JP3456338B2 - Double-sided image forming method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to an image forming apparatus such as a printer, and more particularly, to improvement of a double-sided image forming apparatus capable of forming a double-sided image.

[0002]

2. Description of the Related Art As a conventional double-sided image forming apparatus capable of forming a double-sided image, a first image formed on a latent image carrier such as a photoconductor is transferred onto a first surface of a sheet and fixed, and then the sheet is formed. In general, the sheet is reversed and re-fed, and then the second image formed on the latent image carrier is transferred and fixed on the second surface of the sheet. However, in this method, since the image forming section is passed twice, the productivity per sheet is 1
It becomes slower than / 2 or less, the paper curls at the first fixing, transfer failure at the second transfer and fixing, paper wrinkles,
There are various problems such as easy jamming in the transport path and noise when reversing and refeeding the paper. In terms of productivity, since the conveyance path is long because the paper is reversed and re-fed, and the time other than image formation that is spent for this conveyance is long, it is actually 1/3 or less of that for single-sided recording. Many of them feel very slow to the sensation, which is a practical problem.

As a double-sided image forming apparatus that solves such a problem, for example, as shown in FIG. 14, a first image forming section 210 (a first image forming section 210 in which a first image is formed on a first surface of a sheet by an electrophotographic method). For example, the photoconductor 211, the transfer charger 212, the paper peeling device 213, and other electrophotographic devices (not shown) are provided, and the first image forming unit 210 is provided in a subsequent stage,
A second image forming unit 220 on which a second image is formed on the second surface of the sheet by electrophotography (including, for example, a photoconductor 221, a transfer charger 222, a sheet peeler 223 and other electrophotographic devices not shown). And a sheet on which the first image is transferred on the first surface at the transfer portion of the first image forming unit 210 is held and conveyed by the conveying belt 230 to the transfer portion of the second image forming unit 220 to form the second image. It is known that the second image is transferred to the second surface of the sheet at the image forming portion of the unit 220, and the unfixed toner images on both sides of the sheet are fixed by the fixing device 240 (for example, JP-A-63-63). No. 172280) .

[0004]

However, in this method, since the unfixed image is held on the first side of the sheet at the time of transferring the second side, the pressure from the first side of the sheet is not applied. Can not. Therefore, when the second surface is transferred, the paper is set on the photosensitive member 2
21 cannot be sufficiently adhered, and transfer defects are likely to occur. In addition, since a conveyance member such as the conveyance belt 230 is not provided in the paper path from the second surface transfer unit to the fixing unit, it becomes difficult to control the attitude of the paper from the second surface transfer unit to the fixing unit, and the paper is difficult to control. There is also a technical problem that image distortion is likely to occur at the time of entering the fixing unit. Further, the image forming unit 2
Since two sets of 10,220 are provided, there is also a technical problem that the device becomes large.

As a prior art for solving such a technical problem, for example, as shown in FIG. 15, one photoconductor (for example, a photoconductive drum) carrying a first image and a second image is carried.
310, and the intermediate transfer belt 32 that temporarily holds the first image
0, and further, the first transfer device 341 for transferring the respective images T1 and T2 on the photoconductor 310 to the intermediate transfer belt 320 or the paper P is arranged at the first transfer portion, and A second transfer device 342 for transferring the first image T1 on the intermediate transfer belt 320 onto the paper P at the paper discharge end.
It is known that the sheet peeling device 343 is provided (for example, Japanese Patent Laid-Open No. 1-209470). It is also known that the intermediate transfer belt 320 is provided with a conductive contact roller which can be separated from and brought into contact with the intermediate transfer belt 320 via a charge injection circuit (for example, JP-A-1-209471).

In this method, the first image T1 is formed on the photoconductor 310 and transferred onto the intermediate transfer belt 320 by the first transfer device 341. Subsequently, the second image T2 is formed on the photoconductor 310, the paper P is conveyed between the photoconductor 310 and the intermediate transfer belt 320, and the second image T2 is transferred onto the paper P by the first transfer device 341. To do. Thereafter, the second transfer device 342 transfers the first image T1 on the intermediate transfer belt 320 onto the paper P, the paper separating device 343 separates the paper P from the intermediate transfer belt 320, and the fixing device 350 uses the paper P.
The upper unfixed toner image is fixed.

Although this method can solve the problem of sheet conveyance, the productivity per sheet is 1 / one that of single-sided recording.
Only improves to 2. Further, since the paper P is placed on the intermediate transfer belt 320 holding the first image T1, there is a technical problem that it is difficult to control the attitude of the paper.

The present invention has been made in order to solve the above technical problems, and the productivity per recording material is the same as that at the time of single-sided recording, and there is no transfer failure or image disturbance,
An image forming method capable of double-sided recording with less jam and an apparatus therefor.

[0009]

That is, the present invention is
As shown in FIG. 1, a first image carrier 2 carrying a first image T1 and a second image carrier 3 carrying a second image T2.
And a belt-shaped intermediate transfer member which is provided between the first image carrier 2 and the second image carrier 3 and in which the first image carrier 2 and the second image carrier 3 are arranged in contact with each other. When the images are formed on both sides of the recording material 1 by using the double-sided image forming apparatus including the recording material 4 and the recording material 1 from the direction along the moving direction of the intermediate transfer body 4.
First image formation in which 1 is carried in to the intermediate transfer body 4 and the first image T1 carried on the first image carrier 2 is electrostatically transferred to the intermediate transfer body 4 and then electrostatically transferred to one side of the recording material 1. Steps and second image formation in which the second image T2 carried on the second image carrier 3 is directly electrostatically transferred to the other side of the recording material 1 while holding and conveying the recording material 1 on the intermediate transfer body 4. Or a step of directly electrostatically transferring the first image T1 carried on the first image carrier 2 onto one side of the recording material 1 while holding and conveying the recording material 1 on the intermediate transfer body 4. 1 image forming process and intermediate transfer
The recording material 1 is transferred from the direction along the moving direction of the body 4 to the intermediate transfer body.
The second image T carried into the image carrier 4 and carried on the second image carrier 3
The second image forming step of electrostatically transferring 2 to the intermediate transfer member 4 and then electrostatically transferring it to the other surface of the recording material 1.

In the apparatus configuration for adopting such a double-sided image forming method, as for the first image bearing member 2 and the second image bearing member 3, what is possible if it can carry a monochromatic or color image? The image forming method for the first image carrier 2 and the second image carrier 3 may be an electrophotographic method, an electrostatic transfer method, or any other type (drum shape, belt shape, or a combination thereof). Various methods such as a method and an inkjet method can be adopted. In addition, as for the intermediate transfer member 4, the first image carrier 2,
Any form such as a belt shape or a drum shape may be used as long as the image from the second image carrier 3 can be temporarily held.

