JPH0469900B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to an electrostatic latent image or a magnetic latent image formed on the surface of an image forming body by electrophotography, electrostatic recording, electrostatic printing, etc. Regarding the developing device of a recording device to which toner particles are attached, in particular, a so-called two-component developer in which magnetic carrier particles and toner particles are mixed on the outer circumferential surface of a developer transporting carrier with a built-in magnet body having a plurality of magnetic poles arranged on the circumference. The present invention relates to an improvement in a developing device in which a layer is formed to a thickness that does not contact the surface of an image forming member, and toner particles are caused to fly from the developer layer under an oscillating electric field and adhere to an electrostatic latent image on an image forming member.

[Prior art]

As a developing device such as the one mentioned above,
No. 144452, No. 57-139761, No. 57-147652, No. 57-139761, No. 57-147652, No.
58-48065 and those described in each publication are known. By using a two-component developer, these developing devices can more easily control the triboelectric charging of toner particles than those using a single-component developer for magnetic toner particles, and are less prone to agglomeration of toner particles. As a result, it becomes easier to uniformly form a developer layer on the surface of the developer transport carrier, and furthermore, it becomes easier to control the transfer of toner particles from the developer layer to the image forming body using an oscillating electric field. Therefore, toner particles are transferred from the developer layer to the image forming body under an oscillating electric field without bringing the developer layer into contact with the surface of the image forming body, thereby eliminating the sweeping that is likely to occur when the developer layer is brought into contact with the image forming body. This allows development to be carried out without eyes or fog.

However, even in such a developing device, non-uniformity and fog may occur in the development. In order to prevent this, it is effective to form the developer layer into a uniform thin layer.

However, in conventional developing devices, the thickness of the developer layer is regulated only by a layer thickness regulating member that forms a passage gate for the developer layer. The thinner the layer thickness is, the more uneven the layer thickness becomes. Therefore, it was difficult to form a thin and uniform developer layer. This problem is particularly important in order to obtain high-quality images that reproduce delicate lines, dots, and differences in shading. When a two-component developer whose particles are finer than that of the toner particles is used, the problem becomes even more noticeable because the developer tends to aggregate. There is also the problem that irregularities in regulating layer thickness tend to appear as development irregularities.

On the other hand, in a magnetic brush developing device that brings the developer layer into contact with the surface of the image forming body, the magnetic brush that has passed through the layer thickness regulating member expands from the pressed state and scatters toner particles, thereby causing fogging, etc. In order to prevent this, a magnetic piece is provided on the layer thickness regulating member made of a non-magnetic material, and the toner particles of the magnetic brush that have passed through the layer thickness regulating member become insufficiently charged and scatter, or fogging occurs. In order to prevent this from becoming more likely to occur, a method was developed in 1972, in which a blade made of a non-magnetic elastic material was provided that charged the toner particles by contacting the magnetic brush immediately after passing through the layer thickness regulating member. It is known from Publication No. 107336 and No. 57-9797.

[Object of the Invention] The present invention was made against the background of the above-mentioned prior art, and the present inventors responded to the request for a non-contact developing device to form a thin and uniform developer layer in accordance with U.S. Pat. As a result of examining whether the techniques of both No. 1 and No. 57-9797 can meet the requirements, we found that the method of providing a magnetic piece in the layer thickness regulating member did not produce the desired effect, but the method of providing a blade did not We discovered that, as long as the distance between the regulating member and the developer transport carrier is not extremely narrow, using a blade as a leveling member is effective in making the thickness of the thin developer layer uniform. This was done based on.

That is, in the present invention, a developer layer can be formed thinly and uniformly on a developer transport carrier, and toner particles are caused to fly from the developer layer under an oscillating electric field without bringing the developer layer into contact with an image forming body. The purpose of this invention is to provide a developing device capable of developing a clear toner image free from non-uniformity and fogging.

