JP4424134B2 - Fixing member and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing member used for a fixing device in a copying machine, a printer, or the like using an electrophotographic system, and also relates to an image forming apparatus using the fixing member.

Conventionally, in a copying machine or a printer using an electrophotographic system, a process of fixing an unfixed toner image formed on a recording medium to make a permanent image is called a fixing process. As the fixing step, a solvent fixing method, a pressure fixing method, and a heat fixing method are known.
In the solvent fixing method, solvent vapor is emitted, and there are problems with odor and hygiene. On the other hand, the pressure fixing method has the disadvantage that the fixing property is poor as compared with other fixing methods and the pressure sensitive toner is expensive. The solvent fixing method and the pressure fixing method are caused by these drawbacks, and both of them are hardly put into practical use. Actually, there is a heat fixing method in which the toner is melted by heating and thermally fused to a recording medium. Widely adopted.

  As a heat fixing method, as a conventional general method, a halogen lamp is disposed in either or both of a heating roll and a pressure roll, and either or both of the heating roll and the pressure roll are radiated by the radiant heat of the halogen lamp. A method of heating the surface has been adopted. Specifically, in this heat fixing method, a recording medium on which an unfixed toner image is formed is inserted into a nip where a heating roll and a pressure roll are in pressure contact with each other, and the toner is heated by the heat of the roll surface in the nip. A permanent image was formed by melting and fixing to a recording medium with a nip pressure.

  In this method, since a heat insulating layer such as an air layer exists between the halogen lamp and the surface of the heating roll or pressure roll to be heated, the time until the surface of the roll reaches the fixing possible temperature ( Hereinafter, it is simply referred to as “warm-up time”), which requires a time of about 3 to 8 minutes. Therefore, it is necessary to maintain the temperature of the fixing device at a high temperature to some extent even during the standby time when image formation is not performed, and this is the current situation that occupies most of the power consumption of a copying machine or the like.

On the other hand, a fixing device using a thin film and a fixed heater has been proposed as a fixing device that shortens the time required to reach the fixing temperature (for example, see Patent Documents 1 and 2).
In these fixing devices, a thin film is used to reduce the heat capacity of the heating member as much as possible. However, since the fixed heater has a heat capacity, the warm-up time cannot be substantially eliminated and several seconds to several tens of hours. A rise time of seconds is required.
In addition, it is the fixed heater that is directly heated, and the thin film that is in contact with the fixed heater is indirectly heated by heating it, so that the thermal efficiency is not sufficient. Further, since the fixed heater slides on the rotating thin film, problems such as wear of the fixed heater and the inner surface of the thin film occur.

Therefore, in recent years, using a fixing member in which a metal layer is formed on a substrate, a current is passed through a coil facing or included in the fixing member, and the magnetic field generated by the coil induces the metal layer of the heating member. An electromagnetic induction heating and fixing device that heats a metal layer with an eddy current is proposed (see, for example, Patent Documents 3 and 4).
In this method, the thermal efficiency is very high and the metal layer near the surface of the fixing member generates heat, so that the surface of the fixing member can be instantaneously heated to a fixable temperature. Further, since only the fixing member is in direct contact, the heat taken away can be reduced. Therefore, it is not necessary to keep the fixing member at a certain high temperature during the standby time between print jobs.

  On the other hand, rather than using a hollow or solid metal core material such as a roll type as the base of such a fixing member, it is possible to keep the heat capacity of the fixing member low by using a resin or metal thin film. As a result, the warm-up time can be shortened. An electromagnetic induction heating and fixing device using such a belt-type fixing member includes an electromagnetic induction fixing belt including a metal layer as a fixing member (hereinafter sometimes simply referred to as an “induction fixing belt”), and an addition. The pressure member, the electromagnetic induction coil, and the in-belt pad member.

  The electromagnetic induction coil is included in the induction fixing belt or disposed at a position facing the electromagnetic induction coil. The in-belt pad member is disposed inside the endless induction fixing belt and is pressed against the pressure member via the induction fixing belt to form a nip with the pressure member.

As the base of the induction fixing belt, metal belts such as nickel, iron, and stainless steel (SUS), and heat-resistant resins such as thermosetting polyimide, aromatic polyamide (aramid), and liquid crystal polymer are often used. Properties common to these include heat resistance and high strength.
The liquid crystal polymer used for the substrate is a polymer that exhibits liquid crystallinity in a solution state or a molten state, but a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state is particularly high in strength, high heat resistance, and low linear expansion coefficient. It has excellent properties such as high insulation, low moisture absorption, and high gas barrier properties.

  However, such a fixing member cannot prevent heat from escaping to the inside of the fixing member (the surface of the fixing member that does not come into contact with the recording medium).

