JPH04282673A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To appropriately prevent scattering of toner and to prevent generation of difference due to photosensitive body fatigue according to position. CONSTITUTION:Light emitting quantity of an exposure light source 110 before transfer in a paper range on the photosensitive body is controlled by a control part 112 based on paper width detected by a paper size detection sensor 111. The relationship between shadow potential VD1 before transfer and after exposure, highlight potential VL1 before transfer and after exposure, and electrifying potential VT of developer is ¦VD1¦>=¦VL1+VT¦. In a range outside the paper on the photosensitive body, the light emitting quantity of the exposure light source 110 before transfer is controlled so that the relationship between shadow potential VD1 before transfer and after exposure and highlight potential VL0 before transfer and before exposure are ¦VD1¦>=¦VL0¦.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to an electrophotographic recording device using a dry powder developer, and more specifically, the present invention relates to an electrophotographic recording device using a dry powder developer. The present invention relates to an electrophotographic apparatus that reduces image deterioration.

0002

2. Description of the Related Art An electrophotographic apparatus using a conventional toner (dry powder developer) will be described with reference to FIG. The electrophotographic apparatus includes a main charger 602 that uniformly charges a photoreceptor 601, an optical writing device 603 that writes image information by irradiating light onto the photoreceptor 601, and an optical writing device 603. A developing device 604 that develops the electrostatic latent image on the photoreceptor 601, and a transfer device that transfers the toner image developed by the developing device 604 onto recording paper (not shown) conveyed via a paper conveying path 605. An electric device 606, a separation discharger 607 for separating the recording paper onto which the toner image has been transferred from the photoreceptor 601, a cleaning device 608 for removing residual toner on the photoreceptor 601, and a cleaning device 608 for erasing the residual charge on the photoreceptor 601. and a pre-transfer static elimination lamp 610 that exposes the entire surface of the photoreceptor 601 before transfer in order to improve transfer efficiency, separation performance, cleaning efficiency, etc.

The operation of the conventional electrophotographic apparatus with the above configuration will be explained. Here, a case where a negatively charged photoreceptor such as an organic photoreceptor is used as the photoreceptor 601 is taken as an example.
In the case of a positively charged photoreceptor such as a -Se type photoreceptor or an a-Si type photoreceptor, the value corresponds to the value of the surface potential shown below with a different sign. First, the main charger 602 charges the photoreceptor 60
1 is charged so that the surface potential becomes -800 to -1000V. At this time, in order to obtain a high-quality image, it is necessary to perform charging as uniformly as possible, and efforts have been made to stabilize and make it uniform by using a scorotron or two or more discharge lines.

Next, an optical writing device 603 irradiates a light flux (beam) onto the photoreceptor 601, and the photoconductivity of the photoreceptor 601 cancels out the electric charge charged by the main charger 602, forming a dot. Image information is formed as an electrostatic latent image. In this way, an electrostatic latent image is formed on the photoreceptor 601 in the form of a difference in surface potential.

This electrostatic latent image is obtained as two types of images depending on the developing method of the developing device 604, as shown in FIGS. 7(a) and 7(b). Here, (a) shows a case where development is performed with a toner having a charge polarity opposite to that of the photoconductor 601, and is a method in which the developer is attached to a portion where optical writing is not performed. On the other hand, (b) shows a case where development is performed with a toner having the same charging polarity as that of the photoreceptor 601, and the toner selectively adheres to the location where optical writing has been performed. The images obtained in this way are (a) and (b).
It's exactly like the black and white are reversed.

[0006]Currently, in digital image forming apparatuses such as digital copying machines, light beam printers, and plain paper facsimile machines, the developing method (b) is mainly adopted due to its advantages in reproducibility of one dot and ease of filling solid areas. There is. Here, too, the description will be given assuming that the development was performed using the developing method (b) (so-called negative/positive method).

