JP3376278B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer.

More specifically, a contact charging system, a transfer system,
The present invention relates to a cleanerless image forming apparatus.

[0003]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic device or an electrostatic recording device, an image carrier (charged member) such as an electrophotographic photosensitive member or an electrostatic recording dielectric has a required polarity.
A corona charger (corona discharger) has often been used as a charging device for uniformly charging (including static elimination) the electric potential.

The corona charger is a non-contact type charging device, and is provided with, for example, 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 a member to be charged. In this case, the surface of the image carrier is exposed to a discharge current (corona shower) generated by applying a high voltage to the discharge electrode and the shield electrode so that the surface of the image carrier is charged in a predetermined manner.

Recently, the ozone level is lower than that of corona chargers.
Due to advantages such as low power consumption, a contact type charging device (contact charging device) for charging a charged member by bringing a charging member applied with a voltage into contact with the charged member has been put into practical use as described above. ing.

In the contact charging device, a charged member such as an image carrier is brought into contact with a conductive charging member such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type,
A predetermined charging bias is applied to this charging member (contact charging member / contact charger, hereinafter referred to as contact charging member) to charge the surface of the body to be charged to a predetermined polarity and potential.

Charging mechanism of contact charging (charging mechanism,
In (charging principle), two types of charging mechanisms (1) discharge charging mechanism and (2) direct injection charging mechanism are mixed, and each characteristic appears depending on which one is dominant. FIG. 7 shows typical charging characteristics of each.

(1) Discharge Charging Mechanism This is a mechanism in which the surface of the charged body is charged by the discharge phenomenon occurring in the minute gap between the contact charging member and the charged body.

Since the discharge charging mechanism has a constant discharge threshold between the contact charging member and the member to be charged, 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.

For example, a 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. In this roller charging, the charging mechanism is a discharge charging mechanism. Dominate.

That is, 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 with the body to be charged. Therefore, the charging roller has a large friction resistance, and in many cases, is driven by the body to be charged or driven with a slight speed difference.
Therefore, since the non-contact state cannot be avoided due to the uneven shape of the roller and the adhered matter of the body to be charged, in the conventional roller charging, the discharge charging mechanism is dominant in the charging mechanism.

More specifically, when the charging roller is pressed against the OPC photosensitive member having a thickness of 25 μm as the member to be charged to perform the charging process, about 640 V is applied to the charging roller. When the above voltage is applied, the surface potential of the photoconductor starts to rise, and thereafter, the surface potential of the photoconductor linearly increases with an inclination of 1 with respect to the applied voltage. Hereinafter, this threshold voltage is defined as the charging start voltage Vth (dotted line in FIG. 7).

That is, in order to obtain the photoreceptor surface potential Vd required for electrophotography, Vd + Vth is applied to the charging roller.
More DC voltage is needed than is needed. A system in which only the DC voltage is applied to the contact charging member in this way to charge the image carrier is called a "DC charging system".

However, in the DC charging method, the resistance of the contact charging member fluctuates due to environmental fluctuations, etc., and Vth fluctuates when the film thickness changes due to abrasion of the photoconductor as an image bearing member. It was difficult to set the potential to a desired value.

Therefore, in order to further homogenize the charging, as disclosed in JP-A-63-149669, etc., the DC voltage corresponding to the desired Vd has a peak-to-peak voltage of 2 × Vth or more. An “AC charging method” is used in which an oscillating voltage with an AC component superimposed is applied to a contact charging member to charge the image carrier. This is for the purpose of leveling effect of the potential by AC, and the potential of the image carrier converges on Vd which is the center of the peak of the AC voltage, and is not affected by disturbance such as environment.

However, even in such a contact charging device, since the essential charging mechanism uses the discharge phenomenon from the charging member to the image carrier, the voltage required for charging as described above. Requires a value equal to or higher than the image carrier surface potential + discharge threshold value, and a slight amount of ozone is generated.

Further, when AC charging is performed to make the charging uniform, further ozone is generated, vibration noise (AC charging sound) between the contact charging member and the photoconductor due to the electric field of the AC voltage is generated, and discharge is caused. Deterioration of the surface of the member to be charged becomes remarkable, which is a new problem.

(2) Direct injection charging mechanism This mechanism charges the surface of the charged body by directly injecting the charge from the contact charging member to the charged body. JP 6-3
It is proposed in Japanese Patent No. 921, etc.

The contact charging member of medium resistance is in contact with the surface of the body to be charged, and the charge is directly injected to the surface of the body to be charged without interposing the discharge phenomenon, that is, basically without using the discharge mechanism. . Therefore, even if the voltage applied to the contact charging member is equal to or lower than the discharge threshold value, the body to be charged can be charged to a potential corresponding to the applied voltage (solid line in FIG. 7). This direct injection charging mechanism does not cause the generation of ions, so that no harm is caused by the generation of discharge.

More specifically, a voltage is applied to a contact charging member such as a charging roller, a charging brush, a charging magnetic brush,
This is a mechanism for directly injecting charges by injecting charges into a charge holding member such as conductive particles in a trap order or charge injection layer on the surface of an object to be charged (image carrier). Since the discharge phenomenon is not dominant, the voltage required for charging is only the desired surface of the image carrier, and ozone is not generated.

When a porous roller such as a sponge roller coated with conductive particles for improving the contact charging property is used as the contact member, contact between the contact charging member and the body to be charged is performed. It is possible to make it extremely dense, and it is possible to obtain good chargeability.

Cleanerless Conventionally, in order to reduce the size and cost of an image forming apparatus,
In particular, there are several methods of cleaning (removing) residual toner (transfer residual toner) on the photosensitive member after transfer on the photosensitive member by simultaneously performing charging simultaneous cleaning or developing simultaneous cleaning without providing a dedicated photosensitive member cleaning means. Or have been proposed.

That is, in the transfer type image forming apparatus, the transfer residual toner remaining on the photoconductor (image carrier) after the transfer is removed from the photoconductor surface by the cleaner (cleaning device) to become waste toner. It is desirable that the waste toner does not come out in terms of environmental protection. Therefore, there is also an image forming apparatus in a toner recycling process in which the cleaner is eliminated, and the residual toner after transfer on the photoconductor after transfer is removed from the photoconductor by cleaning at the same time by the developing device and collected and reused in the developing device. Has appeared.

Simultaneous development cleaning means that the toner remaining on the photoconductor after transfer is fogged at the time of the development of the next step and thereafter, that is, the photoconductor is continuously charged and exposed to form a latent image, and the latent image is developed. This is a method of collecting with a take-off bias (fog-removing potential difference Vback which is a potential difference between the DC voltage applied to the developing device and the surface potential of the photoconductor). 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.

Powder coating for contact charging member In the contact charging device, powder is applied to the contact surface of the contact charging member with the surface of the body to be charged in order to prevent uneven charging and to perform stable and uniform charging. Although disclosed in Japanese Patent Publication No. 99442, the contact charging member is driven to rotate by a member to be charged, and the generation of ozone products is remarkably reduced as compared with a corona charger such as a scorotron.
As in the case of the roller charging described above, the principle of charging is still mainly corona charging by discharge. Particularly, 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 the ozone products are more generated by the discharge. Therefore, when the apparatus is used for a long period of time or when the cleanerless image forming apparatus is used for a long period of time, adverse effects such as image deletion due to ozone products are likely to appear.