In the above-mentioned double-sided image forming method, the transfer operation timing of the first image T1 and the second image T2 onto the recording material 1 may be appropriately selected.
From the viewpoint of simplification of the transfer device, it is preferable to perform them at substantially the same time.

In addition, an apparatus invention that embodies the former type of the above-mentioned double-sided image forming method is shown in FIG.
As shown in FIG. 1, a first image carrier 2 carrying a first image T1, a second image carrier 3 carrying a second image T2, a first image carrier 2 and a second image carrier 3 Is provided between and
A double-sided image forming apparatus including an image carrier 2 and a second image carrier 3 and a belt-shaped intermediate transfer member 4 arranged in contact with each other so as to face each other . The image carrier is carried on the first image carrier 1. The intermediate primary transfer means 5 for electrostatically transferring the first image T1 to the intermediate transfer body 4, and the recording material from the direction along the moving direction of the intermediate transfer body 4.
1 is carried into the intermediate transfer body 4, and the first image T1 transferred onto the intermediate transfer body 4 is electrostatically transferred onto one side of the recording material 1 and the intermediate transfer means 6 is recorded on the intermediate transfer body 4. The second image T on the side not transferred to the intermediate transfer body 4 while holding and conveying the material 1.
2 is provided with a direct transfer means 7 which is electrostatically transferred to the other side of the recording material 1.

Further, in the apparatus invention which embodies the latter type of the above-mentioned two-sided image forming method, the first image carrier 2, the second image carrier 3 and the belt-like structure are shown in FIG. 1 (b).
Of an intermediate transfer member 4 double-sided image forming apparatus provided with an intermediate primary transfer means 5 second image T2 which is supported on the second image bearing member 3 is electrostatically transferred to the intermediate transfer member 4, the intermediate Transfer body
The recording material 1 from the direction along the moving direction
An intermediate secondary transfer unit 6 in which the second image T2 transferred to the intermediate transfer member 4 is electrostatically transferred to one side of the recording material 1
And a direct transfer means 7 for electrostatically transferring the first image T1 on the side not transferred to the intermediate transfer body 4 to the other side of the recording material 1 while holding and conveying the recording material 1 on the intermediate transfer body 4. It is characterized by that.

Further, among the above-mentioned double-sided image forming method,
In order to perform the transfer operation timings of the first image T1 and the second image T2 onto the recording material 1 at substantially the same time, the apparatus invention as shown in FIG. 1C may be configured.

In such an apparatus invention, from the viewpoint of preventing jamming of the recording material 1 in the conveying path, it is preferable that the intermediate transfer member 4 also serves as the conveying means for the recording material 1. At this time, it is preferable to use a belt as the intermediate transfer member 4 because the conveyance path of the recording material 1 can be set quite freely and the space can be effectively used.
Further, if the recording material 1 is conveyed to the vicinity of the fixing device by the intermediate transfer body 4, the posture of the recording material 1 can be controlled, so that the recording material 1 can be accurately inserted into the fixing device. Is preferable in that the image disturbance can be prevented. Furthermore, in the case of a type that uses a belt as the intermediate transfer member 4, one of the supporting rolls of the belt is one of the pair of fixing rolls from the viewpoint of making the thrusting position of the recording material 1 into the fixing device extremely stable. It is a fixing roll, and it is preferable to dispose the other fixing roll at a portion facing the fixing roll.

The intermediate secondary transfer means 6 may have a function of transferring the first image T1 or the second image T2 transferred onto the intermediate transfer member 4 to one side of the recording material 1, but the intermediate From the viewpoint of suppressing the image disturbance on the transfer body 4, as the intermediate secondary transfer means 6, the image transferred to the intermediate transfer body 4 is transferred to one surface of the recording material 1 and at the same time the recording material 1 is transferred to the intermediate transfer body 4. It is preferably one that is adsorbed and held.

Furthermore, the first image carrier 2 is carried on the first image carrier 2.
The image T1 and the second image T2 carried on the second image carrier 3
In the type in which the toner is formed by the electrophotographic method, the toners of the same polarity are used, and the polarity of one of the toners is set to the image carrier 2, 3
From the viewpoint of reversing on the top or the intermediate transfer member 4, or eliminating the polarity reversing operation required when using toner of the same polarity, the toner polarities for forming the first image T1 and the second image T2 are changed. it is preferable that Ru varied.

Further, among the types in which the intermediate transfer body 4 also serves as a conveying means for the recording material 1, in a mode in which the intermediate transfer body 4 has a belt shape, the image bearing on the side for directly transferring the image to the recording material 1 is carried out. By arranging the body 2 or 3 so as to face the drive roll of the belt-shaped intermediate transfer body 4, the image carrier 2 or 3 plays a role of a pressing roll when the recording material 1 is attracted to the intermediate transfer body 4, This is preferable because the recording material 1 can be surely attracted to the intermediate transfer member 4. Further, in the type in which the intermediate transfer body 4 also serves as the conveying means for the recording material 1, the image carrier 2 or 3 on the side for directly transferring the image to the recording material 1 is driven at the same speed as the intermediate transfer body 4. This is preferable in that it is possible to reduce the positional deviation when the image on the intermediate transfer member 4 and the image on the image carrier 2 or 3 are transferred to both surfaces of the recording material 1.

Furthermore, in a mode in which the image carrier 2 or 3 is in a roll shape, while the intermediate transfer member 4 is also in a roll shape or a belt shape, the roll image carrier 2 or 3 and the roll intermediate transfer member 4 are formed. Alternatively, it is preferable that the outer diameter of the belt-shaped intermediate transfer member 4 is the same as that of the driving roll, because the speed difference due to the eccentricity error of the roll-shaped member can be suppressed. Further, in the above aspect, the roll-shaped image bearing member 2
Or 3 and the roll-shaped intermediate transfer member 4 or the driving roll of the belt-shaped intermediate transfer member 4 are driven by the same drive source, the speed fluctuation between the image carrier 2 or 3 and the intermediate transfer member 4 is prevented. It is preferable because it can be suppressed.

