JPH06202497A - Image forming device - Google Patents

Abstract

PURPOSE:To restrain irregularities in an image caused by discharge in the vicinity of a transfer nip, and to allow an electric field applying member or an electric field regulating member to abut on a transfer material carrier in a forward direction with respect to a transfer material carrying direction so as to obtain high image quality with excellent transfer efficiency by constituting an electrostatic charging nip where a transfer charging means comes in contact with a transfer material carrier so that it may be in the transfer nip where an image carrier comes in contact with a transfer material. CONSTITUTION:The transfer charging means 4 is provided with a plate-like conductive rubber blade 401 as the electric field applying member, and an electrode 402 impressing voltage on the blade 401. The electric field applying member 401 comes in contact with the image carrier 1 through the transfer material carrier 8 and the transfer material 6. At such a time, the electrostatic charging nip is made narrower than the transfer nip. Thus, toner scattering caused by the discharge out of the transfer nip, especially, near the upstream side is prevented, and the irregularities in the image is restrained. Meanwhile, the discharge is easily performed owing to abutting in the forward direction with respect to the transfer material carrying direction in order to allow the member 401 to uniformly abut on the transfer material carrier 8 with a light pressure, but the discharge restriction is compensated by providing the electric field regulating member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which forms a visible image (toner image) on an image carrier and transfers the toner image onto a transfer material conveyed by a transfer material carrier. The present invention relates to an image forming apparatus of, for example, an electrophotographic system or an electrostatic recording system, and in particular, an image carrier such as an electrophotographic photosensitive member is formed with plural images of different colors, and the images are formed on the same transfer material. A color electrophotographic copying machine that transfers images sequentially,
It can be suitably applied to printers and the like.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus is provided with a plurality of image forming units, each image forming unit forms a toner image of a different color, and the toner images are sequentially transferred to the same transfer material, a so-called color image. Although various forming apparatuses have been proposed, a color recording apparatus using a multicolor electrophotographic system is widely used.

An example of such a color electrophotographic recording apparatus will be briefly described with reference to FIG. 8. In the main body of the color electrophotographic recording apparatus, first, second, third and fourth image forming portions Pa, Pb, Pc, and Pd are provided side by side, and images of different colors are formed through the processes of latent image, development, and transfer. That is, the image forming portions Pa, Pb, Pc, Pd
Are each equipped with a dedicated image carrier, in this example, electrophotographic photosensitive drums 1a, 1b, 1c, 1d.
The toner images on the electrophotographic photosensitive drums 1a, 1b, 1c, and 1d formed of a, Pb, Pc, and Pd are carried and carried on the transfer material carrier 8 that moves adjacent to each image forming portion. The image is transferred onto the transfer material 6. Further, the toner image on the transfer material 6 is heated and pressed by the fixing section 7 to be fixed, and then discharged as a recorded image to the outside of the apparatus.

To explain further, the photosensitive drums 1a, 1b,
The exposure lamps 21a, 21b, 2 are provided on the outer periphery of 1c, 1d.
1c, 21d, drum chargers 2a, 2b, 2c, 2d,
A light source device (not shown), a polygon mirror 17 for scanning the light emitted from the light source device, and potential sensors 22a, 22b, 22c, 22d are provided. Laser light emitted from the light source device is used for polygon mirror 1
7, the photosensitive drum 1 through an fθ lens (not shown)
A, 1b, 1c, and 1d are scanned to form a latent image on each photosensitive drum according to an image signal.

The latent images formed on the respective photosensitive drums are made into toner images by the developing devices 3a, 3b, 3c and 3d containing the respective color developers of cyan, magenta, yellow and black.

This toner image is supplied from the transfer material cassette 60 to the transfer material carrier 8 via the resist roller 13, and is transferred onto the transfer material 6 conveyed through each image forming section by the transfer material carrier 8. To be done.

In this example, the transfer material carrier 8 is a polyethylene terephthalate resin film sheet (PET sheet).
Or a polyvinylidene fluoride resin film sheet, or a dielectric resin film such as a polyurethane resin film sheet, the both ends of which are superposed and joined together,
Either endless or seamless (seamless) belts are used.

