Fixing member and thermal fixing device

Abstract

To provide an anchoring member which can prevent the exfoliation of a surface layer by reducing a shearing force which is generated at an interface between the surface layer and an elastic layer, and can obtain softness, high heat transmission, and a long life.SOLUTION: In an anchoring member composed of at least a base layer, an elastic layer and a surface layer, the elastic layer has a thickness of 200 μm or thicker, a heat transmission rate in a thickness direction of 0.4 W / mK or higher, and a content of contained filler particles with respect to the elastic layer as a whole of 40 vol% to 60 vol%. When setting a range from an interface between the elastic layer and the surface layer to a position of 50 um in the thickness direction of the elastic layer as a region A, and setting a range from a position of 50 μm to a side surface facing the base layer of the elastic layer as a region B, a practical-use spherical degree SA of the filler particle is equal to or higher than 0.80, and the content is equal to or lower than 60 vol% in the region A, and a practical-use spherical degree SB of the filler particle is lower than 0.80, and the content is equal to or lower than 40 vol% in the region B. The practical-use spherical degree SA:SA=(VA / VAe)(1 / 3), and the practical-use spherical degree SB:SB=(VB / VBe)(1 / 3).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a fixing member used in a heat fixing device of an electrophotographic image forming apparatus and a heat fixing device.

Background Art

[0002] As a fixing member used in a heat fixing device of an electrophotographic image forming apparatus such as a printer, a copier, or a facsimile, there is a structure in which an elastic layer containing a rubber excellent in heat resistance such as silicone rubber and a surface layer are laminated on a base layer made of a heat-resistant resin or metal. The surface layer contains a fluororesin that gives excellent releasability to toner. And, in order to give high thermal conductivity in the thickness direction of the elastic layer, the elastic layer may contain a thermal conductive filler (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Among the requirements for further improving the durability of electrophotographic image forming apparatuses, there has been an increasing demand for further extending the life of fixing members. However, in a fixing member having an elastic layer in which a heat flow path is formed by a thermal conductive filler, peeling may occur in the vicinity of the interface between the elastic layer and the surface layer due to long-term use. One aspect of the present disclosure is directed to providing a fixing member having high thermal conductivity in the thickness direction and not peeling between the surface layer and the elastic layer even after long-term use. Another aspect of the present disclosure is directed to providing a heat fixing device capable of stably forming high-quality electrophotographic images.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, there is a fixing member comprising at least a base layer, an elastic layer, and a surface layer, where the thickness of the entire elastic layer is 200 μm or more, the thermal conductivity in the thickness direction of the entire elastic layer is 0.4 W / mK or more, the elastic layer contains filler particles, the content of the filler particles in the entire elastic layer is 40 to 60% by volume, when a range from the interface between the elastic layer and the surface layer to a position 50 μm in the thickness direction of the elastic layer is defined as region A, the practical sphericity SA of the filler particles contained in region A is 0.80 or more, and the content of the filler particles contained in region A is 60% by volume or less, when a range from a position 50 μm in the thickness direction of the elastic layer from the interface between the elastic layer and the surface layer to the surface on the side facing the base layer of the elastic layer is defined as region B, the practical sphericity SB of the filler particles contained in region B is less than 0.80, and the content of the filler particles contained in region B is 40% by volume or more, a fixing member is provided, wherein the practical sphericity SA is calculated by the following formula (3), and the practical sphericity SB is calculated by the following formula (6):SA=(V

[0006] , , / V Ae ) (1 / 3) ···Formula (3)V Ae is the volume of the filler particles in region A, and V SB=(V B / V Be ) (1 / 3) ···Formula (6)V Be is the volume of the filler particles in region B, and V Further, according to another aspect of the present disclosure, there is provided a thermal fixing device including the above fixing member and a pressing member disposed opposite to the fixing member.

Advantages of the Invention

[0007] [Figure 1] This is a schematic diagram of the image forming apparatus in the first embodiment. [Figure 2] This is a schematic diagram of the fixing device in the first embodiment. [Figure 3] This is a schematic diagram of the fixing film in the first embodiment. [Figure 4] This figure shows the first and second cross-sections of the elastic layer of a belt-shaped fixing member. [Figure 5] This is a schematic diagram of the cross-section of the anchoring member. [Figure 6] This is a schematic diagram of the binarization and Voronoi tessellation of a cross-sectional image of an elastic layer. [Modes for carrying out the invention]

[0008] In this specification, the expressions "XX or greater and YY or less" and "XX to YY" that represent numerical ranges mean numerical ranges that include the lower and upper limits, unless otherwise specified. Furthermore, when numerical ranges are described in steps, any combination of the upper and lower limits of each numerical range is disclosed.

[0009] The inventors speculate that the reason why delamination occurs at the interface between the surface layer and the elastic layer due to long-term use of the fixing member described in Patent Document 1 is as follows: During the fixing process, the moving paper is in contact with the surface of the surface layer, so the surface layer tries to follow the transport of the paper. As a result, a large shear force is applied to the interface between the surface layer and the elastic layer. Regarding adhesion between the surface layer and the elastic layer, "adhesion force" and "peel force" are related, and adhesion can be ensured when the relationship "adhesion force > peel force" holds, but delamination occurs when "adhesion force < peel force". The above shear force functions as a peel force. With the recent increase in the process speed of electrophotographic imaging devices, the fixing member is subjected to even higher shear forces. As a result, a situation has arisen where the peel force is greater than the adhesion force between the surface layer and the elastic layer.

[0010] Under these circumstances, the inventors' investigations revealed that the shape of the thermal conductive filler in the elastic layer affects delamination near the interface between the elastic layer and the surface layer. Specifically, when the thermal conductive filler located near the surface of the elastic layer, closer to the surface layer, has a sharp portion, stress concentrates at the sharp portion of the thermal conductive filler when a high shear force is applied to the elastic layer, causing cracks in the elastic layer. The inventors found that as these cracks grow, the elastic layer and the surface layer delaminate near their interface. Therefore, the inventors considered using a thermal conductive filler that does not have a sharp portion. As a result, the thermal conductivity in the thickness direction of the elastic layer sometimes decreased.

[0011] Therefore, the present inventors have found that, from the viewpoint of preventing delamination at the interface between the surface layer and the elastic layer, the shape of the filler particles is preferably round, and from the viewpoint of providing high thermal conductivity in the thickness direction of the elastic layer, the shape of the filler particles is preferably pointed. Here, the inventors found that shear stress tends to concentrate particularly in a thickness region from the surface facing the surface layer of the elastic layer (the interface between the elastic layer and the surface layer) to the opposite surface (the interface between the elastic layer and the base layer) at a distance of 50 μm. This region will hereafter be referred to as "region A". Therefore, a thermal conductive filler with few sharp edges was included in region A. Then, an anchoring member was fabricated and evaluated, which had an elastic layer containing a thermal conductive filler with sharp edges in region B, from 50 μm in the thickness direction of the elastic layer from the interface between the elastic layer and the surface layer to the interface between the elastic layer and the base layer. As a result, it was found that this anchoring member exhibited a high thermal conductivity of 0.40 W / mK or more in the thickness direction of the elastic layer, and that delamination near the interface between the surface layer and the elastic layer was unlikely to occur even after long-term use.

[0012] In other words, a fixing member according to one aspect of the present disclosure comprises at least a base layer, an elastic layer, and a surface layer. The total thickness of the elastic layer is 200 μm or more, and the thermal conductivity of the elastic layer in the thickness direction is 0.4 W / m·K or more. The elastic layer also contains filler particles, and the content of filler particles relative to the total elastic layer is 40% to 60% by volume. Furthermore, when the area from the interface between the elastic layer and the surface layer to a position 50 μm in the thickness direction of the elastic layer is defined as region A, the practical sphericity SA of the filler particles contained in region A is 0.80 or greater, and the content of filler particles contained in region A is 60 volume% or less. In addition, the area from the interface between the elastic layer and the surface layer to a position 50 μm in the thickness direction of the elastic layer to the surface of the elastic layer facing the base layer is defined as region B. The practical sphericity SB of the filler particles contained in region B is less than 0.80, and the content of filler particles contained in region B is 40 volume% or greater. The practical sphericity SA is calculated using the following formula (3), and the practical sphericity SB is calculated using the following formula (6): SA=(V A / V Ae ) (1 / 3) ...Equation (3) V A V is the volume of filler particles in region A. AeThe volume of the circumscribing sphere of the filler particles in region A is SB=(V B / V Be ) (1 / 3) ...Equation (6) V B V is the volume of filler particles in region B. Be is the volume of the circumscribing sphere of the filler particles in region B.

[0013] Next, with reference to the drawings, an electrophotographic component and an electrophotographic image forming apparatus according to one aspect of this disclosure will be described. Figure 1 is a cross-sectional view along the transport direction of recording material in a color electrophotographic printer (hereinafter sometimes simply referred to as "printer") according to one embodiment of the electrophotographic image forming apparatus of the present disclosure.

[0014] The printer shown in Figure 1 is equipped with image forming units 10 for each color: Y (yellow), M (magenta), C (cyan), and Bk (black). The photosensitive drum (photoreceptor) 11 is pre-charged by a charger 12. Then, the photosensitive drum 11 is exposed by a laser scanner 13 to form an electrostatic latent image. The electrostatic latent image is converted into a toner image by a developer 14. The toner image on the photosensitive drum 11 is sequentially transferred by a primary transfer blade 17 to an image carrier, such as an intermediate transfer belt 31. After transfer, any 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 ready for the next image formation.

[0015] Meanwhile, the recording material P is fed one sheet at a time from the paper feed cassette 20 or the multi-feed tray 25 and delivered to the registration roller pair 23. The registration roller pair 23 receives the recording material P and straightens it if it is skewed. Then, the registration roller pair 23 synchronizes with the toner image on the intermediate transfer belt 31 and delivers the recording material P between the intermediate transfer belt 31 and the secondary transfer roller 35. The color toner image on the intermediate transfer belt is transferred to the recording material P by a transfer body, such as the secondary transfer roller 35. Subsequently, the toner image on the recording material P is fixed to the recording material P by heating and pressurizing the recording material P by the fixing device 40.

[0016] The fixing device 40 will be explained with reference to Figure 2. The fixing device 40 shown in Figure 2 is equipped with a film heating type heating device (tensionless type). Although such a heating device was used in this embodiment, it is also possible to use a roller pair type or a film type heating device.

[0017] 43 is a ceramic heater (hereinafter referred to as "heater") used as a heating element. Heater 43 basically consists of a long, narrow ceramic substrate with its length perpendicular to the drawing and an electrically conductive heat-generating resistor layer on the surface of this substrate. It is a low-heat-capacity heater that heats up with a steep rise characteristic when current is passed through the heat-generating resistor layer. Furthermore, it is configured to switch the energized area according to the length width size of the recording material.

[0018] 41 is a fixing rotating body that serves as a heating element for transferring heat. Examples of fixing rotating bodies include fixing rollers, fixing films having an endless shape, and fixing belts having an endless shape.

[0019] 44 is a pressure roller as a pressurizing member, and has a core metal and an elastic layer made of heat-resistant rubber such as silicone rubber or fluororubber, or silicone rubber foam. The pressure roller is arranged so that both ends of the core metal are supported by bearings so that they can rotate freely. The fixing film 41 and heater 43 are placed above the pressure roller 44, parallel to the pressure roller 44, and pressed with a pressing member (not shown). In this way, the lower surface of the heater 43 and the upper surface of the pressure roller 44 are pressed together against the elasticity of the roller elastic layer via the fixing film 41, forming a fixing nip portion T of a predetermined width which serves as a heating portion.

[0020] The pressure roller 44 is driven to rotate at a predetermined peripheral speed in the counterclockwise direction indicated by the arrow by a driving means (not shown). Due to the rotational drive of the pressure roller 44, a rotational force is applied to the cylindrical fixing film 41 by the pressure friction force at the fixing nip portion T between the pressure roller 44 and the fixing film 41. The fixing film 41 then slides in close contact with the downward surface of the heater 43 and enters a state of driven rotation in the clockwise direction indicated by the arrow. The support member (heater holder) 46 also serves as a rotation guide member for the cylindrical fixing film 41.

[0021] The pressure roller 44 is driven to rotate, causing the cylindrical fixing film 41 to rotate along with it, and the heater 43 is energized, causing it to rapidly heat up to a predetermined temperature and reach a temperature-controlled state. In this state, recording material P carrying an unfixed toner image T is introduced between the fixing film 41 and the pressure roller 44 in the fixing nip section T. Then, in the fixing nip section, the toner image-carrying side of the recording material P comes into close contact with the outer surface of the fixing film 41, and the fixing nip section T is clamped and conveyed together with the fixing film 41. During this clamping and conveying process, the recording material P is heated by the heat of the fixing film 41 heated by the heater 43, and the unfixed toner image T on the recording material P is heated and pressurized and melted and fixed onto the recording material P. The recording material P that has passed through the fixing nip section T is separated from the surface of the fixing film 41 by curvature and discharged and conveyed. 45 is a contact thermometer (thermistor) that measures the temperature of the fixing film 41 heated by the heater 43 and passes the detection result to a temperature control means (not shown). 46 is a heater holder, a component that holds the heater 43 which has been heated to a high temperature.

[0022] Next is a cross-sectional view of a fixing film having an endless shape as one embodiment of the fixing rotating body 41 (hereinafter also simply referred to as "fixing film") in a direction perpendicular to the circumferential direction. The fixing film 41 comprises a base layer 41b having an endless shape, an elastic layer 41c provided on the outer peripheral surface of the base layer, and a surface layer 41a on the outer peripheral surface of the elastic layer. The surface layer 41a may be bonded to the surface of the elastic layer 41c opposite to the side facing the base layer with an adhesive layer (not shown).

[0023] (1) Base layer The material of the base layer 41b is not particularly limited, and known materials used as base layers for fixing members such as fixing rotating bodies can be used. For example, metals and alloys such as aluminum, iron, stainless steel, and nickel, as well as heat-resistant resins such as polyimide, can be used. The thickness is not particularly limited, but from the viewpoint of strength, flexibility, and heat capacity, it is preferably 20 μm to 100 μm.

[0024] The outer surface of the base layer 41b may be subjected to a surface treatment to provide adhesion to the elastic layer 41c. The surface treatment can be one or more types of physical treatments such as blasting, lapping, and polishing, or chemical treatments such as oxidation, coupling agent treatment, and primer treatment. When an elastic layer 41c containing silicone rubber is provided on the surface of the base layer 41b, it is preferable to apply a primer treatment to the surface of the base layer 41b in order to improve the adhesion between the base layer 41b and the elastic layer 41c. Examples of primers used for the primer treatment include paints in which a silane coupling agent, a silicone polymer, methyl siloxane hydrogenation, an alkoxysilane, a reaction-accelerating catalyst, and a coloring agent such as red iron oxide are appropriately blended and dispersed in an organic solvent. The primer can be appropriately selected depending on the material of the base layer, the type of elastic layer, or the form of the crosslinking reaction. In particular, when the elastic layer contains a large amount of unsaturated aliphatic groups, a primer containing hydrosilyl groups is preferably used to impart adhesion through reaction with the unsaturated aliphatic groups. Other types of primers include those containing alkoxy groups. Commercially available primers can be used. The priming process also includes applying the primer to the outer surface of the base layer (the surface that adheres to the elastic layer) and drying or firing it.

[0025] (2) Surface layer The surface layer 41a may contain, for example, a fluororesin. Examples of fluororesin layers include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), and PFA. The thickness of the surface layer is not particularly limited, but is preferably 10 to 100 μm, and more preferably 10 to 70 μm.

[0026] (3) Elastic layer The elastic layer 41c is sandwiched between the surface layer 41a and the base layer 41b, and has a thickness of 200 μm or more. By making the total thickness of the elastic layer 200 μm or more, a sufficient nip width can be ensured when the fixing belt is incorporated into the fixing device. There is no particular upper limit to the thickness of the elastic layer, but it is preferable to make it 3 mm (3000 μm) or less. When the fixing member is a fixing belt, the flexibility of the fixing belt can be more reliably maintained by making the thickness of the elastic layer 3 mm or less. In other words, the preferred thickness of the elastic layer is 200 μm or more and 3 mm or less.

[0027] The thermal conductivity in the thickness direction of the entire elastic layer is 0.4 W / mK or higher. A thermal conductivity of 0.4 W / mK or higher in the thickness direction ensures sufficient heat transfer. There is no particular upper limit, but for example, it is 2.0 W / m·K. Therefore, the preferred range for the thermal conductivity in the thickness direction of the elastic layer is 0.4 to 2.0 W / m·K.

[0028] The elastic layer comprises rubber as a binder and filler particles dispersed within the rubber. The rubber material is not particularly limited, and known materials used as elastic layers for fixing members such as fixing rotating bodies can be used, but it is preferable to include silicone rubber, which has excellent heat resistance. Furthermore, addition-curing type liquid silicone rubber is preferably used as the raw material for the silicone rubber.

[0029] To achieve a thermal conductivity of 0.4 W / m·K or higher in the thickness direction of the elastic layer, it is preferable that the filler particles include at least high thermal conductivity filler particles. The material of such high thermal conductivity fillers is not particularly limited, but examples include inorganic materials, especially metals and metal compounds. Specific examples of high thermal conductivity fillers include particles made from the following materials. Silicon carbide (SiC), silicon nitride (Si3N4), boron nitride (BN), aluminum nitride (AlN), alumina (Al2O3), zinc oxide (ZnO), magnesium oxide (MgO), silica (SiO2), copper (Cu), aluminum (Al), silver (Ag), iron (Fe), nickel (Ni), carbon black (C), carbon fiber (C), carbon nanotubes (C), etc. These particles may be used individually or mixed together in any two or more types.

[0030] The content of thermally conductive filler particles in the elastic layer is 40% to 60% by volume. A content of 40% or more makes it easy to achieve a thermal conductivity of 0.4 W / m·K or higher in the thickness direction of the elastic layer. Furthermore, a content of 60% or less prevents an excessive increase in the hardness of the elastic layer. The method for measuring the content of thermally conductive filler particles in the elastic layer will be described later.

[0031] Furthermore, the material constituting the elastic layer may contain a reaction control agent (inhibitor) called an inhibitor to control the reaction initiation time. Known substances such as methyl vinyltetrasiloxane, acetylene alcohols, siloxane-modified acetylene alcohol, and hydroperoxides can be used as reaction control agents. <Method for measuring the content (volume fraction) of filler particles in the elastic layer>

[0032] This section explains how to measure the volume fraction of filler particles contained in an elastic layer. First, the base layer and surface layer are peeled off from the fixing film, leaving only the elastic layer. The specific gravity of the elastic layer is measured using an automatic hydrometer (product name: DSG-1, manufactured by Toyo Seiki Seisakusho). The volume fraction of the filler is calculated using this result, along with the specific gravity of the binder and the specific gravity of the filler in the elastic layer. Furthermore, the volume fraction of filler particles in region A and region B can be confirmed using a thermogravimetric analyzer (TGA) (e.g., product name: TGA851, manufactured by Mettler-Toledo). Specifically, 20 mg of sample is accurately weighed from each region A and region B using a razor or similar tool and placed in an alumina pan used in the thermogravimetric analyzer. The alumina pan containing the sample is set in the thermogravimetric analyzer and heated in a nitrogen atmosphere from room temperature to 800°C at a heating rate of 20°C per minute, and then kept at 800°C for 1 hour. In a nitrogen atmosphere, as the temperature rises, components other than filler particles are decomposed and removed by cracking, and the mass of the sample decreases. As a result, the mass of filler particles contained in the sample can be calculated. Then, the specific gravity of the binder in the elastic layer, the specific gravity of the filler, and the content (volume fraction) of thermally conductive filler particles in each region of the elastic layer are calculated. <Shape of filler particles>

[0033] Next, we will explain the effect of the shape of the filler particles on the delamination between the surface layer and the elastic layer, and on the effect on the thermal conductivity of the elastic layer. When filler particles with pointed ends are dispersed in an elastic layer, under high pressure within the elastic layer, stress concentrates at the pointed ends of the filler particles, making delamination more likely at the interface between the surface layer and the elastic layer. Furthermore, sometimes the stress at the tips of the fillers exceeds the strength of the elastic layer, causing cracks to form, which can then grow and lead to delamination.

[0034] On the other hand, when round filler particles without sharp edges are dispersed in the elastic layer, it is difficult for heat conduction paths to be formed by the filler particles, resulting in a lower thermal conductivity. In other words, from the viewpoint of preventing delamination at the interface between the surface layer and the elastic layer, the shape of the filler particles is preferably round, while from the viewpoint of providing high thermal conductivity to the elastic layer, the shape of the filler particles is preferably pointed. In this disclosure, in region A below, relatively round fillers with a practical sphericity SA of 0.80 or higher are used to suppress stress concentration near the interface between the surface layer and the elastic layer. On the other hand, in region B below, relatively pointed filler particles with a practical sphericity SB of less than 0.80 are used to support a high thermal conductivity in the thickness direction in the elastic layer of the fixing film used in the film heating method. Region A: The area from the interface between the elastic layer and the surface layer to 50 μm in the thickness direction of the elastic layer. Region B: From 50 μm in the thickness direction of the elastic layer, from the interface between the elastic layer and the surface layer, to the interface between the elastic layer and the base layer. Next, the practical sphericity values ​​SA and SB of the filler added to the elastic layer can be calculated as follows.

[0035] <Practical sphericity of region A> (1) First, take a sample from the above-mentioned region A of the elastic layer of the fixing film. (2) Next, the sample taken in (1) was immersed in a silicone solvent (product name: eSolve 21RS, manufactured by Kaneko Chemical Co., Ltd.) to dissolve the silicone resin components. The dissolved solution was dried at room temperature for 1 hour to extract the filler components from within the elastic layer. (3) The extracted filler components were measured using a Coulter particle counting analyzer (product name: CDA-1000, manufactured by Sysmex Corporation) to determine the particle size D50 value (D A ) is measured and the particle volume (V) is measured using the following formula (1). A The volume of the circumscribed sphere is calculated by obtaining the maximum length for each of several hundred to several thousand particles using a flow-type particle image analyzer (product name: FPIA-3000, manufactured by Sysmex Corporation) and taking the arithmetic mean (d A Calculate the max(max) volume of the circumscribing sphere of the filler. Also, calculate the volume VAe This is calculated using the following equation (2). Note that the method for measuring and calculating the volume of the particle and the volume of the circumscribing sphere is not limited; for example, they may be measured by observation using an electron microscope. V A =(4 / 3)πD A 3 ...Equation (1) V Ae =(4 / 3)πd A max 3 ...Equation (2) V A and V Ae Using this, the practical sphericity SA of the filler in region A is derived from equation (3) below. SA=(V A / V Ae ) (1 / 3) ...Equation (3)

[0036] <Practical sphericity SB of region B> A sample is taken from region B of the elastic layer of the fixing film. Next, using the same method as in <Measurement of Sphericity SA in Region A>, after extracting the filler, the particle size D50 value (D) was measured using a Coulter-type particle counting analyzer (product name: CDA-1000, manufactured by Sysmex Corporation). B ) is measured and the particle volume V is calculated using the following equation (4). B The volume of the circumscribed sphere is calculated using a flow-type particle image analyzer (product name: FPIA-3000, manufactured by Sysmex Corporation) by determining the maximum length (d) of each of several hundred to several thousand particles. B Measure the max) and the volume V of the circumscribing sphere of the filler. Be This is calculated using the following equation (5). Note that the method for measuring and calculating the volume of the particle and the volume of the circumscribed sphere is not limited; for example, they may be measured by observation using an electron microscope. V B =(4 / 3)πD B 3 ...Equation (4) V Be =(4 / 3)πd B max 3 ...Equation (5) V B and V BeUsing this, the practical sphericity SB of the filler in region B is derived from equation (6) below. SB=(V B / V Be ) (1 / 3) ...Equation (6)

[0037] The particle size D50 of the filler particles contained in region A and the particle size D50 of the filler particles contained in region B are preferably in the range of 3 μm to 32 μm, and particularly preferably in the range of 5 μm to 30 μm. By setting the particle size D50 within the above range, it is possible to achieve a higher degree of compatibility between imparting high thermal conductivity in the thickness direction of the elastic layer and preventing delamination at the interface between the elastic layer and the surface layer due to long-term use.

[0038] <Measurement of the hardness of the elastic layer> The hardness of the elastic layer was measured by cutting the elastic layer from the fixing film, stacking it to the required thickness for measurement, and measuring the surface layer of the elastic layer according to JIS K7312:1996. Next, we will explain the methods for measuring various physical properties of elastic layers. This section describes the method for measuring the thermal conductivity of an elastic layer in the thickness direction. The thermal conductivity λ of the elastic layer in the thickness direction is calculated using the following formula. λ = α × Cp × ρ In the formula, λ is the thermal conductivity in the thickness direction of the elastic layer (W / (m·K)), and α is the thermal diffusivity in the thickness direction (m 2 / s), Cp is constant-pressure specific heat (J / (kg·K)), ρ is density (kg / m³). 3 ) Here, the values ​​of the thermal diffusivity α in the thickness direction, the specific heat at constant pressure Cp, and the density ρ are determined by the following method.

[0039] ·Thermal diffusivity α The thermal diffusivity α in the thickness direction of the elastic layer is measured at room temperature (25°C) using a periodic heating method thermophysical property measuring device (product name: FTC-1, manufactured by Advance Riko Co., Ltd.). Five rectangular sample pieces measuring 8 mm × 12 mm are cut from the elastic layer using a cutter, and the thickness of each sample piece is measured using a digital length measuring device (product name: DIGIMICRO® MF-501 flat measuring probe φ4 mm; manufactured by Nikon Corporation). Next, the thermal diffusivity α is measured five times for each sample piece using the periodic heating method thermophysical property measuring device, and the average value (m 2 The time ( / s) is calculated. The measurement is performed while applying pressure to the sample piece using a 1 kg weight.

[0040] • Constant pressure specific heat Cp The constant-pressure specific heat of the elastic layer is measured using a differential scanning calorimetry system (product name: DSC823e, manufactured by Mettler-Toledo). Specifically, aluminum pans are used as the sample pan and the reference pan. First, as a blank measurement, both pans are kept at a constant temperature of 15°C for 10 minutes with empty pans, then the temperature is increased to 215°C at a rate of 10°C / min, and the pan is kept at a constant temperature of 215°C for another 10 minutes. Next, 10 mg of synthetic sapphire, whose low-pressure specific heat is known, is used as the reference material, and the measurement is performed using the same program. Then, 10 mg of the sample, the same amount as the reference synthetic sapphire, is cut from the elastic layer, placed in the sample pan, and the measurement is performed using the same program. These measurement results are analyzed using the specific heat analysis software attached to the differential scanning calorimetry device, and the constant-pressure specific heat Cp at a temperature of 25°C is calculated from the average value of the five measurement results.

[0041] ·Density ρ The density of the elastic layer is measured using a dry automatic densimeter (product name: Accupic 1330-01, manufactured by Shimadzu Corporation). Specifically, the volume is 10 cm³. 3Using a sample cell, a sample piece is cut from the elastic layer to fill approximately 80% of the cell volume. After measuring the mass of this sample piece, it is placed in the sample cell. This sample cell is then set in the measuring section of the apparatus, and helium is used as the measuring gas. After gas replacement, volume measurements are performed 10 times. For each measurement, the density of the elastic layer is calculated from the mass of the sample piece and the measured volume, and the average value is determined. Based on the above, the constant-pressure specific heat Cp (J / (kg·K)) and density ρ (kg / m³) of the elastic layer, converted to units, are obtained. 3 ), and the measured thermal diffusivity α(m 2 The thermal conductivity λ in the thickness direction of the elastic layer is calculated from ( / s).

[0042] <Measurement of the Voronoi region in an elastic layer> In a cross-section perpendicular to the circumferential direction of the elastic layer, a Voronoi tessellation is performed using the heat-conducting filler particles exposed in the cross-section as parent points to form a Voronoi region. At this time, it is preferable that the coefficient of variation Avave of the Voronoi region area is 1.0 or less in a 50 μm thickness region A extending from the surface facing the surface layer of the elastic layer to the opposite surface. The formation of a Voronoi region by Voronoi tessellation using the heat-conducting filler particles exposed in the cross-section perpendicular to the circumferential direction of the elastic layer will now be explained.

[0043] When multiple points (hereinafter also referred to as generator points) exist within an image region, all adjacent generator points are connected by straight lines, and perpendicular bisectors are created for each of the basic lines connecting two adjacent generator points. When the perpendicular bisectors extending from adjacent basic lines are connected, a region is created in which a single generator point is enclosed by multiple perpendicular bisectors. This region enclosed by perpendicular bisectors is called a Voronoi region. The points where the lines connecting two adjacent generator points intersect with their perpendicular bisectors indicate the shortest distance from each generator point, and the size (area) of the Voronoi region formed by these perpendicular bisectors represents the distance between adjacent generator points. In other words, if the distance between adjacent generator points is large, the area of ​​the Voronoi region will also be large.

[0044] In this embodiment, the generating point for the Voronoi partition described above is a heat-conducting filler particle. There are two partitioning methods: one based on the centroid of the heat-conducting filler particle and another based on the edges of the heat-conducting filler particle. In this disclosure, the partitioning based on the edges is used. In the partitioning based on the edges, the shortest distance between the edges of two adjacent heat-conducting filler particles is selected, and the region enclosed by the perpendicular bisector of this line becomes the Voronoi region. Specifically, this is done by the following method.

[0045] <Calculation of the coefficient of variation Avave of the area of ​​the Voronoi domain in region A> (1) First, prepare cross-sectional observation samples. For example, if the fixing member is a fixing belt 400 as shown in Figure 4A, take a total of 10 samples 401, each 5 mm long, 5 mm wide, and with a thickness equal to the total thickness of the fixing belt, from 10 arbitrary locations on the fixing belt, as shown in Figure 4B. Sample 401 consists of the surface layer 6, adhesive layer 5, elastic layer 4, and base layer 3 of the cut sample, with the elastic layer having a first cross-section 401-1 in the thickness-circumferential direction and a second cross-section 401-2 in the thickness-axial direction. Five of the 10 obtained samples are polished using an ion beam at the cross-section in the circumferential direction of the fixing belt, i.e., the cross-section including the first cross-section 401-1 of the elastic layer in the thickness-circumferential direction. The remaining five samples are polished using an ion beam at the cross-section perpendicular to the circumferential direction of the fixing belt, i.e., the cross-section including the second cross-section 401-2 of the elastic layer in the thickness-axial direction. For polishing the cross-section with an ion beam, for example, a cross-section polisher can be used. Ion beam polishing of cross-sections prevents the shedding of filler particles from the sample and the inclusion of abrasives, and also allows for the formation of cross-sections with fewer polishing marks.

[0046] (2) Next, the first and second cross-sections of the elastic layer are observed using a laser microscope or scanning electron microscope (SEM) for five samples in which the first cross-section 401-1 of the elastic layer has been polished, and for five samples in which the second cross-section 401-2 of the elastic layer has been polished. For example, when the cross-section is as shown in Figure 5, 402, a 50 μm × 50 μm square cross-sectional image is obtained at any location within a 50 μm thickness region A (Figure 5 403) from the surface facing the surface layer of the elastic layer toward the opposite surface.

[0047] (3) Next, the obtained image, as shown in Figure 6A, is subjected to black and white binarization using commercially available image processing software so that the filler particles 61 appear white and the elastic layer appears black (Figure 6B). For example, the Otsu method can be used as a binarization method. An example of image processing software that can perform such binarization is "Image J" (product name, manufactured by the National Institutes of Health (NIH) in the United States). (4) Next, the white areas of the created binarized image are segmented using the watershed algorithm. This process is necessary because if fillers are close together, multiple fillers may stick together and be recognized as a single filler.

[0048] (5) Finally, Voronoi partitioning is performed on the regions that have been partitioned using the watershed algorithm. Specifically, Voronoi partitioning is performed using the following procedure: Calculate the position of the centroid (point A in Figure 6C) of each white region. Connect all the centroids of adjacent white regions with straight lines to create a base line, and calculate the position of the intersection (point F in Figure 6C) of the base line with the outer perimeter of each partitioned white region. Usually, two of these intersection points F are created on a straight line connecting two centroids, and the perpendicular bisector between these two intersection points is created and used as the partition line. When adjacent regions are touching, sometimes only one intersection point F is created, in which case a line perpendicular to the base line and passing through intersection point F is created and used as the partition line. When the partition lines created from adjacent white regions are connected, a region enclosed by the partition lines is created so as to surround the white region (Figure 6D). In this embodiment, this is defined as the Voronoi region. This Voronoi region can be used as a region that represents the distribution of distances between fillers. The area of ​​each Voronoi region is calculated, and its arithmetic mean is Aave, and its standard deviation is Aσ. The coefficient of variation Av (= Aσ / Aave) is defined as the value obtained by dividing Aσ by Aave. (6) The coefficient of variation Av was calculated for each of the 10 images obtained in (2), and the average value of these was taken as Avave to derive the coefficient of variation of the Voronoi region of the filler in region A of this embodiment. [Examples]

[0049] The fixing member relating to this disclosure will be described in more detail below using examples and comparative examples. Note that the fixing member relating to this disclosure is not limited to the configurations embodied in the examples. Unless otherwise specified, commercially available Grade 1 or Special Grade reagents were used.

[0050] <Preparation of Fillers 1-12> The following three types were prepared as filler materials. • Spherical alumina (Product name: Alnabeads CB-A30S; manufactured by Showa Denko Corporation; practical sphericity = 0.81) • Titanium dioxide (product name: JR-1000; manufactured by Teika Co., Ltd.; practical spheroidal index = 0.70) • Boron nitride (Showbin UHP-2; manufactured by Showa Denko Corporation, practical spheroidal index = 0.29) Then, each of the three filler raw materials described above was subjected to a classification process so that the particle size D50 was 4 μm, 5 μm, 30 μm, and 32 μm. Filler 3 was prepared by subjecting the above-mentioned spherical alumina to a spheroidizing treatment, resulting in a practical spheroidity of 0.93. Filler 11 is obtained by classifying the spherical alumina described above, and then further removing particles with a particle size of 2 μm or less to reduce the dispersion of the particle size distribution. Filler 12 is obtained by classifying the boron nitride described above and then removing particles with a particle size of 2 μm or less to reduce the dispersion of the particle size distribution. Table 1 shows the type of filler, whether or not spheroidization treatment was performed, whether or not particles with a particle size of 2 μm or less were removed, the practical spheroidity, and the particle size D50 for each of fillers 1 to 12.

[0051] [Table 1]

[0052] (Example 1) In Example 1, a fixing film (fixing belt) as shown in Figure 3 was created by a manufacturing method consisting of the following steps 1 to 4. (Process 1) As the base layer, a substrate made of stainless steel (SUS) with an endless belt shape, having an inner diameter of 25 mm, a width of 400 mm, and a thickness of 40 μm was prepared. The outer surface of this substrate was treated with a primer.

[0053] (Process 2) As raw materials for forming the elastic layer, two components, A and B, of an addition-curing liquid silicone rubber (product name: SE1886, manufactured by Toray Dow Corning Co., Ltd.) that does not contain fillers, were prepared and mixed. The mixing ratio was 50 parts by volume of component A and 50 parts by volume of component B, when the total volume was 100 parts by volume. Component B contains a hardening agent for the elastic layer, and the elastic layer can be hardened by increasing the proportion of component B. To 100 parts by volume of the above mixture, 104 parts by volume of filler 2 was added as thermal conductive filler particles. These were applied to the outer surface of the uncured elastic layer 1 using the ring coating method to form an uncured elastic layer B with a thickness of 300 μm.

[0054] Next, 80 volumes of filler 1 were added as thermal conductive filler particles to 100 volumes of liquid silicone rubber mixed with agent A and agent B. In this way, an addition-curing type silicone rubber composition for forming an elastic layer was prepared. These were applied to the outer surface of the above base layer using the ring coating method to form an uncured elastic layer A with a thickness of 50 μm. The two layers, uncured elastic layer A and uncured elastic layer B, were crosslinked by heating at 200°C for 4 hours to form an elastic layer with a total thickness of 350 μm. This resulted in the formation of an elastic layer with a two-layer structure: region A, in which 50% by weight of spherical alumina was added in a range of 50 μm from the interface between the surface layer and the elastic layer; and region B, in which 50% by weight of boron nitride was added in a range of 50 μm to 350 μm from the interface between the surface layer and the elastic layer.

[0055] (Step 3) The base layer on which the elastic layer was formed was rotated circumferentially at a speed of 20 mm / second, and ultraviolet light was irradiated onto the surface of the elastic layer in an atmospheric environment using an ultraviolet lamp positioned 10 mm away 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 the integrated light amount at a wavelength of 185 nm on the irradiated surface was 800 mJ / cm². 2 The irradiation was applied in such a manner that it resulted in the following: Next, an addition-curing silicone rubber adhesive (product name: SE1819CV, a mixture of equal parts of "liquid A" and "liquid B" manufactured by Toray Dow Corning) was applied to the surface of the elastic layer in a nearly uniform manner to a thickness of approximately 20 μm.

