JPH09244365A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the elongation at the rear end of an image. SOLUTION: An image forming device has an image carrier 2 provided with an insulating layer 25 formed on a conductive layer 23 and a photosensitive member 9 provided with a photosensitive layer 93 formed on a conductive layer 92, both being arranged for the insulating layer 25 to be opposed to the photosensitive layer 93. An image is exposed in the state that voltage is applied between both conductive layers 23, 92 and a latent image is formed on the running image carrier 2 by discharge between the photosensitive member 9 and the image carrier 2. The photosensitive layer 93 consists of a charge generating layer 96 to generate charges with the irradiation of light and a charge transporting layer 97 to transport charges, the charge generating layer 96 being linearly formed to be extended perpendicular to the running direction of the image carrier 2.

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 or a printer that forms 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. An image forming process is generally known in which the latent image is developed with toner to form a visible image, which is transferred to a transfer material and fixed. However, the conventional imaging method involving corona discharge leads to environmental damage such as the generation of a large amount of ozone, and has a large effect on the surface of the photoconductor, leading to a reduction in the life of the photoconductor. It is desired to provide a pressed image forming method.

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 photoreceptor 101 made of small pieces and a cylindrical charge holding medium 102 are separately provided. The photoconductor 101 includes a photoconductive layer support 103, a photoconductor electrode 104, and a photoconductive layer 105, which are sequentially stacked. On the other hand, the charge holding medium 102
Is an insulating layer support 106, a charge holding medium electrode 107, and an insulating layer 108, which are sequentially stacked. The photoconductor 101 and the charge holding medium 102 are arranged so that the photoconductive layer 105 and the insulating layer 108 face each other with a gap.

Then, a voltage is applied between the photoconductor electrode 104 and the charge holding medium electrode 107, and the photoconductor 101 is placed in a dark place.
When light is incident on the charge carrier 102 to scan it in the axial direction (main scanning direction), the portion of the photoconductive layer 105 on which light is incident exhibits conductivity, and that portion and the insulating layer 108 of the charge carrier medium 102 are A discharge is generated during this period, and charges are accumulated in the insulating layer 108 of the charge holding medium 102 that has been rotated in the direction of arrow b in the figure to form an electrostatic latent image. The formed electrostatic latent image is developed by the developing device 109 to become a toner image,
The toner image is transferred by transfer charger 110 to paper or film.

[0005]

With the above-described device, the structure shown in FIG.
As shown in (a), an original consisting of a plurality of long and short lines long in the sub-scanning direction is exposed in the main scanning direction to form an electrostatic latent image. Then, as shown in FIG. 10B, the rear end of the electrostatic latent image formed on the charge holding medium 102 extends by ΔL. This elongation ΔL appears more prominently as the image of the longer line. An object of the present invention is to eliminate such elongation of the trailing edge of the image.

[0006]

As a result, the inventors of the present invention have examined the cause of the extension of the trailing edge of the image, and as a result, excess carriers generated in the photoconductor are gradually released even after the end of exposure and discharge continues. As a result, it was found that the stop of the exposure and the stop of the discharge did not coincide with each other, and the trailing edge of the latent image was elongated. Here, the excess carrier includes a carrier of a component having a very low moving speed among the free carriers, and is a carrier that is not discharged during the exposure among the carriers generated by the exposure.

As one of the causes of generation of this excess carrier, in the insulating layer of the image bearing member, the charged area due to the previous exposure and the charged area due to the present exposure overlap, and the potential of the insulating layer has already risen in this overlapped area. However, since the electric field strength applied to the photosensitive layer becomes small, it is conceivable that some of the carriers generated in the exposed region of the photosensitive member are not discharged, but some of them are retained in the photosensitive member as excess carriers. In the present invention, the image elongation of the latent image is eliminated by not generating this excess carrier.

