JPS63231469A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a good visible image by forming a developer carrier of a roller consisting of a central shaft which is made of a rigid body having electrical conductivity, an intermediate layer which is formed on the outer circumference of the central shaft and consists of a porous foamed body having elasticity and a surface layer which is formed on the outer circumference of the intermediate layer and has elasticity. CONSTITUTION:A developing roller 4 which is the developer carrier made into the 3-layered structure consisting of the central shaft 5 which is made of the rigid body having the electrical conductivity, the intermediate layer 6 which is formed on the outer circumference of the shaft 5 and has the elasticity, and the surface layer 7 which is formed on the outer circumference of the layer 6 and has the elasticity. A bias power supply 8 is connected to the central shaft 5. The hardness of the carrier 5 can, therefore, be lowered and the projection from a nip width is obviated. Adhesion of a developer to the part except an electrostatic latent image part, i.e., fogging are prevented by applying a bias voltage to the shaft 5 of the carrier 4 at the time of development; in addition, the projecting parts formed on the surface of the intermediate layer 6 acts as microelectrodes. An excellent edge effect is thereby obtd. and the good visible image is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a developing device used in an electrophotographic recording device, an electrostatic recording device, etc., and in particular, it relates to a developing device used in an electrophotographic recording device, an electrostatic recording device, etc. This relates to a developing device that is transported to a development area and performs development.

[Conventional technology]

A developing device in an electrophotographic recording device or the like uses a two-component developer to develop an electrostatic latent image on an electrostatic latent image carrier into a visible image, and a developing device uses a -component developer to develop the electrostatic latent image on an electrostatic latent image carrier into a visible image. It is well known that there are devices that develop electrostatic latent images. Among these, developing devices that use two-component developers mix and stir two components, toner and carrier, as a developer, and the resulting friction charges the toner. It is possible to obtain a good image by supplying the toner to the electrostatic latent image, but since it is necessary to maintain a constant mixing ratio of toner and carrier, the structure is complicated, and the carrier There is an inconvenience in that maintenance must be performed periodically to prevent deterioration of print quality due to deterioration.

On the other hand, some developing devices using -component developers use magnetic toner and non-magnetic insulating toner as the -component developer, and although both do not have the above-mentioned disadvantages,
The former type of developing device using magnetic toner has the disadvantage that clear colors cannot be obtained when performing color development because the toner contains a magnetic substance.

Therefore, the latter developing device using a non-magnetic insulating toner and a one-component non-magnetic insulating developer is attracting attention.

A developing device using this -component non-magnetic insulating toner includes:
A non-contact method in which a developer carrier faces the electrostatic latent image carrier with a certain gap in the development area, and a contact method in which the developer carrier is brought into pressure contact with the electrostatic latent image carrier. However, in recent years, both of these methods have been published, for example, in Japanese Patent Application Laid-Open No. 60-230673,
As shown in Japanese Patent No. 238876, a developer carrier is formed into a roller or a belt, and a frictional charging member is placed on the outer periphery of the roller or belt, and a frictional charging member is brought into contact with or closely opposed to the developer carrier, and one-component non-magnetic insulating toner is passed between them. Many structures have been proposed in which the toner is charged and developed using the insect-repelling friction.

Therefore, among the developing devices that charge the negative component non-magnetic insulating toner, in the contact type developing device described above, the electrostatic latent image carrier is based on a conductive rigid pipe, such as a pipe made of aluminum. When the developer carrier is formed as a material, by forming the developer carrier in an elastic material and bringing it into pressure contact with the electrostatic latent image carrier, uniform contactability can be obtained in the entire axial direction, and A predetermined nip width (contact length) serving as a development area is obtained.

FIG. 4 is a partial cross-section showing a conventional developing device of this type. In the figure, 1 is an electrostatic latent image carrier (hereinafter referred to as a photosensitive drum) having a photoconductive layer formed using a conductive rigid pipe as a base material. ), it rotates at a constant speed in the direction of arrow a.

