JPH02214877A - Developing method for electrostatic latent image - Google Patents

Abstract

PURPOSE:To obtain the coexistence of the reproducibility of a black solid and that of a fine line and a dot by retransferring a part of toner to a developer carrier by magnetic force after one-component containing magnetic toner is transferred to an electrostatic latent image carrier from the developer carrier by an electric potential difference. CONSTITUTION:An unidirectional electric field is formed in a space of a developing part where the electrostatic latent image carrier 1 faces the developer carrier 2 which incorporates a magnet 3 and carries a magnetic developer 4. The developer 4 is transferred to the electrostatic latent image carrier 1 by electric effects, and consecutively is reversely transferred by magnetic effects. By impressing a voltage on the unidirectional electric field, in such a manner, the sufficient amount of developer in allowed to stick to the edge of an image part also, and the developer 4 excessively stuck is reversely transferred to the developer carrier 2 from the electrostatic latent image carrier 1 by the magnetic effects. Therefore, a sharp, high-contrast, moderately edged image free from base soil can be obtained. Thus, the coexistence of the reproducibility of a black solid and that of a fine line and a dot can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application Page 2 The present invention relates to a method for developing an electrostatic latent image used in copying machines, laser printers, electrostatic plotters, and the like. In particular, it relates to a developing method using -component toner.

Conventional technology In general, in developing electrostatic latent images, there are two methods: one is to develop using a two-component developer consisting of toner and carrier, and the other is to develop using a one-component developer consisting only of toner without using carrier. There is.

In the two-component development method, in order to obtain good print quality, it is necessary to always maintain the mixing ratio of toner and carrier, that is, the toner concentration, at an appropriate value. Therefore, a toner concentration control device is required, and this device is extremely expensive, resulting in an increase in cost. Furthermore, this toner concentration control device required adjustment, and maintenance and inspections were complicated. In recent years, in view of these points, attention has been paid to developing methods that do not require an expensive toner density control device and do not require maintenance.

As a developing method that satisfies such requirements, there is a one-component developing method that uses a developer made only of toner without using a key. In this -component development method, a one-component nonmagnetic toner layer is formed on a toner carrier, the toner is triboelectrically charged to a predetermined polarity by a triboelectric charging member, and the toner layer and the electrostatic latent image carrier are brought into contact with each other. A voltage is applied between the electrostatic latent image carrier and the toner carrier to cause the toner to fly to the electrostatic latent image carrier by the Coulomb force generated by the voltage. The first method of developing a latent image (Journal of the Society of Electrophotography, Vol. 26, No. 2 (
(1987)), a magnetic brush made of conductive component magnetic toner is formed on a conductive metal toner carrier containing a cornerstone roller, and the electrostatic latent image carrier is rubbed with this magnetic brush. A second method of depositing toner and developing an electrostatic latent image (U.S. Pat. No. 3,909,268);
A toner carrier is disposed adjacent to an electrostatic latent image carrier, the toner carrier is insulated from a conductive support and the support, and a plurality of microscopic particles are electrically insulated from each other. The toner on the toner carrier is frictionally charged to a predetermined polarity by a frictional charging member, and a constant voltage is applied to the conductive support and the back electrode of the electrostatic latent image carrier. A third method of developing an electrostatic latent image (
JP-A-67-114163) and the like are generally well known.

Problems to be Solved by the Invention Incidentally, the image obtained by the first method is good with little background smudge (that is, a phenomenon in which an originally white image turns dark due to toner).

The reproducibility of electrostatic latent images such as fine lines and halftone dots deteriorates. In addition, the edges in the solid printed area lack sharpness, that is, the outline of the solid printed area is not clear and blurred, and furthermore, the gap between the electrostatic latent image carrier and the toner carrier is 50 μm to 500 μm. However, there were drawbacks such as the fact that the gap was very narrow and it was very difficult to manage the tolerance of this gap.

Furthermore, in the second method, the negative component magnetic toner is electrically conductive, and development is performed using phenomena such as dielectric polarization and electrostatic induction. reproducibility is insufficient. 5. Also, when an electrostatic latent image is developed into a visible image and then electrostatically transferred to paper, since the toner is conductive, the charged charge leaks and the transfer is interrupted. There are drawbacks such as reduced efficiency.

In addition, the third method requires removing the electric charge generated by frictional charging with the toner from multiple microelectrodes that are insulated from each other on the surface of the toner carrier, which poses problems in terms of structure and reliability. There is. Furthermore, the toner carrier has a special layer structure and is expensive in terms of cost.

Therefore, an object of the present invention is to provide a new and low-cost developing device that has high printing quality that combines the above-mentioned defects, solid black reproducibility, and fine line/halftone dot reproducibility. A method for developing an electrostatic latent image is provided.

Means for Solving the Problems The present invention provides a method in which an electrostatic latent image carrier and a developer carrier containing a magnet and carrying a magnetic developer are made to face each other in a developing section, and a unidirectional electric field is formed in the gap between the developing sections. a first step in which the developer is transferred to the electrostatic latent image carrier by an electrical action, and a second step in which the transferred developer is reversely transferred by a magnetic action; By adopting a method of developing based on the difference between the forces that act electrically and magnetically on the magnetic developer,
This can solve the above problem.

For production The effect of this technical means is as follows.

That is, the developer is transferred from the developer carrier to both the image area and the non-image area on the electrostatic latent image carrier.
By applying a unidirectional electric field, a sufficient amount of developer can be applied even to the edges of the image area. Thereafter, the developer attached to the non-image area and the developer excessively attached to the image area are reversely transferred from the electrostatic latent image carrier to the developer carrier by magnetic action.
It is possible to obtain sharp, high-contrast images with moderate edge effects and no background smudges.