Further, if the circumference of the intermediate transfer member 4 is set to be an integral multiple of the circumference of the image bearing member 2 or 3, the contact positional relationship between the image bearing member 2 or 3 and the intermediate transfer member 4 is set. This is preferable because it can be kept constant at all times and the positional deviation during transfer can be reduced. Further, by setting the rotation speed of the fixing roll, which is the fixing device, to be equal to or lower than the rotation speed of the intermediate transfer member 4, it is possible to prevent image disturbance due to the leading end of the recording material 1 being pulled by the fixing device. It is preferable in that it can

Next, the operation of the above-mentioned technical means will be described. First, in the type shown in FIG.
The intermediate primary transfer means 5 transfers the first image T1 carried on the first image carrier 2 to the intermediate transfer body 4, and the intermediate secondary transfer means 6 transfers the first image T1 transferred on the intermediate transfer body 4. T1 is transferred onto one side of the recording material 1 (first image forming step). Then
The direct transfer means 7 is the second transfer side which is not transferred to the intermediate transfer body 4.
The image T2 is transferred to the other side of the recording material 1 (second image forming step).

Further, in the type shown in FIG. 1B, the intermediate primary transfer means 5 transfers the second image T2 carried on the second image carrier 3 to the intermediate transfer body 4, and the intermediate secondary transfer. The means 6 transfers the second image T2 transferred onto the intermediate transfer member 4 to one side of the recording material 1 (second image forming step). Then, the direct transfer means 7 transfers the first image T1 on the side not transferred to the intermediate transfer member 4 to the other surface of the recording material 1 (first image forming step).

Further, in FIG. 1C, the intermediate secondary transfer means 6 and the direct transfer means 7 work substantially at the same time, and the recording material 1
The first image T1 and the second image T2 are simultaneously transferred to both surfaces of the.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. First Embodiment FIG. 2 shows a schematic configuration of a first embodiment of a double-sided image forming apparatus to which the present invention is applied. In the figure, the double-sided image forming apparatus includes a first image forming unit 10a on which a first image is formed.
(Including a photosensitive drum 11a, a transfer corotron 12a and other electrophotographic devices (charging device, exposure device, developing device, cleaning device, etc.) not shown), and a second image forming section 10b (photosensitive drum 11b, transfer corotron 12b, etc.) An electrophotographic device (not shown) (including a charging device, an exposure device, a developing device, a cleaning device, etc.), and the first image forming unit 10.
a and the intermediate transfer belt 20 in which the transfer portions of the second image forming unit 10b are arranged to face each other. In the present embodiment, the transfer corotron 1 of the first image forming unit 10a
Reference numeral 2a denotes a device for transferring (primary transfer) the first toner image T1 on the photosensitive drum 11a onto the intermediate transfer belt 20.
A suction transfer corotron 30 is provided at a portion facing the paper suction portion on the way from the transfer portion of a to the transfer portion of the second image forming unit 10b, and the paper P is electrostatically attracted to the intermediate transfer belt 20. The image on the intermediate transfer belt 20 is transferred onto the paper P (secondary transfer). Further, reference numeral 31 is a peeling corotron 31 for peeling off the paper P adsorbed on the intermediate transfer belt 20, 32 is a fixing device for fixing an unfixed toner image on the peeled paper P, 33 is a paper tray, and 34 is a paper tray. Is a transport (for example, vacuum transport) that vertically conveys the paper P in the paper tray 33 to the paper suction portion of the intermediate transfer belt 20.

In the present embodiment, the intermediate transfer belt 2
0 is wound between a drive roll 21 and a driven roll (tension roll for tension adjustment) 22, and the transfer corotrons 12a and 12b of the first image forming unit 10a and the second image forming unit 10b are both intermediate transfer. It is arranged on the back side of the belt 20. The intermediate transfer belt 20 is
A resin such as polyimide, acryl, vinyl chloride, polyester, or polycarbonate, or various kinds of rubber is mixed with an appropriate amount of an antistatic agent such as carbon black to have a volume resistivity of 10 ⁹ to 10 ¹³ Ω · cm. , Its thickness is set to 0.3 mm, for example.

Further, in the present embodiment, the toner of the developing device (not shown) is a negatively charged toner, and a positive toner image T1 and a toner image of the photosensitive drum 11b are formed on the surface of the photosensitive drum 11a by a well-known electrophotographic process. A toner image T2 of a mirror image is formed on the surface. Further, the driving rollers 21 of the photosensitive drums 11a and 11b and the intermediate transfer belt 20 have the same outer diameter, and are driven by the same driving source. Furthermore, the transfer corotron 12a has a direct current of +300 μm.
A, DC current of transfer corotron 12b +250 μA,
Adsorption transfer corotron 30 has a DC current of +200 μA, and peeling corotron 31 has an AC voltage of 8 kVp-p / 600 Hz.
A direct current of 20 μA was superposed on and applied. In the present embodiment, the transfer corotrons 12a and 12b and the suction transfer are used.
Although the corotron is used as the corotron 30, a bias roll may be used.

Next, an image forming process of the double-sided image forming apparatus according to this embodiment will be described. First, the first toner image T1 formed on the first photosensitive drum 11a is transferred by the transfer corotron 12a onto the intermediate transfer belt 20 which moves at substantially the same speed as the photosensitive drum 11a, while the paper from the paper tray 33 is transferred. P is conveyed to the paper suction portion of the intermediate transfer belt 20 via the transport 34 at the same timing, and the toner image T1 on the intermediate transfer belt 20 is transferred to the first surface of the paper P by the suction transfer corotron 30. P is directly adsorbed on the intermediate transfer belt 20. Subsequently, the second toner image T2 is formed on the second photosensitive drum 11b in synchronization with the rotation of the intermediate transfer belt 20, and is transferred onto the second surface of the paper P by the transfer corotron 12b. After that, the paper P is peeled from the intermediate transfer belt 20 by the peeling corotron 31, and then both sides of the paper P are simultaneously fixed by the fixing device 32.

As described above, the paper P is conveyed vertically by the transport 34, the image on the intermediate transfer belt 20 is transferred, and at the same time, the paper P is attracted to the intermediate transfer belt 20. The sheet P can be conveyed to the fixing unit without disturbing the image, and a double-sided image without image disturbance can be obtained at the same recording speed as that for the single-sided sheet. Further, the photosensitive drums 11a and 11b and the driving roller 21 of the intermediate transfer belt 20 have the same outer diameter and are driven by the same driving source, so that the photosensitive drums 11a and 11b are driven.
And the speed difference between the intermediate transfer belt 20 and
It was possible to accurately align the images on both the front and back sides.

