JPH0713414A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device capable of always obtaining a sharp and stable high-quality image without fogging in a developing system using one component type toner. CONSTITUTION:This developing device is equipped with a toner carrier 14, a toner supply member 13 supplying the toner 11 to the outer peripheral surface of the toner carrier 14, and a toner layer thickness regulating member 15 abutting on the outer peripheral surface of the toner carrier 14. In this device, the one component type toner supplied to the outer peripheral surface of the toner carrier 14 is formed to a thin layer by the member 15, and the toner thin layer is made to come close to or come in contact with the a latent image holding body 17 so as to visualize an electrostatic latent image held on the image holding body 17; and the toner supply member 13 is formed of a material which has elasticity and whose surface, at least, has volume resistance <=10<4>OMEGA.m.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for visualizing an electrostatic latent image in an electrophotographic device or an electrostatic recording device.

[0002]

2. Description of the Related Art A technique for forming and holding an electrostatic latent image on a latent image holder and developing the formed and held electrostatic latent image into a visible image, that is, image formation using an electrophotographic method. The method has been widely known, and has been widely used in electrophotographic devices (copiers), electrostatic recording devices, and the like. And, in the electrophotographic apparatus and the electrostatic recording apparatus, a dry developing method is adopted for developing the electrostatic latent image, and
This dry developing method is divided into a method using a two-component toner composed of toner and carrier and a method using a one-component toner containing no carrier.

In this dry development, in the development method using a two-component toner, the carrier and the toner are mixed and stirred, and sufficient mutual contact is given to the toner to give a charge close to a saturated state. Therefore, the toner can obtain a sufficient amount of charge necessary for developing the electrostatic latent image, and there is an advantage that it is easy to obtain a visible image without density unevenness. On the other hand, there is a limit to downsizing of the developing device including the toner storage portion, and there is a problem that the formed image is deteriorated due to a change in the mixing ratio of the toner forming the two-component toner and the carrier. is there. That is, in the case of a two-component toner, the toner component is consumed in the developing process, which inevitably causes a change in the mixing ratio of the toner and the carrier, which causes image deterioration and the like. In order to maintain the image quality, careful toner management during development is required.

On the other hand, from the viewpoint that it is relatively easy to downsize the developing device and the mixing ratio of the toner components does not change, the developing system using the one-component toner is drawing attention, and the developing method using the one-component toner is used. Methods and developing devices have also been proposed. FIG. 8 is a cross-sectional view showing an outline of a developing mechanism of a developing system using a one-component toner. A roller type toner carrier (the peripheral surface of which is in contact with the peripheral surface of the latent image carrier 1) is rotated. A developing roller) 2, a toner supply member 3 whose peripheral surfaces are in pressure contact with each other while rotating in the same direction as the toner carrier 2.
The toner layer thickness regulating member 4 abutting on the peripheral surface of the toner carrier 2 is provided. Development in this developing device is performed as follows. First, the toner 5 is supplied from the toner supply member 3 to the toner carrier 2 between the toner carrier 2 and the toner supply member 3 whose peripheral surfaces are in pressure contact with each other while rotating in the same direction. Next, the toner carrier 2
The toner 5 supplied to the peripheral surface is thinned by the toner layer thickness regulating member 4 and electrostatically adheres to the latent image holding member 1 whose peripheral surface contacts and rotates to form an electrostatic latent image. Visualize. In this developing method, the toner 5 is charged in a region where the peripheral surfaces of the toner carrier 2 and the toner supply member 3 are in pressure contact with each other, a region where the toner carrier 2 and the toner layer thickness regulating member 4 are in contact with each other, and the like. .

