JP7347980B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming apparatus.

A fixing device includes an endless belt heated by a heating member, and a nip forming member provided inside the belt and forming a fixing nip between the belt and a pressure member arranged outside the belt. known (for example, Patent Document 1). In such a fixing device, since the belt has a low heat capacity, a fixing device with short warm-up time and low power consumption can be realized. In such a fixing device, lubricity is improved by interposing a lubricant in the sliding portion between the nip forming member and the belt. Further, from the viewpoint of reducing the driving torque of at least one member constituting the sliding portion, a technique is disclosed in which a lubricant having a low viscosity at room temperature or at low temperature is used.

For example, Patent Document 2 discloses a composition containing two types of linear perfluoropolyether oils having different molecular weights and polytetrafluoroethylene as a lubricant.

Here, when the fixing device is repeatedly driven and stopped, a heat cycle consisting of heating and cooling of the sliding part is repeated, and the ability of the sliding part to retain lubricant decreases. A pump-out phenomenon in which the lubricant flows out may occur. Furthermore, when a conventional lubricant is used in a fixing device, the fluidity of the lubricant may increase, and the lubricant retention of the sliding portion may deteriorate. For this reason, in the conventional technology, it is not possible to achieve both torque reduction and pump-out suppression, and image quality may deteriorate.

The present invention has been made in view of the above, and an object of the present invention is to provide a fixing device and an image forming apparatus that can form high-quality images over a long period of time.

In order to solve the above-mentioned problems and achieve the objects, the fixing device of the present invention includes an endless belt, a pressure member provided on the outside of the belt and arranged opposite to the belt, and a heating member that heats the belt. and a nip forming member provided inside the belt to form a fixing nip between the belt and the pressure member. A perfluoropolyether oil having a lubricant composition interposed therebetween, the lubricant composition being represented by the following general formula (1) and having a kinematic viscosity at 40° C. of 92 mm ² /sec to 310 mm ² /sec. (A) and polytetrafluoroethylene powder (B) having an average primary particle diameter in the range of 0.2 μm or more and 0.4 μm or less, and the content of the polytetrafluoroethylene powder (B) is 5 μm or less. % by weight or more and 17.5% by weight or less, and the lubricant composition has a first shear viscosity of 1 Pa·s or more and 15 Pa·s or less at 25°C and a shear rate of 10/sec, and The perfluoropolyether oil (A) and The content of other components other than the polytetrafluoroethylene powder (B) is 0% by weight or more and 10% by weight or less.

RfO(CF ₂ CF ₂ O) _m (CF ₂ O) _n Rf General formula (1)

In the general formula (1), Rf is a perfluoro lower alkyl group having 1 or more carbon atoms and 4 or less, m and n are each an integer of 0 or more, and the sum of m and n is 30 or more and 190 or less, The CF ₂ CF ₂ O and CF ₂ O groups are randomly bonded in the main chain.

According to the present invention, it is possible to form high-quality images over a long period of time.

FIG. 1 is a schematic diagram showing an example of an image forming apparatus according to an embodiment. FIG. 2 is a schematic diagram showing an example of the fixing device according to the embodiment. FIG. 3 is a schematic diagram illustrating an example of a fixing device according to modification 1. FIG. 4 is a schematic diagram showing an example of a fixing device according to modification 2. FIG. 5 is a diagram showing changes in torque depending on the thermal history of the lubricant composition.

A fixing device and an image forming apparatus according to this embodiment will be described below.

(First embodiment)
The fixing device of this embodiment includes an endless belt, a pressure member provided on the outside of the belt and arranged to face the belt, a heating member that heats the belt, and a pressure member provided on the inside of the belt between the belt and the pressure member. and a nip forming member that forms a fixing nip between the fixing device and the fixing device. In the fixing device of this embodiment, a lubricant composition is interposed between the inner surface of the belt and the nip forming member.

First, the lubricant composition used in the fixing device of this embodiment will be described.

<Lubricant composition>
The lubricant composition of the present embodiment includes a perfluoropolyether oil (A) represented by the following general formula (1) and having a kinematic viscosity of 50 mm ² /sec to 400 mm ² /sec at 40°C, and an average primary polytetrafluoroethylene powder (B) having a particle size in the range of 0.15 μm or more and 1.00 μm or less, and the content of the polytetrafluoroethylene powder (B) is 5% by weight or more and 17.5% by weight. % or less, and when a heat cycle of heating at 150° C. for 30 minutes and then cooling to 25° C. is repeated five times, the torque at each of the five heat cycles at 150° C. is less than 2,000 μNm.

RfO(CF ₂ CF ₂ O) _m (CF ₂ O) _n Rf General formula (1)

By having the above structure, the lubricant composition of the present embodiment can achieve both torque reduction and pump-out suppression.

The lubricant composition of this embodiment is used, for example, by interposing it in a sliding part, which is a part where members come into contact with each other. Examples of the members constituting the sliding portion include a bearing and a shaft disposed inside the bearing, a belt member, and a pressure member that presses the belt member from the inside or outside of the belt member. Note that the members constituting the sliding portion are not limited to these, as long as they are members constituting a region (sliding portion) where the members come into contact with each other.

The lubricant composition of this embodiment is used by being interposed between the sliding part of the fixing device, that is, the inner surface of the belt and the nip forming member (details will be described later). In this embodiment, the region between the inner surface of the belt and the nip forming member will be referred to as a sliding section.

In this embodiment, the torque refers to the driving torque of a member (specifically, a fixing belt, which will be described in detail later) that constitutes the sliding portion. When the member is a shaft (rotating body) disposed inside a bearing, torque means the rotational torque of the motor that drives the shaft. When one member of a pair of members constituting a sliding part is configured to be driven (relatively moved) with respect to the other member, the term "torque" refers to the driving torque of the driving part that drives the member. .

Pump-out is caused by repeated driving and stopping of the members that make up the sliding part (for example, a belt that is a driven member), and a repeated heat cycle consisting of heating and cooling of the sliding part. , refers to a phenomenon in which the lubricant retention of the sliding part decreases and the lubricant flows out from the sliding part. Heat cycles are sometimes referred to as thermal history.

The lubricant composition of the present embodiment contains the perfluoropolyether oil (A) and the polytetrafluoroethylene powder (B) in an amount of 5% by weight or more and 17.5% by weight or less. It has become clear that it is possible to achieve both torque reduction and pump-out suppression.

The details of each component will be explained below.

<Perfluoropolyether oil (A)>
The perfluoropolyether oil (A) according to the present embodiment is represented by the above general formula (1) and has a kinematic viscosity at 40° C. of 50 mm ² /sec to 400 mm ² /sec.

The kinematic viscosity of the perfluoropolyether oil (A) at 40°C is preferably 50 mm ² /sec to 400 mm 2 /sec, more preferably 80 ^{mm 2 /} sec to 350 mm ² /sec, and 90 mm ² /sec. More preferably, the speed is 320 mm ² /sec or less.

The kinematic viscosity of the perfluoropolyether oil (A) can be measured according to the method of JIS Z8803.

