JP2010181621A - Non-rotary pressure member having cross-linked fluororesin layer and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-rotary pressure member that has, as a releasing layer, a cross-linked fluororesin layer outstandingly excellent in abrasion resistance. <P>SOLUTION: The non-rotary pressure member is disposed in the fixing unit of an electrophotographic image forming apparatus. The non-rotary pressure member is a cross-linked fluororesin compound material in which a cross-linked fluororesin layer is formed on a base material, wherein when an abradant with a three-dimensional structure formed by uniformly applying and joining polishing abrasive grains to a nylon non-woven fabric, and 2 kgf weight are placed in that order on the cross-linked fluororesin layer, and the rotary body consisting of both of the abradant and the weight is revolved at 200 rpm, an abrasion loss at an integrated revolution of 100,000 is ≤10 μm. A method for manufacturing the member is also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-rotating pressure member having a cross-linked fluororesin layer formed on a substrate, and a method for producing the same. The non-rotating pressure member of the present invention has a markedly excellent abrasion resistance of the cross-linked fluororesin layer, and therefore is disposed facing and pressed against the fixing roller or the fixing belt in the fixing unit of the electrophotographic image forming apparatus. It can be suitably used as a non-rotating pressure member.

  In image forming apparatuses such as electrophotographic (including electrostatic recording) copying machines, facsimiles, and laser beam printers, generally, a charging process for uniformly and uniformly charging the surface of a photoconductor; image exposure is performed. A process of forming an electrostatic latent image on the photoreceptor; a developing process of attaching a toner (developer) to the electrostatic latent image to form a toner image; The image is formed by a series of processes including a projector) a transfer process for transferring onto a recording medium such as a sheet; and a fixing process for fixing an unfixed toner image on the recording medium.

  In the fixing step, generally, an unfixed toner image on a recording medium is heated and pressurized to be fixed on the recording medium. In the fixing process, a fixing unit (referred to as a “fixing device”) is generally provided with a roller pair including a fixing roller having a built-in heating means such as an electric heater, and a pressure roller disposed opposite to the fixing roller. Is using). A recording medium on which an unfixed toner image is formed is passed through a nip portion formed by pressing both rollers, and the unfixed toner image is fixed on the recording medium by heating and pressing.

  In the above-described fixing unit, it is necessary to rotatably support a pair of rollers including a fixing roller and a pressure roller, and to rotate them in synchronization with each other, which complicates the structure of the apparatus and reduces the size of the apparatus. Is difficult. Since it takes time to raise the surface temperature of the fixing roller to the fixing temperature by the built-in heating means, the waiting time until the image forming apparatus can be operated after the power is turned on becomes long. In order to solve some or all of these problems, fixing units having various structures have been proposed.

  For example, Japanese Patent Laid-Open No. 2000-194210 (Patent Document 1) discloses a film heating type heating apparatus and an image forming apparatus including the heating apparatus as a fixing unit. As shown in a schematic cross-sectional view in FIG. 1, the heating device includes a fixed heating body 5, an endless belt-like film 4 that slides on the surface of the heating body 5, and the heating body 5 through the film 4. And a non-rotating pressure member 3 that forms a nip portion in opposition to and in pressure contact with. The heating body 5 is held by the heating body holding member 6 in the film 4. The non-rotating pressure member 3 is fixed on the holding member 2. A small rotary pressure member 1 is disposed adjacent to the pressure member 3. The rotary pressure member 1 serves as a driving roller and rotates the film 4.

  For example, as shown in FIG. 2, the non-rotating pressure member 3 has a release layer 22 made of a fluororesin on a pad-like pressing member 21 made of a heat-resistant elastic material having good heat insulation. It has a provided structure. As the elastic material, silicone rubber, fluorine rubber, foamed silicone rubber, polyurethane sponge, or the like is used. As the fluororesin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), or the like is used.

  The outer peripheral surface of the rotating film 4 slides with respect to the surface of the non-rotating pressure member 3. When a recording medium 7 on which an unfixed toner image 8 is carried as a material to be heated is transported to a heating device, the recording medium 7 is rotated with the film 4 by a rotating film 4 and a small rotary pressing member 1. The pressure member 1 and the non-rotating fixed member 3 are conveyed to two nip portions where the pressure member 1 and the non-rotating fixed member 3 are in pressure contact with each other, and heated and pressurized there. As a result, the unfixed toner image 8 is fixed on the recording medium 7.

  The heating device disclosed in Patent Document 1 can use a heating element 5 with a low heat capacity such as a ceramic heater, and can use a thin film 4 with a low heat capacity as a heat transfer member. As a result, the temperature of the heating body 5 rises, and the nip portion where the film 4 and the non-rotating pressure member 3 are in pressure contact can be quickly heated to a predetermined fixing temperature. By using the non-rotating pressure member 3, the width of the nip portion can be widened, so that it is not necessary to use a large pressure roller. Therefore, when a large pressure roller is used, the amount of heat taken away by the pressure roller can be reduced.

  In JP-A-8-11503 (Patent Document 2), a metal heat-resistant cylindrical heat-resistant belt having a heater lamp and a reflector disposed therein is opposed to a flat guide plate. A fixing device is disclosed that heats and presses a recording sheet on which an unfixed toner image is formed by elastic deformation in the radial direction when the heat resistant belt is pressed against a guide plate. The flat guide plate is disposed on the heat insulating member. The heat insulating member can be moved in the vertical direction by an eccentric cam. The flat guide plate is fixed and serves as a non-rotating pressure member. When this fixing unit is used, the nip width formed between the cylindrical heat-resistant belt and the guide plate can be made variable. In order to reduce the friction coefficient of the guide plate and improve the releasability, the surface of the guide plate is covered with a fluororesin such as PTFE.

  Japanese Patent Application Laid-Open No. 8-241000 (Patent Document 3) includes a fixing roller and a pressure member disposed in pressure contact with the outer peripheral surface of the fixing roller, and is not yet determined between the fixing roller and the pressure member. In a fixing device for fixing a non-fixed toner image on a recording material by conveying a recording material having a contact toner image, a heat-resistant sheet based on glass fiber is disposed between a fixing roller and a pressure member. A fixing device is disclosed. The heat-resistant sheet is formed by coating or impregnating a glass fiber base material with a fluororesin such as PFA or PTFE. The heat resistant sheet is a non-rotating fixed pressure sheet.

  Japanese Patent Laid-Open No. 9-179422 (Patent Document 4) uses a heat-resistant sheet having the same structure as the fixing device described in Patent Document 3 and formed from a synthetic resin material containing polyimide in PTFE. A fixing device is disclosed.

  Japanese Patent Application Laid-Open No. 9-179441 (Patent Document 5) and Japanese Patent No. 3158030 (Patent Document 6) have the same structure as the fixing device described in Patent Document 3, and are made of fluororesin such as PFA and PTFE. A fixing device using a heat-resistant sheet formed from a synthetic resin material mixed with a heat-resistant filler is disclosed.

  Japanese Patent Application Laid-Open No. 8-69189 (Patent Document 7) discloses a fixing device having a structure in which a fixing roller is pressed against a heat-resistant member disposed on the outer peripheral surface of the fixing roller. The fixing roller has a thin aluminum cylindrical body provided with a silicone rubber coating layer, and a heater lamp is inserted into the shaft core. The heat-resistant member is made of a heat-resistant elastic member, and the surface thereof is provided with a fluororesin coating layer having a small friction coefficient and heat resistance. The heat resistant member is fixed to the frame.

