JP2002162835A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of stably producing an image of high quality without causing a change in an electrical resistance with a lapse of time. SOLUTION: As to the image forming device equipped with an intermediate transfer body, the intermediate transfer body is provided with at least two or more layers including a base layer and a surface layer on a metallic cylindrical substrate, and at least one of the layers contains electronic conductive filler of <=pH 5.0 and the conductivity is based on electron conduction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer, and more particularly, to a method of transferring a toner image formed on an image carrier to an intermediate transfer member once and then transferring the toner image to the intermediate transfer member. The present invention relates to an image forming apparatus that obtains a reproduced image by transferring the image to a recording medium such as a sheet.

[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.

The body of the material constituting the transfer surface of the intermediate transfer body
The product specific resistance is generally 1 × 10 ⁸Ωcm to 1 × 1
0¹⁴It must be a semi-conductive region of Ωcm. This
Has a resistance of 10⁸If less than ΩCm, intermediate from image carrier
Static electricity holding the charge of the unfixed toner image transferred to the transfer body
Electrostatic force stops working, causing electrostatic repulsion between toners
The image and the fringe electric field near the image edge
The toner scatters around (blur) around the
There is a problem that a large image is formed.
0¹⁴If it is higher than Ωcm, the charge holding power is large.
In addition, the surface of the intermediate is charged by the transfer electric field in the primary transfer.
May require a static elimination mechanism.
You.

However, it is very difficult to control the resistance value of the resin material in the semiconductive region, and it is difficult to stably obtain a desired resistance value by adding ordinary conductive carbon black to ordinary resin material. Almost not. For this reason, it is necessary to measure and select the resistance values of all the semiconductive intermediate transfer members, thereby increasing the cost. For example, as described in Polymer Processing, Vol. 43, No. 4, 1977, Sumita et al., When carbon black is added to a polymer such as a resin material, the amount of carbon black added is small. The reason for this is that the conductivity is small, carbon black forms a conductor circuit from a certain threshold value, the conductivity is rapidly improved, and a medium resistance value cannot be obtained.

In order to impart conductivity to the material constituting the intermediate transfer member, a method of imparting a conductive agent for imparting electronic conductivity, such as carbon black, to the composition material, and a method of imparting a conductive agent for imparting ionic conductivity, respectively are provided. There is a way to do that. But,
When a conductive agent for imparting ionic conductivity is provided, the change in the electric resistance value in the plane of the intermediate transfer member is extremely small.
It is desirably five digits or less, and as described above, there is a portion having a large conductivity, and there is little problem that the surface resistance is reduced due to the concentration of the electric field there. On the other hand, the electric resistance value largely fluctuates due to environmental changes in temperature and humidity. For example, a high temperature and high humidity environment (H / H environment) of 30 ° C. and 85% RH.
There is a problem that the difference in electric resistance between the low temperature and low humidity environment (L / L environment) of 10 ° C. and 15% RH is 1.5 to 4 digits (logΩ).

Further, in general, an ionic conductive type conductive agent requires a large amount of the ionic conductive type conductive agent in order to obtain an electric resistance value at low temperature and low humidity to obtain a predetermined resistance value. If the amount is increased, the ionic conductive agent oozes out of the surface of the intermediate transfer member and migrates (bleeds out) to the surface of the image carrier, which causes a new problem that image deterioration, contamination, and erosion of the photosensitive material are likely to occur. Occurs.

Japanese Patent Application Laid-Open No. 5-129555 proposes an image forming apparatus using a drum-shaped intermediate transfer member. In this image forming apparatus, as an intermediate transfer member, a conductive species such as carbon black or the like is added to polycarbonate or Teflon (registered trademark) on a substrate of an aluminum drum to obtain a volume resistivity of 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm. A high-rigidity intermediate transfer drum on which a semiconductive layer is formed is used. In Japanese Patent Application Laid-Open No. 10-123851, a conductive support such as aluminum has a volume resistance of 10 ⁸ Ω.
There has been proposed an intermediate transfer drum in which a seamless tube is coated with a polycarbonate resin material in which carbon black is dispersed in a conductive elastic material such as silicone rubber having a size of not more than 1 cm.

However, in the case of the above-described carbon black-dispersed polycarbonate or carbon black-dispersed ethylene tetrafluoroethylene copolymer, 1,000 or more sheets shorter than the width of an intermediate transfer member such as a postcard are continuously transferred. Later, when a halftone (magenta 30%) image was transferred, there was a problem that the paper running portion slipped through. This white spot defect was particularly remarkable in a low-temperature and low-humidity environment of 10 ° C. and 15% RH. The paper running part slips off because the surface resistivity of the paper running part of the intermediate transfer body is lower than that of the peripheral part due to the peeling discharge between the intermediate and the paper at the time of peeling the paper at the secondary transfer part. This is because the transfer efficiency is lower than that of the peripheral site.

The electric field dependence of the surface resistivity of carbon black-dispersed polycarbonate and carbon black-dispersed ethylene tetrafluoroethylene copolymer is 0.8 to 0.8.
It is a level of 1.5 digits (log Ω / □), and it is considered that the concentration of the electric field due to the transfer voltage deteriorates the resin component around the portion having high conductivity and lowers the surface resistivity. The electric field dependence of the surface resistivity is large because it is difficult to uniformly disperse the carbon black in the resin component constituting the intermediate transfer member. Therefore, it is considered that there is a locally large conductive portion, and the electric field concentrates there.

