JPS6113269A - Developing device - Google Patents

Abstract

PURPOSE:To form stably a uniform thin developer layer by providing a leveling member with a wide interval downstream from a blade which controls the layer thickness of the developer supplied from a developer accumulating part to a developer carrier. CONSTITUTION:A developer carrier 2 is turned counterclockwise to supply the developer from a developer accumulating part 6 to an electrostatic latent image on an image forming body and to develop the latent image. A blade 7 which controls the height of the developer is provided. A developer leveling member 12 formed with a rigid member or an elastic member is attached downstream from the blade 7. Thus, the uniform thin developer layer is formed stably on the surface of the developer carrier 2, and vivid pictures of high quality are formed even if fined carrier particles and toner particles are used.

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 on the surface of an image forming body by electrophotography, electrostatic recording, electrostatic printing, magnetic recording, or the like. Regarding the developing device of a recording device that attaches toner particles to an image, in particular, a layer of a so-called two-component developer in which magnetic carrier particles and toner particles are mixed is formed on one developer transport/reject surface, and the developer layer is developed under an oscillating electric field. The present invention relates to an improvement in a developing device that causes toner particles to fly from the surface of the image forming body and adhere to a latent image on an image forming member.

[Prior art]

As a developing device as described above, Japanese Patent Application Laid-Open No. 56-14445
No. 2, No. 57-139761, No. 57-147652
No. 58-48065 are known. By using a two-component developer, these developing devices can more easily control the triboelectric charging of magnetic toner particles than when using a single-component developer.
Due to the agglomeration of toner particles, it is not easy to form a uniform developer layer on the surface of the developer transport carrier. The transfer of toner particles from the developer layer to the image forming body can be easily controlled by moving the toner particles 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. This allows development to be carried out without scratches or fogging, which are likely to occur in materials brought into contact with the image forming body.

However, even in such a developing device, non-uniformity and fogging may occur in the development. In order to prevent this, it is effective to form the developer layer into a uniformly 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, so that the developer is absorbed onto the surface of the developer transport carrier. The thinner the layer thickness is, the more uneven the layer thickness becomes. When υ is large, it is 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 toner particles of .mu.m are made into finer particles and a 92-component developer is used, the problem becomes even more noticeable because the developer tends to aggregate. There is also the problem that unevenness in regulation of layer thickness tends to appear as development unevenness.

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 its pressed state and scatters toner particles, thereby causing fogging and the like. In order to prevent this, a magnetic piece is provided on the layer thickness regulating member made of a non-magnetic material, and toner particles of the magnetic brush that have passed through the layer thickness regulating member are insufficiently charged and are scattered, or the cover is In order to prevent this, a method has been implemented in which a blade made of a non-magnetic elastic material is provided which charges the toner particles by contacting the magnetic brush immediately after passing through the layer thickness regulating member. Publications No. 54-107336 and No. 57-97
It is known from Publication No. 97.

[Purpose of the invention]

The present invention has been 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 U.S. Pat.
As a result of examining whether the techniques of both Publications No. 36 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. It was discovered that by using it as a leveling member, it is effective to make the thickness of a thin developer layer uniform, and this work was made based on this knowledge.

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 that can develop clear toner images without unevenness or fogging.

〔Effect of the invention〕

In the present invention, a developer layer containing a mixture of magnetic carrier particles and toner particles is formed on the surface of a developer transporting carrier, and the toner particles are ejected from the developer layer under an oscillating electric field to form a latent image on an image forming member. In the developing device for adhesion, a leveling member is provided which comes into contact with the developer layer with a gap between the layer thickness regulating member that regulates the layer thickness of the developer layer and the developer carrying carrier that is larger than the gap with respect to the developer carrying carrier. The developing device is characterized in that it is provided close to the layer thickness regulating member and on the downstream side thereof, and with this configuration, the above object is achieved.

〔Example〕

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

FIG. 1.2 and FIGS. 3 and 4 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, numeral 1 has an image forming layer made of a photoreceptor or dielectric material such as Se on its surface, and is charged (not shown).

