JPS6211342B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing method using a one-component developer in an electrophotographic copying machine or the like.

Conventionally, in a dry development method using a two-component developer consisting of toner and carrier, a bias voltage that is the same as or slightly higher than the potential of the background area, that is, the non-image area, is applied to the development electrode in order to prevent background staining during development. was being applied.

Similarly, in a developing method using a one-component developer consisting only of toner, it is necessary to prevent background staining.

In order to perform this bias development, the surface of the developing roller or electrode must be made of at least an electrically conductive material. However, depending on the developing method, it is not possible to use a conductive developer donor member. For example, when developing an electrostatic latent image by attaching a one-component developer to the surface of a silicone rubber roller, it is preferable that the rubber roller has elasticity so that it can be rotated in contact with the electrostatic latent image. This is because the toner has good adhesion, the contact area with the electrostatic latent image carrier during development is large, and the carrier is not damaged. If conductive particles such as carbon are mixed into rubber to apply a bias voltage,
Although it becomes conductive, rubber hardening increases. Furthermore, in order to obtain a sharp image, if the edge effect is used to bring a conductive developer donor close to the electrostatic latent image carrier with a small gap, the opposite electrode effect becomes larger and the edge effect is insufficient. It may become ineffective.

In addition, when a one-component developer is moved on a developer donor and the one-component developer is triboelectrified by mechanical friction between the two, depending on the type of developer, the material on the insulating surface may be Sometimes you have to use it.

As described above, when the developer donor member is made of an electrically insulating material at least on the surface, a bias voltage to prevent background staining cannot be applied to the developer donor member. It was hot.

An object of the present invention is to detect the potential on the surface of an electrostatic latent image carrier when developing an electrostatic latent image, and to determine the appropriate level for a developer donor having at least an electrically insulating surface, depending on the detected surface potential. An object of the present invention is to provide a developing method that produces a bias effect.

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

FIG. 1 shows an embodiment of the present invention, with reference numeral 1
is a photoreceptor on which an electrostatic latent image 2 is formed.
A developing roller 3 is rotating in the direction of the arrow in the vicinity of the photoreceptor 1 at a constant speed or faster so as to move in the same direction in the vicinity of the photoreceptor 1.
The developing roller 3 has an electrically insulating layer 5 formed on the surface of a conductive support shaft 4. The support shaft 4 is grounded, and the electrical insulation layer 5 has a volume resistivity value.
Constructed from silicone rubber, resin, etc. with a resistance of 10 ^{to 14} Ωcm or more. A one-component developer T (hereinafter referred to as toner) consisting only of toner is attached to the surface of the developing roller 3, and the toner T is removed by a scraping plate 6 provided in contact with the developing roller 3. After development, it is removed from the surface of the developing roller 3. A corona discharger 7 is provided opposite the developing roller 3 that has passed through the scraping plate 6. A high voltage having the same polarity as the electrostatic latent image is applied to the corona discharger 7, and the electrical insulating layer 5 is charged by corona discharge. Since this corona discharger 7 exists in a developing container 8 that houses the developing roller 3, its surroundings are covered with a cover 9 to prevent toner from adhering thereto. Next, a sufficient amount of toner in the developer container 8 is supplied onto the charged insulating layer 5. The toner is supplied by a brush roller 10 that rotates in the direction of the arrow while being partially buried in the toner layer in the developer container 8. The material of the brush of the brush roller 10 may be one that is separated from the toner in the triboelectric charging order and that triboelectrically charges the toner to a positive polarity.
If the brush comes into contact with the insulating layer 5,
Naturally, electrically insulating materials must be used. Note that as the toner supply means, any means capable of dispersing toner other than the brush roller can be used. When the developing roller 3 receives the toner supply, excess toner is removed by the toner layer thickness regulating member 11 attached to the developing container 8 at the portion where it moves upward, so that the developing roller 3 has a constant thickness. Form a toner layer.
The toner layer thickness regulating member 11 can also serve as a frictional charging member made of a material that frictionally charges the toner to a positive polarity, but a separate frictional charging member may also be provided. In addition, the toner may be charged by corona discharge.

By the way, to explain the developing action using FIG. 2, there is a negative charge on the surface of the insulating layer 5 of the developing roller 3, and a toner layer is formed on the surface of the insulating layer 5. There is toner that is electrically charged. Since the polarity of the electrostatic latent image on the photoreceptor 1 is negative, development is performed by electrostatically attracting toner of opposite polarity.
On the other hand, in the non-image area, a small amount of negative charge remains and there is an attraction force that attempts to attract the toner, but the attraction force that attracts the toner due to the electrical charge on the developing roller 3 is stronger, and the non-image area In the image area, toner is prevented from moving to the photoreceptor 1. The volume resistivity value of the toner used here is such that the electric charge on the developing roller 3 does not leak to the toner.
It is a high resistance toner with a resistance of 10 ^{to 14} Ωcm or more.

The bias effect for performing bias development is as described above, but a method for changing this bias effect is to adjust the voltage applied to the corona discharger as shown in Figure 1 to change the charging voltage. You should do it. If it is difficult to adjust the high voltage power supply side, it is possible to relatively control the charge on the medicine by using a scorotron and controlling the charge by changing the voltage applied to the grid. Similar to the two-component development method, the charging voltage is set to be equal to or slightly higher in absolute value than the potential of the background portion.

