JPH08234579A - Transfer device for image forming device - Google Patents

Abstract

PURPOSE: To uniformly and effectively perform the charge removing of a part used for electric-field transfer by a transfer means, to stably maintain satisfactory transfer-capability and to prevent deterioration of image quality which is caused by toner scatter, etc., due to an electric field generated in the vicinity of the transfer part or in the vicinity of the part where transfer paper is separated from the transfer means. CONSTITUTION: The transfer device comprises an image carrier 1, the transfer means 7 which is in pressure contact with the image carrier 1 and made of a material whose resistance decreases by the application of pressure, and charge removing means 11 and 12 which eliminate charges held on the transfer means 7. The charge removing means 11 and 12 are arranged in such positions as to press, before the subsequent transfer, the part subjected to the electric-field transfer by the transfer means 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to a transfer device of an image forming apparatus used in an electrophotographic image forming apparatus such as a facsimile and performing electric field transfer using a transfer belt or a transfer roller.

[0002]

2. Description of the Related Art Conventionally, a photosensitive drum that develops an electrostatic latent image to form a visible image, and a transfer nip portion that is in contact with the photosensitive drum are formed, and a transfer paper is passed through the transfer nip portion. And a bias voltage applying unit that applies a transfer bias voltage to the transfer belt. The visible image on the photosensitive drum is transferred onto the transfer belt while applying the transfer bias voltage by the bias voltage applying unit. A transfer device configured to transfer onto paper is known. However, since the transfer belt (or transfer roller) has a non-uniform volume resistance, the transfer electric field becomes non-uniform, the transfer efficiency is reduced, and the static elimination becomes non-uniform. As a countermeasure against this, for example, in Japanese Unexamined Patent Publication No. 5-200904, a transfer belt obtained by mixing a polyvinylidene fluoride resin and a conductive filler, extruding into a tube to form a film, and cutting the film at a predetermined length in the direction perpendicular to the axial direction. In addition, the volume electric resistance value of each part of the transfer belt is 10 ⁸ to 10 ¹⁷ Ω · cm, and the maximum value is in the range of 1 to 100 times the minimum value, which is excellent in durability and is seamless. Semiconductive transfer belts are disclosed.

Further, in Japanese Patent Laid-Open No. 3-158874, a layer made of a solid or sponge pressure conductive rubber is formed around a core metal, and the pressure conductive rubber is made of silicon. A composite material made by combining metal with rubber. In its natural state, it is in an insulating state with a resistance value of 10 MΩ or more.
A transfer roller, which is a material whose resistance changes to a conductive state of 0Ω or less, is disclosed. In addition, JP-A-3-62370
In the publication, a medium-height convex portion for promoting the separation of the transfer paper is formed in the substantially central portion of the grounding roller, so that the transfer paper can be reliably separated from the transfer belt and the transfer belt can be prevented from coming off. Is disclosed.

[0004]

However, among the above-mentioned conventional transfer devices, in the case of the seamless semi-conductive transfer belt, the unevenness of the volume resistance of the transfer belt has a ratio between the maximum value and the minimum value of 1. Although it is in the range of up to 100 times, it is difficult to obtain sufficient uniformity in consideration of the type of transfer paper and environmental compatibility. Therefore, due to non-uniformity of the transfer electric field at the time of low temperature and low humidity, when using high resistance paper (including OHP sheet) or thick paper, and transfer dust at the time of re-copy when partial dehumidification of the transfer belt occurs, There is a problem that a transfer failure such as a decrease in transfer rate is likely to occur. Further, in the transfer roller having the layer made of the pressure conductive rubber, a large amount of residual charge exists on the surface of the transfer roller after the transfer, but since the charge eliminating means is not provided, the residual charge is carried. In many cases, the surface cannot be sufficiently discharged before it is used for transfer again after being rotated once, and there is a problem that a defective image is likely to occur due to transfer dust and the like.

Further, in the transfer belt device in which the convex portion having a middle height is formed in the substantially central portion of the grounding roller, the grounding roller for neutralizing the transfer belt comes into contact with the transfer belt by having a convex portion locally. There is a case where static electricity is insufficient because the surface of the contact roller does not come into contact at a portion to be statically eliminated.
That is, as in the case of the transfer roller, a transfer failure due to insufficient static elimination of the transfer belt is likely to occur. Therefore, the present invention solves the above-mentioned problems of the related art, uniformly and efficiently removes the electric field of the transfer means, and can stably maintain good transferability. An object of the present invention is to provide a transfer device of an image forming apparatus capable of preventing deterioration of image quality due to toner scattering due to an electric field generated near a portion or a portion where a transfer sheet is separated from a transfer unit.

