JP2000098759A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simultaneous transfer/fixation system image forming device capable of stably obtaining an image of high quality. SOLUTION: Recording paper guides 7-1 and 7-2 are arranged so that the extending lines of the guides 7-1 and 7-2 towards a pressure roll 2-2 may separately cross points R1 and R2 on the surface of a 1st pressure roll 2-2, that is, on the surface which comes into contact with the surface carrying the toner image of an intermediate transfer body 1, among a pair of pressure rolls 2-1 and 2-2, then, the recording paper comes into contact with the surface between the points R1 and R2 of the pressure roll 2-2 before the recording paper comes into contact with the intermediate transfer body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic printer, a copying machine, a facsimile and the like.

[0002]

2. Description of the Related Art An electrostatic latent image formed on a photoreceptor and visualized with toner to form a toner image, which is conventionally widely used, is then electrostatically transferred to a recording medium. In an image forming apparatus that performs fixing and fixing, there is a problem that density unevenness occurs in an image or toner is scattered in a transfer portion to lower resolution and dot reproducibility.

[0003] This is largely due to an electrostatic transfer process in which a toner image carried on an image carrier is electrostatically transferred to a recording medium. That is, in the transfer method using the electrostatic transfer process, it is difficult to uniformly and efficiently transfer the toner image formed on the image carrier onto the recording medium. In the electrostatic transfer process, the transfer efficiency of the toner depends on the intensity of the electric field applied to the toner layer (hereinafter referred to as E).
t), when the intensity of the electric field reaches a certain level, a so-called Paschen discharge occurs and E
t decreases, and the transfer efficiency starts to decrease. That is, the transfer efficiency shows a peak at a certain Et value. It is said that the peak value of the transfer efficiency is not 100%, but at most about 95%. As described above, since the transfer efficiency of the toner layer depends on Et, the toner must be kept constant irrespective of the thickness of the toner layer, the unevenness of the surface of the recording medium represented by paper, and the unevenness of the electrical properties. Since the transfer efficiency changes due to surface unevenness and unevenness in electrical properties due to the layer thickness and the transfer position of the recording medium, image unevenness occurs.

In a so-called intermediate transfer system in which a single-color toner image independently formed on an image carrier is temporarily transferred onto an intermediate transfer member and then transferred to a recording medium, surface irregularities and electrical properties are sufficiently reduced. Since the electrostatic transfer is performed on the controlled intermediate transfer member, a uniform image without unevenness is easily obtained. However, the toner image transferred onto the intermediate transfer member is multilayered, and has three or more layers at a large number and one layer or less at a small number. It is difficult to apply a constant electric field to collectively and uniformly electrostatically transfer such a toner layer to a recording medium represented by paper, and Et tends to be non-uniform. Therefore, in the electrostatic transfer method, not all of the color toner images superimposed on the intermediate transfer member are transferred to the recording medium, and a part of the toner image remains on the intermediate transfer member. This residual amount of toner varies depending on the thickness of the toner layer formed on the intermediate transfer member. Therefore, the color balance of the color image obtained on the recording medium may be lost, and a desired color image may not be obtained. Also, due to the surface irregularities of the recording medium paper, the paper and the intermediate transfer body do not completely adhere to each other, causing an uneven gap between the two and disturbing the transfer electric field,
Since toner scattering occurs due to the Coulomb repulsion between the powder toners, the image quality may be degraded.

In order to avoid the problems caused by the electrostatic transfer method, for example, Japanese Patent Publication No. 46-41679 discloses that a toner image formed on a photoreceptor is adhesively transferred to an intermediate transfer member. A method is disclosed in which toner is thermally transferred from an intermediate transfer member to a recording medium.

For example, Japanese Patent Publication No. 64-1024 and Japanese Patent Publication No. 64-1027 disclose an intermediate transfer member in which toner images transferred on an endless belt-like intermediate transfer member are overlapped with each other. A method is disclosed in which the toner image on the intermediate transfer body is transferred and fixed onto the recording medium by pressing the recording medium and the recording medium against each other with a heating roll and a pressing roll.

Also, Japanese Patent Publication No. 57-20632, Japanese Patent Publication No. 58-36341, and Japanese Patent Publication No. 64-10
No. 23 discloses that after a toner image transferred onto an endless belt-shaped intermediate transfer member is heated to a temperature equal to or higher than the melting point of the toner, the intermediate transfer member is pressed against a recording medium to record the toner image on the intermediate transfer member. In transferring and fixing on the medium, the intermediate transfer body and the recording medium are brought into pressure contact with each other, and then the moving intermediate transfer body and the recording medium are brought into contact for a long time. A method is disclosed in which the heat transfer to the medium is sufficiently performed so that the transfer and fixing of the toner to the recording medium are surely performed.

Japanese Patent Application Laid-Open Nos. 5-19642 and 5-249798 disclose an intermediate transfer member and a recording medium so that a toner image is completely transferred from the intermediate transfer member to a recording medium. A transfer / fixing method is disclosed in which heating and pressurizing are performed in a contact state, and then cooling is performed until the cohesive force between the toners becomes larger than the adhesive force between the toner and the intermediate transfer body, and then the recording medium is peeled from the intermediate transfer body. .

In the transfer fixing method as described above, since the transfer of the toner image to the recording medium is performed in a non-electrostatic manner, deterioration of the image quality in the transfer step hardly occurs, the transfer efficiency of the toner is high, and the sharpness is improved. There is an advantage that a high-quality image with high degree of gloss and good color balance and high gloss can be obtained in a color image.

[0010]

However, the so-called simultaneous transfer fixing system, in which transfer and fixing are performed by heating and pressing, has the following problems. That is, in this simultaneous transfer fixing method, a recording medium such as paper is brought into close contact with a heated intermediate transfer body and heated and pressed, and the intermediate transfer body and the recording medium are conveyed while being kept in close contact with each other. Since the recording medium is separated from the intermediate transfer member after cooling below, it is necessary to keep the pressurized intermediate transfer member and the recording medium in close contact with each other. If the recording medium floats or partially peels off from the intermediate transfer body after pressurization and before the recording medium is peeled off from the intermediate transfer body, the glossiness of that part is lower than that of other closely adhered parts, and the glossiness is lower. Since unevenness is generated, the image quality is significantly reduced. Further, if the recording medium is separated from the intermediate transfer member when the temperature of the toner is equal to or higher than the melting temperature, a so-called offset phenomenon occurs, and a part of the toner remains on the intermediate transfer member, and the image quality deteriorates to an unacceptable level. Would.

