JP2843064B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for supplying a one-component developer to an electrostatic latent image formed on a latent image carrier to perform development.

[Prior Art] Generally, in various image forming apparatuses such as copiers, printers, and facsimiles, an electrostatic latent image corresponding to an image is formed on a latent image carrier such as a photoconductor, and the electrostatic latent image is formed on the latent image carrier. On the other hand, toner is supplied from a developer carrier provided in the developing device, and development is performed, whereby a visible image is obtained.

The developer carrying member is formed in a roller shape or the like, and a developer replenishing means also formed in a roller shape or the like is in contact with the developer replenishing region. It is attached. Further, a developer thinning regulating means formed in a blade shape or a roller shape is provided in contact with the developer thinning region formed downstream of the developer supply region. Then, the new toner stored in the toner storage section in the developer replenishing area is replenished to the developer carrier by the action of the developer replenishing means, and when the toner adheres to the surface of the developer carrier, The toner adhered on the surface of the developer carrier is uniformly thinned in the developer thinning region by the leveling action of the thinning regulating means. Further, the uniformly thinned toner is sent to a developing area formed on the downstream side of the developer thinning area and selectively supplied to an electrostatic latent image, thereby performing a developing operation. It has become.

As the above-mentioned developer carrying member, an elastic roll made of a conductive simple substance or one having a dielectric layer (toner protective layer) on a conductive substrate is generally used.

[Problems to be Solved by the Invention] However, in the above-described conventional device, when the developer carrier is made of a conductive substance, short leak from the photoconductor naturally occurs easily, and the resistance value is reduced. It is almost impossible to arbitrarily select and set the hardness at the same time. Generally, either one is set independently or both are set to a certain compromise value.However, for example, setting the hardness to JISA30 ゜ or less and the resistance to 10 ⁶ Ωcm or less, etc. Have difficulty. In the case where a dielectric layer is provided on a conductive substrate, a bias voltage is increased, and a difference occurs in the exchange of electric charges including toner in an image portion and a non-image portion, so-called, An afterimage may occur. In addition, the temperature characteristics of the dielectric layer are very poor (for example, NBR changes by one or two digits)
Therefore, this greatly affects the development characteristics. For example, when the temperature is lowered, the density is reduced and the background is soiled.

Accordingly, it is an object of the present invention to provide a developing device including a developer carrier capable of always achieving good developing characteristics.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method in which a toner is sent to a development area while holding toner on the surface of a developer carrier, and the toner is applied to an electrostatic latent image under a predetermined developing bias. In the developing device configured to supply and develop, the developer carrier includes an elastic holding layer made of an insulating member, and a surface resistance layer provided outside the elastic holding layer. The developing bias is applied to a conductive toner replenishing roller disposed in contact with the surface resistance layer.

[Operation] In the means having such a configuration, since the surface portion of the developer carrying member is made conductive, a developing operation similar to a normal conductive roll is performed. At this time, two contact portions including a contact portion between the photoconductor and the developer carrier and a contact portion between the developer carrier and the conductive toner supply roller are included in the middle of the short leak path from the photoconductor. And
When either of these two contact portions is interrupted at a predetermined timing, the leak path is satisfactorily blocked. In addition, since the above-mentioned leak path is formed in a long circular shape and a thin layer shape on the surface portion of the developer carrying member, the resistance of the leak path is increased, and this also causes the leakage. Can be suppressed.

On the other hand, the degree of elasticity of the developer carrier is almost determined by the elastic holding layer serving as an insulating member, and is hardly affected by the thin surface resistance layer. Therefore, the hardness of the developer carrying member is arbitrarily determined by selecting a predetermined elastic holding layer.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In the embodiment shown in the figure, a photosensitive drum 1 as a latent image carrier has a photoconductive layer on a grounded substrate, and is rotationally driven in a fixed direction by a drive mechanism not shown. . The photoconductor drum 1 is formed of, for example, an organic photoconductor (OPC), and includes a charging charger 2.
Is initially uniformly charged to a predetermined potential, and an electrostatic latent image is formed by the image forming action of the optical image by the exposure optical system 3. This electrostatic latent image is developed by the toner supplied from the developing device 4. A visible toner image is obtained. The formed toner visible image is transferred to transfer charger 5.
The toner is transferred to the recording paper side and sent out, and the toner remaining on the photosensitive drum 1 after the transfer is removed by the cleaning device 6.

A developing roller 42 as a developer carrier is rotatably supported in a developing casing 41 of the developing device 4 so that the developing roller 42 elastically contacts the surface of the photosensitive drum 1 in a developing area. Are located. The photosensitive drum 1 and the developing roller 42 are driven to rotate in opposite directions as indicated by the respective arrows, that is, in the same direction at a contact portion between the two, and a developing region where a developing operation is performed is provided at the contact portion between the two. Are formed as described above.

The developing roller 42 includes, from the center side, a cored bar 42a, an elastic holding layer 42b made of an insulating member, and a surface resistance layer 42c formed in a thin layer on the surface of the elastic holding layer 42b. ing. As the elastic holding layer 42b, various rubber-based elastic bodies can be used, and a thermoplastic elastic body such as a styrene-based, olefin-based, urethane-based, polyester-based, or vinyl chloride-based can also be used. On the other hand, as the surface resistance layer 42c, a general rubber, plastic, or a material obtained by mixing a powder of carbon, ceramic, metal, or the like so as to have a necessary resistance value is used, and the elastic holding layer 42b The resistance value is lower by one digit or more, preferably by two digits or more. Specifically, various rubbers such as NBR, CR, EP, silicon, hydrin, urethane, etc., various plastics such as epoxy, fluorine and ethylene, and modified resins thereof are employed. When the resistance value is set to about 10 ⁸ Ωcm, carbon powder is mixed around 5 to 20 wt%, and when the resistance value is set to about 10 ⁶ Ωcm, 20 to 30 wt% or more carbon powder is mixed. It has become so.

As an example of the developing roller 42, the diameter is 20 mm, the resistance value is 10 ¹⁰ Ωcm, the elastic holding layer 42b made of NBR, NB
20 μm of the surface resistance layer 42c with a resistance value of 10 ³ Ωcm mainly composed of R
The nip width with the photosensitive drum 1 is set to 0.1 to 0.2 mm.

Further, a toner replenishing roller 43 as a conductive rotating roller member is arranged in contact with the developing roller 42, and a power supply circuit 44 applies a developing bias to the toner replenishing roller 43. As an embodiment of the developing bias, a DC bias of 1 KV, AC 1 KV, and a frequency of 1 KC is employed. A predetermined bias voltage is also applied to the metal core 42a of the developing roller 42 from the power supply circuit 45.

The toner supply roller 43 has a resistance of 10 ⁸ Ω with respect to the core metal 43a.
The conductive roll 43b is wound around the following conductive roll 43b, and a sponge roll, a metal roll, a rubber roll, or the like having an arbitrary surface shape is employed as the conductive roll 43b.

As an example of the toner supply roller 43, the diameter is 10 m.
m, a sponge-like conductive roll having a resistance value of 10 ³ Ωcm is used, and the nip width with the developing roller 42 is 0.5
It is appropriately selected in the range of 1010 mm, and is rotationally driven at a linear speed of 100-300 mm / sec in the direction of the arrow shown in the figure.

As the toner used in this embodiment, toner having a particle size of 1 to 30 μm is employed.

Further, in the toner transport area between the developing roller 42 and the developing area, a toner layer regulating blade 46 as a thinning regulating means for thinning the toner supplied and adhered to the surface of the developing roller 42 is provided. It is arranged so as to be in contact with the developing roller.

In the apparatus according to such an embodiment, first, exposure writing is performed on the surface of the uniformly charged photosensitive drum 1 to form an electrostatic latent image corresponding to an image. Toner is selectively supplied to the electrostatic latent image from the developing roller 42 of the developing device 4 in a developing area, whereby the electrostatic latent image is developed to obtain a visible image. I have. The developing roller 42 is replenished with new toner in the developing casing 41 by a toner replenishing roller 43 in a developer replenishing area.
The toner adhered on the surface of the toner is uniformly thinned by the toner layer regulating blade 46 in the developer thinning region, and is sent to the developing region.

In this case, the surface portion of the developing roller 42 is a surface resistance layer 42c.
As a result, the developing operation is performed in the same manner as a normal conductive roll. At this time, a short leak path is formed by the photosensitive drum 1, the developing roller 42, and the toner replenishing roller 43.
In the course of the short leak path, the photosensitive drum 1
And a contact portion between the developing roller 42 and the toner replenishing roller 43. A contact portion between the two contact portions is interrupted at a predetermined timing. The leak path is made to be shielded. In addition, the leak path is
The surface resistance layer 42c forms a long circular and thin layer on the surface of the developing roller 42, so that the substantial resistance of the leak path is increased. Therefore, the conventional leak phenomenon is prevented. From experiments, it has been confirmed that a preferable development result can be obtained by setting the resistance value of the surface resistance layer 42c lower, and the development can be performed at a lower voltage than that of a conventional roll having a dielectric layer.

Further, the degree of elasticity of the developing roller 42 is almost determined by the elastic holding layer 42b made of an insulating member, and is hardly affected by the thin layer surface resistance layer 42c. Therefore, the hardness of the developing roller 42 is arbitrarily determined by selecting the elastic holding layer 42b as a predetermined one.

As another embodiment of the developing roller 42, a resistance value of 10 ¹⁴ Ω
Some have an elastic holding layer 42b of 50 cm to 70 mm made of CR rubber (chloroprene rubber). At this time, there was almost no change in the image obtained when the developing bias output from the power supply circuit 44 was 500 V and the developing bias output from the power supply circuit 45 was 0 to 700 V. Elastic retention layer
This is probably because 42b is high.

Further, as still another embodiment of the developing roller 42, there is a developing roller provided with an elastic holding layer 42b made of silicone rubber having a resistance value of 10 ⁶ Ωcm, and the other conditions are the same as those in the above embodiment. Good results were obtained.

Further, a coat layer is applied to the surface of the developing roller 42 as needed. In this case, the resistance value of the coat layer is set to a value between the elastic holding layer 42b and the surface resistance layer 42c.
Specifically, 10 wt% of aluminum powder is added to silicon resin having a resistance value of 10 ⁶ cm to make 10 ¹⁰ Ωcm, and the thickness is 10 μm.
And then, it is set to be employed in the first embodiment described above with measured values of Rv ≒ 10 ^7.

[Effects of the Invention] As described above, in the present invention, a surface resistance layer is provided outside an elastic holding layer made of an insulating member to form a developer carrier, and the developer carrier is arranged in contact with the developer carrier. Since the developing bias is applied through the conductive toner replenishing roller, it is possible to suppress leakage from the photoconductor and arbitrarily determine the degree of elasticity of the developer carrier. Therefore, according to the present invention, good development characteristics can always be realized, and image quality can be improved.

Further, since the voltage is supplied to the surface resistance layer by the toner replenishing roller, it is not necessary to separately provide a member for supplying the voltage, and the device can be used inexpensively, so that the apparatus can be configured at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing a developing device using one-component toner according to one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Developing device, 42 ... Developing roller, 42b ... Elastic holding layer, 42c ... Surface resistance layer, 43 ...
Toner supply roller, 43: conductive roll body, 44: power supply circuit.

Claims (1)

(57) [Claims] A developing device for feeding toner to an electrostatic latent image under a predetermined developing bias to perform development by feeding the toner to a developing area while holding the toner on the surface of a developer carrier; The developer carrier has an elastic holding layer made of an insulating member,
A surface resistance layer provided outside the elastic holding layer, and the developing bias is applied to a conductive toner supply roller disposed in contact with the surface resistance layer. Developing device.