JPH04149490A - Image formation device - Google Patents

Abstract

PURPOSE:To prevent a pressing member from being charged excessively or irregularly, to eliminate a defect in attracting a recording material and its jamming, and to obtain excellent images which are free from a transfer irregularity and a transfer omission by providing a conductive part at the part of the pressing member which is positioned at the place of a charge applying means. CONSTITUTION:The charge applying means 9 gives electric charges to a recording material, which is electrostatically attracted and held on a flexible recording material carrying member 6a such as a recording material carrying sheet. When the recording material is held on the recording material carrier member 6a in contact by pressing the recording material carrying member 6a by the pressing member 23, the conductive part 24 is provided at the part of the pressing member 23 which is positioned at the place of the charge applying means 9 to prevent the pressing member 23 from being charged electrostatically too much or irregularity. Consequently, the recording material is neither attracted defectively nor jammed and excellent images which have neither a transfer irregularity nor a transfer omission are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and particularly relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and in particular to a method for transferring a toner image formed on an image carrier to a flexible recording material. The present invention relates to an image forming apparatus that electrostatically transfers an image onto a recording material held on a supporting member to obtain an image on the recording material.

For example, in a color electrophotographic copying machine, a toner image of each color formed on an image carrier using an electrophotographic method is transferred onto a recording material by a transfer device to obtain a color image on the recording material. .

A typical transfer device is equipped with a transfer drum as a recording material carrier, and the transfer drum has a recording material carrying sheet, such as polyethylene terephthalate or polyfluoride, as a flexible recording material carrying member between both end frames of a cylindrical shape. It is made by winding a film-like dielectric sheet such as vinylidene resin into a cylindrical shape.

The recording material is supplied to the transfer drum of the transfer device, and the edge of the recording material is mechanically fixed and held by a gripper provided on a part of the circumferential surface of the transfer drum, or when it is wound, for example, on the carrier sheet side or Corona discharge is performed from the recording material side to create an electrostatic adhesion force between the carrier sheet and the recording material to attract and hold the recording material on the carrier sheet (Japanese Patent Laid-Open No. 55-32079). (see issue).

In order to adsorb and hold the recording material described above, a corona discharger is provided as a charge imparting means on the inside of the recording material adsorption position of the carrier sheet (on the back side of the surface opposite to the recording material holding surface). Accordingly, a conductive roller that faces the corona discharger and rolls into contact with the recording material is disposed on the outside of the carrier sheet (on the recording material holding surface side) to transfer the toner constituting the toner image on the image carrier to the recording material. A charge of opposite polarity to the frictional charging polarity is applied.

In a color electrophotographic copying machine, each time a toner image of each color is formed on an image carrier, a toner image is electrostatically transferred onto a recording material that is attracted and held on a carrier sheet as described above. This is done for all the toner images of multiple colors by multiple transfer in which the transfer drum is rotated multiple times, thereby producing a color image by superimposing the toner images of multiple colors on the recording material.

The recording material onto which the toner images of multiple colors have been transferred is then used to weaken the electrostatic attraction force (Coulomb force) between the recording material and the carrier sheet using a corona discharger, and then the separation member is removed. By placing it between the recording material and the carrier sheet,
The recording material is separated from the carrier sheet.

In the above, if there is a local gap between the recording material and the carrier sheet when the recording material is adsorbed and held on the carrier sheet, a transfer failure may occur at the gap, or even worse. In order to prevent this from occurring, so-called jamming of the recording paper may occur due to the gaps, an elastic material is installed inside the carrier sheet near the recording material suction position and extends from the upstream side in the direction of rotation of the carrier sheet. A pressing member is provided that presses the carrier sheet by contacting the carrier sheet, thereby bringing the carrier sheet into close contact with the recording material electrostatically attracted and held on the carrier sheet,
It has been proposed to prevent the occurrence of gaps (see Japanese Patent Laid-Open No. 2-157779).

However, simply providing a pressing member near the recording material adsorption position (on the inside of the carrier sheet) causes a problem because the charging member becomes unevenly charged due to corona discharge when the recording material is attracted to and held on the carrier sheet. .

