JP5748092B2 - Toner carrier, developing device, and image forming apparatus - Google Patents

Description

  The present invention relates to a large-sized and high-speed image forming apparatus using an intermediate transfer belt, and more particularly to an image forming apparatus suitable for full-color image formation.

  In recent years, in the full-color electrophotographic apparatus, there is an intermediate transfer belt system in which developed images of four colors of yellow, magenta, cyan, and black are once superimposed on an intermediate transfer belt and then collectively transferred to a transfer medium such as paper. It is used.

  As such a full-color electrophotographic apparatus, there is an apparatus that uses a four-color developing device for one photoconductor, performs primary transfer onto an intermediate transfer belt, and then transfers it onto a transfer medium such as paper. Due to the slowness, a four-tandem tandem system is used for high-speed printing, in which photoconductors are arranged for four colors and each color is transferred directly onto a transfer medium such as paper.

However, in this method, there are fluctuations due to the environment of the transfer medium such as paper, and it is very difficult to match the position accuracy of overlapping each color image, causing a color misregistration image. For this reason, in order to prevent color misregistration, it has become the mainstream to adopt the intermediate transfer method in the recent four-tandem method.

  Under such circumstances, the required characteristics (high-speed transfer, positional accuracy) of the intermediate transfer belt are also stricter than before, and it is necessary to satisfy the characteristics corresponding to these requirements. Yes. In particular, for positional accuracy, it is required to suppress fluctuations 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, polyimide resin, which is mainly a high elastic modulus and high heat resistance resin, is mainly used as an intermediate transfer belt material.

As a material using such a polyimide resin, Japanese Patent Application Laid-Open No. 2008-225182 discloses that the surface roughness (Ra) of the inner surface of the belt is 0. 0 so as to reduce the contact area with the driving roller. A polyimide belt is disclosed in which the generation of abrasion powder is suppressed without changing the slidability of the inner surface of the belt by setting the maximum surface roughness (Rmax) to 15 to 0.6 [mu] m and 3 to 15 [mu] m.

In Patent Document 2 (Japanese Patent Laid-Open No. 2005-74914), a heat pipe including a cavity for circulating a heat medium is provided on the peripheral wall so that the temperature of the peripheral wall of the mold to which the polyamideimide precursor solution is applied is uniform. An apparatus for manufacturing a tubular article is disclosed that includes an arranged cylindrical mold and an electromagnetic induction coil that electromagnetically heats the mold, and the resin is heated and cured without temperature unevenness.

In Patent Document 3 (Japanese Patent Laid-Open No. 2001-142313), since the balance between flexibility and rigidity is poor and the durability as an intermediate transfer belt is not sufficient, the balance between flexibility and rigidity is improved. A component formed by imide bonding of a fully aromatic skeleton that is a tetracarboxyl residue and a p-phenylene skeleton that is a diamine residue, and an imide bond between a wholly aromatic skeleton that is a tetracarboxyl residue and a diphenyl ether skeleton A copolymer obtained by repeating the B component and / or a blend obtained by mixing a polymer having the A component as a repeating unit and a polymer having the B component as a repeating unit, An intermediate transfer member is formed of a polyimide resin in which R is (65-W) or less, where R is the mol% of the component A and W is the weight part of the conductive filler relative to the polyimide resin. It has been disclosed.

In Patent Document 4 (Japanese Patent Application Laid-Open No. 2004-77576), a tensile load at 1% elongation in the circumferential direction is 25 N so that swell is hardly generated when tension is applied and stable image formation is not affected by humidity. A seamless belt made of polyimide resin having a flatness of 0.5 mm or less and a hygroscopic expansion coefficient of 30 ppm /% RH or less is disclosed.
(Change position)

In recent years, however, color electrophotographic image forming apparatuses have become large and the number of printed sheets has been increased, and a color image forming apparatus having extremely high speed and high durability and stability has been demanded. In such a color image forming apparatus, since a large-sized apparatus is driven at high speed, it is necessary to increase the belt circumferential length and perform high-speed driving even in the intermediate transfer belt. An image forming apparatus using such an intermediate transfer belt Then, a new problem that does not become a problem in the conventional image forming apparatus is born.

One of them is that high-speed rotation causes slippage between the intermediate transfer belt and the roller that drives the belt, and color misregistration is likely to occur, the belt is likely to be damaged when the belt is deviated, and environmental fluctuations. On the other hand, the dimensional change amount of the belt becomes large, and this is a problem of the conveyance stability such as the belt conveyance being unstable.

Another problem is that if the belt size is increased, when the polyimide belt is manufactured, the mold with the resin solution applied is heated and dried and cured. This is a problem that it cannot be suppressed and the variation of the characteristic value becomes large in one belt.

Such a problem did not become a problem when used with the conventional belt size or belt linear speed, but it is a new problem caused by driving a large belt at high speed. The inventions described in the first to fourth aspects have been made by examining a conventional size belt that has not been increased in size, and cannot cope with an intermediate transfer belt of an image forming apparatus that has been increased in size and speed.

That is, in patent document 1, in the Example, it is a thing of the conventional size like the precursor belt is manufactured with the cylindrical metal mold | die with an internal diameter of 30 mm, and there exists said problem in the enlarged belt. Therefore, there are cases where sufficient belt transportability cannot be obtained, and detailed investigations have not been made on the resin. Therefore, there is a possibility that the characteristic value of the belt varies and a large dimensional change occurs during moisture absorption.

According to Patent Document 2, in the production of a large-sized belt, temperature unevenness still occurs, resulting in variations in belt characteristics, and a sufficient effect cannot be obtained. Moreover, due to a specific resin, variations in belt characteristics occur. It does not suppress.

In the patent document 3, in the Example, it is a belt of a conventional size like the polyamic acid is apply | coated to the inner surface of a metal mold | die with an internal diameter of 300 mm, and centrifugal molding is carried out, From the molding method, the belt back surface is roughened. In addition, the intermediate transfer belt using the A component in which the wholly aromatic skeleton, which is a tetracarboxyl residue, and the p-phenylene skeleton, which is a diamine residue, has an imide bond, shows a decrease in the tear strength. In the long-term use, the intermediate transfer belt using the B component formed by the imide bond between the wholly aromatic skeleton and the diphenyl ether skeleton, which are tetracarboxyl residues, easily cracks from the end of the belt, and the tensile elastic modulus is not sufficient. In case of color image, color misalignment will occur, so use A component and B component to balance flexibility and rigidity. Necessary, transport stability due to dimensional changes and speed to humidity changes are not taken into account, to prepare a large belt, if used there is a possibility that the problem.