Photoreceptor 60 after passing through developing device 604
As mentioned above, the surface potential of No. 1 is as shown in (b), but this is within the image width, that is, within the range where optical writing is performed. Considering the potential state of the entire surface of the photoreceptor 601, first, the length of the photoreceptor 601 is defined by the size of the recording paper used in the apparatus. For example, as shown in FIG. 8(a), the photoreceptor 6
01 is the maximum and vertical feeding of A3 paper is possible, the photoreceptor 60
The length, optical writing width, development width, etc. of 1 must be 297 mm or more. Here, with such a photoreceptor 601, A3
Assuming that, for example, A4 paper, which is smaller than paper, is fed vertically, the surface potential of the photoreceptor 601 is not only inside the A4 paper, but also within the A3 width outside of the A4 paper (image-formable area). Also, photoreceptor fatigue must be taken into account.

FIGS. 8(b), 8(c), and 8(d) show the movement of the surface potential of the photoreceptor 601 at the inside and outside positions of A4 paper, and the surface potential after development is as shown in FIG. 8(b). As shown in the figure, the inside of the optical A4 paper is divided into a negative high potential area and a low potential area with developer by optical writing, and the outside of the A4 paper is in a state of negative high potential given by charging. be. When the transfer discharger 606 discharges a positive charge with the opposite polarity to the toner onto the surface of the photoreceptor 601 in this state, the surface potential after the transfer discharge is as shown in FIG. Since it receives the positive charge directly and is originally at a high negative potential, the electric field created with the transfer discharger 606 is strong, and a large positive current flows into it, resulting in a high charge on the positive side. On the other hand, inside A4,
Since the recording paper is interposed between the surface portion of the photoreceptor 601 and the transfer discharger 606, the flow of positive charge is reduced, resulting in a positive charging potential shape as shown in the figure.

Next, in order to neutralize the positive charge remaining on the back side of the recording paper and to make it easier to separate the recording paper from the photoreceptor 601, a separation discharger 607 discharges an alternating current shifted to the negative side. , the surface potential after separated discharge is shown in the same figure (d
), it becomes almost 0V on the outside of A4 paper, and A
4, the surface portion of the photoreceptor 601 and the transfer discharger 60
Since the recording paper is still interposed between the photoreceptor 601 and the photoreceptor 601, negative charges do not flow into the photoreceptor 601, and the potential is maintained on the positive side, not much different from that after the transfer discharge.

As described above, the movement of the potential on the surface of the photoreceptor 601 differs from place to place, and the flow of discharge current and its amount also differ, so the degree of fatigue of the photoreceptor 601 also differs, resulting in an uneven image. For example, when the same location is repeatedly written with light, such as the side lines of a document, the frame of a table, or the vertical lines of graphics, photofatigue occurs because a photocharge is generated and a photocurrent flows only in that location. As the area increases, the photosensitivity decreases and the charged potential decreases compared to other locations. For this reason, when an image pattern such as a halftone with a dot configuration is output, it appears in the form of an afterimage or is output as dirt on the background part.

On the other hand, in areas where optical writing is performed relatively infrequently, such as between characters or near the sides of the paper, the generation and movement of photoelectric charges in the photoreceptor are small, so that Charges trapped on the surface and discharge generated ions cannot be neutralized, resulting in accumulation, spread of electric field, decrease in surface resistance, etc., resulting in a decrease in image resolution, dot drift, or disappearance. The outside part of the A4 paper mentioned above is
Since more positive charges are applied in the transfer area, the positive charges are likely to enter the inside of the photoreceptor 601, and the positive charges are trapped inside, resulting in a decrease in image resolution, dot drift, and dot disappearance. Remarkable.

These problems can be alleviated by applying uniform light to the entire surface of the photoreceptor 601 before transfer. That is, by applying uniform light with the pre-transfer static elimination lamp 610, optical fatigue is made uniform and large differences in fatigue are eliminated, and by applying uniform light, a photoelectric charge is generated to capture the photoreceptor 601. It neutralizes electric charges and suppresses deterioration.

Here, the emission wavelength of the pre-transfer static elimination lamp 610 is a wavelength to which the photoreceptor 601 is sensitive, and is the same wavelength as that of the optical writing device 603 and the static elimination lamp 609, or
It is common to use a wavelength close to that. As mentioned above, the surface potential of the photoreceptor 601 after development is as shown in FIG. A photocurrent flows in the negative high potential area, and the potential of that area can be lowered.

