JP3193228B2 - Contact charging particles used in particle charging method and image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to printers, to contact charging particles used in the particle charging process for uniformly charging the electrophotographic photosensitive member in an image forming apparatus such as a copying machine.

[0002]

2. Description of the Related Art F. Since the invention of electrophotography by Carlson (U.S. Pat. No. 2,297,691),
Various improvements and developments have been made based on this method. An electrophotographic method represented by the Carlson method is widely used at present, and its basic process is to uniformly charge a photosensitive member, form a latent image by selective exposure, form a toner image with a developer, transfer and fix.

As a method for uniformly charging the photosensitive member, there are a non-contact method such as corona charging and solid discharge, and a contact method such as roller charging, brush charging, particle charging and friction charging. Among them, corona charging is most widely used, but has problems in that charging becomes unstable during long-term use, influence of ozone on human bodies, and adhesion of discharge products to photoconductors. On the other hand, in the contact method, roller charging is being put to practical use, and generation of ozone is small. However, on the other hand, roller charging can cause photoconductor damage due to abnormal discharge,
There are problems such as uneven charging and environmental stability. In addition, there are two types of brush electrification: one that uses a flat brush made of conductive thin fibrous wire fixed and one that rotates it. There is a problem of performance degradation.

The particle charging method using conductive particles is a method of forming a magnetic brush with magnetic particles and injecting electric charges through the magnetic particles, using magnetic particles of about 10 ³ to 10 ⁷ Ω · cm. The photosensitive member was charged by applying a high bias voltage of 1 KV or more. For example, in Japanese Patent Application Laid-Open No. 61-57958, 10 ⁶ Ω · c
A charging bias voltage of 2000 V is applied to the m magnetic particles. JP-A-59-133569 states that a surface potential of 500 V can be obtained by applying a voltage of 600 V by using magnetic particles having a conductivity of 10 ^-7 V / cm.

However, it is difficult to uniformly charge these conventional systems, and there is a problem that the particulate charging agent migrates and adheres to the surface of the photoreceptor after the charging process. Was provided with a blade for removing the charging agent particles. In addition, if the chargeability of the photoreceptor is increased by increasing the conductivity of the particulate charging agent, the injected charge concentrates on minute defects on the surface of the photoreceptor, which may cause the destruction of the photoreceptor. Did not.

[0006]

[0008] The present invention is to prevent dielectric breakdown, thereby uniformly charging an object by contact particle charging contact
And to provide a charging particles tactile and images forming method using the same.

[0007]

SUMMARY OF THE INVENTION The present invention is applicable to the particle charging method of the present invention .
Contact charging particles have (hereinafter, referred to as a two-component system) is to inject charge to the photosensitive member in contact voltage is applied, a contact charging particles for charging the photosensitive member surface, and conductive magnetic particles And a mixture with high-resistance magnetic particles having an electric resistance and an average particle size larger than the particles.

[0008]

[0009]

According to the image forming method of the present invention, a rotating drum-shaped electrophotographic photosensitive member is charged in the dark; and the charged photosensitive member is selectively irradiated with light to form an electrostatic image comprising a high potential portion and a low potential portion. Forming a latent image on a photoconductor; developing the electrostatic latent image with a developer to form a toner image composed of toner on the photoconductor; transferring the toner image onto a member to be transferred; In the image forming method using an electrophotographic method of fixing on a transfer paper, the contact charging particles are brought into contact with the surface of a rotating drum-shaped photoreceptor in a state restrained by a magnetic member. It is characterized in that a charge is injected into the photoreceptor through the contact charging particles to charge the surface of the photoreceptor. In addition,
In the following examples, the contact zone used in the particle charging method of the present invention is described.
The charging particles are described as “granular charging agent”.

[0011]

FIG. 1 is an explanatory view showing an embodiment in which the charging method of the present invention is applied to an image forming system using an electrophotographic photosensitive member. A charging unit 21, an exposure unit (LED exposure optical system 41), a developing unit 51, a transfer unit 71, and a fixing unit 81 are arranged around the drum-shaped photoconductor 11 in which the photoconductive layer 15 is formed on the conductive support 13. Are arranged. The photoconductor 11 may be a belt-shaped (sheet-shaped).

As the photoconductor 11, an a-Si photoconductor,
Appropriate materials such as an OPC-based photoconductor (organic photoconductor) and a Se-based photoconductor can be employed. The photoconductor 11 rotates in the P direction, and is first charged in the dark by the charging unit 21.

