JP2014044378A - Flexible exothermic body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a surface temperature of a flexible exothermic body.SOLUTION: In an exothermic belt (flexible exothermic body) which has a conductive material 222 dispersed in a polyimide resin 221 and includes an exothermic layer which generates heat due to electrification, the conductive material contained in the exothermic layer is a flat (belt-like) and curved fibrous material, or at least partly a twisted fibrous conductive material in a form of shavings.

Description

  The present invention relates to a flexible heating element.

  In electrophotographic printers and copiers, after a toner image is formed on a sheet, the sheet is generally fixed by heat and pressure by a fixing device. The fixing device includes a fixing roller having a heat source inside a hollow cylindrical tube mainly made of a material having heat conductivity such as metal, and a pressure roller that presses the fixing roller. The rollers press against each other to form a nip. The fixing roller and the pressure roller rotate while the sheet is held by the nip, and the sheet is conveyed while being heated and pressed.

Further, from the idea of bringing the heat source closer to the paper, a fixed and supported heat source, a heat-resistant belt (fixing belt) that is conveyed while being pressed against the heat source, and an elastic roller that closely contacts the paper to the heat source via the belt A belt heating method has been proposed in which an unfixed toner image on a sheet is heated and fixed on the sheet by applying heat from a heat source to the sheet through a belt.
Such a belt heating type fixing device can use a low-heat-capacity heater or a thin film that quickly rises in temperature, thus enabling power saving and shortening the wait time (quick start). This is an effective technique having the advantage that the temperature rise in the apparatus of the image forming apparatus can be suppressed.

  As described above, conventionally, a heat source such as a heater is built in the fixing roller and heated, or the belt is pressed against the heat source and heated, but recently, instead of this, the belt itself is replaced. A heat generating belt (flexible heat generating element) in which a heat generating layer that generates heat when energized is formed is used from the idea of a heat source. The fixing device provided with the heat generating belt has a shorter time and heat energy required for heating up to the fixing temperature and has better thermal efficiency than a method and configuration in which the fixing roller includes a heat source.

  The heat generating layer that generates heat when energized is a layer in which a conductive material is mainly contained and dispersed in a heat-resistant resin, and a carbon material having excellent thermal conductivity is often used as the conductive material contained. For example, a fixing device including a heat generating belt having a heat generating layer in which carbon nanomaterials such as carbon nanofibers and carbon nanotubes are dispersed in a polyimide resin is known (for example, see Patent Document 1).

JP 2009-109997 A

However, the conventional heat generating belt has a problem that when the heat is generated by energization, the resistance of the heat generating belt changes with the voltage application time. The reason why the resistance changes will be described later.
The heat generating belt can generate heat uniformly if the resistance of the entire belt is uniform. However, the above problem causes the resistance of the entire belt not only to change, but also to change depending on the belt location. However, uneven resistance will occur.
The power supply circumstances of the area and environment where the image forming apparatus including the fixing device is used are different, and the applied voltage for energizing is generally constant, so that the power changes when the resistance changes. For this reason, the amount of heat supplied becomes unstable with respect to the amount of heat necessary for fixing, so that the surface temperature of the heat generating belt becomes unstable, resulting in unevenness in the finish of the fixing process and image quality. In order to maintain a constant surface temperature, it is necessary to control the voltage applied to the heat generating belt, and it is a problem as a device to always control the voltage according to the resistance that changes irregularly.

  An object of the present invention is to realize uniform heat generation by suppressing resistance variation of a flexible heating element that generates heat by energization, such as a heat generating belt, and reducing resistance unevenness.

In order to solve the above problems, the invention described in claim 1
In a flexible heating element containing a conductive material in at least a heat-resistant resin and having a heat generating layer that generates heat when energized,
The conductive material is a flat and bent fiber material, and at least a part of the conductive material has a twisted shape.

The invention according to claim 2 is the flexible heating element according to claim 1,
When the maximum width of the conductive material is A and the length is B, the aspect ratio (A / B) of the conductive material is 0.025 or more and 0.25 or less.

