Patent Application
20140153986
1. Field of the Invention
The present invention relates to a fixing member, a method of producing the fixing member, and a fixing device. This fixing member is used for fixing a toner image on a sheet in a copying machine, a printer, a facsimile machine, and a multifunction peripheral (MFP) comprising a plurality of these functions.
2. Description of the Related Art
Conventionally, a fixing device by which a toner image is fixed on a sheet (recording material) by heating and pressurizing the sheet on which the toner image has been formed has been employed in image forming apparatuses such as copying machines and the like. For the purpose of enhancing a function of the fixing member used in such a fixing device, it has been proposed to devise a surface layer of the fixing member.
In Japanese Patent Application Laid-Open No. 2004-101970, for the purpose of preventing toner from transferring from the sheet to the fixing member (enhancing a toner releasing property), it has been proposed that many grooves along its lengthwise direction are formed in a circumferential direction on the surface layer of the fixing member.
However, in the technique described in Japanese Patent Application Laid-Open No. 2004-101970, the surface layer of the fixing member is ground down and an initial groove shape cannot be kept as fixing processing is repeatedly performed. Consequently, it becomes difficult to keep the toner releasing property over a long period of time.
Thus, adding filler particles to the surface layer of the fixing member may be conceivable. In Japanese Patent Application Laid-Open No. 2007-304374, although the purpose is not enhancing the toner releasing property but enhancing a heat conductivity of the fixing member, it has been proposed that carbon nanotubes or carbon nanofibers is added as a filler to the surface layer of the fixing member.
However, when a whisker-shaped (rod-shaped) filler is added to the surface layer of the fixing member as described in Japanese Patent Application Laid-Open No. 2007-304374, the present inventor has found that a problem may occur depending on how to add it (orientation of the filler).
In detail, it is not specifically described how to add the filler in Japanese Patent Application Laid-Open No. 2007-304374, but the present inventor has found that, for example, when the filler is randomly oriented, it is likely to occur that a chemical affinity between the surface layer of the fixing member and the toner is increased and the toner releasing property is lowered.
Therefore, when the filler is randomly oriented in the surface layer of the fixing member, an amount of the toner that transfers from the sheet to the fixing member may be increased and an image quality may be decreased.
As described above, when the whisker-shaped (rod-shaped) filler is added to the surface layer of the fixing member, it becomes difficult to enhance the toner releasing property, depending on how to orient the filler.
The present invention is directed to a fixing member that can enhance a toner releasing property, a method of producing the fixing member, and a fixing device.
The present invention is further directed to a fixing member that can prevent quality loss of an image even in the use of the fixing member over a long period of time, a method of producing the fixing member, and a fixing device.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, the fixing member, the method of producing the fixing member, and the fixing device according to an exemplary embodiment of the present invention will be described specifically.
First, an image forming unit that forms a toner image on a sheet P (recording material) will be described.
The printer illustrated in
The toner image is formed according to the following procedure in each image forming unit. This electrophotographic image forming process is common in the respective image forming units. Thus, one image forming unit as a representative will be described.
The photosensitive drum 11 is evenly charged in a predetermined polarity (negative polarity in the present exemplary embodiment) by the charging device 12. Subsequently, an electrostatic latent image is formed according to image data to be output on the photosensitive drum 11 by a laser scanner (exposure device) 13. The electrostatic latent image formed on the photosensitive drum 11 as described above is developed using toner T (regular charging polarity is the negative polarity in the present exemplary embodiment) by the developing device 14 to make the toner image.
Subsequently, the toner image formed on the photosensitive drum 11 is transferred onto an intermediate transfer member 31 via a primary transfer member 17 to which a bias with predetermined polarity (positive polarity in the present exemplary embodiment) has been applied. After the primary transfer, residual toner left on the photosensitive drum 11 is collected by the cleaning device 15 and prepared for a subsequent image formation.
Through the above image forming process, the toner image of each color is sequentially superposed and transferred on the intermediate transfer member 31, and conveyed to a secondary transfer portion.