Japanese Patent Application Laid-Open No. Hei 7-152262 discloses that silicon rubber or carbon black obtained by adding carbon black as a suitable elasticity and a suitable conductivity to the surface of an aluminum drum having a thickness of 3 mm is added. There is disclosed an image forming apparatus in which an intermediate transfer drum on which an elastic layer made of urethane rubber is formed and a highly rigid image carrier drum. However, in this intermediate transfer member, the first to fourth transfer from the image carrier to the intermediate transfer member is performed.
The primary transfer voltage for sequential multiple transfer of color toner images is
It is applied with a polarity (+) opposite to that of the toner, for example, +600
The range is from V to +3000 V, and there is a problem that the resistance changes by one digit or more when running for 30 KPV.

Since it is difficult to uniformly disperse carbon black in an elastic material such as silicon rubber or urethane rubber constituting the intermediate transfer member, carbon black is unevenly dispersed in the elastic material. Therefore, it is considered that there is a locally large conductive portion, and the electric field due to the transfer voltage is concentrated there.

As the above countermeasure, Japanese Patent Laid-Open No. 11-95570
In Japanese Patent Application Laid-Open Publication No. H11-264, it has been proposed to use, as an elastic layer material of an intermediate transfer drum having an elastic layer, epichlorohydrin rubber, which is a polar elastic material, because resistance unevenness is unlikely to occur. Further, Japanese Patent Application Laid-Open No. 9-1900
In Japanese Patent Publication No. 91, the change in the electric resistance value due to the application of the voltage is defined as the initial resistance value R1 and the resistance value R after applying a direct current of 5 mA per 1 m ² of surface area of the intermediate transfer body for 5 hours continuously.
2 with 0.1 ≦ R2 / R1 ≦ 10 and 5.0
An intermediate transfer member that satisfies the relationship of × 10 ⁴ Ω ≦ R2 ≦ 5.0 × 10 ⁹ Ω has been proposed, and a resistance is obtained by using a polar elastic material such as NBR or epichlorohydrin rubber, which has relatively high resistance. It has been proposed to adjust.

However, these polar elastic materials such as epichlorohydrin rubber have large fluctuations in electrical resistance to environmental changes in temperature and humidity.
85% RH high temperature and high humidity environment (H / H environment) and 10 ℃, 1
There is a problem that the difference in electric resistance from a low-temperature and low-humidity environment (L / L environment) of 5% RH is 1.5 digits (logΩ).

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, an object of the present invention is to provide an image forming apparatus capable of stably supplying a high-quality image without a change in electric resistance value over time.

[0015]

The above object is achieved by the following means. That is, the present invention provides: <1> an image forming apparatus provided with an intermediate transfer member, wherein the intermediate transfer member is formed on a metallic cylindrical substrate by forming two or more layers including at least a base layer and a surface layer. PH at which at least one of the layers exhibits conductivity by electron conduction
An image forming apparatus comprising 5.0 or less of an electron conductive filler. <2> The underlayer has a JIS-A hardness of 30 degrees or less,
The image forming apparatus according to <1>, wherein the image forming apparatus includes an elastic material having a compression strain of 10% or less and a thickness of 3 to 10 mm. <3> The image forming apparatus according to <1> or <2>, wherein the surface layer contains the electron conductive filler. <4> The image forming apparatus according to any one of <1> to <3>, wherein the content of the electron conductive filler is 2 to 40% by weight.

BEST MODE FOR CARRYING OUT THE INVENTION The image forming apparatus of the present invention comprises an intermediate transfer member, and the intermediate transfer member is formed on a metallic cylindrical substrate by forming two or more layers including at least a base layer and a surface layer. A layer, and at least one of the layers contains an electron conductive filler having a pH of 5.0 or less (hereinafter, simply referred to as an “electron conductive filler”) that develops conductivity by electron conduction.

Since the image forming apparatus of the present invention includes the above-mentioned intermediate transfer member, it is possible to stably supply high-quality images without a change in electric resistance over time. The intermediate transfer member is a drum type having at least one layer containing the electron conductive filler, and by using this electron conductive filler, the effect of the oxygen-containing functional group attached to the surface is improved. In addition, the dispersibility in the binder resin is improved, the resistance variation of the intermediate transfer body can be reduced, the electric field dependency is also reduced, and the electric field concentration due to the transfer voltage becomes difficult. In addition, since the surface of the electron conductive filler is oxidized, excessive current does not easily flow even by repeated voltage application, and the carbon characteristics due to surface oxidation due to the excessive current do not significantly change. Changes in the dynamic characteristics can be prevented. Further, since the electron conductive filler is uniformly dispersed, a change in the dispersion state of the electron conductive filler due to minute repeated deformation at the transfer site is reduced. As a result, the resistance change due to the transfer voltage is prevented, the uniformity of the electric resistance is improved, the dependence on the electric field is small, the resistance change due to the environment is small, and the occurrence of image quality defects such as a white paper running part is suppressed. An intermediate transfer member capable of obtaining high image quality. For this reason, there is no change in the electric resistance value over time, and a high-quality image can be stably supplied. Further, in the image forming apparatus of the present invention, since the intermediate transfer body is in the form of a drum, the circumferential length changes in a range of 10 ° C. to 50 ° C. assumed under a machine use environment (M / C use environment). There is no problem in that the driving system can be simplified.

Here, the reduction in resistance due to the transfer voltage and the occurrence of white spots due to the reduction 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 transfer voltage is applied to a transfer portion (nip portion) formed by a drum-shaped intermediate transfer body 301 and a transfer roller 303 at the same time as a sheet (recording medium) 304 is passed, and a secondary transfer is performed. Is performed. Immediately after the secondary transfer, the surface of the drum-shaped intermediate transfer body 301 (paper side) is charged to the plus side, and the surface of the paper 304 (intermediate transfer body side) is charged to the minus side. A peeling discharge occurs between the substrate 304 and the substrate. Due to this discharge phenomenon, the surface of the intermediate transfer member 301 is altered, a new conductive path is formed, and the resistance is reduced. When the electric field dependence is large, the intermediate transfer member 3
Electric field concentration occurs on the surface of the intermediate transfer member 301, and the surface of the intermediate transfer member 301 is easily deteriorated.

