JPH06230692A - Transfer device and image forming device using the same - Google Patents

Abstract

PURPOSE:To provide stable transfer performance without being affected by fluctuations in humidity by providing a high-resistant member whose resistance value has humidity dependency on the counter electrode of a corona electrode. CONSTITUTION:A transfer carrying belt device is composed of a transfer carrying belt, a pair or holding rollers 32 and 33, a brush electrode 40 and a corona transfer device 50. The transfer device 50 is provided with wire-side plates 52 consisting of a material having the electrical characteristic of the same humidity dependency as that of a transfer belt base body 31a made of urethane rubber on both sidewalls of a back plate 51. In his constitution, even if the total current in the discharge of a transfer pole is constant, a current flowing through the wire-side plates 52 is increased in accordance with the humidity and the current of a transfer belt is decreased to compensate a change in the electrical characteristic of the transfer carrying belt, so that the stable transfer performance can be fulfilled without being affected by the fluctuations in the humidity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device that electrostatically supports and conveys a recording paper to transfer the recording paper to the recording paper by electrostatic or physical means, and an image forming apparatus using the transfer device.

[0002]

2. Description of the Related Art Conveying means which comprises a belt made of an insulating material such as a dielectric material and electrostatically supports and conveys recording paper is already known (US Pat. No. 2,567,882, US Pat.
57,325). The former is one in which a recording paper is charged and a conductive member and a dielectric member are attached to each other to be adsorbed on a two-layered conveyor belt for conveyance. The latter is one in which a single-layer dielectric conveyor belt is supported and stretched by two rollers. Discharge devices are provided independently for attracting and transferring recording paper.

However, these have the following problems.

The first problem is that the insulating charged particles (toner) electrostatically transferred onto the recording paper during the separation of the recording paper and the conveyor belt are disturbed, which adversely affects the transferred image. Could give.

The second problem is that the recording paper itself holds the electric charges necessary for transferring the toner particle image on the image forming body, and the recording paper is in direct contact with the image forming body. There is a problem caused by that. Specifically, a. When the recording paper acts as an electric resistor that connects the charge supply source and the charge absorption source that removes the electric charge, the amount of electric charge held by the recording paper changes depending on the magnitude of the electric resistance value of the recording paper. Generally, there is not only one type of recording paper, and the electric resistance may change greatly depending on environmental conditions, particularly humidity conditions, and it is difficult to obtain good transfer performance under all environments for all types of recording paper. Also, b. The recording paper having a high potential true charge may cause dielectric breakdown of the photosensitive layer of the image forming body and damage the photosensitive layer.

The third problem is that the mechanical rigidity of the recording paper itself determines the force for imparting an electric charge and electrostatically adsorbing the recording paper to the recording medium to separate it from the image forming body. This is a problem that arises. Specifically, a. When a recording paper having a small thickness and low rigidity is used, even if a small amount of electric charge remains on the recording paper, there is a high risk that the separation of the paper from the image forming body will occur and paper jam will occur. b. Since the recording paper is separated from the image forming body by the rigidity of the recording paper itself, the separation requires a certain time determined by the rigidity of the recording paper. Therefore,
c. When the rotation speed of the image forming body is high, the separation speed of the recording paper is relatively slow, and the risk of separation failure and paper jam is increased. d. When the recording paper is curled, it is anxious about the transportability.

Several transport belt devices have been proposed that solve the above problems.

One of them is a transfer device in which a recording paper is contacted with the charged transfer belt and the transfer belt is in contact with the transfer belt prior to the transfer position and passes through a grounded conductive member (JP-A-62-62). -147473). This is because the charge accumulated on the surface of the dielectric at the time of charging the conveyor belt is partially transferred to the recording paper, and this and the dielectric induced on the belt dielectric connected to ground or an appropriate bias means at the time of charging. By attracting electric charges of opposite polarities to those of the portions, a strong electrostatic attraction force is realized between the recording paper and the conveyor belt, and the recording paper is stably conveyed without deviation during transfer. Further, in the transfer method of electrostatically transferring the image by the charged particles, the charge transferred to the recording paper strongly attracts the charged particles, and the image disturbance is prevented even when the conveying belt and the recording paper are separated. This alleviated the first problem somewhat. Further, since the electrostatic force is brought into close contact with the belt while pressing the recording paper against the belt, curling of the recording paper is not a problem. Alleviated part of the third problem.

