JP2003255640A - Polyimide resin endless belt and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide resin endless belt in which the tensile strength is increased, the coefficient of thermal expansion is decreased and the dimensional stability is improved, and to provide a method for manufacturing the belt. <P>SOLUTION: The polyimide resin endless belt is characterized by containing a carbon nanotube or a fibrous substance. The method for manufacturing the same is also provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductor in an image forming apparatus such as an electrophotographic copying machine or a laser printer.
The present invention relates to a polyimide resin endless belt that is preferably used as a charging belt, a transfer belt, a fixing belt, and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, various rotating bodies made of metal, plastic, or rubber are used as a photosensitive body, a charging body, a transfer body, a fixing body, and the like. In order to downsize the device or improve the performance, it is sometimes preferable that the rotating body is deformable, and a resin belt is used for that. In this case, if the belt has a seam, a defect due to the seam occurs in the output image. Therefore, the seamless endless belt is preferable. The required characteristics of using an endless belt as a rotating body are that the coefficient of thermal expansion is small, that mechanical properties such as tensile strength are sufficient, that dimensional stability is good against elongation, and that electrical resistance varies depending on the application. There is something that can be controlled, and a polyimide resin can be cited as a suitable resin material.

In order to produce an endless belt from a polyimide resin, for example, as described in JP-A-57-74131, a polyimide precursor solution is applied to the inner surface of a cylindrical body, dried while rotating, and a centrifugal molding method, There was an inner surface coating method described in JP-A No. 62-19437, in which a polyimide precursor solution was spread on the inner surface of a cylindrical body. However, in the method of forming a film on these inner surfaces, it is necessary to remove the film from the cylindrical body and mount it on the outer mold when heating the polyimide precursor, which is a disadvantage in that it takes man-hours.

As another method for producing an endless belt, for example, as described in JP-A-61-273919, a polyimide precursor solution is applied to the surface of a core by a dip coating method, dried, and heated. There is also a method of peeling the polyimide resin film from the core. With this method, the number of steps for transferring to an outer mold is unnecessary, but since the polyimide precursor solution has a very high viscosity, it was difficult to apply a uniform thickness when the film thickness was large.

By the way, although the polyimide resin has already been applied in various fields, further improvement in characteristics is always desired. At that time, since there is a limit to the improvement of the resin itself, additives such as powders and whiskers are dispersed and used together. Specifically, a resin composition made of glass fiber or carbon fiber is known, but when such a fiber itself is applied to a belt, it is difficult to form a film by coating, for example, in a thin thickness, There is a problem that irregularities of fibers appear on the belt surface, and it is difficult to use it as a belt.

On the other hand, in addition to the above-mentioned glass fibers and carbon fibers, there are carbon nanotubes which have recently been receiving attention,
It is possible to obtain an excellent functional material by combining this carbon nanotube and a polyimide resin.
No. 160, and the proposal discloses a resin composition for an insulating material which has an extremely low dielectric constant and good insulating properties and is also excellent in heat resistance. There was no.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the various problems in the prior art and achieve the following objects. That is, an object of the present invention is to provide a polyimide resin endless belt having an increased tensile strength, a reduced thermal expansion coefficient, and an improved dimensional stability, and a method for producing the same.

[0008]

The above problems can be solved by the following means. That is, the present invention is a polyimide resin endless belt containing <1> carbon nanotubes.

<2> A surface layer is formed on a polyimide resin coating film, and the carbon nanotubes are contained in the polyimide resin coating film and also in the surface layer. <1> Is a polyimide resin endless belt.

<3> A polyimide resin endless belt containing a fibrous substance.

<4> The polyimide resin endless belt according to <3>, wherein the fibrous substance is composed of an inorganic needle-like single crystal.

<5> The above-mentioned <3> or the above-mentioned <3> characterized in that the fibrous substance is contained in the polyimide resin coating as well as in the surface layer on the polyimide resin coating. The polyimide resin endless belt according to <4>.

<6> A step of applying a polyimide precursor solution containing carbon nanotubes or a fibrous substance to the surface of a columnar or cylindrical core to form a polyimide precursor coating film, and the polyimide precursor coating film. , Dry, heat,
A method for producing a polyimide resin endless belt, comprising: a step of forming a polyimide resin coating; and a step of peeling the polyimide resin coating from the columnar or cylindrical shape.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The polyimide resin endless belt of the present invention is characterized by containing carbon nanotubes or fibrous substances. The polyimide resin endless belt of the present invention, the carbon nanotubes or fibrous substances are well dispersed in the polyimide resin, are not easily deformed by being entangled well with the resin, not only increase the strength of the resin but also increase the coefficient of thermal expansion. It can be kept small. The polyimide resin endless belt of the present invention containing such carbon nanotubes or fibrous substances can increase tensile strength, reduce thermal expansion coefficient, and improve dimensional stability.

The carbon nanotube is a cylindrical hollow fiber made of carbon, and its length is several tens times or more of its diameter. Specifically, the diameter is preferably 0.0
05-1 μm, length 1-100 μm, more preferably diameter 0.01-0.5 μm, length 1-10 μm
It is preferable to use the above in consideration of the step of applying the polyimide precursor solution and the thickness of the coating film. Carbon nanotubes can be produced by a known method such as a method of thermally decomposing using a catalyst, an arc discharge method, a laser evaporation method, or the like.

The content of carbon nanotubes is preferably 4 to 40% by weight, more preferably 5 to 30% by weight, based on the polyimide resin.

The fibrous substance refers to a substance in which fine needle-like single crystals are entangled with each other in a fibrous form. Specific examples thereof include zinc oxide, titanium oxide, potassium titanate, aluminum borate, silicon carbide and nitride. Preferable ones are those in which minute acicular single crystals made of silicon, graphite or the like are entangled with each other to form a fiber. As described above, since the fibrous substance is a single crystal, it is characterized in that the strength (tensile strength, elastic modulus, etc.) is very strong.

The length of the fibrous substance is 1 to 50 μm, and the diameter is about 0.05 to 5 μm, which is preferable in consideration of the step of applying the polyimide precursor solution and the thickness of the coating film, and more preferably the length. Is 2 to 40 μm, and the diameter is 0.1 to
It is 4 μm.

The content of the fibrous substance is 4 to 40% by weight with respect to the polyimide resin, more preferably 5 to 30%.
% By weight.

In the polyimide resin endless belt of the present invention, the coefficient of thermal expansion can be reduced by incorporating carbon nanotubes or fibrous substances into the polyimide resin. The coating becomes easy to remove from the columnar or cylindrical core. That is, in order to produce a polyimide resin endless belt, usually, a polyimide precursor solution is applied to the surface of a cylindrical or cylindrical core, dried and heated, and then the polyimide resin film is peeled from the cylindrical or cylindrical core. However, the polyimide resin generally has a strong shrinking force during the heating reaction, and it is not easy to extract it from the columnar or cylindrical core. Therefore, the columnar or cylindrical core is peeled off by utilizing the property that the columnar or cylindrical core shrinks more than the polyimide resin when the polyimide resin is heated and reacted, and then cooled. Therefore, the difference between the coefficient of thermal expansion of the polyimide resin and the coefficient of thermal expansion of the columnar or cylindrical core can be increased, and in the present invention, it can be easily peeled.