[0006]

The gist of the present invention resides in that, in claim 1, an image carrier and a transfer unit composed of a member which is brought into pressure contact with the image carrier and whose resistance value is reduced by pressurization. In the transfer device of the image forming apparatus, which is provided with a charge removing unit that removes electric charges carried by the transfer unit, and performs transfer of an electric field by sandwiching and passing a transfer sheet between the pressure contact portions, the charge removing unit is The portion of the transfer means used for the electric field transfer is arranged so as to be pressed before it is used in the next transfer. Further, in claim 2, the image carrier and the image carrier are pressed against each other. A transfer belt that is supported by a plurality of tension rollers and that has a resistance value that decreases by pressurization, and the transfer paper is sandwiched and passed through these pressure contact portions to perform electric field transfer. Multiple ten Two of the pressure rollers are arranged in the rotation direction of the image carrier and arranged so that the transfer belts are brought into pressure contact with the image carrier, respectively, to form an upstream pressure roller and a downstream pressure roller, and During the electric field transfer,
The transfer belt surface potential at the position of the upstream pressure contact roller is set to be lower than the transfer belt surface potential at the position of the downstream pressure contact roller, or the surface potential shifted in the direction opposite to the transfer polarity is maintained.

Further, according to a third aspect of the present invention, there is provided an image carrier, and a transfer means which is brought into pressure contact with the image carrier, and transfer of an image forming apparatus for performing electric field transfer by sandwiching and passing a transfer paper between these pressure contact parts. In the apparatus, the transfer means is composed of a member whose resistance value is reduced by light irradiation, and the light irradiation for irradiating light to a corresponding portion of the transfer means for pressing the transfer paper against the image carrier during the electric field transfer. According to a fourth aspect of the present invention, the use portion of the transfer means that has completed the electric field transfer is provided with a light irradiation and neutralization means for performing the light irradiation and static elimination before using for the next electric field transfer. Placed,
Moreover, in Claim 5, the said light irradiation static elimination is performed at least before the cleaning process of the said transfer means.

According to a sixth aspect of the present invention, there is provided a transfer of an image forming apparatus comprising an image carrier and a transfer belt which is in pressure contact with the image carrier, and the transfer paper is sandwiched and passed through these pressure contact parts to perform electric field transfer. In the apparatus, the transfer belt has a light-transmitting property, and a light irradiating unit is provided for irradiating light to a corresponding portion of the transfer belt that presses the transfer paper against the image carrier during the electric field transfer. According to claim 7, the image carrier is provided with a transfer belt which is pressed against the image carrier and is supported by at least two tension rollers including the transfer paper separating position. In a transfer device of an image forming apparatus that performs electric field transfer by sandwiching and passing paper,
The tension roller arranged at the transfer paper separating position is
A portion of the transfer belt has a convex portion having a diameter slightly larger than that of the roller, and the transfer belt is neutralized at a position different from the portion in contact with the tension roller having the convex portion. Further, in claim 8, an image carrier and a transfer unit that is in pressure contact with the image carrier are provided,
In a transfer device of an image forming apparatus for performing electric field transfer by sandwiching / passing a transfer paper between these pressure contact parts, the transfer means reduces the resistance value by pressurization, decreases the resistance value by light irradiation, or Being composed of a member having at least two of the respective properties of having transparency.

According to a ninth aspect of the present invention, an image carrier, an intermediate transfer belt that is in pressure contact with the image carrier, and a transfer unit that is in pressure contact with the intermediate transfer belt are provided, and a pressure contact portion between the intermediate transfer belt and the transfer unit is provided. In a transfer device of an image forming apparatus that performs electric field transfer by sandwiching and passing a transfer sheet between the intermediate transfer belt and the intermediate transfer belt, the intermediate transfer belt is made of a member whose resistance value is reduced by pressurization. The belt is made of a member whose resistance value is reduced by light irradiation, and the intermediate transfer belt according to claim 11 has a volume specific resistance value of 10 ⁸ to 10 ¹⁷ Ω · cm and a light transmittance. And a light irradiating means for irradiating light to a portion of the belt which is in pressure contact with the image carrier when the toner image is transferred from the image carrier to the intermediate transfer belt,
Further, in claim 12, the intermediate transfer belt has at least two characteristics among the characteristics that the resistance value is decreased by pressurization, the resistance value is decreased by light irradiation, or that the intermediate transfer belt is light transmissive. It consists of members.

[0010]

Therefore, according to the first aspect, the portion of the transfer means used for the electric field transfer is pressed by the charge removing means to reduce the resistance before it is used in the next transfer, so that the charge is efficiently removed. Further, in claim 2, the transfer belt surface potential at the position of the upstream pressure contact roller at the time of the electric field transfer is made lower than the transfer belt surface potential at the position of the downstream pressure contact roller, or is shifted in a direction opposite to the transfer polarity. By maintaining the surface potential, the transfer belt resistance is reduced in the transfer nip region without applying an electric field on the upstream side of the transfer nip.

According to a third aspect of the present invention, when the electric field is transferred,
By irradiating the corresponding portion of the transfer means that presses the transfer paper against the image carrier by the light irradiation means, the resistance is high on the upstream side of the transfer nip and low on the transfer nip portion, and the transfer efficiency is improved. Further, in claim 4, the light irradiation and static elimination means performs light irradiation and static elimination on the portion of the transfer means after the electric field transfer is finished, before the next electric field transfer is performed. The resistance is remarkably reduced and the charge is efficiently removed. Further, in the fifth aspect, the light irradiation charge removal is performed at least before the cleaning step of the transfer unit, so that efficient charge removal is performed before the cleaning, and cleaning is facilitated.

