JPH11272047A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the elongation of the bottom end of an image, in an image forming device. SOLUTION: The image forming device is provided with an image carrier 2, a photoreceptor 9, a voltage applying means 13, an optical scanner means 8 and a driving means 3 for the image carrier 2. The electric dischargeable region 100 of the photoreceptor 9 is provided with a distance from a main scanning axis M in the range of one-half of the spot diameter of light with which the photoreceptor 9 is irradiated from the optical scanning means 8, which is equal to or less than 400 μm on the downstream side in a sub-scanning direction S2 with respect to the main scanning axis M of the optical scanning means 8.

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 such as a copying machine and a printer for forming an electrostatic latent image on an image carrier.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a printer, an electrostatic latent image carrier such as a photoconductor is charged by a charging device and then exposed to form an electrostatic latent image. There is generally known an image forming process in which a latent image is developed with a toner to form a visible image, which is transferred to a transfer material and fixed.
However, in the conventional image forming method involving corona discharge,
It leads to environmental destruction such as generation of a large amount of ozone,
In recent years, it has been desired to provide an image forming method which suppresses the generation of ozone since the influence on the surface of the photoreceptor is large and the life of the photoreceptor is reduced.

As a low-ozone image forming method, for example, a method described in Japanese Patent Application Laid-Open No. 1-293358 has been proposed. In this image forming method, as shown in FIG. 9, a photoconductor 101 composed of small pieces and a cylindrical charge holding medium 102 are separately provided. The photoreceptor 101 has a photoconductive layer support 103, a photoreceptor electrode 104, and a photoconductive layer 105 sequentially laminated. On the other hand, the charge holding medium 102
Is formed by sequentially laminating an insulating layer support 106, a charge storage medium electrode 107, and a dielectric layer 108. The photoconductor 101 and the charge holding medium 102 are arranged such that the photoconductive layer 105 and the dielectric layer 108 face each other with a gap.

Then, a voltage is applied between the photosensitive member electrode 104 and the charge holding medium electrode 107, and the photosensitive member 101 is placed in a dark place.
When light is incident on the photoconductive layer 105 in the axial direction (main scanning direction), which is the front and back direction in FIG. 9, the portion of the photoconductive layer 105 where the light is incident shows conductivity, and this portion and the charge holding A discharge is generated between the insulating layer 108 of the medium 102 and the charge holding medium 1 rotated and driven in the direction of arrow b in the figure.
The electric charges are accumulated in the insulating layer 108 of No. 02 to form an electrostatic latent image. The formed electrostatic latent image is developed by the developing device 109 to become a toner image, and this toner image is transferred to paper or film by the transfer charger 110.

[0005]

As shown in FIG. 10 (a), an original consisting of a plurality of long and short lines in a sub-scanning direction, which is a direction orthogonal to the main scanning direction, is used by using the above-described apparatus. Exposure is performed in the main scanning direction to form an electrostatic latent image.
Then, as shown in FIG. 10B, the charge holding medium 10
An extension ΔL occurs at the rear end of the image of the electrostatic latent image formed in FIG. This elongation ΔL becomes more conspicuous as the image of the line becomes longer. SUMMARY OF THE INVENTION It is an object of the present invention to eliminate such elongation at the rear end of an image.

[0006]

As a result of studying the cause of the extension of the trailing edge of the image, the present inventors have found that excess carriers generated in the photoconductor are gradually released even after the end of exposure, and that discharge continues. It has been found that the stop of the exposure and the stop of the discharge do not coincide with each other, and the rear end of the latent image is elongated. Here, the excess carrier refers to a carrier present in the photoreceptor or, in the case of a stacked photoreceptor, a carrier complemented by a trap formed near the interface or a very high free carrier moving speed. It is a carrier of a slow component. The present invention is intended to eliminate the image expansion of the latent image due to the excess carrier by limiting an area where discharge of the photoconductor can occur (an area where discharge can occur).

Accordingly, the present invention provides an image carrier having a first conductive layer, an insulating layer formed on the first conductive layer, and a second conductive layer.
A conductive layer, and a photosensitive layer formed on the second conductive layer, a photosensitive body in which the insulating layer of the image carrier and the photosensitive layer are arranged to face each other, the first and the second Voltage applying means for applying a voltage between the two conductive layers, light scanning means for irradiating the photosensitive member with light to scan in the main scanning direction, and running on the image carrier in a sub-scanning direction orthogonal to the main scanning direction. And driving means for causing the voltage application means to perform the first and second driving.
An image is formed by irradiating the photosensitive member with light from the optical scanning means while applying a voltage between the conductive layers to perform image exposure, and forming a latent image on the traveling image carrier by discharging between the photosensitive member and the image carrier. In the forming apparatus, the dischargeable area of the photoconductor is located on the downstream side of the main scanning axis of the optical scanning unit in the sub-scanning direction. The image forming apparatus is provided in a range of 0.5 times or more and 400 μm or less of the spot diameter.

