JPS59174865A - Developing device - Google Patents

Abstract

PURPOSE:To improve and stabilize picture quality and to increase a device in operation speed and size easily by providing a counter electrode impressed with a voltage having the polarity opposite to the electrostatic charge polarity of magnetic toner to correct a visible picture by the magnetic toner. CONSTITUTION:When a developed toner image on a recording medium 4 approaches the counter electrode 5 impressed with the voltage having the polarity opposite to that of the electrostatic charge polarity of the magnetic toner, excessive magnetic toner other than magnetic toner coupling strongly with the electrostatic latent image by Coulomb force is recovered by an electrostatic field applied to a correction gap d3 to stick onto the counter electrode 5. This recovered magnetic toner is rotated as shown by an arrow C and scraped off the counter electrode 5 by a scraper 7 provided near a recovery gap d4, and then recovered to a magnet roll 1 to be reused for development. Thus, the picture quality is improved and stabilized. Further, the device is increase in operation speed and size without high-precision work nor adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device using a magnetic brush developing method that visualizes an electrostatic latent image formed on a recording medium using magnetic toner.

Conventionally, there has been a device of this type as shown in FIG.

In the figure, 0D is a cylindrical magnet with multiple magnetized poles on its surface, and αa is the OD of this cylindrical magnet.
It is a cylindrical sleeve made of a conductive and non-magnetic material that encloses the magnet roll (1).

(2) is a doctor blade made of conductive and non-magnetic material, (3) is a developer container, (4) is a recording medium capable of holding an electrostatic latent image, (41) is a photoconductive layer, ( 421F
i. It is a conductive substrate.

In the above configuration, the gap between the sleeve o2) and the doctor blade (2) is called the doctor gap d1, and the gap between the recording medium (4) and the sleeve (121) is called the development gap d.
Set it to 2. Further, the cylindrical magnet OD is magnetized as shown in Fig. 1 and is fixed in the state shown in the figure, and the sleeve (12
The + bamboo moves in the direction of arrow A in the figure at the same speed as the recording medium (4). The moving direction of the recording medium (4) is the direction shown by arrow B in the figure.

Next, the operation will be explained. When the sleeve 021 rotates in the direction of arrow A in the figure, high-resistance or insulating magnetic toner (developer) is drawn out from the developer container (3) and is regulated by the doctor blade (2). only is fed onto the sleeve (12). At this time, if the doctor gap dl is less than 0.4 m, it will be difficult to supply uniform and stable magnetic toner onto the sleeve (12), and conversely, if the doctor gap dl is 0.4 m or less, it will be difficult to uniformly charge the magnetic toner. There are disadvantages such as not being able to carry out the process, so it is generally selected to be around 0.5 traces. Doctor gap d1 to sleeve a2
The magnetic roller supplied in an appropriate amount above is charged by the time it reaches the development area (development gap d2 set point). In the development area, the development cap d2 satisfies d1≦dz<? The magnetic toner is set to +, and the magnetic toner comes into contact with the recording medium (4) and adheres to an electrostatic latent image with a polarity opposite to the charged polarity of the magnetic toner, thereby forming a visible image.

Since the conventional developing device is configured as described above, it is difficult to clearly reproduce the electrostatic latent image on the recording medium (4) with high resistance or l'i insulating magnetic toner. There were disadvantages such as excess magnetic toner adhering to the area around the electrostatic latent image and a large amount of magnetic toner scattering.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional ones. A counter electrode is provided in the developing device to face the recording medium, and a voltage having a polarity opposite to the charged polarity of the magnetic toner is applied to the counter electrode. is applied, thereby making it possible to collect excess magnetic toner on the recording medium.
High precision processing.

The objective is to provide a device that can handle increased size and dual speed without making adjustments, and can also form high-quality images.

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 2, (1) is a magnet roll, which consists of a cylindrical magnet till having a plurality of magnetic poles on its surface, and a sleeve ( 12). (2) is a doctor blade, (3) is a developer container, and (4) is a recording medium, which is a photoconductor (4υ
and a conductive substrate (4'll). (5) is a rotatable counter electrode formed in a columnar or cylindrical shape made of conductive and non-magnetic material, and (6) is a polarity of charge of the magnetic toner. (7) is a scraper, which can be made of an insulating material or
Alternatively, the scraper (7) is provided to prevent the power supply voltage from leaking to other members.