The second feature is that the recording paper is passed between a conveyor belt composed of at least two layers of a dielectric and a conductor and a conductive brush which is opposed to the conveyor belt and is grounded prior to the transfer position. Disclosed is one in which a recording sheet discharging member for preventing image disturbance is arranged at a position separated from a conveyor belt, and a charging means for precharging is provided as a cleaning performance improving function in front of a cleaning member for the conveyor belt. (Japanese Patent Laid-Open No. 01-154074). With such a structure, the same effects as those of the transfer device disclosed in JP-A-62-147473 can be obtained, and the following effects can be further obtained.

The first effect is that the conductive brush in the grounded state, which is provided in the vicinity of the dielectric layer of the conveyor belt so as to face it, repeats the charging / discharging cycle for each revolution of the conveyor belt, and therefore the surface potential of the belt. Is very stable, and the transferred image remains stable. The second effect is that since the recording paper is charged with a polarity opposite to the charging polarity of the conveyor belt, the recording paper is conveyed at a separation position between the recording paper and the conveyor belt with a current equal to or higher than a certain value. The corona discharge has the same polarity as the belt. By arranging the corona discharge electrode so that it is also scattered on the recording paper before separation, it is possible to greatly reduce the change in the electric field before and after the separation position of the recording paper, so that a high-quality transfer image without image distortion can be obtained. I will get it. The first and second problems are solved by the above two effects.

In Japanese Patent Laid-Open No. 63-83762, the charge-giving means is provided in the vicinity of the vicinity of the toner particle conveying means and the belt means by using a semiconductor material having an electric resistance of 10 ¹⁰ to 10 ¹³ Ωcm of the belt means. By supplying an electric charge to the portion of the recording paper, the recording paper is fed by the electrostatic force of the polarization electrification by the electrostatic induction of the recording paper and the electrification of the belt means without directly giving the electric charge to the recording paper fed by the paper feeding means. The belt means is adapted to be sucked and conveyed. The transfer of the toner particles is performed by making the electric charge applied to the belt means by the electric charge giving means have a polarity opposite to that of the electric charges of the toner particles on the conveying means. Further, since the recording paper does not have a true charge but is attracted to the belt means by the polarization charge, it is not necessary to remove the charge of the recording paper when separating the toner particle conveying means and the recording paper. The electrostatic attraction force to the recording medium acts as a forcing force to separate the recording paper from the toner particle transporting means, so that the recording is more stable than that of the conventional device that depends on the mechanical rigidity of the recording paper. It is disclosed that the paper can be separated. With such a configuration, the above-mentioned first problem, second problem and third problem have been solved.

[0012]

However, in the so-called electrostatic photography process, the electrostatic force contributes largely. If the atmosphere becomes humid in the image forming apparatus that employs the electrostatographic process, a discharge phenomenon is likely to occur, so that an appropriate electrostatographic process cannot be performed. In particular, a transfer apparatus that electrostatically supports and conveys a recording sheet to transfer the recording sheet to the recording sheet by an electrostatic or physical means, and an image forming apparatus that uses the transfer apparatus have large problems. Hereinafter, this problem will be specifically described with reference to FIGS. 4 and 5.

FIG. 5 is a schematic view showing a corona discharge device used in a general conveyor belt device.

