JPS5933916B2 - Toner layer forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner layer forming apparatus, and more particularly to a toner layer forming apparatus for obtaining a visible image using a one-component magnetic toner.

Conventionally, as dry developing methods for developing electrostatic charge patterns, there are two-component developing methods and one-component developing methods when classified based on the composition of the developer.

In the former, the developer consists of a mixture of carrier particles such as iron powder or glass beads and toner particles that actually develop the electrostatic image. This two-component development method has the drawbacks of fluctuations in image density due to changes in the mixing ratio of carrier particles and toner particles, and deterioration of image quality due to deterioration of carrier particles. On the other hand, the latter one-component development method does not have the drawbacks of the above-mentioned two-component development method because carrier particles are not present, and is a promising development method.

Generally known and used one-component developers have magnetic properties within the toner particles due to frictional electrification caused by relative movement and the need for a means to transport the developer to the development area facing the electrostatic image. It is meant to contain powder. However, the content of the magnetic powder is naturally limited because heat, pressure, or other means are used to fix the toner image on the transfer paper. . In practice, magnetic powder occupies 10% to 60% by weight of toner particles, but due to the difference in specific gravity between resin and magnetic powder, the volume occupancy of magnetic powder in toner particles is about 20% or less. Since the volume occupancy of the magnetic powder in the toner is very small, the behavior of the toner in the magnetic field is different from that of the magnetic powder alone, and it becomes difficult to form a long brush with sparse density at the magnetic pole position. Therefore, when the thickness of the toner layer on the toner support member is regulated to several tens of thousands of layers, the toner layer on the support member tends to be uneven and non-uniform. The non-uniformity of the toner layer on this supporting member is easily reproduced directly in the developed image, and since the toner layer is dense, variations in layer thickness may cause it to come into contact with the surface of the photoconductor, which is an electrostatic image holding member. There is a risk of the toner clumping or damaging the photoconductor.

Therefore, in this sense, in a developing method using a one-component magnetic layer, it is necessary to form a uniform thin layer of toner on a toner support member. Generally, in order to regulate the layer thickness of powder or granular material on a support member, a thickness regulating member is brought close to the surface of the supporting member to form a slit, and when the supporting member moves relative to the thickness regulating member. The actual thickness-regulated toner layer thickness is somewhat thicker than the above-mentioned slit spacing. For this reason, in the development of one-component magnetic toner, in order to form a thin layer of toner, conventionally the thickness regulating member had to be placed extremely close to the toner supporting member, which required mechanical precision. Furthermore, toner that has aggregated due to various reasons may get stuck in the minute gaps of the slits, and the toner layer may not be formed in those areas.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device that eliminates all of the above-mentioned drawbacks of conventional one-component magnetic toner developing devices.

To briefly describe a preferred embodiment of the present invention, a magnetic body is fixed on the surface of a rotating non-magnetic cylinder having a fixed magnet inside, facing and close to the pole position of the internal fixed magnet. As the magnetic cylinder rotates, the layer thickness of the magnetic toner formed on the surface of the non-magnetic cylinder is made smaller than the gap between the actual adjacent magnetic body and the surface of the non-magnetic cylinder by the action of a magnetic field, and This forms a uniform toner layer.

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 developing device according to the present invention can be applied.Of course, the present invention is not limited to this.

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 electrostatic image forming process is the so-called Carlson process, or Japanese Patent Publication No. 42-23910, No. 43-24748,
The processes described in JP 42-19748, JP 44-13437, etc., and other processes can be applied.
Reference numeral 4 denotes a developing device according to the present invention, which forms a toner particle visual image in accordance with the electrostatic image on the photoreceptor 1.

5 is 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 electrostatic image of the soil 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, and for reusing the photoreceptor.

FIG. 2 shows one embodiment of the developing device according to the present invention.

In the figure, 1 is a photosensitive drum as an electrostatic image holding means. A developer support member 8 is provided facing the electrostatic image holding means 1, and is a non-magnetic cylinder (hereinafter referred to as a sleeve) that rotates in the direction of arrow a in the figure.

9 is a magnet fixedly provided within the sleeve 8;
It has at least a magnetic pole for pumping up an insulating one-component magnetic developer onto a cylinder and transporting it to a developing area, a developer applying magnetic pole, and a developing magnetic pole.

