JP2001272845A - Magnetic particle for charging and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnetic particles for charging excellent in charging uniformity and durability which prevents splashing of toner, to provide a charging member which uses the particles, to provide an image forming apparatus and a process cartridge which realize high image quality by mounting the electrifying member on a charging device. SOLUTION: The magnetic particles consists of magnetic particles the surface of which is treated with a silicone oil, and the ratio of the minor axial length to the major axial length (minor axial length/major axial length) of the particles having >=5 μm maximum chord length in the magnetic particles shows >=0.08 standard deviation The volume resistivity of the particles ranges 1×104 to 1×109 Ωcm. The amount of the silicon oil used for the treatment is >=0.0001 wt.% to <=1wt.% to the whole magnetic particles. The charging member, charging device, image forming apparatus and process cartridge are constituted by using the above magnetic particles for charging.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging magnetic particle used for a member for charging an object to be charged, a charging member using the charging magnetic particle, a charging device using the charging member, and an image forming apparatus. And a process cartridge, a copier, a printer,
Applied to facsimile etc.

[0002]

2. Description of the Related Art As a charging device for an image forming apparatus, a means utilizing corona discharge has been conventionally used. However, since a large amount of ozone is generated, it is necessary to provide a filter. However, there was a problem in that the running cost was increased.

In order to solve such problems, a contact charging device has been developed in which a roller-shaped charging member (charging roller) is brought into contact with the surface of a photoreceptor to perform charging. This is due to the narrow space formed near the contact between the charging roller and the photoconductor,
This is a method of charging a photoreceptor by generating a discharge that can be interpreted by Paschen's law, and has been found to have the effect of minimizing the generation of ozone.

[0004] Contact-type charging is performed by discharging from a charging roller to a photoreceptor. Therefore, charging is started by applying a voltage higher than a certain threshold voltage. Generally, if a voltage higher than the threshold is applied, the surface potential of the photoconductor increases linearly with a slope of 1. Therefore, this threshold voltage is set to the charging start voltage V
When defined as th, in order to obtain the photoconductor surface potential Vd,
The charging roller requires a DC voltage of Vd + Vth. In such DC charging, if the environment changes, the resistance value of the charging roller changes, so that the potential of the photoconductor may fluctuate.

On the other hand, Japanese Patent Laid-Open Publication No.
As disclosed in JP-A-3-149669, the desired V
A charging method is used in which a voltage obtained by superimposing an AC voltage having a peak-to-peak voltage of 2 × Vth or more on a DC voltage corresponding to d is applied to a charging roller. This is for the purpose of averaging the surface potential due to alternating current, and since the surface potential of the photoconductor converges to Vd, which is the median of the peaks of the AC voltage, it is less affected by disturbances such as the environment. There is.

However, since the charging roller is made of a solid material such as rubber, vibration occurs due to an electric field of an applied AC voltage at a contact portion with the photoconductor, and as a result, noise (AC charging noise) is generated. ) Can be a problem. In addition, fine powder such as toner and paper powder may adhere to the surface of the charging roller that comes into contact with the photoreceptor, but in such a case, the charging becomes partially non-uniform and a fog image is generated. There was also.

For this reason, a technique has been studied in which a magnetic brush is used as a charging member, in which magnetic particles having a relatively small contact load to the photoreceptor are held on the surface of a cylindrical conductive sleeve enclosing the magnet by the magnetic force of the magnet. ing. As a charging method using magnetic particles, two methods have been proposed in combination with a photoreceptor.

One is a method in which a charge injection layer is provided on a surface layer of a photoreceptor, and charges are directly injected through the contact with the charge injection layer to charge the photoreceptor. The other is a method using a normal photoreceptor and utilizing the discharge of magnetic particles and minute voids on the surface of the photoreceptor. As a disclosure of magnetic particles used as a charging member, Japanese Patent Application Laid-Open No. S59-133569 discloses particles coated with iron powder, and the particles are held on a magnet roll to be charged by applying a voltage. A method is disclosed.

[0009] However, the remaining problem of these techniques is that it is difficult to obtain stable charging properties during continuous use. For example, as disclosed in Japanese Patent Application Laid-Open No. 6-301265, a magnetic brush has been proposed. There has been proposed a configuration in which toner is replenished so as to keep the amount of toner present therein constant, thereby stabilizing resistance. All of the above methods use a discharge phenomenon in a minute gap, and have a problem that the surface of the photoreceptor is damaged by a product generated by the discharge, and the image is likely to be deteriorated or image flow under high temperature and high humidity. It still remained.

Further, in Japanese Patent Application Laid-Open No. 6-258918, charging particles are obtained by mixing particles having a particle size of 10 ⁸ to 10 ¹⁰ Ωcm and 30 to ¹⁰⁰ μm with particles having a particle size of 10 ⁸ Ωcm or less and 30 to 100 μm. However, Japanese Unexamined Patent Publication
Japanese Patent Publication No. 274005 discloses that particles of 5 × 10 ⁵ Ωcm or more and particles of 5 × 10 ⁴ Ωcm or less are mixed and used as charging particles. There has been proposed a form of mixing particles having a relatively high resistance with low conductivity.

[0011] These have good chargeability due to the particle size and resistance of the particles to be mixed, but if the particle size of the mixed particles is relatively close and the resistance is far away, the particles with low resistance are exposed during use. Since it gathers on the body surface, even if it has good pinhole resistance in the initial stage, it tends to cause pinhole leakage during use. Also, if the particle size is far,
Although it is possible to suppress the tendency of particles having low resistance to separate, there is a problem that particles having low resistance leak out particularly in a low humidity environment.

Furthermore, Japanese Patent Application Laid-Open No. 8-6355 proposes a mixture of magnetic particles having a smooth surface and magnetic particles having an uneven surface. In these, the effect of increasing the durability is described, but further improvement of the durability is desired. Although various proposals have been made above, in the sense of practical use, as far as the present inventor can know, there is no example where a magnetic brush is used as a photosensitive member charging member in an image forming apparatus such as a copying machine on the market. There is nothing.

It is disclosed that magnetic particles obtained by kneading and grinding magnetite and a resin are used as magnetic particles for charging (JP-A-5-94068, JP-A-7-72667, etc.). Therefore, there is a tendency that charging magnetic particles leak from the charging member. Since the resin magnetic particles have a high resin content on the surface and a small magnetic particle content ratio as a conductive path, resistance tends to increase due to surface contamination, and it is difficult to improve durability.

As described above, with respect to magnetic particles as a photosensitive member charging member, it has been insufficient to study the desirable physical properties and their effects from the viewpoint of physical properties. Further development of suitable configurations of the particles is desired.

On the other hand, a cleaning device in an image forming apparatus is a device in which a cleaning member is pressed against a photoreceptor to block remaining transfer toner and scrape the collected toner into a waste toner container. Is used. It is excellent in collecting residual toner after transfer because it comes into direct contact with the photoreceptor, but requires the disposal of waste toner, requires a cleaning container, and inevitably increases the size of the photoreceptor. Has been pointed out as wear (short life). Therefore, a simultaneous development cleaning method (or cleaner-less) has been proposed as a waste toner-less system.

This method is a technique in which untransferred toner remaining on a photoreceptor after a transfer step is passed through a charging step, and is collected in a developing device using a potential difference between the charged photoreceptor and a developing unit. This method, which does not require toner disposal, is an effective means from the viewpoints of effective use of consumables by reusing toner, ecological measures, long life by preventing abrasion of the photoconductor, and downsizing of the image forming apparatus. .

Conventionally, Japanese Patent Application Laid-Open No. Sho 59-13357 discloses a technique for simultaneous cleaning or cleanerless development.
No. 3, JP-A-62-203182, and JP-A-6-203182
JP-A-3-133179, JP-A-64-20587, JP-A-2-51168, JP-A-2-3027
No. 72, JP-A-5-2287, JP-A-5-2
No. 289, JP-A-5-53482, JP-A-5-53482
-61383. These known techniques use a corona, a brush, or a roller, and still have problems such as contamination of the surface of the photoreceptor due to discharge products and non-uniform charging, and have not been able to satisfy all requirements. for that reason,
A cleanerless technique using a so-called magnetic brush, which has a relatively small contact load to the photoreceptor and holds magnetic particles with a magnet body, as a charging member is being studied.

For example, Japanese Patent Application Laid-Open No. Hei 4-21873 proposes an image forming apparatus which does not require a cleaning device by using a magnetic brush to which an AC voltage having a peak value exceeding a discharge limit value is applied. ing. Further, Japanese Patent Application Laid-Open No. Hei 6-118855 proposes an image forming apparatus equipped with a magnetic brush electrification cleaning device without an independent cleaning device. Examples of magnetic particles used include iron, chromium, nickel, and cobalt. Such as metals or alloys or compounds thereof, ferric oxide, γ-ferric oxide, chromium dioxide, manganese oxide,
Ferrite, manganese-copper alloy, and those coated with styrene resin, vinyl resin, ethylene resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, or dispersed magnetic fine particles There are disclosures of particles and the like obtained by using a resin contained as a component.