Here, the coefficient of thermal expansion of the cylindrical or cylindrical core is
The larger the better, the better the heat of the metal material that can be used as the core.
The expansion coefficient of aluminum is 23 × 10^-6/ K, 18-8
SUS is 18 × 10^-6/ K, copper is 17 × 10^-6/ K, iron
Is 12 × 10^-6/ K, brass is 18 × 10^-6/ K, Nicke
15 × 10^-6/ K (both at room temperature), too large
Not a good value. On the other hand, the coefficient of thermal expansion of polyimide resin is small
How good it is! The coefficient of thermal expansion of various polyimide resins is
3,3 ', 4,4'-biphenyltetracarboxylic acid dinone
Water (BPDA) and p-phenylenediamine (PDA)
Consisting of 12 × 10^-6/ K, BPDA and 4,4 '
-21 x 1 consisting of diaminodiphenyl ether
0 ^-6/ K, pyromellitic dianhydride (PMDA) and 4,
20 consisting of 4'-diaminodiphenyl ether
× 10^-6/ K, 3,3 ', 4,4'-benzophenone
Tracarboxylic dianhydride and 4,4'-diaminodipheny
50 x 10 consisting of methane^-6/ K, 3, 3 ',
4,4'-benzophenone tetracarboxylic dianhydride and
24 consisting of 4,4'-diaminobenzophenone
× 10^-6/ K, etc., considering the coefficient of thermal expansion of the core material
And even compared to the largest aluminum,
The smaller ones generally consist of BPDA and PDA
There is only one kind.

In using a polyimide resin endless belt,
It is preferable that various candidate materials can be selected so that a wide range of requirements can be met. However, the price of BPDA is higher than that of other monomers, and the polyimide resin endless belt using the same has a disadvantage of being expensive. A polyimide resin that does not use BPDA has an advantage in that the price is low, but has a problem that the coefficient of thermal expansion does not become smaller than that of aluminum.

Therefore, although the cost is low, if the thermal expansion coefficient is reduced by adding carbon nanotubes or fibrous substances to a polyimide resin having a large thermal expansion coefficient, the selection range of candidate materials can be increased. Further, if a polyimide resin that does not use BPDA is used, it is possible to suppress the price increase. The polyimide resin used here is BPDA.
It is preferable to use a base material synthesized from an acid anhydride other than the above and a diamine. Of course, a polyimide resin made of BPDA may be used to adjust the characteristics such as strength. Any diamine may be used.

The polyimide resin endless belt of the present invention comprises a polyimide resin coating, and the resin coating contains carbon nanotubes or fibrous substances. Also,
The polyimide resin endless belt of the present invention may have a form having a surface layer such as a releasable resin film on the polyimide resin film depending on the application. In this case, although described later, the carbon nanotube or the fibrous substance is In addition to being contained in the polyimide resin coating, it can be contained in the surface layer.

Here, the coefficient of thermal expansion of the polyimide resin coating containing carbon nanotubes or fibrous substances should be smaller than that of the columnar or cylindrical core body used,
Specifically, it is preferably 10 × 10 ^{−6 to} 25 × 10 ⁻⁶ / K, and more preferably 12 × 10 ^{−6 to} 22 × 10 ⁻⁶ / K.

As described above, in the present invention, if the relationship that the coefficient of thermal expansion of the columnar or cylindrical core used in the production is higher than the coefficient of thermal expansion of the polyimide resin film to be produced, the carbon The material and amount of the nanotubes and fibrous substances, and further the material of the cylindrical core,
Although not limited, the difference between the coefficient of thermal expansion of the polyimide resin film and the coefficient of thermal expansion of the cylindrical core is 5 × 10 ⁻⁶ / K.
It is preferably not less than 8 × 10 ⁻⁶ / K, more preferably not less than 8 × 10 ⁻⁶ / K.

Hereinafter, the polyimide resin endless belt of the present invention will be described in more detail together with its preferable manufacturing method (method of manufacturing the polyimide resin endless belt of the present invention). The method for producing the polyimide resin endless belt of the present invention is a step of forming a polyimide precursor coating film by applying a polyimide precursor solution containing carbon nanotubes or a fibrous substance to the surface of a cylindrical or cylindrical core (hereinafter, And a step of forming a polyimide resin film by drying and heating the polyimide precursor coating film (hereinafter referred to as "polyimide resin film forming step"). And a step of peeling the polyimide resin coating from the columnar or cylindrical core (hereinafter referred to as “polyimide resin coating peeling step”). Also, if necessary,
You may have another process.

-Polyimide precursor coating film forming step-The polyimide precursor is N-methylpyrrolidone, N, N-
It is synthesized by dissolving both in an aprotic polar solvent such as dimethylacetamide, acetamide, N, N-dimethylformamide. The concentration, viscosity, etc. at the time of synthesis are selected appropriately.

A known dispersion method such as a ball mill, a sand mill, or a roll mill can be used to add the carbon nanotubes or the fibrous substance to the polyimide precursor solution. There is also a method of synthesizing a polyimide precursor after dispersing carbon nanotubes or fibrous substances in a monomer solution of either an acid anhydride or a diamine, or both.

In the step of forming a polyimide precursor coating film, the polyimide precursor solution is applied to the surface of a cylindrical or cylindrical core body to form a polyimide precursor coating film. Immersion coating method of immersing the core body in the polyimide precursor solution and pulling it up, flow coating method of discharging the polyimide precursor solution onto the surface of the cylindrical or cylindrical core body while rotating the core body, and a blade for metalling the film with a blade at that time An existing known method such as a coating method can be adopted. In the above-mentioned flow coating method or blade coating method, the coating is spirally formed by horizontally moving the coating portion, but since the polyimide precursor solution dries slowly, the seam is naturally smoothed. Incidentally, "applying to the surface of a cylindrical core or a cylindrical core" means the surface of the side surface of the cylindrical core including the cylinder,
And, when it has a layer on the surface, it means coating on the surface of the layer.

When the polyimide precursor solution is applied by the dip coating method in the step of forming the polyimide precursor coating film, the viscosity of the polyimide precursor solution is so high that the film thickness may be too thicker than the desired value. is there. In that case, for example, a dip coating method in which the film thickness is controlled by the following annular body can be applied.

The dip coating method in which the film thickness is controlled by the annular body will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram showing an example of an apparatus used in the dip coating method in which the film thickness is controlled by a ring. However, the figure shows only the main part of coating, and other devices are omitted. As shown in FIG. 1, in this dip coating method, an annular body 5 having a hole larger than the outer diameter of the cylindrical core 1 is floated on a polyimide precursor solution 2 filled in a coating tank 3 Is a coating method in which the cylindrical core body 1 is immersed in the polyimide precursor solution 2 and then pulled up.

FIG. 2 is an enlarged perspective view of an essential part for explaining the installation state of the annular body 5 shown in FIG. As shown in FIG. 2, an annular body 5 having a hole 6 having a diameter larger than the outer diameter of the cylindrical core body 1 by a constant gap is floated on the liquid surface of the polyimide precursor solution 2.

The ring-shaped body 5 floats on the liquid surface of the polyimide precursor solution 2 and its material is preferably one that is not corroded by the polyimide precursor solution 2, and examples thereof include various metals and various plastics. Further, the structure of the annular body 5 may be, for example, a hollow structure so that the polyimide precursor solution 2 easily floats on the liquid surface.