In the above general formula (1), Rf is a perfluoro lower alkyl group having 1 to 4 carbon atoms, and more preferably 1 to 2 carbon atoms. Specifically, Rf is a trifluoromethyl group, a pentafluoroethyl group, or the like. Among these, Rf is preferably a trifluoromethyl group.

In the above general formula (1), the sum of m and n is 30 or more and 190 or less. Further, in the above general formula (1), the ratio of m to n (m/n) is preferably 1 or more.

The CF ₂ CF ₂ O groups and CF ₂ O groups of the perfluoropolyether oil (A) represented by the above general formula (1) are randomly bonded into the main chain of the perfluoropolyether oil (A). Become.

CF ₂ CF ₂ O groups and CF ₂ O groups are randomly bonded means that the main chain of the linear perfluoropolyether oil (A) is composed of one or more CF ₂ CF ₂ O groups. It has a structure in which repeating units and one or more repeating units of CF ₂ O group are arranged alternately, and the main chain direction of the number of repeating units of CF ₂ CF ₂ O group and the number of repeating units of CF ₂ O group This means that there is no regularity in the arrangement of .

The perfluoropolyether oil (A) may be used alone or in combination of two or more.

<Polytetrafluoroethylene powder (B)>
The polytetrafluoroethylene powder (B) is a polytetrafluoroethylene (PTFE) resin powder having an average primary particle diameter of 0.15 μm or more and 1.00 μm or less.

In this embodiment, the average primary particle diameter means the number average primary particle diameter. The average primary particle size of the polytetrafluoroethylene powder (B) can be observed, for example, using a SEM (scanning electron microscope).

The average primary particle diameter of the polytetrafluoroethylene powder (B) according to the present embodiment is 0.15 μm or more and 1.00 μm or less, preferably 0.2 μm or more and 0.5 μm or less.

When the average primary particle size of the polytetrafluoroethylene powder (B) is smaller than 0.15 μm, pump-out is likely to occur. Without being bound by theory, it is believed that a lubricant containing PTFE resin powder smaller than the above particle size range contains PTFE resin as a thickener along with perfluoropolyether oil (A) that expands at high temperatures. Powder is also likely to move from the sliding part, and it is thought that pump-out can easily occur. On the other hand, if a powder with an average primary particle size larger than 0.15 μm is used, the gaps between the powder particles become wider, making it easier for perfluoropolyether oil to move at high temperatures. It is thought that the thickener that retains the ether oil is not washed away by the expansion and contraction of the base oil due to thermal history and remains near the sliding part, and by retaining the perfluoropolyether oil, suppresses lubricant discharge due to pump-out. .

On the other hand, if the average primary particle size of the polytetrafluoroethylene powder (B) is larger than 1 μm, the thickening effect will be reduced. In order to solve this problem, it is necessary to increase the amount of polytetrafluoroethylene powder (B) added, which increases the sliding torque.

Moreover, when the average primary particle diameter of the polytetrafluoroethylene powder (B) is larger than 1 μm, the thixotropy of the lubricant composition decreases. In addition, when a comparative lubricant composition containing polytetrafluoroethylene powder (B) having an average primary particle diameter of more than 1 μm is interposed in the sliding part, the belt (fixing belt described later) which is a member constituting the sliding part ) is likely to cause linear unevenness, which is thought to reduce the quality of the formed image.

The average secondary particle diameter of the polytetrafluoroethylene powder (B) is preferably 1 μm or more and 20 μm or less, more preferably 1 μm or more and 10 μm or less. When the average secondary particle size is within this range, the polytetrafluoroethylene powder (B) can be easily dispersed in the lubricant composition, and a lubricant resin composition with uniform low torque can be provided. .

In addition, in this embodiment, the average secondary particle diameter means the number average secondary particle diameter. The average secondary particle diameter of the polytetrafluoroethylene powder (B) can be measured, for example, by observation using an SEM (scanning electron microscope), microtrack method, or light transmission method.

The polytetrafluoroethylene powder (B) of this embodiment is obtained by polymerizing monomers by methods such as emulsion polymerization, suspension polymerization, and solution polymerization. In the present invention, polytetrafluoroethylene powder (B) obtained by emulsion polymerization is preferred.

The polytetrafluoroethylene powder (B) obtained by emulsion polymerization is a powder with a small particle size that satisfies the above average primary particle size, has a large specific surface area, and has a large oil absorption amount. Therefore, the polytetrafluoroethylene powder (B) obtained by emulsion polymerization is difficult to separate in the lubricant composition, and a stable lubricant composition can be obtained.

The weight average molecular weight of the polytetrafluoroethylene powder (B) of this embodiment is preferably 1,000 to 1,000,000. The weight average molecular weight of the polytetrafluoroethylene powder (B) can be calculated from values obtained by differential scanning calorimetry, viscoelasticity, and melt flow rate measurements.

The content of the polytetrafluoroethylene powder (B) in the lubricant composition is 5% by weight or more and 17.5% by weight or less, and 5% by weight or more and 10% by weight or less, based on the lubricant composition. Even better.

If the content of the polytetrafluoroethylene powder (B) is less than 5% by weight, the obtained lubricant composition will be too soft and fluid, and there is a concern that it may flow out from the lubricated area. On the other hand, if the content of polytetrafluoroethylene powder (B) is more than 17.5% by weight, the resulting lubricant composition is too hard, making it difficult to provide low sliding torque and cope with pump-out due to thermal history. becomes difficult.

<Other ingredients>
The lubricant composition of this embodiment may further contain other components. The content of the other components in the lubricant composition is preferably 0% by mass or more and 10% by mass or less. Here, "0% by mass" means a form that does not contain other components.

Examples of the other components include rust preventives and the like.

<Method for preparing lubricant composition>
The lubricant composition of this embodiment can be prepared by a conventionally known method. For example, the lubricating grease composition of this embodiment can be obtained by stirring and mixing perfluoropolyether oil (A) and polytetrafluoroethylene powder (B) and passing the mixture through a roll mill or the like.

<Measurement of lubricant composition>
The lubricant composition of this embodiment has the following characteristics if it has the above composition. The lubricant composition of the present embodiment was heated to 150°C, held for 30 minutes, cooled to 25°C, and held for 30 minutes, which was repeated five times. The torque is less than 2000μNm.

Furthermore, the lubricant composition of the present embodiment has a first shear viscosity (η ₁₀ ) of 1 Pa·s or more and 15 Pa·s or less at 25°C and a shear rate of 10/sec, and The thixotropy index, which is the ratio (η ₁₀ /η _{100 ) of the first shear viscosity (η 100 )} to the second shear viscosity (η ₁₀₀ ), is in the range of 1.2 to 5.0.

By setting the lubricant composition as described above, the lubricant composition of the present embodiment has the torque, the first shear viscosity (η ₁₀ ), and the thixotropy index ((η ₁₀ )/(η ₁₀₀ )) can be realized.

Therefore, it is considered that the lubricant composition of this embodiment can achieve both torque reduction and pump-out suppression.

The shear viscosity (first shear viscosity (η ₁₀ ), second shear viscosity (η ₁₀₀ )) of the lubricant composition of the present embodiment and the torque of each of the five heat cycles at 150° C. /It can be measured using a plate-type rotational viscometer (for example, Rotary Rheometer MCR302 manufactured by Anton Paar).