According to Patent Document 4, the diameter of the final seamless belt can be about 100 to 700 mm, which is a conventional belt size. Although the dimensional change with respect to humidity change can be suppressed, the intermediate transfer belt is enlarged and high speed is achieved. Since the conveyance stability due to the change is not taken into consideration, there is a problem in the conveyance stability due to the slip of the belt, and the belt end may be damaged due to the deviation of the running belt.

Accordingly, the present invention has been made in view of the above problems, and in an image forming apparatus using an intermediate transfer belt that is large and driven at a high speed, the conveyance stability of the intermediate transfer belt is improved and the belt is moved within the belt. It is an object of the present invention to provide an image forming apparatus capable of outputting high-quality images over a long period of time with less variation in characteristics.

In order to obtain a large and high-speed intermediate transfer type image forming apparatus, it is necessary to drive the intermediate transfer belt at a high speed of 2000 mm or more and a belt linear speed of 350 mm / sec or more. When the intermediate transfer belt is driven at a high speed, slip is likely to occur between the intermediate transfer belt and the roller for driving the belt, the dimensional change of the belt is large with respect to environmental fluctuations, and the conveyance stability is deteriorated. Misalignment is likely to occur, belt deviation occurs during running, and the belt is easily damaged. In addition, as the belt size increases, the variation in characteristic values increases in one belt. There is a problem.

Therefore, as a result of intensive studies on the intermediate transfer belt, the present inventors have driven the intermediate transfer belt at a high speed by appropriately controlling the surface roughness of the back surface of the intermediate transfer belt (the surface that contacts the drive roller of the intermediate transfer belt). However, the intermediate transfer belt can be prevented from being damaged due to slippage or belt deviation, and if the intermediate transfer belt is made of a specific polyimide resin, the coefficient of hygroscopic expansion is reduced, and the belt dimensions change with respect to environmental fluctuations. It has been found that the amount of variation in characteristic values can be reduced in one belt, and the present invention has been completed.

That is, the said subject is solved by (1)-(7) of this invention.
(1) “An image forming apparatus that transfers a toner image formed on an electrostatic latent image carrier onto a recording medium via an intermediate transfer belt that is driven at 350 mm / sec or more,
The intermediate transfer belt is formed of at least a polyimide resin, has a circumference of 2000 mm or more, a back surface (inner surface) surface roughness Ra of 0.2 to 0.4 μm, and a moisture absorption linear expansion coefficient of 19.6 ppm /%. RH or less, and the polyimide resin is a polyimide resin component (S component) in which 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine are imide-bonded, and 3,3 ′, 4 , 4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether imide-bonded polyimide resin component (component A) are blended, and the weight ratio (S / A) of the component S to component A is 30/70 to 40/60 image forming apparatus, ”
(2) “The intermediate transfer belt is characterized in that the difference ρv10−ρv100 is 2.0 or less when the common logarithmic values of volume resistance at the time of 10V application and 100V application are ρv10 and ρv100, respectively. The image forming apparatus according to item (1) "
(3) “The image forming apparatus according to (1) or (2) above, wherein the toner forming the toner image has a circularity of 0.95 to 0.98”,
(4) “The image forming apparatus according to any one of (1) to (3) above, wherein a volume average particle diameter of a toner forming the toner image is 4 μm to 8 μm”. ,
(5) “Image forming apparatus according to item (4), wherein the toner forming the toner image has a volume average particle diameter of 4 μm to 5.2 μm”;
(6) "The image forming apparatus according to any one of (1) to (5) above, further comprising a solid lubricant applying device that applies a lubricant to the surface of the intermediate transfer belt" ,
(7) “Image forming apparatus according to item (6), wherein the lubricant is zinc stearate”

According to the present invention, the surface roughness Ra of the back surface (inner surface) of the intermediate transfer belt is 0.2 μm to 0.4 μm, so that even if a large intermediate transfer belt is driven at high speed, there is no belt slip. Thus, stable belt driving is possible, and damage to the belt due to deviation of the running belt is difficult to occur. Furthermore, by setting the belt's hygroscopic linear expansion coefficient to 22 ppm /% RH or less, there is little dimensional change of the belt with respect to changes in humidity, and stable belt driving is possible even with respect to environmental fluctuations.

Furthermore, a polyimide resin component (S component) in which 3,3 ′, 4,4′-biphenyltetraarbonic dianhydride and p-phenylenediamine are imide-bonded to a polyimide resin used for the belt, and 3,3 ′, 4,4'-biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether imide-bonded polyimide resin component (component A) are blended, and S component to A component weight ratio (S / A) By setting the ratio to 10/90 to 40/60, even when temperature unevenness occurs in a large mold, variation in belt characteristics is small, and the hygroscopic linear expansion coefficient can be suppressed to 22 ppm /% RH or less.

Further, when the common logarithmic value of the volume resistance at the time of 10V application and 100V application is ρv10 and ρv100, respectively, the difference ρv10−ρv100 is set to 2.0 or less so that the resistance with time Stable image quality is obtained with little change.

When the circularity of the toner used is 0.95 or more and 0.98 or less, the transferability is improved, the image quality is improved, and the toner has a volume average particle diameter of 4 μm to 8 μm. Is improved, and a high-definition image is obtained. By setting the volume average particle diameter of the toner to 4 μm to 5.2 μm, an extremely high-definition image can be obtained.

In addition, by installing a lubricant application device that applies a lubricant on the intermediate transfer belt, good cleaning properties can be maintained even when a toner with a high degree of circularity or a small-diameter toner is used. By using zinc, stable cleaning properties can be secured.

It is a figure which shows the measuring apparatus of a hygroscopic linear expansion coefficient used by this invention. 1 is a diagram showing an embodiment of an image forming apparatus of the present invention.

Embodiments of the present invention will be described below. The present invention is a high-speed and highly durable image forming apparatus that is driven at a peripheral length of an intermediate transfer belt of 2000 mm or more and a belt linear speed of 350 mm / sec or more.

