JP2002283368A - Polyimide belt - Google Patents

Abstract

(57) [Problem] To provide a polyimide belt used for an electrophotographic apparatus such as a laser beam printer or a facsimile, which can realize a low price of the electrophotographic apparatus. SOLUTION: In the endless belt mainly composed of polyimide, conductive inorganic powder is dispersed so that the surface resistivity of the outer peripheral surface is larger than the surface resistivity of the inner peripheral surface. It is a polyimide belt. The polyimide belt of the present invention does not require a surface coat layer having a high surface resistivity, which has been conventionally required, or the thickness thereof can be extremely reduced, so that the polyimide belt can be provided at low cost. As a result, an electrophotographic apparatus incorporating the intermediate transfer / fixing belt can be provided at low cost, and the spread of the electrophotographic apparatus can be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to a polyimide belt used for an electrophotographic device such as a laser beam printer, a facsimile, and a composite device thereof.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, a uniform charge is formed on a photoreceptor made of a conductive material, an electrostatic latent image is formed by a laser beam or the like that modulates an image signal, and then the toner is charged with a charged toner. The latent image is developed into a toner image. Next, the toner image is transferred to a recording medium such as paper directly or via an intermediate transfer member to obtain a desired image.

Here, a method in which a toner image on a photosensitive member is primarily transferred to an intermediate transfer member, and then a secondary transfer of the toner image on the intermediate transfer member to a recording medium such as paper, that is, an image employing an intermediate transfer system The intermediate transfer belt used in the forming apparatus is, for example, polyvinylidene fluoride (JP-A-5-200904).
No.), polycarbonate (JP-A-6-228335)
No.), a blend of an ethylene-tetrafluoroethylene copolymer and a polycarbonate (JP-A-6-149083)
A conductive endless belt in which a conductive agent such as carbon black is dispersed in a thermoplastic resin such as No.

Further, in recent years, a method of fixing a toner image on a recording medium by heating the intermediate transfer member, that is, an intermediate transfer and fixing method has been disclosed in Japanese Patent Application Laid-Open No. 6-258960. The endless belt used in this method includes
It is required to have mechanical strength to withstand the stress during driving and to withstand heat of about 250 ° C. given during fixing. From this demand, a polyimide resin having both high mechanical strength and heat resistance is used as a material used for the intermediate transfer and the fixing belt.

One of the characteristics required for the polyimide belt used in the intermediate transfer system is a volume resistivity, which preferably has a so-called medium resistance of about 5 × 10 ^{6 to} 5 × 10 ¹⁰ Ω · cm. It has been. Here, when the resistance is uniform with respect to the thickness of the belt, when the belt having the above volume resistance value is used as an intermediate transfer member, the toner of the toner image is transferred out of the normal transfer position and is transferred. It is known that a so-called phenomenon occurs. In order to prevent this, a method of coating the surface of the belt with a surface layer having a resistance value which is about one digit higher is usually adopted. However, in this method, it is essential that the surface coat layer has a thickness of about 10 to 20 μm. Therefore, this method excessively demands not only the processing cost but also the raw material cost of the surface coat layer, which has been a major factor in increasing the unit price of the polyimide belt. For further spread of the electrophotographic apparatus, it is an essential requirement to reduce the price. However, the high unit price of the polyimide belt also hinders the spread of the electrophotographic apparatus, and this is one of the items that electrophotographic apparatus manufacturers are extremely impoverished.

In order to solve the above problem, Japanese Patent Laid-Open No. 10-2
No. 26028 discloses a technique in which the surface resistivity of an outer peripheral surface of an endless belt containing polyamideimide as a main component is larger than that of an inner peripheral surface. However, since polyamideimide is significantly inferior in heat resistance and hydrolysis resistance to polyimide, it cannot be used for toner fixing applications involving heating at about 250 ° C., and therefore is not practically used for intermediate transfer and fixing methods. There is a problem that it cannot be used.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been developed in comparison with a conventional belt.
An object is to provide an inexpensive polyimide belt.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies on the manufacturing method and cross-sectional structure of a polyimide belt, and as a result, have found that a polyimide belt having a specific cross-sectional structure achieves the above object. As a result, the present invention has been completed.

