Rotating body for fixing, heat fixing device, and electrophotographic image forming device

Abstract

This rotating body for fixing is capable of satisfying all of suppression of wrinkles of a surface layer in continuous use, suppression of gloss unevenness of an image, and fixability. This rotating body for fixing is provided with at least an endless base layer, an elastic layer on the outer circumferential surface side of a base body, and a surface layer fixed to the outer circumferential surface side of the elastic layer with an adhesive layer therebetween. The thermal conductivity of the elastic layer in the thickness direction is 1.0 W / mK or more, and if A is designated as the linear expansion coefficient of the elastic layer at a temperature of 200°C measured while pulling, in the rotation axis direction of the rotating body for fixing, the elastic layer removed from the rotating body for fixing, and B is designated as the linear expansion coefficient of the surface layer at a temperature of 200°C measured while pulling, in the rotation axis direction of the rotating body for fixing, the surface layer removed from the rotating body for fixing, A > B, and A-B is at least 2.0%.

Description

Fixing rotor, heat fixing device and electrophotographic image forming apparatus

[0001] The present invention relates to a fixing rotor used in an electrophotographic image forming apparatus, a heat fixing device, and an electrophotographic image forming apparatus.

[0002] Fixing members used in heat fixing devices of electrophotographic image forming apparatuses (hereinafter also referred to as "image forming apparatuses") such as printers, copiers, and facsimiles include film-shaped or roller-shaped fixing rotors. For example, fixing members are known that have a film- or roller-shaped substrate made of heat-resistant resin or metal, an elastic layer made of heat-resistant rubber or the like formed on the substrate as needed, and a surface layer containing a fluororesin that has excellent releasability for toner. Here, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), which has excellent heat resistance, is preferably used as the fluororesin contained in the surface layer.

[0003] In recent years, from the perspective of environmental friendliness, there has been a demand for reducing waste by extending the lifespan of fixing members. One of the challenges in extending the lifespan of materials used in fixing members is "surface wrinkles." This occurs when the fixing member is used over a long period of time, and the strength of the surface layer material gradually decreases due to repeated heat cycles of temperature increase and decrease.

[0004] For example, when a fluororesin tube material is used as the surface layer of a fixing member, the fluororesin tube is tightly stretched to cover the surface of the fixing member at the time of manufacture. However, repeated heat cycles cause repeated thermal expansion and contraction of the tube material, gradually loosening the tension of the fluororesin tube. As this loosening increases, "wrinkles" occur on the surface layer of the fixing member.

[0005] If these wrinkles extend to the area where a toner image is formed, wrinkle marks will be transferred onto the fixed toner image, causing an image defect and necessitating replacement of the fixing member. Patent documents 1 to 3, for example, disclose a method for solving this problem, in which a fluororesin tube used in the fixing member is pre-treated to be thermally shrinkable. By imparting thermal shrinkage, the linear expansion coefficient during heating is reduced, and the amount of thermal expansion and contraction during a heat cycle is reduced, thereby reducing the loosening of the tension of the surface layer and suppressing the occurrence of wrinkles.

[0006] JP 2008-200954 A JP 2020-106561 A JP 2009-186617 A

[0007] However, the present inventors recognized that the inventions of Patent Documents 1 to 3 have the following problems: In methods for imparting heat shrinkage to fluororesin tubes manufactured by extrusion molding, a method of imparting heat shrinkage after extrusion is often used, which increases the number of tube manufacturing steps and increases manufacturing costs. Also, only fluororesin materials that can be imparted with heat shrinkage can be used, which imposes restrictions on material selection.

[0008] Furthermore, when using a heat-shrinkable fluororesin tube, the heat shrinkage of the tube during manufacturing tightens the elastic layer, increasing the apparent hardness of the fixing member. This reduces the fixing member's ability to conform to the irregularities of the media, which can lead to poor image quality, such as uneven gloss. To prevent "surface wrinkles," it is also effective to increase the linear expansion coefficient of the elastic layer at the actual operating temperature and apply tension to the surface layer. To increase the linear expansion coefficient of the elastic layer, it is effective to minimize the amount of heat-conductive filler in the rubber of the elastic layer. However, this can impair the thermal conductivity of the elastic layer and reduce fixability.

[0009] As described above, it is difficult to satisfy all of the requirements for suppressing wrinkles on the surface layer, suppressing uneven gloss in the image, and achieving good fixability. This disclosure relates to a fixing rotor that can satisfy all of the requirements for suppressing wrinkles on the surface layer during continuous use, suppressing uneven gloss in the image, and achieving good fixability. This disclosure also relates to a heat fixing device and an electrophotographic image forming apparatus that include the fixing rotor.

[0010] The present disclosure relates to a fixing rotor, the fixing rotor comprising at least an endless base layer, an elastic layer on an outer peripheral surface side of the base layer, and a surface layer fixed to the outer peripheral surface side of the elastic layer via an adhesive layer, wherein the thermal conductivity of the elastic layer in the thickness direction is 1.0 W / mK or more, and the thermal conductivity of the elastic layer in the thickness direction is 1.0 W / mK or more, and the elastic layer removed from the fixing rotor is pulled in the rotation axis direction of the fixing rotor with a load of 25 mN while being heated from 25°C to 250°C at a heating rate of 10°C / min, and in a TMA curve where the horizontal axis is temperature and the vertical axis is linear expansion coefficient, A is the linear expansion coefficient at a temperature of 200°C, The surface layer removed from the fixing rotor is pulled in the direction of the rotation axis of the fixing rotor with a load of 25 mN while the temperature is raised from 25°C to 250°C at a temperature rising rate of 10°C / min to obtain a TMA curve with the horizontal axis being temperature and the vertical axis being linear expansion coefficient, where B is the linear expansion coefficient at a temperature of 200°C, and A>B and A-B is 2.0% or more.

[0011] The present disclosure relates to a heat fixing device having a heating member and a pressure member arranged opposite the heating member, wherein at least one of the heating member and the pressure member is the above-mentioned fixing rotor.

[0012] The present disclosure relates to an electrophotographic image forming apparatus equipped with a heat fixing device, the heat fixing device having a heating member and a pressure member arranged opposite the heating member, and at least one of the heating member and the pressure member being the fixing rotor.

[0013] According to the present disclosure, a fixing rotator is provided that can suppress wrinkles in the surface layer during continuous use, suppress uneven gloss in images, and provide good fixability. Also, according to the present disclosure, a heat fixing device and an electrophotographic image forming apparatus that include the fixing rotator are provided.

[0014] FIG. 1 is a schematic diagram of an image forming apparatus in this embodiment. FIG. 2 is a schematic diagram of a fixing device in this embodiment. FIG. 3 is a schematic diagram of a fixing belt in this embodiment. FIGS. 4A and 4B are an overhead view and a cross-sectional view of a corona charger. FIGS. 5A and 5B are diagrams showing a first cross section and a second cross section of the elastic layer of a fixing rotor. FIGS. 6A to 6D are schematic diagrams showing a method for confirming the degree of alignment and alignment angle of fillers in the elastic layer. FIG. 7 is a partially enlarged view of a grid used in a corona charger. FIGS. 8A to 8C are diagrams of TMA curves in this embodiment.

[0015] In the present disclosure, expressions such as "XX or more and YY or less" or "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. Furthermore, when a numerical range is described in stages, the upper and lower limits of each numerical range can be arbitrarily combined. Furthermore, in the present disclosure, expressions such as "at least one selected from the group consisting of XX, YY, and ZZ" mean any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ. Note that when XX is a group, multiple XXs may be selected, and the same applies to YY and ZZ.

[0016] Next, specific examples (examples) of the embodiment of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the following examples. Figure 1 is a cross-sectional view of a color electrophotographic printer, which is an example of an image forming apparatus of this embodiment, taken along the sheet transport direction. In this embodiment, the color electrophotographic printer is simply referred to as a "printer."

[0017] The printer shown in FIG. 1 includes image forming units 10 for the colors Y (yellow), M (magenta), C (cyan), and Bk (black). Photosensitive drums 11 are pre-charged by chargers 12. Then, a latent image is formed on the photosensitive drums 11 by a laser scanner 13. The latent image is converted into a toner image by a developing unit 14. The toner images on the photosensitive drums 11 are sequentially transferred by a primary transfer blade 17 to an image carrier, such as an intermediate transfer film 31. After transfer, any toner remaining on the photosensitive drums 11 is removed by a cleaner 15. As a result, the surface of the photosensitive drums 11 is cleaned in preparation for the next image formation.