In the figure, the corona discharge device is one in which a wire side resin plate made of, for example, modified PPE is provided on the side wall of a back plate b made of SUS304, and the center of the back plate, for example, the wire side plate distance 7.5 ± 0.2.
mm, wire side resin plate distance 5 ± 0.3 mm, wire back plate distance 7.5 ± 0.1 mm, and a 0.03 mm diameter discharge wire w made of WO ₃ is stretched so as to have an effective discharge length of 301 mm. . With the above configuration, humidity dependence is eliminated and stable discharge can always be performed with a constant effective discharge length.

In comparison with this, the volume resistivity is 10 ¹⁰ to 10 ¹¹ Ω.
Since the electrical characteristics of the conveyor belt and the recording paper (plain paper) having a thickness of 0.5 cm and a thickness of 0.5 mm have humidity dependency as described later, there are problems described later.

FIG. 4 is a graph showing that the electrical characteristics (volume resistivity value) of a general insulating transfer / conveying belt and recording paper depend on humidity.

In the graph, the vertical axis represents the volume resistivity ρ
And the horizontal axis represents the relative humidity in the image forming apparatus. A curve B shows a volume specific resistance value of a general transfer conveyance belt, and a curve P shows a general volume specific resistance value of a recording sheet. Curves B and P show that the volume resistivity greatly changes due to the fluctuation of the relative humidity. Particularly, the volume resistivity of the recording paper largely changes due to a slight humidity change as compared with the transfer / conveying belt. It shows that there is a tendency to do.

Therefore, the corona discharge device described above discharges stably without being affected by humidity fluctuations, but the electrical characteristics of the transfer conveyor belt and recording paper fluctuate when the humidity is high at 30 ° C. and 80% relative humidity. As a result, leakage occurs through the transfer / transport belt or the recording paper, or the charge on the back surface of the transfer / transport belt is easily injected into the surface insulating layer, and the electric field in the transfer area is increased to easily generate the electric field. . There is a problem that transfer cissing occurs due to discharge. On the other hand, for example, at a low humidity of 10 ° C. and a relative humidity of 20%, the charge on the back surface of the transfer conveyor belt is unlikely to leak, but it is difficult to inject it into the high-resistance rubber layer, and on the contrary, the transfer electric field is insufficient and transfer unevenness is likely to occur There is a problem.

In order to solve such a problem, a heater is provided in the image forming apparatus, and in the high humidity season, the heater is overheated to alleviate the above problems. However, in the above configuration, the humidity cannot be adjusted sufficiently.

In order to solve such a problem, the present applicant has provided a charge applying means for adsorbing a recording paper on the surface side of a transfer / conveying belt having a transfer discharge electrode on the back side of the toner image of the image forming body, and The charge applying means detects the current flowing when it is in direct contact with the transfer / conveying belt, and pays attention to the fact that the detected current value fluctuates at low temperature and low humidity and at high temperature and high humidity, and based on the current value, the process speed ( 12mm / sec, 37mm / sec, 74
mm / sec), and proposes an image forming device that can always obtain a stable image regardless of environmental temperature and humidity by controlling the developing bias, toner concentration, exposure intensity, etc. corresponding to the process speed. (Patent application 4-41
No. 305). The applicant proposes a new device to solve the above problems.

A first object of the present invention is to provide a transfer device which can realize stable transfer performance without being affected by humidity fluctuations.

A second object of the present invention is to provide an image forming apparatus capable of obtaining a high quality transferred image without being affected by a change in environmental conditions.

[0023]

SUMMARY OF THE INVENTION A transfer device for achieving the first object of the present invention is a transfer device for transferring a toner image on an image forming body onto a recording paper via a transfer / conveying belt which holds a discharge charge by a corona electrode. Then, a high-resistance member having a humidity-dependent resistance value is provided on the counter electrode of the corona electrode.

An image forming apparatus for achieving the second object of the present invention is an image forming apparatus for electrostatically transferring a toner image of an image forming body onto a recording sheet on a conveyor belt having a transfer discharge electrode on the back side. The conveyor belt has a highly insulating layer of 10 ¹⁴ Ωcm or more.
The discharge current is controlled by controlling the transfer electrode shield potential according to the humidity, which is composed of a substrate of a high resistance rubber layer of 10 ⁶ to 10 ¹³ Ωcm.

