JPS5872971A - Developing device - Google Patents

Abstract

PURPOSE:To improve the charging efficiency for a high-resistance toner and prevent the occurrence of clogging due to foreign matters in the toner, by forming the bottom face of a charged giving member approximately in parallel with the tangential direction of a sleeve. CONSTITUTION:The tip of a charge giving electrode is formed into a plane, and the charge giving electrode is so arranged that this plane is parallel with the tangential direction of the part of a cylindrical sleeve 2 which faces to this electrode. Thus, when the same charge quantity is given to a toner, a voltage applied across electrodes is lowered to a very low level; and therefore, the charging efficiency is improved considerably, and the discharge between electrodes due to foreign matters or the like in the toner is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device using a -W fusible toner, and more particularly, to a developing device using a high resistance magnetic toner having a specific resistance value of 10'' to 101 sp1.

Various developing devices that use one-component magnetic toner are known, but if the magnetic toner used in these devices is roughly divided into specific resistance values, those using low-resistance toner with a value of 10" or less, and those using low-resistance toner with a value of 10" or less, A high resistance toner having a value of ~10'' SΩ1 may be conveniently used.

In the case of a phenomenon method using a low resistance toner having a value of 101101 or less, a so-called conductive toner, the toner retains a charge by electrostatic induction or electric polarization by the electric field caused by the electrostatic agR on the carrier. Consider the a1 phenomenon.

Next, the developed conductive toner is transferred to copy paper using a transfer method that utilizes an electric field, such as electrostatic transfer or bias transfer. Charge exchange is easily carried out between the toner and the toner, and only the charge is transferred at the transfer voltage 4'F, and the toner is not transferred.
The disadvantage is that only low concentration and low quality tt moat can be obtained.

Therefore, in order to prevent the charge exchange between the copy paper and the toner, which causes the above-mentioned inconvenience, a method of using copy paper that has been insulated and has a high resistance has been considered.
It is currently being put into practical use. However, although this method achieves the intended purpose, it has drawbacks such as higher costs due to processing and lack of versatility due to the need to use special paper. Ru.

Furthermore, a method has been considered to avoid the above-mentioned disadvantage by increasing the resistance of the charge-exchanged toner, but this method does not require any special treatment on the copy paper and is low-cost. This method is considered to be very useful as it expands the versatility of copying paper, but on the other hand, as the specific resistance of the toner increases to 1011 to 10'Ω1, the electric field caused by the latent image charge also causes electrostatic induction of the charge. It has the essential drawback that electric polarization cannot be easily induced and is difficult to be detected.

In response to this, various methods have been devised to improve the development efficiency by imparting an electric charge to this high-resistance toner within a developing machine prior to development.

There are various methods of applying electric charge, such as Sirona charging, frictional charging, and electrode charging.However, Co-charging is mechanically complex and expensive, while frictional charging has charge polarity limited by the material, and can be easily contaminated. This method is unfavorable in terms of the one-cycle method because it has the disadvantage that the amount of charge changes depending on the temperature, moisture, and the like. This point electrode charging method is mechanically simple, and is resistant to dirt and environmental changes, so it is considered to be the most effective method as a current method for producing high-resistance toner. However, in the conventional method, it is necessary to apply a very low voltage to the electrode in order to give a sufficient charge tt' to the toner, and if some foreign matter gets mixed into the toner, the electrode and cylindrical sleeve It is easy for electrical discharge to occur between the electrode and the sleeve, and this electrical discharge not only seriously damages the electrode and sleeve surface, but also sometimes damages the power supply.In response to this, several improvement plans have been proposed. There is. One of them, as seen in JP-A No. 52-67640, is to provide an arc-shaped electrode along the surface of a cylindrical sleeve to increase the contact area with the toner and improve charging efficiency. be. This method certainly improves charging efficiency, but on the other hand, it requires precision in electrode setting, which makes this setting difficult, and foreign matter in the toner can become trapped, causing discharge between the electrodes. It has the disadvantage of being elusive.

Furthermore, in Utility Model Application Publication No. 56-26755, the electrode T is arranged so as to become gradually narrower in the direction of movement of the toner, which improves contact with the toner and increases charging efficiency, but has the same drawbacks as above. I have Y.

Therefore, the purpose of the present invention is to improve the charging efficiency of high-resistance toner in the range of 1011 to 10'Ω, to prevent clogging caused by foreign matter in the toner, and to prevent damage to the power supply due to the release type. An object of the present invention is to provide a current device having a regulating material.

Is the purpose of this invention a magnet inside? In a phenomenon device using -component high-resistance magnetic toner, the sleeve has a sleeve, and a charge imparting member faces the surface of the sleeve. This can be achieved by a developing device that has a w% characteristic.