However, there is room for study on the preferred form of the magnetic particles for charging, and there remains a technical problem from the viewpoint of magnetic particles suitable for the cleanerless method.

[0020]

As described above, there is a demand for a magnetic particle for charging having a suitable structure as a charging member, and a charging device, an image forming apparatus, and the like, which have uniform charging over a long period of time and have excellent durability. A process cartridge is desired. Also, in a cleanerless image forming method typified by a simultaneous development and cleaning method, an image forming apparatus that appropriately processes transfer residual toner and has high image quality is desired.

An object of the present invention is to provide magnetic particles for charging which are excellent in charging uniformity, prevent toner scattering and have excellent durability, and a charging member using the same, and mounted on a charging device. An object of the present invention is to provide an image forming apparatus and a process cartridge which achieve high image quality. Also,
An object of the present invention is to prevent abrasion of the photoreceptor, maintain high image quality as an image forming apparatus, and achieve a longer life of the photoreceptor. Still another object of the present invention is to provide a charging device and an image forming apparatus which are equipped with a cleaner-less system using a magnetic brush charging member and are stable over a long period of time.

[0022]

According to the present invention, there is provided a magnetic particle for charging comprising magnetic particles whose surface is treated with silicone oil, wherein the maximum chord length of the magnetic particles is 5 μm. The standard deviation of the ratio of the minor axis length to the major axis length (minor axis length / major axis length) of the above particles is 0.08 or more, and the volume resistivity is 1 × 10 ⁴ to 1 × 10 ^9. Ωcm, and the treatment amount of the silicone oil is not less than 0.0001% by weight and not more than 1% by weight based on the total amount of the magnetic particles.

The present invention also provides a conductive part to which a voltage is applied, a magnet having the conductive part on its surface, and the charging magnetic particles carried on the conductive part by the magnetic force of the magnet. A charging member having a charging member and a power supply for applying a voltage to the conductive portion, wherein the charging member faces an image carrier on which an electrostatic latent image is formed. And a charging device that contacts the image carrier and charges the image carrier.

Further, the present invention provides an image carrier on which an electrostatic latent image is formed on the surface, the charging device for charging the surface of the image carrier, and irradiating the charged image carrier with light. An exposure device that forms an electrostatic latent image; a developing device that supplies a developer to the surface of the image carrier to visualize the electrostatic latent image formed on the surface of the image carrier; and a developing device that visualizes the electrostatic latent image formed on the surface of the image carrier. A transfer device for transferring a latent image to a transfer material.

The present invention is also used in this image forming apparatus, and removes, from the image carrier, the charging device and at least the developer remaining on the image carrier, the developing device, and the transferred image carrier. The present invention provides a process cartridge integrally formed with at least one selected from the group consisting of cleaning devices that can be detachably attached to an image forming apparatus main body.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The charging magnetic particles of the present invention comprise magnetic particles whose surface has been treated with silicone oil. The magnetic particles include particles having a maximum chord length of 5 μm or more, and particles having a maximum chord length of 5 μm or more have a standard deviation of short axis length / long axis length, which is the ratio of the short axis length to the long axis length. 0.08 or more, and the volume resistance value is 10 ⁴ to 10 ⁹ Ωcm. The magnetic particles for charging of the present invention in which such magnetic particles are surface-treated with silicone oil are more effective in improving image quality and durability than the magnetic particles for charging described in the prior art.

In image formation, it is generally recognized that foreign matter such as toner, a free external additive, or paper powder is mixed into a charging member. As a result, (1) charging property accompanying durability And (2) toner scattering is known.

First, the causes of (1) include a decrease in contact between the charging member and the image bearing member (photoreceptor), an increase in resistance of the charging member, and the like. Good surface releasability due to surface treatment with oil, high surface cleaning performance between the magnetic particles for charging due to variation in shape due to the standard deviation of 0.08 or more, and high contact with the photoreceptor For this reason, when the charging member that carries the charging magnetic particles of the present invention on the surface is configured, the resistance of the charging member is prevented from rising even when particles and foreign substances are mixed and contaminated. Can be charged.

Next, the toner scattering (2) is a phenomenon in which the toner once mixed in the charging member scatters around the charging member. When scattering occurs, image quality may be degraded due to adhesion to the photoreceptor or inhibition of the exposure process. In the present invention, since the surface of the magnetic particles for charging is treated with silicone oil, toner scattering is prevented, and good image quality can be obtained.

It is known that toner scattering is related to an increase in transfer residual toner, high humidity conditions, high-speed rotation of a charging member, and the like. For example, when an image having a high image ratio is continuously formed, the amount of transfer residual toner increases, and the amount of toner mixed into the charging member may increase. Even in such a case, the charging magnetic particles of the present invention can prevent toner accumulation and surface contamination on the charging member due to their releasability, and can prevent toner scattering and resistance fluctuation of the charging member.

Under high humidity conditions, the chargeability of the toner is reduced by the influence of moisture, and the toner is liable to be scattered in the charging device. Since the magnetic particles for charging of the present invention have high contact properties, they exhibit an excellent effect of triboelectric charging to the toner, and can prevent toner scattering. Further, for example, even in a model having a high process speed such that the charging device performs charging while rotating on the photoconductor at a high speed, the effect of preventing accumulation and contamination of toner works effectively.

Further, in recent years, an image forming apparatus of a simultaneous development type (cleanerless) in which a cleaning apparatus for collecting transfer residual toner on a photoreceptor is removed has been commercialized. In this image forming apparatus, it has been considered that prevention of toner scattering, fluctuation of resistance, ghost image, and the like is more severe because the transfer residual toner always exists in the charging nip portion (the portion where the charging device and the photoconductor are opposed).

However, by using the magnetic particles for charging of the present invention, the toner remaining after transfer in the charging device is efficiently taken in and discharged, so that the toner is not accumulated, and at the same time, a good charge-imparting property for the toner is obtained. Prevents scattering. Further, in the present invention, the surface of the magnetic particles for charging has good releasability and a cleaning effect of the surfaces of the magnetic particles for charging can be obtained, and the contamination by the toner can be suppressed even after long-term use. Further, since the contact property between the magnetic particles for charging and the surface of the photoreceptor is high, the photoreceptor can be sufficiently charged even if the transfer residual toner component exists in the charging nip portion.

The operation and effect of the present invention will be exemplified by using an image forming apparatus of a reversal developing system equipped with a simultaneous developing cleaning system. This image forming apparatus (FIG. 1)
Photoconductor (image carrier) 1 having a photosensitive layer on a conductive substrate
0, a magnetic brush charging device (charging device) 20 for charging the photoconductor 10 by applying a voltage in contact with the photoconductor 10 and a latent image forming unit (exposure device) for forming an electrostatic latent image on the photoconductor 10 And 30, a cleaning means which is disposed close to or in contact with the photoreceptor 10 to develop the electrostatic latent image to form a toner image and collects transfer residual toner remaining on the photoreceptor 10 after transfer. Two-component developing device (developing device) 40, toner image from photoconductor 10 on paper (transfer material)
A transfer roller (transfer device) 50 for transferring the toner image to the paper 70, a transport belt 60 for transporting the paper 70 on which the toner image has been transferred to the next stage, a fixing device 80 for fixing the toner image transferred to the paper 70 to the paper 70, Etc.

FIG. 2 schematically illustrates the magnetic brush charging device 20. The magnetic brush charging device 20 includes a magnet roll (magnet body) 21 as a magnetic force generating member, a non-magnetic (SUS, aluminum, etc.) electrode sleeve (conductive sleeve) 22 rotatably provided on the outer periphery thereof, The surface of the sleeve 22 is made of magnetic particles (magnetic brush) 23 for charging, which is held by the magnetic force of the magnet roll 21 to form a magnetic brush.
4, a charging bias (applied voltage) is applied by a power supply (not shown). The electrode sleeve 22 is rotatably set by the frame 25. Charging is performed by DC voltage
C charging, AC charging in which an AC voltage is superimposed on a DC voltage, and the like are employed.

The magnetic brush is a rotatable electrode sleeve 2
2, the photosensitive member 10 is charged while rotating in the opposite direction or in the forward direction at an arbitrary peripheral speed difference while being in contact with the photosensitive member 10. Also, charging in a fixed state without rotation is possible. The amount of the charging magnetic particles 23 forming the magnetic brush is:
50-500mg / c to stabilize chargeability
m ² , preferably 100 to 300 mg / cm ² , and the magnetic brush charging device 20 may hold and circulate extra charging magnetic particles in the magnetic brush charging device 20.

In the case of the reversal developing method, the photoreceptor 10 is negatively charged by the magnetic brush charging device 20, exposed to form an electrostatic latent image, and then the toner charged to the same negative polarity as the photoreceptor charging polarity is subjected to reversal development. To form a toner image on the photosensitive member 10. This toner image is electrostatically transferred to the paper 70 by a positive transfer bias and becomes a copy image via the fixing device 80, but a part of the toner image remains on the photoreceptor 10 as transfer residual toner.