That is, the polyimide belt of the present invention is such that in an endless belt mainly composed of polyimide, the surface resistivity of the outer peripheral surface is larger than the surface resistivity of the inner peripheral surface.
It is characterized in that the conductive inorganic powder is dispersed. Particularly, the inorganic powder is dispersed such that the surface resistivity of the belt outer peripheral surface is 1.1 to 100 times the surface resistivity of the inner peripheral surface.

[0010] Here, the "belt outer peripheral surface" according to the present invention means that when a polyimide belt is incorporated in an electrophotographic apparatus,
A surface on which a recording medium such as paper contacts. The “belt inner peripheral surface” according to the present invention refers to a surface on the opposite side of the belt outer peripheral surface.

Further, according to the present invention, the polyimide resin 1
At least 1 to 5 parts by weight of conductive carbon black (hereinafter, carbon black) and 1 part of inorganic powder (hereinafter, inorganic filler) other than carbon black are added to 00 parts by weight.
A polyimide belt formed from a resin composition blended with 50 to 50 parts by weight of the polyimide belt.
The object can be preferably achieved by setting the degree of orientation of the inorganic filler existing in No. 3 to be 0.2 or more larger than the degree of orientation of the inorganic filler existing in the inner third of the polyimide belt. Here, the outside 1/3 and the inside 1 of the polyimide belt
/ 3 means the outermost and innermost sides when the polyimide belt is divided into three concentric circles so as to have the same thickness.

The shape of the inorganic filler is not particularly limited, and a known shape can be applied to the present invention. Among them, a plate, a needle, and a column are particularly preferably used.
In particular, when the average aspect ratio of the inorganic filler is 10 or more, preferably 20 or more, the orientation of the inorganic filler can be preferably controlled.

In the polyimide belt having the above structure, the reason why the surface resistivity of the inner peripheral surface is smaller than the surface resistivity of the outer peripheral surface is that the orientation of the inorganic filler is disturbed.
That is, it is considered that the decrease in the degree of orientation of the inorganic filler causes an increase in the number of contact points between adjacent inorganic fillers. Therefore, it is considered that the electric resistance in the direction parallel to the surface, that is, the surface resistivity, is smaller on the inner peripheral surface of the polyimide belt than on the outer peripheral surface of the belt.

In the polyimide belt according to the present invention in which the above conditions are achieved, the surface resistivity of the outer peripheral surface of the belt is higher by about one digit than the surface resistivity of the inner peripheral surface of the belt. Does not require a high surface coat layer,
Alternatively, there is an advantage that the thickness can be extremely reduced. The surface resistivity of the belt outer peripheral surface is preferably 1.1 to 100 times that of the inner peripheral surface. When the surface resistivity of the outer peripheral surface of the belt is less than 1.1 times that of the inner peripheral surface, the effect of the present invention cannot be sufficiently exhibited, which is not preferable. On the other hand, when the value exceeds 100 times, the discharge takes precedence and the charging time is too short, which is not preferable.

The surface resistivity according to the present invention is obtained by measuring a sample under a constant atmosphere of 20 to 25 ° C. and 45 to 65% RH.
After standing for 4 hours or more, 100-500V under the same atmosphere
Is a value measured using the applied voltage of.

The degree of orientation according to the present invention is defined as follows: when a part of a belt is held horizontally, the belt surface at the horizontal part is used as a main axis, and the inclination angle θ of the inorganic filler long axis from the main axis is used. Is a value represented by the following equation. Here, the inorganic filler for obtaining the degree of orientation is selected at random from a portion held horizontally in the belt. Orientation degree = <3 cos ² θ-1> / 2

The type of the inorganic powder introduced into the resin is not particularly limited as long as at least carbon black and an inorganic filler are introduced. For example, the most effective method for controlling the resistance value is to mix a suitable amount of conductive inorganic powder such as carbon black in a resin. Oxide particles, titanium oxide, various inorganic particles, and whiskers formed of a film with a conductive material such as a metal oxide can be used, and the same effect as carbon black can be obtained. Further, an ionic conductive substance such as LiCl can be added. The purpose of controlling the thermal conductivity includes, for example, aluminum nitride, boron nitride, alumina, silicon carbide, silicon, silica, graphite and the like. Above all,
Boron nitride is preferred because it has a high heat conduction function, exhibits a releasing effect, is chemically stable, and is harmless.

