JP2003122098A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method which can carry out stable electrostatic charging for a long period even when high-ratio images are continuously outputted by preventing a photosensitive body from having a defective electrostatic charging. SOLUTION: In a pre-rotation processing carried out prior to image formation, the photosensitive body 1 and a roller electrostatic charger 3 begin to be driven and at this time, an electrostatic charging roller is rotated at a rotating speed for discharge mode which is faster than that in normal image formation. It is confirmed that untransferred toner is discharged from the roller electrostatic charger. As the rotating speed of an electrostatic charging member is increased, the change to discharge the untransferred toner per unit time increases, so that the discharge efficiency of toner ticking on the electrostatic charging roller is improved. In the pre-rotation for image formation, a rotating speed having a 150% circumferential speed ratio to the circumferential speed of the photosensitive body is set as the discharge mode for image formation. After the pre-rotation, the rotating speed of the electrostatic charging roller is lowered to a 40% circumferential speed ratio for the image formation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method in which an electrostatic latent image formed on an image carrier corresponding to an image to be recorded is developed with a developer and recorded on a sheet or the like.

[0002]

2. Description of the Related Art In an image forming method used in an electrophotographic apparatus, an electrostatic recording apparatus, etc., there are various methods for forming an electrostatic latent image on an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric. The method is known.

For example, in electrophotography, an image pattern is exposed after uniformly charging a photosensitive member using a photoconductive material as a latent image carrier to a desired polarity and potential. A method of forming a latent image is common.

Conventionally, a corona charger (corona discharger) has been often used as a charging device for uniformly charging (including static elimination) the latent image carrier to a desired polarity and potential.

The corona charger is a non-contact type charging device, which is provided with a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode, and the discharge opening is made to face the image carrier, which is an image carrier, so as not to contact the image carrier. The image carrier surface is exposed to a discharge current (corona shower) generated by applying a high voltage to the discharge electrode and the shield electrode to charge the image carrier surface to a predetermined potential.

In recent years, as a charging device for an electrostatic latent image carrier or the like, a contact charging device has been proposed and put into practical use because it has advantages such as low ozone and low power as compared with a corona charger. .

In such a contact charging type charging device, the charging member to be brought into contact with the image carrier has various forms such as a roller type (charging roller), a fur brush type, a magnetic brush type and a blade type (charging blade). Yes, and there are various suggestions for improvement.

Charging mechanism of contact charging (charging mechanism,
In the charging principle), two types of charging mechanisms, a discharge charging mechanism and a direct injection charging mechanism, are mixed, and each characteristic appears depending on which one is dominant.

Discharge Charging Mechanism This is a mechanism in which the surface of the image carrier is charged by a discharge phenomenon that occurs in a minute gap between the contact charging member and the image carrier. Since the discharge charging mechanism has a constant discharge threshold in the contact charging member and the image carrier, it is necessary to apply a voltage higher than the charging potential to the contact charging member. Further, compared with a corona charger, the generation amount is remarkably small, but generation of a discharge product is unavoidable in principle, so that a harmful effect due to active ions such as ozone is unavoidable.

Direct injection charging mechanism A system in which the surface of the image bearing member is charged by directly injecting charges from the contact charging member into the image bearing member. It is also called direct charging, injection charging, or charge injection charging. More specifically, the contact charging member of medium resistance contacts the surface of the image carrier,
The charge is directly injected to the surface of the image carrier without using the discharge phenomenon, that is, basically without using discharge. Therefore, even if the applied voltage to the contact charging member is equal to or lower than the discharge threshold value, the image carrier can be charged to a potential corresponding to the applied voltage. Since this charging system does not generate ions, no harm is caused by the discharge products. However, since it is direct injection charging, the contact property of the contact charging member to the image carrier greatly affects the charging property. Therefore, in order to contact the image carrier more frequently, the contact charging member needs to have a denser contact point, a speed difference with the image carrier, and the like.

(Roller charging) In the contact charging device, a roller charging method using a conductive roller (charging roller) as a contact charging member is preferable from the viewpoint of stability of charging and is widely used.

The above-mentioned discharge charging mechanism is dominant in the charging mechanism in the conventional roller charging.

The charging roller is made of a conductive or medium-resistance rubber material or foam. Further, there is also one in which these are laminated to obtain desired characteristics.

The charging roller has elasticity in order to obtain a constant contact state with the image carrier, and therefore has a large frictional resistance, and in many cases, is driven by the image carrier or driven with a slight speed difference. It Therefore, even if the direct injection charging is attempted, the deterioration of the absolute charging ability, the lack of contact, the uneven contact due to the roller shape, and the uneven charge due to the adhered matter on the photosensitive member cannot be avoided.

FIG. 8 is a graph showing an example of charging efficiency of contact charging in electrophotography. The horizontal axis represents the bias applied to the contact charging member, and the vertical axis represents the charging potential of the image carrier obtained at that time. The charging characteristic in the case of roller charging is represented by A. That is, charging starts after the discharge threshold of about -500V is exceeded. Therefore, when charging to -500V, a DC voltage of -1000V is applied, or in addition to a charging voltage of -500V DC, an AC voltage of 1200V between peaks is applied so as to always have a potential difference of a discharge threshold value or more. Then, the method of converging the potential of the image carrier to the charging potential is general.

More specifically, when the charging roller is brought into pressure contact with the image bearing member, the surface potential of the photosensitive member begins to rise when a voltage above a certain level is applied, and thereafter. Causes the surface potential of the image carrier to increase linearly with the applied voltage. This threshold voltage is defined as the charging start voltage Vth.

That is, in order to obtain the image carrier surface potential Vd required for electrophotography, Vd + Vt is applied to the charging roller.
More DC voltage than required, h, is required. The method of charging only by applying the DC voltage to the contact charging member in this way is called "DC charging method".

However, in DC charging, the resistance value of the contact charging member fluctuates due to environmental fluctuations, etc. Further, when the image carrier is scraped and the film thickness changes, Vth fluctuates, so that the potential of the image carrier is changed. It was difficult to obtain the desired value.

Therefore, as disclosed in Japanese Patent Laid-Open No. 63-149669, a DC voltage corresponding to a desired Vd has a peak-to-peak voltage of 2 × Vth or more in order to further uniformize the charging. An “AC charging method” is used in which a voltage with an AC component superimposed is applied to a contact charging member. This is for the purpose of leveling the potential by the alternating current, and the potential of the image carrier is V which is the center of the peak of the alternating voltage.
It converges on d and is not affected by disturbances such as the environment.

However, even in such a contact charging device, since the essential charging mechanism uses the discharge phenomenon from the contact charging member to the image carrier, as described above, it is applied to the contact charging member. The voltage to be applied is required to have a value higher than the surface potential of the image carrier, and a slight amount of ozone is generated.

Further, when AC charging is performed to make the charging uniform, further generation of ozone and vibration noise of the contact charging member and the image carrier due to the electric field of AC voltage (AC charging sound).
And the deterioration of the surface of the image bearing member due to the discharge became remarkable, which was a new problem.

Japanese Patent Publication No. 7-99442 discloses a structure in which a contact charging member is coated with powder on its contact surface with the surface of an image carrier in order to prevent uneven charging and to perform stable uniform charging. However, contact charging member (charging roller)
Is driven by the image carrier (photoreceptor) (no speed difference drive), and the generation of ozone products is much less than that of a corona charger such as a scorotron, but the principle of charging is the roller charging described above. As in the case of No. 1, the discharge charging mechanism is still mainly used. In particular, in order to obtain more stable charging uniformity, a voltage in which an AC voltage is superimposed on a DC voltage is applied, so that ozone products are more likely to be generated by the discharge. Therefore, when the device is used for a long period of time, adverse effects such as image deletion due to ozone products are likely to appear. Further, when applied to a cleanerless image forming apparatus, it becomes difficult for the applied powder to be uniformly attached to the charging member due to the mixture of the transfer residual toner, and the effect of uniform charging is diminished.

Further, in JP-A-5-150539, in an image forming method using contact charging, toner particles or silica fine particles which cannot be completely cleaned by blade cleaning during repeated image formation on the surface of the charging means. It is disclosed that the toner contains at least developer particles and conductive particles having an average particle size smaller than that of the developer particles in order to prevent charging inhibition due to adhesion and accumulation. However, the contact charging or the proximity charging used here is based on the discharge charging mechanism and not the direct injection charging mechanism, but has the above-mentioned problems due to the discharge charging. Further, when applied to a cleaner-less image forming apparatus, a large amount of conductive fine powder and transfer residual toner pass through the charging process, which affects the charging property, as compared with the case where a cleaning mechanism is provided. No consideration is given to the recoverability of the conductive fine powder and the transfer residual toner in the developing step, and the influence of the recovered conductive fine powder and the transfer residual toner on the development characteristics of the toner. Further, when the direct injection charging mechanism is applied to the contact charging, the conductive fine powder is not supplied to the contact charging member in a necessary amount, and charging failure occurs due to the influence of the transfer residual toner.

In proximity charging, it is difficult to uniformly charge the image bearing member with a large amount of conductive fine powder and transfer residual toner, and the effect of leveling the transfer residual toner pattern cannot be obtained. A pattern ghost is generated to shield the pattern image exposure. Further, when the power is interrupted or paper is jammed during image formation, the inside of the machine is significantly contaminated with toner.

On the other hand, Japanese Patent Laid-Open No. 10-307454,
As disclosed in Japanese Patent Application Laid-Open No. 10-307457, a method has been proposed in which a charging member and an image carrier are provided with a speed difference, and direct injection charging is performed via conductive fine powder.

In the above-mentioned publication, due to the presence of the conductive fine powder for the purpose of assisting charging, the contact charging member can contact with the image bearing member at a speed difference at the charging contact portion between the image bearing member and the contact charging member. , The conductive fine powder that is in close contact with the image carrier via the conductive fine powder, that is, the conductive fine powder present in the charging contact portion of the contact charging member and the image carrier, rubs the surface of the image carrier with no gap. Thus, the electric charge can be directly injected into the image carrier. That is, the charging of the image bearing member by the contact charging member is dominated by the direct injection charging due to the presence of the conductive fine powder.

