JPH056083A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a high and uniform density image without a ghost by developing by giving a high triboelectric charge to a single component developer in the condition that a contact pressure on a developer carrier is low without impairing the elasticity of a developer restricting member and preventing the excess charge of the developer on the developer carrier. CONSTITUTION:This device is provided with a coating layer 26b made of a triboelectric charge material having a polarity opposed to the triboelectric charge polarity of the toner 24 of a single component developer on the surface of an elastic blade 26 and an electrically conductive resin layer 21b containing an electrically conductive fine particles on the surface of a developing sleeve 21. Since the coating layer 26b having an electric charge of the polarity opposed to that of the toner 24, a high electric charge is given to the toner 24 in the condition that the contact pressure on the sleeve 21 is low without impairing the elasticity of the blade 26 and also, since the electrically conductive resin layer 21b is arranged on the sleeve 21, the electric charge is reduced even if the excess charge is given to the toner 24 and the image having a desired performance is obtd. by developing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device using a one-component developer used in an image forming apparatus such as an electrophotographic apparatus.

[0002]

2. Description of the Related Art An electrostatic latent image formed on an image carrier is developed using a carrier-free developer contained in a two-component developer, a so-called one-component developer (hereinafter also simply referred to as toner). Developing devices for performing the above are known.

Such a developing device includes a developer carrying member for carrying toner to a developing portion opposite to the image carrying member for developing an electrostatic latent image on the image carrying member, and a developing agent carrying member for contacting the developer carrying member. And a regulating member that regulates the thickness of the toner layer that is brought into contact with and is conveyed to the developing unit.

Strictly speaking, at the time when the developer layer is formed, the regulating member is not in direct contact with the developer carrying member, and a thin developing layer is formed between it and the developer carrying member. The developer layer is present and the developer layer is pressed against the developer carrying member, but in the state where no developer is present,
Since the regulating member is urged to directly contact the developer carrying member, in the present specification, for the sake of convenience, such regulating member also comes into contact with the developer carrying member even when the developer layer thickness is regulated. To do.

By the way, a developer carrying member (usually a sleeve or a roller; hereinafter simply referred to as a developing sleeve unless necessary) is generally made of metal such as aluminum, to which a developing bias voltage is applied. Further, the toner is rubbed on the surface of the developing sleeve and has a triboelectric charge of the polarity for developing the electrostatic latent image.

[0006]

However, since the metal surface of the developing sleeve is extremely thinly oxidized, it does not exhibit ohmic characteristics with respect to the weak triboelectric charge of the toner. Therefore, a ghost, which is a print history, is likely to occur on a developed image, and a reduction in image density is likely to occur due to a reduction in developing efficiency due to a toner charge-up phenomenon during continuous printing of a large number of sheets.

The phenomenon of ghost occurs in a portion where only a thin development is performed even if printing is performed because a non-printing portion (white background) continues, and a portion where dark development is performed because printing is continued. This is a phenomenon in which density unevenness occurs.

When this ghost occurs, there is a clear difference in the toner particle size distribution of the lowermost layer of the toner layer on the developing sleeve between the toner consuming portion and the toner non-consuming portion, and the toner is differentiated into the toner lowermost layer of the non-consuming portion. Layers have been formed. Since the fine powder has a large surface area per volume, the triboelectric charge amount per mass is larger than that of the one having a large particle size. On the other hand, since this excess charge is hard to escape to the developing sleeve, the fine powder is It is strongly electrostatically bound to the developing sleeve by its own mirror power. For this reason, the toner on the portion on which the fine powder layer is formed cannot be sufficiently frictionally charged with the developing sleeve, so that the developing ability is deteriorated,
It will appear as a ghost on the image.

It is also considered that fine powder causes charge-up which tends to occur during continuous printing of a large number of sheets.

In the toner layer regulating portion on the developing sleeve, the toner is regulated to a predetermined layer thickness by using a regulating member (for example, an elastic blade) that comes into contact with the developing sleeve.
The regulated toner layer on the developing sleeve is actually composed of several layers, and there is the fine powder layer as described above in the bottom layer, and in the state where the toner forms several layers on it. Present on the developing sleeve. This means that the probability of the toner coming into contact with and rubbing against the surface of the developing sleeve changes depending on the position where the toner is present in the regulating portion, that is, whether the toner is near or far from the surface of the developing sleeve. To do.

That is, the toner located near the surface of the developing sleeve comes into contact with the developing sleeve and is rubbed frequently, so that the triboelectric charge is sufficiently imparted.
However, the toner at a position distant from the surface of the developing sleeve (a position away from the surface of the developing sleeve by about 3 to 6 toners) is reduced in the number of times of contact and rubbing with the surface of the developing sleeve, and sufficient triboelectric charge is imparted. Not only, the image density is lowered, but also a large amount of rubbing occurs between the toner particles, which may cause triboelectrification to a polarity opposite to the desired triboelectrification polarity, resulting in a so-called reversal toner. This reversal toner causes so-called reversal fog that adheres to the background portion of the latent image on the photosensitive drum, and when the reversal fog is very large, it may be transferred onto the transfer paper in the worst case.

This problem is particularly likely to occur when the toner, which is the first toner to be used, contacts the developing sleeve a small number of times. Further, particularly when the average particle diameter of the toner is small, the amount of toner carried to the developing unit without sufficiently contacting the developing sleeve is large, and in this case also the above-mentioned problem is likely to occur.

Therefore, an object of the present invention is to prevent ghosts and to prevent a decrease in image density due to the charge-up phenomenon of a one-component developer at the time of continuous printing of a large number of sheets. To provide a developing device capable of surely imparting triboelectric charges to a developer located on an upper layer of a developer layer without applying load, preventing reversal fog and improving image density. Is.

