JPS598831B2 - Toner layer forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner layer forming device in a device that develops an electrostatic image with a developer, for example. The present invention relates to a toner layer forming apparatus that regulates the thickness of a layer of toner adhered to a toner support while interposing the toner.

Conventionally, methods employed in developing devices for electrophotography and electrostatic recording are broadly classified into dry developing methods and wet developing methods.

The former method is further divided into methods using a two-component developer and methods using a single-component developer. Two-component developing methods include magnetic brush methods using iron powder carriers,
There are cascade methods using bead carriers, fur brushes using fur, etc. Furthermore, the one-component development methods include the powder cloud method, in which toner particles are sprayed, and the contact development method, in which toner particles are brought into direct contact with the electrostatic latent image surface. (also referred to as donor development), a jumping development method in which toner particles are not brought into direct contact with an electrostatically cleaned image surface, but are charged and flown toward the latent image surface by an electric field having an electrostatic latent image; magnetic conductive There is the MagneDry method, which develops by bringing a toner into contact with the electrostatic latent image surface. Two-component development methods inevitably use a developer mixture of carrier particles and toner particles, and as the developing process normally consumes a much larger amount of toner particles than one carrier particle, mixing both carrier particles and toner particles is necessary. It inherently has drawbacks such as the ratio changes, resulting in fluctuations in the density of the suspended image, and the image quality deteriorates due to deterioration of the carrier particles, which are difficult to consume, due to long-term use. On the other hand, in one-component developing methods, the MagneDry method using magnetic toner and the contact developing method using no magnetic toner, the toner comes into contact with the entire surface of the surface to be developed, that is, both the image area and the non-image area. There is a problem in that toner tends to adhere even to non-image areas, resulting in so-called background fog and dirt. (This fog stain was a drawback that also occurred in the two-component developing method.) Also, in the powder cloud method, it is unavoidable that powdered toner particles adhere to the non-image area. It has the disadvantage that background fog cannot be removed. Furthermore, in the so-called di-amping development method, which belongs to the one-component development method, toner is uniformly applied to a carrier such as a sheet, and then the toner is placed facing an electrostatic image holding surface with a small gap between the toner and the toner carrier. A method is known in which toner is attracted and attached to an electrostatic image holding surface by the electric charge of an electrostatic image (Japanese Patent Publication No. 41-9475, US Pat. No. 2,839,400, etc.). This method has the advantage that not only the toner is not attracted to the non-image area where there is no static charge, but also the toner and the non-image area do not come into contact with each other, so that the above-mentioned fogging is less likely to occur. Furthermore, since a single carrier particle is not used, there is no variation in the mixing ratio as described above, and there is no deterioration of the carrier particle. However, this method has not yet been put into practical use due to various drawbacks described below.

(1) Practical uniform coating is difficult.

Although an electric field is applied in order to make the toner adhere to the toner carrier sheet in advance, it is difficult to obtain uniform adhesion. As a method for uniformly applying toner, a well-known rigid blade is used, but unlike a liquid, it is difficult to apply particles uniformly and thinly, and uneven application tends to occur. Since this unevenness is directly reproduced during development, it is not suitable for practical image reproduction. As a solution to this problem, the surface of the sheet that carries the toner is covered with cloth.
There is also a method of using paper or the like to embed toner in these fibers, but it is difficult to produce toner particles with a finer texture than the roughness of the fibers, and it is difficult to say that uniform application is possible. On the other hand, the cascade development method in which toner is applied to a sheet-like carrier in advance requires a large-sized apparatus, which is also impractical. (
2) It is difficult to uniformly separate the toner from the toner carrier. When the next applied toner layer faces the electrostatic image,
It is necessary to uniformly separate the toner and transfer it to the image surface, but if this transfer does not occur uniformly, uniform development will not be achieved. This kind of uniform toner separation is
It depends on the surface properties of the sheet carrying the toner, and is also affected by the conditions during delivery to the carrier, and furthermore, the characteristics of the toner, and so far no one has reached a practical level. (3) Low resolution.