<Image forming device>
Next, the image forming apparatus of this embodiment will be explained.

FIG. 1 is a schematic diagram showing an example of an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 is an image forming apparatus including the fixing device 20 of this embodiment.

The image forming apparatus 1 is a color laser printer, and four image forming sections 4Y, 4M, 4C, and 4K are provided in the center of the apparatus main body. Each of the image forming units 4Y, 4M, 4C, and 4K accommodates developers of different colors, yellow (Y), magenta (M), cyan (C), and black (K), corresponding to the color separation components of a color image. The configuration is the same except for the

Each of the image forming units 4Y, 4M, 4C, and 4K includes a drum-shaped photoreceptor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoreceptor 5, and a charging device 6 that supplies toner to the surface of the photoreceptor 5. It includes a developing device 7, a cleaning device 8 for cleaning the surface of the photoreceptor 5, and the like. In FIG. 1, only the photoreceptor 5, charging device 6, developing device 7, and cleaning device 8 included in the black image forming section 4K are labeled, and the other image forming sections 4Y, 4M, and 4C are designated by reference numerals. The symbol is omitted.

An exposure device 9 for exposing the surface of the photoreceptor 5 is provided below each of the image forming units 4Y, 4M, 4C, and 4K. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, etc., and is configured to irradiate the surface of each photoreceptor 5 with laser light based on image data.

A transfer device 3 is disposed above each image forming section 4Y, 4M, 4C, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as a transfer body, four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, a secondary transfer backup roller 32, and a cleaning roller. A backup roller 33, a tension roller 34, and a belt cleaning device 35 are provided.

The intermediate transfer belt 30 is an endless, that is, an annular belt. The intermediate transfer belt 30 is stretched from the inside by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. In this embodiment, the intermediate transfer belt 30 is rotated (rotated) in the direction of the arrow in FIG. 1 by the rotation of the secondary transfer backup roller 32 .

The four primary transfer rollers 31 each sandwich the intermediate transfer belt 30 with each photoreceptor 5 to form a primary transfer nip. Further, a power source (not shown) is connected to each primary transfer roller 31, and a predetermined direct current voltage (DC) and/or alternating current voltage (AC) is applied to each primary transfer roller 31. The secondary transfer roller 36 and the secondary transfer backup roller 32 sandwich the intermediate transfer belt 30 to form a secondary transfer nip. Further, like the primary transfer roller 31 , a power source (not shown) is also connected to the secondary transfer roller 36 , and a predetermined direct current voltage (DC) and/or alternating current voltage (AC) is applied to the secondary transfer roller 36 . It has become so.

The belt cleaning device 35 includes a cleaning brush and a cleaning blade that are arranged to come into contact with the intermediate transfer belt 30. A waste toner transfer hose (not shown) extending from the belt cleaning device 35 is connected to an entrance of a waste toner container (not shown).

A bottle accommodating section 2 is provided at the top of the main body of the image forming apparatus 1, and four toner bottles 2Y, 2M, 2C, and 2K containing replenishing toner are removably attached to the bottle accommodating section 2. has been done. A supply path (not shown) is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7, and each toner bottle 2Y, 2M, 2C, 2K is connected to each other through this supply path. Toner is supplied to the developing device 7.

On the other hand, at the bottom of the main body of the image forming apparatus 1, there are provided a paper feed tray 10 that accommodates paper P as a recording medium, a paper feed roller 11 that carries out the paper P from the paper feed tray 10, and the like. Recording media include, in addition to plain paper, cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, and the like. Further, the image forming apparatus 1 may be provided with a manual paper feeding mechanism.

A conveyance path R is provided inside the main body of the image forming apparatus 1 for discharging the paper P from the paper feed tray 10 through the secondary transfer nip and out of the apparatus. In the conveyance path R, a pair of registration rollers 12 are disposed upstream of the position of the secondary transfer roller 36 in the paper conveyance direction, as a conveyance means for conveying the paper P to the secondary transfer nip.

Further, a fixing device 20 for fixing the unfixed image transferred to the paper P is disposed downstream from the position of the secondary transfer roller 36 in the paper transport direction. Details of the fixing device 20 will be described later.

Further, a pair of paper ejection rollers 13 for ejecting the paper out of the apparatus is provided downstream of the fixing device of the image forming apparatus 1 in the paper transport direction on the transport path R. Furthermore, a paper ejection tray 14 is provided on the upper surface of the main body of the image forming apparatus 1 for storing paper ejected to the outside of the apparatus.

In the image forming apparatus 1 configured as described above, when an image forming operation is started, each photoreceptor 5 in each image forming section 4Y, 4M, 4C, and 4K is rotated clockwise in the figure by a drive device (not shown). The charging device 6 uniformly charges the surface of each photoreceptor 5 to a predetermined polarity. The charged surface of each photoreceptor 5 is irradiated with laser light from the exposure device 9, and an electrostatic latent image is formed on the surface of each photoreceptor 5. At this time, the image information exposed to each photoreceptor 5 is monochrome image information obtained by separating a desired full-color image into yellow, magenta, cyan, and black color information. By supplying toner from each developing device 7 to the electrostatic latent image formed on each photoreceptor 5 in this way, the electrostatic latent image is developed (visualized) as a toner image. .

Further, when the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, causing the intermediate transfer belt 30 to travel around in the direction indicated by the arrow in the figure. Then, a constant voltage or constant current controlled voltage having a polarity opposite to the charged polarity of the toner is applied to each primary transfer roller 31 . As a result, a transfer electric field is formed in the primary transfer nip between each primary transfer roller 31 and each photoreceptor 5.

Thereafter, as each photoreceptor 5 rotates, when the toner image of each color on the photoreceptor 5 reaches the primary transfer nip, the toner image on each photoreceptor 5 is generated by the transfer electric field formed in the primary transfer nip. are transferred onto the intermediate transfer belt 30 in a superimposed manner. In this way, a full-color toner image is carried on the surface of the intermediate transfer belt 30. Furthermore, the toner on each photoreceptor 5 that has not been completely transferred to the intermediate transfer belt 30 is removed by the cleaning device 8 . Thereafter, the surface of each photoreceptor 5 is neutralized by a static eliminating device (not shown), and the surface potential is initialized.

At the lower part of the image forming apparatus 1, the paper feed roller 11 starts rotating, and the paper P is sent out from the paper feed tray 10 to the conveyance path R. The paper P sent out to the conveyance path R is timed by the registration rollers 12 and sent to a secondary transfer nip between the secondary transfer roller 36 and the secondary transfer backup roller 32. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip.

Thereafter, as the intermediate transfer belt 30 rotates, when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip, the transfer electric field formed in the secondary transfer nip causes the toner image on the intermediate transfer belt 30 to toner images are transferred onto the paper P at once. At this time, residual toner on the intermediate transfer belt 30 that has not been completely transferred to the paper P is removed by a belt cleaning device 35, and the removed toner is conveyed to a waste toner container (not shown) and collected.

Thereafter, the paper P onto which the toner image has been transferred is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged out of the apparatus by the paper discharge roller 13 and is stocked on the paper discharge tray 14.