The invention according to claim 3 is the flexible heating element according to claim 1 or 2,
The conductive material includes a fiber material having a radius of curvature of at least 100 μm.

The invention according to claim 4 is the flexible heating element according to any one of claims 1 to 3,
The conductive material is a stainless fiber material.

The invention according to claim 5 is the flexible heating element according to any one of claims 1 to 4,
The heat generating layer contains the conductive material in an amount of 15% by volume to 60% by volume.

The invention according to claim 6 is the flexible heating element according to any one of claims 1 to 5,
The volume resistivity is 0.08 × 10 ⁻⁴ (Ω · cm) or more and 10.00 × 10 ⁻⁴ (Ω · cm) or less.

  According to the present invention, it is possible to realize uniform heat generation and stabilize the surface temperature of the flexible heating element by suppressing the resistance fluctuation of the flexible heating element that generates heat by energization and reducing the resistance unevenness. it can.

It is an image figure of the fibrous conductive material disperse | distributed in a polyimide resin. It is the schematic of the coating device of the heat generating layer coating liquid. FIG. 2 is a schematic diagram illustrating a fixing device including a heat generating belt. FIG. 4 is a cross-sectional view of the fixing device taken along line IV-IV in FIG. 3. It is an expanded sectional view of the V section of FIG. It is explanatory drawing which shows the measuring method of resistance of a heat generating belt. It is a figure which shows the SEM photograph of a stainless microfiber.

Hereinafter, an embodiment of a heating belt, which is a flexible heating element of the present invention, will be described with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.
The “flexibility” of the flexible heating element according to the present invention is a property that can be bent or bent.

The heat generating belt according to the present invention is provided in a fixing device of an electrophotographic image forming apparatus, and is used for a heating / pressing process for fixing a toner image formed on a sheet to the sheet.
It is essential that the heat generating belt has at least a heat generating layer that generates heat when energized. However, the heat generating belt may be a single heat generating layer or a laminated body with layers having other functions.

  For example, a reinforcing layer for supplementing the strength of the heat generation layer, an elastic layer for securing a heat capacity necessary for continuously fixing a sheet on which an unfixed toner image is mounted, and for fixing a toner image on a sheet reliably. Alternatively, the heat generating belt may be a lamination of a release layer or the like for preventing the toner image immediately after fixing from transferring to the heat generating belt side.

  In the case of the laminated heat generating belt as described above, it is desirable that the release layer, the elastic layer, the heat generating layer, and the reinforcing layer are formed in order from the side facing the toner image. The order of the layers may be reversed, and any one of the other layers excluding the heat generation layer may be omitted.

  As a form of the heat generating belt of the present embodiment, a description will be given by taking as an example a heat generating belt formed of a release layer, an elastic layer, a heat generating layer, and a reinforcing layer in order from the side facing the toner image.

<Heat generation layer>
The resin constituting the heat generating layer in the heat generating belt of the present invention includes a polyimide resin, and may include a resin described later.
The heat generating layer is a layer formed by containing and dispersing a conductive material in a heat resistant resin. The heat-resistant resin here refers to a resin having a short-term heat resistance of 200 ° C. or higher and a long-term heat resistance of 150 ° C. or higher.

Examples of such heat resistant resins include polyphenylene sulfide (PPS), polyarylate (PAR), polysulfone (PSF), polyethersulfone (PES), polyetherimide (PEI), polyimide (PI), and polyamideimide (PAI). ), Polyether ether ketone (PEEK) resin and the like, and the resin constituting the heat generating layer in the heat generating belt of the present invention is particularly preferably a polyimide resin.
A heating element made of a polyimide resin as a base material, in which a fibrous conductive material, which is a fibrous conductive material, is dispersed in the polyimide resin is formed into an endless shape. Is done.

  A polyimide resin is prepared by imidating a polyamic acid solution prepared by mixing and heating a tetracarboxylic dianhydride and a diamine compound in an approximately equimolar amount and heating and polycondensation reaction. be able to.

  Examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride. Anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride 2,2′-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, berylene-3,4,9,10-tetracarboxylic acid bis Anhydrides, bis (3,4-dicarboxyphenyl) ether dianhydride, ethylenetetracarboxylic dianhydride and the like can be mentioned. Alternatively, these derivatives can also be used.

  Examples of the diamine compound include p-phenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide. 3,3′-diaminodiphenylsulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3′-dimethyl-4,4′-biphenyldiamine, benzidine, 3,3′-dimethyl Benzidine, 3,3′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylpropane, 2,4-bis (β-amino-tert-butyl) toluene, bis (p-β- Amino-tert-butylphenyl) ether, bis (p-β-methyl-6- Minophenyl) benzene, bis-p- (1,1-dimethyl-5-amino-pentyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di ( p-aminocyclohexyl) methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2, 11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 1,12-diaminocyclohexane, Examples include 1,10-diamino-1,10-dimethyldecane, 1,12-diaminooctadecane, and 2,2-bis [4- (4-aminophenoxy) phenyl] propane.

  Any of the above tetracarboxylic dianhydrides and diamine compounds may be used alone or in combination of two or more.

The tetracarboxylic dianhydride and the diamine compound are mixed in an organic polar solvent.
Examples of the organic polar solvent include N, N-dialkylamides such as N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide and the like. In addition to the above, dimethyl sulfoxide, hexamethyl phosphortriamide, N-methyl-2-pyrrolidone, pyridine, dimethyl sulfoxide, tetramethylene sulfone, dimethyl tetramethylene sulfone and the like can be mentioned. Any of these may be used alone or in combination of two or more.

  By heating the polyamic acid to about 200 to 450 ° C., the imidization reaction proceeds and the polyamic acid is converted to polyimide. However, by using a catalyst or a dehydrating agent, the imidization reaction may be advanced at a lower temperature. it can. The catalyst is not particularly limited as long as the imidization reaction is promoted, and examples thereof include imidazoles, secondary amines, and tertiary amines. Examples of the dehydrating agent include organic carboxylic acid anhydrides, N, N′-dialkylcarbodiimides, lower fatty acid halides, halogenated lower fatty acid anhydrides, arylphosphonic acid dihalides, thionyl halides, and the like.

Examples of the fibrous conductive material include pure metal fibers made of gold, silver, iron, aluminum, etc., alloy fibers made of stainless steel, etc., non-metallic fibers made of carbon (also called carbon), graphite (also called graphite), etc. Can be mentioned.
In the present invention, among the fibrous conductive materials, those that are flat (band-shaped) bent and at least a part of which is kinked are used.
Here, the shape that is bent and twisted in a flat shape (strip shape) refers to a shape like so-called “waste dust”, and refers to a shape in which a flat and long fiber material is curled in its longitudinal direction and width direction. The sawdust fiber materials may have different shapes or may have substantially the same shape.
When the maximum width of the fibrous conductive material is A and the length is B, the aspect ratio (A / B) of the fibrous conductive material is preferably 0.025 or more and 0.25 or less. The fibrous conductive material preferably includes a fiber material having a radius of curvature of 100 μm or more (curvature of 0.01 [1 / μm] or less).
In particular, the fibrous conductive material used in the present invention is preferably a stainless fiber formed by cutting a stainless material. Thus, when the stainless microfiber formed by cutting the stainless material is observed with an electron microscope, it can be seen that streaks are formed along the cutting direction on the surface of the stainless microfiber.

A method for calculating the radius of curvature will be described.
First, the generated heat generation layer was observed with a scanning electron microscope at a magnification of 3000 times as shown in FIG. 7, and an electronic image of an arbitrary region of 60 μm × 40 μm was taken at a different location, and the However, electronic images are taken until the number of fibrous conductive materials is confirmed to be 400 or more. The radius of curvature of the fibrous conductive material confirmed in the photographed image is calculated using the Luzex image analysis method.
In particular, the fibrous conductive material used in the present invention is preferably a stainless fiber formed by cutting a stainless material. When the stainless microfiber formed by cutting the stainless material in this way is observed with an electron microscope, it can be seen that streaks along the cutting direction are formed on the surface of the stainless microfiber (see FIG. 7).