That is, in the image forming apparatus of the present invention, the image carrier having the insulating layer formed on the conductive layer and the photosensitive member having the photosensitive layer formed on the conductive layer are arranged so that the insulating layer and the photosensitive layer face each other. An image forming apparatus, which is arranged and performs image exposure by irradiating light from a light source in a state where a voltage is applied between both conductive layers, and forms a latent image on a running image carrier by discharge between the photoconductor and the image carrier. In the above, the photosensitive layer has a charge generation layer that generates a charge by irradiation of light and a charge transport layer having a charge transport function, and the charge generation layer is arranged in a direction orthogonal to the traveling direction of the image carrier. It is formed in the shape of an extending strip.

In the image forming apparatus constructed as described above, in a state in which a voltage is applied between the conductive layer of the photoconductor and the conductive layer of the image carrier, the photosensitive layer is moved in the direction orthogonal to the running direction of the image carrier. An image is exposed on the extended charge generating layer. This creates a pair of carriers in a limited area within the photosensitive layer. Free carriers of the generated carrier pairs move to the surface of the photosensitive layer. Due to this phenomenon, the electric field between the photosensitive layer and the image carrier rises to generate discharge, and an electrostatic latent image is formed on the image carrier.

At this time, the region of the photosensitive layer in which the charge generation layer is present is limited, and discharge occurs in the limited region on the image bearing member to be charged. Therefore, the charging areas do not overlap each other in the traveling direction on the image carrier, and the generation of excess carriers can be prevented. Therefore, all of the carriers generated in the charge generation layer of the photosensitive layer are consumed for discharging, and the latent image formed on the insulating layer of the image carrier is not elongated.

Further, it is preferable that the width of the charge generation layer is formed to be narrower than the diameter of light emitted from the light source in the traveling direction of the image carrier. By forming in this way, the charge amount distribution in the running direction of the charging area on the image carrier becomes rectangular, and the charging area can be uniformly charged,
The sharpness of the formed image is high.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image forming apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of the image forming apparatus 1 according to the first embodiment.
Shows a partially enlarged configuration diagram of the photoconductor 9 and the image bearing belt 2, which are essential parts. At the center of the image forming apparatus 1, an image bearing belt 2 as an image bearing member is disposed. The image bearing belt 2 is rotated in the direction of arrow a by a driving roller 3 which is rotated by a driving device (not shown) and a heating roller 4 which is provided in parallel with the driving roller 3.

As shown in FIG. 2, the image bearing belt 2 has a conductive layer 23 formed on the surface of a base 21 made of a dielectric material, and a dielectric layer 25 serving as an insulating layer formed on the conductive layer 23.
Specifically, thickness 50 μm, width 25 cm, perimeter 30 cm
The conductive layer 23 is provided on the base 21 made of the polyimide film, and the dielectric layer 25 made of fluororesin having a thickness of several μm is further provided on the conductive layer 23. Also, the conductive layer 23
Are grounded by the conductive line 12. The structure of the image carrier is not limited to such a belt, and may be drum-shaped. Image carrying belt 2 described above
A latent image forming device 5, a developing device 6, and a transfer roller 7 are sequentially arranged in the surroundings of in the direction of arrow a in the figure.

The latent image forming device 5 comprises an optical system 8 and a photoconductor 9 arranged between the optical system 8 and the image carrying belt 2. The optical system 8 includes a housing 81 in which a semiconductor laser generator, which is a light source, a collimator lens, a polygon mirror, an Fθ lens, a reflection mirror, and the like are arranged, and the exposure slit 8 is formed on the wall surface of the housing 81.
2 are formed. The optical system 8 is configured such that a laser beam 83 generated by a semiconductor laser
To the photoreceptor 9 from above, so that image exposure can be performed.