2 is a device housing (hereinafter referred to as a toner tank); 3 is a one-component non-magnetic insulating developer (hereinafter referred to as a toner) stored in the toner tank 2; 9
10 is a flexible member such as a leaf spring fixed to the bottom of the toner tank 2, and 10 is a frictional charging member (hereinafter referred to as a blade) fixedly held at the free end of the flexible member 9.

Reference numeral 13 denotes a developer carrier (hereinafter referred to as a developing roller) made of an elastic material such as rubber.
The toner is held in the toner tank 2 so as to be pressed against the surface of the photosensitive drum 1 with a predetermined pressure to obtain a predetermined nip width, and rotates in the direction indicated by the arrow. The blade 10 is in contact with it.

In this configuration, the toner 3 in the toner tank 2 is stirred and spread by a stirring member (not shown), and is sent to the contact area between the developing roller 13 and the blade 10, where it is sandwiched between the surfaces of the two and frictionally charged. Ru.

This frictionally charged toner 3 is transferred to the developing roller 13.
The layer of the toner 3 attached to the developing roller 13 is regulated into a uniform thin layer by the blade 10, and then the layer of the toner 3 attached to the developing roller 13 is regulated into a uniform thin layer. Toner 3 is supplied from the developing roller 13 to the electrostatic latent image carried and conveyed by the photosensitive drum 1 in the area, and the toner 3 adheres to the electrostatic latent image, so that the electrostatic latent image becomes a toner image or a visible image. .

Note that the circumferential speed of the developing roller 13 is generally set to be faster than the circumferential speed of the photosensitive drum 1 in order to increase the toner supply capacity.

[Problem that the invention seeks to solve]

There are the following problems.

That is, FIG. 5 is an enlarged view of the main part of FIG. 4, and as seen in this figure, the developing roller 13 is in pressure contact with the photosensitive drum 1, so the developing roller 13 moves from the free state shown by the two-dot chain line to the photosensitive drum 1. The developing roller 13 is made of a relatively hard elastic material such as rubber, so it rotates due to friction with the photosensitive drum 1 during rotation. 13at protruding from the nip width on the rear side of the direction
arise.

This protrusion 13a is restored when the elasticity of the developing roller 13 overcomes the frictional force, but the occurrence and recovery of the protrusion 13a are repeated during the rotation of the developing roller 213, and this phenomenon causes density unevenness in the toner image. However, since load fluctuations are applied not only to the power system but also to the power system, there is a problem in that it is difficult to obtain a good visible image due to these changes.

Further, since development is performed simply by pressing the developing row 213t against the photosensitive drum 1 and rotating it, the edge effect deteriorates, and from this point of view as well, it is difficult to obtain a good visible image.

Furthermore, since the rotational load on the photosensitive drum 1 and the developing roller 13 is large due to the above-described frictional load fluctuation, a power system having a large driving force is required to rotate them, which leads to an increase in cost.

The present invention was made to solve the problem of stiffness, and provides a developing device that can obtain good visible images with no density unevenness and excellent edge effect, and can reduce costs. The purpose is to achieve this goal.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention includes a developer carrier (developing roller) in pressure contact with an electrostatic latent image carrier (photosensitive drum), and a triboelectric charging member (blade) on the outer periphery of the developer carrier. In a developing device that uses a one-component non-magnetic insulating developer as a developer, the developer carrier is made of a conductive rigid body. a central axis; an intermediate layer made of an elastic porous foam formed around the central axis;
The three-layer structure includes an elastic surface layer formed on the outer periphery of the intermediate layer, and a bias power source is connected to the central axis.

[Effect]

In the present invention having the above-described structure, the developer carrier has a structure having an intermediate layer made of porous foam and an elastic surface layer, so that the hardness of the developer carrier is lower than that of the conventional hardness. This makes it possible to suppress frictional load fluctuations with the static latent image carrier, and also equalizes the pressing pressure in the axial direction. Protrusion from the nip width can be eliminated.