[0005]

By the way, when the electrostatic latent image is visualized (developed) with a one-component toner, the flying amount or the adhering amount of the toner 5 on the latent image holding member 1 depends on the toner. It largely depends on the amount of charge of the toner 5 conveyed to the surface of the carrier 2. Therefore, in order to obtain a stable image, the magnitude and stability of the charge amount of the toner 5 are important. However, in the case of the developing device using the one-component toner, compared to the case of the developing device using the above-mentioned two-component toner, the toner 5 and the charge applying portion (toner carrier 2,
The contact time and contact probability with the toner supply member 3, the toner layer thickness regulating member 4, etc.) are extremely small. Therefore, the amount of charge applied to the toner 5 is small, the amount of charge is non-uniform, or the amount of charge is not reproducible. That is, in the case of the developing system using the one-component toner, the flying amount or the adhesion amount of the toner 5 on the latent image holding member 1 is likely to change, and an image (image quality) obtained in accordance with the change in the adhesion amount or the like. Instability is a practical problem. Especially during long-term (continuous) development,
Problems such as a decrease in image density due to a reduction in the charge amount of the toner 5 and toner adhesion (fogging) to a white background portion on the latent image carrier 1 occur. As described above, the developing method using a one-component toner still has inconvenient problems while being paid attention to practical use, and it is desired to greatly improve or eliminate these problems.

The present invention has been made in consideration of the above circumstances, and in a developing system using a one-component toner,
An object of the present invention is to provide a developing device capable of obtaining a stable, high-quality image without sharpness and fog.

[0007]

A developing device according to the present invention comprises a toner carrier, a toner supply member for supplying toner to the outer peripheral surface of the toner carrier, and a toner contacting the outer peripheral surface of the toner carrier. The toner layer thickness regulating member is provided, and the one-component toner supplied to the outer peripheral surface of the toner carrier is thinned by the toner layer thickness regulating member, and the thin toner layer is brought close to or in contact with the latent image carrier. In a developing device for visualizing the electrostatic latent image held by the latent image holding member,
The toner supply member has elasticity and at least the surface thereof is made of a material having a volume resistance of 10 ⁴ Ω · m or less.

That is, according to the present invention, in the developing system using the one-component toner, during the toner charging operation of the charge applying portion such as the toner carrier, the toner supplying member, and the toner layer thickness regulating member,
The surface volume resistance of the toner supply member has a great influence,
And the knowledge that metal powder or a metal thin film is suitable for the adjustment of the surface volume resistance, and more specifically, it is an important point to set the surface volume resistance to 10 ⁴ Ω · m or less. It was made based on. That is, the inventors of the present invention have examined the relationship between the toner supply member having elasticity as the charge applying portion and the rising of the charging of the toner. As a result, the rising of the charge amount and the like are recognized depending on the material of the toner supply member. I found that.
Here, FIG. 1 is a characteristic diagram illustrating the relationship between the material of the elastic layer of the toner supply member and the charging rise characteristic of the one-component toner. As shown in FIG. When the material of the toner supply member having the property of being metallic is made to have conductivity, the rising change of charging as shown by the curve a is obtained, and when the material of the toner supply member is made of carbon to be made conductive as usual. Indicates the rising change of charging as shown by the curve b. Moreover, when the material of the toner supply member is carbon and conductivity is imparted, some toner is not negatively charged as indicated by the broken line in FIG. As described above, at least the surface of the toner supplying member having elasticity in the charge applying portion is formed of a material having a volume resistance of 10 ⁴ Ω · m or less (more preferably 10 ³ Ω · m or less), so that the rise of charging can be achieved. Due to the good chargeability, the required charge is sufficiently applied to the toner even in the one-component system toner development method in which the charge application time or the charge application contact probability is small.
It was confirmed for the first time that it could be performed reliably, and the present invention has been achieved based on such facts.

Although the charge application to the negatively charged toner has been described here, according to the present invention, the required charge can be sufficiently and surely applied to the positively charged toner. . Further, in the present invention, the entire elastic layer of the toner supply member may be formed of the material having the resistance value, or only the surface may be covered. However, if the volume resistance of the entire elastic layer is extremely small, an electric current is generated between the toner carrier and the toner supply member, which makes it difficult to apply a predetermined developing bias to the toner carrier.
It is more preferable to form a toner supply member by coating a substrate having a resistance value of about 10 ⁴ to 10 ⁷ Ω · m with a material having a volume resistance of 10 ⁴ Ω · m or less.

