JP2001001354A - Manufacture of endless belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce thickness unevenness of a film by coating an inner periphery of a cylindrical mold with a coating liquid as a raw material of a belt, rotating the mold to centrifugal mold an endless film of the liquid, heating the liquid after the liquid becomes a uniform thickness, and drying to solidify the liquid. SOLUTION: In the case of manufacturing an endless belt, first, an inner periphery of a cylindrical mold 1 is spirally coated with a polyamide acid solution 3 as a raw material of the belt. That is, a predetermined amount of the solution 3 is discharged while moving a discharge nozzle 2 inserted from one side of the mold 1 at a constant speed in an axial direction of the mold 1 in the state that the mold 1 is slowly rotated. Then, the mold 1 is rotated at a high seed (about 1,000 r.p.m.) to centrifugal cast the solution 3 on the inner periphery of the mold 1 to form an endless film on the inner periphery of the mold 1. While rotating the mold 1, the solution 3 is heated by a heating means, a solvent DMAC in the solution 3 is evaporated. Drying and solidifying of the solution 3 are expedited by the evaporation of the solvent to obtain a desired endless bent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying an application liquid as a belt material in a cylindrical mold, and rotating the mold to form an endless film of the application liquid on the inner peripheral surface of the mold by centrifugal molding. And a method for producing an endless belt in which the coating liquid is dried and solidified by heating.

[0002]

2. Description of the Related Art Conventionally, seamless endless belts have been used in various belt devices. For example, in an image forming apparatus such as an electrophotographic copying machine, a facsimile, or a printer, a transfer belt as a carrier for a toner image or a transfer material is employed.

As a method for manufacturing the above-mentioned transfer belt, a centrifugal molding method has been widely used. Hereinafter, a method for producing a polyimide transfer belt by a centrifugal molding method will be described. First, a polyimide precursor solution as a coating liquid is applied to the inner surface of a cylindrical centrifugal molding mold by spraying or poured from a nozzle, and the mold is rotated at high speed to flow the solution into the mold by centrifugal force. Extend. The solution is formed as an endless film on the inner peripheral surface of the mold by maintaining the high-speed rotation for a predetermined time and centrifugal force at this time.
Further, while the mold is being rotated, the solution is heated by a heating means (not shown) to evaporate the solvent component in the solution. Due to the evaporation of the solvent component, the solution is dried and solidified, and the endless film of the coating solution is fixed on the inner peripheral surface of the mold. Furthermore, a polyimide transfer belt can be obtained by heating this endless film at a high temperature to cure (imide ring closure). The curing treatment by heating may be performed by removing the endless film from the mold for centrifugal molding and using another heating furnace, or may be performed by continuously heating and heating while rotating the mold.

In the above-described transfer belt, uniformity of film thickness is an important characteristic. However, the conventional manufacturing method has a problem in that the film thickness varies due to a deviation of the rotation center axis of the centrifugal molding die and irregularities on the inner surface of the die. If the film thickness varies, the resistance value varies in the film thickness direction, which results in a lack of uniformity of an image and further causes a transfer omission.
In addition, the endless belt is generally stretched and driven by a plurality of rollers, but if the film thickness variation in the axial direction of the roller is large, the belt moves to one end of the roller during the driving,
The belt may be wrinkled or torn. Therefore, it is desirable that the thickness of the endless belt be as uniform as possible.

In order to eliminate such variations in the thickness of the endless film, it is necessary to minimize the deviation of the center axis of rotation of the mold and the irregularities on the inner surface of the mold. However, in order to suppress these completely, high precision is required for the equipment for attaching the mold and the processing technology of the mold itself (for example, roundness, straightness, etc.). There was a problem that it would not be suitable for practical use.

Various methods have been proposed for preventing variations in film thickness due to deviation of the center axis of rotation of the mold and irregularities on the inner surface of the mold. For example, Japanese Patent Application No. 10-353830 proposes that after a release layer is provided on the inner peripheral surface of a mold by centrifugal molding, a coating liquid is centrifugally formed on the release layer. According to this, since the coating liquid is centrifugally molded on the release layer having the perfect circular surface formed by centrifugal molding, the endless film of the coating liquid has a perfect circular surface, and the rotation center axis of the mold is A uniform film can be formed without being affected by misalignment or irregularities on the inner surface of the mold.