  Japanese Patent Laying-Open No. 2004-246132 (Patent Document 8) discloses a fixing device including a fixing roller and a non-rotating fixed pressure sheet member. A non-rotating fixed pressure sheet is brought into pressure contact with the fixing roller, and the gist of the unfixed toner image formed therebetween is conveyed and fixed. The non-rotating fixed pressure sheet member is obtained by coating the surface of a polyimide sheet with PTFE.

  The fixing devices disclosed in Patent Documents 1 to 8 can contribute to downsizing and energy saving of the device. A fixing device using a fixing belt (an endless belt-like film) instead of the fixing roller can greatly shorten the rise time of the image forming apparatus. However, these fixing devices have a problem that the durability of the non-rotating pressure member is insufficient.

  Specifically, the non-rotating pressure member disclosed in the cited document 1 has a structure in which a release layer made of a fluororesin is provided on a pad-like pressing member. An endless belt-like film is slid on the surface of the release layer while being pressed. A recording medium on which an unfixed toner image is formed is conveyed between the release layer and the film, and heated and pressurized. A release layer formed from a fluororesin has a small coefficient of friction and excellent toner releasability, but has insufficient wear resistance.

  Even if the fixing roller and the pressure roller face each other and are pressed against each other and the rollers are rotated, the fluororesin layer provided on the surface of the pressure roller does not wear quickly. On the other hand, in the method in which the fixing roller or the fixing belt is slid on the surface of the non-rotating pressure member, a strong frictional force due to sliding is applied to the fluororesin layer of the non-rotating pressure member. The wear of the steel tends to progress. Therefore, in the heating device (fixing unit) having the above structure, as the image formation is repeated, the release layer made of the fluororesin on the non-rotating pressure member receives friction due to sliding with the film and the like. Will wear out.

  A flat guide plate having a fluororesin coating layer (Patent Document 2), a heat-resistant sheet made of a glass fiber base material coated or impregnated with a fluororesin (Patent Document 3), and a synthetic resin material containing PTFE containing polyimide Heat-resistant sheet (Patent Document 4), heat-resistant sheet (Patent Documents 5 and 6) formed from a synthetic resin material in which a heat-resistant filler is mixed in a fluororesin, and a fluororesin coating layer is formed on the surface of the elastic member The non-rotating fixed pressure sheet member (Patent Document 8) in which the surface of the polyimide sheet is coated with PTFE and the non-rotating fixed pressure sheet member (Patent Document 8) still have a problem of insufficient durability due to wear of the fluororesin. .

  If the release layer made of fluororesin is worn at an early stage, the recording medium cannot be smoothly passed between the rotating or rotating fixing roller or fixing belt and the non-rotating pressure member. Increasing the thickness of the fluororesin layer can prevent premature wear, but there are problems such as poor fixing due to uneven wear of the fluororesin layer, degradation of image quality, and peeling of the fluororesin layer from the substrate. It tends to occur. Therefore, in the practical use of a fixing unit using a non-rotating pressure member having a fluororesin layer, a dramatic improvement in the durability of the non-rotating pressure member is strongly demanded.

  It is known that when fluororesin is irradiated with a radiation such as electron beam or γ-ray and cross-linked, properties such as mechanical properties, creep resistance, radiation resistance, wear resistance, and adhesion to other materials are improved. Yes. A fluororesin is chemically stable and easily decomposes when irradiated with radiation at room temperature. When a fluororesin is irradiated with radiation such as an electron beam or γ-ray at a temperature equal to or higher than its melting point in the absence of oxygen, a network-like crosslinked structure can be introduced.

  For example, in JP-A-2002-225204 (Patent Document 9), the surface of a base material is coated with a fluororesin, and then the surface of the fluororesin film is irradiated with ionizing radiation in an oxygen-free atmosphere. There has been disclosed a method for producing a modified fluororesin coating material in which a cross-linking reaction of a resin and a chemical reaction between a fluororesin and a substrate surface are caused simultaneously, thereby achieving strong adhesion between the two.

  Conventionally, it has not been proposed to provide a non-rotating pressure member disposed in a fixing unit of an electrophotographic image forming apparatus with a cross-linked fluororesin layer cross-linked by radiation irradiation as a release layer. Furthermore, according to the conventional method, although a crosslinked fluororesin layer having improved wear resistance compared to the uncrosslinked fluororesin layer can be formed, it is required for the release layer of the non-rotating pressure member of the fixing unit. Achieving a high degree of wear resistance has been an extremely difficult task.

JP 2000-194210 A JP-A-8-115033 JP-A-8-241000 JP-A-9-179422 JP-A-9-179441 Japanese Patent No. 3158030 JP-A-8-69189 JP 2004-246132 A JP 2002-225204 A

  An object of the present invention is a non-rotating pressure member disposed in a fixing unit of an electrophotographic image forming apparatus, which has a cross-linked fluororesin layer having a remarkably excellent wear resistance as a release layer. It is in providing a pressure member and its manufacturing method.

  As a result of intensive studies to solve the above problems, the present inventors formed an unfired and uncrosslinked fluororesin layer on the substrate, and then fired at a temperature equal to or higher than the melting point of the fluororesin, Next, the wear resistance was remarkably improved by the method of irradiating the fired uncrosslinked fluororesin layer with a specific irradiation dose at a temperature within a specific range in an atmosphere having a specific oxygen concentration. It has been found that a composite material having a cross-linked fluororesin layer can be obtained.

  By adopting such a combination of multiple selected conditions, the fluororesin layer is effectively cross-linked without deteriorating the fluororesin, and a cross-linked fluororesin layer with significantly improved wear resistance is formed. can do. In the composite material obtained by the production method of the present invention, the crosslinked fluororesin layer exhibits a high degree of wear resistance required for a non-rotating pressure member. The present invention has been completed based on these findings.

  According to the present invention, there is provided a non-rotating pressure member disposed in a fixing unit of an electrophotographic image forming apparatus, the non-rotating pressure member having a crosslinked fluorine resin layer formed on a substrate. The cross-linked fluororesin layer is a resin composite material, and the abrasive grains were uniformly applied and bonded to the nylon nonwoven fabric on the cross-linked fluororesin layer in accordance with the rotational abrasion test method disclosed in the present specification. A three-dimensional structure, circular abrasive with a diameter of 75 mmφ and a weight of 2 kgf are placed in this order, and a rotating body consisting of both the abrasive and the weight is rotated at 200 rpm, 100,000 cumulative rotations A non-rotating pressure member is provided which is a cross-linked fluororesin layer having a weight loss by number of 10 μm or less.

Further, according to the present invention, there is provided a method for producing a non-rotating pressure member disposed in a fixing unit of an electrophotographic image forming apparatus,
(1) Step 1 of forming an unfired and uncrosslinked fluororesin layer on the substrate;
(2) Step 2 of heating and baking the fluororesin layer to a temperature in the range from the melting point (Tm) of the fluororesin to a temperature 150 ° C higher than the melting point (Tm + 150 ° C);
(3) The temperature of the fired uncrosslinked fluororesin layer is within the range from a temperature (Tm-50 ° C) lower by 50 ° C than the melting point (Tm) of the fluororesin to a temperature (Tm + 50 ° C) higher by 50 ° C than the melting point. Step 3 for adjusting the temperature; and (4) Irradiation with an irradiation dose in the range of 1 to 1000 kGy is applied to the temperature-adjusted uncrosslinked fluororesin layer in an atmosphere with an oxygen concentration of 0.1 to 1000 ppm, Step 4 of crosslinking the uncrosslinked fluororesin;
By this, the manufacturing method of the non-rotating pressure member including the process of forming a crosslinked fluororesin layer is provided.

