JP4419583B2 - Endless belt and fixing belt manufacturing method - Google Patents

Description

The present invention is, for example, a method of manufacturing the endless belt and the fixing belts are preferably used in an electrophotographic apparatus such as a copying machine or a laser printer.

  The endless belt is used for conveying an object, driving a rotating device, and the like. There are two types of endless belts, one made of metal and one made of resin. Resin is preferably used in terms of ease of handling and cost. Especially, the thing made from a polyimide resin is the most preferable from a viewpoint of durability and heat resistance. Hereinafter, polyimide is abbreviated as PI as appropriate.

  When the inner surface of the belt is slid as the endless belt, an endless belt having a small frictional resistance on the inner surface, that is, improved slidability is desired. For example, in the fixing device described in Patent Document 1, since a pressure member is disposed and pressed on the inner surface of the belt, it is desirable that the slidability be good.

In order to improve the slidability of the PI resin, there is a method of dispersing a solid lubricant in the PI resin as described in Patent Documents 2 and 3. Examples of the solid lubricant include fluorine resin powders such as molybdenum disulfide, tungsten disulfide, graphite, boron nitride, and polytetrafluoroethylene (PTFE).
However, when a solid lubricant is contained in the PI resin, there is a disadvantage that the original strength of the PI resin is lowered, and it is not suitable for use in a thin film such as a belt. In order to supplement the strength, there is a means for further containing carbon fiber or the like in the PI resin, but this is not a sufficient method because surface smoothness may be lowered.

  On the other hand, in the fixing belt, a non-adhesive layer is provided on the surface of a heat-resistant resin belt typified by polyimide resin for the releasability of the toner to be fixed. Examples of the material include fluorine resins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). For non-adhesive layers, carbon powder, inorganic compound powders such as titanium oxide and barium sulfate, etc. for improving wear resistance and electrostatic offset, affinity with toner adhesion prevention oil, etc. You may include materials other than a fluororesin.

  In order to form a fluororesin layer on the surface of the PI resin layer, since the fluororesin is insoluble in a solvent, a paint in which a fluororesin powder is dispersed in a solvent such as water using a surfactant is used. After coating on the layer, the solvent is dried, fired and heated to melt. Further, as described in Patent Document 4, a fluororesin dispersion may be applied to the surface of the PI precursor, and at the time of heating, PI resin generation and fluororesin firing may be performed at the same time. This is advantageous because the adhesiveness of the fluororesin layer is improved.

Since the PI resin layer in the fixing belt is required to have strength against pulling and bending, it is inconvenient to contain a solid lubricant as described above for slidability. Therefore, it has been desired to improve the slidability of the belt without including a solid lubricant in the PI resin as a base material.
Japanese Patent Application Laid-Open No. 11-133776 JP-A-7-97517 JP-A-11-1067779 JP-A-63-218349

In view of the above, an object of the present invention is to solve the above conventional problems. That is, the present invention aims at providing without reducing the inherent strength, the endless belt having a high sliding property, and a manufacturing method of the fixing belts which an endless belt using with the PI resin.

As a result of studies to solve the above problems, the present inventors have found that the following problems can be solved by the present invention. That is, the present invention
<1> A coating film forming process for forming a first polyimide precursor layer in which a solid lubricant is dispersed and a second polyimide precursor layer in this order on the surface of the core, and the coating film forming process. A resin film forming step of forming a polyimide film having a first polyimide resin layer and a second polyimide resin layer by subjecting the first polyimide precursor layer and the second polyimide precursor layer thus formed to heat treatment When manufacturing method of the endless belt which comprises a resin film extraction step of extracting the polyimide film from the core body, in this order.

< 2 > In the resin film extraction step, the difference ( ^BA ) between the thermal expansion coefficient A of the polyimide film and the thermal expansion coefficient B of the core is 10 × 10 ⁻⁶ / K or less, and At one end, a cylindrical body having the same outer diameter as the core body and a through-hole on the side surface is joined, a belt is fitted around the cylindrical body, and air is applied to the polyimide film formed on the core body. After pasting so as not to leak, the pressurized air is injected into the gap between the surface of the core body and the polyimide film through the through hole from the inside of the cylindrical body, and the polyimide film is peeled off and removed. The method for producing an endless belt according to < 1 >.

< 3 > A coating film forming step for forming a first polyimide precursor layer (sliding layer) in which a solid lubricant is dispersed and a second polyimide precursor layer in this order on the surface of the core, A fluororesin coating film forming step of forming a fluororesin coating film layer by applying a fluororesin coating on the second polyimide precursor layer on the outside after film formation, and the first film formed in the coating film forming process The polyimide precursor layer, the second polyimide precursor layer, and the fluororesin coating film layer formed in the fluororesin coating film forming step are subjected to heat treatment, so that the first polyimide resin layer and the second polyimide are heated. to form a polyimide film having a resin layer, the resin skin withdrawn and the resin film forming step of forming a fluororesin layer on the polyimide film, the polyimide film wherein the fluorine resin layer is formed from a core body Method for producing a fixing belt which comprises a sampling step, in this order.

<4> at least, in the fluororesin coating film forming step, after forming the fluororesin coating layer, according to <3>, wherein the shed 30 ° C. or more air flow to the fluorocarbon resin coating layer This is a method for manufacturing a fixing belt.