The fibrous conductive material preferably has a content volume ratio in the heat generation layer of 15% by volume to 60% by volume. As the fibrous conductive material has a larger mass ratio in the heat generating layer, the contact area between the fibrous conductive materials increases, so that the heat generating layer has a lower resistance.
Further, since the fibrous conductive material in the present invention is in the form of sawdust and has a shape curled in the longitudinal direction and the width direction, the number of contact points between the fibrous conductive materials in the heat generation layer increases. The resistance change of the layer can be suppressed, and as a result, the resistance change of the heat generating belt can be suppressed.

FIG. 1 is an image diagram of a fibrous conductive material dispersed in a polyimide resin.
As shown in FIG. 1, fibrous conductive materials 222 are overlapped in the polyimide resin 221. When a voltage is applied to the endless heating element, free electrons move between the fibrous conductive materials 222. In FIG. 1, the arrows illustrate the movement of free electrons. During the movement, free electrons collide with molecules existing in the endless heat generating body, so that the molecules vibrate and heat is generated.

Polyimide resin is excellent in heat resistance, but expands and contracts depending on temperature. When the position of the fibrous conductive material changes due to expansion and contraction of the polyimide resin and the contact area between the fibrous conductive materials changes, the resistance of the endless heating element changes.
The fibrous conductive material in the present invention is in the form of sawdust and has a shape curled in the longitudinal and width directions, and there are many contact points between the fibrous conductive materials in the endless heating element, Some are in contact so as to get entangled. Therefore, even if the position of the fibrous conductive material changes due to expansion and contraction of the polyimide resin, it is difficult to leave and a new contact is likely to occur, so the decrease in the contact area between the fibrous conductive materials is suppressed, and the necessary contact It is easy to secure the area, and it is easy to suppress the resistance change of the endless heating element.

The heat generating belt preferably has a volume resistivity (Ω · cm) in the range of 0.08 × 10 ⁻⁴ or more and 10.00 × 10 ⁻⁴ or less (Ω · cm) from the viewpoint of heat generation.

(Production method of heat generation layer)
As one embodiment of a method for manufacturing a heat generating layer, a manufacturing method including the following steps may be mentioned.

(1) Step of preparing a polyamic acid solution Tetracarboxylic dianhydride and a diamine compound are dissolved in an organic polar solvent in equimolar amounts. The melt is mixed, heated, and subjected to a polycondensation reaction to prepare a polyamic acid solution.

(2) Step of preparing a dispersion of a fibrous conductive material A fibrous conductive material is dispersed in the polyamic acid solution prepared in the step (1) to prepare a dispersion of a fibrous conductive material, and a heating layer A coating solution is prepared. The dispersion method is not particularly limited, and for example, the dispersion can be performed using a nanomizer, ultrasonic wave, ball mill, sand mill, basket mill, homogenizer, or the like.
The content (volume%) of the fibrous conductive material in the polyamic acid solution is preferably in the range of 15 to 60 volume% from the viewpoint of the strength of the heat generating belt.
In addition, the viscosity of the obtained dispersion is generally in the range of 1 to 100 Pa · s, which is optimal in terms of coating. The viscosity is a value measured at a temperature of 25 ° C. using a measuring instrument TVB10 (manufactured by Toki Sangyo Co., Ltd.).

(3) Heat-generating layer production process The coating film of the heat-generating layer coating solution prepared in step (2) is formed endlessly. The application method of the heating layer coating solution is not particularly limited, but from the viewpoint of uniformity of film thickness, ease of control, etc., a spiral coating method in which the coating is performed on the surface of the mold while rotating the cylindrical mold Is preferred. For example, as shown in FIG. 2, a cylindrical mold a1 is set in the coating apparatus, and the endless heating element coating liquid is discharged from the nozzle a2 of the coating apparatus while rotating the mold a1 at a constant rotational speed. Apply evenly. After drying this and removing the organic polar solvent, the imidization reaction is allowed to proceed to produce a heat generating layer. The imidization reaction may proceed by baking at a high temperature of about 300 to 450 ° C., or may proceed by low temperature heating using a catalyst and a dehydrating agent.
In addition, the reinforcement layer mentioned later can also be produced similarly.