Here, the direction in which the laser beam 83 is scanned and exposed is the width direction of the image carrying belt 2 (front and back direction in FIG. 1).
And this direction is called the main scanning direction. Further, the traveling direction of the image carrying belt 2 (the vertical direction in FIG. 1) which is orthogonal to the main scanning direction is called the sub-scanning direction. Further, in the present embodiment, the diameter R of the exposure spot 19 in the sub-scanning direction is 140.
An optical system 8 that performs scanning exposure with μm is used. It should be noted that the diameter R of the exposure spot 19 is, as shown in FIG. 4, 1 / when the maximum light amount in the spot central portion is 1 in the light amount distribution decreasing from the central portion of the exposure spot toward the outside.
e The diameter of a range having a light amount of ² or more.

As shown in FIG. 2, the photosensitive member 9 has a structure in which a transparent conductive layer 92 and a photosensitive layer 93 are sequentially laminated on a transparent substrate 91. The transparent substrate 91 is a transparent glass plate. The transparent conductive layer 92 includes an ITO film 94 which is a conductive material,
It is composed of a polyamide resin layer 95 which is an injection preventing layer. The ITO film 94 of the translucent conductive layer 92 has a first power source 13
Is connected.

The photosensitive layer 93 has a semiconductor laser beam (wavelength 78).
(0 nm) or LED light (wavelength 680 nm), which is a function-separated type having good sensitivity to long-wavelength light and has a carrier generation function (CGL) 96 and a free carrier transport function. Charge transport layer (CTL)
It consists of 97 and. As shown in FIG. 3, the charge generation layer 96 is formed in a strip shape having a width d in the sub-scanning direction of 90 μm and extending narrowly in the main scanning direction.

A spacer 10 made of fluororesin is provided between the photoconductor 9 and the image bearing belt 2 as shown in FIG.
Thus, an air gap is provided, and the photosensitive layer 93 of the photoconductor 9 and the dielectric layer 25 of the image bearing belt 2 are arranged to face each other via the air gap. Since the photosensitive member 9 is not in contact with the image bearing belt 2, the surface of the photosensitive member 9 is not contaminated even if foreign matters are conveyed as the image bearing belt 2 travels, and a stable latent image is formed. Can be done easily. Further, the member to be the spacer 10 is not particularly limited to the fluororesin, but may be any member as long as it has a small coefficient of friction with the image carrying belt 2 and is hard to be scratched.

The developing device 6 includes a toner containing portion 61 containing a one-component developer (hereinafter referred to as toner) and a developing sleeve 62 arranged in the vicinity of the image carrying belt 2.
The supply roller 63 supplies toner to the developing sleeve 62 by stirring the toner stored in the toner storage portion 61. The toner used in the developing device 6 is of a negative charging type and has a mean particle size of 10 μm obtained by kneading, pulverizing and classifying a mixture containing a bisphenol A type polyester resin and carbon black as main components by a known method. is there. An appropriate developing bias voltage is applied to the developing sleeve 62 in order to prevent background fogging.

The transfer roller 7 faces the heating roller 4 with the image bearing belt 2 interposed therebetween, and
It is arranged in pressure contact with. The recording paper S is passed between the transfer roller 7 and the image carrying belt 2.

In the image forming apparatus 1 configured as described above, the process of latent image formation will be described first.
A voltage (V _C ) of 1.5 kV is applied to the translucent conductive layer 92 of the photoconductor 9 by the first power supply 13. Therefore, an electric field due to a potential difference of 1.5 kV is formed between the conductive layer 23 of the image bearing belt 2 and the translucent conductive layer 92 which are grounded.

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 passes through the transparent substrate 91 (support). Then, the light passes through the transparent conductive layer 92 and reaches the photosensitive layer 93. A charge generating layer 9 formed in a strip shape extending in the main scanning direction.
6 generates a carrier pair when absorbing light in the presence of an electric field. Among the generated carrier pairs, the freed carriers move toward opposite electrodes having opposite polarities. At this time, the freed positive carriers move to the surface of the photosensitive layer 93 through the charge transport layer 97. As a result, the electric field between the gaps on the surface of the photosensitive layer 93 and the surface of the image bearing belt 2 rises. When this electric field exceeds a threshold value determined by the passion law, discharge is generated, and the surface of the dielectric layer 25 of the image bearing belt 2 corresponding to the exposure position of the photoconductor 9 is charged to form an electrostatic latent image. .

At this time, tentatively, as shown in FIG.
Dielectric layer 2 of image-bearing belt 2 by this (second) exposure
When the charged area of 5 partially overlaps with the charged area of the previous (first) exposure (area k), the potential of the overlapped area k has already risen. FIG. 6 shows the state of the potential distribution between the photoconductor 9 and the image bearing belt 2 at this time. In this figure, the vertical axis represents the potential, the horizontal axis represents the position (distance), and the slope of the graph represents the strength of the electric field. The solid line shows the potential distribution when the surface of the dielectric layer 25 is charged, and the broken line shows the potential distribution when the surface of the dielectric layer 25 is not charged.

As is apparent from FIG. 6, the dielectric layer 25
When the surface is charged, the potential difference between the transparent conductive layer 92 of the photoconductor 9 and the surface of the dielectric layer 25 of the image bearing belt 2 becomes small. Then, the inclination of the graph becomes smaller, and the photosensitive layer 93
The electric field between the air gap between the and dielectric layer 25 and the electric field formed in the photosensitive layer 93 both weaken. Then, the moving speed of the carriers generated in the charge generation layer 96 in the present exposure in the photosensitive layer 93 becomes slow, and a part of the carrier is not discharged and the photosensitive layer 93 is not discharged.
Retained inside as excess carrier. As described above, the excess carriers form space charges in the photosensitive layer 93 and cause elongation of the trailing edge of the image.

However, the charge generation layer 96 of the photoreceptor 9 is
Is formed in a band shape extending in the main scanning direction, and the region where the carrier pair is generated is limited to the region where the charge generation layer 96 exists, even if the irradiation region of the laser beam 83 is expanded. Therefore, the area where the upper and lower parts of the laser beam 83 in the sub-scanning direction are cut becomes the exposure area of the photoconductor. As a result, as shown in FIG. 5B, the dielectric layer 2 of the image bearing belt 2 is
The charge distribution in the sub-scanning direction discharged above 5 has a rectangular shape with both ends cut and is uniformly charged. In addition, overlapping of charged areas is eliminated, and generation of excess carriers is prevented. By thus forming the charge generation layer 96 in a strip shape that narrowly extends in the main scanning direction, generation of excess carriers can be suppressed, and discharge ends in synchronization with the end of exposure.
A desired latent image that is almost the same as the exposed image can be formed.

Here, the traveling speed (system speed) V _S of the image bearing belt 2 will be described. In the case of this case,
As shown in (b), by using the dielectric layer 25 in a state where the charged areas in the sub-scanning direction do not overlap, the effect is remarkably exhibited. Therefore, it is necessary to appropriately set the traveling speed V _S of the image bearing belt 2. In order to prevent the charged areas from overlapping, a value obtained by dividing the width W of the charged areas in the sub-scanning direction by the exposure interval time, that is, the time from the first exposure to the second exposure, causes the image carrying belt 2 to travel. it is the speed V _S.

The width W in the sub-scanning direction is determined by the charge generation layer 96.
Is determined by the width d in the sub-scanning direction and the exposure spot diameter R of the laser light. When the width d of the charge generation layer 96 in the sub-scanning direction is equal to or smaller than the exposure spot diameter R of the laser light 83, the width of the charged region on the dielectric layer 25 charged in one main scan in the sub-scanning direction is: It is almost equal to the width d in the sub-scanning direction. vice versa,
When the width d of the charge generation layer 96 in the sub-scanning direction is larger than the exposure spot diameter R of the laser light 83, the width in the sub-scanning direction of the charged region on the dielectric layer 25 that is charged in one main scan is:
It may be considered as the exposure spot diameter R of the laser beam 83.