[0025]

【Example】

Embodiment 1 FIG. 1 is an explanatory view showing an embodiment of the transfer device of the present invention.

The image forming body 10 is a drum having a diameter of about 100 mm (hereinafter referred to as "photosensitive drum 10"), in which an OPC photosensitive layer 12 is formed on an aluminum base 11, and the pressing roller has a diameter of 8 mm. A metal roller having a length of about 300 mm is supported by a pressing member in the vicinity of the central portion and is supported by bearings at both ends, and is 7-9 mm upstream from the transfer device 50.
At the position of, the air between the photosensitive drum 10 and the transfer / conveyance belt 31 is removed, so that a better contact state is obtained, and the surface of the recording paper P is not affected by unevenness or carrier adhesion. It is possible to obtain good transferability and transferability without unevenness in the width direction of the recording paper.

The transfer / transport belt device 30 is a transfer / transport belt.
31 and a pair of holding rollers 32 and 33, a brush electrode 40, and a corona transfer device 50. The corona transfer device 50 is 0.8 ± 0.08 mm from the photosensitive drum via the transfer / conveying belt 31 when driven.
The recording paper P, which is held by the paper feed cassette by the paper feed mechanism, is fed to the transfer area by the transfer / transport belt 31. The corona transfer device 50 applies a constant voltage having a polarity opposite to that of the toner to the discharge wire. As a result, the toner images on the peripheral surface of the photosensitive drum 10 are collectively transferred onto the recording paper P. The structure and operation of each member will be described below.

The transfer / transport belt 31 has a resistance of 10 ¹⁴ Ω · cm or more in which a fluororesin coating layer 31b is formed on the surface of a base 31a made of urethane rubber which is a high resistance layer of 10 ⁶ to 10 ¹³ Ω · cm. , An endless rubber belt with a thickness of 0.2 to 1.0 mm,
A rib may be provided to prevent deviation during rotation.
If the transfer / conveyance belt 31 is provided with a charge eliminating mechanism, PE
A high resistance belt such as a film of T or the like or a film coated with these may be used. The urethane rubber layer 31a has the above-mentioned problems because it has humidity-dependent electrical characteristics.

The holding rollers 32, 33 stretch the transfer / conveying belt 31, and the shaft 32a of the holding roller 32 on the upstream side is grounded directly or through a non-linear element. As a result, the shaft 32a is used as a counter electrode of the charge applying means 40. Further, the electrostatic charge generated on the transfer / conveyance belt 31 is leaked. Therefore, it is possible to prevent the electrostatic charge generated on the back surface of the transfer / conveyance belt 31 from being accumulated and discharged to cause noise or an image defect. A frequency of 300 to 5 KHz and V _pp (300 to 1.
The recording paper P may be separated from the transfer conveyance belt 31 by superimposing and applying the DC voltage V _DC (200 to 1 kV) on the AC voltage of 5 KV).

In the transfer device 50, wire side plates 52 made of a material having the same electrical characteristics as the transfer conveyance belt base 31a, such as urethane rubber, having temperature dependence are provided on both side walls of a back plate 52 made of SUS304. The effective discharge length is 30 at the approximate center of the back plate 51, for example, the wire / zide plate distance of 7.5 ± 0.2 mm, the wire side plate distance of 5 ± 0.3 mm, and the wire / back plate distance of 7.5 ± 0.1 mm.
A discharge wire 53 made of WO ₃ and having a diameter of 0.08 mm is stretched so as to be 1 mm. Rated output 6.5KV for discharge wire 53
A constant current source 54 of / 250 μA is connected. The back plate 51 is grounded to zero potential. Further, the transfer device 50 is provided with a high-resistance member having humidity dependency by being bonded via a conductive adhesive, and the discharge efficiency is controlled so as to automatically follow the humidity dependency of the transfer / transport belt. To do so. The area of the temperature-dependent high-resistance member bonded to the back plate may be changed as needed. It may be provided on the entire surface, specifically on the back plate and both side plates. In this case, since the plate functions as a capturing member, the high resistance member is grounded.