< 5 > At least in the fluororesin coating film forming step, the method of forming the fluororesin coating film layer is a dip coating method, and when the core body is pulled up after being immersed, the core body is heated to 30 ° C. or higher. method for producing a fixing belt according to, characterized in that heating <3> or <4>.

< 6 > In the dip coating method, an annular body provided with a hole larger than the outer diameter of the core body cross section is installed in the coating liquid filled in a coating tank in a freely movable state, After the core is immersed in the coating liquid through the hole, the annular body is lifted from the coating liquid surface, and the bottom surface of the annular body is not separated from the coating liquid surface (a height that does not separate). And controlling the core body relatively from the coating liquid,
The method for manufacturing a fixing belt according to < 5 >, wherein an inner wall of the hole of the annular body is an inclined surface, and an inclination angle thereof is 1 to 10 ° with respect to a vertical line.

< 7 > The method for manufacturing a fixing belt according to < 6 >, wherein a sinking prevention member is provided on the annular body to adjust a mass of the annular body.

< 8 > In the fluororesin coating film forming step, when there is a defect in the fluororesin coating film layer, the fluororesin coating film layer is removed, and the fluororesin coating material is applied again to apply the fluororesin coating. The method for producing a fixing belt according to any one of < 3 > to < 7 >, comprising a fluororesin coating film reforming step for forming a film layer.

< 9 > The method according to any one of < 3 > to < 8 >, further comprising a cutting step of cutting both ends of the polyimide film on which the fluororesin layer is formed after the film removal step. A method for manufacturing a fixing belt.

According to the present invention can be provided without lowering the intrinsic strength with the polyimide resin, an endless belt and a manufacturing method of the fixing belts using the same having high slidability.

Hereinafter, the endless belt according to the present invention, the fixing belt using the endless belt, and the manufacturing method thereof will be described in detail.

<Endless belt>
The endless belt in the present invention is provided with a first polyimide resin layer (sliding layer) and a second polyimide resin layer from the inner peripheral surface side, and a solid lubricant is provided in the first polyimide resin layer. Is distributed.

The PI resin used for the first and second polyimide resin layers is 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter abbreviated as BPDA) and p-phenylenediamine (hereinafter referred to as PDA). (Hereinafter abbreviated as S type); composed of BPDA and 4,4′-diaminodiphenyl ether (hereinafter abbreviated as A type); pyromellitic dianhydride (PMDA) and 4,4 Containing '-diaminodiphenyl ether (hereinafter abbreviated as K-type); Containing 3,3', 4,4'-benzophenonetetracarboxylic dianhydride and 4,4'-diaminodiphenylmethane; 3,3 Various materials such as', 4,4'-benzophenone tetracarboxylic dianhydride and 4,4'-diaminobenzophenone are used.
However, when the endless belt is used as the fixing belt, the S-type is optimal from the viewpoint of strength.

  In order to form the PI resin layer, a method of applying a precursor solution of these materials to the surface of the core, drying, and heating can be employed.

In the present invention, a first polyimide resin layer in which a solid lubricant is dispersed is provided inside the second polyimide resin layer. In the present specification, the first polyimide resin layer may be referred to as a sliding layer.
For dispersing the solid lubricant, a known disperser such as a ball mill, a sand mill, a roll mill, a counter collision disperser, an ultrasonic disperser, or the like is used. The thickness of the sliding layer is preferably in the range of 2 to 20 μm. Since the sliding layer does not need to be as strong as the second polyimide resin layer, any of the above PI resins may be used. The thickness of the second polyimide resin layer as the endless belt is preferably in the range of 25 to 250 μm.

In order to form the sliding layer, a solid lubricant powder dispersion may be applied to the inner surface of the PI resin endless belt and heated to form a film.
Also, instead of applying the sliding layer to the inner surface of the PI resin endless belt, the sliding layer solution (PI resin precursor solution in which a solid lubricant is dispersed) is first applied to the surface of the core, and then PI The resin precursor solution is applied (coating film forming process), then heat-treated to form a polyimide film (resin film forming process), the polyimide film is extracted from the core (resin film extracting process), and an endless belt May be produced. Although this method will be described later, this method not only shortens the production process, but also has the advantage that adhesion is greatly improved by the simultaneous progress of the imidization reaction of both.

In the endless belt as described above, since the sliding layer in which the solid lubricant is dispersed is provided on the inner peripheral surface, it is possible to reduce the frictional resistance on the inner surface and improve the sliding property on the inner peripheral side. Become.
In addition, about a solid lubricant etc., it demonstrates with the below-mentioned manufacturing method.

<Fixing belt>
The fixing belt has a non-adhesive layer provided on the surface of the endless belt in the present invention. That is, the fluororesin layer is provided on the second polyimide resin layer of the endless belt in the present invention. By providing the fluororesin layer, the toner releasability can be improved.

The fluororesin layer preferably contains carbon nanotubes (CNT). CNT is a cylindrical hollow fiber made of carbon, and examples thereof include those having a length several tens of times the diameter. Specifically, the diameter is preferably 0.005 to 1 μm and the length is 1 to 100 μm; more preferably, the diameter is 0.01 to 0.5 μm and the length is 1 to 10 μm. Although it may be called a carbon nanofiber depending on the size, it is collectively referred to as CNT in this specification.
CNTs are manufactured by known methods such as thermal decomposition using a catalyst, arc discharge method, laser evaporation method, etc., and are excellent in strength, wear resistance, low friction, electrical conductivity, thermal conductivity, etc. Material.

