JP2011033960A - Endless belt and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an endless belt which prevents an image failure when started after a long-time stop, in an image forming apparatus. <P>SOLUTION: The endless belt includes a substrate layer 11 having a thin section 11a whose average film thickness is smaller than that of other portions, and is 5% or more smaller than that of a thick section 11b. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an endless belt. In particular, the present invention relates to an endless belt used in an electrophotographic image forming apparatus such as a copying machine, a laser beam printer, and a facsimile.

  As an image forming apparatus for forming and recording an image by an electrophotographic method, a copying machine, a laser printer, a video printer, a facsimile, a complex machine of these, and the like are known. In these apparatuses, a conveyance belt that conveys recording paper, a transfer belt that conveys the toner image transferred at the primary transfer position to the secondary transfer position, and an unfixed toner image on the recording paper while moving the recording paper. A fixing belt for fixing on the recording paper is used. These endless belts are required to have excellent heat resistance and mechanical strength. For example, endless belts having an inner layer formed of a polyimide resin and an outer layer formed of a fluorine resin have been proposed (for example, patents). Reference 1).

  In recent years, image forming apparatuses have been remarkably advanced in speed, cost, and size. In particular, downsizing of the apparatus has become a particularly important issue because it can save space in offices and the like and reduce transportation costs. On the other hand, there is a desire to use an endless belt with a long circumference in order to increase the speed. In order to increase the speed and reduce the size, for example, an endless belt having a long circumference is stretched using a thin (high curvature) roll. However, there is a problem that the portion of the endless belt that contacts the roll is deformed (for example, the arc shape of the roll is transferred) and the image is defective when the apparatus is used again while the device is not used for a long period of time or the like. Some devices take measures such as automatically rotating the belt and shifting the position when it is not used for a long time, but it is necessary to keep the power on.

Japanese Patent Laid-Open No. 08-80580

  The present invention has been made to solve the above-described conventional problems, and a main object of the present invention is to generate an image defect when the image forming apparatus is used again even when the image forming apparatus is stopped for a long time. It is to provide an endless belt capable of suppressing the above.

The endless belt according to the present invention includes a base material layer having a thin part with an average film thickness thinner than that of other parts, and an average film thickness of the thin part being 5% or more thinner than that of the thick part.
In a preferred embodiment, a plurality of the thin portions are formed in the circumferential direction.
In preferable embodiment, the said base material layer is formed with the heat resistant resin.
In a preferred embodiment, the heat resistant resin is a polyimide resin.
In a preferred embodiment, a surface layer is provided, and the surface layer is formed of a fluorine-based resin.
In a preferred embodiment, an intermediate layer formed between the base material layer and the surface layer is provided, and the intermediate layer is formed of an elastomer.
According to another aspect of the present invention, an image forming apparatus is provided. The image forming apparatus includes a roll that is rotationally driven, the endless belt, and a positioning unit that positions the thin portion of the endless belt so as to contact the roll when stopped.
According to still another aspect of the present invention, a method for manufacturing an endless belt is provided. In one embodiment, a manufacturing method is as follows: a cylindrical die having an annular lip formed at the lower end is moved upward in a cylindrical mold in which a gas is circulated from below; And a step of applying a resin liquid to the inner peripheral surface of the mold, and at least one narrow portion having a lip width of 5% or more narrower than other portions is formed on the lip.
The manufacturing method in another embodiment includes a step of applying a resin liquid to the inner peripheral surface of a rotating cylindrical mold, the viscosity of the resin liquid is 50 to 7500 Ps, and the predetermined circumferential direction of the mold The position is applied so that the coating amount at the position is 5% or less smaller than other parts.

  By using the endless belt of the present invention, even when the image forming apparatus is stopped for a long time, it is possible to suppress the occurrence of image defects when the image forming apparatus is used again. Specifically, the endless belt of the present invention has a thin portion having an average film thickness thinner than that of other portions, and includes a base material layer in which the average film thickness of the thin portion is 5% or more thinner than that of the thick portion. . By using such an endless belt and stopping the image forming apparatus in a state where the roll is in contact with the thin portion, the tension is concentrated on the thin portion. The thin-walled portion is less deformed by tension than other parts, and even if it is deformed, it recovers to its original shape in a short time. In this manner, the occurrence of image defects can be suppressed by suppressing the deformation of the endless belt (base material layer).

