JP6079275B2 - Intermediate transfer belt and image forming apparatus using the same - Google Patents

Description

  The present invention relates to an intermediate transfer belt and an image forming apparatus using the same.

  Conventionally, in an electrophotographic image forming apparatus, a belt, particularly a seamless belt, is used as a member for various purposes. Particularly in recent full-color image forming apparatuses, an intermediate transfer belt system in which developed images of four colors of yellow, magenta, cyan, and black are once color-superposed on an intermediate transfer medium and then collectively transferred to a transfer medium such as paper. Is used.

Such an intermediate transfer belt system has been used in a system that uses four color developing devices for one photoconductor, but has a drawback in that the printing speed is slow. For this reason, as a high-speed print, a four-tandem tandem method is used in which the photoreceptors are arranged for four colors and each color is continuously transferred to paper.
However, in this method, there are fluctuations due to the environment of the paper, etc., and it is very difficult to match the position accuracy of overlapping each color image, causing a color shift of the image.
Therefore, in recent years, it has become the mainstream to adopt the intermediate transfer method for the quadruple tandem method.

  Under such circumstances, intermediate transfer belts also have stricter required characteristics (high-speed transfer, positional accuracy) than before, and it is necessary to satisfy the characteristics corresponding to these requirements. ing. In particular, for positional accuracy, it is required to suppress variations due to deformation such as elongation of the belt itself due to continuous use. Further, the intermediate transfer belt is laid out over a wide area of the apparatus, and is required to be flame retardant because a high voltage is applied for transfer. In order to meet such demands, a polyimide resin that is a high elastic modulus and high heat resistance resin is mainly used as an intermediate transfer belt material.

  As an abnormal image generated in the transfer process, there is a so-called “white spot” in which toner is not transferred to an image portion, and a fine white spot is generated in a portion that is not transferred. “White spots” are likely to occur under conditions such as a low temperature and low humidity environment where a high transfer bias is applied, the back side during double-sided printing, and a paper type with high resistance.

As means for solving such “white spots”, it is known that a multilayer belt in which a layer having high resistance is laminated on the belt outer peripheral surface side can be solved. (For example, Japanese Patent Application Laid-Open No. 11-282277 of Patent Document 1, Japanese Patent Application Laid-Open No. 2009-258699 of Patent Document 2, Japanese Patent Application Laid-Open No. 2010-122437 of Patent Document 3)
It is considered that the high pressure resistance layer is laminated on the belt outer peripheral surface side to increase the pressure resistance of the belt and suppress the occurrence of “white spots”.

  On the other hand, when such a polyimide belt is used in an image forming apparatus, the temperature in the apparatus rises to about 50 ° C., and the belt gradually receives the influence of the temperature due to long-term use. Side). Therefore, there has been a problem that running failure and cleaning failure occur due to the warp of the belt, and durability is lowered.

  Japanese Patent Application Laid-Open No. 2005-309181 of Patent Document 4 proposes an intermediate transfer belt in which materials having different thermal expansion coefficients are laminated on an intermediate transfer belt, and a warp suppressing member is incorporated at the end of the belt that warps outward. ing. However, this proposed technique is not only easily worn by contact with the restraining member, but also the transfer pressure varies easily between the central part and the end part, resulting in variations in transfer performance, and is required for recent image forming apparatuses. There is a problem that a product that can satisfy a high level of image quality cannot be obtained.

  Japanese Patent No. 4396959 of Patent Document 5 proposes a semiconductive belt having an outer layer and an inner layer mainly composed of polyimide resin, and a difference in linear expansion coefficient between the outer layer and the inner layer being 30 ppm / ° C. or less. ing. However, although this proposed technique is good at the beginning, it gradually warps to the outer peripheral surface side during long-term use, and there is a problem that durability is low. Furthermore, the present invention is different in that it does not depend on the presence or absence of a difference in linear expansion coefficient, and is warped inward in advance.

  The present invention has been made in view of the above-described prior art, and provides an intermediate transfer belt that is excellent in durability without causing poor running due to warping of the belt and image unevenness, as well as the intermediate transfer belt. It is an object of the present invention to provide an image forming apparatus using a transfer belt.

As a result of intensive studies, the inventors of the present invention used a polyimide containing pyromellitic dianhydride and a diaminodiphenyl ether component as a base layer to warp inward, and adjust the amount of internal warping by laminating a polyimide without warping thereon. It has been found that a highly durable intermediate transfer belt free from running defects can be provided by offsetting (releasing) the belt warpage that occurs during long-term use in an image forming apparatus (previously warped inward).
In general, a polyimide containing pyromellitic dianhydride and a diaminodiphenyl ether component causes the coating film to greatly warp inward when it is released after drying in a mold due to the properties of the material. For this reason, the use of the above polyimide alone is not practical because of large warpage. Therefore, the present inventors have completed another invention by laminating another polyimide having no warp on the polyimide and adjusting the amount of warp.
Therefore, the above problems are solved by the following (1) to (8) of the present invention.
(1) A polyimide laminated intermediate transfer belt to which a toner image obtained by developing a latent image formed on an image bearing member with toner is transferred, an inner layer comprising a base material layer, and the base material layer An outer layer formed thereon, and the base material layer includes a polyimide having at least a structural unit derived from pyromellitic acid and a structural unit derived from diaminodiphenyl ether, and warps inward of the intermediate transfer belt An intermediate transfer belt having an amount of 1.0 mm or more and 10.0 mm or less. "
(2) “The intermediate transfer belt according to (1) above, wherein the average thickness of the base material layer is 20 μm or more and 80 μm or less, and the average thickness of the total belt film thickness is 40 μm or more and 140 μm or less.”
(3) “The intermediate transfer belt according to (1), wherein the outer layer contains 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride.”
(4) “The intermediate transfer belt according to (1), wherein the outer layer contains 4,4′-oxydiphthalic dianhydride”.
(5) “Intermediate transfer belt according to (1) above, wherein the belt circumferential length is 2000 mm or more.”
(6) “Intermediate transfer belt according to (1), which is a seamless belt”
(7) “An image carrier on which a latent image is formed and capable of carrying a toner image, a developing unit for developing the latent image formed on the image carrier with toner, and a toner image developed by the developing unit And an intermediate transfer belt on which the toner image carried on the intermediate transfer belt is secondarily transferred onto a recording medium. The intermediate transfer belt is configured as described in (1) to (6). Or an intermediate transfer belt according to any one of the above.
(8) “Full-color image forming apparatus according to (7), wherein a plurality of latent image carriers each having a developing unit for each color are arranged in series.”