<Fixing device>
Next, the fixing device 20 provided in the image forming apparatus 1 of this embodiment will be described in detail.

FIG. 2 is a schematic diagram showing an example of the fixing device 20 of this embodiment.

The fixing device 20 includes a fixing belt 21 , a pressure roller 22 , a heat source 23 , and a nip forming member 27 .

The fixing belt 21 is an example of an endless belt. Fixing belt 21 is rotatably supported.

Specifically, the fixing belt 21 is a metal belt made of nickel or SUS, or an endless belt (or film) made of a resin material such as polyimide. The surface layer of the fixing belt 21 has a release layer such as an MPFA or PTFE layer, and has release properties to prevent toner from adhering. An elastic layer formed of a silicone rubber layer or the like may be provided between the base material of the fixing belt 21 and the PFA or PTFE layer. If there is no silicone rubber layer, the heat capacity will be small and the fixing performance will be improved, but when the unfixed image is crushed and fixed, minute irregularities on the surface of the fixing belt 21 will be transferred to the image and the solid areas of the image will be distorted. A problem occurs in that skin-like gloss unevenness (Yuzu skin image) remains. To improve this, it is necessary to provide a silicone rubber layer of 100 [μm] or more. The deformation of the silicone rubber layer absorbs minute irregularities and improves the Yuzu skin image.

The pressure roller 22 is an example of a pressure member. The pressure roller 22 is provided on the outside of the fixing belt 21 and is arranged to face the outside surface of the fixing belt 21 . Note that the outside of the fixing belt 21 means the outer peripheral surface side of the endless, that is, annular, fixing belt 21.

The pressure roller 22 has an annular or cylindrical shape, and as the pressure roller 22 rotates, the fixing belt 21 disposed opposite to the pressure roller 22 also rotates. As the paper P passes through the fixing nip N between the rotating pressure roller 22 and the fixing belt 21, the toner image transferred to the paper P is fixed to the paper P.

The pressure roller 22 has, for example, an elastic rubber layer provided on the outer periphery of a core metal (not shown), and a release layer (PFA or PTFE layer) provided on the surface to obtain release properties. The pressure roller 22 is rotated by receiving driving force from a drive source such as a motor provided in the image forming apparatus 1 via a gear. Further, the pressure roller 22 is pressed against the fixing belt 21 side by a spring or the like, and has a predetermined nip width due to the elastic rubber layer being crushed and deformed. The pressure roller 22 may be a hollow roller, or may include a heat source such as a halogen heater. The elastic rubber layer may be solid rubber, but if there is no heater inside the pressure roller 22, sponge rubber may be used. Sponge rubber is more desirable because it has better heat insulation and makes it difficult for the fixing belt to lose heat.

Both the fixing belt 21 and the pressure roller 22 have a shape that extends longer than the width of the paper P in a direction perpendicular to the rotation axis, that is, in a direction perpendicular to the paper surface in FIG. transport.

The heat source 23 is an example of a heating member that heats the fixing belt 21. The heat source 23 heats the fixing belt 21 . In this embodiment, two heat sources 23 (heat source 23A, heat source 23B) are provided as the heat source 23. In this embodiment, it is provided inside the fixing belt 21. The inside of the fixing belt 21 means the inner peripheral surface side of the fixing belt 21. The heat source 23 is, for example, a halogen heater. The heat source 23A and the heat source 23B are each longitudinally long rod-shaped members, and both ends of the heat source 23A and the heat source 23B in the longitudinal direction are fixedly held on a side plate or a holder of the fixing device 20.

The nip forming member 27 is an example of a nip forming member. The nip forming member 27 is provided inside the fixing belt 21 and forms a fixing nip N between the fixing belt 21 and the pressure roller 22.

The fixing belt 21 is heated by radiant heat from a halogen heater as a plurality of heat sources 23 (23A, 23B) provided inside. Note that the heat source 23 is not limited to a halogen heater. The reflecting plate 28 (28A, 28B) can reflect the radiant heat from the heat source 23 and efficiently heat the fixing belt 21.

The nip forming member 27 is arranged inside the fixing belt 21. The nip forming member 27 is brought into contact with the inner circumferential surface of the fixing belt 21, and its thickness does not change due to the pressure applied by the pressure roller 22, and the nip forming member 27 transfers heat.

For the nip forming member 27, metals such as iron, nickel, titanium, aluminum, and copper, and alloys such as stainless steel, brass, and aluminum alloys are used in consideration of thermal conductivity and mechanical strength. Further, the surface of the nip forming member 27 may be coated for the purpose of improving slidability, imparting corrosion resistance, and retaining grease by forming a physical shape. The coating contains fillers such as carbon materials, graphite, polytetrafluoroethylene, boron nitride, and solid lubricants such as molybdenum sulfide, and uses heat-resistant resins such as polyamide-imide resin, epoxy resin, and acrylic resin as a binder. Paint is used.

A base member 24 and a stay member 25 that reinforces the base member 24 are provided on the surface of the nip forming member 27 opposite to the surface that contacts the fixing belt 21 .

The stay member 25 is a member that reinforces the base member 24. The stay member 25 is disposed across the width direction of the fixing belt 21 and fixedly supports the base member 24. Since the base member 24 is fixedly supported by the stay member 25, the base member 24 is prevented from being bent due to the pressure from the pressure roller 22, and is uniform in the axial direction (longitudinal direction) of the pressure roller 22. A wide nip width can be obtained.

The base member 24 is made of a heat-resistant member with high mechanical strength and a heat-resistant temperature of 200° C. or higher, particularly a heat-resistant resin such as polyimide (PI) resin or polyether ether ketone (PEEK) resin, reinforced with glass fiber. It is preferable to configure. As a result, deformation of the base member 24 due to heat is prevented in the toner fixing temperature range, and a stable state of the fixing nip portion is ensured.

Furthermore, a temperature detection section 29 is provided on the outside of the fixing belt 21 . The temperature detection unit 29 detects the surface temperature (fixing temperature) of the fixing belt 21. The detection result of the surface temperature is used for temperature control of the heat sources 23 (heat sources 23A, heat sources 23B).

Furthermore, a separation unit 40 is arranged on the paper P discharge side of the fixing nip N. The separation unit 40 guides the conveyance of the paper P to the fixing nip N and separates the paper P from the fixing belt 21 .

In this embodiment, the sliding portion S between the inner surface of the fixing belt 21 and the nip forming member 27 is provided with the lubricant composition of the embodiment described above.

That is, the sliding portion S is an area between the inner surface of the fixing belt 21 and the nip forming member 27, and is an area where the nip forming member 27 contacts the inner circumferential surface of the fixing belt 21. In other words, the sliding portion S is a contact area with the nip forming member 27 on the inner circumferential surface of the fixing belt 21 .

The lubricant composition interposed in the sliding portion S means that the lubricant composition is applied to the sliding portion S (that is, between the inner surface of the fixing belt 21 and the nip forming member 27). It means that.

Note that the lubricant composition is preferably applied to the entire surface of the nip forming member 27 that comes into contact with the fixing belt 21 .