In order to bring the intermediate transfer member and the recording medium into close contact with each other, it is necessary to reduce the difference in expansion and contraction caused by the heat of both. In the case of the intermediate transfer member and the recording medium having a large difference in expansion and contraction, both are distorted after being pressurized and are easily peeled off. As a countermeasure for this, most of the problems can be solved by selecting a material having an appropriate heat shrinkage and expansion characteristic for the intermediate transfer member or by making the surface of the intermediate transfer member elastic.

However, even if the floating and peeling between the intermediate transfer member and the recording medium due to the difference in thermal expansion and contraction between the intermediate transfer member and the recording medium are suppressed, the recording medium may be wavy when the intermediate transfer member comes into contact with the recording medium. If the sheet enters the pressurizing section without being in close contact with the intermediate transfer member, the distortion appears after the pressurization, and a part of the recording medium is easily peeled off.

Further, depending on the adhesive force between the two after the pressurization, there is a problem that the recording medium is peeled off from the intermediate transfer body before reaching the peeling portion, and the image quality is degraded. The adhesive force between the intermediate transfer body and the recording medium after pressurization consists of the viscosity of the toner, the adhesive force on the surface of the intermediate transfer body, and the electrostatic adhesive force due to frictional charging between the two at the pressurizing section. Since the viscosity differs depending on the image, it is not possible to depend on the viscosity, and it is difficult to control the adhesive force of the surface of the intermediate transfer member and the electrostatic adhesion force due to triboelectric charging, because they vary greatly with time and environmental conditions.

As described above, in order to obtain a high quality image by the simultaneous transfer fixing method, after the intermediate transfer member and the recording medium are pressurized, the cooling period is required until the recording medium is separated from the intermediate transfer member. During this time, it is extremely important to keep the intermediate transfer member and the recording medium in close contact with each other. The conventional transfer fixing method does not address this problem, and it is difficult to stably obtain a high-quality image.

The present invention has been made in view of the above circumstances, and has as its object to provide an image forming apparatus of a simultaneous transfer and fixing system capable of stably obtaining a high-quality image.

[0016]

According to a first image forming apparatus of the present invention, which achieves the above object, an image carrier which carries a toner image on a surface thereof and circulates in a predetermined direction, and has a A toner image forming means for forming a toner image, an intermediate transfer member which receives the toner image formed by the toner image forming means, carries the toner image, and transports the toner image in a predetermined direction; Primary transfer means for transferring the transferred toner image to the intermediate transfer member, supplying a predetermined recording medium to the transfer and fixing position in accordance with the timing at which the toner image carried on the intermediate transfer member is transported to a predetermined transfer and fixing position The recording medium supply unit, which is provided, and the recording medium supplied by the recording medium supply unit are superimposed on the toner image on the intermediate transfer body, and the intermediate transfer body, the toner image, and the recording medium are kept in close contact with each other. In an image forming apparatus including a transfer and fixing unit including a pair of pressing members that transfers and fixes the toner image to the recording medium by heating and pressing, the recording medium supply unit is configured to move the toner image to the transfer and fixing position. The recording medium is so contacted that the leading end of the supplied recording medium is brought into contact with the first pressing member of the pair of pressing members, which is in contact with the surface of the intermediate transfer member that carries the toner image. It is characterized by supplying.

The second object of the present invention to achieve the above object is as follows.
The image forming apparatus includes an image carrier that carries a toner image on its surface and circulates in a predetermined direction, a toner image forming unit that forms a toner image on the image carrier, and a toner image formed by the toner image forming unit. An intermediate transfer member that carries the toner image and transfers the toner image in a predetermined direction, a primary transfer device that transfers the toner image formed by the toner image forming device to the intermediate transfer member, and an intermediate transfer member that carries the toner image. Recording medium supply means for supplying a predetermined recording medium to the transfer / fixing position in accordance with the timing at which the applied toner image is conveyed to a predetermined transfer / fixing position, and the recording medium supplied by the recording medium supply means to the intermediate transfer member The intermediate transfer member, the toner image, and the recording medium are superimposed on the toner image above, and the toner image is applied to the recording medium by heating and pressing while keeping the recording medium in close contact with the toner image. In an image forming apparatus provided with a transfer fixing unit including a pair of pressure members for copying and fixing, after being heated and pressurized by the transfer fixing unit on the downstream side of the transfer fixing unit in the moving direction of the intermediate transfer member. Wherein the recording medium is provided with an electrostatic charge applying means for applying an electrostatic charge having an areal density of 20 μC / m ² or more.

The third object of the present invention to achieve the above object is as follows.
The image forming apparatus includes an image carrier that carries a toner image on its surface and circulates in a predetermined direction, a toner image forming unit that forms a toner image on the image carrier, and a toner image formed by the toner image forming unit. And an intermediate transfer body that carries the toner image and transfers it in a predetermined direction, a primary transfer unit that transfers the toner image formed by the toner image forming unit to the intermediate transfer body, A recording medium supply unit for supplying a predetermined recording medium to the transfer / fixing position in synchronization with a timing at which the carried toner image is conveyed to a predetermined transfer / fixing position; and a recording medium supplied by the recording medium supply unit for the intermediate transfer. The intermediate transfer member, the toner image, and the recording medium are superimposed on the toner image on the body, and the toner image is heated and pressed while keeping the recording medium in close contact with the toner image. An image forming apparatus comprising: a transfer fixing unit including a pair of pressure members for transferring and fixing, and a separating unit configured to separate a recording medium having a toner image transferred and fixed on the surface by the transfer fixing unit from the intermediate transfer body. In the peeling section, the leading end of the recording medium that has begun to peel off from the intermediate transfer body, which is arranged close to the branch point where the intermediate transfer body and the recording medium that has begun to peel off from the intermediate transfer body forms, is moved away from the intermediate transfer body A separation assisting member that guides in the direction and is not in contact with the intermediate transfer member.

[0019]

Embodiments of the present invention will be described below.

This embodiment is a combination of the first image forming apparatus of the present invention, the second image forming apparatus of the present invention, and the third image forming apparatus of the present invention.

FIG. 1 is a schematic configuration diagram showing a first embodiment of the image forming apparatus of the present invention.

