aluminum. An elastic layer 61 containing silicone rubber or the like as a main component is formed on the outer peripheral surface of the core metal 60, and a mold release layer (outermost layer) containing PTFE, PFA, FEP or the like as a main component is formed on the outer peripheral surface of the elastic layer 61. ) 62 is formed.
Here, PTFE is polytetrafluoroethylene, PFA is polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and FEP is tetrafluoroethylene / hexafluoropropylene copolymer. The fixing roller 51 is rotatably supported and is rotationally driven in the clockwise direction by a drive motor (not shown).

The heating unit 52 heats the fixing roller 51. It is composed of a ceramic heater (hereinafter referred to as a heater) 63 as a heating source, a heating film 64 (endless belt) as a heating member, a heating film guide 65 which is a support for rotatably supporting the heating film 64, and the like. ing. The heating unit 52 is pressurized against the fixing roller 51, and forms a heating nip between the fixing roller 51 and the heating film 64.

The pressurizing unit 53 sandwiches and conveys the recording medium 11 with the fixing roller 51 while pressurizing the recording medium 11. It is composed of a pressure film 66 (rotatable endless belt) as a pressure member, a pressure film guide 67 which is a support for rotatably supporting the pressure film 66, a sliding member 68, and the like. .. The sliding member 68 is fixed to the pressure film guide 67, and is rubbed against the inner peripheral surface of the rotating pressure film 66 at the contact surface between the fixing roller 51 and the pressure film 66. The pressure unit 53 is pressed against the fixing roller 51, and forms a pressure nip between the fixing roller 51 and the pressure film 66.
At the time of printing, the heat generated by the ceramic heater 63 provided in the heating unit 52 is transferred to the pressurizing unit 53 via the heating film 64 and the fixing roller 51, and is maintained at a high temperature of 100 ° C. to 150 ° C. ..

In the heating film 64 and the pressure film 66, a release layer is formed on the outer peripheral surface of the base layer of a heat-resistant resin such as a polyimide resin or a polyetheretherketone resin. Examples of the resin used for the release layer include polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and polytetrafluoroethylene (PTFE).

The heating film 64 and the pressure film 66 rotate in a counterclockwise direction as the fixing roller 51 rotates. Fluorine-based lubricating grease, which is a lubricant, is applied to the inner peripheral surfaces of the heating film 64 and the pressure film 66 in order to reduce the rotational torque.
The recording medium 11 passes through a pressure nip formed between the fixing roller 51 and the pressure film 66. The heat supplied from the heater 63 heats the surface of the fixing roller 51 via the heating film 64 in the heating nip portion. The unfixed toner image on the recording medium 11 is melted by the heat received from the heated fixing roller 51 and the pressure in the pressure nip, and is fixed on the recording medium 11.

The sliding member 68 backs up from the inside and pressurizes the fixing roller 51 while rubbing against the inner peripheral surface of the pressure film 66.
The width of the sliding member 68 is longer than the width of the heater 63, and the width of the heater 63 is provided so as to be longer than the width of the recording medium 11.

Here, if a material having a high thermal conductivity such as pure aluminum or an aluminum alloy is used for the sliding member 68, the heat of the non-paper-passing portion, which has become hot, is transferred to the paper-passing portion having a relatively low temperature. The effect of equalizing the temperature unevenness in the longitudinal direction can be obtained. Since the heat supplied to the outside of the recording medium 11 is also transferred to the recording medium 11 via the sliding member 68, it is possible to suppress an excessive temperature rise in the non-paper-passing portion, and even a small-sized recording medium is large. It enables image formation at an output speed equivalent to or slightly slower than that of a recording medium of a size.
Further, the sliding member 68 of the present embodiment may be provided with an alumite-treated layer on the sliding surface in contact with the inner peripheral surface of the pressure film 66 in order to improve wear resistance.

