JPS60241068A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent the fluctuation in the density of a developed image and fogging of the white ground by supplying a prescribed voltage to a conductive base material which supports a photosensitive body, irradiating a light signal to the surface of a photosensitive drum which is maintained at zero potential by an AC corona electrifier and exposing the drum surface. CONSTITUTION:The photosensitive drum 1 has a photosensitive body 2 on the surface layer and is supported from the inside by the conductive base material 3. The material 3 is connected to a DC power source 4 and is maintained under the prescribed potential. The AC corona electrifier 5 is connected to an AC power source 6 which is set at about 10Hz-1kHz frequency and about 2-10kV voltage to maintain uniformly the surface of the drum 1 at zero potential. A light signal is irradiated from a light signal source 7 such as laser scanning head and LED array head to the surface of the drum 1 which is maintained uniformly at zero potential by the electrifier 5. The electrostatic latent image is thus formed on the drum 1 surface by which the fluctuation in the density of the developed image and fogging of the white ground is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to electrophotographic devices such as copying devices and recording devices that are stable against changes in environmental temperature and humidity.

(Prior Art) Conventionally, electrophotographic apparatuses have employed a method of applying a uniform charge to the surface of a photosensitive drum using a corona charger and then irradiating the photosensitive drum with a light image as a method of forming an electrostatic latent image.

However, although the corona charger is operated by a DC high-voltage power supply and forms a uniform surface potential of the photosensitive drum, the DC corona charger uses DC voltage to generate corona discharge due to fluctuations in the temperature or humidity of the surrounding environment. Because of this, it is difficult to maintain a constant potential at all times due to the influence of the conventional development process.For this reason, the developed image density fluctuates in normal development, and the white background becomes smudged in reverse development. Also, in addition to this,
Conventionally, a static eliminator has been disposed in front of the corona charger to remove the electric charge on the photosensitive drum and to uniformize the surface potential, thereby eliminating the electric charge using light or the like.

(Objective of the Invention) In order to eliminate these drawbacks, the object of the present invention is to stabilize the surface potential of a photosensitive drum and prevent density fluctuations in developed images and fogging on white backgrounds.

Another object of the present invention is to eliminate the need for optical static elimination.

(Structure of the Invention) In order to achieve the above object, the present invention performs corona charging using an alternating current voltage, and also applies a predetermined potential to the photoconductor supporting conductive base material of the photoconductor drum, and maintains it at a stable zero potential. The device is configured to form a stable electrostatic latent image on the surface of the photosensitive drum by providing an exposure means for irradiating the surface of the photosensitive drum with an optical signal. The present invention will be described in detail below with reference to examples.

(Embodiment) FIG. 1 is an explanatory diagram showing an embodiment of the present invention. In the figure, 1 is a photosensitive drum having a photosensitive member 2 on the surface layer and a conductive base material 3.
is supported on the inside. The photoreceptor 2 is made of amorphous selenium, amorphous silicon, organic optical semiconductor, etc., and the conductive base material 3 is connected to a DC power source 4 and has a voltage of 0 to ±100O.
A potential of about V is applied. The polarity of DC power supply 4 is
If the photoreceptor 2 is a member that exhibits photosemiconductor characteristics with respect to positive charges, a negative potential is applied; conversely, if it is a member that exhibits photosemiconductor characteristics with respect to negative charges, a positive potential is applied. . Reference numeral 5 denotes an AC corona charger, which is generally used as a charger for static elimination, and generates positive and negative charges. 6 is an AC power source for an AC corona charger with a frequency of 10H2 to 1kHz
The level and voltage are determined to be approximately 2 kV to 1 okV. 7 is an optical signal source such as a laser scanning head or an LED array head, and 8 is a developer, and a developer roll 9 causes toner 1o to adhere to the electrostatic latent image on the photosensitive drum 1.

The developing roll 9 is given a potential by a DC power supply 1, and the potential is approximately equal to the DC power supply for normal development, and is approximately zero potential for reverse development. A transfer charger 12 transfers the toner image developed and adhered to the surface of the photosensitive drum 1 onto a sheet of paper 13 . The transferred paper 13 is passed through the 14I'i fixing device 1- to be fixed and output. Note that the toner remaining on the surface of the photosensitive drum 1 is removed and cleaned using a 15Ff-cleaner.