However, in the above proposal, it is necessary to select a liquid having a specific gravity greater than the specific gravity of the coating liquid as the liquid for forming the release layer, and the degree of freedom in selecting the material of the release layer is small. In addition, even if the inner peripheral surface of the mold having a perfectly round surface is formed, once the mold is removed from the device, it is difficult to attach the rotating shaft with high accuracy as described above when re-attaching or attaching to another device. For this reason, it is not always possible to secure a perfect circular position on the surface of the release layer. In this method, it is conceivable that the mold having the perfect circular surface is continuously used without removing it from the apparatus.However, the mold after centrifugal molding is in a high temperature state. Since the viscosity changes, it is necessary to return the mold temperature to room temperature before applying. For this reason,
There is a disadvantage that the cooling time is unnecessarily long and the production efficiency is rather deteriorated.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing an endless belt using a centrifugal molding method. An object of the present invention is to provide a method of manufacturing an endless belt which can obtain a belt having a small thickness variation even when there is a deviation of an axis or unevenness of an inner surface of a mold.

[0009]

In order to achieve the above object, the invention of claim 1 is to apply a coating liquid as a belt material in a cylindrical mold, and rotate the mold to form a liquid in the mold. In a method for producing an endless belt in which an endless film of a coating liquid is centrifugally formed on a peripheral surface and the coating liquid is dried and solidified by heating, the coating liquid is cast over the entire belt forming area of the inner peripheral surface of the mold. After the coating liquid has a uniform liquid thickness, and before the liquid thickness of the coating liquid fluctuates due to deviation of the center axis of rotation of the mold or irregularities on the inner surface of the mold, the coating liquid is dried and solidified. Is characterized by heating.

Observation of the state of centrifugal casting of the coating solution on the inner peripheral surface of the mold revealed that the coating solution was immediately affected by the displacement of the center axis of rotation of the mold and the unevenness of the inner surface of the mold immediately after being applied to the mold. It was found that the coating liquid did not fluctuate, but the coating liquid spread over the entire belt forming area on the inner peripheral surface of the mold, and there was a state in which the liquid thickness once became uniform. However, if the coating liquid is dried and solidified before the liquid thickness varies due to the influence of the deviation of the center axis of rotation of the mold and the unevenness of the inner surface of the mold, and the heating timing is too early, the coating liquid will not be sufficiently cast. Drying and solidification in an unsatisfactory state makes it impossible to obtain an endless film having a uniform liquid thickness over the entire belt forming area on the inner peripheral surface of the mold. Therefore, in the method for producing an endless belt according to claim 1, after the coating liquid has been cast over the entire belt forming area on the inner peripheral surface of the mold to have a uniform liquid thickness, Heating is performed so that the coating liquid dries and solidifies before the thickness of the coating liquid fluctuates due to misalignment or irregularities on the inner surface of the mold. By drying and solidifying the coating liquid in this manner, an endless film having a uniform liquid thickness can be obtained over the entire belt forming area on the inner peripheral surface of the mold, and furthermore, the deviation of the rotation axis of the mold and the unevenness of the inner surface of the mold. The coating liquid does not fluctuate under the influence of the above. Therefore, even when the rotation axis of the mold is deviated or the inner surface of the mold has irregularities, a belt having a small thickness variation can be obtained. In addition, by performing the heating as described above, the time required for the drying and solidifying step of the coating liquid can be reduced as compared with the related art, and the production efficiency can be improved.

According to a second aspect of the present invention, in the method for producing an endless belt according to the first aspect, the viscosity of the coating solution is 1000 c.
p or more.

In the method for producing an endless belt according to the present invention, since the viscosity of the coating solution is 1000 cp or more, the fluidity of the coating solution is low, and the influence of the deviation of the rotation axis of the mold and the unevenness of the inner surface of the mold is reduced. It is hard to receive. The upper limit of the viscosity of the coating solution is
Any range may be used as long as it can be centrifugally cast according to the coating solution used.

According to a third aspect of the present invention, in the method for producing an endless belt according to the first or second aspect, the coating liquid is spirally applied on the inner peripheral surface of the mold.

In the method for producing an endless belt according to the third aspect, the coating liquid spirally applied on the inner peripheral surface of the mold spreads uniformly in the axial direction of the mold and is cast in a short time. Therefore,
The time affected by the displacement of the rotation axis of the mold or the irregularities on the inner surface of the mold can be shortened, and the fluctuation of the coating solution can be further suppressed. Further, in order to make the spreading of the coating liquid in the axial direction of the mold more uniform, the liquid streaks of the coating liquid injected in a spiral shape are arranged at equal intervals when viewed in the axial cross section of the die. ,
It is desirable to inject a coating solution.

According to a fourth aspect of the present invention, there is provided the method for producing an endless belt according to the first or second aspect, wherein the coating liquid is applied on the inner peripheral surface of the mold in a spot-like manner. is there.