When the transfer material carrier 8 starts to rotate,
The transfer material 6 delivered from the transfer material cassette 60 is supplied from the registration rollers 13 onto the transfer material carrier 8. At this time, the image writing signal is turned on, an image is formed on the first photosensitive drum 1a at a certain timing, and a toner image is formed. This toner image is transferred onto the transfer material by the electric field or charge imparting action of the transfer charging means 4a which is a corotron. At this time, the transfer material 6 is the transfer material carrier 8
The toner image is held on the upper side by electrostatic attraction, and in this state, the toner image is transferred to the next second image forming unit Pb and further to the subsequent image forming units, and the toner images are respectively transferred. The transfer material 6 to which the toner image of the fourth image forming portion Pd is transferred in this manner is neutralized by the separation charging device 14 and the peeling charging device 15, whereby the electrostatic attraction force is attenuated, and the transfer material carrying member 8 is formed. And is conveyed to the fixing unit 7.

The fixing unit 7 is provided with a fixing roller 71 and a pressure roller 72, and heats and presses the toner image fed on the transfer material to form a fixed image.

After transfer, the photosensitive drums 1a, 1b, 1c, 1
The developer remaining on the surface of the photoconductor cleaning section 5a
5b, 5c, 5d, and are ready for the subsequent latent image formation. Further, the developer remaining on the transfer material carrier 8 is neutralized by the belt static eliminator 12 to remove the electrostatic adsorption force, and then the belt cleaning unit 9 has a relative speed with respect to the transfer material carrier 8. It is scraped off by the rotating fur brush 16. As a belt cleaning means, a blade or a non-woven fabric,
Or the combination of these is generally often used.

In the above structure, in order to transfer the toner image formed on the image carrier 1 such as the photosensitive drum onto the transfer material 6 in a good condition, the contact point upstream of the image carrier 1 and the transfer material carrier 8 is upstream. A regulating member for blocking the transfer electric field may be disposed on the side. That is, in order to faithfully reproduce the toner image on the image carrier 1, the transfer electric field is regulated to prevent the coloring agent particles forming the toner image, so-called toner, from scattering. is necessary.

For this reason, as shown in FIGS. 8 and 9, as a transfer charging means, a regulating member 403 (403a, 403b, 403c, 403c,
403d) may be provided, but the easiest configuration is often to use a brush-shaped (FIG. 10) or plate-shaped (FIG. 11) electrode 4, particularly a plate-shaped electrode. That is, the plate-shaped contact electrode 4 includes the plate-shaped conductive blade 401 as an electric field applying member, and the blade 401
A predetermined voltage is applied to the electrode via the electrode 402. Also in this case, it has been proposed to provide the electric field regulating member 403 on the upstream side of transfer.

[0013]

However, in the above-mentioned conventional plate-like transfer charging means 4, the width of the image carrier 1 in contact with the transfer material or the transfer material carrier 8 (hereinafter referred to as "transfer material nip"). Also, since the width (hereinafter referred to as “charging nip”) where the transfer material carrier 8 and the electric field applying member 401 are in contact with each other is wider, when the electric field regulating member 403 is not in contact with the transfer material carrier 8. At the tip of the electric field regulating member 403, that is, upstream of the vicinity of the charging nip, the electric field regulating member 403 has no effect, and therefore discharge occurs in the non-contact area between the transfer material 6 and the image carrier 1 and the image is disturbed. Further, when the electric field regulating member 403 is in contact with the transfer material carrying member 8, due to frictional charging of the electric field regulating member 403, similarly, the transfer material 6 and the image carrying body 1 are in the non-contact area. Disturbance occurs.

On the other hand, at the time of transfer, if the contact pressure between the image carrier 1 and the transfer material 6 is too strong, the toner is suppressed on the image carrier 1 and is not transferred onto the transfer material, but on the image carrier. It is known that residual development occurs.

Therefore, the electric field regulating member 403 and the electric field applying member 401 need to be brought into contact with the transfer material carrier 8 at a low pressure as much as possible, but there is a problem that when the pressure is reduced, uneven charging occurs. there were. Therefore, it has been proposed that the electric field applying member 401 or the electric field regulating member 403 is brought into contact with the transfer material transport direction in the forward direction to reduce the pressure, but in this case, the transfer on the upstream side is performed. There is a drawback in that the image disturbance in the non-contact area between the material and the image carrier 1 is increased.

