JPH05158332A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To obtain a stable high-density image with little fogging even in the case of using conductive magnetic toner having compartively large resistance by forming alternating electric field between a developing sleeve and a transparent conductive layer. CONSTITUTION:The transparent conductive layer 1b of a photosensitive drum 1 is grounded, and pulsating voltage obtained by superposing DC voltage impressed from a DC power source 27 on AC voltage impressed from an AC power source 26 is impressed on the developing sleeve 5b holding the conductive magnetic toner T.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device for forming a toner image on the surface of a photosensitive member by exposing the surface of the photosensitive member to a developer to charge the surface of the photosensitive member and performing exposure according to a writing signal. The present invention relates to a photographic device.

[0002]

2. Description of the Related Art In the conventional electrophotographic apparatus, the electrophotographic method based on the application of the Carlson process is widely used. In this method, the surface of the photoconductor having the photoconductive layer is uniformly charged by using a charger, and exposure is performed according to a writing signal by the exposure device, so that the charged charge of the portion irradiated with light is removed. As a result, an electrostatic latent image is formed on the surface of the photoconductor. Then, conductive toner (hereinafter referred to as toner) charged with a polarity opposite to that of the charge on the surface of the photoconductor adheres to the electrostatic latent image, so that a visible image is formed on the surface of the photoconductor by the toner. It has become so.

That is, in the above-mentioned electrophotographic apparatus, the image portion (non-exposed portion) on the surface of the photoconductor in which the charge has not been removed
By the electric field that acts between the toner and the non-magnetic and conductive developing sleeve that holds the toner, charge is injected into the toner, and then the toner is generated as the magnet disposed inside the developing sleeve rotates. By being rotated and conveyed, a toner image is formed on the electrostatic latent image of the image portion on the surface of the photoconductor.

However, in the electrophotographic apparatus to which the Carlson process is applied as described above, the charge potential on the surface of the photosensitive member must be sufficiently high in order to sufficiently inject charge into the toner. Therefore, in order to charge the photoconductor, a charger by discharge is used. However, when such a charger is used, ozone is generated, so that the charger and the surface of the photoreceptor are deteriorated. I was invited. Further, since the toner adheres to the non-exposed portion to form an image portion, it is extremely inefficient in an electrophotographic apparatus such as a printer for writing.

Therefore, as an image forming method which does not require a charger for discharging as described above, a photosensitive member having a transparent conductive layer and a photoconductive layer formed on a cylindrical transparent support is used. While the voltage is applied between the transparent conductive layer and the non-magnetic developing sleeve that holds the toner, the toner is held in contact with the toner held by the developing sleeve to charge the surface of the photosensitive member and A method has been adopted in which a toner image is formed on the surface of a photoconductor by performing exposure according to a write signal from the support side.

That is, the contact area between the photosensitive member and the toner is
It has a certain width, and electric charges are injected into the surface of the photoconductor through the toner during this period so that the surface of the photoconductor has approximately the same potential as the toner. Then, when exposure according to the write signal is performed on the downstream side in the rotation direction of the photoconductor in the contact area with the toner on the photoconductor surface, the dielectric constant of the photoconductor at the exposure position changes, and the surface potential decreases. At this time, a suction force is generated between the toner charged by the developing sleeve and the exposure position on the surface of the photoconductor, so that a toner image is formed on the surface of the photoconductor.

As described above, by forming a toner image on the surface of the photosensitive member without using a charger for discharging,
It is possible to prevent deterioration of the surface of the photoconductor, and to attach toner to the exposed area to form the image area, and not attach toner to the non-exposed area, so it is possible to efficiently obtain a good image with less background stain. Becomes Further, since the transparent conductive layer of the photoconductor is used as the counter electrode and a voltage is applied to the developing sleeve carrying the toner, charges can be efficiently injected into the toner layer. The body surface can be uniformly charged, and a stable electrostatic latent image can be formed.