The amount of the inorganic powder contained in the belt is not particularly limited. However, if the amount is too small, the intended performance cannot be sufficiently exhibited, and it is not preferable. If the amount is too large, the toughness of the resin is deteriorated. Therefore, from the above viewpoint, the composition in the polyimide belt is preferably such that the inorganic powder is in the range of 2 to 55 parts by weight with respect to 100 parts by weight of the polyimide.

The following methods can be used to control the degree of orientation of the inorganic filler in the polyimide belt. First, after applying the polyimide precursor solution to the inner surface or outer surface of the mold, the solvent is removed to some extent by a method such as drying under reduced pressure and drying under heating. Next, a method is effective in which the polyimide precursor belt is removed from the mold, a mold having an outer shape smaller than the inner diameter of the belt is inserted into the belt, and imidization is performed by heating. The difference between the inner diameter of the polyimide precursor belt when removed from the mold and the outer diameter of the mold to be inserted into this belt is not preferable because wrinkles occur in the imidized belt if it is too large, and it is too small. The desired degree of orientation of the inorganic powder cannot be obtained, and as a result, the polyimide belt may not exhibit high toughness, which is not preferable. Therefore, the difference between the inner diameter of the polyimide precursor belt when removed from the mold and the outer diameter of the mold inserted into the belt is preferably in the range of 0.3 to 20 mm.

As described above, the polyimide belt of the present invention exhibits the greatest effect when used for intermediate transfer and fixing in which the intermediate transfer and fixing are performed on the same belt. It can be preferably used also for fixing. In addition, as long as the polyimide belt of the present invention is in the above-mentioned application range, a device to be incorporated is not particularly limited. For example, a monocolor electrophotographic apparatus having only a single color (usually black) in the apparatus, a color electrophotographic apparatus in which a toner image carried on a photoreceptor is sequentially and primarily transferred to an intermediate transfer belt, and a developing apparatus for each color Any of a tandem-type color electrophotographic apparatus in which a plurality of latent image carriers provided with a device are arranged in series on an intermediate transfer belt may be used.

The polyamic acid is obtained, for example, by polymerizing an aromatic tetracarboxylic acid component and a diamine component in an organic polar solvent.

The aromatic tetracarboxylic acid component according to the present invention is not particularly limited. For example, butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3- Dimethyl-1,2,3,4
-Cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,5-
Tricarboxycyclopentylacetic acid dianhydride, 3,5
6-tricarboxynorbonane-2-acetic acid dianhydride,
2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, bicyclo [2 , 2,2] -Octo-
Aliphatic or alicyclic tetracarboxylic dianhydride such as 7-ene-2,3,5,6-tetracarboxylic dianhydride; pyromellitic dianhydride, 3,3 ′, 4,4′- Benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'
-Biphenylsulfonetetracarboxylic dianhydride, 1,
4,5,8-naphthalenetetracarboxylic dianhydride,
2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenylethertetracarboxylic dianhydride, 3,3 ′, 4,4′-dimethyldiphenylsilanetetracarboxylic Acid dianhydride, 3,3 ',
4,4'-tetraphenylsilanetetracarboxylic dianhydride, 1,2,3,4-furantetracarboxylic dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride , 4,4′-bis (3,4-dicarboxyphenoxy) diphenylsulfone dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 3,3 ′,
4,4'-perfluoroisopropylidene diphthalic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, bis (phthalic acid) phenylphosphine oxide dianhydride, p-phenylene- Bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (triphenylphthalic acid) dianhydride, bis (triphenylphthalic acid) -4,4'-diphenyl ether dianhydride, bis (triphenylphthalic acid) ) Aromatic tetracarboxylic dianhydrides such as -4,4'-diphenylmethane dianhydride;
3,3a, 4,5,9b-Hexahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-
1,3-dione, 1,3,3a, 4,5,9b-hexahydro-5-methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan- 1,3-dione, 1,3,3a, 4,5,9b-hexahydro-8-methyl-5- (tetrahydro-2,5-
Examples thereof include aliphatic tetracarboxylic dianhydrides having an aromatic ring such as dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione. These tetracarboxylic dianhydrides can be used alone or in combination of two or more.

