JP2024115303A - Fixing member and its manufacturing method, fixing device, and electrophotographic image forming apparatus - Google Patents

Abstract

[Problem] To provide a fixing member having a surface layer containing a fluororesin, capable of reducing the absolute value of the electrostatic potential, increasing electrostatic decay when left unattended, and preventing electrostatic offset. [Solution] A fixing member having a laminated structure having at least a substrate, an elastic layer, and a surface layer containing a fluororesin in this order, the surface resistivity of the elastic layer being 1×1014 Ω/□ or more, the surface resistivity of the fluororesin surface layer being 1×1015 Ω/□ or more, the surface layer containing a fluororesin, the surface layer having an area A having voids and an area B which is solid, the area B being located closer to the outer periphery of the fixing member in the thickness direction of the surface layer than the area A, and an ion conductive agent being present in at least some of the voids. [Selected Figure] Figure 4

Description

This disclosure relates to a fixing member used in a heat fixing device of an electrophotographic image forming apparatus, a manufacturing method thereof, a fixing device, and an electrophotographic image forming apparatus.

Fixing members used in the fixing devices of electrophotographic image forming devices such as printers, copiers, and facsimiles come in the form of films or rollers. These fixing members include a heat-resistant resin or metal film or roller-shaped fixing member having a heat-resistant resin or metal substrate, an elastic layer on the substrate, and a release layer on the elastic layer. Here, the release layer often contains a fluororesin that has excellent releasability to toner.

Fluororesin is most likely to be negatively charged in the triboelectric series. Therefore, when the surface of the fixing member, i.e., the outer surface of the release layer, rubs against paper or a pressure member during the process of forming an electrophotographic image, the release layer of the fixing member becomes charged, and electrostatic offset may occur in which unfixed toner electrostatically adheres to the release layer of the fixing member.

Patent document 1 discloses a fixing device equipped with a fixing member whose surface material that comes into contact with the toner image contains at least a fluororesin and an ion-conductive electrical resistance control material that has a melting point equal to or higher than the maximum operating temperature of the fixing device. It also describes that such a fixing device can prevent the occurrence of electrostatic offset.

Japanese Patent Application Publication No. 08-220907

At least one aspect of the present disclosure is directed to providing a fixing member and a manufacturing method thereof that can stably exhibit the effect of preventing electrostatic offset over a long period of time. At least one aspect of the present disclosure is directed to providing a fixing device that contributes to the stable formation of high-quality electrophotographic images. Furthermore, at least one aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that can form high-quality electrophotographic images.

According to at least one aspect of the present disclosure,
A fixing member having at least a base layer, an elastic layer, and a surface layer in this order,
The surface resistivity of the elastic layer is 1× ¹⁰ Ω/□ or more,
The surface resistivity of the surface layer is 1×10 ¹⁵ Ω/□ or more,
The surface layer contains a fluororesin,
The surface layer has a porous region A having pores and a solid region B,
The region B is located closer to the outer circumferential surface of the fixing member than the region A in the thickness direction of the surface layer, and an ion conductive agent is present in at least some of the pores.

One aspect of the present disclosure is a method for producing the fixing member, comprising the steps of:
The surface layer is characterized in that it is produced by the following process:
(i) providing a fluororesin layer;
(ii) immersing the fluororesin layer in a bath of perfluoropolyether (PFPE) to impregnate the PFPE into the fluororesin layer from the outer surface opposite to the elastic layer;
(iii) removing the PFPE impregnated into the fluororesin layer from the outer surface to form pores opening to the outer surface;
(iv) introducing an ion conductive agent into the pores;
(v) contacting an outer surface of the fluororesin with a hot plate heated to a temperature equal to or higher than the melting point of the fluororesin to seal the pores near the outer surface and densify the outer periphery of the surface layer.

One aspect of the present disclosure is a fixing device including a fixing member having a surface layer containing a fluororesin, a pressure member that presses an outer peripheral surface of the fixing member to form a nip portion with the fixing member, and a heating member that heats the fixing member, wherein the fixing member is the above-mentioned fixing member.
One aspect of the present disclosure is an electrophotographic image forming apparatus including the fixing device described above.

One aspect of the present disclosure is to provide a fixing member in which a surface layer includes a porous conductive region A having pores containing an ionic conductive agent on the elastic layer side and an insulating region B on the outer periphery, thereby reducing the absolute value of the electrostatic potential, improving electrostatic decay when left unused, and making it possible to prevent electrostatic offset.
Further, one aspect of the present disclosure can provide a fixing device including such a fixing member and an electrophotographic image forming layer.

1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present disclosure. 1 is a schematic diagram of a fixing device according to an embodiment of the present disclosure. 1 is a schematic cross-sectional view of a fuser member according to an embodiment of the present disclosure. 3A to 3C are schematic cross-sectional views of the process of a surface layer of a fixing member according to an embodiment of the present disclosure. 1 is a schematic diagram for explaining why electrostatic offset can be suppressed by a fixing member having a surface layer. FIG. 1 is a schematic diagram of a charge potential measuring device according to an embodiment of the present disclosure.

In this disclosure, unless otherwise specified, the description of a numerical range such as "XX or more and YY or less" or "XX to YY" means a numerical range including the upper and lower limits which are the endpoints. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any way.

When the present inventors studied the fixing member according to Patent Document 1, they found that the electrostatic offset prevention effect of the fixing member according to Patent Document 1 gradually decreased. According to the study by the present inventors, it was believed that the change over time in the electrostatic offset prevention effect of the fixing member according to Patent Document 1 was due to the ionic conductive agent in the surface layer of the fixing member bleeding to the surface. Here, although the change over time in the electrostatic offset prevention effect due to bleeding can be prevented with an electronic conductive agent, when the conductivity of the surface layer is expressed by an electronic conductive agent, leakage may occur due to aggregation of the electronic conductive agent in the surface layer. Therefore, the present inventors further studied to solve the electrostatic offset problem using a method other than the conventional method of dissipating the charge accumulated in the surface layer by utilizing the conductivity of the surface layer.
As a result, it was found that a fixing member having the following configuration can maintain the effect of preventing electrostatic offset for a long period of time.

<Configuration>
A fixing member having a base layer, an elastic layer, and a surface layer in this order, the elastic layer having a surface resistivity of 1× ¹⁰ Ω/□ or more, and the surface layer having a surface resistivity of 1× ¹⁰ Ω/□ or more. The surface layer contains a fluororesin, and has a porous region A on the side facing the elastic layer and a solid region B on the outer periphery of the fixing member, and an ionic conductive agent is contained in the pores of region A.
One of the reasons why a fixing member having the above configuration can stably prevent electrostatic offset over time is thought to be as follows. Depending on the amount of charge on the outer surface of the surface layer, the ionic conductive agent is polarized into anions and cations in the conductive region and localized in the thickness direction of the conductive region, thereby neutralizing the charge on the outer surface. In the above configuration, the ionic conductive agent in the surface layer is less likely to bleed to the outer surface of the surface layer due to the presence of dense region B. Therefore, the amount of ionic conductive agent in the surface layer is prevented from decreasing over time, and it is thought that the effect of preventing electrostatic offset is maintained over time.

At least one embodiment of a fuser member will now be described with reference to the drawings, without the present disclosure being limited thereto.
1 is a schematic cross-sectional view of a color electrophotographic printer, which is an example of an image forming apparatus according to the present embodiment, taken along the sheet transport direction. Hereinafter, the color electrophotographic printer will be simply referred to as the "printer".
The printer shown in FIG. 1 includes image forming units 10 for the colors Y (yellow), M (magenta), C (cyan), and Bk (black). This allows color printing and monochrome printing. A photosensitive drum 11 is pre-charged by a charger 12. Then, a latent image is formed on the photosensitive drum 11 by a laser scanner 13. The latent image is turned into a toner image by a developing unit 14. The toner image on the photosensitive drum 11 is sequentially transferred to an image carrier, for example, an intermediate transfer belt 31, by a primary transfer blade 17. After transfer, the toner remaining on the photosensitive drum 11 is removed by a cleaner 15. As a result, the surface of the photosensitive drum 11 becomes clean and is prepared for the next image formation.

Meanwhile, recording material (sheets P) are sent out one by one from the paper feed cassette 20 or the multi-paper feed tray 25 and fed into the registration roller pair 23. The registration roller pair 23 first receives the sheet P and straightens it out if it is skewed. The registration roller pair 23 then synchronizes with the toner image on the intermediate transfer belt 31 and sends the sheet P between the intermediate transfer belt 31 and the secondary transfer roller 35. The toner image on the intermediate transfer belt 31 is transferred to the sheet P by pressure applied by the secondary transfer roller 35 and the opposing roller 34, which serve as transfer bodies. The toner image T on the sheet P is then fixed to the sheet P as a fixed image T' by the sheet P being heated and pressurized by the fixing device 40.

Next, the fixing device used in this embodiment will be described. FIG. 2 is a schematic diagram of the fixing device 40, which is a film heating type fixing device (tensionless type). This film heating type is used in this embodiment, but it can also be implemented on the surface layer of a roller pair type or film type fixing device.

A ceramic heater 43 (hereafter referred to as the heater) serves as a heating element. The heater 43 is basically composed of a long and thin ceramic substrate with the longitudinal direction perpendicular to the drawing and an electrically-heated resistor layer provided on the substrate surface. It is a low-heat capacity heater that heats up with a steep rise in temperature as a whole when electricity is applied to the resistor layer. In addition, the heater is configured to be able to switch the energized area according to the longitudinal width size of the recording material (sheet P).
Reference numeral 41 denotes a cylindrical (endless) heat-resistant fixing member serving as a heating member for transmitting heat, and is loosely fitted onto a support member including the heater 43. Fig. 3 is a partially enlarged cross-sectional view of the fixing member 41 in this embodiment, which corresponds to the region G in Fig. 2. This fixing member has a laminated structure of at least a surface layer 41a, an elastic layer 41c, and a base layer 41d, and is an endless belt (endless belt) in this example.
Reference numeral 42 denotes a pressure roller having heat resistance and elasticity as a pressure member, which has a core metal 46 and an elastic layer 47 made of heat-resistant rubber such as silicone rubber or fluororubber, or a silicone rubber foam, and is disposed with both ends of the core metal supported by bearings for free rotation. The fixing member 41 and heater 43 are disposed above the pressure roller 42, parallel to the pressure roller 42 with respect to the heater 43 side, and pressed by a pressing member (not shown). As a result, the lower surface of the heater 43 and the upper surface of the pressure roller 42 are pressed against each other via the fixing member 41 against the elasticity of the elastic layer 47 of the pressure roller, forming a fixing nip portion N of a predetermined width as a heating portion.
The pressure roller 42 is driven to rotate at a predetermined peripheral speed in the counterclockwise direction indicated by the arrow by a driving means (not shown). A rotational force acts on the fixing member 41 due to the frictional force of pressure contact between the pressure roller 42 and the fixing member 41 at the fixing nip N caused by the rotational drive of the pressure roller 42. The inner surface of the fixing member 41 is in close contact with the lower surface of the heater 43 and slides against it, resulting in a driven rotation state in the clockwise direction indicated by the arrow. The support member also serves as a rotation guide member for the endless fixing member 41.
The pressure roller 42 is driven to rotate, and the fixing member 41 is driven to rotate accordingly. In addition, the heater 43 is energized to rapidly heat up to a predetermined temperature and is in a temperature-controlled state, and the sheet P carrying the unfixed toner image T is introduced between the fixing member 41 and the pressure roller 42 in the fixing nip N. In the fixing nip N, the toner image-carrying side of the sheet P is in close contact with the outer peripheral surface of the fixing member 41 and is sandwiched and conveyed through the fixing nip N together with the fixing member 41. During this sandwiching and conveying process, the sheet P is heated by the heat from the fixing member 41 heated by the heater 43, and the unfixed toner image T on the sheet P is heated and pressed onto the sheet P, melted, and fixed as a fixed image T'. The sheet P that has passed through the fixing nip N is separated from the outer peripheral surface 41S of the fixing member 41 by the curvature and conveyed to be discharged.
Reference numeral 44 denotes a contact thermometer (thermistor) which measures the temperature of the fixing member 41 heated by the heater 43 and transmits the detection result to a temperature control means (not shown).
A heater holder 45 is a member for holding the heater 43 that has been heated to a high temperature.

Next, at least one embodiment of the fixing member will be described in detail.
The fixing member is a rotating body, and examples of the rotating body include a fixing roller, a fixing film, and a fixing belt. In the following, a case where the fixing member is a fixing belt having an endless shape (hereinafter, may be simply referred to as a "fixing belt") will be described as an example.
As shown in Fig. 3, the fixing belt is an endless fixing member having at least a laminated structure of an endless base layer 41d, an elastic layer 41c provided on the outer peripheral surface of the base layer, and a surface layer 41a provided on the outer peripheral surface of the elastic layer. 41S is the outer peripheral surface (also called the outer surface) of the fixing member. In addition, an adhesive layer 41b made of resin may be provided on the surface of the elastic layer 41c opposite to the side facing the base layer, thereby improving the adhesion between the surface layer 41a and the elastic layer 41c.

(1) Base layer The material of the base layer is not particularly limited, and any known material used as a base layer of a fixing member such as a fixing rotor can be used. For example, metals and alloys such as aluminum, iron, stainless steel, and nickel, and heat-resistant resins such as polyimide are used. The thickness 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. Since the base layer has an endless shape, it has an inner surface on the inside of the endless shape and an outer surface on the outside.
The outer surface of the base layer may be subjected to a surface treatment to improve adhesion to the elastic layer. The surface treatment may be one or a combination of physical treatments such as blasting, lapping, and polishing, and chemical treatments such as oxidation, coupling agent, and primer treatment.
When an elastic layer containing silicone rubber is provided on the outer surface of the base layer, it is preferable to perform a primer treatment on the outer surface of the base layer in order to further improve the adhesion between the base layer and the elastic layer. Examples of the primer used for the primer treatment include paints in which a silane coupling agent, a silicone polymer, 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. The primer can be appropriately selected depending on the material of the base layer, the type of the elastic layer, or the form of the crosslinking reaction. In particular, when a material containing a large number of unsaturated aliphatic groups is used for the elastic layer, a primer containing a hydrosilyl group that can impart adhesion by reacting with the unsaturated aliphatic group is preferably used. Conversely, when a material containing a large number of hydrosilyl groups is used for the elastic layer, a primer containing an unsaturated aliphatic group is preferably used.
Other examples of the primer include those containing an alkoxy group. A commercially available primer can be used. The primer treatment includes a step of applying the primer to the outer surface of the base layer (the surface to be bonded to the elastic layer) and drying or baking the primer.
When the fixing member is in the form of a fixing roller, the base layer has a hollow cylindrical or solid cylindrical shape, and when it is made of a metal material or the like, it is sometimes called a core bar.

(2) Elastic layer The material of the elastic layer is not particularly limited, and any known material used as an elastic layer of a fixing member can be used. The elastic layer preferably contains silicone rubber, which has excellent heat resistance. In addition, as the raw material of the silicone rubber, an addition curing type liquid silicone rubber is preferably used.
The thickness of the elastic layer can be appropriately designed in consideration of the surface hardness of the fixing member and the width of the fixing nip portion to be formed. When the fixing member is a fixing belt, the thickness of the elastic layer is preferably in the range of 100 μm to 3000 μm. By setting the thickness of the elastic layer in this range, a sufficient width of the fixing nip portion can be secured when the fixing member is incorporated into the fixing device. That is, by setting the thickness of the elastic layer to 100 μm or more, the surface of the fixing member can be made to better follow the unevenness of the recording material. In addition, by setting the thickness of the elastic layer to 3000 μm or less, sufficient heat can be supplied from the fixing member to the recording material to fix the unfixed toner.
The elastic layer may contain a filler, which is added to control the thermal conductivity, heat resistance, and elastic modulus.
Specific examples of the filler include non-conductive fillers such as 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), and titanium oxide ( _TiO2 ).
The surface resistivity of the surface of the elastic layer facing the surface layer is 1× ¹⁰ Ω/□ or more in order to better exhibit the charge neutralization effect of the surface layer described below. In addition, within a range not exceeding the above surface resistivity, the elastic layer can contain a thermally conductive filler or an electrically conductive filler in order to improve thermal conductivity in the thickness direction.

The material constituting the elastic layer may also contain a reaction control agent (blocking agent) called an inhibitor to control the reaction start time. Known substances such as methylvinyltetrasiloxane, acetylene alcohols, siloxane-modified acetylene alcohol, and hydroperoxides are used as reaction control agents.

(3) Adhesive layer The adhesive layer is a layer that is optionally provided to improve the adhesion between the elastic layer and the surface layer. For example, when silicone rubber is used for the elastic layer, an addition curing type silicone rubber adhesive is used. These have the uncrosslinked component of silicone rubber, and when heated, they bond with the uncrosslinked component of the inner surface treatment layer of the surface layer and the elastic layer, thereby bonding the surface layer and the elastic layer. Here, it is preferable that the adhesive layer does not have the conductivity that allows the transfer of charges between the elastic layer and the surface layer, in order to better express the charge neutralization effect by the surface layer described later.

4, the surface layer 41a has an area A411 having voids 413 and a solid area B412. The area B412 is located closer to the outer surface of the fixing belt than the area A411. An ion conductive agent 414 is present in at least a part of the voids 413 in the area A411.
The reason why electrostatic offset can be suppressed by a fixing member having such a surface layer is not clear, but the following mechanism is considered as one possibility. As shown in Fig. 5, when the outer surface of the surface layer 41a is rubbed by the movement of the recording material 500 in the direction of the arrow A in the fixing process of an electrophotographic image, the vicinity of the outer surface of the surface layer is negatively charged, and the side closer to the elastic layer in region B is positively charged. Then, in response to the polarization of region B, the anions of the ion conductive agent in region A move to the side closer to region B, and the cations of the ion conductive agent move to the side closer to the elastic layer in region A. As a result, it is considered that the negative charge on the outer surface of the surface layer is relaxed by the cations in region A, and the charge of the entire surface layer is neutralized.
The correctness of this mechanism is considered to be evident from the results of the following experiment. The inventors prepared the following electrophotographic belt. It has a laminated structure of a base layer, an elastic layer on the base layer, an insulating adhesive layer, and a surface layer (thickness 9 μm), the surface resistivity of the elastic layer is 1×10 ¹⁴ Ω/□, and the surface resistivity of the surface layer is 1×10 ¹⁵ Ω/□. The surface layer contains a fluororesin, and has a porous region A (porosity 0.5%, thickness 0.5 μm) on the side facing the elastic layer, and a solid region B (thickness 8.5 μm) on the outer periphery of the fixing member. The holes in the region A were filled with an ion conductive agent. After the outer surface of this electrophotographic belt was neutralized, a grid part of a corona discharger was placed with a gap of 10 mm from the outer surface, and a voltage of −5 kV was applied to the corona discharger for 15 seconds. The potential of the outer surface was measured at 0.1 second intervals, starting from the point (0 seconds) when the application of voltage to the corona discharger was stopped. As a result, the highest potential was −620 V 10 seconds after the discharge was stopped. On the other hand, when the same measurement was performed on an electrophotographic belt as a control example in which the pores were not filled with an ion conductive agent, the highest surface potential of the surface layer was −750 V. That is, although the surface layer and the elastic layer were insulating, the outer surface of the electrophotographic belt according to one embodiment of the present disclosure was difficult to charge. From this, it is considered that the effect achieved by the fixing member according to the present disclosure is not obtained by discharging the charge of the surface layer, but by charge neutralization (charge relaxation).

In addition, in the fixing member according to the present disclosure, the grid part of the corona discharger was placed with a gap of 10 mm from the outer surface. A voltage of -5 kV was applied to the corona discharger for 15 seconds, and the potential of the outer surface was measured at 0.1 second intervals starting from the point of time when the voltage application to the corona discharger was stopped (0 seconds). From the viewpoint of preventing electrostatic offset, the surface potential at this time is preferably -700 V or more (approaching 0 V), particularly -650 V or more, and even more preferably -600 V or more.

The thickness of region A of the surface layer is preferably 0.5 μm or more and 6 μm or less, and more preferably 1 μm or more and 5 μm or less. The porosity of the holes in region A is preferably 1% or more and 30% or less. On the other hand, region B, which is dense, is preferably a region that has substantially no pores, that is, a solid region, and is preferably a region from the outer surface of the surface layer to a depth of at least 4 μm. However, the presence of pores is permitted within the scope of the present disclosure. Specifically, the porosity is preferably less than 1%. The lower limit of the porosity is 0%. The porosity of region B is preferably 0% or more and less than 1%. The method of determining region A and region B, and the method of measuring the porosity and thickness of each region will be described later.

The surface resistivity of the surface layer must be 1×10 ¹⁵ Ω/□ or more. When the surface resistivity of the surface layer is 1×10 ¹⁵ Ω/□ or more, it is possible to prevent current leakage, which causes loss of surface charge of a recording material such as paper during the fixing process.

The surface layer contains a fluororesin. Examples of the fluororesin include tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), perfluoropolyether (PFPE), polytetrafluoroethylene (PTFE), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). As the fluororesin used, as shown in the manufacturing method described later, it is preferable to use a copolymer or mixed material that can dissolve some components from the surface layer to form holes, and it is more preferable to use PFA. The thickness of the surface layer is preferably 100 μm or less, more preferably 6 μm to 70 μm, and even more preferably 6 μm to 50 μm. For example, a fluororesin tube can be used for the surface layer, and the inner surface of such a tube can be previously subjected to sodium treatment, excimer laser treatment, ammonia treatment, or plasma etching treatment to improve adhesion to the elastic layer or adhesive layer.