FIG. 2 is a schematic diagram illustrating a situation in which white spots occur in halftone. As shown in FIG.
The paper traveling section 4 of the intermediate transfer member 400 after the continuous copying of 00 sheets (for example, in a low temperature and low humidity environment of 10 ° C. and 15% RH)
01, a decrease in resistance occurs 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 401 having lower resistance than the non-paper traveling unit 402 ((b) in FIG. 2). As a result, white spots occur. In particular, the occurrence of this white spot is caused when the surface resistivity of the paper traveling portion 401 is 1.1 digits (log Ω / log) higher than that of the non-paper traveling portion 402.
□) It is easy to occur when the temperature is lower than the above. -Intermediate transfer body-

The intermediate transfer member is formed on a metallic cylindrical substrate by
Two or more layers including at least an underlayer and a surface layer (a layer corresponding to a transfer surface) are sequentially formed, and the underlayer is an elastic layer or an intermediate layer (a layer provided between the elastic layer and the surface layer).
The underlayer may be composed of only one layer, or may be composed of a plurality of layers. In the present invention, at least one of these layers contains an electron conductive filler, but from the viewpoint of exhibiting particularly good transferability, it is preferably contained in the surface layer.

The electron conductive filler develops conductivity by electron conduction and has a pH of 5.0 or less.
H 4.5 or less, more preferably pH 4.0 or less. When the electron conductive filler exceeds pH 5.0,
The effect of the oxygen-containing functional group attached to the surface cannot be obtained, the dispersibility in the binder resin is reduced, the resistance variation of the intermediate transfer body, the electric field dependence is deteriorated, and the transfer voltage is reduced. Electric field concentration occurs.

As the electron conductive filler, pH 5.0 is used.
The following carbon blacks (hereinafter may be referred to as “acidic carbon blacks”) may be mentioned. This acidic carbon black can be produced by oxidizing carbon black to impart a carboxyl group, a quinone group, a lactone group, a hydroxyl group, or the like to the surface. This oxidation treatment is carried out in a high-temperature atmosphere by contacting with air and reacting with air, a method of reacting with nitrogen oxides and ozone at normal temperature, and an air oxidation at high temperature followed by ozone oxidation at low temperature. It can be performed by a method or the like. In particular,
The oxidized carbon black can be manufactured by a contact method. The contact method includes a channel method, a gas black method, and the like, which can be appropriately selected and performed.

Here, the pH of the oxidized carbon black is
It is determined by preparing an aqueous suspension of carbon black and measuring with a glass electrode. Further, the pH of the oxidized carbon black can be adjusted depending on conditions such as a treatment temperature and a treatment time in the oxidation treatment step.

The acidic carbon black has a volatile content of 1
-25%, more preferably 2-2%.
It is suitable that the content is 0%, more preferably 3.5 to 15%. When the volatile content is less than 1%, the effect of the oxygen-containing functional group attached to the surface is lost, and the dispersibility in the binder resin may be reduced. On the other hand, when it is higher than 25%, when dispersing in the binder resin, the amount of decomposition of the oxygen-containing functional group attached to the surface increases, or
When the amount of water or the like adsorbed by the oxygen-containing functional group on the surface increases, there may be a problem that the appearance of the obtained molded product is deteriorated. Therefore, by setting the volatile content within the above range, the dispersion in the binder resin can be further improved. The volatile content can be determined from the ratio of organic volatile components (carboxyl group, quinone group, lactone group, hydroxyl group, etc.) that are generated when the carbon black is heated at 950 ° C. for 7 minutes.

Specific examples of the acidic carbon include “REGAL 400R” (pH 4.0, volatile content 3.5%) and “MONARCH 1300” (pH 2.
5, volatiles 9.5%), Degussa's “Colo
r Black FW200 "(pH 2.5, volatile matter 2
0%), “SPECIAL BLACK 4” (pH 3
%, Volatile content 14%), "PRINTEX150T" (p
H4, volatile content 10%), "PRINTEX140T"
(PH 5, volatile matter 5%), "PRINTEX U" (p
H5, volatile matter 5%). The oxidized carbon black may be used alone or in combination with other carbon blacks as long as it is used as an electron conductive filler that exhibits main conductivity.

The content of the electron conductive filler is preferably 2 to 40% by weight with respect to the binder resin from the viewpoint of obtaining good dispersibility in the binder resin and good electrical properties.
Preferably 10 to 25% by weight, more preferably 15 to 2% by weight.
0% by weight. When the content is out of the above range, the composition may be too hard, or may not be able to obtain good electric characteristics.

The electron conductive filler is generally dispersed in a binder resin to form each layer in the intermediate transfer member. Examples of the binder resin include a resin material, an elastic material, and a blend material thereof. Examples of the resin material include resin materials such as polyimide, polyester, polyetheretherketone, polyamide, polyamideimide, polyetherimide, polycarbonate, polyvinylidene fluoride (PVDF), and polyfluoroethylene-ethylene copolymer (ETFE); And resin materials using these as main raw materials.
Examples of the elastic material include a material obtained by blending one or more of polyurethane, chlorinated polyisoprene, NBR, chloropyrene rubber, EPDM, hydrogenated polybutadiene, butyl rubber, and silicone rubber. it can.

