JP3371594B2 - Electrostatic double-sided printing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic printing apparatus such as an electrophotographic printer or a copying machine, and more particularly, to an electrostatic double side capable of printing on both sides of a printing material such as paper or plastic sheet simultaneously in one process. Related to a printing device.

[0002]

2. Description of the Related Art As a method for printing on both sides of a material to be printed such as paper, a method of double-sided printing in one process by fixing toner images transferred on both sides at the same time, and a first method on one side After transferring and fixing the toner image, reverse the material to be printed and transfer the second toner image to the other surface.
There is a method of performing double-sided printing in two processes by fixing.

The former concept of the double-sided printing method in one process is old, and Japanese Patent Publication No. 51-13022 discloses the construction of this one-process double-sided printing apparatus and the deviation of the transfer position on both sides of the paper as exposure timing and A method for correcting the shape of the photoconductor is also described.

Most of the double-sided printing apparatuses of this type which are already on the market are double-sided printing in the latter two processes, and the method of performing in one process has not yet been put into practical use.

[0005]

Several factors can be considered as the reason why the method of performing double-sided printing in one process is not put to practical use.

(1) Instability when transferring a toner image to both sides of a printing material (a) In the configuration of the double-sided printing device described in Japanese Patent Publication No. 51 13022, the first and second toner images A transfer corotron is used to transfer the toner image from the carrier to the printing material.

The problem in this case will be described with reference to FIG. SeTe on the surface of the conductive substrate 1a such as aluminum.
A first toner image carrier composed of a photoconductor drum on which a photoconductor 2a composed of is formed; and a photoconductor drum formed on the surface of a conductive substrate 1b such as aluminum formed of SeTe. The second toner image carrier is arranged on both sides of the material 10 to be printed such as paper or plastic sheet.

In the first toner image carrier, a positive charge is applied on the toner image carrier by the charger 3a, and an electrostatic latent image is formed by light irradiation from the exposure section 5a. A first toner image 7 is formed on the electrostatic latent image portion by the developing device 6. 12a is an erase lamp, and 13a is a photoconductor cleaner.

In this case, when the first toner image is transferred from the first toner image carrier to the material 10 to be printed, the transfer corotron 31 causes the negative charge 3 below the material 10 to be printed.
0 is given. Therefore, the positively charged second toner image 19 on the second toner image carrier flies to the printing material 10 before the transfer position due to the electrostatic attraction force acting between the second toner image carrier and the negative charge 30. "Scattering before transfer"
Occurs and the image quality deteriorates significantly.

(B) At the time of transferring the second toner image, the first toner image 7 is not fixed on the printing material 10. Therefore, depending on the charging polarity of the second toner, the transfer electric field of the transfer corotron 20 causes the first toner image 7 to be transferred. However, there is a problem that the first toner image 7 is disturbed and the inside of the corotron is contaminated because the toner of No. 1 is attracted to the corotron wire.

(2) When the printing material 10 is conveyed at high speed,
A part of the unfixed toner image formed on the lower side (rear surface) of the material to be printed 10 may drop off due to the action of gravity, resulting in deterioration of image quality.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, to transfer a high-quality toner image to both surfaces of a printing material, to ensure the stability of adhesion of the toner image to the printing material, and to simultaneously perform both surfaces. An object of the present invention is to provide an electrostatic double-sided printing device capable of double-sided printing by one process such as fixing.

[0013]

In order to achieve the above-mentioned object, a first aspect of the present invention is directed to a first upstream side of a material to be printed in the conveying direction.
The second image forming means is provided on the downstream side in the conveying direction, and the conveying path of the printing material is formed between the first image forming means and the second image forming means. The photoconductor of the image forming unit and the photoconductor of the second image forming unit have the same charge polarity, and the charge polarity of the toner used in the first image forming unit and the charge polarity of the toner used in the second image forming unit are the same. A first transfer device which has the same polarity and transfers the first toner image formed by the first image forming unit onto the printing material;
The material to be printed is printed by the first transfer device on a material to be printed conveying path formed between the second toner image formed by the second image forming unit and the second transfer device for transferring the second toner image to the material to be printed. and the charging polarity of the first toner image is a second transfer unit of the charging polarity and charge applying means for varying the same polarity is provided that is transferred to, the electrostatic
The load applying means is a surface of the printing material on which the first toner image is transferred.
With a metal roller as a counter electrode in contact with the surface opposite to
And, it is characterized in that the first toner image and second toner image mutually different charge polarities to both sides of the printing material is transferred.