Second Embodiment FIG. 3 shows a schematic structure of a second embodiment of a double-sided image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the double-sided image forming apparatus is substantially the same as that of the first embodiment, but unlike the first embodiment, the drive roll 2 of the intermediate transfer belt 20 is different.
The photosensitive drum 11b of the second image forming unit 10b is disposed at a position facing 1 and the transfer corotron 12b of the second image forming unit 10b is disposed at a position away from the intermediate transfer belt 20. The paper P is supplied to the transfer portion of the forming unit 10b, and the paper suction corotron 40 is provided inside the intermediate transfer belt 20 (in the present embodiment, inside the drive roll 21) facing the second photosensitive drum 11b. Then
The transfer corotron 4 is provided near the peeling corotron 31.
1 is provided, and the toner image on the intermediate transfer belt 20 is printed on the paper P.
It is designed to be transferred on top. The same components as those in the first embodiment are designated by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted here. The same applies to each of the following embodiments.

In this embodiment, the toner of the developing device (not shown) is a negatively charged toner, and the transfer corotron 1 is used.
DC current +300 μA for 2a, transfer corotron 12b
DC current +200 μA, transfer corotron 41 DC current +200 μA, paper adsorption corotron 40 AC voltage 8 kVp-p / 600 Hz DC current 20 μA, peeling corotron 31 AC voltage 8 kVp-p / 60
A direct current of 20 μA was superimposed on 0 Hz and applied.

Next, an image forming process of the double-sided image forming apparatus according to this embodiment will be described. First, the second toner image T2 formed on the second photosensitive drum 11b is transferred onto the second surface of the paper P by the transfer corotron 12b.
Is directly adsorbed on the second photosensitive drum 11b. Then, the paper P is moved toward the intermediate transfer belt 20 by the paper suction corotron 40. On the other hand, the transfer corotron 12 transfers the first toner image T1 formed on the first photosensitive drum 11a.
The toner is transferred to the intermediate transfer belt 20 by a, and the first toner image T1 on the intermediate transfer belt 20 is moved to the sheet suction portion in synchronization with the timing of the sheet suction by the sheet suction corotron 40. After that, the toner image T1 on the intermediate transfer belt 20 is transferred by the transfer corotron 41 near the fixing device 32.
Is transferred to the first surface of the paper P, and the paper P is separated from the intermediate transfer belt 20 by the separating corotron 31, and then both sides of the paper P are simultaneously fixed by the fixing device 32.

As described above, the image on the second photosensitive drum 11b is transferred, and at the same time, the paper P is adsorbed and conveyed to the second photosensitive drum 11b, and is intermediate at the nip portion between the second photosensitive drum 11b and the intermediate transfer belt 20. By moving to the transfer belt 20 side, the paper P without disturbing the image on the intermediate transfer belt 20.
Since it can be adsorbed on the intermediate transfer belt 20, a double-sided image without image distortion can be obtained at the same recording speed as that for one side per sheet.

Third Embodiment FIG. 4 shows a schematic configuration of a third embodiment of a double-sided image forming apparatus to which the present invention is applied. In the figure, the basic structure of the double-sided image forming apparatus is substantially the same as that of the second embodiment, but unlike the second embodiment, the image carrier of the second image forming unit 10b is the photosensitive belt 13b, and the intermediate transfer is performed. The structure of the belt 20 is partially changed. In the present embodiment, the photosensitive belt 13b is stretched around a pair of holding rolls 14b and 15b, and the intermediate transfer belt 20 is the driving roll 2.
It is stretched around the three and three driven rolls 24 to 26, and the conveyance path of the paper P is linearly secured. The paper suction corotron 40 disposed in the intermediate transfer belt 20 is provided on one side of the holding roller 15b of the photosensitive belt 13b.
The holding roll 15b is arranged at a position opposed to the above, and functions as a pressing roll when the paper P is attracted to the intermediate transfer belt 20. Therefore, even in this form,
The image forming process is performed by substantially the same operation as in the second embodiment.

Fourth Embodiment FIG. 5 shows a schematic configuration of a fourth embodiment of a double-sided image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the double-sided image forming apparatus is substantially the same as that of the first embodiment, but unlike the first embodiment, the inside of the intermediate transfer belt 20 facing the second photosensitive drum 11b (in the present embodiment, driven) Roll 21
A transfer corotron 12 in which the second toner image T2 formed on the second photosensitive drum 11b is transferred to the paper P is shown in (inside).
b and the peeling / adsorbing corotron 42 for peeling the paper P attracted to the photosensitive drum 11b and adsorbing to the intermediate transfer belt 20 are arranged in parallel, and the intermediate transfer belt 20 is provided near the fixing device 32 of the intermediate transfer belt 20. A transfer corotron 41 for transferring the upper first toner image T1 to the paper P side is provided, and further, without using the peeling corotron 31, a driven roll (tension roll) 2 of the intermediate transfer belt 20 near the fixing device 32 is provided.
2 is electrically grounded.

In the present embodiment, the toner of the developing device (not shown) is a negatively charged toner, the transfer corotron 12a has a direct current of +300 μA, the transfer corotron 12b has a direct current of +300 μA, and the peeling / adsorption corotron 42 has a DC current of 50 μA is superimposed on AC voltage of 8 kVp-p / 600 Hz, and DC current of transfer corotron 41 +
250 μA was applied.

Next, an image forming process of the double-sided image forming apparatus according to this embodiment will be described. First, the first toner image T1 formed on the first photosensitive drum 11a is transferred by the transfer corotron 12a onto the intermediate transfer belt 20 which moves at substantially the same speed as the photosensitive drum 11a. The sheet P is conveyed to the transfer portion of the second image forming portion 10b at the timing when it reaches the transfer portion of the second image forming portion 10b. Then, in synchronization with the rotation of the intermediate transfer belt 20, the second toner image T2 formed on the second photosensitive drum 11b is transferred onto the second surface of the paper P by the transfer corotron 12b, and by the peeling / adsorption corotron 42. Second
The sheet P electrostatically attracted to the photosensitive drum 11b is attracted to the intermediate transfer belt 20. Then, the transfer corotron 41 transfers the first toner image T1 on the intermediate transfer belt 20 onto the paper P.
Transfer to the first surface of. After that, since the driven roll 22 is electrically conductive and is grounded, the paper P can be peeled off from the intermediate transfer belt 20, and the fixing device 32 fixes both surfaces of the paper P at the same time.

As described above, the image on the second photosensitive drum 11b is transferred, and at the same time, the paper P is adsorbed and conveyed to the intermediate transfer belt 20, and the image on the intermediate transfer belt 20 is transferred in the vicinity of the fixing device 32. Since the sheet P can be adsorbed to the intermediate transfer belt 20 without disturbing the image on the intermediate transfer belt 20 , a double-sided image without image disturbance can be obtained at the same recording speed as that for one side per sheet.