Therefore, a fixing member having a short warm-up time and high thermal efficiency has been proposed by providing a heat insulating layer on the inner surface of the hollow cylindrical member heated by the energy supply means (see, for example, Patent Document 5). The heat insulating layer of the fixing member is composed of a glass layer formed by baking hollow glass beads on the inner surface of the hollow cylindrical member, or a pair of glass members with an air layer interposed therebetween.
JP-A-63-313182 JP-A-4-044074 JP 11-352804 A JP 2000-188177 A JP 2001-135472 A

  However, since the fixing member formed with the heat insulating layer is composed only of a glass material that is inflexible and brittle, the heat insulating layer itself is destroyed when an impact is applied. It is easy to expect and difficult to use for a long period of time, and is considered to be inferior in reliability. In addition, the fixing member is practically incapable of being used in the form of a belt or the like that requires flexibility, and is inferior in versatility.

Further, when the heat insulating layer is a glass layer formed by baking hollow glass beads on the inner surface of the hollow cylindrical member, it is inferior in productivity because it must be baked at a high temperature. Further, when a pressing member is provided on the inner peripheral surface side of the fixing member in order to adjust the pressing force between the fixing member and the pressing member disposed opposite to the fixing member, a heat insulating layer made of only a brittle material. May be destroyed.
Furthermore, it is difficult to ensure good lubricity between the two using a lubricant. This is because the surface irregularity of the inner peripheral surface of the fixing member is too large due to the glass beads constituting the heat insulating layer, so that the contact between the inner peripheral surface of the fixing member and the pressing member is not a surface contact but a point contact. In addition, it is expected that the lubricant cannot be uniformly dispersed at both interfaces.

  On the other hand, with respect to the configuration in which the heat insulating layer is composed of a pair of glass members with an air layer interposed therebetween, a specific method of forming the heat insulating layer having such a configuration is not described in Patent Document 5 at all. However, questions remain about feasibility. In addition, since the layered continuous air layer is formed between the pair of glass members, it is expected that it is difficult to ensure the strength of the heat insulating layer, and is considered to be inferior in practicality. For these reasons, such a configuration is extremely poor in feasibility and practicality.

Therefore, an object of the present invention is to solve the above problems.
That is, the present invention provides a fixing member having a short warm-up time, high thermal efficiency, excellent strength, versatility and manufacturability and high reliability, and an image forming apparatus using the fixing member for a fixing device. The issue is to provide.

The above-mentioned subject is achieved by the following present invention.
That is, the fixing member of the present invention is
<1> A polyimide solution or a polyimide precursor solution in which a hollow member of an organic material is dispersed is used as a base material, and a metal layer and a surface layer are laminated on the base material. the to Rukoto a fixing member characterized.
<2> The fixing member according to <1>, wherein the organic material is a resin.
<3> The fixing member according to <2>, wherein the resin is acrylic or cross-linked acrylic.
< 4 > The fixing member according to any one of <1> to <3>, wherein an elastic layer is laminated between the metal layer and the surface layer.
< 5 > The fixing member according to any one of <1> to < 4 >, wherein the fixing member is heated by an electromagnetic induction device.
< 6 > The fixing member according to any one of <1> to < 5 >, wherein the polyimide film is an endless belt.

The image forming apparatus according to the present invention includes:
< 7 > An image forming apparatus using the fixing member according to any one of <1> to < 6 > in a fixing device.

  As described above, according to the present invention, a fixing member having a short warm-up time, high thermal efficiency, excellent strength, versatility, and manufacturability and high reliability, and the fixing member are used as a fixing device. The used image forming apparatus can be provided.

The fixing member of the present invention uses , as a base material, a polyimide film obtained by firing a polyimide solution or a polyimide precursor solution in which a hollow member of an organic material is dispersed , and at least a metal layer is formed on the base material. and characterized that you laminate surface layer, the image forming apparatus of the present invention, a the constant wear member is characterized by using the fixing device.
Hereinafter, the fixing member and the image forming apparatus of the present invention will be described in detail.

<Fixing member>
The fixing member of the present invention can be used for a fixing device in a copying machine or the like using an electrophotographic method, and can be particularly suitably used for an electromagnetic induction heating fixing device.
The shape of the fixing member of the present invention is not particularly limited, and can be used in a roll shape or a belt shape such as an endless belt. Since it can be used even in a belt shape that requires flexibility, the fixing member of the present invention is highly versatile, and it is possible to manufacture fixing devices having various forms and specifications.

The fixing member of the present invention, a polyimide film described above as a base material, on to the substrate, a Rukoto be stacked at least a metal layer and the surface layer is essential, other optionally elastic layer or the like Can be provided. Particularly, it preferred embodiments for use in the fixing device of the electric magnetic induction heating method.
Hereinafter, each layer constituting the fixing member of the present invention will be described.