Further, in Japanese Patent Application Laid-Open No. 5-150539, in an image forming method using contact charging, charging inhibition is caused by toner particles or silica fine particles adhering to the surface of a charging means during repeated image formation for a long time. In order to prevent the above, it is disclosed that the developer contains at least developer particles and conductive particles having an average particle size smaller than the developer particles. However, this contact charging is due to the discharge charging mechanism, not the direct injection charging mechanism, and there is the above-mentioned problem due to the discharge charging.

[0027]

1) As described in the above-mentioned section of the prior art, in contact charging, if a simple one such as a charging roller or a fur brush is used as the contact charging member, direct injection is not possible. In order to perform charging, the surface of the contact charging member was rough, and a close contact with the member to be charged was not secured, and direct injection charging was impossible.

Therefore, in the contact charging, even if a simple member such as a charging roller or a fur brush is used as the contact charging member, the direct injection charging having excellent charging uniformity and stable for a long period of time can be realized. It is expected that ozone-less direct injection charging with a low applied voltage will be realized with a simple configuration.

2) In the cleanerless image forming apparatus, when the contact charging device is used as the charging means for the charged body (image carrier), the transfer residual toner remaining on the surface of the charged body after transfer is removed. Since no cleaner is used, the transfer residual toner remaining on the surface of the charged body after the transfer is directly carried to the charging section, which is the contact portion between the charged body and the contact charging member, by the movement of the charged body surface, and the transfer residual toner is transferred. Is left in accordance with the previous image pattern, or the transfer residual toner is attached to the surface of the contact charging member in accordance with the image pattern. Or appear,
When an image is formed for a long period of time, there is a problem that the toner adhesion portion becomes defective in charging (uneven charging) and becomes black in the case of reversal development.

Therefore, the present invention uses a simple member such as a charging roller or a fur brush as the contact charging member in the image forming apparatus of the contact charging type, the transfer type, and the cleaner, and the transfer residual toner of the contact charging member. Regardless of contamination due to contamination, excellent direct charge charging without ozone with excellent applied uniformity and low applied voltage can be realized stably over a long period of time, that is, a simple configuration using a contact charging member such as a charging roller or a fur brush is preferable. Aiming to realize direct injection charging and toner recycling process, and to output stable high-quality images for a long period of time with no image deletion, even in halftone images during long-term printing, and without uneven charging. To do.

[0031]

The present invention is an image forming apparatus having the following configuration.

(1) A body to be charged, charging means for charging the body to be charged, latent image forming means for forming an electrostatic latent image on the charging surface of the body to be charged, and the electrostatic latent image as a developer. And a developing unit that visualizes the toner image as a toner image, and a transfer unit that transfers the toner image to a recording material. After the developing unit transfers the toner image to the recording material, cleaning is performed to recover the toner remaining on the charged body. an image forming apparatus serving as a means, before Symbol charging means comprises a flexible charging member to form a member to be charged and the nip, and the charging member is supported conductive particles at least on the nip portion by the charging member are moved with a speed difference relative to the charged member surface, the charging member, a voltage is sign <br/> pressure, an elastic foam on the surface thereof, conductively coating the conductive particles to the charging member A particle coating member, and the conductive particle coating section Is an elastic foam roller, the contact with the charging member to move while having a speed difference relative to the charging member, the surface cell diameter of the conductive particles coated member is greater than the surface cell diameter of the charging member An image forming apparatus characterized by the above.

[0033]

[0034]

[0035]

(2) The image forming apparatus according to claim 1, wherein the conductive particle coating member counter-rotates with respect to the charging member at a contact portion with the charging member.

[0037]

[0038]

(3) The resistance value of the conductive particles is 1 × 10
And characterized in that ¹² (Omega · cm) or less (1) The
Is the image forming apparatus according to (2) .

(4) The resistance value of the conductive particles is 1 × 10
¹⁰ (Omega · cm), wherein the less is (1) The
Is the image forming apparatus according to (2) .

(5) The particle size of the conductive particles is 10 nm
It is characterized in that the size is 1 pixel or less (1)
The image forming apparatus according to any one of (4) to (4) .

(6) The volume resistance of the outermost surface layer of the body to be charged is 1 × 10 ¹⁴ (Ω · cm) or less, according to any one of (1) to (5) Image forming apparatus.

(7) The member to be charged is an electrophotographic photosensitive member, and the volume resistance of the outermost surface layer of the electrophotographic photosensitive member is 1 × 10.
The image forming apparatus described in any one of (1) to (6) , which is ⁹ (Ω · cm) or more and 1 × 10 ¹⁴ (Ω · cm) or less.

(8) The image forming apparatus according to any one of (1) to (7) , wherein the charging member is rotated by a counter with respect to the body to be charged in the nip portion.

[0045]

[0046]

(9) The image forming apparatus according to any one of (1) to (8) , wherein the latent image forming unit is an image exposing unit.

(10) The image forming apparatus according to any one of (1) to (9) , wherein the conductive particle coating member is present above the charging member in the direction of gravity.

<Operation> a) Conductive particles are particles (charging accelerating particles) for the purpose of assisting charging, and the conductive particles are used as a nip portion (charging nip portion) between an object to be charged and a flexible contact charging member. ), Due to the lubricant effect (lubrication effect, friction reduction effect) of the particles, the contact charging member, for example, has a large frictional resistance and is left in contact with the surface of the charged body with a speed difference. Even with an elastic charging roller that has been difficult to operate, it becomes possible to easily and effectively bring it into contact with the surface to be charged with a speed difference. The contact charging member comes into close contact with the surface of the body to be charged through the conductive particles and contacts the body to be charged more frequently.

By providing a speed difference between the contact charging member and the member to be charged, the chances that the conductive particles come into contact with the member to be charged in the nip portion between the contact charging member and the member to be charged are remarkably increased, and high contact is achieved. Since the conductive particles existing in the nip portion between the contact charging member and the charged body rub against the surface of the charged body without a gap, the charge can be directly injected into the charged body, and the contact charging can be performed. Direct injection charging is dominant in the contact charging of the member to be charged by the member due to the presence of the conductive particles.

Therefore, it is possible to obtain a high charging efficiency which has not been obtained by the conventional roller charging and the like, and it is possible to give the charged body a charging potential almost equal to the voltage applied to the contact charging member.

As a structure for providing a speed difference, the contact charging member is rotationally driven to provide a speed difference between the member to be charged and the contact charging member. Preferably, in order to temporarily collect and level the transfer residual toner on the member to be charged, which is carried to the charging unit, on the contact charging member, the contact charging member is rotationally driven, and the rotation direction is the surface of the member to be charged. It is desirable to be configured to rotate in the direction opposite to the moving direction (counter direction). That is, it is possible to predominantly perform direct injection charging by temporarily separating the transfer residual toner on the member to be charged by reverse rotation and performing charging.

