JP2007140049A - Polyimide belt and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide belt having a coefficient of friction on the inner face of the belt being hardly influenced by the surface roughness of the surface, achieving stable driving control and eliminating electrification failure by driving, and to provide a method for manufacturing the belt. <P>SOLUTION: The polyimide belt is obtained by imidization by heating a resin solution which essentially comprises a polyamide acid solution containing a fluorine filler by 2 to 20 wt.% and a carbon filler by 3 to 30 wt.%, and is characterized in that when the inner surface of the polyimide belt is subjected to roughening treatment into a surface roughness (Ra) ranging from 0.05 μm to 0.35 μm, the coefficient of friction (μ) on the inner circumference face of the belt before and after the roughening treatment is in the range of 0.05 to 0.25; and that the gradient of an approximated line representing a relation between the coefficient of friction (μ) and the surface roughness (Ra) is in the range of -1/3 to 1/3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a polyimide belt manufactured using a resin solution mainly composed of a polyamic acid solution containing a fluorine filler and a carbon filler as a raw material, and a method for manufacturing the same. More specifically, the present invention relates to a polyimide belt and a manufacturing method thereof in which the friction coefficient of the inner surface of the polyimide belt is hardly affected by the roughness of the surface, and stable drive control is possible.

  Conventionally, polyimide resin materials have been put to practical use in a wide range of fields from aerospace to electrical and electronic materials because of their high mechanical strength and heat resistance. Among them, seamless tubular bodies made of polyimide resin include functional belts such as fixing belts, transfer belts, intermediate transfer belts, conveyance belts, and photoreceptor belts of electrophotographic image forming apparatuses such as copying machines, laser beam printers, and facsimile machines. It is used as a base material.

In particular, the fixing belt conveys the transfer body while pressurizing and heating the unfixed toner image, so that the strength that can withstand the tension between the rolls, the heat resistance that can withstand the heating temperature of the roll, and the deviation at the belt end are controlled. At the same time, there is an increasing demand for rigidity that does not cause buckling and flexibility that is necessary to separate excess toner. Furthermore, recently, in order to obtain high-speed and high-quality images, surface flexibility and conductivity are required.

  As a method for solving these problems, after kneading the thermally conductive inorganic filler in the polyamic acid solution, the solution added and mixed with the imidization accelerator is cast into a cylindrical SUS, and heat treated, so that the thermal conductivity and tear strength are improved. An excellent belt has been proposed (see Patent Document 1).

JP 2004-138655 A

However, the belt obtained from the polyamic acid solution containing an inorganic filler using the imidization accelerator in Patent Document 1 can suppress cracking or crushing during and after molding by improving tear strength. However, due to the influence of the thermally conductive inorganic filler, the slipping property with the roll during driving of the belt is poor, and the belt must be stretched excessively, so that it is weak against belt tearing.

  Further, when the roughness of the inner surface of the belt changes with continuous driving, the friction coefficient with respect to the roughness greatly fluctuates, resulting in unstable driving torque, resulting in image misalignment. Was. Furthermore, when used as a conductive belt, it is difficult to control the surface resistance of the belt by blending an inorganic filler, and discharge, noise, and paper sticking due to charging problems have been problems.

  Therefore, the present invention has been made in view of the above problems, and the object thereof is to make the friction coefficient of the inner surface of the polyimide belt less susceptible to the surface roughness of the surface, and to achieve stable drive control and drive. An object of the present invention is to provide a polyimide belt and a method for manufacturing the same that eliminates a charging problem.

The polyimide belt of the present invention is mainly composed of a polyamic acid solution containing 2 to 20% by weight of a fluorine filler and 3 to 30% by weight of a carbon filler having a conductivity index of 50 or more and 400 or less, based on the polyimide resin solid content. A polyimide belt obtained by converting the resin solution to imide by heating,
When the inner surface of the polyimide belt is roughened within a range where the surface roughness (Ra) is 0.05 μm or more and 0.35 μm or less, the friction coefficient (μ) of the inner peripheral surface of the belt before and after the roughening treatment is 0.05. It is a range of 0.25 or less, and the slope of the approximate straight line between the friction coefficient (μ) before and after the roughening treatment and the surface roughness (Ra) is in a relationship of −1/3 to 1/3. To do. The “approximate straight line” can be obtained as a regression line by the least square method.

  Here, it is preferable that the common logarithm of the surface resistance of the polyimide belt is 1 to 8 (Ω / □).

Further, the “conductivity index” is obtained by the following formula.
(Equation 1)
Conductivity index = (specific surface area × DBP oil absorption) ^1/2 / (1 + volatile content)
Here, the “DBP oil absorption amount” is a value obtained by substituting the void volume in a constant weight of carbon black with a liquid and using the capacity as a structure index. More specifically, it refers to the amount (ml) of oil contained per 100 g of carbon black, and is measured by an absorption meter using dibutyl phthalate as the oil (oil absorption amount described in JIS K 6211). A method (mechanical method)). The “specific surface area” is measured by a BET method (a method in which a specific surface area of a sample is obtained from the amount of molecules adsorbed on the powder particle surface at the temperature of liquid nitrogen by adsorbing the molecules).

