JP5013700B2 - Image heating device - Google Patents

Description

  The present invention relates to an image heating apparatus suitable for use as a heating and fixing apparatus mounted on an image forming apparatus such as a printer, a copying machine, or a facsimile using an electrophotographic technique or an electrostatic recording technique.

  Examples of the image heating device include a fixing device that fixes an unfixed image on a recording material, and a gloss increasing device that increases the glossiness of an image by heating the image fixed on the recording material.

Conventionally, in an image forming apparatus, contact heating type apparatus is widely as apparatus for heating and fixing an unfixed toner image is formed and carried on the recording material as a solid Chakugazo. In this contact heating type fixing device, a rotatable heating member (hereinafter referred to as a fixing roller) having a surface temperature in contact with a recording material heated to a predetermined fixing temperature is brought into contact with the recording material at a nip portion. Te is for heating and fixing an unfixed toner image on the recording material as a solid Chakugazo.

  As the heating method of the fixing roller, there are an internal heating method and an external heating method (surface heating method). In the internal heating method, a heating means (heating source: heater) is disposed inside the fixing roller, and the fixing roller is heated from the inside to heat the surface of the fixing roller to a predetermined fixing temperature. In the external heating method, a heating unit is provided outside the fixing roller, and the fixing roller is heated from the outside to heat the surface of the fixing roller to a predetermined fixing temperature.

  Since the external heating system heats the fixing roller from the outside by the heating means, the surface of the fixing roller can be rapidly heated. Therefore, the warm-up time is shortened as compared with the internal heating type apparatus.

The apparatus of external heating type, and that of the non-contact type which is disposed a heating means in a non-contact with the fixing roller to heat the fixing roller in radiant heat, disposed in contact with the heating means with respect to the fixing roller Then, it is roughly classified into a contact type device that heats the fixing roller by heat conduction.

  Patent Documents 1 and 2 describe non-contact devices. Patent Document 3 describes a contact-type device.

  In the contact-type device of Patent Document 3, a small-diameter heating roller is brought into contact with the outer peripheral surface of the fixing roller as a heating unit. In this case, the small diameter heating roller is heated in a short time by a built-in heater such as a halogen heater, and the heating temperature of the fixing roller surface is increased in order to heat the fixing roller surface directly by the heating roller. It was.

  In these methods of heating the surface of the fixing roller from the outside, the elastic layer of the fixing roller is made of a silicone rubber or foamed silicone rubber having a low thermal conductivity as a heat insulating layer, and a fluororesin release layer is coated thereon as a surface layer. Is formed.

Furthermore, Patent Document 3 proposes a configuration in which a high thermal conductive silicone rubber layer is interposed between a heat insulating layer and a release layer as a heat storage layer. Accordingly, since the fixing roller surface is directly heated from the outside, the fixing roller surface can be rapidly heated, and the warm-up time is shortened. In addition, since the fixing roller has an elastic layer, it is possible to prevent the occurrence of uneven image gloss when the fixing roller uniformly contacts an unfixed image.
Japanese Patent Laid-Open No. 7-152271 Japanese Patent Laid-Open No. 9-54510 JP 2004-317788 A

  However, even with the above-described conventional external heating type fixing device, it is possible to achieve excellent performance in all of the shortening of the temperature rising time at the time of startup, the reduction of power consumption, and further high speed, high image quality, safety and durability. Is very difficult.

  For example, when the surface of a fixing roller having an elastic layer is externally heated by a heat source such as a halogen heater as in the non-contact type apparatus of Patent Documents 1 and 2, the recording material is fixed when the fixing roller is contaminated with toner. It may wind around the roller. When energization of the halogen heater is started in this state, there is a problem that the recording material is directly heated by the halogen heater.

  Further, in the contact-type device of Patent Document 3, the heat roller that heats the surface of the fixing roller is aimed to reduce the warm-up time. However, if the heating roller has a small diameter, The heating nip cannot be formed sufficiently. For this reason, the heat on the surface of the heating roller could not be efficiently transferred to the fixing roller, and as a result, the warm-up time was not as fast as expected. In order to improve this, when the diameter of the fixing roller or the heating roller is increased, the heat capacity increases, and it is difficult to shorten the warm-up time. In addition, due to poor heating efficiency, when the image forming apparatus is speeded up, it is difficult to maintain the surface of the fixing roller at a predetermined temperature when continuous printing is performed, resulting in poor fixing or reduced throughput. Had to be forced.

  In order to shorten the warm-up time, when using a roller with an elastic layer of the fixing roller in the form of a sponge, such as foamed silicone rubber, and with a PFA tube coated on the surface as a release layer, warm-up Time is shortened. However, the fixing roller surface temperature at which the toner image on the recording material can be fixed needs to be set high in the fixing nip portion. This is because the heat capacity is reduced because the fixing roller gives priority to heat insulation, and it becomes difficult to secure a sufficient amount of heat necessary for heat fixing at the fixing nip portion. Further, since the surface of the fixing roller has a heat insulating property, the amount of heat from the heating roller is not actively transferred. For this reason, it has been necessary to maintain the heating roller surface temperature at a temperature that is ten times higher than the fixing roller surface temperature. For this reason, high heat resistance has been required for the heating roller holding member and members around the heating roller.

  As a method for avoiding this, Patent Document 3 proposes that the elastic layer of the fixing roller is divided into two layers, the lower layer is a heat insulating layer, and the uppermost layer is a high thermal conductive silicone rubber layer. It is described so as to solve the above problems by storing heat.

  However, Patent Document 3 describes that a fluororesin layer is formed as a release layer on the surface of the fixing roller. Usually, the fluororesin layer has a low thermal conductivity, and according to our research, even if the fluororesin layer is formed as a thin layer of about 10 μm to 20 μm, the fluororesin layer is not a thermal barrier layer. As a result, the following problems occur.

  First, it takes time to diffuse the heat from the surface of the external heating roller to the high thermal conductive elastic layer that is the heat storage layer of the fixing roller. Therefore, in order to spread a sufficient amount of heat to the high thermal conductivity elastic layer, which is the heat storage layer of the fixing roller, the temperature of the heating roller is set high, and the temperature of the surface of the fixing roller is accordingly maintained, and eventually maintained at a high temperature. I had to do it.

  Furthermore, when the heat stored in the high thermal conductive elastic layer of the fixing roller is transmitted to the toner image on the recording material at the fixing nip, the fluororesin layer inhibits heat transfer.

  From the above, even when a high thermal conductive silicone rubber as a heat storage layer is interposed between the heat insulating layer and the release layer, it is sufficient when the warm-up time is shortened and the image forming apparatus is speeded up. Provisional fixing performance could not be provided.

  As described above, even in the case of a conventional external heating type fixing device, the time from receiving a print signal to heating and fixing a recording material on which an unfixed toner image is formed without consuming electric power during standby (hereinafter, (First printout time) cannot be reduced sufficiently. Accordingly, a fixing device that achieves high speed of the image forming apparatus, heats and fixes an image including a halftone image in a high quality state, achieves a long durability life, and achieves sufficient fixing performance for a recording material. Not realized.

  The present invention has been made to solve the above-mentioned problems of the prior art. Its purpose is to shorten the warm-up time and first printout time, reduce power consumption, achieve high performance in all aspects such as high speed, high image quality, long life, and safety, and provide an image that provides stable fixing performance. It is to provide a heating device.

In order to achieve the above object, a typical configuration of the image heating apparatus according to the present invention includes a rotatable heating member, a heating means for heating the heating member from the outside , and recording between the heating member. A pressure member that forms a nip portion for heating an image on the material, and an image heating apparatus that heats the recording material carrying the image by nipping and conveying the recording material at the nip portion. A heat insulating elastic layer is formed, a heat conductive filler is mixed in at least the outermost layer, and a heat conductive layer having a higher thermal conductivity than the heat insulating elastic layer is formed, and the heating means includes a flexible member. The heating member is brought into contact with the heating member and heated by a heating source from the inside to heat the heating member, and the flexible member has a thermal conductivity of at least 1 W / m · K or more. and said pressure member, 0.2 W / m · And it comprises the following having a thermal conductivity, which comprises a rotatable flexible member, and the elastic pressure member is pressed between the heating member via the flexible member It is characterized by that.

  According to the above apparatus configuration, an image that achieves stable image heating performance by achieving superior performance in all of the shortening of the heating time at the time of startup, the reduction of power consumption, and further high speed, high image quality, and long life. A heating device can be provided.

(1) Image Forming Apparatus FIG. 3 is a schematic configuration diagram of the image forming apparatus in this embodiment. This image forming apparatus is a laser printer using an electrophotographic process, and forms and outputs an image corresponding to image information input from an external device (not shown) such as a host computer on a recording material.

  Reference numeral 1 denotes a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) that is an image carrier, and is driven to rotate in a clockwise direction indicated by an arrow at a predetermined speed based on a print start signal. The peripheral surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by a charger 2. Image information is written on the uniformly charged surface by a laser scanner unit 3 constituted by unitizing a polyhedral mirror 3a, a polyhedral mirror rotating motor (not shown), a laser unit (not shown), and the like. The The laser scanner unit 3 outputs a laser beam L modulated in accordance with a time-series electric digital pixel signal of image information input from an external device to the printer, and scans the charging processing surface of the photosensitive drum 1 with the laser beam L. Exposure. Thereby, an electrostatic latent image of image information is formed on the photosensitive drum surface. The electrostatic latent image is developed as a toner image by the developing device 4. The toner images are sequentially transferred onto the surface of the recording material P at a transfer nip portion that is a pressure contact portion between the photosensitive drum 1 and the transfer roller 5.

  The recording material P is stacked and placed on the sheet stacking table 8a of the paper feed tray 8, and is picked up one by one from the uppermost recording material by the paper feed roller 9 driven at a predetermined control timing, and conveyed. It is sent to the resist portion by the roller 10 and the transport roller 10a. The registration portion includes a registration roller 11 and a registration roller 11a. The leading end of the recording material P is temporarily received by the nip portion to correct the skew of the recording material P, and then the recording material P is transferred to the transfer nip portion at a predetermined control timing. To feed.

  The recording material P that has received the transfer of the toner image at the transfer nip is separated from the surface of the photosensitive drum 1 and conveyed to the fixing device 12. The surface of the photosensitive drum after separation of the recording material is cleaned by removing residual deposits such as transfer residual toner by the cleaner 6 and repeatedly used for image formation.

The fixing device 12 heats the fixing an unfixed toner image on the recording material P as a solid Chakugazo. The recording material exiting the fixing device 12 is discharged onto a paper discharge tray 15 by a paper discharge unit including an intermediate paper discharge roller 13 and a paper discharge roller 14.

  Further, a cooling fan 16 is attached to the side surface of the printer main body, and the outside air is taken into the apparatus by appropriately rotating the fan 16 to cool the temperature rising portions such as the image forming unit and the electrical board in the apparatus. . A temperature detection means 17 such as a thermistor is attached in the vicinity of the cooling fan 16, and when the outside air is taken in by the cooling fan 16, the temperature of the environment in which the printer is installed is detected. The detection result is fed back to the temperature control sequence of the fixing device 12.