Meanwhile, the sheet P is sent one by one from a paper supply cassette 20 or a multiple paper supply tray 25, and fed to a registration roller pair 23. The registration roller pair 23 once stops the movement of the sheet and corrects an orientation of the sheet when the sheet is oblique. Further, the registration roller pair 23 feeds the sheet P to between the intermediate transfer member 31 and the secondary transfer member 35 in synchronization with the toner image on the intermediate transfer member 31. The full-color toner image of four colors on the intermediate transfer member 31 is secondarily transferred collectively onto the sheet P via the secondary transfer member 35 to which the predetermined polarity (positive polarity in the present exemplary embodiment) has been applied. Subsequently, the toner image formed on the sheet P is fixed on the sheet P by heating and pressurizing the sheet P in the fixing device 40.
Subsequently the fixing device 40 will be described.
The fixing device of a heat roller method composed of a pair of two rollers is used in the present exemplary embodiment. More specifically, the fixing device 40 according to the present exemplary embodiment includes a fixing roller (fixing member) 42 and a pressing roller (nip forming member) 43 pressed to the fixing roller 42. And, the unfixed toner image is fixed on the sheet P by sandwiching the sheet P with the fixing roller 42 and the pressing roller 43 in the nip portion (fixing nip portion) formed between the fixing roller 42 and the pressing roller 43 and feeding the sheet P through the nip portion.
In the present exemplary embodiment, the fixing device of the heat roller type is described as an example, but the present invention can be applied without being limited to such a configuration. It is possible to use a fixing belt in place of the fixing roller and use a pressing belt in place of the pressing roller. Further, it is also possible to replace both the fixing roller and the pressing roller with the fixing belt and the pressing belt.
A halogen heater 41 (hereinafter simply referred to as a heater) is a heating unit, and extends in a direction perpendicular to a paper plane in
The metal core (basic layer) 42c is a hollow cylindrical member using a heat resistant material having a thickness of 2 mm or more so that a shape of a roller structure is not deformed with a load and can withstand the load. As the metal core 42c, it is preferable to use a metal material such as stainless steel (SUS) and nickel, and SUS having a thickness of 3 mm and a diameter of 60 mm was used in the present exemplary embodiment.
As the elastic layer 42b, it is preferable to use a rubber material, specifically silicone rubber or fluorine rubber having a thickness of 1 mm to 10 mm so as to ensure a fixing nip width utilizing deformation of the elastic layer. As the elastic layer 42b, the silicone rubber having a rubber hardness of 10 degrees (JIS-A), a heat conductivity of 1.3 W/m·k and a thickness of 4 mm was used in the present exemplary embodiment.
The surface layer (toner releasing layer) 42a is formed using a fluorine-based resin material having a thickness of 100 μm or less and preferably 20 to 70 μm as a base. As the fluorine-based resin to be the base that composes the surface layer 42a, it is preferable to use polytetrafluoroethylene (PTFE), tetrafluoroethylene hexafluoropropylene copolymer (FEP), or tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA). In the present exemplary embodiment, PFA was used as the base that composes the surface layer. Also being described later, whisker-shaped filler particles F have been added.
A method of forming the surface layer 42a can include a method of covering the elastic layer with a tube molded body formed cylindrically and a method of applying and burning resin on the elastic layer 42b. The latter method is used in the present exemplary embodiment.
The pressing roller (nip forming member, pressing member) 43 is composed of a metal core and an elastic layer composed of heat resistant rubber such as silicone rubber and fluorine rubber or a foam body of the silicone rubber. Both ends of the metal core are rotatably supported with bearings. A nip portion N with a predetermined width is formed along a sheet feeding direction by arranging the aforementioned fixing roller 42 above the pressing roller 43 and pressing the pressing roller 43 against the fixing roller via pressing force member (spring) (not illustrated). The silicone rubber having a thickness of 2 mm was used as the elastic layer and a cylindrical member having a diameter of 60 mm and composed of SUS having a thickness of 2 mm was used as the metal core in the present exemplary embodiment.