The contact charging member can be moved in the same direction as the moving direction of the surface of the member to be charged so as to have a speed difference, but the charging property of the direct injection charging is the peripheral speed of the member to be charged and the peripheral speed of the contact charging member. Therefore, in order to obtain the same peripheral speed ratio as in the reverse direction, the rotation speed of the contact charging member in the forward direction is larger than that in the reverse direction, so moving the contact charging member in the reverse direction causes rotation. It is advantageous in terms of number. The peripheral speed ratio described here is the peripheral speed ratio (%) = (contact charging member peripheral speed−charged member peripheral speed) / charged member peripheral speed × 100 (contact charging member peripheral speed is the charging member at the nip portion). A positive value when the surface moves in the same direction as the surface of the body to be charged).

Thus, even when a charging roller, a fur brush or the like having a relatively simple structure is used as the contact charging member, the applied bias required for charging the contact charging member is equivalent to the charging potential required for the member to be charged. Voltage is enough,
It is possible to realize a stable and safe contact charging method or device that does not use a discharge phenomenon.

B) Further, since the charging member is in contact with the member to be charged with a speed difference, the pattern of the transfer residual toner from the transfer portion to the charging portion is disturbed in the cleanerless image forming apparatus. It is possible to prevent the occurrence of a ghost image in a halftone image in which the residual ghost, which is mainly caused by the residual toner after transfer, is apt to stand out.

C) By bringing the charging member into contact with the member to be charged with a speed difference, the charging member becomes the member to be charged in the vicinity of the nip portion between the charging member composed of an elastic body and the member to be charged. As compared with the case of driven rotation, it is greatly deformed, and the conductive particles existing in the nip portion between the charging member and the body to be charged are easily transferred onto the body to be charged, and as the device is used, The conductive particles existing in the nip portion are reduced.

In the present invention, conductive particles are applied to the charging member.
By having the conductive particle coating member to be coated , the conductive particles are sequentially replenished to the nip portion between the charging member and the body to be charged, and stable direct injection charging performance can be exhibited without any trouble even in long-term use.

[0058] The conductive particles coated member can be uniformly stably applied supplying the conductive particles to the charging member by rotating made to have a speed difference relative to the charging member.

Further, by setting the surface property of the conductive particle coating member to be more than that of the charging member, the particles can be more stably applied and supplied. That is, conductive particle coating
The surface cell diameter of the cloth member is larger than the surface cell diameter of the charging member.
The more stable the application and supply of particles, the better
You can

[0060]

D) Since the image forming apparatus is cleaner-less, the transfer residual toner remaining on the surface of the body to be charged after the transfer is moved to the charging portion which is a nip portion between the body to be charged and the contact charging member. It is carried and adheres to and mixes with the contact charging member. Even if the transfer residual toner adheres to or mixes with the contact charging member as described above, the conductive particles are present in the nip portion between the member to be charged and the contact charging member, so that the contact charging member comes into close contact with the member to be charged. Characteristics and contact resistance, it is possible to maintain ozone-less direct charging stably at a low applied voltage for a long period of time regardless of contamination by transfer residual toner on the contact charging member, and to provide uniform charging property. I can.

The transfer residual toner adhering to and mixed with the contact charging member is gradually discharged from the contact charging member onto the member to be charged and reaches the developing section along with the movement of the surface of the member to be charged, and cleaning (recovery) is performed simultaneously with the developing means in the developing means. To be done.

E) The volume resistance of the outermost surface layer of the member to be charged or the electrophotographic photosensitive member is 1 × 10 ¹⁴ (Ω · cm) or less, or 1 × 10 ⁹ (Ω · cm) or more and 1 × 10 ¹⁴ (Ω).・ C
By being m) or less, the electrostatic latent image can be maintained, and sufficient chargeability can be imparted even in an apparatus having a high process speed, and direct injection charging can be predominantly realized.

[0064]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Reference Example 1> (FIGS. 1 to 3) FIG. 1 is a schematic configuration model view of an example of the images forming apparatus.

[0065] The image forming apparatus of the present embodiment is a transfer type electrophotographic process, a contact charging method, Cree Nare scan, the process cartridge type laser printer (recording apparatus).

(1) The overall schematic structure 1 of the printer is a member to be charged (image bearing member), and in this example, a rotating drum type negative polarity OPC photosensitive member (negative photosensitive member, hereinafter referred to as photosensitive drum) having a diameter of 30 mm. ). The photosensitive drum 1 is rotationally driven in the clockwise direction indicated by an arrow at a peripheral speed of 50 mm / sec (= process speed PS, printing speed).

Reference numeral 2 denotes a conductive elastic roller (hereinafter referred to as a charging roller) as a contact charging member (contact charger) which is disposed in contact with the photosensitive drum 1 with a predetermined pressing force. Reference numeral n denotes a charging nip portion (charging portion) between the photosensitive drum 1 and the charging roller 2. In this charging nip portion n, conductive particles m
(Hereinafter, referred to as charge promoting particles). The charging roller 2 is rotationally driven in the charging nip portion n in a direction (counter) opposite to the rotation direction of the photosensitive drum 1, and contacts the surface of the photosensitive drum 1 with a speed difference. Further, a predetermined charging bias is applied from the charging bias applying power source S1. As a result, the peripheral surface of the rotary photosensitive drum 1 is uniformly contact-charged to a predetermined polarity and potential by the direct injection charging method.

In this example, a DC voltage of -700 V is applied as a charging bias from the charging bias applying power source S1 to the charging roller 2. The surface of the photosensitive drum 1 is uniformly charged by a direct injection charging method to a potential almost equal to the voltage applied to the charging roller 2.

The structure of the charging roller 2, the charging accelerating particles m, and the direct injection charging will be described later in more detail.

Reference numeral 3 is a laser beam scanner (exposure device) including a laser diode, a polygon mirror and the like.
The laser beam scanner 3 outputs a corresponding time series electrical digital pixel signals of the intended image information intensity-modulated laser light, the rotating photosensitive drum 1 with the laser beam
Then, the uniformly charged surface is subjected to scanning exposure L. By this scanning exposure L, an electrostatic latent image corresponding to the target image information is formed on the surface of the rotary photosensitive drum 1. A developing device 4 develops the electrostatic latent image on the surface of the rotating photosensitive drum 1 as a toner image by the developing device 4 at the developing portion a. The developing device 4 of this example is a reversing developing device 4 using a one-component magnetic toner (negative toner) as the developer t. 4a includes a magnet roll 4b,
The developer carrying / conveying member is a non-magnetic rotary developing sleeve, and the rotary developing sleeve 4a is coated with the developer t in a thin layer by the regulating blade 4c. The layer thickness of the developer t with respect to the rotary developing sleeve 4a is regulated by the regulation blade 4c,
In addition, an electric charge is given.

The developer coated on the rotary developing sleeve 4a is conveyed by the rotation of the sleeve 4a to a developing portion (developing area portion) a which is an opposing portion between the photosensitive drum 1 and the sleeve 4a. Further, the developing bias applying power source S2 is applied to the sleeve 4a.
A developing bias voltage is applied. As the developing bias voltage, a DC voltage of -500 V and a rectangular AC voltage having a frequency of 1800 Hz and a peak-to-peak voltage of 1600 V were used. As a result, the electrostatic latent image on the photosensitive drum 1 side is developed with toner.

