JPH09319272A - Device and method for image forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and method for an image forming capable of forming the image of excellent quality by preventing charge up of the developer and scattering of the developer onto the non image part. SOLUTION: In this device, each of process units 100 is severally provided with a pre-transfer static eliminator 3 arranged between a transfer position where respective developer image on a photoreceptor drum 1 is transferred to a paper sheet P and a developing device 9. This pre-transfer static discharger 3 is severally arranged on the position so as to let a surface potential of the photoreceptor drum 1 in the transfer position decreased to the extent of not becoming below the half-tone potential, by discharging the potential on the non-image part. In other words, the respective pre-transfer static eliminator 3 is arranged on the position so as to making the developer stuck on the image part possible to be transferred on the paper sheet P without being charged up and without scattering.

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, and more particularly, to a developer image developed for each color component on an image carrier provided in an electrophotographic color copying machine, a color printer or the like. The present invention relates to an image forming apparatus that repeatedly forms multiple images on a transfer material to form an image.

[0002]

2. Description of the Related Art As a conventional method for forming a full-color image, an independent photoconductor for each color component,
An image forming apparatus including first to fourth stations including an exposure device, a developing device, a transfer device, and a cleaning device has been put into practical use.

In this image forming apparatus, four photoconductors provided in each station are arranged horizontally, and the transfer material is conveyed by an insulating belt and a corona charger that convey the transfer material so as to contact the respective photoconductors. The developer images of the respective colors are transferred in multiple layers. That is, the developer image formed on each photoconductor for each color component is repeatedly multi-transferred to the transfer material to form a color image.

However, in the transfer device using such a corona charger, the transfer bias is 6 to 9 kV.
There is a problem that the voltage is extremely high and dangerous, and a large amount of ozone harmful to the human body is generated.

Since an insulating belt is used,
Since the belt carrier is charged by the repeated application of the transfer bias, it is necessary to use the charge eliminator to remove the charge from the insulating belt.

Further, in such multiple transfer, for example, in the first station, the developer image formed by the first color developer is transferred to the transfer material, and then in the second station, the transfer image is transferred. When the developer image formed by the second color developer is transferred to the material in multiple,
Discharge is generated in the minute gap between the photoconductor and the transfer material at the station, and the developer transferred onto the transfer material is charged up at the first station. The charge-up of the developer image on the material to be transferred weakens the transfer electric field at the third station, which causes a problem that the transfer efficiency is deteriorated.

That is, in the case of multiple transfer, discharge between the photoconductor and the material to be transferred at the second and third stations causes the developer transferred at the preceding station to be charged up, so that the following station is charged. However, there is a problem that the transfer electric field is weakened.

In order to solve the above problems, Japanese Patent Publication No. 10625/1985 and Japanese Patent Laid-Open No. 280530/1992.
According to the publication, there is proposed a transfer device capable of executing a transfer process at a relatively low voltage of about 1 to 2 kV and capable of reducing the amount of ozone generated. This transfer device has a conductive roller and a semiconductive belt in which conductive carbon is dispersed in an insulating resin. Since this semi-conductive belt does not continue to be charged, it does not require a static eliminator to neutralize the belt.

Further, at the time of transfer for transferring the developer image, in order to prevent the transferred material from being electrostatically adsorbed to the charged photosensitive material after the contact between the photosensitive material and the transferred material, Prior to transferring the developer image to the transfer material, there is known a technique of applying a pre-transfer light erasing device that irradiates a light beam to eliminate static electricity on an unexposed area, that is, a non-image area where the developer is not attached. There is.

[0010]

However, in such a conventional pre-transfer photo-erasing device, the potential of the photo-conductor surface, especially the unexposed portion, is changed by irradiating the photo-conductor with the charge-eliminating light.
The potential before the charging is lowered, and it is not possible to control it to an arbitrary potential.

Therefore, in order to prevent the charge-up of the developer, even if the pre-transfer photo-erasing device is applied to prevent the discharge between the photosensitive member and the transfer material, the potential of the unexposed portion is exposed. The potential becomes lower than that of the image portion where the developer is attached, that is, the developer attached to the image portion is scattered to the non-image portion side.

As described above, the scattering of the developer on the non-image area causes the problem that the image quality of the image formed by the multi-transfer of the developer of each color component is deteriorated.

Therefore, an object of the present invention is to prevent the charge-up of the developer and the scattering of the developer to the non-image portion, thereby forming an image of good quality and an image forming apparatus. To provide a method.

[0014]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned problems, and an image carrier which is rotatably provided at a rotational peripheral speed v and holds an image corresponding to image data has a predetermined initial stage. Charging means for charging to a surface potential, and exposing means for forming an electrostatic latent image corresponding to image data on the image carrier by irradiating the image carrier charged by the charging means with light to expose the image carrier. Developing means for developing the electrostatic latent image formed on the image bearing member to form a developer image,
A transfer unit that transfers the developer image formed on the image carrier to a transfer material at a predetermined transfer position, and is located between the position where the developing unit is arranged and the transfer position. A charge removing unit for removing charge from the body, the initial surface potential of the image carrier is V0, the residual potential after charge removal is Ver, and the surface potential of the image carrier after charge removal by the charge removing unit is Ver + (V0 If the time required to decay to −Ver) / 2 is t and the time required to decay to Ver is t ′, the distance A from the position where the charge eliminating means is arranged to the transfer position is v × t. = L, v × t ′ = L ′,
The present invention provides an image forming apparatus characterized by being defined in a range represented by L <A <L '.

According to the invention, the first developer image forming means for forming a first developer image corresponding to the first color component of the image data on the first image carrier, and the first developer image forming means. A first transfer means for transferring the first developer image formed by the first developer image forming means onto the transfer material, and a second image carrier rotatably provided at a rotational peripheral speed v. After charging to a predetermined initial surface potential and exposing the charged image carrier to form an electrostatic latent image corresponding to the second color component of the image data, the electrostatic latent image is developed. A second developer image forming means for forming a second developer image by means of static electricity, and a charge eliminating means for removing electricity from the image carrier carrying the second developer image formed by the second developer image forming means. Means and a second developer image on the second image carrier from which the charge is removed by the charge removing means, Second transfer means for transferring onto the transferred material to be transferred, wherein the initial surface potential of the second image carrier is V0, the residual potential after static elimination is Ver, and static elimination is performed by the static elimination means. When the time required for the surface potential of the second image carrier after being attenuated to Ver + (V0-Ver) / 2 is t, and the time required for it to be attenuated to Ver is t ', the static elimination means is described. To the transfer position by the second transfer means is v × t = L, v ×
When t ′ = L ′, there is provided an image forming apparatus characterized by being defined in a range represented by L <A <L ′.