  According to the present invention, since the belt and the base material layer side (inner side) are warped in advance (inward warping), there is no running failure due to belt end warping (outward warping) to the outer peripheral surface side that occurs during long-term use. An intermediate transfer belt to be mounted on a durable electrophotographic apparatus can be provided.

FIG. 3 is a diagram illustrating a layer configuration example of an intermediate transfer belt used in the present invention. It is a principal part schematic diagram which shows an example of the image forming apparatus equipped with the seamless belt which concerns on this invention. It is a principal part schematic diagram which shows another example of the image forming apparatus equipped with the seamless belt which concerns on this invention.

In an electrophotographic apparatus, a seamless belt is used for several members, and an intermediate transfer member (intermediate transfer belt) is one of important members that require electrical characteristics. The intermediate transfer belt of the present invention will be described below.
The seamless belt of the present invention comprises an intermediate transfer belt type electrophotographic apparatus [a so-called so-called image carrier (for example, a photosensitive drum) in which a plurality of color toner developed images sequentially formed are sequentially superimposed on the intermediate transfer belt. The apparatus is preferably equipped as an intermediate transfer belt in an apparatus that performs primary transfer and performs secondary transfer of the primary transfer image collectively onto a recording medium].
FIG. 1 shows a layer structure of an intermediate transfer belt preferably used in the present invention. As a constitution, a high resistance polyimide layer 12 having a high resistance is laminated on a polyimide base layer 11 containing at least pyromellitic dianhydride and a diaminodiphenyl ether component.

<Base material layer>
The base material layer includes at least a polyimide having a structural unit derived from pyromellitic acid and a structural unit derived from diaminodiphenyl ether, and further includes other components as necessary.

-Polyimide-
The polyimide has at least a structural unit derived from pyromellitic acid and a structural unit derived from diaminodiphenyl ether, and further includes other structural units as necessary.

-Structural unit derived from pyromellitic acid-
The structural unit derived from pyromellitic acid can be introduced into the polyimide by synthesizing polyimide using at least one of pyromellitic acid and pyromellitic dianhydride.

  The content of the structural unit derived from the pyromellitic acid in the polyimide is not particularly limited and may be appropriately selected depending on the purpose. However, the molar amount relative to the total amount of the structural unit derived from the polyvalent carboxylic acid in the polyimide is not limited. The ratio (structural unit derived from pyromellitic acid / total amount of structural unit derived from polyvalent carboxylic acid) is preferably 0.1 to 1.0, more preferably 0.2 to 1.0, and 0.3 to 1 0.0 is particularly preferred. When the content is within the particularly preferable range, it is advantageous in that it tends to be warped.

-Structural unit derived from diaminodiphenyl ether-
The structural unit derived from the diaminodiphenyl ether can be introduced into the polyimide by synthesizing the polyimide using diaminodiphenyl ether.

  Examples of the diaminodiphenyl ether include 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, and the like.

  There is no restriction | limiting in particular as content of the structural unit derived from the said diamino diphenyl ether in the said polyimide, Although it can select suitably according to the objective, The molar ratio (diamino) with respect to the structural unit total amount derived from the amine compound in the said polyimide. 0.1 to 1.0, more preferably 0.2 to 1.0, and particularly preferably 0.3 to 1.0 in terms of structural unit derived from diphenyl ether / total amount of structural unit derived from amine compound. When the content is within the particularly preferable range, it is advantageous in that flexibility is increased.

-Other structural units-
The other structural unit is not particularly limited and may be appropriately selected depending on the purpose. For example, a structural unit derived from a polyvalent carboxylic acid (excluding a structural unit derived from pyromellitic acid) And structural units derived from amine compounds (excluding structural units derived from the diaminodiphenyl ether).

  When the polyimide contains the other structural units as appropriate, the mechanical strength (high elasticity) and flexibility of the base material layer can be appropriately set.

Examples of the structural unit derived from the polyvalent carboxylic acid include a structural unit derived from an aromatic tetracarboxylic acid. Examples of the structural unit derived from the aromatic tetracarboxylic acid include a structural unit derived from 4,4′-oxydiphthalic acid and a structural unit derived from 3,3 ′, 4,4′-biphenyltetracarboxylic acid. Can be mentioned.
The structural unit derived from the aromatic polyvalent carboxylic acid is introduced into the polyimide by synthesizing the polyimide using at least one of the aromatic polyvalent carboxylic acid and the aromatic polyvalent carboxylic acid anhydride. Can do.

  Examples of the aromatic polyvalent carboxylic acid anhydride include 4,4′-oxydiphthalic dianhydride, ethylenetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 3,3 ′, 4,4. '-Benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2' , 3,3′-biphenyltetracarboxylic dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis ( 3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane Bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxylphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, , 2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2 , 7,8-phenanthrenetetracarboxylic dianhydride and the like. These may be used individually by 1 type and may use 2 or more types together.

Examples of the structural unit derived from the amine compound include a structural unit derived from an aromatic diamine compound. Examples of the structural unit derived from the aromatic diamine compound include a structural unit derived from p-phenylenediamine.
The structural unit derived from the aromatic diamine compound can be introduced into the polyimide by synthesizing polyimide using the aromatic diamine compound.

  Examples of the aromatic diamine compound include m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, bis (3-aminophenyl) sulfide, (3-amino Phenyl) (4-aminophenyl) sulfide, bis (4-aminophenyl) sulfide, bis (3-aminophenyl) sulfide, (3-aminophenyl) (4-aminophenyl) sulfoxide, bis (3-aminophenyl) sulfone , (3-aminophenyl) (4-aminophenyl) sulfone, bis (4-aminophenyl) sulfone, 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3, 3'-diaminodiphenylmethane, 3,4 ' Diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] methane, 1,1-bis [4- (3- Aminophenoxy) phenyl] ethane, 1,1-bis [4- (4-aminophenoxy) phenyl] -ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [ 4- (4-aminophenoxy) phenyl] ethane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2, 2-bis [4- (3-aminophenoxy) phenyl] butane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3 3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,3-bis (3-aminophenoxy) Benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (3- Aminophenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4 -(3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) sulfide Enyl] sulfoxide, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 4,4′-bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [3- (3-aminophenoxy) benzoyl] diphenyl ether, 4, 4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4, 4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, bis [4- {4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4 -(4-aminophenoxy) phenoxy] -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, and the like. These may be used individually by 1 type, and may use 2 or more types together.

  When the polyimide contains the other structural units as appropriate, the mechanical strength (high elasticity) and flexibility of the base material layer can be appropriately set.