Therefore, as shown in the charging characteristic B of FIG.
A high charging efficiency, which has not been obtained by conventional roller charging or the like, can be obtained, and a potential almost equal to the voltage applied to the contact charging member can be applied to the image carrier.

(Toner Recycle Process = Cleanerless System) In an image forming apparatus of a transfer type, transfer residual toner remaining on the image carrier after transfer is removed from the surface of the image carrier by a cleaner (cleaning device). Although it becomes waste toner, it is desirable that this waste toner does not appear in terms of environmental protection. Therefore, in the toner recycling process, the cleaner is eliminated, and the transfer residual toner on the photoconductor after the transfer is removed from the image carrier by "development simultaneous cleaning" by the developing device and collected and reused in the developing device. Image forming apparatuses have also appeared.

Simultaneous development cleaning means that the toner remaining on the image carrier after transfer is developed during the subsequent steps, that is, the image carrier is continuously charged and exposed to form a latent image, and the latent image is developed. Sometimes, it is a method of collecting with a fog removal bias (fog removal potential difference Vback which is a potential difference between the DC voltage applied to the developing device and the surface potential of the image carrier). According to this method, the transfer residual toner is collected by the developing device and reused after the next step, so that it is possible to eliminate the waste toner and reduce the troublesome maintenance. Further, since the cleaner is not used, there is a large space advantage, and the image forming apparatus can be significantly downsized.

An image forming method in which the direct injection charging and the toner recycling system are combined will be described below.

FIG. 3 is a schematic view of an embodiment of the contact charging device 3 using the direct injection charging method.

In FIG. 3, the contact charging device 3 is a device using a conductive elastic roller 30 (hereinafter referred to as a “charging roller”) as a contact charging member, and includes a core metal 31 and a core metal 3.
1 is a flexible member made of rubber or foam medium resistance layer 3
A charging roller 30 formed by forming 2;
Outer peripheral surface of the charging roller 30 (that is, outer peripheral surface of the medium resistance layer 32)
In the initial stage, the conductive fine powder 33 is applied on the charging roller 30 and then supplied with the transfer residual toner 34.
And a charging bias voltage applying power source S1 for applying a charging bias to the charging roller 30.

The charging roller 30 is made substantially parallel to the photosensitive member 1 as an image bearing member so that both ends of the cored bar 31 are supported.
The medium resistance layer 32 is arranged in pressure contact with a predetermined pressing force against the elasticity of the medium resistance layer 32 to form a charging contact portion which is a contact portion between the charging roller 30 and the photoconductor 1. The width n of the charging contact portion is not particularly limited, but is preferably 1 mm or more, more preferably 2 mm or more in order to obtain stable and dense adhesion between the conductive elastic roller and the image carrier.

The charging roller 30 has a charging contact portion which is in a clockwise direction as indicated by an arrow which is opposite to the rotation direction of the photosensitive member 1 or a charging contact portion which is in the forward direction with respect to the rotation direction of the photosensitive member 1. The surface of the photosensitive member 1 is rotatably driven in the clockwise direction, and the surface of the photosensitive member 1 is rubbed against the medium resistance layer 32 holding the conductive fine powder 33 at the charging contact portion.

Then, the charging bias voltage applying power source S1 applies a predetermined charging bias to the conductive fine powder 33 through the charging roller 30 with a predetermined polarity and potential of a DC voltage (V DC alone: DC application system) or alternating. The outer peripheral surface of the photosensitive member 1 which is applied with an oscillating voltage (V DC + V AC: AC application system) superimposed with the voltage V and is rotationally driven is uniformly charged to a predetermined polarity and potential by the direct injection charging system.

Next, the behavior of the toner base particles and the conductive fine powder 33 during the image forming process when the conductive fine powder 33 is externally added to the toner base particles will be described.

The conductive fine powder 33 contained in the toner is
During development of the electrostatic latent image on the photoconductor 1 in the developing step (not shown), an appropriate amount is transferred to the photoconductor 1 together with the toner mother particles.

The toner image on the photoconductor 1 is transferred to a recording medium (not shown) in a transfer step (not shown). Photoconductor 1
A part of the conductive fine powder 33 also adheres to the recording medium, but the rest remains adhered and held on the photoconductor 1. When transfer is performed by applying a transfer bias having a polarity opposite to that of the toner, the toner is attracted and actively transferred to the recording medium side, but the conductive fine powder 33 on the photoconductor 1 is conductive. Therefore, it is not positively transferred to the recording medium side, but a part thereof is attached to the recording medium side, but the rest is attached and retained on the photoconductor 1 and remains.

In the image forming method using no cleaner, the transfer residual toner 34 remaining on the surface of the photoconductor 1 after transfer and the above-mentioned residual conductive fine powder 33 are generated by the photoconductor 1 and the charging roller 3.
The photosensitive member 1 is carried as it is to the charging unit, which is the contact unit of 0, by the movement of the photosensitive member 1, and adheres to and mixes with the charging roller 30.

Therefore, the direct injection charging of the photoconductor 1 is performed with the conductive fine powder 33 interposed in the contact portion between the photoconductor 1 and the charging roller 30.

Due to the presence of the conductive fine powder 33, the close contact property and the contact resistance of the charging roller 30 to the photoconductor 1 are obtained irrespective of the contamination due to the adhering / mixing of the transfer residual toner 34 to the charging roller 30. Therefore, it is possible to favorably charge the photoconductor 1 by the charging roller 30.

The transfer residual toner 34 adhering to and mixed with the charging roller 30 is evenly charged to the same polarity as the charging bias by the charging bias applied from the charging roller 30 to the photosensitive member 1, and gradually from the charging roller 30. Is discharged onto the photoconductor 1 and reaches the developing unit as the photoconductor 1 moves.
Simultaneous development cleaning (collection) is performed in the development process.

Further, as the image formation is repeated, the conductive fine powder 33 contained in the toner is transferred to the photoconductor 1 in the developing section and is moved to the charging section via the transfer section by the movement of the photoconductor 1. Since the conductive fine powder is continuously supplied to the charging unit one after another, even if the conductive fine powder 33 is reduced or deteriorates due to dropping or the like in the charging unit, it is possible to prevent the deterioration of the charging property. And good chargeability is stably maintained.

By using this direct injection charging method, an image carrier having a surface layer in which conductive fine particles are dispersed on an organic photoconductor (OPC), or an amorphous silicon photoconductor (a-Si) is used. Since the charging of the image bearing member does not utilize the discharge phenomenon that is performed by using the corona charger, it is possible to achieve complete ozoneless and low power consumption type charging.

In electrophotography, a photoconductive material forming a photosensitive layer of a photoconductor has high sensitivity and a high SN ratio [photocurrent (Ip) / dark current (Id)], and has a spectral characteristic of an electromagnetic wave irradiated. Having a suitable absorption spectrum, having a fast photoresponsiveness, and having a desired dark resistance value,
Characteristics such as being harmless to the human body when used are required. In particular, in the case of a photoreceptor for an image forming apparatus incorporated in an image forming apparatus used in an office as an office machine, long-term stability of image quality and image density is considered in consideration of being used in a large amount for a long period of time. Is also an important point.

Hydrogenated amorphous silicon (hereinafter referred to as "a-Si:" is used as a photoconductive material exhibiting excellent properties in this respect.
“H”), for example, Japanese Patent Publication No. 60-350
JP-A-59-59 describes application as a photoconductor for an image forming apparatus.

In such a photoreceptor for an image forming apparatus, generally, a conductive support is heated to 50 ° C. to 400 ° C., and a vacuum deposition method, a sputtering method, an ion plating method, Thermal CVD method, optical CVD method, plasma CV
A photoconductive layer made of a-Si is formed by a film forming method such as D method. Among them, the plasma CVD method, that is, the method of decomposing the source gas by direct current or high frequency or microwave glow discharge to form the a-Si deposited film on the support is put to practical use as a suitable one.

Further, in JP-A-54-83746, a conductive support and a-Si containing a halogen atom as a constituent element (hereinafter referred to as "a-Si: X").
A photoconductor for an image forming apparatus including a photoconductive layer has been proposed. In the publication, 1 halogen atom is added to a-Si.
By containing 40 to 40 atomic%, high heat resistance,
Good electrical conductivity as the photoconductive layer of the photoreceptor for image forming apparatus,
It is said that optical characteristics can be obtained.

Further, in Japanese Patent Application Laid-Open No. 57-115556, a photoconductive member having a photoconductive layer formed of an a-Si deposited film is electrically and darkly applied, such as its dark resistance value, photosensitivity and photoresponsiveness. In order to improve the use environment characteristics such as optical and photoconductive characteristics and moisture resistance, and further the stability over time, silicon atoms and carbon are formed on the photoconductive layer composed of an amorphous material with silicon atoms as a base material. A technique for providing a surface barrier layer composed of a non-photoconductive amorphous material containing atoms is described.

Further, Japanese Patent Application Laid-Open No. 60-67951 discloses a technique relating to a photoconductor in which a translucent insulating overcoat layer containing amorphous silicon, carbon, oxygen and fluorine is laminated. 62-168161
The publication describes a technique of using, as the surface layer, an amorphous material containing silicon atoms, carbon atoms, and 41 to 70 atomic% hydrogen atoms as constituent elements.

Furthermore, JP-A-57-158650 discloses that the content of hydrogen is 10 to 40 atomic%, and the infrared absorption spectrum is 2100 × 10 ⁻¹ cm and 2000 × 10 ^−1.
It is described that by using a-Si: H having an absorption coefficient ratio of cm absorption peak of 0.2 to 1.7 for the photoconductive layer, a highly sensitive and high-sensitivity photoreceptor for an image forming apparatus can be obtained. ing.

