Fixing member and heat fixing device

Abstract

To provide a long-life fixing member which has high thermal conductivity and is free from peeling between a surface layer and an elastic layer even in long-term use.SOLUTION: The fixing member includes at least a base layer having an endless shape, an elastic layer provided on an outer peripheral surface of the base layer, and a surface layer provided on the outer peripheral surface of the elastic layer, wherein the base layer contains at least one selected from the group consisting of aluminum, iron, copper, nickel, stainless steel, brass, polyimide, polyamide-imide, and polyetheretherketone, the elastic layer has a thickness of 200 μm or more and a thermal conductivity of 0.40 W / mK or more in a layer thickness direction, the content of the thermally conductive filler particles in the elastic layer is 40 volume% or more and 60 volume% or less, and the coefficient of variation of an area of a Voronoi region, Avave, is less than 1.0, in which the area of the Voronoi region is formed by Voronoi splitting with the area from the interface between the elastic layer and the surface layer to a thickness of 50 μm in the direction of the thickness of the elastic layer as region A, and with the heat-conductive filler particles exposed in region A of the cross-section as the base point, in a cross-section in a direction perpendicular to a circumferential direction of the elastic layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a fixing member and a heating fixing apparatus used in a heating fixing apparatus of an electrophotographic image forming apparatus. [Background technology]

[0002] Fixing components used in the heating and fixing devices of electrophotographic image forming machines such as printers, copiers, and facsimile machines come in film or roller forms. These fixing components are known to have an elastic layer formed on a heat-resistant resin or metal film or roller-shaped substrate, with the elastic layer being made of heat-resistant rubber or the like as needed, and the surface layer containing a fluororesin that has excellent release properties for toner. The elastic layer of the fixing component is required to have high elasticity and high thermal conductivity. Therefore, the elastic layer is blended with an inorganic filler with high thermal conductivity as a thermal conductive filler in rubber such as silicone rubber. In recent years, there has been a growing demand to further improve the thermal conductivity of fixing materials in order to increase print speed and improve image quality. Patent Document 1 discloses a fixing material in which a heat channel is formed within an elastic layer using a thermal conductive filler to improve thermal conductivity. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 5054924 [Overview of the project] [Problems that the invention aims to solve]

[0004] As described in Patent Document 1, it was possible to improve the thermal conductivity of the elastic layer by forming a heat channel in the elastic layer with a heat conductive filler. However, when using a fixing member in which a heat channel is formed in the elastic layer with a heat conductive filler, a large localized shear force may be applied near the interface between the elastic layer and the surface layer, and with long-term use, the elastic layer may delaminate at the interface between the elastic layer and the surface layer. One aspect of this disclosure aims to provide a fixing member that has high thermal conductivity in the thickness direction and does not delaminate between the surface layer and the elastic layer even after long-term use. Another aspect of this disclosure aims to provide a thermal fixing apparatus that can stably form high-quality electrophotographic images. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, a fixing member comprising at least a base layer having an endless shape, an elastic layer provided on the outer peripheral surface of the base layer, and a surface layer on the outer peripheral surface of the elastic layer, The base layer comprises at least one selected from the group consisting of aluminum, iron, copper, nickel, stainless steel, brass, polyimide, polyamide-imide, and polyetheretherketone. The elastic layer comprises rubber and heat-conducting filler particles dispersed in the rubber. The thickness of the elastic layer is 200 μm or more. The thermal conductivity of the elastic layer in the thickness direction is 0.40 W / mK or higher. The content of the thermal conductive filler particles in the elastic layer is 40% by volume or more and 60% by volume or less. In a cross-section perpendicular to the circumferential direction of the elastic layer, the region from the interface between the elastic layer and the surface layer to a thickness of 50 μm in the thickness direction of the elastic layer is defined as region A, and the coefficient of variation Av of the Voronoi region formed by Voronoi tessellation using the heat-conducting filler particles exposed in region A of the cross-section as the parent points is calculated as follows: ave A fixing member is provided, characterized in that the value is 1.0 or less. Furthermore, according to another aspect of the present disclosure, a thermal fixing apparatus is provided that comprises the fixing member described above and a pressing member disposed opposite to the fixing member. [Effects of the Invention]

[0006] According to one aspect of the present disclosure, it is possible to obtain a long-life fixing member that has high heat conductivity in the thickness direction and in which the surface layer and the elastic layer are less likely to peel even after long-term use. Further, according to another aspect of the present disclosure, it is possible to obtain a heat fixing device that contributes to the stable formation of high-quality electrophotographic images.