[0014]

The above object can be achieved by the developing device according to the present invention. In summary, the present invention regulates a one-component developer carried on a developer carrying member by a developer regulating member in contact with the developer carrying member so that the thin film of the developer is deposited on the developer carrying member. While forming the layer, the developer is carried by the developer carrying member to a developing unit facing the image carrying member, and the latent image formed on the image carrying member is developed by the developer in the developing unit. In a developing device that visualizes the developing agent, a conductive resin layer containing conductive fine particles is provided on the surface of the developer carrier, and the developer is rubbed on the surface of the developer regulating member on which the developer is rubbed. And a triboelectrifying material layer having a polarity opposite to that of the triboelectrifying polarity.

[0015]

1 is a cross-sectional view of an essential part of an embodiment of a developing device of the present invention, and FIG. 2 is a cross-sectional view of an image forming apparatus equipped with the developing device of FIG.

First, a schematic structure of the image forming apparatus will be described with reference to FIG.

As shown in FIG. 2, the image forming apparatus includes a scanner unit 1 including a laser, a polygon mirror, and a correction lens system. The laser light 11 modulated according to the image signal is output from the scanner unit 1, reflected by the folding mirror 2, and irradiated onto the photosensitive drum 3 of the image carrier. This photosensitive drum 3 is an OPC (organic photoconductor)
And the like, and is uniformly negatively charged in advance by the primary charger 4 which is a corona charger. The photosensitive drum 3 is exposed by the irradiation of the laser beam 11 to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 3 is developed with the magnetic toner 24 as a one-component magnetic developer in the developing device 5 of this embodiment, and is visualized as a toner image.

On the other hand, the recording material 7 such as plain paper or plastic sheet stacked and stored in the cassette 7a is electrostatically applied to the photosensitive drum 3 by the paper feed roller p up to the registration roller r which is temporarily stopped. It is sent in synchronization with the formation of the latent image. The registration roller r transfers the recording material 7 to the photosensitive drum 3
In synchronism with the tip of the electrostatic latent image formed above, the electrostatic latent image is conveyed to the positive transfer charger 6 composed of a corona discharger. After the toner image on the photosensitive drum 3 is transferred to the recording material 7 by the transfer charger 6, the recording material 7 is conveyed to a fixing device 8 along a conveyance guide g, where the toner image is permanently fixed on the recording material 7. , Discharged outside the image forming apparatus.

The toner 24 remaining on the photosensitive drum 3 is
After being removed by the cleaning device 9, it is exposed by the pre-exposure device 10 to erase the charging history.

The photosensitive drum 3, the primary charger 4, the developing device 5, the cleaning device 9 and the like are integrally built in the cover K as a cartridge of the image forming unit.
The image forming apparatus main body is detachably provided. The cover K has a function of blocking light and preventing dust from adhering to the photosensitive drum 3 when the cartridge is removed from the main body of the image forming apparatus.

The developing device of the present invention will be described with reference to FIG.

The developing device 5 is provided with a non-magnetic developing sleeve 21 as a developer carrier in a developer container 30 containing a magnetic toner 24 as a one-component developer, and the developing sleeve 21 is the developer container 30. 1 is rotatably installed at a position of an opening facing the photosensitive drum 3 of FIG. 1, and a magnet 22 having a plurality of magnetic poles N and S alternately formed is fixedly installed in the developing sleeve 21. At the position of the developer container 30 on the developing sleeve 21, an elastic blade 26 made of rubber or a metal plate spring as a developer regulating member is attached to a metal plate 27 by adhesion.

The elastic blade 26 is hung from above the developing sleeve 21 and extends on the developing sleeve 21 at the abdomen of the free end extending in the direction opposite to the rotation direction of the developing sleeve 21 (which may be the same direction). Is in contact with. The toner 24 carried on the developing sleeve 21 has an elastic blade 26.
The thickness of the toner layer is regulated while the toner passes through the area where the toner abuts, so that a thin toner layer 25 is formed on the developing sleeve 21. Further, the toner 24 acquires triboelectrically-charged charges having a polarity for developing the latent image by friction with the developing sleeve 21, but is most actively triboelectrified when regulated by the elastic blade 26.

Toner layer 2 regulated by elastic blade 26
The layer thickness 5 is smaller than the minimum gap between the developing sleeve 21 and the photosensitive drum 3 in the developing section. Therefore, so-called non-contact development is performed. Then, as a developing bias, a vibration bias voltage obtained by superimposing a DC voltage on an AC voltage is applied to the developing sleeve 21 as a developing bias. As a result, efficient development is achieved even though it is non-contact development. These matters also apply to other embodiments described later.

According to the invention, said elastic blade 26
Has a coating layer 26b made of a triboelectrifying material having a polarity opposite to that of the toner 24 on the surface thereof.
In this embodiment, the toner 24 is negatively charged and has a thickness of 1.
On the surface of a blade body 26a made of urethane rubber of 3 mm, a coating layer 26 made of a polyamide resin of a positively charging material
The elastic blade 26 is formed by thinly providing b to a thickness of 20 μm.

According to the elastic blade 26 described above, since the polyamide resin forming the coating layer 26b has a positive charging property and an electron donating property, the negative charging toner 24 contacts the coating layer 26b and rubs against it. If so, negatively and favorably triboelectrified. Therefore, the upper layer of the toner layer 25 on the developing sleeve 21 is given sufficient negative triboelectric charge by the elastic blade 26, and the toner layer 25 extends from the lower layer to which the triboelectric charge is given from the developing sleeve 21 to the upper layer. All layers will have a uniform and high charge.