Further, according to the present invention, first developer image forming means for forming a first developer image corresponding to the first color component of the image data on the first image carrier, and the first image forming means. First transfer means for bringing the transfer material into contact with the image carrier and transferring the first developer image onto the transfer material, and applying a first transfer voltage to the first transfer means. The first image applying means for charging and the second image bearing member rotatably provided at the rotational peripheral speed v are charged to a predetermined initial surface potential, and the charged image bearing member is exposed to expose the image. Second developer image forming means for forming an electrostatic latent image corresponding to the second color component of the data and then developing the electrostatic latent image to form a second developer image;
A charge removing unit for removing charge from the image bearing member carrying the second developer image formed by the second developer image forming unit;
The second image bearing member, which has been subjected to the charge removal by the charge removing means, is brought into contact with the transfer material on which the first developer image is transferred, and the second developer is applied on the transfer material. A second transfer means for transferring an image and a second voltage application means for applying a second transfer voltage to the second transfer means are provided, and the initial surface potential of the second image carrier is V0. , The residual potential after static elimination is V
er, and the second charge is removed by the charge removing means.
Surface potential of the image carrier of Ver + (V0-Ver) / 2
When the time required to decay to t is t and the time required to decay to Ver is t ′, the distance A from the charge eliminating means to the transfer position by the second transfer means is v × t.
= L, v × t ′ = L ′, there is provided an image forming apparatus characterized by being defined in a range represented by L <A <L ′.

Furthermore, according to the present invention, the first developer image corresponding to the first color component of the image data is formed on the image carrier rotatably provided at the rotational peripheral speed v. A developer image forming unit and the image carrier are charged to a predetermined initial surface potential, and the charged image carrier is exposed to form an electrostatic latent image corresponding to the second color component of the image data. After being formed, the electrostatic latent image is developed to form a second developer image, and a second developer image forming means, and a second developer formed by the second developer image forming means. A charge removing unit for removing charge from the image bearing member carrying an image, and an image bearing member with the charge removed by the charge removing unit after transferring the first developer image onto the transfer target member. A transfer unit for transferring the second developer image above multiple times, and the initial surface potential of the image carrier is V0, The residual potential after charging is set to Ver, and the time required for the surface potential of the image carrier after being discharged by the discharging unit to decrease to Ver + (V0-Ver) / 2 is reduced to t and Ver. The time required is t '
Then, the distance A from the charge eliminating means to the transfer position by the transfer means is v × t = L, v × t ′ = L ′,
There is provided an image forming apparatus characterized by being defined in a range represented by L <A <L '.

Furthermore, according to the present invention, the charge generating portion and the charge transporting portion are evenly dispersed in one layer while being provided so as to be rotatable at the rotational peripheral velocity v so as to hold an image corresponding to the image data. Charging means for charging the image carrier formed by the single-layer type organic photoconductor to a predetermined initial surface potential, and by exposing the image carrier charged by the charging means with light to expose it. An exposure unit that forms an electrostatic latent image corresponding to image data on the image carrier, a developing unit that develops the electrostatic latent image formed on the image carrier to form a developer image, and the image carrier Transfer means for transferring the developer image formed on the transfer material to a transfer material at a predetermined transfer position, and is located between the position where the developing means is arranged and the transfer position, and neutralizes the image carrier. Neutralizing means, the initial stage of the image carrier Assuming that the surface potential is V0 and the residual potential after static elimination is Ver, the time required for the surface potential of the image bearing member after being neutralized by the static eliminating means to decay to Ver + (V0-Ver) / 2 is t and Ver. Assuming that the time required for the attenuation is t ′, the distance A from the position where the static eliminating unit is arranged to the transfer position is v × t = L, v ×
When t ′ = L ′, there is provided an image forming apparatus characterized by being defined in a range represented by L <A <L ′.

Furthermore, according to the present invention, an electrostatic latent image is formed by uniformly charging the image bearing member to the initial surface potential V0 and irradiating the image bearing member with light for exposure. A latent image forming step, a developing step of forming a developer image by developing the electrostatic latent image, a charge removing step of removing charge from the image carrier on which the developer image is formed, and a charge removing step of the image carrier. When the residual potential after static elimination is Ver, when the surface potential of the image carrier is between Ver + (V0-Ver) / 2 and Ver, the development formed on the image carrier on the transfer material. An image forming method comprising: a transfer step of transferring an agent image.

Further, according to the present invention, the first image carrier is uniformly charged to a predetermined potential, and the first image carrier is irradiated with light corresponding to image data to be exposed. An electrostatic latent image corresponding to the first color component of image data is formed, and the electrostatic latent image is developed with a developer of the first color component to form a first developer image. Developer image forming step, and a first image formed on the first image carrier
The first transfer step of transferring the developer image of 1 to the transfer material, and the second image carrier is uniformly charged to the initial surface potential V0, and light corresponding to the image data is applied to the second image carrier. By irradiating and exposing, an electrostatic latent image corresponding to the second color component of the image data is formed, and the electrostatic latent image is developed with a developer of the second color component to form a second developer. Second forming an image
Second developer image forming step, a charge removing step of removing charge from the second image carrier on which the second developer image is formed,
When the residual potential after static elimination of the image carrier of is set to Ver,
The surface potential of the second image carrier is Ver + (V0-Ve
r) / 2 to Ver, the second developer image formed on the second image carrier is transferred to the transfer material to which the first developer image is transferred. Transfer process of
An image forming method comprising:

Still further, according to the present invention, the image carrier is uniformly charged to a predetermined potential, and the image carrier is irradiated with light corresponding to the image data to be exposed to expose the first image data. A first developer image forming step of forming an electrostatic latent image corresponding to a color component and developing the electrostatic latent image with a developer of a first color component to form a first developer image; , A first transfer step of transferring the first developer image formed on the image carrier to a transfer material, and an initial stage of the image carrier transferred in the first transfer step. The electrostatic latent image corresponding to the second color component of the image data is formed by uniformly charging the surface potential V0 and exposing the image carrier with light corresponding to the image data. Second development for forming a second developer image by developing the latent image with a developer of a second color component An image forming step, a static elimination step of eliminating static electricity by irradiating the image bearing body on which the second developer image is formed with light, and a residual potential after static elimination of the image bearing body is Ver. The surface potential of the image carrier is Ver.
A second transfer image of the second developer image formed on the image bearing member to a transfer material to which the first developer image has been transferred when it is between + (V0-Ver) / 2 and Ver. And an image forming method including: a transfer step.

Furthermore, according to the present invention, an image carrier formed of a single-layer type organic photoconductor in which a charge generating part and a charge transporting part are uniformly dispersed in one layer is made uniform to an initial surface potential V0. And a latent image forming step of forming an electrostatic latent image by irradiating the image bearing member with light to expose it, and a developer image is formed by developing the electrostatic latent image. When the developing step, the static elimination step of neutralizing the image carrier on which the developer image is formed, and the residual potential after static elimination of the image carrier is Ver, the surface potential of the image carrier is Ver + ( V0-Ver) / 2 to Ver, and a transfer step of transferring the developer image formed on the image carrier to the transfer material when the image forming method is provided. It

According to the image forming apparatus and the image forming method of the present invention, the discharging means is arranged between the position where the developing means is arranged and the transfer position to discharge the unexposed portion of the image carrier. The distance A from the position to the transfer position is v × t
= L, v × t ′ = L ′, it is defined within the range represented by L <A <L ′. That is, after the electrostatic latent image formed on the image carrier is developed and the developer image is formed,
By irradiating the light beam by the charge eliminating means, the unexposed portion on the image carrier, that is, the portion which is maintained at the initial potential V0 without being exposed by the exposing means is eliminated. Then, after the surface potential of the unexposed portion is attenuated from the initial potential V0 to Ver + (V0-Ver) / 2 and before the residual potential Ver is reached, the developer image is transferred onto the material to be transferred at a predetermined transfer position by the transfer means. Is transcribed.