[Embodiment 5] FIG. 6 shows a schematic configuration of Embodiment 4 of a double-sided image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the double-sided image forming apparatus is substantially the same as that of the first embodiment, but unlike the first embodiment, a paper suction corotron 40 is provided in the intermediate transfer belt 20, and a peeling corotron 31 is used. Instead, the driven roll (tension roll) 22 of the intermediate transfer belt 20 near the fixing device 32 is electrically grounded. Further, in the present embodiment, the first toner image T1 has a positive polarity and the second toner image T2 has a negative polarity. Further, the transfer corotron 12a has a direct current of −300 μA,
A direct current of +350 μA was applied to the transfer corotron 12b, and a direct current of −200 μA was applied to the paper suction corotron 40.

Next, the image forming process of the double-sided image forming apparatus according to this embodiment will be described. First, the first toner image T1 formed on the first photosensitive drum 11a is transferred by the transfer corotron 12a onto the intermediate transfer belt 20 which moves at substantially the same speed as the photosensitive drum 11a, while the paper on the intermediate transfer belt 20 is transferred. The paper P from the paper tray 33 is conveyed through the transport 34 at the timing when the first toner image T1 reaches the suction portion, and the paper suction corotron 40 in the intermediate transfer belt 20 intermediates the paper P as it is. Adsorb on the transfer belt 20. Then, the second toner image T2 is synchronized with the rotation of the intermediate transfer belt 20.
Is formed on the second photosensitive drum 11b, and the transfer corotron 1
The first toner image T1 on the intermediate transfer belt 20 is transferred to the first surface of the paper P at the same time as being transferred to the second surface of the paper P by 2b. After that, since the driven roll 22 is electrically conductive and is grounded, the paper P can be peeled off from the intermediate transfer belt 20, and the fixing device 32 fixes both surfaces of the paper P at the same time.

As described above, the paper P is transferred to the intermediate transfer belt 2
When the toner image on the intermediate transfer belt 20 and the toner image on the second photosensitive drum 11b have opposite polarities and are simultaneously transferred to both sides of the sheet, the two-sided image having no image distortion is formed on the sheet 1. It was possible to obtain the same recording speed per sheet as on one side.

Sixth Embodiment FIG. 7 shows a schematic configuration of a sixth embodiment of a double-sided image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the double-sided image forming apparatus is substantially the same as that of the first embodiment, but unlike the first embodiment, the drive roll 21 of the intermediate transfer belt 20 is different.
The second photosensitive drum 11b is arranged so as to face the
The outer diameters of the photosensitive drum 11b and the drive roll 21 are set to be the same, and they are driven at the same speed by the same drive source. Further, the peeling corotron 31 is not used, and the intermediate transfer belt 20 near the fixing device 32 is not used. The driven roll (tension roll) 22 is electrically conductive and is grounded.

The operation of this embodiment is performed by the intermediate transfer belt 2
The procedure is substantially the same as that of the first embodiment, except that the paper P is peeled from 0 by making the driven roll 22 of the intermediate transfer belt 20 conductive and grounding it. As described above, the drive roll 2
By disposing the second photosensitive drum 11b so as to face 1
A speed difference between the intermediate transfer belt 20 and the second photosensitive drum 11b at the transfer portion of the second photosensitive drum 11b was unlikely to occur, and the images on the front and back surfaces of the paper P could be accurately aligned.

Seventh Embodiment FIG. 8 shows a schematic configuration of a seventh embodiment of a double-sided image forming apparatus for color image formation to which the present invention is applied. In the figure, the basic configuration of the double-sided image forming apparatus is the same as that of the first embodiment.
(See FIG. 2), but the first image forming unit 10
a, the second image forming unit 10b is different from that of the first embodiment. The first image forming unit 10a in the present embodiment includes a photosensitive drum 11a and a latent image forming device (for example, a charging device or an exposure device) (not shown) that forms an electrostatic latent image for each color component on the photosensitive drum 11a. A rotary developing device 16a for developing an electrostatic latent image for each color component formed on the photosensitive drum 11a with corresponding color toner, and the photosensitive drum 11a.
Each color toner image T1 (Y (yellow), M
A transfer roll 17a for sequentially transferring (magenta), C (cyan), and K (black) onto the intermediate transfer belt 20;
A cleaning device (not shown) for removing the residual toner on the photosensitive drum 11a is provided. On the other hand, the second image forming unit 10b includes the photosensitive drum 11b and the photosensitive drum 1b.
A latent image forming device (not shown) that forms an electrostatic latent image for each color component on 1b (eg, charging device, exposure device)
And a rotary developing device 1 for developing an electrostatic latent image for each color component formed on the photosensitive drum 11b with corresponding color toner.
6b and the toner image of each color (Y (yellow), M (magenta), C (cyan), K (black)) that is rotated in synchronization with the photosensitive drum 11b and is formed on the photosensitive drum 11b is sequentially transferred. The transfer roller 18b, the transfer roller 17b that collectively transfers the toner images T2 of the respective colors that have been multi-transferred onto the intermediate transfer roller 18b onto the paper P held on the intermediate transfer belt 20, and the residual toner on the photosensitive drum 11b is removed. A cleaning device (not shown) is provided.

Further, in the present embodiment, the intermediate transfer roll 18b can be separated from the intermediate transfer belt 20 and is separated during image formation on the intermediate transfer roll 18b. Also,
The peripheral length of the intermediate transfer belt 20 was set to be three times the peripheral length of the first photosensitive drum 11a. Further, the rotary developing devices 16a, 16
The toner of b is a negatively charged toner, and the transfer roll 1
A direct current of +25 μA was applied to each of 7a and 17b, a direct current of +200 μA was applied to the adsorption transfer corotron 30, and a direct current of 20 μA was applied to the peeling corotron 31 at an alternating voltage of 8 kVp-p / 600 Hz.

Next, an image forming process of the double-sided image forming apparatus according to this embodiment will be described. First photosensitive drum 1
1a onto the intermediate transfer belt 20 for each first color (YMC
K) After the toner images T1 are sequentially transferred, the paper P is transferred from the paper tray 33 via the transport 34 to the paper adsorption site at the timing when the first transferred toner images T1 of the multiple colors reach the paper adsorption site. Transport to. The toner image T1 on the intermediate transfer belt 20 is transferred onto the first surface of the paper P by the suction transfer corotron 30, and the paper P is sucked onto the intermediate transfer belt 20 as it is. Then, in synchronization with the rotation of the intermediate transfer belt 20, the second colors (YM and YM) sequentially transferred from the second photosensitive drum 11b onto the intermediate transfer roll 18b.
CK) The toner image T2 is transferred onto the paper P by the transfer roll 17b.
Transfer to the second surface of. After that, the paper P is peeled off from the intermediate transfer belt 20 by the peeling corotron 31, and then both sides of the paper P are simultaneously fixed by the fixing device 32.