[0056] (Step 4) The following fluororesin tube, whose inner surface has been 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. Fluoropolymer tubing: Product name: 959HP-Plus, manufactured by Mitsui Chemours Fluoroproducts, 20 μm thickness, melting point 306°C

[0057] Then, the base layer, which was covered with an elastic layer and a surface layer, was placed in an electric furnace set to a temperature of 200°C, heated for 1 hour to cure the adhesive and bond the fluororesin tube onto the elastic layer, and both ends were cut to obtain a fixing film with a width of 350 mm. In the evaluation of this embodiment, the fixing device shown in Figure 2 and the fixing member shown in Figure 3 were used.

[0058] (Evaluation of fixing characteristics of a fixing device using the fixing member of this embodiment) Next, we evaluated the fixing characteristics when using the fixing device for the fixing member used in this embodiment. In this example, the fixing device shown in Figure 2 and the fixing member shown in Figure 3 were used.

[0059] (Peel resistance evaluation) Using the fixing device shown in Figure 2, the total pressure was set to 300 N, the rotation speed of the pressure roller to 200 mm / s, and the temperature of the outer periphery of the fixing film in contact with the recording material was controlled to 130°C. GF-C081 (manufactured by Nippon Paper Industries Ltd.) was used as the recording material. If the evaluation score was S to C according to the evaluation criteria below, it was determined that the effects of this disclosure were obtained.

[0060] (Evaluation Criteria) Rank S: No delamination between the surface layer and the elastic layer is observed even after continuous use up to 1,000 sheets. Rank A: If the number of sheets exceeds 900,000 but is less than 1,000,000, delamination will occur between the surface layer and the elastic layer. Rank B: If the number of sheets exceeds 800,000 but is less than 900,000, delamination will occur between the surface layer and the elastic layer. Rank C: If the number of sheets exceeds 700,000 but falls below 800,000, delamination will occur between the surface layer and the elastic layer. Rank D: If the number of sheets used continues to less than 700,000, delamination will occur between the surface layer and the elastic layer.

[0061] (Evaluation of retention) A modified Canon digital commercial printer (product name: imageRUNNER ADVANCE C5560, manufactured by Canon) was used as the unfixed image forming apparatus. Specifically, the electrophotographic image forming apparatus was modified to allow arbitrary setting of the fixing temperature, process speed, DC voltage VDC of the developer carrier, charging voltage VD of the electrostatic latent image carrier, and laser power. For image output evaluation, an FFh image (solid image) with the desired image ratio was output, and the VDC, VD, and laser power were adjusted so that the amount of toner on the FFh image on the paper was as desired, and an unfixed image was output under the following conditions.

[0062] FFh is a hexadecimal value representing 256 gradations, where 00h is the first gradation (white area) of the 256 gradations, and FFh is the 256th gradation (solid area). Paper: GF-C081 (81.0g / m 2 (Sold by Canon Marketing Japan Inc.) Toner coverage on paper: 0.70 mg / cm² 2 (Adjusted by the DC voltage VDC of the developer carrier, the charging voltage VD of the electrostatic latent image carrier, and the laser power) Evaluation image: A 2cm x 5cm rectangular solid blue image is placed in the center of the A4 paper shown above.

[0063] Next, using the fixing device shown in Figure 2, the pressure was set to a total pressure of 300 N, the rotation speed of the pressure roller to 200 mm / s, and the temperature of the outer edge of the fixing film in contact with the recording material was controlled to 130°C. "GF-C081" (product name, manufactured by Nippon Paper Industries Ltd.) was used as the recording material. The above unfixed images were passed through five consecutive sheets of paper, and the fixation of the fifth image was evaluated. The percentage decrease in image density was used as the evaluation index for fixation.

[0064] The image density reduction rate is determined using an X-Rite color reflectance densitometer (500 series: manufactured by X-Rite). First, the image density of the central area is measured. Next, 4.9 kPa (50 g / cm³) is applied to the area where the image density was measured. 2 The image was fixed using Silbon paper with a load of ) applied and rubbed (5 times back and forth), and the image density was measured again. Then, the percentage decrease in image density before and after friction was calculated using the following formula. The obtained percentage decrease in image density was evaluated according to the following evaluation criteria. Image density reduction rate = (Image density before friction - Image density after friction) / Image density before friction × 100 If the evaluation criteria below result in an A to C rating, it is judged that the effects of this disclosure have been achieved.

[0065] (Evaluation Criteria) Rank A: Image density reduction rate is less than 3% Rank B: Image density reduction rate is 3% or more, but less than 5%. Rank C: Image density reduction rate is 5% or more, but less than 8%. Rank D: Image density reduction rate is 8% or more.

[0066] <Examples 2-21, Comparative Examples 1-6> When the total volume of liquid silicone rubber (product name: SE1886, manufactured by Toray Dow Corning) components A and B was set to 100, a mixture was prepared using the mixing ratios shown in Table 2 to create uncured elastic layers B and A. Fillers were prepared by mixing the volume and type of filler shown in Table 2 with 100 volume parts of the mixture. Furthermore, in Examples 2 and 3 and Comparative Example 1, the thickness of the uncured elastic layer B was changed to 150 μm, 2950 μm, and 40 μm, respectively, so that the total thickness of the elastic layer would be as shown in Table 2.

[0067] [Table 2]

[0068] The volume density of the entire elastic layer of the fabricated fixing film, the volume densities of the fillers in regions A and B, the volume density of the fillers in the entire elastic layer, the average particle size of the fillers in the entire elastic layer, the thermal conductivity in the thickness direction of the elastic layer, the hardness of the elastic layer, and the coefficient of variation of the Voronoi region were determined. In addition, peel durability and fixing performance were evaluated based on the same evaluation method as in Example 1. These results are shown in Table 3.

[0069] [Table 3]

[0070] As shown in Table 3, the fixing films according to Examples 1 to 11 were able to maintain high thermal conductivity in the thickness direction of the elastic layer while preventing delamination at the interface between the surface layer and the elastic layer even after long-term use. In particular, the fixing films according to Examples 12 to 14 used a thermally conductive filler with a particle size D50 of 5 μm or more and 32 μm or less. As a result, the fixing films according to Examples 12 to 14 were able to increase the thermal conductivity in the thickness direction of the elastic layer compared to the fixing film according to Example 1, while also preventing delamination at the interface between the surface layer and the elastic layer even after long-term use.