[Structure of the invention]

The present invention provides a layer of developer containing a mixture of magnetic carrier particles and toner particles on the outer circumferential surface of a developer transporting carrier having a built-in magnet and having a plurality of magnetic poles disposed on its circumference, to a thickness that does not make contact with the surface of an image forming body. In a developing device in which toner particles are formed on a developer layer and attached to an electrostatic latent image on an image forming body by flying toner particles from the developer layer under an oscillating electric field, the magnetic body is attached to a surface where the outer peripheral surface of the developer transporting carrier is on the surface of the image forming body. A stationary magnet body is used in which N and S magnetic poles are arranged before and after a developing area close to the surface so that the lines of magnetic force in the developing area are approximately parallel to the outer circumferential surface of the developer transport carrier, and the layer thickness of the developer layer is A leveling member is placed in contact with the developer layer whose layer thickness is regulated by the layer thickness regulating member, with a distance between the layer thickness regulating member and the developer transporting carrier that regulates the thickness of the layer and the developer transporting carrier. A developing device characterized in that it is provided close to a thickness regulating member,
This configuration achieves the above object.

〔Example〕

Hereinafter, the present invention will be explained with reference to illustrated examples.

1 and 2 and 3 are a schematic sectional view and a partial sectional view, respectively, showing an example of the developing device of the present invention.

In the figure, 1 is a drum that has an image forming layer made of a photoreceptor or dielectric such as Se on its surface, and an electrostatic latent image is formed on the image forming layer by a charging/exposure device (not shown). The image forming body 2, which rotates in the direction of the arrow, is a developer transport carrier having a smooth surface or an uneven surface of about 10 to 500 μm, and is usually made of conductive non-magnetic material such as aluminum or stainless steel. formed of material. The surface of the developer transport carrier 2 is preferably made insulating or semi-insulating by a resin or oxide coating. When the surface of the developer transport carrier 2 is made insulating or semi-insulating, even if a bias voltage is applied to the developer transport carrier 2 and thereby an oscillating electric field is generated in the development area A, electrodrop development will not occur. Therefore, the developer transport carrier 2
It becomes easy to apply a sufficient bias voltage to control the transfer of toner particles.

3 is a bias power supply that applies a bias voltage to the developer transport carrier 2 via the protective resistor 4 and forms an oscillating electric field between the image forming body 1 whose base portion is grounded and the developer transport carrier 2; , which is a magnet provided inside the developer transport carrier 2. The magnet body 5 has a plurality of N and S magnetic poles arranged in the circumferential direction on its surface,
The N and S magnetic poles are normally magnetized to a magnetic flux density of 500 to 1500 Gauss.

The developer transporting carrier 2 is stationary, and the developer transporting carrier 2 rotates to the left, and the developer in the developer reservoir 6 is transferred to the developer transporting carrier 2 in the form of toner particles attached to magnetic carrier particles due to the magnetic force of the N and S magnetic poles of the magnet body 5. The adsorbed developer is moved in the same direction by the rotation of the developer transport carrier 2, and the layer thickness is controlled by the layer thickness regulating member 7 made of a non-magnetic or magnetic material. The formation of the developer layer is regulated. The arrangement of the magnetic poles N and S in the magnet body 5 is such that the N and S magnetic poles are arranged before and after the developing area A. It forms a magnetic field approximately parallel to the surface. As a result, the developer layer in the developing area A is kept low and thin, and the gap between the developer transport carrier 2 and the layer thickness regulating member 7 can be widened, while the developer layer in the developer transport carrier 2 is kept thin. The distance to the image forming body 1 can be further narrowed, and the movement of toner particles can be easily controlled by the oscillating electric field.

That is, in this developing device, in the developing area A, the developer layer on the developer transport carrier 2 is located on the image forming body 1.
The toner particles are used under conditions such that toner particles fly from the developer layer under an oscillating electric field and adhere to the latent image on the image forming body 1 without contacting the surface of the image forming member 1 .

A cleaning blade 8 returns the developer layer remaining on the developer transport carrier 2 after passing through the development area A to the developer reservoir 6, and a cleaning blade 9 stirs the developer in the developer reservoir 6 to mix it uniformly. , a stirring roller that frictionally charges the toner particles, and 10 a toner supply roller that supplies toner particles from the toner hopper 11 to the developer reservoir 6.