-Polyimide film-
The polyimide film used for the fixing member of the present invention is obtained by firing a polyimide solution or a polyimide precursor solution in which a hollow member of an organic material is dispersed.
By dispersing the hollow member of organic material, the polyimide film obtained by firing contains air (voids) in the film, and therefore has lower thermal conductivity than the polyimide film that does not contain air, and heat insulation. The film is highly effective.

  In addition, since the organic material that is the shell of the hollow member is fired, the film obtained by firing apparently has no shell and the polyimide film contains air. In addition, there is an advantage that the amount of air (porosity) contained in the polyimide film and the size of foaming can be easily controlled by the amount of the hollow member to be dispersed and the firing temperature.

Here, the hollow member of the organic material must satisfy the following two requirements.
(1) Do not dissolve when dispersed in polyimide solution or polyimide precursor solution
(2) The apparent shell disappears upon firing. Incidentally, in the above, “does not dissolve” means that the solubility when dispersed in an 18% by mass solution of polyimide or polyimide precursor (liquid temperature: 25 ° C.) is 30%. Indicates the following. In addition, “apparently no shell” means that the shell (that is, organic material) cannot be clearly distinguished in the polyimide film, and does not mean that the shell disappears completely. .

  The organic material used in the present invention is not particularly limited as long as it satisfies the above requirements, but is more preferably a resin, and among them, the viewpoint of satisfying the above two requirements well Therefore, acrylic or cross-linked acrylic is particularly preferable.

  Especially in the case of cross-linked acrylic, the solvent resistance is improved, the shell is hardly dissolved when dispersed in a polyimide solution or a polyimide precursor solution, and the time from dispersion to application / drying, the so-called pot life can be lengthened. There are advantages such as.

  The polyimide film containing voids produced by this method does not leave the shell of the dispersed hollow member, so that even when bending or pressure stress is applied, the shell breaks, the shells rub against each other, the shell There is no problem such as unevenness due to, and it becomes a tough film. Therefore, it becomes a preferable film when used as a heat insulating film for a fixing member.

  Furthermore, since the polyimide film containing voids produced by this method has no shell, it is easy to make the film thickness uniform, and it is also preferable when laminating a metal layer and a surface layer. When the thickness unevenness of the polyimide film exceeds 10 μm, adhesion with the metal layer is difficult to obtain, and when stress of pressure or bending is applied, metal fatigue is likely to occur and durability is difficult to obtain. There is a problem.

  In addition, the polyimide film surface may be roughened to improve the adhesion to the metal layer, etc., but in a film in which a conventional glass hollow member is dispersed, by roughening the glass shell, It may break, and as a result, there is a problem that holes are opened in the polyimide film, but since the film obtained by dispersing the hollow member of organic material has no shell, there is also an advantage that holes are difficult to open is there.

Here, the porosity of the polyimide film in the present invention is preferably 10% or more, and more preferably 30% or more. When the porosity is less than 10%, a high heat insulating effect may not be obtained. In addition, the higher the porosity, the better in terms of obtaining a high heat insulating effect, but if it is too high, it may be difficult to ensure the strength, so 80% or less is preferable.
In determining the porosity, the mass of the hollow member contained in the film may be ignored, and can be determined by calculation from the specific gravity of the polyimide film including the voids and the specific gravity of the polyimide film not including the voids.

  Further, from the viewpoint of thermal conductivity, it is preferably 0.25 W / m · ° C. or less, and more preferably 0.20 W / m · ° C. or less.

(Production method of polyimide film)
First, a hollow member made of an organic material is dispersed and mixed in a polyimide solution or a polyimide precursor solution.
As for the particle size of the hollow member which is solid content, 3-30 micrometers is preferable. If the particle size is less than this, it may be difficult to increase the porosity, and if the particle size is larger than this, it may be difficult to obtain a uniform film thickness and strength.

  In addition, since this coating liquid contains the hollow member which is solid content, it is preferable in order to improve the dispersibility of the hollow member in a coating liquid to reduce a viscosity using a suitable solvent. When the viscosity is high, the dispersibility of the hollow member deteriorates, and it is necessary to devise a dispersion method. However, if the viscosity is too low, uneven film thickness is likely to occur during drying, and optimization of the drying conditions may be difficult.

  From the above, the viscosity of the coating liquid in which the hollow member is dispersed is preferably adjusted within a range from about half to about ¼ of the viscosity of the polyimide solution or the polyimide precursor solution. A range of about 1 Pa · s (at 30 ° C.) is preferable.

  As the coating method of the coating liquid, roll coater method, blade coater method, air knife coater method, gate roll coater method, bar coater method, size press method, shim sizer method, spray coat method, gravure coat method, curtain coater method, The dip coat method etc. are mentioned.

  The coating film obtained by these methods is dried while raising the temperature stepwise to form a polyimide film containing voids. For example, when producing an endless polyimide belt, it can be obtained by applying the coating liquid to a pipe made of aluminum or the like by the above coating method and drying it while raising the temperature stepwise. .