A drum-shaped image forming body rotating in the direction of the arrow on which an electrostatic latent image is formed on the image forming layer by an exposure device etc.; 2 is a developer transporting carrier having a smooth surface or an uneven surface of about 10 to 500 μm; It is usually made of a conductive, non-magnetic material such as aluminum or stainless steel. The surface of the developer transport carrier 2 is preferably made insulating or semi-insulating by a resin or an oxide film. 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 an oscillating electric field is generated in the development area A,
Dielectric breakdown such as that caused by lightning strikes is less likely to occur, and therefore it becomes easier to apply a sufficient bias voltage to the developer transport carrier 2 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;
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, and the N and S magnetic poles are normally magnetized to a magnetic flux density of 500 to 15 gauss.

In the developing device shown in FIG. 1, the magnet body 5 rotates in the right direction, the developer transport carrier 2 rotates in the opposite direction, and the N of the magnet body 5 rotates in the right direction.
Due to the magnetic force of the S magnetic pole, the developer at the bottom of the developer reservoir is attracted to the surface of the developer transport carrier 2 in the form of magnetic carrier particles and toner particles, and the adsorbed developer is transferred to the developer transport carrier 2 and the magnet body. 5, the developer transport carrier 2 is moved in the same direction as the rotating direction of the developer transport carrier 2, and the layer thickness is regulated by a layer thickness regulating member 7 made of a non-magnetic or magnetic material to form a developer layer. is to be carried out. On the other hand, the second
In the developing device shown in Figures 1 to 4, the magnet body 5 is stationary, the developer transport carrier 2 rotates to the left, and the developer layer similarly moves in the same direction as the rotation of the developer transport carrier 2. It is something that is formed. Furthermore, in the developing device shown in FIG. 2, the arrangement of the magnetic poles N and S in the magnet body 5 forms a horizontal magnetic field approximately parallel to the surfaces of the developer transport carrier 2 and the image forming body 1 in the developing area A. On the other hand, the developing device shown in Figures 3 and 4 is
The developing device differs from the developing device shown in FIG. 2 in that the magnetic poles N and S in the magnet body 5 are arranged to form a perpendicular magnetic field in the developing area A. In addition, as in the developing device shown in FIG.
The rotating magnet has the advantage that even if there is some variation in the thickness of the developer layer, the effect is canceled out by the rotation of the magnet body 5. As for the rotating magnet body 5,
In addition to the example shown in FIG. 1, there are cases in which the developer transport carrier 2 is stationary and the developer layer is transported only by the rotation of the magnet 5, and in which the developer transport carrier 2 is rotated in the same direction as the magnet 5. In some cases, the developer layer is transported in the opposite direction. The present invention can be applied to any of these developing devices. Further, in the developing device shown in FIG. 2, the developer layer in the developing area A is kept low and thin, and therefore the gap between the developer transport carrier 2 and the layer thickness regulating member 7 can be widened, while the developer transport carrier The gap between the image forming member 2 and the image forming member 1 can be made much narrower.
The developing device shown in FIGS. 3 and 4 is preferable in that it has the advantage of being able to easily control the transfer of toner particles using an oscillating electric field. In the above-mentioned developing device, in the developing area A, the developer layer on the developer transport carrier 2 does not come into contact with the surface of the image forming member 10, and toner particles and sometimes carrier particles fly from the developer layer under an oscillating electric field. It is used under the condition that it adheres to the latent image on the image forming body 1.

Reference numeral 8 denotes a cleaning blade that returns the developer layer remaining on the developer transport carrier 2 after passing through the development area A to the developer reservoir, and 9 stirs the developer in the developer reservoir to uniformly mix it. , an agitation roller that triboelectrically charges toner particles, 1
0 is a toner supply roller that supplies toner particles from the toner hopper 11 to the developer reservoir.