On the other hand, in JP-A-60-95551, in order to improve the image quality of an amorphous silicon photoconductor, charging, exposure, development and transfer are performed while maintaining the temperature in the vicinity of the photoconductor surface at 30 to 40 ° C. By performing the image forming process as described above, there is disclosed a technique of preventing the reduction of the surface resistance due to the adsorption of water on the surface of the photoconductor and the resulting image deletion.

[0053]

However, in the image forming apparatus, the roller charging method using the direct injection charging described above as the charging means of the photosensitive member 1 as the image bearing member has various peculiar problems to be overcome. To do. One of them was the following problem.

Not a low ratio image like a character image,
If you continue to take high ratio images such as solid images and photographic images,
Since the transfer residual toner 34 is larger than when the character image is formed,
This means that the charging roller 30 is more likely to come into contact with the transfer residual toner 34, and the charging roller 30 is contaminated with the transfer residual toner 34, resulting in poor charging.

That is, the transfer residual toner 34 adhering to and mixed with the charging roller 30 is uniformly charged to the same polarity as the charging bias by the charging bias applied from the charging roller 30 to the photosensitive member 1, and is gradually discharged from the charging roller 30. However, the relationship between the amount of transfer residual toner 34 adhered / mixed and the amount of transfer residual toner 34 discharged is adhered / mixed transfer residual toner 34> discharged transfer residual toner 3
Therefore, the conductive fine powder 33 cannot maintain the close contact property of the charging roller 30 with the photoconductor 1, and the charging roller 30 cannot charge the photoconductor 1 properly.

An object of the present invention is to provide an image forming method capable of preventing the above-mentioned charging failure and performing stable charging for a long period of time even when a high ratio image is continuously output.

[0057]

According to a first aspect of the present invention, there is provided a charging step of charging an image carrier by bringing a charging member into contact with at least the image carrier to apply a charging bias, and the image forming method. An image forming step of forming an electrostatic latent image on a charged surface of a carrier, and a developing step of visualizing the electrostatic latent image with toner, the image carrying after the developing step transfers the toner image to a recording medium. In the image forming method which also serves as a cleaning step for collecting the residual toner remaining on the body, the charging step is performed in a state where electrically conductive charge promoting particles are present in the contact portion between the charging member and the image carrier. And a discharging step of moving the transfer residual toner adhering to the charging member to the image carrier by controlling the moving speed of the charging member by the rotation at the contact portion. It is the formation method.

According to this method, the initial charging performance can be maintained without the contamination of the transfer roller residual toner on the charging roller, and the transfer residual toner is discharged from the charging roller to the image forming area. Fog caused by the can also be prevented.

In the second aspect of the present invention, in the charging step, the moving speed of the surface of the charging member forming the contact portion and the moving speed of the surface of the image carrier have a relative speed difference. The image forming method according to claim 1, which is a step of charging the image carrier.

According to the invention of claim 3 of the present invention,
3. The image forming method according to claim 1, wherein the charging step is a step of charging the image carrier while the charging member and the image carrier move in opposite directions.

According to these methods, the opportunity for the conductive fine powder to come into contact with the image carrier at the contact portion between the contact charging member and the image carrier is significantly increased, and higher contact property can be obtained. Direct injection chargeability can be improved.

In the invention according to claim 4 of the present invention, in the charging step, the image carrier is charged by applying a voltage to a roller member having an Asker C hardness of 50 degrees or less. The image forming method according to 1 above.

According to this method, the roller can be pressed against the image carrier with a predetermined pressing force against the elasticity of the medium resistance layer formed on the cored bar of the roller member.

According to a fifth aspect of the present invention, in the charging step, the volume resistivity is 10 ³ Ω · cm or more and 10 ⁸ Ω · c.
5. The step of charging the image bearing member by applying a voltage to a roller member having a size of m or less.
The image forming method described in 1 above.

According to this method, a sufficient contact state between the roller member and the image carrier can be obtained, and at the same time, it can function as an electrode having a resistance low enough to charge the moving image carrier.

According to a sixth aspect of the present invention, in the charging step, at least a contact portion between the charging member and the image carrier and / or
Alternatively, the conductive fine powder contained in the developer adheres to the image carrier in the developing step in the vicinity thereof, and remains on the image carrier even after the transfer step and is carried and interposed. Items 1-5
The image forming method described in 1 above.

Further, in the invention according to claim 7 of the present invention, the volume resistivity of the conductive fine powder is at least 1 × 10 ⁹
The image forming method according to claim 6, wherein the image forming method is Ω · cm or less, preferably 1 × 10 ⁶ Ω · cm or less.

According to these methods, the image carrier can be charged more favorably.

[0069]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a charging member used in the present invention,
The conductive fine powder and the photoconductor will be described.

In the charging step of the image forming method of the present invention, a conductive charging member (contact charging member / contact charger) of a roller type (charging roller), a fur brush type, a blade type or the like is brought into contact with the image carrier. Then, a contact charging device for applying a predetermined charging bias to the contact charging member to charge the surface of the image bearing member to a predetermined polarity and potential is used. Although it is possible to obtain good chargeability by applying a DC bias alone to the contact charging member, a DC voltage may be superposed with an alternating voltage (AC voltage).

As the waveform of the alternating voltage, a sine wave, a rectangular wave, a triangular wave or the like can be appropriately used. Further, it may be a pulse wave formed by periodically turning on / off the DC power supply. Thus, as the waveform of the alternating voltage, a bias whose voltage value changes periodically can be used.

In the present invention, the charging member preferably has elasticity in providing a contact portion for interposing the conductive fine powder between the charging member and the image carrier, and a voltage is applied to the charging member. Therefore, it is preferable that the image carrier is electrically conductive so as to be charged. Therefore, the charging member may be a conductive elastic roller, a magnetic brush contact charging member having a magnetic brush portion in which magnetic particles are magnetically restrained, and the magnetic brush portion is in contact with the image carrier, or a brush composed of conductive fibers. Preferably there is.

If the hardness of the conductive elastic roller is too low, the shape is not stable, so that the contact property with the image carrier is deteriorated. Further, the conductive fine powder is added to the contact portion between the charging member and the image carrier. By interposing the body, the surface layer of the conductive elastic roller is scraped or damaged, and stable chargeability cannot be obtained. Further, if the hardness is too high, not only the charging contact portion cannot be secured with the image bearing member, but also the micro contact property to the surface of the image bearing member is deteriorated, so that the Asker C hardness is from 25 degrees to 50 degrees. It is in a preferable range.

The conductive elastic roller has elasticity to obtain a sufficient contact state with the image carrier, and at the same time to charge the moving image carrier, for example, the conductive elastic roller is used as a flexible member. It is made by forming a medium resistance layer of rubber or foam. The medium resistance layer is formulated with a resin (for example, urethane), conductive particles (for example, carbon black), a sulfiding agent, a foaming agent, etc., and is formed on the core metal 31 in a roller shape. After that, if necessary, the surface can be cut and the shape can be adjusted to form a conductive elastic roller.
In addition, it is preferable that the surface of the roller has minute cells or irregularities in order to interpose the conductive fine powder.

The material of the conductive elastic roller is not limited to the elastic foam, and the material of the elastic body is ethylene-propylene-diene polyethylene (EPD).
M), urethane, butadiene acrylonitrile rubber (N
Examples of the rubber material include BR), silicone rubber, isoprene rubber, etc., in which a conductive material such as carbon black or metal oxide is dispersed for resistance adjustment, and those obtained by foaming these materials. It is also possible to adjust the resistance by using an ion conductive material without dispersing the conductive material or in combination with the conductive material.

The flexibility of the contact charging member increases the chances of the conductive fine powder coming into contact with the image carrier at the contact portion between the contact charging member and the image carrier, thus obtaining high contact property. This is preferable in that it is possible to improve the direct injection charging property. That is, the contact charging member comes into close contact with the image carrier through the conductive fine powder, and the conductive fine powder present at the contact portion between the contact charging member and the image carrier slides on the surface of the image carrier without a gap. By rubbing, the charging of the image bearing member by the contact charging member is dominated by the stable and safe direct injection charging that does not use the discharge phenomenon due to the presence of the charging promoting particles.

It is important that the conductive elastic roller has elasticity to obtain a sufficient contact state with the image carrier and at the same time functions as an electrode having a resistance low enough to charge the moving image carrier. . On the other hand, it is necessary to prevent voltage leakage when a defective portion such as a pinhole exists on the image carrier. When an electrophotographic photosensitive member is used as the image bearing member, 10 ³ to 10 is required to obtain sufficient chargeability and leak resistance.
The resistance is preferably ⁸ Ω, more preferably 10 ⁴ to
The resistance is preferably 10 ⁷ Ω. The resistance of the roller is
Direct system 3 so that a total pressure of 1 kg is applied to the core of the roller.
In a state where the roller was pressure bonded to a 0 mm cylindrical aluminum drum, 100 V was applied between the core metal and the aluminum drum, and measurement was performed.

Regarding the speed difference between the charging member and the image carrier, specifically, the surface of the charging member is moved and driven to provide the speed difference with the image carrier. It is preferable that the charging member is rotationally driven, and that the rotation direction thereof is opposite to the moving direction of the surface of the image carrier.

It is possible to move the surface of the charging member in the same direction as the moving direction of the surface of the image carrier to give a speed difference, but the charging property of the direct injection charging is the peripheral speed of the image carrier and the charging property of the charging member. Since it depends on the ratio of peripheral speeds, in order to obtain the same peripheral speed difference as in the reverse direction, the number of rotations of the charging member in the forward direction is higher than in the reverse direction, so moving the charging member in the reverse direction causes rotation. It is advantageous in terms of number.

The relative moving speed ratio described here is the relative moving speed ratio (%) = (peripheral speed of charging member-peripheral speed of image carrier) / peripheral speed of image carrier × 100 (the peripheral speed of the charging member is the charging speed). It is a positive value when the surface of the charging member moves in the same direction as the surface of the image carrier at the contact portion).