Here, FIG. 2 shows, as an example, a fixing device 20 having a configuration that does not include a storage section for storing a lubricant composition. Therefore, since the fixing device 20 of this embodiment is not configured to store the lubricant composition, it is possible to suppress the amount of the lubricant composition used, and it is possible to achieve cost reduction. However, since the amount of the lubricant composition used is small, it is necessary to suppress outflow of the lubricant composition due to heating and cooling, that is, a pump-out phenomenon in which the lubricant composition flows out from the sliding portion S. In particular, if the lubricant composition flows out to a region at the end of the nip forming member 27 that is not in contact with the fixing belt 21, the lubricant composition in the sliding portion S may be depleted.

Furthermore, in the fixing device 20 shown in FIG. 2, the heating area Q heated by the heat source 23 on the inner surface of the fixing belt 21 and the area where the fixing nip N in the fixing belt 21 is formed are different areas. There is. Therefore, the lubricant composition present in the region of the inner surface of the fixing belt 21 that is not heated by the heat source 23 has a lower viscosity than the lubricant composition present in the heating region Q. Therefore, when the lubricant composition flows out from the sliding portion S, the inner surface of the fixing belt 21 is likely to be abraded due to the contact with the nip forming member 27.

Further, when the abrasion powder on the inner surface of the fixing belt 21 is mixed into the lubricant composition, the viscosity of the lubricant composition further increases, and the lubricity at the sliding portion S is likely to decrease. Further, wear powder tends to accumulate at the end of the nip forming member 27, making it easier for the wear powder to absorb the lubricant composition, further reducing the lubricity of the sliding portion S.

Here, as mentioned above, the lubricant composition of this embodiment has the above-mentioned unique structure.

That is, as described above, in the lubricant composition of the present embodiment, when the heat cycle described above is repeated five times, the torque at each of the five heat cycles at 150° C. is less than 2000 μNm.

In this way, the lubricant composition interposed in the sliding portion S of the fixing device 20 of this embodiment exhibits very little change in torque even after repeated heat cycles. This indicates that a phenomenon in which the lubricant composition flows out from the sliding portion S (pump-out) is less likely to occur. Therefore, the lubricant composition of the present embodiment can suppress a decrease in lubricant retention of the sliding part S due to repetition of a heat cycle consisting of a pair of heating and cooling of the sliding part S. For this reason, in the fixing device 20 of the present embodiment, even if the fixing device 20 is repeatedly driven and cooled by being left unattended, the lubricant composition leaks less from the sliding portion S, which significantly extends the life of the fixing device 20. It is possible to extend it to

Furthermore, the lubricant composition of the present embodiment has a first shear viscosity (η ₁₀ ) of 1 Pa·s or more and 15 Pa·s or less at 25°C and a shear rate of 10/sec, and The thixotropy index, which is the ratio ((η _{10 )/(η 100 )) of the first shear viscosity (η 10 ) to the} second shear viscosity (η 100 ), is 1.2 or more and 5.0 or less.

If the first shear viscosity (η ₁₀ ) and thixotropy index are within the above ranges, when the lubricant composition is interposed in the sliding portion S of the fixing belt 21, the lubricant composition is moved by the influence of gravity. The occurrence of outflow is suppressed, and good slidability can be achieved. Furthermore, it is possible to reduce the torque of the fixing belt 21 at low temperatures and at normal temperatures.

Therefore, by interposing the lubricant composition of the present embodiment in the sliding portion S, which is the area between the nip forming member 27 and the fixing belt 21 in the fixing device 20, the fixing device 20 of the present embodiment and The image forming apparatus 1 including the fixing device 20 can suppress wear of the fixing belt 21, reduce generation of abrasion powder, and reduce torque.

Therefore, the image forming apparatus 1 and fixing device 20 of this embodiment can form high-quality images over a long period of time.

Furthermore, in the image forming apparatus 1 and the fixing device 20 of this embodiment, it is possible to reduce the torque, so it is possible to reduce power consumption and improve reliability. Furthermore, the lifespan of the image forming apparatus 1 and the fixing device 20 can be significantly extended.

Further, in the image forming apparatus 1 and the fixing apparatus 20 of the present embodiment, pump-out can be suppressed, so that it is possible to provide the image forming apparatus 1 and the fixing apparatus 20 in which contamination due to outflow of the lubricant composition is suppressed. I can do it. Note that the fixing device 20 of this embodiment may have a configuration in which the base member 24 is provided with a heating mechanism. In this case, the output of the heat source 23 can be set low.

(Modification 1)
The configuration of the fixing device 20 is not limited to the configuration shown in the above embodiment. FIG. 3 is a schematic diagram showing an example of the fixing device 20B of this modification. Fixing device 20B is a modification of fixing device 20. Note that in FIG. 3, the same functions and the same components as those of the fixing device 20 shown in FIG. 2 are given the same reference numerals, and detailed description thereof will be omitted.

The fixing device 20B includes a fixing belt 21, a pressure roller 22, a heat source 23, a base member 24, a stay member 25, a nip forming member 27, a temperature detection section 29, and a separation unit 40. . The fixing device 20B has the same configuration as the fixing device 20 in FIG. 2 except that it includes one heat source 23 and does not include the reflecting plate 28 (28A, 28B).

Further, in the fixing device 20B of this modification, like the fixing device 20 of the above embodiment, the sliding portion S between the inner surface of the fixing belt 21 and the nip forming member 27 is provided with the lubricant of the above embodiment. The agent composition is interposed.

Therefore, similarly to the fixing device 20 of the above embodiment, the fixing device 20B can reduce torque and suppress pump-out in the fixing device 20B. That is, the fixing device 20B of this modification and the image forming apparatus 1 including the fixing device 20B can suppress the wear of the fixing belt 21, reduce the generation of abrasion powder, and reduce the torque.

Furthermore, as described above, the fixing device 20B of this modification has a configuration in which the reflecting plate 28 is not provided. Therefore, the heat source 23 heats not only the fixing belt 21 but also the stay member 25. Therefore, the nip forming member 27 is heated by the heat source 23 via the base member 24 and the stay member 25B.

Therefore, the slidability of the sliding portion S immediately after the fixing device 20B is activated can be made better than that of the fixing device 20 of the above embodiment (see FIG. 2).

Therefore, in addition to the effects of the fixing device 20 of the above-described embodiment, the fixing device 20B of this modification can form high-quality images over a long period of time.

Note that the base member 24 of the fixing device 20B of this modification may be configured to include a heating mechanism. In this case, the output of the heat source 23 may be set low, or the structure may not include the heat source 23.

(Modification 2)
The configuration of the fixing device 20 is not limited to the configurations shown in the embodiment and the modification described above. FIG. 4 is a schematic diagram showing an example of a fixing device 20C of this modification. The fixing device 20C is a modification of the fixing device 20. Note that in FIG. 4, the same functions and the same components as those of the fixing device 20 shown in FIG. 2 are given the same reference numerals, and detailed description thereof will be omitted.

The fixing device 20C includes a fixing belt 121, a pressure roller 22, an IH (induction heating) coil unit 44, a base member 24, a stay member 25, a nip forming member 27, a temperature detection section 29, and a separation unit. 40.