In the image forming apparatus of the present invention, the dischargeable basin of the photosensitive member is provided in the above-mentioned range. No discharge occurs between them. Therefore, after the exposure is completed, the discharge due to the excess carrier does not occur on the downstream side of the photoconductor in the sub-scanning direction, and the image can be faithfully reproduced without causing the image to expand in the traveling direction of the image carrier.

More specifically, the second conductive layer is partially provided on the downstream side in the sub-scanning direction with respect to the main scanning axis of the optical scanning means, so that the dischargeable area of the photosensitive member is formed in the second conductive layer. Set to a range.

The photosensitive layer may be partially provided on the downstream side in the sub-scanning direction with respect to the main scanning axis of the optical scanning means,
The dischargeable area of the photoconductor may be set in the range.

Further, the photoreceptor includes a photosensitive mask for preventing light from entering the photosensitive layer, and the photosensitive mask is partially provided on the downstream side in the sub-scanning direction with respect to the main scanning axis of the optical scanning means. The dischargeable area of the photoconductor may be set in the range.

Further, the image forming apparatus may further include a surface electrode layer formed on a surface of the photosensitive layer of the photosensitive member facing the first conductive layer of the image carrier, and a bias voltage applied to the surface electrode layer. Bias voltage applying means for applying voltage, the surface electrode layer may be partially provided on the downstream side in the sub-scanning direction of the optical scanning means, and the dischargeable area of the photoconductor may be set in the range.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the image forming apparatus of the present invention will be described with reference to the drawings. (First Embodiment) FIGS. 1 to 3 show an image forming apparatus 1 according to a first embodiment of the present invention. As shown in FIG. 1, an image bearing drum 2 serving as an image bearing member is disposed at the center of the image forming apparatus 1. This image bearing drum 2
The vehicle is driven in the direction of arrow a by a driving device 3 as a driving means.

As shown in FIG. 2, the image bearing drum 2 has a conductive layer 23 formed on the surface of an aluminum alloy base 21 as a conductor, and a polycarbonate resin is applied thereon to form a dielectric layer as an insulating layer. 25 is provided. The base 21 is grounded by a conductive wire (not shown). The structure of the image carrier is not limited to the drum shape, but may be a belt shape. Around the image bearing drum 2, a latent image forming device 5, a developing device 6, and a transfer roller 7 are sequentially arranged in the direction of arrow a in the figure.

The latent image forming apparatus 5 comprises an optical system 8 constituting optical scanning means, and a photosensitive member 9 disposed between the optical system 8 and the image bearing roller 2. The optical system 8 is
A semiconductor laser generator, a collimator lens, a polygon mirror, an Fθ lens, a reflection mirror, and the like are arranged in a housing 81. An exposure slit 82 is formed in a wall surface of the housing 81. The optical system 8 is configured so that a laser beam 83 generated by a semiconductor laser generator is applied to the photoconductor 9 from an exposure slit 82 to perform image exposure. Here, the direction in which the laser beam 83 scans and exposes is the axial direction of the image carrier drum 2 (the front and back direction in FIGS. 1 and 2), and this direction is hereinafter referred to as the main scanning direction S1. The traveling direction of the image bearing drum 2 perpendicular to the main scanning direction (the vertical direction in FIG. 2) is referred to as a sub-scanning direction S2.

The photosensitive member 9 has a structure in which a light transmitting conductive layer 92 and a photosensitive layer 93 are sequentially laminated on a light transmitting substrate 91 as shown in FIG. 2, and as shown in FIG. Is a long and narrow rectangular parallelepiped having a long length L and a short width W in the sub-scanning direction S2.