[0018] Meanwhile, sheets P are fed one by one from the paper feed cassette 20 or the multi-paper feed tray 25 in the direction of arrow 3 and fed into the registration roller pair 23. The registration roller pair 23 temporarily receives the sheet P and straightens it out if it is skewed. The registration roller pair 23 then feeds the sheet between the intermediate transfer film 31 and the secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer film 31. The color toner image on the intermediate transfer film is transferred onto the sheet P by a transfer body, such as the secondary transfer roller 35. The toner image on the sheet is then fixed to the sheet by applying heat and pressure to the sheet by the heat-fixing device 40.

[0019] The image forming apparatus is provided with a heat fixing device. The heat fixing device will be described. A belt (film) heating type heating device (tensionless type) as shown in the schematic configuration diagram of heat fixing device 40 in FIG. 2 was used.

[0020] Reference numeral 43 denotes a ceramic heater (hereinafter referred to as heater) serving as a heating element. The heater 43 is basically composed of a thin, elongated ceramic substrate with its longitudinal direction perpendicular to the drawing and an energized heat-generating resistor layer provided on the surface of the substrate. It is a low-heat-capacity heater that increases in temperature with a steep rise in temperature as a whole when current is applied to the heat-generating resistor layer. The fixing rotor may be a pressure member such as a pressure belt or pressure roller. In a heat-fixing device, at least one of the heating element and the pressure member may be the fixing rotor of the present disclosure.

[0021] As an example of a fixing rotating body, reference numeral 41 denotes a cylindrical (endless) heat-resistant fixing belt serving as a heating member for transmitting heat, which is loosely fitted onto the outside of a support member including the heater 43. The fixing belt 41 in this embodiment is as shown in Fig. 3, and is a fixing belt having a composite structure including, for example, a surface layer 41a, an adhesive layer 41b, an elastic layer 41c, and a base layer 41d.

[0022] The heat-fixing device has a heating member 41 and a pressure member 44 disposed opposite the heating member. Reference numeral 44 denotes a heat-resistant elastic pressure roller serving as the pressure member. It consists of a core and an elastic layer made of heat-resistant rubber such as silicone rubber or fluororubber, or a silicone rubber foam. Both ends of the core are supported by bearings for free rotation. The fixing belt 41 and heater 43 are disposed above the pressure roller 44, parallel to the pressure roller 44 with respect to the heater 43 side, and are pressed by a pressing member (not shown). This causes the lower surface of the heater 43 and the upper surface of the pressure roller 44 to be pressed against each other via the fixing belt 41 against the elasticity of the roller's elastic layer, forming a fixing nip T of a predetermined width as a heating section.

[0023] The pressure roller 44 is driven to rotate counterclockwise as indicated by the arrow at a predetermined peripheral speed by a driving means (not shown). The rotation of the pressure roller 44 generates a frictional pressure between the pressure roller 44 and the fixing belt 41 at the fixing nip T, which acts as a rotational force on the cylindrical fixing belt 41. The fixing belt 41 then slides in close contact with the downward surface of the heater 43, rotating clockwise as indicated by the arrow. The support member also serves as a rotation guide member for the cylindrical fixing belt 41.

[0024] The pressure roller 44 is driven to rotate, causing the cylindrical fixing belt 41 to rotate in a driven state, and the heater 43 is energized, causing the heater to heat up quickly to a predetermined temperature and enter a temperature-regulated state. In this state, a recording material P carrying an unfixed toner image T is introduced into the fixing nip between the fixing belt 41 and the pressure roller 44. Then, in the fixing nip, the toner image-bearing side of the recording material P comes into close contact with the outer surface of the fixing belt 41, and the recording material P is sandwiched and transported to the fixing nip together with the fixing belt 41. During this sandwiching and transport process, the recording material P is heated by the heat of the fixing belt 41 heated by the heater 43, and the unfixed toner image T on the recording material P is heated and pressurized onto the recording material P, melting and fixing it. After passing through the fixing nip, the recording material P separates from the surface of the fixing belt 41 and is then discharged and transported.

[0025] A contact thermometer (thermistor) 45 measures the temperature of the fixing belt 41 heated by the heater 43 and passes the detection result to a temperature control means (not shown). A heater holder 46 is a member that holds the heater 43 that has been heated to a high temperature.

[0026] Next, the fixing rotor will be described. Examples of the fixing rotor include a fixing film, a fixing belt, and a fixing roller. The fixing rotor of the present disclosure includes at least an endless base layer, an elastic layer, and a surface layer, in this order. Other layers may be provided between each layer as needed. The fixing rotor includes at least an endless base layer, an elastic layer on the outer peripheral surface side of the base layer, and a surface layer fixed to the outer peripheral surface side of the elastic layer via an adhesive layer. Below, a fixing belt will be described in detail as an example of the fixing rotor.

[0027] The fixing belt 41 is as shown in Fig. 3. The fixing belt has a base layer 41d, an elastic layer 41c covering the outer surface of the base layer, and a surface layer 41a covering the surface of the elastic layer opposite to the side facing the base layer. The surface layer 41a is adhered to the surface of the elastic layer 41c opposite to the side facing the base layer by an adhesive layer 41b.

[0028] In the present disclosure, the linear expansion coefficients of the elastic layer and the surface layer have the following relationship: The elastic layer removed from the fixing rotor is pulled in the direction of the rotation axis of the fixing rotor with a load of 25 mN while the temperature is raised from 25° C. to 250° C. at a heating rate of 10° C. / min., and in the TMA curve with the horizontal axis being temperature and the vertical axis being linear expansion coefficient, the linear expansion coefficient at a temperature of 200° C. is defined as A. The surface layer removed from the fixing rotor is pulled in the direction of the rotation axis of the fixing rotor with a load of 25 mN while the temperature is raised from 25° C. to 250° C. at a heating rate of 10° C. / min., and in the TMA curve with the horizontal axis being temperature and the vertical axis being linear expansion coefficient, the linear expansion coefficient at a temperature of 200° C. is defined as B.

[0029] In this case, it is satisfied that A>B and A-B is 2.0% or more. When these conditions are satisfied, it is possible to suppress both wrinkles in the surface layer and uneven gloss in the image. The inventors consider the reason for this as follows.

[0030] First, when the linear expansion coefficient of the elastic layer is greater than that of the surface layer (A > B), tension is applied to the surface layer in the direction of the rotation axis, and it is believed that the greater the tension (A - B) applied to the surface layer, the more tension can be maintained until the end of the durability test of a fixing member that is repeatedly bent, and the more wrinkles can be suppressed. On the other hand, from the perspective of gloss unevenness, gloss unevenness is caused by uneven toner melting, which depends on the microscopic conformity to paper irregularities, so it is preferable that the tension (A - B) of the surface layer, which affects the microscopic conformity, is small. The inventors believe that the range in which both the suppression of wrinkles and gloss unevenness are achieved is A > B, and A - B is 2.0% or more.

[0031] The reason why the temperature of 200°C was selected for measuring the linear expansion coefficient is that this temperature is close to the actual operating temperature that the surface layer reaches when used as a fixing device. Furthermore, A-B is preferably 2.0 to 7.0%, more preferably 2.0 to 5.2%, and even more preferably 2.1 to 5.0%.

[0032] Furthermore, in the fixing rotor, the thermal conductivity of the elastic layer in the thickness direction must be 1.0 W / mK or higher. By satisfying this thermal conductivity, the fixing performance will be further improved. Therefore, by satisfying the specific relationship between A and B above and setting the thermal conductivity of the elastic layer in the thickness direction within a specific range, it is possible to suppress wrinkles in the surface layer, suppress uneven gloss in the image, and achieve good fixing performance. The thermal conductivity of the elastic layer in the thickness direction is preferably 1.0 to 3.0 W / mK, more preferably 1.1 to 2.0 W / mK, and even more preferably 1.2 to 1.6 W / mK.

[0033] (1) Base Layer The material of the base layer 41d is not particularly limited, and known materials used as base layers for fixing belts and other rotating bodies can be used. Examples of suitable materials include metals and alloys such as aluminum, iron, stainless steel, and nickel, as well as heat-resistant resins such as polyimide. The base layer preferably contains at least one selected from the group consisting of nickel, copper, iron, and aluminum, and more preferably stainless steel. The thickness of the base layer 41d is not particularly limited, but is preferably 20 μm to 100 μm, and more preferably 20 μm to 50 μm, from the standpoints of strength, flexibility, and heat capacity.

[0034] The outer surface of the base layer 41d may be subjected to a surface treatment to impart adhesion to the elastic layer, such as physical treatments like blasting, lapping, and polishing, or chemical treatments like oxidation, coupling agent treatment, and primer treatment, either singly or in combination.

[0035] The surface of the base layer 41d is preferably subjected to a primer treatment to improve adhesion between the base layer and the elastic layer. Examples of the primer used for the primer treatment include paints prepared by appropriately blending and dispersing a silane coupling agent, a silicone polymer, a hydrogenated methylsiloxane, an alkoxysilane, a reaction-accelerating catalyst, and a colorant such as red iron oxide in an organic solvent.