[0008]

However, as described above, by bringing the toner into contact with the surface of the photoconductor, the surface of the photoconductor is charged, and the toner is exposed on the surface of the photoconductor by performing exposure according to the write signal. An electrophotographic apparatus that forms an image has a problem that when a toner having a relatively large resistance is used, a stable image with high density and less fog cannot be obtained.

[0009]

In order to solve the above-mentioned problems, an electrophotographic apparatus according to claim 1 is provided with a transparent conductive layer and a photoconductive layer formed on a transparent support, and
While being held by the developer holding member, the surface of the photoconductor is charged by bringing the toner into which the charge has been injected into contact,
An electrophotographic apparatus for forming a visible image by causing toner to adhere to an exposure position on a surface of a photoconductor by performing exposure according to a writing signal from the transparent support side of the photoconductor,
It is characterized in that it has a voltage applying means for forming an alternating electric field between the developer holding member and the transparent conductive layer.

In order to solve the above-mentioned problems, an electrophotographic apparatus according to a second aspect is the electrophotographic apparatus according to the first aspect, in which one of the transparent conductive layer of the photoconductor and the developer holding member is electro-deposited. It is characterized in that the pulsating current voltage in which the DC voltage and the AC voltage are superposed is applied to the other by the voltage applying means.

In order to solve the above-mentioned problems, an electrophotographic apparatus according to a third aspect of the present invention is the electrophotographic apparatus according to the first aspect, wherein the voltage applying means includes a transparent conductive layer of the photoconductor and a developer holding member. It is characterized in that voltages of different polarities are applied.

[0012]

According to the structure of claim 1, since an alternating electric field is formed between the transparent conductive layer of the photoconductor and the developer holding member by the voltage applying means, a toner having a relatively high resistance is used. Even in this case, the charge held in the toner held by the developer holding member is sufficiently injected, and the photoconductor is also sufficiently charged in the contact area with the toner via the toner. Therefore, a stable image with high density and less fog can be obtained.

According to the second aspect of the invention, one of the transparent conductive layer of the photoconductor and the developer holding member is electrically grounded, and the other has a DC voltage and an AC voltage. Since the pulsating current voltage superposed with is applied, an alternating electric field is formed between the transparent conductive layer of the photoconductor and the developer holding member. Therefore, even when a toner having a relatively large resistance is used, the charge is sufficiently injected into the toner, and the surface of the photoconductor is sufficiently charged.
A stable image with high density and less fog can be obtained.

According to the third aspect of the invention, voltages having different polarities are applied to the transparent conductive layer of the photoconductor and the developer holding member by the voltage applying means. Therefore, since the potential difference between the developer holding member and the transparent conductive layer can be made larger, charge injection into the toner held in the developer holding member is sufficiently performed, and via this toner, Since the surface of the photoconductor is also sufficiently charged within the contact area with the toner, it is possible to obtain a stable image with high density and less fog.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 4, the electrophotographic apparatus of this embodiment is provided with a cylindrical photosensitive drum (photosensitive member) 1 rotatable in the direction A in the apparatus. A developing device 2 is provided on the right side of the photosensitive drum 1, an exposing device 7 is provided inside the photosensitive drum 1, and a transfer / fixing belt 8 is provided above the photosensitive drum 1.

The developing device 2 includes a developing tank 3 for storing a conductive magnetic toner T as a developer, and a stirring roller 4 rotatably provided in the developing tank 3 for stirring the conductive magnetic toner T. A toner carrier 5 arranged at a position facing the photoconductor drum 1 in the opening 3a of the developing tank 3, and a doctor blade 6 fixedly provided at a position below the toner carrier 5 in the opening 3a of the developing tank 3. It consists of and.

The toner carrier 5 extends along the longitudinal direction of the photosensitive drum 1 and has N polarity and S in the circumferential direction.
A magnetic roller 5a in which magnets with polarities are alternately arranged and a non-magnetic conductive member such as aluminum or martensitic stainless steel, and a developing device provided so as to cover the outer peripheral surface of the magnetic roller 5a. And a sleeve (developer holding member) 5b.