  By including this in the fluororesin layer, it is possible to improve the wear resistance of the fluororesin layer, improve the slidability, and the like. Furthermore, by imparting electrical conductivity to the fluororesin layer, it is possible to prevent the phenomenon of toner scattering due to static electricity during fixing. Further, the heat conductivity of the fluororesin layer is improved, so that heat propagation is improved and the time to reach a predetermined temperature is shortened.

  In order to contain CNT in the fluororesin dispersion, a known dispersion method such as a ball mill, a sand mill, or a roll mill can be used. The content of CNT is preferably 4 to 40% by mass, more preferably 5 to 30% by mass with respect to the fluororesin.

<Method for producing endless belt and fixing belt>
Fixing belt of the present invention is obtained by utilizing the endless belt of the present invention. Therefore, the endless belt manufacturing method of the present invention is also referred to while the fixing belt manufacturing method of the present invention is described.

The method for producing a fixing belt of the present invention includes a coating film forming step in which a first polyimide precursor layer in which a solid lubricant is dispersed and a second polyimide precursor layer are formed in this order on the surface of a core. The fluororesin coating film forming step of forming a fluororesin coating film layer by applying a fluororesin coating on the second polyimide precursor layer on the outside after the coating film formation, and the coating film forming step, the first polyimide precursor layer and the second polyimide precursor layer, and the fluororesin coating film formed by subjecting to heat treatment a fluororesin coating layer formed in step, the first polyimide resin layer and the second to form a polyimide film having a polyimide resin layer, a resin film forming step of forming a fluororesin layer on the polyimide film, the polyimide film wherein the fluorine resin layer is formed from a core body Comprising a resin film extraction step of taking can, in this order.

As a method for applying the fluororesin powder dispersion, there are a spray coating method and a coating method in which the liquid is cast while rotating the core, but the dip coating method is most preferable. The thickness of the PI resin layer as the fixing belt is preferably in the range of 25 to 200 μm, and the thickness of the fluororesin layer (non-adhesive layer) is preferably in the range of 5 to 50 μm.
Hereinafter, each step will be described.

(Coating film formation process)
The material of the core used as an object to be coated is preferably a metal such as aluminum, nickel or stainless steel. The shape is preferably cylindrical. The surface of the core may be plated with chrome or nickel, or covered with a fluororesin or silicone resin. It is preferable to apply a release agent to the surface of the core so that the PI resin does not adhere.

When the PI resin described later is heated, residual solvent and reaction product water generated from the inside of the film may swell to cause the PI resin film to swell. This is particularly noticeable when the film thickness of the polyimide film exceeds 50 μm. In that case, roughening the surface of the core is effective.
As for the roughness of the roughening, the surface roughness (Ra) is preferably about 0.2 to 2 μm. Examples of the roughening method include blasting, cutting, sandpaper peeling, and the like. By roughening, the residual solvent or water vapor generated from the PI film can be discharged to the outside through a slight gap formed between the core and the PI film, and no blistering occurs.

In the present invention, prior to the application of the PI precursor, the PI precursor solution in which the solid lubricant powder is dispersed is applied to the surface of the core. As the method, the PI precursor solution is flattened with a spatula while allowing the solution to flow from the nozzle to the core surface, and the nozzle and spatula are moved horizontally from one end of the core to the other end to apply the solution. There is (spiral coating method).
Examples of the solid lubricant powder include molybdenum disulfide and graphite.

Another preferred coating method is a dip coating method. However, when the PI precursor solution has a high viscosity, if the film thickness becomes too thick, as described in JP-A-2002-91027, an annular body provided with holes larger than the outer diameter of the core body Thus, there is a method for controlling the film thickness of the PI precursor solution. This method will be described with reference to FIG. 1 which is a schematic cross-sectional view of the coating process (the figure shows only the main coating part and the peripheral part is omitted).
In addition, "applying on a core body" shows apply | coating on the layer on the surface of a core body, and when it has a layer on this surface. Further, “raising the core” is a relative relationship with the coating liquid level, and includes the case of “stopping the core and lowering the coating liquid level”.

Application | coating is performed by putting the solution 2 in the application tank 3, immersing the core body 1 in it, and making it raise then, as shown in FIG. 1, and the coating film 4 is formed. On the solution 2, an annular body 5 having a circular hole 6 larger than the outer diameter of the core body 1 is installed in a freely movable state. Since the wet film thickness of the coating film 4 is determined by the gap between the core body 1 and the hole 6, the inner diameter of the hole 6 is set from a desired film thickness. Product of fractional concentration).
In order to prevent the annular body 5 from sinking, legs or arms that support the annular body 5 may be provided on the outer peripheral surface of the annular body 5 or the coating tank 3.

An annular coating method improved from the dip coating method is shown in FIG. In this case, the solution 2 is put in the annular coating tank 7, and coating is performed by passing the core body 1 from the lower part to the upper part in the drawing. An annular sealing material 8 made of a flexible plate material such as polyethylene or silicone rubber is provided at the bottom of the annular coating tank 7 so that the solution 2 does not leak. Intermediate bodies 9 are attached above and below the core body 1.
The annular coating method has an advantage that the amount of the solution 2 is smaller than that of the dip coating method shown in FIG. The annular body 5 is installed on the solution 2 in a freely movable state as in the case of FIG.