According to a sixth aspect of the present invention, during the electric field transfer,
By irradiating the corresponding portion of the transfer belt that presses the transfer paper to the image carrier with light by the light irradiation means,
The image carrier is irradiated with light through the transfer belt and the transfer paper,
In a positive developed image, the surface potential of the image carrier is attenuated and the transfer rate is improved. Further, in claim 7, the transfer paper is easily separated by the convex portion of the tension roller arranged at the transfer paper separating position and having a diameter slightly larger than the diameter of the roller, and the charge removal of the transfer belt is performed. By performing the transfer at a position different from the portion having the convex portion in contact with the tension roller, the transfer belt is uniformly discharged. Further, in claim 8, among the respective characteristics of the transfer means, the resistance value is decreased by pressurization, the resistance value is decreased by light irradiation, or the property is light transmissive.
By having at least two characteristics together and having a composite function, it contributes to downsizing and cost reduction of the device.

According to a ninth aspect of the invention, the intermediate transfer belt made of a member whose resistance value decreases by pressurization can be obtained by controlling the pressurization of a necessary resistance value, and it is easy to obtain the conditions for obtaining good transfer. Can be set to. Further, in the tenth aspect, the intermediate transfer belt made of a member whose resistance value is reduced by light irradiation can be obtained by controlling the light irradiation amount to obtain a necessary resistance, and the conditions for obtaining good transfer can be easily set. . Further, in claim 11, the volume resistivity value is 10
^{When the} toner image is transferred from the image carrier to the intermediate transfer belt of ⁸ to 10 ¹⁷ Ω · cm, which is made of a light-transmissive member, the portion of the belt that is in pressure contact with the image carrier is irradiated with light. As a result, the light transmitted through the transfer paper reaches the image carrier, and in the case of a positive developed image, the surface potential of the image carrier below the toner image is reduced, and the transfer efficiency is improved. Further, in claim 12, the intermediate transfer belt has at least two characteristics among the characteristics that the resistance value is reduced by pressurization, the resistance value is reduced by light irradiation, or that the intermediate transfer belt is light transmissive. By having multiple combined functions, it contributes to downsizing and cost reduction of the device.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a photosensitive drum 1 which is an image carrier
In proximity to or in contact with the separation claw 60 of the transfer paper P, the cleaning device 61, the charge eliminating lamp 2, the charging charger 3,
An image exposure unit 4 for forming an electrostatic latent image on the photosensitive drum 1,
A developing device 5 and a transfer belt 7 which is a part of a transfer belt unit 6 which is a transfer unit are arranged. The transfer belt 7 is an endless belt which is supported by a transfer voltage applying roller 8 and a tension roller 13, and at a predetermined position below the transfer belt 7, charge removing rollers 11 and 12 for performing charge removal of the transfer belt 7 are nipped and pressed. It is arranged in the shape of. A transfer power source 9 is connected to the transfer voltage applying roller 8, and a transfer power source output control system 10 is connected to the transfer power source 9.

The transfer belt 7 is 10 ¹⁰ Ω without pressure.
-It is desirable that the material has a volume resistivity of cm or more, and the transfer voltage applying roller 8 presses a predetermined pressure (preferably 0.1 N / cm ² or more) by one digit or more, and most of the materials are those whose volume resistivity decreases. Is configured. However, in order to reduce the surface friction coefficient and to prevent leakage, the surface is coated with a thin film of a low friction coefficient substance or high resistance substance having a thickness of several μm to several tens of μm.

Further, a cleaning blade 14 which contacts the tension roller 13 via the transfer belt 7 and cleans the transfer belt 7 is arranged, and the recovery coil 6 is provided below the cleaning blade 14.
A toner receiver 63 containing 2 is arranged. The transfer belt unit 6, the transfer belt 7, the transfer voltage applying roller 8, the tension roller 13, the charge eliminating rollers 11 and 12, the cleaning blade 14, and the like.

Further, the transfer belt 7 is provided on the transfer paper P conveyance path.
A registration roller 64 is arranged on the upstream side of. In the above structure, the original document illuminated by the halogen lamp (not shown) is projected onto the photosensitive drum 1 by the image exposure unit 4. At this time, the negative charge on the photosensitive drum 1 disappears due to the intensity of light, and an electrostatic latent image is formed. Next, the developing device 5 attaches toner to the electrostatic latent image on the photosensitive drum 1 to form a visible image. A negative bias voltage lower than the charging potential of the photoconductor drum 1 is applied to a developing sleeve (not shown) in the developing device 5, so that the toner positively positively charged by the stirring of the developing carrier is transferred to the latent image on the photoconductor drum 1. It is attached to the image to form the image.