Further, in the developing device according to the present invention, the roller type toner carrier and the toner supply member are rotated in the same direction, and the peripheral speed of the roller type toner carrier is A.
(Mm / sec), the peripheral speed of movement of the endless toner supply member is B (mm / sec), and the contact width between the toner carrier and the toner supply member is x (mm). It is desirable to set to satisfy the relationship of t = x / A + x / B> 0.005, where t (sec) is the time during which the toner stays between and. Here, the toner supply member is generally a roller type, but may be, for example, an endless belt type or a fur brush type.

[0011]

According to the present invention described above, the one-component toner is supplied to the toner carrier through the toner supply member having elasticity and at least the surface of which is made of a material having a volume resistance of 10 ⁴ Ω · m or less. The toner is provided with a required electric charge in the process of being conveyed by the toner supply member, at the time of being supplied from the toner supply member to the toner carrier, and the like. In other words, the toner supply member having elasticity and at least the surface of which is made of a material having a volume resistance of 10 ⁴ Ω · m or less plays a role of a carrier of a developing method using a two-component toner, so that the one-component toner can be easily formed. In addition, since the charging is performed reliably and uniformly, it is possible to develop a high-quality image in a stable state.

[0012]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 2 is a cross-sectional view of the essential parts of an image forming apparatus equipped with the developing device of the present invention. In FIG. 2, reference numeral 10 denotes a toner container containing a one-component toner 11, and in the toner container 10, a toner stirrer 12 and a toner supply member 13 are arranged as toner supply means. And
By the toner stirrer 12 and the toner supply member 13,
The toner 11 is conveyed onto the outer peripheral surface of the roller type toner carrier 14.

The roller type toner carrier 14 is made of a metal such as aluminum or stainless steel, or a hard or soft resin such as phenol resin, acrylic resin, urethane resin, fluororesin, polyamide resin, polyester resin or epoxy resin. Further, a magnet roller having a composite of these or the like and having magnetic poles inside may be adopted. Preferably, as the roller type toner carrier 14, a non-magnetic (or non-magnetized) developing roller having elasticity and conductivity is exemplified. For example, a metal shaft on which a conductive rubber layer having a resistance value of 10 ⁸ Ω · m ² or less is concentrically arranged, or a silicone resin, a urethane resin, or a fluororesin on the conductive rubber layer. Such as those coated with a resin layer, those with a high resistance or insulating rubber roller peripheral surface coated with a conductive resin layer, or those with semiconductive rubber roller peripheral surfaces provided with microelectrodes that are electrically insulated from each other, etc. Is mentioned.

The conductive rubber layer is made of, for example, urethane rubber, silicone rubber, ethylene propylene rubber,
The resistance value is adjusted to 10 ⁸ Ω · m ² or less by dispersing conductive carbon particles, metal particles, or metal fibers in NBR, chloroprene rubber, butyl rubber, or the like. In this example, a hardness of 30 degrees (JIS K-6301 A
The thickness of the urethane rubber layer of the type hardness tester is 5 mm (resistance value 10 ⁶ Ω
(M ² or less), a roller type toner carrier (developing roller) formed by coating a urethane coating film with a thickness of 20 to 200 μm as a conductive rubber layer on the outer peripheral surface thereof is attached.

Further, the base material of the toner supply member 13 preferably has a surface roughness of at least about 10 μm (corresponding to the diameter of the toner) or more in consideration of the conveying ability of the one-component toner 11 and the desired charging. To obtain the rising characteristics,
It is necessary that the roller-type toner carrier 14 has elasticity such that it can contact the roller-type toner carrier 14 with a predetermined contact width, and it is preferable that the roller-type toner carrier 14 is softer than the roller-type toner carrier 14. More specifically, a foamed flexible foam having abrasion resistance and appropriate conductivity, which does not solidify by the invasion of the one-component toner 11, for example, a sponge or polyurethane of chloroprene rubber or silicone rubber in which conductive carbon is dispersed. , Density 0.01-0.2 g / cm ³ , hardness 15-50
kgf / cm ² (measured with JIS K-6401), cell number 100 to 20
00 pieces / 25 mm, resistance value of 10 ⁴ to 10 ⁷ Ω · m is desirable. Then, in imparting conductivity to this type of foamed flexible foam, for example, conductive carbon may be added and blended in advance, and by foaming this, a flexible foam having conductivity and flexibility may be obtained. Alternatively, it can be obtained by first forming a flexible foam and impregnating it with conductive carbon. In the embodiment, as the toner supply member 13, a metal shaft having an outer diameter of 5 mm is concentrically formed with a density of 0.1 g / cm ³ and a hardness of 30 kgf / cm ² (J
(Measured by IS K-6401), a roller type consisting of a conductive polyurethane foam layer with a surface resistance value of 10 ⁵ Ω · m (outer diameter 12 mm) is used as the base material, and the required surface volume resistance is The thing which gave the process for giving was attached.

