Fixing rotor, fixing device, electrophotographic image forming apparatus, and method for manufacturing fixing rotor

Abstract

To provide a rotating body for fixing that can maintain high toner releasability for a longer time than before.SOLUTION: A rotating body for fixing has a base layer, an elastic layer, and a surface layer in this order. The surface layer includes PFA and PFPE. The surface layer has holes that open in a first surface constituting an outer surface of the rotating body for fixing. At least part of the holes includes the PFPE. When a specific first observation area is placed on the first surface of the surface layer in which the PFPE in the holes is removed, and the ratio of the total sum of the areas of the holes in the first observation area to the area of the first observation area is defined as P1, and when a specific second observation area is placed on a cross section of the surface layer in which the PFPE in the holes is removed, the cross section including the entire thickness portion of the surface layer along the circumferential direction of the rotating body for fixing, and the ratio of the total sum of the areas of the holes in the second observation area to the area of the second observation area is defined as P2, P2 / P1 is 1.3 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a fixing rotatable member, a fixing device, and an electrophotographic image forming apparatus. [Background technology]

[0002] In a fixing device used in an electrophotographic image forming apparatus (hereinafter also referred to as an "image forming apparatus") such as a copier or laser printer, a pair of rotating bodies, such as a pair of heated rollers, a film and a roller, a belt and a belt, are pressed together. A recording medium, such as paper, carrying an image formed with unfixed toner is introduced into the pressure contact area formed between these rotating bodies (hereinafter referred to as the "fixing nip"), and the unfixed toner is heated and melted, thereby fixing the image to the recording medium. The fixing rotating body that comes into contact with the unfixed toner image on the recording medium may be called a fixing roller, a fixing film, or a fixing belt, depending on its form. In recent years, the paper media used for forming electrophotographic images has become increasingly diverse. For example, 2 There is a demand for a fixing member that can handle thin paper such as paper rolls. However, because such thin paper has low rigidity, when a fixing member such as a conventional fixing rotor is used, melted toner adheres to the surface of the fixing rotor during thermal fixing, causing the thin paper to wrap around the fixing rotor. In order to stably form an electrophotographic image on thin paper, it is necessary to provide the surface of the fixing rotor with high toner releasability. Patent Document 1 discloses a fixing member whose surface layer contains a fluororesin and perfluoropolyether (hereinafter also referred to as "PFPE") and can maintain high toner releasability for a long period of time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 181796 [Non-patent literature]

[0004] [Non-Patent Document 1] "Journal of the Japan Adhesion Society", Japan Society of Adhesion, 1972, Vol. 8, No. 3, pp. 131-141 [Non-patent document 2] IEEE Transactions on Image Processing Vol.4, Issue: 3, March 1995, pp. 370-378 [Non-patent document 3] IEEE Transactions on SYSTEMS, MAN, AND CYBERNETICS, vol. SMC-9, No.1, Jan 1979, pp.62-66 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the studies of the present inventors, the fixing member disclosed in Patent Document 1 exhibits excellent toner release properties over a long period of time. However, in the surface layer of the fixing member disclosed in Patent Document 1, the fluorinated oil exists without phase separation from the fluorinated resin (paragraph

[0018] of Patent Document 1). In this case, there is a limit to the amount of fluorinated oil that can be contained in the surface layer. Therefore, in order to impart excellent toner release properties over a longer period of time to a fixing rotating body, the present inventors recognized that technological development is necessary to provide a fixing rotating body that can retain a larger amount of PFPE and can stably supply the PFPE to its outer surface. One aspect of the present disclosure is to provide a fixing rotating body that can maintain high toner releasability for a longer period than conventionally possible, and a manufacturing method thereof. The present invention aims to provide a fixing device and an electrophotographic image forming apparatus that can stably form high-quality electrophotographic images over a long period of time. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a fixing rotating body having a base layer, an elastic layer, and a surface layer in this order, the surface layer comprises a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer and a perfluoropolyether; the surface layer has pores that open to a first surface that constitutes the outer surface of the fixing rotor, At least a portion of the pores contain the perfluoropolyether; a first observation region having a length of 8 μm and a width of 11 μm is placed on the first surface of the surface layer from which the perfluoropolyether in the pores has been removed, and P1 is the ratio of the sum of the areas of the openings observed in the first observation region to the area of ​​the first observation region; A second observation region measuring 8 μm in length and 11 μm in width is placed on a cross section of the surface layer from which the perfluoropolyether in the pores has been removed, the cross section including the entire thickness of the surface layer along the circumferential direction of the fixing rotor, and when the ratio of the sum of the areas of the pores observed in the second observation region to the area of ​​the second observation region is defined as P2, A fixing rotor having a P2 / P1 ratio of 1.3 or greater is provided. According to another aspect of the present disclosure, there is provided a fixing device including the fixing rotator described above and a heating unit for heating the fixing rotator. According to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above-described fixing device. According to yet another aspect of the present disclosure, there is provided a method for manufacturing a fixing rotor, comprising: (i) preparing a laminate having a base layer in the shape of an endless belt or a roller, an elastic layer on the outer peripheral surface of the base layer, and a resin layer containing a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer on the outer peripheral surface of the elastic layer; (ii) immersing the laminate in a first perfluoropolyether heated to a temperature of 300°C ± 50°C to impregnate the resin layer with the perfluoropolyether; (iii) a step of cooling the laminate obtained in the step (ii) in which the perfluoropolyether has been impregnated into the resin layer; (iv) removing at least a portion of the perfluoropolyether impregnated in the resin layer using a fluorine solvent to form pores in the resin layer that are open to the first surface of the resin layer; and (v) A method for producing a fixing rotor is provided, which includes a step of incorporating a second perfluoropolyether into at least a portion of the pores to obtain a fixing rotor having a surface layer containing the second perfluoropolyether in at least a portion of the pores. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, a fixing rotating body and an electrophotographic image forming apparatus can be obtained that can maintain high toner releasability for a long period of time. Also, according to another aspect of the present disclosure, a fixing device and an electrophotographic image forming apparatus can be obtained that can stably form high-quality electrophotographic images for a long period of time. [Brief explanation of the drawings]

[0008] [Figure 1] 1A is a surface observation image of the resin layer of the fixing rotating member described in Example 1, (B) is a cross-sectional image of the resin layer observed in a cross section along the belt circumferential direction, and (C) is a cross-sectional image of the surface layer. [Figure 2] Schematic cross-sectional view of the fixing belt (A) and fixing roller (B) [Figure 3] Schematic cross-sectional view of a fixing device using a fixing belt [Figure 4] Schematic cross-sectional view of a fixing device using a fixing roller [Figure 5] Schematic cross-sectional view showing one embodiment of an electrophotographic image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0009] The expressions "XX or more and YY or less" or "XX to YY" that represent a numerical range mean a numerical range including the endpoints, that is, the lower limit and the upper limit, unless otherwise specified. When numerical ranges are stated in stages, the upper and lower limits of each numerical range can be combined in any way.

[0010] The present inventors have conducted extensive research to obtain a fixing rotor that can maintain excellent toner releasability even after long-term use. As a result, they have found that the above-mentioned object can be achieved by having a surface layer containing tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), having pores that open to a first surface that constitutes the outer surface of the fixing rotor, at least some of the pores containing perfluoropolyether, and setting the opening ratio P1 of the pores on the outer surface and the porosity P2 of the openings in the cross section within the above-mentioned ranges. The surface layer has pores, which allow the surface layer to contain PFPE in the pores, and therefore the fixing rotor can retain more PFPE in its surface layer than the surface layer disclosed in Patent Document 1, which retains PFPE in a fluororesin without phase separation. Furthermore, since the pores are open to the first surface of the surface layer that constitutes the outer surface of the fixing rotor, the PFPE in the pores can be transferred to the first surface. Furthermore, by setting the relationship between the ratio P1 of the opening area per unit area of ​​the outer surface of the surface layer and the ratio P2 of the pore area per unit area of ​​the cross section of the surface layer to P2 / P1≧1.3, the amount of PFPE transferred to the outer surface can be controlled. As a result, it is believed that the fixing rotor according to this embodiment can maintain excellent toner releasability for a longer period of time compared to the fixing member according to Patent Document 1.

[0011] The fixing rotor will be described in detail below. 1. Rotating body for fixing The fixing rotating body is, for example, a fixing roller, a fixing film, a fixing belt, etc. The fixing rotating body has a base layer, an elastic layer, and a surface layer in this order. 2(A) and 2(B) are cross-sectional views showing different embodiments of the fixing rotor. Fig. 2(A) shows a fixing rotor having an endless belt shape (hereinafter also referred to as "fixing belt 11"), and Fig. 2(B) shows a roller-shaped fixing rotor (hereinafter also referred to as "fixing roller 12"). 2(A) and 2(B) has a base layer 13, an elastic layer 14 that covers the outer surface of the base layer, and a surface layer 15 that covers the surface of the elastic layer opposite to the side facing the base layer. The surface layer 15 may be adhered to the surface of the elastic layer 14 opposite to the side facing the base layer by an adhesive layer (not shown).

