JPH0364780A - developing device - Google Patents

Abstract

PURPOSE:To improve development characteristics and image quality by impressing a development bias through a conductive member disposed in contact with a developer carrying member formed by depositing a thin-layer-like surface resistance layer on an elastic holding layer consisting of an insulating member. CONSTITUTION:The developer carrying member 42 has the elastic holding layer 42b consisting of the insulating member and the surface resistance layer 42c deposited in the form of a thin layer on the surface of the elastic holding layer 42b. The development bias is impressed to the conductive member 43 disposed in contact with the developer carrying member 42. Either of the two contact parts; the contact part of a photosensitive body 1 and the developer carrying member 42 and the contact part of the developer carrying member 42 and the conductive member 43 is, therefore, intermitted at the prescribed timing and a leak route is shut off. The leak is suppressed by the resistance of the surface resistance layer 42c of the developer carrying member 42 as well. Further, the degree of the elasticity of the developer carrying member 42 can be determined as desired by selecting the elastic holding layer 42b. The development characteristic and image quality are improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device that supplies 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 devices such as copying machines, printers, and facsimile machines, an electrostatic latent image corresponding to an image is formed on a latent image carrier such as a photoreceptor, and this electrostatic latent image is On the other hand, toner is supplied from a developer carrier provided in a developing device to perform development, thereby obtaining a visible image.

The above-mentioned developer carrier is formed in the shape of a roller or the like, and a developer replenishing means also formed in the shape of a roller or the like is in contact with the developer supply area of the developer carrier. It is attached. Further, a developer thinning regulating means formed in the shape of a blade or roller is attached in contact with the developer thinning region formed downstream of the developer supplying region. Then, in the developer replenishment area, the new toner stored in the toner storage section is replenished to the developer carrier by the action of the developer replenisher, and as a result, the toner is deposited on the surface of the developer carrier. The toner deposited on the surface of the developer carrier is uniformly thinned in the developer thinning region by the leveling action of the thinning regulating means. Furthermore, this uniformly thin layered toner is superior in quality! The developer is fed into a development area formed downstream of the developer thinning area and selectively supplied to the static '21tWI image, thereby performing a development operation.

The above-mentioned developer carrier may be an elastic roll made of a conductive single body or a dielectric layer (toner protection layer) on a conductive base.
) is generally used.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional device, when the developer carrier is made of a conductive element, short circuits from the photoreceptor naturally occur.
Leakage is likely to occur, and it is almost impossible to arbitrarily select the resistance value and arbitrarily set the hardness at the same time.

- Inside the shell, one is set independently, or both are set at a certain compromise value, but for example, the hardness is J
It is difficult to set the resistance to less than 10''Ω when the ISA is less than 30°.

Furthermore, in the case of a dielectric layer provided on a conductive substrate, the bias voltage may be increased, or there may be a difference in the exchange of charges including toner between the image area and the non-image area, so-called Afterimages may occur. Also, the temperature characteristics of the dielectric layer are very poor (for example, in NBR, 1 to 2
(changes by an order of magnitude), which has a large effect on the development characteristics.

For example, at low temperatures, the density decreases and the skin becomes stained.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a developing device equipped with a developer carrier that can always achieve good developing characteristics.

[Means for Solving the Problems] In order to achieve the above object, the present invention supplies toner to a developing area while retaining it on the surface of a developer carrier, and applies the toner to an electrostatic latent image under a predetermined developing bias. In the developing device, the developer carrying member includes an elastic holding layer made of an insulating member, and a surface resistance layer coated in a thin layer on the surface of the elastic holding layer. The development bias is applied to a conductive member placed in contact with the developer carrier.

[Function] In the means having such a configuration, since the surface portion of the developer carrier is made conductive, a developing operation similar to that of a normal conductive roll is performed.

At this time, the short leak path from the photoreceptor includes two contact parts: a contact part between the photoreceptor and the developer carrier, and a contact part between the developer carrier and the conductive material. By connecting or disconnecting either of these two contact portions at a predetermined timing, the leak path can be satisfactorily shielded. In addition, since the leak path is formed in a long circumferential shape and in a thin layer on the surface of the developer carrier, the resistance of the leak path is increased, which also prevents leaks. It can be suppressed.

