JPS6323175A - Developing device - Google Patents

Abstract

PURPOSE:To miniaturize a developing device and to realize two-color development with high quality of a picture, by constituting the developing agent of the developing device of 1st and 2nd developing agents, which have different colors and are electrified in opposite polarities, and electrically selectively separating the two developing agents from a sleeve to a developing roller so as to make one-color development. CONSTITUTION:Toner is constituted of 1st and 2nd developing agents and the 1st developing agent corresponding to block is a magnetic developing agent composed of a resin material and magnetic material. The 2nd developing agent corresponding to color is a nonmagnetic developing agent composed of a resin material. By using an electrification control agent, the 1st and 2nd developing agents are electrified in opposite polarities. In copying with color, setting is made so that the 1st developing agent (black, 10<13>-10<16>OMEGA.cm resistance) can easily be charged in positive and the 2nd developing agent (red, 10<13>OMEGA.cm resistance) can easily be charged in negative. On a sleeve 16, the 2nd developing agent is triboelectrified in negative and forms a thin layer on a developing roller 24, and then, performs normal development on the non-exposed area of a photosensitive drum 12 electrified in positive.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a developing device that can be used in electrostatic printers and electronic copying machines, and particularly to a developing device that can perform two-color development.

Conventional technology There have been many methods for two-color development, but most of them are methods in which two types of latent images are developed separately using two developing devices each using a different toner. in the case of,
Since two developing devices are used, the overall size of the device increases, and toner from the upstream developing device gets mixed into the downstream developing device.

Further, as another method, Japanese Patent Application Laid-open No. 55-43533 discloses a method in which development is performed using two-color, one-component high-resistance nonmagnetic toner having bands W of opposite polarity.

(c) Problems to be Solved by the Invention When using two developing devices in the above-mentioned prior art, the problem is that toner from the upstream developing device gets mixed into the downstream developing device, for example, when the brush of the developing roller is exposed to light. Although it is effective to switch between contacting and non-contacting the developing roller and changing the bias of the developing roller, the problem of increased size remains.

Furthermore, in the case of the method disclosed in Japanese Patent Application Laid-open No. 55-43533, since there are toners of two colors on the developing roller, deterioration in image quality such as flanges and fogging cannot be avoided.

The present invention has been developed with the above problems in mind, and it is an object of the present invention to provide a developing device that can be miniaturized and is capable of high-quality two-color development.

(2) Means for Solving the Problems The present invention provides a developer chamber in which developer is stored, a developing roller disposed in contact with or close to the photoreceptor drum, and a developing roller having a magnetic field generating means inside. In the developing device, the developer forms a magnetic brush of the developer, and a sleeve is provided so that the magnetic brush contacts the developing roller without approaching the photoreceptor drum. It is characterized by being composed of a first developer and a second developer that are charged with opposite polarities.

(e) Two developers having different polarities depending on the working color are electrically selectively separated from the sleeve to the developing roller to develop only one color.

Embodiment FIG. 1 is a sectional view showing a main part of an embodiment of this invention. It includes a developer chamber 14 having an opening disposed near the developer chamber 14.
The photosensitive drum 12 is of a boss charge type, and can be selected between ten-band wide and one-band wide by a charging means (not shown). Inside the developer chamber 14 is a rotatable sleeve 16 that has a width approximately equal to the photoreceptor drum 12 and is made of a non-magnetic material such as aluminum, that is, a material that can block the passage of magnetic flux. A drive mechanism (not shown) is provided. This sleeve 16 has a direct current i1: file
One terminal of is connected and the other terminal is grounded.

DC M, R19 is switching switch 30V, 400V.
Can be switched to 400V.

Inside the sleeve 16, a magnet (magnetic field generating means) 20 assembled into an inner cylindrical shape is provided. The ai stone 20 is placed on the sleeve 16 by magnetic attraction! It is used to form a magnetic brush for toner (developer). Sleeve 16
A doctor blade 22 is provided on the top of the developer chamber 14 for adjusting the height of the formed magnetic plan, and this doctor blade 22 is fixed to a part of the developer chamber 14 .

A developing roller 24 that rotates in contact with the photosensitive drum 12 is provided on the left side of the sleeve 16, that is, on the downstream side.

On the surface of this developing row 224, an elastic body 26 having elasticity, such as conductive rubber, is provided.
The thickness of the elastic body N26 is set to, for example, 0.2 to 0.8 m. The reason why the developing roller 24 is provided with the elastic body Ji126 is to prevent the surface of the photosensitive drum 120 from being damaged even when the developing roller 24 rotates in contact with the photosensitive drum 12.

The developing roller 24 is further supplied with AC tfy1. <average bias 0V) One terminal of the 18 is connected and the other terminal is grounded. This AC power source 18 is for applying vibration to the developer at the developing position.

Further, 25 is a repellent roller that removes toner remaining on the developing roller 24.

Here, the structure of the toner stored in the developer chamber 14 will be described below.

For two-color development, the toner is composed of a first developer and a second developer.