In the developing device of the present invention, the gap between the developer transport carrier 2 and the developer transport carrier 2 is equal to or larger than the gap between the layer thickness regulating member 7 and the developing device contacts the developer layer immediately after being formed by the layer thickness regulating member 7. A leveling member 12 is provided to make the surface smoother.

The leveling member 12 in the developing device shown in FIGS. 1 to 3 is made of a rigid body, and the leveling member 12 in the developing device shown in FIG.
is made of elastic material. The leveling member 12 shown in Fig. 1.2.4 has a plate-like surface that comes into contact with the developer layer to level the surface, but the leveling member 12 shown in Fig. 3 has a thick wall. The end surface of the plate comes into contact with the developer layer to level it.

For example, the leveling member 12 shown in FIGS. 1 and 2 may be made of an elastic body such as a spring plate.

By providing such a leveling member 12, the gap between the layer thickness regulating member 7 and the developer transport carrier 2 is narrowed, and even if the relative variation in the layer thickness of the developer layer becomes large due to this, the variation is reduced. As a result of being leveled by the leveling member 12,
It becomes possible to form a thin and uniform developer layer. Furthermore, the leveling member 12 eliminates streaks that are likely to occur due to clogging of the regulating portion of the layer thickness regulating member 7. 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 using the oscillating electric field in the development area A. , it is possible to develop clear toner images without unevenness or fogging.

This leveling member 12 may be one that forms a developer passage gate like the layer thickness regulating member 7, or one that forms a passage gate for the developer, or
Since the blade does not triboelectrically charge the toner particles like the blade in Japanese Patent No. 97, there is no possibility that the developer will accumulate at the leveling member 12 and cause clogging. Therefore, as in the examples shown in FIGS. 1 to 3, the leveling member 12 can be made of a rigid body, and when it is made of a rigid body, it can be developed as much as possible without causing elastic displacement, compared to when it is made of an elastic body. Make the layer thickness 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 replaced with an elastic body. It is safe to do so in order to prevent such developer from accumulating. The leveling member 12 is not limited to a plate-like member, and a rigid member may be cylindrical, and an elastic member may be a fine-mesh brush-like member.

Since the developing device of the present invention performs development by generating a high oscillating electric field in the developing area, the leveling member 12 is placed close to the layer thickness regulating member 7 so as not to cause breakdown of the electric field. It is installed on the downstream side. 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 one voltage that is the same as or similar 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. In addition, the generation of an oscillating electric field in the development area A is not limited to the examples shown in FIGS. 1 and 2, but a control electrode such as a wire electrode or a net electrode that prevents the transfer of toner particles may be provided in the development area A. It may also be done by applying an oscillating voltage 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 hinders the passage of the developer layer.

The rigid leveling member 12 shown in Fig. 1 and WJ2 is preferably made of an aluminum plate with a thickness of about 21 m1, and the leveling member 12 made of an elastic body having a similar shape or the like is preferably used. An elastic equalizing member 1 as shown in FIG.
2 is preferably made of a polyethylene terephthalate plate with a thickness of about 50 μm. As mentioned above, the equalizing 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, and another resin plate, a thin bronze plate with a thickness of 20 to 300 μm, a stainless steel plate, etc. may be used for the elastic leveling member 12. You can do it. 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., but is not limited thereto. It's okay to be hurt. Further, the leveling member 12 is preferably installed at a position close to the magnetic pole of the magnet body 5 in a developing device in which the magnet body 5 is stationary. At this time, the magnetic field at the leveling member position is 300 Gauss or more, preferably 500 Gauss or more.
~1000 Gauss is preferred. At a position where the magnetic field is strong, 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, thereby eliminating unevenness and fogging. A clear toner image can be developed. As for the non-contact development conditions for this purpose, the developer transport carrier 2 is maintained at a surface gap of several tens to 2000 μm with respect to the image forming body 1, and the developer layer is formed into an image by the layer thickness regulating blade 7 and the leveling member 12. It is preferable to form the layer to have a uniform thickness so as to be close to the surface of the formed body 1 without contacting it. If the surface gap between the image forming body 1 and the developer transport carrier 2 is made too narrow, the developer layer will be separated from the developer transport carrier 2.
If it is difficult to form the toner particles uniformly on the surface of the toner, it becomes impossible to sufficiently supply the toner particles to the development area A, making it difficult to perform clear development. Also, the surface gap is 2
If it greatly exceeds 000 μm, the toner particle transfer control by the oscillating electric field will not be effective, and a sufficient development density will not be obtained. Then, the surface gap is expressed as 1
Range of 0-2000 μm, preferably 500-1500
If the thickness is 100 to 1000 μm, the developer layer should be 100 to 1000 μm.
It can be uniformly formed on the surface of the developer transporting carrier 2 with a thickness of , and the transfer of toner particles can be effectively controlled by the oscillating electric field.