Therefore, an object of the present invention is to make the charging nip narrower than the transfer nip, thereby suppressing image disturbance due to discharge or the like in the vicinity of the transfer nip, and at the same time, the electric field applying member or the electric field restricting member is provided in the transfer material conveying direction. On the other hand, it is an object of the present invention to provide an image forming apparatus capable of achieving a high image quality with good transfer efficiency by achieving a light pressure without causing image distortion by abutting in the forward direction.

[0017]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
An image carrier on which a visible image is formed, a transfer material carrier that carries and conveys a transfer material, and the transfer material carrier on the side of the transfer material carrier opposite to the image carrier, at least when an electric field is applied. And a transfer charging unit disposed so as to contact the transfer member, the transfer charging unit applying an electric field to the transfer material and the image carrier via the transfer material carrier, In an image forming apparatus configured to transfer an image onto the transfer material, an area where the transfer charging unit contacts the transfer material carrier is in an area where the image carrier and the transfer material contact each other. And an image forming apparatus. Preferably, the transfer charging means is composed of a plate-shaped member,
The plate-shaped member is in contact with the transfer material carrier in the forward direction with respect to the moving direction of the transfer material carrier.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. FIG. 2 shows an embodiment of the image forming apparatus of the present invention. The image forming apparatus of this embodiment has the same overall configuration as the color electrophotographic recording apparatus described above with reference to FIG. 8, and only the configuration of the transfer charging means 4 is different. Therefore, in the following description, the transfer charging unit 4 will be described, and the description of the entire configuration of the apparatus will be omitted.

Embodiment 1 FIG. 1 shows an embodiment of the transfer charging means constructed according to the present invention. In this embodiment, the transfer charging means 4 has a plate-shaped conductive rubber blade 401 as an electric field applying member and an electrode 402 for applying a voltage to the blade 401. As the plate-shaped conductive rubber blade 401, generally, SBR, BR, EPDM, urethane, silicon rubber, chloroprene, epichlorohydrin rubber and the like are blended with a conductive filler such as carbon black to have an electric resistance value of 10 ² to 10 10. The value controlled to any value within the range of ¹⁰ Ω is used. Also, the hardness is JIS A, 40-
Those within the range of 80 ° are preferable.

The transfer charging means 4 having such a structure will be briefly described by using the impedance R (≡V / I) defined when the applied current is I and the applied voltage is V.

Electrode 4 for applying voltage to the electric field applying member 401
The impedance with respect to the potential difference V _O between 02 and the charging nip is R _O, and the impedance obtained by subtracting R _O from the impedance R is R _T. At this time, R _O
In order to obtain a high image quality, it is necessary that it does not become too large with respect to R _T.

That is, it is essential that the impedance R does not become 10 ² times or more (10 ² order or more) larger than the impedance R _T.

The impedance R _T is an impedance of the transfer material carrier 8, the transfer material 6, the toner, the image carrier 1, and a space formed when they are in contact with each other, and the electric field applying member 401 is made of metal or the like. Can be measured.

On the other hand, the impedance R is R> 10.
^{At 2} _RT , the applied voltage becomes unnecessarily high and discharge occurs, the toner particles forming a toner image scatter, and a good image cannot be obtained. Further, as shown in FIG. 2, when toner particles of different colors are sequentially transferred in multiples for each color, the impedance increases due to the charges accumulated on the transfer material carrier 8 and the transfer material 6, and the applied voltage of the fourth color is Since it becomes higher, the scattering of the toner particles due to the discharge becomes more likely to occur.
Therefore, in order to reproduce clearly transferring the image multicolor successively transferred, R ≒ R _T, that is, it is preferable to minimize the R _O. However, it is known that when the electric field applying member 401 is made of a low resistance member such as metal, image defects such as uneven charging occur. Therefore, a resistance of 10 ² Ω or more is used.

The above will be briefly described with reference to FIGS. 3 and 4. 3 is similar to that of FIG.
Shows the state of being in contact with the image carrier 1 via the transfer material carrier 8 and the transfer material 6.

Here, the distance from the image carrier 1 to the back surface of the transfer material carrier 8 via the toner layer and the transfer material 6 is l, and the distance from the back surface of the transfer material carrier to the electrode 402 of the electric field applying member 401. Be r. Further, FIG. 4 schematically shows a case where a high voltage power source for applying an electric field is set to V and a contact resistance R _S exists between the transfer impedance R _T and the electric field applying member impedance R _O. By the way, in general, the applied voltage V
It is known that the dielectric breakdown distance is related to (kv) in that a discharge phenomenon occurs unless the distance is more than a predetermined distance.

First, consider a case where the resistance R _O of the electric field applying member 401 is smaller than the contact resistance R _S. At this time, the contact resistance R _S is moved relative to two bodies of contact, and will vary by both potential difference, etc., generally 10 ⁰
It is in the range of about 10 ² (Ω).

Here, _{assuming that the} distance between contacts is r _s (mm), in addition to r _s << 0, the current I has a transfer impedance R _T of generally 10 ⁸ to 10 ⁹ (Ω) and an applied voltage of 1 as well. -10 (kV), that is, R _S << R _T , V _S << V _T
Therefore, the voltage output from the power supply V (kV)
Does not follow the fluctuation of R _S , and if a constant current I flows, a local discharge phenomenon occurs. Therefore, high image quality cannot be obtained with the electric field applying member 401 having a resistance R _O lower than the contact resistance R _s .

Next, consider the case where the resistance R _O is higher than the contact resistance R _s . From Fig. 4, the resistance (R _T + R _S
+ R _O ) (Ω), applied voltage V = (V _T + V _S + V
_O ) (kV) is applied, and the distance between them is (r + 1) (m
m). Here, the transfer material 6 is generally 5 × 10.
^The thickness of the paper is about ^{-2 to} 5 × 10 ^-1 (mm), and the transfer material carrier 8 has a handling strength and electrostatic capacity of 5 ×.
Since there are many dielectric films of about 10 ^{−2 to} 5 × 10 ⁻¹ (mm) and the thickness of the toner particle layer is on the order of 10 ⁻² mm, the distance 1 is 10 ⁻¹ to 10 ^0. (Mm).

[0030] In addition, applied voltage in the fourth color, etc. when multiple transfer is generally from 10 kV, since fewer but approximately even 1kV is required, considering that V _S is 10 ⁰ ~10 ² (Ω), the applied voltage is expressed by V = V _T + V _O. Therefore, considering the relationship of dielectric breakdown, the applied voltage V
However, even if V _O is on the order of being negligible with respect to V _T , 1 to 10 (kV) is applied, while at a distance r + 1 and a distance l is 1 (mm) or less,
The distance r between the electrode 402 and the transfer material bearing member 8, depending on the applied voltage V, it is necessary 10 ⁰ ~10 ¹ (mm) or more, this is a critical value is determined by the applied voltage V However, those that are too thin (or short) are unsuitable.

[0031] Also, in this way, when the electric field applying member having a resistance value R _O as R _S ≦ R _O ≦ R _T is satisfied, it is possible to obtain a high-quality.

Next, V_T <V_O Or above
R_S R compared to_O R is small _S Than above
High, V_S Voltage becomes large, the applied voltage
Pressure V is V_T Is not dominated by V_O Or V_S By
Will be ruled. In this case, R_S > R_O so,
R_S Contrary to the case in which the transfer current I is discharged between_Sor
Is R_O Is controlled and controlled by the fluctuation of
Conditions such as the electric capacity of the transfer material and the electric resistance.
Due to the change, it cannot be controlled to apply the optimum transfer current.
Between the transfer material carrier 8 and the image carrier 1
(Distance 1) or discharge occurs between the transfer material 6 and the image carrier 1.
It becomes unsuitable as a transfer system such as twisting.

Here, the above-mentioned control of current and voltage means a constant current between (r + 1) which is generally used, or
This is the case when constant voltage control is performed.

In the present invention, the charging nip is made narrower than the transfer nip so that
In particular, it is possible to prevent toner scattering due to electric discharge in the vicinity of the upstream, but on the other hand, when the electric field applying member 401 contacts the transfer material carrying member 8 in the forward direction with respect to the transfer material conveying direction. As described above, the discharge easily occurs near the upstream side outside the transfer nip.

In FIG. 3, assuming that the most upstream point of the transfer nip is A, the above-mentioned dielectric breakdown distance does not hold from the point A'which is the rear surface of the transfer material carrier 8 with respect to point A. Under the conditions, the image distortion was remarkable. That is, in FIG. 3, when the electric field applying member 401 is tilted, the distance X in the drawing becomes gradually shorter, which promotes the above tendency. However, such a tendency does not always cause discharge in the vicinity of the upstream of the transfer nip only when the above-mentioned relationship of dielectric breakdown is not established, and fine discharge causes the image carrier or the toner and the surface of the transfer material. If there is a potential difference with the electric field applying member in the forward direction with respect to the transport direction, the discharge near the transfer nip occurs. It was shown that the toner scattering by the toner tends to be promoted.

In this embodiment, the transfer material carrier 8 is 1
The transfer current is I = 1 using a 50 μm thick PVdF sheet.
2 μA, applied voltage V is 2 kV in sequence from the first color, 2.
It was set to 7 kV, 3.2 kV, and 3.4 kV. Further, as the electric field applying member 401, a conductive rubber blade of EPDM having a thickness of 1 mm is used, and its resistance R _O is R _O ≈10 ⁶ Ω (10 ⁸
Ω / □).

Further, as can be seen from the above description, by providing the electric field regulating member 403 as shown in FIG. 11 upstream of the conductive rubber blade 401 of FIG. 3, it is possible to further suppress the upstream discharge, In addition, by inclining in the forward direction, it is possible to make uniform contact with light pressure.

In the above description, the upstream of the transfer nip has been described. This is because the potential difference is larger on the upstream side and discharge is more likely to occur, and the image carrier 1 and the transfer material are also formed on the downstream side. There is peeling discharge 6 and the like, and the same can be said.

Second Embodiment In the first embodiment, the transfer charging means 4 has been described in which the electric field applying member 401 is a conductive rubber blade. However, the present invention is not necessarily limited to the transfer charging means.

5 and 6 show a plate-shaped conductive brush which is another embodiment of the transfer charging means 4 used in the present invention.

FIG. 5 shows the transfer charging means 4 provided on the aluminum electrode 405 by surrounding the conductive fiber 407 as an electric field applying member with a mesh holding member 406 so as not to spread. Also, FIG. 6 shows that a thin P member is used instead of the mesh holding member 406.
The transfer charging means 4 in which the conductive fiber 407 is held by the ET film 408 and provided on the aluminum electrode 405 is shown.

As described above, even if the brush-like electric field applying member 407 that easily spreads is configured so as not to spread, the charging nip can be narrower than the transfer nip.
Further, by providing the PET film 408 as shown in FIG. 6, it is possible to serve also as the effect of the electric field regulating member described above.

Embodiment 3 In each of the above-mentioned embodiments, the image forming apparatus of the present invention has a plurality of image carriers 1 and the transfer material 6 is conveyed by the belt-shaped transfer material carrier 8 and transferred. However, the present invention is not limited to this.

FIG. 7 shows a color electrophotographic recording apparatus which is an example of another image forming apparatus which can embody the present invention. One image forming section is provided in the main body of the color electrophotographic recording apparatus of this embodiment.

That is, the exposure lamp 21, the drum charger 2, and the outer periphery of the image carrier 1 which is an electrophotographic photosensitive drum,
A light source device (not shown) and a polygon mirror 17 for scanning the light emitted from the light source device are provided.
Laser light emitted from the light source device is used for polygon mirror 1
7, the photosensitive drum 1 through an fθ lens (not shown)
Are scanned to form a latent image on the photosensitive drum 1 according to the image signal.

The developing device for converting the latent image into a toner image is a rotary developing device 3, which includes a yellow developing device 3a, a magenta developing device 3b, a cyan developing device 3c, and a black developing device 3.
d is mounted on the rotating body. This developing device 3a, 3b,
Cyan, magenta, yellow, and black color developers are filled in predetermined amounts in 3c and 3d, and toner images of respective colors are formed on the photosensitive drum 1 according to the latent image.

On the other hand, the transfer material 6 delivered from the transfer material cassette 60 is delivered to the transfer material carrier 8 via the registration rollers 13. In this embodiment, the transfer material carrier 8 is a transfer drum, and the outer periphery thereof is made of a dielectric resin such as a polyethylene terephthalate resin film sheet (PET sheet), a polyvinylidene fluoride resin film sheet, or a polyurethane resin film sheet. A transfer sheet, which is a film, is wound and configured.

The operation of the entire color image forming apparatus will be briefly described for the case where an image is formed in the four colors. The photosensitive drum 1 rotating in the direction of the arrow in the figure is uniformly charged by the charger 2, and then image exposure is performed by the laser light modulated by the yellow image signal of the document, so that the photosensitive drum 1 is exposed. An electrostatic latent image is formed. This latent image is developed by the yellow developing device 3a which is fixed at the developing position in advance to form a toner image.

On the other hand, the transfer material 6 advanced by the transfer material cassette 60 via the paper feed roller and the paper feed guide is pushed out in the direction along the transfer drum 8. At this time, the transfer material 6
Are pressed against the transfer drum 8 by the suction roller 12, and almost at the same time, the suction charging device 1 oppositely arranged.
When 2 acts, it is electrostatically carried on the transfer drum 8. The transfer drum 8 rotates in the direction of the arrow in the figure in synchronization with the photosensitive drum 1, and the toner image developed by the yellow developing device 3a is transferred to the transfer charging unit 4 at the transfer portion.
Transcribed by The transfer drum 8 keeps rotating as it is and prepares for transfer of the next color, for example, magenta.

On the other hand, the photosensitive drum 1 has a cleaning member 5
Then, the latent image is formed again by the following magenta image signal. During this time, the developing device 3 is rotated so that the magenta developing device 3b is fixed at a predetermined developing position and performs predetermined magenta development. Then, the above-described steps are similarly repeated for cyan and black to form a four-color visible image on the transfer material 6. When this step is completed, the transfer material 6 is separated from the transfer drum 8 by the separation claw and sent to the fixing device 7 by a conveyor belt or the like.

The fixing section 7 is provided with a fixing roller 71, a pressure roller 72, etc., and heats and presses the transferred transfer material 6 to form a toner image as a fixed image.

Further, the developer remaining on the transfer drum 8 is
After the charge is removed by the charge removers 14 and 15 to remove the electrostatic attraction force, the charge is scraped off by the rotary fur brush 16 provided in the cleaning device 9.

By arranging the transfer charging means 4 having each of the above-mentioned configurations at the transfer portion, the same effect as described above can be obtained.

[0054]

As described above, in the image forming apparatus according to the present invention, the charging nip is made narrower than the transfer nip to suppress the image disturbance due to the discharge in the vicinity of the transfer nip, and the electric field applying member or the electric field applying member. Makes it possible to reduce the pressure without causing image distortion by bringing the electric field regulating member into contact with the transfer material transport direction in the forward direction, and thereby obtain a high image quality with good transfer efficiency.

[Brief description of drawings]

FIG. 1 is a sectional view of a transfer charging unit that can be used in an image forming apparatus according to the present invention.

FIG. 2 is a sectional view of an embodiment of an image forming apparatus according to the present invention.

FIG. 3 is a cross-sectional view illustrating the operation of the transfer charging device according to the present invention.

FIG. 4 is an equivalent circuit diagram illustrating the operation of the transfer charging device according to the present invention.

FIG. 5 is a perspective view showing another embodiment of the transfer charging means according to the present invention.

FIG. 6 is a perspective view showing another embodiment of the transfer charging means according to the present invention.

FIG. 7 is a cross-sectional view of another embodiment of the image forming apparatus according to the present invention.

FIG. 8 is a sectional view of a conventional image forming apparatus.

FIG. 9 is a sectional view showing a conventional transfer charging means.

FIG. 10 is a sectional view showing another example of a conventional transfer charging means.

FIG. 11 is a sectional view showing another example of a conventional transfer charging means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 4 Transfer charging means 6 Transfer material 8 Transfer material carrier 401, 407 Electric field applying member 402, 405 Electrode 403 Electric field regulating member 406, 408 Holding member

Claims (2)

[Claims] 1. An image carrier on which a visible image is formed, a transfer material carrier that carries and conveys a transfer material, and a side of the transfer material carrier opposite to the image carrier, at least when an electric field is applied. A transfer charging unit arranged so as to contact the transfer material carrier, the transfer charging unit applying an electric field to the transfer material and the image carrier via the transfer material carrier, In an image forming apparatus configured to transfer a visible image on a body onto the transfer material, a region where the transfer charging unit contacts the transfer material carrier is in contact with the image carrier and the transfer material. An image forming apparatus characterized by being in an area. 2. The transfer charging means is composed of a plate-shaped member, and the plate-shaped member is in contact with the transfer material carrier in the forward direction with respect to the moving direction of the transfer material carrier. Image forming device.