The translucent substrate 91 is made of a transparent glass plate. The light-transmitting conductive layer 92 is made of an ITO film, and is connected to the first power supply 13. Further, the photosensitive layer 93 is made of a semiconductor laser light (wavelength 780 nm) or LE.
A charge generation layer (CGL) 96 having a function for negative charging and having a good sensitivity to long wavelength light such as D light (wavelength 680 nm) and having a carrier pair generation function, and a free carrier transport function Charge transport layer (CTL) 97 having
Consists of

As shown in FIGS. 2 and 3, the position and orientation of the photosensitive member 9 with respect to the optical system 8 are such that the laser beam 83 is applied to the central position of the photosensitive member 9 in the sub-scanning direction S2 (width W direction). The length L direction of the photoconductor 9 is set to coincide with the main scanning direction S1. Therefore, the main scanning direction S of the scanned laser beam 83 indicated by a dashed line in FIG.
The locus 1 (main scanning axis M) is a bisector in the width W direction of the photoconductor 9.

As shown in FIGS. 2 and 3, the light-transmitting conductive layer 92 is provided over the entire length L of the photosensitive member 9 in the length direction.
However, the light-transmitting conductive layer 92 extends in the width W direction of the photoconductor 9 from the upstream end of the light-transmitting substrate 91 in the sub-scanning direction S2, beyond the main scanning axis M, and with respect to the main scanning axis M. Sub scanning direction S2
It is provided only up to a position separated by a distance a on the downstream side.

The area where the light-transmitting conductive layer 92 of the photosensitive member 9 exists is an area where discharge can occur between the image bearing rollers 2 when the laser beam 83 is irradiated (dischargeable area 100).
However, in a region where the translucent conductive layer 92 does not exist on the downstream side of the photoconductor 9 in the sub-scanning direction S2, even if the laser beam 83 is irradiated, no carrier pair is generated in the photoconductive layer 93, and No discharge occurs between the roller 2 and the roller 2. As described above, in the first embodiment, by setting the position of the end portion 92a on the downstream side in the sub-scanning direction S2 of the light-transmitting conductive layer 92 at a position separated by the distance a from the main scanning axis M, the sub-scanning direction S2 On the downstream side, the dischargeable area 100 of the photoconductor 9 is limited to a range from the main scanning axis M to the distance a. The photosensitive layer 93
Are provided in the entire length L direction and width W direction of the photoconductor 9.

The distance a is determined in relation to the diameter (spot diameter D _s ) of the laser beam 83 irradiated on the photosensitive member 9. Incidentally, the spot diameter D _S is, for example, 100Myuemu～1
It is about 50 μm. First, regarding the lower limit of the distance a, as shown in FIG.
So as not to protrude from the 00, 0 of the spot diameter D _S.
5 times (50 m to be in a range spot diameter D _S of the
75 μm) or more. Next, it is necessary to set the upper limit of the distance a so as to prevent the extension of the rear end of the image. As a result of various experiments and studies by the present inventors, it has been found that the upper limit is preferably 400 μm or more. did.

The developing device 6 includes a toner container 61 for storing a one-component developer (hereinafter, referred to as a toner), a developing sleeve 62 disposed close to the image bearing drum 2,
A supply roller 63 for stirring the toner contained in the toner containing section 61 and supplying the toner to the developing sleeve 62;

The transfer roller 7 is arranged in pressure contact with the image bearing roller 2. The recording paper S is passed between the transfer roller 7 and the image bearing roller 2.

Next, the formation of a latent image by the image forming apparatus 1 having the above configuration will be described. The light-transmitting conductive layer 92 of the photoreceptor 9 is, for example, 1.5 kV
In this case, between the conductive layer 23 of the image bearing roller 2 and the translucent conductive layer 92, which are grounded,
An electric field is formed by a voltage difference of 1.5 kV. When the photoconductor 9 is irradiated with the laser beam 83 emitted by the optical system 8 in the state where the electric field is formed as described above, the laser beam 83 transmits through the light-transmitting substrate 91 and the light-transmitting conductive layer 92. As a result, the charge reaches the charge generation layer 96 of the photosensitive layer 93. Charge generation layer 9
6 generates a carrier pair when absorbing light in the presence of an electric field. Of the generated carrier pairs, the free carriers move in the direction of the opposite electrodes having opposite polarities. At this time, the free carriers that have become free move through the charge transport layer 97 to the surface of the photosensitive layer 93. As a result, the electric field in the gap between the surface of the photosensitive layer 93 and the surface of the image bearing roller 2 increases. When the electric field exceeds a threshold determined by the passion rule, discharge occurs, and the surface of the dielectric layer 25 of the image bearing drum 2 corresponding to the exposure position of the photoconductor 9 is charged to form an electrostatic latent image. .