The developer t, that is, the one-component magnetic toner is prepared by mixing the binder resin, the magnetic particles, and the charge control agent, and carrying out the steps of kneading, pulverizing and classifying, to which a fluidizing agent and the like are externally added. It was created by adding it as an agent. The weight average particle diameter (D4) of the toner was 7 μm.

Reference numeral 5 denotes a medium resistance transfer roller as a contact transfer means, which is pressed against the photosensitive drum 1 at a predetermined pressure to form a transfer nip portion b. A transfer material P as a recording material is fed to the transfer nip portion b from a paper feed portion (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to the transfer roller 5 from a transfer bias applying power source S3. Then, the toner image on the photosensitive drum 1 side is sequentially transferred to the surface of the transfer material P fed to the transfer nip portion b. In this embodiment, a roller resistance value of 5 × 10 ⁸ Ω is used and +20.
Transfer was performed by applying a DC voltage of 00V. That is, the transfer material P introduced into the transfer nip portion b is nipped and conveyed through the transfer nip portion b, and the toner image formed and carried on the surface of the rotary photosensitive drum 1 is sequentially pressed by the electrostatic force with the transfer nip portion b. Transferred by pressure.

The photosensitive drum 1 is fed to the transfer nip portion b.
The transfer material P on which the toner image on the side is transferred is separated from the surface of the rotary photosensitive drum 1 and is introduced into a fixing device 9 such as a thermal fixing system.
It is ejected outside the device as a copy).

Reference numeral 6 denotes a means for supplying conductive particles (conductive particles), that is, charge promoting particles m. In this example, the photosensitive material is exposed between the transfer nip portion b and the charging nip portion n between the charging roller 2 and the photosensitive drum 1. An appropriate amount of charging promoting particles m is applied and supplied onto the surface of the drum 1. The charging promoting particles m applied and supplied to the surface of the photosensitive drum 1 are carried to the charging nip portion n between the charging roller 2 and the photosensitive drum 1 by the subsequent rotation of the photosensitive drum 1, and are replenished to the charging nip portion n.

The above-mentioned charging-promoting particle supplying means 6 will be described in more detail later.

The printer of this example is cleanerless, and the transfer residual toner remaining on the surface of the rotary photosensitive drum 1 after the toner image is transferred onto the transfer material P is not removed by a dedicated cleaner (cleaning device), and the photosensitive drum is removed. Along with the rotation of 1, the charging-promoting particle supply means 6 parts and the charging roller 2 parts reach the developing part a, and the developing device 4 collects them by cleaning at the same time (toner recycling process).

Reference numeral 7 is a process cartridge which can be attached to and detached from the printer body. The process cartridge of this example is a process cartridge in which four process devices including the photosensitive drum 1, the charging roller 2, the developing device 4, and the charging accelerating particle supply means 6 are collectively attachable to and detachable from the printer body. The combination of process equipment to be made into a process cartridge is not limited to the above, and is arbitrary. 8
Numeral 8 is a guide member for attaching / detaching the process cartridge to / from the printer body.

(2) Charging Roller 2 The charging roller 2 as a flexible contact charging member in this example is formed by forming the medium resistance layer 2b of rubber or foam on the core metal 2a.

The medium resistance layer 2b is made of resin (for example, urethane),
It was formulated with conductive particles (for example, carbon black), a sulfiding agent, a foaming agent, etc., and formed into a roller shape on the core metal 2a. After that, if necessary, the surface is polished to a diameter of 12 mm,
A charging roller 2 which is a conductive elastic roller having a longitudinal length of 200 mm was prepared.

The foaming cell diameter of the charging roller 2 is about 20 μm.

When the roller resistance of the charging roller 2 of this example was measured, it was 100 kΩ. The roller resistance is φ30 so that a total pressure of 1 kg is applied to the core metal 2a of the charging roller 2.
With the charging roller 2 pressed onto an mm aluminum drum,
100 V was applied between the core metal 2a and the aluminum drum, and the measurement was performed.

Here, the charging roller 2 which is a contact charging member.
Is important to function as an electrode. That is, it is necessary to impart elasticity to obtain a sufficient contact state with the charged body and at the same time have a resistance sufficiently low to charge the moving charged body. On the other hand, it is necessary to prevent voltage leakage when there is a low breakdown voltage defect site such as a pinhole on the charged body. When an electrophotographic photosensitive member is used as the member to be charged, 10 ⁴ to 10 ⁷ is required to obtain sufficient charging property and leak resistance.
A resistance of Ω is desirable.

If the hardness of the charging roller 2 is too low, the shape is not stable, so that the contactability with the member to be charged is deteriorated, and if the hardness is too high, the charging nip portion cannot be secured between the member and the charged member. Since the micro contact property to the surface of the member to be charged is deteriorated, the Asker C hardness is preferably in the range of 25 to 50 degrees.

The material of the charging roller 2 is not limited to the elastic foam, and the material of the elastic body is EPD.
Examples thereof include M, urethane, NBR, silicone rubber, a rubber material in which a conductive material such as carbon black or a metal oxide is dispersed in IR or the like for resistance adjustment, or a material obtained by foaming these. In addition, especially without dispersing a conductive substance,
It is also possible to adjust the resistance by using an ion conductive material.

The charging roller 2 is disposed so as to be pressed against the photosensitive drum 1 as the member to be charged with a predetermined pressing force against elasticity, and in this embodiment, a charging nip portion having a width of 3 mm is formed. .

In this example , the charging roller 2 is placed at the charging nip portion n between the charging roller 2 and the photosensitive drum 1 with the charging accelerating particles m interposed therebetween. It was rotationally driven in the clockwise direction of the arrow at about 80 rpm so as to move in the opposite directions at a constant speed. That is, the surface of the charging roller 2 as the contact charging member has a speed difference with respect to the surface of the photosensitive drum 1 as the member to be charged.

The core metal 2a of the charging roller 2 is applied with a DC voltage of -700 V from the charging bias applying power source S1 as a charging bias.

(3) Charge promoting particle supplying means 6, charge promoting particles m. The charging accelerating particle supply means 6 of this example has a roller 6a as a charging accelerating particle coating member and a housing 6b in which charging accelerating particles m are filled and housed, and the roller 6a is partially exposed to the outside of the housing 6b. And is in contact with the charging promoting particles m in the housing 6b. The externally exposed portion of the roller 6a is in contact with the surface of the photosensitive drum 1.

The charging-promoting particle application roller 6a is preferably a foam or a member having irregularities on its surface, and urethane foam, EPDM foam, fur brush, or the like is desirable.

In this example , a urethane foam roller having an outer diameter of 10 mm and a longitudinal width of 250 mm formed concentrically and concentrically with the rotating shaft was used as the charging-promoting particle coating roller 6a.
The surface cell diameter of the charging-promoting-particle coating roller 6a is about 20 μm.
m. The photosensitive drum 1 has a very uniform surface property as compared with the coating roller 6a. In this example , the charging-promoting particle coating roller 6a is brought into contact with the photosensitive drum 1, and the contact portion is rotated forward in the direction of rotation of the photosensitive drum 1 at a speed of 150% of the rotational peripheral speed of the photosensitive drum 1. To give a speed difference.