  In the image forming unit, the photosensitive drum 1, the charger 2, the developing device 4, and the cleaner 6 are configured as a unit as a process cartridge 7 that can be detachably attached to the printer main body.

(2) Fixing device 12
FIG. 1 is a schematic cross-sectional view of a fixing device 12 as an image heating device of an external heating method in this embodiment, and FIG. 2 is a schematic front view.

  Reference numeral 30 denotes a fixing roller (fixing member, fixing rotating body) as a rotatable heating member that heats an image on the recording material at the nip portion. Reference numeral 40 denotes a rotatable pressure roller as a pressure member. Reference numeral 20 denotes a heating unit as heating means for heating the fixing roller 30 from the outside.

  As will be described later, the fixing roller 30 includes a cored bar 31, a heat insulating elastic layer 32 formed in a roller shape on the outer periphery thereof, and a high heat conductive layer 33 as an outermost layer (a releasable layer) formed on the outer side thereof. , An elastic roller. The fixing roller 30 is disposed such that both ends of a cored bar 31 are rotatably supported between unillustrated apparatus side plates via bearings 34, respectively.

  As will be described later, the pressure roller 40 is an elastic roller having a cored bar 41, an elastic layer 42 formed in a roller shape on the outer periphery thereof, and a releasable layer 43 formed as an outermost layer on the outer side thereof. is there. The pressure roller 40 is arranged on the lower side of the fixing roller 30 substantially in parallel with the fixing roller, and both ends of the cored bar 41 are rotatably supported between the apparatus side plates (not shown) via bearings 44, respectively. The pressing mechanism shown in the figure is pressed against the lower surface of the fixing roller 30 with a predetermined pressing force. Thus, a fixing nip portion (pressure nip portion) Nt having a predetermined width is formed between the fixing roller 30 and the pressure roller 40 in the recording material conveyance direction.

  As will be described later, the heating unit 20 includes a plate-like heater 21 as a heating source and a heat insulating stay holder 24 that supports the heater 21. Moreover, it has a cylindrical heating film 23 as a flexible member (film-like member) that is loosely fitted on the holder 24 that supports the heater 21.

  The heating unit 20 is arranged in parallel with the fixing roller on the upper side of the fixing roller 30 with the heater 21 facing downward, and both end portions of the holder 24 are pressed down by the pressing springs 26 with a predetermined force. As a result, the heater 21 is pressed against the upper surface of the fixing roller 30 via the heating film 23, and a heating nip portion Nh having a predetermined width is formed between the heating unit 20 and the fixing roller 30 in the rotation direction of the fixing roller 30. The

  The length dimensions of the roller portions of the fixing roller 30 and the pressure roller 40 (the direction perpendicular to the recording material conveyance direction on the recording material conveyance path surface) and the length dimension of the effective heat generating portion of the heating unit 20 (the same) are fixed. It is larger than the maximum sheet passing width W of the apparatus.

  The fixing roller 30 is rotationally driven in a clockwise direction at a predetermined speed in FIG. 1 by a rotational force transmitted from a drive motor (not shown) to a drive gear 35 fixed to one end of the cored bar 31. The pressure roller 40 rotates following the rotation of the fixing roller 30. Further, the cylindrical heating film 23 of the heating unit 20 is brought into close contact with the surface of the heater 1 following the rotation of the fixing roller 30 and rotates around the stay holder 24 while sliding on the heater surface. The stay holder 24 also functions as a rotation guide member for the heating film 23. Further, the movement of the rotating heating film 23 in the thrust direction is restricted by the end flange 25.

  The pressure roller 40 and the heating film 23 can be configured to be driven by separate driving means.

  The rotating fixing roller 30 is heated from the outside of the roller by the heater 21 via the heating film 23 in the heating nip portion Nh, and the unfixed toner image T on the recording material P is heated and fixed at the fixing nip portion Nt. Necessary and sufficient heat is given.

As described above, the recording material P is transferred to the fixing device 12 after the toner image is transferred and formed by the image forming unit. The leading edge of the recording material is guided to the fixing nip portion Nt by a fixing inlet guide 51 made of heat-resistant grade PET, PBT, PPS or the like, and is nipped and conveyed by the fixing nip portion Nt. In nipping conveying process of the recording material, the recording material P is heated by the fixing roller 30, also receives the nip pressure, the unfixed toner image T is heat-pressure fixing as a solid Chakugazo the surface of the recording material P. The recording material that has exited the fixing nip Nt is separated from the surface of the fixing roller 30 and guided to a fixing discharge guide 52 formed of a heat-resistant grade PET, PBT, PPS, or the like, and then to the paper discharge unit. It is conveyed.

  That is, the energization heating resistor layer of the heater 21 is energized while the fixing roller 30, the pressure roller 40, and the heating film 23 are rotated, and the surface temperatures of the heater 21 and the fixing roller 30 are kept at a predetermined temperature. In this state, the recording material P on which the unfixed toner image T is formed is introduced into the fixing nip portion Nt, whereby the unfixed toner image T on the recording material P is heated and fixed to obtain a fixed image.

The state of the toner image T and the fixing roller 30 in the fixing nip portion Nt at this time will be described with reference to FIG. When the recording material P on which the unfixed toner image T is formed is introduced into the fixing nip portion Nt, the toner image T is pressed by the surface of the fixing roller 30 and is crushed. At this time, since the fixing roller 30 has elasticity, it is slightly deformed corresponding to the unevenness of the toner image T. As a result, the high thermal conductive layer 33 which is the outermost layer of the fixing roller 30 is recessed so as to wrap the toner image T. As a result, the contact area of the fixing roller 30 increases with respect to the toner image T, and heat is efficiently transferred from the fixing roller 30 to the toner image T on the recording material P. Thus, the toner image T on the recording material P is stuck to the recording material P as a fixed images. In particular, since the fixing roller 30 is an elastic member as shown in the present embodiment, even if the toner image is on a recording material having a large surface roughness, the surface of the fixing roller can follow the unevenness of the recording material P. And fixing uniformity on the recording material P can be obtained. Further, the heat supply to the toner image T mainly uses the heat stored in the high heat conductive layer 33 which is the outermost layer of the fixing roller 30. Therefore, it is possible to immediately store the amount of heat necessary for the high heat conductive layer 33 and efficiently transfer it to the toner image T.

  The fixing device of this embodiment having such a configuration can simultaneously achieve a short warm-up time and a short first print time, low power consumption, and fixing uniformity.

  The heating nip portion Nh and the fixing nip portion Nt are formed at different positions on the circumference of the fixing roller 30. The shorter the distance between the heating nip portion Nh and the fixing nip portion Nt on the periphery of the fixing roller, the less heat is radiated into the air and the heat escape to the inside of the fixing roller. Heat can be transported efficiently.

  On the other hand, when the positions of the fixing nip portion Nt and the heating nip portion Nh are opposed to each other with a half rotation of the fixing roller as shown in FIG. 1, the pressing force of the heater 21 to the fixing roller 30 and the pressure roller 40 are The pressure applied to the fixing roller 30 cancels each other out. Therefore, the bending of the fixing roller 30 can be suppressed to a low level, and the strength required for the cored bar is reduced, so that there is an advantage that the diameter can be easily reduced and the heat capacity can be easily reduced.

  When the diameter of the fixing roller 30 is reduced, as a result, the distance between the heating nip portion Nh and the fixing nip portion Nt can also be shortened. Therefore, when there is no need for a large difference in the pressure applied to the fixing roller 30 between the heater 21 and the pressure roller 40, the fixing nip portion Nt and the heating nip portion Nh are preferably arranged to face each other as shown in FIG. .

(3) Fixing roller 30
In the present embodiment, the fixing roller 30 is described as an example of the heating member, but the heating member may be configured in a belt shape having flexibility. In the following description of the present embodiment, a part of the description is added if the belt is unique.

  Further, the thermal conductivity of the heat insulating elastic layer 32 and the high thermal conductive layer 33 of the fixing member 30, the film-like member 23 of the heating unit 20, or various materials described below is measured in the following manner.

  That is, a test piece is cut out from each layer, film-like member, or various materials. About the test piece, the thermal diffusivity of the thickness direction is measured with the Fourier-transform type temperature thermal diffusivity measuring apparatus (model number FTC-1, ULVAC-RIKO Co., Ltd. product). And the heat conductivity of the thickness direction of each layer or a film-like member or various materials is calculated | required from the following formula.

Thermal conductivity = thermal diffusivity × specific gravity × specific heat Specific gravity is determined by measuring the above test piece with an electronic hydrometer (model number SD-200L, manufactured by Alpha Mirage Co., Ltd.).

  The specific heat is obtained by measuring the test piece with a differential scanning calorimeter (model number DSC8240, manufactured by Rigaku Corporation).

(3-1) Core 31
The cored bar 31 is made of aluminum, iron, SUM material, or the like. The form may be solid or a hollow cylinder, and the form is not limited.

(3-2) Insulating elastic layer 32
A heat insulating elastic layer 32 formed by the following method is formed outside the cored bar 31. When the heating member is a fixing belt, the following heat insulating elastic layer 32 is formed using a heat resistant resin such as polyimide or a metal such as SUS / Ni as a base layer.

  The heat insulating elastic layer 32 is, for example, a silicone rubber composition, and is a silicone obtained by blending 0.1 to 200 parts by weight of a hollow filler having an average particle size of 500 μm or less with 100 parts by weight of a thermosetting organopolysiloxane composition. It is formed by heat-curing the rubber composition.

  Here, as the hollow filler, there is a microballoon material or the like that reduces the thermal conductivity like sponge rubber by having a gas portion in the cured product. Such materials may be any of glass balloons, silica balloons, carbon balloons, phenol balloons, acrylonitrile balloons, vinylidene chloride balloons, alumina balloons, zirconia balloons, shirasu balloons and the like.

Specific examples of the inorganic microballoon are listed below, but the present invention is not limited thereto. Examples of the Shirasu balloon include winlite manufactured by Ijichi Kasei Co., Ltd. and Sankilite manufactured by Sanki Kogyo Co., Ltd. Examples of the glass balloon include Caloon made by Nippon Sheet Glass Co., Ltd., Cellstar made by Asahi Glass Co., Ltd., and Glass Bubbles Filler made by 3M Co., Ltd. Examples of the silica balloon include Q-CEL manufactured by Asahi Glass Co., Ltd. Examples of the fly ash balloon include CEROSHERES manufactured by PFAMARKETING. As the alumina balloon, BW manufactured by Showa Denko KK can be mentioned . Examples of the zirconia balloon include HOLLOW ZIRCONIUM SPHEES manufactured by ZIRCOA. Examples of the carbon balloon include Kureha Fair, Kureha Fair.

  The hollow filler itself is preferably elastic. For example, a hollow balloon made of a thermoplastic resin, particularly a vinylidene chloride, acrylonitrile, methacrylonitrile, acrylic acid ester, a polymer of acrylate ester or a copolymer of two or more of these is suitable.

  Furthermore, examples of the thermally expandable microballoon material include Matsumoto Microsphere-F Series from Matsumoto Yushi Seiyaku Co., Ltd., Expandance Series from Expancel, and the like. In the case of a thermally expanded microballoon, the unexpanded resin microcapsule usually has a diameter of about 1 to 50 μm, and is expanded at an appropriate heating temperature to form a substantially spherical shape having a diameter of about 10 to 500 μm. It can be a close sphere.