  According to the present invention, a non-rotating pressure member having a crosslinked fluororesin layer with significantly improved wear resistance is provided. The abrasion resistance of the fluororesin layer can be evaluated by a rotational wear test described later. The non-rotating pressure member having a cross-linked fluororesin layer obtained by the production method of the present invention has a cumulative number of rotations of 100,000 when a rotating body composed of both an abrasive and a weight is rotated at 200 rpm. Even in this case, the wear loss is very low. The non-rotating pressure member having a cross-linked fluororesin layer of the present invention is notably excellent in wear resistance, and there is no cracking in the cross-linked fluororesin layer, and adhesion between the cross-linked fluororesin layer and the substrate is improved. Is also excellent.

It is sectional drawing which shows an example of the fixing apparatus of a film heating system. It is sectional drawing which shows an example of a non-rotating pressurization member. FIG. 3 is an explanatory diagram of a rotational wear test.

  Examples of the fluororesin used in the present invention include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Can be mentioned. These fluororesins can be used alone or in combination of two or more.

  Among these fluororesins, PTFE, PFA, and a mixture thereof are preferable from the viewpoint of heat resistance and wear resistance, and PTFE alone or a mixture of PTFE and PFA is more preferable. In order to form a crosslinked fluororesin layer having a high degree of wear resistance, it is particularly preferable to use PTFE alone. When PTFE and PFA are used in combination, the mass ratio of the two is preferably in the range of 10:90 to 90:10, more preferably 30:70 to 70:30, particularly preferably 40:60 to 60:40. It is.

  As the fluororesin, in the form of dispersion such as PTFE dispersion, PFA dispersion, and FEP dispersion in which fluororesin particles are colloidally dispersed in an aqueous medium, from the viewpoint of coating properties on a substrate. It is preferable to use it. These fluororesin dispersions may contain two or more fluororesins. As the fluororesin, a powder coating can be used if desired.

  As the fluororesin, an unfired and uncrosslinked one is used. The melting point of the fluororesin means a crystalline melting point (Tm) detected as a melting peak when the temperature is raised at a rate of temperature rise of 10 ° C./min using a differential scanning calorimeter (DSC). The typical melting point of each fluororesin is as follows. The melting point of PTFE is 327 ° C. The melting point of PFA is 310 ° C. The melting point of FEP is 275 ° C.

  When each fluororesin is a copolymer containing a small amount of the second component or the third component as a copolymer component, the melting point thereof may vary from the above-mentioned typical melting point value. In the present invention, when two or more kinds of fluororesins are used in combination, the melting point means the highest melting point among those melting points. For example, when a fluororesin composed of a mixture of PTFE and PFA is used, the melting point of the fluororesin means the melting point of PTFE (Tm = 327 ° C.).

  In the present invention, the melting point (Tm) of a fluororesin is defined as the melting point of an unfired and uncrosslinked fluororesin used as a starting material. The melting point of fluororesin may fluctuate due to firing or crosslinking, but the melting point when determining the firing temperature and irradiation temperature means the melting point of the unfired and uncrosslinked fluororesin used as a raw material. It shall be.

  If desired, the fluororesin can contain additive components such as organic or inorganic fillers, colorants, plasticizers, and stabilizers. Examples of the filler include glass fiber, boron nitride, silicon carbide, and alumina. When the fluororesin is filled with a heat conductive filler such as boron nitride or silicon carbide, the non-rotating pressure member stores heat, so that energy efficiency can be improved. A fluororesin powder encapsulating a thermally conductive filler such as boron nitride or silicon carbide can also be used. From the viewpoint of greatly improving the abrasion resistance of the cross-linked fluororesin layer while maintaining the non-adhesiveness, nonbleeding, chemical resistance, heat resistance, etc. of the fluororesin, the fluororesin does not contain any additive component Is preferably used.

  As the base material, a material made of a material that exhibits thermal stability at the firing temperature and irradiation temperature of the fluororesin is generally used. Materials constituting the substrate include metals such as aluminum, iron, copper, and stainless steel; ceramics such as aluminum oxide, silicon nitride, silicon carbide, and tungsten carbide; glass; polyimide resin, polyamideimide resin, and polyetheretherketone resin Heat-resistant synthetic resins such as; The metal may be an alloy. As the stainless steel, magnetic or nonmagnetic stainless steel can be used.

  According to the production method of the present invention, the irradiation temperature can be set to a temperature lower than the melting point of the fluororesin, and a short irradiation process can be employed. Rubber materials such as silicone rubber and thermoplastic elastomer can also be used.

  The shape of the substrate is not particularly limited, and may be any shape that can be used as a non-rotating pressure member in various fixing devices such as a plate, a film (including a sheet), and a block. As a base material, it is preferable that they are a metal plate, a synthetic resin board, a synthetic resin film, a glass fiber sheet, and an elastic member (for example, pad-shaped elastic member). The substrate may be a single layer or a multilayer having a plurality of layers each having a different material. Examples of the multilayer substrate include a composite substrate having an aluminum / stainless layer structure.

  The substrate can be used without performing a surface treatment. In order to improve the adhesion between the substrate and the cross-linked fluororesin layer, the surface of the substrate can be etched or sandblasted. By chemical or electrochemical etching treatment, fine irregularities can be formed on the surface of the substrate, and the adhesion between the uncrosslinked fluororesin layer and the crosslinked fluororesin layer and the substrate can be improved.

  In many cases, the metal substrate is preferably etched on its surface. For example, when an aluminum substrate is used, an electrochemical etching process can be performed by using the aluminum substrate as an anode and energizing in an aqueous ammonium chloride solution. As a surface treatment method for the substrate, a sandblast treatment method can be employed. The adhesion between the substrate and the cross-linked fluororesin layer can also be improved by applying a primer to the surface of the substrate instead of the surface treatment. However, primer treatment is not suitable for technical fields that require high heat resistance.

  If the surface roughness of the substrate is excessively increased by the surface treatment, the surface roughness of the cross-linked fluororesin layer is excessively increased and the non-adhesiveness is lowered. On the other hand, if the surface roughness of the crosslinked fluororesin layer is too small, the smooth passage of the recording medium (transfer paper) in the nip portion may be hindered. The surface roughness Ra (JIS B 0601) of the crosslinked fluororesin layer is usually 0.08 μm or more, preferably 0.45 μm or more, more preferably 1.0 μm or more. The upper limit of the surface roughness Ra of the cross-linked fluororesin layer is usually 5 μm, and in many cases about 3 μm. It is preferable to adjust the surface roughness of the substrate so that the surface roughness desired for the crosslinked fluororesin layer can be achieved.

The method for producing a non-rotating pressure member of the present invention includes the following steps 1 to 4:
(1) Step 1 of forming an unfired and uncrosslinked fluororesin layer on the substrate;
(2) Step 2 of heating and baking the fluororesin layer to a temperature in the range from the melting point (Tm) of the fluororesin to a temperature 150 ° C higher than the melting point (Tm + 150 ° C);
(3) The temperature of the fired uncrosslinked fluororesin layer is within a range from a temperature (Tm-50 ° C) lower by 50 ° C than the melting point (Tm) of the fluororesin to a temperature (Tm + 50 ° C) higher by 50 ° C than the melting point. Step 3 for adjusting the temperature; and (4) Irradiation with an irradiation dose in the range of 1 to 1000 kGy is applied to the temperature-adjusted uncrosslinked fluororesin layer in an atmosphere with an oxygen concentration of 0.1 to 1000 ppm, Step 4 of crosslinking the uncrosslinked fluororesin;
Is included.

