JPS60165660A - Developing method - Google Patents

Abstract

PURPOSE:To obtain an image high in quality by forming 2 kinds of magnetic powders different in triboelectricity contained in a resin, and using one of them for a toner and the other for a carrier. CONSTITUTION:One of 2 kinds of magnetic powders different in triboelectricity contained in a resin is used for a toner and the other is used for a carrier. A photoconductive layer 3 made of Se as a base is formed on the surface of a grounded conductive substrate 2 to form a photosensitive drum 1. The drum 1 is rotated in the direction of the arrow A, and electrostatically charged to +700V at the time of uniform charging. Bias voltage obtained by superposing AC voltage on DC voltage is applied through a protective resistor 9 to the surface of a developing sleeve 4, with a voltage applicator 8, and the sleeve 4 and a magnetic roll 5 are rotated anticlockwise in a low speed to carry out development. As a result, an image high in quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dry developing method applicable to electrophotographic copying machines and the like.

Conventional configurations and their problems In general, as a developing method for an electrostatic latent image formed on a photoreceptor,
Many methods are known, such as a liquid development method, a magnetic brush method, and a cascade method, and among them, the magnetic brush method is widely used. This magnetic brush method uses a magnetic developer, and as described in JP-A No. 52-17881, fixed magnetic poles are placed inside a rotatable developing sleeve made of a non-magnetic conductor. , a sleeve rotation type in which a developer layer is formed by rotating the developer sleeve and transporting the developer, a so-called magnetic brush, which is brought into contact with a photoreceptor on which an electrostatic latent image is formed to develop the electrostatic latent image. There is something like that. Alternatively, as described in Japanese Patent Application Laid-Open No. 62-67336, there is a magnetic roll rotation type in which an electrostatic latent image is developed by rotating a magnetic roll placed inside a developing sleeve made of a non-magnetic conductor. or JP-A-54-116233 and JP-A-64-
As described in Japanese Patent No. 119935, there is a method in which a developing sleeve and a magnetic roll are rotated in the same direction for development.

On the other hand, as a developer having magnetism suitable for such a magnetic brush method, there is a developer described in JP-A-57-10150, etc., which both contain a magnetic material in a resin and have different triboelectrification properties. One of the two types of magnetic powder is used as toner,
A developer in which the other is mixed with the other as a carrier has been proposed, and a method in which the developing sleeve and the magnetic roll are rotated in opposite directions has been proposed as the most suitable method for such a developer ( Japanese Patent Publication No. 68-206166
Publication No.).

Copied images obtained using such developers and development methods have features such as good halftone reproducibility, uniform density at the periphery of solid images and good edge sharpness, and small gamma values. be. however,
In order to obtain a high-density image, it is necessary to rotate the developing sleeve or magnetic roll at high speed.

For example, in the case where development is performed such that the photoreceptor, the developing sleeve, and the magnetic roll all move in the same direction in the developing section, the moving speed of the photoreceptor (i.e., process speed) is 16 otvrb/sea, and the developing sleeve (outer diameter 31 At a rotation speed of 110 rpm for the magnetic roll (8 poles) and 1300 rpm for the magnetic roll (8 poles), images with high density and the above-mentioned characteristics can be obtained (Matsumura et al.: National Te
Chnical Report, vol, 28
, &4゜P, 677.1982). Furthermore, even when the developing sleeve and magnetic roll are rotated in opposite directions, the same number of rotations as in the above example is required in order to obtain a high-density, high-quality copy image. It is assumed that.

The high-speed rotation of such developing sleeves or magnetic rolls causes noise or vibration, and 61 companies have recommended that electrophotographic copying machines to which such developing methods are applied be installed in offices, stores, schools, etc. Assuming this is not desirable. Furthermore, as the developing sleeve or the magnetic roll rotates at high speed, the load on the regulating blade section that regulates the thickness of the developer layer increases, and uneven rotation tends to occur. The uneven rotation causes density unevenness, so-called jitter, on the copied image, which is undesirable. Therefore, it is necessary to increase the capacity of the motor that serves as the driving source for the developing sleeve and the magnetic roll.

Therefore, by using a developer made by mixing two types of magnetic powders, both of which contain magnetic substances in resin and have different triboelectric properties, one of which is used as a toner and the other as a carrier, a developing sleeve or a magnetic roll is manufactured. Rotate at low speed,
A method of obtaining high quality images is desired.

OBJECTS OF THE INVENTION The object of the present invention is to use one of two types of magnetic powders, both of which contain magnetic substances in their resins and have different triboelectric charging properties, as a toner;
To provide a method for obtaining high quality images by rotating a developing sleeve or a magnetic roll at low speed using a developer made of a mixture of various carriers.