1 is a schematic view illustrating an endless belt according to a preferred embodiment of the present invention and illustrating a method for measuring an average thickness. It is the elements on larger scale of the cross section of FIG. (A) is sectional drawing of the base material layer by preferable embodiment of this invention, (b) is sectional drawing of the base material layer by another preferable embodiment of this invention. It is a schematic sectional drawing which shows the manufacturing method of the endless belt by preferable embodiment of this invention. It is a top view which shows the lip shape of the die | dye used for the manufacturing method of the endless belt by preferable embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these specific embodiments.

A. Endless Belt FIG. 1 shows an endless belt 10 according to a preferred embodiment of the present invention, and FIG. 2 is a partially enlarged view of the cross section of FIG. The endless belt 10 includes a base layer 11, a surface layer 12 provided on the outer peripheral side of the base material layer 11, and an intermediate layer 13 provided between the base material layer 11 and the surface layer 12. FIGS. 3A and 3B are cross-sectional views of the base material layer 11. The base material layer 11 has the thin part 11a whose average film thickness is thinner than another site | part. The thin portion 11a is formed in a groove shape along the axial direction. As shown in FIG. 3, the cross-sectional shape of the thin portion 11a is an inclined thin portion formed so that the film thickness gradually decreases from the thick portion 11b. The thin portion 11a has an average film thickness that is 5% or more thinner than the thick portion 11b. The endless belt 10 is preferably used while being stretched around a roll in the image forming apparatus. When the image forming apparatus is stopped in a state where the roll hits the thin portion 11a, the tension is concentrated on the thin portion. The thin-walled portion is less deformed by tension than other parts, and even if it is deformed, it recovers to its original shape in a short time. In this manner, the occurrence of image defects can be suppressed by suppressing the deformation of the endless belt (base material layer). Here, the “average film thickness” refers to an average value of the measurement results obtained by measuring the film thickness of the base material layer at five or more points along the axial direction as indicated by 11c in FIG. The average thickness of the thin portion is preferably 5 to 25% thinner than that of the thick portion, and more preferably 5 to 10% thinner. By setting the range, the occurrence of image unevenness can be suppressed. The thickness of the base material layer can be set to any appropriate value. Typically, the thickness is 20 to 90 μm.

  The thin part may be formed at one place in the circumferential direction as shown in FIG. 3 (a), or may be formed at two or more places (plural) in the circumferential direction as shown in FIG. 3 (b). . The number of thin-walled portions and the formation location can be appropriately determined according to, for example, the number and arrangement of rolls used.

  Arbitrary appropriate structures are employ | adopted for the endless belt of this invention. Specifically, as shown in FIG. 2, a laminate including a base material layer and other layers (surface layer and / or intermediate layer) may be used, or a single-layer material including only the base material layer may be used. Good. Even in the case of a laminated body, the occurrence of image defects can be suppressed by providing the base material layer on which the thin portion is formed. The thickness of each layer can be set to any appropriate value. The thickness of the surface layer is preferably 5 to 40 μm, more preferably 10 to 20 μm. The thickness of the intermediate layer is typically 0.5 to 300 μm.

  The base material layer is typically formed of any appropriate resin. Preferably, it is formed of a heat resistant resin. Examples of the heat resistant resin include polyimide resins, polyamideimide resins, polyetherimide resins, polyarylate resins, polycarbonate resins, polysulfone resins, polyphenylene sulfide resins, and the like. Among these, a polyimide resin is preferable. This is because it has excellent heat resistance and high mechanical strength.

  Examples of the polyimide resin include a copolymer of tetracarboxylic dianhydride or a derivative thereof and a diamine compound.

  Specific examples of the tetracarboxylic dianhydride include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetra Carboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalene Tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,2′-bis (3,4 Dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ) Ete Dianhydride, ethylene tetracarboxylic dianhydride, and the like.

  Specific examples of the diamine compound include p-phenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,3′-dichlorobenzidine, 4,4 ′. -Diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, m-phenylenediamine, 3,3'-dimethyl-4,4'-biphenyldiamine, benzidine, 3,3'-dimethylbenzidine 3,3′-dimethoxybenzidine, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenylpropane, 2,4-bis (β-amino-t-butyl) Toluene, bis (p-β-amino-t-butylphenyl) ether Bis (p-β-methyl-δ-aminophenyl) benzene, bis-p- (1,1-dimethyl-5-amino-pentyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m- Xylylenediamine, p-xylylenediamine, di (p-aminocyclohexyl) methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylene Diamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethyl To heptamethylenediamine, 3-methyl Ptamethylenediamine, 5-methylnonamethylenediamine, 2,11-diaminododecane, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 1,12 -Diaminooctadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane and the like.