The porosity can be controlled to a desired value depending on the dispersion concentration of the hollow member and the drying temperature condition.
Moreover, as thickness of a polyimide film, 30 micrometers-200 micrometers are preferable. If it is 30 μm or less, it is difficult to obtain the strength of the film, and if it is 200 μm or more, it is difficult to obtain flexibility.

-Metal layer-
Metal layer constituting the fixing member of the present invention, in the fixing device of the pressurizing heat fixing method, a layer for being heated by a heater or the like. In particular, in the electromagnetic induction heating method, this is a layer for generating heat by generating an eddy current by a magnetic field generated from a coil provided in the fixing device.
In the fixing member of the present invention, by providing a polyimide film including voids inside the metal layer, the heat generated by the metal layer can be hardly transmitted (difficult to escape), and the warm-up time can be shortened. This makes it possible to reduce the amount of heat energy required for fixing. Therefore, it is possible to further enhance the energy saving effect that is characteristic of the electromagnetic induction heating and fixing device, and to increase the selectivity of the material in contact with the polyimide film and to improve the reliability by not increasing the heat. .
Here, a metal layer particularly used in an electromagnetic induction heating type fixing device will be described.

The thickness of the metal layer is preferably in the range of 3 to 50 μm, more preferably in the range of 3 to 30 μm, and still more preferably in the range of 5 to 20 μm.
When the thickness of the metal layer is less than 3 μm, the resistance value of the metal layer becomes high, so that it may be difficult to generate sufficient eddy current, heat generation is insufficient, and the warm-up time becomes long or fixing. It may not be possible to heat to a possible temperature. Further, when the thickness of the metal layer exceeds 50 μm, although sufficient heat generation is obtained, the heat capacity of the metal layer itself is increased, so that the warm-up time may be increased.

  For the metal layer, a metal that generates electromagnetic induction is used. As such a metal, for example, nickel, iron, copper, gold, silver, aluminum, steel, chromium and the like can be selected. Of these, copper, nickel, aluminum, iron, and chromium are suitable in consideration of cost, heat generation performance, and workability, and copper is particularly preferable.

  The metal layer may have a single layer structure or may be composed of two or more layers. In particular, when the metal layer is produced using a plating method, the first metal layer formed on the polyimide film surface by electroless plating and the surface of the first metal layer formed by electrolytic plating It is preferably formed of at least two layers with the second metal layer.

  Conventionally, in a fixing member having a metal layer, when a thin metal layer is formed on a flexible substrate such as polyimide, in order to improve the adhesion between the substrate and the metal layer, vapor deposition or sputtering using a vacuum facility The PVD (Physical Vapor Deposition) method is often used. However, in the film forming method using a vacuum facility, the cost may be increased because batch processing is required particularly for a cylindrical substrate such as a fixing belt.

  On the other hand, the electroless plating method is low in cost, but the metal film formed by the electroless plating method has weak adhesion to the polyimide film. In order to compensate for this, the surface on which the metal layer is formed (that is, the outer surface of the polyimide layer) is preferably a surface made of a heat-resistant resin or the like roughened by blasting or the like. In this case, it is low-cost and sufficient adhesion can be obtained between the metal layer and the polyimide film.

  In addition, since the metal layer formed by electroless plating tends to have a lower density and higher resistance than a metal film formed by electroplating, the metal layer is a combination of electroless plating and electroplating. It is preferable to form them. In this case, the metal layer is first formed of a first metal layer formed on the outer surface of the polyimide layer by electroless plating and a second metal layer formed on the surface of the first metal layer. The first metal layer can ensure adhesion to the polyimide layer, and the second metal layer can reduce the resistance of the entire metal layer.

  In the case of a metal layer having such a two-layer structure, it is preferable that the first metal layer formed by electroless plating is formed of at least one kind of metal among nickel, copper, and chromium. This is because the first metal layer formed by electroless plating is a layer used as an electrode for electrolytic plating of the second metal layer, and a certain low resistance is required. Furthermore, by using nickel or copper, it is possible to prevent the second metal layer from being oxidized and deteriorated by oxygen transmitted through the polyimide film layer.

  Moreover, it is preferable that the 2nd metal layer formed by electrolytic plating is a layer containing copper. Since copper has a lower resistance than metals such as iron and nickel and can be formed by electrolytic plating, a high-performance film is easily formed as a metal layer of an electromagnetic induction heating type fixing member.

-Elastic layer-
The fixing member of the present invention may be provided with an elastic layer between the surface layer and the metal layer. By providing the elastic layer, a uniform pressure can be applied to a recording medium such as paper, and a high-quality fixed image can be obtained. In particular, since a full-color high-quality printed matter is recently preferred, it is preferable to provide an elastic layer between the surface layer and the metal layer.