As shown in FIG. 1, this image forming apparatus comprises:
A full-color tandem image forming apparatus using four colors of black, yellow, magenta, and cyan, a light beam scanning device 20, image carriers 9_1, 9_2, 9_3, 9_4, chargers 10_1, 10_2, 10_3, 10_4, and a developing device 1
1, 12, 13, 14, intermediate transfer body 1, primary transfer means 5
0_1, 50_2, 50_3, 50_4, preheating roll 4, aluminum plate 5, recording medium supply means 7, tray 15, transfer and fixing means 2, electrostatic charge applying means 8, cooling device 1
6, a roll 6_1, a peeling part roll 6_2, and a peeling auxiliary member 32.

The light beam scanning device 20 shown in FIG.
The developing units 11, 12, 13, and 14 correspond to a toner image forming unit according to the present invention.

Next, the configuration and operation of each section of the image forming apparatus will be described.

The intermediate transfer member 1 includes a preheating roll 4, a roll 6_1, a peeling unit roll 6_2, and a transfer fixing unit 2.
And circulates in the direction of arrow B. Four image carriers 9_1, 9_2, 9_3, and 9_4, each of which rotates in the direction of arrow A in contact with the intermediate transfer member 1, are arranged, and a photosensitive layer is formed on the surface of each of the image carriers. . The surface of each of these image carriers is connected to a charger 1
After being uniformly charged by 0_1, 10_2, 10_3, and 10_4, exposure is performed by a light beam scanning device 20 that is turned on and off by a light beam pulse width modulation device based on a density signal, and an electrostatic latent image is formed. In the case of a copier, the exposure by light beam scanning may be exposure through reflected light of a document through a color separation filter. The electrostatic latent images formed on the respective image carriers are developed by developing units 11, 12, 13, and 14 containing black, yellow, magenta, and cyan toners, respectively. Each color toner image of the digital image is formed on each image carrier. These color toner images are transferred to the primary transfer units 50_1 and 50_1.
By 0_2, 50_3, and 50_4, electrostatic transfer is sequentially performed on the intermediate transfer body 1 in a superimposed manner, and a multicolor toner image is formed on the intermediate transfer body 1. The multicolor toner image is conveyed in the direction of arrow B by the intermediate transfer body 1 and reaches the preheating roll 4 provided upstream of the transfer and fixing position T in the direction of movement of the intermediate transfer body.

The pre-heating roll 4 is a hollow roll heated by a lamp 4a disposed inside, and comes into contact with the back surface of the intermediate transfer body 1 before transfer and fixing opposite to the surface carrying the toner image. The intermediate transfer member 1 and the toner image are preheated. Since the preheating roll 4 has a structure that covers the entire circumference of the lamp 4a, the calorific value of the lamp 4a is transmitted to the preheating roll 4 with almost no loss, and
Thus, a high-power lamp can be applied, so that a high amount of heat per unit area can be supplied to the intermediate transfer body 1 through the preliminary heating roll 4. As a material of the preheating roll 4, a metal material having good heat conductivity and high strength can be used. In this embodiment, an aluminum hollow roll having a thickness of 2 mm and an outer diameter of 40 mm is used. By coating the inner surface of the roll with black, radiant heat from the lamp 4a can be efficiently absorbed and transmitted to the intermediate transfer member 1. Downstream of the pre-heating roll 4 in the direction of movement of the intermediate transfer member, an aluminum plate 5 whose surface in contact with the back surface of the intermediate transfer member 1 that bears the toner image is slightly curved. A planar heater 5a for heating an aluminum plate is attached to the back surface. By appropriately setting the wiring pattern of the energizing heating element of the planar heater 5a, the distribution of the calorific value of the planar heater 5a can be easily changed, and in addition to the effect of reducing the temperature unevenness due to the use of the metal body. Since the contact length with the intermediate transfer member 1 can be made relatively long, the intermediate transfer member 1 can be uniformly heated. Note that another material may be used instead of the aluminum plate 5, and the material is not particularly limited to aluminum as long as it has good heat conductivity. By using a material having good heat conductivity, an effect that the intermediate transfer body 1 can be uniformly heated can be obtained. In the present embodiment, the aluminum plate 5 has a thickness of 3 mm in consideration of strength and the like. As the planar heater 5a, a silicone rubber heater in which an electric heating element is covered with a silicone rubber layer is used. It is desirable to make the silicone rubber layer as thin as possible, since heating can be performed efficiently by reducing the thermal resistance from the energizing heating element to the aluminum plate 5. In this embodiment, a 0.5 mm thick silicone rubber layer is provided. The planar heater can easily change the calorific value distribution of the planar heating member by arbitrarily changing the wiring pattern of the energizing heating element.

By arranging the preheating roll 4 and the aluminum plate 5 on the upstream side of the transfer and fixing position T in the direction of movement of the intermediate transfer member, the toner before the intermediate transfer member 1 is pressed together with the recording paper P by the transfer and fixing means. The image can be melted, and simultaneous transfer and fixing can be performed without substantially using the heating sources 3_1 and 3_2 inside the pressure rolls 2_1 and 2_2 that constitute the transfer and fixing unit 2. In the present embodiment, a toner having a melting temperature of 115 ° C. is used, and the intermediate transfer body 1 is heated to 165 ° C. before the intermediate transfer body 1 and the recording paper P are pressed to bring the toner into a molten state. The surface temperature of the pressure roll 2_2 is controlled to 100 ° C. in order to avoid image disturbance due to heat of the back side image. In addition,
The toner melting temperature is based on a value measured by a flow tester CFT-500 manufactured by Shimadzu Corporation. That is, using a flow tester type CFT-500, 1.5 g of toner previously molded by a pressure molding machine was applied with a load of 98 N (10 kgf), a nozzle diameter of 0.5 mm, a nozzle length of 1 mm, and a temperature increase rate of 5 ° C. / Extrude from the nozzle under the conditions of minutes. The toner outflow amount was measured in steps of 3 ° C. in the temperature range from 60 ° C. to 150 ° C., and the apparent viscosity η ′ (poi
se), and the temperature at which the apparent viscosity η ′ becomes 10 ⁴ poise is defined as the toner melting temperature.

