JPH08320614A - Developer carrier and developing device - Google Patents

Abstract

PURPOSE: To avert the occurrence of sleeve ghosts and to obtain images having high image quality by providing the above developer carrier with a conductive particulate-contg. resin layer on its front surface, thereby removing or lessening the mirroring power acting between the fine powder toners existing near the front surface and the developer carrier. CONSTITUTION: The developer carrier 14 has the resin layer 18 contg. conductive particulates of an average grain size of about 20 microns on the front surface of a conductive developer carrier member 17. The conductive particulate-contg. resin layer 18 is composed by distributing secondary particles therein in such a manner that the conductive particulates are exposed on the surface layer and that the extreme surface part is formed to a gravel road-like state. An oxidized film layer 19 is usually formed on the surface of the metallic developer carrier 17 when the metallic conductive developer carrier 17 constituting the developer carrier 14 is made of nonmagnetic aluminum or stainless steel products. Such conductive particulate-contg. resin layer 18 is formed on this oxidized film layer 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a developing device for forming a latent image on an image bearing member such as an electrophotographic photosensitive member or an electrostatic recording dielectric and for visualizing the latent image. More particularly, the present invention relates to a developer carrier that carries and conveys the developer in the developer container from the developer container to a developing area facing the image carrier, and a developing device including the developer carrier. .

[0002]

2. Description of the Related Art Conventionally, a latent image is formed on an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric by an electrophotographic system or an electrostatic recording system, and the latent image is visualized by a developing device. As for the image forming apparatus, various developing devices have been proposed, and at present, the developing device shown in FIG. 8 is generally used.

Referring to FIG. 8, a developing device 10 is arranged so as to face the image carrier 1, and a developer container 12 for accommodating the developer 11 and the developer 11 in the developer container 12 are developed. A developer carrier 14 that carries and conveys the developer container 12 to a developing area 13 facing the image carrier 1. The developer carrying member 14 may have any structure, but it is usually formed of a non-magnetic material in the shape of a sleeve or an endless belt, and a magnet 15 is disposed inside (the developer carrying member 1).
Since 4 is usually sleeve-shaped as shown in the figure,
Hereinafter referred to simply as "developing sleeve"). Aluminum or stainless steel is used as the non-magnetic material. or,
The developing device 10 is carried by the developing sleeve 14 and is supported by the developing area 1.
A developer regulating member 16 is provided to regulate the developer 11 conveyed to the developing roller 3 to a predetermined thickness and form a thin developer layer on the developing sleeve 14.

Such a developing device is one of the developing agents.
It is suitable for visualizing a latent image on an image carrier by jumping development using a component magnetic toner.

Further, the one-component magnetic toner which is subjected to jumping development is for controlling the charge amount (hereinafter referred to as "tribo") of the one-component magnetic toner so as to increase the image density and obtain an image with less roughness. It is known to externally add substances such as vapor phase silica (hereinafter referred to as “dry silica”) and wet process silica (hereinafter referred to as “wet silica”) to a toner. For example, dry silica showing a strong negative property is added to a negative polarity toner containing 60 parts by weight of magnetite in styrene-acrylic (adding 10 parts by weight of HMDS per 100 m ² to 100 m ² of vapor phase method silica and heating. The processed) is added externally.

Further, the developing sleeve in the conventional developing device is made of a metal such as aluminum or stainless steel as mentioned above, but an oxide film is formed on the surface of these so-called conductive sleeves. The contact resistance when in contact with the developer shows a considerably high value in the low electric field spread by the toner.

[0007]

However, with a developer to which silica having a negative property that is strong against negative toner is externally added, a sleeve ghost, which is a history of the print pattern, is generated on the developing sleeve, which is a print image. Also appears. The sleeve ghost generated in the case of the developer in which negative silica is externally added to the negative toner becomes a positive ghost as shown in FIG. That is, when the printing (image output) is performed after the non-printing portion (white background) continues, the printing portion only performs the light development (a) portion, and the dark development is performed because the printing is continued. The portion (b) which is exposed is generated, resulting in uneven density.