That is, if uneven charging occurs on the pressing member due to corona discharge when the recording material is attracted to and held on the carrier sheet, the attraction electric field due to the corona discharge is affected, causing unevenness in the attracting electric field and causing uneven charging on the carrier sheet. let When this uneven charging of the carrier sheet occurs, uneven transfer and image omission occur in a direction parallel to the direction of movement of the carrier sheet, degrading image properties such as image quality.

When image formation is performed continuously, recording materials are attracted and held one after another on the carrier sheet, so the pressing member of the carrier sheet is overcharged by the attraction electric field, and the charging potential gradually increases (so-called A charge-up phenomenon occurs. This charge-up phenomenon weakens the adsorption electric field, causing partial adsorption failure of the recording material to the carrier sheet, and eventually causing jamming of the recording material.

The above describes the case of a color image forming apparatus in which the transfer device is equipped with a transfer drum wrapped with a recording material carrying sheet made of a flexible dielectric sheet, and the problems with the pressing member of the carrying sheet are explained. However, when a plurality of image forming units including photosensitive drums are arranged in parallel, a flexible dielectric belt is attached to the underside of the plurality of photosensitive drums as a common recording material carrying member for the plurality of image forming units. In a color image forming apparatus in which a transfer device of each image forming unit is configured by arranging an endless recording material conveying belt, a similar problem occurs when a pressing member for the recording material conveying belt is provided.

Therefore, an object of the present invention is to electrostatically attract and hold a recording material onto a flexible recording material carrying member such as a recording material carrying sheet by applying a charge to the recording material using a charge applying means, and to When holding the recording material on the recording material supporting member by pressing the recording material supporting member with the pressing member, the pressing member is prevented from being excessively charged or unevenly charged. It is an object of the present invention to provide an image forming apparatus capable of obtaining a good image without defective suction or jamming of a recording material, and without uneven transfer or omission of transfer.

for The above object is achieved by an image forming apparatus according to the present invention.

In summary, the present invention is directed to the recording material holding surface side of the recording material suction position of a flexible recording material carrying member for supporting a transfer material for transferring a toner image formed on an image carrier, or the opposite side thereof. A charge applying means is disposed on the surface side of the recording material to electrostatically attract and hold the recording material on the supporting member. Pressing to hold the recording material on the support member in close contact with the support member by pressing a portion of the support member near the recording material adsorption position on the same side as the self-charge applying means. The parts are
The image forming apparatus is arranged close to the charge applying means, and is characterized in that a conductive portion is provided in a portion of the pressing member located at the position of the charge applying means.

According to one aspect of the present invention, the pressing member extends from the upstream side in the moving direction of the recording material carrying member and contacts the recording material carrying member, the recording material carrying member is a dielectric sheet or a dielectric belt, and the electric charge is applied to the pressing member. The means is a corona discharger.

On a good plate Examples of the present invention will be described in detail below.

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus of the present invention.

In FIG. 1, 1 is a photosensitive drum as an image carrier;
The photosensitive drum 1 is pivotally supported at its center and rotated in the direction of the arrow. Around the photosensitive drum 1, a primary charger 2, an optical system 3, and a developing device 4 are arranged opposite to the photosensitive drum 1 in the direction of rotation thereof.
, a secondary charger 5 are arranged.

The primary charger 2 applies a uniform primary charge to the photosensitive drum 1, and the optical system 3 applies a color-separated optical image or a corresponding optical image to the surface of the photosensitive drum 1 at a predetermined timing.
Forms an electrostatic latent image. The optical system 3 uses a laser beam exposure device or the like.

Further, the developing device 4 is movable in the tangential direction facing the surface of the photosensitive drum 1, and has four developing devices each specially storing magenta toner, cyan toner, yellow toner, and black toner as developers. It is equipped with 4M, 4C14Y and 4B. The developing device 4 has a developing device containing toner of a color corresponding to the electrostatic latent image formed on the photosensitive drum 1 facing the photosensitive drum 1, and the toner in the opposing developing device electrostatically contacts the photosensitive drum. The toner particles fly to the surface of the photosensitive drum 1 and adhere to the electrostatic latent image on the photosensitive drum 1, and the electrostatic latent image is developed and visualized as a toner image.