  In the polyimide belt of the present invention, the friction coefficient of the inner surface of the belt is not easily affected by the surface roughness of the surface, and stable driving control and charging problems due to the driving are eliminated.

  In addition, it is a preferred embodiment that a rubber elastic layer and / or a fluororesin release layer is formed on the outer surface side of the polyimide belt of the present invention and used for the fixing belt.

In addition, the method for producing a polyimide belt of the present invention comprises a polyamide acid containing 2 to 20% by weight of a fluorine filler and 3 to 30% by weight of a carbon filler having a conductivity index of 50 or more and 400 or less based on the polyimide resin solid content. A preparation step for preparing a resin solution containing the solution as a main component, a coating step for applying the resin solution to the inner surface of the cylindrical mold, and centrifugal molding for uniforming the surface of the resin film formed by coating. A process for removing the solvent after centrifuging, and an imide conversion step for converting the imide,
When a polyimide belt inner surface obtained with a surface roughness (Ra) in the range of 0.05 μm or more and 0.35 μm or less is roughened, the friction coefficient (μ) of the inner peripheral surface of the belt before and after the roughening treatment is The range is from 0.05 to 0.25, and the slope of the approximate straight line between the coefficient of friction (μ) before and after the roughening treatment and the surface roughness (Ra) is in the range of −1/3 to 1/3. It is characterized by.

  As described above, the polyimide belt obtained by this manufacturing method is such that the friction coefficient of the belt inner surface is not easily affected by the surface roughness of the surface, and stable driving control and charging problems due to the driving are eliminated. It becomes.

Hereinafter, the present invention will be described in detail.

<Raw material for polyimide belt>
As the polyamic acid solution which is the main component of the resin solution in the present invention, a known polyamic acid solution can be used, and a polyamic acid solution obtained by polymerizing an acid dianhydride and a diamine in a solvent is used. When the aromatic polyimide resin is used, a belt having suitable mechanical strength and heat resistance can be obtained.

  Examples of suitable acid dianhydrides include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid dianhydride. Anhydride, 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride Products, 1,4,5,8-naphthalenetetracarboxylic dianhydride and the like.

  On the other hand, examples of the diamine include 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3 , 3′-diaminodiphenylsulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3′-dimethyl4,4′-biphenyldiamine, benzidine, 3,3′-dimethylbenzidine, 3 , 3′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenylpropane, and the like.

  A suitable solvent can be used for the polymerization reaction of these acid anhydrides and diamines, but polar solvents are preferably used from the viewpoint of solubility and the like. Specifically, N, N-dimethylformamide, N , N-dimethylacetamide, N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethyl sulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine, dimethyl sulfoxide, Tetramethylene sulfone, dimethyltetramethylene sulfone, etc. are conceivable. These may be used alone or in combination.

  Furthermore, phenols such as cresol, phenol and xylenol, benzonitrile, dioxane, butyrolactone, xylene, cyclohexane, hexane, benzene, toluene and the like can be mixed alone or in combination with the organic polar solvent.

  A polyamic acid solution is obtained by reacting the acid anhydride (a) and the diamine (b) in an organic polar solvent. The monomer concentration (concentration of (a) + (b) in the solvent) at that time is set according to various conditions, but is preferably 5 to 30% by weight. The reaction temperature is preferably set to 80 ° C. or less, particularly preferably 5 to 50 ° C., and the reaction time is preferably 0.5 to 10 hours.

  The viscosity of the polyamic acid solution to be applied is preferably about 10 to 10000 poise, preferably about 50 to 5000 poise (B-type viscometer, 23 ° C.). If the viscosity is 10 poises or less, so-called sagging or repellency of the coating layer is likely to occur, and it becomes difficult to obtain a uniform coating thickness. On the other hand, if it exceeds 10,000 poise, it is necessary to apply a high pressure at the time of discharge, and the leveling effect by centrifugal molding is difficult to be obtained, which is not preferable.

  In addition, the fluorine filler added to the polyamic acid solution and the material of the fluororesin release layer are not particularly limited as long as they contain fluorine atoms in the molecule. Specifically, polytetrafluoroethylene (PTFE) and its modified product, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene Copolymer (FEP), tetrafluoroethylene-vinylidene fluoride copolymer (TFE / VdF), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPA), polychlorotrifluoroethylene (PCTFE) , Chlorotrifluoroethylene-ethylene copolymer (ECTFE), chlorotrifluoroethylene-vinylidene fluoride copolymer (CTFE / VdF), polyvinylidene fluoride (PVdF), polyvinyl fluoride ( VF) and the like. PTFE, PFA, or a mixed system thereof is preferred from the viewpoints of wear resistance, releasability from toner, and heat resistance.