Furthermore, by applying a bias voltage to the central axis of the developer carrier using a bias power supply during development, it is possible to prevent the developer from adhering to areas other than the electrostatic latent image, so-called fog, and the intermediate layer is made of porous foam. Therefore, since the protrusions formed on the surface act as microelectrodes, an excellent edge effect can be obtained and a good visible image can be obtained.

Furthermore, since frictional load fluctuations can be suppressed, the rotational load on the electrostatic latent image carrier and developer carrier can be reduced, so the single driving force of the power system can be smaller than in the past. This will also help reduce costs.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of the developing device according to the present invention, and FIG. 2 is an enlarged view of the main part of FIG.
The photosensitive drum is the same as that shown in FIG. 5 and rotates counterclockwise at a constant speed as indicated by arrow a.

2 is a toner tank; 3 is toner; 4 is a developing roller comprising a central shaft 5, an intermediate layer 6, and a surface layer 7; 8 is a bias power source; 9
10 is a flexible member such as a leaf spring, 10 is a blade, 114 is an agitating member, and 12 is a toner blocking member.These 2 to 12 constitute the developing device of this embodiment.The details thereof will be explained below. do.

First, a predetermined amount of toner 3 is stored in a toner tank 2, an opening is provided on the side of the toner tank 2 facing the photosensitive drum 1, and the developing roller 4 is placed in an intermediate layer. 6'1
The surface layer T is placed and held inside the opening so that it is elastically deformed and pressed against the surface of the photosensitive drum 1 with a predetermined nip width, and is photosensitive by a driving force transmitted to the central shaft 5 by a driving source (not shown). As the drum 1 rotates, it rotates in the clockwise direction indicated by the arrow.

The center shaft 5 of the developing roller 4 is made of a rigid conductive material such as stainless steel, and a bias power source 8 is connected to the center shaft 5. Toner 3 to areas other than the static latent image
A bias voltage is applied to the central shaft 5 to prevent adhesion and development, the so-called fogging phenomenon.

Further, an intermediate l1I formed on the outer periphery of the central shaft 5
6) It is made of an elastic porous foam such as polyurethane foam, but this porous foam is
As shown in the figure, a protrusion 6a serves as a microelectrode.
The number of cells is 100 or more so that the bubbles 6b are uniformly formed on the surface at minute intervals, and the volume resistance is 108 Ω to maintain the effectiveness of the bias voltage applied to the central axis 5. It is preferable that it be smaller than the mouth.

Then, a surface layer T formed on the outer periphery of this intermediate layer 6
has minute irregularities with a roughness of 3 to 30 μm on the surface in order to obtain toner conveying force, and is not affected by holes that disturb the electrostatic latent image on the photosensitive drum 1 or pinholes on the surface layer of the photosensitive drum 1. It is made of an elastic material with a volume resistivity of 109 Ω or more and good releasability from the toner 3, but its thickness is 150 μm or less in order to maintain the clarity of the image. It is desirable that the material has a triboelectrification series far away from that of the toner 3.

It should be noted that the charging polarity of the toner 3 due to frictional electrification is, for example, positive when the photosensitive drum 1 has negative charging polarity in the case of normal development, and negative in the case of reverse development.

On the other hand, the blade 10 is for frictionally charging the toner 3 to form a uniform thin layer of the toner 3 on the surface layer 7 of the developing roller 4, and is provided at a predetermined position with the surface layer 7 at a position below the developing roller 4. It is held and biased by a flexible member 9 so as to be in contact with the toner 3 with a pressure of 2.5 mm.The material of the flexible member 9 is desirably one that has a triboelectrification series that is distant from the toner 3, similar to the surface layer T described above.

The flexible member 9 is fixed to the bottom of the toner tank 2 by suitable fixing means.

The stirring member 11 is rotatably disposed within the toner tank 2 so as to be located behind the pressure contact portion between the developing roller 4 and the blade 10, and the stirring member 11 has a rotating shaft that is rotated by a drive source (not shown). It is composed of a plurality of agitating blades and the like provided around the agitating blade, and functions to agitate the toner 3 in the toner tank 2 and supply the toner 3 to the pressure contact portion.