  In step 1, an unfired and uncrosslinked fluororesin layer is formed on the substrate. In order to form a fluororesin layer on a substrate, a method of applying a fluororesin dispersion on the substrate by a dipping method, a spin coating method, a spray coating method, or the like and drying is usually employed. The fluororesin layer can also be formed by a method of applying a fluororesin powder coating on the substrate. Examples of the powder coating method include electrostatic coating and fluidized dipping. It is preferable to employ a fluororesin dispersion coating method from the viewpoint of easily forming a uniform and thin coating film.

  The thickness of the fluororesin layer is preferably within a range where a uniform cross-linked structure can be formed through transmission of radiation such as an electron beam. The thickness of the fluororesin layer is preferably within a range in which characteristics such as wear resistance and mechanical properties required for a non-rotating pressure member having a cross-linked fluororesin layer can be sufficiently exhibited. The thickness of the fluororesin layer is usually 1 to 200 μm, preferably 3 to 150 μm, more preferably 4 to 100 μm, and particularly preferably 5 to 50 μm. Since the fluororesin layer crosslinked by irradiation with radiation is excellent in wear resistance, the thickness thereof can be reduced. In many cases, good results can be achieved by setting the thickness of the fluororesin layer within the range of 5 to 30 μm.

  In step 2, the fluororesin layer on the substrate is baked by heating to a temperature in the range from the melting point (Tm) of the fluororesin to a temperature 150 ° C higher than the melting point (Tm + 150 ° C). This temperature is called the firing temperature.

  The firing temperature is in the range of Tm to (Tm + 150 ° C), preferably (Tm + 5 ° C) to (Tm + 135 ° C), more preferably (Tm + 10 ° C) to (Tm + 125 ° C). When the fluororesin is PTFE (Tm = 327 ° C.), the firing temperature is 327 to 477 ° C., preferably 332 to 462 ° C., more preferably 337 to 452 ° C. If the firing temperature is too low, it is difficult to form a uniform and flat fluororesin layer, and cracks may occur in the crosslinked fluororesin layer. On the other hand, if the firing temperature is too high, thermal degradation of the fluororesin tends to occur.

  The firing time is usually in the range of 1 to 60 minutes, preferably 5 to 40 minutes, more preferably 10 to 30 minutes, depending on the firing temperature. If the firing time is too short, it becomes difficult to form a fluororesin layer having a uniform thickness and a flat surface. If the firing time is too long, the fluororesin is thermally deteriorated, and the production efficiency and energy efficiency are lowered. By calcination, a crosslinked fluororesin layer having excellent wear resistance and adhesion to the substrate can be formed after the irradiation step.

  Firing can be performed batchwise by a method in which the base material on which the unfired and uncrosslinked fluororesin layer is formed is held in a heating furnace maintained at the firing temperature. The base material on which the fluororesin layer is formed may be placed on a hot plate and fired by a method of heating at a predetermined temperature for a predetermined time. The base material on which the fluororesin layer is formed is placed on the hot plate on the base material side, and a heater built in the hot plate is energized, or the hot plate is heated by an external heating means. By using a hot plate, the temperature of the fluororesin layer can be accurately set within a desired range.

  When firing is performed in a continuous process, a method of passing a heating zone in a heating furnace (baking furnace) while a base material on which an unfired and uncrosslinked fluororesin layer is formed is placed on a conveyor belt and travels. Can be adopted. Examples of the heating zone include a structure in which a plurality of sets of heaters arranged so as to face each other in the vertical direction are arranged along the running direction of the conveyor belt. It is also possible to adopt a method in which a base material on which a fluororesin layer is formed is placed on a hot plate, and this is further placed on a conveyor belt for running.

  In step 3, the temperature of the uncrosslinked fluororesin layer baked in step 2 is 50 ° C. lower than the melting point (Tm) of the fluororesin (Tm−50 ° C.) and 50 ° C. higher than the melting point (Tm + 50 ° C.). Adjust the temperature within the range up to. This temperature is called the irradiation temperature. That is, Step 3 is a step for setting the uncrosslinked fluororesin layer after firing to a predetermined irradiation temperature.

  The irradiation temperature is in the range of (Tm−50 ° C.) to (Tm + 50 ° C.), but from the viewpoint of wear resistance, it is preferably (Tm−35 ° C.) to (Tm + 35 ° C.), more preferably (Tm−30 ° C.). ° C) to (Tm + 30 ° C). If the irradiation temperature is too low, the abrasion resistance of the crosslinked fluororesin layer tends to be insufficient. If the irradiation temperature is too high, thermal degradation may occur, and the wear resistance tends to decrease.

  When the fluororesin is PTFE, the irradiation temperature is in the range of 277 to 377 ° C, preferably 292 to 362 ° C, more preferably 297 to 357 ° C. Even when the fluororesin is a mixture of PTFE and PFA, the irradiation temperature is preferably within the above range.

  Since the uncrosslinked fluororesin layer after firing is already fired at a high temperature equal to or higher than the melting point, if the irradiation temperature is increased, thermal degradation may occur. In such a case, in the production method of the present invention, the temperature of the uncrosslinked fluororesin layer baked in Step 3 is 35 ° C. lower than the melting point (Tm) of the fluororesin (Tm−35 ° C.). It is preferable to adjust to a temperature in the range up to less than, and more preferably to a temperature in the range from (Tm-30 ° C.) to less than the melting point. Thus, by suppressing irradiation temperature low, the thermal deterioration of an uncrosslinked fluororesin layer can be suppressed and energy cost can also be reduced.

  Even when the irradiation temperature is set to a temperature equal to or higher than the melting point (Tm) of the fluororesin, the temperature of the uncrosslinked fluororesin layer baked in the step 3 is 35 ° C. higher than the melting point from the melting point (Tm) of the fluororesin. It is preferable to adjust to a temperature within the range of (Tm + 35 ° C.), more preferably to a temperature within the range of (Tm + 30 ° C.) from the melting point, and to a temperature within the range of (Tm + 25 ° C.) from the melting point. It is particularly preferred. Thus, by suppressing the irradiation temperature to a low level, it is possible to form a crosslinked fluororesin layer having excellent wear resistance while suppressing thermal deterioration of the uncrosslinked fluororesin layer and energy cost.

  In order to adjust the fired uncrosslinked fluororesin layer to the irradiation temperature, the substrate (composite material) on which the uncrosslinked fluororesin layer is formed is held in a heating furnace maintained at a predetermined temperature, or on the substrate side. The hot plate is placed on the hot plate and energized by a heater built in the hot plate, or the hot plate is heated by an external heating means. When a hot plate is used, the temperature of the uncrosslinked fluororesin layer can be accurately set to an irradiation temperature within a desired range.