A cleaning plate made of a rubber material may be provided to remove the toner, paper dust and the like adhering to the surface of the transfer / transport belt 31.

Since the brush electrode is made of conductive rayon of 10 ⁴ to 10 ⁶ Ωcm, the shaft 32 a of the holding roller 32 is arranged as an opposite electrode, and the DC power source 41 is connected to the brush electrode 40.
The recording paper P is attracted to the transfer / conveying belt 31 by the generation of an electric field. That is, the recording paper P causes the dielectric polarization by passing the electric field generated by the brush electrode, so that the transfer / conveyance belt 31 stably conveys the recording paper P.

[0033] FIG. 3 is a graph showing the humidity dependency of the transfer belt I _B current flowing through the transfer conveying belt side of the transfer device of the present embodiment. I _P indicates the humidity dependence of the discharge current flowing on the back plate / side plate side. In the graph, the vertical axis represents the transfer current I (μA), and the horizontal axis represents the relative humidity (%).

The transfer device of this embodiment has wire side plates on both side walls of the back plate 51 of the transfer electrode, which is made of a material such as urethane rubber having substantially the same electrical characteristics as the transfer / transport belt body 31a and humidity dependence. By providing 52,
Even if the total current when the transfer pole is discharged is constant, the current flowing on the back plate / side plate side increases according to the humidity, and the transfer belt current is compensated for the change in the electrical characteristics of the transfer conveyance belt. Since it will decrease, stable transfer performance can be realized without being affected by humidity fluctuations.

Embodiment 2 FIG. 2 is an explanatory view showing an embodiment of the image forming apparatus of the second invention.

Although not closely related to the present invention, an image forming process for forming toner images of a plurality of layers on the image forming body 10 will be briefly described. Generally, I would like to call this process KNC (Konica New Process).

The photosensitive drum 10 is a PCL using a light emitting diode or the like in order to eliminate the history of the photosensitive member due to pre-printing.
To remove the charge. Following this, the photosensitive drum 10 is uniformly charged with V _H (-600 to -800 V) on its peripheral surface by a grid and corona discharge wire whose potential is maintained at V _G (-550 to -850 V). Given.

The peripheral surface of the photosensitive drum 10 is subjected to image exposure based on an image signal by image exposure means. As a result, a latent image is formed in the main scanning direction. Photosensitive drum 10
A latent image is also formed in the sub-scanning direction by the rotation of. In this way, a latent image is formed on the peripheral surface of the photosensitive drum 10 by imagewise exposure in the main and sub-scanning directions. In this embodiment, the character portion is exposed to light, so that the character portion has a lower potential V _L (-100 to 0 V). A so-called inverted latent image will be formed.

At the peripheral edge of the photosensitive drum 10, there are provided developing units respectively containing developers such as yellow, magenta, cyan and black toners and carriers.

The developing device carries a developer on a developing sleeve having a built-in magnet by electrostatic force and conveys the developer to a developing area. At this time, the developer is layered on the developing sleeve by the layer forming rod.
The developer regulated to a layer thickness of 300 to 600 μm is a carrier in which ferrite is used as a core and is coated with an insulating resin around it, a polyester as a main material, a pigment according to the color and a charge control agent, silica, titanium oxide, etc. And a toner to which is added.

The gap between the developing sleeve and the photosensitive drum in the developing area is 0.4 to 1.0 mm, which is larger than the layer thickness of the developer, and an AC bias of V _AC (1.5 to 3.0 KV _PP ) and V _DC (-500 to Apply a DC bias of -700V superimposed. Since V _DC and V _H and the toner charge have the same polarity, V
_The toner, which has been given the opportunity to be separated from the carrier by _AC , does not adhere to the V _H portion, which has a higher potential than V _DC ,
It adheres to the V _L portion having a lower potential than V _DC and is visualized. This is the inversion phenomenon as described above.