Brief Description of the Drawings

[0007] [Figure 1] It is a schematic diagram of an image forming apparatus in a first embodiment. [Figure 2] It is a schematic diagram of a fixing device in a first embodiment. [Figure 3] It is a schematic diagram of a fixing film in a first embodiment. [Figure 4] It is a diagram showing a first cross section and a second cross section of an elastic layer of a fixing member in a belt form. [Figure 5] It is a schematic diagram of a cross section of a fixing member. [Figure 6] It is a schematic diagram of binarization and Voronoi division of a cross-sectional image of an elastic layer.

Mode for Carrying Out the Invention

[0008] In this specification, descriptions such as "○○ or more and ×× or less" and "○○ to ××" representing a numerical range mean a numerical range including the lower limit and the upper limit which are endpoints, unless otherwise specified. Further, when the numerical ranges are described stepwise, any combination of the upper limit and the lower limit of each numerical range is disclosed. Hereinafter, a fixing belt having an endless belt shape according to at least one embodiment of the present disclosure will be described in detail. Note that the technical scope of the present disclosure is not limited to the following description.

[0009] The inventors speculate the following as to why delamination occurs at the interface between the surface layer and the elastic layer when the fixing member described in Patent Document 1 is used over a long period of time. 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. Our investigations have shown that when the microscopic strain generated between the heat-conducting filler particles in the elastic layer due to shear is large, the peeling force increases. This microscopic strain depends on the distance between the heat-conducting filler particles, and if the distance between the heat-conducting filler particles is non-uniform, the magnitude of the microscopic strain becomes uneven. As a result, the peeling force increases locally, making it easier for delamination to occur between the surface layer and the elastic layer.

[0010] Therefore, it is thought that by making the distance between heat-conducting filler particles uniform, the unevenness of microscopic strain can be reduced, thereby suppressing delamination between the surface layer and the elastic layer. However, if the distance between heat-conducting filler particles is made uniform, it becomes difficult to form heat channels in the thickness direction of the elastic layer, and the thermal conductivity in the thickness direction of the elastic layer decreases. Here, the inventors found that shear stress tends to concentrate particularly in a 50 μm thickness region (hereinafter also referred to as "region A") from the surface facing the surface layer of the elastic layer (interface between the elastic layer and the surface layer) to the opposite surface (interface between the elastic layer and the base layer). Therefore, the inventors improved the dispersibility of the thermally conductive filler in region A to make the distance between thermally conductive filler particles uniform, while agglomerating the thermally conductive filler in regions other than region A. By doing so, they found that delamination between the surface layer and the elastic layer could be suppressed while maintaining a thermal conductivity of 0.40 W / mK or higher in the thickness direction of the elastic layer.

[0011] In other words, a fixing member according to one aspect of the present disclosure comprises at least a base layer having an endless shape, an elastic layer provided on the outer circumferential surface of the base layer, and a surface layer on the outer circumferential surface of the elastic layer. The base layer contains at least one selected from the group consisting of aluminum, iron, copper, nickel, stainless steel, brass, polyimide, polyamide-imide, and polyetheretherketone. Furthermore, the elastic layer comprises rubber and heat-conducting filler particles dispersed in the rubber, the thickness of the elastic layer is 200 μm or more, and the content of the heat-conducting filler particles in the elastic layer is 40% by volume or more and 60% by volume or less. Furthermore, when a Voronoi partition is performed in a cross-section perpendicular to the circumferential direction of the elastic layer, using the heat-conducting filler particles exposed in the cross-section as parent points to form a Voronoi region, the coefficient of variation Av of the area of ​​the Voronoi region in region A below is ave It is 1.0 or less. • Region A: A region with a thickness of 50 μm extending from the surface facing the surface layer of the elastic layer toward the opposite surface. Furthermore, the thermal conductivity of the elastic layer in the thickness direction is 0.40 W / mK or higher.

[0012] Figure 1 is a cross-sectional view of a color electrophotographic printer, which is an image forming apparatus according to one embodiment of the present disclosure, and is a cross-sectional view along the direction of transport of the recording material. In this embodiment, the color electrophotographic printer is simply referred to as "printer". 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 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.

[0013] 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 fuser 40.