The lower layer portion of the toner layer 25 is negatively charged by friction with the developing sleeve 21. Further, it is preferable that a small amount of silica fine particles that are triboelectrically negatively charged is externally added to the toner 24 in order to improve fluidity.
These matters are also common to other embodiments.

Therefore, according to the developing device of this embodiment, the toner layer 25 is conveyed by the developing sleeve 21 to the developing portion facing the photosensitive drum 3, and the toner 24 is fed with the toner 24.
By developing the above electrostatic latent image, it is possible to obtain an image with high density and no sleeve ghost or fog.

Further, since the polyamide resin coating layer 26b of the elastic blade 25 is much thinner than the blade body 26a made of urethane rubber, the elastic blade 26 does not impair the rubber elasticity of the blade body 26a and the developing sleeve 21 is not damaged. Since a uniform contact pressure is obtained in the longitudinal direction of the developing sleeve 21, the toner layer 25 can be a thin layer that is uniform in the longitudinal direction of the developing sleeve 21.

According to the present invention, the developing sleeve 21 has, as shown in FIGS. 3 and 4, a conductive resin layer 21b containing conductive fine particles and having a volume resistance of 10 ² to 10 ⁻³ Ωcm on its surface. It is provided. In this embodiment, the developing sleeve 21
Forms an oxidation resistant resin layer 21b containing conductive fine particles on the surface of a developing sleeve substrate 21a made of an aluminum pipe having a diameter of 16 mm (the surface of which is roughened with No. 100 mesh alundum abrasive grains). It has become. The resin layer 21b has a volume resistance of 10 ² to 10 ⁻³ Ωcm, and its surface has secondary particles 2 made of conductive fine particles and a resin.
1c protrudes and becomes uneven.

A developing sleeve 2 having an oxidation resistant conductive resin layer 21b containing the above-mentioned conductive fine particles formed on the surface thereof.
According to 1, the contact resistance between the toner 24 and the surface of the developing sleeve 21 can be reduced, and even when the toner 24 is overcharged, the excess charge of the toner 24 can be leaked through the conductive fine particles of the resin layer 21b. Therefore, the mirroring force acting on the toner 24 in the direction of the developing sleeve 21 can be reduced, and the developability of the toner 24 can be improved.

A specific example of this embodiment will be described below.

A resin solution prepared by dispersing carbon black fine particles of conductive fine particles and graphite fine particles in a phenol resin in an appropriate amount is applied on the surface of the developing sleeve base 21a of an aluminum pipe having a diameter of 16 mm to a thickness of 5 μm, The conductive resin layer 21b was formed by thermosetting to obtain the developing sleeve 21. In the developing sleeve 21, 600
A magnet 22 having four magnetic poles of ˜850 gauss was incorporated.

Magnetite 1 on styrene-acrylic resin
00 parts were kneaded and pulverized to obtain a toner having a particle size distribution center of 5 to 8 μm, and silica 1.
2% by weight was added and this was used as a negatively chargeable toner 24.

The thickness is 1.3 mm and the hardness is 65 degrees (JIS-
On the surface of the urethane rubber blade body 26a of A), an alcohol-soluble nylon such as Pratamide (manufactured by Nippon Rilsan Co., Ltd.) or Toresin (manufactured by Teikoku Chemical Industry Co., Ltd.) is used as a polyamide resin, and the nylon concentration is 10 to 20% by weight. What was adjusted to a methanol solution was coated with a thickness of 20 μm by a dipping method to form a coating layer 26b, and an elastic blade 26 was obtained. The elastic blade 26 is elastically deformed to exert a linear pressure of 17 g / c on the surface of the developing sleeve 21.
abutted at m.

When the developing device 5 having the above-described structure is incorporated in the image forming apparatus of FIG. 2 and used for development, an image is formed and a continuous printing experiment is conducted. Immediately after replenishment to the developing sleeve 21, an image having a uniform reflection density of 1.4 or more in the longitudinal direction of the developing sleeve 21 was obtained, and the image was good without sleeve ghost and fog. After printing 20,000 sheets,
When the coating layer 26b made of polyamide resin of the elastic blade 26 was examined, the thickness was about 8 μm, and it was found that the coating layer 26b still had the effect of imparting triboelectric charge to the toner 24.

In the present invention, as described above, even if the contact pressure of the elastic blade 26 on the developing sleeve 21 is low, sufficient triboelectric charge can be applied to the toner 24, but the contact pressure is low. Therefore, the conductive resin layer 21b on the surface of the developing sleeve 21 was not scraped, and good developing property was maintained. In addition, the adhesion of the toner 24 on the elastic blade 26 was not recognized.

When the thickness of the coating layer 26b on the surface of the elastic blade 26 exceeds 200 μm, the elastic blade 26 is less likely to be elastically deformed, so that the developing sleeve 2 of the elastic blade 26 is prevented.
The contact pressure on the developing sleeve 21 tends to be non-uniform in the longitudinal direction of the developing sleeve 21, and the toner layer 2 formed on the developing sleeve 21.
The thickness of No. 5 is likely to be uneven. Therefore, the thickness of the coating layer 26b is preferably 200 μm or less, more preferably 150 μm.
m or less.

In the above embodiment, as the elastic blade 26, the one in which the coating layer 26b made of polyamide resin is formed on the surface of the blade body 26a made of urethane rubber is used, but the blade body 26a is replaced by urethane rubber. Silicone rubber, butyl rubber or the like may be used, and the coating layer 26b may be replaced by a polyamide resin and may be made of a positively chargeable substance having an electron donating property such as polyvinyl alcohol or cellulose. When the toner 24 is positively charged, a negatively charged substance having an electron attracting property is selected for the coating layer 26b. Specifically, Teflon, vinyl chloride, etc. are preferable.