Further, by providing a relative speed difference between the moving speed of the surface of the charging member forming the charging contact portion and the moving speed of the surface of the image carrier, the contact charging member and the image carrier are brought into contact with each other. This is preferable in that it is possible to significantly increase the chances of the conductive fine powder coming into contact with the image bearing member in the area, to obtain higher contact property, and to improve the direct injection charging property.

By interposing the conductive fine powder in the contact portion between the contact charging member and the image carrier, the lubricating effect (friction reducing effect) of the conductive fine powder is provided between the contact charging member and the image carrier. It is possible to provide a speed difference without a significant increase in torque and significant abrasion of the surfaces of the contact charging member and the image carrier.

If the amount of the conductive fine powder present in the contact portion between the image carrier and the contact charging member is too small, the lubricating effect of the particles cannot be sufficiently obtained, and the contact between the image carrier and the contact charging member will not be achieved. Due to the large friction, it is difficult to rotationally drive the contact charging member on the image carrier with a speed difference. That is, the driving torque becomes excessively large, and the surface of the contact charging member or the image bearing member is scraped if the driving torque is excessively rotated. Further, the effect of increasing the chance of contact by the conductive fine powder may not be obtained, and sufficient charging performance may not be obtained. On the other hand, if there is too much intervention,
Dropping of the conductive fine powder from the contact charging member remarkably increases, which adversely affects image formation.

(Conductive Fine Powder) a) Content The content of the conductive fine powder in the whole toner is 1 to 10.
It is preferable that the content is wt%. When the content of the conductive fine powder is less than 1% by weight with respect to the total amount of the toner, the charging of the image bearing member is satisfactorily performed by overcoming the charging inhibition due to the adhesion and mixing of the insulating transfer residual toner to the contact charging member. A sufficient amount of electrically conductive fine powder to cause the charging cannot be present in the contact area between the charging member and the image carrier or in the charging area in the vicinity thereof, resulting in a decrease in charging performance and poor charging. Also,
If the content is more than 10% by weight, the amount of the conductive fine powder collected by simultaneous cleaning at the time of development will be too much, which will reduce the chargeability and developability of the toner in the developing section, resulting in a decrease in image density and toner scattering. Cause The content of the conductive fine powder in the whole toner is 1.5 to 5% by weight.
And is preferably good.

B) Resistance The resistance of the conductive fine powder is 10 ⁹ Ω · cm or less. When the resistance of the conductive fine powder is larger than 10 ⁹ Ω · cm, the conductive fine powder is interposed in the contact area between the charging member and the image carrier or in the charging area in the vicinity thereof, and the conductive fine powder of the contact charging member is formed. Even if the close contact with the image bearing member through the body is maintained, the charging promoting effect for obtaining good charging property cannot be obtained.

In order to sufficiently bring out the charge accelerating effect of the conductive fine powder and to stably obtain good chargeability, the resistance of the conductive fine powder is brought into contact with the surface portion of the contact charging member or the image carrier. It is preferably smaller than the resistance of the part.

Furthermore, the resistance of the conductive fine powder is 10 ⁶ Ω.
It is preferably not more than cm in order to overcome charging inhibition due to adhesion and mixing of the insulating transfer residual toner to the contact charging member and to charge the image carrier better.

On the other hand, the resistance of the conductive fine powder is 10 ⁻¹ Ω.
It is preferable that the particle size be at least cm since the fine powder is charged and developed in the non-image area to promote charging.

C) Average Particle Size The conductive fine powder preferably has a volume average particle size of 0.5 to 10 μm. When the average particle diameter of the conductive fine powder is small, the content of the conductive fine powder in the whole toner must be set small in order to prevent the deterioration of the developing property. When the average particle size of the conductive fine powder is less than 0.5 μm,
It was not possible to secure an effective amount of conductive fine powder, and during the charging process, adhesion to the insulating transfer residual toner on the contact charging member
It is possible to interpose a sufficient amount of conductive fine powder in the charging area of the charging member and the image carrier or in the charging area in the vicinity thereof so as to overcome the charge inhibition due to the mixture and to charge the image carrier satisfactorily. This is not possible and charging failure is likely to occur. From this viewpoint, the average particle size of the conductive fine powder is preferably 0.8 μm.
m or more, and more preferably 1.1 μm or more and less than 5 μm.

The average particle size of the conductive fine powder is 10 μm.
If it is larger than m, the conductive fine powder that has fallen off the charging member blocks or diffuses the exposure light for writing the electrostatic latent image, causing defects in the electrostatic latent image and degrading the image quality. Furthermore, if the average particle size of the conductive fine powder is large, the number of particles per unit weight decreases, so the conductive fine powder is charged in consideration of the decrease and deterioration due to the conductive fine powder falling off from the charging member. In order to continuously supply and interpose the conductive fine powder to the contact area between the member and the image carrier or in the charging area in the vicinity thereof, the contact charging member transfers the conductive fine powder to the image carrier via the conductive fine powder. In order to maintain a fine contact and to stably obtain a good chargeability,
It is necessary to increase the content of the conductive fine powder in the entire toner. However, if the content of the conductive fine powder is too large, the chargeability and the developability of the toner as a whole, especially in a high humidity environment, are lowered, and the image density is lowered and the toner is scattered. From such a viewpoint, the average particle diameter of the conductive fine powder is preferably 5 μm or less.

D) Light Transmission The conductive fine powder is preferably a transparent, white or light-colored conductive fine powder, which is preferable because the conductive fine powder transferred onto the transfer material is not noticeable as fog. good. Even in the sense that the exposure light in the latent image forming step is not hindered, the conductive fine powder is preferably transparent, white or light-colored conductive fine powder, and more preferably, the transmittance of the conductive fine powder to the exposure light is high. It is preferably 30% or more.

In the present invention, the light transmittance of particles was measured by the following procedure. The transmittance is measured in a state where one layer of conductive fine powder of a transparent film having an adhesive layer on one side is fixed. The light was irradiated from the vertical direction of the sheet, and the light transmitted to the back surface of the film was condensed to measure the light amount. The transmittance of the particles was calculated as the net amount of light from the amount of light when only the film was attached to the particles. Actually X-Rite 3
It was measured using a 10T transmission densitometer.

E) Material As the conductive fine powder in the present invention, carbon fine powder such as carbon black and graphite; copper, gold,
Fine powder of metal such as silver, aluminum, nickel; metal oxide such as zinc oxide, titanium oxide, tin oxide, aluminum oxide, indium oxide, silicon oxide, magnesium oxide, barium oxide, molybdenum oxide, iron oxide, tungsten oxide; A metal compound such as molybdenum, cadmium sulfide, potassium titanate, or a composite oxide thereof can be used by adjusting the particle size and particle size distribution as necessary. Among these, inorganic oxide fine particles such as zinc oxide, tin oxide and titanium oxide are particularly preferable.

Further, for the purpose of controlling the resistance value of the conductive inorganic oxide, a metal oxide doped with an element such as antimony or aluminum, and fine particles having a conductive material on the surface can be used. For example, titanium oxide fine particles surface-treated with tin oxide / antimony, stannic oxide fine particles doped with antimony, or stannic oxide fine particles are used.

(Measurement Method) a) Average Particle Size and Particle Size Distribution To measure the average particle size and particle size distribution of the conductive fine powder in the present invention, use a Coulter LS-230 type laser diffraction particle size distribution measuring device. A liquid module was attached, and measurement was performed in a measurement range of 0.04 to 2000 μm. As a measuring method, a trace amount of a surfactant is added to 10 cc of pure water,
To this, 10 mg of a conductive fine powder sample was added and dispersed with an ultrasonic disperser (ultrasonic homogenizer) for 10 minutes.
The measurement was performed for 90 seconds with one measurement, and the volume average particle diameter was calculated based on the result.

In the present invention, as a method for adjusting the particle size and particle size distribution of the conductive fine powder, the manufacturing method and the manufacturing conditions are set so that the primary particles of the conductive fine powder can obtain a desired particle size and particle size distribution at the time of manufacturing. In addition to the method of setting, a method of aggregating small particles of primary particles, a method of crushing large particles of primary particles or a method by classification, and the like are possible, and further, of the base particles having a desired particle size and particle size distribution. A method of attaching or fixing conductive particles to a part or all of the surface, a method of using a conductive fine powder having a form in which a conductive component is dispersed in particles having a desired particle size and particle size distribution, and the like are also possible. It is also possible to adjust the particle size and particle size distribution of the conductive fine powder by combining these methods.

The particle size when the particles of the conductive fine powder are formed as an agglomerate is defined as the average particle size of the agglomerate. There is no problem that the conductive fine powder exists not only in the state of primary particles but also in the state of agglomeration of secondary particles. Whatever the state of aggregation, the form is not limited as long as it is present as an aggregate in the charging area between the charging member and the image carrier or in the charging area in the vicinity thereof, and the function of assisting or promoting charging can be realized.

B) Resistance In the present invention, the resistance of the conductive fine powder was measured by the tablet method and normalized. That is, the bottom area is 2.26c
Approximately 0.5 g of a powder sample was put in a cylinder of m ² , 15 kg of pressure was applied to the upper and lower electrodes, a voltage of 100 V was applied at the same time, a resistance value was measured, and then normalized to calculate a specific resistance.

Now, the photoconductor used in one embodiment of the present invention will be described.

For the direct injection charging method, a commonly used organic photoreceptor or the like can be used, but preferably,
When an organic photoconductor having a surface layer having a material having a resistance of 10 ⁹ to 10 ¹⁴ Ω · cm or an amorphous silicon photoconductor is used, charge injection charging can be realized.
It is effective in preventing ozone generation and reducing power consumption. In addition, it becomes possible to improve the charging property.

(Organic Photoreceptor (OPC)) Charging Roller 33
As the constitution of the photosensitive layer of the laminated type photoreceptor opposed to, a charge generation layer and a charge transport layer are laminated in this order on a conductive support. The conductive support may be any one as long as it has conductivity, for example, a metal such as aluminum, copper, chromium, nickel, zinc and stainless formed into a drum or a sheet, aluminum and copper, etc. Metal foil laminated on a plastic film, aluminum, indium oxide, tin oxide, etc. deposited on a plastic film, metal with a conductive substance applied alone or with a binder resin, a plastic film or paper, etc. Is mentioned.