The toner image on the intermediate transfer member 1 that has passed through the portion of the aluminum plate 5 and reached the transfer fixing position T is heated while the intermediate transfer member 1, the toner image, and the recording paper P are kept in close contact with each other. A pair of pressure rolls 2_ that press together
The image is transferred and fixed on the recording paper P by the transfer and fixing unit 2 composed of 1, 2_2. A pair of pressure rolls 2_
Heat sources 3_1 and 3_2 for heating these pressure rolls are arranged inside 1 and 2_2. The pair of pressure rolls 2_1 and 2_2 correspond to the pressure means according to the present invention.

The recording paper P is supplied with recording paper guides 7_1 and 7_1 at the timing when the toner image reaches the transfer and fixing position T.
The recording medium is supplied from the paper tray 15 to the transfer and fixing position T by a recording medium supply unit 7 including a registration roll 7_2 and a registration roll 7_3.

In this embodiment, the recording medium supply means 7
Is a recording medium (recording paper P) supplied to the transfer fixing position T
Of the pair of pressure rolls 2_1 and 2_2,
The recording paper P is configured to be supplied so as to be in contact with the first pressure roll 2_2 on the side of the intermediate transfer body 1 that is in contact with the surface of the intermediate transfer body 1 that carries the toner image. The detailed configuration and operation of the recording medium supply means will be described later.

Intermediate transfer member 1 carrying a plurality of color toner images
The toner image is pressed and heated by the pressure rolls 2_1 and 2_2 together with the recording paper P, so that the toner image is softened and melted, penetrates into the recording paper P, and then solidifies, whereby the transfer and fixing are completed.

A corona discharger 8_1 which applies an electrostatic charge to the recording paper P heated and pressurized by the transfer and fixing means 2 downstream of the pressure rolls 2_1 and 2_2 in the direction of movement of the intermediate transfer member. Roll 8_2 and constant current power supply 8_
3 is provided. The detailed configuration and operation of the electrostatic charge applying means 8 will be described later.

A cooling device 16 is provided downstream of the electrostatic charge applying means 8 in the moving direction of the intermediate transfer member. The cooling device 16 cools the intermediate transfer body 1 and the recording paper P, which are conveyed integrally by the transfer fixing means, whereby the toner is coagulated and solidified, and strong adhesion between the toner and the recording paper P is achieved. Forces arise.

The intermediate transfer body 1 and the recording paper P cooled by the cooling device 16 are separated from the separation roll 6_ having a small radius of curvature.
2, the recording paper P has its stiffness and the separation assisting member 32.
By such an action, the toner image is peeled off from the intermediate transfer body 1 together with the toner image to complete a color image. The surface of the toner image transferred and fixed on the recording paper P is smoothed to have a high gloss following the surface of the intermediate transfer member 1. The detailed configuration and operation of the separation assisting member 32 will be described later.

Image carriers 9_1, 9_2, 9_3, 9_4
As various inorganic photoreceptors (Se, a-Si, a-S
In addition to iC and CdS, various organic photoconductors can be used. The toner is formed of a thermoplastic binder containing a dye such as yellow, magenta, and cyan, and a known material can be used.

In this embodiment, the intermediate transfer member 1 is
It has a two-layer structure consisting of a base layer and a surface layer. As the base layer, a 75 μm-thick polyimide film to which carbon black was added was used. In order to electrostatically transfer the toner image from the image carrier to the intermediate transfer member without image disturbance, the volume resistivity of the base layer was carbon black. Was adjusted to 10 ¹⁰ Ω · cm. The base layer is, for example, a polyester, polyethylene terephthalate, polyethersulfone, polyetherketone, polysulfone, polyimide, polyimideamide, a polymer such as polyamide, having a thickness of 10 μm to
It is possible to use a high heat resistant sheet of 300 μm. Further, as the surface layer, a rubber hardness of 40 degrees is used to enhance the adhesion between the intermediate transfer body and the recording paper in a state where the toner image is interposed between the intermediate transfer body and the recording paper when performing the simultaneous transfer and fixing to the recording paper. A 50 μm thick silicone copolymer is used, and the volume resistivity is adjusted to 10 ¹⁴ Ω · cm in order to electrostatically transfer the toner image from the image carrier to the intermediate transfer member without image disturbance. Silicone copolymers have moderate elasticity, and their surface shows adhesiveness to toner at room temperature, and has properties that make it easy to release molten and fluidized toner. The toner can be efficiently transferred to paper, and is optimal as a surface layer material for an intermediate transfer member. In addition, as a surface layer, for example, thickness 1-100
A resin layer having a high releasability of μm, that is, a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, polytetrafluoroethylene, or the like may be used.

As the pressure rolls 2_1 and 2_2, a metal roll coated with a heat-resistant elastic layer such as silicone rubber on a metal roll can be used. Pressure roll 2_1, 2_2
, Halogen lamps are arranged as heating sources 3_1 and 3_2. In the present embodiment, the pressure rolls 2_1,
Both 2_2 have a hardness of 30 on a hollow aluminum roll.
Outer diameter of 50 mm with a thickness of 2.0 mm laminated with silicone rubber
mm. The nip pressure is 5.5 ×
It is set to 10 ⁵ Pa. The nip width at this time is approximately 7.5 mm.

In this embodiment, the pressure rolls 2_1 and 2_2 are used as a pair of pressure members. However, the pressure members are not limited to only the pressure rolls. Any member may be used as long as it can uniformly pressurize the sheet 1 and the recording sheet P without floating or shifting. For example, one pressure roll and one fixed pad may be combined, or a set of fixed pads may constitute a pressing member. Further, in the present embodiment, a halogen lamp is used as the heating sources 3_1 and 3_2 of the pressing member, but the heating source is not limited to the halogen lamp, and other known heating means can be used.

In the vicinity of the transfer / fixing position T, a recording medium supply means 7 comprising recording paper guides 7_1 and 7_2 and a registration roll 7_3 is provided, and a paper tray 15 for storing recording paper P is provided. It is connected to. A recording paper sheet discharged from the paper tray 15 to the registration roll 7_3 in the recording paper supply path and from the separation roll 6_2 having a small radius of curvature from which the recording paper P is separated from the intermediate transfer body 1 to the outside of the apparatus. In the middle of the route, the recording paper P
Paper reversing unit 23 for performing double-sided recording, recording paper transport direction switching member 22, and paper feed rolls 25_1 and 25_1.
A recording paper reversing mechanism including 5_2, 25_3, 25_4, and 25_5 is provided. During double-sided recording, the recording paper P
The recording paper P, which has been transferred and fixed to the first surface and has been peeled off from the intermediate transfer body 1 by the peeling roll 6_2, is guided to the recording paper reversing unit 23 by the recording paper transport direction switching members 21 and 22. Paper feed roll 2 with front and back reversed
5_1, 25_2, 25_3, 25_4, and 25_5 are supplied to the resist roll 7_3. After the inverted recording paper P is transferred and fixed to the second surface by the transfer and fixing means 2, the recording paper P is peeled off from the intermediate transfer body 1 by the peeling unit roll 6_2 and discharged outside the machine. Image recording is performed on both sides of the recording paper P as described above.