[0012] (1) Base layer The material of the base layer 13 is not particularly limited, and may be any known material used as a base layer for a fixing member such as a fixing rotor, etc. For example, metals and alloys such as aluminum, iron, stainless steel, and nickel, and heat-resistant resins such as polyimide may be used. In the fixing belt 11, a substrate having an endless belt shape may be used as the base layer 13. In this case, the material of the base layer 13 may be, for example, nickel, stainless steel, or polyimide, which has excellent heat resistance. The thickness of the base layer 13 is not particularly limited, but is preferably 20 μm or more and 100 μm or less from the viewpoints of strength, flexibility, and heat capacity.

[0013] In the fixing roller 12, for example, a solid or hollow core is used as the base layer 13. The core may be made of a metal or alloy such as aluminum, iron, or stainless steel. When a hollow core is used, it is possible to provide a heat source inside. The outer surface of the base layer 13 may be subjected to a surface treatment to impart adhesion to the elastic layer 14. The surface treatment may be one or a combination of physical treatments such as blasting, lapping, or polishing, or chemical treatments such as oxidation, coupling agent treatment, or primer treatment.

[0014] When the elastic layer 14 containing silicone rubber is provided on the surface of the base layer 13, it is preferable to apply a primer treatment to the surface of the base layer 13 in order to improve the adhesion between the base layer 13 and the elastic layer 14. The primer used in the primer treatment may be, for example, a paint in which a silane coupling agent, a silicone polymer, a hydrogenated methylsiloxane, an alkoxysilane, a reaction-accelerating catalyst, and a colorant such as red iron oxide are appropriately mixed and dispersed in an organic solvent.

[0015] The primer can be appropriately selected depending on the material of the base layer 13, the type of elastic layer 14, or the form of crosslinking reaction. In particular, when the elastic layer 14 contains a large amount of unsaturated aliphatic groups, a primer containing a hydrosilyl group is preferably used to impart adhesiveness by reacting with the unsaturated aliphatic groups. When the elastic layer 14 contains a large amount of hydrosilyl groups, a primer containing an unsaturated aliphatic group is preferably used. Other examples of primers include those containing alkoxy groups. Commercially available primers can be used. The primer treatment includes a step of applying the primer to the outer surface of the base layer 13 (the surface to be bonded to the elastic layer 14) and drying or baking the primer.

[0016] (2) Elastic layer There are no particular limitations on the material of the elastic layer 14, and any known material that is used as an elastic layer for a fixing rotor can be used. It is preferable that the elastic layer 14 contains silicone rubber, which has excellent heat resistance. In addition, addition-curing liquid silicone rubber is preferably used as the raw material for the silicone rubber. The thickness of the elastic layer 14 can be appropriately designed taking into consideration the surface hardness of the fixing rotor and the width of the fixing nip portion to be formed. When the fixing rotor is the fixing belt 11, the thickness of the elastic layer 14 is preferably 100 μm or more and 500 μm or less, and more preferably 200 μm or more and 400 μm or less.

[0017] When the fixing rotating body is the fixing roller 12, the thickness of the elastic layer 14 is preferably 0.1 mm (100 μm) or more and 3.0 mm or less, and more preferably 0.3 mm (300 μm) or more and 2.0 mm or less. By setting the thickness of the elastic layer 14 within this range, a sufficient width of the fixing nip portion can be ensured when the fixing rotatable body is incorporated into a fixing device. Furthermore, since the elastic layer contains silicone rubber, which has poor chemical affinity with fluorine oil, the fluorine oil contained in the surface layer is less likely to migrate to the elastic layer even with long-term use, and is instead supplied primarily to the surface of the fixing rotor.

[0018] The elastic layer 14 may contain a filler, which is added to control the thermal conductivity, heat resistance, and elastic modulus. Specifically, these include silicon carbide (SiC), silicon nitride (Si3N4), silica (SiO2), boron nitride (BN), aluminum nitride (AlN), alumina (Al2O3), iron oxide (Fe2O3), zinc oxide (ZnO), magnesium oxide (MgO), titanium oxide (TiO2), copper (Cu), aluminum (Al), silver (Ag), iron (Fe), nickel (Ni), carbon black (C), carbon fiber (C), and carbon nanotubes (C). can be done.

[0019] (3) Surface layer The surface layer 15 contains tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and perfluoropolyether (PFPE). As shown in FIG. 1(B), the surface layer has pores 3 that open to a first surface 101 that constitutes the outer surface of the fixing rotor. The outer surface of the fixing rotor is defined as the surface that comes into contact with unfixed toner on the recording material during fixing. Here, it is preferable that the pores 3 do not have a shell. In other words, it is preferable that the walls of the pores 3 are composed of a solid portion of the surface layer, specifically a resin portion 1 containing PFA. At least some of the pores contain perfluoropolyether (PFPE) 4. For example, the pores are filled with PFPE.

[0020] Furthermore, the surface layer satisfies the following requirements: Requirement) A first observation region measuring 8 μm in length and 11 μm in width is placed on the first surface of the surface layer obtained by removing the PFPE in the pores from the first surface side using a solvent, and the ratio of the sum of the areas of the openings observed in the first observation region to the area of ​​the first observation region (hereinafter also referred to as the "opening rate") is defined as P1. A second observation region measuring 8 μm in length and 11 μm in width is placed at a predetermined position on a cross section of the surface layer obtained by removing the PFPE in the pores from the first surface side using a solvent, the cross section including the entire thickness of the surface layer in the direction along the circumferential direction of the fixing rotor, and the ratio of the sum of the areas of the pores observed in the second observation region to the area of ​​the second observation region (porosity) is defined as P2. P2 / P1 must be 1.3 or greater.

[0021] By making P1 and P2 have the above-mentioned relationship, the surface layer can retain a sufficient amount of PFPE, and can stably transfer this PFPE to the first surface.P2 / P1 is preferably 5.0 or more, more preferably 7.0 or more.On the other hand, from the viewpoint of balancing the amount of PFPE that the surface layer can retain and the transfer of this PFPE to the first surface, the upper limit is preferably 20.0 or less, more preferably 15.0 or less.Therefore, P2 / P1 is preferably 1.3 or more and 20.0 or less.

[0022] P1 is calculated as follows: The first surface of the surface layer constituting the outer surface of the fixing rotor is observed with a scanning electron microscope, and an SEM image (magnification 10,000 times) of an observation area of ​​8 μm vertical × 11 μm horizontal on the first surface is obtained. The resolution is set to a resolution that allows individual openings to be recognized (for example, 717 pixels vertical × 986 pixels horizontal). The SEM image is converted into an 8-bit grayscale image using image processing software (product name: Image-J, manufactured by the National Institutes of Health (NIH)). A median filter is applied to the resulting grayscale image, and then binarization processing is performed using the image processing software to obtain a binary image. The binarization processing uses the YEN method disclosed in Non-Patent Document 2 to distinguish between the portions corresponding to the apertures and the portions corresponding to the PFA in the SEM image. Then, in the obtained binary image, the ratio of the number of pixels in the portion corresponding to the opening to the number of pixels in the entire image is calculated. In the present disclosure, observation regions are placed at any 10 locations on the first surface of the surface layer, and the arithmetic mean value of the ratios calculated from each observation region is designated as P1. Note that the 10 locations where the observation regions are placed are positions where the observation regions do not overlap each other. Specific methods will be described in the examples below.

[0023] P2 is calculated as follows: A sample is cut out from the surface layer, showing a cross section of the surface layer in the direction along the circumferential direction of the fixing rotor. At this time, the cross section includes the entire thickness of the surface layer. A predetermined position on the cross section of the cut sample is observed with a scanning electron microscope. An SEM image of a rectangular observation area of ​​8 μm long x 11 μm wide on the cross section is obtained with a resolution that allows pores appearing on the cross section to be recognized (for example, 717 pixels long x 986 pixels wide). The SEM image is binarized using numerical calculation software (product name: MATLAB (registered trademark); manufactured by MathWorks) to obtain a binary image. The binarization process uses Otsu's method described in Non-Patent Document 3 to distinguish between the parts corresponding to voids and the parts corresponding to PFA in the SEM image. Then, the ratio of the number of pixels in the parts corresponding to voids in the binary image to the number of pixels in the entire image is calculated. In the present disclosure, the thickness direction of the surface layer of the cross section is defined as follows. (1) A position where the upper end of the observation area is 1 μm from the first surface side of the cross section toward the second surface side on the opposite side, and the long side of the observation area is parallel to the first surface; (2) A position where the midpoint between the first surface and the second surface of the cross section coincides with the center of gravity of the observation area, and the long side of the observation area is parallel to the first surface; and (3) A position where the lower end of the observation area is 1 μm from the second surface toward the first surface, and the long side of the observation area is parallel to the second surface. The samples for the above operation are taken from three locations every 120° in the circumferential direction of the fixing rotor. Therefore, the arithmetic mean value of the nine ratios calculated from a total of nine SEM images is defined as P2.