[0014] Next, a fixing device according to one aspect of the present disclosure will be described. Figure 2 shows a schematic configuration diagram of the fixing device 40, which uses a film heating type heating device (tensionless type). In this embodiment, such a heating device was used, but it can also be implemented with a roller pair type or a film type heating device.

[0015] 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.

[0016] 41 is a cylindrical (endless) heat-resistant fixing film that serves as a heating element for transferring heat, and is loosely fitted onto the support member (heater holder) including the heater 43. The structure of the fixing film 41 in this embodiment is as shown in Figure 3, and is a fixing film having a three-layer composite structure including at least a surface layer 41a, an elastic layer 41c, and a base layer 41b.

[0017] Reference numeral 44 denotes a heat-resistant elastic pressure roller as a pressurizing member, consisting of a core metal and an elastic layer made of heat-resistant rubber such as silicone rubber or fluororubber, or silicone rubber foam, with both ends of the core metal supported by bearings so as to be freely rotatable. 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's elastic layer via the fixing film 41, forming a fixing nip portion N of a predetermined width which serves as a heating portion.

[0018] 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 N 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.

[0019] The pressure roller 44 is driven to rotate, causing the cylindrical fixing film 41 to rotate along with it. Power is also supplied to the heater 43, 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 N. The toner image-carrying side of the recording material P then adheres closely to the outer surface of the fixing film 41 in the fixing nip section N, and the fixing nip section N 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, melting and fixing it onto the recording material P. The recording material P that has passed through the fixing nip section N 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.

[0020] The fixing member of this disclosure comprises a base layer having an endless shape, an elastic layer provided on the outer circumferential surface of the base layer, and a surface layer on the outer circumferential surface of the elastic layer. The fixing film 41 in this disclosure is as shown in Figure 3. The fixing film has a base layer 41b, an elastic layer 41c covering its outer surface, and a surface layer 41a covering the surface of the elastic layer 41c opposite to the side facing the base layer. The surface layer 41a may be bonded to the surface of the elastic layer 41c opposite to the side facing the base layer 41b with an adhesive layer (not shown).

[0021] (1) Surface layer The thickness of the surface layer 41a is not particularly limited, but for example, it is 10 μm or more, 100 μm or less, and particularly 10 to 70 μm. Furthermore, the surface layer preferably contains a fluororesin because it has excellent toner release properties. Examples of fluororesins include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA).

[0022] (2) Base layer The material of the base layer 41b includes at least one selected from the group consisting of aluminum, iron, copper, nickel, stainless steel, brass, polyimide, polyamide-imide, and polyetheretherketone. The thickness is not particularly limited, but for example, from the viewpoint of strength, flexibility, and heat capacity, it is preferably 20 μm to 100 μm. The outer surface of the base layer 41b may be subjected to a surface treatment to provide adhesion to the elastic layer 41b. 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.

[0023] 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.

[0024] (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. A thickness of 200 μm or more in the elastic layer ensures a sufficient nip width when the fixing belt is incorporated into the fixing device. While there is no particular upper limit to the thickness of the elastic layer, it is preferably, for example, 5 mm or less. That is, a preferred thickness range for the elastic layer is 200 μm or more and 5 mm or less, and a particularly preferred thickness range is 200 μm or more and 500 μm or less. The elastic layer may have a multilayer structure and may include rubber and heat-conducting filler particles dispersed in the rubber. The elastic layer 41c preferably contains silicone rubber with excellent heat resistance. Furthermore, addition-curing liquid silicone rubber is preferably used as the raw material for the silicone rubber.

[0025] High thermal conductivity is required for the thermal conductive filler particles, and inorganic materials, especially metals and metal compounds, are preferred. Specifically, the following can be listed, and these can be used individually or in mixtures of two or more: High thermal conductivity fine powders such as 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), and carbon nanotubes (C).

[0026] The content of thermally conductive filler particles in the elastic layer is between 40% by volume and 60% by volume. A content of 40% by volume or more ensures sufficient thermal conductivity of the elastic layer. A content of 60% by volume or less prevents the elastic layer from becoming excessively hard. The method for measuring the content of thermally conductive filler particles in the elastic layer is shown below.