In the first embodiment, the light-transmitting conductive layer 92 is provided only at a position a distance a away from the scanning main axis M on the downstream side in the sub-scanning direction S2, and the photosensitive member on the downstream side in the sub-scanning direction S2 is provided. Nine dischargeable areas 100 are limited to this range. Therefore, in a region outside the dischargeable region 100 on the downstream side of the photoconductor 9 in the sub-scanning direction S2, the translucent conductive layer 9
No electric field is generated between the photosensitive member 9 and the image bearing roller 2 even when a voltage is applied to the roller 2. Therefore, in this region, even when the laser beam 83 is irradiated, no movable carrier pair is generated, and no discharge occurs between the photoconductor 9 and the image bearing drum 2. Accordingly, after the exposure, the discharge due to the excess carrier does not occur on the downstream side of the photosensitive member 9 in the sub-scanning direction S2. An electrostatic latent image is formed.

The electrostatic latent image formed on the image bearing drum 2 is
The toner is conveyed to the developing unit and developed by the developing device 6.
Thereafter, the toner image formed on the image bearing roller 2 is transferred to the recording paper S by the transfer roller 7.

Next, a specific experiment performed to confirm the effect of the above-described image forming apparatus of the first embodiment, that is, the effect of eliminating the extension of the rear end of the image will be described. In this experiment, the distance a from the main scanning axis M to the downstream end 92a of the translucent conductive layer 92 in the sub-scanning direction S2 was varied, and as shown in FIG. A line having a dot width of 30 mm and two lines in the sub-scanning direction S2 continuous with the line in the main scanning direction S1 and the downstream end in the sub-scanning direction S2.
A test pattern consisting of a line having a dot width of 40 mm was exposed to laser light 83, and the elongation ΔL shown in FIG. 5B was measured.

As a common condition of all the experimental examples,
The polycarbonate resin constituting the dielectric layer 25 of the image bearing drum 2 is applied to a thickness of 10 μm. Further, the photoconductor 9 is a translucent substrate 91 formed of a glass plate having a thickness of 1 mm.
An ITO film constituting the light-transmitting conductive layer 92 is deposited on the surface thereof, and a polyamide resin is applied thereon by 0.5 μm. Thereafter, a phthalocyanine pigment is applied as a 0.5 μm coating as the charge generation layer 96 of the photosensitive layer 93, and a hydrazone compound and a polycarbonate resin are applied as a charge transport layer 97 at a ratio of 4: 5 at 15 μm. Furthermore, the thickness d of the air layer
_a (distance from the surface of the photosensitive layer 93 to the surface of the dielectric layer 25) is 30 μm, the system speed (peripheral speed of the image bearing drum 2) is 38 mm / sec, and the amount of exposure light for exposing the photosensitive member 9 is 0.35.
mW / dot, the diameter of the exposure spot 19 at the time of exposure is set to 14
It was set to 0 μm. Except for the distance a, other configurations, materials, and the like are also unified.

[0029]

[Table 1]

Table 1 shows the experimental results of the experimental examples and comparative examples. In Table 1, the case where the amount of elongation ΔL was 0.05 mm or less was evaluated as ○, and the case where it exceeded 0.05 mm was evaluated as ×. As shown in Table 1, in Experimental Examples 1 to 3 in which the distance a was set to 400 μm or less, the evaluation was ○, whereas Comparative Example 1 to Comparative Example in which the distance a was set to be larger than 400 μm. In 3, the evaluation is x. Therefore, in order to eliminate the trailing edge extension of the image, the distance a is set to 400
It can be confirmed that it is preferable to set the thickness to μm or less.

(Second Embodiment) A second embodiment of the present invention shown in FIG.
In the embodiment, the charge generation layer 96 of the photosensitive layer 93 is provided in the entire length L direction of the photoconductor 9, but in the width W direction of the photoconductor 9, the sub-scanning direction S <b> 2 It is provided only from the upstream end beyond the main scanning axis M to a position at a distance a downstream of the main scanning axis M in the sub-scanning direction S2. The distance a, as in the first embodiment, more than 0.5 times the spot diameter D _S of the laser beam 83 40
It is set to 0 μm or less.

The area of the photosensitive member 9 where the charge generation layer 96 exists is a dischargeable area 100 where discharge can occur between the image bearing rollers 2 when irradiated with the laser beam 83.
Dischargeable area 100 downstream of photoconductor 9 in sub-scanning direction S2
Outside the range, the charge generation layer 96 does not exist, so that no movable carrier pair is generated even when the laser beam 83 is irradiated, and no discharge occurs between the carrier pair and the image bearing roller 2.