The transfer residual toner moves to the magnetic brush charging device 20 as the photoreceptor 10 rotates. Transfer residual toner is
The original negatively charged toner and the positively charged toner inverted to the positive polarity by the transfer exist in a non-uniformly mixed state.

Of the transfer residual toner, the positively charged toner is electrostatically attracted to the magnetic brush supplying negative charges near the charging nip formed by the magnetic brush and the photoconductor 10, and is taken into the magnetic brush. It is. The taken-in toner receives a negative charge from the charging magnetic particles 23 and is inverted to the same negative polarity as the charging polarity of the photoconductor 10. Since the magnetic particles for charging of the present invention have excellent contact properties between the magnetic particles for charging, the magnetic particles for charging can be efficiently contacted with the toner mixed therein. The toner whose polarity has been inverted is electrostatically ejected onto the photoconductor 10 from the charging nip using a potential difference from the photoconductor 10. As a result, the toner is not accumulated in the magnetic brush charging device 20 and the scattering of the toner is prevented.

By the way, in a high humidity state, it is easy for the toner to have a chargeability due to the presence of moisture. Since the taking-in and discharging of the toner is performed by the electrostatic action, the toner charging by the magnetic particles for charging is important. In the present invention, the surface of the magnetic particles is hydrophobized by treating the surface of the magnetic particles with silicone oil, so that the toner can be charged sufficiently even under high humidity conditions without the influence of moisture.

Further, since the toner charge can be made more uniform by the triboelectrification property of the silicone oil molecules, in addition to the effect of preventing the scattering and the fluctuation of the resistance, the effect of improving the recoverability of the toner in the two-component developing device 40 is also obtained. Can be

On the other hand, the transfer residual toner of the negative polarity passes through the charging nip portion while being dispersed by the charging magnetic particles 23. In the image forming apparatus, the magnetic particles for charging have excellent contact with the photoconductor 10, and even if such toner is present in the charging nip portion, the charging of the photoconductor is sufficiently performed and the ghost image is prevented. Since the chargeability of the toner is also made uniform, no scattering occurs and the recoverability in the two-component developing device 40 is good. Further, the transfer residual toner patterned on the photoreceptor 10 is sufficiently scattered by the electrostatic or mechanical action of the magnetic particles for charging and does not affect the exposure even when the image ratio is high. (Elimination of patterning). As described above, toner scattering is prevented even at high humidity,
Sufficient charging can be performed even at low humidity where charging is severe, so that good images can be obtained over a long period of time.

Here, the simultaneous development and cleaning is exemplified by the reversal development system, but the present invention is not limited to the reversal development system. For example, in the case of a regular development type image forming apparatus, a means for introducing a device for inverting the polarity of the toner between the charging device and the developing device is introduced, and the toner charging property is developed by frictional charging in the charging device. By using means for controlling the polarity of the toner, the effects of the present invention can be sufficiently exhibited.

In general, in the contact charging system, the surface of the photoconductor is rubbed when the charging member comes into contact with the photoconductor. For this reason, it has been reported that scratches and shaving unevenness occur on the surface of the photoreceptor, particularly when the photoreceptor is made of an organic material, but the magnetic particles for charging of the present invention are treated by silicone oil treatment. Lubricity is imparted, and an effect of preventing damage to the photoreceptor besides preventing contamination of the charging member is obtained. Therefore, by using the charging magnetic particles of the present invention, damage to the photoconductor can be eliminated, and the life of the photoconductor can be extended.

The silicone oil used in the present invention includes dimethyl silicone oil, silanol-terminated silicone oil, modified silicone oil modified by introducing various organic groups into the side chain or terminal, and methyl silicone having hydrogen introduced into the side chain. Hydrogen silicone oil or the like can be used.

Examples of the modified silicone oil include amino-modified, alcohol-modified, epoxy-modified, carboxyl-modified, methacryl-modified, phenol-modified, mercapto-modified, alkoxy-modified, polyether-modified, fatty acid ester-modified, alkyl-modified, styryl-modified, and fluorine-modified. The modified silicone oil is not limited to the modification with only a single type of substituent, and may be, for example, two or more substituents such as an amino group and an alkoxy group, and an amino group and an epoxy group. May be denatured.

In the present invention, it is preferable that the silicone oil binds to the surface of the magnetic particles and the oils bind to each other. For example, when the treatment amount is large, there is a concern that the flowability of the obtained magnetic particles for charging may be reduced if the proportion of unreacted substances is large. When the surface of the photoreceptor to be used is substantially a non-crosslinked resin, the unreacted processing agent may permeate the surface of the photoreceptor, causing clouding or cracking. Furthermore, it is desired that the magnetic particles for charging of the present invention can be imparted with stable triboelectric charging properties over a long period of time. Such silicone oils preferably have a reactive functional group, and include methyl hydrogen silicone oil, amino-modified silicone oil, alcohol-modified silicone oil, carboxyl-modified silicone oil, alkoxy-modified silicone oil, epoxy-modified silicone oil, Examples thereof include those in which the ends of dimethyl silicone oil are silanolized.

The treatment amount of the silicone oil used for the surface treatment of the magnetic particles in the present invention is preferably 0.0001 to 1% by weight based on the total amount of the magnetic particles. The amount of silicone oil processed is 0.0001
If the amount is less than 10% by weight, the effect of the silicone oil may not be recognized.
If the ratio exceeds the above range, the flowability of the magnetic particles for charging may be deteriorated, and the magnetic particles may not be practically used. In this sense, the processing amount of the silicone oil is more preferably 0.001% by weight or more and 0.5% or more.
% By weight or less is preferred. In the present invention, the treatment amount of the silicone oil is 1% by weight or less, preferably 0.5% by weight or less. Since a resistance value substantially equal to that of the magnetic particles not to be present can be obtained, the production stability and the quality stability are higher than when the conductive particle-dispersed resin is used for the surface treatment of the magnetic particles.

The surface treatment of the magnetic particles with silicone oil can be carried out according to a conventional method. For example, the above treatment amount is diluted with a solvent such as 2-butanone or toluene,
An example is a treatment method in which the magnetic particles are coated on the particle surface using a stirring device such as a mixer, the solvent is volatilized, and the coating is cured at about 120 to 150 ° C. for about 1 hour.

In the magnetic particles for charging of the present invention, for particles having a maximum chord length of 5 μm or more, the standard deviation of the ratio of the minor axis length to the major axis length (minor axis length / major axis length) of the particles is as follows. 0.0
It is important that it is 8 or more. The maximum string length is
The length of a straight line connecting the two most distant points on the surface of the magnetic particle, and the minor axis length and major axis length are the shape of the magnetic particle represented by a plane figure in a cross-sectional view, projection view, etc. Is the length of the short axis and the length of the long axis when is replaced with an ellipse by a method such as image analysis.

The minor axis length of particles having a maximum chord length of 5 μm or more /
If the standard deviation of the major axis length is less than 0.08, the variation in the shape is too small, and the contact with the photoreceptor and the surface cleaning property may not be sufficient. As described above, it is considered that the magnetic particles for charging have a shape of the magnetic particles suitable for the contact property and the cleaning property, thereby producing an effect. The standard deviation of the minor axis length / major axis length of particles having a maximum chord length in the range of 5 to 20 μm is 0.0.
When the particle size is 8 or more, the surface cleaning property of the larger magnetic particles becomes larger, which is a preferable configuration.
If it is 0 or more, the above effect is further improved, so that it is more preferable.

Here, a method of measuring the standard deviation of the minor axis length / major axis length of the magnetic particles will be described. To measure the standard deviation of the minor axis length / major axis length of magnetic particles, use Hitachi FE
-SEM (S-800) can be used, and 100 particle images magnified 500 times are extracted at random, and based on the image information, for example, limageAnalyzerV
10 (manufactured by Toyobo Co., Ltd.) and can be measured by performing statistical processing on the results of image analysis.

An example of the analysis will be described in detail. First, from an electron micrograph, an image signal that has passed through a stereomicroscope is input to an analyzer, and the image information is binarized. Next, the following analysis is performed based on the binarized image information. For details, there is a detailed description in the instruction manual of "lmageAnalyzer V10" (manufactured by Toyobo Co., Ltd.). That is to take the ratio of the height. The procedure is as follows.

For particles such as magnetic particles or toner,
When the specific gravity of the small area △ s = △ u · △ v at the coordinates (u, v) is set to 1 for the binarized shape, the binary value of the particle with respect to the origin (X, Y) through reduction centroids shape (second moment M _x in the horizontal axis, the second moment M _y in the vertical axis) the second moment about the horizontal and vertical axes, respectively M _x = ΣΣ (u- X) ² M _y = ΣΣ (v−Y) ² , the synergistic moment of inertia M _xy is M _xy = ΣΣ (u−X) · (v−Y), and the angle み in the following equation is Has two solutions.