[0036] The primer can be appropriately selected depending on the material of the base layer, the type of the elastic layer, or the form of crosslinking reaction. In particular, when the elastic layer contains a large amount of unsaturated aliphatic groups, a primer containing a hydrosilyl group is preferably used to impart adhesion by reacting with the unsaturated aliphatic groups. When the elastic layer contains a large amount of hydrosilyl groups, a primer containing an unsaturated aliphatic group is preferably used.

[0037] Other examples of primers include those containing alkoxy groups. Commercially available primers can be used. The primer treatment includes applying the primer to the outer surface of the base layer (the surface to be bonded to the elastic layer) and drying or baking it.

[0038] (2) Elastic Layer The elastic layer is a layer that imparts flexibility to the fixing rotor to ensure a fixing nip in a thermal fixing device. When the fixing rotor is used as a heating element that comes into contact with toner on paper, the elastic layer also functions as a layer that imparts flexibility to the surface of the heating element so that it can conform to the unevenness of the paper. The elastic layer contains rubber as a matrix and a thermally conductive filler dispersed in the rubber. More specifically, for example, the elastic layer contains rubber and a thermally conductive filler, and is composed of a cured product obtained by curing a composition that contains at least rubber raw materials (base polymer, crosslinking agent, etc.) and a thermally conductive filler.

[0039] The rubber is preferably silicone rubber. A composition containing at least rubber raw materials (base polymer, crosslinking agent, etc.) and thermally conductive particles is hereinafter also referred to as a silicone rubber composition. When the silicone rubber composition is liquid, the thermally conductive filler is easily dispersed, and the elasticity of the elastic layer to be produced can be easily adjusted by adjusting the degree of crosslinking depending on the type and amount of the thermally conductive filler.

[0040] The matrix is ​​responsible for the function of exhibiting elasticity in the elastic layer. From the viewpoint of exhibiting the above-mentioned function of the elastic layer, the matrix preferably contains silicone rubber. Silicone rubber is preferable because it has high heat resistance that allows it to maintain flexibility even in an environment where the non-paper passing area reaches a high temperature of about 240°C. As the silicone rubber, for example, a cured product of an addition-curing liquid silicone rubber composition described below can be used.

[0041] Liquid silicone rubber compositions typically contain the following components (a) to (d): Component (a): a linear organopolysiloxane having an unsaturated aliphatic group; Component (b): an organopolysiloxane having silicon-bonded active hydrogen; Component (c): a catalyst; and Component (d): a thermally conductive filler. Each component will now be described.

[0042] Component (a): Linear Organopolysiloxane Having an Unsaturated Aliphatic Group The linear organopolysiloxane having an unsaturated aliphatic group is an organopolysiloxane having an unsaturated aliphatic group such as a vinyl group, and has a structure in which siloxane bonds are connected in a linear chain. Examples of the linear organopolysiloxane having an unsaturated aliphatic group include at least one selected from the group consisting of compounds represented by the following formula (1) and compounds represented by formula (2):

[0043] In formula (1), m １ represents an integer of 0 or more (preferably 500 to 1100), and n1 represents an integer of 3 or more (preferably 10 to 40). １ each independently represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an unsaturated aliphatic group, provided that R １ At least one of R represents a methyl group; ２ each independently represents an unsaturated aliphatic group.

[0044] In formula (2), n ２ represents an integer of 1 or more (preferably 500 to 1100), and R ３ each independently represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an unsaturated aliphatic group, provided that R ３At least one of R represents a methyl group; ４ each independently represents an unsaturated aliphatic group.

[0045] In formula (1) and formula (2), R １ and R ３ Examples of the monovalent unsubstituted or substituted hydrocarbon group containing no unsaturated aliphatic group that can be represented by the formula (I) include the following groups: Unsubstituted hydrocarbon group: Alkyl group (e.g., methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group). Aryl group (e.g., phenyl group). Substituted hydrocarbon group: Substituted alkyl group (e.g., chloromethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, 3-cyanopropyl group, 3-methoxypropyl group).

[0046] The organopolysiloxanes represented by formula (1) and formula (2) have at least one methyl group directly bonded to the silicon atom that forms the chain structure. １ and R ３ Preferably, 50% or more of each group are methyl groups, and all of the R １ and R ３ It is more preferable that R in formula (1) and formula (2) is a methyl group. ２ and R ４ Examples of unsaturated aliphatic groups that can be represented by include the following groups. That is, examples of unsaturated aliphatic groups include vinyl groups, allyl groups, 3-butenyl groups, 4-pentenyl groups, and 5-hexenyl groups. Among these groups, R ２ and R ４ is preferably a vinyl group.

[0047] From the viewpoint of moldability, the component (a) has a viscosity of 1000 mm ２ / s or more 20000mm ２ / s or less, and ２ / s or more 8000mm ２ / s or less is more preferable. ２ / s or more, it is easy to adjust the hardness required for the elastic layer, ２ When the viscosity is 1 / s or less, the filler can be easily oriented by an electric field. The viscosity (kinematic viscosity) can be measured using a capillary viscometer, a rotational viscometer, or the like, in accordance with JIS Z 8803:2011. The amount of component (a) is preferably 55% by volume or more based on the liquid silicone rubber composition used to form the elastic layer, from the viewpoint of durability, and 70% by volume or less from the viewpoint of heat conductivity.

[0048] Component (b): Organopolysiloxane having silicon-bonded active hydrogen. Organopolysiloxanes having silicon-bonded active hydrogen react with the unsaturated aliphatic groups of component (a) under the action of a catalyst, functioning as a crosslinking agent to form a cured silicone rubber. Any organopolysiloxane having a Si-H bond can be used as component (b). In particular, from the viewpoint of reactivity with the unsaturated aliphatic groups of component (a), it is preferable to use an organopolysiloxane having an average of three or more silicon-bonded hydrogen atoms per molecule.

[0049] Specific examples of component (b) include the linear organopolysiloxane shown in formula (3) below and the cyclic organopolysiloxane shown in formula (4) below.

[0050] In formula (3), m ２ represents an integer of 0 or more (preferably 10 to 30), and n ３ represents an integer of 3 or more (preferably 5 to 20), and R ５ each independently represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an unsaturated aliphatic group. In formula (4), m ３ represents an integer of 0 or more (preferably 10 to 30), and n ４ represents an integer of 3 or more (preferably 5 to 20), and R ６ each independently represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an unsaturated aliphatic group.

[0051] R in formula (3) and formula (4) ５ and R ６Examples of the monovalent unsubstituted or substituted hydrocarbon group not containing an unsaturated aliphatic group that can be represented by R １ Among these, R ５ and R ６ Preferably, 50% or more of each group are methyl groups, and all of the R ５ and R ６ is more preferably a methyl group.

[0052] Component (c): Catalyst Examples of catalysts used in forming silicone rubber include hydrosilylation catalysts for accelerating the curing reaction. Known substances such as platinum compounds and rhodium compounds can be used as hydrosilylation catalysts. The amount of catalyst used can be determined appropriately and is not particularly limited.

[0053] Component (d): Thermally conductive filler The thermally conductive filler (hereinafter simply referred to as "filler") is selected taking into consideration its own thermal conductivity, specific heat capacity, density, particle size, dielectric constant, etc. Examples of thermally conductive fillers used for the purpose of improving the heat transfer properties of inorganic substances, particularly metals, metal compounds, etc. include the following: silicon carbide, silicon nitride, boron nitride, aluminum nitride, alumina, zinc oxide, magnesium oxide, silica, copper, aluminum, silver, iron, nickel, metallic silicon, and carbon fiber. Furthermore, from the viewpoints of the thermal conductivity, electrical resistance, and dielectric constant of the filler itself, it is more preferable to use at least one filler selected from the group consisting of alumina, zinc oxide, metallic silicon, silicon carbide, boron nitride, and magnesium oxide. Furthermore, from the viewpoint of the heat resistance of the elastic layer, ionic impurities (Na ＋ Metallic silicon and silicon carbide, which have less of the above-mentioned ions, are more preferred.

[0054] In a TMA curve, where the horizontal axis is temperature and the vertical axis is linear expansion coefficient, obtained by heating the elastic layer from 25°C to 250°C at a heating rate of 10°C / min while pulling the elastic layer with a load of 25 mN in the direction of the rotation axis of the fixing rotor, A is the linear expansion coefficient at a temperature of 200°C. The linear expansion coefficient A is, for example, 2.7 to 6.5%, and preferably 3.0 to 5.0%. If A is 3.0% or more, crystal formation can be performed while applying stress to the surface layer in the direction of the rotation axis of the fixing rotor in the surface layer processing step described below, thereby further reducing the linear expansion coefficient of the surface layer. If A is 6.0% or less, the linear expansion coefficient of the surface layer can be reduced, and gloss unevenness can be further suppressed.