On the other hand, for the conductive resin layer 21b containing the conductive fine particles on the surface of the developing sleeve 21, those in which carbon black fine particles and graphite fine particles are dispersed in an appropriate amount in phenol resin are used. T
Conductive ceramics such as iO ₂ , SnO ₂ , and Si alkoxide can be used. As the resin, it is preferable to select one having excellent dispersibility and abrasion resistance, such as epoxy resin, polyethylene resin, polypropylene resin,
Methacrylic resin, polyacetal resin, etc. can be used.

However, when graphite fine particles are used as the conductive fine particles, since the fine particles of the graphite have a large solid lubricity, the fine toner particles that are excessively charged on the developing sleeve 21 and are strongly attracted by the mirror force are attracted. ,
Graphite fine particles are preferable as the conductive fine particles because they have the advantage that they can be easily detached from the developing sleeve 21 and are easily used for development. When such fine toner is strongly adsorbed on the developing sleeve 21, the toner supplied onto the developing sleeve 21 is prevented from being triboelectrically charged with the developing sleeve 21.

Another embodiment of the present invention will be described.

The feature of this embodiment lies in that in the developing device shown in FIG. 1 of the previous embodiment, the elastic blade 26 is used.
The thickness of the coating layer 26b having a charge-donating property on the toner 24 is set to an amount that is scraped off by friction with the developing sleeve 21 due to regulation of the toner 24 at the initial stage of the developing operation.
As a result, it is possible to improve the prevention of the decrease in the image density due to the excessive charging of the toner 24 caused by the continuous use of the developing device in the low humidity environment.

Since the other points of this embodiment are the same as those of the previous embodiment, the following description will be made with reference to the developing device of FIG.

As the elastic blade 26 according to this embodiment,
An elastic blade was prepared in which a coating layer 26b of polyamide resin was formed to a thickness of 0.5 to 1.0 μm on the surface of a blade body 26a made of urethane rubber having a thickness of 1.3 mm and a hardness of 65 degrees (JIS-A). (0.5-1.0 μm nylon coating layer blade). Then, this was used in the developing device 5 of FIG. 1, the developing device 5 was incorporated into the image forming apparatus of FIG. H. The image was formed under the low temperature and low humidity environment and the continuous printing experiment was conducted.

For comparison, an elastic blade (urethane blade) made entirely of urethane rubber without a coating layer, and a coating layer 26b of polyamide resin on the surface of the blade body 26a made of urethane rubber used in the previous embodiment. An elastic blade 26 (20 μm nylon coating layer blade) provided with a thickness of 20 μm was used, and a continuous printing experiment similar to the above was tried.

As a result, the relationship between the reflection density of the obtained image and the number of prints is shown in FIG.

As shown in FIG. 5, when a urethane rubber blade is used as a whole, the image density is reduced at the initial stage of printing due to insufficient triboelectric charge of the toner.
When a blade having a coating layer 26b of polyamide resin with a thickness of 20 μm provided on the surface of a blade body 26a made of urethane rubber is used, a decrease in image density due to excessive charging of toner is observed after printing 1000 sheets.

On the other hand, the blade body 26 made of urethane rubber
A coating layer 26b of polyamide resin is formed on the surface of a by 0.5 to
With the blade of this embodiment provided with a thickness of 1.0 μm, a high image density was obtained due to the good effect of the triboelectric charge of the polyamide resin to the toner at the beginning of printing, and 1000 or more sheets were printed. After printing, the polyamide resin coating layer 26b on the elastic blade 26 is scraped off (abrasion), so that a high density is obtained without a decrease in image density due to excessive charging of the toner, and a continuous printing experiment is performed from the beginning of printing. Until the end, good images were always obtained with high density.

As is apparent from the above, the elastic blade 26 in this embodiment is particularly effective when a toner having a high resistance value that easily overcharges is used as the toner 24 for development.

The optimum value of the thickness of the coating layer 26b, which is the charge-providing functional layer of the elastic blade 26, is the material of the coating layer 26b, the resistance value of the toner 24 used, the particle size, and the developing sleeve 21 of the elastic blade 26. Contact pressure of the developing sleeve 21
It depends on the surface hardness, surface roughness, etc.

In this embodiment, the toner 24 has a resistance value of 10
Conductive particles are formed on the surface of the developing sleeve base 21a made of an aluminum pipe having a diameter of ¹⁴ Ωcm, a particle diameter of 5 to 8 μm, an abutting pressure of the elastic blade 26 on the developing sleeve 21 of 20 g / cm, and the developing sleeve 21 having a diameter of 16 mm. The conductive resin layer 21b having a volume resistance of 10 ² to 10 ⁻³ Ωcm is formed.
When the thickness of the coating layer 26b of the polyamide resin of 2.0 is more than 2.0 μm, the toner 24 is excessively charged in a low humidity environment. Therefore, when the coating layer 26b is made of the polyamide resin, the thickness thereof is 2. 0 μm or less, preferably 1.5 μm
Hereafter, it is more preferable that the thickness is 1.0 μm or less.

Still another embodiment of the present invention will be described.

The present embodiment is characterized in that the elastic blade 26 having the coating layer 26b having a charge-donating function to the toner 24 is applied to a developing device in which the toner 24 used is a non-magnetic one-component developer. .

FIG. 6 is a sectional view of the main part of the developing device of this embodiment.