In order to achieve the above object, the second invention of the present invention
Is a first image forming unit on the upstream side in the conveying direction of the printing material.
However, a second image forming unit is provided on the downstream side in the transport direction,
Printing is performed between the first image forming unit and the second image forming unit.
A material conveyance path is formed, and the photosensitive member of the first image forming unit is formed.
The charging polarities of the photoconductors of the second image forming unit are the same.
And the charging polarity of the toner used in the first image forming unit
And the toner used in the second image forming unit has the same charge polarity.
And the first toner formed by the first image forming unit.
A first transfer device for transferring an image to a printing material and a second image type
Transfer the second toner image formed by the forming means onto the printing material
On the printing material conveyance path formed between the second transfer device and
, The first transfer device transferred to the printing material by the first transfer device.
The charging polarity of the toner image is the same as the charging polarity of the second transfer device.
The first transfer device is provided with a charge applying means for changing to
Is the first toner through the transfer roller or transfer belt.
The voltage of the opposite polarity to the toner charge of the image is transferred to the first toner image.
A transferring device for applying on a surface opposite to the shooting faces, the
The electric charge imparting means transfers the first toner image on the printing material.
A metal roller as a counter electrode in contact with the surface opposite to the surface
The first side of the printed material having different charging polarities from each other
A toner image and a second toner image are transferred.
It is something.

[0015]

[Action]

(1) Improvement of instability at the time of transferring a toner image to both surfaces of a printing material (a) As a method of transferring a first toner image, a voltage having a polarity opposite to the toner charge of the first toner image is opposite to that of the printing surface. Since a charge of opposite polarity is applied via the transfer roller or transfer belt applied to the side surface, after the transfer position, the surface (second toner image transfer surface) opposite to the print surface of the printing material is transferred. Leaves no charge. Further, when the pressure transfer using the pressure roller is performed, there is originally no electric charge. Therefore, “pre-transfer scattering” at the time of transferring the second toner image as shown in FIG.
That problem does not occur.

(B) Since the charging polarity of the charged electric charge of the first toner image is the same as the polarity of the power source connected to the transfer corotron used for transferring the second toner image, or substantially zero. Since the first toner is not attracted to the electric field of the transfer corotron, the problem that the toner adheres to the corona wire and contaminates the corotron does not occur.

(2) Improving the stability of adhesion of unfixed toner images to the surface of the printing material during transportation of the printing material (paper) The charged charges of the respective toner images formed on both surfaces of the printing material after transfer are opposite to each other. Because of the polarity, a suction force works by sandwiching the paper between the toners, and the toner image is firmly attached to the surface of the printing material.

[0018]

EXAMPLES Example 1 FIG. 1 is a diagram for explaining Example 1 of the present invention.
A first photosensitive drum having a photoconductor 2a made of SeTe formed on the surface of a conductive substrate 1a such as aluminum;
Similarly, SeT is formed on the surface of the conductive substrate 1b such as aluminum.
The second photoconductor drum on which the photoconductor 2b made of e is formed is arranged on both sides of the printing material 10 such as paper such as continuous paper or cut paper or a plastic sheet.

In the first photoconductor drum, a positive charge is applied to the photoconductor drum by the charger 3a, and the exposure unit 5a is exposed.
An electrostatic latent image is formed by irradiating light from. The first toner image 7 is formed by developing this with the developing device 6. 12a is an erase lamp, and 13a is a photoconductor cleaner. A bias roller 8 has a DC bias voltage VT having a polarity opposite to that of the toner charge (plus).
B is applied by the power supply 11.

As the bias roller 8, a metal roller or a metal roller having conductive rubber formed on its surface is used. By the roller transfer with the bias roller 8, the first
Toner image 7 is transferred to the upper surface of the printing material 10. The value of the bias voltage VTB varies depending on the charge amount of the toner and the conveyance speed of the printing material 10, but is usually 300 to −.
It is 1000V. The charge of the first toner image 7 is A
The electric charge from the static eliminator 14 to which the C power source 15 is connected is adjusted to be negative or substantially zero. Reference numeral 16 in the drawing denotes a metal roller which serves as a counter electrode of the corona wire of the static eliminator 14.