The diamine used next is not particularly limited as long as it is a diamine. For example, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminophenylethane,
4,4′-diaminophenyl ether, 4,4′-didiaminophenyl sulfide, 4,4′-didiaminophenyl sulfone, 1,5-diaminonaphthalene, 3,3
-Dimethyl-4,4'-diaminobiphenyl, 5-amino-1- (4'-aminophenyl) -1,3,3-trimethylindane, 6-amino-1- (4'-aminophenyl) -1, 3,3-trimethylindane, 4,4'-
Diaminobenzanilide, 3,5-diamino-3′-trifluoromethylbenzanilide, 3,5-diamino-
4'-trifluoromethylbenzanilide, 3,4'-
Diaminodiphenyl ether, 2,7-diaminofluorene, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4′-methylene-bis (2-chloroaniline), 2,2 ′, 5,5′- Tetrachloro-4,
4'-diaminobiphenyl, 2,2'-dichloro-4,
4'-diamino-5,5'-dimethoxybiphenyl,
3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl ] Propane, 2,2-bis [4
-(4-aminophenoxy) phenyl] hexafluoropropane, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) -biphenyl, 1,3'-bis (4- Aminophenoxy) benzene, 9,9-bis (4-aminophenyl) fluorene, 4,4 ′-(p-phenyleneisopropylidene) bisaniline, 4,4 ′-(m-phenyleneisopropylidene) bisaniline, 2,2 ′ -Bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane, 4,4'-bis [4- (4-amino-2-trifluoromethyl) phenoxy] -octafluorobiphenyl and the like Aromatic diamine; two amino groups bonded to an aromatic ring such as diaminotetraphenylthiophene and the nitrogen of the amino group Aromatic diamine having a heteroatom other than a child; 1,1-methaxylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, nonamethylenediamine, 4,4-diaminoheptamethylene Diamine, 1,4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopentadienylenediamine, hexahydro-4,7-methanoindanylene dimethylenediamine, tricyclo [6,2,1,
0 ^2.7 ] -undecylenedimethyldiamine, 4,4 '
-Aliphatic diamines such as methylenebis (cyclohexylamine) and alicyclic diamines.
These diamine compounds can be used alone or in combination of two or more. As the diamine, it is preferable to use an aromatic diamine, but it is not particularly limited.

The organic polar solvent used in the polyamic acid formation reaction in the present invention includes, for example, sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylformamide and the like.
A formamide solvent such as N-diethylformamide,
Acetamide solvents such as N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-
Pyrrolidone-based solvents such as pyrrolidone and N-vinyl-2-pyrrolidone; phenol-based solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenols, and catechol; ether-based solvents such as tetrahydrofuran, dioxane, and dioxolane Solvents, alcohol solvents such as methanol, ethanol, butanol, etc., cellosolves such as butyl cellosolve or hexamethylphosphoramide, γ-butyrolactone, etc. can be mentioned, and it is desirable to use these alone or as a mixture, and more preferably xylene Aromatic hydrocarbons such as toluene can also be used. The solvent is not particularly limited as long as it dissolves the polyamic acid.

