JP2001324879A - Intermediate transfer member and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer body which prevents the degradation in resistance by transfer voltage, improves the uniformity of the electric resistance, is little in dependence on electric fields, is little in the change of resistance by the environment and has stable electric characteristics, and an image forming device which makes it possible to obtain high-quality transfer images stably for a long period of time. SOLUTION: This intermediate transfer body is constituted by incorporating carbon black of a pH <=5 and an ion conductive polymer into a composition material and this image forming device has such intermediate transfer body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to an intermediate transfer member used for an image forming apparatus using an electrophotographic method, such as a printer, a facsimile, or a multifunction peripheral thereof, and an image forming apparatus including the same. After transferring to the transcript,
The present invention relates to an intermediate transfer member used for an image forming apparatus which transfers the image onto a transfer target such as paper to obtain a reproduced image, and an image forming apparatus including the same.

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic method is:
A uniform charge is formed on an image carrier made of a photoconductive photoreceptor made of an inorganic or organic material, and an electrostatic latent image is formed with a laser beam or the like that modulates an image signal. The latent image is developed into a visualized toner image. Then, the required reproduced image is obtained by electrostatically transferring the toner image via an intermediate transfer member or directly to a transfer material such as recording paper. Particularly, as an image forming apparatus employing a system in which a toner image formed on the image carrier is primarily transferred to an intermediate transfer member, and a toner image on the intermediate transfer member is secondarily transferred to recording paper, Japanese Patent Laid-Open No. The one disclosed in 206567 and the like is known.

Materials used for an image forming apparatus employing the intermediate transfer member system include polycarbonate resin (JP-A-06-095521), PVDF (polyvinylidene fluoride) (JP-A-5-200904, and JP-A-6-200904). JP-A-228335), polyalkylene phthalate (JP-A-6-149081), a blend material of PC (polycarbonate) / PAT (polyalkylene terephthalate) (JP-A-6-149083), ET
FE (Ethylene tetrafluoroethylene copolymer) / P
A proposal has been made to use a conductive endless belt of a thermoplastic resin such as a blend material of C, ETFE / PAT, and PC / PAT (Japanese Patent Application Laid-Open No. 6-149079). In addition, Japanese Patent Publication No. 2560727 proposes a carbon black dispersed polyimide seamless belt.

The electrical resistance value of the intermediate transfer member is controlled within a predetermined range in order to obtain high quality transfer image quality, and the in-plane variation (maximum and minimum resistance values) of the intermediate transfer member. However, it is required that the electrical resistance value does not change significantly even when the use environment conditions change, and that high quality can be stably obtained. For example, in practice, 10
It is required that the change in electric resistance between a low temperature and low humidity environment of 15 ° C. and 15% RH and a high temperature and high humidity environment of 28 ° C. and 85% RH be within 1.5 digits. In order to impart conductivity to the material constituting the intermediate transfer member in this manner, there is a method of imparting a conductive agent for imparting electron conductivity or a conductive agent for imparting ionic conductivity to the composition material.

[0005] As the conductive agent for imparting electron conductivity,
For example, in the case of a resin material in which ordinary carbon black is dispersed alone, there is little change in electric resistance value due to environmental changes in temperature and humidity, but it is difficult to uniformly disperse ordinary carbon black. The in-plane variation of the values tends to increase. Further, since the voltage dependence of the resistance value is large, electric field concentration occurs in the transfer portion, and there is a problem that the electric resistance value is reduced by the transfer voltage.

Further, when an ionic conductive polymer is applied as a conductive agent, the variation of the electric resistance value in the surface of the intermediate transfer member is extremely small, for example, 0.6 digits (log Ω / log).
□) The following are preferable values. On the other hand, the fluctuation of the electric resistance value due to environmental changes of temperature and humidity is large, for example, 28
High temperature and high humidity environment (H / H environment) of 85% RH and 10%
The difference of electric resistance value between low temperature and low humidity environment of 15 ℃ and 15% RH
There is a problem that there are 1.5 to 4 digits (logΩ / □).

[0007] Japanese Patent Application Laid-Open No. H8-110711 proposes using a material obtained by dispersing an ionic conductive type conductive agent and a material obtained by dispersing an electron conductive type conductive agent. However, in the case of a configuration having two or more layers, the higher resistance layer governs the resistance of the belt, so that the material of the high resistance layer exhibits the behavior of the conductivity type. For example, when a layer of a material in which an electron conductive type conductive agent is dispersed has a higher resistance than a layer of a material in which an ion conductive type conductive agent is dispersed, resistance variation is large, There is a problem such as a large nature.

As a countermeasure against such a problem, it is conceivable to mix and combine ordinary carbon black and an ion conductive polymer. However, when ordinary carbon black is used, it is secondary aggregated and becomes conductive. The conductivity of carbon black is non-uniform because it is easy to form a chain of carbon black, and when using ordinary carbon black, there is a problem that the resistance in the belt surface varies widely.

[0009]

As described above, in the prior art, in order to obtain a high-quality transfer image, the electric resistance value of the intermediate transfer member is controlled within a predetermined range, and the in-plane of the intermediate transfer member is controlled. It is required that the variation (the value of the maximum value and the minimum value of the resistance value) is small and that the electrical resistance value does not largely change even if the use environment conditions change. Further, it is necessary for the long-term durability test to have a small variation in the electric resistance value in order to always obtain a high-quality transferred image.