The conventionally known deamping development method employs a method of electrostatically depositing toner onto a toner carrier, and even if a relatively thin toner layer is formed on the carrier, the toner particles' It is thought that when the gap with the electrostatic image surface becomes about 3 ml due to mutually repelling charges, the toner separates from the surface of the carrier and flies toward the electrostatic image surface.

However, with such a wide gap, it takes a long time for the toner to separate from its carrying surface and fly toward the electrostatic image surface.
The toner is susceptible to the effects of the airflow flowing through the gap during flight, the gravity of the toner, and vibrations of the electrostatic image surface and toner carrier, and the developed image is likely to be disturbed. Furthermore, the electric field of the electrostatic image of fine lines and fine letters does not reach the toner carrying surface faithfully, and the fine lines and fine letters become thin, or the toner no longer flies, which tends to result in a very low resolution. On the other hand, if the above-mentioned gap is too narrow, images of thin lines and fine letters tend to become collapsed images of thick lines, making it difficult to obtain faithful images. It is an object of the present invention to eliminate all of the conventional drawbacks and to provide a toner layer forming device for an electrostatic image developing device that has high fidelity and stable image quality. Specifically, the present invention provides (1) obtaining a uniform toner layer using a simple device; (2) Maintain an extremely thin toner layer with uniform thickness in the developing section. (3) Obtain a toner layer that allows uniform toner separation from opposing electrostatic latent image surfaces.

As a result, the background fog phenomenon is completely eliminated in non-image areas,
Another object of the present invention is to provide a toner layer forming device in an electrostatic image developing device, which allows a uniform, high-resolution toner surface image to be obtained in an image area.

In order to achieve the above object, the present invention provides a toner layer forming apparatus having the following features or embodiments. (
1) A moving toner support means for supporting and transporting magnetic toner on a surface, means for supplying magnetic toner onto the toner support means, and a side of the toner support means opposite to the surface that supports the toner. a layer of magnetic toner disposed close to the toner support means within a range where the stationary magnetic field generated by the fixed magnetic field generation means extends beyond the toner support means; 1. A toner layer forming device comprising: a magnetic member for regulating thickness.

(2) The toner layer forming apparatus according to item 1, wherein the magnetic member is arranged to face the magnetic pole of the magnetic field generating means.

(3) The toner layer forming apparatus according to item 1 or 2, wherein the magnetic member has a portion that concentrates lines of magnetic force from the magnetic field generating means.

(4) The toner layer forming apparatus according to any one of items 1 to 3, wherein the magnetic member is a magnet.

(5) The toner layer forming apparatus according to any one of items 1 to 4, wherein the magnetic toner is a one-component insulating toner. Embodiments of the apparatus according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic configuration of an example of a copying device or a recording device to which a toner layer forming apparatus according to the present invention can be applied.

Of course, it is not limited to this. In the figure, reference numeral 1 denotes a photosensitive drum including a photoconductive layer, and either one with or without an insulating layer on the surface can be used, and of course, a sheet-shaped or belt-shaped one is also possible. Reference numeral 2 represents a known photosensitive charging device, and 3 represents a light image irradiation device that projects an original image, a light image, or a light beam modulated by an image signal.

An electrostatic image is formed on the photoreceptor 1 by these. This electromagnetic image formation process is called carnoreson pronocess, or Japanese Patent Publication No. 42-23910, No. 43-24748.
No. 42-19748, No. 44-1343
The process described in Publication No. 7, etc., and other processes can be applied.

Reference numeral 4 denotes a developing device having a toner layer forming device according to the present invention, which forms a toner particle visual image in accordance with the electrostatic image on the photoreceptor 1.

Reference numeral 5 denotes a device for transferring the toner image onto a transfer material 6.