  The addition amount of the fluorine filler is 2 to 20% by weight, more preferably 4 to 15% by weight, based on the polyimide resin solid content in the polyimide resin composition. If it exceeds 20% by weight, the elastic modulus becomes extremely low, which is not preferable. If it is less than 2% by weight, the coefficient of friction increases, which is not preferable.

  In addition, examples of the carbon filler in the present invention include channel black, furnace black, ketjen black, acetylene black, and the like. These may be used alone or a plurality of types of carbon black may be used in combination. In addition, depending on the application, it is preferable to use one that prevents oxidative degradation such as oxidation treatment or graft treatment, or that has improved dispersibility in a solvent.

  The conductivity index of carbon is preferably 50 or more and 400 or less. If it is 50 or less, it is difficult to obtain a surface resistance having a common logarithm of 8 (Ω / □) or less, and carbon having a surface resistance of 400 or more is not preferable because of poor dispersibility. Examples of carbon that can be used in the present invention are shown below.

  The content of the carbon filler is appropriately determined depending on the type of carbon black to be added depending on the purpose, but as a functional belt for an image forming apparatus, the polyimide in the polyimide resin-based composition is used due to its mechanical strength. It is 3 to 30% by weight, more preferably 10 to 25% by weight, based on the resin solid content. If it is less than 3% by weight, the relationship between the friction coefficient (μ) before and after the roughening treatment and the slope of the approximate straight line of the surface roughness (Ra) is maintained in the range of −1/3 to 1/3 in combination with the fluorine filler. Not only is it difficult to do this, but the common logarithm of the surface resistance of the belt exceeds 8 (Ω / □), causing electrical trouble. If it exceeds 30% by weight, the mechanical strength is weakened and it tends to tear during driving.

<Manufacturing method of polyimide belt>
The method for producing a polyimide belt of the present invention preferably includes the following steps.
(1) A polyamic acid solution containing 2 to 20% by weight of a fluorine filler and 3 to 30% by weight of a carbon filler having a conductivity index of 50 or more and 400 or less relative to the solid content of the polyimide resin in the polyimide resin composition. A preparation process for preparing a resin solution having a main component.
(2) A coating process for coating the resin solution on the inner surface of the cylindrical mold.
(3) Centrifugal molding step for centrifugal molding to make the surface of the resin film formed by application uniform.
(4) Imide conversion step of removing solvent and converting imide after centrifugal molding.

  The coating process is exemplified by a method in which a resin solution containing a polyamic acid solution as a main component is applied to the inner surface of the cylindrical mold by moving the cylindrical mold in the axial direction of the dispenser while rotating. However, the present invention is not particularly limited thereto. For example, a resin solution containing a polyamic acid solution as a main component may be attached to the inner surface of the mold with a dispenser or the like, and then finished to a predetermined thickness with a hard sphere or the like. .

  The centrifugal molding step is centrifugal molding in which a mold to which a resin solution is applied is rotated, and the applied resin film is smoothed and defoamed.

  Here, the rotational speed in the circumferential direction of the mold performed for centrifugal molding depends on the diameter of the mold, the viscosity of the resin solution (or the polyamic acid solution that is the main component thereof), and the application state, but is 100 rpm or more and 5000 rpm or less. Is preferred. If it is 100 rpm or less, the leveling effect and defoaming effect of the coating film due to centrifugal force are difficult to obtain, and if it exceeds 5000 rpm, the mechanical load increases and the mold is eccentric due to vibration, and the coating thickness in the longitudinal direction of the mold Is not preferable.

  In the imide conversion step, the resin film is solidified or cured by heating or solvent extraction, and further imide conversion is performed by heating at a high temperature. In addition, the imide conversion after centrifugal molding may be performed by raising the mold to the imide conversion temperature or higher to form a polyimide belt, or the belt that is stopped in a state where the resin film in the mold is heated and solidified is removed from the mold. The imide conversion may be performed after taking out and replacing the belt with a metal pipe.

  In the polyimide belt of the present invention, the thickness of the belt is preferably set to be 50 μm or more and 200 μm or less. When the thickness of the belt is less than 50 μm, the rigidity of the belt end portion loses the load applied by the shift control, and the belt tends to buckle, which is not preferable. When the thickness exceeds 200 μm, the separation roll, which is one of the rolls to be stretched, is not preferable because the belt has a large radius of curvature and the toner on the belt is not sufficiently separated.

  The addition of the filler to the polyimide belt of the present invention is at least two types of fluorine filler and carbon filler. Other fillers include metals such as aluminum, conductive polymers such as polyaniline, and the like, and one or more can be used as appropriate.