The fixing device 20C includes a fixing belt 121 instead of the fixing belt 21, and an IH coil unit 44 instead of the heat source 23. Further, the fixing device 20B includes a soft ferrite 45, a temperature-sensitive magnetic alloy 50, and a magnetic field shielding plate 51.

The fixing belt 121 is an example of an endless belt. Fixing belt 121 is rotatably supported. Note that the fixing belt 121 is similar to the fixing belt 21 except that it has a layered structure for IH fixing.

Specifically, the fixing belt 121 has a structure for IH fixing, and is, for example, an endless belt with a multilayer structure consisting of a base layer, a heat generating layer, a multifunctional layer, an elastic layer, and a release layer from the inside. For example, the base layer is made of seamless polyimide with a diameter of 30 mm, the heat generating layer is made of copper which is a thin non-magnetic metal, the composite functional layer is made of nickel, the elastic layer is made of silicone rubber, and the release layer is made of PFA resin, with a total thickness of about 300 μm. be. The release layer of the fixing belt 121 ensures releasability for toner.

Similar to the above embodiment, the base member 24 is disposed across the width direction of the fixing belt 121 and is fixedly supported by the stay member 25. Therefore, the base member 24 and the nip forming member 27 are prevented from being bent due to the pressure from the pressure roller 22, and a uniform nip width can be obtained in the axial direction (longitudinal direction) of the pressure roller 22. When the pressure roller 22 is rotated in the direction of the arrow in FIG. 2 by a drive unit (not shown), the fixing belt 121 is also rotated in the direction of the arrow with this rotation.

The IH coil unit 44 is an example of a heat source, and heats the fixing belt 121 from the outside of the fixing belt 121. The IH coil unit 44 is disposed outside the fixing belt 121 in a region opposite to the fixing nip N without contacting the fixing belt 121. A temperature-sensitive magnetic alloy 50 and a magnetic field shielding plate 51 are provided inside the fixing belt 121 in a region facing the IH coil unit 44 . The temperature-sensitive magnetic alloy 50 and the magnetic field shielding plate 51 are arranged without contacting the inner peripheral surface of the fixing belt 121. The magnetic field shielding plate 51 is made of aluminum, for example.

That is, the fixing device 20C of this modification is an IH fixing type fixing device 20. In the IH fixing method, the fixing belt 121 and the IH coil unit 44 are sandwiched between two ferromagnetic materials, a soft ferrite 45 and a temperature-sensitive magnetic alloy 50, and the magnetic flux generated from the IH coil unit 44 is efficiently converted into thermal energy. By doing so, the fixing belt 121 is heated.

In this modification, the temperature detection section 29 is arranged near the IH coil unit 44 and detects the surface temperature on the fixing belt 121. The surface temperature detection result is used for temperature control of the IH coil unit 44.

In the fixing device 20C of this modification, like the fixing device 20 of the above embodiment, the sliding portion S between the inner surface of the fixing belt 121 and the nip forming member 27 contains the lubricant composition of the above embodiment. Things are intervening.

Therefore, the fixing device 20C can reduce torque and suppress pump-out in the fixing device 20C, similarly to the fixing device 20 of the above embodiment. That is, the fixing device 20C of this modification and the image forming apparatus 1 including the fixing device 20C can suppress wear of the fixing belt 121, reduce generation of wear powder, and reduce torque.

Therefore, the fixing device 20C of this modification can perform high-quality image formation over a long period of time, similarly to the fixing device 20 of the above embodiment. Note that the base member 24 of the fixing device 20C of this modification may be configured to include a heating mechanism.

Examples are shown below to explain the present invention in more detail, but the present invention is not limited to these Examples. Note that the symbols correspond to the respective configurations described above with reference to the figures.

The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.

<Preparation of perfluoropolyether oil (A)>
As the perfluoropolyether oil (A), the following three types, A1, A2, and A3, were prepared.
・A1: Perfluoropolyether Kinematic viscosity at 40°C: 92 mm ² /sec In general formula (1), Rf = trifluoromethyl group, m + n = 40 to 180
・A2: Perfluoropolyether Kinematic viscosity at 40°C: 159 mm ² /sec In general formula (1), Rf = trifluoromethyl group, m + n = 40 to 180
・A3: Perfluoropolyether Kinematic viscosity at 40°C: 310 mm ² /sec In general formula (1), Rf = trifluoromethyl group, m + n = 40 to 180

<Preparation of polytetrafluoroethylene powder (B)>
The following two types, B1 and B2, were prepared as polytetrafluoroethylene powder (B).
・B1: Polytetrafluoroethylene emulsion polymerized product Average primary particle size: 0.2 μm to 0.4 μm
Average secondary particle diameter: 5μm
・B2: Polytetrafluoroethylene emulsion polymerized product Average primary particle size: 0.125 μm
Average secondary particle diameter: 4μm

<Lubricant composition 1 to lubricant composition 5, comparative lubricant composition 1 to comparative lubricant composition 4>
Any one of A1, A2, A3, which is the perfluoropolyether oil (A) prepared above, and B1 or B2, which is the polytetrafluoroethylene powder (B), are mixed in the content (wt%) shown in Table 1. ), kneaded in a three-roll mill, defoamed, and prepared lubricant compositions 1 to 5 of Examples 1 to 5 and comparative lubrications of Comparative Examples 1 to 4. A lubricant composition 1 to a comparative lubricant composition 4 were obtained. Note that the content (% by weight) shown in Table 1 indicates the content based on 100% by weight of the lubricant composition (comparative lubricant composition).

<Evaluation>
For each of lubricant compositions 1 to 5 and comparative lubricant compositions 1 to 4, the shear viscosity (first shear viscosity (η ₁₀ ), second shear viscosity (η ₁₀₀ )), thixotropy index ((η ₁₀ )/(η ₁₀₀ )), and torque at each of five heat cycles at 150° C. were measured. The various test methods are as follows.

The measurement was performed using a rotary rheometer MCR302 manufactured by Anton Paar under the following conditions.

Shear viscosity: Measured using parallel plates with a gap of 0.1 mm. Specifically, the gap between a 25mm diameter plate (movable plate) and the opposing plate (fixed plate) was 0.1mm, the temperature was set at 25℃, and the temperature was set at 25℃ under a constant temperature (25℃) environment. When the movable plate is rotated for 2 minutes at a shear rate of 10/sec with lubricant composition 1 interposed in the gap, the average value of the shear viscosity for the last 10 seconds is determined as the first shear viscosity of lubricant composition 1. It was measured as viscosity (η ₁₀ ). Similarly, when the movable plate was rotated for 2 minutes at a shear rate of 100/sec while the temperature was set at 25°C, the average value of the shear viscosity for the last 10 seconds was calculated for the second shear viscosity of lubricant composition 1. It was measured as viscosity (η ₁₀₀ ). Note that the shear viscosity (first shear viscosity, second shear viscosity) was recorded every second, and the average value of the shear viscosity at 10 points obtained from 1 minute 51 seconds to 2 minutes was calculated.