In the transfer process, the registration roller 64
The transfer sheet P that has been conveyed to and is on standby is sent out from the registration roller 64 in time with the toner image on the photosensitive drum 1. At the same time when the leading edge of the transfer paper P reaches the vicinity of the contact portion between the photosensitive drum 1 and the transfer belt 7, the transfer bias voltage is transferred from the transfer power supply 9 to the transfer voltage applying roller 8.
Is applied to the transfer belt 7, and an electric charge having a polarity opposite to the polarity of the toner on the photosensitive drum 1 is applied to the transfer belt 7 to perform the transfer. In this embodiment, a positive toner is developed on the photosensitive drum 1 whose surface is charged to −800 V, and a voltage of −3 Kv to −7 Kv is applied to the transfer voltage applying roller 8 to transfer the toner to the transfer paper P.

When a transfer bias voltage is applied by the transfer voltage applying roller 8, the transfer paper P is charged and the photosensitive drum 1
At the same time that the toner image of is transferred to the transfer paper P, an electrostatic force is generated by the true charge on the transfer belt 8 and the polarization charge of the transfer paper P, and the transfer paper P is adsorbed on the transfer belt 8 and exposed. Separate from body drum 1. The transfer paper P that is transferred and conveyed is
The charge removing rollers 11 and 12 gradually remove the charge via the transfer belt 7, and the charge amount is relaxed. Then, the transfer paper P having the weakened electrostatic attraction is separated from the transfer belt 7 at the position of the tension roller 13. At this time, on the transfer belt 8 being conveyed, toner scattered without being transferred onto the transfer paper P, residual toner directly attached to the transfer belt 8 and paper dust emitted from the transfer paper P are also present. These are scraped off by the cleaning blade 14 and fall on the toner receiver 63. The paper dust and the toner collected in the toner receiver 63 are conveyed from the transfer belt unit 6 to a waste toner collecting bottle (not shown) of the copying machine body by the collecting coil 64.

On the other hand, after the transfer, the toner remaining on the photosensitive drum 1 is scraped off by the cleaning device 61. Finally, in order to erase the residual charges on the photoconductor drum 1 after cleaning, the entire surface is exposed by the discharge lamp 2 to prepare for the next copy.

Next, an embodiment based on claim 1 will be described. At the time of transfer, the transfer voltage is applied by being pressed by the transfer voltage applying roller 8 so that only the contact portion of the transfer belt 7 with the photosensitive drum 1 is in a proper resistance state suitable for transfer. Then, by applying pressure again by the static elimination rollers 11 and 12, the electric resistance is reduced and the static elimination is efficiently performed. As described above, the transfer belt 7 does not cause the discharge phenomenon accompanied by the toner movement at all except for the pressure contact portion with the photosensitive drum 1. However, the portion of which the pressurization state at the time of transfer is released becomes a non-pressurization state while carrying a relatively large amount of residual electric charge, and thus becomes a high resistance state, but is repressurized by the charge eliminating rollers 11 and 12. Has become low resistance.

FIG. 2 shows the case of a transfer roller. In FIG. 2, the transfer roller 15 includes a core portion 15a made of a rigid metal body, an insulating layer 15b, a medium resistance layer 15c of 10 ⁸ to 10 ¹² Ω, and The transfer roller 15 is composed of an elastic layer 15d whose resistance is reduced by pressurization, and the transfer voltage applying roller 8 and the charge eliminating roller 16 are arranged in contact with the transfer roller 15.
It is desirable that the specific resistance of the elastic layer 15d be reduced by one digit or more when a predetermined value or more is applied to the non-pressurized state. By the core portion 15a of the transfer roller 15 and the static elimination roller 16, the elastic layer 15d is pressure-compressed to reduce the volume specific resistance by one digit or more as compared with the non-pressurized state. Reference numeral 65 is an insulating member.

In this structure, the elastic layer 15a of the transfer roller 15 has a low resistance due to the pressure applied by the pressure contact with the photosensitive drum 1, and the discharge phenomenon accompanied by the toner movement does not occur at all except the pressed portion. . Then, as in the embodiment of FIG. 1, the static elimination roller 16 presses again to reduce the electrical resistance and efficiently eliminate static electricity. The circuit resistance Re between the transfer voltage applying roller 8 and the ground (A, middle resistance layer 15b, C, charge eliminating roller 16),
Transfer voltage applying roller 8 and transfer roller 15 in the transfer nip region
Re >> Rt is desirable for the relationship with the circuit resistance Rt between the surfaces (A / medium resistance layer 15b / A / transfer roller 15 surface).

Next, an embodiment based on claim 2 will be described. As shown in FIG. 3, the overall structure is substantially the same as that of the embodiment shown in FIG. 1, but a transfer belt tension roller 28 is used instead of the transfer voltage applying roller 8, and a transfer voltage applying roller 29 is separately transferred. The transfer paper P is provided on the belt 7.
The transfer belt tension roller 28 and the transfer voltage applying roller 29 are used to increase the adhesion between the transfer belt tension roller 28 and the image carrier 1.
The transfer nip width is wide. Then, a static eliminator plate 31 is arranged in place of the static eliminator rollers 11 and 12, and the transfer belt tension roller 28 has constant voltage elements 32 and 3.
3 are connected.

