JP2562296B2 - Electrophotographic device using amorphous silicon - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic apparatus using an amorphous silicon-based photoconductor, and more specifically, to prevent surface deterioration of the photoconductor. The present invention relates to an electrophotographic apparatus in which printing durability is remarkably improved without occurrence of image deletion at high humidity.

(Prior Art) An amorphous silicon-based photoconductor layer has high surface hardness, is sensitive to light on the long wavelength side, and has good sensitivity itself. Therefore, it has attracted attention as a photoconductor for electrophotography. ing.

In FIG. 2 showing a conventional electrophotographic apparatus, an amorphous silicon-based photoconductor layer 2 is provided on the surface of a driven and rotated metal drum 1. Around this drum 1,
Main charging corona charger (positive charging type) 3; Image exposure mechanism including lamp 4, original supporting transparent plate 5 and optical system 6; Image mechanism 8 having toner 7; Toner transfer corona charger (positive charging type) 9; A corona charger 10 for paper separation; a static elimination lamp 11; and a cleaning mechanism 12 are provided in this order.

First, the photoconductor layer 2 is charged with a positive charge by the corona charger 3. Next, the original to be copied with the lamp 4
Illuminate 13 and expose photoconductor layer 2 with the light beam image of the original through optical system 6 to form an electrostatic latent image corresponding to the original image. The electrostatic latent image is developed with the toner 7 by the developing mechanism 8. The transfer paper 14 is supplied so as to come into contact with the drum surface at the position of the toner transfer charger 9, and a positively charged corona charge having the same polarity as the electrostatic image is performed from the back surface of the transfer paper 14 to transfer the toner image to the transfer paper 14. Transfer to. The transfer paper 14 on which the toner image has been transferred is electrostatically separated from the drum by AC static elimination of the separation corona charger 10 and sent to a processing area such as a fixing area (not shown).

After the toner transfer, the photoconductor layer 2 is entirely exposed by the static elimination lamp 11 to erase the residual charge, and then the cleaning mechanism.
The residual toner is removed by 12.

(Problems to be Solved by the Invention) However, a photoreceptor having an amorphous silicon-based photoconductor layer on a conductive substrate is obtained by repeating a copying process such as charging, image exposure, development and transfer. There are drawbacks that surface deterioration occurs, image deletion occurs at high humidity during long-term use, and the printing durability of the photoreceptor is still generally low.

The reason for this is that ozone is generated due to the use of corona discharge for charging the photoconductor, which oxidizes the surface of the photoconductor or oxidizes nitrogen in the air. It is recognized that it is caused by adhesion to the surface and the surface becoming hydrophilic.

Such a phenomenon is peculiar to the amorphous silicon photoconductor and has not been observed in the conventional photoconductor. This is because the surface of an amorphous selenium-based photoconductor or an organic photoconductor is relatively soft, and a deteriorated portion is formed on the photoconductor surface due to friction with a cleaning blade or rubbing with a developing magnetic brush. This is because, while this portion is scraped, such a scraping effect cannot be expected in an amorphous silicon-based photoconductor having high surface hardness.

Therefore, the technical problem of the present invention is to prevent the deterioration of the surface of the amorphous silicon photoconductor, and to significantly improve the printing durability of the amorphous silicon photoconductor without causing image deletion at high humidity. To provide a device.

(Means for Solving the Problems) According to the present invention, an electrophotographic photosensitive member having an amorphous silicon-based photoconductor layer on a conductive substrate, and an electrophotographic photosensitive member disposed along a moving path of the photosensitive member. In an electrophotographic apparatus consisting of a main charging mechanism, an image exposure mechanism, a developing mechanism, a transfer mechanism and a cleaning mechanism, all charging mechanisms are non-corona type band electrode contact type,
And, as a main charging mechanism, a charging conductive rubber roller is used, which is made of a polyurethane elastomer having conductivity imparted by embedding a web or sheet of conductive fibers, and the conductive fibers extend from the root to the tip. An electrophotographic apparatus is provided in which the rubber roller is in surface contact with the photoconductor at a linear pressure of 0.5 to 2 kg / cm.

(Operation) In FIG. 1 showing the schematic arrangement of the electrophotographic apparatus of the present invention, members common to the respective members of the conventional apparatus shown in FIG.
It is indicated by a common imprint number. First, in the apparatus of the present invention, all the charging mechanisms are of the non-corona type band electrode contact type. The strip electrode contact system means a system in which a strip electrode, which is a conductor, contacts an uncharged layer to perform charging.