In the main developing device 5, the developing sleeve 21 is
A conductive resin layer 21b containing conductive fine particles is provided on the surface of a developing sleeve base 21a made of a stainless steel pipe, and has an outer diameter of 16 mm. The developing sleeve 21 is rotationally driven in the direction of arrow A. A coating roller 28 made of polyurethane foam having an outer diameter of 8 mm is pressed against the developing sleeve 21. The application roller 28 rotates in the direction of the arrow B to supply the new toner 24 in the developer container 30 onto the developing sleeve 21 while removing the residual toner 24 after development on the developing sleeve 21.

In this embodiment, the toner 24 is a non-magnetic toner as described above, and specifically, 7 to 10 in which a red azo pigment is internally added to styrene-acrylic resin.
The one having the center of particle size distribution in μm was used.

The elastic blade 26 has a thickness of 1 mm,
A blade body 26a made of urethane rubber having a hardness of 65 degrees (JIS-A) and having a coating layer 26b of a polyamide resin 25 μm on the surface was used. The elastic blade 26 was brought into contact with the developing sleeve 21 with a linear pressure of 21 g / cm.

When the developing device 5 having the above-described structure is incorporated into the image forming apparatus of FIG. 2 and used for development, an image is formed and printed. Even when the toner 24 is initially used, the toner is evenly distributed in the longitudinal direction of the developing sleeve 21. An image having a reflection density of 1.2 or more was obtained, and the image was good without sleeve ghost and fog.

Unlike the magnetic one-component developer, the non-magnetic one-component developer such as the toner 24 used in this embodiment does not contain a high melting point substance therein, so that the developing sleeve 21 and the elastic blade 26 are combined. Fusing is likely to occur at the contact portion, and streak-like unevenness is likely to occur on the image due to development. According to this embodiment, however, the contact pressure can be lowered to 21 g / cm, so that the problem of streak-like unevenness in the image does not occur.

Also in this embodiment, the toner 24 of the elastic blade 26 is the same as in the second embodiment.
The thickness of the charge-donating coating layer 26b can be set to an amount that can be scraped off by friction with the developing sleeve 21 in the initial use of the developing device, and similarly, sufficient triboelectric charge after the start of use can be obtained. It is possible to improve the prevention of excessive electrification of the toner 24 in the state where the electric charge is easily obtained.

Another embodiment of the present invention will be described in detail.

FIG. 7 is a sectional view of still another embodiment of the developing apparatus of the present invention, and FIG. 12 is a sectional view of a color image forming apparatus equipped with the developing apparatus of FIG.

First, the color image forming apparatus of FIG. 12 will be described. The image forming apparatus is a color image forming apparatus using a laser beam as a light source, and the developing apparatus of the present invention is applied to the developing apparatus 5M for magenta, the developing apparatus 5C for cyan, the developing apparatus 5Y for yellow, and the developing apparatus for black. The developing device 5B is provided.

The image forming process of this image forming apparatus will be described. First, the surface of the photosensitive drum 3 of the image carrier is uniformly primary-charged by the primary charger 4 to V _D = -700V. Next, image exposure based on magenta image information of the first color is performed by the laser beam 11, and V _{L is formed} on the photosensitive drum 3.
An electrostatic latent image of -50V is formed. Then this latent image
Reversal development with magenta toner is performed by the magenta developing device 5M to visualize the image as a magenta toner image. on the other hand,
A transfer material (not shown) is held in advance on the transfer drum 12, and the magenta toner image on the photosensitive drum 3 is transferred onto the transfer material.

After the transfer of the magenta toner image onto the transfer material is completed, the photosensitive drum 3 cleans the toner remaining after the transfer with the cleaner 9
After cleaning by (1), the primary charging unit 4 again uniformly performs primary charging, and image exposure based on the image information of the second color cyan is performed to form an electrostatic latent image. The latent image is reversely developed with cyan toner by the cyan developing device 5C,
It is visualized as a cyan toner image, and is transferred onto the transfer material held on the transfer drum 12 in an overlapping manner.

Similarly, the electrostatic latent image is formed by image exposure, the yellow toner image of the third color is formed by development by the yellow developing device 5Y, the image is transferred onto a transfer material, and then electrostatically formed by image exposure. The latent image is formed, the black toner image of the fourth color is formed by the development by the black developing device 5B, and the transfer onto the transfer material is performed. Thus, the magenta toner image, the cyan toner image, and the yellow toner image are formed on the transfer material. Also, a color image in which four color toner images of the black toner image are superimposed is obtained.

The transfer material on which the toner images of four colors have been transferred is separated from the transfer drum 12 and then sent to a fixing device (not shown) where the toner images are fixed to be a permanent image.

Next, the structure of the developing device to which the present invention is applied will be described by taking the yellow developing device 5Y as an example.

The developing device 5Y for yellow includes the developer container 3
The toner transport member 31Y is provided in 0Y, a rotatable developing sleeve (or roller) 21Y having a conductive resin coating layer as a developer carrier, and a coating roller 28Y that transports toner near the developing sleeve 21Y. Coating roller 2
The 8Y rotates so as to have a relative speed with respect to the developing sleeve 21Y, and applies the negative polarity non-magnetic toner as a one-component developer contained in the developer container 30Y onto the developing sleeve 21Y. In order to favorably perform this coating, it is preferable that the coating roller 28Y is sponge-shaped, knurled, or brush-shaped processed. The toner applied on the developing sleeve 21Y is regulated to have a predetermined layer thickness by the elastic blade 26Y.

A blow-out prevention sheet 32Y for preventing the toner from blowing out of the developer container 30Y is disposed below the developing sleeve 21Y.