The toner carrier 5 is the magnetic roller 5
By the alternating magnetic field generated as a rotates in the B direction, the conductive magnetic toner T is held on the surface of the developing sleeve 5b, and the magnetic roller 5a is rotated in the B'direction opposite to the B direction. It is designed to be transported. Further, the doctor blade 6 holds the conductive magnetic toner T held on the surface of the developing sleeve 5b and conveyed in the B'direction as described above.
The transport amount of is adjusted to a predetermined amount.

As shown in FIG. 1, the photosensitive drum 1 has a surface of an optically transparent cylindrical transparent support 1a,
A transparent conductive layer 1b made of a sputtered film such as In ₂ O ₃ or SnO ₂ ,
A photoconductive layer 1c made of a photoconductive material such as Se, ZnO, CdS, or amorphous Si is sequentially laminated.
In this embodiment, the transparent conductive layer 1b has a film thickness of
An In ₂ O ₃ layer having a thickness of 0.5 μm is formed, and an amorphous Si layer having a thickness of 3 μm is formed as the photoconductive layer 1c.

The conductive magnetic toner T is prepared by kneading a resin made of styrene-acrylic copolymer with magnetic powder such as iron powder and ferrite, carbon black, etc., and pulverizing it to several tens to several tens of μm. It is composed of powder.

The developing sleeve 5b is connected via an AC power supply 26 to a positive electrode side of a DC power supply 27 whose negative electrode side is grounded. Therefore, the developing sleeve 5b is applied with a pulsating current voltage in which a DC voltage of 20V applied from the DC power supply 27 and an AC voltage of ± 5V and 10kHz applied from the AC power supply 26 are superimposed. .. In addition, the transparent conductive layer 1b of the photosensitive drum 1 has a DC power source 27
It is grounded together with the negative electrode side.

As shown in FIG. 4, the exposure device 7 arranged in the photosensitive drum 1 is composed of an LED array in which a short focus lens is combined with a light emitting diode, and an exposure control device (not shown). Light is emitted toward the developing device 2 in accordance with the write signal from the.

The transfer / fixing belt 8 is formed in an endless belt shape using a film material mainly composed of a polyimide resin having excellent mechanical strength and high heat resistance. The transfer / fixing belt 8 is a transfer roller 9 made of a conductive elastic member disposed above the photosensitive drum 1.
A heating device 10 to be described later, which is arranged on the left side of the transfer roller 9 and slightly above, and a tension roller 11 which is arranged on the lower left side of the heating device 10.
It is wrapped around these so as to surround and from the outside. The transfer / fixing belt 8 is sandwiched between the photosensitive drum 1 and the transfer roller 9 by the photosensitive drum 1 and the transfer roller 9.

The heating device 10 has a conductive magnetic toner T transferred onto the surface of the transfer / fixing belt 8 as described later.
Is for heating and melting, and a planar Mo-based heating resistor 10a is printed on an alumina ceramic substrate, and
It is composed of a ceramic heater in which a glass coat is printed and laminated. Then, the heating device 10 is configured to rapidly raise the temperature to a predetermined heating temperature by energizing the heating resistor 10a, and this heating surface directly contacts the surface of the transfer / fixing belt 8. Are arranged as follows.

A pressure roller 12 that rotates while applying a pressing force in a direction toward the heating device 10 via the transfer / fixing belt 8 is provided on the upper portion of the heating device 10.
The pressure roller 12 is configured to sandwich the transfer paper P conveyed by the recording material conveying means 14 described later at the pressure contact portion with the transfer / fixing belt 8. ..

Further, in the electrophotographic apparatus, as shown in FIG. 5, a cooling fan 24 for cooling the transfer / fixing belt 8 from below and a main motor 13 as a drive source of the apparatus are provided.
And the above-mentioned recording material conveying means 14 for conveying the transfer paper P to the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12,
A paper output unit 21 for discharging the transfer paper P from the inside of the apparatus is provided.