In addition, in an apparatus in which the traveling speed (system speed) V _{S of} the image bearing belt 2 is predetermined, the charging width (charging in one main scan is calculated from the product of the exposure interval time and the traveling speed V _S. The width of the charge generation layer 96 in the sub-scanning direction may be set to an appropriate value.

Specifically, the exposure interval time of the laser beam 83 is 2.24 ms (a unique value determined by the laser scanning speed), and the width d of the charge generation layer 96 in the sub-scanning direction is 90.
The exposure spot diameter R of the laser beam 83 is 140 μm.
Therefore, the width of the charging region in the sub-scanning direction is 90 μm. Therefore, the traveling speed (system speed) V _S of the image bearing belt 2 is (90 × 10 ⁻⁶ ) ÷ (2.24 × 10
^-3 ), 40 mm / s.

Next, the process after formation of the latent image will be described. The electrostatic latent image formed on the image bearing belt 2 is conveyed to the developing section by the rotation of the driving roller 3 and the heating roller 4,
The toner is developed by the developing device 6. After that, the toner image formed on the image carrying belt 2 is further transferred to the driving roller 3
Also, it is conveyed by the rotation of the heating roller 4, is heated by the heating element 11 provided inside the heating roller 4, and is simultaneously transferred onto the recording sheet S by the transfer roller 7. At this time, the toner image is melted and transferred, so that the toner does not remain on the image bearing belt 2 and is almost completely transferred to the recording paper S and is fixed at the same time.

As the photoconductor 9 of the above-mentioned embodiment,
The one manufactured by the following method is used. First, a translucent substrate 91 having a substantially plate shape that is long in the main scanning direction, specifically, a width in the main scanning direction of 250 mm, a width in the sub scanning direction of 30 mm,
An ITO film 94 is formed on the surface of a transparent glass plate having a thickness of 3 mm to a thickness of about 0.2 μm by a known ion plating method (the area resistance of the ITO film is about 100 Ω / □),
Further, a conductive layer 9 having a polyamide resin of about 0.5 μm applied thereon by a dipping method as an injection preventing layer 95.
The substrate on which 2 was formed was used as a substrate.

The strip-shaped charge generation layer 96 extending in the main scanning direction as shown in FIG. 3 is obtained by bringing a mask sheet having strip-shaped slits into close contact with the surface of the conductive layer 92 of the substrate and dipping the photosensitive coating shown below. On the conductive layer 92 using
Application is performed so that the film thickness after drying is 0.15 μm, and then the mask sheet is removed to form the charge generation layer 96 extending in the main scanning direction.

The photosensitive paint used for the charge generation layer 96 is τ
(Tau) type metal-free phthalocyanine 1 part by weight, polyvinyl butyral resin 2 parts by weight, and tetrahydrofuran 100
Parts by weight were placed in a ball mill pot and dispersed for 24 hours. At this time, the viscosity of the photosensitive coating is 15c at 20 ° C.
p. Further, as the polyvinyl butyral resin,
The degree of acetylation is 3 mol% or less, the degree of butylation is 70 mol%, and the degree of polymerization is 1000. The charge generation layer 96 is formed by adhering a mask sheet and applying a solution of a photosensitive material dissolved in a solvent. However, the charge generating layer 96 may be formed by vapor-depositing the photosensitive material on a substrate to which the mask sheet is adhered. You can

Next, the charge generation layer 9 formed in the band shape
8 parts by weight of a hydrazone compound represented by the following structural formula (formula 1), 0.1 parts by weight of an orange dye, and 10 parts by weight of a polycarbonate resin on tetrahydrofuran and 18
A coating solution dissolved in a solvent consisting of 0 parts by weight was applied by a depping method and dried to form a charge transport layer 97 having a film thickness of 21 μm.