The second toner image 19 is formed on the photoconductor 2b by the same process in the second photosensitive drum. The toner image 19 also has a positive charging polarity, and the toner image 19 is transferred to the lower surface of the printing material 10 by the transfer corotron 20 connected to the negative DC power supply 21.

At this time, the charge of the first toner image 7 is changed from positive to negative or substantially zero by the static eliminator 14, so that the first toner image 7 is attracted to the wire of the transfer corotron 20 and is transferred. 20 will not be contaminated.

On the other hand, the transfer corotron 20 gives a negative charge to the upper surface of the printing material 10 and the first toner image 7. For this reason, since the charging polarities of the toners are different on both sides of the printing material 10, a suction force works by sandwiching the printing material 10 to each other, so that both toner images 7 and 19 are printed on the printing material 10.
Firmly attached to. Therefore, the toner image 19 on the lower surface does not fall off when the printing material 10 is conveyed.

Although 8 is described as a bias roller here, 8 is a pressure roller, and the material 10 to be printed is pressed against the photosensitive drum by the pressure roller, whereby the toner image 7 on the photosensitive drum is printed on the material to be printed. It may be pressure-transferred to 10.

Reference numerals 22 and 23 in the figure are heat rolls, and an elastic body such as silicon rubber or fluororubber is formed on the surface of an aluminum tube, and perfluoroalkoxy copolymer (PFA) or polytetrafluoroethylene is formed on the elastic body. (P
This is a so-called soft roll structure in which a fluorine-based resin coating film having excellent releasability such as TFE) is formed, and has a heater lamp inside.

In the case of single-sided fixing, the fixing device has a pair structure of a heat roll and a backup roll. In the present invention, a double roll of heat roll is used for simultaneous double-sided fixing, and a soft roll serves as a backup roll. I am making it. In order to exert the effect of a soft roll, that is, an elastic layer, it is desirable that the thickness of the elastic layer such as silicon rubber or fluororubber be 50 μm or more. Here, one photoconductor drum is used as each of the first and second toner image carriers, but in the case of multicolor printing, a plurality of photoconductor drums are respectively arranged.

In this embodiment, positively charged SeTe is used as the photoconductor and positively charged toner is used by the reversal development method. However, a negatively charged organic photoconductor (OPC) is used as the photoconductor. Alternatively, negatively charged toner may be used. In this case, the polarity of the transfer device is opposite to that of this embodiment.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. 2 and 5. The difference from Embodiment 1 is that two color toner images are formed on the photoconductor drum by the tri-level method.

A first photosensitive drum having an organic photoconductor (OPC) 2a formed on the surface of a conductive substrate 1a made of aluminum or the like, and an organic photoconductor on the surface of a conductive substrate 1b made of aluminum or the like. Second (OPC) 2b formed
The photosensitive drums are arranged on both sides of the material 10 to be printed.

The photoconductor drum is negatively charged by the charger 3a, and the surface potential of the photoconductor drum becomes V0 as shown in FIG.
An electrostatic latent image having three potential levels of 0, V0 / 2, and VR is formed. The bias voltage VB11 is applied to the developing device 6a by the bias power source 9a, and the bias voltage VB12 is applied to the developing device 6b by the bias power source 9b.
The positively charged toner 7a adheres to the area of the voltage V0 by regular development, and the negatively charged toner 7b adheres to the area of the potential VR by reversal development. In this embodiment, 7a is a color toner and 7b is a black toner. In this way, a two-color toner image is formed on the photosensitive drum in one process. In this embodiment, V0 is 700V and VR is 100.
V and VB11 are 500V, and VB12 is 300V.