In the developing device of the present invention, the gap between the developer transport carrier 2 and the layer thickness regulating member 7 is greater than or equal to the gap between the layer thickness regulating member 7 and the developer layer immediately after being formed by the layer thickness regulating member 7. A leveling member 12 is provided which comes into contact with the surface.

The leveling member 12 in the developing device shown in FIGS. 1 and 2 is made of a rigid body, and the leveling member 12 in the developing device shown in FIG. 3 is made of an elastic body. The leveling member 12 in FIGS. 1, 2, and 4 has a plate-like surface that comes into contact with the developer layer to level the surface, but the leveling member 12 in FIG. 2 is a thick plate. The end surface of the shape comes into contact with the developer layer to level it.

By providing such a leveling member 12, the gap between the layer thickness regulating member 7 and the developer transport carrier 2 can be adjusted in the developing area A where the lines of magnetic force are approximately parallel to the outer peripheral surface of the developer transport carrier 2. Even if the thickness is narrowed so that a non-contact developer layer is obtained on the image forming body 1, and therefore the relative variation in the thickness of the developer layer becomes large, the variation is smoothed out by the leveling member 12. , it becomes possible to form a thin and uniform developer layer.
That is, the layer thickness regulating member 7 is controlled by the leveling member 12.
The streaks that tend to occur due to clogging of the regulating section in the filter also disappear. Therefore, conditions can be easily set to appropriately narrow the gap between the developer transport carrier 2 and the image forming body 1 and to effectively control the transfer of toner particles by the oscillating electric field in the development area A. , it is possible to develop clear toner images without non-uniformity or fogging.

This leveling member 12 does not form a developer passage gate like the layer thickness regulating member 7, nor does it triboelectrically charge toner particles like the blade in Japanese Utility Model Application Publication No. 57-9797. , developer is not accumulated at the leveling member 12 and clogging does not occur due to this. Therefore, as in the example shown in FIGS. 1 and 2, the leveling member 12 can be made of a rigid body, and when it is made of a rigid body, it is less likely to undergo elastic displacement than when it is made of an elastic body. To make the thickness of the developer layer more uniform. However, if the thickness of the developer layer regulated by the layer thickness regulating member 7 varies greatly or the developer layer contains aggregated toner particles, the leveling member 12 may be used. It is safe to use an elastic body to prevent such developer from accumulating. The leveling member 12 is not limited to a plate-like member, and a rigid member may be a cylindrical member, and an elastic member may be a fine-mesh brush member.

Since the developing device of the present invention performs development by generating a high oscillating electric field in the developing area A,
The leveling member 12 is provided close to the layer thickness regulating member 7 on the downstream side so as not to cause breakdown of the electric field. Furthermore, in order to prevent the leveling member 12 from causing breakdown, the leveling member 12 should be insulated (made of an insulating material or supported via an insulator), or
It is preferable to apply the same or similar voltage to the voltage for forming the oscillating electric field to the leveling member 12.
This also applies to the layer thickness regulating blade 7. Note that if the leveling member 12 is made of a conductive material and grounded, breakdown is likely to occur. Furthermore, the oscillating electric field is generated in the development area A by the first
The present invention is not limited to the example shown in the figure, but a control electrode such as a wire electrode or a net electrode that does not impede the transfer of toner particles may be provided in the development area A, and an oscillating voltage may be applied thereto.

The leveling member 12 may be made of a magnetic material or a non-magnetic material, but it is preferably made of a non-magnetic material since it does not impede the passage of the developer layer. The rigid leveling member 12 shown in FIGS. 1 and 2 is preferably made of an aluminum plate with a thickness of about 2 mm, and the leveling member 12 made of an elastic body having a similar shape is preferably used. The elastic leveling member 12 shown in FIG. 3 is preferably made of a polyethylene terephthalate plate having a thickness of about 50 μm. As described above, the leveling member 12 formed of an aluminum plate is supported via an insulator or is further applied with a voltage. Of course, a resin material or other metal material may be used for the rigid leveling member 12, or an elastic leveling member 12 may be used.
Other resin plates and phosphor bronze plates with a thickness of 20 to 300 μm,
A stainless steel plate or the like may be used.
When the leveling member 12 is made of a resin material, even if the leveling member 12 is not specifically designed to triboelectrically charge the toner particles, it imparts triboelectricity to the toner particles, so at least undesirable reverse polarity can be avoided. It is preferable to use a material that does not generate highly charged toner.