  The thickness of the elastic layer is preferably in the range of 30 to 500 μm. If the thickness of the elastic layer is less than 30 μm, it may be difficult to apply pressure uniformly, and it may be difficult to obtain a high-quality fixed image. On the other hand, when the thickness of the elastic layer exceeds 500 μm, it may be difficult to transfer heat generated in the metal layer to the surface (outer surface), and it may be difficult to shorten the warm-up time or increase the printing speed.

  In addition, as a material which comprises the elastic layer provided between a surface layer and a metal layer, rubber | gum etc. which have silicone rubber, fluororubber, fluorocarbonsiloxane as a main component can be utilized.

-Surface layer-
Fixing member of the present invention, Ru provided most superficial layer having a releasing property with respect to the recording medium as a layer provided on the outside (the release layer). The surface layer is required to have a function (releasability) to prevent the fused toner from adhering to the fixing member when the unfixed toner image is adhered to the surface of the recording medium in a molten state. It is necessary to comprise a material having

  The material having such releasability can be selected from known materials, but a fluorine-based compound is preferably used. For example, fluororubber, polytetrafluoroethylene (PTFE), and perfluoroalkyl vinyl ether are used. A fluororesin such as a polymer (PFA) or a tetrafluoroethylene hexafluoropropylene copolymer (FEP) can be used.

  The thickness of the surface layer is preferably 10 to 100 μm, and more preferably 20 to 50 μm. If the thickness of the surface layer is less than 10 μm, the surface layer may be worn due to repeated friction at the edge of the recording medium. On the other hand, when the thickness of the surface layer exceeds 100 μm, the flexibility of the surface may be lost, and as a result, the force of crushing the toner acts to impair the granularity of the fixed image, and the warm-up time may be prolonged. .

-Manufacturing method of fixing member-
Next, the manufacturing method of the fixing member of the present invention will be described. The fixing member of the present invention can be produced using a known method in the same manner as a fixing member including a conventional metal layer. For example, each layer is formed by laminating a metal layer and a surface layer in this order on a polyimide film (substrate) using a known film formation method such as liquid phase film formation or gas phase film formation, or a film in advance. Each layer formed in a shape may be laminated to form a laminate, or a combination of the two may be laminated, or extrusion may be used.

  In this case, when forming each layer, liquid phase film formation or vapor phase film formation can be used, but liquid phase film formation can be used for any layer, and vapor phase film formation can be used for formation of a metal layer. . In the former case, when forming the surface layer and the elastic layer, for example, the materials constituting these layers are dissolved or dispersed in an appropriate solvent to prepare a coating solution, and the coating solution is applied and dried. A method of firing can be used.

  In addition, as a coating method of a coating liquid, the method similar to the method enumerated in (Manufacturing method of a polyimide film) is mentioned.

<Fixing device and image forming apparatus>
Next, an electromagnetic induction heating type fixing device using the fixing member of the present invention and an image forming apparatus using the fixing device will be described.
The fixing device according to the present invention includes at least the fixing member of the present invention described above, an electromagnetic induction heating device that applies a magnetic field to the fixing member, and a pressure member that abuts the surface (outer surface) of the fixing member. Is included. The fixing by the fixing device is performed by the heat of the fixing member heated by the electromagnetic induction heating device when the recording medium on which the unfixed toner image is formed is inserted through the contact portion between the fixing member and the pressure member. The unfixed toner image is heated and fixed on the surface of the recording medium by the pressing force between the fixing member and the pressure member.

Next, the fixing device according to the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of an electromagnetic induction heating fixing device using the fixing member of the present invention as a fixing belt.
In FIG. 1, reference numeral 10 denotes a metal layer and a surface layer laminated in this order on the surface of a polyimide film having voids where the arithmetic average roughness Ra (specified in JISB0601-2001) is 0.1 to 5 μm. 1 is a formed fixing member (fixing belt) of an endless belt according to the present invention.

  A pressure roll 11 is disposed in contact with the outer peripheral surface of the fixing belt 10, and a nip is formed between the fixing belt 10 and the pressure roll 11. The pressure roll 11 has a configuration in which an elastic body layer 11b made of silicone rubber or the like and a surface layer 11c made of a fluorine-based compound are laminated in this order on the outer peripheral surface of the base 11a.

  On the inner peripheral surface side of the fixing belt 10, a pressing member 13 is installed at a position facing the pressure roll 11. The pressing member 13 is in contact with the inner peripheral surface of the fixing belt 10 to locally increase the nip pressure, a nip pad 13c made of silicone rubber or the like for holding the nip head 13b, and the nip pad. It is comprised from the support body 13a which supports 13c.

  Further, an electromagnetic induction heating device 12 incorporating an electromagnetic induction coil is provided at a position opposite to the side where the pressure roll 11 is provided with the fixing belt 10 as a center. This electromagnetic induction heating device 12 changes an generated magnetic field by an excitation circuit by applying an alternating current to an electromagnetic induction coil, and by applying a magnetic field to a metal layer included in the fixing belt 10, An eddy current is generated in the metal layer.