Reference numeral 24a in the figure is a corotron before transfer, which is AC
A power supply or an AC power supply on which a positive DC voltage is superimposed is connected. A positive charge is applied to the toners 7a and 7b on the photosensitive drum, and as a result, the toner 7b that was negatively charged is also changed to positively charged. First on the photoconductor drum
The toner image 7 is transferred to the upper surface of the printing material 10 by roller transfer using the bias roller 8 to which a negative voltage is applied. On the other hand, the two-color toner image 19 is also formed on the second photoconductor drum by the same process. In this embodiment, 19a is a positively charged color toner, and 19b is a negatively charged black toner. Reference numeral 24b denotes a pre-transfer corotron, to which an AC power source or an AC power source on which a negative DC voltage is superimposed is connected. Negative charges are applied to the toners 19a and 19b on the photosensitive drums, and as a result, the toner 19a that was positively charged also changes to negatively charged.

In this embodiment, the AC voltage is 1 to 2 kHz, 2
The absolute values of kV and DC voltage were set to 4 to 5 kV. This second
The toner image 19 is transferred to the lower surface of the material 10 to be printed by the transfer corotron 20 to which the negative DC power source 21 is connected.

Since the charge of the first toner image 7 is positive, the static eliminator 14 used in the first embodiment is unnecessary.
That is, by making the polarities of the first toner image 7 and the second toner image 19 opposite to each other, the static eliminator 14 becomes unnecessary.

A positive charge is applied to the upper surface of the material 10 to be printed and the first toner image 7 by the transfer corotron 20. In this way, since the charging polarities of the toners are different on both sides of the printing material 10, a suction force works by sandwiching the printing material 10 to each other, so that both toner images 7 and 19 are firmly attached to the printing material 10, and the printing material 10 is printed. The toner image 19 on the lower surface does not fall off when the material 10 is conveyed.

(Embodiment 3) Next, Embodiment 3 of the present invention will be described with reference to FIGS. The difference from Embodiments 1 and 2 is that the toner images are simultaneously transferred to both surfaces of the material 10 to be printed without using a transfer device. The first and second photosensitive drums are OPCs.
It is a photoconductor drum.

A DC bias power source 26 is connected to the conductive substrate 1a of the first photosensitive drum to apply a DC voltage VD, and the conductive substrate 1b of the second photosensitive drum is held at ground potential by grounding. A predetermined potential difference is applied between the conductive base 1a and the conductive base 1b.

A two-color image using two-color toners (7a, 7b) is formed on the first photosensitive drum by the same process as in the second embodiment. Reference numeral 24a denotes a pre-transfer corotron, which is connected to an AC power source 25a on which a negative DC power source is superposed, imparts a negative charge to the two-color toners 7a and 7b on the photosensitive drum, and the toner 7a that has been positively charged is also negatively charged. Change to.

A two-color image using two-color toners (19a, 19b) is formed on the second photosensitive drum by the same method. A pre-transfer corotron 24b is connected to an AC power source 25b on which a positive DC power source is superposed, and a positive charge is applied to the two-color toners 19a and 19b on the photosensitive drum. As a result, the toner 19b that is negatively charged. Also changes to a positive charge. An area 27 where the first and second photosensitive drums face each other and nips is a transfer area.

FIG. 6 shows the surface potentials of the first and second photosensitive drums and the toner potential. In the case of this embodiment, V0
Is set to -700V. The two-color toner (7a, 7b) on the first photoconductor drum is given a negative charge by the AC power supply 25a on which the negative DC power supply is superposed, so that the surface potential of the photoconductor (including the toner image portion) is To rise. On the other hand, the two-color toner (1
9a, 19b) is an AC on which a positive DC power supply is superimposed.
Since a positive charge is applied by the power supply 25b, the surface potential of the photoconductor (including the toner image portion) is reduced.

As a result, the potential difference between the region of the first photoconductor having the lowest potential and the region of the second photoconductor having the highest potential in absolute value is ΔV. This value varies depending on the resistance value of toner, the amount of adhesion, and the amount of charge application, but it is about -50 to -20.
A range of 0V is suitable.

As described in the first embodiment, in roller transfer, −300 to −100 V is applied to the bias roller. Therefore, in this embodiment, the DC bias voltage VD of the conductive substrate 1a of the first photosensitive drum is -250 to -800V.
By setting the above range, it is possible to transfer the toners of opposite polarities on the first and second photosensitive drums to both printing surfaces of the printing material 10 in the transfer area 27 by the same mechanism as the roller transfer. it can. As a result, it is possible to perform transfer on both sides at the same time without using the transfer device as in the first and second embodiments, and it is possible to reduce the size and cost of the apparatus.

