JPH0451026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic latent image or a magnetic latent image formed by electrophotography, electrostatic recording, electrostatic printing, or magnetic recording. Regarding the improvement of a device for developing with toner, in particular, a developer layer is formed on the surface of a developer transport carrier, and an oscillating electric field is generated between the developer transport carrier and the image carrier to develop a latent image on the image carrier surface. This invention relates to improvements in developing devices.

[Prior art]

The above-mentioned developing device is disclosed in Japanese Patent Application Laid-Open No. 50-30537,
No. 55-18656, No. 56-144452, No. 57-139761
No. 57-147652, No. 58-48065, etc. Such a developing device is also used under the condition that the developer layer on the developer transport carrier surface is brought into contact with the image carrier surface, but the toner is transferred from the developer layer on the developer transport carrier surface to the image carrier by the action of the oscillating electric field. Since the toner is easily transferred to the surface of the image carrier, it is preferable to use the developer layer under the condition that it does not come into contact with the surface of the image carrier, so that no streaks occur in the recorded image and it is possible to easily control fogging in which toner adheres to the background. On the other hand, such a developing device has a problem in that the toner tends to scatter out of the developing device from the gap between the developing device and the image carrier due to the action of the oscillating electric field. This becomes more noticeable when the condition is such that it does not come into contact with the body surface.

On the other hand, without applying a bias electric field such as an oscillating electric field between the developer transport carrier and the image carrier, a portion of the developing device frame adjacent to the image carrier that surrounds the outside of the developer transport carrier is placed close to the image carrier surface. An electrode plate is provided and a predetermined potential is applied to the electrode plate to suppress local contrast effects or to prevent toner from scattering from the gap between the developing device and the image carrier. The developing device is USP3926516
This method is known from Japanese Patent Application Laid-Open No. 58-46365.

Therefore, in a developing device that generates an oscillating electric field between the developer transport carrier and the image carrier as described above,
It is easily possible to adopt the techniques described in USP 3926516 and JP 58-46365 to prevent the developer from scattering.
In this case, USP No. 3926516 and Japanese Patent Application Laid-open No. 58-
As described in Publication No. 46365, even if a DC bias voltage is applied to the electrode plate provided in the developing device frame, an alternating electric field is generated between the developer transport carrier and the electrode plate, so toner scattering is sufficiently prevented. No effect can be obtained, and depending on the conditions, the toner may warp and scatter more, causing more noticeable fogging on the image.

[Purpose of the invention]

The present invention solves the problem that toner tends to scatter in a developing device that generates an oscillating electric field between a developer transport carrier and an image carrier without sacrificing the advantage that clear images can be easily obtained. The purpose is to provide a developing device that solves this problem.

[Structure of the invention]

The present invention provides a developing device that forms a developer layer on a surface of a developer transport carrier, generates an oscillating electric field between the developer transport carrier and an image carrier, and develops a latent image on the image carrier surface with toner. , an electrode member is provided in a portion of a developing device frame that surrounds the outside of the developer transport carrier and is close to the image carrier;
Between the electrode member and the developer transport carrier, an alternating current voltage and a DC voltage having the same phase of the oscillating electric field are applied to the electrode member, so that the oscillating electric field is unidirectional in the direction from the electrode member to the developer transport carrier. The present invention provides a developing device characterized by generating an electric field of 1, and achieves the above object with this configuration.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a partial configuration diagram of a recording device showing an example of the developing device of the present invention, and FIG. 2 is a power supply circuit diagram for applying a bias voltage to a developer transport carrier and an electrode member.