  Further, an inorganic filler or the like may be attached to the surface for the purpose of giving the strength of the hollow filler. In this case, in order to sufficiently reduce the thermal conductivity in the silicone rubber composition, the true specific gravity of the hollow filler is preferably 0.01 to 1.0, more preferably 0.01 to 0.5. It is.

  However, when a thermally expanded microballoon is used, the true specific gravity of the microballoon when not expanded is preferably about 0.5 to 1.4. If the true specific gravity is too small, not only is it difficult to mix and handle, but the pressure resistance of the hollow filler is insufficient and it is destroyed during molding, making it impossible to reduce the weight and decrease the thermal conductivity. Moreover, when specific gravity is too large, the thickness of the shell of a hollow filler will be large, and the case where a heat conductivity fall may not become enough.

  The average particle diameter of the hollow filler is 500 μm or less, preferably 300 μm or less. If the average particle size is too large, the hollow filler will be destroyed by the injection pressure at the time of molding, resulting in problems such as increased thermal conductivity and increased surface roughness after roll molding. . The lower limit of the average particle diameter of the hollow filler is not particularly limited, but is usually 10 μm, particularly 20 μm.

  The average particle diameter of the hollow filler can be usually obtained as a weight average value (or median diameter) by a laser light diffraction method.

  The amount of the hollow filler is 0.1 to 200 parts by weight, preferably 0.2 to 150 parts by weight, more preferably 0.5 to 100 parts by weight with respect to 100 parts by weight of the thermosetting organopolysiloxane composition. Part.

  In this case, it is preferable to blend so that the content of the hollow filler in the silicone rubber composition is 10 to 80%, particularly 15 to 75% by volume. If the volume ratio is too small, the decrease in thermal conductivity is insufficient, and if it is too large, molding and blending are difficult, and the molded product may be brittle without rubber elasticity.

  In addition, when the thermally expanded microballoon is mixed with the organopolysiloxane composition without being expanded, it is considered that the microballoon is thermally expanded. For example, about 100 to 10 parts by weight of the organopolysiloxane composition, about 0.1 to 10 parts by weight of unexpanded microballoons are mixed and heat-cured to form a heat insulating elastic layer with good heat insulation.

  On the other hand, as the thermosetting organopolysiloxane composition, a thermosetting organopolysiloxane composition having a known composition for forming a silicone rubber layer can be used. It may be of type.

  The structure of the organopolysiloxane composition basically has a linear structure, but may partially have a branched structure, a cyclic structure, or the like.

  The molecular weight is not particularly limited, and it can be used from a liquid with a low viscosity to a raw rubber with a high viscosity. However, in order to cure and become a rubbery elastic body, the viscosity at 25 ° C. is 100 centipoises or more, and is usually preferably 100 to 1,000,000, particularly 500 to 100,000.

  In the thermosetting organopolysiloxane composition, as other components, if necessary, a filler, a reinforcing agent, a conductive agent, a hydrosilylation reaction control agent, a heat-resistant agent, an internal release agent, an adhesiveness imparting agent, It is optional to mix a thixotropic agent, a continuous foaming agent and the like. Examples of the filler include silica fine particles and calcium carbonate. The reinforcing agent is, for example, a silicone resin. Examples of the conductive agent include carbon black, conductive zinc white, and metal powder. Examples of the hydrosilylation reaction control agent include nitrogen-containing compounds, acetylene compounds, phosphorus compounds, nitrile compounds, carboxylates, tin compounds, mercury compounds, sulfur compounds, and the like. Examples of the heat-resistant agent are iron oxide and cerium oxide. The internal mold release agent is, for example, dimethyl silicone oil. The foaming agent is, for example, triethylene glycol.

  Here, it is desirable that the silicone rubber composition has a cured product (silicone rubber) having a thermal conductivity of 0.15 W / m · K or less, preferably 0.13 W / m · K or less. It is preferable to adjust the blending composition so as to achieve the above. If the thermal conductivity is higher than 0.15 W / m · K, the object of the present invention cannot be achieved.

  The thickness of the heat-insulating silicone rubber layer is not particularly limited, but in order to form a small-diameter fixing roller 30 having an effective heat-insulating property and not having an excessively large heat capacity, 2.0 to 5. 0 mm, preferably 2.5 to 4.0 mm is preferable.

  The outer diameter of the fixing roller 30 is desirably a low heat capacity of φ22 mm or less.

  On the other hand, when a fixing belt is used as the heating member, the thickness of the heat insulating silicone rubber layer is preferably set to about 0.5 to 2.0 mm.

(3-3) High thermal conductivity layer (release layer) 33
At least one high thermal conductive layer 33 is formed on the outer surface of the fixing roller 30 as a releasable layer, and the thermal conductivity of the high thermal conductive layer 33 is 0.35 W / m · K or more, preferably 0.8. It is desirable that the thickness is 38 W / m · K or more and the thickness is 20 to 200 μm. When the high thermal conductive layer 33 is formed by a plurality of layers, the thermal conductivity of the entire multilayer is 0.35 W / m · K or more, preferably 0.38 W / m based on the thickness and thermal conductivity of each layer. -It can be a layer of K or more. Also in this case, it is desirable that the thermal diffusivity, specific heat, and specific gravity of a plurality of layers are measured by the above measuring devices so as to obtain a desired thermal conductivity. However, if the heat conductivity of the outermost layer is too low, the diffusion of heat from the heating member deteriorates, so even if the high heat conductive layer is formed of a plurality of layers, the heat conductivity of the outermost layer is slightly However, it is preferable to raise it. Therefore, after the thermal conductivity of the lower layer of the plurality of high thermal conductive layers is formed with a layer exceeding 0.35 W / m · K, the outermost layer is a layer with a slightly higher thermal conductivity (0.35 W / m It is also possible to form a thin film (which may be lower than m · K).

  The high heat conductive layer 33 is formed on the outermost surface of the fixing roller, is heated by the heating unit 20 at the heating nip portion Nh, and contacts the unfixed toner image on the recording material at the fixing nip portion Nt.

  For this reason, the material used for the high thermal conductive layer 33 is required to have good heat resistance and toner releasability. Examples of preferable materials that satisfy such requirements include fluororesin, polyphenylene sulfide, and polysulfone. Furthermore, polyetherimide, polyethersulfone, polyetherketone, liquid crystal polyester, polyamideimide, polyimide, silicone rubber and the like can be exemplified.

  The fluorine resin layer is formed of a fluorine resin coating agent or a fluorine resin tube. Examples thereof include polytetrafluoroethylene resin (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA). Furthermore, a fluoroethylene polypropylene copolymer resin (FEP), a polyvinylidene fluoride resin (PVDF), a polyvinyl fluoride resin (PVF), etc. can be mentioned.

  The coating may be any method such as latex, Daiel latex (made by Daikin Industries, Ltd., fluorine latex), dipping coating using a dispersion, or spray coating.

  However, the materials listed above have low thermal conductivity, and the object of this example is not achieved when they are used as they are. Therefore, it is preferable to form the high thermal conductive layer 33 by adding a member having high thermal conductivity to the above material.

  For example, as one method, a layer in which 10 vol% to 50 vol% of a powdery high thermal conductive filler made of a material having a thermal conductivity of at least 10.0 W / m · K or more is mixed in the silicone rubber is used as the heat insulating elastic layer 32. The top is coated with a thickness of about 10 to 150 μm. Furthermore, a layer in which 10 vol% to 50 vol% of a powdery high thermal conductive filler made of a material having a thermal conductivity of at least 10.0 W / m · K or more is mixed in PFA with a thickness of 10 to 50 μm is formed on the outer surface. These two layers constitute a high thermal conductive layer 33.

  The above powdery high thermal conductive filler includes, for example, metal oxides such as AlN, graphite, and alumina, metals such as carbon nanotubes, diamond, aluminum, titanium alloys, and copper alloys, ticker boron, ticker silicon, silicon carbide, and crystallinity. Such as silica.

  Alternatively, the PFA mixed with the high thermal conductive filler is directly formed as the high thermal conductive layer 33 on the outer surface of the heat insulating elastic layer 32 with a thickness of 20 to 200 μm to be the outermost layer.

  Alternatively, a silicone solid rubber layer mixed with a high thermal conductive filler is formed on the outer surface of the heat insulating elastic layer 32 with a thickness of 20 to 200 μm to be the outermost layer.

  However, when a high thermal conductive filler is mixed in the silicone solid rubber layer, there is a concern that the releasability is lowered. Therefore, it is better to take measures such as simultaneously mixing a member with good releasability such as fluororesin particles into the solid rubber layer, or enriching the low molecular components of the solid rubber layer in advance.

  When forming a plurality of layers mixed with a high heat conductive filler as the high heat conductive layer 33 formed on the surface of the fixing roller, the particle size of the high heat conductive filler to the outermost layer is the surface property of the outermost layer. Take care not to lower it. That is, the average particle diameter is 3.5 μm or less, preferably 3 μm or less.

  Moreover, as long as it is a means to achieve high thermal conductivity, the type of filler material is not limited, and the shape of the filler may be any shape, and in order to achieve the purpose of this embodiment There are no restrictions.

(3-4) Manufacturing Method of Fixing Roller 30 The manufacturing method of the fixing roller 30 is not particularly limited. A heat insulating elastic layer 32 having a thermal conductivity of 0.15 W / m · K or less is formed on a metal core 31. Further, any manufacturing method may be used as long as at least one high thermal conductive layer 33 having a thickness of 20 to 200 μm and a thermal conductivity of 0.35 W / m · K or more is formed on the outermost layer.

  Several examples of the method for manufacturing the fixing roller 30 according to this embodiment will be described below with reference to FIGS. However, in this embodiment, the heating member is not limited to the fixing roller, and may be a flexible belt-shaped fixing belt. In this case, instead of the following core metal, a metal core mold may be inserted into the inside of a heat-resistant resin belt made of polyimide or the like as if it were handled in the same manner as the core metal of the following manufacturing method.

  31, 32, and 33 are the core metal, the heat insulating elastic layer, and the high thermal conductive release layer of the fixing roller 30 as described above.

  Reference numeral 101 denotes a cylindrical mold for silicone rubber casting. Reference numeral 102 denotes an end cap mold having a casting hole 103. Reference numeral 104 denotes an end cap mold positioned opposite to the end cap mold 102. Reference numeral 105 denotes a chuck member that holds the cored bar 31. For example, the cored bar 31 is inserted into the cylindrical mold 101, the end caps 102 and 104 are mounted at the ends, and the end cored bar chuck member 105 is mounted. It is fixed inside. At this time, for example, PFA powder mixed with a high thermal conductive filler is electrostatically adsorbed in advance on the inner surface of the cylindrical mold 101, or a fluororesin tube 33 mixed with a high thermal conductive filler is extruded. You can keep it. Alternatively, a method in which a liquid fluororesin such as a PFA dispersion mixed with a high thermal conductive filler is previously applied to the inner surface of the cylindrical mold and dried.