[0024] P1 is preferably 1.0% or more, more preferably 1.5% or more, and even more preferably 3.0% or more, and the upper limit is preferably 15.0% or less, more preferably 10.0% or less. When P1 is 1.0% or more, the migration of the surface layer of PFPE in the pores to the first surface is not easily hindered, and stable toner release properties can be imparted to the first surface.Furthermore, when P1 is 15.0% or less, excessive migration of PFPE in the pores to the first surface can be suppressed, which contributes to maintaining stable toner release properties over a long period of time.Therefore, for example, the preferred range of P1 is 1.0% or more and 15.0% or less, and the particularly preferred range is 1.5% or more and 10.0% or less.

[0025] P2 is preferably 20.0% or more, more preferably 25.0% or more. There is no particular upper limit, but it is preferably 60.0% or less, more preferably 50.0% or less. When P2 is 20.0% or more, the surface layer can retain more PFPE, and the first surface can be provided with stable toner release properties over a longer period of time. On the other hand, when P2 is 60.0% or less, wear of the surface layer can be better prevented. Therefore, for example, a preferred range of P2 is 20.0% or more and 60.0% or less, and a particularly preferred range is 25.0% or more and 50.0% or less.

[0026] The average opening diameter of the openings on the outer surface of the surface layer is preferably 1 nm or more and 5 μm or less, more preferably 50 nm or more and 140 nm or less. Setting the average opening diameter within the above range contributes to maintaining stable, excellent toner releasability. The average opening diameter of the openings on the first surface is the average diameter of circles having the same area as the area of ​​the portions corresponding to the openings in the binarized image used to calculate P1 described above. Specific methods will be described later.

[0027] The thickness of the surface layer is preferably 12 μm or more and 100 μm or less, and more preferably 15 μm or more and 85 μm or less.

[0028] <pfa> The PFA contained in the surface layer will be described in detail below. PFA is a copolymer of perfluoroalkyl vinyl ether (hereinafter referred to as "PAVE") and tetrafluoroethylene (hereinafter referred to as "TFE"). The perfluoroalkyl chain preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 to 3 carbon atoms. The PAVE is preferably selected from perfluoromethyl vinyl ether (CF2=CF-O-CF3), perfluoroethyl vinyl ether (CF2=CF-O-CF2CF3) and perfluoropropyl vinyl ether (CF2=CF-O-CF2CF2CF3). The melting point of PFA is preferably 280°C to 320°C, and more preferably 290°C to 310°C.

[0029] As the PFA, commercially available products can be used, and specific examples are given below. "451HP-J", "959HP-Plus", "350-J", "950HP-Plus" (all product names, manufactured by Mitsui Chemours Fluoroproducts); "P-66P", "P-66PT", "P-802UP" (all product names, manufactured by AGC); "AP-230", "AP-231SH", etc. (all product names, manufactured by Daikin Industries, Ltd.); "6502N" (product name, manufactured by 3M).

[0030] <Perfluoropolyether (PFPE)> The PFPE contained in at least a portion of the pores will be described in detail. The PFPE contained in the pores may be referred to as a second PFPE to distinguish it from the PFPE (first PFPE) used to form the pores, which will be described later. However, this does not mean that the second PFPE is the same PFPE as the first PFPE. The second PFPE is not particularly limited, and known PFPEs can be used. Preferred examples include PFPEs having a structure represented by the following formula (1). The PFPE is preferably one that becomes oily at the melting point of PFA.

[0031] [ka]

[0032] (In formula (1), a, b, c, d, e, and f each independently represent 0 or a positive integer, satisfying 1≦a+b+c+d+e+f≦600, and at least one of a, b, c, and d being a positive integer.) In addition, the order of the repeating units in formula (1) is not limited to the order described above. Furthermore, each repeating unit in formula (1) may exist in a plurality of places in PFPE. That is, the PFPE represented by formula (1) may be a block copolymer or a random copolymer.

[0033] Examples of commercially available PFPEs include PFPEs having a structure represented by the following formula (2) (e.g., Demnum S-200, Demnum S-65 (all trade names); manufactured by Daikin Industries, Ltd.), PFPEs having a structure represented by the following formula (3) (e.g., Krytox XHT-1000, Krytox VPF16256, Krytox GPL-107, Krytox GPL-106, Krytox GPL-105, Krytox GPL-104, Krytox GPL-103, Krytox GPL-102, Krytox GPL-101 (all trade names); manufactured by Chemours), PFPEs having a structure represented by the following formula (4) (e.g., Fomblin M60, Fomblin M100, Fomblin Z25 (all trade names); manufactured by Solvay, Inc.), and the like. and PFPE represented by the following formula (5) (for example, Fomblin Y45, Fomblin Y25 (both trade names); manufactured by Solvay Specialty Polymers). The perfluoropolyether preferably has at least one structure selected from the group consisting of the following formulas (2) to (5).

[0034] [ka] (In formula (2), n is a positive number, and n is a number in the range that makes the viscosity of PFPE at a temperature of 40°C range from 30 mPa·s to 500 mPa·s.)

[0035] [ka] (In formula (3), n' is a positive number, and n' is a number within the range of 10 mPa·s to 2500 mPa·s for the viscosity of PFPE at a temperature of 40°C.)

[0036] [ka] (In formula (4), n" and m are each independently a positive number, m / n" is a number that is 0.5 or greater and 2 or less, and n" + m is a number that causes the viscosity of the PFPE at a temperature of 40°C to be in the range of 20 mPa s to 1400 mPa s.)

[0037] [ka]

[0038] (In formula (5), n''' and m' are each independently a positive number, m' / n''' is a number that is 20 or greater and 1000 or less, and n'''+m' is a number that causes the viscosity of the PFPE at a temperature of 40°C to fall within the range of 20 mPa s to 1200 mPa s.)

[0039] The viscosity of the second PFPE is preferably 300 mPa·s to 2500 mPa·s, and more preferably 350 mPa·s to 2000 mPa·s. A PFPE in this viscosity range contributes to stable migration of the surface layer from the pores to the first surface. The viscosity here is measured using a rheometer (TA Instruments: DHR-2) equipped with a cone-plate type cone angle of 1° and a cone radius of 20 mm, at a measurement temperature of 40°C and a shear rate of 100 s -1 The viscosity value is the value after rotating for 60 seconds.

[0040] In addition, commercially available PFPEs within the above viscosity range include, for example, "Krytox GPL-105" (viscosity 301 mPa·s), "Krytox GPL-106" (viscosity 459 mPa·s), "Krytox GPL-107" (viscosity 852 mPa·s), "Krytox VPF16256" (viscosity 1403 mPa·s), "Krytox XHT-1000" (viscosity 1941 mPa·s), "Fomblin M60" (viscosity 586 mPa·s), and "Fomblin M100" (viscosity 1327 mPa·s).

[0041] The content of perfluoropolyether in the surface layer is preferably 20% by mass or more and 60% by mass or less, more preferably 25% by mass or more and 45% by mass or less. When the content is 20% by mass or more, the toner releasability is maintained well even during long-term use. When the content is 60% by mass or less, wear of the surface layer due to use can be more reliably prevented.

[0042] <Method of manufacturing the fixing rotor> A non-limiting example of a method for producing the fixing rotor according to one embodiment of the present disclosure includes the following steps (i) to (v). Step (i): preparing a laminate having a base layer having an endless belt shape or a roller shape, an elastic layer on the outer peripheral surface of the base layer, and a resin layer containing PFA on the outer peripheral surface of the elastic layer; Step (ii): A step of contacting a first PFPE heated to a temperature close to the melting point of PFA with a surface of the resin layer opposite to the surface facing the elastic layer, thereby impregnating the first PFPE into the resin layer; Step (iii): cooling the laminate obtained in Step (ii), in which the first PFPE is impregnated into the resin layer, to room temperature (e.g., 20°C to 35°C, preferably 25°C); Step (iv) removing at least a portion of the first PFPE impregnated in the resin layer from the first surface side of the resin layer using a fluorine solvent to form pores in the resin layer that are open to the first surface of the resin layer; and Step (v) is a step of incorporating a second PFPE into at least some of the pores to form the resin layer into a surface layer according to the present disclosure, thereby obtaining a fixing rotating body having a surface layer containing the second PFPE in at least some of the pores.