Further, around the photosensitive drum 1, as shown in FIG. 1, a static eliminator 27 for removing static charge on the surface of the photosensitive drum 1 and a cleaning blade 28 for removing toner are disposed.

Further, on the right side of the photosensitive drum 1, a transfer device 6 is installed.
A is provided so as to be in contact with the surface of the photosensitive drum 1 or to be slightly separated from the surface. The transfer drum 6A has a recording material carrying sheet 6a, which is a flexible recording material carrying member, between both cylindrical end frames, a dielectric constant of 3.0 to 13.0, a volume resistivity of 109 to 1014 Ωcm, and a thickness of 70 to 200 μm. A dielectric sheet that satisfies at least two of the following conditions, such as a polyvinylidene fluoride (PVdF) film, is wrapped around a cylinder.

As shown in FIG. 1, a transfer corona charger 7 is disposed inside the recording material carrying sheet 6a (on the back side opposite to the recording material holding surface) at a transfer position facing the photosensitive drum 1. Furthermore, an adsorption corona discharger 19 is provided at a recording material adsorption position upstream of the transfer position in the rotational direction of the transfer drum 6A. On the outside (recording material holding surface side) of the carrier sheet 6a, a conductive roller 20 that faces the corona discharger 19 and rolls into contact with the recording material P is disposed as necessary.

The recording material P supplied to the attraction position of the carrier sheet 6a is electrostatically attracted and held onto the carrier sheet 6a by an attraction electric field caused by the charge applied to the recording material P by corona discharge from the corona discharger 19. .

Further, on the downstream side of the recording material adsorption position of the carrier sheet 6a, a corona discharger 10.11 for static electricity removal is provided sandwiching the carrier sheet 6a, and a pusher is further provided to separate the recording material P from the carrier sheet 6a. The support rollers 12 and 13 support the support sheet 6a.
A separating blade 14 is arranged in the vicinity thereof. If necessary, a corona discharger 29 is installed near the separation blade 14 to generate AC corona discharge in order to prevent image disturbance due to peeling discharge that occurs when the recording material P is separated from the carrier sheet 6a. It's good to do it.

Furthermore, on the downstream side, there is a brush roller 15 for cleaning the transfer material holding surface of the carrier sheet 6a, and if necessary, a corona discharger or a brush-type static eliminator for removing adhesive force (residual Coulomb force and Van der Waals force). 16 are provided.

The recording material P separated by the separation blade 14 is transferred to the conveyor 1
The toner image is supplied to the fixing roller 18 via the recording material P, and the toner image transferred onto the recording material P is fixed.

Further, a recording material supplying means consisting of a pair of registration rollers 21 and the like for supplying the recording material P to the holding surface of the carrier sheet 6a via a guide 22 is provided immediately upstream of the corona discharger 19 and the conductive roller 20.

As shown in FIG. 2, a pressing member is further provided near the recording material suction position inside the recording material carrying sheet 6a in order to adsorb and hold the recording material P onto the carrying sheet 6a. 23 are provided. The pressing member 23 is made of an elastic member, extends from the upstream side in the rotational direction to the carrier sheet 6a within the discharge width of the corona discharger 19, and comes into elastic contact with the carrier sheet 6a to press the carrier sheet 6a. The recording material P that is attracted and held on top of the carrier sheet 6a is brought into close contact with the carrier sheet 6a to prevent a gap from forming between the carrier sheet 6a and the recording material P.

This pressing member 23 is made of a synthetic resin film such as polyethylene, polypropylene, polyester, polyethylene terephthalate, etc., having a volume resistivity of 1010 Ωcm or more, preferably 1014 Ωcm or more, and is perpendicular to the rotation direction of the carrier sheet 68 at the suction position. It is arranged over the entire area in the direction. In this example, a polyethylene terephthalate resin film was used for the pressing member 23.

A carrier sheet 6 that is elastically pressed by the tip of the pressing member 23
The position B is on the back surface of the carrier sheet 6a and corresponds to the position where the recording material P of the carrier sheet 6a has finished contacting, the position where contact has started, or a position as close as possible to this. suitable.