  In polyimide belts that contain fluorine filler but not carbon filler, the inner surface roughness (Ra) and friction coefficient (μ) are in a proportional relationship, and the inner surface roughness (Ra) and friction coefficient before and after roughening treatment. The slope (μ / Ra) of the regression line of the least square method of (μ) exceeds 1/3 although it depends on the number of filler parts, and the friction coefficient is greatly influenced by the roughness. This is not preferable because, in actual use, the coefficient of friction also varies due to variations in the inner surface roughness that changes with time, resulting in uneven belt driving and image unevenness.

  On the other hand, in the polyimide belt containing the carbon filler without containing the fluorine filler, the inner surface roughness (Ra) and the friction coefficient (μ) are in inverse proportion, and the inner surface roughness (Ra) and the friction coefficient (μ). The slope (μ / Ra) of the regression line of the least square method is less than −1/3 depending on the number of filler parts, and the friction coefficient (μ) is greatly influenced by the inner surface roughness (Ra). On the other hand, if the roughening process is performed on the inner surface of the belt after forming the belt, it is possible to reduce the variation in the inner surface roughness (Ra) due to the actual change over time and the variation in the friction coefficient (μ). However, a carbon-dispersed polyimide belt with fundamentally poor slipperiness can obtain a friction coefficient of 0.25 or less, which provides a practically good driving state unless the inner surface roughness (Ra) is roughened by 0.2 μm or more. Since this is not possible, it is necessary to perform roughening treatment. However, the roughening process for that purpose is complicated, and accuracy is difficult to obtain.

  Therefore, in the present invention, the inner surface roughness (Ra) is in the range of 0.05 μm or more and 0.35 μm or less by dispersing two types of fluorine filler 2 to 20 wt% and carbon filler 3 to 30 wt% in the polyimide belt. The coefficient of friction (μ) is controlled to be 0.05 or more and 0.25 or less, and the slope (μ / Ra) of the regression line of the least square method of the inner surface roughness (Ra) and the friction coefficient (μ) is −1/3. A relationship of ~ 1/3 can be obtained.

  Here, if the coefficient of friction (μ) is less than 0.05, a stretched roll and a slip are generated, and if it exceeds 0.25, it is not preferable because an excessive driving force is applied to cause tearing.

  The “roughening treatment” in the present invention is performed in order to evaluate the characteristics of the polyimide belt, and a specific treatment method is appropriately set. For example, a polishing method such as sandpaper and sandblasting is exemplified. The In order to obtain reproducibility, for example, it is preferable to set the polishing material, roughness, load, speed, number of times, and the like. As an example, there is exemplified a method in which sandpaper # 1000 and a lapping film (3M company, particle size 9 μm) are used as the abrasive, the load is 1 kg / Φ50 mm cylinder, and the number of polishing is 10 times.

  Examples of the method for laminating the rubber elastic layer and the fluororesin release layer on the polyimide belt of the present invention include spray coating, dipping, and dispenser application.

  In addition, the lamination process may take a process of forming a polyimide belt and then laminating a rubber elastic layer and a fluororesin release layer on the outside, or a fluororesin release layer, a rubber elastic layer, and a polyimide on the inner surface of the mold. The steps of stacking in order and taking out from the mold after forming a belt may be taken. These processes can be freely selected according to the dimensional accuracy, characteristics and molding cost of the belt.

  In addition, when laminating the fluororesin release layer, a primer may be provided in the middle in order to strengthen the adhesive force with the rubber elastic layer. Further, the fluororesin release layer may be laminated by covering the rubber elastic layer on the rubber elastic layer and then shrinking by heating.

  The raw material for the rubber elastic layer is appropriately selected from natural rubber, synthetic rubber, silicone rubber and the like.

[Example]
Examples and the like specifically showing the configuration and effects of the present invention will be described below. The evaluation and test items in the examples and the like were measured as follows. In addition, this invention is not limited to this Example.
1. Tensile modulus measuring machine: Orientec UTM1000 Tensilon or equivalent chuck spacing: 30 mm
Tensile speed: 100 mm / min Calculation method of tensile elastic modulus: Calculated from the slope of the maximum tangent of the stress-strain curve. Test piece: A punched piece with a JIS K 6301 No. 3 dumbbell is used.
2. Tear strength Measured according to the JIS K 7128-1 trouser tear method. Take the length of the test piece in the belt axis direction, and put a slit of 75 ± 1 mm in the center of the width. Next, the leg of the test piece is attached to the chuck and pulled under the following conditions by a tensile tester.
Test piece: length 150 mm x width 75 mm (with a 75 ± 1 mm slit)
2. Tensile speed: 20 mm / min Surface roughness (Ra)
Measuring instrument: Surfcom 554A (Tokyo Seimitsu Co., Ltd.)
Measurement length: 4mm
Speed: 0.3mm / sec
Stylus load: 70mg
Cut-off: 0.8mm
Ra: arithmetic average roughness Friction coefficient measuring machine: Orientec AFT-15B
Mating material: φ10 steel ball Speed: 150 mm / min Load: 200 g
5. A four-probe probe (MCP-TP03P) connected to a surface resistance Loresta-GP (Mitsubishi Chemical) was pressed against the belt surface for measurement.