In the prior art, when ordinary carbon black is dispersed in a polyimide resin as a conductive fine powder, secondary aggregation occurs, and a conductive chain is easily formed, resulting in a large in-plane variation in electric resistance value. Cheap. Then, since the in-plane variation of the electric resistance value is large, the applied voltage is concentrated in the transfer portion, and the electric resistance value is reduced by the applied voltage. In particular,
For example, when a half-tone (magenta 30%) image is transferred after continuously transferring 1000 or more sheets shorter than the width of the intermediate transfer member such as a postcard, a problem has occurred in that the paper running section has a margin. This white spot defect was particularly remarkable in a low-temperature and low-humidity environment of 10 ° C. and 15% RH. The paper running section slips off because the applied voltage at the secondary transfer section causes a peeling discharge between the intermediate and the paper when the paper is peeled, and the surface resistivity of the paper running section of the intermediate transfer body. However, this is because the transfer efficiency is lower than that of the peripheral region, and the transfer efficiency is lower than that of the peripheral region. It is assumed that the carbon black contained in the belt is oxidized by repeated voltage application, the conductivity increases, and the resistance decreases. In addition, the lowering of the resistance tends to be large when the dispersibility of the carbon black contained in the belt is poor.

Such a decrease in resistance is not preferable because complicated replacement of the intermediate transfer member leads to an increase in maintenance work and running costs.

An object of the present invention is to solve the above conventional problems and achieve the following objects. That is, an object of the present invention is to prevent a decrease in resistance due to a transfer voltage, improve uniformity of electric resistance, reduce electric field dependence, and furthermore, have a small change in resistance due to the environment, and an intermediate transfer member having stable electric characteristics. And an image forming apparatus capable of obtaining a high-quality transfer image stably for a long period of time.

[0013]

The above object is achieved by the following means. That is, the present invention provides an intermediate transfer member characterized in that <1> a composition material contains carbon black having a pH of 5 or less and an ion conductive polymer.

<2> The content of carbon black having a pH of 5 or less is 5% by weight or more and less than 25% by weight, and the content of the ionic conductive polymer is 10% by weight or more and less than 50%. An intermediate transfer member according to <1>.

<3> The surface resistivity is 1 × 10 ¹⁰ to 1 × 1
0 < ¹⁴ Ω / □, <1> or <2>
> The intermediate transfer member described in (1).

<4> The intermediate transfer member according to any one of <1> to <3>, wherein the composition material is a polyimide resin material.

<5> An image forming apparatus comprising the intermediate transfer member according to any one of <1> to <4>.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The intermediate transfer member of the present invention comprises a composition material containing carbon black having a pH of 5 or less and an ion-conductive polymer. Occurs when an electron conductive conductive agent is used alone by using a carbon black having a pH of 5 or less as a conductive agent to impart electronic conductivity and an ion conductive polymer as a conductive agent to impart ionic conductivity. Large electric field dependence is reduced, furthermore, it is possible to suppress the in-plane variation of the electric resistance value caused by the electric field dependence, and occurs when the conductive agent imparting ionic conductivity is used alone, It is possible to reduce the fluctuation range of the electric resistance value due to the difference between the environment of the electric resistance value at low temperature / low humidity and high humidity / high temperature. In addition, carbon black having a pH of 5 or less is less likely to cause secondary aggregation due to the effect of the oxygen-containing functional group attached to the surface thereof, and can have a high dispersibility in a composition material. Also have high resistance. By using a carbon black having a pH of 5 or less as a conductive agent for providing electron conductivity and an ion-conductive polymer as a conductive agent for providing ionic conductivity, it is possible to improve the uniformity of electric resistance particularly. it can. Therefore, resistance reduction due to transfer voltage is prevented, uniformity of electric resistance is improved, electric field dependence is small, resistance change due to environment is small, stable electric characteristics are obtained, and paper running part is whitened out. This is an intermediate transfer member capable of obtaining high image quality in which occurrence of image quality defects is suppressed.

Here, the drop in resistance due to the transfer voltage and the occurrence of white spots due to the drop in resistance will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating a reduction in resistance of a secondary transfer portion of an intermediate transfer member. As shown in FIG. 1, a support roller 1 is interposed via a belt-shaped intermediate transfer body 101.
A transfer voltage is applied to the secondary transfer portion (nip portion) formed by the transfer roller 02 and the transfer roller 103 at the same time as the sheet (transfer object) 104 is passed, and secondary transfer is performed. Immediately after the secondary transfer, the surface (paper side) of the belt-shaped intermediate transfer body 101 is charged to the plus side, and the surface of the paper 104 (intermediate transfer body side) is charged to the minus side. Separation discharge occurs between the semiconductor device and the semiconductor device 104. Due to this discharge phenomenon, the surface of the intermediate transfer member 101 is altered, a new conductive path is formed, and the resistance is reduced. If the electric field dependency is large, the electric field is concentrated on the surface of the intermediate transfer member 101, and the surface of the intermediate transfer member 101 is easily deteriorated, so that the resistance is reduced.