Further, fixing means for temporarily fixing the annular body 5 may be provided so that the annular body 5 is located at the center of the coating tank 3. As such fixing means, there are means for providing legs on the annular body 5, means for fixing the coating tank 3 and the annular body 5, and the like. However, when these fixing means are used, as will be described later, the fixing means is detachable so that the annular body 5 can freely move when the cylindrical core 1 is pulled up after being immersed. Will be placed.

The gap between the outer diameter of the cylindrical core 1 and the diameter of the hole 6 is adjusted in consideration of the desired coating film thickness. Desired coating thickness,
That is, the dry film thickness is the product of the wet film thickness and the concentration of nonvolatile components in the polyimide precursor solution 2. From this, the desired wet film thickness is determined. The gap between the outer diameter of the cylindrical core 1 and the diameter of the hole 6 is preferably 1 to 2 times the desired wet film thickness. The reason why it is set to 1 to 2 times is that the distance of the gap does not always become the wet film thickness due to the viscosity and / or the surface tension of the polyimide precursor solution 2. Thus, the desired diameter of the hole 6 is obtained from the desired dry film thickness and the desired wet film thickness.

The wall surface of the hole 6 provided in the annular body 5 may be configured to be substantially perpendicular to the liquid surface of the floating polyimide precursor solution 2. For example, it may be a straight line shown in the cross-sectional view shown in FIG. 1 and the straight line may be perpendicular to the liquid surface of the polyimide precursor solution 2, or may be configured in another form. For example, as shown in FIG.
The lower part soaked in the polyimide precursor solution 2 is wide, the upper part is narrow, and it has an inclined shape 7. As shown in FIG. 3B, the lower part soaked in the polyimide precursor solution 2 is wide and the upper part is narrow.
A curved surface 8 and, as shown in FIG. 3 (c),
An example is a bent surface shape 10 in which the lower part immersed in the polyimide precursor solution 2 is wide and the upper part is narrow. In particular, FIG.
As shown in (a) to (c), a polyimide precursor solution 2
It is preferable that the lower part soaked in is wide. Further, the wall surface of the hole 6 provided in the annular body 5 is also preferably used, in which the streak-like projections are provided along the dipping / pulling direction of the cylindrical core body. Here, FIG. 3 shows the shape of the wall surface of the hole provided in the annular body, where (a) is an inclined wall surface, (b) is a curved wall surface, and (c) is a curved wall surface. It is a schematic sectional drawing shown.

When the dip coating is carried out, the cylindrical core 1 is provided with holes 6
And is immersed in the polyimide precursor solution 2. that time,
The cylindrical core body 1 is prevented from coming into contact with the annular body 5. Then, the cylindrical core 1 is pulled up through the hole 6. On this occasion,
The coating film 4 is formed by the gap between the cylindrical core 1 and the hole 6. The pulling rate is 100 to 1500 mm / mi
It is preferably about n. The solid content concentration of the polyimide precursor solution preferable for this coating method is 10 to 40% by mass,
The viscosity is 1 to 100 Pa · s.

The annular body 5 can freely move on the liquid surface of the polyimide precursor solution 2. Moreover, the hole 6 of the annular body is circular, and the outer circumference of the cylindrical core 1 is also circular. Therefore, when pulling up the cylindrical core 1 through the hole 6, the frictional resistance between the cylindrical core 1 and the annular body 5 becomes constant,
The annular body 5 moves. That is, when pulling up the cylindrical core 1,
When the gap between the annular body 5 and the cylindrical core 1 is narrowed at a certain position, the frictional resistance is increased in the narrowed portion. On the other hand, on the other side, the frictional resistance decreases,
The frictional resistance may be temporarily non-uniform. However, since the annular body 5 moves freely, the outer circumference of the cylindrical core body 1 is circular, and the hole 6 of the annular body is circular, such frictional resistance is uniform from a non-uniform state. The annular body 5 moves so as to be in such a state. Therefore, the annular body 5
Does not come into contact with the cylindrical core 1.

Further, the position where the frictional resistance is uniform is a position where the circular shape of the outer periphery of the cylindrical core 1 and the circular shape of the hole 6 of the annular body are substantially concentric. Therefore, even if the center of the circle of the cross section of the cylindrical core 1 is displaced within the allowable range in the axial direction, the annular body 5 moves to follow it. Therefore, it is possible to provide the cylindrical core 1 with a constant wet film thickness.

The annular body 5 is set in a freely movable state so that it can move on the polyimide precursor solution 2 with a slight force. As a method for this, the annular body 5 is floated as shown in FIG. In addition to the above method, there are a method of supporting the annular body 5 with a roll or a bearing, a method of supporting the annular body 5 with air pressure, and the like.

When the cylindrical core body 1 is lifted from the polyimide precursor solution 2 through the hole 6 of the annular body 5, the polyimide precursor solution 2 intervenes to cause frictional resistance between the cylindrical core body 1 and the annular body 5. Occurs, the lifting force acts on the annular body, and the annular body may be slightly lifted. When the annular body 5 is slightly lifted in this way, the gap between the annular body 5 and the cylindrical core body 1 changes, so that the annular body 5 has a frictional resistance with the cylindrical core body 1 as described above. It moves horizontally so that the gap becomes constant in all directions. In this way the annular body 5
In order to operate, the annular body 5 must be lifted to some extent, preferably when it is lifted by 2 mm or more. The rising force becomes stronger as the rising speed (pulling speed) of the cylindrical core 1 increases. However, if the ring-shaped body 5 is lifted and separated from the liquid surface of the polyimide precursor solution 2, the ring-shaped body 5 will drop to the liquid surface at the end of the rise of the cylindrical core body 1. Bubbles are caught in the precursor solution 2, which is very inconvenient when repeating the coating operation.

For this reason, when the cylindrical core 1 is raised, it is preferable that the annular body 5 is lifted to a certain height without being too high or too low. For that purpose, it is preferable to detect the height of the annular body 5 from the liquid surface of the polyimide precursor solution 2 and adjust the rising speed of the cylindrical core body 1. That is, when the ring-shaped body 5 is lifted high to move away from the liquid surface of the polyimide precursor solution 2, the rising speed is slowed, and conversely, when the lifted amount of the ring-shaped body 5 is small, the speed is increased. In order to detect the height of the ring-shaped body 5 from the liquid surface of the polyimide precursor solution 2, various mechanical or optical detection devices may be used. For convenience, it is also possible to visually determine the height of the annular body 5 from the liquid surface of the polyimide precursor solution 2 and manually adjust the speed.

Further, the coating device used in the dip coating method is a cylindrical core body holding means for holding the cylindrical core body, and, if desired, a first moving means and / or a first moving means for vertically moving the holding means. You may have a 2nd moving means which moves the container which accommodates a polyimide precursor solution up and down. The holding means, the first moving means, and / or the second moving means may have a deflection in a plane that intersects the pulling direction during movement. Even in such a case, the annular body 5 can move according to the shake.

By applying such a dip coating method in which the film thickness is controlled by the annular body, the sagging at the upper end portion of the cylindrical core is reduced due to the use of the highly viscous polyimide precursor solution. The film thickness can be made uniform.

