JPS6254280A - Printing device - Google Patents

Abstract

PURPOSE:To obtain a stable high picture quality by providing a electrode opposite to a photoconductive layer formed on a conducting substrate, light- irradiating the light conducting layer while the electric potential difference is kept between the substrate and the electrode and forming the static latent image at the photoconductive layer. CONSTITUTION:The electric field is applied by a light transmitting electrode plate 23 provided at the outer circumferential part of the photosensitive drum, and then, the charge is selectively injected and remains only at the part irradiated by a light spot 30, and the positive or negative surface electric potential appears in accordance with the charge polarity. Consequently, by executing the laser beam scanning by the beam scanning system and executing the beam irradiating selectively while the photosensitive drum is rotated at the constant rotation speed, the static latent image is formed. The toner powder is selective stuck in accordance with the residual charge by the static electric power caused by developing the toner powder to give the suitable electrification charge by giving the suitable developing bias electric potential in accordance with the latent image polarity in a developing device 24, and the static latent image is developed. Thus, the high picture quality is obtained stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a printing apparatus, particularly an electrophotographic printer, and more particularly to a method for forming an optical and electrostatic latent image on a photoreceptor.

[Prior Art] Electrophotographic printers have the characteristics of high resolution, high quality printing, and high speed printing. As the processing speed of computers increases, there is a growing demand for printing devices that can output large amounts of data in a short period of time.Furthermore, as the fields of application of computers expand, printers are gaining the ability to create documents, print images, etc. The fields of application of high-speed, high-resolution electrophotographic page printers are expanding.

In conventional electrophotographic printers, images are printed through a process as shown in FIG. That is, the photosensitive drum 103 having the photoconductive layer 1(')2 laminated on the circumferential surface of the aluminum tube 101 is rotated at a constant speed. Around the photosensitive drum 103, there is a charging section 10.
1. Exposure section (indicated by light beam 105), development section 106,
A transfer section 107, a cleaning section]08, and a static eliminator 109 are arranged in this order. Charging part] In 04, a Flotron is used to apply a high voltage of about 4 to 6 kV between a tungsten wire with a diameter of about 50 μrn and a housing arranged around it to generate a corona discharge. The surface of the photosensitive drum 103 is charged to 400 to 600 V with the ions.

Depending on the characteristics of the photoconductive layer 102, the charging polarity is selected so that the photoconductive layer 102 is positively or negatively charged. To explain the case of negative charging below, the surface of the photoconductive layer 102 is charged to about -400 to -600V with respect to the grounded base tube 101. Next, in the exposure section, the photoconductive layer 102 is selectively exposed to a light beam of 1.5 degrees according to the image signal. The part that receives the light irradiation loses almost all of its charge due to photoconductivity, and the surface potential changes to almost the same potential as the raw tube, and the surface of the photoconductive layer 102 is electrostatically charged depending on whether or not it is irradiated with light. ) is formed into an image. A method is known in which the surface of the photosensitive drum 103 is selectively exposed, for example, by using 1/- laser light scanned by a polygon mirror. (LT S P 346535
2, US Pat. No. 3,922,485) There is also a method in which the light from the light source is selectively blocked by a liquid crystal shutter array disposed close to the outer peripheral surface of the photosensitive drum, and an image of the shutter surface is formed on the drum. is also known. (Unexamined Japanese Patent Publication No. 56
92078, Japanese Patent Laid-Open No. 56-98073) A method is also known in which light emitting diodes are multiplied in a line and are selectively turned on. (Unexamined Japanese Patent Publication No. 5
5-98879, JP-A-57-40 In the developing section 106,
The electrostatic latent image on the photosensitive drum 1.03-1 is developed with toner powder and visualized. For example, in a forward development system using a two-component developer, the toner is on the surface of the photoconductive layer (41).
The stirred I-ner is charged with a carrier having a polarity and a charging order such that it is frictionally charged to the opposite polarity.