[0027] <Method for measuring the content of thermally conductive filler particles in an elastic layer> The content of thermally conductive filler particles in the elastic layer can be confirmed using a thermogravimetric analyzer (TGA) (e.g., product name: TGA851, manufactured by Mettler-Toledo). Cut out a portion of the elastic layer with a razor or similar tool, accurately weigh approximately 20 mg, and place it in an alumina sample pan used with the apparatus. Set the sample pan containing the sample in the apparatus and heat it in a nitrogen atmosphere from room temperature to 800°C at a heating rate of 20°C per minute, and then maintain a constant temperature of 800°C for 1 hour. In a nitrogen atmosphere, as the temperature rises, components other than thermally conductive filler particles are decomposed and removed by cracking without oxidation, thus reducing the mass of the sample. By comparing the mass before and after measurement, the weight of thermally conductive filler particles contained in the elastic layer can be calculated. The content of thermally conductive filler particles in the elastic layer can be calculated from the specific gravity of the thermally conductive filler particles used.

[0028] In this disclosure, when a Voronoi partition is performed on a cross-section of an elastic layer in a direction perpendicular to the circumferential direction, with heat-conducting filler particles exposed on the cross-section as parent points, and a Voronoi region is formed, the coefficient of variation Av of the area of ​​the Voronoi region in the following region A is ave The coefficient of variation Av is less than or equal to 1.0. ave By keeping the value below 1.0, the uneven distribution of heat-conducting fillers in region A is suppressed, preventing shear stress from concentrating in specific areas. As a result, delamination at the interface between the surface layer and the elastic layer can be prevented. • Region A: A region with a thickness of 50 μm extending from the surface facing the surface layer of the elastic layer toward the opposite surface.

[0029] Furthermore, in regions other than region A of the elastic layer, that is, regions adjacent to region A and located closer to the base layer than region A (hereinafter also referred to as "region B"), the coefficient of variation of the area of ​​the Voronoi region Bv ave It is preferable that the coefficient of variation Bv is between 1.5 and 4.0. ave By having a value of 1.5 or higher, the thermal conductivity in the thickness direction of the elastic layer can be set to 0.40 W / mK or higher. Also, the coefficient of variation Bv ave By keeping the value below 4.0, variations in the hardness of the elastic layer can be suppressed.

[0030] <Formation of Voronoi domains> This section describes the formation of a Voronoi region by Voronoi tessellation using heat-conducting filler particles exposed in a cross-section perpendicular to the circumferential direction of an elastic layer, with the heat-conducting filler particles exposed in the cross-section as parent points. 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 these 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 represent 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.

[0031] In this disclosure, the generating point for the above Voronoi partition 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 method based on the edges is used. In the partitioning method 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 in the following way.

[0032] <Coefficient of variation of the area of ​​the Voronoi domain in region A (Av) ave Calculation > (1) First, prepare cross-sectional observation samples. For example, if the fixing member is a fixing belt 400 as shown in Figure 4A, then, as shown in Figure 4B, 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. 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.

[0033] (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 5A, a 50 μm × 50 μm square cross-sectional image is obtained at any location within a 50 μm thickness region A (Figure 5A 403) from the surface facing the surface layer of the elastic layer toward the opposite surface.

[0034] (3) Next, as shown in Figure 6A, the obtained image is subjected to black and white binarization using commercially available image 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. (4) Further, perform region division on the white part of the created binary image using the watershed algorithm. Since when the fillers are close to each other, multiple fillers may stick together and be recognized as one filler, this process needs to be performed.

[0035] (5) Finally, perform Voronoi division on the regions divided by the watershed algorithm. Specifically, the Voronoi division is performed according to the following procedure. Calculate the positions of the centroids (point A in FIG. 6C) of each region of the white part. Connect all the centroids of adjacent regions of the white part with straight lines, and use this as the basic straight line. Calculate the positions of the intersections (point F in FIG. 6C) between the outer periphery of the divided region of each white part and the basic straight line. Usually, two intersections are created on one straight line connecting the centroids. Create the perpendicular bisector between these two intersections and use this as the dividing line. When there is only one intersection F created when the adjacent parts are in contact, create a line perpendicular to the basic straight line and passing through the intersection F and use this as the dividing line. When the dividing lines created from adjacent regions of the white part are connected, regions surrounded by the dividing lines are generated so as to surround the white region (FIG. 6D). In this embodiment, this is defined as the Voronoi region. This Voronoi region can be used as a region representing the distribution of the distances between the fillers. Calculate the area of each Voronoi region, and when the arithmetic mean value is A ave , the standard deviation is Aσ, the value obtained by dividing Aσ by A ave is defined as the coefficient of variation Av (= Aσ / A ave ).