FIG. 2 is a detailed configuration diagram near the pair of pressure rolls of the present embodiment.

FIG. 2 shows a recording paper guide 7_1, which supplies the recording paper P to a transfer / fixing position T formed by a nip between the pressure rolls 2_1, 2_2 and the pressure rolls 2_1, 2_2.
7_2 and a corona discharger 8_ provided downstream of the pressure rolls 2_1 and 2_2 in the direction of movement of the intermediate transfer member.
1, an electrostatic charge applying means 8 including a metal roll 8_2 and a constant current power supply 8_3 is shown.

In the recording paper guides 7_1 and 7_2, an extension line from each of the recording paper guides 7_1 and 7_2 to the pressure roll 2_2 carries the toner image of the intermediate transfer member 1 of the pair of pressure rolls 2_1 and 2_2. The recording paper P is disposed so as to intersect with the points R1 and R2 on the surface of the first pressure roll 2_2 on the side in contact with the surface to be contacted, and between the points R1 and R2 before contacting the intermediate transfer member 1. It comes into contact with the surface of the pressure roll 2_2. With such a configuration, the nip of the pressure rolls 2_1 and 2_2 can be prevented without the recording paper P directly contacting the intermediate transfer body 1 heated to a high temperature and deforming unevenly due to the heat of the intermediate transfer body 1. You can enter the department. For this reason, peeling of the recording paper due to distortion between the intermediate transfer body and the recording paper after pressing hardly occurs, and it is easy to maintain the close contact state between the two. Further, the recording paper P does not contact the intermediate transfer body 1 before the nip portion, so that the toner image on the intermediate transfer body 1 is not disturbed. There is no disturbance. In addition, as a result of variously changing the positions and angles of the recording paper guides 7_1 and 7_2 to evaluate image disorder, image unevenness, and gloss unevenness, the intermediate transfer member 1 is moved to the intermediate transfer body 1 before the recording paper P comes into contact with the pressure roll 2_2. In the configuration in which the recording paper P is supplied to the transfer and fixing position T so that the recording paper P is in contact with the recording paper P, it has been confirmed that an image at the leading end is disturbed or the leading end of the recording paper P becomes dirty, thereby causing a problem. When the recording paper P is configured to come into contact with the pressure roll 2_2 before coming into contact with the intermediate transfer member 1, transfer and fixing of an image is generally performed satisfactorily, but the transfer and fixing are performed with the recording paper guides 7_1 and 7_2. When the angle θ between the recording medium P and the intermediate transfer body 1 before entering the recording sheet P increases, the recording paper P once in contact with the pressure roller 2_2 separates from the pressure roller 2_2 and intermittently moves before entering the transfer fixing unit. Contact with the body 1 may cause an image disorder. That is, the intermediate transfer body 1 and the recording paper guide 7 before entering the transfer fixing section
It is better to set the angle θ between _1 and 7_2 small,
By setting the angle to about 20 degrees or less, the transfer and fixing of the image can be suitably performed.

A corona discharger 8_1, which is provided downstream of the pressure rolls 2_1, 2_2 in the direction of movement of the intermediate transfer member,
The electrostatic charge applying means 8 including the metal roll 8_2 and the constant current power supply 8_3 is for applying an electrostatic charge to the recording paper P heated and pressed by the pressure rolls 2_1 and 2_2. A corona discharger 8_1, which is a non-contact charger, is provided on the recording paper P side;
Of the shield current is fed back to the constant current power supply 8_3 to control the dynamic current id by the charge applied from the wire of the corona discharger 8_1 to the recording paper P side to be constant. By controlling in this way, the recording paper P is not affected by the dielectric thickness, environment, etc.
By always supplying a constant amount of charge to the recording paper P, the surface density of the charge applied to the recording paper P can be made constant. The metal roll 8_2 is a grounding roll provided so as to face the corona discharger 8_1 and to contact the surface of the intermediate transfer body 1 opposite to the surface in contact with the recording paper P. As a result, charges of the opposite polarity are introduced to the intermediate transfer body 1 in an amount substantially equal to the charge applied to the recording paper P from the corona discharger 8_1, and the intermediate transfer body 1 and the recording paper P are electrostatically strong. It will be adsorbed.

Next, the following test was performed to confirm the effect of the above-described electrostatic charge applying means 8. Using the image forming apparatus of the present embodiment shown in FIG. 1, image formation was performed with the moving speed of the intermediate transfer body 1 set to 260 mm / s and the discharge width of the corona discharger 8_1 in the width direction of the intermediate transfer body set to 300 mm. The charge density σ provided by the corona discharger 8_1 is calculated from the dynamic current id by Expression 1.

Σ = id / (0.3 × 0.26) [C / m ² ] Equation 1 FIG. 3 shows the surface density of the electrostatic charge applied to the recording paper and the adhesion between the intermediate transfer member and the recording paper. It is a graph which shows the relationship with a degree.

As the recording paper P, among commercially available plain papers, a recording paper having a basis weight of 56 gsm (S paper manufactured by Fuji Xerox Co., Ltd.), which is a thin paper, and a recording paper having a basis weight of 209 gsm (Daishowa Paper Co., Ltd.), which is a thick paper Old white paper). The degree of adhesion between the intermediate transfer body 1 and the recording paper P is determined by visually observing the behavior of the recording paper P and determining the image unevenness and gloss unevenness after the transfer and fixing by sensory evaluation. As the image, a highlight image with a small amount of toner (area ratio 3
0% or less), and the test was conducted in a state where the influence of the adhesive force due to the toner was suppressed. In FIG. 3, the mark “○” indicates the intermediate transfer body 1
Indicates that the recording paper was not lifted from the surface and the image was formed well without any unevenness of the image. The mark △ indicates that the recording paper was slightly lifted but no defect was observed on the image and no problem The crosses indicate that the recording paper is lifted or peeled off and unevenness in density and gloss is observed in the image and the image quality is unacceptable.