Here, as shown in FIG. 2, due to the difference in the surface state between the charging promotion particle coating roller 6a and the photosensitive drum 1, the charging promotion particle m in the housing 6b is formed on the peripheral surface of the rotating charging promotion particle coating roller 6a. Attached to the housing 6
b is carried out to the outside and is applied and supplied to the surface of the rotary photosensitive drum 1.
It reaches the charging nip portion n and is replenished to the charging nip portion n.

Further, as shown in FIG. 3, by arranging the charging promoting particle coating roller 6a above the photosensitive drum 1 in the direction of gravity, the charging promoting particles m separated from the surface of the coating roller 6a are also deposited on the photosensitive drum 1. Can be applied accurately.

.. In this embodiment, as the charge promoting particles m, conductive zinc oxide particles having a specific resistance of 10 ⁶ Ω · cm and an average particle size of 3 μm were used.

As the material of the particles m, various conductive particles such as conductive inorganic particles such as other metal oxides, a mixture with organic substances, or those subjected to surface treatment can be used.

The particle resistance is preferably 10 ¹² Ω · cm or less, more preferably 10 ¹⁰ Ω · cm or less, because the electrical resistance is transferred via the particles.

The resistance was measured by the tablet method and normalized. That is, a powder sample of about 0.5 g was placed in a cylinder having a bottom area of 2.26 cm ² , 15 kg of pressure was applied to the upper and lower electrodes, and at the same time, a voltage of 100 V was applied to measure the resistance value and then normalized to obtain a specific resistance. Was calculated.

Further, the charge-accelerating particles are preferably white or nearly transparent so that they do not hinder the exposure, and are therefore preferably non-magnetic.

The particle size is 50 in order to obtain good charging uniformity.
μm or less is desirable. The lower limit of the particle size is 10 nm as a limit for stably obtaining the particles. In the present invention, the particle size when the particles form an aggregate is defined as the average particle size of the aggregate. To measure the particle size, 100 or more particles were extracted from observation by an optical or electron microscope, the volume particle size distribution was calculated with the maximum chord length in the horizontal direction, and the 50% average particle size was determined.

There is no problem that the charge promoting particles exist not only in the state of primary particles but also in the state of agglomeration of secondary particles. Whatever the aggregated state, the form is not important as long as the function as the charge promoting particles can be realized as the aggregate.

The charge-accelerating particles are preferably colorless or nearly white particles so as not to hinder the latent image exposure particularly when used for charging the photoreceptor. Further, in the case of performing color recording, it is desirable that the particles are colorless or close to white considering that the charge promoting particles are partially transferred from the photosensitive member to the recording material P. Further, in order to prevent light scattering by particles at the time of image exposure, it is desirable that the particle size is equal to or smaller than the constituent pixel size.

(4) Direct injection charging. By interposing the charging-promoting particles m that are conductive particles (conductive particles) in the charging nip portion n between the photosensitive drum 1 that is the body to be charged and the charging roller 2 that is the contact charging member, the lubricant effect of the particles m As a result, even if the elastic charging roller itself has a large frictional resistance and it is difficult to bring it into contact with the surface of the photosensitive drum 1 with a speed difference as it is, the elastic charging roller can be contacted with the surface of the photosensitive drum 1 by itself. It is possible to easily and effortlessly and effectively bring them into contact with each other with a speed difference, and the charging roller 2 is in close contact with the surface of the photosensitive drum 1 through the charging accelerating particles m, so that it is higher. It comes in contact with the photosensitive drum surface at a certain frequency.

By providing a speed difference between the charging roller 2 and the photosensitive drum, the chances of the charging promoting particles m coming into contact with the photosensitive drum at the nip portion between the charging roller 2 and the photosensitive drum 1 are significantly increased, and high contact is achieved. Can get sex,
The charge promoting particles m existing in the nip portion between the charging roller 2 and the photosensitive drum 1 rub the surface of the photosensitive drum without any gap, so that the charge can be directly injected into the surface of the photosensitive drum, and the charging roller 2 contacts the photosensitive drum. Charge is electrification promoting particles m
The direct injection charge becomes dominant due to the presence of Therefore, it is possible to obtain a high charging efficiency that cannot be obtained by the conventional roller charging and the like, and it is possible to apply a charging potential substantially equal to the voltage applied to the contact charging member to the member to be charged.

Thus, even when the charging roller 2 having a relatively simple structure is used as the contact charging member, the applied bias required for charging the charging roller 2 is the photosensitive drum 1.
A voltage equivalent to the required charging potential is sufficient, and a stable and safe contact charging method or device that does not use the discharge phenomenon can be realized.

If the intervening amount of the charging promoting particles m in the charging nip portion n between the photosensitive drum 1 and the charging roller 2 as the contact charging member is too small, the lubricating effect due to the particles cannot be sufficiently obtained, and the charging roller 2 is not able to obtain the effect. Since the friction between the photosensitive drum 1 and the photosensitive drum 1 is large, it is difficult to rotationally drive the charging roller 2 on the photosensitive drum 1 with a speed difference. In other words, the driving torque becomes excessively large, and the surface of the charging roller 2 or the photosensitive drum 1 is scraped if it is forcibly rotated. Further, the effect of increasing contact opportunities due to the particles may not be obtained, and sufficient charging performance may not be obtained. On the other hand, if the intervening amount is too large, the fall of the charging promoting particles from the charging roller 2 remarkably increases, which adversely affects the image formation.

According to the experiment, the intervening amount is preferably 10 ³ pieces / mm ² or more. When it is less than 10 ³ pieces / mm ² , sufficient lubrication effect and effect of increasing contact opportunity cannot be obtained, and charging performance is deteriorated.

More preferably, 10 ^{3 to} 5 × 10 ⁵ pieces / mm
The intervening amount of ² is preferred. If it exceeds 5 × 10 ⁵ particles / mm ² , the amount of the particles falling onto the photosensitive member 1 remarkably increases, and the exposure amount to the photosensitive drum 1 becomes insufficient regardless of the light transmittance of the particles themselves. When it is 5 × 10 ⁵ particles / mm ² or less, the amount of particles that fall off is suppressed to a low level, and the adverse effect can be improved. When the amount of particles dropped on the photosensitive drum 1 in the range of the amount of inclusion is measured, it is 10
^{Since it was 2} to 10 ⁵ pieces / mm ² , it is desired that the existing amount that does not have a bad effect on image formation be 10 ⁵ pieces / mm ² or less.

A method of measuring the intervening amount and the existing amount on the photosensitive drum 1 will be described.

It is desirable to directly measure the intervening amount at the charging nip portion n between the charging roller 2 and the photosensitive drum 1, but most of the particles existing on the photosensitive drum 1 before coming into contact with the charging roller 2 move in the opposite direction. However, in the present invention, the amount of particles on the surface of the charging roller 2 immediately before reaching the charging nip portion n is defined as the intervening amount, because the charging roller 2 is peeled off by the contacting charging roller 2.