  The surface layer is preferably formed of a fluororesin. It is because it is excellent in releasability. Examples of the fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), fluoroethylene vinyl ether ( FEVE) and the like. These may be used alone or in combination of two or more.

  The intermediate layer is formed of, for example, an elastomer. Any appropriate elastomer can be adopted as the elastomer. As is generally known, an elastomer is a high-molecular substance exhibiting elasticity, and has a mechanical property (rubber elasticity) that is easily changed by an external force, but almost recovers to its original shape immediately after removing it.

  Examples of the elastomer include vulcanized rubber such as natural rubber and synthetic rubber, thermoplastic elastomer, elastic fiber such as spandex and polycarbonate elastic fiber, and elastic foam such as sponge rubber and foam rubber.

  Examples of the synthetic rubber include styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), ethylene-propylene rubber (EPM, EPDM), and acrylonitrile-butadiene rubber (NBR). , Chloroprene rubber (CR), acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO, GECO, GPCO), chlorinated polyethylene (CM), chlorosulfonated polyethylene (CSM), urethane rubber (U), fluoro rubber (FKM, FEPM, FFKM), silicone rubber (MQ, PMQ), polysulfide rubber (OT, EOT), phosphazene rubber (FZ, PZ) and the like.

  The thermoplastic elastomer is a polymer material that exhibits properties of vulcanized rubber at room temperature, is plasticized at high temperature, and can be molded by a plastic processing machine, and is referred to as TPE. Examples of the thermoplastic elastomer include polystyrene-based TPE such as polystyrene-polyisoprene-polystyrene block copolymer (SIS), polyolefin-based TPE, polyester-based TPE, polyurethane-based TPE, 1,2-polybutadiene-based TPE, and polychlorinated. Examples thereof include vinyl TPE and polyamide TPE.

  The endless belt (base material layer, surface layer and / or intermediate layer) of the present invention may contain any appropriate additive depending on the purpose. Examples of the additive include a slidable filler, a heat conductive filler, a conductive filler, a heat insulating filler, and an abrasion resistant filler.

B. Production Method The endless belt of the present invention can be produced by any appropriate method as long as the above-described configuration is obtained. This will be specifically described below.

(Manufacturing method 1)
FIG. 4 is a schematic view illustrating a method of manufacturing an endless belt according to a preferred embodiment of the present invention. In the present embodiment, the endless belt (base material layer) moves upward in a cylindrical die 30 in which an annular lip 31 is formed at the lower end in a cylindrical mold 20 in which gas is circulated from below. Then, the resin liquid 40 is extruded from the lip 31 and applied to the inner peripheral surface 20a of the mold. The gas in the mold 20 is circulated by injecting gas from a vent 21 a formed in the bottom surface 21. As the gas, for example, air, nitrogen, a rare gas such as argon or helium, or the like can be used. The gas flow rate, the distance between the inner peripheral surface of the mold and the lip of the die, and the blow ratio (ratio between the inner diameter of the mold and the diameter of the lip) are applied by the resin liquid extruded from the lip to the inner peripheral surface of the mold. As long as it can be done, it can be set to any suitable value.

  FIG. 5 is a plan view showing a lip shape of a die according to a preferred embodiment. The annular lip 31 is formed with at least one narrow portion having a lip width of 5% or more narrower than other portions. Preferably it is 5-25% narrowly formed, more preferably 5-10% narrowly formed. By forming such a narrow part on the annular lip, an endless belt (base material layer) having a thin part can be obtained. The lip width can be set to any appropriate value depending on the inner diameter of the cylindrical mold 20, the dimensions of the desired endless belt, and the like. In the illustrated example, narrow portions 31a and 31a are formed around the positions of 0 ° and 180 °. Thus, a desired endless belt can be produced by appropriately selecting the lip width and the position and number of narrow portions.