In FIG. 1, reference numeral 1 has an electrophotographic photoreceptor layer, dielectric layer, or magnetic recording layer on its surface and rotates in the direction of the arrow, and is formed by a known electrostatic latent image forming device or magnetic latent image forming device. An image carrier on which an electrostatic latent image or a magnetic latent image is formed, 2 a developer transport carrier made of a non-magnetic material such as stainless steel or aluminum, and 3 a plurality of developer transport carriers on the surface provided inside the developer transport carrier 2. This is a magnet body having N and S magnetic poles in the circumferential direction. In the figure, the magnet body 3 rotates in the direction of the arrow, and the developer is transferred to the surface of the developer transport carrier 2 which is stationary or rotates in the opposite direction to the magnet body 3. This shows that the developer layer is adsorbed to form a developer layer, and the developer layer moves in the direction of the arrow. However, since the magnet 3 is stationary,
It may be such that the developer layer moves together with the surface of the developer transport carrier 2 as the developer transport carrier 2 rotates. If the magnet body 3 is rotating, the N and S magnetic poles are usually of equal magnetic flux density of 500 to 1500 Gauss, but if it is stationary, the N and S magnetic poles are opposite to the image carrier 1. Usually, the magnetic flux density of one magnetic pole is made larger than the magnetic flux density of other magnetic poles. 4 is a layer thickness regulation plate that regulates the thickness of the developer layer formed on the surface of the developer transport carrier 2; 5 is a layer thickness regulating plate that regulates the thickness of the developer layer formed on the surface of the developer transport carrier 2; A cleaning blade 6 removes the developer layer from the surface of the developer transport carrier 3; 6 a developer reservoir for supplying developer to the surface of the developer transport carrier 3; 7 a developer reservoir 6;
8 is a stirring roller that stirs the developer so that it is easily adsorbed on the developer transport carrier 3, and uniformly mixes the developer when the developer is a two-component developer consisting of toner particles and carrier particles; a developer replenishment hopper for replenishing the developer (toner particles in the case of a two-component developer); 9 a developer replenishment roller having a concave portion on its surface for dropping toner from the developer replenishment hopper into the developer reservoir 6; 10; a bias power source 12,1 which applies a bias voltage to the developer transport carrier 2 through a protective resistor 11 to generate an oscillating electric field between the metal base portion and the grounded image carrier 1;
2' is an electrode member provided via an insulator on the developing device frame surrounding the outside of the developing area A; 13 is a developer transport carrier by applying a bias voltage to the electrode members 12, 12' via a protective resistor 14; This is a bias power source that generates a polar unidirectional electric field between the developer layer and the electrode members 12, 12' to prevent toner from adhering to the electrode members 12, 12'. Here, the electrode members 12, 12'
is not in contact with the image carrier 1 and the image carrier 1 is
It is installed in close proximity to the toner image formed on the developer carrier 1 so as not to destroy it, and preferably not in contact with the developer layer of the developer transport carrier 1, and its mounting position is as shown in the figure in the developing device. Even inside,
Or it could be outside. The shape of the electrode members 12, 12' is not limited to a plate shape, but may be a columnar shape. Although an oscillating electric field is generated between the developer transport carrier 2 and the image carrier 1, a unidirectional electric field is generated between the developer transport carrier 2 and the electrode members 12, 12' because Bias power supplies 10 and 13
This can be achieved by configuring as shown in FIG.

In FIG. 2, the structure surrounded by the one-dot chain line is the bias power supply 10 that applies a bias voltage to the developer transport carrier 2, and the structure surrounded by the two-dot chain line is the bias power supply 10 that applies the bias voltage to the electrode members 12, 12'. This is the power source 13. The bias power supply 10 including a common sine wave oscillation circuit and amplification circuit is set under conditions such that the developer is easily transferred from the developer layer of the developer transport carrier 2 to the image carrier 1 and does not cause fogging. The bias power supply 13, which consists of a transformer and a DC power supply circuit that boosts the voltage using a common sine wave oscillation circuit and an amplifier circuit, is set to Clear development can be achieved by setting the conditions to show a potential difference that does not result in reverse polarity even if there is a direct current potential difference or a vibration component of polarity that prevents toner from adhering to the electrode members 12, 12'. It does not cause fogging, and the developing device and image carrier 1 are
The result is that toner does not scatter from the gaps.

That is, the developing conditions used in the developing device of the present invention are such that an oscillating electric field is applied between the developer transport carrier 2 and the image carrier 1 to facilitate the transfer of toner from the developer layer to the image carrier 1. , it is preferable to set the conditions such that the developer layer of the developer transport carrier 2 does not come into contact with the surface of the image carrier 1.
Set the gap between the image carrier 1 and the developer transport carrier 2 to several tens of
In the range of 2000 μm, it is preferable that the thickness of the developer layer formed on the developer transport carrier 2 is increased so as not to contact the surface of the image carrier 1. Image carrier 1
If the gap between the developer transport carrier 2 and the developer carrier 2 becomes too narrow than several tens of micrometers, it becomes difficult to form a uniform developer layer, and it becomes difficult to perform stable and clear development. Furthermore, if the gap greatly exceeds 2000 μm, the effect of the oscillating electric field between the developer transport carrier 2 and the image forming body 1 will be reduced, making it impossible to obtain a sufficient developed density. And the edge effect also becomes larger. In this way, when the gap between the developer transport carrier and the image carrier becomes extreme, it becomes impossible to make the thickness of the developer layer on the developer transport carrier appropriate. Within this range, the developer layer can be formed with an appropriate thickness. Therefore, by forming the developer layer so that it does not come into contact with the surface of the image carrier 1 and is as close to the surface as possible, it is possible to perform clear development without sweeping or fogging.