The pressing member 23 has a thickness of 10 μm to 20 mm in order to be able to apply an appropriate pressing force to the supporting sheet 6a and not to significantly affect the adsorption electric field by the adsorption corona discharger 19. It is preferable that the thickness be 50 to 500 μm, and very good results have been obtained.

Now, according to the present invention, as shown in FIGS. 2 and 3, a conductive part 24 is provided on the tip of the pressing member 23. The conductive portion 24 may be placed on the support sheet 6a side of the pressing member 23 as shown by the solid line in FIG. 2, or may be placed on the adsorption corona discharger 19 side as shown by the dashed line.

In principle, the material of the conductive part 24 may be any material as long as it has a volume resistivity of 1010 Ωcm or less, and will be described in detail later, but as long as it satisfies this volume resistivity, it is sufficiently effective for the purpose of the present invention. can get. Therefore, for example, the conductive portion 24 can be formed using a mixture that satisfies the above volume resistivity by dispersing a conductive substance into a high-resistance substance. Of course, the conductive portion 24 can also be formed using one type of material that satisfies the volume resistivity.
Needless to say, this is preferable.

In order to form the conductive portion 24 on the pressing member 23, an appropriate method may be used depending on the form of the material to be used, such as coating a required material on the pressing member 23, or pasting a material in the form of a sheet. It can be formed by any method. conductive material 24
For example, a thin SUS plate, aluminum foil, or the like is suitably used as the sheet-like member forming the .

It is preferable that the conductive part 24 is formed in the area where the discharge for adsorption is actually performed, and in this embodiment, the conductive part 24 is
The conductive portion 24 was provided over a length of 7 mm from a position approximately 1 mm away from the tip of the pressing member 23 that contacted the carrier sheet 6a. At this time, the thickness of the conductive portion 24 was 30 μm.

It is not preferable to provide the conductive portion 24 near the most distal end of the pressing member 23 because it will be rubbed by the carrier sheet 6a, causing damage or wear.

Conversely, place the conductive part 24 at a distance of, for example, 5 mm from the tip of the pressing member 23.
If they are formed at a distance greater than this, the effects brought about by the present invention will be reduced, which is also not preferable.

In the image forming apparatus, with the above-described configuration, the surface of the photosensitive drum 1 is uniformly charged by the primary charger 2, and the optical system 3 first irradiates the surface with a color image that has passed through, for example, a green filter. A latent image mainly containing magenta components is formed on the surface of the photosensitive drum 1 . In synchronization with this feeding of the latent image, the developing device 4 moves in a tangential direction with respect to the photosensitive drum 1, so that the developing device 4M containing magenta developer faces the photosensitive drum 1, and the electrostatic charge is applied to the latent image. The toner is caused to fly and adhere, and is developed, making the latent image visible as a magenta toner image.

On the other hand, the recording material P is introduced into the guide 22 by the action of the pair of registration rollers 21, and further guided to the position of the conductive roller 20 along the surface of the carrier sheet 6a. Here, the recording material P is electrostatically adsorbed and held on the carrier sheet 6a by the corona discharger 19, and is sent to the transfer position with the photosensitive drum 1.

In this case, the timing of feeding the pair of registration rollers 21 and the timing of latent image formation by the optical system 3 are synchronized and coincide at the transfer position. At the above-mentioned transfer position, the transfer corona discharger 7 works to generate a transfer electric field, and the toner image on the photosensitive drum 1 is transferred and held onto the recording material P by the charge applied to the carrier sheet 6a.

The toner remaining on the photosensitive drum 1 is neutralized by a static eliminator 27 and then removed by a blade 28, thereby cleaning the surface of the photosensitive drum 1. On the other hand, the recording material P attracted to the carrier sheet 6a is transferred to the transfer drum 6 while carrying the toner image.
As it rotates, it moves and passes between the corona dischargers 10.11, but at this time the corona dischargers 10.11 are not activated. Further, the pressing rollers 12 and 13 are also separated from the carrier sheet 6a, and the brush roller 15 and the corona discharger or brush type static eliminator 16 are also separated from the conductive roller 2.
0 is also separated from the carrier sheet 6a, passes between the corona discharger 19 and the conductive roller 20, and is sent to the transfer position again without disturbing the toner image on the recording material P supported by Coulomb force. It will be done.