Reference numeral 10 denotes a doctor blade that applies magnetic toner 12 to the surface of the sleeve 8 and regulates the thickness of the toner layer formed.According to the present invention, the material of the doctor blade 10 is a magnetic material (magnet, iron, permalloy, etc.).

The insulating toner particles in the toner layer 11 whose thickness is regulated by the doctor blade 10 come into sliding contact with the surface of the sleeve 8 as the sleeve 8 rotates, and due to this friction, the insulating toner particles have a polarity opposite to that of the latent image. is charged with electricity. After that, the photosensitive drum 1 reaches a developing area, and the electrostatic charge pattern on the photosensitive drum 1 is visualized. FIG. 3 is an enlarged view of the toner layer thickness regulating section of the developing device based on the above embodiment.

Reference numeral 13 denotes a fixed magnet provided in the sleeve 8 facing the doctor blade 10, with its magnetic pole facing toward the doctor blade.

At this time, the lines of magnetic force produced by the magnet 13 reach the surface of the tip of the magnetic blade 10 that faces the sleeve 8 . If the doctor blade is a non-magnetic material, only the attractive force (magnetic force, electrostatic adsorption force, van der Waalska, etc.) to the toner support member surface 8 acts on the magnetic toner, so that the magnetic toner is formed as the sleeve rotates. The toner layer becomes thicker.

Therefore, it is necessary to exert a force in the thickness regulating section to separate the magnetic toner from the surface of the rotating sleeve. Magnetic powder is subjected to force in a magnetic field from areas where magnetic lines of force are sparse to areas where they are dense, that is, at locations where there is a magnetic flux density gradient.

Therefore, when the doctor blade 10 is made of a magnetic material,
In order for the magnetic toner to receive an attractive force from the surface of the sleeve 8 toward the doctor blade side, at least the following relationship is required between the width A of the tip of the magnetic blade and the width B of the magnetic pole of the fixed magnet inside the sleeve 8.

The smaller Af)'-B, the more concentrated the lines of magnetic force are on the magnetic blade, and the more effective the toner layer regulation by this magnetic force becomes.

Here, the magnet roll 9 as shown in Fig. 2 is magnetized (N-
In the case of the configuration (S-N-S-N-S, 6 magnetic poles), in order to determine the magnetic pole width B of the fixed magnet pole in the sleeve 8, the distribution of the surface magnetic flux density of the magnet is determined as shown in Fig. 4. Draw a magnetic pole corresponding to the tip of the magnetic blade above (N pole in the case shown)
The magnetic pole width having a half value of the peak value of the surface magnetic flux density distribution is defined as the above-mentioned magnetic pole width B.

As a result of the experiment, the magnetic blade tip width A ranges from 0.1 mm to 5 mm, and the magnetic pole width B of the fixed magnetic pole at the corresponding position.
is 0.1m77! ~15m7! It has been found that it is best to select a value that satisfies A≦B within the range of L.

In particular, in order to form a uniform and thin layer as a developer layer, A is preferably 0.5m7I1 to 1mm. B is 0.5mm
It is preferable to select a value that satisfies A≦B within the range of ~10 times. In the above-described embodiments of the present invention, a uniform toner layer smaller than the toner layer regulating slit interval can be formed, and a developing device for one-component magnetic toner can be easily realized.

FIG. 5 shows experimentally obtained data on the relationship between the distance between the magnetic blade and the toner support and the toner layer thickness at the magnetic pole position.

As an example, using three types of insulating one-component magnetic toner, the toner layer thickness at the magnetic pole position on the toner support means with respect to the distance (x axis) between the iron doctor blade and the toner support means (
y-axis).

The toner was (a) 55 parts polyester, 20 parts magnetite, 2 parts carbon, 2 parts charge control agent with external addition of 0.1% colloidal silica, (b) 50 parts polystyrene, 40 parts magnetite, charge control agent. 3 parts of agent, 6 parts of carbon with external addition of 0.1% colloidal silica,
(c) A mixture of 50 parts of polystyrene, 40 parts of magnetite, 3 parts of a charge control agent, and 6 parts of carbon was used.

Further, the magnetic pole of the magnet was disposed closest to the electrostatic image holding member and the toner carrier, and the surface magnetic flux density at that time was set to 800 Gauss. As can be seen, it is generally recognized that when the gap between the doctor blade 10 and the toner support 8 is in the range of approximately 50 to 200 μ, the toner layer thickness increases as the gap increases.

On the other hand, when the gap is in the range of about 200 to 350 microns, the toner layer thickness does not increase to the extent that the gap increases, but remains the same or increases slightly. It can also be seen that the toner layer thickness itself (at the magnetic pole position) is always formed thinner than the above-mentioned gap. Examples according to the present invention are shown below. There is a development method called diamping development that uses one-component magnetic toner (for example,
9475, etc.).

In this developing method, toner is applied thinly and uniformly to the surface of a toner support member, and then the toner is applied to the surface of the toner support member, and then the toner is applied to the surface of the toner support member. At that time, a gap is provided between the surface of the toner layer and the surface of the electrostatic image. Therefore, since the toner does not come into direct contact with the non-image areas of the electrostatic image, phenomena such as background fog do not occur in the developed image. However, in this development method, the toner is subjected to force by the electric field created between the electrostatic latent image and the sleeve that acts as the development electrode (which may be assisted by applying a bias electric field), so the distance between the electrodes cannot be increased. It is undesirable to remove toner particles from the toner. The distance between the electrodes is approximately several 1001 tm. Therefore, it is necessary to form a toner layer smaller than the distance between the electrodes, but if the developing device according to the present invention is used,
It is possible to easily create a prescribed toner layer. In experiments conducted by the present inventors, the magnetic flux density of the fixed magnet inside the non-magnetic sleeve was 1000 Gauss, and the magnetic pole width B-5m77! ; The magnetic blade, which is the thickness regulating member, is made of iron and has a tip width of A-0.
, 5 mm were opposed to each other with a gap of 300 μm from the sleeve surface, and the gap between the photosensitive drum and the sleeve in the developing area was 300 μm.

The insulating magnetic toner used contained styrene as the resin component.
1 part by weight of magnetite was kneaded and ground into 3 parts by weight of maleic acid, and the average particle size was about 8 μm. The regulated toner layer thickness was approximately 100 Itm, and when the sleeve and photosensitive drum were rotated at a constant circumferential speed (110 mm/Sec), a good developed image could be obtained. Of course, the present invention is not limited to the above embodiments.

The development support means may be configured to apply a development bias electric field between it and the latent image holder. Further, the present invention is not limited to developing electrostatic latent images, but can also be applied to an apparatus for developing magnetic latent images formed on a magnetic recording medium.

The present invention has solved all the conventional drawbacks by providing a developing device having the following features.

(1) A developer supporting means 11 provided opposite to the latent image holding means 1, a means for supplying magnetic developer 12 onto the developer supporting means, and a magnetic developer 12 supplied onto the developer supporting means. In a developing device having means for regulating the layer thickness of developer,
The developer thickness regulating means includes a fixed magnetic field generating means 9 provided on the back surface of the developer supporting means, and a fixed magnetic field generating means 9 fixedly provided opposite to the fixed magnetic field generating means and close to the surface of the developer supporting means. A developing device comprising means 10 for converging lines of magnetic force from a magnetic field generating means.

(2) The developing device according to item 1, wherein the magnetic force line focusing means is a magnetic material.

(3) In the electrostatic image developing device according to item 1, the magnetic force line focusing means is a magnetic material, and the width of the tip of the magnetic material facing the surface of the developer supporting means is the same as the magnetic pole of the fixed magnetic field generating means. A developing device characterized by being smaller than its width.

(4) Magnetic and electrically insulating one-component developer 1
2, and a movable electrostatic latent image holding means 1, which rubs the developer particles and charges the developer particles to a polarity opposite to that of the electrostatic latent image. A developer supporting sleeve 8 to be obtained, and a developer supporting sleeve 8 fixedly fixed inside the sleeve and having at least a developing magnetic pole at a position facing the latent image holding means and a developer applying magnetic pole at a position where a developer layer is formed on the sleeve. A magnetic body 9 is provided, and a magnetic body is arranged opposite to the magnetic pole with a predetermined gap from the outer circumferential surface of the sleeve at a position corresponding to the developer-coated magnetic pole of the magnet body to focus lines of magnetic force from the developer-coated magnetic pole. The developer layer having a body 10 and having a predetermined thickness is formed on the outer circumferential surface of the sleeve by cutting off the developer layer that stands up along the lines of magnetic force with the tip surface of the magnetic body. Characteristic developing device.

(5) In the developing device according to item 4, the width of the tip end surface of the magnetic body is A, and the magnetic pole width of the developer-applied magnetic pole is B.
A developing device that satisfies A≦B, where A≦B.