Incidentally, in order to improve the transferability, the visible image may be charged in advance by corona discharge or the like before transfer. Also, photoreceptor 1
It is also possible to adopt a so-called electrostatic image transfer method in which the upper electrostatic image is once transferred to another image carrier and then converted into a visible image by the developing device 4. Reference numeral 7 denotes a cleaning device for cleaning and removing residual toner on the photoreceptor 1 after transfer, for reusing the photoreceptor.

FIG. 2 shows a first embodiment of a developing device to which the present invention can be applied. In the figure, numeral 1 denotes a photosensitive drum as an electrostatic image holding means, which may of course be in the form of a belt or sheet. Reference numeral 8 denotes a toner support means provided opposite to this holding means, and the one shown is a non-magnetic cylinder.

Reference numeral 9 denotes a magnet as a magnetic field generating means provided in the cylinder, and has at least a magnetic pole for pumping the developer onto the cylinder, and more preferably has a developing magnetic pole at the developing position, between which the toner is drawn. It has a transport magnetic pole as appropriate.

Reference numeral 10 denotes a doctor blade that regulates the thickness of the magnetic toner 12 thus supplied to the cylinder.

The toner 12 adheres to the toner support means 8, which rotates in the direction of the arrow and comes into contact with the non-image area of the latent image on the electrostatic image bearing means 1 while applying the toner guided onto the means. Develop without having to do anything. The thickness of the toner layer 11 is regulated by the magnet roll 9 and the doctor blade 10.
Preferably, the thickness of the toner layer is limited to 30 to 100 μm. In a magnetic field, magnetic toner forms a string along the lines of magnetic force, and its density is significantly lower than in a normal state. Therefore, if the toner thickness is controlled with a doctor blade in the magnetic field, it can be controlled to be much thinner than if it is controlled in the area where the magnetic field does not reach. In areas where the magnetic field does not reach,
If an attempt was made to control the toner with a blade, the distance between the doctor blade and the toner support means 8 would have to be made very small, which would be mechanically difficult. Further, such a narrow gap is easily clogged with aggregated toner, which poses a problem in stability. The effect of the magnet 9 can be recognized as long as the doctor blade 10 is within the range covered by the magnetic field of the magnet, but especially when the magnetic poles are facing the doctor blade 10, as shown in Fig. 3, it is difficult to regulate it thinly. can. Furthermore, if the doctor blade 10a is a magnetic material as in the present invention, the static magnetic field from the magnetic pole N facing the tip of the doctor blade is concentrated as shown in FIG. 4, and the brush-like toner is spread between the toner support means and the doctor blade. They form a curtain-like pattern to prevent toner from seeping through. The toner slightly dragged by the toner support means 8 only passes through the surface of the toner support means a little. Therefore, the toner layer 11 is thinner than the gap between the doctor blade 10a and the toner support means 8, as shown in the figure, and can be made extremely thin as described above. If a magnet is used as the doctor blade 10a, the magnetic field in this part will be even stronger and more effective. Another embodiment of a developing device to which the present invention can be applied will be described below with reference to FIG.

In this figure, elements common to those shown in FIG. 2 are given the same reference numerals. In the embodiment shown in FIG. 5, when the electrostatic image holding surface 1 moves in the direction of the arrow, the multipolar permanent magnet 9 is fixed, so the non-magnetic cylinder 8 that is the toner support is moved between the electrostatic image holding surface 1 and the electrostatic image holding surface 1. By rotating in the same direction, the one-component insulating ferromagnetic toner 12 sent from the toner container 13 is applied onto the non-magnetic cylindrical surface, and the friction between the cylindrical surface and the toner particles causes the toner particles to be electrostatically charged. Gives a charge of opposite polarity to the image charge.

Furthermore, by arranging the iron doctor blade 10b close to the cylindrical surface (with an interval of 50 μm to 500 μm) and facing one magnetic pole (S pole in the figure) of the multipolar permanent magnet 9, the thickness of the toner layer can be reduced. thinner than the above distance (30μ~3
00μ, preferably 30μ to 100μ) and uniformly. The cylinder speed is adjusted so that the surface speed and preferably the internal speed of the toner layer are substantially equal to, or close to, the speed of the electrostatic image bearing surface. Instead of iron, a permanent magnet may be used as the doctor blade 10b to form opposing magnetic poles. In the above embodiments, the doctor blade may be integrated with the toner container.