Further, the toner carrier (developing roller)
A toner layer thickness regulating member 15 for contacting the outer peripheral surface and thinning the one-component toner 11 is arranged in proximity to the toner container 10. Then, the toner layer thickness regulating member 15
Is pressed against the outer peripheral surface of the toner carrier 14 by the pressing force of the spring 16, and the toner layer carried on the outer peripheral surface of the toner carrier 14 passes through the toner layer thickness regulating member 15 to form a thin layer. Be converted. The toner layer thickness regulating member 15
The radius of the curved surface is about 0.1 to 20 mm, and even 0.5
It is preferably set to about 10 mm. The toner layer thickness regulating member 15 is made of, for example, metal such as aluminum or stainless steel, or phenol resin, acrylic resin,
Hard or soft resin such as urethane resin, fluororesin, polyamide resin, silicone resin, melanin resin, polystyrene resin, polyester resin, epoxy resin,
Further, it is composed of a composite body of these, or an elastic body such as urethane rubber or silicone rubber.

Further, in FIG. 2, reference numeral 17 denotes a latent image holding member (photosensitive drum) arranged to face the toner carrying member (developing roller) 14, and a required electrostatic latent image is formed by the exposure light 18. It has the function to be done. The latent image carrier 17 on which the electrostatic latent image is formed is in contact with the toner carrier 14 having a thin toner layer on the outer peripheral surface thereof, and the one-component toner
By attaching 11 onto the electrostatic latent image, the latent image carrier
The electrostatic information (electrostatic latent image) recorded in 17 is visualized. The visible image formed here is
For example, the one-component toner that remains on the toner carrier 14 while being transferred and recorded on the recording paper by the transfer device 19
The recovery member 20 collects the toner 11 in the toner container 10. In FIG. 2, reference numeral 21 is a charger for applying a required electrostatic charge to the latent image carrier 17, 22 is a power source for supplying a required current to the toner supply member 13 and the toner carrier 14, and 23 is a protective resistor.

By the image forming apparatus having the developing device having the above-mentioned structure, electrostatic information (electrostatic latent image) is obtained under the following conditions.
Was visualized (developed).

First, as the one-component toner 11, various one-component toners including known binder resins, colorants, charge control agents, waxes, anti-caking agents and the like can be used. Here, polyester is used. A negatively chargeable toner having a volume average particle diameter of 10 μm was used, which was composed of 92 parts by weight of resin, 4 parts by weight of copper phthalocyanine pigment, 2 parts by weight of low molecular weight polypropylene, and 0.5 parts by weight of hydrophobic silica as an external additive.

The toner charge amount Q / m (μC / g) on the surface of the toner carrier 14 passes through the toner layer thickness regulating member 15 and is conveyed to the latent image carrier 17 side. A value obtained by sucking the one-component toner 11 adhering to the surface with a vacuum cleaner or the like and dividing the amount of charge (Q) generated at that time by the amount of the sucked one-component toner (m) was used.