--- Polyimide synthesis method--
The polyimide, particularly the aromatic polyimide, is insoluble in solvents and the like due to its rigid main chain structure and has an infusible property. Therefore, for example, the polyimide first synthesizes a polyimide precursor (polyamic acid or polyamic acid) that is soluble in an organic solvent by a reaction between an aromatic polyvalent carboxylic acid anhydride and an aromatic diamine compound. The polyamic acid is synthesized by various methods at the polyamic acid stage, and then cyclized (imidized) by subjecting the polyamic acid to a dehydration reaction by heating or a chemical method. Taking the reaction of obtaining an aromatic polyimide as an example, an outline of one example of the method for synthesizing the polyimide is shown in the following reaction formula (I).

ただし、前記反応式（Ｉ）中、Ａｒ^１は、少なくとも１つの芳香族基を有する４価の芳香族残基を表わし、Ａｒ^２は、少なくとも１つの芳香族基を有する２価の芳香族残基を表わす。

In the reaction formula (I), Ar ¹ represents a tetravalent aromatic residue having at least one aromatic group, and Ar ² represents a divalent aromatic residue having at least one aromatic group. Represents a group.

  Here, in the present invention, the structural unit derived from tetracarboxylic acid which is the aromatic polyvalent carboxylic acid is a structural unit represented by the following general formula (1) having a structure obtained by removing a nitrogen atom from an imide bond. means. The same applies to the structural unit derived from pyromellitic acid.

ただし、前記一般式（１）中、Ａｒ^１は、前記反応式（Ｉ）中のＡｒ^１と同じである。

However, in the general formula (1), Ar ¹ is the same as Ar ¹ in the reaction formula (I).

  Moreover, the structural unit derived from the said aromatic diamine compound means the structural unit represented by following General formula (2) remove | excluding two carbonyl groups from the imide bond. The same applies to the structural unit derived from the diaminodiphenyl ether.

ただし、前記一般式（２）中、Ａｒ^２は、前記反応式（Ｉ）中のＡｒ^２と同じである。

However, Ar ² in the general formula (2) is the same as Ar ² in the reaction formula (I).

  For example, a polyimide precursor (polyamic acid) can be obtained by performing a polymerization reaction in an organic solvent using substantially equimolar amounts of the aromatic polyvalent carboxylic acid anhydride and the aromatic diamine compound. At this time, at least one of the pyromellitic acid and the pyromellitic dianhydride and the diaminodiphenyl ether are used in order to obtain the polyimide.

There is no restriction | limiting in particular as an organic solvent used for the polymerization reaction of the said polyamic acid, Although it can select suitably according to the objective, An organic polar solvent is preferable.
Examples of the organic polar solvent include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; N, N-dimethylacetamide and N, N- Acetamide solvents such as diethylacetamide; Pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; Phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, catechol, etc. Phenol solvents such as tetrahydrofuran, dioxane and dioxolane; alcohol solvents such as methanol, ethanol and butanol; cellosolv solvents such as butyl cellosolve; hexamethylphosphoramide and γ-butyrolactone It is. These may be used individually by 1 type and may use 2 or more types together. Among these, N, N-dimethylacetamide and N-methyl-2-pyrrolidone are preferable because of high solubility and easy polymerization.

A method for synthesizing the polyimide precursor is illustrated below.
First, in an inert gas atmosphere such as argon or nitrogen, the diamine compound containing at least the 4,4′-diaminodiphenyl ether is dissolved in the organic solvent or dispersed in a slurry. To this solution, the above-described aromatic polycarboxylic acid anhydride containing at least the pyromellitic dianhydride, or a derivative thereof is added (may be in a solid state, in a solution state dissolved in an organic solvent, or in a slurry state. ), A ring-opening polyaddition reaction occurs with heat generation, the viscosity of the solution is rapidly increased, and a high molecular weight polyamic acid solution is obtained.
There is no restriction | limiting in particular as reaction time in the synthesis | combination of the said polyimide precursor, According to the objective, it can select suitably, For example, about 30 minutes-12 hours are mentioned.
There is no restriction | limiting in particular as reaction temperature in the synthesis | combination of the said polyimide precursor, Although it can select suitably according to the objective, -20 degreeC-100 degreeC is preferable and it is more preferable that it is 60 degrees C or less.

  The above is an example. Contrary to the addition procedure in the reaction, the aromatic polycarboxylic acid anhydride or derivative thereof is first dissolved or dispersed in an organic solvent, and the aromatic diamine compound is added to this solution. You may let them. The aromatic diamine compound may be added in a solid state, in a solution state dissolved in an organic solvent, or in a slurry state. That is, the mixing order of the aromatic polycarboxylic dianhydride and the aromatic diamine compound is not limited. Further, an aromatic tetracarboxylic dianhydride as an aromatic polyvalent carboxylic acid anhydride and an aromatic diamine compound may be simultaneously added to an organic polar solvent for reaction.

  As described above, the polyamic acid is uniformly mixed in the organic polar solvent by polymerizing the aromatic polyvalent carboxylic acid anhydride or derivative thereof and the aromatic diamine compound in an organic polar solvent in an equimolar amount. A polyimide precursor solution is obtained in a dissolved state.

The polyamic acid can be imidized by a heating method (1) or a chemical method (2). The heating method (1) is a method of converting polyamic acid to polyimide by, for example, heat treatment at 200 ° C. to 350 ° C., and is a simple and practical method for obtaining polyimide (polyimide resin). On the other hand, the chemical method (2) is a method in which a polyamic acid is reacted with a dehydrating cyclization reagent (such as a mixture of a carboxylic acid anhydride and a tertiary amine) and then heat-treated to completely imidize, (1 The method (1) is often used because the method is more complicated and costly than the method of heating.
In order to exhibit the intrinsic performance of polyimide, it is preferable to complete imidization by heating to a temperature above the glass transition temperature of the corresponding polyimide.

-Other ingredients-
The other component is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include an electric resistance adjusting material, a dispersion aid, a reinforcing material, a lubricant, a heat conducting material, and an antioxidant. It is done.

<Surface layer (high resistance layer)>
The surface layer to be laminated on the base material layer may be any polyimide as long as it is the above-mentioned polyimide other than the structural unit derived from pyromellitic acid, and is 3, 3 ′, 4, 4 ′ in terms of flexibility and strength. -It is desirable to contain biphenyltetracarboxylic dianhydride or 4,4'-oxydiphthalic dianhydride, and to make resistance higher than a base material layer.