Next, a method of forming a latent image in an embodiment of the present invention in which the photoreceptor 2 is made of a member exhibiting photosemiconductor properties with respect to positive charges will be described. FIG. 2 is an explanatory diagram showing the potential of each part of this embodiment, and (a) shows that the surface potential of the photoreceptor 2 has become almost zero potential due to the AC corona charger 5; A conductive base material 3 is provided on the surface of the photoreceptor 2.
This is because a charge of opposite polarity to the potential of is attached to the surface, making the surface potential zero. Further, (1)) indicates the potential of the conductive base material 3, which is set to a constant potential of -400V by the DC power supply 4 as described above. In this state, when light is irradiated from the optical signal source 7, the surface charge on the exposed portion of the photoreceptor 2 is removed, and the surface potential becomes the potential of (b), that is, the electrically conductive base material, as shown by the broken line. 3 is approximately equal to 1400V, while the non-exposed portion maintains its previous state, that is, the state of (,). Then, the surface charge is erased by subsequent exposure, so that the electric potential of the conductive base material 3 appears. That is,
On the surface of the photosensitive drum 1, exposed areas and non-exposed areas are formed as latent images in response to the irradiation from the optical signal source 7.

Furthermore, to explain the development of the present invention in this embodiment, we will first discuss the case of regular development which is generally carried out in copying machines (5). A potential equal to the potential of the conductive base material 3 as shown in FIG. 2(b) is applied. At this time, since an electric field is generated only in the non-exposed area, the charged toner 1o is attached by electrostatic attraction. On the other hand, since no electric field is generated in the exposed area, toner 10 does not adhere. Further, in the case of reversal development used in printers, etc., the first position of the developing roll 9 is set to almost zero and is made equal to that shown in FIG. 2 (,). In this case, an electric field is generated only in the exposed area and toner adhesion occurs.

In the present invention, the processes of transfer, fixing, and cleaning are performed by known methods, and it goes without saying that the polarity of the transfer charger 12 is selected to be opposite to the polarity of the toner 10.

Next, the static elimination process of this invention will be explained.

Generally, a static eliminating light or an AC charger is used to erase the charge remaining on the photoreceptor 2, but without this static eliminating process, a uniform potential cannot be obtained during the next charging process. However, this invention does not require a static elimination light or an AC corona charger for static elimination (6). This is because the surface potential of the photoreceptor 2 is uniformly charged to zero potential by the AC corona charger 5K, which is provided to prevent the DC corona charger from being affected by environmental temperature and humidity. be. Therefore, the AC corona charger 5 can perform static elimination and conventional primary charging at the same time.

By the way, if the photoreceptor 2 is made of a material that exhibits photosemiconductor properties with respect to negative charges, the above-mentioned effect can be achieved by applying a positive potential to the conductive base material of the photoreceptor drum and applying a corresponding potential to other parts. The same functions and effects as those of the embodiment can be obtained.

(Effects of the Invention) As explained above, in this invention, since the photoreceptor is charged by an AC corona charger, even if the amount of corona generation changes, the amount of positive and negative corona charges fluctuates by almost the same amount. The charged potential of the photoreceptor does not vary from zero and can be stably maintained at zero potential despite changes in ambient temperature and humidity, so the voltage of the AC corona generation power source does not need to be finely adjusted.
Since the AC corona charger of this invention has both charging and static elimination functions, there is no need to provide a separate means for static elimination unlike conventional devices, so it has many effects such as making the device more convenient. It is something.

Therefore, the present invention can be used in copying machines and printers as an electrophotographic device that is stable against changes in environmental temperature, humidity, etc.

[Brief explanation of the drawing]

FIG. 1 is a detailed explanatory diagram of the present invention, and FIG. 2 is an explanatory diagram of the latent image potential of the present invention. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Photoconductor, 3... Conductive base material, 4.1... DC power supply, 5... AC corona charging 1
device, 6... AC type, source, 7... optical signal source, 8... developer, 9... developing roll, 10... toner, 12...
...Transfer charger, 13...Paper, 14...Fixer,
15...Cleaner. Patent applicant Oki Electric Industry Co., Ltd. U0

Claims (1)

[Claims] means for supplying a predetermined voltage and pressure to a conductive base material supporting the photoreceptor of the photosensitive drum; an AC corona charger for uniformly bringing the surface of the photosensitive drum to zero potential; and a means for uniformly bringing the surface of the photosensitive drum to zero potential by the AC corona charger. 1. An electrophotographic apparatus comprising: an exposure means for irradiating an optical signal onto the surface of a held photosensitive drum, thereby forming an electrostatic latent image on the surface of the photosensitive drum.