Note that the operation of the corona discharger 19 and the contact of the conductive roller 20 with the recording material P are completed before the leading edge of the toner image on the recording material P reaches the positions of the corona discharger 19 and the conductive roller 20. Therefore, when the recording material P passes through this gap, no charge for adsorption is applied to the recording material P. Furthermore, before the leading edge of the toner image reaches the transfer position, development with the magenta developer has been completed, and the color image that has passed through the red filter has already been contrasted with the photosensitive drum 1 by the optical system 3. The developing device 4 moves the cyan developing device 4C to face the photosensitive drum 1, and develops the latent image by electrostatically flying and adhering toner to the latent image, thereby visualizing the latent image as a cyan toner image.

Therefore, at the transfer position, the cyan toner image is transferred onto the recording material P, superimposing the previous magenta toner image.

In this way, a green filter, a red filter, and a blue filter are sequentially applied to the optical system 3 to form a color-separated latent image of the same image multiple times on the photosensitive drum 1, and a developer corresponding to the latent image is formed on the photosensitive drum 1. Mazenk developer, cyan developer, and yellow developer are supplied from the developing device 4 to the photosensitive drum 1 to realize a color image as a whole.

It goes without saying that the order in which the filter and developer are supplied can be appropriately selected as required.

After the last toner image, in this embodiment a yellow toner image using a yellow developer, is transferred onto the recording material P, when it passes between the corona dischargers 10 and 11, these are activated to eliminate static electricity. , the pressing rollers 12 and 13 are pressed against the carrier sheet 6a, and the curvature at this portion is increased to help peel off the recording material P from the carrier sheet 6a. Further, the separation blade 14 comes into contact with or approaches the carrier sheet 6a to separate the tip and end of the recording material P from the carrier sheet 6a, and the separated recording material P is supplied to the fixing roller 1 via the conveyor 17. , the toner image is fixed. During separation, it is preferable to use a corona discharger 29 to prevent image disturbance due to peeling discharge. Further, the surface of the carrier sheet 6a after separating the recording material P is cleaned by the brush 15, but if the remaining toner remains electrostatically attached at this time, the cleaning will not be sufficient, so corona Removing this with a discharger or brush-type static eliminator 16 makes cleaning more effective.

In this way, a color image is formed.

Incidentally, when a filter is not used in the optical system 3 and when the developing device 4B for black color developer is placed opposite to the photosensitive drum 1 in the developing device 4, normal black and white copying is realized. In this case, since the transfer is performed only once, the image can be formed only by the functions of each component corresponding to the final development in color copying.

Further, in the final stage of color development, a black image formed by white exposure and a black developer may be superimposed.

When an image was formed in the manner described above, a good image was obtained without any recording material adsorption failure or jamming, and without uneven image transfer or missing transfer.

In the present invention, as described above, it is possible to form a good image without defective adsorption of the recording material and without uneven image transfer, etc., probably due to the following reasons.

The surface potential near the pressing part of the pressing member during the adsorption process of the recording material P to the recording material carrying sheet 6a wound around the transfer drum 6A of the transfer device 6 is compared with that when a conventional pressing member is used and that according to the present invention. When the pressure member 23 provided with the conductive portion 24 was measured and compared, the results shown in FIG. 3 were obtained.

It can be seen that in the pressing member 23 provided with the conductive portion 24 according to the present invention, both the magnitude and amplitude of the potential on the surface thereof are smaller than those of the conventional pressing member.At the same time, the supporting sheet 6
It has been found that the surface potential of a also follows the surface potential of the pressing member. This is considered to be because the adsorption electric field is influenced by the surface potential of the pressing member 23.

After further investigation, it was found that the areas where uneven transfer occurs on the image are areas where the surface potential of the portion of the carrier sheet 6a pressed by the pressing member 23 differs greatly. When comparing the surface potential graph in Figure 3 with the areas where no transfer unevenness occurs on the image when using a conventional pressing member, the areas where good transfer is possible are shown by two solid lines. It turned out to be the inner area. It has also been found that the amplitude of the surface potential of the suppressing portion of the carrier sheet 6a has a greater influence than the absolute value on the occurrence of uneven transfer.