Further, the toner blocking member 12 is for preventing leakage of the toner 3 from inside the toner tank 2.
The upper end portion of the toner tank 2 is fixed to the ceiling, and the lower end portion lightly contacts the surface layer I of the developing roller 24 due to its flexibility.

In addition to the developing device configured as described above, a charger and an exposure device (not shown) are provided around the photosensitive drum 1.

A transfer device, a static eliminator, a cleaning device, a fixing device, and the like are arranged according to the recording process.

Next, to explain the operation, first, while the photosensitive drum 1 is rotating in the direction of the arrow &, the surface of the photosensitive drum 1 is uniformly charged by a charger (not shown).
Subsequently, exposure is performed by an exposure device (not shown) to form an electrostatic latent image on the photosensitive drum 1.The position where this electrostatic latent image contacts the developing roller 24 due to the rotation of the photosensitive drum 1, that is, the developing area It is transported to the area.

On the other hand, in the developing device, simultaneously with the rotation of the photosensitive drum 1, the developing roller 24 is rotated in the direction of the arrow (not shown) by a drive source.
A bias voltage is applied from the bias power source 8 to the center shaft 5 of the developing row 24, and the stirring member 11 is also rotated in a predetermined direction by a drive source (not shown).

As the stirring member 11 rotates, the toner 3 in the toner tank 2 is stirred, and the toner 3 is pushed and supplied to the pressure contact portion between the developing roller 4, the surface layer T, and the blade 10. is charged by friction between the surface layer 7 and the blade 10.

Here, the charged toner 3 adheres to the surface layer T,
The toner 3 is conveyed to the developing area by the rotation of the developing roller 4, and at this time, the layer of toner 3 adhering to the surface layer 7 is uniformly thinned by the blade 10.

This thinned toner 3 is then supplied to the electrostatic latent image on the photosensitive drum 1 in the development area and is attracted and adhered to the developing vessel, whereby the electrostatic latent image is converted into a toner image as a visible image. However, at this time, the central axis 5 of the developing roller 4
Since the bias bias voltage is applied by the bias power supply 8 as described above, the minute protrusions 6a on the surface of the intermediate layer 6 serve as electrodes, so that a toner image with no edge effect can be obtained.

This toner image is conveyed to the ninth transfer area by the rotation of the photosensitive drum 1, where it is transferred to paper by a transfer device (not shown), and then fixed to the paper by a fixing device, and then placed on the photosensitive drum 1. The remaining toner 3 is removed by a cleaning device after being subjected to a static eliminating process by a static eliminating device.

On the other hand, after the development, the toner 3 remaining on the surface layer T of the developing roller 4 passes through the toner blocking member 12 due to the rotation of the developing roller 4, and is collected into the toner tank 2. It will be reused.

FIG. 3 shows experimental results showing the relationship between the image precision and the bias voltage in the above-described embodiment.

The developing roller 4 in this experiment had a central shaft 5 made of a stainless steel shaft, an intermediate layer 6 made of polyurethane foam with a degree of foaming of 250 cells, and a volume resistivity of 10 Ωα, and a surface layer 7 with a thickness of The silicon coating had a length of 130 μm and a volume resistance of 109 m, and the overall outer diameter was 20 mm.

The developing roller 24 is in pressure contact with the photosensitive drum so as to obtain a nip width of 40 ua, and a blade 10t made of urethane rubber with a volume resistance of 10 and 2 openings is brought into contact with the developing roller 24. did.

In this configuration, the surface potential of the photosensitive drum 1 is -700
V, and set the circumferential speed of the photosensitive drum 1 to 50)/
B % The developing roller 4 is rotated in the directions of arrows a and l at a circumferential speed of 100/B, and the toner solid image density (o
When the optical density (O, D: optical density) was measured, as shown in FIG.
When the temperature is higher than V, the result shows that stains are generated in the background.

Therefore, it can be seen that under the above conditions, a good toner image can be obtained in the range of -300 to -700V.