With the above structure, a full-color image can be recorded on both sides of the paper P at high speed.
Further, the circumference of the intermediate transfer belt 20 is set to the first photosensitive drum 11
By making it an integral multiple of the perimeter of a, the positional relationship between the intermediate transfer belt 20 and the first photosensitive drum 11a becomes constant, and the color shift between the toner images T1 of each color (YMCK) can be suppressed.

[Embodiment 8] FIG. 9 shows a schematic configuration of Embodiment 8 of a double-sided image forming apparatus for color image formation to which the present invention is applied. In the figure, the basic configuration of the double-sided image forming apparatus is substantially the same as that of the seventh embodiment, but unlike the seventh embodiment, the first image forming unit 10a rotates in synchronization with the photosensitive drum 11a and the photosensitive drum 11a. An intermediate transfer roll 18a for sequentially transferring the toner images (Y (yellow), M (magenta), C (cyan), K (black)) of the respective colors formed on the top is provided. The same components as those in the seventh embodiment are designated by the same reference numerals as those in the seventh embodiment, and detailed description thereof will be omitted here. Therefore, in the present embodiment, the toner images T1 of the first colors (YMCK) sequentially transferred from the first photosensitive drum 11a onto the intermediate transfer roll 18a are transferred by the transfer roll 17a to the intermediate transfer belt 20.
After batch-transferring to the paper, the sheet P is conveyed from the paper tray 33 to the paper suction site via the transport 34 at the timing when the first color toner images T1 reach the paper suction site. The toner image T1 on the intermediate transfer belt 20 is transferred onto the first surface of the paper P by the suction transfer corotron 30, and the paper P is sucked onto the intermediate transfer belt 20 as it is. Then, in synchronization with the rotation of the intermediate transfer belt 20, the second color (YMCK) toner images T2 of the respective colors (YMCK) sequentially transferred from the second photosensitive drum 11b onto the intermediate transfer roll 18b are transferred.
The image is transferred onto the second surface of the paper P by 7b. After that, the paper P is peeled off from the intermediate transfer belt 20 by the peeling corotron 31, and then both sides of the paper P are simultaneously fixed by the fixing device 32.

Ninth Embodiment FIG. 10 shows a schematic configuration of a ninth embodiment of a double-sided image forming apparatus for color image formation to which the present invention is applied. In the figure, the basic configuration of the double-sided image forming apparatus is substantially the same as that of the eighth embodiment, but the configurations of the first image forming unit 10a and the second image forming unit 10b are different from those of the eighth embodiment. The same components as those in the eighth embodiment are designated by the same reference numerals as those in the eighth embodiment, and detailed description thereof will be omitted here. In the present embodiment, each of the image forming units 10a and 10b includes the photosensitive drums 11a and 11b and the photosensitive drums 11a and 11b.
a latent image forming device (not shown) for forming an electrostatic latent image for each color component on b, and a plurality of retractor type developing devices 19a for sequentially visualizing each color component latent image on the photosensitive drums 11a, 11b. , 19b, transfer rolls 17a, 17b for transferring the multiple toner images formed on the photosensitive drums 11a, 11b to the intermediate transfer belt 20 or the paper P, and a cleaning device for removing the residual toner on the photosensitive drums 11a, 11b. Is equipped with. In the present embodiment, the image forming units 10a and 10b are the photosensitive drums 11a and 11b.
After superimposing the toner images of the respective color components on the intermediate transfer belt 2
Basically, an image forming process similar to that of the eighth embodiment is performed except that the image is collectively transferred onto 0 or the sheet P.

10th Embodiment FIG. 11 shows a schematic configuration of a 10th embodiment of a double-sided image forming apparatus for color image formation to which the present invention is applied. In the figure, the first image forming unit 10a of the double-sided image forming apparatus,
The configuration of the second image forming unit 10b is different from that of the eighth and ninth embodiments. The same components as those in the eighth and ninth embodiments are designated by the same reference numerals as those in the eighth and ninth embodiments, and detailed description thereof will be omitted here. In the present embodiment, the first image forming unit 10a is located below the intermediate transfer belt 20 from the upstream side to Y (yellow), M (magenta), C (cyan), and K.
Four photosensitive drums 11 for each color component in the order of (black)
a (specifically, 11a (Y), 11a (M), 11a
(C) and 11a (K)) are arranged in parallel, while the second image forming unit 10b is arranged above the intermediate transfer belt 20 from the upstream side to the four color components of K, Y , M, and C. One photosensitive drum 11b (specifically, 11b (K), 11b
( Y ), 11b (M), 11b ( C )) are arranged in parallel, and an electrostatic latent image for each color component is formed around each of the photosensitive drums 11a, 11b, and the corresponding electrostatic image is formed. A toner image forming device (for example, a charging device, an exposure device, a developing device) (not shown) for developing with toner,
Transfer rolls 17a and 17b arranged corresponding to the transfer portions of the four photosensitive drums 11a and 11b and sequentially transferring the toner images of the respective colors formed on the four photosensitive drums 11a and 11b to the intermediate transfer belt 20 or the paper P, A cleaning device (not shown) for removing the residual toner on each of the photosensitive drums 11a and 11b is provided. Therefore, in the present embodiment, each photosensitive drum 1 of the first image forming unit 10a is
After the toner images T1 respectively formed on the 1a group are multi-transferred onto the intermediate transfer belt 20, the paper P is transferred onto the intermediate transfer belt 2.
Adsorb on 0. Then, on the paper P, the second image forming unit 1
After the toner images T2 respectively formed on the photosensitive drums 11b of 0b are multi-transferred, the toner image T1 is transferred from the intermediate transfer belt 20 to the paper P. After this, the intermediate transfer belt 2
After peeling the paper P from 0, the fixing device 32 fixes the both surfaces of the paper P at the same time.