As the coating method of the photosensitive layer formed on these conductive supports, methods such as spray coating, beam coating and dip coating are used. At that time, it is usually necessary to fix and support the conductive support, and in order to keep the coating liquid from adhering to the indicating member, an uncoated region may remain at the end of the support. is there.
Further, when the coating is applied up to the edges, the coating liquid may drip on the edges. The flange, which is the end support member to be installed to support the photoconductor on the main body, is installed at the correct angle, and the polishing process of the end of the conductive support member is required to maintain the alignment accuracy of the photoconductor. It is desirable to allow the existence of an uncoated area as much as possible in the production of a photoreceptor.

In one embodiment of the present invention, a negatively charged organic photosensitive member is used, which is a photosensitive drum in which the following five layers (1) to (5) are provided in order from the bottom on a drum base made of aluminum having a diameter of 30 mm. Using.

The first layer is a subbing layer, which is a conductive layer having a thickness of 20 μm provided to smooth out defects and the like in an aluminum base (hereinafter referred to as an aluminum base).

The second layer is a positive charge injection preventing layer, which plays a role of preventing the positive charges injected from the aluminum substrate from canceling out the negative charges charged on the surface of the photoreceptor, and the amylan resin and methoxymethylated nylon. 1 × 10 ⁶ Ω ・
It is a medium resistance layer having a thickness of 1 μm whose resistance is adjusted to about cm.

The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs when exposed to light.

The fourth layer is a charge transport layer, which is a polycarbonate resin in which hydrazone is dispersed, and is a P-type semiconductor. Therefore, the negative charges charged on the surface of the photoconductor cannot move in this layer, and only the positive charges generated in the charge generation layer can be transported to the surface of the photoconductor.

The fifth layer is a charge injection layer, which is a coating layer of a material in which SnO ₂ ultrafine particles are dispersed in a binder of an insulating resin. Specifically, a material in which 70% by weight of SnO ₂ particles having a particle size of about 0.03 μm, which is obtained by doping an insulating resin with antimony that is a light-transmitting insulating filler to reduce resistance (conductivity), is dispersed in the resin. Coating layer.

The coating solution thus prepared was applied by dipping to a thickness of about 4 μm to form a charge injection layer.
At this time, a 5 mm uncoated region of the photosensitive layer was present at the end on the back side of the photoreceptor.

(Amorphous Silicon Photoreceptor (a-S
i)) As for the amorphous silicon type photoconductor (a-Si), as described in the section of the above-mentioned conventional technique, conventionally, the electrical, optical and photoconductive characteristics and the use of the photoconductor for an image forming apparatus are used. Environmental characteristics have improved, and the image quality has improved accordingly.

FIG. 4 is a schematic configuration diagram for explaining the layer configuration of the amorphous silicon type photosensitive member for an image forming apparatus of one embodiment of the present invention.

Photoreceptor 2 for image forming apparatus shown in FIG.
In No. 00, a photosensitive layer 202 is provided on a support 201 for a photosensitive body. The photosensitive layer 202 is a-Si:
The photoconductive layer 203 is made of H and X and has photoconductivity.

FIG. 4B is a schematic structural view for explaining another layer structure of the photosensitive member for an image forming apparatus of one embodiment of the present invention. The image forming apparatus photoconductor 200 includes a photosensitive layer 202 on a support 201 for the photoconductor. The photosensitive layer 202 is made of a-Si: H, X and has a photoconductive layer 203 having photoconductivity, and an amorphous silicon-based and / or amorphous carbon-based surface layer 204.
It consists of and.

FIG. 4C is a schematic configuration diagram for explaining another layer configuration of the photoconductor for an image forming apparatus of one embodiment of the present invention. The image forming apparatus photoconductor 200 includes a photosensitive layer 202 on a support 201 for the photoconductor. The photosensitive layer 202 is made of a-Si: H, X and has a photoconductive layer 203 having photoconductivity, and an amorphous silicon-based and / or amorphous carbon-based surface layer 204.
An amorphous silicon-based charge injection blocking layer 205 between the photoconductive layer 203 and the support 201, and the photoconductive layer 203.
And 205 'between the surface layer 204.

FIGS. 4D and 4E are schematic configuration diagrams for explaining still another layer configuration of the photoreceptor for an image forming apparatus of one embodiment of the present invention. Photoreceptor 2 for image forming apparatus
In No. 00, a photosensitive layer 202 is provided on a support 201 for a photosensitive body. The photosensitive layer 202 is a photoconductive layer 2
Charge generation layer 2 made of a-Si: H, X that composes 03.
07 and charge transport layer 208, and an amorphous silicon-based and / or amorphous carbon-based surface layer 204
The charge injection blocking layer 20 between the photoconductive layer 203 and the support 201 and / or the photoconductive layer 203 and the charge injection blocking layer.
5, 205 '.

FIG. 4 (f) is a schematic constitutional view for explaining still another layer constitution of the photoconductor for an image forming apparatus of one embodiment of the present invention. The image forming apparatus photoconductor 200 includes a photosensitive layer 202 on a support 201 for the photoconductor. The photosensitive layer 202 is composed of a charge generation layer 207 and charge transport layer 208 made of a-Si: H, X which constitutes the photoconductive layer 203, and an amorphous silicon-based and / or amorphous carbon-based surface layer 204. There is. Although not particularly shown, the photoconductive layer 203
There may be charge injection blocking layers 205, 205 'between the substrate and the support 201 and / or in the photoconductive layer 203 and the charge injection blocking layer.

A) Support The support may be either electrically conductive or electrically insulating. As the conductive support, Al, Cr, Mo, Au,
Examples thereof include metals such as In, Nb, Te, V, Ti, Pt, Pd, and Fe, and alloys thereof such as stainless steel. Further, at least the surface of the electrically insulating support such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polystyrene, or polyamide synthetic resin film or sheet, on which the photosensitive layer is formed, of the electrically insulating support. A conductively treated support can also be used.

B) Photoconductive layer In one embodiment of the present invention, in order to effectively achieve the object, it is formed on a support 201 and, if necessary, an undercoat layer (not shown), and is exposed to light. The photoconductive layer 203 forming a part of the layer 202 is formed by a vacuum deposition film forming method by appropriately setting numerical conditions of film forming parameters so as to obtain desired characteristics. Specifically, for example, a glow discharge method (low frequency CVD method, high frequency CVD method or microwave C
AC discharge CVD method such as VD method, or DC discharge CVD method
Method, etc.), sputtering method, vacuum deposition method, ion plating method, photo CVD method, thermal CVD method, and various thin film deposition methods. These thin film deposition methods are appropriately selected and adopted depending on factors such as manufacturing conditions, load level under capital investment, manufacturing scale, and characteristics desired for a photoreceptor for an image forming apparatus to be produced. Since it is relatively easy to control the conditions for manufacturing a photoconductor for an image forming apparatus having characteristics, a glow discharge method, particularly a high frequency glow discharge method using a power supply frequency of RF band, μW band or VHF band is used. Is preferred.

In order to form the photoconductive layer 203 by the glow discharge method, it is basically known that silicon atoms (S
i) a source gas for supplying Si, a source gas for supplying H that can supply hydrogen atoms (H) and / or a source gas for supplying X that can supply halogen atoms (X),
It is introduced into a reaction vessel whose inside can be decompressed in a desired gas state to cause glow discharge in the reaction vessel, and a-Si: H on a predetermined support 201 which is installed at a predetermined position in advance. , X may be formed.

Further, as a raw material gas for supplying a halogen atom used in one embodiment of the present invention, a gaseous state such as a halogen gas, a halide, an interhalogen compound containing a halogen, a silane derivative substituted with a halogen or the like is effective. Preferred are halogen compounds which can be gasified. Further, further, it can be gasified or gasified with silicon atoms and halogen atoms as components.
A silicon hydride compound containing a halogen atom can also be mentioned as an effective one.

In general, a-Si has a weak n-type conduction characteristic when it does not contain the conductivity controlling atom. Therefore, in the negative a-Si of the present invention, the conductivity controlling atom is contained (doped). You don't have to
Alternatively, an atom for controlling conductivity may be contained as needed, for example, to expand the latitude of production stability.

Examples of the atoms for controlling the conductivity include so-called impurities in the semiconductor field,
Atoms belonging to Group IIIb of the Periodic Table giving p-type conductivity (hereinafter abbreviated as “Group IIIb atoms”) or atoms belonging to Group Vb of the Periodic Table giving n-type conductivity (hereinafter “V”).
(abbreviated as “group b atom”) can be used.

Specific examples of the group IIIb atom include boron (B), aluminum (Al), gallium (Ga),
There are indium (In), thallium (Tl) and the like, and B, Al and Ga are particularly preferable. As the group Vb atom,
Specifically, phosphorus (P), arsenic (As), antimony (S)
b), bismuth (Bi), etc., and P and As are particularly preferable.

As a raw material for introducing a Group Vb atom, PH ₃ and P are effectively used for introducing a phosphorus atom.
₂ H ₄ etc., phosphorus hydride, PH ₄ I, PF ₃ , PF ₅ , PC
Examples thereof include phosphorus halides such as l ₃ , PCl ₅ , PBr ₃ , PBr ₅ , and PI ₃ . In addition, AsH ₃ , AsF ₃ ,
AsCl ₃ , AsBr ₃ , AsF ₅ , SbH ₃ , SbF
₃ , SbF ₅ , SbCl ₃ , SbCl ₅ , BiH ₃ , B
iCl ₃ , BiBr _{3 and the} like can also be mentioned as effective starting materials for introducing a Group Vb atom.