The present invention will be explained below based on the drawings.

FIG. 1 shows the most common conventional device. 1 in the diagram is 1d
It is an il image carrier on which an electrostatic charge pattern is recorded. Opposed to this is a non-magnetic cylindrical sleeve 2 containing a magnet.
A developing sleeve (hereinafter referred to as a developing sleeve) is arranged around which high-resistance magnetic toner 6 (hereinafter referred to as a toner) is magnetically held and conveyed in the direction of the arrow. The layer thickness of the toner 6 is regulated in advance, or a desired amount of charge of a desired polarity is applied by a charge applying bias and a soldering source 4. This toner then forms an electrostatic charge patter yvjA on the ll1ii1 image carrier 1, forming a visible vR'lk:. At this time, the developing sleeve 2 is connected to an image bias power source 5, so that the visible range can be adjusted appropriately.

The charging efficiency of the image ff1l carrier from the electrode at this time is
It is shown by the line (Otori) in the figure. The measurement conditions at this time were: Electrode shape: Sharp tip Material: Aluminum Width: 260 m Gear between electrodes: 0.5 mm Sleeve rotation speed: 250 rpwa (φ37) Toner resistance: 100 countries, and under the above conditions. The results of measuring the current flowing between the electrode and the sleeve are plotted against the voltage. If we calculate the apparent resistance RaY of the toner from this graph, we get 6.0X from the formula Rm=v/l (V: voltage, I: electric R).
It is calculated as 10” (Ω).

Next, an embodiment of the device of the present invention will be described.

Figure 2 shows an example of its configuration, but basically it is based on the conventional example 1.
Same as the figure.

Specifically, the electrode tip surface is flat, and this surface is parallel to the tangential (plane) direction of the opposing portions of the cylindrical sleeve 2.

The charging efficiency of the image carrier by the electrodes at this time is shown by line (b) in FIG. The measurement conditions are the same as in the conventional example except that the electrode thickness is d=4-. Similarly, from this graph, the apparent resistance Rbt is calculated as 1.5X10” (Ω)
It can be seen that the Ra' has decreased to 1/4 compared to the conventional example. Therefore, the charging efficiency has increased by 4 times.

As described above, in the embodiment according to the present invention, the charging efficiency is significantly improved, and when trying to apply the same amount of charge (electricity*>W) to the toner, the voltage applied between the electrodes is significantly reduced compared to the conventional device. This can be suppressed to a low level (l/4 in the example), and it is also possible to prevent discharge between the IT electrodes due to foreign matter in the toner.Furthermore, the shape of the tip of the electrode is made planar in this way, and the sleeve By arranging the portion t facing the sleeve parallel to the tangential (plane) direction on the sleeve, clogging due to foreign matter is less likely to occur.In other words, in the conventional device, the portion of the electrode closest to the sleeve is point (line) shaped. This is because it has exactly the same performance as a layer thickness regulating member with a sharp tip.

Next, we investigated the charging efficiency when the width of the bottom surface of the electrode was changed, and the results were as shown in Figure 4. As is clear from this graph, the charging efficiency improves linearly until the width of the bottom surface of the electrode reaches 4 mm, and when it exceeds 4 mm, it tends to become saturated. Therefore, it is desirable that there be 4 or more electrodes on the bottom surface of the electrode according to the present invention.

It is clear that the above can be said in common for all three lid-type developing methods: sleeve simultaneous rotation/magnet roll fixation, sleeve fixation/magnet roll rotation, and sleeve rotation/magnet roll rotation. Dew.

As described above, according to the present invention, the specific resistance value is 1011 to 10
When using high-resistance toner from Japan, it has a simple electrode and toner thickness regulating material that has good charging efficiency to the toner and prevents discharge between the electrodes due to clogging caused by foreign matter in the toner. A developing device can be provided.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic diagram of a conventional developing device, FIG. 2 is a schematic diagram of an embodiment of the developing device according to the present invention, and FIG. 3 is a schematic diagram of a conventional developing device. FIG. 4 is a graph showing the charging efficiency of the llii image carrier from the electrode of the device shown in the figure, and FIG. 4 is a graph showing the relationship between the inside of the bottom surface of the electrode and the charging efficiency. Code in the figure:

Claims (1)

[Claims] In a developing device using -component high resistance magnetic toner, which has a sleeve having a magnet inside and a charge imparting member facing the surface of the sleeve, the shape of the bottom surface of the charge imparting member is approximately parallel to the tangential direction of the sleeve. A developing device characterized by: 1.