In the method for producing an endless belt according to the present invention, the coating liquid applied in a spot-like manner on the inner peripheral surface of the mold spreads in the mold axial direction and the circumferential direction and is cast in a short time. Therefore, the time affected by the displacement of the rotation axis of the mold and the irregularities on the inner surface of the mold can be shortened, and the fluctuation of the coating solution can be suppressed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, an endless transfer belt as a carrier for a toner image or a transfer material in an image forming apparatus such as an electrophotographic copying machine, a facsimile, and a printer is manufactured. The method will be described. In the present embodiment, a transfer belt using polyimide as a basic material is formed.

First, a centrifugal molding method according to the transfer belt manufacturing method of the present embodiment will be described. FIG. 1 is an axial sectional view of a cylindrical mold 1 for centrifugal molding. The chain line in the figure indicates the rotation axis of the mold 1 in the centrifugation step. In this embodiment, an aluminum mold is used as the mold 1. The polyamic acid solution 3 is used as a coating liquid as a polyimide belt material. Polyamic acid is dissolved in a specific organic solvent, and imide ring closure by heat or catalyst,
It has the property of changing to polyimide. In this embodiment, a commercially available polyimide precursor solution (manufactured by Toray: Torenis # 3000) is used as the polyamic acid, and the polyamide is diluted to an arbitrary concentration with NN dimethylacetamide (hereinafter referred to as DMAC) as an organic solvent. Use an acid solution.

The belt manufacturing process according to the centrifugal molding method of this embodiment includes a coating process of injecting and coating the above-mentioned polyamic acid solution 3 into a mold 1, centrifugal casting of the polyamic acid solution 3 by rotation of the mold 1, and centrifugal casting. A series of steps including a drying and solidifying step of heating and drying and solidifying the polyamic acid solution 3 thus obtained, and a curing step of transferring an endless film of the polyamic acid solution 3 dried and solidified to a heating furnace and performing high-temperature curing (imide ring closure). Consists of

[Applying Step] In FIG. 1, a polyamic acid solution 3 is spirally applied on the inner peripheral surface of the mold 1. Specifically, while the mold 1 is slowly rotated, the ejection nozzle 2 is inserted from one side of the mold 1, and the ejection nozzle 2 is moved at a constant speed in the axial direction of the mold 1 while the inner peripheral surface of the mold 1 is moved. A predetermined amount of the polyamic acid solution 3 is discharged upward. At this time, FIG.
In the cross section of the mold 1 in the axial direction, the liquid streaks of the polyamic acid solution 3 are arranged at equal intervals.

[Dry solidification step] Next, the mold 1 was
The polyamic acid solution 3 is centrifugally cast on the inner peripheral surface of the mold 1 by high-speed rotation at rpm. By maintaining this high-speed rotation for a predetermined time, the polyamic acid solution 3 is
An endless film is formed on the inner peripheral surface of the mold 1. While the mold 1 is being rotated, the polyamic acid solution 3 is heated by a heating means (not shown) to evaporate the solvent DMAC in the solution 3. Due to the evaporation of the solvent, the solution 3 is dried and solidified, and the endless film is fixed on the inner peripheral surface of the mold 1.

[Curing process] In order to finally finish the dried and solidified endless film into a polyimide belt,
Once mold 1 was removed from the centrifuge for belt production, 30
Place in another heating furnace maintained at 0 ° C., heat for 30 minutes, and cure (imide ring closure). In the curing treatment by heating, after the endless film is dried and solidified, the mold 1 may be rotated and the temperature may be continuously raised and heated. The endless film after the curing treatment is separated from the mold 1 after cooling,
Thereby, an endless transfer belt using polyimide as a basic material can be obtained.

By the way, in the transfer belt manufactured as described above, if there is a variation in the film thickness of the belt, there is a variation in the resistance value in the film thickness direction. Omission may occur. The belt film thickness is determined by the liquid thickness of the polyamic acid solution 3 formed on the inner surface of the mold 1, but as described above, the liquid thickness varies due to the deviation of the rotation center axis of the mold 1 and irregularities on the inner surface of the mold. There is a risk that it will. Here, the relationship between the occurrence of the liquid thickness variation and the deviation of the rotation center axis of the mold 1 and the irregularities on the inner surface of the mold will be described in detail.