The charging unit 21 includes a magnetic brush roller 23 (magnetic member) including a mag roller 25 and a conductive charging sleeve 27, a magnetic granular charging agent 29, and a charging bias power supply 31. Granular charging agent 2
9 is a charging bias power supply 31 via a charging sleeve 27.
Voltage is applied from the photoconductor 11 and contacts the photoconductor 11
The magnetic brush roller 23 is magnetically coupled to the magnetic brush roller 23 to form a so-called magnetic brush, and contacts with the photoreceptor 11 as the magnetic brush roller 23 rotates (in the M direction). While rotating. In addition, even if the magnetic brush roller 23 is not rotated, uniform charging is possible, and the granular charging agent can be stirred and moved only by rotating the photoconductor 11.

The photoreceptor 11 having a uniformly charged surface is exposed to an image by an LED exposure optical system 41. By the image exposure, the surface potential of the exposed portion is selectively reduced, and an electrostatic latent image composed of a low potential portion and a high potential portion is formed.

In the embodiment shown in FIG. 1, the potential of a portion corresponding to a future image portion is reduced by the LED exposure optical system 41 in consideration of use as a printer. The LED exposure optical system 41 is a combination of an LED array in which LED chips are linearly arranged by the number of recording pixels and an imaging optical system such as a selfoc lens, but a rotating mirror is used instead of the LED exposure optical system. And a laser exposure optical system using an f-θ lens, or a copying optical system that irradiates reflected light from an original document when applied to a copying machine. Alternatively, the rear image may be exposed from the inside of the photoconductor 11. The photoreceptor 11 on which the electrostatic latent image is formed is developed by the developing unit 51.

The developing unit 51 supplies a developer 91 to the surface of the photoconductor 11 by a developing roller 53 rotating in the S direction. A developing bias power source 59 for applying a developing bias voltage between the photoconductor 11 and the developing roller 53 is connected to the conductive developing sleeve 57 of the developing roller 53. The developing roller 53 includes a mag roller 55 having several magnetic poles (N and S poles) in a conductive developing sleeve 57.

At the time of development, a bias voltage is applied from a developing bias power source 59 to develop the developing roller 53 and the photosensitive member 1.
1, a developing bias electric field is generated. By the development, the toner 93 in the developer 91 selectively adheres to the electrostatic latent image on the photoconductor, and an image composed of the toner is formed on the photoconductor 11. The toner 93 is transferred to the transfer unit 7
At 3, the image is transferred onto the paper 95 by the transfer roller 73 to which a negative bias voltage is applied by the transfer bias power supply 75. Reference numeral 69 denotes a registration roller that sends out the paper 95.

Next, the transfer toner is supplied to the fixing unit 81.
Is fixed on the paper 95 by the fixing roller 83 (heating roller). Reference numeral 85 denotes a pressure roller. The residual toner remaining on the photoconductor 11 without being transferred at the time of transfer is removed by the cleaning blade 99. In the above description, the case where the photoconductor 11 is positively charged and an image is formed by reversal development using a two-component developer has been described. However, other developers such as a one-component developer, and other developments such as a regular development method Processes can also be applied.

Next, the granular charging agent of the present invention will be described in the order of a two-component system and a one-component system. In the present invention, the two-component magnetic particles and the one-component magnetic particles are mixed and finally mixed. It can also be a fine granular charging agent. The granular charging agent of the present invention is composed of an aggregate of magnetic particles for charging, and the required basic average particle size, volume resistivity, and magnitude of magnetic force are common to the two-component system and the one-component system.

The average particle size of the magnetic particles for charging is 60 μm or less, preferably 10 to 60 μm. 10 ² to 10 ⁸ Ω · cm, preferably 1
It has a volume resistivity value of 0 ³ to 10 ⁷ Ω · cm. In addition,
The volume resistivity of the present invention is an inner diameter 20 with an electrode at the bottom.
1.5 g of particles in a Teflon cylindrical body having a diameter of 20 mm.
It is a value measured by inserting an electrode of mmφ and applying a load of 1 kg from above.

The granular charging agent is 1 kilooersted (1
It preferably has a magnetic force of 40 emu / g or more in a magnetic field of KOe), more preferably 50 to 100 emu / g.
g. In the case of the two-component granular charging agent, the charging agent is composed of conductive magnetic particles having a conductive magnetic surface and high-resistance magnetic particles having a high-resistance particle surface. The conductive magnetic particles are 10 ⁶ Ω · cm or less, preferably 10 ¹ to 10 ⁵ Ω · c.
m, more preferably 10 ² to 10 ⁴ Ω · cm. On the other hand, the high-resistance magnetic particles have a volume resistivity of 10 ⁶ Ω · cm or more, preferably 10 ⁶ to 10 ¹⁵ Ω · cm, and more preferably 10 ⁶ to 10 ¹² Ω · cm.

Both the conductive magnetic particles and the high-resistance magnetic particles
The average particle size is 60 μm or less, preferably 10 to 60
μm. In particular, the conductive magnetic particles have an average particle size of 5 to 50.
μm is most suitable, and high-resistance magnetic particles have an average particle size of 2
0 to 60 μm is optimal. Further, it is desirable to set the average particle size of the high-resistance magnetic particles to be larger than the average particle size of the conductive magnetic particles, whereby the effect of preventing carrier pulling is further improved, and the charged contact surface with respect to the photoconductor is reduced. This increases the charge-imparting ability and further facilitates the movement of the conductive magnetic particles, so that the rotation of the photoconductor facilitates the stirring of the particulate charge agent. Note that carrier pulling refers to development in which magnetic particles for charging are removed from the magnetic force of the magnetic brush roller 23 and migrate and adhere to the surface of the photoconductor.

In the case of high-resistance magnetic particles, 10 μm
It is desirable that the proportion of particles having a particle size of m or less be 5% by weight or less, preferably 2% by weight or less, and the presence of particles having a small particle size be excluded. As described above, by not allowing small particles to exist, the occurrence of carrier pull is further prevented.

The mixing ratio of the conductive magnetic particles A and the high-resistance magnetic particles B is preferably in the range of A / B = 95/5 to 5/95 by weight, and more preferably 90/10 to 10/90. ,
More preferably, it is 80/20 to 20/80. If an attempt is made to obtain the characteristics required for charging with only the conductive magnetic particles, the charges concentrate on minute defects of the photoreceptor during charging,
Pinholes frequently occur, resulting in photoconductor failure.

Further, when paper dust, residual toner, dust in the air, etc. adhering to the photoreceptor enter the particulate charging agent, the resistance of the particulate charging agent changes, and it becomes impossible to provide a required amount of charge to the photoreceptor. Sometimes. Further, a problem that occurs when the conductive magnetic particles move to the surface of the photoconductor due to the electrostatic induction is likely to occur.

On the other hand, the following effects can be obtained by using high-resistance magnetic particles in combination to form a granular charging agent. (1) The phenomenon (carrier pulling) in which the conductive magnetic particles move to the photoreceptor surface can be prevented. (2) The high-resistance magnetic particles attract the paper powder and the toner particles by electrostatic force, and maintain the charging ability by the conductive magnetic particles. (3) The high-resistance magnetic particles function as a kind of resistance layer, preventing charge from concentrating on minute defects of the photoreceptor, and enabling stable charging.

In the case of a one-component granular charging agent, in each particle, a part of the surface that can come into contact with other particles forms a conductive surface, and the other part forms a high-resistance surface. However, the surface forms a so-called sea / island structure. The volume resistivity of the conductive surface is preferably 10 ⁷ Ω · cm or less, preferably 10 ³ to 10 ⁶ Ω · cm, and more preferably 10 ⁴ to 1.
0 is a ^{6 Ω} · cm. On the other hand, the volume resistivity of the high-resistance surface is 10 ⁶ · cm or more, preferably 10 ⁷ to 10 ¹⁵ Ω · c.
m, more preferably 10 ⁸ to 10 ¹² Ω · cm. 1
In the charging magnetic particles of the component-based particulate charging agent, the ratio of the area occupied by the conductive surface and the high-resistance surface is not particularly limited,
Either one may be broad or the same.

By providing a conductive surface and a high-resistance surface on one magnetic particle for charging as described above, the same operation and effect as those of the above-described two-component granular charging agent can be obtained, and conversely, a uniform surface can be obtained. This effect cannot be obtained with the charging magnetic particles having the following formulas, even if they have a volume resistivity value specified in the present invention.

As shown in FIG. 1, the particulate charging agent of the present invention is stirably restrained by a magnetic member such as a magnetic brush roller to form a charging agent reservoir, and the charging bias voltage is applied via the particulate charging agent. Is applied to the photoreceptor, and charge is injected to charge the surface of the photoreceptor. In the charging method of the present invention, the charging efficiency with respect to the applied voltage is very good. As an example, the case of an a-Si photosensitive member is shown in Table 1 below.

[0030]

[Table 1]

The magnitude of the applied voltage or the potential of the photosensitive member to be charged in the charging method of the present invention is not particularly limited, and can be appropriately set according to the image forming system and the photosensitive member to be used. In addition, from the viewpoint of taking advantage of the characteristic that the charging efficiency is good as described above, the method is suitable for a low charging method, and is preferably charged to a charging voltage of 500 V or less, more preferably 400 V or less, and further preferably 30 V or less. ~ 30
0V.

The two-component conductive magnetic particles can be produced, for example, by the following method. (1) The surface of metal powder such as iron powder is oxidized to adjust resistance and stabilize. (2) The magnetic fine particles are dispersed and supported in a binder resin, pulverized, classified into a predetermined size to obtain magnetic resin particles,
Further, the surface is subjected to a conductive treatment. In this case, a magnetic brush having a small specific gravity and a soft ear can be formed, but a weak magnetic force may cause carrier pulling.

The surface can be made conductive by fixing conductive fine particles such as carbon black to the surface.
It can also be carried out by the following surface conduction methods (4), (5), (7) and (8). (3) Particles having a certain magnetism, resistance and particle size can be obtained from various metals by a melt spray called an atomizing method. Specific examples of the metal include stainless steel, nickel, iron, cobalt, and various alloys. (4) Particles having a certain resistance can be obtained by the coating method. For example, 10 ⁸ Ω · c
By coating the surface of the m ferrite particles with a conductive resin, conductive particles of 10 ³ Ω · cm can be obtained.

(5) Plating method: By plating a conductive metal on the surface of the particles, the surface resistance of the particles can be adjusted. Specifically, for example, there is an electroless nickel plating method. (6) Sintering method: Conductive magnetic particles can be obtained by sintering particles having appropriate conductivity and magnetism at a high temperature. If necessary, reduction with hydrogen may be performed.

(7) Polymerization method: A polymerizable monomer such as ethylene is supplied together with conductive fine particles such as carbon black to the surface of magnetic particles such as a metal such as iron and an oxide such as ferrite to form a polymerizable monomer such as ethylene. A method for forming, on a surface, a conductive coating in which conductive fine particles are dispersed in a synthetic resin. This method is disclosed in JP-A-60-106808 and JP-A-2-18.
No. 7771, and the like. (8) Thin-film forming method: A conductive metal or compound is formed on the surface of the magnetic particles by vacuum deposition, sputtering, CVD, or the like, to give a certain conductivity.

As the two-component high resistance magnetic particles, for example, magnetic particles such as ferrite can be used as they are. Further, the magnetic resin particles of the above (2) can be used as they are, and in this case, the electric resistance can be controlled by the resin used. Further, the resistance can be adjusted by fixing fine particles having appropriate resistance to these surfaces and forming a surface coating layer.

The one-component magnetic particles for charging can be produced by applying the above-mentioned methods (2), (4), (5) and (8) to partially form a conductive portion on the surface. . In addition, a sheet is prepared by laminating a plurality of thin layers of a high-resistance synthetic resin containing magnetic fine particles and a thin layer of a conductive synthetic resin containing conductive fine particles. It can also be obtained by:

[0038]

According to the present invention, the granular charging agent (wrinkle)
In addition, by providing a conductive portion and a high-resistance portion in the contact charging particles used in the particle charging method , and controlling the average particle size and the volume specific resistance, no ozone is generated,
A photoreceptor or the like can be uniformly charged. Further, even when a minute defect is present in the photoconductor, abnormal concentration of the injected charge is prevented, and the photoconductor can be stably charged. Furthermore, by continuous use, even if paper dust or residual toner adhering to the photoreceptor is mixed into the particulate charging agent, the conductivity as the charging agent is maintained to prevent deterioration of the charging performance, and stable charging is achieved. Can do it. Further, the charging voltage can be reduced, and the charging efficiency is very good.

[0039]

【Example】

Example 1 A ferrite carrier having an average particle diameter of 40 μm, a volume resistivity of 2 × 10 ⁸ Ω · cm, and a magnetic force of 59 emu / g (in a magnetic field of 1 KOe) was prepared to obtain high-resistance magnetic particles. The ratio of particles having a particle diameter of 20 μm or less in the high-resistance magnetic particles was 1% by weight. On the other hand, JP-A-60-1068
No. 08, the ethylene monomer is polymerized on the surface of the ferrite in the presence of carbon black, the ferrite particles are coated with a carbon black-containing polyethylene resin, the average particle diameter is 15 μm, and the volume resistivity is 3 × 10 ² Ω.・
cm, and a magnetic force of 55 emu / g (at 1 KOe) were obtained.

As shown in FIG.
Using the apparatus shown in (1), the photosensitive member is charged by applying a charging bias voltage of 200 V while stirring the particulate charging agent only by rotating the photosensitive member without rotating the magnetic brush roller. The potential was measured. In addition, continuous operation was performed, and it was confirmed whether or not pinholes were generated due to the destruction of the photosensitive layer. At this time, as the granular charging agent, the high-resistance magnetic particles and the conductive magnetic particles described above were used in a ratio of 10/0 to 0/0.
The evaluation results are shown in Table 2 below, using the compounds blended at / 10.

[0041]

[Table 2] * 1) Mixing ratio of high resistance magnetic particles / conductive magnetic particles

Example 2 A conductive surface portion having a resistance of 1 × 10 ² Ω · cm and a resistance of 3 ×
The charging magnetic particles having a magnetic force of 58 emu / g in a magnetic field of 1 KOe and an average particle diameter of 35 μm were prepared by changing the area ratio of the surface portion having a high resistance of 10 ⁸ Ω · cm in the same manner as in Example 1. The surface potential after charging and the presence or absence of destruction of the photosensitive layer were evaluated. The results are shown in Table 3.

[0043]

[Table 3]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an image forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Photoconductor 13 Conductive support 15 Photosensitive layer 21 Charging unit 23 Magnetic brush roller 25 Mag roller 27 Charging sleeve 29 Granular charging agent 31 Charging bias power supply 41 LED exposure optical system 51 Developing unit 53 Developing roller 55 Mag roller 57 Sleeve 59 Developing bias power supply 71 Transfer Unit 73 Transfer Roller 77 Transfer Bias Power Supply 81 Fixing Unit 83 Fixing Roller 85 Pressure Roller 91 Developer 93 Toner 95 Paper 99 Cleaning Blade

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeki Tsukahara 2-14-9 Tamagawadai, Setagaya-ku, Tokyo Inside Kyocera Corporation Tokyo Yoga Office (72) Inventor Shinji Yamane 2- 14 Tamagawadai, Setagaya-ku, Tokyo No. 9 Inspector Yayoichi Inoue in the Tokyo Yoga Office of Kyocera Corporation (56) References JP-A-6-186822 (JP, A) JP-A-6-186823 (JP, A) JP-A-6-258918 (JP, A) JP-A-6-289689 (JP, A) JP-A-6-295115 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/02 G03G 15/02-15 / 02 103 G03G 15/09-15/095

Claims (4)

(57) [Claims] 1. A particle charging method for injecting a charge into a photosensitive member to which a voltage is applied and contacting the photosensitive member to charge the surface of the photosensitive member.
A contact charging particle , comprising: a conductive magnetic particle; and an electric resistance and an average particle
Contact charging particles for use in a particle charging method, comprising a mixture with high-resistance magnetic particles having a large diameter . 2. The high-resistance magnetic particles have a particle size of 10
The particles for contact charging used in the particle charging method according to claim 1, wherein the proportion of particles having a particle size of μm or less is 5% by weight or less . 3. A rotating drum-shaped electrophotographic photosensitive member is darkened.
Charged downward; selectively irradiates the charged photoreceptor with light
An electrostatic latent image consisting of a potential part and a low potential part is formed on the photoconductor
Developing the electrostatic latent image with a developer and applying toner on the photoreceptor
Forming a toner image; transferring the toner image onto a member to be transferred
Electronic transfer to fix the transferred toner image on the transfer paper
In an image forming method using a true method, Claims 1 to 1 with respect to the surface of a rotating drum-shaped photoconductor.
The particles for contact charging according to any one of 2 above,
Contact in a state of being restricted by the
To charge the photoconductor surface by charging the photoconductor.
And an image forming method. 4. A magnetic member for rotating the contact charging particles.
4. Contacting the photoreceptor in a state restrained by
The image forming method as described in the above.