FIG. 2 is a schematic diagram illustrating a situation in which white spots occur in halftone. As shown in FIG.
Paper running unit 2 in intermediate transfer body 200 after continuous copying of 00 sheets (for example, in a low-temperature and low-humidity environment of 10 ° C. and 15% RH)
01, the resistance is reduced as shown in FIG.
Middle (a)). When a halftone of 30% of magenta is copied in such a state, it is difficult to print on the paper traveling unit 201 having lower resistance than the non-paper traveling unit 202 ((b) in FIG. 2). As a result, white spots occur. In particular, the occurrence of the white spots is caused by the surface resistivity of the paper traveling unit 201 being 1.1 digits (logΩ / log) higher than that of the non-paper traveling unit 202.
□) It is easy to occur when the temperature is lower than the above.

Carbon black having a pH of 5.0 or less (hereinafter sometimes referred to as "acidic carbon black").
Can be obtained by oxidizing carbon black on the surface to provide an oxygen-containing functional group (for example, a carboxyl group, a quinone group, a lactone group, a hydroxyl group, etc.) on the surface. This oxidation treatment is carried out in a high-temperature atmosphere by contacting and reacting with air in the air, by a method of reacting with nitrogen oxides or ozone at room temperature, and by a method of oxidizing air at a high temperature followed by ozone oxidation at a low temperature And the like.

The acidic carbon black has a pH of 5.0 or less, preferably has a pH of 4.5 or less, and more preferably has a pH of 4.0. This pH can be determined by preparing an aqueous suspension of carbon black and measuring with a glass electrode. Further, the pH can be adjusted by conditions such as a processing temperature and a processing time.

Specific examples of the acidic carbon black include:
SPECIAL BLACK4 (Degussa,
PH 3.5, specific surface area: 180 (m ² / g), DBP oil absorption: 280 (cc / 100 g), volatile matter: 14.0
%), SPECIAL BLACK250 (Degus
sa company, specific surface area: 40 (m ² / g), DBP oil absorption: 48 (cc / 100 g), volatile matter: 2.0%), P
printx 150T (manufactured by Degussa, PH
4. Specific surface area: 110 (m ² / g), DBP oil absorption: 4
00 (g / 100 g), volatile content: 10%), Print
exU (manufactured by Degussa, PH 4.5, specific surface area:
110 (m ² / g), DBP oil absorption: 460 (g / 10
0g), volatile content: 5%), BLACK PEARLS
L (manufactured by Cabot Corporation, specific surface area: 138 (m ² / g),
DBP oil absorption: 55 (cc / 100 g), volatile content: 5.
0%)).

Examples of the ion conductive polymer include polyaniline, polythiophene, polyacetylene, polypyrrole, polyphenylenevinylene and the like. These conductive polymers can be used in a undoped state or a doped state.

In the intermediate transfer member of the present invention, the content of carbon black having a pH of 5 or less is 5% by weight or more and less than 25% by weight (preferably 10% by weight or more and 20% by weight), and the content of an ion conductive polymer is Is 10% by weight or more and 50%
It is preferably less than 20% by weight (preferably 20% by weight or more and 40% by weight). By using a combination of carbon black having a pH of 5 or less and an ion-conductive polymer in the above-mentioned fixed amount range with respect to the composition material, more effectively occurs when the electron-conductive conductor is used alone. , A large electric field dependency is reduced, and furthermore, an in-plane variation in electric resistance value caused by the electric field dependency can be suppressed, and occurs when a conductive agent imparting ionic conductivity is used alone,
It is possible to reduce the fluctuation range of the electric resistance value due to the difference between the environment of the electric resistance value at low temperature / low humidity and high humidity / high temperature.

As the composition material, a resin material, an elastic material,
And blended materials thereof. As the resin material, for example, resin materials such as polyimide, polyester, polyetheretherketone, polyamide, polycarbonate, polyvinylidene fluoride (PVDF), and polyfluoroethylene-ethylene copolymer (ETFE), and these are used as main raw materials A resin material may be used. As elastic materials, polyurethane, chlorinated polyisoprene,
NBR, chloropyrene rubber, EPDM, hydrogenated polybutadiene, butyl rubber, silicone rubber, etc. may be used alone or as a blend of two or more materials.
Among these, a polyimide resin is preferable. This polyimide resin is a material having a high Young's modulus, and is less deformed by driving (stress of a support roll, a cleaning blade, etc.), so that image defects such as color shift can be prevented. .

As the polyimide resin, a resin obtained by subjecting a polyamic acid, which is a precursor of the polyimide resin, to imide conversion by heating is preferable. The polyamic acid can be obtained by dissolving a substantially equimolar mixture of a tetracarboxylic dianhydride or a derivative thereof and a diamine in an organic polar solvent and reacting in a solution state.