Next, a case where a magnetic toner having magnetism is used as the one-component toner will be explained with reference to FIG.

A non-magnetic sleeve 12 is rotating in the direction of the arrow in the vicinity of the photoreceptor 1, and the sleeve 12 is electrically conductive and grounded. An electrically insulating layer 13 is formed on the surface of the sleeve 12. Inside the sleeve 12, permanent magnets 14 ₁ to 14 ₄ have S poles,
The north poles are arranged alternately, and the magnetic toner is magnetically attracted to the surface of the sleeve 12 and conveyed to the developing section. One-component magnetic toner is contained in the developer container 8, and the toner in the developer container 8 is supplied to the sleeve 12 by a toner pumping roller 15. The toner pumping roller 15 consists of a non-magnetic sleeve 16 rotating in the direction of the arrow and a magnetic roller 17 fixedly provided inside the sleeve 16.
Of the 7 magnetic poles, the magnetic pole facing the magnet 14 ₁ is required to be arranged so that the N pole having the opposite polarity to the magnet 14 ₁ is located. This ensures replenishment of toner from the toner pumping roller 15 to the sleeve 12. Of course magnetic roller 17
It is more desirable to increase the magnetic force of the magnet ₁₄₁ .

Now, the magnetic toner that has passed through the developing section is removed from the surface of the sleeve 12 by the scraping plate 6. At the position where the toner is removed, the magnetic force is close to zero, allowing the toner to fall under its own weight. A conductive charging roller 18 is provided to rotate in contact with the surface of the sleeve 12 from which toner has been completely removed. A DC voltage having the same polarity as the electrostatic latent image is applied to the charging roller 18 . The principle of charging the electrically insulating layer 13 by the charging roller 18 is the same as that of conventionally known roller charging. The charging potential by this charging roller 18 is the potential (residual potential) of the non-image area of the photoreceptor 1.
The voltage is the same as or slightly higher in absolute value. The potential varies depending on the type of photoreceptor used. The charging potential of the electrically insulating layer 13 is determined by detecting the surface potential of the non-image area of the photoreceptor 1 using a surface potentiometer. A cover 9 is provided around the charging roller 18 to prevent toner contained in the developer container 8 or floating toner from adhering to the charging roller 18 .

The magnetic toner in the developer container 8 is stirred by stirring blades 19,
It is triboelectrically charged by the pumping roller 15, the doctor 11, or the like. Therefore, the materials of the stirring blade, sleeve 15, and doctor 11 are selected so that they are separated from the toner in the triboelectrification order and that can charge the toner to a positive polarity.
The charging potential of the developing roller, which is a developer donor, is determined by detecting the surface potential of the non-image area (background area) of the photoreceptor using a surface electrometer.

FIG. 4 shows a developing device in which the surface potential of the photosensitive drum 20 is detected by a surface electrometer 21, and the charging potential of the developing roller 22 is controlled in accordance with the detected potential. The surface electrometer 21 is
A probe or detection electrode 23 disposed close to the photoreceptor drum 20 and provided on the front side of the developing section A, an amplification circuit 24 for amplifying the current detected by the detection electrode 23, and The voltage control circuit 25 includes a connected power supply. The detection electrode 23 is elongated in the width direction of the photoreceptor drum 20 and has the same length as the image area, or has one or more dot shapes. In the former case, the average potential on the photoreceptor drum 20 is detected, but since the area of the non-image area is usually much larger than that of the image area, it is assumed to be approximately equal to the background potential. Detected. On the other hand, in the latter case, the skin potential itself can be detected. In this way, the voltage control circuit 25 automatically controls the voltage applied to the charging means 26 according to the detected potential, and the voltage applied to the developing roller 22 is automatically controlled.
The upper insulating layer is charged to a potential that is the same as the potential of the skin portion of the photoreceptor drum 20 or slightly higher in absolute value.

In the above-described embodiments, a case was described in which a photoreceptor was used as an intermediate recording medium, but the present invention can be similarly applied to an electrostatic recording device that directly forms an electrostatic latent image on a dielectric material.

As described above, according to the present invention, in a developing method using a developer donor with an insulating surface and an electrically insulating one-component toner, during development of an electrostatic latent image,
Since the developer donor can be given a bias effect according to the background area of the photoreceptor, bias development without background staining can be performed, and sharp images with excellent resolution can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the principle of bias development of the present invention, and FIGS. FIG. 2 is a cross-sectional view of a developing device showing an example. 1...Photoreceptor, 3, 22...Developing roller,
5, 13... Electric insulating layer, 6... Scraping plate, 7
... Corona discharger, 9 ... Cover, 12 ... Sleeve, 18 ... Charging roller, 21 ... Surface electrometer, 26 ... Charging means.

Claims (1)

[Scope of Claims] 1. Charge at least the surface of a developer donor whose surface is electrically insulating to the same polarity as the electrostatic latent image on the electrostatic latent image carrier, and In the method of developing the electrostatic latent image by supplying a high-resistance one-component developer, the surface potential of the background portion of the electrostatic latent image carrier is detected with a surface electrometer, and the detected surface potential and A developing method in which the above surface is charged to a potential that is the same or slightly higher in absolute value. 2. The developing method according to claim 1, wherein the surface of the developer donor is charged by corona discharge.