In the present example, toner is positively charged and attached to a magnetic brush of a magnetic carrier that rubs the surface of the photosensitive drum 103 by rotation of a non-magnetic sleeve that has a built-in permanent magnet and has a negative potential with respect to the blank tube 101. 103 Toner powder contacts and rubs the surface and selectively adheres to areas having a negative residual potential due to electrostatic force, forming an L-toner image corresponding to the residual charge pattern on the photosensitive drum 103. 9 Furthermore, magnetic component toner is developed. is also known. In the transfer section 107, the toner image on the surface of the photosensitive drum 103 is transferred onto the recording paper 110 by the transfer charger 107. The recording paper 110 is conveyed at the same speed as the circumferential speed of the photosensitive drum while maintaining a small constant distance from the photosensitive drum, and the back side of the recording paper 110 is charged with a polarity opposite to that of the toner. Due to the corona discharge generated in the corotron, the toner on the surface of the photoreceptor 103 is attracted and transferred onto the recording paper by electrostatic force.

The toner image on the recording paper 2 is heated and fixed to the recording paper in the fixing unit 'a111. Pressure fixing is also known, in which the toner is fixed to the recording paper by passing it between rollers to which pressure is applied in addition to heat.

The cleaning unit 108 removes toner remaining on the surface of the photosensitive drum 10:3 without being transferred to the recording paper. A method of cleaning the surface of the photosensitive drum 103 by wiping the toner off using a rotating fur brush roller.
65755), a method of cleaning by pressing a rubber blade (Japanese Patent Laid-Open No. 44-2034), etc. are used.

In the static eliminator 109, the photosensitive drum is uniformly exposed to light using a fluorescent lamp or the like, and residual charges are eliminated by photoconductivity, thereby erasing the electrostatic latent image.

[Problems with the Prior Art] The prior art described above has the following problems because the surface of the photosensitive drum is charged by a corotron. That is, corona discharge in the corotron ionizes oxygen in the air, producing ozone. Ozone not only produces a bad odor, but is also harmful to the human body and has safety concerns.
Have a health problem. Furthermore, it also has the disadvantage that the photoconductive layer of the photosensitive drum is deteriorated by ozone. In particular, the performance of the organic photoconductive layer is significantly degraded by ozone, so in practice, for example, a mechanism is provided to remove the deteriorated layer on the surface of the photoconductive layer by polishing the surface of the photosensitive drum by a certain amount depending on the number of sheets printed. The deterioration characteristics caused by ozone are a factor in determining the number of prints a photosensitive drum can last. Furthermore, since the coro-6-tron ionizes and discharges molecules in the air, its lJ
Due to the principle of J-manufacturing, performance changes depending on the environmental conditions of the atmosphere.

It also has the disadvantage that stable image quality cannot be obtained because it is particularly sensitive to pressure and humidity. In addition, the wires used in corotrons are placed under a high electric field, so
Because the wire attracts foreign matter in the air and its charging ability decreases, it is necessary to periodically remove foreign matter from the wire surface to keep it clean, and it also requires maintenance because it may need to be cut during long-term use.

The present invention has been made to solve various problems peculiar to these corotrons, and its purpose is to realize a printing device that can stably obtain high image quality. Still another object is to simplify the apparatus and realize a low-cost printing apparatus. Another objective is to realize a printing device that requires no maintenance and is highly operable.

[Means for Solving the Problems] In the electrophotographic printer of the present invention, an electrode provided close to the photoconductive layer applies light while applying an electric field between it and the conductive base material of the leading conductive layer. An electrostatic latent image is formed by exposing the conductive layer to light, injecting charge into the photoconductive layer and leaving it to remain so that the surface potential changes selectively.