First, the variation in the liquid thickness due to the displacement of the center axis of rotation of the mold 1 will be described. 2 and 3 are circumferential sectional views showing the inner surface 1a of the mold for centrifugal molding and the polyamic acid solution 3 as a coating liquid applied to the inner surface 1a. FIG. 2 shows a state in which the polyamic acid solution 3 is centrifugally formed with a uniform thickness without any deviation in the rotation center axis. On the other hand, FIG. 3 shows a state in which the rotation center axis is displaced and the liquid thickness varies. In the method of manufacturing the transfer belt, in the case of FIG. 2, the liquid surface S of the polyamic acid solution 3 centrifugally cast on the inner surface 1a of the mold is:
It is formed in a perfect circle around the rotation axis O. At this time,
The liquid thickness D is uniform all over the mold. On the other hand, in the case of FIG. 3, the liquid surface S ′ of the polyamic acid solution 3 is formed in a perfect circle around the rotation axis O ′ due to the displacement of the rotation center axis. This is because the liquid surfaces S and S ′ are formed when the cohesive force of the surface energy of the polyamic acid solution 3 and the force of the uniform acceleration field due to the centrifugal force are balanced. This is because they are equidistant from each rotation axis. As shown in FIG. 3, when the rotation center axis of the mold is displaced, the liquid thickness D of the polyamic acid solution 3 formed on the inner surface 1a of the mold varies from the minimum liquid thickness Dmin to the maximum liquid thickness Dmax. Regarding the thickness of the endless film after the polyamic acid solution 3 has been dried, solidified and cured, when the solid content of the polyamic acid solution 3 is α, d = α · D. The endless film to be formed also varies from the minimum film thickness α · Dmin to the maximum film α · Dmax.

Next, a description will be given of film thickness variations due to irregularities on the inner surface of the mold. FIG. 4 is a schematic diagram of a cross section in the liquid thickness direction of the polyamic acid solution 3 applied to the inner surface 1a for centrifugation. FIG. 5 is a schematic diagram of a cross section in the thickness direction of the endless film after the polyamic acid solution 3 is dried, solidified, and cured. In the method of manufacturing the transfer belt, FIG.
The liquid surface S formed on the inner surface of the mold 1 by centrifugal force is formed in a perfect circle which is an equal acceleration field by centrifugal force. However, the liquid thickness D is affected by the unevenness of the inner surface of the mold 1, for example, as shown by D ₁ , D ₂ , D ₃ and D ₄ in the figure, due to the displacement of the center axis of rotation of the mold and the unevenness of the inner surface of the mold. Each is different.

In this state, the polyamic acid solution 3 is dried and solidified.
After the curing process, as shown in FIG.
The side that is in close contact with the inner surface 1a is the
Undulation occurs along the convex shape. Also, the membrane table
Also on the surface side, the solid content of the polyamic acid solution 3 is α
(In FIG. 5, the solid content rate is 50%, that is, α = 0.5)
Since the thickness d of the endless film is d = α · D,
Unevenness with 1 / α irregularities on one internal surface
State. The endless film thickness d at this time is d in the figure. ₁, D
₂, D₃And d₄Will vary as shown in
Become.

As described above, when the rotational axis of the mold 1 is displaced or the inner surface of the mold 1 has irregularities, the thickness of the polyamic acid solution 3 varies, so that the endless film after molding is formed. The thickness will vary. In order to eliminate the variation in the thickness of the endless film, it is necessary to minimize the displacement of the rotation axis of the mold 1 and the irregularities on the inner surface of the mold 1 as described above. However, there is a problem that it is not suitable for practical use.

The inventors of the present invention observed the state of centrifugal casting of the polyamic acid solution 3 to reduce the variation in the thickness of the endless film due to the displacement of the rotation axis of the mold 1 and the irregularities on the inner surface of the mold 1. I found a way to suppress it. First, the observation result of centrifugal casting of the polyamic acid solution 3 when the rotation axis of the mold 1 is shifted will be described. 6 (a) to 6 (e)
FIG. 3 is a schematic diagram showing a casting state of a polyamic acid solution 3 observed when the solution 3 was centrifugally cast. FIG.
(A) is an enlarged view of a state in which the liquid streaks of the polyamic acid solution 3 are arranged at equal intervals in the axial section of the mold 1 shown in FIG. 1, and the polyamic acid solution 3 is placed in the rotating mold 1. The state immediately after application is shown. Subsequently, as shown in FIG. 6 (b), the respective liquid streaks are crushed in the axial direction of the mold due to centrifugal force, and further, as shown in FIG. State. FIG. 6D shows a state at the moment when the liquid streaks are further centrifugally cast and the liquid streaks come into contact with each other. Due to this contact, the ends of the individual liquid streaks rise rapidly and approach a uniform film thickness. Then, almost instantaneously, a state in which the polyamic acid solution 3 had a uniform liquid thickness was observed as shown in FIG. When the rotation of the mold 1 was further continued, a change in the liquid thickness of the polyamic acid solution 3 due to the displacement of the rotation axis of the mold 1 was confirmed.

According to the above observation results, the polyamic acid solution 3 applied in the rotating mold 1 is immediately applied to the mold 1.
The liquid thickness does not fluctuate due to the deviation of the rotation axis and the unevenness of the inner surface of the mold 1, but, as shown in FIG. It was found that the liquid film was dispersed due to the misalignment of the rotation axis and the irregularities on the inner surface of the mold 1. In other words, the state changed from the state in which the liquid thickness D becomes uniform throughout the mold as shown in FIG. 2 to the state in which the liquid thickness variation occurred as shown in FIG.

Next, the results of observation of the casting state of the polyamic acid solution 3 and the fluctuation of the film thickness when the inner surface of the mold 1 has irregularities will be described. 7A and 7B show the casting state of the polyamic acid solution 3 observed when the solution 3 was centrifugally cast, and FIG. 7C shows the state of FIG. 7B. FIG. 3 is a schematic view showing an endless film when the solution 3 is dried and solidified. When the centrifugal casting of the polyamic acid solution 3 proceeds,
As shown in FIG. 7A, the liquid streaks of the polyamic acid solution 3 arranged at regular intervals come into contact with each other, and undulation occurs along the irregularities of the mold, but the state of a uniform liquid film is almost instantaneously formed. Was observed. Then, when the rotation of the mold 1 was further continued, the polyamic acid solution 3 changed to a state shown in FIG. 7B in which the liquid surface was formed in a perfect circular shape in which an equal acceleration field of centrifugal force was generated. At this time, a liquid thickness variation corresponding to the unevenness of the inner surface of the mold occurs. Thereafter, when the polyamic acid solution 3 in which the liquid thickness variation occurs is dried and solidified, undulation according to the concave and convex of the mold is generated on both surfaces of the endless film,
A film thickness variation proportional to the liquid thickness variation was observed. However, as described above, the degree of undulation due to the unevenness of the mold is different between the endless film surface side and the side in close contact with the mold.

According to the above observation results, even when the inner surface of the mold has irregularities, the polyamic acid solution 3 applied in the rotating mold 1 has a variation in the liquid thickness immediately following the irregularity of the mold after being applied. Rather than being generated, undulations are formed following the irregularities of the mold 1, but after a state of uniform liquid thickness, the liquid surface is then formed into a perfect circle with an equal acceleration field of centrifugal force. It turned out that the thickness varied.

Based on these observation results, the present inventors have made the polyamic acid solution 3 having a uniform liquid thickness.
It is expected that if the liquid thickness fluctuates due to the deviation of the rotation axis of the mold or the unevenness of the inner surface of the mold, the dispersion of the film thickness of the transfer belt can be suppressed. went.

[Experiment 1] Here, in the actual coating step and the drying and solidifying step, the polyamic acid solution 3 was used as shown in FIG.
It is difficult to strictly recognize which casting state is shown in FIGS. 3, 6, and 7. So, in this experiment,
By varying the time from when the rotation speed of the mold 1 reaches 1000 rpm to when the heating of the polyamic acid solution 3 is started, the solution 3 is assumed to be in a different casting state, and is obtained after the solution 3 is dried and solidified. The thickness of each of the obtained endless films is measured. Thus, it is confirmed whether or not the liquid can be dried and solidified before the liquid thickness fluctuates due to the deviation of the rotation axis of the mold or the unevenness of the inner surface of the mold. In this experiment,
As the polyamic acid solution 3, the polyimide precursor solution was
It was diluted to 30% with a MAC, and adjusted to a solid content of 15% (solid content ratio α = 0.15) and a viscosity of 1200 cp. The mold 1 used had an inner diameter of 180 mm. In addition, the mold 1 has a rotational axis shift during rotation and has irregularities on the inner surface of the mold. Irregularities (hereinafter collectively referred to as “mold deflection”) were measured. As a method of measuring mold deflection,
For example, as shown in FIG. 8, a method of recording the displacement of the movable contact L using a dial gauge can be adopted.

In FIG. 1, the polyamic acid solution 3 is spirally applied on the inner peripheral surface of the mold 1 as described above, and
High-speed rotation was performed at 00 rpm. Then, after a lapse of a predetermined time t, the polyamide acid solution 3 in the mold 1 was heated at 70 ° C. to be dried and solidified while the rotation of the mold 1 was continued. At this time, the predetermined time t is such that the rotational speed of the mold 1 is 1000 rpm.
Means the time from when the temperature reaches the time when the heating of the polyamic acid solution 3 is started, and was changed as shown in Table 1 below. Thereafter, the dried and solidified endless film of the polyamic acid solution 3 is
Further, the coating was cured by heating at 300 ° C. for 30 minutes in another heating furnace, and the endless film was separated from the mold 1 and released.

FIG. 9 and Table 1 below show the results of an examination of the relationship between the previously measured mold deflection and the thickness of the endless film formed on a portion corresponding to an arbitrary location where the mold deflection was measured. Also,
FIG. 10 shows the thickness distribution of the endless film under each condition. Note that the type deflection shown in FIG. 9 is defined as follows. When the average displacement position recorded by the dial gauge L is set to 0, a value below the average displacement position is plus and a value above the average displacement position is minus, and the displacement position at an arbitrary position on the inner peripheral surface of the mold is defined as The difference from the average displacement position was defined as the size of the mold deflection. In addition, when the target film thickness is set to 0, the film thickness shown in FIG. 9 is represented as plus when the target film thickness is larger than the target film thickness and as minus when the target film thickness is smaller than the target film thickness.

[Table 1]

When the predetermined time t is 0 minutes, the heating timing is too early and the polyamic acid solution 3 is dried and solidified in a state where the casting is insufficient, so that the polyamic acid solution 3 is uniformly formed over the entire belt forming area on the inner peripheral surface of the mold. An endless film having a liquid thickness could not be obtained. On the other hand, if the time t is longer than 10 minutes, the polyamic acid solution 3 fluctuates for a long time under the influence of the displacement of the rotation axis of the mold and the irregularities on the inner surface of the mold, and the correlation between the mold deflection and the film thickness becomes strong. At the same time, the film thickness variation increased. On the other hand, when the predetermined time t is 1 to 5
In minutes, the time affected by the displacement of the rotation axis of the mold and the irregularities on the inner surface of the mold is short, so that the fluctuation of the polyamic acid solution 3 can be suppressed, there is no correlation with the mold deflection, and the film thickness is intended to be uneven. Was within ± 10%. From this result, it was found that the film thickness variation can be suppressed by heating so that the polyamic acid solution 3 is dried and solidified before being affected by the deviation of the rotation axis of the mold and the irregularities on the inner surface of the mold.

Therefore, in the method of manufacturing the transfer belt of the present embodiment, the polyamic acid solution 3 is cast over the entire belt forming area on the inner peripheral surface of the mold 1 to have a uniform liquid thickness. Before the thickness of the polyamic acid solution 3 fluctuates due to the deviation of the rotation axis and the unevenness of the inner surface of the mold, heating is performed so that the solution 3 is dried and solidified. Specifically, for example, using the polyamic acid solution 3 and the mold 1 used in the above Experiment 1, the polyamic acid solution 3 is spirally applied on the inner peripheral surface of the mold 1, and the mold 1 is rotated at a high speed of 1000 rpm. After a predetermined time set between 1 minute and 5 minutes, the solution 3
Heat at 0 ° C. As a result, an endless film with a uniform liquid thickness can be obtained over the entire belt forming area on the inner peripheral surface of the mold, and the coating liquid fluctuates due to the influence of the deviation of the rotation axis of the mold and the irregularities on the inner surface of the mold. Therefore, even if the rotation axis of the mold is shifted or the inner surface of the mold has irregularities, it is possible to obtain a belt having a small thickness variation. In addition, by performing the heating as described above, the drying and solidification step can be shortened as compared with the related art, and the production efficiency can be improved.

[Experiment 2] In Experiment 1, the viscosity of the polyamic acid solution 3 was kept constant (1200 cp), and after the rotational speed of the mold 1 reached 1000 rpm,
The time t until the heating was started was changed variously. However, when the viscosity was different, the casting state of the solution was different. It may not be possible to control it. Therefore, in this experiment, the predetermined time t was set to 5 minutes, in which good results were obtained in Experiment 1, and the polyamic acid solution 3
The variation in the film thickness due to the deviation of the rotation axis of the mold and the unevenness of the inner surface of the mold is confirmed by changing the viscosity of the mold. In this experiment, the same mold 1 as in Experiment 1 was used, and the viscosity of the polyamic acid solution 3 was changed from 600 to 7000 cp.

In FIG. 1, the polyamic acid solutions 3 having different viscosities as described above were applied such that the trajectory on the inner peripheral surface of the mold 1 was spiral, and the mold 1 was rotated at a high speed of 1000 rpm. After a lapse of 5 minutes, the polyamic acid solution 3 in the mold 1 was dried and solidified while the rotation of the mold 1 was continued. Thereafter, the dried and solidified endless film of the polyamic acid solution 3 was cured by heating at 300 ° C. for 30 minutes in another heating furnace, and the endless film was peeled off from the mold 1 and demolded. FIG. 11 shows the thickness distribution of the endless film under each condition. From this, it was found that the higher the viscosity of the polyamic acid solution 3, the lower the fluidity, the less the influence of the displacement of the rotation axis of the mold and the unevenness of the inner surface of the mold, and the more the film thickness variation can be suppressed. In this experiment, as shown in FIG. 10, when the viscosity was 1000 cp or more, an endless film having a relatively small variation in film thickness could be formed.

Therefore, in the method of manufacturing a transfer belt according to the present embodiment, the polyamide acid solution 3 having a viscosity of 1000 cp or more is used in order to reduce the influence of the rotational axis of the mold and the unevenness of the inner surface of the mold. Preferably, it is used. The upper limit of the viscosity may be within a range that can be centrifugally cast according to the coating solution used.

In the above-described embodiment, the method of applying the polyamic acid solution 3 is a method of applying the solution 3 spirally on the inner peripheral surface of the mold 1 (hereinafter, referred to as a “spiral applying method”). However, the present invention is not limited to this. However, the spiral coating method is preferable in the following points. As shown in FIG. 1, since the liquid streaks of the polyamic acid solution 3 are arranged at equal intervals in the axial section of the mold, the solution 3 spreads uniformly in the axial direction, and is applied in a short time. The liquid flows. Therefore, it is preferable in that the time affected by the displacement of the rotation axis of the mold and the irregularities on the inner surface of the mold can be shortened, and the fluctuation of the coating liquid can be further suppressed. Further, in the spiral coating method, in order to make the polyamic acid solution 3 spread in the axial direction of the mold 1 more uniformly, the coating liquid injected spirally when viewed in the axial cross section of the mold 1. It is more preferable to inject such that the liquid streaks are at equal intervals.

As a coating method other than the spiral coating method, for example, a spray spot coating method in which the polyamic acid solution 3 is applied in a spot pattern on the inner peripheral surface of the mold 1 by spraying can be adopted. Also in this spray spot coating method, the polyamic acid solution 3
Is cast over the entire belt forming area on the inner peripheral surface of the mold 1 to have a uniform liquid thickness, and the liquid thickness of the polyamic acid solution 3 due to displacement of the rotation axis of the mold 1 and irregularities on the inner surface of the mold 1 By heating the solution 3 so as to dry and solidify before the fluctuation occurs, an endless film having a uniform liquid thickness can be obtained over the entire belt forming area on the inner peripheral surface of the mold. Moreover, since the coating liquid applied in a spot shape on the inner peripheral surface of the mold spreads in the axial direction and circumferential direction of the mold and flows in a short time, the influence of the displacement of the rotational axis of the mold and the irregularity of the inner surface of the mold are reduced. The receiving time is short, and the fluctuation of the coating liquid can be suppressed. This makes it possible to obtain a belt having a small variation in film thickness even when the rotation axis of the mold is shifted or the inner surface of the mold has irregularities. However, in the spray spot application method, since the spot-like polyamic acid solution 3 spreads in the mold axis direction and the circumferential direction, the flow overlap between the spot-like liquids is complicated. If the heating timing is too early to dry and solidify the polyamic acid solution 3 before the liquid thickness varies due to the influence of the deviation of the rotation center axis of the mold and the irregularities on the inner surface of the mold, the solution 3 cannot be cast. It is dried and solidified in a sufficient state, and a spot-like thin film portion is formed. For this reason, compared with the spiral coating method, the time required for casting over the entire belt forming area on the inner peripheral surface of the mold and obtaining a uniform liquid thickness is longer, and the casting time over the entire belt forming area on the inner peripheral surface of the mold is uniform. While the liquid thickness is large, it is affected by the displacement of the rotation axis of the mold and the unevenness of the inner surface of the mold, but in this embodiment,
The film thickness variation was within ± 15% of the target film thickness, which was within an allowable range.

[Comparative Example] A case where a one-shot application method was adopted as a method for applying the polyamic acid solution 3 will be described.
In this comparative example, using the same polyamic acid solution 3 and mold 1 as in the above embodiment,
At a stretch into the central bottom in the axial direction of
The solution 3 was rotated at a high speed at 00 rpm, and after a lapse of a predetermined time t, the solution 3 was heated at 70 ° C. The optimum heating timing was searched by variously changing the predetermined time t. In any case,
The variation in film thickness with respect to the intended film thickness was ± 20% or more, and it was difficult to form a uniform film. This is because in the one-shot application method, the polyamic acid solution 3 swells in one place and must flow in the axial direction and circumferential direction of the mold from that state to be uniform, so that the belt forming on the inner peripheral surface of the mold is formed. This is because the time required for casting over the entire area to reach a uniform liquid thickness is long, and during that time, it is affected by displacement of the rotation axis of the mold and irregularities on the inner surface of the mold.