[0055] The linear expansion coefficient of the elastic layer can be controlled by adjusting the ratio of silicone rubber as a matrix, which has a large linear expansion coefficient as a single substance, to the thermally conductive filler, which has a small linear expansion coefficient as a single substance. Increasing the silicone rubber ratio to increase the linear expansion coefficient to 3.0% or more may result in a decrease in thermal conductivity. Therefore, it is preferable to achieve thermal conductivity with a small amount of filler by orienting the thermally conductive filler in the thickness direction using the electric field application process described below.

[0056] Furthermore, compared to a configuration in which the filler is randomly arranged, by aligning the filler in the thickness direction, the filler becomes relatively sparse in the direction of the rotation axis of the fixing rotor facing the thickness direction, which reduces the influence of the inorganic filler with a low linear expansion coefficient, and as a result, the linear expansion coefficient of the entire elastic layer in the direction of the rotation axis of the fixing rotor can be maintained high. Therefore, the electric field application process makes it easy to satisfy the thermal conductivity of the elastic layer in the thickness direction while satisfying the relationship between A and B described above.

[0057] It is preferable to orient the filler by charging the surface before curing the rubber in the elastic layer. Therefore, the rubber is preferably electrically insulating or semiconductive, and for example, a cured silicone polymer can be used as described below.

[0058] The filler may be surface-treated from the viewpoint of affinity to silicone and electrical resistance. Specifically, fillers such as alumina, silica, and magnesium oxide, which have active groups such as hydroxyl groups on their surfaces, may be surface-treated with a silane coupling agent, hexamethyldisilazane, or the like. Metal fillers may be surface-treated by forming an oxide film. Furthermore, the electrical resistance may be adjusted for the entire silicone rubber composition. Even fillers with relatively low electrical resistance can be used in combination with a second filler with high electrical resistance to adjust the electrical resistance of the entire composition. The particle size of the filler is preferably 0.1 μm or more and 100 μm or less, and more preferably 0.3 μm or more and 30 μm or less. The particle size referred to here refers to the volume average particle size.

[0059] (2-2) Confirmation of the Orientation State of the Thermally Conductive Filler in the Elastic Layer The thermally conductive filler can be oriented in the thickness direction of the elastic layer in the electric field application process described below. By aligning the filler in the thickness direction, it is easy to achieve thermal conductivity with a small amount of filler. Furthermore, compared to a configuration in which the filler is randomly arranged, by aligning the filler in the thickness direction, the filler becomes relatively sparse in the direction of the rotation axis of the fixing rotor facing the thickness direction, which reduces the influence of the inorganic filler with a low linear expansion coefficient. As a result, the linear expansion coefficient of the entire elastic layer in the direction of the rotation axis of the fixing rotor can be maintained high.

[0060] The arrangement state of the thermally conductive filler can be confirmed by performing a two-dimensional Fourier transform using a binary image obtained from a cross-sectional image of the elastic layer. Specifically, the procedure is as follows. First, a measurement sample is prepared. For example, if the fixing rotor is a fixing belt 41 as shown in FIG. 5A, a total of 10 samples 401, each 5 mm long and 5 mm wide, and the entire thickness of the fixing belt, are taken from 10 locations in the central portion of the fixing belt in the rotational axis direction, one at equal intervals in the circumferential direction, as shown in FIG. 5B.

[0061] Of the ten samples obtained, for five samples, the cross section in the circumferential direction of the fixing belt, i.e., the cross section including the first cross section 401-1 in the circumferential direction of the elastic layer, is polished using an ion beam. For the remaining five samples, the cross section in the direction perpendicular to the circumferential direction of the fixing belt, i.e., the cross section including the second cross section 401-2 in the thickness of the elastic layer and the rotation axis direction, is polished using an ion beam. A cross-section polisher is used for polishing the cross section using an ion beam. Polishing the cross section using an ion beam can prevent the filler from falling off from the sample and the abrasive from being mixed in, and can also form a cross section with fewer polishing marks.

[0062] Next, for five samples in which the first cross section of the elastic layer was polished, and for five samples in which the second cross section of the elastic layer was polished, the polished cross sections were observed using a laser microscope (OLS3000, manufactured by Olympus Corporation) or a scanning electron microscope (SEM) (S4700, manufactured by Hitachi Corporation) to obtain cross-sectional images of a 150 μm x 100 μm area (Figure 6A). The obtained images were then binarized using commercially available image software (Image-J) to make the filler area white and the silicone rubber area black (Figure 6B). The Otsu method was used for binarization.

[0063] Furthermore, by performing a two-dimensional Fourier transform analysis on this filler image, ellipse plots showing the direction and degree of filler alignment were obtained (Figures 6C and 6D, respectively). Because the two-dimensional Fourier transform itself has a peak in the direction perpendicular to the periodicity of the binarized image, the ellipse plots are the results of the two-dimensional Fourier transform with a phase shift of 90°. The alignment angle Φ can be calculated from the angle formed by the semi-major axis of this ellipse plot, and the filler alignment degree f, defined as f = 1 - (y / x) where x is the semi-major axis and y is the semi-minor axis, can be calculated.

[0064] The arrangement angle Φ represents the arrangement direction of the filler, and in Figures 6C and 6D, the 90°-270° direction represents the thickness direction of the elastic layer, and the 0°-180° direction represents the circumferential direction or rotation axis direction of the elastic layer. Therefore, the closer the arrangement angle Φ is to 90°, the more the filler is arranged in the thickness direction. Furthermore, the degree of arrangement f represents the flattening of the ellipse and is a value greater than or equal to 0 and less than 1. When f is 0, the ellipse becomes circular, representing a completely random state with no arrangement, and as f approaches 1, the flattening of the ellipse increases, and the degree of arrangement of the filler also increases.

[0065] In this way, a total of ten binarized images are obtained: a first binarized image measuring 150 μm x 100 μm at five locations on the first cross section in the thickness-circumferential direction of the elastic layer; and a second binarized image measuring 150 μm x 100 μm at five locations on the second cross section in the thickness-rotation axis direction of the elastic layer. Then, in the binarized images, the average area ratio occupied by the thermally conductive filler, the average degree of orientation f of the thermally conductive filler, and the average orientation angle Φ of the thermally conductive filler are measured. Each average value is calculated by averaging the values ​​at a total of ten locations.

[0066] The average degree of orientation (f) of the thermally conductive filler is preferably 0.10 to 0.50, more preferably 0.13 to 0.35. When f is 0.10 or more, thermal conductivity is easily exhibited, and when f is 0.50 or less, low hardness of the elastic layer is easily achieved. The average degree of orientation (f) can be controlled by the grid voltage (Vp-p), application time, frequency, etc. in the electric field application step described below.

[0067] The average alignment angle Φ of the thermally conductive filler is preferably 28 to 90°, more preferably 30 to 90°, and may be 30 to 55°. The direction where Φ is 90° corresponds to the thickness direction of the elastic layer, so the closer Φ is to 90°, the more aligned the filler is in the thickness direction. Therefore, by having Φ within the above range, thermal conductivity in the thickness direction can be improved. Here, 30° and 150° are mirror images of each other with respect to the 90° boundary, and therefore are synonymous in terms of heat transfer function in the thickness direction. Therefore, the alignment angle is expressed as 0 to 90°. The average alignment angle Φ can be controlled by the grid voltage (Vp-p), application time, frequency, etc. in the electric field application process described below.

[0068] The average area percentage (%) of the thermally conductive filler is preferably 27 to 45%, more preferably 30 to 45%. Here, the area percentage of the filler refers to [(total area of ​​the filler in the binarized image × 100) / (area of ​​the binarized image)]. When the average area percentage of the filler is 27% or more, the distance between the fillers is appropriate, a sufficiently large local electric field can be generated when an electric field is applied, and sufficient alignment can be achieved. Furthermore, when the average area percentage of the filler is 45% or less, the hardness of the elastic layer can be sufficiently reduced.

[0069] (2-3) Step of Applying an Electric Field to the Elastic Layer Hereinafter, as one embodiment, a corona charger 2 and a step of applying an electric field to the elastic layer using the corona charger will be described. Corona charging methods include a scorotron method that has a grid electrode between the corona wire and the body to be charged, and a corotron method that does not have a grid electrode. However, from the viewpoint of controllability of the surface potential of the body to be charged, the scorotron method is preferred.

[0070] 4A and 4B, the corona charger 2 includes a front block 201, a rear block 202, and shields 203 and 204. A discharge wire 205 is stretched between the front block 201 and the rear block 202, and when a charging bias is applied from a high-voltage power supply, the discharge wire 205 discharges and charges the surface of the uncured elastic layer 41c on the base layer, which serves as the member to be charged.