In this embodiment, a positive potential is applied to the conductive substrate 1a of the first photosensitive drum and the conductive substrate 1b of the second photosensitive drum is set to the ground potential. On the contrary, the conductive substrate 1a is used. May be set to the ground potential and a positive potential may be applied to the conductive substrate 1b. It is also possible to apply different voltages to both the bases 1a and 1b to give a predetermined potential difference between the bases 1a and 1b.

As the material of the photosensitive member, negatively charged OPC is used here, but positively charged SeTe or As2 is used.
Se3, and the positively charged OP that has been attracting attention recently
C can also be used.

(Embodiment 4) FIG. 4 shows Embodiment 4 of the present invention, showing an electrostatic double-sided printing apparatus capable of performing multi-color or full-color printing in one process on both sides of a printing material. As shown in FIG.
An organic photoconductor (OPC) 2a is formed on the surface of the conductive substrate 1a.
And a third photoconductor drum on which an organic photoconductor (OPC) 2c is formed on the surface of the conductive substrate 1c.
The first toner image carrier composed of the photosensitive drum is disposed above the printing material 10.

On the other hand, the second photoconductor drum in which the organic photoconductor (OPC) 2b is formed on the surface of the conductive substrate 1b, and the organic photoconductor (OPC) on the surface of the conductive substrate 1d.
A second toner image carrier composed of a fourth photosensitive drum on which 2d is formed is disposed below the printing material 10. The respective photosensitive drums are arranged so as to face each other as shown in FIG.

Two-color toner images are formed on each photoconductor drum by tri-level development, and 7a, 7b, 7
c and 7d are yellow, magenta, cyan and black toners, respectively, and 19a, 19b, 19c and 19d are yellow, magenta, cyan and black toners, respectively.

Toners 7a, 7b and 7c, 7d on the first toner image carrier disposed above the material 10 to be printed.
Is charged negatively by the pre-transfer corotrons 24a and 24c, and all are negatively charged.

On the other hand, the toners 19a, 19b and 1 on the second toner image carrier disposed below the material 10 to be printed.
9c and 19d are positively charged by the pre-transfer corotrons 24b and 24d, and are all positively charged.

The conductive substrates 1a and 1c of the first and third photosensitive drums are at ground potential, and the conductive substrates 1b and 1d of the second and fourth photosensitive drums are positive DC power sources as bias power sources. 28 and 29 are applied.

First, the toners 7a, 7b and 19a, 19b are simultaneously transferred to the upper and lower surfaces of the material 10 to be printed, and then the toner 7 is respectively transferred to the upper and lower surfaces of the material 10 to be printed.
c, 7d and 19c, 19d are transcribed simultaneously. As a result, four color toners having different polarities are formed on both surfaces of the printing material 10 without disturbing the transferred image.

This state is shown in FIG. In addition, as the voltage values of the bias power sources 28 and 29, the bias power source 29
By increasing the voltage value of
The transfer performance of d, 19c, and 19d can be improved. After that, it is fused and fixed by a double-sided fixing device as shown in FIG. 3, and a multi-color image or a full-color image can be formed on both surfaces of the printing material 10.

In each of the above-described embodiments, the photoconductor drum having the photoconductor layer formed on the surface of the aluminum tube is shown.
As the form of the photoconductor drum, it is also possible to apply a conductive elastic body or one in which a photoconductive layer is formed on a substrate with a thin conductive layer provided on the elastic body, which allows uniform transfer to both sides of the printing material. And it can be done efficiently.

[0053]

According to the present invention, the following effects can be obtained.

(1) It is possible to perform high-quality transfer on both sides of the material to be printed without scattering of toner and disturbance of image quality.

(2) Since the charged electric charges of the respective toners on the surface of the material to be printed have opposite polarities across the surface to be printed, they are firmly attached to the material to be printed by the electrostatic attraction force of the both, so that the material to be printed is The phenomenon that the toner falls off during the transportation of the sheet does not occur.

(3) Photoreceptor of first image forming means and second
By providing the potential difference applying means for applying a potential difference between the image forming means and the photoconductor, the transfer device can be omitted, so that the size and cost of the apparatus can be reduced.

(4) A multi-color image or a full-color image can be printed on both sides of a printing material by one process.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image forming unit of an electrostatic double-sided printing apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an image forming unit of an electrostatic double-sided printing device according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an image forming unit of an electrostatic double-sided printing device according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of an image forming unit of an electrostatic double-sided printing apparatus according to a fourth embodiment of the present invention and a schematic diagram of a toner adhesion state on a printing material.

FIG. 5 is an explanatory diagram showing the principle of tri-level development.

FIG. 6 is an explanatory diagram showing the principle of simultaneously transferring a two-color image to both surfaces of a printing material in the electrostatic double-sided printing device according to the third embodiment.

FIG. 7 is a configuration diagram around a drum of a conventional electrostatic double-sided printing device.

[Explanation of symbols]

1 Conductive Substrate of Photoreceptor Drum 2 Photoconductor 5 Exposure Area 6, 17 Developing Machine 7 First Toner (Image) 8 Bias Roller 9, 18 Biasing Power Supply 10 of Developing Machine 10 Printed Material 11 Bias Roller Power Supply 14 Static Eliminator 19 Second Toner (Image) 20 Second Toner Transfer Corotron 22, 23 Heat Roll 24 Pre-Transfer Corotron 26, 28, 29 Bias Power Supply 30 for Conductive Substrate of Photoreceptor Drum Electric Charge for Printing Material 31 First Corotron for toner transfer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-63-197979 (JP, A) JP-A-6-27757 (JP, A) JP-A-57-63559 (JP, A) JP-A-5- 53392 (JP, A) JP-A-2-97984 (JP, A) JP-A-7-209926 (JP, A) JP-A-6-206348 (JP, A) JP-A-5-66689 (JP, A) European Patent Application Publication 629924 (EP, A 1) (58) Fields searched (Int.Cl. ⁷ , DB name) G03G 15/00 G03G 15/01 G03G 15/16

Claims (2)

(57) [Claims] 1. A first image forming means is provided on the upstream side in the conveying direction of a printing material, and a second image forming means is provided on the downstream side in the conveying direction. The first image forming means and the second image forming means. A conveyance path for the printing material is formed between the photosensitive members of the first image forming unit and the photosensitive member of the second image forming unit, and is used for the first image forming unit. A first transfer device for transferring the first toner image formed by the first image forming unit onto the printing material, the charge polarity of the toner being the same as that of the toner used for the second image forming unit, and , The printing target is printed by the first transfer unit on the printing material transport path formed between the second toner image formed by the second image forming unit and the second transfer unit that transfers the second toner image to the printing target. A charge that changes the charging polarity of the first toner image transferred onto the material to the same polarity as the charging polarity of the second transfer device. An applying unit is provided, and the charge applying unit transfers the first toner image of the printing material.
Metal electrode as a counter electrode in contact with the surface opposite to the ground surface.
An electrostatic double-sided printing device having a first and second toner images having different charging polarities and transferred to both surfaces of a printing material. 2. A first image is provided on the upstream side of the printing material in the conveying direction.
The second image forming means is provided on the downstream side in the transport direction.
Kicked Printing is performed between the first image forming unit and the second image forming unit.
A material transport path is formed, Sensitivity of the photoreceptor of the first image forming unit and the second image forming unit
A first image forming device having the same charge polarity of the photoconductor
For the charging polarity of the toner used in the step and the second image forming means
Toner has the same charge polarity, The first toner image formed by the first image forming unit is printed.
The first transfer device for transferring to the printing material and the second image forming means
The second toner image, which transfers the formed second toner image to the printing material,
On the print material conveyance path formed between the transfer device and the first
By the transcriber Of the first toner image transferred to the printing material
A charge that changes the charging polarity to the same as the charging polarity of the second transfer device.
A loading means is provided, The first transfer device includes a transfer roller or a transfer belt.
The voltage of the opposite polarity to the toner charge of the first toner image.
Transfer applied to the surface opposite to the surface on which the toner image 1 is transferred
A vessel, The charge applying unit transfers the first toner image of the printing material.
Metal electrode as a counter electrode in contact with the surface opposite to the ground surface.
Have la, First toner having different charging polarities on both sides of the material to be printed
Image and a second toner image are transferred, and electrostatic
Double-sided printing device.