In the intermediate transfer member, the underlayer, particularly the elastic layer,
It is preferable that an elastic material having an IS-A hardness of 30 degrees or less and a compressive strain of 5% or less be contained, and the layer thickness be 3 to 10 mm. In particular, as an intermediate transfer member, the roll hardness capable of stably obtaining a uniform nip width and nip pressure is in the range of 30 to 60 ° as Asker C, and JIS-A hardness is used as a material constituting the elastic layer. Preferably 10
The uniform nip width and nip pressure are stabilized by using an elastic material having a degree of not less than 30 degrees and preferably not less than 15 degrees and not more than 25 degrees, preferably in a range of 3 to 10 mm, more preferably in a range of 4 to 7 mm. Can be obtained. Also,
The binder resin (elastic material) used for the underlayer, especially the elastic layer,
70 so as not to hinder the recovery of the elastic deformation of the cylindrical elastic layer.
The compression set at 22 ° C. for 22 hours is preferably 5% or less, more preferably 3% or less. Therefore, among the binder resins constituting each of the above-described layers, the underlayer,
In particular, as a binder resin (elastic material) constituting the elastic layer,
Silicon rubber, urethane rubber, or the like can be suitably used. However, other materials can also be used as long as the above characteristics are satisfied.

The electric field dependence of the surface resistivity of the intermediate transfer member is preferably 0.6 digits (logΩ / □) or less, and more preferably 0.5 digits (logΩ / □). The electric field dependence of the surface resistivity is 0.6 digits (logΩ /
In the case of □), the electric field concentration due to the transfer voltage as described above is more unlikely to occur, so that the surface resistivity of the paper traveling portion is reduced, and in a halftone image, the image quality defect such as the white missing of the paper traveling portion. Can be prevented from occurring.
The electric field dependency of the surface resistivity indicates a difference in common logarithm of the surface resistivity under the conditions of an applied voltage of 100 V (electric field intensity of 100 V / cm) and an applied voltage of 1000 V (electric field intensity of 1000 V / cm). The surface resistivity can be measured according to a measuring method described later.

The intermediate transfer member preferably has an environment fluctuation width of 1.0 digit (logΩ / □) or less, more preferably 0.6 digit (logΩ / □) or less. This environmental fluctuation range is the difference between the common logarithmic value of the surface resistivity at 30 ° C. 85% RH and the temperature at 10 ° C. 15% RH. By using the electron conductive filler of the electron conductive type, 30 ° C. 85
The difference between the common logarithmic value of the surface resistivity due to the environment of% RH and 10 ° C and 15% RH can be suppressed to 1.0 digit or less,
It is possible to improve the environmental resistance generated when the ion conduction type is used. The surface resistivity is determined by applying an applied voltage of 1
It is a value under the condition of 00V, and can be measured according to a measuring method described later.

Here, the surface resistivity ρs of the intermediate transfer member is:
It can be obtained as follows. As shown in FIGS. 3A and 3B, the surface resistivity ρs of the intermediate transfer member is 8 m in diameter longer than the axial length L (cm) of the intermediate transfer member 500.
The two metal rolls 501 and 502 of m are separated by 10 mm in the circumferential direction of the intermediate transfer body 500 as a distance L (cm) between the two metal rolls, and the plate-shaped insulator 503 is cut by 0.2 mm. And two metal rolls 50
An applied voltage V (V) (100 V) was applied between the first and second 502, and a current value I (A) after 10 seconds was measured.
It can be calculated by s = LV / GI. In the following formula (1), L is the axial length of the intermediate transfer member (c
m) and G indicate the distance (cm) between two metal rolls.

-Image Forming Apparatus- 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 having the above-described intermediate transfer body. The image forming apparatus of the present invention may have a configuration in which the image is transferred to the recording medium after being transferred to the intermediate transfer body, that is, may be configured to have two transfer steps, or may be continuously and repeatedly transferred to the intermediate transfer body and then transferred to the recording medium. That is, a configuration having three or more transfer steps may be employed. More specifically, for example, a first transfer unit that primarily transfers a toner image formed on an image carrier onto an intermediate transfer body, and a second transfer that transfers the toner image transferred on the intermediate transfer body to a transfer target body An image forming apparatus comprising: a first transfer unit for primary-transferring a toner image formed on an image carrier onto a first intermediate transfer body; and transferring the toner image transferred on the first intermediate transfer body to a second transfer unit. Examples include an image forming apparatus including a second transfer unit that transfers the toner image onto the intermediate transfer member, and a third transfer unit that performs a tertiary transfer of the toner image transferred onto the second intermediate transfer member to the transfer target. Specifically, a normal mono-color image forming apparatus in which only a single-color toner is stored in a developing device, or primary transfer of a toner image carried on an image carrier such as a photosensitive drum to an intermediate transfer body is sequentially repeated. The image forming apparatus may be a color image forming apparatus, a tandem type color image forming apparatus in which a plurality of image carriers having developing units for each color are arranged in series on an intermediate transfer member, or the like.

Hereinafter, the image forming apparatus of the present invention will be described.
This will be described with reference to the drawings. FIG. 4 shows a schematic configuration diagram of an example of the image forming apparatus of the present invention. The image forming apparatus shown in FIG. 4 includes an image carrier that forms an electrostatic latent image according to image information;
A developing device for visualizing the electrostatic latent image formed on the image carrier as a toner image with toner, a primary transfer unit for transferring the toner image carried on the image carrier onto an intermediate transfer body, and the intermediate transfer Secondary transfer means for transferring a toner image on the body to a recording medium, wherein the intermediate transfer body is the drum-shaped intermediate transfer body having the above-described configuration.

In the image forming apparatus shown in FIG. 4, a schematic diagram of an image forming apparatus using a drum-shaped intermediate transfer member is shown in FIG.
The surface of a photoreceptor (image carrier) 101 formed by applying a photoreceptor material on an aluminum pipe is uniformly charged by a charger 102, and then the image information emitted from an image writing device 104a is applied to the image information. By the corresponding scanning exposure 104b,
An electrostatic latent image is formed on the surface of the photoconductor. This electrostatic latent image is
The developing unit 105 of the developing unit 105 corresponding to the color information of the electrostatic latent image formed this time develops and visualizes.