--- Electrical resistance adjuster ---
The electrical resistance adjuster is a filler (or additive) that adjusts the electrical resistance in the base material layer.
Examples of the electric resistance adjusting material include metal oxide, carbon black, an ionic conductive agent, and a conductive polymer material.
Examples of the metal oxide include zinc oxide, tin oxide, titanium oxide, zirconium oxide, aluminum oxide, and silicon oxide. In addition, in order to improve dispersibility, the metal oxide may be subjected to surface treatment in advance.
Examples of the carbon black include ketjen black, furnace black, acetylene black, thermal black, and gas black.
Examples of the ionic conductive agent include tetraalkyl ammonium salt, trialkyl benzyl ammonium salt, alkyl sulfonate, alkyl benzene sulfonate, alkyl sulfate, glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene. Examples include fatty alcohol esters, alkyl betaines, and lithium perchlorates.
Examples of the conductive polymer material include polyparaphenylene, polyaniline, polythiophene, polyparaphenylene vinylene, and the like.
The electrical resistance adjusting material may be used alone or in combination of two or more.

The content of the electrical resistance adjusting material in the present invention is not particularly limited and can be appropriately selected according to the purpose. However, when the electrical resistance adjusting material is the carbon black, the base material layer, 10 mass%-25 mass% are respectively preferable with respect to a surface layer, and 15 mass%-20 mass% are more preferable. Moreover, when the said electrical resistance adjusting material is the said metal oxide, 1 mass%-50 mass% are preferable with respect to the said base material layer and a surface layer, and 10 mass%-30 mass% are more preferable.
When the content is less than the lower limit value of the preferred range, the effect of adjusting the electrical resistance may not be sufficiently obtained. When the content exceeds the upper limit value of the preferred range, the mechanical strength of the intermediate transfer belt is increased. May decrease.

There is no restriction | limiting in particular as average thickness of the said base material layer and a surface layer, Although it can select suitably according to the objective, 20 micrometers-80 micrometers are preferable, and 30 micrometers-70 micrometers are more preferable. When the average thickness is less than 20 μm, the amount of internal warpage becomes too small, and when the average thickness exceeds 80 μm, the internal warp of the intermediate transfer belt becomes too large. The average thickness of the entire belt is preferably 40 μm to 140 μm, more preferably 50 μm to 120 μm. If the average thickness of the entire belt is less than 40 μm, the belt is likely to be cut off from the end portion, and if it exceeds 140 μm, the belt is liable to be broken by bending with the roller.
The average thickness is an average value when 10 thicknesses are arbitrarily measured. The thickness can be measured by, for example, an electric micrometer manufactured by Anritsu.

The electric resistance of the intermediate transfer belt is not particularly limited and may be appropriately selected according to the purpose. However, due to the above-described abnormal image problem such as white spots, the back surface has a surface resistance value of 1 × 10 ⁸ Ω / □ to 1 × 10 ¹⁴ Ω / □, the surface is 1 × 10 ⁹ Ω / □ to 1 × 10 ¹⁵ Ω / □ to increase the surface resistance of the surface, and the volume resistance value is 1 × 10 ⁷ Ω · cm to 1 ×. It is preferably 10 ¹³ Ω · cm.

  As the base material layer, an endless base material layer is preferable.

-Formation method of base material layer and surface layer-
The method for forming the intermediate transfer belt is not particularly limited and may be appropriately selected depending on the purpose. For example, the electrical resistance adjusting material may be added to the polyimide precursor solution (polyamic acid solution) as necessary. A coating liquid in which the above-mentioned other components are dispersed is prepared, and after the coating liquid is applied to a support, a layer is formed by treatment such as heating, and a polyamic acid that is a polyimide precursor The method of forming by performing conversion (imidation) from a to polyimide is mentioned.
There is no restriction | limiting in particular as said support body, According to the objective, it can select suitably, For example, a cylindrical metal metal mold | die etc. are mentioned.

An example of a method for manufacturing the intermediate transfer belt will be specifically described.
While slowly rotating a cylindrical mold, for example, a cylindrical metal mold, a coating liquid containing a polyimide precursor is applied to the entire outer surface of the cylindrical mold with a liquid supply device such as a nozzle or a dispenser. Apply and cast (form a coating) so that it is uniform. Thereafter, the rotation speed is increased to a predetermined speed, and when the predetermined speed is reached, the rotation speed is maintained at a constant speed and the rotation is continued for a desired time. And the solvent in a coating film is evaporated at the temperature of 80 to 150 degreeC, raising temperature gradually, rotating. In this process, it is preferable to efficiently circulate and remove atmospheric vapor (such as a volatilized solvent). When a self-supporting film is formed, the mold is transferred to a heating furnace (firing furnace) capable of high-temperature processing, and the temperature is raised stepwise, and finally high-temperature heat processing (firing) at about 250 ° C to 450 ° C. The polyimide precursor is imidized to some extent. At this time, if the imidization is complete, the adhesiveness with the polyimide with the surface layer to be laminated next is deteriorated. After sufficiently cooling, the surface layer coating solution is then applied and dried in the same manner as the substrate layer, and the polyimide precursor is sufficiently imidized here.

<War amount of intermediate transfer belt>
The amount of warpage of the intermediate transfer belt can be obtained by using a sample cut into a 10 cm square and measuring the portion with the largest warpage after leaving it in a 25 ° C., 50 RH environment for 24 hours. In addition, outward curvature (warp to the surface layer side) is negative, and internal warpage (warpage to the base material layer side) is positive. According to this measurement method, the warp amount of the belt is preferably in the range of +1.0 mm to +10.0 mm, more preferably +2.0 mm to +8.0 mm. The effect is low at +1.0 mm or less, and warping occurs immediately during paper feeding. If it is +10 mm or more, the amount of inner warp is too large, and belt running failure occurs from the initial stage of paper feeding, which is not preferable.

  The intermediate transfer belt preferably has a peripheral length of 2000 mm or more and has a seamless shape in order to increase the speed, image quality, and the number of photosensitive drums (developing units) in recent electrophotographic apparatuses.

<Image forming apparatus>
For example, the seamless belt manufactured by the above-described method performs primary transfer by sequentially superimposing a plurality of color toner developed images sequentially formed on an image carrier on an intermediate transfer belt, and the primary transfer image is recorded. It can be suitably used as an intermediate transfer belt of a so-called intermediate transfer type electrophotographic apparatus that performs secondary transfer collectively onto a medium, and can form an electrophotographic image forming apparatus capable of forming a high-quality image.
The seamless belt used in the belt constituting unit provided in the image forming apparatus according to the present invention will be described in detail below with reference to a schematic diagram of the relevant part. The schematic diagram is an example, and the present invention is not limited to this.
FIG. 2 is a schematic diagram of a main part for explaining an image forming apparatus equipped with a seamless belt obtained by the manufacturing method according to the present invention as a belt member. The intermediate transfer unit 500 including the belt member shown in FIG. 2 includes an intermediate transfer belt 501 that is an intermediate transfer member stretched around a plurality of rollers. Around the intermediate transfer belt 501, a secondary transfer bias roller 605 that is a secondary transfer charge applying unit of the secondary transfer unit 600, a belt cleaning blade 504 that is an intermediate transfer member cleaning unit, and a lubricant for a lubricant application unit. A lubricant application brush 505 or the like that is an application member is disposed so as to face each other.