  This eddy current is converted into heat (Joule heat) by the electric resistance of the metal layer, and as a result, the surface (outer peripheral surface) of the fixing belt 10 generates heat. The electromagnetic induction heating device 12 may be installed upstream of the rotation direction B indicated by a single arrow in FIG. 1 with respect to the nip region in the fixing belt 10.

  In this electromagnetic induction heating and fixing device, the fixing belt 10 is rotated in the direction of arrow B by a driving device (not shown), and the pressure roll 11 is also driven and rotated in the direction of arrow C. In this state, the recording medium 15 on which the unfixed toner image 14 is formed is inserted in the nip portion of the fixing device in the direction of arrow A, and is fixed to the recording medium 15 while applying pressure with the unfixed toner image 14 in a molten state. It is a device to let you. The driving method may be either belt driving (roll is driven) or roll driving (belt is driven).

  FIG. 2 shows a schematic explanatory diagram for explaining the principle of the electromagnetic induction heating method. In FIG. 2, 16 is an electromagnetic induction heating device, 16a is an electromagnetic induction coil, 17 is a fixing belt, 17a is a base (polyimide film), 17b is a metal layer, and 17c is a surface layer.

  The electromagnetic induction heating device 16 is disposed on the surface of the fixing belt 17 on the side where the surface layer 17c is provided, and an alternating current is applied to the electromagnetic induction coil 16a by an excitation circuit (not shown). An alternating magnetic field that is substantially orthogonal to the surface of the film is formed.

  The heat generation principle of the metal layer 17b by this electromagnetic induction action will be described below. When an alternating current is applied to the electromagnetic induction coil 16a by an excitation circuit (not shown), the magnetic flux repeatedly generates and disappears around the electromagnetic induction coil 16a. When this magnetic flux crosses the metal layer 17b of the fixing belt 17, an eddy current is generated in the metal layer 17b so as to generate a magnetic field that hinders the change of the magnetic flux. Joule heat is generated by the eddy current and the specific resistance of the metal layer 17b.

  The eddy current flows almost concentrated on the surface of the metal layer 17b on the side of the electromagnetic induction heating device 16 due to the skin effect, and generates heat with electric power proportional to the skin resistance Rs of the metal layer 17b. Here, when the angular frequency is ω, the magnetic permeability is μ, and the specific resistance is ρ, the skin depth δ is expressed by the following equation (1).

    Formula (1) δ = (2ρ / ωμ) × (1/2)

Further, the skin resistance R s is expressed by the following formula (2).
Formula (2) Rs = ρ / δ = (ωμρ / 2) × (1/2)

The electric power P generated in the metal layer 17b of the fixing belt 17 is expressed by the following expression (3), where Ih is the current flowing through the fixing belt 17.
・ Formula (3) P∫Rs∫ | Ih | 2dS

Therefore, if the skin resistance Rs is increased or the current Ih is increased, the electric power P can be increased and the amount of heat generation can be increased. Here, the skin depth δ (m) is expressed by the following expression (4) by the frequency f (Hz) of the excitation circuit, the relative permeability μr, and the specific resistance ρ (Ωm).
Formula (4) δ = 503 (ρ / (fμr)) × (1/2)

  This indicates the depth of absorption of electromagnetic waves used in electromagnetic induction, and the intensity of electromagnetic waves is 1 / e or less deeper than this, and conversely most energy is absorbed to this depth. Yes.

Here, the thickness of the metal layer 17b is preferably thicker (1 to 100 μm) than the skin depth represented by the above formula. If the thickness of the metal layer 17 b is smaller than 1 [mu] m, there are cases where efficiency because most of the electromagnetic energy can not be absorbed worse.

The fixing device as described above can be used for a known electrophotographic image forming apparatus using heat fixing as a fixing unit.
Specifically, the image forming apparatus includes an image carrier, a charging unit that charges the surface of the image carrier, and a latent image forming unit that forms a latent image on the charged surface of the image carrier. A developing unit that develops the latent image with a developer to form a toner image; a transfer unit that transfers the toner image to a transfer target; and a fixing unit that heat-fixes the toner image on a recording medium. It is preferable to have a configuration. In this case, the above-described fixing device is used as the fixing unit.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
(1) Formation of endless polyimide film A polyimide varnish (Uvarnish S) manufactured by Ube Industries, Ltd. was mixed with a cross-linked acrylic hollow member (average diameter 10 μm, hollow ratio 32%) so as to have a mass ratio of 100: 5, Φ30 mm, It was applied to an aluminum pipe having a length of 500 mm, and the aluminum pipe was heated to 380 ° C. stepwise to obtain a polyimide film containing an endless void having an inner diameter of 30 mm, a length of 450 mm, and a thickness of 100 μm. The porosity of this film is 30% as calculated from the specific gravity, and the thermal conductivity calculated therefrom is 0.18 W / m · ° C.