From FIG. 3, it can be seen from FIG. 3 that the amount of electrostatic charge applied to the intermediate transfer member 1 and the recording paper P is sufficient and there is no problem in image quality.
It turns out that it is ^two or more. Note that the polarity of the charge applied in the present embodiment is the same minus polarity as the charge polarity of the recording paper P due to the triboelectric charge slightly observed when no charge is applied. That is, the triboelectricity of the intermediate transfer body 1 and the recording paper P is grasped in advance, and the polarity of the charge to be applied is determined to determine the electrostatic charge between the intermediate transfer body 1 and the recording paper P that have passed through the pressure rolls 2_1 and 2_2. It is possible to surely adsorb and transport without weakening the adhesive force.

As described above, it is one of the general methods that the image forming apparatus of the present embodiment is provided with an electrostatic charge on the recording paper after transfer and fixing to maintain the close contact between the intermediate transfer member and the recording paper. However, simply applying a high voltage to an electrostatic charge applying means such as a corona discharger or an electrostatic brush changes the amount of charge applied due to the electrical characteristics and the dielectric thickness of the recording paper P, and as a result, Then, the electrostatic adhesion between the intermediate transfer body 1 and the recording paper P changes, and the close contact between the two cannot be stably maintained. Electromagnetics teaches that the electrostatic adhesion between the intermediate transfer member 1 and the recording paper P is determined by the electric field strength between the two, and that the electric field strength is determined by the amount of charge held by the two. Therefore, the present inventors have proposed an intermediate transfer member 1
The required charge amount was determined by examining the relationship between the surface density of the charge applied to the recording paper P and the degree of adhesion between the two, and the surface density was 20 μC
/ M ² or more to give a static charge of 209
It has been clarified that the sheet can be transported to a gsm thick paper without peeling, and a high-quality image can be obtained. Note that the degree of adhesion between the intermediate transfer body 1 and the recording paper P was determined by evaluating image unevenness and gloss unevenness after transfer and fixing.
Assuming that the relative permittivity of the intermediate transfer body 1 and the recording paper P is 3, a charge of ²⁰ μC / m ² is approximately 750 gf /
It is calculated that an adhesive force of m ² acts.

FIG. 4 is a schematic structural view of the vicinity of the peeling section S in the image forming apparatus of the present embodiment.

At the peeling section S, the intermediate transfer body 1 is wound around a peeling section roll 6_2, and the recording paper P is rolled around the peeling section roll 6_
The recording paper P is configured to be peeled off at the waist by the curvature of 2. In the simultaneous transfer fixing type image forming apparatus, a configuration in which the recording paper P is peeled by the curvature of the intermediate transfer body and the waist of the recording paper is generally used. It has been found that it is better to set the diameter to 30 mm or less to have a large curvature and wind the intermediate transfer body 1 over a larger angle. However, in the case of thin and stiff recording paper, such a configuration does not allow stable peeling, and may cause a trouble such as a paper jam. Therefore, the peeled portion S
In addition, a paper jam may be caused by providing a separation assisting member 32 that continuously and mechanically guides the recording paper P, whose leading end has started to peel, in a non-contact manner with the intermediate transfer body 1 in a direction away from the intermediate transfer body 1. It is possible to stably obtain a high-quality image.

In the present embodiment, the intermediate transfer member 1 is wound around the separation portion roll 6_2 having a diameter of 20 mm by approximately 90 degrees, and the branch formed by the intermediate transfer member 1 and the recording paper P that has begun to be separated from the intermediate transfer member 1. An exfoliation assisting member 32 is provided which is not in contact with the intermediate transfer body 1 disposed in the vicinity of the point B. The recording sheet P that has begun to be separated from the intermediate transfer member 1 is mechanically guided by the separation auxiliary member 32 in a direction away from the intermediate transfer member 1. In the present embodiment, the peeling assisting member 32 is configured by disposing five claw-like members in the width direction of the intermediate transfer body at a position approximately 1 mm from the surface of the intermediate transfer body 1. The present invention is not limited to such a configuration, and it may be configured by one or a plurality of plate-like or block-like ones. The provision of the non-contact separation assisting member 32 on the intermediate transfer body 1 allows the thin transfer paper to be reliably separated without damaging the intermediate transfer body 1. For example, even recording paper having a basis weight of 56 gsm (S paper manufactured by Fuji Xerox Co., Ltd.), which is a weak paper, can be peeled off without causing a paper jam.

In the present embodiment, as shown in FIG. 4, the charge of the recording paper P is removed at a position upstream of the separation assisting member 32 in the moving direction of the intermediate transfer member and opposed to the separation portion roll 6_2. An exfoliating part static eliminator 30 is provided. A corona discharger is used as the peeling unit static eliminator 30,
The opposite peeling portion roll 6_2 is a metal roll and is grounded. The exfoliating section static eliminator 30 is connected to the high-voltage AC power supply 31, and removes the charged charges of the recording paper P passing therethrough by AC discharge.

The exfoliating portion neutralizer 3 in the present embodiment.
The 0 and the high-voltage AC power supply 31 correspond to the recording medium static elimination means according to the present invention. By this recording medium discharging means, the intermediate transfer body 1 in a close contact state at the peeling section S
And the electrostatic adhesion between the recording paper P and the recording paper P can be reduced or eliminated, so that the recording paper P can be reliably separated from the intermediate transfer member 1 and can be stably provided without causing a paper jam or the like. High quality images can be obtained. Further, by using the exfoliating portion neutralizer 30, the degree of contact of the recording paper P with the exfoliation assisting member 32 can be reduced, and the toner image portion due to the recording paper P rubbing against the exfoliation assisting member 32 can be reduced. Obstacles such as rubbing marks can be avoided. In this embodiment, the basis weight is 56 g, which is thin thin paper.
Even sm recording paper (S paper manufactured by Fuji Xerox Co., Ltd.) can be peeled off without causing paper jam and a good image can be obtained.