As described above, in the second embodiment, the photosensitive layer 93
Of the charge generation layer 96 on the downstream side in the sub-scanning direction S2
Is set at a position separated by a distance a from the main scanning axis M, so that the dischargeable area 100 of the photoconductor 9 is limited to a range from the main scanning axis M to the distance a on the downstream side in the sub-scanning direction S2. doing. Therefore, the extension of the rear end of the image can be eliminated as in the first embodiment.

(Third Embodiment) A third embodiment of the present invention shown in FIG.
In the embodiment, the surface on the photosensitive layer 93 side of the translucent substrate 91 is
A photosensitive mask 111 is provided. This photosensitive mask 1
Numeral 11 is provided in the entire length L direction of the photoconductor 9, but in the width w direction of the photoconductor 9, light is transmitted from a position spaced a distance a from the main scanning axis M to the downstream side in the sub scanning direction S <b> 2. Substrate 9
No. 1 is provided only to the downstream end in the sub-scanning direction S2. The distance a, as in the first embodiment, is set below 400 [mu] m 0.5 times the spot diameter D _S of the laser beam 83.

In the area of the photosensitive member 9 where the photosensitive mask 111 does not exist, the irradiated laser beam 83 reaches the photosensitive layer 93, so that a dischargeable area 100 where discharge can occur between the image bearing rollers 2 is formed. The sub-scanning direction S of the photoconductor 9
In the area where the photosensitive mask 111 is provided on the downstream side, the irradiated laser beam 83 does not reach the photosensitive layer 93, so that no discharge occurs between the laser beam 83 and the image bearing roller 2.

As described above, in the third embodiment, the photosensitive mask 111 is moved from the main scanning axis M to the downstream side in the sub-scanning direction S2 by the distance a.
The dischargeable area 100 is provided at a distance a from the main scanning axis M on the downstream side in the sub-scanning direction S2 by providing the light-transmitting substrate 91 from the position separated from the main scanning axis S to the downstream end in the sub-scanning direction S2.
It is limited to the range up to. Therefore, the extension of the rear end of the image can be eliminated as in the first embodiment.

(Fourth Embodiment) A fourth embodiment of the present invention shown in FIG.
In the embodiment, the surface electrode layer 113 connected to the second power supply 112 is provided on the surface of the photosensitive layer 93. The surface electrode layer 113 is provided on the entire length L direction of the photoconductor 9, but is separated from the main scanning axis M by a distance a in the sub scanning direction S <b> 2 downstream in the width w direction of the photoconductor 9. It is provided only from the position to the downstream end of the translucent substrate 91 in the sub-scanning direction S2. The distance a, as in the first embodiment, is set below 400 [mu] m 0.5 times the spot diameter D _S of the laser beam 83.

On the surfaces of the surface electrode layer 113 and the photosensitive layer 93, an insulating surface protective layer 115 is provided. The surface protective layer 115 is for protecting the surface electrode layer 113 during discharge, but is not necessarily provided.

In the image forming apparatus of the fourth embodiment, at the time of image formation, a voltage is applied to the light transmitting conductive layer 92 and the surface electrode layer 113 by the first and second power supplies 13 and 112, respectively. The light-transmitting conductive layer 9 is formed by the first electrode 13.
2 is higher than the bias voltage applied to the surface electrode layer 113 by the second power supply 112. For example, a voltage of 1.5 kV is applied to the translucent conductive layer 92, and a bias voltage of 50 V is applied to the surface electrode layer 113.

An area where the photosensitive mask 111 does not exist is a dischargeable area 100 where discharge can occur between the photosensitive mask 111 and the image bearing roller 2. On the other hand, the surface electrode layer 113 of the photosensitive layer 93
Is applied to the surface electrode layer 113 as described above, so that the voltage between the surface electrode 113 and the conductive layer 32 is set to a voltage that does not discharge (50 V in the present embodiment). Therefore, the generated carriers are captured by the surface electrode 113. Therefore, no discharge occurs between the region of the photoconductor 9 where the surface electrode layer 113 is provided and the image bearing drum 2.

As described above, in the fourth embodiment, the surface electrode layer 113 is moved from the main scanning axis M to the downstream side in the sub-scanning direction S2 by the distance a.
At a position from the main scanning axis M to the distance a from the main scanning axis M on the downstream side in the sub-scanning direction S2. Is limited to the range. Therefore, the extension of the rear end of the image can be eliminated as in the first embodiment.