For this reason, there is a problem that the developer attached to the exposed portion at the halftone potential level on the image carrier scatters to the unexposed portion which has been reduced to a level below the residual potential Ver by the neutralization. Can be prevented.

Therefore, an image of good quality can be formed on the transfer material. Further, in the image forming apparatus and the image forming method in which a plurality of image carriers are arranged in a predetermined order, the charge eliminating means corresponds to the image carriers arranged after the first stage and before the last stage. Is provided. That is, an image carrier that holds a developer image of a second color component different from the first color component that is transferred and superimposed on the developer image of the first color component that is transferred onto the transfer material. Is provided so as to eliminate the unexposed portion.

Therefore, the developer image of the second color component is first
Of the developer image of the first color component formed on the transfer material by the transfer bias applied when the developer image of the color component is transferred onto the transfer material to be transferred. You can prevent up.

Therefore, when the developer images of the third color component different from the first and second color components are transferred in an overlapping manner, the transfer efficiency of the charged up developer image of the first color component is improved. Deterioration can be prevented, and a plurality of developer images can be transferred in multiple layers onto a single transferred material while maintaining good transfer efficiency. Therefore, a full-color image with good image quality can be provided.

Further, in the image forming apparatus and the image forming method provided with the developing means in which the developers of a plurality of color components are contained in the single image carrier, the charge eliminating means is transferred onto the material to be transferred. Provided so as to neutralize the unexposed portion of the image carrier that holds the developer image of the second color component different from the first color component that is transferred and superimposed on the developer image of the first color component. Has been.

Therefore, the developer image of the second color component is first
Of the developer image of the first color component formed on the transfer material by the transfer bias applied when the developer image of the color component is transferred onto the transfer material to be transferred. You can prevent up.

Therefore, when the developer images of the third color component different from the first and second color components are transferred in an overlapping manner, the transfer efficiency of the charged up developer image of the first color component is improved. Deterioration can be prevented, and a plurality of developer images can be transferred in multiple layers onto a single transferred material while maintaining good transfer efficiency. Therefore, a full-color image with good image quality can be provided.

Furthermore, according to the image forming apparatus and the image forming method, an image carrier using an image carrier formed of a single-layer type organic photoconductor in which a charge generating part and a charge transporting part are uniformly dispersed in one layer is provided. , In the single-layer type organic photoconductor, the charge generated by the charge generating portion existing near the surface can immediately cancel the charge on the surface of the image carrier, but the charge generated in the bulk is the surface of the image carrier. It takes longer to be transported, and the surface potential decays relatively slowly. That is, this single-layer organic photoreceptor is a photoreceptor having a relatively low sensitivity.

Therefore, it becomes easy to control the surface potential of the image carrier. That is, the time t required for the surface potential of the image carrier to decay from the initial surface potential V0 to Ver + (V0-Ver) / 2 and the time t ′ required to decay to the residual potential Ver become longer, and t and The range L <A <L ′ of the installation position of the static eliminator determined by t ′ can be widened.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an image forming apparatus according to the present invention will be described in detail below with reference to the drawings, and FIG. 1 shows an example of a color image forming apparatus of the present invention.

As shown in FIG. 1, this color image forming apparatus has a photosensitive drum 1a which is an image carrier.
The photosensitive drum 1 has a cross-sectional diameter of 40 mm and a width of 2 mm.
It is formed of a 66 mm cylindrical laminated organic photoreceptor. The photosensitive drum 1a is provided so as to be rotatable in a direction indicated by an arrow in FIG.

Around the photoconductor drum 1a, the following mechanism is arranged along the rotation direction of the photoconductor drum. That is, the charging roller 5a that functions as a charging unit that uniformly charges the surface of the photosensitive drum 1a to a predetermined potential is provided in contact with the surface of the photosensitive drum 1a. The charging roller 5a is formed of, for example, a conductive rubber roller.

An exposure device 7a which functions as an exposure means for exposing the charged photosensitive drum 1a to form an electrostatic latent image is disposed downstream of the charging roller 5a. The exposure device 7a has a phosphor disposed on a surface facing the photosensitive drum 1a, and emits the phosphor in accordance with image data, thereby forming an electrostatic latent image on the photosensitive drum 1a. It is formed by a solid scanning head to be formed.

A developing device 9a, which stores a developer of a predetermined color component and functions as a developing means for developing the electrostatic latent image formed by the exposure device 7a by the developer, is arranged downstream of the exposure device 7a. It is set up. The developing device 9a contains, for example, a yellow-based developer.

A pre-transfer charge eliminator which functions as a charge eliminator for radiating a light beam to the photoconductor drum 1a to eliminate charges on the photoconductor drum 1a is provided downstream of the developing device 9a.
That is, the LED lamp 3a is provided.

As shown in FIG. 2, the LED lamp 3a has a plurality of green LEDs 31 having an emission wavelength of 565 nm arranged in a line on a substrate 32. The intensity of the light emitted by the LED lamp 3a is set so that the potential of the photosensitive drum 1a can be sufficiently reduced.

A corona charger or an ion jet, for example, may be applied to this image forming apparatus as another charge removing means for removing the charges on the photosensitive drum. On the downstream side of the LED lamp 3a, there is provided a conveyor belt 11 that is in contact with the photosensitive drum 1a at a predetermined transfer position and that conveys the paper P that is the material to be transferred.

The conveyor belt 11 is made of a semiconductive material and has a width substantially equal to the width of the photosensitive drum 1a. The transport belt 11 is formed in an annular shape, and a tension roller 13 and a drive roller 15 are provided on the upstream side and the downstream side of the transport belt 11, respectively. The transport belt 11 is provided with a tension roller 13
And along the outer circumference of the drive roller 15.

In this color image forming apparatus, the distance between the tension roller 13 and the driving roller 15 is, for example, 300 mm. Tension roller 13
The driving roller 15 is provided rotatably in the directions of arrows i and j in the figure. With the rotation of the drive roller 15, the transport belt 11 is driven in the direction of arrow e in the figure, and the tension roller is driven by the drive of the transport belt 11.

The transport speed of the transport belt 11 is controlled to be equal to the rotation speed of the photosensitive drum 1a. Further, the tension roller 13 and the driving roller 15 are grounded to prevent the semiconductive conveyance belt 11 from being charged.