The oscillating electric field formed between the developer transport carrier 2 and the image forming body 1 in order to facilitate the separation of toner particles from the developer layer is generated by applying a bias power supply 3 to the developer transport carrier 2 so that the effective value of the alternating current component is 200 to 200. 5000 V, frequency 100 Hz ~ 1
0 kHz, preferably 300-4000 V.

Preferably, a bias voltage of 1 to 5 kHz is applied, thereby exhibiting an effective field strength of 300 to 5000 V/m+. 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 fogging. Of course, it can also be used.

Note that even when a control electrode is provided in the development area and a bias voltage is applied thereto, it goes without saying that the bias voltage can have a direct current component as well as an alternating current component. 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. Further, 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 reverse 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.

Furthermore, the developing device of the present invention can also be applied to developing magnetic latent images by using toner particles containing a magnetic substance.

The developing device of the present invention is composed of a mixture of magnetic carrier particles with an average particle size of tens of micrometers to hundreds of micrometers and non-magnetic toner particles with an average particle size of tens of micrometers, 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, it is necessary to use a developer with a weight average particle size of 1.
Toner particles of ~20 μm and weight average particle size of 5-50 μm
It is preferable to use a developer consisting of a mixture of magnetic carrier particles, and further, the magnetic carrier particles may be insulating particles such as particles whose surfaces are coated with a resin film or resin particles containing dispersed magnetic particles. This is preferable because a high bias voltage can be applied to the developer transport carrier 2.

The insulating property of the carrier particles is 108ΩC11 or more in terms of resistivity.
Special K 10. The resistivity is preferably greater than or equal to ΩC-. This resistivity is determined by placing the particles in a container with a cross-sectional area of 0.50 CI + 12 and tapping them, then applying l on the packed particles.
This value is obtained by applying a load of K17cm2 and reading the current value when applying a voltage that generates an electric field of 100OV/cm between the load and the bottom electrode.If this resistivity is low, the developer transport When a bias voltage is applied to the carrier, charge is injected into the carrier particles, making it easier for the carrier particles to adhere to the surface of the image carrier, or for bias voltage breakdown to occur more easily.

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, and the coulter counter ( Coulter M) and Omnicon Alpha (Bausch & Lomb).

Next, a more specific embodiment of the present invention will be described.

Example 1 In the developing device shown in FIG.
It is assumed that the magnet body 5 is rotated at 65τpm in the direction of the arrow with an unevenness of about 0 μm formed, and the magnet body 5 is rotated at 700 rpm in the direction of the arrow with eight N and S magnetic poles having a magnetic flux density of 900 Gauss provided on the surface at equal intervals in the circumferential direction. It is assumed that it rotates at The layer thickness regulating blade 7 is made of non-magnetic stainless steel so that the same voltage as that of the developer transport carrier 2 is applied, and the rigid leveling member 12 is also made of non-magnetic stainless steel with a thickness of 11 m and is L-shaped. It was formed to be electrically integrated with the layer thickness regulating blade 7.