  When powder is electrostatically adsorbed on the inner surface of the cylindrical mold or when liquid fluororesin is applied to the cylindrical mold, the fluororesin is previously heated at a high temperature of 360 to 410 ° C. before the silicone rubber casting described later. Is fired for 1 to 3 hours to form a highly heat-conductive fluororesin layer.

  When the high thermal conductivity fluororesin powder or the high thermal conductivity fluororesin tube is formed as a release layer, the contact surface with the silicone rubber layer may be previously subjected to a treatment that favors adhesion with the silicone rubber. preferable. Examples of such treatment include corona discharge treatment, sodium naphthalene method, sputter etching method, liquid ammonia method, inert gas plasma treatment, and excimer laser treatment. Furthermore, a primer treatment may be applied to improve the adhesion durability.

  In the above state, a liquid silicone composition mainly composed of organopolysiloxane containing a balloon such as a microballoon is injected from the casting hole 103 of the end cap mold 102.

  As a previous step, a high heat conductive silicone solid rubber layer mixed with a high heat conductive filler is applied to the inner surface of the high heat conductive fluororesin tube attached to the inner surface of the cylindrical mold 101 by a method such as spray coating, with a predetermined thickness, Keep dry. A high thermal conductive surface layer having a predetermined thickness may be formed in a plurality of layers by such a method.

  Alternatively, the heat insulating elastic layer 32 is formed on the cored bar 31 with a liquid silicone composition mainly composed of an organopolysiloxane containing a balloon such as a microballoon. Thereafter, a high heat conductive silicone solid rubber layer is formed on the surface to a predetermined thickness by spray coating or other methods, and then precure is performed. Further, there is a method in which a high heat conductive fluororesin layer is coated on the outer layer by post-processing by a method such as dipping coating or spray coating. Alternatively, there is a method of coating by post-processing such as a method in which a heat-shrinkable high heat conductive fluororesin tube is inflated with air and a roller coated with the high heat conductive silicone solid rubber layer is inserted into the tube and then thermally contracted.

  A manufacturing method, an order, etc. can be determined arbitrarily. In this case, in order to ensure the adhesive strength with the high thermal conductive silicone solid rubber layer provided inside the high thermal conductive fluororesin layer, the surface of the high thermal conductive silicone solid rubber such as corona discharge treatment or inert gas plasma treatment is used. It is desirable to perform a modification treatment. Moreover, you may perform a primer process.

  Although it is necessary to cure the silicone rubber composition formed as described above, the curing conditions are not particularly limited. Generally, it is heated and cured (precured) at 100 to 150 ° C. for 10 minutes to 2 hours, further formed to the outermost layer and removed from the cylindrical mold at a temperature of 180 to 200 ° C. for 2 to 4 hours. Time post cure is preferred.

  In addition, the process for performing the pre-curing varies depending on each manufacturing process, and it is desirable to perform according to the manufacturing process.

  Further, when the outermost layer is a coating agent of a highly heat-conductive fluororesin (when a roller-shaped member having a heat insulating layer is formed first and the outermost layer is coated on the outer surface), it is several at a temperature of 360 ° C. to 400 ° C. Apply heat from the surface for a minute. Thereby, the manufacturing method of melt | dissolving a fluororesin once and forming a highly heat-conductive fluororesin layer after cooling is mentioned.

  Moreover, as a silicone rubber composition which forms the heat insulation elastic layer 32, there exists the method of adding a water absorbing polymer and water other than adding said hollow filler.

  Such a silicone rubber composition includes 100 parts by weight of an organopolysiloxane composition, 0.1 to 50 parts by weight of a water-absorbing polymer, 10 to 200 parts by weight of water, a curing catalyst such as a platinum compound catalyst, SiH It is prepared by adding a crosslinking agent such as a polymer. This may be thermoformed to form the heat insulating elastic layer 32.

  In this case, heating is performed in the following three or two stages. That is, in the first stage, the silicone base polymer is not substantially cured and moisture is not evaporated, and the mold is formed by heating at 100 ° C. or less, preferably 50 to 80 ° C. for 10 to 30 hours.

  Next, in the second stage, the molded product is heated to 120 to 250 ° C., preferably 120 to 180 ° C. for 1 to 5 hours, to evaporate water contained in the water and impurities contained in the water. . Depending on the heating conditions when the moisture evaporates, each independent bubble may be converted into an open cell structure or may not be converted. If the curing speed is high, the number of independent bubbles increases without conversion, and if controlled so that substantial curing due to crosslinking does not occur, the structure is converted to an open cell structure.

  In the final third stage, the obtained foam is heated at 180 to 300 ° C., preferably at 200 to 250 ° C. for 2 to 8 hours, to proceed with curing, so that a desired porous rubber-like elastic body is obtained. Complete the silicone rubber layer.

  In the case of two-stage heating, there is a method in which the two stages after the heating stage are continuously performed at the same heating temperature. In this case, since curing is performed at a high temperature, there is a tendency that curing is performed with independent bubbles.

Moreover, as a silicone rubber composition which forms the heat insulation elastic layer 32, the sponge-like silicone rubber layer widely used conventionally can be mentioned. This is an elastic layer obtained by foaming silicone rubber, and can also be used in this embodiment. Examples of the foamed silicone rubber include a method of adding a pyrolytic foaming agent and a method of molding a foam using hydrogen gas by-produced during curing as a foaming agent. However, the method of adding a pyrolytic foaming agent has been problematic in terms of the toxicity and odor of the decomposition gas, and in the case of using a platinum catalyst as the curing catalyst, there has been a problem of inhibition of curing by the blowing agent. Furthermore, in the method using hydrogen gas by-produced during curing, there are problems such as the flammability of hydrogen gas and caution when handling uncured products during storage. In addition, there is a problem that it is difficult to obtain a foamed silicone rubber having fine and uniform cells in molding such as injection molding in a mold. Since it was difficult to form minute and uniform cells, the cell diameter in the foamed silicone rubber was easily formed non-uniformly, the cell wall thickness was also non-uniform, and the strength varied greatly. From this, it has been confirmed that when formed as a small-diameter fixing roller or a fixing belt, if the fixing member is continuously tensioned with a small radius of curvature, the weak cell wall is broken and bubbles are broken. In addition, it has been difficult to achieve both durability and heat insulation with foamed silicone rubber. That is, when the silicone rubber foam of uneven foaming diameter, increasing the expansion ratio to increase the thermal insulation cell walls become thinner constituting the elastic layer, that a foam breaking is more likely to occur by the durability.

  Therefore, in the present embodiment, when the foamed silicone rubber is used as the heat insulating elastic layer 32 of the fixing roller or the fixing belt, the speed of the image forming apparatus and the life of the fixing apparatus can be used only within a certain range.

  From the above, the heat insulating elastic layer 32 is a liquid mainly composed of a balloon such as a microballoon or an organopolysiloxane containing a water-absorbing polymer from the viewpoint of speeding up the image forming apparatus and extending the life of the fixing apparatus. It is more suitable to form from a silicone composition.

(4) Heating means 20
The heating unit 20 shown in FIGS. 1 and 2 as a heating unit for heating the fixing roller 30 from the outside includes a plate heater 21, a heating film 23, a stay holder 24, and the like.

(4-1) Heater 21
As shown in the schematic cross-sectional view of FIG. 6, the plate heater 21 as a heating source includes an insulating ceramic such as alumina or aluminum nitride, or a substrate 21 a made of heat resistant resin such as polyimide, PPS, or liquid crystal polymer. The substrate 21a is an elongated thin plate member having a longitudinal direction in the drawing as a longitudinal direction, and the length dimension is larger than the maximum sheet passing width W of the fixing device.

Along the longitudinal direction on the surface of the substrate 21a (fixing roller facing surface), for example, an energization heating resistance layer 21b such as Ag / Pd (silver palladium), RuO ₂ , Ta ₂ N, etc. is formed by screen printing or the like with a thickness of about 10 μm It is formed by coating in the form of a line or a thin strip of about 1 to 5 mm.

  On the surface side of the heater, a protective sliding layer 21c may be provided that protects the energization heating resistor layer 21b within a range that does not impair the thermal efficiency. However, it is preferable that the thickness of the protective sliding layer 21c is sufficiently thin and the surface property is improved. Examples of the material include polyimide (PI), perfluoroalkoxy resin (PFA), polytetrafluoroethylene resin (PTFE), and tetrafluoroethylene-hexafluoropropylene resin (FEP). Furthermore, ethylene tetrafluoroethylene resin (ETFE), polychlorotrifluoroethylene resin (CTEF), polyvinylidene fluoride (PVDF), etc. are mentioned.

  The resin material as described above is coated alone or mixed to form the protective sliding layer 21c. Alternatively, a protective sliding layer 21c may be considered in which a dry coating lubricant made of graphite, diamond-like carbon (DLC), molybdenum disulfide, or the like, glass coating or the like is coated alone or mixed with the resin layer.

  Further, when aluminum nitride or the like having good thermal conductivity is used as the substrate 21a, the energization heating resistor layer 21b is formed on the side opposite to the fixing roller side (substrate back side) with respect to the substrate 21a. Also good.

  The heat insulating stay holder 24 that fixes and holds the heater 21 is formed of a heat resistant resin such as liquid crystal polymer, phenol resin, PPS, PEEK, etc., and the lower the thermal conductivity, the more efficient the heat efficiency when heating the heating film 23. Get higher. Therefore, a hollow filler such as a glass balloon or a silica balloon may be included in the resin layer.

  On the side opposite to the heating film 23 of the heater 21, a temperature detection means 22 such as a thermistor for detecting the temperature of the substrate 21 a raised in accordance with the heat generation of the energization heat generation resistance layer 21 b is disposed. This temperature detection means 22 is provided for the purpose of controlling the temperature of the heater 21.

  As the temperature control method, the duty ratio, wave number, etc. of the voltage applied to the energization heating resistor layer 21b from the electrode part (not shown) at the longitudinal end of the heater 21 are appropriately set according to the signal of the temperature detection means 22 To control. Thereby, the heater 21 generates heat, and the inner surface of the heating film 23 is heated and temperature-controlled. The effective heat generation area width in the longitudinal direction of the heater 21 is larger than the maximum sheet passing width of the fixing device.

  The detected temperature information from the temperature detecting element 22 is sent via the temperature control unit 100 to the triac element 101 as an energization driver. The triac element 101 performs energization ON / OFF to the AC power source 102 based on the energization signal of the temperature control unit 100.

  As a temperature control method, a temperature control method is performed so that the temperature of the heater 21 is set to a predetermined temperature, and a temperature detection element is also brought into contact with the surface of the fixing roller so that the temperature of the fixing roller surface is set to a predetermined temperature. There is a method of performing power control to

(4-2) Heated film 23
The heating film () 23 as a flexible member (film-like member) has a function of transmitting heat generated by the heater 21 to the surface high thermal conductive layer 33 of the fixing member 30 in the heating nip portion Nh. It is loosely fitted outside the stay holder 24 that supports the heater 21, forms a heating nip portion Nh while being interposed between the heater 21 and the fixing roller 30, and rotates following the rotation of the fixing roller 30. To do. Alternatively, a configuration in which a driving unit is separately provided and the heating film itself is rotationally driven may be employed.