Examples of the tetracarboxylic dianhydride include pyromellitic acid, naphthalene-1,4,5,8-tetracarboxylic acid, naphthalene-2,3,6,7-tetracarboxylic acid, 2,3,5 6-biphenyltetracarboxylic acid,
2,2 ′, 3,3′-biphenyltetracarboxylic acid,
3,3 ′, 4,4′-biphenyltetracarboxylic acid,
3,3 ', 4,4'-diphenylethertetracarboxylic acid, 3,3', 4,4'-benzophenonetetracarboxylic acid, 3,3 ', 4,4'-diphenylsulfonetetracarboxylic acid, , 3 ', 4,4'-Azobenzenetetracarboxylic acid, bis (2,3-dicarboxyphenyl)
Methane, bis (3,4-dicaroxyphenyl) methane, β, β-bis (3,4-dicaroxyphenyl) propane, β, β-bis (3,4-dicaroxyphenyl) hexafluoropropane and the like can be mentioned. Can be

As the diamine, m-phenyldiamine, p-phenyldiamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4-diaminochlorobenzene, m-xylylenediamine, p-xylylenediamine 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,
4'-diaminonaphthalebiphenyl, benzidine, 3,
3-dimethylbenzidine, 3,3′-dimethoxybenzidine, 3,4′-diaminodiphenyl ether, 4,
4'-diaminodiphenyl ether (oxy-p, p '
-Dianiline; ODA), 4,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone,
4,4'-diaminophenylsulfone, 4,4'-diaminoazobenzene, 4,4'-diaminodiphenylmethane, β, β-bis (4-aminephenyl) propane and the like.

Examples of the organic polar solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide,
Dimethyl sulfoxide, hexamethylphosphortriamide and the like can be mentioned. These organic polar solvents can be used in combination with phenols such as cresol, phenol and xylenol, and hydrocarbons such as hexane, benzene and toluene, if necessary. These may be used alone or in combination of two or more.

As the polyimide resin, a resin obtained by heating a polyamic acid obtained by a reaction between an aromatic tetracarboxylic dianhydride and an aromatic diamine is particularly preferable. Specifically, DuPont Co., Ltd.
Polypyromellitic imide based imide resin such as "Kapton HA", polybiphenyltetracarboxylic imide based resin such as "UPILEX S" by Ube Industries, "UPILEX R" by Ube Industries, Mitsui Toatsu Chemicals Industrial Co., Ltd.
Preferable examples include polybenzophenonetetracarboxylic acid imide-based resin such as "LARC-TPI (thermoplastic polyimide resin)".

The intermediate transfer member of the present invention has a surface resistivity of 1 ×
10 ¹⁰ Ω / □ to 1 × 10 ¹⁴ Ω / □, preferably 1 × 10
It is preferable that the resistance is ¹¹ Ω / □ to 1 × 10 ¹³ Ω / □.
If the surface resistivity is higher than 10 ¹⁴ Ω / □, peeling discharge is likely to occur at the post nip portion where the image transfer member and the intermediate transfer member of the primary transfer portion are peeled off. Missing image quality defects may occur. on the other hand,
If it is less than 10 ⁹ Ω / □, the electric field strength in the pre-nip portion becomes strong, and the gap discharge in the pre-nip portion is likely to occur, which may cause a problem that the graininess of the image quality deteriorates. Therefore, by setting the surface resistivity within the above range, it is possible to prevent the occurrence of white spots due to discharge that occurs when the surface resistivity is high and the deterioration of image quality that occurs when the surface resistivity is low. The surface resistivity indicates the surface resistivity on the transfer surface.

In the intermediate transfer member of the present invention, the surface resistivity can be measured according to JIS K6991 using a circular electrode (for example, HR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.). Specifically, for example, it can be measured using the circular electrode shown in FIG. FIG.
3A is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode for measuring surface resistivity. The circular electrode shown in FIG. 3 includes a first voltage application electrode A and a plate-shaped insulator B. The first voltage applying electrode A has a columnar electrode portion C and a cylindrical ring-shaped electrode having an inner diameter larger than the outer diameter of the columnar electrode portion C and surrounding the columnar electrode portion C at regular intervals. Part D
And The intermediate transfer member T is sandwiched between the plate-shaped insulator B and the columnar electrode portion C and the ring-shaped electrode portion D of the first voltage application electrode A, and the columnar electrode portion C and the ring of the first voltage application electrode A are interposed. A current I (A) flowing when a voltage V (V) is applied between the electrode and the electrode D is measured, and the following equation (1) is obtained.
As a result, the surface resistivity ρs (Ω / □) of the intermediate transfer body T can be calculated. Here, in the following equation (1), d (m
m) indicates the outer diameter of the columnar electrode portion C. D (mm) indicates the inner diameter of the ring-shaped electrode portion D.

Equation (1) ρs = π × (D + d) / (D−d) × (V / I)

The intermediate transfer member of the present invention has a volume resistivity of 1 ×.
10 ⁸ Ωcm to 1 × 10 ¹⁴ Ωcm, preferably 1 × 10
Is suitably a ^{10 Ωcm~1} × ^{10 12 Ωcm.}
If the volume resistivity is less than 10 ⁸ ΩCm, an electrostatic force for holding the charge of the unfixed toner image transferred from the image carrier to the intermediate transfer member is less likely to work, so that the static electricity between the toners is reduced. Due to the electric repulsion and the force of the fringe electric field near the image edge, the toner may be scattered around the image (blurring), and a problem that an image with large noise is formed may occur. On the other hand, the volume resistivity is 10 ¹⁴ Ωcm
If it is higher, the charge retaining force is large, so that there is a case where a problem that a charge eliminating mechanism is required because the surface of the intermediate body is charged by the transfer electric field in the primary transfer. Therefore, by setting the volume resistivity within the above range, it is possible to prevent the toner from scattering or a problem requiring a charge eliminating mechanism.