<Example 1>
(KCA type)
To N-methyl-2-pyrrolidone (NMP), 22 wt% of Vulcan (XC-72, Cabot Corporation, conductivity index = 85) and 4 wt% of PTFE powder (KTL-8 Kitamura) were sequentially added and stirred sufficiently. 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is dissolved as an acid component, and approximately equimolar amount of p-phenylenediamine is dissolved as an amine component (monomer concentration: 20% by weight), and the reaction is conducted at room temperature with stirring. Then, the mixture was stirred while heating to 70 ° C. to prepare a polyamic acid solution having a viscosity of 2000 poise measured at 23 ° C. using a B-type viscometer.

  Furthermore, isoquinoline corresponding to 1 wt% of the polyamic acid solution was stirred and mixed at room temperature.

  Next, while fixing the rectangular die-type dispenser, while rotating the cylindrical mold having a length of 600 mm and a diameter of 80 mmφ, the resin solution containing the polyamic acid solution as a main component is transferred from one end of the inner surface of the cylindrical mold to the other. While feeding to the end, it was spirally applied to the inner surface of the cylindrical mold, and the unevenness of the wrapping part of the coating surface was leveled while rotating the mold at 3000 rpm for 3 minutes to obtain a uniform coating surface. .

  Next, while rotating the mold at 60 rpm, the solvent was removed stepwise to 220 ° C. to remove the solvent. The belt base material before imide conversion was released from the cylindrical mold, replaced with an aluminum pipe, and heated at 400 ° C. for 20 minutes to perform imide conversion.

  The dimensions of the polyimide belt obtained as described above were 580 mm in length, 80 mm in diameter, and 75 μm in thickness. The common logarithm of the surface resistance was 3.8 (Ω / □), the tear strength was 6.3 N / mm, and the tensile modulus was 5000 Mpa.

  Next, this belt was spray-coated with methyl silicone rubber (Toray Dow Corning, DX35-2083) and then heated to form a 200 μm elastic layer. Further, a primer (Mitsui Dupont Fluorochemical, PRM-027-3) and a FEP dispersion paint (Mitsui Dupont Fluorochemical, ENA-020-45) are spray coated and heated on the silicone rubber, respectively, to 10 μm and 20 μm, respectively. A release layer was formed to prepare a fixing belt.

  The fixing belt is stretched between an aluminum heating roll having a diameter of 40 mm and an aluminum roll having a diameter of 20 mm, and an aluminum pressure roll covered with silicone rubber having a diameter of 40 mm is attached to the fixing belt portion that is associated with the heating roll from the opposite side. The nip width was set to 10 mm by applying a pressure of 0.2 Mpa. The recording paper was poured such that the heating roll temperature was 170 ° C. and the linear velocity of the fixing belt was 120 mm / sec, so that the toner came to the surface of the fixing belt.

  As a result, no release offset occurred after toner fixing. Even after printing 100,000 sheets, the driving of the belt was stable, and image shift, edge damage, buckling, and delamination were not observed.

Here, the relationship between the friction coefficient (μ) and the surface roughness (Ra) when the polyimide belt is roughened is shown below. When the friction coefficient before the roughening treatment (μ ₀ ) is 0.18, the surface roughness (Ra ₀ ) is 0.11 μm, and the friction coefficient (μ ₁ ) after the first roughening treatment is 0.17 μm. The surface roughness (Ra ₁ ) was 0.19 μm, and when the coefficient of friction (μ ₃ ) after the second stage roughening treatment was 0.16, the surface roughness (Ra ₃ ) was 0.26 μm. It was. The slope (μ / Ra) when the least squares regression line was determined for these three points was −0.159 (rounded down to four decimal places) (see FIG. 1A). “Roughening treatment” uses sandpaper # 1000 as a polishing material, a wrapping film (3M company, particle size 9 μm), a load of 1 kg / Φ50 mm cylinder, a number of polishing times 5 times, and a first-stage roughening treatment. Again, the number of times of polishing was set to 5 times for the second-stage roughening treatment. The friction coefficient and the surface roughness were measured before the roughening treatment, after the first roughening treatment, and after the second roughening treatment.