The visualized toner image is applied to the photosensitive member 10
In the transfer area P _{1 where the first} transfer roller 1 and the intermediate transfer drum (intermediate transfer member) 110 are in contact with each other, a voltage is applied between the intermediate transfer drum 110 and the photosensitive member 101 from a power source (not shown) from the photoconductor 101 to the surface of the intermediate transfer drum 110. Is transferred by applying. The surface of the photoreceptor 101 after the transfer is irradiated with light from a discharge lamp 108 to be discharged, and the toner remaining on the surface of the photoreceptor 101 is removed by the cleaning device 103.

The above process is repeated a plurality of times, and each time a developing device 105K having a developer of a different color according to the image information,
The toner images are developed and visualized by 105Y, 105M, and 105C, sequentially transferred and laminated from the surface of the photoconductor 101 to the intermediate transfer drum 110, and a plurality of toner images are laminated and formed on the surface of the intermediate transfer drum 110.

A color toner image formed on the surface of the intermediate transfer drum 110 is formed by coating the intermediate transfer drum 110 and a metal shaft with an elastic material having a resistance of about 10 ⁸ Ω. 106 (secondary transfer unit), the intermediate transfer drum 110
Due to the voltage applied between the transfer roller 106 and the transfer roller 106, the image is collectively transferred from the surface of the intermediate transfer drum 110 to the recording material 111 conveyed by the paper conveyance roller 109. A peeling charger may be used instead of the transfer roller. Further, a peeling charger may be provided near the transfer area together with the transfer roller. The toner image collectively transferred to the surface of the recording material 111 is conveyed to the fixing device 107 and fixed by the fixing device 107.

Next, an example of the structure of the intermediate transfer drum 110 will be described with reference to FIG. In the intermediate transfer drum 110 of the present embodiment, a rubber elastic layer 203 for forming a stable transfer area is formed on a base material 204, and a leakage prevention and a rubber elastic layer An intermediate layer 202 functioning as a bleed block layer that blocks bleeding of the bleed component is formed, and a surface layer 201 having a high toner release property is formed on the intermediate layer 202. At least one of these layers contains the above-mentioned electron conductive filler.

The image forming apparatus shown in FIG. 4 includes an image carrier for forming an electrostatic latent image corresponding to image information, and a developing device for visualizing the electrostatic latent image formed on the image carrier with a toner as a toner image. Device and a toner image carried on the image carrier
A primary transfer means for transferring the toner image on the first intermediate transfer member, a secondary transfer means for transferring the toner image on the first intermediate transfer member to a second intermediate transfer member, and the second intermediate transfer member Tertiary transfer means for transferring the upper toner image onto a recording medium;
At least one of the above-described first intermediate transfer members is the drum-shaped intermediate transfer member having the above-described configuration.

FIG. 6 shows another example of the image forming apparatus of the present invention. The image forming apparatus shown in FIG. 6 is a drum-shaped photosensitive member (image bearing member) having a photosensitive layer on the surface corresponding to four colors of black (K), yellow (Y), magenta (M), and cyan (C). Body) 101K, 101Y, 101
M, 101C and chargers 102K, 102Y, 102M, 102C for uniformly charging these photosensitive members, respectively.
Image writing devices 104K, 104Y, and 104K that irradiate the uniformly charged photoconductors with image light to form electrostatic latent images.
104M, 104C and four developing devices 105K, 105Y, 105 containing developers of respective colors of K, Y, M, C.
M, 105C and the four photoconductors 101K, 101
Two photoconductors 101 among Y, 101M, and 101C
A first intermediate transfer drum (intermediate transfer member) 110A that contacts the first and second photoconductors 101M and 101Y.
C, a first intermediate transfer drum 110B that contacts both of these two first intermediate transfer drums 110A and 110B, and a second intermediate transfer drum 110C that contacts both of these two first intermediate transfer drums 110A and 110B. A transfer roller 106 for collectively transferring the superimposed transferred toner image onto the recording material 111 conveyed by the paper conveyance roller 109
(Tertiary transfer means) and a fixing device 107 for fixing the toner image on the recording material 111.

Each photoconductor 101K, 101Y, 101M,
An electrostatic latent image corresponding to each color is formed on 101C,
Each of the developing devices 105K, 105Y, 105M, and 105C is developed with each color toner to form a toner image of each color. Each photoconductor 101K, 101Y, 101M, 101C
Of the upper color toner images, the toner images on the photoconductors 101K and 101Y are superimposed and transferred to one first intermediate transfer drum 110A, and the toner images on the photoconductors 101M and 101C are the other toner images. 1 intermediate transfer drum 110
B is over-transferred. Each color toner image transferred to the two first intermediate transfer drums 110A and 110B is
The toner image on the second intermediate transfer drum 110C is superimposed and transferred onto the second intermediate transfer drum 110C, and the toner image on the second intermediate transfer drum 110C is collectively transferred onto the recording material 111 as described above.
7, the image is fixed on the recording material 111.

[0041]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, these embodiments do not limit the present invention. In the text, "parts" means "parts by weight".
Means

(Example 1) Intermediate transfer member (drum type 9
It was produced as follows. Shaft length 248mm, outer diameter 32
The vicinity of both ends of an aluminum pipe tube having a diameter of 2 mm is subjected to lathe processing, and a flange having a rotating shaft is press-fitted into this processed portion. Furthermore, the outer diameter tolerance of the outer surface of the aluminum tube is set to 0.
A support member, that is, a pipe (cylindrical base), finished with an outer diameter deflection accuracy of 0.01 mm or less and 0.01 mm or less was used.