  To adjust the calcined uncrosslinked fluororesin layer to the irradiation temperature in a continuous process, while the substrate on which the calcined uncrosslinked fluororesin layer is formed is placed on a conveyor belt and travels, the heating zone in the heating furnace It is possible to adopt a method of passing the filter. Examples of the heating zone include a structure in which a plurality of sets of heaters arranged so as to face each other in the vertical direction are arranged along the running direction of the conveyor belt. This continuous heating step is preferably arranged as a step following the continuous baking step. In this case, the temperature of the heater in the first half of the heating zone in the heating furnace is set to the firing temperature, and the temperature of the heater in the second half is set to the irradiation temperature. It is also possible to adopt a method in which a base material on which an uncrosslinked fluororesin layer is formed is placed on a hot plate, and this is further carried on a conveyor belt.

  Since the baked uncrosslinked fluororesin layer is already heated to a high temperature, the time for adjusting to the irradiation temperature can be shortened. The time for adjusting the irradiation temperature depends on the thickness of the uncrosslinked fluororesin layer, the firing temperature, the irradiation temperature, the type of radiation, etc., but is usually 3 to 60 seconds, preferably 5 to 40 seconds, more preferably 10 to 10 seconds. Within 30 seconds. As described above, the time for adjusting to the irradiation temperature can be shortened and is more efficient as it is shorter, but the upper limit can be set to about 5 minutes or 30 minutes as desired.

  In step 4, the uncrosslinked fluororesin layer is crosslinked by irradiating the temperature-adjusted uncrosslinked fluororesin layer with radiation having an irradiation dose of 1 to 1000 kGy in an atmosphere having an oxygen concentration of 0.1 to 1000 ppm. . By this step 4, a cross-linked fluororesin layer containing a fluororesin cross-linked by radiation irradiation is formed.

  Examples of radiation include α rays (particle beams of helium-4 nuclei emitted from radionuclides that undergo α decay), β rays (negative electrons and positrons emitted from nuclei), and electron beams (almost constant kinetic energy). Particle beam such as electron beam, generally generated by accelerating thermionic electrons in vacuum; gamma ray (emitted and absorbed by transitions between energy levels of nuclei and elementary particles, pair annihilation of elementary particles, pair production, etc.) Ionizing radiation such as an electromagnetic wave having a short wavelength).

  Among these radiations, from the viewpoint of crosslinking efficiency and operability, electron beams and γ rays are preferable, and electron beams are more preferable. In particular, an electron beam has advantages such as easy availability of an electron beam irradiation apparatus, simple irradiation operation, and the ability to employ a continuous irradiation process.

  After adjusting the temperature of the uncrosslinked fluororesin layer after firing to the irradiation temperature, it is preferable to irradiate the radiation immediately in order to avoid thermal degradation and increase energy efficiency. The radiation dose is in the range of 1-1000 kGy. From the viewpoint of wear resistance, the irradiation dose is preferably in the range of 50 to 1000 kGy, more preferably 65 to 1000 kGy, and particularly preferably 70 to 1000 kGy. When the thickness of the uncrosslinked fluororesin layer is relatively thin, the upper limit of the irradiation dose can be lowered to preferably 250 kGy, more preferably 200 kGy.

  From the viewpoint of obtaining a cross-linked fluororesin layer having a high tensile elongation at break and excellent flexibility, the irradiation dose is preferably set to a low level in the range of 65 to 250 kGy, more preferably 70 to 200 kGy. From the viewpoint of obtaining a cross-linked fluororesin layer having remarkably excellent wear resistance, the lower limit of the irradiation dose is preferably 80 kGy, more preferably 90 kGy, and particularly preferably 100 kGy.

  If the irradiation dose is too small, the crosslinking density cannot be sufficiently increased, and it becomes difficult to sufficiently improve the adhesion and wear resistance of the crosslinked fluororesin layer to the substrate. When the irradiation dose is too large, the adhesion of the cross-linked fluororesin layer to the base material and the wear resistance are improved, but the elongation of the cross-linked fluororesin layer may be reduced and cracks may occur.

  The atmosphere in the irradiation region is an atmosphere having an oxygen concentration of 0.1 to 1000 ppm. Conventionally, it has been considered that irradiation cross-linking of a fluororesin needs to be performed in the absence of oxygen or in an oxygen-free atmosphere. According to the research results of the present inventors, it has been found that adjusting the oxygen concentration within a certain range rather contributes to improving the wear resistance of the crosslinked fluororesin layer. From the viewpoint of wear resistance, the oxygen concentration in the radiation irradiation region is preferably 1 to 100 ppm, more preferably 2 to 50 ppm, and particularly preferably 3 to 20 ppm.

  In order to maintain the oxygen concentration in the irradiation region within the above range, for example, the irradiation region is sealed and evacuated, or an inert gas such as nitrogen gas is allowed to flow in the irradiation region, or air in the irradiation region is supplied. After removing by evacuation, a method of flowing an inert gas can be employed. As the inert gas, it is efficient to use nitrogen gas having a low oxygen concentration, which is advantageous in terms of cost.

  More specifically, as a method of maintaining the oxygen concentration in the radiation irradiation region within the above range, a chamber having an irradiation window made of titanium foil on the upper surface is used, and the inside of the chamber is evacuated to remove air. A method of flowing an inert gas after evacuating the chamber; a method of flowing an inert gas into the chamber; and the like. A continuous process can be performed by continuously transporting an object to be irradiated (a substrate having an uncrosslinked fluororesin layer heated to an irradiation temperature after firing) and irradiating it with an electron beam while flowing an inert gas. Irradiation crosslinking can be performed. A conveyor belt can be used to continuously convey the irradiated object. It is also possible to adopt a method in which an object to be irradiated is placed on a hot plate and sequentially conveyed by a conveyor belt while precisely controlling the irradiation temperature.

  As another method of performing irradiation in a continuous process, a method using a continuous firing furnace can be exemplified. As a continuous baking furnace, the thing of the structure which has arrange | positioned several sets of the heater arrange | positioned facing up and down along the running direction of a conveyor belt can be illustrated. The heater temperature in the first half of the heating zone is set to the firing temperature, and the heater temperature in the second half is set to the irradiation temperature. An irradiation device is arranged at the end of the heating zone. A cooling unit is provided after the irradiation device.

  The entire heating zone, irradiation region, and cooling unit are surrounded by a housing or chamber, and the firing step and the irradiation step are continuously performed while an inert gas is allowed to flow through the inside. In the irradiation region, an irradiation window made of titanium foil is arranged so that outside air does not flow.

  Even if the irradiation area is sealed, a small amount of air is mixed from the outside. It is desirable to continue to flow an inert gas such as nitrogen gas having a low oxygen concentration from the gas cylinder and to precisely control the oxygen concentration in the irradiation region in consideration of a small amount of air from the external environment. Therefore, it is preferable to control the oxygen concentration in the irradiation region based on the oxygen concentration in the inert gas to be used and the actually measured value of the oxygen concentration in the irradiation region. The oxygen concentration in the irradiated region is not necessarily proportional to the wear resistance of the crosslinked fluororesin layer. If the oxygen concentration in the irradiated region is too high or too low, the wear resistance tends to decrease. When the irradiation temperature is controlled to a temperature lower than the melting point of the fluororesin, the wear resistance of the crosslinked fluororesin layer can be less dependent on the oxygen concentration in the irradiated region.

  When the substrate has a three-dimensional shape other than a flat shape such as a film, sheet, or plate, for example, while rotating the substrate, radiation such as an electron beam is irradiated on the entire uncrosslinked fluororesin layer. It is desirable to irradiate uniformly. The irradiation time is substantially instantaneous when a scanning electron beam irradiation apparatus is used.