  A stainless steel shaft having an outer diameter substantially the same as the inner diameter of the endless polyimide film was inserted into the inner surface of the endless polyimide film thus obtained, and an alumina abrasive having a particle diameter of 100 μm at a cumulative 50% point particle diameter. The outer peripheral surface of the polyimide film was roughened by sandblasting in which grains were sprayed on the outer peripheral surface of the endless polyimide film. The 50% cumulative height is described in JIS R6002. The arithmetic average roughness Ra on the outer peripheral surface of the polyimide film after roughening was 3.0 μm.

(2) Formation of metal layer The belt whose surface was roughened was thoroughly washed with isopropyl alcohol. Next, an alkaline etching solution (aqueous solution) having a composition of sodium hydroxide 100 g / L and isopropyl alcohol 100 mL / L is heated to 60 ° C., and the cleaned belt is immersed in this for 5 minutes to chemically etch. The solution was neutralized with an acid treatment solution (an aqueous solution having a composition of 35 mass% hydrochloric acid 50 mL / L).

  Thereafter, the neutralized belt was immersed in a 30% by mass aqueous solution of palladium chloride heated to 40 ° C. for 5 minutes to activate the outer peripheral surface. Subsequently, an electroless plating solution in which this belt is heated to 40 ° C. (in 1 L of ion-exchanged water, aqueous ammonia having a composition containing 25 g of nickel sulfate, 50 g of sodium pyrophosphate, and 25 g of sodium hypophosphite) In an aqueous solution added so as to be 10), and a nickel layer having a thickness of 1 μm was formed on the outer peripheral surface thereof.

  Furthermore, after acid-treating the nickel layer surface by immersing in dilute sulfuric acid for 1 minute, a copper sulfate plating bath (an aqueous solution having a composition containing 70 g of copper sulfate and 200 g of sulfuric acid in 1 L of ion exchange water) is added. Electrolytic plating was performed by applying a current of 5 A for 40 minutes in a state controlled at 0 ° C. to form a 15 μm thick copper layer on the nickel layer surface.

(3) Formation of surface layer After sufficiently washing the surface of the two-layered belt composed of a polyimide layer / metal layer containing voids thus obtained, a commercially available PFA paint (made by DuPont, water-based) was applied to the surface of the metal layer. Dispersion paint EN-510CL) was coated by a dip coating method and baked in a nitrogen gas atmosphere at 380 ° C. for 40 minutes to form a PFA layer having a thickness of 30 μm.

  The three-layer belt thus obtained is further left in an oven at 200 ° C. for 100 hours, so that a metal layer and a surface layer made of PFA are formed on the outer peripheral surface of the polyimide substrate containing voids. Were obtained in this order to obtain a fixing belt.

  When the interface adhesion between the polyimide layer and the metal layer of the obtained fixing belt was visually confirmed, the adhesion was good. Further, this fixing belt was used as a fixing belt 10 of an electromagnetic induction heating fixing device having the configuration shown in FIG. 1, and an actual machine test was performed to evaluate a fixed image and durability.

  In addition, as the pressure roll member 11 of the electromagnetic induction heating and fixing device used in the actual machine test, a silicone rubber having a rubber hardness (Asker C hardness) of 50 degrees (measured with an ASKER-C hardness meter, manufactured by Kobunshi Keiki) is meat. A roll 5 mm thick and formed on a solid shaft (SUS304, diameter 15 mm) was used.

  Further, the electromagnetic induction heating device 12 incorporating the electromagnetic induction coil was installed on the inner peripheral surface side of the fixing belt 10 upstream of the rotational direction (arrow B direction) with respect to the nip region.

-Evaluation-
Deterioration of image quality, interfacial adhesion between polyimide layer and metal layer, and heat generation when 100,000 sheets of Fuji Xerox J paper on which an unfixed toner image is formed are tested as above. The warm-up time as a characteristic was evaluated.

  As a result, there was no deterioration in image quality after passing 100,000 sheets, and there was no problem in both fixing property and offset property. Further, when the interface between the polyimide layer and the metal layer after passing through 100,000 sheets at the initial stage was visually confirmed, no deterioration was observed, and it was found that sufficient adhesion was obtained. Moreover, when the polyimide film itself was also confirmed visually, generation | occurrence | production of a crack, a crack, etc. was not recognized.

  The warm-up time was 6 seconds with 1100 W input power before and after 100,000 sheets were passed, and there was no change before and after the sheets were passed. As described above, since no deterioration was observed in the heat generation characteristics over time and no change was visually observed, it was found that the polyimide layer containing voids did not deteriorate.

(Comparative Example 1)
Instead of a polyimide film containing voids, a fixing belt is produced in the same manner as in Example 1 except that a film having only the same thickness and made of polyimide is formed using Ube Industries' polyimide varnish (Euvarnish S). Then, the warm-up time was evaluated in the same manner as in Example 1. The warm-up time was about 6.5 seconds when the input power was 1100 W, and it was confirmed that the warm-up time was longer than that of the fixing belt of Example 1.