However, if the potential is casually lowered, for example, as shown in FIG. 9, the light from the optical writing device 603 directly reaches the photoreceptor 601 at the negative high potential portion, so the sensitivity of the photoreceptor 601 decreases. Perform optical attenuation of the potential as expected,
The pre-exposure dark area potential VD0 becomes the post-exposure dark area potential VD1,
On the other hand, since toner is attached to the optically written portion due to development, the light from the optical writing device 603 is absorbed by the toner, is scattered and attenuated, and the amount reaching the surface of the photoreceptor 601 is small. Therefore, the bright area potential VL0 before exposure becomes the bright area potential VL1 after exposure. Therefore, as a result |V
D1|≦|VL1|, and as shown in the figure, there was an inconvenience that toner scattering occurred.

To solve this problem, as shown in Japanese Patent Application Laid-Open No. 60-32077, the relationship between the post-exposure dark area potential VD1 and the post-exposure bright area potential VL1 is always |VD1|≧| An electrophotographic apparatus is provided in which pre-transfer exposure is controlled so that VL1|.

[0016]

However, according to the electrophotographic apparatus disclosed in Japanese Patent Application Laid-Open No. 60-32077, |V
Although D1|≧|VL1| is set to prevent toner from scattering, toner (developer)
are charged particles and have a potential VT as a developer layer, so even if |VD1|≧|VL1|, toner scattering may occur. Specifically, as shown in FIG.
0, even if the pre-transfer exposure is performed so that |VD1|≧|VL1|, |VD1|≦|VL1+VT |
In this case, there was a problem that toner scattering occurred. In addition, the outside area of the paper (outside of A4 paper) is directly exposed to transfer discharge (plus charge) for a longer period of time, and fatigue of the photoreceptor due to carrier traps is more rapid than in the inside area of the paper (inside of A4 paper). According to exposure, since the entire surface of the photoreceptor is exposed to a uniform amount of light, there is a problem that fatigue of the photoreceptor varies depending on the location, resulting in image deterioration.

The present invention has been made in view of the above, and an object of the present invention is to appropriately prevent toner scattering and to prevent differences in photoreceptor fatigue depending on location.

[0018]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a developing means for applying a dry powder developer to an optical writing area formed on a photoreceptor, and In an electrophotographic apparatus equipped with a transfer means for transferring the attached developer from the photoreceptor onto the recording paper, the electrophotographic apparatus is provided between the developing means and the transfer means, and emits light along the axial direction of the photoreceptor. A pre-transfer exposure means that can adjust the amount of light, a detection means that detects the paper width of the recording paper, and a dark area potential VD1 after the pre-transfer exposure in the paper area on the photoconductor based on the paper width detected by the detection means. , bright area potential VL after pre-transfer exposure
1, and the charging potential VT of the developer is |VD1
The amount of light emitted by the pre-transfer exposure means is controlled so that |≧|VL1+VT|
The present invention provides an electrophotographic apparatus including a control means for controlling the amount of light emitted from a pre-transfer exposure means so that the relationship of L0 satisfies |VD1|≧|VL0|.

In order to achieve the above object, the present invention also provides a developing means for adhering a dry powder developer to an optical writing area formed on a photoreceptor, and a developing means for adhering a dry powder developer to an optical writing area formed on a photoreceptor; In an electrophotographic apparatus equipped with a transfer means for transferring an agent from a photoconductor onto a recording paper, a pre-transfer exposure means disposed between a developing means and a transfer means, and a pre-transfer exposure means disposed between a pre-transfer exposure means and a developing means. and a potential detecting means for detecting the sum of the bright area potential VL0 before the pre-transfer exposure and the charged potential VT of the developer, and the dark area potential after the pre-transfer exposure based on the detection result of the potential detecting means. VD1, bright area potential V after pre-transfer exposure
The relationship between L1 and the charging potential VT of the developer is |VL
1+VT |≦|VD1|≦(|VL1+VT |+1
00), and a control means for controlling the amount of light emitted from the pre-transfer exposure means so that the amount of light emitted from the pre-transfer exposure means is 00).