  The non-rotating pressure member of the present invention is remarkably excellent in wear resistance of the cross-linked fluororesin layer, and also excellent in crack resistance of the cross-linked fluororesin layer and adhesion between the substrate and the cross-linked fluororesin layer. Yes. Therefore, a crack does not generate | occur | produce in a crosslinked fluorine resin layer, or a crosslinked fluorine resin layer does not peel.

  The adhesion between the substrate and the cross-linked fluororesin layer can be evaluated by a cross-cut test [JIS K 5400 (1998 edition)]. The cross cut test is a test in which 100 mm cross cuts are made by making a 1 mm square penetrating flaw on the fluororesin layer, and an adhesive tape is attached thereon and peeled off. The cross-linked fluororesin composite material of the present invention does not peel 100 cross-cuts even when the cross-cut test is repeated 300 times.

  The abrasion resistance of the crosslinked fluororesin layer can be evaluated by a rotational abrasion test. In the rotational wear test, a composite base material was fixed, and a 3M Scotch Bright (registered trademark) # 3000 (75 mm diameter) and a 2 kgf weight were placed in this order on the cross-linked fluororesin layer. This is a test method in which a rotating body consisting of 3000 and a weight is rotated at 200 rpm, and the relationship between the total number of revolutions (times) and the film thickness reduction due to wear (wear loss) is measured. Scotch Bright is an abrasive having a three-dimensional structure in which abrasive grains (aluminum oxide or silicon carbide) are uniformly applied and bonded to a nylon nonwoven fabric.

  The cross-linked fluororesin layer of the present invention has a film thickness reduction amount (wear loss) of 10 μm or less, preferably 8.0 μm or less, even when the cumulative number of rotations in the rotational wear test is 100,000. More preferably, it is 5.0 μm or less, particularly preferably 4.0 μm or less, and exhibits excellent wear resistance. By controlling the irradiation crosslinking conditions, the wear loss of the crosslinked fluororesin layer can be reduced to 3.0 μm or less, and further to 2.0 μm or 1.0 μm or less.

  The cross-linked fluororesin layer of the present invention is excellent in adhesion to the base material, and by selecting the irradiation conditions, the cross-linked fluororesin layer is prevented from peeling or cracking while being resistant. Abrasion can be remarkably increased.

  As the irradiation condition, the temperature of the uncrosslinked fluororesin layer baked in the step 3 is a temperature in a range from 35 ° C. lower than the melting point (Tm) of the fluororesin (Tm−35 ° C.) to less than the melting point. Then, in the step 4, the uncrosslinked fluororesin layer whose temperature was adjusted was irradiated with radiation having an irradiation dose in the range of 65 to 1000 kGy in an atmosphere having an oxygen concentration in the range of 1 to 100 ppm. And a method of crosslinking an uncrosslinked fluororesin.

  In the irradiation conditions described above, the irradiation temperature is more preferably a temperature within a range from (Tm-30 ° C.) to less than the melting point. The oxygen concentration is more preferably in the range of 2 to 50 ppm, particularly preferably 3 to 20 ppm. The lower limit of the irradiation dose is preferably 70 kGy, particularly preferably 100 kGy.

  As other preferable irradiation conditions, the temperature of the uncrosslinked fluororesin layer baked in Step 3 is a temperature within the range from the melting point (Tm) of the fluororesin to a temperature 35 ° C higher than the melting point (Tm + 35 ° C). Then, in the step 4, the uncrosslinked fluororesin layer whose temperature was adjusted was irradiated with radiation having an irradiation dose of 65 to 1000 kGy in an atmosphere having an oxygen concentration of 1 to 100 ppm. And a method of crosslinking an uncrosslinked fluororesin.

  In the irradiation conditions described above, the irradiation temperature is more preferably from the melting point to (Tm + 30 ° C.), particularly preferably from the melting point to (Tm + 25 ° C.). The oxygen concentration is more preferably in the range of 2 to 50 ppm, particularly preferably 3 to 20 ppm. The lower limit of the irradiation dose is preferably 70 kGy, particularly preferably 100 kGy.

  Specific examples of the non-rotating pressure member of the present invention include a plate-like non-rotating pressure member (non-rotating pressure plate) in which a cross-linked fluororesin layer is formed on a metal plate such as an aluminum alloy or stainless steel; a polyimide film, etc. Non-rotating pressure member having a cross-linked fluororesin layer formed on a synthetic resin film; Non-rotating pressure member having a cross-linked fluororesin layer formed on a glass fiber sheet; Cross-linking on an elastic member (for example, a pad-like elastic member) And a non-rotating pressure member having a fluororesin layer formed thereon.

  Examples of the fixing unit in which the non-rotating pressure member of the present invention is disposed include, but are not limited to, those having the following structure.

1) A fixing roller including a heating unit, and a non-rotating pressure member that forms a nip portion so as to face and press against the fixing roller, and between the rotating fixing roller and the fixed non-rotating pressure member A fixing unit that transports a recording medium on which an unfixed toner image is formed to the nip portion, and heats and pressurizes the recording medium to fix the unfixed toner image on the recording medium.

  In the fixing unit, by driving the fixing roller, the recording medium on which the unfixed toner image is formed is conveyed to the nip portion between the rotating fixing roller and the fixed non-rotating pressure member, and heated and pressed. . For the fixing roller, a fluororesin layer is usually formed on the surface of a hollow cylindrical cored bar made of aluminum, iron, stainless steel (SUS) or the like via a heat-resistant rubber layer such as silicone rubber, if necessary. Is. A typical example of the non-rotating pressure member is a non-rotating pressure plate having a cross-linked fluororesin layer provided on a plate substrate, but a film (including a sheet) on which a cross-linked fluororesin layer is formed is supported. It may have other structures such as a structure fixed on top.

2) A fixed heating body, a fixing belt having the heating body disposed therein, a driving roller that faces and presses against the fixing belt, and a non-rotating pressurization that faces and presses against the fixing belt to form a nip portion. A recording medium on which an unfixed toner image is formed is conveyed to the nip portion between the fixing belt rotated by the driving roller and the fixed non-rotating pressure member, and heated and pressurized, A fixing unit for fixing the unfixed toner image on the recording medium;

  In the fixing unit, the fixing belt is rotated by the driving roller. The fixing belt is formed by forming a fluororesin layer directly on a surface layer of a flexible tube such as a polyimide film or a thin SUS sleeve, or via a heat resistant rubber layer such as silicone rubber. The heating element is disposed inside the fixing belt and does not slide on the inner peripheral surface of the fixing belt. The heating element may be an electric heater or a combination of a heater lamp and a reflector.

3) A fixed heating body, a fixing belt that slides against the heating body on the inner peripheral surface, a driving roller that faces and presses a part of the heating body via the fixing belt to form a nip portion, and the fixing A non-rotating pressure member that forms a nip portion by facing and press-contacting a part of the heating body via a belt is formed, the fixing belt is rotated by the driving roller, and unfixed in the two nip portions. A fixing unit that transports a recording medium on which a toner image has been formed, heats and pressurizes the recording medium, and fixes the unfixed toner image on the recording medium.

  The fixing unit includes the structure shown in FIG. The fixing belt is rotated by a small driving roller. There are two nip portions between the heating body and a non-rotating pressure member (for example, a non-rotating pressure plate) and between the heating body and the driving roller.