The intermediate transfer belt used in the present invention has a back surface (intermediate transfer belt) so as to suppress slippage of the intermediate transfer belt and deviation of the running belt and improve conveyance stability even when driven at high speed. The surface roughness Ra of the surface in contact with the driving roller is 0.2 μm to 0.4 μm.

In this way, by setting the roughness of the back surface of the belt within the above range, even if the belt is driven at high speed, the slip of the intermediate transfer belt is suppressed and the deviation of the running belt can be suppressed. Hard to occur. When the roughness of the back surface of the belt is larger than 0.4 μm, the contact area between the belt and the driving roller is reduced. Therefore, slip is likely to occur between the driving roller and the belt when driven at high speed. On the other hand, when Ra is less than 0.2 μm, the frictional force between the driving roller and the belt is large, so that when the belt is deviated during running, the force applied when the belt end rubs against other members increases. The belt end is easily damaged and the conveyance stability is also deteriorated.

The surface roughness Ra in the present invention was measured with a surface roughness meter (SURFCOM 1400D) manufactured by Tokyo Seimitsu Co., Ltd. according to “JIS B0601: 2001”. The measurement conditions were a measurement speed of 0.6 mm / sec, a cut-off value of 0.8 mm, and a measurement length of 2.5 mm. Three locations in the belt circumferential direction and three locations in the belt width direction (center and both ends) The back surface of the belt was measured at 9 locations (3 locations in the circumferential direction x 3 locations in the width direction), and the average value was used.

The intermediate transfer belt used in the present invention has a moisture absorption linear expansion coefficient of 22 ppm /% RH or less. Even with belts using the same material and the same coefficient of hygroscopic expansion, the longer the belt circumference, the larger the dimensional change itself, and the more likely the conveyance failure occurs with humidity change, but the hygroscopic expansion coefficient is 22 ppm / By controlling to less than% RH, even when a large belt is used, the dimensional change is small with respect to the humidity change, and stable belt driving can be performed.

The hygroscopic linear expansion coefficient in the present invention was measured with an elongation measuring apparatus shown in FIG. This elongation measuring device 1 is provided below a pair of arms 2 and 3 that support both ends of a sample sheet, a lower arm 3, a weight (made of aluminum) 4 that adjusts a linear pressure applied to the sample, and a weight 4. And a reflection type laser microgauge 5 disposed below. And the measurement of a hygroscopic linear expansion coefficient is performed so that the distance between the inner ends of the arms 2 and 3 is 50 mm for a sample polyimide sheet cut into a predetermined shape (width 10 mm, length 70 mm) from the center of the seamless belt. And the weight of the aluminum weight 4 is adjusted so that the linear pressure applied to the sample is 150 g / cm.

Next, the sample is mounted, and the elongation measuring device in which the linear pressure is adjusted is put in a constant temperature and humidity chamber, and in both environments of 35 ° C./85% (RH: relative humidity) and 35 ° C./35% (RH: relative humidity). The amount of elongation was measured, the difference (ΔL) was determined, and the hygroscopic linear expansion coefficient was calculated using the following equation.
Hygroscopic linear expansion coefficient (ppm /% RH) = (ΔL / 50 mm) / 50%
The amount of elongation is obtained by measuring the distance between the lower portion of the weight 4 and the laser micro gauge 5 with a reflective laser micro gauge 5 provided at the lower portion of the weight 4.

The polyimide resin used for the intermediate transfer belt of the present invention includes a polyimide resin component (S component) in which 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine are imide-bonded; A polyimide resin obtained by blending a polyimide resin component (component A) in which 3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether are imide-bonded is used, and S component and A component The weight ratio (S / A ratio) is 10/90 to 40/60.

Polyimide resin in which 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether are imide-bonded has good folding resistance by MIT, high tear strength, Although the characteristics can be obtained, since the dimensional change at the time of moisture absorption is large, when the intermediate transfer belt is long, it is greatly extended to the belt due to environmental fluctuations, and there is a problem in the conveyance stability.

Suppression of dimensional change at the time of moisture absorption can be achieved by using a polyimide resin component (component A) in which 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether are imide-bonded, This can be achieved by blending 3 ′, 4,4′-biphenyltetracarboxylic dianhydride and a polyimide resin component (S component) in which p-phenylenediamine is imide-bonded, and in particular, 3,3 ′, 4,4 When the ratio of the polyimide resin component (S component) in which imide-bonding of '-biphenyltetracarboxylic dianhydride and p-phenylenediamine is 10% by weight or more, even when a large belt is used, the dimensional change during moisture absorption is reduced. Even when the environment changes, the belt conveyance stability can be ensured, and sufficient mechanical / electrical characteristics can be obtained.

  On the other hand, when the ratio of the polyimide resin component (S component) in which 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine are imide-bonded is more than 40% by weight, a large belt Variation in the characteristic value within one belt increases.

Therefore, even when a large belt is produced, the dimensional change of the belt due to moisture absorption is small, and there is no large variation in characteristics within one belt. To obtain sufficient mechanical / electrical characteristics, 3, 3 ′, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is added to a polyimide resin component (component A) in which 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether are imide-bonded. And a polyimide resin component (S component) in which p-phenylenediamine is imide-bonded, and the weight ratio (S / A ratio) of the S component and the A component needs to be 10/90 to 40/60.

The intermediate transfer belt used in the present invention preferably contains a filler (or additive) for adjusting electric resistance, a so-called electric resistance adjusting material, in the polyimide resin. Examples of such an 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 order to improve dispersibility, the metal oxide may be subjected to surface treatment in advance. .

Examples of carbon black include ketjen black, furnace black, acetylene black, thermal black, and gas black.

Examples of the ionic conductive agent include tetraalkylammonium salts, trialkylbenzylammonium salts, alkylsulfonates, alkylbenzenesulfonates, alkyl sulfates, glycerol fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylenes. Ethylene fatty alcohol ester, alkyl betaine, lithium perchlorate, etc. are mentioned, and these may be used in combination.
The electrical resistance adjusting material in the present invention is not limited to the above exemplary compounds.

  In the present invention, the electric resistance adjusting material contained in the intermediate transfer belt is 8 to 13 (LogΩ / □) in the common logarithm of the surface resistivity, and 6 to 12 (LogΩ · cm) in the common logarithm of the volume resistivity. However, from the viewpoint of mechanical strength, it is necessary to select and add an amount in such a range that the molded film is brittle and does not easily break.