The recording material conveying means 14 is disposed above the photosensitive drum 1, the developing device 2 and the transfer / fixing belt 8 and has a transfer paper supply opening (not shown) as its constituent member. From the transfer / fixing belt 8 to the pressure contact portion of the pressure roller 12, a conveyance guide plate 15, a paper feed actuator 16 and paper feed rollers 18 and 18 arranged near the transfer paper supply opening. And the registration rollers 19 arranged on the way of the conveyance guide plate 15.
19 and a sheet feeding solenoid 20 that controls the rotation of the registration rollers 19 and 19.

The paper output means 21 is a transfer / fixing belt 8
It is disposed on the left side of the pressure contact portion between the pressure roller 12 and the pressure roller 12, and as its constituent member, connects the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12 to a transfer paper discharge opening (not shown). A paper output guide plate 22 forming a paper path, a paper output actuator 23 arranged in the vicinity of the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12, and a conveyance arranged on the end side of the paper output guide plate 22. And rollers 25, 25.

Next, the operation of the electrophotographic apparatus having the above structure will be described below.

First, the transfer paper feeding means (not shown)
When a sheet of transfer paper P is fed from the transfer paper supply opening,
When the leading edge of the transfer paper P pushes up the paper feed actuator 16, a paper feed detection switch (not shown) detects the supply of the transfer paper P and sends a paper feed detection signal to the main motor 13 to drive the drive source. The main motor 13 is driven to rotate. Next, the rotation of the main motor 13 is transmitted to the paper feed rollers 18 and 18 via a rotation transmission mechanism (not shown), whereby the paper feed rollers 18 and 18 are rotated, and the rotation of the paper feed rollers 18 and 18 is performed. Accordingly, the transfer paper P is conveyed to the registration rollers 19 and 19.

As described above, the registration roller 19.1
The transfer sheet P conveyed to the sheet 9 is transferred to the registration rollers 19 and 19
Since the rotation is stopped by the control of the paper feeding solenoid 20, the conveyance is temporarily stopped. At this time, the sheet feeding rollers 18, 18 are in a state of sandwiching the rear end side of the transfer sheet P, and the resistance of the roller surface is small, so that the transfer sheet P is stopped when the transfer sheet P is stopped. It is slipped on both sides.

Here, the electrophotographic apparatus is in a standby state,
If the print start signal is not generated within the predetermined time, the main motor 13 is stopped. On the other hand, when the print start signal is generated in the standby state, all the rotating parts other than the registration rollers 19 are rotated by the rotation transmission mechanism.

Next, the developing process of the conductive magnetic toner T will be described with reference to FIGS.

First, the conductive magnetic toner T stored in the developing tank 3 is held on the surface of the developing sleeve 5b by the alternating magnetic field generated by the rotation of the magnetic roller 5a in the B direction, as shown in FIG. At the same time, it is conveyed on the surface of the developing sleeve 5b in the B'direction which is the opposite direction to the A direction which is the rotation direction of the photosensitive drum 1. At this time, the developing sleeve 5
As described above, a pulsating current voltage obtained by superimposing the AC voltage from the AC power supply 26 on the DC voltage from the DC power supply 27 is applied to b, and the transparent conductive layer 1b of the photosensitive drum 1 is at the ground potential. ing. As a result, an alternating electric field is formed between the developing sleeve 5b and the transparent conductive layer 1b, and in the contact area between the conductive magnetic toner T held on the surface of the developing sleeve 5b and the photosensitive drum 1. The conductive magnetic toner T, into which electric charges have been injected by the developing sleeve 5b, is rotated and conveyed toward the upstream portion in the moving direction of the photoconductor.

During this period, the photoconductive layer 1 on the surface of the photosensitive drum 1 is passed through the conductive magnetic toner T from the developing sleeve 5b.
Electric charge is injected into c, and the photoconductive layer 1c is charged to substantially the same potential as the developing sleeve 5b. Therefore, in the part where the conductive magnetic toner T and the photoconductive layer 1c are separated, the conductive magnetic toner T is predominantly acted on by the magnetic force generated by the magnetic roller 5a, and therefore adheres to the photosensitive drum 1. do not do.