In the intermediate transfer member of the present invention, the volume resistivity can be measured according to JIS K6991 using a circular electrode (for example, HR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.). Specifically, for example, FIG.
Can be measured using a circular electrode shown in FIG. FIG.
FIGS. 3A and 3B are a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode for measuring volume resistivity. The circular electrode shown in FIG. 4 includes a first voltage applying electrode A ′ and a second voltage applying electrode B ′. The first voltage applying electrode A ′ has a cylindrical electrode portion C ′ and an inner diameter larger than the outer diameter of the cylindrical electrode portion C ′, and has a cylindrical shape surrounding the cylindrical electrode portion C ′ at a constant interval. And a ring-shaped electrode portion D ′. Columnar electrode part C 'and ring-shaped electrode part D' in the first voltage applying electrode A '
The intermediate transfer member T 'is sandwiched between the first voltage applying electrode B' and the second voltage applying electrode B ', and the voltage V ( The current I (A) flowing when V) is applied is measured, and the volume resistivity ρv (Ωcm) of the intermediate transfer body T can be calculated by the following equation (2). Here, in the following equation (2), t indicates the thickness of the intermediate transfer body T.

Equation (2) ρv = 19.6 × (V / I) × t

The intermediate transfer member of the present invention may have either a belt shape or a drum shape, but the belt shape is preferable from the viewpoint of the degree of freedom of arrangement of other subsystems and the ease of handling. The intermediate transfer member of the present invention, when in the form of a belt, comprises a single layer or a plurality of elastic layers, and at least one composition material of the elastic layers contains carbon black having a pH of 5 or less and an ionic conductive polymer. I do. On the other hand, in the case of the drum shape, a single layer or a plurality of elastic layers are provided on the substrate, and p
It contains H5 or less carbon black and an ion conductive polymer. A configuration in which a surface coat layer is provided on the elastic layer may be adopted. Further, in the intermediate transfer member of the present invention, as a configuration other than using a polyimide resin film containing an oxidized carbon black as at least one of the elastic layers, for example, a layer configuration, a type of a substrate, and the like have conventionally known configurations. Can be taken.

The thickness of the intermediate transfer member of the present invention can be appropriately determined according to the purpose of use in the case of a belt shape.
Generally, from mechanical characteristics such as strength and flexibility, 20 to 5
It is preferably about 00 μm, particularly preferably 50 to 200 μm.
μm.

The intermediate transfer member of the present invention comprises a first transfer means for primarily transferring a toner image formed on an image carrier onto the intermediate transfer member, and a transfer member for transferring the toner image transferred onto the intermediate transfer member to a transfer member. This is used for an image forming apparatus provided with a second transfer unit for performing secondary transfer to the image forming apparatus. Further, the intermediate transfer member of the present invention, in the case of a belt shape, in a transfer area for transferring a toner image to a transfer target,
It may be used as a transfer / conveying belt for conveying the transfer object.

(Image Forming Apparatus) The image forming apparatus of the present invention includes the intermediate transfer member of the present invention. An image forming apparatus according to the present invention includes a first transfer unit that primarily transfers a toner image formed on an image carrier onto an intermediate transfer body, and a secondary transfer unit that transfers the toner image transferred onto the intermediate transfer body onto a transfer target body. An image forming apparatus of an intermediate transfer system including a second transfer unit for transferring, and using the intermediate transfer body of the present invention as the intermediate transfer body. Also,
An image forming apparatus provided with the intermediate transfer member of the present invention as a transfer conveyance belt for conveying the transfer object to a transfer area where the toner image is transferred to the transfer object. By providing the intermediate transfer member of the present invention, a high-quality transfer image can be obtained stably for a long period of time.

The image forming apparatus of the present invention is not particularly limited as long as it is an intermediate transfer body type image forming apparatus. For example, a normal monocolor image containing only a single color toner in a developing device is used. Forming apparatus, a color image forming apparatus that repeats primary transfer of a toner image carried on an image carrier to an intermediate transfer body sequentially, and a plurality of image carriers having developing units for each color are serially arranged on the intermediate transfer body. And a tandem type color image forming apparatus arranged. Specifically, the image carrier, charging means for uniformly charging the image carrier surface, exposure means for exposing the image carrier surface to form an electrostatic latent image, and developing the latent image formed on the image carrier surface Developing means for developing a toner image by using an agent, a fixing means for fixing a toner image on a transfer-receiving material, a cleaning means for removing toner and dust adhered to an image carrier, and a toner remaining on the surface of the image carrier. It can be arbitrarily provided by a known method, if necessary, such as a static eliminator for removing the electrostatic latent image.

As the image carrier, a conventionally known one can be used, and as the photosensitive layer, a known one such as an organic or amorphous silicon can be used. When the image bearing member is cylindrical, it can be obtained by a known manufacturing method such as extruding aluminum or an aluminum alloy and then surface-treating. It is also possible to use the belt-shaped image carrier.

The charging means is not particularly limited. For example, conductive or semiconductive rollers, brushes, films,
Known chargers such as a contact-type charger using a rubber blade and the like, a scorotron charger and a corotron charger using corona discharge, and the like can be used. Among these, a contact-type charger is preferable because of its excellent charge compensation ability. The charging unit normally applies a direct current to the electrophotographic photoreceptor, but may apply an alternating current further superimposed.

The exposure means is not particularly limited. For example, a semiconductor laser beam, LE
A light source such as D light and liquid crystal shutter light, or an optical system device capable of exposing these light sources to a desired image through a polygon mirror is exemplified.