(Ionic Conductive Agent)
The ionic conductive agent present in at least a portion of the pores 413 is not particularly limited, and any material that can be introduced into the pores of the porous region A can be used, and from the viewpoint of introduction during the impregnation process, it is preferable that the material be soluble in an ionic liquid or a solvent.
As the ionic conductive agent, an ionic liquid having a combination of the following cations can be preferably used. Examples of the cations include ammonium-based cations, imidazolium-based cations, pyridinium-based cations, piperidinium-based cations, pyrrolidinium-based cations, and phosphonium-based cations. _{Examples of} anions include _ClO4- ^{, Br-} , ^Cl- , _AlCl4- , _Al2Cl7- ^, _NO3- ^, _{BF4- , PF6-} ^, _CH3COO- , ^CF3COO- _{, CF3SO3- ,} ⁽ _{CF3SO2 )} ^3C- _{, AsF6-} ^, _{SbF6- , F} ⁽ _{HF ) n-} ^{, CH3CH2OSO3- , H2PO4-} _{, CF3CF2CF2CF2SO3-} ^, _{CF3CF2CF2COO-} ^, _{N- ( SO2CF3 )} ² _, ^and _{the like} ^.
Among these, it is particularly preferable to use an ionic liquid having a chemical structure represented by the following formula (1), which is available as, for example, "FC-4400" (product name, manufactured by 3M Japan) or "IL-A2" (product name, manufactured by Koei Chemical Co., Ltd.).
(n-C ₄ H ₉ ) ₃ (CH ₃ )N ⁺ N ^- (SO ₂ CF ₃ ) ₂ (1)

The amount of ionic conductive agent contained in region A is not particularly limited, but is preferably 1% by mass or more and 30% by mass or less (1 to 30% by mass), and more preferably 5% by mass or more and 15% by mass or less (5 to 15% by mass), based on the surface layer. By keeping the content within the above range, charge neutralization or charge relaxation of the fixing member can be more easily achieved.

(Determination of Area A and Area B)
The determination of region A and region B of the surface layer is carried out by observing a cross section of the surface layer in the thickness direction.
First, a cross-sectional sample in which the cross section of the surface layer is exposed is cut out from the surface layer of the fixing belt using a cryomicrotome (manufactured by Leica Microsystems). The cross section includes the entire thickness of the surface layer. Here, when the fixing member is a fixing belt having an endless shape, the cross section of the surface layer may be a cross section along the circumferential direction of the fixing belt, or a cross section along the axial direction perpendicular to the circumferential direction. Then, the ionic conductive agent in the pores is removed from the obtained cross-sectional sample. The method of removing the ionic conductive agent is not particularly limited, but at least one example is a method of washing the cross-sectional sample with a solvent in which the ionic conductive agent is soluble and the fluororesin is insoluble. Examples of the solvent include water and ethanol.

Next, the cross-section of the surface layer of the cross-section sample is observed with a scanning electron microscope (SEM) to obtain an SEM image of a rectangular first observation area of 0.5 μm in length and 20 μm in width. At this time, the vertical direction of the observation area is aligned with the thickness direction of the surface layer. Also, the outer surface of the surface layer is aligned with the upper end of the observation area. The resolution is set to 717 pixels in length and 986 pixels in width so that voids appearing in the cross section can be recognized. The obtained SEM image is binarized using a numerical calculation software (product name: MATLAB (registered trademark), manufactured by MathWork Co., Ltd.) to obtain a binarized image. For the binarization, the Otsu method described in Non-Patent Document 1 is used to distinguish between the parts in the SEM image that correspond to voids and the parts that correspond to fluororesin. Then, the ratio of the number of pixels in the parts that correspond to voids in the binarized image to the number of pixels in the entire SEM image is calculated, and this is taken as the porosity.

Next, a SEM image is obtained in the same manner as above for the second observation region obtained by shifting the observation region by 2 microns in the depth direction of the surface layer. That is, the upper end of the second observation region coincides with the lower end of the first observation region. Then, binarization and porosity calculation are performed for the second observation region in the same manner as above. Thereafter, the porosity of the observation region is measured every 2 μm in the thickness direction of the surface layer, and the upper end of the observation region where the porosity first becomes 1% or more is set as the boundary between region A and region B. That is, region B refers to a region in which the porosity calculated by the above method is 0% or more and less than 1%. Moreover, region A refers to a region in which the porosity calculated by the above method is 1% or more. Here, the porosity of region B is preferably 0.5% or less, particularly 0.1% or less, from the viewpoint of more reliably preventing the ion conductive agent in the pores of region A from bleeding to the outer surface. Moreover, it is preferable that the porosity of region A is preferably 1% or more, particularly 5% or more, from the viewpoint of sufficiently containing the ion conductive agent. The upper limit of the porosity is not particularly limited, but from the viewpoint of more reliably maintaining the strength of the surface layer, it is preferably 30% or less, and particularly preferably 15% or less. Therefore, the preferred range of the porosity of region A is 1% or more and 30% or less, and particularly 5% or more and 15% or less.
The thickness of region B refers to the distance from the outer surface of the surface layer of the cross-sectional sample to the boundary. The thickness of region A refers to the distance from the boundary to the surface of the surface layer on the elastic layer side. The thickness of the surface layer is the sum of the thicknesses of regions A and B.

(Method of Manufacturing Fixing Member)
First, the aforementioned member (also called the substrate) that will be the base layer of the laminated structure is prepared. If the substrate is a member that is easily deformed, such as an endless belt, a core or the like is inserted to suppress deformation during the manufacturing process. If necessary, the substrate is subjected to a surface treatment, such as a primer treatment.
Next, an elastic layer is formed on the substrate. The method for forming the elastic layer is not particularly limited, and a conventionally known method can be used. For example, a method can be used in which the material for the elastic layer (addition curing type silicone rubber composition) is applied to the outer surface of the substrate by a ring coating method, and then heated to cure.
The surface of the elastic layer thus formed can be subjected to a surface treatment in order to improve adhesion with the next layer to be formed, etc. When an addition-curing silicone rubber adhesive is applied as the surface treatment, ultraviolet treatment or the like can be preferably applied.
Next, an adhesive layer is formed. The adhesive layer may have any thickness that allows it to be formed uniformly, for example, it is applied to a thickness of about 1 to 10 μm. When using a fluororesin tube as the surface layer, the adhesive layer can be made uniform in thickness by squeezing out excess adhesive after covering the fluororesin tube.

Next, the surface layer is formed. When a fluororesin tube is used as the surface layer, an ion conductive agent is introduced into the surface layer as follows. For reference, schematic cross-sectional views of the surface layer process are shown in Figure 4. In these cross-sectional views, the impregnated material and the communicating holes are depicted so as to appear in the same cross section, but the present invention is not limited to this.
(i) A step of preparing a fluororesin layer 411, for example a member covered with a fluororesin tube.
(ii) A step of immersing the fluororesin layer (member including the fluororesin tube) in a bath of perfluoropolyether (hereinafter, "PFPE") heated to near the melting point of the fluororesin, for example, when the fluororesin is PFA, 300° C.±50° C., preferably 300° C.±25° C., and leaving the member to stand for preferably 20 seconds to 5 minutes, more preferably 30 seconds to 2 minutes, to impregnate the fluororesin tube with PFPE412 from the outer surface of the fluororesin tube opposite the side facing the elastic layer.
(iii) A process of immersing the member obtained through the process (ii) in a solvent capable of dissolving PFPE, thereby removing the PFPE impregnated in the PFA tube from the outer surface of the fluororesin tube to form holes (communicating holes) 413 opening on the outer surface of the fluororesin tube and extending in the thickness direction within the fluororesin tube.
(iv) A step of immersing the member having the pores formed therein in a container containing an ionic conductive agent to introduce the ionic conductive agent into the pores.
(v) A process in which the member obtained through the process (iv) is brought into contact with a metal plate (hot plate) heated to a temperature equal to or higher than the melting point of the fluororesin, thereby sealing the pores in the vicinity of the outer surface of the fluororesin tube and densifying the outer periphery of the surface layer.