In the present invention, a charging conductive rubber roller 15 is used instead of the main charging corona charger 3 shown in FIG.
The conductive rubber roller 15 has a peripheral surface 16 that is pressed against the surface of the drum photoconductor layer 2, and the peripheral surface 16 is connected to a main charging power source 18 by a connection 17. Thus, on the peripheral surface 16 of the conductive rubber roller 15 for charging, the conductive substrate 1 of the photoconductor is formed.
On the other hand, a constant voltage is applied, and the electrostatic charge having a constant voltage is uniformly supplied.

In this apparatus, the photoconductor layer 2 is developed by the developing mechanism 8.
The transfer of the toner image formed on the surface of the sheet to the transfer paper 14 is also performed by the non-corona method. That is, in the transfer area, the transfer roller electrode 19 is arranged so as to be pressed against the surface of the photoconductor layer 2 having the toner image via the transfer paper 14, and the roller electrode 19 is transferred by the connection 20. Connected to the power supply 21. As a result, the back surface of the transfer paper 14 is charged by the roller electrode 19 so as to have the same polarity as the charge of the photoconductor layer 2, and the toner image is transferred.

Further, the separation of the transfer paper 14 on which the toner is transferred from the photosensitive drum is performed by utilizing the curvature of the photosensitive drum.
Is performed by using a mechanical separation mechanism such as.

According to the present invention, since all charging mechanisms in the electrophotographic apparatus are of the non-corona type band electrode contact type, discharge products such as ozone and nitrogen oxides are not generated, so that the surface deterioration of the photosensitive layer is prevented. It is possible to significantly improve the printing durability of the photoconductor without forming a hydrophilic surface. Further, there is no dew condensation on the surface of the photosensitive layer at high humidity, no image deletion occurs, and the use of a drum heater, which is conventionally required to prevent this, can be omitted.

In the present invention, performing the main charging by pressure contact with the peripheral surface of the conductive rubber roller brings about a particular advantage in connection with the use of the amorphous silicon-based photoconductor layer as the photoconductor. That is, the amorphous silicon photoconductor has a larger electrostatic capacitance than other photoconductors, for example, a selenium photoconductor or an organic photoconductor, and as a result, movement of charges to the surface due to pressure contact with electrodes or It has the advantage that the injection is easy. In addition, the conductive rubber roller used in the present invention, due to its elasticity or cushioning property, is brought into close contact with the surface of the photoconductor with substantially no air gap, and charges can be easily transferred or injected onto the surface of the photoconductor. Further, since the photoconductor drum and the electrode are separated gradually along the periphery of both, it is possible to smoothly perform the troubles such as discharge.

(Example) In the present invention, as the amorphous silicon-based photoconductor layer 2, any one known per se is used. For example, amorphous silicon deposited on a substrate by plasma decomposition of silane gas is used. It is used, and it is doped with hydrogen, halogen, etc., and further boron, phosphorus, etc.
It may be one doped with a Group V or Group V element.

Typical amorphous silicon photoconductors have a dark conductivity of 10 ^-12 Ω ^-1 · cm ^-1 , photoconductivity> 10 ^-7 Ω ^-1 · cm.
^-1 , the optical band gap is 1.7 to 1.9 eV, the amount of bonded hydrogen is 5 to 20 atomic%, and the dielectric constant of the film is 11.5-1.
It is in the range of 2.5. The amorphous silicon photoconductive layer can be positively or negatively charged depending on the doping species.

As the conductive rubber roller 15, used is a web or sheet of conductive fibers such as carbon fiber, metal fiber, metallizing organic fiber, etc., particularly preferably a web or sheet of carbon fiber embedded in polyurethane elastomer to impart conductivity. To be done. In embedding such a web or sheet, it is important that the fibers extend from the root to the tip of the roller to be formed. For example, as a method of imparting conductivity to an elastomer, it is known to blend a conductive pigment such as carbon black or metal powder. In the method of blending such a conductive pigment, the electrical resistance of the elastomer is increased. In order to reduce the value to a level that satisfies the value, a large amount of pigment must be blended, and the blending of such a large amount of pigment loses the desired physical properties as an elastomer, making the roller hard and brittle. I will end up. Moreover, even if the electric resistance value can be lowered to a certain level,
Since the metal powder and the like are dispersed in the elastomer in an island shape, a conductive path is not formed from the root to the tip of the roller, and therefore it cannot be said that the conductivity is sufficient. However, in the present invention, by embedding a web or sheet of conductive fibers so that the conductive fibers are distributed so as to extend from the root of the roller to the tip thereof, the photoconductor which the roller is in contact with from the root of the roller. A conductive path is formed even on the surface (amorphous silicon photoconductive layer surface), and the roller exhibits stable and high conductivity,
Further, the flexibility and elasticity of the polyurethane elastomer can be secured. By using such a conductive rubber roller 15 as a charging roller, a good conductive path is always formed even when the contact pressure of the roller with respect to the photoconductor is set to a level such that a toner film layer is not formed. Thus, the surface of the photoconductor can be charged stably and uniformly. Further, even if the roller is worn, a good conductive path is always secured, so that the uniform charging property is not impaired. In particular, since the amorphous silicon-based photoconductor has high hardness and is apt to wear the roller, such a characteristic is a great advantage.