[0036] (6) Calculate the coefficient of variation Av for each of the 10 images obtained in (2), and the average value of them is Av ave is used to derive the coefficient of variation of the Voronoi region of the fillers in region A of this embodiment. As a method for controlling the coefficient of variation of the area of the Voronoi region of the thermally conductive fillers in region A, a method of adjusting the particle size distribution of the filler particles can be mentioned.

[0037] <Calculation of the coefficient of variation Bv of the area of the Voronoi region in region B ave (1) Following the same procedure as in region A, for example, if the fixing member is a fixing belt 400 as shown in Figure 4A, then, as shown in Figure 4B, a total of 10 samples 401, each measuring 5 mm in length, 5 mm in width, and having a thickness equal to the total thickness of the fixing belt, were taken from 10 arbitrary locations on the fixing belt. Five of the obtained samples were polished using an ion beam to form a cross-section in the circumferential direction of the fixing belt, i.e., a cross-section including the thickness of the elastic layer minus the first cross-section 401-1 in the circumferential direction. The remaining five samples were polished using an ion beam to form a cross-section perpendicular to the circumferential direction of the fixing belt, i.e., a cross-section including the thickness of the elastic layer minus the second cross-section 401-2 in the axial direction.

[0038] (2) Next, for five samples in which the first cross-section 401-1 of the elastic layer has been polished, the first cross-section 401-1 is observed using a laser microscope or scanning electron microscope (SEM), and cross-sectional images are obtained for region B other than region A (Figure 5B 404). Next, for five samples in which the second cross-section 401-2 of the elastic layer has been polished, the second cross-section 401-2 is observed using a laser microscope or scanning electron microscope (SEM), and cross-sectional images are obtained for region B other than region A (Figure 5B 404). For the cross-sectional images, a total of three 50 μm × 50 μm square images are obtained at arbitrary locations in each of the three regions B1, B2, and B3 (Figure 5 404-1, 404-2, 404-3), which are obtained by dividing region B into three equal parts in the thickness direction.

[0039] (3) The acquired image is subjected to the same procedure as in region A: grayscale binarization, region segmentation using the watershed algorithm, and Voronoi segmentation. For the images acquired in regions B1, B2, and B3, the area of ​​each Voronoi region is calculated, and the arithmetic mean of these areas is taken as B1. ave B2 ave B3 ave And the standard deviations of each were set to B1σ, B2σ, and B3σ. Then, B1σ was set to B1 ave The value obtained by dividing by is the coefficient of variation B1v, and B2σ is B2 ave The value obtained by dividing by is the coefficient of variation B2v, and B3σ is B3 aveThe value obtained by dividing by is defined as the coefficient of variation B3v, and the average of B1v, B2v, and B3v is taken as the coefficient of variation Bv.

[0040] (4) For the 10 samples obtained in (2), calculate the coefficient of variation Bv for each, and then average them to obtain Bv ave The coefficient of variation of the Voronoi region of the filler within region B was then derived. In addition to rubber and thermally conductive filler particles, other additives may be added to the elastic layer according to desired properties. Examples of other additives include flocculants.

[0041] In this disclosure, the coefficient of variation Bv of the Voronoi region area in region B of the elastic layer other than region A. ave It is preferable that the ratio is between 1.5 and 4.0, and as a method to achieve this, it is preferable to add a flocculant in region B of the elastic layer and adjust the amount added. In region B, the adhesion of the flocculant to the surface of the thermal conductive filler particles reduces the dispersibility of the thermal conductive filler particles in the rubber, and the coefficient of variation of the Voronoi region area Bv ave It can improve.

[0042] As a flocculant, it is preferable to use a compound that has high affinity for thermally conductive filler particles and, conversely, low compatibility with rubber, possessing multiple alcohol groups (alcoholic hydroxyl groups, or functional groups derived from alcoholic hydroxyl groups), and that does not produce unwanted side reactions during rubber curing. Specifically, the following are examples: ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), propylene glycol (PG), glycerin (GLC), etc. These flocculants can be used individually or in combination.

[0043] The thermal conductivity of the elastic layer in the thickness direction is 0.40 W / mK or higher. This range ensures good adhesion. The measurement method is shown below.