[0020]

[Operation] In the electrophotographic apparatus of the present invention, the control means:
Based on the paper width detected by the detection means, in the paper area on the photoreceptor, the relationship between the dark potential VD1 after pre-transfer exposure, the bright potential VL1 after pre-transfer exposure, and the charging potential VT of the developer is | The amount of light emitted by the pre-transfer exposure means is controlled so that VD1|≧|VL1+VT|, and in the area outside the paper on the photoreceptor, the relationship between the dark area potential VD1 after the pre-transfer exposure and the bright area potential VL0 before the pre-transfer exposure is established. However, |VD1|≧|VL0|
The amount of light emitted from the pre-transfer exposure means is controlled so that

In the electrophotographic apparatus of the present invention, the control means determines the dark area potential VD1 after the pre-transfer exposure and the light area potential VL after the pre-transfer exposure based on the detection result of the potential detection means.
1, and the relationship between the charging potential VT of the developer is |VL1
+VT |≦|VD1|≦(|VL1+VT |+10
The amount of light emitted from the pre-transfer exposure means is controlled so that the amount of light emitted from the pre-transfer exposure means is 0).

[0022]

[Example] The electrophotographic apparatus of the present invention will be described below [Example 1]
, [Example 2], and [Example 3] will be described in this order with reference to the drawings.

[Embodiment 1] An electrophotographic apparatus according to Embodiment 1 will be described with reference to FIG. 1. The electrophotographic apparatus includes a main charger 102 that uniformly charges a photoreceptor 101, and a photoreceptor 1.
01, a developing device 104 that develops an electrostatic latent image formed on the photoreceptor 101 by the optical writing device 103, and a paper conveyance path 105. A transfer discharger 106 transfers the toner image developed by the developing device 104 to a recording paper (not shown) conveyed via the photoreceptor 1.
A separation discharger 107 for separating from the photoconductor 1
Cleaning device 108 for removing residual toner on 01
and a static elimination lamp 1 for erasing the residual charge on the photoreceptor 101.
09, and a plurality of LEDs 110b in the width direction of the photoconductor 101 (direction perpendicular to the rotational direction of the photoconductor 601) (see FIG. 2).
a pre-transfer exposure light source 110 arranged with
11, and a control section 112 that controls the amount of light from the pre-transfer exposure light source 110 based on the detection signal 11.

Next, referring to FIG. 2, the pre-transfer exposure light source 1
10 is shown in detail. Pre-transfer exposure light source 110
As shown in the figure, it consists of a plurality of LEDs 110b, and each LED 110b is connected to two resistors R, r (R>r) via an electronic switch 110a. Here, the resistance value R is determined by the relationship between the dark area potential VD1 after pre-transfer exposure of the photoreceptor 101, the light area potential VL1 after pre-transfer exposure, and the charged potential VT of the toner: |VD1|≧|VL1
+VT | is the value at which the LED 110b emits light, and the resistance value r is such that the relationship between the dark potential VD1 after pre-transfer exposure and the bright potential VL0 before pre-transfer exposure is |VD1|≧
This is the value at which the LED 110b emits light so that |VL0|.

The control operation of the control section 112 in the above configuration will be explained. When recording paper is fed from a paper feed unit (not shown) with the start of copy processing, the paper size detection sensor 111 detects the paper size of the recording paper (for example, A4 paper), and the control unit Output to 112. The control unit 112
Based on the paper size, the electronic switch 110a of the LED 110b corresponding to the position inside the A4 paper is switched to the resistor r, and the electronic switch 110a of the LED 110b corresponding to the position outside the A4 paper is switched to the resistor R. after that,
A pre-transfer exposure light source 110 performs pre-transfer exposure on the surface of the photoreceptor 101 that has passed through the developing device 104 and has been developed. FIG. 3 shows the exposure amount of the pre-transfer exposure light source 110 at this time. As mentioned above, on the inside of the A4 paper (area inside the paper), the resistor R is connected, so the exposure amount is small, and on the outside of the A4 paper (area outside the paper), the resistor r is connected, so The amount of exposure is large.