According to experiments and consideration by the present inventors, it has been found that the mechanism of such ghost formation is deeply related to the layer of fine powder (particle size 5 to 6 μm or less) formed on the developing sleeve. . That is, there is a clear difference in the particle size distribution of the toner lowermost layer of the developing sleeve between the toner consuming portion and the toner non-consuming portion on the developing sleeve, and the fine powder layer may be formed on the toner lowermost layer of the non-consuming portion. Do you get it.

Since the toner fine powder forming the fine powder layer has a large surface area per volume, the triboelectric charge amount per mass is large as compared with a toner having a large particle diameter, and the toner is reflected on the developing sleeve by its mirroring power. On the other hand, it is strongly restrained electrostatically. For this reason, the toner on the portion where the fine powder layer is formed cannot be sufficiently frictionally charged with the developing sleeve, so that the developing ability is deteriorated and appears as a sleeve ghost on the image.

As described above, the present inventors have found that the sleeve ghost is a phenomenon caused by the formation of the fine powder layer and the charging of the toner largely depending on the frictional charging with the developing sleeve. The present invention has been made based on such novel knowledge.

Therefore, an object of the present invention is to provide a conductive fine particle-containing resin layer on the surface to remove or reduce the mirroring force acting between the fine toner particles and the developer carrying member located near the surface. It is an object of the present invention to provide a developer carrier capable of avoiding the occurrence of a sleeve ghost and obtaining a high-quality image, and a developing device equipped with the developer carrier.

[0012]

The above objects are achieved by the developer carrier and the developing device according to the present invention. In summary, the present invention is a developer carrier characterized in that the electric resistance of the surface is reduced by providing a resin layer containing conductive particles on a metal substrate having an oxide film on the surface. Preferably, the metal substrate is aluminum whose surface is blasted.

According to another aspect of the present invention, a developer container containing the developer and the developer in the developer container are carried and conveyed to a developing area for developing the electrostatic image on the image carrier. In a developing device having a developer carrier, the developer carrier has a metal base material having an oxide film on the surface, and a conductive particle-containing resin provided on the metal base material for reducing the electric resistance of the surface. Provided is a developing device having a layer. According to one embodiment, the developer is negative toner. The developing device further has an elastic blade that regulates the layer thickness of the developer.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a developer carrier and a developing device according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows an embodiment of an image forming apparatus using a developing device equipped with a developer carrying member according to the present invention. In this embodiment, the image forming apparatus includes an image carrier 1 such as a drum-shaped electrophotographic photosensitive member or a dielectric.
Have. Around the image carrier 1, the electrostatic latent image forming unit 20,
A developing device 10 for visualizing the latent image on the image carrier 1, a transfer separation unit 30 for transferring the visualized image on the image carrier 1 to a transfer material, and residual development on the image carrier 1. A cleaning unit 40 for cleaning the agent is arranged. Latent image forming unit 2
0, the transfer unit 30, and the cleaning unit 40 are well known to those skilled in the art, and a detailed description thereof will be omitted.

The developing device 10 carries and conveys a developer container 12 for accommodating the developer, and the developer in the developer container 12 from the developer container 12 to a developing area 13 facing the image carrier 1. And a developer carrier 14 for Although the developer carrying member 14 is formed in a sleeve shape in this embodiment, it may be formed in an endless belt shape, and the magnet 15 is arranged inside.

Further, the developing device 10 is provided with a magnetic blade 16 which regulates the thickness of the developer layer on the developer carrier 14 together with the opposing magnetic poles.

The developer 11 conveyed from the developer container 12 to the developing area 13 by the developer carrier 14 is sprung by the developing magnetic pole of the magnet 15 and is connected to the developer carrier 3 by a power source ( (Not shown) causes the developer on the developer carrier 14 to carry an image by an electric field formed between the latent image on the image carrier 1 and the developer carrier 14, preferably an alternating electric field such as AC. It flies to the body 1 and visualizes the latent image on the image carrier.