Further, the photosensitive drum 1a is the conveyor belt 11
A power supply roller 23a functioning as a transfer unit connected to a bias power supply (not shown) is provided at a position facing the photosensitive drum 1a via the conveyor belt 11 at the transfer position in contact with the transfer belt 23. This feeding roller 23
The bias voltage is supplied to the developer image formed on the photosensitive drum 1a via the paper P and the conveyance belt 11 using the a, so that the developer image is transferred onto the paper P.

A blade cleaning device 17a and a discharge lamp 19a are provided downstream of the transfer position between the photosensitive drum 1a and the sheet P. After the transfer of the developer image, the blade cleaning device 17a
The developer remaining on a is scraped off by a blade and removed.

The discharge lamp 19a is formed of a tungsten lamp, and is used to discharge the surface of the photosensitive drum 1a after transfer. The surface of the photosensitive drum 1a is neutralized by the static elimination lamp 19a, one cycle of the image forming process is completed, and the photosensitive drum 1a which has not been charged in the next image forming process is charged again by the charging roller 5a.

The above-mentioned photosensitive drum 1a and charging roller 5
a, exposure device 7a, developing device 9a, pre-transfer static eliminator 3a, blade cleaning device 17a, and static eliminator lamp 19a
As shown in FIG. 1, the color image forming apparatus in which the first process unit 100a is configured by the first process unit 100a, the second process unit 100b, and the second process unit 100b having the same configuration along the transport direction of the transport belt 11,
Third process unit 100c and fourth process unit 100d (hereinafter collectively referred to as process unit 100
And)).

That is, the photoconductor drums 1b, 1c, and 1d (hereinafter collectively referred to as the photoconductor drum 1), which are the same as the photoconductor drum 1a, are provided substantially at the center of each process unit 100.

Further, each process unit 100 has the same charging rollers 5b, 5c, 5d as the charging roller 5a provided in contact with the surface of the photosensitive drum 1 (hereinafter, referred to as "charging roller 5a").
The charging roller 5 is generically called).

Downstream of the charging roller 5, in order,
The same exposure devices 7b, 7c, and 7d as the exposure device 7a (hereinafter collectively referred to as the exposure device 7), and the same developing devices 9b, 9c, and 9d as the developing device 9a (hereinafter collectively referred to as the developing device 9). ), The pre-transfer static eliminator 3a, which is the same as the pre-transfer static eliminator 3a
c, 3d (hereinafter, collectively referred to as pre-transfer static eliminator 3), blade cleaning devices 17b, 17c, 17d (hereinafter collectively referred to as blade cleaning device 17), which are the same as the blade cleaning device 17a, and a static elimination lamp. The same static elimination lamps 19b, 19c, and 19d as 19a (hereinafter collectively referred to as static elimination lamp 19) are provided.

Each developing device 9 contains a developer corresponding to a different color component. For example, the first process unit 1
The developing device 9a of 00a contains a first color component, for example, a yellow-based developer. Second process unit 10
The developing device 9b of 0b stores a second color component, for example, a magenta-based developer. Third process unit 100
The developing device 9c for c stores a third color component, for example, a cyan-based developer. The developing device 9d of the fourth process unit 100d contains a fourth color component, for example, a black developer.

Incidentally, the developing devices 9 containing the developers corresponding to such color components do not have to be arranged in the order as shown in this example. Each process unit 100
Is in the vicinity of the transfer position where the sheet P conveyed by the conveyance belt 11 and each photoconductor drum 1 abut, that is, the position facing the photoconductor drum 1, and contacts the back surface of the conveyance belt 11. Power supply rollers 23a, 23b, 23c, and 23d (hereinafter, referred to as transfer means)
(Collectively referred to as power supply rollers 23). The power supply rollers 23 are disposed in one-to-one correspondence with the respective photosensitive drums 1 so as to rotate following the movement of the transport belt 11. Each power supply roller 23 is connected to a bias power source (not shown).

Next, the image forming process of the above-mentioned image forming apparatus, that is, the color image forming apparatus will be described. First, the photosensitive drum 1 of each process unit 100 is rotated at a predetermined rotation speed.

Subsequently, an AC superimposed DC bias is applied to the charging roller 5 which is in contact with the photosensitive drum 1, and the surface of the photosensitive drum 1 is uniformly charged to about -500V. Then, the exposure device 7 irradiates the photoconductor drum 1 uniformly charged by the charging roller 5 with a light beam corresponding to the image data, so that the photoconductor drum 1 can be processed with the image data. An electrostatic latent image is formed.

Subsequently, the electrostatic latent image is developed with the pre-fully charged developers of the respective colors housed in the developing device 9 to form a developer image. Subsequently, the photosensitive drum 1 is irradiated with a light beam by the pre-transfer static eliminator 3,
Unexposed portions, that is, non-image portions where no developer image is formed, are discharged.

On the other hand, the paper P is sent onto the conveyor belt 11 at the timing of rotation of the photosensitive drum 1 so that the front end of the paper P and the front end of the developer image are aligned with each other. At the same time as the paper P is conveyed to the suction roller unit 24, a suction bias is applied. As a result, the surface of the paper P is charged, and the opposite side of the belt (tension roller 13 side) is charged to the opposite polarity. The sheet P can be attracted to the transport belt by the electrostatic force of the charged charge.

When the paper P is conveyed to the transfer position, a voltage of, for example, about + 1000V is applied to the conveyor belt 11 from each power supply roller 23 as a bias voltage. By applying this bias voltage, the power supply roller 23 is
A transfer electric field is formed between and.

That is, first, the first process unit 1
00a, the photosensitive drum 1a and the power supply roller 23a
And the photosensitive drum 1a
The developer image corresponding to the above first color component is transferred onto the sheet P, and the sheet P carrying this developer image is conveyed and reaches the photosensitive drum 1b.

Subsequently, in the second process unit 100b, the developer image corresponding to the second color component formed on the photosensitive drum 1b is first moved by the transfer electric field between the photosensitive drum 1a and the power feeding roller 23a. And is transferred onto the developer image transferred onto the image.

The sheet P is further conveyed, and the third process unit 100c and the fourth process unit 100.
Also at d, the developer images corresponding to the third and fourth color components are similarly transferred in multiple layers.

Since the conveyor belt 11 is formed of a semi-conductive member, the conveyor belt 11 itself does not charge up and the conveyor belt 11 does not need a charge eliminating process.

As described above, the sheet P carrying the image formed by the multiple transfer is conveyed from the conveying belt 11 to a fixing device (not shown), and the image is thermally fixed on the sheet P. After the paper P is separated from the transport belt 11, the surface of the transport belt 11 is cleaned by the blade cleaning device 16.

Next, the material of the conveyor belt 11 will be described in detail. The material of the conveyor belt 11 is, for example, thermosetting polyimide, and is seamlessly formed into an annular shape with a width of 270 mm and a diameter of 80 mm by the imidization reaction after being injected into the mold. The thickness of the conveyor belt 11 is 100 μm
It is.