[0035]

Embedded image

Regarding the photosensitive layer 93, known materials may be appropriately selected as the charge generating material, the charge transporting material, the binder resin, the additive, etc. according to the purpose. In addition, the photosensitive material is not limited to the organic material, and an inorganic material such as zinc oxide, cadmium sulfide, selenium alloy, amorphous silicon alloy, amorphous germanium alloy may be used. Further, a publicly known undercoat layer may be provided for the purpose of improving charging performance, image quality, adhesion to a substrate and the like. The transparent substrate 91 is not particularly limited as long as it is a substrate that is transparent to the light to be exposed and serves as a support.

Instead of the ITO film 94 used for the conductive layer 92, a transparent conductive material that can be patterned on a substrate such as glass or a transparent resin may be used.
However, the area resistance is 1000Ω to avoid voltage drop.
It is preferable to use a material having a thickness of / □ or less. The method of forming the conductive layer 92 is not limited to the method described above, and the conductive material layer may be formed by a method such as vapor deposition or sputtering instead of the ion plating method. Further, the injection prevention layer 95 is not limited to the polyamide resin, and a known material having a light transmitting property may be used.

The material of the dielectric material that can be used for the base 21 and the dielectric layer 25 of the image bearing belt 2 of the above-described embodiment is not limited to the above-mentioned polyimide or fluororesin, but may be polyethylene, polypropylene, ionomer. , Polyvinyl alcohol, polyvinyl acetate, ethylene vinyl acetate copolymer, poly-4-methylpentene-
1, polymethyl methacrylate, polycarbonate polystyrene, acrylonitrile methyl acrylate copolymer,
Acrylonitrile butadiene styrene copolymer, polyterephthalate ethylene, polyuretanelastomer, cellulose acetate, cellulose triacetate, cellulose nitrate, cellulose propionate, cellulose acetate butyrate, ethyl cellulose, regenerated cellulose, nylon 6, nylon 66, nylon 11, nylon 12 , Polysulfone, polyether sulfone, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, polyvinylidene chloride, vinylidene chloride, vinyl chloride copolymer, vinyl nitrile rubber alloy, polytetrafluoroethylene, polychlorotrifluoroethylene, polyfluoride Materials such as vinyl, polyvinylidene fluoride, and polyethylene tetrafluoroethylene copolymer may be used.

However, the electric resistivity of the material of the dielectric layer 25 is preferably 10 ¹¹ Ωcm or more in order to prevent the charging potential from decreasing with time. Also, the dielectric layer 25
The thickness is not particularly limited as long as the strength is within a range that does not cause a problem in practical handling and durability.
Generally, it is considered that about 2 to 100 μm is appropriate.

Next, the image forming apparatus 1 of the above-described embodiment
A concrete experiment conducted for confirming the effect of the above, that is, the effect of eliminating the elongation at the trailing edge of the image will be described. This experiment was carried out by changing various conditions by using the image bearing belt 2 and the photoconductor 9 having the strip-shaped charge generation layer 96 extending in the main scanning direction shown in FIGS. As conditions common to all the experimental examples, the voltage V _C applied to the conductive layer 92 of the photoreceptor 9 is 1.5 kV, and the film thickness d _p of the photosensitive layer 93 is 21 μ.
m, air layer thickness d _a (from the surface of the photosensitive layer 93 to the dielectric layer 25
The distance to the surface) was 30 μm, and the film thickness d _i of the dielectric layer 25 of the image bearing belt 2 was 15 μm. Further, the exposure light amount for exposing the photoconductor 9 was set to 0.35 mW / dot. Other configurations, materials and the like are the same as those in the above-described embodiment.

Table 1 shows the conditions of the experimental examples and comparative examples and the experimental results thereof. In Experimental Examples 1 to 5, the exposure spot diameter R of the laser beam was 140 μm, and the strip-shaped charge generation layer 96 was used.
The width d in the sub-scanning direction was changed. Next, Experimental Examples 6 to 10
Then, the exposure spot diameter R of the laser beam is set to 200 μm,
Similar to Experimental Examples 1 to 5, the width d of the strip-shaped charge generation layer 96 in the sub-scanning direction was changed. Further, as a comparative example, using a flat conductive layer on the entire surface, the exposure spot diameter R of the laser beam was set to 140 μm and 200 μm, and the system speed V was set.
_Shows that _S is changed.