Next, as shown in FIG. 2, the photosensitive drum 1
When the LED corresponding to the write signal is sequentially selected from the exposure device 7 to perform the exposure at the portion C immediately before the conductive magnetic toner T is separated from the conductive magnetic toner T, the charges injected into the photoconductive layer 1c are neutralized. The surface potential of the photoconductive layer 1c becomes substantially the same as that of the transparent conductive layer 1b, so that a potential difference occurs between the photoconductive layer 1c and the developing sleeve 5b.

Thereafter, due to the potential difference as described above, charges are injected again from the developing sleeve 5b through the conductive magnetic toner T into the photoconductive layer 1c, but before the charges are sufficiently injected, the photosensitive drum 1 is discharged. 3 and the developing sleeve 5b are separated from each other, the conductive magnetic toner T is, as shown in FIG. 3, in an electric charge-injected state, an electric field that acts between the developing sleeve 5b and the surface of the photosensitive drum 1, and the photosensitive drum. 1 receives the action of the Van der Waals force or the like acting between 1 and the conductive magnetic toner T, and shakes off the magnetic force of the magnetic roller 5a,
By adhering to the surface of the photosensitive drum 1, a toner image corresponding to the writing signal is formed on the surface of the photosensitive drum 1.

As described above, as shown in FIG. 5, the toner image formed on the surface of the photosensitive drum 1 is applied to the transfer roller 9 with a voltage having the opposite polarity to the injected charge of the toner image. As a result, it is transferred onto the surface of the transfer / fixing belt 8 at the pressure contact portion between the photosensitive drum 1 and the transfer roller 9. On the other hand, a CPU (not shown) of an engine controller (not shown) so that the toner image on the surface of the transfer / fixing belt 8 and the transfer sheet P correspond to each other at the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12 on the heating device 10. A signal is output from the Central Processing Unit) to the sheet feeding solenoid 20, so that the rotation stop state of the registration rollers 19 is released, and the transfer sheet P is released.
However, it is conveyed to the pressure contact portion between the transfer / fixing belt 8 and the pressure roller 12 at a timing such that the front end portion thereof matches the front end portion of the transfer / fixing belt 8.

Then, a transfer / transfer of the above toner image is performed.
Since the fixing belt 8 and the transfer paper P are conveyed while being overlapped between the heating device 10 and the pressure roller 12,
The transfer and fixing of the toner image on the transfer paper P are simultaneously performed. That is, when the transfer paper P is sent out while being pressed against the transfer / fixing belt 8 and the pressure roller 12, the releasability of the conductive magnetic toner T heated and melted by the heating device 10 is higher than that of the transfer paper P. However, since the surface of the transfer / fixing belt 8 is better, most of the conductive magnetic toner T on the surface of the transfer / fixing belt 8 is transferred / fixed onto the transfer paper P.

After that, the transfer paper P on which the above toner image has been transferred and fixed is pushed up by the paper output actuator 23 and is discharged from the apparatus through the transfer paper discharge opening by the rotation of the conveying rollers 25. Then, after the transfer paper P is discharged to the outside of the apparatus and a predetermined time has elapsed, the heating device 10
When the heating resistor 10a is energized and the driving of the main motor 13 is stopped, the series of operations described above ends.

As described above, in the electrophotographic apparatus of this embodiment, the transparent conductive layer 1b of the photosensitive drum 1 is grounded, and the developing sleeve 5b carrying the conductive magnetic toner T is supplied from the DC power supply 27. Apply a DC voltage of 20V,
Further, an AC voltage of ± 5 V and 10 kHz was superimposed from the AC power supply 26.

As a result, an alternating electric field is formed between the developing sleeve 5b and the transparent conductive layer 1b of the photosensitive drum 1,
Even when the conductive magnetic toner T having a relatively large resistance is used, the charge is sufficiently injected from the developing sleeve 5b to the conductive magnetic toner T, so that the conductive magnetic toner T is used.
Thus, the surface of the photoconductor drum 1 is also sufficiently charged in the contact area with the toner. Therefore, a stable image with high density and less fog could be obtained.