  In the case of carbon black, the content of the electric resistance adjusting material in the present invention is 10 to 25 wt%, preferably 15 to 20 wt% of the total solid content in the coating liquid. Moreover, as content in the case of a metal oxide, it is 1-50 wt% of the total solid of a coating liquid, Preferably it is 10-30 wt%.

  More preferably, when the common logarithmic value of the volume resistance at the time of 10V application and 100V application is ρv10 and ρv100, the difference ρv10−ρv100 is preferably 2.0 or less. By reducing the voltage dependency of the resistance in this way, a stable image can be obtained over time.

Next, the polyimide resin used in the present invention will be described.
Aromatic polyimide is obtained via reaction of polyamic acid (polyimide precursor) by reaction of aromatic polyvalent carboxylic acid anhydride (or derivative thereof) and aromatic diamine. Polyimide used in the present invention Uses 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride as the aromatic polyvalent carboxylic acid anhydride and p-phenylenediamine and 4,4′-diaminodiphenyl ether as the aromatic diamine.

In the following description, unless otherwise specified, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is described as an aromatic polycarboxylic anhydride, p-phenylenediamine and 4,4 '-Diaminodiphenyl ether is described as an aromatic diamine.

  Aromatic polyimide is insoluble in solvents and the like due to its rigid main chain structure and has an infusible property. Therefore, first, a polyimide precursor (polyamic acid) that is soluble in an organic solvent is synthesized by a reaction between an aromatic polycarboxylic acid anhydride and an aromatic diamine, and is molded by various methods at the polyamic acid stage. Processing is performed, and then the polyamic acid is dehydrated by heating or a chemical method to be cyclized (imidized) to obtain polyimide. The outline of the reaction for obtaining the aromatic polyimide is shown in the following formula (1).

Where Ar ¹ is

Ａｒ^２は、

Ar ² is

である。

It is.

  In the case of obtaining an aromatic polyimide, a polyimide precursor (polyamic acid) is obtained by polymerization reaction in an organic polar solvent using substantially equal moles of the aromatic polycarboxylic acid anhydride component and the aromatic diamine component. Then, the polyamic acid is dehydrated to cyclize and imidize. Below, the manufacturing method of a polyamic acid is demonstrated concretely.

Here, examples of the organic polar solvent used in the polymerization reaction for obtaining the polyamic acid include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, and formamide such as N, N-dimethylformamide and N, N-diethylformamide. Solvents, acetamide solvents such as N, N-dimethylacetamide, N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, phenol, o-, m- Or phenol solvents such as p-cresol, xylenol, halogenated phenol, catechol, ether solvents such as tetrahydrofuran, dioxane, dioxolane, alcohol solvents such as methanol, ethanol, butanol, cellosolve such as butyl cellosolve Or hexamethylphosphoramide, etc. can be mentioned γ- butyrolactone, to use them alone or as a mixed solvent desirable.
The solvent is not particularly limited as long as it dissolves the polyamic acid, but N, N-dimethylacetamide and N-methyl-2-pyrrolidone are particularly preferable.

  As an example of producing a polyimide precursor, first, one or more kinds of diamines are dissolved in the above organic solvent or dispersed in a slurry state in an inert gas atmosphere such as argon or nitrogen. When at least one aromatic polycarboxylic acid anhydride (or derivative thereof) is added to this solution (either in a solid state, in a solution state dissolved in an organic solvent, or in a slurry state), heat is generated. Thus, a ring-opening polyaddition reaction occurs, and the viscosity of the solution rapidly increases, and a high molecular weight polyamic acid solution is obtained. In this case, the reaction temperature is usually controlled to −20 ° C. to 100 ° C., desirably 60 ° C. or less. The reaction time is about 30 minutes to 12 hours.

  The above is an example. Contrary to the addition procedure in the reaction, first, aromatic tetracarboxylic dianhydride or a derivative thereof is dissolved or dispersed in an organic solvent, and the aromatic diamine (substantially , "Diamine") may be added. The diamine 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 tetracarboxylic dianhydride component and the diamine component is not limited. Further, the aromatic tetracarboxylic dianhydride and the diamine may be simultaneously added to the 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 component in about an equimolar amount in the organic polar solvent. A polyimide precursor solution is obtained in a dissolved state.

  The polyimide precursor solution in the present invention (polyamic acid solution: “coating solution containing a polyimide resin precursor”) can be synthesized as described above, but it can be easily used as an organic solvent. A state in which the polyamic acid composition is dissolved, that is, what is marketed as a so-called polyimide varnish can also be obtained and used. Manufactured).

  Mix and disperse fillers (for example, electrical resistance adjusting agents, or additives such as dispersion aids, reinforcing materials, lubricants, heat conduction materials, antioxidants, etc.) into the synthesized or obtained polyamic acid solution as necessary. Thus, a coating solution is prepared. The coating liquid is applied to a support (molding mold) as described later, and then subjected to a treatment such as heating, whereby conversion (imidation) from polyamic acid, which is a polyimide precursor, to polyimide is performed.

The polyamic acid can be imidized by the heating method (1) or the chemical method (2) as described above.
The heating method (1) is a method of converting polyamic acid to polyimide by, for example, heat treatment at 200 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 (for example, a mixture of a carboxylic acid anhydride and a tertiary amine, etc.) and then heated to completely imidize, Compared with the heating method of (1), since it is a complicated and expensive method, the method of (1) is usually used frequently.
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.

The progress of imidization (degree of imidization) can be evaluated by a commonly performed method for measuring the imidization rate.
As a method for measuring such an imidization rate, for example, nuclear magnetic resonance calculated from an integral ratio of 1H attributed to an amide group near 9 to 11 ppm and 1H attributed to an aromatic ring near 6 to 9 ppm. Various methods such as spectroscopy (NMR method), Fourier transform infrared spectroscopy (FT-IR method), quantification of moisture accompanying imide ring closure, carboxylic acid neutralization titration method, etc. are used. Infrared spectroscopy (FT-IR method) is the most common method.