After blasting the surface of the pipe and applying a primer, the pipe was inserted into a mold and placed. As carbon black, Degussa having a pH of 4 and a volatile content of 10% was used.
A low-temperature curing type conductive liquid silicone rubber having a volume resistivity of 10 ⁵ Ωcm obtained by adding 23 parts of “PRINTEX150T” manufactured by the company was injected, cured and molded. This was taken out of the mold and subjected to secondary curing at 200 ° C. for 30 minutes.
The thickness of the rubber elastic layer is 5 mm, and the hardness of the elastic material is JI.
The SA hardness is 20 degrees, and the amount of compressive strain is 2%.

Next, after applying the primer, a solution prepared by mixing 17 parts by weight of fluorocarbon rubber, titanium oxide as a conductive material, and a curing agent in a butyl acetate solution was applied onto the silicone rubber by a spray gun, and then applied. Is air dried for 10 minutes, then dried at a temperature of 60 ° C. for 10 minutes to a thickness of 20 μm.
m of intermediate layers were formed. The hardness of the used fluoro rubber is JI
The SA hardness is 65 degrees and the volume resistivity is 10 ⁸ Ωcm.

Next, as a component constituting the surface layer (transfer surface) on the intermediate layer, De, which has a pH of 2.5 and a volatile content of 20%, is used.
gussa “Color Black FW20
The components according to the following Formulation Example 1 containing 4 parts by weight of “0” (conductive agent) were mixed by a sand mill. 100 parts of this surface layer forming component was diluted with 100 parts of xylene, and the viscosity was adjusted to prepare a conductive paint. This conductive paint is coated on the surface of the intermediate layer obtained by the above-described method, and
Heating at 60 ° C. for 30 minutes formed a 20 μ thick surface layer.

-Mixing example 1 of material constituting surface layer (transfer surface)-Polyester resin ... 80 parts ("Byron 30SS" manufactured by Toyobo Co., Ltd.)-Melamine resin ... 20 parts ("Super Beckamine G-821-60" manufactured by Toyobo Co., Ltd.)-Fluororesin powder ... 10 parts ("Rublon L-5" manufactured by Daikin Industries, Ltd.)-Carbon black ... ··· 4 parts (“Color Black FW200” manufactured by Degussa (pH 2.5, volatile matter 20%)

The surface resistivity of the intermediate transfer member is 10 ^11.0
Ω / □, electric field dependence of surface resistivity is 0.3 digit (log
Ω / □). The volume resistance value was ^108.7 Ω.

Example 2 The same pipe as in Example 1 was used, and the surface of the pipe was blasted, coated with a primer, inserted into a mold, and placed in a mold. As carbon black, a pH of 4 and a volatile content of 10% were used. Degussa P
Urethane rubber having a volume resistivity of 10 ⁵ Ωcm, to which 18 parts of “RINTEX150T” was added, was injected, cured and molded. This was taken out of the mold and further subjected to secondary curing at 150 ° C. for 30 minutes. The thickness of the rubber elastic layer is 5 mm, the hardness of the elastic material is 25 degrees in JISA hardness, and the amount of compressive strain is 3%.

Next, on the elastic layer, 40 parts of an acrylic resin having silicon as a terminal group and 60 parts of a urethane resin as solid components, 35 parts of a fluororesin powder, and a Degussa having a pH of 4 and a volatile matter of 10% as carbon black at a pH of 4 Company's "P
RINTEX150T ”5 parts of a coating solution is spray-coated, left at room temperature for 10 minutes, and then pre-dried in a 50 ° C atmosphere for 30 minutes, then held and cured at 180 ° C for 30 minutes to form a 20 μm thick surface layer. Was obtained.

The surface resistivity of the intermediate transfer member is 10 ^11.5
Ω / □, the electric field dependency of the surface resistivity is 0.5 digits (log
Ω / □). The volume resistance value was ^108.3 Ω.

(Example 3) Using the same pipe as in Example 1, the surface of the pipe was blasted, and a primer was applied. Then, the pipe was inserted and set in a mold. As carbon black, pH 5.7 and volatile matter Urethane rubber having a volume resistivity of 10 ⁶ Ωcm, to which 0.9% of granular acetylene black manufactured by Denki Kagaku Kogyo KK was added by 15 parts by weight, was injected, cured and molded. Take this out of the mold and add another 150
Secondary cured at 30 ° C for 30 minutes. The thickness of this rubber elastic layer is 5
mm and hardness are 25 degrees in JISA hardness. Further, on this elastic layer, the same surface layer as in Example 1 was applied and formed.
An intermediate transfer drum was obtained.

The surface resistivity of the intermediate transfer member was 10 ^11.0
Ω / □, electric field dependence of surface resistivity is 0.3 digit (log
Ω / □). The volume resistance value was ^108.2 Ω.

(Comparative Example 1) The same pipe as in Example 1 was used, and the surface of the pipe was blasted, coated with a primer, inserted into a mold, and placed as a carbon black at pH 9 and a volatile content of 1. 5% neutral carbon black "Ketsuchien Black EC" manufactured by Lion Aguso Co., Ltd.
A urethane rubber having a volume resistivity of 10 ^5.5 Ωcm to which two parts were added was injected, cured and molded. This was taken out of the mold and further subjected to secondary curing at 150 ° C. for 30 minutes. The thickness of the rubber elastic layer is 5 mm, the hardness of the elastic material is 22 degrees in JIS-A hardness, and the amount of compressive strain is 4%.