The developer layer is formed on the developer transport carrier 2 by:
It is preferable to use the conditions in which the magnet body 3 is formed by rotating it as shown in the illustrated example. As a result, the formed developer layer is undulated in a wavy manner to the developer transport carrier 2.
Therefore, new developer is supplied to the development area A one after another, and even if there is some unevenness in the thickness of the developer layer, this effect will not be a practical problem due to the above-mentioned undulations. be sufficiently covered so that it does not occur. The image carrier 1 and the developer layer may move in the same direction as in the illustrated example, or may move in opposite directions. It is preferable that the moving speed of the developer layer is equal to or higher than the moving speed of the image carrier 1 in order to obtain a clear image. However, if the developer layer is disturbed by the rotation of the magnet body 1, Clear images can be obtained even if the moving speed of the developer layer is slow.

Furthermore, the developing device of the present invention has two components consisting of toner particles and carrier particles, which can easily control the triboelectric charging of the developer and, therefore, can effectively control the toner transfer by means of an oscillating electric field. Preferably, a developer is used. The oscillating electric field makes it easier for the toner particles to separate from the carrier particles and transfer to the image bearing member 1, so that the conventional toner particles with an average particle size of tens of micrometers and the conventional toner particles with an average particle diameter of several tens to hundreds of micrometers Using a two-component developer consisting of toner particles with an average particle size of 10 μm or less and magnetic carrier particles with an average particle size of several tens of μm or less has better reproducibility than a two-component developer consisting of magnetic carrier particles. This is preferable from the viewpoint of obtaining high-quality images. In this regard, in a developing device that does not generate an oscillating electric field between the developer transport carrier 2 and the image carrier 1, if the toner particles and carrier particles are made into fine particles as described above, the Coulomb force during development will Due to the influence of Waals force, so-called fogging occurs in which toner particles adhere to the ground area of the image background, and it is difficult to prevent fogging even by applying a DC bias voltage to the developer transport carrier. However, it becomes difficult to control the triboelectrification of toner particles, causing problems such as agglomeration becoming more likely to occur, and carrier particles also becoming attached to the latent image area of the image bearing member. It has been difficult to use particles and carrier particles.

According to the developing device of the present invention, even if a two-component developer consisting of finely divided toner particles and carrier particles is used, the oscillating electric field applied between the developer transport carrier 2 and the image forming body 1 causes the developer to The result is that the toner particles are easily separated individually from the developer layer of the transport carrier 2 and do not adhere to the latent image due to Coulomb force, causing fogging or edge effects. Further, even if the toner particles are easily separated from the developer layer, toner particles may be separated between the electrode members 12, 12' and the developer transport carrier 2.
A unidirectional electric field with a polarity that prevents the toner from adhering to the toner particles 12, 12' is generated, and this is caused by the application of a bias voltage having a DC component of the same polarity as the charging of the toner particles to the electrode members 12, 12'. In this case, toner particles are prevented from scattering from the gap between the developing device and the image carrier 1, and the oscillating electric field state between the developer transport carrier 2 and the image carrier 1 is not disturbed. Therefore, clear development with excellent image reproducibility is achieved. Although the direct current component of the bias voltage applied to the electrode members 12, 12' has a scattering prevention effect even if it is 0 or has a polarity opposite to that of the toner, there is a drawback that the toner tends to adhere to the electrodes.

In the present invention, it is preferable to provide an insulating or semi-insulating film on the surfaces of the developer transport carrier 2 and the electrode members 12, 12' because a high bias voltage can be applied thereto. It is also preferable that the toner particles and carrier particles are spherical, and the carrier particles are made into insulating magnetic particles by an insulating film or the like.

〔Example〕

Further, the present invention will be explained by specific examples.