The developing means can be appropriately selected according to the purpose. For example, there is a known developing method in which a one-component developer or a two-component developer is brought into contact or non-contact with a brush or a roller to develop. And a developing device.

As the first transfer means, for example, a belt,
Known transfer chargers such as a contact-type transfer charger using a roller, a film, a rubber blade, and the like, a scorotron transfer charger using a corona discharge, and a corotron transfer charger are used. Among these, a contact-type transfer charger is preferable because of its excellent transfer charge compensation ability. In the present invention, a peeling charger and the like can be used in addition to the transfer charger.

Examples of the second transfer unit include a contact-type transfer charger such as a transfer roller exemplified as the first transfer unit, a scorotron transfer charger, and a corotron transfer charger. Among these, a contact-type transfer charger is preferable as in the first transfer unit. When the contact type transfer charger such as a transfer roller is pressed strongly, an image transfer state can be maintained in a good state. Also, when a contact-type transfer charger such as a transfer roller is pressed at the position of the roller for guiding the intermediate transfer member, the operation of transferring the toner image from the intermediate transfer member to the transfer target member can be performed in a good state. become.

The light neutralizing means includes, for example, a tungsten lamp, an LED, and the like, and the light quality used in the light neutralizing process includes, for example, white light from a tungsten lamp and the like, and red light such as LED light. . The intensity of the irradiation light in the photo neutralization process is usually set so as to be several times to 30 times the amount of light showing the half-life exposure sensitivity of the electrophotographic photosensitive member.

The fixing means is not particularly limited, and includes a fixing device known per se, such as a heat roller fixing device and an oven fixing device.

The cleaning means is not particularly limited, and a known cleaning device may be used.

Hereinafter, as an example of the image forming apparatus of the present invention, a color image forming apparatus in which primary transfer is repeated will be described. FIG. 5 is a schematic configuration diagram illustrating an example of the image forming apparatus of the present invention. The image forming apparatus shown in FIG. 5 includes a photosensitive drum 1 as an image carrier, a transfer belt 2 as an intermediate transfer member, a bias roller 3 as a transfer electrode, a tray 4 for supplying a sheet as a transfer target, and B ( A developing device 5 using black (toner) toner, a developing device 6 using Y (yellow) toner, a developing device 7 using M (magenta) toner, a developing device 8 using C (cyan) toner, a belt cleaner 9, a peeling claw 13, a belt roller 21, 23 and 24, backup roller 2
2, conductive roller 25, electrode roller 26, cleaning blade 31, sheet bundle 41, pickup roller 42,
And a feed roller 43.

In the image forming apparatus shown in FIG. 5, the photosensitive drum 1 rotates in the direction of arrow A, and its surface is uniformly charged by a charging device (not shown). An electrostatic latent image of the first color (for example, B) is formed on the charged photosensitive drum 1 by image writing means such as a laser writing device. This electrostatic latent image is developed with toner by the developing device 5 to form a visualized toner image T. The toner image T reaches the primary transfer portion on which the conductive roller 25 is disposed by the rotation of the photosensitive drum 1, and the toner image T is made static by applying an electric field of opposite polarity to the toner image T from the conductive roller 25. While being electrically attracted to the transfer belt 2, primary transfer is performed by rotation of the transfer belt 2 in the direction of arrow B.

Hereinafter, similarly, the second color toner image, the third color toner image
A color toner image and a fourth color toner image are sequentially formed and superimposed on the transfer belt 2 to form a multiple toner image.

The multi-toner image transferred to the transfer belt 2 reaches the secondary transfer section where the bias roller 3 is installed by the rotation of the transfer belt 2. The secondary transfer section includes a bias roller 3 provided on the surface of the transfer belt 2 on which the toner image is carried, a backup roller 22 disposed from the back side of the transfer belt 2 so as to face the bias roller, and the backup roller 22. The electrode roller 26 is configured to rotate while being pressed against.

The paper 41 is taken out one by one from a bundle of paper stored in the paper tray 4 by a pickup roller 42, and is fed by a feed roller 43 between the transfer belt 2 of the secondary transfer portion and the bias roller 3 at a predetermined timing. Sent by The toner image carried on the transfer belt 2 is transferred to the fed sheet 41 by the pressure conveyance by the bias roller 3 and the backup roller 22 and the rotation of the transfer belt 2.

The sheet 41 onto which the toner image has been transferred is separated from the transfer belt 2 by operating the separation claw 13 at the retracted position until the primary transfer of the final toner image is completed, and is conveyed to a fixing device (not shown), and is pressed. / The toner image is fixed by the heat treatment to be a permanent image. The transfer belt 2 on which the transfer of the multi-toner image onto the paper 41 has been completed is subjected to removal of residual toner by a belt cleaner 9 provided downstream of the secondary transfer unit to prepare for the next transfer. Also, the bias roller 3
Is a cleaning blade 31 made of polyurethane or the like.
Are attached so that they are always in contact with each other, and foreign matters such as toner particles and paper dust adhered by transfer are removed.