<Evaluation method of grease composition>
<Measurement of torque>
In the heating device 50, each grease composition was interposed on the inner peripheral surface of the heating film 64 in contact with the heater 63 and the inner peripheral surface of the pressure film 66 in contact with the sliding member 68.
The heating device 50 was incorporated into the image forming apparatus shown in FIG. 1, and the heating film 64 and the pressure film 66 were brought into contact with the fixing roller 51. Then, while the fixing roller 51 is rotationally driven, the heater 63 is heated to raise the temperature of the heating film 64, the fixing roller 51, and the pressure film 66 to the same level as during the heating and fixing operation, and the temperature is raised on the shaft of the fixing roller 51. The drive torque T1 was measured.
Next, with the pressure film 66 separated from the fixing roller 51 and only the heating film 64 in contact with the fixing roller 51, the fixing roller 51 is driven to drive the heating film 64 to rotate, and the fixing roller 51 is also driven. The drive torque T2 on the shaft was measured.
(The drive torque T1-the drive torque T2) was calculated, and the torque of the pressurizing unit 53 was obtained.

The heating device of FIG. 2 is incorporated into the image forming apparatus shown in FIG. 1, and stick slip while outputting 5000 sheets of the following A4 size plain paper as recording paper in an environment of a temperature of 23 ° C. and a relative humidity of 50%. It was confirmed that there was no abnormal noise due to.
・ A4 size plain paper (basis weight 75 g / m ² , manufactured by Canon Marketing Japan, GF-C081)
Further, the drive torque T1 and the drive torque T2 before and after the output of the 5000 images were measured, and the torque of the pressurizing unit was calculated. The initial torque of the pressurizing unit was about 0.15 Nm. The rate of increase in torque of the pressurizing unit before and after durability was calculated using the following formula, and ranked as follows.
Increase rate [%] = ((Torque after endurance-Torque before endurance) / Torque before endurance) x 100

[Rank of torque increase rate of pressurizing unit]
・ L ・ ・ ・ Increase rate is less than 20% compared to the initial stage ・ M ・ ・ ・ Increase rate is 20% or more and less than 50% compared to the initial stage ・ H ・ ・ ・ Increase rate is 50% or more compared to the initial stage

<Observation of grease>
-Observation of unused grease Acceleration voltage 2 kV, magnification of thickener (PTFE particles) in unused grease composition using a field emission scanning electron microscope (Hitachi High-Technologies Corporation, "S4800"). It was observed and photographed under 10000 times observation conditions.
FIG. 3A is an example of an electron micrograph (length 7 μm × width 10 μm) in which a thickener (PTFE particles, particle diameter 200 nm) in an unused grease composition is photographed.

-Observation of grease after durability The grease after durability was collected from the inner peripheral surface of the pressure film, diluted with a fluorine-based solvent (3M, trade name Novec7100), and then the solvent and solid content were separated by a centrifuge. ..
The obtained solid content was dried under reduced pressure at a temperature of 60 ° C. for 1 hour using a vacuum dryer.
The dried sample was observed and photographed under the above observation conditions using the above field emission scanning electron microscope.
FIG. 3B is an example of an electron micrograph (length 7 μm × width 10 μm) of a thickener (PTFE particles) in the grease composition after durability.

The degree of fibrillation is the ratio (area ratio) of the area of the fibrillated (fibrous) PTFE particles by binarizing the PTFE particles in the unused grease composition and the PTFE particles in the durable grease composition. And.
Examples of the device / function for binarization include the following.
Circular particle separation of the binarized image processing function of the image analysis device "Luzex AP" (manufactured by Nireco), and circular particle analysis of the binarized image processing function of the image analysis software "PopImaging" (manufactured by Digital Being Kids) And circular area division function using Watershed algorithm.

