JP2519414B2 - Electrophotographic equipment - 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. 3 showing a conventional electrophotographic apparatus, an amorphous silicon photoconductor layer 2 is provided on the surface of a metal drum 1 which is driven and rotated. 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; Developing 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 formed by repeating copying processes 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 photoreceptor or an organic photoreceptor is relatively soft, and a surface-deteriorated portion is formed on the photoreceptor due to friction with a cleaning blade or rubbing against 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 the equipment.

(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,
Further, as the main charging mechanism, a conductive rubber blade made of a polyurethane elastomer in which the tip is in contact with the amorphous silicon-based photoconductive layer, the polishing agent is dispersed inside, and the conductivity is imparted by the conductive fiber is used. An electrophotographic apparatus characterized by the above is provided.

(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 reference 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 a layer to be charged to perform charging.

In the present invention, a charging conductive rubber blade 15 is used instead of the main charging corona charger 3 shown in FIG. The conductive rubber blade 15 has a tip portion 16 that is pressed against the surface of the drum photoconductor layer 2, and the other end portion is connected to a main charging power source 18 by a connection wire 17. Thus, a constant voltage is applied to the tip 16 of the charging conductive rubber blade 15 with respect to the conductive substrate 1 of the photoconductor,
By the relative movement of the blade tip 16 and the photoconductor layer 2,
The surface of the photoconductor layer 2 is uniformly supplied with an electrostatic charge of a constant voltage.

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.
It is easily 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 use of a drum heater, which has been conventionally required to prevent this, can be omitted.

In the present invention, performing the main charging by pressing the tip of the conductive rubber blade having the abrasive dispersed therein brings about an additional advantage in addition to eliminating the disadvantage due to the corona charging. That is, it is possible to effectively remove the residual toner and the photosensitive layer surface deterioration component adhering to the surface of the photosensitive layer by applying a pressure contact sliding force to the surface of the photosensitive member at the time of main charging. Such deterioration components can be removed because the amorphous silicon photoconductor has a very high hardness and does not wear itself even with a high pressure contact force. Further, when the photoconductor layer is charged by the non-corona type band electrode contact method, if the toner film layer is formed on the conductor layer, the photoconductor layer is present in the portion where the toner film layer is present. As a result of an increase in the contact resistance between the electrode and the strip electrode, the charging current decreases and the photoconductor layer surface is insufficiently charged.However, in the method of the present invention, the removal of the toner film is also effective. Therefore, the occurrence of defective charging and uneven charging can be effectively eliminated. When the abrasive particles are dispersed and present in the conductive rubber blade for charging, the above-mentioned action is performed particularly effectively.

(Advantageous Effects of the Invention) According to the apparatus of the present invention described above, the surface deterioration of the amorphous silicon photoconductor is effectively prevented, and the printing durability is remarkably exhibited without causing image deletion at high humidity. It is possible to provide a copying machine or a printer in which the cost of the apparatus is significantly reduced because the high voltage generating apparatus is not required.

(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 doped with a Group V or Group V element.

The physical properties of a typical amorphous silicon photoconductor are as follows: dark conductivity 10 ^-12 Ω ^-1 cm ^-1 , activation energy <0.85e.
V, photoconductivity> 10 ^-7 Ω ^-1 cm ^-1 , optical bandgap
It is 1.7 to 1.9 eV, the amount of bound hydrogen is 5 to 20 atomic%, and the dielectric constant of the film is in the range of 11.5 to 12.5. This amorphous silicon photoconductive layer can be positively or negatively charged depending on the doping species.

As the conductive rubber blade, used is one in which a polyurethane elastomer is mixed with conductive fibers such as carbon fibers, metal fibers, and metallizing organic fibers to impart conductivity.

As the abrasive compounded in the conductive rubber, silica stone powder,
Silica, corundum, boron nitride, boron carbide, silicon carbide, aluminous abrasives, zirconia-alumina, etc. are used, preferably in an amount of 1 to 15% by weight in the conductive rubber.