Specifically, the rotation of the photosensitive drum 1 and the charging roller 2 is stopped in the state where the charging bias is not applied, and the surfaces of the photosensitive drum 1 and the charging roller 2 are covered with a video microscope (OVM1000N made by OLYMPUS) and a digital still recorder. (DELTIS SR-3100)
Taken in.

The charging roller 2 is brought into contact with the slide glass under the same conditions as when the charging roller 2 is brought into contact with the photosensitive drum 1, and the contact surface is formed from the rear surface of the slide glass by a video microscope with an objective lens of 1000 times. I took more than 10 shots. In order to separate individual particles from the obtained digital image, binarization with a certain threshold,
The number of regions where particles were present was measured using a desired image processing software.

The amount of existence on the photosensitive drum 1 was also measured by photographing the photosensitive drum 1 with the same video microscope and performing the same processing. The adjustment of the intervening amount is
This was done by changing the amount of penetration between the housing and the roller.

.. By bringing the charging roller 2 into contact with the photosensitive drum 1 with a speed difference, the charging roller 2 is driven by the photosensitive drum 1 in the vicinity of the charging nip portion between the charging roller 2 and the photosensitive drum 1 made of an elastic body. The charging-promoting particles m existing in the nip portion between the charging roller 2 and the photosensitive drum 1 are easily deformed as compared with the case of rotating, and are easily transferred to the photosensitive drum, and the charging roller 2 and the photosensitive drum 1 are used as the apparatus is used. The conductive particles existing in the nip portion between and are reduced.

The charging-promoting-particle supplying means 6 successively replenishes the nip portion between the charging roller 2 and the photosensitive drum 1 with the charging-promoting particles m to keep the amount of the charging-promoting particles in the nip portion always within a predetermined range. Therefore, it plays a role of ensuring stable direct injection charging performance even when used for a long period of time.

In the present embodiment, as described above, during the period from the transfer nip portion b to the charging nip portion n between the charging roller 2 and the photosensitive drum 1, the charging accelerating particle supplying means 6 applies an appropriate amount to the surface of the photosensitive drum 1. The charging promoting particles m are applied and supplied. The charging promoting particles m applied and supplied to the surface of the photosensitive drum 1 are carried to the charging nip portion n between the charging roller 2 and the photosensitive drum 1 by the subsequent rotation of the photosensitive drum 1, and are replenished to the charging nip portion n.

The charging promotion particle applying member of the charging promotion particle supplying means 6 is rotated by a speed difference with respect to the photosensitive drum 1 to rotate the applying roller 6a, which has a surface more rough than the photosensitive drum, to rotate the photosensitive drum. It is possible to uniformly and stably coat and supply the charge-accelerating particles to No. 1. That is, a predetermined amount of charge promoting particles can be uniformly and stably supplied to the charging nip portion n between the charging roller 2 and the photosensitive drum 1.

(5) Cleanerless and prevention of ghost image generation. The printer of this example is cleanerless, and the transfer residual toner remaining on the surface of the rotating photosensitive drum 1 after the toner image is transferred onto the transfer material P is not removed by a dedicated cleaner, and the charging is promoted as the photosensitive drum 1 rotates. Particle supply means 6
Part, the charging roller 2 part, to the developing part a, and is collected by the developing simultaneous cleaning in the developing device 4.

Even if the transfer residual toner adheres to and mixes with the charging roller 2, the charging promoting particles m are still present on the photosensitive drum 1 and the charging roller 2.
Since it exists in the nip portion n of the charging roller 2 and the contact resistance of the charging roller 2 to the photosensitive drum 1 can be maintained with high precision, regardless of contamination by the transfer residual toner of the charging roller 2, a low applied voltage and ozoneless The direct injection charging can be stably maintained for a long time, and uniform charging property can be provided.

The transfer residual toner adhering to and mixed with the charging roller 2 is gradually discharged from the charging roller 2 onto the photosensitive drum 1 and reaches the developing section a as the photosensitive drum surface moves.
Simultaneous development cleaning is performed in the developing device 4. As described above, the simultaneous cleaning with the developing process is performed by developing the latent image by developing the latent image by continuously charging the photosensitive member with the toner remaining on the photosensitive member 1 after the transfer in the subsequent image forming process, that is, exposing the photosensitive member. At this time, it is recovered by the fog removing bias of the developing device, that is, the fog removing potential difference Vback which is the potential difference between the DC voltage applied to the developing device and the surface potential of the photoconductor. In the case of reversal development as in the printer of this example , this simultaneous cleaning of development is an electric field for collecting toner from the dark portion potential of the photoconductor to the developing sleeve and an electric field for adhering toner from the developing sleeve to the light portion potential of the photoconductor. Is made by the action of.

.. In this example , the charging promoting particle supply means 6 is arranged between the transfer nip portion b and the charging nip portion n between the charging roller 2 and the photosensitive drum 1, and the charging promoting particle application roller 6a is provided to the photosensitive drum 1. And the charging roller 2 is in contact with the photosensitive drum 1 with a speed difference, and therefore remains on the surface of the rotating photosensitive drum 1 after the toner image is transferred onto the transfer material P. When the residual toner after transfer passes through the charging-promoting particle coating roller 6a and the charging roller 2 as the photosensitive drum 1 rotates, the pattern of the residual transfer toner is disturbed and destroyed, and the residual transfer toner causes a ghost. It is possible to prevent the occurrence of a ghost image in a halftone image that is easily noticeable.

In this example , the charging-promoting-particle applying roller 6a of the charging-promoting-particle supplying means 6 is a urethane foam roller as described above, and this roller 6a is rotated at a speed of 150% relative to the photosensitive drum 1. Therefore, the transfer residual toner can be disturbed while the charging promoting particles m contained in the housing 6b are applied and supplied to the surface of the photosensitive drum 1. As a result, even when the image pattern of the image forming apparatus without a cleaner is disturbed by the surface shape of the urethane foam roller 6a as the charging accelerating particle application member and the transfer efficiency is reduced, the transfer residual toner causes This is effective in preventing the generation of ghost images in halftone images.

Reference Example 2 (FIG. 4) This reference example is the same as the printer (FIG. 1) of Reference Example 1 described above.
Charging promoting particle applying roller 6a of charging promoting particle supplying means 6
As shown in FIG. 4, the photosensitive drum 1 is rotated in contact with the photosensitive drum 1 with a counter rotation speed difference, and the charging promoting particles m are applied and supplied to the surface of the photosensitive drum 1. As a result, the charge-accelerating particles can be supplied more stably, and stable image quality without ghost images can be obtained even when the apparatus is used for a long period of time.

Other configurations of the printer are the same as those of the printer of the reference example 1 , and therefore the repetitive description will be omitted.