(Equation 1) Furthermore, the moment of inertia M の in the axial direction that forms an angle と with the horizontal axis
_{Is, MΘ = M x · (cosΘ} ) 2 + M y · (sinΘ) 2 -M xy
· Sin2Θ, which is calculated by substituting the two solutions of the aboveΘ
The smaller of Θ is the main axis. Furthermore, on any axis,
When the points corresponding to (1 / MΘ) ^0.5 are plotted, they form an ellipse. If this principal axis coincides with the principal axis of inertia, the direction of taking a small value of MΘ is A, and the larger one is B, It becomes an ellipse. The ratio of the short axis length / long axis length in the ^{A · x 2 + B · y} 2 = 1 The present invention is to provide more elliptical, the minor axis length / long axis length ratio = (A / B) It can be represented by ^0.5 .

Particles having a maximum chord length in the range of 5 μm to 20 μm are found, for example, by searching for particles having a maximum chord length of 5 μm to 20 μm from the above electron micrographs, thereby obtaining a chargeable particle. The magnetic particles can be analyzed by the method described above.

The preferable average diameter of the magnetic particles for charging is in the range of 10 to 200 μm. When the average diameter of the magnetic particles for charging is smaller than 10 μm, the magnetic particles for charging are likely to leak from the charging member or the like, and the transportability of the magnetic particles for charging as a magnetic brush may be poor. On the other hand, if the average diameter of the magnetic particles for charging is larger than 200 μm, sufficient effects such as a decrease in uniform chargeability and a decrease in long-term durability may not be obtained.

The average diameter of the magnetic particles for charging is 40 μm when used in the injection charging method described later.
When the average particle diameter exceeds the above range, the charging uniformity in the injection charging method tends to be low. In view of these, the more preferable average diameter of the magnetic particles for charging is 15 to 30 μm.

The average particle size and particle size distribution of the magnetic particles for charging according to the present invention can be determined, for example, by using a laser diffraction type particle size distribution measuring apparatus HER.
Using 0S (manufactured by JEOL Ltd.), the minimum value is set to 0.5 μm, and the range of 1.80 μm to 350 μm is divided into 31 logarithms and measured, and the average diameter can be defined as a 50% volume median diameter.

As the magnetic particles used in the present invention, ferrite particles are preferably used. The magnetic particles used in the present invention can be produced by pulverizing a mass of ferrite, but it is preferable to pulverize the ferrite particles from the viewpoint of efficiency. A preferred method for producing magnetic particles is from 20 μm
A method of pulverizing 200 μm ferrite particles is exemplified. Ferrite compositions include copper, zinc, manganese,
Those containing a metal element such as magnesium, iron, lithium, strontium and barium are preferably used.

The magnetic particles may be used as they are after pulverizing while controlling the shape distribution, or may be used after being appropriately classified. Further, the magnetic particles, the particle size and shape can be changed by pulverizing the ferrite particles, and if necessary, mixed with magnetic particles having different shapes or magnetic particles having different particle sizes, or mixed with other particles. It is possible to adjust, for example, the standard deviation and the average diameter of the magnetic particles by such mixing. The fine powder generated by the pulverization is removed within the scope of the present invention by performing a classification step.However, the fine powder can be simultaneously coated by a step of coating silicone oil on the surface of the magnetic particles. A classification step can also be performed, and the effect of simplifying the step for removing fine powder can be obtained.

In the present invention, magnetic particles substantially having a ferrite composition are preferably used, and the heat loss of the magnetic particles is preferably 0.5% by weight or less. If the loss on heating of the magnetic particles is more than 0.5% by weight, the chargeability of the magnetic particles for charging is reduced, and a sufficient effect may not be obtained.

The loss on heating of the magnetic particles can be measured according to a conventional method, for example, by measuring the weight before and after the high temperature treatment by thermal analysis such as glass transition temperature (Tg).

The magnetic particles for charging of the present invention have a volume resistivity of 1 × 10 ⁴ Ωcm or more and 1 × 10 ⁹ or more.
It is important that the resistance is Ωcm or less. If the volume resistivity is lower than 1 × 10 ⁴ Ωcm, pinhole leakage may occur. If the volume resistance exceeds 1 × 10 ⁹ Ωcm, charging of the photoconductor may be insufficient. In the sense of preventing leakage of the charging magnetic particles, the volume resistance of the magnetic particles is
1 × 10 ⁶ Ωcm or more is more preferably used. Note that the volume resistance value of the magnetic particles can be adjusted to a suitable range by adjusting the types and proportions of substances such as metal elements contained in the magnetic particles.

To introduce an example of a method for measuring the volume resistance value of magnetic particles, a cell A shown in FIG. 3 is filled with magnetic particles, and electrodes 11 and 12 are arranged so as to be in contact with the magnetic particles.
A method of applying a voltage between the electrodes and measuring a current flowing at that time can be shown. The measurement conditions in this case were as follows: the contact area between the filled magnetic particles and the electrode was 2 cm ² , the thickness was 1 mm, and the load on the upper electrode was 10 k in an environment of 23 ° C. and 65%.
g, the applied voltage can be 100V. Note that 13
Is a guide ring which is a member for guiding the electrodes 11 and 12, 14 is an ammeter for measuring a current flowing between the electrodes, 1
5 is a voltmeter for measuring the voltage between the electrodes, 16 is a constant voltage device for applying a voltage between the electrodes, 17 is a measurement sample, 1
Reference numeral 8 denotes an insulator that insulates the periphery of both electrodes during measurement.

Further, the preferred volume resistance distribution of the present invention is:
The difference is that the difference in volume resistance between the magnetic particles having a relatively small particle size and the magnetic particles having a relatively large particle size is small. For example,
When the volume resistance value of the magnetic particles having a relatively small particle diameter is lower than 1/10 of the volume resistance value of the magnetic particles having a relatively large particle diameter, when an oscillating voltage is applied to the charging member, particularly in a low humidity environment. In this case, the magnetic particles for charging having a relatively small particle diameter and a low resistance have a strong tendency to fall off from the charging member. In particular, in the case of the cleaner-less image forming method, the tendency to drop off is even stronger.

Furthermore, the particle diameter is relatively close and the volume resistance value is 1
When magnetic particles different by more than an order of magnitude are mixed and used, during use, the charging magnetic particles having a low resistance are biased toward the surface of the photoreceptor, and pinhole leak tends to occur due to the bias of the low-resistance particles.

Preferably, in the magnetic particles, when the volume resistance of particles having a maximum chord length in the range of 5 μm to 20 μm is Ra, and the volume resistance of particles having a maximum chord length exceeding 20 μm is Rb, 0.5 ≦ Ra / Rb ≦ 5.0, more preferably 1.0 ≦ Ra / Rb ≦ 5.0. When the volume resistance value is in such a range,
The volume resistance value of the magnetic particles having a relatively small particle size and the magnetic particles having a relatively large particle size is preferable, and as described above, the drop of the magnetic particles for charging from the charging member and the pinhole leak are more reduced. It is preferable in suppressing.

In the measurement of the volume resistivity of the magnetic particles, when the particles in the range of 5 μm to 20 μm are separated from the particles exceeding 20 μm, the following separation methods can be exemplified. That is, the mesh size is 5 μm
And prepare a 20 μm sieve. These sieves
It has a size of Φ75mm × H20mm.
It is preferable that the method of forming the openings of m or 20 μm can be adjusted by increasing the wire diameter of the sieve by plating or the like as necessary. Next, open from above, 25μ
m, 20 μm, 5 μm
0.5 g of magnetic particles is placed on a sieve having a size of 0.5 μm and sufficiently vibrated to collect magnetic particles having a 20 μm pass and a 5 μm ON. Further, what was left on the 5 μm sieve was further subjected to 1961P
The particles in the 5 μm pass are removed by a differential pressure a (200 mmAq). This sample is used for measuring the volume resistivity of particles in the range of 5 μm to 20 μm. To measure the volume resistivity of particles exceeding 20 μm, two of the above sieves are used.
The magnetic particles on 0 μm and 25 μm are mixed to form a sample.

The charging member of the present invention has a conductive portion to which a voltage is applied and a magnet having the conductive portion on the surface, and the above-described charging magnetic particles are formed on the conductive portion. An excellent charging member can be constituted by carrying the particles by magnetic force.

Although various forms are known for the charging member, the charging member of the present invention is arranged such that the charging member is close to or in contact with the photosensitive member, and the magnetic particles for charging contact the photosensitive member. It is preferable to charge the photoreceptor in order to exhibit the advantage of the magnetic particles for charging, and as such a charging member,
For example, a magnetic brush charging member in which the conductive portion is formed of a cylindrical conductive sleeve containing a magnet body can be exemplified. This charging member may have a configuration in which the magnet body and the conductive portion rotate integrally, but more preferably a configuration in which the conductive portion rotates relative to the magnet body.

A charging device according to the present invention includes the charging member described above and a power supply for applying a voltage to the conductive portion, and is opposed to an image carrier (photoreceptor) on which an electrostatic latent image is formed. The charging member is disposed, and the charging member contacts the photoconductor and charges the photoconductor. In the charging device of the present invention, the injection charging method can be preferably used.