In the above configuration, the gap between the doctor blade (2) and the sleeve 02) is the doctor gap d1, the gap between the recording medium (4) and the sleeve α2) is the development gap d2,
The gap between the counter electrode (5) and the recording medium (4) is defined as a correction gap d3, and the gap between the counter electrode (5) and the sleeve α is defined as a recovery gap d4. In addition, sleeve shouts, recording media (4
) and the counter electrode (5) are indicated by arrows A and B in FIG. 2, respectively.

Rotate in the direction shown by arrow C. In addition, sleeve 02゜1
Eyebrow-1 7 Conductive base.

Next, the operation will be explained.

The electrostatic latent image on the recording medium (4) is visualized in the same manner as the conventional image explained using FIG.

The visible image after development (the toner has adhered to it and is now visible) may be affected by excess magnetic toner sticking to the electrostatic latent image, or by background smudges, as mentioned above. There are many visible images. When the visualized toner image approaches the counter electrode (5) to which a voltage with a polarity opposite to the charged polarity of the magnetic toner is applied, the electrostatic latent image and the magnetic toner that are strongly coupled by Coulomb force are removed. Excess magnetic toner (magnetic toner around the silent wheel @ image and as a background stain) is collected by the electrostatic field applied to this correction cap d3, and the
(The correction gap d3 is such that the magnetic toner adhering to the recording medium +41 can pass through it more easily. Therefore, the gap d3 is at least three times the average particle diameter of the magnetic toner. However, if this is applied too widely, the voltage for recovery will become high and the formation of parallel electric field will deteriorate,
~0.3 rrah is desirable.

The magnetic toner collected on the opposing electrode (5) in this way is removed from the opposing electrode (5) by the scraper (7) provided near the collection gap d4 by rotating in the direction of arrow C in the figure. After being processed, it is collected by the magnet roll (1) and can be used for development again. Note that the moving speed of the counter electrode (51) is the same as that of the recording medium (4).
It is desirable that the movement speed be equal to or greater than the movement speed of .

In the above embodiments, it has been shown that a conductive cylinder or cylinder is used as the rotating opposing pole, but it is clear that it may be constructed of a belt.

Further, although the direction of rotation of this counter electrode was set to be opposite to the direction of rotation of the recording medium and the magnet roll in the correction range, these may be set in four directions. However, this gift requires the installation position of the scraper (7) to be as shown in Figure 3. That is, since the rotation direction is opposite to that of the embodiment shown in FIG. 2, the scraper (7) is placed on top, and the peeled magnetic toner is easily collected by the magnet roll (1). The purpose is to prevent the running of magnetic toner, which is a developer, on the magnet roll (1) from being adversely affected.

In addition, in the above embodiment, as the rotation method of the magnet roll, the magnet fixed/sleeve rotation method was described, but this rotation method is not limited to this, and it can be either magnet rotation/sleeve fixed or magnet/sleeve self-rotation method. Also, good toner wrinkle feeding and visualization become possible.

As described above, according to the present invention, since a counter electrode to which a voltage with a polarity opposite to the charged polarity of the magnetic toner is applied is provided in the developing device, it is possible to correct the visible @ mound caused by the magnetic toner. This has the effect that high-quality images can be stably formed, and that a high-speed, large-sized developing device can be configured without requiring high-sheath processing or adjustment.

[Brief explanation of drawings]

FIG. 2 is a cross-sectional side view showing a conventional developing device, FIG. 2 is a cross-sectional side view showing a developing device according to an embodiment of the present invention, and FIG. 3 is a cross-sectional side view of a developing device showing another embodiment of the present invention. FIG. (1)... Magnet roll, (4)... Recording medium, (5
)...Counter electrode, (6)...Power source. In addition, the same reference numerals in the figures are the same or omit the contrasting parts.

Claims (1)

[Claims] (1) A recording medium that holds an electrostatic latent image on its surface, a magnet roll that is provided facing the recording medium and causes magnetic toner to adhere to the electrostatic latent image, and when viewed in the direction of movement of the recording medium. A counter electrode is provided facing the recording medium on the downstream side of the magnet roll for collecting excess magnetic toner on the recording medium, and a voltage having a polarity opposite to the charged polarity of the magnetic toner is applied to the counter electrode. A developing device characterized by comprising: a power source that applies .