Further, as a component constituting a surface layer (transfer surface) on the elastic layer, granular acetylene black (conductive agent) manufactured by Denki Kagaku Kogyo KK having a pH of 5.7 and a volatile content of 0.9% was used. The components according to the following Formulation Example 2 were added in a sand mill. This component for forming a surface layer system 10
0 parts were diluted with 100 parts of xylene to adjust viscosity,
The conductive paint was prepared. This conductive paint was coated on the surface of the elastic layer obtained by the above-mentioned method, and heated at 160 ° C. for 30 minutes to form a 20 μ thick surface layer.

-Example of the composition of the material constituting the surface layer (transfer surface) 2-Polyester resin ... 80 parts ("Byron 30SS" manufactured by Toyobo Co., Ltd.)-Melamine resin ... 20 parts ("Super Beckamine G-821-60" manufactured by Toyobo Co., Ltd.)-Fluororesin powder ... 10 parts ("Rublon L-5" manufactured by Daikin Industries, Ltd.)-Carbon black ... 3.5 parts (granular acetylene black (pH 5.7, volatile content 0.9%) manufactured by Denki Kagaku Kogyo KK)

The surface resistivity of the intermediate transfer member was 10 ^11.2
The electric field dependence of Ω / □ and surface resistivity is 1.2 digits (log
Ω / □). The volume resistance value was ^108.6 Ω.

(Comparative Example 2) The same pipe as in Example 1 was used.
(Ethylene propylene diene monomer: EP33 manufactured by Nippon Synthetic Rubber Co., Ltd.) 100 parts by weight at pH 5.7 and a volatile content of 0.1.
18 parts of 9% granular acetylene black manufactured by Denki Kagaku Kogyo Co., Ltd. and a blowing agent (Vinihole AC # 3 manufactured by Eiwa Chemical Co., Ltd.)
15 parts and sulfur (Tsurumi Chemical Industry 200 mesh) 1
Part and a mixture obtained by kneading a part of a vulcanization accelerator (NOCSELA CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) with an open roll are wound, press-vulcanized and foamed at 170 ° C. for 15 minutes, and the foam is molded. An elastic layer was obtained. The thickness of the rubber elastic layer is 5 mm, and the roll hardness is 40 ° in Asker C hardness. Further, on this elastic layer, the same surface layer as that of Comparative Example 1 was formed by coating to obtain an intermediate transfer drum.

The surface resistivity of the intermediate transfer member is 10 ^11.0
The electric field dependence of Ω / □ and surface resistivity is 1.2 digits (log
Ω / □). The volume resistance value was ^108.6 Ω.

Comparative Example 3 On the same pipe and elastic layer as in Example 3, p was used as a material for forming the surface layer (transfer surface).
H5.7 and a thickness of 0.14 obtained by adding 15 parts of granular acetylene black manufactured by Denki Kagaku Kogyo KK having a volatile content of 0.9%.
mm of a polycarbonate resin-based film material to form a surface layer to obtain an intermediate transfer drum.

The surface resistivity of the intermediate transfer member is 10 ^11.6
Ω / □, electric field dependence of surface resistivity is 1.5 digits (log
Ω / □). Further, the volume resistance value was ^108.8 Ω.

(Comparative Example 4) On the same pipe and elastic layer as in Example 3, as a material constituting the surface layer (transfer surface), an ion conductive polymer was used as a block type polymer having polyether as a main segment. Sanyo Chemical Industry Co., Ltd.
A surface layer is formed by coating a polycarbonate resin-based film material having a thickness of 0.14 mm obtained by adding 35 parts of "Pelestat 6321" manufactured by Nissan Co., Ltd. to obtain an intermediate transfer drum.

The surface resistivity of the intermediate transfer member was 10 ^12.2
Ω / □, electric field dependence of surface resistivity is 0.2 digits (log
Ω / □). Further, the volume resistance value was 10 ^9.2 Ω.

(Comparative Example 5) On the same pipe and elastic layer as in Example 1, p was used as a material for forming the surface layer (transfer surface).
0.14 mm-thick ETFE (ethylene tetrafluoroethylene copolymer) resin-based film obtained by adding 12 parts by weight of “Ketschien Black EC”, a neutral carbon black with a volatile content of 1.5% and manufactured by Lion Aguso Co., Ltd. The material is coated to form a surface layer and an intermediate transfer drum is obtained.

The surface resistivity of this intermediate transfer member was 10 ^11.9
The electric field dependence of Ω / □ and surface resistivity is 2.1 digits.
Further, the volume resistance value was 10 ^9.1 Ω.

(Evaluation) The obtained intermediate transfer bodies of Examples 1 to 3 and Comparative Examples 1 to 5 were evaluated as follows. Further, the intermediate transfer member 11 is added to the image forming apparatus shown in FIG.
Prepared as 0, 100 postcards in an environment of 10 ° C and 15% RH
Resistance change of the surface resistivity of the paper running portion after zero sheet copy;
Evaluation was made on the occurrence of white spots in the paper running portion when 30% magenta was copied after copying 1000 postcards. Table 1 shows the results.

—Surface Resistivity, Its Electric Field Dependence, and Environmental Fluctuation Range— The surface resistivity of the intermediate transfer member, its electric field dependence, and environmental fluctuation range were measured and calculated as described above.

-Variation of Surface Resistivity-The variation of the surface resistivity of the intermediate transfer member is determined by dividing the intermediate transfer member into three parts in the axial direction and dividing it into eight parts in the circumferential direction. , 502 were measured in the same manner as the surface resistivity except that two metal rolls (diameter 8 mm, shaft length 50 mm) shorter than the shaft length of the intermediate transfer member were used (FIG. 3A). And (b)). The variation was defined as the difference between the maximum value and the minimum value when the measured surface resistivity at 24 points was a logarithmic value.