The heat generating layer thus produced can be suitably used as a heat generating layer of a heat generating belt provided in a fixing device or the like.
That is, the heat generation layer contains 15% by volume or more and 60% by volume or less of the fibrous conductive material, and the volume resistivity (Ω · cm) is 0.08 × 10 ⁻⁴ or more and 10.00 × 10 ⁻⁴ or less. Since it is (Ω · cm), it generates heat suitably and is used for fixing processing of a toner image.

  Next, an embodiment of a heat generating belt and a fixing device including the heat generating belt will be described.

<Fixing device>
FIG. 3 is a schematic diagram of the fixing device according to the present embodiment. 4 is a cross-sectional view of the fixing device taken along line IV-IV in FIG.
As shown in FIGS. 3 and 4, the fixing device includes a fixing roller 1 </ b> A, a pressure roller 1 </ b> B, and a heat generating belt 2. The fixing roller 1 </ b> A is disposed inside the heat generating belt 2, and the fixing roller 1 </ b> A and the pressure roller 1 </ b> B are in contact with each other through the heat generating belt 2. The paper P conveyed to the fixing roller 1A and the pressure roller 1B is sandwiched between nips N formed by the pressure contact between the fixing roller 1A and the pressure roller 1B, heated by the heating belt 2, and the fixing roller 1A and the pressure roller. The fixing process is performed by the pressure applied by 1B.

The fixing roller 1 </ b> A and the pressure roller 1 </ b> B are configured substantially the same, and include a core metal 11, an elastic body 12, and the like as illustrated in FIG. 4.
As the metal core 11, aluminum having good thermal conductivity is mainly used, but nonmagnetic stainless steel materials, heat resistant glass, and the like can also be used.
The elastic body 12 is made of synthetic rubber such as silicone rubber or fluorine rubber.
In addition, you may provide the coating layer which coat | covers the surface of the elastic body 12 with fluororesins, such as PFA.

During the fixing process, both ends of the core metal 11 of the pressure roller 1B are urged by urging means (not shown), and the pressure roller 1B comes into pressure contact with the fixing roller 1A via the heat generating belt 2.
Further, the fixing roller 1A and the pressure roller 1B are rotated around a cored bar 11 by receiving a rotational drive by a drive unit (not shown). Due to the rotation of the fixing roller 1A and the pressure roller 1B, the sheet is conveyed while being fixed.

<Heat belt>
FIG. 5 is an enlarged cross-sectional view of the heat generating belt 2 at a portion V in FIG.
As shown in FIG. 5, the heat generating belt 2 includes a reinforcing layer 21, a heat generating layer 22, an elastic layer 23, and a release layer 24 in order from the side in contact with the fixing roller 1 </ b> A.

The reinforcing layer 21 is provided to maintain strength. As the reinforcing layer 21, it is preferable to use the same material as the base material used for the heat generating layer 22, that is, a polyimide resin.
The reinforcing layer 21 preferably has a layer thickness in the range of 20 to 80 μm.
When the strength is improved by increasing the thickness of the heat generating layer 22, the reinforcing layer 21 can be omitted.

As described above, the heat generating layer 22 is formed by dispersing a fibrous conductive material in a polyimide resin as a base material.
The heat generating layer 22 preferably has a layer thickness of 50 to 200 μm.

  The heat generating layer 22 generates heat when energized. As shown in FIGS. 3 and 5, at both ends of the heat generating belt 2, a power receiving unit 25 is provided in place of the elastic layer 23 and the release layer 24. The power receiving unit 25 is an electrode, a conductor, or the like. The power feeding unit 3 is provided adjacent to the power receiving unit 25, and the power feeding unit 3 is urged by the urging unit 4 and contacts the power receiving unit 25 during the fixing process. The power receiving unit 25 supplies the current supplied from the power source 6 via the power supply unit 3 to the heat generating layer 22. The solid arrows in FIG. 5 indicate the flow of current supplied to the heat generating layer 22.