Subsequently, a method of producing the surface layer 42a of the fixing roller (fixing member) (method of applying and forming the surface layer) will be described with reference to
Being described below, the present exemplary embodiment is characterized in that the wisker-shaped filler particles F are added to the surface layer 42a so that the long axis direction thereof are aligned and oriented substantially along the rotation direction of the fixing roller, in order to enhance the toner releasing property of the surface layer 42.
First, a PFA resin dispersion in which PFA resin is dispersed in a liquid (AD—2CRE manufactured by Daikin Industries Ltd.), which is a base resin of the surface layer 42a is prepared. Then, the filler particles are added to and dispersed in the PFA resin dispersion to produce a coating agent.
Subsequently, the precursor of the PFA resin is coated onto the metal core on which the elastic layer has been formed using a coating agent coating mechanism 51 in which the coating agent has been housed. In the spin-coating method, the coating agent to be the surface layer is coated over the entire area in the lengthwise direction of the elastic layer by rotating the metal core on which the elastic layer has been formed and relatively moving (coming down) the metal core at a predetermined speed for the coating mechanism 51.
Subsequently, the coating agent coated onto the elastic layer 42b is dried and heated at 320° C. for 15 minutes to form a film. As a result, the surface layer having a thickness of 20 μm is formed.
A principle that the wisker-shaped filler particles are aligned in the rotation direction X as illustrated in
Subsequently, a type of the filler and the toner releasing property were verified. Conditions of surface layer materials used for verification experiments are summarized as illustrated in the following Table 1.
In Table 1, no filler was added in Comparative Example 1, spherical silica (particle diameter: 1 to 2 μm) as the filler particles was added in an amount of 5% by weight in Comparative Example 2, and the whisker-shaped filler particles were added in an amount of 5% by weight in present exemplary embodiment. The PFA resin was used as the base of the surface layer in all of the cases. The whisker refers to a whisker-shaped crystal, and the filler particle illustrating a whisker shape is collectively referred to as the whisker-shaped filler particle in the present exemplary embodiment. This can also be referred to as a rod-shaped filler particle.
As a material for the whisker-shaped (rod-shaped) filler particles, it is preferable to use carbon fibers, ZnO (zinc oxide), TiO2 (titanium dioxide), or 2Al2O3.B2O3 (aluminum borate). In the present exemplary embodiment, 2Al2O3.B2O3 that had a high affinity with the PFA resin and was difficult to cause peel of the filler particles even when a fixing processing was repeatedly performed was used as the filler. A mixture of the carbon fibers, ZnO, TiO2 and 2Al2O3.B2O3 may also be used as the filler, and at least one of the carbon fibers, ZnO, TiO2 and 2Al2O3.B2O3 can be included.
The rod-shaped particles having a diameter of 1 to 2 μm, a length of 5 to 10 μm, and an aspect ratio of 5 to 10 were used as the filler. The aspect ratio refers to a ratio of a length of the lengthwise direction to a length of a short direction of the filler particle.
Here, the aspect ratio and a method of measuring the aspect ratio are described referring to
α=L/W (Formula 1)
For example, in the case of a rod-shaped particle as illustrated in
A method of evaluating the aspect ratio of the filler particles dispersed in the base resin of the surface layer material includes following methods. When a pyrolysis temperature of the filler particle is higher than that of the base resin in the surface layer, the base resin in the surface layer is sufficiently heated to a temperature at which pyrolysis occurs and burned out, and the aspect ratio can be obtained by measuring the shape of the remaining filler particles under an electron microscope. When the pyrolysis temperature of the filler particle is lower than that of the base resin in the surface layer, the fixing roller is cut (along a direction perpendicular to a rotation axis line direction) using a metal cutter to obtain its cross section. And, the aspect ratio can be obtained by measuring the shape of the filler particle in the cross section under the electron microscope.