Embodiment 7, -7 Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, an electrostatic latent image carrier 1 (hereinafter referred to as photoreceptor 1) having an electrostatic latent image formed on its surface is rotating in the direction indicated by the arrow in the figure. The developer carrier 2 (hereinafter referred to as sleeve 2), which is opposed to the photoreceptor 1 with an appropriate gap, is rotating in the direction of arrow B in the figure, so that the circumferential speed with the photoreceptor 1 is approximately equal. has been adjusted to. As shown in the figure, the magnet RO/I/3 contained in the sleeve 2 is magnetized so that the outer circumferential sides thereof are of the same polarity above and below, sandwiching the closest portion of the photoreceptor 1 and sleeve 2. This prevents any attraction force from acting on the magnetic toner 4 at the portion closest to the sleeve. Well, the sleeve 2 is supplied with a high voltage power supply 6 with a bias voltage sufficient to cause the negatively charged magnetic toner 4 on the outer circumference of the sleeve to fly to the non-image area, that is, the area that will become a white image when transferred to recording paper. I'm applying a lot of energy. 5 is a doctor blade for thinning the magnetic toner. The developing device according to one embodiment of the present invention is configured as described above.

Next, the developing process of the developing method of the present invention will be explained with reference to FIG. A pattern of electrostatic charges is formed on the surface of the photoreceptor 7 shown in FIG. 2a, corresponding to an image to be obtained. If we assume that the development method is a reversal development method, 8 in the figure is a non-image area, 9 is an image area, and the charged potential of the non-image area 8 is -eoov.

Let the charging potential of the image area be oV. As described above, when the photoreceptor 7 carrying the electrostatic latent image moves to the development area, the second
It will be in the state shown in the figure. In the figure, 1o is a sleeve, and 11 is a power supply for applying a bias voltage VB between the photoconductor back chamber $i13 and the sleeve 10, and the negatively charged magnetic toner 12 is a power source for applying a bias voltage VB between the photoreceptor rear chamber $i13 and the sleeve 10. On the other hand, it was F in the image section. In the L1 non-image area, F8D (FoD
A force due to an electric field of <F8L) acts, and an amount of magnetic toner adheres to the photoreceptor T in accordance with the magnitude of the force.

As a result of the processing in the first step described above, FIG.
The magnetic toner 11 adheres to the photoreceptor 7 in the state shown in FIG.

9 Vane Subsequently, when the photoreceptor γ rotates, as shown in Figure 2 d,
The magnet 14 is now present inside the sleeve 1o. The magnetic action of this magnet 14 causes the magnetic toner 1
1, and as shown in Figure 2d, in the image area F□
L, non-image area becomes FmDO force. This is the second step. As a result of the processing in the second step, as shown in FIG. 2e, all the magnetic toner 11 adhering to the non-image area 8 is returned to the sleeve 1o, and
Also, only the necessary amount of toner 11 attached in excess is left on the photoreceptor 7 and returned to the sleeve 1o.

As described above, the developing process of the developing method based on the present invention has been shown in FIG. - As an embodiment, it is possible to have a configuration as shown in FIG. 3, and 16 in the figure is an area where the toner flies in the first process, and 16 is an area where the toner flies in the second process. It is.

By using such a developing method, it was possible to improve the defects in conventional developing methods. In other words, even with environmental changes, background smear does not occur, and the moderate edge effect makes it possible to obtain sharp fine line reproducibility and solid black image edges. .

Effects of the Invention As described above, according to the present invention, by using a magnetic developer, it is possible to obtain excellent printing quality without background smearing and with good fine line reproducibility, and also to improve environmental stability. It became possible to obtain good image quality.

This system is applicable not only to reversal development but also to forward development, and it goes without saying that the gap between the photoreceptor and the sleeve may be larger or smaller than the developer layer thickness.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a developing device which is an embodiment of the present invention, and FIG. 2 is a sectional view of essential parts showing the developing process related to the developing method of the present invention. and C indicate the developer transfer step, and d and e indicate the developer reverse transfer step. FIG. 3 is a sectional view of essential parts of a developing device which is an embodiment of the 11-vane invention. 1...Photoreceptor, 2...Sleeve, 3.
... Magnet roll, 4 ... Magnetic developer, 5 ... Doctor blade, 6 ... Power supply, End ... Photoreceptor, 8 ... ...Charged part (non-image part), 9...Exposed part (image part), 1°...
...Sleeve, 11...Magnetic toner, 12.
...Power source, 13...Back electrode of photoreceptor,
14... Magnet, 15... Transfer area, 16... Counter transfer area. Name of agent: Patent attorney Shigetaka Awano and one other person (d
) figure

Claims (1)

[Claims] A step of forming an electrostatic latent image of an image to be obtained on an electrostatic latent image carrier, and a magnet disposed opposite to the electrostatic latent image carrier and having a magnet therein A step of causing a one-component magnetic toner to be carried on an encapsulated developer carrier, and providing a potential difference between the electrostatic latent image carrier and the developer carrier, which are arranged opposite to each other, and the potential difference causes the a step of transferring one-component magnetic toner carried on a developer carrier to the electrostatic latent image carrier; and one-component magnetic toner transferred to the developer carrier by the magnetic force of the magnet in the developer carrier. A method for developing an electrostatic latent image, comprising the step of retransferring a portion of the toner to the developer carrier.