  The resin liquid 40 is injected into the die 30 in advance. The resin liquid contains the material for forming the base material layer and, if necessary, the above additives. The resin liquid can be adjusted to any appropriate viscosity. Preferably it is 50-7500Ps, More preferably, it is 1000-3000Ps. By adjusting to such a viscosity, an endless belt (base material layer) can be produced satisfactorily. When using the said polyimide resin, the polyamic acid solution obtained by making tetracarboxylic dianhydride and a diamine compound react can be used as a resin liquid, for example. The viscosity of the polyamic acid solution can be adjusted by adjusting its concentration. The concentration of the polyamic acid solution is preferably 15 to 25 wt%, more preferably 18 to 22 wt%.

  An endless belt (base material layer) can be obtained by heat-treating the resin liquid applied to the inner peripheral surface of the mold. The heating condition can be set to any appropriate condition. When the polyimide resin is used, the heat treatment is preferably performed in two stages. The first heat treatment is preferably performed to such an extent that the resin liquid applied to the inner peripheral surface of the mold is dried to form a resin film, and the resin film can have a self-supporting property. Specifically, the heating temperature is preferably 150 to 250 ° C, more preferably 200 to 280 ° C. The heating time is preferably 25 to 60 minutes. The second heat treatment may be performed by removing the obtained resin film from the mold or may be performed while the resin film is attached to the mold. When peeling a resin film from a metal mold | die, Preferably, it heat-processes using the inner metal mold | die which can support a resin film from an inner surface. The second heat treatment is preferably performed to such an extent that the ring-closure imidization reaction can proceed. Preferably it is 320-410 degreeC, More preferably, it is 380-400 degreeC. The heating time is preferably 35 to 90 minutes.

(Manufacturing method 2)
In another preferred embodiment, the endless belt of the present invention is produced by applying a resin liquid to the inner peripheral surface of a rotating cylindrical mold (rotary centrifugal molding method). Specifically, the resin liquid is spirally applied to the rotating mold by discharging the resin liquid from the nozzle and running the nozzle or the mold in parallel with the rotation axis of the mold. Here, the coating is performed such that the coating amount at a predetermined position in the circumferential direction of the mold is adjusted to be 5% or less smaller than other portions. Any appropriate method can be adopted as the adjustment method. For example, there is a method of reducing the discharge amount of the resin liquid nozzle at a predetermined interval for a predetermined time. Specifically, for example, when it takes 10 seconds for the mold to make one rotation, the discharge amount of the resin liquid is reduced every 3 seconds for 2 seconds, that is, between 0 to 2 seconds and 5 to 7 seconds. To do. Another example of the adjustment method is a method of increasing the rotational speed of the mold at a predetermined position in the circumferential direction. Specifically, for example, the rotational speed of the mold is increased at the positions of 0 to 30 ° and 180 to 210 °. After the resin liquid is applied in a spiral shape, the spiral application surface (application unevenness) is made uniform on the inner surface of the mold by the centrifugal force of rotation.

  The resin liquid contains the material for forming the base material layer and, if necessary, the above additives. In the present embodiment, the viscosity of the resin liquid is preferably 50 to 7500 Ps, more preferably 1000 to 3000 Ps. If the viscosity of the resin liquid is less than 50 Ps, the thickness of the coating film may be uniform while the mold is rotating, and a thin portion may not be formed. On the other hand, if it is larger than 7500 Ps, the coating unevenness is not corrected in the rotary centrifugal molding, and a uniform coated surface may not be formed. When using the said polyimide resin, the density | concentration of a polyamic-acid solution becomes like this. Preferably it is 15-25 wt%, More preferably, it is 18-22 wt%.

  An endless belt (base material layer) can be obtained by heat-treating the resin liquid applied to the inner peripheral surface of the mold. The heat treatment is as described in the manufacturing method 1 above.

  Any appropriate material can be adopted as the material of the cylindrical mold used in any of the above manufacturing methods. From the viewpoint of heat resistance, metal, glass, ceramics and the like are preferably used. Further, any appropriate method can be adopted as a method of peeling the endless belt (resin film) formed on the inner peripheral surface of the cylindrical mold. For example, the method etc. which pressure-feed gas (for example, air) from the micro through-hole previously formed in the surrounding wall of a cylindrical metal mold | die etc. are mentioned. In addition, the peeling workability | operativity can be improved by giving the mold release process by silicone resin etc. to the internal peripheral surface of a cylindrical metal mold | die beforehand.