Eleventh Embodiment FIG. 12 shows a schematic configuration of an eleventh embodiment of a double-sided image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the double-sided image forming apparatus is substantially the same as that of the first embodiment, but unlike the first embodiment, the suction conveyance belt 51 of the paper P is opposed to the drive roll 21 of the intermediate transfer belt 20. Arranged,
A pair of holding rolls 52, 53 of the suction conveyance belt 51
Intermediate transfer belt 20 facing one holding roll 53
A paper suction corotron 40 is provided inside the fixing unit 3
Transfer corotron 4 with peeling corotron 31 near 2
1 is provided, and the toner image on the intermediate transfer belt 20 is printed on the paper P.
It is designed to be transferred on top.

According to the present embodiment, the first photosensitive drum 1
Timing at which the first toner image T1 formed on 1a is transferred by the transfer corotron 12a onto the intermediate transfer belt 20 which moves at substantially the same speed as the photosensitive drum 11a, and the first toner image T1 reaches the paper suction portion. In accordance with the above, the sheet P is adsorbed and conveyed by the adsorption conveyance belt 51, and the sheet adsorption corotron 40 in the intermediate transfer belt 20 adsorbs the sheet P onto the intermediate transfer belt 20. Subsequently, the second toner image T2 is formed on the second photosensitive drum 11b in synchronization with the rotation of the intermediate transfer belt 20, and the paper P is transferred by the transfer corotron 12b.
Transfer to the second surface of. After that, the transfer corotron 41 and the peeling corotron 31 arranged at a position facing the intermediate transfer belt 20 near the fixing device 32 are used.
After the upper first toner image T1 is transferred onto the first surface of the paper P and the paper P is separated from the intermediate transfer belt 20, the fixing device 32
Both sides of the paper P are fixed at the same time.

As described above, by controlling the attitude of the paper P when adsorbing onto the intermediate transfer belt 20, the first toner image T1 on the intermediate transfer belt 20 can be adsorbed without disturbing the paper when adsorbing onto the paper. .

[Embodiment 12] This embodiment is the same as Embodiments 1 to 11 described above.
The speed of the fixing device 32 (for example, a pair of fixing rolls) is set to be the same as or slightly slower than the speed of the intermediate transfer belt 20, and an image obtained by pulling the paper when the leading edge of the paper enters the fixing device 32. It is possible to effectively prevent the disturbance. Further, it is preferable that the distance from the final transfer portion to the fixing device 32 is longer than the maximum paper length.

13th Embodiment FIG. 13 shows a schematic configuration of a 13th embodiment of a double-sided image forming apparatus to which the present invention is applied. In the figure, the double-sided image forming apparatus is one of the holding rolls of the intermediate transfer belt 20,
For example, the driven roll 22 is one of the fixing rolls 32a of the fixing device 32, and the other fixing roll 32b of the fixing device 32 is provided at a portion facing the driven roll 22. Other configurations are similar to those of the first embodiment. is there. Therefore, according to the present embodiment, after the toner images are transferred to both sides of the sheet by the same operation as in the first embodiment, the driven roll 22 fixes the both sides at the same time by the fixing device 32 which also serves as the fixing roll 32a. . As described above, the driven roll 22, which is one of the holding rolls of the intermediate transfer belt 20, is also used as the fixing roll 32a of the fixing device 32, and the fixing device 32 is arranged on the intermediate transfer belt 20. Fixer 3
It is not necessary to control the posture of the paper P between the fixing device 32 and the fixing device 32.
It was possible to more reliably prevent the image distortion when entering the.

[0055]

As described above, according to the double-sided image forming apparatus of the present invention, the belt-shaped intermediate transfer member is provided between the first image carrier and the second image carrier. In a mode in which the first image carrier and the second image carrier are arranged in contact with each other so as to face the intermediate transfer member, respectively, the first image carried on the first image carrier or the second image carrier carried on the second image carrier. The intermediate primary transfer means for electrostatically transferring any one of the formed second images to the intermediate transfer body, and the recording material from the direction along the moving direction of the intermediate transfer body.
An intermediate secondary transfer unit that carries in the intermediate transfer member and electrostatically transfers the first image or the second image transferred on the intermediate transfer member to one side of the recording material, and the intermediate of the first image or the second image. Since a direct transfer means for electrostatically transferring the image on the side not transferred to the transfer body to the other side of the recording material is provided, a double-sided image having no image distortion and no positional deviation between the front and back sides is recorded on one recording material. It can be obtained at the same recording speed as that for one side. Also,
According to the double-sided image forming apparatus of the present invention, the double-sided image forming method of the present invention, that is, the belt-shaped intermediate transfer member is provided between the first image carrier and the second image carrier, An image forming apparatus in which an image carrier and a second image carrier are arranged in contact with each other so as to face the intermediate transfer member, and either the first image forming step or the second image forming step is performed along the moving direction of the intermediate transfer member. direction
Is an indirect transfer method in which a recording material is carried in from an intermediate transfer body and the image is electrostatically transferred to the recording material via the intermediate transfer body, and the other is an image recording material while holding the recording material on the intermediate transfer body. A double-sided image forming method, which is a direct transfer method of electrostatically transferring to, can be easily embodied.

In the present invention, the first image and the second image
If the transfer operation of the image to the recording material is performed almost at the same time, the transfer device can be shared, and the number of transfer devices can be reduced accordingly, and the power consumption and the cost can be reduced. You can

Furthermore, in the present invention, if the intermediate transfer member 4 is also used as the conveying means for the recording material 1, the recording material can be accurately conveyed and jam of the recording material in the conveying path can be prevented. be able to.

Furthermore, in the present invention, as an intermediate secondary transfer means, if the image transferred to the intermediate transfer body is transferred to one side of the recording material and at the same time the recording material is adsorbed and held on the intermediate transfer body, the intermediate transfer is performed. The recording material can be attracted to the intermediate transfer member without disturbing the image on the body.

Further, in the present invention, in the type in which the first image carried on the first image carrier and the second image carried on the second image carrier are formed by electrophotography, the first image If the polarities of the toners for the second image formation are different, the polarity reversal operation required when using the toners of the same polarity can be eliminated, and the structure of the double-sided image forming apparatus can be simplified accordingly. be able to.

In the type in which the intermediate transfer member is composed of a belt in the present invention, one of the supporting rolls of the belt is one fixing roll of a pair of fixing rolls, and the other is provided at a portion facing the fixing roll. By arranging the fixing roll of, it is possible to stably convey the recording material to the fixing portion, and it becomes unnecessary to control the attitude from when the recording material leaves the intermediate transfer belt until it enters the fixing roll. Image distortion can be effectively prevented.

[Brief description of drawings]

1A to 1C are explanatory views showing the configuration of a double-sided image forming apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing a double-sided image forming apparatus according to the first embodiment.