  Further, from the above results, the difference in warm-up time between the fixing belts of Example 1 and Comparative Example 1 is that the polyimide layer including voids has a better heat insulating effect, that is, the thermal conductivity is smaller. It turned out to be due to.

(Example 2)
A metal layer was applied and formed by the same method as in Example 1, and a silicone rubber (X-34-1053AB) manufactured by Shin-Etsu Silicone Co., Ltd. was applied and formed as an elastic layer on the metal layer with a film thickness of 200 μm and dried by heating. Further, a PFA layer having a thickness of 30 μm was formed on the elastic layer in the same manner as in Example 1 to prepare a fixing belt.

  The fixing belt was tested for 100,000 sheets in the same manner as in Example 1. As a result, the image quality did not deteriorate after passing 100,000 sheets, and there was no problem in both the fixing property and the offset property. Further, when the interface between the polyimide layer and the metal layer after passing through 100,000 sheets at the initial stage was visually confirmed, no deterioration was observed, and it was found that sufficient adhesion was obtained. Moreover, when the polyimide film itself was also confirmed visually, generation | occurrence | production of a crack, a crack, etc. was not recognized.

  The warm-up time was 9.5 seconds when the input power was 1100 W before and after 100,000 sheets were passed, and there was no change before and after the passing. As described above, since no deterioration was observed in the heat generation characteristics over time and no change was visually observed, it was found that the polyimide layer containing voids did not deteriorate.

  In addition, the image quality after passing 100,000 sheets was examined in more detail, but it was determined that both black-and-white printing and full-color printing were sufficient.

(Comparative Example 2)
Instead of a polyimide film containing voids, a fixing belt is produced in the same manner as in Example 2 except that a film made of only polyimide and having an equivalent thickness is formed using a Ube Industries polyimide varnish (Euvarnish S). And warm-up time was evaluated. As a result, it was confirmed that 10.5 seconds and 10.5 seconds took longer than Example 2.

  Further, from the above results, the difference in warm-up time between the fixing belts of Example 2 and Comparative Example 2 is that the polyimide layer containing voids has a better heat insulating effect, that is, the thermal conductivity is smaller. It turned out to be due to.

(Comparative Example 3)
(1) Formation of endless polyimide film using glass beads Hollow glass beads (average diameter 3 μm, hollow ratio 87%) were mixed with Ube Industries' polyimide varnish (Euvanis S) at a volume ratio of 3: 1. In the same manner as in Example 1, a polyimide film containing an endless void having a thickness of 100 μm was obtained. The porosity of this film was 22%, and the thermal conductivity calculated therefrom was 0.22 W / m · ° C.
Next, the outer peripheral surface of the polyimide film was roughened by the same method as in Example 1. At this time, when the appearance of the polyimide film was inspected, it was found that there were dozens of holes. The arithmetic average roughness Ra after roughening was 6.4 μm. A close observation of the holed area revealed a glass bead fragment.
Next, a metal layer was formed by the same method as in Example 1. When the appearance was inspected after the formation of the metal layer, a hole was found.
If there is a hole in the metal layer, abnormal heat is generated when induction heating is performed. Therefore, the production of the belt was interrupted here, and evaluation with an actual machine was not performed.

1 is a schematic cross-sectional view showing an example of an electromagnetic induction heating and fixing apparatus according to the present invention in which a heat fixing member according to the present invention is used as a heat fixing belt. It is a schematic explanatory drawing for demonstrating the principle of an electromagnetic induction heating system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,17 Fixing belt 11 Pressure roll 11a Base body 11b Elastic body layer 11c Surface layer 12, 16 Electromagnetic induction heating device 13 Press member 13a Support body 13b Nip head 13c Nip pad 14 Unfixed toner image 15 Recording medium 16a Electromagnetic induction coil 17a Substrate (polyimide film)
17b Metal layer 17c Surface layer

Claims (7)

Polyimide solution or polyimide precursor solution and the hollow member is dispersed in the organic material, a polyimide film obtained by being fired as the substrate, on to the substrate, to laminate at least a metal layer and a surface layer Rukoto A fixing member characterized by the above.   The fixing member according to claim 1, wherein the organic material is a resin.   The fixing member according to claim 2, wherein the resin is acrylic or cross-linked acrylic. Fixing member according to any one of claims 1 to 3, characterized in that laminating the elastic layer between the surface layer and the metal layer. Fixing member according to any one of claims 1-4, characterized in that it is heated by electromagnetic induction device. Fixing member according to any one of claim 1 to 5, wherein the polyimide film is an endless belt. The fixing member according to any one of claims 1 to 6, the image forming apparatus, characterized by using the fixing device.

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