On the other hand, the degree of elasticity of the developer carrier is determined mostly by the elastic retaining layer made of an insulating member, and is hardly affected by the thin surface resistance layer. Therefore, the hardness of the developer carrier depends on the elastic retaining layer. It can be arbitrarily determined by selecting a predetermined value.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

In the embodiment shown in the figure, a photosensitive drum l as a latent image carrier has a photoconductive layer on a grounded substrate, and is rotated in a fixed direction by a drive mechanism (not shown). being moved. The photoreceptor drum 1 is made of, for example, an organic photoreceptor (○pc), and is initially charged uniformly to a predetermined potential by a charging charger 2.
An electrostatic latent image is formed by the imaging action of the optical image by the exposure optical system 3, and this electrostatic latent image is developed with toner supplied from the developing device 4 to obtain a toner visible image. The formed toner visible image is transferred to the recording paper side by a transfer charger 5 and sent out, and the toner remaining on the photoreceptor drum 1 after the transfer is removed by a cleaning device 6.
It is designed to be removed by

A developing roller 42 serving as a developer carrier is pivotally supported in the developing casing 41 of the developing device 4, and this developing roller 42 is attached to the photosensitive drum l in the developing area.
is arranged so as to be in elastic contact with the surface of the The photosensitive drum 1 and the developing roller 42 are each rotated in opposite directions, that is, in the same direction at the contact portion between the two, as shown by the arrows, and there is a developing area where the developing operation is performed at the contact portion between the two. is formed as described above.

The developing roller 42 includes a core metal 42a from the center side,
The elastic retaining layer 42b made of an insulating material and the elastic retaining layer 1
The surface resistance layer 4 is deposited in a thin layer on the surface of 42b.
2c is provided.

As the elasticity retaining fi 42b, various types of rubber-based elastic bodies can be used, as well as thermoplastic elastic bodies such as styrene-based, olefin-based, and urethane-based.

Polyester-based materials, vinyl chloride-based materials, etc. can also be used. On the other hand, the surface resistance layer 42c is made of general rubber, plastic, or mixed with powder of carbon, ceramic, metal, etc. to provide the necessary resistance value, and the elasticity retaining M42b is used as the surface resistance layer 42c.
The resistance value is lowered by at least one order of magnitude, preferably by at least two orders of magnitude. Specifically, various rubbers such as NBR, CRlEP, silicone, hydrin, botanical, or epoxy,
Various plastics such as fluorine and ethylene.

Furthermore, these modified resins are also being used. In addition, when the resistance value is set to about 10'Ω, carbon powder is mixed in around 5 to 20wt%, and the resistance value is set to about 10'Ω.
If it is set to ready level, carbon powder is 20~30v.
It is designed to be mixed in an amount of t% or more.

As an example of the developing roller 42, the diameter is 20 am,
Elastic retention layer 42 made of NBR with a resistance value of 101@Ω
For b, a surface resistance layer 42c mainly made of NBR and having a resistance value of 103Ω is applied in a WIWI shape of 20 μm to 100 μm, and the nip width with the photoreceptor drum 1 is 0.1 to 0.2 m. being done.

Further, a toner replenishment roller 43 as a member of a conductive rotating roller is disposed in contact with the developing roller 42 , and a power supply circuit 44 is connected to the toner replenishment roller 43 .
A developing bias is applied from . Examples of developing bias include DCIKV, ACIKV, and frequency IK.
C has been adopted. Note that a predetermined bias voltage is also applied to the core metal 42a of the developing roller 42 from the power supply circuit 45.

The toner replenishing roller 43 has one unit per core metal 43a.
The conductive roll body 43b is wound around a conductive roll body 43b having a resistance of 0''Ω or less, and the conductive roll body 43b is a sponge roll having an arbitrary surface shape.

Metal rolls, rubber rolls, etc. are used.

As an example of the toner supply roller 43, the diameter is 10
A sponge-like conductive roll with a length of 1 m and a resistance value of 103Ω0 is used, and the nip width with the developing roller 42 is appropriately selected in the range of 0.5 to 10 mgm, and the roll is 100 to 300 m in the direction of the arrow shown in the figure. It is designed to be rotated at a linear velocity of /see.

The toner used in this example is as follows.

Particles having a particle size distribution of 1 to 30 μm are used.