[0043] The present inventors speculate as follows about the mechanism by which the fixing rotor according to one aspect of the present disclosure is formed by the above method. In step (ii), the first surface of the resin layer is brought into contact with the first PFPE at a temperature near the melting point of the PFA contained in the resin layer (temperature 300°C ± 50°C (preferably 290°C to 325°C)), thereby impregnating the first PFPE into the resin layer.

[0044] Since the resin layer impregnated with the first PFPE in step (ii) is in a high temperature state, Following step (i), in step (iii), the resin layer is cooled to room temperature, for example, about 25°C. Then, in step (iv), the first PFPE in the resin layer is removed using a solvent. By this, open pores are formed on the first surface of the resin layer at the locations where the first PFPE was present in the resin layer. The surface layer formed through the steps (iii) and (iv) has a pore area ratio P2 per unit area in a cross section parallel to the circumferential direction that is greater than the opening area ratio P1 per unit area on the first surface. The reason for this is believed to be as follows. When the PFA tube, which has thermally expanded due to the high temperature in step (ii), shrinks during the cooling step in step (iii), the first surface of the resin layer cools faster than the surface on the elastic layer side, resulting in a greater degree of shrinkage. As the first surface side shrinks, the first PFPE present near the first surface of the resin layer is pushed out of the resin layer from the first surface. As a result, the openings in the first surface of the resin layer shrink. Meanwhile, the first PFPE that has penetrated deep into the resin layer in the thickness direction, for example, to the vicinity of the surface on the elastic layer side, remains within the resin layer without being expelled even when the resin layer shrinks. Therefore, the size of the aggregated portions of the first PFPE that become voids after the first PFPE is removed is hardly reduced. As a result, the ratio (P2 / P1) of the porosity P2 to the opening ratio P1 at the first surface of the surface layer formed through step (iv) increases.

[0045] Here, the value of P2 / P1 can be adjusted by the amount of the first PFPE impregnated into the resin layer in step (ii). That is, by increasing the amount of PFPE impregnated into the resin layer, the voids inside the resin layer can be increased, and the value of P2 increases. Furthermore, by increasing the amount of PFPE impregnated into the resin layer, the number of openings on the first surface of the resin layer also increases, and the value of P1 increases. Here, although the reason is unclear, the degree of increase in P1 due to an increase in the amount of PFPE impregnated into the resin layer is greater than the degree of increase in P2. Therefore, by increasing the amount of the first PFPE impregnated into the PFA tube, P2 / P1 can be adjusted to be smaller.

[0046] In order to achieve the above-mentioned preferred range of P2, it is preferable that the amount of the first PFPE impregnated into the resin layer in step (ii) is such that the content ratio of the first PFPE is preferably 25% by mass to 60% by mass, and particularly 30% by mass to 45% by mass, based on the mass of the resin layer containing the first PFPE.

[0047] The amount of the first PFPE impregnated into the resin layer can be adjusted, for example, by the temperature of the first PFPE during impregnation, the viscosity of the first PFPE, and the contact time between the resin layer and the first PFPE. Specifically, the higher the temperature within the temperature range near the melting point of PFA (250 to 350°C), the lower the viscosity of the first PFPE, and the longer the contact time, the more the amount of the first PFPE impregnated into the resin layer can be increased.

[0048] Here, the preferred viscosity of the first PFPE is preferably 10 mPa·s to 400 mPa·s, and more preferably 30 mPa·s to 350 mPa·s. Commercially available PFPEs in this viscosity range include Krytox GPL-101 (viscosity 12 mPa·s), Krytox GPL-102 (viscosity 26 mPa·s), Krytox GPL-103 (viscosity 54 mPa·s), Krytox GPL-104 (viscosity 111 mPa·s), Fomblin M03 (viscosity 30 mPa·s), and Krytox GPL-105 (viscosity 301 mPa·s).

[0049] For example, if the viscosity of the first PFPE is 301 mPa·s, the thickness of the resin layer containing PFA is 20 μm, the melting point of the resin layer is 296°C, and the temperature at the time of contact between the resin layer and the first PFPE is 310°C, a PFPE-impregnated resin layer having a first PFPE content of 30 mass% can be produced with a contact time of 1 minute. Here, the content is defined as the percentage (%) of the mass of the PFPE impregnated in the resin layer relative to the sum of the mass of the resin layer itself and the mass of the PFPE impregnated in the resin layer. In the above example, if a PFPE with a viscosity of 111 mPa s is used as the first PFPE and other conditions are the same, a PFPE-impregnated resin layer with a first PFPE content of 41 mass% can be produced.Furthermore, in the above example, if the temperature during contact is 300°C and other conditions are the same, a PFPE-impregnated resin layer with a first PFPE content of 26 mass% can be produced.

[0050] On the other hand, the PFPE used in the examples of Patent Document 1, "Krytox GPL106," has a viscosity of 459 mPa·s. When such a PFPE was contacted with a resin layer containing PFA at a temperature of 345°C for 5 minutes, a PFPE-impregnated resin layer with a PFPE content of 24% by mass was obtained. However, with this level of PFPE content, the PFPEs did not aggregate within the resin layer. Therefore, even when the PFPE was subsequently eluted using a fluorine-based solvent, no voids were formed in the resin layer.

[0051] In producing the fixing rotor, any method can be used to bring the resin layer and the first PFPE into contact as long as the PFPE can be brought into contact with the resin layer at a temperature near the melting point of the PFA resin contained in the resin layer. The resin layer to be contacted with the first PFPE may be a resin layer in a laminate in which a base layer, an elastic layer, and a resin layer are laminated in advance, or a PFA sheet or PFA tube for the resin layer may be prepared and used in a state in which the surface to be bonded to the elastic layer is masked. In addition, examples of the contact method include a dipping method.

[0052] In step (iv), to remove the first PFPE impregnated into the resin layer, the resin layer is immersed in a solvent capable of dissolving the first PFPE but not dissolving PFA so that the first surface of the resin layer is wet. Here, the "solvent capable of dissolving PFPE" refers to, for example, a solvent that dissolves 10 g or more of PFPE per 100 g of solvent at 25°C. On the other hand, the "solvent that does not dissolve PFA" refers to a solvent that dissolves 1 g or less of PFA per 100 g of solvent at 25°C. Examples of such solvents include hydrofluoroether (trade name: Novec 7600; manufactured by 3M). Furthermore, in step (iii), when removing the first PFPE from the resin layer, it is preferable to apply ultrasonic waves to the resin layer in order to promote the removal of the first PFPE from the resin layer.

[0053] The method for manufacturing a fixing rotor according to one aspect of the present disclosure will be described more specifically. Step (i) A laminate in which a base layer, an elastic layer containing silicone rubber, and a resin layer containing PFA are laminated in this order is attached to a dipping device.

[0054] Step (ii) The laminate is immersed in a bath of PFPE heated to near the melting point of PFA (300°C±50°C (preferably 290°C to 325°C)) and left standing for preferably 20 seconds to 5 minutes, more preferably 30 seconds to 2 minutes (e.g., 1 minute) (impregnation step-1). It was found that in the impregnation step 1, the higher the contact temperature between the resin layer and the first PFPE and the lower the viscosity of the PFPE, the greater the amount of impregnation. The contact temperature and the viscosity of the PFPE can be appropriately selected as long as an impregnation amount equal to or greater than a certain amount at which the above-mentioned specific pores can be formed is achieved. In the impregnation step-1, when the heating temperature of the first PFPE is X°C and the melting point of PFA is Y°C, XY is preferably 0°C to 40°C, more preferably 3°C to 20°C.

[0055] Step (iii) The laminate is removed from the first PFPE bath and allowed to cool to room temperature. Step (iv) After cooling, the laminate is immersed in a solvent capable of dissolving the first PFPE, and the first PFPE impregnated in the resin layer is eluted from the openings on the first surface of the resin layer (pore forming step). This step forms pores in the resin layer that are open to the first surface.

[0056] Step (v-1): The laminate having the resin layer having voids obtained through the above steps is immersed in a bath of the second PFPE and left for preferably 5 to 30 minutes, more preferably 10 to 20 minutes (e.g., 15 minutes), thereby allowing the second PFPE to be impregnated into the voids in the resin layer (impregnation step-2). The temperature of the second PFPE in this step is preferably a temperature that can promote the impregnation of the second PFPE into the pores and does not cause the openings on the first surface of the resin layer to disappear. As a non-limiting example, the lower limit of the temperature of the second PFPE in this step is preferably 180°C or higher, and the upper limit is preferably 280°C or lower, more preferably 230°C or lower.