Alternatively, it may be inclined in the direction of the cylinder 8. The toner support means does not have to be cylindrical, and may be belt-shaped or other shapes. As described above, in the present invention, a one-component ferromagnetic powder is used as the toner, and in order to achieve stable and easily controllable toner retention on the toner support, a nonmagnetic cylinder containing a fixed multipolar permanent magnet is used. was used as a toner support, and a thin magnetic plate or a doctor blade made of a permanent magnet was placed close to the cylindrical surface in order to form a thin and uniform toner layer.

Holding the toner layer on the toner support surface using a magnetic field in this way produces a much more uniform, stable, and easily controllable latent image than holding the toner layer using van der Waalska or electrostatic attraction. It has become clear that toner transfer to surfaces can be achieved. In addition, when a magnetic doctor blade is used, opposing magnetic poles are formed between the magnetic poles of a fixed permanent magnet included in the toner support, and the toner particle chains are forced to stand up between the doctor blade and the toner support. This is advantageous in controlling the thickness of the toner layer on other parts of the toner support, for example, the part facing the electrostatic image surface.
Further, by applying such forced movement to the toner, the toner layer becomes more uniform, thereby achieving a thin and uniform toner layer formation that could not be achieved with a non-magnetic doctor blade. The composition and material of each element commonly used in each of the above embodiments will be explained here. First, as a magnetic toner, one having an average particle size of 5 to 10 μm was used, which was formed by a well-known method by mixing 50 parts of polystyrene, 40 parts of magnetite, 3 parts of a charge control agent, and 6 parts of carbon. .

Of course, other known magnetic toners can also be used. As the toner support, an aluminum material was used as a non-magnetic material, and the material was made into a cylindrical shape as shown in the figure. The magnet has a magnetic pole located closest to the electrostatic image holding member (potential contrast: about 600 V) and the toner support, and the surface magnetic flux density is within the range of about 600 to 1,300 Gauss, for example, 800 Gauss. I chose. An example of the development phenomenon to which the present invention can be applied is that, as already mentioned, in the non-image area of the electrostatic image holding surface, the toner layer is kept in non-contact, and in the image area, the toner layer holds the electrostatic image. A toner layer is formed that transfers to the surface and is used for development.

During the transfer, the toner layer corresponding to the image area increases in thickness in the direction of the electric field due to the attraction of the electric field, and the magnetic field acts on the toner layer in this area, causing the toner in this area to grow erect like an elongated spike at the magnetic pole position (hereinafter referred to as This phenomenon is called the "toner elongation" phenomenon. Therefore, when the surface layer of the toner layer and the electrostatic image holding surface are close to each other, this elongated part of the toner directly contacts the image area of the electrostatic image holding surface, causing the toner to elongate. When the support and the electrostatic image-bearing surface are separated from each other, toner remains on the electrostatic image-bearing surface and completes development. This method differs from the so-called contact development method or diamping development method in that during development, the toner does not come into contact with the non-image area, but develops by the phenomenon that the toner comes into contact with the image area due to the above-mentioned toner elongation phenomenon. Conceivable. If the gap between the surface layer of the toner layer and the electrostatic image holding surface is larger than the above, in addition to the phenomenon caused by the toner elongation as described above, the toner may stretch but still not contact the electrostatic image holding surface. It is thought that a developing state occurs due to a phenomenon in which the toner that has not been used stands up in the electric field and flies as if the tip of the spike is torn off and reaches the electrostatic image holding surface.

According to this example, development can be performed in which the above-described toner elongation phenomenon and the accompanying flying phenomenon are added depending on the gap between the electrostatic image holding surface and the toner support.