It is preferable that the leveling member 12 is installed as described above so that the gap between it and the developer transport carrier 2 can be adjusted using screws, rivets, etc.; however, the leveling member 12 is not limited thereto.
It may be fixed with adhesive or the like. Also,
The leveling member 12 is preferably installed at a position close to the magnetic poles of the magnet body 5. At this time, the magnetic field at the leveling member position is preferably 300 Gauss or more.
500-1000 Gauss is preferred. At such a magnetic field position, the developer layer conveying force of the developer conveying carrier 2 is strong, so that the leveling member 12 is prevented from blocking the passage of the developer layer and collecting more developer than necessary. .

As described above, according to the developing device of the present invention provided with the leveling member 12, the developer layer can be formed uniformly and thinly on the developer transport carrier 2, and there is no non-uniformity or fog. A clear toner image can be developed. As a non-contact development condition for this purpose, the number of developer transport carriers 2 to the image forming body 1 is several tens of times.
It is preferable to maintain a surface gap of ~2000 μm and form the developer layer to a uniform layer thickness so that it is brought close to the surface of the image forming body 1 without contacting it using the layer thickness regulating blade 7 and the leveling member 12. If the surface gap between the image forming member 1 and the developer transport carrier 2 is made too narrow, it will be difficult to uniformly form a developer layer on the surface of the developer transport carrier 2, and the toner particles will not be sufficiently distributed in the development area A. This makes it difficult to perform clear development. Furthermore, if the surface gap greatly exceeds 2000 μm, the toner particle transfer control by the oscillating electric field will not be performed effectively, making it impossible to obtain a sufficient developed density. Then, the surface gap is
When the thickness is in the range of 10 to 2000 μm, preferably 500 to 1500 μm, the developer layer can be uniformly formed on the surface of the developer transport carrier 2 with an appropriate thickness of 100 to 1000 μm, and the toner particles can be effectively transferred by the oscillating electric field. can be controlled.

A bias power supply 3 generates an oscillating electric field between the developer transport carrier 2 and the image forming body 1 to facilitate separation of toner particles from the developer layer.
The effective value of the AC component is 200 to 5000V, and the frequency is 100V.
Hz~10kHz, preferably 300~4000V, 1~5kHz
By applying a bias voltage of , the effective value of
It is desirable that it exhibits an electric field strength of 300 to 5000 V/mm. The bias voltage applied to the developer transport carrier 2 by the bias power supply 3 is superimposed with a DC voltage of an appropriate magnitude having the same polarity as the potential of the non-image area of the image forming member 1 in order to prevent the occurrence of fogging. Of course, it can be used as

Note that even in the case where a control electrode is provided in the development area A and a bias voltage is applied thereto, it goes without saying that the DC component as well as the AC component can be superimposed on the bias voltage. In this case, a DC voltage or an AC voltage is also applied to the developer transport carrier 2. In this case, the AC component applied to the developer transport carrier 2 may have a frequency different from that of the AC component applied to the control electrode.

The waveform of the AC component of the bias voltage applied to the developer transport carrier 2 and the control electrode is not limited to a sine wave, but may be a triangular wave or a rectangular wave. Furthermore, by appropriately setting the voltage and polarity of the DC component of the bias voltage, the developing device of the present invention can be applied not only to positive development but also to reversal development. In the case of reversal development, the DC component of the bias voltage is set to a voltage approximately equal to the accepted potential in the non-image background portion of the image forming member.