In the case of transferring a single-color image, the primary-transferred toner image T is immediately secondary-transferred and conveyed to a fixing device.
In the case of transferring a multicolor image by superimposing a plurality of colors, the rotation of the transfer belt 2 and the rotation of the photosensitive drum 1 are synchronized so that the toner images of the respective colors exactly coincide with each other in the primary transfer portion, and the toner images of the respective colors are shifted. Not to be. In the secondary transfer section, an output pressure (transfer voltage) having the same polarity as the polarity of the toner image is applied to the electrode roller 26 which is in pressure contact with the backup roller 22 disposed opposite to the bias roller 3 via the transfer belt 2. The toner image is transferred to the paper 41 by electrostatic repulsion. As described above, an image can be formed.

[0059]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, these embodiments do not limit the present invention.

Example 1 According to the composition shown in Table 1, N
-Carbon black Printex 150T (Degussa) dried in methyl-2-pyrrolidone (NMP)
Company, PH4, specific surface area: 110 (m ² / g), DBP
Oil absorption: 400 (g / 100 g), volatile matter: 10%)
Were mixed in a ball mill for 6 hours at room temperature. 3,3 ′, 4,4′-
Biphenyltetracarboxylic dianhydride (BPDA) 29
4.2 g and p-phenylenediamine (PDA)
2 g were dissolved in a nitrogen atmosphere and reacted with stirring at room temperature for 4 hours to obtain a polyamic acid solution containing carbon black.

N-methyl-2-pyrrolidone (NMP) 20
20 g of Ponianiline powder was added to 0 g, and the mixture was stirred at 5000 rpm for 1 hour using an auto-homomixer to dissolve and obtain a 10 wt% concentration of a undoped polyaniline solution.

After adding a predetermined amount of the polyaniline solution to the carbon black-containing polyamic acid solution, the mixture was stirred at room temperature for 1 hour using a stirring blade to obtain a desired blending amount of the carbon black and polyaniline-containing polyamic acid solution.

Next, this polyamic acid solution is applied to the inner surface of a cylindrical mold using a bullet-shaped traveling body so as to have a uniform thickness, and then, while rotating at 250 rpm, 60 ° C. from the outside of the mold. Hot air for 30 minutes and then at 150 ° C for 60 minutes.
After heating at 200 ° C. at a rate of 2 ° C./min, and further heating at 200 ° C. for 30 minutes, the temperature was returned to room temperature to obtain a translucent film.

After releasing the semi-cured film,
Put on the outside of the cylindrical mold, 5 from 200 ° C to 400 ° C
The temperature was increased by heating at a rate of ° C / min, and after removing dehydration ring-closing water and performing imide conversion, the temperature was returned to room temperature and peeled from the mold.
An endless polyimide belt having a thickness of 80 μm was obtained.

(Examples 2 to 4, Comparative Examples 1 to 9) Tables 1 and 2
An endless polyimide belt was obtained in the same manner as in Example 1, except that the type and amount of carbon black (CB) were changed according to the composition of

(Evaluation) In the endless polyimide belts obtained in Examples 1 to 4 and Comparative Examples 1 to 9, the surface resistivity, the volume resistivity, the environmental fluctuation width of the surface resistivity, the electric field dependence of the surface resistivity, The in-plane variation of the surface resistivity was examined. further,
The endless polyimide belt is mounted on the image forming apparatus shown in FIG.
After the continuous copying of (30K) sheets, the amount of decrease in the surface resistivity of the paper running section was examined. The results are shown in Tables 1 and 2. In addition, each measurement was performed as shown below.

-Surface Resistivity- The surface resistivity in this example was measured using a circular electrode shown in FIG. 3 (HR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd .; 22 ° C. using the inner diameter Φ30 mm and outer diameter Φ40 mm of the ring-shaped electrode part D)
In a / 55% RH environment, a voltage of 100 V was applied, and a current value after 10 seconds was obtained and calculated as described above.

-Measurement of Volume Resistivity- The volume resistivity in the present embodiment was measured using a circular electrode shown in FIG. 4 (HR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd .: external system of columnar electrode portion C). 22 ° C. using Φ16 mm, inner diameter Φ30 mm of ring-shaped electrode part D, outer diameter Φ40 mm)
Under a / 55% RH environment, a voltage of 100 V was applied, and a current value after 30 seconds was obtained, and calculated as described above.

—Environmental Fluctuation Range of Surface Resistivity— The environmental fluctuation width in this embodiment is a high-temperature high-humidity (H / H) environment (28 ° C./85% RH) and a low-temperature low humidity (L / L) (10 ° C.)
/ 15% RH) was calculated as the difference between the logarithmic value of the surface resistivity and the environment.

-Electric Field Dependence of Surface Resistivity-The electric field dependence of the surface resistivity in the present embodiment is determined by applying an applied voltage of 1
00V (electric field 143V / cm) and applied voltage 1000V
(Electric field 1429 V / cm) as the difference in logarithmic value of the surface resistivity under the condition of (electric field 1429 V / cm).

-In-plane variation of surface resistivity-In-plane variation (ΔR) of surface resistivity in the present embodiment is:
The endless belt was divided into eight parts in the circumferential direction and three parts in the width direction. The surface resistivity was measured at 24 points on the belt surface, the logarithmic value of the surface resistivity was obtained, and the difference between the maximum value and the minimum value was calculated.

The amount of decrease in surface resistivity after continuous copying of 30,000 (30K) sheets- The amount of decrease in surface resistivity after continuous copying of 30,000 sheets in this embodiment is determined by the initial surface resistivity and the amount of decrease after continuous copying of 30,000 sheets. Was calculated as the difference between the logarithmic value and the surface resistivity.