As shown in FIG. 10 (a), each of the experimental examples and the comparative examples has a length of 10 mm to 40 mm and a width of 4 mm.
A test pattern consisting of dot vertical lines (lines in the sub-scanning direction) is exposed by laser light, and the line length extension ΔL (see FIG. 10B) of the toner image actually reproduced on the recording paper S is measured. did.

A very good condition in which the measured value of ΔL is in the range of ± 30 μm ◎ A good condition in the range of ± 50 μm ○ A less disturbing condition in the range of ± 100 μm ◇ Within the range of ± 200 μm A somewhat anxious state was evaluated as Δ, and a practically problematic state with a fluctuation range of more than that was evaluated as ×. In addition, * was added to the line images themselves which caused breaks or blurring and caused practical problems.

[0044]

[Table 1]

According to the results of Experimental Examples 1 to 10 and Comparative Examples 1 to 8, main scanning is performed in comparison with the case where the charge generation layer 96 is provided on the entire surface in the same size as the transparent substrate 91 of the photosensitive member 9. It is apparent that the one in which the strip-shaped charge generation layer 96 extending in the direction is provided has significantly improved the elongation at the rear end of the image. Further, it is apparent that setting the width d of the strip-shaped charge generation layer 96 in the sub-scanning direction to be smaller than the exposure spot diameter R of the laser beam is effective for the extension of the image.

FIG. 7 shows a diagram of another embodiment of the charge generation layer. This FIG. 7 corresponds to FIG. 3 of the above embodiment. In this embodiment, except for the shape of the charge generation layer 98, the other parts have substantially the same configuration as the above-mentioned embodiment, and the same parts are denoted by the same reference numerals and their description is omitted. Is omitted.

The charge generation layer 98 shown in FIG. 7 is formed in a strip shape in which the charge generation layer 96 shown in FIG. 3 is continuously extended in the main scanning direction, whereas it is intermittently formed in the main scanning direction. There is. The gap b between the intermittent charge generation layers may be in a range that does not affect the image when developed on the image carrier. With such a configuration, there is an advantage that a lateral flow of charges in the main scanning direction in the photoconductor is prevented and a clearer image can be obtained.

FIG. 8 shows an image forming apparatus of another embodiment which performs exposure from the surface side of the photosensitive layer 93. In this image forming apparatus 40, the optical system 8 is arranged inside the image carrying belt 41 so that the irradiation direction of the laser beam is from the surface side of the photosensitive layer 93 (the surface side facing the image carrying belt 41). is there. Therefore, it is necessary to form the image carrying belt 41 so as to have a light transmitting property. The charge transport layer 97 of the photosensitive layer 93 is also formed so as to have a light-transmitting property.

On the other hand, on the contrary, the support 91 that holds the photosensitive layer 93 of the photosensitive member 9 and the conductive layer 92 of the photosensitive member 9 do not need to have a light-transmitting property. In addition, since the optical system 8 is installed inside the image carrying belt 41, it is necessary to make the inside of the belt large, and the auxiliary roller 44 is provided. The other parts have almost the same configuration as the above-mentioned embodiment, and are denoted by the same reference numerals, and the description thereof will be omitted.

In the case of the structure shown in FIG. 8 as well, the photoconductor 9 is formed into a strip shape in which the charge generation layer 96 extends in the main scanning direction as in FIGS. As a result, the dielectric layer 25 of the image carrying belt 41 is discharged and the charged regions formed do not overlap. Therefore,
It is possible to effectively deal with the stretch of the image (stretching of the trailing edge of the latent image).