The annular body 5 is installed in a freely movable state so that it can move on the solution 2 with a slight force. As a method for this, the annular body is supported by a roll or a bearing in addition to a method of floating on the liquid. And a method of supporting an annular body with air pressure.
When the core body 1 is lifted from the solution through the hole 6 of the annular body 5, a frictional resistance is generated between the core body 1 and the annular body 5 due to the presence of the solution 2, and a rising force acts on the annular body 5, The annular body 5 is slightly lifted. At this time, the annular body 5 moves so that the frictional resistance with the core body 1 is constant in the circumferential direction, and the gap is constant, so that the applied film thickness is uniform in the circumferential direction. That is, the coating film 4 having a uniform film thickness is formed on the core body 1.

  When the PI precursor solution in which the solid lubricant powder is dispersed on the core body is applied and then dried, a first polyimide precursor layer containing the solid lubricant powder is formed. The drying temperature is preferably 50 to 200 ° C. and the drying time is preferably 30 to 200 minutes. At the time of drying, the coating film before drying has a reduced viscosity and is susceptible to drooping due to the influence of gravity. In this case, the core body is rotated horizontally at about 10 to 60 rpm with the axis direction horizontal. It is good.

Next, a PI precursor solution for forming the second polyimide precursor layer is applied on the first polyimide precursor layer containing the solid lubricant powder. The application method may be the same as the application method of the PI precursor solution in which the solid lubricant powder is dispersed. After the application, a drying process is performed in the same manner as described above to form a second polyimide precursor layer.
In the case of producing an endless belt, then the coating film is subjected to heat treatment forming the formed in step a first polyimide precursor layer and the second polyimide precursor layer to form a polyimide film ( Resin film forming step), this polyimide film is extracted from the core (resin film extracting step), and an endless belt is produced (the heat treatment will be described later, and is omitted here). The contents of the resin film extracting step and the provision of a cutting step and the like are the same as in the case of the fixing belt manufacturing method.

(Fluorine resin coating film forming process)
In this step, in order to manufacture the fixing belt, the fluororesin dispersion is applied on the PI resin film or the PI precursor film. In the case of dip coating, first, a coating treatment is applied to the end portion of the PI resin film or PI precursor film and the exposed metal portion of the core surface. If necessary, a lid is fitted on the lower end side of the core.

  As shown in FIG. 3, the covering process includes a method of applying the adhesive tape 15 so as to cover the end of the polyimide precursor layer 18 and the core surface exposed portion together with the lid 10, and a wide width instead of the adhesive tape. A method of expanding and covering the rubber band can be applied.

  Another covering process will be described with reference to FIG. FIG. 4 shows a side view of the core body 1 on which the PI precursor layer 18 is formed, and is an example in which an adhesive tape 70 is wound around and attached to one end thereof. In this case, the center of the core body is made vertical with the side to which the adhesive tape 70 is attached as the lower end. Even if the core surface is exposed on the opposite side, that is, the upper end side, the fluororesin dispersion does not adhere to the core surface unless it is immersed in the fluororesin dispersion. It does not matter if it is not covered. Of course, if that part is covered, it is more reliable.

  Next, as shown in FIG. 5, the core body 1 is attached to the holding member 11, dipped in the fluororesin dispersion 16 in the coating tank 17, and pulled up to apply the fluororesin dispersion to the fluororesin coating layer. 19 is formed. In addition to storing the fluororesin dispersion 16 in the coating tank 17, as shown in FIG. 6, an external tank 12 having a capacity equal to or larger than the volume of the core 1 is provided outside the coating tank 17, and the pump 13 You may supply from the lower part of the application tank 17, overflow from the upper part, and may circulate.

  By circulating in this way, sedimentation and aggregation of the fluororesin dispersion 16 can be prevented, and the surface of the liquid can always be kept fresh. Circulating with the external tank 12 can reduce the total amount of the expensive fluororesin dispersion rather than installing another paint tank outside and circulating the fluororesin overflowing from the upper part of the coating tank 17. There is also an advantage that foaming does not easily occur due to the liquid falling into the external paint tank. It is also preferable to add a filter 14, a viscometer, a diluting liquid adding device and the like to the circulation path.

  Further, the shape of the inner wall of the hole 6 provided in the annular body 5 is such that, as shown in the cross-sectional views of FIGS. 5 and 6, the lower part immersed in the coating liquid has a wide gap with the core and the upper part is narrow. In addition to the inclined surface that is an oblique straight line, a stepped shape or a curved shape may be used, but an inclined surface is preferable in view of ease of manufacture. In the case of an inclined surface, it will be described with reference to FIG. 7. The inclination angle 55 of the inner wall is preferably 1 to 10 ° with respect to the vertical line 54. The smaller the inclination angle, the stronger the frictional force and the stronger the effect of uniforming the gap with the outer diameter of the core, but the lower the coating speed, the minimum value is about 1 °. If the inclination angle exceeds 10 °, the effect of uniforming the gap with the outer diameter of the core body becomes weak, which is not preferable.

  Moreover, as shown in FIG. 7, it is preferable to adjust the mass of an annular body by providing a sinking prevention member in the annular body. By doing in this way, a coating speed can be adjusted. Furthermore, it is simple and preferable to attach the mass adjusting member 56 to the sinking prevention member 51. In this case, the center of gravity of the mass adjusting member 56 is preferably lower than the minimum inner diameter portion of the hole of the annular body.