When applying the fluctuation range of the surface potential that enabled good transfer when using a conventional pressing member to the surface potential when using the pressing member 23 provided with the conductive portion 24 of the present invention, it was found that ( In the area inside the two dotted lines in FIG. 3), it can be confirmed that good transfer is performed and a high-quality image is obtained. It was also found that the smaller the absolute value of the surface potential, the wider the area where transfer unevenness does not occur.

Furthermore, even when image formation is performed continuously, the pressing member 23 having the conductive portion 24 does not cause the so-called charge-up phenomenon, and as described above, the magnitude and amplitude of the surface potential are always small ( As a result, it was confirmed that the pressing member 23 does not cause partial adsorption failure of the recording material P, and thus does not cause so-called jamming, even when performing continuous image formation.

The reason why both the magnitude and amplitude of the surface potential of the pressing member 23 can be reduced in this way is considered to be due to the reasons described below.

Since the suppressing member 23 having the conductive part 24 according to the present invention has a volume resistivity of 10I0Ωcm or less,
The charge is easily discharged from the top of the pressing member 23 where the charge is accumulated by the corona discharge by the adsorption corona discharger 19, compared to a pressing member made of polyester resin or the like, and as a result, the surface of the pressing member 23 is This is understood to be because the potential is kept low. In addition, since the conductive portion 24 allows charge to easily move within its surface, unevenness in surface potential can be reduced.

Furthermore, if the pressing member 23 made of a polyester resin film is left as it is, an abnormally large electric charge may be accumulated in some parts due to frictional electrification with the support sheet 6a.
In this case as well, the action of the conductive portion 24 provided on the pressing member 23 makes it possible to reduce its surface potential and amplitude.

In this embodiment, the adsorption corona discharger 19 and the pressing member 23 are arranged on the back side of the supporting sheet 6a opposite to the recording material holding surface, that is, on the inside. It goes without saying that the same effect can be obtained even if the adsorption corona discharger 19 and the pressing member 23 are arranged on the recording material holding surface side of the carrier sheet 6a, that is, on the outside. Furthermore, even in this case, a corona discharger 19 is provided on the opposite side of the carrier sheet 6a.
By arranging the conductive roller 20 opposite to the
A good layer effect can be obtained.

In the above, only the conductive part 24 is provided on the pressing member 23, but as a result of further research, it is possible to apply an appropriate bias voltage to the conductive part 24 or to apply a self-bias through an appropriate resistance. It was also found that a similar effect can be obtained even when the device is grounded.

FIG. 4 is a sectional view showing a pressing member of a recording material carrying sheet in another embodiment of the image forming apparatus of the present invention. The image forming apparatus of this embodiment is characterized in that a protective member 30 is provided on the conductive portion 24 of the pressing member 23, and the other configurations are the same as the image forming apparatus shown in FIG.

As a result of continued research and experiments, the present inventors discovered that a protective member 3 is placed on the conductive part 24 of the pressing member 23, as shown in FIG.
It has been discovered that when 0 is provided, wear of the conductive portion 24 can be prevented and durability can be significantly improved.

The protective member 30 is preferably made of polyethylene terephthalate resin having a thickness of about 75 μm, for example, and is preferably provided so as to cover the conductive portion 24 .

According to this embodiment, since the protective member 30 is provided on the conductive part 24 of the pressing member 23, there is no fear of abrasion of the conductive part 24, and the conductive part 24 can be formed up to the most extreme part of the pressing member 23. As a result, the same effects as in the previous example could be exhibited even better.

The present invention can also be embodied in a multicolor electrophotographic copying apparatus having four image forming units (1) to (4) as shown in FIG.