In the polyimide precursor coating film forming step, in addition to the above dip coating method, an annular coating method as shown in FIG. 4 can be applied. Here, FIG. 4 is a schematic configuration diagram showing an example of an apparatus used for the annular coating method. In FIG. 4, a difference from FIG. 1 is that an annular sealing material 9 capable of passing the cylindrical core 1 is provided at the bottom of the annular coating tank 3 ′. An annular seal material 9 is attached to the bottom of the annular application tank 3 ', and the annular core 3 is inserted into the center of the annular sealing material 9 to form the annular application tank 3'.
Then, the polyimide precursor solution 2 is stored. This prevents the polyimide precursor solution 2 from leaking. The cylindrical core body 1 is sequentially lifted from the lower part to the upper part of the annular coating tank 3 ′, and the annular seal material 9 is inserted therethrough,
The coating film 4 is applied to the surface. The function of the annular body 5 is the same as that described above. In such an annular coating method, the annular coating tank 3 '
Can be made smaller than the dip coating tank 3, so that there is an advantage that the required amount of the solution can be small.

-Polyimide resin film forming step-In the polyimide resin film forming step, the coating film is not deformed even when left standing for the purpose of removing excessive aprotic polar solvent remaining in the polyimide precursor coating film. Do some drying. Drying temperature is 50-120 ° C, drying time is 30-
200 minutes is preferred. At that time, since the aprotic polar solvent is extremely slow to dry, the polyimide precursor film is apt to sag under the influence of gravity during the drying. In that case, with the longitudinal direction of the coated core body horizontal, 1
It is preferable to dry while rotating at about 0 to 60 rpm. In addition to heating, it is also effective to apply wind. The drying temperature is preferably increased stepwise or at a constant rate within the time period in order to reduce formation of bubbles in the dissolved gas of the aprotic polar solvent.

In the step of forming a polyimide resin film, after the drying, the polyimide precursor coating film is formed by heating the polyimide precursor coating film at preferably 300 to 450 ° C., more preferably around 350 ° C. for 20 to 60 minutes. can do. When heating, the polyimide resin film may swell if the solvent remains, so it is preferable to completely remove the residual solvent before heating. At a temperature of 250 ° C.
It is preferable to heat-dry for 30 minutes to remove the residual solvent, and then to raise the temperature stepwise or at a constant rate to heat to form a polyimide resin film.

In the step of forming the polyimide resin film, the polyimide precursor coating film may be contacted with a specific solvent which does not dissolve the polyimide precursor but can dissolve the aprotic polar solvent. . As a result, the aprotic polar solvent exudes from the polyimide precursor coating film into the specific solvent, and the specific solvent permeates instead. here,
Since the polyimide precursor is insoluble in the specific solvent, the polyimide precursor is deposited, and the polyimide precursor coating film is solidified to the extent that the coating film is not deformed even when it is allowed to stand to form a polyimide precursor coating film. As a result, the above-mentioned drying process is performed quickly, and the drying time can be shortened.

The contact between the polyimide precursor coating film and the specific solvent is preferably performed immediately after the step of forming the polyimide precursor coating film. After the application of the polyimide precursor solution, the DMAC contained in the coating film dries slowly at room temperature as described above, so the coating film remains wet forever, and the coating film always hangs downward due to the influence of gravity. Therefore, immediately after the application of the polyimide precursor, the polyimide precursor coating film is brought into contact with a specific solvent to solidify the polyimide precursor coating film, whereby the sagging can be prevented.

As a method of contacting the polyimide precursor coating film with the specific solvent, a method of immersing the polyimide precursor coating film in the specific solvent is preferable. Or you may spray. If the method of applying the polyimide precursor is a centrifugal molding method, the rotation of the cylindrical core may be stopped and immersed in a specific solvent, but while the cylindrical core is being rotated, the coating of the polyimide precursor on the inner surface is performed. You may spray a specific solvent.

When the polyimide precursor is deposited, the elution amount of the aprotic polar solvent from the polyimide precursor coating changes depending on the time of contacting the polyimide precursor coating with the specific solvent. When the aprotic polar solvent is completely removed from the coating film, the precipitated and solidified polyimide precursor film may become brittle, so the aprotic polar solvent remains in an amount of about 5 to 50% by mass. Is preferred. The contact time of the polyimide precursor coating film with the specific solvent for that depends on the film thickness of the polyimide precursor coating film,
About 10 seconds to 10 minutes is preferable. The thicker the film thickness of the polyimide precursor coating film, the more the aprotic polar solvent contained, and therefore it is preferable to lengthen the contact time. Upon contact, the specific solvent penetrates into the polyimide precursor coating film to some extent.

As the specific solvent to be brought into contact with the polyimide precursor coating film, a solvent in which the polyimide precursor is insoluble and which can dissolve an aprotic polar solvent is used. Specifically, water, alcohols (for example,
Methanol, ethanol, etc.), hydrocarbons (eg, hexane, heptane, toluene, xylene etc.), ketones (eg acetone, butanone etc.), esters (eg ethyl acetate etc.) can be mentioned. These may be used alone or as a mixture, but water or a mixture containing water is most preferable because it is the easiest to handle.

In the step of forming the polyimide resin film, when the treatment of bringing the polyimide precursor coating film into contact with the specific solvent is performed, the specific solvent that has penetrated into the formed polyimide precursor film and the residual aprotic polar solvent Drying is performed for the purpose of removing. The drying condition is preferably 50 to 120 ° C. for 10 to 60 minutes. Since the aprotic polar solvent is less likely to evaporate between the specific solvent and the aprotic polar solvent, a state in which the aprotic polar solvent remains in the polyimide precursor film is formed. In this state, the precipitated polyimide precursor is brought into a dissolved state again and becomes transparent. Then, after the drying as described above, the polyimide resin film can be formed by heating the polyimide precursor film at preferably 300 to 450 ° C., more preferably around 350 ° C. for 20 to 60 minutes.

-Polyimide resin film peeling step-After heating, a polyimide resin endless belt is obtained through a step of peeling the formed polyimide resin film from the cylindrical core. If necessary, the endless belt may be subjected to cutting, punching, tape winding, or the like at the end.

In the present invention, examples of the columnar or cylindrical core which is the base of the polyimide resin endless belt include:
Metals such as aluminum, copper and stainless steel can be preferably used, but from the viewpoint of a large coefficient of thermal expansion,
It is more preferably aluminum. When the columnar or cylindrical core is made of aluminum, if it is heated to, for example, 350 ° C., its strength is reduced and deformation is likely to occur. Such thermal deformation of aluminum is likely to occur when strain is accumulated during cold working into a cylindrical core shape. In order to remove such distortion, there is a method of annealing aluminum. However, since thermal deformation also occurs due to annealing, it is necessary to perform processing into a predetermined shape after that. Annealing is a method of heating an aluminum material to 300 to 400 ° C. and naturally cooling it in air.

When the coating liquid of the polyimide precursor is directly applied to the surface of the metallic cylindrical or cylindrical core, the polyimide resin coating formed in the polyimide resin coating forming step has a cylindrical or cylindrical core. Since there is a high possibility that it will adhere to the surface, the surface of the cylindrical or cylindrical core should be
It is more preferable that releasability is imparted. In order to impart releasability, the surface of the columnar or cylindrical core is plated with chromium or nickel, the surface is coated with a fluororesin or silicone resin, or the surface of the polyimide resin is prevented from adhering to it. It is effective to apply a release agent to the.

If the residual solvent cannot be completely removed during drying, or if the water generated during heating cannot be completely removed, swelling of the polyimide resin film may be unavoidable. This is a remarkable problem especially when the thickness of the polyimide resin film exceeds 50 μm. In that case, the surface of the cylindrical or cylindrical core is
It is effective to roughen the surface to about 0.2 to 2 μm. As a result, the residual solvent or water vapor generated from the polyimide resin film can be discharged to the outside through a slight gap formed between the cylindrical or cylindrical core body and the polyimide resin film, and swelling can be prevented. . For the roughening of the surface of the columnar or cylindrical core, there are methods such as blasting, cutting and sanding.

The polyimide resin endless belt of the present invention thus obtained is used as a photosensitive member, a charged member, a transfer member, an image forming apparatus such as an electrophotographic copying machine or a laser printer.
It can be used for endless belts such as fixing bodies.

When the polyimide resin endless belt of the present invention is used as a conductor such as a transfer member or a contact charger, since carbon nanotubes have conductivity, the resistance value may be adjusted by the blending amount thereof. You may use together the electroconductive substance of. Examples of such a conductive substance include, for example, carbon black, carbon beads obtained by granulating carbon black, carbon fibers, carbon-based substances such as graphite, metals or alloys such as copper, silver and aluminum, tin oxide, indium oxide, Antimony oxide, SnO ₂ -In ₂
Examples thereof include O ₃ composite oxide and conductive metal oxides such as conductive titanium oxide.

When the polyimide resin endless belt of the present invention is used as a fixing member, it is effective to form a releasable resin film on the belt surface in order to improve the releasability of the toner adhering to the surface. . The material of the releasable resin film is polytetrafluoroethylene (PTFE),
Fluorine resins such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP) are preferable. In addition, carbon powder may be dispersed in the releasable resin coating to improve durability and electrostatic offset, but carbon nanotubes and fibrous substances are also used to improve abrasion resistance. Better.

In order to form these fluororesin coatings, a method of dipping the aqueous dispersion on the surface of the endless belt and baking it is preferable. Further, when the adhesion of the fluororesin coating film is insufficient, there is a method of applying and forming a primer layer on the belt surface in advance, if necessary. Examples of the material for the primer layer include polyphenylene sulfide, polyether sulfone, polysulfone, polyamideimide, polyimide and derivatives thereof, and it is preferable that at least one compound selected from fluororesins is further included.

As described above, in order to form the primer layer and the fluororesin coating on the belt, they may be formed by coating on the surface of the polyimide resin coating, but by coating the polyimide precursor solution (or a specific solvent). After contacting with),
After drying the solvent, the primer layer and the fluororesin dispersion may be applied and then heated to simultaneously perform the imidization condensation reaction and the baking treatment of the fluororesin coating. In this case, the adhesion of the fluororesin coating may become strong even without the primer layer.

The thickness of the polyimide resin endless belt of the present invention is preferably in the range of 25 to 200 μm. The thickness of the primer layer provided as necessary is preferably in the range of 0.5 to 10 μm. Further, the thickness of the fluororesin coating is 2 to 30 μm.
A range of m is preferred.

[0065]

EXAMPLES The present invention will be described more specifically below with reference to examples. However, each of these examples does not limit the present invention.

(Example 1) -Polyimide precursor coating film forming step-As a polyimide precursor solution, a solution prepared by synthesizing PMDA and 4,4'-diaminodiphenyl ether in N, N-dimethylacetamide was prepared. Solid content concentration is 22%
(Wt%, the same applies hereinafter), and the viscosity was adjusted to about 20 Pa · s. Next, 10% of carbon nanotubes manufactured by Showa Denko (diameter of about 20 nm, length of about 2 μm) was added to the solid content and dispersed by a sand mill to prepare a polyimide precursor solution.

Using this polyimide precursor solution, a polyimide precursor coating film was formed by a dip annular coating method as shown in FIG. First, the polyimide precursor solution is applied to the inner diameter 80
mm and a height of 500 mm were placed in a cylindrical container (coating tank 3 in FIG. 1). As the cylindrical core 1, a cylinder having an outer diameter of 30 mm and a length of 400 mm was prepared. This cylindrical core 1 is
An aluminum tube having an outer diameter of 32 mm and a length of 400 mm is heated at 350 ° C. for 10 minutes and allowed to cool naturally, and then the surface is cut to have an outer diameter of 30 mm, and the surface is further blasted with spherical alumina particles. It was produced by roughening Ra to 0.8 μm. A silicone release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface and baked at 300 ° C. for 1 hour.
On the other hand, as the annular body 5, an outer diameter of 65 mm, an inner diameter of 40 mm,
A hollow body made of stainless steel having a height of 30 mm was prepared, and a Teflon (R) ring having an outer diameter of 40 mm, a triangular cross section, and an inner diameter of the narrowest portion of 31 mm was fitted inside the hollow body (Fig. 3 ( (having a curved wall surface shown in c))
Was prepared and floated on the solution.

Next, the annular body 5 was fixed so as not to move, and the cylindrical core body 1 was inserted therein at a speed of 1 m / min with the longitudinal direction being vertical, and immersed in the solution. Then, the fixing of the annular body 5 was released, and the cylindrical core body 1 was pulled up at a speed of 0.3 m / min. The annular body 5 does not come into contact with the cylindrical core 1 during the pulling up, and the cylindrical core 1 has a wet film thickness of about 500.
A μm polyimide precursor coating was formed.

-Polyimide resin film forming step- Immediately thereafter, the film was immersed in water and left for 5 minutes. When the cylindrical core was pulled up, the polyimide precursor became a precipitate and a film was formed on the cylindrical core. The water droplets on the surface were wiped off, and then the cylindrical core was placed in a drying oven. The set temperature was 50 ° C. at the beginning, and the temperature was gradually raised to 100 ° C. after 1 hour. After this drying, the film became transparent. Further, it was heated and dried at 150 ° C. for 20 minutes and 200 ° C. for 20 minutes to completely remove N, N-dimethylacetamide and water. Then, it heated at 350 degreeC for 30 minute (s).

-Polyimide resin film peeling step-After the cylindrical core was cooled to room temperature, the film was taken out to obtain an almost uniform endless belt having a film thickness of 60 µm. The coefficient of thermal expansion of the coating was 15 × 10 ^-6 / K, so it was 23 × 10 ^-6 / K for aluminum (cylindrical core).
It was much smaller, which allowed the coating to be extracted from the cylindrical core. Since the release agent was applied to the surface of the cylindrical core, the coating did not adhere. Also,
When the tensile strength of the endless belt was measured, it was 190M
It was Pa.

Comparative Example 1 In Example 1, carbon nanotubes were not dispersed in the polyimide precursor solution,
Others were similarly made to produce a polyimide resin film. After the cylindrical core had cooled to room temperature, it was attempted to remove the coating, but the coating could not be removed because the coating contracted strongly. A polyimide resin composed of PMDA and 4,4′-diaminodiphenyl ether has a coefficient of thermal expansion of 20 × 10 ⁻⁶ /
Since it is K, there is only a slight difference as compared with aluminum (cylindrical core), so it is considered that it could not be extracted. Further, the film was cut off and the tensile strength was measured, and it was 150 MPa, which was lower than the result of Example 1.