If the difference between the maximum thickness and the minimum thickness of the polyimide belt is too large, it causes wrinkling. The wrinkling of the belt induces a reduction in image quality when transferring or fixing is performed, so it is necessary to reduce the wrinkling as much as possible. From this point, it is desirable that the difference between the maximum thickness and the minimum thickness of the polyimide belt is not more than 20% of the average thickness of the polyimide belt.
The belt thickness referred to here is a thickness that can be measured by a thickness meter that measures the distance between a flat plate and an area of 5 mm ² or more in contact with the belt, and a protrusion having a width of 50 μm or less specifically present on the belt surface. It ignores the height of things.
In addition, the thickness of the polyimide belt is not preferable from the viewpoint of thermal conductivity and resistance value if too thick, and preferably too thin and the strength of the polyimide belt cannot be sufficiently secured at the same time the effect of the present invention cannot be sufficiently exhibited. Absent. Therefore, considering the use of the belt, the thickness of the belt is 10 to 5
It is desirably 00 μm, preferably 30 to 150 μm.

In this polyimide belt, a layer having another component may be appropriately laminated on the outer layer. Examples of the outer layer include, but are not limited to, polytetrafluoroethylene, polyvinylidene fluoride, and the like. Introducing an inorganic powder such as carbon black into these resins to impart conductivity may be appropriately selected.

Next, an example of a specific method for forming a polyimide belt will be described.

The aromatic tetracarboxylic acid component and the diamine component are polymerized in an organic solvent to obtain a polyimide resin precursor solution. Next, a total of 2 to 55 parts by weight of two or more inorganic powders is added to the solution based on 100 parts by weight of the dry weight of the polyamic acid resin.

As a method for incorporating the inorganic powder, a method in which the inorganic powder is mixed in an organic solvent, followed by a polymerization reaction of the aromatic tetracarboxylic acid component and the diamine component in the organic solvent, and during the polymerization reaction There is a method in which an inorganic powder or a dispersion thereof is mixed into a solution after the step or the completion of the reaction.

As a method for dispersing the inorganic powder and reducing the size of the aggregates, physical methods such as stirring with a mixer or a stirrer, parallel rolls, ultrasonic dispersion, and chemical methods such as introduction of a dispersant are used. An exemplary method is illustrated, but the method is not limited to this.

Next, this solution is uniformly applied to the inner surface or the outer surface of a cylindrical mold. As the molding die, any of various conventionally known materials such as resin, glass, ceramic, etc., can operate well as the molding die according to the present invention. Providing a glass coat, a ceramic coat, or the like on the surface of the mold, and using a silicone-based or fluorine-based release agent may be appropriately selected. Further, the mold for controlling the film thickness, the clearance of which has been adjusted with respect to the molding die, is moved in parallel through the molding die, thereby eliminating an excess solution and making the thickness of the solution on the molding die uniform. If a uniform thickness control of the solution is performed at the stage of applying the solution onto the mold, a mold for controlling the film thickness is not particularly required.

Next, the mold coated with the polyimide resin precursor solution is heated or placed in a reduced pressure environment to volatilize 30% or more, preferably 50% or more of the contained solvent, thereby exhibiting self-supporting properties. Let it.

Next, the polyimide precursor was removed from the molding die, and the inner diameter of the polyimide precursor belt was 0.5 mm.
A mold having an outer shape smaller by about 20 mm is inserted into a polyimide precursor belt, and the mold is heated at 200 ° C. to 450 ° C., so that the imide conversion reaction proceeds. Thereafter, the resin is removed from the mold, and a desired polyimide belt can be obtained.

[0034]

Next, embodiments of the polyimide belt and the method of manufacturing the same according to the present invention will be described in more detail.

[0035]

EXAMPLE In a vessel equipped with stirring blades, 1500 g of dimethylformamide (DMF) sufficiently dehydrated with a molecular sieve was added, and 200 g of 4,4'-diaminodiphenyl ether was added thereto, and the mixture was stirred until it was completely dissolved.

This system was cooled to about 0 ° C., and 218 g of pyromellitic dianhydride was gradually added thereto, followed by thorough stirring. Stop stirring when the viscosity of the system reaches about 300 Pa · s,
A polyamic acid solution was obtained.

Next, 60 g of the metal filler TM-200 (manufactured by Otsuka Chemical Co., Ltd.) and 300 g of DMF are placed in another container, stirred well, and further subjected to an ultrasonic disperser to uniformly disperse the metal filler in the dispersion. I let it. TM-20
0 is a plate-like filler having an average aspect ratio of 20
That is all.