[0073]

[Table 1]

[0074]

[Table 2]

As shown in Tables 1 and 2, when the ion-conductive polymer was used alone as in Comparative Examples 1 to 3, the dispersion in the belt surface was small, but the high-temperature and high-humidity environment (28 ° C./85% R
H) and the low-temperature and low-humidity environment (10 ° C./15% RH) have a problem that the fluctuation range of the surface resistivity is 1.9 digits or more.

As in Comparative Examples 4 to 6, carbon black exceeding pH 5 (pH
5.7 granular acetylene black: Denki Kagaku Kogyo Co., Ltd.
) Alone, the fluctuation range of the surface resistivity in an environment is small, but the electric field dependence is large, the variation in the belt surface is large, and the partial resistance decrease at the transfer voltage described above. It can be seen that there is a problem such as the occurrence of image quality defects due to this.

As shown in Comparative Examples 7 and 8, carbon black (P) exceeding pH 5 was used as a conductive agent for imparting electron conductivity.
H5.7 granular acetylene black (manufactured by Denki Kagaku Kogyo KK) and an ionic conductive polymer are used in combination in an environment with a higher surface resistivity than when the ionic conductive polymer is used alone. The fluctuation range becomes smaller.
Electric field dependence is smaller than in the case where a conductive agent that imparts electronic conductivity is used alone, and variations in the belt surface are reduced, and the partial resistance decrease at the transfer voltage tends to be reduced. It can be seen that the variation in the surface resistivity in the environment and the partial decrease in resistance at the transfer voltage are insufficient for the value required for the intermediate transfer member.

As in Comparative Example 9, when a combination of ketchen black (manufactured by Lion Aguso Co., Ltd.) having a pH of 9 and a ionic conductive polymer was used as a conductive agent for imparting electron conductivity as ordinary carbon black. The fluctuation range of the surface resistivity in the environment is smaller than that in the case of using the ion conductive polymer alone. Electric field dependence is smaller than in the case where a conductive agent that imparts electronic conductivity is used alone, and variations in the belt surface are reduced, and the partial resistance decrease at the transfer voltage tends to be reduced. In comparison with the values required for the intermediate transfer member, Comparative Example 9
In the case of (1), it can be seen that the dispersion in the belt surface is large, and this is a level at which the above-described partial resistance reduction at the transfer voltage becomes a problem.

Examples 1 to 4 are different from the comparative example.
It can be seen that, when carbon black having a pH of 5 or less and an ionic conductive polymer are used in combination as described above, the intended electrical characteristics can be stably obtained. In particular,
It can be seen that the environmental fluctuation range of the surface resistivity can be suppressed within 1.5 digits (logΩ / □).

[0080]

As described above, according to the present invention, resistance reduction due to transfer voltage is prevented, uniformity of electric resistance is improved,
It is possible to provide an intermediate transfer body having a small electric field dependence, a small change in resistance due to the environment, and having stable electric characteristics, and an image forming apparatus capable of obtaining a high-quality transfer image stably for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a reduction in resistance of a secondary transfer portion of an intermediate transfer member.

FIG. 2 is a schematic diagram illustrating a situation in which white spots occur in halftone.

FIG. 3 is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode for measuring surface resistivity.

FIG. 4 is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode for measuring volume resistivity.

FIG. 5 is a schematic configuration diagram illustrating an example of the image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Intermediate transfer body 102 Support roller 103 Transfer roller 104 Paper 200 Intermediate transfer body 201 Paper running part 202 Non-paper running part A First voltage application electrode B Second voltage application electrode C Column-shaped electrode part D Ring-shaped electrode part A ' One voltage application electrode B 'Plate-shaped insulator C' Column-shaped electrode part D 'Ring-shaped electrode part T, T' Intermediate transfer member 1 Photosensitive drum (image carrier) 2 Transfer belt (intermediate transfer member) 3 Bias roller 4 Paper tray 5 Black developing device 6 Yellow developing device 7 Magenta developing device 8 Cyan developing device 9 Belt cleaner 13 Peeling claw 21, 23, 24 Belt roller 22 Backup roller 25 Conductive roller 26 Electrode roller 31 Cleaning blade 41 Paper (transfer object) ), Sheet bundle 42 pickup roller 43 feed roller T toner

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masao Nakamura 1-8-5 Hara-cho, Fukaya-shi, Saitama Nitto Denko Corporation (72) Inventor Toshihiko 1-8-5 Hara-cho, Fukaya-shi, Saitama Nitto Denko F term (reference) 2H032 AA05 BA09

Claims (5)

[Claims] 1. An intermediate transfer member comprising a composition material containing carbon black having a pH of 5 or less and an ion conductive polymer. 2. The content of carbon black having a pH of 5 or less is 5% by weight or more and less than 25% by weight, and the content of an ion conductive polymer is 10% by weight or more and less than 50%. 2. The intermediate transfer member according to 1. 3. The surface resistivity is from 1 × 10 ¹⁰ to 1 × 10 ^14.
The intermediate transfer member according to claim 1, wherein the intermediate transfer member is Ω / □. 4. The intermediate transfer member according to claim 1, wherein the composition material is a polyimide resin material. 5. An image forming apparatus comprising the intermediate transfer member according to claim 1.