[0057] Step (v-2) The laminate obtained through the above steps is removed from the bath of the second PFPE, and the second PFPE adhering to the outer surface is removed to obtain a fixing rotor according to one embodiment of the present disclosure. In this step, the method for removing the excess second PFPE attached to the surface is not particularly limited, and examples thereof include washing with a fluorine solvent, removing with air, wiping with a nonwoven fabric, etc. Examples of the method for washing with a fluorine solvent include removing with fibers such as nonwoven fabric impregnated with a fluorine solvent.

[0058] 2. Fixing device The fixing device includes a fixing rotor and a heating means for heating the fixing rotor, for example, a heating rotor and a pressure rotor disposed to form a fixing nip with the heating rotor. Examples of combinations of a heating rotor and a pressure rotor include a heating roller and an elastic pressure roller arranged opposite the heating roller, and a heating film and an elastic pressure roller arranged in contact with the heating film. Other examples of combinations of a heating rotor and a pressure rotor include a heating belt and an elastic pressure roller arranged in contact with the heating belt, and a heating belt and an elastic pressure belt arranged in contact with the heating belt.

[0059] (1) Fixing device using a fixing belt FIG. 3 is a cross-sectional view of a fixing device including a fixing belt 11 for heating and an elastic pressure roller 19, taken along the circumferential direction of the fixing belt. The fixing belt 11 is the fixing belt described above as the fixing rotating body. The fixing belt 11 is loosely fitted around a belt guide member 16. A pressure rigid stay 18 is inserted inside the belt guide member 16. The belt guide member 16 is formed, for example, from a resin having heat resistance and heat insulation properties.

[0060] The heating means is, for example, a heater arranged in contact with the inner circumferential surface of the fixing belt. A ceramic heater 17 is provided as a heat source at the position where the belt guide member 16 and the inner surface of the fixing belt 11 come into contact. The ceramic heater 17 is fitted into and fixed in a groove provided along the longitudinal direction of the belt guide member 16. The ceramic heater 17 generates heat when electricity is applied by means not shown. The elastic pressure roller 19 has an elastic layer 19b made of hardened silicone rubber provided on the circumferential surface of a stainless steel core 19a. A surface layer 19c made of fluororesin is provided on the circumferential surface of the elastic layer 19b. The thickness of the surface layer 19c is, for example, 50 μm.

[0061] A pressure spring (not shown) is compressed between each end of the pressure rigid stay 18 and a spring receiving member (not shown) on the device chassis side, thereby applying a downward force to the pressure rigid stay 18. This causes the ceramic heater 17 disposed on the underside of the belt guide member 16 to The lower surface of the ceramic heater 17 and the upper surface of the elastic pressure roller 19 are in pressure contact with each other with the fixing belt 11 sandwiched therebetween to form a predetermined fixing nip portion N. That is, the lower surface of the ceramic heater 17 is disposed in contact with the inner circumferential surface of the fixing belt 11. A recording medium P, which is a heated object and on which an image is formed with unfixed toner G, is sandwiched and conveyed through this fixing nip N at a conveying speed V. This heats and pressurizes the toner image. As a result, the toner image melts and mixes colors, and is then cooled to fix the toner image on the recording medium P.

[0062] (2) Thermal fixing device using a fixing roller FIG. 4 is a cross-sectional view taken along the circumferential direction of a fixing roller in a thermal fixing device that includes a fixing roller 12 for heating, an elastic pressure roller 19 arranged opposite the fixing roller 12, and a heater 20 that is a heating means for the fixing roller 12. The fixing roller 12 is the fixing roller described above as a rotating body for fixing. The fixing roller 12 has an elastic layer 14 formed on the outer peripheral surface of a hollow core metal as a base layer 13, and a release surface layer 15 formed on the outer surface thereof.

[0063] The fixing roller 12 and the elastic pressure roller 19 are rotatably pressed against each other by a pressure means (not shown), forming a fixing nip N. A heater 20 is installed inside the fixing roller 12 and the elastic pressure roller 19 as a heat source to supply the heat necessary to melt the unfixed toner G. A halogen heater is generally used as the heater 20. In some cases, multiple halogen heaters are installed inside according to the size of the recording medium P being conveyed.

[0064] A rotational force is applied to the fixing roller 12 and the elastic pressure roller 19 through the base layer (metal core) 13 and the end of the metal core 19a by means not shown, and the rotation is controlled so that the moving speed of the surface of the fixing roller 12 is approximately equal to the conveying speed V of the recording medium P. In this case, the rotational force may be applied to either the fixing roller 12 or the elastic pressure roller 19, and the other may be rotated by being driven, or the rotational force may be applied to both. The recording medium P, which is the heated object on which an image is formed with unfixed toner G, is sandwiched and conveyed through the fixing nip N of the fixing device thus formed. This heats and pressurizes the toner image. As a result, the toner image is melted and mixed, and then cooled, thereby fixing the toner image on the recording medium P.

[0065] 3. Electrophotographic image forming apparatus The electrophotographic image forming apparatus may have a known configuration. Examples include multifunction machines, copiers, fax machines, printers, etc. that use electrophotography. Here, a color laser printer will be used as an example to provide an outline of the overall configuration of an electrophotographic image forming apparatus. Figure 5 is a schematic cross-sectional view of a laser printer 40. The laser printer 40 shown in Figure 6 has an image forming unit having electrophotographic photosensitive drums 39 (hereinafter referred to as "photosensitive drums 39") that rotate at a constant speed for each of the colors yellow (Y), magenta (M), cyan (C), and black (K). The laser printer 40 also has an intermediate transfer member 38 that holds the color image developed and multi-transferred in the image forming unit and further transfers it to a recording medium P fed from a feed unit.

[0066] The photosensitive drums 39 (39Y, 39M, 39C, 39K) are driven to rotate counterclockwise as shown in FIG. 5 by a driving means (not shown). Around the photosensitive drum 39, in the direction of rotation, there are arranged, in order, a charging device 21 (21Y, 21M, 21C, 21K) that uniformly charges the surface of the photosensitive drum 39, a scanner unit 22 (22Y, 22M, 22C, 22K) that irradiates a laser beam based on image information to form an electrostatic latent image on the photosensitive drum 39, a developing unit 23 (23Y, 23M, 23C, 23K) that attaches toner to the electrostatic latent image to develop it into a toner image, and a developing unit 24 (24Y, 24M, 24C, 24K) that develops the electrostatic latent image. There are primary transfer rollers 24 (24Y, 24M, 24C, 24K) that transfer the upper toner image to the intermediate transfer body 38 at the primary transfer section T1, and cleaning units 25 (25Y, 25M, 25C, 25K) that have cleaning blades that remove residual toner remaining on the surface of the photosensitive drum 39 after transfer.

[0067] During image formation, a belt-like intermediate transfer body 38 stretched over rollers 26, 27, and 28 rotates, and the toner images of each color formed on each photosensitive drum 39 are superimposed and transferred onto the intermediate transfer body 38 as a primary transfer, thereby forming a color image. The recording medium P is conveyed to the secondary transfer portion T2 by a conveying means so as to be synchronized with the primary transfer onto the intermediate transfer body 38. The conveying means has a feeding cassette 29 storing a plurality of recording media P, a feeding roller 30, a separation pad 31, and a pair of registration rollers 32. During image formation, the feeding roller 30 is driven to rotate in accordance with the image forming operation, separating the recording media P in the feeding cassette 29 one by one, and conveying the recording media P to the secondary transfer portion T2 by the pair of registration rollers 32 in synchronization with the image forming operation.

[0068] A movable secondary transfer roller 33 is disposed at the secondary transfer portion T2. ​​The secondary transfer roller 33 is movable in a substantially vertical direction. During image transfer, the secondary transfer roller 33 is pressed against the intermediate transfer body 38 with a predetermined pressure via the recording medium P. At the same time, a bias is applied to the secondary transfer roller 33, and the toner image on the intermediate transfer body 38 is transferred to the recording medium P. Because the intermediate transfer body 38 and the secondary transfer roller 33 are both driven, the recording medium P sandwiched between them is conveyed in the direction of the left arrow shown in FIG. 5 at a predetermined conveying speed V, and is then conveyed by a conveyor belt 34 to the next process, a fixing unit 35. In the fixing unit 35, heat and pressure are applied to fix the transferred toner image onto the recording medium P. The recording medium P is then discharged onto a discharge tray 37 on the top surface of the device by a pair of discharge rollers 36. By applying the fixing devices illustrated in Figures 3 and 4 to the fixing section 35 of the electrophotographic image forming apparatus illustrated in Figure 5, an image forming apparatus can be obtained that can provide high-quality images with excellent image uniformity. [Example]

[0069] The present invention will be specifically described below using examples, but the present invention is not limited to the following examples.