As the elastic layer 23, an elastic body having heat resistance is used. Examples of such an elastic body include silicone rubber and fluorine rubber, and specific examples include silicone rubber KE1379 (manufactured by Shin-Etsu Chemical Co., Ltd.), silicone rubber DY356013 (manufactured by Toray Dow Corning), and the like.
The layer thickness of the elastic layer 23 is preferably about 20 to 200 μm in consideration of fixability and thermal conductivity.

  The release layer 24 is provided so that the toner T on the paper P in contact with the heat generating belt 2 is easily separated from the heat generating belt 2. As the release layer 24, for example, a fluororesin is used, and examples thereof include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether polymer, and tetrafluoroethylene-hexafluoropropylene. The layer thickness of the release layer 24 is preferably about 5 to 30 μm.

(Method for manufacturing heat generating belt)
The heating belt 2 can be manufactured by the following method, but the manufacturing method is not limited to this.

(Formation of reinforcement layer)
Only the polyamic acid solution of the method for producing a heat generating layer described above is prepared, and a cylindrical mold a1 is set in a coating apparatus as shown in FIG. The mold a1 is made of aluminum, iron, brass, stainless steel, or the like, and a fluorine-based or silicone-based release agent is applied to the outer peripheral surface in advance in consideration of releasability from the mold. While the mold a1 is rotated at a constant rotational speed, the nozzle a2 of the coating apparatus is also moved parallel to the direction of the arrow C at a speed optimum for coating with respect to the cylindrical axis of the mold, and then the polyamic acid solution is discharged. Apply evenly. Thereafter, it is heated to 120 ° C. and dried for 40 minutes.

(Formation of heat generation layer)
A heating layer coating solution is uniformly applied on the dried coating film of the reinforcing layer. The application method and drying conditions are the same as those of the reinforcing layer. This is heated to 120 ° C. and dried for 40 minutes. Thereafter, the reinforcing layer 21 and the heat generating layer 22 are formed by baking at 400 ° C. for 20 minutes.
(Formation of elastic layer and release layer)
An elastic layer coating solution prepared in advance is applied onto the heat generating layer 22. Next, after heating at 150 ° C. for 30 minutes for primary vulcanization, heating is performed at 200 ° C. for 4 hours for secondary vulcanization to form the elastic layer 23.
A release layer coating solution is applied onto the elastic layer 23 to form the release layer 24. Finally, after cooling to room temperature, the heat generating belt 2 is obtained by releasing from the mold a1.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to these.
(Method for manufacturing heat generating belt)

(Formation of reinforcement layer)
Only the polyamic acid solution of the method for producing a heat generating layer described above is prepared, and a cylindrical mold a1 is set in a coating apparatus as shown in FIG. The mold a1 is made of aluminum, iron, brass, stainless steel, or the like, and a fluorine-based or silicone-based release agent is applied to the outer peripheral surface in advance in consideration of releasability from the mold. While the mold a1 is rotated at a constant rotational speed, the nozzle a2 of the coating apparatus is also moved parallel to the direction of the arrow C at a speed optimum for coating with respect to the cylindrical axis of the mold, and then the polyamic acid solution is discharged. Apply evenly. Thereafter, it is heated to 120 ° C. and dried for 40 minutes.

(Formation of heat generation layer)
A heating layer coating solution is uniformly applied on the dried coating film of the reinforcing layer. The application method and drying conditions are the same as those of the reinforcing layer. This is heated to 120 ° C. and dried for 40 minutes. Thereafter, the reinforcing layer 21 and the heat generating layer 22 are formed by baking at 400 ° C. for 20 minutes.