According to the present invention, the developer carrying member 14 is used.
2, has a resin layer 18 containing conductive fine particles having an average particle size of about 20 mm on the surface of the conductive developer carrying member 17, and the conductive fine particle-containing resin layer 18 is Average volume resistivity is less than 10 ² Ωcm to 10
^-2 Ωcm, more preferably 10 ^-2 Ωcm or less, preferably 7 × 10 to 7 × 10 ^-2 Ωcm, and the conductive fine particles appear on the surface layer and the outermost surface layer portion. Is composed of secondary particles distributed so as to form a gravel path.

As will be described later, when the metallic conductive developer carrying member 17 constituting the developer carrying body 14 is made of non-magnetic aluminum or stainless steel material, as shown in FIG. A metal developer carrying member 1
An oxide film layer 19 is usually formed on the surface of No. 7, and the conductive fine particle-containing resin layer 18 as described above is formed on the oxide film layer 19.

Next, the formulation of the conductive fine particle-containing resin layer of this embodiment will be described.

The resin solution prepared with the above composition is applied by a coating method, a dipping method, or a spray method.
Approximately 1.0 μm on the surface of the developer carrier made of aluminum blasted with Alundum # 400
.About.1.5 .mu.m, more preferably 1.5 .mu.m or more and about 30 .mu.m. Next, in this example, since a phenol resin was used as the resin, heat curing was performed at 150 ° C. for 30 minutes in a drying furnace.

The surface resistivity and volume resistivity of the conductive fine particle-containing resin layer at this time are the resistance of the conductive fine particle-containing resin layer film formed on PET (polyethylene terephthalate) under the same film forming conditions. It was obtained by measuring the rate with Loresta AP Intelligent manufactured by Mitsubishi Petrochemical.
In this example, it was about 7.0 × 10 ⁻¹ Ωcm.

Next, the contact resistance of the developer carrying member 14 according to this embodiment with the developer was examined by the measuring method described below.

FIG. 3 shows the measuring device, and FIG. 4 shows the direction of the current flowing through the developer carrying member 14 during the measurement.

In this measurement, a minute voltage was applied to the voltage applying brush 52 by the minute voltage applying device and the minute voltmeter 51 while the developer carrying member 14 was rotated at about 100 rpm in the direction of the arrow. The voltage application brush was manufactured by Torayca (carbon brush) manufactured by Toray. The diameter of each filament constituting the brush was about 5 microns, the length was about 8 mm, the width was about 5 mm, and the total weight of the brush was about 10 mg.

The current from the developer carrying member 14 was taken out by the current drawing brush 53 and measured by the minute ammeter 54. At this time, the distance L between the voltage applying brush 52 and the current drawing brush 53 was about 150 mm.

The current I flowing with respect to the applied voltage V is measured by the above-mentioned measuring device to perform so-called VI measurement.
The contact resistance on the surface of the developer carrying member 14 was measured by performing the heating in the range of 0 microvolt to several volts.

By studying the VI characteristics thus obtained, the conventional developer carrier should be expressed as V = I × R (R is resistance) for a minute voltage of several volts or less. It was found that the barrier was formed by the oxide layer having high resistance. However, even with such a conventional developer carrier, the conductive fine particle-containing resin layer of this example is formed on the surface of the conventional developer carrier having a barrier layer according to the present invention.
V = I × R even under a minute voltage of 00 microvolts
It has been found that the above condition is satisfied and the behavior is as if flowing better than the conventional developer carrier.

Further, in this experiment, the conductive fine particle-containing resin layer was studied to have a layer thickness of 0.5 to 30 microns, but within the scope of this study, as shown in FIG. It is considered that the current flow is mostly a → b → d → f.

FIG. 5 shows a conventional developer carrier measured by the VI measuring apparatus according to this experiment, and a conductive fine particle-containing resin layer coated on the conventional developer carrier of the present embodiment. The VI characteristics of the developer carrying member are shown (curve (a) shows a conventional example, and curve (b) shows this embodiment). Note that the experimental results shown in FIG. 5 are obtained by using the Solarto in place of the minute voltage applying device and the minute voltmeter 51 and the minute ammeter 54 described in FIG.
n1286 potentiostat (distributor, manufactured by Toyo Technica) was used for the two-terminal method.