In another container, 15 g of carbon black 3030B (manufactured by Mitsubishi Chemical Corporation) and DMF3
After adding 00 g, the mixture was stirred well and placed on an ultrasonic dispersing machine.

The above-obtained metal filler dispersion and carbon black dispersion were placed in the same beaker in an amount of 9 parts each.
8 g and 45 g were collected and stirred well. In this beaker, 300 g of the polyamic acid solution obtained above was dissolved and stirred well. In this way, a mixed solution containing about 3 parts by weight of carbon black and about 25 parts by weight of a metal filler based on 100 parts by weight of the dry weight of the polyamic acid resin was obtained.

The thus obtained polyamic acid
A metal filler-carbon black mixed solution was applied to an inner diameter of 82
The solution was applied to the entire inner surface of the cylindrical glass mold by pouring it into a cylindrical glass mold having a length of 450 mm and a length of 450 mm.

Next, a mold having a clearance of 0.7 mm with respect to the inner diameter of the glass mold is moved in the glass mold so that a 0.7 mm thick polyimide precursor is formed inside the glass mold. A solution layer was formed.

This glass mold was sealed in a square vacuum dryer having a side of 60 cm, and the pressure in the vacuum dryer was reduced to 10 ^-1 Pa by a rotary pump (manufactured by Ulvac), and the vacuum was reduced to 3 ^-1 Pa. It dried under reduced pressure for hours. In order to prevent the volatile solvent from damaging the inside of the rotary pump, a cold trap was installed between the vacuum dryer and the rotary pump to prevent the volatile solvent from being trapped.

Next, the polyimide precursor belt was removed from the glass mold using compressed air, and a mold having an outer diameter of 80 mm was inserted into the belt. By placing this mold in an oven and raising the temperature from room temperature to 380 ° C over about 30 minutes,
The imide conversion reaction was allowed to proceed. Thereafter, the mold was allowed to cool at room temperature, the resin was removed from the mold, and the desired polyimide belt was obtained.

The surface resistivity of the obtained polyimide belt was evaluated by the following method. 10 from the polyimide belt
A test piece of × 10 cm ² was cut out at 23 ° C. and 55% RH.
After being allowed to stand in the atmosphere for 24 hours or more, the measurement was carried out under the same atmosphere using a high resistance measuring device R8340 (manufactured by Advantest Co., Ltd.) equipped with a resistivity chamber R12702A. As a result, the surface resistivity of the outer peripheral surface was 5.4 × 10 ⁹ Ω / □, and the surface resistivity of the inner peripheral surface was 6.3 × 10 ⁸ Ω / □.

The degree of orientation of the inorganic filler in the obtained polyimide belt was evaluated by the following method. Five test pieces were cut out at random from the polyimide belt, and the section was observed with a scanning electron microscope (SEM). SEM
Was observed at an accelerating voltage of 15 kV and an observation magnification of 1000 using JSM-100 (JEOL Ltd.). The observation site was photographed, and the photograph was taken into a computer at a resolution of 300 dpi using an image scanner. In this way, five photographs were taken into a computer, and 50 inorganic fillers were randomly picked up from each photograph.

Since the carbon black is in a lump, the inorganic powder observed linearly at an observation magnification of 1000 can be determined to be the plate-like filler TM-200. 5 obtained
NIHima, an image analysis software, from the photos
The orientation degree of the inorganic filler in the polyimide belt was evaluated by measuring the inclination angle θ in the major axis direction of the inorganic filler with the belt surface as a main axis using the Ge1.6 and applying the above-described orientation degree conversion formula. .

As a result, the outer 1/3 of the polyimide belt
The degree of orientation of the inorganic filler existing in the polyimide belt was 0.91, and the degree of orientation of the inorganic filler existing in the inner third of the polyimide belt was 0.37.

A transfer test was performed using this polyimide belt. As a result, there was no image defect such as transfer dust, and an extremely good image could be stably supplied.