Although one embodiment of the present invention has been described above, the present invention is not limited to this, and various changes can be made in details.

For example, in the embodiment described above, the blade 1 is attached to the developing roller 4.
Although the toner blocking member 12 is in full contact with each other, it is also possible to have a structure in which they face each other with a predetermined gap between them.
If it is made of a conductive material and grounded, it is possible to obtain a good image.

・ [Effects of the Invention] As explained above, the present invention provides an electrostatic latent image carrier having a central shaft made of a rigid conductive body and an intermediate member formed of an elastic porous foam formed on the outer periphery of the central shaft. Because the structure consists of a layer and an elastic surface layer formed around the outer periphery of this intermediate layer, the hardness can be lowered compared to conventional ones.
This makes it possible to suppress fluctuations in frictional load when the electrostatic latent image carrier is rotated in pressure contact with the electrostatic latent image carrier, and the pressing pressure in the axial direction is also uniform, so that there is no nip in the developer carrier as in the conventional case. Extrusion from the width will no longer occur.

During development, a bias voltage is applied to the center axis of the developer carrier by a bias power supply, so that the one-component non-magnetic insulating developer adheres to areas other than the electrostatic latent image, so-called fogging. In addition, since the intermediate layer is a porous foam, the protrusions formed on the surface act as microelectrodes, resulting in an excellent edge effect. This has the effect that a good visible image without density unevenness can be obtained on the image carrier.

Furthermore, since frictional load fluctuations can be suppressed as described above, the rotational load on the electrostatic latent image carrier and developer carrier is also reduced.
As a result, the driving force of both drive systems can be reduced, so it is possible to reduce costs, and the volume resistivity 'c of the surface layer of the developer carrier
to9Ω0 or more, and the volume resistivity of the intermediate layer is 108
Since it is less than Ω, the electrostatic latent image is not disturbed by the intermediate layer, and even if there is a pinhole in the electrostatic latent image carrier, it has the advantage of preventing current from leaking into the pinhole. There is also.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the developing device according to the present invention, FIG. 2 is an enlarged view of the main part of FIG. 1, FIG. 3 is a diagram showing experimental results of the embodiment of FIG. The figure is a partial sectional view showing a conventional example, and FIG. 5 is an enlarged view of the main part of FIG. 4. 1: Photosensitive drum 2: One tank of toner, 3. :) Chi 4: Developing roller 5: Center shaft 6: Intermediate layer 7: Surface layer - 8 = Bias power source 9: Flexible member 10 Ni blade 11: Stirring member 12: Toner blocking member Patent applicant Oki Electric Industry Co., Ltd. agent Person Patent Attorney Takashi Kanakura 2 Cross-sectional diagram showing one embodiment of the present invention 1 = Enlarged view of the main part of Figure 1 Tsumugi 2 = Development Beias (V) Diagram showing the experimental results of the embodiment 3 l

Claims (1)

[Scope of Claims] 1. A developer carrier that rotates in pressure contact with an electrostatic latent image carrier that rotates at a constant speed; the one-component non-magnetic insulating developer supplied between the tribo-charging member and the developer carrier; In a developing device that develops an electrostatic latent image on an electrostatic latent image carrier by conveying a developer to a pressure contact portion with the electrostatic latent image carrier by a developer carrier, the developer carrier is made of a conductive material. A roller consisting of a central shaft made of a rigid body having a central axis, an intermediate layer made of a porous foam having elasticity formed around the outer periphery of the central axis, and a surface layer having elasticity formed around the outer periphery of the intermediate layer. A developing device characterized by having a bias power supply connected to the shaft. 2. The volume resistivity value of the intermediate layer of the developer carrier is 10^8
Ωcm or less, and the volume resistivity of the surface layer is 10^
The developing device according to claim 1, characterized in that the resistance is 9 Ωcm or more. 3. The developing device according to claim 1, wherein the porous foam constituting the intermediate layer of the developer carrier has a degree of foaming of 100 or more cells.