As shown in Figure 2, the first developer corresponding to black color is a magnetic developer made of a resin material and a magnetic material.
For example, the second developer corresponding to red) is a non-magnetic developer made of a resin material.

Further, the triboelectric charge order position of the resin material of the first developer (for example, styrene resin) and the resin material of the second developer (for example, styrene resin) is different from the triboelectric charge of the magnetic material of the first developer. Make both the weights larger or smaller relative to the ranking position. This can be controlled by mixing a charge control agent into the first and second developers. Examples of the charge control agent include bis(tertiary-butylsalicylic acid) chromium complex and Zapon Fast Black B1 salt picic acid bimaleic acid copolymer for charging, and nigrosine and polyaminoethyl cellulose for charging.

Further, as the structure of the developer, the one shown in FIG. 3 can be considered. That is, both the first and second developers are made of a non-magnetic material, and a carrier made of a magnetic material is mixed therein, and by using the same charge control agent as above, the first and second developers are made of a non-magnetic material. They are charged with opposite polarities.

Another option is to use magnetic materials for both the first and second developers, but it is difficult to produce colors (for example, red) (because the original color of the magnetic material is dark), so it is not suitable for two-color development. Not suitable.

The operation of the embodiment shown in FIG. 1 will be explained. When making color copies, the average bias of the developing roller 24 is Ov.
Fixed, the bias of the sleeve 16 is -400V, and the photosensitive drum 12 is charged with +600V.

In this example, the first developer (black, resistivity 1013-1
016 Ω·an) is easily charged to 10, and the second developer (red, 10 13 Ω·mark or more) is easily charged to −.

Under the above conditions, the second developer is tribo-charged on the sleeve 16 to form a thin layer on the developing row 224, and regular development is carried out on the non-exposed portion of the photosensitive drum 12, which is fully charged.

When copying in black, use sleeve 1 instead of when copying in color.
6 bias to +400■, photosensitive drum 12 to -6
Charge to 00v.

Under this condition, a thin layer of highly charged first developer material is formed on developer roller 24, contrary to color copying, and -
Regular development is performed on the non-exposed area of the charged photoreceptor drum 12.

Further, another embodiment is shown in FIG.

The difference from the embodiment shown in FIG. 1 is that the photosensitive drum 12 is not a boss charge type but a unipolar charge type, and the +aoov charge is fixed. In addition, the DC electric fi19 is +
300■ and -300V, and furthermore, in addition to tR18, an II is provided in which the average bias can be switched between +200■ and +400V by means of a switching contact piece 32.

The operation will be explained. For color copying, the average bias of the developing row 224 is set to +200V, and the bias of the sleeve 16 is set to -300V. Under these conditions, a thin layer of the second developer with a single charge is completely formed on the developing roller 24, and the non-exposed area of the photosensitive drum 12 is properly developed.

When making a black copy, set the average bias of the developing roller 24 to +
400V, and the bias of the sleeve 16 is set to +900V.

Under this condition, a thin film of the first developer charged with a charge is formed on the developing roller 24 and is reversely developed on the exposed portion of the photosensitive drum 12. This embodiment can be used in an electrostatic printer that exposes a photoreceptor drum using an LED head or the like.

(G) Effects of the Invention As is clear from the above description, the present invention can provide a /J% type developing device capable of two-color development with high image quality.

Furthermore, only the developing device of the present invention can handle -color-only development, two-color development, regular or reversal development, etc.

[Brief explanation of the drawing]

Figure 1 shows the developing device of the present invention! A cross-sectional view of the embodiment, FIG.
FIG. 3 is a diagram showing the structure of the toner, and FIG. 4 is a sectional view of another embodiment.

Claims (1)

[Scope of Claims] 1. A developing roller disposed in contact with or close to a developer chamber containing developer and a photoreceptor drum, and having a magnetic field generating means inside to form a magnetic brush for the developer. In a developing device including a sleeve in which the magnetic brush is provided in contact with the developing roller without coming close to the photosensitive drum, the developers are charged with different colors and have opposite polarities. A developing device comprising a first developer and a second developer. 2. The first developer is an insulating magnetic developer made of a resin material and a magnetic material, and the second developer is a non-magnetic developer made of a resin material, and the resin of the first developer is The triboelectric charge order positions of the material and the resin material of the second developer are either larger than or both smaller than the triboelectric charge order position of the magnetic material of the first developer. A developing device according to claim 1. 3. The developing device according to claim 1, wherein the first and second developers are made of a non-magnetic material and are mixed with a carrier made of a magnetic material. 4. The photoreceptor is a boss charge photoreceptor, and by changing the charging polarity of the boss charge photoreceptor and the bias applied to the sleeve, one of the first and second developers can be selectively used. The developing device according to any one of claims 1 to 3, wherein the developing device is configured to supply the developing roller to the developing roller. 5. The photoreceptor is a unipolar charged photoreceptor, and by changing the polarity of the bias applied to the sleeve and the bias applied to the developing roller, one of the first and second developers can be used. The developing device according to any one of claims 1 to 3, wherein the developing device selectively supplies the developing roller to the developing roller.