It is preferable that a fluororesin powder having a particle size of 0.1 to 20 μm is dispersed in the fluororesin dispersion. Moreover, you may mix the powder of a several particle size. For example, a mixture of fluororesin powder having a relatively large particle size and fluororesin powder having a relatively small particle size may be used. As the solvent for the fluororesin dispersion, water, alcohols such as ethanol and butanol, glycols such as ethylene glycol, and esters thereof may be used in combination.
Moreover, you may add surfactant, a viscosity modifier, etc. When materials other than fluororesins such as carbon powder, titanium oxide, and barium sulfate are included, these may be mixed and dispersed in the fluororesin dispersion. A material to which a surfactant is added is very easy to foam, and once the foam is formed, the foam is difficult to disappear. Therefore, it is preferable to perform a defoaming treatment prior to application. Defoaming methods include methods such as decompression, centrifugation, filtration, and application of ultrasonic waves, in addition to standing for a long time.

  The solid content concentration of the fluororesin dispersion is preferably 10 to 70%, and the viscosity is preferably about 0.1 to 1 Pa · s, although it depends on the applied film thickness. When the concentration of the fluororesin dispersion changes due to evaporation of the solvent, it may be adjusted by adding water, alcohol or the like.

  When applying the fluororesin dispersion, the pulling speed of the core is about 50 to 500 mm / min, although it depends on the desired film thickness. In the case where dripping occurs in the coating film of the fluororesin dispersion at the time of pulling up, it is preferable to provide the blower device 20 shown in FIGS. 5 and 6 to apply an air flow to the coating film to promote drying of the solvent. The airflow applied to the coating film is preferably applied in a circular or annular manner so as to be uniform in the circumferential direction rather than from one direction. As such a blower, those described in Japanese Patent No. 2844784 and Japanese Patent No. 2629417 are preferable.

  In order to further accelerate the drying of the coating film of the fluororesin dispersion, the air flow is more preferably a warm air of 30 ° C. or higher than air at normal temperature. However, if the temperature is too high, drying unevenness will occur, so the temperature should be about 100 ° C. or less.

As another means for promoting drying of the coating film of the fluororesin dispersion, heating the core may be used in combination. However, if the heated core is immersed in the fluororesin dispersion, not only the temperature of the fluororesin dispersion changes, but also the temperature of the core decreases, which is not preferable. It should be done after raising. The heating temperature is preferably 30 ° C. or higher. However, like the air flow, if the temperature is too high, drying unevenness occurs.
As a heating method of the core body, as shown in FIG. 8, a method of attaching (pasting) a heating device 170 (for example, a planar heater) to the inside of the core body 1 can be mentioned.

The wind speed of the airflow is preferably about 1 to 10 m / min. If this is weak, the effect of promoting drying is small, and if it is too strong, defects such as streaks and unevenness may occur in the coating film. Moreover, when the airflow which hits the coating film flows into the coating tank, the liquid surface is shaken or the solvent is dried on the liquid surface. Therefore, it is preferably applied upward so that the airflow does not flow into the coating tank. An air flow can be used as the air flow.
By applying an air flow to the coating film of the fluororesin dispersion liquid, drying of the solvent is promoted, so that the coating film is dried soon before sagging occurs.

(Resin film formation process)
After application of the fluororesin dispersion, the solvent is dried by placing it at room temperature to 150 ° C. for 5 to 20 minutes. Before and after drying, the previously formed coating treatment is removed. Thereafter, when heated at a temperature of 350 to 450 ° C. for 20 to 60 minutes, the PI precursor contained in the sliding layer and the PI layer undergoes a condensation reaction to form a polyimide composed of a first polyimide resin layer and a second polyimide resin layer. A film is formed. Further, the fluororesin powder is melted to form a fluororesin layer. At this time, since the residual solvent in the PI precursor film may cause swelling of the film, it is preferable to increase the temperature stepwise or slowly until the temperature is reached.

(Resin film removal process)
Thereafter, the slidable endless belt or the fixing belt is manufactured by cooling to room temperature and removing the core.

Here, in the resin film extraction step, the difference ( ^BA ) between the thermal expansion coefficient A of the polyimide film and the thermal expansion coefficient B of the core body is set to 10 × 10 ⁻⁶ / K or less, and one end of the core body A cylindrical body having the same outer diameter as that of the core body and a through-hole on the side surface is joined to the portion, a belt is fitted around the cylindrical body, and air leaks into the polyimide film formed on the core body. After pasting so that there is no pressure, it is preferable to inject pressurized air into the gap between the surface of the core and the polyimide film through the through hole from the inside of the cylindrical body, and peel off the polyimide film.
When the difference (B−A) exceeds 10 × 10 ⁻⁶ / K, the resin film may be peeled off due to the shrinkage of the cylindrical core body after heating even if the method of the present invention is not used.

  This will be specifically described with reference to FIG. As shown in FIG. 9A, a cylindrical body 13 provided with a through-hole 110 is prepared and joined to the core body 1 on which a PI resin film (not shown) is formed (FIG. 9B). In this case, “joining” indicates a joined state in which pressurized air does not leak, and a method can be adopted in which both are fitted with a sealing material sandwiched, or an adhesive tape is applied to the joint between the two. . In addition, when pipes are welded, or when stainless steel plate materials are rolled and welded to produce a cylinder, there may be a change in the hardness of the stainless steel on the core surface. Heat treatment is recommended.