In addition to this example, the material of the conveyor belt 11 is resin such as polycarbonate, polyethylene terephthalate, polytetrafluoroethylene (Teflon), polyvinylidene fluoride, various polymer alloys synthesized, or the above-mentioned plural resins. It may be a belt having a multi-layer structure in which

The electric resistance value in the thickness direction per 1 cm ^{2 of the} conveyor belt 11 is about 10 ¹¹ Ω · cm ² . The measurement of this electric resistance value was carried out by sandwiching the electrodes made of stainless steel having a weight of 1 kg, applying a voltage of 500 V, and having an area of 7.1 cm ^2.
The current flowing through the counter electrode of was measured and obtained. The atmosphere during this measurement is normal temperature and normal humidity.

Next, a method of defining the installation position of the LED lamp 3 as the pre-transfer charge eliminator will be described. As shown in FIG. 3, the photosensitive drum 1 is charged by the charging roller 5 to a predetermined initial surface potential, for example, -500V, and then,
The exposure device 7 irradiates and exposes a light beam. By this exposure, the unexposed portion is maintained at a substantially initial surface potential, but the exposed portion becomes an intermediate potential, for example, a halftone potential of −200V.

Then, the developer is supplied from the developing device 9, and the developer is selectively attached to the exposed portion at the halftone potential lower than the initial surface potential. Then, before the developer is transferred to the paper P, the pre-transfer charge eliminator 3 irradiates the light beam with light to remove the charge.

At this time, when the surface potential of the photosensitive drum 1 is lowered to a residual potential level lower than the halftone potential by photo-electrification as in the comparative example, it is adhered to the exposed portion. There is a problem that the developer scatters on the unexposed portion having a lower potential.

On the other hand, according to the pre-transfer charge eliminator 3 provided in the image forming apparatus of the present invention, before the potential on the surface of the photosensitive drum 1 is completely reduced to the residual potential level, that is, the developer is exposed to the unexposed portion. The pre-transfer charge eliminator 3 is arranged at a position where the developer on the photosensitive drum 1 can be transferred onto the paper P before the phenomenon of scattering occurs.

That is, the photosensitive drum 1 is the charging roller 5
Let V0 be the initial surface potential charged by, and Ver be the residual potential remaining after the photosensitive drum 1 is exposed, and the surface potential of the unexposed portion after the charge removal is Ver + (V0-Ver).
Let t be the time required to decay to / 2, t'be the time required to decay the surface potential of the unexposed portion after static elimination to Ver, and let the peripheral velocity of the photosensitive drum be v (mm / sec). v × t = L (mm) and v × t ′ = L ′ (mm)
The pre-transfer static eliminator 3 is installed on the upstream side of the transfer position, that is, on the developing device side by a distance between the position and the position, and the photosensitive drum is irradiated with the light beam.

That is, assuming that the upstream distance from the transfer position where the pre-transfer static eliminator 3 is installed is A (mm), the distance A
Can be defined as L <A <L '. In the case of a binary image in which the exposure intensity by the exposure device is only on / off, the surface potential of the photosensitive drum becomes the residual potential Ver by the exposure. Therefore, the surface potential of the photosensitive drum after static elimination is
Since it is more than Ver and lower in the range, it is more preferable. Therefore, the installation position A of the pre-transfer charge eliminator is preferably closer to L ′ from the transfer position.

In an image forming apparatus capable of forming a multi-valued image by switching the exposure intensity to another stage, when a halftone image is formed, the installation position A of the pre-transfer charge eliminator is as close to L as possible. Is desirable.
That is, the halftone potential is a potential between the initial potential and the residual potential of the photosensitive drum.

Therefore, in order to prevent the developer adhering to the exposed portion of the halftone potential level from scattering to the unexposed portion, the surface potential of the photosensitive drum after the charge elimination should not be lower than this halftone potential. There is a need. On the other hand, in the exposed portion of the halftone potential, the amount of the developer supplied by the developing device is also small, so that the scattering amount of the developer is also small at a certain potential level. This potential level is a potential of approximately Ver + (V0-Ver) / 2.

FIG. 4 shows an optical attenuation curve of the photoconductor drum used in this embodiment due to optical neutralization.
This light decay curve is measured by the static measurement method. As shown in FIG. 4, according to this photosensitive drum, after the initial surface potential was charged to −500 V, it was photo-erased, so that the residual potential level was about −1 after about 1 second.
The surface potential is attenuated to 00V.

FIG. 5 shows a measurement of the relationship between the surface potential and the halftone potential after static elimination at the transfer position of the photosensitive drum having the light attenuation characteristic as shown in FIG. 4 and the scattering condition of the developer. The result. That is, as shown in FIG.
When the initial surface potential of the photoconductor drum is −500V and the residual potential is −100V, the surface potential after static elimination is about −300.
It can be seen that the phenomenon in which the developer is scattered is prevented even when the potential after the charge removal becomes lower than the halftone potential near V. In other words, the electric potential −300 V after the neutralization is Ver +
(V0-Ver) / 2 = -100V + (-500V + 1
00V) / 2 = -300V.

Then, as shown in FIG. 4, the surface potential of the photosensitive drum is Ver + (V0-Ver) / 2 = -300.
The time t required to decay to V is about 0.3 sec,
The time t ′ required to decay to the residual potential Ver = −100V is about 1.0 sec, and if the peripheral velocity of the photosensitive drum is v = 50 mm / sec, L = v × t = 50 ×
0.3 = 15 mm, L ′ = v × t ′ = 50 × 1.0 = 5
0 mm.

Therefore, the pre-transfer charge eliminator 3 is located 15 to 50 mm upstream from the transfer position between the photosensitive drum and the sheet.
That is, it is arranged at the position where the developing device is arranged. By arranging the pre-transfer charge eliminator at the position thus defined, it becomes possible to control the surface potential of the photosensitive drum of the non-image area, which has been subjected to the charge removal, to a potential higher than that of the image area. It is possible to prevent the developer adhering to the area from scattering to the non-image area.

The first to fourth process units 100a, 100b, 100c, 10 as shown in FIG.
In the color image forming apparatus having 0d, the pre-transfer charge eliminator arranged at the position defined by the above-described method is at least the second and third process units 100b.
And 100c.

That is, first, the first process unit 1
At 00 a, the electrostatic latent image formed on the photoconductor drum 1 a is developed by the yellow developer and transferred to the paper P.

Then, in the second process unit 100b, when the pre-transfer charge eliminator is not applied, the surface potential of the unexposed portion on the photosensitive drum 1b, that is, the non-image portion is maintained at the initial surface potential V0. It is in a broken state. In this state, when a transfer bias is applied and an electric field is formed in order to multiple-transfer the developer images formed by the magenta-based developer on the photoconductor drum 1b onto the paper P, an electric field is formed and the photoconductor drum and the paper P are formed. A discharge is generated in a small gap between and. Due to this discharge, the electric charge on the photosensitive drum moves to the yellow developer already transferred onto the paper, and the yellow developer is charged up.

Subsequently, in the third process unit 100c, for example, when the cyan developer image formed in the third process unit 100c is multi-transferred onto the charged yellow developer on the sheet P, ,
The transfer electric field in the third process unit 100c is weakened by the charge of the yellow developer that has been charged up, and the transfer efficiency of the cyan developer is deteriorated.