[0071] Similar to the configuration of a typical corona charger, a high voltage is applied to a discharge wire 205 serving as a discharge member. The ion flow obtained by discharge to the shields 203 and 204 is controlled by applying a high voltage to a grid 206, thereby controlling the surface of the elastic layer 41c to a desired charging potential. At this time, since the base layer 41d or the core 101 holding the base layer 41d is grounded (not shown), it is possible to generate a desired electric field in the elastic layer 41c by controlling the surface potential of the elastic layer 41c.

[0072] To explain the manufacturing method of the fixing rotor of the above embodiment in detail, first, an elastic layer made of silicone rubber containing a thermally conductive filler is formed on a base layer. Next, as shown in FIG. 4A, a corona charger 200 is placed adjacent to and facing the uncured elastic layer 41c of the fixing rotor 41 in the width direction. A voltage is applied to the grid 206 of the corona charger 2, and the fixing rotor 41 is rotated at 141 rpm for 160 seconds in a discharged state, thereby charging the surface of the elastic layer. The distance between the surface of the elastic layer and the grid 206 can be 1 mm to 10 mm. By charging the surface of the elastic layer 41c in this manner, an electric field is generated within the elastic layer, orienting the thermally conductive filler. The elastic layer is then cured by heating or other means, thereby fixing the filler orientation.

[0073] From the viewpoint of generating an effective electrostatic interaction in the filler, the voltage applied to the grid 206 is preferably in the range of 0.1 kV to 3 kV in absolute value (0.2 to 6 kV in Vpp in the case of AC application). When using an electric field to form the filler orientation in the thickness direction of the elastic layer, it is important to generate an electric field in the thickness direction of the elastic layer 41c. If the sign of the applied voltage is the same as the sign of the voltage applied to the wire, the effect obtained is the same whether the voltage is negative or positive, although the direction of the electric field will be reversed.

[0074] Furthermore, when AC charging is used to suppress the liquid surface flow described below, it is desirable to match the waveform phases of the wire and grid. Depending on the type of thermally conductive filler, it may be difficult to form an orientation of the irregular filler. In this case, it is desirable to increase the voltage applied to the grid 206. This is presumably related to the dielectric constants of the silicone rubber component and the thermally conductive filler. When the difference in dielectric constant between the silicone rubber and the filler is large, it is possible to form an orientation of the irregular filler with a relatively small applied voltage.

[0075] On the other hand, if the voltage applied to the grid 206 is too high, the electrostatic repulsive force due to the surface charge of the elastic layer will increase, causing the liquid surface to flow, which may result in a decrease in the surface properties of the elastic layer 41c. Therefore, it is more preferable that the voltage applied to the grid 206 be in the range of 0.1 kV to 1.5 kV in absolute value (1.2 to 3 kV in Vpp when AC is applied). This liquid surface flow can be alleviated by applying AC charging.

[0076] Here, we will explain the grid as a control electrode stretched in the longitudinal direction of the opening of the corona charger. Hereinafter, unless otherwise specified, the grid refers to a grid having a plurality of openings (through holes) that penetrate the grid in a mesh-like pattern. Figure 7 is an enlarged view of a portion of the grid 206 viewed from the elastic layer side to explain an example of the grid's outer shape.

[0077] As shown in FIG. 7 , the central portion of the grid 206 in the short direction (the direction in which the shields 203 and 204 in FIG. 4B face each other) is mesh-shaped, and both ends of the short direction are beam portions with a width of 1.5±0.1 mm, as shown in (6). The width of the through-holes in the grid 206 is 0.312±0.03 mm, as shown in (1). The angle of the through-holes relative to the longitudinal direction of the grid 206 is 45±1°, as shown in (3). (2) is the thickness of the mesh material, which is 0.071±0.03 mm. In addition, between the mesh portions, beams with a width of 0.1±0.03 mm, as shown in (4), are arranged in the longitudinal direction at intervals of 6.9±0.1 mm, as shown in (5), to suppress deflection of the grid 206.

[0078] From the viewpoint of making the charged potential on the surface of the elastic layer more uniform, it is preferable to etch a shape pattern including a width of 1.0 mm or less for the through-holes of the mesh. Furthermore, the higher the area ratio of the mesh portion to the through-hole portion, the easier it is to make the charged potential uniform. A flat grid 206 can be placed between the discharge wire 205 and the surface of the elastic layer. From the viewpoint of making the charged potential on the surface of the elastic layer more uniform, it is preferable that the distance between the surface of the elastic layer and the grid 206 be in the range of 1 mm to 10 mm.

[0079] As shown in FIG. 7 , this flat grid 206 is tensioned by tensioning sections disposed on the front block 201 and the rear block 202. Operating the knobs on the tensioning sections releases the support for the grid 206, allowing it to be easily attached and detached. Furthermore, a portion of the flat plate of the grid 206 near the tensioning section is bent, providing some flexibility. Therefore, even when the grid 206 is tensioned by the corona charger 2, it can move to some extent when subjected to an external force. The flat grid may be a mesh-like grid as shown in FIG. 7 , but is not limited to this shape. For example, a flat grid with a honeycomb structure as disclosed in Japanese Patent Application Laid-Open No. 2005-338797 may also be used.

[0080] For example, the configuration shown in FIG. 4A can be used to control the potential of the surface of the elastic layer in the direction of the rotation axis of the fixing rotor. While a voltage is being applied to the grid 206, the entire elastic layer 41c can be charged by rotating the core 101 around its central axis. It is preferable that the rotation speed of the fixing rotor be 10 rpm to 500 rpm, and that the treatment time be 20 seconds or more in order to stably form filler orientation. Examples of treatment times include 20 to 200 seconds. Thus, by controlling the surface potential and the time for applying the electric field, it is possible to control the formation of orientation in the irregular filler.

[0081] Although stainless steel, nickel, molybdenum, tungsten, etc. may be used for the discharge wire 205, it is preferable to use tungsten, which is an extremely stable metal. The discharge wire stretched inside the shield may have a circular cross section or a sawtooth cross section.

[0082] Furthermore, the diameter of the discharge wire 205 is preferably 40 μm to 100 μm. By keeping the diameter of the discharge wire within this range, it is possible to prevent the discharge wire from being cut by ions during discharge, and it is also possible to eliminate the need to excessively increase the voltage required to generate a corona discharge. The voltage applied to the discharge wire 205 can be either a DC voltage or an AC voltage. In the case of an AC voltage, a frequency of approximately 0.01 Hz to 1000 Hz is preferred. The voltage can be generated by outputting a rectangular wave, a sine wave, or the like using an arbitrary waveform generator.

[0083] (3) Adhesive Layer The adhesive layer 41b is not particularly limited as long as it can bond the elastic layer and the surface layer. For example, an addition-curing silicone rubber adhesive can be used. The addition-curing silicone rubber adhesive contains uncrosslinked silicone rubber components, and when heated, it bonds with the inner surface treatment layer of the surface layer and the uncrosslinked components of the elastic layer, thereby bonding the surface layer and the elastic layer.

[0084] The thickness of the adhesive layer is preferably 20 μm or less. By setting the thickness to 20 μm or less, the thermal resistance of the fixing rotor can be set low, and heat from the inner surface (substrate side) can be efficiently transferred to the recording material (recording medium). The thickness of the adhesive layer can be, for example, 1 to 20 μm, or 2 to 10 μm.

[0085] (4) Surface Layer The material of the surface layer 41a is not particularly limited, but preferably contains a fluororesin. Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer (PFA). PFA is preferred from the standpoint of releasability and rigidity. Commercially available PFAs can be used. Specific examples include AP-230 (trade name, manufactured by Daikin Industries, Ltd.), AP-231SH (trade name, manufactured by Daikin Industries, Ltd.), which is a PFA with fully fluorinated terminal groups, and 451HP-J (trade name, manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.), which has a small spherulite size. The thickness of the surface layer 41a is preferably 100 μm or less, and more preferably 10 to 70 μm.

[0086] The inner surface of the surface layer 41a can be treated in advance with sodium, excimer laser, ammonia, or plasma etching to improve adhesion. In the examples of the present disclosure, a 20 μm-thick PFA tube obtained by extrusion molding was used. It is preferable that the surface layer is not a heat-shrinkable tube. This can suppress an increase in hardness in the center, making it less likely to lose conformability, and maintaining flexibility, thereby further suppressing gloss unevenness.

[0087] The PFA tube can be produced, for example, by extruding molten PFA through a cylindrical die. Such a PFA tube is rapidly cooled during the extrusion process, causing rapid crystallization, resulting in crystals oriented in the extrusion direction and a low degree of crystallinity. After the PFA tube is coated on the surface of the elastic layer 41c to form the surface layer 41a, the surface layer is subjected to a heat treatment, as described below, to increase the degree of crystallinity and form spherulites on the surface of the surface layer.