Still another embodiment of the image forming apparatus of the present invention shown in FIG. 5 includes four image forming units I to IV arranged in parallel. Each image forming unit I~■ is a photosensitive drum 1a~1.
d, and around it are primary chargers 28 to 2d, exposure means 38 to 3d, developing devices 48 to 4d, and transfer chargers 7a to 7d.
, static eliminators 10a to 10d and 11a to 11d, and cleaners 28a to 28d are arranged. Furthermore, in order to constitute a transfer device for each of the image forming units (1-1) to (2), a photosensitive drum la is provided as a common recording material carrying member for these image forming units (1-1 to (1)) in a manner that passes through each of the image forming units (1-1) to (2).
An endless recording material conveyance belt 25 made of a flexible dielectric belt is arranged below Id.

In addition, near the recording material adsorption position where the recording material P fed by the recording material supply circuit including a paper feed roller (not shown) comes into contact with the conveyance belt 25, there is an outer side of the conveyance belt 25 (recording material holding surface side). An adsorption corona electric appliance 19 and a pressing member 23 are provided. If necessary, a conductive roller 20 is provided on the inside of the conveyor belt 25 (on the back side of the recording material holding surface and the surface of the rod), facing the corona discharger 19.

The conveyance edge material P fed to the recording material adsorption position of the conveyance belt 25 is electrostatically attracted and held on the conveyance belt 25 by the suction corona discharger 19, and is then attached to each of the photosensitive drums 18 to 1d.
The image is transported to the transfer position.

In this embodiment as well, since the conductive portion 24 is provided on the pressing member 23 that presses the conveyor belt 25, as in the previous embodiment, there is no occurrence of poor adhesion or jamming of the recording material P, and there is no uneven transfer of the image. Good image formation without omissions can be performed.

As explained above, in the image forming apparatus of the present invention, the recording material is transferred to a flexible recording material carrying member such as an edge material carrying sheet by applying a charge to the recording material by the charge applying means. In addition to electrostatically adsorbing and holding the recording material on the recording material supporting member, when the recording material is held on the recording material supporting member by pressing the recording material supporting member with a pressing member so that the recording material is brought into close contact with the recording material supporting member, an electric charge is applied to the pressing member. Since the conductive part is provided in the part located at the location of the means, it is possible to prevent excessive charging or uneven charging on the pressing member, and to achieve good results without poor suction or jamming of the recording material, and without uneven transfer or missing transfer. You can get the image.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus of the present invention. FIG. 2 is a sectional view showing a pressing member for a recording material carrying sheet in the image forming apparatus of FIG. 1. FIG. FIG. 3 is a graph showing the surface potential near the pressing portion of the pressing member shown in FIG. 2 during the recording material adsorption step, together with the surface potential near the pressing portion of the conventional pressing member. FIG. 4 is a sectional view showing a pressing member of a recording material carrying sheet in another embodiment of the image forming apparatus of the present invention. FIG. 5 is an overall configuration diagram showing still another embodiment of the image forming apparatus of the present invention. ], 1a to 1d Two photosensitive drums 6: Transfer device 6A: Transfer drum 6a: Recording material carrying sheet 19: Adsorption corona discharger 20: Conductive roller 23: Carrying sheet pressing member 24: Conductive portion 25: Recording material conveying belt 30: Protective member Figure 442 Figure 4 + Figure 3 transcription (Whisper Award

Claims (1)

[Scope of Claims] 1) The recording material holding surface side of the recording material suction position of a flexible recording material carrying member for carrying a transfer material for transferring the toner image formed on the image carrier, or the opposite side thereof. A charge applying means for applying a charge to the recording material to electrostatically attract and hold it on the supporting member is disposed on the surface side of the recording material supporting member, and the charge applying means of the recording material supporting member is disposed. on the same side as the affected side,
A pressing member that presses a portion of the supporting member near the recording material adsorption position to tightly hold the recording material on the supporting member is disposed close to the charge applying means. An image forming apparatus characterized in that a conductive portion is provided in a portion of the pressing member located at the location of the charge applying means. 2) The image forming apparatus according to claim 1, wherein the pressing member extends from the upstream side in the direction of movement of the recording material supporting member and presses the supporting member by elastically abutting the recording material supporting member. 3) The image forming apparatus according to claim 1 or 2, wherein the recording material carrying member is a dielectric sheet or a dielectric belt. 4) Claim 1, wherein the charge applying means is a corona discharger.
, 2 or 3. The image forming apparatus according to .