JPS5882265A - Developing method - Google Patents

Abstract

PURPOSE:To obtain an image always free from fogs as compared with latent images with respect to a method for developing the latent images, by using a one-component magnetic developer by applying AC bias upon a developing sleeve in the stage of nondeveloping and applying DC bias upon the sleeve coated with the developer. CONSTITUTION:A one-component magnetic developer 5 of high insulation characteristic charged negative is charged into a developing hopper 7. While film thickness is regulated with a doctor blade 4, the developer 5 is coatd on a coating sleeve 1. The coating sleeve is rotated as an arrow to stick the toner on the latent images on a photosensitive drum 8 via a developing sleeve 2. In this case AC voltages ae applied upon both of the sleeve 1 and the sleeve 2 by an AC bias power source 11 and a bias power source 10 for coating to make the film thickness of the developer 5 constant. In the stage of nondeveloping, AC bias is applied upon the sleeve 2 alone and DC bias is applied upon the coating sleeve to keep the magnetic brush 5' of the sleeve 5 clean.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing method for developing a latent image using a one-component magnetic developer. Various methods have been known for developing a latent image using a one-component developer, or Among the proposed 0ζO methods, the toner transfer development method is known to be unique. This method involves applying a monocomponent developer agent as a thin layer uniformly onto the developer holding means, and then applying a thin layer of the developer to the surface of the thin layer of developer. This is a method in which the electrostatic latent image surfaces are opposed to each other with a small gap, and the developer is imaged on the developer holding means by the electrostatic attraction. 2,839,400)) According to this method, the latent image potential is not only not attracted to the am agent in the non-image area, but also the developer does not come into contact with the non-image area, so the capillary Excellent development is carried out with no blemishes. Furthermore, since no carrier particles are used, good effects such as no fluctuation in the developer mixing ratio and no deterioration of the carrier particles can be obtained.

In addition, the applicant has proposed a completely new developing method as described in Japanese Patent Application Laid-open Nos. 55-18656-9 and the like as a different developing method.

In this development method, a one-component magnetic developer, a developer holding means (non-magnetic), and a magnetic field generating means are arranged in this order, and a uniform thin layer of developer is formed on the developer holding means by the magnetic force of the magnetic field generating means. are formed and placed facing each other with a minute gap separated so that the surface layer of this thin developer layer does not touch the electrostatic latent image forming surface Km, while an alternating bias voltage is applied as a developing bias voltage to 11, and furthermore, the electrostatic latent image is Development is performed by changing the gap between the surface and the developer holding means over time. According to this development method, in the early stage of development, the developer reaches the non-image areas of the electrostatic latent image to develop the halftone area, and over time, the developer reaches only the image area. Compared to the former developing method, this method provides the effect of good reproducibility of ^-7 tones and development without capri. The developing method, in which the developer is placed facing the developer, provides extremely superior effects in terms of development performance, image reproducibility, developer life, etc. compared to the conventional method. As a method to form a uniform thin layer of
There is a method using a magnetic doctor blade, but this
Not suitable for pressure fixing toners. Because the distance between the magnetic doctor blade and the developer holding means is thin layer coating, the toner cannot help but appear in a minute layer of about 300 μm.
This is because the agent is pressed against the agent holding means and the surface is hardened.To solve this phenomenon, a conventional roller coat development method has been proposed.Figure 1 shows the roller coat development method. In the schematic diagram of the apparatus, ol is a coating sleeve roller (hereinafter referred to as a coating sleeve) that carries a developer supply carrier, 2 is a developing sleeve roller that is a developing agent carrier (hereinafter referred to as a development sleeve), and 3 and 9 are coating sleeves. 1 has a fixed magnet provided therein, 4 is a doctor blade, 5 is an insulating magnetic component developer (hereinafter also referred to as toner), 6 is a developer coated in a thin layer on the surface of the developing sleeve 2, and 7 is a 0 coating sleeve 1 which is a developer hopper
At zero rotation (in the illustrated example, it rotates in the same counterclockwise direction as the developing sleeve 2), the magnetic brush 5' held on the sleeve surface and rotating is struck against the surface of the developing sleeve 2 and rubbed against the insulating developer. At the same time as the charge is applied, a thin layer 6 of developer is applied to the surface of the developing sleeve 2 by the action of mirror image force, etc. The thin layer 6 of developer thus formed on the surface of the developing sleeve 2 As it rotates, the sensor L approaches the optical drum surface 8 (the surface of the holder) and so-called jumping development is achieved. 9 is a fixed magnet provided inside the developing sleeve 2.0 In the developing device shown in FIG. Furthermore, since the distance between the developer application areas is wide (approximately 1 m5), the load applied to the developer at the developer application area is reduced, and conventional types such as developer sticking can be avoided. The difficulties that occurred with the device of
In addition, since the formation principle of the thin toner layer formed on the developing sleeve relies on the electric charge held by the toner particles themselves, unlike conventional developing devices that use magnetic force, It has the advantage that the variation is small and the value of the amount of retained charge is also large on average.