[0088] In the present disclosure, in a TMA curve where the horizontal axis is temperature and the vertical axis is linear expansion coefficient, obtained by heating the surface layer 41a from 25°C to 250°C at a temperature increase rate of 10°C / min while pulling the surface layer 41a with a load of 25 mN in the direction of the rotation axis of the fixing rotor, the linear expansion coefficient at a temperature of 200°C is defined as B. B is, for example, -0.5 to 2.0%, and preferably 0 to 1.5%. If B is 1.5% or less, wrinkles in the surface layer after durable use are less likely to occur, and if B is 0% or more, gloss unevenness can be further suppressed.

[0089] The linear expansion coefficient B can be controlled by the crystallinity of the surface layer. For example, by subjecting the surface layer to a heat treatment to increase the crystallinity, the linear expansion coefficient B can be easily reduced. It is preferable to control the heat treatment and cooling rate on the elastic layer. By controlling the heat treatment and cooling rate on an elastic layer with a relatively high linear expansion coefficient, crystalline portions are easily formed when stress is applied in the direction of the rotation axis of the fixing rotor. Furthermore, controlling the cooling rate makes it easier to further increase the crystalline portions. As a result, the linear expansion coefficient is easily reduced.

[0090] Furthermore, when a measurement sample taken from the surface layer is subjected to calorimetry using a differential scanning calorimeter (DSC) by heating from 25° C. to 400° C. at a heating rate of 20° C. / min, the endothermic curve obtained during the heating process preferably shows an endothermic amount of 21 J / g or more. Hereinafter, an example will be described in which the surface layer 41 a is made of PFA, but the present invention is not limited to this.

[0091] The heat absorption during the temperature rise process is the heat absorption due to the crystalline melting of PFA. The crystallinity of PFA can be calculated by dividing the heat absorption value by the heat of complete crystalline melting of PTFE (92.9 J / g). When the heat absorption value is 21 J / g or more, there are many crystalline portions, and the linear expansion coefficient in the rotation axis direction of the fixing rotor can be reduced.

[0092] A method for achieving a heat absorption of 21 J / g or more includes, during the manufacturing process of the fixing rotor, heating the surface layer 41a after formation to a temperature above the melting point of PFA, and then controlling the cooling rate to promote crystallization of PFA.

[0093] Although the specific method is not particularly limited, the following methods for heat treatment of the surface layer can be used.

[0094] To heat the entire fixing rotor, an upright cylindrical heating cylinder capable of heating up to 330°C or higher is used. A band heater equipped with a thermocouple is installed inside the heating cylinder to control the heating temperature of the fixing rotor. The heating temperature is preferably between the melting temperature of PFA and 350°C or lower. The heating time may be any time long enough to allow the temperature of the surface layer to reach the desired temperature, and examples include 1 to 20 minutes, 1 to 10 minutes, and 2 to 5 minutes.

[0095] After heating is completed, the cooling rate of the fixing rotor is controlled by controlling the cooling rate of the heating barrel. For example, the cooling rate can be controlled by providing an air supply nozzle on the outer periphery of the heating barrel and adjusting the air flow rate. The slower the cooling rate in the crystallization temperature range of PFA, the more the crystallization of PFA can be promoted, and it is preferable to adjust the cooling rate so that the heat absorption is 21 J / g or more. The cooling rate is preferably controlled until the temperature of the surface layer falls below the crystallization temperature range of PFA. The cooling rate is, for example, 5 to 50°C / min, or 10 to 30°C / min.

[0096] The present disclosure will be described in more detail below using examples.

[0097] (1) Preparation of Liquid Addition-Cure Silicone Rubber Composition First, 100 parts by mass of a silicone polymer having vinyl groups, which are unsaturated aliphatic groups, only at both ends of the molecular chain and methyl groups as unsubstituted hydrocarbon groups containing no other unsaturated aliphatic groups, was prepared as component (a). This silicone polymer (trade name: DMS-V35, manufactured by Gelest, viscosity 5000 mm) ２ / s) will be referred to as "Vi" hereinafter.

[0098] Next, 160 parts by mass of metallic silicon (product name: #350, manufactured by Kinsei Matec Co., Ltd.) as component (d) thermally conductive filler was added to Vi and thoroughly mixed to obtain mixture 1.

[0099] Next, 0.2 parts by mass of 1-ethynyl-1-cyclohexanol (manufactured by Tokyo Chemical Industry Co., Ltd.), a cure retarder, dissolved in the same weight of toluene was added to the mixture 1 to obtain a mixture 2.

[0100] Next, 0.1 parts by mass of a hydrosilylation catalyst (platinum catalyst: a mixture of 1,3-divinyltetramethyldisiloxane platinum complex, 1,3-divinyltetramethyldisiloxane, and 2-propanol) as component (c) was added to mixture 2 to obtain mixture 3.

[0101] Furthermore, as component (b), a silicone polymer having a linear siloxane skeleton and having silicon-bonded active hydrogen groups only on the side chains (trade name: HMS-301, manufactured by Gelest Co., Ltd., viscosity 30 mm ２ 2.0 parts by mass of SiH (SiH 2 O 3 / s, hereinafter referred to as "SiH") was weighed out. This was added to Mixture 3 and mixed thoroughly to obtain a liquid addition-curable silicone rubber composition.

[0102] (2) Preparation of Fixing Belt A SUS endless belt with an inner diameter of 24 mm, a width of 400 mm, and a thickness of 30 μm was prepared as the base layer. During the entire manufacturing process, the endless belt was handled with a core inserted inside. A primer (product name: DY39-051A / B; manufactured by Dow Corning Toray Co., Ltd.) was applied uniformly to the outer peripheral surface of the base layer to a dry weight of 20 mg. After the solvent was dried, the belt was baked for 30 minutes in an electric furnace set at 160°C. The silicone rubber composition described above was applied to a thickness of 250 μm on the primer-treated base layer using a ring coating method. This is referred to as the uncured endless belt.

[0103] Next, a corona charger with a charging area width of 295 mm was positioned facing the uncured endless belt along its generator line, and an AC electric field was applied to the surface of the uncured elastic layer while the uncured endless belt was rotated at 100 rpm. The conditions were: current supplied to the discharge wire of the corona charger: ±150 μA; grid electrode potential: ±300 V (Vp-p: 600 V); frequency: 0.025 Hz; charging time: 160 seconds; and distance between the grid electrode and the belt: 3 mm. The charged uncured endless belt was heated in an electric furnace at 160°C for 1 minute (primary curing), and then heated in an electric furnace at 200°C for 30 minutes (secondary curing) to cure the silicone rubber composition, thereby obtaining an endless belt with a cured elastic layer.

[0104] Next, an addition-cure silicone rubber adhesive (product name: SE1819CV A / B; manufactured by Dow Corning Toray Co., Ltd.) was applied uniformly to the surface of the cured elastic layer of the endless belt to a thickness of approximately 10 μm as an adhesive layer. Meanwhile, PFA (product name: AP-231SH; manufactured by Daikin Industries, Ltd.) was extruded to an inner diameter of 23 mm and a thickness of 20 μm to form a fluororesin tube with an etched inner surface as a surface layer. The fluororesin tube was then laminated onto the endless belt with the adhesive layer while expanding its diameter. The belt surface was then uniformly rubbed from above the fluororesin tube, thereby squeezing excess adhesive out from between the elastic layer and the fluororesin tube until the thickness was approximately 5 μm. The endless belt was heated for 1 hour in an electric furnace set at 200°C to cure the adhesive and fix the fluororesin tube to the elastic layer.

[0105] The obtained endless belt was inserted into a heating cylinder with an inner diameter of φ42 mm and heated by a band heater inside the heating cylinder. The heating control temperature of the end of this fixing rotor was 330 ° C, and the heating was controlled so that the actual temperature of the surface layer was equal to or higher than the melting temperature of PFA. The heating time was 3 minutes after the fixing belt was placed in the heating cylinder, which was a time sufficient for the actual temperature of the surface layer to reach the desired temperature. After 3 minutes had passed since the insertion, the heating cylinder was cooled to 200 ° C at a rate of 20 ° C / min, and then removed from the heating cylinder into a room temperature atmosphere. Both ends of the obtained endless belt were cut to obtain a fixing belt with a width of 336.5 mm.

[0106] (3) Evaluation of Characteristics of Elastic Layer of Fixing Belt (3-1) Thermal Conductivity of Elastic Layer in Thickness Direction The thermal conductivity λ of the elastic layer in the thickness direction was calculated using the following formula: λ=α×C ｐ ×ρ In the formula, λ is the thermal conductivity of the elastic layer in the thickness direction (W / (m·K)), α is the thermal diffusivity in the thickness direction (m ２ / s), C ｐ is the specific heat at constant pressure (J / (kg K)), ρ is the density (kg / m ３ ) where the thermal diffusivity α in the thickness direction and the specific heat at constant pressure C ｐ The values ​​of ρ and density were determined by the following method.