<Preparation of heating layer coating solution>
100 g of polyamic acid (Ube Industries, Ltd .: U-Varnish S301) and 18 g of the conductive material shown in Table 1 and below were sufficiently mixed with a planetary mixer to prepare a heating layer coating solution. Note that 100 g of polyamic acid (Ube Industries, Ltd .: U-Varnish S301) may be replaced with 66 g of polyamideimide (Hitachi Chemical Industries, Ltd .: HPC-9100).
Examples 1 to 5: Scrap-like stainless steel fibers (JFE Techno-Research Corporation: SMF300)
Comparative Example 1; Linear stainless steel fiber (Nippon Seisensha: NASRON fiber)
Comparative Example 2; linear graphite fiber (manufactured by Nippon Graphite Fiber Co., Ltd .: XN-100)
Comparative Example 3; spherical graphite powder (manufactured by Nippon Graphite Co., Ltd .: UP)

<Surface treatment of mold>
A silicone mold release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) is applied to the outer peripheral surface of a stainless steel cylinder having an outer diameter of 32 mm and a length of 400 mm, followed by baking at 300 ° C. for 1 hour. A mold a1 provided with a mold agent layer was obtained.

<Formation of heat generation layer>
The exothermic layer coating solutions (Examples 1 to 5 and Comparative Examples 1 to 3) prepared as described above were applied to the surface of the mold so as to have a film thickness of 500 μm. After drying at 150 ° C. for 30 minutes, heat treatment was carried out at 400 ° C. for 20 minutes to imidize to form a heat generation layer that was an endless heat generating element.

<Formation of elastic layer>
Next, a primer (manufactured by Shin-Etsu Chemical Co., Ltd .: X331565) was brushed on the surface of the heat generating layer and dried at room temperature for 30 minutes.
Further, a composition in which a first silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd .: KE1379) and a second silicone rubber (manufactured by Toray Dow Corning Silicone Co., Ltd .: DY356013) are mixed at a ratio of 2: 1 in advance is formed on the outer surface of the heat generating layer. A silicone rubber layer was formed by coating to 200 μm.
Thereafter, primary vulcanization was performed at 150 ° C. for 30 minutes, and post-vulcanization was further performed at 200 ° C. for 4 hours to form an elastic layer on the surface of the heat generating layer. The hardness of this elastic layer was 26 degrees.

<Formation of release layer>
After cleaning the surface of the elastic layer, the elastic layer together with the stainless steel tube is immersed in a PTFE resin dispersion (manufactured by DuPont: 30J) as the first fluororesin, taken out after 3 minutes, and dried at room temperature for 20 minutes. Then, the fluorine resin on the surface was wiped off with a cloth.
Next, PTFE resin and PFA resin were mixed at a ratio of 7: 3, and a fluororesin dispersion (made by DuPont: 855-510) was a second fluororesin adjusted to a solid content concentration of 45% and a viscosity of 110 mPa · s. The elastic layer was immersed together with the stainless steel tube, and the second fluororesin was coated to a film thickness of 15 μm, dried at room temperature for 30 minutes, and then heat-treated at 230 ° C. for 30 minutes.
After that, the tube was passed through a tube furnace having an inner diameter of 100 mm with the furnace temperature set at 270 ° C. in about 10 minutes, and the coated second fluororesin was fired.

  After cooling, the layered tubular material composed of the heat generation layer, the elastic layer, and the release layer was separated from the mold (stainless steel tube) to obtain the intended heat generation belt.

<Evaluation of heat generating belt>
About the produced heat generating belt (Examples 1-5, Comparative Examples 1-3), the following item was evaluated.

<1> Volume resistivity [Ω · cm]
As shown in FIG. 6, copper tape b2 (CU-35C, manufactured by Sumitomo 3M) was applied to the heat generation layer portions at both ends of the heat generation belt b1 to form electrodes.
A power source b3 (PCR2000L, manufactured by Kikusui Electronics Co., Ltd.) and an LCR meter b4 (3532-80, manufactured by Hioki Electric Co., Ltd.) were connected between the electrodes. An AC voltage was applied by the power source b3, and the resistance [Ω] between the electrodes was measured by the LCR meter b4. The voltage to be applied was set so that the surface temperature of the heat generating belt b1 was 180 ° C. The surface temperature is a value measured by a digital radiation temperature sensor FT-H20 (manufactured by Keyence Corporation).
The volume resistivity [Ω · cm] was calculated from the measured initial resistance [Ω], the distance z [mm] between the electrodes, and the thickness of the heating belt b1 (thickness of the heating layer) [μm].