(Example 2) In Example 1, the polyimide precursor solution used was 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride and 4,4'-diaminobenzophenone. An endless belt was produced in the same manner as in Example 1 except for the above. Since the thermal expansion coefficient of the coating was 16 × 10 ⁻⁶ / K, the coating could be extracted from the cylindrical core. The tensile strength of the endless belt was measured and found to be 180 MPa.

Comparative Example 2 In Example 2, when the carbon nanotube was not added to the polyimide precursor solution, the film could not be extracted. Since the thermal expansion coefficient of this coating was 24 × 10 ⁻⁶ / K, which was larger than that of aluminum (cylindrical core), it is considered that the coating could not be extracted. Further, when the film was cut off and the tensile strength was measured, it was 140 MPa, which was lower than the result of Example 2.

Example 3 In the same polyimide precursor solution as in Example 1, 10% of the same carbon nanotubes as in Example 1 and 4% of carbon black (trade name: Conductex 975; (Columbian Carbon Co., Ltd.) was added and dispersed by a sand mill. The reason why carbon black is used together is to adjust the resistance value.

Using this polyimide precursor solution, a polyimide precursor coating film was formed by an annular coating method as shown in FIG. As the cylindrical core body 1, an aluminum cylinder having an outer diameter of 160 mm and a length of 400 mm was prepared, and the surface thereof was subjected to a roughening treatment and a silicone-based release agent treatment as in Example 1. On the other hand, as the annular body 5, the inner wall has an inclined surface shape, and has an outer diameter of 195 mm, a minimum portion inner diameter of 161.5 mm, and a height of 30 mm, which is a hollow body made of aluminum (the inclined surface wall surface shown in FIG. 3A). Thing)) was produced.

The inner surface of the cylindrical core 1 has an inner diameter of 156 m.
It was passed through an annular coating tank 3 ′ having an inner diameter of 250 mm and a height of 50 mm, to which an annular seal material 9 made of polyethylene having a central hole of m was attached. And the annular coating tank 3 '
The polyimide precursor solution 2 was put in the above, the annular body 5 was arranged, the cylindrical core body 1 was raised at 0.3 m / min, and coating was performed. As a result, a polyimide precursor coating film 4 having a wet film thickness of about 750 μm was formed on the surface of the cylindrical core body 1.

-Polyimide resin film forming step-Next, while the cylindrical core is horizontal and rotated at 30 rpm, it is dried at room temperature for 5 minutes and then at 80 ° C for 20 minutes, 10 minutes.
It was dried by heating at 0 ° C. for 1 hour. Subsequently, the cylindrical core was placed vertically and heated at 200 ° C. for 30 minutes and 380 ° C. for 30 minutes.

-Polyimide resin film peeling step-After cooling to room temperature, the polyimide resin film was removed to obtain an endless belt having a thickness of 75 µm. The coefficient of thermal expansion of the belt was 16 × 10 ^-6 / K, so it was considerably smaller than that of aluminum (cylindrical core) of 23 × 10 ^-6 / K, so that the film could be extracted from the cylindrical core. It was Since the release agent was applied to the surface of the cylindrical core, the coating did not adhere. The tensile strength of the endless belt was measured and found to be 180 MPa. Furthermore, when the volume resistance of the belt is measured, it is about 10 ⁹
It was Ωcm and could be used as a transfer belt for electrophotography.

Comparative Example 3 Instead of using carbon nanotubes in Example 3, only 15% of carbon black was added and dispersed by a sand mill. Otherwise, in the same manner as in Example 3, a polyimide resin film was formed on the surface of the cylindrical core body. However, since this film was strongly contracted, it could not be extracted from the cylindrical core. Since the thermal expansion coefficient of this coating was 24 × 10 ⁻⁶ / K, which was larger than that of aluminum (cylindrical core), it is considered that the coating could not be extracted. Further, when the film was cut off and the tensile strength was measured, it was 130 MPa, which was lower than the result of Example 3.

Example 4 Using the same polyimide precursor solution as in Example 1, a polyimide precursor coating film was formed by an annular coating method as shown in FIG. As the cylindrical core 1, an aluminum cylindrical body having an outer diameter of 68 mm and a length of 400 mm was prepared, and the surface thereof was subjected to surface roughening treatment and treatment with a silicone-based release agent as in Example 1. On the other hand, as the annular body 5, the inner wall has an inclined surface shape, the outer diameter is 110 mm, the inner diameter of the minimum portion is 69 mm, and the height is 30 mm, and the hollow body is made of aluminum (having the inclined wall surface shown in FIG. 3A). )
Was produced.

The cylindrical core 1 has an inner diameter of 66 mm on its bottom surface.
It was passed through an annular coating tank 3 ′ having an inner diameter of 150 mm and a height of 50 mm, to which an annular seal material 9 made of polyethylene having a central hole of 1 was attached. Then, the polyimide precursor solution 2 is placed in the annular coating tank 3 ′, the annular body 5 is arranged,
The cylindrical core 1 was lifted at 0.5 m / min to apply the coating. As a result, a polyimide precursor coating film 4 having a wet film thickness of about 500 μm was formed on the surface of the cylindrical core body 1.

-Polyimide resin film forming step-Next, while the cylindrical core is horizontal and rotated at 20 rpm, it is dried at room temperature for 5 minutes, and then at 80 ° C for 20 minutes, 1 minute.
It was heated and dried at 00 ° C. for 1 hour. As a result, a polyimide resin coating film having a thickness of about 150 μm was fixed.

Then, at one end of the cylindrical core 1, the width 2
0 mm polyester tape (trade name: No. 31B,
Nitto Denko Co., Ltd. was wound around the entire circumference to cover the exposed portion of the cylindrical core and the PI precursor coating. Next, PF
Dispersion water-based paint of A (Product name: AW500
0, manufactured by Daikin Industries, Ltd., inner diameter 90 mm, height 480 mm
The cylindrical core was dipped in the coating tank in a vertical direction with the coating portion covered with the polyester tape being on the lower side, and the polyimide precursor coating film on the upper portion was left by 5 mm.
Then, it was pulled up at a speed of 0.3 m / min to form a PFA coating film. After drying at 80 ° C. for 10 minutes, the polyester tape was removed. Further, it was heated and dried at 150 ° C. for 20 minutes and then at 200 ° C. for 20 minutes. Then 38
The PFA coating film was baked while heating at 0 ° C. for 30 minutes to form a polyimide resin film.

-Polyimide resin film peeling step-After cooling to room temperature, the polyimide resin film is peeled from the cylindrical core body 1, and the polyimide resin film having a thickness of 75 μm is coated with 30
An endless belt having a PFA layer with a thickness of μm could be obtained. Since the thermal expansion coefficient of the coating was 15 × 10 ⁻⁶ / K,
It was considerably smaller than 23 × 10 ⁻⁶ / K of aluminum (cylindrical core), and therefore the film could be extracted from the cylindrical core. Since the release agent was applied to the surface of the cylindrical core, the coating did not adhere. The tensile strength of the endless belt was measured and found to be 190 MPa. Moreover, the obtained endless belt could be suitably used as a transfer belt for electrophotography.