Further, in the image evaluation, the surface speed of the latent image carrier (photosensitive drum) 17 was set to 40 mm / sec, the surface potential was uniformly charged to -500 V by corona discharge from the charger 21, and the exposure light 18 After recording the image information with the laser as
The toner carrying member (developing roller) 14 to which -200 V was applied and which was rotated at a surface speed of 80 mm / sec was pressed against the peripheral surface of the latent image holding member 17 to carry out required reversal development. To supply the one-component toner 11 to the toner carrier 14, the toner supply member (toner supply roller) 13 is moved to a surface speed of 60 mm.
The developed toner image was transferred onto a recording paper by DC corona discharge of 5 KV in the transfer device 19 and then heat-fixed. Example 1 A developing device of the image forming apparatus shown in FIG. 2 has a roller type structure in which a conductive polyurethane foam layer 13a is concentrically arranged with respect to the metal shaft. As schematically shown in the configuration, a developing device equipped with a toner supply member 13 in the form of a seamless nickel film 13b having a mesh pattern on the outer peripheral surface thereof is used to charge the toner on the toner carrier 14 surface. The quantity was measured and the image was evaluated. Here, the surface volume resistance of the toner supply member 13 was 10 ² Ω · m.

First, the toner charge amount on the surface of the roller type toner carrier 14 shows a good value of -3 μC / g, and it is possible to form a clear image without toner fog on a white background, and a line image. Was clear, the solid image was uniform, and sufficient density was obtained with good reproducibility. Also, after the life test of 10,000 sheets, the initial state of both the image and the charge amount is maintained,
A clear image without deterioration was obtained.

Further, in the roller type toner supply member 13 of the developing device, a seamless nickel film 13b having a mesh pattern for covering the outer peripheral surface is formed by sandblasting as shown in FIG.
Similar results were obtained with a seamless nickel film 13c having z (ten-point average roughness) = about 20 μm. In addition, instead of coating the outer peripheral surface of the roller type toner supply member 13 with a nickel film, another metal film such as copper (Cu), aluminum (Al) or stainless steel (SUS) may be used. , Similar results were obtained.

COMPARATIVE EXAMPLE 1 In Example 1, the roller type toner supplying member 13 included in the developing device has a conductive polyurethane concentrically with respect to the metal shaft, as schematically shown in FIG. By the image forming apparatus using the toner supply member 13 having only the foam layer 13a (surface volume resistance, 10 ⁵ Ω · m), the toner charge amount on the surface of the toner carrier 14 is measured and the image is similarly measured. When evaluated, the toner charge amount was +2.5 μC / g, the line image was unclear, the solid image was also light in density, and the toner amount was about the same as the toner fog on the white background, which was not practical. I didn't get it.

Embodiment 2 As a developing device of the image forming apparatus shown in FIG. 2, a roller type structure is used in which a conductive polyurethane foam layer 13a is concentrically arranged with respect to the metal shaft. As shown schematically in FIG. 1, a developing device equipped with a toner supply member 13 in which the outer peripheral surface thereof is covered with a nickel plating layer 13d having a thickness of about 3 μm is used. The toner charge amount and the image evaluation were performed. Here, the surface volume resistivity of the toner supply member 13 was 10 ⁰ Ω · m.

First, the toner charge amount on the surface of the roller type toner carrier 14 shows a good value of -3.5 μC / g, and it is possible to form a clear image without toner fog on a white background portion, and the line The image was clear, the solid image was uniform, and sufficient density was obtained with good reproducibility. Further, even after the life test of 10,000 sheets, the initial state of both the image and the charge amount was maintained, and a clear image without deterioration was obtained.

Further, in the above, the nickel plating layer 1
Instead of 3d, a semiconductive oxide layer such as tin oxide or ITO is vapor-deposited on the outer peripheral surface of the conductive polyurethane foam layer 13a, and the surface volume resistance is set to 10 ⁴ Ω · m or less. As in the case, good results were obtained.

Embodiment 3 As a developing device of the image forming apparatus shown in FIG. 2, a roller type structure is used in which a conductive polyurethane foam layer 13a is concentrically arranged with respect to the metal shaft. As schematically shown in Fig. 1, the conductive polyurethane foam layer 13a is further impregnated with a solid content solution of about 80 parts by weight of silver metal powder and about 20 parts by weight of a binder resin, and the outer surface is covered with silver powder 13e. Using a developing device equipped with the toner supply member 13 in the attached form, the toner charge amount on the surface of the toner carrier 14 was measured and the image was evaluated. Here, the surface volume resistance of the toner supply member 13 was 10 ³ Ω · m.