In this way, after the visualization of the first color is completed, the two-color image forming process is subsequently started. That is, uniform charging is performed by the scorotron charger 21, and a latent image based on the image data of the second color is formed by the image exposure means.
At this time, the charge elimination by the PCL performed in the image forming process for the first color is not performed in order to prevent the toner attached to the image portion for the first color from scattering due to a rapid decrease in the surrounding potential.

Twice all over the photosensitive drum 10 circumferential surface V
A latent image similar to that of the first color is formed on the portion of the photoconductor having the _H potential and having no image of the first color, and development is performed.

However, in the portion where the image having the first color image is developed again, the latent image of V _M is formed due to the light shielded by the toner of the first color and the electric charge of the toner itself, and V _M and V _DC The development is performed according to the potential difference between.
Incidentally, the first color and for collapsing the balance of the second color, there is also an intermediate potential to be _{V H> V M (-100~-} 300)> V L to reduce the exposure amount of one color. For the third and fourth colors, the same image forming process as the second color is performed, and the photosensitive drum 10
Visual images of four colors are formed on the peripheral surface.

Next, the main structure of the image forming apparatus of this embodiment will be described.

The image forming apparatus controls the back plate potential of the transfer electrode according to the output of the humidity sensor s,
The transfer efficiency is controlled to a predetermined level without being affected by changes in humidity.

Since the image forming apparatus has substantially the same structure as the transfer apparatus shown in FIG. 1, these members are designated by the same reference numerals and the description thereof will be omitted. The configuration unique to this embodiment will be described below.

The transfer electrode 50 has substantially the same structure as shown in FIG. 5, and has a back plate 51 made of SUS304 and a wire side resin plate made of, for example, modified PPE provided on the side wall thereof, and substantially at the center, for example, the wire. Side plate distance 7.5 ± 0.2
mm, the wire side resin plate distance is 5 ± 0.3 mm, and the wire / back plate distance is 7.5 ± 0.1 mm. The discharge wire 53 made of WO ₃ and having a diameter of 0.08 mm is stretched so that the effective discharge length is 301 mm. . As a new structure, a variable power source 55 is connected to the back plate 51, and the variable power source 55 can control the output voltage by the process CPU 70. The constant power source 54 connected to the discharge wire 53 is the same as that in FIG. 1, and is a constant current source of 6.5 KV / 250 μA.

The humidity sensor S detects the humidity installed in the transfer / conveying belt in the image forming apparatus, and detects the two-terminal impedance element, the electrolyte sensor, the polymer insulating film sensor, the ceramic sensor, and the electromagnetic wave. Any of a microwave hygrometer, an infrared hygrometer, an ultraviolet hygrometer, a material utilizing a change in a substance constant, and a material utilizing a chemical change may be used as long as it is used as an electric signal.

The process CPU 70 controls the image forming process by driving and controlling the above-mentioned process means. The process CPU 70 stores the back plate voltage value corresponding to the humidity, and controls the output voltage of the variable voltage source 55 based on the detection signal value from the humidity sensor S, thereby performing the transfer belt current control. The transfer performance of the device is controlled to a predetermined level.

Table 1 shows experimentally obtained conditions under which standard-temperature standard-humidity (NN) is used as a reference to control electrostatic process conditions so that images of the same level can be obtained without being affected by temperature and humidity. showed that.