Next, a belt 14 that closely matches the outer diameter of the cylindrical body is fitted around the cylindrical body, and the resin film formed on the core body is pasted using an adhesive tape or the like so that air does not leak. The belt 14 may be an endless belt prepared in advance, or may be a belt in which a resin film is wound and pasted together.
Thereafter, as shown in FIG. 9, when the air tube 15 is connected to the through hole 110 of the cylindrical body 13 and pressurized air is injected, the compressed air is injected inside the belt 14 to expand the belt 14, Pressurized air is also injected into the gap between the core 1 and the PI resin film (not shown) formed on the surface thereof, and the PI resin film expands, so that the PI resin film can be peeled off. is there.
If the size of the through-hole 110 provided in the cylindrical body is too large, the liquid may enter and become clogged, and if it is too small, the amount of pressurized air injected is insufficient, so a range of about 0.5 to 4 mm in diameter is preferable. In addition, since it is necessary to inject a certain amount of pressurized air at the time of peeling of the PI resin film, it is preferable to provide two or more through holes having a diameter of 3 mm or less, and when the diameter is 1 mm or less. It is preferable that four or more are provided.
Although this method requires extra man-hours, there is an advantage that a process of providing a through hole in the cylindrical core is unnecessary and there is no possibility that the solution enters the through hole. If the hole diameter is large, the solution may enter the hole and close the hole. In that case, it is better to scrape the solution that has entered, or to blow the solution by injecting air from the inside of the hole. .

(Fluorine resin coating film reforming process)
In the fluororesin coating film forming step, when there is a defect in the fluororesin coating film layer, the fluororesin coating film layer is removed, and the fluororesin coating material is applied again to remove the fluororesin coating film layer. It is preferable to provide a fluororesin coating film reforming step to be formed.

  Prior to this process, the coating film of the fluororesin dispersion is observed to try to find defects. Defects include `` bups '' caused by fluororesin agglomerates and solid foreign matter mixed in the dispersion, `` foils '' and `` dents '' caused by oily foreign matter, and `` bubbles '' in the liquid. In addition to “bubbles”, “pops”, “dents” caused by the bursting of bubbles, “streaks” caused by tailing without bubbles being applied, “unevenness” caused by dirt on the PI film, etc. ”Occurs or there are various defects.

  When these defects are present in the coating film, it is useless because it is only a defective product even if it is heated and fired. Therefore, in the present invention, the defective coating film is removed and regenerated. Since the coating film of fluororesin dispersion is a powder film, it can be easily removed, but the removal method is a method of wiping with paper or the like, a method of immersing the coating film in water and peeling it off, There are methods such as scraping with a member, and a plurality of methods may be used in combination. After removing the coating film, the fluororesin dispersion is applied again.

(Other processes)
Furthermore, if necessary, after passing through a resin film extraction step, a cutting process step of cutting both ends of the polyimide film formed with the fluororesin layer to make the lengths of the ends uniform, and adjusting the surface roughness A polishing process step or the like may be provided.
The polishing process may be either a dry method or a wet method. As a dry method, there is a method of polishing using sand paper or a polishing film. As a wet method, there is a method of performing the same thing as the above through a liquid such as water.

  Hereinafter, the present invention will be specifically described with reference to the following examples.

[Example 1]
As a PI precursor solution, an S-type precursor solution prepared by synthesizing BPDA and PDA in N, N-dimethylacetamide and having a solid content concentration of 20% and a viscosity of about 10 Pa · s was prepared. In this, molybdenum disulfide powder having an average particle size of 0.4 μm was mixed at a solid content ratio of 10% by weight with respect to the coating solution, and dispersed by a ball mill to obtain a sliding layer coating solution.

  A cylindrical body having an outer diameter of 68 mm was prepared by cutting the surface of an aluminum base tube having an outer diameter of 70 mm and a length of 400 mm. The surface was roughened to Ra 0.8 μm by blasting with spherical alumina particles (Fuji Seisakusho, particle size 105-125 μm), and then a silicone mold release agent (trade name: KS700, Shin-Etsu Chemical Co., Ltd.) )) Was applied and baked at 300 ° C. for 1 hour to obtain a core.

As an application tank 7 in FIG. 2, an annular tank having an inner diameter of 120 mm and a height of 50 mm was prepared, and a 0.5 mm thick polyethylene annular seal 8 having a 66 mm circular hole formed in the bottom surface was attached. As the annular body 5, an aluminum ring having a height of 25 mm, an outer diameter of 84 mm, an inner diameter of the minimum portion 6 of 68.4 mm, and an inner surface as shown in FIG. 2 was prepared. Three arms were attached to the outside and placed on an annular tank. The intermediate body 9 was attached to the upper and lower sides of the core body 1, and the solution 2 was put through the annular tank.
Subsequently, the core 1 was raised at a speed of 400 mm / min. Meanwhile, the annular body 5 was lifted by about 20 mm, but it did not come into contact with the core body 1, and a coating film serving as a sliding layer having a wet film thickness of about 0.2 mm was formed on the surface of the core body 1. .

  After coating, the core was rotated at 10 rpm and placed in a 120 ° C. drier, and after 30 minutes, the first polyimide precursor layer having a thickness of about 80 μm was formed.