As shown in FIG. 4, an intermediate transfer member discharging means 33 is provided downstream of the peeling portion roll 6_2 in the direction of movement of the intermediate transfer member. The intermediate transfer body discharging means 33 is for removing charge from the intermediate transfer body 1 after the recording paper is peeled off, and a pair of corona dischargers 33_1 arranged on the front and back surfaces of the intermediate transfer body 1 so as to face each other. , 33_2 and high-voltage AC power supplies 33_3, 33_4. By disposing the intermediate transfer body discharging means 33 having such a configuration, it is possible to uniformly remove charges remaining non-uniformly on the intermediate transfer body 1 due to peeling of the recording paper P at the peeling section S.

In general, an electrostatic transfer unit is widely used as a unit for transferring a toner image formed on an image carrier onto an intermediate transfer member. In the image forming apparatus of this embodiment, an electrostatic primary unit is also used. Transfer devices 50_1, 50_2, 50_3
50_4 are used. In order to stably transfer the toner image onto the intermediate transfer body 1 during the electrostatic transfer, the charged state of the intermediate transfer body 1 needs to be stable. If electric charges having the same polarity as the charged polarity of the toner remain on the surface of the intermediate transfer member 1, a substantial transfer electric field is reduced, and the amount of toner transferred to the intermediate transfer member 1 is reduced. May occur. Therefore, in the image forming apparatus of the present embodiment, the intermediate transfer member static elimination means 33 is provided, and before the transfer of the toner image from the image carriers 9_1, 9_2, 9_3, and 9_4 to the intermediate transfer member 1, the intermediate transfer member 1 By stabilizing the charging potential, it is possible to stably and continuously transfer toner images from the image carriers 9_1, 9_2, 9_3, and 9_4 to the intermediate transfer member 1, and to obtain high-quality images without density unevenness. Can be obtained stably. It should be noted that the phase of the alternating current between the pair of corona dischargers 33_1 and 33_2 can be shifted by half a wavelength to further enhance the static elimination effect.

The intermediate transfer body discharging means 33 is not limited to a pair of corona dischargers, but may be a corona discharger provided on one side of the intermediate transfer body 1 and a grounded metal roll provided at an opposite position. May be combined. In the present embodiment, by using the corona dischargers 33_1 and 33_2,
The charge potential of the intermediate transfer body 1 that has passed through this area can be eliminated to approximately 0V. The potential of the intermediate transfer body 1 after static elimination does not necessarily need to be approximately 0 V, and may be in a charged state as long as the potential is stable.

Next, a second embodiment of the image forming apparatus of the present invention will be described.

FIG. 5 is a schematic configuration diagram showing a second embodiment of the image forming apparatus of the present invention.

In the second embodiment, as in the first embodiment, the first image forming apparatus of the present invention, the second image forming apparatus of the present invention, and the third image forming apparatus of the present invention Of the present embodiment.

The image forming apparatus shown in FIG. 5 is different from the image forming apparatus according to the first embodiment shown in FIG. 1 in the structure of three means, that is, an electrostatic charge applying means, a recording medium discharging means, and an intermediate transfer body discharging means. And the other configurations are exactly the same. That is, in the second embodiment, as the electrostatic charge applying means 8 ', the conductive brush 8_4 is arranged so as to be in contact with the recording paper P, and a constant amount of electric charge is applied to the recording paper P from the constant current power supply 8_5. Like that. The conductive brush 31_1 is a recording medium P
The conductive brush 31_1 is connected to a high-voltage AC power supply 31_2. In addition, as an intermediate transfer member static elimination means, conductive brushes 33_5 and 33_6 are arranged so as to be in contact with the front and back surfaces of the intermediate transfer member 1, and these conductive brushes 33_5 and 33_6 are connected to high-voltage AC power supplies 33_7 and 33_8, respectively. I have. If the resistance of these conductive brushes is too low, high pressure leaks due to pinholes in the intermediate transfer body 1 or the recording paper P and affects the image, and the operation of the apparatus becomes unstable due to electric discharge. It is preferable to use one having a resistivity of 10 ⁴ Ω · cm to 10 ⁷ Ω · cm.

The use of a conductive brush has the advantage that it is environmentally friendly with almost no generation of ozone as compared with the case where a corona discharger is used. In this embodiment, 10
^The electrostatic charge applying means 8 'is formed by using a brush material of ⁶ Ω · cm, and the conductive brush 8_4 applies 20 μm to the recording paper P from the conductive brush 8_4.
After giving a charge amount of C / m ² or more, the recording medium charge elimination means and the intermediate transfer body charge elimination means are constituted by using the same brush material so that the recording paper P and the intermediate transfer body 1 are respectively charge-eliminated. When an image was formed, good images could be continuously obtained without causing paper jams and without density unevenness or gloss unevenness in both thin paper and thick paper as in the first embodiment.

In this embodiment, the conductive brushes are disposed on both the front and back surfaces of the intermediate transfer member 1 as the intermediate transfer member discharging means.
It is not necessary to arrange conductive brushes on both the front and back surfaces of the device, and a conductive brush may be arranged on only one of the front surface and the back surface and the other may be grounded.

The parts of the configuration of the present embodiment that are not specifically described are the same as those of the first embodiment, and thus description thereof is omitted.

In this embodiment, the conductive brush is used as the contact type electrostatic charge applying means, the recording medium charge eliminating means, and the intermediate transfer body charge eliminating means. However, these means are not limited to the brush member. Alternatively, a conductive or semiconductive roll member or film member may be used.

[0065]

As described above, according to the first image forming apparatus of the present invention, the leading end of the recording medium supplied to the transfer / fixing position is supplied so as to first contact the pressing member. The recording medium before the transfer and fixing is prevented from being deformed by the heat of the high-temperature intermediate transfer body. Further, according to the second image forming apparatus of the present invention, since the recording paper after transfer and fixation is given an electrostatic charge, the close contact state between the intermediate transfer body and the recording paper is maintained, and the recording paper reaches the peeling portion S. Before this, the recording paper is prevented from peeling off from the intermediate transfer member. Further, according to the third image forming apparatus of the present invention, the recording sheet whose leading end has been peeled off without being in contact with the intermediate transfer body is continuously and mechanically moved away from the intermediate transfer body in the peeling section S. The provision of the guiding auxiliary peeling member prevents paper jam. Therefore, with the image forming apparatus of the present invention, it is possible to realize an image forming apparatus of a simultaneous transfer and fixing system capable of stably obtaining a high-quality image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a first embodiment of an image forming apparatus of the present invention.