Table 2 illustrates results of the verification experiment for the toner releasing property in each surface layer illustrated in Table 1.
In this verification experiment, as a fixing condition, the temperature was adjusted by 10° C. so that the temperature of the fixing roller and the pressing roller was 130 to 200° C., a pressurizing force was 100 kgf as a total pressure, and a rotation speed of the fixing roller was 200 mm/s. A sheet used is “OK Prince high quality paper” of A4 size (manufactured by Oji Paper Co., Ltd., weighing 52 g/m2). A toner image of 1.2 mg/cm2 was evenly formed and fixed in an entire imageable area on the sheet.
In the evaluation of the toner releasing property, a case where the sheet was appropriately separated from the fixing roller was evaluated as OK, whereas a case where the sheet twined around the fixing roller to cause a jam was evaluated as NG.
First, Comparative Example 2 in which silica was added is discussed. From Table 2, it has been found that whereas a separable temperature (highest temperature at which the sheet can be separated from the surface layer) was 170° C. in Comparative Example 1 in which no filler was added, the separable temperature dropped in Comparative Example 2 in which silica was added as the filler.
As illustrated in
From these observation results, the reduction of the toner releasing property is considered to be associated with the following two factors.
First, surface energy of the base resin that composes the surface layer is increased by adding the filler to increase a chemical affinity with the toner. Thereby, it is considered that adhesiveness of the toner to the surface layer is increased to reduce the toner releasing property.
Second, the concavoconvex state is randomly formed on the surface, and thus, a phenomenon that the melted toner is fitted in concave portions where silica is closely packed occurs easily. If such a phenomenon occurs, a stronger force for releasing the toner is required, and thus the toner releasing property seems to be reduced.
Subsequently, the case according to the present exemplary embodiment where the whisker-shaped filler particles were added is considered.
As illustrated in
Subsequently, the reason why the toner releasing property is enhanced by orienting the whisker-shaped filler particles to the circumferential direction X in this way will be described referring to
On the other hand, when the whisker-shaped filler particles are added as illustrated in
From the above results, the surface layer having the high toner releasing property could be made by adding the whisker-shaped filler particles so that the long axis direction thereof is aligned and oriented to the rotation direction of the fixing roller.
Subsequently, verification experiments were carried out for a coating method of the coating agent and the toner releasing property. Conditions for the surface layer materials used for the verification experiments are summarized as illustrated in the following Table 3.
Here, in order to describe superiority of the spin-coating method employed in the present exemplary embodiment, a spray coating method is described as Comparative Example 3.
In the spray coating method, a precursor of the PFA resin is applied using a spray mechanism 50 onto the metal core on which the elastic layer has been formed, and the precursor having a desired thickness is burned to make the surface layer. The desired thickness after being burned can be controlled by controlling a concentration and a viscosity of the precursor and a thickness of the applied precursor.
The fixing condition and the method of determining the toner releasing property are the same as the aforementioned techniques. The results are summarized as illustrated in the following Table 4.
From the above results, the surface layer having the high toner releasing property could be made by adding the whisker-shaped filler particles and employing the spin-coating method.
A verification experiment was carried out for a relationship between the filler shape (aspect ratio) and the toner releasing property. In this verification experiment, levels 1 to 8 were verified by changing the aspect ratio (long axis length/short axis length) of the filler particle. In this verification experiment, the rod-shaped filler particle (
First, the aspect ratio and the toner releasing property are focused. In the present exemplary embodiment, the experiment was carried out using the rod-shaped filler particles having various aspect ratios. Specifically, the filler particles having the aspect ratio ranging from 1 to 10 were added.