[0107] Thermal diffusivity α The thermal diffusivity α in the thickness direction of the elastic layer was measured at room temperature (25°C) using a cyclic heating method thermal property measurement device (trade name: FTC-1, manufactured by Advance Riko Co., Ltd.). Sample pieces with an area of ​​8 × 12 mm were cut from the elastic layer with a cutter to prepare a total of five sample pieces, and the thickness of each sample piece was measured using a digital length measuring device (trade name: DIGIMICRO (registered trademark) MF-501 flat probe φ4 mm; manufactured by Nikon Corporation). Next, a total of five measurements were made for each sample piece, and the average value (m ２ The thermal diffusivity α in the thickness direction of the silicone rubber elastic layer was found to be 9.31×10 －７ m ２ / s.

[0108] ・Specific heat at constant pressure C ＰThe constant pressure specific heat of the elastic layer was measured using a differential scanning calorimeter (trade name: DSC823e, manufactured by Mettler Toledo K.K.). Specifically, aluminum pans were used as the sample pan and the reference pan. First, as a blank measurement, both pans were empty and kept at a constant temperature of 15°C for 10 minutes, then the temperature was increased to 215°C at a rate of 10°C / min, and the temperature was kept constant at 215°C for another 10 minutes. Next, 10 mg of synthetic sapphire with a known low-pressure specific heat was used as a reference material, and measurements were performed using the same program. Next, a 10 mg measurement sample, the same amount as the synthetic sapphire reference material, was cut out from the elastic layer and set in the sample pan, and measurements were performed using the same program. These measurement results were analyzed using specific heat analysis software attached to the differential scanning calorimeter, and the constant pressure specific heat C at 25°C was calculated from the average of five measurement results. Ｐ As a result, the specific heat at constant pressure of the silicone rubber elastic layer was found to be 1.05 J / (g·K).

[0109] Density ρ The density of the elastic layer was measured using a dry automatic density meter (product name: Accupyc 1330-01, manufactured by Shimadzu Corporation). ３ A sample cell of 1.0 mm was used, and a sample piece was cut out from the elastic layer so as to fill approximately 80% of the cell volume. The mass of this sample piece was measured and then placed in the sample cell. This sample cell was set in the measurement section of the device, and helium was used as the measurement gas. After gas replacement, volume measurements were carried out 10 times. The density of the elastic layer was calculated from the mass of the sample piece and the measured volume for each measurement, and the average value was obtained. As a result, the density of the silicone rubber elastic layer was found to be 1.53 g / cm. ３ It was.

[0110] From the above, the unit converted specific heat of the elastic layer at constant pressure C ｐ (J / (kg·K)) and density ρ (kg / m ３ ), and the measured thermal diffusivity α(m ２ The thermal conductivity λ of the elastic layer in the thickness direction was calculated from the thermal conductivity λ (m·K) of the elastic layer, and was found to be 1.5 W / (m·K).

[0111] (3-2) Linear expansion coefficient of the elastic layer in the direction of the rotation axis of the fixing rotor <Method for measuring the thermal expansion coefficient> First, the elastic layer is isolated from the fixing rotor. Specifically, the elastic layer can be isolated by inserting a razor or the like into the substrate-elastic layer interface and the surface layer-elastic layer interface. Then, the elastic layer is cut into a 20 mm x 2 mm strip to be used as a sample. The strip is cut so that the rotation axis direction is 20 mm.

[0112] Next, a sample was placed on a sample attachment using a thermomechanical analyzer (TMA), and measurements were performed under the following conditions: Apparatus: Thermomechanical analyzer TMA / SDTA2+ (trade name, manufactured by Mettler Toledo) Load: 25 mN Temperature: 25°C to 250°C at a rate of 10°C / min, then held for 5 minutes, and then cooled from 250°C to 25°C at a rate of 10°C / min The linear expansion coefficient A was calculated as follows: A = ((L2e - L1e) / L1e) × 100, where L1e is the length of the fixing rotor in the direction of the rotation axis at a temperature of 25°C, and L2e is the length of the fixing rotor in the direction of the rotation axis when the temperature was 200°C.

[0113] (3-3) Linear expansion coefficient of the surface layer in the direction of the rotation axis of the fixing rotor First, the surface layer is isolated from the fixing rotor. Specifically, the surface layer is peeled off from the substrate together with the elastic layer, and the elastic layer bonded to the surface layer is dissolved in a solvent, thereby isolating only the surface layer. Then, the surface layer is cut into strips of 20 mm x 2 mm to prepare samples. The strips are cut so that the direction of the rotation axis is 20 mm.

[0114] Next, a sample was placed on a sample attachment using a thermomechanical analyzer (TMA), and measurements were performed under the following conditions: Apparatus: Thermomechanical analyzer TMA / SDTA2+ (trade name, manufactured by Mettler Toledo) Load: 25 mN Temperature: 25°C to 250°C at a rate of 10°C / min, then held for 5 minutes, and then cooled from 250°C to 25°C at a rate of 10°C / min When the length of the fixing rotor in the direction of the rotation axis at a temperature of 25°C is denoted as L1s and the length of the fixing rotor in the direction of the rotation axis at a temperature of 200°C is denoted as L2s, the linear expansion coefficient B was calculated as follows: B = ((L2s - L1s) / L1s) × 100

[0115] Examples of the results for the linear expansion coefficients of the elastic layer and the surface layer are shown in Figures 8A-C. Figure 8A shows the linear expansion coefficient of the elastic layer. It was confirmed that the filler in the elastic layer was oriented in the thickness direction by applying an electric field, thereby increasing the linear expansion coefficient in the direction of the rotation axis of the fixing rotor. Figure 8B shows the linear expansion coefficient of the surface layer. For the surface layer, by performing a heat treatment and controlling the cooling rate on an elastic layer with a high linear expansion coefficient in the direction of the rotation axis of the fixing rotor, crystalline portions are formed with stress applied in the direction of the rotation axis of the fixing rotor. Furthermore, by controlling the cooling rate, the number of crystalline portions increases, reducing the linear expansion coefficient. As a result, the difference in the linear expansion coefficients at 200°C between the surface layer and the elastic layer is shown by the arrow in Figure 8C.

[0116] (3-4) Method for measuring the heat absorption amount of the surface layer First, the surface layer is isolated from the fixing rotor. Specifically, the surface layer is peeled off from the substrate together with the elastic layer, and the elastic layer bonded to the surface layer is dissolved in a solvent, whereby only the surface layer can be isolated.

[0117] The endothermic peak temperature and endothermic amount are measured using a differential scanning calorimeter (trade name: Q2000, manufactured by TA Instruments). The melting points of indium and zinc are used for temperature correction of the detector, and the heat of fusion of indium is used for heat correction. Specifically, 4 mg of the surface layer is precisely weighed and placed in an aluminum pan. An empty aluminum pan is used as a reference, and measurements are performed at a temperature rise rate of 20°C / min within a measurement range of 25°C to 400°C. The temperature is raised to 400°C once and held for 5 minutes, and then cooled to 25°C at a temperature drop rate of 20°C / min. During the temperature rise process, the area enclosed by the temperature-endothermic amount curve including the endothermic peak and the baseline is taken as the endothermic amount. From the above, the endothermic amount of the measured surface layer was 25 J / g.

[0118] (4) Evaluation with Actual Machine (Wrinkle Resistance, Image Gloss Unevenness, Fixability) (Evaluation Method) Next, the evaluation method in this example will be described. (Evaluation 1: Wrinkle Resistance with Paper Passage) Evaluation was carried out using the prepared fixing rotor and the heat fixing device shown in FIG. 2. The evaluation conditions were as follows: Test environment: room temperature 23°C, humidity 50% Process speed: 200 mm / sec Print speed: 30 sheets / min Paper passing conditions: a grid image was formed on GF-C081 (manufactured by Nippon Paper Industries Co., Ltd., 81 g paper, A4 size), and the paper was passed continuously.