Thixotropy index: The first shear viscosity (η ₁₀ ) at a shear rate of 10/sec and the second shear viscosity (η ₁₀₀ ) at a shear rate of 100/sec are measured as described above at a measurement temperature of 25°C, and these shear viscosities are The ratio was defined as the thixotropy index.
Thixotropy index (TI value) = [η ₁₀ ]/[η ₁₀₀ ]

The above measurements and calculations were performed for each of Lubricant Compositions 1 to 5 and Comparative Lubricant Compositions 1 to Comparative Lubricant Compositions 4. The measurement results of shear viscosity (first shear viscosity (η ₁₀ ), second shear viscosity (η ₁₀₀ )) and calculation results of thixotropy index (TI value) ((η ₁₀ )/(η ₁₀₀ )) are shown in the table below. Shown in 1.

Thermal History Measurement Thermal history was measured for each of Lubricant Compositions 1 to 5 and Comparative Lubricant Compositions 1 to Comparative Lubricant Compositions 4. Similarly to the above, a rotary rheometer MCR302 manufactured by Anton Paar was used with a plate having a diameter of 25 mm. The gap was set to 0.1 mm.

After measuring the shear viscosity at 25°C, a heat cycle consisting of the following steps (1) and (2) was repeated five times.

(1) With the rotation of the plate stopped, the temperature of the plate was heated to 150°C, and the torque was measured after holding the temperature at 150°C for 30 minutes (torque at 150°C).
(2) After lowering the temperature of the plate and cooling it to 25°C, the temperature was maintained at 25°C for 30 minutes.

The torque value, like the shear viscosity, was measured using a rotary rheometer MCR302 manufactured by Anton Paar using a parallel plate with a diameter of 25 mm. The gap was set to 0.1 mm, the temperature was set to 25° C., and the torque value for the final 10 seconds was calculated by rotating for 2 minutes at a shear rate of 10/sec.

The measurement results of torque at 150°C for each of lubricant compositions 1 to 5 and comparative lubricant compositions 1 to 4 during heat cycles 1 to 5 are as follows: It is shown in Table 2 and FIG. Table 2 also shows the torque at 150°C for 1 to 5 heat cycles for each of Lubricant Compositions 1 to 5 and Comparative Lubricant Compositions 1 to 4. showed the maximum value.

As shown in Table 1, the first shear viscosity (η ₁₀ ) of Lubricant Compositions 1 to 5 is 1 Pa·s or more and 15 Pa·s or less, and the thixotropy index (TI value: (η ₁₀ )/ (η ₁₀₀ )) was 1.2 or more and 5.0 or less. On the other hand, in Comparative Lubricant Compositions 1, 2, and 4, at least one of the first shear viscosity (η ₁₀ ) and the thixotropy index (TI value: (η ₁₀ )/(η ₁₀₀ )) was outside the above range. .

In addition, as shown in Table 2 and FIG. 1, when the heat cycle of heating at 150°C and cooling to 25°C was repeated 5 times for lubricant compositions 1 to 5, the heat cycle was 150°C. The torque at each of the five times at ℃ was less than 2000 μNm. On the other hand, the torques of Comparative Lubricant Compositions 1 to 4 during the five heat cycles at 150° C. included values exceeding 2000 μNm.

Therefore, from these evaluation results, lubricant compositions 1 to 5 are more effective at reducing torque and suppressing pump-out than comparative lubricant compositions 1 to 4. It was confirmed that it is possible to achieve this goal.

<Example 1 to Example 3, Comparative Example 1 to Comparative Example 2>
The fixing device of a color laser printer SP C840 (manufactured by Ricoh) was taken out, and a test machine incorporating the fixing device 20 shown in FIG. 2 was prepared.

(Example 1)
The lubricant composition 1 prepared above was applied to the sliding portion S between the inner surface of the fixing belt 21 and the nip forming member 27 in the fixing device 20. Specifically, the lubricant composition 1 was applied over the entire surface of the nip forming member 27 facing the fixing belt 21 at a coating amount of 10 to 45 mg/cm ² per unit area. After the coating, the fixing device 20 was assembled into the color laser printer SP C840, and a running test was conducted in a temperature environment of 15°C. In the running test, a series of processes in which six sheets were continuously printed and then paused for 50 seconds was repeated several times, and the transition of the fixing torque (of the fixing belt 21) was measured. Torque detector SS-050 (manufactured by Ono Sokki) was used for torque measurement. Then, based on the change in fixing torque, it was evaluated whether printing a specified number of sheets (300,000 sheets) was possible.

(Example 2 to Example 3, Comparative Example 1 to Comparative Example 2)
In addition, Example 1 was used except that lubricant composition 2, lubricant composition 4, comparative lubricant composition 2, and comparative lubricant composition 3 were used in place of lubricant composition 1. Torque was measured and evaluated in the same manner.

The evaluation results are shown in Table 3.

In addition, in Table 3, A, B, and C each indicate the following.
A: The specified number of sheets can be printed with a margin B: The specified number of sheets can be printed C: The specified number of sheets cannot be printed

Note that the above-mentioned evaluation result "A", which means that the specified number of sheets can be printed with a margin, means that no image quality deterioration occurs even if the specified number of sheets (300,000 sheets mentioned above) are printed. In addition, the above evaluation result "B" means that the specified number of sheets can be printed within the specified number of printed sheets (300,000 sheets above), and although slight fading and color misalignment may occur, the image quality is within the acceptable range. means a state of being. Further, the above evaluation result "C", ``unable to print the specified number of sheets'', means that an unacceptable abnormal image occurs within the specified number (300,000 sheets) of the specified number of printed sheets. Alternatively, it means that a paper jam occurs and printing becomes impossible.

As shown in Table 3, when each of lubricant composition 1, lubricant composition 2, and lubricant composition 4 is interposed in the sliding part S, comparative lubricant composition 2 and comparative lubricant composition The image quality was improved compared to the case where each of 3 was interposed in the sliding portion S.

<Example 4 to Example 6, Comparative Example 3 to Comparative Example 4>
The fixing device of a color laser printer SP C841 (manufactured by Ricoh Co., Ltd.) was taken out, and a test machine incorporating the fixing device 20C having the configuration shown in FIG. 4 was prepared.

(Example 4)
The lubricant composition 2 prepared above was applied to the sliding portion S between the inner surface of the fixing belt 121 and the nip forming member 27 in the fixing device 20C. Specifically, the lubricant composition 2 was applied over the entire surface of the nip forming member 27 facing the fixing belt 121 at a coating amount of 10 to 45 mg/cm ² per unit area. Then, the fixing device 20C after coating was assembled into the color laser printer SP C841, and a running test was conducted in a temperature environment of 28°C. In the running test, a series of processes in which 18 sheets were continuously printed and then paused for 110 seconds was repeated multiple times, and the transition of the fixing torque (of the fixing belt 121) was measured. A torque detector SS-050 (manufactured by Ono Sokki) was used for torque measurement. Then, based on the change in fixing torque, it was evaluated whether printing a specified number of sheets (300,000 sheets) was possible.

(Example 5 to Example 6, Comparative Example 3 to Comparative Example 4)
In addition, Example 4 was used, except that lubricant composition 3, lubricant composition 5, comparative lubricant composition 1, and comparative lubricant composition 4 were used in place of lubricant composition 2. Torque was measured and evaluated in the same manner.

The evaluation results are shown in Table 4. Note that the evaluation criteria for A, B, and C in Table 4 are the same as in Table 3.