  The configuration of the heating film 23 is very important in the present embodiment in the same manner as the configuration of the fixing roller 30 in that the heat is efficiently stored in the high heat conductive layer 33 on the surface of the fixing roller 30.

  In particular, in the heating nip portion Nh, sufficient diffusion of heat to the high thermal conductive layer 33 that constitutes the outermost surface of the fixing roller 30 is to achieve high thermal efficiency and to set the temperature control temperature of the heater 21 low. It becomes important to.

  That is, in FIG. 6, the amount of heat generated by energization of the energization heating resistor layer 21b of the heater 21 is transferred to a portion having a low temperature. Therefore, the heat flow of arrow A or arrow D occurs. At this time, in order to supply a sufficient amount of heat to the high heat conduction layer 33 formed on the outermost surface of the fixing roller 30 which is the original purpose in this embodiment, the heat flow of the arrow C is increased and the high heat conduction layer 33 is supplied. Must diffuse enough. Therefore, the heat flow of the arrow A is increased, and the amount of heat flowing in the direction other than the direction of the fixing roller 30 such as the arrow B (the heat flow transmitted to the heating film without contributing to the temperature rise of the fixing roller 30) and the arrow D is reduced. It is effective to do.

  In particular, when the environment in which the image forming apparatus is installed is a low temperature environment, it is assumed that the recording material itself is also cooled in the paper feed tray 8. Further, when a recording material having a good surface property and a small roughness is conveyed to the fixing nip portion Nt, the amount of heat flowing from the surface of the fixing roller 30 to the recording material increases.

  When the surface of the fixing roller 30 whose temperature has dropped at the fixing nip portion Nt reaches the heating nip portion Nh again, it is necessary to sufficiently store the heat from the heater 21 in the high heat conductive layer 33 on the outermost surface of the fixing roller again. For this purpose, it is required that the heat flow of arrows A and C is large.

  According to our research, the thermal conductivity required for the heating film 23 is 1.0 W / m · K or more, more preferably 2.0 W / m · K or more as a condition satisfying the above.

  Further, it has been confirmed that the heat capacity greatly contributes as a physical property required for the heating film 23. That is, even if a member having very high thermal conductivity is used, if the heat flow indicated by the arrow B in FIG. Moreover, this greatly contributes to the thickness and outer diameter of the heating film 23 other than the material of the heating film 23.

That is, when the thickness of the heating film 23 is thick, the flow of heat to the arrow B where the thermal resistance becomes small increases. In addition, when the outer diameter is large, the heat radiation area to the air other than the heating nip portion Nh is increased, so that the heating film 23 once heated in the heating nip portion Nh rotates once and rotates again. It will be cooled enough to reach. As a result, the amount of heat is used to heat the heating film itself every turn. From this, the heat capacity for one rotation of the heating film 23 per unit length (1 cm) in the direction (longitudinal direction) orthogonal to the recording material conveyance direction is at most 0.4 J / K, more preferably 0. .35J / K or less is desirable.

  In view of the above, as the heating film 23, a base layer formed of a metal member alone or an alloy, or a base layer in which a large amount of a high thermal conductive filler made of powder in a heat resistant resin such as polyimide (PI) is mixed may be formed. It is effective.

  In the above, the metal member is, for example, stainless steel (SUS), nickel (Ni), titanium (Ti), copper (Cu), or the like. The high thermal conductive filler made of powder is, for example, metal particles, metal oxide, artificial diamond, graphite, or the like.

A method for producing the base layer using the metal member is not particularly limited, and examples thereof include a spinning method, a deep drawing method, a rolling method, a drawing method, and a method using an electroforming production method. The thickness is preferably 50 μm or less, more preferably 40 μm or less, considering flexibility. The outer diameter is preferably φ26 mm or less, more preferably φ24 mm or less. Further, the surface of the heating film 23 that contacts the fixing roller 30 needs to have good releasability in order to prevent toner contamination and achieve a long life. In particular, since the heating film 23 is configured so as not to contact with the recording medium P, once the dirt contaminated heated film surface to spit on the recording material little by little is difficult, compared to the surface of the fixing roller, separation of heating the film surface The moldability must be good.

  For this reason, it is desirable that the fluororesin layer is formed thin on the surface. Fluorine resin such as polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA). Furthermore, they are a fluorinated ethylene polypropylene copolymer resin (FEP), a polyvinylidene fluoride resin (PVDF), a polyvinyl fluoride resin (PVF), and the like.

  However, as described above, since the high thermal conductivity is important for the heating film 23, it is desirable that the thickness of the fluororesin layer formed on the surface layer be suppressed as much as possible to 20 μm or less. Alternatively, the fluororesin layer may be mixed with a filler having high thermal conductivity within a range that does not impair the releasability.

  Even in the case of a heating film formed of a plurality of layers as described above, it is desirable that the thermal conductivity from the inner surface to the outer surface be 1.0 W / m · K or more. More preferably, it is desirable to set it as 2.0 W / m * K or more. Further, it is desirable that the heat capacity (including a plurality of layers) of the heating film 23 in one rotation direction is 0.4 J / K or less, more preferably 0.35 J / K or less.

  In the present embodiment, the plate heater 21 that slides in contact with the heating film 23 is used as the heating source. However, the heating source may be a non-contact heating source included in the heating film 23.

  FIG. 7 shows a configuration when the non-contact heating source 27 is used. Examples of the non-contact heating source 27 include heaters such as halogen heaters and carbon heaters. In this case, in order to efficiently absorb the radiant heat from the heater 27, it is better to form a black coating absorbing layer on the inner surface of the heating film 23.

  As a black coating method, the oil content on the inner surface of the heating film 23 is removed, and a paint such as Okitsu # 8000 (trade name, manufactured by Mie Yushi Kogyo Co., Ltd.) is applied as a black paint, for example. This Okitsu # 8000 is a black metal pigment or black metal compound pigment dispersed in a solvent together with a silicone resin binder and dissolved, and contains a black pigment, inorganic pigment, silicone resin (methylphenyl silicone base), and solvent. It is. As a baking condition after application, baking is performed at 300 ° C. for about one hour. Of course, any material other than # 8000 black paint may have a high infrared absorption rate.

(5) Pressure roller 40
The pressure roller 40 is formed by forming an elastic layer 42 and a releasable layer 43 on the outermost surface of a core bar 41 made of aluminum, iron, SUM, or the like.

  As the pressure roller 40, the fixing nip portion Nt is formed by contact pressure with the fixing roller 30. However, if the flow of heat from the surface of the fixing roller is suppressed as much as possible, the temperature increase speed of the surface of the fixing roller is increased.

  Therefore, the elastic layer 42 is preferably formed from a liquid silicone composition mainly composed of an organopolysiloxane containing a balloon such as a microballoon or a water-absorbing polymer, like the heat insulating elastic layer 32 of the fixing roller 30. .

  The silicone rubber composition desirably has a cured product (silicone rubber) having a thermal conductivity of 0.15 W / m · K or less, preferably 0.13 W / m · K or less, and achieves such thermal conductivity. Thus, it is preferable to adjust the composition.

  Examples of the release layer 43 include polytetrafluoroethylene resin (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA). Furthermore, a fluoroethylene polypropylene copolymer resin (FEP), a polyvinylidene fluoride resin (PVDF), a polyvinyl fluoride resin (PVF), etc. can be mentioned.

  The coating can be formed by latex, Daiel latex (Daikin Kogyo Co., Ltd., fluorine-based latex), dipping coating using a dispersion, spray coating, or the like. Unlike the outermost layer of the fixing roller 30 described above, it is preferable that the thermal conductivity is low, and it is more appropriate not to mix a high thermal conductive filler or the like.

(6) Verification Experiment As described above, the first printout time of the fixing device 12 in this embodiment, the settable heater set temperature, the set temperature of the fixing roller surface, and the fixing uniformity were confirmed.

  The image forming apparatus used was a laser beam printer having a process speed of 260 mm / sec and performing 45 prints per minute.

  The basic components of the fixing device used in the experiment will be described.

(6-1) Fixing roller 30
The core metal 31 is a SUM core metal having an outer diameter of 12 mm. The heat insulating elastic layer 32 is a silicone rubber layer containing a hollow filler having a thickness of 3.5 mm. The high thermal conductive layer 33 has a two-layer structure in which a silicone solid rubber layer mixed with various high thermal conductive fillers having a thickness of 100 μm and a PFA coat mixed with various high thermal conductive fillers as a top layer are coated with a thickness of 15 μm. Is a layer.

  The hollow filler contained in the heat insulating elastic layer 32 of silicone rubber is an acrylonitrile balloon having a particle size of 80 μm. 30 parts by weight of this was mixed with 100 parts by weight of the organopolysiloxane composition, a small amount of triethylene glycol was blended so that bubbles were connected, and heat-cured to obtain a heat insulating elastic layer 32. The heat conductivity of the heat insulating elastic layer portion was set to 0.12 W / m · K.

  Further, the heat conductivity of the high heat conductive silicone solid rubber layer and the PFA coat layer provided outside was confirmed by variously shaking.

(6-2) Heating unit 20
The plate heater 21 was obtained by screen-printing an energization heating resistor layer 21b formed from an Ag / Pd paste on an AlN substrate 21a having a thickness of 0.6 mm and a width of 8 mm.

  The heating film 23 is made of a SUS304 seamless metal film having an outer diameter of 24 mm and a thickness of 40 μm and a thermal conductivity of 15 W / m · K as a base layer, and a 4 μm thick primer layer and a 10 μm thick PFA coat layer are sequentially coated on the surface layer. The formed one was used. The heat conductivity of the heating film 23 to which the PFA coat is applied is 13.6 W / m · K.

(6-3) Pressure roller 40
A pressure roller in which a 3.5 mm thick hollow filler-containing silicone rubber layer 42 was coated on a 12 mm SUM cored bar 41 and a PFA tube was coated on the outermost layer 43 with a thickness of 30 μm was used.

  With the above configuration, 98 N (10 kgf) pressure was applied between the heating unit 20 and the fixing roller 30, and the heating nip portion Nh was formed with a width of 5 mm. Further, a pressure of 196 N (20 kgf) was applied between the fixing roller 30 and the pressure roller 40 to form a fixing nip portion Nt having a width of 7 mm.

  Table 1 summarizes fillers mixed in the high thermal conductive silicone solid layer and the PFA coating layer formed on the surface layer of the fixing roller 30 and their physical properties. Two types of crystalline silica having different thermal conductivities were prepared and used for confirmation. The average particle diameter of the filler was all unified to 3.5 μm.

  The above filler was mixed in each layer to produce a silicone rubber layer and a PFA coat layer having different thermal conductivities, and experiments were conducted.

  Table 2 shows the types of fixing rollers manufactured as Experiments 1 to 9. The types of fillers mixed are indicated by # 1 to 5 in Table 1. The unit of the mixing amount is vol%, λ indicates the thermal conductivity of each layer in the state where the filler is mixed, and the unit is W / m · K. Further, each layer of Experiment 1, the PFA coat layer of Experiment 2, and the silicone solid rubber layer of Experiment 3 are in a state in which no high thermal conductive filler is mixed.

  A printing operation was started by a laser beam printer with each of the above configurations, and a recording material on which an unfixed toner image was formed was fixed by heating with a fixing device incorporating each fixing roller.

  At that time, the first printout time (FPOT), the durability performance, and the fixing roller surface temperature and the heater temperature when the fixing performance was sufficient were compared and evaluated.

For confirmation of the fixing performance, Fox River Bond paper (manufactured by Fox River Paper) having a basis weight of 90 g / m ² was used. The power when the heater 21 is energized to the energization heating resistor layer 21b is set to 1000 W. The temperature of the heater 21 is controlled to a predetermined temperature in each configuration. It was confirmed.

As a method for evaluating the fixing performance of an unfixed toner image on a recording material, a cellophane tape is stuck on the recording material toner image after heat fixing, and the cellophane tape is peeled off after pressing for 1 minute at a surface pressure of 50 g / cm ² . Evaluation was performed based on the degree of image defects (defects removed by tape) in the toner image at that time. The case where the image defect exceeded 5% of the original toner image was determined as NG (defect).

  The first printout time was measured from when the laser printer received a print signal and started to operate until the unfixed image on the recording material was discharged onto the paper discharge tray after being heat-fixed.

Regarding durability performance, A4 size recording material having a basis weight of 80 g / m ² was continuously printed, and the printing operation was continued until a problem occurred in the fixing roller 30, and the number of sheets passed without problems was counted.

  Table 3 shows the evaluation results when each fixing roller is used by the above evaluation method. In the table, the unit of FPOT is the number of seconds, the temperature of the fixing roller and the heater indicates the temperature when fixing is possible, and the unit is ° C.

  From the above results, it is shown in Experiments 1 and 2 and Experiments 4 to 9 that the provision of a heat storage layer having a high thermal conductivity on the outermost layer of the fixing roller 30 has the effect of lowering the fixing roller surface temperature and the heater temperature control temperature that can be fixed. From the result of.

  This is because the amount of heat necessary to fix the unfixed toner image on the recording material can be stored.

  In Experiment 3, the fixing temperature is slightly lower than in Experiments 1 and 2, but the effect is small. This is because the layer that diffuses heat by high heat conduction is as thin as 15 μm, and the silicone solid layer inside has a low thermal conductivity, so that heat hardly diffuses.

  Further, it can be seen from the comparison between Experiments 1 and 2 and Experiments 3 to 9 that when the heat conduction on the surface of the fixing roller is low, not only the fixing temperature becomes high but also the FPOT becomes slow.

  Also, in Experiments 7 and 8, where heat is likely to diffuse, the FPOT is slightly faster than in Experiments 4-6 and 9, because the fixing roller temperature and heater temperature that can be fixed are lower, and the temperature rise time is shorter. It depends.

  In Experiment 6, the outermost layer has a thermal conductivity of 0.32 W / m · K. However, the silicone solid rubber layer formed in the lower layer was 0.38 W / m · K, and the thermal conductivity of these two layers was measured to be 0.35 W / m · K.

  From the above, even when a layer having a thermal conductivity of 0.35 W / m · K or less is formed on the outermost layer, the layer in the plurality of surface layers as a whole has a high heat of 0.35 W / m · K or more. What is necessary is just to be formed with the conductive layer. As a result, it has been found that the fixing roller temperature and the heater temperature at which fixing can be performed can be lowered, and further sufficient durability performance can be obtained.

  In Experiment 4, the amount of filler mixed in the PFA coating layer on the surface layer exceeded 50 vol%. In such a coating, the surface becomes hard, and the coating is repeatedly deformed at the fixing nip portion Nt and the heating nip portion Nh. The layer became unbearable, causing problems such as cracking. As a result, defects on the image are likely to appear.

  In addition to the above experiment, when the durability performance was confirmed by shaking the amount of filler mixed into the silicone solid rubber layer provided inside the PFA coat layer, cracking occurred in the rubber layer due to durability when the filler content exceeded 50%. I found it easier to do.

  Therefore, the thermal conductivity of the filler mixed on the surface of the fixing roller is set to 10 W / m · K or more, and the filler mixed amount of the mixed filler is set to 50 vol% or less, preferably 45 vol% or less, thereby obtaining a desired thermal conductivity. In addition, durability can be improved.

  In Experiments 1 to 3, the inner surface of the heating film was scraped due to the durability of 100,000 to 150,000 sheets, leading to failure. This is because the temperature of the heater is as high as 285 ° C. or more, and the heating film is damaged due to the influence of shavings due to deformation of the holding member and wear of the heater surface and the inner surface of the heating film. In particular, it has been found that the durability of the heater for heating is severe with respect to durability.

  In addition, we evaluated graphite and diamond having a thermal conductivity of 800 W / m · K or more as other fillers in the silicone solid rubber layer and PFA coat layer, respectively. As a result, it was found that a target high thermal conductive layer (thermal conductivity of 0.35 W / m · K or higher) can be achieved with an amount of 10 vol% or more.

  In addition, the average particle diameter of the filler mixed in the PFA coat layer on the outermost surface of the fixing roller was confirmed by shaking. As a result, when the thickness exceeds 3.5 μm, the surface roughness of the fixing roller exceeds Rz = 4.0 μm, and when a halftone image is heat-fixed, small fixing unevenness occurs on the image. In the case of a filler of 3 μm or less, no particular problem was found on the image.

  From the above results, as the outermost layer of the fixing roller 30, a heat conductive filler is mixed as follows, and a high heat conductive layer of 0.35 W / m · K or more, preferably 0.38 W / m · K or more. It has been found desirable to form That is, a filler having a mean particle size of 3.5 μm or less, preferably 3.0 μm or less, and a thermal conductivity of 10 W / m · K or more is mixed in an amount of 10 vol% or more and 50 vol% or less to form a high thermal conductive layer.

  Further, in order to confirm the thickness of the outermost layer of the fixing roller 30, the FPOT was confirmed by shaking the thickness of the silicone solid rubber layer in the fixing roller of Experiment 5 from 0 μm to 250 μm (Experiments 10 to 15). The results are shown in Table 4.

  Here, the total thickness is the total thickness of the silicone solid rubber layer as the high thermal conductive layer 33 and the PFA coat. The heater temperature indicates the heater temperature in a fixable state as described above, and its unit is ° C.

  From the above experiment, when the total thickness of the high heat conductive layer, which is the surface layer of the fixing roller, is less than 20 μm, the heat storage amount is insufficient as in the above-described experiment, so the heater temperature must be set high. It was. Therefore, the durability performance was inferior.

  If the total thickness of the high heat conductive layer was 20 μm or more, the temperature of the heater 21 could be suppressed to a heater temperature that allowed up to 280,000 durable sheets.

  In addition, when the total thickness of the high thermal conductive layer exceeds 200 μm, the amount of the heat at the heating nip portion Nh that diffuses toward the inside of the fixing roller increases, so that the FPOT tends to be delayed. . In addition, as the thickness of the high thermal conductive layer increases, the temperature of the heater 21 must be increased. This is a result of having to increase the electric power supplied to the heater 21 because the heat is further diffused into the fixing roller.

  From the above, it is desirable that the thickness of the high thermal conductive layer provided on the outermost layer of the fixing roller is set to 20 μm or more and 200 μm or less.

  Further, the amount of microballoons mixed with the heat conductivity of the heat insulating elastic layer 32 formed inside the high heat conductive layer 33 provided on the outermost layer of the fixing roller 30 was confirmed. As a result, if the thermal conductivity exceeds 0.15 W / m · K, the escape of heat to the inside becomes large, and the heater temperature must be set high. Furthermore, it was confirmed that a lot of FPOT was applied.

  Further, it has been found that by setting the thermal conductivity of the heat insulating elastic layer 32 to 0.13 W / m · K or less, there is almost no influence on the heater temperature and FPOT.

  From the above, it is desirable that the heat conductivity of the heat insulating elastic layer 32 formed inside the fixing roller is set to 0.15 W / m · K or less, preferably 0.13 W / m · K or less.

  Next, using the fixing roller of Experiment 8 above, the heat conductivity of the base material of the heating film 23 of the heating unit 20 and the heat capacity per unit length (1 cm) in the longitudinal direction are changed, and the heater in a state where FPOT and fixing are possible. Was confirmed (Experiments 15 to 29).

  Tables 5 and 6 show the configuration and results of the heating film 23 of each experiment. The unit of thermal conductivity is W / m · K, the heat capacity per unit length (1 cm) is J / K, FPOT is seconds, and the control temperature of the heater for heating is ° C.

Experiments 16 to 22 in Table 5 evaluated Fox River Bond paper as rough paper with a basis weight of 75 g / m ^{2 in} a 25 ° C. environment.

Experiments 23 to 29 in Table 6 evaluated Springhill paper (manufactured by International Paper Co., Ltd.) as a cardboard having a good surface property with a basis weight of 199 g / m ^{2 in} a 10 ° C environment.

  From the above experiments, it can be seen that in order to suppress the FPOT and the heater temperature, it is necessary to increase the thermal conductivity of the heating film 23 and to suppress the heat capacity to a small value.

  In particular, the heater temperature at which fixing is possible differs depending on the environment in which the image forming apparatus is used and the type of recording material. In particular, when the heat conductivity of the heating film 23 is lower than 1.0 W / m · K or the heat capacity per unit length is larger than 0.4 J / K, the fixing roller 30 can be fixed. Takes time. Further, it is greatly affected by the environmental temperature and the recording material.

  Also, considering the durability, as described above, it is advantageous that the temperature of the heater 21 is lower. In order to obtain sufficient durability performance, the thermal conductivity of the base material of the heating film 23 is 2.0 W / It is preferably m · K or more.

  As described above, when the influence of the environmental temperature and the recording material is too great, even if the environment and the type of the recording material used by the image forming apparatus are detected by any method, the same fixing is performed for all the recording materials. It becomes difficult to maintain performance. This is because there are multiple factors such as the ambient temperature and the type of recording material, so there is a limit to the detection capability of each, and considering the variation in detection results, it is optimal for all environments and recording materials. It is difficult to perform a proper temperature control.

  From the above results, in the fixing device according to the present embodiment, the thermal conductivity of the base material of the heating film 23 is 1.0 W / m · K or more, preferably 2.0 W / m · K or more. And as a heat capacity per unit length (1 cm) in the longitudinal direction of the base material of the heating film 23, it is desirable that it is 0.4 J / K or less.

  Further, in order to confirm the effect of the fixing uniformity of this embodiment, the case where the halftone image is heat-fixed on various recording materials in Experiment 8 and the case where the film heating method of FIG. The images were compared.

  The fixing device using the film heating method shown in FIG. 8 is disclosed in JP-A-63-313182, JP-A-2-157878, JP-A-4-44075 to 4-44083, and JP-A-4-209800-204984. It is proposed in the gazette. No power is supplied to the fixing device during standby, and standby heating is not performed. Specifically, this is an apparatus for fixing a toner image on a recording material between a heater unit and a pressure roller via a thin film having a small heat capacity. Reference numeral 70 denotes a film assembly. A plate heater 71 in which an energization heating resistance layer is formed on a ceramic plate such as alumina or aluminum nitride is fixed to a stay holder 74 formed of a heat resistant resin. The stay holder 74 has a heat-resistant thin film 73 (hereinafter referred to as a fixing film) made of a resin such as polyimide or a metal such as SUS that is loosely fitted. In addition, the heater 71 includes a fixing film 73 in a close-contact sliding state, and a pressure roller (elastic roller) 60 that is in pressure contact with the fixing film 73 interposed therebetween. The fixing film 73 is conveyed and moved in the direction of the arrow by the rotational force of the pressure roller 60 while closely contacting and sliding on the heater 71 at the fixing nip portion Nt. The temperature of the heater 71 is detected by a temperature detection means 72 such as a thermistor disposed on the back surface of the heater, and fed back to an energization control unit (not shown) to heat and adjust the temperature of the heater 71 to a constant temperature (fixing temperature). Is done. Various image forming apparatuses such as printers and copiers using such a film heating type fixing device can eliminate standby heating during standby because of high heating efficiency and rising speed. Further, it has many advantages over the conventional heat roller type fixing device, such as shortening the warm-up time.

For comparative evaluation, a halftone image in which an image for one dot line and a non-image portion for two dot lines were alternately formed on a recording material with a 600 dpi image, and a solid black image printed on the entire surface were used. The heated fixing the recording material having a different surface of the basis weight of ^{60g / m 2 ~199g / m 2} . The fixing unevenness was visually identified in five stages, and rank samples were prepared and visually evaluated. Rank is an integer from 1 to 5, 1 is poorest, 5 is the most level is good, each printed halftone image and the solid black image by five, each 10 sheets according to the type of the recording medium The average rank of the rank was compared.

  As a result, in this example, all the recording materials were evaluated in the range of 4 to 5 in the rank, whereas in the conventional film heating method (FIG. 8), the rank was 2 to 4 and a large difference depending on the recording material. was there.

  This is because, in the conventional film heating method, the recording material P on which the unfixed toner image T is formed contacts the non-elastic film as the fixing member, and therefore, the fixing unevenness particularly occurs when the recording material cannot be uniformly contacted. This is because they tend to occur.

  As described above, this embodiment provides a fixing device that achieves stable fixing performance by achieving superior performance in all aspects such as shortening the temperature rising time at startup, reducing power consumption, and further achieving high speed, high image quality, and long life. It becomes possible to do.

  The following is a summary of the above examples.

A heating and fixing member that heat-fixes the unfixed image as a fixed image on the recording material by passing the recording material on which the unfixed image is formed through a nip formed between the fixing member and the pressure member. And a fixing roller or a fixing belt.

  The fixing roller or the fixing belt has a heat insulating layer as described below on the outside of aluminum, iron cored bar, or heat resistant resin.

  1) It is formed by heat forming after forming a compound in which 0.1 to 200 parts by weight of a hollow filler having an average particle size of 500 μm or less and 100 parts by weight of an organopolysiloxane composition are blended with a curing catalyst such as a platinum compound catalyst. Insulation layer.

  2) Alternatively, 0.1 to 50 parts by weight of a water-absorbing polymer, 10 to 200 parts by weight of water, a curing catalyst such as a platinum compound catalyst, and a crosslinking agent such as a SiH polymer are added to 100 parts by weight of the organopolysiloxane composition. A heat insulating layer formed by heat forming after forming the added composition.

  3) A heat insulating layer made of foamed silicone rubber molded by a method of adding a pyrolytic foaming agent to silicone rubber or a method of molding a foam using hydrogen gas by-produced during curing as a foaming agent.

  As a result, the thermal conductivity inside the fixing roller or the fixing belt is set to 0.15 W / m · K or less.

  Further, on the outside of the heat insulating layer, a single layer or a fluorocarbon resin layer in which 10 vol% to 50 vol% of a high thermal conductive filler made of a material having a thermal conductivity of at least 10.0 W / m · K is mixed. , Formed of multiple layers. A thickness of 20 μm to 200 μm on the outermost surface of the fixing roller or fixing belt is formed by a member having a thermal conductivity of 0.35 W / m · K or more.

  Therefore, the fixing roller or the fixing belt has a heat insulating layer inside and a high heat conductive layer on the outermost surface. With this configuration, it is possible to rapidly heat and store the surface of the fixing member by rapidly heating the fixing member surface layer having a low heat capacity and a short circumference by external heating.

  In particular, a fixing member in which a balloon-containing silicone elastic layer or a balloon-containing silicone elastic layer and a heat insulating layer of a system in which the bubbles are uniformly dispersed in the elastic layer with a substantially uniform and fine particle size is effective. is there. That is, even if the fixing member is made to have a small peripheral length and a bending with a small curvature radius at the time of deformation due to pressurization in the heating nip portion or the fixing nip portion is given to the fixing member, there is no weak portion like the silicone sponge layer. Therefore, the possibility of reaching bubble breakage is reduced like the silicone sponge layer. For this reason, it is suitable for reducing the hardness of the heat insulating elastic layer, and a long life can be achieved by securing a sufficient margin against breakage due to bending.

  Further, the fixing roller or fixing belt formed as described above is a constituent element of the fixing member, and heating means for heating the surface from the outer surface of the fixing roller or fixing belt is provided.

  Heat fixing by passing a recording material on which an unfixed image is formed through a fixing nip formed by pressurizing at a predetermined pressure between the fixing roller or the fixing belt and a pressure member, for example, a pressure roller. To implement.

  Further, as the heating means, a high heat conductive thin film which has been blackened on the inner surface by infrared radiation such as a halogen lamp or a carbon heater, or a high heat conductive thin film which is heated by contact with a plate-like heating member such as a ceramic heater is used. To heat the surface of the fixing member.

  The high thermal conductive thin film is formed with a member having a thermal conductivity of 1 W / m · K or more as a base material and a thickness of 50 μm or less and an outer diameter of 26 mm or less, and a heat capacity for one rotation in a rotation direction per unit length (1 cm). Is 0.4 J / K or less.

  The elastic layer of the pressure roller is made of an organopolysiloxane composition mixed with a hollow filler, or an organopolysiloxane composition containing a water-absorbing polymer and water, as in the case of a fixing roller. Layer. Alternatively, a bubble-containing silicone elastic layer is formed. Alternatively, a silicone sponge elastic layer is formed by foaming silicone rubber. The thermal conductivity of the elastic layer is set to 0.15 W / m · K or less.

  Alternatively, a heat-resistant resin film is provided as a pressure member as a member having a thermal conductivity of 0.2 W / m · K or less. A backup member having an elastic layer is disposed inside the resin film. The elastic layer is a balloon-containing silicone elastic layer produced from an organopolysiloxane composition mixed with a hollow filler or an organopolysiloxane composition containing a water-absorbing polymer and water. Alternatively, a bubble-containing silicone elastic layer or a silicone sponge elastic layer formed by foaming silicone rubber is used. A pressure member that forms a fixing nip between the fixing roller or the fixing belt via the resin film may be provided.

  Further, the surface of the highly heat conductive thin film as the heating member and the surface of the fixing member having high heat conduction on the surface layer are conveyed in a close contact state at the heating nip portion. For this reason, the heat is smoothly transferred from the high heat conductive thin film to the surface of the fixing member, and heat is sufficiently accumulated in the high heat conductive layer on the surface of the fixing member at the heating nip portion. As a result, a sufficient amount of heat is supplied to heat and fix the unfixed toner image on the recording material at the fixing nip portion. In particular, the amount of heat once stored in the high thermal conductive layer of the fixing member at the heating nip is immediately transferred from the outer surface of the high thermal conductive layer to the recording material at the fixing nip, and the shortage is stored by the thickness of the high thermal conductive layer. The amount of heat is supplied immediately. Therefore, heat storage of the necessary heat amount to the high thermal conductive layer of the fixing member is efficiently performed at the heating nip portion, and supply of heat amount necessary for heating and fixing the unfixed toner image is efficiently performed at the fixing nip portion. Further, since heat diffusion to the inside of the fixing member is blocked by the internal heat insulating layer, it is not necessary to supply an extra amount of heat. As a result, it is possible to reduce the power consumption of the heater and the surface temperature of the highly heat conductive thin film as a heating member.

  Due to the above effects, as a result, the time required for heating the fixing member surface by the heating means is short, and the quick start property is very excellent. For this reason, the fixing nip portion can be rapidly heated at the same time as the start of the image forming operation even if no power is supplied to the heating source in a state where the image forming operation is not performed. It is not necessary to perform standby heating, and it is possible to configure a heat fixing device that saves energy and has extremely little warm-up time and first printout time.

  Further, as the pressure member, the material used for the elastic layer is a balloon-containing silicone elastic layer, a bubble-containing silicone elastic layer, or a silicone sponge layer as in the case of the internal member of the fixing member. 15 W / m · K or less. This makes it possible to further increase the quick start performance by suppressing the amount of heat flowing out from the surface of the fixing member heated externally to the pressure member side. It is possible to further reduce the warm-up time and the first printout time.

  In the fixing nip portion, the surface of the fixing member is in contact with the surface on which the unfixed image is formed. The fixing uniformity is achieved by the effect of wrapping the toner image on the recording material due to the elasticity of the surface of the fixing member. As a result, it is possible to achieve image uniformity and prevent uneven fixing in a halftone image. As a result, high image quality can be achieved at the same time.

  As described above, this configuration provides a fixing device that can achieve stable performance by achieving excellent performance in all of the shortening of the temperature rising time at the time of startup, the reduction of power consumption, and further high speed, high image quality, and long life. It becomes possible.

  The configuration of the fixing device of this embodiment is shown in FIGS. Constituent members / portions common to those of the fixing device of the first embodiment are denoted by common reference numerals, and description thereof is omitted.

  In this embodiment, the fixing roller facing surface of the plate heater 21 of the heating unit 20 is formed in a concave shape corresponding to the curved surface of the fixing roller 30. Thereby, the width | variety of the heating nip part Nh can be formed widely even with a low pressurizing force.

  Further, as the pressure member 40, a pressure member 45 having a heat insulating plate shape (flat or having a concave shape with respect to the fixing roller similarly to the heater 21) is used. A resin film 46 having heat insulation and heat resistance is interposed between the pressure member 45 and the fixing roller 30 as a rotatable flexible member (film-like member). In other words, the fixing nip portion Nt formed between the pressure member 40 and the fixing roller 30 can be realized with a light pressure.

  This provides a fixing device that can reduce the load on the fixing roller 30 and can be sufficiently applied to increase the speed and durability.

  Further, since the torque reduction during rotation of the fixing roller can be achieved and the load on the drive motor provided in the image forming apparatus can be reduced, the image forming apparatus can be configured with a smaller drive motor. The miniaturization itself is achieved.

  The configuration of the fixing device in this embodiment will be described more specifically. The configuration of the fixing roller 30 is the same as that of the fixing roller of the first embodiment. The heating film 23 of the heating unit 20 is formed of a base material having a thermal conductivity of 1.0 W / m · K or more, preferably 2.0 W / m · K or more. A heater 21 for heating from the inside of the heating film 23 is disposed.