As shown in FIG. 5, the conventional developer carrier has a so-called V-shape.
= I × R, the curve has a high slope and the resistance is high in the low voltage region. Also, it can be seen that the slope becomes gentler as the voltage becomes higher. In the case of this embodiment, the voltage and current change linearly,
It is understood that since the conductive fine particle-containing resin layer is formed and the conductive fine particles are projected on the surface, the resin layer serves as a charge leak site.

The developer carrying member of this embodiment was incorporated into a developing device having a structure as shown in FIG. 1 and mounted on an image forming apparatus, which is an electrophotographic copying machine, to output an image. The development was performed using a non-contact jumping development method. still,
The developing bias was AC bias Vpp1600V, frequency 1800 Hz, and the distance between the developer carrier and the image carrier was about 300 μm.

Further, in the image forming experiment of this embodiment, the developer was a reversal developing system using a negative polarity developer in which a positive ghost is relatively likely to appear.

In the image forming apparatus having the developer carrier according to the present invention, the obtained image has no or very little positive ghost. On the other hand, when a conventional developing device having a developer bearing member was incorporated and an image was output, a positive ghost appeared considerably.

This is because the developer carrier constructed according to the present invention has the property of facilitating the transfer of charges from the developer to the developer carrier even under a low voltage of 1 volt or less as shown in FIG. Therefore, the charge of fine powder in the vicinity of the developer carrier, which is the cause of positive ghost, is lowered, the mirroring force by the developer itself is reduced, and the fine powder becomes easier to separate from the developer carrier. It is considered that the reduction effect was obtained.

In the present invention, the effect can be obtained by coating the conventional developer carrier in a thin layer as in this embodiment. However, the conventional conductive developer carrier is aluminum or stainless steel (SUS). The metal is used, and the surface is oxidized when seen in detail. This is as shown in FIG. According to the present invention, even in a developer carrying member having an oxide film having a relatively low barrier on its surface, the same effect can be obtained by forming a conductive fine particle-containing resin layer thereon.

That is, when the conductive fine particle-containing resin layer is provided on the surface, the conductive fine particles are formed so as to project, so that the conductive fine particle-containing resin layer serves as a charge leak site. It is considered that this is because the barrier of the oxide film can be penetrated.

By further imparting surface lubricity to the conductive fine particle-containing resin layer described in the above embodiment, the positive gooset reduction effect is ensured, and the operating time of the developer increases. It is possible to reduce the contamination caused by the developer on the developer carrier.

An example is as follows.

The resin solution prepared with the above composition is applied by a coating method, a dipping method, or a spray method.
The surface of a developer carrying member made of aluminum and blasted with Alundum # 400 was coated with about 6 μm. Next, in this example, since a phenol resin was used as the resin, heat curing was performed at 150 ° C. for 30 minutes in a drying furnace. The surface resistivity and volume resistivity of the conductive fine particle-containing resin layer at this time are the resistance of the conductive fine particle-containing resin layer film formed on PET (polyethylene terephthalate) under the same film forming conditions. It was obtained by measuring the rate with Loresta AP Intelligent manufactured by Mitsubishi Petrochemical. In this example, it was about 7.0 × 10 ⁻¹ Ωcm.

According to this embodiment, not only the effect of reducing the sleeve ghost could be obtained, but also the effect of reducing the contamination of the developer bearing member by the developer was remarkable. That is,
By imparting solid lubricity to the surface of the developer carrying member, it was possible to prevent the concentration from lowering in durability. It is considered that this is because the surface of the developer carrying member has lubricity, which makes it difficult for contaminants to adhere to the surface.

The above effect can also be obtained by applying a resin containing conductive fine particles obtained by the following formulation onto the surface of the developer carrying member.

The resistivity of the resin layer film containing conductive fine particles prepared by this formulation was about 7.0 × 10 ^-1 Ωcm. Regarding graphite, the particle size was changed, but it worked effectively between 0.3 μm and 7 μm regardless of whether artificial or natural.