The developing device of the present invention is composed of a mixture of magnetic carrier particles with an average particle size of 10-odd μm to several hundred μm and non-magnetic toner particles with an average particle size of 10-odd μm, similar to conventional two-component developers. A developer is also used, but in order to obtain high-quality images that reproduce delicate lines, dots, and differences in shading, toner particles with a weight average particle size of 1 to 20 μm and a magnetic carrier with a weight average particle size of 5 to 50 μm are required. It is preferable to use a developer consisting of a mixture of magnetic particles and magnetic carrier particles, and furthermore, the magnetic carrier particles are insulating particles such as particles whose surfaces are coated with a resin film or resin particles containing fine magnetic particles dispersed therein. is preferable because a high bias voltage can be applied to the developer transport carrier 2. The carrier particles preferably have an insulating property with a resistivity of 10 ⁸ Ωcm or more, particularly 10 ¹³ Ωcm or more. This resistivity is calculated by placing particles in a container with a cross-sectional area of 0.50 ^cm2 , tapping them, applying a load of 1Kg/ ^cm2 on the packed particles, and applying a voltage of 1000V/cm between the load and the bottom electrode. This value is obtained by reading the current value when a voltage that generates an electric field is applied. If this resistivity is low, when a bias voltage is applied to the developer transport carrier, charge is injected into the carrier particles. Carrier particles tend to adhere to the surface of the image forming member, or bias voltage breakdown tends to occur.

According to the developing device of the present invention, as described above, the developer layer can be stably formed on the developer transport carrier 2, and the transfer of toner particles can be efficiently controlled by the oscillating electric field. Therefore, even if finely divided toner particles or carrier particles are used, the toner particles can be easily transferred from the developer layer to the latent image on the image forming member 1 under non-contact development conditions, thereby achieving high image quality. Images can be reproduced.
The weight average particle diameter of the toner particles and carrier particles is measured using a Coulter Counter (manufactured by Coulter) or Omnicon Alpha (manufactured by Botsulom).

〔Effect of the invention〕

According to the developing device of the present invention, it is possible to stably form a uniform thin developer layer in the development area on the developer transport carrier, and therefore, the toner particles are transferred from the developer layer by the oscillating electric field. It has the excellent effect of being able to effectively control and reproducing high-quality images with excellent clarity even when using developers made of finely divided carrier particles and toner particles. can get.

[Brief explanation of the drawing]

1 and 2 and 3 are a schematic sectional view and a partial sectional view, respectively, showing an example of the developing device of the present invention. DESCRIPTION OF SYMBOLS 1... Image forming body, 2... Developer transport carrier, 3... Bias power supply, 4... Protective resistor, 5... Magnet, 6... Developer reservoir, 7... Layer thickness regulating blade, 8... Cleaning blade, 9... Stirring roller , 10... Toner supply roller, 11... Toner hopper, 12... Leveling member.

Claims (1)

[Scope of Claims] 1. A developer layer containing a mixture of magnetic carrier particles and toner particles is brought into contact with the surface of an image forming body on the outer peripheral surface of a developer transporting carrier having a built-in magnet and having a plurality of magnetic poles disposed on its circumference. In a developing device in which toner particles are formed in a layer having a thickness such that the outer circumferential surface of a developer transporting carrier is not imaged, the toner particles are caused to fly from the developer layer under an oscillating electric field and adhere to an electrostatic latent image on an image forming member. A stationary magnet body has N and S magnetic poles arranged before and after a developing area close to the surface of the forming body so that the lines of magnetic force in the developing area are approximately parallel to the outer peripheral surface of the developer transport carrier, and the developer layer The layer thickness regulating member contacts the developer layer whose layer thickness is regulated by the layer thickness regulating member with a distance from the developer transporting carrier equal to or greater than the distance from the developer transporting carrier. A developing device characterized in that a member is provided close to a layer thickness regulating member. 2. The developing device according to claim 1, wherein the leveling member is a rigid member. 3. The developing device according to claim 1, wherein the leveling member is an elastic member. 4. The developing device according to any one of claims 1 to 3, wherein the leveling member is provided close to one magnetic pole position of the magnet body.