When the surface layer using such a filler was observed using the laser microscope, it could be confirmed that the surface layer containing the filler particles having the aspect ratio of 5 or more exhibited the state as illustrated in
Here, an orientation property (degree of orientation) of the filler particles in each aspect ratio is described using an orientation rate. The orientation rate A in this verification experiment was calculated by a following formula 2 when 50 filler particles were observed using an optical microscope and the number of particles satisfying −30°≦θ≦30° where an angle θ was made by the long axis direction of the filler particle and the rotation direction X of the fixing roller is N (see
A=(N/50)×100(%) (Formula 2)
As a result, the orientation rate was 75% in the filler having the aspect ratio of 5 or more and 50% or less in the filler having the aspect ratio of 3 or less. Therefore, it is found that the orientation property (degree of orientation) of the filler particle depends on the aspect ratio. Accordingly, it is found that it is better to include the filler particles having the aspect ratio of 5 or more and oriented within ±30° against the rotation direction X of the fixing roller in an amount of 75% or more among the filler particles added to the surface layer. When such a condition is satisfied, the toner releasing property can be enhanced.
Subsequently, focusing on the condition in which the maximum peak height Rp satisfies Rp≧2 μm (levels 5 to 8), the relationship between the aspect ratio and the toner releasing property is considered. The separable temperature (highest temperature at which the sheet can be separated from the surface layer) was further increased and the toner releasing property was enhanced in the conditions where the aspect ratio is 5 to 10, while in the aspect ratio of 1 to 3, the toner releasing property was equivalent to that in Comparative Example 1 (no filler was added).
When the filler particle has the small aspect ratio, a rotation force of the filler against an coating flow is weakened, and easiness to align the particles depending on a direction of the coating flow as illustrated in
Next, the condition of adding the filler particles having the aspect ratio of 5 to 10 is focused concerning the maximum peak height Rp and the separable temperature (the highest temperature at which the sheet can be separated from the surface layer) as well as image formation. Under the condition where the maximum peak height satisfies Rp≧1 μm, the separable temperature (the highest temperature at which the sheet can be separated from the surface layer) rose, and it could be confirmed that the toner releasing property was improved.
A verification experiment was carried out for durability of the surface layer. In this verification experiment, a roughening treatment with a wrapping film was given to the surface layer in Comparative Example 4 so that this surface layer has the same surface roughness as that in present exemplary embodiment. The methods of determining the fixing condition and the separable temperature (the highest temperature at which the sheet can be separated from the surface layer) were the same as above. Also in this verification experiment, in order to verify whether the roughness of the surface layer was kept or not over a long period of time, the sheets on which no toner image was formed (aforementioned OK Prince high quality papers) as many as illustrated in Table 6 were continuously passed through the fixing nip portion. Subsequently, the unfixed toner image was formed in an imageable area on the sheet (OK Prince high quality paper) as described above, and then a separative property of the sheet (toner releasing property) was determined when the fixing processing was performed. The results of this verification experiment are summarized as illustrated in the following Table 6.
In Comparative Example 4, the surface layer had the maximum peak height Rp of 1 μm by giving the roughening treatment using the wrapping film, and thus the high toner releasing property was obtained without dropping the separable temperature at a stage up to 100,000 sheets. However, the separable temperature dropped at a stage of 200,000 sheets and dropped to the same level as that in Comparative Example 1 at a stage of 300,000 sheets (Rp=0.3 μm).
On the other hand, in the configuration of the present exemplary embodiment, even when the surface layer was ground down due to passage of the sheets, a new filler in the surface layer is exposed. Thus, the initial concavoconvex state (Rp=1 μm) was kept at the stage of 500,000 sheets, and the toner releasing property could be kept in the use over a long period of time.
From the above results, according to the configuration of present Example, it is possible to provide the surface layer of the fixing member having the high toner releasing property over a long period of time.
Subsequently, a second exemplary embodiment will be described. In the first exemplary embodiment described above, in terms of enhancing the toner releasing property on the surface layer of the fixing roller (fixing member), it has been found that the whisker-shaped filler particles are aligned/oriented in the surface layer to nearly follow the rotation direction of the fixing roller. In present exemplary embodiment, the investigation was carried out in terms of “output image quality” in addition to the viewpoint found in the first exemplary embodiment.