In this structure, the transfer voltage applying roller 2
Reference numeral 9 denotes a photosensitive drum 1 which applies a pressure of 0.1 N / cm ² or more to the transfer belt 7 so as to reduce the volume resistivity of the transfer belt 7.
Since it is strongly pressed against, the transfer efficiency can be kept high, and the transfer rate of the high density image area can be kept at 90% or more in all environments. Further, the voltage of the transfer belt tension roller 28 is kept low (including ground) so that a high electric field cannot be generated between the photosensitive drum 1 and the transfer belt 7 immediately before the formation of the transfer nip. At this time, the transfer belt relationship during transfer voltage applied V ₂₈ of the tension roller 28 and the transfer time of the applied voltage V ₂₉ of the transfer voltage applied roller 29 when V ₂₈ is positive polarity, V _28>
When V ₂₉ > 0 (V) and V ₂₈ has a negative polarity, V ₂₈ <V
₂₉ <0 (V), and | V ₂₈ | is usually 1 to 4 kV, | V ₂₉ |
Is usually 0 to 1 kV.

Next, an embodiment based on claims 3, 4, and 5 will be described with reference to FIG. This embodiment is shown in FIG.
However, the transfer belt 34 preferably has a volume resistivity of 10 ¹⁰ Ω · cm or more in the dark, and its electrical resistance is reduced by light irradiation (may be reduced to one digit or less). It is also preferable to use a material having a photoconductor particle dispersion system. Also,
Not only the transfer voltage applying roller 8 but also the transfer voltage applying roller 36 is provided separately. Then, the transfer voltage applying roller 8
And the tension roller 13 respectively, and inside the transfer belt 34, a transfer area light emitting element 37 serving as a light irradiating means is provided.
And a static elimination area light emitting element 38 which is a light irradiation static elimination means. Further, the tension roller 13 is grounded for static elimination.

In this structure, at the time of transfer, first, the transfer belt 34 acts as a high resistance member on the upstream side of the transfer nip portion, that is, in order to prevent image deterioration such as transfer scattering from occurring. 34. The light is not radiated to the transfer belt 34 from the upstream side, and the resistance is lowered in the transfer nip portion forming area.
Light is emitted by the transfer area light emitting element 37 between the transfer voltage applying roller 8 and the transfer voltage applying roller 36. As a result, the transfer belt 34 with the transfer electric field applied
The resistance is remarkably reduced, and highly efficient transfer is performed.

The transfer belt 34 that has passed through the transfer nip portion is charged, and is neutralized before rotating and returning to the transfer nip again (by the contact type shown in FIG. 1 or the non-contact type by discharge not shown). ) Is required, the static elimination area light emitting element 38 irradiates the transfer belt 34 with light to eliminate static electricity by the tension roller 13 to remarkably reduce its resistance to enhance the static elimination efficiency.

Further, if this optical charge elimination is carried out prior to the cleaning of the transfer belt 34 by the cleaning blade 14, the adhesive force between the transfer belt 34 and the toner is reduced, and the load on the cleaning blade 14 is reduced, which is favorable. Cleaning is performed. Although related to claim 8, when the transfer belt 34 is configured to have not only photoconductivity but also light transmissivity, the irradiated light passes through the transfer belt 34 and further through the transfer paper. In order to reach the photosensitive drum 1, the surface potential of the toner adhering portion is reduced and the transfer efficiency is further improved when the positive developing method in which toner is adhered to the charged portion of the photosensitive drum 1 is used.

Next, an embodiment based on claim 6 will be described. As shown in FIG. 5, this embodiment has substantially the same structure as the embodiment of claim 5 shown in FIG. 4, except that the transfer belt 39 has a light transmitting property. (Mainly volume specific resistance is preferably 10 ⁸ to 10 ¹⁷ Ω · cm), a transfer belt tension roller 28 is arranged instead of the transfer voltage applying roller 8, and the transfer voltage applying roller 3 is used.
6 is that the transfer power source 9 and the transfer power output control system 10 are connected to each other, the static elimination plate 31 is placed in contact with the transfer belt 39, and the static elimination area light emitting element 38 is removed. In this configuration, when the transfer area light emitting element 37 irradiates the transfer nip area with light,
As described above, light is transmitted in the order of the transfer belt 39, the transfer paper P, and the toner image, and in the case of positive development, the surface potential of the toner adhering portion is reduced and the transfer efficiency is improved.

Next, an embodiment based on claim 7 will be described. In this embodiment, as shown in FIG.
The configuration is substantially the same as that of the embodiment of claim 2 shown in FIG. 3, except that a transfer paper separating section tension roller 45 is arranged instead of the tension roller 13, and the cleaning blade 14 is used as a neutralizing plate 31. The point is that they are arranged so as to come into pressure contact with each other via the transfer belt 7. As shown in FIG. 2B, the transfer paper separating section tension roller 45 is provided with a convex portion 45a having a diameter slightly larger than the diameter of the roller 45 near the center in the axial direction. In this configuration, the transfer paper P is the transfer paper separating section tension roller 4
It is easily separated by the convex portion 45a of No. 5. The charge on the transfer belt 7 is removed by the tension roller 4 on the transfer paper separating section.
When the transfer paper P is carried, a non-uniform discharge that disturbs the unfixed toner image occurs when the transfer paper P is carried. Therefore, after the transfer paper P is separated, the charge removal plate 13 and the cleaning blade 14 are used. Eliminates static electricity efficiently while reducing transfer resistance under pressure.