[0049]

Comparative Example 1 A polyimide belt was prepared in the same manner as in Example 1 except that ET-300W (manufactured by Ishihara Sangyo Co., Ltd.) was used as the inorganic filler.
The average aspect ratio of ET-300W is 1. The surface resistivity of the outer peripheral surface of this polyimide belt is 5.1 × 10 ⁹
Ω / □, and the surface resistivity of the inner peripheral surface is 5.4 × 10 ⁹ Ω
/ □. The aspect ratio of the inorganic filler is 1
Therefore, the degree of orientation could not be evaluated. Further, a transfer test was performed using this polyimide belt.
Several to several tens of transferred dusts were visually observed in the area of cm ² .

[0050]

[Comparative Example 2] Metal filler HJ-
A polyimide belt was prepared in the same manner as in Example 1 except that No. 1 (made by Ishihara Sangyo Co., Ltd.) was used. HJ-1 is an ellipsoidal filler having an average aspect of 5 to 8. The surface resistivity of the outer peripheral surface of this polyimide belt was 2.8 × 10 ⁸ Ω / □, and the surface resistivity of the inner peripheral surface was 3.4 × 10 ⁸ Ω / □. The degree of orientation of the inorganic filler present in the outer third of the polyimide belt is 0.3.
78, and the degree of orientation of the inorganic filler existing in the inner third of the polyimide belt was 0.59. Further, a transfer test was performed using this polyimide belt.
Several to several tens of transferred dusts were visually observed in the area of cm ² .

[0051]

As described above, the surface resistivity of the outer peripheral surface of the polyimide belt according to the present invention is higher than that of the inner peripheral surface. Since a layer becomes unnecessary or its thickness can be extremely reduced, a polyimide belt can be provided at low cost. As a result, an electrophotographic apparatus incorporating the intermediate transfer / fixing belt can be provided at low cost, and the spread of the electrophotographic apparatus can be promoted.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 79/08 C08L 79/08 Z G03G 15/16 G03G 15/16 15/20 102 15/20 102 // B29K 79:00 B29K 79:00 B29L 29:00 B29L 29:00 F term (reference) 2H033 AA23 AA31 BA12 BE09 2H200 FA09 FA13 GB22 GB40 JC04 JC13 JC15 JC16 MA02 MA13 MA14 MA17 MA20 MB04 4F071 AA60 AB03 AD06 AE15 A17 AF17 BC01 4F205 AA40 AB11 AB18 AC05 AG16 AR20 GA06 GB01 GC01 GC04 GE24 GF02 GN24 GW06 4J002 CM041 DA007 DA027 DA036 DE137 DE147 DF017 DJ007 DJ017 DK007 FA017 FA067 FA077 FA117 FB077 FD016 FD017 FD116 FD117 GF00 GM01

Claims (6)

[Claims] 1. An endless belt made of a resin composition containing a polyimide resin as a main component, wherein a surface resistivity of an outer peripheral surface is larger than a surface resistivity of an inner peripheral surface. 2. The polyimide belt according to claim 1, wherein the surface resistivity of the outer peripheral surface is 1.1 to 100 times the surface resistivity of the inner peripheral surface. 3. An endless belt made of a resin composition containing a polyimide resin as a main component and carbon black and an inorganic powder other than carbon black, and other than carbon black present in the outer third of the endless belt. Of the inorganic powder other than carbon black present in the inside 1/3 of the endless belt is 0.
The polyimide belt according to claim 1, wherein the polyimide belt is larger than the polyimide belt by two or more. 4. The method according to claim 1, wherein the resin composition is a polyimide resin.
The polyimide belt according to claim 3, which is a resin composition containing 1 to 5 parts by weight of carbon black and 1 to 50 parts by weight of an inorganic powder other than carbon black when the amount is 00 parts by weight. 5. The polyimide belt according to claim 3, wherein the resin composition contains at least one kind of inorganic powder having an average aspect ratio of 10 or more. 6. The polyimide belt according to claim 1, which is used for intermediate transfer and / or fixing of an electrophotographic apparatus.