To embed a web or sheet of conductive fiber so that it extends from the root to the tip of the roller, for example, the web or sheet is wound around a roller made of polyurethane elastomer and heated to a temperature above the melting point or softening point of the elastomer. And a method of embedding the web or sheet, or a method of locating the web or sheet in a mold and pouring a polyurethane elastomer into the mold to perform molding.

The conductive fiber web or sheet may be in the form of, for example, a non-woven fabric, a woven fabric, a gauze, a net or the like. Further, the web or sheet may be previously treated with a silane coupling agent or the like in order to enhance the adhesion with the polyurethane elastomer.

As the polyurethane elastomer, a polyurethane rubber conventionally used in this field, or a polyurethane composed of a soft segment derived from a polyester polyol or a polyether polyol and a hard segment derived from an aromatic diisocyanate is generally used.

The amount of conductive fibers embedded in the form of a web or a sheet can be largely changed within the range in which the roller has conductivity, but in general, the volume of polyurethane elastomer is increased.
The range of 50 to 700 mg, especially 70 to 550 mg per cc satisfies the object of the present invention.

The charging voltage applied to the conductive rubber roller 15 may be such that the surface potential of the photoconductive layer is 200 to 500 V. For this purpose, the roller applied voltage is 500 to 2000 V.
Bolts are preferred.

Further, in the present invention, it is important that the contact pressure of the conductive rubber roller 15 with respect to the photoconductor is set in the range of 0.5 to 2 kg / cm as the linear pressure (pressure per roller length). That is, when the linear pressure is higher than 2 kg / cm, it is difficult to prevent the above-mentioned pressure-bonded toner from being formed because the pressure contact force between the photoconductor and the roller is high. On the other hand, if it is lower than 0.5 kg / cm, the contact width between the roller and the photoconductor becomes narrow, and it becomes difficult to uniformly charge the toner.

The contact between the conductive rubber roller 15 and the photosensitive drum may be such that they are substantially non-slipping, that is, sliding contact is made at the same speed, and between them is 0.5 to 3 cm / sec.
They may be in contact with each other so that there is a difference in speed. Further, the conductive rubber roller 15 may be positively driven, or may be driven according to the rotation of the photosensitive drum.

In the present invention, image exposure uses a laser diode, a light emitting diode, a liquid crystal diode, etc. in addition to a copy exposure method in which a light source, a lens, and a reflecting mirror are used to perform exposure with transmitted light or reflected light from an original Can also be used, and in the case of a laser diode, rotational scanning by a hollygon is performed. When the latter luminous body is used, the light image is exposed by digital signal control,
The function as a printer is given.

[Brief description of drawings]

FIG. 1 is a schematic sectional view for explaining the process of the electrophotographic apparatus of the present invention, and FIG. 2 is a schematic sectional view for explaining the process of the conventional electrophotographic apparatus. 2 ... Amorphous silicon photoconductor layer 4 ... Lamp 6 ... Optical system 8 ... Development mechanism 12 ... Cleaning mechanism 15 ... Charging conductive rubber roller 19 ... Transfer roller electrode

Claims (1)

(57) [Claims] 1. An electrophotographic photosensitive member having an amorphous silicon photoconductor layer on a conductive substrate, and a main charging mechanism, an image exposing mechanism, a developing mechanism arranged along a moving path of the photosensitive member. In an electrophotographic apparatus consisting of a transfer mechanism and a cleaning mechanism, all charging mechanisms are of non-corona type electrode contact type, and conductivity is imparted by embedding a conductive fiber web or sheet as a main charging mechanism. A charging conductive rubber roller made of polyurethane elastomer and having the conductive fiber extending from the root to the tip is used, and the rubber roller is in surface contact with the photosensitive member at a linear pressure of 0.5 to 2 kg / cm. An electrophotographic device characterized in that