The present inventors speculate as follows as to why the fixing member having the surface layer according to one embodiment of the present disclosure can be obtained by the method including the above-mentioned steps (i) to (v). First, in step (ii), the outer surface of the fluororesin tube is brought into contact with PFPE at a temperature near the melting point of the fluororesin contained in the surface layer (for example, when the fluororesin is PFA, the temperature is 300°C ± 50°C), thereby impregnating the PFPE into the fluororesin tube. After step (ii) and before step (iii), the surface layer is cooled to room temperature, and in the process, the fluororesin tube that expanded in step (ii) shrinks. As a result, the PFPE near the outer surface of the fluororesin tube is released to the outside of the fluororesin tube. On the other hand, the PFPE that has permeated from the outer surface of the fluororesin tube and penetrated to the inside away from the outer surface of the fluororesin tube is not released by the shrinkage caused by cooling of the fluororesin tube, and remains in the fluororesin tube. Next, in step (iii), PFPE is removed from the surface layer by a solvent, forming pores on the outer surface of the surface layer at the sites where PFPE was present. For the above reasons, a porous fluororesin tube is formed in which the porosity is higher on the side opposite the outer surface, i.e., the side closer to the elastic layer, than on the outer surface side of the fluororesin tube. In step (iv), an ion conductive agent is introduced into the pores thus formed, and the member formed in step (iii) is immersed in a container filled with the ion conductive agent and left to stand for about 10 minutes to 1 hour. At this time, the fluororesin tube is expanded by heating, thereby shortening the impregnation time. Furthermore, the outer surface of the fluororesin tube made porous in step (v) is pressurized under heat to crush the pores near the outer surface of the fluororesin tube and solidify it.

In step (ii), the amount of PFPE impregnated into the fluororesin tube can be adjusted, for example, by the temperature and viscosity of the PFPE during impregnation, and the contact time between the fluororesin tube and PFPE. Specifically, the higher the temperature range near the melting point of the fluororesin (when the fluororesin is PFA, the temperature is 250 to 350°C), the lower the viscosity of the PFPE, and the longer the contact time, the more the amount of PFPE impregnated into the fluororesin tube can be increased. Here, the preferred viscosity of PFPE (40°C) is preferably 10 mPa·s to 400 mPa·s, more preferably 30 mPa·s to 350 mPa·s. Commercially available PFPEs in this viscosity range include PFPE lubricants from the Krytox (registered trademark) series manufactured by Chemours, such as GPL-101 (viscosity 12 mPa·s), GPL-102 (viscosity 26 mPa·s), GPL-103 (viscosity 54 mPa·s), GPL-104 (viscosity 111 mPa·s), GPL-105 (viscosity 301 mPa·s), and GPL106 (viscosity 458 mPa·s), as well as Fomblin (registered trademark) series from Solvay Japan, such as M03 (viscosity 30 mPa·s).

In step (iii), in order to remove the PFPE impregnated in the fluororesin tube, the fluororesin tube is immersed in a solvent capable of dissolving PFPE but not dissolving fluororesin so that the surface of the fluororesin tube is wet. Here, the "solvent capable of dissolving PFPE" may be, for example, a solvent that dissolves 10 g or more of PFPE per 100 g of solvent at a temperature of 25° C. On the other hand, the "solvent that does not dissolve fluororesin" may be a solvent that dissolves 1 g or less of fluororesin per 100 g of solvent at 25° C. When the fluororesin is PFA, for example, hydrofluoroether (product name: Novec7600; manufactured by 3M) may be used as the above solvent. In addition, applying ultrasonic waves to the fluororesin tube during removal of PFPE from the fluororesin tube in step (iii) is preferable in terms of accelerating removal of PFPE from the fluororesin tube.

In the above steps (ii) to (iii), a member in which a fluororesin tube is coated on an elastic layer is formed, and then the fluororesin tube is made porous. However, the method of forming the surface layer according to the present disclosure is not limited to this. For example, the surface layer according to the present disclosure can also be formed by a method in which a single fluororesin tube is made porous by impregnating it with PFPE as described above and removing the impregnated PFPE, and then the porous fluororesin tube is bonded and fixed on an elastic layer, and then impregnated with an ion conductive agent. In the case where the fluororesin tube is impregnated with PFPE by immersing the fluororesin tube in PFPE, it is preferable to mask the inner surface of the fluororesin tube before immersing the fluororesin tube in PFPE. This is to prevent impregnation of PFPE from occurring from the inner surface of the fluororesin tube.

In the ionic conductive agent introduction step in step (iv), in the case of an ionic liquid, the fluororesin tube is immersed in the liquid and the ionic conductive agent is introduced into the formed pores. At this time, the tube can be expanded by heating, opening the opening. When the tube is then returned to room temperature, it shrinks, pushing out the ionic conductive agent near the opening to the outside, reducing the amount of ionic conductive agent remaining on the outer surface during the subsequent solidification step (v). Note that the ionic conductive agent adhering to the surface of the fluororesin tube is removed by wiping it off, etc.

Step (v) is a process for sealing the pores near the outer surface of the porous fluororesin tube to reduce the surface resistivity at the outer surface of the surface layer. According to the study by the present inventors, the higher the temperature of the hot plate, the thicker the dense region B formed near the outer surface can be. Here, the temperature of the hot plate, the pressing force of the member with the porous surface layer against the hot plate, and the processing time may be appropriately selected as long as the surface resistivity measured at the outer surface of the surface layer can be densely formed to satisfy the value according to the present disclosure. In addition, the method of sealing the pores near the outer surface is not limited to this, and for example, a method of applying hot air to the outer surface and heating the outer surface side of the surface layer can be mentioned.
The thickness of region B of the surface layer may be set to such a degree that the ion conductive agent introduced into region A does not bleed out at the operating temperature of the fixing member.

The invention disclosed herein will be explained in detail below with reference to examples, but the disclosure is not limited to these examples.

(Evaluation Method)
The evaluation method in this disclosure will be described.

(Evaluation 1-1: Evaluation of the porosity of the entire surface layer)
The porosity was calculated as follows.
A cross-sectional sample showing a cross-section of the PFA tube in the thickness direction along the circumferential direction of the laminate was cut out using a cryo-ultramicrotome (manufactured by Leica Microsystems) for a laminate produced by removing PFPE from a PFA tube produced in the examples described below. The cross-section included the entire thickness of the surface layer. Next, the cross-section was observed with a scanning electron microscope (SEM), and an SEM image of an observation area having a square shape with a side of 5 μm (5 μm in thickness direction × 5 μm in circumferential direction) was obtained. The resolution was set to 448 pixels per side so that pores appearing in the cross-section could be recognized. The obtained SEM image was binarized using a numerical calculation software (product name: MATLAB (registered trademark), manufactured by MathWork) to obtain a binarized image. The binarization process used Otsu's method to distinguish between the part corresponding to the pores in the SEM image and the part corresponding to the PFA. Then, the ratio of the number of pixels of the part corresponding to the pores in the binarized image to the number of pixels of the entire image was calculated.
In addition, cross-sectional samples were cut out from three locations at 120° intervals in the circumferential direction of the laminate. Thus, 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 average of these nine ratios was taken as the porosity.