First, the toner charge amount on the surface of the roller-type toner carrier 14 shows a good value of -1.9 μC / g, and it is possible to form a clear image without toner fog on a white background, and the line The image was clear, the solid image was uniform, and sufficient density was obtained with good reproducibility. Furthermore, even after the life test of 10,000 sheets, the initial state of both the image and the charge amount was maintained, and a clear image without deterioration was obtained.

Further, in the above, instead of adhering the silver powder 13e, silver metal powder or other metal powder, tin oxide or I
A semi-conductive oxide layer such as TO is added and blended in advance with the polyurethane resin, and this polyurethane resin is foamed. For example, as shown schematically in FIG.
The surface volume resistance of 10 ⁴ Ω
Even when the conductive polyurethane foam layer 13a having a thickness of m or less was formed, good results were obtained as in the case described above.

[0032]

As described above, according to the developing device of the present invention, the uniform and required charge is applied to the one-component toner supplied from the toner supply member to the surface of the toner carrier. Not only is this easy, but this uniform and required charge imparting function is retained and exhibited for a long period of time.
In other words, without causing structural complication, it is possible to reliably improve and stabilize the charging characteristics of the one-component toner supplied for development, and it is possible to obtain sharp, fog-free, high-quality toner. Images will always be available.

[Brief description of drawings]

FIG. 1 is a characteristic diagram illustrating a relationship between a material of an elastic layer of a toner supply member and a charge rising characteristic of a one-component toner.

FIG. 2 is a cross-sectional view showing a configuration example of a main part of an image forming apparatus including a developing device according to the present invention.

FIG. 3 is a cross-sectional view schematically showing a first example of a main part configuration of a toner supply member included in the developing device according to the present invention.

FIG. 4 is a cross-sectional view schematically showing a second main part configuration example of a toner supply member included in the developing device according to the present invention.

FIG. 5 is a cross-sectional view schematically showing a third main part configuration example of a toner supply member included in the developing device according to the present invention.

FIG. 6 is a cross-sectional view schematically showing a fourth main configuration example of a toner supply member included in the developing device according to the present invention.

FIG. 7 is a cross-sectional view that schematically shows a fifth main configuration example of the toner supply member included in the developing device according to the present invention.

FIG. 8 is a sectional view for explaining a developing mechanism using a one-component toner.

FIG. 9 is a cross-sectional view schematically showing a configuration of a main part of a toner supply member included in a conventional developing device.

[Explanation of symbols]

1, 17 ... Latent image carrier (photosensitive drum) 2, 14 ... Toner carrier (developing roller) 3, 13 ... Toner supply member 4, 15 ... Toner layer thickness regulating member 5, 11 ... One-component toner 10 ... Toner container
12 ... Toner stirrer 13a ... Conductive polyurethane foam layer 13b, 13c ... Nickel film 13d ... Nickel plating layer 13e ... Silver powder 16 ... Spring 18 ... Exposure light 19 ...
Transfer device 20 ... Recovery member 21 ... Charger 22 ...
Power supply 23… Protection resistance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideyuki Nishizawa Inventor Hideki Nishizawa, Komukai-shi, Kawasaki-shi, Kanagawa No. 1, Toshiba R & D Center, Ltd. Toshiba Town No. 1 Inside Toshiba Research and Development Center

Claims (1)

[Claims] 1. A toner carrier, a toner supply member for supplying toner to the outer peripheral surface of the toner carrier, and a toner layer thickness regulating member that is in contact with the outer peripheral surface of the toner carrier. The one-component toner supplied to the outer peripheral surface of the toner carrier by the toner layer thickness regulating member is made into a thin layer, and the thin layer of the toner is brought close to or in contact with the latent image carrier, and the electrostatic image held by the latent image carrier is A developing device for converting a latent image into a visible image, wherein the toner supply member has elasticity and at least the surface is made of a material having a volume resistance of 10 ⁴ Ω · m or less.