[0071] Furthermore, in Examples 15-17, by increasing the proportion of component B in the liquid silicone rubber (product name: SE1886, manufactured by Toray Dow Corning Co., Ltd.) component A, the proportion of the hardener in the elastic layer was increased, thereby increasing the hardness of the elastic layer and improving peel resistance. A JIS-A hardness of 9° to 25° is preferable because it allows for both improved peel resistance and improved adhesion. Finally, in Example 18, by cutting out fillers with a particle size of 2 μm or less, the dispersion of the filler particle size distribution was reduced, and the non-uniformity of the distance between fillers in the elastic layer was eliminated, thereby achieving a further extension of the peel durability life. In this way, by controlling the shape and amount of filler in the elastic layer near the surface layer, it is possible to reduce the shear force generated at the interface between the surface layer and the elastic layer, thereby preventing surface layer delamination and providing a fixing member that is flexible, has high thermal conductivity, and has a long lifespan. This disclosure includes the following components.

[0072] [Configuration 1] A fixing member comprising at least a base layer, an elastic layer, and a surface layer, The total thickness of the elastic layer is 200 μm or more. The thermal conductivity in the thickness direction of the entire elastic layer is 0.4 W / m·K or higher. The elastic layer contains filler particles, The content of filler particles in the entire elastic layer is 40% to 60% by volume. When the region A is defined as the area from the interface between the elastic layer and the surface layer to a position 50 μm in the thickness direction of the elastic layer, the practical sphericity SA of the filler particles contained in region A is 0.80 or higher, and the content of filler particles contained in region A is 60 volume% or less. When region B is defined as the range from a point 50 μm in the thickness direction of the elastic layer from the interface between the elastic layer and the surface layer to the surface of the elastic layer facing the base layer, the practical sphericity SB of the filler particles contained in region B is less than 0.80, and the content of filler particles contained in region B is 40 volume% or more. The practical sphericity SA is calculated by the following formula (3), and the practical sphericity SB is calculated by the following formula (6) for the fixing member: SA=(V A / V Ae ) (1 / 3) ...Equation (3) V A V is the volume of filler particles in region A. Ae The volume of the circumscribing sphere of the filler particles in region A is SB=(VB / V Be ) (1 / 3) ...Equation (6) V B V is the volume of filler particles in region B. Be is the volume of the circumscribing sphere of the filler particles in region B.

[0073] [Configuration 2] The fixing member according to configuration 1, wherein the particle size D50 of the filler particles contained in region A and the particle size D50 of the filler particles contained in region B are both 5 μm to 32 μm. [Configuration 3] The fixing member according to configuration 1 or 2, wherein the hardness of the elastic layer, as measured according to JIS K7312, is 9° to 25°. [Structure 4] The fixing member according to any one of configurations 1 to 3, wherein the fixing member is a fixing film having an endless shape.

[0074] [Composition 5] In a cross-section of the elastic layer in a direction perpendicular to the circumferential direction, The fixing member according to configuration 4, wherein when a Voronoi tessellation is performed with the filler particles exposed in the cross-section as the parent points, the arithmetic mean of the areas of each Voronoi region formed is Aave, and the standard deviation is Aσ, and the coefficient of variation calculated by the following formula in region A is 1.0 or less. Coefficient of variation = (Aσ / Aave) [Composition 6] A thermal fixing apparatus comprising a fixing member described in any of configurations 1 to 5, and a pressurizing member disposed opposite to the fixing member. [Explanation of symbols]

[0075] 10: Image forming unit 11: Photosensitive drum 12: Charger 13: Laser Scanner 14: Developer 15: Cleaner 17: Primary transfer blade 20: Paper feed cassette 25: Multi-purpose paper tray 23: Resistola vs. 31: Intermediate transfer belt 35: Secondary transfer roller 40: Fuser 41: Fixing film 41a: Surface layer 41b: Base layer 41c: Elastic layer 43: Heating element (heater) 44: Pressure roller 45: Contact type thermistor 46: Heater holder 403: Area A 404: Area B P: Recording material T: Toner

Claims

1. A fixing member comprising at least a base layer, an elastic layer, and a surface layer, The total thickness of the elastic layer is 200 μm or more. The thermal conductivity in the thickness direction of the entire elastic layer is 0.4 W / m·K or higher. The elastic layer contains filler particles, The content of filler particles in the entire elastic layer is 40% to 60% by volume. When the region A of the elastic layer is defined as the area from the interface between the elastic layer and the surface layer to a position 50 μm in the thickness direction of the elastic layer, the practical sphericity SA of the filler particles contained in region A is 0.80 or more, and the content of filler particles contained in region A is 60 volume% or less. When the region B of the elastic layer is defined as the area from a point 50 μm in the thickness direction of the elastic layer from the interface between the elastic layer and the surface layer to the surface of the elastic layer facing the base layer, the practical sphericity SB of the filler particles contained in region B is less than 0.80, and the content of filler particles contained in region B is 40 volume% or more. The fixing member is characterized in that the practical sphericity SA is calculated by the following formula (3), and the practical sphericity SB is calculated by the following formula (6): SA = (V Ａ / V Ａｅ ) （１／３） ... Equation (3) V Ａ V is the volume of filler particles in region A. Ａｅ The volume of the circumscribing sphere of the filler particles in region A is SB = (V Ｂ / V Ｂｅ ) （１／３） ・・・ Equation (6) V Ｂ is the volume of the filler particles in region B, V Ｂｅ is the volume of the circumscribed sphere of the filler particles in region B.

2. The fixing member according to claim 1, wherein the particle size D50 of the filler particles contained in region A and the particle size D50 of the filler particles contained in region B are both 5 μm or more and 32 μm or less.

3. The fixing member according to claim 1, wherein the hardness of the elastic layer, as measured according to JIS K7312, is 9° to 25°.

4. The fixing member according to claim 1, wherein the fixing member is a fixing film having an endless shape.

5. In a cross-section of the elastic layer in a direction perpendicular to the circumferential direction, The fixing member according to claim 4, wherein when a Voronoi tessellation is performed with the filler particles exposed in the cross-section as the parent points, the arithmetic mean of the areas of each Voronoi region formed is Aave, and the standard deviation is Aσ, and the coefficient of variation calculated by the following formula in region A is 1.0 or less. Coefficient of variation = (Aσ / Aave)

6. A thermal fixing apparatus comprising a fixing member according to any one of claims 1 to 5, and a pressurizing member disposed opposite to the fixing member.

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