In the developing device shown in FIGS. 1 and 2,
The bias power supply 10 has an AC voltage of 2KHz, 1KV and -
A bias voltage in which a DC voltage of 150V is superimposed is applied to the developer transport carrier 2, and the bias power supply 13 is connected to a 2KHz, 1KV AC voltage with the same phase as +
A bias voltage superimposed on an AC voltage of 100V was applied to the electrode members 12, 12'. and,
The image carrier 1 has an image forming layer made of an organic photoconductor OPC on its surface, and has a diameter of 120 mm in the direction of the arrow.
The surface was rotated at a surface speed of mm/sec so that an electrostatic latent image of -500V was formed on the surface against a background potential of -50V. The gap between the image carrier 1 and the developer transport carrier 2, that is, the gap in the development area A, is 700 μm.
The number of rotations in the left direction of the developer transport carrier 2 with an outer diameter of 30 mm is
The rotation speed in the direction of the arrow of the magnet 3, which has 8 equally spaced N and S magnetic poles with a magnetic flux density of 900 gauss and 65 rpm, is
700 rpm, the distance between the layer thickness regulating blade 4 made of a magnetic material and the developer transport carrier 2 is 400 μm, and the developer has a weight average particle size of about 30 μm and a resistivity of about 1 × 10 with magnetic powder dispersed in the resin. A two-component developer (developer for EP 310 manufactured by Minolta) consisting of insulating carrier particles of ¹⁴ Ωcm and insulating non-magnetic toner particles with a weight average particle diameter of 14 μm was used, and developer transport carrier 2 was used.
The electrostatic latent image on the image carrier 1 was developed under conditions such that the thickness of the developer layer formed thereon was approximately 500 μm. The toner image obtained by development was transferred onto plain paper by a corona discharge transfer device (not shown) and fixed by a roller fixing device with a surface temperature of 140°C.

The recorded images obtained were extremely clear and high in density, with no edge effects or fog.Fifty thousand sheets of recording paper were subsequently obtained, and the recorded images remained stable and unchanged from beginning to end. I was able to get it.
Further, toner particles did not scatter from the gap between the developing device and the image carrier 1.

On the other hand, if no bias voltage is applied to the electrode members 12 and 12' and they are kept in a floating state or grounded state, the scattering of toner particles is significant and the maximum number of sheets of recording paper that can be obtained is 10,000 sheets. It was hot.
Furthermore, when only a DC voltage is applied to the electrode members 12 and 12', the scattering of toner particles is not reduced much compared to when the electrode members 12 and 12' are in a floating state or in a grounded state, and the clarity of the recorded image is impaired. This effect was more noticeable.

Note that the developer transport carrier 2 and the electrode members 12, 1
The AC component of the bias voltage applied to 2' is 100~
10000Hz preferably 1000~5000Hz effective value 200~
At 5000V, the effective value between image carrier 1 is 300~
It is preferable that the electric field strength is 3000V/mm, and the waveform is not limited to a sine wave.
It may be a rectangular wave or a triangular wave.

〔Effect of the invention〕

According to the developing device of the present invention, it is possible to perform clear development without fogging or edge effects, and the excellent effect that developer is not scattered from the gap with the image carrier can be obtained.

In the present invention, the oscillating electric field that is generated between the developer transport carrier and the image carrier is not limited to the illustrated example.
An electrode wire, an electrode net, etc. may be stretched between the two, and a bias voltage may be applied thereto.

The developing device of the present invention can be used to develop a magnetic latent image by using magnetic toner particles as the developer.

[Brief explanation of drawings]

FIG. 1 is a partial configuration diagram of a recording device showing an example of the developing device of the present invention, and FIG. 2 is a power supply circuit diagram for applying a bias voltage to a developer transport carrier and an electrode member. 1... Image carrier, 2... Developer transport carrier, 3...
... Magnet body, 4 ... Layer thickness regulation blade, 5 ... Cleaning blade, 6 ... Developer reservoir, 7 ... Stirring roller, 8 ... Developer replenishment hopper, 9 ... Developer replenishment roller, 10 ... Bias power supply, 11...
...Protective resistor, 12, 12'... Electrode member, 13...
...Bias power supply, 14...Protection resistor.

Claims (1)

[Scope of Claims] 1. A developer layer is formed on the surface of a developer transport carrier, an oscillating electric field is generated between the developer transport carrier and an image carrier, and a latent image on the image carrier surface is developed with toner. In the developing device, an electrode member is provided in a portion of a developing device frame surrounding the outside of the developer transport carrier near the image carrier,
An alternating current voltage and a direct current voltage having the same phase as the oscillating electric field are applied to the electrode member to generate unidirectionality between the electrode member and the developer transport carrier in the direction from the electrode member to the developer transport carrier. A developing device characterized in that it generates an electric field. 2. The developing device according to claim 1, wherein a part of the electrode member is arranged so as to have a surface facing the image carrier surface. 3. The developing device according to claim 1 or 2, wherein the developer layer on the developer transport surface is formed thinner than the gap between the image carrier and the developer transport carrier.