[0070] In this example, a fixing member, which is a fixing rotating body, was produced using the following PFA resin and perfluoropolyether. (Fluorine resin) PFA-1: "959HP-Plus" (product name, manufactured by Mitsui-Chemours Fluoroproducts) PFA-2: "451HP-J" (product name, manufactured by Mitsui-Chemours Fluoroproducts) (perfluoropolyether) PFPE-1: "Krytox GPL104" (trade name, manufactured by Chemours, 111 mPa·s (40°C)) PFPE-2: "Krytox GPL105" (product name, manufactured by Chemours, 301 mPa·s (40°C)) PFPE-3: "Krytox VPF16256" (trade name, manufactured by Chemours, 1403 mPa·s (40°C)) PFPE-4: "Krytox XHT-1000" (product name, manufactured by Chemours, 1941 mPa·s (40°C)) PFPE-5: "Fomblin M100" (product name, manufactured by Solvay Specialty Polymers, 1327 mPa·s (40°C)) PFPE-6: "Krytox GPL106" (trade name, manufactured by Chemours, 459 mPa·s (40°C))

[0071] [Example 1] <Production of fixing belt> [Preparation of a laminate having a base layer, an elastic layer, and a resin layer containing PFA] As the base layer, a substrate having an endless belt shape made of electroformed nickel with an inner diameter of 30 mm, a width of 400 mm, and a thickness of 40 μm was prepared. The outer peripheral surface of this substrate was treated with a primer. The raw material for forming the elastic layer was an addition-curing liquid silicone rubber (product name: SE1886, manufactured by Dow Corning Toray Co., Ltd.) containing no filler. To 61 parts by volume of this liquid silicone rubber, 38 parts by volume of spherical alumina (product name: Alnabeads CB-A30S, manufactured by Showa Denko K.K.) was added as a spherical filler, and 1 part by volume of vapor-grown carbon fiber (product name: VGCF-S, manufactured by Showa Denko K.K., aspect ratio = 100, average fiber length = 10 μm) was added as an irregular-shaped filler. The addition-curable silicone rubber composition for forming the elastic layer was prepared in this way and applied to the outer peripheral surface of the substrate by ring coating, followed by heating at 200°C for 4 hours to crosslink the layer of addition-curable silicone rubber composition and form an elastic layer 300 μm thick. While the substrate on which the elastic layer was formed was rotated in the circumferential direction at a speed of 20 mm / sec, the surface of the elastic layer was irradiated with ultraviolet light in an atmospheric environment using an ultraviolet lamp positioned 10 mm away from the surface of the elastic layer. The ultraviolet lamp used was a low-pressure mercury ultraviolet lamp (product name: GLQ500US / 11, manufactured by Toshiba Lighting & Technology Corporation), and the integrated light intensity of the 185 nm wavelength on the irradiated surface was 800 mJ / cm. 2 The irradiation was carried out so that Next, an addition-curing silicone rubber adhesive (product name: SE1819CV, a mixture of equal amounts of "liquid A" and "liquid B" manufactured by Dow Corning Toray Co., Ltd.) was applied uniformly to the surface of the elastic layer to a thickness of approximately 20 μm. Next, a fluororesin tube (PFA-1, 20 μm thick, melting point 296°C) with its inner surface treated to be hydrophilic was placed over the belt, and the belt surface was uniformly rubbed from above the fluororesin tube to remove excess adhesive from between the elastic layer and the fluororesin tube. Then, the elastic layer and the base layer covered with the fluororesin tube were placed in an electric furnace set at a temperature of 200°C and heated for 1 hour to harden the adhesive and adhere the fluororesin tube to the elastic layer. Both ends were then cut to obtain a laminate for a fixing belt having a width of 343 mm.

[0072] [Contact impregnation of first PFPE] (Impregnation process-1) The first PFPE (PFPE-1) was placed in a measuring cylinder made of borosilicate glass. The measuring cylinder was entirely wrapped with a heating wire covered with a heat insulating material and heated to a PFPE temperature of 310° C. The prepared preliminary fixing belt was attached to a dipping device, and the laminate was immersed in the heated PFPE for 1 minute and then removed. <Evaluation A-1: ​​Measurement of the content of the first PFPE in the resin layer impregnated with the first PFPE> The content of the first PFPE in the obtained resin layer impregnated with the first PFPE was measured by the following method. That is, a laminated sample of an elastic layer and a resin layer was cut out from the laminate. Then, the laminated sample was immersed in a silicone resin dissolving agent (trade name: e-solv 21RS, manufactured by Kaneko Chemical Co., Ltd.) to dissolve the silicone rubber in the elastic layer, thereby removing the elastic layer from the laminated sample. In this way, a measurement sample consisting only of the entire thickness of the resin layer was prepared. This measurement sample was measured using a thermogravimetric analyzer (TGA) under the following conditions, and the content (mass%) of the first PFPE relative to the resin layer containing the first PFPE was calculated. Apparatus: TGA851 (trade name, manufactured by METTLER TOLEDO) Atmosphere: In air Temperature: 425℃ In the profile of measurement time-weight loss rate obtained by the above-mentioned thermogravimetric analysis, the slope becomes constant and the linear least squares approximation formula is obtained from the region where only PFA decreases.Then, the intercept of this linear least squares approximation formula is set as PFA content (mass%), and the first PFPE content (mass%) is calculated as 100-PFA content.

[0073] (Vacancy formation process) After cooling the laminate obtained in the impregnation step-1 to room temperature (25°C), the laminate was immersed for 10 minutes in a measuring cylinder containing a separately prepared fluorine solvent (trade name: Novec 7300, manufactured by 3M). The measuring cylinder was then placed in the water tank of an ultrasonic cleaning device (trade name: Bransonic (model 2510J-DTH); manufactured by Emerson Japan Co., Ltd.), and ultrasonic waves were applied for 60 minutes. After treatment, the laminate was removed from the measuring cylinder and left in an environment at 25°C for 60 minutes to dry. In this way, a laminate was obtained from which the PFPE present on the surface and inside of the resin layer had been removed. The obtained laminate had a white appearance when visually inspected, confirming the formation of pores in the resin layer. FIGS. 1(A) and 1(B) are schematic diagrams of images of the first surface of the resin layer of the obtained laminate and the cross section of the laminate in the circumferential direction observed with a scanning electron microscope. FIG. 1(A) is a schematic diagram of an SEM image of the first surface. A resin portion 1 containing PFA and openings 2 were observed. FIG. 1(B) is a schematic diagram of an SEM image of a cross section of the resin layer in the circumferential direction of the laminate. A resin portion 1 containing PFA and pores 3 were observed. It was also observed that the pores 3 opened to the first surface 101, providing openings on the first surface.

[0074] <Evaluation A-2: Calculation of Opening Ratio P1, Average Opening Diameter, and Porosity P2 on the First Surface of the Surface Layer (Resin Layer)> The opening ratio P1 and the average opening diameter on the first surface of the surface layer (resin layer) were calculated as follows. The surface of the laminate obtained in the pore forming step from which the first PFPE had been removed, i.e., the surface of the resin layer opposite the side facing the elastic layer, was observed with a scanning electron microscope, and an SEM image (magnification 10,000 times) of a rectangular observation area measuring 8 μm in length and 11 μm in width was obtained. The image was 717 pixels long and 986 pixels wide to allow the apertures to be recognized. The acquired SEM images were converted to 8-bit grayscale images using image processing software (Image-J, manufactured by the National Institutes of Health (NIH)). A median filter was applied to the obtained grayscale image, and then binarized using the image processing software to obtain a binary image. The binarization process used the YEN method to distinguish between the portions corresponding to the apertures and the portions corresponding to the PFA in the SEM image. The ratio of the number of pixels corresponding to the apertures in the obtained binary image to the number of pixels in the entire image was calculated. Here, observation regions were placed at 10 random locations on the surface of the resin layer having apertures, and the arithmetic mean of the ratios calculated from each observation region was defined as the aperture ratio P1. Note that the observation regions were positioned so that they did not overlap each other. The area of ​​the portion corresponding to the opening in each binarized image was approximated by a perfect circle of the same area, and the average opening diameter was calculated as the arithmetic mean value of the diameters of the perfect circles (hereinafter referred to as the circle equivalent diameter).