Structure of the Invention The developing method of the present invention both contains a magnetic material in the resin,
A developer made of a mixture of two types of magnetic powders having different triboelectric charging properties is attached by magnetic force to the outer surface of a rotatable developing sleeve made of a non-magnetic conductive material and having a built-in rotatable magnetic roll, Furthermore, a developer layer formed on the outer surface of the developing sleeve, the thickness of which is regulated by a regulating blade provided near the developing sleeve, is brought into contact with the photoconductor on which the electrostatic latent image is formed. When visualizing an electrostatic latent image, a bias voltage containing an alternating current component is applied between the developing sleeve and the conductive support layer of the photoreceptor. According to this method, the developing sleeve or Even if the magnetic roll is rotated at a lower speed than the conventional method, high-quality images can be obtained.

DESCRIPTION OF EMBODIMENTS The structure of the present invention and its effects will be explained together with specific examples.

The inventors used a selenium photoreceptor drum to carry out a series of copying processes including uniform charging of the photoreceptor, image exposure, development, transfer to plain paper, fixation of the transferred image, and neutralization and cleaning of the photoreceptor after transfer. We have manufactured an electrophotographic copying machine that can perform the following functions and in addition, the configuration of the developing section can be changed arbitrarily. The figure schematically shows a developing section of an embodiment of a copying machine according to the present invention.

The photosensitive drum 1 has a selenium-based photoconductive layer 3 formed on the surface of a grounded conductive support layer 2, as shown by arrow A.
It rotates in the direction shown in the figure at a moving speed of 150wIL/SeC, and is charged to +γooV when uniformly charged. The developing sleeve 4, which is made of non-magnetic metal and has an outer diameter of 31 m and an axial length of 26 m, and an 8-pole magnetic roll 6 built therein, have rotational directions and rotational speeds that can be independently set as desired. It has become. The regulating blade 6 that regulates the layer thickness of the developer layer 7 formed on the outer surface of the developing sleeve 4 is made of a magnetic material, and the distance between the regulating blade 6 and the developing sleeve 4 (hereinafter referred to as the gap) and the photosensitive The distance between the body drum 1 and the developing sleeve 4 (hereinafter referred to as a gap d) can be set arbitrarily.

Furthermore, a bias voltage obtained by superimposing an arbitrary DC voltage and an arbitrary AC voltage can be applied to the outer surface of the developing sleeve 4 by a voltage applying device 8 via a protective resistor 9. The developer is a toner containing 26% by weight of magnetite fine particles in a resin, and has an average particle size of 12μ.
m2 The amount of charge measured by the well-known blow-off method is 114μc
/q magnetic powder, the carrier is a resin containing fine magnetite particles with a weight coefficient of 6o, and the average particle size is 32
μm2 The amount of charge measured by the well-known blow-off method is 3 μm at the neck.
c/q magnetic powder, and a mixture of toner 6q and carrier 14q was used.

Then, the gap was set to 0.4, the gap d was set to 0.46, and the rotation of the developing sleeve 4 and the magnetic roll 6 was rotated counterclockwise in the figure, and the developing sleeve was set at 80 tpm.
, the magnetic roll f 950 rpm, the developer is conveyed in the direction of arrow B, and development is performed at portion C.

The DC component of the bias voltage from the voltage application device is +100
V, the AC component has an amplitude of 6ooV.

9. Copying was carried out using a voltage in which a sinusoidal AC voltage with a frequency of I KHz was superimposed, and a case where the bias voltage was simply a DC voltage of +100 cm.

With the former, a clear copy image with high density and good gradation reproducibility and little capri was obtained, whereas with the latter, a copy image with low density and lack of sharpness was obtained. Further, even if the gap and the gap d were changed with the latter bias voltage setting, a high-quality image that could be obtained with the former bias voltage setting could not be obtained. 1. To obtain a high quality image with the latter bias voltage setting, the rotational speed of the developing sleeve and magnetic roll should be set to 1100 rpm or higher, respectively.
It had to be at least 20 rpm.

Next, the inventors used an organic photoreceptor in which an organic photoconductor layer was formed on the surface of a conductive support layer, and as in the electrophotographic copying machine described above, the configuration of the developing section could be changed arbitrarily. We prototyped an electrophotographic copying machine that could do this, and conducted experiments similar to those described above. The developer is a toner containing 26% by weight of magnetite fine particles in a resin, and has an average particle size of 1371 mm.
, well-known Pro 1o-'・-5 Magnetic powder with a charge amount of +7.4 μc/q by the one-off method, and a carrier containing 75% by weight of magnetite fine particles in a resin, with an average particle size of 31 μm. A magnetic powder having a charge amount of 10.3 μc/q by a well-known blow-off method was used in combination with toner 6q and carrier 14 (i).