The developing sleeve 21Y and the photosensitive drum 3 described above.
Are not in contact with each other, and they are held with a space of 100 to 500 μm. The toner regulated to a predetermined layer thickness by the elastic blade 26Y is conveyed to the developing position facing the photosensitive drum 3 as the developing sleeve 21Y rotates, and the toner adheres to the electrostatic latent image on the photosensitive drum 3 there. Then, the electrostatic latent image is developed and visualized as a toner image. At the time of this development, the bias control device 2 is attached to the developing sleeve 21Y.
A developing bias is applied from the bias power source 29 controlled by 9 '.

The developing bias is applied by superimposing an AC voltage V _PP (a peak-to-peak voltage) on a DC voltage V _DC , V _DC is -500 to -100 V, and V _PP is several 100 to several 1000 V. It is said that The distance between the photosensitive drum 3 and the developing sleeve 21Y (hereinafter referred to as SD distance) is 30.
When it is 0 μm, the AC voltage required for obtaining a good image by development is V _PP = 1200 to 2400V, preferably V _PP = 1600 to 2000V.

The developing device 5Y for yellow has been described above. The developing device 5M for magenta and the developing device 5 for cyan.
The C and black developing devices 5B are also similarly configured,
In FIG. 12, in the magenta developing device 5M and the like,
The members that have the same functions as the members of the yellow developing device 5Y are
Corresponding reference numerals are attached.

Now, these developing devices 5Y-5B are shown in FIG.
The developing device of the present invention shown in FIG.

As shown in FIG. 7, the developing device 5 of the present invention.
Includes a developing sleeve 21 in the developer container 30. The material of the base of the developing sleeve 21 is aluminum,
Metal such as stainless steel or plastic with excellent rigidity is preferable.

According to the present invention, the surface of the developing sleeve 21 is provided with an oxidation resistant conductive resin layer 21b which does not depend on a metal and is free from the formation of an oxide film. This is because if the developing sleeve 21 is simply made of aluminum, it is easily oxidized and there is a problem in reducing the contact resistance with the toner.

In this embodiment, the conductive resin layer 21b is made of a coating-forming polymer containing dispersed and contained conductive carbon black powder and graphite powder, and the conductive carbon black powder and graphite powder have conductivity. I am making it. The conductive carbon black powder and the graphite powder are exposed on the surface of the resin layer 21b and function as leak sites of the excessively charged toner. Further, since the graphite powder has a strong solid lubricity, the toner fine powder is easily separated from the surface of the resin layer 21b. As a result, formation of the fine toner powder layer on the surface of the resin layer 21b can be prevented, and sleeve ghosts can be prevented from occurring.

Examples of the above-mentioned coating forming polymer include styrene resin, vinyl resin, polyether sulfone resin, polycarbonate resin, polyphenylene oxide resin, polyamide resin, fluororesin, fibrin resin, acrylic resin and the like. A thermoplastic resin or a thermosetting resin such as an epoxy resin, a polyester resin, an alkyd resin, a phenol resin, a melamine resin, a polyurethane resin, a urea resin, a silicone resin or a polyimide resin can be used, and further a photocurable resin or the like can be used.

Among them, silicone resin, resin having releasability such as fluorine resin, polyether sulfone resin, polycarbonate resin, polyphenylene oxide resin,
Resins having excellent mechanical properties such as polyamide resins, polyester resins, polyurethane resins and styrene resins are more preferable.

The volume resistivity of the conductive resin layer 21b is in the range of 10 ^-3 to 10 ² Ωcm, and the developing bias is applied to the resin layer 21b by the bias power source 29.

The elastic blade 26 is made of an elastic member such as urethane rubber or phosphor bronze as the base 26a, and contacts the developing sleeve 21 to rub the toner carried on the developing sleeve 21.

According to the present invention, the coating layer 26b that is triboelectrically charged to the opposite polarity to the triboelectric charging polarity of the toner is provided on at least the rubbing surface of the elastic blade 26 on the developing sleeve 21 that is rubbing against the toner. In this embodiment, the elastic blade 2
The sheet member 26b made of a material having a property of frictionally charging the surface of 6 which is frictionally charged to the opposite polarity to the frictional charging polarity of the toner.
Is attached to form the coating layer. It is preferable that the sheet member 26b has a strong charging ability.

In this example, an experiment was carried out using a toner for CLC-200 manufactured by Canon Inc. as a non-magnetic toner of a one-component developer. Since this toner exhibits a negative (negative) triboelectric chargeability, nylon, cellophane, etc. exhibiting a strong positive (positive) triboelectric chargeability are used as the sheet member 26b, but from the viewpoint of abrasion resistance, environmental stability, etc., nylon is used. Is preferred.

When urethane rubber is used for the elastic blade base 26a and strong positive triboelectric charging nylon or cellophane is used for the sheet member 26b, the triboelectric charge amount (specific charge amount q / m) and reversal fog level of the toner are used. In addition, as a reference, in combination with the case where a strong negative triboelectrifying PTFE is used for the sheet member 26b and the case where the urethane rubber base 26a of the elastic blade is left as it is without attaching the sheet member 26b,
It shows in Table 1.

The developing bias is a DC voltage V _DC = -3.
AC voltage V _pp = 200 with a frequency of 1.5 kHz at 50 V
The superposed 0V was used, and the SD interval was set to 300 μm.

[0087]

[Table 1]

As is clear from Table 1, the elastic blade 2
When the sheet member 26b of No. 6 is made of a strong positive triboelectric charging nylon sheet and cellophane sheet, the triboelectric charge is applied to the toner more reliably than when the elastic blade 26 is a urethane rubber base. Also, it can be seen that reverse fog can be prevented.

On the contrary, when a strong negative triboelectrifying PTFE sheet is used for the sheet member 26b, it is observed that the triboelectrification charge inclines toward the positive side as a whole of the toner layer, although the negative toner is used. Sometimes.