In each of the above embodiments, the semiconductor laser is used as the light source for exposing the photoconductor 9, but the present invention is not limited to this, and any other device can be used as long as the photoconductor 9 can be appropriately exposed. A known exposure method such as an LED method, an LED method, a liquid crystal shutter method, and a PLZT method can be used. Also, by changing the characteristics of the developer,
It goes without saying that it is possible to develop the unexposed area without developing the exposed area.

When the charge generating layer 96 is provided as in the present case, the width of the charge generating layer 96 in the sub-scanning direction is narrowed and the system speed V _{S is} not required even if the exposure optical system is made fine.
By appropriately setting, the pixel density in the sub-scanning direction can be increased, and a high-definition image can be created. Therefore, high definition can be achieved at low cost. In addition, when the width of the charge generation layer 96 is sufficiently narrow with respect to the width of the irradiation light that exposes the photosensitive layer 93 in the sub-scanning direction, the shake of the laser light is corrected, particularly when the exposure is performed with the laser light. Even if it does not exist, the charge generation layer 96 is exposed by only a part of the irradiation light to generate a carrier pair, so that the latent image of a straight line can be formed without shaking the latent image in synchronization with the shake of the laser light.

[0053]

As is apparent from the above description, according to the present invention, the charge generation layer forming the photosensitive layer is formed in a strip shape extending in the main scanning direction so that the charged areas on the image carrier overlap. It is possible to suppress the generation of excess carriers. Therefore, the discharge is promptly performed at a point corresponding to the exposure position of the photoconductor, and the discharge is promptly stopped when the exposure is completed, so that the image is faithfully generated without causing the image to extend particularly in the traveling direction of the image carrier. The image can be reproduced.

[Brief description of drawings]

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

FIG. 2 is an enlarged view of a main part of the image forming apparatus shown in FIG.

FIG. 3 is a diagram showing a pattern shape of a charge generation layer of a photoconductor.

FIG. 4 is a diagram showing a light amount distribution of laser light.

5A is a diagram showing a charging area and a charging amount on an image carrying belt when a light shielding layer is not provided, and FIG.
It is a figure which shows a charging area and a charging amount when a light shielding layer is provided and charging areas do not overlap.

FIG. 6 is a diagram showing a potential distribution when a voltage is applied to the conductive layer.

FIG. 7 is a diagram showing the same pattern shape as FIG. 3 showing another embodiment in which the shape of the charge generation layer is changed.

FIG. 8 is a diagram showing a schematic configuration diagram of an image forming apparatus of another embodiment according to the invention.

FIG. 9 is a view showing a conventional image forming apparatus.

FIG. 10A is a diagram showing a test pattern of an original image, and FIG. 10B is a diagram showing a conventional example of a toner image of the test pattern.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Image carrying belt (image carrying body), 3
... drive roller, 4 ... heating roller, 5 ... latent image forming device, 6
... developing device, 9 ... photoconductor, 13 ... first power source, 23 ... conductive layer, 25 ... dielectric layer (insulating layer), 92 ... translucent conductive layer, 9
3 ... Photosensitive layer, 96, 98 ... Charge generating layer, 97 ... Charge transporting layer.

Claims (2)

[Claims] 1. An image carrier having an insulating layer formed on a conductive layer and a photosensitive member having a photosensitive layer formed on the conductive layer are arranged such that the insulating layer and the photosensitive layer face each other, and a voltage is applied between the conductive layers. In the image forming apparatus, an image is formed by irradiating a photoconductor with light from a light source in a state of being applied, and a latent image is formed on a running image carrier by discharge between the photoconductor and the image carrier. Has a charge generation layer that generates a charge when irradiated with light and a charge transport layer that has a charge transport function, and the charge generation layer is formed in a strip shape extending in a direction orthogonal to the traveling direction of the image carrier. An image forming apparatus characterized by the above. 2. The image forming apparatus according to claim 1, wherein a width of the charge generation layer is narrower than a diameter of light emitted from the light source in a traveling direction of the image carrier.