In this electrophotographic copying machine, the moving speed of the photoreceptor is 14 o
ar/sea The uniform charging potential is -650V, the gap is 0.61B, the gap d is 0.81B, the direction of movement of the developing sleeve in the area where development is performed is the same as the direction of movement of the photoreceptor, and the rotation speed is 10V. Orpm, the magnetic roll was rotated in the opposite direction to the developing sleeve at 75 Orpm, and a bias voltage of 1-150V DC voltage was applied with an amplitude of 5o by a voltage application device.
Copying was carried out in the case where a rectangular wave alternating current voltage with an oV frequency of 800 Hz was superimposed and in the case where a direct current voltage of -160 cm was simply used. With the former, a clear copy image was obtained with high density, good gradation reproducibility, and little capri, whereas with the latter, a copy image with low density and lack of sharpness was obtained, although there was little capri. Ta. In addition, even if the gap and the gap d are changed with the latter bias voltage setting, it is not possible to obtain an image as high as that obtained with the former bias voltage setting, and it is not possible to obtain an image of the same quality. In this case, the rotation speed of the developing sleeve and magnetic roll should be set to 140 rpm or higher and 1.
I had to make it over 100 Orp.

As described above, a mixture of two types of magnetic powders, both of which contain magnetic substances in resin and have different triboelectric properties, is used as a developer, and electrostatic charge is generated using a magnetic brush method using both rotation of a developing sleeve and a magnetic roll. When developing a latent image, if a bias voltage containing an AC component is applied between the developing sleeve and the conductive support layer of the photoreceptor, the rotational speed of the developing sleeve and magnetic roll is lowered than before, and a high-quality image can be produced. I found out that I can get it. The inventors further investigated the alternating current component of the bias voltage and found that the frequency was 100
Remarkable effects were obtained at frequencies of Hz or higher, preferably 500 Hz or higher. When the frequency exceeds 10 KHz, the power loss of the power supply increases, making it difficult to put it into practical use. As for the width, it is effective at 200V or more, it is noticeable at 600V or more, and it is difficult to maintain insulation in the developing area at 1.6KV or more.

It is unclear why applying a bias voltage containing an alternating current component produces the above effect, but the alternating current component produces an alternating electric field in the gap between the developing sleeve and the photoreceptor,
This seems to cause the toner to vibrate in the gap and promote development.

However, the DC component of the bias voltage is effective in preventing fogging of the image base, as in the past, and should be set to an appropriate value depending on the exposure amount.

Effects of the Invention The present invention is characterized in that a developer made by mixing two types of magnetic powders, both of which contain a magnetic material in their resin and have different triboelectric properties, is a rotatable non-magnetic powder with a built-in rotatable magnetic roll. A developer layer is formed on the outer surface of the developing sleeve by being attached by magnetic force to the outer surface of the developing sleeve made of a magnetic conductor and having a layer thickness regulated by a regulating blade provided near the developing sleeve. , a bias containing an alternating current component between the developing sleeve and the conductive support layer of the photoreceptor when bringing the electrostatic latent image into contact with the photoreceptor on which the electrostatic latent image is formed. This is a developing method characterized by applying a voltage, and with this method, an excellent effect can be obtained in that a high-quality image can be obtained by rotating the developing sleeve or magnetic roll at a lower speed than before. By rotating the developing sleeve or magnetic roll at a low speed, it is possible to reduce the noise or vibration of the electrophotographic copying machine to which this developing method is applied, or to reduce the capacity or diameter of the motor that serves as the drive source.
This developing method is very effective in downsizing electrophotographic copying machines to which it is applied.

[Brief explanation of the drawing]

The figure is a schematic diagram of a developing section of an electrophotographic copying machine for explaining the present invention. 1... Photoreceptor, 2... Conductive support layer, 3
...Photoconductive layer, 4...Development sleeve,
6...magnetic roll, 6...regulating blade, 7...developer layer, 8...electrode 14.
1. Pressure application device, 9...protective resistance.

Claims (1)

[Scope of Claims] 0) A rotatable non-magnetic roller with a built-in magnetic roll, in which a developer made by mixing two types of magnetic powders, both of which contain magnetic particles in a resin and have different triboelectric charging properties, is rotatable. It is attached by magnetic force to the outer surface of the developing sleeve made of magnetic conductor.
Further, the layer thickness is regulated by a regulating blade provided near the developing sleeve, and the layer is formed on the outer surface of the developing sleeve. When visualizing the electrostatic latent image by bringing the developer layer into contact with the photoreceptor on which the electrostatic latent image is formed, a bias containing an alternating current component is provided between the developing sleeve and the conductive support layer of the photoreceptor. A developing method characterized by applying a voltage. Q) The developing method according to claim 1, wherein the frequency of the alternating current component of the bias voltage is from 100 Hz to 10 KHz. (3) DC component and AC component are superimposed on the bias voltage 2
. 1. A developing method according to claim 1.