In the Fourier transform infrared spectroscopy (FT-IR method), the imidization rate is defined as, for example, the following formula (a).
That is, assuming that (A) is the number of moles of imide groups at the firing stage (imidation treatment stage) and (B) is the number of moles of imide groups when 100% imidized (theoretical), Is done.
Imidation ratio (%) = [(A) / (B)] × 100 (a)

  The number of moles of the imide group in this definition can be determined from the absorbance ratio of the characteristic absorption of the imide group measured by the FT-IR method. For example, as a typical characteristic absorption, the imidization ratio can be evaluated using the following absorbance ratio.

(1) Absorbance ratio between 725 cm ⁻¹ (immobilization band of imide ring C═O group), which is one of characteristic absorptions of imide, and 1,015 cm ⁻¹ of characteristic absorption of benzene rings.
(2) Absorbance ratio between 1,380 cm ⁻¹ (inflection vibration band of imide ring C—N group), which is one of characteristic absorptions of imide, and 1,500 cm ⁻¹ of characteristic absorption of benzene rings.
(3) Absorbance ratio between 1,720 cm ⁻¹ (immobilization vibration band of imide ring C═O group) which is one of characteristic absorptions of imide and 1,500 cm ⁻¹ of characteristic absorption of benzene ring.
(4) 1,720 cm ⁻¹ which is one of characteristic absorptions of imide and 1,670 cm ⁻¹ (interaction between amide group N—H bending vibration and C—N stretching vibration) Absorbance ratio.
Moreover, if it is confirmed that the multiple absorption band derived from the amide group over 3000 to 3300 cm ⁻¹ disappears, the reliability of imidization completion is further increased.

  The resin used in the present invention comprises 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether formed by imide bonding, and a polyimide resin component and 3,3 ′, 4,4. Since a polyimide resin component in which ′ -biphenyltetracarboxylic dianhydride and p-phenylenediamine are imide-bonded is used, for example, a polyimide precursor solution obtained by mixing and stirring the polyimide precursor solution of each resin is used. Can be produced.

  Next, a method for producing an intermediate transfer belt using the coating liquid containing the polyimide resin precursor will be described.

  As a method for forming an intermediate transfer belt, a method of applying a coating liquid to the inner surface of a mold (cylindrical mold) as in centrifugal molding is widely known. Since the air surface is not in contact, the back surface of the belt becomes a smooth surface, and it is difficult to produce the belt having the roughness of the present invention.

Therefore, in the present invention, a method of applying a coating liquid containing a polyimide resin precursor to the outer surface of a mold (cylindrical mold) with a nozzle or a dispenser is preferable. In this method, the surface in contact with the outer surface of the mold is the back surface of the belt, so if the rough surface processing is performed on the outer surface of the mold, the rough surface is reflected on the back surface of the belt. Roughening is performed so that the surface roughness Ra of the belt back surface is 0.2 to 0.4 μm.

Next, while slowly rotating the cylindrical metal mold, the coating liquid is applied and cast (forms a coating film) so that the coating liquid is uniformly applied to the entire outer surface of the cylinder with a liquid supply device such as a nozzle or dispenser. To do. 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 about 80-150 degreeC, heating up gradually while 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 is performed at about 250 ° C. to 450 ° C. And sufficiently polyimide resin precursor or imidization. After the imidization is completed, the target seamless belt (intermediate transfer belt) is obtained by taking out the cylindrical mold on which the molded film is formed by slow cooling and releasing from the cylindrical mold (demolding). .
In addition, you may form a mold release agent or a mold release layer in a metal mold | die so that mold release may be made easy from a cylindrical metal mold | die.

The toner used in the present invention preferably has a circularity of 0.95 or more. By using such a nearly spherical toner, the transfer rate can be improved and the image quality can be improved. However, if the circularity is greater than 0.98, the residual toner on the image carrier and the belt is removed. In the cleaning process, cleaning defects are likely to occur. Therefore, the circularity of the toner used is preferably 0.95 or more and 0.98 or less.

Further, since the toner reproducibility is improved by reducing the diameter of the toner, the volume average particle diameter of the toner is preferably 4 μm or more and 8 μm or less, and more preferably 4 μm or more and 5.2 μm or less. . However, if the toner is too small, a cleaning failure is likely to occur in the cleaning process, so a size of 4 μm or more is necessary.
The volume average particle diameter and circularity of the toner were measured using FPIA-2100 manufactured by Sysmex.

In the toner of the present invention, for example, an organic solvent liquid of a toner material containing at least a resin material for a binder and / or a prepolymer thereof, a colorant, and a release agent in an organic solvent is dispersed in fine droplets in an aqueous medium. Then, the organic solvent and the aqueous medium are removed, or the prepolymer in the droplets is crosslinked and / or extended during or after the dispersion, and then the organic solvent and the aqueous medium are used. It can manufacture by removing.

  Preferably, at least in an organic solvent, a compound having active hydrogen and a polymer having a site capable of reacting with the compound, or a self-polymerizable material having active hydrogen and a site capable of reacting with it in the molecule at the same time The organic solvent and the aqueous system are dissolved or dispersed, preferably in the form of a composition containing them, after reacting with or reacting with the active hydrogen reactive site. It can be produced by removing the medium, washing and drying.

The degree of circularity of the toner can also be adjusted by adjusting the stirring strength during the reaction or by stirring vigorously after drying. Moreover, as a resin material or / and its prepolymer, various materials can be used, but especially a polyester resin or / and a polyester prepolymer can be preferably used.
These are merely examples, and the spherical toner may of course be manufactured by a method other than such a manufacturing method.

Next, the image forming apparatus used in the present invention will be described. The present invention is a high-speed and highly durable image forming apparatus using intermediate transfer. Therefore, the intermediate transfer belt used in the present invention is driven at a belt circumferential length of 2000 mm or more and a belt linear velocity of 350 mm / sec or more.

The image forming apparatus used in the present invention is preferably an image forming apparatus in which a plurality of photosensitive drums are arranged side by side along a single intermediate transfer belt so that high-speed printing can be performed even during color image printing. As an example of such an image forming apparatus, reference numeral 2 denotes four photosensitive drums (21BK), (21Y), and (21M) for forming toner images of four different colors (black, yellow, magenta, and cyan). , (21C) is a four-drum type digital color printer.

  In FIG. 2, the printer main 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 electrophotography. 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 the image writing unit (12). Send to. 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, and corresponds to each color signal described above. An image corresponding to each color signal in the image carrier (photoreceptor) (21BK), (21M), (21Y), (21C) having four writing optical paths and provided for each color of the image forming unit 13 Writing is performed to form a latent image on the image carrier (photoconductor).