(Evaluation 1-2: Judgment of Area A and Area B)
The cross-section of the surface layer of the cross-section sample prepared in the above evaluation 1-1 was observed with a scanning electron microscope (SEM), and an SEM image of a rectangular first observation region with a length of 0.5 μm and a width of 20 μm was obtained. At this time, the length of the observation region was aligned with the thickness direction of the surface layer. In addition, the outer surface of the surface layer was aligned with the upper end of the observation region. The resolution was set to 717 pixels lengthwise and 986 pixels widthwise so that the pores appearing in the cross section could be recognized. The obtained SEM image was binarized using a numerical calculation software (product name: MATLAB (registered trademark), manufactured by MathWork Co., Ltd.) to obtain a binarized image. The binarization process used the Otsu method described in Non-Patent Document 1 in order to distinguish between the portion corresponding to the pores in the SEM image and the portion corresponding to the fluororesin. Then, the ratio of the number of pixels of the portion corresponding to the pores in the binarized image to the number of pixels of the entire SEM image was calculated, and this was taken as the porosity.
Next, a SEM image was obtained in the same manner as above for the second observation region, which was obtained by shifting the observation region by 2 microns in the depth direction of the surface layer. That is, the upper end of the second observation region was made to coincide with the lower end of the first observation region. Then, for the second observation region, binarization and porosity calculation were performed in the same manner as above. Thereafter, the porosity of the observation region was measured every 2 μm in the thickness direction of the surface layer. Then, the upper end of the observation region where the porosity first became 1% or more was taken as the boundary between region A and region B. Then, the distance from the outer surface of the surface layer of the cross-sectional sample to the above boundary was taken as the thickness of region B, and the distance from the above boundary to the surface of the elastic layer side of the surface layer was taken as the thickness of region A. The thickness of the surface layer was taken as the sum of the thicknesses of region A and region B.

(Evaluation 2: Evaluation of surface resistivity of surface layer and elastic layer)
First, the surface layer was separated from the fixing film of the fixing belt by the following method.
A razor is inserted between the elastic layer and the base layer, and the elastic layer and the surface layer are peeled off from the base layer. The peeled off laminate of the elastic layer and the surface layer is immersed in a resin dissolving agent (product name: e-Solv 21RS, manufactured by Kaneko Chemical Co., Ltd.), placed in a water tank of an ultrasonic cleaning device (product name: Bransonic (model 2510J-DTH), manufactured by Emerson Japan Co., Ltd.), and ultrasonic waves are applied for 60 minutes to dissolve the elastic layer. The laminate is taken out, washed with water, and wiped with toluene and ethanol to obtain an isolated body.
Thereafter, the thickness of the surface layer was measured using a micrometer. The surface resistivity of the surface layer was measured by a method conforming to JIS K 6911. Specifically, the surface resistivity was measured by applying a UR-SS probe to each sample using a high resistivity meter (product name: Hirester UX MCP-HT800, manufactured by Nitto Seiko Analytech Co., Ltd.). During the measurement, a value obtained by applying DC 500 V for 20 seconds and then measuring was taken as the surface resistivity (Ω/□) of the surface layer.
The surface resistivity (Ω/□) of the elastic layer was also measured in the same manner as for the surface layer.

(Evaluation 3: Evaluation of surface potential)
To measure the surface potential, the charge on the fixing belt was first removed by wiping the surface of the fixing belt with a nonwoven wiper (product name "Bencotto" (registered trademark of Asahi Kasei Corporation), manufactured by Ozu Sangyo Co., Ltd.) soaked in ethanol. (Hereinafter, this action will be referred to as "surface de-electrification").
Next, as shown in FIG. 6, while rotating the fixing belt 502 by a motor via a shaft, the surface was charged by the corona charger 501, and the surface potential was measured by the surface potential meter 503. After the fixing belt 502 was fixed to a bearing, the grid part of the corona discharger 501 was arranged so as to have a gap of 10 mm from the surface of a certain phase (defined as phase A) in the longitudinal direction of the fixing belt 502. The surface potential meter 503 was installed so as to have a gap of 8 mm from the center part of the fixing belt 502 of a phase (defined as phase B) rotated 180° in the circumferential direction from phase A in a direction perpendicular to the longitudinal direction of the fixing belt 502. In this state, the fixing belt 502 was rotated, and measurement was started when the surface potential in the circumferential direction of the fixing belt 502 was ±10 V or less. If it was not ±10 V or less, the surface was de-electrified again until it was ±10 V or less.
After the static electricity was removed, the fixing belt 502 was rotated at 60 rpm, and the surface was charged by applying −5 kV to the corona discharger 501, and the potential was measured. At this time, the surface potential was obtained at intervals of 0.1 seconds, and the average potential when the corona charger 501 applied a voltage of −5 kV for 14 to 15 seconds was taken as the surface potential.

(Evaluation 4: Evaluation of electrostatic offset)
Using the fixing member produced by the method shown in the examples, evaluation was carried out in the fixing device shown in Fig. 2. The evaluation conditions were as follows.
Test environment: room temperature 25 degrees, humidity 10%,
Process speed: 150 mm/sec
Paper passing conditions: The main body, fixing member, and pressure member were all neutralized with an ionizer. After that, 100 sheets were passed continuously to form a grid image on CS-068 (product name, Nippon Paper Industries Co., Ltd., 68g paper) that had been left in a test environment for 10 days. After that, 5 sheets were passed to form halftone images on both sides of Office70 (product name, Nippon Paper Industries Co., Ltd., 70g paper).
An iR-ADV C3835F (product name, manufactured by Canon Inc.) was used as the image forming apparatus. The image rank was evaluated by visually observing the increase or decrease in density of five halftone images obtained under the above paper passing conditions, and the presence or absence of electrostatic offset was evaluated according to the following criteria.
(Evaluation Criteria)
Rank A: No toner offset.
Rank B: Toner offset is very slightly observed.
Rank C: Toner offset is slightly observed.
Rank D: Toner offset is clearly observed.

(Rating 5: Durability rating)
Using the fixing member produced by the method shown in the examples, evaluation was carried out in the fixing device shown in Fig. 2. The evaluation conditions were as follows.
Test environment: room temperature 25 degrees, humidity 50%,
Process speed: 150 mm/sec
Paper passing conditions: A grid image was formed on CS-068 (68g paper, A4 size, manufactured by Nippon Paper Industries Co., Ltd.), and the paper was passed continuously. Every 100,000 sheets, GC-C081 (68g paper, SRA3 size, manufactured by Nippon Paper Industries Co., Ltd.) was passed through, and the presence or absence of offset caused by peeling of the surface layer at the edge of the A4 when the paper was passed through was confirmed. If offset was confirmed, it was regarded as durability NG, and was evaluated according to the following criteria.
(Evaluation Criteria)
Rank A: No toner offset occurs after printing 500,000 or more sheets.
Rank B: No toner offset occurs after printing 400,000 or more sheets.
Rank C: No toner offset occurs on 300,000 sheets or more.
Rank D: Toner offset occurs at less than 300,000 sheets.