[0119] Every 100,000 sheets, Mondi Color Copy (250g paper, SRA3 size, manufactured by Mondi Co., Ltd.) was passed through, and the presence or absence of scratches caused by wrinkles on the fixing rotor was checked at the edge of the A4 paper passing area. If scratches were found, it was considered to have reached the end of its service life, and was evaluated according to the following criteria: (Evaluation criteria) Rank A: No scratches caused by wrinkles occurred at 400,000 sheets Rank B: Scratches caused by wrinkles occurred at 400,000 sheets Rank C: Scratches caused by wrinkles occurred at 300,000 sheets Rank D: Scratches caused by wrinkles occurred by 200,000 sheets

[0120] (Evaluation 2: Evaluation of Image Gloss Unevenness) Evaluation was performed using the prepared fixing rotor in the heat fixing device shown in FIG. 2. The evaluation conditions were as follows: Test environment: room temperature 25°C, humidity 50% Process speed: 200 mm / sec Print speed: 30 sheets / min Paper feed conditions: black toner was applied at 0.4 mg / cm on Vitality (manufactured by Xerox Corporation, 75 g paper, A4 size). ３ A 100 mm x 100 mm image was formed, and the level of gloss unevenness was visually confirmed and evaluated according to the following criteria: (Evaluation criteria) A: Toner image gloss unevenness caused by the unevenness of the paper is hardly visible B: Toner image gloss unevenness caused by the unevenness of the paper is slightly visible C: Toner image gloss unevenness caused by the unevenness of the paper is noticeable D: Toner image gloss unevenness caused by the unevenness of the paper is particularly noticeable

[0121] (Evaluation 3: Fixability) Evaluation was carried out using the prepared fixing rotor in the heat fixing device shown in FIG. 2. The evaluation conditions were as follows: Test environment: room temperature 23°C, relative humidity 50% Process speed: 200 mm / sec Print speed: 30 sheets / min Paper passing conditions: a grid image was formed on GF-C081 (manufactured by Nippon Paper Industries Co., Ltd., 81 g paper, A4 size), and the paper was passed continuously.

[0122] Specifically, the fixing temperature of the heat fixing device was adjusted to the surface temperature of the fixing rotor in the copier, and five solid cyan images were formed in succession, and the image density of the fifth solid image was measured. Next, the toner surface of the solid image was heated to 4.9 kPa (50 g / cm ２ The toner surface was rubbed three times in the same direction with Silbon paper under a load of 10 ...

[0123] Example 2 A fixing belt was obtained in the same manner as in Example 1, except that the blending amount was changed so that the area ratio of the filler in the elastic layer was 31%.

[0124] Example 3 A fixing belt was obtained in the same manner as in Example 1, except that the time for the electric field application treatment for forming the elastic layer was changed to 30 seconds and the resin of the PFA tube was changed to 451HP-J (trade name, manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.).

[0125] Example 4 A fixing belt was obtained in the same manner as in Example 1, except that the time for the electric field application treatment for forming the elastic layer was changed to 20 seconds and the resin of the PFA tube was changed to 451HP-J (trade name, manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.).

[0126] Example 5 A fixing belt was obtained in the same manner as in Example 1, except that the blending amount was changed so that the area ratio of the filler in the elastic layer was 30%.

[0127] Example 6 A fixing belt was obtained in the same manner as in Example 1, except that the blending amount was changed so that the area ratio of the filler in the elastic layer was 29%.

[0128] Example 7 A fixing belt was obtained in the same manner as in Example 1, except that the blending amount was changed so that the area ratio of the filler in the elastic layer was 28%.

[0129] Example 8 A fixing belt was obtained in the same manner as in Example 1, except that the blending amount was changed so that the area ratio of the filler in the elastic layer was 38%.

[0130] Example 9 A fixing belt was obtained in the same manner as in Example 1, except that the filler in the elastic layer was changed to boron nitride (product name: SGP; manufactured by Denka Co., Ltd.) and the filler area ratio was changed to 20%.

[0131] Example 10 A fixing belt was obtained in the same manner as in Example 1, except that the filler in the elastic layer was changed to boron nitride (product name: SGP; manufactured by Denka Co., Ltd.) and the filler area ratio was changed to 30%.

[0132] Example 11 A fixing belt was obtained in the same manner as in Example 1, except that the blending amount of the filler in the elastic layer was changed so that the area ratio of the filler in the elastic layer was 45% and the resin of the PFA tube was changed to 451HP-J (trade name, manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.).

[0133] Comparative Example 1 A fixing belt was obtained in the same manner as in Example 1, except that the blending amount was changed so that the area ratio of the filler in the elastic layer was 25%.

[0134] Comparative Example 2 A fixing belt was obtained in the same manner as in Example 1, except that the blending amount was changed so that the area ratio of the filler in the elastic layer was 50% and the electric field application treatment was not carried out.

[0135] Comparative Example 3 A fixing belt was obtained in the same manner as in Example 1, except that the surface layer was not heated to a temperature equal to or higher than the melting point of PFA after it was formed.

[0136] <Comparative Example 4> A fixing belt was obtained in the same manner as in Example 1, except that after forming the surface layer, the belt was heated to a temperature equal to or higher than the melting point of PFA, and then the step of cooling the heating barrel to 200°C at a rate of 20°C / min was not carried out, but the belt was taken out of the heating barrel into a room temperature atmosphere and rapidly cooled.

[0137] Comparative Example 5: A fixing belt was obtained in the same manner as in Example 1, except that the filler content in the elastic layer was changed to 25% by area, no electric field application treatment was performed, and the surface layer was not heated to a temperature equal to or higher than the melting point of PFA after formation.

[0138] The results of these evaluations are summarized in the table below.

[0139] In Table 1, the area percentage is the area percentage of the thermally conductive filler. h-BN means boron nitride. The examples shown in this example were able to satisfy all of the requirements for suppressing wrinkles in the surface layer, suppressing uneven gloss in the image, and improving fixability.

[0140] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the present disclosure. Therefore, the following claims are appended to clarify the scope of the present disclosure. This application claims priority based on Japanese Patent Application No. 2024-085736, filed May 27, 2024, the entire contents of which are incorporated herein by reference.

[0141] 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-paper feed tray, 23: Registration roller pair, 31: Intermediate transfer film, 35: Secondary transfer roller, 40: Heat fixing device, 41: Fixing belt, 41a: Surface layer, 41b: Base layer, 41c: Elastic layer, 41d: Inner layer, 43: Heating element, 44: Pressure roller, 45: Contact thermistor, 46: Heater holder, 101: Core, 200: Corona charger, 201: Front block, 202: Rear block, 203, 204: Shield, 205: Discharge wire, 206: Grid, 401-1 First cross section, 401-2 Second cross section, P: Recording material, T: Toner

Claims

1. A fixing rotor comprising at least an endless base layer, an elastic layer on the outer peripheral surface side of the base, and a surface layer fixed to the outer peripheral surface side of the elastic layer via an adhesive layer, wherein the thermal conductivity of the elastic layer in the thickness direction is 1.0 W / mK or more, and wherein the elastic layer removed from the fixing rotor is pulled in the direction of the rotation axis of the fixing rotor with a load of 25 mN while being heated from 25°C to 250°C at a heating rate of 10°C / min, and in a TMA curve where the horizontal axis is temperature and the vertical axis is linear expansion coefficient, the linear expansion coefficient at a temperature of 200°C is defined as A, The surface layer removed from the fixing rotor is pulled in the direction of the rotation axis of the fixing rotor with a load of 25 mN while the temperature is raised from 25°C to 250°C at a temperature rising rate of 10°C / min to obtain a TMA curve with the horizontal axis being temperature and the vertical axis being linear expansion coefficient, where B is the linear expansion coefficient at a temperature of 200°C, and A>B and A-B is 2.0% or more.

2. The fixing rotating member according to claim 1, wherein the elastic layer contains silicone rubber, and the surface layer contains fluororesin.

3. The fixing rotating member according to claim 1 or 2, wherein A is 3.0 to 5.0%.

4. The fixing rotating member according to any one of claims 1 to 3, wherein B is 0 to 1.5%.

5. The fixing rotor according to any one of claims 1 to 4, wherein the elastic layer comprises rubber and a thermally conductive filler dispersed in the rubber, and in a total of ten binarized images consisting of a first binarized image of 150 μm x 100 μm in size at five locations on a first cross section in the thickness-circumferential direction of the elastic layer and a second binarized image of 150 μm x 100 μm in size at five locations on a second cross section in the thickness-rotational axis direction of the elastic layer, the average area ratio of the thermally conductive filler is 27 to 45%, the average degree of orientation f of the thermally conductive filler is 0.10 to 0.50, and the average orientation angle Φ of the thermally conductive filler is 28 to 90°.

6. The fixing rotor according to any one of claims 1 to 5, wherein the base layer contains at least one selected from the group consisting of nickel, copper, iron, and aluminum.

7. The fixing rotating body according to any one of claims 1 to 6, wherein the fixing rotating body is a fixing belt.

8. A heat fixing device having a heating member and a pressure member arranged opposite to the heating member, wherein at least one of the heating member and the pressure member is a fixing rotor according to any one of claims 1 to 7.

9. An electrophotographic image forming apparatus equipped with a heat fixing device, the heat fixing device having a heating member and a pressure member disposed opposite the heating member, and at least one of the heating member and the pressure member being the fixing rotatable member described in any one of claims 1 to 7.

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