[0044] <Method for measuring the thermal conductivity in the thickness direction of an elastic layer> The thermal conductivity λ in the thickness direction of the elastic layer 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.

[0045] ·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.

[0046] • 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 Co., Ltd.). 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 no pans inside, 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.

[0047] ·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, 10 cm 3 Using 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). [Examples]

[0048] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the embodiments of this disclosure are not limited thereto. Unless otherwise specified, commercially available Grade 1 or Special Grade reagents were used.

[0049] <Preparation of Fillers 1-3> Spherical alumina (product name: Alnabeads CB-A30S, manufactured by Showa Denko Corporation) was classified using a sieve to obtain fillers 1-3 having 50% particle size (D50), 5% particle size (D5), and 95% particle size (D95) values ​​as shown in Table 1. For fillers 1-3, measurements and analyses were performed using a Coulter Multisizer III (manufactured by Beckman Coulter) according to the instrument's operating manual, and the 50% particle size (D50), 5% particle size (D5), and 95% particle size (D95) were determined from the particle size distribution. The D50, D5, and D95 ​​values ​​of the fillers used in the examples and comparative examples are shown in Table 1.

[0050] [Table 1]

[0051] <Example 1> In this example, a fixing film as shown in Figure 3 was prepared. As the base layer, a substrate made of stainless steel with an endless belt shape, measuring 25 mm in inner diameter, 400 mm in width, and 40 μm in thickness, was prepared. The outer surface of this substrate was treated with a primer. As a raw material for forming the elastic layer, an addition-curing liquid silicone rubber (product name: SE1886, manufactured by Toray Dow Corning Co., Ltd.) without fillers was prepared. 9.0 wt% ethylene glycol was uniformly mixed and stirred with the liquid silicone rubber as a flocculant to prepare the mixture. 100 volumes of filler 1 was added to 100 volumes of the mixture as thermal conductive filler particles. These were applied to the outer surface of the base layer using a ring coating method to form an uncured elastic layer 2 (region B) with a thickness of 300 μm.

[0052] Next, 100 volumes of filler 2, used as thermal conductive filler particles, were added to 100 volumes of this liquid silicone rubber and stirred to mix. In this way, an addition-curing type silicone rubber composition for forming an elastic layer was prepared. These were then applied to the outer surface of the uncured elastic layer 2 using the ring-coating method to form an uncured elastic layer 1 with a thickness of 50 μm. The uncured elastic layer 1 (region A, Figure 5A 403) and uncured elastic layer 2 (region B, Figure 5A 404) were crosslinked by heating at 200°C for 4 hours to form an elastic layer with a thickness of 350 μm.

[0053] 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:

[0054] 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. Next, a fluororesin tube with a hydrophilic inner surface was placed over the belt, and the belt surface was uniformly rubbed over 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 thick, melting point 306°C)

[0055] 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. Next, the thermal conductivity in the thickness direction of the elastic layer of the fabricated fixing film and the coefficient of variation of the Voronoi region were determined. Furthermore, hardness uniformity, peel durability, and fixing performance were evaluated based on the following evaluation methods. These results are shown in Table 2.

[0056] <Evaluation of hardness variations> Using a micro rubber hardness tester (MD-1TYPE-C hardness tester, manufactured by Polymer Instruments Co., Ltd.), measurements were taken at three points in total: both ends and the center, located 15 mm to 25 mm from the edge of the fixing film. A total of four measurements were taken at 90° intervals around each point in the circumferential direction. The standard deviation of the 12 obtained rubber hardness measurements was calculated and evaluated according to the following criteria.

[0057] (Evaluation Criteria) Rank A: Standard deviation is less than 2.0°. Rank B: Standard deviation is between 2.0° and less than 3.5°. Rank C: Standard deviation is between 3.5° and 5.0°. Rank D: Standard deviation is 5.0° or greater.

[0058] <Evaluation of peeling durability> 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 according to the following criteria was A to C, it was determined that the effects of this disclosure were obtained.

[0059] (Evaluation Criteria) Rank A: No delamination is observed between the surface layer and the elastic layer even after continuous use up to 900,000 sheets. Rank B: If the process continues for more than 800,000 units but less than 900,000 units, delamination will occur between the surface layer and the elastic layer. Rank C: If the number of units sold 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.

[0060] <Evaluation of retention> A modified Canon imageRUNNER ADVANCE C5560 digital commercial printer was used as the unfixed image forming apparatus. The modifications included allowing free 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.