Example 1
(Method of Manufacturing Fixing Belt)
Next, a method for producing the fixing member used in this example will be described. In this example, a fixing belt including a fixing member having a surface layer 41a as shown in FIG. 4 was produced by a manufacturing method including steps 1 to 4.
(Step 1)
As a base layer, a belt material having an endless shape made of SUS with an inner diameter of 25 mm, a width of 400 mm, and a thickness of 40 μm was prepared. The outer peripheral surface of this belt material was subjected to a primer treatment.
(Step 2)
As a raw material for forming the elastic layer, an addition-curing liquid silicone rubber (product name: SE1886, manufactured by Dow Corning Toray Co., Ltd.) not containing a filler was prepared. To this liquid silicone rubber, spherical alumina (product name: Alnabeads CB-A30S, manufactured by Showa Denko K.K.) was added as a spherical filler. In this way, an addition-curing silicone rubber composition for forming the elastic layer was prepared. These were applied onto the outer peripheral surface of the above-mentioned substrate by a ring coating method, and then heated at a temperature of 200°C for 4 hours to crosslink the layer of the addition-curing silicone rubber composition, thereby forming an elastic layer having a thickness of 300 μm.
The surface resistance of this elastic layer was measured by the method described in Evaluation 2, and was found to be 1×10 ¹⁵ Ω/□.
(Step 3)
The belt material on which the elastic layer was formed was rotated in the circumferential direction at a moving speed of 20 mm/sec, and the surface of the elastic layer was irradiated with ultraviolet light in an air atmosphere using an ultraviolet lamp arranged at a distance of 10 mm from the surface of the elastic layer. A low-pressure mercury ultraviolet lamp (product name: GLQ500US/11, manufactured by Toshiba Lighting & Technology Corporation) was used as the ultraviolet lamp, and irradiation was performed so that the integrated light amount of a wavelength of 185 nm on the irradiated surface was 800 mJ/ ^cm2 .
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 to the surface of the elastic layer to a thickness of approximately 5 μm.
(Step 4)
A 9 μm thick fluororesin tube (Gunze Co., Ltd.) 959HP-PLUS (Mitsui-Chemours Fluoroproducts Co., Ltd.) was placed over the belt to form a surface layer. The belt surface was uniformly rubbed from above the fluororesin tube to remove excess addition-curing silicone rubber adhesive from between the elastic layer and the fluororesin tube.
Then, the belt coated with the elastic layer and the surface layer was placed in an electric furnace set at a temperature of 200° C. and heated for 1 hour to harden the adhesive, thereby bonding the fluororesin tube onto the elastic layer, and both ends were cut to obtain a fixing belt with a width of 350 mm.

(Step 5)
Next, a method for adding an ion conductive agent as an additive to the surface layer of the fixing belt will be described in detail.
This process is carried out in the following order:
(1) Perfluoropolyether (PFPE) impregnation process PFPE was placed in a measuring cylinder made of borosilicate glass. A heating wire covered with a heat insulating material was wrapped around the entire measuring cylinder, and the temperature of the PFPE was heated to 280°C. The prepared fixing belt was attached to a dipping device, immersed in the heated PFPE for 1 minute, and then removed. As the PFPE, GPL104 (viscosity: 111 mPa·s (40°C)), GPL105 (viscosity: 304 mPa·s (40°C)) and GPL106 (viscosity: 458 mPa·s (40°C)) from the Krytox (registered trademark) series, which is a PFPE lubricant manufactured by Chemours, were used. The porosity was controlled by controlling the viscosity of the PFPE.
In this embodiment, a liquid in which GPL105 and GPL106 were mixed in a mass ratio of 50:50 was used.
(2) Hole Forming Step The laminate obtained in the above PFPE impregnation step was immersed in a measuring cylinder containing a fluorine solvent (product name: Novec7300, manufactured by 3M) for 10 minutes, and then the measuring cylinder was placed in a water tank of an ultrasonic cleaning device (product name: Bransonic (model 2510J-DTH), manufactured by Emerson Japan), and ultrasonic waves were applied for 60 minutes. After the treatment, the laminate was removed from the measuring cylinder and left in an environment at a temperature of 25°C for 60 minutes to dry. In this way, a laminate was obtained from which the PFPE present on the outer surface and inside of the PFA tube was removed. The obtained laminate had a white appearance when visually observed, and it was confirmed that voids were formed in the PFA tube. When the outer surface (first surface) of the PFA tube of the obtained laminate and the cross section in the circumferential direction of the laminate were confirmed by SEM, a resin part and an opening were confirmed on the outer surface, and voids communicating with the resin part were observed on the cross section. It was also observed that the pores were in contact with the openings, and the communicating holes were connected to the outside.
The porosity of this laminate was calculated by the method described in Evaluation 1, and it was confirmed to be 0.5%.
(3) Ion Conductive Agent Introduction Step The laminate having pores formed in the surface layer was immersed in a measuring cylinder containing "FC-4400" (product name, manufactured by 3M Japan) represented by the above formula (1) as an ion conductive agent for 30 minutes to introduce the ion conductive agent into the pores of the surface layer. After removing from the measuring cylinder, the ion conductive agent attached to the surface was wiped off. Here, it was confirmed that the ion conductive agent had been introduced into the pores of the obtained laminate at the stage when the white to colored (color of the elastic layer) was visually observed.
(4) Solidification process The surface of the laminate with the ion conductive agent introduced into the pores was pressed against a hot plate heated to 310° C. while rotating a fixing belt having a fixing member at 10 rpm to bring the entire outer periphery of the surface into contact. As a result, the fluororesin tube of the surface layer was heated to above its melting point to close the through holes in the pore-containing region formed on the surface, thereby solidifying the outer periphery of the surface layer. The obtained surface layer was as shown in FIG. 4. As a result, it was confirmed that the thickness of the pore-containing region A was 0.5 μm.
The surface resistivity of this surface layer was measured by the method described in Evaluation 2, and was found to be 1×10 ¹⁵ Ω/□.

(Examples 2 to 10)
In the manufacturing method of the fixing belt of Example 1, the type of PFPE used in the PFPE impregnation process and the rotation speed of the fixing member in the densification process were controlled in this embodiment to produce a laminate by controlling the porosity and the thickness of the region A having pores.
Specifically, when the porosity was 1%, GPL104 and GPL105 were mixed in a mass ratio of 5:95. When the porosity was 30%, GPL104 and GPL105 were mixed in a mass ratio of 95:5. When the porosity was 30.5%, only GPL104 was used.
Furthermore, when the thickness of the region A having holes was set to 1 μm, the fixing belt having the fixing member was rotated at 12 rpm, when the thickness was set to 5 μm, the fixing belt was rotated at 28 rpm, and when the thickness was set to 6 μm, the fixing belt was rotated at 32 rpm.
The surface layers were prepared using fluororesin tubes having thicknesses of 9 μm, 10 μm, 50 μm, and 51 μm, respectively, and the thicknesses were defined as the thicknesses of the surface layers.