Next, the same S-type precursor solution as described above was prepared. However, the viscosity was about 30 Pa · s. This was put into the coating tank 7 of the same size. The annular body 5 has the same shape, but the inner diameter of the minimum portion 6 is 69.2 mm.
Subsequently, the core 1 was raised at a speed of 400 mm / min. In the meantime, the annular body 5 was lifted by about 20 mm, but it did not contact the core body 1. As a result, a second polyimide precursor layer having a wet film thickness of about 0.5 mm was formed.

After coating, the core was rotated at 10 rpm and placed in a drying oven at 120 ° C., and taken out after 60 minutes. A PI precursor film having a thickness of about 150 μm was formed. In this state, the film could not be removed from the core.
Next, the core was heat treated at 150 ° C. for 20 minutes, 220 ° C. for 20 minutes, and 380 ° C. for 30 minutes to form a polyimide film having a first polyimide resin layer and a second polyimide resin layer. . After the core cooled to room temperature, the polyimide film was removed from the core, and an endless belt having a 75 μm thick second polyimide resin layer on a 10 μm thick first polyimide resin layer (sliding layer) was obtained. .
The tensile strength of the endless belt was 420 MPa. This is almost the same strength as the PI resin layer alone.

[Example 2]
In Example 1, the same result as in Example 1 was obtained even when a graphite powder having a volume average particle size of 2.0 μm was used instead of the molybdenum disulfide powder in the sliding layer.

[Comparative Example 1]
In Example 1, molybdenum disulfide powder was mixed in an S-type precursor solution having a viscosity of about 30 Pa · s at a solid content ratio of 10% by weight and dispersed by a ball mill. Using this solution, a 75 μm thick PI resin layer was formed in the same manner without forming a sliding layer on the core. The tensile strength of this PI resin layer was 280 MPa, which was lower than the result of Example 1. It is considered that the tensile strength was reduced because the molybdenum disulfide powder was contained in the PI resin.

Example 3
In Example 1, the lid 10 was fitted on one end of the core before heating, which was coated with the sliding layer and the PI precursor and dried, as shown in FIG. 3, and the adhesive tape 15 having a width of 20 mm was wrapped around the lid. Fixed.

  As a fluororesin coating material, a PFA aqueous coating material (concentration 60%, viscosity 500 mPa · s) containing ethanol and t-butanol was prepared in addition to water. Among these, as solids, PFA powder (large particles) having a particle size of about 17 μm is 55% by mass, PFA powder (small particles) having a particle size of about 1 μm is 40% by mass, and barium sulfate powder having a particle size of about 5 μm. 5% by weight of the body is dispersed. This liquid was left under a reduced pressure of 20 hPa for 12 hours for defoaming treatment.

As shown in FIG. 6, the external tank 12 having an inner diameter of 150 mm and a height of 160 mm was attached to the outside of the coating tank 17 having an inner diameter of 90 mm and a height of 480 mm. The dispersion liquid 16 is filled in the coating tank 17 and further filled up to 30 mm from the lower part of the external tank 12, and circulated at a flow rate of 2 liters / minute with a pump 13 (trade name: sign pump, manufactured by Tokushu Kika Kogyo Co., Ltd.). . This pump has a characteristic that the shear stress applied to the liquid is small. Aggregates were removed through the 200 mesh filter 14 in the circulation path. At the upper part of the coating tank 17, an annular air blower 20 that attaches an airflow of 5 m / min in an annular direction toward the upper 45 ° is attached.
The core body 1 was attached to the holding member, and the PI precursor film 18 was immersed in the paint 16 leaving 5 mm from the top (immersion treatment). Next, the core body 1 was pulled up at a speed of 0.2 m / min while applying an air flow to form a PFA coating film 19.

After completion of the pulling, the adhesive tape was removed, the lid was removed, and then the hot air at 120 ° C. was placed in a drying furnace descending from above for 5 minutes to dry.
Next, the core was heated at 150 ° C. for 20 minutes, 220 ° C. for 20 minutes, and 380 ° C. for 30 minutes to cause the PI resin to react, and the PFA coating film was baked. After the core body cooled to room temperature, the core body was removed to obtain a fixing belt having a 75 μm thick PI resin layer on a 10 μm thick sliding layer and a 40 μm thick PFA layer thereon.
The fixing belt could be manufactured by cutting both ends so that the length was 340 mm.

Example 4
A fixing belt was prepared in the same manner as in Example 3 except that 5% by mass of carbon nanotubes (made by Showa Denko, diameter: about 150 μm, length: about 10 μm) was added to the fluororesin coating material.

(Evaluation of fixing belt)
The fixing belts obtained in Examples 3 and 4 were evaluated by the idler evaluation machine shown in the schematic cross-sectional view of FIG.
In the drawing, the heat fixing roll 21 is connected to a motor (not shown) and rotated, and a heating source 22 is installed therein. On the other hand, a pressurizing unit 27 having a pressure pad 23, an oil supply source 24, and a sliding sheet 25 has a fixing belt 26 rotatably attached to the outer periphery thereof. The fixing belt 26 obtained in Examples 3 and 4 has its outer peripheral surface pressed against the surface of the heat fixing roll 21 to form a pressure contact portion (nip), and the heat fixing roll 21 is rotated in the direction of arrow R. Along with this, it rotates following.

  A pressure pad 23 is arranged on the inner peripheral surface of the fixing belt 26 so as to press the inner peripheral surface of the fixing belt 26 via the sliding sheet 25 so that the nip can be formed. The nip load in the nip portion is adjusted by adjusting the pressing force.