In the lowermost layer of the toner layer on the developing sleeve 21 regulated by the elastic blade 26, the surface of the developing sleeve 21 rubs against the toner, so that the toner is triboelectrically charged negatively. In the upper layer, the toner, which is more strongly negatively frictionally charged than the toner itself, rubs against the toner, and becomes positively charged toner (so-called reversal toner). Therefore, the toner layer as a whole has negatively charged frictional charge. The applied amount is small, and the triboelectrified charge is inclined to the positive side. This also increases reversal fog.

As described above, the sheet member 26b made of a material such as nylon having a strong positive triboelectric charging property is attached to the elastic blade 26, and the toner is rubbed, so that the toner is surely given a negative triboelectric charge. It was confirmed that it was possible to prevent the reversal fog.

In the present invention, as described above, the developing device 5
A conductive oxidation-resistant resin layer 21b is provided on the surface of the developing sleeve 21 to prevent sleeve ghost and charge-up during continuous printing of a large number of sheets.
It is conceivable that the presence of the resin layer 21b reduces the triboelectric charge that the developing sleeve 21 itself gives to the toner, as compared with the conventional aluminum developing sleeve.

However, the sheet member 2 having a strong positive triboelectric charging property.
Since the toner is rubbed by 6b, even if the conductive resin layer 21b is formed on the surface of the developing sleeve 21, the triboelectric charge is not lowered and is stably applied. Further, since the conductive resin layer 21b is formed on the surface of the developing sleeve 21, the mirroring force of the toner on the developing sleeve 21 is weakened, so that the toner is easily separated from the developing sleeve 21 by the developing bias, and the developing efficiency is improved. Is also increased.

Therefore, the image forming apparatus shown in FIG. 12 is equipped with the developing devices 5Y to 5B to which the developing device 5 described above is applied, so that the image density can be reduced due to the sleeve ghost and charge-up during continuous printing of a large number of sheets. In addition to being prevented, stable application of triboelectric charges can be achieved, and image quality and environmental characteristics are stabilized.

Regarding the amount of toner carried on the developing sleeve 21 after being regulated by the elastic blade 26, as described above, if the toner layer on the developing sleeve 8 is thin, the image density is lowered, and if it is too thick, the developing sleeve is too thin. In addition to the toner that rubs against the sheet 21 and the sheet member 26b, the amount of toner that rubs against each other at the intermediate position of the toner layer increases, and stable triboelectric charging cannot be achieved. The amount of toner carried on the sleeve 21 is 0.3 to 1.
5 mg / cm ² , preferably 0.5-1.0 mg / cm
It should be ² . This is achieved by appropriately setting the contact pressure of the elastic blade 26 against the developing sleeve 21.

In this embodiment, a negative triboelectric charging toner is used as the non-magnetic toner, but if a material such as PTFE or polyimide having a strong negative triboelectric charging property is used for the sheet member 26b, a positive triboelectric charging toner is obtained. It can also be used with the same effect.

Further, also in a developing device having a rigid developer regulating member and an elastic developing sleeve, a conductive coating layer is formed on the elastic developing sleeve surface, and when a negative toner is used, The developer regulating member is made of a material such as glass or acrylic that has a strong positive triboelectric charge in the charging series, and when positive toner is used, the rigid developer regulating member is made of PTFE or the like and has a strong negative triboelectric charge. The same effect as described above can be obtained by using a material having

The developing sleeve 21 used in the present invention.
The volume resistivity of the conductive resin layer 21b on the surface has been confirmed by experiments conducted by the inventors of the present invention to be preferably 10 ² Ωcm or less. Not only the resin layer 21b but also the developing sleeve 21
The effect of the present invention can be obtained even if the whole is formed.

FIG. 8 is a sectional view showing the main part of still another embodiment of the developing device of the present invention. The developing device is also used in the color image forming apparatus, like the developing device in FIG.

The present developing device is characterized in that at least the surface of the elastic blade 26 on the developing sleeve 21 on which the toner is rubbed and the surface on the opposite side thereof are coated with a coating layer that is triboelectrically charged to the opposite polarity to the triboelectric charging polarity of the toner. 26b is formed by applying a resin having the above properties. Coating layer 26
Similarly, it is preferable that the charging ability of b is strong. Other configurations of the present developing device are the same as those of the developing device of FIG. 7, and the same reference numerals as those in FIG. 8 denote the same members in FIG.

Also in this embodiment, as in the case of the embodiment shown in FIG. 7, as the one-component developer, the above-mentioned Canon C
A negative triboelectric non-magnetic toner such as a toner for LC-200 is used, while the coating layer 26b is
It is formed by applying a resin such as nylon, cellophane, or acrylic having strong positive triboelectricity.

The amount of toner carried on the developing sleeve 21 is
Similarly, after the regulation by the elastic blade 26, 0.3 to 1.
5 mg / cm ² , preferably 0.5-1.0 mg / cm
It is considered to be ² .

In this embodiment, the negative triboelectric charging toner is rubbed by the strong positive triboelectric charging coating layer 26b of the elastic blade 26, so that the triboelectric charge of the toner by the elastic blade 26 is similarly generated. In addition to the effect of stable application, the coating layer 26b can be easily formed by simply applying a resin having a positive triboelectric charging property to the elastic blade 26.
Since it can be formed, it has advantages that the working process is simplified, the productivity is improved, and the cost is reduced.

When a toner having a positive triboelectric charging property is used, the coating layer 26b may be formed of a resin having a strong negative triboelectric charging property as described above.

FIG. 9 is a sectional view of the essential portions of a developing device according to still another embodiment of the present invention. The developing device is also used in the color image forming apparatus, like the developing device in FIG.