  As the photoconductors (21BK), (21M), (21Y), and (21C) that are the image carriers of the image forming unit (13), a normal OPC photoconductor is used, and the photoconductors (21BK) and (21M) are used. ), (21Y), and (21C) are black (BK), magenta (M), magenta (M), and a charging device, and a latent image on each image carrier (photoconductor) is developed into a toner image. Developing devices (20BK), (20M), (20Y), (20C) for yellow (Y) and cyan (C) colors, primary transfer bias rollers (23BK), (23M) as primary transfer means, (23Y), (23C), a cleaning device (not shown), a photosensitive member neutralizing device (not shown), and the like are provided. The developing devices (20BK), (20M), (20Y), and (20C) use a two-component magnetic brush developing system that includes toner and a carrier.

The intermediate transfer belt (22), which is a belt component, includes the photosensitive members (21BK), (21M), (21Y), and (21C) and the primary transfer bias rollers (23BK), (23M), and (23Y). , (23C), and the toner images of the respective colors formed on the respective photoreceptors are sequentially superimposed and transferred.

  On the other hand, the transfer paper P is fed from the paper feed unit (14) and then carried on the transfer conveyance belt (50), which is a belt component, via the registration roller (16). When the intermediate transfer belt (22) and the transfer conveying belt (50) come into contact with each other, the toner image transferred onto the intermediate transfer belt (22) is transferred to a secondary transfer bias roller (60) as a secondary transfer unit. ) For secondary transfer (collective transfer). 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). After the image transferred by the fixing device (15) is fixed, the transfer paper P is discharged out of the printer main body. Is done.

  Residual toner remaining on the intermediate transfer belt (22) without being transferred during the secondary transfer is removed from the intermediate transfer belt (22) by the belt cleaning member (25). A lubricant application device (27) is disposed downstream 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. In particular, a small-diameter toner or a toner with a high degree of circularity has poor cleaning properties, so it is desirable to apply a lubricant. As the solid lubricant, conventionally known lubricants can be used, and particularly good cleaning properties can be obtained with zinc stearate.

  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.

A coating solution was prepared as follows, and a seamless belt was produced using this coating solution.
[Preparation of belt]
<Preparation of coating solution>
First, a polyimide varnish (U-varnish S; Ube Industries, Ltd.) having a polyimide resin precursor obtained by reacting 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine as an S component. And polyimide varnish mainly composed of a polyimide resin precursor obtained by reacting 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether as component A -Varnish A (manufactured by Ube Industries) is measured so that the weight ratio (S / A) in terms of polyamic acid solid content of U-varnish S and U-varnish A is 10/90.

Subsequently, a dispersion of carbon black (Special Black 4; manufactured by Evonik Degussa) prepared and dispersed in N-methyl-2-pyrrolidone so that the carbon black content was 17% by weight of the polyamic acid solid content was accommodated. In a bead mill, U-varnish S and U-varnish A were thoroughly mixed with stirring to prepare a coating solution.

<Manufacture of intermediate transfer belt>
Next, a cylindrical mold A having an outer diameter of 700 mm and a length of 400 mm roughened by blasting is used, and the coating liquid is applied while rotating the cylindrical mold at 50 rpm (times / minute). It apply | coated with the dispenser so that it might cast on a cylindrical outer surface uniformly. 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 110 ° 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. Thus, the temperature was raised to 320 ° C. and heat treatment (firing) was performed for 60 minutes to obtain a seamless belt. Next, this seamless belt end was cut to obtain an intermediate transfer belt A having a circumferential length of 2200 mm, a width of 376 mm, and a thickness of 60.2 μm.

[Evaluation of belt characteristic values]
Next, characteristic values of the obtained belt were evaluated. Measurement items and measurement methods are shown below.

<Surface roughness on the back of the belt>
The surface roughness of the back surface of the belt (the surface that was in contact with the outer surface of the mold) was measured according to JIS B0601: 2001 by Tokyo Seimitsu Co., Ltd. (SURFCOM 1400D). The measurement conditions were a measurement speed of 0.6 mm / sec, a cut-off value of 0.8 mm, and a measurement length of 2.5 mm. Measure the back of the belt at a total of 9 locations (3 locations in the circumferential direction x 3 locations in the width direction), 3 locations in the belt circumferential direction and 3 locations in the belt width direction (center and both ends). Using.

<Voltage resistance voltage dependency>
The measurement was performed using a URS probe with a Hirester (Mitsubishi Chemical). For volume resistance, measurement is performed on the back surface of the belt, measurement at the time of application of 10 V / 10 seconds and measurement at the time of application of 100 V / 10 seconds, and when the common logarithm of each volume resistance value is ρv10, ρv100, The voltage dependency of the volume resistance was evaluated using the difference value (ρv10−ρv100).

<Dispersion of surface resistance>
The surface resistance value when 500 V / 10 seconds were applied to the back side of the belt was measured using a URS probe at Hiresta (manufactured by Mitsubishi Chemical). Measurements were made at a total of 9 locations (3 locations in the circumferential direction × 3 locations in the width direction), 3 locations in the belt circumferential direction and 3 locations in the belt width direction (center and both ends), and the average value was used.
For the common logarithmic values of the surface resistance values at nine locations, the average value and the ratio between the MAX value and the MIN value (MAX / MIN) were calculated. The ratio between the MAX value and the MIN value (MAX / MIN) was used as an evaluation value for variation in surface resistance.

<Hygroscopic linear expansion coefficient>
The moisture absorption linear expansion coefficient is a distance between the inner ends of the arms 2 and 3 of a sample polyimide sheet cut into a predetermined shape (width 10 mm, length 70 mm) from the center of the seamless belt in the apparatus shown in FIG. After adjusting the weight of the aluminum weight 4 so that the linear pressure applied to the sample is 150 g / cm, the elongation measuring device is placed in a constant temperature and humidity chamber, and 35 ° C./85% (RH: Relative humidity) and 35 ° C./35% (RH: relative humidity) were measured for the amount of elongation, the difference (ΔL) was determined, and the hygroscopic linear expansion coefficient was calculated using the following equation.
Hygroscopic linear expansion coefficient (ppm /% RH) = (ΔL / 50 mm) / 50%
The amount of elongation was determined by measuring the distance between the lower part of the weight 4 and the laser micro gauge 5 with a reflective laser micro gauge 5 provided at the lower part of the weight 4.
These test results are summarized in Table 1.
In Table 1, volume resistance ρv is a measured value when 100 V / 10 seconds are applied.