FIG. 3 is a schematic configuration diagram showing a double-sided image forming apparatus according to a second embodiment.

FIG. 4 is a schematic configuration diagram showing a double-sided image forming apparatus according to a third embodiment.

FIG. 5 is a schematic configuration diagram showing a double-sided image forming apparatus according to a fourth embodiment.

FIG. 6 is a schematic configuration diagram showing a double-sided image forming apparatus according to a fifth embodiment.

FIG. 7 is a schematic configuration diagram showing a double-sided image forming apparatus according to a sixth embodiment.

FIG. 8 is a schematic configuration diagram showing a double-sided image forming apparatus according to a seventh embodiment.

FIG. 9 is a schematic configuration diagram showing a double-sided image forming apparatus according to an eighth embodiment.

FIG. 10 is a schematic configuration diagram showing a double-sided image forming apparatus according to a ninth embodiment.

FIG. 11 is a schematic configuration diagram showing a double-sided image forming apparatus according to a tenth embodiment.

FIG. 12 is a schematic configuration diagram showing a double-sided image forming apparatus according to an eleventh embodiment.

FIG. 13 is a schematic configuration diagram showing a double-sided image forming apparatus according to a thirteenth embodiment.

FIG. 14 is a schematic configuration diagram showing an example of a conventional double-sided image forming apparatus.

FIG. 15 is a schematic configuration diagram showing another example of a conventional double-sided image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recording material, 2 ... 1st image carrier, 3 ... 2nd image carrier, 4
... intermediate transfer member, 5 ... intermediate primary transfer means, 6 ... intermediate secondary transfer means, 7 ... direct transfer means, T1 ... first image, T2 ... second
Image, P ... Paper, 11a, 11b ... Photosensitive drum, 13b
... Photosensitive belt, 18a, 18b ... Intermediate transfer roll, 20
... Intermediate transfer belt, 12a, 12b ... Transfer corotron,
17a, 17b ... Transfer roll, 30 ... Adsorption transfer corotron, 40 ... Paper adsorption corotron, 41 ... Transfer corotron

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Sanshin 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Zerox Co., Ltd. (56) References JP-A-1-209471 (JP, A) JP-A-7-209923 ( JP, A) JP 62-50867 (JP, A) JP 2-306262 (JP, A) JP 63-197979 (JP, A) JP 4-163562 (JP, A) JP Flat 8-292614 (JP, A) JP-A-4-303851 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 106 G03G 15/00 550

Claims (8)

(57) [Claims] 1. A first image carrier (2) carrying a first image (T1), a second image carrier (3) carrying a second image (T2), and a first image carrier. The first image carrier (2) and the second image carrier (2) are provided between the second image carrier (2) and the second image carrier (3).
A belt shape in which the image bearing members (3) face each other and are in contact with each other.
When a double-sided image forming apparatus equipped with the intermediate transfer body (4) is used to form an image on both sides of the recording material (1), the recording material is moved from the direction along the moving direction of the intermediate transfer body (4).
(1) is carried into the intermediate transfer body (4), the first image (T1) carried on the first image carrier (2) is electrostatically transferred onto the intermediate transfer body (4), and then the recording material (1) Image forming step of electrostatically transferring to one surface of the second image carrier (3) while holding and conveying the recording material (1) on the intermediate transfer body (4). And a second image forming step of directly electrostatically transferring T2) to the other side of the recording material (1). 2. A first image carrier (2) carrying a first image (T1), a second image carrier (3) carrying a second image (T2), and a first image carrier. The first image carrier (2) and the second image carrier (2) are provided between the second image carrier (2) and the second image carrier (3).
A belt shape in which the image bearing members (3) face each other and are in contact with each other.
While forming the image on both sides of the recording material (1) by using the double-sided image forming apparatus equipped with the intermediate transfer body (4), while holding and conveying the recording material (1) on the intermediate transfer body (4). a first image forming step of transferring directly electrostatically to one side of the recording material (1) the first image (T1) which is carried on the first image bearing member (2), in the moving direction of the intermediate transfer member (4) Recording material from the direction along
(1) is carried into the intermediate transfer body (4), the second image (T2) carried on the second image carrier (3) is electrostatically transferred to the intermediate transfer body (4), and then the recording material (1 2.) A second image forming step of electrostatically transferring the image onto the other side. 3. The method according to claim 1, wherein the transfer operation of the first image (T1) and the second image (T2) to the recording material (1) is performed substantially at the same time. Double-sided image forming method. 4. A first image carrier (2) carrying a first image (T1), a second image carrier (3) carrying a second image (T2), and a first image carrier. The first image carrier (2) and the second image carrier (2) are provided between the second image carrier (2) and the second image carrier (3).
A belt shape in which the image bearing members (3) face each other and are in contact with each other.
A double-sided image forming apparatus including the intermediate transfer member (4), which is carried on a first image (T1) or a second image carrier (3) carried on a first image carrier (2). Second image (T2)
Any one of which is electrostatically transferred to the intermediate transfer body (4), and a recording material from a direction along the moving direction of the intermediate transfer body (4).
(1) is carried into the intermediate transfer body (4) , and the intermediate transfer body (4)
The first image (T1) or the second image (T2) transferred onto the recording material (1) is electrostatically transferred onto one side of the recording material (1), and an intermediate secondary transfer means (6) and an intermediate transfer body (4). While holding the recording material (1), the image on the side not transferred to the intermediate transfer body (4) of the first image (T1) or the second image (T2) is electrostatically applied to the other side of the recording material (1). A double-sided image forming apparatus comprising a direct transfer means (7) for transferring. 5. The double-sided image forming apparatus according to claim 4, wherein the intermediate transfer member (4) also serves as a conveying means for the recording material (1). 6. The apparatus according to claim 5, wherein the intermediate secondary transfer means (6) transfers the image transferred to the intermediate transfer member (4) onto one side of the recording material (1) and at the same time transfers the recording material (1). A double-sided image forming apparatus characterized by being adsorbed and held on an intermediate transfer member (4). 7. A device according to claim 4, wherein the first image (T1) carried on the first image carrier (2) and the second image (T1) carried on the second image carrier (3). A double-sided image forming apparatus characterized in that the toner polarity for forming the first image (T1) and the second image (T2) is different in the type in which T2) is formed by electrophotography. 8. The type according to claim 5, wherein the intermediate transfer member (4) is composed of a belt, and one of the supporting rolls of the belt is one of the pair of fixing rolls, A double-sided image forming apparatus, characterized in that the other fixing roll is disposed at a portion facing this.