  When the endless belt is a laminate, preferably, the base material layer is formed in advance by the above-described production method, and the intermediate layer and / or the surface layer is formed on the surface thereof. Arbitrary appropriate methods can be employ | adopted for the formation method of an intermediate | middle layer. For example, the method of apply | coating the coating liquid (for example, solution, dispersion) containing the formation material (for example, elastomer) of the said intermediate | middle layer to the base material layer surface, and drying is mentioned. Examples of the coating method include spray coating, spin coating, roll coating, brush coating, dipping, and dispenser coating.

  Arbitrary appropriate methods can be employ | adopted for the formation method of surface layer. As a specific example, there is a method in which the surface layer forming material (for example, fluorine-based resin) is formed into a tubular shape by melt extrusion, and this tubular body is deposited on the surface of the base material layer or the intermediate layer. Another specific example is a method in which a coating liquid (for example, a solution or a dispersion) containing the surface layer forming material is applied to the surface of the base layer or the intermediate layer and dried. As a coating method, the same method as the above intermediate layer can be used. In order to prevent the generation of voids, the drying is preferably carried out by removing the solvent in the coating solution and then raising the temperature to the melting point of the forming material (fluorine resin) or higher. In the drying step, a ring-closing imidization reaction of the base material layer may be performed.

C. Image Forming Apparatus The image forming apparatus of the present invention includes a roll that is rotationally driven, the endless belt, and a positioning unit that positions the thin portion of the endless belt (base material layer) so as to contact the roll when stopped. When positioning, the endless belt can be processed appropriately. For example, the outer peripheral surface or inner peripheral surface of the endless belt is marked with paint or a seal, or a sensor hole is formed. The endless belt can be used for any appropriate application in the image forming apparatus. Specifically, it can be used as a conveying belt, a transfer belt, and a fixing belt. Of these, it is particularly preferably used as a fixing belt.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

[Example 1]
(Preparation of resin solution)
In N-methyl-2-pyrrolidone, p-phenylenediamine and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride are dissolved so as to have an equimolar amount and a solid content concentration of 20 wt%. The reaction was carried out with stirring in a nitrogen atmosphere at room temperature. Thereafter, the mixture was kept warm at 70 ° C. to obtain a polyamic acid solution (resin solution) having a viscosity of 3000 Ps.

(Molding)
As shown in FIG. 5, a cylindrical die for φ200 in which an annular lip having narrow portions at 0 ° and 180 ° positions was prepared. The lip width of the narrow portion was adjusted to 0.855 mm, and the lip width of other portions was adjusted to 0.9 mm. The obtained resin solution was poured into this die.
The die was set in a die having an inner diameter of φ200, and as shown in FIG. 4, the resin solution was applied to the inner peripheral surface of the die by pushing out the resin solution from the lip while moving the die upward.
The mold to which the resin liquid was applied was gradually heated to 220 ° C. to dry and solidify the resin liquid, and then the mold was cooled. The resin film thus obtained was once peeled from the mold and heated to 380 ° C. while being supported from the inner surface by the inner mold to obtain an endless belt.

(Measurement of average film thickness)
Both ends of the obtained endless belt were cut off to have an axial length of 320 mm, and an average film thickness was determined every 45 ° in the circumferential direction. The average film thickness was determined by measuring the 7-point film thickness at intervals of 40 mm in the axial direction and calculating the average value of the measurement results.
The average film thicknesses at 0 ° and 180 ° in the circumferential direction were 66 μm and 65 μm, respectively. The average film thickness at the other six locations (circumferential directions 45 °, 90 °, 135 °, 225 °, 270 ° and 315 °) was 69 to 71 μm. In this way, thin portions were formed at 0 ° and 180 ° positions.

(Evaluation)
The obtained endless belt was held for 96 hours in a state of being stretched on two axes using a φ10 roll. At this time, the roll hit the thin portion and stretched by applying a load of 5 kg to each shaft.
After that, when the endless belt was rotated by setting a guide parallel to the line connecting the shaft centers at a position 6 mm away from the line connecting the shaft centers of the two axes (gap 1 mm with the lower surface of the belt), the endless belt was There was no problem in running performance, such as contact with the guide.