Similarly, due to the discharge generated in the minute gap between the photosensitive drum 1c and the paper P in the third process unit 100c, the second process unit 100b is discharged.
The magenta-based developer transferred by is charged up. Then, in the fourth process unit 100d,
When multiple transfer of the black developer onto the paper P is performed, the transfer electric field is weakened by the charged magenta developer, and the transfer efficiency of the black developer is deteriorated.

Therefore, in order to prevent such deterioration of the transfer efficiency, the pre-transfer charge eliminator 3 arranged based on the above-described defining method is provided in at least the second and third process units 100b and 100c. Must be applied.

By disposing the pre-transfer charge eliminator 3 at a predetermined position, it is possible to prevent the developer from scattering and prevent the transfer failure due to the deterioration of the transfer efficiency. As a result, it is possible to improve the image quality of the color image formed by multiple-transferring the developers of the different color components onto the paper P.

The pre-transfer charge eliminator as described above can be applied to not only the color image forming apparatus shown in FIG. 1 but also the intermediate transfer type color image forming apparatus shown in FIG. is there. In the following description, the same components as those applied to the color image forming apparatus shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

That is, as shown in FIG. 6, this color image forming apparatus has a photosensitive drum 1 which functions as an image carrier, and the photosensitive drum 1 rotates around the photosensitive drum 1. A charging roller 5, an exposure device 7, a developing unit 9 ′, a pre-transfer charge eliminator 3, an intermediate transfer member 111, and a cleaning device 21 are provided along the direction.

The developing section 9'has a developing device capable of supplying the photosensitive drum 1 with developers corresponding to a plurality of color components. That is, the developing unit 9'contains a first color component, for example, a yellow developer, and develops the electrostatic latent image formed on the photoconductor drum 1 by the first developing device 9a and the second color developing device 9a. A second developing device 9b that contains a component, for example, a magenta developer, and develops the electrostatic latent image formed on the photosensitive drum 1,
A third developing unit 9c that contains a third color component, for example, a cyan-based developer, and develops the electrostatic latent image formed on the photosensitive drum 1, and a fourth color component, for example, a black-based development. It has a fourth developing device 9d which contains the agent and develops the electrostatic latent image formed on the photosensitive drum 1.

The intermediate transfer member 111 is formed in a cylindrical shape,
The photoconductor drum 1 is abutted along the longitudinal direction at a predetermined transfer position. Then, this intermediate transfer member 111
Are rotatably provided according to the rotation of the photosensitive drum 1. A power supply roller 23 that applies a transfer bias to the photosensitive drum 1 is provided at a position inside the intermediate transfer member 111 that faces the photosensitive drum 1.

The pre-transfer charge eliminator 3 is located upstream of the transfer position where the photosensitive drum 1 and the intermediate transfer member 111 are in contact with each other,
That is, it is provided at the position defined by the above-described defining method on the side where the developing unit 9'is provided.

That is, the distance A (mm) on the upstream side from the transfer position where the pre-transfer charge eliminator 3 is installed is within the range defined by L <A <L '. In addition, L and L'are as already defined.

According to the color image forming apparatus as shown in FIG. 6, first, in the first image forming process, the surface of the photosensitive drum 1 is set to a predetermined potential by the charging roller 5.
For example, it is uniformly charged to -500V.

Then, the exposure device 7 irradiates the charged surface of the photosensitive drum 1 with a light beam corresponding to the image data. Then, an electrostatic latent image corresponding to the image data is formed on the photosensitive drum 1.

Subsequently, the electrostatic latent image on the photosensitive drum 1 is developed by the yellow developer housed in the first developing device 9a to form a yellow developer image. Then, the power supply roller 23 transfers the yellow developer image formed on the photosensitive drum 1 to the sheet P held on the intermediate transfer body 111.

The surface of the photosensitive drum 1 is cleaned by the cleaning device 21. continue,
Similarly, in the second image forming process, the photosensitive drum 1 is charged and exposed, and thereafter, the photosensitive drum 1 is developed by the magenta-based developer housed in the second developing device 9b, and the developer on the photosensitive drum 1 is developed. An image is formed. Then, before transferring the developer image to the intermediate transfer member 111, the pre-transfer static eliminator 3
By irradiating the photoconductor drum 1 with the light beam, the unexposed portion is discharged. Then, the developer image on the photosensitive drum 1 is transferred onto the paper P held on the intermediate transfer member 111 in an overlapping manner.

Subsequently, similarly, in the third image forming process, after the photosensitive drum 1 is charged and exposed,
It is developed with a cyan-based developer housed in the third developing device 9c, and a developer image is formed on the photosensitive drum 1.
Then, before the developer image is transferred to the intermediate transfer member 111, the pre-transfer charge eliminator 3 irradiates the photoconductor drum 1 with a light beam, so that the unexposed portion is discharged. Then, the developer image on the photosensitive drum 1 is transferred onto the paper P held on the intermediate transfer member 111 in an overlapping manner.

Then, similarly, in the fourth image forming process, after the photosensitive drum 1 is charged and exposed,
It is developed by the black-based developer accommodated in the fourth developing device 9d, and transferred onto the sheet P held on the intermediate transfer member 111 in an overlapping manner.

Subsequently, the sheet P is conveyed to a fixing device (not shown), is pressurized and melted, and the color image is fixed on the sheet. As described above, in the color image forming apparatus shown in FIG. 6, at least in the second and third image forming processes, after the electrostatic latent image on the photosensitive drum 1 is developed, the developer image is transferred to the predetermined position. The light beam is emitted before being transferred to the sheet held by the intermediate transfer member 111 at the position. Then, the unexposed portion on the photosensitive drum 1 is discharged.

Therefore, in the second image forming process, when a transfer bias is applied to the photosensitive drum 1 from the power feeding roller 23, the discharge in the minute gap between the photosensitive drum and the paper is prevented. Therefore, it is possible to prevent charge-up of the developer corresponding to the first color component transferred by the first image forming process.

Therefore, in the third image forming process, the problem that the transfer efficiency is lowered by the charged up developer can be prevented, and a color image of good quality can be formed on the paper.

Similarly, in the third image forming process, when a transfer bias is applied from the power supply roller 23 to the photosensitive drum 1, discharge in the minute gap between the photosensitive drum and the paper is prevented. It is also possible to prevent the charge up of the developer.

Therefore, in the fourth image forming process, it is possible to prevent the problem that transfer efficiency is deteriorated by the charged up developer, and it is possible to form a color image of good quality on a sheet.

By the way, in the color image forming apparatus as described above, the laminated organic photoconductor applied to the photoconductor drum has a charge generating layer and a charge transporting layer, and the functions are separated by separating them. It has achieved sensitivity.

On the other hand, in the single-layer type organic photoreceptor, charge generation sites and charge transport sites coexist in one layer and are uniformly dispersed. Therefore, the characteristics of the single-layer type organic photoconductor are affected by the dispersion state, and the sensitivity is slightly lower than that of the function-separated type laminated organic photoconductor.