As shown in FIG. 4(a), on the inside of the A4 paper, by connecting a resistor R and causing the LED 110b to emit light, the dark area potential VD0 before the pre-transfer exposure → the dark area potential VD1 after the pre-transfer exposure, and the transfer Bright area potential VL0 before pre-exposure becomes bright area potential VL1 after pre-transfer exposure, and the relationship between VD1, VL1, and VT becomes |VD1|≧|VL1+VT|, so transfer is possible without toner scattering. Pre-exposure can be performed. Specifically, since the toner charging potential VT is -200V and the bright area potential VL1 after pre-transfer exposure is -100V,
The dark potential VD1 after the pre-transfer exposure is about -300V.

On the other hand, there is no fear of toner scattering on the outside of A4 paper, and transfer discharge (
The exposure time is long when the photoreceptor is directly exposed to the positive charge (positive charge), which leads to fatigue of the photoreceptor due to carrier traps, etc., so increase the exposure amount.
Because it is necessary to generate a photocurrent and neutralize the trapped charge,
It is desirable to reduce VD1 to a point approximately equal to VL0. Here, as shown in FIG. 4(b), by connecting a resistor r on the outside of the A4 paper, the exposure amount is increased.
VD1|≧|VL0|.

By switching the exposure amount between the inside and outside of the paper (recording paper) in this way, it is possible to appropriately prevent toner scattering, and also to prevent differences in photoreceptor fatigue depending on the location. be able to. In Example 1, the light emission intensity was switched to two levels by switching the magnitude of the load resistance of the LED 110b using the resistors R and r. However, by controlling the supply voltage to each LED 110b, the light emission intensity ( Of course, it is also possible to switch the exposure amount.

[Example 2] In Example 1, the dark area potential VD1 after pre-transfer exposure and the bright area potential VL after pre-transfer exposure
1, and the toner charging potential VT is |VD1
Pre-transfer exposure light source 1 so that |≧|VL1+VT |
10 to obtain an appropriate dark potential VD1 that does not cause toner scattering. At this time, |VD1
Even if |≧|VL1+VT| is satisfied, if the light intensity of the pre-transfer exposure light source 110 is reduced and there is a difference between VD1 and VL1+VT, the effect of stabilizing the image will be weakened. Further, when VL1+VT decreases, it is better to irradiate more light and cause more photocurrent to flow in order to stabilize the image. On the other hand, in a developing device that uses a powder developer such as toner, the amount of toner adhering to the photoconductor tends to fluctuate depending on the surrounding environment and changes over time, and the potential VT of the developer layer changes due to changes in the amount of adhesion. do. Therefore,
In Example 2, the amount of toner adhesion after development is detected, and the light source 1 is
By setting the amount of light 14 to an appropriate amount, it is possible to provide an electrophotographic apparatus that can stably obtain an appropriate dark area potential VD1 without causing toner scattering.

FIG. 5 shows the configuration of an electrophotographic apparatus according to a second embodiment, in which an optical sensor 1 for measuring the amount of reflected light on the surface of a photoreceptor 101 is shown.
13, a light source 114 for pre-transfer exposure, a voltage/current supply device 116 that supplies voltage/current to the light source 114, and a dark area potential VD1 after pre-transfer exposure, based on the detection results of the optical sensor 113, and a pre-transfer dark potential VD1. The relationship between the bright area potential VL1 after exposure and the toner charging potential VT is |VL1+VT |≦
A control unit 115 that controls the voltage/current supply device 116 so that |VD1|≦(|VL1+VT |+100)
It is equipped with Here, the control unit 115 calculates the charging potential VT of the toner portion from the detection circuit 115a that inputs the amount of reflected light from the optical sensor 113 and converts it into the amount of toner, and the amount of toner and the known charging potential VT0 of the toner. It further includes an arithmetic circuit 115b that calculates the sum of the charged potential of the toner portion and the bright area potential VL0 of the photoreceptor before the pre-transfer exposure. Note that the other configurations are the same as those in the first embodiment, so explanations will be omitted.