[Real machine evaluation test]
Next, the actual machine attached to the actual machine of the manufactured belt was evaluated.
<Evaluation image forming apparatus>
A belt A having an inner circumferential length of 2200 mm, a width of 376 mm, and a thickness of 60.2 μm is mounted on a tandem type image forming apparatus as shown in FIG. 2, and the intermediate transfer belt is set at a linear speed of 425 mm / sec. The actual machine test was conducted.
<Evaluation toner>
As the toner, toner A prepared by a polymerization method having a volume average particle diameter of 5.2 μm and a circularity of 0.95 was used.

<Running test evaluation>
The test environment was two environments, and the test was performed by changing the environment in the order of HH environment (32 ° C., 80%) and LL environment (10 ° C., 15%). In each environment, a printing test was conducted to output 100K character images at a printing rate of 5% at 100 P / J (total 200 K sheets). At the end of running in each environment, we checked for the occurrence of abnormal images and machines, and output full images, halftone images, and fine line images. The ranking image quality was evaluated using rank samples for solid image uniformity, halftone uniformity, and fine line reproducibility.
In the rank sample, the highest rank is 5, and a rank of 2.5 or higher is an acceptable level in actual use.

<Production of belt>
It was produced in the same manner as in Example 1 except that the mixing ratio of U-varnish S and U-varnish A was changed to 20/80 by the weight ratio (S / A) in terms of polyamic acid solid content, and the circumference was 2200 mm. A belt B having a width of 376 mm and a thickness of 60.3 μm was obtained. Various characteristic values of the belt B are summarized in Table 1.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the attached belt was changed to belt B. The test results are summarized in Table 2.

<Production of belt>
Production was performed in the same manner as in Example 1 except that the mixing ratio of U-varnish S and U-varnish A was changed to 40/60 by weight ratio (S / A) in terms of polyamic acid solid content, and the circumference was 2200 mm. A belt C having a width of 376 mm and a thickness of 61.4 μm was obtained. Various characteristic values of the belt C are summarized in Table 1.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the attached belt was changed to belt C.
The test results are summarized in Table 2.

<Production of belt>
The mixing ratio of U-varnish S and U-varnish A is changed to 30/70 by weight ratio (S / A) in terms of polyamic acid solid content, and the mold is mold B (the same size as mold A) The surface was sandblasted, but the production was performed in the same manner as in Example 1 except that the surface roughness was changed to a mold having a surface roughness larger than that of the mold A, and the circumference was 2200 mm, the width was 376 mm, and the thickness was 60.8 μm. Belt D was obtained. Various characteristic values of the belt D are summarized in Table 1.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the attached belt was changed to belt D. The test results are summarized in Table 2.

<Production of belt>
Fabrication was performed in the same manner as the belt B of Example 2, and a belt E was obtained.
<Evaluation of actual machine>
Evaluation was carried out in the same manner as in Example 1 except that the toner B (volume average particle diameter: 6.8 μm, circularity: 0.95) prepared by the polymerization method and using the belt E was used. The test results are summarized in Table 2.

<Production of belt>
Fabrication was performed in the same manner as the belt B of Example 2, and a belt F was obtained.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the toner C (volume average particle diameter: 8.1 μm, circularity: 0.95) prepared by the polymerization method and using the belt F was used. The test results are summarized in Table 2.

<Production of belt>
Fabrication was performed in the same manner as the belt B of Example 2, and a belt G was obtained.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the toner D (volume average particle diameter: 8.4 μm, circularity: 0.93) prepared by the pulverization method using the belt G was used. The test results are summarized in Table 2.

[Comparative Example 1]
<Production of belt>
The mixing ratio of U-varnish S and U-varnish A was changed to 20/80 by weight ratio (S / A) in terms of polyamic acid solid content, and the mold was mold C (the same size as mold A) The surface was sandblasted, but the surface was made in the same manner as in Example 1 except that the surface was changed to a mold having a smoother surface than the mold A). The circumference was 2200 mm, the width was 376 mm, and the thickness was 59. An 8 μm belt H was obtained. The belt characteristics are summarized in Table 1.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the attached belt was changed to belt H. In the test of the LL environment, severe damage occurred on the belt end side due to the deviation of the belt. Since the image is disturbed at the edge of the image, the subsequent test is stopped. The test results are shown in Table 2.

[Comparative Example 2]
<Production of belt>
A mold in which the mixing ratio of U-varnish S and U-varnish A was changed to 40/60 by weight ratio (S / A) in terms of polyamic acid solid content, and the mold used was the same as in Example 4. A belt I having a peripheral length of 2200 mm, a width of 376 mm, and a thickness of 60.4 μm was obtained in the same manner as in Example 1 except that B was changed. Various characteristic values of the belt I are summarized in Table 1.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the attached belt was changed to belt I.
In the HH environment test, color misregistration due to belt slip occurred frequently, so the test was stopped. The test results are shown in Table 2.

[Comparative Example 3]
<Production of belt>
The mixing ratio of U-varnish S and U-varnish A was prepared in the same manner as in Example 1, except that the weight ratio (S / A) in terms of polyamic acid solid content was changed to 5/95. A belt J having a length of 2200 mm, a width of 376 mm, and a thickness of 60.8 μm was obtained. Various characteristic values of the belt J are summarized in Table 1.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the attached belt was changed to belt J.
In the HH environment test, color misregistration due to belt slip occurred frequently, so the test was stopped. The test results are shown in Table 2.

[Comparative Example 4]
<Production of belt>
The mixing ratio of U-varnish S and U-varnish A was prepared in the same manner as in Example 1, except that the weight ratio (S / A) in terms of polyamic acid solid content was changed to 50/50. A belt K having a length of 2200 mm, a width of 376 mm, and a thickness of 60.9 μm was obtained. Various characteristic values of the belt K are summarized in Table 1.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the attached belt was changed to belt K. The test results are summarized in Table 2.