FIG. 7 shows a light attenuation curve A of a single-layer type organic photoconductor and a light attenuation curve B of a laminated organic photoconductor by the static measurement method. As shown in FIG. 7, in the case of a single-layer type organic photoconductor, the charges generated by the charge generation sites existing near the surface can immediately cancel the charges on the surface of the photoconductor, but the charges generated in the bulk. Takes a long time to be transported to the surface of the photoreceptor, and the surface potential decays into a broad curve.

As described above, according to the present invention, before transferring the developer image formed on the photoconductor onto the paper, the potential of the unexposed portion on the photoconductor is eliminated to obtain the surface potential of the photoconductor. Therefore, a photoreceptor having a broad light-attenuating characteristic such as a single-layer type organic photoreceptor is advantageous because it lowers the voltage to a level not lower than the halftone potential.

Therefore, the single-layer type organic photoconductor is shown in FIG. 6 and the color image forming apparatus having the first to fourth process units shown in FIG. By applying the color image forming apparatus having the first to fourth developing devices to such a single photosensitive drum, it becomes easier to control the surface potential of the photosensitive member. That is, the time t required for the surface potential of the photoconductor to decay from the initial surface potential V0 to Ver + (V0−Ver) / 2 and the time t ′ required to decay to the residual potential Ver become longer, and t and t The range of installation positions of the pre-transfer static eliminator determined by 'can be expanded.

In the description of the color image forming apparatus using the laminated organic photoconductor, an example in which the photoconductor is negatively charged has been described, but a positive charge type may be used. That is,
When a positively charged organic photoconductor is applied, the polarity of the charging bias by the charging roller is positive, the charge of the developer is positive, the polarity of the developing bias is positive, and the polarity of the transfer bias is negative. The other image forming processes are the same as those in the above-described example.

An example of the material for the single-layer type positive charging photoreceptor will be described. 10 parts by weight of a perylene-based organic pigment as a charge-generating photosensitive material, 80 parts by weight of a diamine derivative as a charge-transporting material, and 100 parts by weight of a polycarbonate resin are dissolved and dispersed in a predetermined amount of tetrahydrofuran, which is used as a coating solution for a photosensitive layer. A 40-mm aluminum tube is dip-coated to a thickness of 20 μm to form a single-layer positively charged organic photoreceptor.

As described above, according to the image forming apparatus of the present invention, before the developer image formed on the photoconductor drum is transferred onto the paper, the pre-transfer charge eliminator is used for the light beam to the photoconductor drum. By irradiating with, the electric potential of the unexposed portion on the photosensitive drum is eliminated. Therefore, the charge up of the developer can be prevented, and the deterioration of the transfer efficiency can be prevented.

The pre-transfer static eliminator is arranged upstream of the transfer position where the developer image on the photosensitive drum is transferred onto the paper, and the developer image formed on the photosensitive drum is transferred onto the paper. Before transfer to, the electric potential of the unexposed area on the photoconductor, that is, the non-image area, is removed, and the surface potential of the photoconductor drum is lowered to the halftone potential at the transfer position. ing. Therefore, the problem that the developer is scattered on the non-image portion is solved.

Therefore, an image of good quality can be formed. The color image forming apparatus described in the embodiments of the present invention may be a color printer or may be applied as a color copying apparatus by mounting a scanner section.

[0112]

As described above, according to the present invention, it is possible to form an image of good quality by preventing the charge up of the developer and the scattering of the developer to the non-image area. An image forming apparatus and an image forming method can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a color image forming apparatus including first to fourth process units according to an embodiment of the image forming apparatus of the present invention.

2 is a cross-sectional view schematically showing a pre-transfer static eliminator applied to the color image forming apparatus shown in FIG.

FIG. 3 is an explanatory diagram for explaining the principle of the present invention.

FIG. 4 is a diagram showing light attenuation characteristics of a photoconductor applied to the image forming apparatus of the present invention.

5 is a measurement result obtained by measuring a relationship between a surface potential and a halftone potential after static elimination at a transfer position of a photoconductor having the light attenuation characteristic shown in FIG. 4 and a scattering state of a developer. .

FIG. 6 is a sectional view schematically showing a color image forming apparatus according to another embodiment of the image forming apparatus of the present invention.

FIG. 7 is a diagram showing the light attenuation characteristics of a single-layer type organic photoconductor and a laminated organic photoconductor as photoconductors applied to the image forming apparatus of the present invention.

[Explanation of symbols]

 1 (1a to 1d) ... Photosensitive drum 3 (3a to 3d) ... Pre-transfer charge eliminator 5 (5a to 5d) ... Charging roller 7 (7a to 7d) ... Exposure device 9 (9a to 9d) ... Developer 11 ... Conveyor belt 13 ... Tension roller 15 ... Drive roller 17 (17a to 17d) ... Blade cleaning device 19 (19a to 19d) ... Static elimination lamp 23 (23a to 23d) ... Power supply roller 100a ... First process unit 100b ... Second process unit 100c ... Third process unit 100d ... Fourth process unit 111 ... Intermediate transfer member

Claims (9)