—Volume Resistance Value— The volume resistance value Rv of the intermediate transfer member is shown in FIGS. 7A and 7B.
As shown in the figure, the intermediate transfer member 600 is
A metal plate 601 larger than the axial length of 0 is pressed with a load of 1 kg, a voltage of 500 V is applied between the metal plate 601 and the metal support of the intermediate transfer body 600, and a current value after 10 seconds is measured. It was calculated by the formula Rv = V / I.

—Volume Resistance of Elastic Layer— The variation in the volume resistance of the elastic layer was determined by preparing a sample of an intermediate transfer member having only the elastic layer of each sample, and dividing the intermediate transfer member into three in the axial direction. , Divided into eight in the circumferential direction,
Using a metal roll (diameter: 8 mm, length: 50 mm) instead of the metal plate 601 at 24 points, pressed against the intermediate transfer member with a bite amount of 0.1 mm, and applied a voltage of 100
The current value was measured in the same manner as the above-mentioned volume resistance value except that V was applied (see FIGS. 7A and 7B). In addition,
The variation was defined as the difference between the maximum value and the minimum value when the measured volume resistance values at 24 points were logarithmic values.

The amount of decrease in surface resistivity after continuous copying of 1000 sheets is as follows. The amount of decrease in surface resistivity after continuous copying of 1000 sheets is determined by the initial surface resistivity and the surface resistance after continuous copying of 1000 sheets. It was calculated as the difference between the logarithm and the ratio.

-Occurrence of white spots after continuous copying of 1000 sheets-The occurrence of white spots in this embodiment is visually determined.
A level having no problem in image quality was evaluated as ○, and a level having a problem in image quality was evaluated as x.

[0072]

[Table 1]

Table 1 shows the following. In Examples 1 and 2, the elastic layer and the surface layer were used as conductive agents,
An acidic carbon of 5 or less was used, the change in electrical resistance due to temperature and humidity was small, the variation in the plane was as small as 0.5 digit or less, and the change in resistance with time was not so large. In Example 3, since carbon black having a pH of 5.7 was used for the elastic layer, the in-plane variation of the volume resistance value of the elastic layer was 0.1%.
Although it increased to eight orders of magnitude, the material constituting the surface layer was pH 5
Since the following acidic carbon was used, the electric field dependence on the surface layer was small, and the change in resistance with the lapse of time was at a level without a problem in image quality.

In Comparative Examples 1, 2, 3 and 5, carbon black having a pH of 9 and pH 5.7 was used as a conductive agent for the material constituting the elastic layer and the surface layer. The in-plane variation of the volume resistance value of the layer is large,
In addition, since the in-plane variation of the surface resistance value of the surface layer is as large as 0.8 digits or more and the electric field dependence is 1 digit or more, the electric field is concentrated at the transfer voltage, and the resistance changes with time.
In the paper running section, an image quality defect that appears white was generated.
In Comparative Example 4, since the ionic conductive polymer was used as the material forming the surface layer, the environmental fluctuation of the surface resistivity was 1.
There was a problem that the number was increased to eight digits.

From these facts, by adopting the structure of the image forming apparatus of the present invention, the transfer efficiency is high, and the image forming apparatus of the present invention does not cause image quality defects such as image dropout and can record a high quality image. It can be seen that a simplified image forming apparatus can be realized.

[0076]

As described above, according to the present invention, it is possible to provide an image forming apparatus capable of stably supplying a high-quality image without a change in electric resistance over 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.

FIGS. 3A and 3B are a schematic view (a) and a schematic perspective view (b) illustrating a method for measuring the surface resistivity.

FIG. 4 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention.

FIG. 5 is a configuration diagram of an intermediate transfer drum used in the embodiment.

FIG. 6 is a schematic configuration diagram illustrating another example of the image forming apparatus of the present invention.

FIGS. 7A and 7B are a schematic view (a) and a schematic perspective view (b) illustrating a method for measuring a volume resistance value.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photoconductor drum (image carrier) 2 intermediate 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 intermediate transfer member cleaner 10 transfer roller 13 peeling Claw 21 Belt roller 22 Backup roller 23 Belt roller 24 Belt roller 25 Conductive roller 26 Electrode roller 31 Cleaning blade 41 Recording paper 42 Pickup roller 43 Feed roller T Toner image 101 Photoconductor (image carrier) 101 (K, Y, M) , C) Black, yellow, magenta, cyan photoconductor 102 Charger 102 (K, Y, M, C) Black, yellow, magenta, cyan charger 103 Cleaning device 104a Image writing device 104b Scanning exposure 104 (K, Y , M, C) Black, yellow, magenta, cyan image writing device 105 (K, Y, M, C) black, yellow, magenta, cyan developing device 106 transfer roller 107 fixing device 108 static elimination lamp 109 paper transport roller 110 intermediate transfer drum (intermediate) Transfer member) 110 (A, B) first intermediate transfer drum (intermediate transfer member) 110C second intermediate transfer drum (intermediate transfer member) 111 recording material 201 surface layer 202 intermediate layer 203 rubber elastic layer 204 base material

Claims (4)

[Claims] 1. An image forming apparatus provided with an intermediate transfer body, wherein the intermediate transfer body has at least two layers including a base layer and a surface layer on a metallic cylindrical substrate, An image forming apparatus, wherein at least one of the layers contains an electron conductive filler having a pH of 5.0 or less that exhibits conductivity by electron conduction. 2. The method according to claim 1, wherein the underlayer contains an elastic material having a JIS-A hardness of 30 degrees or less and a compressive strain of 10% or less, and a thickness of 3 to 10 mm. 2. The image forming apparatus according to 1. 3. The image forming apparatus according to claim 1, wherein the surface layer contains the electron conductive filler. 4. The content of the electron conductive filler is 2 to 4.
The image forming apparatus according to claim 1, wherein the content is 40% by weight.