[Fibrilization degree]
The degree of fibrillation can be calculated using the following formula for calculating the degree of fibrillation.
Fibrilization degree = (F / A) x 100 (%)
F + N = A
F: Area of the fibrillated particle portion N: Area of the non-fibrillated particle portion (circular particle) A: Area of the entire region

If there is a portion on which the non-fibrillated particles are placed on the fibrillated particles, the following shall be applied.
Area of non-fibrilized particle part N = Area of non-fibrilized particle part on the outermost surface Area of fibrillated particle part F = (Area of the entire region A-Not fibrillated on the outermost surface Area of particle part N)

[Fibrilization degree of the entire thickener]
The degree of fibrillation (fibrosis) of the thickener (PTFE particles) in the grease composition after durability varies depending on the place on the inner peripheral surface of the pressure film from which the film was collected (collection place). Therefore, the thickening agent (PTFE particles) was collected from the following collection sites (3 locations).
Sampling place 1: Central part of the inner peripheral surface of the pressure film in the longitudinal direction Sampling place 2, 3: Both ends of the inner peripheral surface of the pressure film in the longitudinal direction (about 30 mm from one end and from the other end) Position of about 30 mm)
The degree of fibrillation at each collection site was calculated using the above-mentioned formula for calculating the degree of fibrillation.

Each collection site was ranked as follows based on the degree of fibrilization of the collection sites 1 to 3.
Rank:
・ A ・ ・ ・ Fibrilization degree is less than 10% ・ B ・ ・ ・ Fibrilization degree is 10% or more and less than 50% ・ C ・ ・ ・ Fibrilization degree is 50% or more Collection location 1-3 If two or more of the three locations are in the same rank, that rank is used as the overall rank of the thickener. When the ranks of the three sampling locations 1 to 3 were all different, the second rank was taken as the rank of the entire thickener.

<Examination results>
The grease compositions of Production Examples 1 to 5 were used in Examples 1 to 5, and the evaluation results are shown in Tables 3 to 7. Further, the grease compositions of Production Examples 6 to 12 were used in Comparative Examples 1 to 7, and the evaluation results are shown in Tables 8 and 9.

<Example 1>
As shown in Table 3, when the grease composition of Production Example 1 is used, the torque increase rate of the pressure film is low in the heating device, no abnormal noise is generated due to stick slip, and stable printing can be performed. rice field. In addition, it was confirmed that the thickener in the grease composition after printing was less fibrillated.

<Example 2>
As shown in Table 4, when the grease composition of Production Example 2 was used, the torque increase rate of the pressure film was low in the heating device, and no abnormal noise was generated due to stick slip. In addition, it was confirmed that the thickener in the grease composition after printing was less fibrillated.

<Example 3>
As shown in Table 5, when the grease composition of Production Example 3 was used, the torque increase rate of the pressure film was low in the heating device, and no abnormal noise was generated due to stick slip. In addition, it was confirmed that the thickener in the grease composition after printing was less fibrillated.

<Example 4>
As shown in Table 6, when the grease composition of Production Example 4 was used, the torque increase rate of the pressure film was low in the heating device, and no abnormal noise was generated due to stick slip. In addition, it was confirmed that the thickener in the grease composition after printing was less fibrillated.

<Example 5>
As shown in Table 7, when the grease composition of Production Example 5 was used, the torque increase rate of the pressure film was low in the heating device, and no abnormal noise was generated due to stick slip. In addition, it was confirmed that the thickener in the grease composition after printing was less fibrillated.

<Comparison example>
As shown in Table 8, in Comparative Example 1 using the grease composition of Production Example 6, the torque increase rate of the pressure film was high in the heating device, and abnormal noise due to stick slip was generated. It was also found that the thickener in the grease composition after printing was often fibrillated.
Further, as shown in Tables 8 and 9, Comparative Examples 2 to 7 using the grease compositions of Production Examples 7 to 12 have a higher torque increase rate of the pressure film than the examples in the heating device, and are being printed. There was an abnormal noise due to stick slip. It was also found that the thickener in the grease composition after printing was often fibrillated. As compared with Examples, it was found that the content of the inorganic oxide particles with respect to 100 parts by mass of the thickener was ineffective at 5 parts by mass.