<2> Resistance change The produced heat generating belt is mounted on bizhubC550 (manufactured by Konica Minolta Business Technologies), and the heat generating belt is taken out after printing 900,000 sheets at a printing rate of 5%. The resistance change from the initial resistance measured previously was evaluated according to the following criteria.
○: | (resistance after endurance) − (initial resistance) | / (initial resistance) <1%
Δ: 1% ≦ | (resistance after endurance) − (initial resistance) | / (initial resistance) <3%
×: 3% ≦ | (resistance after endurance) − (initial resistance) | / (initial resistance)
Among ○, △, and X, ○ and △ are acceptable levels.

<3> Fixability Each of the produced heat generating belts is mounted on bizhubC550 (manufactured by Konica Minolta Business Technologies, Inc.), and a density test is performed on the toner image density after initial printing and after printing 900,000 sheets at a printing rate of 5%. The fixing property was evaluated as follows from the fixing unevenness that appeared as a difference in density.
A: Fixing unevenness is not confirmed.
B: Although fixing unevenness can be confirmed, it is within an allowable range.
C: Large fixing unevenness can be clearly confirmed.
Among A to C, A and B are assumed to be acceptable levels.

  The evaluation results for each item are shown in Table 1.

As shown in Table 1, it can be seen that the heat generating belts of Examples 1 to 4 have a volume resistivity of 10 × 10 ⁻⁴ [Ω · cm] or less, and the resistance is reduced. Moreover, both the resistance change and the fixing property were acceptable levels. The heat generating belt of Example 5 was slightly inferior in fixability.
And it is understood that the heat generating belts of Examples 1 to 5 have a resistance change of less than 3% and can stabilize the surface temperature of the heat generating belt.
On the other hand, the heat generating belts of Comparative Example 1 and Comparative Example 2 have a large resistance change of 3% or more, which indicates that it is difficult to stabilize the surface temperature of the heat generating belt. In addition, it can be seen that the heat generating belt of Comparative Example 3 has a volume resistivity of 20 × 10 ⁻⁴ [Ω · cm], and the resistance is not reduced.

  As described above, the heat generating belt according to the present invention can stabilize the surface temperature thereof, can stabilize the finish of the fixing process, and can improve the image quality.

  The application of the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention.

1A fixing roller 1B pressure roller 2 heating belt (flexible heating element)
21 Reinforcing layer 22 Heat generation layer 221 Polyimide resin 222 Fibrous conductive material (conductive material)
23 Elastic layer 24 Release layer 25 Power receiving unit 3 Power feeding unit P Paper T Toner

Claims (6)

In a flexible heating element containing a conductive material in at least a heat-resistant resin and having a heat generating layer that generates heat when energized,
The flexible heating element, wherein the conductive material is a flat and bent fiber material, and at least a part of the conductive material has a twisted shape.   The aspect ratio (A / B) of the conductive material when the maximum width of the conductive material is A and the length is B is 0.025 or more and 0.25 or less. A flexible heating element as described in 1.   The flexible heating element according to claim 1, wherein the conductive material includes a fiber material having a radius of curvature of 100 μm or more.   The flexible heating element according to claim 1, wherein the conductive material is a stainless fiber material.   The flexible heating element according to any one of claims 1 to 4, wherein the heat generating layer contains the conductive material in an amount of 15% by volume to 60% by volume. 6. The volume resistivity is 0.08 × 10 ⁻⁴ (Ω · cm) or more and 10.00 × 10 ⁻⁴ (Ω · cm) or less. 6. Flexible heating element.