In this example , the urethane foam roller 6a, which is the charging-promoting-particle applying member of the charging-promoting-particle supplying means 6, is brought into contact with the photosensitive drum 1, and the photosensitive drum 1 and the counter 5 are rotated at a constant speed.
It rotates at 0% speed (peripheral speed is 25 mm / sec) (rotational direction is the same direction), and the charging promoting particles m filled in the housing 6b are applied and supplied to the surface of the photosensitive drum 1. As a result, in the configuration of the image forming apparatus having no cleaner, the charge-promoting particles m can be uniformly applied to the surface of the photosensitive drum 1 while disturbing the image pattern of the transfer residual toner by the rotation having the peripheral speed difference from the surface shape of the foaming roller 6a. Even when the transfer efficiency is lowered, it has an effect of preventing a ghost image which is conspicuous in a halftone image due to the transfer residual toner, and has a good charging performance.

<Embodiment 1> (FIG. 5) In this embodiment, as shown in FIG. 5, the charging promoting particles m are applied and supplied to the charging roller 2 by the charging promoting particle supplying means 6, and the charging roller 2 and the photosensitive drum are charged. The charging nip portion n of No. 1 is replenished.

Since the other printer configurations are the same as those of the printer of the reference example 1 , the repetitive description will be omitted.

In this embodiment, the charging-promoting-particle coating roller 6a of the charging-promoting-particle supplying means 6 is brought into contact with the charging roller 2, and the coating roller 6a is moved in the forward direction of the charging roller 2 relative to the charging roller 2. The charging-promoting particles m filled in the housing 6b are applied to the charging roller 2 by rapidly rotating at 150%.

Therefore, the coating roller 6a is in contact with the charging roller 2, and in this embodiment, the surface cell diameter of the charging roller 2 is about 20 μm, which is the same as the reference example 1, and the surface cell diameter of the coating roller 6a is about the same. It was set to 50 μm.

By adopting a device structure for applying and supplying the charging promoting particles to the charging roller 2 by the charging promoting particle supplying means 6, the charging promoting particles can be applied and supplied without increasing the number of devices around the photosensitive drum. It is effective for downsizing. In this configuration, even if the transfer efficiency decreases and the transfer residual toner adheres to the surface of the charging roller, the charging promoting particle application roller 6a can apply the charging promoting particles while disturbing the transfer residual image on the surface of the charging roller. It is possible to prevent the generation of a ghost image while maintaining the above, and further downsize the device.

By counter-rotating the coating roller 6a with respect to the charging roller 2, the transfer residual toner is disturbed and the charging effect of the charging promoting particles is further improved.

Second Embodiment (FIG. 6) In this embodiment, in the printer of the first embodiment , the resistance of the surface layer of the photosensitive drum 1, which is the member to be charged, is adjusted to more stably and uniformly charge. Do. In this embodiment, a charge injection layer is provided on the surface of the photoconductor of the photoconductor drum 1 to further stably and uniformly charge the photoconductor.

The surface of the charge injection layer used in this example contains a lubricant such as tetrafluoroethylene resin (trade name: Teflon) to improve transfer efficiency, and the particles have good releasability. Therefore, charge-accelerating particles were used as reference example 1 (Fig. 1) and reference.
The configuration of applying to the charging roller 2 as in Example 1 (FIG. 5) is more effective than the configuration of applying to the photosensitive drum 1 as in Example 2 (FIG. 4). Thus, in this example embodiment
1 was provided with a charge injection layer on the surface of the photosensitive member of the photosensitive drum 1 in the configuration of a printer to be applied to the charging roller 2 as shown in (Figure 5).

FIG. 6 is a schematic diagram of the layer structure of the photosensitive drum 1 used in this embodiment and provided with a charge injection layer on its surface. That is, the photosensitive drum 1 is a general coating in which an undercoat layer 12, a positive charge injection prevention layer 13, a charge generation layer 14, and a charge transport layer 15 are applied in this order on an aluminum drum base (Al drum base) 11. By applying the charge injection layer 16 to the organic photosensitive drum, the charging performance is improved.

The charge injection layer 16 is composed of a photo-curing acrylic resin as a binder and conductive particles (conductive filler).
SnO ₂ ultrafine particles 16a (diameter of about 0.03μ
m) A lubricant such as a tetrafluoroethylene resin, a polymerization initiator and the like are mixed and dispersed, and after coating, a film is formed by a photo-curing method.

An important point of the charge injection layer 16 is the resistance of the surface layer. In the charging method that directly injects electric charges, it is possible to transfer the electric charges more efficiently by reducing the resistance on the photosensitive drum 1 side. On the other hand, when it is used as a photoconductor, it is necessary to hold the electrostatic latent image for a certain period of time, so that the volume resistance value of the charge injection layer 16 is 1 × 10 ⁹ to
The range of 1 × 10 ¹⁴ (Ω · cm) is suitable.

Even when the charge injection layer 16 is not used as in this structure, the same effect can be obtained when the charge transport layer 15 is in the above resistance range.

Further, the surface layer has a volume resistance of about 10 ¹³ Ωcm.
The same effect can be obtained by using the amorphous silicon photoconductor or the like.

<Evaluation of Reference Examples 1 and 2 and Examples 1 and 2> Table 1 shows the superiority of Reference Examples 1 and 2 and Examples 1 and 2 together with Comparative Examples.

[0139]

[Table 1] [Comparative Example] In the comparative example, in the printer of Reference Example 1 or 2, the charging promoting particle applying roller 6a of the charging promoting particle supplying means 6 is rotated by being driven by the photosensitive drum 1 to apply and supply the charging promoting particles to the photosensitive drum 1. That is the case.

[Evaluation of Charging Performance] In each example, the charging performance was evaluated by image recording apparatuses having different printing speeds (printer, printing speed 50 mm / sec and 1
00 mm / sec), and the ghost image was evaluated as superior or inferior. The rotation speeds of the charging roller 2 were set so that the peripheral speed ratios were the same even for image recording apparatuses having different printing speeds.

There are an exposure ghost and a transfer residual ghost in the ghost (ghost pattern). The exposure ghost is generated in the second round when the image-exposed portion in the first round of the photosensitive drum 1 has insufficient chargeability. It means that it develops into a ghost image because of poor charging. In the case of a cleanerless case, the transfer residual ghost is a ghost image due to the transfer residual toner hindering charging and causing charging failure. Here, both ghost images were evaluated together according to the following criteria. The ghost evaluation is 100 unless the number of sheets is stated.
Printing was performed after printing one sheet (A4 lengthwise direction).

X: No ghost pattern is seen in the white background portion after exposure, but a ghost pattern is seen in the halftone portion after exposure.

Δ: No ghost pattern is observed in both the white background portion and the halftone portion after exposure.

◯: No ghost pattern is observed in both the white background portion and the halftone portion after exposure after printing 1000 sheets.

⊚: No ghost pattern is observed in any of the white background portion and the halftone portion after exposure after printing 5000 sheets.

As is clear from Table 1, the coating roller 6a
In the comparative example in which the photosensitive drum 1 was driven to rotate, the charging property was not satisfied in any speed device.

In Reference Example 1 in which the coating roller 6a was rapidly rotated with respect to the photosensitive drum 1, a good image without ghost was initially obtained at any speed.

By counter-rotating the coating roller 6a with respect to the photosensitive drum 1 as in Reference Example 2, a good image was obtained even after printing 1000 sheets.