FIG. 2 is a detailed configuration diagram near a pair of pressure rolls of the present embodiment.

FIG. 3 is a graph showing the relationship between the surface density of electrostatic charge applied to a recording sheet and the degree of adhesion between the intermediate transfer member and the recording sheet.

FIG. 4 is a detailed configuration diagram near a peeling section S in the image forming apparatus of the present embodiment.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Intermediate transfer body 2 Transfer fixing means 2_1, 2_2 Pressure roll 3_1, 3_2 Heat source 4 Preheating roll 4a Lamp 5 Aluminum plate 5a Planar heater 6_1 Roll 6_2 Peeling roll 7 Recording medium supply means 7_1, 7_2 Recording paper guide 7_3 Resist roll 8, 8 'Static charge applying means 8_1 Corona discharger 8_2 Metal roll 8_3, 8_5 Constant current power supply 8_4 Conductive brush 9_1, 9_2, 9_3, 9_4 Image carrier 10_1, 10_2, 10_3, 10_4 Charger 11, 12, 13, 14 Developing device 15 Tray 16 Cooling device 20 Light beam scanning device 21, 22 Recording paper transport direction switching member 23 Recording paper reversing unit 25_1, 25_2, 25_3, 25_4, 25_5
Paper feed roll 30 Stripper static eliminator 31 High voltage AC power supply 31_1 Conductive brush 31_2 High voltage AC power supply 32 Separation assisting member 33 Intermediate transfer member static elimination means 33_1, 33_2 Corona discharger 33_3, 33_4, 33_7, 33_8 High voltage AC power supply 33_5, 33_6 Conductivity Brush 50_1, 50_2, 50_3, 50_4 Primary transfer unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Daisuke Yoshino 430 Nakai-cho, Nakai-cho, Ashigara-kami, Kanagawa Prefecture Inside Fuji Xerox Fuji Xerox Co., Ltd. F-term (reference) 2H032 AA02 AA15 BA09 BA21 BA28 CA13 DA03 DA04 DA08 DA11

Claims (6)

[Claims] 1. An image bearing member carrying a toner image on a surface thereof and circulating in a predetermined direction, a toner image forming means for forming a toner image on the image bearing member, and a toner formed by the toner image forming means. An intermediate transfer member that receives the image, carries the toner image, and conveys the toner image in a predetermined direction; a primary transfer device that transfers the toner image formed by the toner image forming device to the intermediate transfer member; A recording medium supply unit for supplying a predetermined recording medium to the transfer / fixing position in accordance with a timing at which the toner image carried by the recording medium is conveyed to the predetermined transfer / fixing position; and a recording medium supplied by the recording medium supply unit. The toner image is transferred onto the recording medium by heating and pressurizing the intermediate transfer body, the toner image, and the recording medium while keeping the recording medium in close contact with the toner image on the intermediate transfer body. In an image forming apparatus including a transfer and fixing unit including a pair of pressure members for transferring and fixing, the recording medium supply unit may set a front end of a recording medium supplied to the transfer and fixing position to the pair of pressure members. Wherein the recording medium is supplied so as to be brought into contact with a first pressure member on the side of the intermediate transfer member which is in contact with the surface carrying the toner image. 2. An image carrier that carries a toner image on its surface and circulates in a predetermined direction, a toner image forming unit that forms a toner image on the image carrier, and a toner formed by the toner image forming unit An intermediate transfer member that receives the image, carries the toner image, and conveys the toner image in a predetermined direction; a primary transfer device that transfers the toner image formed by the toner image forming device to the intermediate transfer member; A recording medium supply unit for supplying a predetermined recording medium to the transfer / fixing position in accordance with a timing at which the toner image carried by the recording medium is conveyed to the predetermined transfer / fixing position; and a recording medium supplied by the recording medium supply unit. The toner image is transferred onto the recording medium by heating and pressurizing the intermediate transfer body, the toner image, and the recording medium while keeping the recording medium in close contact with the toner image on the intermediate transfer body. In an image forming apparatus provided with a transfer fixing unit including a pair of pressure members for transferring and fixing, on the downstream side in the intermediate transfer body moving direction from the transfer fixing unit,
An image forming apparatus comprising: an electrostatic charge applying unit that applies an electrostatic charge having a surface density of 20 μC / m ² or more to a recording medium heated and pressed by the transfer fixing unit. 3. An image carrier that carries a toner image on its surface and circulates in a predetermined direction, a toner image forming unit that forms a toner image on the image carrier, and a toner formed by the toner image forming unit. An intermediate transfer member that receives the image, carries the toner image, and conveys the toner image in a predetermined direction; a primary transfer device that transfers the toner image formed by the toner image forming device to the intermediate transfer member; A recording medium supply unit for supplying a predetermined recording medium to the transfer / fixing position in accordance with a timing at which the toner image carried by the recording medium is conveyed to the predetermined transfer / fixing position; and a recording medium supplied by the recording medium supply unit. The toner image is transferred onto the recording medium by heating and pressurizing the intermediate transfer body, the toner image, and the recording medium while keeping the recording medium in close contact with the toner image on the intermediate transfer body. An image forming apparatus comprising: a transfer fixing unit including a pair of pressure members for transferring and fixing, and a separating unit configured to separate a recording medium having a surface onto which a toner image has been transferred and fixed from the intermediate transfer body by the transfer fixing unit. In the peeling section, the tip of the recording medium that has begun to be peeled off from the intermediate transfer body is disposed in proximity to a branch point formed by the intermediate transfer body and the recording medium that has begun to peel off from the intermediate transfer body. An image forming apparatus comprising: a separation assisting member that is guided in a direction away from the transfer member and that is not in contact with the intermediate transfer member. 4. The image forming apparatus according to claim 3, further comprising a recording medium discharging unit that removes an electrostatic charge of the recording medium, on an upstream side of the separation unit in a direction in which the intermediate transfer member moves. 5. The image forming apparatus according to claim 3, further comprising an intermediate transfer member discharging unit that removes an electrostatic charge of the intermediate transfer member, downstream of the separation unit in the moving direction of the intermediate transfer member. apparatus. 6. An apparatus according to claim 1, further comprising an electrostatic charge applying means for applying an electrostatic charge to the recording medium heated and pressurized by said transfer and fixing means, downstream of said transfer and fixing means in the moving direction of the intermediate transfer member. The image forming apparatus according to claim 4, wherein: