JPS6299771A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a device suitable for binary developing and can obtain a good reproduced picture by holding a specific relation between the resistivity and specific dielectric constant of a dielectric layer. CONSTITUTION:A toner carrier 5 has, from the surface in order, an insulating layer 11, a dielectric layer 12 and a conductive substrate 13. The conductive substrate 13 is supported rotatably by the frame of a developing device, and connected to a power source for applying bias. However, it is insulated from the frame of the developing device. A material in which the relation log10y<0.15 x+7.5(x>1) holds, where y is resistivity and x is specific dielectric constant, is used for the dielectric layer 12. Thus, a toner carrier suitable for binary developing can be obtained.

Description

[Detailed description of the invention] ``Gisa'' β Dobarge The present invention relates to a so-called contact development type developing device.

In particular, the present invention relates to a developing device that performs so-called binary development.

In a contact development type developing device, a thin layer of toner is generally formed on a toner carrier, and the toner carrier and the latent image carrier are brought into contact with each other through the thin layer of toner to form a latent image. Develop the latent image on the carrier. In this case, the toner carrier is generally made of an elastic material in order to ensure appropriate contact pressure between the toner carrier and the latent image carrier.

In addition, when developing the latent image on the latent image carrier, in order to prevent charge from being injected into the latent image from the toner carrier, the surface of the toner carrier, that is, the surface that comes into contact with the latent image carrier, is coated. It is known to form an insulating layer. Further, a conductive base is provided inside the insulating layer and the elastic body to apply a bias voltage to the toner carrier.

By the way, as an aspect of the developing device, there is so-called binary development in which the reproduction of intermediate colors is not a problem. In order to perform this binary development satisfactorily, development characteristics such as a large so-called development γ (gamma) or a large saturated toner adhesion amount are required. Here, the development γ refers to the rate of change in the amount of toner adhering to the latent image carrier with respect to the change in the electric field between the toner carrier and the latent image carrier. Further, the saturated adhesion amount of toner refers to the maximum amount of toner that can adhere to the latent image carrier.

Conventionally, when manufacturing a developing device, the developing characteristics were not adjusted by taking into account the properties of the toner carrier. Therefore, development is performed without knowing whether the toner carrier is set to the best condition for performing binary development.

-1- Zenichi In view of the above points, the present inventors conducted various experiments regarding the relationship between toner carriers and development characteristics. As a result, it was found that the development characteristics are largely dependent on the elastic body of the toner carrier, and that the elastic body in this case functions as a dielectric layer. Furthermore, when certain conditions regarding the relationship between the resistivity and relative permittivity of the dielectric layer are satisfied, the development characteristic that is suitable for binary development, that is, the development γ increases, and the saturated toner adhesion amount also increases. I understand. especially.

When the resistivity of the dielectric layer is y and the relative permittivity is X, the relationship between them is 10g1o y <0.15 x +7.5
(x) 1), it was found that development characteristics suitable for binary development can be obtained.

The present invention was made based on the above findings, and
The purpose is to provide a toner carrier suitable for binary development in a developing device that performs contact development.

Structure The above object is to configure the toner carrier to have an insulating layer 1, an elastic dielectric layer, and a conductive base supporting the dielectric layer in order from the surface, and to set the resistivity of the dielectric layer to y,
And if we take the relative dielectric constant as another factor, then let's log the difference between them. y <0.15x +7.5 (x
> 1) is achieved by making the relationship hold true.

Hereinafter, the present invention will be explained based on Examples.

FIG. 1 is a side sectional view of one embodiment. First, an outline of the structure and operation of the developing device will be explained using this figure.

The toner 2 (either magnetic or non-magnetic) in the 1-chi hopper 1 is conveyed to a toner replenishing member 4 by an agitator 3. The toner supply member 4 is made of a material such as polyurethane. The toner carried to the toner replenishing member 4 moves as the toner replenishing member 4 rotates counterclockwise, is charged by friction with the toner carrier 5, and adheres to the surface of the toner carrier 5 due to the action of the electric charge. .

The toner attached to the toner carrier 5 is
During the rotation, the toner layer thickness regulating member 6 forms a uniform thin layer with a thickness of one or two toner particles with a particle size of about 10 μm, and at the same time, the toner layer thickness regulating member 6 rotates in the counterclockwise direction. It is further charged due to the friction between it and 6. The toner thus charged comes into contact with the electrostatic latent image formed on the photoreceptor 7 as a latent image carrier, and develops the electrostatic latent image. The toner that did not contribute to development returns to the toner supply member 4 again.

When the development operation is repeated, each of the above steps is repeated.

In FIG. 1, reference numeral 8 denotes a pressure mechanism for pressurizing the toner thickness regulating member 6. As shown in FIG. 9 is a sealing member, 10
is a support member that supports the toner thickness regulating member 6;

As shown in the figure, the toner carrier 5 is insulated from the surface M!
11, a dielectric layer 12, and a conductive substrate 13. The conductive substrate 13 is rotatably supported by the frame of the developing device, and further connected to a power source for applying a bias, but is insulated from the frame of the developing device. Assuming that the resistivity of the dielectric layer 12 is y and the relative permittivity is X,
Between them 10gtoy<0.15x+7.5 (x>1)
A material that satisfies the following relationship is used. If this is shown in a graph, it becomes the shaded area in FIG. Materials falling in this shaded area include nitrile rubber, urethane rubber, and conductivity imparting agents such as Ketjenblack and C.
There are silicone rubbers in which metal powders such as u, Ni, etc. are dispersed.

The insulating layer 11 is made of acrylic urethane, soft epoxy,
Silicone rubber or the like is used.

The dielectric layer 12 is made of a material that is both dielectric and elastic, and under the action of this elasticity, the insulating layer 11 of the toner carrier and the photoreceptor 7 come into contact with each other via the toner.

For example, three types of insulation materials are prepared for the dielectric layer 12 using high nitrile rubber B, low nitrile rubber C, and silicone rubber D in which Ketjen Black is dispersed.

The resistivity-relative permittivity characteristics of these materials are shown in B and C in Figure 2.
, D, and both fall within the shaded area. In addition, acrylic urethane is used as the material for the insulating layer 11, a material for positive charging is used as the toner, and silicone resin is used as the toner layer thickness regulating member.

When the developing device shown in Fig. 1 was operated under the above conditions, toner;! The IF current was +15 μc/g.

In addition, the developing electric field (V) between the toner carrier 5 and the photoreceptor 7
The results shown in FIG. 3 were obtained as the relationship between the amount of toner adhered to the photoreceptor 7 (mg/ci) and the amount of toner adhered to the photoreceptor 7 (mg/ci). In the same figure, B
, C, and D indicate the material of the dielectric layer 12, respectively.

This is the result when C and D are used. As can be seen from the graph, curves B, C, and D all have a large development γ (corresponding to the slope of the straight line portion) and a large amount of saturated toner adhesion. Therefore, it is convenient as a development characteristic when performing binary development.

For reference, the dielectric layer 12 was formed of a material outside the shaded area in FIG. 2, such as silicone rubber A, and was used for development. The results are as shown by curve A in FIG. With this characteristic, the development γ is small and the saturated toner adhesion amount is also small, so it is not suitable for binary development.

Effects According to the present invention, a toner carrier suitable for binary development using a contact development method can be obtained, and thereby a good reproduced image can be obtained.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of one embodiment, FIG. 2 is a graph showing the resistivity-relative permittivity characteristics of the dielectric layer, and FIG. 3 is a graph showing the development results. 5... Toner carrier 2... Toner 7... Latent image carrier 11... Insulating layer] 2... Dielectric layer
13... Conductive substrate agent Patent attorney Italy
Takehisa Fuji, 'w'-";1.'-' Fig. 2 [Ωcm)

Claims (1)

[Claims] In a developing device that forms a thin layer of toner on a toner carrier and develops a latent image on the latent image carrier by bringing the toner carrier and the latent image carrier into contact through the thin layer of toner, The toner carrier has, in order from the surface, an insulating layer, an elastic dielectric layer, and a conductive base supporting the dielectric layer,
When the resistivity of the dielectric layer is y and the relative permittivity is x, log_1_0y<0.15x+7.5 (x>1
) A developing device characterized by having the following relationship.