  A position detection mark (not shown) is provided on the outer peripheral surface or the inner peripheral surface of the intermediate transfer belt 501. However, on the outer peripheral surface side of the intermediate transfer belt 501, it is necessary to devise a position detection mark that avoids the passing area of the belt cleaning blade 504, which may be difficult to arrange. A position detection mark may be provided on the inner peripheral surface side of the intermediate transfer belt 501. An optical sensor 514 serving as a mark detection sensor is provided at a position between the primary transfer bias roller 507 and the belt driving roller 508 where the intermediate transfer belt 501 is bridged.

  The intermediate transfer belt 501 includes a primary transfer bias roller 507, a belt driving roller 508, a belt tension roller 509, a secondary transfer counter roller 510, a cleaning counter roller 511, and a feedback current detection roller 512, which are primary transfer charge applying units. It is stretched around. Each roller is formed of a conductive material, and each roller other than the primary transfer bias roller 507 is grounded. The primary transfer bias roller 507 is applied with a transfer bias controlled to a predetermined current or voltage according to the number of superimposed toner images by a primary transfer power source 801 controlled at a constant current or voltage. ing.

  The intermediate transfer belt 501 is driven in the arrow direction by a belt driving roller 508 that is driven to rotate in the arrow direction by a drive motor (not shown). The intermediate transfer belt 501 as a belt member is usually a semiconductor or an insulator and has a single-layer or multi-layer structure. However, in the present invention, a seamless belt is preferably used, thereby improving durability. Excellent image formation can be realized. Further, the intermediate transfer belt is set to be larger than the maximum sheet passing size in order to superimpose the toner images formed on the photosensitive drum 200.

  A secondary transfer bias roller 605 serving as a secondary transfer unit is attached to and separated from a belt outer peripheral surface of the intermediate transfer belt 501 in a portion stretched around the secondary transfer counter roller 510 by a contact / separation mechanism, which will be described later. It is configured to be able to contact and separate. The secondary transfer bias roller 605 is disposed so as to sandwich the transfer paper P, which is a recording medium, between the portion of the intermediate transfer belt 501 stretched around the secondary transfer counter roller 510 and a constant current. A transfer bias having a predetermined current is applied by a secondary transfer power source 802 to be controlled.

  The registration roller 610 feeds the transfer sheet P, which is a transfer material, between the secondary transfer bias roller 605 and the intermediate transfer belt 501 stretched around the secondary transfer counter roller 510 at a predetermined timing. The secondary transfer bias roller 605 is in contact with a cleaning blade 608 as a cleaning unit. The cleaning blade 608 is for removing the adhering matter adhering to the surface of the secondary transfer bias roller 605 for cleaning.

  In the color copying machine having such a configuration, when an image forming cycle is started, the photosensitive drum 200 is rotated in a counterclockwise direction indicated by an arrow by a drive motor (not shown), and Bk ( Black) toner image formation, C (cyan) toner image formation, M (magenta) toner image formation, and Y (yellow) toner image formation are performed. The intermediate transfer belt 501 is rotated clockwise by the belt driving roller 508 as indicated by an arrow. As the intermediate transfer belt 501 rotates, the primary transfer of the Bk toner image, the C toner image, the M toner image, and the Y toner image is performed by the transfer bias by the voltage applied to the primary transfer bias roller 507. Finally, the respective toner images are formed on the intermediate transfer belt 501 in the order of Bk, C, M, and Y.

For example, the Bk toner image formation is performed as follows. In FIG. 2, a charging charger 203 uniformly charges the surface of the photosensitive drum 200 to a predetermined potential with a negative charge by corona discharge. The timing is determined based on the belt mark detection signal, and raster exposure with laser light is performed based on the Bk color image signal by a writing optical unit (not shown).
When this raster image is exposed, the charge proportional to the exposure light amount disappears in the exposed portion of the surface of the photosensitive drum 200 that is initially uniformly charged, and a Bk electrostatic latent image is formed. When the negatively charged Bk toner on the developing roller of the Bk developing device 231K comes into contact with this Bk electrostatic latent image, the toner does not adhere to the remaining portion of the photosensitive drum 200, and the charge is not charged. The toner is attracted to the unexposed portion, that is, the exposed portion, and a Bk toner image similar to the electrostatic latent image is formed.

  The Bk toner image formed on the photosensitive drum 200 in this manner is primarily transferred onto the belt outer peripheral surface of the intermediate transfer belt 501 that is rotating at a constant speed while being in contact with the photosensitive drum 200. Some untransferred residual toner remaining on the surface of the photoreceptor drum 200 after the primary transfer is cleaned by the photoreceptor cleaning device 201 in preparation for reuse of the photoreceptor drum 200. On the photosensitive drum 200 side, the process proceeds to the C image forming process after the Bk image forming process, and reading of C image data by a color scanner starts at a predetermined timing. By writing laser light with the C image data, the photosensitive drum A C electrostatic latent image is formed on the surface of 200.

Then, after the rear end portion of the previous Bk electrostatic latent image passes and before the front end portion of the C electrostatic latent image reaches, the revolver developing unit 230 is rotated, and the C developing machine 231C is developed. The C electrostatic latent image is developed with C toner. Thereafter, the development of the C electrostatic latent image area is continued. When the rear end of the C electrostatic latent image passes, the revolver developing unit is rotated in the same manner as in the case of the previous Bk developing machine 231K, and the next The M developing machine 231M is moved to the developing position.
This is also completed before the leading edge of the next Y electrostatic latent image reaches the developing position. Note that the M and Y image forming steps are the same as the Bk and C steps described above because the operations of reading color image data, forming an electrostatic latent image, and developing are the same as those described above.