[0061] 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.

[0062] Next, 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 edge 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. 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.

[0063] 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 Apply a load and rub the fixed image with Silbon paper (5 back-and-forth motions), then measure the image density 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 based on the following criteria is A to C, we will conclude that the effects of this disclosure have been achieved.

[0064] (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.

[0065] <Example 2> A fixed film was obtained in the same manner as in Example 1, except that the thickness of the uncured elastic layer 2 was changed to 150 μm. <Example 3> A fixed film was obtained in the same manner as in Example 1, except that the thickness of the uncured elastic layer 2 was changed to 2950 μm.

[0066] <Example 4> The amount of filler 2 was changed to 67 parts by volume. The amount of filler 1 was changed to 67 parts by volume. A fixed film was obtained in the same manner as in Example 1, except that the amount of ethylene glycol was changed to 6.0 wt%.

[0067] <Example 5> The amount of filler 2 was changed to 150 parts by volume. Change the amount of filler 1 to 150 parts by volume. A fixing film was obtained in the same manner as in Example 1, except that ethylene glycol was not used.

[0068] <Example 6> A fixing film was obtained in the same manner as in Example 1, except that filler 2 was changed to filler 3. <Example 7> A fixing film was obtained in the same manner as in Example 1, except that ethylene glycol was not used.

[0069] <Example 8> The amount of filler 2 was changed to 122 parts by volume. The filler ratio of 1:100 parts by volume was changed to filler ratio 4 (silicon carbide (SiC) powder (product name: GC-1000J, manufactured by Yakushima Electric Co., Ltd.)):122 parts by volume. A fixing film was obtained in the same manner as in Example 1, except that ethylene glycol: 9.0 wt% was changed to glycerin: 6.3 wt%.

[0070] <Example 9> A fixed film was obtained in the same manner as in Example 1, except that the amount of ethylene glycol was changed to 8.6 wt%. <Example 10> A fixed film was obtained in the same manner as in Example 1, except that the amount of ethylene glycol was changed to 3.9 wt%. <Example 11> A fixed film was obtained in the same manner as in Example 1, except that the amount of ethylene glycol was changed to 7.1 wt%.

[0071] <Comparative Example 1> A fixed film was obtained in the same manner as in Example 1, except that the thickness of the uncured elastic layer 2 was changed to 130 μm. <Comparative Example 2> The amount of filler 2 was changed to 54 volumes. The amount of filler 1 was changed to 54 parts by volume. A fixed film was obtained in the same manner as in Example 1, except that the amount of ethylene glycol was changed to 4.9 wt%.

[0072] <Comparative Example 3> The amount of filler 2 was changed to 185 parts by volume. The amount of filler 1 was changed to 185 parts by volume. A fixing film was obtained in the same manner as in Example 1, except that ethylene glycol was not used. <Comparative Example 4> A fixing film was obtained in the same manner as in Example 1, except that filler 2 was changed to filler 1.

[0073] <Comparative Example 5> A fixed film was obtained in the same manner as in Example 1, except that filler 2 was changed to filler 3, the thickness of the uncured elastic layer 1 was changed to 350 μm, and the uncured elastic layer 2 was not formed. In Examples 2-11 and Comparative Examples 1-5, the thermal conductivity in the thickness direction of the elastic layer of the fabricated fixing film and the coefficient of variation of the Voronoi region were determined. Furthermore, hardness uniformity, peel durability, and fixing performance were evaluated based on the same evaluation method as in Example 1. The physical property results for each of these examples and comparative examples are shown in Table 2, and the evaluation results are shown in Table 3.

[0074] [Table 2]

[0075] [Table 3]