In the charging method as described above, in the area where the conductive magnetic toner T and the photosensitive drum 1 are in contact with each other,
It suffices that the photoconductive layer of the photosensitive drum 1 be applied with an electric field and the developing sleeve 5b be conductive. Therefore, the configuration is the reverse of that of this embodiment, that is, the transparent conductive layer 1b of the photosensitive drum 1 is used. Even when the voltage is applied to the developing sleeve 5b and the developing sleeve 5b is grounded, the present invention can be applied.

Further, depending on the characteristics of the toner used,
The developing sleeve 5b is formed on the transparent conductive layer 1b of the photosensitive drum 1.
In some cases, it may be better to apply a voltage having a polarity different from that.
In this case, in addition to the above configuration, it is necessary to provide another DC power source (voltage applying means) whose negative electrode side is connected to the transparent conductive layer 1b of the photosensitive drum 1. Also at this time, a sufficient image density can be obtained with an applied voltage of several volts.

[0046]

The electrophotographic apparatus according to the invention of claim 1
As described above, the voltage applying means for forming an alternating electric field is provided between the developer holding member and the transparent conductive layer.

Therefore, even when a toner having a relatively high resistance is used, it is possible to obtain a stable image with high density and less fog.

In the electrophotographic apparatus according to the second aspect of the present invention, as described above, either one of the transparent conductive layer of the photoconductor and the developer holding member is electrically grounded, and the other is
The voltage application means applies a pulsating current voltage in which a DC voltage and an AC voltage are superimposed.

Therefore, since an alternating electric field is formed between the transparent conductive layer of the photoconductor and the developer holding member, even when a toner having a relatively high resistance is used, the density is high and the fogging is small and stable. The effect of being able to obtain the reproduced image is obtained.

In the electrophotographic apparatus according to the third aspect of the present invention, as described above, the voltage application means is configured to apply voltages of different polarities to the transparent conductive layer of the photoconductor and the developer holding member. ..

Therefore, since the potential difference between the developer holding member and the transparent conductive layer can be made larger, it is possible to obtain a stable image with high density and less fog.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state where a surface of a photosensitive drum is charged by contact with a conductive magnetic toner in an electrophotographic apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state where the surface of the photosensitive drum is neutralized by exposure.

FIG. 3 is an explanatory diagram showing a state in which a toner image is formed on the surface of the photosensitive drum.

FIG. 4 is a vertical sectional view showing a photosensitive drum, a developing device, an exposing device, and a transfer / fixing belt in the electrophotographic apparatus.

FIG. 5 is a schematic configuration diagram showing various components constituting the electrophotographic apparatus.

[Explanation of symbols]

 1 Photoreceptor Drum (Photoreceptor) 1a Transparent Support 1b Transparent Conductive Layer 1c Photoconductive Layer 5a Developing Sleeve (Developer Holding Member) 26 AC Power Supply (Voltage Applying Means) 27 DC Power Supply (Voltage Applying Means) T Conductive Magnetic Toner

Claims (3)

[Claims] 1. A surface of a photoreceptor having a transparent conductive layer and a photoconductive layer formed on a transparent support is brought into contact with a toner held by a developer holding member and charged with an electric charge. Is an electrophotographic apparatus that forms a visible image by attaching toner to an exposed position on the surface of the photoconductor by exposing the photoconductor to a transparent support side of the photoconductor and performing exposure according to a writing signal. An electrophotographic apparatus comprising a voltage applying means for forming an alternating electric field between a holding member and a transparent conductive layer. 2. One of the transparent conductive layer and the developer holding member of the photoreceptor is electrically grounded, and the other is
2. The electrophotographic apparatus according to claim 1, wherein a pulsating voltage in which a DC voltage and an AC voltage are superimposed is applied by the voltage applying means. 3. The electrophotographic apparatus according to claim 1, wherein the voltage applying means applies voltages having different polarities to the transparent conductive layer of the photoconductor and the developer holding member.