(Comparative Example 1)
A fixing belt was produced in the same manner as in Example 1, except that a fluororesin tube having a surface layer containing 1 wt % carbon particles was used.
(Comparative Example 2)
A fixing belt was produced in the same manner as in Example 1, except that carbon particles were added to the addition curing silicone rubber composition for forming the elastic layer so that the carbon particles accounted for 30 wt % of the total composition.
(Comparative Example 3)
The porous layer was filled with carbon particles in the same manner as in Example 1. In the manufacturing method, the porous layer was filled with the particles by impregnating GPL104 with a liquid in which carbon particles were suspended.
(Comparative Example 4)
In the manufacturing method of the fixing belt of Example 1, step 5 was not carried out, and a surface layer to which no additive was introduced was used.
Tables 1 and 2 show the shapes and evaluation results of the fixing belts produced in Examples 1 to 10 and Comparative Examples 1 to 4.

In this way, when the fixing belts produced by the methods described in Examples 1 to 10 were used, it was possible to obtain fixing belts which were able to prevent electrostatic offset and had high durability.
In contrast to this, in the comparative examples 1 and 2, electrostatic offset occurred due to conductive leakage caused by agglomeration of carbon in the surface layer and elastic layer.
In Comparative Examples 3 and 4, the ion conductive agent had no charge neutralizing effect, and therefore electrostatic offset occurred.

The present disclosure includes the following configurations.
[Configuration 1]
A fixing member having a laminated structure including at least a base layer, an elastic layer, and a surface layer in this order,
The surface resistivity of the elastic layer is 1× ¹⁰ Ω/□ or more,
The surface resistivity of the surface layer is 1×10 ¹⁵ Ω/□ or more,
The surface layer contains a fluororesin,
The surface layer has a porous region A having pores and a solid region B,
The region B is located closer to the outer circumferential surface of the fixing member than the region A in the thickness direction of the surface layer, and an ion conductive agent is present in at least some of the pores.
[Configuration 2]
The fixing member according to [Configuration 1], wherein a grid portion of a corona discharger is disposed with a gap of 10 mm from the outer surface of the surface layer, and when a voltage of -5 kV is applied to the corona discharger for 15 seconds, the surface potential of the surface layer is -650 V or less.
[Configuration 3]
The fixing member according to [Configuration 1] or [Configuration 2], wherein the region B is a region from the outer surface of the surface layer to a depth of at least 4 μm.
[Configuration 4]
The fixing member according to any one of [Configuration 1] to [Configuration 3], wherein the porosity of the region A is 1% or more and 30% or less.
[Configuration 5]
The fixing member according to any one of [Configuration 1] to [Configuration 4], wherein the porosity of the region B is 0% or more and less than 1%.
[Configuration 6]
The fixing member according to any one of [Configuration 1] to [Configuration 5], wherein the thickness of region A of the surface layer is 1 μm or more and 5 μm or less.
[Configuration 7]
The fixing member according to any one of [Configuration 1] to [Configuration 6], wherein the ionic conductive agent is an ionic liquid having a chemical structure represented by the following formula (1):
(n-C ₄ H ₉ ) ₃ (CH ₃ )N ^{+ -} N(SO ₂ CF ₃ ) ₂ (1)
[Configuration 8]
The fixing member according to any one of [Configuration 1] to [Configuration 7], wherein the surface layer has a thickness of 6 μm or more and 50 μm or less.
[Configuration 9]
A fixing device comprising: a fixing member having a surface layer containing a fluororesin; a pressure member that presses the outer peripheral surface of the fixing member to form a nip portion with the fixing member; and a heating member that heats the fixing member, wherein the fixing member is the fixing member described in any one of [Configuration 1] to [Configuration 8].
[Configuration 10]
An electrophotographic image forming apparatus comprising the fixing device according to [Configuration 9].

The present disclosure also includes the following methods.
[Method 1]
A method for producing the fixing member according to any one of [Configuration 1] to [Configuration 8],
The surface layer is produced by the following steps:
(i) providing a fluororesin layer;
(ii) immersing the fluororesin layer in a bath of perfluoropolyether (PFPE) to impregnate the PFPE into the fluororesin layer from the outer surface opposite to the elastic layer;
(iii) removing the PFPE impregnated into the fluororesin layer from the outer surface to form pores opening to the outer surface;
(iv) introducing an ion conductive agent into the pores;
(v) contacting an outer surface of the fluororesin with a hot plate heated to a temperature equal to or higher than the melting point of the fluororesin to seal the pores near the outer surface and densify the outer periphery of the surface layer.

REFERENCE SIGNS LIST 1 Electrophotographic image forming apparatus 40 Fixing device 41 Fixing member 41a Surface layer 41b Adhesive layer 41c Elastic layer 41d Base layer 41S Outer circumferential surface 42 Pressure roller 43 Heater 44 Contact thermometer
45 Heater holder 411 Fluororesin layer 412 Impregnated PFPE
413 Vacancy 414 Ionic conductive agent (ionic liquid)
415 Area A
416 Area B
P: recording material T: toner N: fixing nip

Claims (11)

A fixing member having a laminated structure including at least a base layer, an elastic layer, and a surface layer in this order,
The surface resistivity of the elastic layer is 1× ¹⁰ Ω/□ or more,
The surface resistivity of the surface layer is 1×10 ¹⁵ Ω/□ or more,
The surface layer contains a fluororesin,
The surface layer has a region A having voids and a region B which is solid,
The region B is located closer to the outer circumferential surface of the fixing member than the region A in the thickness direction of the surface layer, and an ion conductive agent is present in at least some of the pores. The fixing member according to claim 1, in which a grid part of a corona discharger is disposed with a gap of 10 mm from the outer surface of the surface layer, and the surface potential of the surface layer is -650 V or more when a voltage of -5 kV is applied to the corona discharger for 15 seconds. The fixing member according to claim 1, wherein the region B is a region extending from the outer surface of the surface layer to a depth of at least 4 μm. The fixing member according to claim 1, wherein the porosity of the region A is 1% or more and 30% or less. The fixing member according to claim 1, wherein the porosity of the region B is 0% or more and less than 1%. The fixing member according to claim 1, wherein the thickness of region A of the surface layer is 1 μm or more and 5 μm or less. The fixing member according to claim 1 , wherein the ionic conductive agent is an ionic liquid having a chemical structure represented by the following formula (1):
(n-C ₄ H ₉ ) ₃ (CH ₃ )N ^{+ -} N(SO ₂ CF ₃ ) ₂ (1) The fixing member according to claim 1, wherein the thickness of the surface layer is 6 μm or more and 50 μm or less. A method for producing the fixing member according to any one of claims 1 to 8, comprising the steps of:
The surface layer is produced by the following steps:
(i) providing a fluororesin layer;
(ii) immersing the fluororesin layer in a bath of perfluoropolyether (PFPE) to impregnate the PFPE into the inside of the fluororesin layer from the outer surface opposite to the side facing the elastic layer;
(iii) removing the PFPE impregnated into the fluororesin layer from the outer surface to form pores opening to the outer surface;
(iv) introducing an ion conductive agent into the pores;
(v) contacting an outer surface of the fluororesin with a hot plate heated to a temperature equal to or higher than the melting point of the fluororesin to seal the pores near the outer surface and densify the outer periphery of the surface layer. A fixing device comprising a fixing member having a surface layer containing a fluororesin, a pressure member that presses the outer peripheral surface of the fixing member to form a nip portion with the fixing member, and a heating member that heats the fixing member, the fixing device being characterized in that the fixing member is the fixing member described in any one of claims 1 to 8. An electrophotographic image forming apparatus comprising the fixing device according to claim 10.

Images