  The Bk, C, M, and Y toner images sequentially formed on the photosensitive drum 200 in this manner are sequentially aligned on the same surface on the intermediate transfer belt 501 and primarily transferred. As a result, a toner image having a maximum of four colors superimposed on the intermediate transfer belt 501 is formed. On the other hand, at the time when the image forming operation is started, the transfer paper P is fed from a paper feed unit such as a transfer paper cassette or a manual feed tray, and is waiting at the nip of the registration roller 610. When the leading edge of the toner image on the intermediate transfer belt 501 reaches the secondary transfer portion where the nip is formed by the intermediate transfer belt 501 stretched around the secondary transfer counter roller 510 and the secondary transfer bias roller 605. Then, the registration roller 610 is driven so that the leading edge of the transfer paper P coincides with the leading edge of the toner image, and the transfer paper P is conveyed along the transfer paper guide plate 601, and the transfer paper P and the toner image are transferred. Resist alignment is performed.

  In this way, when the transfer paper P passes through the secondary transfer portion, the four-color superimposed toner image on the intermediate transfer belt 501 is transferred by the transfer bias applied by the secondary transfer power source 802 to the secondary transfer bias roller 605. Are collectively transferred (secondary transfer) onto the transfer paper P. After the transfer paper P is conveyed along the transfer paper guide plate 601 and passed through a portion facing the transfer paper neutralization charger 606 composed of a static elimination needle disposed on the downstream side of the secondary transfer portion, the transfer paper P is discharged. Then, it is sent toward the fixing device 270 by the belt conveying device 210 which is a belt component (see FIG. 3). Then, after the toner image is melted and fixed at the nip portions of the fixing rollers 271 and 272 of the fixing device 270, the transfer paper P is sent out of the apparatus main body by a discharge roller (not shown), and is stacked face up on a copy tray (not shown). Is done. Note that the fixing device 270 may be configured to include a belt component if necessary.

  On the other hand, the surface of the photosensitive drum 200 after the belt transfer is cleaned by the photosensitive member cleaning device 201 and is uniformly discharged by the discharging lamp 202. Further, residual toner remaining on the outer peripheral surface of the intermediate transfer belt 501 after the toner image is secondarily transferred to the transfer paper P is cleaned by the belt cleaning blade 504. The belt cleaning blade 504 is configured to be brought into contact with and separated from the belt outer peripheral surface of the intermediate transfer belt 501 at a predetermined timing by a cleaning member separating and contacting mechanism (not shown).

  On the upstream side of the belt cleaning blade 504 in the movement direction of the intermediate transfer belt 501, a toner seal member 502 that is in contact with and away from the outer peripheral surface of the intermediate transfer belt 501 is provided. The toner seal member 502 receives the falling toner that has fallen from the belt cleaning blade 504 when cleaning the residual toner, and prevents the falling toner from being scattered on the transfer path of the transfer paper P. The toner seal member 502 is brought into contact with and separated from the belt outer peripheral surface of the intermediate transfer belt 501 together with the belt cleaning blade 504 by the cleaning member separating and contacting mechanism.

  The lubricant 506 scraped by the lubricant application brush 505 is applied to the outer peripheral surface of the intermediate transfer belt 501 from which the residual toner has been removed in this way. The lubricant 506 is made of, for example, a solid body such as zinc stearate, and is disposed so as to come into contact with the lubricant application brush 505. Further, residual charges remaining on the outer peripheral surface of the intermediate transfer belt 501 are removed by a neutralizing bias applied by a belt neutralizing brush (not shown) that is in contact with the outer peripheral surface of the intermediate transfer belt 501. Here, the lubricant application brush 505 and the belt neutralizing brush are brought into contact with and separated from the belt outer peripheral surface of the intermediate transfer belt 501 at a predetermined timing by respective contact and separation mechanisms (not shown). .

  Here, in the case of repeat copy, the operation of the color scanner and the image formation on the photosensitive drum 200 are performed at a predetermined timing following the first color (Y) image formation process of the first sheet and the first color of the second sheet. The process proceeds to the image forming process (Bk). Further, the intermediate transfer belt 501 has a second Bk toner in the area cleaned by the belt cleaning blade 504 on the outer peripheral surface of the belt following the batch transfer process of the first four-color superimposed toner image to the transfer paper. The image is first transferred. After that, the operation is the same as the first sheet. The above is a copy mode for obtaining a four-color full-color copy. In the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and number of times. In the case of the single color copy mode, only the predetermined color developing machine of the revolver developing unit 230 is set in the developing operation state until the predetermined number of sheets is completed, and the belt cleaning blade 504 is kept in contact with the intermediate transfer belt 501. The copy operation is performed in the state.

In the above-described embodiment, the copying machine having only one photosensitive drum has been described. However, the present invention can seamlessly include a plurality of photosensitive drums as shown in a configuration example in the schematic diagram of the main part in FIG. The present invention can also be applied to an image forming apparatus arranged side by side along one intermediate transfer belt made of a belt.
FIG. 3 shows a configuration of a four-drum type digital color printer including four photosensitive drums 21BK, 21Y, 21M, and 21C for forming toner images of four different colors (black, yellow, magenta, and cyan). An example is shown.

  In FIG. 3, the printer body 10 includes an image writing unit 12, an image forming unit 13, and a paper feeding unit 14 for performing color image formation by an electrophotographic method. Based on the image signal, the image processing unit converts the image into black (BK), magenta (M), yellow (Y), and cyan (C) color signals for image formation and transmits them to the image writing unit 12. To do. The image writing unit 12 is a laser scanning optical system including, for example, a laser light source, a deflector such as a rotary polygon mirror, a scanning imaging optical system, and a mirror group. Image writing corresponding to each color signal is performed on image carriers (photoconductors) 21BK, 21M, 21Y, and 21C that have a writing optical path and are provided for each color of the image forming unit 13.

  The image forming unit 13 includes photoconductors 21BK, 21M, 21Y, and 21C that are image carriers for black (BK), magenta (M), yellow (Y), and cyan (C). As each photoconductor for each color, an OPC photoconductor is usually used. Around the photoreceptors 21BK, 21M, 21Y, and 21C, there are a charging device, an exposure unit for laser light from the writing unit 12, and developing devices 20BK, 20M, 20Y for black, magenta, yellow, and cyan, respectively. 20C, primary transfer bias rollers 23BK, 23M, 23Y, and 23C as primary transfer means, a cleaning device (not shown), and a photosensitive member static elimination device (not shown) are arranged. The developing devices 20BK, 20M, 20Y, and 20C use a two-component magnetic brush developing system. The intermediate transfer belt 22, which is a belt component, is interposed between the photosensitive members 21BK, 21M, 21Y, and 21C and the primary transfer bias rollers 23BK, 23M, 23Y, and 23C, and is formed on the photosensitive members. The toner images of each color are sequentially superimposed and transferred.