[0076] This disclosure includes the following components. [Configuration 1] A fixing member comprising at least a base layer having an endless shape, an elastic layer provided on the outer circumferential surface of the base layer, and a surface layer provided on the outer circumferential surface of the elastic layer, The base layer comprises at least one selected from the group consisting of aluminum, iron, copper, nickel, stainless steel, brass, polyimide, polyamide-imide, and polyetheretherketone. The elastic layer comprises rubber and heat-conducting filler particles dispersed in the rubber. The thickness of the elastic layer is 200 μm or more. The thermal conductivity of the elastic layer in the thickness direction is 0.40 W / mK or higher. The content of the thermal conductive filler particles in the elastic layer is 40% by volume or more and 60% by volume or less. In a cross-section of the elastic layer in a direction perpendicular to the circumferential direction, Region A is defined as the region from the interface between the elastic layer and the surface layer to a thickness of 50 μm in the thickness direction of the elastic layer. The coefficient of variation Av of the area of ​​the Voronoi region formed by Voronoi tessellation using the heat-conducting filler particles exposed in region A of the cross-section as the parent points. ave A fixing member characterized by having a coefficient of 1.0 or less. [Configuration 2] The coefficient of variation Bv of the area of ​​the Voronoi region formed by Voronoi tessellation using the heat-conducting filler particles exposed in region B other than region A of the cross-section as the parent point. ave The fixing member described in configuration 1, wherein the ratio is 1.5 or more and 4.0 or less. [Configuration 3] The fixing member according to configuration 1 or 2, wherein the thermal conductive filler includes at least one selected from the group consisting of silicon carbide, silicon nitride, boron nitride, aluminum nitride, alumina, zinc oxide, magnesium oxide, silica, copper, aluminum, silver, iron, nickel, carbon black, and carbon fiber. [Structure 4] The fixing member according to any one of configurations 1 to 3, wherein the thickness of the elastic layer is 200 μm or more and 5 mm or less. [Composition 5] The fixing member according to any one of configurations 1 to 4, wherein the thickness of the surface layer is 10 μm or more and 100 μm or less. [Composition 6] The fixing member according to any one of configurations 1 to 5, wherein the elastic layer includes silicone rubber. [Composition 7] The fixing member according to any one of configurations 1 to 6, wherein the surface layer contains a fluororesin. [Structure 8] A thermal fixing apparatus comprising a fixing member described in any of configurations 1 to 7, and a pressurizing member disposed opposite to the fixing member. [Explanation of Symbols]

[0077] 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 body 44: Pressure roller 45: Contact type thermistor 46: Heater holder P: Recording material T: Toner 401-1: 1st cross section 401-2:Second cross section 402: Cross-section 403: Area A 404: Area B 404-1: Area B1 404-2: Area B2 404-3: Area B3 61: Filler particles A: Center of gravity F: Intersection

Claims

1. A fixing member comprising at least a base layer having an endless shape, an elastic layer provided on the outer circumferential surface of the base layer, and a surface layer provided on the outer circumferential surface of the elastic layer, The base layer comprises at least one selected from the group consisting of aluminum, iron, copper, nickel, stainless steel, brass, polyimide, polyamide-imide, and polyetheretherketone. The elastic layer comprises rubber and heat-conducting filler particles dispersed in the rubber. The thickness of the elastic layer is 200 μm or more. The thermal conductivity of the elastic layer in the thickness direction is 0.40 W / mK or higher. The content of the thermal conductive filler particles in the elastic layer is 40% by volume or more and 60% by volume or less. In a cross-section perpendicular to the circumferential direction of the elastic layer, the region A is defined as the area from the interface between the elastic layer and the surface layer to a thickness of 50 μm in the thickness direction of the elastic layer, and the coefficient of variation Av of the area of ​​the Voronoi region formed by Voronoi tessellation using the heat-conducting filler particles exposed in region A of the cross-section as the parent points is... ａｖｅ A fixing member characterized by having a value of 1.0 or less.

2. The coefficient of variation Bv of the area of ​​the Voronoi region formed by Voronoi tessellation using the heat-conducting filler particles exposed in region B other than region A of the cross-section as the parent point. ａｖｅ The fixing member according to claim 1, wherein the ratio is 1.5 or more and 4.0 or less.

3. The fixing member according to claim 1, wherein the thermal conductive filler includes at least one selected from the group consisting of silicon carbide, silicon nitride, boron nitride, aluminum nitride, alumina, zinc oxide, magnesium oxide, silica, copper, aluminum, silver, iron, nickel, carbon black, and carbon fiber.

4. The fixing member according to claim 1, wherein the thickness of the elastic layer is 200 μm or more and 5 mm or less.

5. The fixing member according to claim 1, wherein the thickness of the surface layer is 10 μm or more and 100 μm or less.

6. The fixing member according to claim 1, wherein the elastic layer comprises silicone rubber.

7. The fixing member according to claim 1, wherein the surface layer comprises a fluororesin.

8. A thermal fixing apparatus comprising a fixing member according to any one of claims 1 to 7, and a pressurizing member disposed opposite to the fixing member.

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