<Example 2>
(KCA type)
To N-methyl-2-pyrrolidone (NMP), 22 wt% of Vulcan (XC-72, Cabot Corporation, conductivity index = 85) and PTFE powder (KTL-8 Kitamura) 8 wt% were sequentially added, and after sufficient stirring, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is dissolved as an acid component, and approximately equimolar amount of p-phenylenediamine is dissolved as an amine component (monomer concentration: 20% by weight), and the reaction is conducted at room temperature with stirring. Then, the mixture was stirred while heating to 70 ° C. to prepare a polyamic acid solution having a viscosity of 2000 poise measured at 23 ° C. using a B-type viscometer.

  Furthermore, isoquinoline corresponding to 1 wt% of the polyamic acid solution was stirred and mixed at room temperature.

  Next, while fixing the rectangular die-type dispenser, while rotating the cylindrical mold having a length of 600 mm and a diameter of 80 mmφ, the resin solution containing the polyamic acid solution as a main component is transferred from one end of the inner surface of the cylindrical mold to the other. While feeding to the end, it was spirally applied to the inner surface of the cylindrical mold, and the unevenness of the wrapping part of the coating surface was leveled while rotating the mold at 3000 rpm for 3 minutes to obtain a uniform coating surface. .

  Next, while rotating the mold at 60 rpm, the solvent was removed stepwise to 220 ° C. to remove the solvent. The belt base material before imide conversion was released from the cylindrical mold, replaced with an aluminum pipe, and heated at 400 ° C. for 20 minutes to perform imide conversion.

  The obtained polyimide belt had a length of 580 mm, a diameter of 80 mmφ, and a thickness of 75 μm. The characteristics of the polyimide belt were a common logarithm of surface resistance of 4.0 (Ω / □), a tear strength of 5.9 N / mm, and a tensile modulus of 4000 Mpa.

  Next, this belt was spray-coated with methyl silicone rubber (Toray Dow Corning, DX35-2083) and then heated to form a 200 μm elastic layer. Further, a primer (Mitsui Dupont Fluorochemical, PRM-027-3) and a FEP dispersion paint (Mitsui Dupont Fluorochemical, ENA-020-45) are spray coated and heated on the silicone rubber, respectively, to 10 μm and 20 μm, respectively. A release layer was formed to prepare a fixing belt.

  The fixing belt is stretched between an aluminum heating roll having a diameter of 40 mm and an aluminum roll having a diameter of 20 mm, and an aluminum pressure roll covered with silicone rubber having a diameter of 40 mm is attached to the fixing belt portion that is associated with the heating roll from the opposite side. The nip width was set to 10 mm by applying a pressure of 0.2 Mpa. The recording paper was poured such that the heating roll temperature was 170 ° C. and the linear velocity of the fixing belt was 120 mm / sec, so that the toner came to the surface of the fixing belt.

  As a result, no release offset occurred after toner fixing. Even after printing 100,000 sheets, the driving of the belt was stable, and image shift, edge damage, buckling, and delamination were not observed.

The relationship between the friction coefficient (μ) and the surface roughness (Ra) when the polyimide belt is roughened is shown below. When the friction coefficient (μ ₀ ) before the roughening treatment is 0.10, the surface roughness (Ra ₀ ) is 0.09 μm, and the friction coefficient (μ ₁ ) after the first roughening treatment is 0.11. The surface roughness (Ra ₁ ) was 0.14 μm, and when the coefficient of friction (μ ₃ ) after the second-stage roughening treatment was 0.11, the surface roughness (Ra ₃ ) was 0.21 μm. It was. The slope (μ / Ra) when the least squares regression line was determined for these three points was 0.081 (rounded down to four decimal places) (see FIG. 1B). The roughening treatment method is the same as that in the first embodiment.

<Comparative Example 1>
(KUCA type)
To N-methyl-2-pyrrolidone (NMP), furnace black 22 wt% (special black 4, Degussa, conductivity index = 15) and PTFE powder (KTL-8 Kitamura) 4 wt% were sequentially added and stirred sufficiently. 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride as the acid component, and a mixture (molar ratio 8: 2) of p-phenylenediamine and 4,4′-diaminodiphenyl ether as the amine component. Mole was dissolved (monomer concentration 20% by weight), reacted while stirring at room temperature, then stirred while heating to 70 ° C. to prepare a polyamic acid solution having a viscosity of 2000 poise measured at 23 ° C. using a B-type viscometer. .

  Furthermore, isoquinoline corresponding to 1 wt% of the polyamic acid solution was stirred and mixed at room temperature.