However, since the amount of charge on the toner increases, and the amount of charge increases in a low-humidity environment, the toner strongly adheres to the surface of the developing sleeve, and this gradually accumulates, causing some toner to be partially deposited on the sleeve surface. A thick layer is formed,
Finally, this thick layer of toner comes into contact with the surface of the photosensitive drum, causing defects such as capri.

The present invention aims to solve the above-mentioned conventional drawbacks and provide a novel developing method.

The present invention provides a developing device that supplies developer from a developer supplying carrier to a developing carrier and develops a latent image on an image carrier with the developer. Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of a developing device to which the present invention can be applied. The same members as in FIG. 1 are denoted by the same reference numerals. In this embodiment, an example is shown in which alternating current is applied to the developing sleeve and direct current is applied to the coating sleeve. An alternating voltage is applied between the developing sleeve 2 and the photosensitive drum 8 by a first bias source 10, for example, an alternating voltage with a frequency of 1000 Hz and a peak-to-peak voltage Vp-p = 2000 V is applied. DC voltage is applied to the coating sleeve 1 from the second bias power supply 11 for toner coating.
According to experiments, when using highly insulating magnetic toner that is negatively charged, the thickness of the toner was approximately 100 μm when the voltage of the application sleeve 1 was Ov;
When a voltage of 0 V was applied, the thickness of the toner layer on the developing sleeve became approximately 80μ. Furthermore, when the bias voltage of application sleeve 1 was -500 VK, the thickness of the toner on the surface of the developing sleeve increased. By changing the bias voltage applied to the coating sleeve 1 in this way, the thickness of the layer of toner applied to the surface of the developing sleeve can be changed, and therefore, the thickness of the toner layer corresponding to this can be changed. The developing characteristics when developing the latent image on the drum 8 can be changed.The alternating voltage applied to the developing sleeve 2 and image carrier 8 was hardly affected by the bias voltage applied to the coating sleeve 1. 0 (1) in FIG. 3 shows yet another example of the bias voltage application method of the conventional sleeve coat developing device. The same alternating current (ζ) voltage is applied to accelerate developer supply and development. Figure 3 indicates the time of development, and B indicates the time of non-development.
During non-development, the potential of the photosensitive drum 8 is such that no development occurs even if the sleeve is rotated (for example, 0 V). (2) in FIG. 3 is an embodiment according to the present invention. The bias voltage of the coating sleeve 1 is switched for a certain period C during the non-development time B, and the voltage is such that the toner returns from the developing sleeve 2 to the coating sleeve 1.

According to an experiment in which a voltage is applied, the AC bias voltage of the developer waiter has a frequency f of 400 to 1000 Hz and a peak-to-peak voltage vp-p of 800 to 2000 V.

When the DC component is VDCO ~ 200V, the bias voltage applied to the coating roller during non-development B is VDC = 5
It was found that it is sufficient to apply a voltage of 00 to 1500V.

In this way, by returning the toner to the applicator sleeve at each copy interval or at the end of copying, uneven toner application on the developing sleeve can be prevented.Toner is returned from the developing sleeve to the applicator sleeve by the developing sleeve. Regarding the above point, it is enough to do it once every several 10 to several 100 sheets.
Therefore, the width C in FIG. 3 does not necessarily have to match the entire circumference of the sleeve. As stated above, 1. In the present invention, a portion of the developer attached to the developing carrier is transferred each time to the coating carrier. Since we decided to return to O

[Brief explanation of the drawing]

11 is a sectional view of a conventional developing device, FIG. 2 is a sectional view of a developing device to which the present invention can be applied, and FIG. 3 is a sequence diagram of bias voltages applied to the developing sleeve and coating sleeve. , 1... Coating sleeve, 2... Developing sleeve, 3, 9... Magnet, 4... Doctor blade, 5, 5'... Magnetic toner, 6... Toner thin layer, 7... ...Hopper, 8...Image carrier% 10...
- Represents an AC bias power supply, 11...bias power supply for toner application.

Claims (2)

[Claims] (1) - Forming a magnetic brush of component magnetic developer on a developer supply carrier using a magnetic field, and bringing the magnetic brush close to the image carrier and in contact with the surface of the developer carrier. . A developing method comprising a developing device which forms a thin layer of developer on the developing carrier and conveys the thin layer of developer to a developing section to develop the surface of the image carrier. (2) A bias voltage is applied between the developer supplying carrier and the developing carrier, and the developer is supplied from the developer supplying carrier to the developing carrier during development, and the bias is applied during non-development. 10. The developing method according to claim 10, wherein the developer is returned from the developing carrier to the developer supplying carrier. i) During development, apply an AC bias voltage to both the 1 development carrier and the developer supply carrier, and when not developing,
Developing method 0 according to claim 2, characterized in that an AC bias voltage is applied only to the developing carrier, and #i DC bias voltage is applied to the developer supplying carrier.