Example 5 A solution prepared by synthesizing PMDA and 4,4′-diaminodiphenyl ether in N, N-dimethylacetamide was prepared as a polyimide precursor solution. The solid content concentration was adjusted to 22% (weight%, the same applies hereinafter), and the viscosity was adjusted to about 20 Pa · s. Next, 20% potassium titanate fiber (trade name: Tismo, manufactured by Otsuka Chemical, average length 15 μm, average diameter 0.45) based on the solid content.
μm) was added and dispersed by a sand mill.

Using this polyimide precursor solution, a polyimide precursor coating film was formed by a dipping annular coating method as shown in FIG. First, the polyimide precursor solution is applied to the inner diameter 80
mm and a height of 500 mm were placed in a cylindrical container (coating tank 3). The cylindrical core 1 has an outer diameter of 30 mm and a length of 400 m.
A cylinder of m was prepared. This cylindrical core has an outer diameter of 32 m.
m, 400 mm long aluminum tube was heated at 350 ° C. for 10 minutes and allowed to cool naturally, then the surface was cut to have an outer diameter of 30 mm, and the surface was Ra. It was prepared by roughening to 8 μm. A silicone release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface and baked at 300 ° C. for 1 hour. on the other hand,
The annular body 5 has an outer diameter of 65 mm, an inner diameter of 40 mm, and a height of 3
A 0 mm stainless steel hollow body was made, and inside this,
A Teflon (R) ring having an outer diameter of 40 mm, a triangular cross section and an inner diameter of 31 mm at the narrowest part is fitted (having a curved wall surface shown in FIG. 3C) is prepared. Floated in solution.

Next, the annular body 5 was fixed so as not to move, and the cylindrical core body 1 was inserted therein at a speed of 1 m / min with the longitudinal direction being vertical, and immersed in the solution. Then, the fixing of the annular body 5 was released, and the cylindrical core body 1 was pulled up at a speed of 0.3 m / min. The annular body 5 does not come into contact with the cylindrical core 1 during the pulling up, and the cylindrical core 1 has a wet film thickness of about 500.
A μm polyimide precursor coating was formed.

-Polyimide Resin Film Forming Step- Immediately thereafter, the film was immersed in water and left for 5 minutes. When the cylindrical core was pulled up, the polyimide precursor became a precipitate and a film was formed on the cylindrical core. The water droplets on the surface were wiped off, and then the cylindrical core was placed in a drying oven. The set temperature was 50 ° C. at the beginning, and the temperature was gradually raised to 100 ° C. after 1 hour. After this drying, the film became transparent. Further, it was heated and dried at 150 ° C. for 20 minutes and 200 ° C. for 20 minutes to completely remove N, N-dimethylacetamide and water. Then, it heated at 350 degreeC for 30 minute (s).

-Polyimide resin film peeling step-After the cylindrical core was cooled to room temperature, the film was taken out to obtain a substantially uniform endless belt having a film thickness of 60 µm. The coefficient of thermal expansion of the coating was 15 × 10 ^-6 / K, so it was 23 × 10 ^-6 / K for aluminum (cylindrical core).
It was much smaller, which allowed the coating to be extracted from the cylindrical core. Since the release agent was applied to the surface of the cylindrical core, the coating did not adhere. Also,
When the tensile strength of the endless belt was measured, it was 200M.
It was Pa.

(Comparative Example 4) In Example 5, without dispersing potassium titanate fiber in the polyimide precursor solution,
Others were similarly obtained to obtain a polyimide film. After the cylindrical core had cooled to room temperature, it was attempted to remove the coating, but the coating could not be removed because the coating contracted strongly. PM
Polyimide consisting of DA and 4,4'-diaminodiphenyl ether has a coefficient of thermal expansion of 20 x 10 ^-6 / K, so there is only a slight difference compared to aluminum (cylindrical core), so it cannot be extracted. It is thought that
The film was cut off and the tensile strength was measured. As a result, it was 150 MPa, which was lower than the result of Example 5.

Example 6 In Example 5, the polyimide precursor solution used was 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 4,4′-diaminobenzophenone. An endless belt was produced in the same manner as in Example 5 except for the above. Coefficient of thermal expansion is 1
Since it was 6 × 10 ⁻⁶ / K, the coating could be extracted from the cylindrical core. The tensile strength of the endless belt was measured and found to be 180 MPa.

(Comparative Example 5) In Example 6, when the potassium titanate fiber was not added to the polyimide precursor solution, the film could not be extracted. Since this coating has a coefficient of thermal expansion of 24 × 10 ⁻⁶ / K, which is larger than that of aluminum (cylindrical core), it is considered that the coating could not be extracted. Further, when the film was cut off and the tensile strength was measured, it was 140 MPa, which was lower than the result of Example 6.

Example 7 In the same polyimide precursor solution as in Example 5, 14% of conductive potassium titanate fiber (trade name: Dentol, manufactured by Otsuka Chemical Co., Ltd.) based on the solid content thereof was used.
And 4% of carbon black (trade name: Conductex 975, manufactured by Columbian Carbon Co., Ltd.) were added and dispersed by a sand mill. Using carbon black together
This is to adjust the resistance value.

Using this polyimide precursor solution, a polyimide precursor coating film was formed by an annular coating method as shown in FIG. As the cylindrical core body 1, an aluminum cylinder having an outer diameter of 160 mm and a length of 400 mm was prepared, and the surface thereof was subjected to a surface roughening treatment and a silicone-based release agent treatment as in Example 5. On the other hand, the annular body 5 has an outer diameter of 195 mm,
A hollow body made of aluminum having an inner diameter of 165 mm and a height of 30 mm, and the inner wall thereof is provided with streaky protrusions along the dipping / pulling direction of the cylindrical core body 1 so that the minimum inner diameter is 161.5 mm. The thing was produced.

The cylindrical core 1 has an inner diameter of 165 m on its bottom surface.
It was passed through an annular coating tank 3 ′ having an inner diameter of 250 mm and a height of 50 mm, to which an annular seal material 9 made of polyethylene having a central hole of m was attached. And the annular coating tank 3 '
The polyimide precursor solution 2 was put in the above, the annular body 5 was arranged, the cylindrical core body 1 was raised at 0.3 m / min, and coating was performed. As a result, a polyimide precursor coating film 4 having a wet film thickness of about 750 μm was formed on the surface of the cylindrical core body 1.

-Polyimide resin film forming step-Next, while the cylindrical core is horizontal and rotating at 60 rpm, it is dried at room temperature for 5 minutes and then at 80 ° C for 20 minutes, 10 minutes.
It was dried by heating at 0 ° C. for 1 hour. Subsequently, the cylindrical core was placed vertically and heated at 200 ° C. for 30 minutes and 380 ° C. for 30 minutes.

-Polyimide resin film peeling step-After cooling to room temperature, the polyimide resin film was removed to obtain an endless belt having a thickness of 75 µm. The coefficient of thermal expansion of the coating was 16 × 10 ^-6 / K, so it was much smaller than 23 × 10 ^-6 / K of aluminum (cylindrical core), and therefore the coating could be extracted from the cylindrical core. It was Since the release agent was applied to the surface of the cylindrical core, the coating did not adhere. The tensile strength of the endless belt was measured and found to be 190 MPa. Furthermore, when the volume resistance of the belt is measured, it is about 10 ⁹
It was Ωcm and could be used as a transfer belt for electrophotography.

(Comparative Example 6) In Example 7, instead of using the conductive potassium titanate fiber, only 15% of carbon black was added and dispersed by a sand mill. Otherwise, in the same manner as in Example 3, a polyimide resin film was formed on the surface of the cylindrical core body. However, since this film was strongly contracted, it could not be extracted from the cylindrical core. It is considered that the coating could not be extracted because the thermal expansion coefficient was 24 × 10 ⁻⁶ / K, which was larger than that of aluminum (cylindrical core). Further, when the film was cut off and the tensile strength was measured, it was 130 MPa, which was lower than the result of Example 3.

Example 8 Using the same polyimide precursor solution as in Example 5, a polyimide precursor coating film was formed by an annular coating method as shown in FIG. As the cylindrical core 1, an aluminum cylindrical body having an outer diameter of 68 mm and a length of 400 mm was prepared, and the surface thereof was subjected to surface roughening treatment and treatment with a silicone-based release agent as in Example 1. On the other hand, as the annular body 5, the inner wall has an inclined surface shape, the outer diameter is 110 mm, the inner diameter of the minimum portion is 69 mm, and the height is 30 mm, and the hollow body is made of aluminum (having the inclined wall surface shown in FIG. 3A). )
Was produced.

The cylindrical core 1 has an inner diameter of 66 mm on its bottom surface.
It was passed through an annular coating tank 3 ′ having an inner diameter of 150 mm and a height of 50 mm, to which an annular seal material 9 made of polyethylene having a central hole of 1 was attached. Then, the polyimide precursor solution 2 is placed in the annular coating tank 3 ′, the annular body 5 is arranged,
The cylindrical core 1 was lifted at 0.5 m / min to apply the coating. As a result, a polyimide precursor coating film 4 having a wet film thickness of about 500 μm was formed on the surface of the cylindrical core body 1.

-Polyimide resin film forming step-Next, while the cylindrical core is horizontal and rotated at 20 rpm, it is dried at room temperature for 5 minutes, and then at 80 ° C for 20 minutes, 1 minute.
It was heated and dried at 00 ° C. for 1 hour. As a result, a polyimide resin coating film having a thickness of about 150 μm was fixed.

Then, at one end of the cylindrical core, a width of 20 m
m polyester tape (trade name: No. 31B, Nitto Denko) was wrapped around the circumference to cover the exposed portion of the cylindrical core and the PI precursor coating. Next, a dispersion water-based paint of PFA (trade name: AW5000, manufactured by Daikin Industries, Ltd.) was placed in a coating tank having an inner diameter of 90 mm and a height of 480 mm, and the cylindrical core body and the coating portion covered with the polyester tape were placed therein. The lower side was made vertical, and the upper portion of the polyimide precursor coating was dipped leaving only 5 mm. Then, it was pulled up at a speed of 0.3 m / min to form a PFA coating film. After drying at 80 ° C. for 10 minutes, the polyester tape was removed. Further, 20 minutes at 150 ℃, followed by 2
It was dried by heating at 00 ° C. for 20 minutes. Then 380 ° C
Was heated for 30 minutes to form a polyimide resin film and the PFA coating film was baked.

-Polyimide resin film peeling step-After cooling to room temperature, the polyimide resin film is peeled off from the cylindrical core, and 30 μm is formed on the 75 μm thick polyimide resin film.
An endless belt having an m-thick PFA layer could be obtained. Since the thermal expansion coefficient of the coating was 15 × 10 ⁻⁶ / K,
It was considerably smaller than 23 × 10 ⁻⁶ / K of aluminum (cylindrical core), and therefore the film could be extracted from the cylindrical core. Since the release agent was applied to the surface of the cylindrical core, the coating did not adhere. The tensile strength of the endless belt was measured and found to be 200 MPa. Moreover, the obtained endless belt could be suitably used as a transfer belt for electrophotography.

From these examples, by using a polyimide resin containing carbon nanotubes or fibrous substances,
In addition to increasing the strength, or due to the coefficient of thermal expansion, even if a polyimide resin that cannot be extracted from the core originally is used,
It can be seen that the core can be easily pulled out. It is also understood that the range of selection of the polyimide resin material that can be used as the endless belt can be widened.
Further, it is found that the polyimide resin can be made to have semiconductivity by including carbon nanotubes.

[0105]

As described above, according to the present invention, it is possible to provide a polyimide resin endless belt having an increased tensile strength, a reduced thermal expansion coefficient and an improved dimensional stability, and a method for producing the same.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an apparatus used in a dip coating method in which a film thickness is controlled by an annular body.

FIG. 2 is an enlarged perspective view of an essential part for explaining the installation state of the annular body shown in FIG.

3A and 3B show the shapes of the wall surfaces of the holes provided in the annular body, wherein FIG. 3A is an inclined wall surface, FIG. 3B is a curved wall surface, and FIG. FIG.

FIG. 4 is a schematic configuration diagram showing an example of an apparatus used in the annular coating method.

[Explanation of symbols]

1 Cylindrical core 2 Polyimide precursor solution 3 coating tanks 3'ring coating tank 4 Polyimide precursor coating 5 ring 6 Annular hole 7 Inclined annular inner wall 8 curved inner wall 9 Annular sealing material 10 Bent surface-shaped annular body wall

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 79/08 C08L 79/08 Z 4F205 G03G 15/02 101 G03G 15/02 101 4J002 15/16 15/16 15/20 102 15/20 102 21/00 350 21/00 350 350 B29K 79:00 B29K 79:00 B29L 29:00 B29L 29:00 F-term (reference) 2H033 BA11 2H035 CA05 CB06 2H171 FA07 FA30 GA32 GA40 PA03 PA05 PA08 QA09 QA24 QB01 QC05 QC37 QC40 UA03 UA10 UA14 UA19 UA24 UA25 VA02 VA05 XA03 2H200 GB22 HB13 JB06 JB45 JB47 JC15 JC17 LC03 LC04 LC09 LC10 MA04 MA14 MA20 MC20 4F072 AA02 AA07 AB08 AB10 AB13 AD45 AL19 4F205 AA40 AB18 AB24 AB25 AG16 GA06 GB01 GC01 GC04 GE24 GF02 GN13 GN21 GN29 4J002 CM041 DA016 DA026 DE106 DE136 DE186 DJ006 DK006 FA046 FD016 GF00 GH00 GM01 HA05

Claims (6)

[Claims] 1. A polyimide resin endless belt comprising carbon nanotubes. 2. The surface layer is formed on the polyimide resin coating film, and the carbon nanotubes are contained in the polyimide resin coating film and also in the surface layer. Endless belt made of polyimide resin. 3. A polyimide resin endless belt containing a fibrous substance. 4. The endless belt of polyimide resin according to claim 3, wherein the fibrous substance is made of an inorganic needle-shaped single crystal. 5. The polyimide resin coating film is configured to include a surface layer, and the fibrous substance is contained in the polyimide resin coating film and also in the surface layer. The polyimide resin endless belt according to 1. 6. A step of applying a polyimide precursor solution containing carbon nanotubes or a fibrous substance to the surface of a columnar or cylindrical core to form a polyimide precursor coating film, the polyimide precursor coating film comprising: A method of manufacturing a polyimide resin endless belt, comprising: a step of drying and heating to form a polyimide resin film; and a step of peeling the polyimide resin film from the columnar or cylindrical shape.