  As shown in FIG. 10, the heater 21 is a heater having a curvature close to the curvature of the surface high thermal conductive layer 33 of the fixing roller 30 and having a concave shape on the fixing roller side. For example, an energization heating resistor layer 21b such as Ag / Pd is provided inside a flexible heater base 21d such as a thin polyimide layer. Alternatively, an extremely thin metal foil having a thickness of about 5 μm to 30 μm is formed inside the heater base 21d as the energization heating resistor layer 21b.

  According to our research, the heater 21 having a curved surface may be a rigid heater. However, in order to bring the fixing roller 30 and the heating film 23 into a close contact state with a low pressure, the heater 21 is flexible. A heater member having a thickness is more preferable. Furthermore, heat resistance is required. Therefore, it is preferable to form a material such as polyimide, polyamideimide, or PEEK material having a thickness of 200 μm or less as the heater base material 21d. Further, an elastic layer having a heat insulating property may be interposed between the heat insulating stay holder 24 on the side opposite to the fixing roller 30 of the heater 21.

  As a method for manufacturing the heater, for example, a polyimide sheet having a thickness of about 30 μm is used as the base material 21d. A paste-like conductor mainly composed of Ag / Pd is formed thereon by a method such as screen printing. In addition, there is a method of forming a sandwich structure in which a polyimide layer having a thickness of about 30 μm is coated on the conductor and the conductor is sandwiched between the polyimide layers.

  In addition, the heater 21 does not necessarily need to be made of the same material on the fixing roller 30 side and the heat insulating stay holder 24 side of the energization heating resistor layer 21b. The heat conductivity of the heater base material on the heat insulating stay holder 24 side may be formed of a member lower than the heat conductivity of the heater base material on the fixing roller 30 side. However, since the heater 21 is heated to a high temperature, it is better to adjust the coefficient of thermal expansion of each member as close as possible.

  In addition, a heat-resistant resin varnish such as a polyimide precursor is poured into a mold, a metal foil conductor is placed thereon, and a heat-resistant resin varnish such as a polyimide precursor is similarly poured thereon. And it does not necessarily limit about heater manufacturing methods, such as the method of forming the heater 21, by drying and baking and imidating.

  Further, as the pressing member 40, a configuration in which the surface high heat conductive layer 33 is heated and stored by the heating unit 20 so as not to take heat as much as possible from the fixing roller 30 is effective for shortening the warm-up time and the first print time.

  As a configuration for that purpose, it is desirable to use a member having a high heat insulation and a small heat capacity. Further, it is desirable to form a wide fixing nip width with the fixing roller 30 in order to sufficiently supply heat to the unfixed toner image on the recording material.

  From the above, the pressurizing member 40 in this embodiment includes a heat-resistant resin film as the pressurizing film 46 as a member having a thermal conductivity of 0.2 W / m · K or less. Then, a backup member (elastic pressure member) 45 having a silicone sponge elastic layer as described below is disposed inside the resin pressure film 46, and the fixing roller 30 is interposed via the resin pressure film 46. The fixing nip portion Nt is formed between the two.

  The silicone sponge elastic layer is a balloon-containing silicone elastic layer or a bubble-containing silicone elastic layer produced from an organopolysiloxane composition mixed with a hollow filler, or an organopolysiloxane composition containing a water-absorbing polymer and water. . Or it is a silicone sponge elastic layer formed by foaming silicone rubber.

  Further, the heat insulating backup member 45 is held by a heat insulating holding member 47. Further, at least the fixing roller 30 side of the heat insulating backup member 45 having elasticity may be provided with a concave shape in accordance with the curvature of the fixing roller 30.

  In order to confirm the effect of the above configuration, in the configuration of Experiment 8 shown in Example 1 described above, the heater is a flexible polyimide heater of the present example, and the pressure member is a pressure film. The experiment was conducted.

  As a configuration used in the experiment, a heater having a width of 8 mm was prepared as a heater 21 in which an energization heating resistance layer mainly composed of Ag / Pd was formed in the middle of a polyimide having a thickness of 80 μm. In order to form the heating nip portion Nh, the pressing force between the heating member and the fixing member was 49 N (5 kgf), which was half that of the first embodiment.

  The flexible heater 21 is mounted on a heat insulating stay holder 24 having a curvature radius of 11 mm and having a concave shape on the fixing roller 30 side. As a result, the heater 21 having a curvature radius of 11 mm has a concave shape on the fixing roller 30 side. Pressurized.

  With the above configuration, the heating nip portion Nh has a width of 6 mm. With the applied pressure of 98 N (10 kgf) shown in Example 1, the heating nip portion Nh can be formed with a width wider than 5 mm.

  Further, as the pressing member 40, a silicone sponge layer having a thickness of 3 mm, a width of 10 mm, and a thermal conductivity of 0.13 W / m · K was used as the backup member 45. The pressure film 46 is a polyimide film having a wall thickness of 50 μm and an outer diameter of φ18 mm mixed with 15 vol% of glass beads having an average particle diameter of 1 μm. The glass beads used had a thermal conductivity of 0.09 W / m · K, and the polyimide film mixed with the glass beads had a thermal conductivity of 0.16 W / m · K. A PFA coat having a thickness of 10 μm is formed on the surface of the pressure film 46 as a toner release layer.

  Further, the fixing roller side of the backup member 45 formed of a silicone sponge layer has a concave shape with a radius of curvature of 11 mm, and a pressure of 98 N (10 kgf) is applied between the fixing roller 30 and the pressure member. . As a result, the width of the fixing nip portion Nt formed between the fixing roller 30 and the pressure film 46 is formed to 8 mm, and from the fixing nip portion Nt having a width of 7 mm with a pressure of 196 N (20 kgf) in the first embodiment. Widely formed.

  With the above configuration, durability performance and fixing roller rotation torque were confirmed. As a result, with regard to the durability performance, in Experiment 8 of Example 1, the image defect started to occur due to wear on the surface of the fixing roller at about 350,000 sheets, whereas in this example, the image defect occurred up to 400,000 sheets. It was possible to print without doing.

  Further, the fixing roller rotational torque was also reduced by 30% from Experiment 8 of Example 1.

  In particular, the long life of the fixing device and the miniaturization of the image forming apparatus due to the low torque meet the market needs, and these are achieved by the present embodiment.

  As described above, in this embodiment, at least the contact shape of the heater and the pressure member is made to easily follow the fixing member in order to form a wide nip width (heating nip width or fixing nip width) even with a low pressure. It is advantageous. Furthermore, since the load on the surface of the fixing member can be reduced, it is possible to extend the life until a failure occurs. Further, when the fixing member is driven, the driving torque can be reduced and the load applied to the driving motor is reduced. Therefore, the motor can be downsized and the image forming apparatus can be downsized.

  Each of the above examples is an example of the best mode of the present invention, but the present invention is not limited to the configurations shown in these examples. That is, various modified configurations are possible within the scope of the idea of the present invention.

  1) For example, the heating means and the pressure member can be brought into pressure contact with and separated from the fixing roller by a contact / separation mechanism, and are brought into pressure contact with the fixing roller at a predetermined control timing when the fixing device is in operation. Sometimes, it can be configured to be separated from the fixing roller. Accordingly, it is possible to prevent the fixing roller elastic layer from being sagged due to the heating means and the pressure member always being in pressure contact with the fixing roller.

  2) The rotatable heating member for heating the image on the recording material at the nip portion is not limited to the roller form of the embodiment, and may be a flexible endless belt form.

  3) The image heating apparatus of the present invention is not limited to the heat fixing apparatus of the embodiment, but an image heating apparatus that modifies the surface properties such as gloss by heating a recording material carrying an image, an image heating apparatus that is supposed to be worn, etc. Further, it can be used as an apparatus for overheating a recording material carrying an image.

1 is a schematic cross-sectional view of a fixing device according to Embodiment 1. FIG. Similarly a schematic front view. 1 is a schematic diagram of an image forming apparatus according to Embodiment 1. FIG. FIG. 6 is a schematic diagram for explaining behavior in a fixing nip portion. Schematic of an example of a fixing roller manufacturing apparatus. FIG. 3 is a schematic diagram illustrating a heat flow near a fixing nip portion. FIG. 10 is a schematic cross-sectional view of another configuration example of the fixing device. FIG. 10 is a schematic cross-sectional view of a fixing device (film heating method) according to a conventional example. FIG. 6 is a schematic cross-sectional view of a fixing device according to a second embodiment. The partial expansion schematic diagram of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Heating means (heating unit), 21 ... Heater (heating source), 22 ... Temperature detection means, 23 ... Heating film (film-like member), 24 ... Heat insulation stay holder, 30 ... Heating member (fixing member), 32 ... heat insulating elastic layer, 33 ... high thermal conductive layer, 40 ... pressure member (pressure roller), 42 ... heat insulating elastic layer, T ... -Toner, P ... Recording material

Claims (10)

A rotatable heating member, a heating means for heating the heating member from the outside, and a pressure member for forming a nip portion for heating an image on the recording material between the heating member and the image. In the image heating apparatus that heats the recording material carrying the recording medium by being nipped and conveyed at the nip portion,
The heating member has a heat insulating elastic layer formed therein, and a heat conductive filler is mixed in at least the outermost layer to form a heat conductive layer having a higher thermal conductivity than the heat insulating elastic layer. Has a configuration in which a flexible member is brought into contact with the heating member, and the flexible member is heated from the inside by a heating source to heat the heating member, and the flexible member has at least 1 W / m · K. The pressurizing member has the above-described heat conductivity, and includes a rotatable flexible member having a heat conductivity of 0.2 W / m · K or less. An image heating apparatus comprising an elastic pressure member pressed between the heating member and the heating member.   2. The image heating apparatus according to claim 1, wherein 10 vol% to 50 vol% of a heat conductive filler made of a material having a heat conductivity of at least 10 W / m · K is mixed in the heat conductive layer. .   3. The image heating apparatus according to claim 1, wherein an average particle diameter of the heat conductive filler mixed in the heat conductive layer is 3.5 μm or less.   The image heating apparatus according to claim 1, wherein the heat conductive layer has a heat conductivity of at least 0.35 W / m · K or more.   4. The image according to claim 1, wherein the thermal conductive layer has a thermal conductivity of at least 0.35 W / m · K and a thickness of 20 μm to 200 μm. Heating device.   The image heating apparatus according to claim 1, wherein the heat insulating elastic layer has a thermal conductivity of 0.15 W / m · K or less.   The heat-insulating elastic layer is formed by firing and curing after forming a blend in which a hollow filler is blended with an organopolysiloxane composition, or a blend in which a water-absorbing polymer and water are blended in an organopolysiloxane composition. The image heating apparatus according to claim 1, wherein the image heating apparatus is an image heating apparatus.   8. The flexible member according to claim 1, wherein a heat capacity for one rotation in a rotation direction per 1 cm in a direction orthogonal to the recording material conveyance direction is 0.4 J / K or less. Image heating device.   The image heating apparatus according to claim 1, wherein the heating source is in contact with an inner surface of the flexible member, and the side of the heating member is held in a concave shape. .   The image heating apparatus according to claim 1, wherein a side of the heating member of the elastic pressure member is held in a concave shape.