On the other hand, the transfer paper P is fed from the paper feed unit 14 and then carried by the transfer conveyance belt 50, which is a belt component, via the registration roller 16. When the intermediate transfer belt 22 and the transfer conveyance belt 50 come into contact, the toner image transferred onto the intermediate transfer belt 22 is subjected to secondary transfer (collective transfer) by a secondary transfer bias roller 60 as a secondary transfer unit. )
As a result, a color image is formed on the transfer paper P. The transfer paper P on which the color image is formed is conveyed to the fixing device 15 by the transfer conveying belt 50, and after the image transferred by the fixing device 15 is fixed, it is discharged out of the printer main body.

  The residual toner that is not transferred during the secondary transfer and remains on the intermediate transfer belt 22 is removed from the intermediate transfer belt 22 by the belt cleaning member 25. A lubricant application device 27 is disposed on the downstream side of the belt cleaning member 25. The lubricant application device 27 includes a solid lubricant and a conductive brush that rubs the intermediate transfer belt 22 to apply the solid lubricant. The conductive brush is always in contact with the intermediate transfer belt 22 and applies a solid lubricant to the intermediate transfer belt 22. The solid lubricant has an effect of improving the cleaning property of the intermediate transfer belt 22, preventing the occurrence of filming, and improving the durability.

  EXAMPLES Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited by these examples, and these examples are appropriately modified without departing from the gist of the present invention. Is also within the scope of the present invention. The amount of warpage of the belt was measured using a sample cut into a 10 cm square, and the most warped portion was measured with positive internal warpage and negative external warpage.

<Example 1>
“Preparation of polyimide precursor solution A1”
Pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (DDE) are polymerized in a molar ratio of 1: 1 in N-methyl-2-pyrrolidone (NMP) to give a solid content of 20% and a viscosity of 8. A polyimide precursor solution A1 of 3 Pa · s (25 ° C.) was prepared.

“Preparation of carbon black dispersion A1 and base layer coating liquid A1 ”
A solution prepared by mixing Special Black 4 manufactured by Evonik Degussa, the above polyimide precursor solution A1 and NMP at a weight ratio of 12:13:75 was dispersed for 10 hours with a ball mill made of φ1 mm zirconia media to prepare a carbon black dispersion A1 . Thereafter, the carbon black dispersion A1 and the polyimide precursor solution A1 were mixed so that the carbon black solid content was 17.4%, and sufficiently stirred and degassed to prepare a base layer coating solution A1.

"Preparation of polyimide base belt A"
Next, a metal cylinder having an outer diameter of 700 mm and a length of 360 mm roughened by blasting is used as a mold, and this cylinder mold is rotated at 50 rpm (times / minute) while the base layer coating liquid is used. A1 was applied with a dispenser so as to be uniformly cast on the outer surface of the cylinder. When the predetermined amount was completely poured and the coating film was spread evenly, the number of revolutions was increased to 100 rpm, introduced into a hot air circulating dryer, gradually heated to 120 ° C. and heated for 60 minutes. Further, the temperature is raised and heated at 200 ° C. for 20 minutes, the rotation is stopped, and it is slowly cooled to take out the cylindrical mold on which the formed film is formed, and this is introduced into a heating furnace (firing furnace) capable of high-temperature processing. In particular, the temperature was raised to 260 ° C. and heat-treated (baked) for 20 minutes to obtain a polyimide base layer belt A having a thickness of 40 μm.

"Preparation of polyimide precursor solution A2"
3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-diaminodiphenyl ether (DDE) at a molar ratio of 1.0: 1.0, N-methyl-2-pyrrolidone ( NMP) polymerized to 18% solids. A polyimide precursor solution A2 having a viscosity of 6.3 Pa · s (25 ° C.) was prepared.

“Preparation of carbon black dispersion A2 and base layer coating liquid A2”
A solution prepared by mixing Special Black 4 manufactured by Evonik Degussa, the above polyimide precursor solution A2 and NMP at a weight ratio of 12:13:75 was dispersed for 9 hours in a ball mill made of Φ 1 mm zirconia media to prepare a carbon black dispersion A2. Thereafter, the carbon black dispersion A2 and the polyimide precursor solution A2 were mixed so that the carbon black solid content was 14.0%, and sufficiently stirred and degassed to prepare a base layer coating solution A2.

"Preparation of intermediate transfer belt A"
Next, the base layer coating liquid A2 was applied on the polyimide base layer belt A by a dispenser so as to be uniformly cast on the outer surface of the cylinder while rotating the cylindrical mold at 50 rpm (times / minute). . When the predetermined amount was completely poured and the coating film was spread evenly, the number of revolutions was increased to 100 rpm, introduced into a hot air circulating dryer, gradually heated to 120 ° C. and heated for 60 minutes.
Further, the temperature is raised and heated at 200 ° C. for 20 minutes, the rotation is stopped, and it is slowly cooled to take out the cylindrical mold on which the formed film is formed, and this is introduced into a heating furnace (firing furnace) capable of high-temperature processing. In particular, the temperature was raised to 320 ° C. and heat-treated (baked) for 60 minutes. After sufficiently cooling, the mold was released from the mold to obtain an intermediate transfer belt A having a total film thickness of 70 μm. The amount of warpage of the belt at this time was plus 2.5 mm.

<Example 2>
An intermediate transfer belt B was obtained in the same manner as in Example 1 except that the film thickness of the polyimide base layer belt A of Example 1 was 25 μm and the film thickness of the outer layer (surface layer) was 40 μm. The amount of warpage of the belt at this time was plus 1.2 mm.

<Example 3>
An intermediate transfer belt C was obtained in the same manner as in Example 1 except that the film thickness of the polyimide base layer belt A of Example 1 was 75 μm and the film thickness of the outer layer (surface layer) was 30 μm. The amount of warpage of the belt at this time was plus 9.6 mm.

<Example 4>
An intermediate transfer belt D was obtained in the same manner as in Example 1 except that the film thickness of the polyimide base layer belt A of Example 1 was 70 μm and the film thickness of the outer layer (surface layer) was 80 μm. The amount of warpage of the belt at this time was plus 7.2 mm.

<Example 5>
In Example 1, the polyimide precursor A1 of the base material layer was changed to the following.
3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (DDE) in a molar ratio of 0.6: 0. Polymerization was performed at 4: 1.0 in N-methyl-2-pyrrolidone (NMP) to prepare a polyimide precursor solution E having a solid content of 20% and a viscosity of 13.2 Pa · s. Thereafter, a seamless belt E was obtained in the same manner as in Example 1. The amount of warpage of the belt at this time was plus 1.6 mm.