In the charging device of the present invention, the durability of the charging device can be further extended by increasing (supplying) and circulating the magnetic particles for charging in the charging device. Further, by using a magnet having an appropriate magnetic force as a magnet body of the charging member, or by disposing a charged particle regulating member that regulates the amount of magnetic particles for charging adhered to the conductive portion, the conductive member can be electrically conductive. The amount and density of the magnetic particles for charging on the conductive portion can be made appropriate.

Means for circulating the magnetic particles for charging may be mechanical stirring, a magnetic pole structure capable of circulating the magnetic particles for charging, or magnetic particles for charging in the container storing the magnetic particles for charging. It is preferable to provide a member for moving the member. As such a member, for example, a screw member provided behind the magnetic brush for stirring the magnetic particles for charging, or a configuration in which a repulsion pole is provided and the recoating is performed while peeling off the magnetic particles for charging,
Providing an obstruction member or the like that obstructs the flow of the magnetic particles for charging in the charging device may be provided.

In the injection charging method, a conductive substrate, a photosensitive layer formed on the conductive substrate, and a charge formed farthest from the conductive substrate so as to form the outermost surface of the photosensitive member. By using a photoreceptor having an injection layer,
With respect to the application of the DC voltage from the charging device, a charging potential of 80% or more, and even 90% or more can be obtained.

Further, by the injection charging method, a further ozone-less charging method can be realized in comparison with the charging method (charging method using discharge) interpreted according to Paschen's law. At the time of exposure, it plays a role of more efficiently releasing the charged charges to the conductive substrate, and can reduce the residual potential. Therefore, it is possible to obtain the effect of suppressing the fluctuation of the contrast and obtaining a uniform image.

As the power source for applying a voltage to the photosensitive member, a known power source can be used. Examples of the power source voltage include a DC voltage and a DC voltage with an AC voltage (oscillation voltage) superimposed thereon. Etc. can be exemplified,
In particular, it is preferable that an AC voltage (oscillating voltage) is superimposed on a DC voltage, and stable charging can be obtained against disturbances such as mechanical accuracy due to the oscillating voltage.

In the injection charging method, since the potential of the photosensitive member follows the applied voltage, if the peak-to-peak voltage is too large, the potential of the charged surface of the photosensitive member may undulate, causing image fogging and the like. . Therefore, the applied oscillation voltage is 1
The frequency is preferably about 00 Hz to 10 kHz, and the peak-to-peak voltage is preferably 1000 V or less, more preferably 100 V or more and 1000 V or less.
More preferably, it is 300 V or more and 1000 V or less. As the waveform, a sine wave, a rectangular wave, a sawtooth wave, or the like can be used.

The charge injection layer of the photoreceptor can be made of a material having a medium resistance by dispersing an appropriate amount of light-transmitting and conductive particles in an insulating binder resin. Forming an inorganic layer having the same is also an effective means. In the case where the charge injection layer is formed at the position farthest from the conductive substrate, the volume resistivity of the charge injection layer is as follows. 1 × 10 ⁸ Ωcm to 1 × 10 ¹⁵ Ωc
It is preferably in the range of m. Volume resistance value is 1 × 10
If it is smaller than ⁸ Ωcm, the electrostatic latent image cannot be held,
In a high-temperature and high-humidity environment, image deletion may occur, and if the resistance value exceeds 1 × 10 ¹⁵ Ωcm, sufficient charge from the charging member cannot be sufficiently received, and poor charging may occur.

More preferably, the volume resistivity is from 1 × 10 ¹⁰ Ωcm to 1 × 1 from the viewpoint of image deletion under high temperature and high humidity conditions.
0 ¹⁵ [Omega] cm, when also considering more rapid environmental change, etc., the volume resistivity of the charge injection ^{layer, 1 × 10 12 Ωcm~1 × 10} 15
It is preferably Ωcm. The volume resistance value of the charge injection layer can be adjusted by the type and amount of the material used, such as the binder resin and the conductive particles.

Here, the method of measuring the volume resistance of the charge injection layer is not particularly limited as long as the volume resistance of the layered sample can be measured. For example, polyethylene having a conductive film deposited on the surface thereof may be used. A charge injection layer is formed on a terephthalate (PET), and the charge injection layer is measured by applying a voltage of 100 V at 23 ° C. and 65% environment using a volume resistance measuring device (4140B pAMATOR manufactured by Hewlett-Packard Company). The method can be illustrated.

The particle size of the conductive particles dispersed in the charge injection layer is preferably 0.3 μm or less, more preferably 0.1 μm or less from the viewpoint of light transmission. The amount of the conductive particles is 2 to 2 parts by weight based on 100 parts by weight of the binder resin.
It is 50 parts by weight, preferably 2 to 190 parts by weight. If the amount is less than 2 parts by weight, a preferable volume resistance value of the charge injection layer may not be obtained, and if it exceeds 250 parts by weight, the film strength tends to decrease, and the charge injection layer may be easily scraped. The thickness of the charge injection layer is preferably 0.1 to 0.1.
It is 10 μm, more preferably 1 to 7 μm.

Preferably, the charge injection layer contains a lubricant powder. The expected effect is that the friction between the photosensitive member and the charging member during charging is reduced, the nip involved in charging is enlarged, and the charging characteristics are improved. Further, since the releasability on the surface of the photoconductor is improved, the magnetic particles for charging are less likely to adhere. In particular, as the lubricant particles, it is preferable to use a fluororesin, a silicone resin, or a polyolefin resin having a low critical surface tension. Particularly preferably, a tetrafluoroethylene resin is used. In this case, the amount of the lubricant powder added is preferably
2 to 50 parts by weight, more preferably 5 parts by weight,
４０40 parts by weight. When the amount is less than 2 parts by weight, the amount of the lubricant powder is not sufficient, so that the effect of improving the chargeability of the photoreceptor is not sufficient, and the transfer residual toner may increase from the viewpoint of a cleanerless device. If it exceeds 50 parts by weight,
The resolution of the image and the sensitivity of the photoconductor may decrease.

In the photoreceptor, when the surface layer is coated with an inorganic layer, the photoconductive layer (photosensitive layer) thereunder is preferably amorphous silicon, and is formed on a cylinder (conductive base) by glow discharge or the like. Preferably, a blocking layer, a photoconductive layer and a charge injection layer are sequentially formed.

As the photosensitive layer, conventionally known ones can be used. For example, if it is an organic material, a fluorinated cyanine pigment, an azo pigment or the like can be used. Further, the photoreceptor, in addition to the charge injection layer and the photosensitive layer described above, a layer having another function, for example, to enhance the adhesion between the protective layer and the photosensitive layer between the surface protective layer and the photosensitive layer, Alternatively, an intermediate layer intended to function as a charge barrier layer can be exemplified. As the material of the intermediate layer, for example, commercially available resin materials such as epoxy resin, polyester resin, polyamide resin, polystyrene resin, acrylic resin, and silicone resin can be used.

Specific examples of the conductive substrate for the photoreceptor include metals such as aluminum, nickel, stainless steel and steel, plastics or glass having a conductive film, and conductive paper. The material of the above-described layer formed on the photoreceptor is not particularly limited as long as it has a desired function, in addition to the materials exemplified above, and is made of an organic material. It may be made of an inorganic material, or may contain both of them.

In the present invention, when the voltage applied by the power supply is a DC voltage on which an oscillating voltage is superimposed, it is possible to reduce the vibration noise caused by the oscillating electric field. One reason for this is that vibrations are absorbed by variations in the shape of the magnetic particles for charging. Further, when the thickness of the peripheral surface of the conductive substrate of the photoreceptor is 0.5 mm or more and 3.0 mm or less, the effect of absorbing the vibration is remarkable. If the thickness of the conductive substrate is smaller than 0.5 mm, the dimensional stability may be insufficient. If the thickness of the conductive substrate exceeds 3.0 mm, the rotational torque increases and the material cost increases. This can be costly.

The image forming apparatus of the present invention comprises the above-described photoreceptor, the above-described charging device, an exposure device for irradiating the charged photoreceptor with light to form an electrostatic latent image, and a method for applying a developer to the photoreceptor. The developing device includes a developing device that supplies the electrostatic latent image to visualize the image and a transfer device that transfers the visualized electrostatic latent image (toner image) to a transfer material such as paper or OHP.

As the exposure apparatus used in the present invention, known means such as a laser and an LED can be used.

As the developing device used in the present invention, a known device can be used, and may be a developing device capable of supplying a one-component developer to a photoreceptor, or a two-component developer. It may be a developing device that can be supplied to the body. As the developing device, more specifically, a developing device that opens to face the photoconductor and stores the developer therein, and a developing device that is provided at the opening of the developing device and is arranged to face the photoconductor and A developing device having at least a developing roller for supplying the developer to the photoconductor and a regulating member for regulating the amount of the developer carried on the developing roller can be exemplified. Particularly preferred developing devices in the image forming apparatus of the present invention include, for example,
An example of a developing device for simultaneous development and cleaning capable of collecting the transfer residual toner on the photoreceptor can be exemplified.