[0075] The porosity P2 was calculated as follows. A cross-sectional sample was cut out from the resin layer of the laminate from which the first PFPE had been removed using a cryo-ultramicrotome (manufactured by Leica Microsystems) so that the cross-section of the resin layer in the circumferential direction of the laminate was visible. The cross-section included the entire thickness of the resin layer. Next, the cross-section was observed using a scanning electron microscope, and an SEM image of an observation area of ​​8 μm in length × 11 μm in width was obtained. The resolution was set to 717 pixels in length and 986 pixels in width so that pores appearing in the cross-section could be recognized. The obtained SEM image was binarized using numerical calculation software (trade name: MATLAB (registered trademark), manufactured by MathWorks) to obtain a binarized image. An image was obtained. The binarization process used Otsu's method to distinguish between the parts corresponding to pores and the parts corresponding to PFA in the SEM image. The ratio of the number of pixels in the parts corresponding to pores in the binarized image to the number of pixels in the entire image was calculated. The SEM images were taken at three positions in the thickness direction of the cross section of the cross-sectional sample, as specified in the following (i) to (iii). (i) In the cross section of the cross-sectional sample, the upper end of the observation area is 1 μm from the surface on one side of the surface layer (hereinafter also referred to as the "first surface") to the surface on the other side (hereinafter also referred to as the "second surface"), and the long side of the observation area is parallel to the first surface. (ii) A position in the cross section of the cross-sectional sample where the midpoint between the first surface and the second surface of the surface layer coincides with the center of gravity of the observation area, and the long side of the observation area is parallel to the first surface. (iii) In the cross section of the cross-sectional sample, the lower end of the observation area is 1 μm from the second surface of the surface layer toward the first surface, and the long side of the observation area is parallel to the second surface. Furthermore, cross-sectional samples were cut out from three locations at 120° intervals in the circumferential direction of the laminate. Therefore, a total of nine SEM images were obtained by the above operation, and nine ratios were calculated based on the binarized images created from each SEM image. The arithmetic mean value of these nine ratios was taken as the porosity P2.

[0076] (Impregnation process-2) Next, the laminate having a resin layer with voids obtained through the above-mentioned void formation step was subjected to the following procedure: The second PFPE (PFPE-3) was placed in a borosilicate glass measuring cylinder. The measuring cylinder was entirely wrapped with a heating wire covered with a heat insulating material and heated so that the PFPE temperature reached 200° C. Next, the laminate was attached to a dipping device, and the entire laminate was immersed in the heated second PFPE for 15 minutes and then removed. Next, the second PFPE adhering to the outer surface of the removed laminate was removed using a nonwoven fabric impregnated with a fluorine-based solvent (product name: Novec 7300; manufactured by 3M). Thus, a fixing belt according to this example was obtained. A schematic image of a cross section of the surface layer of the obtained fixing belt in the circumferential direction, observed with a scanning electron microscope, is shown in FIG. 1(C). It was confirmed that the pores 3 observed in FIG. 1(B) were filled with the second PFPE 4 in the impregnation step 2.

[0077] <Evaluation A-3: Measurement of the content of the second PFPE in the surface layer> For the obtained fixing belt, prepare a measurement sample consisting of only the entire thickness of the surface layer in the same manner as in the evaluation A-1.Measure this measurement sample using a thermogravimetric analyzer (TGA) under the following conditions, and calculate the content ratio (mass%) of the second PFPE in the surface layer relative to the total mass of the surface layer, including the mass of the second PFPE in the pores. Apparatus: TGA851 (trade name, manufactured by METTLER TOLEDO) Atmosphere: Air ·Temperature: 425℃ In the profile of measurement time-weight loss rate obtained by above-mentioned thermogravimetric analysis, the slope becomes constant, and the linear least squares approximation formula is obtained from the region where only PFA decreases.Then, the intercept of this linear least squares approximation formula is taken as PFA content ratio (mass%), and the content of second PFPE is calculated as 100-PFA content ratio.

[0078] <Performance evaluation as a fixing belt> The obtained fixing belt was subjected to the following evaluations B-1 and B-2. (Evaluation B-1: Evaluation of the presence or absence of toner offset) The fixing belt was mounted on an electrophotographic image forming apparatus (product name: imageRUNNER-ADVANCE C5051; manufactured by Canon Inc.) in which the angle of the paper separation claws had been adjusted. Then, A4 size paper (manufactured by International Paper, basis weight 75 g / m 2 An image forming process was carried out to form a 10 cm x 10 cm solid cyan image on a sheet of paper. The fixing temperature was 180°C and the paper transport speed was 300 mm / sec. Then, when the number of sheets on which a cyan solid image was formed reached 1, 10,000, and 300,000, an A4-sized thin plain paper (product name: CS-520, basis weight 52 g / m) was used. 2 A sheet of a 10 cm x 10 cm cyan solid image was formed on the paper by passing it through a paper feeder (Canon Inc.). The solid image formed on the thin plain paper was observed visually and under a microscope and evaluated according to the following criteria. (Evaluation criteria) Rank A: Neither toner offset nor toner missing occurs. Rank B: Toner offset and slight toner loss are observed. Rank C: Both toner offset and toner loss are observed. Rank D: Plain paper Thin paper stuck to the fixing belt.

[0079] (Evaluation B-2: Measurement of surface free energy) In Evaluation 1, the surface free energy of the outer surface of the fixing belt immediately before forming a solid image on thin plain paper was calculated using the "Kitazaki-Hata method" described in Non-Patent Document 1. Specifically, the contact angles of water, n-hexadecane, and diiodomethane were measured on the outer surface of the fixing belt (measurement environment: temperature 23°C, relative humidity 55%). Next, using the measurement results of each contact angle, the surface free energy was calculated from the "extended Fowkes equation" in accordance with the "Kitazaki-Hata theory" described in Non-Patent Document 1 above. A contact angle meter (trade name: DM-501, manufactured by Kyowa Interface Science Co., Ltd.) was used for the measurement, and analytical software (trade name: FAMAS, manufactured by Kyowa Interface Science Co., Ltd.) was used for the surface free energy analysis.

[0080] [Example 2] A laminate including a resin layer having voids was produced in the same manner as in Example 1, except that the temperature during contact between the resin layer and the first PFPE in the impregnation step-1 was set to the temperature shown in Table 1. Furthermore, the impregnation step-2 and subsequent steps were carried out in the same manner as in Example 1 to produce a fixing belt No. 2. The results of evaluations A-1 to A-3 and evaluations B-1 and B-2 for the obtained fixing belt No. 2 are shown in Tables 1 and 2. [Example 3] A laminate including a resin layer having voids was produced in the same manner as in Example 1, except that the first PFPE in the impregnation step-1 was changed to one shown in Table 1. Furthermore, the impregnation step-2 and subsequent steps were carried out in the same manner as in Example 1 to produce a fixing belt No. 3. The results of evaluations A-1 to A-3 and evaluations B-1 and B-2 for the obtained fixing belt No. 3 are shown in Tables 1 and 2. [Examples 4 to 5] The type of the second PFPE used in the impregnation step-2 was changed as shown in Table 1. Otherwise, fixing belts Nos. 4 to 5 according to Examples 4 to 5 were produced in the same manner as in Example 3. The results of evaluations A-1 to A-3 and evaluations B-1 and B-2 for the obtained fixing belts Nos. 4 to 5 are shown in Tables 1 and 2. [Examples 6 to 7] Laminates having a resin layer having voids were produced in the same manner as in Example 1, except that the thickness of the resin layer was changed as shown in Table 2. Furthermore, from the impregnation step-2 onwards, fixing belts Nos. 6 to 7 were produced in the same manner as in Example 3. The results of evaluations A-1 to A-3 and evaluations B-1 and B-2 for the obtained fixing belts Nos. 6 to 7 are shown in Tables 1 and 2. [Example 8] The material type of the resin layer in the impregnation step 1 and the temperature at which it contacted the first PFPE are shown in Table 1. Except for the changes shown, a laminate including a resin layer having voids was produced in the same manner as in Example 1. Furthermore, from the impregnation step-2 onwards, fixing belt No. 8 was produced in the same manner as in Example 1. The results of evaluations A-1 to A-3 and evaluations B-1 and B-2 for the obtained fixing belt No. 8 are shown in Tables 1 and 2.

[0081] [Comparative Example 1] A laminate having a base layer, an elastic layer, and a resin layer containing PFA was prepared in the same manner as in Example 1, and this was designated as fixing belt No. C-1 according to this comparative example. The results of evaluations B-1 and B-2 for this fixing belt No. C-1 are shown in Table 2. Note that, because fixing belt No. C-1 did not undergo impregnation step-1, the pore-forming step, and the second impregnation step, evaluations A-1 to A-3 were not performed.

[0082] Comparative Example 2 A laminate having a resin layer having voids was produced in the same manner as in Example 1, except that the material type of the first PFPE was changed to that shown in Table 1 in the method described in Example 1. This laminate was designated as fixing belt No. C-2 according to this comparative example. The results of evaluations A-1 to A-2 and evaluations B-1 to B-2 for the obtained fixing belt No. C-2 are shown in Tables 1 and 2. Note that, since fixing belt No. C-2 according to this comparative example did not undergo impregnation step-2, evaluation A-3 was not performed.