<Example 6>
In Example 1, the polyimide precursor A2 of the surface layer was changed to the following.
4,4′-oxydiphthalic dianhydride (ODPA) and 4,4′-diaminodiphenyl ether (DDE) were polymerized in N-methyl-2-pyrrolidone (NMP) at a molar ratio of 1.0: 1.0. A polyimide precursor solution F having a solid content of 20% was prepared. Thereafter, a seamless belt F was obtained in the same manner as in Example 1. The amount of warpage of the belt at this time was plus 2.7 mm.

<Example 7>
A seamless belt G was obtained in the same manner as in Example 1 except that 4,4′-diaminodiphenyl ether of the polyimide precursor A1 of the base material layer was changed to 3,4′-diaminodiphenyl ether. At this time, the amount of warping of the belt B was plus 2.2 mm.

<Example 8>
A seamless belt H was obtained in the same manner as in Example 1 except that 4,4′-diaminodiphenyl ether of the polyimide precursor A2 in the surface layer was changed to p-phenylenediamine (PDA). At this time, the amount of warpage of the belt H was plus 1.1 mm.

<Example 9>
In Example 1, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) of polyimide precursor A2 in the surface layer was changed to 4,4′-oxydiphthalic dianhydride (ODPA). A seamless belt I was obtained in the same manner as in Example 1 except for the above. At this time, the amount of warping of the belt I was plus 3.7 mm.

<Comparative Example 1>
An intermediate transfer belt J was obtained in the same manner as in Example 1 except that the film thickness of the base material layer of Example 1 was 15 μm and the film thickness of the outer layer (surface layer) was 100 μm. At this time, the amount of warp of the belt J was plus 0.5 mm.

<Comparative Example 2>
An intermediate transfer belt K was obtained in the same manner as in Example 1 except that the film thickness of the base material layer of Example 1 was 100 μm and the film thickness of the outer layer (surface layer) was 20 μm. At this time, the amount of warp of the belt K was plus 14.7 mm.

<Comparative Example 3>
An intermediate transfer belt L was obtained in the same manner as in Example 1 except that the thickness of the base material layer of Example 1 was 60 μm and the outer layer (surface layer) was not applied. The amount of warpage of the belt L at this time was plus 18 mm.

The intermediate transfer belts A to K of each of the above examples and comparative examples were mounted on the electrophotographic apparatus shown in FIG. 2 and 10,000 sheets were passed, and running failure due to belt warpage was confirmed. At this time, the belt in which the running failure did not occur once was marked as ◯, the running failure after 1 to 10 times was marked as △, and the others were marked as x.
In addition, the density unevenness at the end and the center was also confirmed, where no density unevenness was indicated by ◯, some of the density was low, but the actual usable level was Δ, the density unevenness was large, and the actual unusable level was x.
The results are shown in Table 1.

  As described above, with the configuration of the present invention, an intermediate transfer belt excellent in durability that does not cause poor running due to warping of the belt and image unevenness, and the intermediate transfer belt can be obtained. An image forming apparatus can be provided.

(About Figure 1)
11 PMDA polyimide base layer (inner layer)
12 Polyimide surface layer (outer layer)
(About Figure 2)
P Transfer paper L Laser light 70 Static elimination roller 80 Ground roller 200 Photosensitive drum 201 Photosensitive drum cleaning device 202 Static elimination lamp 203 Charging charger 204 Potential sensor 205 Image density sensor 210 Belt conveying device 230 Revolver developing unit 231Y Y developing machine 231K Bk developing machine 231C C developing machine 231M M developing machine 270 fixing device 271 and 272 fixing roller 500 intermediate transfer unit 501 intermediate transfer belt 502 toner seal member 503 charging charger 504 belt cleaning blade 505 lubricant application brush 506 lubricant 507 primary transfer bias roller 508 Belt drive roller 509 Belt tension roller 510 Secondary transfer counter roller 511 Cleaning counter roller 512 Feedback current detection sensor 513 Toner image 514 Optical sensor 600 Secondary transfer unit 601 Transfer paper guide plate 605 Secondary transfer bias roller 606 Transfer paper neutralization charger 608 Cleaning blade 610 Registration roller 801 Primary transfer power source 802 Secondary transfer power source (about FIG. 3)
P Transfer paper 10 Printer body 12 Image writing unit 13 Image forming unit 14 Paper feeding unit 15 Fixing device 16 Registration roller 20BK, 20M, 20Y, 20C Developing device 21BK, 21M, 21Y, 21C Photoconductor 22 Intermediate transfer belt 23BK, 23M , 23Y, 23C Primary transfer bias roller 25 Belt cleaning member 26 Drive roller 27 Lubricant coating device 50 Transfer conveyance belt 60 Secondary transfer bias roller 70 Transfer voltage application power source

JP-A-11-282277 JP 2009-258699 A JP 2010-122437 A JP 2005-309181 A Japanese Patent No. 4396959

Claims (8)

An intermediate transfer belt to which a toner image obtained by developing a latent image formed on an image carrier with toner is transferred,
The intermediate transfer belt has a structure in which an inner polyimide layer composed of a base material layer and an outer polyimide layer formed on the base material layer are laminated, and the base material layer includes at least pyromellitic acid. An intermediate transfer belt comprising a polyimide having a structural unit derived from the above and a structural unit derived from diaminodiphenyl ether, wherein the amount of warpage to the inside of the intermediate transfer belt is 1.0 mm or greater and 10.0 mm or less. 2. The intermediate transfer belt according to claim 1, wherein an average thickness of the base material layer is 20 μm or more and 80 μm or less, and an average thickness of the total thickness of the intermediate transfer belt is 40 μm or more and 140 μm or less. The intermediate transfer belt according to claim 1, wherein the outer layer includes a polyimide having a structural unit derived from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. The intermediate transfer belt according to claim 1, wherein the outer layer includes a polyimide having a structural unit derived from 4,4′-oxydiphthalic dianhydride. The intermediate transfer belt according to claim 1, wherein a peripheral length of the intermediate transfer belt is 2000 mm or more. The intermediate transfer belt according to claim 1, wherein the intermediate transfer belt is a seamless belt.   A latent image is formed and an image carrier capable of carrying a toner image; a developing unit that develops the latent image formed on the image carrier with toner; and a toner image developed by the developing unit is primarily transferred. The intermediate transfer belt according to claim 1, and a transfer unit that secondarily transfers the toner image carried on the intermediate transfer belt to a recording medium. An image forming apparatus comprising an intermediate transfer belt.   The image forming apparatus according to claim 7, wherein the image forming apparatus is a full color image forming apparatus in which a plurality of latent image carriers having developing units for respective colors are arranged in series.

Images