Further, the same effect could be obtained by using a solid lubricant as the lubricant. The prescription at that time was as follows. In addition to molybdenum disulfide, boron nitride or the like can be used as the solid lubricant.

In each of the above examples, a phenol resin was used as the resin forming resin layer containing conductive fine particles, but in addition, vinyl chloride, vinyl acetate, a polymer of vinyl chloride and vinyl acetate, polyester, polystyrene, PMMA. ,
Cellulose acetate, butyral, melamine, epoxy resin, water-based casein, etc. can be used as well.

Furthermore, not only the above-mentioned thermoplastic and thermosetting resins but also UV (ultraviolet) curing resins can be used in the same manner. However, in the case of a UV curable resin, the film thickness cannot be made too thick in consideration of the curing conditions, but it can be made sufficiently thick when used in combination with a thermosetting resin or a thermoplastic resin.

In the above description, a negative developer was used as the developer, but it will be apparent that a blur developer can be used as well.

Further, in the above-mentioned embodiment of the present invention, aluminum is used as the metal of the developer carrying member in Alundum # 400.
I explained using sandblasted in
The same effect can be obtained by using aluminum after the drawing process, and a metal other than aluminum can be used.

The structure of the developing device according to the present invention is not limited to the structure shown in FIG. 1, and as shown in FIGS. 6 and 7, a rigid magnetic blade is used as the developer layer thickness regulating member. Alternatively, an elastic blade or a metal plate may be used.

[0051]

As described above, in the developer carrier according to the present invention, the electric resistance of the surface is reduced by providing the resin layer containing the conductive particles on the metal base material having the oxide film on the surface. In addition, since the developing device of the present invention is configured to include the developer carrying member having such a characteristic configuration, the developing device of the present invention can be applied to the electrode softly contacted with the surface of the conductive fine particle-containing resin layer. On the other hand, when the voltage applied is less than 5 V, the flowing current increases as compared with the case where the conductive fine particle-containing resin layer is not provided, and the ratio of the applied voltage to the current is 1000 μm. Since it is configured to be almost constant when a low voltage up to a volt is applied, the positive sleeve ghost can be eliminated or a significant reduction effect can be exhibited, and a high quality image can be obtained. Toi With the features.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of an image forming apparatus to which a developing device having a developer carrying member according to the present invention can be applied.

FIG. 2 is a partial cross-sectional view of a developer carrying member constructed according to the present invention.

FIG. 3 is an explanatory diagram illustrating an outline of a measuring device for measuring the resistivity of a developer carrying member.

FIG. 4 is an explanatory diagram showing a form of an electric current flowing on a surface of a developer carrying member.

FIG. 5 is a graph showing VI characteristics of a developer carrier constructed according to the present invention and a conventional developer carrier.

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

FIG. 7 is a cross-sectional view of another embodiment of a developing device constructed according to the present invention.

FIG. 8 is a sectional view of a conventional developing device.

FIG. 9 is a plan view of a copy for explaining a sleeve ghost.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 10 Developing device 12 Developer container 13 Development area 14 Developer carrier 17 Developer carrying member 18 Conductive fine particle containing resin layer 19 Oxide film layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Keiji Okano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A developer carrying member characterized in that the electric resistance of the surface is reduced by providing a resin layer containing conductive particles on a metal base material having an oxide film on the surface. 2. The developer carrying member according to claim 1, wherein the metal base material is aluminum whose surface is blasted. 3. A developer having a developer container for containing the developer, and a developer carrier for carrying and carrying the developer in the developer container to a developing area for developing an electrostatic image on the image carrier. In the apparatus, the developer carrier has a metal base material having an oxide film on the surface, and a conductive particle-containing resin layer provided on the metal base material for reducing the electric resistance of the surface. Development device. 4. The developing device according to claim 3, wherein the developer is a negative toner. 5. The developing device according to claim 3, further comprising an elastic blade that regulates the layer thickness of the developer.