The control operation of the control section 115 in the above configuration will be explained. The photoreceptor 101 is detected by the optical sensor 113.
When the amount of reflected light on the surface is detected, the control unit 115 converts the amount of reflected light into the amount of toner using the detection circuit 115a. continue,
The charging potential VT of the toner portion is calculated from the toner amount and the known charging potential VT0 of the toner, and the charging potential VT of the toner portion and the bright area potential VL0 of the photoconductor before the pre-transfer exposure is calculated.
The sum (VL1+VT) is calculated. Furthermore, the control unit 1
15, the relationship between the dark potential VD1 after pre-transfer exposure, the bright potential VL1 after pre-transfer exposure, and the toner charging potential VT is |VL1+VT |≦|VD1|≦(|VL1+
Voltage/current supply device 1 so that VT | +100)
16 to perform proper pre-transfer exposure via light source 114.

[Embodiment 3] In Embodiment 3, although illustrations and detailed descriptions of the configuration are omitted, instead of the reflection type optical sensor of Embodiment 2, an electrostatic induction type electrometer and an electrode vibration type electrometer were used. , a rotating sector type electrometer, or a vibratory capacitance type electrometer. Since the potential measured by these electrometers is (VL1+VT) itself, the control unit determines whether the exposure amount is |VL1+V based on the measured values of the electrometers.
T |≦|VD1|≦(|VL1+VT |+100)
The voltage/current supply device 116 is controlled so as to perform appropriate pre-transfer exposure via the light source 114.

As described above, in Examples 2 and 3, changes in the toner adhesion amount due to environmental changes and changes over time are accurately reflected in the toner charging potential VT, and the exposure amount is adjusted to |VL1+VT|≦| VD1｜≦(｜VL1+VT
|+100), it is possible to stably obtain an appropriate exposure amount.

[0034]

[Effects of the Invention] As explained above, the electrophotographic apparatus of the present invention includes a developing means for attaching a dry powder developer to an optical writing area formed on a photoconductor, and a developing means for attaching a dry powder developer to an optical writing area formed on a photoreceptor; In an electrophotographic apparatus equipped with a transfer means for transferring a developer from a photoreceptor onto a recording paper, an electrophotographic device disposed between the developing means and the transfer means and adjusting the amount of emitted light along the axial direction of the photoreceptor. Based on the paper width detected by the paper width detected by the paper width detected by the paper width, the dark area potential VD1 after the pre-transfer exposure and the pre-transfer The relationship between the bright area potential VL1 after exposure and the charging potential VT of the developer is |VD1|≧|V
The amount of light emitted by the pre-transfer exposure means is controlled so that L1+VT| Since it is equipped with a control means for controlling the amount of light emitted by the pre-transfer exposure means so that |≧|VL0|, it is possible to appropriately prevent toner scattering and prevent differences in photoreceptor fatigue depending on location. be able to.

Further, the electrophotographic apparatus of the present invention includes a developing means for applying a dry powder developer to an optical writing area formed on a photoreceptor, and a developing means for applying a dry powder developer to an optical writing area formed on a photoreceptor; In an electrophotographic apparatus equipped with a transfer means for transferring onto recording paper from above, a pre-transfer exposure means is disposed between the developing means and the transfer means, and a pre-transfer exposure means is disposed between the pre-transfer exposure means and the developing means. , and a potential detection means for detecting the sum of the bright area potential VL0 before the pre-transfer exposure and the charging potential VT of the developer;
Based on the detection results of the potential detection means, a dark potential VD1 after pre-transfer exposure, a light potential VL1 after pre-transfer exposure, and
The relationship between the charging potential VT of the developer is |VL1+VT |
≦|VD1|≦(|VL1+VT|+100) Since it is equipped with a control means for controlling the amount of light emitted from the pre-transfer exposure means so that can be prevented from occurring.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of an electrophotographic apparatus according to a first embodiment.

FIG. 2 is an explanatory diagram showing the configuration of a paper size detection sensor.

FIG. 3 is an explanatory diagram showing the amount of exposure in an area inside the paper and an area outside the paper.