As shown in Table 8 and Comparative Examples 2 to 4, when the content of the inorganic oxide particles with respect to 100 parts by mass of the thickener is 5 parts by mass, the maximum value P2 of the particle diameter of the inorganic oxide particles in the grease composition is large. It was unclear, and the shape of the particle size distribution was not the bimodal distribution as illustrated in FIG.
As shown in Table 9 and Comparative Examples 6 to 7, similarly, when the content of the inorganic oxide particles with respect to 300 parts by mass of the thickener is 5 parts by mass, the particle size of the inorganic oxide particles in the grease composition is the same. The maximum value P2 was unclear, and the shape of the particle size distribution was not a bimodal distribution as illustrated in FIG.
As shown in Comparative Example 5, even if 50 parts by mass of the inorganic oxide particles (spherical silica particles) are added, the particle size P1 at which the number of particles of the thickener is maximum and the number of particles of the inorganic oxide particles are maximum. When the relationship with the particle size P2 was P1> P2, the thickening agent was often fibrillated after printing.

11 Recording medium (recording paper)
20 Paper feed unit 21 Paper feed roller 22Y, 22M, 22C, 22K Photosensitive drum (photoreceptor)
23Y, 23M, 23C, 23K Charger 24Y, 24M, 24C, 24K Scanner unit 25Y, 25M, 25C, 25K Toner cartridge 26Y, 26M, 26C, 26K Developer 27Y, 27M, 27C, 27K Photosensitive drum cleaning means 28 resist Roller 29 Resist roller 30 Intermediate transfer body 31Y, 31M, 31C, 31K Primary transfer means 32 Secondary transfer roller 33 Charging means for residual toner 34 Drive roller 40 Control unit 50 Heating device (fixing unit)
51 Fixing roller 52 Heating unit 53 Pressurizing unit 54, 55 Paper ejection roller 56 Discharging tray 60 Core metal 61 Elastic layer 62 Release layer 63 Ceramic heater 64 Heating film 65 Heating film guide 66 Pressurizing film 67 Pressurized film guide 68 Moving members

Claims (5)

A grease composition containing a base oil, a thickener, and inorganic oxide particles.
The base oil contains perfluoropolyether and
The grease composition has a maximum number of two particles derived from each of the thickener and the inorganic oxide particles in a volume-based particle size distribution.
The thickening agent has a particle size P1 in which the number of particles is maximized in the range of a particle size of 0.1 μm to 0.5 μm.
The inorganic oxide particles have a particle diameter P2 in which the number of particles is maximized in the range of a particle diameter of 0.15 μm to 3.0 μm.
A grease composition characterized in that the P1 and the P2 have a relationship of P1 <P2. The grease composition according to claim 1, wherein the content of the inorganic oxide particles is 10 parts by mass to 50 parts by mass with respect to 100 parts by mass of the thickener. The grease composition according to claim 1 or 2, wherein the inorganic oxide particles are at least one selected from the group consisting of silicon oxide particles, aluminum oxide particles, and magnesium oxide particles. A heating device that heats the toner image while transporting the recording material carrying the toner image in the nip portion.
A rotating body that comes into contact with the recording material carrying the toner image, and
An endless belt that rotates in accordance with the rotating body,
A support that rotatably supports the endless belt and
A nip portion forming member that is supported by the support and comes into contact with the inner peripheral surface of the endless belt to form the nip portion together with the rotating body via the endless belt.
Have,
A heating device according to any one of claims 1 to 3, wherein the grease composition according to any one of claims 1 to 3 is provided between the endless belt and the nip portion forming member. The heating device according to claim 4, wherein the rotating body is a fixing roller and has a heater for heating the surface of the fixing roller.

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