Specifically, a verification experiment was carried out for a relationship between the roughness of the surface layer and the output image quality. In this verification experiment, the rod-shaped filler (aspect ratio of 5) illustrated in
The roughness of the surface layer of the fixing roller was evaluated by measuring the maximum peak height Rp using the surface roughness meter (DSF500 manufactured by Kosaka Laboratory Ltd.) (according to JI51994) in the same manner as in The first exemplary embodiment. The separable temperature (the highest temperature at which the sheet can be separated from the surface layer of the fixing member) was determined in the same manner as in The first exemplary embodiment. Concerning the output image quality, a fault (gloss unevenness of an image) on an output image after the fixing processing was checked visually. Then, a case of no fault was evaluated as OK and a case of having the fault was evaluated as NG. The filler particle shapes examined in this verification experiment and experimental results are summarized as illustrated in the following Table 7.
From these results, a quality loss (occurrence of the fault) was observed on the output image after the fixing processing when the maximum peak height satisfies Rp≧4 μm. Therefore, it is found that it is preferable that the maximum peak height Rp is in the range of 1 μm≦Rp≦3 μm while the condition where the aspect ratio is 5 or more as described in the first exemplary embodiment is satisfied. Therefore, by employing the configuration of the present exemplary embodiment, the satisfied level of the separable temperature (the highest temperature at which the sheet can be separated from the surface layer) can be obtained, as well as the satisfied level of the quality for the output image can be obtained.
As described above, by aligning/orienting the whisker-shaped filler particles in the surface layer to nearly follow the rotation direction of the fixing roller as well as satisfying the maximum peak height of 1 μm≦Rp≦3 μm on the surface layer, it is possible to prevent the quality loss of the output image compared with the configuration of the first exemplary embodiment.
A third exemplary embodiment will be described referring to
As illustrated in
As illustrated in
In the elastic layer 44b, it is preferable to use a rubber material, specifically silicone rubber or fluorine rubber having a thickness of 1000 μm or less and preferably 500 μm or less in order to reduce a heat capacity and enhance a quick starting property. The silicone rubber having a rubber strength of 10 degrees (JIS-A), a heat conductivity of 1.3 W/m·k and a thickness of 300 μm was used in the present exemplary embodiment.
The basic layer 44c is a metal layer. In order to enhance the quick starting property as with the elastic layer 44b, it is preferable to use a heat resistant material, specifically SUS or nickel having a thickness of 100 μm or less and preferably 50 μm or less and 20 μm or more for the basic layer. In the present exemplary embodiment, a cylindrical nickel metal film having a thickness of 30 μm and a diameter of 25 mm was used.
Also in the fixing device using the fixing belt 44 according to the present exemplary embodiment, it is possible to enhance the toner releasing property as is with the first exemplary embodiment.
The configuration of the present exemplary embodiment may also satisfy the configuration of the second exemplary embodiment, i.e., that the maximum peak height Rp on the surface layer of the fixing belt 44 is 1 μm≦Rp≦3 μm. In that case, it is possible to prevent the quality loss of the output image.
As described above, the present invention has been specifically described with reference to the first exemplary embodiment, second exemplary embodiment, and the third exemplary embodiment, and it is also possible to replace various configurations with known configurations within the scope of the thought of the present invention.
Also in the first to third exemplary embodiments described above, the fixing member typified by the fixing roller or the fixing belt has been described to have the triple layer structure composed of the basic layer, the elastic layer, and the surface layer, but, for example, the elastic layer may be omitted and the surface layer may be formed directly on the basic layer.
Further in the first to third exemplary embodiments described above, the configuration in which the whisker-shaped filler is added to the surface layer of the fixing member typified by the fixing roller or the fixing belt has been described, but the configuration is not limited to such a configuration. For example, the same configuration in which the wisker-shaped filler is added to the surface layer may also be applied to the pressing roller and the pressing belt. In this case, the pressing roller and the pressing belt would work as the fixing member according to the present invention.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2012-263252, filed Nov. 30, 2012, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-263252 | Nov 2012 | JP | national |