Note that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the first to fourth embodiments, the dischargeable area 100 is the entire width w direction of the photoconductor 9 upstream of the main scanning axis M in the sub-scanning direction S2. The dischargeable area 100 upstream of the main scanning axis M in the sub-scanning direction S2 may be narrowed within a range not less than 0.5 times the diameter.

[0043]

As is apparent from the above description, in the present invention, the dischargeable area of the photosensitive member is located downstream of the main scanning axis with respect to the main scanning axis of the optical scanning means. The spot diameter of the light emitted from the optical scanning means to the photoreceptor on the downstream side in the sub-scanning direction is set within a range of 0.5 times or more and 400 μm or less. Therefore, no discharge occurs between the photoconductor and the image carrier in a range exceeding the above-mentioned range on the downstream side of the photoconductor in the sub-scanning direction. Therefore, after the exposure is completed, the discharge due to the excess carrier does not occur on the downstream side of the photoconductor in the sub-scanning direction, and the image can be faithfully reproduced without causing the image to expand in the traveling direction of the image carrier.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the image forming apparatus according to the first embodiment.

FIG. 3 is a front view showing a photoconductor.

FIG. 4 is a partially enlarged view of a photoconductor.

FIG. 5A is a schematic diagram showing a test pattern in an experiment, and FIG. 5B is a schematic diagram showing elongation occurring in the test pattern.

FIG. 6 is an enlarged view of a main part of an image forming apparatus according to a second embodiment of the present invention.

FIG. 7 is an enlarged view of a main part of an image forming apparatus according to a third embodiment of the present invention.

FIG. 8 is an enlarged view of a main part of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating a conventional image forming apparatus.

FIG. 10A is a schematic diagram illustrating a test pattern of a document image, and FIG. 10B is a schematic diagram illustrating a toner image of the test pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image carrying roller (image carrier) 23 Conductive layer (first conductive layer) 25 Dielectric layer (insulating layer) 3 Driving motor (driving means) 6 Developing device 8 Optical system (optical scanning means) 9 Photoconductor 13 Power supply (voltage application means) 91 Translucent substrate 92 Translucent conductive layer (second conductive layer) 93 Photosensitive layer 96 Charge generation layer 97 Charge transport layer 100 Dischargeable area 111 Photomask 112 Power supply (bias voltage) Application means) 113 Surface electrode layer 104 Surface protective layer

Claims (5)

[Claims] A first conductive layer; an image carrier having an insulating layer formed on the conductive layer; a second conductive layer; and a photosensitive layer formed on the second conductive layer. A photoconductor arranged so that the insulating layer of the image carrier and the photoconductive layer face each other; a voltage application unit for applying a voltage between the first and second conductive layers; Light scanning means for scanning in the main scanning direction by irradiating light; driving means for moving the image carrier in a sub-scanning direction orthogonal to the main scanning direction; An image forming apparatus that irradiates light from a light scanning unit to a photoconductor while applying a voltage between layers to perform image exposure, and forms a latent image on a traveling image carrier by discharging between the photoconductor and the image carrier. In the above, the dischargeable area of the photoconductor is located forward of a main scanning axis of the optical scanning unit. An image is provided on the downstream side in the sub-scanning direction in a range of 0.5 times or more and 400 μm or less of a spot diameter of light irradiated from the main scanning axis to the photoconductor from the optical scanning unit. Forming equipment. 2. The method according to claim 1, wherein the second conductive layer is partially provided on the downstream side in the sub-scanning direction with respect to a main scanning axis of the optical scanning unit, and a dischargeable area of the photoconductor is set in the range. The image forming apparatus according to claim 1. 3. The photosensitive layer is provided partially on the downstream side in the sub-scanning direction with respect to the main scanning axis of the optical scanning means, and a dischargeable area of the photoconductor is set in the range. 2. The image forming apparatus according to 1. 4. The photosensitive member includes a photosensitive mask for preventing light from entering the photosensitive layer, and the photosensitive mask is partially provided on the downstream side in the sub-scanning direction with respect to the main scanning axis of the optical scanning means. 2. The image forming apparatus according to claim 1, wherein a dischargeable area of the photoconductor is set to the range. 5. An image forming apparatus comprising: a surface electrode layer formed on a surface of a photosensitive layer of the photosensitive member facing a first conductive layer of the image carrier; and applying a bias voltage to the surface electrode layer. 2. A bias voltage applying unit, wherein the surface electrode layer is partially provided downstream of the optical scanning unit in a sub-scanning direction, and a dischargeable area of the photoconductor is set in the range. Image forming apparatus.