FIG. 4 is an explanatory diagram showing the dark potential VD1 after pre-transfer exposure in the paper inner region and the dark potential VD1 after pre-transfer exposure in the outer paper region in Example 1;

FIG. 5 is an explanatory diagram showing the configuration of an electrophotographic apparatus according to a second embodiment.

FIG. 6 is an explanatory diagram showing the configuration of a conventional electrophotographic apparatus.

FIG. 7 is an explanatory diagram showing the surface potential of a photoreceptor.

FIG. 8 is an explanatory diagram showing changes in potential in an area inside the paper and an area outside the paper.

FIG. 9 is an explanatory diagram showing scattering when |VD1|≦|VL1|.

FIG. 10 is an explanatory diagram showing scattering when |VD1|≦|VL1+VT|.

[Explanation of symbols]

101 Photoreceptor
102 Main charger 103 Optical writing device
104 Developing device 105 Paper transport path
106 Transfer discharge device 107 Separation discharge device
108 Cleaning device 109 Static elimination lamp
110 Pre-transfer exposure light source 110a Electronic switch
110b LED 111 Paper size detection sensor 11
2 Control unit 113 Optical sensor
114 Light source 115 Control unit
115a Detection circuit 115b Arithmetic circuit
116 Voltage/current supply device VD0 Dark area potential before pre-transfer exposure V
D1 Dark potential after pre-transfer exposure VL0 Bright potential before pre-transfer exposure V
L1 Bright area potential after pre-transfer exposure VT Charged potential of toner

Claims (4)

[Claims] 1. A developing means for attaching a dry powder developer to an optical writing area formed on a photoconductor, and a transfer device for transferring the attached developer from the photoconductor onto a recording paper via the developing means. an electrophotographic apparatus comprising: a pre-transfer exposure means disposed between the developing means and the transfer means, and capable of adjusting the amount of emitted light along the axial direction of the photoreceptor; A detection means detects the paper width of the recording paper, and based on the paper width detected by the detection means, in the paper area on the photoreceptor, a dark potential VD1 after pre-transfer exposure, a bright potential VL1 after pre-transfer exposure, The amount of light emitted from the pre-transfer exposure means is controlled so that the relationship between the charging potential VT of the developer becomes |VD1|≧|VL1+VT| Dark potential VD
1 and the bright area potential VL0 before pre-transfer exposure is |VD
1. An electrophotographic apparatus comprising: a control means for controlling the amount of light emitted from the pre-transfer exposure means so that 1|≧|VL0|. 2. A developing means for attaching a dry powder developer to an optical writing area formed on the photoreceptor, and a transfer device for transferring the attached developer from the photoreceptor onto a recording paper via the developing means. an electrophotographic apparatus comprising: a pre-transfer exposure means disposed between the developing means and the transfer means; and a pre-transfer exposure means disposed between the pre-transfer exposure means and the developing means; A potential detection means detects the sum of the bright area potential VL0 before pre-exposure and the charging potential VT of the developer, and based on the detection result of the potential detection means, the dark area potential VD1 after the pre-transfer exposure, and the dark area potential VD1 after the pre-transfer exposure. The relationship between the bright area potential VL1 and the charging potential VT of the developer is |VL1+VT|≦
An electrophotographic apparatus comprising: a control means for controlling the amount of light emitted from the pre-transfer exposure means so that |VD1|≦(|VL1+VT|+100). 3. The potential detection means includes an electrostatic induction type electrometer, an electrode vibration type electrometer, a rotating sector type electrometer,
3. The electrophotographic apparatus according to claim 2, wherein the electrophotographic apparatus is one of a vibratory capacitance type electrometer. 4. The potential detection means includes an optical sensor that measures the amount of light reflected from the surface of the photoreceptor, and converts the amount of reflected light from the optical sensor into an amount of developer, and calculates the amount of developer and the known charging potential of the developer. VT, and further includes an arithmetic circuit that calculates the charging potential of the developer portion and the bright area potential VL0 of the photoreceptor before exposure before transfer. An electrophotographic apparatus according to claim 2.