[Example 2]
(Molding)
The resin liquid prepared in the same manner as in Example 1 was applied to the inner peripheral surface of a rotating mold (inner diameter φ200) by discharging it from a nozzle (width 50 mm, lip width 1 mm). Here, the mold was rotated once in 12 seconds, and between 0 to 2 seconds and 6 to 8 seconds, the amount of resin liquid discharged was reduced by halving the number of rotations of the pump.
Thereafter, the coated surface was made uniform (rotational molding) at a rotational speed of 1200 rpm, and the same heat treatment as in Example 1 was performed to obtain an endless belt.

(Measurement of average film thickness)
Both ends of the obtained endless belt were cut off to have an axial length of 320 mm, and an average film thickness was determined every 30 ° in the circumferential direction. The average film thickness was determined by measuring the 7-point film thickness at intervals of 40 mm in the axial direction and calculating the average value of the measurement results.
The average film thicknesses in the circumferential directions 30 ° and 210 ° were 60 μm and 62 μm, respectively. The average film thickness at the other 10 locations (circumferential direction 0 °, 60 °, 90 °, 120 °, 150 °, 180 °, 240 °, 270 °, 300 ° and 330 °) was 66 to 71 μm. Thus, the thin part was formed in the position of 30 degrees and 210 degrees.

(Evaluation)
When the obtained endless belt was evaluated in the same manner as in Example 1, there was no problem in running performance.

[Example 3]
Silicone rubber (manufactured by Dow Corning Toray) is applied to the surface of the endless belt obtained in Example 1 with a dispenser so as to have a thickness of 150 μm, and then PFA (manufactured by Mitsui Dupont Fluorochemical) has a thickness of 10 μm. Was spray-coated and heated to 340 ° C. stepwise to form a three-layer laminate.

(Evaluation)
When the obtained laminate was evaluated in the same manner as in Example 1, no problem occurred in running performance.

<Comparative Example 1>
(Molding)
An endless belt was obtained in the same manner as in Example 1 except that a die adjusted to have a lip width of 0.9 mm over the entire circumference was used.

(Measurement of average film thickness)
When measured in the same manner as in Example 1, the average film thickness was 69 to 71 μm at all points (0 °, 45 °, 90 °, 135 °, 180 °, 225 °, 270 °, and 315 °). .

(Evaluation)
Since the obtained endless belt was not formed with a thin-walled portion, it was evaluated in the same manner as in Example 1 except that the endless belt was stretched without being particularly positioned. There was a problem.

<Comparative Example 2>
The surface of the endless belt obtained in Comparative Example 1 was treated in the same manner as in Example 3 to obtain a three-layer laminate.

(Evaluation)
When evaluated in the same manner as in Comparative Example 1, the surface of the endless belt contacted the guide, causing a problem in running performance.

  The endless belt of the present invention can be suitably used as a conveying belt, a transfer belt, and a fixing belt used in an image forming apparatus.

10 Endless Belt 11 Base Material Layer 12 Surface Layer 13 Intermediate Layer 20 Mold 30 Die 40 Resin Solution

Claims (9)

  An endless belt comprising a base material layer having a thin-walled portion whose average film thickness is thinner than other portions, and an average film thickness of the thin-walled portion being 5% or more thinner than that of the thick-walled portion.   The endless belt according to claim 1, wherein a plurality of the thin portions are formed in the circumferential direction.   The endless belt according to claim 1, wherein the base material layer is formed of a heat resistant resin.   The endless belt according to claim 3, wherein the heat resistant resin is a polyimide resin.   The endless belt according to any one of claims 1 to 4, further comprising a surface layer, wherein the surface layer is made of a fluorine-based resin.   The endless belt according to claim 5, further comprising an intermediate layer formed between the base material layer and the surface layer, wherein the intermediate layer is formed of an elastomer. A rotationally driven roll;
The endless belt according to any one of claims 1 to 6,
An image forming apparatus comprising: positioning means for positioning so that the thin portion of the endless belt hits the roll when stopped. Inside the cylindrical mold in which gas is circulated from below, while moving the cylindrical die having an annular lip formed at the lower end, the resin liquid is pushed out from the lip and the inner peripheral surface of the mold Including a step of applying a resin liquid to
The method for producing an endless belt, wherein the lip is formed with at least one narrow portion having a lip width of 5% or more narrower than other portions. Including a step of applying a resin liquid to the inner peripheral surface of a rotating cylindrical mold,
The viscosity of the resin liquid is 50-7500 Ps,
A method for producing an endless belt, wherein the coating is adjusted so that the coating amount at a predetermined position in the circumferential direction of the mold is 5% or less smaller than other portions.

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