Suitable conductive rubber blades include polyurethane elastomers having conductive fibers embedded therein. Embedding conductive fibers in polyurethane elastomers offers significant advantages for the mechanical and electrical properties of the blade. That is, as a method of imparting conductivity to the elastomer, as already pointed out, carbon black, it is known to blend a conductive pigment such as metal powder, in the method of blending such a conductive pigment, In order to reduce the electric resistance value of the elastomer to a satisfactory level, 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, and the blade is hard. It has the drawback of being brittle. On the other hand, according to this aspect of the present invention, when the conductive fiber is embedded in the polyurethane elastomer, excellent conductivity can be imparted to the blade tip by blending a remarkably small amount of fiber,
It does not lose the excellent elastic properties, flexibility or abrasion resistance of the polyurethane elastomer. Moreover, since the conductive fiber used in this aspect of the present invention is extremely flexible, a stable conductive path is formed even when the exposed end portion of the conductive fiber is in good contact with the surface of the photoconductor. Since it extends from the tip of the blade to the root, even if the tip of the blade wears during long-term use, the conductive fibers are always exposed at the tip, and there is an advantage that the excellent conductivity is not lost. As the conductive fiber, it is best to use carbon fiber from the viewpoint of easy blending with polyurethane and various physical properties as a fiber. However, it is also possible to use other fine metal fibers or various synthetic fibers that have been subjected to conductive treatment.

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

When blending or embedding the conductive fiber in the polyurethane elastomer, it is important to allow the fiber to extend from the root to the tip of the elastic blade to be formed, as described above. The conductive fibers are oriented in the above direction of the blade so that the conductive fibers are arranged in a multi-filament or spun yarn in the width direction, or the web, nonwoven fabric, woven cloth, gauze, net, etc. It is used by embedding it in polyurethane elastomer.

To embed the conductive fiber in the polyurethane elastomer, a sheet of the polyurethane elastomer and a web or sheet of the conductive fiber are superposed and passed through a roller at a temperature not lower than the melting point or softening point of the polyurethane elastomer, and the web is removed. Or a method of embedding a sheet in an elastomer, a method of sandwiching conductive webs or a sandwich of conductive polyurethane webs between two sheets of polyurethane elastomers, and cross-linking both sheets to integrate them, and a conductive fiber web. Alternatively, a method in which a sheet is positioned in a mold and a polyurethane elastomer is poured into the mold to mold the sheet is used. Although the amount used is larger than when using conductive fibers in the form of long fibers, conductive fibers are blended in polyurethane in the form of fleece or short fibers to form a matrix of short fibers in polyurethane. By doing so, conductivity can be imparted.

In order to improve the adhesion between the conductive fiber and the polyurethane elastomer, the fiber can be pretreated with a silane coupling agent or the like.

The amount of conductive fibers to be embedded in the polyurethane elastomer can be widely changed within the range where conductivity is imparted to the blade tip, but generally 2 to 180 mg, particularly 4 to 160 mg of fibers per cm ^{2 of} polyurethane elastomer area is used. If it is contained, the object of the present invention can be satisfied.

The charging voltage applied to the conductive rubber blade may be such that the surface potential of the photoconductor layer is 200 to 500 V, for which the blade applied voltage is 500 to 200.
0 volt is preferred. The contact pressure between the conductive rubber blade and the photoconductor is generally in the range of 1 to 5 kg / cm as a linear pressure (pressure per blade length).

The contact between the conductive rubber blade and the photoconductor is No. 2-A.
As shown in the figure, the countercurrent contact method in which the direction toward the tip 16 of the blade 15 and the direction of rotation of the photoconductor 2 face each other, or the direction toward the tip 16 of the blade 15 is light as shown in FIG. 2-B. A co-current contact method along the rotating direction of the conductor 2 can be adopted, but the former method is preferable from the viewpoint of discharge prevention. Further, in the case of FIG. 2-A, it is desirable that the contact angle α between them is generally within the range of 15 to 80 degrees.

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, and the function as a printer is provided.

[Brief description of drawings]

FIG. 1 is a schematic sectional view for explaining the process of the electrophotographic apparatus of the present invention, and FIGS. 2-A and 2-B explain the contact position of the conductive rubber blade of the electrophotographic apparatus of the present invention. FIG. 3 is a diagram for explaining the process of the conventional electrophotographic apparatus. 2 ... Amorphous silicon photoconductor layer, 4 ... Lamp, 6
...... Optical system, 8 …… Developing mechanism, 12 …… Cleaning mechanism, 15 …… Charging conductive rubber blade, 19 …… Transfer roller electrode.

Claims (3)

(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 the non-corona type strip electrode contact type, and the main charging mechanism is the contact between the amorphous silicon photoconductor layer and the tip, and polishing. An electrophotographic apparatus comprising a conductive rubber blade made of a polyurethane elastomer having an agent dispersed therein and having conductivity imparted by conductive fibers. 2. The electrophotographic apparatus according to claim 1, wherein the abrasive is blended in an amount of 1 to 15% by weight. 3. The electrophotographic apparatus according to claim 1, wherein the conductive fibers are blended in an amount of 2 to 180 mg per cm ^{2 of} polyurethane elastomer area.