As in Embodiment 1 , the application roller 6a is brought into contact with the charging roller 2 and the application roller 6a is quickly rotated with respect to the charging roller 2, so that the apparatus can be downsized and the reference can be made.
It has the same ghosting prevention effect as that of Consideration 1 .

Further, by using the outermost surface layer of the photoreceptor as the charge injection layer as in Example 2 , it is possible to maintain a good image without ghost even after printing 5000 sheets.

Further, the image flow caused by the resistance of the surface of the photoconductor due to adsorption of ozone products and the latent image being blurred (flowing) is apt to occur in a high temperature and high humidity environment. In particular, no image deletion was seen.

<Others> 1) The charging roller 2 as a flexible contact charging member is not limited to the charging roller of the embodiment.

[0153]

[0154]

2) The coating roller 6a as the charging accelerating particle coating member is not limited to the urethane foam roller of the embodiment.
Absent.

3) As for the charging bias or the developing bias applied to the charging roller 2 or the developing sleeve 4a, an alternating voltage (AC voltage) may be superimposed on the DC 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 rectangular 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.

4) The image exposing means for forming an electrostatic latent image is not limited to the laser scanning exposing means for forming a digital latent image as in the embodiment, but a normal analog type. Other light emitting elements such as image exposure and LEDs may be used, or a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter may be used as long as it can form an electrostatic latent image corresponding to image information.

The photosensitive drum 1 may be an electrostatic recording dielectric material or the like. In this case, after the primary surface of the dielectric surface is uniformly charged to a predetermined polarity and potential, the target electrostatic latent image is written and formed by selectively neutralizing with a neutralizing means such as a neutralizing needle head or an electron gun.

5) In the embodiment, the reversal developing device 4 using the one-component magnetic toner has been described as an example of the developing device 4, but the structure of the developing device 4 is not particularly limited. It may be a regular developing device.

6) The recording medium to which the toner image is transferred from the photosensitive drum 1 may be an intermediate transfer body such as a transfer drum.

7) An example of the method for measuring toner particle size will be described. As a measuring device, Coulter Counter TA-2
Interface (manufactured by Nikkaki) and CX that outputs number average distribution and volume average distribution using a mold (manufactured by Coulter)
-1 Connect a personal computer (made by Canon),
As the electrolytic solution, a 1% NaCl aqueous solution is prepared using primary sodium chloride.

As the measuring method, 100 to 100% of the electrolytic aqueous solution is used.
Surfactant as a dispersant in 150 ml, preferably
Add 0.1 to 5 ml of alkylbenzene sulfonate, and add 0.5 to 50 mg of the measurement sample.

The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the Coulter Counter TA-2 type was used to make a particle size of 2 to 40 μm using a 100 μ aperture as an aperture. The distribution is measured to obtain the volume average distribution. The volume average particle size is obtained from the obtained volume average distribution.

[0165]

As described above, according to the present invention, the contact charging method, transfer method, the image forming apparatus of a cleaner-less, with a simple member, such as charging low la as a contact charging member, moreover transfer residual of the contact charging member Regardless of toner contamination, ozone-free direct injection charging with excellent charging uniformity and low applied voltage can be stably realized for a long period of time, that is, charging low
Achieves good direct injection charging and toner recycling process with a simple configuration using a contact charging member such as La , and there is no image deletion, even in halftone images in long-term printing, there is no charging unevenness or ghost image, It is possible to stably output a high-quality good image for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus of Reference Example 1 .

FIG. 2 is a model diagram for explaining reference example 1 (No. 1)

FIG. 3 is a model diagram for explaining reference example 1 ( No. 2)

FIG. 4 is a partial view of the image forming apparatus of Reference Example 2 .

FIG. 5 is a schematic configuration diagram of the image forming apparatus according to the first embodiment .

FIG. 6 is a layer configuration model diagram of a photoconductor in which a charge injection layer is provided on the surface in Example 2 .

FIG. 7: Charging characteristic graph

[Explanation of symbols]

1 Photosensitive drum (charged member, image bearing member) 2 Charging roller (contact charging member) 3 Laser beam scanner (exposure device) 4 developing device 4a Development sleeve 4d magnet roll t Developer (toner) 5 Transfer roller 6 Charge-promoting particle supply means 6a Charge accelerating particle coating member (coating roller) 6b housing m Charge-promoting particles (conductive particles) 7 Process cartridge 9 Fixing device P transfer material

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-103878 (JP, A) JP-A-9-190046 (JP, A) JP-A-7-36322 (JP, A) JP-A-5- 241423 (JP, A) JP-A-7-5748 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103

Claims (10)

(57) [Claims] 1. A charged body, charging means for charging the charged body, latent image forming means for forming an electrostatic latent image on a charged surface of the charged body, and the electrostatic latent image by a developer. A cleaning unit that has a developing unit that visualizes a toner image and a transfer unit that transfers the toner image to a recording material, and collects the toner remaining on the charged body after the developing unit transfers the toner image to the recording material. an image forming apparatus serving as a pre SL charging means comprises a flexible charging member to form a member to be charged and the nip, at least before the said charging member
The conductive member is carried in the nip portion, and the charging member is moved with a speed difference with respect to the surface of the body to be charged .
A voltage is applied , an elastic foam is provided on the surface thereof, and a conductive particle coating member that coats the conductive particles on the charging member is provided. The conductive particle coating member is an elastic foam roller.
Ri, the contact with the charging member to move while having a speed difference relative to the charging member, the surface Se of the conductive particles coated member
The image forming apparatus is characterized in that the diameter of the charging hole is larger than the surface cell diameter of the charging member. 2. The image forming apparatus according to claim 1, wherein the conductive particle coating member counter-rotates with respect to the charging member at a contact portion with the charging member. 3. The resistance value of the conductive particles is 1 × 10 ¹²
(Ω · cm) or less, The claim 1 or
2. The image forming apparatus according to item 2 . Resistance according to claim 4, wherein said conductive particles, 1 × 10 ¹⁰
(Ω · cm) or less, The claim 1 or
2. The image forming apparatus according to item 2 . Particle size of wherein said conductive particles, 10 nm or more 1
The pixel size is less than or equal to the size of the pixel.
The image forming apparatus according to any one of 4 above. Wherein said volume resistivity of the outermost surface layer of the member to be charged 1
× 10 14 ^(Ω · cm) image forming apparatus according to claim 1, any one of the 5, characterized in that less. 7. The charged body is an electrophotographic photoreceptor,
The volume resistance of the outermost surface layer of the electrophotographic photoreceptor is1 x 10
⁹ (Ω · cm) or more 1 × 10 ¹⁴ (Ω · cm)Below
The method according to any one of claims 1 to 6, characterized in that
Image forming device. Wherein said charging member, image forming apparatus according to any one of claims 1 to 7, characterized in that rotates counter against the member to be charged in the nip. Wherein said latent image forming means, the image forming apparatus according to any one of claims 1 to 8, characterized in that the image exposure means. Wherein said conductive particles coated member, the image forming apparatus according to any one of claims 1 to 9, characterized in that present above in the gravity direction than the charging member.