In this way, by utilizing the toner elongation phenomenon in which the toner layer stands up and grows in the image area of the electrostatic image holding surface and develops by coming into direct contact with the electrostatic image holding surface, the amount of toner that flies through the development gap can be reduced. This reduces the influence of the airflow flowing through the lever gap, the gravity of the toner itself, and the vibrations of the electrostatic image holding surface and toner support, thereby improving faithful image reproducibility and image quality. A microscopic image of excellent image quality with no fogging is obtained, and it is good if the gap size of each part is set to meet this condition. In order to sufficiently guarantee the toner coverage, the gap between the toner surface layer (in the non-image area where no upright growth occurs) and the electrostatic image holding surface must be kept to three times or less the thickness of the toner layer. Further, as an acceptable condition for development which mainly involves the above-mentioned toner elongation and also allows toner flying, the above-mentioned gap should be 10 times or less the thickness of the toner layer. According to experiments and theoretical analysis including the above-mentioned considerations, the gap D in the developing section between the toner support and the electrostatic image holding surface is preferably 50μ≦D≦500μ.

The upper limit value is the fine print (10
0μ) with good resolution, and the lower limit is an appropriate value determined in relation to the thickness of the toner layer. and the thickness a of the toner layer supported on the toner support
According to experiments, a thin layer of about 30μ≦a≦300μ is preferable. During development, the toner layer stands up due to the presence of a magnetic field, but as mentioned above, the height of the toner layer is thought to be about three times the thickness of the toner layer, so it takes a long time for the toner surface layer to reach the electrostatic image holding surface. In this case, it is necessary that the gap b between the toner surface layer and the electrostatic image holding surface be such that b≦300μ.

In general, good results were obtained when b≧1. As a means for holding the toner support body with a predetermined gap with respect to the electrostatic image holding surface in this way, positioning members such as spacers, rollers, and pressure springs that abut against the electrostatic image holding surface or its back electrode are used. It can be used to combine it with a toner-bearing surface to achieve that purpose. In addition to the above-mentioned effects, the developing device according to the present invention is particularly applicable to a transfer-type copying device or recording device, and can produce an extremely excellent transfer effect, thereby achieving an extremely high image quality on plain paper, etc. It is possible to reproduce images with good quality and no background fog.

The present invention is not limited to the above embodiments, but includes various embodiments that are conceptually included.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic diagram of an apparatus to which the toner layer forming apparatus according to the present invention can be applied, FIG. 2 is a sectional view of an embodiment of a developing device to which the present invention can be applied, and FIG. FIG. 4 is an explanatory diagram illustrating the principle of the toner layer forming apparatus according to the present invention, and FIG. 5 is an explanatory diagram illustrating the principle of the toner layer forming apparatus according to the present invention. It is a sectional view showing an example. 1... Electrostatic image holding means, 8... Developer supporting means, 9... Magnetic field generating means, 10, 10a
, 10b...Means for regulating the thickness of the developer.

Claims (1)

[Scope of Claims] 1. A movable toner support means for supporting and transporting magnetic toner on a surface, means for supplying magnetic toner onto the toner support means, and a surface of the toner support means that supports toner. a magnetic field generating means fixedly disposed on the opposite side of the fixed magnetic field generating means, and disposed close to the toner supporting means within a range in which a static magnetic field formed by the fixed magnetic field generating means extends beyond the toner supporting means. and a magnetic member for regulating the layer thickness of the magnetic toner. 2. The toner layer forming apparatus according to claim 1, wherein the magnetic member is arranged to face the magnetic pole of the magnetic field generating means. 3. The toner layer forming apparatus according to claim 1 or 2, wherein the magnetic member has a portion that concentrates lines of magnetic force from the magnetic field generating means. 4. The toner layer forming apparatus according to claim 1, wherein the magnetic member is a magnet. 5. The toner layer forming apparatus according to claim 1, wherein the magnetic toner is a one-component insulating toner.