C) Surface Layer In one embodiment of the present invention, an amorphous silicon-based and / or amorphous carbon-based surface layer is further formed on the photoconductive layer 203 formed on the support 201 as described above. It is preferable to form 204. The surface layer 204 has a free surface, and is provided mainly for achieving the object of the present invention in moisture resistance, continuous repeated use characteristics, electrical pressure resistance, use environment characteristics, and durability.

The surface layer 204 may be made of any material as long as it is an amorphous silicon type material. For example, the surface layer 204 contains hydrogen atoms (H) and / or halogen atoms (X), and further contains carbon atoms. Amorphous silicon (hereinafter referred to as "a-SiC: H, X"), hydrogen atom (H) and / or halogen atom (X), and further amorphous silicon containing oxygen atom (hereinafter referred to as "a-
SiO: H, X "), hydrogen atom (H) and /
Alternatively, amorphous silicon containing a halogen atom (X) and further containing a nitrogen atom (hereinafter referred to as “a-SiN: H,
X "), a hydrogen atom (H) and / or a halogen atom (X), and further contains at least one of a carbon atom, an oxygen atom and a nitrogen atom (hereinafter referred to as" a-SiCON: H "). , X ”) and the like are preferably used.

The surface layer 204 is formed, for example, by a glow discharge method (low frequency CVD method, high frequency CVD method or microwave C method).
AC discharge CVD method such as VD method, or DC discharge CVD method
Method), a sputtering method, a vacuum deposition method, an ion plating method, a photo CVD method, a thermal CVD method, or any other known thin film deposition method. These thin film deposition methods are appropriately selected and adopted depending on factors such as manufacturing conditions, a load level under capital investment, manufacturing scale, and desired characteristics of a photoreceptor for an image forming apparatus to be manufactured.

The thickness of the surface layer 204 in one embodiment of the present invention is usually 0.01 to 3 μm, preferably 0.0
It is desirable that the thickness is 5 to 2 μm, optimally 0.1 to 1 μm. If the layer thickness is less than 0.01 μm, the surface layer may be lost due to abrasion or the like during use of the photoconductor, and if it exceeds 3 μm, deterioration of electrophotographic properties such as increase of residual potential may be observed. .

In addition, it is preferable to use an amorphous carbon film containing carbon as a main component (hereinafter referred to as “AC: H”) as the surface layer. Furthermore, an amorphous carbon film having a bond with fluorine inside and / or on the outermost surface (hereinafter referred to as “AC: H:
(Denoted as "F") is preferably used.

AC: H has excellent water repellency and low friction,
Further, it has a hardness as high as or higher than that of a-SiC, and has an effect of preventing blurring of an image even in a high humidity environment even when the environmental countermeasure heater is removed. Further, it is possible to reduce the movement of the charging-promoting particles and the magnetic particles to the photoreceptor and the abrasion of the photoreceptor due to mechanical friction.

D) Charge Injection Blocking Layer In the photoreceptor for an image forming apparatus of one embodiment of the present invention,
Between the photoconductor support 201 and the photoconductive layer 203, a charge injection blocking layer 205 having a function of blocking injection of charges from the photoconductor support 201 side is provided, and between the photoconductive layer 203 and the surface layer 204. In between, a charge injection blocking layer 205 'having a function of blocking injection of charges from the surface layer side may be provided.

The charge injection blocking layer 205 described above is replaced with a lower injection blocking layer (UBL).
er), and a charge injection blocking layer 205 ′ described later is referred to as an upper injection blocking layer (Top Blocking Layer).

These charge injection blocking layers are provided on the support side when the photosensitive layer is charged with a constant polarity on its free surface.
Alternatively, it has a function of preventing charges from being injected from the surface layer side to the photoconductive layer side. It is preferable to have so-called polarity dependence, which does not exhibit such a function when subjected to a charging treatment of opposite polarity.

In order to impart such a function, the charge injection blocking layer contains a relatively large number of atoms or the like which control the conductivity, as compared with the photoconductive layer.

The conductivity-controlling atoms contained in the layer may be uniformly distributed in the layer, or they may be contained in the layer thickness direction, but are not uniformly distributed. There may be a portion that contains it in a uniformly distributed state. When the distribution concentration is non-uniform, it is preferable that the UBL 205 is contained in the support side, and the TBL 205 ′ is contained in the surface layer side so that the distribution is large. In either case, in the in-plane direction parallel to the surface of the support, it is necessary that the content is evenly distributed and is evenly distributed from the viewpoint of achieving uniform properties in the in-plane direction.

As the atoms contained in the charge injection blocking layer for controlling the conductivity, there may be mentioned so-called impurities in the field of semiconductors, such as “group III atom” or “group V atom”.
Group atoms can be used.

In one embodiment of the present invention, the thickness of the charge injection blocking layer is preferably 0.05 to 5 μm, more preferably 0. 5 μm from the viewpoint of obtaining desired electrophotographic characteristics and economical effects. It is desirable that the thickness is 1 to 4 μm, and optimally 0.5 to 3 μm.

In the photoconductor for an image forming apparatus of one embodiment of the present invention, for the purpose of further improving the adhesion between the support 201 and the photoconductive layer 203 or the UBL 205, for example, Si ₃ N ₄ , SiO ₂ , SiO, or composed of an amorphous material containing a silicon atom as a host and containing a hydrogen atom and / or a halogen atom, a carbon atom and / or an oxygen atom and / or a nitrogen atom, and the like. An adhesion layer may be provided. Further, as described above, a light absorption layer may be provided to prevent the occurrence of interference patterns due to the reflected light from the support.

Each of the above layers is formed by a high frequency plasma CVD method (RF-PC) using an RF band of 13.56 MHz or the like.
VD) and a course using the VHF band of 50 to 450 MHz are manufactured by a known apparatus and a film forming method such as a plasma CVD method (VHF-PCVD).

(Examples) The present invention will be specifically described below with reference to production examples and examples, but the present invention is not limited thereto. All parts in the following formulations are parts by weight.

(Conductive fine powder) Primary particle size 0.1
Volume average particle diameter 1. 0.3 μm of zinc oxide primary particles was obtained by granulating by pressure, and obtained by air classification.
Fine particle zinc oxide having a particle size distribution of 5 μm and a particle size distribution of 0.5 μm or less is 35% by volume and 5 μm or more is 0 number% (resistance 15
The conductive fine powder 1 has a resistance of 00 Ω · cm and a transmittance of 35%.

This conductive fine powder 1 was observed under a scanning electron microscope at 300 times and 30,000 times.
It consisted of 0.3 μm zinc oxide primary particles and 1-4 μm agglomerates.

A light source with a wavelength of 740 nm was used in accordance with the exposure light wavelength of 740 nm of the laser beam scanner used for image exposure in the image forming apparatus of the embodiment, and the transmittance in this wavelength range was 310T transmission type manufactured by X-Rite. When measured using a densitometer, the transmittance of this conductive fine powder 1 was about 35%.

Next, an example of manufacturing the charging member used in the examples of the present invention will be described.

(Manufacturing Example of Charging Member) A medium resistance urethane foam in which a 6φ, 264 mm SUS roller is used as a core metal, and urethane resin, carbon black as conductive particles, a sulfidizing agent, a foaming agent, etc. are prescribed on the core metal. The layer is formed into a roller shape,
Further, the shape and surface property were adjusted by cutting and polishing, and a charging roller of 12φ and 234 mm was prepared as a flexible member.

The obtained charging roller has a resistance of 10 ⁵ Ω.
cm, and the hardness was 30 degrees in Asker C hardness.

(Amorphous Silicon Photoreceptor) VHF
-With buffer by PCVD method Negative charging drum A lower blocking layer, a photoconductive layer, a buffer layer, and a surface layer were formed on a cylindrical AL substrate under the conditions shown in Table 1 by using the plasma CVD apparatus by VHF shown in FIG. The layers were sequentially laminated to complete a light receiving member used for negative charging.

[0148]

[Table 1]

[Embodiment 1] Hereinafter, the case where the present invention is applied to an electrophotographic image forming apparatus will be described in detail.

FIG. 1 is a schematic sectional view of an image forming apparatus used in the present invention, and FIG. 3 is a schematic view of a contact charging device.

In FIG. 1, when a copy start signal is input, the photoconductor 1 is rotated in the direction of the arrow, uniformly discharged by the pre-exposure lamp 8, and then charged to a predetermined potential by the charger 3. Is charged.

Here, the photosensitive member 1 is a rotary drum type electrophotographic photosensitive member, and in this embodiment, alternating current: H (amorphous silicon photosensitive member, layer structure of FIG. 4C) having a diameter of 30 mm is used. , Are rotated in the clockwise direction indicated by an arrow at a process speed (peripheral speed) of 210 mm / sec.

The charging device 3 is a roller charging device 3 as a contact charging member that is in contact with the photoconductor 1, and is in a clockwise direction indicated by an arrow, which is a direction opposite to the rotation direction of the photoconductor 1 at the charging contact portion. It is driven to rotate, and the surface of the photosensitive member 1 is at the charging contact portion.
Charging roller 3 holding conductive fine powder 33 as shown in FIG.
It is rubbed with 0. A charging bias of DC voltage -500V is applied to the roller charger 3 from the charging bias voltage applying power source S1 to the conductive fine powder 33 through the charging roller 30 by the charging bias voltage applying power source S1.
Due to the direct injection charging, the outer peripheral surface of the photoconductor 1 is approximately -450.
It is uniformly charged to V.

On the other hand, in the reader unit, the original document G placed on the original table 10 becomes a unit 9 in which the original document irradiation lamp, the short focus lens array and the CCD sensor are integrated to scan the original document while illuminating the original document. , The illumination scanning light reflected from the document surface is imaged by the short focus lens array and CC
It is incident on the D sensor. The CCD sensor is composed of a light receiving section, a transfer section and an output section. An optical signal is converted into a charge signal in the CCD light receiving unit, and sequentially transferred to the output unit in synchronization with a clock pulse in the transfer unit, and the charge signal is converted into a voltage signal in the output unit, amplified, reduced in impedance, and output. The obtained analog signal is subjected to known image processing, converted into a digital signal, and sent to the printer section.