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

In the apparatus of this embodiment, first, exposure writing is performed on the surface of the photosensitive drum 1 which is charged in a negative manner, and an electrostatic latent image corresponding to an image is formed. Toner is selectively supplied to this electrostatic latent image from the developing roller 42 of the developing device 4 in the development area, whereby the electrostatic latent image is developed and a visible image is obtained. There is.

The developing roller 42 is replenished with new toner in the developing casing 41 by the toner capturing roller 43 in the developer replenishing area, and the developing roller 4
The toner adhered to the surface of the toner 2 is uniformly made into a thin layer by a toner layer regulating blade 46 in the developer g layer forming area and sent to the developing area.

In this case, the surface of the developing roller 42 has a surface resistance of 1 and a surface resistance of 15.
Since the roller 42c is kept in a constant conductive state, a developing operation similar to that of a normal conductive roll is performed. At this time, a short leak path is formed by the photoreceptor drum 1, the developing roller 42, and the toner replenishment roller 43. It includes two contact parts: a contact part and a contact part between the developing roller 42 and the toner replenishment roller 43, and when either of these two contact parts is interrupted at a predetermined timing, the leak path is shielded. It is meant to be done. In addition, the leak path is formed in the form of a long circumference and a thin layer on the surface of the developing roller 42 by the surface resistance layer 42c, thereby increasing the effective resistance of the leak path. . Therefore, the leak phenomenon that occurs in the conventional case is prevented. It has been confirmed through experiments that preferable development results can be obtained by setting the resistance value of the surface resistance layer 42c lower, and development can be performed at a lower voltage than conventional rolls having an attractive layer. .

Further, the degree of elasticity of the developing roller 42 is almost determined by the elasticity retention [42b] made of the insulating member, and is hardly influenced by the surface resistance [42c] of the thin layer. Therefore, the hardness of the developing roller 42 can be arbitrarily determined by selecting a predetermined elastic retaining layer 42b.

Another example of the developing roller 42 has a resistance value of 101
JIS made of 4Ω CR rubber (chloroprene rubber)
Some devices include an elastic retaining layer 42b of A50 to 70''.At this time, the image obtained when the developing bias output from the power supply circuit 44 is 500V and the developing bias output from the power supply circuit 45 is 0 to 700V. Almost no change was observed.This is thought to be due to the high elasticity retention layer 42b.

Further, as yet another embodiment of the developing roller 42, an elastic retaining layer 42 made of silicone rubber having a resistance value of 106Ω is used.
There was one with b, and similar good results could be obtained by making other conditions similar to those of the above example.

Furthermore, a coating layer is applied to the surface of the developing roller 42 as required. The resistance value of the coating layer in this case is set to a value between the elasticity retaining layer 42b and the surface resistance [42C]. Specifically, a silicone resin with a resistance value of 101 Ω is filled with aluminum powder in a low percentage to form io'' ΩG, and the thickness is 10 μm, and the measured value of Rv 410' is adopted in the first embodiment described above. It is said that

[Effects of the Invention] As described above, the present invention provides tI! ! A resistive surface layer in the form of a 'gI layer is applied to the elastic retaining layer consisting of the edge member to form a developer carrier, and a developing bias is applied through a conductive member placed in contact with the developer carrier. Therefore, leakage from the photoreceptor can be suppressed and the degree of elasticity of the developer carrier can be arbitrarily determined. Therefore, according to the present invention, good development characteristics can always be achieved and image quality can be improved.

[Brief explanation of drawings]

The figure is an explanatory longitudinal cross-sectional view showing a developing device using one-component toner in one embodiment of the present invention. 1... Photosensitive drum, 2... Developing device, 42...
Developing roller, 42b... Elastic retention layer, 42c...
Surface resistance layer, 43... Toner supply roller, 43...
- Conductive roll body, 44... power supply circuit. (1 idiot) 705-

Claims (1)

[Scope of Claims] A developing device in which toner is held on the surface of a developer carrier and sent to a developing area, and the toner is supplied to an electrostatic latent image under a predetermined developing bias to perform development. , the developer carrier includes an elastic holding layer made of an insulating member;
and a surface resistance layer deposited in a thin layer on the surface of the elasticity retaining layer, and the developing bias includes:
A developing device characterized in that a voltage is applied to a conductive member placed in contact with the developer carrier.