The feature of the present embodiment is that the elastic blade 26 is not only provided with a coating layer having a property of frictionally charging with a polarity opposite to the frictional charging polarity of the toner, on the sliding surface of the elastic blade 26 which is slid with the toner. By forming an elastic material such as urethane rubber in which resin particles having the above properties are dispersed,
That is, the elastic blade 26 itself has properties similar to those of the coating layer.

As the resin particles having the above-mentioned properties, for example, CLC-200 manufactured by Canon having negative triboelectric charging property is used.
When the toner for use is used, resin particles having a strong positive triboelectric charging property such as nylon and acrylic may be used.

The average particle size of the resin particles is 0.05 to 50.
If the average particle size is smaller than 0.05 μm,
If the triboelectric charge cannot be imparted to the toner sufficiently and the average particle size is larger than 50 μm, the toner cannot be evenly applied onto the developing sleeve 21, and the toner layer is streaked. This causes unevenness and adversely affects the image.

However, if the elastic blade 26 is formed by dispersing resin particles in urethane rubber or the like, a skin layer 26 'made of urethane rubber or the like is formed on the surface layer of the elastic blade 26 as shown in FIG. As a result, the resin particles 26'b are not exposed, so that the resin particles 26'b and the toner are not rubbed against each other and the triboelectric charge is insufficiently applied. Therefore, so that the resin particles 26'b and the toner rub against each other,
After molding the elastic blade 26, it is necessary to carry out surface polishing on at least the portion rubbed with the toner to expose the resin particles 26'b on the surface at the rubbed portion, as shown in FIG.

However, once the resin particles 26'b are exposed on the surface, the resin particles 26'b are always exposed on the surface due to the abrasion of the elastic blade 26. It is unnecessary.

Also in this embodiment, the negative frictionally chargeable toner is rubbed by the elastic blade 26 having the strong positive triboelectric chargeability with the dispersed resin particles, and similarly, the toner is similarly rubbed by the elastic blade 26. The triboelectric charge is applied stably.

[0112]

As described above, in the developing device of the present invention, since the conductive resin layer which is unrelated to the formation of the oxide film is provided on the surface of the developer carrier, the ghost is prevented and a large number of sheets are formed. It is possible to prevent excessive charge-up of the one-component developer during continuous printing, and to prevent a decrease in image density due to excessive charge-up. Further, a material having a property of being triboelectrically charged with a polarity opposite to that of the triboelectric charging polarity of the developer on at least a rubbing surface of the developer regulating member which is in contact with the developer carrying body and which slides on at least a one-component developer on the developer carrying body Since the layer is provided, the developer can be stably and sufficiently imparted with a triboelectric charge having a desired polarity.

Further, the conductive resin layer of the developer carrying member is more easily worn than metal, but since the developer regulating member has the above-mentioned structure and the developer is easily charged by friction, the conductive resin layer is not easily worn. The contact pressure of the developer regulating member to the developer carrying member can be reduced so as to prevent it. Further, by reducing this contact pressure, it is possible to secure a sufficient amount of developer that can be conveyed to the developing section, which contributes to the improvement of image density.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an embodiment of a developing device of the present invention.

FIG. 2 is a cross-sectional view of an image forming apparatus including the developing device of FIG.

FIG. 3 is a sectional view of the vicinity of the surface of a developing sleeve provided in the developing device of FIG.

FIG. 4 is a perspective view of the surface of the developing sleeve.

FIG. 5 is a graph showing the relationship between the number of prints and the reflection density of an image in a continuous print test using an elastic blade and another elastic blade in another embodiment of the developing device of the present invention.

FIG. 6 is a cross-sectional view of essential parts of a developing device according to still another embodiment of the present invention.

FIG. 7 is a sectional view of still another embodiment of the developing device of the present invention.

FIG. 8 is a cross-sectional view of essential parts of a developing device according to still another embodiment of the present invention.

FIG. 9 is a cross-sectional view of an essential part of still another embodiment of the developing device of the present invention.

FIG. 10 is a cross-sectional view showing a state before polishing processing of an elastic blade provided in the developing device of FIG.

FIG. 11 is a sectional view showing a state in which the elastic blade is also subjected to polishing.

12 is a sectional view of a color image forming apparatus including the developing device of FIG.

[Explanation of symbols]

3 photosensitive drum 5 Development device 21 Development sleeve 21b Conductive resin layer 24 toner 26 Elastic Blade 26b coating layer

Continued front page    (72) Inventor Masa Ojima             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Masaharu Okubo             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation

Claims (4)

[Claims] 1. A one-component developer carried on a developer carrying body is regulated by a developer regulating member abutting the developer carrying body, and a thin layer of the developer is formed on the developer carrying body. While being formed, the developer is conveyed by the developer carrying member to a developing section facing the image carrying body, and the latent image formed on the image carrying body is developed by the developer in the developing section. In the developing device for visualization, on the surface of the developer carrying member,
A conductive resin layer containing conductive fine particles is provided, and a triboelectrifying material layer having a polarity opposite to the triboelectrifying polarity of the developer is provided on the surface of the developer regulating member on which the developer is rubbed. Characteristic developing device. 2. The developing device according to claim 1, wherein the conductive fine particles are carbon black fine particles or graphite fine particles. 3. The developing device according to claim 1, wherein the developer regulating member has a rubber blade surface coated with a triboelectrification material having a polarity opposite to the triboelectrification polarity of the developer. 4. The thin layer of the developer formed on the developer carrying member is thinner than the minimum gap between the developer carrying member and the image carrying member in the developing section. ,
2 or 3 developing devices.