  Next, while fixing the rectangular die-type dispenser, while rotating the cylindrical mold having a length of 600 mm and a diameter of 80 mmφ, the resin solution containing the polyamic acid solution as a main component is transferred from one end of the inner surface of the cylindrical mold to the other. While moving to the end, it was applied spirally to the inner surface of the cylindrical mold, and the unevenness of the wrapping part of the coating surface was leveled while rotating the mold at 1000 rpm for 3 minutes to obtain a uniform coating surface. . Next, while rotating the mold at 30 rpm, it was heated stepwise to 350 ° C. to remove the solvent and perform imide conversion. Next, the mold was released from the mold, and the resulting polyimide belt had a length of 580 mm, a diameter of 80 mmφ, and a thickness of 75 μm. The characteristics of the polyimide belt were a common logarithm of surface resistance of 10.5 (Ω / □), a tear strength of 7.1 N / mm, and a tensile modulus of 4500 Mpa.

  Next, this belt was spray-coated with methyl silicone rubber (Toray Dow Corning, DX35-2083) and then heated to form a 200 μm elastic layer. Further, a primer (Mitsui Dupont Fluorochemical, PRM-027-3) and a FEP dispersion paint (Mitsui Dupont Fluorochemical, ENA-020-45) are spray coated and heated on the silicone rubber, respectively, to 10 μm and 20 μm, respectively. A release layer was formed to prepare a fixing belt.

  The fixing belt is stretched between an aluminum heating roll having a diameter of 40 mm and an aluminum roll having a diameter of 20 mm, and an aluminum pressure roll covered with silicone rubber having a diameter of 40 mm is attached to the fixing belt portion that is associated with the heating roll from the opposite side. The nip width was set to 10 mm by applying a pressure of 0.2 Mpa. The recording paper was poured such that the heating roll temperature was 170 ° C. and the linear velocity of the fixing belt was 120 mm / sec. As a result, after the toner was fixed, dust that was an image defect occurred.

The relationship between the friction coefficient (μ) and the surface roughness (Ra) when the polyimide belt is roughened is shown below. When the friction coefficient (μ ₀ ) before the roughening treatment is 0.19, the surface roughness (Ra ₀ ) is 0.08 μm, and the friction coefficient (μ ₁ ) after the first roughening treatment is 0.17. The surface roughness (Ra ₁ ) was 0.15 μm, and when the coefficient of friction (μ ₃ ) after the second-stage roughening treatment was 0.16, the surface roughness (Ra ₃ ) was 0.23 μm. It was. The slope (μ / Ra) when the least squares regression line was calculated for these three points was −0.202 (rounded down to the fourth decimal place) (see FIG. 1C). The roughening treatment method is the same as that in the first embodiment.

<Comparative example 2>
(KC type)
Example 1 was the same as Example 1 except that the PTFE powder of Example 1 was not added. The obtained polyimide belt had a length of 580 mm, a diameter of 80 mmφ, and a thickness of 75 μm. The characteristics of the polyimide belt were a common logarithm of surface resistance of 3.6 (Ω / □), a tear strength of 6.8 N / mm, and a tensile modulus of 5700 MPa.

  Similarly, when a fixing belt formed with an elastic layer and a release layer is incorporated in the fixing section and the recording paper is flowed, the driving speed varies between the belt end portion and the center portion of 3000 sheets, image deviation occurs, and the belt end portion Began to break and buckled with 20,000 sheets.

Here, the relationship between the friction coefficient (μ) and the surface roughness (Ra) when the polyimide belt is roughened is shown below. When the friction coefficient (μ ₀ ) before the roughening treatment is 0.34, the surface roughness (Ra ₀ ) is 0.08 μm, and the friction coefficient (μ ₁ ) after the first roughening treatment is 0.27. The surface roughness (Ra ₁ ) was 0.16 μm, and when the coefficient of friction (μ ₃ ) after the second-stage roughening treatment was 0.25, the surface roughness (Ra ₃ ) was 0.24 μm. It was. The slope (μ / Ra) when the least squares regression line was determined for these three points was −0.553 (rounded down to the fourth decimal place) (see FIG. 1D). The roughening treatment method is the same as that in the first embodiment.

<Comparative Example 3>
(KA insulation type)
Example 1 was the same as Example 1 except that no carbon was added. The obtained polyimide belt had a length of 580 mm, a diameter of 80 mmφ, and a thickness of 75 μm. The characteristics of the polyimide belt were insulating properties (surface resistance of 10 ¹⁴ Ω / □ or more), tear strength of 8.4 N / mm, and tensile modulus of 4900 Mpa.

  Similarly, when a fixing belt formed with an elastic layer and a release layer is incorporated in the fixing section and the recording paper is flowed, the driving speed varies at the belt end portion and the central portion with 3000 sheets, image displacement occurs, and peeling offset, etc. , Charging failure (discharge, noise, paper sticking) occurred.