4) The non-rotating fixed member, which includes a fixing roller, a non-rotating pressure member that faces and presses against the fixing roller to form a nip portion, and a heating unit integrated with the non-rotating pressure member and is fixed to the rotating fixing roller A fixing unit that transports, heats and presses a recording medium on which an unfixed toner image is formed to the nip portion between the pressing member and fixes the unfixed toner image on the recording medium.

  In the fixing unit, the fixing roller may include a heating unit or may not include a heating unit. A plate or film (including a sheet) provided with a cross-linked fluororesin layer on the surface of the substrate is fixed to the heating means. Depending on the shape of the heating means, a cross-linked fluororesin layer may be directly formed at a location facing and pressed against the fixing roller. In this fixing unit, heating is performed from the back surface of a recording medium such as transfer paper.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The measurement methods and evaluation methods for various physical properties and characteristics are as follows.

(1) Cracks Cross-linked fluororesin layers crosslinked by irradiation with radiation were visually observed to evaluate the presence or absence of cracks. An uncrosslinked fluororesin layer was also evaluated in the same manner.

(2) Cross cut test A cross cut test was performed in accordance with the provisions of JIS K 5400 (1998 edition) of Japanese Industrial Standards. An operation of making 100 cross-cuts with a 1 mm square penetrating scratch on the cross-linked fluororesin layer on the substrate, and sticking an adhesive tape [CT405AP-18 manufactured by Nichiban Co., Ltd.] on it and peeling it off Went. For each sample, the operation of applying and peeling the adhesive tape was performed 300 times, and the remaining number of sheets of the 300th grid (sheet / 100) was examined.

(3) Rotational wear test A rotational wear test was performed by the method shown in FIG. The composite material in which the cross-linked fluororesin layer 32 was formed on the base material 31 was screwed onto the fixing member 33 on the base material 31 side. The fixing member 33, the base material 31, and the cross-linked fluororesin layer 32 constitute a fixing portion 37. On the cross-linked fluororesin layer 32, an abrasive 35 having a diameter of 75 mmφ, a thickness of 8 mm, and a weight of 1.8 gf and a circular cross section (3M Scotch Bright # 3000 (registered trademark)) and a 2 kg weight 34 are placed in this order. . The abrasive 35 and the weight 34 constitute a rotating part 36. The rotating unit 36 is rotated at 200 rpm (number of rotations per minute). When the cumulative number of rotations reached each predetermined value, the amount of decrease in the thickness of the crosslinked fluororesin layer was measured. The amount of decrease in the thickness of the cross-linked fluororesin layer (wear loss) was measured using an eddy current digital film thickness meter [EDY-II, manufactured by Sanko Electronic Laboratory Co., Ltd.] that can detect a change in thickness of 0.1 μm. It was measured. The case of an uncrosslinked fluororesin layer was also evaluated in the same manner.

[Example 1]
As a base material, a disk having a diameter of 360 mm and a thickness of 1.7 mm formed from an aluminum alloy (JIS-3003; Al—Mn alloy) was used. An aluminum disk was used as an anode, and electrochemical etching was performed in an aqueous ammonium chloride solution with an electric quantity of 25 coulomb / cm ² to form fine irregularities on the surface of the aluminum disk.

  A PTFE dispersion (D-10FE, manufactured by Daikin) was spin-coated on the surface-treated aluminum disc and dried to form an unfired and uncrosslinked PTFE layer having a thickness of 11 μm. The composite material having the uncrosslinked PTFE layer was baked by being held in a heating furnace maintained at 410 ° C. for 20 minutes.

  The base material having the fired uncrosslinked PTFE layer was placed on a hot plate and adjusted to a temperature of 300 ° C. This hot plate was conveyed by the conveyor belt to the irradiation area | region of the conveyor type | formula electron beam irradiation apparatus by NHV Corporation. In the chamber of the electron beam irradiation apparatus, nitrogen gas having an oxygen concentration of 0.1 ppm was flowed to maintain the oxygen concentration in the irradiation region at 3.4 ppm. PTFE was crosslinked by irradiating an electron beam with an acceleration voltage of 1.16 MeV from above the uncrosslinked PTFE layer so that the irradiation dose was 100 kGy. The thickness of the crosslinked PTFE layer of the composite material thus obtained was 11 μm. The results are shown in Table 1.

[Examples 2 to 8 and Comparative Examples 1 to 3]
A composite material in which a crosslinked fluororesin layer was formed on a substrate was produced in the same manner as in Example 1 except that the thickness of the PTFE layer and the irradiation temperature were changed as shown in Tables 1 and 2. The results are shown in Tables 1 and 2.

(Discussion)
From the results of Tables 1 and 2, the following can be understood.

(1) In the case where the fluororesin layer was not irradiated and crosslinked (Comparative Example 1), the wear loss at an accumulated rotational speed of 25,000 times exceeded 10 μm, the wear resistance was poor, and non-rotating pressure was applied. It is a composite material that lacks durability as a member.

(2) When the irradiation temperature is too low (Comparative Examples 2 and 3), the wear amount exceeds 10 μm at the time when the cumulative number of revolutions is 50,000 times or 75,000 times, and the non-rotating pressure member Is a composite material with insufficient durability and wear resistance.

(3) As shown in Examples 1 to 5, even when the irradiation temperature is lower than the melting point (327 ° C.) of PTFE, from a temperature (Tm-50 ° C.) lower by 50 ° C. than the melting point (Tm) of the fluororesin. The temperature is adjusted to below the melting point, preferably 35 ° C. lower than the melting point (Tm) of the fluororesin (Tm−35 ° C.) to below the melting point, and then the oxygen concentration is preferably 1 to 100 ppm. More preferably, the amount of wear loss is 3.0 μm or less even when the cumulative number of revolutions is 100,000 by irradiation crosslinking in an atmosphere controlled within the range of 2 to 50 ppm, particularly preferably 3 to 20 ppm. Can be reduced to 2.0 μm or 1.0 μm or less.

(4) As shown in Examples 5 to 8, even when the irradiation temperature is higher than the melting point (327 ° C.) of PTFE, the temperature is within the range of 50 ° C. higher than the melting point (Tm + 50 ° C.). By adjusting, a composite material having a wear loss of 10 μm or less can be obtained even when the cumulative number of revolutions is 100,000. In order to reduce the wear loss preferably to 8.0 μm or less, more preferably 5.0 μm or less, and particularly preferably 4.0 μm or less, the irradiation temperature is more preferably from the melting point (Tm + 30 ° C.), particularly preferably from the melting point ( It can be seen that it is desirable to set the temperature within the range of (Tm + 25 ° C.). Even at this irradiation temperature, it is desirable to carry out irradiation crosslinking in an atmosphere in which the oxygen concentration is preferably controlled within the range of 1 to 100 ppm, more preferably 2 to 50 ppm, and particularly preferably 3 to 20 ppm.

[Example 9]
As a base material, a disk having a diameter of 360 mm and a thickness of 1.7 mm formed from an aluminum alloy (JIS-3003; Al—Mn alloy) was used. An aluminum disk was used as an anode, and electrochemical etching was performed in an aqueous ammonium chloride solution with an electric quantity of 25 coulomb / cm ² to form fine irregularities on the surface of the aluminum disk.

  A PTFE dispersion (D-10FE, manufactured by Daikin) was spin-coated on the surface-treated aluminum disc and dried to form an unfired and uncrosslinked PTFE layer having a thickness of 11 μm. The composite material having the uncrosslinked PTFE layer was baked by being held in a heating furnace maintained at 410 ° C. for 20 minutes.

  The base material having the fired uncrosslinked PTFE layer was placed on a hot plate and adjusted to a temperature of 300 ° C. This hot plate was conveyed by the conveyor belt to the irradiation area | region of the conveyor type | formula electron beam irradiation apparatus by NHV Corporation. In the chamber of the electron beam irradiation apparatus, nitrogen gas having an oxygen concentration of 0.1 ppm was flowed to maintain the oxygen concentration in the irradiation region at 3.4 ppm. PTFE was crosslinked by irradiating an electron beam with an acceleration voltage of 1.16 MeV from above the uncrosslinked PTFE layer so that the irradiation dose was 60 kGy. The thickness of the crosslinked PTFE layer was 12 μm. The results are shown in Table 3.

[Examples 10 to 16]
A composite material in which a crosslinked PTFE layer was formed on a substrate was produced in the same manner as in Example 9 except that the irradiation dose was changed as shown in Table 3. The results are shown in Table 3.

(Discussion)
From the results in Table 3, it can be seen that even when the irradiation dose is increased to 1000 kGy, a crosslinked fluororesin layer with significantly excellent wear resistance can be formed. From the viewpoint of obtaining a cross-linked fluororesin layer having a high tensile elongation at break and excellent flexibility, the irradiation dose is preferably set to a low level in the range of 65 to 250 kGy, more preferably 70 to 200 kGy. From the viewpoint of obtaining a cross-linked fluororesin layer having remarkably excellent wear resistance, the lower limit of the irradiation dose is preferably 80 kGy, more preferably 90 kGy, and particularly preferably 100 kGy.

  The non-rotating pressure member having the crosslinked fluororesin layer of the present invention can be used by being disposed in a fixing unit of an electrophotographic image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Small rotation pressure member 2 Holding member 3 Non-rotation pressure member 4 Film 5 Heating body 6 Heating body holding member 7 Recording medium 8 Unfixed toner image 21 Pad-shaped pressing member (base material)
22 Release layer 31 Base material 32 Cross-linked fluororesin layer 33 Fixed member 34 Weight 35 Abrasive material 36 Rotating part 37 Fixed part

Claims (10)

A non-rotating pressure member disposed in a fixing unit of an electrophotographic image forming apparatus,
The non-rotating pressure member is a crosslinked fluororesin composite material in which a crosslinked fluororesin layer is formed on a substrate, and
The crosslinked fluororesin layer has a three-dimensional structure in which abrasive grains are uniformly applied to and bonded to a nylon nonwoven fabric on the crosslinked fluororesin layer in accordance with the rotational abrasion test method disclosed in the present specification, and has a diameter of 75 mmφ. When an abrasive material having a circular cross section and a weight of 2 kgf are placed in this order and a rotating body composed of both the abrasive material and the weight is rotated at 200 rpm, the wear loss at an accumulated number of revolutions of 100,000 is 10 μm or less. A non-rotating pressure member characterized by being a crosslinked fluororesin layer.   The non-rotating pressure member according to claim 1, wherein the cross-linked fluororesin layer is a cross-linked fluororesin layer cross-linked by irradiation with radiation.   A fixing roller including a heating unit; and a non-rotating pressure member that forms a nip portion so as to face and press against the fixing roller, and the nip between the rotating fixing roller and the fixed non-rotating pressure member 2. A non-rotating pressure member used in a fixing unit that conveys a recording medium on which an unfixed toner image is formed to a part, and heats and pressurizes the recording medium to fix the unfixed toner image on the recording medium. Or the non-rotating pressurization member of 2.   A fixed heating body, a fixing belt having the heating body disposed therein, a driving roller opposed to and in pressure contact with the fixing belt, and a non-rotating pressure member facing and pressed against the fixing belt to form a nip portion. A recording medium on which an unfixed toner image is formed is conveyed to the nip portion between the fixing belt that is rotated by the drive roller and the fixed non-rotating pressure member, and is heated and pressed, and the undefined 3. The non-rotating pressure member according to claim 1, wherein the non-rotating pressure member is a non-rotating pressure member used in a fixing unit for fixing a received toner image on the recording medium.   A fixed heating body, a fixing belt that slides against the heating body on an inner peripheral surface, a driving roller that faces and presses a part of the heating body via the fixing belt to form a nip portion, and the fixing belt. A non-rotating pressure member that forms a nip portion by being opposed to and pressed against a part of the heating body via the drive roller, and the fixing belt is rotated by the driving roller, and an unfixed toner image is formed on the two nip portions. 3. The non-rotating pressure member according to claim 1, wherein the non-rotating pressure member is a non-rotating pressure member used in a fixing unit that transports, heats and presses the recording medium on which the toner image is formed and fixes the unfixed toner image on the recording medium. Pressure member.   The non-rotating pressure member fixed to the rotating fixing roller includes a fixing roller, a non-rotating pressure member that forms a nip portion by being opposed to and pressed against the fixing roller, and a heating unit integrated with the non-rotating pressure member. Non-rotating pressure used in a fixing unit that transports, heats and presses a recording medium on which an unfixed toner image is formed to the nip portion between the member and fixes the unfixed toner image on the recording medium. The non-rotating pressure member according to claim 1 or 2, which is a member.   The non-rotating pressure member according to any one of claims 1 to 6, wherein the base material is a metal plate, a synthetic resin plate, a synthetic resin film, a glass fiber sheet, or an elastic member. A method of manufacturing a non-rotating pressure member disposed in a fixing unit of an electrophotographic image forming apparatus,
(1) Step 1 of forming an unfired and uncrosslinked fluororesin layer on the substrate;
(2) Step 2 of heating and baking the fluororesin layer to a temperature in the range from the melting point (Tm) of the fluororesin to a temperature 150 ° C higher than the melting point (Tm + 150 ° C);
(3) The temperature of the fired uncrosslinked fluororesin layer is within a range from a temperature (Tm-50 ° C) lower by 50 ° C than the melting point (Tm) of the fluororesin to a temperature (Tm + 50 ° C) higher by 50 ° C than the melting point. Step 3 for adjusting the temperature; and (4) Irradiation with an irradiation dose in the range of 1 to 1000 kGy is applied to the temperature-adjusted uncrosslinked fluororesin layer in an atmosphere with an oxygen concentration of 0.1 to 1000 ppm, Step 4 of crosslinking the uncrosslinked fluororesin;
The manufacturing method of the non-rotating pressurization member including the process of forming a bridge | crosslinking fluororesin layer by this.   In step 3, the temperature of the fired uncrosslinked fluororesin layer is adjusted to a temperature within a range of 35 ° C. lower than the melting point (Tm) of the fluororesin (Tm−35 ° C.) to less than the melting point, In the step 4, the uncrosslinked fluororesin layer whose temperature has been adjusted is irradiated with radiation within a range of 65 to 1000 kGy in an atmosphere with an oxygen concentration within a range of 1 to 100 ppm. The manufacturing method of Claim 8 which bridge | crosslinks.   In step 3, the temperature of the fired uncrosslinked fluororesin layer is adjusted to a temperature within the range from the melting point (Tm) of the fluororesin to a temperature 35 ° C higher than the melting point (Tm + 35 ° C), and then the step 4, the uncrosslinked fluororesin layer is crosslinked by irradiating the temperature-adjusted uncrosslinked fluororesin layer with radiation having an irradiation dose in the range of 65 to 1000 kGy in an atmosphere having an oxygen concentration in the range of 1 to 100 ppm. The manufacturing method of Claim 8.

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