In the printer section, a digital signal of the above image information output from the laser exposure means 2 including a solid-state laser element, a polygon mirror rotating at a high speed, and the like is applied to the charged surface of the photoconductor 1. The scanning exposure E is performed by the intensity-modulated laser beam, and an electrostatic latent image corresponding to the image information of the original image is formed on the peripheral surface of the photoconductor 1. The electrostatic latent image is developed as a toner image by the developing device 4 using magnetic one-component insulating toner. 41 is a diameter of 16 mm including a magnet roller 42 (not shown)
This non-magnetic developing sleeve of
Is coated with the above-mentioned negative toner and is fixed at a distance of 200 μm from the surface of the photoconductor 1, and is rotated at a constant speed with the photoconductor 1 to apply a development bias voltage from a development bias power source S2 (not shown) to the development sleeve 41. To do. Applied voltage is −
A jumping phenomenon is performed between the developing sleeve 41 and the photoconductor 1 by using a DC voltage of 350 V superimposed on a rectangular AC voltage having a frequency of 1.8 MHz and a peak-to-peak voltage of 1.6 kV.

On the other hand, the transfer material P as a recording material from the paper feeding section
Is supplied to the pressure contact nip portion (transfer portion) T between the photosensitive member 1 and the transfer roller 7 having a medium resistance, which is brought into contact with the photosensitive member 1 with a predetermined pressing force, at a predetermined timing. To be done. A transfer bias applying power source S3 is applied to the transfer roller 7.
A predetermined transfer bias voltage is applied from (not shown).

In this embodiment, the transfer roller resistance value is 5 × 10.
Transfer was carried out by applying a direct current voltage of +2000 V using an ⁸ Ω one.

The transfer material P introduced into the transfer section T is nipped and conveyed by the transfer section T, and the toner images formed and carried on the surface of the photoconductor 1 are sequentially subjected to electrostatic force and pressing force. Will be transcribed.

Further, the transfer material P on which the toner image is transferred is received.
Is separated from the surface of the photoconductor 1 and introduced into a fixing device 6 such as a heat fixing system to fix a toner image, and is discharged outside the device as an image formed product (print, copy).

In the electrophotographic apparatus of this embodiment, the cartridge 11 includes the four process equipments of the photosensitive member 1, the roller charger 3, and the developing device 4, and is attached / detached to / from the main body of the image forming apparatus at once. The device is a replaceable cartridge type device, but is not limited to this.

Next, the roller charger 3 used in this embodiment will be described.

In FIG. 3, the contact charging device 3 is a device using a conductive elastic roller 30 (hereinafter referred to as “charging roller”) as a contact charging member, and includes a core metal 31 and a core metal 3.
1 is a flexible member made of rubber or foam medium resistance layer 3
A charging roller 30 formed by forming 2;
Outer peripheral surface of the charging roller 30 (that is, outer peripheral surface of the medium resistance layer 32)
In the initial stage, the conductive fine powder 33 is applied on the charging roller 30 and then supplied with the transfer residual toner 34.
And a charging bias voltage applying power source S1 for applying a charging bias to the charging roller 30.

The charging roller 30 is made substantially parallel to the photosensitive member 1 as an image bearing member so that both ends of the cored bar 31 are borne.
The medium resistance layer 32 is arranged in pressure contact with a predetermined pressing force against the elasticity of the medium resistance layer 32 to form a charging contact portion which is a contact portion between the charging roller 30 and the photoconductor 1. The width n of the charging contact portion is not particularly limited, but is preferably 1 mm or more, more preferably 2 mm or more in order to obtain stable and dense adhesion between the conductive elastic roller and the image carrier.

The charging roller 30 has a charging contact portion, which is a clockwise direction indicated by an arrow which is opposite to the rotation direction of the photosensitive member 1, or a charging contact portion, which is a forward direction with respect to the rotation direction of the photosensitive member 1. The surface of the photosensitive member 1 is rotatably driven in the clockwise direction, and the surface of the photosensitive member 1 is rubbed against the medium resistance layer 32 holding the conductive fine powder 33 at the charging contact portion.

Then, the charging bias voltage applying power source S1 applies a predetermined charging bias to the conductive fine powder 33 through the charging roller 30 with a direct current voltage (V DC alone: direct current application system) having a predetermined polarity and potential, or alternating. The outer peripheral surface of the photosensitive member 1 which is applied with an oscillating voltage (V DC + V AC: AC application system) superimposed with the voltage V and is rotationally driven is uniformly charged to a predetermined polarity and potential by the direct injection charging system.

Further, the behavior of the toner base particles and the conductive fine powder 33 during the image forming process when the conductive fine powder 33 is externally added to the toner base particles will be described.

The conductive fine powder 33 contained in the toner is
During development of the electrostatic latent image on the photoconductor 1 in the developing step (not shown), an appropriate amount is transferred to the photoconductor 1 together with the toner mother particles.

The toner image on the photoreceptor 1 is transferred to a recording medium (not shown) in a transfer step (not shown). Photoconductor 1
A part of the conductive fine powder 33 also adheres to the recording medium, but the rest remains adhered and held on the photoconductor 1. When transfer is performed by applying a transfer bias having a polarity opposite to that of the toner, the toner is attracted and actively transferred to the recording medium side, but the conductive fine powder 33 on the photoconductor 1 is conductive. Therefore, it is not positively transferred to the recording medium side, but a part thereof is attached to the recording medium side, but the rest is attached and retained on the photoconductor 1 and remains.

In the present invention in which a cleaning device is not present, the transfer residual toner 34 remaining on the surface of the photoconductor 1 after transfer and the above-mentioned residual conductive fine powder 33 are the contact portions of the photoconductor 1 and the charging roller 30. The photoconductor 1 is carried to the charging section as it is and is attached to and mixed with the charging roller 30.

Therefore, the direct injection charging of the photoconductor 1 is performed with the conductive fine powder 33 interposed in the contact portion between the photoconductor 1 and the charging roller 30.

Due to the presence of the conductive fine powder 33, the close contact property and the contact resistance of the charging roller 30 to the photoconductor 1 are maintained regardless of the contamination due to the adhesion and mixing of the transfer residual toner 34 on the charging roller 30. Therefore, it is possible to favorably charge the photoconductor 1 by the charging roller 30.

The transfer residual toner 34 adhering to and mixed with the charging roller 30 is uniformly charged to the same polarity as the charging bias by the charging bias applied from the charging roller 30 to the photoconductor 1, and is gradually discharged from the charging roller 30. Is discharged onto the photoconductor 1 and reaches the developing unit as the photoconductor 1 moves.
Simultaneous development cleaning (collection) is performed in the development process.

Further, as the image formation is repeated, the conductive fine powder 33 contained in the toner is transferred to the photoconductor 1 in the developing section and carried by the movement of the photoconductor 1 to the charging section via the transfer section. Since the conductive fine powder is continuously supplied to the charging unit one after another, even if the conductive fine powder 33 is reduced or deteriorates due to dropping or the like in the charging unit, it is possible to prevent the deterioration of the charging property. And good chargeability is stably maintained.

The control method for preventing contamination of the charging roller used in this embodiment will be described below.

FIG. 2 is a sequence chart showing a method of controlling the discharging operation of the roller charging device 3 in the image forming apparatus of this embodiment. In FIG. 2, driving of the photoconductor 1 and the roller charger 3 is started in a pre-rotation process performed prior to image formation. At this time, the rotation speed of the charging roller is for the discharge mode, and during normal image formation. Rotate at a faster speed than the rotation speed of. A well-known variable motor was used to control the rotation speed. In the present invention, it has been confirmed that the transfer residual toner is discharged from the charging device along the path as shown in FIG. 3, and there is also a component that circulates on the charging roller. That is, when the number of rotations of the charging member is increased, the chances of discharging the transfer residual toner per unit time are increased, and the discharging efficiency of the toner attached on the charging roller is improved. When the peripheral speed ratio of the charging roller and the amount of toner discharged from the charging roller per unit time were actually examined, it was confirmed that the relationship shown in FIG. 5 was established. In this embodiment, the rotation speed of the peripheral speed ratio of 150% with respect to the peripheral speed of the photoconductor is set as the ejection mode during the pre-rotation of image formation.

When the pre-rotation operation is completed, the rotation speed of the charging roller is reduced to 40% in peripheral speed for image formation. Peripheral speed ratio 4
0% is a condition that the chargeability can be maintained without any problem in the paper passing durability test of 5% which is a normal image ratio, but the printing rate is 40%.
In the high-density image passing durability test, the deterioration of the charging property was observed due to the durability of about 10,000 sheets. Further, if the number of rotations is increased until the time of normal image formation, abrasion of the photoconductor is promoted, which is not preferable. Generally, the relationship between the abrasion of the photoconductor and the peripheral speed ratio of the charging roller is as shown in FIG. 6, and therefore the peripheral speed ratio should be as small as possible. Further, if the ejection sequence is executed even during image formation, the image is formed in a state where the ejection amount is large, and there is a problem that the collectability of the ejected toner in the developing unit becomes insufficient and fogging occurs on the image. .

In the roller charger 3 as described above, the discharge sequence is performed at the time of pre-rotation other than the time of image formation, so that when a high-ratio image with a printing rate of 40% is durable, 10,000 sheets can be used. Although the charging failure occurred, the initial charging performance can be maintained without the contamination by the transfer residual toner 34 of the charging roller 30 being observed even if the structure of the present embodiment is used to endure 50,000 sheets. I was able to. Also,
By setting the ejection sequence outside the image forming area, it was possible to prevent fogging due to insufficient collection of the transfer residual toner 34 at the developing portion.

[Embodiment 2] FIG. 5 is a sequence chart showing a method of controlling the discharge of the roller charging device 3 at the time of image formation for explaining the second embodiment of the present invention.