[0052]

[Table 1]

About + 6KV rated current 250μA flows from the high voltage constant current power source to the wire of the transfer pole, about 80μA on the transfer conveyor belt side and 100μ on the back plate side.
The current of A is distributed. In order to maintain stable transfer performance under each environment of LL, NN and HH, the potential of the back plate is + 150V in order to make the transfer belt current larger than that in NN when LL, and smaller than that in NN when HH. Therefore, the potential of the back plate was set to -100V. At this time, the transfer belt current flowing to the transfer conveyance belt side is about 60 μA,
It changed to about 45 μA. Moreover, not only can it be set to three levels of LL, NN, and HH, but also 5 steps, 7 steps and further stepless adjustment is possible.

The back plate potential can also be in the range of -200V to + 1000V.

Table 1 shows that the photoconductor charging potential is such that the grid voltage V _G applied to the grid of the scorotron charger is controlled according to the environment so that V _H does not fluctuate depending on the environment. The developing bias is the developing bias applied to the sleeve of the developing device and is controlled according to the environment.
This shows that the change in the charge amount of the developer due to the environmental change is compensated. The image exposure amount indicates that the laser exposure amount by the exposure unit is controlled according to the environmental conditions to compensate the sensitivity change due to the environmental condition change of the photoconductor.
~ Indicates the control conditions for controlling independently to eliminate the influence of the environment.

With the above-described structure, the image forming apparatus of the present embodiment controls the process conditions shown in Table 1 and the above-mentioned back plate potential on the basis of the detection signal from the humidity sensor s. It is possible to obtain a high-quality transferred image without being affected by fluctuations. Further, a variable resistor can be used instead of the variable voltage source 55. This results in a low price.

The transfer device 50 of this embodiment is not limited to this, and may be the transfer device shown in FIG. Further, although the corona charging device is shown as the transfer device, the transfer device is not limited to this, and the same effect can be obtained even if the charging is performed by using a conductive roller or a charging means using a brush.

[0058]

According to the first aspect of the present invention, it is possible to provide a transfer device capable of realizing stable transfer performance without being affected by humidity fluctuations.

According to the second aspect of the invention, it is possible to provide an image forming apparatus capable of obtaining a high quality transferred image without being affected by changes in environmental conditions.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a transfer device of the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of the image forming apparatus of the second invention.

FIG. 3 is a graph showing the humidity dependence of the transfer current in the transfer device of this embodiment.

FIG. 4 is a graph showing that the electrical characteristics of a general insulating transfer / transport belt and recording paper depend on humidity.

FIG. 5 is a schematic view showing a corona discharge device used in a general transfer / transport belt device.

[Explanation of symbols]

 10 Image Forming Body (Photosensitive Drum) 11 Conductive Substrate 12 Photosensitive Layer 31 Transfer Conveyor Belt 32 Holding Roller 33 Holding Roller 40 Brush Electrode 41 DC Power Supply 50 Transfer Device 51 Back Plate 52 Wire Side Plate 53 Discharge Wire 54 Power Supply 55 Variable Power Supply 60 Paper removal electrode 61 AC / DC superimposed power supply 70 Process CPU

Claims (4)

[Claims] 1. A transfer device for transferring a toner image on an image forming body onto a recording paper via a conveyor belt for holding a discharge charge by a corona electrode, wherein a resistance value of humidity resistance of a counter electrode is opposite to that of the corona electrode. A transfer device comprising a high resistance member. 2. A transfer device according to claim 1, wherein the conveyor belt comprises a substrate having a highly insulating layer of 10 ¹⁴ Ωcm or more and a high resistance rubber layer of 10 ⁶ to 10 ¹³ Ωcm. 3. An image forming apparatus for electrostatically transferring a toner image of an image forming body onto a recording paper on a conveyor belt having a transfer discharge electrode on the back surface, wherein the conveyor belt is a highly insulating layer of 10 ¹⁴ Ωcm or more. And a base of a high resistance rubber layer of 10 ⁶ to 10 ¹³ Ωcm, and the discharge current is controlled by controlling the transfer electrode shield potential according to humidity. 4. The image forming apparatus according to claim 4, wherein a variable power source or a variable resistor is connected to the transfer shield.