Next, an embodiment based on claim 9 will be described with reference to FIG. A developing device 27 and an intermediate transfer belt 17, which is a transfer unit, are arranged in contact with the photosensitive drum 1. The intermediate transfer belt 17 is an endless belt and is supported by an intermediate transfer voltage applying roller 23 and a transfer roller counter electrode roller 24. At a predetermined position on the inner surface side of the intermediate transfer belt 17, the intermediate transfer belt 17 is neutralized and the cleaning blade 14 is removed. A static elimination roller 25 that applies pressure is arranged in contact. The intermediate transfer power supply 18 is connected to the intermediate transfer voltage applying roller 23.
However, the intermediate transfer power source 18 includes an intermediate transfer power source output control system 19
Are connected respectively. T is toner.

This intermediate transfer belt 17 has a volume resistivity of a predetermined pressure (preferably 0.1) when no pressure is applied.
Most of them are composed of materials whose volume resistivity decreases by more than one digit at N / cm ² or more). Further, a transfer roller 20 that is in contact with the transfer roller counter electrode roller 24 via the intermediate transfer belt 17 is arranged.
However, a transfer power supply output control system 10 is connected to the transfer power supply 9. The transfer roller 20 has a volume resistivity of a predetermined pressure (preferably 0.1) in a non-pressurized state.
(N / cm ² or more), it is desirable to use a material whose volume resistivity decreases by one digit or more. Then, the cleaning blade 14 separates from the intermediate transfer belt 17 when the untransferred image is carried on the surface of the intermediate transfer belt 17, and the transfer paper P
When the toner residual image is cleaned after the toner image is transferred to the belt 17, the belt 17 comes into contact with the belt 17.

Further, the developing device 27 includes a yellow developing section 2
7a, a magenta developing section 27b, a cyan developing section 27c, and a black developing section 27d. In this configuration, the resistance value of the intermediate transfer belt 17 is reduced by
When the intermediate transfer voltage is applied by the intermediate transfer power supply 18 at the pressure contact portion between the photosensitive drum 1 and the intermediate transfer voltage application roller 23, and at the contact portion between the transfer roller counter electrode roller 24 and the transfer roller 20 by the transfer power supply 9. When the transfer voltage is applied to transfer the intermediate transfer image to the transfer paper P and when the charge is removed by the charge removing roller 25, the transfer process and the charge removing process are efficiently performed.

Next, an embodiment based on claim 10 will be described. As shown in FIG. 8, this embodiment has substantially the same structure as the embodiment of claim 9 shown in FIG. 7, except that the intermediate transfer voltage applying roller 23 and the discharging roller 25 are in the vicinity. In the intermediate transfer area light emitting element 3 which is a light irradiation means
7a, the transfer area light emitting element 37, and the static elimination area light emitting element 38 are respectively arranged, and the intermediate transfer belt 46 is made of a material whose resistance is reduced by light irradiation. Intermediate transfer area light emitting element 37a and neutralization area light emitting element 38
Is preferably arranged so that light does not leak to the upstream side of the photosensitive drum 1. Incidentally, 32 and 33 are constant voltage elements. With this configuration, during the intermediate transfer and the transfer to the transfer paper P, the resistance of the intermediate transfer belt 46 is prevented from decreasing and the high electric field is not applied at the intermediate transfer nip portion and the upstream side of the transfer nip portion. From the downstream side to the intermediate transfer area light emitting element 3
Light is radiated by 7a and the transfer area light emitting element 37 to reduce the resistance value of the intermediate transfer belt 17 in the transfer nip area. Further, also on the downstream side of the static elimination roller 25, light is emitted by the static elimination area light emitting element 38 to reduce the resistance value, and the static elimination is efficiently performed.

Next, an embodiment based on claim 11 will be described. As shown in FIG. 9, this embodiment has substantially the same structure as that of the embodiment of claim 10 shown in FIG. 8, except that a material that transmits light instead of the intermediate transfer belt 46 is used. The intermediate transfer belt 49 configured as described above is used, and the intermediate transfer area light emitting element 37a is arranged upstream of the intermediate transfer voltage applying roller 23 and the transfer nip portion of the photosensitive drum 1. In this structure, during intermediate transfer, the intermediate transfer area light emitting element 37a irradiates light, and the light transmitted through the intermediate transfer belt 49 reaches the photoconductor drum 1 and, in the case of a positive developed image, the toner image lower part. Since the surface potential of the photosensitive drum 1 is reduced, the transfer efficiency is improved.