[Operation] The process of forming an electrostatic latent image in the configuration of the present invention will be explained with reference to FIG. The photosensitive drum is an aluminum tube 1
4 as a base material, a photoconductive layer 13 and a transparent insulating layer 12 are laminated, and a light-transmitting electrode plate IJ is provided in which a transparent electrode 16 is laminated on glass adjacent to and facing the outer peripheral surface of the photosensitive drum. A voltage is applied between this and the raw tube 14. At this time, when the photosensitive drum is irradiated through the light-transmitting electrode plate 11, a charge Q is induced in the photoconductive layer 13 on the side closer to the light-transmitting electrode plate 11. This charge-induced process can be explained qualitatively as follows.

S - Area of the light emitting part (spot area) Cor condenser volume formed between the light transparent electrode plate and the aluminum tube during light irradiation CL - distance between the light transparent electrode plate and the surface of the photoconductive layer 1, - Transparent insulating layer thickness T - Photoconductive layer thickness ερ - Vacuum dielectric constant εr - Transparent insulating layer dielectric constant Q - Induced charge ■ - As applied voltage, CQ + J "Eoεrs / (tlt) (U, s
/rl) + LεrS/l)Q'' Cod V. However, for simplicity, the time required for charge transfer caused by the time constant due to the bright resistance of the photoconductive layer is ignored in the old publication.This state Then, as the photosensitive drum rotates in the direction shown by the arrow, the above-mentioned light irradiation area (in the figure) is A charge (indicated by the &'f line) selectively remains, and a surface potential is applied to the surface of the photosensitive drum via the transparent insulating layer 12. Therefore, an electrostatic latent image is formed.

EXAMPLES] The present invention will be described below based on Examples. An example of the first fruit is shown in FIG. As explained in FIG. 1, the photoconductive layer 28 and the transparent insulating layer 29 are formed on the aluminum tube 21. A voltage V is applied between the light-transmitting electrode plate 23 disposed close to the outer periphery of the drum and the aluminum tube 21 of the photosensitive ram 1-'. The photosensitive drum rotates in the direction indicated by the arrow in the figure. Developing unit 2 along the rotation direction
4, a transfer roller 25 and a cleaner 22 are arranged. The transfer roller 25 is a metal roller provided with an insulating layer 31 on its surface. Although various structures of the developing device 24 and the cleaner 22 are known, they are related to the present invention or the electrostatic latent image forming method, and their internal structure, operating principle, etc. will be omitted.

Next, the operation of the printer of the first embodiment shown in this drawing will be explained. Photoconductive layer 28 provided on the outer periphery of the photosensitive drum
An electric field is applied by the light-transmissive electrode plate 23, and as explained in FIG. A (negative in the illustrated case) surface potential is created. An electrostatic latent image is formed by rotating a photosensitive drum called Tit at a constant rotational speed and selectively irradiating the laser beam by performing two laser beam scans using a scanning thread made of a polygon mirror (not shown).

In the developing device 24, an appropriate charge is applied according to the polarity of the latent image] - The toner powder is selected according to the residual charge by the electrostatic force generated by applying an appropriate developing bias potential and developing the toner powder. The electrostatic latent image is developed. By placing the photosensitive drum and the recording paper 26 facing each other and applying a transfer bias to the transfer roller 31 so as to have a potential of opposite polarity to the charged charge of the toner powder, the toner powder is statically transferred from the photosensitive drum toward the recording paper. It receives electricity and is transferred to recording paper. Further, the recording paper 26 passes through a fixing roller 27 held at a high temperature while being under pressure, and the toner powder is melted.
It sticks to the recording paper. Residual I/toner remaining without being transferred onto the recording paper of the photosensitive drum 2 is collected by a cleaner 22, and the surface of the photosensitive drum is cleaned and kept clean.Furthermore, the charge remaining after being injected is erased by a static eliminator 31. 1
End cycle.

According to the above configuration, unlike conventional electrophotographic printers, a corotron is not used for uniform charging before exposure, and there is no discharge phenomenon when forming an electrostatic latent image, so no ozone is generated and a long time is achieved. No ozone odor is emitted even during continuous operation.

In addition, since the surface of the photoconductive layer is protected by an insulating layer,
The photoconductive layer does not deteriorate even after long-term use, and the life of the photosensitive drum can be extended. Unlike a corotron, the light-transmissive electrode does not cause electric field concentration, so there is no adsorption of foreign matter, and since it does not use small-diameter wires, it can be maintenance-free without wire cutting.

Next, FIG. 3 shows another embodiment. In Figure 3,
The counter electrode 53 disposed close to the outer peripheral surface of the photosensitive drum 5]
It is made of a metal plate having slits 54, and a potential is applied between it and the aluminum tube of the drum.

The photoconductive layer and others are the same as in the first embodiment.

Since the slit width is minute, the electric field generated in the photoconductive layer is substantially the same as in the first embodiment, and an electrostatic latent image is formed as before. In this case, since there is no absorption or reflection of light in the counter electrode unlike in the case of a light-transmitting electrode plate, there is an advantage that light irradiation can be performed with high efficiency.

FIG. 4 shows a third embodiment. Drum 6 made of glass
1, a transparent conductive layer 66, a photoconductive layer 64, a transparent insulating layer 65
are sequentially stacked. By irradiating the photoconductive layer 64 with the light beam 62 through the glass drum 61 and the photoconductive layer 62 while maintaining a potential difference between the counter electrode 63 and the transparent conductive layer, the photobeam is irradiated as in the previous example. Charge is selectively injected and remains only in the area, forming an electrostatic latent image. In this case, since only the drum 61 and the transparent electrode 66 are present in the optical path, the light sources can be placed close to each other. Therefore, when an exposure apparatus using a liquid crystal shutter array or L E 1') is used, there is an advantage that the apparatus can be formed compactly. In this example, an example of a structure in which an insulating layer is provided on a photoconductive layer for surface protection has been described, but as is clear from the principle of latent image formation, the number of insulating layers 17 is not necessarily required, and the photoconductive layer is Of course, the present invention can also be applied to a structure in which there is no insulating layer between layers.

[Effect] In the present invention, latent image formation consisting of a photoconductive layer and an insulating layer.
Electrostatic latent image formation on the second layer is performed by applying an electric field and irradiating optical beams with electrodes placed close to and facing the latent image forming layer, thereby realizing a printing device that can stably obtain high image quality. can. Furthermore, the device can be simplified and downsized, and a low-cost printing device can be realized. Requires no maintenance and is highly operable.
Furthermore, a printing device with a longer life can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the principle of forming an electrostatic latent image according to the present invention. FIG. 2 is a configuration diagram of a printer showing a first embodiment of the invention, and FIG. 3 is a diagram showing a second embodiment of the invention. FIG. 4 is a diagram showing a third embodiment of the present invention. FIG. 5 is a configuration diagram of a conventional printer. 13...Photoconductive layer 12...Insulating layer 11.23...Light transparent electrode plate 53.63...Counter electrode 15.30.52.62.105...Light beam FIG.

Claims (1)

[Claims] 1) An electrode is provided opposite to a photoconductive layer formed on a conductive base material, and the photoconductive layer is irradiated with light while maintaining a potential difference between the base material and the electrode, and 1. A printing device configured to form an electrostatic latent image on a photoconductive layer. 2) The printing apparatus according to claim 1, wherein the electrode facing the photoconductive layer is light-transmissive, and light is irradiated through the light-transmissive electrode. 3) The printing apparatus according to claim 1, wherein the electrode facing the photoconductive layer has a slit, and light is irradiated through the slit. 4) The printing apparatus according to claim 1, wherein the photoconductive layer is formed on a transparent conductive base material, and the light is irradiated through the base material. 5) The printing device according to claim 1, characterized in that an insulating layer is laminated on the photoconductive layer.