[Comparative Example 5]
<Production of belt>
A belt L having a circumference length of 2200 mm, a width length of 376 mm, and a thickness of 60.1 μm was prepared except that the used varnish was not mixed with U-varnish S and only U-varnish A was used. Obtained. Various characteristic values of the belt L are summarized in Table 1.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the attached belt was changed to belt L. In the HH environment test, color misregistration due to belt slip occurred frequently, so the test was stopped. The test results are shown in Table 2.

[Comparative Example 6]
<Production of belt>
The used varnish does not mix U-varnish A, uses only U-varnish S, and uses a mold D in which the inner surface of the cylinder is mirror-finished. The inner surface of the mold D is dispensed by a dispenser. A belt M having a peripheral length of 2200 mm, a width of 376 mm, and a thickness of 60.1 μm was obtained except that the coating solution was prepared by a centrifugal molding method in which coating solution was uniformly applied / dried / cured. It was. Various characteristic values of the belt M are summarized in Table 1.
<Evaluation of actual machine>
Evaluation was performed in the same manner as in Example 1 except that the attached belt was changed to the belt M.
In the test of the LL environment, severe damage occurred on the belt end side due to the deviation of the belt. Since the image is disturbed at the edge of the image, the subsequent test is stopped. The test results are shown in Table 2.

ここで、吸湿線膨張係数は、ｐｐｍ／％ＲＨ、表面抵抗ρｓは、LogΩ／□、体積抵抗率ρｖは、LogΩ・cmである。

Here, the hygroscopic linear expansion coefficient is ppm /% RH, the surface resistance ρs is LogΩ / □, and the volume resistivity ρv is LogΩ · cm.

As shown in Tables 1 and 2, in Examples 1 to 7, a polyimide resin component (S component) in which 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine are imide-bonded, and The weight ratio (S / A) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride to the polyimide resin component (component A) in which 4,4′-diaminodiphenyl ether is imide-bonded is 10/90 to 40/60, the surface roughness Ra of the back surface is 0.2 to 0.4 μm, the coefficient of hygroscopic expansion is 22 ppm /% RH or less, and the variation in surface resistance is small. It is 5 or more and is a level acceptable in actual use.

In Examples 5 to 7, since the toner particle size used is large, the image quality rank is 2.5 to 3.5. However, in Examples 1 to 4 in which the toner particle size is small, the image quality rank is In the first and second embodiments, in which the voltage dependency is small, particularly, the image quality rank is 4.

On the other hand, in Comparative Examples 1 and 6, since the surface roughness Ra of the belt back surface is small, the frictional force between the driving roller and the belt is large, the belt is biased during running, and the belt end is severely damaged. In Example 2, the roughness of the back surface of the belt is large and the contact area between the belt and the driving roller is reduced, so that slip occurs between the driving roller and the belt. In Comparative Examples 3 and 5, the S component in the resin is Since there is not a small amount, the coefficient of linear expansion of moisture absorption is large, and the belt slips due to large elongation during running of the intermediate belt, resulting in color misregistration. In Comparative Example 4, since the S component in the resin is high, the variation in surface resistance is large and the voltage dependency is large. Therefore, in solid and halftone images, the image rank is 2, which is not in a practically acceptable range. .

As described above, the present invention is a polyimide used for the belt, with the surface roughness Ra of the back surface (inner surface) of the intermediate transfer belt being 0.2 μm to 0.4 μm, the moisture absorption linear expansion coefficient of the belt being 22 ppm /% RH or less. The resin is composed of a polyimide resin component (S component) in which 3,3 ′, 4,4′-biphenyltetraarbonic dianhydride and p-phenylenediamine are imide-bonded, and 3,3 ′, 4,4′-biphenyltetra. A carboxylic acid dianhydride and a polyimide resin component (component A) imide-bonded with 4,4′-diaminodiphenyl ether are blended, and the weight ratio (S / A) of the component S to the component A is 10/90 to 40 /. Therefore, even in an image forming apparatus in which the intermediate transfer belt has a peripheral length of 2000 mm or more and the linear speed is driven at a high speed of 350 mm / sec or more, the intermediate transfer belt slips or stretches. Without generating, in which color shift can be no good image formation.

DESCRIPTION OF SYMBOLS 1 Elongation measuring apparatus 2, 3 Arm 4 Weight 5 Laser micro gauge 11 Image forming apparatus 12 Image writing part 13 Image forming part 14 Paper feeding part 15 Fixing apparatus 16 Registration roller 20BK, 20M, 20Y, 20C Developing apparatus
21BK, 21M, 21Y, 21C Image carrier 22 Intermediate transfer belt 23 Bias roller 25 Cleaning member 26 Drive roller 27 Lubricant coating device 50 Transfer conveyance belt 60 Secondary transfer bias roll

JP 2008-225182 A JP-A-2005-74914 JP 2001-142313 A JP2004-77576

Claims (7)

An image forming apparatus that transfers a toner image formed on an electrostatic latent image carrier to a recording medium via an intermediate transfer belt that is driven at 350 mm / sec or more,
The intermediate transfer belt is formed of at least a polyimide resin, has a circumference of 2000 mm or more, a back surface (inner surface) surface roughness Ra of 0.2 to 0.4 μm, and a moisture absorption linear expansion coefficient of 19.6 ppm /%. RH or less, and the polyimide resin is a polyimide resin component (S component) in which 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine are imide-bonded, and 3,3 ′, 4 , 4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether imide-bonded polyimide resin component (component A) are blended, and the weight ratio (S / A) of the component S to component A is An image forming apparatus, wherein the image forming apparatus is 30/70 to 40/60 . 2. The difference ρv10−ρv100 is 2.0 or less when the intermediate transfer belt has ρv10 and ρv100 as common logarithmic values of volume resistance when 10 V and 100 V are applied, respectively. The image forming apparatus described in 1. The image forming apparatus according to claim 1, wherein the toner forming the toner image has a circularity of 0.95 to 0.98. 4. The image forming apparatus according to claim 1, wherein the toner forming the toner image has a volume average particle diameter of 4 μm to 8 μm. The image forming apparatus according to claim 4, wherein a volume average particle diameter of the toner forming the toner image is 4 μm to 5.2 μm. The image forming apparatus according to claim 1, further comprising a solid lubricant application device that applies a lubricant to a surface of the intermediate transfer belt. The image forming apparatus according to claim 6, wherein the lubricant is zinc stearate.

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