The transfer belt obtained by the belt manufacturing method according to the present embodiment was used as an intermediate transfer belt in an actual copying machine, and an output image was evaluated. Images were obtained. In addition,
If the endless film having the large unevenness of the mold 1 and the film undulation is used as it is as a transfer belt, an abnormal image such as white spots may be generated, and thus it is necessary to correct the undulation. As a method for correcting undulation, for example, the endless film having undulation can be easily corrected by covering it with a metal mold having an outer diameter slightly smaller than that of the endless film and reheating. As a result of using the corrected endless film as a transfer belt, no abnormal image was generated.

[0045]

According to the first to fourth aspects of the present invention, there is provided an excellent effect that a belt having a small film thickness variation can be obtained even when there is a displacement of the rotation axis of the mold or irregularities on the inner surface of the mold. is there. In addition, there is an effect that the drying and solidification step can be shortened and the production efficiency is improved. Further, when the obtained belt is used as a transfer belt of an image forming apparatus, there is an excellent effect that excellent image uniformity can be formed and a good image without transfer omission can be formed. .

In particular, according to the second aspect of the invention, there is an effect that the fluidity of the coating liquid is low and the coating liquid is hardly affected by the displacement of the rotation axis of the mold and the irregularities on the inner surface of the mold.

In particular, according to the third and fourth aspects of the present invention, the spreading of the coating solution in the axial direction of the mold is uniform and the coating solution is cast in a short time. There is an excellent effect that the time affected by the unevenness can be reduced and the fluctuation of the coating solution can be suppressed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a method of manufacturing an endless belt by a centrifugal molding method according to an embodiment.

FIG. 2 is a circumferential sectional view of a mold showing a state in which a coating liquid is formed by centrifugal molding with a uniform liquid thickness.

FIG. 3 is a circumferential cross-sectional view of the mold, showing a state in which the coating liquid is subjected to centrifugal molding due to a fluctuation in the liquid thickness due to a shift of the rotation center axis of the mold.

FIG. 4 is a sectional view in the liquid thickness direction of the coating liquid, showing a state in which the coating liquid is subjected to centrifugal molding in which the liquid thickness fluctuates due to irregularities on the inner surface of the mold.

FIG. 5 is a sectional view in the thickness direction of the endless film after the coating liquid shown in FIG. 4 is dried, solidified and cured.

FIG. 6 is a schematic diagram for explaining a casting state of a coating liquid caused by centrifugal force.

FIGS. 7A and 7B are schematic diagrams for explaining another casting state of a coating liquid by centrifugal force. (C) is a schematic diagram for explaining the endless film after the drying, solidification, and curing treatments.

FIG. 8 is an explanatory view for explaining a method for measuring the displacement of the rotation axis of the mold and the unevenness on the inner surface of the mold.

FIG. 9 is a graph showing the relationship between the magnitude of deflection of the inner peripheral surface of the mold and the thickness of the endless film according to Experiment 1.

FIG. 10 is a graph showing a film thickness distribution of an endless film according to Experiment 1.

11 is a graph showing a film thickness distribution of an endless film according to Experiment 2. FIG.

[Explanation of symbols]

 Reference Signs List 1 mold 1a mold inner surface 2 discharge nozzle 3 polyamic acid solution (coating liquid)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/16 G03G 15/16 // B29L 29:00 F term (Reference) 2H032 BA09 BA18 3F024 BA03 CA08 4F202 AG16 AR17 CA04 CB01 CC07 CN01 4F205 AG16 AR17 GA01 GB01 GC04 GF03 GF24 GN01 GN10 GN11 GN13 GN21 GN24 4F213 AG16 AR17 WA03 WA32 WA37 WA39 WA58 WA83 WB01 WC03 WF24 WK03

Claims (4)

[Claims] 1. A coating liquid as a belt material is applied in a cylindrical mold, and by rotating the mold, an endless film of the coating liquid is centrifugally formed on the inner peripheral surface of the mold. In the method for producing an endless belt which is dried and solidified by heating, after the coating liquid is cast over the entire belt forming area of the inner peripheral surface of the mold to have a uniform liquid thickness, and the rotation of the mold A method for producing an endless belt, wherein heating is performed so that the coating liquid is dried and solidified before a liquid thickness variation due to a deviation of a central axis or irregularities on an inner surface of a mold. 2. The method for producing an endless belt according to claim 1, wherein the viscosity of the coating solution is 1000 cp or more. 3. The method for producing an endless belt according to claim 1, wherein the coating liquid is spirally applied on an inner peripheral surface of the mold. 4. The method for producing an endless belt according to claim 1 or 2, wherein the coating liquid is applied in spots on the inner peripheral surface of the mold.