[0037]

As described above, according to the first aspect of the present invention, the charge eliminating means is arranged at a position where the portion of the transfer means used for the electric field transfer is pressurized before being used for the next transfer. Therefore, the resistance can be reduced by the pressurization at the time of charge removal, the charge can be removed efficiently, and a good transferred image can be obtained. Further, according to claim 2, two of the plurality of tension rollers are arranged in the rotational direction of the image bearing member, and the transfer belts are arranged so as to be in pressure contact with the image bearing member. A side pressure contact roller and a downstream pressure contact roller, and a transfer belt surface potential at the position of the upstream pressure contact roller at the time of the electric field transfer is lower than a transfer belt surface potential at the position of the downstream pressure contact roller;
Alternatively, since the surface potential shifted in the direction opposite to the transfer polarity is maintained, the transfer belt resistance can be reduced in the transfer nip area without applying an electric field that causes transfer dust on the upstream side of the transfer nip, and good transfer scattering can be obtained. A transfer image can be obtained.

According to a third aspect of the present invention, the transfer means comprises a member whose resistance value is reduced by light irradiation, and which corresponds to the transfer means for pressing the transfer paper against the image carrier during the electric field transfer. Since the light irradiation means for irradiating light to the portion is provided, at the time of transfer, high resistance can be achieved on the upstream side of the transfer nip and low resistance can be achieved at the transfer nip portion, and a good transferred image with less transfer dust can be obtained. it can. Further, according to claim 4, since the light irradiation charge-eliminating means for performing light irradiation charge-eliminating before using for the next electric field transfer is arranged in the portion of the transfer means where the electric field transfer is completed, The transfer belt resistance can be remarkably reduced by light irradiation at the time of charge removal, and the charge can be efficiently removed. According to the fifth aspect, since the light irradiation charge removal is performed at least before the cleaning step of the transfer unit, efficient charge removal is performed before cleaning, and good cleaning can be performed with a low load. It is possible to reduce the driving torque of the transfer unit and improve the durability of the transfer belt.

According to a sixth aspect of the present invention, the transfer belt has a light-transmitting property, and at the time of the electric field transfer, light is applied to a corresponding portion of the transfer belt that presses the transfer paper against the image carrier. Since the light irradiating means for irradiating the image carrier is provided, the image carrier is irradiated with light through the transfer belt and the transfer paper, and in the positive development image, the surface potential of the image carrier can be attenuated to improve the transfer rate. In addition, the inside of the transfer belt can be used as a place for installing the static elimination light source of the image carrier before or after the transfer. Further, according to claim 7, the tension roller arranged at the transfer paper separating position has a convex portion having a diameter slightly larger than the diameter of the roller in a part thereof, and Since the static elimination is performed at a position different from the portion in contact with the tension roller having the convex portion, the static elimination of the transfer belt can be performed uniformly,
It is possible to stably maintain good transferability.

According to the eighth aspect, the transfer means has at least 2 of the characteristics that the resistance value is reduced by pressurization, the resistance value is reduced by light irradiation, or the light transmission property is exhibited. Since the transfer means has a composite function, it is easy to construct a system that contributes to downsizing and cost reduction of the apparatus. Further, according to claim 9, since the intermediate transfer belt is composed of a member whose resistance value is reduced by pressurization, a necessary resistance value can be obtained by controlling pressurization, and good transfer can be obtained. The required conditions can be easily set. Further, according to claim 10, since the intermediate transfer belt is made of a member whose resistance value is reduced by light irradiation, the resistance of the intermediate transfer belt can be controlled by the light irradiation amount, and good transfer can be obtained. Conditions can be set easily.

According to the eleventh aspect, the intermediate transfer belt has a volume specific resistance value of 10 ⁸ to 10 ¹⁷ Ω · cm, is made of a light transmissive member, and is the image carrier. When the toner image is transferred from the intermediate transfer belt to the intermediate transfer belt, light is irradiated to a portion of the belt that is in pressure contact with the image carrier, so that the pre-transfer or simultaneous static elimination light source can be arranged inside the transfer belt, and the apparatus becomes large in size. A good transferred image can be obtained without According to claim 12, the intermediate transfer belt has at least two of the characteristics that the resistance value is reduced by pressurization, the resistance value is reduced by light irradiation, or that the intermediate transfer belt has light transmittance. Since the intermediate transfer belt has a composite function, it becomes easy to configure a system that contributes to downsizing and cost reduction of the apparatus.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a transfer device according to an embodiment of the present invention (claim 1).

FIG. 2 is a schematic configuration diagram showing another embodiment of the transfer device according to claim 1.

FIG. 3 is a schematic configuration diagram showing a transfer device according to a second aspect.

FIG. 4 is a schematic configuration diagram showing a transfer device according to claims 3, 4, and 5.

FIG. 5 is a schematic configuration diagram showing a transfer device according to a sixth aspect.

FIG. 6 is a schematic configuration diagram showing a transfer device according to a seventh aspect.

FIG. 7 is a schematic configuration diagram showing a transfer device according to a ninth aspect.

FIG. 8 is a schematic configuration diagram showing a transfer device according to a tenth aspect.

FIG. 9 is a schematic configuration diagram showing a transfer device according to an eleventh aspect.