The relationship between the friction coefficient (μ) and the surface roughness (Ra) when the polyimide belt is roughened is shown below. When the friction coefficient (μ ₀ ) before the roughening treatment is 0.08, the surface roughness (Ra ₀ ) is 0.12 μm, and the friction coefficient (μ ₁ ) after the first roughening treatment is 0.10. The surface roughness (Ra ₁ ) was 0.18 μm, and when the friction coefficient (μ ₃ ) after the second-stage roughening treatment was 0.15, the surface roughness (Ra ₃ ) was 0.26 μm. It was. The slope (μ / Ra) when the least-squares regression line was determined for these three points was 0.484 (rounded down to the fourth decimal place) (see FIG. 1 (e)). The roughening treatment method is the same as that in the first embodiment.

<Comparative example 4>
(KCA type)
Example 1 was the same as Example 1 except that the PTFE powder of Example 1 was changed to 1 wt%. The obtained polyimide belt had a length of 580 mm, a diameter of 80 mmφ, and a thickness of 75 μm. The characteristics of this polyimide belt were a common logarithm of surface resistance of 3.7 (Ω / □), a tear strength of 6.7 N / mm, and a tensile elastic modulus of 5500 Mpa.

  Similarly, a fixing belt formed with an elastic layer and a release layer is incorporated in the fixing unit, and when recording paper is flowed, the driving speed varies at the belt end and the center with 10,000 sheets, and image misalignment occurs. Began to break and buckled with 30,000 sheets.

The relationship between the friction coefficient (μ) and the surface roughness (Ra) when this polyimide belt is roughened is shown below. When the friction coefficient before the roughening treatment (μ ₀ ) is 0.18, the surface roughness (Ra ₀ ) is 0.24 μm, and the friction coefficient (μ ₁ ) after the first roughening treatment is 0.20. The surface roughness (Ra ₁ ) was 0.18 μm, and when the coefficient of friction (μ ₃ ) after the second-stage roughening treatment was 0.21, the surface roughness (Ra ₃ ) was 0.16 μm. It was. The slope (μ / Ra) when the least squares regression line was determined for these three points was −0.365 (rounded down to the fourth decimal place) (see FIG. 1F). The roughening treatment method is the same as that in the first embodiment.

  According to the above embodiment, the polyimide belt of the present invention is an imide-converted resin solution mainly composed of a polyamic acid solution containing 2 to 20% by weight of a fluorine filler and 3 to 30% by weight of a carbon filler. The coefficient (μ) is 0.05 or more and 0.25 or less, the roughness Ra at that time is in the range of 0.05 to 0.35 μm, and the inner surface friction coefficient (μ) and the surface roughness (Ra) Polyimide belt having a slope (μ / Ra) in the range of −1/3 to 1/3 and a common logarithm of surface resistance of 1 to 8 (Ω / □) when a regression line of the least square method is obtained When a belt in which at least one of a rubber elastic layer or a fluororesin release layer is laminated on this polyimide belt is used as a fixing belt of an electrophotographic image forming apparatus, there is no peeling offset and no image shift and durability. Excellent Performance can be obtained.

Diagram showing the relationship between the coefficient of internal friction and surface roughness

Claims (4)

A polyimide resin solution containing 2 to 20% by weight of a fluorine filler and 3 to 30% by weight of a carbon filler having a conductivity index of 50 or more and 400 or less is heated to form an imide resin by heating. A polyimide belt obtained by conversion,
When the inner surface of the polyimide belt is roughened in a range where the surface roughness (Ra) is 0.05 μm or more and 0.35 μm or less, the friction coefficient (μ) of the inner peripheral surface of the belt before and after the roughening treatment is 0. The range is from 05 to 0.25, and the slope of the approximate straight line between the coefficient of friction (μ) before and after the roughening treatment and the surface roughness (Ra) is in the range of −1/3 to 1/3. A polyimide belt.   The polyimide belt according to claim 1, wherein a common logarithm of surface resistance of the polyimide belt is 1 to 8 (Ω / □).   A fixing belt formed by forming a rubber elastic layer and / or a fluororesin release layer on the outer surface side of the polyimide belt according to claim 1. Preparation for preparing a resin solution mainly composed of a polyamic acid solution containing 2 to 20% by weight of a fluorine filler and 3 to 30% by weight of a carbon filler having a conductivity index of 50 or more and 400 or less with respect to the polyimide resin solid content Process,
An application step of applying the resin solution to the inner surface of the cylindrical mold;
Centrifugal molding process for centrifugal molding to homogenize the resin film surface formed by application,
After the centrifugal molding, solvent removal, an imide conversion step of imide conversion, and a polyimide belt manufacturing method comprising:
Friction coefficient of the inner peripheral surface of the belt before and after roughening treatment when the inner surface of the polyimide belt obtained by the production method is roughened within a range of surface roughness (Ra) of 0.05 μm or more and 0.35 μm or less. (Μ) is in the range of 0.05 to 0.25, and the slope of the approximate straight line between the friction coefficient (μ) before and after the roughening treatment and the surface roughness (Ra) is −1/3 to 1/3. The manufacturing method of the polyimide belt characterized by the above-mentioned.

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