[0083] Comparative Example 3 In the impregnation step-1 in the method described in Example 1, the material type of the first PFPE and the temperature during contact were changed as shown in Table 1. The result of evaluation A-1 on the obtained laminate, that is, the content of PFPE in the resin layer containing the first PFPE obtained in the impregnation step-1, was 24 mass%. When this laminate was subjected to the pore-forming step described in Example 1, the first PFPE in the resin layer could not be removed. The reason for this is unclear; however, it is believed that the impregnation amount was small, so the first PFPE did not aggregate or bond in the resin layer, and the first PFPE penetrated between PFA molecules, preventing it from being dissolved with a solvent. Therefore, impregnation step-2 was not performed, and the laminate obtained up to impregnation step-1 was designated as fixation belt No. C-3 of this comparative example. The results of evaluations A-1 and B-1 to B-2 for the obtained fixation belt No. C-3 are shown in Tables 1 and 2. As described above, pores could not be formed in the resin layer even by the pore-forming step, and therefore impregnation step-2 was not performed. Therefore, evaluations A-2 and A-3 were not performed.

[0084] [Comparative Examples 4 and 5] A substrate whose outer peripheral surface was treated with a primer was prepared in the same manner as in Example 1. The primer-treated surface of the substrate was covered with an expanded porous PTFE tube (product name: Poreflon HP-010-30; manufactured by Sumitomo Electric Fine Polymers, Inc.) to obtain a laminate having a porous resin layer. A second PFPE was introduced into the pores in the resin layer in the same manner as in impregnation step 2 of Example 1, except that this laminate was used. The contact time with the second PFPE was 3 minutes for Comparative Example 4 and 9 minutes for Comparative Example 5. The laminates whose resin layers were impregnated with the second PFPE were designated fixing belts No. C-4 and C-5, respectively. The results of evaluations A-2 to A-3 and evaluations B-1 to B-2 for fixing belts No. C-4 and C-5 are shown in Tables 1 and 2.

[0085] Comparative Example 6 A substrate whose outer peripheral surface was treated with a primer was prepared in the same manner as in Example 1. Subsequently, an amorphous fluoropolymer (trade name: Teflon (registered trademark) AF2400, manufactured by Chemours) was dissolved in a fluorine solvent (trade name: Novec7300, manufactured by 3M) to prepare a 2.0 mass % solution. The substrate was immersed in the solution, and a film was applied by a dipping method to a thickness of 20 μm. The substrate was coated with the solution on its outer periphery. The immersion time was 10 seconds, and the lifting speed was 30 mm / sec. The substrate, on whose outer periphery a coating film of the solution was formed, was dried in an oven at 160°C for 15 minutes to obtain a laminate having a porous polytetrafluoroethylene (PTFE) film on its surface. Except for using this laminate, the pores of the porous PTFE film were impregnated with PFPE-3 in the same manner as in impregnation step-2 of Example 1 to obtain a fixing belt according to this comparative example. The results of evaluations A-2 to A-3 and evaluations B-1 to B-2 for the obtained fixing belt are shown in Tables 1 and 2.

[0086] Table 1 shows the formulations of the fixing belts produced in Examples 1 to 8 and Comparative Examples 1 to 6.

[0087] [Table 1] * [Mass of impregnated PFPE / (Mass of impregnated PFPE + Mass of the resin layer itself)] x 100 *1 is the content ratio of the first PFPE in the PFPE-impregnated resin layer obtained in the impregnation step-1. *2 is the content ratio of the second PFPE in the surface layer.

[0088] Table 2 shows the evaluation results of the fixing rotating bodies produced in Examples 1 to 8 and Comparative Examples 1 to 6.

[0089] [Table 2]

[0090] From Table 2, it is clear that the fixing rotating members of the examples can maintain excellent toner releasability even after long-term use, and as a result, can form high-quality electrophotographic images. [Explanation of symbols]

[0091] 1: resin portion containing PFA, 2: opening, 3: void, 4, PFPE, 101: first surface< / pfa>

Claims

1. A fixing rotating body having a base layer, an elastic layer, and a surface layer in this order, the surface layer comprises a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer and a perfluoropolyether; the surface layer has pores that open to a first surface that constitutes the outer surface of the fixing rotor, At least a portion of the pores contain the perfluoropolyether; a first observation region having a length of 8 μm and a width of 11 μm is placed on the first surface of the surface layer from which the perfluoropolyether in the pores has been removed, and the ratio of the sum of the areas of the openings observed in the first observation region to the area of ​​the first observation region is defined as P1; A second observation region measuring 8 μm in length and 11 μm in width is placed on a cross section of the surface layer from which the perfluoropolyether in the pores has been removed, the cross section including the entire thickness of the surface layer along the circumferential direction of the fixing rotor, and when the ratio of the sum of the areas of the pores observed in the second observation region to the area of ​​the second observation region is defined as P2, A fixing rotating member, characterized in that P2 / P1 is 1.3 or more.

2. The P1 is 1.0% or more and 15.0% or less, 2. The fixing rotating member according to claim 1, wherein the P2 is 20.0% or more and 60.0% or less.

3. 3. The fixing rotating member according to claim 1, wherein the content of the perfluoropolyether in the surface layer is 20% by mass or more and 60% by mass or less.

4. 4. The fixing rotator according to claim 1, wherein the average opening diameter of the openings in the outer surface of the surface layer is 1 nm or more and 5 μm or less.

5. 5. The fixing rotating member according to claim 1, wherein the surface layer has a thickness of 12 μm or more and 100 μm or less.

6. The fixing rotating member according to any one of claims 1 to 5, wherein the perfluoropolyether has a structure represented by the following formula (1): 【Chemistry 1】 (In formula (1), a, b, c, d, e, and f each independently represent 0 or a positive integer, satisfy the relationship 1≦a+b+c+d+e+f≦600, and at least one of a, b, c, and d represents a positive integer.)

7. The fixing rotating member according to any one of claims 1 to 5, wherein the perfluoropolyether has at least one structure selected from the group consisting of the following formulas (2) to (5): (In formula (2), n is a positive number, and n is a number in the range that makes the viscosity of PFPE at a temperature of 40°C range from 30 mPa·s to 500 mPa·s.) (In formula (3), n' is a positive number, and n' is a number in the range that makes the viscosity of PFPE at a temperature of 40°C range from 10 mPa·s to 2500 mPa·s.) (In formula (4), n" and m are each independently a positive number, m / n" is a number that is 0.5 or more and 2 or less, and n" + m is a number that causes the viscosity of PFPE at a temperature of 40°C to be in the range of 20 mPa s to 1400 mPa s.) (In formula (5), n''' and m' are each independently a positive number, m' / n''' is a number that is 20 or more and 1000 or less, and n'''+m' is a number that makes the viscosity of PFPE at a temperature of 40°C in the range of 20 mPa·s to 1200 mPa·s.)

8. 8. The fixing rotating member according to claim 1, wherein the P2 / P1 ratio is 5.0 or more.

9. 9. The fixing rotor according to claim 1, wherein the fixing rotor is a fixing belt having an endless belt shape.

10. 10. The fixing rotating member according to claim 1, wherein the P2 / P1 ratio is 20.0 or less.

11. A fixing device comprising: the fixing rotator according to any one of claims 1 to 10; and a heating means for heating the fixing rotator.

12. the fixing rotating body is a fixing belt having an endless belt shape, 12. The fixing device according to claim 11, wherein the heating means is a heater disposed in contact with the inner circumferential surface of the fixing belt.

13. An electrophotographic image forming apparatus comprising the fixing device according to claim 11 or 12.

14. A method for manufacturing a fixing rotating body, comprising: (i) preparing a laminate having a base layer having an endless belt shape or a roller shape, an elastic layer on the outer peripheral surface of the base layer, and a resin layer containing a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer on the outer peripheral surface of the elastic layer; (ii) immersing the laminate in a first perfluoropolyether heated to a temperature of 300°C ± 50°C to impregnate the resin layer with the perfluoropolyether; (iii) a step of cooling the laminate obtained in the step (ii) in which the perfluoropolyether has been impregnated into the resin layer; (iv) removing at least a portion of the perfluoropolyether impregnated in the resin layer using a fluorine solvent to form pores in the resin layer that are open to the first surface of the resin layer; and (v) a step of incorporating a second perfluoropolyether into at least a portion of the pores to obtain a fixing rotor having a surface layer containing the second perfluoropolyether in at least a portion of the pores.

15. 15. The method for manufacturing a fixing rotator according to claim 14, wherein the viscosity of the first perfluoropolyether is 10 mPa·s to 400 mPa·s.

16. 16. The method for manufacturing a fixing rotating member according to claim 14, wherein the fluorine solvent is a solvent that dissolves the first perfluoropolyether but does not dissolve the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

17. The method for manufacturing a fixing rotatable member according to any one of claims 14 to 16, wherein the viscosity of the second perfluoropolyether is 300 mPa·s to 2500 mPa·s.

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