The developer is a resin with a weight average particle size of about 30 μm and magnetic powder dispersed therein, with a specific resistance of about II×1014Ωa.
Using a developer consisting of insulating carrier particles of m and insulating non-magnetic toner particles having a weight average particle diameter of 14 μm, the gap between the layer thickness regulating blade 7 and the developer transport carrier 2 is set to 300 μm, and the high layer thickness is A developer layer having a thickness of approximately 700 μm was formed, and the developer layer was leveled by a leveling member 12 whose gap with the developer transport carrier 2 was set to 500 μm.

As a result, the developer was not collected at the leveling member 12, and the thickness of the developer layer became much more uniform than when the leveling member 12 was not provided. Development by this developer layer is performed by reducing the surface gap between the image forming body 1 and the developer transporting carrier 2, which have a scratch-forming layer made of an organic photoconductor OPC and rotate at a surface speed of K 120 w/BeC in the direction of the arrow. 900μ
The test was carried out under the conditions set at m.

The latent image formed on the image forming body 1 is an electrostatic latent image with an image area potential of -500V compared to a non-image background area potential of -50V. 2 kHz, 1.5 kv alternating voltage and -15
A bias voltage with a DC voltage of 0 V superimposed was applied. The same bias voltage was applied to the layer thickness regulating member 7 and the leveling member 12 in order to prevent the oscillating electric field in the developing area from breaking down.

The toner image developed under the above conditions is transferred by corona discharge onto plain paper by a transfer device (not shown), and the surface temperature is 1
It was fixed by a heat roller fixing device at 40°C. The recorded image obtained by this method is free from non-uniformity and fogging.
Subsequently, 50,000 sheets of recording paper were obtained in the same manner, with high density and extremely clear images. Since the uniformity of the developer layer was maintained by the member 12, a clear recorded image that remained stable and unchanged from beginning to end was obtained. On the other hand, if the leveling member 12 is not provided, the clogging that occurs at the layer thickness regulating member 7 will cause large unevenness in the developer layer, and the effect will be recorded. This appeared in the image, and the maximum amount of recording paper that could be obtained was about 10,000 sheets, and streaks and roughness were observed in the recorded image.

Embodiment 2 The leveling member 12 was formed in the same shape as the leveling member 12 in FIG. 1 using a resin plate made of polyethylene terephthalate with a thickness of 50 μm. Examples except that they are set so that they are in contact with each other without a developer layer, and the gap widens to about 500 μm when a nine-layer developer layer formed by the layer thickness regulating member 7 and having a thickness of about 700 μm passes through. 50,000 pieces of recording paper were obtained under exactly the same conditions as in 1. The results were the same as in Example 1.

〔Effect of the invention〕

According to the developing device of the present invention, it is possible to stably and uniformly form a thin developer layer on the developer transport carrier, and therefore, the transfer of toner particles from the developer layer by the oscillating electric field can be effectively controlled. Even if a developer made of micronized carrier particles or toner particles is used, an excellent effect can be obtained in that a high-quality image with excellent clarity can be reproduced with less interference.

[Brief explanation of the drawing]

1, 2 and 3.4 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... Protection resistor, 5
...Magnet, 6.Developer reservoir, 7.
... layer thickness regulation blade, 8 ... cleaning blade, 9 ... stirring roller, 10 ... toner supply roller, 11 ... toner hopper, 12 ... leveling member. Patent applicant: Konishiroku Photo Industry Co., Ltd. Figure 1 f Figure 2 f Figure 3 Figure 乎Figure

Claims (4)

[Claims] (1) A developer layer containing a mixture of magnetic carrier particles and toner particles is formed on the surface of a developer transporting carrier, and the toner particles are caused to fly from the developer layer under an oscillating electric field and adhere to the latent image on the image forming body. In a developing device, a leveling member that comes into contact with the developer layer with a gap to the developer transport carrier that is equal to or larger than the gap between the layer thickness regulating member that regulates the layer thickness of the developer layer and the developer transport carrier is layered. A developing device characterized in that it is provided close to and downstream of a 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 a magnetic pole included in a developer transport carrier.