[Claims] 1. A charging unit that is rotatably provided at a rotational peripheral speed v and that charges an image carrier that holds an image corresponding to image data to a predetermined initial surface potential, and the image charged by the charging unit. Exposure means for forming an electrostatic latent image corresponding to image data on the image carrier by irradiating the carrier with light for exposure, and developing and developing the electrostatic latent image formed on the image carrier. Developing means for forming a developer image, transfer means for transferring the developer image formed on the image carrier to a transfer material at a predetermined transfer position, a position where the developing means is arranged, and the transfer position And a charge removing unit that removes charge from the image carrier, the initial surface potential of the image carrier is V0, the residual potential after charge removal is Ver, and the image after the charge is removed by the charge removing unit. The surface potential of the carrier is Ver + (V0-Ver) Assuming that the time required to decay to 2 is t and the time required to decay to Ver is t ′, the distance A from the position where the charge eliminating means is arranged to the transfer position is v × t = L, v ×
An image forming apparatus characterized in that when t ′ = L ′, it is defined within a range represented by L <A <L ′. 2. A first developer image forming means for forming a first developer image corresponding to a first color component of image data on a first image carrier, and the first developer image formation. The first transfer means for transferring the first developer image formed by the means onto the transfer material, and the second image carrier rotatably provided at the rotational peripheral speed v are set to a predetermined initial surface potential. The charged image carrier is exposed to light to form an electrostatic latent image corresponding to the second color component of the image data, and then the electrostatic latent image is developed to produce a second image.
A second developer image forming means for forming a developer image, and a charge removing means for removing charge from the image bearing member carrying the second developer image formed by the second developer image forming means, Second transfer means for transferring the second developer image on the second image carrier, which has been subjected to the charge removal by the charge removal means, onto the transfer material to which the first developer image has been transferred; The initial surface potential of the second image carrier is V0, the residual potential after static elimination is Ver, and the surface potential of the second image carrier after static elimination is Ver + ( V0-V
er) / 2, where t is the time required to decay to Ver and t'is the time required to decay to Ver, the distance A from the charge eliminating means to the transfer position by the second transfer means is A.
Is defined within a range represented by L <A <L ′ when v × t = L and v × t ′ = L ′. 3. A first developer image forming means for forming a first developer image corresponding to a first color component of image data on the first image carrier, and the first image carrier. A first transfer means for bringing the transferred material into contact and transferring the first developer image onto the transferred material; and a first voltage for applying a first transfer voltage to the first transfer means. The application unit and the second image carrier rotatably provided at the rotational peripheral speed v are charged to a predetermined initial surface potential, and the charged image carrier is exposed to the second image data of the second image data. After the electrostatic latent image corresponding to the color components is formed, the electrostatic latent image is developed and the second
A second developer image forming means for forming a developer image, and a charge removing means for removing charge from the image bearing member carrying the second developer image formed by the second developer image forming means, The second image bearing member, which has been subjected to the charge removal by the charge removing means, is brought into contact with the transfer material on which the first developer image is transferred, and the second developer is applied on the transfer material. A second transfer means for transferring an image; and a second voltage applying means for applying a second transfer voltage to the second transfer means. The initial surface potential of the second image carrier is V0. , The residual potential after static elimination is Ver, and the surface potential of the second image carrier after static elimination by the static elimination unit is Ver + (V0-V).
er) / 2, where t is the time required to decay to Ver and t'is the time required to decay to Ver, the distance A from the charge eliminating means to the transfer position by the second transfer means is A.
Is defined within a range represented by L <A <L ′ when v × t = L and v × t ′ = L ′. 4. A first developer image forming means for forming a first developer image corresponding to a first color component of image data on an image carrier rotatably provided at a rotational peripheral speed v, The image carrier is charged to a predetermined initial surface potential, and the charged image carrier is exposed to form an electrostatic latent image corresponding to the second color component of the image data. Second developer image forming means for developing the latent image to form a second developer image, and the image bearing for carrying the second developer image formed by the second developer image forming means. Charge removing means for removing charge from the body, and second developer on the image carrier after the transfer of the first developer image onto the transfer material, and then charge removal on the transfer material by the charge removing means A transfer unit for transferring images in multiplex, the initial surface potential of the image bearing member is V0, and the residual potential after static elimination is Ver. Assuming that the time required for the surface potential of the image carrier after being discharged by the discharging unit to decay to Ver + (V0-Ver) / 2 is t, and the time required to decay to Ver is t ', The distance A from the charge eliminating unit to the transfer position by the transfer unit is v × t = L, v
An image forming apparatus characterized by being defined in a range represented by L <A <L ′ when xt ′ = L ′. 5. A single-layer type organic photosensitive member which is rotatably provided at a rotational peripheral velocity v, holds an image corresponding to image data, and has a charge generating portion and a charge transporting portion uniformly dispersed in one layer. Charging means for charging the image carrier formed by the body to a predetermined initial surface potential; and irradiating the image carrier charged by this charging means with light to expose the image carrier to image data. Exposure means for forming a corresponding electrostatic latent image, developing means for developing the electrostatic latent image formed on the image carrier to form a developer image, and developer image formed on the image carrier A transfer unit that transfers the image to a transfer target material at a predetermined transfer position, and a charge removing unit that is located between the position where the developing unit is arranged and the transfer position and that removes the charge of the image carrier, The initial surface potential of the image carrier is V0, and the residual after static elimination Letting the potential be Ver, the time required for the surface potential of the image bearing member after being neutralized by the neutralizing means to decay to Ver + (V0−Ver) / 2 is t, and the time required to decay to Ver is t ′. Then, the distance A from the position where the charge eliminating unit is arranged to the transfer position is v × t = L, v ×
An image forming apparatus characterized in that when t ′ = L ′, it is defined within a range represented by L <A <L ′. 6. A charging step of uniformly charging the image bearing member to an initial surface potential V0, and a latent image forming step of forming an electrostatic latent image by irradiating the image bearing member with light for exposure. A developing step of forming a developer image by developing the electrostatic latent image, a charge eliminating step of eliminating charge of the image carrier on which the developer image is formed, and a residual potential of the image bearing body after charge elimination of Ver. Then, the surface potential of the image carrier is Ver + (V0-Ve
r) / 2 to Ver, and a transfer step of transferring the developer image formed on the image bearing member onto the transfer material, the image forming method. 7. A first color of image data is obtained by uniformly charging the first image carrier to a predetermined potential and exposing the first image carrier with light corresponding to image data. A first developer image forming step of forming an electrostatic latent image corresponding to a component and developing the electrostatic latent image with a developer of a first color component to form a first developer image; A first transfer step of transferring the first developer image formed on the first image carrier to a transfer material, and uniformly charging the second image carrier to an initial surface potential V0, By irradiating the second image carrier with light corresponding to the image data to expose it, an electrostatic latent image corresponding to the second color component of the image data is formed. A second developer image forming step of forming a second developer image by developing with a color component developer; and A neutralization step of neutralizing the second image bearing member that is, the second residual potential after neutralization of the image carrier when the Ver of the surface potential of the second image bearing member Ver + (V
When it is between 0-Ver) / 2 and Ver, the second developer image formed on the second image carrier is transferred to the transfer material to which the first developer image is transferred. An image forming method comprising: a second transfer step. 8. An electrostatic charge corresponding to a first color component of image data is obtained by uniformly charging the image carrier to a predetermined potential and exposing the image carrier to light corresponding to image data. A first developer image forming step of forming a latent image and developing the electrostatic latent image with a developer of a first color component to form a first developer image; A first transfer step of transferring the formed first developer image to a transfer material; and uniformly charging the image carrier transferred in the first transfer step to an initial surface potential V0. Then, by irradiating the image carrier with light corresponding to the image data to expose it, an electrostatic latent image corresponding to the second color component of the image data is formed. A second developer image forming step of forming a second developer image by developing with a component developer; When the static elimination step of static elimination by irradiating light to the image bearing member on which the agent image is formed and the residual potential after static elimination of the image bearing member is Ver, the surface potential of the image bearing member is Ver + ( V0-Ve
r) / 2, a second transfer step of transferring the second developer image formed on the image carrier to the transfer material to which the first developer image has been transferred when it is between Ver and Ver. And an image forming method comprising: 9. A charging step of uniformly charging an image bearing member formed of a single-layer type organic photoconductor in which a charge generating portion and a charge transporting portion are uniformly dispersed in one layer to an initial surface potential V0. A latent image forming step of forming an electrostatic latent image by irradiating the image bearing member with light to expose it; a developing step of developing the electrostatic latent image to form a developer image; When the static elimination step of neutralizing the image bearing member on which the image is formed and the residual potential after static elimination of the image bearing member is set to Ver, the surface potential of the image bearing member is Ver + (V0-Ve).
r) / 2 to Ver, and a transfer step of transferring the developer image formed on the image bearing member onto the transfer material, the image forming method.