[Explanation of symbols]

 1 image carrier 7,15, etc transfer means 7,34,39 transfer belt 13,28,29 tension roller 28 upstream pressure contact roller 29 downstream pressure contact roller 11,12,31 charge removal means 37,37a, 38 light irradiation means 45a Convex part 17,46,49 Intermediate transfer belt

Claims (12)

[Claims] 1. An image carrier, a transfer unit composed of a member that is brought into pressure contact with the image carrier and whose resistance value is reduced by pressurization, and a destaticizing unit that eliminates electric charges carried by the transfer unit. In the transfer device of the image forming apparatus for performing the electric field transfer by sandwiching / passing the transfer paper between these pressure contact portions, the charge eliminating unit uses the portion of the transfer unit used for the electric field transfer in the next transfer. A transfer device for an image forming apparatus, wherein the transfer device is arranged at a position where pressure is applied to the front. 2. An image carrier, and a transfer belt made of a member which is in pressure contact with the image carrier and is supported by a plurality of tension rollers and whose resistance value is reduced by pressurization. In a transfer device of an image forming apparatus that performs electric field transfer by sandwiching and passing paper, two of the plurality of tension rollers are arranged in a rotation direction of the image carrier, and each of the plurality of tension rollers carries an image carrier of the transfer belt. They are arranged so as to be in pressure contact with the body to serve as an upstream pressure contact roller and a downstream pressure contact roller, and the transfer belt surface potential at the position of the upstream pressure contact roller at the time of the electric field transfer is the surface of the transfer belt at the position of the downstream pressure contact roller. Lower potential than potential,
Alternatively, the transfer device of the image forming apparatus is characterized in that the surface potential shifted in the direction opposite to the transfer polarity is maintained. 3. A transfer device of an image forming apparatus, comprising: an image carrier and a transfer means that is in pressure contact with the image carrier; and a transfer paper is sandwiched and passed through these pressure contact parts to perform electric field transfer. The means includes a member whose resistance value is reduced by light irradiation, and is provided with light irradiation means for irradiating light to a corresponding portion of the transfer means that presses the transfer paper against the image carrier during the electric field transfer. And a transfer device for an image forming apparatus. 4. A light irradiation charge-eliminating means for performing light irradiation charge-eliminating before using for the next electric field transfer is arranged in a portion of the transfer means where the electric field transfer has been completed. Item 3. A transfer device of the image forming apparatus according to item 3. 5. The transfer device of an image forming apparatus according to claim 4, wherein the light irradiation charge removal is performed at least before a cleaning step of the transfer means. 6. A transfer device of an image forming apparatus, comprising: an image carrier; and a transfer belt which is in pressure contact with the image carrier, wherein transfer paper is sandwiched and passed through these pressure contact parts to perform electric field transfer. The belt has a light-transmitting property, and is provided with a light irradiating unit that irradiates light to a corresponding portion of the transfer belt that presses the transfer paper against the image carrier during the electric field transfer. Transfer device of image forming apparatus. 7. An image carrier and a transfer belt which is pressed against the image carrier and is supported by at least two tension rollers including a transfer paper separating position. The transfer paper is sandwiched between these pressure contact parts. In a transfer device of an image forming apparatus that performs electric field transfer by passing, the tension roller arranged at the transfer paper separating position is
A portion of the transfer belt has a convex portion having a diameter slightly larger than that of the roller, and the transfer belt is neutralized at a position different from the portion in contact with the tension roller having the convex portion. A transfer device of an image forming apparatus, which is characterized in that 8. A transfer device of an image forming apparatus, comprising: an image carrier and a transfer means that is in pressure contact with the image carrier, and a transfer paper is sandwiched and passed through these pressure contact parts to perform electric field transfer. The image forming device is characterized in that the means comprises a member having at least two characteristics among the characteristics that the resistance value is decreased by pressurization, the resistance value is decreased by light irradiation, or the light transmittance is present. Equipment transfer device. 9. An image carrier, an intermediate transfer belt which is in pressure contact with the image carrier, and a transfer unit which is in pressure contact with the intermediate transfer belt, and a transfer sheet is sandwiched between the intermediate transfer belt and the pressure contact portion of the transfer unit. A transfer device for an image forming apparatus, which performs electric field transfer by passing the intermediate transfer belt, wherein the intermediate transfer belt is made of a member whose resistance value is reduced by pressurization. 10. The transfer device of the image forming apparatus according to claim 9, wherein the intermediate transfer belt is made of a member whose resistance value is reduced by light irradiation. 11. The intermediate transfer belt has a volume resistivity value of 10 ⁸ to 10 ¹⁷ Ω · cm, is made of a light-transmissive member, and is a toner image from the image carrier to the intermediate transfer belt. 10. The transfer device of the image forming apparatus according to claim 9, further comprising: a light irradiation unit that irradiates light to a portion of the belt that is in pressure contact with the image carrier when the image is transferred. 12. The intermediate transfer belt is made of a member having at least two of the characteristics that the resistance value is reduced by pressurization, the resistance value is reduced by light irradiation, or that the intermediate transfer belt has optical transparency. The transfer device of the image forming apparatus according to claim 9, wherein the transfer device is formed of: