JPH07152293A - Image forming device - Google Patents

Abstract

PURPOSE:To form a uniform image without causing image irregularities resulting from an increase in residual potential, even in the use of a small-diameter photosensitive drum. CONSTITUTION:The photoreceptor drum 13 is composed of a conductive substrate 30 and a photosensitive film 12, formed on the surface of the substrate 30. This photoreceptor drum 13 makes more than one rotation in order to form an image. The photosensitive film 12 is electrified by corona discharge carried out by a main electrifier 14. The electrified photosensitive film 12 is exposed by an optical device 15, so that an electrostatic latent image is formed. The electrostatic latent image on the photosensitive film 12 is developed by a developing device 16. A destaticizing brush 24, arranged upstream from the main electrifier 14, applies the photosensitive film 12 a bias voltage having the opposite polarity to the electrification polarity of the photosensitive film 12. Thus, the residual potential of the photosensitive film 12 is sufficiently removed before the film is electrified by the main electrifier 14.

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 using an electrophotographic technique, and more particularly to an image forming apparatus for forming an image by charging and image exposing a single-layer organic photosensitive drum having a small diameter.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic technique has been actively developed as an electrostatic copying apparatus or a printing apparatus. In recent years, in order to reduce the size of the image forming apparatus, an image forming apparatus using a small-diameter photosensitive drum has been proposed.

FIG. 3 is a system diagram of an image forming apparatus 1 using a conventional electrophotographic technique. The image forming apparatus 1 includes a rotatable photosensitive drum 3 having a photosensitive film 2 formed on its surface, a main charger 4 for uniformly applying a predetermined amount of electric charge to the photosensitive film 2, and a photosensitive film 2. An optical device 5 for exposing and forming an electrostatic latent image on the photoconductor film 2, a developing device 6 for developing the electrostatic latent image on the photoconductor film 2, and a photoconductor film 2 are formed. A transfer device 8 for transferring the toner image onto the recording paper 7, a cleaning device 9 having a cleaning blade for removing the toner remaining on the photosensitive drum 3, and an electric charge remaining on the photosensitive drum 3 are removed, A discharge lamp 10 for setting the surface potential of the photosensitive drum 3 to a predetermined uniform potential.
And so on.

According to the image forming apparatus 1, the main charger 4 uniformly applies a predetermined amount of electric charge to the photoconductor film 2, and then the optical device 5 irradiates the photoconductor film 2 with light. An electrostatic latent image is formed on the film 2. Thereafter, the developing device 6 supplies the toner onto the photoconductor film 2 to visualize the electrostatic latent image. The toner image on the photoconductor drum 3 is transferred to the transfer device 8
Is transferred onto the recording paper 7. After the transfer, the toner remaining on the photosensitive drum 3 is removed by the cleaning device 9. Next, the static elimination lamp 10 irradiates the photoconductor film 2 with light, removes the electric charge remaining on the photoconductor film 2, and equalizes the surface potential of the photoconductor film 2 to a predetermined potential. After that, the main charger 4 charges the photosensitive drum 3 again. These series of processes are continuously and repeatedly performed by rotating the photosensitive drum 3 many times with respect to one recording paper 7.

In the prior art, an inorganic material or an organic material is used as a photosensitive material forming the photosensitive film 2. Se-based materials, amorphous Si-based materials, etc. are used as the inorganic materials. In recent years, organic materials are often used in terms of safety and workability. Organic photoreceptors using organic materials are classified into laminated organic photoreceptors and single-layer organic photoreceptors. Among these, the single-layer organic photoconductor is preferable from the viewpoint of ease of production.

[0006]

However, the single-layer organic photoconductor film generally has a high residual potential even after charge elimination. Further, there is a problem that the charge potential at the time of charging becomes low due to the photocarriers remaining in the photosensitive layer showing the high residual potential. Further, there is a problem that the photoconductor film having a good chargeability during the short use time also becomes fatigued as the use time becomes longer, trap sites increase, and the chargeability decreases.

Therefore, when the photoconductor film having such a problem is used in the image forming apparatus using the small-diameter photoconductor drum 3, the following problems occur.

FIG. 4 shows the residual potential after static elimination and the surface potential after charging of the photoconductor film 2 for each revolution when an image is formed on one sheet of recording paper 7 through a multi-pass process. Show. As can be seen from FIG. 4, as the number of turns increases, the residual potential increases, which causes the surface potential of the photosensitive film 2 to decrease. As a result, the problem of image unevenness occurs.

The present invention has been made in order to solve the above problems, and even when a small-diameter photosensitive drum is used, the unevenness of the image caused by the increase of the residual potential does not occur, and the image is uniform. It is an object of the present invention to provide an image forming apparatus capable of forming various images.

[0010]

An image forming apparatus of the present invention comprises a conductive substrate and a photoconductor film formed on the surface of the substrate, and rotates more than one rotation for one image. A photosensitive member, a charging means arranged near the photosensitive member for charging the photosensitive film by corona discharge, and an exposing means for irradiating the charged photosensitive film with light corresponding to an image. A developing unit arranged downstream of the exposing unit along the rotation direction of the photosensitive member, and arranged upstream of the charging unit along the rotating direction of the photosensitive member, Bias applying means for applying a bias voltage having a polarity opposite to the charging polarity of the photoconductor film to the photoconductor member is provided, thereby achieving the above object.

The bias applying means may be a brush.

[0012]

In the image forming apparatus of the present invention, the photoconductor member comprises a conductive base and a photoconductor film formed on the surface of the base. The photoreceptor member is rotated more than one revolution to form one image. The photoconductor film is charged by corona discharge by the charging means. The charged photoconductor film is exposed by the exposure means to form an electrostatic latent image. The electrostatic latent image on the photoconductor film is developed by developing means. The bias voltage applying unit arranged upstream of the charging unit applies a bias voltage having a polarity opposite to the charging polarity of the photoconductor film to the photoconductor member. As a result, the residual potential can be sufficiently removed before being charged by the charging means. Therefore, there is no variation in development for each cycle. As a result, a uniform image having no unevenness is formed.

[0013]

EXAMPLES Examples of the present invention will be described below.

In the image forming apparatus of the present embodiment, the photosensitive drum is rotated more than one rotation, so that in the process of forming one image, the residual potential is sufficiently removed for each revolution. Removal, which results in the formation of a high quality image with no image unevenness. The number of rotations of the photosensitive drum for one image is not always an integer.

An example of the present invention will be described below in the case of using a positive charging type single-layer organic photoreceptor film as an example.

FIG. 1 shows an image forming apparatus 1 according to an embodiment of the present invention.
It is a systematic diagram which shows the structure of 1. This image forming apparatus 11
As shown in FIG. 1, a rotatable small-diameter photoconductor drum 13 in which a photoconductor film 12 made of a single-layer type organic photoconductor is formed on a surface of a drum base 30 made of a metal material such as aluminum. The main charger 14 that uniformly applies a desired amount of electric charge to the body film 12 and the photoconductor film 12 are exposed to expose the body film 12.
Optical device 1 for generating light for forming an electrostatic latent image thereon
5, a developing device 16 for developing the electrostatic latent image on the photoconductor film 12 with toner, a transfer device 18 for transferring the toner image on the photoconductor drum 13 to the recording paper 17, etc., and after the transfer of the toner image,
A cleaning device 19 for removing the toner remaining on the photoconductor drum 13 and an electric charge remaining on the photoconductor drum 13 are removed to make the potential on the photoconductor film 12 uniform to a predetermined potential. A static elimination lamp 20 and the like are provided.

The main charger 14 employs a scorotron charger, and has a discharge wire 21 for corona discharge, a shield case 22 surrounding the discharge wire 21, and a shield case 22 open to the photosensitive drum 13 side. And a metal grid 23 provided in the opening.
A power supply 25 for supplying a current required for corona discharge is connected to the discharge wire 21 of the main charger 14. The shield case 22 is grounded.

Generally, the saturated charging potential Vs of the photosensitive film 12 is
However, it is desirable to carry out main charging so as to be in the range of 500 to 1000 V, particularly 700 to 850 V. Therefore, when performing corona discharge, it is desirable to apply a high voltage of 4 to 7 kV to the discharge wire 21 of the main charger 14.

FIG. 2 is a system diagram showing the arrangement of the photoconductor drum 13, the main charger 14, the developing device 16, and the charge eliminating lamp 20 of this embodiment. Charger width W1 of the main charger 14
Is, for example, 11 mm, and the opening width W of the grid 23 is
2 is 220 mm as an example. The distance L1 between the grid 23 and the photoconductor drum 13 is 1.0 mm as an example. The diameter of the photosensitive drum 13 is, for example, φ30 m.
m, and in this case, one sheet of image is formed by A4R (297 mm) standard paper in a process of about 3.2 revolutions.

The image forming apparatus 1 of this embodiment has a charge eliminating brush 24 between the charge eliminating lamp 20 on the surface of the photosensitive drum 13 and the main charger 14. The charge removal brush 24 has a bias potential having a polarity opposite to the charging polarity of the photoconductor film 12.
As for the bias potential of the static elimination brush 24, the residual potential after static elimination by the static elimination brush 24 is the saturated charging potential V of the photoconductor film 12.
It is set to be 10% or less of s. By setting in this way, the dispersion of the surface potential after charging due to the deterioration of the charging ability of the photoconductor film 12 becomes negligible in image formation.

In order to sufficiently perform the charge removal, the charge removal lamp 20
It is also possible to increase the amount of static elimination light. However, in that case, the flare light of the static elimination lamp 20 is incident on the main charger 14, which adversely affects the charging characteristics of the photoconductor film 12. Therefore, it is necessary to perform sufficient charge removal by a method other than increasing the amount of charge removal light, like the charge removal brush 24 used in this embodiment.

The optical device 15 used for image exposure is
An optical system including a lens or a reflecting mirror, or a laser light oscillator is used. The developing device 16 includes a developing roller 16 a that supplies the charged toner of the one-component developer or the two-component developer to the surface of the photoconductor film 12. As the transfer device 18, a corona charger similar to the main charger 14 or a contact type charger is used.

In the present embodiment, it is desirable that the static elimination light amount of the static elimination lamp 20 on the photoconductor film 12 is 5 LUX · SEC or more, particularly 10 LUX · SEC or more. On the other hand, 200L
If it is UX · SEC or more, deterioration of quality occurs due to light fatigue of the photoconductor film 12. As the static elimination lamp 20, any visible light source such as a halogen lamp, a fluorescent lamp, a cold cathode ray tube, or a neon lamp such as red or green can be used. Alternatively, a monochromatic light source such as an LED (light emitting diode) of red, yellow, green or the like can be used.

The photoconductor film 12 of this embodiment is a positive charging type single-layer organic photoconductor film, and is formed by mutually dispersing a binder resin, a charge transport medium and a charge generating substance. As the charge generating substance, any organic photoconductive pigment known per se is used. In particular, phthalocyanine pigments, perylene pigments,
Photoconductive organic pigments such as quinacridone pigments, pyranthrone pigments, disazo pigments and trisazo pigments are used alone or in combination of two or more.

As the charge transport medium, a medium in which a charge transport substance is dispersed in a resin medium is used. As the charge transport material, any hole transport material or electron transport material known per se is used for the purpose of the present invention. Examples of suitable hole transport materials are poly-N-vinylcarbazole, phenanthrene, N-ethylcarbazole, 2,5-diphenyl-1,3,4-oxadiazole, 2,5-bis (4
-Diethylaminophenyl) -1,3,4-oxadiazole, bis-diethylaminophenyl-1,3,6-
Oxadiazole, 4,4'-bis (diethylamino)
-2,2'-dimethyltriphenylmethane, 2,4,5
-Triaminophenylimidazole, 2,5-bis (4
-Diethylaminophenyl) -1,3,4-triazole, 1-phenyl-3- (4-diethylaminostyryl) -5- (4-diethylaminophenyl) -2-pyrazoline, p-diethylaminobenzaldehyde- (diphenylhydrazone), etc. , Or a combination of a plurality of these. 2 examples of suitable electron transport materials
-Nitro-9-fluorenone, 2,7-dinitro-9-
Fluorenone, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2-nitrobenzothiophene, 2,4,8-trinitrothioxanthone, dinitroanthracene, dinitroacridine, It is used in any one of dinitroanthoquinone and the like, or a combination of a plurality thereof.

Various binder resins, for example, styrene polymers, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-
Maleic acid copolymer, acrylic polymer, styrene-acrylic copolymer, styrene-vinyl acetate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy Examples of various polymers include resins, polycarbonates, polyarylates, polysulfones, diallylphthalate resins, silicone resins, ketone resins, polyvinyl butyral resins, polyether resins, phenol resins, and photocurable resins such as epoxy acrylates and urethane acrylates. To be done. A photoconductive polymer such as poly-N-vinylcarbazole can also be used as the binder resin.

The charge generating substance to be present in the photoreceptor film 12 is suitably in the range of 0.1 to 50 parts by weight, particularly 0.5 to 30 parts by weight, per 100 parts by weight of the binder resin. It is suitable that the charge transport substance is in the range of 20 to 500 parts by weight, particularly 30 to 200 parts by weight, per 100 parts by weight of the binder resin. The thickness of the photoreceptor film 12 is preferably in the range of 10 to 40 μm, particularly 22 to 32 μm in view of high surface potential, printing durability and sensitivity.

As the electroconductive drum substrate 30 of the photosensitive drum 12, an aluminum tube, an aluminum tube subjected to alumite treatment, and a conductive resin substrate are generally used. The organic photoconductor layer as the photoconductor film 12 is formed by using a resin, N, N-dimethylformamide,
An amide-based solvent such as N, N-dimethylacetamide;
Cyclic ethers such as tetrahydrofuran and dioxane; dimethyl sulfoxide; aromatic solvents such as benzene, toluene, xylene; ketones such as methyl ethyl ketone; N-
Methyl-2-pyrrolidone; dissolved in a solvent such as phenol and phenols such as cresol, and the charge-generating substance is dispersed therein to obtain a coating composition. This composition is applied to the conductive drum substrate 30 to form the photoconductor film 12.

The present invention has a remarkable advantage in the case of a positive charging type organic single layer photoreceptor, and the positive charging type also has an advantage that less ozone is generated at the time of main charging. In the case of the positive charging type, it is preferable to use a perylene pigment, an azo pigment or a combination thereof as the charge generating substance, and to use 2,6-dimethyl-2 ′, 6′-di te as the charge transporting substance.
Diphenoquinone derivative such as rt-butyldiphenoquinone, 3,3′-dimethyl-N, N, N ′, N′-tetrakis-4-methylphenyl (1,1′-biphenyl)-
It is preferable to use diamine compounds such as 4,4′-diamine, fluorene compounds and hydrazone compounds.

In the above embodiments, the drum-shaped substrate on which the photosensitive film is formed is used as the photosensitive member, but a belt-shaped substrate on which the photosensitive film is formed may be used.

Although the image forming apparatus of the present invention has been described as an electrostatic copying machine in the above embodiment, the image forming apparatus of the present invention forms an image by an electrophotographic method regardless of the electrostatic copying machine. Any image forming apparatus may be used.

[0032]

As is apparent from the above description, according to the image forming apparatus of the present invention, even when a small-diameter photoconductor drum is used, sufficient charge elimination is performed to charge the photoconductor drum. It is possible to prevent the deterioration of the performance, thereby eliminating the variation of the surface potential for each revolution, so that the image formation can be performed uniformly.

[Brief description of drawings]

FIG. 1 is a system diagram of an image forming apparatus 11 according to an exemplary embodiment of the present invention.

FIG. 2 is a system diagram showing an arrangement state of the present embodiment.

FIG. 3 is a system diagram of a conventional image forming apparatus 1.

FIG. 4 is a graph showing a residual potential after static elimination and a surface potential after charging of the photosensitive film 2 in each revolution in the image forming apparatus of FIG.

[Explanation of symbols]

 11 image forming apparatus 12 photoconductor film 13 photoconductor drum 14 main charger 16 developing device 19 cleaning device 20 static eliminator lamp 21 discharge wire 22 shield case 23 grid 24 static eliminator brush 25 power source 30 drum base

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Ichiro Yamazato Ichiro Yamazato 1-22 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd. (72) Takuji Terada 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (72) Inventor Hiroyuki Sako 1-228 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (72) Inventor Yu Watanabe 1-228 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (72) Inventor Keizo Kimoto 1-228 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd.

Claims (2)

[Claims] 1. A photoconductor member comprising a conductive substrate and a photoconductor film formed on the surface of the substrate, the photoconductor member being rotated more than one rotation for one image, and the photoconductor member of the photoconductor member. Charging means arranged in the vicinity to charge the photoconductor film by corona discharge, exposure means for irradiating the charged photoconductor film with light corresponding to an image, and along the rotation direction of the photoconductor member, A developing unit disposed downstream of the exposing unit, and a bias having a polarity opposite to the charging polarity of the photosensitive film disposed upstream of the charging unit along the rotation direction of the photosensitive member. An image forming apparatus comprising: a bias applying unit that applies a voltage to the photosensitive member. 2. The image forming apparatus according to claim 1, wherein the bias applying unit is a brush.