As shown in Table 4, when each of lubricant composition 2, lubricant composition 3, and lubricant composition 5 is interposed in the sliding part S, comparative lubricant composition 1 and comparative lubricant composition 4 Compared to the case where each of these is interposed in the sliding portion S, the image quality can be improved.

<Example 7, Comparative Example 5>
The fixing device of a color laser printer SP C840 (manufactured by Ricoh Co., Ltd.) was taken out, and a test machine incorporating the fixing device 20B having the configuration shown in FIG. 3 was prepared.

(Example 7)
The lubricant composition 2 prepared above was applied to the sliding portion S between the inner surface of the fixing belt 21 and the nip forming member 27 in the fixing device 20B. Specifically, the lubricant composition 2 was applied over the entire surface of the nip forming member 27 facing the fixing belt 21 at a coating amount of 10 to 45 mg/cm ² per unit area. Then, the fixing device 20B after coating was assembled into the color laser printer SP C840, and a running test was conducted in a temperature environment of 15°C. In the running test, a series of processes in which 4 sheets were printed continuously and then paused for 60 seconds was repeated multiple times, and the transition of the fixing torque (of the fixing belt 21) was measured. Torque detector SS-050 (manufactured by Ono Sokki) was used for torque measurement. Based on the change in fixing torque, a specified number of sheets (300,000 sheets) was used. Then, based on the change in fixing torque, it was evaluated whether printing a specified number of sheets (300,000 sheets) was possible.

(Comparative example 5)
Further, torque was measured and evaluated in the same manner as in Example 7, except that Comparative Lubricant Composition 3 was used instead of Lubricant Composition 2.

The evaluation results are shown in Table 5. Note that the evaluation criteria for A and C in Table 5 are the same as in Table 3.

As shown in Table 5, when lubricant composition 2 was interposed in the sliding part S, image quality was improved compared to when comparative lubricant composition 3 was interposed in the sliding part S.

<Example 8>
90.5% by mass of A2, which is the perfluoropolyether oil (A) prepared above, and (B) polytetrafluoroethylene powder (emulsion polymerized product, average primary particle size 0.40 μm, average secondary particle size 5 μm) ) 9.5% by mass was kneaded using a three-roll mill and defoamed to prepare lubricant composition 6.

In the same manner as in Example 1, the fixing device of a color laser printer SP C840 (manufactured by Ricoh Co., Ltd.) was taken out and lubricant composition 6 was used instead of lubricant composition 1. A lubricant composition 6 was applied to the sliding portion S.

After the coating, the fixing device 20 was assembled into the color laser printer SP C840, and a running test was conducted in a temperature environment of 24°C. In the running test, a series of processes in which 10 sheets were printed continuously and then paused for 60 seconds was repeated multiple times, and the transition of the fixing torque (of the fixing belt 21) was measured. Torque detector SS-050 (manufactured by Ono Sokki) was used for torque measurement. Then, based on the change in fixing torque, it was evaluated whether printing a specified number of sheets (300,000 sheets) was possible.

As a result, an evaluation result of "A" indicating that "a specified number of sheets can be printed with a margin" was obtained. Therefore, even when lubricant composition 6 was used, image quality was improved.

Japanese Patent Application Publication No. 2008-096929 JP2003-206491A

Claims (7)

An endless belt, a pressure member provided on the outside of the belt and arranged opposite to the belt, a heating member that heats the belt, and a pressure member provided on the inside of the belt between the belt and the pressure member. A fixing device comprising: a nip forming member forming a fixing nip therebetween;
A lubricant composition is interposed between the inner surface of the belt and the nip forming member,
The lubricant composition comprises:
Perfluoropolyether oil (A) represented by the following general formula (1) and having a kinematic viscosity at 40° C. of 92 mm ² /sec to 310 mm ² /sec, and an average primary particle size of 0.2 μm to 0.4 μm. Contains polytetrafluoroethylene powder (B) in the following range, the content of the polytetrafluoroethylene powder (B) is 5% by weight or more and 17.5% by weight or less,
The lubricant composition includes:
The first shear viscosity at 25° C. and a shear rate of 10/sec is 1 Pa·s or more and 15 Pa·s or less, and the thixotropy index is the ratio of the first shear viscosity to the second shear viscosity at 25° C. and a shear rate of 100/sec. is in the range of 1.2 or more and 5.0 or less,
The content of other components other than the perfluoropolyether oil (A) and the polytetrafluoroethylene powder (B) in the lubricant composition is 0% by weight or more and 10% by weight or less,
Fusing device.
RfO(CF ₂ CF ₂ O) _m (CF ₂ O) _n Rf General formula (1)
[In general formula (1), Rf is a perfluoro lower alkyl group having 1 to 4 carbon atoms, m and n are each an integer of 0 or more, and the sum of m and n is 40 to 180; , CF ₂ CF ₂ O groups and CF ₂ O groups are randomly bonded in the main chain. ] An endless belt, a pressure member provided on the outside of the belt and arranged opposite to the belt, a heating member that heats the belt, and a pressure member provided on the inside of the belt between the belt and the pressure member. A fixing device comprising: a nip forming member forming a fixing nip therebetween;
A lubricant composition is interposed between the inner surface of the belt and the nip forming member,
The lubricant composition comprises:
Perfluoropolyether oil (A) represented by the following general formula (1) and having a kinematic viscosity at 40° C. of 92 mm ² /sec to 310 mm ² /sec, and an average primary particle size of 0.2 μm to 0.4 μm. Contains polytetrafluoroethylene powder (B) in the following range, the content of the polytetrafluoroethylene powder (B) is 5% by weight or more and 17.5% by weight or less,
The average secondary particle diameter of the polytetrafluoroethylene powder (B) is in the range of 1 μm or more and 10 μm or less,
The content of other components other than the perfluoropolyether oil (A) and the polytetrafluoroethylene powder (B) in the lubricant composition is 0% by weight or more and 10% by weight or less,
Fusing device.
RfO(CF ₂ CF ₂ O) _m (CF ₂ O) _n Rf General formula (1)
[In general formula (1), Rf is a perfluoro lower alkyl group having 1 to 4 carbon atoms, m and n are each an integer of 0 or more, and the sum of m and n is 40 to 180; , CF ₂ CF ₂ O groups and CF ₂ O groups are randomly bonded in the main chain. ] The lubricant composition includes:
When a heat cycle of heating at 150 °C for 30 minutes and then cooling to 25 °C is repeated 5 times, the torque measured with a rheometer at each of the 5 heat cycles at 150 °C is less than 2,000 μNm.
The fixing device according to claim 1 or claim 2 . The perfluoropolyether oil (A) has a kinematic viscosity at 40° C. of 50 mm ² /sec or more and 400 mm ² /sec or less,
The fixing device according to any one of claims 1 to 3. The content of the polytetrafluoroethylene powder (B) is in the range of 5% by weight or more and 10% by weight or less,
The fixing device according to any one of claims 1 to 4. A region heated by the heating member on the belt and a region where the fixing nip is formed on the belt are different regions;
The fixing device according to any one of claims 1 to 5 . An image forming apparatus comprising the fixing device according to claim 1 .

Images