This developing device utilizes the potential difference of the developing bias applied between the developing roller and the photosensitive member,
A developing device capable of supplying the developer from the developing device to the photoconductor and collecting the transfer residual toner from the photoconductor to the developing roller by the potential difference is used. In the present invention, since the above-described magnetic particles for charging are used, the charging device can uniformly charge the photosensitive member, and can uniformly charge the transfer residual toner. The transfer residual toner can be efficiently collected in the developing device. With such a configuration, a cleaning device for removing transfer residual toner from the photoreceptor becomes unnecessary, which is advantageous for miniaturization of the image forming apparatus, is also advantageous for preventing the photoreceptor from being scraped, and is advantageous in developing. It is also advantageous for effective use of the agent.

The developing method used in the image forming apparatus of the present invention is not particularly limited. However, in the case of the image forming apparatus of the simultaneous cleaning type without the cleaning device, reversal development is preferable. It is preferable that the roller and the photoconductor are in contact with each other. For example, a contact two-component development method, a contact one-component method and the like are mentioned as suitable development methods. When the developer on the developing roller and the transfer residual toner can come into contact with each other on the photoreceptor, in addition to the electrostatic action, a rubbing force is applied, and the recoverability of the transfer residual toner is improved. Further, regarding the developing bias applied to the developing,
The C component is preferably between the black portion (image exposed portion) and the potential of the white background portion.

The developer may be a two-component developer or a one-component developer. However, in the case of using a developing device capable of simultaneous development and cleaning, the transfer residual toner is charged by a charging device. Is preferable, and there is a preferable range in the triboelectric charging property between the used toner and the magnetic particles for charging. The range means the toner charge amount (tribo value) measured by the ratio of the used toner 7 to the charging magnetic particles 100 of the present invention.
Is the same as the charging polarity of the photoconductor, and its absolute value is 1 to
It is 90 mC / Kg. Preferably, 5 to 80 mC / K
g, more preferably 10 to 40 mC / Kg, and the toner charge amount in such a range is suitable for taking in and discharging the transfer residual toner in the charging device and charging characteristics of the photoconductor. .

As a method of measuring the toner charge amount, for example, a mixture obtained by adding 200 mg of toner to 40 g of magnetic particles for charging under an environment of 23 ° C. and a relative humidity of 60% is used.
Put in a polyethylene bottle of 0-100 ml capacity
Take a seismic image by hand, load the mixture of toner and magnetic particles for charging as magnetic particles for the charging member, then load a metal drum of the same size as the photoreceptor to be used, and load a DC with the same polarity as the toner charging polarity. An example is a method in which a bias is applied to a charged portion, the photosensitive member is driven under the conditions for charging, and the charge amount of the toner transferred from the charging member onto the metal drum is measured.

As the transfer device used in the present invention, a known method such as a belt and a corona transfer device is used in addition to the rollers described above.

In the image forming apparatus of the present invention, in addition to the above-described apparatuses and the like, other apparatuses can be included as constituent elements. As such a device, for example, the cleaning device can be exemplified. In the case of using a developing device capable of simultaneous cleaning with the development, for example, the photosensitive member after the transfer process and before the charging process is used. An example of a photoconductor potential control member that works is provided. By attaching the photoconductor potential control member, the stability of image formation is improved, and it is particularly effective in the simultaneous development cleaning system.

As the photosensitive member potential control member, ordinary means for controlling the charging of the photosensitive member can be used. For example, a member that emits light to control the photosensitive potential, or a conductive member disposed in contact with or in close proximity thereto Rollers, blades, fur brushes and the like can be exemplified, and rollers and fur brushes are particularly preferred. In the case where a voltage is applied to these members to control the potential of the photoconductor, it is preferable that the polarity is controlled to be opposite to that of the charging step by the charging device. The reason is that the photoconductor potential is adjusted to a lower side before the charging step, and the history of the preformed image is erased to assist the charging uniformity.

When the transfer residual toner is transferred from the charging member from which the transfer residual toner has been recovered to the developing portion by using the surface of the photoreceptor and collected and reused, the charging bias (applied voltage) for charging the photoreceptor is changed. Although it is feasible even if it is not used, it is conceivable that an excessive amount of toner may be mixed into the charging member in the case of transfer paper jam or when continuously taking images with a high image ratio.

In this case, during the image forming operation, it is possible to move the toner from the charging member to the developing device by utilizing a portion where no image is formed on the photosensitive member. In this case, the toner can be moved to the photoreceptor at the time of pre-rotation, post-rotation, or between transfer sheets. Also in this case,
It is also preferable to change the charging bias so that the toner is more easily transferred to the photosensitive member than the charging member. As a method of applying a bias that makes it easier for toner to come out of the charging member, the AC component is set to a smaller peak-to-peak voltage or is made a DC component, or the peak-to-peak voltage is made the same, and the waveform is changed to change the AC effective There is a method of lowering the value.

In the present invention, a process cartridge which is used in the image forming apparatus and is based on the charging device can be constituted. This process cartridge, in addition to the charging device, at least the photoconductor, the developing device,
And one or more members selected from the group consisting of the cleaning devices are integrally configured and detachably mounted to the image forming apparatus main body.

The process cartridge takes into consideration the characteristics of each device used in the image forming apparatus, the type of developer used, the image forming method to be adopted, or the expected degree of consumption of the developer and the like. Thereby, each device can be configured in combination. Examples of such a combination include a charging device and a photoconductor, a charging device and a developing device, a charging device and a cleaning device, a charging device and a photoconductor and a developing device, a charging device and a photoconductor and a cleaning device, and a charging device and a developing device. And a cleaning device. Each of these devices is configured to be integrally supported by a support member made of, for example, plastic, and the support member is configured to be detachable from the image forming apparatus main body, so that the process cartridge of the present invention is provided. Can be configured as

[0101]

EXAMPLES Examples of the present invention are shown below, and the present invention will be described more specifically. First, an example of the production of magnetic particles will be described below as an example of the configuration, material, production method and the like of the member used in the present invention.

[Production Example 1 of Magnetic Particles] Fe ₂ O ₃ (55 mol%), CuO (22 mol%), ZnO (23 mol%)
After adding 0.06 parts by weight of phosphorus to an oxide containing as a main component and pulverizing and mixing, water, a dispersant, and 1% by weight of polyvinyl alcohol as a binder were added to form a slurry. The slurry is granulated by a spray drier method.
By baking at 150 ° C., CuZn ferrite was obtained.
After firing, the powder was crushed and classified to obtain spherical particles having an average diameter of 52 μm. The standard deviation of the minor axis length / major axis length of the magnetic particles was 0.06, and the magnetization at 8 × 10 ⁴ A / m (1 KOe) was 60 Am ² / kg (57 emu / g). The heat loss of the magnetic particles was 0.2% by weight. This is designated as Magnetic Particle 1.

[Production Example 2 of Magnetic Particles] The magnetic particles 1 were pulverized by a vibration mill and deformed, and then the fine powder was cut to obtain magnetic particles having an average diameter of 30 μm. This is referred to as “magnetic particles 2”.

[Magnetic Particle Production Examples 3 and 4] In the magnetic particle production example 2, the classification conditions on the coarse powder side were changed, and the average diameter was 25 μm.
m and 20 μm magnetic particles were obtained. These are referred to as magnetic particles 3 and 4, respectively.

[Magnetic Particle Production Example 5] The amount of phosphorus added was 1.
Ferrite was produced in the same manner as in Magnetic Particle Production Example 1 except that the amount was 5 parts by weight. As a result, sintering of the particles progressed, and a ferrite mass having high bulkiness was obtained. This was crushed by a hammer mill and further crushed by a vibration mill, and then fine powder and coarse powder were cut to obtain magnetic particles 5 having an average diameter of 35 μm. The loss on heating of the magnetic particles was 0.2% by weight.

[Production Example 6 of Magnetic Particles] After pulverizing and mixing Fe ₂ O ₃ (55 mol%), MnO (30 mol%), and MgO (15 mol%), water, a dispersant, and a binder were used. A slurry was prepared by adding 1% by weight of polyvinyl alcohol. The slurry was granulated by a spray drier method and fired in an electric furnace with an adjusted oxygen partial pressure to obtain MnMg ferrite. After firing, crushing and classification were performed to obtain spherical particles of about 45 μm. This is pulverized by a vibration mill to deform the particles, and then the fine powder and the coarse powder are cut, and the average diameter is 26 μm.
m of magnetic particles 6 were obtained. 8 × 10 ⁴ A / m (1 KOe)
Is 60 Am ² / kg, which is the same level as that of the magnetic particles 1.
(57 emu / g). The heat loss of the magnetic particles was 0.15% by weight.

[Production Example 7 of Magnetic Particles] In Production Example 6 of magnetic particles, the classification conditions on the coarse powder side were changed to obtain magnetic particles having an average diameter of 15 μm. This is magnetic particles 7.

[Magnetic Particle Production Example 8] The magnetic particles 2 were treated with methyl hydrogen silicone oil (manufacturer: Shin-Etsu Silicone) in which a part of the methyl group in the side chain of dimethyl silicone oil was substituted with hydrogen. For the treatment, 100 parts by weight of magnetic particles and 0.1 part by weight of a silicone oil diluted with a 2-butanone solvent were added to a NOWA mixer, followed by heating and mixing at 60 ° C. After evaporating the solvent, 150
C. for 1 hour to cure the surface. Before and after processing
No remarkable difference was recognized in the particle size and the resistance value. This is designated as magnetic particles 8.

[Magnetic Particle Production Examples 9 and 10] The magnetic particles 3 and 7 were treated with amino-modified silicone oil having amino groups introduced at both ends of dimethyl silicone oil (manufacturer: Shin-Etsu Silicone). For the treatment, 100 parts by weight of magnetic particles and 0.1 part by weight of a silicone oil diluted with a 2-butanone solvent were added to a NOWA mixer, followed by heating and mixing at 60 ° C. After the solvent was evaporated, it was heated at 130 ° C. for 1 hour using a dryer to cure the surface. These are referred to as magnetic particles 9 and 10, respectively.

[Production Example 11 of Magnetic Particles] To 100 parts by weight of magnetic particles 4, 0.1 part by weight of alcohol-modified silicone oil (manufactured by Shin-Etsu Silicone) diluted with a 2-butanone solvent was added, and the same as in Production Example 9 of magnetic particles. The magnetic particles 11 were obtained by performing the above steps.

[Production Example 12 of Magnetic Particles] The magnetic particles 5 were treated with an alkyl-modified silicone oil (manufacturer: Shin-Etsu Silicone) in which part of the methyl group in the side chain of dimethyl silicone oil was substituted with an alkyl group having 4 or more carbon atoms. . Except that the treating agent and the magnetic particles were changed, the same procedure was performed as in the case of the magnetic particle production example 9 to obtain magnetic particles 12.

[Magnetic Particle Production Example 13] A magnetic particle 6 was obtained by treating a magnetic particle 6 with a silicone oil (manufacturer: Shin-Etsu Silicone) modified with a different functional group of an amino group and an alkoxy group. Table 1 shows the physical properties of the obtained magnetic particles 1 to 13.

[0113]

[Table 1]

Next, an example of manufacturing a photoconductor (image carrier) will be described below. [Photoreceptor Production Example 1] An OPC photoreceptor was prepared by laminating a photosensitive layer on a φ30 mm aluminum cylinder, and a charge injection layer was provided on the outermost surface. The laminated layers are the first, second, third, fourth and fifth layers (charge injection layer) in order from the aluminum cylinder.
It is. The first layer is an undercoat layer. In order to smooth the defects of the aluminum cylinder and to prevent the occurrence of moire due to the reflection of the laser exposure, a 20 μm conductive film made by dispersing conductive titanium oxide in a phenol resin was provided. The second layer is a positive charge injection prevention layer. In order to prevent the positive charge injected from the aluminum cylinder side from canceling out the negative charge charged on the surface of the photoreceptor, a layer made of amylan resin adjusted to 6 × 10 ⁶ Ωcm and methoxymethylated nylon is formed to about 1 μm did. The third layer is a charge generation layer. In order to generate positive and negative charge pairs by laser exposure, a resin layer in which a disazo pigment was dispersed was formed to a thickness of about 0.5 μm. 4th
The layer is a charge transport layer. Hydrazone was dispersed in a polycarbonate resin to form a P-type semiconductor layer. This layer has a function of transporting positive charges generated in the charge generation layer to the surface of the photoconductor, and negative charges charged on the surface of the photoconductor cannot move through this layer. The fifth charge injection layer is a conductive resin layer in which tin oxide is dispersed in a photocurable acrylic resin. Tin oxide is ultrafine particles having an average diameter of about 0.03 μm which is made conductive by doping with antimony, and 150 parts by weight are dispersed with respect to 100 parts by weight of the photocurable acrylic resin. The resistance is 8.5 × 10 ¹² Ωcm. In the charge injection layer, 15 parts by weight of polytetrafluoroethylene resin particles and 1 part by weight of a dispersant were dispersed for the purpose of improving the surface slipperiness. This is designated as Photoconductor 1.

Next, a production example of the developer will be described below. [Developer Production Example 1] 100 parts by weight of a polyester resin, 2.0 parts by weight of a metal-containing azo dye, and low molecular weight polypropylene 3.
After 5 parts by weight and 4.5 parts by weight of carbon black were dry-mixed, they were kneaded by a twin-screw kneading extruder set at 150 ° C. The obtained kneaded product was air-cooled, finely pulverized by an air-flow type pulverizer, and then subjected to air classification to adjust the particle size distribution. 1.5 parts by weight of hydrophobized titanium oxide was externally added to 100 parts by weight of the classified product to prepare a toner having a weight average particle diameter of 7.5 μm. A developing carrier 10 obtained by coating this toner with nickel zinc ferrite having an average diameter of 60 μm and a silicone resin.
Developer 1 was obtained by mixing 6 parts by weight with respect to 0 parts by weight.

[Developer Production Example 2] 100 parts by weight of styrene, 18 parts by weight of n-butyl acrylate, 5 parts by weight of low molecular weight polypropylene, 6 parts by weight of carbon black, 2.5 parts by weight of a metal-containing azo dye, and an azo initiator And 50 parts by weight of pure water in which calcium phosphate was dispersed.
In addition to 0 parts by weight, the mixture was dispersed by a homomixer, and finally polymerized at 70 ° C. for 11 hours while gradually increasing the temperature. This was filtered and washed, and then dried and classified. To this classified product (100 parts by weight), hydrophobically treated titanium oxide (1 part by weight) and hydrophobically treated silica (1 part by weight) were externally added to prepare a toner having a weight average diameter of 6.5 μm. 6 parts by weight of this toner was mixed with 100 parts by weight of a developing carrier obtained by coating an acryl-modified silicone resin on nickel zinc ferrite having an average diameter of 60 μm to obtain a developer 2.

Next, an example of the image forming apparatus will be described below, and a method of evaluating an image formed by the image forming apparatus will be described.

[Example of Image Forming Apparatus] First, a digital copying machine (GP55, manufactured by Canon Inc.) using a laser beam was prepared as an image forming apparatus. The GP 55 is provided with a corona charger for charging, a one-component developing unit employing a one-component jumping developing method for development, and a corona charger, a blade cleaning unit, and a pre-charging exposure unit for transfer. The charger, the cleaning means, and the photoreceptor are an integrated unit. The process speed is 150 mm / s. This example was modified as described below, and this example was performed. (1) Process speed; set to 200 mm / s. (2) Developing device: A two-component developer was modified so that it could be used, and simultaneous cleaning with development was made possible. The developing bias is −
A rectangular wave of 1000 Vpp / 3 KHz is superimposed on a DC component of 500 V. (3) Charging device: As shown in FIG. 2, a 16φ conductive non-magnetic sleeve containing a magnet roller was provided. This conductive sleeve has a coating density of 180 mg / cm
^The magnetic particles produced in the above Production Example were supported so as to be ² . The magnetic brush charger was rotated in the direction opposite to the rotation of the photoreceptor, and the rotation peripheral speed of the charger was set to 240 mm / s. The charging bias is 1 KH at a DC voltage of -700 V.
z, a rectangular wave oscillation voltage of 700 Vpp is superimposed. The gap between the conductive sleeve and the photoconductor was set to 0.5 mm. (4) Transfer means: Changed to a roller transfer method, and removed the pre-charge exposure means. (5) Cleaner; remove the cleaning blade,
The developing simultaneous cleaning type copying apparatus was used.

Next, an evaluation method will be described. 6% manuscript A4 landscape feed, 20k sheets (20,000 sheets) continuous image output
Image fog on paper and fine line reproducibility were evaluated, and uniform charging property and image definition were confirmed. Further, for the purpose of evaluating toner scattering, 5k sheets (5
(000 sheets), continuous image formation was performed, and the image fog was reevaluated. At the same time, the flying state of each of the charged member, the photosensitive member, and the periphery of the exposure after the endurance was visually evaluated. After the endurance, the developing device was removed, the toner was discharged from the charging member to the photosensitive member, the charge amount of the discharged toner was measured, and the control state of the toner charging property was investigated. Further, the state of surface scraping and flaws of the durable photoreceptor was measured. The endurance environment is 30 ° C./80% relative humidity (H /
H), 23 ° C./relative humidity 60% (N / N), 15 ° C./relative humidity 10% (N / L).

In the image fog evaluation, JISZ8722
Using a reflection densitometer (TC-6MC, Tokyo Denshoku Technical Center) based on the (0-45 degree method), the difference (%) before and after image formation was calculated and judged by fog density. Tables 2 to 5 show the evaluation levels of image fogging, fine line reproducibility, in-machine scattering state, and photoreceptor abrasion, respectively. A fog of less than 2% is judged as having no practical problem.

[0121]

[Table 2]

[0122]

[Table 3]

[0123]

[Table 4]

[0124]

[Table 5]

Example 1 A magnetic brush charging device composed of magnetic particles 9 surface-treated with amino-modified silicone oil and a developer 2 (polymerized toner) were mounted on the above-described image forming apparatus, and image durability was performed in each environment. Was. As a result, 6% image 2
At 0k sheet durability, image fogging and fine line reproducibility were maintained at the initial level, and there was no problem with toner scattering and scratches and scraping of the photoreceptor.

Next, when the 6% image was changed to the 10% image and the durability of 5k sheets was continuously performed, toner scattering was prevented even in the H / H environment where toner scattering is likely to occur.
Uniform charging was performed even in an N / L environment. Table 6 shows the evaluation results for the 10% image. Further, the discharged toner is controlled to have the same polarity as the developing toner. Furthermore, no image disturbances due to scratches on the photoreceptor and uneven shavings were found.

As described above, there was no image disturbance due to the transfer residual toner as a whole, toner scattering and image fogging were suppressed, and high-definition image quality was achieved. Longer life was also achieved by preventing photoconductor damage.

[Examples 2 to 5] The same durability evaluation was performed as in Example 1, except that the magnetic particles 9 were changed to magnetic particles 10, 8, 13, and 11. Table 6 shows the evaluation results. As a result, the polarity of the transfer residual toner was controlled to be the same as that of the developing toner, toner scattering and image fogging were prevented, fine line reproducibility was good, and high image quality similar to that of Example 1 was achieved. Photoreceptor damage was similarly prevented.

Example 6 The same durability evaluation was performed as in Example 1, except that the magnetic particles 9 were changed to the magnetic particles 12. Table 6 shows the evaluation results. As a result, the polarity of the discharged toner is controlled to be the same as that of the developing toner in all environments. In the H / H environment, the value of the toner charge amount was slightly reduced, but the toner was scattered to such an extent that adhesion was partially observed. Was done. In other environments, toner scattering,
Image fog and fine line reproducibility were at the same level as in Example 1, and high image quality was achieved. Photoreceptor damage was similarly prevented.

Comparative Example In Example 1, magnetic particles 9
Was changed to the magnetic particles 1 and the same durability evaluation was performed. Table 6 shows the evaluation results. As a result, 6% image 2
Although some toner scattering was observed at 0k sheet durability, image fogging was at a level at which there was no practical problem. Next, when the durability of 5k sheets of 10% image was continued, toner scattering frequently occurred, and the image force blur exceeded 2%. In the photoreceptor, image quality deterioration due to shaving unevenness is partially confirmed, and the life of the photoreceptor has not been attained.

[0131]

[Table 6]

[0132]

According to the present invention, there is provided a magnetic particle for charging comprising magnetic particles whose surface is treated with silicone oil,
Among the magnetic particles, the standard deviation of the ratio of the minor axis length to the major axis length (minor axis length / major axis length) of particles having a maximum chord length of 5 μm or more is 0.08 or more, and the volume resistance value is 1 × 10 ⁴ -1 ×
The charging amount of the magnetic particles is 10 ⁹ Ωcm, and the amount of the silicone oil to be treated is 0.0001% by weight or more and 1% by weight or less based on the total amount of the magnetic particles. In each of the environmental conditions, charging was made uniform and toner scattering was prevented. Further, the polarity control of the discharged toner is also efficiently performed. As a result, in the image forming apparatus provided with the charging device, image fog is suppressed for a long period, and high image quality with excellent fine line reproducibility is achieved.
Further, scratches and shaving unevenness of the photoreceptor are suppressed, long-term image quality can be maintained, and a long life of the photoreceptor is achieved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an image forming apparatus as an example of the present invention.

FIG. 2 is a sectional view of the magnetic brush charging device shown in FIG.

FIG. 3 is a schematic view showing an example of a measuring device for measuring a volume resistance value of magnetic particles.

[Explanation of symbols]

 Reference Signs List 10 photoconductor (image carrier) 11, 12 electrode 13 guide ring 14 ammeter 15 voltmeter 16 constant voltage device 17 measurement sample 18 insulator 20 magnetic brush charging device (charging device) 21 magnet roller (magnet) 22 electrode sleeve (Conductive sleeve) 23 Magnetic particles for charging (magnetic brush) 24 Contacts 25 Frame 30 Latent image forming device (exposure means) 40 Two-component developing device (developing device) 50 Transfer roller (transfer device) 60 Conveyor belt 70 Paper ( Transfer material) 80 Fixing device A cell

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // G03G 15/24 G03G 15/08 507B (72) Inventor Toshio Takamori 3-30-2 Shimomaruko, Ota-ku, Tokyo Kyano 2H003 AA18 BB11 CC04 DD03 2H068 AA05 AA08 AA54 AA58 FA27 FC15 2H077 AA37 AC16 AD11 EA01 2H078 AA29 AA35 BB01 CC08 DD15 DD39 DD43 DD66 5E040 AB03 AB09 BC05 CA07 NN00 NN05

Claims (18)

[Claims] 1. A charging magnetic particle comprising magnetic particles whose surface has been treated with silicone oil, wherein the ratio of the short axis length to the long axis length of the magnetic particles having a maximum chord length of 5 μm or more ( The standard deviation of (short axis length / long axis length) is 0.08 or more, and the volume resistance value is 1 × 10 ⁴ to 1
× 10 ⁹ Ωcm, and the treatment amount of the silicone oil is 0.0001% by weight or more and 1% by weight or less based on the total amount of the magnetic particles. 2. The method according to claim 1, wherein the silicone oil is at least one of methyl hydrogen silicone oil, amino-modified silicone oil, alcohol-modified silicone oil, carboxyl-modified silicone oil, alkoxy-modified silicone oil, and epoxy-modified silicone oil. The magnetic particles for charging according to claim 1. 3. The magnetic material for charging according to claim 1, wherein the particles having a maximum chord length in the range of 5 μm to 20 μm have a standard deviation of minor axis length / major axis length of 0.08 or more. particle. 4. The charging magnetic particle according to claim 3, wherein the standard deviation is 0.10 or more. 5. When the volume resistance of particles having a maximum chord length in the range of 5 μm to 20 μm is Ra and the volume resistance of particles having a maximum chord length exceeding 20 μm is Rb, 0.5 ≦ Ra.
2. The charging magnetic particle according to claim 1, wherein /Rb≦5.0. 6. The ratio Ra / Rb is 1.0 ≦ Ra / Rb ≦
6. The magnetic particles for charging according to claim 5, wherein the particle diameter is 5.0. 7. The magnetic particles for charging according to claim 1, wherein the magnetic particles are produced by pulverizing ferrite particles. 8. The magnetic particles for charging according to claim 1, wherein the heat loss of the magnetic particles is 0.5% by weight or less. 9. A conductive part to which a voltage is applied, a magnet body having the conductive part on the surface, and the conductive body according to any one of claims 1 to 8, And a magnetic particle for charging carried by magnetic force. 10. The conductive sleeve according to claim 9, wherein the conductive portion has a cylindrical shape, and is a conductive sleeve enclosing the magnet body and provided rotatably relative to the magnet body. Charging member. 11. A charging device comprising: the charging member according to claim 9; and a power supply that applies a voltage to a conductive portion of the charging member, wherein the charging member has an electrostatic latent image. A charging device for charging an image carrier in contact with the image carrier formed on the surface. 12. The charging device according to claim 11, wherein the power supply applies a DC voltage on which an oscillating voltage is superimposed to the conductive portion. 13. The oscillating voltage having a peak-to-peak voltage of 1000
13. The charging device according to claim 12, wherein the voltage is V or less. 14. The image carrier comprises a conductive substrate, a photosensitive layer formed on the conductive substrate, and a charge injection layer formed on the photosensitive layer and forming a surface layer of the image carrier. And the volume resistance value of the charge injection layer is 1 × 10 ⁸ to 1 × 10
The charging device according to claim 11, wherein the charging device has a resistance of ^15? Cm. 15. The conductive substrate is formed in a cylindrical shape, and the thickness of the conductive substrate is 0.5 mm or more and 3.0 m or more.
The charging device according to claim 14, wherein m is equal to or less than m. 16. An image carrier on which an electrostatic latent image is formed, a charging device for charging the surface of the image carrier, and irradiating the charged image carrier with light to form an electrostatic latent image. An exposure device that supplies developer to the surface of the image carrier to develop an electrostatic latent image formed on the surface of the image carrier, and a developing device that transfers the developed electrostatic latent image to a transfer material. An image forming apparatus having a transfer device for transferring, wherein the charging device is the charging device according to any one of claims 11 to 15. 17. The image forming apparatus according to claim 16, wherein the developing device collects the developer remaining on the image carrier after the transfer from the image carrier. 18. An image carrier used in the image forming apparatus according to claim 16, wherein the charging device and at least the developer remaining on the image carrier, the developing device, and the transferred image carrier are transferred to the image carrier. A process cartridge, wherein one or more members selected from the group consisting of a cleaning device for removing the toner from the image forming apparatus are integrally formed and detachably mounted on the image forming apparatus main body.