In this embodiment, the discharging sequence by the rotation number UP of the charging roller performed in the first embodiment is performed not only in the pre-rotation but also in the post-rotation. Other conditions are the same as in Example 1.

In the roller charger 3 as described above, the discharge sequence is performed by the pre-rotation and the post-rotation other than the time of image formation, so that the conventional printing is less than 10,000 sheets in the paper passing durability with the high image ratio of 60%. However, in the present embodiment, even if 50,000 sheets were carried out, the initial charging performance could be maintained without the contamination by the transfer residual toner 34 on the charging roller 30 being observed. Further, it is possible to prevent the fog caused by the transfer residual toner 34 being discharged from the charging roller to the image forming area, which is a problem due to this.

In particular, when an amorphous silicon type photoconductor (a-Si) is used as the photoconductor 1, the followability of the charging voltage to the applied voltage as shown in FIG.
However, when the charging roller is contaminated with the transfer residual toner 34, the charging failure becomes remarkable.
By using the present invention, it was possible to maintain the initial charging performance in the same manner as above.

Further, in the first and second embodiments, the discharge mode of the transfer residual toner 34 is explained as the control in the front rotation and the rear rotation, but the present invention is not limited to this, and it is performed between the sheets. Needless to say, is more effective.

[Embodiment 3] In this embodiment, the developing conditions are changed during the discharging sequence. Since the amount of discharge from the charging roller is large during the discharge sequence, when non-contact jumping development is used as in the embodiment of the present invention, it is assumed that the normal development VbacK cannot be used for recovery. In that case, the uncollected toner becomes dirty on the transfer roller or returned to the charging member. On the other hand, in this embodiment, the peak-to-peak (Vp) of the AC component of the developing bias is generated during the discharging sequence.
A method of increasing p) or reducing the distance between the developing roller and the image carrier was used. By doing so, the electric field strength of the AC bias that contributes to the drum surface is increased, and a large electric field can be applied to the discharged toner on the drum without greatly changing the developing potential, and the collectability of the discharged toner is improved. That is, by using the AC bias of a strong electric field, a large peeling force can be given to the toner on the drum surface, and even during the discharging sequence in which the amount of discharged toner is large, it is possible to prevent defective collection in the developing unit. However, it is not preferable to use these developing conditions during normal image formation. When used during normal image formation, when outputting images with low density and low image ratio, only toner with high developability is consumed for development, or external additives externally added to the toner base are easily consumed. The so-called selective development is likely to occur, and only toner with low developability is accumulated in the developing device, or the amount of external additives changes to reduce the developing ability, leading to a decrease in output image density and an increase in fog. Become. That is, it is preferably provided only during non-image formation during the ejection sequence as in the present embodiment.

In the first, second, and third embodiments, although the charging application bias is not particularly described, the discharge residual toner is further discharged by superimposing an AC bias that does not discharge as a charging bias during the discharging sequence. Can be improved, which is advantageous for contamination of the charging roller.

[0185]

As described above, the present invention is an image forming method having the following features, which prevents the above-mentioned charging failure and is stable for a long period of time even when a high ratio image is continuously output. It is effective to provide an image forming apparatus which can be charged and which is free from fogging even when outputting a high-ratio image.

That is, according to the first aspect of the present invention, at least a charging step of charging the image bearing member by bringing a charging member into contact with the image bearing member and applying a charging bias thereto, and charging the image bearing member An image forming step of forming an electrostatic latent image on the surface, and a developing step of visualizing the electrostatic latent image with toner, and the developing step transfers the toner image to a recording medium and then remains on the image carrier. In the image forming method which also serves as a cleaning step for collecting the residual toner, the charging step is carried out in the state where the charge promoting particles having conductivity are present in the contact portion between the charging member and the image carrier, An image forming method further comprising a discharging step of moving the transfer residual toner adhering to the charging member to the image carrier by controlling the moving speed of the charging member due to rotation at the contact portion. It is the law.

According to this method, the initial charging performance can be maintained without the contamination of the transfer roller residual toner on the charging roller, and the transfer residual toner is discharged from the charging roller to the image forming area. Fog caused by the can also be prevented.

Further, in the invention according to claim 2 of the present invention,
The charging step is a step of charging the image carrier while the moving speed of the surface of the charging member forming the contact portion and the moving speed of the surface of the image carrier have a relative speed difference. The image forming method according to claim 1.

Further, in the invention according to claim 3 of the present invention, the charging step is a step of charging the image carrier while the charging member and the image carrier move in opposite directions. The image forming method according to Item 1 or 2.

According to these methods, the chances of the conductive fine powder coming into contact with the image carrier at the contact portion between the contact charging member and the image carrier are significantly increased, and higher contact property can be obtained. Direct injection chargeability can be improved.

According to the invention of claim 4 of the present invention,
The image forming method according to claim 1, wherein the charging step charges the image carrier by applying a voltage to a roller member having an Asker C hardness of 50 degrees or less. .

According to this method, it is possible to press against the image carrier with a predetermined pressing force against the elasticity of the medium resistance layer formed on the cored bar of the roller member.

Further, in the invention according to claim 5 of the present invention, in the charging step, an image carrier is obtained by applying a voltage to a roller member having a volume specific resistance of 10 ³ Ω · cm or more and 10 ⁸ Ω · cm or less. 5. The image forming method according to claim 1, wherein the image forming method is a step of charging.

According to this method, a sufficient contact state between the roller member and the image carrier can be obtained, and at the same time, it can function as an electrode having a resistance low enough to charge the moving image carrier.

The invention according to claim 6 of the present invention is
In the charging step, the conductive fine powder contained in the developer adheres to the image bearing member in the developing step at least in the contact portion and / or the vicinity of the charging member and the image bearing member, and the image bearing is performed even after the transfer step. 6. The image forming method according to claim 1, wherein the image forming method remains on the body and is intervened.

Further, in the invention according to claim 7 of the present invention, the volume resistivity of the conductive fine powder is at least 1 × 10 ⁹
The image forming method according to claim 6, wherein the image forming method is Ω · cm or less, preferably 1 × 10 ⁶ Ω · cm or less.

According to these methods, the image carrier can be charged more favorably.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus when an embodiment of the present invention is applied to an electrophotographic system.

FIG. 2 is a time chart of a discharge mode control method according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a conventional roller charging device and the present invention.

FIG. 4 is a schematic diagram illustrating a layer structure of an amorphous silicon-based photoconductor of the present invention.

FIG. 5 is a diagram showing the relationship between the peripheral speed ratio of the charging roller and the amount of toner discharged from the charging roller per unit time.

FIG. 6 is a correlation diagram of the abrasion of the photoconductor with respect to the peripheral speed ratio between the charging roller and the photoconductor.

FIG. 7 is a time chart showing a second control method in a discharge mode according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating charging efficiency according to a conventional charging method.

[Explanation of symbols]

1 photoconductor 2 Laser exposure means 3 roller charger 4 developing device 6 fixing device 7 Transfer roller 8 Pre-exposure lamp 30 charging roller 31 core metal 32 Middle resistance layer 33 Conductive fine powder 34 Transfer residual toner 201 Support for Photoreceptor 202 Photosensitive layer 203 Photoconductive layer 204 surface layer 205, 205 'charge injection blocking layer 207 Charge generation layer 208 charge transport layer

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA17 DA38 ED02 ED03 ED08                       ED09 EE02 EE03 EE06 EF07                 2H077 AA37 AC16 AD06 AD31 AD36                       EA13 GA04                 2H200 FA08 FA18 FA20 GA14 GA16                       GA18 GA23 GA29 GA34 GA35                       GA44 GA49 GA57 GB02 GB22                       GB25 GB37 GB50 HA02 HA21                       HA28 HB08 HB12 HB14 HB17                       HB22 HB43 HB45 HB46 HB47                       HB48 JA02 JA26 JA28 JB10                       LA18 LA19 LA23 LC01 LC02                       LC06 MA03 MA04 MA08 MA14                       MB01 MB04 MB06 MC02 MC06                       MC15 MC16 NA02 NA04 NA05                       NA06 NA09 PA11 PA24

Claims (7)

[Claims] 1. A charging step of charging at least an image carrier by bringing a charging member into contact with the image carrier and applying a charging bias, and an image formation for forming an electrostatic latent image on the charged surface of the image carrier. An image which also has a step and a developing step of visualizing the electrostatic latent image with toner, and which also serves as a cleaning step of collecting residual toner remaining on the image carrier after the developing step transfers the toner image to a recording medium. In the forming method, in the charging step, charging is performed in a state where electrically conductive charge promoting particles are present in the contact portion between the charging member and the image carrier, and rotation of the charging member in the contact portion is performed. An image forming method comprising: a discharging step of discharging the transfer residual toner adhering to the charging member to the image carrier by controlling the moving speed by the method. 2. In the charging step, the moving speed of the surface of the charging member forming the contact portion and the moving speed of the surface of the image carrier are
The image forming method according to claim 1, which is a step of charging the image carrier while having a relative speed difference. 3. The image forming method according to claim 1, wherein the charging step is a step of charging the image carrier while the charging member and the image carrier move in opposite directions. 4. The Asker C hardness is 50 in the charging step.
The image forming method according to claim 1, wherein the image bearing member is charged by applying a voltage to the roller member having a temperature of not more than 100 degrees. 5. The volume resistivity is 10 ³ Ω in the charging step.
5. The image forming method according to claim 1, which is a step of charging the image bearing member by applying a voltage to a roller member of not less than cm and not more than 10 ⁸ Ω · cm. 6. In the charging step, the conductive fine powder contained in the developer adheres to the image bearing member in the developing step at least in the contact portion and / or the vicinity of the charging member and the image bearing member, and the transferring step. 6. The image forming method according to claim 1, wherein after the step, the image remains on the image carrier and is carried and interposed. 7. The volume resistivity of the conductive fine powder is at least 1 × 10 ⁹ Ω · cm or less, preferably 1 × 10 ⁶
The image forming method according to claim 6, wherein the image forming method is Ω · cm or less.