The sliding sheet 25 is made of a glass fiber sheet impregnated with polytetrafluoroethylene (PTFE), and the arithmetic average roughness Ra of the surface of the sliding sheet 25 in contact with the fixing belt 26 is 3.1 μm. is there.
The oil supply source 24 is disposed in contact with the inner peripheral surface of the fixing belt so that oil can be supplied to the inner peripheral surface of the fixing belt 26 when the fixing belt 26 rotates.

In the idle rotation evaluation, an appropriate amount of an amino-modified silicone oil having a viscosity of 300 cs (manufactured by Shin-Etsu Chemical Co., Ltd.) is applied to the surface of the sliding sheet 25 that contacts the fixing belt 26, and then the fixing belt 26 is attached to the outer periphery of the pressure unit 27 did.
Next, the nip load is set to 440 N (severe conditions for increasing the load), the rotation speed of the heat fixing roll 21 is set to 74.4 rpm, the surface temperature of the heat fixing roll 21 is set to 175 ° C., and the heat fixing roll is moved in the direction of arrow R And the load torque of the motor connected to the heat fixing roll 21 was measured. The load torque was obtained by measuring the current value flowing through the motor and converting it.

The initial load torque of the fixing belt of Example 3 was 2.0 × 10 ⁻² N · m, and there was almost no change even after 2 hours. Further, the fixing belt of Example 4 hardly changed even after 2 hours . Hand, the initial load torque of the fixing belt 2 provided with no sliding layer is the initial and after 2 hours 3.0 × 10 ^-2 N · m, greater than the frictional resistance that of Example 3.

  Moreover, the belt which provided the fluororesin layer in the endless belt of the comparative example 1 had the edge part fracture | ruptured after 1 hour, when the same test was carried out. This is probably because the strength is insufficient.

[Reference example]
When 1000 fixing belts were produced under the conditions of Example 3, in the fluororesin coating film forming step, the fluororesin coating film layer was removed for those having defects in the fluororesin coating film layer. Again, the fluororesin paint was applied to form a fluororesin coating film layer (fluororesin coating film re-forming step).
By providing such a process, it was possible to reduce defects of the PI resin endless belt having the fluororesin layer. That is, even if there is a defect in the fluororesin layer, it is removed and re-applied before heating and baking, so that the PI film can be recycled without being discarded.

It is a schematic sectional drawing which shows the coating method of a polyimide precursor. It is a schematic sectional drawing which shows the other application | coating method of a polyimide precursor. It is explanatory drawing which performs a coating process on a lid. It is a side view for demonstrating another coating process. It is the schematic which shows the dip coating method of a fluororesin dispersion. It is the schematic of the dip coating method of the fluororesin dispersion using a circulation type coating tank. It is the schematic block diagram which attached the mass adjustment member of the annular body to the sinking prevention member provided in the annular body. It is the schematic which shows the aspect which provided the heating apparatus inside the core. (A) is explanatory drawing at the time of using the cylindrical body provided with the through-hole, (b) is explanatory drawing at the time of joining the cylindrical body provided with the through-hole to the core body. FIG. 2 is a schematic cross-sectional view of a fixing device.

Explanation of symbols

1 ... cylindrical body, 2 ... solution, 3 ... coating tank,
4 ... coating film, 5 ... annular body, 6 ... hole of annular body,
7 ... annular coating tank, 8 ... annular sealing material, 9 ... intermediate,
10 ... Lid, 11 ... Holding member, 12 ... External tank,
13 ... Pump, 14 ... Filter, 15 ... Coating member,
16 ... fluororesin dispersion, 17 ... dip coating tank, 18 ... polyimide precursor film,
19 ... coating film, 20 ... air blower, 21 ... heat fixing roll,
22 ... Heat source (halogen heater), 23 ... Pressure pad, 24 ... Oil supply source,
25 ... sliding sheet, 26 ... fixing belt, 27 ... pressure unit,
30 ... Empty turning evaluation machine

Claims (3)

On the surface of the core body, the first polyimide precursor layer in which the solid lubricant is dispersed and the second polyimide precursor layer are formed in this order, and the coating film forming process and the coating film forming process A resin film forming step of forming a polyimide film having a first polyimide resin layer and a second polyimide resin layer by heat-treating the first polyimide precursor layer and the second polyimide precursor layer ; A method for producing an endless belt, comprising: a resin film extracting step of extracting a polyimide film from a core in this order. A coating film forming step of forming a first polyimide precursor layer in which a solid lubricant is dispersed on the surface of the core body and a second polyimide precursor layer in this order; A fluororesin coating film forming step of forming a fluororesin coating film layer by applying a fluororesin coating on the polyimide precursor layer, the first polyimide precursor layer formed in the coating film forming process, and the first Heat treatment is performed on the polyimide precursor layer 2 and the fluororesin coating layer formed in the fluororesin coating layer forming step to form a polyimide coating having a first polyimide resin layer and a second polyimide resin layer. And a resin film forming step of forming a fluororesin layer on the polyimide film, a resin film extracting step of extracting the polyimide film formed of the fluororesin layer from a core, Method for producing a fixing belt characterized in that it comprises in this order. In the fluororesin coating film forming step, when there is a defect in the fluororesin coating film layer, the fluororesin coating film layer is removed, and the fluororesin coating material is applied again to form a fluororesin coating film layer. The method for producing a fixing belt according to claim 2 , further comprising a step of forming a fluororesin coating film to be formed.

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