(6) In the developing device according to item 5, the A is 0.
1 to 5 mm, and A≦ from the range where B is 0.1 to 15 mm.
A developing device characterized in that it is selected so as to satisfy B.

(7) In the developing device according to item 5, the A is 0.
5 fins ~ 1m 7L. A developing device, wherein the B is selected from a range of 0.5n to 10n so as to satisfy A≦B.

Incidentally, the apparatus is a device in which conductive magnetic toner is attached to the outer peripheral surface of a fixed sleeve having a rotating magnet roll by the magnetic force of the magnet roll, and the toner is transported and developed by rotating the magnet roll. A magnetic body is placed opposite to the outer circumferential surface of the sleeve, and the layer thickness of the toner adhering to the outer circumferential surface of the sleeve is regulated to a constant level by the magnetic force generated by the magnet roll and the magnetic body. The device is described in Japanese Patent Application Laid-Open No. 53-125844.

However, the method described in this publication uses a monoconductive magnetic toner to induce a charge of opposite polarity to the electrostatic image charge to the toner, and the toner is attached to the electrostatic image side by the attraction force. 2. The thickness of the toner layer regulated by the above-mentioned magnetic material is made thicker than the developing gap between the sleeve and the electrostatic image carrier. 3. The sleeve is fixed and the magnet roll inside it is rotated. 4. Also, the magnetic poles on the magnet roll side facing the above magnetic body are N-S-N...
..., and the magnetic field acting between the two is varied by the rotation of the magnet roll. However, in the embodiment according to the present invention, each of these elements is not included, and 1
In the case of developing an electrostatic latent image, insulating magnetic toner is used to charge the electrostatic latent image to a polarity opposite to that of the electrostatic latent image due to friction with the sleeve (and the toner itself) (in addition, corona discharge, etc.) The toner charged to a predetermined constant polarity is transferred from the sleeve surface by the latent image potential (the toner transfer is effected by applying a bias electric field to each other). )
In particular, the toner layer thickness regulated by the magnetic blade facing the two sleeves is kept to a thickness of several hundred microns, which is thinner than the development gap between the sleeve and the latent image carrier;
3. The sleeve is rotated and the magnet roll therein is fixed; 4. The strength of the magnetic field acting between the magnetic blade and the magnet roll and the distribution of magnetic lines of force are uniform without fluctuation. This forms a uniform thin layer on the sleeve. Therefore, compared to the above-mentioned conventional methods, this method has the advantage that a more uniform thin layer can be easily formed and a high-quality, homogeneous microscopic image can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic structural explanatory diagram of an example of an image forming apparatus to which the developing device according to the present invention can be applied, FIG. 2 is a cross-sectional view of an embodiment of the developing device according to the present invention, and FIG. 3 is a magnetic body thereof. An enlarged view of the blade part, Figure 4 is an explanatory diagram for determining the magnetic pole width,
FIG. 5 is a graph showing data showing the relationship between the toner layer thickness at the magnetic pole position and the distance between the magnetic blade and the toner support. 1...Latent image holding means, 11...Developer supporting means, 12...Magnetic developer, 9...
・Magnetic field generating means, 10... Means for focusing magnetic lines of force.

Claims (1)

[Scope of Claims] 1. A moving toner support means, means for supplying magnetic toner onto the toner support means, a fixed magnetic field generation means provided on the back surface of the toner support means, and the fixed magnetic field generation means. and a magnetic body for regulating the layer thickness of the magnetic toner layer which is fixedly disposed close to the surface of the toner supporting means opposite to the toner supporting means, the width of the tip of the magnetic body is A, and the above-mentioned width of the magnetic field generating means is When the width of the magnetic pole corresponding to the tip of the magnetic material is B, A≦B
A toner layer forming device that satisfies the following. 2. In the toner layer forming apparatus according to claim 1, the above A is 0.1 mm to 5 mm, and the above B is 0.1 mm to 5 mm.
A toner layer forming device characterized in that the toner layer is selected from a range of 1 to 15 mm so as to satisfy A≦B. 3. In the toner layer forming apparatus according to claim 1, the above A is 0.5 mm to 1 mm, and the above B is 0.5 mm.
A toner layer forming device characterized in that the toner layer is selected from a range of mm to 10 mm so as to satisfy A≦B.